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Hints for Beginners in Amateur Chemistry
Join in the Fun of Experimenting at Home! This Article Tells How Easy It Is to Start
By RAYMOND B. WAILES
IF YOU have been following this series of articles for some time, you probably have already set up a more or less complete chemical workshop in which to carry on your experiments. However, there is always a new crop of beginners coming along—newcomers who would like to join the fun and who need some simple advice on equipment and working methods. Old-timers surely won’t begrudge this space to help others get started in the fascinating pastime of amateur chemistry—and perhaps their own memories will be refreshed with a pointer or two.
Queer Machine Checks Up on Ether Drift
SCIENTISTS at Jena, Germany, have constructed one of the most amazing and odd-appearing measuring devices on record. It is an apparatus to measure the drift of the ether, that impalpable substance which, according to one school of thought, fills the space in which the universe swims. Theoretically the motion of the earth, passing through this ether, should set up a drift comparable to the breeze generated by the motion of an automobile through the air.
How can you not love an article with quotes like this:
“By the time you get down near Absolute Zero everything in the world is frozen harder than a pawnbroker’s heart…”
When this article was written the record low temperature achieved by scientists was .0015 K. The current record is 0.00000000045 K.
So You Think THIS Is Cold?
Teeth chattering? Fingers numb? Well it’s warm compared to what the lab boys call Absolute Zero.
By Lawrence Sanders
“Tis IS BITTER cold and I am sick at heart,” quoth Hamlet. And right now most citizens are hunching along, swaddled to the ears against the cold and muttering, “You said a mouthful, Bard.”
Is it cold enough for you?
As a matter of fact, it probably is cold enough for you—whether you live in Weeping Water, Neb. or Hiram, Ga. One man’s heat wave is another man’s cold snap and a Key Wester can be just as uncomfortable at 40° F as a Bald Eagle, Minn, resident when the mercury goofs off to—40 °F.
How TO CONVERT OLD ELECTRIC LIGHT BULBS INTO CHEMICAL GLASSWARE
By Earl D Hay
EXPERIMENTS in an amateur chemical laboratory are much more interesting when they are made with the same kind of apparatus as that used in professional laboratories. As a rule, however, the home chemist experiences a great – shortage of flasks and endeavors to use various kinds of bottles as makeshifts, little realizing that he may make from burned-out electric light bulbs a great variety of useful flasks like those sold by chemical supply houses at from 20 to 75 cents each. The lamps used in the average home vary in size from 25 to 200 watts and are suitable for small Florence or boiling flasks. Larger flasks are made from 300-, 500-, and 1,000-watt lamps, which can be obtained from the janitors of stores and linemen of the city lighting companies.
Dry ice is very interesting stuff! Get yourself a chunk (handling it with gloves) and perform the simple experiments illustrated here.
DRY ice is solid carbon dioxide. It’s very interesting stuff. For one thing, it sublimes at room temperature; that is, although a solid, it evaporates to form a gas without passing through the liquid state. The mist you see formed by dry ice is water “squeezed” out of the air because it has been chilled below the dewpoint.
Glass Making Easy for Home Chemist
By Raymond B. Wailes
BECAUSE of its importance in glass making and other industries, silicon opens a particularly interesting experimental field to the home chemist. In nature, silicon is almost as plentiful as oxygen. Yet, it hides itself well in its compounds. It never is found free and uncom-bined and can be separated from its associates only through clever chemical thievery in the laboratory.
Industrially, silicon is obtained by heating sand—a compound of silicon and oxygen—and coke to a high temperature in an electric furnace. The white-hot coke steals the oxygen from the sand to form carbon monoxide and frees the silicon. Although the amateur chemist will have no electric furnace in which to duplicate this process, he can obtain a similar result by heating sand and powdered magnesium over his ordinary laboratory gas burner.
Scientific Experiments with Toys
By Raymond B. Wailes
Many Novelty, Toy and “Jokers” Supply Stores sell small glass “meters” or “thermometers.” as they are called, attached to a card supposed to represent the quantity of intoxicating liquor the individual can consume, a state of health, denote a fortune, etc. The items are designed to provoke mirth and hilarity, but they operate on a scientific principle and can be used admirably for demonstrating some physical laws. What to do and how to conduct the experiments are details covered in the accompanying text.
Eclipse to Check Einstein
Astronomers Journey Halfway Around the World to Study Five-Minute Spectacle, as the Moon Blots the Sun’s Face
By GEORGE LEE DOWD, JR.
EINSTEIN’S theory of relativity receives a new test in the wilds of Sumatra in the Dutch East Indies on May 9, when leading astronomers of Europe and America study and photograph a remarkable five-minute total eclipse of the sun, for which they will have journeyed halfway around the world. The duration of the eclipse, and the fact that this island off the Malay Peninsula lies directly in its path, offer an unusual opportunity for scientific observation. The average eclipse lasts only from one to four minutes, and the longest possible duration of a total eclipse for a single observer is seven minutes and fifty-eight seconds.
Weird Stunts with Aluminum in the Home Laboratory
Electrical Experiments You Can Perform with This Most Useful Metal—An Easy Way to Purify Water Containing Sediment
By Raymond B. Wailes
OUTWARDLY aluminum is one of the least spectacular elements of the earth. Yet in the home laboratory, weird stunts reveal the strange properties that make it one of the world’s most useful metals.
Although at one time worth its weight in silver, chemistry has made aluminum one of our commonest metals. According to leading scientists, its uses will continue to grow. Even now railroads, steamships, and airplanes make use of its physical qualities for lightness combined with strength.
Most important of its chemical properties is its unquenchable thirst for oxygen. Pure aluminum left in the air soon becomes coated with an oxide. It is this characteristic that makes its impossible to obtain the metal in its free state and also forms the basis of thermit welding (P.S.M., Aug. ’33, p. 50) and many other modern processes in industry.
To the home chemist, this fast-forming oxide of aluminum offers the means of performing two novel electrical experiments. For the first, immerse two sheets of aluminum foil in a small jar or beaker containing a solution of baking soda (sodium bicarbonate). Connect one sheet directly to one side of the house lighting circuit and the other sheet through a series-connected lamp to the other side.
Crime-Detection Tests FOR THE Home Chemist
How Hidden Fingerprints May Be Found by Using Iodine Vapor — Forgeries Also Are Revealed by This Remarkable Element
By Raymond B. Wailes
NEW thrills await the home chemist who experiments with iodine. Besides its queer properties and varied uses, it serves as the gateway to a new branch of chemistry—the mysterious and interesting art of scientific crime detection.
With iodine, the amateur experimenter can transform his home laboratory into a miniature crime bureau. In a few hours, he can master some of the chemical tricks that aid the modern sleuth in his search for hidden fingerprints, clever check alterations, and forgeries.
First, however, the amateur must learn how to obtain this active element in its free state. For years, it was recovered commercially from a giant type of seaweed called kelp. Now it is obtained from the solutions left behind when Chile saltpeter is crystallized in large quantities. | <urn:uuid:6d1e7fe0-3866-4308-911c-04d9ad21614a> | 2.78125 | 1,840 | Content Listing | Science & Tech. | 46.204602 |
Useful datasets for satellite data processing
The mapping of global parameters such as SST, albedo, terrain types,
surface elevation, emissivity…have been widely produced from polar
satellites, serving as important input parameters for users who are processing
This page provides a list of parameters together with data volumes and formats, links to documentation and sites from where you can download/request the datasets.
§ Land surface types and emissivity models
§ Land surface LST/emissivities,
§ SST and albedo, snow cover
§ elevation and type atlas
§ Global atmospheric circulation statistics/analysis
Land surface types and emissivity modelsEmissivity models developed by Snyder et al (1998) have been applied to 14 emissivity classes by combining different land cover classes extracted from the International Geosphere-Biosphere Program (IGBP) to generate a range of emissivity spectra for each class. This range is generated by varying the many factors which affect the emissivity for example the viewing angle, water content, vegetation density, growth state…This allow to estimate the mean, maximum and minimum surface emissivities at each wavelength for each of the 14 classes.
Snyder et al (1998) ‘Classification-based emissivity for land surface temperature measurement from space’ Int. J. Remote Sensing, 1998, vol 19, no14
Land cover characterization
The Global Land Cover Characterization (GLCC) is a series of global land cover classification datasets that are based on the classification of 1-km AVHRR 10-day NDVI (Normalized Difference Vegetation Index ) composites. The AVHRR source imagery dates from April 1992 through March 1993. Ancillary data sources included digital elevation data, ecoregions interpretation, and country- or regional-level vegetation and land cover maps. It allows to separate land and water surfaces with a good accuracy.
A land classification using MODIS following the IGBP classification scheme is available at http://modis-atmos.gsfc.nasa.gov/ECOSYSTEM/. It is a global static dataset stored on an equal-angle rectangular grid at 1-minute resolution. Data are stored in HDF format and the size is about 1.1GB. The dataset is generated from the official MODIS land ecosystem classification dataset, MOD12Q1 October 15, 2000.Land surface emissivities
Different emissivity atlas are available through the web.
The ASTER spectral library http://speclib.jpl.nasa.gov/ which is a compilation of almost 2000 spectra of natural and man made materials, includes data from three other spectral libraries: the Johns Hopkins University spectral library made by Salisbury and D’Aria (2004), the Jet Propulsion Laboratory spectral library, and the United States Geological Survey spectral library.
The ASTER library is available on CD-ROM at no charge. The Johns Hopkins University spectral library includes emissivity spectra of about 80 samples of soils, rocks, different vegetation types and snow/ice within the 2-14 um spectral range at about 2cm-1 resolution;
The MODIS UCSB (University of California) Emissivity Library
http://www.icess.ucsb.edu/modis/EMIS/html/em.html is a collection of Emissivity laboratory measurements of natural (water, ice, snow, soil, minerals and vegetation) and manmade materials, from about 3um to 15um. Data are directly accessible on line for the desired material.
Monthly and routine MODIS land surface LST/emissivities at a 0.05degree resolution, in HDF format, size of about 625 MB, are distributed by:
P. Francis (2003) has developed an IR land surface emissivity atlas
for NWP applications. See the documentation:
University of Wisconsin-Madison IR Land Surface Emissivity database: http://cimss.ssec.wisc.edu/iremis/
Monthly and pentade global SST climatologies with a resolution of 9 km
are available at:
SST and albedo
Size is about 188MB each file in compressed form. Software to read the data is also available on the site.
Also routine SST products from AVHRR, MODIS,ATSR and GOES instruments
are also available in HDF format on the same site . See
Different temporal and spatial resolution are offered.
Daily, eight-day and monthly albedo and NDVI climatologies are generated
from MODIS observations at a 1 minute resolution, HDF format. See:
Daily operational snow cover analysis is provided by NESDIS at: http://www.ssd.noaa.gov/PS/SNOW/index.html\
Elevation and type atlasA global digital elevation model 30 arc (approximately 1 kilometer) topography database
http://eros.usgs.gov/#/Find_Data/Products_and_Data_Available/gtopo30_info , available at no charge via ftp, is divided in 33 subsets to facilitate the distribution, each of them with a size of about 50MB.
Coastlines can be extracted at different resolution (0.2, 1, 5, 25 km) using the GMT (Generic Mapping Tools) software developed by scientists at University of Hawaii and NOAA, available at: http://gmt.soest.hawaii.edu/
Also two datasets for the surface type (flag sea/land) and for the surface
elevation at a 1/6*1/6 degrees resolution are part of the IAPP or AAPP
ATOVS pre-processing packages. See:
Global atmospheric circulation statistics/analysisGlobal monthly AVHRR climatology over land from 5 years of GAC data at. 0.15 degree resolution. Climatologies include TOA, surface reflectances, NDVI, T4, T5, PWI at:
Global atmospheric circulation statistics/analysis from the Geophysical
Fluid Dynamics Laboratory based on 15 years of weather station, ship,
and buoy data at a 5*2.5degrees resolution | <urn:uuid:c637f179-1458-4133-81a8-f9378174c35f> | 2.734375 | 1,297 | Content Listing | Science & Tech. | 30.30125 |
There are two methods of including a file in PHP: include and require.
<?php include "file.php"; require "file.php"; ?>
They both perform essentially the same function, but have one major difference: include will only throw a warning if there is a problem during the include process; require, however, will halt execution in this scenario. Therefore, a script's dependencies will often be called with require.
Additionally, there exist many code libraries, class definitions, and variable declarations that you will want to separate into an include file, but that should only be called into the current script once. To ensure that these libraries are only included once, php includes the include_once() and require_once()functions. Each time one of these functions is called, the php parser remembers which file it has called. If another include_once()or require_once attempts to load the same file, the parser will simply skip the command. It will produce no error or warning, it will simply act as though the command had executed successfully. This is because, in fact, it has. IMPORTANT: If you include a file once with include_once() and then later using include(), the file will be included a second time. If a file is included using include_once() and a call to the same file is made by require_once(), it will not be included again. Include_once() and require_once() have the same 'memory,' as it were.
<?php include_once "file.php"; require_once "file.php"; ?> | <urn:uuid:724731a4-3d53-4271-ad4f-cfdd9a6c8576> | 2.984375 | 325 | Tutorial | Software Dev. | 39.528769 |
The C API code is distributed with MySQL. It is included in the
mysqlclient library and allows C programs to
access a database.
Many of the clients in the MySQL source distribution are written in
C. If you are looking for examples that demonstrate how to use the C
API, take a look at these clients. You can find these in the
client directory in the MySQL source
Most of the other client APIs (all except Connector/J and
Connector/NET) use the
mysqlclient library to
communicate with the MySQL server. This means that, for example, you
can take advantage of many of the same environment variables that
are used by other client programs, because they are referenced from
the library. See Chapter 4, MySQL Programs, for a list of these
The client has a maximum communication buffer size. The size of the buffer that is allocated initially (16KB) is automatically increased up to the maximum size (the maximum is 16MB). Because buffer sizes are increased only as demand warrants, simply increasing the default maximum limit does not in itself cause more resources to be used. This size check is mostly a check for erroneous statements and communication packets.
The communication buffer must be large enough to contain a single
SQL statement (for client-to-server traffic) and one row of returned
data (for server-to-client traffic). Each thread's communication
buffer is dynamically enlarged to handle any query or row up to the
maximum limit. For example, if you have
BLOB values that contain up to 16MB
of data, you must have a communication buffer limit of at least 16MB
(in both server and client). The client's default maximum is 16MB,
but the default maximum in the server is 1MB. You can increase this
by changing the value of the
max_allowed_packet parameter when
the server is started. See Section 7.5.3, “Tuning Server Parameters”.
The MySQL server shrinks each communication buffer to
net_buffer_length bytes after each
query. For clients, the size of the buffer associated with a
connection is not decreased until the connection is closed, at which
time client memory is reclaimed.
For programming with threads, see Section 188.8.131.52, “How to Make a Threaded Client”. For creating a standalone application which includes the "server" and "client" in the same program (and does not communicate with an external MySQL server), see Section 17.5, “libmysqld, the Embedded MySQL Server Library”.
MySQL Enterprise. MySQL Enterprise subscribers will find more information about using the C API in the Knowledge Base articles, The C API. Access to the MySQL Knowledge Base collection of articles is one of the advantages of subscribing to MySQL Enterprise. For more information, see http://www.mysql.com/products/enterprise/advisors.html. | <urn:uuid:fa28998b-9c25-411a-8bd0-17f1a7e811d9> | 3.015625 | 615 | Documentation | Software Dev. | 52.544776 |
C. Frederick Hansen
The thermodynamic and transport prorerties of high-temperature air are found in closed form starting from approximate partition functions for the major components in air and neglecting all minor components. The compressibility, energy, entropy, the specific heats, the speed of sound, the coefficients of viscosity and of thermal conductivity, and the Prandtl numbers for air are tabulated from 500 degrees to 15,000 degrees K over a range of pressure from 0.0001 to 100 atmospheres. The enthalpy of air and the mol fractions of the major components of air can easily be found from the tabulated values for compressibility and energy. It is predicted that the Prandtl number for fully ionized air will become small compared to unity, the order of 0.01, and this implies that boundary layers in such flow will be very transparent to heat flux.
An Adobe Acrobat (PDF) file of the entire report: | <urn:uuid:8fa7ce1e-5a53-4497-bdd7-ac411a0ad7ce> | 2.75 | 195 | Academic Writing | Science & Tech. | 43.423947 |
Wrapping D's structs is similar to wrapping classes. In fact, many of the operations are identical.
void wrap_struct(T, char structname = symbolnameof!(T), Params...) ();
- T is the struct being wrapped.
- structname is the name of the struct as it will appear in Python.
- Params is a series of struct types (defined below), which define the various members of the struct.
As with calls to
wrap_class, calls to
wrap_struct must occur after calling
To expose the data members, member functions, and properties of the struct, you must pass a series of struct template instantiations to
struct Member(char realname, char name=realname);
- This exposes a data member of the struct to Python. The member must be a convertible type. The realname is the member's actual name. name is the name of the data member as it will be used in Python. This defaults to realname.
struct Def(alias fn, char name = symbolnameof!(fn), fn_t = typeof(&fn));
- This wraps a member function of the struct. It is in fact exactly the same
Defstruct template used to wrap class methods, including the lack of support for default arguments.
struct StaticDef(alias fn, char name = symbolnameof!(fn), fn_t = typeof(&fn), uint MIN_ARGS = minArgs!(fn));
- This wraps a static member function of the struct. It is the same
StaticDefstruct template used to wrap static class member functions, and also includes support for default arguments.
struct Property(alias fn, char name = symbolnameof!(fn), bool RO = false);
- This wraps a property. It is the same
Propertystruct template used to wrap class properties.
struct Repr(alias fn);
- This allows you to expose a member function of the struct as the Python type's
__repr__function. The member function must have the signature
char function(). It is the same
Reprstruct template used when wrapping classes.
- This allows the user to specify a different overload of opApply than the default. (The default is always the one that is lexically first.) It is the same
Iterstruct template used in class wrapping.
struct AltIter(alias fn, char name = symbolnameof!(fn), iter_t = implementationDetail);
- This wraps alternate iterator methods as Python methods that return iterator objects. It is the same
AltIterstruct template used in class wrapping.
is_wrapped template is available for wrapped structs, just like it is for wrapped classes.
It is important to note that wrapping a struct
S makes both
S itself and
S* available as convertible types.
Support for operator overloading in structs is identical to that available for classes.
D does not support struct inheritance. Therefore, Pyd does not provide any support for struct inheritance. However, the Python type wrapping the D struct can be subclassed from within Python. Users should not expect polymorphic behavior if they attempt to pass instances of any subclasses back to D. | <urn:uuid:6120c112-c543-48d0-bba6-4c820339d3c0> | 3.015625 | 670 | Documentation | Software Dev. | 57.230281 |
It turns out that the tangent bundle construction is actually a functor. Given a smooth map between smooth manifolds, we will get a smooth map . Yes, we’d usually write for a functor’s action on a map, but the notation is pretty classical.
So if we’re given a tangent vector we want to get a tangent vector . And since we already have sending points of to points of , it only makes sense to ask that . That is, in terms of the tangent bundle projection functions, we can write . In other words, the projection will be a natural transformation from the tangent bundle functor to the identity functor.
Anyway, this means that for each we’ll get a map . Since these are both vector spaces, it only stands to reason that we’d have a linear map. We haven’t yet established the connection between our “tangent vectors” and the geometric notion, but we do have a notion from multivariable calculus of a linear map that takes tangent vectors to tangent vectors: the Jacobian, which we saw as a certain extension of the notion of the derivative. We will find that our map is the analogue of the same concept on manifolds, and so we will call it the derivative of .
So here’s our definition: if is a differentiable map in some open set and if , then we define our map by
where is any smooth function on a neighborhood of . That is, is a linear functional on ; if represents a germ at we can compose it with to represent a germ at , and then we can apply itself to this germ. It should be immediately clear that this construction is linear in . | <urn:uuid:da5f48db-e177-477c-8fd2-11cd959284da> | 2.984375 | 358 | Personal Blog | Science & Tech. | 59.420921 |
|At the center of our Milky Way Galaxy,
a mere 27,000 light-years away,
lies a black hole with 4 million times the mass of the Sun.
Fondly known as Sagittarius A* (pronounced A-star),
the Milky Way's black hole is
fortunately mild-mannered compared
to the central black holes in
distant active galaxies, much
more calmly consuming material around it.
From time to time it does flare-up, though.
A recent outburst lasting several hours is captured in
this series of premier X-ray images
from the orbiting
Spectroscopic Telescope Array (NuSTAR).
Launched last June 13, NuSTAR is the first to provide
of the area surrounding Sgr A* at X-ray energies higher than
those accessible to Chandra and XMM observatories.
Spanning two days of NuSTAR observations,
the recent flare sequence is illustrated in the panels at the far right.
X-rays are generated in material heated to over 100 million
degrees Celsius, accelerated to nearly the speed of light as it
falls into the Miky Way's central black hole.
The main inset X-ray image
spans about 100 light-years.
In it, the bright white region represents the hottest material closest
to the black hole, while the pinkish cloud likely belongs to a
nearby supernova remnant. | <urn:uuid:374a0efa-6982-446e-af33-e95e5a935e1c> | 3.328125 | 297 | Knowledge Article | Science & Tech. | 48.320405 |
1. (Science: zoology) a shark of the genus Sphyrna or Zygaena, having the eyes set on projections from the sides of the head, which gives it a hammer shape. The Sphyrna zygaena is found in the North atlantic. Called also hammer fish, and balance fish.
2. (Science: zoology) a fresh water fish; the stone-roller.
Results from our forum
The Diplocaulus was an amphibian whose head was in the shape of a boomerang some what like a hammerhead shark.Does this mean it was an ancestor of the hammerhead shark no [Appearences are often deceptive].The diplocaulus probably became extinct.The reason why diplocaulus ...
See entire post | <urn:uuid:72419c69-62b8-402d-8ff2-93eee7d7cd31> | 3.328125 | 166 | Structured Data | Science & Tech. | 58.629443 |
Aquatic Habitat Protection
Several power plants withdraw large quantities
of cooling water from the Hudson River
There are several programs within the Division of Fish, Wildlife and Marine Resources that focus on the protection of aquatic habitat including the Protection of Waters program, the Instream Habitat Protection program, and the work of the Bureau of Habitat's Steam-Electric Unit to minimize the adverse aquatic impact from cooling water use by power plants and other industrial and commercial facilities. Staff in these programs evaluate the impact of existing and proposed construction, development or water use on streams, rivers and other waterbodies.
This policy describes the reductions in impingement mortality and entrainment required to minimize the adverse environmental impact caused by industrial facilities operating a cooling water intake structure (CWIS) in connection with a point source thermal discharge. The operation of CWIS causes injury and mortality to fish and other aquatic organisms through impingement at the intake and/or entrainment through the cooling system. Through this policy, the Department identifies closed-cycle cooling or its equivalent as the performance goal for best technology available (BTA) pursuant to Section 704.5 of 6NYCRR, and Section 316(b) of the federal Clean Water Act in State Pollutant Discharge Elimination System (SPDES) permits issued by the Department in accordance with ECL Article 17, Title 8, and Part 750 of 6NYCRR.
The Department has made a Determination of Non-Significance (PDF) (71 KB) which means that the policy will not have a significant adverse impact on the environment and a draft impact statement will not be prepared. Furthermore, the many public comments on the draft policy have been summarized and addressed in a Response to Public Comments (PDF) (94 KB) document.
The Dunkirk Generating Station, located on the
shores of Lake Erie
The Bureau of Habitat's Steam-Electric Unit (SEU), is made up of biologists who work to mitigate the adverse aquatic impacts resulting from the operation of industrial and commercial cooling water use. Steam-electric stations such as fossil fuel and nuclear generating plants use by far the greatest volume of cooling water from our lakes, rivers and marine district. Other users of cooling water in New York include commercial offices (air conditioning) and the cement, salt and sugar industries.
As a consequence of withdrawing water for cooling, fish and other aquatic life may be drawn into the facility and killed when larger individuals become impinged on the intake screens (designed to keep debris in the water from entering the plant), or when early life stages of fish such as eggs and larvae and other small aquatic life pass through the screen mesh and into the station (a process called entrainment). In 2005, the United States Geological Survey (USGS) estimated that New York ranks 3rd among the nation in using once through cooling water for steam electric power generation (USGS 2005 water use report) . Based on data collected by the Steam Electric Unit, New York steam electric plants use over 6 trillion gallons of cooling water annually, resulting in the impingement and entrainment of more than 17 billion fish of all life stages each year. A technical report (PDF) (928 KB) evaluating the relationship between cooling water use, electrical generation, and impingement and entrainment impacts has been produced by the Department and is available here. Adverse impacts to aquatic life can also occur through the discharge of cooling water (the temperature often raised by 10 to 20 degrees F) back to the lake or river, a process known as thermal pollution. Thermal pollution can kill fish outright, block fish migrations, cause the growth of nuisance species, and create other problems as well.
These fish were killed due to impingement
on a cooling water intake screen
The goal of the SEU is to minimize the mortality to fish caused by the operation of cooling water intakes. Both Section 316(b) (www.epa.gov/waterscience/316b/basic.htm) of the federal Clean Water Act and New York State regulations (6NYCRR Part 704) provide the legal basis for our program. These laws and regulations protect our waters from thermal pollution, and require that cooling water intake structures make use of the best technology available (BTA) to minimize adverse environmental impacts. Staff review proposals for the construction of new power plants and periodically assess the operational impacts of existing stations located throughout the State. New power plants are required to use the most protective intake technologies. For existing stations, studies are conducted to determine the magnitude of impact and the actions necessary to minimize those adverse effects. BTA can be implemented through a number of ways, and each power plant, whether new or old, presents its own conditions and problems which require site specific assessment. BTA determinations can include many different mitigative technologies and often more than one technology is required at a single facility. Mitigation is aimed at minimizing adverse environmental impacts, but not at a social and economic cost that is wholly disproportionate to the related environmental benefit.
New Power Plants
The SEU is at the national forefront in applying state of the art technology to achieve BTA for mitigating impacts from cooling water intakes. For new power plants, these include requiring the use of evaporative, air cooled and hybrid cooling towers to reduce cooling water use by 95% or more, fine wedge wire intake screening and/or aquatic filter barriers to prevent fish impingement and minimize the entrainment of early life stages of fish.
The deregulation of the electric industry in New York State resulted in more than 60 proposals to build new power plants, primarily along the Hudson River estuary, the New York City harbor area, and in Long Island. Although only a few of these proposed plants were ever built, they all use a closed cycle cooling system and protective intake structures, or equivalent mitigation, to minimize impacts on aquatic resources. The Athens Generating Station, in Greene County near the Hudson River was the first major power plant to come on line under the NYS Public Service Commission's Article X siting law. The 1,080 MW station began operating in the later part of 2003. The station uses dry cooling towers and withdraws only 180,000 gallons of water per day. The withdrawal of this water results in very little impact on the aquatic organisms of the Hudson River.
In December 2001, EPA issued final regulations under Section 316(b)of the federal Clean Water Act, establishing location, design, construction and capacity standards for cooling water intakes at new (Phase I) facilities. All new electrical generating stations that withdraw more than 2 million gallons per day (MGD) of cooling water are regulated. In New York State, those subject facilities must comply with both 316(b) and NYCRR 704.5 requirements.
Existing Power Plants
The existing older power plants in the state in many ways present the most difficult challenge for the unit. Retrofitting new technologies on old systems that were never designed for such use always presents difficulties. A careful site specific assessment of the station's impacts and the feasibility and costs of alternatives are required before a decision on BTA can be made. Technologies that have been required to mitigate impacts at existing stations include:
- Modified Ristroph-type intake screens and return systems designed to reduce impingement stresses and safely return fish to the waterbody installed at the Dunkirk (Lake Erie) and Huntley (Niagara River) Generating Stations, in addition, fine mesh screens to reduce entrainment of early life stages of fish being tested at Dunkirk Station, beginning in 2011;
- An acoustic deterrent system installed at the J. A. FitzPatrick Nuclear Generating Station (Lake Ontario) to keep alewife from entering the cooling water intake;
- Forced generation outages to reduce cooling water use during fish spawning periods at Hudson River plants;
- A barrier net installed at the Bowline Station (Hudson River) to exclude adult fish from the intake structure;
- Operational restrictions to reduce cooling water flow during the winter period at several stations;
- Deployment of an aquatic filter barrier to exclude all life stages of fish from the water intake at the former Lovett Generating Station (Hudson River - station now retired);
- Installation of variable speed pumps and scheduling of unit outages, to minimize cooling water use and reduce fish mortality, completed at the Ravenswood Generating Station (East River). Compliance monitoring to begin in 2012, with biological sampling to occur from January 2013 to December 2014;
- Variable speed pumps and a fish deterrent system installed at the Danskammer Generating Station (Hudson River);
- Installed variable speed pumps (December 2009) and modified Ristroph-type intake screens/fish return system (March 2012) at Astoria Unit 50 (East River). Installation to be completed at Unit 30 by December 2013. Evaluation of the use of fine mesh intake screens also required;
- Installed modified fine mesh Ristroph-type intake screens and a low stress fish return system at the Arthur Kill Generating Station (Arthur Kill tidal strait). Compliance monitoring (impingement and entrainment sampling) to begin in June 2012.
- Installation of a prototype fine mesh (0.6 mm) modified Ristroph-type intake screen in intake bay No. 8 at the East River Station (East River) in May 2012. Compliance testing (impingement and entrainment sampling) to begin in 2013.
- Installation of variable speed pumps and modified Ristroph-type intake screens and low stress fish return system at Port Jefferson Station (Port Jefferson Harbor/Long Island Sound) by December 2014.
Where impacts are large, the optimal approach from our standpoint is to repower an existing facility into a state-of-the-art power plant. The facility can thus be redesigned into an efficient new station (e.g. using combined cycle technology) that will reduce fuel use, greatly increase thermal efficiency and minimize impacts to air and water. By incorporating BTA in the design phase, the projects can more easily accommodate technologies such as closed cycle cooling, and the most protective intake structures. In addition, this approach results in the re-use of an existing industrial site rather than disturbance to a greenfield site. The old 400 MW Albany Steam Generating Station, a once through cooled plant was successfully repowered into the Bethlehem Energy Center (BEC), a 750 MW highly efficient, combined cycle station. Through use of the combined cycle process and mechanical draft cooling towers, cooling water was reduced from approximately 500 MGD to less than 10 MGD. The new BEC began commercial operation in mid 2005. Almost twice as much electricity is now being produced at far lower impacts to the aquatic resource.
In September 2004, final regulations under Section 316(b) of the Clean Water Act became effective for cooling water intakes at existing power plants that withdraw a minimum of 50 MGD of cooling water. Staff incorporated elements of this regulation, commonly referred to as the Phase II rule, into the BTA decision making process, to be used in conjunction with NYCRR Part 704.5. However, in January 2007, the U.S. Circuit Court of Appeals for the Second Circuit remanded most provisions of the Phase II rule on grounds which included inconsistency with the Clean Water Act. EPA later suspended the rule, effective July 9, 2007. By this action, however, EPA did not suspend the provision which directs permitting authorities (such as DEC) to establish BTA requirements for existing facilities on a case by case basis, using best professional judgement. On April 20, 2011, EPA again proposed a rule to establish requirements to achieve BTA under section 316(b) of the CWA. Public comments on the draft rule were received until August 18, 2011. A final rule was scheduled to be issued by no later than July 27, 2012. However, under a modified settlement agreement, this date has been extended to June 27, 2013.
For more information on the unit's activities please contact Chuck Nieder at 518-402-9216.
In-Stream Habitat Protection
The Bureau of Habitat's Instream Habitat Protection Unit primarily functions to mitigate the adverse environmental impacts from the operation of hydroelectric stations. The operation of hydroelectric plants can cause serious ecological impacts. Fish can be killed directly as they pass through the turbines used to produce electricity. Water impounded by hydroelectric dams may cause downstream river sections to completely dry up, turn flowing rivers into ponds, and prevent upstream spawning migration of fish.
There are currently over 200 hydroelectric projects in New York State. Once every 30 to 50 years these projects are relicensed by the Federal Energy Regulatory Commission (FERC). Since the FERC relicensing process is governed by federal regulations, state laws are preempted except that we must issue a 401 Water Quality Certificate. This certificate contains conditions that will ensure water quality standards for the protection of aquatic resources are met by the project. The manner in which the project is operated can have a dramatic effect on the fish and wildlife resources. Many projects historically operated by using large drawdowns in the impoundment to release large flows through their turbines, and then shutting off flows to the river. The drawdowns in the impoundment and the shutting off of flow to the river cause serious impacts to aquatic resources. DEC staff participates in the federal process where we request studies needed to evaluate the impacts of the project and then recommend mitigation. A large group of hydroelectric projects (most owned by Niagara Mohawk Power Corp.) that were due to be relicensed in 1993 (the Class of '93) are nearly all completed. After many years of discussion and disagreement on how the projects should be operated, DEC, NMPC and a host of other interested parties have completed settlement agreements on all but one of these projects.
Aquatic Base Flow
The Instream Habitat Protection Unit also evaluates non-hydroelectric projects proposing stream base flow alterations that may result in adverse impacts to aquatic resources such as water withdrawals for snowmaking or reservoir releases. This work is conducted under the authority of Article 15 and the 401 Water Quality Certificate portion of the Clean Water Act.
For further information on the activities of the Instream Habitat Protection Unit, contact Mark Woythal at 518-402-8847.
More about Aquatic Habitat Protection:
- Daily Power Plant Cooling Water Use by State - Comparison of total daily cooling water used by steam-electric power plants in each state. | <urn:uuid:93c192b5-cbb7-4065-9b0a-dbba5268a854> | 2.765625 | 2,962 | Knowledge Article | Science & Tech. | 29.265168 |
Definitions for absorption band
a dark band in the spectrum of white light that has been transmitted through a substance that exhibits absorption at selective wavelengths
one of any number of ranges of wavelengths of electromagnetic radiation absorbed by a substance
Use the citation below to add this definition to your bibliography:
"absorption band." Definitions.net. STANDS4 LLC, 2013. Web. 21 May 2013. <http://www.definitions.net/definition/absorption band>. | <urn:uuid:642cc4b9-85a3-4d89-a629-d492d79d7b5b> | 2.90625 | 98 | Structured Data | Science & Tech. | 49.077698 |
Contact: Maria Martinez
Southwest Research Institute
Caption: Shown is an off-center, low-velocity collision of two protoplanets containing 45 percent and 55 percent of the Earth's mass. Color scales with particle temperature in kelvin, with blue-to-red indicating temperatures from 2,000 K to in excess of 6,440 K. After the initial impact, the protoplanets re-collide, merge and form a rapidly spinning Earth-mass planet surrounded by an iron-poor protolunar disk containing about 3 lunar masses. The composition of the disk and the final planet's mantle differ by less than 1 percent.
Credit: Southwest Research Institute
Usage Restrictions: May be used for educational and informational purposes only.
Related news release: New model reconciles the Moon's Earth-like composition with the giant impact theory of formation | <urn:uuid:ccffb165-e287-492e-9000-07d965f1d171> | 3.109375 | 178 | Truncated | Science & Tech. | 32.899158 |
|CHP Home||GenChem Analytical Instrumentation Index|
The underlying principles that determine chromatographic separations are dynamic behaviors that depends on partitioning and mass transport. These phenomena are too complex to model directly, and chromatography theory consists of empirical relationships to describe chromatographic columns and the separation of peaks in chromatograms.
The retention of an analyte by a column is described by the capacity factor, k', where:
k' = tr - tm ------- tmwhere tr is the time for the analyte to pass through the column, and tm is the time for mobile phase to pass through the column.
The resolution of chromatographic columns is described by the theoretical plate height, H, or the number of theoretical plates, N. These two quantities are related by:
N = L / H
where L is the length of the column.
H and N provide useful measures to compare the performance of different columns for a given analyte. Useful expressions are:
H = L W2 / 16 tr2
N = 16 (tr / W)2
where W is the width of the peak at its base.
|Top of Page| | <urn:uuid:57515403-3689-4fb0-9198-5d2aa4880936> | 2.84375 | 244 | Knowledge Article | Science & Tech. | 38.848571 |
Here's an article detailing on what's happened and what it might mean.
CERN reported that a neutrino beam fired from a particle accelerator near Geneva to a lab 454 miles (730 kilometers) away in Italy traveled 60 nanoseconds faster than the speed of light. Scientists calculated the margin of error at just 10 nanoseconds.
It could very likely be an error, but if it's true this could be very interesting.
Did it really go beyond the speed of light, or did some other phenomena occur. | <urn:uuid:4a24a1e3-6408-4384-9cc4-dd5eee3f121e> | 2.703125 | 110 | Comment Section | Science & Tech. | 56.302818 |
Green machine is our weekly column on the latest advances in environmental technologies
Pond scum. The term surfaces in every news report about the decades-long effort to get energy from algae. But more respect for the tiny creatures may soon be in order: industry and governments have started pouring billions into alga power.
Just the basic facts make you wonder why algae aren't powering our civilisation already. The single-celled phytoplankton produce half our planet's oxygen and are the fastest-growing green organisms known. In shallow seawater ponds on land, they can use sunlight and sewage to turn concentrated carbon dioxide – flue gas from coal burning, say – into usable hydrocarbons, half of which can almost be poured straight into a diesel engine.
"Ten million hectares of algae could supply all US transportation fuel," says Greg Mitchell of the Scripps Institution of Oceanography in La Jolla, California. That's less than 3 per cent of the area farmed in the US – and algae can live in seawater in the desert.
Too good to be true? Until recently, it seemed so. After the 1970s fuel shocks, the US launched the Aquatic Species Program (ASP) to investigate algae. It eventually built 1000 square metres of ponds at Roswell, New Mexico, and found many promising algal strains. But it concluded in 1996 that diesel from algae would cost twice as much as diesel from oil – at least at oil prices then.
So the ASP ended, and focus shifted to bioethanol from maize. Enthusiasm for that has dimmed, however, as it conflicts with our need for farmland for food.
One option has been to look at making bioethanol from inedible land plants. But interest has also swung back to algae. Last year oil giant ExxonMobil committed $600 million to develop algal fuels with genome pioneer Craig Venter. Since then projects have mushroomed: John Benemann, formerly a lead investigator on the ASP, estimates that $2 billion could be flowing into algal energy projects between 2009 and 2011.
ExxonMobil believes it will be able to sell algal diesel through existing refineries and petrol stations. Last month the first jet engine powered entirely by algae oil flew at an air show in Berlin, Germany.
Algae can produce 10 times as much energy per hectare as land-grown oil crops, says Mark Hildebrand of Scripps, because "they float. They don't have to spend half their [energy] building stalks to support themselves."
Instead, they make more cells until they run out of nutrients such as nitrogen. Then they stop dividing, but keep photosynthesising, storing the results as an oil droplet that can eventually take up more than half the cell.
One simple chemical reaction makes this oil into a diesel fuel that releases less particulate, sulphur-oxide and nitrogen-oxide pollutants than petroleum-based diesel. The remaining algal biomass can also be burned as fuel, though may be worth more as livestock feed, especially for fish. That means less damage to the environment, and less demand for overtaxed fisheries, soil and water to catch or grow feed.
Algae do present problems, however. One is that they don't grow and make oil at the same time – and that impedes industrial production. Algae can be grown until they use up all the nitrogen in their water. Then they stop multiplying – but before they switch to making oil, they cannibalise their own proteins for any spare nitrogen. Then they start making oil, but with damaged photosynthetic machinery that is less productive.
One family, the diatoms, solves that problem, says Hildebrand: they make intricate cell walls from silica, and start making oil when there is no more silica to grow. So they can produce oil without damaging themselves.
Scaling up algae production has been plagued by teething trouble and short-term financing. One high-profile start-up, GreenFuels Technologies, built the most ambitious pilot plant yet – it used CO2 from a power plant in Arizona – but went broke last year, a victim of unruly algal growth and expensive growth chambers.
The cheapest way to grow algae is in large open ponds, but these risk being invaded by algal "weeds" and algae-eating zooplankton. Mixed algal communities, perhaps with different species to match the seasons, might out-compete interlopers, says Hildebrand.
But even if growth problems are resolved, harvesting the oil is expensive. Benemann thinks there is promise in algae that spontaneously settle to the bottom of their tanks, or one kind that excretes oil in a capsule which resists oil-eating bacteria. Industrialising this process will require much R&D.
A little means a lot
And ultimately, production will require suitable climate, land, water, nutrients and CO2, all at one site. Even using waste land, seawater, sewage and smokestack CO2, Benemann thinks this will limit the potential for algal biomass to the equivalent of 1 per cent of the CO2 now being released, or less. "But that's still a gargantuan amount. Let's hope we can do that much."
We won't without more long-term funding, says Mitchell. But he is sanguine about the pay-off. "The US has been subsidising corn ethanol at $5 billion a year. Half that amount for 15 years in algae could solve the water, fuel, energy, feed and farmland crises humanity faces."
Read previous Green machine columns: The dream of green cars meets reality, Tackling the plastic menace, Bacteria will keep CO2 safely buried, Recycled batteries boost electric cars, It's your eco-friendly funeral, Cars could run on sunlight and CO2, Hitting the lights in wasteful offices, Cementing greener construction, Generating more light than heat.
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Green Machine: A New Push For Pond Scum Power.
Mon Jul 12 23:17:44 BST 2010 by W G Treharne
I have to support the work being done on algae.The diatoms solve the problem of self damage.
I have already mentioned that algae can be grown in glass towers and I hoped that the algae or diatoms full of oil would sink to the bottom thus helping the harvesting process.A difficulty is that oil is lighter than water so perhaps algae or diatoms will rise to the top when they are full of oil.
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Stressed Plastic Turning White
Why does colored plastic turn white when bent? example -
Lime green pen cap
There are two possible reasons for this: crystal formation due to cold
drawing or a process known as crazing. Essentially what is happening is
that the amount of refraction (bending of light) increases either due to
the increased size or organization of crystals in the plastic or an
increased amount of micro-fissures in the sample.
Plastics are semi-crystalline. This means that they are often a mixture of
crystals embedded in a matrix of amorphous polymers. If the crystal size
grows then that increased size may interact with light more and make the
sample opaque. Alternatively if the small crystals in the sample orient
themselves well relative to each other, than the incident beam may scatter
more as it interacts with these organized crystals and these will also make
the sample look opaque as less light transmits to your eye. Crystals can
grow or become more organized when you pull on a plastic sample without
heating it. Heat often has the effect of allowing the polymers to move
around or slip past each other so that pulling on the plastic does not
cause better organization of the crystals. However, if the sample is cold,
the molecules or do not have enough kinetic energy to wiggle around and so
they get oriented in the direction of the pull (kind of like the way
uncooked pasta will organized themselves in straight lines relative to
each other, but cooked pasta will be more disorganized).
The other explanation -crazing- is the development of small cracks in the
sample. Here the crystals are already big and organized so that when you
pull on the plastic, the spaces between the crystals increase and result
in little cracks or fissures. The difference in the density of the cracks
and the crystals cause the light entering the sample to bend or scatter.
We perceive this as a diminishing of the light reaching our eye and a
Hope this clarifies the effect for you.
Greg (Roberto Gregorius)
Click here to return to the Material Science Archives
Update: June 2012 | <urn:uuid:c183b25c-7c55-46c1-adaa-c737c45ca703> | 3.234375 | 452 | Knowledge Article | Science & Tech. | 39.328603 |
*Note: This is an abbreviated Project Idea, without notes to start your background research, a specific list of materials, or a procedure for how to do the experiment. You can identify abbreviated Project Ideas by the asterisk at the end of the title. If you want a Project Idea with full instructions, please pick one without an asterisk.
This implies that not all of the potential energy is converted to the kinetic energy of the bounce. But conservation of energy requires that the energy must be the same before and after the ball is dropped? Where does the energy go? Bounce a ball 100 times, then hold it in your hand. In your other hand hold a ball that wasn't bounced. What is the difference? (See: Goodstein, 1999, pp. 22–23.)
The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.
If you like this project, you might enjoy exploring these related careers:
Physicists have a big goal in mind—to understand the nature of the entire universe and everything in it! To reach that goal, they observe and measure natural events seen on Earth and in the universe, and then develop theories, using mathematics, to explain why those phenomena occur. Physicists take on the challenge of explaining events that happen on the grandest scale imaginable to those that happen at the level of the smallest atomic particles. Their theories are then applied to human-scale projects to bring people new technologies, like computers, lasers, and fusion energy.
Our universe is full of matter and energy, and how that matter and energy moves and interacts in space and time is the subject of physics. Physics teachers spend their days showing and explaining the marvels of physics, which underlies all the other science subjects, including biology, chemistry, Earth and space science. Their work serves to develop the next generation of scientists and engineers, including all healthcare professionals. They also help all students better understand their physical world and how it works in their everyday lives, as well as how to become better citizens by understanding the process of scientific research.
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- Black holes are theoretical structures in spacetime predicted by the theory of general relativity. Nothing can escape a black hole’s gravity after passing inside its event horizon.
- Approximate quantum calculations predict that black holes slowly evaporate, albeit in a paradoxical way. Physicists are still seeking a full, consistent quantum theory of gravity to describe black holes.
- Contrary to physicists’ conventional wisdom, a quantum effect called vacuum polarization may grow large enough to stop a hole forming and create a “black star” instead.
Black holes have been a part of popular culture for decades now, most recently playing a central role in the plot of this year’s Star Trek movie. No wonder. These dark remnants of collapsed stars seem almost designed to play on some of our primal fears: a black hole harbors unfathomable mystery behind the curtain that is its “event horizon,” admits of no escape for anyone or anything that falls within, and irretrievably destroys all it ingests.
To theoretical physicists, black holes are a class of solutions of the Einstein field equations, which are at the heart of his theory of general relativity. The theory describes how all matter and energy distort spacetime as if it were made of elastic and how the resulting curvature of spacetime controls the motion of the matter and energy, producing the force we know as gravity. These equations unambiguously predict that there can be regions of spacetime from which no signal can reach distant observers. These regions—black holes—consist of a location where matter densities approach infinity (a “singularity”) surrounded by an empty zone of extreme gravitation from which nothing, not even light, can escape. A conceptual boundary, the event horizon, separates the zone of intense gravitation from the rest of spacetime. In the simplest case, the event horizon is a sphere—just six kilometers in diameter for a black hole of the sun’s mass.
This article was originally published with the title Black Stars, Not Holes. | <urn:uuid:8778c819-f6f2-46b9-9dae-48a9f6f915e0> | 3.984375 | 421 | Truncated | Science & Tech. | 29.258381 |
Impact of UML Techniques in Test Case Generation
UML is a standard language that used in business modeling for specifying, visualizing and constructing the software artifacts. UML provides the capability to enhance (explore) the static structure and dynamic behavior of a software system. Different UML strategies and techniques are implemented during the whole software development life cycle. This paper explains the UML2.0 testing for test case generation. In this paper, the focuses will be on effective use of UML techniques and test-case generation in order to make suitable executions. | <urn:uuid:3787f3a7-5f7c-4e66-8fe8-a19cce85bc2e> | 2.734375 | 113 | Truncated | Software Dev. | 22.240833 |
“The total number of stars in the Universe is larger than all the grains of sand on all the beaches of the planet Earth.”
~ Carl Sagan
When I was young I would imagine that if the earth were the size of a baseball then perhaps the sun would be the size of a beach-ball and that they’d be about 20-ft (6 meters) apart at that scale. This seems about right, but it turns out to be very VERY wrong. If the earth was the size of a baseball, the sun would be almost 27-ft (8 meters) in diameter, already more than the distance I imagined separated the two. The distance between the baseball-size earth and the 27-ft diameter sun is about a half-mile.
In other words, imagine a ball that’s nearly three stories high, and you’d have to walk a half-mile to find a baseball-sized earth. The baseball:earth scale isn’t practical to construct a model.
But do astronomical models ever meaningful scale? That is, can we construct a scale model of the solar system and some nearby stars? Let’s see what happens.
Scale the earth down to a single grain of sand on the beach. Imagine a normal sandy beach like the one pictured above, and use an an average sand particle of about 1 mm, nothing exceptional.
At this grain-of-sand:earth scale, we would have a softball-size sun about 38-ft (12 meters) away from the grain of sand earth. This model would fit within most actual beaches, except on this beach, there’d only be 31 grains of sand that have been discovered so far (and four pieces of gravel, and a bunch of silt, but we’ll get to that).
Our moon on this scale would be about an inch away from the grain-of-sand earth, it would be an even smaller particle of sand. The furthest human beings have set foot is only one-inch on this beach.
Mars is another grain of sand, and its moons are so small they wouldn’t be visible, too small even to be called silt.
Jupiter would be 161-ft (49 meters) away from the grain-of-sand earth, but Jupiter would be too large to be considered sand, it would appropriately be called gravel. Jupiter would be the size of a small marble. About 50 meters away from the grain-of-sand earth is a marble-size Jupiter. This beach has four marbles revolving around a softball-size sun. Interestingly, there is more sand revolving around the marbles than there is sand revolving around the softball-size sun. Most of the objects on this beach are tiny bits of silt, i.e., particles too small to be considered grains of sand.
The furthest man-made object, the Voyager spacecrafts, would be far too microscopic to be visible on this beach, but these microscopic spacecraft would be almost a mile away from the softball-size sun.
The grain-of-sand-scale model so far is a pretty lonely beach. This beach would go about a mile inland, a vast and open beach with 31 grains of sand, four marbles of gravel, countless silt particles thrown about (most of it would be invisible to the naked eye). The English language has precise words for silt, sand, and gravel; unfortunately, for solar system objects the English language isn’t as discriminating. Astronomically, we lump gravel together with sand and if they happen to be spherical and revolve around a star we call them “planets”. Some grains of sand are not planets only because they revolve around gravel. A bit silly, and if you’ve ever wondered why Pluto isn’t considered a planet, remember that it’s smaller than Earth’s moon, and would barely be visible as a grain of sand on this scale. Debates about Pluto completely miss the point: our knowledge of the solar system is far deeper than “there are 9 planets, no wait, 8 planets”.
Looking at the grain-of-sand earth, this is about the smallest reasonable scale that we can model, and so far this model fills a one-mile radius. We can count 31 grains of sand, four marbles, and bands of silt revolving within a mile-radius around the softball-size sun.
And this is just our solar system, we’re not into the universe, not yet. Let’s venture out to the closest star.
On this grain-of-sand-scale, the nearest star, Alpha Centauri, would be a bit larger than a softball (about 5.3 inches in diameter). And if our lonely beach with a tiny handful of sand, silt, and gravel were in Los Angeles, then you’d have to walk all the way to Tennessee (somewhere between Memphis and Nashville) to get to Alpha Centauri.
Walking from Los Angeles to Tennessee is far but not unreasonable with basic provisions. Unfortunately, at this scale, the speed of light would also be scaled down. We tend to think that the speed of light is fast, but at this grain-of-sand-scale, the speed of light is slower than a sloth. It’s about 0.05 miles-per-hour, about 84 meters-per-hour (277 feet-per-hour). How long would it take a sloth to get from Los Angeles to Nashville? It doesn’t matter, because at this scale the sloth would be faster than light.
84 meters per hour, that’s the speed that light would travel at this tiny scale, and hence it would take over 16 hours to get across the beach (from the sun to the edge of the solar system).
Those Voyager spacecraft, on this grain-of-sand-scale, are traveling less than half-a-centimeter every hour. That is slower than bamboo grows. When you imagine the solar system, realize that these objects are so far apart that both light and gravity are moving at a snails-pace relative to the distances; and that these scaled down objects would move slower than a plant grows. How long would it take a plant to grow from Los Angeles to Nashville?
Let’s look at the night sky, what about the north star, Polaris?
On this grain-of-sand-scale, Polaris is much bigger than the softball-sized sun, it’s about 16-ft (almost 5 meters) in diameter, and it’d be about 321,000 km away … so even at this grain-of-sand-scale, even though we have to go cross-country to get to the nearest softball-size star, for other stars we’d leave the earth. In the case of Polaris we’d almost be to the moon, and we wouldn’t find a softball, we’d find a 16-foot diameter bolder representing Polaris.
And what about the larger objects in our galactic neighborhood, for example, the star Betelgeuse would be over 220-ft (67 meters) in diameter, 474,000 km away from the grain-of-sand earth. On a clear night you may be able to see the Andromeda galaxy, on our grain-of-sand-scale this Andromeda model would be so large as to fill our actual inner solar system, but it’d be 1.8 billion kilometers away. The brightest quasar viewable from earth, 3C 273, on a grain-of-sand scale would be 1.8 trillion kilometers away.
Even at this tiny scale, a model of the solar system fits within a mile-wide beach, but to model our neighboring stars we’d leave earth and our model becomes as large as the thing we’re trying to model.
The problem with scale models of astronomy is that we try to model the physical stuff and forget that the largest and most interesting thing to model is the empty space itself. The size of a solar system, the size of a galaxy; like our lonely beach with 31 particles of sand; it’s mostly empty space.
This is why astronomical models aren’t to scale, the range of size within human intuition is simply too narrow, we have to continually abstract and abstract and can lose our bearings on just how big and how far away these objects are. Fortunately, it is within the poetry of mathematics that we can artfully express these abstractions. Mathematics becomes the language to convey these otherwise non-intuitive concepts, opening the universe to intelligence beyond scaled models.
For this scaling, we’re using the following size descriptors:
- Silt: 0.002 mm to 0.0625 mm
- Sand: 0.0625 mm to 2 mm
- Gravel: 2 mm to 64 mm
To simplify the scaling, imagine the earth is a 1mm grain of sand, this puts the earth:grain-of-sand scale at 12756200000 : 1
Using that scale,
- A silt particle models any object 25 km to 797 km in diameter
- A sand particle models any object 797 km to 25,512 km in diameter
- A piece of gravel models objects up to 816,397 km in diameter
This gives us the following models,
- Gravel: Jupiter, Saturn, Uranus, Neptune
- Sand: Mercury, Venus, Earth, Luna, Mars, Ganymede, Titan, …
- Silt: Dysnomia, Chaos, Enceladus, Proteus, Hale-Bopp, …
At this scale, the model of the Sun (which is 1.391 million km) is too large for gravel; and scaled down to 4.3 inches is about the size of a softball, but to keep with the metaphor we would call this a Cobble stone. | <urn:uuid:8e0bc7b0-a414-4c9b-a3fa-d07e4cd82cf4> | 3.953125 | 2,079 | Personal Blog | Science & Tech. | 64.983395 |
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There are several ways to measure the speed of the fastest spacecraft and each definition gives credit to a different craft. We will look at four categories in this article: fastest escape speed from Earth’s atmosphere, fastest speed on a solar escape, fastest based on plain old-fashioned km/h, and fastest reentry speed.
The New Horizons space probe is the fastest spacecraft based on its velocity as it escaped the Earth’s atmosphere and gravity. The probe hit 57,600 km/h as it pulled away from its terrestrial tethers.
Next, the spacecraft with the highest rate of speed while on a solar escape trajectory(leaving our solar system) is Voyager 1 at 62,100 km/h. Currently, there are four space probes on trajectories to leave our solar system and expand our knowledge of what is beyond.
Based on pure speed per kilometer are the Helios solar probes. Helios 2 was the fastest during its closest solar approach, but both vehicles exceeded 250,000 km/h.
The fastest spacecraft while reentering Earth’s atmosphere was the Stardust probe. The comet sampling probe hit a comfortable 46,660 km/h while returning samples of comet material and interstellar dust.
Just for fun, the Galileo space probe holds the record for the fastest entry of the atmosphere of another planet. Galileo hit 173,770 km/h on its way to impacting the surface of Jupiter.
As you can see, the fastest spacecraft is based on a clear set of parameters. Hopefully, these answers meet your needs. Feel free to search out database if you have additional parameters you want to use.
We have written many articles about the fastest spacecraft for Universe Today. Here’s an article about the location of the New Horizons spacecraft, and here’s an article about New Horizons’ mission to Pluto.
We’ve also recorded an entire episode of Astronomy Cast all about Dwarf Planets. Listen here, Episode 194: Dwarf Planets. | <urn:uuid:cdd0fc6e-8ecd-4d25-a40e-e62fced36a3d> | 3.21875 | 428 | Knowledge Article | Science & Tech. | 53.077637 |
Bug of the Week
Green Weevil, Red Weevil (Family Curculionidae)
The BugLady loves weevils – chunky beetles with antennae placed partway between the top and tip of their Jimmy Durante snouts. Weevils (Family Curculionidae) are the largest family in the beetle order Coleoptera, which is the largest order in Class Insecta, which is the largest class in the Phylum Arthropoda, which is, by several orders of magnitude, the largest Phylum in the Kingdom Animalia (when the BugLady first learned biology there were only two kingdoms, plant and animal, plus a few troublesome critters that hovered in between). Eighty percent of animals are (bone-free) arthropods, and seventy-five percent of arthropods are insects, and every fifth living thing is a beetle.
Many weevils are, well, small and drab. Here are two showy weevils – one alien and one native, one green and one red, one a minor pest and the other a big pest (the BugLady doesn’t like to assign plusses or minuses to insects, but then the BugLady doesn’t grow roses, either).
The BugLady will insert a little confusion right up front. The alien Green Immigrant Leaf Weevil (Polydrusus sericeus) has an also-alien doppelganger named the Pale green weevil (Polydrusus impressifrons). In one account the BugLady read, the Green Immigrant leaf weevil (GILW) was referred to as Polydrusus sericeus impressifrons , aka Polydrusus impressifrons, so it would seem that some taxonomic revision may be in the works. The Polydrusus that the BugLady sees in the strawberry patch each summer may be P. impressifrons; she will look closer this year. At any rate, the life histories and modus operandi of the two are similar, so the BugLady will “call” this one Polydrusus sericeus (because of the black lines on the elytra) and take any resulting flack.
GILWs made their way from Europe to New York by 1906. Today they can be found all over the northeastern portion of North America, including Canada. Metallic, green scales overlay a black body, and the color may fade to grayish-green as they age. With snouts that are short and wide, they are in the broad-nosed weevil bunch.
Eggs are laid in the soil in summer, and the newly-hatched larvae burrow into and feed on what one source called “fine root tissue.” They spend the winter underground as larvae, eat a little more in spring and then pupate, emerging as adults in late May or June.
Adult GILWs nibble along the leaf edges and sometimes the buds of a number of fruit and forest trees (they especially like yellow birch). Most sources admit that they seldom get populous enough to cause injury to a tree’s crown; the damage is mainly cosmetic. But there are some new studies going on about the impact of root-feeding grubs on forest tree germination that may be incriminating.
A few Cool-Facts about GILWs:
- They are listed in a manual called Dangerous Insects Likely to be Introduced in the United States Through Importations , printed in 1917 by the USDA. The BugLady will make no comment on their inclusion in a 1917 government publication when they had already been here for at least 10 years.
- When they fall out of their trees into the water, which is a frequent occurrence, they become trout food. Fly fishermen call these inadvertent additions to the water’s surface fauna “terrestrials” and make lures that copy them.
- A number of studies were done through the UW Department of Entomology on the potential impact of the higher CO2 levels (predicted to accompany global climate change) on invasive beetles in northern Wisconsin. Preliminary results suggest that female life spans and fertility are lowered. The BugLady is wondering how many other organisms will be affected this way.
The Rose Curculio (RC) can be found throughout the northern half of the US and southern Canada, coast to coast (western individuals are a different species). As its name suggests, roses are its BFF ( best friend forever ) but blackberry and raspberry plants will do in a pinch. It’s native to North America but is mentioned on a site called Biosecurity New Zealand (which imposes stern restrictions on Korean imports) and is listed as present in Russia and England.
As gardeners know, the RC (Merhynchites bicolor) is not there just to smell the roses. This lovely, red, long-legged weevil lays her eggs (there may be some parthenogenesis – virgin birth – going on with RCs) in the “hips” (fruit) and the buds of roses. This she does by using the chewing mouthparts located at the end of her long, black snout to bore a small hole in the hip/bud, after which she turns around and inserts an egg. For all the notoriety that this insect has garnered, there is considerable confusion about what the larva does and when. The larva develops (eats) in the hip or the bud. The larva overwinters in the hip, and pupates and emerges in spring. The larva develops in the bud, overwinters in the soil, and eats in spring. The eggs are laid in late spring and the larva feeds on the flower’s reproductive parts (and can even complete its life cycle in buds that have been clipped and discarded). The larva pupates underground and emerges the next spring.
The drilling done by the female can weaken the stalk just below the flower, causing it to droop. To add insult to injury, adult RCs also feed on roses. She loves the pollen, and she will chew into unopened flower buds to get at it. When the flower opens, the petals all have little punctures in them. She’ll also feed on the tender shoots.
A fair amount of ink has been devoted to discussions about the RC’s favorite color of roses. Although they evolved with wild roses (mostly pink) and some say that their taste in domestic roses run to pink, they’ve been seen on roses of all sizes, shapes and colors.
For the chemically-inclined, there are a number of products designed to stop the RC, and parasitic nematodes are a biological control of the larvae in the soil. An alternate method is to hand-pick the adults from rose plants and drop them in a dish of soapy water (alarmed adults bail and play dead, so just knocking them off the plant will make them plunge into the soapy water below); deadhead the roses religiously; and keep damaged buds out of the compost heap (which will otherwise turn into a giant incubator for the larvae).
The Bug Lady | <urn:uuid:ba88b45f-b352-4a24-b637-fa7f8b470103> | 3.203125 | 1,485 | Knowledge Article | Science & Tech. | 47.237157 |
Vast Hot Gas Plume May Be A Passing Attraction
The Chandra image of the Centaurus galaxy cluster shows a long plume-like feature resembling a twisted sheet. The plume is some 70,000 light years in length and has a temperature of about 10 million degrees Celsius. It is several million degrees cooler than the hot gas around it, as seen in this temperature-coded image in which the sequence red, yellow, green, blue indicates increasing gas temperatures. The cluster is about 170 million light years from Earth.
The plume contains a mass comparable to 1 billion suns. It may have formed by gas cooling from the cluster onto the moving target of the central galaxy, as seen by Chandra in the Abell 1795 cluster. Other possibilities are that the plume consists of debris stripped from a galaxy which fell into the cluster, or that it is gas pushed out of the center of the cluster by explosive activity in the central galaxy. A problem with these ideas is that the plume has the same concentration of heavy elements such as oxygen, silicon, and iron as the surrounding hot gas. | <urn:uuid:86982c2e-3a05-498b-b05f-af5010a74e7f> | 3.734375 | 223 | Knowledge Article | Science & Tech. | 47.36875 |
Certainly one for the Potential list…
Many have argued under the climate change mitigation banner that so-called ‘old-growth’ (let’s call them primary forests henceforth to distinguish them from [usually] younger secondary forests) do not provide net carbon uptake because most of their growth has occurred in the past. In other words, they provide a carbon store, but do not take much more out of the atmosphere once they’ve attained a certain ecological equilibrium. This was a major impediment for the argument that protecting such forests could be achieved economically by valuing them in national or global carbon-trading schemes. It was a shame considering that it seems the economic incentives to protect such forests were falling on deaf ears because (a) governments and industry tend to regard the quick turn-around option of timber extraction as more economically sensible and (b) of the difficulty of valuing ecosystem services provided by primary forests.
But not so, say Luyssaert and colleagues! After scouring an array of studies and databases they conclude that forests between 15 and 800 years of age do in fact continue to uptake carbon and so are not carbon ‘neutral’. Brilliant! With this latest evidence in hand, I hope the economic incentives to preserve the little remaining primary forests around the world and the ecosystem services they provide will encourage governments and industry to invest more in their preservation than their destruction. It’s worth noting here too that once such forests are destroyed (e.g., timber extraction), the majority of their stored carbon (both actual and potential via future carbon uptake) are released back to the atmosphere, thus exacerbating climate change. As such, valuing the preservation of pristine forests on the carbon-trading market should receive a far higher weighting that secondary plantations or other sequestration schemes. | <urn:uuid:203d1152-ab9f-4a47-86e8-c36c392be15e> | 2.875 | 370 | Personal Blog | Science & Tech. | 26.80427 |
The number of square meters in the helium flux tube, which in the plasma density diagrams appears to be approx. 5 times larger than the sun, is 758,733,957,500,000 sq/metres. This equals a average current density of any cross section of the flux tube at 1,896,834,893,750,000,000,000 amps assuming a homogenous cross section. If we use the voltage of Jupiter's moon, Io's flux tube as a guess(I would like to use the current values as well but I do not have an area for this value), 400,000v * 1,896,834,893,750,000,000,000A = 7,587,339,575,000,000,000,000,000,000 watts or
7.5 * 10^26 watts per interstellar helium flux tube, of which there are 2 of them crossing the sun. The potential across the sun is the difference of the 2 flux tubes assuming one is positive and one is negative, or one is in and one is out, which is 15 *10^52 watts. Each pole of the sun is responsible for 1/2 of the 4*10^26 watts of the total output of the sun, or 2 * 10^26 watts.
The sun power output is 4*10^26 watts, which is well within the potential of an individual flux tube. | <urn:uuid:20960124-6e88-41e9-95f5-fae6f5193dc6> | 2.6875 | 294 | Comment Section | Science & Tech. | 82.862321 |
(Submitted November 24, 1997)
Where is the closest neutron star?
The neutron star which we currently rank as "nearest to Earth" is a radio
pulsar called J0108-1431. It is within 100 parsecs of the Sun. A parsec is
a unit of distance in astronomy; it is equal to 3.26 light years, or 3.1 x
for the Ask an Astrophysicist Team | <urn:uuid:dbbb9723-e836-497c-80e0-235fb2526e71> | 2.859375 | 94 | Q&A Forum | Science & Tech. | 85.274571 |
How Did Structure Form in the Universe?
The Big Bang theory is widely considered to be a successful theory of cosmology, but the theory is incomplete. In its simplest form, the Big Bang theory assumes that matter and radiation are uniformly distributed throughout the universe and that general relativity is universally valid. While this can account for the existence of the cosmic microwave background radiation and explain the origin of the light elements, it does not explain the existence of stars, galaxies and large-scale structure. The famous "Deep Field Image" taken by the Hubble Space Telescope, shown below, provides a stunning view of such structure. How did these structures form? Most cosmologists believe that the galaxies that we observe today grew from the gravitational pull of small fluctuations in the nearly-uniform density of the early universe. These fluctuations leave an imprint in the cosmic microwave background radiation in the form of temperature fluctuations from point to point across the sky. The WMAP satellite measures these small fluctuations in the temperature of the cosmic microwave background radiation and in turn probe the early stages of structure formation.
The solution of the structure problem must be built into the framework of the Big Bang theory. WMAP's observations provide the type of data needed to form detailed theories to answer these questions. | <urn:uuid:dd48d675-c876-4635-afc0-df98ad7583c5> | 4.1875 | 251 | Knowledge Article | Science & Tech. | 30.488292 |
Let p(x) = x^5 + ax + b where a and b are real numbers.
a.) prove that p(x) has exactly one real root if a > 0.
b.) What is the maximum number of real roots p(x) may have? Justify your answer.
I am going to use the root-location theorem.Originally Posted by Susie38
If is countinous on and have opposite signs then there exists a number such as, .
You have, thus,
Find the critical points,
Thus, but since we have, thus there are no critical points (because it yields imaginary numbers). Because the function is always increasing. Meaning that it intersects the x-axis only once. Thus, there is only one real root.
Actually that is not necessarily true. It would have been correct to state that since,Originally Posted by ThePerfectHacker
We can make the function as large and as small as we like. Meaning that we can choose values such as it is negative and positive. Then apply the root location theorem.
Hello,Originally Posted by Susie38
I presume that you have to answer this question if a, b are real numbers (without any restrictions).
By the first derivative (compare ThePerfectHacker's answer) you can only calculate 2 turning points if a < 0 .
Place the maximum over the x-axis and the minimum below the x-axis and you'll get a maximum number of 3 intercepting points with the x-axis, that means you get a maximum fo 3 roots.
I've attached a diagram with a family of functions:
The red graphs show what happens if the value of b has been changed.
The black graphs show what happens when the value of a has been changed. The domain of a and b is [-2,2]. | <urn:uuid:e3a8a76d-a8b6-4607-bcde-a045cfb0c0af> | 2.9375 | 381 | Q&A Forum | Science & Tech. | 68.871312 |
Image: A vectorA vector is an object that has a magnitude and a direction. Geometrically, we can picture a vector as a directed line segment, whose length is the magnitude of the vector and with an arrow indicating the direction. The direction of the vector is from its tail to its head.
Image file: vector.png
Source image file: vector.svg
Source image type: Inkscape SVG
This image is found in the pages | <urn:uuid:6aba2f7d-572d-4ab1-8271-713f439730f6> | 3.515625 | 95 | Truncated | Science & Tech. | 48.31189 |
The latest Arctic Report Card was published yesterday at the American Geophysical Union’s Fall Meeting in San Francisco, and it makes grim reading. Apart from last summer’s new record low sea ice minimum, all the indicators of warming are pointing in the wrong direction. The Arctic is making a rapid transition to a new climate state. Highlights of the report (from the press release):
- Snow cover: A new record low snow extent for the Northern Hemisphere was set in June 2012, and a new record low was reached in May over Eurasia.
- Sea ice: Minimum Arctic sea ice extent in September 2012 set a new all-time record low.
- Greenland ice sheet: There was a rare, nearly ice sheet-wide melt event on the Greenland ice sheet in July, covering about 97 percent of the ice sheet on a single day.
- Vegetation: The tundra is getting greener and there’s more above-ground growth. During the period of 2003-2010, the length of the growing season increased through much of the Arctic.
- Wildlife & food chain: In northernmost Europe, the Arctic fox is close to extinction and vulnerable to the encroaching Red fox. Massive phytoplankton blooms below the summer sea ice suggest that earlier estimates of biological production at the bottom of the marine food chain may have been ten times lower than was occurring.
- Ocean: Sea surface temperatures in summer continue to be warmer than the long-term average at the growing ice-free margins, while upper ocean temperature and salinity show significant interannual variability with no clear trends.
- Weather: Most of the notable weather activity in fall and winter occurred in the sub-Arctic due to a strong positive North Atlantic Oscillation, expressed as the atmospheric pressure difference between weather stations in the Azores and Iceland. There were three extreme weather events including an unusual cold spell in late January to early February 2012 across Eurasia, and two record storms characterized by very low central pressures and strong winds near western Alaska in November 2011 and north of Alaska in August 2012.
It’s well worth digging down beyond the executive summary to look at the individual reports for key elements in the Arctic — there’s a lot of detail to digest, all of it fascinating, much of it sobering, if not downright scary. This is rapid climate change, happening now. I wonder if anyone in Doha will notice? | <urn:uuid:347dbdf0-a819-47b9-ad77-ce1dd9065895> | 2.9375 | 499 | Personal Blog | Science & Tech. | 38.859991 |
Meteor. As the term is commonly used, a meteor is a small celestial body that enters the atmosphere of the earth. To astronomers, however, a meteor is the streak of light such an object produces as it passes through the earth's atmosphere and the object itselfwhether in the atmosphere or in outer spaceis a meteoroid. This article uses the common definition.
Meteors that produce extremely bright streaks of light are called fireballs, and those that explode in the air, bolides. In popular usage, meteors are often referred to as falling stars, or shooting stars. Meteorites are meteors that reach the earth's surface.
Meteors travel at speeds ranging from 7 to 45 miles (11 to 72 km) per second relative to the earth and are visible only briefly as they travel through the upper atmosphere. Most meteors first become visible at heights of 50 to 75 miles (80 to 120 km). The friction between meteors and the air at these heights produces enough heat to vaporize the meteors' outer material and to cause the meteors and the air they pass through to glow. At heights of 35 to 50 miles (56 to 80 km) the meteors cease to be visible. By then, the larger ones have been slowed so they no longer glow, and the smaller ones have been completely vaporized. Some, called micrometeoroids, are so small that they are slowed by the atmosphere before they heat up enough to vaporize and glow. Micrometeoroids drift through the atmosphere like dust.
It is estimated that every day there are billions of meteors, although most of them cannot be seen. On a dark, clear night an observer can usually see five or more meteors an hour. More meteors can be seen after midnight than before because the earth, as it moves in its orbit, sweeps up meteoroids before it; after midnight an observer is on the side of the earth that faces the direction of the earth's orbital motion. Meteors are only rarely visible during daylight hours.
Studies of the paths taken by meteors through the atmosphere have shown that almost all of them were in orbit around the sun and therefore belonged to the solar system. (A few remain of questionable origin.) Meteors are thought to be the remains of comets and asteroids that have broken up. Most meteors are no larger than a grain of sand. A few, however, are extremely large, weighing many tons.
At times, large numbers of meteors fall in a short period. These occurrences are called meteor showers. Observations of as many as 60,000 meteors an hour have been made. All the meteors that form part of a shower travel in the same direction in parallel paths. Because of the effect of perspective, they seem to radiate from a single point in the sky. This point is called the radiant. Most meteor showers are named for the constellation in which their radiant is located. The radiant of the Leonids, for example, is in the constellation Leo.
Meteor showers are produced by swarms of meteoroids that travel around the sun in elliptical orbits that cross the earth's orbit. A meteor shower occurs when the earth passes through a swarm; the earth passes through a given swarm at the same time every year. A meteor shower may have more meteors some years than others, because meteoroid swarms are not spread out evenly in their orbits.
Meteoroid swarms are thought to be the debris from comets. Several swarms travel in the same orbits as known comets. In one case, a comet (Biela's Comet) failed to return at the expected time in 1872, and a meteor shower occurred instead.
|Important meteor showers|
|Shower||Date of peak||Period of activity||Parent body|
|Quadrantids||Jan. 4||Jan. 1 to Jan. 6||2003 EH1|
|Lyrids||April 22||April 16 to April 25||Comet Thatcher|
|Eta Aquariids||May 4||April 19 to May 28||Comet Halley|
|Perseids||Aug. 12||July 17 to Aug. 24||Comet Swift-Tuttle|
|Orionids||Oct. 21||Oct. 2 to Nov. 7||Comet Halley|
|Leonids||Nov. 17||Oct. 31 to Nov. 23||Comet Tempel-Tuttle|
|Geminids||Dec. 13||Nov. 27 to Dec. 18||3200 Phaethon|
|Ursids||Dec. 22||Dec. 17 to Dec. 26||Comet Tuttle| | <urn:uuid:7a0ba34c-8827-486f-9305-987f4c6e2caf> | 4 | 967 | Knowledge Article | Science & Tech. | 64.400951 |
Given any collection of permutations, we define two group algebra elements.
Notice that doesn’t have to be a subgroup, though it often will be. One particular case that we’ll be interested in is
so we have a nice factorization of this element.
Now if is a tableau, we define the associated “polytabloid”
Now, as written this doesn’t really make sense. But it does if we move from just considering Young tabloids to considering the vector space of formal linear combinations of Young tabloids. This means we use Young tabloids like basis vectors and just “add” and “scalar multiply” them as if those operations made sense.
As an example, consider the tableau
Our factorization lets us write
And so we calculate
Now, the nice thing about is that if we hit it with any permutation , we get . | <urn:uuid:c7e68219-a737-4b55-8cd2-863e3eaac9b6> | 2.765625 | 194 | Tutorial | Science & Tech. | 45.477122 |
When Laplace's equation is expressed in terms of orthogonal curvilinear co-ordinates, it takes the familiar form
where (λ, μ, ν) are the co-ordinates, and dλ/h1, dμ/h2, dν/h3 the elements of arc in the directions in which only λ, μ, or ν respectively increase.
In the application to solids of revolution and potential problems associated with them, we invariably choose ν as the azimuthal angle φ of rotation about the axis of symmetry, and then h3 = 1/ρ, where ρ is distance from that axis. If λ and μ are chosen as identical with ξ and η in the complex substitution
z + iρ = F(ξ) = F(ξ + iη),
where F is any function, and the axis of revolution is that of z, we have further,
h1 = h2 = h
where h is the common value, and Laplace's equation becomes
and takes an especially convenient form for problems involving boundary conditions on the surfaces of revolution ξ = constant or η = constant.
The only solutions of (2) which have been effectively discussed hitherto are either (a) product solutions of the form
V = f1(ξ)f2(η)f3(φ),
where each f contains only one variable, or (b) of the form
V = f1(ξ)f2(η)f3(φ)F(ξ, η),
where F is a mixed function of two variables. Type (a) includes all the usual forms in terms of spherical and spheroidal harmonics in their various general aspects, while the toroidal functions and special functions relating to two spheres belong to (b).
We shall show that every problem in (a) can furnish the solution of another in (b), in an analytical sense, which is in fact a representation of the familiar geometrical process of inversion, but which is not readily derived from it in any direct manner. The precise analytical, as distinct from geometrical, correspondence between the two problems is of some importance. | <urn:uuid:bcee3209-ad43-4a4a-9185-ddfa63a6da94> | 2.78125 | 470 | Academic Writing | Science & Tech. | 34.650443 |
Science Fair Project Encyclopedia
In mathematics, a geometric progression (also inaccurately known as a geometric series, see below) is a sequence of numbers such that the quotient of any two successive members of the sequence is a constant called the common ratio of the sequence.
Thus without loss of generality a geometric sequence can be written as
where r ≠ 0 is the common ratio and a is a scale factor. Thus the common ratio gives a family of geometric sequences whose starting value is determined by the scale factor. Pedantically speaking, the case r = 0 ought to be excluded, since the common ratio is not even defined; but the sequence that is always 0 is included, by convention.
For example, a sequence with a common ratio of 2 and a scale factor of 1 is
- 1, 2, 4, 8, 16, 32, ....
and a sequence with a common ratio of 2/3 and a scale factor of 729 is
- 729 (1, 2/3, 4/9, 8/27, 16/81, 32/243, 64/729, ....) = 729, 486, 324, 216, 144, 96, 64, ....
and finally a sequence with a common ratio of −1 and a scale factor of 3 is
- 3 (1, −1, 1, −1, 1, −1, 1, −1, 1, −1, ....) = 3, −3, 3, −3, 3, −3, 3, −3, 3, −3, ....
Compare this with an arithmetic progression showing linear growth (or decline) such as 4, 15, 26, 37, 48, .... Note that the two kinds of progression are related: taking the logarithm of each term in a geometric progression yields an arithmetic one.
A geometric series is, strictly speaking, the sum of the numbers in a geometric progression. Thus the geometric series for the n terms of a geometric progression is
Multiplying by equals since all the other terms cancel in pairs.
Rearranging gives the convenient formula for a geometric series:
An interesting relationship for a geometric series is given by:
- (1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 + 256 +...)
can be written as
- (1 + 2 + 4)(1 + 8 + 64 +...)
Since a geometric series is a sum of terms in which two successive terms always have the same ratio,
- 4 + 8 + 16 + 32 + 64 + 128 + 256 + ...
is a geometric series with a common ratio of 2. This is the same as 2 × 2x where x increases by one for each number. It is called a geometric series because it occurs when comparing the length, area, volume, etc. of a shape in different dimensions.
The sum of a geometric series whose first term is a power of the common ratio can be computed quickly with the formula
which is valid for all natural numbers m ≤ n and all numbers x≠ 1 (or more generally, for all elements x in a ring such that x − 1 is invertible). This formula can be verified by multiplying both sides with x - 1 and simplifying.
Using the formula, we can determine the above sum: (29 − 22)/(2 − 1) = 508. The formula is also extremely useful in calculating annuities: suppose you put $2,000 in the bank every year, and the money earns interest at an annual rate of 5%. How much money do you have after 6 years?
- 2,000 · 1.056 + 2,000 · 1.055 + 2,000 · 1.054 + 2,000 · 1.053 + 2,000 · 1.052 + 2,000 · 1.051
- = 2,000 · (1.057 − 1.05)/(1.05 − 1)
- = 14,284.02
An infinite geometric series is an infinite series whose successive terms have a common ratio. Such a series converges if and only if the absolute value of the common ratio is less than one; its value can then be computed with the formula
which is valid whenever |x| < 1; it is a consequence of the above formula for finite geometric series by taking the limit for n→∞.
Also useful is the formula
which can be seen as x times the derivative of the infinite geometric series. This formula only works for |x| < 1, as well.
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details | <urn:uuid:4eee6a60-15b0-4045-bb8f-34aa51cb8b2f> | 3.953125 | 972 | Knowledge Article | Science & Tech. | 83.074073 |
The large stellar association cataloged as
NGC 206 is
nestled within the dusty arms of neighboring
Andromeda (M31), 2.5 million light-years distant.
Seen near the center of
gorgeous close-up of the southwestern
Andromeda's disk, the bright, blue
NGC 206 indicate its youth.
Its youngest massive stars are less than 10 million years old.
Much larger than the clusters of young stars
in the disk
of our Milky Way galaxy known as open or galactic clusters,
spans about 4,000 light-years.
That's comparable in size to the giant stellar nurseries
NGC 604 in nearby spiral
M33 and the
in the Large Magellanic Cloud.
Bob and Janice Fera | <urn:uuid:e9a0c0d5-aa9e-48b4-9271-35eee56ae1b7> | 2.953125 | 164 | Knowledge Article | Science & Tech. | 69.297262 |
Video transcript: Reindeer see a weird and wonderful world of ultraviolet light
Video shows images of Arctic reindeer, their low light habitat and an image of the 3-man team to start with, in this continuous video slideshow
Lead researcher Professor Glen Jeffery narrates
In the Arctic reindeer we have got one animal who has adapted itself so well to its visual environment it is using bits of visual information that we can't see and it makes sense to the animal.
My name is Glen Jeffery and I am from University College London and I'm a visual scientists. I am interested in vision, how we see the world and how other animals see the world because very often they see a very different world from us.
Video shows a boat on land in low, scattered light conditions making the image cast very blue
The Arctic reindeer is an animal that has an extreme visual world because for three months of the year it is completely dark and for three months of the year it is bright for 24 hours a day. When you are in the Arctic you get a lot of scattered light particularly when the sun is just around the horizon. When that happens the scattered light becomes very very blue. For us, we stop seeing in the violet but for some animals, very very few animals, they see down into the ultra violet, into a much much deeper world. We don't see it. So one of the questions that we had was do these animals up in this environment actually use UV? Do they use ultraviolet light?
Video shows images of the reindeer and themselves as they follow the herd using an all-terrain vehicle on half-tracks
So far the only mammals that we know that do that are actually a few rodents and a few bats; it is not common, it's very uncommon. The interesting finding that we had was that Arctic reindeer see deep into the UV. By using UV light that we cannot see at all they're actually managing to avoid the animals that are likely to eat them, look at the world and see objects they want to eat a hell of a lot more clearly coming through the snow and the ice and they are also able to look at the signals and messages left by their own type of animal and different types of animal by being able to find their urine.
We went up to the Arctic with two cameras sitting next to one another. One camera could see in the UV and one camera saw the normal visual world that we did. So the idea would be that we see what we see and then sitting next to it, hopefully we see what the reindeer sees.
To do this properly we wanted to follow a herd of animals through the snow seeing what they see and the great advantage here was that the Norwegian army gave us a 'go anywhere' vehicle that we could pile all our equipment into and follow a herd. The answer was really interesting.
Video shows two images: Animal urine on snow in normal light, which just shows up and the same image using UV light which makes the urine show up dark grey on the white snow
The world in UV is rather different but it's different in a subtle way. First thing was that their urine was very very dark in UV so what we would see as a very very light smear on the snow they saw in enhanced contrast - it was almost dark grey on white. So they could see where other animals had been peeing and maybe that is a big advantage for them because they'll then go over it and they'll smell it, they'll derive information about the other animal from being able to identify it.
Video shows lichen in normal light which looks pale grey
The other thing that was actually quite impressive was that many of the lichens that they love, some of them would do almost anything for a certain kind of lichen. When you shine UV light on it, it goes black so if you have got a little bit of lichen sticking up through the snow it looks like a bit of grey on a white background but not to the reindeer - that's actually black on white, it's a hard contrast image so that really helps it.
An interesting thing also, is that these animals, when you look at them in UV, when you point the UV camera specifically at them, you actually find that their fur absorbs UV and also they'll see their predators. A natural predator for them up there historically would have been the wolf and the wolf's fur absorbs a lot of UV.
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Earth Sciences: Year In Review 1998Article Free Pass
These earthquakes were located in almost real time by the U.S. Geological Survey (USGS) in Golden, Colo. This service, which began in 1928, made a major leap forward in 1958 when a rudimentary program was developed to calculate earthquake epicenters by computer, and it made another in the early 1960s when the U.S. government developed and deployed standard seismograph systems to 125 sites around the globe. Although it had been continually upgraded and modernized, the network provided only a portion of the data used in the location process. One of the items tabulated was the number of station reports used in each determination. This number frequently reached 200 and for a very large shock exceeded 500. The USGS routinely located 15,000-20,000 events each year. The depth, seismic moment, several types of magnitude, and other factors were included with each epicenter.
In spite of the large number of active stations, there were areas of the Earth that were not well covered because its surface is about 70% water. To help alleviate this problem, the Scripps Institution of Oceanography, La Jolla, Calif., and the Woods Hole (Mass.) Oceanographic Institution formed an international group, the Ocean Seismic Network. They planned to install 20 permanent ocean-bottom seismometers in remote locations to augment data from existing stations. In 1998, with funding from the Ocean Drilling Program and the National Science Foundation, scientists successfully installed a pilot station south of Hawaii that included a seismometer in a borehole, a broadband seismometer on the ocean floor, and another in the bottom mud. The stations were designed to include magnetometers, acoustic arrays, climate and ocean current instruments, and tsunami (tidal wave) detectors.
Studies during the year were aimed at determining the nature of the upwelling of melt materials of the undersea mantle beneath the East Pacific Rise. The Mantle Electromagnetic and Tomography Experiment, funded by the U.S. National Science Foundation, engaged scientists from nine institutions from around the world. Fifty-one ocean-bottom seismometers were deployed in the region, where the plates were spreading at a rate of 15 cm (6 in) per year, among the fastest anywhere on the Earth. After researchers gathered seismic data for six months, an array of more than 40 instruments that measured the electromagnetic fields generated in the Earth by particle currents in the ionosphere was installed, and data from the instruments were gathered for another year. The detection of slow seismic velocities across the array indicated the existence and concentration of melt materials and passive, plate-driven flow, and the conductivity measurements revealed whether the melt areas were connected. The melt distribution was found to be asymmetrical, with a concentration to the west of the crest of the East Pacific Rise. This seemed to indicate that the magma forms over a relatively broad area and then is concentrated to go to the surface along the narrow ridge to form crust. Investigators were not sure whether the asymmetry was due to thermal structure or geologic composition.
The well-defined seismic discontinuity at a depth of 410 km (255 mi) was widely believed to be due to a high-pressure phase change in olivine, but recent studies revealed that the increase in velocity in some areas was too large to be explained by that mechanism. Two scientists from Ehime University, Matsuyama, Japan, postulated that the problem was in the assumption of a fixed composition for olivine. They concluded that olivine must, in varying degrees, exchange its iron and magnesium with other minerals in the mantle such as garnet majorite. In this manner the olivine would become denser and sustain a higher velocity.
Volcanoes had long been recognized as prone to landslides because of the relatively unconsolidated materials that form their slopes, but it was usually assumed that an eruption was required before the slopes would give way. Recently, however, researchers at Open University in the U.K. discovered that an eruption is not necessary. While studying a long-dormant volcano in Nicaragua, Benjamin van Wyk de Vries found that two conditions make a volcano susceptible to such slides. First, the crevices must be filled with hot acidic gas, which weakens the rocks. Second, the weight of the mountain tends to push the weakened material outward at the base. This is usually a gradual, evenly distributed ring of material around the base, but if the terrain is such that the force is directed asymetrically, an avalanche may occur. Since dormant volcanoes were not monitored, de Vries feared that many populated areas of the world were in unrecognized danger of landslides.
The Tsunami Warning System, centred on Oahu in Hawaii, was founded by the U.S. Coast and Geodetic Survey after the devastating wave produced by the magnitude-7.8 Aleutian earthquake on April 1, 1946. The effectiveness of the system depended on the difference between the velocity of the sea wave, up to 965 km/h (600 mph), and the seismic wave velocities, ranging up to 29,000 km/h (18,000 mph). Through timely reporting of seismograph readings from stations of the international circum-Pacific network, large shocks could be located in minutes, and, if the epicentre was in an area where a tsunami might be generated, warnings could be issued to all points. This system worked well many times and saved hundreds of lives. Since only a small percentage of likely large shocks produce tsunamis, however, there was a problem with false alarms. To reduce this problem a network of tide stations was queried to determine whether a wave had actually been generated. This method was time-consuming, however, and its effectiveness was limited by communications difficulties.
The National Oceanic and Atmospheric Administration had by 1998 begun to set up a supporting network of ocean-bottom pressure recorders and seismic detectors in several areas believed likely to generate tsunamis. The data from these instruments were to be used to develop methods of detecting and locating tsunamis in real time and thus allow more warning time and the calculation of more exact arrival times and wave heights.
The Ocean Drilling Program (ODP) continued its long-term objectives of establishing the history of sea-level change and its influence on sedimentation. ODP Leg 174A began drilling 129 km (80 mi) east of Atlantic City, N.J. Some 800 cores were obtained and then submitted for laboratory studies. The information was then to be combined with the oxygen isotopic record. The coordinated analyses of these data were expected to provide a more accurate history of global sea-level change.
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From the standpoint of planetary detections, the small red stars called M dwarfs are all but ideal. Their size is an advantage because radial velocity and transit methods should find it easier to pull the signature of smaller planets out of the statistical noise. Not so long ago, that wouldn’t have seemed important because the search for terrestrial worlds seemed confined to G- and K-class stars not too different from our Sun. But more and more theory is piling up as to why a terrestrial-sized planet in the habitable zone of an M dwarf could harbor life.
So these are important stars, especially when you add in the fact that they account for 75 percent or so of all the stars in the Milky Way (that statistic is admittedly subject to change as we learn more about other stars, especially brown dwarfs). And that makes the recent flare on EV Lacertae quite interesting. Some sixteen light years from Earth, the star is young (300 million years), dim (shining with one percent of Sol’s light) and small (its mass and diameter being a third that of the Sun). And although far too dim to pick out with the naked eye under normal circumstances, the recent monster flare it emited would have made it easy to see.
Once again we can thank the Swift satellite for the detection. Although intended to hunt gamma ray bursts (GRBs), Swift often does double duty, as in the recent case of a supernova caught just as it exploded. When the satellite detected the EV Lacertae flare, detailed measurements followed. The flare was thousands of times stronger than solar flares in our own system, of a magnitude that Rachel Olsten (NASA GSFC) calls “unprecedented.” Osten adds: “This star has a record of producing flares, but this one takes the cake.”
Image : An artist’s depiction of the incredibly powerful flare that erupted from the red dwarf star EV Lacertae. Credit: Casey Reed/NASA.
So now we are developing the ability to watch flares on other stars as they develop, with the help of Swift and other space-based resources like Chandra and XMM-Newton. That’s useful data as we ponder life’s chances around M dwarfs, where intense magnetic activity can generate flares like this one, capable of damaging a planetary atmosphere. This seems to be the thorniest issue of all, for although we can develop plausible scenarios for habitable climates on such worlds, their sheer proximity to their parent star could make frequent flares an evolutionary wildcard, if not prohibiting the development of life altogether. The range of flare activity possible on M dwarfs — some are far more benign than others — should be a factor as we fine-tune our target lists for future space-based observatories. | <urn:uuid:e1d8ebf1-4026-4707-97c6-6f9ed19c3f84> | 3.96875 | 572 | Knowledge Article | Science & Tech. | 45.055811 |
What's New Restoring an ancient Great Lakes fish WMUK – Kalamazoo, MI (5/22) Sturgeon have lived in the Great Lakes longer than humans have walked the earth, but the ancient fish now need our help to stay here. A new project is trying to do that by rebuilding habitat for lake sturgeon in Michigan’s Kalamazoo River.
State rejects dune road request WZZM-TV – Grand Rapids, MI (5/13) A western Michigan lawmaker says the state Department of Environmental Quality has rejected a proposal to build a 1,200-foot private driveway across a strip of government-owned Lake Michigan dune habitat.
Restoring wetlands step in Lake Erie plan The Columbus Dispatch (5/6) A project restoring 2,500 acres into wetlands along western Lake Erie is a small but important step toward creating a new home for wildlife and cleaning water runoff from farm fields that feeds harmful algae, conservation organizations say.
Great Lakes salmon are the focus of new video series (4/4) Underwater footage of wild-spawned salmon in Michigan streams show the challenges faced by young fish. Participants in MDNR’s Salmon in the Classroom program can use this series as a refresher on the salmon’s life cycle and Great Lakes ecology.
The Great Lakes ecosystem's sand dunes, coastal marshes, rocky shorelines, lakeplain prairies, savannas, forests, fens, wetlands and other landscapes contain features that are either unique to or best represented within the Great Lakes Basin, according to a 1994 biodiversity report by The Nature Conservancy.
For example, the Great Lakes sand dunes are one of the largest systems of freshwater sand dunes in the world, ranging from high, forested dunes and linear dune ridges commonly backing sand beaches, to active dune fields covering thousands of acres, such as those near Ludington, Michigan. Native dune species include the dune thistle (Cirsium pitcheri), Houghton's goldenrod (Solidago houghtonii) and the Lake Huron locust (Trimerotropis huroniana).
Some of the last, best examples of the continent's most imperiled savanna communities lie along the lakeplains of the southern Great Lakes, near Windsor, Ontario, and along the southern shores of Lake Michigan, in particular. Also occurring in the lakeplains is a unique community of arctic and prairie species that persists from the colder, then dryer climatic periods following glaciation. Often called by the Scandinavian name "alvar," these communities are scattered in an arc that follows the Niagaran Escarpment from upper Michigan through southern Ontario and to northwestern New York. Never widespread, this remarkable open bedrock landscape remains intact in only a handful of places.
The extensive freshwater marshes of the Great Lakes coasts also are unique in ecological character, size and variety. They range from small wetlands nestled in scattered bays to extensive shoreline wetlands such as those of southwestern Lake Erie, freshwater estuaries such as the Kakagon Sloughs of northern Wisconsin and the enormous freshwater delta marshes of the St. Clair River.
EPA Great Lakes Restoration Initiative U.S. Environmental Protection Agency This U.S. EPA Great Lakes National Program Office webpage provides up-to-date information on the President's budget proposal to allocate $475 million towards an EPA-led interagency Great Lakes Restoration Initiative.
Habitat Advisory Board Great Lakes Fishery Commission The Great Lakes Fishery Commission has long recognized that habitat quality and quantity relates directly to determining which measures will ensure maximum sustained productivity of Great Lakes fish.
Habitat Management Programs U.S. Fish and Wildlife Service This index provides information about the various habitat management programs in the National Wildlife Refuge System.
NOAA Restoration Center National Oceanic and Atmospheric Administration (NOAA) The NOAA Restoration Center enhances living marine resources to benefit the nation's fisheries by restoring their habitats.
Prairies in the Prairie State Presented by the Openlands Project and the Illinois State Museum, this exhibit discusses the environment, plants and animals, and human interaction of the Midewin Tallgrass Prairie
Prairies of Illinois Illinois Department of Natural Resources Illinois is known as the "Prairie State," part of the vast grassland in central North America. Learn about the remnants of tallgrass prairie and related flora and fauna through this series of maps, photos and historic overviews.
Education Habitattitude U.S. Fish and Wildlife Service Adopt a conservation mentality: Protect our environment by not releasing unwanted fish and aquatic plants into the wild. Find out what you can do to help this growing problem on this site.
Living By Water Project The mission of the Project is "working towards healthier human and wildlife habitat along the shorelines of Canada", and to help shoreline residents obtain information to protect their property, prevent problems like erosion, and protect water quality, fish and wildlife habitat. | <urn:uuid:73cbc645-8d71-410d-9138-540ebbe5b96f> | 2.875 | 1,016 | Content Listing | Science & Tech. | 25.558305 |
Changing drivers of deforestation provide new opportunities for conservation
Tropical deforestation claimed roughly 13 million hectares of forest per year during the first half of this decade, about the same rate of loss as the 1990s. But while the overall numbers have remained relatively constant, they mask a transition of great significance: a shift from poverty-driven to industry-driven deforestation and geographic consolidation of where deforestation occurs. These changes have important implications for efforts to protect the world's remaining tropical forests in that environmental lobby groups now have identifiable targets that may be more responsive to pressure on environmental concerns than tens of millions of impoverished rural farmers. In other words, activists have more leverage than ever to impact corporate behavior as it relates to deforestation. According to research by Tom Rudel of Rutgers University, from the 1960s through the 1980s, a large proportion of deforestation was the result of government policies promoting rural development, including agricultural loans and road construction. These initiatives, particularly in Brazil and Indonesia, drove large-scale deforestation by small landholders. Today, economic stability, an increasingly global financial market, and a worldwide commodity boom are conspiring to create a ripe environment for development by the private sector. While centrally planned development projects and poverty alleviation programs were once the engines of road construction and colonization schemes, the political impetus today for large infrastructure projects comes from industry interests seeking to facilitate access to international markets. Surging demand for grain, driven by the thirst for biofuels and rising standards of living in developing countries, are fueling the trend.
Although many are dismayed by what they see as greater capacity to destroy forests, the recent shift from poverty-driven deforestation to industry-driven deforestation may offer new opportunities for rainforest conservation in that it is easier for pressure groups to target corporations and enterprises rather than tens of millions of poor farmers who are simply trying to put food on the table for their families. A good example can be seen in Greenpeace's Slaughtering the Amazon report released this past June. The report linked some of the world's most prominent brands — Nike, Toyota, Prada, and others — to destruction of the Amazon rainforest. The fallout from the report was immediate. Some of the world's largest beef and leather buyers suspended contracts with suppliers associated with Amazon forest clearing. The Brazilian government announced a crackdown and fines, raided the offices of powerful cattle companies, and called for a review of loan programs. Government ministers joined the private sector in demanding new chain-of-custody controls for suppliers to ensure that cattle products were not contributing to deforestation. The largest cattle producers and traders soon responded with a moratorium on Amazon deforestation and a promise to implement improved supply-chain tracking mechanisms. The Brazilian cattle industry may now be on the cusp of transitioning from being the world's largest single driver of deforestation to a critical component in helping slow climate change.
|Since the 1990s deforestation has become increasingly concentrated. Recently published research by Matt Hansen of South Dakota State University suggests an even more dramatic shift in recent years. His work, which is based off of high resolution satellite imagery, shows that Brazil and Indonesia accounted for 61 percent of tropical deforestation between 2000 and 2005, rather than the 43 percent reported by the U.N. Food and Agriculture Organization (FAO). |
But while the shift in Brazil and some other parts of the world would seem to herald a shift towards greater concern over environmental performance among the largest drivers of deforestation, difficulties remain. Some markets — notably India and China but even in the U.S. and Europe in some cases — there is less consumer preference for environmentally-friendly goods. Further, "greenwashing," or the misrepresentation of the environmental qualities of a product, also presents challenges for efforts to meaningfully reduce industry's impact on the planet. Finally, industrial activities can often create a strong economic impetus for infrastructure development that further promotes forest clearing. However an emerging emphasis on the values that ecosystems afford humanity may take some pressure off forests by creating opportunities for corporations to profit from protecting — rather than destroying — wildlands. For example, the proposed Reducing Emissions from Deforestation and Degradation (REDD) mechanism could provide incentives for traditional forest destroyers to embrace forests as valuable assets. The net result could be enterprise-driven preservation of wild lands. Of course, the key to the success of this effort is ensuring that rural populations and forest dwellers share in the proceeds. Without their partnership, deforestation is not going to disappear. For a more nuanced discussion of this concept, take a look at New strategies for conserving tropical forests, a paper I wrote with Dr. William Laurance last year.
| To be effective, green NGOs should be careful to avoid "blackwashing" or using the same tactics corporations use to blatantly misrepresent environmental realities. Lying to the public undermines the credibility of activist groups and undermines support for protecting the environment, doing long-term damage to the cause. |
Labels: animals, ecology, endangered species, environment, forest
Employing dogs to save endangered species and places.
For millennia dogs have been helpers to humans: they have herded and protected livestock, pulled sleds, hunted game, led the blind, located people after disasters, and sniffed out drugs. Now a new occupation can be added: conservation aide. Working Dogs for Conservation (WDC) was co-founded by Megan Parker in 2000: the idea, to use dogs' impeccable scent capabilities for conservation initiatives, appears so logical and useful when Parker talks about it, one is surprised it took environmentalists so long to realize the potential of dogs. "Our mission is to benefit science and conservation by working with detection dogs. We help save wildlife by supporting conservation efforts to gather information on rare species in an accurate and non-invasive way," explains Parker. "We train dogs to detect rare samples and they excel at finding trained target odors from endangered species scats to invasive weeds on a huge landscape." WDC has worked on a wide variety of projects across all regions of the United States. For example, they worked with the Wildlife Conservation Society (WCS) on The Carnivore Connectivity Project where the dogs located scats of wolves, cougars, black and grizlly bears along the Idaho-Montana border. "Thanks to our team of dogs, we’re proud to report that this work led to the protection of critical wildlife corridors by closing more than 40 miles of roads and preventing a development in a sensitive area," says Parker. The group has also helped survey the comeback of moose in the Adirondacks and located threatened plants in Oregon and invasive snails in Hawaii, among many other projects. Parker says for each of these projects the dog's nose is key: "canids have evolved as amazing scenting machines. Their noses, and the vast majority of their brains, are built to detect and discriminate small quantities of odor, picking out single scents among the millions of other scents in the environment. Dogs have been selectively bred for thousands of years to serve myriad human purposes, yet most dogs retain the architecture and ability to scent incredibly well." WDC has even worked overseas: detecting snakes in the tropics of Guam, locating wild dog and cheetah scat in Kenya, and working with the Andean Cat Project in Argentina to find one of the world's rarest felines. "We have really learned from our mistakes while working internationally, where the work periods are typically short and the work intense in unfamiliar territory where we have to find dogs and train handlers, which is different from how we usually work," Parker says. Despite such challenges, Parker believes that the program could easily be implemented in other countries.
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Different thermal conductivity of gases and liquids.
Thermal conductivity is the ability of any substance to conduct heat.
It's similar to different substances having different electrical
conductivity (i.e. different resistance)
Experiment 1: Thermal conductivity
Two equally sized rods. One made of metal, the other one of glass. Take
one end into hand. Heat other end with lighter/candle/bunsen
burner/whatever you have. You will notice that the metal rod will heat
up much faster than the glass one.
Metal has a better thermal conductivity than glass. Therefore, heat
gets transferred much faster.
Experiment 2: Subjective Sensation
Bucket of water at room temperature. Put one hand in bucket. Hold for
several minutes. You will notice that the hand in the water will feel
colder than the other one.
Water has a better thermal conductivity than air. The heat from your
hand gets transferred faster to the water in the bucket than to the
air. Therefore, it's "colder", though both substances have the same
Similar experiment can also be conducted with e.g. a metal surface vs.
a plastic surface. The metal will always feel colder, because heat from
your body will be dissipated faster.
Now, what about that spray can? What's that got to do with it?
A spray can consists of three parts: Metal body, compressed gas and
some liquid (paint, deodorant, whatever). We can omit the other parts,
like cap etc.
When you take the can into your hand, heat from your body is conducted
to the metal body (good conductivity=fast transfer) and then to the
compressed gas inside (bad conductivity=slow transfer).
Now, when you shake that can, the liquid within gets dispersed into
tiny drops. Some of these drops don't flow right back to the bottom,
but instead cling to the metal can. This affects heat flow, of course:
transfer). Almost like sticking the hand into water. You know the
|dumb , question|
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|DUMB Question - are PV Solar Cells using the Photoelectric effect to generate current ?||unamerican||Physics Forum||1||08-19-2005 01:08 PM|
|Dumb Guy Question, Elemental Isomers||Charles||Chemistry Forum||17||02-22-2004 06:50 AM|
|Dumb question||Charlie Johnson||Chemistry Forum||23||09-08-2003 05:21 PM| | <urn:uuid:39d15e8b-9e2c-493f-b28e-e728033a861a> | 3.546875 | 637 | Comment Section | Science & Tech. | 62.199872 |
Chandrayaan-1 will map the Moon at high resolution and different wavelengths to help understand the origin and evolution of our only natural satellite. The mission will make a detailed study of the Moon's mineralogy, and will generate a digital 3D atlas of the Moon's surface. The mission will also look for water ice around the poles.
Once the spacecraft reaches the closest point to the Moon along the lunar transfer orbit, the major 'lunar orbit insertion' manoeuvre will decelerate it to allow the Moon's gravity to capture it into an elliptical lunar orbit. A series of manoeuvres will progressively lower the altitude of Chandrayaan-1 around the Moon until it reaches its final 100 km-high circular orbit.
Three of these instruments were provided by Europe: the X-ray and infrared spectrometers (C1XS and SIR-2) for mineralogical and chemical mapping of the surface, and the SARA instrument, the first lunar experiment dedicated to studying the interaction between the solar wind and the lunar surface. The delivery to ISRO of the three instruments, provided by the UK, Germany and Sweden, respectively, was coordinated by ESA under an agreement signed with ISRO in 2005.
The Chandrayaan-1 Imaging X-Ray Spectrometer (C1XS) was developed by the Rutherford Appleton Laboratory (RAL) in the UK in collaboration with the ISRO Satellite Centre, Bangalore. It will measure the abundance of magnesium, aluminium, silicon, iron and titanium over the surface of the Moon.
The SMART Near-Infrared Spectrometer (SIR-2) was developed by the Max Planck Institute for Solar System Science, Germany. It will explore the mineral resources of the Moon, the formation of its surface features and the different layers of the Moon's crust.
The Sub-kiloelectronvolt Atom Reflecting Analyser (SARA) was developed by the Swedish Institute of Space Physics in collaboration with the Space Physics Laboratory of the Vikram Sarabhai Space Centre in Thiruvananthapuram, India. It will study the way the Moon's surface interacts with the solar wind, and the surface's magnetic anomalies.
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Laser pulses at relativistic intensities (more than 1018 W/cm2) create fast electrons which penetrate and exit the target. In case of a solid target - generally a foil- the target rear surface develops a cloud of electrons. These electrons are usually referred to as an electron sheath, and their huge electric field in the order of 10 billions of volts per cm accelerates ions away from the surface. The accelerated ions are normally surface contaminations, and the dominating species are protons, which are provided by adhered water or carbon-hydrides. This acceleration is perpendicular to the rear surface of the foil and is called target normal sheath acceleration (TNSA). Figure 1 shows a simplified sketch of the process; ref.: Cowan 2004.
Laser generated proton beams show a variety of interesting properties:
Image of a laser generated proton beam created at Lawrence Livermore National Laboratory with the Petawatt installation in 1999.
Image of radiochromic film showing the imprint of a proton beam, which has been shaped by grooves on the target rear surface. This proves the capability of shaping as well as the high beam quality (low emittance).
Examples of radiography achieved with laser generated proton beams: The left portion shows a radiograph of an ICF capsule. The right part shows an assembly with thin plastic film made visible behind a tantalum cover. The lines on the lower section are 60µm copper wires (performed at the 100TW facility of LULI in Palaiseau, France).
Possible scenario for proton driven fast ignition: Protons are generated in a production target (a), which is protected from the hohlraum (d) radiation by two gold shields (b,c), ; ref.: Geissel 2005. | <urn:uuid:b2e863a7-b0ec-468c-ae99-83a8e7b0a0e0> | 3.4375 | 370 | Knowledge Article | Science & Tech. | 37.619881 |
Foraging Ecology of the Leatherback Turtle
The leatherback turtle is a powerful ocean traveler that ranges from the Arctic Circle to the edges of the Antarctic convergence zone. This unique pelagic reptile spends most of its life at sea, but females haul out onto tropical beaches every two to four years to lay their eggs. Much has been learned about the animals reproductive biology from studies conducted on nesting beaches, where the females, eggs, and hatchlings are easily accessible, yet little is known about leatherbacks in the marine environment, where they remain elusive and difficult to study. The need to achieve a better understanding of this part of the animals life history has become increasingly urgent as Pacific populations continue to decline to the brink of extinction, despite intense conservation efforts on the nesting beaches. The Pacific Leatherback Recovery Plan (http://swfsc.nmfs.noaa.gov/PRD/Seaturtle/) has identified the need to identify forage areas, to determine marine habitat needs, and to describe migratory patterns among the highest priorities for action. Monterey Bay is one of the first index areas to have been established for in-water studies of this species.
|Leatherback turtles aggregate in Monterey Bay in late summer. photo William J. Douros for NOAA/MBNMS
Leatherbacks have been known to occur in Monterey Bay for some time, but it was not until 2000 that we achieved an exciting breakthrough with our first attempts to capture foraging animals (see Ecosystem Observations 2000). Prior telemetry studies had been limited to post-nesting movements of females tagged on nesting beaches.
We attached satellite transmitters to two adult females in September 2000 and tracked the animals as they migrated west; we continued to receive data from one of the turtles for eighteen months as she crossed the Pacific to the Mariana Trench, just north of the main nesting beach in North Papua, when she turned and began swimming east toward the central Pacific. Despite making this long migration back to the nesting areas in Papua, this turtle appears not to have nested, raising questions about factors that might influence timing of nesting and migratory behavior.
This pilot study was expanded in 2001 and is now a permanent component of the National Marine Fisheries Service (NMFS) Southwest Fisheries Science Centers Sea Turtle Research Program, which partners with the Monterey Bay National Marine Sanctuary, Moss Landing Marine Laboratories, University of California Santa Cruz, and Hubbs-Sea World Research Institute. Having established the capacity to capture animals at sea, we increased field effort in 2002 and have now deployed transmitters on a total of thirteen animals, including three males. All were adults, with the largest one weighing 580 kilograms. Genetic results from six samples analyzed so far indicate that the animals are from western Pacific nesting stocks, most likely North Papua, Papua New Guinea, or the Solomon Islands.
We are currently tracking eight turtles (six females and two males), which were tagged in September 2002. As in previous years, the turtles moved rapidly westward after release. One of the turtles has turned around approximately 800 kilometers offshore and recently returned inshore and is currently just south of Monterey Bay. One of the females tagged in 2001 traveled north and foraged around the Gulf of the Farallones for two months before she began a westward migration.
Satellite telemetry is one aspect of a multi-faceted approach to studying the foraging ecology of leatherbacks that involves genetic, biochemical, behavioral, ecological, and oceanographic studies. In addition to looking at long-range movement and pelagic migrations, we are beginning to gain new insights into how leatherbacks interact with the marine environment by focusing on the Monterey Bay ecosystem.
Monterey Bay is one of several areas along the central California coast where leatherbacks aggregate during late summer. Other areas where we have observed the highest densities using aerial surveys include waters off Point Reyes, south of Point Arena, and in the Gulf of the Farallones. These areas represent upwelling shadows or regions where larval fish, crabs, and gelatinous organisms are retained during upwelling relaxation.
|Figure 1. Leatherback sea turtle sightings in Monterey Bay
We hypothesize that leatherback turtle abundance is linked to the hydrographic retention of zooplankton and subsequent concentration of scyphomedusan prey (jellies and similar animals) in these coastal areas during relaxation of upwelling-favorable winds. When upwelling diminishes at the end of summer, sea surface temperatures along the coast tend to rise markedly. Observations suggest that leatherbacks move into Monterey Bay along with the 14-15o C water. The frequency, duration, and relaxation of upwelling-favorable winds can influence food web development in this region, including the occurrence and concentration of leatherback prey, such as scyphomedusae. Observations suggest that leatherbacks seek out the sea nettle (Chrysora spp.) to feed on in Monterey Bay, even though they have several different types of jellyfish to choose from. A better understanding of the factors that influence distribution and abundance of this jellyfish may help shed light on the local movement and dive behavior of the leatherbacks in the bay. )
In 2001 locations where turtles were seen during fine-scale aerial surveys corresponded to the 50- to 100-meter depth contours throughout the bay (Figure 1). Local hydrographic features may have influenced prey distributions, and future work will attempt to map turtles behavior against a three dimensional matrix of physical and biotic factors that describe its forage habitat. In 2002 pop-up archival tags (PATs) were attached to four of the turtles in addition to the satellite-linked dive recorders previously used. These PATs were programmed to collect fine-scale dive and temperature data that are archived and transmitted to orbiting satellites once the PAT releases and pops to the surface. Once these data are analyzed we will be able to look at foraging behavior on a finer scale than has previously been possible.)
The sanctuary will continue to play a key role in the recovery effort for Pacific leatherbacks by providing a unique venue to study foraging animals. Monterey Bay is perhaps one of the best-studied marine ecosystems in the world, with a wealth of data now available from various projects monitoring the physical characteristics of the marine environment using remote observing systems, such as the deep-ocean moorings deployed by Monterey Bay Aquarium Research Institute that report subsurface temperature, salinity, and current information, or ship-based transect studies across the sanctuary. We will be able to integrate physical and biological oceanographic data from these studies with results from our telemetry and aerial survey work to understand better how the leatherbacks interact with their ocean environment. We will also be able to develop new models to predict their oceanic distribution in order to help formulate appropriate at-sea conservation measures to complement the ongoing efforts on the nesting beaches.
Peter H. Dutton1, Scott Benson(1), and Scott A. Eckert(2)
(1)NOAA-National Marine Fisheries Service, Southwest
Fisheries Science Center
(2)Hubbs-Sea World Research Institute | <urn:uuid:8435590d-8ca8-43fe-bbe3-b3c28d3b3ff6> | 3.921875 | 1,469 | Academic Writing | Science & Tech. | 23.501461 |
are enzymes that elongate DNA molecules by adding nucleotides to the 3' end of a strand. The typical reaction involved is a nucleophilic attack. (Abeles, 1992
Polymerases in E. coli
The primary role of DNA Polymerase I (abreviated Pol I) in DNA replication is the removal of RNA primers present on the newly replicated DNA strand and the subsequent filling in of the resulting gaps between Okazaki fragments with nucleotides complementary to those present on the sequences of the template strand corresponding to the gap. Pol I does not possess a mechanism for linking these nucleotides with phosphodiester bonds, resulting in nicks along the sequence over which Pol I is active. (Lehman et al. 1958
) DNA polymerases rarely make errors, making fewer than one mistake per 10 million nucleotides added (Kunkel and McCulloch ,2008
). The nick left behind is connected by Ligase
DNA Polymerase II is responsible for repairing mutations in DNA molecules. When DNA polymerase II was replaced with a mutant version of Pol II, the mutation rate in the organism was more than 3 times that in an organism with a functioning Pol II. (Foster et al. 1995
)DNA Polymerase II is only used in DNA repair.
Pol III is composed of three sub units: α, є, and Ѳ. In addition to being a 5'-> 3' polymerase, it has both 3'→5' exonuclease activity and 5'→3' exonuclease activity. The 5'-> 3' exonuclease activity must start hydrolyzing the 5' end of a single-strand DNA polymer, but can continue hydrolysis into a double-stranded region (McHenry and Crow 1978
Discovery of DNA Polymerases
The enzyme DNA polymerase was discovered in the year 1955 Lehman 2003
. The first DNA polymerase, called DNA polymerase I or Pol I, was isolated from E. coli
by Arthur Kornberg during his time as the chairman of the Department of Microbiology at the Washington University School of Medicine. Subsequently, he and his colleages succeeded in elucidating a large portion of the mechanism of DNA replication in E. coli, for which Kornberg would be jointly awarded the 1959 Nobel Prize in Physiology or Medicine (Berg and Lehman 2007
) (Nicole et al. 2005
Kornberg and his team treated the E. coli
with streptomycin to obtain two different fractions of the cell extracts. The supernatant was free of any nucleic acids and the precipitate did contain nucleic acid. Each of these two fractions were divided further into two more fractions according to heat stability. The heat labile fraction of the precipitate was determined to be the DNA polymerase because of its capacity to catalyze the formation of phosphdiester bonds. (Lehman 2003
) DNA polymerase II, (Pol II), was discovered in 1970, 14 years after the original Pol I was isolated in E. coli
. Kornberg and Malcolm L. Gefter made the discovery while studying the role of Pol I in E. coli
DNA replication. Pol I was originally believed to be the only DNA polymerase taking part in DNA replication, but that was falsified through a 1969 study by British biologist John Cairns and his lab assistant Paula De Lucia. Cairns was able to isolate a distinctly different mutant form of Pol I. Treatment of this mutant form allowed Kornberg and Gefter to isolate Pol II
(Tessman and Kennedy 1994
DNA polymerase reaction
All DNA-dependent DNA polymerases operate in approximately the same way. The substrates are the 3'-hydroxyl end of the growing DNA strand, and a deoxyribonucleoside triphosphate or dNTP.
The oxygen in 3'-OH makes a nucleophilic attack on the alpha phosphate (the one closest to the sugar) of the dNTP. The oxygen has two orbitals full of electrons that aren't involved in bonding, and they are attracted to large nuclei with multiple protons, such as the phosphate nucleus. When these electrons move toward the phosphorus nucleus, there is the possibility of forming a covalent bond between the phosphorus and that oxygen. However, in order for this to happen, one of the oxygens already bound to the phosphorus must be displaced. Normally, this would be quite difficult, as the covalent bond between the oxygen and phosphorus is quite stable. In this case, though, one of those oxygens already bound to the phosphorus is also bound to another phosphate – see the figure above. In fact, it's bound to a group of two phosphates, called pyrophosphate (and also a Mg2+ ion, which is a cofactor for the enzyme). This group of two phosphates is an example of what is known as a "good leaving group." If the pyrophosphate group leaves the dNTP, it will quickly react with water to form two inorganic phosphates (Pi). Since pyrophosphate is so unstable and reactive, it doesn't last long at all in water; this means that its concentration is always low. Think of the reactions like this:
--> dNMP + pyrophosphate
---> dNMP + 2 Pi
Since the pyrophosphate concentration is always quite low, the reaction equilibrium is shifted forward; in other words, it's relatively likely that the pyrophosphate will come off the dNTP. That means that it's pretty easy to displace the oxygen in that pyrophosphate from the alpha phosphorus, so the nucleophilic attack succeeds. The result is that the dNMP (a deoxyribonucleoside monophosphate, or nucleotide) becomes covalently bound to the 3' carbon of the sugar at the end of the DNA strand, thus lengthening the strand by one nucleotide. Then the process repeats (Abeles, 1992
Why can't this happen at the other end of the strand?
Why 3' -> 5' won't work
Assume that the active site of DNA polymerase is going to orient the incoming dNTP so that a 5'-3' bond would form (rather than joining the 5' carbon of the dNTP to the 5' end of the DNA strand, upside down). So instead, the dNTP would be coming down toward the 5' end of the existing strand with its 3' OH down, to make a nucleophilic attack on the 5' phosphate of the DNA strand.
In order for the nucleophilic attack to succeed, an oxygen has to leave the phosphate on the 5' end of the DNA strand, but there's nothing else attached to it. It's not a good leaving group at all, so this reaction isn't favored. Therefore, DNA always grows from the 5' to 3' direction, by adding nucleotides onto the 3' end of the existing strand .
Abeles RH, Frey PA, Jencks WP. Biochemistry. Boston:Jones and Bartlett, 1992.
Berg P, & Lehman IR. (2007). Retrospective: Arthur Kornberg (1918-2007). Science (New York, N.Y.). 318(5856), 1564.
Foster et al. (1995). Proofreading-defective DNA polymerase II increases adaptive mutation in Escherichia coli . Biochemisty, 92(17).
Kunkel, T.A., & McCulloch S.D. (2008). The fidelity of DNA synthesis by eukaryotic replicative and translesion synthesis polymerases. Cell Research, 18, (http://www.nature.com/cr/journal/v18/n1/abs/cr20084a.html)
Lehman, I. R.; Bessman, M. J.; Simms, E. S.; Kornberg, A. (July 1958). "Enzymatic Synthesis of Deoxyribonucleic Acid. I. Preparation of Substrates and Partial Purification of an Enzyme from Escherichia coli". J. Biol. Chem. 233 (1): 163–170
Lehman I.R., (2003). "Reflections: Discovery of DNA Polymerase". The Journal of Biological Chemistry. Vol. 278. No. 37. Issue Sptember 12. 34733-34738]Full text
McHenry, C.S., C. Weldon (July 1978). "DNA polymerse III of Escherichia coli
: purification and identification of subunits".The J. Biol. Chem. 254 (5): 1748-1753. Full PDF Text
Nicole Kresge, Robert D. Simoni, Robert L. Hill (2005). Arthur Kornberg's Discovery of DNA Polymerase I. J. Biol. Chem. 280, 46. Full text
Tessman I., & Kennedy M. (1994). DNA polymerase II of Escherichia coli in the bypass of abasic sites in vivo. Genetics, 136, 439-448. Full PDF Text | <urn:uuid:90b7235e-e0fa-4587-a855-7d199f753010> | 3.296875 | 1,927 | Knowledge Article | Science & Tech. | 58.929896 |
This fact sheet explores the science of climate and weather through the lens of the Australian Alps. Here the various forms of precipitation are described as well as past, present and projected future weather patterns.. Ozone depletion, ultra violet radiation and climate change are also explored. A glossary and list of references is included.
Download the factsheet
- Climate and weather of the Australian Alps (PDF - 330KB)
- Climate and weather of the Australian Alps (DOCX - 312KB)
High Stakes - by Matthew Higgins
Australia's snow country occupies a tiny part of the nation's landmass, yet it is highly significant. In this short film, National Museum of Australia Senior Curator Matthew Higgins explores the Snowy Mountains in winter. Join Matthew on a cross-country ski trip as he visits historic huts, tells about natural heritage, enjoys the aesthetic power of the white peaks, and ponders the threat of climate change. Will Australia lose its snow country? If it does, what will be the impacts, not just on skiers, but on whole species, and even on our food bowl, the Murray-Darling Basin? | <urn:uuid:419349c3-5e6e-4b06-a86c-81c0c73fe282> | 3.265625 | 231 | Content Listing | Science & Tech. | 50.385 |
|Every programmer has his or her opinion as to what information should be included with the program code. Most programmers add comments with their code in order to remind themselves, and anyone else, what the code does and how it does it. When deciding what information to include ask yourself what you would need to be told about the program if someone else had written the program and now you were asked to run and maintain it. |
Most of the programs that you write will have more than one page of code. Each page of code will be saved as a PHP program file. (filename.php3) There are two places in the program file where you will want to add some informational comments. | <urn:uuid:464b2b8f-5810-4c02-af39-f83ed9697b00> | 2.90625 | 138 | Truncated | Software Dev. | 57.629268 |
Reinhardt’s scholarship focuses on the history of industrial research, the emergence of instrumentation, and chemistry’s links to physics, biology, medicine, and technology.
Join us for a tasty history lesson in the art and science of re-creating Revolutionary-era ales.
From Chemical Heritage
Conflicts in Chemistry: The Case of Plastics
Science on Tap
Detail of Chemistry, Engraved by J. Chapman
Portrait of F. W. Clarke.
Donato d’Eremita, Dell' elixir vitae (1624)
Prototype for the Perkin-Elmer Model 12 Infrared Spectrophotometer
Sears Chemistry Set, ca. 1958
Detail of The Chemist, Edward Allen Schmidt, 19th century
Comparison of Fertilizers, Fixed Nitrogen Research Laboratory
Otto Tachenius, Hippocrates chymicus (1677)
Celluloid Trading Card
©2010 Chemical Heritage Foundation | <urn:uuid:779054ba-7f1a-493c-869c-0b0e017992a4> | 2.6875 | 207 | Content Listing | Science & Tech. | 25.920172 |
Before Einstein, it was known that a beam of light pushes against matter; this is known as radiation pressure. This means the light has momentum. A beam of light of energy E has momentum E/c. Einstein used this fact to show that radiation (light) energy has an equivalent mass.
Consider a cylinder of mass M (see accompanying figure-"energy"). A
pulse of light with energy E is emitted from the left side. The cylinder
recoils to the left with velocity v=E/(Mc). If the mass of the cylinder
is large, it doesn't move far before the light reaches the other side.
So, the light must travel a distance L, requiring time t=L/c. In this time,
the cylinder travels a distance x=vt=[E/(Mc)](L/c).
Einstein reasoned that the center of mass of an isolated system doesn't just move on its own. So, the motion of the cylinder must be compensated by the motion of some other mass. Let's assume the light has mass m. Then, Mx=mL, since the cylinder moves x to the left and the light moves L to the right. Substituting the expression for x given above, the equation can be simplified to E=mc2.
From the fact that light has momentum, Einstein showed that light energy has the characteristics of mass also. In other words, energy has inertia. It turns out that all energy has this feature. That's because one form of energy can be transformed into another. So, if one kind of energy has this characteristic, all forms of energy do.
Einstein himself explains the meaning of E=mc2 in this sound clip.
The fine print: The word proof is in quotes above because this is not truly a rigorous proof. Simplifications and approximations were made to facilitate understanding. Some of these are easy to eliminate at the expense of a little more algebra. Some of them are of a more fundamental nature and require significant modification of the gedankenexperiment. However, the basic concepts are correct and this "proof" conveys the essence of the connection between mass and energy.
Back to the Syllabus
to the home page.
This page is copyright ©1997-2005 by G. G. Lombardi. All rights reserved. | <urn:uuid:ce2ddfef-01e2-48c8-93f9-1df4e35b7b95> | 4.28125 | 479 | Knowledge Article | Science & Tech. | 63.031974 |
Not quite. We’d have to get out of Earth first. In a billion years, our Earth would no longer be habitable.
Our best option, according to Ray Villard, news director for the Hubble Space Telescope, is for us to
… come up with a strategy to build artificial mini-planets – essentially flying city-states — that would modify their orbits to migrate along with the petulant Sun’s expanding and shrinking habitable zone. As the white dwarf cools, the wagon train of space habitats would move inward. Raw materials would be harvested from in-falling comets and asteroids. Explorers would be free to travel outward to visit surviving planets and moons. Given our passion for survival, bolstered by super-technology, the future for mankind could truly stretch on indefinitely, beyond even the life of the Sun.
That’s hope for you.
(Source: Living in a Dying Solar System) | <urn:uuid:c6a795a1-04e0-44a6-b763-66b54fc39a7d> | 2.90625 | 192 | Personal Blog | Science & Tech. | 52.709728 |
Bartusiak, Marcia F., Burke, Barbara, Chaikin, Andrew, Greenwood, Addison, Heppenheimer, T.A., Hoffman, Michelle, Holzman, David, Maggio, Elizabeth J., Moffat, Anne Simon. "6 Clocks in the Earth? The Science of Earthquake Prediction." A Positron Named Priscilla: Scientific Discovery at the Frontier. Washington, DC: The National Academies Press, 1994.
The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
A Positron Named Priscilla: Scientific Discovery at the Frontier
FIGURE 6.5Schematic diagram showing inferred motion on the San Andreas fault during the Loma Prieta earthquake. Along the southern Santa Cruz Mountains segment of the fault, the Pacific and North American plates meet along an inclined plane that dips approximately 70 degrees southwest. Plate motion is mostly accommodated by about 6.2 feet of slip along a strike of this plane and by 4.3 feet of reverse slip, in which the Pacific plate moves up the fault and overrides the North American plate. The amounts of fault slip and vertical surface deformation were determined from geodetic data. (Modified from a figure by M. J. Rymer. Reprinted from USGS, 1989, p. 6.)
deep underground (see Figure 6.5). The fault slip itself did not reach the surface to produce a trace, but surface waves achieved a magnitude of 7.1. As reported by the USGS, the ground shaking collapsed sections of the Bay Bridge and Interstate 880 (in Oakland); began fires in San Francisco's Marina district; ultimately caused 62 deaths and 3757 injuries; destroyed 963 homes; damaged another 18,000, leaving 12,000 temporarily homeless; and ultimately will have cost some $10 billion. These statistics rate it as one of America's most serious natural disasters. As such, it raises questions about how long-term forecasting fits into the American political infrastructure, since in the context of work done by Ellsworth, Agnew, Sieh, and many others, the USGS in the Science article classified Loma Prieta as "an anticipated event."
Californians have felt thousands of earthquakes over the decades, | <urn:uuid:e31b11c8-c9b6-4592-b5af-869bb1ce1b49> | 3.203125 | 486 | Truncated | Science & Tech. | 45.689082 |
The speed of sound is a term used to describe the speed of sound waves passing through an elastic medium.
The speed varies with the medium employed (for example, sound waves move faster through water than through air), as well as with the properties of the medium, especially temperature.
The term is commonly used to refer specifically to the speed of sound in air.
At sea level, at a temperature of 21 degrees Celsius (70 degrees Fahrenheit) and under normal atmospheric conditions, the speed of sound is 344 m/s (1238 km/h or 770 mph).
The speed varies depending on atmospheric conditions; the most important factor is the temperature.
Humidity has little effect on the speed of sound, nor does air pressure by itself.
Air pressure has no effect at all in an ideal gas approximation.
This is because pressure and density both contribute to sound velocity equally, and in an ideal gas the two effects cancel out, leaving only the effect of temperature.
Sound usually travels more slowly with greater altitude, due to reduced temperature.
For more information about the topic Speed of sound, read the full article at Wikipedia.org, or see the following related articles:
Recommend this page on Facebook, Twitter,
and Google +1:
Other bookmarking and sharing tools: | <urn:uuid:3f3d9fbf-8d45-44cc-ae23-ae5bc9925345> | 4.3125 | 262 | Knowledge Article | Science & Tech. | 45.407049 |
We ran into a problem at first with our plots when we plotted the mean versus the variance of our data and we found that it was not linear like we expected it to be. After some thought, we found that the variance of one of our images does not show the true variance in the data since the image itself has low and high intensities corresponding to the brightness of the image itself. What we want is how the measured intensities at each pixel varies due to noise. By subtracting two identical images taken at different times we can remove the variations in intensity due to just the image itself and isolate the sum of the noise. Now we can calculate the variation of the images by using the difference image which only contains the noise. However, when we take the difference between the two images we have to remember to take into account how the error propagates when we combine two sets of data, each with its own inherent errors. This will be discussed in Section 4.3.1. | <urn:uuid:b0131c19-cc7a-423a-b262-4456c803fb28> | 3.46875 | 197 | Academic Writing | Science & Tech. | 50.875261 |
Astronomers have announced the discovery of a planet with about three times the Earth’s mass orbiting the nearby red dwarf star Gliese 581. That in itself is cool news; a planet like that is very hard to detect.
But the amazing thing is that the planet’s distance from the star puts it in the Goldilocks Zone: the region where liquid water could exist on its surface!
Gliese 581 is about 20 light years away, and astronomers think the planet in the habitable zone is one of at least six in that star system. The new exoplanet orbits much closer to its star than Earth orbits the sun, but its star is a red dwarf, so it needs to be closer to stay warm enough to support liquid water.
But just how like the Earth is this new world? And what does it mean for the prevalence of ‘Goldilocks” planets out there? To find out, read the rest of the post at Bad Astronomy. And check out the scientists’ paper about Gliese 581 (pdf).
Bad Astronomy: Possible earthlike planet found in the Goldilocks zone of a nearby star!
80beats: Astronomers Find 2 Giant Exoplanets Locked in an Endless Dance
80beats: Kepler’s Early Results Suggest Earth-Like Planets Are Dime-a-Dozen
80beats: Temperate, Jupiter-Sized World Resembles the Planets of Our Solar System | <urn:uuid:8269e4a4-730b-498f-906c-5078bf0480a6> | 3.421875 | 309 | Personal Blog | Science & Tech. | 59.1655 |
3.9.1 Fundamental types
6 Values of type bool are either true or false.*42) [Note: there are no signed, unsigned, short, or long bool types or values. ] As described below, bool values behave as integral types. Values of type bool participate in integral promotions (4.5).
*42) Using a bool value in ways described by this International Standard as ‘‘undefined,’’ such as by examining the value of an uninitialized automatic variable, might cause it to behave as if is neither true nor false.
4.5 Integral promotions
4 An rvalue of type bool can be converted to an rvalue of type int, with false becoming zero and true becoming one.
5 These conversions are called integral promotions. | <urn:uuid:044168cd-19f4-48a1-b2ed-99271332b3dd> | 2.90625 | 162 | Documentation | Software Dev. | 53.669672 |
Figure 4.15.7 illustrates the conformal mapping of the strip onto the whole -plane cut along the real axis from to −1 and 1 to , where and (principal value). Corresponding points share the same letters, with bars signifying complex conjugates. Lines parallel to the real axis in the -plane map onto ellipses in the -plane with foci at , and lines parallel to the imaginary axis in the -plane map onto rectangular hyperbolas confocal with the ellipses. In the labeling of corresponding points is a real parameter that can lie anywhere in the interval .
In the graphics shown in this subsection height corresponds to the absolute value of the function and color to the phase. See also About Color Map.
The corresponding surfaces for , , and are similar. In consequence of the identities | <urn:uuid:51e2b5fc-c516-4257-8398-f31fd0fb2100> | 3.25 | 169 | Documentation | Science & Tech. | 45.821061 |
NASA will hold a news conference at 11 a.m. PST on Thursday, Dec. 2, to discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life.
After much speculation, what we all now know was revealed at the press conference:
Researchers conducting tests in the harsh environment of Mono Lake in California have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes arsenic for phosphorus in its cell components.
Source: xkcd. "According to a new paper published in the journal Science, reporters are unable to thrive in an arsenic-rich environment."
A discovery that according to NASA means that "the fundamental knowledge about what comprises all known life on Earth" has changed and that "the definition of life has just expanded". Hyperbolic much? The paper that describes these new findings was published in advance yesterday in Science, find the link at the bottom of the post, and there are indications that associated papers with more details will be published in the coming months.
It's been exciting to follow the reporting pretty much directly as it's happened and I've been Tweeting and Facebooking the story unfolding almost in real time since yesterday. All in all this story has been a great exercise in observing how online science reporting works and how blogs and social media works within this context.
By this time yesterday the furore was on:
Phil Plait's Bad Astronomy blog was very early in giving a measured but enthusiastic summary; "NASA's real news: bacterium on Earth that lives off arsenic!", so enthusiastic that a few errors, now corrected, made their way in. For the best and most sensible summary and background I would point to Carl Zimmer's excellent post "Of Arsenic and Aliens", which was posted simultaneously with NASA's press conference. Soon enough SciTech news sites started picking up the story: WIRED titled its report "NASA Finds New Arsenic-Based Life Form in California". New Scientist sank to new and lower lows with the headline "Arsenic-based bacteria point to new life forms", although they do a good job at presenting the doubts that remain about the finding. The Guardian's science pages started tracking the story pretty soon as well, posting links to the different reports as they were coming in: "Nasa unveils new life form: Bacteria that thrive on arsenic".
The somewhat fallacious tendency to call this a "new life form" becomes really apparent at this point, no doubt fueled by the sensationalistic NASA press conference and its astrobiology angle. Many reports give the impression that the arsenic-thriving bacteria represent some sort of "alternative" branch of life, or a primordially ancient form of life that we weren't aware of, which is incorrect, or that the bacteria were discovered incorporating arsenic into their cellular mechanisms in their natural environment, which is also incorrect.
Here in Sweden the major newspapers also ran spectacular headlines about the "new life form": Dagens Nyheter wrote "New life form discovered in a lake of arsenic", and Svenska Dagbladet followed with the not quite as wrong "The bacteria that lives on arsenic".
An interesting aspect in the stream of information is how the story itself has evolved since the first reports and the press conference. At first it wasn't clear from many reports if they had actually proven that the arsenic-thriving bacteria incorporated arsenic instead of phosphorus into their DNA, and what exactly the evidence was. Some reports presented doubts about the evidence, some didn't, but several have had to append or correct their information. Many still remain tentative about whether or not the evidence is sufficient to claim that arsenic was incorporated into the bacteria's DNA, not to speak of other cellular components that include phosphorus such as the cell membranes and ATP. This is all "science as usual", but the "science-report-by-press-conference" strategy doesn't exacly mirror the long and tentative process of scrutiny that all scientific findings have to go through even after publication.
I think that perhaps our demands for a clear and instant message are too high?
Aside from Carl Zimmer's post, I can recommend the following science blogger's takes on the story: Greg Laden's "NASA's new organism, the meaning of life, and Darwin's Second Theory", which focuses on the evolutionary implications, and PZ Myers' "It's not an arsenic-based life form", which very clearly describes the actual experiments and findings. Ed Yong's "Mono Lake bacteria build their DNA using arsenic (and no, this isn’t about aliens)" also adds some background to the field of study of arsenic-loving microorganisms and warns against going overboard with the conclusions.
Notice how RealScientists(TM) avoid writing about "new life forms".
In the end though, there's no doubt this is an exciting and significant finding, and the reason this will become THE scientific story of 2010, at least attention-wise, is not just because of the shrewd media strategy. Yet I can't help but being a bit cynical about the whole THIS WILL CHANGE EVERYTHING 4-EVER!!!!1 hype, especially since it very easily can lead to widespread misconceptions about biology.
Wolfe-Simon, F., Switzer Blum, J., Kulp, T.R., Gordon, G.W., Hoeft, S.E., Pett-Ridge, J., Stolz, J.F., Webb, S.M., Weber, P.K., Davies, P.C.W., Anbar, A.D., Oremland, R.S. (2010). A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus Science : 10.1126/science.1197258 | <urn:uuid:d9071274-ff4f-499c-9c78-013732b06be8> | 3.21875 | 1,190 | Personal Blog | Science & Tech. | 51.963574 |
||This article needs additional citations for verification. (February 2010)|
A mathematical joke is a form of humor which relies on aspects of mathematics or a stereotype of mathematicians to derive humor. The humor may come from a pun, or from a double meaning of a mathematical term, or from a lay person's misunderstanding of a mathematical concept. These jokes are frequently inaccessible to those without a mathematical bent.
Mathematician and author John Allen Paulos in his book Mathematics and Humor described several ways that mathematics, generally considered a dry, formal activity, overlaps with humor, a loose, irreverent activity: both are forms of "intellectual play"; both have "logic, pattern, rules, structure"; and both are "economical and explicit".
Pun-based jokes
Some jokes use a mathematical term with a second non-technical meaning as the punchline of a joke.
- Q. What's purple, commutes and is worshipped every other evening?
- A. A bi-nightly venerated abelian grape. (A pun on Finitely-generated abelian group.)
- Person 1: What's the integral of 1/cabin with respect to cabin?
- Person 2: A log cabin.
- Person 1: No, a houseboat; you forgot to add the C!
The first part of this joke relies on the fact that the primitive (formed when finding the antiderivative) of the function 1/x is log(x). The second part is then based on the fact that the antiderivative is actually a class of functions, requiring the inclusion of a constant of integration, usually denoted as C—something which calculus students may forget. Thus, the indefinite integral of 1/cabin is "log(cabin) + C", or "A log cabin plus the sea", i.e., "A houseboat."
This type of joke was featured in an episode of The Simpsons, "Bart the Genius." Bart cheated on an exam and as a result was placed into a gifted school. However, since he did not have previous exposure to calculus, he was unable to see the humor in this exchange with his teacher:
- So y = r cubed over 3. And if you determine the rate of change in this curve correctly, I think you'll be pleasantly surprised. [The class, except for Bart, laughs] Don't you get it, Bart? Differential dy = 3 r squared dr over 3, or r squared dr, or r dr r.
Jokes with numeral bases
- There are only 10 types of people in the world: those who understand binary, and those who don't.
This joke mocks non-humorous and often divisive/polarizing phrases that begin with "there are two types of people in the world...". The humor of the joke relies on an ambiguous meaning of the expression 10, which in the binary numeral system is equal to the decimal number two.
Another pun using different radices, sometimes attributed to computer scientists, asks:
The humor lies in the similarity of the abbreviation for October/Octal and December/Decimal, and the coincidence that the two representations equal the same amount (31 Octal is Decimal).
Stereotypes of mathematicians
Some jokes are based on stereotypes of mathematicians tending to think in complicated, abstract terms, causing them to lose touch with the "real world".
Many compare mathematicians to other professions, typically physicists, engineers, or the "soft" sciences in a form similar to an Englishman, an Irishman and a Scotsman. The joke generally shows the other scientist doing something practical, while the mathematician does something less useful such as making the necessary calculation but not performing the implied action. Some examples:
- A physicist, a biologist and a mathematician are sitting in a street café watching people entering and leaving the house on the other side of the street. First they see two people entering the house. Time passes. After a while they notice three people leaving the house. The physicist says, "The measurement wasn't accurate." The biologist says, "They must have reproduced." The mathematician says, "If one more person enters the house then it will be empty."
Mathematicians are also shown as averse to making sweeping generalizations from a small amount of data, even if some form of generalization seems plausible:
- An astronomer, a physicist and a mathematician are on a train in Scotland. The astronomer looks out of the window, sees a black sheep standing in a field, and remarks, "How odd. All the sheep in Scotland are black!" "No, no, no!" says the physicist. "Only some Scottish sheep are black." The mathematician rolls his eyes at his companions' muddled thinking and says, "In Scotland, there is at least one sheep, at least one side of which appears to be black from here some of the time."
Jokes may also poke fun at particular habits attributed to mathematicians, such as overuse of the word "obvious":
- A mathematics professor is giving a lecture to his students and writing equations on a blackboard. He says, "At this point, it is obvious that this equation can be derived from that one." He pauses, then turns his back on the class and spends an hour filling the entire blackboard with more work. Finally he turns and announces triumphantly, "Yes, I was correct; it is obvious!"
A classic joke involving stereotypes is the "Dictionary of Definitions of Terms Commonly Used in Math Lectures." Examples include "Trivial: If I have to show you how to do this, you're in the wrong class" and "Similarly: At least one line of the proof of this case is the same as before."
Non-mathematician's math
This category of jokes comprises those that exploit common misunderstandings of mathematics, or the expectation that most people have only a basic mathematical education, if any.
- A museum visitor was admiring a Tyrannosaurus fossil, and asked a nearby museum employee how old it was. "That skeleton's sixty-five million and three years, two months and eighteen days old," the employee replied. "How can you know it that well?" she asked. "Well, when I started working here, I asked a scientist the exact same question, and he said it was sixty-five million years old—and that was three years, two months and eighteen days ago."
Mock mathematics
A form of mathematical humor comes from using mathematical tools (both abstract symbols and physical objects such as calculators) in various ways which transgress their intended scope. These constructions are generally devoid of any substantial mathematical content, besides some basic arithmetic.
Mock mathematical reasoning
A set of equivocal jokes applies mathematical reasoning to situations where it is not entirely valid. Many of these are based on a combination of well-known quotes and basic logical constructs such as syllogisms:
Premise I: Knowledge is power. Premise II: Power corrupts. Conclusion: Therefore, knowledge corrupts.
Another set of jokes relate to the absence of mathematical reasoning, or misinterpretation of conventional notation:
That is, the limit as x goes to 8 from above is a sideways 8 or the infinity sign, in the same way that the limit as x goes to three from above is a sideways 3 or the Greek letter omega.
The "d's" from the first part of the equation are cancelled out and leave only one over x times x, equaling one. The first and last part of the equation are correct: the derivative of a first degree variable is 1, however the intermediate process is not mathematically sound, as "d" is not an algebraic expression but an operator.
Calculator spelling
Calculator spelling is the formations of words and phrases by entering a number and turning the calculator upside down. The words can be accompanied by stories involving numbers that lead to the solution. For example: "142 workers and 154 civilians fought over 69 oil fields for 5 days. What did they fight over?" 14215469 x 5 = 71077345, which, when read upside down, appears roughly to be "ShELL OIL." This appears correctly only when the open-top '4' is used by the calculator.
Math limericks
This is read as follows:
- A dozen, a gross, and a score
- Plus three times the square root of four
- Divided by seven
- Plus five times eleven
- Is nine squared and not a bit more.
Doughnut and coffee mug topology joke
An oft-repeated joke is that topologists can't tell a coffee cup from a doughnut, since a sufficiently pliable doughnut could be reshaped (by a homeomorphism) to the form of a cup by creating a dimple and progressively enlarging it, while shrinking the hole into a handle.
See also
- [Mathematics and Humor by John Allen Paulos]
- Matt Parker, math stand-up comedian
- Dana O'Briain: School of hard sums
- Dave Gorman - stand-up math comedy
- Weisstein, Eric W., "Abelian Group", MathWorld., citing Renteln, P. and Dundes, A. "Foolproof: A Sampling of Mathematical Folk Humor." Notices Amer. Math. Soc. 52, 24-34, 2005.
- polyb (April 6, 2005). "Quick and Witty!". Physics Forums. Retrieved February 28, 2013.
- Nestler, Andrew. "r dr r". Retrieved 2010-01-12.
- Calculus Humor, Dictionary of Definitions of Terms Commonly Used in Math Lectures from Calculus humor
- Xu, Chao (2008-02-21). "A mathematical look into the limit joke". Retrieved 2008-04-19.
- "Math Mayhem". Lhup.edu. Retrieved 2011-06-29.
- Differential Equations: A Dynamical Systems Approach : Higher-Dimensional Systems. Books.google.com. 1995-03-30. Retrieved 2011-06-29.
Further reading
- Paul Renteln and Alan Dundes (2004-12-08). "Foolproof: A Sampling of Mathematical Folk Humor" (PDF). Notices of the AMS 52 (1). | <urn:uuid:da443479-1c20-4758-8e26-98e30c4de9fc> | 3.265625 | 2,169 | Knowledge Article | Science & Tech. | 51.543102 |
This article has been moved to the location below
Music is what feelings sound like! Friday, Sep 7 2007
Nuclear Ice Age? Sunday, Jun 3 2007
ancient and atomic bombs and fission and fusion and gurudev and half life and hitxp and ice age and iceage and India and indian and laser and Mahabharat and mahabharatha and nuclear and nukes and radiation and thermonuclear and tritium and vedas and vedic and vega and WMD 9:54 pm
This post is the next part of my previous post ‘Ancient Nuclear War‘
Many people have asked me a sensible question about ancient nuclear wars. If it were really true that ancient Mahabharata war was a nuclear war, then where is the leftover radiation?
Well, a very good question indeed. I love enquiring deep into things
Nuclear bombs leave traces in the form of nuclear radiation which may last from few hundred to few thousand years depending on the half life of the nuclear fuel used and produced in the explosions. The larger the nuclear bomb, the more the leftover radiation!!
Well, but this is definitely not the case with thermonuclear bombs. Thermonuclear bombs are based on hydrogen and hence do not leave any radiational remnants. Tritium used in thermonuclear bombs has a half life of about only 10 years!
Nuclear explosions are used in modern thermonuclear weapons to generate high temperature required to start the fusion chain of hydrogen. But compared to equally destructive nuclear weapons, thermonuclear weapons leave very small amount of nuclear radiation from its fission based core.
Moreover, if the ancients had used some other technology (other than nuclear fission, say for ex: lasers) to initiate fusion reaction in thermonuclear weapons, then any question of left over radiation is almost completely ruled out!!
Now let’s get back to the proof that we have about ancient nuclear war. As stated in ‘Ancient Nuclear War‘ the very first proof is a clear description of the effects of nuclear weapons itself used in the war.
Then we have the huge casualty caused in this ancient world war which lasted only for about 18 days! Both warring sides were almost completely wiped out in this war. No side got a decisive victory. This itself is a striking feature of a nuclear war as we all know. In a nuclear war there are no winners, there are only survivors, if at all.
Next, the large amount of glass is an indication of a nuclear explosion or of any high temperature activity followed by immediate cooling. As found in modern nuclear testing sites like in Nevada desert, etc glass is a natural by-product of high temperature nuclear explosions which melts the clay and sand and cools it immediately afterwards to below its glass transition temperature.
Such glass covered areas have been discovered under the ancient site of Mohen Jo Daro of Indus valley civilization. Then we have the example of libyan desert glass spread over an area of 100 sq km, etc
Now one might argue that this is also possible in case of asteroid impacts! Well, yes, but then asteroid impacts live a crater proportionate to the impact energy, in other words proportionate to the amount of glass available!
In case of libyan desert we can again argue that probably the crater has been closed by the desert sand! But what about Mohen Jo Daro?
The previous ice age ended about 10000 years back. Vedas mention about vega being the pole star. Vega was pole star during the previous ice age. Could it be that, the previous ice age itself was a result of the thermonuclear mahabharata war?
A large scale thermonuclear world war where all countries of that period on earth took part in, causing a global destruction where both the warring sides were wiped out completely (estimated loss of life runs upto 14 billion!), well the Mahabharata war itself as a result of its nuclear weapons might have caused a new ice age to arrive.
The dust clouds resulting out of nuclear explosions prevent sunlight from entering into the earth’s lower layers and hence cool down the earth, and in large scale nuclear strikes these dust clouds stay on for years to come there by causing a nuclear ice age!
Was the previous ice age a nuclear ice age?
Will we witness another nuclear ice age? | <urn:uuid:f8ec3d8b-91e5-4f88-807e-e71625c38ea0> | 2.84375 | 899 | Personal Blog | Science & Tech. | 48.239556 |
Interspersed amongst the sprawling urban development of southern California are remnants of a once-widespread habitat type, coastal sage scrub. This semi-arid habitat is home to nearly 100 species that are either endangered, threatened, or of conservation concern, including the secretive and declining Southern California rufous-crowned Sparrow (Aimophila ruficeps canescens).
Coastal sage scrub habitat, home of the California Rufous-crowned Sparrow.
© Scott Morrison
When housing developments, roads, and shopping centers are built in or near coastal sage scrub, they create “islands” of habitat dispersed in an urban sea. For many birds, such habitat fragmentation creates a serious problem. Small patches of suitable habitat have less food and more predators, such as raccoons and house cats, which infiltrate from adjacent developed areas. Consequently, bird nesting success is often reduced. Over time, bird populations in fragments may disappear entirely.
Rufous-crowned sparrows are much less common in fragmented patches of habitat than in large, intact areas. To find out why rufous-crowned sparrows were declining in smaller patches, Scott Morrison of The Nature Conservancy and Douglas Bolger of Dartmouth College investigated a likely culprit: reduced nesting success in fragmented habitat. But surprisingly, nesting success did not differ between large expanses of coastal sage scrub and habitat fragments adjacent to urban areas.
Morrison and Bolger next teamed up with Scott Sillett of the Smithsonian Migratory Bird Center to examine whether survival of adult sparrows differed between intact and fragmented habitat. They hypothesized that adult sparrows living in the interior of large habitat patches would have a better chance of survival from year to year, compared with sparrows living along the developed edges of habitat reserves.
Rufous-crowned sparrows are non-migratory, permanent residents in coastal southern California, and adults remain on their territories throughout the year, so higher mortality in fragmented habitat could lead to localized declines.
From 1997 to 2000, hundreds of sparrows were captured and each bird was outfitted with a unique combination of colored leg bands. In subsequent years, scientists used binoculars to re-sight the marked birds.
The percentage of adult sparrows surviving from year to year was remarkably high for a small bird—about 70 percent for females and 75 percent for males. Most individuals were re-sighted year after year in the same territory, paired with the same mate. Interestingly, although survival in dry years might have been slightly lower in edge habitat, survival in general did not appear to differ.
This research also raised a cautionary note for scientists investigating survivorship of songbirds. Despite marking hundreds of birds and monitoring for multiple years, scientists were limited in their ability to conclude with statistical certainty fragmentation affected survival. Moreover, they discovered that the ability of researchers to detect this cryptic species depends strongly on annual rainfall; in dry years the birds tend to be much less detectable. These findings illustrate the difficulties that scientists encounter in searching to understand the dynamics of wild populations in a changing world.
So the search continues to find the cause of the rufous-crowned sparrow's decline in southern California. Scientists will be looking closely at young birds in fragmented landscapes, to see how far they disperse from their natal territory and how well they survive their first year of life—two aspects of the avian life cycle that are extremely challenging to study. Teasing apart the effects of development on sensitive species like the rufous-crowned sparrow will help conservationists prevent further declines of biodiversity.
This article summarizes the information in this publication:
Morrison, S. L., Bolger, D. T. and Sillett, Terence Scott 2004. Annual survivorship of the sedentary Rufous-crowned sparrow: no detectable effects of edge or rainfall in southern california. The Auk, 121: 904-916.
The Rufous-crowned Sparrow (Aimophila ruficeps) is a nonmigratory passerine that displays an area-sensitive distribution pattern of abundance in fragmented coastal sagescrub habitat of southern California. To determine if habitat fragmentation negatively affected adult survival, we used Cormack-Jolly-Seber models to compare annual survival probabilities of adult sparrows breeding in habitat adjacent to urban-developed edges to those of birds breeding in the interior of large habitat expanses in San Diego County, 1997-2000. During that period, an El Niño event brought heavy rainfall to the study area, and a La Niña event brought drought. Annual survival probabilities were relatively high for a small passerine (females: 0.69 ± 0.05 SE; males: 0.74 ± 0.04 SE) but, given our data, did not differ between habitat types or with rainfall. Annual resighting probabilities for the birds were strongly associated with variation in rainfall, being high in the wet year and low in the dry year. Mate- and site-fidelity were apparently high, and surveys during the nonbreeding season documented that the sparrows stayed paired and on territories year-round. We hypothesize that the high apparent survivorship of this species is related to its nonmigratory habit and its tendency to curtail reproductive effort during periods of food scarcity. Although our survivorship analysis suggests that the urban-wildland interface does not adversely affect survival of territorial Rufous-crowned Sparrows, our power to detect an effect of habitat edge on survival was low. Thus, we urge caution in concluding that edge effects do not have an ecologically important influence on survival rates in this species.
Teachers, Standards of Learning, as they apply to these articles, are available for each state. | <urn:uuid:595103b7-b621-4e43-a38b-1e4f9c331e0e> | 3.4375 | 1,192 | Academic Writing | Science & Tech. | 28.134003 |
It described a 4 p.m. heavy gale that increased to a perfect hurricane wind, with the shifting of winds by noon the next day. The shift of winds from the northeast to the northwest told Mock that the storm track passed to the east of the Rebecca.
Using the logs and protests, Mock was able to correlate the precise location of ships with the hourly weather and create a map of the storm’s path through the Gulf of Mexico.
“Its initial approach was toward Mississippi, but then it turned northwest toward Louisiana as it approached landfall in the afternoon on Aug. 19,” Mock said. “The USS Enterprise had the most detailed wind observations at New Orleans. A change in winds to the southwest around local midnight tells me that the storm center skimmed as little as five kilometers to the west of New Orleans.”
To further understand the hurricane’s formation and dissipation, Mock reviewed records stretching as far north as Ohio and east to South Carolina. Included among them were meteorological records by James Kershaw in Camden, S.C., which are part of the collections of USC’s South Caroliniana Library.
“I wanted to collect data from a wide area to understand the weather patterns, pressure systems and the very nature of the 1812 hurricane,” said Mock. “A better understanding of hurricanes of the past for a wide area provides a better understanding of hurricane formation and their tracks in the future.” | <urn:uuid:202a668a-0cf3-4572-907f-cd936a7e3d40> | 3.484375 | 302 | Knowledge Article | Science & Tech. | 56.968503 |
This little freshwater snail, probably a Helisoma sp., created a record of its movement in the fine sediment layer covering the rocks on the bottom of a shallow pool next to a creek.
Bioturbation is the disturbing and mixing of soils and sediments by organisms that live or feed in them or simply pass thru them. It is a widespread phenomenon that takes place at different scales: the large mass of soil brought up among the exposed roots of a wind-toppled oak tree and the few-millimeter thick sediment layer disturbed along the trail of a tiny aquatic snail are both examples of bioturbation.
A recent review by Meysman et al.1 presents a good introduction to the subject. Charles Darwin was apparently the first naturalist to approach bioturbation from a scientific angle. The result was his book The formation of vegetable mould, through the action of worms, with observations on their habits.
Bioturbation is especially obvious on the ocean floor where many mollusks, worms and crustaceans live buried in the sediment while others plow thru it in search of food. The result is a complex interaction of biological and physical events: "Benthic organisms modify the microtopography of the ocean floor via pellet production, track formation and different types of construction, such as mounds and pits... This biologically induced roughness modifies the hydrodynamics above the sediment layer, which in turn affects erosion and resuspension."
However, Meysman et al. point out that "for most landscapes and seascapes, the importance of the biological imprint compared with purely physical processes remains largely unknown." To return to my original example, how significant is really the reworking of aquatic sediments by snails when a flooding creek after a heavy rain storm can remove or deposit more sediment than can a river full of snails over many, many generations?
When a process is as common as bioturbation, it becomes difficult to rule out what is not bioturbation. Is the imprinting of footprints in mud count as bioturbation? If the formation of footprints had a significant impact in the lives of other organisms, I suppose the process would be bioturbation. What about the weathering of rock outcrops by microorganism and plant roots? Many rock types start out as sediments and weathered rocks eventually turn into soil. But where do we draw the line?
Meysman et al. also assign a "revolutionary" position to bioturbation in the grand scheme of evolution: "Benthic fauna had to adapt to the newly emerging bioturbated sediment conditions, thereby fuelling the 'Cambrian explosion'". But that is pure speculation.
1Filip J.R. Meysman, Jack J. Middelburg and Carlo H.R. Heip. Bioturbation: a fresh look at Darwin’s last idea. Trends in Ecology and Evolution 21:688, 2006. Abstract & Glossary | <urn:uuid:3bec6e3c-5a19-468f-98f7-b44ae6e17697> | 3.859375 | 622 | Personal Blog | Science & Tech. | 46.429282 |
Dr. Joan Girona of the Institute of Agroalimentary Research and Technology in Catalonia, Spain, studies irrigation and the water and nutrient needs of fruit trees. In a recent study, he wanted to measure the absorption of photosynthetically active radiation (PAR) for use in analyzing growth and fruit production issues. Transpiration from fruit trees and overall evapotranspiration in orchards is closely related to absorption of solar radiation by the tree canopy, so this study would help researchers more accurately measure these processes.
The more measurements he could make, the truer Dr. Girona’s results would be, so he tried a few methods to accurately capture the needed data. First he set up a network of 32 sensors at various points on the ground around the fruit trees to measure light as it came from many angles. Dr. Girona and his fellow researchers found that the values were too distant from each other for good modeling of sun movement. To get enough measurements in a net of this sort, they would need more than 1200 sensors, along with the associated dataloggers and multiplexers—impossible with the resources available.
As they thought about how to get measurements from so many points, they came up with a way to move the sensors around the measurement area precisely and quickly. They mounted the instruments—Apogee pyranometers and Campbell Scientific dataloggers—on small-scale model trains and ran the system on carefully laid-out tracks covering a large area around trees in an orchard. They placed metal markers every couple of inches along the track, and electromagnetic detectors on the train sensed these markers and signaled the datalogger to take a measurement at each point. Dr. Girona tried both Campbell Scientific’s CR800 and CR216, but settled on the CR800 because of the higher reading frequency he needed.
The thousands of measurements taken each run are downloaded to a computer and provide a bounty of data for the researchers. This innovative solution to a measurement need proved so productive that the scientists are building a new system with a few improvements, and plan to run it on many different orchards in 2009.
Resources and Links | <urn:uuid:99c08aa2-2d92-4800-8ab8-02c181b83d3b> | 3.625 | 444 | Knowledge Article | Science & Tech. | 39.530393 |
Conversion of values to readable Strings.
Minimal complete definition: showsPrec or show.
Derived instances of Show have the following properties, which are compatible with derived instances of Text.Read.Read:
* The result of show is a syntactically correct Haskell expression containing only constants, given the fixity declarations in force at the point constructor names defined in the data type, parentheses, and spaces. When labelled constructor fields are used, braces, commas, field names, and equal signs are also used.
* If the constructor is defined to be an infix operator, then showsPrec will produce infix applications of the constructor.
* the representation will be enclosed in parentheses if the precedence of the top-level constructor in x is less than d (associativity is ignored). Thus, if d is 0 then the result is never surrounded in parentheses; if d is 11 it is always surrounded in parentheses, unless it is an atomic expression.
* If the constructor is defined using record syntax, then show will produce the record-syntax form, with the fields given in the same order as the original declaration.
For example, given the declarations
> infixr 5 (:^:)
> data Tree a = Leaf a | Tree a (:^:) Tree a
the derived instance of Show is equivalent to
> instance (Show a) => Show (Tree a)
> showsPrec d (Leaf m) = showParen (d > app_prec) $
> showString "Leaf " . showsPrec (app_prec+1) m
> showsPrec d (u (:^:) v) = showParen (d > up_prec) $
> showsPrec (up_prec+1) u .
> showString " (:^:) " .
> showsPrec (up_prec+1) v
Note that right-associativity of :^: is ignored. For example,
* show (Leaf 1 (:^:) Leaf 2 (:^:) Leaf 3) produces the string "Leaf 1 (:^:) (Leaf 2 (:^:) Leaf 3)".
utility function converting a Char to a show function that simply prepends the character unchanged.
utility function that surrounds the inner show function with parentheses when the Bool parameter is True.
The shows functions return a function that prepends the output String to an existing String. This allows constant-time concatenation of results using function composition.
equivalent to showsPrec with a precedence of 0.
utility function converting a String to a show function that simply prepends the string unchanged.
Gets the string for a constructor
Show a signed RealFloat value using scientific (exponential) notation (e.g. 2.45e2, 1.5e-3).
In the call showEFloat digs val, if digs is Nothing, the value is shown to full precision; if digs is Just d, then at most d digits after the decimal point are shown.
Show a signed RealFloat value using standard decimal notation (e.g. 245000, 0.0015).
In the call showFFloat digs val, if digs is Nothing, the value is shown to full precision; if digs is Just d, then at most d digits after the decimal point are shown.
First arg is whether to chop off trailing zeros
Show a signed RealFloat value to full precision using standard decimal notation for arguments whose absolute value lies between 0.1 and 9,999,999, and scientific notation otherwise.
Show a signed RealFloat value using standard decimal notation for arguments whose absolute value lies between 0.1 and 9,999,999, and scientific notation otherwise.
In the call showGFloat digs val, if digs is Nothing, the value is shown to full precision; if digs is Just d, then at most d digits after the decimal point are shown.
Show non-negative Integral numbers in base 16.
Show non-negative Integral numbers in base 10.
Shows a non-negative Integral number using the base specified by the first argument, and the character representation specified by the second.
Show a list (using square brackets and commas), given a function for showing elements.
Convert a character to a string using only printable characters, using Haskell source-language escape conventions. For example:
> showLitChar '\n' s = "\\n" ++ s
Show more results | <urn:uuid:b4a1f314-e266-4a8e-adba-439600cf5de3> | 3.46875 | 962 | Documentation | Software Dev. | 55.417476 |
|Contents||Inline elements, block-level elements|
|Contained in||Inline elements, block-level elements|
The DEL element contains content that has been deleted. This element is useful in marking changes from one version of a document to the next. Through style sheets, authors can suggest an appropriate rendering, such as not displaying the deleted content or rendering the text with a strike-through style.
DEL may be used as either a block-level element or an inline element. If used as an inline element (e.g., within a P), then DEL may not contain any block-level elements.
The optional CITE attribute of DEL gives a URI with information on why the content was deleted. A brief explanation for the deletion can be given with the TITLE attribute, which may be rendered as a "tooltip" by some browsers.
The optional DATETIME attribute specifies the date and time of the deletion. The value is case-sensitive and of the form YYYY-MM-DDThh:mm:ssTZD. See the values section for a full explanation of this format.
An example follows:
<DEL CITE="http://www.w3.org/TR/REC-html40-971218/appendix/changes.html#h-A.1.3" DATETIME="1997-12-19T00:00:00-05:00" TITLE="XMP is obsolete"><P>The XMP element contains preformatted text in which markup other than an end tag is treated as literal text.</P></DEL>
To accommodate old browsers that pre-date DEL, authors may wish to use a font style element such as STRIKE (deprecated in HTML 4) to attempt to convey the meaning of DEL to non-supporting visual browsers. The previous example could also be marked up as follows:
<DEL CITE="http://www.w3.org/TR/REC-html40-971218/appendix/changes.html#h-A.1.3" DATETIME="1997-12-19T00:00:00-05:00" TITLE="XMP is obsolete"><P><STRIKE>The XMP element is used for preformatted text in which markup other than an end tag is treated as literal text.</STRIKE></P></DEL> | <urn:uuid:cf85b83c-cd57-4fc3-9923-a54d3677247c> | 3.53125 | 509 | Documentation | Software Dev. | 70.382455 |
Since the last post, the neutron generator has been set-up and checked to see that it works. So what to do with it next? Throw it into a swimming pool!
We plan to run the neutron generator under 5 metres (16ft) of water next to XENON1T, see the figure. For XENON1T, the water acts for two purposes: to shield the detector from environmental neutrons, and to veto any highly energetic cosmic ray muons that interact near the detector.
When we ordered the generator, we of course specified that it should be water tight to this depth. However, it’s obvious that we should test it ourselves before putting it next to the detector. This is to see if it leaks under water, if any of the attached cables and hoses are not perfectly sealed. This is also to test that it sinks unaided, as it could have been that air in the hoses made the generator set-up too buoyant.
So we contacted the Boilermaker Aquatic Center, the nearest clean body of water we could think of, and they said they would be happy to help. The deep end of the diving pool is 17ft deep, which was more than enough for us. To check for leaks, we put colour saturation desiccant crystals inside the end of each cable, at the point where each cable attaches to the generator. These crystals would then change colour if they were in contact with water. We then went down when the pool was closed, with all cables and hoses attached to test the water tightness and buoyancy. Needless to say, the generator itself was not powered at any point, and so could not produce any neutrons during the test. We then left the generator underwater for an hour, to make completely sure that there was not even a small leak.
The results of the test were very positive. The generator sank, and the dessicant remained dry inside all cables. In short, everything looks good
We would like to thank David Fraseur, Terry Huntley and James Barnett at the Boilermaker Aquatic Center for all their help in this test, we couldn’t have done it without you! | <urn:uuid:c76285ab-55d8-4b6b-a4a6-8611fc5d14c0> | 2.8125 | 453 | Personal Blog | Science & Tech. | 60.489737 |
- Chemists cross-link carbon nanotubes to form thin mats
One of the most innovative developments to come from the discovery of carbon nanotubes is that of nanotube paper and thin films. 'Black paper' is now commercially available for the next generation of high-tech electronics.
Steve F. A. Acquah, Darryl N. Ventura and Harold W. Kroto
Flexible black multi-walled nanotube paper.
Black is the new white in paper. However, this paper is not for writing. Carbon nanotube paper represents a potential new phase for these materials as they find application in the development of flexible electrodes and batteries. In this article we discover how this is being done. But first we have to go back to the basics.
Back to basics
Initially scientists used high pressure techniques and ion beams to fuse the tubes together, and then turned their attention to modifying the surface of the nanotubes to create defects that could be further exploited. However, modifying the nanotube surface is not an easy process. There is a fine balance between adding functional groups and changing the outer layers of nanotubes, and thus altering its electronic and structural properties. The reason why carbon nanotubes exhibit such properties is because of the graphitic structure, specifically its sp2 bonding. A SWCNT is essentially a rolled-up graphene sheet, so any modification to this single layer could eliminate the properties we want.
One type of structural defect is a Stone-Wales defect, which is made up of two seven-membered rings and two five-membered rings, (1) and (2). Other defects may simply be pre-existing holes or tears on the sidewall of a tube. In 1998 Richard Smalley, professor of physics at Rice University in Houston, Texas, US, discovered that defects on the nanotubes could be oxidised to carboxyl groups by adding concentrated nitric acid, or a mixture of nitric and sulfuric acids to reduce the reaction time.
This reaction soon became the preferred method for exploiting the defect sites on carbon nanotubes. During the oxidation process, the nanotube structure is further disrupted resulting in additional holes and tears.
Figure 1 (Top) Unreacted thiol group attached to a CNT; (bottom) gold nanocrystals attached to mat surface group
The nanotubes can also be modified by mechanical processes, such as ball-milling. In this process, MWCNTs are put into a ball-mill, which is degassed to prevent oxygen becoming a reactant. To add thiol groups, for example, to the surface of the nanotube, a constant supply of hydrogen sulfide is introduced into the vessel, which is sealed and ball-milled for a few days.1 After purification, thiolated MWCNTs (MWCNT-SH) are ready for use.
At Florida State University we have been looking at ways of covalently cross-linking carbon nanotubes. We wanted to find out why other researchers were having such difficulties doing this and, if we could overcome these difficulties, we hoped we would form mat-like structures for a host of new applications.
Our experimental work focused on covalently cross-linking MWCNT-SH using benzoquione following the Michael addition pathway (see Scheme 1). The original idea came from cross-linking techniques used in biochemistry to attach maleimide-based molecular labels to the amino acid cysteine.
Scheme 1 Michael addition mechanism
A closer look at benzoquinone shows that there are two possible positions of reactivity on each C=C bond, resulting in the two adducts with respect to the thiolated positions on the quinone. The 2,5-dithioMWCNT-1,4-cyclohexanedione product may occur when steric interactions from the nanotube govern the chemical reaction though if two nanotubes were to orient themselves parallel or end-on, then the 2,6-dithioMWCNT 1,4-cyclohexanedione configuration may dominate (see Scheme 2).2 Fortunately, for the purposes of cross-linking, either product is beneficial.
Scheme 2 Assembly of cross-linked mat
Our method of nanotube mat formation is a modified filtration-from-suspension (FFS) technique whereby the nanotubes are heated in a reaction flask with the cross-linker then poured into a vacuum filtration funnel. We control the temperature by using a heat gun, which as well as heating the reaction also encourages the cross-linking process. The average diameter of the MWCNT-SH we use is 9.5 nm with the lengths typically <1 m. The degree of coverage by thiol groups over the surface of the nanotubes is between 0.5 and 1 per cent.
With the right concentration of cross-linker, we can produce a flexible mat, the thickness of which is controlled simply by the diameter of the filtration funnel, and we typically achieve between 80 and 270 m in thickness across the mat. We also find that a concentration ratio of 5:1 (benzoquinone : MWCNT-SH by weight) is optimum in producing flexible mats. Higher concentrations of cross-linkers result in over cross-linking and brittle mats. The 5:1 mat can be folded just like regular paper and even rolled up.
As an added benefit of our technique, we can attach various sizes of gold nanocrystal (up to 13 nm) to the un-reacted thiol groups on the surface of the nanotube mat (see Fig 1). This could potentially lead to tailored functional nanocrystals, such as quantum dots, on the surface of the mats which could be used in such applications as photovoltaics.
Of interest, vertically aligned nanotubes, which are used to make carbon nanotube paper, are revealing new properties. In some cases, for example, these mats can absorb 97-99 per cent of the wavelength of light, resulting in one of the blackest materials known aside from a black body (which absorbs all electromagnetic radiation).3
Our success in making cross-linked mats is quite remarkable since to-date the closest match for this type of nanotube paper, the so-called 'buckypaper', from SWNCTs and DWCNTs, has required high pressure techniques and ion beams to fuse the tubes together. (Ion beam fusing is the bombardment of carbon nanotubes with species such as CF3+ that cause functionalisation, defects and cross-linking with nanotubes.) Other researchers have produced buckypaper by filtering SWCNTs with surfactants, such as Triton X-100 - 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol.
Buckypaper is commercially available and typically costs around $200 for a 40 mm diameter sample made from SWCNTs or DWCNTs.4 With the cost for production of carbon nanotubes falling, there will soon be highly competitive rates for buckypaper and other nanotube-based advanced materials.
A carbon nanotube touch-screen interface
Ben Wang, director of the High-Performance Materials Institute in the US and professor in the industrial and manufacturing engineering department at Florida State University, US, is currently exploring different methods of manufacturing nanotube composites for use in applications, ranging from body armour to flat-panel displays. In addition to processing buckypaper, the team is also exploring the effect of surfactants and nanotube alignment on the conductive and mechanical properties of buckypaper. To-date the researchers have found that both nanotube alignment and resins can improve the characteristics of CNT thin films. Their findings are attracting much attention in the engineering community to the extent that companies such as AT&T, Boeing, BP, Lockheed Martin, Motorola, and Sun Microsystems are now sponsoring their research. Wang's latest nanotube project, Nanotubes optimised for lightweight exceptional strength (NOLES), is set to receive $3.2m from congressional funding in 2010.
Potential of thin-film CNTs
Nanotube films have the potential to be used in displays for e-books
Nanotube films have also been in development for the past 10 years, the difference between these films and buckypaper residing in the type of preparation and inclusion of polymers. Unidym, a company based in California, US, is one of the first companies to produce nanotube films. These conductive sheets have the potential to be used in applications such as LCD screens which Unidym has already demonstrated as a prototype in collaboration with Silicon Display Technology based in Seoul, Korea. Other applications include e-books and flexible thin-film solar cells, an area of research in the Kroto research group at Florida State University.
However, as with many developments in science, potential of carbon nanotubes to enhance our way of life, may come with a price. Recently health and safety concerns have arisen about the size of these tubes and their similarities to asbestos. Although there has yet to be a case where carbon nanotubes have caused mesothelioma (a type of cancer that is mostly attributed to long-term exposure to asbestos) in people, the fear is that we may be entering a phase where the development of new materials containing nanotubes supersedes the research into their health and safety. Fortunately the Environmental Protection Agency (EPA) has now started a scheme whereby businesses can register and submit information about nanomaterials in their products to help provide a 'scientific foundation for regulation'.6 This is a step in the right direction even if involvement is on a voluntary basis.
While research into carbon nanotube-based systems is progressing well, there is a new carbon compound on the block causing a stir in research labs. Graphene is a single layer of sp2 -bonded carbon, and many of the applications currently being considered with CNTs would also be applicable to graphene with the advantage that the entire structure of the latter is available to react. However, it remains to been seen whether graphene will elicit as much interest as carbon nanotubes.
Steve Acquah is a postdoctoral associate and director of GEOSET at Florida State University, 95 Chieftan Way, Tallahassee, Florida 32306, and can be contacted at: firstname.lastname@example.org. Darryl Ventura is a doctoral student working in the department of chemistry, and Sir Harold Kroto is Francis Epps professor of chemistry at the same institution.
1. Z. Konya et al, Chem. Phys. Lett., 2002, 360, 429.
2. D. N. Ventura et al, Carbon, 2010, 48, 987.
3. K. Mizuno et al, PNAS, 2009, 106 (15), 6044.
4. NanoLab, Newton MA 02458, US.
5. A. E. Aliev et al, Science, 2009, 323, 1575.
6. US Environmental Protection Agency Office of Pollution Prevention and Toxics: Nanoscale materials stewardship program - interim report, 2009. | <urn:uuid:64ef31a1-d607-46f1-86cf-1585b04a0276> | 3.453125 | 2,365 | Academic Writing | Science & Tech. | 39.884611 |
A left to right algorithm for squaring 1.7 would look like
This illustrates the formula for squaring a binomial
The 2ab are the two .7 in blue in the computation.
If we use this technique to verify the next decimal place we get
In this case, we can let a = 1.7; because we know from the previous step that 1.72 = 2.89. If we let b = .03, then the 2ab are the two .051s that are in the blue box, and .032 = .0009.
We could get the two .051 by doubling the 1.7 and multiplying that by the .03. We could get everything that is added to the 2.89 by the following process.
When we add the 2.89 we get
This represents a tremendous streamlining in the guess and check process; because we can use the results of the previous step, and add in the results of the extra place of accuracy as simply as possible.
We are simplifying the formula for squaring a binomial
To check the square of 1.732, let a = 1.73 and b = .002. We know that 1.732 = 2.9929. Then to compute
When we add this to the 2.9929, we get | <urn:uuid:a4f99913-6886-489e-b167-298568e6a0a6> | 3.359375 | 275 | Tutorial | Science & Tech. | 99.121799 |
The Pleurastrophyceae comprises less than a dozen genera and a handful of species. The group is not as well-defined as the other groups of green algae, because it was first recognized as a group only in 1984. What makes the group distinctive is the way in which the cells divide during mitosis.
Pleurastrophyceans have a metacentric spindle, a trait rare among green algae and not known from other protist groups (Mattox & Stewart 1984). Unlike the usual pattern of cell division, the basal bodies or centrioles (depending on which is present) do not migrate to the poles of the cell before the spindle forms. It is believed that in most other groups, the basal bodies act as a center from which the spindle formation and movement is coordinated, but this does not seem to be the case here.
A further oddity of pleurastophyte cell division is that the cleavage furrow that divides the cytoplasm forms from one side only, rather than pinching from both sides.
Tetraselmis : A putatively "primitive" pleurastrophycean. This is the only genus assigned to this group to retain the plesiomorphy of flagellar scales; it may actually be a micromonad.
Like most members of the closely related Chlorophyceae, all Pleurastrophyceae are found in freshwater and soil, not in marine habitats. But, like the Ulvophyceae, they have an "11 o'clock-5 o'clock" flagellar arrangement. Unlike either group, all known reproduction is asexual.
Strictly speaking, the Pleurastrophyceae have no fossil record. However, the genera Trebouxia, Pseudotrebouxia, and Myrmecia are the most common green algae found associated with fungi to form lichens, which are known from fossils as early as the Devonian.
Try the Protist Image Data Base for information about Tetraselmis.
Image used on this page provided courtesy the PID, and should not be used without their permission. | <urn:uuid:97899fe3-3b20-4bf3-b183-eca541dc3491> | 3.71875 | 453 | Knowledge Article | Science & Tech. | 39.75375 |
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Mars rovers are starting to generate less power.
The Mars rovers are starting to generate less power these days because Mars is starting to slip into Winter. In order to compensate for the reduced amount of light falling on the rovers' solar panels, engineers have begun a new lower-power communications plan. The rovers will only receive information in the morning, and transmit through Mars Odyssey twice a day. The rovers will also take more naps during the day to conserve battery power.
The launch of the European Space Agency's Rosetta spacecraft was delayed for 24-hours because of high winds at the launch site at Kourou, French Guiana. The Ariane 5 rocket is now due to lift off on Friday morning at 0736 UTC (2:36 am EST). Rosetta has a launch instant, not a launch window. This means that it has to get off the launch pad within a few seconds, or it needs to be delayed for a full day. The spacecraft has until May 17 to fly in order to reach Comet 67P/Churyumov-Gerasimenko by 2014; otherwise, controllers will need to choose a new target.
Astronomers have spent the last five years trying to explain a strange star called KH 15D, which winks on an off, sometimes with eclipses that last 24 hours. One theory is that there was a blob of protoplanetary material orbiting the star, occasionally blocking our view. By looking into historical images of the object, Astronomers think they might have a new scenario that better explains their observations. They think it could be a double star system with a disk of material surrounding it and rotating with a wobble. This would explain the unusual eclipses.
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On Earth, certain conditions in our atmosphere give rise to powerful storms - thunderstorms, blizzards, tornadoes, hurricanes, and the like. The Sun also has an atmosphere, and incredible storms that dwarf Earthly storms (in terms of the vast amounts of energy involved). Sometimes they blast forth from the Sun's surface into the solar atmosphere.
The two main types of storms on the Sun are solar flares and Coronal Mass Ejections (CMEs). The two are closely related, though scientists are still trying to work out the exact details of the relationship between flares and CMEs. Both are associated with tangled magnetic fields in the neighborhood of active regions on the Sun's surface. Like a rubber band that is twisted until it snaps, the tangled magnetic fields around an active region release energy when they "snap". The energy emitted in a matter of minutes by a solar flare can be as much as is associated with 100 hurricanes on Earth!
Solar flares emit energy in the form of electromagnetic radiation, including X-rays, ultraviolet radiation, visible light, and radio waves. The photons emitted by a flare arrive at Earth in just over eight minutes after the flare erupts on the Sun, having traveled the intervening distance at the speed of light. Flares also generate high-energy electrons and protons, which reach the Earth somewhat later. A solar flare typically lasts a few minutes to as long as an hour.
CMEs are explosions in the corona, a part of the Sun's atmosphere. These explosions expel a huge bubble of several billion tons of gas and plasma into space. A CME typically releases about the same amount of energy as a flare, though over a period of several hours instead of minutes. If the CME is "aimed" at Earth, it generally takes between one to four days to reach us from the Sun.
If the energy from a solar storm is directed at Earth, it can produce dramatic and dangerous results. Astronauts on spacewalks are in danger of increased radiation exposure, and electronic components on satellites can be fried. Earth's magnetic field and atmosphere shield those of us on the ground from most of the dangerous radiation associated with solar storms. Sometimes, if we're lucky, these storms can offer us a wonderful treat, for the the beautiful displays of the aurora (Northern and Southern Lights) are indirect results of solar storms.
Some "seasons" are stormier than others on the Sun. Sunspots, the visible manifestations of the powerful magnetic fields at active regions, are more prevalent during "storm seasons" on the Sun. The number of sunspots rises and falls in an 11-year cycle, and an increase in the sunspot count signals an increase in solar activity and the accompanying solar storms. | <urn:uuid:03c1f682-0345-4446-9b7e-c4c53ab4565f> | 3.734375 | 561 | Knowledge Article | Science & Tech. | 43.349872 |
Here are two minimal example programs using the TCP/IP protocol: a server that echoes all data that it receives back (servicing only one client), and a client using it. Note that a server must perform the sequence socket(), bind(), listen(), accept() (possibly repeating the accept() to service more than one client), while a client only needs the sequence socket(), connect(). Also note that the server does not send()/recv() on the socket it is listening on but on the new socket returned by accept().
# Echo server program import socket HOST = '' # Symbolic name meaning the local host PORT = 50007 # Arbitrary non-privileged port s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind((HOST, PORT)) s.listen(1) conn, addr = s.accept() print 'Connected by', addr while 1: data = conn.recv(1024) if not data: break conn.send(data) conn.close()
# Echo client program import socket HOST = 'daring.cwi.nl' # The remote host PORT = 50007 # The same port as used by the server s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((HOST, PORT)) s.send('Hello, world') data = s.recv(1024) s.close() print 'Received', `data` | <urn:uuid:d69bbd42-579d-4267-9e73-f9d5e5149da0> | 3.09375 | 314 | Documentation | Software Dev. | 71.399839 |
Sponges are sessile organisms that attach to a firm substrate. There are about 30 species of freshwater sponges in North America, all belonging to the family Spongillidae. Sponges typically live in still waters, and are found regularly in larger rivers, lakes, wetlands, and in streams near lake outlets. They have simple bodies with no organs or differentiated tissues, but different cells in the colony play different roles. Freshwater sponge colonies have numerous microscopic holes through which water passes into the sponge, and a few large holes through which water leaves.
Sponges serve as food for a variety of other aquatic invertebrates, including caddisflies, midges, and spongillaflies. Sponges can reproduce sexually but are highly variable in the sex they choose to be. One may produce only male gametes one year and female gametes the next year. They can also multiply by starting a number of new colonies if fractured by disturbance, and they have a strong ability to regenerate.
The Xerces Society has profiled a rare freshwater sponge endemic to western Montana and known only from three lakes, Ephydatia cooperensis. | <urn:uuid:1888b695-28dd-48d1-9d5c-42b46bae46bf> | 4.21875 | 243 | Knowledge Article | Science & Tech. | 27.973763 |
Our sun is alone in space; it is a single star 4.26 light years away from its closest stellar neighbour (α Proxima Centauri). For many other stars this is not the case, it has been estimated that between 50%– 66% of all stars are in binary (a two star system) or even larger multiple star systems (with more than two stars).
A binary system can have several configurations – The two can orbit a common centre of gravity (termed a barycentre) which lies between the two, or the lower mass star can orbit the higher mass star just as Earth orbits the sun.
These configurations also create three distinct physical types of binary star – Detached Binaries, Semi-detached Binaries and Contact Binaries.
Detached binaries are essentially two stars that orbit far enough apart so that one does not have a significant affect on the other – i.e. each star evolves independently and as normal.
A semi-detached binary is a pair with a more involved interaction. One star fills it Roche Lobe – This is the area of space within which the star’s gravity is stronger than that its partner – the other does not fill its Roche Lobe. This results in a process of matter transfer off the larger star to the smaller one. This matter forms a disk as it spirals round its new star. Eventually friction reduces its speed and it falls on to the surface of the star – it does not fall directly onto the star due to the conservation of angular momentum. A semi-detached binary may evolve form a detached binary after the more massive star swells as it leaves the main sequence by giant formation.
Contact binaries occur when both stars fill their Roche Lobes, this results in the outer atmospheres of both stars joining to form a shared ‘common envelope’. This envelope causes friction which slows the orbits of both stars. This decrease in orbital velocity can eventually (but not in every case) cause both stars to merge entirely forming a higher mass, single star.
As well as the three physical kinds of binaries there are also four observational types of binary stars – Visual, Spectroscopic, Eclipsing and Astrometric.
Visual binaries are far enough apart that their identity as a binary can be determined by direct observation using high powered binoculars or telescopes. The brighter star of the pair is generally accepted to be the primary star with the dimmer being the secondary. It is harder to separate two very bright stars, or a very bright and a very dim star in this way as the stars can appear as one object due to glare.
Spectroscopic binaries can’t be separated by standard observation alone due to the stars proximity to one another and/or due to the effect of glare. This may mean that the stars can only be distinguished from one another through analysis of their spectra. The movement of the stars in their orbits causes the spectral absorption lines (the gaps in the light spectrum of a star due to absorption by the various elements that make up the star – see here) to shift towards either the red or blue end of the spectrum due to the Doppler Shift. When a star is moving away from the observer – i.e. us – its spectrum shifts towards the red end – it redshifts. As a star moves towards the Earth its spectrum shifts the opposite way – towards to the blue end – it blueshifts. When these movements have been recorded several times in a regular pattern, astrophysicists can confirm that the star is orbiting a point in space and may even be able to identify its partner. This type gets its name as they are identified through examination of their spectra hence spectroscopic.
Sometimes the nature of a binary system can be determined by monitoring for any changes in the luminosity of a ’star’. Some stars fluctuate in brightness over a period of days or weeks some of these will be eclipsing binaries. If the stars brightness increases it is likely to be a flare star, a Cepheid variable or a nova. Some ’stars’ luminosity can drop for a short period at then increase back to normal levels, what’s more these ’stars’ may have more than one dip in a luminosity cycle. These are likely to be eclipsing binaries – meaning that whilst they appear as a single star to the naked eye they are in fact pairs of stars that reveal their true nature by passing in front of one another. As can be seen in the animation below when one star passes in front of the other some of the light from the other star is blocked making the apparent brightness drop. This is most noticeable when the dimmer star passes in front of the brighter star. This type gets its name from the way in which the stars eclipse one another hence eclipsing binaries.
It is important to note that a binary system can fall into several of these groups for example – An eclipsing binary system might also be a spectroscopic system as well.
More Complex Multiple Star Systems
A ternary system – containing three stars – may have all three stars orbiting a shared point however this seems to be uncommon as such set ups would not remain gravitationally stable for long.
More likely is a situation where two stars orbit the larger ‘primary’ centre star, these two stars may also be binary i.e. they orbit each other. An example of such a system is Gliese 570 (which also has a brown dwarf orbiting the primary, talk about crowded!).
Another possibility is a pair of binary stars with a third star on a longer orbit – an example of such a system may be Alpha Centauri AB – The central pair contains the fourth brightest star in the sky; the slightly larger than the sun the G2V class α Centauri A (for more information on spectral classes of stars see – Spectral Classes Explained) its partner, the smaller and less luminous K1V class α Centauri B (which should not be confused β Centauri a blue supergiant). They are potentially orbited by our closest star Proxima Centauri however it is currently unclear whether Proxima is actually orbiting the pair or whether it is a matter of a coincidental alignment of trajectories (they may just be moving in the same way through space relative to each other) or perhaps they all shared an origin in a star cluster that has since dispersed.
Please note – Both the small animations used in this post are free from copyright
A planet orbiting a star is in actual fact still orbiting the barycentre, though this is a special case where the barycentre lies within the space occupied by the parent star. Multiple planets in a system – such as our own – can actually cause the barycentre to occur outside the parent star if their is enough mass contained within the orbiting planets.
- The Worlds with Two Suns | The Young Astronomers on Binary Stars Blitzed – Updated
- Ed.A on Image of the Week – A Peculiar Pencil – 18/09/2012
- Saint on SS 433 – A Magnificent Microquasar
- SS 433 – A Magnificent Microquasar » The Young Astronomers on Binary Stars Blitzed – Updated
- John Fairweather on A Star’s Death Giving Life to a Monster – Recovered
- New Post from @Lightbulb500 - The Worlds With Two Suns - bit.ly/RUQKuk 6 months ago
- We will also be posting about our plans for the next while both here, on the blog and our Facebook page - on.fb.me/RUQCuA 6 months ago
- Sorry for the long delay in posts, we have all been very busy. We will hopefully have a more regular post program shortly. 6 months ago
- Our latest Image of the Week highlights the star cluster NGC 1929 and the surrounding nebula N44 - bit.ly/QbkwY6 - by @Lightbulb500 8 months ago
- New post by @Lightbulb500 - How to Understand Spectra – Part 2 - bit.ly/NveYoX 8 months ago
TagsAGN Astronomy Astrophysics Big Bang Black Holes Cassini Chandra Curiosity Emission Nebulae ESA ESO Exoplanets Galaxies Gravity High Mass Stars HST Hubble Hubble Space Telescope Image of the Week Infra-red IOTW ISS Kepler Life LMC Mars NASA Nebula Nebulae Planets Russia Saturn Solar System Spacecraft Spitzer Starbirth Star death Star Formation Stars Star Sailor Podcast Supernova Supernovae VLT WISE Young Astronomers | <urn:uuid:3a122acf-ec5f-4e5c-b07a-6a18667badf1> | 4.03125 | 1,768 | Knowledge Article | Science & Tech. | 45.951276 |
Morriën, W.E. and Engelkes, T. and Macel, M. and Meisner, A. and Van der Putten, W.H. (2010) Climate change and invasion by intracontinental range-expanding exotic plants: the role of biotic interactions. Annals of Botany, 105, 843-848. ISSN 0305-7364.
Restricted to KNAW only
Official URL: http://dx.doi.org/10.1093/aob/mcq064
Background and Aims: In this Botanical Briefing we describe how the interactions between plants and their biotic environment can change during range-expansion within a continent and how this may influence plant invasiveness. Scope: We address how mechanisms explaining intercontinental plant invasions by exotics (such as release from enemies) may also apply to climate-warming-induced range-expanding exotics within the same continent. We focus on above-ground and below-ground interactions of plants, enemies and symbionts, on plant defences, and on nutrient cycling. Conclusions: Range-expansion by plants may result in above-ground and below-ground enemy release. This enemy release can be due to the higher dispersal capacity of plants than of natural enemies. Moreover, lower-latitudinal plants can have higher defence levels than plants from temperate regions, making them better defended against herbivory. In a world that contains fewer enemies, exotic plants will experience less selection pressure to maintain high levels of defensive secondary metabolites. Range-expanders potentially affect ecosystem processes, such as nutrient cycling. These features are quite comparable with what is known of intercontinental invasive exotic plants. However, intracontinental range-expanding plants will have ongoing gene-flow between the newly established populations and the populations in the native range. This is a major difference from intercontinental invasive exotic plants, which become more severely disconnected from their source populations.
|Institutes:||Nederlands Instituut voor Ecologie (NIOO)|
|Deposited On:||01 Jul 2010 02:00|
|Last Modified:||24 Apr 2012 16:44|
Repository Staff Only: item control page | <urn:uuid:389a5d95-e250-442b-bb5a-925bdb877957> | 2.703125 | 467 | Academic Writing | Science & Tech. | 33.817279 |
A: Dragging an image is a multistage process where one has to first erase the image previously drawn then move the coordinates of the image to a new position and finally redraw the image at the new position. Apart from that, one has to handle the mouse messages 'WM_LBUTTONDOWN', 'WM_MOUSEMOVE' and 'WM_LBUTTONUP'. Here are the basic steps to have the effect of dragging an image using mouse.
Data members are to be defined, which are to be used in view class, like the image as a 'CBitmap' object point of insertion of the image and pointer to the cursor point.
Both the 'InvalidateRect()' calls can be combined to a single 'Invalidate()' without bothering to evaluate the rectangles to be invalidated. But this will give a flickering effect each time you move the image since the whole client area will be invalidated.
And finally, clean up the pointer to cursor position in 'OnLButtonUp()' function (of 'WM_LBUTTONUP' message).
pCursor = NULL;
This will give a smooth effect of dragging when the bitmap image is small.
One can also store the background image before a bitmap is displayed and reinsert the background image when the image is moved. Though result is smoother in this case, it needs more involved coding.
Last edited by Andreas Masur; November 4th, 2006 at 12:46 PM. | <urn:uuid:fd6a4314-d96b-44a3-ae09-2eb985365cc5> | 2.90625 | 309 | Q&A Forum | Software Dev. | 41.580096 |
There are two elements to why the universe appears to be so orderly: the physical laws of that govern the universe are the same everywhere, and astronomical objects are very, very, very far from each other.
Consider two objects, one much larger than the other, and both very far from anything else. Because of gravity (which works the same everywhere), the smaller will either move in an ellipse around the larger, or fly by following a hyperbolic trajectory, and disappear into the distance. The exact starting position and velocity will affect only the particulars of the ellipse or hyperbola, but any set of starting conditions will result on one of those two.
Now consider the solar system. If you take something (much smaller than the sun) and stick it somewhere at random in the solar system and give it a random velocity, chances are very good that it will follow a hyperbolic trajectory or an elliptical orbit, because everything else is so widely spaced that it is unlikely to come close enough to anything else for it to matter much: the situation is very probably almost like the two-object scenario above, and the resultant path for the object is very probably almost what it would have been in that scenario.
Of course, the "very probably" and "almost" here are important. There are plenty of exceptions where objects pass near objects other than the sun, and you need to take the gravity of Jupiter and other planets into account to calculate paths to high precision.
If you look at objects where no atmosphere is present to wear away the evidence (eg the moon, Mars), you see plenty of evidence that there have been plenty of collisions, and of course these collisions are still ongoing (eg Schumacher-Levy 9).
In systems that aren't so simple, such as star clusters or our galaxy, the situation is more complex. The main reason why galaxies and star clusters look so orderly is that the distances between the stars is so vast that, even when the stars are moving very fast, the change we see in their overall pattern over the course of a human lifetime is very slight.
Even over longer timescales, though, the density is small enough that there are few collisions or even close interactions (see Binney & Tremaine's book, Galactic Dynamics, pp. 187-190). Instead, stars follow a potential due to the collective gravity of all the matter in the galaxy. In a roughly spherical system, this might result in roughly elliptical orbits, but might also result in rosette like (unclosed) trajectories (see Binney & Tremaine pp103-110). In a system were most interactions are gravitational, asymmetries in the distribution of distant stars are just as important as nearby stars. (Although the gravity of a nearby mass drops as the distance squared, the amount of matter at a given distance increases as the distance squared.)
The specific orbits of stars within these potentials are not particularly ordered. You can see this if you compare the the smoothness in the distribution of young stars with those of old ones. Young stars tend to form in clumps ("star forming regions," places where there is a gas cloud under the right conditins for star formation, eg LH 95, IC 5146), so galaxies with lots of young stars tend to have visible structure (sometimes messy like I Zw 18 and NGC 4214, sometimes not, as in NGC 5248) the details of which depend on the dynamics of the gas in the galaxy. Over time, though, only the densest clumps remain together (because of their mutual gravity); otherwise, the variety of trajectories taken by different stars from the same star forming region will spread it out over time. Galaxies with mostly very old stars, like M 87, therefore, tend to be mostly very smooth, with a population of very dense clumps (globular clusters) which show up in our images as point sources because they are so far away. (Globular clusters in our own galaxy can be resolved, spectacularly, into individual stars; see, for example, M 13 and M 3.)
Interestingly, the underlying randomness (disorder) in the trajectories of stars leads to interesting instances of apparent order. Just as the random motions of molecules in a gas allow us to use statistical laws to make precise descriptions of the behaviour of gas, the random trajectories of stars in globular clusters results in a surprising uniformity in their appearance. See this paper by Madsen. (Globular clusters are old enough and compact enough that interactions between individual stars can actually be important; see Binney & Tremaine p190).
On even larger scales, dramatic interactions between galaxies are quite common. NGC 3227 is a nice example; more can be seen here. In the case of smaller galaxies merging with the Milky Way, we can see the different trajectories of individual stars from the smaller galaxy spreading them out more smoothly over our galaxy. Several of these seem to be going on at once in the "Field of streams". | <urn:uuid:d34e7287-404a-4386-b45b-d4312fa7fda7> | 3.28125 | 1,029 | Q&A Forum | Science & Tech. | 35.96657 |
Manipulating Clouds from the Ground
Cloud seeding is partly a science, partly a black art.
This segment is part of the Engineers of the New Millennium: The Global Water Challenge Special Report.
Transcript: Nevada's Cloud Wranglers
Tom Swofford: Once the solution flow starts to go, you'll actually be able to see the flame through the bottom of the drum—it'll be a large orange flame comes out. Now we're in normal operation. We're seeding clouds.
Phil Ross: Cloud seeding is partly a science, partly a black art. You have to work through a lot of statistics just to see if anything's happening. Under ideal conditions, seeding may increase precipitation by up to 10 percent. Arlen Huggins, a scientist at the Desert Research Institute, explains.
Arlen Huggins: The ideal cloud is actually relatively shallow. We're looking for clouds that aren't particularly efficient at producing precipitation. Usually the very, very deep clouds are also very, very cold and produce a lot of ice and snow on their own. And as the cloud tops lower, there's a lot less natural ice in them.
Phil Ross: I asked Huggins what he does with all the snow.
Arlen Huggins: I do absolutely nothing with it. Nature just takes over, and as the spring, as it gradually warms up, the snow starts to melt, runs into the streams, and that becomes Nevada's water supply, pretty much.
Phil Ross: We climb into a truck and drive past the flat desert plain to the pine-clad hills half an hour west of Reno—to Troy.
Phil Ross: Arriving at a road underpass at the foot of a hill, we park and follow Tom Swofford, a field technician, past the puddles at the bottom and up a steep hill knee-deep in snow. A chilly breeze rises as we climb, and we all put on our hats and gloves.
Phil Ross: I'm standing beside a sheet-metal box about the size of an office cubicle. On it, there's a 10-foot tower topped by what looks like an oil drum. The fuel consists of acetone, in which a tiny bit of silver iodide has been dissolved. When you burn the acetone, the silver iodide wafts away as microscopic crystals.
Arlen Huggins: The flow rate is set so it burns about a third of a gallon an hour—so 3 hours, you burn a gallon. A typical episode is roughly 8 hours, or 9 hours, make it even, so 3 gallons.
Phil Ross: And in those 3 gallons you'll get a certain amount of powder. If I were to hold all that powder in my hand, it would be just a few handfuls?
Arlen Huggins: It wouldn't even be that much.
Phil Ross: I ask Arlen how much snow it could produce.
Arlen Huggins: You can increase the precipitation rate by about a half to 1 millimeter an hour. So, say you were able to create a half an inch of snow—so, a half an inch of snow times 35 square miles, and then you'd have the volume.
Phil Ross: Let the record show that it comes to 41 million cubic feet of snow, which melts out to 30 million gallons of water—enough to supply Reno's homes for one day.
Tom Swofford: You'll hear a loud click. That'll be the valve opening to allow propane, you'll hear this whoosh, the propane, and the flame will light.
Tom Swofford: Once the solution flow starts to go, you'll actually be able to see the flame through the bottom of the drum—it'll be a large orange flame comes out. The solution will start to flow—there it comes, right now.
Tom Swofford: Now we're in normal operation, we're seeding clouds.
Phil Ross: I'm in a garage almost as big as a hangar, peering at a glass box the size of a refrigerator. It's a cloud chamber, and the scientists are using it to measure some of the effects of their cloud-seeding work.
Arlen Huggins: What you're hearing is the compressor from the refrigeration unit that cools down the cloud chamber. Take the flashlight and shine it in there, and you can see the cloud that's being created. It's just like a fog.
Phil Ross: It contains a cloud of water vapor that's kept way below the freezing point, yet that water can't freeze, because there are no seeds on which ice can form. But when a mote of silver iodide drifts into the chamber, kapow! You get a tiny crystal of ice. To see how well the chamber does its job, we stand 30 feet away and burn a match that's been dipped in silver iodide solution. Then, we wait.
Phil Ross: That was the first one.
Arlen Huggins: See 'em? Did you see the little glints of light?
Phil Ross: Yes.
Phil Ross: Each beep is an ice crystal, each crystal a potential flake of snow, the source of more than 90 percent of the water drunk in Reno.
It all starts with a few handfuls of powder. Mighty storms from tiny seeds do grow. I'm Phil Ross. | <urn:uuid:69154b5e-f811-4fd7-b44b-e80963322417> | 3.09375 | 1,128 | Audio Transcript | Science & Tech. | 73.921356 |
Spiders / Scorpions: Spiders Jump With Deadly Accuracy in Green Light
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Spiders Jump With Deadly Accuracy in Green Light
January 26, 2012—Researchers have discovered a unique visual attribute that jumping spiders use in attacking and catching prey. The arachnids use what is called image defocus-proven in part by videos that show spiders jumping with deadly accuracy in green light (and fumbling in red). | <urn:uuid:4615b6bb-12eb-45e6-8283-c35188326941> | 2.75 | 132 | Truncated | Science & Tech. | 44.299588 |
Photosynthesis Problem Set 1
Problem 4 Tutorial: Result of electron transport
During photosynthetic electron transport, the interior compartment of the thylakoid membranes becomes:
|| The thylakoid membranes are sac-like structures with a lipid bilayer separating the interior compartment from the stroma. Enzymes of photosynthetic electron transport are integral membrane proteins. In the dark, hydrogen ions are relatively evenly distributed between the stroma (outside) and inner thylakoid space (inside).
|| In contrast to dark reactions, a pH gradient forms during light reactions. Integral membrane proteins pump protons (H+) across the thylakoid membrane during light-dependent electron transport. The concentration of protons can be nearly 1000 times higher inside the thylakoids than in the stroma.
The Biology Project
University of Arizona
Thursday, October 3, 1996
Contact the Development Team
All contents copyright © 1996. All rights reserved. | <urn:uuid:70fcc09c-e96f-44b3-a9f4-6f9ccc56dd89> | 3.375 | 196 | Tutorial | Science & Tech. | 20.760625 |
Experts in Emulsions
Colloids formed by the combination of two immiscible liquids such as oil and water. Lipid-in-water emulsions are usually liquid, like milk or lotion. Water-in-lipid emulsions tend to be creams. The formation of emulsions may be aided by amphiphatic molecules that surround one component of the system to form MICELLES. | <urn:uuid:d3d4eb0e-2ce2-462f-8182-e9ca700ab45a> | 3.09375 | 86 | Knowledge Article | Science & Tech. | 40.042857 |
This is an drawing of the Galileo probe exploring Jupiter's environment.
Click on image for full size
Image from: The Jet Propulsion Laboratory
The Atmosphere of Icy Moons
The icy moons have no atmosphere. The reason they have no atmosphere is because they do not have enough gravity. The smaller the body is the lower its gravity, so moons have much less gravity than a planet has. Because there is little gravity, an icy moon cannot hold onto an atmosphere for very long.
An atmosphere can come from inside a moon. Some icy moons may have active surfaces, such as Europa, where the surface may "crack" and release molecules for an atmosphere from inside the moon.
However they get there, molecules may float around a moon for a while, but whatever "atmosphere" may be created disappears as soon as it is made.
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Many exciting discoveries were made about Europa during the Galileo mission. The surface of Europa is unusual, even for an icy moon. It appears that the surface is pretty new, rather than being ancient....more
Amalthea was discovered by E Barnard in 1872. Of the 17 moons it is the 3rd closest to Jupiter. Amalthea is about the size of a county or small state. Amalthea is named after the goat in Greek mythology...more
Callisto was first discovered by Galileo in 1610. It is the 2nd largest moon in the solar system, and is larger than the Earth's moon. It is about as big as the distance across the United States. Callisto...more
Measurements by the Galileo spacecraft have been shown that Callisto is the same inside from the center to the surface. This means that Callisto does not have a core at the center. This means that, unlike...more
Many different types of surface are shown in this picture. In the front is a huge crater, which goes for a long way over the surface. This crater could be compared to that of Mimas. They both show that...more
The surface of Callisto is deeply marked with craters. Craters are the little white marks in the picture. It looks like it might be the most heavily cratered body in the whole solar system. And some of...more
Europa was first discovered by Galileo in 1610, making it one of the Galilean Satellites. It is Jupiter's 4th largest moon, 670,900 km ( miles) from Jupiter. Europa's diameter is about half the distance...more | <urn:uuid:9b107d08-ad4e-4197-b40b-2f37c8f1b321> | 3.84375 | 557 | Content Listing | Science & Tech. | 56.677192 |
September 13, 2012 by Administrator
The basic idea of the KUKA youBot API is to represent a robot system as a combination of decoupled functional sub-systems. That is, this API represents manipulator arm and base platform as the combination of several joints. At the same time each joint is defined as a combination of a motor and a gearbox.
There are three main classes in the youBot API that a user should be aware of. These are
YouBotManipulator class that represents youBot arm as the aggregation of several joints and a gripper
YouBotBaseclass that represents youBot base platform
YouBotJoint class that represents joints which make up both the manipulator and the base
A default method to install youBot software is to use “ROS” as installation tool (not as middleware). The second option is to use CMake to compile the driver. For both methods you have to download the source files first.
$ cd /home/youbot
$ git clone https://github.com/youbot/youbot_driver.git
ROS as compile tool
Compiling with rosmake is usually a bit more convenient compared to calling CMake directly, thus it is
the recommended way. This method requires an installed instance of ROS. It is important to add the
/home/youbot/youbot_driver folder to the $ROS_PACKAGE_PATH environment variable, so that ROS can find this directory (for more information see KUKA-youBot-UserManual chapter 8.1.1). After that you can compile the driver as follows:
$ rosmake youbot_driver
After the build process has finished without failures the driver is ready for use.
CMake as compile tool
If ROS is not available, you can also call CMake directly to compile the youbot drivers. First download the driver sources as described above. In order to compile enter in a command shell:
$ cd youbot_driver
$ mkdir build
$ cd build
$ cmake ..
If no error occurs the driver is now ready to use. In order to let other applications find it, you need to add an environment variable $YOUBOTDIR that points to the driver's folder:
$ gedit ~/.bashrc
Insert the following line:
To make the change active just start a new command window or enter
$ source ~/.bashrc
Every youBot joint is represented as a youBot::YouBotJointclass in the API. At this stage the API does not make a distinction if it is a base joint which powers a wheel or a manipulator joint. youBot::YouBotBase and youBot::YouBotManipulator are aggregate classes that allow access to a particular joint instance through youBot::YouBotJoint.
In order to set and get setpoint values or read some sensors from joints, one has to use the youBot::JointData group of classes, e.g. youBot::JointVelocitySetpoint or youBot::JointSensedCurrent. To configure parameters of a joint you have to use the JointParameter group of classes. This could be for instance youBot::MaximumPositioningSpeed. For more detailed information on class and methods please refer to the API documentation. | <urn:uuid:353e6c96-ea14-480b-98d2-058e6fd0b1ad> | 2.953125 | 690 | Documentation | Software Dev. | 42.640639 |
The following particular features are also provided:
- encode into lines of a given length (#b64encode)
- decode the special format specified in RFC2047 for the representation of email headers (decode_b)
A simple encoding and decoding.
require "base64" enc = Base64.encode64('Send reinforcements') # -> "U2VuZCByZWluZm9yY2VtZW50cw==\n" plain = Base64.decode64(enc) # -> "Send reinforcements"
The purpose of using base64 to encode data is that it translates any binary data into purely printable characters. It is specified in RFC 2045 (http://www.faqs.org/rfcs/rfc2045.html).
If you’re wondering what the base64 format is used for, here are some examples:
HTTP Basic authentication: encode your username and password as one string, and add it as a header of an HTTP request. When a page requiring basic authentication gets called from a browser it results in a generic Username/Password dialog from that browser. See also http://en.wikipedia.org/wiki/Basic_access_authentication
Encode the binary content of images to base64 and embed it in XML documents, for example in web services
For more information see http://en.wikipedia.org/wiki/Base64
Just note that the encoded (character) data is about 30% larger than un-encoded (binary) data. | <urn:uuid:e643b5f3-092b-4061-8ced-50e3934bfa6e> | 3.390625 | 321 | Documentation | Software Dev. | 40.5055 |
|weak interaction or weak force|
|physics interaction See electroweak interaction weak nuclear interaction, Also called: weak nuclear force an interaction between elementary particles that is responsible for certain decay processes, operates at distances less than about 10--15 metres, and is 1012 times weaker than the strong interaction. The weak interaction and electromagnetic interactions are now described by the unifying electroweak theory|
|weak force or weak force|
|a scrap or morsel of food left at a meal.|
|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
|weak force (wēk) Pronunciation Key
The fundamental force that acts between leptons and is involved in the decay of hadrons. The weak nuclear force is responsible for nuclear beta decay (by changing the flavor of quarks) and for neutrino absorption and emission. It is mediated by the intermediate vector bosons (the W boson and the Z boson), and is weaker than the strong nuclear force and the electromagnetic force but stronger than gravity. Some scientists believe that the weak nuclear force and the electromagnetic force are both aspects of a single force called the electroweak force. Also called weak nuclear force, weak interaction. Compare electromagnetic force. | <urn:uuid:e88ef8f3-16d1-47bd-85a0-aa6118291127> | 3.59375 | 260 | Structured Data | Science & Tech. | 30.349928 |
Whitney embedding theorem
- The strong Whitney embedding theorem states that any smooth real m-dimensional manifold (required also to be Hausdorff and second-countable) can be smoothly embedded in the real 2m-space (R2m), if m > 0. This is the best linear bound on the smallest-dimensional Euclidean space that all m-dimensional manifolds embed in, as the real projective spaces of dimension m cannot be embedded into real (2m − 1)-space if m is a power of two (as can be seen from a characteristic class argument, also due to Whitney).
- The weak Whitney embedding theorem states that any continuous function from an n-dimensional manifold to an m-dimensional manifold may be approximated by a smooth embedding provided m > 2n. Whitney similarly proved that such a map could be approximated by an immersion provided m > 2n − 1. This last result is sometimes called the weak Whitney immersion theorem.
A little about the proof
The general outline of the proof is to start with an immersion f : M → R2m with transverse self-intersections. These are known to exist from Whitney's earlier work on the weak immersion theorem. Transversality of the double points follows from a general-position argument. The idea is to then somehow remove all the self-intersections. If M has boundary, one can remove the self-intersections simply by isotoping M into itself (the isotopy being in the domain of f), to a submanifold of M that does not contain the double-points. Thus, we are quickly led to the case where M has no boundary. Sometimes it is impossible to remove the double-points via an isotopy—consider for example the figure-8 immersion of the circle in the plane. In this case, one needs to introduce a local double point.
Once one has two opposite double points, one constructs a closed loop connecting the two, giving a closed path in R2m. Since R2m is simply connected, one can assume this path bounds a disc, and provided 2m > 4 one can further assume (by the weak Whitney embedding theorem) that the disc is embedded in R2m such that it intersects the image of M only in its boundary. Whitney then uses the disc to create a 1-parameter family of immersions, in effect pushing M across the disc, removing the two double points in the process. In the case of the figure-8 immersion with its introduced double-point, the push across move is quite simple (pictured).
This process of eliminating opposite sign double-points by pushing the manifold along a disc is called the Whitney Trick.
To introduce a local double point, Whitney created a family of immersions αm : Rm → R2m which are approximately linear outside of the unit ball, but containing a single double point. For m = 1 such an immersion is defined as
Notice that if α1 is considered as a map to R3 i.e.:
then the double point can be resolved to an embedding:
Notice β1(t1, 0) = α1(t1) and for a ≠ 0 then as a function of t1, β1(t1, a) is an embedding. Define
α2 can similarly be resolved in R5, this process ultimately leads one to the definition:
The key properties of αm is that it is an embedding except for the double-point αm(1, 0, … , 0) = αm(−1, 0, … , 0). Moreover, for |(t1, … , tm)| large, it is approximately the linear embedding (0, t1, 0, t2, … , 0, tm).
Eventual consequences of the Whitney trick
The Whitney trick was used by Steve Smale to prove the h-cobordism theorem; from which follows the Poincaré conjecture in dimensions m ≥ 5, and the classification of smooth structures on discs (also in dimensions 5 and up). This provides the foundation for surgery theory, which classifies manifolds in dimension 5 and above.
Given two oriented submanifolds of complementary dimensions in a simply connected manifold of dimension ≥ 5, one can apply an isotopy to one of the submanifolds so that all the points of intersection have the same sign.
The occasion of the proof by Hassler Whitney of the embedding theorem for smooth manifolds is said (rather surprisingly) to have been the first complete exposition of the manifold concept precisely because it brought together and unified the differing concepts of manifolds at the time: no longer was there any confusion as to whether abstract manifolds, intrinsically defined via charts, were any more or less general than manifold extrinsically defined as submanifolds of Euclidean space. See also the history of manifolds and varieties for context.
Sharper results
Although every n-manifold embeds in R2n, one can frequently do better. Let e(n) denote the smallest integer so that all compact connected n-manifolds embed in Re(n). Whitney's strong embedding theorem states that e(n) ≤ 2n. For n = 1, 2 we have e(n) = 2n, as the circle and the Klein bottle show. More generally, for n = 2k we have e(n) = 2n, as the 2k-dimensional real projective space show. Whitney's result can be improved to e(n) ≤ 2n − 1 unless n is a power of 2. This is a result of Haefliger–Hirsch (n > 4) and C.T.C. Wall (n = 3); these authors used important preliminary results and particular cases proved by M. Hirsch, W. Massey, S. Novikov and V. Rokhlin. At present the function e is not known in closed-form for all integers (compare to the Whitney immersion theorem, where the analogous number is known).
Restrictions on manifolds
One can strengthen the results by putting additional restrictions on the manifold. For example, the n-sphere always embeds in Rn + 1 – which is the best possible (closed n-manifolds cannot embed in Rn). Any compact orientable surface and any compact surface with non-empty boundary embeds in R3, though any closed non-orientable surface needs R4.
If N is a compact orientable n-dimensional manifold, then N embeds in R2n − 1 (for n not a power of 2 the orientability condition is superfluous). For n a power of 2 this is a result of A. Haefliger–M. Hirsch (n > 4) and F. Fang (n = 4); these authors used important preliminary results proved by J. Bo'echat-A. Haefliger, S. Donaldson, M. Hirsch and W. Massey. Haefliger proved that if N is a compact n-dimensional k-connected manifold, then N embeds in R2n − k provided 2k + 3 ≤ n.
Isotopy versions
A relatively 'easy' result is to prove that any two embeddings of a 1-manifold into R4 are isotopic. This is proved using general position, which also allows to show that any two embeddings of an n-manifold into R2n + 2 are isotopic. This result is an isotopy version of the weak Whitney embedding theorem.
Wu proved that for n ≥ 2, any two embeddings of an n-manifold into R2n + 1 are isotopic. This result is an isotopy version of the strong Whitney embedding theorem.
As an isotopy version of his embedding result, Haefliger proved that if N is a compact n-dimensional k-connected manifold, then any two embeddings of N into R2n − k + 1 are isotopic provided 2k + 2 ≤ n. The dimension restriction 2k + 2 ≤ n is sharp: Haefliger went on to give examples of non-trivially embedded 3-spheres in R6 (and, more generally, (2d − 1)-spheres in R3d). See further generalizations.
See also
- See section 2 of Skopenkov (2008)
- Hassler Whitney; collected papers. Hassler Whitney, James Eells, Domingo Toledo. Nelson Thornes, 1992
- Lectures on the h-cobordism theorem. John Milnor. Princeton University Press. 1965
- Embeddings and immersions, by Masahisa Adachi, translated by Kiki Hudson
- Skopenkov, A. (2008), "Embedding and knotting of manifolds in Euclidean spaces", In: Surveys in Contemporary Mathematics, Ed. N. Young and Y. Choi, London Math. Soc. Lect. Notes. 347 (2): 248–342, arXiv:math/0604045 | <urn:uuid:98333d40-eea9-4be4-9fce-b074712bb1a2> | 2.953125 | 1,911 | Knowledge Article | Science & Tech. | 58.779694 |
Slide 3 of 13
What is Aerosol Single-Scattering Albedo?
- w0 = a measure of the amount of aerosol light extinction due to scattering
- We periodically switch a 1-micrometer impactor in line to remove supermicron aerosols. This talk will focus on the submicron aerosols. Most of the absorption occurs here.
- Heat to maintain a maximum sample RH of 40%. This is done in order to ensure that the aerosol is dry, and that the aerosol radiative properties being measured are intrinsic to the aerosol and not dependent on water content. | <urn:uuid:40534cc7-8a35-41e9-953b-207a98a48933> | 3.046875 | 128 | Truncated | Science & Tech. | 45.91 |
How can you calculate the closest point(s) between
two circular orbits which are not in the same plane or orientation?
I have not looked at this specific problem but the general approach is as
follows. If you have the equations of the two orbits, you can write an
equations describing the distance between two arbitrary points, a point on
each curve. Then you find the minimum or maximum of this function.
As s first step, you can try solving this problem in 2-D (i.e., two circles
in the same plane) and then generalize to 3-D.
Dr. Ali Khounsary
Advanced Photon Source
Argonne National Laboratory
Argonne, IL 60439
Click here to return to the Mathematics Archives
Update: June 2012 | <urn:uuid:c2aea030-f0f8-4aeb-a55b-290d430b3750> | 2.75 | 167 | Q&A Forum | Science & Tech. | 57.521824 |
Rotational Speed and Orbital Parameters
If we could change the rotational speed of the moon, would
this momentum change necessarily change its orbital parameters?
In the short run, giving the Moon a spin would not affect its orbit around the Earth.
In the long run, the energy of that spin might gradually be
transferred to its orbital motion and consumed,
by means of tidal deformation of the moon.
Personally I do not how much coupling to tidal stresses happens
in a cold, all-solid body like the Moon.
The degree of coupling could be much less than that of largely-fluid Earth
if the moon is infinitely rigid or perfectly elastic,
or it could be much greater
if there is any yield or crumbly sliding deformation within the body.
Perhaps you have heard:
the spin energy of the Earth has been partly transferred to moon's orbit
over the time since the Moon was created, driving the Moon farther out
and slowing the Earth's day/night cycle.
This is the type of coupling I am referring to above.
If you are speaking about the rotational speed of the moon on its axis,
Then no, that will not affect its orbital parameters.
If you change the speed of the moon's orbit around the earth, the moon will
move out to a more distant orbit until its velocity vector parallel to the
surface of the earth equals its velocity Vector that points toward the
center of the earth.
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Update: June 2012 | <urn:uuid:195cd5e1-893b-4fc9-9978-df4610b91e77> | 3.421875 | 317 | Q&A Forum | Science & Tech. | 47.622467 |
The Spider Assassin (Archaeidae)
As the sun sets, the high pitched buzz of cicadas winds down and a chorus of frogs greet the night. An array of insects and animals with adaptations and appearance so bizarre as to be almost incredulous emerge. Amongst the oddest are the Archaeids.
These strange spiders go by a variety of names which reflect their form and behaviour, though they are most commonly referred to as spider assassins and pelican spiders. The former epithet refers to their araneophagic diet, while the latter pays homage to their morphologically unique ‘necks’ (actually an extension of the cephalothorax). Despite the natural interest which these spiders garner by their looks alone, little is known about their natural history which can be explained by a variety of factors; their diminutive size (2-8 mm), nocturnal habits, location under foliage suspended head down, or by their short-range endemism. Not to mention that their cryptic colouration, browns and greys, which facilitate their camouflage as they drop evasively to the leaf litter. As a result, these spiders are poorly represented in the scientific literature, leaving it up to the imagination of the reader or better yet, the observer to fill in the details of their lives.
Even scarcer are images, most of which show specimens preserved in amber from up to 50 million years ago. These relictual specimens from the Mesozoic era bear an unmistakable resemblance to present day Archaeidae, demonstrating a remarkable conservation of phylogenetic traits. These archaeological findings elucidate a former range which extended up into the sclerophyll (woody stemmed plants with evergreen leaves) forests and mesic (moisture-rich environment) heathland of the European Baltic (1), mirrored in the present day ecology of the Austrachaeidae of Australia, to Burma, Kazakstan and the Xunan province, China.
Though no longer present in Europe, recent findings have shown an extended range in Australia from montane to tropical rainforests (2).
As one recedes further and further in geological time, one can observe a progressive shortening of the ‘neck’ and chelicerae until they resemble more and more the infraorder of Mygalomorphae (Orthognathae). The chelicerae now appear to move from side to side rather than up and down as in the Araneomorphae. Therefore, it may be inferred that the length of the neck has evolved hand in hand with the length of the chelicerae. Otherwise as the former lengthens, the distance between the mouth and the chelicerae becomes too great to efficiently transfer the food from one to the other.
Not only can we see a change in this morphometric ratio through time, but also across the various species and genera. Even within the monophyletic graciliosis group (Eriauchenius), the evolution of appropriate ‘neck’ and chelicerae ratios appears to have evolved as two separate events, an interesting example of convergent evolution.
Phylogenetic analyses have placed the Arachaeidae in 3 genera (Eriauchenius, and Afrarchaea [Madagascar, Africa], and Austrarchaea [Australia]) with a combined total of 37 species. Most species can be separated based on gross morphological features present in the pedipalps, the differences in ‘head’ and ‘neck’ (based on various morphometric ratios), eye positions and surface details of the haplogyne (female) genitalia. However, more discerning methods include the use of genetic markers such as mitochondrial c cytochrome oxidase subunit I (COI) and the adjacent COII genes in combination with 12S and 16S mitochondrial DNA (4).
Despite the genetic approach being extremely helpful in clarifying genealogy (found at the base of the Araneomorph lineage, close to where they diverged from the their sister clade, the Mygalomorphs), the deconstructionism of phylogenetic and morphological analyses can only yield helpful insight into the function accompanying the form of preserved specimens. Therefore, the natural history can often only be determined by field observation. Up to this point there is only a small representation of live Archaeid photos which best represent our knowledge of in situ behaviour, and those that exist are divided between the Archaeidae and the sister family Mecysmaucheniidae. The latter being better represented in the literature and having an extended range from Southern South America to New Zealand. Additionally, these spiders lack the araneophagic diet of the Archaeidae and behave more like other generalist spiders. The Archaeidae on the other hand are found in Australia, South Africa and Madagascar with the latter two comprising the lion’s share of the research (this is perhaps due to the relative abundance of specimens in these countries compared to Australia which may have more Archaeid predators).
Bearing this in mind, an excellent dichotomous key with some distinguishing morphological characteristics (the colour of the bars represents the mean morphometric ‘neck’/chelicera ratios) has been created for 15 species of the Eriauchenius genus.
Perhaps the most striking features of this family are the elongated ‘neck’ and slender chelicerae (jaws) with recursive fangs, which together with the head comprise the seemingly teetering cephalothorax. Of note are also the long delicate legs with modified tarsi that enable the legs to extend beyond even the chelicerae. Each of these features; however seemingly bizarre has a specific purpose essential to its predatory, araneophagic diet. The aptly named spider assassin, nomadic in nature and lacking a web of its own can often be found in the leaf litter foraging for prey. As it navigates this landscape, the spider assassin is particularly attuned to finding the draglines of other spiders (a silken line which serves as a safety line) by mechano- and perhaps chemosensory means. With its long forelegs, it traces the path like a skilled hunter until it happens upon its hapless prey and spears it with its long forceps-like chelicerae.
However, Archaeids may also go so far as to invade the webs of other Araneomorphs. With its anterior legs barely touching the outermost draglines of another spider’s web, it may strum the silken lines like a siren, its deadly tune irresistible to its prey. Archaeid pattern recognition of spider-prey courtship web strumming has not yet been been thoroughly investigated. As such there is no evidence that it approaches the complexity of the Portia spp. jumping spiders’ remarkable interspecies differentiation. However, like the Portia they appear to be quite adaptable and opportunistic. This is demonstrated by their boldness in plucking prey right out of their own webs. They achieve this dexterous act of negotiating their prey’s web thanks to the length of their legs, which essentially act as shock absorbers. Simply put, this aspect of their morphology minimizes the amplitude of disturbance such that it is no greater than that normally attributed to more benign natural causes (wind, rain, etc.).
Due to the relatively poor eyesight of most Araneomorphs, the Archaeid is able to approach within striking distance without alerting its prey. Thanks to its disproportionately long chelicerae, it impales its prey without exposing itself to collateral damage. Able to move both horizontally and vertically, the jaws close upon the prey like a vice. The fangs pierce the exoskeleton, and venom is pumped into the other spider. As the poison circulates in the hemolymph, the prey struggles even more violently but the hooked fangs remain embedded. Next, in a still unexplained behaviour, one chelicera lowers 90 degrees in a stereotyped action. Meanwhile the other chelicera holds the prey at a safe distance as it continues to thrash about in its death throes. Minutes pass and the struggling becomes weaker and weaker until it stops entirely. There may be a sporadic jerk, autonomic neurons releasing their final action potentials. But it is now safe to consume. The Archaeid lowers its meal to its mouth and feeds. The proteolytic enzymes in the venom have had time to work, and have broken down the internal organs, rendering them sufficiently liquid to imbibe.
The concomitant lowering of a single chelicera with feeding as aforementioned has yet to be explained. However, a couple plausible theories might account for this behaviour: 1) lowering one chelicera minizes the risk of injury from the potentially dangerous flailing movements of the dying prey or 2) conservation of energy (imagine holding 1 arm out in front of you instead of two).
[Please note that these conclusions are drawn from my own field experience and observations, though I did find a corresponding lecture video seen below (as presented by researcher Hannah Wood) which corroborates my own reasoning. Unfortunately there seems to be a dearth of readily available information with regards to the natural history of Archaeidae.]
At rest, Archaeids dangle head down under leaves or between branches with a dragline or two to support them. This position seems to be the most comfortable to accomodate their unique form (Nb. most online photos have been rotated for easier viewing, often without mention that this is not the in situ behaviour).
Even more poorly understood is the courtship and mating behaviour of Archaeids. The extent of my personal experience is the observation of a single female holding an egg sac well above her head with one of its mid-legs. She was able to maintain this posture while galloping along the bottom of a leaf.
Their cryptic nature and seemingly low abundance have kept Archaeids as one of the best kept secrets of the arachnid world. Fortunately, recent photos (J. Miller, 2008) have spotlighted this fantastic creature, which has since appeared in diverse fora easily accessible to the public. Hopefully this newfangled celebrity will encourage further study and illuminate the many mysteries surrounding one of the strangest spiders on the planet.
As more information becomes available, I will update this Article.
1) Penney D. Afrarchaea grimaldii, a new species of Archaeidae (Araneae) in Cretaceous Burmese amber. Journal of Arachnology 2003: unit 31: pp.122-130. doi:10.1636/0161-8202(2003)031[0122:AGANSO]2.0.CO;2
2) Michael G. Rix, and Mark S. Harvey.Australian Assassins, Part I: A review of the Assassin Spiders (Araneae, Archaeidae) of mid-eastern Australia. ZooKeys 123: 1–100, doi: 10.3897/zookeys.123.1448. http://www.pensoft.net/journals/zookeys/article/1448/australian-assassins-part-i-a-review-of-the-assassin-spiders-araneae-archaeidae-of-mid-eastern-australia.
3) A revision of the assassin spiders of the Eriauchenius gracilicollis group, a clade of spiders endemic to Madagascar (Araneae: Archaeidae). Hannah, Wood. 2008. The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 152, 255–296. http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2007.00359.x/abstract
4) Wood HM, Griswold CE, Spicer GS. Phylogenetic relationships withing an endemic group of Malagasy ‘assassin spiders’ (Araneae, Archaeidae): ancestral character reconstruction, convergent evolution and biogeography. Mol Phylogenet Evol. 2007 Nov;45(2):612-9. Epub 2007 Jul 19. http://www.ncbi.nlm.nih.gov/pubmed/17869131. | <urn:uuid:2f34fd17-713a-4394-ae85-fe16521e8822> | 3.203125 | 2,554 | Academic Writing | Science & Tech. | 37.556985 |
Take a look at the following pictures of U.S. dimes. As you can see, they are slightly different from one another — the date is in the incorrect spot on one of them. Can you tell which one is “wrong”?
Let’s make this a poll:
Don’t look at your pocket change before you answer! In case you don’t have a dime handy, I’ll reveal the correct answer later in the post.
Even though most Americans will say they know what U.S. coins look like, a similar study in 1979 found that people can’t remember the basic details of a penny. More recently, change blindness studies have shown that we are very bad at detecting changes in scenes, even those that seemingly take place before our eyes.
But Luke Rosielle and Jeffrey Scaggs point out that change blindness isn’t much of a problem in the real world because things don’t ordinarily disappear or change right in front of our eyes, or in the moment when we glance away. A much more common type of change happens when we’ve been away for a longer period of time. If you leave town for a few weeks, you might be likely to notice that your favorite coffee shop has been repainted. This is the sort of change we may be more likely to notice. Or are we?
Rosielle and Scaggs showed 48 students pictures of their own college campus, and told them that half had been photoshopped to remove or change prominent campus buildings and monuments. The students carefully observed each picture for 20 seconds, then said whether the photo was accurate or modified. After each photo, they rated their familiarity with the scene on a scale of 1 to 10. On average, the students were familiar with 97 percent of the scenes. However, they failed to identify the changes to 81 percent of the photos!
So even though the students said they recognized the scenes, they flopped at actually noticing what had been modified. Why? Rosielle and Scaggs showed the same scenes to 48 new students from the same campus, but this time they were shown the original and altered pictures side-by-side. These students were asked how difficult it would be for others to identify the changes in the pictures. Interestingly, their ratings matched the errors made by the first group of students: they could predict how good other students would be at identifying changes at a rate significantly better than chance. That said, they still weren’t very good at predicting: they thought students would get about half the answers correct, when in fact they missed over 80 percent!
The researchers showed the same pairs of pictures to 48 students from a different school, who had never seen the original college campus. These students were unable to predict how well students from the original campus would do; their predictions bore no relationship to the actual results.
So it seems that while our memories of scenes aren’t as good as we think they are, the memories are indeed better than nothing. The students from the different university tended to rate the larger changes (those occupying the most pixels on the screen) as easier to spot, but the students who actually attended the school recognized other features as more likely to be noticed. This makes some sense — you’d probably be more likely to notice if your favorite coffee shop closed down than if the same thing happened at a larger place you never visit. But it’s striking that even very familiar places don’t actually stick very well in our memories at all.
If this is the case, then we should expect that our readers didn’t do very well on the two polls above. For comparison, here’s an unaltered photo of a dime:
As you can see, dime B had the date in the correct spot. But both dimes were missing a very large feature: the word “LIBERTY” to the left of Roosevelt’s face. Did you notice all these changes? Let us know in the comments.
Rosielle, L., & Scaggs, W. (2008). What if they knocked down the library and nobody noticed? The failure to detect large changes to familiar scenes Memory, 16 (2), 115-124 DOI: 10.1080/09658210701787765 | <urn:uuid:ad84c8c2-489a-4023-8cf2-18443327e9ea> | 2.734375 | 894 | Personal Blog | Science & Tech. | 60.197428 |
Wednesday, June 20
David Gruber, an assistant professor of biology at Baruch College and research associate at the American Museum of Natural History, is leading a National Geographic Society/Waitt Institute expedition exploring bioluminescent and biofluorescent marine animals in the Solomon Islands.
It’s 3:53 p.m., and from the window of our Solomon Airlines Twin Otter, I can see the lush tropical forests and aquamarine waters of Marovo and Vonavona lagoons below. This is the final leg of the journey into Gizo in the western province of the Solomon Islands. We caught this flight from Honiara, the capital of the Solomon Islands, an archipelago nation comprising nearly 1,000 islands between Papua New Guinea and Vanuatu. It has now been three days of continuous travel since we left Kennedy Airport in New York. On a nearby palm-covered island (now called Kennedy Island) almost 70 years ago, a 28-year-old John F. Kennedy swam ashore, dragging a badly burned crew member after his boat, PT 109, was rammed by the Japanese destroyer Amagiri on Aug. 1, 1943.
The Solomon Islands were one of the strategic centers of the Pacific campaign in World War II, with tens of thousands of young and inexperienced American soldiers locked in vicious battles, including the famous naval battles that took place at Guadalcanal and were later depicted in movies like Terrence Malick’s “The Thin Red Line.”
The scientific goals of this trip are manifold, but above all we are after elusive near-infrared fluorescent and bioluminescent molecules to aid in biomedical research. We have assembled a small team of five scientists, including Vincent Pieribone, a neuroscientist from the John B. Pierce Laboratory and Yale School of Medicine; John Sparks and Robert Schelly, ichthyologists from the American Museum of Natural History; Dan Tchernov, a marine biologist from the Leon Charney School of Marine Sciences at the University of Haifa, in Israel; and Ken Corben, an Emmy-winning underwater cinematographer (who also just so happens to be a former SWAT team member who has spent more than 100 hours filming sharks for National Geographic — experience which may, for better or worse, be of use to us).
The Solomon Islands, part of the Coral Triangle, have possibly the highest diversity of corals and reef fishes in the world, as recorded in a recent survey (more than 500 coral species and more than 3,000 species of fishes). We are here to study this system with modern tools and techniques, like underwater spectrophotometers, narrow excitation bandwidth fluorescence imaging, military-grade low-light custom-built underwater cameras and a RED Epic 5K movie camera capable of obtaining imagery almost 10 times the resolution of high definition.
Each of the members has his own scientific interests, but we have come together on this remote tropical island connected by a common theme: animals that possess the ability to bioluminesce and biofluoresce. Bioluminescent animals produce their own light; biofluorescent animals transform and re-emit existing light. These two processes have attracted and mystified scientists for centuries, but it is surprising how little is known about how they work in the ocean.
Over the past two years, John and I have scoured the scientific literature on bioluminescence and biofluorescence as we assembled the exhibition Creatures of Light: Nature’s Bioluminescence at the American Museum of Natural History. In the process, we were surprised that for certain organisms, like fireflies, there is a wealth of information, but for most other glowing animals, knowledge is remarkably scarce.
We are also out here to better understand the diversity and function of these phenomena. Much of the difficulty lies in making the observations. It requires custom-built cameras, high-tech filters and lighting that incorporates state-of-the art technology. And we have to travel to remote and diverse regions, like the Solomon Islands, and conduct our work underwater. Much of this work has to be done in the dark, after sunset, to capture the eerie glow of these animals.
Once we land, we plan to scope out the nearby coral reefs and plan for our first night of adventure. | <urn:uuid:ab42ed45-ea52-4c64-a353-bb9efca8926c> | 2.9375 | 887 | Personal Blog | Science & Tech. | 30.098377 |
The Brown Bear
The brown bear and grizzly bear are technically one in the same. This amazingly large animal has a reputation as a killer.
The brown bear comes from a family of bears known as "Ursidae." A variety of races and species of this long feared bear are native to Eurasia and the northwestern regions of the United States. As many as 80 species of the brown bear are considered extinct.
GRIZZLY BEAR OR BROWN BEAR?
Taxonomists previously have listed grizzly bears and brown bears as separate species. Technically, they are one in the same, though distinct subspecies do exist.
Brown bears found in the United States are commonly referred to as Grizzly Bears, whereas brown bears that make their home outside the U.S. are often known as simple brown bears.
The North American Grizzly bear has been hunted for centuries; so much so that only a few subspecies still exist. The North American Grizzly bear makes his home almost entirely in Alaska now, and most other subspecies of the brown bear that roamed the central portions of the United States are non-existent.
Eurasian brown bears are 4-7 feet long and weigh 300-550 pounds. The much larger Siberian brown bear weighs nearly 800 pounds, and is similar in size and weight to the North American Grizzly bear, also known as the common U.S. brown bear. This large, menacing animal has a prominent shoulder hump, small ears, and long, straight claws. Brown bears range in color from dark brown through light blonde.
Because of their tremendous size, brown bears rarely climb anything, even as cubs. Surprisingly agile, however, brown bears can run as fast as 30 m.p.h.
Grizzly bears carry a certain reputation for being dangerous, menacing animals. While it is true that brown bears have attacked humans for no apparent reason, most officials say cause for alarm is not necessary. They advise keeping a distance of 100 feet between the bear and you, and avoiding female bears with cubs altogether.
North American grizzly bears (common brown bear) are omnivorous animals, grazing on game, fish, berries and grass. They often store food shallow holes. Brown bears can also be found digging through the ground in search of rodents. Brown bears are methodical feeders who form deep, rutted trails after covering the same ground repeatedly in search of prey.
Brown bears have an amazing sense of smell which, under the right conditions, allows them to detect odors and prey more than a mile away. Bears use their strength and length to stand upright to test wind and smells.
Brown bear mating takes place from May through July, with the peak of activity occurring in early June. Brown bears do not have strong mating ties and individual bears are rarely seen with a mate for more than 7 days. Males often mate with more than one female during breeding season.
Hairless cubs, weighing less than one pound, are born 7 months after conception. Winter dens provide a home for the young. Litter size can range from 1-4 cubs, 2 being most common.
Offspring separate from their mothers around the age of two. After separation, the mother often breeds again immediately and produces a fresh litter of cubs the following year. When food is scarce, it is not uncommon for cubs to stay with their mothers until they are 5 years of age.
THE LONG SLEEP
During the winter months when food is scarce, most brown bears enter dens and begin a period of hibernation that will last the entire season. While in this semi-sleep state, the bear's body temperature, heart rate and other metabolic rates are greatly reduced. The need for food and water is eliminated entirely. Pregnant female brown bears are the first to enter dens, and do so in early fall months. The female bear and newborn cubs are then subsequently the last to exit the den in the spring. Adult males have just the opposite behavior, entering dens last and leaving first.
Brown bears are protected species today, and those that once lived over western North American from Mexico to the northern most regions of the United States are extinct. National parks and zoos house a small number of Eurasian brown bears and as few as 9 or 10 populations of Alaskan brown bears still live in their native coastal area.
Alaska contains over 98 percent of the United States population of brown grizzly bears. Today, the Alaska Department of Fish and Game is responsible for managing Alaskan bears and their population. The grizzly bear is still a hunted animal in Alaska.
Brown bears in the wild have a lifespan of 22-26 years. | <urn:uuid:6713a719-844a-44f6-b3a4-6545bc4417f5> | 3.21875 | 963 | Knowledge Article | Science & Tech. | 59.56686 |
|What if you saw your shadow on Mars and it wasn't human?
Then you might be the robotic
Curiosity landed in
Gale Crater last August and has been busy looking for signs of ancient running water and clues that Mars could once have harbored life.
Curiosity has taken a wide panorama that includes its own shadow in the direction opposite the Sun.
was taken in November from a location dubbed Point Lake, although no water presently exists there.
Curiosity has already discovered several indications of
dried streambeds on Mars, and is scheduled to continue its exploration by climbing nearby
Mt. Sharp over the next few years. | <urn:uuid:7fc46e13-795f-47e6-aa03-77a3a70fc89b> | 3 | 135 | Truncated | Science & Tech. | 47.207064 |
We had one data file, there was no sequence problem
for retrieving the data without order by clause.It was in sequence.
When we added another datafile and index file.
Now when program retrieves the data(no order by
it does not come in sequence. e.g if order numbers are
123456, then it retrieves as 123654.Even I run a
simple select query without order by clause, it does
the same way.
Is it possible that data may be in two different
datafiles and retrieving without order by class
resulted that(no sequency)?
It retrieves data in sequency some time ,but most of
the time it does not.
Adding datafiles to tablespaces doesnot have any effect on the retrival of data.In order to retrieve the data in order u want use ORDER BY clause in ur select statement.
If u want any help regarding ur doubts please write to me at
you are mixing 2 thigs that have no connection: the output of a select statment and the way your data is stord on your machin.
a datafile is a file in a directory, it is where you stor the data in your tables. when you create a table you create it a table space. when you create a tablespace you connct it to a datefile. you can read a lot about it in the oracle documantation (under concepts).
when you ex. a select the system is takeing the data from the datafile in a specific way that has it's own logic, no connection to datafile, but to data in the table, indexes and so on...
Thanks for suggetions.
When we had one data file , it was in sequency without using
order by clause.
The user used to see in sequence (form 4.5). When we added, then it retrieves in sequence some time but most of the time not.
I understand that order by clause will put in sequence.
but, why it was doing before adding second data file?
Oracle will in many cases return the data in the order inserted, particularly if no rows have been deleted from the table with subsequent inserts. However, it was essentially luck. Control everything you can - default behavior has a way of creeping through revisions and system changes. Don't count on it if you can help it. | <urn:uuid:464ec6e4-5e37-44e7-8ea3-d5f825f48fd7> | 2.71875 | 496 | Comment Section | Software Dev. | 61.217667 |
Once upon a time (in the 1960s), the term ‘hacker’ was used to denote a person particularly skilled in a technical area, usually programming. At the same time, “cracker” was used for people who attacked computer systems. This was a niche usage, and consigned mostly to MIT (where the term hacker originated) and its alumni. As the words spread into the popular vocabulary. their meanings changed subtly. Cracking is now generally used to describe the act of beating a single piece of encryption or security (for example, cracking a password), whereas hacking can refer to either using detailed system knowledge to improve a system (eg, kernel hacking) or gaining access to a computer or data through a method not intended (eg, ‘he used a cracked password to hack into the database’).
Go to XPATH Injection on the left-hand side of the screen.
In this example, we will attack the password field to display more information. The password is checked using an XPATH statement that will return every line that matches both the username and password that the user entered. We can subvert this statement and add an OR clause that always returns true, and so matches every line in the database. Enter the username Mike and the password:
test123′ or ‘a’='a
This is placed within quotes by XPATH, so outer quotes aren’t needed. Since this always evaluates to true, it will return every user. Not all web forms allow you to enter text. Sometimes, you have to select from a predetermined list. This doesn’t mean that they are safe from attack, it just means that hackers have to be a bit more cunning.
Think your website’s safe because you have the latest Apache security patches? Badr FERRASSI shows you how the hackers can still get in.
From social networks to shopping and banking, the web has become a part of our dai;ly lives. But how secure is it? Vulnerabilities in servers are generally Identified and patched quickly, but what about the web applications that run on these servers? What if a hacker could compromise these applications and make them do their bidding? Well, that’s exactly what’s happening on the internet every day. in this tutorial, we will use WebGoat, a demonstration web app, to show you the techniques that these hackers are using because understanding the threat is the first step to protecting yourself from it.
- PHP.net ( http://php.net/ ) is, without doubt, the best resource for information about what’s what in PHP. Unparalleled documentation.
- PHP for Absolute Beginners, written by Jason Lengstorf and published by Apress, is a great book for beginners. It’ll take you from knowing nothing to almost a little bit of everything as you build a blog in PHP. It’s pretty big — 408 pages — but you’ll learn a lot. http://www.apress.com/9781430224730
- PHP Cookbook, 2nd Edition is another great resource. Written by Adam Trachtenberg and David Sklar and published by O’Reilly, this 816-pager covers both basic and advanced material: everything from strings to using and building REST and SOAP web services: http://shop.oreilly.com/product/9780596101015.do. O’Reilly has been kind enough to put the first edition up on the web for free: http://commons.oreilly.com/wiki/index.php/PHP_Cookbook
- PHP Tutorials at Nettuts+: ( http://net.tutsplus.com/category/php/ ) Nettuts+ offers some of the best PHP tutorials around.
- All over the web, there are bunches of great sites with great PHP tutorials. If you’re ever stuck, just do a search, and you’re almost guaranteed to find a solution.
I mentioned a few times that there’s no way we could cover every PHP topic, so here’s a super-short list of topics you might want to look into if you’re interested in pursuing PHP. Don’t forget, you can also learn so much more about the topics we did discuss.
Image Processing (with ImageMagick or other extensions)
Object Oriented PHP
PDO (PHP Data Objects)
SQL Injection Attacks
Mail: sending and receiving via IMAP or POP3, etc.
Internationalization / Localization
PHP on the Command Line | <urn:uuid:687ff4bd-ae27-4093-86ec-4f88c6d85336> | 3.234375 | 965 | Personal Blog | Software Dev. | 59.433875 |
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All content Copyright © The University of Reading unless otherwise stated.
This page outlines the some of the work that has been done or is in progress in the Radar Group.Note: the information on this page is rather old, and needs updating.
The main interest in clouds stems from their strong effect on the earth's radiation budget and hence their role in the climate system. Standard cloud observing instruments such as satellite-borne radiometers suffer from poor vertical resolution, but in recent years there has been growing interest in the use of millimetre-wave radar to make high vertical resolution measurements of clouds. A single radar can be used to determine the macroscopic properties of clouds (such as cloud cover and inhomogeneity), while combinations of active instruments can be used to derive microphysical properties (such as water content and particle size). These can be used to directly validate atmospheric models or to test algorithms that could be used by the proposed spaceborne cloud radar and lidar. The work is funded under the Cloud Characteristics project.
Deriving cloud overlap statistics from radar.
Quantifying the effect of cirrus inhomogeneity on emissivity.
Cirrus particle sizing using a spaceborne radar and lidar.
Dual-wavelength measurement of liquid water content in stratocumulus.
Dual-wavelength measurement of ice water content in cirrus.
Weather radarThe polarisation and Doppler capability of the Chilbolton 3-GHz radar, coupled with its very narrow beamwidth, make it an ideal tool with which to study the characteristics of precipitation. Much of the work is focussed towards improving the algorithms used by radars to measure rain rate for the purposes of flood forecasting. Radar also offers the possibility to distinguish between heavy rain and hail. Recent work has included:
Development of attenuation correction algirithms at C-band using ZDR.
Deriving raindrop shape versus size from the consistency of the various polarimetric variables - fundamental to many rain retrieval algorithms.
Distinguishing between convective and stratiform rain using vertical profiles of reflectivity - improves rainrate measurements made by non-polarised radars.
A case study in which oblate hail was observed with a preferred fall mode - could have profound implications for existing hail-detection algorithms.
Mesoscale dynamicsWhen cloud or rain is present, the radars at Chilbolton can measure the velocity component along a line towards the antenna, which enables the wind field associated with mesoscale weather systems to be mapped out. The unique 1/4 degree beamwidth of the 3-GHz radar enables structure on much smaller scales to be resolved which is essential for measuring waves and convection.
Here we present images and preliminary analysis from experiments and new data acquisition systems.
Doppler spectra in stratocumulus on 26 August 1998: bimodal spectra
CWVC 1: 3D visualisation; velocity structure; model comparison
Negative KDP as an indicator of strong electric fields in thunderstorms | <urn:uuid:d5caa585-b502-404e-8792-a9e126a2242f> | 2.6875 | 627 | Content Listing | Science & Tech. | 23.373696 |
British physicist David Tyler on growing doubts about Darwinism in fruit flies
This empirical work is worth noting on two counts. First, we are here considering a mechanism that is central to Darwinian evolution. Positive natural selection of hereditable variation is the key (we are informed) to understanding how descent with modification occurs. However, the first set of empirical data relating to a sexually reproducing species does not confirm that modification works this way. This is why Long's comment is worth repeating: "This research really upends the dominant paradigm about how species evolve". Many scientists have long suspected that the Darwinian mechanisms are inadequate to account for large-scale transformation - these research findings provide empirical support for such doubts.
The other reason for taking an interest in this research is that the Darwinian paradigm has been widely used in the development of drugs for medical use. Whereas the classical view is that genes have specific functions, the new research supports the growing body of evidence that the norm is for genes to have pleiotropic effects. A novel SNP can then be expected to have not one, but many, effects. This has been underplayed by researchers of a darwinian persuasion.
"Based on that flawed paradigm, Rose noted, drugs have been developed to treat diabetes, heart disease and other maladies, some with serious side effects. He said those side effects probably occur because researchers were targeting single genes, rather than the hundreds of possible gene groups like those Burke found in the flies. Most people don't think of flies as close relatives, but the UCI team said previous research had established that humans and other mammals share 70 percent of the same genes as the tiny, banana-eating insect known as Drosophila melanogaster."
Find out why there is an intelligent design controversy: | <urn:uuid:30ce4d15-5b6f-41fa-bb30-ad1f19324bba> | 3.046875 | 362 | Personal Blog | Science & Tech. | 30.023319 |
JSON is a new human readable data format that has become very popular in the last few years, especially in web development.
JSON is very similar to XML. They both try to solve the same problem by creating a simple, human readable format for storing data. Up until recently, XML was used for any type of system that needed to send small portions of data quickly without a database attached. Think API calls that ask for information from the server. For the most part, XML does the job just fine. So what’ the need for JSON?
JSON is claimed to have many benefits over XML, including:
- “Easier” to read
- Faster to parse
- Takes up less space
Although “‘easier’ to read” is a point that’s difficult to measure, the other two points are not.
It’s very easy to see that JSON does indeed require less space to store the same information. After a quick look on the JSON website, you can find several examples that compare the two formats. Just by looking at the page, it’s easy to determine that the JSON representation takes far less characters to describe than its XML counterpart. For instance, the first example (a glossary data structure) requires 502 characters in XML, while only 345 characters in JSON (about 30 % less space).
Now for the “faster to parse” point, which is a bit harder to really test. For this point, I wrote up a quick test to determine how fast I could parse a XML and JSON string into a Java object.
For XML parsing, I used the build in SAX Parser. The SAX Parser allows me to iterate through the XML file and assign XML values to the appropriate value in the object. This method is a bit more cumbersome than what I used for JSON parsing, but certainly not unreasonable.
For JSON parsing, I loaded up the GSON library, which easily converts between JSON and java objects with just a one liner. All that was needed was the class definition itself (i.e. the Book class with properly named fields). This does, however, couple the class variables to the JSON instance. If either the class instance names change, or the JSON field names change, problems will arise.
To begin, I took a fairly simple data structure and created a XML and JSON representation of it. The following two XML and JSON files were created using information from Programming Pearls.
The parsing test was run on both the above XML and JSON files 10,000,000 times. The results are not surprising. JSON is parsed and converted into a Java object about 30% faster than XML.
- Average JSON Run time: 3.647208974029518E-5
- Average XML Run time: 5.011537916910817E-5
My findings are that JSON runs 30% faster and takes up 30% less space than XML. These results seem to be in line with what much of the development community believes in regards to the two formats. The switch to JSON for data handling can net a fairly large increase in performance, while also reducing the amount of space required. | <urn:uuid:ec387919-612f-4839-8b09-8238ce249eeb> | 2.84375 | 656 | Personal Blog | Software Dev. | 64.002576 |
|IUPAC name||Diisobutylaluminium hydride|
|Other names||DIBAH; DIBAL; DiBAlH; DIBAL-H; DIBALH|
|Molecular formula||C16H38Al2 (dimer)|
|Molar mass||142.22 (monomer)|
116–118 °C/1 mmHg
|Solubility in water||hydrocarbon solvents|
|Main hazards||ignites in air|
| Except where noted otherwise, data are given for|
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references
Diisobutylaluminium hydride, DIBAL, DIBAL-H or DIBAH, is a reducing agent with the formula (i-Bu2AlH)2, where i-Bu represents isobutyl (-CH2CH(CH3)2). This organoaluminium compound was investigated originally as a co-catalyst for the polymerization of alkenes.
Like most organoaluminum compounds, the compound’s structure is probably more than that suggested by its empirical formula. A variety of techniques, not X-ray crystallography suggest that the compound exists as a dimer and a trimer, consisting of tetrahedral aluminium centers sharing bridging hydride ligands. Hydrides are small and, for aluminium derivatives, are highly basic, thus they bridge in preference to the alkyl groups.
- (i-Bu3Al)2 → (i-Bu2AlH)2 + 2 (CH3)2C=CH2
Although DIBAH can be purchased commercially as a colorless liquid, it is more commonly purchased and dispensed as a solution in organic solvents such as toluene.
Use in organic synthesis
DIBAH is useful in organic synthesis for a variety of reductions, including converting esters and nitriles to aldehydes. By contrast, LiAlH4 reduces esters and acyl chlorides to primary alcohols, and NaBH4 fails to reduce most esters. DIBAH reacts slowly with electron poor compounds, and more quickly with electron rich compounds. Thus, it is an electrophilic reducing agent whereas LiAlH4 can be thought of as a nucleophilic reducing agent.
DIBAH, like most alkylaluminium compounds, reacts violently with air and water, potentially leading to fires.
- ↑ K. Ziegler, H. Martin and F. Krupp (1960). "Metallorganische Verbindungen, XXVII Aluminiumtrialkyle und Dialkyl-Aluminiumhydride Aus Aluminiumisobutyl-Verbindungen". Justus Liebigs Annalen der Chemie 629 (1): 14-19. doi:10.1002/jlac.19606290103.
- ↑ Mark F. Self, William T. Pennington and Gregory H. Robinson "Reaction of diisobutylaluminum hydride with a macrocyclic tetradentate secondary amine. Synthesis and molecular structure of [Al(iso-Bu)]2[C10H20N4][Al(iso-Bu)3]2: evidence of an unusual disproportionation of (iso-Bu)2AlH" Inorganica Chimica Acta (1990), volume 175, pp. 151-3. doi:10.1016/S0020-1693(00)84819-7.
- ↑ Eisch, J. J. Organometallic Syntheses Volume 2, Academic Press: New York, 1981. ISBN 0-12-234950-4.
- ↑ Galatsis, P. “Diisobutylaluminum Hydride” in Encyclopedia of Reagents for Organic Synthesis John Wiley & Sons: New York, 2001. doi:10.1002/047084289X.rd245
de:Diisobutylaluminiumhydrid Italic text
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