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In industrial engineering , the standard time is the time required by an average skilled operator, working at
a normal pace, to perform a specified task using a prescribed method. [ 1 ] It includes appropriate allowances to allow the person to recover from fatigue and, where necessary, an additional allowance to cover contingent elements which may occur but have not been observed.
Standard time = normal time + allowance
Where;
Normal time = average time × rating factor (take rating factor between 1.1 and 1.2)
Time times for all operations are known.
The standard time can be determined using the following techniques: [ 2 ]
The Standard Time is the product of three factors:
The standard time can then be calculated by using: [ 3 ]
Standard Time = ( Observed Time ) ( Rating Factor ) ( 1 + PFD Allowance ) {\displaystyle {\text{Standard Time}}=({\text{Observed Time}})({\text{Rating Factor}})(1+{\text{PFD Allowance}})}
This industry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Standard_time_(manufacturing) |
Standard time is the amount of time that should be allowed for an average worker to process one work unit using the standard method and working at a normal pace. The standard time includes some additional time, called the contingency allowance , to provide for the worker's personal needs, fatigue , and unavoidable delays during the shift.
The standard time (Ts) is calculated from multiplying the observed time (To) by the performance rating (R) and the personal need, fatigue and unavoidable delays (PFD):
Ts = To*R*(1+PFD) | https://en.wikipedia.org/wiki/Standard_time_in_manufacturing |
Standard wind tunnel models , also known as reference models, calibration models ( French : maquettes d'étalonnage ) or test check-standards are objects of relatively simple and precisely defined shapes, having known aerodynamic characteristics, that are tested in wind tunnels . Standard models are used in order to verify, by comparison of wind tunnel test results with previously published results, the complete measurement chain in a wind tunnel, including wind tunnel structure, quality of the airstream, model positioning, transducers and force balances, data acquisition system and data reduction software. [ 2 ] [ 3 ]
More specifically, standard wind tunnel models are used for:
Besides, results from wind tunnel tests of standard models are used as test cases for verification of computational-fluid-dynamics ( CFD ) computer codes.
In most wind tunnels, standard models are tested during the commissioning and calibration [ 2 ] [ 3 ] [ 4 ] of the facility.
This sometimes has an unfortunate effect that the test results are not as good as they can be,
because the wind tunnel and its measurement system have not yet been optimally tuned at the time of the test. [ 5 ] However, some laboratories
have adopted the practice of periodical testing of a standard model
every couple of years in order to provide a continued confidence in the
reliability of measurements in their wind tunnels
. [ 6 ] [ 7 ]
Standard wind tunnel models are usually (but not always) intended for one of the basic wind tunnel
measurement types, such as the measurement of forces and moments with force balances or measurements of pressure distribution . Results of wind tunnel tests of these models are generally published in the form of nondimensional aerodynamic coefficients (thus being made independent of model size) and made
available to the wind-tunnel community, often in review reports containing inter-facility comparisons of data, [ 5 ] [ 8 ] [ 9 ] [ 10 ] discussing observed scatter of results, different testing conditions, production differences between models etc.
As the majority of wind tunnel tests is related to aeronautics , most
standard wind tunnel models resemble simplified forms of wings , airplanes or missiles .
Such are, for static tests: NACA 0012 and CLARK Y (2D wing-segment models with typical airfoils ), AGARD-B / AGARD-C (generic delta-wing -airplane shapes), ONERA -M (a generic transport-airplane shape), HB-2 (Hypervelocity ballistic model 2, a shape similar to a reentry-body ). For dynamic tests, the often-used standard models are: SDM (Standard dynamic model, a generic fighter-like airplane shape somewhat similar to F-16 )), BFM (Basic finner model, a generic conical-cylindrical missile with four fins at the rear end) and MBFM (Modified basic finner model [ 11 ] ). A number of other standard models exists as well.
With the increased use of wind tunnels in the testing of road vehicles, several standard
models of generic car shapes were defined., [ 12 ] such as the Ahmed body [ 13 ] , [ 14 ] MIRA reference car , [ 15 ] etc.
Some wind tunnel laboratories perform periodical checkouts using internally defined standard models
that are selected from the repository of models previously tested in the facility [ 16 ]
Geometry of a standard wind tunnel model is defined relative to some easily identified
parameter ( see figure ), e.g. body diameter or wing chord . [ 1 ] The geometry is published by the institution proposing the model. Beside the model itself, a standard model support, such as a sting , to be used with the model, is usually defined. An actual model is built to a size suitable for the size of a specific wind tunnel test section, in particular taking care that the frontal blockage of the model (the ratio of the model cross-section area to wind tunnel test section area) is kept well below 1% (except for wall-interference research where the models may be larger).
In order to eliminate the effects of production differences between models in inter-facility comparisons, sometimes the same physical standard model is tested in several wind tunnels [ 8 ]
Wind tunnel
AGARD-B wind tunnel model | https://en.wikipedia.org/wiki/Standard_wind_tunnel_models |
The Standardized Precipitation Evapotranspiration Index ( SPEI ) is a multiscalar drought index based on climatic data. It was developed by Vicente-Serrano et al. (2010) at the Pyrenean Institute of Ecology in Zaragoza, Spain . [ 1 ] It can be used for determining the onset, duration and magnitude of drought conditions with respect to normal conditions in a variety of natural and managed systems such as crops, ecosystems, rivers, water resources, etc. [ 2 ] [ 3 ] [ 4 ]
The SPEI accounts not only for precipitation deficit but also for the role of the increased atmospheric evaporative demand on drought severity. [ 5 ] Evaporative demand is particularly dominant during periods of precipitation deficit. The SPEI calculation requires long-term and high-quality precipitation and atmospheric evaporative demand datasets. These can be obtained from ground stations or gridded data based on reanalysis as well as satellite and multi-source datasets. [ 5 ]
Globally, the SPEIbase and Global Precipitation Climatology Centre (GPCC) drought index datasets are available at a relatively coarse spatial resolution. The SPEIbase is available at 0.5° resolution calculated from the Climatic Research Unit precipitation and potential evapotranspiration datasets. The GPCC drought index provides SPEI datasets at a 1.0° spatial resolution for limited timescales (1, 3, 6, 9, 12, 24, and 48 months). [ 5 ]
Inputs to SPEI datasets can include high-resolution potential evapotranspiration (PET) from the Global Land Evaporation Amsterdam Model (GLEAM) and hourly Potential Evapotranspiration (hPET). GLEAM is a set of algorithms designed to calculate actual evaporation, PET, evaporative stress, and root-zone soil moisture. [ 5 ]
This article about atmospheric science is a stub . You can help Wikipedia by expanding it .
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This hydrology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Standardised_Precipitation_Evapotranspiration_Index |
The consortium for Standardization in Lab Automation (SiLA) is a not-for-profit membership organization formed by software suppliers, system integrators and pharma/biotech companies. It develops and introduces new device and data interface standards allowing rapid integration of lab automation hardware and data management systems. Highly skilled experts of member companies contribute in SiLA's technical work groups. Membership is open for institutions, corporations and individuals active in the life science lab automation industry. The SiLA consortium provides professional training, support and certification services to suppliers and system integrators implementing SiLA compliant interfaces.
SiLA is the global initiative to standardize software interfaces in the field of life science research instrumentation, like autosamplers , and laboratory automation . Instigated by the pharmaceutical industry's need for flexible laboratory automation, the initiative is supported by major device and software suppliers worldwide.
Understanding the mechanisms of life requires extensive, often repetitive, experimentation. Laboratory automation, therefore, has become instrumental to the progress of the life sciences.
Industry provides commercial laboratory devices to perform increasingly sophisticated tasks. However, combining equipment from different providers to work in concert often proves impossible. Exporting captured data from proprietary software for further analysis can be frustrating or impossible.
This situation leads to a waste of resources: Available equipment needs to be replaced for compatibility reasons, software drivers have to be purchased or developed, and data conversion is time-consuming.
Such technical obstacles impede the development of higher level autonomous experimentation systems.
SiLA enables researchers to focus on their scientific questions by reducing equipment connectivity effort to a minimum. This is achieved by using proven, tested and maintained documentation and code.
Advancements seen on the home consumer electronics marked like USB or UPnP triggered the idea of applying a similar approach to the laboratory automation environment. Why was it possible to easily upload pictures from any digital camera on any computer but in the same time not even thinkable to replace a lab device (e.g.: a Shaker ) of one brand with a Shaker of a different brand? Analyzing the situation led to the conclusion that the incompatibility was a result of missing interface definitions. The idea of a standardized interface based on the Common Command Set (CCS) concept was born.
However, SiLA 1.x has some limitations: It is based on XML/Soap which is considered as outdated. Getting started with SiLA 1.x is not an easy process. This led to the proposition of a spin-off group of the SiLA consortium to develop a new standard: SiLA 2. Learning from SiLA 1.x and taking many concepts from it, SiLA 2 had the vision of being as accessible as possible. A major goal is to create a community constantly working on the development of new Features.
SiLA 2 addresses control and data interfaces between devices and process management, LIMS and Enterprise Systems. It is built to connect systems in a laboratory, such as laboratory information management systems , electronic lab notebooks , chromatography software and laboratory devices such as balances, pipettors and various other analytical instruments.
Enhancing the first standard SiLA 1.x by adopting proven concepts and applying already existing open standards and protocols in a "lean and mean" manner, SiLA 2 is designed to enable plug-and-play operations in the laboratory.
SiLA 2 considers every entity in the modern laboratory as a service. Focus on behaviour and service oriented design structures leads to the Feature Definition Language (FDL). SiLA 2 is based on a microservice architecture. Relying on HTTP/2 , SiLA uses Protocol Buffers to serialize payload data. Furthermore, SiLA 2 uses the wire format provided by gRPC .
SiLA 2 can split up into a Core and Feature level. The SiLA Core is written and maintained by the SiLA 2 Working group. SiLA Features are specific extensions that may change and evolve in any way.
SiLA's basic structure consists of a client – server communication model. The SiLA Server (≙ web server ) exposes all its capabilities to the SiLA Client (≙ web client ). Capabilities of the SiLA Server are grouped together as SiLA Features.
The Feature concept serves as a common communication base for subject matter experts (SME), IT experts and end users. Each Feature is described by its Feature Definition, an XML-file containing information about parameters, interactions, data types, return values, etc. It exposes a certain number of Commands which model actions that can be performed by the SiLA Server.
SiLA 2 offers cloud functionality. For connecting, the SiLA-Client and SiLA-Server switch roles and a “reverse-channel” will be established – This way the connection will be initialized by the SiLA-Server which can reside in a local network. Cloud capabilities are given while maintaining regulated security policies and safety by relying on standard gRPC and HTTP/2 connection handling and security models.
SiLA 1.x has been used from 2009 until 2018. But getting started with SiLA 1.x is not an easy process. Furthermore, As SiLA 1.x is based on XML/Soap which is considered outdated. It is now replaced by SiLA 2.
The SiLA device interface standard covers all ISO/OSI levels of the device control interface from physical to application layer.
The interface standard is based on web service/ SOAP communication with the devices. Commands are generally executed in asynchronous manner with an immediate response and a delayed event after completion of the command processing or after an error. Error recovery procedures are also supported and the general behavior of the devices is managed by a state machine. The state machine enables also complex behaviors like parallel processing of commands and command queuing.
By supporting three different integration levels, SiLA provides a unique, standardized interface between lab automation devices and process management systems so that also legacy devices can be integrated in SiLA compliant systems. SiLA compliance can be achieved by providing native, directly embedded SiLA device interfaces or by software only SiLA drivers and/or interface converters. The SiLA Device Control and Data Interface Standard eases and accelerates the integration and adaptation of systems through generic Device Class Interfaces providing Common Command Sets.
By grouping devices of the same functionality device classes can be created. SiLA Common Command Sets define commands for these device classes. SiLA defines the command names, the number of parameters and their names as well as the return data. Since commands and parameters are described in the WSDL documentation tag of the commands web service, a process management software (PMS) can automatically generate a list available commands for each device.
SiLA has defined about 30 device classes and a command library with about 100 commands. Commands range from mandatory commands that are needed to make transitions in the state machine, over required commands for the specific device class, to optional commands for which not every device in the device class might provide the functionality. In addition guidelines for the implementation of supplier-specific device commands and parameters are provided.
Some commands are applicable for almost every device class. For example, the commands SetParameter, GetParameter, ExecuteMethod are widely used. Also PrepareForOutput and PrepareForInput are common because they enable the transport mechanisms to transfer labware items from device to device. The mandatory commands include operations like Reset, Initialize, Abort and Pause. In addition locking a device for exclusive use is provided.
SiLA has formed a not-for-profit membership organisation. SiLA requires members to pay annual membership dues. Details on membership classes and related fees can be found here .
SiLA is a not-for-profit membership corporation with global footprint. Membership is open for institutions, corporations and individuals active in the life science lab automation industry.
The SiLA consortium provides professional training, support and certification services to suppliers and system integrators implementing SiLA compliant interfaces. | https://en.wikipedia.org/wiki/Standardization_in_Lab_Automation |
Standards for Reporting Enzymology Data (STRENDA) is an initiative as part of the Minimum Information Standards which specifically focuses on the development of guidelines for reporting (describing metadata) enzymology experiments. The initiative is supported by the Beilstein Institute for the Advancement of Chemical Sciences . [ 1 ] STRENDA establishes both publication standards for enzyme activity data and STRENDA DB, an electronic validation and storage system for enzyme activity data. Launched in 2004, the foundation of STRENDA is the result of a detailed analysis of the quality of enzymology data in written and electronic publications. [ 2 ] [ 3 ]
The STRENDA project is driven by 15 scientists from all over the world forming the STRENDA Commission [ 4 ] and supporting the work with expertises in biochemistry , enzyme nomenclature , bioinformatics , systems biology , modelling, mechanistic enzymology and theoretical biology .
The STRENDA Guidelines [ 5 ] propose those minimum information that is needed to comprehensively report kinetic and equilibrium data from investigations of enzyme activities including corresponding experimental conditions.
This minimum information is suggested to be addressed in a scientific publication when enzymology research data is reported to ensure that data sets are comprehensively described. This allows scientists not only to review, interpret and corroborate the data but also to reuse the data for modelling and simulation of biocatalytic pathways. In addition, the guidelines support researchers making their experimental data reproducible and transparent. [ 6 ] [ 7 ] [ 8 ] [ 9 ]
As of March 2020, more than 55 international biochemistry journal included the STRENDA Guidelines in their authors' instructions as recommendations when reporting enzymology data. [ 10 ] The STRENDA project is registered with FAIRsharing.org [ 11 ] and the Guidelines are part of the FAIRDOM Community standards for Systems Biology. [ 12 ]
STRENDA DB
STRENDA DB [ 13 ] is a web-based storage and search platform that has incorporated the Guidelines and automatically checks the submitted data on compliance with the STRENDA Guidelines thus ensuring that the manuscript data sets are complete and valid. A valid data set is awarded a STRENDA Registry Number (SRN) and a fact sheet (PDF) is created containing all submitted data. Each dataset is registered at Datacite and assigned a DOI to refer and track the data. After the publication of the manuscript in a peer-reviewed journal the data in STRENDA DB are made open accessible. [ 14 ] [ 15 ] STRENDA DB is a repository recommended by re3data and OpenDOAR . It is harvested by OpenAIRE.
The database service is recommended in the authors' instructions of more than 10 biochemistry journals, including Nature , The Journal of Biological Chemistry , eLife , and PLoS . It has been referred as a standard tool for the validation and storage of enzyme kinetics data in multifold publications [ 16 ] [ 17 ] [ 18 ] [ 19 ] [ 20 ] [ 21 ] A recent study examining eleven publications, including Supporting Information, from two leading journals revealed that at least one omission was found in every one of these papers. The authors concluded that using STRENDA DB in the current version would ensure that about 80% auf the relevant information would be made available. [ 22 ]
Data Management
STRENDA DB is considered a tool for research data management by the research community (e.g. EU project CARBAFIN [ 23 ] ). | https://en.wikipedia.org/wiki/Standards_for_Reporting_Enzymology_Data |
The Standards of Fundamental Astronomy ( SOFA ) software libraries are a collection of subroutines that implement official International Astronomical Union (IAU) algorithms for astronomical computations.
As of February 2009 they are available in both Fortran and C source code format.
The subroutines in the libraries cover the following areas:
As of the February 2009 release, SOFA licensing changed to allow use for any purpose, provided certain requirements are met. [ 1 ] Previously, commercial usage was specifically excluded and required written agreement of the SOFA board. [ 2 ]
This astrophysics -related article is a stub . You can help Wikipedia by expanding it .
This classical mechanics –related article is a stub . You can help Wikipedia by expanding it .
This computer-library -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Standards_of_Fundamental_Astronomy |
A standing crop is the total biomass of the living organisms present in a given environment. [ 1 ] This includes both natural ecosystems and agriculture .
This article about environmental habitats is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Standing_crop |
In radio engineering and telecommunications , standing wave ratio ( SWR ) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide . Impedance mismatches result in standing waves along the transmission line, and SWR is defined as the ratio of the partial standing wave 's amplitude at an antinode (maximum) to the amplitude at a node (minimum) along the line.
Voltage standing wave ratio (VSWR) (pronounced "vizwar" [ 1 ] [ 2 ] ) is the ratio of maximum to minimum voltage on a transmission line . For example, a VSWR of 1.2 means a peak voltage 1.2 times the minimum voltage along that line, if the line is at least one half wavelength long.
A SWR can be also defined as the ratio of the maximum amplitude to minimum amplitude of the transmission line's currents , electric field strength , or the magnetic field strength. Neglecting transmission line loss, these ratios are identical.
The power standing wave ratio ( PSWR ) is defined as the square of the VSWR, [ 3 ] however, this deprecated term has no direct physical relation to power actually involved in transmission.
SWR is usually measured using a dedicated instrument called an SWR meter . Since SWR is a measure of the load impedance relative to the characteristic impedance of the transmission line in use (which together determine the reflection coefficient as described below ), a given SWR meter can interpret the impedance it sees in terms of SWR only if it has been designed for the same particular characteristic impedance as the line. In practice most transmission lines used in these applications are coaxial cables with an impedance of either 50 or 75 ohms , so most SWR meters correspond to one of these.
Checking the SWR is a standard procedure in a radio station. Although the same information could be obtained by measuring the load's impedance with an impedance analyzer (or "impedance bridge"), the SWR meter is simpler and more robust for this purpose. By measuring the magnitude of the impedance mismatch at the transmitter output it reveals problems due to either the antenna or the transmission line.
SWR is used as a measure of impedance matching of a load to the characteristic impedance of a transmission line carrying radio frequency (RF) signals. This especially applies to transmission lines connecting radio transmitters and receivers with their antennas , as well as similar uses of RF cables such as cable television connections to TV receivers and distribution amplifiers . Impedance matching is achieved when the source impedance is the complex conjugate of the load impedance. The easiest way of achieving this, and the way that minimizes losses along the transmission line, is for the imaginary part of the complex impedance of both the source and load to be zero, that is, pure resistances, equal to the characteristic impedance of the transmission line. When there is a mismatch between the load impedance and the transmission line, part of the forward wave sent toward the load is reflected back along the transmission line towards the source. The source then sees a different impedance than it expects which can lead to lesser (or in some cases, more) power being supplied by it, the result being very sensitive to the electrical length of the transmission line.
Such a mismatch is usually undesired and results in standing waves along the transmission line which magnifies transmission line losses (significant at higher frequencies and for longer cables). The SWR is a measure of the depth of those standing waves and is, therefore, a measure of the matching of the load to the transmission line. A matched load would result in an SWR of 1:1 implying no reflected wave. An infinite SWR represents complete reflection by a load unable to absorb electrical power, with all the incident power reflected back towards the source.
It should be understood that the match of a load to the transmission line is different from the match of a source to the transmission line or the match of a source to the load seen through the transmission line. For instance, if there is a perfect match between the load impedance Z load and the source impedance Z source = Z * load , that perfect match will remain if the source and load are connected through a transmission line with an electrical length of one half wavelength (or a multiple of one half wavelengths) using a transmission line of any characteristic impedance Z 0 . However the SWR will generally not be 1:1, depending only on Z load and Z 0 . With a different length of transmission line, the source will see a different impedance than Z load which may or may not be a good match to the source. Sometimes this is deliberate, as when a quarter-wave matching section is used to improve the match between an otherwise mismatched source and load.
However typical RF sources such as transmitters and signal generators are designed to look into a purely resistive load impedance such as 50Ω or 75Ω, corresponding to common transmission lines' characteristic impedances. In those cases, matching the load to the transmission line, Z load = Z 0 , always ensures that the source will see the same load impedance as if the transmission line weren't there. This is identical to a 1:1 SWR. This condition ( Z load = Z 0 ) also means that the load seen by the source is independent of the transmission line's electrical length. Since the electrical length of a physical segment of transmission line depends on the signal frequency, violation of this condition means that the impedance seen by the source through the transmission line becomes a function of frequency (especially if the line is long), even if Z load is frequency-independent. So in practice, a good SWR (near 1:1) implies a transmitter's output seeing the exact impedance it expects for optimum and safe operation.
The voltage component of a standing wave in a uniform transmission line consists of the forward wave (with complex amplitude V f {\displaystyle V_{f}} ) superimposed on the reflected wave (with complex amplitude V r {\displaystyle V_{r}} ).
A wave is partly reflected when a transmission line is terminated with an impedance unequal to its characteristic impedance . The reflection coefficient Γ {\displaystyle \Gamma } can be defined as:
or
Γ {\displaystyle \Gamma } is a complex number that describes both the magnitude and the phase shift of the reflection. The simplest cases with Γ {\displaystyle \Gamma } measured at the load are:
The SWR directly corresponds to the magnitude of Γ {\displaystyle \Gamma } .
At some points along the line the forward and reflected waves interfere constructively, exactly in phase, with the resulting amplitude V max {\displaystyle V_{\text{max}}} given by the sum of those waves' amplitudes:
At other points, the waves interfere 180° out of phase with the amplitudes partially cancelling:
The voltage standing wave ratio is then
Since the magnitude of Γ {\displaystyle \Gamma } always falls in the range [0,1], the SWR is always greater than or equal to unity. Note that the phase of V f and V r vary along the transmission line in opposite directions to each other. Therefore, the complex-valued reflection coefficient Γ {\displaystyle \Gamma } varies as well, but only in phase. With the SWR dependent only on the complex magnitude of Γ {\displaystyle \Gamma } , it can be seen that the SWR measured at any point along the transmission line (neglecting transmission line losses) obtains an identical reading.
Since the power of the forward and reflected waves are proportional to the square of the voltage components due to each wave, SWR can be expressed in terms of forward and reflected power:
By sampling the complex voltage and current at the point of insertion, an SWR meter is able to compute the effective forward and reflected voltages on the transmission line for the characteristic impedance for which the SWR meter has been designed. Since the forward and reflected power is related to the square of the forward and reflected voltages, some SWR meters also display the forward and reflected power.
In the special case of a load R L , which is purely resistive but unequal to the characteristic impedance of the transmission line Z 0 , the SWR is given simply by their ratio:
with the ratio or its reciprocal is chosen to obtain a value greater than unity.
Using complex notation for the voltage amplitudes, for a signal at frequency f , the actual (real) voltages V actual as a function of time t are understood to relate to the complex voltages according to:
Thus taking the real part of the complex quantity inside the parenthesis, the actual voltage consists of a sine wave at frequency f with a peak amplitude equal to the complex magnitude of V , and with a phase given by the phase of the complex V . Then with the position along a transmission line given by x , with the line ending in a load located at x o , the complex amplitudes of the forward and reverse waves would be written as:
for some complex amplitude A (corresponding to the forward wave at x o that some treatments use phasors where the time dependence is according to e − i 2 π f t {\displaystyle e^{-i2\pi ft}} and spatial dependence (for a wave in the +x direction) of e + i k ( x − x o ) . {\displaystyle \ e^{+ik(x-x_{\mathsf {o}})}~.} Either convention obtains the same result for V actual .
According to the superposition principle the net voltage present at any point x on the transmission line is equal to the sum of the voltages due to the forward and reflected waves:
Since we are interested in the variations of the magnitude of V net along the line (as a function of x ), we shall solve instead for the squared magnitude of that quantity, which simplifies the mathematics. To obtain the squared magnitude we multiply the above quantity by its complex conjugate:
Depending on the phase of the third term, the maximum and minimum values of V net (the square root of the quantity in the equations) are ( 1 + | Γ | ) | A | {\displaystyle \ \left(1+|\Gamma |\right)|A|\ } and ( 1 − | Γ | ) | A | , {\displaystyle \ \left(1-|\Gamma |\right)|A|\ ,} respectively, for a standing wave ratio of:
as earlier asserted. Along the line, the above expression for | V n e t ( x ) | 2 {\displaystyle \ |V_{\mathsf {net}}(x)|^{2}\ } is seen to oscillate sinusoidally between | V m i n | 2 {\displaystyle \ |V_{\mathsf {min}}|^{2}\ } and | V m a x | 2 {\displaystyle \ |V_{\mathsf {max}}|^{2}\ } with a period of 2 π / 2 k . This is half of the guided wavelength λ = 2 π / k for the frequency f . That can be seen as due to interference between two waves of that frequency which are travelling in opposite directions.
For example, at a frequency f = 20 MHz (free space wavelength of 15 m) in a transmission line whose velocity factor is 0.67 , the guided wavelength (distance between voltage peaks of the forward wave alone) would be λ = 10 m . At instances when the forward wave at x = 0 is at zero phase (peak voltage) then at x = 10 m it would also be at zero phase, but at x = 5 m it would be at 180° phase (peak negative voltage). On the other hand, the magnitude of the voltage due to a standing wave produced by its addition to a reflected wave, would have a wavelength between peaks of only 1 / 2 λ = 5 m . Depending on the location of the load and phase of reflection, there might be a peak in the magnitude of V net at x = 1.3 m . Then there would be another peak found where | V net | = V max at x = 6.3 m , whereas it would find minima of the standing wave at x = 3.8 m, 8.8 m, etc.
The most common case for measuring and examining SWR is when installing and tuning transmitting antennas . When a transmitter is connected to an antenna by a feed line , the driving point impedance of the antenna must match the characteristic impedance of the feed line in order for the transmitter to see the impedance it was designed for (the impedance of the feed line, usually 50 or 75 ohms).
The impedance of a particular antenna design can vary due to a number of factors that cannot always be clearly identified. This includes the transmitter frequency (as compared to the antenna's design or resonant frequency), the antenna's height above and quality of the ground, proximity to large metal structures, and variations in the exact size of the conductors used to construct the antenna. [ 5 ] (p20.2)
When an antenna and feed line do not have matching impedances, the transmitter sees an unexpected impedance, where it might not be able to produce its full power, and can even damage the transmitter in some cases. [ 5 ] (pp19.4–19.6) The reflected power in the transmission line increases the average current and therefore losses in the transmission line compared to power actually delivered to the load. [ 6 ] It is the interaction of these reflected waves with forward waves which causes standing wave patterns, [ 5 ] (pp19.4–19.6) with the negative repercussions we have noted. [ 5 ] (p19.13)
Matching the impedance of the antenna to the impedance of the feed line can sometimes be accomplished through adjusting the antenna itself, but otherwise is possible using an antenna tuner , an impedance matching device. Installing the tuner between the feed line and the antenna allows for the feed line to see a load close to its characteristic impedance, while sending most of the transmitter's power (a small amount may be dissipated within the tuner) to be radiated by the antenna despite its otherwise unacceptable feed point impedance. Installing a tuner in between the transmitter and the feed line can also transform the impedance seen at the transmitter end of the feed line to one preferred by the transmitter. However, in the latter case, the feed line still has a high SWR present, with the resulting increased feed line losses unmitigated.
The magnitude of those losses are dependent on the type of transmission line, and its length. They always increase with frequency. For example, a certain antenna used well away from its resonant frequency may have an SWR of 6:1. For a frequency of 3.5 MHz, with that antenna fed through 75 meters of RG-8A coax, the loss due to standing waves would be 2.2 dB. However the same 6:1 mismatch through 75 meters of RG-8A coax would incur 10.8 dB of loss at 146 MHz. [ 5 ] (pp19.4–19.6) Thus, a better match of the antenna to the feed line, that is, a lower SWR, becomes increasingly important with increasing frequency, even if the transmitter is able to accommodate the impedance seen (or an antenna tuner is used between the transmitter and feed line).
Certain types of transmissions can suffer other negative effects from reflected waves on a transmission line. Analog TV can experience "ghosts" from delayed signals bouncing back and forth on a long line. FM stereo can also be affected and digital signals can experience delayed pulses leading to bit errors. Whenever the delay times for a signal going back down and then again up the line are comparable to the modulation time constants, effects occur. For this reason, these types of transmissions require a low SWR on the feedline, even if SWR induced loss might be acceptable and matching is done at the transmitter.
Many different methods can be used to measure standing wave ratio. The most intuitive method uses a slotted line which is a section of transmission line with an open slot which allows a probe to detect the actual voltage at various points along the line. [ 7 ]
Thus the maximum and minimum values can be compared directly. This method is used at VHF and higher frequencies. At lower frequencies, such lines are impractically long.
Directional couplers can be used at HF through microwave frequencies. Some are a quarter wave or more long, which restricts their use to the higher frequencies. Other types of directional couplers sample the current and voltage at a single point in the transmission path and mathematically combine them in such a way as to represent the power flowing in one direction. [ 8 ] The common type of SWR / power meter used in amateur operation may contain a dual directional coupler. Other types use a single coupler which can be rotated 180 degrees to sample power flowing in either direction. Unidirectional couplers of this type are available for many frequency ranges and power levels and with appropriate coupling values for the analog meter used.
The forward and reflected power measured by directional couplers can be used to calculate SWR. The computations can be done mathematically in analog or digital form or by using graphical methods built into the meter as an additional scale or by reading from the crossing point between two needles on the same meter.
The above measuring instruments can be used "in line" that is, the full power of the transmitter can pass through the measuring device so as to allow continuous monitoring of SWR. Other instruments, such as network analyzers, low power directional couplers and antenna bridges use low power for the measurement and must be connected in place of the transmitter. Bridge circuits can be used to directly measure the real and imaginary parts of a load impedance and to use those values to derive SWR. These methods can provide more information than just SWR or forward and reflected power. [ 9 ] Stand alone antenna analyzers use various measuring methods and can display SWR and other parameters plotted against frequency. By using directional couplers and a bridge in combination, it is possible to make an in line instrument that reads directly in complex impedance or in SWR. [ 10 ] Stand alone antenna analyzers also are available that measure multiple parameters.
The term power standing wave ratio (PSWR) is sometimes referred to, and defined as, the square of the voltage standing wave ratio. The term is widely cited as "misleading". [ 11 ]
The expression "power standing-wave ratio", which may sometimes be encountered, is even more misleading, for the power distribution along a loss-free line is constant. ...
However it does correspond to one type of measurement of SWR using what was formerly a standard measuring instrument at microwave frequencies, the slotted line . The slotted line is a waveguide (or air-filled coaxial line) in which a small sensing antenna which is part of a crystal detector or detector is placed in the electric field in the line. The voltage induced in the antenna is rectified by either a point contact diode (crystal rectifier) or a Schottky barrier diode that is incorporated in the detector. These detectors have a square law output for low levels of input. Readings therefore corresponded to the square of the electric field along the slot, E 2 ( x ), with maximum and minimum readings of E 2 max and E 2 min found as the probe is moved along the slot. The ratio of these yields the square of the SWR, the so-called PSWR. [ 13 ]
This technique of rationalization of terms is fraught with problems. [ clarification needed ] The square law behavior of the detector diode is exhibited only when the voltage across the diode is below the knee of the diode. Once the detected voltage exceeds the knee, the response of the diode becomes nearly linear. In this mode the diode and its associated filtering capacitor produce a voltage that is proportional to the peak of the sampled voltage. The operator of such a detector would not have a ready indication as to the mode in which the detector diode is operating and therefore differentiating the results between SWR or so called PSWR is not practical. Perhaps even worse, is the common case where the minimum detected voltage is below the knee and the maximum voltage is above the knee. In this case, the computed results are largely meaningless. Thus the terms PSWR and Power Standing Wave Ratio are deprecated and should be considered only from a legacy measurement perspective.
SWR can also have a detrimental impact upon the performance of microwave-based medical applications. In microwave electrosurgery an antenna that is placed directly into tissue may not always have an optimal match with the feedline resulting in standing waves, the presence of which can affect monitoring components used to measure power levels, making such measurements less reliable. [ 14 ] | https://en.wikipedia.org/wiki/Standing_wave_ratio |
Standoff distance is a security term that refers to measures to prevent unscreened and potentially threatening people and vehicles from approaching within a certain distance of a building , car , or other shelter , roadblock or other location, or to a person such as a law enforcement officer or VIP, or to a friendly area / location. [ a ]
Standoff distance is used when a violent criminal is in a fortified position, when hostages are under armed threat from kidnappers , when a bomb is believed to have been placed, or when other unspecified dangers may be lurking. It is a measure of distance used by government, law enforcement, or military operatives handling the situation to protect their own agents and civilians from physical injury or death while the situation is resolved.
Standoff distance may be ensured using fixed physical barriers such as fences or bollards; temporary placement of items to block access (e.g., using law enforcement vehicles or police tape to block a road or bridge); physical features other than barriers (these may appear innocuous, such as the White House lawn or adding an ornamental pond); armed guards or positions (e.g., a police sniper in overwatch ); or deploying police officers with carbines such as an M-4 , instead of just a service sidearm. When police officers have carbines the standoff distance is increased because an attacker who poses a threat can be fired upon from greater distances.
When an armed and violent criminal is sheltered in a location not easily reachable by a tranquilizer round or disabling shot - or lethal ammunition, if authorized by mission leaders - police, military, and counterterrorism officers maintain distance (often out of the direct line of sight and behind cover) while often using a megaphone to call for backup, the arrest of the subject, or to take him/her into custody.
Sniper coverage is used often in these situations, and standard procedure for officers or operatives (or citizens taking part in a citizen's arrest ) is to call for heavily armored backup while maintaining cover themselves. In the wake of active shooter scenarios, some law enforcement agencies have switched to moving in on the suspects, to prevent the gunmen from harming civilians. Therapeutic interventions or diplomatic techniques may be used to talk down the suspects or identified threats and assailants.
In a hostage situation, the primary goal is the safe recovery of the hostages, who are usually held under threat of violence or other prolonged physical harm ( starvation , poisoning , bleeding , illness ) from kidnappers . Thus the situation is treated similarly to situations with other armed attackers under cover, but with even more caution. Snipers are often employed to attempt to provide leverage against the hostage-takers or to fire at the hostage takers if an imminent risk of harm to the hostages is identified.
Unless all kidnappers can be hit and killed by sniper gunfire almost simultaneously, generally extreme prejudice (e.g., shooting at gunmen) is not used as freely due to the danger of other kidnappers killing the hostages, as in the 1972 Munich example.
This is not true in lone wolf situations, where the hostage taker is often shot by a snipers with armor-piercing or wall-piercing ammunition if talk or negotiation resolution is impossible. In all situations the preferred method is to talk the kidnappers into releasing the hostages for ransom or otherwise talking them down using therapeutic or diplomatic techniques, to protect the safety of the hostages and, ideally, have the suspect surrender peacefully.
An explosion is an extremely rapid release of energy in the form of light, heat, sound, and a shock wave. A shock wave consists of highly compressed air traveling radially outward from the source at supersonic velocities. As the shock wave expands, pressures decrease rapidly and, when it meets a surface that is in line-of-sight of the explosion, it is reflected and amplified. Pressures also decay rapidly over time and have a very brief span of existence, measured typically in thousandths of a second, or milliseconds. Diffraction effects, caused by corners of a building or structure, may act to confine the air-blast , the airborne shock wave that results from the detonation of the explosives, prolonging its duration. Late in the explosive event, the shock wave becomes negative, creating suction. Behind the shock wave , where a vacuum has been created, air rushes in, creating a powerful wind or drag pressure on all surfaces of the building. This wind picks up and carries flying debris, acting as fragmentation , in the vicinity of the detonation. In an external explosion, a portion of the energy is also imparted to the ground, creating a crater and generating a ground shock wave analogous to a high-intensity, short-duration earthquake.
Note that the severity of an air-blast event is directly dependent on the explosive, distance, and its confinement. [ 2 ] The chances of survival dramatically increase as the distance from an explosive threat increase. Note that the majority of the deaths affiliated with explosives are those that are within the immediate vicinity and those that are critically injured by debris generated by material within the vicinity of the explosion.
With explosive threats or bombs, the standoff distance used by law enforcement officers depends on the size and type of the bomb. [ 3 ] The smallest standoff distances, about 70 feet (21 m) from the threat, are used for small pipe bombs with about five (5) pounds (2.25 kg) of explosives. [ 3 ] A human suicide bomber with about 20 pounds (9 kg) of explosives strapped to his/her body has a standoff distance of 110 feet (33.5 m). [ 3 ] A briefcase or suitcase bomb with about 50 pounds (22.67 kg) of explosives has a 150-foot (46 m) standoff distance. [ 3 ] Larger car bombs or truck bombs have a much larger standoff distance, as the blast radius is bigger. [ 3 ] A car bomb with a 500-pound (226.79 kg) bomb has a 320-foot (97.5 m) standoff distance. [ 3 ] A small delivery truck-based truck bomb with a 1,000 pound (453.59 kg) bomb has a 640-foot (195 m) standoff distance. [ 3 ] A huge 18-wheeler truck-sized truck bomb with over 60,000 pounds (27215.5 kg) of explosives has a 1,570 foot (478.5 m) standoff distance. [ 3 ] This information is included in the following table, note that the distances for mandatory evacuation are for inside and outside of buildings. [ 3 ] Also, as a word of caution , note that the mandatory evacuation distance does not necessarily ensure safety, and all should proceed to the preferred evacuation distances indicated below. [ 3 ]
Standoff distance is also intended to deter terrorists from using car bombs by making it more difficult for them to cause catastrophic damage. In the wake of the Oklahoma City bombing , many high-risk federal buildings began enforcing standoff distances. It is based on the concept that a blast shock load is essentially a high-pressure front that moves out radially and decays very quickly [ 3 ] - because blast falloff is thus often more exponential than linear , any standoff distance helps increases survival chances for passersby and minimizes danger, though shrapnel mitigates this effect if present.
Hydraulic roadblocks (sometimes wedge-shaped), or bollards can be raised to block approaching vehicles; these can be designed to prevent even a heavy, fast-moving truck from getting through. Jersey barriers and concrete planters filled with dirt have also been used to maintain separation between screened and unscreened traffic. Certain infrastructure at risk of terrorist attack, such as bridges, may not be well-suited to standoff distances since their purpose is for traffic to travel along them.
The effects of various long duration blast overpressures and the associated effect on structures and the human body are summarized below. [ 4 ] Note that this data assumes that the structures and personnel affected by an explosive threat are not protected from debris. | https://en.wikipedia.org/wiki/Standoff_distance |
A standpipe or riser is a type of rigid water piping which is built into multi-story buildings in a vertical position, or into bridges in a horizontal position, to which fire hoses can be connected, allowing manual application of water to the fire. Within the context of a building or bridge, a standpipe serves the same purpose as a fire hydrant . NFPA 14 - Standard for the Installation of Standpipe and Hose Systems regulates the design of standpipe system in the United States. [ 1 ] Some standpipe systems are combined with fire sprinkler systems, using common pipes to supply both the sprinklers and hose connections.
Fire standpipes have two broad types: "Wet" and "Dry". The terms describe their state during normal, non-firefighting situations.
Dry standpipe systems do not contain water in the piping during normal, non-firefighting situations. Water is only introduced when needed for firefighting purposes.
Manual Dry Standpipe System - A standpipe system that is not connected to a water supply and requires water to be pumped into the system via a fire department connection (FDC), often by a fire truck. [ 1 ]
Semiautomatic Dry Standpipe System - A standpipe system that is connected to a water supply and capable of supplying the water at any time, but requires the manual activation of a valve or other control to introduce the water into the system. [ 1 ]
Automatic Dry Standpipe System - A standpipe system that is connected to a water supply and capable of supplying the water at any time, that is kept under air pressure, so that upon the opening of a hose supply connection valve, water is drawn into the system via a dry pipe valve. [ a ] [ 1 ]
Wet standpipe systems contain water at all times.
Manual Wet Standpipe System - A standpipe system that contains water, but requires additional water to be pumped into the system via a fire department connection (FDC), often by a fire truck. [ 1 ]
Automatic Wet Standpipe System - A standpipe system that is connected to a water supply and capable of supplying the water without any action except opening a hose supply connection valve. [ 1 ]
Wet standpipe systems are often more complex and expensive to both install and maintain due to the presence of water always being in the system, and the need to supply water a specific pressures which may require the use of pumps. [ 2 ]
Under NFPA 14, standpipes designs are classified as Class I, II, or III based on intended user, size of hose connections and design pressure. [ 2 ] [ 1 ]
Class I standpipe systems are intended for use by firefighters, and consists of 2.5 inches (64 mm) hose connections to accommodate the fire hoses used by fire departments.
Class I systems must be constructed with 4 inches (100 mm) pipe, and at least 6 inches (150 mm) in buildings with fire sprinkler systems to ensure adequate water supply during usage, and water pressure at the hose connection must be between 100–175 psi (6.9–12.1 bar). [ 1 ]
Class II systems are intended for use by building occupants, such as employees, residents or members of the public, and include a hose station containing a 1.5 inches (38 mm) fire hose and nozzle pre-connected to the standpipe. [ 1 ] Class II systems have become less common in recent years, but are still found in buildings. [ 2 ] 1.5 inches (38 mm) hose no longer than 100 feet (30 m) must be installed and ready for firefighting usage in Class II systems. [ 1 ]
Class II systems are required to be 'wet', except in regions subject to freezing temperatures and on-site personnel, such as an industrial fire brigade, are trained how to activate the system without assistance from the local fire department. [ 1 ] Pipes supplying hose stations on Class II systems do not have a specified size, and must be calculated based on the needs of the specific system. Water pressure at hose connections must be between 65–100 psi (4.5–6.9 bar). [ 1 ]
Class III systems are designed to include both Class I and Class II: An occupant operated 1.5 inches (38 mm) fire hose and 2.5 inches (64 mm) hose connections for firefighters. The system must be able to operate both the occupant hose and a firefighter's hose simultaneously, and comply with the design standards for both systems. [ 2 ] [ 1 ]
NFPA 14 requires that Class I and III standpipe hose connections be found at the main floor landing of exit stairways [ b ] , along exit routes, both sides of fire doors. [ 1 ] Hose connections on standpipes also cannot be blocked by stairway doors, when open or closed positions. [ 1 ]
Class II systems must be located on each floor, with hose stations distributed so an occupant is always within 120–130 feet (37–40 m) of a hose station. [ 1 ]
Standpipe systems are required by the International Building Code (IBC) in the following situations: [ 3 ]
Laying a firehose up a stairwell takes time, and this time is saved by having fixed hose outlets already in place. There is also a tendency for heavy wet hoses to slide downward when placed on an incline (such as the incline seen in a stairwell), whereas standpipes do not move. The use of standpipes keeps stairwells clear and is safer for exiting occupants.
Standpipes go in a direct up and down direction rather than looping around the stairwell, greatly reducing the length and thus the loss of water pressure due to friction loss . Additionally, standpipes are rigid and do not kink, which can occur when a firehose is improperly laid on a stairwell.
Standpipe systems also provide a level of redundancy , should the main water distribution system within a building fail or be otherwise compromised by a fire or explosion.
Standpipes are not fail-safe systems and there have been many instances where fire operations have been compromised by standpipe systems which were damaged or otherwise not working properly. During the One Meridian Plaza fire , firefighters were incapable of fighting the fire due to pressure reduction valves being improperly set too low, preventing fire hoses from operating correctly for the duration of the fire. [ 4 ] The fire's upward spread ultimately stopped when it reached a floor with working fire sprinklers, and burned itself out. Three Philadelphia firefighters died in the fire and the structure was a total loss and demolished years later. [ 4 ] Two New York City firefighters died in the 2007 Deutsche Bank Building fire during its demolition. A factor that hampered extinguishing the fire was the standpipe system had been rendered inoperable during demolition and incorrect information from demolition workers regarding the status of the standpipe. [ 5 ] Firefighters must take precautions to flush the standpipe before use to clear out debris that could obstruct nozzles and hoses and ensure that water is available. [ 6 ]
The One Meridian Plaza fire also highlighted a flaw in standpipe systems which are fed water via a fire department connection; falling debris can damage or completely sever hoses supplying standpipes. [ 4 ] | https://en.wikipedia.org/wiki/Standpipe_(firefighting) |
Stanene [ 1 ] [ 2 ] is a topological insulator , theoretically predicted by Shoucheng Zhang's group at Stanford, [ further explanation needed ] which may display dissipationless currents at its edges near room temperature . It is composed of tin atoms arranged in a single layer, in a manner similar to graphene . [ 3 ] Stanene got its name by combining stannum (the Latin name for tin) with the suffix -ene used by graphene. [ 4 ] Research is ongoing in Germany and China, as well as at laboratories at Stanford and UCLA. [ 5 ]
The addition of fluorine atoms to the tin lattice could extend the critical temperature up to 100 °C. [ 6 ] This would make it practical for use in integrated circuits to make smaller, faster and more energy efficient computers.
Stannenes (Similar name to Stanene) | https://en.wikipedia.org/wiki/Stanene |
Stanford DASH was a cache coherent multiprocessor developed in the late 1980s by a group led by Anoop Gupta, John L. Hennessy , Mark Horowitz , and Monica S. Lam at Stanford University . [ 1 ] It was based on adding a pair of directory boards designed at Stanford to up to 16 SGI IRIS 4D Power Series machines and then cabling the systems in a mesh topology using a Stanford-modified version of the Torus Routing Chip. [ 2 ] The boards designed at Stanford implemented a directory-based cache coherence protocol [ 3 ] allowing Stanford DASH to support distributed shared memory for up to 64 processors. Stanford DASH was also notable for both supporting and helping to formalize weak memory consistency models , including release consistency . [ 4 ] Because Stanford DASH was the first operational machine to include scalable cache coherence, [ 5 ] it influenced subsequent computer science research as well as the commercially available SGI Origin 2000 . Stanford DASH is included in the 25th anniversary retrospective of selected papers from the International Symposium on Computer Architecture [ 6 ] and several computer science books, [ 7 ] [ 8 ] [ 9 ] [ 10 ] [ 11 ] has been simulated by the University of Edinburgh , [ 12 ] and is used as a case study in contemporary computer science classes. [ 13 ] [ 14 ] | https://en.wikipedia.org/wiki/Stanford_DASH |
The Stanford Web Credibility Project , which involves assessments of website credibility conducted by the Stanford University Persuasive Technology Lab , is an investigative examination of what leads people to believe in the veracity of content found on the Web. The goal of the project is to enhance website design and to promote further research on the credibility of Web resources.
The Web has become an important channel for exchanging information and services, resulting in a greater need for methods to ascertain the credibility of websites. In response, since 1998, the Stanford Persuasive Technology Lab (SPTL) has investigated what causes people to believe, or not, what they find online. SPTL provides insight into how computers can be designed to change what people think and do, an area called captology . Directed by experimental psychologist B.J. Fogg , the Stanford team includes social scientists , designers, and technologists who research and design interactive products that motivate and influence their users.
The ongoing research of the Stanford Web Credibility Project includes:
A study by the Stanford Web Credibility Project, How Do People Evaluate a Web Site's Credibility? Results from a Large Study , published in 2002, invited 2,684 "average people" to rate the credibility of websites in ten content areas. The study evaluated the credibility of two live websites randomly assigned from one of ten content categories: e-commerce , entertainment , finance , health , news , nonprofit , opinion or review, search engines , sports , and travel . A total of one hundred sites were assessed.
This study was launched jointly with a parallel, expert -focused project conducted by Sliced Bread Design, LLC . In their study, Experts vs. Online Consumers: A Comparative Credibility Study of Health and Finance Web Sites , fifteen health and finance experts were asked to assess the credibility of the same industry-specific sites as those reviewed by the Stanford PTL consumers. The Sliced Bread Design study revealed that health and finance experts were far less concerned about the surface aspects of these industry-specific types of sites and more concerned about the breadth, depth, and quality of a site's information. Similarly, Consumer Reports WebWatch, which commissioned the study, has the goal to investigate, inform, and improve the credibility of information published on the World Wide Web . Consumer Reports had plans for a similar investigation into whether consumers actually perform the necessary credibility checks while online, and had already conducted a national poll concerning consumer awareness of privacy policies.
The common goals of the three organizations led to a collaborative research effort that may represent the largest web credibility project ever conducted. The project, based on three years of research that included over 4,500 people, enabled the lab to publish Stanford Guidelines for Web Credibility , which established ten guidelines for building the credibility of a website.
The study found that when people assessed a real website's credibility, they did not use rigorous criteria , a contrast to earlier national survey findings by Consumer Reports WebWatch, A Matter of Trust: What Users Want From Web Sites (April 16, 2002). The data showed that the average consumer paid far more attention to the superficial aspects of a site, such as visual cues, than to its content. For example, nearly half of all consumers (or 46.1%) in the study assessed the credibility of sites based in part on the appeal of the overall visual design of a site, including layout, typography, font size and color schemes.
This reliance on a site's overall visual appeal to gauge credibility occurred more often with some categories of sites then others. Consumer credibility-related comments about visual design issues occurred with more frequency with websites dedicated to finance, 54.6%, search engines, 52.6%, travel, 50.5%, and e-commerce sites, 46.2%, and less frequently when assessing health, 41.8%, news, 39.6%, and nonprofit, 39.4%.
"I would like to think that when people go on the Web they're very tough integrators of information, they compare sources, they think really hard," says Fogg, "but the truth of the matter--and I didn't want to find this in the research but it's very clear--is that people do judge a Web site by how it looks. That's the first test of the Web site. And if it doesn't look credible or it doesn't look like what they expect it to be, they go elsewhere. It doesn't get a second test. And it's not so different from other things in life. It's the way we judge automobiles and politicians. | https://en.wikipedia.org/wiki/Stanford_Web_Credibility_Project |
The Stanford arm is an industrial robot with six degrees of freedom , designed at Stanford University by Victor Scheinman in 1969. [ 1 ] The Stanford arm is a serial manipulator whose kinematic chain consists of two revolute joints at the base, a prismatic joint , and a spherical joint . Because it includes several kinematic pairs , it is often used as an educational example in robot kinematics . [ 2 ]
This robotics-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Stanford_arm |
A stanhope or stanho-scope is an optical device that enables the viewing of microphotographs without using a microscope. [ 1 ] [ 2 ] They were invented by René Dagron in 1857. [ 1 ] Dagron bypassed the need for an expensive microscope to view the microscopic photographs by attaching the microphotograph at the end of a modified Stanhope lens . [ 1 ] He called the devices bijoux photo-microscopiques or microscopic photo-jewelry . [ 3 ]
In 1851 John Benjamin Dancer invented microphotographs using a collodion process and a microscope converted to a camera. [ 1 ] This resulted in a microphotograph about 3 square millimetres (0.0047 sq in) in area. [ 1 ] The main disadvantage of Dancer's method was that the viewing of the microphotographs required a microscope which was at the time an expensive instrument. [ 1 ]
In 1857 René Dagron solved the problem by inventing a method of mounting the microphotographs at the end of a small cylindrical lens. [ 1 ] [ 4 ] Dagron modified the Stanhope lens by sectioning the normally biconvex Stanhope lens and introducing a planar section so that the plane was located at the focal length of the convex side of the cylindrical lens. [ 2 ] [ 4 ] This produced a plano-convex lens, where Dagron was able to mount the microscopic photograph on the flat side of the lens using Canada balsam as adhesive. [ 2 ] [ 4 ] This arrangement enabled the picture to be focused. [ 2 ]
The sectioned lens could magnify the microphotograph three hundred times, [ 4 ] so that the viewing of the microphotographs no longer required a bulky and expensive microscope. The modified Stanhope lens was small enough to be mounted in all manner of miniature artifacts such as rings, ivory miniatures, wooden toys etc. [ 1 ] Dagron also designed a special microphotographic camera which could produce 450 exposures approximately 2 by 2 millimetres (0.079 in × 0.079 in) on a 4.5-by-8.5-centimetre (1.8 in × 3.3 in) wet collodion plate. [ 5 ]
The Stanhope optical viewers were mounted inside the bows of violins by French violin maker Jean-Baptiste Vuillaume , probably using Dagron's methods and equipment. [ 2 ] The violin Stanhopes featured the portraits of famous people such as Paganini , Tourte , and Stradivari . [ 2 ]
Dagron's efforts met with great success. [ 6 ] [ 7 ] The viewers were first introduced to the general public at the 1859 International Fair in Paris. [ 1 ] The success of his viewers enabled Dagron to purpose-build a factory dedicated to their production. [ 6 ] As of June 1859, Dagron's factory was manufacturing the stanhopes, mounted in jewellery and souvenirs. In August 1859 he exhibited them at the International Exhibition in Paris where they met with great success. In 1862 he had 150 employees and was manufacturing 12,000 units a day. [ 2 ] In 1860 Dagron obtained the patent for his viewers under the title Bijoux Photomicroscopiques . [ 3 ] Dagron also developed mail order marketing techniques for his viewers. [ 8 ]
In 1862 Dagron published his book Cylindres photo-microscopiques, montés et non montés sur bijoux . [ 9 ] That same year, Dagron displayed the devices at the 1862 International Exhibition in London , where he received an "Honourable Mention" and presented them to Queen Victoria . [ 10 ]
In 1864 Dagron became famous when he produced a stanhope optical viewer which enabled the viewing of a microphotograph 1 square millimetre (0.0016 sq in), (equivalent in size to the head of a pin), [ 11 ] that included the portraits of 450 people. [ 6 ] [ 11 ]
In the early twentieth century Eugène Reymond took control of Dagron's Stanhope lens factory in Gex , France. He was succeeded in the management of the factory by his son Roger. In 1972 the factory, run by Roger Remond, produced the last Stanhope lens made by the traditional methods. In 1998, after Roger's death, the workshop was closed and its equipment dismantled and sold. Stanhope lenses are still manufactured to this day, but they are not produced according to Dagron's methodology. [ 12 ]
In modern times, the most common Stanhopes are usually gold or silver crosses with Christian prayers in the microphotograph. [ 1 ] | https://en.wikipedia.org/wiki/Stanhope_(optical_bijou) |
The Stanhope Demonstrator was the first machine to solve problems in logic. [ 1 ] It was designed by Charles Stanhope, 3rd Earl Stanhope to demonstrate consequences in logic symbolically.
The first model was constructed in 1775. It consisted of two slides coloured red and gray mounted in a square brass frame. This could be used to demonstrate the solution to a syllogistic type of problem in which objects might have two different properties and the question was how many would have both properties. Scales marked zero to ten were used to set the numbers or proportions of objects with the two properties. [ 2 ] [ 3 ] [ 4 ] This form of inference anticipated the numerically definite syllogism which Augustus De Morgan laid out in his book, Formal Logic , in 1847. [ 5 ]
The device was a brass plate about four inches square which was mounted on a piece of mahogany which was three-quarters of an inch thick. There was an opening with a depression in the wood about one and a half inches square and half an inch deep. This opening was called the holon , meaning "whole", and represented the full set of objects under consideration. [ 3 ]
A slide of red translucent glass could be inserted from the right across the holon. A slide of gray wood could be slid under the red slide. When the device was used for the "Rule for the Logic of
Certainty", the gray slider was inserted from the left. When it was used for the "Rule for the Logic of Probability", the gray slider was inserted from above. The red and the gray sliders represented the two affirmative propositions which were being combined. Stanhope called these ho and los . [ 3 ]
At least four of the devices with this square style were built. [ 3 ] In 1879, Robert Harley wrote that he had one which he had been given by Stanhope's great-grandson, Arthur , who had kept one. [ 3 ] [ 6 ] The other two were owned by Henry Prevost Babbage – the son of Charles Babbage , who continued his work on the Analytical Engine . [ 3 ] One of the devices was donated to the Science Museum, London by the last Earl in 1953. [ 7 ] Other styles, such as circular models, were constructed, but these were less convenient. [ 3 ] [ 8 ] | https://en.wikipedia.org/wiki/Stanhope_Demonstrator |
Stanisław Gołąb (July 26, 1902 – April 30, 1980) was a Polish mathematician from Kraków , working in particular on the field of affine geometry .
In 1932, he proved that the perimeter of the unit disc respect to a given metric can take any value in between 6 and 8, and that these extremal values are obtained if and only if the unit disc is an affine regular hexagon resp. a parallelogram . [ 1 ]
He worked at the State Institute of Mathematics , which was incorporated into the Polish Academy of Sciences in 1952. [ 2 ]
This article about a Polish mathematician is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Stanisław_Gołąb |
Stanko Bilinski (22 April 1909 in Našice – 6 April 1998 in Zagreb ) was a Croatian mathematician and academician. He was a professor at the University of Zagreb and a fellow of the Croatian Academy of Sciences and Arts . [ 1 ]
In 1960, he discovered a rhombic dodecahedron of the second kind, the Bilinski dodecahedron . Like the standard rhombic dodecahedron, this convex polyhedron has 12 congruent rhombus sides, but they are differently shaped and arranged. Bilinski's discovery corrected a 75-year-old omission in Evgraf Fedorov 's classification of convex polyhedra with congruent rhombic faces. [ 2 ]
This Croatian biographical article is a stub . You can help Wikipedia by expanding it .
This article about a European mathematician is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Stanko_Bilinski |
Stanley Robert Hart (born 20 June 1935 in Swampscott, Massachusetts ) [ 1 ] is an American geologist , geochemist , leading international expert on mantle isotope geochemistry, and pioneer of chemical geodynamics . [ 2 ]
Hart graduated from MIT with a bachelor's degree in geology in 1956 and a master's degree in geochemistry in 1957 from Caltech . In 1960 he received his doctorate in geochemistry from MIT with thesis Mineral ages and metamorphism under the supervision of Patrick M. Hurley . After a year as a Carnegie Fellow, Hart was from 1961 to 1975 at the Carnegie Institution in Washington, D.C. in the Department of Terrestrial Magnetism. From 1975 to 1989 he was a professor of Earth, Atmospheric and Planetary Sciences at MIT and from 1989 to 1992 a visiting professor there. From 1989 to 2007 he was a Senior Scientist in geology and geophysics at Woods Hole Oceanographic Institution . [ 3 ] He retired from Woods Hole in 2007 as Scientist Emeritus. [ 4 ]
Hart is a leading pioneer in the introduction of geochemistry into the Earth sciences. He developed comparative geochronology, which accounts for geological perturbations in various geochronometers. At the Carnegie Institution of Washington, he worked with George Wetherill , George Tilton , L. T. Aldrich, and G. L. Davis on mapping Precambrian rocks in the USA using comparative geochronology. There Hart became the leader of a group including Thomas Krogh , Albrecht Hofmann , Christopher Brooks, and others. [ 5 ]
According to Claude Allègre : [ 5 ]
Stan has studied basalts in every environment: mid-oceanic ridge basalts, oceanic island basalts, subduction zone basalts, old basalts, Archean basalts. He has also studied basaltic systems in the laboratory, where he was a pioneer in the measurement of partition coefficients for trace elements, but more importantly, he was one of the first to study quantitatively the effect of diffusion and to understand the fundamental problem of how isotopic memories work. His paper with Al Hofmann in the volume honoring Paul Gast is a keystone for geochemistry, isotopic coding with magma, and isotopic memory in solids.
Hart focused on the application of isotopic chemistry to age determination in geology, the geochemical evolution of mantle and oceanic lithosphere , and the geochemistry of strontium, neodymium, and lead isotopes in volcanic rocks. He also studied the long-term behavior of the chemical composition of the oceans due to their interaction with the oceanic crust and the experimental determination of fundamental geochemical properties such as mineral-melt partition coefficients in silicates and solid-state diffusion rates. In 1968, together with John S. Steinhart , he published the Steinhart-Hart equation , which provides a mathematical model of how the temperature and the electrical resistance of a thermistor vary, based upon 3 so-called Steinhart-Hart coefficients. [ 6 ]
He was a co-editor from 1970 to 1972 of the Reviews of Geophysics , from 1970 to 1976 of the Geochimica et Cosmochimica Acta , and from 1975 to 1992 of Physics of the Earth and Planetary Interiors . In 1975/76 he chaired the US National Committee for Geochemistry. [ 7 ] His doctoral students include Erik Hauri .
Hart has three children, one daughter from his first marriage, which ended in divorce in 1978, and a son and a daughter from his second marriage which began in 1980. | https://en.wikipedia.org/wiki/Stanley_Robert_Hart |
In mathematics and especially in algebraic combinatorics , the Stanley symmetric functions are a family of symmetric functions introduced by Richard Stanley ( 1984 ) in his study of the symmetric group of permutations .
Formally, the Stanley symmetric function F w ( x 1 , x 2 , ...) indexed by a permutation w is defined as a sum of certain fundamental quasisymmetric functions . Each summand corresponds to a reduced decomposition of w , that is, to a way of writing w as a product of a minimal possible number of adjacent transpositions . They were introduced in the course of Stanley's enumeration of the reduced decompositions of permutations, and in particular his proof that the permutation w 0 = n ( n − 1)...21 (written here in one-line notation ) has exactly
reduced decompositions. (Here ( n 2 ) {\displaystyle {\binom {n}{2}}} denotes the binomial coefficient n ( n − 1)/2 and ! denotes the factorial .)
The Stanley symmetric function F w is homogeneous with degree equal to the number of inversions of w . Unlike other nice families of symmetric functions, the Stanley symmetric functions have many linear dependencies and so do not form a basis of the ring of symmetric functions . When a Stanley symmetric function is expanded in the basis of Schur functions , the coefficients are all non-negative integers .
The Stanley symmetric functions have the property that they are the stable limit of Schubert polynomials
where we treat both sides as formal power series , and take the limit coefficientwise. | https://en.wikipedia.org/wiki/Stanley_symmetric_function |
The Stanley–Wilf conjecture , formulated independently by Richard P. Stanley and Herbert Wilf in the late 1980s, states that the growth rate of every proper permutation class is singly exponential . It was proved by Adam Marcus and Gábor Tardos ( 2004 ) and is no longer a conjecture. Marcus and Tardos actually proved a different conjecture, due to Zoltán Füredi and Péter Hajnal ( 1992 ), which had been shown to imply the Stanley–Wilf conjecture by Klazar (2000) .
The Stanley–Wilf conjecture states that for every permutation β , there is a constant C such that the number | S n ( β )| of permutations of length n which avoid β as a permutation pattern is at most C n . As Arratia (1999) observed, this is equivalent to the convergence of the limit
The upper bound given by Marcus and Tardos for C is exponential in the length of β . A stronger conjecture of Arratia (1999) had stated that one could take C to be ( k − 1) 2 , where k denotes the length of β , but this conjecture was disproved for the permutation β = 4231 by Albert et al. (2006) . Indeed, Fox (2013) has shown that C is, in fact, exponential in k for almost all permutations.
The growth rate (or Stanley–Wilf limit) of a permutation class is defined as
where a n denotes the number of permutations of length n in the class. Clearly not every positive real number can be a growth rate of a permutation class, regardless of whether it is defined by a single forbidden pattern or a set of forbidden patterns. For example, numbers strictly between 0 and 1 cannot be growth rates of permutation classes.
Kaiser & Klazar (2002) proved that if the number of permutations in a class of length n is ever less than the n th Fibonacci number then the enumeration of the class is eventually polynomial. Therefore, numbers strictly between 1 and the golden ratio also cannot be growth rates of permutation classes. Kaiser and Klazar went on to establish every possible growth constant of a permutation class below 2; these are the largest real roots of the polynomials
for an integer k ≥ 2. This shows that 2 is the least accumulation point of growth rates of permutation classes.
Vatter (2011) later extended the characterization of growth rates of permutation classes up to a specific algebraic number κ≈2.20. From this characterization, it follows that κ is the least accumulation point of accumulation points of growth rates and that all growth rates up to κ are algebraic numbers. Vatter (2019) established that there is an algebraic number ξ≈2.31 such that there are uncountably many growth rates in every neighborhood of ξ, but only countably many growth rates below it. Pantone & Vatter (2020) characterized the (countably many) growth rates below ξ, all of which are also algebraic numbers. Their results also imply that in the set of all growth rates of permutation classes, ξ is the least accumulation point from above.
In the other direction, Vatter (2010) proved that every real number at least 2.49 is the growth rate of a permutation class. That result was later improved by Bevan (2018) , who proved that every real number at least 2.36 is the growth rate of a permutation class. | https://en.wikipedia.org/wiki/Stanley–Wilf_conjecture |
Stannabenzene (C 5 H 6 Sn) is the parent representative of a group of organotin compounds that are related to benzene with a carbon atom replaced by a tin atom. Stannabenzene itself has been studied by computational chemistry , [ 1 ] but has not been isolated.
Stable derivatives of stannabenzene have been isolated. The 2-stannanaphthalene depicted below is stable in an inert atmosphere at temperatures below 140 °C. [ 2 ] The tin to carbon bond in this compound is shielded from potential reactants by two very bulky groups, one tert-butyl group and the even larger 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl or Tbt group. The two Sn-C bonds have bond lengths of 202.9 and 208.1 pm which are shorter than those for Sn-C single bonds (214 pm) and comparable to that of known Sn=C double bonds (201.6 pm). The C-C bonds show little variation with bond lengths between 135.6 and 144.3 pm signaling that this compound is aromatic .
Tbt-substituted 9-stannaphenanthrene was reported in 2005. [ 3 ] At room temperature it forms the [4+2] cycloadduct .
Tbt-substituted stannabenzene was reported in 2010. [ 4 ] At room-temperature it quantitatively forms the DA dimer . | https://en.wikipedia.org/wiki/Stannabenzene |
Stannane / ˈ s t æ n eɪ n / or tin hydride is an inorganic compound with the chemical formula Sn H 4 . It is a colourless gas and the tin analogue of methane . Stannane can be prepared by the reaction of SnCl 4 and Li[AlH 4 ] . [ 1 ]
Stannane decomposes slowly at room temperature to give metallic tin and hydrogen and ignites on contact with air. [ 1 ]
Variants of stannane can be found as a highly toxic , gaseous, inorganic metal hydrides and group 14 hydrides . | https://en.wikipedia.org/wiki/Stannane |
A stannide can refer to an intermetallic compound containing tin combined with one or more other metals; an anion consisting solely of tin atoms or a compound containing such an anion, or, in the field of organometallic chemistry an ionic compound containing an organotin anion (e.g.see [ 1 ] an alternative name for such a compound is stannanide.)
When tin is combined with an alkali or alkaline earth metal some of the compounds formed have ionic structures containing monatomic or polyatomic tin anions ( Zintl ions ), such as Sn 4− in Mg 2 Sn [ 2 ] or Sn 4− 9 in K 4 Sn 9 . [ 3 ] Even with these metals not all of the compounds formed can be considered to be ionic with localised bonding, for example Sr 3 Sn 5 , a metallic compound, contains {Sn 5 } square pyramidal units. [ 4 ]
Ternary (where there is an alkali or alkaline earth metal, a transition metal as well as tin e.g. LiRh 3 Sn 5 [ 5 ] and MgRuSn 4 [ 6 ] ) have been investigated.
Binary (involving one other metal) and ternary (involving two other metals) intermetallic stannides have been investigated. Niobium stannide , Nb 3 Sn is perhaps the best known superconducting tin intermetallics. This is more commonly called "niobium-tin".
There are multiple rare earth stannides, including with dysprosium and yttrium .
Some examples of stannide Zintl ions are listed below. Some of them contain 2-centre 2-electron bonds (2c-2e), others are "electron deficient" and bonding sometimes can be described using polyhedral skeletal electron pair theory (Wade's rules) where the number of valence electrons contributed by each tin atom is considered to be 2 (the s electrons do not contribute). [ 7 ] There are some examples of silicide and plumbide ions with similar structures, for example tetrahedral Si 4− 4 , the chain anion (Si 2− ) n , Pb 4− 4 and Pb 4− 9 . [ 2 ] [ 8 ] | https://en.wikipedia.org/wiki/Stannide |
The Stanton number ( St ), is a dimensionless number that measures the ratio of heat transferred into a fluid to the thermal capacity of fluid. The Stanton number is named after Thomas Stanton (engineer) (1865–1931). [ 1 ] [ 2 ] : 476 It is used to characterize heat transfer in forced convection flows.
S t = h G c p = h ρ u c p {\displaystyle \mathrm {St} ={\frac {h}{Gc_{p}}}={\frac {h}{\rho uc_{p}}}}
where
It can also be represented in terms of the fluid's Nusselt , Reynolds , and Prandtl numbers:
where
The Stanton number arises in the consideration of the geometric similarity of the momentum boundary layer and the thermal boundary layer, where it can be used to express a relationship between the shear force at the wall (due to viscous drag ) and the total heat transfer at the wall (due to thermal diffusivity ).
Using the heat-mass transfer analogy, a mass transfer St equivalent can be found using the Sherwood number and Schmidt number in place of the Nusselt number and Prandtl number, respectively.
S t m = S h L R e L S c {\displaystyle \mathrm {St} _{m}={\frac {\mathrm {Sh_{L}} }{\mathrm {Re_{L}} \,\mathrm {Sc} }}} [ 4 ]
S t m = h m ρ u {\displaystyle \mathrm {St} _{m}={\frac {h_{m}}{\rho u}}} [ 4 ]
where
The Stanton number is a useful measure of the rate of change of the thermal energy deficit (or excess) in the boundary layer due to heat transfer from a planar surface. If the enthalpy thickness is defined as: [ 5 ]
Δ 2 = ∫ 0 ∞ ρ u ρ ∞ u ∞ T − T ∞ T s − T ∞ d y {\displaystyle \Delta _{2}=\int _{0}^{\infty }{\frac {\rho u}{\rho _{\infty }u_{\infty }}}{\frac {T-T_{\infty }}{T_{s}-T_{\infty }}}dy}
Then the Stanton number is equivalent to
S t = d Δ 2 d x {\displaystyle \mathrm {St} ={\frac {d\Delta _{2}}{dx}}}
for boundary layer flow over a flat plate with a constant surface temperature and properties. [ 6 ]
Using the Reynolds-Colburn analogy for turbulent flow with a thermal log and viscous sub layer model, the following correlation for turbulent heat transfer for is applicable [ 7 ]
S t = C f / 2 1 + 12.8 ( P r 0.68 − 1 ) C f / 2 {\displaystyle \mathrm {St} ={\frac {C_{f}/2}{1+12.8\left(\mathrm {Pr} ^{0.68}-1\right){\sqrt {C_{f}/2}}}}}
where
C f = 0.455 [ l n ( 0.06 R e x ) ] 2 {\displaystyle C_{f}={\frac {0.455}{\left[\mathrm {ln} \left(0.06\mathrm {Re} _{x}\right)\right]^{2}}}}
Strouhal number , an unrelated number that is also often denoted as S t {\displaystyle \mathrm {St} } . | https://en.wikipedia.org/wiki/Stanton_number |
A staple gun or powered stapler is a hand-held machine used to drive heavy metal staples into wood, plastic, or masonry . Staple guns are used for many different applications and to affix a variety of materials, including insulation, house wrap, roofing, wiring, carpeting, upholstery, and hobby and craft materials. These devices are also known as trigger tackers . [ 1 ]
There are generally three different types of staple guns distinguished by the power source used to operate the gun: manual , electric (From a cord or battery ), and pneumatic ( Compressed air ). Power staple guns can set staples at a somewhat quicker rate than hand-powered models, but their main advantage is that they can be used continuously for hours with comparatively little fatigue.
Some staple guns have a long nose that allows the staples to be applied into recessed corners. Another special feature may be wire guides for wiring to ensure that the staples will not pierce the wire. The "forward action" staple gun has a handle that points toward the trigger end, in the opposite direction of the traditional staple gun. These tools are easier to squeeze and better place pressure at the front of the tool where the staple is ejected. The first so called "forward action" staple gun was introduced about 1934. [ 2 ]
A hammer tacker is a device somewhat similar to a staple gun, except that the mechanical energy from the user's muscles is stored—as with a hammer —as momentum of the gun itself, rather than as compression of an internal spring. This type of stapler is typically used for insulation, roofing and carpeting.
For most purposes square end staples are used; but some staplers can take rounded end staples for holding cables against a surface.
Typical staple leg lengths are 1 ⁄ 4 ″, 5 ⁄ 16 ″, 3 ⁄ 8 ″, 1 ⁄ 2 ″, 17 ⁄ 32 ″, and 9 ⁄ 16 ″, or 6, 8, 10, 12, and 14 millimetres.
Unlike office staplers , some staple guns lack an anvil, the metal plate with curved slots that office staplers use to bend the legs of the staple inwards or outwards and flatten them against the paper .
Other staple guns have integral anvils. For example, a post stapler can be used to join the bottom flaps of a corrugated box but a blind clincher is used for closing the top of a closed box where post anvils are not possible. Anvils are built into the staple gun and penetrate the corrugated fiberboard : The staple hits the anvils and is crimped onto the box. The curved anvils are then removed.
Most staple guns, especially the hand-powered models, have a spring-like mechanism for storing mechanical energy and delivering it as a sharp and powerful blow. This mechanism is necessary because of the large force needed to drive the staples through solid wood or masonry, and because the staple must be completely inserted before the workpiece has time to move . In the office stapler, by contrast, the staple can be driven directly by the user's muscle power, at a relatively slow speed, because the paper is firmly supported by the anvil. In other words, the staple gun substitutes the workpiece's inertia for the missing anvil. | https://en.wikipedia.org/wiki/Staple_gun |
A stapler is a mechanical device that joins pages of paper or similar material by driving a thin metal staple through the sheets and folding the ends. Staplers are widely used in government, business, offices , workplaces, homes, and schools . [ 1 ]
The word "stapler" can actually refer to a number of different devices of varying uses. In addition to joining paper sheets together, staplers can also be used in a surgical setting to join tissue together with surgical staples to close a surgical wound (much in the same way as sutures ). [ 2 ]
Most staplers are used to join multiple sheets of paper. Paper staplers come in two distinct types: manual and electric. Manual staplers are normally hand-held, although models that are used while set on a desk or other surface are not uncommon. Electric staplers exist in a variety of different designs and models. Their primary operating function is to join large numbers of paper sheets together in rapid succession. Some electric staplers can join up to 20 sheets at a time. [ 3 ] Typical staplers are a third-class lever .
The growing usage of paper in the 19th century created a demand for an efficient paper fastener. [ 4 ]
In 1841 Slocum and Jillion invented a "Machine for Sticking Pins into Paper", which is often believed to be the first stapler. But their patent (September 30, 1841, Patent #2275) is for a device used for packaging pins. In 1866, George McGill received U.S. patent 56,587 [ 5 ] for a small, bendable brass paper fastener that was a precursor to the modern staple. In 1867, he received U.S. patent 67,665 [ 6 ] for a press to insert the fastener into paper. He showed his invention at the 1876 Centennial Exhibition in Philadelphia, Pennsylvania ,where architect Merik Herron help them make the base shape of the staple. and continued to work on these and other various paper fasteners throughout the 1880s. In 1868 an English patent for a stapler was awarded to C. H. Gould, and in the U.S., Albert Kletzker of St. Louis, Missouri, also patented a device.
In 1877 Henry R. Heyl filed patent number 195,603 for the first machines to both insert and clinch a staple in one step, [ 7 ] and for this reason some consider him the inventor of the modern stapler. In 1876 and 1877, Heyl also filed patents for the Novelty Paper Box Manufacturing Co. of Philadelphia, PA, [ 8 ] However, the N. P. B. Manufacturing Co.'s inventions were to be used to staple boxes and books.
The first machine to hold a magazine of many pre-formed staples came out in 1878.
On February 18, 1879, George McGill received patent 212,316 [ 9 ] for the McGill Single-Stroke Staple Press, the first commercially successful stapler. This device weighed over two and a half pounds and loaded a single 1 ⁄ 2 -inch-wide (13 mm) wire staple, which it could drive through several sheets of paper.
The first published use of the word "stapler" to indicate a machine for fastening papers with a thin metal wire was in an advertisement in the American Munsey's Magazine in 1901. [ 4 ]
In the early 1900s, several devices were developed and patented that punched and folded papers to attach them to each other without a metallic clip. The Clipless Stand Machine (made in North Berwick ) was sold from 1909 into the 1920s. It cut a tongue in the paper that it folded back and tucked in. Bump's New Model Paper Fastener used a similar cutting and weaving technology.
In 1941, the type of paper stapler that is the most common in use was developed: the four-way paper stapler . With the four-way, the operator could either use the stapler to staple papers to wood or cardboard, use pliers for bags, or use the normal way with the head positioned a small distance above the stapling plate. The stapling plate is known as the anvil . The anvil often has two settings: the first, and by far most common, is the reflexive setting, also known as the "permanent" setting. In this position, the legs of the staple are folded toward the center of the crossbar. It is used to staple papers which are not expected to need separation. If rotated 180° or slid to its second position, the anvil will be set on the sheer setting, also known as the "temporary" or "straight" setting. In this position, the legs of the staple are folded outwards, away from the crossbar, resulting in the legs and crossbar being in more or less a straight line. Stapling with this setting will result in more weakly secured papers but a staple that is much easier to remove. The use of the second setting is almost never seen, however, due to the prevalence of staple removers and the general lack of knowledge about its use. [ 10 ] Some simple modern staplers feature a fixed anvil that lacks the sheer position.
Modern staplers continue to evolve and adapt to users' changing habits. Less effort or easy-squeeze/use staplers, for example, use different leverage efficiencies to reduce the amount of force the user needs to apply. As a result, these staplers tend to be used in work environments where repetitive, large stapling jobs are routine.
Some modern desktop staplers make use of Flat Clinch technology. With Flat Clinch staplers, the staple legs first pierce the paper and are then bent over and pressed absolutely flat against the paper – doing away with the two-setting anvil commonly used and making use of a recessed stapling base in which the legs are folded. Accordingly, staples do not have sharper edges exposed and lead to flatter stacking of paper – saving on filing and binder space.
Some photocopiers feature an integrated stapler allowing copies of documents to be automatically stapled as they are printed.
In 2012, $80 million worth of staplers were sold in the US. [ 11 ] The dominant US manufacturer is Swingline .
Permanent fastening binds items by driving the staple through the material and into an anvil , a small metal plate that bends the ends, usually inward. On most modern staplers, the anvil rotates or slides to change between bending the staple ends inward for permanent stapling or outward for pinning (see below). Clinches can be standard, squiggled, flat, or rounded completely adjacent to the paper to facilitate neater document stacking.
Pinning temporarily binds documents or other items. To pin, the anvil slides or rotates so that the staple bends outwards instead of inwards. Some staplers pin by bending one leg of the staple inwards and the other outwards. The staple binds the item with relative security but is easily removed.
Tacking fastens objects to surfaces, such as bulletin boards or walls. A stapler that can tack has a base that folds back out of the way, so staples drive directly into an object rather than fold against the anvil. In this position, the staples are driven similar to the way a staple gun works, but with less force driving the staple.
Saddle staplers have an inverted V-shaped saddle for stapling pre-fold sheets to make booklets.
Stapleless staplers , invented in 1910, are a means of stapling that punches out a small flap of paper and weaves it through a notch. A more recent alternative method avoids the resulting hole by crimping the pages together with serrated metal teeth instead.
Surgeons can use surgical staplers in place of sutures to close the skin or during surgical anastomosis .
A skin stapler does not resemble a standard stapler, as it has no anvil. Skin staples are commonly preshaped into an "M." Pressing the stapler into the skin and applying pressure onto the handle bends the staple through the skin and into the fascia until the two ends almost meet in the middle to form a rectangle.
Staplers are commonly used intra-operatively during bowel resections in colorectal surgery . Often these staplers have an integral knife which, as the staples deploy, cuts through the bowel and maintains the aseptic field. The staples, made from surgical steel , are typically supplied in disposable sterilized cartridges. | https://en.wikipedia.org/wiki/Stapler |
A star tracker is an optical device that measures the positions of stars using photocells or a camera. [ 1 ] As the positions of many stars have been measured by astronomers to a high degree of accuracy, a star tracker on a satellite or spacecraft may be used to determine the orientation (or attitude ) of the spacecraft with respect to the stars. In order to do this, the star tracker must obtain an image of the stars, measure their apparent position in the reference frame of the spacecraft, and identify the stars so their position can be compared with their known absolute position from a star catalog. A star tracker may include a processor to identify stars by comparing the pattern of observed stars with the known pattern of stars in the sky.
In the 1950s and early 1960s, star trackers were an important part of early long-range ballistic missiles and cruise missiles , in the era when inertial navigation systems (INS) were not sufficiently accurate for intercontinental ranges. [ 2 ]
Consider a Cold War missile flying towards its target; it initially starts by flying northward, passes over the arctic, and then begins flying southward again. From the missile's perspective, stars behind it appear to move closer to the southern horizon while those in front are rising. Before flight, one can calculate the relative angle of a star based on where the missile should be at that instant if it is in the correct location. That can then be compared to the measured location to produce an "error off" signal that can be used to bring the missile back onto its correct trajectory. [ 2 ]
Due to the Earth's rotation, stars that are in a usable location change over the course of a day and the location of the target. Generally, a selection of several bright stars would be used and one would be selected at launch time. For guidance systems based solely on star tracking, some sort of recording mechanism, typically a magnetic tape , was pre-recorded with a signal that represented the angle of the star over the period of a day. At launch, the tape was forwarded to the appropriate time. [ 2 ] During the flight, the signal on the tape was used to roughly position a telescope so it would point at the expected position of the star. At the telescope's focus was a photocell and some sort of signal-generator, typically a spinning disk known as a chopper . The chopper causes the image of the star to repeatedly appear and disappear on the photocell, producing a signal that was then smoothed to produce an alternating current output. The phase of that signal could be compared to the phase of the chopper to determine angle to the star and this angle could be compared to the expected one on the tape to produce a guidance signal. [ 2 ] Choppers combined with lock-in amplifiers can also help to provide immunity to noise.
Star trackers were often combined with an INS. INS systems measure accelerations and integrate those over time to determine a velocity and, optionally, double-integrate to produce a location relative to its launch location. Even tiny measurement errors, when integrated, add up to an appreciable error known as "drift". For instance, the N-1 navigation system developed for the SM-64 Navaho cruise missile drifted at a rate of 1 nautical mile per hour, meaning that after a two-hour flight the INS would be indicating a position 2 nautical miles (3.7 km; 2.3 mi) away from its actual location. This was outside the desired accuracy of about half a mile.
In the case of an INS, the magnetic tape can be removed and those signals instead provided by the INS. The rest of the system works as before; the signal from the INS roughly positions the star tracker, which then measures the actual location of the star and produces an error signal. This signal is then used to correct the position being generated from the INS, reducing the accumulated drift back to the limit of the accuracy of the tracker. [ 2 ] These "stellar inertial" systems were especially common from the 1950s through the 1980s, although some systems use it to this day. [ 3 ] [ 4 ]
Many models [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] are currently available. There also exist open projects designed to be used for the global CubeSat researchers' and developers' community. [ 10 ] [ 11 ] Star trackers, which require high sensitivity, may become confused by sunlight reflected from the spacecraft, or by exhaust gas plumes from the spacecraft thrusters (either sunlight reflection or contamination of the star tracker window). Star trackers are also susceptible to a variety of errors (low spatial frequency, high spatial frequency, temporal, ...) in addition to a variety of optical sources of error ( spherical aberration , chromatic aberration , etc.). There are also many potential sources of confusion for the star identification algorithm ( planets , comets , supernovae , the bimodal character of the point spread function for adjacent stars, other nearby satellites, point-source light pollution from large cities on Earth, ...). There are roughly 57 bright navigational stars in common use. However, for more complex missions, entire star field databases are used to determine spacecraft orientation. A typical star catalogue for high-fidelity attitude determination is originated from a standard base catalog (for example from the United States Naval Observatory ) and then filtered to remove problematic stars, for example due to apparent magnitude variability, color index uncertainty, or a location within the Hertzsprung-Russell diagram implying unreliability. These types of star catalogs can have thousands of stars stored in memory on board the spacecraft, or else processed using tools at the ground station and then uploaded. [ citation needed ] As space situational awareness sensors, star trackers can be used for space debris detection [ 12 ] and for satellite identification. [ 13 ] | https://en.wikipedia.org/wiki/Star-Sighting |
A ceiling painted with stars frequently occurs as a design motif in a cathedral or Christian church , and replicates the Earth 's sky at night . [ 1 ] Ceilings painted with stars are often found in these buildings because of symbolic associations of stars in Christianity , Judaism , and Islam . [ 2 ] In religious buildings, this decorative feature is often white or gold stars on a blue background. As well as being a decorative technique, star-painted ceilings are also associated with astrology . [ 3 ] It has been used as a way to accurately depict the night sky such as in planetariums . Ceilings painted with stars are also a decorative feature sometimes found in houses, particularly in children's rooms. [ 4 ]
Illustrations, paintings, and murals of the sky, heavens, and stars have a long history as a source of decoration. [ 4 ] The Imperial temple in Palmyra , approximately constructed in the late 2nd century BC, is one of the earliest known examples of a religious building that features star-painted ceilings as a decorative motif. Outside of religious context, this motif has also been found in villas, and bath houses in Palmyra during this same time period. [ 5 ]
Star-painted ceilings have also been found in caves within the Navajo region , with the majority located in the state of New Mexico . The stars painted in this area are presented as cross [x] shapes. [ 6 ] They are painted using various pigments including red, blue, black, yellow, and green. It is believed that the ceilings in this area were painted between 1000 - 1525 AD. [ 6 ]
Vaults in places of worship became a popular place to paint night skies throughout Europe during the 12th to 16th centuries. [ 5 ] This motif of painted vaults, also referred to as starry vaults, is linked to Gothic architecture . An example of a chapel that features star-painted vaults is the Sainte-Chapelle , located in Paris , France. The vaults of the upper-chapel feature gold painted stars on a dark blue background. [ 7 ] The earliest known instance of a star-painted vault related to Christianity is a baptistery at the city of Dura-Europos which is dated approximately 300 AD. The stars in the baptistery were painted white, painted over a blue background, and featured eight points. [ 5 ]
Islamic artists began using complex geometric patterns involving stars as a form of ceiling decoration from the 9th century through to the 16th century. [ 8 ] The shape of the stars took many forms over this period, becoming more embellished over time with complex shapes and details taking centerstage. [ 9 ] For instance, the simple five-pointed star was favoured during the 9th century. While by the 16th century stars with 16 points were more commonly portrayed. [ 8 ]
Into the late 20th and early 21st century, star-painted ceilings have continued to be created. [ 10 ] However, during this period star-painted ceilings have been created more commonly on a commercial scale such as in homes and nurseries. [ 10 ] This decorative feature takes a range of forms but has been created using gold stars on a blue ceiling, black and white, or glow in the dark paint. [ 11 ]
Ceilings that featured stars found in the Roman Empire during the 2nd and 3rd centuries were frequently used as a way to illustrate Mithras . During this time, the deity's cloak was painted dark blue with gold stars painted on top, decorating the cloak. [ 2 ]
In Christianity, stars have a long history as sacred symbols. In churches, pentagrams , which are commonly used to represent stars, are painted on the ceilings of churches and cathedrals. [ 12 ] Unlike stars which are painted solidly and have a variety of points, the pentagram is five-pointed with a hollow centre. Art historian Alva William's states that these pentacles symbolise the five wounds of Christ and is thought to “ ward off evil spirits ”. [ 12 ]
The Star of David is a symbol used in Judaism and can be found painted on the ceilings of some synagogues . [ 2 ] It is represented as a six-pointed hexagram and is associated with “Hebrew mysticism”. [ 12 ] Ceilings that have the Star of David painted on the ceiling include the Sha'ar HaShamayim Synagogue (also known as the “Gate of Heaven Synagogue”). In the synagogue, a large Star of David has been painted on the ceiling with smaller stars surrounding it. [ 13 ]
Stars are a recurring decorative motif in both Christianity and Judaism. However, used for decoration have several different symbolic associations depending on their depiction. [ 2 ]
Stars individually used for decoration have several different symbolic associations in Christianity. [ 4 ] The scholar Jodi Magness suggests that by the 6th century the central dome of churches, often located in the centre of the church, started to become recognised as a ‘heavenly’ place that was symbolically linked to cosmology . [ 2 ] Because of this association, the centre dome is where star-painted ceilings are still often located in religious buildings. This can be seen in churches such as St. Peter's Basilica in Rome and the Siena Cathedral , located in Tuscany . [ 2 ]
Jodi Magness also states that during the 4th century Jewish places of worship represented “the Garden of Eden or Paradise , a place where heaven and earth were united”. [ 2 ] However, during this time many of the star-studded ceilings and domes were created using mosaic tiles rather than paint. [ 2 ] Nevertheless, this connection to heaven and symbolic use of stars can be seen continuing to be recreated into the 19th and 20th centuries, such as seen in the Grand Synagogue of Edirne . The synagogue was built in 1906 and features large vaulted ceilings covered in thousands of small painted white, gold, and black stars on a sky-blue background. [ 14 ]
The depiction of heaven and the sky is a recurring decorative feature that can be found in several Christian churches, chapels, and cathedrals. [ 5 ] These illustrations of heaven and the sky frequently feature the decorative motifs of stars. [ 4 ] This recurring motif is associated with several different artistic and architectural movements. Stars are referred to throughout the Bible , often in symbolic connection to heaven, for example, “the stars of heaven and their constellations”. [ 15 ] It must also be noted that this motif may take on several different meanings depending on the cultural context, time period, and the viewer. [ 4 ]
Historians Ellen Swift and Anne Alwis claim that star-painted ceilings were painted to represent the heavens within the sphere of Christianity and illustrate a heavenly place outside the natural world. [ 5 ] Ceilings decorated in stars have also been found in baptistries. Swift and Alwis state that star-painted ceilings associated with cosmology may have been used as a way to illustrate that the one being baptised was symbolically going to be “reborn into a new world”. [ 5 ]
The Scrovegni Chapel is an example of a star-painted ceiling. It was painted by Giotto di Bondone and his assistants between 1303 - 1305 A.D. [ 16 ] The work depicts scenes from the Bible, with hundreds of geometrically aligned stars mixed into the mural. The eight-pointed stars have been painted gold and cover the vibrant blue arched ceiling. [ 16 ]
Another example of a church featuring star-painted ceilings is the Notre-Dame Basilica in Montreal . The interior of the church was built during the 19th century and is an example of Gothic revival architecture . [ 17 ] Similar to Gothic it features vaults that are decorated with gold painted stars, the gold stars cover the blue vaulted ceilings of the church. [ 17 ]
Much like other religious buildings such as churches and cathedrals, a ceiling decorated in stars is a recurring motif in Synagogues. [ 4 ] Like the Bible, the Torah also references stars, “look heavenward and count the stars”. [ 18 ] Star-painted ceilings are often used as a decoration feature in the central section of a synagogue. [ 2 ]
There are many examples of star-painted ceilings in synagogues, particularly in those built during the late 19th century such as the Synagogue of Modena (La Sinagoga di Modena). This synagogue was built in 1873 and is one of the largest in Italy . [ 19 ] It features a large central dome ceiling which is painted blue and covered in golden stars. [ 19 ] This location of the mural is significant because, as noted before, this area of the synagogue is recognised as a particularly holy place close to heaven. [ 2 ]
Another example of star-painted ceilings as a central decorative motif in a Synagogue is the Eldridge Street Synagogue , located in New York City , which features five-pointed gold stars painted on a blue dome within the building. [ 20 ] The dome which features these stars is well lit with natural lighting because of the multiple stain-glass windows that surround it. As a result, the golden stars reflect the light, creating the illusion that they are glowing. [ 20 ] Another example of a synagogue that features stars painted on the ceiling is Central Synagogue , also located in New York City. Unlike the Eldridge Street Synagogue, the majority of the stars painted in this building have eight points. [ 20 ]
Stars have symbolic value in the Islamic faith. References to stars can be found throughout the Quran, “Behold, We have adorned the skies nearest to the earth with the beauty of stars”. [ 21 ] As there are little to no depictions of human figures in mosques it is common for scripture and decorative features, such as stars, to fill the inside of the religious buildings. [ 22 ]
Many of the geometric patterns featured in the ceilings of Mosques are created using mosaics. [ 22 ] However, there are some, such as the Nasrid palace complex in Spain , that use paint to create the star polygon design. [ 23 ] The ceiling of the Mexuar , one part of the Nasrid palace complex, was designed in the 16th century and features star polygons with eight points. This decorative mural was created using gold paint which was applied to the carved wooden ceiling. [ 23 ]
As well as being a decorative technique, star-painted ceilings have been created which accurately depict the night sky and constellation systems. [ 3 ] While stars painted in religious contexts such as found churches, synagogues, and mosques are more widely referenced there are many instances where stars have been painted on ceilings outside of religious context throughout history . [ 2 ] Some examples of detailed-star painted ceilings are listed below.
A starry mural in New York's Grand Central Terminal depicts a semi-accurate night sky. The ceiling is decorated with over 2,500 stars and illustrates a North American winter night sky around December 1 - February 28. [ 24 ] The constellation arrangement was a replicant of the 1603 star atlas that was created by Johann Bayer . However, the mural is not a fully accurate representation of the night sky as it was painted back to front. [ 24 ]
The mural at the Rijksmuseum in Amsterdam is a contemporary example of a star-painted ceiling. The installation was painted in 2013 and consists of 47,000 painted black stars on a plain white ceiling. The six-pointed stars were hand-painted by Richard Wright and his art team over a period of two months. [ 25 ]
Star-painted ceilings were found in the tomb of Yintun located in Luoyang . The mural is located in the central tomb chamber and is painted on a domed ceiling . [ 26 ] Unlike the common depiction of pointed gold stars on a blue background, the stars painted in the tomb are circular and vary in colour from white to orange. [ 26 ] As well as stars, the mural includes depictions of animals and symbols which historian Feng Shi states represent different constellation systems. [ 26 ]
Star-painted ceilings have also been found in dozens of ancient tombs in Korea . The collection of tombs known as the Complex of Koguryo Tombs (Goguryeo tombs) features complex constellation systems which include detailed illustrations of both the sun and lunar cycles . [ 27 ] One of the tombs that is part of the Complex of Koguryo features the astronomical chart known as Cheonsang Yeolcha Bunyajido (天象列次分野之圖) and is dated 1395 A.D. [ 28 ] The mural itself features a constellation system that includes approximately 1,500 painted and engraved stars that mimic real star systems found in the night sky viewed from Korea during the Joseon dynasty . [ 27 ]
Decorated ceilings have also been used in planetariums. An example of this is the Hamburg Planetarium where a large circular ceiling within the planetarium has been painted blue with star constellations and zodiac signs painted on top in gold. [ 29 ]
The dome of Lovely Lane Methodist Church in Baltimore, designed by Stanford White , was decorated with the stars as they were thought to have appeared in the night sky on the morning of the church's dedication, 6 November 1887. [ 30 ]
Other examples of star-painted ceilings include: | https://en.wikipedia.org/wiki/Star-painted_ceiling |
In polymer science , star-shaped polymers are the simplest class of branched polymers with a general structure consisting of several (at least three) linear chains connected to a central core. [ 1 ] The core, or the center, of the polymer can be an atom , molecule , or macromolecule ; the chains, or "arms", consist of variable-length organic chains. Star-shaped polymers in which the arms are all equivalent in length and structure are considered homogeneous , and ones with variable lengths and structures are considered heterogeneous .
Star-shaped polymers' unique shape and associated properties, [ 2 ] [ 3 ] [ 4 ] such as their compact structure, high arm density, efficient synthetic routes, and unique rheological properties make them promising tools for use in drug delivery , [ 5 ] other biomedical applications , [ 6 ] thermoplastics , [ 7 ] and nanoelectronics [ 8 ] among other applications. [ 1 ]
Star-shaped polymers were first reported by John Schaefgen and Paul Flory in 1948 while studying multichain polymers; they synthesized star-shaped polyamides . [ 9 ] The next major publication regarding star-shaped polymers was in 1962 by Maurice Morton et al. [ 10 ] Their research presented the first study demonstrating a method to create well-defined star-shaped polymers; this route was through living anionic polymerization . Many studies on the characteristics, syntheses, and applications of star-shaped polymers have since been undertaken and remain an active area of study. [ 1 ]
Recommendations on nomenclatures still differ widely across different regulatory bodies ( IUPAC , CAS , MDL ). [ 11 ] According to IUPAC star-shaped polymers are designated by a star prefix which can be further specified as f - star when the number of arms f is known. [ 12 ] An example would be star -(polyA; polyB; polyC) for a variegated (heteroarm) star polymer with three arm species, but an undefined number of arms and distribution of arms. When the number of arms and its distribution is known this can be designated as for example 6- star -(polyA( f 3); polyB( f 3)) where 6 arms exist in total whereof 3 consist of polyA polymer. Stars containing only one species (same chemistry and molar mass) of arms are called regular stars (also called homo-arm). Stars with more than one arm species are designated as variegated stars (hetero-arm).
Star-shaped polymers consist of a multifunctional center from which at least three polymer chains (arms) radiate. [ 13 ] These arms can be chemically identical (homostars) or different (heteroarm stars). Additionally, individual arms may be composed of multiple polymers, resulting in star-block polymers or star copolymers . The unique properties of star-shaped polymers come from their chemical structure as well as the length and number of their arms. [ 13 ]
Some of the most interesting characteristics exhibited by star-shaped polymers are their unique rheological and dynamic properties compared to linear analogues of identical molecular weight and monomer composition. Generally, they have smaller hydrodynamic radii , radii of gyration and lower internal viscosities than linear analogues of the same molecular weight . [ 4 ] [ 1 ] [ 13 ] Internal viscosity increases with increased functionality and molecular weight of branches with the effects of functionality eventually saturating, leaving viscosity dependent only on molecular weight of the arms. [ 4 ] [ 14 ] Heteroarm stars have observed viscosities and hydrodynamic radii higher than homostars. This is due to the increased repulsive interactions that occur as a result of a greater number of heterocontacts between the different arms. [ 1 ] In addition, star-shaped polymers exhibit lower melting points , lower crystallization temperatures and lower degrees of crystallinity than comparable linear analogues. [ 13 ]
The unique self-assembly properties of star shaped polymers make them a promising field of research for use in applications such as drug delivery and multiphase processes such as separation of organic/inorganic materials. Generally, star-shaped polymers have higher critical micelle concentrations , and so lower aggregation numbers, than their analogous, similar molecular weight linear chains. [ 1 ] The addition of functional groups to the arms of star-shaped polymers as well as selective solvent choice can affect their aggregation properties. Increasing the number of functional groups while retaining the same molecular weight decreases aggregation numbers. [ 1 ] Heteroarm polymers have been shown to aggregate into particularly interesting supramolecular formations such as stars, segmented ribbons, and core-shell-corona micellar assemblies depending on their arms' solubility in solution, which can be affected by changes in temperature , pH , solvent , etc. [ 1 ] [ 15 ] These self-assembly properties have implications for solubility of the whole star polymers themselves and for other solutes in solution. For Heteroarm polymers, increasing the molecular weight of soluble chains increases the overall solubility of the star. [ 1 ] Certain Heteroarm star-block polymers have been shown to stabilize water-organic solvent emulsions , while others have demonstrated the ability to increase the solubility of inorganic salts in organic solutions. [ 13 ]
Star-shaped polymers can be synthesized through various approaches. The most common syntheses include an arm-first approach, in which the living chains are used as the initiators, and a core-first approach, in which the core is used as the initiator. [ 16 ]
Other synthetic routes include: controlled sol-gel processes , group transfer polymerization , transition metal catalysis , living anionic polymerization , living cationic polymerization , ring opening polymerization , ring-opening metathesis polymerization (ROMP) , and controlled radical polymerization .
In the arm-first (also known as the "arm-in" or convergent approach [ 1 ] ) method, monofunctional living polymers with known characteristics are used as precursors in the reaction. The active site at the end of their chain can be directly reacted with an appropriately reactive multifunctional polymer core (also known as a linking agent [ 1 ] ) to produce a star-shaped polymer. In this approach the resulting star-polymer consists of homogeneous chain groups. The arm-first synthesis route is arguably the most efficient synthesis of star-shaped polymers. [ 1 ] [ 16 ] This is because each step can be directly controlled and assessed; the arms and core can be isolated and characterized prior to a stoichiometric reaction , and the functionality of the final star-polymer can then be accurately and directly measured.
One common approach to the arm-first synthesis is through anionic polymerization methods. This involves using "arms" that are anionic and reacting them with a core containing deactivating groups for the arms to react with. [ 16 ] The deactivating groups on the core are often chlorosilanes , chlorine leaving groups , or deactivating alkenes . Chlorosilanes serve as especially reactive cores, and can react quantitatively (or very close to quantitatively) with carbanion living polymers; this reaction involves carbanions performing electrophilic substitution with the Si-Cl groups (as shown in the below figure). In a case like this, the resulting arms are all homogeneous and can be well characterized, and the core can also be well characterized, leading to a well-characterized star-shaped polymer. Since both the core and the arms are rather reactive, essentially all Si-Cl undergo electrophilic substitution, and the resulting star-shaped polymers thus have a rather narrow polydispersity index . [ 16 ]
In the core-first approach (also known as the "arm-out" or divergent approach [ 1 ] ), a multifunctional core serves as the initiator simultaneously for several arms. This approach proves to be more complicated than the arm-first approach, in that finding an appropriate and stable core is difficult, and characterizing the synthesized star-polymer is challenging. [ 16 ]
The core-first route was first approached in 1988 through functionalizing DVB using potassium naphthalenide to create a multifunctional core. [ 17 ] The core can than be reacted with ethylene oxide to create a star-shaped polymer. As is typical of most core-first approaches, this scheme had issues with high viscosity and gelation . The star-shaped polymer was characterized by size-exclusion chromatography and light scattering techniques.
While many studies have been published regarding star-shaped polymers, their commercial applications are limited, but growing constantly as research expands. Some commercial applications of star-shaped polymers include: | https://en.wikipedia.org/wiki/Star-shaped_polymer |
StarFire is a wide-area differential GPS developed by John Deere 's NavCom and precision farming groups. StarFire broadcasts additional "correction information" over Inmarsat satellite's L-band frequencies around the world, allowing a StarFire-equipped receiver to produce position measurements accurate to well under one meter, with typical accuracy over a 24-hour period being under 4.5 cm. StarFire is similar to the FAA 's differential GPS Wide Area Augmentation System (WAAS). Since the deployment of StarFire, the wide availability of mobile internet made CORS network a more popular and more precise solution.
StarFire came about after a meeting in 1994 among John Deere engineers who were attempting to chart a course for future developments. At the time, a number of smaller companies were attempting to introduce yield-mapping systems combining a GPS receiver with a grain counter, which produced maps of a field showing its yield. The engineers felt this was one of the most interesting developments in the industry, but the accuracy of GPS, then still using Selective Availability , was simply too low to produce a useful map. The various providers went bankrupt over the next few years.
In 1997, a team was formed to solve the problem of providing a more accurate GPS fix. Along with members of John Deere's engineering team, a small project at Stanford University also took part, along with NASA engineers at the Jet Propulsion Laboratory . [ 1 ] They decided to produce a dGPS system that differed fairly dramatically from similar systems like WAAS .
In theory the GPS signal with Selective Availability turned off offers accuracy on the order of 3 m. In practice, typical accuracy is about 15 m.
Of this 12 m, about 5 m is due to distortion from "billows" in the ionosphere , which introduce propagation delays that makes the satellite appear farther away than it really is. Another 3 to 4 m is accounted for by errors in the satellite ephemeris data, which is used to calculate the positions of the GPS satellites, and by clock drift in the satellite's internal atomic clocks .
dGPS correct for these errors by comparing the position measured using GPS with a known highly accurate ground reference, and then calculating the difference and broadcasting it to users. Some of these corrections apply to any location - the corrections to the clocks and ephemeris data for instance. In contrast, the billows cover only a certain portion of the sky, so a correction measured at any one ground station is only really useful for receivers located nearby. To make the corrections accurate over a large area, one would need to deploy many ground reference stations and broadcast a considerable amount of data for finely divided locations. For instance, WAAS uses twenty-five stations in the continental US, developing a grid spaced 5x5 degrees.
StarFire instead uses an advanced receiver to correct for ionospheric effects internally. To do this, it captures the P(Y) signal that is broadcast on two frequencies, L1 and L2, and compares the effects of the ionosphere on the propagation time of the two. Using this information, the ionospheric effects can be calculated to a very high degree of accuracy, meaning the StarFire dGPS can compensate for variations in propagation delay. The second P(Y) signal is encrypted and cannot be used by civilian receivers directly, but StarFire doesn't use the data contained in the signal; it only compares the phase of the two signals instead. This is expensive in terms of electronics, requiring a second tuner and excellent signal stability to be useful, which is why the StarFire-like solution is not more widely used (at least when it was being created).
With the ionospheric correction handled internally, the StarFire dGPS signal is greatly reduced in the amount of information it needs to carry, which consists of a set of correction signals for the satellite data alone. Since these corrections are globally valid, and there are only 24 satellites in operation at any time, the total amount of information is quite limited. StarFire broadcasts this data at 300 bits per second, repeating once a second. The corrections are generally valid for about 20 minutes. In addition to ephemeris and clock corrections, the signal also contains information on the health of each satellite, offering quality-of-service data in near real-time, with about a 3-second delay in updating the signals from the ground station.
StarFire has developed through two versions. The first, retroactively known as SF1 , offered 1-sigma accuracy of about 1 m. Its error was about 15 to 30 cm, meaning that while the displayed position (absolute accuracy) might be off by about 1 m, it could return you to within centimeters of a previously measured spot (relative accuracy). This was enough for the intended role, field surveying. This system was first offered in 1998, and since its replacement the SF1 signal is apparently now offered for free.
The newer system, SF2 , was introduced in 2004. It dramatically improves accuracy, with a 1-sigma absolute accuracy of about 4.5 cm. In other words, StarFire will leave you within 4.5 cm of a particular geographical point 65% of the time, and be accurate to under 10 cm around 95% of the time (2-sigma). The relative accuracy is likewise improved, to about 2.5 cm. Notably, the SF2 signal supplies corrections for both the American GPS constellation and the Russian GLONASS system.
John Deere introduced the SF3 signal in 2016, slightly improving accuracy and reducing pull-in time by 67% compared to SF2. The company deployed a total of 60 ground-based reference stations to generate the SF3 signal. As with SF2, SF3 supplies corrections for both GPS and GLONASS satellites.
Even if the StarFire correction signal is lost for more than 20 minutes, the internal ionospheric corrections alone result in accuracy of about 3 m. StarFire receivers also receive WAAS signals, ignoring their ionospheric data and using their (less detailed) ephemeris and clock adjustment data to provide about 50 cm accuracy. In comparison, "normal" GPS receivers generally offer about 15 m accuracy, and ones using WAAS improve this to about 3 m.
When initially deployed, StarFire used seven reference stations in the continental US. The corrections generated at these stations are sent to two redundant processing stations (one co-located with a reference/monitor site), and then the resulting signal is uplinked from an east-coast US station. All of the stations are linked over the internet , with dedicated ISDN lines and VSAT links as backups. The resulting signals were broadcast from an Inmarsat III channel.
Additional StarFire networks were later set up in South America, Australia and Europe, each run from their own reference stations and sending data to their own satellites. As use of the system grew, the decision was made to link the various "local area" networks into a single global one. Today the StarFire network uses twenty-five stations worldwide, calculating and uplinking data from the US stations as before. The data collected at these stations is not location-dependent, in contrast to most dGPS, and the large number of sites is used primarily for redundancy.
John Deere also sells a Real Time Kinematic dGPS, StarFire RTK . RTK consists of a small tripod-mounted GPS receiver that uses StarFire signals to perform its own dGPS calculations relative to a point, normally the corner of a field. The unit then broadcasts these corrections over a radio link to the equipment-mounted receivers. RTK offers absolute accuracy of about 2 cm, and relative accuracy in the millimeters. This sort of accuracy is used for fully automated equipment with autodrive systems. | https://en.wikipedia.org/wiki/StarFire_(navigation_system) |
StarHub Limited , commonly known as StarHub , is a Singaporean multinational telecommunications conglomerate and one of the major telcos operating in the country . Founded in 1998, it is listed on the Singapore Exchange (SGX).
StarHub was awarded the license to provide fixed networks and mobile services on 23 April 1998, when the government announced that the telecommunications sector in Singapore would be completely liberalised by 2002. [ 3 ] In 2000, the government announced the date for complete liberalisation would be brought forward to 1 April 2000, and the 49% cap on foreign ownership of public telecommunications companies in Singapore would be lifted. [ 4 ] StarHub was officially launched on 1 April 2000 with ST Telemedia , Singapore Power , BT Group and Nippon Telegraph and Telephone (NTT) as its major shareholders. [ 5 ]
On 21 January 1999, StarHub acquired internet service provider CyberWay and it became a subsidiary within the StarHub group. It was renamed as StarHub Internet on 3 December 1999 in a move to integrate CyberWay into the StarHub brand. [ citation needed ]
In 2001, Singapore Power divested its shares in StarHub and sold its 25.5% stake to ST Telemedia for S$400 million. BT Group subsequently divested its 18% stake as a result of consolidation, after accumulating debt acquired during the bidding round for 3G licences in the United Kingdom. [ citation needed ]
On 1 October 2002, the company merged with Singapore's sole cable television operator, Singapore Cable Vision. As a result of the merger, it acquired SCV's cable television as well as broadband internet access operations. [ 6 ]
StarHub was publicly listed on the Singapore Exchange on 13 October 2004. [ citation needed ]
On 12 January 2007, StarHub announced a 'Strategic Alliance' with Qatar Telecom. [ 7 ]
On 1 May 2009, the Infocomm Development Authority of Singapore announced that StarHub's wholly owned subsidiary, Nucleus Connect, was selected as the Operating Company (OpCo) to design, build and operate the active infrastructure of the Next Generation Nationwide Broadband Network (Next Gen NBN). [ 8 ] Next Gen NBN is now simply known as Nationwide Broadband Network or NBN. [ 9 ]
On 14 July 2009, StarHub announced the retirement of long-standing chief executive Terry Clontz. [ 10 ] Neil Montefiore, the former chief executive of the country's smallest telecommunications company M1 Limited , took over as chief executive officer on 1 January 2010. Terry Clontz remains as a non-executive director of StarHub.
On 1 August 2009, StarHub relocated its corporate office to StarHub Green building at Ubi from its previous office location at StarHub building at Cuppage. [ 11 ]
On 7 February 2013, StarHub announced the retirement of Neil Montefiore as chief executive officer by end February 2013. StarHub's chief operating officer Tan Tong Hai was appointed CEO on 1 March 2013. [ 12 ]
On 13 July 2015, StarHub announced the retirement of Tan Guong Ching as chairman. StarHub's former chief executive officer Terry Clontz was appointed chairman on 15 July 2015. [ 1 ]
In December 2016, StarHub's new innovation centre and converged operations cockpit Hubtricty went operational. [ 13 ] Located at Mediapolis@one-north, [ 14 ] the facility also contains a co-working space and data analytics centre. [ 15 ]
On 29 April 2020, a joint venture between StarHub and M1 Limited was awarded a license to create a 5G network in Singapore by the Singapore Government. [ 16 ]
In August 2021, Starhub announced that it will be launching Nvidia 's GeForce Now in Singapore, the first country in the region and the only local operator in the country to introduce the cloud gaming service. [ 17 ]
On 17 February 2022, StarHub was introduced as a programme partner for DBS #CyberWellness. [ 18 ]
In March 2022, IMDA approves deal for StarHub to buy a majority stake in MyRepublic business. In an article written by Straits Times, [ 19 ] "The Infocomm Media Development Authority (IMDA) has approved local telco StarHub's proposal to buy a majority 50.1 per cent stake in rival Internet service provider MyRepublic's fibre broadband business for residential and enterprise customers in Singapore." The proposed transaction was announced by StarHub and MyRepublic in September last year. At the time, the deal was worth $70.8 million. This would grow Starhub broadband market share from 34% to about 40% in Singapore.
The StarHub group consists of several subsidiaries, [ 20 ] which include:
(StarHub Internet)
StarHub provides mobile services through its subsidiary StarHub Mobile. Since its launch on 1 April 2000, StarHub has been Singapore's fastest growing mobile operator. It has close to two million customers and is the second largest mobile network operator with close to 30% market share. [ 21 ]
On 27 May 2003, it became the first mobile operator in Singapore to commercially launch BlackBerry , a hand-held wireless device providing e-mail, telephone, text messaging, web browsing and other wireless data access. [ 22 ] Customers trials of 3G services began in November 2004, and was released in April 2005.
In January 2005, StarHub announced that it would form an exclusive strategic partnership for i-mode in Singapore with NTT DoCoMo , a subsidiary of StarHub's major shareholder NTT. Customer trials started in October 2005, and the service was launched on 18 November.
On 15 July 2009, StarHub became the first mobile operator in the Asia Pacific region to commercially launch a HSPA+ service. [ 23 ] Branded as MaxMobile Elite , StarHub's HSPA+ service offers download speeds up to 21 Mbit/s nationwide. [ 24 ]
On 19 September 2012, StarHub began the enhancement of its high-speed mobile broadband network with Long Term Evolution (LTE) and Dual Cell High-Speed Packet Access Plus (DC-HSPA+), which improved peak downlink speeds of up to 75 Mbit/s and 42 Mbit/s respectively. [ 25 ]
On 7 March 2013, StarHub became the first telecommunications company in Singapore to offer High Definition (HD) Voice . [ 26 ] Over a year later, the company launched 4G Voice over LTE services. [ 27 ] Both technologies enhance mobile call experience by improving speech clarity and reducing background noise.
In September 2015, StarHub was ranked world's fastest 4G network by independent mobile coverage checker OpenSignal. [ 28 ] Five months later, OpenSignal reported that according to its study, Singapore is the fastest country with LTE. Singapore's StarHub and Singtel as well as Canada's SaskTel tied in the world's fastest operator category. [ 29 ]
As of the second quarter of 2016, StarHub's 4G outdoor coverage was at 99.69%. In comparison, Singtel's coverage was at 99.95% coverage and M1's at 99.29%. [ 30 ]
In November 2016, StarHub and Vodafone renewed their partnership agreement for Singapore for a further three years. [ 31 ] The partnership was formed in 2012 to offer innovative mobile services to enterprise customers. [ 32 ]
On 1 December 2016, StarHub rolled out a travel data plan allowing 2 GB or 3 GB use over 30 days across all mobile networks in nine Asia-Pacific destinations. [ 33 ]
In January 2017, StarHub switched embedded SIM (eSIM) on its 4G network to support devices that come without a physical SIM. [ 34 ] The Samsung Gear S3 Frontier (LTE) is the first eSIM wearable to be made available in Singapore. [ 35 ]
StarHub provides cable television services through its subsidiary Singapore Cable Vision Ltd. Its Hybrid Optical Fibre - Coaxial network reaches 99% of households in Singapore.
In November 2004, it announced the launch of digital cable services over its cable network, which added more channels and allowed greater consumer interactivity. [ 36 ]
On 18 January 2007, StarHub introduced a commercial high definition television service. [ 37 ]
On 7 June 2012, StarHub launched TV Anywhere, a multi-platform service which allows subscribers to watch TV channels and on-demand content on their personal devices such as laptops and tablets. [ 38 ]
On 18 March 2013, StarHub started offering commercial customers StarHub TV on Fibre, its Internet Protocol television (IPTV) service. [ 39 ]
On 8 April 2015, IPTV was rolled out to residential customers. [ 40 ]
On 12 August 2015, an online streaming service called StarHub Go was launched, [ 41 ] and TV Anywhere was merged into it.
StarHub provides broadband internet access through its subsidiaries StarHub Internet and StarHub Online respectively. StarHub Internet was formed after the acquisition of internet access provider CyberWay, while StarHub Online was formed after a merger with Singapore Cable Vision. StarHub has 475,000 home broadband customers as of the third quarter of 2016.
On 3 December 1999, a free surf plan was announced in conjunction with the rebranding of CyberWay, a first in Singapore's consumer internet industry. Customers could surf the internet for free via dial-up and pay only normal local telephone charges. Over 180,000 people signed up for the free surf plan in less than three months since it was announced. [ 42 ]
StarHub provides broadband internet access on the same network it uses for cable television services using cable modems based on the DOCSIS standard.
StarHub is a founding member of the global Wireless Broadband Alliance [ 43 ] and provides wireless broadband services at numerous locations throughout Singapore. In November 2004, it announced an agreement with Connexion by Boeing which provide StarHub customers the ability to access the internet and digital content in flight.
On 28 December 2006, StarHub became the first operator in the world to commercially launch a 100 Mbit/s residential broadband service nationwide. [ 44 ] Known as MaxOnline Ultimate , it is one of three cable broadband services offered by StarHub, the other two being MaxOnline Express and MaxOnline Premium . StarHub also launched 100 Mbit/s, 150 Mbit/s, 200 Mbit/s and 1000 Mbit/s residential fibre broadband service in April 2010. It is known as MaxInfinity Ultimate , MaxInfinity Elite , MaxInfinity Supreme and MaxInfinity Platinum .
In October 2012, StarHub launched two new gamer-centric broadband plans under the name MaxInfinity LVL99 for gamers to enjoy priority. [ 45 ] The plans have since been discontinued.
In November 2014, StarHub started bundling a 100 Mbit/s cable broadband connection with its 1 Gbit/s fibre broadband plans, branded as "Dual Broadband", for customers to get two broadband links in their home. [ 46 ]
StarHub's fixed network, built since inception, extends more than 2,000 km (1,200 mi) around Singapore and directly connects more than 800 commercial buildings. It provides a wide range of fixed network services, broadly categorised as data services and Internet Protocol and Voice services.
Data services include:
Internet protocol services include: | https://en.wikipedia.org/wiki/StarHub |
The StarPeace Project was a global special project first organised in conjunction with the International Year of Astronomy in 2009. [ 1 ] StarPeace project participants held public star parties near a border of their country with a neighboring country. The intention was to show that there are no borders in the real Earth, borders are man-made and science has no borders. [ 2 ] [ 3 ]
In accordance with the goals of the International Year of Astronomy 2009, the Starpeace project has these aims:
StarPeace project is organized by Astronomical Society of Iran and the Sky Peace Organization , a non-governmental, not-for-profit organisation. StarPeace core team composed from Mohammad J. Torabi , Irene Shivaei , Kazem Kookaram , Hooman Najafi and Siavash Saffarian Pour who coordinate and guide StarPeace project with collaborate of their colleagues in more than 30 countries in the globe. [ 4 ] The Astronomical Society of Iran is a non-beneficiary institute, established for the purpose of increasing and improving astronomical activities in Iran, both in research and in education. It seeks to facilitate cooperation and coordination between the scientific and technical centers of the country. [ 5 ]
Anousheh Ansari is an advisor to the StarPeace project. [ 6 ] She was the first woman from the Middle East to go into space, and the first Iranian. Ansari was the fourth self-funded space tourist and the first self-funded woman to fly to the International Space Station. [ 7 ]
StarPeace has affiliated with Yuri's Night , [ 8 ] named after the first human to go into space, Yuri Gagarin .
The StarPeace opening event of 2009 took place between Iran and the United Arab Emirates . On the first two nights of that year, Iranian astronomers held public star parties on Qeshm Island, south of Iran, and around 500 people enjoyed the beauty of the sky on those nights. A similar stargazing party attracted more than 150 people in Dubai . [ 9 ]
A StarPeace event took place between India and Pakistan on February 9, during a penumbral lunar eclipse. An Indian astronomy group in Bhuj , India and a Pakistani astronomy group in Lahore , Pakistan held observing nights and astronomy speeches in SOS Children's Villages for young children. [ 10 ]
In 2010, events were ongoing. [ 11 ] | https://en.wikipedia.org/wiki/StarPeace_Project |
StarTram is a proposed space launch system propelled by maglev technology. The initial Generation 1 facility is proposed to launch cargo only from a mountain peak at an altitude of 3 to 7 kilometres (9,800 to 23,000 ft) using an evacuated tube remaining at local surface level. Annual orbital lift was estimated at approximately 150,000 tons. More advanced technology is required for a Generation 2 system for passengers, with a longer track instead gradually curving up at its end to the thinner air at 22 kilometres (72,000 ft) altitude, supported by magnetic levitation , reducing g-forces when each capsule transitions from the vacuum tube to the atmosphere . A SPESIF 2010 presentation stated that Generation 1 could be completed by the year 2020 or later if funding began in 2010, and Generation 2 by 2030 or later. [ 1 ]
James R. Powell invented the superconducting maglev concept in the 1960s with a colleague, Gordon Danby , also at Brookhaven National Laboratory , which was subsequently developed into modern maglev trains. [ 1 ] Later, Powell co-founded StarTram, Inc. with Dr. George Maise, an aerospace engineer who previously was at Brookhaven National Laboratory from 1974 to 1997 with particular expertise including reentry heating and hypersonic vehicle design. [ 2 ]
A StarTram design was first published in a 2001 paper [ 3 ] and patent, [ 4 ] making reference to a 1994 paper on MagLifter. Developed by John C. Mankins , who was manager of Advanced Concept Studies at NASA, [ 5 ] the MagLifter concept involved maglev launch assist for a few hundred m/s with a short track, 90% projected efficiency. [ 6 ] Noting StarTram is essentially MagLifter taken to a much greater extreme, both MagLifter and StarTram were discussed the following year in a concept study performed by ZHA for NASA's Kennedy Space Center , also considered together by Maglev 2000 with Powell and Danby . [ 7 ] [ 8 ] [ 9 ]
Subsequent design modifies StarTram into a generation 1 version, a generation 2 version, and an alternative generation 1.5 variant. [ 1 ]
John Rather, who served as assistant director for Space Technology (Program Development) at NASA , [ 10 ] said:
It is a little known fact that an effort was made in the mid-1990s by NASA HQ, Marshall Space Flight Center, and key private innovators to change the basic paradigms of space access and development. Generically these efforts involved electromagnetic launch methods and new approaches for high power electrical systems in space. ... StarTram was conceived from first principles to reduce the cost and improve the efficiency of space access by a factor of more than a hundred. ... The overall feasibility and cost of the StarTram approach was validated in 2005 by a thorough “ murder board ” study conducted at Sandia National Laboratory.
The Gen-1 system proposes to accelerate uncrewed craft at 30 g through a 130-kilometer (81 mi) long tunnel, with a plasma window preventing vacuum loss when the exit's mechanical shutter is briefly open, evacuated of air with an MHD pump. (The plasma window is larger than prior constructions, 2.5 MW estimated power consumption itself for 3 metres (9.8 ft) diameter). [ 12 ] In the reference design, the exit is on the surface of a mountain peak of 6,000 metres (20,000 ft) altitude, where 8.78 kilometres per second (5.46 mi/s) launch velocity at a 10-degree angle takes cargo capsules to low Earth orbit when combined with a small rocket burn providing 0.63 kilometres per second (0.39 mi/s) for orbit circularization. With a bonus from Earth's rotation if firing east, the extra speed, well beyond nominal orbital velocity , compensates for losses during ascent including 0.8 kilometres per second (0.50 mi/s) from atmospheric drag . [ 1 ] [ 13 ]
A 40-ton cargo craft, 2 metres (6 ft 7 in) diameter and 13 metres (43 ft) length, would experience briefly the effects of atmospheric passage. With an effective drag coefficient of 0.09, peak deceleration for the mountain-launched elongated projectile is momentarily 20 g but halves within the first 4 seconds and continues to decrease as it quickly passes above the bulk of the remaining atmosphere.
In the first moments after exiting the launch tube, the heating rate with an optimal nose shape is around 30 kW/cm 2 at the stagnation point , though much less over most of the nose, but drops below 10 kW/cm 2 within a few seconds. [ 1 ] Transpiration water cooling is planned, briefly consuming up to ≈ 100 liters/m 2 of water per second. Several percent of the projectile's mass in water is calculated to suffice. [ 1 ]
The tunnel tube itself for Gen-1 has no superconductors, no cryogenic cooling requirements, and none of it is at higher elevation than the local ground surface. Except for probable usage of SMES as the electrical power storage method, superconducting magnets are only on the moving spacecraft, inducing current into relatively inexpensive aluminum loops on the acceleration tunnel walls, levitating the craft with 10 centimeters clearance, while meanwhile a second set of aluminum loops on the walls carries an AC current accelerating the craft: a linear synchronous motor . [ 1 ]
Powell predicts a total expense, primarily hardware costs, of $43 per kilogram of payload with 35-ton payloads being launched 10+ times a day, as opposed to rocket launch prices of $10,000 to $25,000 per kilogram to low Earth orbit at the time. [ 14 ] The estimated cost of electrical energy to reach the velocity of low Earth orbit is under $1 per kilogram of payload: 6 cents per kilowatt-hour contemporary industrial electricity cost, 8.78 kilometres per second (5.46 mi/s) launch kinetic energy of 38.5 MJ per kilogram, and 87.5% of mass payload, accelerated at high efficiency by this linear electric motor . [ 1 ] [ 15 ]
The Gen-2 variant of the StarTram is supposed to be for reusable crewed capsules, intended to be low g-force , 2 to 3 g acceleration in the launch tube and an elevated exit at such high altitude (22 kilometres (14 mi)) that peak aerodynamic deceleration becomes ≈ 1g. [ 1 ] Though NASA test pilots have handled multiple times those g-forces , [ 17 ] the low acceleration is intended to allow eligibility to the broadest spectrum of the general public.
With such relatively slow acceleration, the Gen-2 system requires 1,000 to 1,500 kilometres (620 to 930 mi) length. The cost for the non-elevated majority of the tube's length is estimated to be several tens of millions of dollars per kilometer, proportionately a semi-similar expense per unit length to the tunneling portion of the former Superconducting Super Collider project (originally planned to have 72 kilometres (45 mi) of 5-meter (16 ft) diameter vacuum tunnel excavated for $2 billion) or to some existing maglev train lines where Powell 's Maglev 2000 system is claiming major cost-reducing further innovations. [ 1 ] An area of Antarctica 3 kilometres (9,800 ft) above sea level is one siting option, especially as the ice sheet is viewed as relatively easy to tunnel through. [ 18 ]
For the elevated end portion, the design considers magnetic levitation to be relatively less expensive than alternatives for elevating a launch tube of a mass driver (tethered balloons, [ 19 ] compressive or inflated aerospace-material megastructures ). [ 20 ] A 280-megaamp current in ground cables creates a magnetic field of 30 Gauss strength at 22 kilometres (72,000 ft) above sea level (somewhat less above local terrain depending on site choice), while cables on the elevated final portion of the tube carry 14 megaamps in the opposite direction, generating a repulsive force of 4 tons per meter; it is claimed that this would keep the 2-ton/meter structure strongly pressing up on its angled tethers, a tensile structure on grand scale. [ 3 ] In the example of niobium-titanium superconductor carrying 2 × 10 5 amps per cm 2 , the levitated platform would have 7 cables, each 23 cm 2 (3.6 sq in) of conductor cross-section when including copper stabilizer. [ 4 ]
An alternative, Gen-1.5, would launch passenger spacecraft at 4 kilometres per second (2.5 mi/s) from a mountaintop at around 6000 meters above sea level from a ≈ 270 kilometres (170 mi) tunnel accelerating at ≈ 3 g .
Though construction costs would be lower than the Gen-2 version, Gen-1.5 would differ from other StarTram variants by requiring 4+ km/s to be provided by other means, like rocket propulsion. However, the non-linear nature of the rocket equation still makes the payload fraction for such a vehicle significantly greater than that of a conventional rocket unassisted by electromagnetic launch, and a vehicle with high available weight margins and safety factors should be far easier to mass-produce cheaply or make reusable with rapid turnaround than current 8 kilometres per second (5.0 mi/s) rockets. Dr. Powell remarks that present launch vehicles "have many complex systems that operate near their failure point, with very limited redundancy," with extreme hardware performance relative to weight being a top driver of expense. (Fuel itself is on the order of 1% of the current costs to orbit ). [ 21 ] [ 22 ]
Alternatively, Gen-1.5 could be combined with another non-rocket spacelaunch system, like a Momentum Exchange Tether similar to the HASTOL concept which was intended to take a 4 kilometres per second (2.5 mi/s) vehicle to orbit. Because tethers are subject to highly exponential scaling , such a tether would be much easier to build using current technologies than one providing full orbital velocity by itself. [ 23 ]
The launch tunnel length in this proposal could be reduced by accepting correspondingly larger forces on the passengers. A ≈ 50 to 80 kilometres (31 to 50 mi) tunnel would generate forces of ≈ 10-15 g , which physically fit test pilots have endured successfully in centrifuge tests, but a slower acceleration with a longer tunnel would ease passenger requirements and reduce peak power draw, which in turn would decrease power conditioning expenses. [ 1 ] [ 17 ] [ 24 ]
The StarTram ground facility concept is claimed to be reusable after each launch without extensive maintenance, as it would essentially be a large linear synchronous electric motor . This would shift most of the "requirement for achieving orbit to a robust ground infrastructure," intended to have neither high performance relative to weight requirements nor such as the $25,000 per kilogram of flyable dry weight costs of the Space Shuttle . [ 8 ] The designers estimate a construction cost for Generation 1 of $19 billion, becoming $67 billion for passenger-capable Generation 2. [ 1 ]
The alternative Generation 1.5 design, such as 4 kilometres per second (2.5 mi/s) launch velocity, would be intermediate in velocity terms between Gen-1's 8.8 kilometres per second (5.5 mi/s) and the Maglifter design (which had $0.2 billion estimated cost for 0.3 kilometres per second (0.19 mi/s) launch assist in the case of a 50-ton vehicle). [ 1 ] [ 25 ]
The Generation 2 goal is $13,000 per person. Up to 4 million people could be sent to orbit per decade per Gen-2 facility if as estimated. [ 1 ]
The largest challenge for Gen-1 is considered by the researchers to be sufficiently affordable storage, rapid delivery, and handling of the power requirements. [ 18 ]
For needed electrical energy storage (discharged over 30 seconds with about 50 gigawatt average and about 100 gigawatts peak), SMES cost performance on such unusual scale is anticipated of around a dollar per kilojoule and $20 per kW-peak. [ 1 ] Such would be novel in scale but not greatly different planned cost performance than obtained in other smaller pulsed power energy storage systems (such as quick-discharge modern supercapacitors dropping from $151/kJ to $2.85/kJ cost between 1998 and 2006 while being predicted to later reach a dollar per kJ, [ 26 ] lead acid batteries which can be $10 per kW-peak for a few seconds, or experimental railgun compulsator power supplies). The study notes pulsed MHD generators may be an alternative. [ 1 ]
For MagLifter, General Electric estimated in 1997-2000 that a set of hydroelectric flywheel pulse power generators could be manufactured for a cost equating to $5.40 per kJ and $27 per kW-peak. [ 6 ] For StarTram, the SMES design choice is a better (less expensive) approach than pulse generators according to Powell. [ 1 ]
The single largest predicted capital cost for Gen-1 is the power conditioning, from an initially DC discharge to the AC current wave,
dealing for a few seconds with very high power, up to 100 gigawatts, at a cost estimated to be $100 per kW-peak. [ 1 ] Yet, compared to some other potential implementations of a coilgun launcher with relatively higher requirements for pulse power switching devices (an example being an escape velocity design of 7.8 kilometres (4.8 mi) length after a 1977 NASA Ames study determined how to survive atmospheric passage from ground launch), [ 27 ] which are not always semiconductor-based, [ 28 ] the 130-km acceleration tube length of Gen-1 spreads out energy input requirements over a longer acceleration duration. Such makes peak input power handling requirements be not more than about 2 GW per ton of the vehicle. The tradeoff of greater expense for the tunnel itself is incurred, but the tunnel is estimated to be about $4.4 billion including $1500 per cubic meter excavation, a minority of total system cost. [ 1 ]
The current land speed record of 2.9 km/s was obtained by a sled on 5 kilometers of rail track mostly in a helium-filled tunnel, in a $20 million project. [ 29 ] The Gen-1.5 version of the StarTram for launch of passenger RLVs at 4 km/s velocity from the surface of a mountain would be significantly higher speed with a far more massive vehicle. However, such would accelerate in a lengthy vacuum tunnel without air or gas drag, with levitation preventing hypervelocity physical rail contact, and with 3 orders of magnitude higher anticipated funding. Many challenges including high initial capital cost would overlap with Gen-1, though not having the levitated launch tube of Gen-2. [ 1 ]
Gen-2 introduces particular extra challenge with its elevated launch tube, levitating both the vehicle and part of the tube (unlike Gen-1 and Gen-1.5 which only levitate the vehicle). As of 2010 operating maglev systems levitate the train by approximately 15 millimeters (0.59 in). [ 31 ] [ 32 ] For the Gen-2 version of the StarTram, it is necessary to levitate the track over up to 22 kilometres (72,000 ft), a distance greater by a factor of 1.5 million.
The force between two conducting lines is given by F = ( μ I 1 I 2 l ) / ( 2 π r ) {\displaystyle F=(\mu I_{1}I_{2}l)/(2\pi r)} , ( Ampère's force law ). Here F is the force, μ = μ 0 μ r {\displaystyle \mu =\mu _{0}\mu _{r}} the permeability , I 1 , I 2 {\displaystyle I_{1},I_{2}} the electric currents , l {\displaystyle l} the length of the lines and r {\displaystyle r} their distance. To exert 4,000 kg/m (8,100 lb/yd) over a distance of 20 kilometres (12 mi) in air ( μ r {\displaystyle \mu _{r}} ≈ 1) ground I 1 {\displaystyle I_{1}} ≈ 280 x 10 6 A is needed if levitated I 2 {\displaystyle I_{2}} ≈ 14 x 10 6 A . For comparison, in lightning the maximal current is about 10 5 A, cf. properties of lightning , though resistive power dissipation involved in a current flowing through a conductor is proportional to the voltage drop, high for a lightning discharge of millions of volts in air but ideally zero for a zero-resistance superconductor .
While the performance of niobium-titanium superconductor is technically sufficient (a critical current density of 5 x 10 5 A/cm 2 under the relevant magnetic field conditions for the levitated platform, 40% of that in practice after a safety factor), [ 4 ] uncertainties on economics include a far more optimistic assumption for Gen-2 of $0.2 per kA-meter of superconductor compared to the $2 per kA-meter assumed for Gen-1 (where Gen-1 doesn't have any of its launch tube levitated but uses superconducting cable for a large SMES and within the maglev craft launched). [ 1 ] NbTi was the design choice under the available economies of scale for cooling, since it presently costs $1 per kA-meter, while high temperature superconductors so far still cost much more for the conductor itself per kA-meter. [ 33 ]
If considering a design with an acceleration up to 10 g (which is higher than the re-entry acceleration of Apollo 16 ) [ 34 ] then the whole track must be at least 326 kilometres (203 mi) long for a passenger version of the Gen-2 system. Such length allows use of the approximation for an infinite line to calculate the force. The preceding neglects how only the final portion of the track is levitated, but a more complex calculation only changes the result for force per unit length of it by 10-20% (f gl = 0.8 to 0.9 instead of 1). [ 4 ]
The researchers themselves do not consider there to be any doubt whether the levitation would work in terms of force exerted (a consequence of Ampère's force law) but see the primary challenge as the practical engineering complexities of erection of the tube, [ 18 ] while a substantial portion of engineering analysis focused on handling bending caused by wind. [ 4 ] The active structure is calculated to bend by a fraction of a meter per kilometer under wind in the very thin air at its high altitude, a slight curvature theoretically handled by guidance loops, with net levitation force beyond structure weight exceeding wind force by a factor of 200+ to keep tethers taut, and with the help of computer-controlled control tethers. [ 4 ] | https://en.wikipedia.org/wiki/StarTram |
Star Names: Their Lore and Meaning is an 1899 book by Richard Hinckley Allen, [ 1 ] that discusses the names of stars , constellations , and their histories . [ not verified in body ]
Richard Hinckley Allen (1838, near Buffalo, New York – 1908, Northampton, Massachusetts ) was a youthful polymath with interests in "nature, astronomy, ornithology, and literature" whom his classmates described as "the walking encyclopedia"; after a college year spent at Yale, a pursuit abandoned because of problems with his eyesight, he traveled and then "joined his father’s export trade business". Allen's interest in astronomy, and in star names in particular, may have been stimulated by his coming across such a name with which he was unfamiliar, after which "[h]e spent many years researching astronomical nomenclature... primarily for personal enjoyment". With the encouragement of professors from Yale and Princeton, and from personal friends, Allen proceeded to publish the information he had gathered—as Star-Names and Their Meanings in 1899. [ 2 ] [ 1 ]
First published in 1899 as Star-Names and Their Meanings , [ 1 ] this work collected the origins of the names of stars and constellations from a panoply of sources, some primary but most secondary. [ citation needed ] It also briefly retells the various myths and folklore connected with stars in the Greco-Roman tradition, as well as in the Arabic, Babylonian, Indian and Chinese traditions (for which, however, some modern criticism [ who? ] [ citation needed ] having taken it to task, claiming it to be largely superseded). [ citation needed ]
The book also provides some cursory details about astronomy , at the knowledge level of the end of the 19th century. [ citation needed ] Similarly, astrology and its history are dealt with briefly in the introduction, [ citation needed ] and some other basic astrological references (although downplayed) are scattered throughout the book. [ citation needed ]
Late historian of astronomy Paul Kunitzsch [ 3 ] notes that the "book may be taken as a handbook summing up the state of knowledge arrived at by his time," but that to standards current to his 1979 publication, it was generally unreliable with regard to star names and their derivations. [ 4 ] [ verification needed ] Science fiction writers/editors Algis Budrys and Frederik Pohl called Star Names "a fine book (but hardly 'hammock reading')", in a 1965 review. [ 5 ] In an assessment by amateur classicist Bill Thayer, [ 6 ] the book was presented as mostly accurate in its explanations of Greek and Latin star names, although containing minor historical errors, and overestimates of the age of some Greek temples. [ 7 ] It was also criticised with regard to star names by Gary D. Thompson, an amateur astronomer who maintains its discussion of Arabic, Mesopotamian, and Egyptian constellations and star names are likewise especially unreliable. [ 8 ] | https://en.wikipedia.org/wiki/Star_Names |
Star Walk is an educational astronomy smartphone app developed by Vito Technology which allows users to explore celestial objects in real-time. The application was released in 2009 and is compatible with iOS , Android , and Windows devices. Star Walk has been downloaded by over 10 million users worldwide ever since its release. [ 1 ]
It aims to help people locate and identify over 200,000 stars , planets , constellations , and satellites in the night sky and provide detailed information about these objects.
The application aims to determine the position of celestial objects in the sky, calculated in real-time based on the position of the user. It includes information on star clusters , meteor showers , iridium flares , galaxies , and nebulae as well as the current position of dwarf planets , comets , asteroids , and man-made satellites . [ 2 ]
Star Walk can also display the times of sunrise and sunset for the Sun (and other visible planets) at a particular location, as well as the current moon phase , elevation angle, and day length.
The app can show the map of the night sky in the past and future. In the iOS version, the app uses the camera for the augmented reality feature, combining the image data from the camera with the star map to give the user a real-time view of celestial objects. [ 3 ]
Star Walk 2 is an update of the original Star Walk astronomy application. It has a re-designed interface with 3 camera modes: free roam, manual/scrolling, and augmented reality. The augmented reality view also remains as a holdover from the original app. [ 4 ] In order to explore the night sky objects, the user can orient the device toward the sky so that the application activates the camera and the charted objects can be seen appearing superimposed on live sky objects through the use of augmented reality.
Users can scroll a list of objects visible on any night and from any location on Earth .
In addition to its commercial success, Star Walk has been well-received by critics [ citation needed ] . At WWDC 2010, Star Walk won an Apple Design Award for the iPad version. [ 5 ] In 2012, it won the Parents’ Choice Gold Award in the "Mobile Apps" category, [ 6 ] the Academics' Choice Award, [ 7 ] and the World Summit Award in the "Entertainment and Lifestyle" category. [ 8 ] | https://en.wikipedia.org/wiki/Star_Walk |
A star chart is a celestial map of the night sky with astronomical objects laid out on a grid system. They are used to identify and locate constellations , stars , nebulae , galaxies , and planets . [ 1 ] They have been used for human navigation since time immemorial. [ 2 ] Note that a star chart differs from an astronomical catalog , which is a listing or tabulation of astronomical objects for a particular purpose. Tools using a star chart include the astrolabe and planisphere .
A variety of archaeological sites and artifacts found are thought to indicate ancient made star charts.
The oldest known star chart may be a carved ivory Mammoth tusk, drawn by early people from Asia who moved into Europe, that was discovered in Germany in 1979. This artifact is 32,500 years old and has a carving that resembles the constellation Orion , although it could not be confirmed and could also be a pregnancy chart. [ 3 ]
German researcher Dr Michael Rappenglueck, of the University of Munich, has suggested that drawing on the wall of the Lascaux caves in France could be a graphical representation of the Pleiades open cluster of stars. This is dated from 33,000 to 10,000 years ago. He also suggested a panel in the same caves depicting a charging bison, a man with a bird's head and the head of a bird on top of a piece of wood, together may depict the Summer Triangle , which at the time was a circumpolar formation . [ 4 ] Rappenglueck also discovered a drawing of the Northern Crown constellation in the cave of El Castillo (North of Spain), made in the same period as the Lascaux chart. [ 5 ]
Another star chart panel, created more than 21,000 years ago, was found in the La Tête du Lion cave ( fr ). The bovine in this panel may represent the constellation Taurus , with a pattern representing the Pleiades just above it. [ 6 ]
A star chart drawn 5000 years ago by the Indians in Kashmir, which also depict a supernova for the first time in human history. [ 7 ] The Nebra sky disk , a 30 cm wide bronze disk dated to 1600 BC, bears gold symbols generally interpreted as a sun or full moon, a lunar crescent, several stars including the Pleiades cluster and possibly the Milky Way.
The oldest accurately dated star chart appeared in ancient Egyptian astronomy in 1534 BC. [ 8 ] The earliest known star catalogues were compiled by the ancient Babylonian astronomers of Mesopotamia in the late 2nd millennium BC, during the Kassite Period ( ca. 1531–1155 BC). [ 9 ] The oldest records of Chinese astronomy date to the Warring States period (476–221 BC), but the earliest preserved Chinese star catalogues of astronomers Shi Shen and Gan De are found in the 2nd-century BC Shiji by the Western Han historian Sima Qian . [ 10 ] The oldest Chinese graphical representation of the night sky is a lacquerware box from the 5th-century BC Tomb of Marquis Yi of Zeng , although this depiction shows the positions of the Chinese constellations by name and does not show individual stars. [ 11 ]
The Farnese Atlas is a 2nd-century AD Roman copy of a Hellenistic era Greek statue depicting the Titan Atlas holding the celestial sphere on his shoulder. It is the oldest surviving depiction of the ancient Greek constellations, and includes grid circles that provide coordinate positions. Because of precession , the positions of the constellations slowly change over time. By comparing the positions of the 41 constellations against the grid circles, an accurate determination can be made of the epoch when the original observations were performed. Based upon this information, the constellations were catalogued at 125 ± 55 BC . This evidence indicates that the star catalogue of the 2nd-century BC Greek astronomer Hipparchus was used. [ 12 ]
A Roman era example of a graphical representation of the night sky is the Ptolemaic Egyptian Dendera zodiac , dating from 50 BC. This is a bas relief sculpting on a ceiling at the Dendera Temple complex . It is a planisphere depicting the zodiac in graphical representations. However, individual stars are not plotted. [ 13 ]
The oldest surviving manuscript star chart was the Dunhuang Star Chart , dated to the Tang dynasty (618–907) and discovered in the Mogao Caves of Dunhuang in Gansu , Western China along the Silk Road . This is a scroll 210 cm in length and 24.4 cm wide showing the sky between declinations 40° south to 40° north in twelve panels, plus a thirteenth panel showing the northern circumpolar sky. A total of 1,345 stars are drawn, grouped into 257 asterisms . The date of this chart is uncertain, but is estimated as 705–10 AD. [ 14 ] [ 15 ] [ 16 ]
During the Song dynasty (960–1279), the Chinese astronomer Su Song wrote a book titled Xin Yixiang Fa Yao (New Design for the Armillary Clock) containing five maps of 1,464 stars. This has been dated to 1092. In 1193, the astronomer Huang Shang prepared a planisphere along with explanatory text. It was engraved in stone in 1247, and this chart still exists in the Wen Miao temple in Suzhou . [ 15 ]
In Muslim astronomy , the first star chart to be drawn accurately was most likely the illustrations produced by the Persian astronomer Abd al-Rahman al-Sufi in his 964 work titled Book of Fixed Stars . This book was an update of parts VII.5 and VIII.1 of the 2nd century Almagest star catalogue by Ptolemy . The work of al-Sufi contained illustrations of the constellations and portrayed the brighter stars as dots. The original book did not survive, but a copy from about 1009 is preserved at the Oxford University . [ 14 ] [ 15 ]
Perhaps the oldest European star map was a parchment manuscript titled De Composicione Spere Solide . It was most likely produced in Vienna , Austria in 1440 and consisted of a two-part map depicting the constellations of the northern celestial hemisphere and the ecliptic . This may have served as a prototype for the oldest European printed star chart, a 1515 set of woodcut portraits produced by Albrecht Dürer in Nuremberg , Germany . [ 17 ]
During the European Age of Discovery , expeditions to the southern hemisphere began to result in the addition of new constellations. These most likely came from the records of two Dutch sailors, Pieter Dirkszoon Keyser and Frederick de Houtman , who in 1595 traveled together to the Dutch East Indies . Their compilations resulted in the 1601 globe of Jodocus Hondius , who added 12 new southern constellations. Several other such maps were produced, including Johann Bayer 's Uranometria in 1603. [ 18 ] The latter was the first atlas to chart both celestial hemispheres and it introduced the Bayer designations for identifying the brightest stars using the Greek alphabet. The Uranometria contained 48 maps of Ptolemaic constellations, a plate of the southern constellations and two plates showing the entire northern and southern hemispheres in stereographic polar projection. [ 19 ]
Polish astronomer Johannes Hevelius published his Firmamentum Sobiescianum star atlas posthumously in 1690. It contained 56 large, double page star maps and improved the accuracy in the position of the southern stars. He introduced 11 more constellations, including Scutum , Lacerta , and Canes Venatici .
In 1824 Sidney Hall produced a set of star charts called Urania's Mirror . They are illustrations based on Alexander Jamieson 's A Celestial Atlas , but the addition of holes punched in them allowed them to be held up to a light to see a depiction of the constellation's stars. | https://en.wikipedia.org/wiki/Star_chart |
In geometry , a set S {\displaystyle S} in the Euclidean space R n {\displaystyle \mathbb {R} ^{n}} is called a star domain (or star-convex set , star-shaped set [ 1 ] or radially convex set ) if there exists an s 0 ∈ S {\displaystyle s_{0}\in S} such that for all s ∈ S , {\displaystyle s\in S,} the line segment from s 0 {\displaystyle s_{0}} to s {\displaystyle s} lies in S . {\displaystyle S.} This definition is immediately generalizable to any real , or complex , vector space .
Intuitively, if one thinks of S {\displaystyle S} as a region surrounded by a wall, S {\displaystyle S} is a star domain if one can find a vantage point s 0 {\displaystyle s_{0}} in S {\displaystyle S} from which any point s {\displaystyle s} in S {\displaystyle S} is within line-of-sight. A similar, but distinct, concept is that of a radial set .
Given two points x {\displaystyle x} and y {\displaystyle y} in a vector space X {\displaystyle X} (such as Euclidean space R n {\displaystyle \mathbb {R} ^{n}} ), the convex hull of { x , y } {\displaystyle \{x,y\}} is called the closed interval with endpoints x {\displaystyle x} and y {\displaystyle y} and it is denoted by [ x , y ] := { t y + ( 1 − t ) x : 0 ≤ t ≤ 1 } = x + ( y − x ) [ 0 , 1 ] , {\displaystyle \left[x,y\right]~:=~\left\{ty+(1-t)x:0\leq t\leq 1\right\}~=~x+(y-x)[0,1],} where z [ 0 , 1 ] := { z t : 0 ≤ t ≤ 1 } {\displaystyle z[0,1]:=\{zt:0\leq t\leq 1\}} for every vector z . {\displaystyle z.}
A subset S {\displaystyle S} of a vector space X {\displaystyle X} is said to be star-shaped at s 0 ∈ S {\displaystyle s_{0}\in S} if for every s ∈ S , {\displaystyle s\in S,} the closed interval [ s 0 , s ] ⊆ S . {\displaystyle \left[s_{0},s\right]\subseteq S.} A set S {\displaystyle S} is star shaped and is called a star domain if there exists some point s 0 ∈ S {\displaystyle s_{0}\in S} such that S {\displaystyle S} is star-shaped at s 0 . {\displaystyle s_{0}.}
A set that is star-shaped at the origin is sometimes called a star set . [ 2 ] Such sets are closely related to Minkowski functionals . | https://en.wikipedia.org/wiki/Star_domain |
Star formation is the process by which dense regions within molecular clouds in interstellar space —sometimes referred to as "stellar nurseries" or "star-forming regions"— collapse and form stars . [ 1 ] As a branch of astronomy , star formation includes the study of the interstellar medium (ISM) and giant molecular clouds (GMC) as precursors to the star formation process, and the study of protostars and young stellar objects as its immediate products. It is closely related to planet formation , another branch of astronomy . Star formation theory, as well as accounting for the formation of a single star, must also account for the statistics of binary stars and the initial mass function . Most stars do not form in isolation but as part of a group of stars referred as star clusters or stellar associations . [ 2 ]
Star formation is divided into three groups called "Populations". Population III stars formed from primordial hydrogen after the Big Bang . These stars are poorly understood but should contain only hydrogen and helium. Population II stars formed from the debris of the first stars and they in turn created more higher atomic number chemical elements . Population I stars are young metal-rich (contain elements other than hydrogen and helium) stars like our Sun . [ 3 ]
The initial star formation was driven by gravitational attraction of hydrogen local areas of higher gravity called dark matter halos . As the hydrogen lost energy through atomic or molecular energy transitions, the temperature of local clumps fell allowing more gravitational condensation. Eventually the process leads to collapse in to a start. Details of the dynamics of the Population III stars is now believe to be as complex as star formation today. [ 3 ]
Spiral galaxies like the Milky Way contain stars , stellar remnants , and a diffuse interstellar medium (ISM) of gas and dust. The interstellar medium consists of 10 4 to 10 6 particles per cm 3 , and is typically composed of roughly 70% hydrogen , 28% helium , and 1.5% heavier elements by mass. The trace amounts of heavier elements were and are produced within stars via stellar nucleosynthesis and ejected as the stars pass beyond the end of their main sequence lifetime. Higher density regions of the interstellar medium form clouds, or diffuse nebulae , [ 4 ] where star formation takes place. [ 5 ] In contrast to spiral galaxies, elliptical galaxies lose the cold component [ definition needed ] of its interstellar medium within roughly a billion years, which hinders the galaxy from forming diffuse nebulae except through mergers with other galaxies. [ 6 ]
In the dense nebulae where stars are produced, much of the hydrogen is in the molecular (H 2 ) form, so these nebulae are called molecular clouds . [ 5 ] The Herschel Space Observatory has revealed that filaments, or elongated dense gas structures, are truly ubiquitous in molecular clouds and central to the star formation process. They fragment into gravitationally bound cores, most of which will evolve into stars. Continuous accretion of gas, geometrical bending [ definition needed ] , and magnetic fields may control the detailed manner in which the filaments are fragmented. Observations of supercritical filaments have revealed quasi-periodic chains of dense cores with spacing comparable to the filament inner width, and embedded protostars with outflows. [ jargon ] [ 7 ]
Observations indicate that the coldest clouds tend to form low-mass stars, which are first observed via the infrared light they emit inside the clouds, and then as visible light when the clouds dissipate. Giant molecular clouds, which are generally warmer, produce stars of all masses. [ 8 ] These giant molecular clouds have typical densities of 100 particles per cm 3 , diameters of 100 light-years (9.5 × 10 14 km ), masses of up to 6 million solar masses ( M ☉ ) , or six million times the mass of Earth's sun. [ 9 ] The average interior temperature is 10 K (−441.7 °F ).
About half the total mass of the Milky Way 's galactic ISM is found in molecular clouds [ 10 ] and the galaxy includes an estimated 6,000 molecular clouds, each with more than 100,000 M ☉ . [ 11 ] The nebula nearest to the Sun where massive stars are being formed is the Orion Nebula , 1,300 light-years (1.2 × 10 16 km) away. [ 12 ] However, lower mass star formation is occurring about 400–450 light-years distant in the ρ Ophiuchi cloud complex . [ 13 ]
A more compact site of star formation is the opaque clouds of dense gas and dust known as Bok globules , so named after the astronomer Bart Bok . These can form in association with collapsing molecular clouds or possibly independently. [ 14 ] The Bok globules are typically up to a light-year across and contain a few solar masses . [ 15 ] They can be observed as dark clouds silhouetted against bright emission nebulae or background stars. Over half the known Bok globules have been found to contain newly forming stars. [ 16 ]
An interstellar cloud of gas will remain in hydrostatic equilibrium as long as the kinetic energy of the gas pressure is in balance with the potential energy of the internal gravitational force . Mathematically this is expressed using the virial theorem , which states that, to maintain equilibrium, the gravitational potential energy must equal twice the internal thermal energy. [ 18 ] If a cloud is massive enough that the gas pressure is insufficient to support it, the cloud will undergo gravitational collapse . The mass above which a cloud will undergo such collapse is called the Jeans mass . The Jeans mass depends on the temperature and density of the cloud, but is typically thousands to tens of thousands of solar masses. [ 5 ] During cloud collapse dozens to tens of thousands of stars form more or less simultaneously which is observable in so-called embedded clusters . The end product of a core collapse is an open cluster of stars. [ 19 ]
In triggered star formation , one of several events might occur to compress a molecular cloud and initiate its gravitational collapse . Molecular clouds may collide with each other, or a nearby supernova explosion can be a trigger, sending shocked matter into the cloud at very high speeds. [ 5 ] (The resulting new stars may themselves soon produce supernovae, producing self-propagating star formation .) Alternatively, galactic collisions can trigger massive starbursts of star formation as the gas clouds in each galaxy are compressed and agitated by tidal forces . [ 21 ] The latter mechanism may be responsible for the formation of globular clusters . [ 22 ]
A supermassive black hole at the core of a galaxy may serve to regulate the rate of star formation in a galactic nucleus. A black hole that is accreting infalling matter can become active , emitting a strong wind through a collimated relativistic jet . This can limit further star formation. Massive black holes ejecting radio-frequency-emitting particles at near-light speed can also block the formation of new stars in aging galaxies. [ 23 ] However, the radio emissions around the jets may also trigger star formation. Likewise, a weaker jet may trigger star formation when it collides with a cloud. [ 24 ]
As it collapses, a molecular cloud breaks into smaller and smaller pieces in a hierarchical manner, until the fragments reach stellar mass. In each of these fragments, the collapsing gas radiates away the energy gained by the release of gravitational potential energy . As the density increases, the fragments become opaque and are thus less efficient at radiating away their energy. This raises the temperature of the cloud and inhibits further fragmentation. The fragments now condense into rotating spheres of gas that serve as stellar embryos. [ 26 ]
Complicating this picture of a collapsing cloud are the effects of turbulence , macroscopic flows, rotation , magnetic fields and the cloud geometry. Both rotation and magnetic fields can hinder the collapse of a cloud. [ 27 ] [ 28 ] Turbulence is instrumental in causing fragmentation of the cloud, and on the smallest scales it promotes collapse. [ 29 ]
A protostellar cloud will continue to collapse as long as the gravitational binding energy can be eliminated. This excess energy is primarily lost through radiation. However, the collapsing cloud will eventually become opaque to its own radiation, and the energy must be removed through some other means. The dust within the cloud becomes heated to temperatures of 60–100 K , and these particles radiate at wavelengths in the far infrared where the cloud is transparent. Thus the dust mediates the further collapse of the cloud. [ 30 ]
During the collapse, the density of the cloud increases towards the center and thus the middle region becomes optically opaque first. This occurs when the density is about 10 −13 g / cm 3 . A core region, called the first hydrostatic core, forms where the collapse is essentially halted. It continues to increase in temperature as determined by the virial theorem. The gas falling toward this opaque region collides with it and creates shock waves that further heat the core. [ 31 ]
When the core temperature reaches about 2000 K , the thermal energy dissociates the H 2 molecules. [ 31 ] This is followed by the ionization of the hydrogen and helium atoms. These processes absorb the energy of the contraction, allowing it to continue on timescales comparable to the period of collapse at free fall velocities. [ 32 ] After the density of infalling material has reached about 10 −8 g / cm 3 , that material is sufficiently transparent to allow energy radiated by the protostar to escape. The combination of convection within the protostar and radiation from its exterior allow the star to contract further. [ 31 ] This continues until the gas is hot enough for the internal pressure to support the protostar against further gravitational collapse—a state called hydrostatic equilibrium . When this accretion phase is nearly complete, the resulting object is known as a protostar . [ 5 ]
Accretion of material onto the protostar continues partially from the newly formed circumstellar disc . When the density and temperature are high enough, deuterium fusion begins, and the outward pressure of the resultant radiation slows (but does not stop) the collapse. Material comprising the cloud continues to "rain" onto the protostar . In this stage bipolar jets are produced called Herbig–Haro objects . This is probably the means by which excess angular momentum of the infalling material is expelled, allowing the star to continue to form.
When the surrounding gas and dust envelope disperses and accretion process stops, the star is considered a pre-main-sequence star (PMS star). The energy source of these objects is (gravitational contraction) Kelvin–Helmholtz mechanism , as opposed to hydrogen burning in main sequence stars. The PMS star follows a Hayashi track on the Hertzsprung–Russell (H–R) diagram . [ 34 ] The contraction will proceed until the Hayashi limit is reached, and thereafter contraction will continue on a Kelvin–Helmholtz timescale with the temperature remaining stable. Stars with less than 0.5 M ☉ thereafter join the main sequence. For more massive PMS stars, at the end of the Hayashi track they will slowly collapse in near hydrostatic equilibrium, following the Henyey track . [ 35 ]
Finally, hydrogen begins to fuse in the core of the star, and the rest of the enveloping material is cleared away. This ends the protostellar phase and begins the star's main sequence phase on the H–R diagram.
The stages of the process are well defined in stars with masses around 1 M ☉ or less. In high mass stars, the length of the star formation process is comparable to the other timescales of their evolution, much shorter, and the process is not so well defined. The later evolution of stars is studied in stellar evolution .
Key elements of star formation are only available by observing in wavelengths other than the optical . The protostellar stage of stellar existence is almost invariably hidden away deep inside dense clouds of gas and dust left over from the GMC . Often, these star-forming cocoons known as Bok globules , can be seen in silhouette against bright emission from surrounding gas. [ 36 ] Early stages of a star's life can be seen in infrared light, which penetrates the dust more easily than visible light. [ 37 ] Observations from the Wide-field Infrared Survey Explorer (WISE) have thus been especially important for unveiling numerous galactic protostars and their parent star clusters . [ 38 ] [ 39 ] Examples of such embedded star clusters are FSR 1184, FSR 1190, Camargo 14, Camargo 74, Majaess 64, and Majaess 98. [ 40 ]
The structure of the molecular cloud and the effects of the protostar can be observed in near-IR extinction maps (where the number of stars are counted per unit area and compared to a nearby zero extinction area of sky), continuum dust emission and rotational transitions of CO and other molecules; these last two are observed in the millimeter and submillimeter range. The radiation from the protostar and early star has to be observed in infrared astronomy wavelengths, as the extinction caused by the rest of the cloud in which the star is forming is usually too big to allow us to observe it in the visual part of the spectrum. This presents considerable difficulties as the Earth's atmosphere is almost entirely opaque from 20μm to 850μm, with narrow windows at 200μm and 450μm. Even outside this range, atmospheric subtraction techniques must be used.
X-ray observations have proven useful for studying young stars, since X-ray emission from these objects is about 100–100,000 times stronger than X-ray emission from main-sequence stars. [ 42 ] The earliest detections of X-rays from T Tauri stars were made by the Einstein X-ray Observatory . [ 43 ] [ 44 ] For low-mass stars X-rays are generated by the heating of the stellar corona through magnetic reconnection , while for high-mass O and early B-type stars X-rays are generated through supersonic shocks in the stellar winds. Photons in the soft X-ray energy range covered by the Chandra X-ray Observatory and XMM-Newton may penetrate the interstellar medium with only moderate absorption due to gas, making the X-ray a useful wavelength for seeing the stellar populations within molecular clouds. X-ray emission as evidence of stellar youth makes this band particularly useful for performing censuses of stars in star-forming regions, given that not all young stars have infrared excesses. [ 45 ] X-ray observations have provided near-complete censuses of all stellar-mass objects in the Orion Nebula Cluster and Taurus Molecular Cloud . [ 46 ] [ 47 ]
The formation of individual stars can only be directly observed in the Milky Way Galaxy , but in distant galaxies star formation has been detected through its unique spectral signature .
Initial research indicates star-forming clumps start as giant, dense areas in turbulent gas-rich matter in young galaxies, live about 500 million years, and may migrate to the center of a galaxy, creating the central bulge of a galaxy. [ 48 ]
On February 21, 2014, NASA announced a greatly upgraded database for tracking polycyclic aromatic hydrocarbons (PAHs) in the universe . According to scientists, more than 20% of the carbon in the universe may be associated with PAHs, possible starting materials for the formation of life . PAHs seem to have been formed shortly after the Big Bang , are widespread throughout the universe, and are associated with new stars and exoplanets . [ 49 ]
In February 2018, astronomers reported, for the first time, a signal of the reionization epoch, an indirect detection of light from the earliest stars formed - about 180 million years after the Big Bang . [ 50 ]
An article published on October 22, 2019, reported on the detection of 3MM-1 , a massive star-forming galaxy about 12.5 billion light-years away that is obscured by clouds of dust . [ 51 ] At a mass of about 10 10.8 solar masses , it showed a star formation rate about 100 times as high as in the Milky Way . [ 52 ]
Stars of different masses are thought to form by slightly different mechanisms. The theory of low-mass star formation, which is well-supported by observation, suggests that low-mass stars form by the gravitational collapse of rotating density enhancements within molecular clouds. As described above, the collapse of a rotating cloud of gas and dust leads to the formation of an accretion disk through which matter is channeled onto a central protostar. For stars with masses higher than about 8 M ☉ , however, the mechanism of star formation is not well understood.
Massive stars emit copious quantities of radiation which pushes against infalling material. In the past, it was thought that this radiation pressure might be substantial enough to halt accretion onto the massive protostar and prevent the formation of stars with masses more than a few tens of solar masses. [ 58 ] Recent theoretical work has shown that the production of a jet and outflow clears a cavity through which much of the radiation from a massive protostar can escape without hindering accretion through the disk and onto the protostar. [ 59 ] [ 60 ] Present thinking is that massive stars may therefore be able to form by a mechanism similar to that by which low mass stars form.
There is mounting evidence that at least some massive protostars are indeed surrounded by accretion disks. [ 61 ] Disk accretion in high-mass protostars, similar to their low-mass counterparts, is expected to exhibit bursts of episodic accretion as a result of a gravitationally instability leading to clumpy and in-continuous accretion rates. Recent evidence of accretion bursts in high-mass protostars has indeed been confirmed observationally. [ 61 ] [ 62 ] [ 63 ] Several other theories of massive star formation remain to be tested observationally. Of these, perhaps the most prominent is the theory of competitive accretion, which suggests that massive protostars are "seeded" by low-mass protostars which compete with other protostars to draw in matter from the entire parent molecular cloud, instead of simply from a small local region. [ 64 ] [ 65 ]
Another theory of massive star formation suggests that massive stars may form by the coalescence of two or more stars of lower mass. [ 66 ]
Recent studies have emphasized the role of filamentary structures in molecular clouds as the initial conditions for star formation. Findings from the Herschel Space Observatory highlight the ubiquitous nature of these filaments in the cold interstellar medium (ISM). The spatial relationship between cores and filaments indicates that the majority of prestellar cores are located within 0.1 pc of supercritical filaments. This supports the hypothesis that filamentary structures act as pathways for the accumulation of gas and dust, leading to core formation. [ 67 ]
Both the core mass function (CMF) and filament line mass function (FLMF) observed in the California GMC follow power-law distributions at the high-mass end, consistent with the Salpeter initial mass function (IMF). Current results strongly support the existence of a connection between the FLMF and the CMF/IMF, demonstrating that this connection holds at the level of an individual cloud, specifically the California GMC. [ 67 ] The FLMF presented is a distribution of local line masses for a complete, homogeneous sample of filaments within the same cloud. It is the local line mass of a filament that defines its ability to fragment at a particular location along its spine, not the average line mass of the filament. This connection is more direct and provides tighter constraints on the origin of the CMF/IMF. [ 67 ] | https://en.wikipedia.org/wiki/Star_formation |
Star lore or starlore is the creating and cherishing of mythical stories about the stars and star patterns ( constellations and asterisms ); that is, folklore based upon the stars and star patterns. Using the stars to explain religious doctrines or actual events in history is also defined as star lore. Star lore has a very long history; it has been practiced by nearly every culture recorded in history, dating as far back as 5,500 years ago. It was practiced by prehistoric cultures of the Paleolithic and Neolithic periods as well.
One example of star lore is the inventing of the story of Orion the Hunter and the Scorpius the Scorpion by the ancient Greeks . This ancient culture saw a very startling pattern of bright stars in the winter sky that, from their point of view, resembled a mighty hunter, which they named Orion . During the summer, they saw another startling pattern of bright stars that resembled a scorpion. They noticed that the constellations of Orion and the scorpion were positioned at opposite ends of the sky and were never seen in the sky simultaneously. As one constellation rose above the eastern horizon , the other was setting below the western horizon, and when either one was high in the sky, the other was completely absent. The ancient Greeks felt compelled to explain this phenomenon by composing a story or myth based on the two constellations [ citation needed ] .
The story was that Orion was a mighty and proud hunter who was stung by a scorpion. Orion died of the scorpion's sting and was placed among the stars by the gods. Although the scorpion was destroyed by the gods in vengeance for killing Orion, it was also placed among the stars. In order to prevent Orion and the scorpion from quarreling and fighting with each other in the sky, the gods placed Orion and the scorpion at opposite ends of the sky, and in opposite seasons , so that both of them can never be seen in the sky at the same time.
Another example of star lore is the story behind the constellation Andromeda , also known as "the chained woman". Andromeda was the daughter of the king and queen of Ethiopia , King Cepheus and Cassiopeia . The story goes that because Cassiopeia bragged so much of Andromeda's beauty to the Nereids , daughters of Poseidon , that they complained to their father, who sent a sea monster to destroy the coast of Ethiopia. Cepheus consulted an oracle for assistance and learned that the only way to save his lands was to sacrifice his daughter to Poseidon's monster. [ 1 ]
Andromeda was chained to a rock and left for the sea monster. Perseus , the hero of the story who had just killed the Gorgon Medusa found Andromeda in her distress and immediately, the two fell in love. Perseus asked for her name and refused to leave until he knew it, talking to her until she gave in. Andromeda told him her name, her country, and the reason for her imprisonment on the rock. He then consulted with Cepheus and Cassiopeia, and they decided that if Perseus rescued Andromeda from the sea monster, he could marry her. The story of how he then defeats the monster varies. Ovid describes his killing of the monster as a drawn out bloody battle. Other sources say that Perseus killed the sea monster with the aid of Medusa's head, turning the monster to stone. Andromeda and Perseus were married soon after, [ 2 ] despite already being promised to her uncle, Phineus. At the wedding, Phineus and Perseus got into an altercation, and Perseus turned Phineus to stone using Medusa's head.
The constellation is said to have astrological influences as well. It is said that any man born at the same time Andromeda is said to rise from the sea will be one without mercy; he will be emotionally unmoved even in the presence of grieving parents. The constellation also influences the birth of the executioner, a man who will kill swiftly for money and kill willingly. Sources describe men born with the rise of Andromeda as one who would feel nothing if faced with Andromeda chained to her rock, just as Perseus did and fell in love with the girl. [ 3 ]
The Draco is another example of star lore. In Roman mythology, the constellation is representative of Ladon , the dragon that guarded the golden apples inside the garden, Hesperides . The tree was a wedding gift to Hera when she and Zeus were married, and she planted it on Mount Atlas . Hera tasked the Hesperides to guard the tree and put Ladon around the tree as well to ensure that the Hesperides would not steal the apples. In some sources, Ladon is called the child of Typhon and Echidna , who was half woman and half viper, and had hundreds of heads. In other versions of Ladon's story, the number of heads he had is not at all mentioned and he is described as the offspring of Ceto and Phorcys , two sea deities . [ 4 ]
Contrastingly, in Roman mythology, Draco was one of the Titans who waged war on the Olympic gods for ten years. He was killed by Minerva in the battle and thrown into the sky. [ 5 ] | https://en.wikipedia.org/wiki/Star_lore |
The Star of David theorem is a mathematical result on arithmetic properties of binomial coefficients . It was discovered by Henry W. Gould in 1972.
The greatest common divisors of the binomial coefficients forming each of the two triangles in the Star of David shape in Pascal's triangle are equal:
Rows 8, 9, and 10 of Pascal's triangle are
For n =9, k =3 or n =9, k =6, the element 84 (circled bold) is surrounded by, in sequence, the elements 28, 56, 126, 210, 120 and 36 (bold). Taking alternating values, we have gcd(28, 126, 120) = 2 = gcd(56, 210, 36).
The element 36 (circled italics) is surrounded by the sequence 8, 28, 84, 120, 45 and 9 (italics), and taking alternating values we have gcd(8, 84, 45) = 1 = gcd(28, 120, 9).
The above greatest common divisor also equals gcd ( ( n − 1 k − 2 ) , ( n − 1 k − 1 ) , ( n − 1 k ) , ( n − 1 k + 1 ) ) . {\displaystyle \gcd \left({n-1 \choose k-2},{n-1 \choose k-1},{n-1 \choose k},{n-1 \choose k+1}\right).} [ 1 ] Thus in the above example for the element 84 (in its rightmost appearance), we also have gcd(70, 56, 28, 8) = 2. This result in turn has further generalizations.
The two sets of three numbers which the Star of David theorem says have equal greatest common divisors also have equal products. [ 1 ] For example, again observing that the element 84 is surrounded by, in sequence, the elements 28, 56, 126, 210, 120, 36, and again taking alternating values, we have 28×126×120 = 2 6 ×3 3 ×5×7 2 = 56×210×36. This result can be confirmed by writing out each binomial coefficient in factorial form, using | https://en.wikipedia.org/wiki/Star_of_David_theorem |
A star party is a gathering of amateur astronomers for the purpose of observing objects and events in the sky . Local star parties may be one-night affairs, but larger events can last a week or longer and attract hundreds or even thousands of participants. Many astronomy clubs have monthly star parties during the warmer months. Large regional star parties are held annually and are an important part of the hobby of amateur astronomy. A naturally dark site away from light pollution is typical.
Participants bring telescopes and binoculars of all types and sizes and spend the nights observing astronomical objects such as planets , comets , stars , and deep-sky objects together. Astrophotography and CCD imaging are also very popular. At larger star parties, lectures, swap meets, exhibitions of home-built telescopes , contests, tours, raffles, and other similar activities are common. Commercial vendors selling a variety of astronomical equipment may also be present. As with other hobbyist gatherings, much camaraderie and discussion of various aspects of the hobby occurs at any star party.
The idea of a star party is not new and allegedly goes back at least as far as George III of the United Kingdom , who was passionately interested in astronomy and mathematics . [ 1 ] [ 2 ] On nights when poor weather blocked the view of the real stars and planets, attendants are said to have hung paper lanterns marked with drawings in the trees around the royal palace to provide something else for the King and his guests to spot through their telescopes.
Star parties whose focus is on bringing the stars to the people are often staged in urban areas where people congregate in large numbers. This is in contrast to star parties typically held in remote dark-sky areas more conducive to stargazing.
In the US, notable star parties include the annual Winter Star Party , held in the Florida Keys; the Mid Atlantic Star Party , held on the east coast of the United States; the Oregon Star Party ; the Stellafane Convention , held in Vermont; the Texas Star Party , held in west Texas; and the Okie-Tex Star Party, held near Kenton, Oklahoma. In Canada, Starfest, held near Ayton, Ontario, is organized by the North York Astronomical Association . In the United Kingdom, notable annual star parties include the Spring [1] and Autumn [2] Equinox star parties held at Kelling Heath Holiday Park [3] and Kielder [4] in Northumbria. In Australia, the South Pacific Star Party is held each year. In Sri Lanka, Star Party Sri Lanka is held annually at the University of Peradeniya premises. | https://en.wikipedia.org/wiki/Star_party |
In mathematics , the star product is a method of combining graded posets with unique minimal and maximal elements, preserving the property that the posets are Eulerian .
The star product of two graded posets ( P , ≤ P ) {\displaystyle (P,\leq _{P})} and ( Q , ≤ Q ) {\displaystyle (Q,\leq _{Q})} , where P {\displaystyle P} has a unique maximal element 1 ^ {\displaystyle {\widehat {1}}} and Q {\displaystyle Q} has a unique minimal element 0 ^ {\displaystyle {\widehat {0}}} , is a poset P ∗ Q {\displaystyle P*Q} on the set ( P ∖ { 1 ^ } ) ∪ ( Q ∖ { 0 ^ } ) {\displaystyle (P\setminus \{{\widehat {1}}\})\cup (Q\setminus \{{\widehat {0}}\})} . We define the partial order ≤ P ∗ Q {\displaystyle \leq _{P*Q}} by x ≤ y {\displaystyle x\leq y} if and only if:
In other words, we pluck out the top of P {\displaystyle P} and the bottom of Q {\displaystyle Q} , and require that everything in P {\displaystyle P} be smaller than everything in Q {\displaystyle Q} .
For example, suppose P {\displaystyle P} and Q {\displaystyle Q} are the Boolean algebra on two elements.
Then P ∗ Q {\displaystyle P*Q} is the poset with the Hasse diagram below.
The star product of Eulerian posets is Eulerian.
This article incorporates material from star product on PlanetMath , which is licensed under the Creative Commons Attribution/Share-Alike License . | https://en.wikipedia.org/wiki/Star_product |
A star tracker is an optical device that measures the positions of stars using photocells or a camera. [ 1 ] As the positions of many stars have been measured by astronomers to a high degree of accuracy, a star tracker on a satellite or spacecraft may be used to determine the orientation (or attitude ) of the spacecraft with respect to the stars. In order to do this, the star tracker must obtain an image of the stars, measure their apparent position in the reference frame of the spacecraft, and identify the stars so their position can be compared with their known absolute position from a star catalog. A star tracker may include a processor to identify stars by comparing the pattern of observed stars with the known pattern of stars in the sky.
In the 1950s and early 1960s, star trackers were an important part of early long-range ballistic missiles and cruise missiles , in the era when inertial navigation systems (INS) were not sufficiently accurate for intercontinental ranges. [ 2 ]
Consider a Cold War missile flying towards its target; it initially starts by flying northward, passes over the arctic, and then begins flying southward again. From the missile's perspective, stars behind it appear to move closer to the southern horizon while those in front are rising. Before flight, one can calculate the relative angle of a star based on where the missile should be at that instant if it is in the correct location. That can then be compared to the measured location to produce an "error off" signal that can be used to bring the missile back onto its correct trajectory. [ 2 ]
Due to the Earth's rotation, stars that are in a usable location change over the course of a day and the location of the target. Generally, a selection of several bright stars would be used and one would be selected at launch time. For guidance systems based solely on star tracking, some sort of recording mechanism, typically a magnetic tape , was pre-recorded with a signal that represented the angle of the star over the period of a day. At launch, the tape was forwarded to the appropriate time. [ 2 ] During the flight, the signal on the tape was used to roughly position a telescope so it would point at the expected position of the star. At the telescope's focus was a photocell and some sort of signal-generator, typically a spinning disk known as a chopper . The chopper causes the image of the star to repeatedly appear and disappear on the photocell, producing a signal that was then smoothed to produce an alternating current output. The phase of that signal could be compared to the phase of the chopper to determine angle to the star and this angle could be compared to the expected one on the tape to produce a guidance signal. [ 2 ] Choppers combined with lock-in amplifiers can also help to provide immunity to noise.
Star trackers were often combined with an INS. INS systems measure accelerations and integrate those over time to determine a velocity and, optionally, double-integrate to produce a location relative to its launch location. Even tiny measurement errors, when integrated, add up to an appreciable error known as "drift". For instance, the N-1 navigation system developed for the SM-64 Navaho cruise missile drifted at a rate of 1 nautical mile per hour, meaning that after a two-hour flight the INS would be indicating a position 2 nautical miles (3.7 km; 2.3 mi) away from its actual location. This was outside the desired accuracy of about half a mile.
In the case of an INS, the magnetic tape can be removed and those signals instead provided by the INS. The rest of the system works as before; the signal from the INS roughly positions the star tracker, which then measures the actual location of the star and produces an error signal. This signal is then used to correct the position being generated from the INS, reducing the accumulated drift back to the limit of the accuracy of the tracker. [ 2 ] These "stellar inertial" systems were especially common from the 1950s through the 1980s, although some systems use it to this day. [ 3 ] [ 4 ]
Many models [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] are currently available. There also exist open projects designed to be used for the global CubeSat researchers' and developers' community. [ 10 ] [ 11 ] Star trackers, which require high sensitivity, may become confused by sunlight reflected from the spacecraft, or by exhaust gas plumes from the spacecraft thrusters (either sunlight reflection or contamination of the star tracker window). Star trackers are also susceptible to a variety of errors (low spatial frequency, high spatial frequency, temporal, ...) in addition to a variety of optical sources of error ( spherical aberration , chromatic aberration , etc.). There are also many potential sources of confusion for the star identification algorithm ( planets , comets , supernovae , the bimodal character of the point spread function for adjacent stars, other nearby satellites, point-source light pollution from large cities on Earth, ...). There are roughly 57 bright navigational stars in common use. However, for more complex missions, entire star field databases are used to determine spacecraft orientation. A typical star catalogue for high-fidelity attitude determination is originated from a standard base catalog (for example from the United States Naval Observatory ) and then filtered to remove problematic stars, for example due to apparent magnitude variability, color index uncertainty, or a location within the Hertzsprung-Russell diagram implying unreliability. These types of star catalogs can have thousands of stars stored in memory on board the spacecraft, or else processed using tools at the ground station and then uploaded. [ citation needed ] As space situational awareness sensors, star trackers can be used for space debris detection [ 12 ] and for satellite identification. [ 13 ] | https://en.wikipedia.org/wiki/Star_tracker |
A star trail is a type of photograph that uses long exposure times to capture diurnal circles , the apparent motion of stars in the night sky due to Earth's rotation . A star-trail photograph shows individual stars as streaks across the image, with longer exposures yielding longer arcs . The term is used for similar photos captured elsewhere, such as on board the International Space Station and on Mars . [ 2 ] [ 3 ]
Typical shutter speeds for a star trail range from 15 minutes to several hours, requiring a " Bulb " setting on the camera to open the shutter for a period longer than usual. However, a more practiced technique is to blend a number of frames together to create the final star trail image. [ 4 ]
Star trails have been used by professional astronomers to measure the quality of observing locations for major telescopes .
Star trail photographs are captured by placing a camera on a tripod , pointing the lens toward the night sky , and allowing the shutter to stay open for a long period of time. [ 5 ] Star trails are considered relatively easy for amateur astrophotographers to create. [ 6 ] Photographers generally make these images by using a DSLR or Mirrorless camera with its lens focus set to infinity. A cable release or intervalometer allows the photographer to hold the shutter open for the desired amount of time. Typical exposure times range from 15 minutes to many hours long, depending on the desired length of the star trail arcs for the image. [ 7 ] Even though star trail pictures are created under low-light conditions, long exposure times allow fast films , such as ISO 200 and ISO 400. [ 6 ] Wide-apertures, such as f/5.6 and f/4, are recommended for star trails. [ 5 ] [ 8 ]
Because exposure times for star trail photographs can be several hours long, camera batteries can be easily depleted. Mechanical cameras that do not require a battery to open and close the shutter have an advantage over more modern film and digital cameras that rely on battery power. On these cameras, the Bulb , or B, exposure setting keeps the shutter open. [ 9 ] Another problem that digital cameras encounter is an increase in electronic noise with increasing exposure time. [ 5 ] However, this can be avoided through the use of shorter exposure times that are then stacked in post production software. This avoids possible heat build up or digital noise caused from a single long exposure.
American astronaut Don Pettit recorded star trails with a digital camera from the International Space Station in Earth orbit between April and June, 2012. Pettit described his technique as follows: "My star trail images are made by taking a time exposure of about 10 to 15 minutes. However, with modern digital cameras, 30 seconds is about the longest exposure possible, due to electronic detector noise effectively snowing out the image. To achieve the longer exposures I do what many amateur astronomers do. I take multiple 30-second exposures, then 'stack' them using imaging software , thus producing the longer exposure." [ 10 ] [ 2 ]
Star trail images have also been taken on Mars. [ 11 ] The Spirit rover produced them while looking for meteors. [ 11 ] Since the camera was limited to 60 second exposures the trails appear as dashed lines. [ 11 ]
Star trail photographs are possible because of the rotation of Earth about its axis. The apparent motion of the stars is recorded as mostly curved streaks on the film or detector. [ 5 ] For observers in the Northern Hemisphere , aiming the camera northward creates an image with concentric circular arcs centered on the north celestial pole (very near Polaris ). [ 6 ] For those in the Southern Hemisphere , this same effect is achieved by aiming the camera southward. In this case, the arc streaks are centered on the south celestial pole (near Sigma Octantis ). Aiming the camera eastward or westward shows straight streaks on the celestial equator , which is tilted at angle with respect to the horizon . The angular measure of this tilt depends on the photographer's latitude [ 5 ] ( L ), and is equal to 90° − L .
Star trail photographs can be used by astronomers to determine the quality of a location for telescope observations. Star trail observations of Polaris have been used to measure the quality of seeing in the atmosphere, and the vibrations in telescope mounting systems. [ 12 ] The first recorded suggestion of this technique is from E.S. Skinner's 1931 book A Manual of Celestial Photography . [ 13 ] | https://en.wikipedia.org/wiki/Star_trail |
A star transit is the passage of a star across the field of view of a telescope eyepiece .
The precise observation of star transits is the basis of many methods in astronomy and in geodesy . The measurements can be done in different ways:
This astronomy -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Star_transit |
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds . This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in staple foods such as wheat , potatoes , maize (corn), rice , and cassava (manioc).
Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol . It consists of two types of molecules: the linear and helical amylose and the branched amylopectin . Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight. [ 4 ] Glycogen , the energy reserve of animals, is a more highly branched version of amylopectin.
In industry, starch is often converted into sugars, for example by malting . These sugars may be fermented to produce ethanol in the manufacture of beer , whisky and biofuel . In addition, sugars produced from processed starch are used in many processed foods.
Mixing most starches in warm water produces a paste, such as wheatpaste , which can be used as a thickening, stiffening or gluing agent. The principal non-food, industrial use of starch is as an adhesive in the papermaking process. A similar paste, clothing or laundry starch , can be applied to certain textile goods before ironing to stiffen them.
The word starch is from a Germanic root with the meanings "strong, stiff, strengthen, stiffen". [ 5 ]
Modern German Stärke (strength, starch) is related and refers to the main historical applications, its uses in textiles: sizing yarn for weaving , and starching linen .
The Greek term for starch, amylon (ἄμυλον), which means "not milled", is also related. It provides the root amyl , which is used as a prefix for several carbon compounds related to or derived from starch (e.g. amyl alcohol , amylose , amylopectin ).
Starch grains from the rhizomes of Typha (cattails, bullrushes) as flour have been identified from grinding stones in Europe dating back to 30,000 years ago. [ 6 ] Starch grains from sorghum were found on grind stones in caves in Ngalue , Mozambique dating up to 100,000 years ago. [ 7 ]
Pure extracted wheat starch paste was used in Ancient Egypt , possibly to glue papyrus . [ 8 ] The extraction of starch is first described in the Natural History of Pliny the Elder around 77–79 CE . [ 9 ] Romans used it also in cosmetic creams, to powder the hair and to thicken sauces. Persians and Indians used it to make dishes similar to gothumai wheat halva . Rice starch as surface treatment of paper has been used in paper production in China since 700 CE. [ 10 ] In the mid eighth century production of paper that was sized with wheat starch started in the Arabic world. [ 11 ] Laundry starch was first described in England in the beginning of the 15th century and was essential to make 16th century ruffed collars . [ 12 ]
Plants produce glucose from carbon dioxide and water by photosynthesis . The glucose is used to generate the chemical energy required for general metabolism as well as a precursor to myriad organic building blocks such as nucleic acids , lipids , proteins , and structural polysaccharides such as cellulose . Most green plants store any extra glucose in the form of starch, which is packed into semicrystalline granules called starch granules or amyloplasts . [ 13 ] Toward the end of the growing season, starch accumulates in twigs of trees near the buds. Fruit , seeds , rhizomes , and tubers store starch to prepare for the next growing season. Young plants live on this stored energy in their roots, seeds, and fruits until they can find suitable soil in which to grow. [ 14 ] The starch is also consumed at night when photosynthesis is not occurring.
Green algae and land-plants store their starch in the plastids , whereas red algae , glaucophytes , cryptomonads , dinoflagellates and the parasitic apicomplexa store a similar type of polysaccharide called floridean starch in their cytosol or periplast . [ 15 ]
Especially when hydrated, glucose takes up much space and is osmotically active. Starch, on the other hand, being insoluble and therefore osmotically inactive, can be stored much more compactly. The semicrystalline granules generally consist of concentric layers of amylose and amylopectin which can be made bioavailable upon cellular demand in the plant. [ 16 ]
Amylose consists of long chains derived from glucose molecules connected by α-1,4- glycosidic linkage . Amylopectin is highly branched but also derived from glucose interconnected by α-1,6- glycosidic linkages. The same type of linkage is found in the animal reserve polysaccharide glycogen . By contrast, many structural polysaccharides such as chitin , cellulose, and peptidoglycan are linked by β-glycosidic bonds , which are more resistant to hydrolysis. [ 17 ]
Within plants, starch is stored in semi-crystalline granules. Each plant species has a distinctive starch granular size: rice starch is relatively small (about 2 μm), potato starches have larger granules (up to 100 μm) while wheat and tapioca fall in-between. [ 18 ] Unlike other botanical sources of starch, wheat starch has a bimodal size distribution, with both smaller and larger granules ranging from 2 to 55 μm. [ 18 ]
Some cultivated plant varieties have pure amylopectin starch without amylose, known as waxy starches . The most used is waxy maize , others are glutinous rice and waxy potato starch . Waxy starches undergo less retrogradation , resulting in a more stable paste. A maize cultivar with a relatively high proportion of amylose starch, amylomaize , is cultivated for the use of its gel strength and for use as a resistant starch (a starch that resists digestion) in food products.
Plants synthesize starch in two types of tissues. The first type is storage tissues, for example, cereal endosperm, and storage roots and stems such as cassava and potato. The second type is green tissue, for example, leaves, where many plant species synthesize transitory starch on a daily basis. In both tissue types, starch is synthesized in plastids (amyloplasts and chloroplasts).
The biochemical pathway involves conversion of glucose 1-phosphate to ADP -glucose using the enzyme glucose-1-phosphate adenylyltransferase . This step requires energy in the form of ATP . A number of starch synthases available in plastids then adds the ADP-glucose via α-1,4- glycosidic bond to a growing chain of glucose residues, liberating ADP . The ADP-glucose is almost certainly added to the non-reducing end of the amylose polymer, as the UDP-glucose is added to the non-reducing end of glycogen during glycogen synthesis . [ 19 ] The small glucan chain, further agglomerate to form initials of starch granules.
The biosynthesis and expansion of granules represent a complex molecular event that can be subdivided into four major steps, namely, granule initiation, coalescence of small granules, [ 20 ] phase transition, and expansion. Several proteins have been characterized for their involvement in each of these processes. For instance, a chloroplast membrane-associated protein, MFP1, determines the sites of granule initiation. [ 21 ] Another protein named PTST2 binds to small glucan chains and agglomerates to recruit starch synthase 4 (SS4). [ 22 ] Three other proteins, namely, PTST3, SS5, and MRC, are also known to be involved in the process of starch granule initiation. [ 23 ] [ 24 ] [ 25 ] Furthermore, two proteins named ESV and LESV play a role in the aqueous-to-crystalline phase transition of glucan chains. [ 26 ] Several catalytically active starch synthases, such as SS1, SS2, SS3, and GBSS, are critical for starch granule biosynthesis and play a catalytic role at each step of granule biogenesis and expansion. [ 27 ]
In addition to above proteins, starch branching enzymes (BEs) introduces α-1,6-glycosidic bonds between the glucose chains, creating the branched amylopectin. The starch debranching enzyme (DBE) isoamylase removes some of these branches. Several isoforms of these enzymes exist, leading to a highly complex synthesis process. [ 28 ]
The starch that is synthesized in plant leaves during the day is transitory: it serves as an energy source at night. Enzymes catalyze release of glucose from the granules. The insoluble, highly branched starch chains require phosphorylation in order to be accessible for degrading enzymes. The enzyme glucan, water dikinase (GWD) installs a phosphate at the C-6 position of glucose, close to the chain's 1,6-alpha branching bonds. A second enzyme, phosphoglucan, water dikinase (PWD) phosphorylates the glucose molecule at the C-3 position. After the second phosphorylation, the first degrading enzyme, beta-amylase (BAM) attacks the glucose chain at its non-reducing end. Maltose is the main product released. If the glucose chain consists of three or fewer molecules, BAM cannot release maltose. A second enzyme, disproportionating enzyme-1 (DPE1), combines two maltotriose molecules. From this chain, a glucose molecule is released. Now, BAM can release another maltose molecule from the remaining chain. This cycle repeats until starch is fully degraded. If BAM comes close to the phosphorylated branching point of the glucose chain, it can no longer release maltose. In order for the phosphorylated chain to be degraded, the enzyme isoamylase (ISA) is required. [ 29 ]
The products of starch degradation are predominantly maltose [ 30 ] and smaller amounts of glucose. These molecules are exported from the plastid to the cytosol, maltose via the maltose transporter and glucose by the plastidic glucose translocator (pGlcT). [ 31 ] These two sugars are used for sucrose synthesis. Sucrose can then be used in the oxidative pentose phosphate pathway in the mitochondria, to generate ATP at night. [ 29 ]
In addition to starchy plants consumed directly, 66 million tonnes of starch were processed industrially in 2008. By 2011, production had increased to 73 million tons. [ 32 ]
In the EU the starch industry produced about 11 million tonnes in 2011, with around 40% being used for industrial applications and 60% for food uses, [ 33 ] most of the latter as glucose syrups . [ 34 ] In 2017 EU production was 11 million ton of which 9,4 million ton was consumed in the EU and of which 54% were starch sweeteners. [ 35 ]
The US produced about 27.5 million tons of starch in 2017, of which about 8.2 million tons was high fructose syrup , 6.2 million tons was glucose syrups, and 2.5 million tons were starch products. [ clarification needed ] The rest of the starch was used for producing ethanol (1.6 billion gallons). [ 36 ] [ 37 ]
The starch industry extracts and refines starches from crops by wet grinding, washing, sieving and drying. Today, the main commercial refined starches are cornstarch , tapioca , arrowroot, [ 38 ] and wheat, rice, and potato starches . To a lesser extent, sources of refined starch are sweet potato, sago and mung bean. To this day, starch is extracted from more than 50 types of plants.
Crude starch is processed on an industrial scale to maltodextrin and glucose syrups and fructose syrups. These massive conversions are mediated by a variety of enzymes, which break down the starch to varying extents. Here breakdown involves hydrolysis, i.e. cleavage of bonds between sugar subunits by the addition of water. Some sugars are isomerized. The processes have been described as occurring in two phases: liquefaction and saccharification. The liquefaction converts starch into dextrins . Amylase is a key enzyme for producing dextrin. The saccharification converts dextrin into maltoses and glucose. Diverse enzymes are used in this second phase, including pullanase and other amylases. [ 39 ]
If starch is subjected to dry heat, it breaks down to form dextrins , also called "pyrodextrins" in this context. This break down process is known as dextrinization. (Pyro)dextrins are mainly yellow to brown in color and dextrinization is partially responsible for the browning of toasted bread. [ 40 ]
Starch is the most common carbohydrate in the human diet and is contained in many staple foods . The major sources of starch intake worldwide are the cereals ( rice , wheat , and maize ) and the root vegetables ( potatoes and cassava ). [ 41 ] Many other starchy foods are grown, some only in specific climates, including acorns , arrowroot , arracacha , bananas , barley , breadfruit , buckwheat , canna , colocasia , cuckoo-pint , katakuri , kudzu , malanga , millet , oats , oca , polynesian arrowroot , sago , sorghum , sweet potatoes , rye , taro , chestnuts , water chestnuts , and yams , and many kinds of beans , such as favas , lentils , mung beans , peas , and chickpeas .
Before processed foods, people consumed large amounts of uncooked and unprocessed starch-containing plants, which contained high amounts of resistant starch . Microbes within the large intestine ferment or consume the starch, producing short-chain fatty acids , which are used as energy, and support the maintenance and growth of the microbes. Upon cooking, starch is transformed from an insoluble, difficult-to-digest granule into readily accessible glucose chains with very different nutritional and functional properties. [ 42 ]
In current diets, highly processed foods are more easily digested and release more glucose in the small intestine—less starch reaches the large intestine and more energy is absorbed by the body. It is thought that this shift in energy delivery (as a result of eating more processed foods) may be one of the contributing factors to the development of metabolic disorders of modern life, including obesity and diabetes. [ 43 ]
The amylose/amylopectin ratio, molecular weight and molecular fine structure influences the physicochemical properties as well as energy release of different types of starches. [ 44 ] In addition, cooking and food processing significantly impacts starch digestibility and energy release. Starch has been classified as rapidly digestible starch, slowly digestible starch and resistant starch, depending upon its digestion profile. [ 45 ] Raw starch granules resist digestion by human enzymes and do not break down into glucose in the small intestine - they reach the large intestine instead and function as prebiotic dietary fiber . [ 46 ] When starch granules are fully gelatinized and cooked, the starch becomes easily digestible and releases glucose quickly within the small intestine. When starchy foods are cooked and cooled, some of the glucose chains re-crystallize and become resistant to digestion again. Slowly digestible starch can be found in raw cereals, where digestion is slow but relatively complete within the small intestine. [ 47 ] Widely used prepared foods containing starch are bread , pancakes , cereals , noodles , pasta , porridge and tortilla .
During cooking with high heat, sugars released from starch can react with amino acids via the Maillard reaction , forming advanced glycation end-products (AGEs), contributing aromas, flavors and texture to foods. [ 48 ] One example of a dietary AGE is acrylamide . Recent evidence suggests that the intestinal fermentation of dietary AGEs may be associated with insulin resistance , atherosclerosis , diabetes and other inflammatory diseases. [ 49 ] [ 50 ] This may be due to the impact of AGEs on intestinal permeability. [ 51 ]
Starch gelatinization during cake baking can be impaired by sugar competing for water , preventing gelatinization and improving texture.
Starch can be hydrolyzed into simpler carbohydrates by acids , various enzymes , or a combination of the two. The resulting fragments are known as dextrins . The extent of conversion is typically quantified by dextrose equivalent (DE), which is roughly the fraction of the glycosidic bonds in starch that have been broken.
These starch sugars are by far the most common starch based food ingredient and are used as sweeteners in many drinks and foods. They include:
The modified food starches are E coded according to European Food Safety Authority and INS coded Food Additives according to the Codex Alimentarius : [ 55 ]
INS 1400, 1401, 1402, 1403 and 1405 are in the EU food ingredients without an E-number. [ 56 ] Typical modified starches for technical applications are cationic starches , hydroxyethyl starch , carboxymethylated starches and thiolated starches. [ 57 ]
As an additive for food processing , food starches are typically used as thickeners and stabilizers in foods such as puddings, custards, soups, sauces, gravies, pie fillings, and salad dressings, and to make noodles and pastas. They function as thickeners, extenders, emulsion stabilizers and are exceptional binders in processed meats.
Gummed sweets such as jelly beans and wine gums are not manufactured using a mold in the conventional sense. A tray is filled with native starch and leveled. A positive mold is then pressed into the starch leaving an impression of 1,000 or so jelly beans. The jelly mix is then poured into the impressions and put onto a stove to set. This method greatly reduces the number of molds that must be manufactured.
Resistant starch is starch that escapes digestion in the small intestine of healthy individuals. High-amylose starch from wheat or corn has a higher gelatinization temperature than other types of starch, and retains its resistant starch content through baking , mild extrusion and other food processing techniques. It is used as an insoluble dietary fiber in processed foods such as bread, pasta, cookies, crackers, pretzels and other low moisture foods. It is also utilized as a dietary supplement for its health benefits. Published studies have shown that resistant starch helps to improve insulin sensitivity, [ 58 ] [ 59 ] reduces pro-inflammatory biomarkers interleukin 6 and tumor necrosis factor alpha [ 60 ] [ 61 ] and improves markers of colonic function. [ 62 ] It has been suggested that resistant starch contributes to the health benefits of intact whole grains. [ 63 ]
A cell-free chemoenzymatic process has been demonstrated to synthesize starch from CO 2 and hydrogen. The chemical pathway of 11 core reactions was drafted by computational pathway design and converts CO 2 to starch at a rate that is ~8.5-fold higher than starch synthesis in maize . [ 64 ] [ 65 ]
Papermaking is the largest non-food application for starches globally, consuming many millions of metric tons annually. [ 33 ] In a typical sheet of copy paper for instance, the starch content may be as high as 8%. Both chemically modified and unmodified starches are used in papermaking. In the wet part of the papermaking process, generally called the "wet-end", the starches used are cationic and have a positive charge bound to the starch polymer. These starch derivatives associate with the anionic or negatively charged paper fibers / cellulose and inorganic fillers. Cationic starches together with other retention and internal sizing agents help to give the necessary strength properties to the paper web formed in the papermaking process ( wet strength ), and to provide strength to the final paper sheet (dry strength).
In the dry end of the papermaking process, the paper web is rewetted with a starch based solution. The process is called surface sizing . Starches used have been chemically, or enzymatically depolymerized at the paper mill or by the starch industry (oxidized starch). The size/starch solutions are applied to the paper web by means of various mechanical presses (size presses). Together with surface sizing agents the surface starches impart additional strength to the paper web and additionally provide water hold out or "size" for superior printing properties. Starch is also used in paper coatings as one of the binders for the coating formulations which include a mixture of pigments, binders and thickeners. Coated paper has improved smoothness, hardness, whiteness and gloss and thus improves printing characteristics.
Corrugated board adhesives are the next largest application of non-food starches globally. Starch glues are mostly based on unmodified native starches, plus some additive such as borax and caustic soda . Part of the starch is gelatinized to carry the slurry of uncooked starches and prevent sedimentation. This opaque glue is called a SteinHall adhesive. The glue is applied on tips of the fluting. The fluted paper is pressed to paper called liner. This is then dried under high heat, which causes the rest of the uncooked starch in glue to swell/gelatinize. This gelatinizing makes the glue a fast and strong adhesive for corrugated board production.
Starch is used in the manufacture of various adhesives or glues [ 66 ] for book-binding, wallpaper adhesives , paper sack production, tube winding, gummed paper , envelope adhesives, school glues and bottle labeling. Starch derivatives, such as yellow dextrins, can be modified by addition of some chemicals to form a hard glue for paper work; some of those forms use borax or soda ash , which are mixed with the starch solution at 50–70 °C (122–158 °F) to create a very good adhesive. Sodium silicate can be added to reinforce these formula.
A related large non-food starch application is in the construction industry, where starch is used in the gypsum wall board manufacturing process. Chemically modified or unmodified starches are added to the stucco containing primarily gypsum . Top and bottom heavyweight sheets of paper are applied to the formulation, and the process is allowed to heat and cure to form the eventual rigid wall board. The starches act as a glue for the cured gypsum rock with the paper covering, and also provide rigidity to the board.
A solution of triiodide (I 3 − ) (formed by mixing iodine and potassium iodide ) can be used to test for starch. The colorless solution turns dark blue in the presence of starch. [ 70 ] The strength of the resulting blue color depends on the amount of amylose present. Waxy starches with little or no amylose present will color red. Benedict's test and Fehling's test is also done to indicate the presence of starch.
In the US, the Occupational Safety and Health Administration (OSHA) has set the legal limit ( Permissible exposure limit ) for starch exposure in the workplace as 15 mg/m 3 total exposure and 5 mg/m 3 respiratory exposure over an eight-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 10 mg/m 3 total exposure and 5 mg/m 3 respiratory exposure over an eight-hour workday. [ 71 ] | https://en.wikipedia.org/wiki/Starch |
Starch gelatinization is a process of breaking down of intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen bonding sites (the hydroxyl hydrogen and oxygen) to engage more water. This irreversibly dissolves the starch granule in water. Water acts as a plasticizer .
Three main processes happen to the starch granule: granule swelling, crystallite and double-helical melting, and amylose leaching .
The gelatinization temperature of starch depends upon plant type and the amount of water present, pH , types and concentration of salt, sugar, fat and protein in the recipe, as well as starch derivatisation technology are used. Some types of unmodified native starches start swelling at 55 °C, other types at 85 °C. [ 3 ] The gelatinization temperature of modified starch depends on, for example, the degree of cross-linking , acid treatment, or acetylation.
Gel temperature can also be modified by genetic manipulation of starch synthase genes. [ 4 ] Gelatinization temperature also depends on the amount of damaged starch granules; these will swell faster. Damaged starch can be produced, for example, during the wheat milling process, or when drying the starch cake in a starch plant. [ 5 ] There is an inverse correlation between gelatinization temperature and glycemic index . [ 4 ] High amylose starches require more energy to break up bonds to gelatinize into starch molecules.
Gelatinization improves the availability of starch for amylase hydrolysis . So gelatinization of starch is used constantly in cooking to make the starch digestible or to thicken/bind water in roux , sauce , or soup .
Gelatinized starch, when cooled for a long enough period (hours or days), will thicken (or gel ) and rearrange itself again to a more crystalline structure; this process is called retrogradation . During cooling, starch molecules gradually aggregate to form a gel. The following molecular associations can occur: amylose-amylose, amylose-amylopectin, and amylopectin-amylopectin. A mild association amongst chains come together with water still embedded in the molecule network.
Due to strong associations of hydrogen bonding, longer amylose molecules (and starch which has a higher amylose content) will form a stiff gel. [ 6 ] Amylopectin molecules with longer branched structure, which makes them more similar to amylose, increases the tendency to form strong gels. High amylopectin starches will have a stable gel, but will be softer than high amylose gels.
Retrogradation restricts the availability for amylase hydrolysis to occur, which reduces the digestibility of the starch.
Pregelatinized starch ( Dextrin ) is starch which has been cooked and then dried in the starch factory on a drum dryer or in an extruder making the starch cold-water-soluble. Spray dryers are used to obtain dry starch sugars and low viscous pregelatinized starch powder. [ citation needed ]
A simple technique to study starch gelation is by using a Brabender Viscoamylograph . [ citation needed ] It is a common technique used by food industries to determine the pasting temperature, swelling capacity, shear/thermal stability, and the extent of retrogradation. Under controlled conditions, starch and distilled water is heated at a constant heating rate in a rotating bowl and then cooled down. The viscosity of the mixture deflects a measuring sensor in the bowl. This deflection is measured as viscosity in torque over time vs. temperature and recorded on the computer. The viscoamylograph allows us to observe: the beginning of gelatinization, gelatinization maximum, gelatinization temperature, viscosity during holding, and viscosity at the end of cooling. [ 7 ]
Differential scanning calorimetry (DSC) is another method industries use to examine properties of gelatinized starch. As water is heated with starch granules, gelatinization occurs, involving an endothermic reaction. [ 8 ]
The initiation of gelatinization is called the T-onset. T-peak is the position where the endothermic reaction occurs at the maximum. T-conclusion is when all the starch granules are fully gelatinized and the curve remains stable. | https://en.wikipedia.org/wiki/Starch_gelatinization |
A starch mogul is a machine that makes shaped candies or candy centers from syrups or gels, such as gummi candy . [ 1 ] These softer candies and centers are made by filling a tray with cornstarch , stamping the desired shape into the starch, and then pouring the filling or gel into the holes made by the stamp. When the candies have set, they are removed from the trays and the starch is recycled.
Starch moguls were invented around 1899 and were in common use within the next two decades. [ 1 ] Early designs were built from wood, though were later fabricated in steel.
Starch moguls reduced the number of jobs in candy factories and thereby lowered production costs for candies. [ 1 ] All of the steps were previously performed by hand.
Starch moguls also improved worker safety. Previously, starch rooms tended to have dangerously high levels of starch in the air. Workers would breathe this and develop respiratory illnesses. By reducing the amount of combustible starch in the air, the machines also significantly reduced the risk of dust explosions and fire. [ 1 ]
The starch mogul system is a method of molding candy that allows for the use of materials that are more runny compared to normal processes. It is used in the manufacture of jelly beans [ 2 ] and gummy bears , [ 3 ] [ 4 ] and was formerly used in the manufacture of marshmallows before the advent of the extrusion process. [ 5 ] [ 6 ] The starch mogul system uses a machine with trays of starch. [ 7 ] Each tray has a mold firmly pushed down in it to create cavities in the starch. The cavities are then filled with the candy material, and allowed to cool or harden as necessary. During this time, the starch helps absorb excess water, making the candy moldings handleable. [ 2 ] Finally, the trays are dumped and the candy is separated from the starch, which is then dried and reused by the machine. [ 2 ] Hans Arthur Faerber, founder of NID Pty Ltd, created the current form of the starch mogul system [ 8 ] in 1952.
Potato starch is considered unsuitable, as it has a tendency to clump when drying. More typical choices are wheat, rice, or corn (maize) starch . [ 9 ] | https://en.wikipedia.org/wiki/Starch_mogul |
Starcom Systems Inc. is a company based in Jersey , Channel Islands, specializing in wireless systems for remote tracking , monitoring and protection of a variety of assets. Among the company's products are tracking and security systems for vehicles, shipping containers, merchandise and people. Its two main products are the Helios system, used for location and monitoring of vehicles, and the award-winning Watchlock padlock, which also functions as a digital security system.
The company was founded in 2004, focusing on vehicle tracking for insurance purposes. In 2005, the company introduced a vehicle location and fleet management system which was a predecessor for its later flagship product, Helios. In 2005, the company has opened its regional sales office in Argentina , followed by an office Kenya in 2008. The Helios was released to the market in 2008, followed by other tracking systems for a variety of purposes in 2012.
In 2013, Starcom Systems raised £2.7 million on London's Alternative Investment Market . [ 3 ] The company's total sales in 2013 amounted to $9 million. [ 4 ] In 2014, the company announced that it has to defer the recognition of revenues on orders due to the effects the annexation of Crimea by the Russian Federation has had on a distributor in Ukraine . [ 5 ]
Starcom Systems manufactures several systems for different tracking purposes, each designated for a specific kind of asset.
WatchLock has won the “Physical Security Product of the Year” award at the IFSEC International 2012, Security Industry Awards event. [ 11 ] | https://en.wikipedia.org/wiki/Starcom_Systems |
Founded in 1993 by ex- Microsoft development manager David Snipp [ 2 ] Stardraw is a company that makes audio/visual system integration and design software. [ 3 ]
Stardraw has two different but related sets of software both for the Audio-visual (A/V) market
Stardraw's design software is for creating documentation of audio/visual systems. This includes A/V schematics (similar to a Computer network diagram ), Rack Layouts, Presentation Drawings (Pictorial Schematics), Panel Layouts for custom metalwork, Plan View drawings, and associated reports such as Bills of Materials, Quotations and Cable Schedules.
The software includes preset equipment icons to make it quick to create an illustrations of a A/V system design.
Their software of this type includes
Stardraw control is their Integrated development environment for creating Touchscreen remote control of a wide variety of equipment.
Typical uses include room automation in boardrooms, auditoriums, museums or home theaters, where users use fixed and wireless touch-screens to control devices such as video projectors and displays, PCs, DVD and VCR players and recorders, cameras, teleconferencing systems, audio/video switchers and processing equipment, motorized projection screens, drapes, lighting, HVAC systems, and a wide variety of other types of equipment. Other common uses include entertainment systems, industrial command and control centers, security systems, hotels and restaurants.
What separates their software from rivals AMX and Crestron is that it does not require any special hardware instead it runs on any machine running Microsoft Windows , further more the drivers and scripts for it are written in the general programming language C# rather than a proprietary language and designed in a graphical environment similar to that used by Microsoft's programming languages.
The software also present a Web service interface which enables non-Windows devices to control the software for example Tablet computers such as Apple's iPad [ 4 ]
Sound & Communications Magazine - 20 Years with Stardraw.com
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Starfish , or sea stars, are radially symmetrical , star-shaped organisms of the phylum Echinodermata and the class Asteroidea . [ 1 ] Aside from their distinguishing shape, starfish are most recognized for their remarkable ability to regenerate , or regrow, arms and, in some cases, entire bodies. While most species require the central body to be intact in order to regenerate arms, a few tropical species can grow an entirely new starfish from just a portion of a severed limb. [ 2 ] Starfish regeneration across species follows a common three-phase model and can take up to a year or longer to complete. [ 2 ] Though regeneration is used to recover limbs eaten or removed by predators , starfish are also capable of autotomizing and regenerating limbs to evade predators and reproduce. [ 2 ]
Due to their wide range of regenerative capabilities, starfish have become model organisms for studying how the regenerative process has evolved and diversified over time. While the overall morphological processes have been well documented in many starfish, little is known regarding the underlying molecular mechanisms that mediate their regeneration . Moreover, some researchers hope starfish may one day serve as inspiration for therapeutics aiming to expand the extent to which humans can repair and replace damaged cells or tissues. [ 3 ]
Regenerative ability differs greatly among starfish species, but can generally be classified within three categories: unidirectional regeneration, disk-dependent bidirectional regeneration, and disk-independent bidirectional regeneration. In each case, regenerative capacity is enabled by the uniquely simple body plan of starfish . [ citation needed ]
The typical starfish has five or more arms, or "rays", radiating from a central disk. [ 4 ] Each arm contains a copy of vital organs and is equipped with eyespots , an eye-like structure that helps the starfish differentiate between light and darkness, [ 5 ] and tube feet , which enable locomotion . [ 6 ] All organs connect to the digestive system in the central disk, which also contains the starfish mouth and stomach. [ 5 ] This replication and delocalization of vital organs makes starfish especially resilient to the loss of appendages . In addition to being able to replicate organs, starfish are also capable of regenerating neuron cells. Other cells that are left over from the injury are able to become neural cells and take up functions they would not normally do. [ 7 ] Following injury or amputation , a star fish can survive with its remaining organ copies during the period of regeneration, which ranges from a few months to over a year. [ 2 ]
Though the different Asteroidea species show a great range of variation in regeneration capabilities, an overwhelming number of them have the ability to regenerate lost limbs and tube feet . [ 1 ] Star fish that exhibit unidirectional regeneration, or regeneration that is restricted to a single direction, [ 8 ] are capable of regenerating multiple lost limbs from a disk containing half or more of the original starfish. Unidirectional regeneration is the simplest form of regeneration as the majority of the disk is intact, allowing the starfish to eat, move, and escape predators during the regeneration period. Unidirectional regeneration is also the most common form of regeneration exhibited by starfish as single arms are often removed by predators or shed through autotomy . [ 2 ]
Crown-of-thorns starfish ( Acanthaster planci ), which feed on large swaths of western Pacific coral reefs , are notable unidirectional regenerators. [ 9 ] Starfish of this invasive species are extremely difficult to eradicate because of their ability to regrow when half or more of the original starfish is intact. [ 9 ] Thus, initial population control efforts championed by fishermen and conservationists in the 1960s, which involved sectioning and releasing caught starfish, may have unknowingly exacerbated population outbreaks in the western Pacific coral reefs . [ 10 ]
Bidirectional regeneration is a robust form of regeneration defined by the ability to regrow the main body axis after whole body severance. [ 8 ] [ 11 ] [ 12 ] Starfish that exhibit disk-dependent bidirectional regeneration are capable of regenerating a full starfish when less than half of the original starfish is intact, given that all or part of the central disk is present. The presence of the central disk gives the detached limb access to its original digestive system and mouth, allowing the starfish to move to find food, eat, and hide from predators during recovery. [ 12 ]
The most extensive form of regeneration exhibited by starfish species is disk-independent bidirectional regeneration. In this rare case, a detached starfish limb with no remnants of the central disk is capable of regenerating a full starfish , referred to as a comet form. [ 2 ] In the absence of a mouth or digestive system , the detached arm survives on nutrients stored in the arm until it can regenerate a disk. Without the ability to feed during recovery, disk independent bidirectional regeneration is difficult to execute and requires that the detached arm is in a relatively healthy form. [ 2 ] This vigorous form of regeneration has been identified in Linckia species to a very high degree. [ 13 ] [ 14 ]
Regeneration is an intrinsically conservative post-embryonic developmental process that repairs and replaces cells, tissues, organs, and body parts of a given organism. Furthermore, the arm regenerative process of all starfish species studied to date can be subdivided into three distinct phases: a repair phase, an early regenerative phase, and an advanced regenerative phase. Although diversity exists among starfish in terms of their physiology, morphology, and amputation susceptibility, a generalized regenerative process can be appreciated. [ 15 ] Throughout the regeneration process, the coelomic epithelium is vital. This is a tissue that plays a large role in the formation of new limbs and new organs. [ 16 ] Note, the following section details the regrowth of a starfish's arm following amputation in a unidirectional manner of regeneration.
Immediately following amputation, all starfish must seal their coelomic cavities, particularly the perivisceral coelomic canal , to prevent fluid loss and the entrance of foreign pathogens. This is initially achieved by an emergency mechanism in which the entire arm wall contracts swiftly and powerfully to form a 'hemostatic ring' of sorts. [ 17 ] [ 18 ] [ 19 ]
Additionally, in a process analogous to mammalian platelet clot formation, a morphologically heterogenous population of coelomocytes help prevent the loss of body fluid by forming a clot of cells at the injured perivisceral coelomic canal . Coelomocytes are free-wandering cells that circulate the coelomic fluid , possessing phagocytic , clotting, and cytotoxic functions in most echinoderms . These coelomocytes not only form clots at starfish amputation sites but also help clear the wound site of debris and foreign microorganisms via phagocytosis. [ 20 ]
Re-epithelialization occurs within the first 48 hours post-amputation, in the middle of the repair phase. Interestingly, in contrast to most mammals, starfish accomplish re-epithelialization without any immediate proliferation of epidermal progenitor cells at the wound edge or wound epithelium . [ 21 ] Rather, epidermal cells are stretched inwards from the wound edge, expanding centripetally until a continuous layer is formed. Of note, these stretched epidermal cells maintain their cell-cell junctions in starfish, [ 3 ] whereas in mammals, junctional complexes are disrupted to allow the migration of keratinocytes over the wound. [ 22 ] Subsequently, the wound epithelium becomes increasingly differentiated, thicker, and permanent. Moreover, in some starfish species, such as Echinaster sepositus and Acanthaster planci , a phagocytic syncytium transiently supports the migration of epithelial cells while protecting injured stump tissue from fluid loss and foreign entities. [ 17 ] [ 23 ]
Finally, the end of the repair phase is marked by the formation of a temporary edematous area below the newly established epithelial layer. Overall, this provisional tissue matures over time, to ultimately provide a scaffold for regenerative growth. [ 15 ] In many ways, the edematous area resembles the granulation tissue of mammals, possessing a disorganized mix of fibroblasts , phagocytes , nervous elements, differentiating myocytes , and undifferentiated cells. Early on, phagocytes clear the edematous area of foreign material and degrade leftover debris. Meanwhile, fibroblasts develop the extracellular matrix (ECM) and pockets of collagen fibril . [ 3 ] The area progressively matures over the span of about a week, ultimately containing a more organized extracellular matrix , dispersed collagen fibril bundles, nerve elements, early pigment cells, and other differentiated or undifferentiated cells. [ 24 ] [ 17 ]
The early regenerative phase begins once the injury has healed, and is characterized by an exodus of dedifferentiating myocytes from various anatomical structures towards the regenerating tip. [ 3 ] Throughout this phase, the regenerating coelomic cavities serve as a physical driving force of regrowth. Notably, excess fluid secretion from the coelomic epithelia produces a hypertrophic appearance in the regenerating tip of the coelomic cavities. This hypertrophic state, in turn, produces a pressure that supports the regrowth of canals, particularly the perivisceral coelom and the radial water canal . In addition, the pressure creates a turgidity that physically supports the regenerate's shape until skeleton and muscle formation can occur. [ 15 ]
The early regenerative phase is marked by a large mobilization of various cytotypes from different locations (like the coelomic cavities) towards the edematous regenerating region. [ 21 ] This proximal to distal migration of cells supports the outgrowth of the radial nerve cord from any existing nerve cord remaining post amputation. [ 25 ] Intriguingly, the radial nerve cord and radial water canal (the only two structures that run continuously along the arm) occur in tandem and potentially include an inductive cross-talk relationship. However, it is not currently known which structure induces regrowth and differentiation of the other. [ 3 ] Furthermore, initial regeneration of the radial nerve cord results from proliferation of existing structure as well as the differentiation of supporting cells that create cell ' niches ' for future neuronal growth . Specifically, the supporting cells (believed to be glial cells ) acquire a bipolar shape, implanting opposing cytoplasmic extensions containing regenerative intermediate filament bundles. Niches result from these extensions and house interspersed neurons over time. [ 21 ] [ 25 ]
A blastema -like region also appears during this phase composed of undifferentiated and barely differentiated cells amongst the epidermal tissue and coelom outgrowths (radial water canal and radial nerve cord). Moreover, the perivisceral coelom funnels undifferentiated cells to the blastema -like formation. [ 3 ] Unlike a true blastema , this blastema -like area lacks localization, contains an abundant ECM , and houses organized fiber bundles of collagen . [ 26 ] [ 19 ] As such, while starfish generally follows a morphallactic process of regrowth, the regenerative mechanisms fall somewhere in between a true morphallactic and epimorphic model , in reality. [ 21 ] [ 25 ]
Early skeletogenesis also begins during the early regenerative phase as plates of calcium carbonite deposit into the collagen network developing in the former edematous area. Importantly, near the end of the phase, a small regenerate appears. While less organized than the starfish stump, the regenerate houses the beginnings of a transverse meshwork of collagen fibers , differentiated ossicles , and stereom . Moreover, the pressurized radial water canal starts regenerating the terminal tube foot . This is the first defined structure to regenerate, as cells flow from the inner coelomic walls to the lumen of the tube feet , where they differentiate amongst rearranging muscles. [ 21 ] [ 19 ] [ 25 ]
The last phase – known as the advanced regenerative phase – consists of extensive morphogenesis and differentiation of numerous tissues across the regenerate. [ 15 ] The small regenerate that emerges from the early regenerative phase will morph into a miniature starfish arm come 3–6 months post amputation. [ 3 ] This miniaturized arm will resemble the non-regenerating arms of the starfish, and will continue growing throughout the organism's lifetime. [ 15 ]
Importantly, and especially evident in the last phase, starfish re-growth follows a "distalization-intercalary" regenerative model after arm amputation. [ 27 ] [ 28 ] In this model, the organism first forms the most distal (far away from the stump) structure during regeneration. This new structure, in turn, behaves as a signaling center to organize the development of new structures in relation to old stump tissue. Subsequently, regenerated tissues manifest – or, more accordingly, intercalate – between the limb's stump and the newly formed distal structure. [ 29 ] As noted above, the terminal tube foot is the first defined structure to appear, serving as the distal signaling center that coordinates subsequent regeneration in a proximal to distal direction. [ 21 ] [ 25 ] [ 3 ]
Massive myogenesis (formation of muscular tissue) occurs throughout the advanced regenerative phase. Majority of the muscles regenerate via the same mechanism: dedifferentiated cells from the coelomic body cavity travel towards the regenerating starfish tip before re-differentiating into muscle components. [ 30 ] [ 25 ] Meanwhile, a basal lamina gradually develops around the forming muscle tissue to separate it from the coelomic cavities. [ 3 ] In this manner, terminal tube foot formation is followed by the growth of additional tube feet , ampullae , aboral ossicles , and other musculoskeletal structures in a proximal to distal direction until regeneration is completed. [ 21 ] [ 27 ] [ 18 ] [ 3 ]
Cellular differentiation and completion of the main nervous components take place in the regenerate during this phase. For example, function is regained in the radial nerve cord as it finishes development. Additionally, a densely packed region of glial cells , dendrites , and axons called the neuropil zone reappears. [ 19 ] Over time, pigment-cupped photoreceptors called ocelli develop, leading to the full restoration of the optic cushion (collection of ocelli). [ 3 ] Notwithstanding, the specific mechanisms of neurogenesis throughout this phase remain relatively unknown: the exact role of stem cell , dedifferentiation , and cellular differentiation requires further exploration. [ 25 ]
Though starfish are well understood to utilize their regenerative capabilities to regrow arms eaten or damaged by predators, they are also capable of regenerating arms they have intentionally shed through a process known as autotomy . [ 2 ] Researchers propose that autotomy mediated regeneration may play a role in predator evasion as well as both sexual and asexual reproduction . [ 2 ]
Autotomy is understood to serve a defensive function in starfish . [ 31 ] While arms can be pulled off the starfish body by predators, the starfish can choose to shed its arm in order to evade danger. If the detached limb is eaten or extremely damaged, bidirectional regeneration is unlikely. There are two ways a starfish can lose its limbs from predators. The loss of limbs includes losing an entire limb or multiple from large prey, or flesh being eaten away by smaller prey. Large prey can eat the starfish whole, whereas smaller prey will turn over a starfish and eat at their soft flesh. [ 32 ] Although it is unlikely for bidirectional regeneration, the original starfish can regenerate its lost arm or arms through unidirectional regeneration. [ 33 ]
Starfish sexually reproduce through spawning , meaning that sex cells ( eggs and sperm ) are released into the water and fertilized outside of the body. [ 34 ] Each arm contains gonads that swell with eggs and sperm in female and male starfish, respectively. Early observations of Labidiaster starfish found that autotomized arms were swollen with mature eggs, suggesting that autotomy may be utilized for sexual propagation. Under this theory, starfish shed their arms in order to increase the range of egg dispersion and thus increase the possibility of eggs being fertilized by neighboring male starfish. [ 2 ] Once the egg has been fertilized a blastula is formed. After the formation of the blastula cilia is produced on the cell allowing the cell to move through the water. When the cell later turns into larva, the starfish larva will start to produce its organs before turning into an adult starfish. [ 7 ] The host starfish then regenerates the lost arm through unidirectional regeneration. This theory is challenged by two findings in Lamarck starfish. The first being that very young Lamarck starfish with underdeveloped gonads exhibit autonomy, [ 35 ] and the second being that in Hawaii, Lamarck starfish shed arms throughout the year irrespective of spawning season. [ 2 ]
In asexual starfish reproduction , starfish develop offspring identical to the parent. This can be achieved through arm autotomy or fission. In arm autotomy, starfish typically shed arms with part of the central disk attached. This arm regenerates into a full starfish identical to the original through disk-dependent bidirectional regeneration. In some species, disk independent bidirectional regeneration is utilized to produce new starfish. Several species also produce larvae that are capable of asexual reproduction prior to adulthood through autotomy and budding . [ 36 ]
A less commonly used form of asexual reproduction is fissiparity , reproduction via the division of the disk. [ 37 ] This phenomenon is observed in various degrees in the genres Coscinasterias , Stephanasterias , and Sclerasterias . [ 38 ] In Sclerasterian starfish, fission is restricted to young organisms, while Coscinasterian and Stephanasterian starfish maintain this ability into adulthood. Six-armed starfish capable of fission split their disk into two three-arm halves that both regenerate into a six-armed starfish. [ 2 ] Starfish with seven arms are split into a three-arm and four-arm halves, which both regenerate into a seven arm starfish. [ 2 ] | https://en.wikipedia.org/wiki/Starfish_regeneration |
The Stark effect is the shifting and splitting of spectral lines of atoms and molecules due to the presence of an external electric field . It is the electric-field analogue of the Zeeman effect , where a spectral line is split into several components due to the presence of the magnetic field . Although initially coined for the static case, it is also used in the wider context to describe the effect of time-dependent electric fields. In particular, the Stark effect is responsible for the pressure broadening (Stark broadening) of spectral lines by charged particles in plasmas . For most spectral lines, the Stark effect is either linear (proportional to the applied electric field) or quadratic with a high accuracy.
The Stark effect can be observed both for emission and absorption lines. The latter is sometimes called the inverse Stark effect , but this term is no longer used in the modern literature.
The effect is named after the German physicist Johannes Stark , who discovered it in 1913. It was independently discovered in the same year by the Italian physicist Antonino Lo Surdo . The discovery of this effect contributed importantly to the development of quantum theory and Stark was awarded with the Nobel Prize in Physics in the year 1919.
Inspired by the magnetic Zeeman effect , and especially by Hendrik Lorentz 's explanation of it, Woldemar Voigt [ 2 ] performed classical mechanical calculations of quasi-elastically bound electrons in an electric field. By using experimental indices of refraction he gave an estimate of the Stark splittings. This estimate was a few orders of magnitude too low. Not deterred by this prediction, Stark undertook measurements [ 3 ] on excited states of the hydrogen atom and succeeded in observing splittings.
By the use of the Bohr–Sommerfeld ("old") quantum theory , Paul Epstein [ 4 ] and Karl Schwarzschild [ 5 ] were independently able to derive equations for the linear and quadratic Stark effect in hydrogen . Four years later, Hendrik Kramers [ 6 ] derived formulas for intensities of spectral transitions. Kramers also included the effect of fine structure , with corrections for relativistic kinetic energy and coupling between electron spin and orbital motion. The first quantum mechanical treatment (in the framework of Werner Heisenberg 's matrix mechanics ) was by Wolfgang Pauli . [ 7 ] Erwin Schrödinger discussed at length the Stark effect in his third paper [ 8 ] on quantum theory (in which he introduced his perturbation theory), once in the manner of the 1916 work of Epstein (but generalized from the old to the new quantum theory) and once by his (first-order) perturbation approach.
Finally, Epstein reconsidered [ 9 ] the linear and quadratic Stark effect from the point of view of the new quantum theory. He derived equations for the line intensities which were a decided improvement over Kramers's results obtained by the old quantum theory.
While the first-order-perturbation (linear) Stark effect in hydrogen is in agreement with both the old Bohr–Sommerfeld model and the quantum-mechanical theory of the atom, higher-order corrections are not. [ 9 ] Measurements of the Stark effect under high field strengths confirmed the correctness of the new quantum theory.
Imagine an atom with occupied 2s and 2p electron states . In the Bohr model , these states are degenerate . However, in the presence of an external electric field, these electron orbitals will hybridize into eigenstates of the perturbed Hamiltonian (where each perturbed hybrid state can be written as a superpositon of unperturbed states). Since the 2s and 2p states have opposite parity , these hybrid states will lack inversion symmetry and will possess a time-averaged electric dipole moment. If this dipole moment is aligned with the electric field, the energy of the state will shift down; if this dipole moment is anti-aligned with the electric field, the energy of the state will shift up. Thus, the Stark effect causes a splitting of the original degeneracy.
Other things being equal, the effect of the electric field is greater for outer electron shells because the electron is more distant from the nucleus, resulting in a larger electric dipole moment upon hybridization.
The Stark effect originates from the interaction between a charge distribution (atom or molecule) and an external electric field .
The interaction energy of a continuous charge distribution ρ ( r ) {\displaystyle \rho (\mathbf {r} )} , confined within a finite volume V {\displaystyle {\mathcal {V}}} , with an external electrostatic potential ϕ ( r ) {\displaystyle \phi (\mathbf {r} )} is V i n t = ∫ V ρ ( r ) ϕ ( r ) d 3 r . {\displaystyle V_{\mathrm {int} }=\int _{\mathcal {V}}\rho (\mathbf {r} )\phi (\mathbf {r} )\,d^{3}\mathbf {r} .} This expression is valid classically and quantum-mechanically alike.
If the potential varies weakly over the charge distribution, the multipole expansion converges fast, so only a few first terms give an accurate approximation. Namely, keeping only the zero- and first-order terms, ϕ ( r ) ≈ ϕ ( 0 ) − ∑ i = 1 3 r i F i , {\displaystyle \phi (\mathbf {r} )\approx \phi (\mathbf {0} )-\sum _{i=1}^{3}r_{i}F_{i},} where we introduced the electric field F i ≡ − ( ∂ ϕ ∂ r i ) | 0 {\textstyle F_{i}\equiv -\left.\left({\frac {\partial \phi }{\partial r_{i}}}\right)\right|_{\mathbf {0} }} and assumed the origin 0 to be somewhere within V {\displaystyle {\mathcal {V}}} .
Therefore, the interaction becomes V i n t ≈ ϕ ( 0 ) ∫ V ρ ( r ) d 3 r − ∑ i = 1 3 F i ∫ V ρ ( r ) r i d 3 r ≡ q ϕ ( 0 ) − ∑ i = 1 3 μ i F i = q ϕ ( 0 ) − μ ⋅ F , {\displaystyle V_{\mathrm {int} }\approx \phi (\mathbf {0} )\int _{\mathcal {V}}\rho (\mathbf {r} )d^{3}r-\sum _{i=1}^{3}F_{i}\int _{\mathcal {V}}\rho (\mathbf {r} )r_{i}d^{3}r\equiv q\phi (\mathbf {0} )-\sum _{i=1}^{3}\mu _{i}F_{i}=q\phi (\mathbf {0} )-{\boldsymbol {\mu }}\cdot \mathbf {F} ,} where q {\displaystyle q} and μ {\displaystyle \mathbf {\mu } } are, respectively, the total charge (zero moment ) and the dipole moment of the charge distribution.
Classical macroscopic objects are usually neutral or quasi-neutral ( q = 0 {\displaystyle q=0} ), so the first, monopole, term in the expression above is identically zero. This is also the case for a neutral atom or molecule. However, for an ion this is no longer true. Nevertheless, it is often justified to omit it in this case, too. Indeed, the Stark effect is observed in spectral lines, which are emitted when an electron "jumps" between two bound states . Since such a transition only alters the internal degrees of freedom of the radiator but not its charge, the effects of the monopole interaction on the initial and final states exactly cancel each other.
Turning now to quantum mechanics an atom or a molecule can be thought of as a collection of point charges (electrons and nuclei), so that the second definition of the dipole applies. The interaction of atom or molecule with a uniform external field is described by the operator V i n t = − F ⋅ μ . {\displaystyle V_{\mathrm {int} }=-\mathbf {F} \cdot {\boldsymbol {\mu }}.} This operator is used as a perturbation in first- and second-order perturbation theory to account for the first- and second-order Stark effect.
Let the unperturbed atom or molecule be in a g -fold degenerate state with orthonormal zeroth-order state functions ψ 1 0 , … , ψ g 0 {\displaystyle \psi _{1}^{0},\ldots ,\psi _{g}^{0}} . (Non-degeneracy is the special case g = 1). According to perturbation theory the first-order energies are the eigenvalues of the g × g matrix with general element ( V i n t ) k l = ⟨ ψ k 0 | V i n t | ψ l 0 ⟩ = − F ⋅ ⟨ ψ k 0 | μ | ψ l 0 ⟩ , k , l = 1 , … , g . {\displaystyle (\mathbf {V} _{\mathrm {int} })_{kl}=\langle \psi _{k}^{0}|V_{\mathrm {int} }|\psi _{l}^{0}\rangle =-\mathbf {F} \cdot \langle \psi _{k}^{0}|{\boldsymbol {\mu }}|\psi _{l}^{0}\rangle ,\qquad k,l=1,\ldots ,g.} If g = 1 (as is often the case for electronic states of molecules) the first-order energy becomes proportional to the expectation (average) value of the dipole operator μ {\displaystyle {\boldsymbol {\mu }}} , E ( 1 ) = − F ⋅ ⟨ ψ 1 0 | μ | ψ 1 0 ⟩ = − F ⋅ ⟨ μ ⟩ . {\displaystyle E^{(1)}=-\mathbf {F} \cdot \langle \psi _{1}^{0}|{\boldsymbol {\mu }}|\psi _{1}^{0}\rangle =-\mathbf {F} \cdot \langle {\boldsymbol {\mu }}\rangle .} Since the electric dipole moment is a vector ( tensor of the first rank), the diagonal elements of the perturbation matrix V int vanish between states that have a definite parity . Atoms and molecules possessing inversion symmetry do not have a (permanent) dipole moment and hence do not show a linear Stark effect.
In order to obtain a non-zero matrix V int for systems with an inversion center it is necessary that some of the unperturbed functions ψ i 0 {\displaystyle \psi _{i}^{0}} have opposite parity (obtain plus and minus under inversion), because only functions of opposite parity give non-vanishing matrix elements. Degenerate zeroth-order states of opposite parity occur for excited hydrogen-like (one-electron) atoms or Rydberg states. Neglecting fine-structure effects, such a state with the principal quantum number n is n 2 -fold degenerate and n 2 = ∑ ℓ = 0 n − 1 ( 2 ℓ + 1 ) , {\displaystyle n^{2}=\sum _{\ell =0}^{n-1}(2\ell +1),} where ℓ {\displaystyle \ell } is the azimuthal (angular momentum) quantum number. For instance, the excited n = 4 state contains the following ℓ {\displaystyle \ell } states, 16 = 1 + 3 + 5 + 7 ⟹ n = 4 contains s ⊕ p ⊕ d ⊕ f . {\displaystyle 16=1+3+5+7\;\;\Longrightarrow \;\;n=4\;{\text{contains}}\;s\oplus p\oplus d\oplus f.} The one-electron states with even ℓ {\displaystyle \ell } are even under parity, while those with odd ℓ {\displaystyle \ell } are odd under parity. Hence hydrogen-like atoms with n >1 show first-order Stark effect.
The first-order Stark effect occurs in rotational transitions of symmetric top molecules (but not for linear and asymmetric molecules). In first approximation a molecule may be seen as a rigid rotor. A symmetric top rigid rotor has the unperturbed eigenstates | J K M ⟩ = ( D M K J ) ∗ with M , K = − J , − J + 1 , … , J {\displaystyle |JKM\rangle =(D_{MK}^{J})^{*}\quad {\text{with}}\quad M,K=-J,-J+1,\dots ,J} with 2(2 J +1)-fold degenerate energy for |K| > 0 and (2 J +1)-fold degenerate energy for K=0.
Here D J MK is an element of the Wigner D-matrix . The first-order perturbation matrix on basis of the unperturbed rigid rotor function is non-zero and can be diagonalized. This gives shifts and splittings
in the rotational spectrum. Quantitative analysis of these Stark shift yields the permanent electric dipole moment of the symmetric top molecule.
As stated, the quadratic Stark effect is described by second-order perturbation theory. The zeroth-order eigenproblem H ( 0 ) ψ k 0 = E k ( 0 ) ψ k 0 , k = 0 , 1 , … , E 0 ( 0 ) < E 1 ( 0 ) ≤ E 2 ( 0 ) , … {\displaystyle H^{(0)}\psi _{k}^{0}=E_{k}^{(0)}\psi _{k}^{0},\quad k=0,1,\ldots ,\quad E_{0}^{(0)}<E_{1}^{(0)}\leq E_{2}^{(0)},\dots } is assumed to be solved. The perturbation theory gives E k ( 2 ) = ∑ k ′ ≠ k ⟨ ψ k 0 | V i n t | ψ k ′ 0 ⟩ ⟨ ψ k ′ 0 | V i n t | ψ k 0 ⟩ E k ( 0 ) − E k ′ ( 0 ) ≡ − 1 2 ∑ i , j = 1 3 α i j F i F j {\displaystyle E_{k}^{(2)}=\sum _{k'\neq k}{\frac {\langle \psi _{k}^{0}|V_{\mathrm {int} }|\psi _{k^{\prime }}^{0}\rangle \langle \psi _{k'}^{0}|V_{\mathrm {int} }|\psi _{k}^{0}\rangle }{E_{k}^{(0)}-E_{k'}^{(0)}}}\equiv -{\frac {1}{2}}\sum _{i,j=1}^{3}\alpha _{ij}F_{i}F_{j}} with the components of the polarizability tensor α defined by α i j = − 2 ∑ k ′ ≠ k ⟨ ψ k 0 | μ i | ψ k ′ 0 ⟩ ⟨ ψ k ′ 0 | μ j | ψ k 0 ⟩ E k ( 0 ) − E k ′ ( 0 ) . {\displaystyle \alpha _{ij}=-2\sum _{k'\neq k}{\frac {\langle \psi _{k}^{0}|\mu _{i}|\psi _{k'}^{0}\rangle \langle \psi _{k'}^{0}|\mu _{j}|\psi _{k}^{0}\rangle }{E_{k}^{(0)}-E_{k'}^{(0)}}}.} The energy E (2) gives the quadratic Stark effect.
Neglecting the hyperfine structure (which is often justified — unless extremely weak electric fields are considered), the polarizability tensor of atoms is isotropic, α i j ≡ α 0 δ i j ⟹ E ( 2 ) = − 1 2 α 0 F 2 . {\displaystyle \alpha _{ij}\equiv \alpha _{0}\delta _{ij}\Longrightarrow E^{(2)}=-{\frac {1}{2}}\alpha _{0}F^{2}.} For some molecules this expression is a reasonable approximation, too.
For the ground state α 0 {\displaystyle \alpha _{0}} is always positive, i.e., the quadratic Stark shift is always negative.
The perturbative treatment of the Stark effect has some problems. In the presence of an electric field, states of atoms and molecules that were previously bound ( square-integrable ), become formally (non-square-integrable) resonances of finite width. These resonances may decay in finite time via field ionization. For low lying states and not too strong fields the decay times are so long, however, that for all practical purposes the system can be regarded as bound. For highly excited states and/or very strong fields ionization may have to be accounted for. (See also the article on the Rydberg atom ). [ citation needed ]
The Stark effect is at the basis of the spectral shift measured for voltage-sensitive dyes used for imaging of the firing activity of neurons. [ 10 ] | https://en.wikipedia.org/wiki/Stark_effect |
Stark spectroscopy (sometimes known as electroabsorption/emission spectroscopy ) is a form of spectroscopy based on the Stark effect . In brief, this technique makes use of the Stark effect (or electrochromism) either to reveal information about the physiochemical or physical properties of a sample using a well-characterized electric field or to reveal information about an electric field using a reference sample with a well-characterized Stark effect.
The use of the term "Stark effect" differs between the disciplines of chemistry and physics. Physicists tend to use the more classical definition of the term (see Stark effect ), while chemists usually use the term to refer to what is technically electrochromism . [ 1 ] In the former case, the applied electric field splits the atomic energy levels and is the electric field analog of the Zeeman effect . However, in the latter case, the applied electric field changes the molar absorption coefficient of the sample, which can be measured using traditional absorption or emission spectroscopic methods. This effect is known as electrochromism. | https://en.wikipedia.org/wiki/Stark_spectroscopy |
STARLIMS Corporation (STARLIMS) is a portfolio company of Francisco Partners that provides web-based laboratory information management systems .
The company was founded by Itschak Friedman and Dinu Toiba in Israel in 1986, and developed and sold LIMS software. The company was renamed to STARLIMS. [ 1 ] By 2005, the company's software was installed at the US Centers for Disease Control and Prevention and in systems of state health authorities in 12 US states. [ 2 ] The company held its IPO in the US in 2007. [ 3 ] Friedman was CEO until the company was acquired by Abbott Laboratories in 2009 for $123 million; at that time the company had 160 employees and most of its operations and sales were in the US , the UK , and Hong Kong . [ 1 ] By the time of the sale, STARLIMS was offered as a web application . [ 4 ] Abbott intended to fold STARLIMS' products offerings into its other health information technology businesses in an effort to improve its clinical diagnostics business. [ 4 ] In 2014, Abbott changed the subsidiary's name from STARLIMS to Abbott Informatics. [ 5 ] [ 6 ] In July 2021 Abbott sold STARLIMS to Francisco Partners . [ 7 ]
In August 2023, it was announced STARLIMS had acquired the London -based R&D Electronic Laboratory Notebook (ELN) platform, Labstep for an undisclosed amount. [ 8 ] | https://en.wikipedia.org/wiki/Starlims |
Starlink is a satellite internet constellation operated by Starlink Services, LLC , an international telecommunications provider that is a wholly owned subsidiary of American aerospace company SpaceX , [ 5 ] providing coverage to around 125 countries and territories. [ 6 ] It also aims to provide global mobile broadband . [ 7 ] Starlink has been instrumental to SpaceX's growth. [ 8 ]
SpaceX began launching Starlink satellites in 2019. As of September 2024, the constellation consists of over 7,000 mass-produced small satellites in low Earth orbit (LEO) [ 9 ] that communicate with designated ground transceivers . Nearly 12,000 satellites are planned, with a possible later extension to 34,400. SpaceX announced reaching over 1 million subscribers in December 2022 [ 10 ] and 4 million subscribers in September 2024. [ 11 ]
The SpaceX satellite development facility in Redmond, Washington , houses Starlink research, development, manufacturing, and orbit control facilities. In May 2018, SpaceX estimated the cost of designing, building and deploying the constellation would be at least US$10 billion. [ 1 ] Revenues from Starlink in 2022 were reportedly $1.4 billion with a net loss. A small profit began only in 2023. [ 12 ] [ failed verification – see discussion ] In May 2024 that year's revenue was expected to reach $6.6 billion [ 13 ] but by December the prediction was raised to $7.7 billion. [ 14 ] Revenue was then expected to reach $11.8 billion in 2025. [ 14 ]
Starlink has been extensively used in the Russo-Ukrainian War , a role for which it has been contracted by the United States Department of Defense . [ 15 ] Starshield , a military version of Starlink, is designed for government use. [ 16 ] [ 17 ]
Astronomers raised concerns about the effect the constellation would have on ground-based astronomy, and how the satellites contribute to an already congested orbital environment. [ 18 ] [ 19 ] SpaceX has attempted to mitigate astronometric interference concerns with measures to reduce the satellites' brightness during operation. [ 20 ] The satellites are equipped with Hall-effect thrusters allowing them to raise their orbit, station-keep, and de-orbit at the end of their lives. They are also designed to autonomously and smoothly avoid collisions based on uplinked tracking data. [ 21 ]
Starlink's global satellite internet service has emerged as a significant security concern for nation-states, as it operates independently of local infrastructure and often without governmental approval. In India, during the Manipur conflict , militant groups reportedly used smuggled Starlink devices to bypass government-imposed internet shutdowns. In Iran, Elon Musk personally announced the activation of Starlink in 2022 after the Iranian government blocked the internet to suppress the spread of anti-government protests, enabling citizens to regain uncensored access. These cases illustrate the difficulty governments face in controlling unauthorized satellite communications within their borders. The decentralized and autonomous nature of Starlink's operations presents a growing challenge to national sovereignty and cybersecurity enforcement. [ 22 ] [ 23 ] [ 24 ] [ 25 ]
Constellations of low Earth orbit satellites were first conceptualized in the mid-1980s as part of the Strategic Defense Initiative , culminating in Brilliant Pebbles , where weapons were to be staged in low orbits to intercept ballistic missiles at short notice. The potential for low-latency communication was also recognized and development offshoots in the 1990s led to numerous commercial megaconstellations using around 100 satellites such as Celestri , Teledesic , Iridium , and Globalstar . However, all entities entered bankruptcy by the dot-com bubble burst, due in part to excessive launch costs at the time. [ 26 ] [ 27 ]
In 2004, Larry Williams, SpaceX VP of Strategic Relations and former VP of Teledesic 's "Internet in the sky" program, opened the SpaceX Washington DC office. [ 28 ] That June, SpaceX acquired a stake in Surrey Satellite Technology (SSTL) as part of a "shared strategic vision". [ 29 ] SSTL was at that time working to extend the Internet into space. [ 30 ] However, SpaceX's stake was eventually sold back to EADS Astrium in 2008 after the company became more focused on navigation and Earth observation. [ 31 ]
In early 2014, Elon Musk and Greg Wyler were working together planning a constellation of around 700 satellites called WorldVu , which would be over 10 times the size of the then largest Iridium satellite constellation . [ 32 ] However, these discussions broke down in June 2014, and SpaceX instead filed an International Telecommunications Union (ITU) application via the Norwegian Communications Authority under the name STEAM. [ 33 ] SpaceX confirmed the connection in the 2016 application to license Starlink with the Federal Communications Commission (FCC). [ 34 ] SpaceX trademarked the name Starlink in the United States for their satellite broadband network; [ 35 ] the name was inspired by the 2012 novel The Fault in Our Stars . [ 36 ]
Starlink was publicly announced in January 2015 with the opening of the SpaceX satellite development facility in Redmond, Washington . During the opening, Musk stated there is still significant unmet demand worldwide for low-cost broadband capabilities. [ 37 ] [ 38 ] and that Starlink would target bandwidth to carry up to 50% of all backhaul communications traffic, and up to 10% of local Internet traffic, in high-density cities. [ 39 ] [ 40 ] Musk further stated that the positive cash flow from selling satellite internet services would be necessary to fund their Mars plans . [ 41 ] Furthermore, SpaceX has long-term plans to develop and deploy a version of the satellite communication system to serve Mars . [ 42 ]
Starting with 60 engineers, the company operated in 2,800 m 2 (30,000 sq ft) of leased space, and by January 2017 had taken on a 2,800 m 2 (30,000 sq ft) second facility, both in Redmond. [ 43 ] In August 2018, SpaceX consolidated all their Seattle-area operations with a move to a larger three-building facility at Redmond Ridge Corporate Center to support satellite manufacturing in addition to R&D. [ 44 ] In July 2016, SpaceX acquired an additional 740 m 2 (8,000 sq ft) creative space in Irvine, California (Orange County). [ 45 ] The Irvine office would include signal processing , RFIC , and ASIC development for the satellite program. [ 46 ]
By October 2016, the satellite division was focusing on a significant business challenge of achieving a sufficiently low-cost design for the user equipment. SpaceX President Gwynne Shotwell said then that the project remained in the "design phase as the company seeks to tackle issues related to user-terminal cost". [ 47 ]
In November 2016, SpaceX filed an application with the FCC for a "non- geostationary orbit ( NGSO ) satellite system in the fixed-satellite service using the Ku- and Ka- frequency bands". [ 48 ]
In September 2017, the FCC ruled that half of the constellation must be in orbit within six years to comply with licensing terms, while the full system should be in orbit within nine years from the date of the license. [ 49 ]
SpaceX filed documents in late 2017 with the FCC to clarify their space debris mitigation plan, under which the company was to:
"... implement an operations plan for the orderly de-orbit of satellites nearing the end of their useful lives (roughly five to seven years) at a rate far faster than is required under international standards. [Satellites] will de-orbit by propulsively moving to a disposal orbit from which they will re-enter the Earth's atmosphere within approximately one year after completion of their mission." [ 50 ]
In March 2018, the FCC granted SpaceX approval for the initial 4,425 satellites, with some conditions. SpaceX would need to obtain a separate approval from the ITU. [ 51 ] [ 52 ] The FCC supported a NASA request to ask SpaceX to achieve an even higher level of de-orbiting reliability than the standard that NASA had previously used for itself: reliably de-orbiting 90% of the satellites after their missions are complete. [ 53 ]
In May 2018, SpaceX expected the total cost of development and buildout of the constellation to approach $10 billion (equivalent to $11,950,000,000 in 2023). [ 1 ] In mid-2018, SpaceX reorganized the satellite development division in Redmond and terminated several members of senior management. [ 44 ]
After launching two test satellites in February 2018, the first batch of 60 operational Starlink satellites were launched in May 2019. [ 54 ]
By late 2019, SpaceX was transitioning their satellite efforts from research and development to manufacturing, with the planned first launch of a large group of satellites to orbit, and the clear need to achieve an average launch rate of "44 high-performance, low-cost spacecraft built and launched every month for the next 60 months" to get the 2,200 satellites launched to support their FCC spectrum allocation license assignment. [ 55 ] SpaceX said they will meet the deadline of having half the constellation "in orbit within six years of authorization... and the full system in nine years". [ 56 ]
By July 2020, Starlink's limited beta internet service was opened to invitees from the public. Invitees had to sign non-disclosure agreements , and were only charged $2 per month to test out billing services. [ 57 ] In October 2020 a wider public beta was launched, where beta testers were charged the full monthly cost and could speak freely about their experience. Starlink beta testers reported speeds over 150 Mbit/s, above the range announced for the public beta test. [ 58 ]
Pre-orders were first opened to the public in the United States and Canada in early 2021. [ 59 ]
The FCC had earlier awarded SpaceX with $885.5 million worth of federal subsidies to support rural broadband customers in 35 U.S. states through Starlink. [ 60 ] but the $885.5 million aid package was revoked in August 2022, with the FCC stating that Starlink "failed to demonstrate" its ability to deliver the promised service. [ 61 ] SpaceX later appealed the decision saying they met or surpassed all RDOF deployment requirements that existed during bidding and that the FCC created "new standards that no bidder could meet today". [ 62 ] In December 2023, the FCC formally denied SpaceX's appeal since "Starlink had not shown that it was reasonably capable of fulfilling RDOF's requirements to deploy a network of the scope, scale, and size" required to win the subsidy. [ 63 ]
In March 2021, SpaceX submitted an application to the FCC for mobile variations of their terminal designed for vehicles, vessels and aircraft, [ 64 ] [ 65 ] and later in June the company applied to the FCC to use mobile Starlink transceivers on launch vehicles flying to Earth orbit, after having previously tested high-altitude low-velocity mobile use on a rocket prototype in May 2021. [ 66 ]
In 2022, SpaceX announced the Starlink Business service tier, a higher-performance version of the service. It provides a larger high-performance antenna and listed speeds of between 150 and 500 Mbit/s with a cost of $2500 for the antenna and a $500 monthly service fee. [ 67 ] The service includes 24/7, prioritized support. [ 67 ] Deliveries are advertised to begin in the second quarter of 2022. [ 68 ] The FCC also approved the licensing of Starlink services to boats, aircraft, and moving vehicles. [ 69 ] Starlink terminal production being delayed by the 2020–2023 global chip shortage led to only 5,000 subscribers for the last two months of 2021 but this was soon resolved. [ 70 ]
On December 1, 2022, the FCC issued an approval for SpaceX [ 71 ] to launch the initial 7500 satellites for its second-generation (Gen2) constellation, in three low-Earth-orbit orbital shells , at 525, 530, and 535 km (326, 329 and 332 mile) altitude . Overall, SpaceX had requested approval for as many as 29,988 Gen2 satellites, with approximately 10,000 in the 525–535 km (326 to 332 mile) altitude shells, plus ~20,000 in 340–360 km (210 mile to 220 mile) shells and nearly 500 in 604–614 km (375 to 382 mile) shells. However, the FCC noted that this is not a net increase in approved on-orbit satellites for SpaceX since SpaceX is no longer planning to deploy 7518 V-band satellites at 340 km (210 mi) altitude that had previously been authorized. [ 72 ]
In March 2023, the company reported that they were manufacturing six Starlink "v2 mini" satellites per day as well as thousands of users terminals. The v2 mini has Gen2 Starlink satellite features while being assembled in a smaller form factor than the larger Gen2 sats. The Gen2 satellites require the 9 meter (29.5 foot) diameter Starship in order to launch them. The Starlink business unit had a single cash-flow-positive quarter during 2022 and is expecting to be profitable in 2023. [ 73 ]
In May 2018, SpaceX estimated the total cost of designing, building and deploying the constellation would be at least US$10 billion. In January 2017, SpaceX expected annual revenue from Starlink to reach $12 billion by 2022 and exceed $30 billion by 2025. Starlink was at annual loss in 2021. [ 74 ] Revenues from Starlink in 2022 were reportedly $1.4 billion accompanied by a net loss, with a small profit being reported by Musk starting in 2023. [ 75 ] [ 76 ]
Tensions between Brazil and Elon Musk's business ventures escalated in 2024 as the country's telecom regulator Anatel threatened to sanction Starlink after Brazil's top court upheld a ban on X. Luiz Inácio Lula da Silva supported the decision, citing X's role in allegedly spreading hate and misinformation undermining Brazil's democracy. Judge Alexandre de Moraes had frozen Starlink's accounts, and Starlink refused to comply with an order to block domestic access to X until the freeze was lifted, risking its license to operate. [ 77 ]
The Wall Street Journal reported in October 2024 that Musk had been in regular contact with Russian President Vladimir Putin and other high ranking Russian government officials since late 2022, discussing personal topics, business and geopolitical matters. The Journal reported that Putin had asked Musk to avoid activating his Starlink satellite system over Taiwan , to appease Chinese Communist Party general secretary Xi Jinping . The communications were reported to be a closely held secret in government, given Musk's involvement in promoting the presidential candidacy of Donald Trump , and his security clearance to access classified government information. One person said no alerts were raised by the U.S. government, noting the dilemma of the government being dependent on Musk's technologies. Musk initially voiced support for Ukraine's defense against Russia's 2022 invasion by donating Starlink terminals, but made later decisions to limit Ukrainian access to Starlink, which coincided with Russian pressure in public and in private. [ 78 ] In a November 2024 call with President Volodymyr Zelenskyy , Musk said he will continue supporting Ukraine through Starlink. [ 79 ]
SpaceX has asked its numerous Taiwanese suppliers to move production abroad citing geopolitical risk concerns. [ 80 ] [ 81 ] This move was questioned by the Taiwanese government and resulted in significant anger from the Taiwanese public with citizens pointing out that Starlink was unavailable in Taiwan despite its suppliers underlying the technology and others calling for a boycott of Tesla products. [ 82 ]
In November 2024, SpaceX proposed a constellation of Starlink satellites around Mars, referred to as "Marslink". The proposed system would be capable of providing more than 4 Mbit/s of bandwidth between Earth and Mars as well as imaging services. [ 83 ]
Starting in July 2024, SpaceX began conducting tests on Starlink in cooperation with the Romanian Ministry of National Defense and National Authority for Communications Administration and Regulation (ANCOM). These tests aim at demonstrating that the Equivalent Power Flux Density (EPFD) limit can be safely increased, thus improving the speed and coverage area of Starlink, without affecting classic, geostationary satellites. The results of these tests will be used to help change a rule set by the International Telecommunication Union in the 1990s regarding the limits of non-geostationary satellites. [ 84 ] [ 85 ]
Starlink was part of an investigation by USAID into sexual exploitation and abuse in Ukraine when USAID's Inspector General was fired by President Trump and all employees put on administrative leave. The USAID website was scrubbed of all information related to the Starlink probe. [ 86 ]
In March 2025 the director of the United States Department of Commerce 's rural broadband program resigned criticizing undue emphasis on Starlink from the Trump administration . [ 87 ] [ 88 ] [ 89 ] Musk's involvement in politics has also been protested by a number of Starlink customers. [ 90 ] The Department of Government Efficiency (DOGE) installed a Starlink user terminal at the White House complex which raised conflict of interest concerns. In response the White House said that the terminal was donated by Starlink and approved by legal counsel and the United States Secret Service . [ 91 ] [ 92 ] After the Trump administration launched a series of tariffs , the State Department pushed countries to approve Starlink. Several countries such as India granted regulatory approval to Starlink, hoping that supporting a company owned by Musk would help negotiations to avoid tariffs. [ 93 ]
As of February 2025, Starlink reports the number of its customers [ a ] worldwide as more than 5 million. [ 94 ]
Starlink provides satellite-based internet connectivity to underserved areas of the planet, as well as competitively priced service in more urbanized areas. [ 108 ]
In the United States, Starlink charged, at launch, a one-time hardware fee of $599 for a user terminal and $120 per month for internet service at a fixed service address. [ 109 ] An additional $25 per month allows the user terminal to move beyond a fixed location ( Starlink For RVs ) but with service speeds deprioritized compared to the fixed users in that area. [ 110 ] [ 111 ] Fixed users are told to expect typical throughput of "50 to 150 Mbit/s and latency from 20 to 40 ms", [ 112 ] a study found users averaged download speeds of 90.55 Mbit/s in the first quarter of 2022, but dropped to 62.5 Mbit/s in the second quarter. [ 113 ] A higher performance version of the service ( Starlink Business ) advertises speeds of 150 to 500 Mbit/s in exchange for a more costly $2,500 user terminal and a $500 monthly service fee. [ 67 ] Another service called Starlink Maritime became available in July 2022 providing internet access on the open ocean, with speeds of 350 Mbit/s, requiring purchase of a maritime-grade $10,000 user terminal and a $5,000 monthly service fee. [ 114 ]
Sales are capped to a few hundred fixed users per 20 km (10 mile) "service cell area" due to limited wireless capacity. Starlink alternatively offers a Best Effort service tier allowing homes in capped areas to receive the current unused bandwidth of their cell while they are on the waiting list for more prioritized service. The price and equipment are the same as the residential service at $110 per month. [ 115 ] [ 116 ] To improve the service quality in densely populated areas, Starlink introduced a monthly 1 TB data cap for all non-business users which was enforced starting in 2023. [ 115 ] [ 117 ]
In August 2022, SpaceX lowered monthly service costs for users in select countries. [ 118 ] For example, users in Brazil and Chile saw monthly fee decreases of about 50%. [ 119 ]
According to internet analysis company Ookla , Starlink speeds degraded during the first half of 2022 as more customers signed up for the service. SpaceX has said that Starlink speeds will improve as more satellites are deployed. [ 113 ]
In September 2023, satellite operator SES announced a satellite internet service for cruise lines using both the Starlink satellites in Low Earth Orbit (LEO) and SES' own O3b mPOWER satellite constellation in Medium Earth Orbit (MEO). Integrated, sold and delivered by SES, the SES Cruise mPOWERED + Starlink service claims to combine the best features of LEO and MEO orbits to provide high-speed, secure connectivity at up to 3 Gbit/s per ship, to cruise ships anywhere in the world. In February 2024, SES announced that Virgin Voyages will be the first cruise line to deploy the service. [ 120 ] [ 121 ] [ 122 ]
For future service, T-Mobile US and SpaceX are partnering to add satellite cellular service capability to Starlink satellites. It will provide dead-zone cell phone coverage across the US using the existing midband PCS spectrum owned by T-Mobile. [ 123 ] [ 124 ] Cell coverage will begin with text messaging and expand to include voice and limited data services later, with testing beginning in 2024. [ 125 ] T-Mobile plans to connect to Starlink satellites via existing 4G LTE mobile devices, unlike previous generations of satellite phones, which used specialized radios, modems, and antennas to connect to satellites in higher orbits. [ 7 ] Bandwidth will be limited to 2 to 4 megabits per second total, split across a very large cell coverage area, which would be limited to thousands of voice calls or millions of text messages simultaneously in a coverage area. The size of a single coverage cell has not yet been publicly released. [ 123 ]
The first six cell phone capable satellites launched on January 2, 2024. [ 125 ]
Rogers Communications , in April 2023, signed an agreement with SpaceX for using Starlink for satellite-to-phone services in Canada . [ 126 ] Also in April 2023, One NZ (formerly Vodafone New Zealand) announced that they would be partnering with SpaceX's Starlink to provide 100% mobile network coverage over New Zealand . SMS text service is expected to begin in 2024, with voice and data functionality in 2025. [ 127 ] [ 128 ] In July 2023, Optus in Australia announced a similar partnership. [ 129 ]
On January 8, 2024, it was confirmed by SpaceX that they had successfully tested text messaging using the new Direct-to-Cell capability on T-Mobile's network. [ 130 ]
In December 2022, SpaceX announced Starshield , a separate Starlink service designed for government entities and military agencies. [ 131 ] [ 16 ] [ 17 ] [ 132 ] Starshield enables the U.S. Department of Defense (DoD) to own or lease Starshield satellites for partners and allies. [ 131 ] Cybernews remarked that Starshield was first announced in late 2022, when Starlink's presence in Ukraine showed the importance it can have in modern warfare. [ 133 ] While Starlink had not been adapted for military use, Starshield has the usual requirements for mobile military systems like encryption and anti-jam capabilities. [ 132 ] Elon Musk stated that "Starlink needs to be a civilian network, not a participant to combat. Starshield will be owned by the US government and controlled by DoD Space Force . This is the right order of things." [ 134 ]
Starshield satellites are advertised as capable of integrating a wide variety of payloads. Starshield satellites will be compatible with, and interconnect to, the existing commercial Starlink satellites via optical inter-satellite links. [ 135 ]
In January 2022, SpaceX deployed four national security satellites for the U.S. government on their Transporter-3 rideshare mission. [ 136 ] [ 137 ] In the same year they launched another group of four U.S. satellites with an on-orbit spare Globalstar FM-15 satellite in June. [ 138 ] [ 136 ] [ 139 ] [ 140 ]
In September 2023, the Starshield program received its first contract from the U.S. Space Force to provide customized satellite communications for the military. [ 141 ] This is under the Space Force's new "Proliferated Low Earth Orbit" program for LEO satellites, where Space Force will allocate up to $900 million worth of contracts over the next 10 years. Although 16 vendors are competing for awards, the SpaceX contract is the only one to have been issued to date. [ 142 ] [ 141 ] The one-year Starshield contract was awarded on September 1, 2023. [ 134 ] The contract is expected to support 54 mission partners across the Army, Navy, Air Force, and Coast Guard. [ 134 ]
SpaceX also designs, builds, and launches customized military satellites based on variants of the Starlink satellite bus , with the largest publicly known customer being the Space Development Agency (SDA).
SDA accelerates development of missile defense capabilities, primarily via observation platforms, using industry-procured low-cost low Earth orbit satellite platforms. [ 143 ]
In October 2020, SDA awarded SpaceX an initial $150 million dual-use contract to develop 4 satellites to detect and track ballistic and hypersonic missiles. [ 144 ] The first batch of satellites were originally scheduled to launch September 2022 to form part of the Tracking Layer Tranche 0 of the U.S. Space Force 's National Defense Space Architecture (NDSA), a network of satellites performing various roles including missile tracking. [ 145 ] The launch schedule slipped multiple times but eventually launched in April 2023. [ 146 ] [ 147 ]
In 2020, SpaceX hired retired four-star general Terrence J. O'Shaughnessy who, according to some sources, is associated with Starlink's military satellite development, and according to one source, is listed as a "chief operating officer" at SpaceX. [ 148 ] [ 149 ] While still on active duty, O'Shaughnessy advocated before the United States Senate Committee on Armed Services for a layered capability with lethal follow-on that incorporates machine learning and artificial intelligence to gather and act upon sensor data quickly. [ 150 ]
SpaceX was not awarded a contract for the larger Tranche 1, with awards going to York Space Systems, Lockheed Martin Space, and Northrop Grumman Space Systems. [ 151 ]
In 2019, tests by the United States Air Force Research Laboratory (AFRL) demonstrated a 610 Mbit/s data link through Starlink to a Beechcraft C-12 Huron aircraft in flight. [ 152 ] Additionally, in late 2019, the United States Air Force successfully tested a connection with Starlink on an AC-130 Gunship . [ 153 ]
In 2020, the Air Force used Starlink in support of its Advanced Battlefield management system during a live-fire exercise. They demonstrated Starlink connected to a "variety of air and terrestrial assets" including the Boeing KC-135 Stratotanker . [ 154 ]
Expert on battlefield communications Thomas Wellington has argued that Starlink signals, because they use narrow focused beams, are less vulnerable to interference and jamming by the enemy in wartime than satellites flying in higher orbits. [ 155 ]
In May 2022, Chinese military researchers published an article in a peer-reviewed journal describing a strategy for destroying the Starlink constellation if they threaten national security. [ 156 ] [ 157 ] [ 158 ] The researchers specifically highlight concerns with reported Starlink military capabilities . Musk has declared Starlink is meant for peaceful use and has suggested Starlink could enforce peace by taking strategic initiative. [ 159 ] Russian officials including the head of Russia's space agency Dmitry Rogozin , have warned Elon Musk and criticized Starlink, including warning that Starlink could become a legitimate military target in the future. [ 160 ] [ 161 ]
Starlink was activated during the Russian invasion of Ukraine , after a request from the Ukrainian government. [ 162 ] [ 163 ] Ukraine's military and government rapidly became dependent on Starlink to maintain Internet access. [ 164 ] [ 165 ] [ 155 ] Starlink is used by Ukraine for communication, such as keeping in touch with the outside world and keeping the energy infrastructure working. [ 166 ] [ 167 ]
The service is also notably used for warfare. Starlink is used for connecting combat drones , naval drones , artillery fire coordination systems and attacks on Russian positions. [ 168 ] [ 155 ] SpaceX has expressed reservations about the offensive use of Starlink by Ukraine beyond military communications and restricted Starlink communication technology for military use on weapon systems, [ 169 ] but has kept most of the service online. [ 170 ] [ 171 ] Its use in attacking Russian targets has been criticized by the Kremlin. [ 172 ]
Musk has warned that the service was costing $20 million per month, and a Ukrainian official estimated SpaceX's contributions as over $100 million. [ 167 ] In June 2023, the United States Department of Defense signed a contract with SpaceX to finance Starlink use in Ukraine. [ 173 ] [ 171 ] In February 2025, U.S. negotiators Scott Bessent and Keith Kellogg pressured Ukraine to grant access to its critical minerals by warning of a potential Starlink shutdown, a service crucial to its military operations, as per three sources familiar with the matter. The issue surfaced after Volodymyr Zelenskyy rejected a U.S. proposal for mineral rights in exchange for wartime aid. While Musk denied the claims, Reuters stood by its report. Meanwhile, Donald Trump pushed Ukraine for U.S. access, criticizing Zelenskiy after he dismissed Trump’s stance as Russian-influenced . [ 174 ] Three days after the February 28, 2025, meeting between Trump and Zelenskyy in the White House the U.S. suspended all military aid and a day later also intelligence to Ukraine. [ 175 ]
In October 2023 after the Gaza war started, users shared the hashtag #starlinkforgaza on Elon Musk's social network X (formerly Twitter) , demanding he activate Starlink in Gaza after Internet service in the region was lost. [ 176 ] Musk answered that Starlink connectivity would be provided for aid groups in Gaza . [ 177 ] At the end of November, Musk said the Starlink service would only be provided for Gaza with the approval of the government of Israel. [ 178 ]
The Associated Press reported in 2023 that Brazilian organized criminal groups were making heavy use of Starlink in exploiting remote regions of the Amazon rainforest . [ 179 ]
According to Wired , Starlink supplies key support to scam centers in Southeast Asia with "criminals running multibillion-dollar empires across Southeast Asia appear to be widely using the satellite internet network." Wired identified more than one hundred Starlink devices in use at just one center, KK Park in Myanmar . [ 180 ]
In order to offer satellite services in any nation-state, International Telecommunication Union (ITU) regulations and long-standing international treaties require that landing rights be granted by each country jurisdiction, and within a country, by the national communications regulators . As a result, even though the Starlink network has near-global reach at latitudes below approximately 60°, broadband services can only be provided in 40 countries as of September 2022. [ 181 ] SpaceX can also have business operation and economic considerations that may make a difference in which countries Starlink service is offered, in which order, and how soon. For example, SpaceX formally requested authorization for Canada only in June 2020, [ 182 ] the Canadian regulatory authority approved it in November 2020, [ 183 ] and SpaceX rolled out service two months later, in January 2021. [ 184 ] As of September 2022, Starlink services were on offer in 40 countries, [ 181 ] with applications pending regulatory approval in many more. [ 185 ]
Canada was the first outside country to approve the service with the Innovation, Science and Economic Development Canada announcing regulatory approval for the Starlink low Earth orbit satellite constellation on November 6, 2020. [ 183 ]
In May 2022, Starlink entered the Philippine market, the company's first deployment in Asia, because of a landmark legislative change (RA 11659, Public Services Act) about all-foreign allowance of company ownership in regard to utility entities such as internet and telco companies. Starlink got provisional permission from the country's Department of Information and Communication Technologies (DICT), National Telecommunications Commission (NTC), and Department of Trade and Industry (DTI) and soon began commercial services, aimed at regions with lower internet connectivity. [ 186 ]
In August 2022, SpaceX secured its first contract for services in the passenger shipping industry. Royal Caribbean Group has added Starlink internet to Freedom of the Seas and planned to offer the service on 50 ships under its Royal Caribbean International , Celebrity Cruises , and Silversea Cruises brands by March 2023. [ 69 ] Starlink services on private jet charter flights in the U.S. by JSX airline are expected to begin in late 2022, and Hawaiian Airlines had contracted to provide "Starlink services on transpacific flights to and from Hawaii in 2023." [ 69 ]
In June 2023, a license to offer internet services in Zambia was granted to Starlink by the Zambian Government through its Electronic Government Division – SMART Zambia , after the completion of many trial projects throughout the country. [ 187 ] [ 188 ] [ 189 ] In October 2023, Starlink officially went live in Zambia. [ 190 ] [ 191 ] [ 192 ]
In July 2023, the Mongolian government issued two licenses to SpaceX to provide internet access in the country. [ 193 ]
In July 2023, it was reported by Bloomberg that attempts to sell the service to Taiwan in 2022 fell through when SpaceX insisted on 100% ownership of the Taiwan subsidiary running Starlink in the country. This went against Taiwanese law that required that internet service providers (ISP) are at least 51% controlled by local companies, an impracticality when dealing with a globe-spanning ISP. [ 194 ]
Japan's major mobile provider, KDDI , announced a partnership with SpaceX to begin offering in 2022 expanded connectivity for its rural mobile customers via 1,200 remote mobile towers. [ 195 ]
On April 25, 2022, Hawaiian Airlines announced an agreement with Starlink to provide free internet access on its aircraft, becoming the first airline to use Starlink. [ 196 ] By July 2022, Starlink internet service was available in 36 countries and 41 markets. [ 197 ]
In May 2022, it was announced that regulatory approval had been granted for Nigeria, Mozambique, [ 198 ] and the Philippines. [ 199 ] [ 200 ] In the Philippines, commercial availability began on February 22, 2023. [ 201 ]
In September 2022, trials began at McMurdo Station in Antarctica and from December 2022 on field missions. Antarctica has no ground stations, so polar-orbiting satellites with optical interlinks are used to connect to ground stations in South America, New Zealand, and Australia. [ 202 ] [ 203 ]
In September 2023, the US-based United Against Nuclear Iran started donating subscriptions and terminals to Iranians to allow them to circumvent Iran's internet blackout. [ 204 ] [ 205 ]
In September 2023, it was reported by some Indian news outlets that Starlink would imminently receive its license to operate in India after Starlink was able to meet all regulatory requirements, but that it would still be required to apply for spectrum allocation in order to provide service. [ 206 ] [ 207 ] SpaceX had earlier sold 5000 Starlink preorders in India, [ 208 ] and in 2021 had announced that Sanjay Bhargava, who had worked with Musk as part of a team that founded electronic payment firm PayPal , would head the tech billionaire entrepreneur's Starlink satellite broadband venture in India. [ 209 ] Three months later, Bhargava resigned "for personal reasons" after the Indian government ordered SpaceX to halt selling preorders for Starlink service until SpaceX gained regulatory approval for providing satellite internet services in the country. [ 208 ] In April 2024, it was reported in some Indian news outlets that Starlink had received its "in-principle government approval" and that the approval now "lies at the desk of communications minister Ashwini Vaishnaw". [ 210 ]
In November 2023, Starlink received the licenses to operate in Fiji . [ 211 ] The service was launched in Fiji in May 2024. [ 212 ]
In April 2024, it was reported that the company would begin trial service in Indonesia in May. [ 213 ] Starlink received its license to operate in Indonesia in early May. [ 214 ]
In May 2024, Starlink service was available for pre-order in Sri Lanka , pending regulatory approval. [ 215 ] Starlink received its license to operate in Sri Lanka in August of the same year. [ 216 ]
In August 2024, Starlink received the licenses to operate in Yemen . [ 217 ] Starlink services will soon be implemented through the corporation's sales points distributed across most governorates. These points will provide a full range of services, including device sales, activation, subscription fee payments, and direct technical support. [ 218 ] In April 2025, Houthi rebels in Yemen demanded that residents surrender their Starlink devices. [ 219 ]
In September 2024, United Airlines announced it would install Starlink services on the airline's entire fleet, including mainland and regional aircraft, as part of a plan to offer free high-speed Wi-Fi to all passengers. [ 220 ] [ 221 ] In March 2025, the FAA issued final approval for United to begin equipping its aircraft with Starlink antennas. [ 222 ]
On 22 October 2024, Qatar Airways launched the first Starlink-equipped Boeing 777 flight, flying from Doha to London . [ 223 ] As of November 2024, Morocco is set to give regulatory approval to Starlink by 2025. [ 224 ]
On 11 and 12 March 2025, Indian telecom companies Airtel and Jio have partnered with Starlink to bring satellite internet to India, aiming to improve connectivity in remote areas. [ 225 ] However, the service's rollout is dependent on securing necessary government approvals. [ 226 ] These partnerships promise to expand broadband access, especially in underserved regions. [ 227 ]
In March 2025 Musk claimed that Starlink was unavailable in South Africa because he was not black. The South African government argued against this. [ 228 ] In April 2025, Starlink was given a license to operate in Somalia and Lesotho . [ 229 ] [ 230 ] [ 231 ] [ 232 ]
In 2022, the U.S. State Department and U.S. Treasury Department updated rules regarding export of technology to Iran, allowing Starlink to be exported to Iran in support of the Iranian protests against compulsory hijab , which had triggered extensive government censorship. [ 233 ] Immediately afterwards, Starlink service was activated in Iran. [ 234 ] In 2023, the Iranian government filed a complaint with the ITU against SpaceX for unauthorized Starlink operation in Iran. [ 235 ] In October 2023 and March 2024, the ITU ruled in favor of Iran, dismissing a SpaceX assertion that it should not be expected to verify the location of every terminal connecting to its satellites. [ 235 ] Iran stated that SpaceX was capable of determining their user terminal locations by citing an October 2022 tweet from Musk saying the number of Starlink terminals operating within Iran was "approaching 100". [ 235 ] [ 236 ] Despite the illegality of Starlink usage in Iran, the number of Starlink users has grown exponentially via sales of the terminals on the black market. Iranian officials have acknowledged that 30,000 terminals in the country, providing access to some 100,000 users. [ 237 ]
The internet communication satellites were expected to be smallsats , 100 to 500 kg (220 to 1,100 lb) in mass, and were intended to be in low Earth orbit (LEO) at an altitude of approximately 1,100 km (680 mi), according to early public releases of information in 2015. The first significant deployment of 60 satellites was in May 2019, with each satellite weighing 227 kg (500 lb). [ 54 ] SpaceX decided to place the satellites at a relatively low 550 km (340 mi) due to concerns associated with space debris from failures or low fuel in the space environment , as well as letting them use fewer satellites than what was initially needed. [ 356 ] Initial plans forecasted in January 2015 were for the constellation to be made up of approximately 4,000 cross-linked [ 357 ] satellites; more than twice as many operational satellites as were in orbit in January 2015. [ 40 ]
The satellites employ optical inter-satellite links and phased array beam-forming and digital processing technologies in the Ku and Ka microwave bands (super high frequency [SHF] to extremely high frequency [EHF]) , according to documents filed with the U.S. FCC. [ 358 ] [ 359 ] While specifics of the phased array technologies have been disclosed as part of the frequency application, SpaceX enforced confidentiality regarding details of the optical inter-satellite links. [ 360 ] Early satellites were launched without laser links. The inter-satellite laser links were successfully tested in late 2020. [ 361 ] [ 362 ]
The satellites are mass-produced , at a much lower cost per unit of capability than previously existing satellites. Musk said, "We're going to try and do for satellites what we've done for rockets." [ 363 ] "In order to revolutionize space, we have to address both satellites and rockets." [ 40 ] "Smaller satellites are crucial to lowering the cost of space-based Internet and communications". [ 364 ]
In February 2015, SpaceX asked the FCC to consider future innovative uses of the Ka-band spectrum before the FCC commits to 5G communications regulations that would create barriers to entry , since SpaceX is a new entrant to the satellite communications market. The SpaceX non-geostationary orbit communications satellite constellation will operate in the high-frequency bands above 24 GHz, "where steerable Earth station transmit antennas would have a wider geographic impact, and significantly lower satellite altitudes magnify the impact of aggregate interference from terrestrial transmissions". [ 365 ]
Internet traffic via a geostationary satellite has a minimum theoretical round-trip latency of at least 477 milliseconds (ms; between user and ground gateway), but in practice, current satellites have latencies of 600 ms or more. Starlink satellites are orbiting at 1 ⁄ 105 to 1 ⁄ 30 of the height of geostationary orbits, and thus offer more practical Earth-to-satellite latencies of around 25 to 35 ms, comparable to existing cable and fiber networks. [ 366 ] The system uses a peer-to-peer protocol claimed to be "simpler than IPv6 "; it also incorporates native end-to-end encryption. [ 367 ]
Starlink satellites use Hall-effect thrusters with krypton or argon gas as the reaction mass [ 54 ] [ 368 ] for orbit raising and station keeping . [ 369 ] Krypton Hall thrusters tend to exhibit significantly higher erosion of the flow channel compared to a similar electric propulsion system operated with xenon , but krypton is much more abundant and has a lower market price. [ 370 ] SpaceX claims that its 2nd generation thruster using argon has 2.4× the thrust and 1.5× the specific impulse of the krypton fueled thruster. [ 371 ]
The Starlink system has multiple modes of connectivity including direct-to-cell capability as well as broadband satellite internet service. Direct-to-cell provides connectivity to unmodified cellular phones and is being offered globally in partnership with various national cellular service providers. [ 372 ] [ 373 ] Starlink's broadband internet service is accessed via flat user terminals the size of a pizza box, which have phased array antennas and track the satellites. The terminals can be mounted anywhere, as long as they can see the sky. [ 357 ] This includes fast-moving objects like trains. [ 374 ] Photographs of the customer antennas were first seen on the internet in June 2020, supporting earlier statements by SpaceX CEO Musk that the terminals would look like a "UFO on a stick. Starlink Terminal has motors to self-adjust optimal angle to view sky". [ 375 ] The antenna is known internally as "Dishy McFlatface". [ 376 ] [ 377 ]
In October 2020, SpaceX launched a paid-for beta service in the U.S. called "Better Than Nothing Beta", charging $499 (equivalent to $578.8 in 2023) for a user terminal, with an expected service of "50 to 150 Mbit/s and latency from 20 to 40 ms over the next several months". [ 112 ] From January 2021, the paid-for beta service was extended to other continents, starting with the United Kingdom. [ 378 ]
A larger, high-performance version of the antenna is available for use with the Starlink Business service tier. [ 67 ]
In September 2020, SpaceX applied for permission to put terminals on 10 of its ships with the expectation of entering the maritime market in the future. [ 379 ]
In August 2022, and in response to an open invitation from SpaceX to have the terminal examined by the security community, security specialist Lennert Wouters presented several technical architecture details about the then-current starlink terminals: the main control unit of the dish is a STMicroelectronics custom designed chip code-named Catson which is a quad-core ARM Cortex-A53 -based control processor running the Linux kernel and booted using U-Boot . The main processor uses several other custom chips such as a digital beam former named Shiraz and a front-end module named Pulsarad . The main control unit controls an array of digital beamformers . Each beamformer controls 16 front-end modules. In addition the terminal has a GPS receiver , motor controllers , synchronous clock generation and Power over Ethernet circuits, all manufactured by STMicroelectronics. [ 380 ]
In June 2024, a portable user terminal dubbed "Starlink Mini" was announced to be imminently available. The Mini supports 100 Mbit/s of download speed and will fit in a backpack. [ 381 ] Initial rollout was in Latin America at a $200 price point. [ 382 ]
SpaceX has made applications to the FCC for at least 32 ground stations in United States , and as of July 2020 [update] has approvals for five of them (in five states). Until February 2023, Starlink used the Ka-band to connect with ground stations. [ 383 ] With the launch of v2 Mini, frequencies were added in the 71–86 GHz W band (or E band waveguide ) range. [ 384 ]
A typical ground station [ when? ] has nine 2.86 m (9.4 ft) antennas in a 400 m 2 (4,306 sq ft) fenced in area. [ 385 ]
According to their filing, SpaceX's ground stations would also be installed on-site at Google data-centers world-wide. [ 386 ]
MicroSat-1a and MicroSat-1b were originally slated to be launched into 625 km (388 mi) circular orbits at approximately 86.4° inclination, and to include panchromatic video imager cameras to film images of Earth and the satellite. [ 387 ] The two satellites, "MicroSat-1a" and "MicroSat-1b" were meant to be launched together as secondary payloads on one of the Iridium NEXT flights, but they were instead used for ground-based tests. [ 388 ]
At the time of the June 2015 announcement, SpaceX had stated plans to launch the first two demonstration satellites in 2016, [ 389 ] but the target date was subsequently moved out to 2018. [ 390 ] SpaceX began flight testing their satellite technologies in 2018 [ 390 ] with the launch of two test satellites. The two identical satellites were called MicroSat-2a and MicroSat-2b [ 391 ] during development but were renamed Tintin A and Tintin B upon orbital deployment on February 22, 2018. The satellites were launched by a Falcon 9 rocket, and they were piggy-back payloads launching with the Paz satellite.
Tintin A and B were inserted into a 514 km (319 mi) orbit. Per FCC filings, [ 392 ] they were intended to raise themselves to a 1,125 km (699 mi) orbit, the operational altitude for Starlink LEO satellites per the earliest regulatory filings, but stayed close to their original orbits. SpaceX announced in November 2018 that they would like to operate an initial shell of about 1600 satellites in the constellation at about 550 km (340 mi) orbital altitude, at an altitude similar to the orbits Tintin A and B stayed in. [ 393 ]
The satellites orbit in a circular low Earth orbit at about 500 km (310 mi) altitude [ 394 ] in a high-inclination orbit for a planned six to twelve-month duration. The satellites communicate with three testing ground stations in Washington State and California for short-term experiments of less than ten minutes duration, roughly daily. [ 389 ] [ 395 ]
The 60 Starlink v0.9 satellites, launched in May 2019, had the following characteristics: [ 54 ]
The Starlink v1.0 satellites, launched since November 2019, have the following additional characteristics: [ citation needed ]
The Starlink v1.5 satellites, launched since January 24, 2021, have the following additional characteristics:
These are satellites buses with two solar arrays derived from Starlink v1.5 and v2.0 for military use and can host classified government or military payloads. [ 406 ]
SpaceX was preparing for the production of Starlink v2 satellites by early 2021. [ 407 ] According to Musk, Starlink v2 satellites will be "…an order of magnitude better than Starlink 1" in terms of communications bandwidth . [ 408 ]
SpaceX hoped to begin launching Starlink v2 in 2022. As of May 2022 [update] , SpaceX had said publicly that the satellites of second-generation (Gen2) constellation would need to be launched on Starship , as they are too large to fit inside a Falcon 9 fairing . [ 384 ] However, in August 2022, SpaceX made formal regulatory filings with the FCC that indicated they would build satellites of the second-generation (Gen2) constellation in two different, but technically identical, form factors : one with the physical structures tailored to launching on Falcon 9, and one tailored for the launching on Starship. [ 123 ] [ 409 ] Starlink v2 is both larger and heavier than Starlink v1 satellites.
Starlink second-generation satellites planned for launch on Starship have the following characteristics: [ 3 ] [ 409 ]
In October 2022, SpaceX revealed the configuration of early v2s to be launched on Falcon 9. [ 413 ] In May 2023, SpaceX introduced two more form factors with direct-to-cellular (DtC) capability. [ 414 ]
The first six F9-3 satellites with direct-to-cellular (DtC) capability were launched on January 2, 2024, in Groups 7–9. [ 418 ]
Between February 2018 and May 2024, SpaceX successfully launched over 6,000 Starlink satellites into orbit, including prototypes and satellites that later failed or were de-orbited before entering operational service. [ 9 ] In March 2020, SpaceX reported producing six satellites per day. [ 419 ]
The deployment of the first 1,440 satellites was planned in 72 orbital planes of 20 satellites each, [ 420 ] with a requested lower minimum elevation angle of beams to improve reception: 25° rather than the 40° of the other two orbital shells. [ 393 ] : 17 SpaceX launched the first 60 satellites of the constellation in May 2019 into a 550 km (340 mi) orbit and expected up to six launches in 2019 at that time, with 720 satellites (12 × 60) for continuous coverage in 2020. [ 421 ] [ 422 ]
Starlink satellites are also planned to launch on Starship , an under-development rocket of SpaceX with a much larger payload capability. The initial announcement included plans to launch 400 Starlink (version 1.0) satellites at a time. [ 423 ] Current plans now call for Starship to be the only launch vehicle to be used to launch the much larger Starlink version 2.0. [ citation needed ]
In March 2017, SpaceX filed plans with the FCC to field a second orbital shell of more than 7,500 " V-band satellites in non-geosynchronous orbits to provide communications services" in an electromagnetic spectrum that has not previously been heavily employed for commercial communications services. Called the " Very-low Earth orbit (VLEO) constellation", [ 424 ] it was to have comprised 7,518 satellites that were to orbit at just 340 km (210 mi) altitude , [ 425 ] while the smaller, originally planned group of 4,425 satellites would operate in the K a - and K u -bands and orbit at 1,200 km (750 mi) altitude. [ 424 ] [ 425 ] By 2022, SpaceX had withdrawn plans to field the 7,518-satellite V-band system, superseding it with a more comprehensive design for a second-generation (Gen2) Starlink network. [ 72 ]
In November 2018, SpaceX received U.S. regulatory approval to deploy 7,518 V-band broadband satellites, in addition to the 4,425 approved earlier; [ 426 ] [ 427 ] however, the V-band plans were subsequently withdrawn by 2022. [ 72 ] At the same time, SpaceX also made new regulatory filings with the U.S. FCC to request the ability to alter its previously granted license in order to operate approximately 1,600 of the 4,425 Ka-/Ku-band satellites approved for operation at 1,150 km (710 mi) in a "new lower shell of the constellation" at only 550 km (340 mi) [ 428 ] orbital altitude. [ 393 ] [ 429 ] These satellites would effectively operate in a third orbital shell, a 550 km (340 mi) orbit, while the higher and lower orbits at approximately 1,200 km (750 mi) and approximately 340 km (210 mi) would be used only later, once a considerably larger deployment of satellites becomes possible in the later years of the deployment process. The FCC approved the request in April 2019, giving approval to place nearly 12,000 satellites in three orbital shells: initially approximately 1,600 in a 550 km (340 mi) – altitude shell, and subsequently placing approximately 2,800 Ku- and Ka-band spectrum satellites at 1,150 km (710 mi) and approximately 7,500 V-band satellites at 340 km (210 mi). [ 56 ] In total, nearly 12,000 satellites were planned to be deployed, with (as of 2019) a possible later extension to 42,000. [ 430 ]
In February 2019, a sister company of SpaceX, SpaceX Services Incorporated, filed a request with the FCC to receive a license for the operation of up to a million fixed satellite Earth stations that would communicate with its non-geostationary orbit (NGSO) satellite Starlink system. [ 431 ]
In June 2019, SpaceX applied to the FCC for a license to test up to 270 ground terminals – 70 nationwide across the United States and 200 in Washington state at SpaceX employee homes [ 432 ] [ 433 ] – and aircraft-borne antenna operation from four distributed United States airfields; as well as five ground-to-ground test locations. [ 434 ] [ 435 ]
On October 15, 2019, the United States FCC submitted filings to the International Telecommunication Union (ITU) on SpaceX's behalf to arrange spectrum for 30,000 additional Starlink satellites to supplement the 12,000 Starlink satellites already approved by the FCC. [ 430 ] That month, Musk publicly tested the Starlink network by using an Internet connection routed through the network to post a first tweet to social media site Twitter . [ 436 ]
The chart below contains all v0.9 and first generation satellites (Tintin A and Tintin B, as test satellites, are not included).
Early designs had all phase 1 satellites in altitudes of around 1,100–1,300 km (680–810 mi). SpaceX initially requested to lower the first 1584 satellites, and in April 2020 requested to lower all other higher satellite orbits to about 550 km (340 mi). [ 442 ] [ 443 ] In April 2020, SpaceX modified the architecture of the Starlink network. [ 444 ] SpaceX submitted an application to the FCC proposing to operate more satellites in lower orbits in the first phase than the FCC previously authorized. The first phase will still include 1,440 satellites in the first shell orbiting at 550 km (340 mi) in planes inclined 53.0°, [ 420 ] with no change to the first shell of the constellation launched largely in 2020. [ 445 ] SpaceX also applied in the United States for use of the E-band in their constellation [ 446 ] The FCC approved the application in April 2021. [ 447 ] [ 448 ]
On January 24, 2021 SpaceX released a new group of 10 Starlink satellites, the first Starlink satellites in polar orbits. The launch surpassed ISRO 's record of launching the most satellites in one mission (143), taking to 1,025 the cumulative number of satellites deployed for Starlink to that date. [ 449 ] [ 450 ]
On February 3, 2022, 49 satellites were launched as Starlink Group 4–7. A G2-rated geomagnetic storm occurred on February 4, caused the atmosphere to warm and density at the low deployment altitudes to increase. Predictions were that up to 40 of the 49 satellites might be lost due to drag. [ 451 ] After the event, 38 satellites reentered the atmosphere by February 12 while the remaining 11 were able to raise their orbits and avoid loss due to the storm. [ 452 ] [ 453 ]
In March 2023, SpaceX submitted an application to add V-band payload to the second generation satellites rather than fly phase 2 V-band satellites as originally planned and authorized. [ 454 ] The request is subject to FCC approval.
With the unknown of when Starship will be able to launch the second generation satellites, SpaceX modified the original V2 blueprint into a smaller, more compact one named "v2 mini". This adjustment allowed Falcon 9 to transport these satellites, though not as many, into orbit. [ 460 ] The first set of 21 of these satellites was launched on February 27, 2023. SpaceX committed to reducing debris by keeping the Starlink tension rods, which hold the V2 mini-satellites together, attached to the Falcon 9 second stage. These tension rods were discarded into orbit while launching earlier versions of Starlink satellites. [ 461 ] [ full citation needed ] Observations confirm these V2 mini-satellites host two solar panels like the Starship V2 satellites. [ 462 ]
SpaceX planned to test the deployment system for a new version of their Starlink satellites. On 16 January 2025, S33 was also expected to deploy ten Starlink "simulators," which were also expected to reenter over the Indian Ocean. [ citation needed ] Contact with S33 was lost shortly before its engines were scheduled to shut down. [ 463 ]
The planned large number of satellites has been met with criticism from the astronomical community because of concerns over light pollution . [ 466 ] [ 467 ] [ 468 ] Astronomers claim that their brightness in both optical and radio wavelengths will severely impact scientific observations. While astronomers can schedule observations to avoid pointing where satellites currently orbit, it is "getting more difficult" as more satellites come online. [ 469 ] The International Astronomical Union (IAU), National Radio Astronomy Observatory (NRAO), and Square Kilometre Array Organization (SKAO) have released official statements expressing concern on the matter. Recent studies have proved that the "unintended electromagnetic radiation" affects radio telescopes creating distortions and excessive noise and the IAU Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference was created to manage these new man-made obstacles to space exploration. [ 470 ] [ 471 ] [ 472 ] [ 473 ]
On November 20, 2019, the four-meter (13') Blanco telescope of the Cerro Tololo Inter-American Observatory (CTIO) recorded strong signal loss [ clarification needed ] and the appearance of 19 white lines on a DECam shot (right image). This image noise was correlated to the transit of a Starlink satellite train, launched a week earlier. [ 474 ]
SpaceX representatives and Musk have claimed that the satellites will have minimal impact, being easily mitigated by pixel masking and image stacking . [ 475 ] However, professional astronomers have disputed these claims based on initial observation of the Starlink v0.9 satellites on the first launch, shortly after their deployment from the launch vehicle. [ 476 ] [ 477 ] [ 478 ] [ 479 ] In later statements on Twitter, Musk stated that SpaceX will work on reducing the albedo of the satellites and will provide on-demand orientation adjustments for astronomical experiments, if necessary. [ 480 ] [ 481 ] One Starlink satellite (Starlink 1130 / DarkSat) launched with an experimental coating to reduce its albedo. The reduction in g-band magnitude is 0.8 magnitude (55%). [ 482 ] [ 483 ] Despite these measures, astronomers found that the satellites were still too bright, thus making DarkSat essentially a "dead end". [ 484 ]
On April 17, 2020, SpaceX wrote in an FCC filing that it would test new methods of mitigating light pollution, and also provide access to satellite tracking data for astronomers to "better coordinate their observations with our satellites". [ 485 ] [ 486 ] On April 27, 2020, Musk announced that the company would introduce a new sunshade designed to reduce the brightness of Starlink satellites. [ 485 ] As of 15 October 2020 [update] , over 200 Starlink satellites had a sunshade. An October 2020 analysis found them to be only marginally fainter than DarkSat. [ 487 ] A January 2021 study pinned the brightness at 31% of the original design. [ 488 ]
According to a May 2021 study, "A large number of fast-moving transmitting stations (i.e. satellites) will cause further interference. New analysis methods could mitigate some of these effects, but data loss is inevitable, increasing the time needed for each study and limiting the overall amount of science done". [ 489 ]
In February 2022, the International Astronomical Union (IAU) established a center to help astronomers deal with the adverse effects of satellite constellations such as Starlink. Work will include the development of software tools for astronomers, advancement of national and international policies, community outreach and work with industry on relevant technologies. [ 490 ]
In June 2022, the IAU released a website for astronomers to deal with some adverse effects via satellite tracking. This will enable astronomers to be able to track satellites to be able to avoid and time them for minimal impact on current work. [ 405 ]
The first batch of Generation 2 spacecraft was launched in February 2023. These satellites are referred to as "Mini" because they are smaller than the full-sized Gen 2 spacecraft that will come later. SpaceX uses brightness mitigation for Gen 2 that includes a mirror-like surface which reflects sunlight back into space and they orient the solar panels so that observers on the ground only see the dark sides. [ 411 ] The Minis are fainter than Gen 1 spacecraft despite being four times as large according to an observational study published in June 2023. They are 44% as bright as VisorSats, 24% compared to V1.5 and 19% compared to the original design which had no brightness mitigation. [ 491 ] : Table 3 Minis appear 12 times brighter before they reach the target orbit. [ 491 ]
In October 2023, research published in "Astronomy and Astrophysics Letters" had reportedly found that Starlink satellites were "leaking radio signals" finding that at the site of the future Square Kilometer Array , radio emissions from Starlink satellites were brighter than any natural source in the sky. [ 492 ] The paper concluded that these emissions will be "detrimental to key SKA science goals without future mitigation". [ 493 ] [ 473 ]
The large number of satellites employed by Starlink may create the long-term danger of space debris resulting from placing thousands of satellites in orbit and the risk of causing a satellite collision , potentially triggering a cascade phenomenon known as Kessler syndrome . [ 494 ] [ 495 ] SpaceX has said that most of the satellites are launched at a lower altitude, and failed satellites are expected to deorbit within five years without propulsion. [ 496 ] [ 497 ]
Early in the program, a near-miss occurred when SpaceX did not move a satellite that had a 1 in 1,000 chance of colliding with a European one, ten times higher than the ESA 's threshold for avoidance maneuvers. SpaceX subsequently fixed an issue with its paging system that had disrupted emails between the ESA and SpaceX. The ESA said it plans to invest in technologies to automate satellite collision avoidance maneuvers. [ 498 ] [ 499 ] In 2021, Chinese authorities lodged a complaint with the United Nations, saying their space station had performed evasive maneuvers that year to avoid Starlink satellites. [ 500 ] In the document, Chinese delegates said that the continuously maneuvering Starlink satellites posed a risk of collision, and two close encounters with the satellites in July and October constituted dangers to the life or health of astronauts aboard the Chinese Tiangong space station . [ 501 ] [ 497 ]
All these reported issues, plus current plans for the extension of the constellation, motivated a formal letter from the National Telecommunications and Information Administration (NTIA) on behalf of NASA and the NSF , submitted to the FCC on February 8, 2022, warning about the potential impact on low Earth orbit , increased collision risk, impact on science missions, rocket launches, International Space Station and radio frequencies. [ 502 ]
SpaceX satellites will maneuver if the probability of collision is greater than 10 −5 (1 in 100,000 chance of collision), as opposed to the industry standard of 10 −4 (1 in 10,000 chance of collision). [ 503 ] SpaceX has budgeted sufficient propellant to accommodate approximately 5,000 propulsive maneuvers over the life of a Gen2 satellite, including a budget of approximately 350 collision avoidance maneuvers per satellite over that time period. [ 413 ]
As of May 2022, the average Starlink satellite had conducted fewer than three collision-avoidance maneuvers over the 6 preceding months. [ 413 ]
In addition to the OneWeb constellation , announced nearly concurrently with the SpaceX constellation, a 2015 proposal from Samsung outlined a 4,600-satellite constellation orbiting at 1,400 km (870 mi) that could provide a zettabyte per month capacity worldwide, an equivalent of 200 gigabytes per month for 5 billion users of Internet data, [ 504 ] [ 505 ] but by 2020, no more public information had been released about the Samsung constellation. Telesat announced a smaller 117 satellite constellation in 2015 with plans to deliver initial service in 2021. [ 506 ] Amazon announced a large broadband internet satellite constellation in April 2019, planning to launch 3,236 satellites in the next decade in what the company calls " Project Kuiper ", a satellite constellation that will work in concert [ 507 ] with Amazon's previously announced large network of twelve satellite ground station facilities (the " AWS ground station unit") announced in November 2018. [ 508 ]
In February 2015, financial analysts questioned established geosynchronous orbit communications satellite fleet operators as to how they intended to respond to the competitive threat of SpaceX and OneWeb LEO communication satellites. [ 509 ] In October 2015, SpaceX President Gwynne Shotwell indicated that while development continues, the business case for the long-term rollout of an operational satellite network was still in an early phase. [ 510 ]
By October 2017, the expectation for large increases in satellite network capacity from emerging lower-altitude broadband constellations caused market players to cancel some planned investments in new geosynchronous orbit broadband communications satellites . [ 511 ]
SpaceX was challenged regarding Starlink in February 2021 when the National Rural Electric Cooperative Association (NRECA), a political interest group representing traditional rural internet service providers, urged the U.S. Federal Communications Commission (FCC) to "actively, and aggressively, and thoughtfully vet" the subsidy applications of SpaceX and other broadband providers. At the time, SpaceX had provisionally won $886 million for a commitment to provide service to approximately 643,000 locations in 35 states as part of the Rural Digital Opportunity Fund (RDOF). [ 512 ] The NRECA criticisms included that the funding allocation to Starlink would include service to locations—such as Harlem and terminals at Newark Liberty International Airport and Miami International Airport —that are not rural, and because SpaceX was planning to build the infrastructure and serve any customers who request service with or without the FCC subsidy. [ 512 ] Additionally, Jim Matheson, chief executive officer of the NRECA voiced concern about technologies that had not yet been proven to meet the high speeds required for the award category. Starlink was specifically criticized for being still in beta testing and for unproven technology. [ 513 ]
While Starlink is deployed worldwide, it has encountered trademark conflicts in some countries such as Mexico [ 514 ] and Ukraine. [ 515 ] | https://en.wikipedia.org/wiki/Starlink |
The Starlink Project , referred to by users as Starlink and by developers as simply The Project , was a UK astronomical computing project which supplied general-purpose data reduction software. Until the late 1990s, it also supplied computing hardware and system administration personnel to UK astronomical institutes. In the former respect, it was analogous to the US IRAF project.
The project was formally started in 1980, though the funding had been agreed, and some work begun, a year earlier. It was closed down when its funding was withdrawn by the Particle Physics and Astronomy Research Council in 2005. In 2006, the Joint Astronomy Centre released its own updated version of Starlink and took over maintenance; the task was passed again in mid-2015 to the East Asian Observatory . The latest version was released on 2018 July 19.
Part of the software is relicensed under the GNU GPL while some of it remain under the original custom licence. [ 1 ]
From its beginning, the project aimed to cope with the ever-increasing data volumes which astronomers had to handle. A 1982 paper exclaimed that astronomers were returning from observing runs (a week or so of observations at a remote telescope) with more than 10 Gigabits of data on tape; [ 2 ] at the end of its life the project was rolling out libraries to handle data of more than 4 Gigabytes per single image.
The project provided centrally-purchased (and thus discounted) hardware, professional system administrators, and the developers to write astronomical data-reduction applications for the UK astronomy community and beyond. At its peak size in the late 1980s and early 1990s, the project had a presence at around 30 sites, located at most of the UK universities with an astronomy department, plus facilities at the Joint Astronomy Centre , the home of UKIRT and the James Clerk Maxwell Telescope in Hawaii . The number of active developers fluctuated between five and more than a dozen.
By 1982, the project had a staff of 17, serving about 400 users at six sites, using seven VAXen (six VAX-11/780s and one VAX-11/750 , representing a total of about 6.5 GB of disk space). They were networked from the outset, first with DECNET and later with X.25 .
Between 1992 and 1995 the project switched to UNIX (and switched the networking to TCP/IP), supporting Digital UNIX on Alpha -based systems, and Solaris on systems from Sun Microsystems . By the late 1990s it was additionally supporting Linux , and by 2005 it was supporting Red Hat Linux , Solaris, and Tru64 UNIX . It was about this time that the project open-sourced its software (using the GNU General Public License ; it had previously had an "academic use only" licence), and reworked its build system so that the software could be built on a much broader range of POSIX -like systems, including OS X and Cygwin .
Though it was not explicitly funded to do so, the project was an early participant in the Virtual Observatory movement, and contributed to the IVOA . One of its VO applications was TOPCAT, development of which continues, with AstroGrid funding.
The project produced a number of applications and libraries, including:
The project also produced a number of cookbooks on various astronomical topics.
By the end, the project's code base consisted of around 100 components, totalling around 2,100,000 source lines of code written by the project or curated by it, in various languages including Fortran, C, C++, Java, Perl and Tcl/Tk, plus another 700,000 lines of customised third-party code. [ citation needed ]
At present, though funding for the project has ceased, the software is still available, either as pre-built distributions, or from a Git repository. [ 3 ] The Astrophysics Source Code Library maintains an entry on Starlink. [ 4 ]
The Joint Astronomy Centre took over the maintenance of the Starlink codebase (with support from STFC ), and made the following releases: [ 5 ]
The East Asian Observatory has now taken over co-ordination and maintenance of Starlink software, and it has made the following releases: [ 5 ] | https://en.wikipedia.org/wiki/Starlink_Project |
The Starmus International Festival is an international gathering focused on celebrating astronomy, space exploration, music, art, and the natural sciences. It was founded by astronomer / amateur musician Garik Israelian and musician / astrophysicist Brian May . The festival has featured multiple well-known astronauts and astronomers.
The first festival took place from 20 to 25 June 2011 on Tenerife and La Palma , Canary Islands with the theme "50 Years of Man in Space." In 2014, the book Starmus: 50 Years of Man in Space was published covering the content of the festival. [ 1 ] [ 2 ]
The second festival occurred 22 to 27 September 2014, on Tenerife and La Palma, Canary Islands with the theme "Beginnings: The Making of the Modern Cosmos." The Government of Tenerife announced that the equivalent publicity value from Starmus Festival II (2014) exceeds 170 million euros and that the festival reached 2.4 billion people worldwide. [ 3 ]
The third festival took place in the Canary Islands, on Tenerife and La Palma from 27 June to 2 July 2016 with the theme of "Beyond The Horizon: A Tribute To Stephen Hawking". The festival featured numerous scientists and science communicators including Stephen Hawking , Brian Cox , Richard Dawkins , Brian May , and 11 Nobel laureates . [ 4 ] [ 5 ]
Starmus III held the inaugural awards ceremony for recipients of the Stephen Hawking Medal for Science Communication . The award recipients (chosen by Hawking himself) were composer Hans Zimmer, physicist Jim Al-Khalili and the science documentary Particle Fever . [ 6 ]
The fourth festival took place in Trondheim , Norway, from 18 to 23 June 2017 with the theme of "Life and the Universe". The festival featured eleven Nobel Prize laureates and many astronomers, biologists, chemists, economists, astronauts and artists.
The Stephen Hawking Medal award winners were Neil deGrasse Tyson (science writing), Jean-Michel Jarre (music and arts) and The Big Bang Theory (films). [ 7 ]
The fifth festival took place in Zurich, Switzerland in June 2019 under the theme "A Giant Leap", dedicated to the first step of the man on the Moon. Coinciding with the 50th anniversary of Apollo 11 landing on the Moon. The Stephen Hawking Medal was awarded to Elon Musk , Buzz Aldrin, Brian Eno and the documentary Apollo 11 , screened during the festival for the first time in Europe. [ 8 ] [ 9 ]
The sixth Starmus festival took place 5–11 September 2022 in Yerevan , Armenia with the theme 50 Years on Mars , dedicated to the 50th anniversary of the first landing on Mars . There were opening ceremonies and a concert on the first day. Around 50 scientists, Nobel laureates, engineers, cosmonauts, musicians and artists took part in festival events. Starmus VI hosted a Science Camp "to enable children and people interested in science to more closely get acquainted with the latest scientific and technological achievements." [ 10 ] [ 11 ]
Premiering at the festival was the documentary film Space Inside about the Soviet and Russian cosmonaut Alexei Leonov . The 80-minute film is based on Leonov's last interview and includes footage from the Soviet history of space exploration. [ 12 ] A composition dedicated to the topic of Mars exploration was performed at the closing of the festival; the neo-symphony "March of Mars" by Tigran Jager. [ 13 ]
Winners of the Stephen Hawking Medal were announced as Brian May, Jane Goodall , Diane Ackerman and the NASA Communications Unit. [ 14 ]
The seventh festival took place 12 to 17 May 2024 in Bratislava , Slovakia with the theme "The Future Of Our Home Planet". [ 15 ] A concert on the first day featured performances by Jean-Michel Jarre and Brian May, light and laser displays, and a drone ballet for an audience of 100,000 by the SNP bridge . [ 16 ] They were accompanied by the musicians Claude Samard, Adiescar Chase , Slovak Philharmonic Orchestra and Slovak Philharmonic Choir . [ 17 ]
Some famous expert speakers of the festival programme were anthropologist Jane Goodall, Nobel Prize winners Michel Mayor , Emmanuelle Charpentier and Kip Thorne , and former astronauts Charlie Duke , Chris Hadfield , Kathryn Thornton and Garrett Reisman . [ 18 ]
The Stephen Hawking Medal for Science Communication was awarded to Laurie Anderson , Christopher Nolan , David Attenborough and Sylvia Earle . [ 18 ]
Two Sonic Universe Concerts were held at the Magma Arte & Congresos arena in Tenerife. The 2011 concert was recorded and produced into a CD entitled Starmus - Sonic Universe . [ 19 ] The rock band Nosound recorded their 2014 concert performance and produced a CD/DVD set entitled Teide 2390 . [ 20 ] | https://en.wikipedia.org/wiki/Starmus_Festival |
Stars-AO [ 2 ] also known as Aoi is an experimental cubesat with a small camera packaged. It uses amateur radio frequencies to communicate with the ground.
This spacecraft or satellite related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Stars-AO |
Stars proposed in religion may include: | https://en.wikipedia.org/wiki/Stars_proposed_in_religion |
The Stars virus is a computer virus which infects computers running Microsoft Windows . It was named and discovered by Iranian authorities in April 2011. Iran claimed it was used as a tool to commit espionage . [ 1 ] [ 2 ] Western researchers came to believe it is probably the same thing as the Duqu virus, part of the Stuxnet attack on Iran.
The Stars virus was studied in a laboratory in Iran – that means major vendors of antivirus software did not have access to samples and therefore they could not assess any potential relation to Duqu or Stuxnet . [ 1 ] [ 2 ] Foreign computer experts say they have seen no evidence of the virus, and some even doubt its actual existence. [ 3 ] [ 4 ] Iran is claiming Stars to be harmful for computer systems. It is said to inflict minor damage in the initial stage and might be mistaken for executable files of governmental organizations. [ 1 ] [ 2 ]
This is the second attack claimed by Iran after the Stuxnet computer worm discovered in July 2010, which targeted industrial software and equipment. [ 2 ] [ 5 ]
Researchers came to believe that the Stars virus found by Iranian computer specialists was the Duqu virus. The Duqu virus keylogger was embedded in a JPEG file. Since most of the file was taken by the keylogger only a portion of the image remained. It turned out to be an image taken by the Hubble telescope showing a cluster of stars, the aftermath of two galaxies colliding. Symantec, Kaspersky and CrySyS researchers came to believe Duqu and Stars were the same virus. [ 6 ] [ 7 ] | https://en.wikipedia.org/wiki/Stars_virus |
The start codon is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome . The start codon always codes for methionine in eukaryotes and archaea and a N -formylmethionine (fMet) in bacteria, mitochondria and plastids .
The start codon is often preceded by a 5' untranslated region ( 5' UTR ). In prokaryotes this includes the ribosome binding site .
In all three domains of life, the start codon is decoded by a special "initiation" transfer RNA different from the tRNAs used for elongation. There are important structural differences between an initiating tRNA and an elongating one, with distinguish features serving to satisfy the constraints of the translation system. In bacteria and organelles, an acceptor stem C1:A72 mismatch guide formylation, which directs recruitment by the 30S ribosome into the P site; so-called "3GC" base pairs allow assembly into the 70S ribosome. [ 1 ] In eukaryotes and archaea, the T stem prevents the elongation factors from binding, while eIF2 specifically recognizes the attached methionine and a A1:U72 basepair. [ 2 ]
In any case, the natural initiating tRNA only codes for methionine. [ 3 ] Knowledge of the key recognizing features has allowed researchers to construct alternative initiating tRNAs that code for different amino acids; see below.
Alternative start codons are different from the standard AUG codon and are found in both prokaryotes (bacteria and archaea) and eukaryotes . Alternate start codons are still translated as Met when they are at the start of a protein (even if the codon encodes a different amino acid otherwise). This is because a separate tRNA is used for initiation. [ 3 ]
Alternate start codons (non-AUG) are very rare in eukaryotic genomes: a wide range of mechanisms work to guarantee the relative fidelity of AUG initiation. [ 4 ] However, naturally occurring non-AUG start codons have been reported for some cellular mRNAs. [ 5 ] Seven out of the nine possible single-nucleotide substitutions at the AUG start codon of dihydrofolate reductase are functional as translation start sites in mammalian cells. [ 6 ]
Bacteria do not generally have the wide range of translation factors monitoring start codon fidelity. GUG and UUG are the main, even "canonical", alternate start codons. [ 4 ] GUG in particular is important to controlling the replication of plasmids. [ 4 ]
E. coli uses 83% AUG (3542/4284), 14% (612) GUG, 3% (103) UUG [ 7 ] and one or two others (e.g., an AUU and possibly a CUG). [ 8 ] [ 9 ]
Well-known coding regions that do not have AUG initiation codons are those of lacI (GUG) [ 10 ] [ 11 ] and lacA (UUG) [ 12 ] in the E. coli lac operon . Two more recent studies have independently shown that 17 or more non-AUG start codons may initiate translation in E. coli . [ 13 ] [ 14 ]
Mitochondrial genomes use alternate start codons more significantly (AUA and AUG in humans). [ 15 ] Many such examples, with codons, systematic range, and citations, are given in the NCBI list of translation tables . [ 16 ]
Archaea, which are prokaryotes with a translation machinery similar to but simpler than that of eukaryotes, allow initiation at UUG and GUG. [ 4 ]
These are "alternative" start codons in the sense that they are upstream of the regular start codons and thus could be used as alternative start codons. More than half of all human mRNAs have at least one AUG codon upstream (uAUG) of their annotated translation initiation starts (TIS) (58% in the current versions of the human RefSeq sequence). Their potential use as TISs could result in translation of so-called upstream Open Reading Frames (uORFs). uORF translation usually results in the synthesis of short polypeptides, some of which have been shown to be functional, e.g., in ASNSD1, MIEF1 , MKKS , and SLC35A4. [ 17 ] However, it is believed that most translated uORFs only have a mild inhibitory effect on downstream translation because most uORF starts are leaky (i.e. don't initiate translation or because ribosomes terminating after translation of short ORFs are often capable of reinitiating). [ 17 ]
Translation started by an internal ribosome entry site (IRES), which bypasses a number of regular eukaryotic initiation systems, can have a non-methinone start with GCU or CAA codons. [ 23 ]
Mammalian cells can initiate translation with leucine using a specific leucyl-tRNA that decodes the codon CUG. This mechanism is independent of eIF2. No secondary structure similar to that of an IRES is needed. It proceeds by ribosomal scanning, and a Kozak context enhances initiation efficiency. [ 24 ] [ 25 ] [ 26 ]
Engineered initiator tRNA (tRNA fMet CUA , changed from a MetY tRNA fMet CAU ) have been used to initiate translation at the amber stop codon UAG in E. coli . Initiation with this tRNA not only inserts the traditional formylmethionine , but also formylglutamine, as glutamyl-tRNA synthase also recognizes the new tRNA. [ 27 ] (Recall from above that the bacterial translation initiation system does not specifically check for methionine, only the formyl modification). [ 1 ] One study has shown that the amber initiator tRNA does not initiate translation to any measurable degree from genomically-encoded UAG codons, only plasmid-borne reporters with strong upstream Shine-Dalgarno sites . [ 28 ] | https://en.wikipedia.org/wiki/Start_codon |
In telecommunications , a start signal is a signal that prepares a device to receive data or to perform a function.
In asynchronous serial communication , start signals are used at the beginning of a character that prepares the receiving device for the reception of the code elements.
A start signal is limited to one signal element usually having the duration of a unit interval .
This article related to telecommunications is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Start_signal |
A startup ecosystem is formed by people in startups in their various stages, and various types of organizations in a location (physical or virtual) that are interacting as a system to create and scale new startup companies . These organizations can be further divided into categories such as universities, funding organizations, support organizations (like incubators, accelerators, co-working spaces etc.), research organizations, service provider organizations (like legal, financial services etc.) and large corporations. Local Governments and Government organizations such as Commerce / Industry / Economic Development departments also play an important role in a startup ecosystem. Different organizations typically focus on specific parts of the ecosystem function and startups at their specific development stage(s). [ 1 ] [ 2 ] [ 3 ]
Emerging startup ecosystems are often evaluated using tangible metrics like new products, patents, and venture capital funding. However, Hannigan et al. (2022) [ 3 ] argue that understanding these ecosystems requires considering cultural factors alongside material ones. They emphasize that cultural elements, such as community engagement and shared values, play a crucial role in the growth and success of emerging startup ecosystems. By incorporating both cultural and material perspectives, policymakers can better design incentives and regulations to foster economic growth and innovation in these ecosystems. This approach suggests that building cultural infrastructure is as important as financial and technical support in developing thriving entrepreneurial environments.
Silicon Valley , NYC , Singapore and Tel Aviv are considered examples of global startup ecosystems.
Investors from these roles are linked together through shared events, activities, locations, and interactions. Startup ecosystems generally encompass the network of interactions between people, organizations, and their environment. Any particular start-up ecosystem [ 9 ] is defined by its collection of specific cities or online communities.
In addition, resources like skills, time, and money are also essential components of a start-up ecosystem. The resources that flow through ecosystems are obtained primarily from the meetings between people and organizations that are an active part of those startup ecosystems. These interactions help to create new potential startups and/or to strengthen the already existing ones. There are a few common mistakes that entrepreneurs make [ 10 ] [ 11 ] that end up costing them their business, like inability to secure adequate funding, sudden market downturn and a poor scaling plan. [ 12 ]
Startup ecosystems are controlled by both external and internal factors. External factors, such as financial climate, big market disruptions, and significant transitions, control the overall structure of an ecosystem and the way things work within it. Start-up ecosystems are dynamic entities that progress from formation stages to periodic disturbances (like the financial bubbles ) and then to recovering processes.
Several researchers have created lists of essential internal attributes for startup ecosystems. Spigel [ 13 ] suggests that ecosystems require cultural attributes (a culture of entrepreneurship and histories of successful entrepreneurship), social attributes that are accessed through social ties (worker talent, investment capital, social networks, and entrepreneurial mentors) and material attributes grounded in a specific places (government policies, universities, support services, physical infrastructure, and open local markets). Stam [ 14 ] distinguishes between framework conditions of ecosystems (formal institutions, culture, physical infrastructure, and market demand) with systematic conditions of networks, leadership, finance, talent, knowledge, and support services.
Startup ecosystems in similar environments but located in different parts of the world can end up doing things differently simply because they have a different entrepreneurial culture and resource pool. The introduction of non-native peoples' knowledge and skills can also cause substantial shifts in the ecosystem's functions.
Internal factors act as feedback loops inside any particular startup ecosystem. They not only control ecosystem processes, but are also controlled by them. While some resource inputs are generally controlled by external processes like financial climate and market disruptions, the availability of resources within the ecosystem are controlled by every organization's ability to contribute towards the ecosystem. Although people exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like financial climate.
Employee diversity also affects startup ecosystem functions, as do the processes of disturbance and succession. Startup ecosystems provide a variety of goods and services upon which other people and companies depend on. Thus, the principles of start-up ecosystem management suggest that rather than managing individual people or organizations, resources should be managed at the level of the startup ecosystem itself. Classifying start-up ecosystems into structurally similar units is an important step towards effective ecosystem managing.
There are several independent studies made to evaluate start-up ecosystems to better understand and compare various start-up ecosystems and to offer valuable insights of the strengths and weaknesses of different start-up ecosystems. Startup ecosystems can be studied through a variety of approaches — theoretical studies, studies monitoring specific start-up ecosystems over long periods of time and those that look at differences between start-up ecosystems to elucidate how they work.
Since 2012, San Francisco-based Startup Genome has been the first organization to release comprehensive research reports that benchmark startup ecosystems globally. Under the leadership of JF Gauthier and Marc Penzel, the company has been the first organization to capture the requirements of a startup ecosystem in a data-driven framework. [ 15 ] Startup Genome's work influenced startup policies globally and is supported by thought leaders such as Steve Blank [ 16 ] and has appeared in leading business media such as The Economist , Bloomberg and Harvard Business Review . [ 17 ]
Multiple cities and hubs have been described as global Startup ecosystems. Startup Genome publishes a yearly ranking of global startup ecosystems. [ 18 ] [ 19 ] The study does yearly reports ranking the top 40 global startup hubs. [ 19 ] In addition, StartupBlink, also releases an annual Index ranking global startup ecosystems, which evaluates over 1,000 cities worldwide. [ 20 ] [ 21 ]
from 2025
Startup genome report (2024) | https://en.wikipedia.org/wiki/Startup_ecosystem |
Starvation response in animals (including humans) is a set of adaptive biochemical and physiological changes, triggered by lack of food or extreme weight loss, in which the body seeks to conserve energy by reducing metabolic rate and/or non-resting energy expenditure to prolong survival and preserve body fat and lean mass. [ 1 ]
Equivalent or closely related terms include famine response , starvation mode , famine mode , starvation resistance , starvation tolerance , adapted starvation , adaptive thermogenesis , fat adaptation , and metabolic adaptation .
Ordinarily, the body responds to reduced energy intake by firstly exhausting the contents of the digestive tract along with glycogen reserves present in both muscle and liver cells via glycogenolysis . [ 2 ] After prolonged periods of starvation this store of glycogen runs out, and the body then starts burning fat reserves and consuming muscle and other tissues and uses the proteins within muscle tissue as a fuel source, which results in muscle mass loss. [ 3 ]
The magnitude and composition of the starvation response (i.e. metabolic adaptation) was estimated in a study of 8 individuals living in isolation in Biosphere 2 for two years. During their isolation, they gradually lost an average of 15% (range: 9–24%) of their body weight due to harsh conditions. On emerging from isolation, the eight isolated individuals were compared with a 152-person control group that initially had similar physical characteristics. On average, the starvation response of the individuals after isolation was a 750-kilojoule (180-kilocalorie) reduction in daily total energy expenditure . 250 kJ (60 kcal) of the starvation response was explained by a reduction in fat-free mass and fat mass . An additional 270 kJ (65 kcal) was explained by a reduction in fidgeting . The remaining 230 kJ (55 kcal) was statistically insignificant. [ 4 ]
The energetic requirements of a body are composed of the basal metabolic rate (BMR) and the physical activity level (ERAT, exercise-related activity thermogenesis). This caloric requirement can be met with protein, fat, carbohydrates, or a mixture of those. Glucose is the general metabolic fuel, and can be metabolized by any cell. Fructose and some other nutrients can be metabolized only in the liver, where their metabolites transform into either glucose stored as glycogen in the liver and in muscles, or into fatty acids stored in adipose tissue.
Because of the blood–brain barrier , getting nutrients to the human brain is especially dependent on molecules that can pass this barrier. The brain itself consumes about 18% of the basal metabolic rate: on a total daily intake of 7,500 kJ (1,800 kcal), this equates to 1,360 kJ (324 kcal), or about 80 g of glucose. About 25% of total body glucose consumption occurs in the brain.
Glucose can be obtained directly from dietary sugars and by the breakdown of other carbohydrates . In the absence of dietary sugars and carbohydrates, glucose is obtained from the breakdown of stored glycogen . Glycogen is a readily-accessible storage form of glucose, stored in notable quantities in the liver and skeletal muscle. [ 5 ]
When the glycogen reserve is depleted, glucose can be obtained from the breakdown of fats from adipose tissue . Fats are broken down into glycerol and free fatty acids, with the glycerol being turned into glucose in the liver via the gluconeogenesis pathway .
When even the glucose made from glycerol reserves start declining, the liver starts producing ketone bodies . Ketone bodies are short-chain derivatives of the free fatty acids mentioned in the previous paragraph, and can cross the blood–brain barrier, meaning they can be used by the brain as an alternative metabolic fuel. Fatty acids can be used directly as an energy source by most tissues in the body, but are themselves too ionized to cross the blood–brain barrier [ contradictory ] .
After the exhaustion of the glycogen reserve, and for the next 2–3 days, fatty acids are the principal metabolic fuel. At first, the brain continues to use glucose, because if a non-brain tissue is using fatty acids as its metabolic fuel, the use of glucose in the same tissue is switched off. Thus, when fatty acids are being broken down for energy, all of the remaining glucose is made available for use by the brain.
After 2 or 3 days of fasting, the liver begins to synthesize ketone bodies from precursors obtained from fatty acid breakdown. The brain uses these ketone bodies as fuel, thus cutting its requirement for glucose. After fasting for 3 days, the brain gets 30% of its energy from ketone bodies. After 4 days, this goes up to 75%. [ 6 ]
Thus, the production of ketone bodies cuts the brain's glucose requirement from 80 g per day to about 30 g per day. Of the remaining 30 g requirement, 20 g per day can be produced by the liver from glycerol (itself a product of fat breakdown). This still leaves a deficit of about 10 g of glucose per day that must come from some other source. This deficit is supplied via gluconeogenesis from amino acids from proteolysis of body proteins.
After several days of fasting, all cells in the body begin to break down protein . This releases amino acids into the bloodstream, which can be converted into glucose by the liver. Since much of the human body's muscle mass is protein, this phenomenon is responsible for the wasting away of muscle mass seen in starvation .
However, the body can selectively decide which cells break down protein and which do not. [ citation needed ] About 2–3 g of protein must be broken down to synthesize 1 g of glucose; about 20–30 g of protein is broken down each day to make 10 g of glucose to keep the brain alive. However, to conserve protein, this number may decrease the longer the fasting.
Starvation ensues when the fat reserves are completely exhausted and protein is the only fuel source available to the body. Thus, after periods of starvation, the loss of body protein affects the function of important organs, and death results, even if there are still fat reserves left unused. [ citation needed ] (In a leaner person, the fat reserves are depleted earlier, the protein depletion occurs sooner, and therefore death occurs sooner.)
The ultimate cause of death is, in general, cardiac arrhythmia or cardiac arrest brought on by tissue degradation and electrolyte imbalances.
In the very obese, it has been shown that proteins can be depleted first. Accordingly, death from starvation is predicted to occur before fat reserves are used up. [ 7 ]
During starvation, less than half of the energy used by the brain comes from metabolized glucose. Because the human brain can use ketone bodies as major fuel sources, the body is not forced to break down skeletal muscles at a high rate, thereby maintaining both cognitive function and mobility for up to several weeks. This response is extremely important in human evolution and allowed for humans to continue to find food effectively even in the face of prolonged starvation. [ 8 ]
Initially, the level of insulin in circulation drops and the levels of glucagon , epinephrine and norepinephrine rise. [ 9 ] At this time, there is an up-regulation of glycogenolysis , gluconeogenesis , lipolysis , and ketogenesis . The body's glycogen stores are consumed in about 24 hours. In a normal 70 kg adult, only about 8,000 kilojoules of glycogen are stored in the body (mostly in the striated muscles ). The body also engages in gluconeogenesis to convert glycerol and glucogenic amino acids into glucose for metabolism. Another adaptation is the Cori cycle , which involves shuttling lipid-derived energy in glucose to peripheral glycolytic tissues, which in turn send the lactate back to the liver for resynthesis to glucose. Because of these processes, blood glucose levels remain relatively stable during prolonged starvation.
However, the main source of energy during prolonged starvation is derived from triglycerides . Compared to the 8,000 kilojoules of stored glycogen, lipid fuels are much richer in energy content, and a 70 kg adult stores over 400,000 kilojoules of triglycerides (mostly in adipose tissue). [ 10 ] Triglycerides are broken down to fatty acids via lipolysis. Epinephrine precipitates lipolysis by activating protein kinase A , which phosphorylates hormone sensitive lipase (HSL) and perilipin . These enzymes, along with CGI-58 and adipose triglyceride lipase (ATGL), complex at the surface of lipid droplets. The concerted action of ATGL and HSL liberates the first two fatty acids. Cellular monoacylglycerol lipase (MGL) , liberates the final fatty acid. The remaining glycerol enters gluconeogenesis. [ 11 ]
Fatty acids cannot be used as a direct fuel source. They must first undergo beta oxidation in the mitochondria (mostly of skeletal muscle, cardiac muscle, and liver cells). Fatty acids are transported into the mitochondria as an acyl-carnitine via the action of the enzyme CAT-1. This step controls the metabolic flux of beta oxidation. The resulting acetyl-CoA enters the TCA cycle and undergoes oxidative phosphorylation to produce ATP . The body invests some of this ATP in gluconeogenesis to produce more glucose. [ 12 ]
Triglycerides and long-chain fatty acids are too hydrophobic to cross into brain cells, so the liver must convert them into short-chain fatty acids and ketone bodies through ketogenesis . The resulting ketone bodies , acetoacetate and β-hydroxybutyrate , are amphipathic and can be transported into the brain (and muscles) and broken down into acetyl-CoA for use in the TCA cycle. Acetoacetate breaks down spontaneously into acetone, and the acetone is released through the urine and lungs to produce the “acetone breath” that accompanies prolonged fasting. The brain also uses glucose during starvation, but most of the body's glucose is allocated to the skeletal muscles and red blood cells. The cost of the brain using too much glucose is muscle loss. If the brain and muscles relied entirely on glucose, the body would lose 50% of its nitrogen content in 8–10 days. [ 13 ]
After prolonged fasting, [ clarification needed ] the body begins to degrade its own skeletal muscle. To keep the brain functioning, gluconeogenesis continues to generate glucose, but glucogenic amino acids—primarily alanine—are required. These come from the skeletal muscle. Late in starvation, when blood ketone levels reach 5-7 mM, ketone use in the brain rises, while ketone use in muscles drops. [ 14 ]
Autophagy then occurs at an accelerated rate. In autophagy, cells cannibalize critical molecules to produce amino acids for gluconeogenesis . This process distorts the structure of the cells, [ 15 ] and a common cause of death in starvation is due to diaphragm failure from prolonged autophagy. [ citation needed ]
Bacteria become highly tolerant to antibiotics when nutrients are limited. Starvation contributes to antibiotic tolerance during infection, as nutrients become limited when they are sequestered by host defenses and consumed by proliferating bacteria. [ 16 ] [ 17 ] One of the most important causes of starvation induced tolerance in vivo is biofilm growth, which occurs in many chronic infections. [ 18 ] [ 19 ] [ 20 ] Starvation in biofilms is due to nutrient consumption by cells located on the periphery of biofilm clusters and by reduced diffusion of substrates through the biofilm. [ 21 ] Biofilm bacteria shows extreme tolerance to almost all antibiotic classes, and supplying limiting substrates can restore sensitivity. [ 22 ] | https://en.wikipedia.org/wiki/Starvation_response |
In emulsion polymerization , starve-fed refers to a method of monomer addition where the monomer is introduced gradually into the reaction vessel at a rate that allows the majority of monomer to be consumed by the reaction before more is added. The purpose of this method is generally to control the distribution of different monomers into a copolymer . Many monomers have different reaction rates and so, if all the monomers are added to the system at the same time, tend to react in blocks. This blockiness in the polymer leads to significantly different properties in the final polymer from one with a more statistically random distribution of monomers. [ 1 ]
This method is utilized in synthesizing core-shell latex particles by emulsion polymerization, in order to carefully prepare the final structure.
This chemical process -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Starve-fed |
Statary is a term currently applied in fields such as ecology , ethology , psychology . In modern use it contrasts on the one hand with such concepts as migratory , nomadic , or shifting , and on the other with static or immobile . The word also is of historical interest in its change of meaning as its usage changed.
In current usage in fields such as biology, statary commonly means in a particular location or state, but not rigidly so . Army ant colonies for example are said to be in a statary phase when they occupy one bivouac for an extended period instead of just overnight. This is as opposed to a nomadic phase , in which they travel and forage practically daily. This does not mean that ant colonies in a statary phase do not move nor even that they do not forage while statary; they often do both, sometimes daily. Correspondingly a colony in a nomadic phase does not travel without rest; it bivouacs for the night. The significance of the terms is that the colonies' behaviour patterns differ radically according to their activity phase; one pattern favours maintaining a persistent presence where brood is being raised, whereas the other favours continual nomadic wandering into new foraging grounds. [ 1 ] [ 2 ] Such phases have raised interest in studies in aspects of comparative psychology [ 3 ] and evolution. [ 4 ]
The term statary also applies in contexts other than ants or colonial organisms. Swarm-forming species of locusts go beyond having statary and nomadic phases of behaviour; their growing nymphs actually develop into different adult morphologies, depending on whether the conditions during their growth favour swarming or not. Locusts that adopt the swarming morphology are said to be the migratory morphs , while the rest are called statary morphs. [ 5 ] Effectively similar morphs occur in some other insect species, such as army worm . [ 6 ]
In some technical fields statary need not refer literally to location or motion, but refer figuratively to their having particular characteristic but non-rigid attributes, such as atmospheric pressure. The following section instances examples of such senses occurring in the history of the term.
Statary , from the Latin root statarius , meaning "standing fast", first came into prominent use in the English language in Positions , the work of Richard Mulcaster in the sixteenth century. [ 7 ] He spoke of statarie substance much as, in contemporary English, one might speak of fixed assets or fixed property: "...either rich or poore : landed or unlanded, which is either the having or wanting of the most statarie substance." It is unclear whether he coined the English version of the word.
Samuel Collins also used the word "statary" in the slightly different sense of "ordinary" or "normal" in his 1617 defence of the Bishop of Elie, Lancelot Andrewes : "What is this [in comparison], ... not ... to their stately, but even statarie and ordinarie supremacie in the Church?".
In his Pseudodoxia Epidemica [ 8 ] Sir Thomas Browne used the word in at least two senses; firstly he used it as meaning fixed or regular , as in "...perturbed the observation of festivities and statary solemnities..." secondly he used it in contrast to anniversary (by which he meant "annual" or "seasonal") as in: "...we might expect a regularity in the winds ; whereof though some be statary, some anniversary, and the rest do tend to determine points of heaven, yet do the blasts and undulary breaths thereof maintain no certainty in their course..." In this passage he explicitly does not assert the self-contradiction that winds might be static, but rather that they are unceasing, though variable. In this sense Browne's usage is consistent with the modern technical application.
The word statary appeared in sundry works after Browne's time, for example in the Literary Gazette in the Meteorological Journal , the word was used in reference to winds and barometric readings in much the same sense as that in which Browne had referred to statary winds. [ 9 ]
Lancelot Addison referred to "statary prayers" in his account of his seven years in West Barbary, published in 1671. However, the word never seems to have come into common use, though it did appear in various dictionaries, such as Samuel Johnson 's 1755 Dictionary of the English Language . Such entries did not generally refer to any distinction between the various senses, and in fact some used words such as "stationary" in their definitions, apparently feeling no need for a separate term for the concept of something that has a non-rigid general location around specific coordinates. Accordingly the word was marked as obsolete by the compilers of the Oxford English Dictionary published in the late 19th to early 20th century, [ 7 ] and Webster's Dictionary did likewise in the 1913 unabridged edition. [ 10 ] The Shorter Oxford English Dictionary in turn omitted the entry altogether. [ 11 ] If it had not been resurrected in the role of a technical term, the word statary probably would have disappeared from the language by now. In the sense of "rigidly stationary" it patently is redundant, but in the sense of loosely remaining at particular coordinates, it fills a need in certain fields such as in biology and climatology.
A related sense appeared in the 1623 translation of Xenophon by John Bingham. [ 12 ] As applied to soldiers, statary means: equipped for stationary combat as opposed to skirmishing . [ 7 ]
Eventually, about the early 1930s, the word began to reappear in articles and textbooks, particularly on biological topics. For example, it was used in a prominent textbook of the day, [ 1 ] Norman Maier and associates were applying the concept to ant behaviour; it seems that T. C. Schneirla had elected to use the term in 1932. It had proved useful, and by the end of the 20th century the word was in fairly common use, as can be seen from Google Ngram Viewer . | https://en.wikipedia.org/wiki/Statary |
State-universal coupled cluster ( SUCC ) method is one of several multi-reference coupled-cluster (MR) generalizations of single-reference coupled cluster method. It was first formulated by Bogumił Jeziorski and Hendrik Monkhorst in their work published in Physical Review A in 1981. State-universal coupled cluster is often abbreviated as SUMR-CC or MR-SUCC.
This quantum chemistry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/State-universal_coupled_cluster |
The State Research Center for Applied Microbiology (aka Institute of Microbiology [ 1 ] and NPO Biosintez ; [ 2 ] Russian : Государственный научный центр прикладной микробиологии и биотехнологии ) is a research laboratory in Obolensk, Moscow Oblast .
The facility was built in the 1970s after the Biological Weapons Convention prompted the formation of the Biopreparat directorate at the Soviet Union Ministry of Health . It reached a peak level of activity in the mid-1980s. Facilities at this complex "included at least forty two-story tall fermentation tanks , maintained at Biosafety Level 4 (BSL4) inside huge ring-shaped biocontainment zones in a building called Corpus One." [ 3 ] A variety of bacterial microbes, especially Yersinia pestis , were studied during at minimum the last years of the 20th century. [ 2 ]
As the USSR crumbled, the British and the Americans convinced the Russians to open up for inspection their state laboratory facilities, including their biological ones . [ 1 ] The joint British-American weapons-inspection team toured four Biopreparat facilities in January 1991, including the high-security Obolensk facility. They found that the BSL4 production tanks were capable of making enormous quantities of agent, much like a beer brewery. The inspectors reported the tanks were clean. [ 2 ]
In order to dissuade the staff from collaborating with rogue states, the Nunn–Lugar Cooperative Threat Reduction programme offered incentives to former biological weapons scientists, as well as upgrading the physical security and biosafety of the Obolensk facilities. [ 2 ]
In 1997, a scientist working at the Institute named Pomerantsev published a paper in which were described some genetic modifications to the Anthrax bacteria . [ 4 ]
This article about a Russian building or structure is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/State_Research_Center_for_Applied_Microbiology |
GosNII «Kristall» OJSC ( Gosudarstvenny Nauchno-Issledovatel'skiy Institut «Kristall», State-Owned Scientific-Research Institute "Crystal") (AKA Factory 80) is a chemical factory in Dzerzhinsk (formerly Rastyapino), Nizhny Novgorod Oblast , Russia. It manufactures explosives and non-standard chemical equipment.
The factory was opened in 1953 and is part of the Sverdlova factory . [ 1 ] In 2012 "Kristall" OJSC became part of NPO Pyrotechnic Systems (Moscow region) OJSC, a subdivision of the NPK Tekhmash OJSC holding company, which is in turn part of military industrial giant Rostec . It makes industrial explosives for use in mining, military propellants and ammunition, and medicines made from chemical derivatives. It is also engaged in the research & development and testing of explosives.
An explosion at the factory in August 2018 killed 3 people instantly, followed by 2 more who died in hospital. [ 2 ]
Another explosion on June 1, 2019, completely destroyed the processing facility, caused a fire 100 square meters in area, and injured 38 workers and 41 residents. [ 3 ] Fifteen people were hospitalised for wounds caused by flying shards of broken glass, but no deaths were reported. Five workers were inside the facility when the explosion occurred, but all were evacuated safely.
This article about a chemistry organization is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/State_Research_Institute_Kristall |
State Scientific Research Institute of Aviation Systems or GosNIIAS for short ( Russian : ГосНИИАС ) is a Russian aerospace research centre. Founded by the decree of the Council of Ministers of the USSR on 26 February 1946 from a number of laboratories of the Flight Research Institute for operations research and aviation weapons systems development. The new institute was named NII-2. In March 1994 the institute was re-named with its current name (GosNIIAS). [ 1 ]
Initially, the institute was located in the buildings of the former Sergievo-Elizabethan Asylum . [ 2 ] [ 3 ]
In GosNIIAS, there are six basic departments leading students and graduate students from three universities:
This Russian corporation or company article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/State_Scientific_Research_Institute_of_Aviation_Systems |
In the thermodynamics of equilibrium , a state function , function of state , or point function for a thermodynamic system is a mathematical function relating several state variables or state quantities (that describe equilibrium states of a system) that depend only on the current equilibrium thermodynamic state of the system [ 1 ] (e.g. gas, liquid, solid, crystal, or emulsion ), not the path which the system has taken to reach that state. A state function describes equilibrium states of a system, thus also describing the type of system. A state variable is typically a state function so the determination of other state variable values at an equilibrium state also determines the value of the state variable as the state function at that state. The ideal gas law is a good example. In this law, one state variable (e.g., pressure, volume, temperature, or the amount of substance in a gaseous equilibrium system) is a function of other state variables so is regarded as a state function. A state function could also describe the number of a certain type of atoms or molecules in a gaseous, liquid, or solid form in a heterogeneous or homogeneous mixture , or the amount of energy required to create such a system or change the system into a different equilibrium state.
Internal energy , enthalpy , and entropy are examples of state quantities or state functions because they quantitatively describe an equilibrium state of a thermodynamic system , regardless of how the system has arrived in that state. In contrast, mechanical work and heat are process quantities or path functions because their values depend on a specific "transition" (or "path") between two equilibrium states that a system has taken to reach the final equilibrium state. Exchanged heat (in certain discrete amounts) can be associated with changes of state function such as enthalpy. The description of the system heat exchange is done by a state function, and thus enthalpy changes point to an amount of heat. This can also apply to entropy when heat is compared to temperature . The description breaks down for quantities exhibiting hysteresis . [ 2 ]
It is likely that the term "functions of state" was used in a loose sense during the 1850s and 1860s by those such as Rudolf Clausius , William Rankine , Peter Tait , and William Thomson . By the 1870s, the term had acquired a use of its own. In his 1873 paper "Graphical Methods in the Thermodynamics of Fluids", Willard Gibbs states: "The quantities v , p , t , ε , and η are determined when the state of the body is given, and it may be permitted to call them functions of the state of the body ." [ 3 ]
A thermodynamic system is described by a number of thermodynamic parameters (e.g. temperature, volume , or pressure ) which are not necessarily independent. The number of parameters needed to describe the system is the dimension of the state space of the system ( D ). For example, a monatomic gas with a fixed number of particles is a simple case of a two-dimensional system ( D = 2 ). Any two-dimensional system is uniquely specified by two parameters. Choosing a different pair of parameters, such as pressure and volume instead of pressure and temperature, creates a different coordinate system in two-dimensional thermodynamic state space but is otherwise equivalent. Pressure and temperature can be used to find volume, pressure and volume can be used to find temperature, and temperature and volume can be used to find pressure. An analogous statement holds for higher-dimensional spaces , as described by the state postulate .
Generally, a state space is defined by an equation of the form F ( P , V , T , … ) = 0 {\displaystyle F(P,V,T,\ldots )=0} , where P denotes pressure, T denotes temperature, V denotes volume, and the ellipsis denotes other possible state variables like particle number N and entropy S . If the state space is two-dimensional as in the above example, it can be visualized as a three-dimensional graph (a surface in three-dimensional space). However, the labels of the axes are not unique (since there are more than three state variables in this case), and only two independent variables are necessary to define the state.
When a system changes state continuously, it traces out a "path" in the state space. The path can be specified by noting the values of the state parameters as the system traces out the path, whether as a function of time or a function of some other external variable. For example, having the pressure P ( t ) and volume V ( t ) as functions of time from time t 0 to t 1 will specify a path in two-dimensional state space. Any function of time can then be integrated over the path. For example, to calculate the work done by the system from time t 0 to time t 1 , calculate W ( t 0 , t 1 ) = ∫ 0 1 P d V = ∫ t 0 t 1 P ( t ) d V ( t ) d t d t {\textstyle W(t_{0},t_{1})=\int _{0}^{1}P\,dV=\int _{t_{0}}^{t_{1}}P(t){\frac {dV(t)}{dt}}\,dt} . In order to calculate the work W in the above integral, the functions P ( t ) and V ( t ) must be known at each time t over the entire path. In contrast, a state function only depends upon the system parameters' values at the endpoints of the path. For example, the following equation can be used to calculate the work plus the integral of V dP over the path:
In the equation, d ( P V ) d t d t = d ( P V ) {\displaystyle {\frac {d(PV)}{dt}}dt=d(PV)} can be expressed as the exact differential of the function P ( t ) V ( t ) . Therefore, the integral can be expressed as the difference in the value of P ( t ) V ( t ) at the end points of the integration. The product PV is therefore a state function of the system.
The notation d will be used for an exact differential. In other words, the integral of d Φ will be equal to Φ( t 1 ) − Φ( t 0 ) . The symbol δ will be reserved for an inexact differential , which cannot be integrated without full knowledge of the path. For example, δW = PdV will be used to denote an infinitesimal increment of work.
State functions represent quantities or properties of a thermodynamic system, while non-state functions represent a process during which the state functions change. For example, the state function PV is proportional to the internal energy of an ideal gas, but the work W is the amount of energy transferred as the system performs work. Internal energy is identifiable; it is a particular form of energy. Work is the amount of energy that has changed its form or location.
The following are considered to be state functions in thermodynamics: | https://en.wikipedia.org/wiki/State_function |
A state microbe is a microorganism used as an official state symbol. Several U.S. states have honored microorganisms by nominating them to become official state symbols . The first state to declare an Official State Microbe is Oregon which chose Saccharomyces cerevisiae (brewer's or baker's yeast ) as the Official Microbe of the State of Oregon in 2013 for its significance to the craft beer industry in Oregon. [ 1 ] One of the first proponents of State Microbes was microbiologist Moselio Schaechter , who, in 2010, commented on Official Microbes for the American Society for Microbiology's blog "Small Things Considered" [ 2 ] as well as on National Public Radio's "All Things Considered". [ 3 ] [ 4 ]
In November 2009, Assembly Bill 556 that proposed designating Lactococcus lactis as Wisconsin state microbe was introduced by Representatives Hebl , Vruwink , Williams, Pasch , Danou , and Fields; it was cosponsored by Senator Taylor . [ 5 ] Although the bill passed the Assembly 56 to 41, It was not acted on by the Senate . [ 6 ] The proposed AB 556 simply stated that Lactococcus lactis is the State Microbe and should be included in the Wisconsin Blue Book , [ 7 ] an almanac containing information on the state of Wisconsin , published by Wisconsin's Legislative Reference Bureau.
Lactococcus lactis was proposed as the State Microbe because of its crucial contribution to the cheese industry in Wisconsin. Wisconsin is the largest cheese producer in the United States, producing 3.1 billion pounds of cheese, 26% of all cheese in the US, in more than 600 varieties (2017 data). [ 8 ]
Lactococcus lactis is vital for manufacturing cheeses such as Cheddar , Colby , cottage cheese , cream cheese , Camembert , Roquefort , and Brie , as well as other dairy products like cultured butter , buttermilk , sour cream , and kefir . It may also be used for vegetable fermentations such as cucumber pickles and sauerkraut . [ 9 ]
In January 2013, House Bill 293 was introduced by State Representative James Tokioka ; the proposed bill designates Flavobacterium akiainvivens as the State Microbe of Hawaiʻi . [ 10 ] The bacterium was discovered on a decaying ʻākia shrub by Iris Kuo , a high school student working with Stuart Donachie at the University of Hawaiʻi at Manoa . [ 11 ] [ 12 ] The Hawaiʻian context is strong here because the ʻākia shrub ( Wikstroemia oahuensis ) is native to Hawaiʻi, and the microbe ( Flavobacterium akiainvivens) was first found in Hawaiʻi. The shrub was used by ancient Hawaiʻians for medicine, textiles and for catching fish, while the microbe may have antibiotic properties. [ 10 ]
Although it was favored by the House, the Flavobacterium akiainvivens bill failed to get a hearing in the Senate Technology and Arts Committee (TEC) and could not move forward for a Senate vote. [ 13 ]
In February 2014, Senate Bill 3124 was introduced by Senator Glenn Wakai ; the bill designates Aliivibrio fischeri as the State Microbe of Hawaiʻi. [ 14 ] [ 15 ] Senator Wakai was Chairman of the Senate Technology and Arts Committee that squashed the Flavobacterium legislation. Aliivibrio fischeri was selected because it lives in a symbiotic relationship with the native Hawaiʻian bobtail squid , in which it confers bioluminescence on the squid, enabling it to hunt at night. [ 15 ] Although this is an awesome example of symbiosis , political and scientific controversy erupted because even though the bobtail squid is only found in Hawaiʻi, Aliivibrio fischeri can be found elsewhere. [ 16 ] [ 17 ]
The combined Hawaiʻian Legislature could not agree on which microbe better suited Hawaiʻi, and the proposed legislation was dropped. [ 18 ]
Legislation proposing Flavobacterium akiainvivens as the state microbe was re-introduced in 2017 ( see #Hawaii 2017: Flavobacterium akiainvivens, pending ).
Oregon was the first state to declare an Official State Microbe.
In February 2013, House Concurrent Resolution 12 (HCR-12) was introduced into the Oregon legislative system by Representative Mark Johnson ; the bill designates Saccharomyces cerevisiae (brewer's yeast or bakers yeast) as the Official Microbe of the State of Oregon. [ 19 ] The bill was passed by unanimous vote in the House on April 11; it passed in the Senate by a vote of 28 to 2 on May 23. [ 20 ] Cosponsors of the measure were: Representatives Dembrow , McLane , Vega Pederson , Whisnant , Williamson , and Senators Hansell , Prozanski , and Thomsen . [ 20 ]
HCR-12 recognizes the history of Saccharomyces cerevisiae in baking and brewing, thanks to its ability to convert fermentable sugars into ethanol and carbon dioxide . Most important for Oregon is that the microbe is essential to the production of alcoholic beverages such as mead , wine , beer , and distilled spirits. Moreover, Saccharomyces cerevisiae inspired the thriving brew culture in Oregon, making Oregon an internationally recognized hub of craft brewing . [ 21 ] The craft brewing business brings Oregon $2.4 billion annually, thanks to brewers yeast and talented brewers. [ 22 ]
Streptomyces griseus was chosen for the honor of becoming the New Jersey State Microbe because the organism is a New Jersey native that made unique contributions to healthcare and scientific research worldwide. A strain of S. griseus that produced the antibiotic streptomycin was discovered in New Jersey in “heavily manured field soil” from the New Jersey Agricultural Experimental Station by Albert Schatz in 1943. [ 23 ] Streptomycin is noteworthy because it is: the first significant antibiotic discovered after penicillin ; the first systemic antibiotic discovered in America; the first antibiotic active against tuberculosis ; first-line treatment for plague . Moreover, New Jersey was the home of Selman Waksman , who was awarded the Nobel Prize in Physiology or Medicine for his systematic studies of antibiotic production by S. griseus and other soil microbes. [ 24 ]
On May 15, 2017, Senate Bill 3190 (S3190) was introduced by Senator Samuel D. Thompson (R-12); the bill designates Streptomyces griseus as the New Jersey State Microbe, to be added to the state's other state symbols . On June 1, 2017 Assemblywoman Annette Quijano (D-20) introduced Assembly Bill 4900 (A4900); the bill also designates S. griseus as the New Jersey State Microbe, and is the Assembly counterpart of S3190. [ 25 ]
On December 11, 2017 (the birthday of Dr Robert Koch ) S3190 was unanimously approved by the NJ Senate State Government. Wagering, Tourism & Historic Preservation Committee. Speaking on behalf of the State Microbe were Drs John Warhol, Douglas Eveleigh, [ 26 ] and Max Haggblom. [ 27 ] On January 8, 2018, the full New Jersey Senate unanimously approved (38 to 0) S3190. [ 28 ] The Assembly did not act on its version of the State Microbe legislation.
State Microbe legislation was reintroduced in the New Jersey Senate on February 5, 2018, by Senator Samuel Thompson (R-12); the bill number is S1729. [ 29 ] Similar legislation was reintroduced in the New Jersey Assembly on March 12, 2018; the bill number is A3650. The legislation is sponsored by Assemblywoman Annette Quijano (D-20), ASW Patricia Jones (D-5), Assemblyman Arthur Barclay (D-5), ASM Eric Houghtaling (D-11), and ASW Joann Downey (D-11). [ 30 ]
On June 14, 2018, Senate Bill S1729 was unanimously approved by the NJ Senate State Government, Wagering, Tourism & Historic Preservation Committee. [ 31 ] On July 27, 2018, Senate Bill S1729 was unanimously approved (33 to 0) by the full New Jersey Senate. [ 32 ] From the well of the Senate, Senator Thompson kindly acknowledged the efforts of State Microbe advocates John Warhol, Douglas Eveleigh, Jeff Boyd, and Jessica Lisa.
On September 17, 2018, Assembly Bill A3650 was unanimously approved by the Assembly Science, Innovation, and Technology Committee. [ 33 ] Testifying on behalf of the State Microbe were Drs John Warhol, Douglas Eveleigh, and Jeff Boyd. [ 33 ] On February 25, 2018, The New Jersey Assembly unanimously approved S1729/A3650 by a vote of 76 to 0. [ 34 ]
The final vote in the Senate was March 14, 2019. [ 35 ] The Bill passed by a vote of 34 to 0. [ 36 ]
On May 10, 2019, Governor Murphy signed S1729/A3650 into effect. [ 37 ] This made New Jersey the second state to have an Official Microbe, and the first to have an Official Bacterium.
The Rutgers University School of Environmental and Biological Science (SEBS) Department of Biochemistry and Microbiology hosted a poll for New Jersey State Microbe. The candidates have been Acidithiobacillus thiooxidans (discovered in NJ, 1922), Azotobacter vinelandii (discovered in Vineland , 1903), and Streptomyces griseus ( New Brunswick is home of the streptomycin-producing strain). [ 38 ] S. griseus has been the winning microbe by a 3 to 1 margin. In 2018, they received hundreds of signatures on a petition urging legislators to recognize S. griseus as the State Microbe.
The New Jersey State Microbe was the subject of a presentation by John Warhol at the 2018 Rutgers University Microbiology Symposium. [ 39 ] [ 40 ] Dr Warhol also spoke about the New Jersey State Microbe at the Theobald Smith Society (NJ Chapter of the American Society for Microbiology) Meeting in Miniature at Seton Hall University in April 2018. [ 41 ]
A scientific paper on the political and social process of designating an official state microbe was presented at Microbe 2018, the annual meeting of the American Society for Microbiology. [ 42 ] Titled "How to Get Your Own Official State Microbe" the presentation stressed the importance of clear communication and legislator contact by academic, industrial, and student supporters. The authors were Max Haggblom, Douglas Eveleigh, and John Warhol.
In November 2018, the New Jersey Historical Commission Forum on New Jersey History at Monmouth University was the venue for two presentations on the State Microbe. The first was titled "An Official New Jersey State Microbe! Streptomyces griseus" and the second was "The 75th Anniversary of the Discovery of Streptomycin – 2019". Authors of the presentations were Douglas Eveleigh, Jeff Boyd, Max Haggblom, Jessica Lisa, and John Warhol. [ 43 ] [ 44 ]
In early November 2018, Rutgers University launched a web page recognizing the Selman Waksman Museum at the School of Environmental and Biological Sciences. [ 45 ] The museum is housed in Dr Waksman's former laboratory space in Martin Hall. [ 46 ]
The Eagleton Institute of Politics hosted a Science and Policy Workshop titled "Scientists in Politics" in late November 2018. [ 47 ] Douglas Eveleigh and John Warhol participated, and informed the attendees about the history of microbiology in New Jersey and the importance of the State Microbe as a scientific and cultural symbol for New Jersey.
The Liberty Science Center (LSC) opened a new exhibit on December 13 named "Microbes Rule!" [ 48 ] The installation features interactive learning stations in which museum-goers can discover the many ways that microbes shape life on Earth. The New Jersey State Microbe has a prominent place in the exhibit; Liberty Science Center sponsored a petition for the NJ legislature to vote Yes on behalf of the State Microbe. [ 49 ] Speaking at the opening ceremony for the exhibit were LSC Chief Executive Officer Paul Hoffman , NJ Assemblyman Andrew Zwicker , Rutgers University Department of Biochemistry and Microbiology Chairman Max Haggblom , [ 27 ] Merck Executive Director for Infectious Diseases Todd Black , [ 50 ] American Society for Microbiology Outreach Manager Dr Katherine Lontok, and science author Dr John Warhol of The Warhol Institute.
Following the Senate vote, The New Jersey State Microbe was the subject of local, national, and international media attention. Streaming audio and video interviews were broadcast or posted with Drs Eveleigh, Boyd, Warhol, and Haggblom on CBS News , [ 51 ] News 12 New Jersey, [ 52 ] NPR , [ 53 ] This Week In Microbiology , [ 54 ] and KYWNews Radio . [ 55 ] Electronic and print media coverage included the Asbury Park Press , [ 56 ] NorthJersey.com , [ 57 ] The Philadelphia Inquirer , [ 58 ] NJ.com , [ 57 ] [ 59 ] NJ 101.5 dot com, [ 60 ] NJ Spotlight , [ 61 ] WPG Talk Radio , [ 62 ] Rutgers Today , [ 63 ] Politico , [ 64 ] WSUS , [ 65 ] Sky News , [ 66 ] and Isle of Wight Radio . [ 66 ]
On November 30, 2018, Jeff Boyd was featured on the cover of the Daily Targum in an article titled "Rutgers Professors Nominate Tuberculosis-Curing Bacteria for Official State Microbe". [ 67 ] The story summarized the reasons for the State Microbe (saves lives, creates jobs) and the work that scientists have done to get the microbe recognized by the state legislature. Dr Boyd pointed out that “Microbes shape every aspect of our lives, our environment and the earth” and certainly deserve more recognition. Dr Eveleigh was also interviewed for the article and said "I’d like the governor to sign the legislation in the room of the lab in which streptomycin was discovered.”
On December 13, 2018, the State Microbe was highlighted in press and broadcast coverage by NJTV News [ 68 ] of the opening of Microbes Rule! at the Liberty Science Center.
On Feb 21, Dr Jeffrey Boyd spoke with NJ Monthly for an article titled "Not Your Average Germ: New Jersey Considers a State Microbe". [ 69 ]
On February 26, 2018, after the Assembly vote, Dr John Warhol was interviewed by Rebeca Ibarra [ 70 ] of National Public Radio/ WNYC for comments about the new State Microbe. [ 71 ]
After Governor Murphy signed the State Microbe bill into law on May 10, 2019, additional press coverage developed in a variety of outlets. [ 72 ] [ 73 ] [ 74 ]
The New Jersey State Microbe was featured in two televised interviews in July 2019. The first was on CUNY TV 's [ 75 ] Simply Science hosted by Barry Mitchell "Meet the New Jersey Microbe" featured an inspired Garden State Microbe song rendition on the steps of Dr Waksman's original laboratory. Drs Boyd and Haggblom recounted the story of The New Jersey State Microbe and the importance of microbes in everyday life on Earth. [ 76 ] Dr Warhol appeared on Jersey Matters [ 77 ] hosted by Larry Mendtke. In the segment titled "Jersey Matters-State Microbe", they discussed the importance of the New Jersey State Microbe and the growing need for improved microbe education and awareness. [ 78 ]
In 2017, legislation similar to the original 2013 bill to make Flavobacterium akiainvivens the state microbe was submitted in the Hawaiʻi House of Representatives by Isaac Choy [ 79 ] and in the Hawaiʻi Senate by Brian Taniguchi . [ 80 ] In January 2017, Representative Choy submitted HB 1217 in the Hawaiʻi House of Representatives and Senator Taniguchi submitted the mirror bill SB1212 in the Hawaiʻi Senate . This continues the effort started by James Tokioka in 2013, and later contested in 2014 by Senator Glenn Wakai 's SB3124 bill proposing Aliivibrio fischeri instead. As of December 2017 [update] , Hawaiʻi has no official state microbe.
The world's first antibiotic, penicillin , is produced by a strain of the mold Penicillium rubens (formerly Penicillium chrysogenum ). Though the history of penicillin is centuries long, Scottish physician Alexander Fleming is usually credited with initiating the modern era of penicillin discovery, research, and development when he found the mold ( Penicillium notatum, now also P. rubens ) growing on a culture plate in his laboratory in 1928. Penicillin is effective on gram-positive bacteria . The antibiotic-producing strains of Penicillium in the early years produced relatively low yields of unstable penicillin. The yields were so low that urine from treated patients was collected and the penicillin remaining extracted and reused. At Oxford University in England a team including Dr. Howard Florey, Dr. Ernst Chain and Norman Heatley took up the goal of finding solutions to penicillin recovery issues. After a referral on who best to contact about increasing production, Florey and Heatley secretly came to Peoria Illinois on July 14, 1941, with their penicillin producing mold. WW2 necessitated moving of the work on penicillin to the United States where industrial supplies were not as constrained for the war effort. They met with personnel at the USDA (then Northern Regional Research Laboratory , NRRL, now National Center for Agricultural Utilization Research, NCAUR). There at the "Ag Lab" corn steep liquor, a byproduct of alcohol production, had been used for growing mold cultures in the past. It was found out later that phenylacetic acid, a side chain precursor of penicillin was present in quantity in the liquor and had increased yields. Other additions to the growth media such as lactose(milk sugar) were restricted during the war for penicillin production. Major breakthroughs at the Ag Lab came in the years between 1941 and 1943, when higher yielding strains were isolated. After the isolation trials selected the most promising mold strains, methods for the industrialized production of penicillin were developed there in Peoria, Illinois . The strain having the highest production was found on a moldy cantaloupe in Peoria, IL. This strain was improved upon by research at Cold Spring Harbor Laboratory (formerly the Carnegie Institution of Washington) and the University of Wisconsin. Strains were given out to other researchers and interested industrial firms. The mass production techniques developed at the Ag Lab enabled the United States and its allies to have penicillin available for the D-Day invasion in 1944. After an initial few, eventually about twenty industrial partners helped increase the yields of penicillin. On March 15, 1945, penicillin was made available to the public after being available some months before to hospitals and doctors.
On August 7, 2018, while driving home and listening to National Public Radio's broadcast of "All Things Considered," Gary Kuzniar heard an interesting story about State Microbe designations. The story said that Oregon had already passed legislation ( Saccharomyces cerevisiae ) and other states had started working to declare theirs. The next month Dr. Neil Price was walking in the hallway with two petri dish plasticized mold props and Gary asked him what they were. Neil said that they were penicillin props for a display in "The Ten Most Important Medical Inventions of the World" down at the local museum(Peoria Riverfront Museum). Gary mentioned that he had heard a radio program on state microbes and that the penicillin he had in his hands would be a good candidate for Illinois. It was agreed between them to form the Illinois State Microbe Designation Project to approach the whole logistical thing of doing it.
On February 15, 2019, Senator Dave Koehler introduced SB 1857, legislation that designates Penicillium chrysogenum NRRL 1951 as the Official State Microbe of Illinois. [ 81 ] The bill passed the Senate on April 4 and gained Senator Mattie Hunter as a cosponsor . That same day, the bill was introduced into the Illinois House of Representatives with Rep. Jehan Gordon-Booth as the primary sponsor. The bill was then referred to the State Rules Committee on 4 April 2019 and later to the State Government Administration Committee on 24 April. During the Spring 2019 Illinois Legislative session, it was learned that current DNA analysis on the famous Penicillium chrysogenum strain from the 1940s resulted in a name change to P. rubens. The original nomenclature was based on physical structure and current science relies on the more precise DNA analysis. The senate bill appeared on the 2019 Fall Veto Session docket but it didn't make it to the floor. SB 1857 was considered again in the 2020 Illinois State Spring Pandemic Session but COVID-19 made the session short. The bill was emptied of its contents, other considerations inserted and the bill passed quickly. There was no Fall 2020 Illinois State House Veto Session due to the continuing COVID-19 restrictions. At the start of the 2021 Illinois General Assembly Spring Session parallel bills were started, SB 2004 in the Senate and HB 1879 in the House for an Illinois State Microbe. Again there was a delay in the bill moving and the House bill survived to go forward. The Friday before the end of the session saw this bill amended just three days before the end of the Spring Session. On the last day of the official 2021 Illinois General Assembly Spring Session, about 8:10 pm on the evening of May 31, 2021 the bill HB 1879 designating Penicillium rubens as Illinois' State Microbe was brought up by Representative Ryan Spain and was passed. It then was forwarded to the desk of Illinois Governor J.B. Pritzker on June 29, 2021, to be signed. After about a month and a half the bill was then signed in a public ceremony at the University of Illinois Springfield Campus on August 17, 2021, with the . In the Spring 2021 Session, new bills were introduced in both the IL Senate and House to denote an Illinois State Microbe (SB 2004 and HB1879). The IL House bill survived and was concurred with the IL Senate proceedings. It passed both State Houses on May 31, 2021
Press coverage for the Illinois State Microbe has been enthusiastic. Journalist Phil Luciano of the Journal Star interviewed Neil Price of the National Center for Agricultural Utilization Research. As a representative of the Illinois State Microbe Designation Project he contactied Senator David Koehler and relayed information about the crucial role that Illinois had in the production of penicillin and its effect on world health. [ 82 ] He then gave a witness testimony to the Illinois Senate on March 20, 2019. Additional television coverage was featured on WQAD-TV . [ 83 ]
Promotion, Contact of and Support Letters and Legislation
Gary took this aspect of the project and contacted two people that were currently working for New Jersey's State Microbe (Streptomyces griseous), Dr. Max Haggblom and Dr. John Warhol. Letters of support were requested and put in a folder to be given to the original introducer of an Illinois State Microbe bill (Senator Koehler), each local district legislator and professional organizations throughout the state. Some of the letters were received from Western Illinois University, University of Wisconsin at Madison, Bradley University in Peoria Illinois and the William Dunn School of Pathology at the University of Oxford where the original work by Alexander Fleming was noticed and continued by scientists Howard Florey, Ernst Chain, Norman Heatley and others. Small Penicillium plushes from Giant Microbes were attached to folders containing the letters of support and then given to local legislators and others along with a cantaloupe. A T-shirt has been made that includes an illustration from the Manual of Penicillia by Dr. Kenneth B. Raper and Charles Thom. One of the illustrations done by Dorothy I. Fennell was selected. She worked under Dr. Raper. Permission for this was granted by the book publisher. During the legislation, a painting of an iconic character and one of its commissioner were obtained from the University of Wisconsin at Madison with permission of the Bacteriology Department. "Moldy Mary" is a painting of a young woman at a 1940s downtown Peoria Illinois produce market with a moldy cantaloupe in her hand. The second painting is of the paintings' commissioner himself, Dr. Ken Raper. He is standing in a lab also with a cantaloupe in his hand. Both were available for viewing at the "Ten Most Important Medical Inventions of the World" exhibit at the Peoria Riverfront Museum earlier 2019. | https://en.wikipedia.org/wiki/State_microbe |
In philosophy , a state of affairs ( German : Sachverhalt ), [ 1 ] also known as a situation , is a way the actual world must be in order to make some given proposition about the actual world true; in other words, a state of affairs is a truth-maker , whereas a proposition is a truth-bearer . Whereas states of affairs either obtain or fail-to-obtain , propositions are either true or false . [ 2 ] Some philosophers understand the term "states of affairs" in a more restricted sense as a synonym for "fact". In this sense, there are no states of affairs that do not obtain. [ 2 ]
The early Ludwig Wittgenstein and David Malet Armstrong are well known for their defence of a factualism , a position according to which the world is a world of facts and not a world of things. [ 3 ]
States of affairs are complex entities: they are built up from or constituted by other entities. [ 4 ] [ 5 ] Atomic states of affairs are constituted by one particular and one property exemplified by this particular. [ 6 ] [ 2 ] For example, the state of affairs that Socrates is wise is constituted by the particular "Socrates" and the property "wise". Relational states of affairs involve several particulars and a relation connecting them. States of affairs that obtain are also referred to as facts . [ 2 ] It is controversial which ontological status should be ascribed to states of affairs that do not obtain. [ 6 ] States of affairs have been prominent in 20th-century ontology as various theories were proposed to describe the world as composed of states of affairs. [ 4 ] [ 7 ] [ 8 ]
In a sense of "state of affairs" favored by Ernest Sosa , states of affairs are situational conditions . In fact, in the Cambridge Dictionary of Philosophy , [ 9 ] Sosa defines a condition to be a state of affairs, "way things are" or situation—most commonly referred to by a nominalization of a sentence . The expression "Snow's being white", which refers to the condition snow's being white, is a nominalization of the sentence "Snow is white". [ 9 ] The truth of the proposition that "snow is white" is a nominalization of the sentence "the proposition that snow is white is true". Snow's being white is a necessary and sufficient condition for the truth of the proposition that snow is white. Conditions in this sense may be called situational.
Usually, necessity and sufficiency relate conditions of the same kind. Being an animal is a necessary attributive condition for being a dog. Fido's being an animal is a necessary situational condition for Fido's being a dog.
This article about ontology is a stub . You can help Wikipedia by expanding it .
This article about epistemology is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/State_of_affairs_(philosophy) |
The state postulate is a term used in thermodynamics that defines the given number of properties to a thermodynamic system in a state of equilibrium . It is also sometimes referred to as the state principle. [ 1 ] The state postulate allows a finite number of properties to be specified in order to fully describe a state of thermodynamic equilibrium. Once the state postulate is given the other unspecified properties must assume certain values.
The state postulate says:
The state of a simple compressible system is completely specified by two independent, intensive properties [ 2 ]
A more general statement of the state postulate says:
the state of a simple system is completely specified by r+1 independent, intensive properties where r is the number of significant work interactions. [ 1 ] [ 3 ]
A system is considered to be a simple compressible one in the absence of certain effects which are uncommon in many engineering applications. These are electromagnetic and gravitational fields, surface tension, and motion. For such a system, only two independent intensive variables are sufficient to derive all the others by use of an equation of state . In the case of a more complex system, additional variables must be measured in order to solve for the complete state. For example, if gravitation is significant then an elevation may be required.
Two properties are considered independent if one can be varied while the other is held constant. For example, temperature and specific volume are always independent. However, temperature and pressure are independent only for a single-phase system; for a multiphase system (such as a mixture of gas and liquid) this is not the case. (e.g., boiling point (temperature) depends on elevation (ambient pressure)).
This thermodynamics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/State_postulate |
In computer science , a state space is a discrete space representing the set of all possible configurations of a system. [ 1 ] It is a useful abstraction for reasoning about the behavior of a given system and is widely used in the fields of artificial intelligence and game theory .
For instance, the toy problem Vacuum World has a discrete finite state space in which there are a limited set of configurations that the vacuum and dirt can be in. A "counter" system, where states are the natural numbers starting at 1 and are incremented over time [ 2 ] has an infinite discrete state space. The angular position of an undamped pendulum [ 3 ] is a continuous (and therefore infinite) state space.
State spaces are useful in computer science as a simple model of machines. Formally, a state space can be defined as a tuple [ N , A , S , G ] where:
A state space has some common properties:
For example, the Vacuum World has a branching factor of 4, as the vacuum cleaner can end up in 1 of 4 adjacent squares after moving (assuming it cannot stay in the same square nor move diagonally). The arcs of Vacuum World are bidirectional, since any square can be reached from any adjacent square, and the state space is not a tree since it is possible to enter a loop by moving between any 4 adjacent squares.
State spaces can be either infinite or finite, and discrete or continuous.
The size of the state space for a given system is the number of possible configurations of the space. [ 3 ]
If the size of the state space is finite, calculating the size of the state space is a combinatorial problem. [ 4 ] For example, in the eight queens puzzle , the state space can be calculated by counting all possible ways to place 8 pieces on an 8x8 chessboard. This is the same as choosing 8 positions without replacement from a set of 64, or
This is significantly greater than the number of legal configurations of the queens, 92. In many games the effective state space is small compared to all reachable/legal states. This property is also observed in chess , where the effective state space is the set of positions that can be reached by game-legal moves. This is far smaller than the set of positions that can be achieved by placing combinations of the available chess pieces directly on the board.
All continuous state spaces can be described by a corresponding continuous function and are therefore infinite. [ 3 ] Discrete state spaces can also have ( countably ) infinite size, such as the state space of the time-dependent "counter" system, [ 2 ] similar to the system in queueing theory defining the number of customers in a line, which would have state space {0, 1, 2, 3, ...}.
Exploring a state space is the process of enumerating possible states in search of a goal state. The state space of Pacman , for example, contains a goal state whenever all food pellets have been eaten, and is explored by moving Pacman around the board. [ 5 ]
A search state is a compressed representation of a world state in a state space, and is used for exploration. Search states are used because a state space often encodes more information than is necessary to explore the space. Compressing each world state to only information needed for exploration improves efficiency by reducing the number of states in the search. [ 5 ] For example, a state in the Pacman space includes information about the direction Pacman is facing (up, down, left, or right). Since it does not cost anything to change directions in Pacman, search states for Pacman would not include this information and reduce the size of the search space by a factor of 4, one for each direction Pacman could be facing.
Standard search algorithms are effective in exploring discrete state spaces. The following algorithms exhibit both completeness and optimality in searching a state space: [ 5 ] [ 6 ]
These methods do not extend naturally to exploring continuous state spaces. Exploring a continuous state space in search of a given goal state is equivalent to optimizing an arbitrary continuous function which is not always possible; see mathematical optimization . | https://en.wikipedia.org/wiki/State_space_(computer_science) |
State switching (a.k.a. phenotypic switching ) is a fundamental physiological process in which a cell/organism undergoes spontaneous, and potentially reversible, transitions between different phenotypes . Thus, the ability to switch states/phenotypes ( phenotypic plasticity ) is a key feature of development and normal function of cells within most multicellular organisms that enables the cell to respond to various intrinsic and extrinsic cues and stimuli in a concerted fashion enabling them to ‘make’ appropriate cellular decisions. [ 1 ] Although state switching is essential for normal functioning, the repertoire of phenotypes in a normal cell is limited.
In contrast to normal cells, a striking characteristic of cancer cells is the remarkable degree of phenotypic plasticity they exhibit. For example, cancer cells undergo epithelial to mesenchymal transition (EMT) that plays important roles in their survival, proliferation, and development of resistance to therapeutic treatments, [ 2 ] [ 3 ] or switch to a phenotype that mimics stem cell-like features – the so-called Cancer Stem Cells (CSCs) or Tumour-initiating Cells. Unlike in the case of normal cells, state switching in cancer cells is widely believed to arise due to somatic mutations . [ 4 ] However, there is growing concern that such a deterministic view of a phenomenon that is reversible is not entirely consistent with multiple lines of evidence which indicate that stochasticity may also play an important role in driving phenotypic plasticity. [ 5 ]
A hallmark of the factors implicated in phenotypic switching whether in cancer or in normal cells is that they are Intrinsically disordered proteins (IDPs). That is, they lack a rigid 3D-structure under physiological conditions at least in vitro and exist as conformational ensembles instead. [ 6 ] [ 7 ] However, many IDPs can transition from disorder to order upon interacting with a target [ 8 ] or in response to post-translational modifications such as phosphorylation. [ 9 ] IDPs are particularly enriched in transcriptional regulation, signaling and splicing, and are overexpressed in many pathological states including cancer. [ 10 ] Thus, the products of most oncogenes such as Jun, Fos, Myc, [ 11 ] [ 12 ] the Yamanaka factors namely, OCT3/4 , SOX2 , MYC , NANOG , and KLF4 that induce reprogramming of pluripotent stem (iPS) cells, [ 13 ] and >90% of the Cancer/Testis Antigens [ 14 ] several of which are implicated in EMT [ 15 ] [ 16 ] are predicted, and in many cases experimentally verified, to be IDPs. [ 17 ] [ 18 ] [ 19 ] [ 20 ] Consistent with these observations, the key factors implicated in EMT/MET namely, OVOL1/2, ZEB1 and SNAI1 are also strongly predicted to be IDPs. [ 21 ]
Until the 1990s, it was tacitly assumed that most networks adopt a random architecture wherein an edge (connection) between each pair of nodes has equal probability, independent of the other edges ( Erdős–Rényi model ). However, pioneering work by Barabási and colleagues ( Barabási–Albert model ) [ 22 ] indicated that biological networks, like many other networks they interrogated, adopt an architecture wherein the degree distribution P(k) exhibits a power-law behavior as a function of the degree k. In particular, P(k) ~ k-γ, with only a few nodes (hub nodes) has numerous edges while the majority of the nodes have very few edges. As such, these networks are robust to failure of random nodes but vulnerable to failure of hubs. [ 23 ] In light of the scale-free topology of the PIN, Mahmoudabadi et al. [ 24 ] set out to elucidate whether perturbation to IDP hub proteins could account for such dramatic changes as state switching in the absence of DNA mutations (changes to the DNA sequence) and whether these changes could be passed onto the progeny.
The authors proposed a theoretical model (hereby named the ‘MRK model’ after the main proponents- Gita M ahmoudabadi, Govindan R angarajan , and Prakash K ulkarni) which envisaged that because IDPs have multiple conformational states and rapid conformational dynamics, they are prone to engage in ‘promiscuous’ interactions. These stochastic interactions between the IDPs and their partners result in ‘noise’ , defined as conformational noise. [ 24 ] Indeed, many biological processes are driven by probabilistic events underscoring the importance of ‘noise’ in biological systems. [ 25 ] However, while research on biological noise focused on low gene copy numbers as the predominant source of noise, noise arising from stochastic IDP interactions due to the conformational dynamics of IDPs had not been considered. Thus, the central tenet of the MRK model is that, just as transcriptional noise plays an important role in probabilistic differentiation and adaptation, noise inherent in protein interactions could underlie the activation of latent pathways and cellular transformation. Although the authors chose to highlight the role of IDPs in propagation of transcriptional noise because this type of noise has systematically been studied and is a common feature of cellular processes in both normal and diseased conditions, they also point out that the role of IDPs is not limited to the propagation of transcriptional noise. Rather, the model emphasizes that IDPs could likely relay, and perhaps, even amplify, other intrinsic and extrinsic types of noise and perturbations in the system. Consistent with this argument, there are now numerous examples of remodeling of the IDP conformational ensemble in response to binding and/or post-translational modifications [ 9 ] [ 26 ] to populate a different conformation with huge functional consequences.
Together, these observations tend to suggest that contrary to the prevailing wisdom that phenotype specification is highly deterministic, stochasticity may be a confounding factor in specifying cell fate. This thinking may also help explain how a given cell can reversibly switch phenotypes as seen in EMT and MET or for that matter, a drug-sensitive cell from developing resistance and switching back to drug sensitivity, [ 27 ] or the transformation of a normal cell to a malignant one and its reversal to normalcy. [ 28 ] Indeed, such stochasticity in phenotypic switching is also thought to underlie cellular differentiation, [ 25 ] generation of induced pluripotent stem cells (iPS cells), [ 29 ] tumor heterogeneity [ 30 ] [ 31 ] and emergence of cancer stem cells from non-stem cancer cells. [ 31 ] Implicit in the MRK model, the PIN configuration contains information that can specify the cell's phenotype.
It seems quite reasonable to assume that organisms acquire useful adaptations during their lifetime. Such adaptations are the result of an exploratory search which samples various iterations of potential outputs in order to discern and select the most appropriate ones. Thus, it is plausible that ‘learning’, which can be described as an elaborate and iterative form of phenotypic modification that allows an organism to adjust its response to the same inputs over time based on the outcomes of previous outputs, could have a significant influence on evolution of a new species in the long run. Therefore, it would be quite wasteful to forego the advantage of the exploration performed by the organism to facilitate the evolutionary search for increased fitness if information about the acquired (learned) characteristics (new phenotypes) was not transferred to the genotype or at least retained in some (non-genomic) fashion to facilitate transgenerational inheritance. Indeed, this type of interaction between learning and evolution was independently proposed in the late 1800s by Baldwin, [ 32 ] Osborn [ 33 ] and Morgan [ 11 ] and is often referred to as the ‘ Baldwin effect ’. However, the Baldwin effect remained under-appreciated because of its Lamarckian connotation and consequently it was inferred by many that learning cannot guide evolution.
In 1987, Hinton & Nowlan [ 12 ] using a computer simulation demonstrated that indeed, learning (they actually meant phenotypic plasticity) can be very effective in guiding the evolutionary search. In fact, the authors observed that learning alters (smoothens) the shape of the search space in which evolution operates and predicted that in difficult evolutionary searches that may require many possibilities to be tested, each learning trial can be almost as helpful to the evolutionary search as the production and evaluation of a whole new organism. Thus, logically speaking, the ‘efficiency’ of evolution is greatly enhanced since a learning trial is much faster and far less energy-intensive than that required for the production of a whole organism by random mutations. [ 12 ] Subsequent studies by Behara and Nanjundiah [ 34 ] [ 35 ] [ 36 ] demonstrated that although the relationship may not be as straightforward as was assumed by Hinton & Nowlan, phenotypic plasticity can potentiate evolution even when more realistic fitness schemes are simulated.
Although these computational studies are tantalizing, the real question is, can cancer cells (or other protists , for that matter) really ‘learn’ or ‘make’ decisions? To describe the cell's physiological response to a stimulus as learning/decision making is perhaps a matter of semantics. However, several observations made in protists that lack even the rudiments of a nervous system, much less a brain, suggest that they possess sophisticated mechanisms through which they respond to, ‘anticipate’, and even ‘learn’ from fluctuations and challenges in their environment. [ 37 ] [ 38 ] [ 39 ]
While cancer cells are not protists per se, they exhibit several characteristics that are typical of these simple forms of life. In fact, cancer has been postulated to represents some sort of reversion to a more primitive phenotype – an atavism . [ 40 ] In the atavistic model of cancer progression, tumor cell dedifferentiation is interpreted as a reversion to phylogenetically earlier capabilities. [ 41 ] For example, cancer cells, develop drug resistance, exhibit traits of the persister phenotype (an extremely slow-growing physiological state which makes them insensitive to drug treatment) and quorum sensing (a system of stimulus and response correlated to population density), and display many other collective behaviour capabilities and cooperative strategies necessary for survival under extreme stress. [ 42 ] These characteristics present cancer cells in a different light – smart communicating cells – and tend to portray tumours as societies of cells capable of making decisions. [ 42 ] Thus, the MRK model posits that the stochasticity in interactions of IDPs that are overexpressed in cancer cells could facilitate learning by exploring the network search space and rewiring the network.
But how is the organization of the networks specified? What determines the network dynamics? How does this affect learning? Kulkarni [ 43 ] hypothesized that analogous to the computational models developed by Hinton & Nowlan, and Behera & Nanjundiah, the basic design of the PINs is specified by the genome inasmuch as the expression of the critical nodes in space, time and amplitude are concerned. However, the ultimate organization of the PIN and its ground state threshold would be determined by learning and adapting to the environment in which the organism finds itself. [ 43 ]
For adaptive learning to be inherited, one would anticipate that changes in the genome, whether genetic or epigenetic , would be necessary implying a reversal of information flow from phenotype to genotype. In response to dynamic environmental fluctuations, an organism's PINs constantly process information and organize and reorganize themselves. However, it is postulated [ 43 ] that in response to ‘unanticipated’ environmental changes, several IDPs are overexpressed and the organism explores numerous iterations of network connections many of which are due to the promiscuous nature of these interactions. [ 44 ] This results in a specific output that the organism benefits from, and in resetting the network to a new set-point (threshold). Further, it is postulated that information derived from PIN rewiring can operate across diverse timescales. [ 43 ] Thus, while some of the information particularly that which operates over relatively short timescales maybe retained within the PINS, information that operates over long periods such as cellular transformation, development and evolution, is directly transferred to the genome to effect heritable genetic/epigenetic changes, or via a mechanism similar to genetic assimilation of the acquired character proposed by Waddington . [ 45 ] Several proteins that are involved in epigenetically sculpturing the chromatin are IDPs. [ 46 ]
Insofar as genetic changes are concerned, emerging evidence suggests that a nexus between transcription factors and chromatin remodelers , [ 47 ] and between transcription factors and DNA repair proteins [ 48 ] that are part of large PINs, can facilitate such changes. With regard to genetic assimilation , Waddington proposed that it is the process in which an environmental stimulus that affects the phenotype has been superseded by an internal genetic factor during the course of evolution. While such mechanisms could potentially account for permanent changes in the diploid genome of the cancer cell or other unicellular organisms, how information to activate such an internal genetic switch is transmitted to the germline for stable inheritance in metazoans reproducing sexually remains an important and intriguing question.
Notwithstanding the molecular mechanisms however, an equally important question that needs to be considered here is the evolutionary timescale. A key point in Darwinian evolution is that it works very slowly, over millions of years of geological time, through the gradual, incremental acquisition of small differences. Then how can a cancer cell evolve in such a short time? Perhaps, as has been suggested, [ 49 ] under certain conditions evolution could occur more rapidly than previously envisioned. For example, in the extreme case, in a population of just a few individuals, all sorts of unusual mutations could become fixed simply because the number of individuals was so small and each mutation has a much higher likelihood of survival because competition among mutant forms is lower. Through this process a new species can arise in a few generations. However, in either case, mutations that hold the key arise by chance and without foresight for the potential advantage or disadvantage of the mutation. Furthermore, the underlying implication would be a unidirectional flow of information from genotype to phenotype.
On the other hand, in the scenario resulting from the MRK model wherein learning can guide evolution, changes to the genome arise due to necessity after trial and error and not just by chance, and in a few generations, are fixed. Episodes of rapid change - network rewiring to uncover latent pathway interactions in response to environmental perturbations - could lead to genotypic changes in a relatively short order. In other words, a species need not originate in a series of gradual steps, each resulting from a mutation with a small effect, slowly changing ancestor into descendant. Rather, the genetic changes that lead to the formation of new species have large effects and happen over relatively few generations. Thus, the MRK model implies that informational flow would be bidirectional and has parallels to ideas enunciated by Lamarck although empirical evidence for informational flow from phenotype to genotype is lacking at present. In fact, the inheritance of characteristics induced by the environment has often been opposed to the theory of evolution by natural selection. However, it is important to note that the emergence of non-conventional modes and the diversity of mechanisms for generating and transmitting variations such as the transmission of small interfering RNAs, the transmission of conformational states of IDPs such as prions, or, at the cellular level, the transmission of self-sustaining states of gene regulation, and, at the organismal level, so-called parental effects [ 50 ] could provide additional support for the MRK theory.
Indeed, a recently proposed mathematical model to compare the adaptive value of different schemes of inheritance by Rivoire and Leibler [ 50 ] does appear to lend credence to the MRK model. The authors considered three biological phenomena that are often considered to be either irrelevant to evolution, or absent because “forbidden” namely, i) role of phenotypic plasticity and developmental canalization, ii) reverse flow of information from phenotype to genotype (or its absence), and iii) conditions under which direct integration of information into the transmitted genotype is logically excluded as a consequence of natural selection. Their model allows for variations to be inherited, randomly produced, or environmentally induced, and, irrespectively, to be either transmitted or not during reproduction. The adaptation of the different schemes for processing variations is quantified for a range of fluctuating environments, following an approach that links quantitative genetics with stochastic control theory. When the authors conducted a Gedankenexperiment (German for a thought-experiment) that allowed them to compare the Darwinian and Lamarckian “modalities,” and test the conjecture that each of them is tuned to a different type of selective pressure, they found that the main controlling parameter in the model appears to be the correlation a of the environmental fluctuations, with the Lamarckian modality systematically becoming more favorable when this correlation is large, in line with the intuition that transmitting acquired information is beneficial when the selective pressure experienced by the offspring is sufficiently similar to that experienced by the parents. | https://en.wikipedia.org/wiki/State_switching |
A statement of work ( SOW ) is a document routinely employed in the field of project management . It is the narrative description of a project's work requirement. [ 1 ] : 426 It defines project-specific activities, deliverables and timelines for a vendor providing services to the client. The SOW typically also includes detailed requirements and pricing, with standard regulatory and governance terms and conditions. It is often an important accompaniment to a master service agreement or request for proposal (RFP).
Many formats and styles of statement of work document templates have been specialized for the hardware or software solutions described in the request for proposal . Many companies create their own customized version of SOWs that are specialized or generalized to accommodate typical requests and proposals they receive. However, it is usually informed by the goals of the top management as well as input from the customer and/or user groups. [ 1 ]
Note that in many cases the statement of work is a binding contract. [ 2 ] Master service agreements or consultant/training service agreements postpone certain work-specific contractual components that are addressed in individual statements of work. The master service agreement serves as a master contract governing the terms over potentially multiple SOWs. Sometimes it refers to scope of work. For instance, if a project is done on contract, the scope statement included as part of it can be used as the SOW since it also outlines the work of the project in clear and concise terms. [ 3 ]
A statement of work typically addresses these subjects. [ 4 ] [ 5 ] [ 6 ]
For US government service contracts, the use of SOWs remains strong, although statements of objectives (SOOs) and performance work statements (PWSs) have become increasingly popular due to their emphasis on performance-based concepts such as desired service outcomes and performance standards. SOWs are typically used when the task is well-known and can be described in specific terms. They may be preferred when the government does not desire innovative approaches or considers any deviation in contractor processes a risk. SOOs establish high-level outcomes and objectives for performance and PWSs emphasize outcomes, desired results, and objectives at a more detailed and measurable level, whereas SOWs provide explicit statements of work direction for the contractor or offeror to follow.
SOWs are typically replete with "contractor shall" statements of mandatory compliance (for example, "This task shall be performed in accordance with Agency xyz Directive, dated mm/dd/yyyy"). In practice, SOWs can also be found to contain references to desired performance outcomes, performance standards, and metrics, thus blurring their distinction between SOOs and PWSs. Aside from good practice, there is little government policy guidance that emphatically prescribes how and when to use SOWs versus SOOs or PWSs. Whereas the FAR defines PWS in Part 2 Definitions, and references SOOs and PWSs in Part 37.6 Performance Based Acquisition, SOWs are not addressed.
SOWs are usually contained in the government's solicitation (RFP or RFQ) and carried forward, as may be negotiated with the offeror, into the final contract. In federal solicitations and contracts, SOWs are inserted into Section C "Descriptions/Specifications" of the Uniform Contract Format, [ 8 ] [ 9 ] [ 10 ] but may also be inserted as an attachment in Section J. In task orders, the SOW may simply be included among the terms and conditions of the order itself. The SOW is often supplemented by technical reference documents and attachments. In developing the SOW, it is important to ensure that the statement of work is comprehensive and sufficiently detailed, but that the statements do not duplicate terms and conditions or other provisions elsewhere in the solicitation or contract.
Guidance in MIL-STD-881 and MIL-HDBK-245 says that a work breakdown structure should be used in developing the SOW. This may use the WBS as an outline, where each WBS element (in the same name and numbering) are the sub-parts of the SOW section 3, making the development easier and to improve later billing and tracking. The WBS which focuses on intelligently dividing a hierarchy of the work elements and defining them may then have the SOW in matching sections focus on describing what will be done with that portion or how that portion will be done.
The statement of work should be directly linked to deliverables shown in the CDRL form. This is done by having each CDRL entry include reference to the SOW paragraph(s) that produces or uses the item, and the SOW text should be clear where it is discussing a deliverable by using the title or parenthesizing the item number (for example, "[A-001]"). | https://en.wikipedia.org/wiki/Statement_of_work |
On May 30, 2023, hundreds of artificial intelligence experts and other notable figures signed the following short Statement on AI Risk : [ 1 ] [ 2 ] [ 3 ]
Mitigating the risk of extinction from AI should be a global priority alongside other societal-scale risks such as pandemics and nuclear war.
At release time, the signatories included over 100 professors of AI including the two most-cited computer scientists and Turing laureates Geoffrey Hinton and Yoshua Bengio , as well as the scientific and executive leaders of several major AI companies, and experts in pandemics, climate, nuclear disarmament, philosophy, social sciences, and other fields. [ 1 ] [ 2 ] [ 4 ] Media coverage has emphasized the signatures from several tech leaders; [ 2 ] this was followed by concerns in other newspapers that the statement could be motivated by public relations or regulatory capture. [ 5 ] The statement was released shortly after an open letter calling for a pause on AI experiments .
The statement is hosted on the website of the AI research and advocacy non-profit Center for AI Safety . It was released with an accompanying text which states that it is still difficult to speak up about extreme risks of AI and that the statement aims to overcome this obstacle. [ 1 ] The center's CEO Dan Hendrycks stated that "systemic bias, misinformation, malicious use, cyberattacks, and weaponization" are all examples of "important and urgent risks from AI... not just the risk of extinction" and added, "[s]ocieties can manage multiple risks at once; it's not 'either/or' but 'yes/and. ' " [ 6 ] [ 4 ]
Among the well-known signatories are: Sam Altman , Bill Gates , Peter Singer , Daniel Dennett , Sam Harris , Grimes , Stuart J. Russell , Jaan Tallinn , Vitalik Buterin , David Chalmers , Ray Kurzweil , Max Tegmark , Lex Fridman , Martin Rees , Demis Hassabis , Dawn Song , Ted Lieu , Ilya Sutskever , Martin Hellman , Bill McKibben , Angela Kane , Audrey Tang , David Silver , Andrew Barto , Mira Murati , Pattie Maes , Eric Horvitz , Peter Norvig , Joseph Sifakis , Erik Brynjolfsson , Ian Goodfellow , Baburam Bhattarai , Kersti Kaljulaid , Rusty Schweickart , Nicholas Fairfax , David Haussler , Peter Railton , Bart Selman , Dustin Moskovitz , Scott Aaronson , Bruce Schneier , Martha Minow , Andrew Revkin , Rob Pike , Jacob Tsimerman , Ramy Youssef , James Pennebaker and Ronald C. Arkin . [ 7 ]
The Prime Minister of the United Kingdom , Rishi Sunak , retweeted the statement and wrote, "The government is looking very carefully at this." [ 8 ] When asked about the statement, the White House Press Secretary , Karine Jean-Pierre , commented that AI "is one of the most powerful technologies that we see currently in our time. But in order to seize the opportunities it presents, we must first mitigate its risks." [ 9 ]
Skeptics of the letter point out that AI has failed to reach certain milestones, such as predictions around self-driving cars . [ 4 ] Skeptics also argue that signatories of the letter were continuing funding of AI research. [ 3 ] Companies would benefit from public perception that AI algorithms were far more advanced than currently possible. [ 3 ] Skeptics, including from Human Rights Watch , have argued that scientists should focus on the known risks of AI instead of distracting with speculative future risks. [ 10 ] [ 3 ] Timnit Gebru has criticized elevating the risk of AI agency, especially by the "same people who have poured billions of dollars into these companies." [ 10 ] Émile P. Torres and Gebru both argue against the statement, suggesting it may be motivated by TESCREAL ideologies. [ 11 ] | https://en.wikipedia.org/wiki/Statement_on_AI_risk_of_extinction |
The " Statement on Chemical and Biological Defense Policies and Programs " was a speech delivered on November 25, 1969, by U.S. President Richard Nixon . In the speech, Nixon announced the end of the U.S. offensive biological weapons program and reaffirmed a no-first-use policy for chemical weapons . The statement excluded toxins , herbicides and riot-control agents as they were not chemical and biological weapons, though herbicides and toxins were both later banned. The decision to ban biological weapons was influenced by a number of domestic and international issues.
When Richard Nixon selected Melvin Laird as his Secretary of Defense in early 1969, Laird directed the Department of Defense to undertake a comprehensive review of U.S. biological warfare (BW) programs. [ 1 ] Laird's push for a review of both the chemical and biological programs arose when Congress attempted to push the Pentagon for open, joint Congressional hearings on chemical-biological warfare (CBW). [ 2 ] The Pentagon balked and the result was Laird's memorandum to National Security Advisor Henry Kissinger urging a review of those weapons programs. [ 2 ] Laird's memorandum to Kissinger expresses fear that the United States will be under "increasing fire" for the program and calls for the National Security Council to initiate a study. [ 3 ]
Laird hoped to eliminate the U.S. BW program. [ 1 ] He saw two reasons to kill the BW program. The first was political—eliminating the program could deflect growing protests over Vietnam . The second was budgetary: As a U.S. Representative , Laird had watched Pentagon BW budgets balloon during the Kennedy and Johnson years. [ 1 ] With Laird's impetus, and the concurrence of the National Security Council staff, in late May 1969 Kissinger directed key administration officials to begin a review of CBW "policies, programs and operational concepts" with a report to be issued no later than September. [ 2 ]
Surprisingly, Laird found the Joint Chiefs of Staff receptive to BW elimination as well. In twice weekly meetings with the Joint Chiefs during 1969 Laird found none of the officers opposed to ending the U.S. BW program. [ 1 ] They found the weapons ineffective and militarily useless, especially when compared to the U.S. nuclear arsenal . [ 1 ] The Joint Chiefs made two demands, one was to continue defensive germ warfare research and the other was that they be allowed to maintain the U.S. chemical arsenal as a deterrent to the Soviet Union . [ 1 ]
In June 1969 Kissinger asked a former Harvard colleague, Matthew Meselson to prepare a position paper on U.S. chemical and biological weapons programs. [ 2 ] [ 4 ] Meselson and Paul Doty then organized a private conference to discuss policy issues. The result was a September 1969 paper that not only urged U.S. ratification of the Geneva Protocol but an end to U.S. BW programs. [ 2 ] Meselson and his colleagues argued that a biological attack would likely inflict a great toll on civilian populations while remaining largely militarily ineffective. [ 4 ]
Executive action on BW was followed by congressional action on chemical warfare (CW). In August 1969 the Senate passed an amendment to the Military Procurement Bill which unilaterally renounced first-use of chemical weapons. [ 5 ] The Senate action also issued a moratorium on the acquisition of new chemical weapons as well as de-emphasizing the need for CW readiness. [ 5 ] The bill passed 91–0, although some senators expressed reservations about the CW provisions. [ 5 ]
Nixon issued his "Statement on Chemical and Biological Defense Policies and Programs" on November 25, 1969, in a speech from Fort Detrick . [ 4 ] The same day he gave a speech from the Roosevelt Room at the White House further outlining his earlier statement. [ 2 ] [ 6 ] The statement ended, unconditionally, all U.S. offensive biological weapons programs. [ 7 ] Nixon noted that biological weapons were unreliable [ 7 ] and stated: [ 4 ]
The United States shall renounce the use of lethal biological agents and weapons, and all other methods of biological warfare. The United States will confine its biological research to defensive measures such as immunization and safety measures.
In his speech Nixon called his move "unprecedented"; and it was in fact the first review of the U.S. BW program since 1954. [ 2 ] Despite the lack of review, the BW program had increased in cost and size since 1961; when Nixon ended the program the budget was $300 million annually. [ 2 ] [ 8 ] Nixon's statement confined all biological weapons research to defensive-only and ordered the destruction of the existing U.S. biological arsenal . [ 5 ]
The Nixon statement also addressed the topics of chemical warfare and U.S. ratification of the Geneva Protocol, [ 5 ] which, at the time, the nation had yet to ratify. [ 9 ] On chemical warfare Nixon reaffirmed no-first-use of chemical weapons by the United States . [ 5 ] He also announced that the United States would reconsider ratification of the Geneva Protocol, [ 5 ] which Nixon recommended to the Senate that year. [ 9 ]
The presidential statement purposely omitted certain agents, while others were simply overlooked. In an exception to the no-first-use policy, which his statement reaffirmed, Nixon made a deference for riot-control agents and herbicides . [ 2 ] Both were in use in Vietnam and both had been lightning rods for criticism. [ 2 ] [ 10 ] Nixon promised later memorandums concerning abolition of both types of agents; herbicide use in Vietnam was discontinued in 1970 but riot-control agent use continued. [ 2 ]
The other major omission from Nixon's statement were toxins . His statement did not specifically address toxins, such as ricin , which tend to blur the line between chemical and biological weapons. [ 5 ] As debate within the Army raged over whether toxins were considered chemical or biological weapons concerning the president's order, work on them continued at Fort Detrick , [ 5 ] the "hub" of U.S. biological weapons programs. [ 4 ] For several months following the November order, the Army continued working on staphylococcus enterotoxin type B (SEB). [ 5 ] On February 20, 1970, Nixon added toxins, regardless of their means of production—be it chemical or biological, to the U.S. ban on biological weapons. [ 2 ]
The statement immediately led to National Security Decision Memorandum 35 from Nixon, which was also dated November 25, 1969. [ 2 ] The memorandum also stated that the U.S. government renounced all "lethal methods" and "all other methods" of biological warfare, it also stated that the U.S. would only conduct BW research and development for defensive purposes. [ 2 ]
U.S. biological weapons stocks were destroyed over the next few years. A $12 million disposal plan was undertaken at Pine Bluff Arsenal , [ 1 ] where all U.S. anti-personnel biological agents were stored. [ 5 ] That plan was completed in May 1972 and included decontamination of facilities at Pine Bluff. [ 1 ] [ 5 ] Other agents, including anti-crop agents such as wheat stem rust , were stored at Beale Air Force Base and Rocky Mountain Arsenal . [ 5 ] These anti-crop agents, along with agents at Fort Detrick used for research purposes were destroyed in March 1973. [ 5 ]
Nixon closed his statement, "Mankind already carries in its own hands too many of the seeds of its own destruction. By the examples we set today, we hope to contribute to an atmosphere of peace and understanding between nations and among men." [ 2 ] Shortly after Nixon's statement the United States and the Soviet Union began the SALT arms control talks, which eventually resulted in nuclear arms controls as well as the 1972 Antiballistic Missile Treaty . [ 2 ] The U.S. commitment to end BW programs helped provide the lead for ongoing talks led by the United Kingdom in Geneva. [ 11 ] The Eighteen Nation Disarmament Committee was discussing a British draft of a biological weapons treaty which the United Nations General Assembly approved in 1968 and that NATO supported. [ 2 ] These arms control talks would eventually lead to the Biological Weapons Convention, an international treaty outlawing biological warfare. [ 11 ]
Nixon's renunciation is often overlooked in discussions about his presidency and his presidential legacy. Books about Nixon devote little space to the act and those centered on the topic of arms-control, even less. [ 5 ] The abandonment of an entire class of weapons remains unrepeated in U.S. history. [ 5 ] In addition, Melvin Laird's role in the elimination of offensive U.S. biological capabilities has been largely overlooked. [ 1 ] The official U.S. Army history of the U.S. biological warfare program, which spans from the early Cold War to 1969 and includes an overview of biowarfare research, Fort Derick contracts between U.S. universities and the private industry, as well as testing on human volunteers, was published online by the National Security Archives . [ 12 ]
Scholars and critics have argued that Nixon's decision to ban biological weapons was purely politically motivated. [ 5 ] This move was seen as a way to placate national, Congressional, and international concerns. [ 5 ] It was also seen as a way to progress arms-control talks, additionally it could have stymied the outcry over the use of non-lethal chemical agents in Vietnam. [ 5 ] In reality, the issue was much more complex than even those reasons suggest. [ 13 ] [ 14 ]
Meselson and others had argued that biological weapons amounted to little more than a cheap version of a nuclear weapon, and were easily attainable. [ 4 ] Biological weapons represented a significant threat in the hands of less-well-armed, poorer nations, and Nixon surely recognized this "asymmetrical" threat. [ 13 ] The administration eventually came to the conclusion that any biological threat could be easily countered with the U.S. nuclear arsenal . [ 13 ]
Nixon recognized that the BW program was unpopular and decided that there was no real reason to continue these programs. [ 13 ] While there were some political considerations involved in Nixon's decision, the result brought the topic into international forums for years following his declaration. [ 13 ] The media characterized Nixon's decision as a sudden awareness of the horrific nature of chemical-biological warfare. [ 5 ]
Nixon hoped that the move would bolster both the image of his administration and the United States as a whole. [ 15 ] He also wanted to score points with the Democratic majority in Congress and he had chosen to do this through various arms control measures. [ 5 ] Nixon knew Democrats could not afford to oppose his renunciation of BW programs in light of rising opposition to the use of non-lethal chemicals in Vietnam and other events such as the Skull Valley sheep kill in Utah. [ 5 ] Thus, the idealistic language Nixon used in his November statement was only part of the story. Besides the issue of proliferation raised by Meselson, the specter of growing dissent over Vietnam loomed large, as did the fact that the U.S. had never ratified the Geneva Protocol. [ 14 ] In the end, Nixon was motivated to ban biological weapons in the United States by a host of issues. | https://en.wikipedia.org/wiki/Statement_on_Chemical_and_Biological_Defense_Policies_and_Programs |
Static Context Header Compression (SCHC) is a standard compression and fragmentation mechanism defined in the IPv6 over LPWAN working group at the IETF . It offers compression and fragmentation of IPv6 / UDP / CoAP packets to allow their transmission over the Low-Power Wide-Area Networks (LPWAN) .
Low-Power Wide-Area Network ( LPWAN ) gathers the connectivity technologies tailored for Internet of Things (IoT), allowing for:
The trade-off for achieving these features includes severe limitation in terms of throughput and packet size supported. [ 1 ] Also, LPWAN come with limitations on transmission modalities since, in order to save battery, devices are dormant most of the time and wake up only episodically to transmit and receive data for a short time window.
As a result, the LPWAN use their specific protocols, each adapted to their own specificities. Most importantly, they cannot carry IPv6 , which was designed to allocate addresses to the billions of IoT connected devices.
In the early 2000s, the IETF produced the first wave of mature standards for compression and fragmentation:
Yet, these compression schemes cannot fit the LPWAN specificities. [ 2 ] [ 3 ] [ 4 ]
SCHC associates the benefits of the RoHC context, which provides high flexibility in the fields processing, and of the 6LoWPAN operations to avoid transiting fields that are known by the other side. [ 4 ]
SCHC takes advantage of the LPWAN characteristics (no routing, highly predictable traffic format and content of messages) to reduce the overhead to a few bytes and save network traffic.
The SCHC compression is based on the notion of context . A context is a set of rules that describes the communication context, meaning the header fields. It is shared and pre-provisioned in both the end-devices and the core network. The "static context" assumes that the rule description does not change during transmission. Thanks to this mechanism, IPv6/UDP headers are in most cases reduced to a small identifier.
When compression is not enough, SCHC provides a fragmentation mechanism that works in 3 different ways:
In this mode the SCHC packet is separated in multiple fragments that are blindly sent to the receiver, if the receiver missed any one packet then it won't be able to re build the sent packet.
In this mode the concept of "windows" is used, windows have a predefined size, allowing the receiver to keep a count of which windows or windows parts have been received, at the moment the receiver gets the last fragment from the sender it will calculate which parts of the packets it has missed and send a message describing that to the sender. The sender will then initialize the retransmission of the missing packet parts.
In Ack-Always mode the same retransmission mechanism as for Ack-On-Error is used except that it is not done at the end of the transmission but for each window.
The Generic Framework for Static Context Header Compression and Fragmentation, RFC 8724 has been published in April 2020. It describes the generic framework that can be used on all LPWAN technologies, and more generally on all Internet networks.
Additional work is dedicated to the definition of standard parameter settings and modes of operation to optimize SCHC's performance according to the implemented protocols and the underlying LPWAN technologies:
On May 17, 2022, The LoRa Alliance (global association of companies backing the open LoRaWAN® standard for the internet of things low-power wide-area networks) announced that LoRaWAN now seamlessly supports Internet Protocol version 6 (IPv6) from end-to-end. [ 5 ] By expanding the breadth of device-to-application solutions with IPv6, LoRaWAN's addressable IoT market is also broadened to include internet based standards required in smart electricity metering and new applications in smart buildings, industries, logistics, and homes. The Alliance released a technical specification TS 10–1.0.0 to explain how to use SCHC as an adaptation layer to enable LoRaWAN end-devices to use IPv6-based stacks over LoRaWAN [ 6 ] and expands its certification program to include SCHC over LoRaWAN® Enabling IPv6 Solutions. [ 7 ]
In addition, SCHC is being adopted in a joint standardization effort carried out by the DLMS User Association and the LoRa Alliance for the smart metering industries. [ 8 ] [ 9 ] | https://en.wikipedia.org/wiki/Static_Context_Header_Compression |
In integrated circuit design , static core generally refers to a microprocessor (MPU) entirely implemented in static logic . [ 1 ] A static core MPU may be halted by stopping the system clock oscillator that is driving it, maintaining its state and resume processing at the point where it was stopped when the clock signal is restarted, as long as power continues to be applied. Static core MPUs are fabricated in the CMOS process and hence consume very little power when the clock is stopped, making them useful in designs in which the MPU remains in standby mode until needed and minimal loading of the power source (often a battery ) is desirable during standby. [ 2 ]
In comparison, dynamic core microprocessor designs, those without a static core, only refresh and present valid outputs on their pins during specific periods of the clock cycle. If the clock is slowed, or stopped, the charge on the pin leaks out of the capacitors over time, quickly moving to the default state and no longer being valid. Dynamic designs have to run within a set range of clock frequencies to avoid this problem.
Static core microprocessors include the RCA 1802 , Intel 80386EX , WDC W65C02S , WDC W65C816S and Freescale 683XX family.
Many low-power electronics systems are designed as fully static systems—such as, for example, the Psion Organiser , [ 3 ] the TRS-80 Model 100 , and the Galileo spacecraft . In such a fully static system, the processor has a static core and data is stored in static RAM , rather than dynamic RAM . Such design features allow the entire system to be "paused" indefinitely in a low power state, and then instantly resumed when needed. [ 3 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Static_core |
Static fatigue, sometimes referred to as delayed fracture, describes the progressive cracking and eventual failure of materials under a constant, sustained stress . [ 1 ] (It is different from fatigue , which refers to the deformation and eventual failure of materials subjected to cyclical stresses .) With static fatigue materials experience damage or failure under stress levels that are lower than their normal ultimate tensile strengths . [ 2 ] The exact details vary with the material type and environmental factors, such as moisture presence [ 3 ] and temperature. [ 4 ] [ 5 ] This phenomenon is closely related to stress corrosion cracking . [ 1 ]
Stress corrosion cracking (SCC) happens when a stressed material is in a corrosive (chemically destructive) environment. [ 6 ] One example of SSC embrittlement is when moisture increases static fatigue degradation of glass. [ 7 ] SCC is also seen in hydrogen embrittlement [ 8 ] [ 9 ] and embrittlement of some polymers . [ 10 ]
Plastic deformation happens when stresses flatten, bend, or twist a material until it cannot return to its original shape. [ 11 ] This can create cracks in the material and decrease its lifetime. [ 12 ]
Static fatigue tests can be used to determine the lifespan of a material with different loads and environmental conditions. [ 13 ] [ 14 ] However, accurately assessing a material's true static fatigue life presents challenges, as these tests often require an extended duration and there is significant variability in the results. [ 13 ]
Plastic pipes under water or other fluids experience hydrodynamic forces that can result in fatigue. [ 15 ] The pipes reach failure sooner as temperatures and exposure to aggressive substances increase. [ 15 ] | https://en.wikipedia.org/wiki/Static_fatigue |
Static grass is used in scale models and miniatures to create realistic-looking grass textures. It consists of small coloured fibres charged with static electricity , making them stand on end when sprinkled onto a surface coated with glue that then hardens, holding the fibres in place.
Static grass is usually prepared by applying a layer of glue on the surface, then pouring the fibres on and tipping off the excess. The fibres can also be applied with a shaker, also known as a puffer.
Static grass consists of man-made fibres selected for their ability to hold a static electric charge. They are usually a blend of coloured nylon, rayon, or polyester fibres that are used to more realistically replicate grass on a modeller's layout. The fibres are usually sold by weight in 2, 4, 6, 10 and 12 millimetre lengths, although fibres can be found from as little as 0.5 mm in length.
If using an electronic applicator, the fibres are attracted to the adhesive vertically and "end-on", giving the grass-like effect the modeller requires.
The application sequence is as follows:
Once the basic technique is mastered, advanced techniques can be learned, such as developing differing lengths, dead grass and creating grass tufts, to enhance realism..
Several companies produce static grass products, including PECO , Woodland Scenics , Green Stuff World and WW Scenics .
This wargame -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Static_grass |
Static light scattering is a technique in physical chemistry that measures the intensity of the scattered light to obtain the average molecular weight M w of a macromolecule like a polymer or a protein in solution. Measurement of the scattering intensity at many angles allows calculation of the root mean square radius, also called the radius of gyration R g . By measuring the scattering intensity for many samples of various concentrations, the second virial coefficient, A 2 , can be calculated. [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ]
Static light scattering is also commonly utilized to determine the size of particle suspensions in the sub-μm and supra-μm ranges, via the Lorenz-Mie (see Mie scattering ) and Fraunhofer diffraction formalisms, respectively.
For static light scattering experiments, a high-intensity monochromatic light, usually a laser, is launched into a solution containing the macromolecules. One or many detectors are used to measure the scattering intensity at one or many angles. The angular dependence is required to obtain accurate measurements of both molar mass and size for all macromolecules of radius above 1–2% of the incident wavelength. Hence simultaneous measurements at several angles relative to the direction of the incident light, known as multi-angle light scattering (MALS) or multi-angle laser light scattering (MALLS), are generally regarded as the standard implementation of static light scattering. Additional details on the history and theory of MALS may be found in multi-angle light scattering .
To measure the average molecular weight directly without calibration from the light scattering intensity, the laser intensity, the quantum efficiency of the detector, and the full scattering volume and solid angle of the detector need to be known. Since this is impractical, all commercial instruments are calibrated using a strong, known scatterer like toluene since the Rayleigh ratio of toluene and a few other solvents were measured using an absolute light scattering instrument.
For a light scattering instrument composed of many detectors placed at various angles, all the detectors need to respond the same way. Usually, detectors will have slightly different quantum efficiency , different gains, and are looking at different geometrical scattering volumes. In this case, a normalization of the detectors is absolutely needed. To normalize the detectors, a measurement of a pure solvent is made first. Then an isotropic scatterer is added to the solvent. Since isotropic scatterers scatter the same intensity at any angle, the detector efficiency and gain can be normalized with this procedure. It is convenient to normalize all the detectors to the 90° angle detector.
N ( θ ) = I R ( θ ) − I S ( θ ) I R ( 90 ) − I S ( 90 ) {\displaystyle \ N(\theta )={\frac {I_{R}(\theta )-I_{S}(\theta )}{I_{R}(90)-I_{S}(90)}}}
where I R (90) is the scattering intensity measured for the Rayleigh scatterer by the 90° angle detector.
The most common equation to measure the weight-average molecular weight, M w , is the Zimm equation [ 5 ] (the right-hand side of the Zimm equation is provided incorrectly in some texts, as noted by Hiemenz and Lodge): [ 6 ]
K c Δ R ( θ , c ) = 1 M w ( 1 + q 2 R g 2 3 + O ( q 4 ) ) + 2 A 2 c + O ( c 2 ) {\displaystyle {\frac {Kc}{\Delta R(\theta ,c)}}={\frac {1}{M_{w}}}\left(1+{\frac {q^{2}R_{g}^{2}}{3}}+O(q^{4})\right)+2A_{2}c+O(c^{2})}
where
K = 4 π 2 n 0 2 ( d n / d c ) 2 / N A λ 4 {\displaystyle \ K=4\pi ^{2}n_{0}^{2}(dn/dc)^{2}/N_{\text{A}}\lambda ^{4}}
and
Δ R ( θ , c ) = R A ( θ ) − R 0 ( θ ) {\displaystyle \ \Delta R(\theta ,c)=R_{A}(\theta )-R_{0}(\theta )}
with
R ( θ ) = I A ( θ ) n 0 2 I T ( θ ) n T 2 R T N ( θ ) {\displaystyle \ R(\theta )={\frac {I_{A}(\theta )n_{0}^{2}}{I_{T}(\theta )n_{T}^{2}}}{\frac {R_{T}}{N(\theta )}}}
and the scattering vector for vertically polarized light is
q = 4 π n 0 sin ( θ / 2 ) / λ {\displaystyle \ q=4\pi n_{0}\sin(\theta /2)/\lambda }
with n 0 the refractive index of the solvent, λ the wavelength of the light source, N A the Avogadro constant , c the solution concentration, and d n /d c the change in the refractive index of the solution with change in concentration. The intensity of the analyte measured at an angle is I A (θ) . In these equations, the subscript A is for analyte (the solution) and T is for the toluene with the Rayleigh ratio of toluene, R T being 1.35×10 −5 cm −1 for a HeNe laser . As described above, the radius of gyration, R g , and the second virial coefficient, A 2 , are also calculated from this equation. The refractive index increment dn/dc characterizes the change of the refractive index n with the concentration c and can be measured with a differential refractometer.
A Zimm plot is built from a double extrapolation to zero angle and zero concentration from many angles and many concentration measurements. In its simplest form, the Zimm equation is reduced to:
K c / Δ R ( θ → 0 , c → 0 ) = 1 / M w {\displaystyle \ Kc/\Delta R(\theta \rightarrow 0,c\rightarrow 0)=1/M_{w}}
for measurements made at low angle and infinite dilution since P (0) = 1.
There are typically several analyses developed to analyze the scattering of particles in solution to derive the above-named physical characteristics of particles. A simple static light scattering experiment entails the average intensity of the sample that is corrected for the scattering of the solvent will yield the Rayleigh ratio , R as a function of the angle or the wave vector q as follows:
The scattered intensity can be plotted as a function of the angle to give information on the R g which can simply be calculated using the Guinier approximation (developed by André Guinier ) as follows:
ln ( Δ R ( θ ) ) = 1 − ( R g 2 / 3 ) q 2 {\displaystyle \ln(\Delta R(\theta ))=1-(R_{g}^{2}/3)q^{2}}
where ln(Δ R ( θ )) = ln P ( θ ) also known as the form factor with q = 4πn 0 sin( θ /2)/ λ . Hence a plot of the corrected Rayleigh ratio , Δ R ( θ ) vs sin 2 ( θ /2) or q 2 will yield a slope R g 2 /3 . However, this approximation is only true for qR g < 1 . Note that for a Guinier plot, the value of dn/dc and the concentration is not needed.
The Kratky plot is typically used to analyze the conformation of proteins but can be used to analyze the random walk model of polymers . A Kratky plot can be made by plotting sin 2 (θ/2)ΔR(θ) vs sin(θ/2) or q 2 ΔR(θ) vs q .
For polymers and polymer complexes that are monodisperse ( μ 2 / Γ ¯ 2 < 0.3 {\displaystyle \scriptstyle \mu _{2}/{\bar {\Gamma }}^{2}<0.3} ) as determined by static light scattering, a Zimm plot is a conventional means of deriving the parameters such as R g , molecular mass M w and the second virial coefficient A 2 .
One must note that if the material constant K is not implemented, a Zimm plot will only yield R g . Hence implementing K will yield the following equation:
K c Δ R ( θ , c ) = 1 M w ( 1 + q 2 R g 2 3 + O ( q 4 ) ) + 2 A 2 c + O ( c 2 ) {\displaystyle {\frac {Kc}{\Delta R(\theta ,c)}}={\frac {1}{M_{w}}}\left(1+{\frac {q^{2}R_{g}^{2}}{3}}+O(q^{4})\right)+2A_{2}c+O(c^{2})}
The analysis performed with the Zimm plot uses a double-extrapolation to zero concentration and zero scattering angle resulting in a characteristic rhomboid plot. As the angular information is available, it is also possible to obtain the radius of gyration ( R g ). Experiments are performed at several angles, which satisfy the condition q R g < 1 {\displaystyle qR_{g}<1} and at least 4 concentrations. Performing a Zimm analysis on a single concentration is known as a partial Zimm analysis and is only valid for dilute solutions of strong point scatterers . The partial Zimm however, does not yield the second virial coefficient , due to the absence of the variable concentration of the sample. More specifically, the value of the second virial coefficient is either assumed to equal zero or is inputted as a known value in order to perform the partial Zimm analysis.
If the measured particles are smaller than λ/20, the form factor P(θ) can be neglected ( P(θ) →1). Therefore, the Zimm equation is simplified to the Debye equation, as follows:
K c Δ R ( θ , c ) = 1 M w + 2 A 2 c {\displaystyle {\frac {Kc}{\Delta R(\theta ,c)}}={\frac {1}{M_{w}}}+2A_{2}c}
Note that this is also the result of an extrapolation to zero scattering angle. By acquiring data on concentration and scattering intensity, the Debye plot is constructed by plotting Kc / ΔR(θ) vs. concentration. The intercept of the fitted line gives the molecular mass, while the slope corresponds to the 2nd virial coefficient.
As the Debye plot is a simplification of the Zimm equation, the same limitations of the latter apply, i.e., samples should present a monodisperse nature. For polydisperse samples, the resulting molecular mass from a static light-scattering measurement will represent an average value. An advantage of the Debye plot is the possibility to determine the second virial coefficient. This parameter describes the interaction between particles and the solvent. In macromolecule solutions, for instance, it can assume negative (particle-particle interactions are favored), zero, or positive values (particle-solvent interactions are favored). [ 8 ]
Static light scattering assumes that each detected photon has only been scattered exactly once. Therefore, analysis according to the calculations stated above will only be correct if the sample has been diluted sufficiently to ensure that photons are not scattered multiple times by the sample before being detected. Accurate interpretation becomes exceedingly difficult for systems with non-negligible contributions from multiple scattering. In many commercial instruments where analysis of the scattering signal is automatically performed, the error may never be noticed by the user. Particularly for larger particles and those with high refractive index contrast, this limits the application of standard static light scattering to very low particle concentrations. On the other hand, for soluble macromolecules that exhibit a relatively low refractive index contrast versus the solvent, including most polymers and biomolecules in their respective solvents, multiple scattering is rarely a limiting factor even at concentrations that approach the limits of solubility.
However, as shown by Schaetzel, [ 9 ] it is possible to suppress multiple scattering in static light scattering experiments via a cross-correlation approach. The general idea is to isolate singly scattered light and suppress undesired contributions from multiple scattering in a static light scattering experiment. Different implementations of cross-correlation light scattering have been developed and applied. Currently, the most widely used scheme is the so-called 3D-dynamic light scattering method,. [ 10 ] [ 11 ] The same method can also be used to correct dynamic light scattering data for multiple scattering contributions. [ 12 ]
Samples that change their properties after dilution may not be analyzed via static light scattering in terms of the simple model presented here as the Zimm equation. A more sophisticated analysis known as 'composition-gradient static (or multi-angle) light scattering' (CG-SLS or CG-MALS) is an important class of methods to investigate protein–protein interactions , colligative properties, and other macromolecular interactions as it yields, in addition to size and molecular weight, information on the affinity and stoichiometry of molecular complexes formed by one or more associating macromolecular/biomolecular species. In particular, static light scattering from a dilution series may be analyzed to quantify self-association, reversible oligomerization, and non-specific attraction or repulsion, while static light scattering from mixtures of species may be analyzed to quantify hetero-association. [ 13 ]
One of the main applications of static light scattering for molecular mass determination is in the field of macromolecules, such as proteins and polymers, [ 14 ] [ 15 ] [ 16 ] as it is possible to measure the molecular mass of proteins without any assumption about their shape. Static light scattering is usually combined with other particle characterization techniques, such as size-exclusion chromatography (SEC), dynamic light scattering (DLS), and electrophoretic light scattering (ELS). | https://en.wikipedia.org/wiki/Static_light_scattering |
A static mixer is a device for the continuous mixing of fluid materials, without moving components. [ 1 ] Normally the fluids to be mixed are liquid, but static mixers can also be used to mix gas streams, disperse gas into liquid or blend immiscible liquids . The energy needed for mixing comes from a loss in pressure as fluids flow through the static mixer. [ 2 ] One design of static mixer is the plate-type mixer and another common device type consists of mixer elements contained in a cylindrical (tube) or squared housing. Mixer size can vary from about 6 mm to 6 meters diameter. Typical construction materials for static mixer components include stainless steel , polypropylene , Teflon , PVDF , PVC , CPVC and polyacetal . The latest designs involve static mixing elements made of glass-lined steel.
In the plate type design mixing is accomplished through intense turbulence in the flow. [ 3 ]
In the housed-elements design the static mixer elements consist of a series of baffles made of metal or a variety of plastics . Similarly, the mixer housing can be made of metal or plastic. The housed-elements design incorporates a method for delivering two streams of fluids into the static mixer. As the streams move through the mixer, the non-moving elements continuously blend the materials. Complete mixing depends on many variables including the fluids' properties, tube inner diameter, number of elements and their design. The housed-elements mixer's fixed, typically helical elements can simultaneously produce patterns of flow division and radial mixing:
A common application is mixing nozzles for two-component adhesives (e.g., epoxy ) and sealants (see Resin casting ). Other applications include wastewater treatment and chemical processing. [ 4 ] Static mixers can be used in the refinery and oil and gas markets as well, for example in bitumen processing [ 5 ] or for desalting crude oil. In polymer production, static mixers can be used to facilitate polymerization reactions or for the admixing of liquid additives. [ 6 ]
The static mixer traces its origins to an invention for a mixing device filed on Nov. 29, 1965 by the Arthur D. Little Company . [ 7 ] This device was the housed-elements type and was licensed to the Kenics Corporation and marketed as the Kenics Motionless Mixer. [ 8 ] Today, the Kenics brand is owned by National Oilwell Varco . The plate type static mixer patent was issued on November 24, 1998, to Robert W. Glanville of Westfall Manufacturing. [ 9 ] | https://en.wikipedia.org/wiki/Static_mixer |
In fluid mechanics the term static pressure refers to a term in Bernoulli's equation written words as static pressure + dynamic pressure = total pressure . Since pressure measurements at any single point in a fluid always give the static pressure value, the 'static' is often dropped.
In the design and operation of aircraft , static pressure is the air pressure in the aircraft's static pressure system .
The concept of pressure is central to the study of fluids. A pressure can be identified for every point in a body of fluid, regardless of whether the fluid is in motion. Pressure can be measured using an aneroid , Bourdon tube , mercury column, or various other methods.
The concepts of total pressure and dynamic pressure arise from Bernoulli's equation and are significant in the study of all fluid flows. These two pressures are not pressures in the usual sense - they cannot be measured using a pressure sensor . To avoid potential ambiguity when referring to pressure in fluid dynamics, many authors use the term static pressure to distinguish it from total pressure and dynamic pressure ; the term static pressure is identical to the term pressure , and can be identified for every point in a fluid flow field. The static pressure can be measured in flowing fluid using a hole or tube which is perpendicular to the flow.
In Aerodynamics , L.J. Clancy [ 1 ] writes: "To distinguish it from the total and dynamic pressures, the actual pressure of the fluid, which is associated not with its motion but with its state, is often referred to as the static pressure, but where the term pressure alone is used it refers to this static pressure."
Bernoulli's equation is foundational to the dynamics of incompressible fluids . In many fluid flow situations of interest, changes in elevation are insignificant and can be ignored. With this simplification, Bernoulli's equation for incompressible flows can be expressed as [ 2 ] [ 3 ] [ 4 ]
where:
Every point in a steadily flowing fluid, regardless of the fluid speed at that point, has its own static pressure P {\displaystyle P} , dynamic pressure q {\displaystyle q} , and total pressure P 0 {\displaystyle P_{0}} . Static pressure and dynamic pressure are likely to vary significantly throughout the fluid but total pressure is constant along each streamline. In irrotational flow , total pressure is the same on all streamlines and is therefore constant throughout the flow. [ 5 ]
The simplified form of Bernoulli's equation can be summarised in the following memorable word equation: [ 6 ] [ 7 ] [ 8 ]
This simplified form of Bernoulli's equation is fundamental to an understanding of the design and operation of ships, low speed aircraft, and airspeed indicators for low speed aircraft – that is aircraft whose maximum speed will be less than about 30% of the speed of sound .
As a consequence of the widespread understanding of the term static pressure in relation to Bernoulli's equation, many authors [ 9 ] in the field of fluid dynamics also use static pressure rather than pressure in applications not directly related to Bernoulli's equation .
The British Standards Institution , in its Standard [ 10 ] Glossary of Aeronautical Terms , gives the following definition:
An aircraft's static pressure system is the key input to its altimeter and, along with the pitot pressure system , also drives the airspeed indicator . [ 11 ]
The static pressure system is open to the aircraft's exterior through a small opening called the static port , which allows sensing the ambient atmospheric pressure at the altitude at which the aircraft is flying. In flight, the air pressure varies slightly at different positions around the aircraft's exterior, so designers must select the static ports' locations carefully. Wherever they are located, the air pressure that the ports observe will generally be affected by the aircraft's instantaneous angle of attack . [ 12 ] The difference between that observed pressure and the actual atmospheric pressure (at altitude) causes a small position error in the instruments' indicated altitude and airspeed. [ 13 ] [ 14 ] A designer's objective in locating the static port is to minimize the resulting position error across the aircraft's operating range of weight and airspeed.
Many authors describe the atmospheric pressure at the altitude at which the aircraft is flying as the freestream static pressure . At least one author takes a different approach in order to avoid a need for the expression freestream static pressure . Gracey has written "The static pressure is the atmospheric pressure at the flight level of the aircraft". [ 15 ] [ 16 ] Gracey then refers to the air pressure at any point close to the aircraft as the local static pressure .
The term (hydro)static pressure is sometimes used in fluid statics to refer to the pressure of a fluid at a nominated depth in the fluid. In fluid statics the fluid is stationary everywhere and the concepts of dynamic pressure and total pressure are not applicable. Consequently, there is little risk of ambiguity in using the term pressure , but some authors [ 17 ] choose to use static pressure in some situations.
Aircraft design and operation
Fluid dynamics | https://en.wikipedia.org/wiki/Static_pressure |
In metric theories of gravitation , particularly general relativity , a static spherically symmetric perfect fluid solution (a term which is often abbreviated as ssspf ) is a spacetime equipped with suitable tensor fields which models a static round ball of a fluid with isotropic pressure .
Such solutions are often used as idealized models of stars , especially compact objects such as white dwarfs and especially neutron stars . In general relativity, a model of an isolated star (or other fluid ball) generally consists of a fluid-filled interior region , which is technically a perfect fluid solution of the Einstein field equation , and an exterior region , which is an asymptotically flat vacuum solution . These two pieces must be carefully matched across the world sheet of a spherical surface, the surface of zero pressure . (There are various mathematical criteria called matching conditions for checking that the required matching has been successfully achieved.) Similar statements hold for other metric theories of gravitation, such as the Brans–Dicke theory .
In this article, we will focus on the construction of exact ssspf solutions in our current Gold Standard theory of gravitation, the theory of general relativity. To anticipate, the figure at right depicts (by means of an embedding diagram) the spatial geometry of a simple example of a stellar model in general relativity. The euclidean space in which this two-dimensional Riemannian manifold (standing in for a three-dimensional Riemannian manifold) is embedded has no physical significance, it is merely a visual aid to help convey a quick impression of the kind of geometrical features we will encounter.
We list here a few milestones in the history of exact ssspf solutions in general relativity: | https://en.wikipedia.org/wiki/Static_spherically_symmetric_perfect_fluid |
In cosmology , a static universe (also referred to as stationary , infinite , static infinite or static eternal ) is a cosmological model in which the universe is both spatially and temporally infinite, and space is neither expanding nor contracting. Such a universe does not have so-called spatial curvature ; that is to say that it is 'flat' or Euclidean . [ citation needed ] [ further explanation needed ] A static infinite universe was first proposed by English astronomer Thomas Digges (1546–1595). [ 1 ]
In contrast to this model, Albert Einstein proposed a temporally infinite but spatially finite model - static eternal universe - as his preferred cosmology during 1917, in his paper Cosmological Considerations in the General Theory of Relativity .
After the discovery of the redshift-distance relationship (deduced by the inverse correlation of galactic brightness to redshift) by American astronomers Vesto Slipher and Edwin Hubble , the Belgian astrophysicist and priest Georges Lemaître interpreted the redshift as evidence of universal expansion and thus a Big Bang , whereas Swiss astronomer Fritz Zwicky proposed that the redshift was caused by the photons losing energy as they passed through the matter and/or forces in intergalactic space. Zwicky's proposal would come to be termed ' tired light '—a term invented by the major Big Bang proponent Richard Tolman .
During 1917, Albert Einstein added a positive cosmological constant to his equations of general relativity to counteract the attractive effects of gravity on ordinary matter, which would otherwise cause a static, spatially finite universe to either collapse or expand forever . [ 2 ] [ 3 ] [ 4 ] This model of the universe became known as the Einstein World or Einstein's static universe .
This motivation ended after the proposal by the astrophysicist and Roman Catholic priest Georges Lemaître that the universe seems to be not static, but expanding. Edwin Hubble had researched data from the observations made by astronomer Vesto Slipher to confirm a relationship between redshift and distance , which forms the basis for the modern expansion paradigm that was introduced by Lemaître. According to George Gamow this caused Einstein to declare this cosmological model, and especially the introduction of the cosmological constant, his "biggest blunder". [1]
Einstein's static universe is closed (i.e. has hyperspherical topology and positive spatial curvature), and contains uniform dust and a positive cosmological constant with value precisely Λ E = 4 π G ρ / c 2 {\displaystyle \Lambda _{E}=4\pi G\rho /c^{2}} , where G {\displaystyle G} is Newtonian gravitational constant, ρ {\displaystyle \rho } is the energy density of the matter in the universe and c {\displaystyle c} is the speed of light . The radius of curvature of space of the Einstein universe is equal to
The Einstein universe is one of Friedmann's solutions to Einstein's field equation for dust with density ρ {\displaystyle \rho } , cosmological constant Λ E {\displaystyle \Lambda _{E}} , and radius of curvature R E {\displaystyle R_{E}} . It is the only non-trivial static solution to Friedmann's equations. [ citation needed ]
Because the Einstein universe soon was recognized to be inherently unstable, it was presently abandoned as a viable model for the universe. It is unstable in the sense that any slight change in either the value of the cosmological constant, the matter density , or the spatial curvature will result in a universe that either expands and accelerates forever or re-collapses to a singularity.
After Einstein renounced his cosmological constant, and embraced the Friedmann-LeMaitre model of an expanding universe, [ 5 ] most physicists of the twentieth century assumed that the cosmological constant is zero. If so (absent some other form of dark energy ), the expansion of the universe would be decelerating. However, after Saul Perlmutter , Brian P. Schmidt , and Adam G. Riess introduced the theory of an accelerating universe during 1998, a positive cosmological constant has been revived as a simple explanation for dark energy .
In 1976 Irving Segal revived the static universe in his chronometric cosmology . Similar to Zwicky, he ascribed the red shift of distant galaxies to curvature in the cosmos. Though he claimed vindication in astronomic data, others find the results to be inconclusive. [ 6 ]
In order for a static infinite universe model to be viable, it must explain three things:
First, it must explain the intergalactic redshift . Second, it must explain the cosmic microwave background radiation . Third, it must have a mechanism to re-create matter (particularly hydrogen atoms) from radiation or other sources in order to avoid a gradual 'running down' of the universe due to the conversion of matter into energy in stellar processes . [ 7 ] [ 8 ] With the absence of such a mechanism, the universe would consist of dead objects such as black holes and black dwarfs . | https://en.wikipedia.org/wiki/Static_universe |
Static wicks , also called static dischargers or static discharge wicks , are devices used to remove static electricity from aircraft in flight. They take the form of small sticks pointing backwards from the wings, and are fitted on almost all civilian aircraft. [ 1 ]
Precipitation static is an electrical charge on an airplane caused by flying through rain, snow storms, ice, or dust particles. Charge also accumulates through friction between the aircraft hull and the air. When the aircraft charge is great enough, it discharges into the surrounding air. Without static dischargers, the charge discharges in large batches through pointed aircraft extremities, such as antennas, wing tips, vertical and horizontal stabilizers, and other protrusions. The discharge creates a broad-band radio frequency noise from DC to 1000 MHz, which can affect aircraft communication. [ citation needed ]
To control this discharge, so as to allow the continuous operation of navigation and radio communication systems, static wicks are installed on the trailing edges of aircraft. These include (electrically grounded) ailerons , elevators , rudder , wing , horizontal and vertical stabilizer tips. Static wicks are high electrical resistance (6–200 megaohm ) devices with a lower corona voltage and sharper points than the surrounding aircraft structure. [ citation needed ] This means that the corona discharge into the atmosphere flows through them, and occurs gradually. [ 2 ]
Static wicks are not lightning arresters and do not affect the likelihood of an aircraft being struck by lightning. They will not function if they are not properly bonded to the aircraft. There must be a conductive path from all parts of the airplane to the dischargers, otherwise they will be useless. Access panels, doors, cowls, navigation lights, antenna mounting hardware, control surfaces, etc., can create static noise if they cannot discharge through the static wick. [ citation needed ]
Static dischargers were first proposed in a patent application by Howard Dudley Blanchard in 1920. [ 3 ] At this time most aircraft were constructed from cloth and wood, and rigid body airships were widely used. Therefore, a method of gradually discharging static accumulation was necessary since static discharge on these craft could cause serious damage and start fires. Static discharge is the likely cause of the Hindenburg disaster. [ citation needed ]
The first static wicks were developed by a joint Army-Navy team led by Dr. Ross Gunn of the Naval Research Laboratory and fitted onto military aircraft during World War II. They were shown to be effective even in extreme weather conditions in 1946 by a United States Army Air Corps team led by Capt. Ernest Lynn Cleveland. [ citation needed ]
Dayton Granger, an inventor from Florida, received a patent on static wicks in 1950. [ 1 ] | https://en.wikipedia.org/wiki/Static_wick |
Stationary-wave integrated Fourier-transform spectrometry ( SWIFTS ), or standing-wave integrated Fourier-transform spectrometry , is an analytical technique used for measuring the distribution of light across an optical spectrum . SWIFTS technology is based on a near-field Lippmann architecture. An optical signal is injected into a waveguide and ended by a mirror (true Lippman configuration). The input signal interferes with the reflected signal, creating a standing, or stationary, wave .
In a counter-propagative architecture, the two optical signals are injected at the opposite ends of the waveguide. The evanescent waves propagating within the waveguide are then sampled by optical probes. This results in an interferogram . A mathematical function known as a Lippmann transform, similar to a Fourier transform , is later used to give the spectrum of the light.
In 1891, at the Académie des Sciences in Paris, Gabriel Lippmann presented a colour photograph of the Sun's spectrum obtained with his new photographic plate . [ 1 ] Later, in 1894, he published an article on how his plate was able to record colour information in the depth of photographic grainless gelatin and how the same plate after processing could restore the original colour image merely through light reflection. [ 2 ] He was thus the inventor of true interferential colour photography . He received the Nobel Prize in Physics in 1908 for this breakthrough. Unfortunately, this principle was too complex to use. The method was abandoned a few years after its discovery.
One aspect of the Lippmann concept that was ignored at that time relates to spectroscopic applications. Early in 1933, Herbert E. Ives proposed to use a photoelectric device to probe stationary waves to make spectrometric measurements. [ 3 ] In 1995, P. Connes [ 4 ] proposed to use the emerging new technology of detectors for three-dimensional Lippmann-based spectrometry. Following this, a first realization of a very compact spectrometer based on a microoptoelectromechanical system (MOEMS) was reported by Knipp et al. in 2005, [ 5 ] but it had a very limited spectral resolution. In 2004, two French researchers, Etienne Le Coarer from Joseph Fourier University and Pierre Benech from INP Grenoble , coupled sensing elements to the evanescent part of standing waves within a single-mode waveguide. In 2007, those two researchers reported a near-field method to probe the interferogram within a waveguide. [ 6 ] The first SWIFTS-based spectrometers appeared in 2011 based on a SWIFTS linear configuration.
The technology works by probing an optical standing wave, or the sum of the standing waves in the case of polychromatic light, created by a light to be analyzed. In a SWIFTS linear configuration (true Lippman configuration), the stationary wave is created by a single-mode waveguide ended by a fixed mirror. The stationary wave is regularly sampled on one side of a waveguide using nano-scattering dots. These dots are located in the evanescent field . These nanodots are characterized by an optical index difference with the medium in which the evanescent field is located. The light is then scattered around an axis perpendicular to the waveguide. For each dot, this scattered light is detected by a pixel aligned with this axis. The intensity detected is therefore proportional to the intensity inside the waveguide at the exact location of the dot. This results in a linear image of the interferogram. No moving parts are used. A mathematical function known as a Lippmann transform, similar to a Fourier transform, is then applied to this linear image and gives the spectrum of the light.
The interferogram is truncated. Only the frequencies corresponding to the zero optical path difference at the mirror, up to the farthest dots are sampled. Higher frequencies are rejected. This interferogram’s truncation determines the spectral resolution . The interferogram is undersampled. A consequence of this under-sampling is a limitation of the wavelength bandwidth to which the mathematical function is applied.
SWIFTS technology displays the Fellgett's advantage , which is derived from the fact that an interferometer measures wavelengths simultaneously with the same elements of the detector, whereas a dispersive spectrometer measures them successively. Fellgett's advantage also states that when collecting a spectrum whose measurement noise is dominated by detector noise, a multiplex spectrometer such as a Fourier-transform spectrometer will produce a relative improvement in the signal-to-noise ratio , with respect to an equivalent scanning monochromator , that is approximately equal to the square root of the number of sample points comprising the spectrum. The Connes advantage states that the wavenumber scale of an interferometer, derived from a helium–neon laser , is more accurate and boasts better long-term stability than the calibration of dispersive instruments. | https://en.wikipedia.org/wiki/Stationary-wave_integrated_Fourier-transform_spectrometry |
A stationary engine is an engine whose framework does not move. They are used to drive immobile equipment, such as pumps , generators , mills or factory machinery, or cable cars . The term usually refers to large immobile reciprocating engines , principally stationary steam engines [ 1 ] and, to some extent, stationary internal combustion engines . Other large immobile power sources, such as steam turbines , gas turbines , and large electric motors , are categorized separately.
Stationary engines, especially stationary steam engines were once widespread in the late Industrial Revolution . [ 1 ] This was an era when each factory or mill generated its own power, and power transmission was mechanical (via line shafts , belts , gear trains , and clutches ). Applications for stationary engines have declined since electrification has become widespread; most industrial uses today draw electricity from an electrical grid and distribute it to various individual electric motors instead.
Engines that operate in one place, but can be moved to another place for later operation, are called portable engines . Although stationary engines and portable engines are both " stationary " (not moving) while running, preferred usage (for clarity's sake) reserves the term "stationary engine" to the permanently immobile type, and "portable engine" to the mobile type.
There are many types of stationary engines. [ 2 ] These include:
Stationary engines had a wide range of applications but they were especially used by small companies and operations, requiring power in limited settings at specific sites. [ 3 ]
A flat belt could be used to connect an engine to a flour mill or corn grinder. These machines are popular at old engine shows. Corn grinders would take corn off the cob, and grind up corn into animal feed. flour mills make flour.
Before mains electricity and the formation of nationwide power grids , stationary engines were widely used for small-scale electricity generation . While large power stations in cities used steam turbines or high-speed reciprocating steam engines , in rural areas petrol/gasoline , paraffin/kerosene , and fuel oil -powered internal combustion engines were cheaper to buy, install, and operate, since they could be started and stopped quickly to meet demand, left running unattended for long periods of time, and did not require a large dedicated engineering staff to operate and maintain. Due to their simplicity and economy, hot bulb engines were popular for high-power applications until the diesel engine took their place from the 1920s. Smaller units were generally powered by spark-ignition engines, which were cheaper to buy and required less space to install.
Most engines of the late-19th and early-20th centuries ran at speeds too low to drive a dynamo or alternator directly. As with other equipment, the generator was driven off the engine's flywheel by a broad flat belt. The pulley on the generator was much smaller than the flywheel, providing the required 'gearing up' effect. Later spark-ignition engines developed from the 1920s could be directly coupled.
Up to the 1930s most rural houses in Europe and North America needed their own generating equipment if electric light was fitted. Engines would often be installed in a dedicated "engine house", which was usually an outbuilding separate from the main house to reduce the interference from the engine noise. The engine house would contain the engine, the generator, the necessary switchgear and fuses , as well as the engine's fuel supply and usually a dedicated workshop space with equipment to service and repair the engine. Wealthy households could afford to employ a dedicated engineer to maintain the equipment, but as the demand for electricity spread to smaller homes, manufacturers produced engines that required less maintenance and that did not need specialist training to operate.
Such generator sets were also used in industrial complexes and public buildings – anywhere where electricity was required but mains electricity was not available.
Most countries in the Western world completed large-scale rural electrification in the years following World War II , making individual generating plants obsolete for front-line use. However, even in countries with a reliable mains supply, many buildings are still fitted with modern diesel generators for emergency use, such as hospitals and pumping stations . This network of generators often forms a crucial part of the national electricity system's strategy for coping with periods of high demand.
The development of water supply and sewage removal systems required the provision of many pumping stations . In these, some form of stationary engine (steam-powered for earlier installations) is used to drive one or more pumps , although electric motors are more conventionally used nowadays.
For canals , a distinct area of application concerned the powering of boat lifts and inclined planes . Where possible these would be arranged to utilise water and gravity in a balanced system, but in some cases additional power input was required from a stationary engine for the system to work. The vast majority of these were constructed (and in many cases, demolished again) before steam engines were supplanted by internal combustion alternatives.
Industrial railways in quarries and mines made use of cable railways based on the inclined plane idea, and certain early passenger railways in the UK were planned with lengths of cable-haulage to overcome severe gradients.
For the first proper railway, the Liverpool and Manchester of 1830, it was not clear whether locomotive traction would work, and the railway was designed with steep 1 in 100 gradients concentrated on either side of Rainhill , just in case. Had cable haulage been necessary, then inconvenient and time-consuming shunting would have been required to attach and detach the cables. The Rainhill gradients proved not to be a problem, and in the event, locomotive traction was determined to be a new technology with great potential for further development.
The steeper 1 in 50 grades from Liverpool down to the docks were operated by cable traction for several decades until locomotives improved. Cable haulage continued to be used where gradients were even steeper.
Cable haulage did prove viable where the gradients were exceptionally steep, such as the 1 in 8 gradients of the Cromford and High Peak Railway opened in 1830. Cable railways generally have two tracks with loaded wagons on one track partially balanced by empty wagons on the other, to minimize fuel costs for the stationary engine. Various kinds of rack railways were developed to overcome the lack of friction of conventional locomotives on steep gradients.
These early installations of stationary engines would all have been steam-powered initially.
Many steam rallies , like the Great Dorset Steam Fair , include an exhibit section for internal combustion stationary engines for which purpose the definition is usually extended to include any engine that was not intended primarily for the propulsion of a vehicle. Thus many are in fact portable engines , either from new or having been converted by mounting on a wheeled trolley for ease of transport and may also include such things as marine or airborne auxiliary power units and engines removed from equipment such as motor mowers. These engines have been restored by private individuals and often are exhibited in operation, powering water pumps, electric generators, hand tools, and the like.
In the UK there are few museums where visitors can see stationary engines in operation. Many museums have one or more engines but only a few specialise in the internal combustion stationary engines. Among these are the Internal Fire Museum of Power , in Wales, and the Anson Engine Museum in Cheshire. The Amberley Working Museum in West Sussex also has a number of engines, as does Kew Bridge Steam Museum in London. | https://en.wikipedia.org/wiki/Stationary_engine |
In celestial mechanics , a stationary orbit is an orbit around a planet or moon where the orbiting satellite or spacecraft remains over the same spot on the surface. From the ground, the satellite would appear to be standing still, hovering above the surface in the same spot, day after day. [ 1 ]
In practice, this is accomplished by matching the rotation of the surface below, by reaching a particular altitude where the orbital speed almost matches the rotation below, in an equatorial orbit. [ 1 ] As the speed decreases slowly, then an additional boost would be needed to increase the speed back to a matching speed, or a retro-rocket could be fired to slow the speed when too fast.
The stationary-orbit region of space is known as the Clarke Belt , named after British science fiction writer Arthur C. Clarke , who published the idea in Wireless World magazine in 1945. [ 1 ] A stationary orbit is sometimes referred to as a "fixed orbit".
Around the Earth , stationary satellites orbit at altitudes of approximately 22,300 miles (35,900 km). [ 1 ] Writing in 1945, the science-fiction author Arthur C. Clarke imagined communications satellites as travelling in stationary orbits, where those satellites would travel around the Earth at the same speed the globe is spinning, making them hover stationary over one spot on the Earth's surface. [ 1 ]
A satellite being propelled into place, into a stationary orbit, is first fired to a special equatorial orbit called a " geostationary transfer orbit " (GTO). [ 1 ] Within this oval-shaped ( elliptical ) orbit, the satellite will alternately swing out to 22,300 miles (35,890 km) high and then back down to an altitude of only 100 miles (160 km) above the Earth (223 times closer). Then, at a planned time and place, an attached "kick motor" will push the satellite out to maintain an even, circular orbit at the 22,300-mile altitude. [ 1 ]
An areostationary orbit or areosynchronous equatorial orbit (abbreviated AEO ) is a circular areosynchronous orbit in the Martian equatorial plane about 20,428 km (12,693 mi) from the centre of mass of Mars, any point on which revolves about Mars in the same direction and with the same period as the Martian surface. Areostationary orbit is a concept similar to Earth's geostationary orbit . The prefix areo- derives from Ares , the ancient Greek god of war and counterpart to the Roman god Mars, with whom the planet was identified. The modern Greek word for Mars is Άρης ( Áris ). | https://en.wikipedia.org/wiki/Stationary_orbit |
In mathematics , the stationary phase approximation is a basic principle of asymptotic analysis , applying to functions given by integration against a rapidly-varying complex exponential.
This method originates from the 19th century, and is due to George Gabriel Stokes and Lord Kelvin . [ 1 ] It is closely related to Laplace's method and the method of steepest descent , but Laplace's contribution precedes the others.
The main idea of stationary phase methods relies on the cancellation of sinusoids with rapidly varying phase. If many sinusoids have the same phase and they are added together, they will add constructively. If, however, these same sinusoids have phases which change rapidly as the frequency changes, they will add incoherently, varying between constructive and destructive addition at different times [ clarification needed ] .
Letting Σ {\displaystyle \Sigma } denote the set of critical points of the function f {\displaystyle f} (i.e. points where ∇ f = 0 {\displaystyle \nabla f=0} ), under the assumption that g {\displaystyle g} is either compactly supported or has exponential decay, and that all critical points are nondegenerate (i.e. det ( H e s s ( f ( x 0 ) ) ) ≠ 0 {\displaystyle \det(\mathrm {Hess} (f(x_{0})))\neq 0} for x 0 ∈ Σ {\displaystyle x_{0}\in \Sigma } ) we have the following asymptotic formula, as k → ∞ {\displaystyle k\to \infty } :
Here H e s s ( f ) {\displaystyle \mathrm {Hess} (f)} denotes the Hessian of f {\displaystyle f} , and s g n ( H e s s ( f ) ) {\displaystyle \mathrm {sgn} (\mathrm {Hess} (f))} denotes the signature of the Hessian, i.e. the number of positive eigenvalues minus the number of negative eigenvalues.
For n = 1 {\displaystyle n=1} , this reduces to:
In this case the assumptions on f {\displaystyle f} reduce to all the critical points being non-degenerate.
This is just the Wick-rotated version of the formula for the method of steepest descent .
Consider a function
The phase term in this function, ϕ = k ( ω ) x − ω t {\displaystyle \phi =k(\omega )x-\omega t} , is stationary when
or equivalently,
Solutions to this equation yield dominant frequencies ω 0 {\displaystyle \omega _{0}} for some x {\displaystyle x} and t {\displaystyle t} . If we expand ϕ {\displaystyle \phi } as a Taylor series about ω 0 {\displaystyle \omega _{0}} and neglect terms of order higher than ( ω − ω 0 ) 2 {\displaystyle (\omega -\omega _{0})^{2}} , we have
where k ″ {\displaystyle k''} denotes the second derivative of k {\displaystyle k} . When x {\displaystyle x} is relatively large, even a small difference ( ω − ω 0 ) {\displaystyle (\omega -\omega _{0})} will generate rapid oscillations within the integral, leading to cancellation. Therefore we can extend the limits of integration beyond the limit for a Taylor expansion. If we use the formula,
This integrates to
The first major general statement of the principle involved is that the asymptotic behaviour of I ( k ) depends only on the critical points of f . If by choice of g the integral is localised to a region of space where f has no critical point, the resulting integral tends to 0 as the frequency of oscillations is taken to infinity. See for example Riemann–Lebesgue lemma .
The second statement is that when f is a Morse function , so that the singular points of f are non-degenerate and isolated, then the question can be reduced to the case n = 1. In fact, then, a choice of g can be made to split the integral into cases with just one critical point P in each. At that point, because the Hessian determinant at P is by assumption not 0, the Morse lemma applies. By a change of co-ordinates f may be replaced by
The value of j is given by the signature of the Hessian matrix of f at P . As for g , the essential case is that g is a product of bump functions of x i . Assuming now without loss of generality that P is the origin, take a smooth bump function h with value 1 on the interval [−1, 1] and quickly tending to 0 outside it. Take
then Fubini's theorem reduces I ( k ) to a product of integrals over the real line like
with f ( x ) = ± x 2 . The case with the minus sign is the complex conjugate of the case with the plus sign, so there is essentially one required asymptotic estimate.
In this way asymptotics can be found for oscillatory integrals for Morse functions. The degenerate case requires further techniques (see for example Airy function ).
The essential statement is this one:
In fact by contour integration it can be shown that the main term on the right hand side of the equation is the value of the integral on the left hand side, extended over the range [ − ∞ , ∞ ] {\displaystyle [-\infty ,\infty ]} (for a proof see Fresnel integral ). Therefore it is the question of estimating away the integral over, say, [ 1 , ∞ ] {\displaystyle [1,\infty ]} . [ 2 ]
This is the model for all one-dimensional integrals I ( k ) {\displaystyle I(k)} with f {\displaystyle f} having a single non-degenerate critical point at which f {\displaystyle f} has second derivative > 0 {\displaystyle >0} . In fact the model case has second derivative 2 at 0. In order to scale using k {\displaystyle k} , observe that replacing k {\displaystyle k} by c k {\displaystyle ck} where c {\displaystyle c} is constant is the same as scaling x {\displaystyle x} by c {\displaystyle {\sqrt {c}}} . It follows that for general values of f ″ ( 0 ) > 0 {\displaystyle f''(0)>0} , the factor π / k {\displaystyle {\sqrt {\pi /k}}} becomes
For f ″ ( 0 ) < 0 {\displaystyle f''(0)<0} one uses the complex conjugate formula, as mentioned before.
As can be seen from the formula, the stationary phase approximation is a first-order approximation of the asymptotic behavior of the integral. The lower-order terms can be understood as a sum of over Feynman diagrams with various weighting factors, for well behaved f {\displaystyle f} . | https://en.wikipedia.org/wiki/Stationary_phase_approximation |
Statistical Physics of Particles and Statistical Physics of Fields are a two-volume series of textbooks by Mehran Kardar . Each book is based on a semester-long course taught by Kardar at the Massachusetts Institute of Technology . They cover statistical physics and thermodynamics at the graduate level. [ 1 ] [ 2 ] [ 3 ]
This article about a physics -related book is a stub . You can help Wikipedia by expanding it .
This article about statistical mechanics is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Statistical_Physics_of_Particles |
Statistical associating fluid theory ( SAFT ) [ 1 ] [ 2 ] is a chemical theory, based on perturbation theory , that uses statistical thermodynamics to explain how complex fluids and fluid mixtures form associations through hydrogen bonds . [ 3 ] Widely used in industry and academia, it has become a standard approach for describing complex mixtures. [ 4 ] [ 5 ] [ 6 ] [ 7 ] Since it was first proposed in 1990, SAFT has been used in a large number of molecular-based equation of state [ 8 ] [ 9 ] models for describing the Helmholtz energy contribution due to association.
SAFT is a Helmholtz energy term that can be used in equations of state that describe the thermodynamic and phase equilibrium properties of pure fluids and fluid mixtures. SAFT was developed using statistical mechanics . SAFT models the Helmholtz free energy contribution due to association , i.e. hydrogen bonding. [ 10 ] SAFT can be used in combination with other Helmholtz free energy terms. Other Helmholtz energy contributions consider for example Lennard-Jones interactions, covalent chain-forming bonds, and association (interactions between segments caused by, for example, hydrogen bonding). [ 2 ] SAFT has been applied to a wide range of fluids, including supercritical fluids , polymers , liquid crystals , electrolytes , surfactant solutions, and refrigerants . [ 5 ]
SAFT evolved from thermodynamic theories, including perturbation theories developed in the 1960s, 1970s, and 1980s by John Barker and Douglas Henderson, Keith Gubbins and Chris Gray, and, in particular, Michael Wertheim 's first-order, thermodynamic perturbation theory (TPT1) outlined in a series of papers in the 1980s. [ 2 ] [ 11 ]
The SAFT equation of state was developed using statistical mechanical methods (in particular the perturbation theory of Wertheim [ 12 ] ) to describe the interactions between molecules in a system. [ 1 ] [ 13 ] [ 14 ] The idea of a SAFT equation of state was first proposed by Walter G. Chapman and by Chapman et al. in 1988 and 1989. [ 1 ] [ 13 ] [ 14 ] Many different versions of the SAFT models have been proposed, but all use the same chain and association terms derived by Chapman et al. [ 2 ] [ 13 ] [ 15 ] One of the first SAFT papers (1990) titled "New reference equation of state for associating liquids" by Walter G. Chapman, Keith Gubbins, George Jackson , and Maciej Radosz, [ 2 ] was recognized in 2007 by Industrial and Engineering Chemistry Research as one of the most highly cited papers of the previous three decades. [ 16 ] SAFT is one of the first theories to accurately describe (in comparison with molecular simulation) the effects on fluid properties of molecular size and shape in addition to association between molecules. [ 1 ] [ 2 ] [ 13 ] [ 14 ]
Many variations of SAFT have been developed since the 1990s, including HR-SAFT (Huang-Radosz SAFT), [ 6 ] PC-SAFT (perturbed chain SAFT), [ 17 ] [ 18 ] Polar SAFT, [ 19 ] PCP-SAFT (PC-polar-SAFT), [ 20 ] [ 21 ] [ 22 ] soft-SAFT, [ 23 ] polar soft-SAFT, [ 24 ] SAFT-VR (variable range), [ 25 ] SAFT VR-Mie. [ 26 ] Also, the SAFT term was used in combination with cubic equations of state for describing the dispersive-repulsive interactions, for example in the Cubic-Plus-Association (CPA) equation of state model [ 27 ] and the SAFT + cubic model [ 28 ] and non-random-lattice (NLF) models based on lattice field theory . [ 3 ] | https://en.wikipedia.org/wiki/Statistical_associating_fluid_theory |
Statistical Coupling Analysis (SCA) is a method used in bioinformatics to study how pairs of amino acids in a protein sequence evolve together . It analyzes a multiple sequence alignment (MSA), which is a display of the sequences of many related proteins arranged to highlight similarities and differences. SCA measures how much the amino acid makeup at one position in the protein changes when the amino acid makeup at another position is altered. This relationship is quantified as statistical coupling energy . A higher coupling energy indicates that the amino acids at both positions are more likely to have co-evolved and are therefore functionally or structurally linked. In simpler terms, it helps scientists understand which parts of a protein are working together and how they have changed over evolutionary time. [ 1 ]
Statistical coupling energy measures how a perturbation of amino acid distribution at one site in an MSA affects the amino acid distribution at another site. For example, consider a multiple sequence alignment with sites (or columns) a through z , where each site has some distribution of amino acids. At position i , 60% of the sequences have a valine and the remaining 40% of sequences have a leucine , at position j the distribution is 40% isoleucine , 40% histidine and 20% methionine , k has an average distribution (the 20 amino acids are present at roughly the same frequencies seen in all proteins), and l has 80% histidine, 20% valine. Since positions i , j and l have an amino acid distribution different from the mean distribution observed in all proteins, they are said to have some degree of conservation .
In statistical coupling analysis, the conservation (ΔG stat ) at each site ( i ) is defined as: Δ G i s t a t = ∑ x ( ln P i x ) 2 {\displaystyle \Delta G_{i}^{stat}={\sqrt {\sum _{x}(\ln P_{i}^{x})^{2}}}} . [ 2 ]
Here, P i x describes the probability of finding amino acid x at position i , and is defined by a function in binomial form as follows:
where N is 100, n x is the percentage of sequences with residue x (e.g. methionine) at position i , and p x corresponds to the approximate distribution of amino acid x in all positions among all sequenced proteins. The summation runs over all 20 amino acids. After ΔG i stat is computed, the conservation for position i in a subalignment produced after a perturbation of amino acid distribution at j (ΔG i | δj stat ) is taken. Statistical coupling energy, denoted ΔΔG i, j stat , is simply the difference between these two values. That is:
Statistical coupling energy is often systematically calculated between a fixed, perturbated position, and all other positions in an MSA. Continuing with the example MSA from the beginning of the section, consider a perturbation at position j where the amino distribution changes from 40% I, 40% H, 20% M to 100% I. If, in a subsequent subalignment, this changes the distribution at i from 60% V, 40% L to 90% V, 10% L, but does not change the distribution at position l , then there would be some amount of statistical coupling energy between i and j but none between l and j .
Ranganathan and Lockless originally developed SCA to examine thermodynamic (energetic) coupling of residue pairs in proteins. [ 3 ] Using the PDZ domain family, they were able to identify a small network of residues that were energetically coupled to a binding site residue. The network consisted of both residues spatially close to the binding site in the tertiary fold, called contact pairs, and more distant residues that participate in longer-range energetic interactions. Later applications of SCA by the Ranganathan group on the GPCR , serine protease and hemoglobin families also showed energetic coupling in sparse networks of residues that cooperate in allosteric communication . [ 4 ]
Statistical coupling analysis has also been used as a basis for computational protein design. In 2005, Socolich et al. [ 5 ] used an SCA for the WW domain to create artificial proteins with similar thermodynamic stability and structure to natural WW domains. The fact that 12 out of the 43 designed proteins with the same SCA profile as natural WW domains properly folded provided strong evidence that little information—only coupling information—was required for specifying the protein fold. This support for the SCA hypothesis was made more compelling considering that a) the successfully folded proteins had only 36% average sequence identity to natural WW folds, and b) none of the artificial proteins designed without coupling information folded properly. An accompanying study showed that the artificial WW domains were functionally similar to natural WW domains in ligand binding affinity and specificity . [ 6 ]
In de novo protein structure prediction , it has been shown that, when combined with a simple residue-residue distance metric, SCA-based scoring can fairly accurately distinguish native from non-native protein folds. [ 7 ]
Mutual information | https://en.wikipedia.org/wiki/Statistical_coupling_analysis |
Statistical energy analysis (SEA) is a method for predicting the transmission of sound and vibration through complex structural acoustic systems. The method is particularly well suited for quick system level response predictions at the early design stage of a product, and for predicting responses at higher frequencies. In SEA a system is represented in terms of a number of coupled subsystems and a set of linear equations are derived that describe the input, storage, transmission and dissipation of energy within each subsystem. The parameters in the SEA equations are typically obtained by making certain statistical assumptions about the local dynamic properties of each subsystem (similar to assumptions made in room acoustics and statistical mechanics ). These assumptions significantly simplify the analysis and make it possible to analyze the response of systems that are often too complex to analyze using other methods (such as finite element and boundary element methods).
The initial derivation of SEA arose from independent calculations made in 1959 by Richard Lyon [ 1 ] and Preston Smith [ 2 ] as part of work concerned with the development of methods for analyzing the response of large complex aerospace structures subjected to spatially distributed random loading. Lyon's calculation showed that under certain conditions, the flow of energy between two coupled oscillators is proportional to the difference in the oscillator energies (suggesting a thermal analogy exists in structural-acoustic systems). Smith's calculation showed that a structural mode and a diffuse reverberant sound field attain a state of 'equipartition of energy' as the damping of the mode is reduced (suggesting a state of thermal equilibrium can exist in structural-acoustic systems). The extension of the two oscillator results to more general systems is often referred to as the modal approach to SEA. [ 3 ] [ 4 ] While the modal approach provides physical insights into the mechanisms that govern energy flow it involves assumptions that have been the subject of considerable debate over many decades. [ 5 ] The theory that combines deterministic finite element methods (FEM) and SEA was developed by Phil Shorter and Robin Langley and is called hybrid FEM/SEA theory. [ 6 ] [ 7 ] In recent years, alternative derivations of the SEA equations based on wave approaches have become available. Such derivations form the theoretical foundation behind a number of modern commercial SEA codes and provide a general framework for calculating the parameters in an SEA model. A number of methods also exist for post-processing FE models to obtain estimates of SEA parameters. Lyon mentioned the use of such methods in his initial SEA text book in 1975 but a number of alternative derivations have been presented over the years [ 8 ] [ 9 ] [ 10 ] [ 11 ]
To solve a noise and vibration problem with SEA, the system is partitioned into a number of components (such as plates , shells, beams and acoustic cavities) that are coupled together at various junctions. Each component can support a number of different propagating wavetypes (for example, the bending , longitudinal and shear wavefields in a thin isotropic plate). From an SEA point of view, the reverberant field of each wavefield represents an orthogonal store of energy and so is represented as a separate energy degree of freedom in the SEA equations.
The energy storage capacity of each reverberant field is described by a parameter termed the 'modal density', which depends on the average speed with which waves propagate energy through the subsystem (the average group velocity ), and the overall dimension of the subsystem.
The transmission of energy between different wavefields at a given type of junction is described by parameters termed 'coupling loss factors'. Each coupling loss factor describes the input power to the direct field of a given receiving subsystem per unit energy in the reverberant field of a particular source subsystem.
The coupling loss factors are typically calculated by considering the way in which waves are scattered at different types of junctions (for example, point, line and area junctions). Strictly, SEA predicts the average response of a population or ensemble of systems and so the coupling loss factors and modal densities represent ensemble average quantities.
To simplify the calculation of the coupling loss factors it is often assumed that there is significant scattering within each subsystem (when viewed across an ensemble) so that direct field transmission between multiple connections to the same subsystem is negligible and reverberant transmission dominates. In practical terms, this means that SEA is often best suited for problems in which each subsystem is large compared with a wavelength (or from a modal point of view, each subsystem contains several modes in a given frequency band of interest).
The SEA equations contain a relatively small number of degrees of freedom and so can be easily inverted to find the reverberant energy in each subsystem due to a given set of external input powers. The (ensemble average) sound pressure levels and vibration velocities within each subsystem can then be obtained by superimposing the direct and reverberant fields within each subsystem.
Over the past half century, SEA has found applications in virtually every industry for which noise and vibration are of concern. Typical applications include:
Additional examples can be found in the proceedings of conferences such as INTERNOISE, NOISECON, EURONOISE, ICSV, NOVEM, SAE N&V.
Several commercial solutions for Statistical Energy Analysis are available:
Free solutions: | https://en.wikipedia.org/wiki/Statistical_energy_analysis |
In theoretical physics , statistical field theory ( SFT ) is a theoretical framework that describes phase transitions . [ 1 ] It does not denote a single theory but encompasses many models, including for magnetism , superconductivity , superfluidity , [ 2 ] topological phase transition , wetting [ 3 ] [ 4 ] as well as non-equilibrium phase transitions. [ 5 ] A SFT is any model in statistical mechanics where the degrees of freedom comprise a field or fields. In other words, the microstates of the system are expressed through field configurations. It is closely related to quantum field theory , which describes the quantum mechanics of fields, and shares with it many techniques, such as the path integral formulation and renormalization .
If the system involves polymers, it is also known as polymer field theory .
In fact, by performing a Wick rotation from Minkowski space to Euclidean space , many results of statistical field theory can be applied directly to its quantum equivalent. [ citation needed ] The correlation functions of a statistical field theory are called Schwinger functions , and their properties are described by the Osterwalder–Schrader axioms .
Statistical field theories are widely used to describe systems in polymer physics or biophysics , such as polymer films, nanostructured block copolymers [ 6 ] or polyelectrolytes . [ 7 ]
This quantum mechanics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Statistical_field_theory |
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