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Introduces the fundamentals of XML, including how to read a basic XML document, the XML document structure, and viewing XML source documents. It shows how to build an XML data document, including creating elements and element modes, naming XML objects, and creating declarations and well-formed documents. Building DTDs is explained in detail, along with creating and managing internal, external, and parameter entities. Also includes a detailed discussion of the Document Object Model, Cascading Style Sheets (CSS), and XSL Style Language.
XML has been becoming more and more popular with each year that passes. In this introductory tutorial on XML, topics covered include a break down of the XML document, with a detailed explanation of each part, as well as individual lessons that focus on the basics of a markup language. Entities, elements, and tags are all examples of what makes up the meat of an XML document. In addition to the language itself, there is a small section that lists the most popular editors on the market today. The XML standard was created by W3C to provide an easy to use and standardized way to store self-describing data.
MonoPlane Web Designer (MWD) is a promising and unique technology for rapid development of XML / XSLT / XPath based websites. This is a website development tool for Microsoft .NET framework. Features: Configurable panel-based site layout; Optimized page rendering to minimize page download time; Built-in website Search engine; Configurable support for templated lists with Paging; Unlimited enhancements via plug-in modules. Achieve a level of separation between content editing, graphics design and programming tasks to get your web project up and running in hours or days, not weeks or months. Use provided generic XSL templates or create your own.
Describes XML categories, XML document types and how to create them, the XML DTD, XML elements and attributes along with many examples. It describes a document type definition, what its purpose is and gives an example. Element attributes and process instructions are also covered. This tutorial describes XML uses, XML categories. Markup languages, such as HTML or XML, allow special markup to be embedded with the rest of the text that will enable the program that displays the file to determine how to display the text.
XMLTraining.com supplies XML training courses, XML classes, XML books and XML resources for the IT professional. This data is supplied in different formats which include XHTML web pages, and XML news feeds (RSS 1.0, RSS 2.0 and Atom). Searching for an XML training course or book couldn't be easier with the XMLTraining.com advanced search tools, also available in XML formats. The website is uniquely designed in which it retrieves data from Amazon.com's web services and allows user to search for XML books more accurately.
Accelebrate teaches a wide array of hands-on, instructor-led XML courses, including Core XML training, Mastering XSLT training, Mastering xmlspy training, and other courses. All courses are delivered at client sites for groups of 3-15 attendees and can be customized to these attendees' specific needs. Any development tool can be used. Based in Atlanta, Georgia, Accelebrate welcomes the opportunity to serve clients in the United States, Canada, the Caribbean, and worldwide.
XMLMania.com provides the most up-to-date news source on the World Wide Web. Covering everything XML, this includes forums, XML examples, downloads, tutorials, news releases and more. XMLMania.com provides a free PR service were companies can quickly get their products and articles published on the WWW to a refined audience. XMLMania.com provides RSS news feeds, and Google News feeds via keyword selection, all of which is free. The XMLMania.com website is an example of the semantic web, complying with the latest XHTML and CSS standards.
XML/XSLT Maker is a code generator that can create dynamic, XML/XSLT-based Websites from databases in no time. Supported databases includes Microsoft Access, Microsoft SQL Server, Oracle, or any database with ADO or ODBC connectivity. XML/XSLT Maker can automatically generate both ASP (Active Server Pages) for content and XSLT (Extensible Stylesheet Language Transformation) stylesheet for layout. Using the generated ASP and XSLT stylesheets, users can add, delete, edit, view and search data in the database easily on the Web.
XMLStarlet is a set of command line utilities (tools) which can be used to transform, query, validate, and edit XML documents and files using simple set of shell commands in similar way it is done for plain text files using UNIX grep, sed, awk, diff, patch, join, etc commands. This set of command line utilities can be used by those who deal with many XML documents on UNIX shell command prompt as well as for automated XML processing with shell scripts. Calculate values of XPath expressions on XML files; Modify or edit XML documents. | <urn:uuid:48953aed-32ae-45ff-95d3-348af67cb95d> | 3.234375 | 1,043 | Content Listing | Software Dev. | 48.284224 |
- slide 1 of 4
Instead of directly answering the question of "Do engineers use differential equations?" I would like to take you through some background first and then see whether differential equations are used by engineers.
Years ago when I was working as a design engineer for a shock absorber manufacturing company, my concern was how a hydraulic shock absorber dissipates shocks and vibrational energy exerted form road fluctuations to the car suspension system, how shock absorbers behave in the suspension system, and what are the effects of other elements of this system like the mass of the components, the spring rate of the suspension springs and tires, etc.
My research led me to a paper that used a very complicated nonlinear differential equation to study the functional behavior of hydraulic shock absorbers. Here I have to mention that in those days library and paper research was not as easy as today. Computers and the Internet were not as popular as today, and we had to search through engineering indexes which were annually published books containing abstracts of related published papers and articles and order the ones we wanted, if we could find any.
I am not going to discuss the nonlinear differential equation of hydraulics shock absorber here because it takes its own space and time and, more or less is beyond the scope of this article. All I can say is after reading that paper, I had a vivid idea about the function and behavior of shock absorbers in a suspension system.
Later I used the Gauss-Jordan numerical method to solve differential equation of a damper-spring-mass system (figure 1) in a BASIC program. This way I had a simple simulation program by which I could not only understand the effects of different parameters of the system, but also feel the effects of changing, for instance, spring rate or damping coefficient. This simulating program enabled me to have direct practice of spring mass system as if I were working in a lab with real items. I cannot represent the actual results here because I have retired my old Amiga 500 computer which I used for that program with an up-to-date PC but, the results I got looked like figure 2.
- slide 2 of 4
So Do Engineers Use Differential Equations?
Simulations and simulators are hardware or software means to make one feel as if working in a real environment and gaining direct experience of a simulated subject system. Many engineering simulators use mathematical models of subject systems in the form of differential equations. Perhaps the reason why some engineers and engineering students feel differential equations are not used by engineers is that they are working with simulating and modeling software (such as the one shown in figure 3) and don’t see the actual mathematical model behind them.
- slide 3 of 4
What is a Differential Equation?
A differential equation is the relation between a function and its derivatives. Many engineering principles can be described based on such a relation. For instance in the damper-spring-mass system of figure 1:
x=f(t) is the unknown function of motion of the mass according to time t (independent variable)
-kx is the reactive force exerted by spring
dx/dt is change of distance according to change of time which is called velocity
-cdx/dt is the reactive force exerted by the damper
d2x/dt2 is change of velocity according to change of time which is called acceleration
md2x/dt2 is the force applied to the mass
Based on Newton’s Second Law of motion (F=ma)
md2x/dt2=-kx-cdx/dt or d2x/dt2=-(k/m)x-(c/m)dx/dt
- slide 4 of 4
The objective of solving a differential equation is finding the unknown function (in the above example) known as the answer of the differential equation.
This answer can be shown in analytical form, if applicable, or graphical form (figure 2 in above example) or any other visual form such as figure 4 for visualization of heat transfer in a pump casing, by solving the Heat equation.
Many scientific laws and engineering principles and systems are in the form of or can be described by differential equations. Differential equations are mathematical tools to model engineering systems such as hydraulic flow, heat transfer, level controller of a tank, vibration isolation, electrical circuits, etc.
Wherever it is possible to define a relation between a function and its derivatives, it is possible to make a mathematical model and study and understand the behavior of the system related to that function. | <urn:uuid:497721dc-f127-40e8-9a81-8810f29cb8dd> | 2.734375 | 936 | Truncated | Science & Tech. | 31.414779 |
windstormArticle Free Pass
windstorm, a wind that is strong enough to cause at least light damage to trees and buildings and may or may not be accompanied by precipitation. Wind speeds during a windstorm typically exceed 55 km (34 miles) per hour. Wind damage can be attributed to gusts (short bursts of high-speed winds) or longer periods of stronger sustained winds. Although tornadoes and tropical cyclones also produce wind damage, they are usually classified separately.
Windstorms may last for just a few minutes when caused by downbursts from thunderstorms, or they may last for hours (and even several days) when they result from large-scale weather systems. A windstorm that travels in a straight line and is caused by the gust front (the boundary between descending cold air and warm air at the surface) of an approaching thunderstorm is called a derecho. Gustavus Hinrichs, a physics professor from the University of Iowa and founder of the Iowa Weather Service, applied the term derecho—a Spanish word that means “straight” or “right”—to straight-line winds in 1888. Derechos are capable of causing widespread damage and landscape devastation. For example, the winds of a derecho occurring in northern Minnesota, U.S., on July 4, 1999, peaked at or near 160 km (100 miles) per hour and blew down tens of millions of trees.
Longer-period windstorms have two main causes: (1) large differences in atmospheric pressure across a region and (2) strong jet-stream winds overhead. Horizontal pressure differences may accelerate the surface winds substantially as air travels from a region of higher atmospheric pressure to one of lower. In addition, the vertical turbulent mixing of stronger jet-stream winds aloft can produce strong gusty winds at ground level.
Intense winter storms are frequently the cause of long-lasting windstorms. Such winter low-pressure systems have large horizontal pressure differences and are always accompanied by strong jet-stream winds aloft. In the northeastern United States, windstorms that occur as particularly strong low-pressure systems and move northward along the Atlantic Coast are called “nor’easters.”
Cold fronts associated with such intense low-pressure systems can produce windstorms both as they pass and for a period afterward as colder air flows overhead. Such movement of cold air aloft is particularly effective at causing the downward mixing of jet-stream winds. Windstorms create dust storms and sandstorms in arid and semiarid regions. In North Africa, these cold frontal windstorms are often referred to as haboobs.
Blizzard conditions can occur when the windstorms pass over snow-covered ground. The U.S. National Weather Service issues blizzard warnings when sustained winds or frequent gusts are forecast to be 56 km (35 miles) per hour or greater for at least three hours with sufficient blowing snow to reduce visibility to less than 400 metres (1,300 feet). This type of windstorm also produces dangerous wind chills. A wind speed of 55 km (34 miles) per hour with an air temperature of –6.5 °C (20.3 °F), for example, produces a loss of body heat equivalent to what occurs in calm winds with an air temperature of –29 °C (–20.2 °F). When cold fronts pass over mountains, cold air accelerates even more as it moves downslope. Downslope winds are called fall winds or katabatic winds. Windstorms of this type are called boras or downslope windstorms.
Warm air flowing poleward to the east of intense low-pressure systems can also produce windstorms. In North Africa and the Arabian Peninsula such a windstorm, called khamsin, can transport large amounts of dust and sand northward. When the winds blow over mountains, the warm air is heated even further by compression as it moves toward lower altitudes. A strong, warm windstorm is called a chinook in the northwestern United States and southwestern Canada, a foehn in the European Alps, and a zonda in the Andes Mountains of Argentina. In 1972 a chinook in Boulder, Colo., U.S., produced a wind gust that briefly reached 215 km (134 miles) per hour and caused extensive damage. Locations adjacent to large mountain barriers in the middle and higher latitudes are noted as being particularly vulnerable to downslope windstorms. At lower latitudes these intense low-pressure systems and the associated wind effects of a strong jet stream do not normally occur.
What made you want to look up "windstorm"? Please share what surprised you most... | <urn:uuid:ac36eead-b9df-471f-a5ed-8dbe7e8874a2> | 4.1875 | 954 | Knowledge Article | Science & Tech. | 53.198498 |
We currently think that the universe is some 13.7 billion years old. With that in mind, the zoomed-in cutaway above is pointing to a very, very distant galaxy, which we've observed 420 million years after the big bang. That means the light we're seeing from it spent 13.3 billion years traveling through the cosmos. Whoa.
The galaxy, known as MACS0647-JD, was spotted by the Cluster Lensing And Supernova Survey with Hubble (or CLASH), which is an effort by a global team of researchers captained by Marc Postman of the Space Telescope Science Institute in Baltimore. The group employs a technique called gravitational lensing to study the stars, which involves using a cluster of galaxies as a loose focal point to spot the light of an even more distant object as that light curves around said galaxies.
"This cluster does what no manmade telescope can do," Postman said in a release by NASA. "Without the magnification, it would require a Herculean effort to observe this galaxy." In fact, MACS0647-JD may be so far away that we can't observe it using today's manmade telescopes, which means we can't use spectroscopy to confirm just how distant it really is. Still, the CLASH survey team is "confident the fledgling galaxy is the new distance champion," with MACS0647-JD beating out another faraway galaxy examined by the survey, which was observed 490 million years after the big bang.
Here's more about this fresh observation from NASA:
MACS0647-JD is so small it may be in the first steps of forming a larger galaxy. An analysis shows the galaxy is less than 600 light-years wide. Based on observations of somewhat closer galaxies, astronomers estimate that a typical galaxy of a similar age should be about 2,000 light-years wide. For comparison, the Large Magellanic Cloud, a dwarf galaxy companion to the Milky Way, is 14,000 light-years wide. Our Milky Way is 150,000 light-years across.
So, what's MACS0647-JD up to now? 13 billion years is a pretty long time, after all about the time it took me to play through Borderlands 2. Here's a few thoughts from Dan Coe, also of the Space Telescope Science Institute, who said the following in NASA's release: "This object may be one of many building blocks of a galaxy Over the next 13 billion years, it may have dozens, hundreds, or even thousands of merging events with other galaxies and galaxy fragments." | <urn:uuid:f3107447-c326-4567-8f57-589f64330cad> | 3.265625 | 529 | Personal Blog | Science & Tech. | 57.315656 |
Your program takes a phone number with alphabet as an input, converts it into numeric digits, and outputs the result to the standard output.The phone number is XXXXX of number, alphabet (lowercase and uppercase), and dash(-).Your program outputs numbers only, ignoring all dashes in user's input.You can safely assume that there are at most 40 characters in user's input.You can assume that there's no space in the phone numbers.Have to use switch/case (cctype.h)sample runEnter a phone number: 1-beg-LoTThe numeric digits are(NNN) NNN-NNNN
Language (or Software): C++
Welcome to JustAnswer.
My name is XXXXXXXX XXX I will help you.
If you have any file(s). Zip, upload the file to http://wikisend.com and post download link here.
i have none
When do you need this answer:
this is what i need it for
in the next 8hrs or so
I will provide you answer with in next 30 minutes.
the whole code ?
just like the sample run ?
that would be great
at most 40 character taking in consideration upper and lower case with numbers and dashes
i mean u have the link to the assignment
so how does this work ? i wait for 30 min ?
yes, I have
which compiler are you using?
Dev C++, Code blocks or Visual Studio C++?
im new to this stuff...we use visual studio 2010
Please check back in 30 minutes.
ill be here waiting
Can I use the strings in this?
Download answer from here PhoneNumber_CPP.cpp
You can ask me again using "For LogicPro only" at the start of your questions like other customers to get instant and fresh answers.It will ensure that question is for me.Please bookmark my profile page:http://www.justanswer.com/computer/expert-logicpro/so you can come back and ask me a question anytime.Rate this answer as 'Excellent Service' or ask me if you need more information.
where can i rate u ?
You will see an option to rate the answer. | <urn:uuid:1016957c-a6d5-4cc9-b197-cb5a114494ce> | 3.109375 | 466 | Q&A Forum | Software Dev. | 73.045082 |
Evolving Technology, Advancing Science
July 9–13, 2012
Presented at the Lunar and Planetary Institute
Other Data Sources
Images from all the missions discussed during the Mars Revealed workshop can be found on the Jet Propulsion Laboratory’s Planetary Photojournal website. From the homepage, click on the picture of Mars then use the filters to search for images by mission. The images on this site are mostly press release images so the collection is far from comprehensive, but is a good place to start. Below are links to find more mission imagery and data, though obtaining data is not always practical.
The National Space Science Data Center (NSSDC). The NSSDC has various types of data from all missions but data is not readily available on the NSSDC website. The data typically has to be requested from the institution that archives the data and it is typically not in a useful format.
Mariner 9 Images
Other than doing a Google search, images from Mariner 9 are difficult to find in one place. Most data from Mariner 9 is available through the NSSDC. A free software has been created that can be used to view Mariner 9 images. Information on this software, and how to download it, can be found at http://petermasek.tripod.com/mariner9.html.
Mars Global Surveyor Images
Images found on this website were taken by the Mars Orbiter Camera (MOC).
For further information, contact
Lunar and Planetary Institute
3600 Bay Area Boulevard
Houston, TX 77058 | <urn:uuid:fe40ff19-d36b-40ae-a905-4f71f65a561a> | 3.234375 | 325 | Knowledge Article | Science & Tech. | 45.924572 |
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Explanation of radio bandwidth.
Antony Hewish (1914 - ) received the Nobel Prize for Physics in 1974 along with Sir Martin Ryle for their pioneering research in radio astrophysics.
Sir Martin Ryle (1918 - 1984) received the Nobel Prize for Physics in 1974 along with Antony Hewish for their pioneering research in radio astrophysics.
A series of articles about radio and optical astronomy. The site also deals with 'Big Bang' cosmology. The interactive sections include quizzes and games.
Bar codes may become a thing of the past/ Smart labels, also called radio frequency identification (RFID) tags, could change supermarkets forever. Find out how on this How Stuff Works page.
A site dedicated to building and experimenting with radio electronics, mainly through the use of the crystal set. Information about the society, kits to buy, projects to make, books, tips for science ...
Listen the sound a solar flare makes and other read answers to questions on space weather.
SETI@home is a scientific experiment that uses Internet-connected computers in the Search for Extraterrestrial Intelligence (SETI). You can participate in this citizen science project by running a ...
The site explains the basic of the electromagnetic spectrum and the various wavelengths of which it is composed (Radio Waves, Microwaves , Infrared, the Visible Spectrum, Ultraviolet, Gamma Rays, ...
NASA page about electromagnetic waves with descriptions of such waves and their uses.Covers radio waves, microwaves, infrared, visible light, ultraviolet (UV), x-rays and gamma rays.
Showing 31 - 40 of 42 | <urn:uuid:5272d585-9d33-476d-a26f-cb588f310aee> | 2.75 | 428 | Content Listing | Science & Tech. | 48.559801 |
Newton's Second Law of Motion
Learn about NASCAR racing at the National Science Foundation's Science of Speed website.Flickr Physics
Visit The Physics Classroom's Flickr Galleries and take a visual overview of Newton's laws of motion.Flickr Physics
Visit The Physics Classroom's Flickr Galleries and take a visual exploration of skydiving.Physics of Racing
Enjoy this New York Times science article that discusses that aerodynamic trick used by race car drivers - drafting.
This EJS simulation from Open Source Physics (OSP) contrasts free fall and falling with air resistance.Tracker Video Analysis: Air Resistance
Try a fresh approach to doing physics with this video analysis idea that uses free software from Open Source Physics (OSP).The Laboratory
Looking for a lab that coordinates with this page? Try the Coffee Filter Skydiver Lab from The Laboratory. Requires motion detectors.The Laboratory
Looking for a lab that coordinates with this page? Try the From a Feather to an Elephant from The Laboratory. Requires motion detectors.The Laboratory
Give students a chance to design a study. Try the Falling Body Spreadsheet Lab from The Laboratory.Curriculum Corner
Assess your students' understanding with this survey from The Curriculum Corner.Curriculum Corner
Take your students skydiving with this sense-making activity from The Curriculum Corner.Curriculum Corner
Learning requires action. Give your students this sense-making activity from The Curriculum Corner.Treasures from TPF
Need ideas? Need help? Explore The Physics Front's treasure box of catalogued resources on Newton's second law.
Free Fall and Air Resistance
In a previous unit, it was stated that all objects (regardless of their mass) free fall with the same acceleration - 9.8 m/s/s. This particular acceleration value is so important in physics that it has its own peculiar name - the acceleration of gravity - and its own peculiar symbol - g. But why do all objects free fall at the same rate of acceleration regardless of their mass? Is it because they all weigh the same? ... because they all have the same gravity? ... because the air resistance is the same for each? Why? These questions will be explored in this section of Lesson 3.
- Why do objects that encounter air resistance ultimately reach a terminal velocity?
- In situations in which there is air resistance, why do more massive objects fall faster than less massive objects?
To answer the above questions, Newton's second law of motion (Fnet = m•a) will be applied to analyze the motion of objects that are falling under the sole influence of gravity (free fall) and under the dual influence of gravity and air resistance.
As learned in an earlier unit, free fall is a special type of motion in which the only force acting upon an object is gravity. Objects that are said to be undergoing free fall, are not encountering a significant force of air resistance; they are falling under the sole influence of gravity. Under such conditions, all objects will fall with the same rate of acceleration, regardless of their mass. But why? Consider the free-falling motion of a 1000-kg baby elephant and a 1-kg overgrown mouse.
If Newton's second law were applied to their falling motion, and if a free-body diagram were constructed, then it would be seen that the 1000-kg baby elephant would experiences a greater force of gravity. This greater force of gravity would have a direct affect upon the elephant's acceleration; thus, based on force alone, it might be thought that the 1000-kg baby elephant would accelerate faster. But acceleration depends upon two factors: force and mass. The 1000-kg baby elephant obviously has more mass (or inertia). This increased mass has an inverse affect upon the elephant's acceleration. And thus, the direct affect of greater force on the 1000-kg elephant is offset by the inverse affect of the greater mass of the 1000-kg elephant; and so each object accelerates at the same rate - approximately 10 m/s/s. The ratio of force to mass (Fnet/m) is the same for the elephant and the mouse under situations involving free fall.
This ratio (Fnet/m) is sometimes called the gravitational field strength and is expressed as 9.8 N/kg (for a location upon Earth's surface). The gravitational field strength is a property of the location within Earth's gravitational field and not a property of the baby elephant nor the mouse. All objects placed upon Earth's surface will experience this amount of force (9.8 N) upon every 1 kilogram of mass within the object. Being a property of the location within Earth's gravitational field and not a property of the free falling object itself, all objects on Earth's surface will experience this amount of force per mass. As such, all objects free fall at the same rate regardless of their mass. Because the 9.8 N/kg gravitational field at Earth's surface causes a 9.8 m/s/s acceleration of any object placed there, we often call this ratio the acceleration of gravity. (Gravitational forces will be discussed in greater detail in a later unit of The Physics Classroom tutorial.)
Look It Up!
As an object falls through air, it usually encounters some degree of air resistance. Air resistance is the result of collisions of the object's leading surface with air molecules. The actual amount of air resistance encountered by the object is dependent upon a variety of factors. To keep the topic simple, it can be said that the two most common factors that have a direct affect upon the amount of air resistance are the speed of the object and the cross-sectional area of the object. Increased speeds result in an increased amount of air resistance. Increased cross-sectional areas result in an increased amount of air resistance.
Why does an object that encounters air resistance eventually reach a terminal velocity? To answer this questions, Newton's second law will be applied to the motion of a falling skydiver.
In the diagrams below, free-body diagrams showing the forces acting upon an 85-kg skydiver (equipment included) are shown. For each case, use the diagrams to determine the net force and acceleration of the skydiver at each instant in time. Then use the button to view the answers.
The diagrams above illustrate a key principle. As an object falls, it picks up speed. The increase in speed leads to an increase in the amount of air resistance. Eventually, the force of air resistance becomes large enough to balances the force of gravity. At this instant in time, the net force is 0 Newton; the object will stop accelerating. The object is said to have reached a terminal velocity. The change in velocity terminates as a result of the balance of forces. The velocity at which this happens is called the terminal velocity.
In situations in which there is air resistance, more massive objects fall faster than less massive objects. But why? To answer the why question, it is necessary to consider the free-body diagrams for objects of different mass. Consider the falling motion of two skydivers: one with a mass of 100 kg (skydiver plus parachute) and the other with a mass of 150 kg (skydiver plus parachute). The free-body diagrams are shown below for the instant in time in which they have reached terminal velocity.
As learned above, the amount of air resistance depends upon the speed of the object. A falling object will continue to accelerate to higher speeds until they encounter an amount of air resistance that is equal to their weight. Since the 150-kg skydiver weighs more (experiences a greater force of gravity), it will accelerate to higher speeds before reaching a terminal velocity. Thus, more massive objects fall faster than less massive objects because they are acted upon by a larger force of gravity; for this reason, they accelerate to higher speeds until the air resistance force equals the gravity force.
here. Use the What a Drag! widget below to explore the dependence of the air resistance force upon these four variables. | <urn:uuid:da66d92f-c501-4b60-8b7e-5efae79de822> | 3.390625 | 1,640 | Tutorial | Science & Tech. | 50.849015 |
I inaugurate this blog with an article on PyPy, an implementation of Python very interesting in terms of performances because, as we shall see in this article, it is possible to compete with statically compiled languages such as C or C++. The article will break down as follows:
- What is Python ?
- What are the different implementations of the language ?
- What are the specificities of Pypy ?
- Just-in-time compilation.
- How do you compile and use Pypy ?
- Brief performances overview.
What is Python – Python is a modern programming language classified as a scripting language (it is interpreted, at least in its official implementation, CPython). Being very high level, it offers developers to increase productivity by allowing them to forget about low levels that you need to deal with in other languages such as C, making it a suitable language for learning programming. Indeed, it is easily accessible and quick to learn. Its syntax based on indentation (no braces or keywords to separate « blocks » of instructions) makes it more readable than most languages. Finally, here are some specifics of the language: Type Inference, adanced Object features (OOP), integer of arbitrary size, list comprehension for creating list in an elegent maniere, etc. ..
What are the different implementations of the language ? - The Python language is placed under a free license, there are many implementations, each with their specificities. Here are a few:
- CPython : Official implementation (the best known) written in C.
- Pypy : Implementation that provides a Just-in-Time compiler (JIT).
- ShedSkin : Implementation that use a Python-to-C++ translator. This one provides good performance frone the execution time point of view.
- Stackless : Implementation that does not use the call stack from C and replacing it with a Python-specific data structure . This implementation is largely based on the paradigm of concurrency programming, involving tasklets (a kind of micro-threads) to simulate a parallel execution of programs. The tasklets could be very numerous (hundreds or thousands), communicating one with each other easily, and be paused or awakened instantly, etc. ..
- Jython : Implementation written in Java.
- Iron Python : Implementation written in Java C#.
What are the specificities of Pypy ? - PyPy is an implementation of Python written in Python and featuring (among others), a JIT compiler (see next paragraph) that enable it to deliver performances comparables to most statically-compiled languages (C, C++, etc…). Pypy also offers a reduced memory consumption compared to CPython, and supports most of the libraries available with the official implementation.
Just-in-Time compilation – Since the Python language provides high-level tools (such as advanced object features), it is generally difficult and inefficient (compared to the low-level languages such as C) to compile it statically, so if you search for honorable performances you shouldn’t use static compilation. Fortunately, there is a high performance alternative to the static compilation, which is the JIT compilation (Just-In-Time, or « on the fly »). It is this technology that is used in the PyPy project, offering performance of statically compiled languages such as C or C++ to Python. Let’s see what it is.
The Just-In-Time compilation (or dynamic compilation) is a hybrid approach between the static compilation and interpretation, it aims to achieve performance equal or superior to the conventional static compilation. The JIT compilers convert bytecode into machine code on the fly (at runtime). But to limit the performance loss, several tweaks are used. First, it is possible to cache parts of a program to avoid having to retranslate it unnecessarily during subsequent runs if source code was not modified in the meantime. Second, thanks to a system able to detect hot spots (parts of a program being used very often during the execution), the compiler may decide to bring a part of the program into machine code if this is more interesting than simple interpretation in terms of execution time.
In addition, many optimizations are possible at runtime. A JIT compiler can use the execution context informations to improve program performances. In particular, it is possible to adapt the machine code produced according to the processor architecture or to perform the inlining of dynamic libraries, without losing the advantages of dynamic linkage.
JIT compilation is used by the Java Virtual Machine or the C #.
How do you compile and use Pypy ? - There are two ways to use PyPy. Either your favorite Linux distribution you propose directly from its deposits, in which case you can simply install it, or you can download the sources from the mercurial of PyPy. Beware, however, if you install Pypy from the repositories of your distribution, it may replace an existing version of Python on your computer.
Building from sources : We will see how to download the sources of PyPy, compile it and use the resulting binary. First and foremost, you must know that the compilation of PyPy is extremely resource-hangry (memory and CPU), if you do not have 4 GB of RAM on your computer, you should prefere to install it through you distribution depositories, otherwise you may enter in a endless swap loop ..
Once all the dependencies have been installed, download the source of PyPy by running the following command:
hg clone https://bitbucket.org/pypy/pypy
Then go to the goal directory:
Finally run the script with Python (or with PyPy itself if you have already installed it, which will save you time and memory):
python2 translate.py -Ojit
Enjoy the Mandelbrot’s fractal that will be drawn into your terminal during compilation.
After completing the long process, a binary called pypy-c is normally present in the directory. You can rename and / or move it to use as you wish. It replaces the traditional Python binary, you can use it as follows:
./pypy mon_script.py #Your Python script
Brief performances overview. - Finally, here is a brief overview of PyPy’s performances compared to other implementations / languages available on the official website of PyPy: http://speed.pypy.org/
Last world - All proposals and comments are welcome of course | <urn:uuid:505f3154-07b0-48a1-9f1a-a177486aa012> | 3.03125 | 1,331 | Personal Blog | Software Dev. | 34.260959 |
Bullock, S. H., H. A. Mooney, and E. Medina, eds. 1995. Seasonally dry tropical forests. New York: Cambridge University Press. 450 pp.
Frankie, G. W. 1997. Endangered havens for diversity. Book review of S. H. Bullock et al., eds. Seasonally Dry Tropical Forests (1995). BioScience 47:322–24.
Holdridge, L. R., W. C. Grenke, W. H. Hatheway, T. Liang, and J. A. Tosi Jr. 1971. Forest environments in tropical life zones: A pilot study. Oxford: Pergamon Press. 400+ pp.
Janzen, D. H., ed. 1983. Costa Rican natural history. Chicago: University of Chicago Press. 816 pp.
Janzen, D. H., ed. 1991. Historia natural de Costa Rica. Chicago: University of Chicago Press. 822 pp. Spanish translation of Janzen's 1983 volume.
McDade, L. A., K. S. Bawa, H. A. Hespenheide, and G. S. Hartshorn, eds. 1994. La Selva, ecology and natural history of a Neotropical rain forest. Chicago: University of Chicago Press. 486 pp.
Nadkarni, N., and N. Wheelwright, eds. 2000. Monteverde, ecology and conservation of a tropical cloud forest. New York: Oxford University Press. 573 pp.
Questia, a part of Gale, Cengage Learning. www.questia.com
Publication information: Book title: Biodiversity Conservation in Costa Rica: Learning the Lessons in a Seasonal Dry Forest. Contributors: Gordon W. Frankie - Editor, Alfonso Mata - Editor, S. Bradleigh Vinson - Editor. Publisher: University of California Press. Place of publication: Berkeley, CA. Publication year: 2004. Page number: xi.
This material is protected by copyright and, with the exception of fair use, may not be further copied, distributed or transmitted in any form or by any means. | <urn:uuid:b068183f-d8f0-4a5d-beae-ece60ffb7ee3> | 2.875 | 455 | Content Listing | Science & Tech. | 66.864828 |
If you were to trace human evolution backward in time and space, you’d eventually end up in Africa. There, millions of years ago, animal species evolved to walk upright on two legs and spend more of their lives on the ground than in the trees. Homo sapiens, the species you belong to if you’re reading this article, had appeared on the continent by 200,000 years ago. Your ancestors weren’t alone: Other upright, humanlike species were also around — at least for a while.
Scientists agree on Africa as a starting place because the oldest human bones have been found there. Eventually, ancient humans and other species moved to every other continent except Antarctica and the Americas. But how they evolved, or changed over time, once they left Africa isn’t entirely clear. Eventually, every cousin in the sprawling human family — except H. sapiens — became extinct.
Climate may have played an important part in the evolution of ancient people. Two new studies suggest that during ice ages, steep drops in temperature may have sent ancient species moving to more temperate, or mild, areas. As a result, these species would have been isolated from other populations.
One of the new studies looks at bones found in caves in southwestern China. A team of scientists report that the bones came from an ancient species that looked a lot, but not exactly, like H. sapiens. Either this type of H. sapiens looked different than others, or they belonged to a previously unknown humanlike species.
Darren Curnoe, who studied the bones from China, told Science News that he suspects a new species could have formed when early humans left Africa 120,000 years ago and evolved in isolation for tens of thousands of years. Anthropologists study humankind, and Curnoe, an anthropologist from the University of New South Wales in Sydney, studies human evolution.
On the other han
d, those bones may represent a new species that arose when two others interbred, Christopher Stringer told Science News. Stringer, an anthropologist at the Natural History Museum in London, worked on the other study. He suggests the bones came from a group of ancient H. sapiens that moved into the area and reproduced with a humanlike species called the Denisovans.
In their paper, Stringer and ecologist Jon Stewart from the Bournemouth University in England show how changes in climate have controlled the migration of different types of animals. Studies suggest, for example, that polar bears were once brown bears that became isolated in the north and adapted to the cold conditions.
Stringer and Stewart argue that changes in climate have had a major impact on the evolution and survival of humans and humanlike species, too. Ice age conditions may have driven the H. sapiens in what is now China to live and reproduce with the Denisovans.
The scientists also suggest that Neandertals, another species, may have evolved from an isolated humanlike population in western Asia during ice ages. In addition, the so-called “hobbits,” a short species known to scientists as Homo floresiensis, may also have evolved from other isolated humanlike species.
Not all scientists agree with the idea that dramatic changes in climate drove human migration — and then human evolution — in the way that Stringer and Stewart have outlined. Anthropologist Rick Potts from the Smithsonian Institution in Washington, D.C., told Science News that ancient species had to handle a wide range of environments. They probably could have adapted to the extremes brought on by the ice age and may not have needed to seek safer areas.
POWER WORDS (adapted from the New Oxford American dictionary)
anthropology The study of humankind.
ecology The branch of science that deals with the relations of organisms to one another and to their environments.
evolve To change gradually over successive generations.
species A group of living organisms consisting of similar individuals.
Neandertal An extinct species of human with a receding forehead and prominent brow ridges that was widely distributed in ice-age Europe between about 120,000 and 35,000 years ago.
ice age A time during a past geological period when temperatures dropped and glaciers formed. | <urn:uuid:8aed3082-d669-4398-9564-3560a7bae567> | 4.125 | 865 | Knowledge Article | Science & Tech. | 40.469486 |
"It Was a Mistake" | Sympathy for the Devils | You Get What You Pay For | As the World Warms |
Woe is Us | Up to Speed
Woe Is Us: Ready, set, panic.
If a tree falls in a forest and no one hears it, does it cause an earthquake? After studying the 2010 earthquake in Haiti that killed more than 200,000 people, University of Miami earth scientist Shimon Wdowinski concluded that the temblor may be linked to severe deforestation, which has removed 98 percent of the tree cover in Haiti's mountains.
With no roots to hold them together, the bare hillsides eroded much faster than forested ones would have. Then, in 2008, Haiti was
hit by two hurricanes and two tropical storms. Flooding further hastened erosion, transferring masses of sediment from the mountain slopes to the mouth of the Leogane Delta—just north of the earthquake's epicenter. That shift in weight, Wdowinski believes, was enough to rupture the previously unknown fault.
"Earthquakes have friction forces they have to overcome for the earth to move," he explains. "It's hard to move two blocks if they are [pressed] very tightly together.
If we remove something from on top, we bring it closer to the [point] where the two blocks can slide."
That something doesn't have to be soil. It can also be ice. Researchers from NASA and the U.S. Geological Survey say that a recent uptick in seismic activity in southern Alaska followed the retreat of glacial ice.
In other words, as the planet warms, it may also shake, rattle, and roll.
Up to Speed | <urn:uuid:cf2b0c0b-0040-4c4f-9626-fbdd8af13af4> | 3.1875 | 353 | Knowledge Article | Science & Tech. | 60.937637 |
Hot, Dry, and Cloudy (Artist Concept)
This artist's concept animation shows a cloudy Jupiter-like planet that orbits very close to its fiery hot star. NASA's Spitzer Space Telescope was recently used to capture spectra, or molecular fingerprints, of two "hot Jupiter" worlds like the one depicted here. This is the first time a spectrum has ever been obtained for an exoplanet, or a planet beyond our solar system.
The ground-breaking observations were made with Spitzer's spectrograph, which pries apart infrared light into its basic wavelengths, revealing the "fingerprints" of molecules imprinted inside. Spitzer studied two planets, HD 209458b and HD 189733b, both of which were found, surprisingly, to have no water in the tops of their atmospheres. The results suggest that the hot planets are socked in with dry, high clouds, which are obscuring water that lies underneath. In addition, HD209458b showed hints of silicates, suggesting that the high clouds on that planet contain very fine sand-like particles.
Capturing the spectra from the two hot-Jupiter planets was no easy feat. The planets cannot be distinguished from their stars and instead appear to telescopes as single blurs of light. One way to get around this is through what is known as the secondary eclipse technique. In this method, changes in the total light from a so-called transiting planet system are measured as a planet is eclipsed by its star, vanishing from our Earthly point of view. The dip in observed light can then be attributed to the planet alone.
This technique, first used by Spitzer in 2005 to directly detect the light from an exoplanet, currently only works at infrared wavelengths, where the differences in brightness between the planet and star are less, and the planet's light is easier to pick out. For example, if the experiment had been done in visible light, the total light from the system would appear to be unchanged, even as the planet disappeared from view.
To capture spectra of the planets, Spitzer observed their secondary eclipses with its spectrograph. It took a spectrum of a star together with its planet, then, as the planet disappeared from view, a spectrum of just the star. By subtracting the spectrum of the star from the spectrum of the star and planet together, astronomers were able to determine the spectrum of the planet itself.
Neither of the parent stars for HD 209458b or HD 189733b can be seen with the naked eye. HD 209458b is located about 153 light-years away in the constellation Pegasus, while HD 189733b is about 62 light-years away in the constellation Vulpecula. Both planets zip around their stars in very tight orbits; HD 209458b circles once every 3.5 days, while HD 189733b orbits once every 2.2 days.
Of the approximately 200 known exoplanets, there are 12 besides HD 209458b and HD 189733b whose orbits are inclined in such a way that, from our point of view, they pass in front of their stars. At least three of these transiting exoplanets are bright enough to follow in the footsteps of HD 209458b and HD 189733 and reveal their infrared spectra to Spitzer. Astronomers hope to use Spitzer's spectrograph in the future to study HD 209458b and HD 189733b again in much greater detail, and to examine some of the other candidates for the first time.
Browse Videos in Science Animations
This artist's animation illustrates how silicate crystals like those found in comets can be created by an outburst fr... | <urn:uuid:3a985031-5ecf-4f58-979c-fa7c53626be0> | 4.03125 | 752 | Truncated | Science & Tech. | 54.735306 |
An HTML table with a <thead>, <tfoot>, and a <tbody> element:
The <thead> tag is supported in all major browsers.
The <thead> tag is used to group header content in an HTML table.
Browsers can use these elements to enable scrolling of the table body independently of the header and footer. Also, when printing a large table that spans multiple pages, these elements can enable the table header and footer to be printed at the top and bottom of each page.
The <thead> tag must be used in the following context: As a child of a <table> element, after any <caption>, and <colgroup> elements, and before any <tbody>, <tfoot>, and <tr> elements.
Note: The <thead> element must have one or more <tr> tags inside.
Tip: The <thead>, <tbody>, and <tfoot> elements will not affect the layout of the table by default. However, you can use CSS to style these elements.
None of the HTML 4.01 attributes are supported in HTML5.
|Not supported in HTML5. Aligns the content inside the <thead> element|
|char||character||Not supported in HTML5. Aligns the content inside the <thead> element to a character|
|charoff||number||Not supported in HTML5. Sets the number of characters the content inside the <thead> element will be aligned from the character specified by the char attribute|
|Not supported in HTML5. Vertical aligns the content inside the <thead> element|
The <thead> tag also supports the Global Attributes in HTML.
The <thead> tag also supports the Event Attributes in HTML.
Your message has been sent to W3Schools. | <urn:uuid:423fad72-67ee-4273-9da2-d797df07b721> | 2.96875 | 391 | Documentation | Software Dev. | 59.567647 |
© 2003 - 2007 WELLOG
All Rights Reserved
PART II, PAGE 2
The interaction of acoustic waves in a rock matrix affect velocity and attenuation of the acoustic signal. Rock density, porosity, saturation and fracturing have different affects that contribute to a very complex acoustic signal which contains an abundance of information.
Acoustic tools are designed to generate an acoustic signal (sound wave) having significant energy that will travel through the borehole fluid, rock formation and back through the borehole fluid to an acoustic receiver. Acoustic transmitters may be piezoelectric crystal or magnetostrictive. Both types of transmitters convert electrical energy into mechanical energy. The mechanical energy in the form of an acoustic wave travels into the surrounding formation and is received by an acoustic receiver usually of the piezoelectric type.
Acoustic waves traveling in an elastic media are subject to stress and strain. Most of the interaction of acoustic waves in a rock formation can be described mathematically using the theory of elastic waves in an elastic media. In an elastic medium with small strains, the strain is directly related to the stress that caused it. This relation is referred to as “Hooke’s Law”. The total strain is the sum of the strains produced by the individual stresses.
An acoustic waveform is subject to reflection and refraction. Because the waveform moves in all directions and encounters varying interactions, when waveforms rejoin, they may have constructive or destructive interference with each-other. Among the interactions, Plane waves referred to as “P waves” and shear waves referred to as “S waves” a formed. These waves, called “head waves” are among the first to arrive at the receiver. Various other waves are produced; conical waves, pseudo-Rayleigh waves, and Stoneley or tube waves.
It should be noted that P waves travel faster than S waves.
Example: Sandstone (WY) having density of 2.28 gm/cc ;
Young’s modulus: Poisson’s ratio: Vp: Vs: Vp/Vs: Vs as % of Vp:
0.014 0.060 7470 5130 1.46 68.42%
Matrix velocity – If a rock were truly elastic it would have no porosity. But, rock contains pore spaces, fractures and other discontinuities. The velocity of propagation in a rock matrix is therefore affected by pressure, porosity, pore fluid, fraction of the pore space containing a given fluid (saturation), fluid type and temperature. Pressure has the effect of closing micro-fractures and increasing velocity. Porosity has the effect of reducing velocity of S waves. Temperature affects fluid velocity and therefore has an effect on overall velocity.
Attenuation - Attenuation is greatly increased by increasing porosity. Attenuation decreases with increasing pressure.
Attenuation of both P and S waves are minimum in dry rock. Attenuation for both modes increases as partial saturation occurs. P waves are attenuated twice as much as S waves in partially saturated rock. As total saturation is reached, P wave attenuation is REDUCED and S wave attenuation reaches MAXIMUM.
Velocity of an acoustic wave (Vp) is measured in terms of feet per second. The reciprocal (Dt) is measured in seconds per foot. In the case of rock matrices units are micro-seconds (usec) per foot. Dt is also referred to as “transit time”.
Typical transit times:
Shale 130 – 175 usec per ft. Example: Shale (AZ) Vp = 6372 ft/sec., delta-t = 157 usec per ft.
Sandstone 52.5 – 55.5 usec per ft.
Limestone 47.5 usec per ft. Example: Limestone (PA) = Vp = 10899 ft. per sec., delta-t = 91.7
Dolomite 42.5 usec per ft.
Acoustic logging tools use either one transmitter and two receivers. Two transmitters and two receivers are used to compensate for adverse borehole conditions and is called Borehole Compensation (BHC). A process of subtracting travel times from one transmitter to one receiver then the other, has the effect of giving the resulting formation travel time only.
Using the convention T12 = time from transmitter 1 to receiver 2;
For change in hole diameter (Dd):
T12 – T11 = l/v + Dd/vf , T21 – T22 = l/v + Dd/vf
l = distance between receivers
vf = velocity of sound in fluid
Dd = change in hole diameter
(T21 – T22 + T12 – T11)/2 = l/v
If the tool is tilted:
(T21 – T22 + T12 – T11)/2 = l cos(a)/v
Where: a = tilt angle
Note: tilt angle can usually be ignored due to the length of the tool and the small diameter of hole, cos(a) = 1.
In practice, acoustic logging must be performed in a fluid filled well and the tool must be centralized in the hole.
Dry hole acoustic sondes are held stationary and pressed against the side of the hole for each measurement.
POROSITY FROM ACOUSTIC TOOL:
Porosity (f) is calculated as follows:
f = (Dt(log) - Dt(ma)) / (Dt(f) – D(ma))
Where: Dt(log) is delta-t obtained from the log.
Dt(ma) is the delta-t of matrix rock having no porosity.
Dt(f) is the delta-t of the fluid contained in the pore space.
Typical Dt(f) for water or mud is 188 to 200 microseconds (usec) per ft.
Note: vf is less in mud.
CORRECTION FOR SHALE:
Correction for shale is performed when Dt(sh) exceeds 100 usec per ft.
Multiply the calculated porosity by 100/ Dt(sh)
CORRECTION FOR GAS:
When pore space contains gas, Dt(fluid) increases. The result is optimistic porosity calculations.
In many cases acoustic information is unreliable due to cycle skipping caused by long Dt intervals. | <urn:uuid:13c5a205-7414-4152-95b6-ff59058149d9> | 3.5 | 1,358 | Tutorial | Science & Tech. | 54.576492 |
Despite the need to reduce carbon dioxide emissions, the burning of coal has only been accelerating.
Stories Tagged "electricity"
Researchers demonstrate a significant jump in the efficiency with which heat can be converted directly into electricity.
ArrayPower says its "sequenced inverter" will cut the cost of solar by more than 10 percent.
Such materials could be used to cool computers and buildings, and harvest waste heat in cars.
Researchers achieve a goal they've been after since the 1980s—the advance could make cars and airplanes lighter, and renewable energy more practical.
An Israeli company aims to commercialize microbial fuel-cell technology.
Electricity prices will increase, but your bill could actually come down.
"Tunable" windows would let people adjust light and heat levels, but so far it's been hard to make them affordable.
The new design could lead to cheaper solar cells.
DOE funds will help finance construction of a geothermal facility using advanced technology. | <urn:uuid:d9cfd1b3-140e-4126-94d5-1d104bba1cb8> | 3.171875 | 202 | Content Listing | Science & Tech. | 37.527923 |
The pure musical tone produced by striking a tuning fork is said to have a certain pure pitch or frequency. That frequency is the number of times that the sound waves compress and dilate in a second, or, for water waves and other types of vibration, the number of times the wave rises or falls in a second. Frequencies are given in hertz, abbreviated Hz, a unit of measurement named in honor of Heinrich Hertz, a German physicist who in 1887 first produced electromagnetic waves. One hertz is equal to one cycle of rise and fall per second. The time between the crests is the wave period; it is equal to the reciprocal of the wave frequency.
Human beings can detect sounds having frequencies between 20 and 10,000 Hz. A seismic P wave can refract out of the rock surface into the atmosphere, and if the frequencies are in the audible range, the wave can be heard as a rumble as it travels by the ear. Most earthquake waves have frequencies lower than 20 Hz, and are usually felt by human beings rather than felt. | <urn:uuid:fdddb104-aae7-489d-a8a9-eef6ec6877a0> | 4.21875 | 217 | Knowledge Article | Science & Tech. | 52.242702 |
Glimpsing the Edge of the Universe: Results from the Hubble Space Telescope
Dr. Bruce Margon (University of California, Santa Cruz)
Listen (mp3 file, 24 MB)
The Hubble Space Telescope has circled the Earth 15 times every day for more than 16 years. Dr. Margon, who was until recently the Associate Director for Science for the Hubble, describes the most important discoveries made with the telescope and how it can show us new details of the universe from the solar system to the most distant reaches of space. In addition, he briefly discusses the future of the Hubble and some interesting public reactions to it. | <urn:uuid:5edcb7a2-f82e-46de-a5fc-28f6c28d5c7e> | 2.71875 | 128 | Truncated | Science & Tech. | 43.367231 |
The term “tarantula hawk” applies to more than one species of large wasp. It even applies to more than one genus. Here in the United States, the genera Pepsis and Hemipepsis are the only tarantula hawks, and the largest of our spider wasps in the family Pompilidae. Hemipepsis ustulata is a common species across much of the western U.S., one I have encountered in both Arizona and Colorado.
It is not easy to separate Hemipepsis from Pepsis, but I find that Hemipepsis are matte black in color, not the iridescent blue-black that their relatives are. Hemipepsis also tends to fly earlier in the season than Pepsis, especially in the southwest, but both genera can be found together in the fall, Hemipepsis being in the second generation in autumn. Wing venation is apparently the only sure way to tell the two apart, but most folks understandably don’t want to get that close to such a large, stinging insect to find out which is which.
Tarantula hawks in general have interesting behaviors, especially the males. Dr. John Alcock has studied in-depth the territorial behavior of male Hemipepsis ustulata in the Superstition Mountains near Phoenix, Arizona. They are among the first insects seen in spring, but as the season wears on they become early risers, taking advantage of the brief window of time when Sonoran Desert temperatures are not too cool, but not incinerating, either. They are looking for prominent outposts, often Palo Verde trees atop hills.
Once a male wasp claims a lookout tree, it vigorously defends it from competing males. Most interactions consist of the resident male flying off his perch in a brief foray to chase away the intruder. There is usually only feeble resistance, if any, from the interloper. Males that have been displaced from their own territories, however, are more likely to try and displace another male. This takes the form of long, ascending flights in which the wasps spiral around each other as they climb to heights of thirty feet or more. Sometimes they escalate to altitudes where they can no longer be observed without binoculars.
These aerial duels are contests of both endurance and speed. The faster and fitter male is thus the one more likely to win.
Female wasps cruising past an occupied tree elicit an entirely different response. The resident male gives chase and, if he successfully reaches her, attempts to couple with her in the air and descend to the ground. There, they mate briefly if she is receptive. The male then returns to his perch, which he hopes has not been claimed by another male while he was um, otherwise engaged.
This form of territoriality is called “landmark defense,” and it is the strategy of choice in situations where defense of a resource used by females is impractical or impossible. While blooming palo verde trees might seem to be a nectar source for female tarantula hawks (and they are, for Pepsis chrysothemis), females of Hemipepsis ustulata seem to prefer the flowers of creosote bush, which has a wide and scattered distribution in the landscape.
Once mated, a female tarantula hawk goes about the business of finding occupied tarantula burrows and baiting the spider into battle aboveground. These burrows are also widely scattered. So, male wasps can’t stake out a tarantula “colony” because there is no such thing, at least not for spiders the size needed by the female wasp.
Some of the hunting activities of these wasps may take place at night, or at least at dusk, for I have found females in southeast Arizona coming to blacklights at night. I have also found females feeding on oozing sap of Desert Broom (Baccharis sarothroides). Here in Colorado Springs I have seen both genders at a blooming saltcedar tree (Tamarix sp.), though the female simply circled the tree and flew off again.
Hemipepsis ustulata ranges from southern California east through Nevada to Texas, Oklahoma, and Kansas. It would be well worth it to accumulate more records of this species. More county records are certainly possible, and perhaps state records, too.
Sources: Alcock, John. 1984. “Ridgetop Rendezvous,” Natural History 93: 42-47.
Evans, Howard E. 1997. “Spider Wasps of Colorado (Hymenoptera, Pompilidae): An Annotated Checklist,” Great Basin Naturalist 57(3): 189-197. | <urn:uuid:2b849057-6207-4131-8aff-0bf9905a17a3> | 3.21875 | 994 | Personal Blog | Science & Tech. | 42.426377 |
Some beginner questions.
I am currently trying to learn C++ from a book (Sams teach yourself C++) and I had several questions.
Does using the following.
Instead of calling them again every time have any effect on the programs execution or is it just laziness? With calling them again every time I mean for example.
using namespace std;
Second, I see "#define" used a lot on this forum. According to my book "const" should be used instead. Why is it used so much on this forum? The book mentions that it used to be done like that but that it has been declared obsolete. Not to mention the advantages "const" has over "#define".
std::cout << "\nThis is a line of code!\n";
const unsigned short integer myAge = 25;
usings are just to bring in the namespace. Doesn't effect the program.
I prefer to be explicit:
const is usually the better choice. But there can be cases for the defines. | <urn:uuid:892c2fca-6172-4c6c-aad4-2e0599590579> | 2.96875 | 211 | Comment Section | Software Dev. | 66.993333 |
Interim recovery plan no. 133
Gillian Stack & Andrew Brown
Department of Conservation and Land Management, WA, 2003
|Scientific Name:||Lambertia echinata subsp. occidentalis||Common Name:||Western Prickly Honeysuckle|
|Family:||Proteaceae||Flowering Period:||October - December|
|Dept Region:||South West||Dept District:||Blackwood|
|Shire:||Busselton||Recovery Team:||South West Region Threatened Flora Recovery Team (SWRTFRT)|
Illustrations and/or further information: A. Brown, C. Thomson-Dans and N. Marchant (Eds) (1998) Western Australia's Threatened Flora; V. English (1999) Shrubland Association on Southern Swan Coastal Plain Ironstone, Draft Interim Recovery Plan; G.J. Keighery (1997) A new subspecies of Lambertia echinata (Proteaceae). Nuytsia, 11 (2): 283-284.
Current status: Lambertia echinata subsp. occidentalis was declared as Rare Flora in October 1996 and ranked as Critically Endangered in November 1998. It currently meets World Conservation Union (IUCN, 2000) Red List Category 'CR' under criteria A2c,B1+2ce,C1,D as it is known from a single wild population comprised of less than 100 mature individuals and there is a continuing decline in the quality of the habitat due to Phytophthora cinnamomi infection. The main threats to the subspecies are disease, inappropriate fire regimes, mineral sand mining, waterlogging, weeds and rabbit grazing.
Critical habitat: The critical habitat for Lambertia echinata subsp. occidentalis comprises the area of occupancy of the known population; area of occupancy of translocated populations; similar habitat within 200 metres of known and translocated populations; corridors of remnant vegetation that link populations; the local catchment area; and additional nearby occurrences of similar habitat that do not currently contain the species but may have done so in the past and may still be suitable for further translocations.
Habitat critical to the survival of the species, and important populations: Given that this subspecies is listed as Threatened it is considered that all known habitat for wild and translocated populations is habitat critical.
Benefits to other species/ecological communities: Lambertia echinata subsp. occidentalis occurs on the threatened ecological community "Shrubland Association on Southern Swan Coastal Plain Ironstones (Busselton Area)". Also, several other threatened plant taxa (Brachysema papilio, Petrophile latericola, Chamelaucium roycei ms, Dryandra squarrosa subsp. argillacea and Dryandra nivea subsp. uliginosa) will benefit from recovery actions put in place for the subspecies. Recovery actions for this subspecies will also improve the condition of the associated remnant bushland.
International Obligations: This plan is fully consistent with the aims and recommendations of the Convention on Biological Diversity, ratified by Australia in June 1993, and will assist in implementing Australia's responsibilities under that Convention. However, as Lambertia echinata subsp. occidentalis is not listed under any international agreement, the implementation of other international environmental responsibilities is not affected by this plan.
Role and interests of indigenous people: There are no known indigenous communities interested or involved in the management of areas affected by this plan. Therefore no role has been identified for indigenous communities in the recovery of this species.
Social and economic impacts: The implementation of this recovery plan has the potential to have some minimal economic impact as the subspecies occurs in an area adjacent to a Mining tenement.
Evaluation of the Plans Performance: The Department of Conservation and Land Management, in conjunction with the relevant Recovery Team, will evaluate the performance of this IRP. In addition to annual reporting on progress of listed actions and comparison against the criteria for success and failure, the plan is to be reviewed within five years of its implementation.
Habitat requirements: Lambertia echinata subsp. occidentalis is known from a single wild population at the base of the Whicher Range where it is confined to highly restricted ironstone habitat. The habitat is a winter-wet area of shrubland over shallow sandy soils over ironstone. The plant association in which the taxon occurs is the Threatened Ecological Community (TEC) 'Shrublands on southern Swan Coastal Plain Ironstones', which is ranked Critically Endangered (English 1999).
Existing Recovery Actions: The following recovery actions have been or are currently being implemented -
- Appropriate land managers have been notified of the presence and threatened status of the taxon.
- Seed has been collected from Population 1 on several occasions, and is stored in DCLM's Threatened Flora Seed Centre at -18°C.
- The Botanic Garden and Parks Authority currently have 88 plants of Lambertia echinata subsp. occidentalis from six clones.
- An experimental translocation has been implemented in stages in 1998, 1999, 2000, 2001 and 2002. Plantings during the translocation have occurred in the area of the original population and in two newly vested Nature Reserves.
- In 1997 staff of DCLM's Science Division took samples that positively identified the presence of the plant pathogen Phytophthora cinnamomi (dieback) in the habitat of the subspecies.
- To combat dieback disease, the site containing the Lambertia echinata subsp. occidentalis population was first sprayed with phosphite in April 1998. This action is ongoing.
- Implementation of the recovery actions outlined in the IRP for the TEC 'Shrublands on southern Swan Coastal Plain Ironstones' (English 1999) has commenced and is ongoing. Actions being put in place to protect this community also protect Lambertia echinata subsp. occidentalis.
- An information sheet that describes and illustrates the taxon, threats and recovery actions has been produced.
- A separate information sheet describing and illustrating the TEC in which it occurs has also been produced.
- Blackwood District staff have produced a map that defines areas that are not available for commercial wildflower picking to help prevent illegal picking in the area of the population.
- Staff from DCLM's Blackwood District regularly monitor wild and translocated populations of the taxon.
- The South West Region Threatened Flora Recovery Team is overseeing the implementation of this IRP and will include information on progress in an annual report to DCLM's Corporate Executive and funding bodies.
IRP Objective: The objective of this Interim Recovery Plan is to abate identified threats and maintain or enhance in situ populations to ensure the long-term preservation of the species in the wild.
Criteria for success: The number of individuals within populations and/or the number of populations have increased by 10% or more.
Criteria for failure: The number of individuals within populations and/or the number of populations have decreased by 10% or more.
|1. Coordinate recovery actions||10. Continue rabbit control|
|2. Maintain disease hygiene||11. Conduct further surveys|
|3. Apply phosphate every two years and monitor impact||12. Collect seed and cutting material|
|4. Map critical habitat||13. Obtain biological and ecological information|
|5. Implement the fire management strategy||14. Stimulate the germination of soil-stored seed|
|6. Continue translocation||15. Promote awareness|
|7. Liaise with land managers||16. Review the need for a further recovery actions and/or a full Recovery Plan|
|8. Monitor population||17. Rehabilitate habitat, if necessary|
|9. Continue weed control| | <urn:uuid:ea79944f-2f55-407b-ad52-c4b95aa8e372> | 2.890625 | 1,656 | Knowledge Article | Science & Tech. | 25.646735 |
Fabrication method can affect the use of block copolymer thin films
A new study by a team including scientists from the National Institute of Standards and Technology (NIST) indicates that thin polymer films can have different properties depending on the method by which they are made. The results* suggest that deeper work is necessary to explore the best way of creating these films, which are used in applications ranging from high-tech mirrors to computer memory devices. Thin films spread atop a surface have many applications in industry. Inexpensive organic solar cells might be made of such films, to name one potential use. Typically they're made by dissolving the polymer, and then spreading a small amount of the liquid out on a surface, called a substrate. The solution becomes a film as the solvent dries and the remainder solidifies. But as this happens, stresses develop within the film that can affect its structure.
Manufacturers would like to know more about how to control these stresses to ensure the film does what they want. But scientists who study film formation often use a different method of casting films than a manufacturer would. One method used in industry is "flow coating" -- similar to spreading frosting across a cake. Another method is "spin casting" -- placing a drop of liquid on a substrate that spins rapidly and spreads the droplet out evenly by centrifugal force. Both methods create smooth films generally, but the team decided to examine whether the two methods create different effects in finished films consisting of a self-assembling block copolymer.
"It's an important question because some proposed applications intend to take advantage of these effects," Douglas says.
The team's comparison led to results that surprised them. Although the rapid spinning of spin casting is very dynamic, suggesting it would convey more stress to the resulting film, it actually led to fewer residual stresses than flow coating did. As previous studies have shown that leftover solvent can lead to stresses in the film, the team's new theory is that because the solvent evaporates from the developing film more slowly in flow coating, this solvent discourages the film solids from arranging themselves into the equilibrium structure.
For one example, the practical benefits of this understanding could help manufacturers who propose making computer memory devices from thin films in which the solids arrange themselves as tiny cylinders in the film. Such devices would require the cylinders to stand on end, not lay down flat.
"We find we can get them to stand up much more easily with one casting method than another," Douglas says. "If we can get better results simply by varying the mode of film casting, we need to explore more deeply what happens when you make films by different methods."
- Insights into polymer film instability could aid high tech industriesTue, 13 Jan 2009, 17:43:08 EST
- Radically simple technique developed to grow conducting polymer thin filmsTue, 2 Nov 2010, 9:03:11 EDT
- University of Texas at Austin Team develops a microwave-assisted method for producing thin filmsWed, 19 Dec 2012, 15:14:37 EST
- Watching crystals grow provides clues to making smoother, defect-free thin filmsThu, 21 Jan 2010, 14:38:33 EST
- Nanomechanics: New test measures key properties of polymer thin films and membranesWed, 20 Jul 2011, 11:33:00 EDT
- Fabrication method can affect the use of block copolymer thin filmsfrom Science DailyFri, 4 May 2012, 0:30:23 EDT
- Fabrication method can affect the use of block copolymer thin filmsfrom PhysorgThu, 3 May 2012, 9:30:57 EDT
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Selected answers to common questions:
Direct and indirect variation.
Slope, slope-intercept, standard form.
- Pre-calculus Function Question [2/8/1996]
Does the function f(x)=3De^(1/x) have a local minimum?
- Proof of Perpendicularity [10/23/1999]
How can you prove that two lines (neither vertical) are perpendicular if
and only if the product of the gradients is equal to -1?
- Quadrant [03/25/2001]
What is a quadrant?
- Quadratic Formulas, Equations, Parabolas, Graphing [6/16/1996]
Given 6x^2 + x - 1 = 0, how do I find the roots, the vertex, some
coordinates, and from these graph it?
- Quadratic Inequalities [03/18/2003]
When I solve (x^2 + 1)/4 greater than or equal to (x + 2)/2 , of my
final two answers, only one works.
- Quintic Equations [1/27/1996]
What does Quintic mean?
- Recognizing Functions [09/30/2001]
How do I know when there is a function on a graph?
- Rectangular Hyperbola [06/11/2002]
The graph of a rectangular hyperbola looks nothing like a rectangle.
Where does the name come from?
- Root Multiplicity and Polynomial Functions [11/16/1997]
What effect does multiplicity [e.g. (x+1)(x-2)^2 where -1 has a
multiplicity of 1 and 2 of 2] have on a polynomial function?
- The Roses of Grandi [11/13/2000]
The Roses of Grandi are given by polar equations r = a*sin(n*theta) and r
= a*cos(n*theta) where n is an integer. How can I show that they are
- Rotating Parabolas [01/19/1999]
How do you find a parabola that has a line of symmetry other than a line
parallel to the x-axis or y-axis?
- Shape of the Sine Curve vs. Circle [07/18/2001]
When the equation y = 5sinx is graphed, the curve looks almost linear
except near the points where y = 5. Since the sine curve originates from
the circle, why isn't it completely curvy like a circle?
- Shifting Graphs [08/26/2002]
Why is the graph of y=f(x-c) just the graph of y=f(x) shifted c units
to the right?
- Similar Graphs [12/11/1995]
How would you describe how the two graphs of y = one over the square root
of x squared and y = one over the square root of x squared minus 4 are
similar and dissimilar?
- Sketch a Graph [6/1/1996]
z=(3-2i)^1/2, then find z^.
- Sketching a Function [07/06/1998]
Can you help me piece a function together so that the following hold? It
is increasing and concave up on (-infinity, 1) ...
- Sketching a Polynomial [04/04/2002]
Why should a curve change its position or sign at roots? Can't a curve
have a positive value for all roots?
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How do I sketch the curve y = log natural of x/ (1-x)?
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Why does y = mx + b have to be that way?
- Slope of Lines [8/6/1996]
What is the slope of the line y = -px + 5 if the line goes through (0, -
3)? Why does the y-axis have an infinite slope, and the x-axis have a
slope of 0?
- Slopes of Perpendicular Lines [09/17/1998]
Why are the slopes of perpendicular lines negative reciprocals?
- Solve for Radius [09/09/1997]
Given a circle through three points, what is the equation for the
intersection of the perpendicular bisectors?
- Solving a Fractional Equation [3/10/1996]
Can you help me with this? (M+N)/(N-M) + (M^2+N^2)/(N^2-M^2) - (2M)/(M-N)
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Can you show me the steps for solving conic equations and putting them in
hyperbola, ellipse, or parabola form?
- Solving Inequalities [07/13/1999]
Solve the inequality and express the solution in terms of intervals.
- Standard Form in Linear Equations [11/21/2001]
Where is standard form used?
- The Sum of a Number and Its Reciprocal [11/04/2003]
I need a formal proof showing that the sum of a positive number and its
reciprocal is at least 2. I can prove it algebraically, but I need a
- Symmetry Tests [01/12/1999]
How can you know whether a graph is symmetric to the x-axis, y-axis, or
the origin? What does the symmetry mean?
- Tangents to a Curve That Pass through a Fixed Point [08/08/2008]
How many tangent lines to the curve y = x/(x+1) pass through the point
(1,2)? At which points do those tangent lines touch the curve?
- T-Charts and Graphs [11/11/2001]
Make a table of values for the line y = x/4+4 using x-values of 1,2,3,4,
and 5. Which graph shows the line that passes through the ordered pairs
of the table?
- Testing for Horizontal Asymptotes [09/12/1998]
Is there a rule for testing whether or not an equation has a horizontal
- Translating Functions [08/27/1998]
Find f(2+h), f(x+h), and f(x+h)-f(x)/h where h cannot = 0 for f(x) = x/(x
+ 1). Explain how the following graphs are obtained from the graph of y =
- Translation [9/11/1996]
What does translation mean?
- TV Transmitters [07/22/1997]
If two TV transmitters are within 150 kilometers of each other, they must
be assigned different channels. Construct a graph that shows the given
problem and use it to find the number of channels needed.
- Types of Linear Systems [10/13/1997]
What is meant when a type of linear system is said to be a consistent or
an inconsistent system?
- Understanding Parametric Equations [04/02/1998]
Can you explain the basic principles of parametric equations?
- Units for Inverse Quantity [9/10/1996]
I have a graph of time vs. 1/distance. What units do I use for 1/
distance - cm^-1?
- Uses for Parametric Equations [04/23/1998]
What is a parametric equation used for? Can you give me an example?
- Using Cardan's Formula to find Real Roots [04/13/2000]
How can I show that, although the cubic equation x^3 - 6x = 4 has three
real solutions, Cardan's formula can find them by subtracting appropriate
cube roots of complex numbers?
- Using Descartes' Method of Tangents [10/2/1995]
Given a point P(3,9) on a parabola y=x^2, how do I find the slope of the
tangent to the parabola at point P using Descartes' method of tangents? | <urn:uuid:7361df05-fdf5-432a-bc75-df64018cddea> | 3.796875 | 1,815 | Q&A Forum | Science & Tech. | 79.729059 |
Phoenix was the first to explore the surface of a polar region on Mars, areas rich in water-ice (right).
The spacecraft landed farther north than any previous spacecraft to land on the Martian surface.
It was the first mission in NASA's Mars Scout program.
Phoenix inherited its lander. Originally the lander was to be used for the Mars Surveyor 2001 program, but after the lander portion of that program was cancelled it was kept in a protective, controlled environment.
Phoenix's robotic arm was designed to dig trenches (right), scoop up soil and water ice samples, and deliver these samples for analysis.
The lander's Canadian laser instrument used for studying the atmosphere detected snow falling from clouds on Mars. | <urn:uuid:7cce63d7-0d2d-4916-bc83-8113a26ae882> | 3.9375 | 147 | Knowledge Article | Science & Tech. | 51.149918 |
NASA eClips: Transits
A 'transit' occurs whenever one object moves in front of another object as viewed from your particular location in space. We observe this phenomenon thousands of times every day because we live in a 3-dimensional world that is crowded by many different kinds of objects as we move past them. In astronomy, transits are actually rather rare. The most dramatic ones we hear about involve the moon passing in front of the sun. because the moon and sun appear to be about the same size, we call these transits 'eclipses'. On rare occasions, the planet's Mercury and Venus can be seen as small 'dots' passing across the face of the sun. The light from the sun actually dims by a small amount when this happens, but only astronomers can measure this dimming. As it turns out, we can measure this dimming of distant stars and use it to discover planets orbiting them. The NASA Kepler mission has detected over 700 of these 'transiting exoplanets' since 2009 in a study of over 150,000 stars.
The image to the left shows a lovely transit of the moon across the sun as viewed by the STEREO spacecrafts. Thanks to the many interplanetary spacecraft deployed by NASA, we have the opportunity to see many more amazing transits in the future now that we are not limited by the perspective from only one planet!
In this eClips episode, we discover how scientists used the last Venus transit in 2004, and a geometric technique called parallax, to verify the distance between sun and Earth. Find out what scientists hope to learn the next time Venus makes a shadow on the face of the sun in 2012!
Related Mathematics Problems
These problems provide a mathematical introduction to some of the issues related to transit observations of our sun and distant stars.
Stay tuned for a new math guide to transits to be published in early-2011. Visit the 'books' resource in January.
Problem 118 An Application of the Parallax Effect The STEREO mission views the sun from two different locations in space. By combining this data, the parallax effect can be used to determine how far above the solar surface various active regions are located. Students use the Pythagorean Theorem, a bit of geometry, and some actual STEREO data to estimate the height of Active Region AR-978. [Grade: 8-10 | Topics:Pythagorean Theorem; square-root; solving for variables] [Open PDF]
Problem 196: Angular Size and velocity- Students study a spectacular photo of the ISS passing across the face of the sun, and work out the angular sizes and speeds of the transit to figure out how long the event took in order to photograph it. [Grade: 8-10| Topics: Geometry; Angle measurement][Open PDF] | <urn:uuid:ac47ca8a-3fae-4e9a-aef6-52dcfca644ac> | 4.15625 | 582 | Tutorial | Science & Tech. | 43.624069 |
Energy in the Real World
Solar and Wind are not renewable. The energy from solar and from wind is of course renewable but the devices used to capture the energy of the sun and wind is not renewable. Nor are they green or sustainable.
An oak tree is renewable. A horse is renewable. They reproduce themselves. The human-made equipment used to capture solar energy or wind energy is not renewable. There is considerable fossil fuel energy embedded in this equipment. The many components used in devices to capture solar energy, wind energy, tidal energy and biomass energy – aluminum, glass, copper, rare metals, petroleum in many forms to name a few – are fossil fuel dependent
Aluminum comes from bauxite. It takes considerable energy to refine the bauxite. When I was fourteen, I worked loading trucks in an aluminum extrusion plant. The ingots of aluminum would be heated, pushed through a die to shape, then cut and put on carts. We would take these carts and move them into a small room heated to around 400 degrees Fahrenheit where they were baked.
The history channel on “Modern Marvels” had an excellent show on mining and producing copper. Huge machines the size of a two-story house running on fossil fuels gouge out the earth. The rock being only a very small percent copper must be processed using chemicals and more fossil fuels. Then depending on whether it is the plate for the absorber in the panel or wire for the blower further fossil fuels are needed to create the final product. These products must be transported various places for further manufacturing, again using additional fuels.
There are consequences to the manufacture of solar and wind equipment; including serious air and water pollution, release of deadly chemicals into the environment as well as misuse of humans in mining and processing applications. There is pollution of the air and water that arises from the chemicals used in the manufacturing of the glass, copper, aluminum and other sundry materials in these panels. It does not include the debris from the mining of low percentage ore. From glass can come various noxious chemicals plus particulates in the air of arsenic and lead. Copper and aluminum manufacture (or recycling) also creates water and air pollution problems. To call these “renewable” energy capturing devices and processes green is not correct.
It is also blind to call these devices sustainable. As indicated above, it takes massive amounts of fossil fuels in the mining, extraction, purifying, basic manufacture, final product manufacture and transportation to get the materials to assemble this equipment. Often the electricity used to manufacture these products is powered by coal brought in by 100-car coal train run by a diesel/electric engine. There is simply no way that the energy captured by these devices can be use to reproduce the devices in a sustainable manner.
There is an important accounting system connected to energy decisions. Any system must give more energy than it takes to create/generate. This accounting system is Energy Invested on Energy Returned (EroEI). When it costs more to pull oil from the ground than we get back, then it is over for that well. On any technology, this has to be a main consideration. Many have heard that it takes as much energy to make ethanol as it provides. This makes it a dead end street.
How many units of energy does it take to make a hot air solar collector or a hot water solar collector or a wind generator or a solar electric panel? Each of the components (aluminum, glass, insulation, wires, pumps, blowers, solar cells, etc.) needs to be computed for the accumulated energy cost of the particular technology. This must be compared to life span energy output of the technology. It is important to realize we are talking about the ENERGY output. The financial payback cost is actually secondary in this perspective. Perhaps these energy devices need an energy content label like food has a calorie label.
There are tremendous stresses politically, environmentally, geographically and geologically for fossil fuels. Our money, energy and mineral resources must be used judiciously to repair and upgrade the infrastructure of water, sanitation, and buildings. Energy conservation by insulating, weather stripping, and cutting back are the first line of defense toward energy independence and self-reliance. It is important for the future of energy use to be clear on these matters.
These technologies (solar air panels, solar electric panels, wind, etc.) can be looked at as transitional. This means they can help this generation and maybe the next generation ease down the slope to minimal fossil fuels. I am not saying don’t use these devices. I am suggesting we use them sparingly and wisely.
As fossil fuels become less available, judicious use of the remaining reserves becomes even more important. We must come to realize that fossil fuels (as well as concentrated sources of minerals) are a gift from the earth and previous to life. To mistakenly call solar or wind energy renewable and include the capturing mechanisms leads to both false hopes and perhaps poor allocation of limited fossil fuels and funds.
Copper Ore being loaded into a 300 ton truck for transport to the crusher.
The El Chino mine located near Silver City, New Mexico is an open-pit copper mine.
Alberta oil sands
Bauxite mining in Suriname
An aerial view-bauxite mine and alumina processing in Australia
The Bagger 288 is a bucket-wheel excavator used in strip mining.
Mountaintop removal operation, Boone County, West Virginia
NIGERIA OIL SPILLS
http://luckyrooster.net/2010/06/nigerias-agony-dwarfs-the-gulf-oil-spill/ This type of oil spill is widespread in the Niger Delta.
Amukpe is near a major city of Sapele and therefore attracted attention of the public. In rural areas, such spills would go on for months before any action is taken.
Photo via DOE | <urn:uuid:5e554516-9f51-4794-b573-7875f430f502> | 3.25 | 1,223 | Personal Blog | Science & Tech. | 37.840539 |
Science subject and location tags
Articles, documents and multimedia from ABC Science
Monday, 22 October 2012
Pesticides used in farming are also killing worker bees and damaging their ability to gather food, meaning colonies that are vital for plant pollination are more likely to fail when they are used, according to a new study.
Thursday, 18 October 2012
Spider vision Eight-eyed jumping spiders have a near 360-degree view of the world and can be captivated by humans and nature videos, a new study has found.
Friday, 28 September 2012
The mysterious and widespread collapse of bee colonies in many parts of the world is not due to a lack of genetic diversity.
Tuesday, 4 September 2012
Photo gallery The beauty and brutality of the animal kingdom is brought to life in exquisite detail by the finalists in the 'animal behaviour' category of the 2012 ANZANG Nature Photo Competition at the South Australian Museum.
Thursday, 2 August 2012
A tiny larva came to a sticky end, 370 million years ago, when it plunged into a shrimp-infested swamp and drowned.
Thursday, 26 July 2012
Monarch butterflies with dark orange wings fly further than those with light orange wings, new research has found.
Tuesday, 24 July 2012
The sex sounds flies make can lead to a violent death - luring predator bats to their love nests while their defences are down, a new study reveals.
Wednesday, 20 June 2012
A type of mosquito that breeds underground steadfastly refuses to feed on blood until it has laid its first batch of eggs, say Australian researchers.
Friday, 15 June 2012
Grasshoppers who die frightened leave their mark in the Earth in a way that more mellow ones do not.
Monday, 11 June 2012
A renowned Australian expert on butterflies and moths has been honoured today in the Queen's Birthday list.
Wednesday, 6 June 2012
Flowers in Australia evolved their bright colours to attract native bees, according to new research.
Wednesday, 23 May 2012
Street lights have an unexpectedly strong effect on insect populations, according to a UK study.
Thursday, 17 May 2012
Different species of butterflies speed up the evolution of biodiversity by interbreeding so they can share genes for protective wing patterns, say researchers.
Wednesday, 2 May 2012
The humble and somewhat delicate looking silkworm cocoon is inspiring researchers to develop future materials.
Wednesday, 4 April 2012
Many resting insects breathe intermittently, holding their breath for minutes to hours between brief bouts of gas exchange. | <urn:uuid:469520a4-b7d2-4b47-a72e-5a847d90d38b> | 2.71875 | 516 | Content Listing | Science & Tech. | 42.112304 |
All members of this family have five-petaled flowers in which the superior ovary ripens to form a "pod", technically called a legume, whose two sides split apart, releasing the seeds which are attached to one or both seams. The legumous plants are classified into three subfamilies, sometimes raised to the rank of family in the order Fabales, on the basis of flower morphology (specifically, petal shape):
Faboideae (Fabaceae), previously called Papilionoideae: One petal is large and has a crease in it, the two adjacent petals are on the sides, and the two bottom petals are joined together at the bottom, forming a boat-like structure.
Caesalpinioideae (Caesalpiniaceae): The flowers are zygomorphic , but are very variable, e.g. closely resembling Faboideae flowers in Cercis, while symmetrical with five equal petals in Bauhinia.
Mimosoideae (Mimosaceae): The petals are small, and are frequently globose or spicate and the stamens are the most showy part of the flower.
A significant characteristic of legumes is that they host bacteria in their roots, within structures called root nodules. These bacteria known as rhizobia have the ability to take nitrogen gas (N2) out of the air and convert it to a form of nitrogen that is usable to the host plant ( NO3- or NH3 ). This process is called nitrogen fixation. The legume, acting as a host; and rhizobia, acting as a provider of usable nitrate, form a symbiotic relationship. | <urn:uuid:178cf41b-aa81-4354-8c46-bc895a3cad56> | 3.984375 | 354 | Knowledge Article | Science & Tech. | 27.782925 |
JEXL stands for Java EXpression Language. It's not a part of the GATK as such; it's a software library that can be used by Java-based programs like the GATK. It can be used for many things, but in the context of the GATK, it has one very specific use: making it possible to operate on subsets of variants from VCF files based on one or more annotations, using a single command. This is typically done with walkers such as VariantFiltration and SelectVariants.
In this context, a JEXL expression is a string (in the computing sense, i.e. a series of characters) that tells the GATK which annotations to look at and what selection rules to apply.
JEXL expressions contain three basic components: keys and values, connected by operators. For example, in this simple JEXL expression which selects variants whose quality score is greater than 30:
"QUAL > 30.0"
QUALis a key: the name of the annotation we want to look at
30.0is a value: the threshold that we want to use to evaluate variant quality against
>is an operator: it determines which "side" of the threshold we want to select
The complete expression must be framed by double quotes. Within this, keys are strings (typically written in uppercase or CamelCase), and values can be either strings, numbers or booleans (TRUE or FALSE) -- but if they are strings the values must be framed by single quotes, as in the following example:
"MY_STRING_KEY == 'foo'"
You can build expressions that calculate a metric based on two separate annotations, for example if you want to select variants for which quality (QUAL) divided by depth of coverage (DP) is below a certain threshold value:
"QUAL / DP < 10.0"
You can also join multiple conditional statements with logical operators, for example if you want to select variants that have both sufficient quality (QUAL) and a certain depth of coverage (DP):
"QUAL > 30.0 && DP == 10"
&& is the logical "AND".
Or if you want to select variants that have at least one of several conditions fulfilled:
"QD < 2.0 || ReadPosRankSum < -20.0 || FS > 200.0"
|| is the logical "OR".
It is very important to note that the JEXL evaluation subprogram cannot correctly handle cases where the annotations requested by the JEXL expression are missing for some variants in a VCF record. It will throw an exception (i.e. fail with an error) when it encounters this scenario. The default behavior of the GATK is to handle this by having the entire expression evaluate to FALSE in such cases (although some tools provide options to change this behavior). This is extremely important especially when constructing complex expressions, because it affects how you should interpret the result.
For example, looking again at that last expression:
"QD < 2.0 || ReadPosRankSum < -20.0 || FS > 200.0"
When run against a VCF record with INFO field
it will evaluate to
TRUE because the
FS value is greater than 200.0.
But when run against a VCF record with INFO field
it will evaluate to
FALSE because there is no
ReadPosRankSum value defined at all and JEXL fails to evaluate it.
This means that when you're trying to filter out records with VariantFiltration, for example, the previous record would be marked as PASSing, even though it contains a bad
For this reason, we highly recommend that complex expressions involving OR operations be split up into separate expressions whenever possible. For example, the previous example would have 3 distinct expressions:
"QD < 2.0",
"ReadPosRankSum < -20.0", and
"FS > 200.0". This way, although the
ReadPosRankSum expression evaluates to FALSE when the annotation is missing, the record can still get filtered (again using the example of VariantFiltration) when the
FS value is greater than 200.0.
Currently, VCF INFO field keys are case-sensitive. That means that if you have a
QUAL field in uppercase in your VCF record, the system will not recognize it if you write it differently (
qual or whatever) in your JEXL expression.
The types (i.e. string, integer, non-integer or boolean) used in your expression must be exactly the same as that of the value you are trying to evaluate. In other words, if you have a QUAL field with non-integer values (e.g. 45.3) and your filter expression is written as an integer (e.g. "QUAL < 50"), the system will throw a hissy fit (aka a Java exception).
Note that this last part is fairly advanced and not for the faint of heart. To be frank, it's also explained rather more briefly than the topic deserves. But if there's enough demand for this level of usage (click the "view in forum" link and leave a comment) we'll consider producing a full-length tutorial.
If you are familiar with the VariantContext, Genotype and its associated classes and methods, you can directly access the full range of capabilities of the underlying objects from the command line. The underlying VariantContext object is available through the
For example, suppose I want to use SelectVariants to select all of the sites where sample NA12878 is homozygous-reference. This can be accomplished by assessing the underlying VariantContext as follows:
java -Xmx4g -jar GenomeAnalysisTK.jar -T SelectVariants -R b37/human_g1k_v37.fasta --variant my.vcf -select 'vc.getGenotype("NA12878").isHomRef()'
Groovy, right? Now here's a more sophisticated example of JEXL expression that finds all novel variants in the total set with allele frequency > 0.25 but not 1, is not filtered, and is non-reference in 01-0263 sample:
! vc.getGenotype("01-0263").isHomRef() && (vc.getID() == null || vc.getID().equals(".")) && AF > 0.25 && AF < 1.0 && vc.isNotFiltered() && vc.isSNP() -o 01-0263.high_freq_novels.vcf -sn 01-0263
The classic way of evaluating a boolean goes like this:
java -Xmx4g -jar GenomeAnalysisTK.jar -T SelectVariants -R b37/human_g1k_v37.fasta --variant my.vcf -select 'DB'
But you can also use the VariantContext object like this:
java -Xmx4g -jar GenomeAnalysisTK.jar -T SelectVariants -R b37/human_g1k_v37.fasta --variant my.vcf -select 'vc.hasAttribute("DB")'
Sometimes you might want to write a JEXL expression to evaluate e.g. the AD (allelic depth) field in the FORMAT column. However, the AD is technically not an integer; rather it is a list (array) of integers. One can evaluate the array data using the "." operator. Here's an example:
java -Xmx4g -jar GenomeAnalysisTK.jar -T SelectVariants -R b37/human_g1k_v37.fasta --variant my.vcf -select 'vc.getGenotype("NA12878").getAD().0 > 10'
I have been trying get variants out of a VCF file where the Allele Frequency (AF) is greater than 4%. I have tried both VariantFiltration and SelectVariants but I get different errors with each. Here is my call for SelectVariants:
java -Xmx4g -jar ~/tools/bin/GenomeAnalysisTK.jar -R /home/genome/human_g1k_v37.truseq_mask.fasta -T SelectVariants -o S05-16209-1C_S4_L001_R1_001.30.10.sorted.3perc.vcf --variant S05-16209-1C_S4_L001_R1_001.30.10.sorted.vcf -select "AF > 0.04" -sn "S05-16209-1C_S4_L001_R1_001"
The error is:
MESSAGE: Invalid command line: Invalid JEXL expression detected for select-0 with message ![0,9]: 'AF > 0.04;' > error
For VariantFiltration the call is:
java -Xmx4g -jar ~/tools/bin/GenomeAnalysisTK.jar -R /home/genome/human_g1k_v37.truseq_mask.fasta -T VariantFiltration -o S05-16209-1C_S4_L001_R1_001.30.10.sorted.3perc.vcf --variant S05-16209-1C_S4_L001_R1_001.30.10.sorted.vcf --filterExpression 'AF > 0.040' --filterName "3perc"
The error is:
java.lang.ArithmeticException: Double coercion: java.util.ArrayList:([0.010, 0.010]) at org.apache.commons.jexl2.JexlArithmetic.toDouble(JexlArithmetic.java:1023) at org.apache.commons.jexl2.JexlArithmetic.compare(JexlArithmetic.java:699) at org.apache.commons.jexl2.JexlArithmetic.greaterThan(JexlArithmetic.java:790) at org.apache.commons.jexl2.Interpreter.visit(Interpreter.java:796) at org.apache.commons.jexl2.parser.ASTGTNode.jjtAccept(ASTGTNode.java:18) at org.apache.commons.jexl2.Interpreter.interpret(Interpreter.java:232) at org.apache.commons.jexl2.ExpressionImpl.evaluate(ExpressionImpl.java:65) at org.broadinstitute.sting.utils.variantcontext.JEXLMap.evaluateExpression(VariantJEXLContext.java:267) at org.broadinstitute.sting.utils.variantcontext.JEXLMap.get(VariantJEXLContext.java:233) at org.broadinstitute.sting.utils.variantcontext.JEXLMap.get(VariantJEXLContext.java:118) at org.broadinstitute.sting.utils.variantcontext.VariantContextUtils.match(VariantContextUtils.java:293) at org.broadinstitute.sting.gatk.walkers.filters.VariantFiltration.filter(VariantFiltration.java:331) at org.broadinstitute.sting.gatk.walkers.filters.VariantFiltration.map(VariantFiltration.java:270) at org.broadinstitute.sting.gatk.walkers.filters.VariantFiltration.map(VariantFiltration.java:80) at org.broadinstitute.sting.gatk.traversals.TraverseLoci.traverse(TraverseLoci.java:65) at org.broadinstitute.sting.gatk.traversals.TraverseLoci.traverse(TraverseLoci.java:18) at org.broadinstitute.sting.gatk.executive.LinearMicroScheduler.execute(LinearMicroScheduler.java:62) at org.broadinstitute.sting.gatk.GenomeAnalysisEngine.execute(GenomeAnalysisEngine.java:265) at org.broadinstitute.sting.gatk.CommandLineExecutable.execute(CommandLineExecutable.java:113) at org.broadinstitute.sting.commandline.CommandLineProgram.start(CommandLineProgram.java:236) at org.broadinstitute.sting.commandline.CommandLineProgram.start(CommandLineProgram.java:146) at org.broadinstitute.sting.gatk.CommandLineGATK.main(CommandLineGATK.java:93)
For both I have tried variations of double quotes and different sigfigs. Also, it works when I select on parameters other than AF.
Am I missing something?
I'm trying to use JEXL to filter variants but something isn't working and I can't figure it out. I'm hoping someone can point me in the right direction. My VCF file contains an INFO field 1000g2012Apr_ALL. Some of the variants in my VCF have an entry for this field, some don't. I want to filter my VCF file for entries that are below a certain value or are NULL (empty).
Here's what my command looks like:
java -Xmx4G -jar GenomeAnalysisTK.jar -T SelectVariants -R hg19.fa -V my.vcf -o my.1kgfiltered.vcf -select 'vc.getAttribute("1000g2012Apr_ALL") < 0.01' -select '!vc.hasAttribute("1000g2012Apr_ALL")'
The problem is the 2nd select statement. I can't seem to get a JEXL select statement to give me the entries where 1000g2012Apr_ALL are empty. How do I accomplish this?
I'm currently running variantEval to count up variants per individual stratified by a variety of annotations.
My GATK call looks like:
java -jar /humgen/gsa-hpprojects/GATK/bin/current/GenomeAnalysisTK.jar \ -T VariantEval \ -R Homo_sapiens_assembly19.fasta \ -o output.txt \ -L input.vcf \ -eval input.vcf \ -ST Sample -noST \ -noEV -EV CountVariants \ -ST JexlExpression --select_names "nonsynon" --select_exps "resource.VAT_CDS == 'nonsynonymous' && resource.FOUNDERS_FRQ > 0.05" \ -ST JexlExpression --select_names "synon" --select_exps "resource.VAT_CDS == 'synonymous' && resource.FOUNDERS_FRQ > 0.05" ...
where the VAT_CDS section of the INFO field in the VCF has a functional annotation or is set to "na" if an annotation is unavailable. I'm getting the following error:
but weirdly the error is not consistent (my data is stratified by chromosome and most chromosomes will run without throwing the error while one or two chromosomes do exhibit the error. Do you have any ideas what's causing this behavior?
While running VariantEval, I'm trying to stratify by a JexlExpression by setting using
-ST Sample -ST JexlExpression -select "GQ>20"
This fails with a "variable does not exist" error despite the GQ existing in all genotypes in the vcf. Looking at the code it seems that the pathway that loads the JexlExpression in the VariantEval class specifically does not provide the genotype as context (only the VariantContext) and thus, the context for the Jexl does not include GT and the error is produced.
My question is: Is this a feature or a bug? It seems possible to add the genotype (when the VC only has one, or loop over the genotypes and either OR or AND the results (perhaps another input similar to -isr?), but perhaps I'm missing something subtle?
Would you like this behavior or are you happy with the current operation of jexlExpression?
Dear GATK team,
I'm trying to call variants on some 'haploid' human data (Illumina reads from a mix of clones). I did exactly the following:
crd8% cd /wga/dev/jaffe crd8% mkdir GATK2 crd8% cd GATK2 crd8% (got GenomeAnalysisTK-2.1-12.tar.bz2 from the GATK site on the web) crd8% bunzip2 GenomeAnalysisTK-2.1-12.tar.bz2 crd8% cat GenomeAnalysisTK-2.1-12.tar | tar xf - crd8% cd /local/scratch/jaffe/BroadCRD/fixed crd8% java -jar /wga/dev/jaffe/GATK2/GenomeAnalysisTK-2.1-12-ga99c19d/GenomeAnalysisTK.jar -R /wga/scr2/bigrefs/human19/genome.fasta -T UnifiedGenotyper -I frag.list -o raw2.vcf -U -baq CALCULATE_AS_NECESSARY -nt 48 crd8% java -jar /wga/dev/jaffe/GATK2/GenomeAnalysisTK-2.1-12-ga99c19d/GenomeAnalysisTK.jar -R /wga/scr2/bigrefs/human19/genome.fasta -T VariantFiltration -U -V raw2.vcf -o var.vcf --filterExpression "QD<5.0||AC<2||DP<6" --filterName junk
The last command failed, with output
... INFO 10:38:07,429 TraversalEngine - Location processed.sites runtime per.1M.sites completed total.runtime remaining WARN 10:38:08,453 Interpreter - ![12,18]: 'QD < 5.0 || AC < 2 || DP < 6;' < error java.lang.ArithmeticException: Long coercion: java.util.ArrayList:([1, 1]) at org.apache.commons.jexl2.JexlArithmetic.toLong(JexlArithmetic.java:914) at org.apache.commons.jexl2.JexlArithmetic.compare(JexlArithmetic.java:718) at org.apache.commons.jexl2.JexlArithmetic.lessThan(JexlArithmetic.java:774) at org.apache.commons.jexl2.Interpreter.visit(Interpreter.java:967) at org.apache.commons.jexl2.parser.ASTLTNode.jjtAccept(ASTLTNode.java:18) ...
Can you please suggest a solution? You should be able to access my data, if that would help. Well actually you would have to login to crd8, but you could copy files from there.
Thank you very much. | <urn:uuid:7d2d851a-79cb-4b2a-a922-8e9c4b771d38> | 2.734375 | 4,264 | Documentation | Software Dev. | 63.345558 |
The Water Use Efficiency of Tropical Dry-Forest Trees
Brienen, R.J.W., Wanek, W. and Hietz, P. 2011. Stable carbon isotopes in tree rings indicate improved water use efficiency and drought responses of a tropical dry forest tree species. Trees 25: 103-113.
Noting that "increases in Wi have been observed in short-term experiments of tree responses to elevated CO2 (Norby et al., 1999), and over long-time periods using records of δ13C in tree rings that reflect the global increase in atmospheric CO2 (Feng, 1999; Waterhouse et al., 2004)," Brienen et al. (2011) "analyzed carbon isotope ratios over the last 40 years in tree rings of Mimosa acantholoba, a tropical dry forest pioneer species," in a study conducted "on the Pacific slope of the isthmus of Tehuantepec, close to the village of Nizanda in the state of Oaxaca, South Mexico (16°39'N, 95°00'W)."
The three researchers, representing Austria, Mexico and the United Kingdom, report that the dry-forest tropical M. acantholoba trees "responded strongly to the increase in atmospheric CO2 over the last four decades," as their "Wi increased dramatically by 40%."
Brienen et al. say their results show that "δ13C in tree rings is a promising tool to evaluate long-term responses of tropical trees to increasing CO2," and that such studies "may be used to test DGVMs [dynamic global vegetation models] which predict large-scale die-off of the Amazon rainforest (Betts et al., 2004)," but which they say "remain highly simplistic due to lack of data and understanding of key processes."
Betts, R., Cox, P.M., Collins, M., Harris, P.P., Huntingford, C. and Jones, C.D. 2004. The role of ecosystem-atmosphere interactions in simulated Amazonian precipitation decrease and forest dieback under global climate warming. Theoretical and Applied Climatology 78: 157-175.
Feng, X.H. 1999. Trends in intrinsic water-use efficiency of natural trees for the past 100-200 years: a response to atmospheric CO2 concentration. Geochimica et Cosmochimica Acta 63: 1891-1903.
Nock, C.A., Baker, P.J., Wanek, W., Leis, A., Grabner, M. Bunyavejchewin, S. and Hietz, P. 2010. Long-term increases in intrinsic water-use efficiency do not lead to increased stem growth in a tropical monsoon forest in western Thailand. Global Change Biology 17: 1049-1063.
Norby, R.J., Wullschleger, S.D., Gunderson, C.A., Johnson, D.W. and Ceulemans, R. 1999. Tree responses to rising CO2 in field experiments: implications for the future forest. Plant, Cell and Environment 22: 683-714.
Saurer, M., Siegwolf, R.T.W. and Schweingruber, F.H. 2004. Carbon isotope discrimination indicates improving water-use efficiency of trees in northern Eurasia over the last 100 years. Global Change Biology 10: 2109-2120.
Waterhouse, J.S., Switsur, V.R., Barker, A.C., Carter, A.H.C., Hemming, D.L., Loader, N.J. and Robertson, I. 2004. Northern European trees show a progressively diminishing response to increasing atmospheric carbon dioxide concentrations. Quaternary Science Reviews 23: 803-810. | <urn:uuid:5d9e3eb7-3e3e-46d3-b487-a765ecdc42df> | 2.953125 | 799 | Academic Writing | Science & Tech. | 70.621023 |
Gene-Chips is run by computational chemist Leming Shi, "a fan" of DNA arrays who works as a contractor for the Food and Drug Administration. The site's design is simple yet effective: It's one long page of text sprinkled with hyperlinks. Shi describes how the chips work, the basic setup (robotics for making chips, labeled DNA probes, fluorescence reader, software), who sells them, and applications, which include drug discovery and toxicology. Links to review articles and scores of academic labs and companies provide more details. Patrick Brown's page at Stanford, for instance, has a manual on how to build your own microarray maker. A Cornell site offers a slew of online review articles, and a National Institutes of Health page describes its microarray project. And in one interesting application, a University of Arizona lab used the chips to see which genes are turned on in spermatogenesis in C. elegans worms. | <urn:uuid:f38288c7-e751-43a4-9fe0-be1d0aa31e1e> | 3.03125 | 191 | Knowledge Article | Science & Tech. | 39.23489 |
Alternate name: European Mantid
Family: Mantidae, Mantids view all from this family
Description A large mantis; color ranges from bright green to tan, wing extend beyond tip of abdomen. Large compound eyes tan to chocolate-brown. Distinguished easily by a black-ringed brown spot beneath the fore coxae (walking legs). Similar Chinese Mantis and Carolina Mantis lack brown spot.
Dimensions 2-2 1/2" (50-65 mm) length with wings
Food Primarily diurnal insects such as caterpillars, flies, butterflies, bees, and moths.
Life Cycle Most species of mantis engage in cannibalism, most frequently during mating season with the female eating the male after mating. Eggs are laid in a flat mass left to overwinter attached to exposed twigs above snow. Eggs hatch in late spring almost simultaneously and Nymphs are dispersed by wind or eat one another. 1 generation annually which matures in late summer or early autumn.
Habitat Meadows, on leaves and flowers.
Range Introduced. Found throughout Eastern US n. to Ontario. West to Pacific Northwest.
Discussion Mantises are ambush predators. They camouflage themselves and stand perfectly still, waiting for their prey to stray too near. When it does the mantis then lashes out at remarkable speed. Originating in southern Europe, the Praying Mantis was introduced to North America in 1899 in a shipment of nursery plants. It has been recognized as a beneficial predator, particularly in battling gypsy moths, whose caterpillars it preys on. Unfortunately, their populations are so cannibalistic that they rarely get large enough to have much impact on caterpillar populations. The insect has thrived in many parts of their range and now are found throughout the north-eastern United States and Canada west to the Pacific Northwest. | <urn:uuid:a68513e6-cc4a-4aa9-8ad0-8bab63ee7d7e> | 3.359375 | 377 | Knowledge Article | Science & Tech. | 44.405 |
Credit: NASA/CXC/Ohio State Univ./C.Grier et al.; Optical: NASA/STScI, ESO/WFI; Infrared: NASA/JPL-Caltech
Spiral Galaxy NGC 3627 - The spiral galaxy NGC 3627 is located about 30 million light years from Earth. This composite image includes X-ray data from NASA's Chandra X-ray Observatory (blue), infrared data from the Spitzer Space Telescope (red), and optical data from the Hubble Space Telescope and the Very Large Telescope (yellow). The inset shows the central region, which contains a bright X-ray source that is likely powered by material falling onto a supermassive black hole. A search using archival data from previous Chandra observations of a sample of 62 nearby galaxies has shown that 37 of the galaxies, including NGC 3627, contain X-ray sources in their centers. Most of these sources are likely powered by central supermassive black holes. The survey, which also used data from the Spitzer Infrared Nearby Galaxy Survey, found that seven of the 37 sources are new supermassive black hole candidates. Confirming previous Chandra results, this study finds the fraction of galaxies found to be hosting supermassive black holes is much higher than found with optical searches. This shows the ability of X-ray observations to find black holes in galaxies where relatively low-level black hole activity has either been hidden by obscuring material or washed out by the bright optical light of the galaxy. | <urn:uuid:ac601855-9db4-4f02-b029-13a94b28b000> | 3.78125 | 306 | Knowledge Article | Science & Tech. | 42.230909 |
Pine Tree Cone Production
Name: Myra Jean
We live in Wisconsin and have noticed that the
conifers are especially laden with cones this year. Many other
years the trees have had cones mostly at the top. But this year
many of the trees are heavy with cones top to bottom, to the point
where the look brown rather than the regular rich green of fall.
The branches are bending with the weight of the cones. We are
wondering why so many? Is this part of a conifer's life cycle as
many of the trees aroun our property were planted at the same time?
Is this an indication of a harsh winter? Could you help us out? Thank you.
The phenomenon is called "mast seeding" and is found in many tree species.
Causes are debated, but it is definitely not a predictor of the coming
winter weather. Mast seeding may be a response to favorable growing
conditions in the previous season(s), or a strategy that evolved to increase
reproductive success by sating seed predators in a given year, so that there
is better chance of some seeds surviving to grow. Here is a selection from
the abstract from a technical study on mast seeding, by Kelly and Sork,
from the Annual Review of Ecology and Systematics
"For many years biologists have debated whether mast seeding (the
synchronous intermittent production of large seed crops in perennial plants)
results from weather conditions or is an evolved plant reproductive
strategy. ..... We conclude that masting is often an adaptive reproductive
trait overlaid on the direct influence of weather."
In other words, these authors conclude both factors are responsible.
Click here to return to the Botany Archives
Update: June 2012 | <urn:uuid:f9d5cda6-becb-4bfd-9856-c63997e8ea68> | 3.5625 | 372 | Q&A Forum | Science & Tech. | 51.517703 |
On October 4 and 5, a coronal mass ejection from the sun sent an explosion of particles speeding toward earth. Three days later, those particles hit the earth's magnetic field. The magnetic field funneled the particles into the atmosphere near the poles, where they collided with gases in the upper atmosphere to release dramatic waves of colorful light over Canada's Quebec and Ontario provinces. You don't get to see the green and purple colors in the photo above—taken early on the morning of October 8, 2012, by a NASA satellite—but you do get a pretty good idea for the size and scope of the massive swell of light.
Pointing to the sacredness of the San Francisco Peaks north
of Flagstaff, Arizona, a coalition of Native American tribes has been fighting
the development and expansion of Arizona Snowbowl ski resort since 1979. It remains
the New York Times, despite
having suffered a key legal defeat this winter. A federal court ruled against the
tribes in a nearly decade-old lawsuit that claims the ski resort's plans to use
treated wastewater from Flagstaff's sewage system to make artificial snow for
the resort would interfere with religious practices and mar the mountains.
Wait. The resort will use sewage to make snow? Technically,
yes. That's why the story has garnered lots of attention. But recycling treated
wastewater for applications that do not require potable water is not nearly as
icky, nor as uncommon, as it might sound. This type of water is commonly used for irrigating
golf courses and soccer fields, for example.
While Arizona Snowbowl would be the first resort in the U.S.
to use 100 percent treated wastewater to make snow, it's a common practice in
Europe and in parts of Australia, says Hunter Sykes, an environmental sustainability consultant who closely
tracks the outdoor recreation industry and produced a 2007 documentary about
the environmental impacts of rampant ski resort development called Resorting to Madness. "Most people
who work with wastewater don't see this an issue, because it's not going to
make people sick and, as far as we know, it's not going to contaminate flora or
fauna," he says.
Not everyone is quite so comfortable, though, with the idea of using
treated wastewater for snowmaking. Among the groups that oppose it, on
the grounds that the water may contain chemical inputs from pharmaceuticals and
other potentially hazardous hard-to-trace sources, include the Center for Biological Diversity. Sykes agrees
that there is still much we don't understand about the chemical agents that
persist in treated wastewater and how they could impact the ecosystems into
which they're released, but says if it was up to him, he would use the treated
Taylor McKinnon, public lands campaigns director for
the Center for Biological Diversity points to a study that linked wastewater
effluent released into a creek in Boulder, Colorado, with abnormal fish gender
distributions. "There is an emerging and growing list of compounds
[about which] we don't know the affects," he says, but we know that
endocrine disruptors [in wastewater] will change fish sex ratios. This points
to the need for additional research and more advanced water treatment."
But McKinnon and Sykes do agree on one thing: the real story
here is the increase in snowmaking, industry wide, and the wider environmental
impacts of making snow.
When filmmaker John Downer was in elementary school, he got
down in the dirt of his parents' garden so that he could film the insects,
frogs, and toads using a Super 8 camera.
“I think that kind of, as I look back now, inspired my way of filming,” says
the 59-year-old director. “Which is
to try and get in the animal world.”
He studied zoology in college and then went to work in radio
for the BBC before landing a job
making TV shows for children. One of those shows involved filming life in a
garden with miniaturized cameras that he built. “That was the first time I ever
married advancements in technology with the capturing of images,” says Downer.
From there he got a job on the nation’s top-rated animal
show, “Wildlife on One.” After making a show about snakes, he moved on to birds.
He raised a duck from birth so that it imprinted to him as a parent, and a year
later filmed it while flying in a parascender—a parachute pulled by a vehicle. He
also stripped a Super 8 camera down to a lens, a film cartridge, a motor, and a
battery so that he could put it on the back of a buzzard. The bird flew, and he got some grainy footage. “That was an
inspiration,” he says.
But he knew inspiration wasn’t going to cut it for the film he ultimately wanted to make. He imagined capturing a bird's eye view of the world from multiple species. To do that,
he needed to wait for smaller and more sophisticated technology. Twenty-five years later,
he used drones, POV cams, and ultralights to film the new Discovery Channel
show “Winged Planet” (October 6, 8 P.M. EST). I called him up to find out more about the making of the two-hour-long special.
The video doesn't show the spark, the inciting moment that led the impala herd to bolt across the road directly into the path of a leopard crouching in the tall grass. But it does show the climax, the predator exploding from the brush into an esophagus-targeted leap that lands with such force that it leaves an ungulate reeling hooves over head in mid-air. A leg-jolting suffocation and a pre-dinner drag through the dirt follow.
One of the benefits of so many people having cameras and access to YouTube is the ability to share such rarely witnessed wildlife moments. Here's the description of how MiPixWildife happened upon this clip during a safari:
On May 30, 2012, at 3:00 P.M. MST, a series of thunderstorms formed over central and south central Kansas. They dropped golf ball-sized hail before lining up into a dark vanguard that barraged the countryside ahead with 70 mile per hour winds. News of the derecho—a long-lived line of fast moving thunderstorms with winds of more than 58 mph—led Brian Johnson to grab his camera and venture out to an open field where he had photographed lightning the previous night.
The amateur photographer chases big storms for a series of local radio stations. He fell in love with the behemoths at the age of seven, after witnessing the fury of a tornado up close. "My father still regrets saying the words 'Look at that,'" said Johnson. "Remember, if
you take a frightened child out into a storm to show them how beautiful
nature’s fury can be, they may turn out like me."
"Storms Stitch 1," May 30, 2012; Kechi, Kansas Photo: Brian Johnson
“As a large squall line moved through the area. The National Weather
Service had warned about a large scale Derecho forming and moving
through. This spawned a couple brief severe thunderstorms that dumped
hail on rush hour traffic before the main line moved in. As the bigger
storm moved into the Wichita area, reports were coming in of 70 mph
winds and hail. There is an open farm field roughly two miles from my
house that I shot lightning on the previous night. I sat there for
about 20 minutes before this large squall line pushed through the
clouds. I was hit with a pretty good gust front as it got closer, but
as the winds increased, I decided to get to shelter. This photo was one
of the last ones I took. This story and others are available at www.ruminationofthunder.com and this specific story is at http://www.ruminationofthunder.com/2012_05_01_archive.html."
"Ormond Shelf," May 15, 2012; Ormon Beach, Florida Photo: Jason Weingart
“I'm a photography student at the University of Central Florida. I
began chasing storms a little over three years ago. This day started out
like many other days. I was out on a storm west of the coast,
photographing it even as the National Weather Service issued a severe
warning. The NWS lifted the warning, but I decided to stick with it as
it moved to the coast. Just as it started to move offshore to the east,
it made a turn to the south.
I have shot many storms from the same spot this photo was taken, and I
almost drove by to get a different vantage point, but something told me
to just stop at my spot. I jumped out of my car and ran down to the
beach. To my surprise, there were still several beach-goers taking in
the sight of this massive shelf cloud, as well as a few surfers in the
water, trying to catch one last wave. Of course, there was a Volusia
County lifeguard standing there watching over everyone. I walked down to
the water and took some shots, always keeping an eye on the lifeguard.
As the shelf cloud approached, I swung back behind the guard tower,
waited for him to climb up it and signal to the surfers to exit the
water. I took several shots, then hopped back in my car and tried to
stay south of the storm.
The storm actually pushed back on shore as it moved south, and then
became strong enough for tornado warnings on three separate occasions. I
saw a large wall cloud, another spectacular shelf cloud, and some very
tight rotation in the couple hours I stuck with the storm after I left
the beach in Ormond. Had I known what I already shot there, I probably
wouldn't have even bothered. Definitely my signature shot of the year." | <urn:uuid:f551f1f3-aa56-4301-9445-5614af0c97df> | 2.84375 | 2,136 | Content Listing | Science & Tech. | 56.833542 |
You did not define what this inch of space was composed of.
If this inch of space was air, it would be physically different
than liquid water being in that space. Why is it physically different? Because water is not compressible and maybe not decompressible either. In order for a vacuum to originate in that space, something has to "give way". Water does not give way. Air does.
If this inch of space was pure vacuum, I am afraid you have done something no man has done before, and I would like to ask you how you created that pure vacuum since they do not exist.
If you argue, that, well, no it is not a pure vacuum.. it is... composed of some water vapor.. then.. how did you first break down that water into vapor I will ask. If you argue that well, the space got full of a tiny bit of air, then I will just argue back that I said it was WATER not air.
Air can be changed easily (compressed and decompressed) in size. Water cannot. Air allows practical partial imperfect vacuums to exist. Water since it is not decompressible/compressible in liquid form, does not AFAIK, allow a vacuum to spontaneously exist out of no where. It seems that practical imperfect vacuums (ones we can actually create) need some other gas molecules to exist. Water is not a gas molecule, it is liquid.
If one has ever held a science syringe with thumb on end and pulled the syringe handle, one would know that it is very easy to change air volume in the syringe. However if one fills the plastic syringe with pure water and no air, the syringe gets locked when you try to pull it with thumb in place. Then, as you pull, the syringe busts and cracks or the handle rips into two pieces if you are strong enough. Often the syringe plastic will deform and collapse, imploding.
So, what component is the most likely to "give way" in the system I described? Probably the air inside the balloon. Instead of the air inside the balloon being compressed when under hydrostatic pressure, it will just.. I don't know, stretch out and have lower pressure. Still mind boggling me at this point though. | <urn:uuid:9db1152f-e475-4433-85f5-25152ec17d58> | 3.125 | 475 | Comment Section | Science & Tech. | 65.313545 |
When someone mentions 'salinity' and 'water' in the same sentence, most people think of the ocean, the Gulf or coastal bays. However, simply put, 'salinity' refers to the amount of salts dissolved in water, any water, and that includes "freshwater". Generally speaking, the salts that constitute salinity in oceans are the same as those in lakes and streams; the amount (concentration) of those salts is, of course, much higher in oceans.
The salinity of any waterbody is extremely important to all creatures living in and around it. For example, a slight change in salinity can cause fish, frog or shrimp eggs to float too much (high salinity) or not enough (low salinity), thus reducing or eliminating their chances of development into adults. Salinity is also important for water uses on land by people and wildlife. The saltier the water, the more difficult and expensive it is to prepare for drinking, and the more dangerous it is to apply to crops.
How does water become more or less salty?
The most important sources of salts, and therefore salinity, in all Earth's waters are: (1) washing (dissolving) of salts from the soil and rock of the Earth's crust; (2) precipitation (dust, rain and snow falling into the water) and (3) the evaporation and precipitation cycle. Let's look at a simple example.
Positively and negatively charged elements or "ions" create the salinity of all waters. These ions are found in the soil and rock of Earth's crust, and some, like sodium chloride (NaCl) are incredibly abundant. Often referred to as "common salt" or "common table salt", sodium chloride is comprised of two ions, a positively-charged sodium (Na) cation, and a negatively charged chloride (Cl) anion. When water saturates soil and washes over rock, NaCl is dissolved in the water (that is, the ions separate and bond with the ions of water) and the water becomes more salty; that is, its salinity increases.
As freshwater (streams and springs, for example) reaches marine waters, it mixes and reduces the salinity. These freshwater sources also provide nutrients, oxygen and food for the plants and animals there. The result is an amazing ecosystem, the "estuary," where a tremendous variety and abundance of life can flourish. Over 90% of all of the animal species that dwell within miles of land use the estuaries as their mating or spawning grounds; that is why estuaries are referred to as the nurseries of the oceans.
Protecting the flow of freshwater to estuaries is critically important. Organizations such as the Southwest Florida Water Management District are working to determine the amount of freshwater flows that are necessary to ensure rivers continue to maintain historical salinity patterns in estuaries. Salty water can also enter surface waters through groundwater systems. The process is known as saltwater intrusion, and it occurs as groundwater is pumped for use as public water supply, which allows saltwater to migrate inland. To prevent this problem from continuing, groundwater resources must be conserved. Water conservation on land is critical to protecting life in the Gulf!
Today, most salinity measurements are made with sensors placed directly in the water. These sensors measure the electrical conductivity of the water; that is, they determine the rate at which a tiny electrical current moves through the water. The saltier the water—that is, the higher the concentration of salts—the more rapidly the current will pass through it.
Salinity measurements made in gulfs, bays, oceans and seas (marine waters) are reported as parts per thousand or ppt. The salinity of most oceans and seas (excluding inland seas, such as Great Salt Lake) ranges from 35-37 ppt. The salinity of estuaries (places where freshwater meets marine water) ranges from approximately 8–15 ppt, depending on the amount and quality of freshwater flowing to them. Salinity measurements made in lakes, streams, inland marshes and inland bayous (collectively referred to as "freshwater" because their salinity is much lower than that of marine waters) are reported as specific conductance and in microSiemen (μS) or milliSiemen (mS) rather than parts per thousand (ppt). The specific conductance, or "conductivity," of freshwaters ranges much more widely than do the salinities of marine waters, and can be less than 500 μS (approximately 0.35 ppt) or as high or higher than 5,000 μS (approximately 3.5 ppt), which is salty for freshwater. So, freshwaters with high conductivities are only a fraction as salty as marine and estuarine waters.
Generally speaking, the salinity data that you will find in the Water Atlas is presented as specific conductance. The exceptions to this are where water quality data are presented from marine and estuarine waters. If you want to know the salinity in ppt of water when it is presented as conductivity in μS or visa versa, you need only know the following relationship and then apply some simple algebra.
Relationship: 0 to 70 ppt ≅ 0 to 100,000 μS
Question: What is the salinity in ppt of a freshwater lake where the specific conductance is 5,000 μS?
X ppt = 5,000 μS = 70 ppt x 5,000 μS = 70 ppt x 5,000 μS = 350,000 ppt = 3.5 ppt
70 ppt 100,000 μS 100,000 μS 100,000 μS 100,000
Salinities in near-coastal waters such as estuaries vary seasonally and are influenced by the in-flow of freshwater, or the lack thereof. Conductivities of freshwaters, especially marshes and lakes, can increase during dry times as water evaporates and allows salts to concentrate. Conversely, high rainfall can reduce the salinity in lakes and marshes. Therefore, data may vary with extreme weather events such as droughts and floods. Salinity (and conductivity) data are compared historically. This means that data collected at a sampling location (referred to as a sampling station) through this year are compared with data collected at that station at the same time last year, the year before and so on. Data have been collected for much longer periods at some stations than at others, and this may influence the trend (how the data indicate salinity appears to be changing) at that station. | <urn:uuid:9487002a-00b3-413d-b06e-e6b5f477ecef> | 3.90625 | 1,369 | Knowledge Article | Science & Tech. | 41.935206 |
Now lets see what exactly is HTML (Hyper Text Markup Language). It is a type of data file which is transferred to the client machine. The HTML file gets translated and displayed on the screen if the client is using a Web browser like Netscape Navigator, Microsoft Internet Explorer etc. Let me give you a brief description of HTML.
What is an HTML File?
Go ahead and try it!
If you are running Windows, start Notepad.
If you are using Mac, start SimpleText.
Start TextEdit in OSX and change the following preferences: Open the the "Format" menu and select "Plain text" instead of "Rich text". Then open the "Preferences" window under the "Text Edit" menu and select "Ignore rich text commands in HTML files". If you do not change the preferences above, your HTML code will probably not work.
Type in the following text:
<html> <head><title>Title of page</title></head>
<body> This is my first homepage. <b>This text is bold</b> </body> </html><html> <head><title>Title of page</title></head>
<body> This is my first homepage. <b>This text is bold</b> </body> </html>
Save the file as "firstpage.htm".
Start your Internet browser. Select "Open" (or "Open Page") in the File menu of your browser. A dialog box will appear. Select "Browse" (or "Choose File") and locate the HTML file you just created - "firstpage.htm" - select it and click "Open". Now you should see an address in the dialog box, for example "C:\MyDocuments\firstpage.htm". Click OK, and the browser will display the page.
Lets have a look at print preview of the above example.
Description of the above Example.
We have started the HTML document by using the <html> tag and ended the same by using </html> tag. These two tags tell the browser about the starting and the ending of the document. Points to note:
Remember, use either the .htm or the .html extension while saving an HTML file. Well, it is preferable to use .html extension.
If you are facing any programming issue, such as compilation errors or not able to find the code you are looking for.
Ask your questions, our development team will try to give answers to your questions. | <urn:uuid:fbb1e60d-14b2-4763-8eb8-28e314af1bf7> | 3.671875 | 520 | Documentation | Software Dev. | 70.341769 |
Authors: Azzam AlMosallami
Radio metric data from Pioneer 10/11 indicate an apparent anomalous, constant, acceleration acting on the spacecraft with a magnitude ~ , directed towards the Sun[1,2]. Turyshev examined the constancy and direction of the Pioneer anomaly, and concluded that the data a temporally decaying anomalous acceleration with an over 10% improvement in the residuals compared to a constant acceleration model. Anderson, who is retired from NASA's Jet Propulsion Laboratory (JPL), is that study's first author. He finds, so "it's either new physics or old physics we haven't discovered yet." New physics could be a variation on Newton's laws, whereas an example of as-yet-to-be-discovered old physics would be a cloud of dark matter trapped around the sun. In this paper I introduce the exact solution for the Pioneer anomaly depending on the general theory of relativity and the Hubble's law. According to my solution, there are two terms of decelerations that controls the Pioneer anomaly. The first is produced by moving the Pioneer spacecraft through the gravitational field of the Sun, which causes the velocity of the spacecraft to be decreased according to the Schwarzschild Geometry of freely infalling particle. This deceleration is responsible for varying behaviour of the Pioneer anomaly in Turyshev . The second term is produced by the Hubble's law which is constant and equals to the Hubble's constant multiplied by the speed of light in vacuum.
Comments: 14 pages
[v1] 27 Sep 2011
Unique-IP document downloads: 115 times
Add your own feedback and questions here: | <urn:uuid:7787b7ef-3140-4d5b-980e-55255fab0645> | 3 | 335 | Academic Writing | Science & Tech. | 34.422629 |
Conventional microscopes look through slices of tissue far thinner than a piece of paper. Stained and mounted on slides, the images of cells are like tiny stained glass windows.
But the technology of the past few years has changed microscopes profoundly. Not only can they magnify to a much greater degree, they can dissect specimens with laser beams, chemically analyse them, and even build virtual models of living animals, producing images that are spectacular, revealing and often very beautiful.
At the University of Adelaide in South Australia Adelaide Microscopy has brought
these technologies together in a unique resource for imaging things that can't be seen in any other way.DR MEREDITH WALLWORK:
The most exciting thing about this centre is that people come in here with problems and we can look at things under very high magnification or we can give them the option of looking at things in lower magnification in different ways. And it's very exciting when we can do that by combining these technologies which are really state of the art
Ordinary lenses will get you only so far. Just as cameras can zoom in and magnify so can microscopes, but eventually the laws of light restrict you to magnification of about 1500 times.
Then you have to use beams of electrons, tiny charged particles that can magnify to about 10,000 times.DR MEREDITH WALLWORK:
For example, the scanning electron microscope will allow you to look at the surface, in very fine detail, of an object that you're able to prepare, the sorts of images that people will sometimes seen where they're shown
spider legs and the detail of feathers and things like that, where they're things we can't see in any other way. And you do see nature at its most beautiful in some of those images because they're enormous blowups if you like, of things we would not otherwise see and you see the perfection of nature. It's wonderful.ROB MORRISON:
While those are impressive images they're only a surface view. Other microscopes take you inside a specimen. Some even take you there by laser. A light microscope at high magnification can reveal cells of interest but they're tiny and it's hard to locate them once you remove the slide.
The laser dissecting microscope chops them out while you watch with microscopic precision.DR MEREDITH WALLWORK:
So while you're looking at the tissue under the microscope you can control the laser to cut around the cells of interest, the cells you need to sample, and they will then be sampled into a tube you can take back to the laboratory.ROB MORRISON:
But once cells are cut up
like this they can't be put back together which doesn't help when you want to see inside a specimen without destroying it. If you want to learn how parts of a brain fit together you can fix the brain in plastic then cut it into pieces like a jigsaw puzzle but a light microscope will need that brain cut into thousands of slices thin enough to see through.
You can project them onto plastic sheets, colour those in and put them together in a model, but it's only a model and the original has been destroyed.
A confocal microscope leaves the specimen intact but still provides a transparent virtual model in three dimensions, its various parts revealed in glowing colours. DR MEREDITH WALLWORK:
To do that we need to have a subject that actually glows, that fluoresces. We add stains that fluoresce and those stains will bind to those structures so that they will glow a particular colour. Some might glow green, others red and we can visualise those different colours in the confocal microscope.
And it actually produces slices, much like a CT scanner might slice through your brain but in this case what you're doing is producing fluorescent images through the sample. You're not actually cutting the sample but you're producing a series of images as you focus the microscope through it.
So that series of images can then be taken
to another computer which reconstructs, in three dimensions, the original material. In that way you can then rotate it. You can have a look through that sample and you get a very clear picture of how things are placed in that material in three dimensions.
We can even image live animals. This same process can be done
using a CT scanner. To do that the animals are sedated. They're put into the scanner. We monitor their health, their temperature, their breathing while they're being scanned and that uses x-rays and you can actually look at the structure of the bones and things like that, the hard tissue within these whole animals.ROB MORRISON:
These microscopes combine the latest technologies with some that are centuries old and as more technologies develop that trend will give us even more powerful ways of imaging the world we can't see.DR MEREDITH WALLWORK:
I think imaging is getting bigger and bigger in the sense that I think that scientists are very excited and become quite passionate about the possibility that they can answer questions by seeing things in real time. They can see things as they happen and it means that their science is so much more relevant, and I think to that it means they can answer questions they've never been able to think about answering before. | <urn:uuid:15a213f2-8951-49bb-bba7-fe4d75f60561> | 3.59375 | 1,079 | Audio Transcript | Science & Tech. | 47.014214 |
(CNN) -- Concentrations of greenhouse gases in the Earth's atmosphere reached record highs in 2011, according to new data published by the World Meteorological Organization (WMO).
The WMO's annual Greenhouse Gas Bulletin, released Tuesday, reports that carbon dioxide rose to 390.9 parts per million (ppm), up two ppm on 2010 levels.
Carbon dioxide is the single most important greenhouse gas emitted by humans, says the WMO, and the increases recorded last year are in line with average rises seen each year over the last decade.
Combined with average yearly rises of 1.5 ppm during the 1990s, the WMO says radiative forcing (the warming effect on our climate) by long-lived greenhouse gases has now increased 30% since 1990.
"These billions of tons of additional carbon dioxide in our atmosphere will remain there for centuries, causing our planet to warm further and impacting on all aspects of life on Earth," WMO secretary general Michel Jarraud said in a statement.
According to the WMO, about 375 billion tons of carbon has been released into the atmosphere since the industrial revolution began in 1750, with around half this amount being absorbed by carbon sinks. But natural carbon storage facilities like oceans and forests "will not necessarily continue in the future," say the WMO.
"We've already seen that the oceans are becoming more acidic as a result of the carbon dioxide uptake, with potential repercussions for the underwater food chain and coral reefs," Jarraud said in a statement.
The Swiss-based United Nations agency, which uses data from more than 50 countries to compile the report, also detailed rises in other greenhouse gases including methane and nitrous oxide.
Around 60% of methane released into the atmosphere comes from human activities such as farming, rice agriculture, fossil fuel exploitation, landfill and biomass burning, according to the WMO. In 2011, concentrations reached a new high of 1813 parts per billion (ppb), 259% higher than pre-industrial levels.
Emissions of nitrous oxide -- 40% of which are estimated to come from human activity -- reached 324.2 ppb, up one ppb on the 2010 figure and 120% higher than pre-industrial times.
Richard Allan, from the Department of Meteorology at the UK's University of Reading, said the WMO's latest data confirmed the trend in the rate of rise reported in recent decades.
"What it shows isn't surprising, but it obviously has very important implications for the future well-being of the planet," Allan told CNN.
Even if emission rises were halted now, the planet would continue to warm because of the time it takes for the climate system to return to equilibrium, he said.
"We are committed to the warming for a long time, even if we do take strong action against it now," Allan said. | <urn:uuid:2a71eda9-a333-4ef9-b417-4b2b23e4b303> | 3.703125 | 580 | Truncated | Science & Tech. | 41.108407 |
We live in a strange, beautiful, and often alien-looking world. Case in point: the crystal-clear Jewel Caterpillar of Central and South America, pictured here in all its translucent glory.
This particular caterpillar (which is known more formally as Acraga Coa, and metamorphoses into this equally stunning orange moth) was spotted by photographer Gerardo Aispuru near Cancun, Mexico. Pictured up top is just one in a series of photographs that Aispuru submitted to Project Noah, where he writes:
Photo take in a mangrove area , found this Stoning translucent caterpillar lay on a Red Mangrove tree leaf this morning early. Just can believe there is some species like this around the world. looks like made of glass whit small red mushroom inside every pic. about 3 cm long.
Looking at A. coa's naturally translucent body, I can't help but be reminded of the work of researchers like Atsushi Miyawaki, whose team is working to develop chemical agents that could turn otherwise opaque biological tissue transparent (like that of the mouse embryo on the right in the picture featured here). Are the secrets to next-generation optical imaging hiding in the genes of organisms like the Jewel Caterpillar? | <urn:uuid:83bc6833-ece8-4e69-ba13-4ac1e5ba092c> | 2.75 | 256 | Truncated | Science & Tech. | 36.567153 |
Are there spaces in between air molecules? If yes what is in those
Not only is there empty space in between molecules, there is empty
space INSIDE molecules and atoms!
This question is actually a very old one - the greeks debated
"atomism", with the objection to "atoms" being that if you have
atoms, then you must have empty space between atoms, and this did not
seem to make sense. Well, it turns out to be true - space has a structure
all by itself, and atoms and molecules just move around in it.
Of course, there are electromagnetic fields and other similar things
that penetrate space everywhere, so even empty space is not really
quite empty. So maybe both sides were right.
Click here to return to the Physics Archives
Update: June 2012 | <urn:uuid:237782b1-5fb0-4261-ac67-f658a49514ea> | 2.765625 | 171 | Knowledge Article | Science & Tech. | 41.582273 |
Power was increased by 71% and the figure of merit increased to 1.5
Northwestern University researchers (along with colleagues from University of Michigan and the Jet Propulsion Lab) discovered that adding two metals, antimony and lead, to the well-known semiconductor lead-telluride, produces a thermoelectric material that is more efficient at high temperatures than existing materials. The results are published online in the journal Angewandte Chemie. [H/T Nanowerk
Thermoelectric materials are only 5 to 6 percent efficient today, but the new generation of materials based on recent discoveries including this one at Northwestern, could produce devices with 11 to 14 percent efficiency, says Kanatzidis. The long-term goal is to reach 20 percent.
"The thermal conductivity was not any lower than our earlier results, but we discovered a net gain in electrical conductivity at high temperatures that we didn't expect," said Kanatzidis. "This means we had a net gain in power [71%] coming out of the material that we didn't have before. This was very surprising."
Interestingly, the researchers also discovered that adding lead or antimony alone to the lead-telluride did not produce an improvement. Lead and antimony both had to be present in the lead-telluride to produce the electrical conductivity gain. The electrons scatter less and move faster with the two inclusions than with just one or none.
"This phenomenon will stimulate new scientific inquiries and generate new ideas on how to design even more efficient thermoelectric materials in the future," said Kanatzidis.
2. RTI has been funded for a thermoelectric project with targets in the 20-30% range.
3. The University of Copenhagen is making progress with understanding thermoelectric materials in the group of clathrates, which create crystals full of 'nano-cages'.
Why Thermoelectrics Are Huge for Energy Efficiency
Industrial waste heat is 7 quads in the USA. There is more waste heat from power plants and from cars. Applying thermoelectrics to our current power plants would be like adding 10-30 nuclear power plants and 150-375 coal plants and 500-1500 natural gas plants that would not use any more fuel because it would be from more efficient use of existing power plants.
Heat flows in a car and using thermoelectrics to tap the waste heat. The standard combustion engine is about 30% efficient, but regular diesel engines are about 38% efficient. New diesel engine and free piston engines can reach 50% efficiency or more. The energy for cooling can also be reduced using thermoelectrics.
The 30% energy efficiency is triple the efficiency of todays common thermoelectrics and double most advanced systems and would get to range of using solid state thermoelectrics to replace refrigerators [thermoelectrics can help cool as well as convert heat to electricity] and many small car sized engines. Typical conversion systems become less efficient as they are scaled down to small size. This means there is a crossover point: below some power level thermoelectric technology will tend to be more efficient. Increasing ZT will move the crossover point to higher power levels, increasing the range of applications where thermoelectrics compete. Thus the ZT of 3 to compete with current best car size and refrigerator mechanical systems.
Past coverage of thermoelectrics and refrigerators.
Thermoelectric Figure of Merit
The primary criterion for thermoelectric device viability is the figure of merit given by:
which depends on the Seebeck coefficient, S, thermal conductivity, λ, and electrical conductivity, σ.
High temperature thermoelectrics and ZT, figure of merit | <urn:uuid:6da0cabb-dde1-4d1a-9695-f4464c4e10cf> | 4.03125 | 778 | Knowledge Article | Science & Tech. | 34.388037 |
Goals: This mission, like its twin Venera 12, called for a flyby spacecraft and a lander to explore Venus' ionosphere, atmosphere and surface and the interplanetary environment.
Accomplishments: The flyby craft studied the solar wind, gamma-ray bursts, ultraviolet radiation, and Venus' ionosphere. It passed the planet at a distance of about 35,000 km (about 22,000 miles). The lander probed Venus' atmosphere as it descended and then transmitted data from the surface for 95 minutes. Its camera system and soil-analysis experiment failed, but the mission did report evidence of lightning and thunder, carbon monoxide at low altitudes, and data on isotopes of argon that prompted scientists to question the theory that the original atmospheres of Venus, Earth and Mars were the result of outgassing from volcanoes. | <urn:uuid:33be572e-85ad-4fe4-949b-a83285cca5e0> | 3.734375 | 178 | Knowledge Article | Science & Tech. | 27.187535 |
Learn more physics!
If higgs bosons grab on to particles why do these free particles continue traveling--i.e., per Newton's first law?
- Mehran (age 62)
Many newspaper articles have said that the Higgs field acts like a "cosmic molasses". That's a terrible analogy. Molasses causes friction, which makes things come to rest with respect to the molasses. Yet, as you noted, the Higgs field lets things keep moving freely.
The Higgs field, like all other known basic ingredients of the world, has relativistic symmetry. That means that it doesn't single out one state of motion over any other. What it does have is some interaction energy with most particles, so that even from the point of view that says that a particle is at rest, it already has some energy, or rest mass.
(published on 07/07/2012)
Follow-up on this answer. | <urn:uuid:272582f8-ac26-4cdb-bb9f-40234baf9d33> | 2.90625 | 194 | Q&A Forum | Science & Tech. | 67.213495 |
Science Fair Project Encyclopedia
Saprotroph (also saprobe) is an organism that obtains its nutrients from non-living organic matter, usually dead and decaying plant or animal matter, by absorbing soluble organic compounds.
Saprotrophs cannot make food for themselves, so they are a type of heterotroph. They are useful scavengers, and in sewage farms and refuse dumps break down organic matter into nutrients easily assimilable by green plants.
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:2c36c9e1-b80e-4abd-a11a-10c0cb99ed08> | 3.109375 | 124 | Knowledge Article | Science & Tech. | 30.733333 |
July 25, 2011
The super-heated gas emits X-ray and ultraviolet radiation; Earth’s upper atmosphere absorbs it, which changes our atmosphere’s properties. This can disrupt communication, navigation, and surveillance systems, and also alter the orbits of satellites.
X-ray and ultraviolet radiation, energetic particles, and magnetized plasma clouds from a solar flare or a coronal mass ejection can cause electrical grid blackouts, disrupt navigation systems, and even disable spacecraft components. Solar Dynamics Observatory
CMEs directed toward Earth cause geomagnetic storms, which can wreak havoc on electrical power grids and produce widespread blackouts.
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Dan VandenAkker & Ross Norman
Summer Research 2006
Download the printer friendly Word Document version of this page.
All the experiments on this page involved a radio-frequency oscillator circuit adapted from "Alkali Metal Vapor Spectral Lamps," W.E. Bell, A.L. Bloom, & J. Lynch, Rev. Sci. Instr. Vol. 32, pg 688 (1961). The diagram used to construct the cell is below.
Diagram of RF Circuit
Initial Experiment: create plasma in an enclosed tube of krypton gas.
This experiment involved the plasma discharge cell circuit discussed above, a 400V power supply, a bath of Liquid Nitrogen (LN2), and a glass tube of krypton gas. The power supply was connected to the plasma discharge cell circuit. The coils from the circuit were wrapped around the tube of krypton. The power supply was turned on, the lights were turned down, and the tube of krypton with the coils still wrapped around it was cooled in the LN2 bath. The LN2 bath caused the temperature inside the tube of krypton to drop significantly. Since temperature and pressure are directly related, the pressure also decreased dramatically. Once the pressure was low enough, the electric field generated in the coils caused the ignition of the plasma discharge. As the tube was slowly removed from the LN2 bath and the pressure slowly increased, the large cloud of plasma that had formed between the coils turned into a large ball-like mass of plasma centered between the coils. Larger coil separations would permit multiple large masses all equally spaced between the coils. As the pressure increased, the plasma balls tended to decrease in size and increase in number, appearing to move along the direction of the local electric field. This behavior continued until there were multiple strings of very small plasma masses, each resembling a string of pearls and traveling along the convection currents inside the tube. At some point as the pressure continued to increase, strings of pearls would whip around like "jump ropes" and branch out into the shape of a "pitchfork." More detailed discussion of this behavior can be found at University of Miami's Nonlinear Dynamics Laboratory website. We observed that multiple plasma strings began to repel each other and form periodic patterns around the interior of the glass tube. This additional pattern-formation behavior is closely related to the dielectric barrier discharge research published previously by our group. Below are videos featuring the behavior we observed.
|Examples with small (above), medium (above right), and large (right) coil separations. (Double click on each picture to view video.)|
Second Experiment: recreate the striations found in the initial experiment in a pressure controlled system
This experiment involved the plasma discharge cell circuit discussed above, the same 400V power supply, a pressurized supply of krypton gas, a gas regulator, a pump, a baratron pressure gauge, and additional vacuum parts. We used an old champagne bottle for our gas cell. Below is a photo diagramming the final setup.
Diagram of Vacuum Setup
With this setup, we were able to control the pressure inside the tube by adjusting inlet and outlet valves. Unfortunately, the vacuum setup didn't seem to be perfectly clean, and we therefore didn't have the purest krypton possible. By pouring LN2 into the "kick" of the inverted champagne bottle we were able to freeze some impurities, effectively forming a temporary getter in the vessel. We were able to produce the central mass of plasma as well as smaller plasma balls while monitoring the gas pressure. However, we were unable to reproduce the string-of-pearls striations that we found most interesting in the sealed cell.
Third Experiment: determine the plasma intensity's dependence upon pressure and the plasma ball diameter's dependence upon pressure.
This experiment involved the same setup as the second experiment. However, we also used a video camera with which we zoomed in tight on the region of the champagne bottle where the plasma was created, as well as on the pressure gauge. From each video recording we grabbed frames and analyzed them with Scion Image software. By tracing a line over one plasma ball in Scion Image, we could obtain a graph of optical intensity versus pixel number. This graph could be analyzed for intensity and diameter.
Screen Snapshot of frame analysis with Scion Image software
Scion Image plot with measurements qualitatively described
Excel graphs of our measurements
The the relatively large uncertainties in these measurements are reflected in the vertical scatter of the graphs. The only thing that is sytematically verifiable is that the size of the plasma balls generally decreases as the pressure increases. It may be easier to see this in the videos taken than in the graphs. Below are some of the frames that were pulled from the video footage.
Four images of plasma masses at various pressures between two and eight torr, as measured by a baratron gauge. | <urn:uuid:20b1a37f-ec1a-423a-af83-cc337809c22b> | 3.625 | 1,013 | Academic Writing | Science & Tech. | 41.318554 |
will anybody be able to help me!:) :(
im trying to write a java program really simply using edit plus using things such as println,joptionpane etc to try and do:
Using appropriate techniques design implement and test a simple program that accepts a measurement in stone and pounds from the user, and outputs the measurement in metric.
You should ensure the smooth running of your program through effective use of error checking.
For this assignment you will also need to use the conversion factor between metric and imperial:
1 pound = 0.45359237 kilograms
1 stone = 14 pounds
The imperial input must be accepted in the form stone.pounds, e.g. 14 stone 3 pounds is 14.03.
Help anybody please!!:) | <urn:uuid:8d25d089-50f5-4d4a-a8f4-dea60c7a3aef> | 2.875 | 155 | Q&A Forum | Software Dev. | 67.452273 |
IN THE near vacuum of interstellar space, temperatures hover just above absolute zero, where even the wobbling of atoms grinds to a halt. Dotting this empty, frigid world are huge globs of gas and dust grains, so numerous they block out nearly all light. And outside the shelter of these interstellar clouds, bombarding cosmic and ultraviolet rays slash most molecules to shreds.
Millions of light years away, under the sunshine and palm trees of Mountain View, California, in a lab tucked away in the grounds of NASA's Ames Research Center, Lou Allamandola and his colleagues have been recreating that world of extremes. And in doing so, they have uncovered tantalising hints that life may have emerged not from some warm primordial slime on Earth, but on a dust grain in the icy heart of space.
It's long been suspected that comets made the Earth habitable by delivering water and gases, ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:156b416d-c915-4854-bd3f-e88f78307eae> | 4.0625 | 214 | Truncated | Science & Tech. | 49.196767 |
Mechanics: Momentum and Collisions
Momentum and Collisions: Audio Guided Solution
A 92-kg fullback moving south with a speed of 5.8 m/s is tackled by a 110-kg lineman running west with a speed of 3.6 m/s. Assuming momentum conservation, determine the speed and direction of the two players immediately after the tackle.
Audio Guided Solution
Click to show or hide the answer!
3.3 m/s, 53° S of W
Habits of an Effective Problem Solver
- Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
- Identify the known and unknown quantities in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., m = 1.50 kg, vi = 2.68 m/s, F = 4.98 N, t = 0.133 s, vf = ???.
- Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
- Identify the appropriate formula(s) to use.
- Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.
Read About It!
Get more information on the topic of Momentum and Collisions at The Physics Classroom Tutorial.
Return to Problem Set
Return to Overview | <urn:uuid:5deab528-0ffe-4fbe-9d88-da0aab6daced> | 3.84375 | 300 | Tutorial | Science & Tech. | 66.579544 |
A mind-boggling quantity of information is being presented at the Lunar and Planetary Science Conference. In my first report from the meeting, I try to make sense of the Curiosity and Opportunity sessions.
As February turned to March, Opportunity was conducting some of its final science investigations on Matijevic Hill, the MER team was making preparations for the robot field geologist's trek south for the next winter, and the Mars Exploration Rovers mission was checking off another month of exploration.
Posted by Mat Kaplan on 2013/02/20 07:59 CST
Professor Bell's topic is "Exploring Mars, the Moon, Asteroids, and Comets with Rovers and Landers," and there is no one better to talk about this subject.
With its robot nose to the Martian grindstone, Opportunity completed its ninth year of working on Mars in January, making another significant science discovery in tiny white veins on Matijevic Hill as the Mars Exploration Rover (MER) mission rolled on into Year 10.
Despite the lull of the holidays, the Mars Exploration Rover (MER) mission recorded one of the expedition's best months ever in December as Opportunity and her team confirmed the location of the smectite clay minerals on Matijevic Hill, effectively grabbing the scientific brass ring they came hoping to find at Endeavour Crater. | <urn:uuid:7bac7c0a-c203-4a64-9d20-f19db8ac2a87> | 2.765625 | 272 | Personal Blog | Science & Tech. | 25.378333 |
Pinyon Jay (Gymnorhinus cyanocephalus)
Associated Species: Other species that may use habitats in a similar way and/or respond similarly
to threats, management, and conservation activities include Ash-throated Flycatcher, Juniper
Titmouse, and Bewick's Wren.
Distribution: Pinyon Jays range the semiarid lands of the West. The Colorado Breeding Bird
Atlas map shows them south of a diagonal line drawn from the northwest corner to the southeast
corner of the state (Kingery 1998).
Habitat Requirements: Pinyon Jays are pinyon and juniper obligates in Colorado and over most
of their range. They nest commonly at the lower elevations of pinyon-juniper woodlands, often
where junipers dominate. A few nest in ponderosa pine. They prefer extensive stands far from
high human activity.
Ecology: For these year-round residents, courtship and nesting begins in the winter. Everything
is a group activity. Colonies consist of several dozen pairs, usually with one nest per tree, but
sometimes with up to three. They build deep, bulky nests of twigs and shredded bark in the
bottom half of the tree canopy, often on the south sides of trees. The colony ranges up to 13 km
(8 mi) to find food for the nestlings. This communal species seems relatively safer from predation
and more vulnerable to human intrusion than most other pinyon-juniper species. Common Ravens
may be the primary nestling predators. Pinyon Jays eat many foods, but pinyon nuts and juniper
cones are their staples. Their harvest and storage system allows the use of these foods well
beyond the season of ripeness. They typically locate caches on the south sides of trees, where the
snow melts the soonest (Balda and Bateman 1971).
Management Issues and Conservation Recommendations: Older pinyon and juniper trees
produce the majority of the cones and berries. Manage for large and old age-class trees for high
pinyon nut and juniper berry production.
Pinyon Jays are secretive during the nesting season and will not nest near human activity.
Consider this jay's nesting sites to be road density sensitive.
Status and Reasons for Concern: Pinyon Jays are indicators of healthy pinyon-juniper
woodlands. The Colorado Plateau has high area responsibility for Pinyon Jay, with more than
20% of its range falling within the physiographic area, and the species has a high overall priority
ranking. Partners in Flight in the Intermountain West states uniformly consider it a priority
species. The BBS results for 1969-1996 for Physiographic Area 87 do not show a statistically
significant annual rate of change (P = 0.58, n = 45 routes). Pinyon Jays were present on an
average of 47.84 (SE = 4.97) of the BBS routes run in Physiographic Area 87 in Colorado during
1988-1997, at an average abundance of 9.54 (SE = 2.15) individuals per route. The mean
number of routes run each year was 11.4 (SE = 1.55). This species is monitored by MCB with
Biological Objective: Maintain or increase the species' distribution and abundance, based upon
results of the BBS and MCB monitoring programs. To do this, a target is set to maintain an
average of at least one occurrence per 75 points or at least five birds per 100 points on all MCB
pinyon-juniper woodland transects where they have ever occurred.
Selected References: Andrews and Righter 1992, Balda and Bateman 1971, Kingery 1998. | <urn:uuid:faee4622-7b12-4036-b1fa-7891b1bda940> | 3.375 | 800 | Knowledge Article | Science & Tech. | 49.925993 |
- Remove any labels from the bottle and fill it all the way to the top with water.
- Add a ketchup pack to the bottle.
- If the ketchup floats, you're all set - go to step 4. If the ketchup sinks in the bottle, go to step 5.
- For the floating ketchup pack simply screw the cap on the bottle and squeeze the sides of the bottle hard. If the ketchup sinks when you squeeze it, and floats when you release it, congratulations, you're ready to show it off. If it does not sink when you squeeze it, try a different kind of ketchup pack or try a mustard or soy sauce pack.
- If the ketchup pack sinks, add about 3 tablespoons (45 ml) of salt to the bottle. Cap it and shake it up until the salt dissolves. (Kosher salt will keep the water from getting too cloudy, although it will usually clear up over time if using regular table salt.)
- Continue adding salt, a few tablespoons at a time until the ketchup is just barely floating to the top of the bottle.
- Once it is consistently floating, make sure the bottle is filled to the top with water, and then cap it tightly.
- Now squeeze the bottle. The magic ketchup should sink when you squeeze the bottle and float up when you release it. With some practice you can get it to stop in the middle of the bottle.
This experiment is all about buoyancy and density. Buoyancy describes whether objects float or sink. This usually describes how things float in liquids, but it can also describe how things float or sink in and various gasses.
Density deals with the amount of mass an object has. Adding salt to the water adjusted the water's density to get the ketchup to float. Sound complicated? It is, but here's the basics on the ketchup demo...there is a little bubble inside of the ketchup packet. As we know bubbles float, and the bubble in the ketchup sometimes keeps the heavy packet from sinking. When you squeeze the bottle hard enough, you put pressure on the packet. That causes the bubble to get smaller and the entire packet to become MORE DENSE than the water around it and the packet sinks. When you release the pressure, the bubble expands, making the packet less dense (and more buoyant) and, alas, it floats back up. This demonstration is sometimes known as a CARTESIAN DIVER.
The project above is a DEMONSTRATION. To make it a true experiment, you can try to answer these questions:
1. Do different food packs (ketchup, mustard, soy sauce) have the same density?
2. Does the temperature of the water affect the density of the ketchup packet?
3. Does the size of the bottle affect how much you have to squeeze to get the packet to sink? | <urn:uuid:30a9dbd6-e65d-44a1-8872-05bb64fdc420> | 2.953125 | 598 | Tutorial | Science & Tech. | 71.122005 |
|Global Warming and Land Ice|
Over the past century, sea level has slowly been rising. This is in part due to the addition of water to the oceans through either the melting of or the "calving" off of icebergs from the world's land ice. Many individual mountain glaciers and ice caps are known to have been retreating, contributing to the rising sea levels. It is uncertain, however, whether the world's two major ice sheets-Greenland and Antarctica-have been growing or diminishing. This is of particular importance because of the huge size of these ice sheets, with their great potential for changing sea level. Together, Greenland and Antarctica contain about 75% of the world's fresh water, enough to raise sea level by over 75 meters, if all the ice were returned to the oceans. Measurements of ice elevations are now being made by satellite radar altimeters for a portion of the polar ice sheets, and in the future they will be made by a laser altimeter as part of NASA's Earth Observing System (EOS). The laser altimeter will provide more accurate measurements over a wider area.
The Greenland ice sheet is warmer than the Antarctic ice sheet and as a result, global warming could produce serious melting on Greenland while having less effect in the Antarctic. In the Antarctic, temperatures are far enough below freezing that even with some global warming, temperatures could remain sufficiently cold to prevent extensive surface melting.
Where ice sheets extend outward to the ocean, the ice tends to move out over the surrounding water, forming "ice shelves." There is concern that, with global warming, the water under the ice shelves would be warmer and cause them to break up more readily, forming very large icebergs. If the ice shelves of West Antarctica were to break up, this would release more inland ice in an irreversible process, possibly leading to sea level rises of several meters.
Global Warming Detection and Sea Ice
We need to continue to monitor the location and extent of sea ice and its changes seasonally and interannually. We also need additional studies to determine ice thicknesses and reflectivities. This kind of information can be fed into climate models to attempt to simulate future climate conditions. The same information will also serve as a check on models to see if they are properly simulating existing sea-ice amounts and distributions.
back: Polar Ice | <urn:uuid:68d9a9fc-c0bf-4e73-bbfc-f0f51eec5f6f> | 4.40625 | 476 | Knowledge Article | Science & Tech. | 34.245012 |
The full text of this article is available by subscription only.
Irving P. Krick, one of the first WIDELY-KNOWN commercial meteorologists in the United States, cut a controversial swath across the meteorological field during the middle of the twentieth century and, in so doing, earned both avid fans and fervent critics around the world. Krick’s most ardent supporters point to a number of accomplishments he made over the years, including helping provide weather forecasts for the invasions of Normandy and North Africa during World War II and becoming one of the first proponents of cloud-seeding technology. But many established meteorologists questioned the techniques that Krick used to arrive at his forecasts. Meanwhile, the commercial meteorological activities that grew out of his forecasting techniques after the war aroused the profound ire of the National Weather Bureau when he claimed that he could call the weather far better than its forecasters could. | <urn:uuid:aff974f4-b336-4737-a1a3-3079b6db88d7> | 3.015625 | 184 | Truncated | Science & Tech. | 29.999559 |
Acid rain damages buildings like this one in Copola, Mexico.
Click on image for full size
Have you ever heard of acid rain? Acid rain is what happens when some types of air pollution is washed out of the sky by rain. Sometimes, the pollution can be washed out by snow, sleet, hail, mist or fog, but it is still called acid rain.
Power plants, factories, houses and cars all put pollution into the atmosphere. Sometimes these chemicals return directly to the ground. The rest of the time, they mix with water in the air to form acids. Once the acids form, they can be carried a long way by the wind before being washed out of the air by rain, snow or hail. That is why we call it acid rain.
During the 1970s, scientists in Sweden and Norway noticed that acid rain was hurting their trees and fresh water. Most of the acid rain was caused by pollution that came from other countries. After that, scientists knew that acid rain was an international problem.
Acid rain can have harmful impacts on ecosystems. It makes the soil and water where it falls more acidic. This can hurt or kill plants and animals. Making water more acidic can lead to smaller fish populations. Other species that live in the water are also hurt, like frogs, snails and crayfish. Acid rain affects trees, making them weaker by damaging their leaves. Some types of stone, such as limestone and marble, can be slowly dissolved in acid rain. This can damage buildings and statues.
Shop Windows to the Universe Science Store!Cool It!
is the new card game from the Union of Concerned Scientists that teaches kids about the choices we have when it comes to climate change—and how policy and technology decisions made today will matter. Cool It! is available in our online store
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Nitric acid is a very strong kind of acid. If you got some on your skin, it would burn you! Nitric acid has nitrogen, oxygen, and hydrogen atoms in it. Earth's atmosphere has a very, very tiny bit of nitric...more
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Ammonia is a kind of gas. Ammonia molecules (NH3) have hydrogen and nitrogen atoms in them. The air you breathe has a tiny bit of ammonia in it. When plants and animals die and decay, they give off ammonia....more | <urn:uuid:9c605566-3839-4eb3-916b-03a55f687d5b> | 3.5 | 717 | Knowledge Article | Science & Tech. | 67.698974 |
January 29, 2007
From Original Article By
Earlier this month, amateur fisherman Haruo Kanbe stared out at sea in horror — a monster fish was swimming directly towards him. At first glance the creature snaking through the water looked like a giant eel. The cloudy eyes were especially striking. Triangular teeth flashed inside its open maw.
Normally, the prehistoric creatures dwell between 600 and 1,200 meters (between 1,969 and 3,937 feet) below the ocean surface. Until now, few people have had the opportunity to come face to face with a living specimen.
The frilled shark has hardly changed for 95 million years. That’s why it’s considered a “living fossil.” Unlike other types of shark that evolved later, the frilled shark has six gills on each side instead of five. The first pair of gills is coadunate with the underside of the neck; the protruding tissue gives the shark its name.
One of the creature’s most striking features is that both its upper and its lower jaw are equipped with fork-like, equi-sized teeth.The creature from the depths is one of the rarest fish in the world. Specimens occasionally show up in the Pacific, Indian and Atlantic oceans. They feature on the Red List of Threatened Species compiled annually by the International Union for Conservation of Nature and Natural Resources (IUCN).
Visit the Japanese Marine Park’s website to read the original press release and see more photos. | <urn:uuid:af97642e-d6fc-4293-93e0-366b0b0a4900> | 3.84375 | 315 | Truncated | Science & Tech. | 53.022694 |
That first bullet is the reason that adding the space reads your new line from the buffer.
A directive is one of the following:
A sequence of white-space characters (space, tab, newline, etc.; see isspace(3)). This directive matches any amount of white space, including none, in the input.
• An ordinary character (i.e., one other than white space or '%'). This character must exactly match the next character of input.
Matches a sequence of characters whose length is specified by the maximum field width (default 1); the next pointer must be a pointer to char, and there must be enough room for all the characters (no terminating null byte is added). The usual skip of leading white space is suppressed. To skip white space first, use an explicit space in the format. | <urn:uuid:da6ee8cb-d70c-4ed0-99b0-c64ef2cae2c8> | 3.171875 | 169 | Documentation | Software Dev. | 56.531148 |
Conditions of Use
The sun is a very important energy source.
It gives heat and light to Earth. Plants need light to grow. Light acts with water and carbon dioxide in a plant to make its food.
People use the sun's energy to make electricity. Special solar panels are used to convert (change) the sun's energy into electricity. Some examples are solar calculators and solar powered torches.
What do you think of this information report Room 3? Thanks for helping me edit the spelling and punctuation.
Article posted June 12, 2007 at 03:01 PM •
comment (6) • Reads 559
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Did you also know
that the sun is the most hotteset source in the universe?
Comment Posted on September 9, 2008 at 08:27 PM by
your the smallest and the best writer of all.
Comment Posted on July 18, 2007 at 04:17 PM by
the sun is very important.
Comment Posted on July 18, 2007 at 04:16 PM by
Comment Posted on July 17, 2007 at 04:16 PM by
grat effort keepit up monty.
Comment Posted on June 14, 2007 at 06:45 PM by
About the Blogger
I am the smallest member of the Livewires class. I like cheese, watching the Livewires learn and playing with Marty. | <urn:uuid:67fcce3d-3ca7-4d3e-bddb-9db205ec46d7> | 2.78125 | 290 | Comment Section | Science & Tech. | 78.122879 |
Monday, September 24, 2012 - 18:30 in Astronomy & Space
NASA's rover Curiosity touched a Martian rock with its robotic arm for the first time on Sept. 22, assessing what chemical elements are in the rock called "Jake Matijevic."
- Curiosity on Mars sits on rocks similar to those found in marshes in MexicoTue, 30 Oct 2012, 11:07:11 EDT
- How Martian winds make rocks walkThu, 8 Jan 2009, 14:01:08 EST
- MIT moves toward greener chemistryFri, 3 Sep 2010, 12:51:40 EDT
- Martian rock arrangement not alien handiworkWed, 7 Jan 2009, 13:17:55 EST
- ASU instrument on NASA rover helps identify outcrop of long-sought rare rock on MarsThu, 3 Jun 2010, 14:52:54 EDT | <urn:uuid:f52b34ac-b5ad-4f7c-a68e-cc1aab599e79> | 3.46875 | 177 | Content Listing | Science & Tech. | 35.955 |
One of the first topics we covered in astrogeology is impact craters. They are characterized by circular or ellipitical depressions in a planetary body and sometimes contain central peaks. The shape is a function of the angle at which the impactor hits the body and the central peak is a product of isostatic rebound. The more shallow the angle at which the impactor hits, the more oblique the crater. The central peak forms as the crust in the center “springs” to a higher elevation after the impact. The debris that gets kicked up during this process surrounds the crater and becomes the ejecta blanket.
What’s interesting is that impact craters follow nearly the same pattern throughout the solar system. From Venus to the Moon, and Mercury, they all look fairly similar. | <urn:uuid:931af8ed-f369-4a08-a899-3e47310cb7c1> | 3.90625 | 166 | Personal Blog | Science & Tech. | 48.446591 |
Ever hear the terms "fat," "protein," and "carbohydrate"? That's because of William Prout. Born in 1785, he was the first person in history to figure out the basic components of foodstuffs. A brilliant chemist, he's still best known for having one of the nearest misses in all of science. Probably he shouldn't have named the one wrong hypothesis of his career after himself.
Prout had an interest in food from the moment it was swallowed until well after it had left the body. He was the first to prepare pure urea. He discovered that the stomach juices contained hydrochloric acid. He found out that the feces of a boa constrictor contained a massive amount of uric acid, and kept a boa on hand from then on to harvest a steady supply of the acid for his studies.
You could say that Proud was fascinated by the basic components of almost everything, including all the interesting new elements that were popping up during his lifetime. After going over the results of the many scientists who had managed to find the weights of various elements, Prout noticed something very strange. All of the weights of the elements seemed to be multiples of one particular number. That number was the weight of hydrogen. Prout's Hypothesis was this - that all elements had weights that were multiples of the weight of a hydrogen atom, and therefore a hydrogen atom was the basic building block of the universe.
And that is so close to right. Although each atom is - save for the negligible mass of the electron - an approximate multiple of the weight of a hydrogen atom, the neutron ruined it for Prout. His idea was so close to right, though, that it spurred a massive scientific drive in the right direction. There was a stampede of scientists rushing out to ever-more-correctly weigh the various elements to see if Prout's Hypothesis was correct. When they found that certain elements seemed to break hydrogen's mass into fractions, they began to modify the hypothesis rather than refute it. For example, it was thought that perhaps the basic building block of the universe was a quarter of a hydrogen atom. It was only later that scientists discovered that many elements have different isotopes, the different neutrons of each skewing the measurements of large quantities of the atoms.
The hypothesis remained useful for the next hundred years, and was on Ernest Rutherford's mind when he set about separating hydrogen nuclei from the larger nuclei of other elements. Overall, Prout's idea shows how science works - one idea leading to another, each increasing in accuracy. It's nice to know that being wrong can lead to so much rightness. (I think, though, that both Prout and anyone else would have preferred being right in the first place.)
Illustration by Aleksey Klints via Shutterstock | <urn:uuid:74accdf7-c1e0-48e1-9fec-eb449cced802> | 3.46875 | 578 | Nonfiction Writing | Science & Tech. | 51.348396 |
Pub. date: 2008 | Online Pub. Date: November 27, 2007 | DOI: 10.4135/9781412953948 | Print ISBN: 9781412928168 | Online ISBN: 9781412953948| Publisher:SAGE Publications, Inc.About this encyclopedia
Central Limit Theorem
A series of theorems in mathematical statistics called the central limit theorems provide theoretical justification for approximating the true sampling distribution of many sample statistics with the normal distribution. This entry discusses one such theorem for the sample mean. Similar theorems exist for sample median, sample standard deviation, and sample proportion. The word central in the name of the theorem means ‘fundamental.’ The central limit theorem for the sample mean states that for a large sample size, the sampling distribution of the sample mean X is approximately normal, no matter what the population distribution looks like. The approximation becomes better with increasing sample size. This surprising fact was proved in fairly general form in 1810 by Pierre-Simon Laplace. The graphs in Figures 1 through 5 show the idea of the Central Limit Theorem. Figure 1 is a histogram of a random sample data from a normally distributed Figure ... | <urn:uuid:97deb6b8-11cf-4ded-9974-5f448493dfec> | 3.796875 | 245 | Truncated | Science & Tech. | 44.126288 |
From Latin: rectus "right" + angle
Drag the orange dots on each vertex
to reshape the rectangle.
The rectangle, like the
is one of the most commonly known
quadrilaterals. It is defined as having all four interior angles 90°
Properties of a rectangle
- Opposite sides are
Adjust the rectangle above and satisfy yourself that this is so.
- The diagonals
bisect each other
- The diagonals are
Other ways to think about rectangles
A rectangle can be thought about in other ways:
is a special case of a rectangle where all four sides are the same length.
Adjust the rectangle above to create a square.
- It is also a special case of a
but with extra limitation that the angles are fixed at 90°.
See Parallelogram definition and adjust the parallelogram to create a rectangle.
a rectangle has all the same properties described here, but also, the coordinates of its vertices (corners)
are known. See Rectangle (Coordinate Geometry) for more.
Other rectangle pages:
Area of a rectangle
Perimeter of a rectangle
Rectangle (Coordinate Geometry)
Related polygon topics
Types of polygon
Area of various polygon types
Perimeter of various polygon types
Angles associated with polygons
(C) 2009 Copyright Math Open Reference. All rights reserved | <urn:uuid:c85111a5-288b-4c5c-accb-369825667bc8> | 4 | 297 | Knowledge Article | Science & Tech. | 29.602 |
I. Analog location: The Davis Mountains in
Reasons for: Our location in Houston
is too tropical to be considered as an analog location. Even on our
school grounds, we have too many buildings, plants, trees and people
for it to be like the Moon. We wanted something more similar to the
Moon’s environment. In the Davis Mountains there are remote areas
that make you feel like you are on the Moon. This mountain range was
formed by very heavy volcanic activity during the Cenozoic Era. Volcanoes
here erupted for 10 million years! There is igneous rock here that
reminds us of the basalt you can find on the Moon. But this area would
be a good, isolated environment with little traffic if you travel far
into the mountains.
The weather can be very cold or hot, similar to the Moon. Also, cell
phones may not work, so computers and ham radios may be the way to
communicate, just like when you are on the Moon trying to talk to someone
Reasons Against: Although the mountains are volcanic
and give some desolate places to build a good research station, it
is surrounded on the low lands by vegetation, which is not found on
Spin-off Activity: Our class will participate in
a remote communication exercise, using walkie-talkies. Two teams will
exchange information from different locations: one team will give directions
for building a machine using Legos, while the other team builds it
based on their instructions. The purpose will be to demonstrate what
it might be like to assemble a project in a remote research station
with only radio communication. (Thanks for the idea Mr. Allner!)
II. Research Station: Our research station is built
inside of the actual module that travels to the Moon. It will be able
to land at the site picked, and the astronauts and research team will
work right in the same place they traveled in. After the work is done,
they will be able to take off from the Moon. This will keep the cost
of building a separate research station on the Moon down. It will also
keep the research safe in case of emergency. Our idea is to have the
module land inside of a crater to help protect it from the radiation,
dust, and meteors. In the Davis Mts. the station could be built in
Our finished model is shown built inside of a meteor
crater on the Moon, with half of the terrain showing the backdrop of
the Davis Mts. As you can see, the rocket ship itself (center) houses
the research station. We have included a floor plan and outpost layout.
While we were building the model, many ideas came to us about how
to build so much into such a small space, and changes that needed to
- Building counters or work stations so that they slide into the
- Building sleeping cots that fold up and lock into place when not
- Building a ladder to get between floors (on Earth) that folds up
like a mini-blind.
- We changed the shape of the conference table from a rectangle to
a circle to make more room. It also collapses into the floor, and
is raised only when needed.
- All storage bins and compartments are built into the walls.
- We added an in-situ re-cycling center for water and oxygen inside
the research station, and also a bioregenerative system that would
create an ecosystem between humans, plants, and machines, and would
provide food for eating. Wheat and other plants that would grow well
and produce food sources would be best. Also, we would grow these
plants in recycled water instead of soil. Our light source would
be LED lighting made by solar energy caught by solar panels.
- An instrument panel for flying the spacecraft would be in the communications/computer
station. This area also has a large observation window and several
computer screens where cameras could monitor the surroundings.
- A communication satellite would orbit the Moon and observe conditions
on the surface.
- We added a fan/vacuum system and showers into the airlock area
where returning EVA astronauts could get rid of the Moon dust, etc.
- New spacesuits were designed to be thinner (not as bulky),
yet protective enough for the safety of the astronauts. One of
our pictures shows the different layers of the suit, another
show the “look” of
the future! A Geology EVA suit complete with lasers(for cutting
into rock), form-fiting gloves for easier hand control, and seismic
sensors to detect moonquakes.
- An emergency protective shield area was designed on the top floor
of the research station. It encloses the area with the kitchen, and
quiet space (with books, music, etc) so that astronauts can be protected
for long periods of time from radiation issues, like solar storms,
and still have some things to do while they wait. The window in that
area and the door will have radiation shields that will come down
with the touch of a panic button.
- For astronauts outside, an emergency tunnel located through the
crater wall can give protection from solar events, meteor showers,
etc. It will contain emergency supplies.
- Exercise equipment for cardio-workouts and maintaining muscle strength-bicycles,
treadmills, and resistance machines (can use Elastic bands). A first
aid station with defibrillators will be included.
- Machines were designed from Legos for drilling, and prospecting
for water and minerals. We also have a short range lunar vehicle
(moon buggy) and built a shed for storing them. It is our idea that
future machines on the Moon will have to be made of very lightweight
materials that can be easily assembled (like working with Legos),
yet durable and strong for the Moons terrain. Robotics will be very
- Our machines and robots include: A Walking construction machine.
It “walks” by lifting its “legs” alternately.
This will make it easier to walk over rocks, soil, and other
materials that might stick to wheels. Two ideas for robots include
using them with motorized or pneumatic claws for lifting and
carrying specimens, or attaching drills and other tools. One
can also be used for search and scouting.
- All of the buildings on our Lunar outpost would be permanent, except
for the research station/spaceship.
- The spaceship will have to be big enough to have the research station
in it, yet lightweight enough so that fuel costs can be kept down.
- Materials for this spaceship construction and for the outpost still
have not been decided on.
- Power for the outpost would be a combination of large solar arrays
and back-up batteries.
- For this reason, our crater location on the Moon needs to be in
an area where sunlight is available. Our suggestion is the Northern
part of Mare Imbrium. This location has flat areas suitable for landing
and building on, and also craters for protection It will also give
us sunlight, access to polar icecaps (for water), and some night
time to keep our biorhythms as regular as possible.
Thanks for reading about our plans! | <urn:uuid:f2eee659-b45a-4aac-ad05-0f30909e960b> | 3.78125 | 1,540 | Tutorial | Science & Tech. | 53.046618 |
A 10,000 Pound Elephant Can Be Restrained by a Puny Rope. (Pssst, Your Development Team Can Be Too.)
Elephants can easily grow in excess of 5 tons each, tearing through trees, brush, and even houses if they get in their way. These lumbering giants are roamers by nature, and typically care very little about what obstacles are in their way, as most obstacles they find in their environment are no match for their own gigantic size. Keeping an animal like this in captivity can be quite a challenge. Perhaps a zoo that has the proper facilities and staff can keep these gentle giants confined, but when an elephant is born to a poor farmer on the plains of Africa, the challenge would seem to be much greater to do the same. But in reality, it is actually quite easy.
When an elephant is born in captivity in Africa (and I am using the word ‘captivity’ very loosely here, as there are no pens, no cages, and no fences on the majority of these properties), the owner of the newborn elephant ties the animal to a tree or post with a strong chain, thus preventing the creature from escaping. As the elephant grows during the first few weeks, the chain that binds him is continually tested by the elephant in his attempts to free himself, but as a baby, his efforts are just no match for the chain. As the elephant continues to grow, his attempts to break free of his confinement become less and less frequent as he learns that his might and muscle are no match for the hardiness of the restraint, so confined he stays. Soon after, the elephant simply gives up any attempts to free himself, and thus seemingly is relegated to a life of capture, believing that his strength will never provide the effort necessary to overcome his restraints.
As an adult elephant, having been conditioned by his past experience, he can now easily be tethered to a tree with the puniest of ropes while making no attempt to break free. He makes no attempts at freedom because he carries with him for life the belief that he does not possess the strength and power to break the ties that bind him. This elephant could easily uproot the tree that the rope is attached to, or simply snap the puny rope, but no effort to do so is made because early in life, the elephant learned that he was not capable of doing such a thing, even though he has grown to many times the size that he was when he still had made attempts to free himself.
The rope no longer serves the purpose of physically binding the elephant, for it is not strong enough to accomplish that feat if ever tested. No, now the rope simply serves to confine the animal’s mind, reinforcing the mistaken belief that the elephant’s current capabilities are no greater than they were when he was just a fraction of his current size and strength. The puniest of ropes can bind the largest of elephant, simply because the elephant believes that it can.
So what does the fact that gigantic creatures like elephants can be confined by weak restraints have to do with software development teams?
Our belief about our ability as individuals is often seen through the lens of our past experiences. Too often people suffer failure only to take the circumstances of that failure as a definition of the limits of their abilities. We are just like elephants in this regard, making the mistaken assumption that our past experience equals our future potential, or lack thereof. A team’s behavior is no different, and can often be worse, especially in a corporate climate that reinforces our limits through lack of management support in our efforts to try again that which we failed in the past. We learn too quickly that even if we make an effort to break the rope that binds us, when we are unsuccessful we sub-consciously decide to re-write the definition of our abilities, never to test that definition again.
Now, I am not advocating enduring the classic definition of insanity, doing the same thing over and over expecting different results, although it may sound like I am. In this old adage describing the actions of the insane, it implies that circumstances remain the same, which in life, is rarely the case. If the adult elephant were to once again attempt to break free of the rope, it would not fall into the insane category because the circumstances surrounding the scenario of his captivity have changed. And although these circumstances have changed in reality, they have not changed in the mind and belief of the elephant, thus the force truly confining the adult elephant is not the rope at all, but his own limited beliefs. This is sad for the elephant, because the elephant does not have the luxury of making conscious decisions to challenge a defective set of beliefs based on outdated information. But we do.
Often times, the best course forward for individuals or teams is not the most obvious, it is not the easiest, or it is not the most readily apparent. But individuals and teams rarely make concerted efforts to do more than scratch the surface of possibilities directly in front of them to test whether their current actions will produce the best results possible. Or even simply better than the results they have achieved in the past. The lens of our past experiences through which we view our current situations often does very little to encourage innovative thinking, in fact more often than not, it values only using information from past events that lead to successful conclusions, even when innovative thinking is called for.
Take an old Sufi parable (I have changed some minor details to modernize the story a bit)…
A man was walking down the street late one night, only to come across Darren, an old friend of his, on his hands and knees under the corner streetlight, frantically searching for something. Wanting to help his friend, the man asks what he is looking for so diligently, to which Darren replies that he has lost his house keys. The man gets on his hands and knees to join his friend in the search.
After 30 minutes of combined effort, the man finally asks of Darren “we have searched every crevice within 30 feet of this spot, are you sure that you dropped your keys here?”
Darren replies “no, actually I dropped them about a block away.”
“What!? If you dropped your keys a block away, then why have we been wasting our time looking here?”
“Well, the light was better over here…”
Now as crazy as that may sound, the message of the story is much less absurd. This simple parable illustrates something far more common among software development teams, doing what we have known to work in the past without expending any effort to determine if that past approach is appropriate given new circumstances, requirements, and constraints. The lazy approach to our efforts will often yield shades of success, but very rarely yield extraordinary results, results that exceeded our own beliefs about what was possible. And like the elephant, what we believe to be possible is more often a factor of the limitations of our beliefs about what is possible, rather than what is truly possible.
How do Agile teams take these realities into account and use them for their own benefit?
Retrospectives are forums for communication that are held on regular intervals during the project so that the team can discuss and collaborate on their performance as a team over the past iteration. And just like any other tool, Agile or not, your team will only get out what it puts in. Too often, I hear about or see with my own eyes, retrospectives that prove to be a waste of everyone’s time because the team does not challenge themselves to see beyond their past experiences, to see that their ropes no longer have the power to bind them, but rather these teams get in a room, say everything went as good as it could have gone, and then leave. These retrospectives are not the true retrospectives that assist good Agile teams in their effort to be great. These meetings more resemble those of Cargo Cult Agile teams that go through the motions believing that they will yield the same results.
Agile teams recognize that they must truly be proactive. And being proactive is more than just a buzzword, it is more than reacting at an earlier point in time than the last possible moment, it is a decision to create a better possibility for the sake of having a better possibility as opposed to simply fixing something that is broken. And when something is broken, being proactive involves the team seeing how they contribute to their own problems. When individuals and teams only act when forced to by an outside element, their actions, or more appropriately, their reactions lose the power of creation, for they did not choose to create a better team, a better product component, a better customer relationship, they only chose to act in the light of circumstance. And when that circumstance, when that reason, goes away and the fire gets put out, we all go back to doing what we did before never quite drawing the line between what we were doing before and how those actions started the fire we raced to extinguish. We go in circles and wonder why we live this way, how we got here, and then feel hopeless in our efforts to eventually break the cycle.
Agile teams that practice mastery in the area of retrospectives never leave those meetings without identifying areas of effort that may lead to better results than they achieved in the past. These teams recognize that it is never about the destination, it is about the continual journey that defines what we are capable of, and that definition is never static. Unlike the elephant, great Agile teams question the beliefs about past experiences to determine if they still hold value, and when they don’t, these teams quickly rip that tree from its roots and move on to greener pastures. The alternative is allowing ourselves to be bound by a puny rope, believing that it is not within our capabilities to roam free. And sadly, although we have a choice to break the rope, few teams ever make the decision to do so, but rather spend their time and effort discussing just how strong this rope truly is. | <urn:uuid:04c0983b-dca4-4e57-b603-31e028b18408> | 2.734375 | 2,056 | Personal Blog | Software Dev. | 41.754146 |
With the help of Stokes' theorem, Ampère's integral law (1.4.1) can now be stated as
That is, by virtue of (2.5.4), the contour integral in (1.4.1) is replaced by a surface integral. The surface S is fixed in time, so the time derivative in (1) can be taken inside the integral. Because S is also arbitrary, the integrands in (1) must balance.
This is the differential form of Ampère's law. In the last term, which is called the displacement current density, a partial time derivative is used to make it clear that the location (x, y, z) at which the expression is evaluated is held fixed as the time derivative is taken.
In Sec. 1.5, it was seen that the integral forms of Ampère's and Gauss' laws combined to give the integral form of the charge conservation law. Thus, we should expect that the differential forms of these laws would also combine to give the differential charge conservation law. To see this, we need the identity ( x A) = 0 (Problem 2.4.5). Thus, the divergence of (2) gives
Here the time and space derivatives have been interchanged in the last term. By Gauss' differential law, (2.3.1), the time derivative is of the charge density, and so (3) becomes the differential form of charge conservation, (2.3.3). Note that we are taking a differential view of the interrelation between laws that parallels the integral developments of Sec. 1.5.
Finally, Stokes' theorem converts Faraday's integral law (1.6.1) to integrations over S only. It follows that the differential form of Faraday's law is
The differential forms of Maxwell's equations in free space are summarized in Table 2.8.1. | <urn:uuid:a1bab1f0-3be5-47ce-8486-bc6408048ee6> | 3.078125 | 395 | Academic Writing | Science & Tech. | 71.68819 |
Altering the mechanism of a reaction so that the activation energy is lower is the second major way to speed up the reaction. A catalyst can do this by participating in the activated complex for the rate-limiting step, even though the catalyst itself is neither a reactant nor a product in the overall stoichiometric equation.
A good example of catalysis is provided by the effect of I2 on the rate of isomerization of cis-2-butene. You will recall from the section on rate equations that the rate law for the catalyzed reaction involves the concentration of I2 raised to the one-half power. This implies that half a molecule of I2 (that is, an I atom) is involved in the activated complex, which probably has the structure
Since there is no double bond between the two central C atoms, one end of the activated complex can readily twist around the other.
The currently accepted mechanism for this catalyzed reaction involves three steps:
½ I2 I
I + cis-C4H8 → C4H8I‡ → trans-C4H8 + I
I ½ I2
The first and last steps have coefficients of one-half associated with I2 because each I2 molecule that dissociates produces two I atoms, only one of which is needed to help a given cis-2-butene molecule to read. Note also that for every I2 molecule which dissociates in the first step of the mechanism, an I2 molecule is eventually regenerated by the last step. As a result, the concentration of I2 after the reaction remains exactly the same as before.
If we consider the energetics of each step in the proposed mechanism, we find that much less than the 262 kJ mol–1 activation energy of the uncatalyzed reaction is required. A complete energy profile for the catalyzed process is compared with that of the uncatalyzed one in Fig. 1. The bond enthalpy is 151 kJ mol–1 (from Table 1 in the bond enthalpy section), and so 75.5 kJ mol–1 will be required for formation of the I atom in the first step. An additional increase in energy occurs as the I atom collides with cis-2-butene and bonds with it. Then about 12 kJ mol–1 is required for twisting around the C—C single bond in the activated complex. All told 115 kJ mol–1 is required to go from the initial molecules to the activated complex. When rotation to a trans structure is complete, the I atom dissociates fromtrans-2-buten and eventually reacts with another I atom to form I2. These last two processes involve an overall decrease in energy which is nearly the same as the increase required to achieve the activated complex.
The reduction in activation energy illustrated in Fig. 1 is the chief factor in speeding up the catalyzed reaction.
EXAMPLE Based on activation energies given, how many times larger would the rate constant be for the catalyzed rather than for the uncatalyzed isomerization of cis-2-butene at a temperature of 500 K?
Solution The fraction of molecules which have sufficient energy to achieve the activated complex can he calculated using equation 1 from the section on the effect of temperature on catalysis:
- Fraction (catalyzed) = 10–115 kJ mol–1/(2.303 × 8.314 J K–1 mol–1 × 500K) = 10–12.0 = 1 × 10–12
- Fraction (uncatalyzed) = 10–262 kJ mol–1/(2.303 × 8.314 J K–1 mol–1 × 500K) = 10–27.4 = 4 × 10–28
Since the respective rate constants should be proportional to these fractions,
- = = 2.5 × 1015
Thus at unit concentrations of cis-2-butene and iodine, the catalyzed reaction will be more than 1015 times faster.
Another example of catalysis is involved in the reaction between H2O2 and the I– ion. In discussing this reaction in example 2 in the rate equation section we noted that it is first order in H2O2 and first order in I– ion between pH = 3 and pH = 5. At lower pH values, however, a different mechanism takes over, and the rate law becomes
- Rate = k(cH2O2)(cI–)(cH+)
This indicates that the activated complex contains an additional proton when compared with the uncatalyzed case. This proton apparently adds to the H2O2 molecule, forming H3O2+. Because of the positive charge, less energy increase occurs as an I– ion approaches H3O2+ and the reaction
- H3O2+ + I– → H2O + HOI
has a lower activation energy than
- H2O2 + I– → OH– + HOI
The latter is the rate-limiting step in the mechanism at higher pH (Eqs. (1a), (1b), and (1c) in the reaction mechanisms section), and so protonating H2O2 results in a faster overall reaction. Measurements over a range of temperatures show that the activation energy is lowered from 56 to 43.6 kJ mol–1 by this change of mechanism.
The peroxide-iodide reaction is one example of a great many acid-catalyzed reactions. In most of these the hydrogen ion concentration appears in the rate law, indicating that the activated complex contains an extra proton. The positive charge of this proton allows negative ions to combine more readily with the protonated species. The proton may also shift electron density toward itself and away from some other site in the protonated molecule, allowing a negative species to bond to that site more readily. The net result is a lower activation energy and a more rapid reaction. The preceding examples are illustrative of the three main features of catalysis:
1 The catalyst allows the reaction to proceed via an alternative mechanism.
2 The catalyst is directly involved in this mechanism, but for every step in which a catalyst molecule is a reactant, there is another step where the catalyst appears as a product. Thus there is no net consumption of the catalyst.
3 The catalyzed mechanism results in a faster reaction, usually because the overall activation energy is lowered. | <urn:uuid:6550e7bb-d6c8-4a3c-9a43-d96f1df32d7e> | 3.4375 | 1,334 | Knowledge Article | Science & Tech. | 47.911028 |
>> Study Material
>> IIT JEE Chemistry
>> Physical Chemistry
>> Reversible and Irreversible Cells
Reversible and Irreversible cells
REVERSIBLE AND IRREVERSIBLE CELLS
Daniell cell has the emf value 1.09 volt. If an opposing emf exactly equal to 1.09 volt is applied to the cell, the cell reaction,
Zn + Cu2+ --> Cu + Zn2+
stops but if it is increased infinitesimally beyond 1.09 volt, the cell reaction is reversed.
Cu + Zn2+ --> Zn + Cu2+
Such a cell is termed a reversible cell. Thus, the following are the two main conditions of reversibility:
(i) The chemical reaction of the cell stops when an exactly equal opposing emf is applied.
(ii) The chemical reaction of the cell is reversed and the current flows in opposite direction when the opposing emf is slightly greater than that of the cell.
Any other cell which does not obey the above two conditions is termed as irreversible. A cell consisting of zinc and copper electrodes dipped into the solution of sulphuric acid is irreversible. Similarly, the cell
is also irreversible because when the external emf is greater than the emf of the cell, the cell reaction,
Zn + 2H+ --> Zn2+ + H2
is not reversed but the cell reaction becomes
2Ag + 2H+ --> 2Ag+ + H2 | <urn:uuid:7e2d41b2-0001-4ba5-b787-64944520d0e8> | 2.9375 | 313 | Knowledge Article | Science & Tech. | 51.474574 |
Nitrate and phosphate are useful as fertilizers in agriculture and gardening. Nitrate and phosphate aid agricultural production by producing more abundant crops. However, since the mass production of ammonia during the 1940's by way of the Haber process, it has been noted that a phenomenon known as “nitrate pollution” may occur. This pollution can be demonstrated by conducting this simple experiment. This experiment demonstrates two main ideas. The first is a test of what levels of nitrate and phosphate allow for optimum algal growth. The second demonstrates at which levels of nitrate and phosphate algal blooms may occur, causing harm to an aquatic ecosystem (Freeman, 2002).
b. Given three cultures with different concentrations of nitrate and phosphate, students will evaluate the nitrate and phosphate levels at which an increase in algal growth occurs in a closed system.
It is recommended that students have prior knowledge of algae’s ability to carry out photosynthesis. Also, students should be familiar with laboratory safety.
Nitrate: NO3‾, a compound essential to fertilizing plants. It is, however, a common (dangerous) contaminant of groundwater. For more information, see www.nitrate.com/nitrate1.htm
Phosphate: PO43-, a compound necessary for the growth of plants. It is one of the main nutrients found in fertilizers. For more information, see http://en.wikipedia.org/wiki/Phosphate
Algae: Photosynthetic organisms that live in many habitats, ranging from aquatic environments to the hot desert sands. They are an essential organism for the production of oxygen, as well as an important food source. However, too much algae (known as an algal bloom) can have an adverse effect on an ecosystem, causing many problems. For more information, see http://www.nmnh.si.edu/botany/projects/algae/AlgIntro.htm
Chlorella: a unicellular alga found in soil, water, and tree bark. Botanical names are Chlorella pyrenoidosa, Chlorella vulgaris
Print a PDF of this activity
Effect of Nitrate and Phosphate Levels on the Growth of Algae (9 pages) | <urn:uuid:e1407548-fd3a-432b-b54f-f623135381e5> | 3.8125 | 465 | Tutorial | Science & Tech. | 39.807984 |
Radical New Theory: "Our Universe may be the interior of a black hole existing in another universe” (Today's Most Popular)
“Our own Universe may be the interior of a black hole existing in another universe.” In a remarkable paper about the nature of space and the origin of time, Nikodem Poplawski, a physicist at Indiana University, suggests that a small change to the theory of gravity implies that our universe inherited its arrow of time from the black hole in which it was born.
Poplawski says that the idea that black holes are the cosmic mothers of new universes is a natural consequence of a simple new assumption about the nature of spacetime. Poplawski points out that the standard derivation of general relativity takes no account of the intrinsic momentum of spin half particles. However there is another version of the theory, called the Einstein-Cartan-Kibble-Sciama theory of gravity, which does.
This theory predicts that particles with half integer spin should interact, generating a tiny repulsive force called torsion. In ordinary circumstances, torsion is too small to have any effect. But when densities become much higher than those in nuclear matter, it becomes significant. In particular, says Poplawski, torsion prevents the formation of singularities inside a black hole.
Astrophysicists have long known that our universe is so big that it could not have reached its current size given the rate of expansion we see now. Instead, they believe it grew by many orders of magnitude in a fraction of a second after the Big Bang, the period known as known as inflation.
Poplawski's approach immediately solves the inflation problem, saying that torsion caused this rapid inflation, which means the universe as we see it today can be explained by a single theory of gravity without any additional assumptions about inflation.
Another important corollary of Poplawski's approach is that it makes it possible for universes to be born inside the event horizons of certain kinds of black hole where torsion prevents the formation of a singularity but allows energy density to build up, which leads to the creation of particles on a massive scale via pair production followed by the expansion of the new universe. "Such an expansion is not visible for observers outside the black hole, for whom the horizon's formation and all subsequent processes occur after infinite time," says Poplawski. For this reason, he emphasizes, the new universe is a separate branch of space time and evolves accordingly.
Poplawski's theory also suggests an solution lto why time seems to flow in one direction but not in the other, even though the laws of physics are time symmetric.
Poplawski says the origin of the arrow of time comes from the asymmetry of the flow of matter into the black hole from the mother universe. "The arrow of cosmic time of a universe inside a black hole would then be fixed by the time-asymmetric collapse of matter through the event horizon," he says.. Translated, this means that our universe inherited its arrow of time from its source. "Daughter universes," he says, "may inherit other properties from their mothers," implying that it may be possible to detect these properties, providing an experimental falsifiable proof of his idea.
Casey Kazan via Ref: arxiv.org/abs/1007.0587: Cosmology With Torsion - An Alternative To Cosmic Inflation | <urn:uuid:032e4607-905b-4271-b23d-0e56c3d40663> | 3.171875 | 705 | Personal Blog | Science & Tech. | 30.144099 |
Move the points by dragging them. Reload the page to restore the initial configuration.
There are many proofs known, but one of the most attractive is due to the nineteenth century Belgian mathematician Germinal Dandelin. It has the virtue of being perhaps the most geometric in flavour. This proof has much in common with the best known proof of Desargues' Theorem, in that it can be interpreted in terms of a three-dimensional configuration. Both Desargues' Theorem and Pascal's Theorem assert that three points defined as the intersections of certain pairs of lines in a configuration are collinear. One very natural way to see that three points in a plane are collinear is to find a plane other than the given one containing the three given points, which must all therefore lie on the intersection of two planes. For Desargues' Theorem, this plane is simple to construct, for Pascal's not quite so simple.
The three-dimensional proof of Pascal's Theorem is now well known, but seems to have originated with Dandelin.
H. S. M. Coxeter, The Real Projective Plane, Cambridge Press, 1955. [p. 103]
D. Hilbert and S. Cohn-Vossen, Geometry and the Imagination, Chelsea, 1965. [pp. 102-106]
G. P. Dandelin, MISSING, .
We include below a translation of this paper into English, as well as a set of pictures to illustrate its argument. Although the basic argument is relatively simple and geometrical in anture, it is not so easy to illustrate it convincingly. It is interesting in this regard to examine critically the figures in Bachmann and Hilbert & Cohn-Vossen accompanying their proofs. Bachmann's figures [on p. 253 and p. 254] are schematic in nature, and while the figures in Hilbert & Cohn-Vossen [pp. 104 & 105] are somewhat more realistic, they do not make the argument as transparent as one might wish.
An English translation of Dandelin's paper
A gallery of pictures to accompany Dandelin's paper (work of Tzu-Pei Chen) | <urn:uuid:be0bce54-7424-4913-bc42-aecb616346cb> | 3.078125 | 451 | Knowledge Article | Science & Tech. | 58.24378 |
Benefits And Costs Of Migrating Species
January 19, 2001
Whether by choice or chance, when humans have gone to new places, other species new to those lands have often journeyed with them. While some migrations can impose heavy social costs -- such as the introduction of new diseases -- the benefits are often enormous.
- The potato traveled from the Andes to Europe, North America and elsewhere, as did the tomato; soybeans probably reached the Americas from China; exotic plants and animals have made their way around the world thanks to collectors; and when Europeans migrated overseas, they took along wheat, barley, rye, cattle, pigs, horses, sheep and goats.
- Today, introductions of isolated species to new habitats are occurring with stunning rapidity -- as global imports of agricultural products and industrial raw materials have shot from $55 billion in value in 1965 to $480 billion in 1990, according to the World Resources Institute.
- Yet only a tiny proportion of alien species establish new populations and of those only about one in 10 becomes a pest.
- One in five of the United States' 4,500 exotic species has caused serious economic or ecological harm -- and of the U.S.' threatened native species, 40 percent can blame their decline on the newcomers, experts report.
The costs are hard to quantify. One government estimate puts the cost of a selection of 79 harmful species in the U.S. at a cumulative total of $96 billion since 1900.
If enough people believe that the arrival of alien species means economic harm, more will be spent to prevent it -- and that is already happening. But some scientists believe beneficial species are getting the heave-ho along with their more malevolent brethren.
Source: "New Flora and Fauna for Old," Economist, December 23, 2000.
Browse more articles on Environment Issues | <urn:uuid:9c08b519-dc61-4349-9c31-eaa91bcf35df> | 3.453125 | 378 | Truncated | Science & Tech. | 39.755175 |
MOUNTAINEERS climbing Mount Everest will have to battle with a cloak of ozone that descends over the peak as the day wears on.
During expeditions to Everest in the summer of 2001 and 2002, Tong Zhu from Peking University in Beijing, China, and his colleagues measured ozone and carbon monoxide levels at an altitude of 5000 metres. Taking readings every minute for a week they saw a daily ozone cycle, starting at around 40 parts per billion in the early morning and rising to around 80 ppb by midday, remaining high until midnight (Geophysical Research Letters, DOI: 10.1029/2006GL027726).
The pattern correlated with the katabatic wind - a cool breeze caused by the chill from glaciers, which rolls down the mountain during the day - and suggests that the ozone is being sucked down from the stratosphere. At its peak the ozone is equivalent to mildly polluted city air and could ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:f1080119-d2b6-4a40-b327-9a954f99ec45> | 3.703125 | 216 | Truncated | Science & Tech. | 54.22 |
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Planet Vs. Star
Wed Oct 15 16:34:00 BST 2008 by Anonymous
Actually, size isn't as significant. When they redefined planetary objects (i.e. When Pluto became a dwarf planet, instead of a planet), had to do with the body of mass have a clear orbit, void of interstellar debris. The body can be massive, and still not make it a star (a fusion reactor of sorts). | <urn:uuid:455fa62e-1bc9-4f75-8112-1ead3092262e> | 2.890625 | 92 | Comment Section | Science & Tech. | 70.483094 |
NOAA: Warmest Global Sea-Surface Temperatures for August and Summer
September 16, 2009
Global surface temperature anomalies for the month of August 2009. Temperature is compared to the average global temperature from 1961-1990.
Visualization of world’s land and ocean surface temperature.
High resolution (Credit: NOAA)
The world’s ocean surface temperature was the warmest for any August on record, and the warmest on record averaged for any June-August (Northern Hemisphere summer/Southern Hemisphere winter) season according to NOAA’s National Climatic Data Center in Asheville, N.C. The preliminary analysis is based on records dating back to 1880.
NCDC scientists also reported that the combined average global land and ocean surface temperature for August was second warmest on record, behind 1998. For the June-August 2009 season, the combined global land and ocean surface temperature was third warmest on record.
Global Highlights – Summer
- The June-August worldwide ocean surface temperature was also the warmest on record at 62.5 degrees F, 1.04 degrees F above the 20th century average of 61.5 degrees F.
- The combined global land and ocean average surface temperature for the June-August season was 61.2 degrees F, which is the third warmest on record and 1.06 degrees F above the 20th century average of 60.1 degrees F.
Global Highlights – August
- The worldwide ocean surface temperature of 62.4 degrees F was the warmest on record for any August, and 1.03 degrees F above the 20th century average of 61.4 degrees F.
- Separately, the global land surface temperature of 58.2 degrees F was 1.33 degrees F above the 20th century average of 56.9 degrees F, and ranked as the fourth warmest August on record.
- Large portions of the world’s land mass observed warmer-than-average temperatures in August. The warmest departures occurred across Australia, Europe, parts of the Middle East, northwestern Africa, and southern South America. Both Australia and New Zealand had their warmest August since their records began.
- The Southern Hemisphere average temperatures for land and ocean surface combined were the warmest on record for August.
Other Notable Developments
Current sea ice extent as measured by NOAA's GOES, POES, and DMSP satellites.
Visualization of Arctic sea ice extent.
High resolution (Credit: NOAA)
- For the year to date, the combined global land and ocean surface temperature of 58.3 degrees F tied with 2003 for the fifth-warmest January-August period on record. This value is 0.99 degree F above the 20th century average.
- According to the National Snow and Ice Data Center (NSIDC), Arctic sea ice covered an average of 2.42 million square miles during August. This is 18.4 percent below the 1979-2000 average extent, and is generally consistent with a decline of August sea ice extent since 1979.
- NSIDC data indicated Antarctic sea ice extent in August was 2.7 percent above the 1979-2000 average. This is consistent with the trend during recent decades of modest increases in August Antarctic sea ice extent.
Watch NOAA's visualization of the world’s land and ocean surface temperature.
Watch NOAA's visualization of the Arctic sea ice extent.
NOAA understands and predicts changes in the Earth’s environment, from the depths of the oceans to surface of the sun, and conserves and manages our coastal and marine resources. | <urn:uuid:61a40aaf-3dbd-4f85-a5b8-9b62852b736b> | 3.078125 | 734 | Knowledge Article | Science & Tech. | 51.838135 |
18 May 2011
Posted in WFTV Severe Weather Center 9
Have you ever wondered what a vortex is and how natural vortices including tornadoes, whirlpools and cyclones move the way they do? Try the tornado in a bottle experiment to find out. A vortex is a whirling mass of water, air or fire that creates a visible tornado-like column or spiral. A vortex can be created with the help of angular momentum, surface tension, centripetal force and fluid displacement. This experiment requires the use of super glue and a drill, so kids – don’t try this without an adult!
- Two 2 liter plastic soft drink bottles
- Food coloring (optional)
- Glitter (optional)
- Two bottle lids
- Super glue
- Electrical Tape
- Fill one bottle ¾ full with water.
- Add some food coloring and glitter. (Optional)
- Use the super glue (with a parent’s help) to glue the two bottle lids together, flat sides touching.
- Let dry.
- Drill a hole (with a parent’s help) through the center of both lids with a 9 mm drill bit.
- Screw in one side of the bottle lid to the bottle filled with water. Then, screw the empty bottle onto the other side of the connecting lids.
- Add some electrical tape around the connection to reinforce.
- Turn the bottles over and observe the movement of water from one bottle to the next.
- Try again, but this time give the bottle a few spirals as you set it down. Notice what happens this time.
The first time you turn the bottles over, the surface tension of the water tries to keep the water from flowing down. The weight of the water above it, however, forces the water to bubble up and break through into the second bottle. This is what makes the BLOOP BLOOP sound you hear as it happens several times. Each time this happens, pressure builds up in the bottom of the bottle until the air is forced up into the top bottle over and over until the top bottle is empty.
The second time, the water was directed into a spiral by your swirling motion creating a vortex into the bottom bottle. Gravity works to pull the spinning water down through the hole into the bottom bottle. The angular momentum of the spinning water makes the water at the center of the vortex spin faster than the water closer to the edge of the bottle creating a whirlpool effect.
The vortex created by the swirl lets the air pass through the center of the vortex without disrupting the flow of the water. When you combine this with the forces of water pressure and the gravity force, a centripetal force, or spinning force, makes the water swirl. Notice that the water near the bottom moves faster than the water at the top. The higher the speed, the steeper the curve needed to allow the spinning motion. | <urn:uuid:d5a2bbfa-10de-44e5-99ab-cafebcd68609> | 3.875 | 609 | Tutorial | Science & Tech. | 60.182069 |
Summary: §1.1: NEWTON'S LAW OF COOLING
Imagine some object like a cannon ball suspended in a swimming
pool by a rope. The cannon ball is at some temperature; perhaps
hotter thant the water, perhaps cooler. We can think of it as being a
`point source' of heat flow in or out. We are interested in the tem-
perature T (in degrees centigrade) as a function of time t (in min-
utes). It will be simplest if we measure the temperature relative to
the surrounding water, so T = 0 represents the water temperature.
We would like to understand the function T(t). Another function we
can consider is the derivative T (t) (in degrees per minute.)
One way of approaching this problem is to throw away one of the
variables, time t. We can imagine the STATE SPACE which is the plane
with coordinates (T, T ). A point in the state space is a pair of num-
bers representing a temperature, and a rate of change of tempera-
ture. This represents a possible state the cannon ball could be in. It is
hard to think about the rate of change without thinking about time. | <urn:uuid:df5b9686-ff79-4c5f-bebd-0ef1e88e96fd> | 3.65625 | 258 | Academic Writing | Science & Tech. | 60.154615 |
According to the mythos of the BattleTech tabletop/computer/video games, novels, comics, and anime shows, the principles behind faster-than-light travel will be discovered at Stanford University in just six years. (Get ready, people!)
About a century later, further work will be done on the theories of Drs. Thomas Kearny and Takayoshi Fuchida to create hyperspace energy fields using large, superconductive masses of titanium and germanium. Sounds easy enough, but the system needs huge amounts of energy, so solar sails are used for time-consuming power-ups from stars. (And there are fewer and fewer full service stations!) Furthermore, unlike with other systems, you just can't jump anywheregravitational pull can make "reentry" unstable, so coordinates must be far above a star's ecliptic path. Use of the K-F Drive also does a number on the subatomic particles of the effected region.
Plausibility Factor: For the very fact that using the drives causes so much trauma, let's give this one a 6. | <urn:uuid:bd3bdc2c-d920-444d-ba4b-9117f2268f3b> | 2.921875 | 225 | Listicle | Science & Tech. | 39.80907 |
Data reported by the weather station: 84510 (LEJR)
Latitude: 36.75 | Longitude: -6.06 | Altitude: 27
Weather Jerez de la Frontera aeropuerto
|Main||Year 1985 climate||Select a month|
To calculate annual averages, we analyzed data of 364 days (99.73% of year).
If in the average or annual total of some data is missing information of 10 or more days, this is not displayed.
The total rainfall value 0 (zero) may indicate that there has been no such measurement and / or the weather station does not broadcast.
|Annual average temperature:||19.4°C||364|
|Annual average maximum temperature:||24.2°C||364|
|Annual average minimum temperature:||11.9°C||364|
|Annual average humidity:||62.4%||363|
|Annual total precipitation:||514.87 mm||364|
|Annual average visibility:||13.3 Km||364|
|Annual average wind speed:||15.7 km/h||364|
Number of days with extraordinary phenomena.
|Total days with rain:||63|
|Total days with snow:||0|
|Total days with thunderstorm:||11|
|Total days with fog:||23|
|Total days with tornado or funnel cloud:||0|
|Total days with hail:||2|
Days of extreme historical values in 1985
The highest temperature recorded was 42.4°C on August 4.
The lowest temperature recorded was -4°C on January 16.
The maximum wind speed recorded was 74.1 km/h on January 17. | <urn:uuid:271f2f5a-84fa-464c-8a60-559def2fcbd2> | 2.734375 | 372 | Structured Data | Science & Tech. | 70.489641 |
Downslope flow of ash and rock debris resulting from volcanic activity.
Mount Rainier - Living Safely With a Volcano in Your Backyard [ More info] One of our Nation's most dangerous volcanoes, Mount Rainier has been the source of countless eruptions and volcanic mudflows, and many people live in the areas that will be affected by it.
Mount St. Helens, 1980 to now--what's going on? [ More info] Summarizes the eruptions of this spectacular volcano and the consequences for the surrounding landscape, explains how volcanoes like this form, and how we monitor their activity to mitigate hazards they pose.
Types and effects of volcano hazards [ More info] Describes the 6 main types of hazardous activities and processes associated with volcanoes, including tephra, lava flows, pyroclastic flows, lahars (volcanic mudflows), landslides, and volcanic gas.
Alphabetical Index of Topics
a b c d e f g h i j k l m n o p q r s t u v w x y z | <urn:uuid:1d44e32d-6100-4d50-a6e7-4bde92e553b6> | 3.4375 | 223 | Content Listing | Science & Tech. | 47.430158 |
This is a picture of the meteorite ALH84001.
Click on image for full size
The possible discovery of Life on Mars
In July, 1996, it was announced that Dr. David McKay, along with a team of
scientists at Johnson Space Center (a division of NASA), had discovered
possible fossils of bacteria
in a meteorite named ALH84001 that came from Mars. It was found in the Allen Hills in Antarctica in 1984 after having landed there 12,000 years ago. While many scientists were excited at first, much of the proof offered fell apart. NASA said that after two years of study "a number of lines of evidence have gone away".
Several different chemicals and molecular structures were exciting because they looked similar to byproducts of life on Earth. However, these chemicals and structures can also be created without life. Some are even present in deep space on comets, and scientists do not think that they came from Martian life anymore.
Small spheres were observed in the meteorite which the
scientists in 1996 claimed were the fossilized remains of bacteria. However, they are roughly 1000 times smaller than the smallest bacteria on Earth, so don't resemble any life thought to be possible. Organic (carbon containing) compounds were found with the spheres, but it turned out that the organic compounds became a part of the meteorite after it landed on Earth (possibly when water seeped in a couple times over the 12,000 years the rock laid in Antarctica). Carbon 14, an isotope found on Earth is present in the organic compounds, but not in the spheres.
The environment of Mars in the
past was very different than it is today. Conditions then may have been favorable for the existence of life. Even though the Mars meteorite does not prove life once existed on Mars, it certainly does not disprove the possibility.
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Isotopes are different "versions" of an element. All atoms of an element have the same number of protons. For example, all hydrogen atoms have one proton, all carbon atoms have 6 protons, and all uranium...more
Jupiter's atmospheric environment is one of strong gravity, high pressure, strong winds, from 225 miles per hour to 1000 miles per hour, and cold temperatures of -270 degrees to +32 degrees (freezing temperature)....more
In July, 1996, it was announced that Dr. David McKay, along with a team of scientists at Johnson Space Center (a division of NASA), had discovered possible fossils of bacteria in a meteorite named ALH84...more
Saturn's atmospheric environment is one of strong gravity, high pressure, strong winds, from 225 miles per hour to 1000 miles per hour, and cold temperatures of -270 degrees to +80 degrees. With winds...more
Titan's atmosphere is a lot like the Earth's, except that it is very cold, from -330 degrees to -290 degrees! Like the Earth, there is a lot of Nitrogen and other complex molecules. There also may be an...more
Autotrophs are organisms that can "make their own food" from an inorganic source of carbon (carbon dioxide) given a source of energy. Most autotrophs use sunlight in the process of photosynthesis to make...more
In the warm primordial ocean, aggregates of amino acids, proteins, and other hydrocarbons came together into a form called *coacervates*. Amino acids will spontaneously form coacervates in the same way...more | <urn:uuid:b640ee83-19bb-48dc-8201-4712cf7f20a7> | 3.65625 | 790 | Knowledge Article | Science & Tech. | 52.81512 |
Some of the excited engineers and staff on landing day.
Click on image for full size
Jet Propulsion Laboratory, Pasadena, CA
Headlines declare: Mars Pathfinder Lands on July 4th
The Mars Pathfinder was launched in December 1996 on a Delta II rocket. The spacecraft entered the atmosphere on July 4th, 1997, where a heat shield, parachutes, and airbags helped it land.
After impact the lander put out three solar panels for power. Later on, a camera will map its surroundings, and the Sojourner rover will search the surface of Mars for rocks.
Long ago, water flowed on the plains of Mars. The rocky plain that Mars Pathfinder is landing on is thought to be a previous flood plain. Its name is Ares Vallis. The Sojourner rover will test rock and soil samples in this area.
Mars Pathfinder will finish its surface mission in August 1997.
The Mars Pathfinder is a NASA Discovery Mission. The Pathfinder program was developed in three years and costs under $280 million dollars. It is actually the first of NASA's Discovery Program low-cost series of planetary missions. The motto of the program has become "faster, better, and cheaper"!
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One of the objectives of the Mars Pathfinder mission was the examination of the composition of the soil and how it was laid down. As the Rover traversed the surface exploring the rocks of Mars, it also...more
Because of the failure of the Mars Observer (MO), NASA planned a new Mars Surveyor Program. The Surveyor Program was designed to explore all of the things the MO was suppose to, and a lot more. The Surveyor...more
The goal of the Mars Pathfinder (MPF) mission was to analyze the rocks and soil of Mars. The MPF was actually 2 parts, a lander and a rover. The lander stayed right where it landed while the rover named...more
The Mars Odyssey was launched April 7, 2001, from Florida. After a six-month, 285 million-mile journey, the Odyssey arrived at Mars on October 24, 2001. The Odyssey is in its aerobraking phase right now....more
The Mars 2005 mission is still in the planning stages. It is set to launch in the year 2005. ...more
The Mars Global Surveyor reached Mars in September of 1997. But it didn't make it into its final mapping orbit until February 1999. What took so long? Surveyor needed to reach a near-circular, low-altitude...more
Mars Global Surveyor carries an instrument which measures the heights of things. This instrument is called an altimeter, or "altitude-meter". The graph to the left shows the results returned from Mars...more | <urn:uuid:43c31644-f9fc-411b-9637-7c907444076c> | 3.359375 | 600 | Content Listing | Science & Tech. | 66.699393 |
EXPERIMENT TITLE: What Does It Matter?
CONCEPT(S): Relationship between mass and volume.
VIDEO SEGMENTS (click the links below to view):
LESSON PLAN: Lesson plan (PDF)
Teacher’s Domain Video- Density and Buoyancy: Testing Liquids
Science Education Resource Center at Carleton College- How do I calculate density?
Suite101.com- Density of Objects: Critical Thinking in Action | <urn:uuid:1bb83001-2bfb-4b11-bd8b-684d54c58b78> | 3.15625 | 99 | Truncated | Science & Tech. | 38.532143 |
| Forward | Back | Up | Map | Glossary | Information |
For 300,000 years, protons and atomic nuclei continued to roam about in a almost totally opaque sea of photons, electrons and neutrinos--opaque because the photons couldn't travel far without bumping into another particle. Any electron that combined with a proton or atomic nucleus was immediately knocked off by a traveling photon. Matter and radiation were intimately linked.
But after about 300,000 years, the opaque soup of nuclear matter and radiation began to clear. By this time, the temperature of the universe dropped to 3,000 K. Photons no longer had enough energy to knock electrons free from atomic nuclei and protons. Now the photons were free to travel through the universe, at last decoupled from matter. This era, called recombination, actually lasted about a million years.
Credits and Copyrights
The vast sea of photons created during the earliest epochs prior to recombination persist to this day, in the form of cosmic microwave background that pervades the universe. No longer so energetic after being stretched by the expansion of the universe for roughly 20 billion years, this radiation has cooled to a chilly 2.73 K (minus 270.43 degrees Celsius!). It's nonetheless considered by cosmologists to be one of the clearest signatures of the Big Bang. The uniformity of this radiation--to within a few parts in 100,000--indicates that the universe was extremely smooth around the time of recombination.
Tiny variations have recently been found in this background radiation, indicating minute fluctuations in density of matter and energy at recombination. These fluctuations were eventually amplified by gravity to form the objects which make up our hierarchical universe: stars, galaxies, galaxy clusters and superclusters.
Forward to Galaxy Birth
Return to Big Freeze Out
Up to Cosmic Mystery Tour | <urn:uuid:f64a6704-8f6e-4fbd-80c1-c48fb6548a9c> | 3.703125 | 380 | Knowledge Article | Science & Tech. | 38.617235 |
| Forward | Back | Up | Map | Glossary | Information |
Astrophysicists are using increasingly sophisticated arrays of ground-based and space-borne instruments to look out and back to the most distant (and oldest!) regions of the universe. They're constructing a map of the large-scale organization of the universe that is nothing short of amazing.
Astrophysicists at the Harvard-Smithsonian Center for Astrophysics are undertaking large-scale surveys of part of the universe. Their goal is to construct three-dimensional maps by measuring the cosmological redshifts of galaxies that appear to lie within thin, pie-shaped, adjoining "slices" of space.
Thus far, about 100,000 galaxies have been mapped (by the Center for Astrophysics team and others) from both the Northern and Southern hemispheres, to distances greater than 500 million light years. They already knew two of the galaxy's coordinates just by locating them on the sky with their telescopes. The measured redshift for each galaxy was converted to distance, with increasingly distant galaxies having greater redshifts. This allowed the scientists to plot the third coordinate.
North and South, Sheets and Voids
The first maps, published in 1986, were a great surprise to the
astrophysicists. They had expected to find relative uniformity above the
scale of the already-familiar galaxy clusters. Instead, the first surveys
showed--and subsequent surveys have confirmed--that great clusters of galaxies are
arranged in thin sheets or long filaments. The longest sheet detected, called the
"Great Wall," extends hundreds of millions of light years across the maps.
JPEG Image (52.2 KB); Caption; Credits and Copyright
Interspersed amongst the sheets are great holes, ranging in size from 100 million to 400 million light years in diameter, almost devoid of galaxies. Margaret Geller and John Huchra, two of the scientists on the Center for Astrophysics team, likened the structures to a collection of giant soap bubbles, with the galaxies residing on the surface of the bubble.
Recent observations show, however, that the voids may not be completely empty after all--at least not all of them. Using the Hubble Space Telescope's Goddard high-resolution spectrograph, researchers from the University of Colorado, Boulder have detected clouds of hydrogen gas in nearby voids. Astronomers have detected hydrogen gas clouds before, but they've been in such remote parts of the universe that it was difficult to tell whether they lay in voids.
By extrapolation, researchers have estimated that the gas clouds contained within voids could collectively contain as much mass as there is in the visible galaxies--yet another contributer to the "missing" dark matter. The question is whether the gas clouds are comprised of primordial hydrogen, or are the halos of faint dwarf galaxies.
Scientists have actually peered even further out into the cosmos--to about 2,500 million light years. And, although they haven't actually mapped that part of the universe, what they see are not ever larger walls and voids, but more of the same. There are more powerful telescopes under construction that will allow the astrophysicists to probe even deeper into the universe. Will they see the same structures in the more distant--and younger--universe? Will they detect less structure, or simply different kinds of structures? Time, and the heavens, will tell.
The X-ray perspective
There's another way of looking at large-scale structures--by the X-rays they
emit. Cosmologists believe that gases gravitationally pulled into high
density regions underwent tremendous collisions that produced shock waves,
causing the gases to heat up in many regions to as much as 1-10 million degrees Kelvin. The super-hot
gases emit large amounts of energy in the form of X-rays, detectable through
The Coma Cluster
Astrophysicists have targeted their sights on giant clusters of
galaxies, particulary the Coma Cluster which lies more than 5 times farther away from us than the
JPEG Image (21.5 KB); Caption; Credits and Copyright
Coma Cluster X Ray
The first instrument able to image the X-ray sky, launched in 1978, was the
Einstein Observatory. Einstein detected only the densest (and therefore
hottest) clusters of X-rays at the intersections of galaxy filaments.
JPEG Image (41 KB); Caption; Credits and Copyright
Since that time, the European Space Agency (ESA) and NASA have launched a more sensitive
but less far-reaching instrument, ROSAT (ROentgen SATellite).
JPEG Image (24.5 KB); Caption; Credits and Copyright
Advanced X-Ray Facility
NASA plans to launch an instrument called the Advanced X-ray Astronomical Facility
(AXAF) in the late 1990s. AXAF will be capable of detecting the faint X-rays from
distant galaxies far beyond the reach of either ROSAT or the Einstein Observatory and
with much greater sensitivity. Cosmologists anticipate a wealth of X-ray
JPEG Image (28.5 KB); Caption; Credits and Copyright
Two theories involve dark matter. If neutrinos (hot dark matter) indeed have mass, they would tend to accumulate at the sites of excess density, left over from the density fluctuations of the Big Bang. The gravitational pull of the neutrinos may have pulled in surrounding matter, leading first to the formation of galaxy clusters and superclusters, and later to the formation of galaxies as these larger structures fragmented (the so-called "Top Down" model).
Now, it may seem that the nearly massless neutrinos could not exert much gravitational force, but remember that there are about 100 million neutrinos per cubic meter. Like Senator Everett Dirksen's famous quote about the federal budget ("A billion here and a billion there and pretty soon you're talking big money."), a little mass adds up!
A universe dominated by cold dark matter (weakly interacting massive particles, or WIMPS), on the other hand, suggests that there was a whole spectrum of density fluctuations in the early universe. Under this theory (the "Bottom Up" theory) galaxies form first only at the extreme and rare density peaks, and later the galaxies cluster into larger structures--clusters and superclusters. Most of the cold dark matter would be concentrated in the great voids, outside of the galaxy superclusters.
Michael Norman, an astrophysicist at the University of Illinois at Urbana-Champaign has constructed a computer model that incorporates both cold and hot dark matter, an approach that seems to more nearly approximate the observed structure of the universe.
Norman and Ostriker are part of an NSF-funded HPCC grand challenge project that aims to simulate the evolution of the X-ray universe on a large scale, in anticipation of the AXAF observations to come a few years from now.
Thanks to advances in both instrumentation and computation, closer matching of observation and theory is not only becoming possible, but crucial for further progress in solving the major mysteries of the origins, evolution and fate of the universe.
Cosmology Goes Digital
Return to Mysterious Dark Matter
Up to Our Hierarchical Universe | <urn:uuid:91ac13fb-106b-49aa-8c82-f8cfd36a3bf6> | 3.984375 | 1,510 | Knowledge Article | Science & Tech. | 36.55357 |
flash wrote:Assuming the atmosphere extends to 100 miles, a vertical dive at 60,000 mph gives only 6 seconds to vaporize before it hits the surface. That doesn't seem to be a lot of time. But then the energy is proportional to v2 and 60,000 squared is a big number.
Exactly. The huge forces mean there's no way for a body traveling at (a relatively slow) 27 km/s to maintain that speed in the atmosphere. So the actual descent time becomes much longer than 6 seconds. It need not vaporize all at once; more likely is that it will break up into many small pieces, which either burn up or slow down and survive as meteorites (which land without any of the original velocity).
A 1-meter diameter meteoroid traveling 27 km/s experiences a drag force of more than 800,000 N at a height of 50 km. If it's stony, that's an acceleration of -50 G. That's enough to start breaking up most meteoroids. If a body somehow survived with that size and speed to 30 km, the acceleration increases to over 700 G. Even iron bodies will break up under those conditions.
Why is it that coming in at 60,000 mph horizontally (rather than vertically) make it more likely to survive? Doesn't that just give the energy more time to act?
Because it spends more time in the upper atmosphere, slowing down without encountering the destructive forces (as above) created by moving fast in thicker air. Remember it's that v2
term that dominates. If you can reduce v before the body descends into the deeper atmosphere, it's more likely that material will survive. The meteors that are observed to produce meteorites are usually slow to begin with (~20 km/s) and enter at a shallow angle. They need to be large enough that they can lose 90% or more of their mass to ablation and still leave something behind, but not break apart (or not break apart while still moving very fast) and lose all their mass in a nearly instantaneous burst of ablative loss. | <urn:uuid:e0f373e4-6463-41ee-9086-69312dac0acf> | 3.453125 | 427 | Comment Section | Science & Tech. | 61.408421 |
The stunning video below, shows large leptocephali filmed by divers at three locations within the Indonesian Archipelago from 2009 to 2011.
The observations were made from December to April in Lembeh Strait adjacent to north-eastern Sulawesi Island, at Ambon Island and at Bali.
The leptocephali are about 300 - 400 mm long and appear to be metamorphosing larvae of some type of moray eel of the family Muraenidae. The morphological similarities between these leptocephali and Ribbon Eels, Rhinomuraena quaesita, suggest they may be Ribbon Eel larvae.
The video clip showing the four leptocephali that were filmed by various divers is associated with a published paper by Dr Michael Miller, entitled 'Observations of large muraenid leptocephali in coastal Indonesia: locations of sightings and behavior of the larvae.'
Leptocephali are transparent because they have only a thin layer of muscle over a mucinous pouch inside the body. The pouch contains glucosaminoglycan (GAG) compounds that form a transparent jelly-like substance. The GAGs are converted into tissue during metamorphosis, and thus in addition to being transparent, they are also an energy storage material.
View the Moray Eels list.
Learn more about the Ribbon Eel.
View an image of the head of a metamorphosing muraenid leptocephalus.
Read about Dr Miller's research during his 2009 visit to the Australian Museum. | <urn:uuid:08ecbdcf-7cae-42f4-b74c-05a3c1603594> | 2.921875 | 332 | Knowledge Article | Science & Tech. | 28.765 |
GG cilia have GC-G
image by Cambrian Liu
Many cells from all eras of evolution, from bacteria to humans, possess specialized tails called cilia that can perform a variety of functions. In bacteria, cilia can be used to provide locomotion and structural support. In zebrafish, cilia are used to model organs asymmetrically during the development of the animal. The image shows a specialized set of neurons (in green) in the mouse's nose called the Grueneberg ganglion. These neurons, which are thought to be involved in the sense of smell, possess cilia (in red) that house proteins directly involved in sensing smells from the surrounding environment. Unlike cilia found in other neurons, which stick out from the cell surface, the cilia of the Grueneberg ganglion follow the contour of the cell, giving a "wrap-around" impression. | <urn:uuid:6af3514a-2260-4346-8a12-a91f7a7f8348> | 3.4375 | 184 | Knowledge Article | Science & Tech. | 38.542378 |
Given the large amount of science news published online and in print each day, it's always nice to find follow-ups on the relatively obscure topics posted here.
And so I smiled earlier today when I saw on ScienceDaily an article about the latest research on CoRoT-7b, the fast-orbiting exoplanet some 500 light years away that was mentioned in my last post. Readers may recall that astronomers recently determined that CoRoT-7b is just slightly less than twice the diameter of Earth, about five times Earth's mass, and similar in structure.
Structure--meaning rocky--is the key, because other similarities with Earth today are practically non-existent.
Apart from orbiting its star so rapidly (once every 3 days, 17 hours), CoRoT-7b is only about 1.6 million miles away from it -- 23 times less than the distance from our Sun to Mercury. And if this isn't distinctive enough, one side of the planet always faces its star while the other is in shadow, which means the exposed surface is extremely hot. Just how hot is it? The estimated surface temperature--literally the source of yesterday's news--is about 4,220 degrees Fahrenheit.
Because of the extremely high surface temperature, "The only atmosphere this object has is produced from vapor arising from hot molten silicates in a lava lake or lava ocean," according to Bruce Fegley of Washington University's Department of Earth and Planetary Sciences, who modeled CoRoT-7b's atmosphere with Laura Schaefer of WU's Planetary Chemistry Laboratory.
Lakes or possibly oceans of molten lava are interesting enough to think about, but all the vapor from those molten silicates apparently makes things even stranger.
Reporting the features of their silicate atmosphere model in the October 1 issue of The Astrophysical Journal, Fegley and Schaefer suggest that CoRoT-7b's atmosphere is mostly composed of sodium, postassium, silicon monoxide, and--big surprise to people like me--oxygen, which comes from all that vaporized surface rock. ScienceDaily quotes Fegley on the implications of the chemistry:
"As you go higher the atmosphere gets cooler and eventually you get saturated with different types of 'rock' the way you get saturated with water in the atmosphere of Earth. But instead of a water cloud forming and then raining water droplets, you get a 'rock cloud' forming and it starts raining out little pebbles of different types of rock."
Verfiable or not, the fact that planetary scientists can make this kind of inference based data collected from so far away is nothing short of astonishing.
Next stop: Carl Edward Sagan
Banner bus photo credit: Dorothy Delina Porter | <urn:uuid:2be4da8b-78b7-430f-8b8e-8d01b370de7d> | 3.4375 | 558 | Personal Blog | Science & Tech. | 30.165303 |
As I mentioned earlier, I’m teaching a first-year seminar this semester called “Science or Nonsense?” On Monday and Wednesday this week we discussed some math/stats/numeracy topics. We talked about the Sally Clark murder trial, the prosecutor’s fallacy, the use of DNA testing in law enforcement, Simpson’s paradox, the danger of false positives, and the 2009 mammogram screening recommendations.
I made a GeoGebra applet to illustrate the dangers of false positives. So I thought I’d share that here. Here’s the statement of the problem.
Suppose Lenny Oiler visits his doctor for a routine checkup. The doctor says that he must test all patients (regardless of whether they have symptoms) for rare disease called analysisitis. (This horrible illness can lead to severe pain in a patient’s epsylawns and del-tahs. It should not to be confused with analysis situs.) The doctor says that the test is 99% effective when given to people who are ill (the probability the test will come back positive) and it is 95% effective when given to people who are healthy (it will come back negative).
Two days later the doctor informs Lenny that the test came back positive.
Should Lenny be worried?
Surprisingly, we do not have enough information to answer the question, and Lenny (being pretty good at math) realizes this. After a little investigating he finds out that approximately 1 in every 2000 people have analysisitis (about 0.05% of the population).
Now should Lenny be worried?
Obviously he should take notice because he tested positive. But he should not be too worried. It turns out that there is less than a 1% chance that he has analysisitis.
Notice that there are four possible outcomes for a person in Lenny’s position. A person is either ill or healthy and the test may come back positive or negative. The four outcomes are shown in the chart below.
|Positive||true positive||false positive|
|Negative||false negative||true negative|
Obviously, the two red boxes are the ones to worry about because the test is giving the incorrect result. But in this case, because the test came back positive, we’re interested in the top row.
For simplicity, suppose the city that is being screened has a population of 1 million. Then approximately (1000000)(0.0005)=500 people have the illness. Of these (500)(.99)=495 will test positive and (500)(0.01)=5 will test negative. Of the 999,500 healthy people (999500)(.05)=49975 will test positive and (999500)(.95)=949525 will test negative. This is summarized in the following chart.
Thus, 495+49975=50470 people test positive, and of these only 495 are ill. So the chance that a recipient of positive test result is sick is 495/50470=0.0098=0.98%. That should seem shockingly low! I wonder how many physicians are aware of this phenomenon.
You can try out this or other examples using this GeoGebra applet that I made. | <urn:uuid:94e7ed6b-06db-4381-b32d-727f411609d7> | 2.96875 | 681 | Personal Blog | Science & Tech. | 59.157768 |
The Sepiidae have a tropical/temperate distribution. They are mostly shallow-water animals although they are known from depths of about 600 m (Lu and Roper, 1991). They have an unusual biogeographic pattern (seen below, in white) in which they are absent from the Americas. Young, et al. (1998) suggest that by the time the family evolved in the Old World, the northern migration bridge across the Atlantic was closed to these warm water species.
Figure. Chart showing the distribution of the Sepiidae (white areas). Chart modified from Young et al. (1998).
No one has provided updates yet. | <urn:uuid:78a3518a-3379-4e1a-a4a0-ced53c377ead> | 3.078125 | 131 | Knowledge Article | Science & Tech. | 57.03902 |
hastable uses some hash function on an object to store.
This hash function essentially calculates the position of the object in the table.
If we use a
HashMap and the size can not fit more elements then these collections are resized to accomodate more elements.
This means that each stored element must be rehashed to calculate the new position in the new bigger table.
My question is the following(that the above are correct):
I read that
String calculates its
hashcode by using the characters that it stores and additionally that the
hashvalue is stored internally (cached) for best performance since it does not have to be recalculated.
This is the part I don't get.If the
hashcode is based on the characters the
String stores then how is the position in the
Is there some extra logic using the
String? So the
hashcode is not actually the | <urn:uuid:838f38d3-2c68-4a58-824d-eb1a764dd8d4> | 2.71875 | 190 | Q&A Forum | Software Dev. | 43.283691 |
Three colour (BVI) image of a distant overdense region of galaxies taken by the Hubble Space Telescope. The image is focused on a spiral galaxy similar to the Milky Way but located at z = 1, i.e. 8 billion years ago. Twice the mass of the Milky Way, it has a star formation rate thirty times higher due to the surrounding galaxy overdensity.
Observational Cosmology has reached an important turning point. After years of seeking the parameters that govern the evolution of the Universe, there seems to be increasing consensus in acknowledging the dominant influence of dark matter on baryons and that of dark energy on dark matter. Paradoxically, the behaviour of the two “dark” components that make up 95% of the energy content of the Universe is easy to model (dark matter is nondissipative and subject only to gravity, while dark energy acts as an anti-gravitational factor), even though our knowledge of their nature remains highly speculative. This has led to the scientific community’s leaning increasingly toward what has become the conundrum that best stands up to theoretical attack: the behaviour of baryons and the origin of the light we receive from stars, galaxies and galaxy clusters. It is now acknowledged that it is not possible to understand how galaxies form and evolve without using the entire electromagnetic spectrum to study their various components (stars, gasses and dust) in their different states (neutral, ionized, young/old, dense/not very dense).
last update : 10-18 00:00:00-2005 (604)
Quantification of the star-formation and black-hole growth rate in galaxies Until the middle of the last decade, mergers of galaxies and the star formation episodes triggered by these phenomena had been considered as a major, even dominant, ... More »
The giant gas ring in Leo, formed when two galaxies collided
An international team led by astrophysicists from the Lyon Observatory (CRAL, CNRS/INSU, Université Lyon 1) and the AIM laboratory (CEA-Irfu, CNRS, Université Paris 7) has just shed some light on the origins of the giant gas ring in ... More »
The most famous collision of galaxies decoded using ‘high-resolution’ simulations
‘High-resolution’ numerical simulations carried out by scientists at the Astrophysics Department of the CEA-Irfu/AIM have just revealed that the most famous galactic collision ever, the Antennae collision, produces far more stars ... More »
The dark galaxy may just be tidal debris (15 novembre 2007)
What is a galaxy ? Stars, gas, some dust and surrounding them an invisible dark matter halo. The discovery a few years ago of a so-called « dark galaxy » devoid of its most famous component - the stars - raised a lot of interest in ... More »
The hot gas found in stars produced by laser pulses
A major international collaboration , involving researchers from the CEA-IRFU Astrophysics Department, CEA-IRAMIS and CEA-DAM, has succeeded in measuring for the first time the effects of light absorption by nickel in high temperature plasmas ... More » | <urn:uuid:90294861-e4f1-45b9-9aac-99e6354a73a0> | 3.265625 | 661 | Content Listing | Science & Tech. | 39.680907 |
Equals and hashcode methods are two primary but yet one of most important methods for java developers to be aware of. Java intends to provide equals and hashcode for every class to test the equality and to provide a hash or digest based on content of class. Importance of hashcode increases when we use the object in different collection classes which works on hashing principle e.g. hashtable and hashmap. A well written hashcode method can improve performance drastically by distributing objects uniformly and avoiding collision. In this article we will see how to correctly override hashcode() method in java with a simple example. We will also examine important aspect of hashcode contracts in java. This is in continuation of my earlier post on overriding equals method in Java, if you haven’t read already I would suggest go through it.
General Contracts for hashCode() in Java
1) If two objects are equal by equals() method then there hashcode returned by hashCode() method must be same.
2) Whenever hashCode() mehtod is invoked on the same object more than once within single execution of application, hashCode() must return same integer provided no information or fields used in equals and hashcode is modified. This integer is not required to be same during multiple execution of application though.
3) If two objects are not equals by equals() method it is not require that there hashcode must be different. Though it’s always good practice to return different hashCode for unequal object. Different hashCode for distinct object can improve performance of hashmap or hashtable by reducing collision.
To better understand concept of equals and hashcode and what happens if you don’t override them properly I would recommend understanding of How HashMap works in Java
Overriding hashCode method in Java
We will follow step by step approach for overriding hashCode method. This will enable us to understand the concept and process better.
1) Take a prime hash e.g. 5, 7, 17 or 31 (prime number as hash, results in distinct hashcode for distinct object)
2) Take another prime as multiplier different than hash is good.
3) Compute hashcode for each member and add them into final hash. Repeat this for all members which participated in equals.
4) Return hash
Here is an example of hashCode() method
It’s always good to check null before calling hashCode() method on members or fields to avoid NullPointerException, if member is null than return zero. Different data types has different way to compute hashCode.Integer members are simplest we just add there value into hash, for other numeric data-type are converted into int and then added into hash. Joshua bloach has full tables on this. I mostly relied on IDE for this.
Better way to override equals and hashCode
In my opinion better way to override both equals and hashcode method should be left to IDE. I have seen Netbeans and Eclipse and found that both has excellent support of generating code for equals and hashcode and there implementations seems to follow all best practice and requirement e.g. null check , instanceof check etc and also frees you to remember how to compute hashcode for different data-types.
Let’s see how we can override hashcode method in Netbeans and Eclipse.
1) Write your Class.
2) Right click + insert code + Generate equals() and hashCode().
1) Write your Class.
2) Go to Source Menu + Generate hashCode() and equals()
Things to remember while overriding hashcode in Java
1. Whenever you override equals method, hashcode should be overridden to be in compliant of equals hashcode contract.
2. hashCode() is declared in Object class and return type of hashcode method is int and not long.
3. For immutable object you can cache the hashcode once generated for improved performance.
4. Test your hashcode method for equals hashcode compliance.
5. If you don't override hashCode() method properly your Object may not function correctly on hash based collection e.g. HashMap, Hashtable or HashSet.
Complete example of equals and hashCode
Writing equals and hashcode using Apache Commons EqualsBuilder and HashCodeBuilder
EqualsBuilder and HashCodeBuilder from Apache commons are much better way to override equals and hashcode method, at least much better than ugly equals, hashcode generated by Eclipse. I have written same example by using HashCodebuilder and EqualsBuilder and now you can see how clear and concise they are.
Related Java tutorials | <urn:uuid:79ea8e4f-a415-48ee-8a0c-60a5be5736e6> | 3.5 | 944 | Personal Blog | Software Dev. | 41.86727 |
This is an intriguing question, I have read many different opinions but nothing to clearly substantiate their claims. Others in the Scientific arena when pressed are afraid to give an answer. Checking the JPL data which is an ephemeris produced by the Jet Propulsion Laboratory shows that Jupiter certainly doesn’t orbit around the SSB (although at first because of an error I made, it looked as if it did) and probably orbits around the Jupiter/Sun barycenter. After checking the Jupiter/Sun distances (which I will refer to as the radius vector which is quite different from the semi-major axis) through JPL it became obvious there was a substantial variance each orbit that was measured each time in the same place. Originally I saw this as an opportunity to look for a solid link between Angular Momentum and the Solar modulation re the planets, but soon discovered Jupiter and all the other planets have a modulating Perihelion/Aphelion distance. The quest was on the find out why and involved many weeks searching for any data I could find. Others on this site got involved and I even emailed an Astronomer but to no avail, very sparse detail available. Dr Svalgaard suggested it was a result of planetary perturbations and while correct his understanding was also far from complete. Below is an account of the progress along with what I think is the complete answer to what perturbs Jupiter and how.
My research shows the Jupiter/Sun distance varies on average 300,000 km each orbit of Jupiter. Check graphic above.
The Earth is seen to orbit the Sun directly. If we use NASA’s JPL data it shows the Earth/Sun distance is varying by 0.0001AU per year (approx 15000 km). The AU measure is the average distance between the Sun and Earth. If we measure The Earth to SSB (solar system barycenter) distance it shows a much larger variance.
What I have done is measure the Jupiter/Sun distance at exactly the same point in the elliptical orbit of Jupiter each 4331.572 days, this should isolate any aphelion/perihelion changes. I also measured the Jupiter/SSB distances.
As can be seen in the first graphic there is a large variance each orbit between BOTH measurements (Sun & SSB). This makes it hard to pinpoint any point of orbit, although the variances seem smaller on average with the Jupiter/Sun data. I also compared the Heliocentric longitude (angle away from Sun) and found each Jupiter/Sun reading had an angle of 359 deg, but the solar position at perihelion does return very closely to the same position each orbit.
The above graph was made from reliable data by blogger JimP (thanks for the spreadsheet). Once blown up it shows some remarkable detail. It shows the Perihelion distance (closest point) for each Jupiter orbit over 400 years. There is a definite pattern, what causes this modulation? The movement between the closest and furthest perihelion is 1.2 million km’s , the Sun is capable of moving 1.5 million km’s from the barycenter, Neptune’s radius vector moves by 1.4 million km. Importantly the corresponding movement at the other end (aphelion) is the same value on each orbit but in the opposite direction, if one end shortens the other end lengthens.
Jupiter/Sun distances 1600-2020 with Jup/Sat conjuncture, Jup/Sat opposition and Jup/Sat quadrature (square) positions plotted for every third occurrence. Note the phase change around 1880. If the Variance in distance is caused by angular momentum J/S conjunction & J/S opposition both produce high angular momentum. Regular reader lgl and myself suspect the other Jovians need to come into the equation, but what is needed is a new method of displaying angular momentum other than Carl’s graph. A total strength with both J/S conjuncture and J/S opposition shown as high points instead of a sine wave is required, manipulation of the current JPL data via a spreadsheet can do it. Update: There is a new article covering this.
Saturn/Sun distance showing the same 60 yr pattern as Jupiter. After 1880 they are in unison with Jupiter but not before. There is a reason for these fluctuations but I have not found any literature on this phenomena.
This diagram has been adapted from “Linkages between solar activity, climate predictability and water resource development” Alexander et al. Bailey has been criticized for claiming the Sun-Earth distance varies by the Sun-SSB distance, although not correct there is a fluctuation caused in the same manner as per Jupiter but to a smaller degree….0.0001 AU.
UPDATE 27/05/09: Here is another suggestion Dr. Svalgaard has provided to explain the modulating Jupiter Perihelion.
“The general principle is that to change the orbit, you have to apply a force along the orbit, so Saturn’s effect is largest when it is ‘to the side’ (approximately quadrature I think the astrological term is), rather than in conjunction. All of this has been understood for 250 years, and there are no other forces involved. Saturn doesn’t ‘push’ (gravity is attractive, not repulsive). And the Sun is not ‘dragging’: the force is always along the line connecting two bodies.
To recapitulate how Kepler’s second law works: To move an orbit out a bit (increase perihelion distance if you are near perihelion), you apply a force along the orbit in the same direction as the movement of the planet, e.g. by Saturn being ahead of Jupiter. That force produces a ‘delta-v’ (google it), which ‘lifts’ the orbit a bit out of the gravitational well, to another (higher) orbit, where it actually moves slower than before. Because of the periodic movements, the lifting is counteracted over time by a similar but oppositely directed movement, so that the semi-axis stays constant. This takes a couple of orbits to accumulate, so you have to consider the integrated effects over many years.”
There is substantial merit in Dr. Svalgaard’s rejigged explanation, but there still remains some pertinent questions. The explanation works well for perturbations occurring in the 1/2 to 3/4 region before Perihelion, but perhaps not so well in others. Dr. Svalgaard explains its a matter of the smaller background oscillations that make it hard to track the source of the perturbation. This is plausible but maybe a little weak and may be the reason it is near impossible to find any reliable data on this topic via the web. In particular I have questions why the “force along the orbit” fails to work when Jupiter approaches Perihelion and actually looks to have an opposite effect. Remember, when Jupiter & Saturn are in conjunction the Perihelion distance is at its shortest, but as you can see in the following diagrams the substantial pull along the orbit fails to elevate Jupiter’s orbit to a higher state.
The red dots signifies Perihelion in this 1762 example:
I wanted to see the perturbation affects plotted with successive orbits to see how the planets contribute to Jupiter’s orbit changes. Although fairly easy when you know a couple of tricks (thanks to Dr. Svalgaard) this task took me many days. I plotted the JPL data into excel and once the orbit was expanded to a size too big to display here it was easy to see each individual orbit. I was lucky with my data selection because it included a very strong perturbation of the 1987 Perihelion. The orbit has Jupiter doing a fly past Saturn, Uranus and Neptune before Perihelion which manages to take it away from its more normal path by 6 million kilometers. Once Jupiter passes all 3 planets its orbit is dramatically “braked” which brings it back into line around Perihelion, but still manages a very long perihelion distance. This is a good example of the perturbation theory in practice.
The corresponding planetary view shows the relative positions of planets which line up with the above average perturbation.
So do we have a situation where the perturbation theory works in some parts of the orbit only? Could other forces be overriding this perturbation? The orbit changing mechanics have been described as speeding up the planets velocity (I have serious reservations that this occurs) which raises it up the gravity well to a higher orbit before settling into a slower overall velocity.
UPDATE:After much research I think I finally have the cause for Jupiter’s Perihelion distance modulation….and it surprising how little is known or published in this area. The above example is not worded very well and leads you to think an acceleration lifts the orbit higher then slows the velocity (that’s at least how I read it), from what I now understand it actually happens in reverse…the acceleration moves the orbit closer (following Kelper’s 2nd Law) but then unlike a rocket using boost, Jupiter is then immediately subjected to deceleration from Saturn’s gravity which slows velocity in turn lengthening the radius vector or raising Jupiter to a higher orbit. As Jupiter moves further away from Saturn the Sun takes over and reins in its sibling and waits for the next perturbation. So now it becomes obvious, and completely explains why a Jupiter/Saturn conjunction causes a short Perihelion, Jupiter is always in acceleration mode during this lineup which causes it to move closer and the plotted orbit agrees. Also of note, Neptune and Uranus also help out and can be strong when together as we see elsewhere on this site.
The orbit spreadsheet is able here: http://users.beagle.com.au/geoffsharp/jup_orbit1940-2009.xls | <urn:uuid:695750c9-91ac-466c-ab8e-968a49cf2bb1> | 2.71875 | 2,091 | Personal Blog | Science & Tech. | 45.871252 |
|Google Maps shows you the Cape Verde Islands in|
relation to the rest of the Eastern Atlantic Basin
Typically we end up with approximately two Cape Verde type storms per season. July, August, and September are the prime months for development, but we can see them in June and October as well. Katia and Ophelia were classified as Cape Verde hurricanes last season. Other notable Cape Verde storms in recent years include Ike (2008), Ivan (2004), Frances (2003), Isabel (2003), and Floyd in 1999. Andrew, Hugo, Gilbert, Gloria, Donna, the 1938 Long Island Express, the hurricane of 1933, and the deadliest of all US storms, the 1900 Galveston hurricane were all also Cape Verde storms. So Cape Verde hurricanes are also associated with monster storms because when hitting the US (or elsewhere), many have been monster, deadly, and damaging storms.
Very rough estimates, using NOAA's historical hurricane archive, suggests roughly once every four years or so, one of these will hit the US Mainland. There may be more official or proven statistics out there on that, but I was unable to locate any. Of more interest: Of the 128 storms or remnants of storms to pass within 200 nautical miles of northern Delaware (which includes the entire Delaware Valley, west to Altoona and east to about 150 miles offshore of NJ) since the 1800s, roughly 16 would be classified as "true" Cape Verde storms (forming within about 600 miles of the Cape Verde Islands). About 1/3 of storms or remnants of storms impacting the Delaware Valley or Jersey Shore form east of the Lesser Antilles.
So the bottom line: The longest lasting, occasionally powerful hurricanes we see in the Atlantic are very often the Cape Verde storms. And we'll watch to see if our latest Cape Verde type storm, Isaac, amounts to another notch in the belt. | <urn:uuid:2b10e986-5445-48d6-8160-686b745bfc5a> | 2.765625 | 389 | Personal Blog | Science & Tech. | 42.252231 |
by Dan Lester
|If humans could get close to the planetary surface, perhaps just in orbit above it, truly cognitive teleoperation could be achieved at multiple sites with high-quality virtual presence.|
This vision seriously colors the public view of space robotics in ways that are less than constructive. While Spirit and Opportunity move, see, and can even touch, they conform only loosely to that public view of robots. Cassini can move and see also, but the popularization of the word “robot” fits it even less well. It doesn’t have legs, arms, or even wheels! Certainly Robonaut 2 on the International Space Station is widely appreciated as a robot, because although it hasn’t really done much yet, it has a head and fingers, and it can even sign a greeting and shake a hand!
As noted in my earlier essay (see “Human spaceflight, and the reason for (almost) being there”, The Space Review, July 5, 2011), using machines to bring our cognition to new places in space is an effort seriously handicapped by distance, the speed of light, and resulting communication delays. When we think of such machines operated from Earth, they involve some level of autonomy. We upload an instruction set and a task plan, tell the machine to please be careful, let it do what we tell it to do, and wait patiently until it reports back. It’s not unlike a parent-child relationship. It is in this way that human exploration looks comparatively attractive in that, by physically going somewhere, humans can really experience a venue in a fully cognitive and, shall we say, adult manner, on time scales consistent with the human reaction time.
For space applications at a distance (Mars, for example), control from the Earth involves many minutes of delay that make teleoperation highly non-cognitive. As a teleoperator, it’s hard to feel like you’re really there, though Mars Exploration Rover operators have claimed to be able to do so at some level. But if humans could get close to the planetary surface, perhaps just in orbit above it, truly cognitive teleoperation could be achieved at multiple sites with high-quality virtual presence. This strategy, of space exploration by telepresence, was envisioned independently by Fred Singer and Marvin Minsky in the late 1970s, a time at which our technology simply wasn’t up to the task. It is now.
In this way, much as for the teleoperation we do now with machines on Earth—in mines, on the deep sea floor, and even for surgery—the machines hardly require any autonomy. These “robots”, as we call them, can be just tools that extend the senses and dexterity of a human to a particular site, which may be distant. In this way, automobiles are telerobots that we all use, as we sit in the drivers seat. With a steering wheel, levers, and pedals, we remotely control the actions of the wheels underneath. Not exactly control at a distance, but not conveniently close. We watch the gauges, as well as look out the window, to sense the performance of the vehicle. Bulldozers are telerobots that move earth in response to commands given from the cab on top. These are tools that extend (and can even magnify) our dexterity and strength. Telephones are tools that extend our auditory presence. Are they really “robots”? Certainly not in Issac Asimov’s model. I hardly worry about the morality or faithfulness of my car. But these machines are physical extensions of the person using them, who may well say “I, Robot”, with some accuracy. The “I” is that controller person, whose cognition and dexterity is just being transmitted somewhere else. It isn’t the machine, which is just a tool in which that cognition and dexterity is manifested.
|The word “robot” can be distressingly imprecise.|
In this short essay, it is worth touching on a recent paper in the journal Astronomy and Geophysics titled “Dispelling the myth of robotic efficiency” by Ian Crawford at Birkbeck, University of London. Crawford has chosen to give new breath to the exasperatingly archaic humans-versus-robots argument about space exploration. He concludes, somewhat differently than the view of physicists Bob Park and Steve Weinberg, that humans are vastly better than robots for doing space science. Crawford does add somewhat to the discussion by attempting a real value assessment, as in science-per-dollar, though his assessment is debatable in many respects. His definition of “robots” is clearly restrictive, as in robots without astronauts, and robots controlled from Earth. In the Singer and Minsky picture of on-orbit telerobotics, such a view is unreasonably narrow. A different question about robots and space exploration is perhaps more germane. Given that human cognition is highly advantageous to space science, what is the best way to bring that human cognition to an exploration site? It may be that machines can be a big help.
In these ways, the word “robot” can be distressingly imprecise. To a layperson, the word connotes some level of intelligence that, I suppose in a very loose and generous way, my automobile might just have a little bit of. But the machines that we will teleoperate on distant planets, ideally from a control station suitably close by, will be remote control tools: cameras to help us see, haptic sensors to help us feel, and the equivalent of prosthetics to help us manipulate, rather than machines with any sense of “self”. Now, some level of autonomy might still be valuable in improving their operational efficiency, and certainly our powers could be expanded, but the zero-order architecture is one in which these units are simply extensions of… us.
Perhaps we shouldn’t call these things robots at all, with all the Asimovian baggage that word carries. Maybe “cognibot,” which transmits our cognition to another place, or “humabot,” which brings our humanity to a new venue. Perhaps “telepresences,” as suggested by futurist/ideonomist Pat Gunkel. Maybe just “electromechanical puppet” or, even simpler, “marionette.” But when we talk about achieving tasks in space with low latency control, with modern sensors and high-dexterity haptically-enabled manipulators, let’s not fall back on the tired excuse, “Oh, but robots can’t do that.” Because these aren’t robots. They’re us. One step removed. | <urn:uuid:45ccad84-8f79-44fe-99ea-33dc8b125689> | 2.90625 | 1,417 | Nonfiction Writing | Science & Tech. | 40.448367 |