text large_stringlengths 148 17k | id large_stringlengths 47 47 | score float64 2.69 5.31 | tokens int64 36 7.79k | format large_stringclasses 13 values | topic large_stringclasses 2 values | fr_ease float64 20 157 |
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An efficient implementation of maps from integer keys to values (dictionaries).
These modules are intended to be imported qualified, to avoid name clashes with Prelude functions, e.g.
import Data.IntMap (IntMap) import qualified Data.IntMap as IntMap
The implementation is based on big-endian patricia trees. This data
structure performs especially well on binary operations like
intersection. However, my benchmarks show that it is also
(much) faster on insertions and deletions when compared to a generic
size-balanced map implementation (see Data.Map).
- Chris Okasaki and Andy Gill, "Fast Mergeable Integer Maps", Workshop on ML, September 1998, pages 77-86, http://citeseer.ist.psu.edu/okasaki98fast.html
- D.R. Morrison, "/PATRICIA -- Practical Algorithm To Retrieve Information Coded In Alphanumeric/", Journal of the ACM, 15(4), October 1968, pages 514-534.
Operation comments contain the operation time complexity in
the Big-O notation http://en.wikipedia.org/wiki/Big_O_notation.
Many operations have a worst-case complexity of O(min(n,W)).
This means that the operation can become linear in the number of
elements with a maximum of W -- the number of bits in an
(32 or 64). | <urn:uuid:96e519f4-d41b-42a1-a595-b5d0799e6f5a> | 2.796875 | 303 | Documentation | Software Dev. | 46.998333 |
Chandra: Exploring the Invisible Universe
Sources: NASA and Harvard-Smithsonian Center for Astrophysics.
NASA's most powerful X-ray telescope, called the Chandra X-ray Observatory (CXO), was launched from the space shuttle Columbia on July 23, 1999. The spacecraft could remain in orbit for 25–50 years and the scientific mission should last about 5–15 years. Named in honor of the late Indian-American Nobel laureate Subrahmanyan Chandrasekhar, it was formerly known as the Advance X-ray Astrophysics Facility (AXAF).
X-rays are a high energy, invisible form of light. They are produced in the cosmos when gas is heated to millions of degrees by violent and extreme conditions. Much of the matter in the universe is so hot that it can be observed only with X-ray telescopes. The CXO is designed to study some of the great mysteries of the universe such as flaring stars, exploding stars, black holes, and vast clouds of hot gas in galaxy clusters. The telescope has eight times greater resolution and is 20 to 50 times more sensitive than any previous X-ray telescope.
Unlike the Hubble Space Telescope's circular orbit that is relatively close to the Earth, the Chandra X-ray Observatory has been placed in a highly elliptical (oval-shaped) orbit. At its closest approach to Earth, the observatory travels at an altitude of about 9,942 mi (16,000 km). At its farthest, 82,646 mi (133,000 km), it travels almost one-third of the way to the Moon. Due to this elliptical orbit, the telescope circles the Earth every 64 hours, carrying it far outside the belts of radiation that surround our planet. This radiation, while harmless to life on Earth, can overwhelm the observatory's sensitive instruments. The X-ray observatory is outside this radiation long enough to take 55 hours of uninterrupted observations during each orbit. During periods of interference from Earth's radiation belts, scientific observations are not taken.
During 2003, CXO, in conjunction with the Hubble Space Telescope, produced amazing images of the high-energy particles and magnetic fields of the Crab Nebula. The observatory discovered a galaxy with two supermassive black holes and also sent images of our closest supermassive black hole, Sagittarius A. In 2004, CXO reimaged the remnants of Cassiopeia A, which it had first photographed five years previously. The new photos showed bipolar jets reaching about 10 lightyears from the neutron star and revealed that the expanding cloud is rich in iron.
Chandra, along with the Hubble telescope, the Compton Gamma-Ray observatory, and the Aug. 2003-launched Spitzer telescope, is part of NASA's Great Observatories Program, designed to explore the universe by means of visible, ultraviolet, and near-infrared light (Hubble); X-rays (Chandra); gamma rays (Compton); and infrared radiation (Spitzer).
Information Please® Database, © 2007 Pearson Education, Inc. All rights reserved.
More on Chandra Exploring the Invisible Universe from Infoplease: | <urn:uuid:a3384ffc-f65a-4f42-b281-1c7df78e1e36> | 4.15625 | 643 | Knowledge Article | Science & Tech. | 41.020861 |
Polymers and UV Sensitivity
Date: June 2006
Why polymers with aromatic groups inside their
chain (as polycarbonate or PET) are less sensitive to UV then
polymers with side aromatic groups (PS)?
The UV sensitivity of a polymer depends on many factors than the
nominal chemical formula. Commercial polymers are most often
"formulated" with any number of additives to achieve a desired
balance of properties. So your statement may not be universally
true. Neglecting that caveat, the UV degradation process involves
the absorption of UV radiation (usually by the aromatic group) to
form a free radical that then initiates a series of different
reactions -- hydrogen abstraction, chain scission, ..., and so on.
An appended aromatic group is more mobile than an aromatic group in
the primary polymer chain, so it has more freedom to initiate these
degradation reactions. The aromatic group in the main chain is "tied
down" so the degradation reactions "tend" to be slower.
One of the reasons is that aromatic groups within the main chain
(such as those in PET) may be conjugated through carbonyl groups or
heteroatoms. Such combination of aromaticity, conjugation and
heteroatoms tends to lower the light absorption onset and the lambda
max (the wavelengths that the polymer can absorb). Moreover, this
combination also allows for multiple quantum levels of absorption so
that many different wavelengths can be absorbed.
Polymers with aromatic groups in the side chain (such as
polystyrene) are not conjugated since the aromatic group is
separated by the single bonds of the main chain.
However, polymers with side chains that have conjugation and
heteroatoms within the side chain are UV sensitive.
Greg (Roberto Gregorius)
Click here to return to the Material Science Archives
Update: June 2012 | <urn:uuid:d4347849-1af8-4540-a417-1bbcc7562d0b> | 2.734375 | 400 | Knowledge Article | Science & Tech. | 28.948231 |
Revista Brasileira de Ciência do Solo
Print version ISSN 0100-0683
CAMPOS, José Ricardo da Rocha et al. Pedochronology and development of peat bog in the environmental protection area pau-de-fruta - Diamantina, Brazil. Rev. Bras. Ciênc. Solo [online]. 2010, vol.34, n.6, pp. 1965-1975. ISSN 0100-0683. http://dx.doi.org/10.1590/S0100-06832010000600021.
In the region of the Serra do Espinhaço Meridional, peat bog is formed in hydromorphic environments developed in sunken areas on the plain surfaces with vegetation adapted to hydromorphic conditions, favoring the accumulation and preservation of organic matter. This pedoenvironment is developed on the regionally predominant quartzite rocks. Peat bog in the Environmental Protection Area - APA Pau-de-Fruta, located in the watershed of Córrego das Pedras, Diamantina,Brazil, was mapped and three representative profiles were morphologically characterized and sampled for physical, chemical and microbiological analyses. The organic matter was fractionated into fulvic acid (FA), humic acids (HA) and humin (H). Two profiles were sampled to determine the radiocarbon age and δ13C. The structural organization of the three profiles is homogeneous. The first two layers consist of fibric, the two subsequent of hemic and the four deepest of sapric peat, showing that organic matter decomposition advances with depth and that the influence of mineral materials in deeper layers is greater. Physical properties were homogeneous in the profiles, but varied in the sampled layers. Chemical properties were similar in the layers, but the Ca content, sum of bases and base saturation differed between profiles. Contents of H predominated in the more soluble organic matter fractions and were accumulated at a higher rate in the surface and deeper layers, while HA levels were higher in the intermediate and FA in the deeper layers. Microbial activity did not vary among profiles and was highest in the surface layers, decreasing with depth. From the results of radiocarbon dating and isotope analysis, it was inferred that bog formation began about 20 thousand years ago and that the vegetation of the area had not changed significantly since then.
Keywords : Organosols; soil organic matter; humic substances; microbial activity; radiocarbon dating; δ13C. | <urn:uuid:6deb5aee-af9e-4484-a314-0d3fac1f5ca5> | 2.953125 | 527 | Academic Writing | Science & Tech. | 36.411364 |
Studying the Cartesian Diver 2.25
Taking principles developed by Greek philosopher Archimedes more than 2,000 years ago, students constructed their own Cartesian Diver to study the relationship between buoyancy and density.
The Cartesian Diver is named for 17th century French scientist René Descartes although his connection to the experiment has never been found. A more correct name might be the Maggiotti Diver since it was Galileo’s student Raffaelo Maggiotti who claimed to have invented the device.
In the modern version of the experiment, students take a plastic pipette (medicine dropper) and thread a metal nut onto the stem. This is the diver.
The diver is partially filled with water—just enough so it barely floats upright in a container of water.
The diver is inserted into a soft drink bottle of water and the bottle is capped.
Now the fun begins.
When the bottle is squeezed, the diver dips down deeper into the bottle. When pressure is released, it quickly rises back to the top.
Why does it happen? Added pressure on the bottle compresses the air in the diver. It becomes more dense and sinks in the water.
It’s the same principle fish use to sink or float when a muscle squeezes or relaxes around an air sac. Similarly, submarines can be made to rise or sink by pumping water in and out of tanks.
|< Prev||Next >| | <urn:uuid:0458075b-5a4d-43b8-903c-684a33ea9b5d> | 3.78125 | 301 | Nonfiction Writing | Science & Tech. | 55.37181 |
In the previous php mysql tutorial
we went over the basics of php and mysql. With some information on installing the software(s).
Setting up a MYSQL Database
Before we go any further the first thing we need to do is create a database so we know what to build our php scripts around. For this tutorial we are going to base our examples on an address book application. Really database construction is a whole tutorial on it own, If you are planning to create a fairly complex site your going to need a database to match. Here is a list of mysql relational database pages.
1. Mysql Relational Database training couse - http://www.wellho.net/course/mqfull.html
2. Official MYSQL Relational database white paper, features some good information. - http://www.mysql.com/it-resources/wh...s/embedded.php
Okay back to our tutorial, there is a few ways in which you can create the database for example you can use a powerful GUI application called phpmyadmin http://www.phpmyadmin.net/
for more information on installing phpmyadmin visit the site. or you can manually do it using a php script both are as acceptable as each other but do try out phpmyadmin.
Okay now we need to decide on what we want our database to store and how it stores the information. Considering we are going to use an address book as our tutorial lets consider what we will need to take from the user in order to make it a useful program. Here is a list of fields that we will be using during this tutorial feel free to add your own if you feel confident enough just remember to keep the changes consistant though the series of this tutorial:
# First Name
- Pretty obvious
# Last Name
- Again… Pretty obvious
# The persons phone number
- We’ll assume the maximum a phone number can have in the UK is 11 Digits I think it is true in the UK (were I’m from)… I could be wrong.
# Mobile Number
This will store the mobile phone number of that person allowing 11 numbers to be stored as the mobile number.
# The persons email address
- This will store the email address of that person.
# Country Of Residence
- This is were the individual is residin.
Great, now we know what we want out of our database lets go on to create the tables using a php script, but feel free to use phpmyadmin here is a tutorial for phpmyadmin A quick note: http://www.micfo.com/flash/php.htm
This tutorial is fantastic as it’s a flash tutorial so it’s super quick to understand and do for yourself.
PHP Script: creating tables for the database
To create a table in php all you need to do is execute the following code once, on your system and php will create everything requested.
@mysql_select_db($db) or die( "Unable to select database Please contact the administrator.");
$query="CREATE TABLE address_book (id int(7) NOT NULL auto_increment,first_name varchar(50) NOT NULL,last_name varchar(50) NOT NULL,phone_number varchar(11) NOT NULL,mobile varchar(11), email varchar(50) NOT NULL,PRIMARY KEY (id),UNIQUE id (id))";
Okay now i’ll explain each element:
Lines 1-3: These are the variables which store our username, password and name of database all are required to connect to mysql. You can find out your username, password and database name through phpmyadmin, cpanel or your web hosts technical support.
Line 4: this is the mysql connect function it tells mysql your connection credentials and trys to login.
Line 5: Once mysql connect ‘connects’ us it then uses mysql_select_db function to tell mysql which database we would like to access. If for any reason we cannot connect due to server outage or mysqls off then the following error will be returned to the users browser.
“Unable to select database Please contact the administrator.”
Lines 6-10 - Will Create the SQL query:
# CREATE TABLE address_book - Creates the table address_book in the database we specified in line 5.
# id int(7) NOT NULL auto_increment - Create the ‘id’ field allowing upto 7 numbers to be entered no other characters will be allowed beacause we have specified this field int which means integer. its another way of saying number in mathematical slang. The auto_increment means to add one so the first entry will be 1 the second 2 and so on.
# first_name varchar(50) NOT NULL - This creates the first_name field and sets it to a maximum number of letters, characters or numbers in this case it’s fifty varchar() means you can enter letters, characters or numbers into the mysql field. NOT NULL is another way of saying not empty.
# last_name varchar(50) NOT NULL, - Creates the first name field. Limited to 50 chars.
# phone_number varchar(11) NOT NULL, - Creates the phone_number field. Limited to 11 chars. NOT NULL so the field is required.
# mobile varchar(11) - Creates the mobile field. Limited to, again 11 chars. This field is not required. as NOT NULL is not specified.
# email varchar(50) NOT NULL, - Creates the email field again not required and limited to 50 chars.
# PRIMARY KEY (id),UNIQUE id (id))”; - This means the ‘id’ field is the primary key or in other words the field is used mainly for indentification. UNIQUE means that this field cannot contain muliple records with the same ‘id’.
Now all you need to do is upload the code in a text file and run the script in your browser, Once you’ve ran it then check in phpmyadmin to see if the table and fields have been created.
See the web version at my blog www.chauy.com
, why not have a quick look in the php tutorials
section if you have a little free time.
Part 3 Coming Soon. Thanks for letting me ramble | <urn:uuid:4b6ec204-7d5c-47e3-b686-8feb6d4466ce> | 2.90625 | 1,375 | Comment Section | Software Dev. | 63.891374 |
Weight and mass are not synonymous.
Weight is a force.
The weight of an object depends on its location - things can weigh differently in different places.
The first thing to realize about weight is that weight is not the same as mass, even though the terms are used synonymously in everyday life. Mass measures inertia - it is a property of an object. Weight is a force - something that happens to an object.
Physicists and engineers all agree that weight is a force, but there is considerable disagreement and confusion about what force weight is - different textbooks say different things, and some textbooks say different things in different places. Mostly, opinion is divided into two camps. For some people, "weight is the force of gravity", and for others "weight is what a scale reads". You might think that the two statements are equivalent - but they aren't. There are advantages and (unfortunately) disadvantages with either point of view.
Our text, among others, says:
Weight: The force of gravity upon a body.1
This is not the intuitive, laymen's definition of weight. You can't feel the force of gravity. You feel the floor pushing up on you, not the downward pull of the Earth. You don't feel pulled toward the Earth, even when you jump into the air.
There is a standard definition of weight, given by the International Organization for Standardization (ISO) which says:
The weight of a body in a specified reference system is that force which, when applied to the body, would give it an acceleration equal to the local acceleration of free fall in that reference system. - ISO 31-3 "Quantities and Units. Part 3, Mechanics", 19922
Can this be simplified without losing precision? Yes! It turns out that this definition of weight is equivalent to saying:
Weight is what a scale reads.3
which is equivalent to saying:
An object's weight equals the force required to support it.4
It seems at first that this is a much more natural, practical and useful way to look at weight than associating weight directly with the force of gravity. ("What a scale reads" and "the force of gravity" are not always equivalent - see The Elevator Problem for details...) This definition - weight is what a scale reads - also fits quite naturally with the idea of "weightlessness".
In order to use this definition effectively in applications requires a pretty sophisticated understanding of Newton's Laws - particularly Newton's Third Law - which most beginning physics students generally don't have. (No offense intended...)
In this course, we will follow the text's lead, and say that an object's weight equals its mass times g.
1 Hewitt, Conceptual Physics, p32
2 Weight - An Official Definition, Mario Iona, The Physics Teacher, Vol 37, p. 238 (April 1999)
3 adapted from Weight - An Accurate, Up-to-Date, Layman's Definition, Roy Bishop, The Physics Teacher, Vol. 37, p. 238-239 (April 1999)
Weight and Gravity - The Need for Consistent Definitions, Richard C. Morrison, The Physics Teacher, Vol 37, p. 51-52 (January 1999)
Weight - A Pictorial View, Andrzej Sokolowski, The Physics Teacher, Vol 37, p. 340 (April 1999)
Weight - Don't Use the Word at All, Ronald Brown, The Physics Teacher, Vol. 37, p. 341 (April 1999) | <urn:uuid:2cbb6efa-05f2-489e-be06-975c3bb4f754> | 3.65625 | 722 | Knowledge Article | Science & Tech. | 62.420323 |
Black Sea chemistry and biodiversity is highly coupled with the lack of vertical currents, present in oceans or bigger seas. (Some ) effects are limited salinity in the top layers - and many ocean fish species cannot live in black sea - and limited space for life (under 50 meters there is no oxygen)
Can the jellyfish population (which is exploding now) change the stratification of water layers enough that the highly saline waters from bottom go up, and oxygen goes down, allowing a completely new ecosystem here?
If yes, what are the outcomes of such prospects? Besides the potentially catastrophic release of hydrogen sulphide form the bottom, can it be an improvement for the biodiversity here? | <urn:uuid:b4b49e1b-19ac-462e-a777-8c7270dd857e> | 2.8125 | 137 | Q&A Forum | Science & Tech. | 25.033816 |
How should you start? What are the best and easiest ways to create a website, and what is each of these languages people talk about?
HTML, CSS & PHP.
ASP & C#.
So you want to learn programming? Interested in those shiny websited, applications you use at your job, or maybe the huge amounts involved with about each and every ICT project?
In this article i will give you some advice as how to start, and a short explanation about every language. I will try to put it in understandable language with only good to know information for a starting programmer.
To start. There are a lot of languages and manners as to how to program. Even a website can be programmed in a lot of ways. I will tell you about three.
1. HTML, CSS and PHP.
HTML is the language you need to build up the structure of your webpage. You create colums, descide where images and text will be placed, and design the structure. However, this will be combined with CSS. CSS is kindof the definition about how the HTML looks. To explain: If you create a column with HTML, you can use CSS to define the size, color, etc.
PHP is the language/script used for calculations. If you have a page, and have a button on it, you can look at it like this: The button is made with HTML. CSS is used to edit the button. and PHP is the function from the button. Meaning if you click on it, PHP will be used to do whatever the button is supposed to do.
2. ASP.net and C#.
ASP.net is from Microsoft, and often used by people with a bit more then no experience. Where some people think PHP is a unprofessional, both of these ‘languages’ have their pro’s and cons. For example hosting is cheaper when using PHP, but ASP is easier to use. Why? Because there are a lot of boundaries. Where in PHP you can program anything, with ASP you are limited to C#. C# is object oriented, making it a lot more organised and easier to use. Especially large applications are easier in C#, because PHP doesnt give immediate feedback when you type a weird or bad piece of code.
To give a bit more explanation about ASP and C# rather then PHP: ASP is the front of the website. You can use HTML and CSS in combination with ASP. To give you and example: If you create a column, you do that with HTML. If you want to give it certain sizes or a different color, you use CSS. But instead of using an HTML button, you use an ASP button. This ASP button is immediatly combined with a C# method. I prefer this method, because when used right, it gives you a lot of control over your applications.
SO: When someone clicks on the ASP button, a method from C# will be called. And in that method you can define what should happen. Another good difference is that each HTML/ASP page has just one C# code page. Making everything even more clear and preventing unknown effects in your code.
Known to some, and not to other people. But its also possible to build websites just by searching online. There are plenty of webbuilders that just allow you to drag and drop your content. This is a good option if you are not going to use your site for anything with money or advertising. Because you dont write your own code, you also cant add certain tricks in your code to make them show up on google a couple of spots higher. If you just want to show information or have a forum, its THE option that takes little time. If you want to build a webshop or a site that uses advertisements to earn you ‘big money’ you should consider building it.
SO: If you are new, and just want to try some stuff: Go start with HTML and CSS. Just get a development kit like HTML KIT or dreamweaver. When you have a bit more experience, consider adding PHP to actually create a webshop or something. After you did that, its a lot of fun to try a programming language like JAVA or C#. I will create another article where i talk about real programming languages. But if you dont want that/did that, its a good idea to start with ASP and C# applications. Its hard to learn without experience, but when you have that experience its easy to use.
Your choice, and have fun! Feel free to ask any question! | <urn:uuid:0d960089-f23b-457d-bacd-4351cd994a03> | 2.984375 | 945 | Tutorial | Software Dev. | 71.902623 |
The Pennsylvania Migration Count (PAMC)
Posted: April 30, 2011
Saturday 14 May, 2011
*What is the Pennsylvania Migration Count? The Pennsylvania Migration Count (PAMC) was established to gather annual data on migratory bird populations, and to help answer some fundamental questions regarding their distribution throughout Pennsylvania. PAMC is an annual one-day snapshot of bird populations within our state. Which species are present, and where are they? How many are there? Do migratory patterns change from year to year? Do populations of specific species change from year to year? Which birds are thriving, and more importantly, which are struggling? By identifying declining or otherwise at-risk species, it is hoped that steps can be taken toward assisting their future survival.
*How does it work? The Pennsylvania Migration Count takes place each spring on the second Saturday in May, in conjunction with International Migratory Bird Day. PAMC is similar to the Christmas Bird Count (CBC). The difference is that PAMC takes place on a countywide basis, rather than within the confines of a CBC circle. The rules are simple: spend some time in the field counting all birds encountered in a specified area, and keep track of miles traveled and time spent counting. Participants are free to roam their favorite county birding locales at any time during the 24 hour period, starting at 12:01am, counting every bird that they find. Totals are passed along to county compilers, who, in turn, report to the state compiler. The state compiler maintains the PAMC data, and an annual report is published in Pennsylvania Birds, the journal of the Pennsylvania Society for Ornithology (PSO).
*When was it initiated? The Pennsylvania Migration Count originated as part of the continent-wide North American Migration Count (NAMC) in 1992, when there were 141 observers in 10 Pennsylvania counties. The count grew steadily in popularity in PA over the years, and was renamed PAMC in 2003, reflective of the fact that the national count was struggling everywhere but in Pennsylvania. Last year 704 observers from 40 counties participated in the PAMC. They counted 153,429 birds of 219 different species in over 2248 field hours. This year there are already more counties committed while we are always looking for more people to help.
*How can I get invovled? Birders of all skill levels can help out with the count. Beginning at midnight with the songs of the Whip-poor-wills and the hooting of the Great Horned Owls, the PAMC is a great way to spend time outside. Whether you tally birds in your backyard, at your feeders, the local little league ballfield, along the river, on a lake, at your camp or spend time hiking through a state park, your observations count. Forms and information for PAMC participation are available from your county compiler, or go online at http://www.pabirds.org/PAMC/Index.html Data can be submitted via e-mail or post. If participating or for more information, please contact the county compiler first, to avoid duplicate submissions from the same area. If no compiler, contact PSO@PABIRDS.ORG for submission or assistance. | <urn:uuid:36bf9314-d4d8-4099-8cc0-b6429af059e2> | 2.921875 | 670 | Knowledge Article | Science & Tech. | 51.242219 |
Michael Fowler UVa
A very simple spreadsheet animating the process. Press and hold the end of thescrollbar.
This spreadsheet plots the motion of a damped oscillator: you can specify the initial conditions and degree of damping, and find critical damping.
An external driving force is added to the previous spreadsheet: see how damping and resonance compete.
Find out how the period of a real pendulum varies with the amplitude.
From Vladimir Vasc, in the
Kinds of waves in one dimension: transverse, longitudinal, traveling, standing.
How applying F = ma to a little piece of string leads to an equation that describes many different waves.
What happens to a wave when it reaches the end of the string?
Deriving the Wave Equation for sound waves in a pipe. Energy density and power in a sound wave in a pipe.
Extending the Wave Equation to higher dimensions. Huygens’ picture of wave propagation. Young’s two-slit measurement of the wavelength of light.
Finding these forces and applying Newton’s Law to a small piece of string is the way to the Wave Equation. Flashlet by Patrick LeDuc.
Water Waves from Two Point Sources Java Applet by Santosh Pisharody | <urn:uuid:44a01fb0-da41-4401-a8f8-a3d25f28f66e> | 3.8125 | 268 | Content Listing | Science & Tech. | 52.64 |
At the end of the pre-equilibrium stage, or a thermalizing process, the residual nucleus is supposed to be left in an equilibrium state, in which the excitation energy is shared by a large number of nucleons. Such an equilibrated compound nucleus is characterized by its mass, charge and excitation energy with no further memory of the steps which led to its formation. If the excitation energy is higher than the separation energy, it can still eject nucleons and light fragments (d, t, He, ). These constitute the low energy and most abundant part of the emitted particles in the rest system of the residual nucleus. The emission of particles by an excited compound nucleus has been successfully described by comparing the nucleus with the evaporation of molecules from a fluid . The first statistical theory of compound nuclear decay is due to Weisskopf and Ewing. | <urn:uuid:81b8cb71-e3aa-45ef-b0df-7bc6fd7e32b7> | 3.4375 | 176 | Academic Writing | Science & Tech. | 35.0125 |
Now for the solution to the question in my previous post, which asked what you can learn about , given the sequence of integers .
Nick Johnson commented:
Well, the obvious thing one can learn given just |(10^n)r| is the first n digits of the decimal expansion of r.
For example, when we are given , we can say with confidence that . If we wait long enough, we can learn as many decimal digits of as we want; in particular, to learn the first n decimal digits of , we can just wait for the th item of the list.
This seems like an awfully long time to wait, though. Not only that, but if we only look at the first, tenth, hundredth, thousandth,… elements of the sequence, we would be ignoring almost all the information in the sequence! Intuitively, it seems that we should be able to do better by taking more of the sequence into account. And indeed, we can.
The key is to realize that
Do you see why? Taking the floor of something never makes it bigger, so (in fact, it can never be equal since is irrational, but that’s not important for our purposes). Also, taking the floor of something reduces it by some amount less than one, so adding one to the floor gives us something bigger than the original; hence . Dividing through by n, we find that
That is, if the nth element of the sequence is k, then we know that must be between k/n and (k + 1)/n. Of course, this works for any number r, not just for .
Let’s see how this works. The first few numbers in the sequence are . After seeing the 3, we know that . After seeing the 6, we know that — so we have a better upper bound now (3.5) than we did before (4). After seeing the 9, we know , and so on. Notice that our lower bound hasn't changed yet. That won't happen until we get to , when we learn that . So our new lower bound is 3.125. But the upper bound at this step, 26/8 = 3.25, is actually worse than the upper bound that we would have found on the previous step, namely 22/7 = 3.142857… So in general, the upper and lower bounds that we find in each step might not be better than all the previous ones; we can just keep the greatest lower bound and the least upper bound that we've seen so far.
So, how good are these bounds? I wrote a little program to compute the best upper and lower bounds for various points in the sequence. Here's a table showing the best lower and upper bounds at various points in the sequence, and the decimal digits they give us confidence about.
|Term||Best bounds||so far|
As you can see, this method does much better than the method of just looking at powers of ten! At n = one million, we already know ten decimal digits of pi; by looking just at the one millionth element of the sequence, we would only know six digits. It turns out that in general, it is the case (which I will not prove) that on average, we can get approximately twice as many decimal digits by finding best upper and lower bounds this way instead of just looking at powers of ten.
In a future post I hope to make a graph of these upper and lower bounds and talk a little bit more about what’s going on—it turns out to be pretty interesting stuff! | <urn:uuid:4201c3df-ede8-4f27-8d22-88f160649446> | 3.5625 | 743 | Personal Blog | Science & Tech. | 74.837493 |
No, not because it was too young to drink! Scientists at the Max Planck Institute for Extraterrestrial Physics were looking at some X-ray objects, and discovered something really weird: a very bright X-ray source moving out of a galaxy at nearly 3,000 kilometers/second! This thing is a goner. If our Sun were moving at even one quarter of that speed, it would get thrown out of our galaxy.
Now, here’s the kicker: this isn’t just any old object getting tossed out of a galaxy, it is a huge black hole! How huge? About 300,000,000 times the mass of our Sun. You read that number right: 300,000,000. So there’s no way this is anything other than a black hole. We’ve only ever found objects this massive at the center of galaxies, where they presumably help hold it together. So how is it that this one is getting kicked out?
Well, the only things that ever give off enough energy to move something that massive that quickly are either giant mergers or giant explosions. But this would have had to be the most powerful supernova in history to cause a nearby black hole that massive to move that quickly. The only explanation that Stephanie Komossa’s team has come up with is that this happened from a huge merger of two humongous black holes. Simulations show that it might have looked something like this:
Up until now, this has only been predicted theoretically, and never observed. The only way that a merger can cause a kick like this is by emitting gravitational waves; this would be another piece of indirect evidence for gravitational radiation, and this is also the exact type of merger that LISA is being designed to look for.
This means a number of cool things, including:
- There are some galaxies that lose their supermassive black holes in the center. Could the Milky Way, with its puny 3,000,000 solar mass black hole, have had this happen in the past?
- Galaxies and their black holes might have formed together, but that’s no guarantee they’ll end up together.
- If the theories are correct, we will be able to detect the gravitational waves coming from these mergers directly in the relatively near (~15 years) future.
So this is big news! I wonder what happens to these ejected black holes? Do they just travel through intergalactic space, eating up whatever’s in their way like giant death stars?
Or do they find their way into other galaxies and merge with them, creating super-duper-massive black holes? It makes me so happy that we can ask these questions, and that we’re starting to understand how one more thing in the Universe works. You can read the full press release here. Hooray for science! | <urn:uuid:24a02fc5-372b-48a7-b1a2-2fca23e74741> | 3.546875 | 593 | Personal Blog | Science & Tech. | 59.908153 |
Record Melting in Greenland
Here's what I think: The knuckle-dragging foolishness about global warming of the sort we're seeing in Montana or hearing on NPR isn't going to last much longer, because things are going to get very serious very soon. This image from microwave data from NASA's invaluable Earth Observatory shows anomalous days of melting for 2010--a new record, 50 days more than usual.
Melting ice in Greenland freshens the seas near the Arctic and contributes to rising sea levels around the world. It is unclear just how much melting ice from Greenland will push sea levels up, largely because the melting is occurring much more quickly than scientists predicted. Current estimates call for an increase of up to 0.6 meters by 2100.
That's two feet. The consequences of even a one-foot rise in global sea level will get everyone's attention in a hurry. If we don't want to go there, though, we've can't afford to dawdle now. | <urn:uuid:980bcf18-f42c-47bd-b030-7b13af8feee8> | 2.984375 | 203 | Personal Blog | Science & Tech. | 62.996525 |
, common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s the Burgundy snail
, Roman snail
, edible snail
or escargot, is a species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of large, edible, air-breathing land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
, a terrestrial
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
pulmonate gastropod mollusk in the family Helicidae
The Helicidae, sometimes known as the typical snails, are a taxonomic family of small to large, air-breathing, land snails. In other words, they are terrestrial pulmonate gastropod mollusks....
. It is a European
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
This species is frequently farmed
Heliciculture, or snail farming is the process of farming or raising land snails specifically for human consumption, and more recently, to obtain snail slime for cosmetics use....
, and is called by the French name escargot when it is used in cooking.
Distribution of Helix pomatia
south-eastern and central Europe:
- Germany - Listed as a specially protected species in annex 1 of the Bundesartenschutzverordnung.
- Czech Republic - least concern species (LC). Its conservation status in 2004-2006 is favourable (FV) in the report for the European commission
The European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....
in accordance with the Habitats Directive.
- In south-western Bulgaria up to an altitude of more than 1600 m.
- north and central Balkans
Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...
- Republic Of Macedonia
- Great Britain: in the west and south of England in southern areas on chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
soils. Its common name in the UK is "Roman snail" because it was introduced to the island by the Romans during the Roman period
Roman Britain was the part of the island of Great Britain controlled by the Roman Empire from AD 43 until ca. AD 410.The Romans referred to the imperial province as Britannia, which eventually comprised all of the island of Great Britain south of the fluid frontier with Caledonia...
(AD 43-410). In England only (not the rest of the UK) the Roman snail is a protected species under the Wildlife and Countryside Act 1981
The Wildlife and Countryside Act 1981 is an Act of Parliament in the United Kingdom and was implemented to comply with the Directive 2009/147/EC on the conservation of wild birds...
, making it illegal to kill, injure, collect or sell these snails.
- central France
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
- Listed as a protected species.
- south Sweden
- In central and southern parts of Sweden, Norway and Finland, there are isolated and relatively small populations. It is not native to these countries, but is likely to have been imported by monks from Southern Europe during medieval times.
- western Belarus
- western Ukraine (Uzhgorod)
- Russia: introduced to Moscow, Kursk
Kursk is a city and the administrative center of Kursk Oblast, Russia, located at the confluence of the Kur, Tuskar, and Seym Rivers. The area around Kursk was site of a turning point in the Russian-German struggle during World War II and the site of the largest tank battle in history...
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
: introduced to Kiev
Kiev or Kyiv is the capital and the largest city of Ukraine, located in the north central part of the country on the Dnieper River. The population as of the 2001 census was 2,611,300. However, higher numbers have been cited in the press....
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
is creamy white to light brownish, often with indistinct brown colour bands. The shell has 5-6 whorls
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...
. The aperture
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
is large. The apertural margin is white and slightly reflected in adult snails. The umbilicus is narrow and partly covered by the reflected columellar margin.
The width of the shell is 30–50 mm. The height of the shell is 30–45 mm.
In south-eastern Europe Helix pomatia
lives in forests and open habitats, gardens, vineyards, especially along rivers, confined to calcareous substrate. In central Europe in open forests and shrubland on calcareous substrate. It prefers high humidity and lower temperatures, needs loose soil to burrow in order to hibernate and lay its eggs. It lives up to 2100 m in the Alps, usually below 2000 m. In south England it is restricted to undisturbed grassy or bushy wastelands, usually not in gardens, with a low reproduction rate and low powers of dispersal.
Average distance of migration reaches 3.5–6 m.
This snail is hermaphroditic
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
. Reproduction in central Europe occurs from end of May onwards.
Eggs are laid in June and July, in clutches of 40-65 eggs. The size of the egg is 5.5-6.5 mm or 8.6 × 7.2 mm. Juveniles hatch after 3–4 weeks, and may consume their siblings under unfavourable climate conditions. Maturity is reached after 2–5 years. The life span is up to 20 years. 10 year-old individuals are probably not uncommon in natural populations. The maximum lifespan is 35 years.
Aestivation is a state of animal dormancy, characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions...
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
, this species creates a calcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
An epiphragm is a temporary structure which can be created by many species of shelled, air-breathing land snails, terrestrial pulmonate gastropod mollusks. It can also be created by freshwater snails when temporary pools dry up....
in order to seal the opening of the shell.
This species is listed in IUCN red list
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
as Least Concern. It is found at http://www.iucnredlist.org/apps/redlist/details/156519/0.
is threatened by continuous habitat destructions and drainage, usually less threatened by commercial collections. There were many unsuccessful attempts to establish the species in various parts of England, Scotland and Ireland; it only survived in natural habitats in southern England, and is threatened by intensive farming and habitat destruction. It is of lower concern in Switzerland and Austria, but in many regions there are restrictions on commercial collecting.
In popular culture
In the 2005 film What Is It?
What Is It? is the name of a 2005 dramatic film written, starring, funded and directed by Crispin Hellion Glover. It is described by IMDb as "The adventures of a young man whose principal interests are snails, salt, a pipe, and how to get home...
several of these snails appear: some die by crushing, others by salting.
Roumyantseva E. G. & Dedkov V. P. (2006). "Reproductive properties of the Roman snail Helix pomatia
L. in the Kaliningrad Region, Russia". Ruthenica 15
: 131-138. abstract | <urn:uuid:57c6d1da-b1a0-41e3-8af7-56026114418a> | 3.25 | 2,442 | Knowledge Article | Science & Tech. | 51.010237 |
milleporeArticle Free Pass
millepore, also called stinging coral, or pepper coral, (Millepora), any of a genus of invertebrate marine animals comprising the order Milleporina (phylum Cnidaria). Millepores are common in shallow tropical seas to depths of 30 metres (about 100 feet). Unlike the true corals, which belong to the class Anthozoa, millepores are closely related to the hydra. Both hydras and the millepores belong to the class Hydrozoa. Some species form branching treelike growths up to 50 centimetres (about 20 inches) high. Others form massive and shapeless or leaflike growths. Most are whitish, yellowish, or beige in colour. As with other cnidarians, they bear powerful stinging structures called nematocysts, which are used for defense and for capturing food.
What made you want to look up "millepore"? Please share what surprised you most... | <urn:uuid:5647e6f4-92dd-4950-a153-369ad58bd5fa> | 3.875 | 217 | Knowledge Article | Science & Tech. | 38.006364 |
The old parable says that if you teach a man to fish, you will feed him for a lifetime. But what if there were no fish to be caught?
In the Abrolhos region of Brazil’s Bahia state, CI and its network of partners are working to make sure that never happens.
The coastal waters there contain the most diverse concentration of marine life in the South Atlantic. The vibrant corals and extensive mangroves shelter hundreds of species, many of which live their entire lives within a few kilometers of the shore, providing residents of the region with their primary source of protein. But in recent decades, illegal fishing and destructive industrial and aquaculture practices increasingly threatened that abundance — and the livelihoods of the local communities who suffered the consequences.
Now, the tide is turning. By supporting the creation of the Corumbau Marine Extractive Reserve, CI helped to demonstrate how truly understanding and valuing the natural capital that sustains communities can pay far-reaching dividends. Through the establishment of both protected no-take zones and areas that allow fishing, the fish populations not only recovered — they thrived. And, as the fish from the no-take zones spilled over into the fishable waters, local fishermen saw an increase in their catch — nearly tripling their take of some commercially important species alone.
This bounty not only directly improved the livelihoods of local communities, it revitalized the regional economy as well, bringing with it the expansion of services like electricity and secondary education — services to which many in the region had never before had access. These positive changes also led to new, more sustainable opportunities in tourism, now the primary source of income in the region.
When CI began its program in Brazil, Abrolhos Marine National Park was the only marine protected area in the region. Since then, CI has helped to nearly quadruple the area protected and co-managed with local communities. And through ongoing scientific research into the connections between ecosystems, CI continues to inform marine protection practices that safeguard both biodiversity and human well-being. | <urn:uuid:161605d9-bfed-442c-a18c-9e65495de1de> | 2.984375 | 418 | Knowledge Article | Science & Tech. | 25.079565 |
Interviewee: Stephen Fodor.
Stephen Fodor talks about the photolithographic technique used to synthesize pieces of DNA on the surface of GeneChips™.
(DNAi Location: Manipulation > Techniques > Large-scale analysis > Interviews >
GeneChips™, step by step)
The way we make these DNA chips is that we actually build the DNA step by step at each location on one of these chips. In a process known as photolithography we excite with light a certain region on the chip and that prepares that particular site for chemical reaction. One of the four building blocks, A, C, G or T are applied and wherever we shine the light, that building block will stick and grow. And so we go through a multiple number of steps in this way, over literally millions of different sites on a large piece of glass, and what we get are literally millions of different precise locations on the chip, each with their own different strand of DNA on it.
stephen fodor,dna chips,manipulation techniques,dnai,precise locations,piece of glass,interviewee,chemical reaction,building blocks,strand
Igor Dawid and Thomas Sargent explain how they developed subtractive mRNA hybrization to find genes expressed by different cell types. Pat Brown and Steve Fodor show how genomes can be screened with DNA arrays and GeneChips� | <urn:uuid:1c139f2f-f759-46be-833d-d669d6797763> | 3.234375 | 294 | Audio Transcript | Science & Tech. | 33.361268 |
For some people, the best part about buying a new car is its factory-fresh new car smell, a distinctive aroma created when the chemicals and residual solvents used to manufacture dashboards, car seats, carpeting and other vehicle appointments outgas and fill the cabin.
While the scent may be alluring to some, many researchers believe exposure to these gases isn't particularly healthy — so unhealthy, in fact, that some recommend that drivers keep their new cars ventilated while driving.
Outgassed solvents, epoxies, lubricants, and other materials aren't especially wholesome for contamination-sensitive telescope mirrors, thermal-control units, high-voltage electronic boxes, cryogenic instruments, detectors and solar arrays, either. As a result, NASA engineers are always looking for new techniques to prevent these gases from adhering to instrument and spacecraft surfaces and potentially shortening their lives.
A group of technologists has created a low-cost, easy-to-apply solution, which is more effective than current techniques.
Led by Principal Investigator Sharon Straka, an engineer at NASA's Goddard Space Flight Center in Greenbelt, Md., the team has created a new, patent-pending sprayable paint that adsorbs these gaseous molecules and stops them from affixing to instrument components. Made of zeolite, a mineral widely used in industry for water purification and other uses, and a colloidal silica binder that acts as the glue holding the coating together, the new molecular adsorber is highly permeable and porous — attributes that trap the outgassed contaminants. Because it doesn't contain volatile organics, the material itself doesn't cause additional outgassing.
"It looks promising," Straka said. "It collects significantly more contaminants than other approaches."
Advantages Over Current Techniques
Instrument developers currently use zeolite-coated cordierite devices that look like hockey pucks. Because each individual puck has limited adsorbing capabilities, instrument designers must install multiple units, which require complex mounting hardware. "These devices are big, heavy and chunky, and take up a lot of real estate," explained Co-Principal Investigator Mark Hasegawa, of NASA Goddard.
The new paint, however, overcomes these limitations by providing a low-mass alternative. Because technicians can spray the paint directly onto surfaces, no extra mounting equipment is necessary. In addition, technicians can coat adhesive strips or tape and then place these pieces in strategic locations within an instrument, spacecraft cavity, or vacuum system, further simplifying adsorber design. "This is an easy technology to insert at a relatively low risk and cost," Hasegawa said "The benefits are significant."
Since its development, Northrop Grumman, Redondo Beach, Calif.; the European Space Agency; the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder; and Spica Technologies of Hollis, N.H., have expressed interest in using the material, Straka said. In addition, NASA's ICESat2 ATLAS project is evaluating its use, pending the outcome of additional tests, she said.
The team plans to tweak its recipe to enhance the paint's performance and experiment with different pigments, mainly black, to create a coating to absorb stray light that can overcome the light scientists actually want to gather. Straka also believes the technology could be used on the International Space Station or future space habitats to trap pollutants and odors in crew quarters.
"We're ready for primetime," Straka said. "The coating is undergoing qualification tests and is ready for infusion into flight projects or ground vacuum systems."
Lori Keesey | Source: EurekAlert!
Further information: www.nasa.gov
Further Reports about: contamination-sensitive telescope mirrors > cryogenic instruments > Goddard Space Flight Center > high-voltage electronic boxes > NASA > thermal-control units > volatile organics
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Ascophyllum nodosum with epiphytic sponges and ascidians on variable salinity infralittoral rock
Ecological and functional relationships
The biotope is found in very shallow submerged rocky habitats in lagoons, subject to variable or permanently reduced salinity conditions. These particular habitat conditions lead to a variety of seaweed-dominated communities which include fucoids and green filamentous species. The fucoids, more typical of intertidal habitats, penetrate into the subtidal under the reduced salinity conditions which are not tolerated by kelps.
The biotope is dominated by dense stands of Ascophyllum nodosum. The species, and the other macroalgae in the biotope, increase the amount of space available for attachment, they provide shelter from wave action, desiccation and heat, and they are an important food source. High abundances of the characterizing algae may contribute to the oxygen budget of lagoons. In the North Atlantic for example, Ascophyllum nodosum is of great ecological importance because of its high abundance on most sheltered rocky shores, where it must be a major contributor to the oxygen budget of shallow waters to a wide range of intertidal animals (Stengel & Dring, 1997).
Ascophyllum nodosum plants provide a substratum for a variety of attached animal species including the sponge Halichondria panicea, the sea squirts Ciona intestinalis and Botryllus schlosseri and some erect bryozoans.
Growth of epiphytic sponges and ascidians may be slower than in tide-swept habitats because the biotope has weak tidal streams and wave exposure and so will have a limited supply of suspended particles necessary for suspension feeding. However, low water flow environments will favour active rather than passive suspension feeders.
Seasonal and longer term change
has a very long life span where individual fronds can survive for 10-15 years and the holdfast for several decades. The longevity of A. nodosum
contributes to the stability of the biotope. Other fucoid plants found in the biotope, such as Fucus serratus
, have life spans in the order of 3-5 years. However, growth rates of macroalgae do show seasonal changes. For example, in Strangford Lough in Northern Ireland, Stengel & Dring (1997) observed the growth of Ascophyllum nodosum
to be highly seasonal with low growth rates during November and December, and highest growth rates in late spring and early summer. A decline in growth in mid-summer was observed at all shore levels. Faunal groups in the biotope are also likely to show seasonal variation in growth rates and recruitment.
Habitat structure and complexity
Fucoid biotopes provide a variety of habitats and refugia for other species. The dense beds of Ascophyllum nodosum
and the other fucoids in the biotope increases the structural complexity of the habitat providing a variety of resources that are not available on bare rock. Fronds provide space for attachment of encrusting or sessile epifauna and epiphytic algae and provide shelter from wave action, desiccation and heat for invertebrates. For example, the immediate effects of the removal of Ascophyllum
plants are to: destroy the epifauna and flora; increase desiccation; increase predation; increase erosion and aid settlement of other species (Boaden & Dring, 1980). Crevices in the bedrock and overhangs on fucoid rocky shores also increase habitat complexity by providing refugia for a variety of species.
On rocky shores, only about 10% of the primary production is directly cropped by herbivores (Raffaelli & Hawkins, 1996) and this is likely to be similar for lagoon-like habitats. Macroalgae, such as Ascophyllum nodosum
and other fucoids, exude considerable amounts of dissolved organic carbon which are taken up readily by bacteria and may even be taken up directly by some larger invertebrates. Dissolved organic carbon, algal fragments and microbial film organisms are continually removed by the sea and can make a contribution to the food of many marine species through the production of planktonic larvae and propagules which contribute to pelagic food chains. However, in lagoon-like habitats such as the SIR.AscSAs biotope, where tidal flows and wave exposure are weak larvae and propagules probably enter the food chain of local ecosystems rather than inshore subtidal or offshore ecosystems.
Many rocky shore plants and animals, possess a planktonic stage: gamete, spore or larvae which float in the plankton before settling and metamorphosing into adult form. This strategy allows species to rapidly colonize new areas that become available such as gaps created by storms. For these organisms it has long been evident that recruitment from the pelagic phase is important in governing the density of populations on the shore (Little & Kitching, 1996). Both the demographic structure of populations and the composition of assemblages may be profoundly affected by variation in recruitment rates.
- Fucoid plants are recruited from pelagic sporelings that settle on the substratum. Recruitment of Ascophyllum nodosum is generally poor and in the intertidal few germlings are found on the shore. However, in the sheltered conditions of the lagoon-like SIR.AscSAs biotope, recruitment from local plant stands may be more effective.
- The sponges and ascidians characterizing the biotope all have planktonic larvae and are fairly short-lived. There is therefore, high recruitment and high turnover.
Time for community to reach maturity
The time for an Ascophyllum nodosum
community to reach maturity is likely to be many years because the main characterizing species has very poor recruitment and is very slow growing. Ascophyllum nodosum
does not reach sexual maturity until about 5 years of age and, in the intertidal, individual fronds can live to be up to 15 years old and whole plants for several decades. In their work on fucoid recolonization of cleared areas at Port Erin, Knight and Parke (1950) observed that even eight years after the original clearance there was still no sign of the establishment of an Ascophyllum nodosum
population. There is a long-recognised shortage of sporelings (David, 1943) and the failure of the species to recolonize denuded areas for decades. However, the species is extremely fertile every year and Printz (1956) suggests it must be assumed that some special combination of climatic or environmental conditions is needed for an effective recolonization. If plants are not removed completely Ascophyllum nodosum
plants cut within 10-15cm of the base recover fully in 4-5 years (Printz, 1956). The epiphytic species are likely to colonize algae very rapidly. Most epiphytic species are likely to have planktonic larvae and rapid growth so that colonization of the algae will be rapid. For example, settlement of new colonies of Halichondria panicea
within one year is likely and the species increases in size by about 5% per week (Barthel, 1988). Recovery of the sea squirt Ciona intestinalis
, may take a little longer if adult populations have been lost because the species probably has limited dispersal because the larval stage is very short (hours or days) and larvae are often retained near the adults by mucus threads. However, in Plymouth reproduction is recorded as occurring all year round so recovery from loss within a few years should be possible. Even if some other epiphytic species take longer to return the recovery of the biotope is likely to limited by the recovery of the key species Ascophyllum nodosum
Information on the biotope has been based greatly on the general biology and ecology of Ascophyllum nodosum in the more common intertidal full salinity habitat. It is possible that in reduced and variable salinity lagoonal habitats life history characteristics of the species, such as growth rates, longevity and reproduction may be different.
This review can be cited as follows:
Ascophyllum nodosum with epiphytic sponges and ascidians on variable salinity infralittoral rock.
Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line].
Plymouth: Marine Biological Association of the United Kingdom.
Available from: <http://www.marlin.ac.uk/habitatecology.php?habitatid=328&code=1997> | <urn:uuid:4298afaa-1554-4eea-a48a-cefe22f09d5d> | 3.46875 | 1,852 | Knowledge Article | Science & Tech. | 20.701197 |
Do the Sources of
by Prakhar Naithani and Zack Heath
In this web page, you'll learn about the severe drought problems that NC has been through since the summer of 2007-2008.
You'll learn about how their water supply is in need and the course this battle will take and has taken to get the thirst in control before it can really cost them and is causing them.
This research we have done is through our curiosity of the fact about what has happened since the drought and using data and some research information, we have come up with an explanation about the influence of NC's water supply to the region's ability to withstand a drought. | <urn:uuid:e3208849-2544-4ade-8675-952a6fc9f32e> | 2.890625 | 134 | Truncated | Science & Tech. | 48.5 |
The color of light produced by a hot object depends on its temperature. This has to do with the fact that more energetic light produced a different wavelength of light. The wavelength, frequency, and energy of light are related by
This can be observed visually by considering a traveling wave. Consider a point
located in space, being moved up and down as it "sits" on a traveling wave. How often
that point oscillates will depend on the wavelength and the wave speed.
Notice how as the wave speed decreases and the wave length increases, the blue dot moves back and forth less often (i.e. has a lower frequency).
The amount of radiation given off by a hot object depends on two things, how hot it is, and what wavelength you are observing. The energy per unit area per wavelength is
Here h is Planck's constant (6.626E-34 Js), k is Boltzmann's constant (1.381E-23 J/K), and c is the speed of light (2.998E8 m/s). Units are in Watts per square meter per meter. The units make sense here if you think of the total energy given off as the blackbody radiation added up over the entire surface area of the object (Watts per square meter) and then summed up over all the different wavelengths of light (per meter).
The curve that this equation gives us changes over a wide range of both intensity and wavelength, and is usually plotted as a log-log plot. When blackbody emmission is observed, while we see light at many wavelengths, there will be one wavelength which is more prevalent than any of the others. This wavelength is approximately | <urn:uuid:52d29173-120f-4d5f-946b-77e8755f5b74> | 4.1875 | 346 | Knowledge Article | Science & Tech. | 60.397941 |
Your Environmental Footprint
Calculate your footprint and learn how to have less of an impact on the environment.
What is an environmental footprint?
Everything we do affects the environment around us, creating an environmental footprint that tells a great deal about us as individuals and as a society. As the world's
population increases, humans are encroaching upon wilderness areas and destroying habitats at an alarming rate. As a result, we are reducing biodiversity, causing the
extinction of many plants and animals, and ultimately threatening our own survival. But there are ways that you can assess and reduce the negative impact that your normal
daily routine can have on the environment. Below are some tools to help you determine how much of an impact your lifestyle is having on the natural world around you and
how to reduce that impact.
How are YOU impacting the environment?
There is no way to entirely eliminate the effect human beings have on the environment. But armed with the knowledge of how our everyday activities affect the world around
us, we can strive to pollute less and lower our energy use. Here are two different ways to measure YOUR impact, and learn how you can reduce it!
This carbon calculator from the U.S. Environmental Protection Agency determines your impact on the climate via carbon emissions. It uses your transportation and electrical habits to determine specifically what your carbon footprint is and offers ideas on how to reduce emissions and save money.
Calculate YOUR carbon footprint .
Calculate Your Footprint:
This footprint calculator takes into account where you live, how you travel, and what you eat, and it tells you how big your environmental footprint is. What if everyone
shared your lifestyle? How many planets would we need to sustain all of us? This calculator suggests answers to these questions and more.
Calculate YOUR ecological footprint .
Want to change your footprint?
Here are a few simple tips and tricks you can use to lessen your environmental impact!
Click each one to learn more.
Reduce, resuse, recycle — and compost.
- Carry a canvas grocery bag instead of using plastic bags in stores. Single-use plastic bags are a huge source of pollution. If you forgot your reusable canvas grocery bag, re-use those plastic bags, and when they're done, take them back to the grocery store. Many major chains have bag-recycling services.
- Avoid extra packaging where possible — for example, produce like potatoes, handled with care, probably don't need their own little plastic bag inside your grocery bag. And if all you're carrying out of the store is a single item like a loaf of bread, why get a plastic grocery bag to carry it in? By avoiding extra packaging, you save both energy and landfill space.
- Buy used instead of new. If you can find a lovely piece of furniture on Craigslist, in a thrift store, or through a friend, purchasing it instead of something new cuts down on material and energy resources that go into making and shipping a brand-new product. And you'll probably save yourself some money, too.
- Shipping something? Reusing packaging material, from cardboard boxes to plastic and "peanuts," saves even more energy than recycling.
- Aluminum cans are one of the greatest recycling successes, and aluminum is the only common recyclable material that can endlessly recycle without breaking down. Does your beverage of choice come in both cans and plastic bottles? Choose the former — and recycle it when you're done.
- Check the recycling numbers on your plastics to see what can be tossed into the recycling bin, instead of the trash. The more that gets recycled, the less goes into landfills or, worse, escapes into the great oceanic garbage patches — which contain great quantities of discarded plastic.
- Compost your yard and kitchen waste. This waste, which includes leaves, grass, and vegetable scraps, makes up 30% of trash — an amount you can significantly reduce by composting. You can do it yourself with a little research, or ask your city disposal organization — many cities are offering composting bins along with trash and recycling bins these days.
Save energy at home.
- Watch for vampire electricity drains — turn off the computer and game consoles when you're not using them, unplug the coffeepot (anything with a digital display continues to consume energy even if "off"), and turn off lights if you're not in the room.
- Look for energy efficient light bulbs — compact fluorescent lights have come a long way, and you can purchase fluorescent bulbs that imitate the warm glow of incandescence but can last ten times the lifespan of a traditional incandescent bulb.
- Replacing your appliances? Look for energy-efficient models — they will not only save energy, but also save you money when you run them.
- Lower your thermostat a bit in the winter and raise it in the summer; wearing a sweater during the winter and short sleeves in the summer saves energy and reduces pollution.
- Keep your windows and doors up-to-date and sealed, and keep your house insulated so that heat doesn't escape. Your heaters and air conditioners will not need to work as hard to maintain a comfortable temperature, and your energy bill will reflect the savings.
Cut emissions & reduce toxic chemicals.
- Consider efficiency when purchasing new cars or appliances. Look for fuel-efficient cars — there's quite a variety in today's market.
- Drive less often — alternative transportation can save you money even as it cuts emissions. Also look for opportunities to use public transit, bicycles, and carpools. Fuel economy decreases rapidly over 60 mph, so if you drive, try not to speed. And keep your tires inflated to recommended levels to increase their lifespan and save fuel.
- Buy local. When you buy local produce, it doesn't have to be trucked halfway across the country. That shrinks your carbon footprint. Lower your general consumption and choose products that take fewer resources to create.
- Dispose of old paint, chemicals, and oil properly. Don't put batteries, antifreeze, paint, motor oil, or chemicals in the trash. Use proper toxic disposal sites; your city or county disposal organization can guide you, so give them a call. Never buy more chemicals than you need.
- Reduce your use of heavy chemical pesticides and herbicides for your lawn and garden. That stuff gets into the water — fertilizer runoff is considered a major contributor to hypoxic "dead zones" in oceans and large lakes, where virtually nothing, including the fish, can live. Wean your plants off of chemical dependency and focus on increasing soil quality with organic mulches, composts, and the properly recommended application of organic nutrients, as well as beneficial soil bacteria and mycorrhiza. Your plants will be healthier for it.
- Eat less meat. Feedlots concentrate an unnaturally large number of animals and are a major source of organic pollution. In tropical areas, rainforest is cleared for cattle pasture. Local and organic foods reduce the energy costs of transportation and the excessive use of pesticides.
- Quit smoking. Second-hand smoke is a major indoor air pollutant and health hazard. When you quit, both you and your family will lead longer and healthier lives.
Conserve precious water.
- Check your home regularly for leaks, such as dripping faucets and running toilets, and fix them. You'd be amazed how much water can be wasted because of "minor" drips — water that is becoming an increasingly precious commodity.
- Take shorter showers and don't leave the tap running while you brush your teeth. It may seem like small water savings, but a shower a day and a couple of brushings really add up.
- Filling your high-efficiency dishwasher to capacity with dirty dishes before running it is the most eco-friendly way to do dishes. If you need to do some dishes by hand, don't leave the tap running. Fill a small bowl with soapy water to wash with and, instead of rinsing one dish at a time, wash as many dishes as your (clean) sink can hold before rinsing.
- Gradually reduce how often you water your lawn. Watering once a week during really tough dry spells should suffice, and if you water deeply rather than more often, it'll be healthier for it. Soggy lawns also attract moles, so you'll be doing yourself an extra little favor by drying it out.
- Water lawns and gardens only in the evenings or very early mornings. If you water during the heat of the day, most of that water is evaporating and not doing a bit of good to your plants.
- Plant native or drought-tolerant garden plants. They need less water than grass, can be very beautiful, and create habitat for birds and beneficial insects. Talk to a local nursery to see what fares well in your area.
Preserve wilderness, educate, & advocate.
- Plant native trees and plants in your yard. Your local nursery can probably help you pick out what will fare best in your mini-ecosystem, and the birds and butterflies, among others, will really appreciate your efforts.
- Plant native trees and plants in your neighborhood. If you're involved in neighborhood planting of public areas, talk to others about using native instead of introduced species to maintain wildlife habitat and reduce water and nutrient requirements. Many local organizations are involved with the planting of natives and the removal of invasive species in parks; join them and help out — many hands make light work!
- Take a walk in the woods with friends or family. Teaching our loved ones, especially our children, to love and care for natural spaces is an important part of caring for our future and will help them connect the dots between family recycling efforts and the natural world those efforts protect.
- Keep your cat indoors; if kitty wants to go out, purchase a harness and a leash and make sure you are on the other end of it while he or she explores. The American Bird Conservancy estimates that over 100 million birds are killed by cats every year. And your cat will probably have a longer lifespan indoors — away from the cars, dogs, coyotes, raccoons, parasites, and diseases that are also lurking outside.
- Stay informed. Keeping an eye on political and commercial developments that may affect the environment means that you can have an informed say in what ends up happening, whether through voting, sending letters to the city council, or asking a corporation to change their policy.
- Volunteer or lobby for the environment. Try working locally and globally to save natural places, reduce urban sprawl, lower pollution and prevent the destruction of wilderness areas for timber and oil.
Oh, yes. And don't forget to click every day ...
... to preserve habitat for wildlife, here at The Rainforest Site. Thank you for caring and for keeping it green!
A word about carbon ...
Carbon is a natural part of every known life form on Earth, and it is one of the most common elements on our planet. By itself, carbon is not a bad thing. But humans affect
the balance of the world's atmospheric gasses every day by how we live, travel, and choose to consume. Today, our actions are releasing carbon in the form of CO2 at an
alarming rate, leading to global warming.
Carbon travels in cycles. When we burn or destroy solid carbon-containing substances, whether by fuel ignition (gas-powered engines, energy from coal, natural gas, and even
wood fires) or artificially accelerated decay (burning forests to create pasture for beef cattle), we speed up the rate at which solid carbon becomes gas. Conservation of
fossil fuels and natural resources is one way to cut down on the amount of carbon dioxide we release into the atmosphere, but how do we take the CO2 that is already there
and restore it to a solid form? The answer is simple: Plant a tree.
Trees are carbon sinks. They absorb and process carbon much like people breathe oxygen. Through photosynthesis, some of that carbon is converted to solid form and stays
that way until the tree dies. By saving existing trees, and by planting more native trees in places where they can thrive, we can positively affect the atmosphere and
A final note ...
We can help safeguard the environment by becoming aware of the repercussions of our choices in life. Learning how to change your impact and being proactive in countering
the effects of global warming and environmental degradation are great ways to help. Take a moment to breathe the air and to look at the world around you. There are natural
wonders everywhere that are worthy of our admiration and respect. We must take steps to preserve and protect that beauty for ourselves and for generations to come.
In addition to all of the things you can do to help, please remember that you can make the world a better place every day here at The Rainforest Site, one click at a time.
Don't forget to click to save vital habitat every day! Visit The Rainforest Site, and click today. | <urn:uuid:69ddbede-93a1-465d-b721-cb008395c336> | 3.453125 | 2,692 | Tutorial | Science & Tech. | 48.948954 |
I have heard that there is no limit on the growth of trees, but then why do some trees, such as boxelders and poplars, tend to live shorter than redwoods, for example? Some advertisements for improved lombardy poplars state that their trees have an extended life span, up to 75 years?
Although most plants can potentially reproduce sexually, there are some plants that effectively always reproduce by shedding off branches that when fall in the right conditions, grow into new 'clones' of the same tree, which the exact genetic material. In these cases, it is advantageous for the tree to be able to survive as long as possible. Plants that reproduce sexually by the cross of two different individuals have a recombined genetic material in every generation, and the survival of that plant with that new genome is usually shorter. | <urn:uuid:994a4dad-f80f-49c5-ab65-fa5429d20dbd> | 3.515625 | 170 | Q&A Forum | Science & Tech. | 34.595 |
Hey, although I am novice with programming in c++, I would like to know "how to make a game." (I know that phrase is throw around alot)
I'm not going to attempt to any time soon, but I would like to know what it takes.
What are the steps and what do I need to know to do so? Could I make a simple tic tac toe game with only c++? Or do I need to know how to use something like opengl? And what exactly is opengl? Is it a programming language? Can it be compiled in a c++ compiler like bloodshed dev c++? If it's not a language, how do I associate it with c++?
Any help's appreciated. | <urn:uuid:86996e9b-7a74-470e-9911-8fad8bf2811a> | 2.765625 | 151 | Q&A Forum | Software Dev. | 82.238305 |
Average Temperature of the Northern Hemisphere based on published research. The black line at the right is instrumental data recorded since 1856; follow the link to see the other sources. Figure created by Robert A. Rohde and distributed under a Creative Commons License.
Today representatives from numerous countries and organizations are starting a conference in Copenhagen to discuss the changing climate. The meeting was intended to produce a new international treaty to replace the Kyoto Protocols from 1998. Whether such a treaty will be signed this month remains to be seen; some news reports have indicated that negotiations might continue into early next year.
Even if a treaty is signed, it is likely to result in lower emissions reductions than needed. The scientific consensus appears to be that the highest atmospheric carbon levels that the climate can tolerate without triggering catastrophic change is about 350 parts per million. Even that level would trigger some rather uncomfortable effects. Since we are already above that level, emissions need to be cut deeply rather than just stabilized. Most accounts I have read suggest cutting global carbon emissions 80% by 2050, with a somewhat lesser goal by 2020. In the past few months, Obama has suggested cutting U.S. emissions 4% by 2020 (with more cuts later), while European leaders offer a 20% cut (3o% if the U.S. agrees to do it to) by 2020.
To some extent, making a smaller cut now could start the ball rolling towards deeper cuts later. However, this present an element of risk. To date, temperature changes have tended to match the worst case forecasts presented by the IPCC. If that trend continues, even faster and deeper cuts may be necessary to forestall catastrophic changes. Our governments really ought to make a serious start now. | <urn:uuid:fc374bea-c85b-479f-a483-ec90f6cf8be3> | 3.21875 | 346 | Personal Blog | Science & Tech. | 46.881666 |
Declares an exception handler.
An exception handler may be declared to respond to a specific exception condition or one or more of the exception class groups SQLEXCEPTION, SQLWARNING or NOT FOUND. An exception handler that responds to one or more exception class groups is called a general exception handler.
A specific exception condition may be specified by using an SQLSTATE value or a condition name, see DECLARE CONDITION. An exception handler that responds to one or more specific exception conditions is called a specific exception handler.
The keywords CONTINUE, EXIT and UNDO affect the flow of control behavior subsequent to the execution of the exception handler.
If CONTINUE is specified, the flow of control continues by executing the SQL statement immediately following the statement that raised the error, after the handler has executed.
If EXIT is specified, the flow of control exits the compound statement within which the exception handler is declared after the handler has executed.
If UNDO is specified, all the changes made by the SQL statements in the ATOMIC compound statement, within which the handler is declared, (or by any SQL statements triggered by those changes) are cancelled. Then the handler is executed and the flow of control exits the compound statement.
An UNDO exception handler can only be declared within an ATOMIC compound statement.
An exception handler must be either a general or a specific exception handler, it cannot respond to both an exception class group and a specific exception condition.
The same exception condition must not be specified more than once, whether by SQLSTATE value or by condition name, in an exception handler declaration.
Within a given scope, only one specific exception handler may be declared for a particular exception condition.
If string is specified, it must have length five and contain only alphanumeric characters.
Within a given compound statement, if both a general and a specific exception handler have been declared to respond to a given exception condition, the specific exception handler will handle the exception.
If no exception handlers have been declared to respond to an exception condition in the compound statement within which the error was raised, the exception condition is propagated out to the enclosing compound statement or to the calling environment.
The above does not apply to exception conditions with the NOT FOUND and SQLWARNING class, these are not propagated by the exception handling mechanism in absence of an exception handler defined to handle them.
SQLWARNING covers SQLSTATE values beginning with 01.
NOT FOUND covers SQLSTATE values beginning with 02.
SQLEXCEPTION covers all other SQLSTATE values (including implementation-defined values), except those beginning with 00.
ExampleS1: BEGIN DECLARE EXIT HANDLER FOR SQLEXCEPTION BEGIN ... ... END; ... ... END S1;
For more information, see Return Status and Conditions or the Mimer SQL Programmer's Manual, Declaring Exception Handlers.
Mimer Information Technology AB
Voice: +46 18 780 92 00
Fax: +46 18 780 92 40 | <urn:uuid:a7943fd5-dedd-467e-91dc-f667e053aeca> | 3.015625 | 620 | Documentation | Software Dev. | 38.815588 |
Table of Contents
This chapter explains some concepts of the KCachegrind, and introduces terms used in the interface.
Cost counts of event types (like L2 Misses) are attributed to cost entities, which are items with relationship to source code or data structures of a given program. Cost entities not only can be simple code or data positions, but also position tuples. For example, a call has a source and a target, or a data address can have a data type and a code position where its allocation happened.
The cost entities known to KCachegrind are given in the following. Simple Positions:
An assembler instruction at a specified address.
- Source Line of a Function
All instructions that the compiler (via debug information) maps to a given source line specified by source file name and line number, and which are executed in the context of some function. The latter is needed because a source line inside of an inlined function can appear in the context of multiple functions. Instructions without any mapping to an actual source line are mapped to line number 0 in file
All source lines of a given function make up the function itself. A function is specified by its name and its location in some binary object if available. The latter is needed because binary objects of a single program each can hold functions with the same name (these can be accessed e.g. with
dlsym; the runtime linker resolves functions in a given search order of binary objects used). If a profiling tool cannot detect the symbol name of a function, e.g. because debug information is not available, either the address of the first executed instruction typically is used, or
- Binary Object
All functions whose code is inside the range of a given binary object, either the main executable or a shared library.
- Source File
All functions whose first instruction is mapped to a line of the given source file.
Symbol names of functions typically are hierarchically ordered in name spaces, e.g. C++ namespaces, or classes of object-oriented languages; thus, a class can hold functions of the class or embedded classes itself.
- Profile Part
Some time section of a profile run, with a given thread ID, process ID, and command line executed.
As can be seen from the list, a set of cost entities often defines another cost entity; thus, there is a inclusion hierarchy of cost entities.
Call from instruction address to target function.
Call from source line to target function.
Call from source function to target function.
(Un)conditional jump from source to target instruction.
(Un)conditional jump from source to target line.
Jumps between functions are not allowed, as this makes no sense in a call graph; thus, constructs like exception handling and long jumps in C have to be translated to popping the call stack as needed.
Arbitrary event types can be specified in the profile data by giving them a name. Their cost related to a cost entity is a 64-bit integer.
Event types whose costs are specified in a profile data file are called real events. Additionally, one can specify formulas for event types calculated from real events, which are called inherited events. | <urn:uuid:94b7368f-d05b-479d-ad0e-98f181b5d71e> | 2.984375 | 657 | Documentation | Software Dev. | 43.046437 |
Sesquiterpenes are a class of terpenes that consist of three isoprene units and have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be acyclic or contain rings, including many unique combinations. Biochemical modifications such as oxidation or rearrangement produce the related sesquiterpenoids.
Sesquiterpenes are found naturally in plants and insects, as semiochemicals, e.g. defensive agents or pheromones.
When geranyl pyrophosphate reacts with isopentenyl pyrophosphate, the result is the 15-carbon farnesyl pyrophosphate, which is an intermediate in the biosynthesis of sesquiterpenes such as farnesene. Oxidation can then provide sesquiterpenoids such as farnesol.
With the increased chain length and additional double bond, the number of possible ways that cyclization can occur is also increased, and there exists a wide variety of cyclic sesquiterpenes. In addition to common six-membered ring systems such as is found in zingiberene, a constituent of the oil from ginger, cyclization of one end of the chain to the other end can lead to macrocyclic rings such as humulene.
In addition to common six-membered rings such as in the cadinenes, one classic bicyclic sesquiterpene is caryophyllene, from the oil of cloves, which has a nine-membered ring and cyclobutane ring. Additional unsaturation provides aromatic bicyclic sesquiterpenoids such as vetivazulene and guaiazulene.
Dictyophorine A and B
Two novel sesquiterpenes have been identified from the fruit bodies of the fungus, named dictyophorine A and B. These compounds are based on the eudesmane skeleton (a common structure found in plant-derived flavors and fragrances), are the first eudesmane derivatives isolated from fungi. The dictyophorines promote the synthesis of nerve growth factor in astroglial cells.
- Kawagashi et al., pp. 1203-1205.
- Kawagishi et al. (1997.)"Dictyophorines A and B, two stimulators of NGF-synthesis from the mushroom Dictyophora indusiata.Phytochemistry1997, volume 45, issue 6,pp. 1203–1205. | <urn:uuid:b0b68892-5acb-464a-890f-847ab8a101e0> | 3.140625 | 539 | Knowledge Article | Science & Tech. | 22.780775 |
The mimic octopus, which can imitate flatfish and sea snakes to dupe potential predators, may well be the king of impersonation. By creatively configuring its limbs, adopting characteristic undulating movements, and displaying conspicuous color patterns, the mimic octopus can successfully pass for a number of different creatures that share its habitat, several of which are toxic. Now, scientists have conducted DNA analysis to determine how this remarkable adaptation evolved.
- Octopus mimics flatfish and flaunts itThu, 26 Aug 2010, 9:44:33 EDT
- Fish mimics octopus that mimics fishWed, 4 Jan 2012, 16:35:03 EST
- A convincing mimic: Scientists report octopus imitating flounder in the AtlanticWed, 3 Mar 2010, 17:48:56 EST
- New fossil tells twisted tale of how flatfishes ended up with two eyes on one side of headWed, 9 Jul 2008, 13:36:11 EDT
- An eye gene colors butterfly wings redThu, 21 Jul 2011, 17:04:51 EDT | <urn:uuid:05b16748-1081-4f36-8980-1c27437aa27a> | 2.75 | 218 | Content Listing | Science & Tech. | 21.829386 |
Conventions Used in This Book
This book uses several conventions to help you prioritize and reference the information it contains.
In addition, the following special elements provide information beyond the basic instructions:
From concept to deployment, C#Builder Kick Start provides the information you need to begin building .NET applications with Borland C#Builder for Microsoft .NET.
I'm very interested in hearing your comments about
C#Builder Kick Start
. You are welcome to contact me at jmayo@MayoSoftware.com. I also
Part I: Overview of C#Builder and the C# Programming Language
Chapter 1. Introducing .NET and the C#Builder IDE
Borland is the first independent software vendor to license the .NET Framework from Microsoft. The benefit of this is that applications created with C#Builder are fully compatible with any other .NET application or library.
Because C#Builder is about building .NET applications quickly, it helps to understand why .NET is important, what it is, and how it works. The information in this section is not all-inclusive, but still very important. Understanding this basic information about .NET will enable you to answer many questions in the future.
In the past, languages, operating systems, and platforms were built for a different age, when the primary platform for applications was the desktop computer. When programs moved from the desktop to the Internet, existing tools needed additional APIs and other capabilities. Most often, these new capabilities were bolted onto the side of the language or tool to coerce them into working on the Internet. Although conventional tools have done remarkably well and brought the Internet to where it is today, there are still many challenges to
.NET was created to support the new age of Internet computing applications. Issues such as deployment, security, and versioning have become significant problems, which .NET addresses. A central part of .NET is the
Common Language Runtime (
, a virtual code execution engine that supports deployment, security, and versioning of code. With native compiled code, such capabilities are not possible. Because .NET
What Is .NET?
.NET is a platform for building distributed applications. It is
Windows Forms is a set of libraries for building graphical
ADO.NET is a set of object-oriented classes for building data
ASP.NET includes a Web Forms programming model, in which Web-based applications can be built and run over the Internet and accessed with a browser. This is an improved Web programming model in which code is actually compiled on the server but rendered to the client as traditional HTML. It is object-oriented and supports a server-based component model, promoting reusability.
Web Services are a new platform-independent and standards-based approach for enabling interoperability between heterogeneous systems on the Internet. .NET Web Services use the object-oriented infrastructure of the ASP.NET programming model, but still expose an open-standards message-based model. Using
These are just a few of the more popular application types that can be built with .NET. If you become familiar with the vast .NET Framework BCL, you will discover that it offers more capabilities to meet any need.
Base Class Library
The .NET Base Class Library (BCL) contains thousands of reusable types that increase productivity in building .NET applications. Because of BCL's size, it takes time to learn everything that is available. You can often save time by searching the BCL before duplicating a custom type that already exists.
As you start out, it is good to get a general overview of what is in the BCL and know where to look. Table 1.1 shows the major namespaces and descriptions of BCL types.
Table 1.1. .NET Namespaces
Common Language Runtime
The Common Language Runtime (CLR) is an execution engine with the primary purpose of providing managed execution of .NET code. The central point to remember about the CLR is the word "managed." The CLR
Managed code is not compiled to native machine code. Rather, it is compiled to Microsoft Intermediate Language (MSIL), which I'll refer to as just IL. Much like Java byte code (or just byte code), IL is an assembler-like language. However, one of the primary conceptual differences between byte code and IL is the fact that IL does not have an interpreted specification. IL is loaded and Just-In-Time (JIT) compiled to machine code in memory by the CLR at runtime. Another difference between Java byte code and IL is that IL is designed
.NET programs are composed of assemblies, which are the logical atomic unit of deployment, identification, and security. They
Another important feature to know about the CLR is how it loads and executes code. Understanding this process
Figure 1.1. CLR application management.
As soon as a .NET program begins execution, Windows detects that this is a .NET assembly and starts up the CLR. The CLR then identifies the program entry point and begins the Resolve Types process, in which it finds out where a given type is located. Identified assemblies are loaded by the Loader process.
This process illustrates why the .NET compiler is called a JIT compiler—types are loaded on an as-needed basis or just-in-time. The verification process ensures type safety and security. If the JIT compiler encounters a type that it needs, it will
The initial JIT compilation represents a noticeable performance hit, occurring when an application first starts. Subsequent performance of loads will vary, depending on the type retrieved. As hinted, these are only initial delays, and performance
After a type has been compiled to machine code, the memory manager handles it. Value types (structs) are allocated on the stack and reference types (classes) are allocated on the heap. Periodically, the garbage collector kicks in to clean up unused heap objects in a mark-and-sweep fashion. The garbage collector maintains generations, cleaning up
In-memory code is native machine code that has already been JIT compiled and can be fed directly to the CPU. The in-memory working set will
When the CPU needs to execute type
The CLR is central to all that happens in .NET. Understanding how it works is the key to writing well-behaved code that
Another important part of .NET is the concept of multilanguage support. IL is designed to support many languages. In fact, there are currently dozens of languages that target the CLR by compiling to IL. Besides C#, .NET ships with Visual Basic .NET, JScript .NET, J# .NET, and Managed C++. Other
The glue that holds all these languages together is referred to as the Common Type System (CTS). Although each language represents types in a unique manner, the underlying behavior and semantics of each type are the same to the CLR. The CTS defines which members a type may have: Field, Methods, Events, Properties, and Indexers. It also specifies their scope and visibility: public, internal, protected, protected internal, and private. Of course, this description is given through the perspective of C# keywords: Other languages may differ in keyword, but the underlying semantics of the CLR remain the same.
Why multiple languages? For a better perspective of the reasoning behind this approach, consider a large business with multiple software projects. It is often the case that the languages in many of these projects are different. Unless the developers are using a component technology such as COM, they are probably not getting much reuse of code between projects. Having multiple languages that target a single platform has more potential for reuse, which is an important business benefit.
The ability to code in multiple languages has benefits in business-to-business commerce also. The third-party component market is huge, with more companies joining the .NET arena every day. These companies can code their components in any .NET language they choose. These components are reusable by any other .NET application, regardless of the language it is being written in. Multiple language support in .NET opens new markets to component vendors that, in the past, might have been difficult to support and reach.
The Common Language Specification (CLS) was created to address these problems. The CLS is
C#Builder is an | <urn:uuid:1197f691-0e63-4ea6-a780-5012f9cd667e> | 2.734375 | 1,698 | Truncated | Software Dev. | 45.586455 |
Q: How to avoid problems with include files?
A: If you declare a class in your code the compiler normally needs to know some information about the used class like e.g. size. But if you just uses a pointer or a reference, the compiler doesn't need to know those information at that point since pointers or references are always the same size (4 bytes on a windows system). So you just need to tell the compiler that there will be a class - in this case called 'CSomeClass' - which will be used later by that declared pointer or reference. In this case you can use the so-called 'forward declaration'...
In this example you would need to provide the complete definition of 'some_class' since 'foo' will create one instance of it. Therefore the compiler needs to know the exact size of the class and how it looks like...
In this case you only have a pointer to 'some_class'. Since the size of a pointer is independent from the size of the object it is pointing to the compiler just needs to know that there is somewhere a class named 'some_class' is defined...
Most of the time forward declarations are used to prevent circular includes. Consider this
In this case you will end up with circular includes. While compiling the 'one.hpp' header file the header file 'two.hpp' will be included. While compiling 'two.hpp' header file the 'one.hpp' will be included. While compiling...
This will give problems even if you use inclusion guards like
Therefore it is not necessarely a good idea to include all the needed header files within your header file. Using forward declarations will avoid those circular includes...for additional information about the whole subject take a look at the following FAQ...
// Your class declaration | <urn:uuid:fed80f46-97c0-4bf9-a874-6c18c0a58ad3> | 3.3125 | 373 | Q&A Forum | Software Dev. | 58.417628 |
Atmospheric Pressure |
Surface Wind Velocity and Direction |
Atmospheric Humidity ||
Precipitation | Clouds | Special Instruments | Weather Satellites |
A. Pilot Balloon/Theodolite
A Pilot Balloon is a meteorological balloon that is filled with gas lighter than air. When the pilot balloon is used in conjunction with a theodolite it is used to determine the speed and direction of winds at different levels of the atmosphere.
Radiosonde, an airborne instrument used for measuring pressure, temperature and relative humidity in the upper air is the radiosonde. he instrument is carried aloft by a meteorological balloon inflated with hydrogen. The radiosonde has a built-in high frequency transmitter that transmits data from the radiosonde meter and recorded on the ground by a specially designed radiosonde receiver.
A more sophisticated version of this instrument is the rawindsonde. The rawindsonde is an electronic device used for measuring wind velocity, pressure, temperature and humidity aloft. It is also attached to a balloon and as it rises through the atmosphere, it makes the required measurements.
Another special instrument is the Rawin which is short for Radar and Wind. It is an electronic device that measures pressure, temperature and humidity.
E. Wind Finding Radar|
Another instrument is the Wind Finding Radar. It determines the speed and direction of winds aloft by means of radar echoes. A radar target is attached to a balloon and it is this target that is tracked by ground radar. The bearing and time of interval of the echoes is evaluated by a receiver.
F. Weather Surveillance Radar|
A Weather Surveillance Radar is of the long range type which detects and tracks typhoons and cloud masses at distance of 400 kilometers or less. This radar has a rotating antenna disk preferably mounted on top of a building free from any physical obstruction. Radio energy emitted by the transmitter and focused by the antenna shoots outward through the atmosphere in a narrow beam. The cloud mass, whether it is part of a typhoon or not, reflects a small fraction of the energy back to the antenna. This reflected energy is amplified and displayed visually on a radar scope. The distance or slant range of the target from the radar is determined through the elapsed time the signal is transmitted and then received as an echo. Its direction is determined by the direction at which the focused beam is pointing at the instant the echo is received. The radar is a useful tool in tracking and monitoring tropical cyclones. | <urn:uuid:1b22dba6-20ca-47b7-a079-4b4686528f03> | 3.703125 | 506 | Knowledge Article | Science & Tech. | 34.607537 |
In "Algebra Functions," a function is described as a set of data that has one distinct output (y) for each input (x). A function also describes the relationship between inputs (x) and outputs (y). As a testament to the various patterns between x and y, several types of functions exist.
- Absolute Value
Each type of Algebraic function is its own family and possesses unique traits. If you want to understand the characteristics of each family, study its parent function, a template of domain and range that extends to other members of the family. This article focuses on the linear parent function.
Linear Parent Function Characteristics
- The equation of the linear parent function is y = x.
- Refer to Linear Parent Function for the graph of y = x.
- Domain: All real numbers
- Range: All real numbers
- The slope, or rate of change, is constant.
Linear Function Flips, Shifts, and Other Tricks
Family members have common and contrasting attributes. If your dad has a big nose, then you probably have one as well. Nonetheless, just as you are different from your parents, so is a subsequent function different from its parent.
Note: Any changes to the equation will alter the graph.
y = x+1
The graph shifts up 1 unit.
The graph shifts down 4 units.
Changes in Steepness
The graph becomes steeper.
y = ½x
The graph becomes flatter.
The graph flips and slopes downward, instead of upward. (See Calculate a Negative Slope.) | <urn:uuid:4b5c6d3e-9246-4d2e-aa2f-117fdffdc40d> | 3.96875 | 328 | Tutorial | Science & Tech. | 58.653947 |
One result of a workshop held in 2008 that “broad research themes within theoretical computer science…that have potential for a major impact in the future, and distill these research directions into compelling “nuggets” that can quickly convey their importance to a layperson” is this set of nuggets. Among the summary of nuggets we find quantum computing and three questions:
In the wake of Shor’s algorithm, one can identify three basic questions:
(1) First, can quantum computers actually be built? Can they cope with realistic rates of decoherence — that is, unwanted interaction between a quantum computer and its external environment? Alternatively, can we find any plausible change to currently-accepted laws of physics such that quantum computing would *not* be possible?
(2) Second, what would the actual capabilities of quantum computers be? For example, could they efficiently solve NP-complete problems? Though quantum computers would break many of today’s cryptographic codes (including RSA), can other practical codes be found that are secure against quantum attacks?
(3) Third, does quantum computing represent the actual limit of what is efficiently computable in the physical world? Or could (for example) quantum gravity lead to yet more powerful kinds of computation?
I would have added (a) are quantum computers useful for physical simulation of chemistry, biology, and physics?, (b) can quantum computing theory overcome roadblocks that have plagued classical computational complexity?, and (c) is quantum computing useful for understanding how to build classical algorithms for simulating physical systems? | <urn:uuid:77b0bb39-e3a0-4693-b0d7-cc9f8864375b> | 2.828125 | 321 | Personal Blog | Science & Tech. | 29.207988 |
Space is a challenging place. We think of it as mostly empty, but that is not completely true. The vast sea of space in our solar system is filled with powerful radiation and bombarded with high-speed atomic particles. In addition, the Sun generates a continuous stream of particles that we call the "solar wind." The high energy radiation, the high energy particles, and the solar wind could prove dangerous to life here on Earth's surface. Earth's planetary shield -- the Earth's magnetic field working together with our atmosphere -- protects us.
Every magnet generates a magnetic field. Several objects in our solar system also have their own massive magnetic fields: the Sun, Earth, Mercury, Jupiter, Saturn, Uranus, and Neptune. The magnetic field around a planet that extends into space is called a magnetosphere. The magnetospheres of the planets interact with the particles from the Sun -- the solar wind. Within the magnetosphere, charged particles spiraling along the Earth's magnetic field toward the poles create beautiful aurorae, the northern and southern lights, when they interact with our atmosphere.
Magnetic fields can also create hazards. Magnetospheres trap high energy particles into radiation belts around planets. The distant gas giant planets do not need protection from the solar wind; instead, their powerful radiation belts create a serious hazard for spacecraft, as do our own Van Allen radiation belts here on Earth.
Earth's magnetosphere does more than shield us from the constant barrage of high-energy particles. It also protects our atmosphere and oceans from the solar wind, which would otherwise gradually erode them away into space. Mars' lack of a magnetosphere may be partly responsible for the thinness of its atmosphere and absent oceans. A magnetosphere on Venus could have prevented this planet's primordial water from escaping into space.
Given these critical roles, it is not surprising that several missions are actively investigating these planetary shields. The ongoing MESSENGER mission is mapping out Mercury's magnetic field, as is Cassini at Saturn, and Juno is on its way to do the same at Jupiter. The Solar Dynamics Observatory is also monitoring the Sun and its magnetic field to explore its impact on the near Earth space environment..
Explore this topic to investigate magnetic fields and planetary magnetospheres, through a variety of activities and mission resources. It's attractive stuff! | <urn:uuid:bfef28e7-2b0f-4f58-addf-1ce513a58e2e> | 3.96875 | 472 | Knowledge Article | Science & Tech. | 38.278173 |
Saturday 15 June
Eastern Cape dwarf cycad (Encephalartos caffer)
Eastern Cape dwarf cycad fact file
- Find out more
- Print factsheet
Eastern Cape dwarf cycad description
This rare plant typically has an underground stem, with a small portion on top, the stem is only very rarely branched and may be as much as 40 cm long (2). Emerging from the top are long, pinnate, dark green leaves up to a metre long. These often have a distinctive ruffled, feathery appearance, caused by the numerous, clustered leaflets being irregularly twisted from the central stalk and pointing out in different directions (2) (4). New leaves are brown and woolly at first but most of the hair is lost as they mature, although they never become completely smooth or glossy. Both male and female plants bear single reproductive cones made up of a series of spiraled scales, which become greenish-yellow when mature. In the female, two largish, glossy, scarlet-coloured seeds are formed on top of each cone scale (2).
- Stem length: up to 40 cm (2)
- Stem width: up to 25 cm (2)
- Leaf length: 40 – 100 cm (2)
- Cone length: up to 30 cm (2)
- Cone width: up to 15 cm (2)
- Seed length: up to 3.8 cm (2)
Eastern Cape dwarf cycad biology
Cycads are dioecious, meaning that there are separate male and female plants, and the female produces seeds while the male produces pollen. Plants of this taxon have generally been considered to be wind pollinated, but several recent studies suggest that insect pollination is more likely. The seeds produced are typically large with a hard, stony layer (sclerotesta) beneath a fleshy outer coat (sarcotesta), attracting animals such as birds, rodents and small mammals, which serve as dispersal agents. In most cases, the fleshy coat is eaten off the seed rather than the entire seed being consumed. Cycads are long-lived and slow-growing, with slow recruitment and population turnover (6).
All cycads posses ‘coralloid' (meaning coral-like) roots. These roots contain symbiotic cyanobacteria that fix gaseous nitrogen from the atmosphere and provide essential nitrogenous compounds to the plant. This can be a great advantage, as many cycads grow in nutrient-poor habitats (6).Top
Eastern Cape dwarf cycad range
Approximately 10,000 mature individuals are confined to the Eastern Cape Province of South Africa (1).Top
Eastern Cape dwarf cycad habitatTop
Eastern Cape dwarf cycad status
Classified as Near Threatened (NT) on the IUCN Red List 2007, and listed on Appendix I of CITES (3).Top
Eastern Cape dwarf cycad threats
The Eastern Cape dwarf cycad was one of the first three Cape cycads to be declared endangered by the Cape provincial nature conservation authorities. Collectors have seriously depleted numbers in certain areas, particularly in easily-accessible terrain. Large numbers have also been destroyed by conversion of land to agriculture, such as in the Humansdorp and Albany districts (2).Top
Eastern Cape dwarf cycad conservation
A few viable colonies are protected on state-owned land, and a large colony occurs in the Cape provincial cycad reserve near Grahamstown, where plants are regularly inspected. Here, many seedlings can be seen amongst the mature plants, and the species therefore seems to be in no immediate danger of extinction (2).Top
Find out more
For more information on the Eastern Cape dwarf cycad see:
- Cycad Society of South Africa:
Authenticated (17/09/07) by Dr John Donaldson, Chief Director of Conservation Science, Head of Kirstenbosch Research Centre, South African National Biodiversity Institute.Top
- A group of bacteria that is able to photosynthesise and contain the pigment chlorophyll. They used to be known as ‘blue-green algae'. They are thought to have been the first organisms to produce oxygen; fossil cyanobacteria have been found in 3000 million year old rocks. As they are responsible for the oxygen in the atmosphere they have played an essential role in influencing the course of evolution on this planet.
- Male and female flowers are borne on separate plants.
- In plants, a compound leaf where the leaflets (individual ‘leaves’) are found on either side of the central stalk.
- Symbiotic relationship
- Relationship in which two organisms form a close association, the term is now usually used only for associations that benefit both organisms (a mutualism).
- An open grassy plain.
- IUCN Red List (September, 2007)
- Cycad Society of South Africa (December, 2006)
- CITES (October, 2006)
- Jurassic Garden (December, 2006)
- Donaldson, J. (2007) Pers. comm.
- Royal Botanic Gardens Sydney – The Cycad Pages (December, 2006)
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The various ecological and economic benefits of tropical marine seascapes and their biodiversity are under threat by a variety of sources, including human development and climate change. Globally, mangroves are being cleared at a quicker rate than tropical rainforests, and tropical fisheries are significantly over-fished. Overfishing of species that graze on algae and seaweeds on the reef can disrupt the ecosystem’s overall balance and prevent new corals from growing. Overfishing also removes the adult grazing fish that are most attractive to larger predator fish, and increases predation on juvenile fish before they’ve had a chance to breed.
Coral bleaching events—when corals lose the symbiotic algae within their tissues that provide them with much of their energy through photosynthesis-- have increased in recent years due to global climate change and warming water temperatures. Scientists also acknowledge that the limestone skeletons of corals will become weakened as seas become more acidic, taking up more carbon dioxide as atmospheric concentration increases. Without healthy coral reefs, tropical marine seascapes can’t maintain their wide varieties of species—and all the benefits they confer to surrounding communities.
One of the key tools for reducing the effects of these and other threats to tropical seascapes is the establishment of marine reserves. These areas, where tourism is actively encouraged but fishing and other destructive activities are banned, can increase the health of many tropical habitats. Reefs in protected areas therefore tend to be more biodiverse and more resilient—so while such reserves cannot directly prevent the effects of climate change (or hurricanes), they can give reefs and the species that depend on them better odds for recovery, after major bleaching events or storms, for example.
For marine reserves to be successful, they must be well designed. If marine reserves are placed in areas with naturally poor-quality habitat there will be very few benefits to wildlife. A number of guidelines are available to coastal managers to help them site their marine reserves. Central among these is to try and include sea grass, mangrove, and coral reef habitats in reserves because of the importance of the interactions between them. However, most tropical seascapes include many types of mangrove and coral reef areas, with differing characteristics and qualities. Which types, and how many, should be included in a marine reserve or a network of reserves? How close to each other do they need to be? What species do they need to shelter? Answering these and related questions is critically important throughout The Bahamas, the wider Caribbean, and indeed anywhere coral reefs exist.
Meet the Scientists
Dr. Alastair Harborne
NERC Independent Research Fellow
University of Exeter, UK
Dr. Harborne is a coral reef ecologist with wide ranging interests in fish and coral ecology and the overarching aim to use ecological insights to aid biodiversity conservation. His key research interest concerns the processes affecting the abundance of reef fishes on coral reefs, and he also studies the landscape ecology of reefs and the design and effects of marine reserves. He’s worked on coral reef ecosystems for nearly ten years, and holds a PhD from The University of Exeter (UK) and a BSc from Southampton University (UK). He is a member of the Ecology and Conservation Biology research group at Exeter, the UK coordinator for Reef Check since 1997, and a founding member of the Reef Conservation-UK committee. A frequently published author and co-author in scientific media, he has also given multiple interviews for mass media outlets like the BBC on coral conversation issues. He is a certified PADI Rescue Diver and Emergency First Responder with more than 550 logged dives in the Caribbean, South East Asia, South Pacific and the Red Sea, and has worked with volunteers for a non-governmental organization in Central America for many years.
Dr. Rod Wilson
Associate Professor in Integrative Animal Physiology
University of Exeter, UK
Dr. Wilson is a comparative physiologist and his research uses multi-disciplinary approaches to provide a broader understanding of homeostasis (the ways an organism regulates itself to maintain a fairly stable biological condition) in animals, with a particular focus upon fish. This includes studies of how anthropogenic (human-caused) and natural environmental changes affect fish physiology and behavior, as well as projects on the welfare and environmental enrichment of laboratory fish. Dr. Wilson is a member of the Ecotoxicology and Ecophysiology research group at Exeter, and holds both a BSc and a PhD from the University of Birmingham (UK). He is the Assistant Editor for the Journal of Fish Biology and Co-Editor for Serial Advances in Experimental Biology.
Dr. Andrew Gill
Senior Lecturer in Aquatic Ecology
Cranfield University, UK
Dr. Andrew Gill started his career in 1989 as a NERC-funded research assistant at Leicester University. Following his Ph.D., he worked for three years with a coral reef conservation organization on field projects, mapping reef communities and providing scientific advice and support for the development of marine protected areas in Belize and the Philippines. On returning to the UK in 1996, Andrew took up a temporary lectureship in fish and fisheries biology at Liverpool University, and in 1999 set up a new postgraduate course in restoration ecology and was appointed course director. In late 2003, Andrew moved to Cranfield to take up his current position as lecturer in applied aspects of aquatic ecology. Andrew manages the environmental water management option on the water management postgraduate program. Andrew graduated in zoology (marine and fisheries biology) from Aberdeen University in Scotland, and subsequently studied for his Ph.D. in fish behavioral ecology at Leicester University. He is a member of the Fisheries Society of the British Isles, a member of the Society for Ecological Restoration International, a member and scientific advisor to the Shark Trust, a member of British Ecological Society and a BES representative, and a member and visiting fellow of the Marine Biological Association UK. He is currently the marine and aquatic editor for the international journal Biological Conservation.
Dr. Katherine Sloman
University of the West of Scotland, UK
Dr. Katherine Sloman graduated from the University of Wales, Swansea, in 1997, and then received her Ph.D. from the University of Glasgow in 2000 following work on stress responses in salmon. She then undertook a series of postdoctoral research projects in fish physiology before becoming a lecturer and then senior lecturer at the University of Plymouth (UK). In 2010 she moved to the University of the West of Scotland to continue her work on ecotoxicology and environmental physiology. Katherine is the author of numerous research papers and book chapters, and is a member of organizations including the Society of Experimental Biology, the Fisheries Society of the British Isles, and the Association for the Study of Animal Behaviour. She has also taught extensively to undergraduates and supervised many post-graduate students. | <urn:uuid:30dc6fec-90f0-461d-9824-a6f0c4ead7ba> | 4 | 1,388 | Knowledge Article | Science & Tech. | 24.18617 |
a. Surface Layer: from surface down to a few hundred meters. This layer is heated or cooled by the air above and/or sunlight. Significant mixing can occur that equalizes the temperature.
b. Main Thermocline: always characterized by a rapid drop in temperature to near 35 F. Essentially all the deep water is isothermal at 35 F.
c. Deep Layer: isothermal, but characterized by a positive gradient due to pressure affect on sound velocity. Provided the water is deep enough, there will be sufficient velocity increase to turn sound "rays" back around towards surface, leading to a convergence zone effect.
Of these three sections, only the surface layer will exhibit a seasonal variation. Figure 1. Illustrates the effects:
a. Winter: surface is essentially isothermal due to significant mixing caused by storms and wind. Pressure effect makes this layer slightly positive. Provides the best chance for a surface duct propagation.
b. Summer: maximum heating of surface water tends to create a significant negative gradient. The warm water will extend deeper through conduction and lower the point at which the main thermocline begins.
c. Spring/Fall: Transitional cases between summer and fall. Note, it is more difficult to produce a positive gradient by cooling the surface water in Fall. Any cooling is disrupted by convective upcurrents that destroy the stratification. This leads to the winter isothermal layer. | <urn:uuid:3a468221-65be-4f68-83df-f0936a016c49> | 4.1875 | 288 | Knowledge Article | Science & Tech. | 43.911375 |
Victorian-Era Pressed Flowers Help Ecologists Study Climate Change
Here's an extremely cool tidbit of environmental news. Ecologists are studying collections of pressed plants from Victorian England to learn more about climate change. The early spider orchids from Southern England are in collections with notes showing the exact day in spring when they were picked, dating from 1848 to1958. Ecologists are comparing those with dates when the same flower blossomed in the wild from 1975 to 2006.
After cross-checking their research with local temperature records, they wrote the following in the Journal of Ecology: "Warmer years were associated with earlier flowering ... In both cases flowering was advanced by about six days per 1 degree Celsius (1.8 Fahrenheit) rise in average spring temperature."
Read the details at Yahoo Green News. Just try not to cringe while reading some of the baseless "GLOBAL WARMING IS A HOAX!" comments on the bottom. ;-) | <urn:uuid:b487aece-6a6a-4c17-9fb6-3aeb8442ba9a> | 3.140625 | 196 | Personal Blog | Science & Tech. | 48.154649 |
Spiders are invertebrate creatures in the araneae order of the class arachnida in the phylum arthropoda. A spider has up to eight eyes, eight legs and seven silk-producing glands in its abdomen. These glands secrete proteins that are extruded through spinnerets to produce different kinds of silk. Many spiders, particularly orb, funnel, sheet and cob-weaving spiders, use this silk to build webs with which to catch prey.
We’ll focus on orb-weavers because their webs are the most recognizable. Their webs are complex nets of strong dragline threads (frame, spokes) radiating out from the center; and elastic, sticky catching threads spiraling into the center. An orb-weaver begins its web with radial and framework threads using dragline silk, providing a foundation upon which to spiral the sticky catching threads. The spiders then create an auxiliary spiral to help the radial threads support the spider’s weight as it builds. Next, the spider uses, and subsequently destroys, the auxiliary spiral as a guide to create the catching spiral, which it dots with glue. What is perhaps the most amazing part of this hour-long process is that orb-weaving spiders often have poor eyesight and weave using only their sense of touch.
The sticky, complex nets of silk used for the catching spiral are effective hunting tools, but have often made people wonder how the spiders themselves avoid entangling themselves in their own webs. Many people believe that spiders have special oils that repel the stickiness of their threads. This, however, has never been proven. Scientists are still not entirely certain how most spiders manage to avoid ending up ensnared in their own trap, but there are a few accepted theories. Spiders can spin different kinds of silk, and not all of their silk is sticky. In fact, in a spider web only the silk used for the intricate catching spirals are dotted with glue, so spiders know which threads to avoid. In addition to producing different kinds of silk, web-spinning spiders also have an extra set of claws on their feet. All spiders have two claws on their feet; web-spinning ones have three. These claws are used to grasp threads and provide traction as the spider moves along.
Spider silk itself is interesting to scientists because of the irreversible transformation it makes from a water soluble liquid inside the spider, to a non-water soluble thread outside of the body. The reaction has nothing to do with the thread’s exposure to air once it exits the spider; rather scientists believe it has to do with the act of pulling on the thread that realigns the molecules into a solid form.
Scientists are interested in spider silk for manufacturing purposes, specifically the viscid (sticky for catching prey) and dragline (strong for stiff radials and framework) threads. The viscid thread is comparable to rubber in elasticity, but has more strength. The dragline thread is comparable to steel and Kevlar® (bulletproof material) in stiffness, but is more elastic and able to absorb higher impact.
What makes spiders truly unique in their silk-producing abilities is that they are the only animals that use this silk for multiple purposes. Their multiple silk glands each produce different kinds of silk to aid in mating rituals, create shields for protection from predators, encase their eggs and, of course, weave webs.
Animal Diversity Web -
Site sponsored by the University of Michigan, Department of Zoology covers information about many animal species, including general information, natural history, classification and images.
How Stuff Works -
Section of a larger article on spiders describing web spinning behavior.
- “New” spider species weaves uncommonly regular webs - Article on National Geographic website about a new species of spider; also goes into some detail about web-weaving activities of spiders in general.
- The Spider Myths site -
Web site hosted by the Burke Museum of Natural History and Culture at University of Washington refuting the urban legend that spiders avoid entangling themselves in spider webs because of oils on their feet. Find other misconceptions about spiders from the Spider Myths home page.
- Spider sense: fast facts on extreme arachnids -
Article on National Geographic website detailing fun facts about spiders.
- Bower, Joe. Web masters. Audubon, v. 104, Jan./Feb. 2002: 20-23.
- Conniff, Richard. Deadly silk. National geographic, v. 200, Aug. 2001: 30-45.
- Foelix, Rainer F. Biology of spiders. 2nd ed. New York, Oxford University Press, Inc.; Stuttgart, George Thieme Verlag, 1996. 330 p.
- Kumar, Nitin, and Gareth H. McKinley. Spider silk. In McGraw-Hill encyclopedia of science and technology. 10th ed., v. 17. New York, McGraw-Hill Co., 2007. p. 269-271.
- Punzo, Fred. Spiders: biology, ecology, natural history, and behavior. Leiden, Boston, Brill. 428 p.
- Spiders. In Firefly encyclopedia of insects and spiders. Edited by Christopher O’Toole. Toronto, Ont., Buffalo, NY, Firefly Books, Ltd., 2002. p. 200-213.
more print resources...
Search on "Arachnida," " cobweb weavers," "insects behavior," "orb weavers," "predation biology," "spiders," or "spider webs"
in the Library of Congress Online
Spider web, with a spider barely visible near the center of the web. Photo from the National Biological Information Infrastructure Web site. (Site no longer available.)
The web of an orb weaver. From the Fish and Wildlife Service's National Digital Library Web site.
Raindrops on a spider web. Photo from the Medline Plus Web site.
This spider has decorated its web to attract more prey. Photo from the National Park Service Web site. Read more about these "home decorators" in this article on the National Geographic Home page: Artistic" Spiders Trap Prey With Light, Study Finds.
Black and Yellow Garden Spider. Photo from the National Biological Information Infrastructure Web site.
Garden Spider egg sac suspended on silk lines on a garden plant. Photo from the National Biological Information Infrastructure Web site.
Daddy Long Legs - Did you know that the harvestman, often called the Daddy Long Legs, is not a spider? Read more about it here. Photo by Sally King, and on the Bandalier National Monument, NPS Web site. | <urn:uuid:a5c377e5-82bc-4764-abde-00aef99d5935> | 4.125 | 1,370 | Knowledge Article | Science & Tech. | 52.801198 |
You may want to save this post at Uncommon Descent, in case it disappears down the memory hole.
If you’ve been following Intelligent Design, you’ve probably run across William Dembski’s notion of Complex Specified Information, or CSI. Basically, the argument is that if a system has CSI above a certain level, then it was intentionally designed (just as “Wherefore art thou Romeo” exhibits design, while “Mp YuMsAAVVa UU MbMZlPVJryn Viw MfHyNA FHh” doesn’t). Living beings (or their genomes) have sufficiently-high CSI, and were therefore designed. QED.
So the question from day one has been, “so how exactly does one calculate CSI and get an actual number?” From what I’ve seen, the standard answer is “go read Dembski’s book”. None of my local libraries have Dembski’s book, but from the reviews I’ve read, I gather that for all his talk about CSI, he never gets around to sitting down and describing how to calculate it.
And now for some reason, the people at Chez Dembski have invited someone going by the name of MathGrrl (whom I guess to be a frequent commenter; I stopped reading the comments there a long time ago, so I don’t know) to write a guest post. And not only that, but one in which she basically asks, “so anyway, how does one calculate CSI?”.
The first fifty comments consist mostly of “Yeah, well, evolution doesn’t explain it!” and handwaving, followed by a bunch of comments from MathGrrl to individual commmenters, all “Yes, but that doesn’t help me calculate CSI.”
Which is odd: you’d think that the first dozen or so comments would be links to FAQs, and maybe some Mathematica code to do the calculation. But no. And it’s not because they’re too busy to answer MathGrrl’s question, since a lot of them go on at length about how she’s not asking the right questions, or not using CSI correctly, or maybe some other measure of complexity would be better suited. But I’m not seeing a whole lot of anything that looks like math.
The thread looks, to me, like a gaggle of astrologers arguing about the proper way to calculate a horoscope.
So once again, getting information out of creationists is like pulling teeth.
Update, Mar. 25, 2011: The 200-comment mark has been reached, and no definition in sight. In fact, comment #201, by PaV, says:
To provide a “rigorous definition” of CSI in the case of any of those programs would require analyzing the programs in depth so as to develop a “chance hypothesis”. This would require hours and hours of study, thought, and analysis.
You come here and just simply “ask” that someone do this. Why? You do it.
In other words, “Math is hard! Develop our theory for us!”
(Update, Aug. 4: Fixed typo.) | <urn:uuid:36f1d128-1556-4954-91da-f4f5ae3d36a8> | 2.6875 | 707 | Comment Section | Science & Tech. | 63.221458 |
The classic example of an introduced-species-gone-awry gets even worse. Not only do living cane toads regularly kill many of Australia’s endemic predators that hunt and eat the hopping meals, dead toads—common roadkill along Australia’s highways—are threatening local aquatic fauna.
Cane toads have blighted Australia every since the animals were introduced to the continent in order to control beetles that were damaging sugar cane crops. In addition to being largely unsuccessful in controlling the beetle population, the toads bred prolifically, decimating natural predators such as snakes and lizard, which were poisoned by toxins produced by the toad called bufatoxins.
Researchers had assumed that dead toads, which line highways and find their way into streams and ponds, wouldn't pose a threat to aquatic organisms because bufatoxins are not water-soluble. But according to a new study published in Biological Invasions, even dead toads can kill. Researchers collected dead and dried toads from roadsides and soaked the amphibians in water, together with several native aquatic organisms such as fish and tadpoles. Most of animals died within a day, suggesting that the toads produce other deadly toxins that have yet to be identified.
"Previously you thought, 'Well, okay, a dead cane toad is an ex-toad. It's no longer any problem,' " Michael Tyler, a herpetologist at the University of Adelaide, North Terrace, in Australia told ScienceNOW. "What these guys have done is to demonstrate that it remains a very serious conservation problem."
(Read The Scientist's feature article on the controversial genetically-engineered virus being designed to Stop the Cane Toad.) | <urn:uuid:5d16dc9b-5517-415f-880c-934ff5d26cec> | 3.390625 | 351 | Truncated | Science & Tech. | 30.083954 |
INCREASING RAIN IN THE DESERT:
three continents come new ways of solving an old problem
Scientists believe it may be possible
to increase rainfall in arid areas. (Photo by Digital Vision/Getty
Because of a population boom in the United Arab Emirates (UAE), government
leaders are facing a fundamental challenge: keeping up with demand
for water. The mostly desert country, which has grown from about 50,000
residents in 1975 to more than 3 million today, relies on desalination
plants and underground aquifers. But desalination is very costly, and
the aquifers are quickly becoming depleted.
In the past few years, the UAE has begun to explore an innovative solution.
What if modern technology could produce more rain?
Scientists at NCAR, the UAE Department of Water Resource Studies, University of the Witwatersrand in South Africa, and elsewhere are analyzing
the potential for cloud seeding. They hope to find storm clouds that
can be induced to release rain over regions where the water would most
benefit society by falling on crops or replenishing aquifers.
“This is a multidisciplinary analysis that considers hydrology,
cloud science, atmospheric chemistry, and other disciplines,” explains
NCAR scientist Roelof Bruintjes, who oversees the project. “Increasing
the rainfall is just one aspect. We also have to consider what the
impact would be. It might not help to seed clouds over a desert. If
90% of the rainfall evaporates, it may not be worth it.”
Making droplets bigger
NCAR is building on weather modification projects it has led or participated
in over the last few years in Mexico and South Africa. The center has
refined a technique to increase the size of particles in clouds and
promote the coalescence of water droplets. Called hygroscopic
this technique uses flares mounted on aircraft to seed clouds with
small salt particles. Water droplets can bond to the particles and
grow large enough to fall out of the cloud
Initially, researchers used airplanes and a network of radars to examine
clouds that form along the UAE’s coast during the winter. But
only about 10 frontal systems form during a typical winter, and fewer
than half contain the convective motions needed to produce rain.
Researchers next turned to the Oman Mountains, which form the boundary
between Oman and the UAE. Although the mountains had received little
attention from climate scientists in the past, the team discovered
that clouds there typically form and release rain during about 40 days
in the months of June, July, and August.
NCAR’s Roelof Bruintjes (left) with
Al Mangoosh, director of UAE’s Department
of Water Resources Studies. (Photo by Brant Foote, NCAR.)
The research team has launched a randomized experiment to seed clouds
over the mountains, measure the resulting rainfall, and trace the
movement of the water once it reaches the ground.
If cloud seeding produces significantly more rain in the area, the
UAE can compare the costs and benefits with desalination and decide
whether to launch a multiyear cloud seeding program.
In the near future, NCAR is likely to expand its research on weather
modification to other regions as well. Oman is considering working
with the center to build on the UAE program, and officials as far
away as Thailand may explore the technology.
The African nation of Burkina Faso, where many rely on subsistence
farming, may also benefit from weather modification. With technical
assistance from NCAR, Burkina Faso has implemented a pair of state-of-the-art
software systems to support cloud seeding efforts. The software is
used to display and analyze radar data about cloud systems and precipitation,
thereby guiding cloud seeding operations and helping scientists evaluate
Bruintjes cautions that weather modification is still a developing
field. In Mexico and South Africa, hygroscopic seeding trials produced
more rain 30 to 60 minutes after seeding. But researchers need to
conduct more experiments to evaluate the extent to which overall
precipitation was increased.
Even if hygroscopic seeding proves effective in the UAE, that does
not assure its success somewhere else. Only certain types of clouds
produce rain. And air pollution may complicate the situation by changing
the dynamics of clouds and precipitation.
Bruintjes stresses that nations interested in weather modification
need to conduct thorough research before launching a full-scale program.
“If cloud seeding works in one area, it may not work in another,” Bruintjes
says. “We shouldn’t just go out there and seed clouds
blindly and hope for the best.”
More information about the UAE
rainfall enhancement project
Accurate weather forecasts are much needed in Africa,
especially where tropical cyclones and floods pose an ongoing
threat. But the continent has relatively few observing
stations for monitoring the skies, and forecasters are
limited by lack of access to data and models appropriate
for the weather conditions in their regions.
Emmanuel Kploguede of the African School of Meteorology
and Civil Aviation. (Photo ©Daily
To improve the situation, UCAR is working with collaborators
in Europe and Africa on an initiative known as the African
Satellite Meteorology and Training Project (ASMET). The
goal is to train African meteorologists to interpret data
from European satellites that gather atmospheric information
UCAR’s Marianne Weingroff and the rest of the ASMET
team, including instructors at regional meteorological training
centers in Kenya, Niger, and South Africa, produce educational
modules on topics such as forecasting tropical cyclones and
integrating satellite imagery with model data. The modules
are used at the training centers to teach hundreds of African
meteorologists each year. They are also disseminated to forecast
offices to permit self-paced training. EUMETSAT, the European
Organisation for the Exploitation of Meteorological Satellites,
funds the project and distributes the modules on compact
discs and the Web.
Better forecasts, including daily and seasonal rainfall predictions,
are critical to Africa, where millions of lives depend on
the current year’s crops from farms of all sizes. “ASMET
modules are making a real contribution to the improvement
of forecasts in Africa,” says Emmanuel Kploguede, a
member of the ASMET team and instructor at the African School
of Meteorology and Civil Aviation in Niamey, Niger. “This
is particularly important because most African countries
are in the tropics where the weather can change quickly—either
helping farmers by distributing rain widely or hurting society
with strong storms that can flood croplands, livestock areas,
More Middle Eastern and African Collaborations:
Restoring Lake Victoria
of Africa’s Climate
Overview | Asia | Middle
East/Africa | Oceania/Antarctica | Europe | The
Americas | Global Research | Worldwide
| NCAR | UCAR | UOP| | <urn:uuid:fc320ed6-5ed7-4b8f-829b-48a137a9e0c8> | 3.515625 | 1,528 | Knowledge Article | Science & Tech. | 27.821489 |
Hurricanes (Tropical Cyclones)
Hurricane season in the Atlantic begins June 1st and ends November 30th so there's always a chance for some hurricane excitement when you go to the Eastern Shore.
Divine Wind: The History and Science of Hurricanes
q QC944.E43 2005
"With exceptionally clear prose, Emanuel explains the atmospheric forces that restrict hurricanes to tropical latitudes and upends popular misconceptions about their frequency, noting that the problem for research scientists is not why hurricanes develop, but why they hardly happen." -- Booklist
Breach of Faith: Hurricane Katrina and the near Death of a Great American City
HV636 2005 .N4 H66 2006
Horne, the metro editor of the New Orleans Times-Picayune, gives an account of what happened after the levees broke. Browse the library catalog for many more books on Hurricane Katrina, 2005.
The Perfect Storm: A True Story of Men Against the Sea
In October of 1991, three storms converge in the Western Atlantic off Gloucester, Massachusetts to form the "Perfect Storm" with winds up to 100 miles an hour and waves that topped 110 feet. In the middle of it is the Andrea Gail, a swordfishing vessel with a six-man crew.
Black Cloud: The Great Florida Hurricane of 1928
Largely forgotten and unnamed, the September 16, 1928 hurricane took the lives of 7,000 people. Kleinberg presents vivid pictures of dozens of individual ordeals and recounts the tale of black suffering in the region around Lake Okeechobee, which appears in Zora Neale Hurston's novel, Their Eyes Were Watching God.
Isaac's Storm: A Man, a Time, and the Deadliest Hurricane in History
F394.G2 L37 1999
This is an account of the 1900 hurricane that hit Galveston, Texas and killed more than 6,000 people. It is told from the perspective of Isaac Cline, then the senior U.S. Weather Bureau official in Galveston. The weather bureau ignored forecasts from Cuban meteorologists, who had accurately predicted the Galveston storm's course and true scale.
Hurricane Watch: Forecasting the Deadliest Storms on Earth
Learn the science and history of hurricanes from meteorologist Williams and science journalist Sheets.
Category 5: The Story of Camille, Lessons Unlearned from America's Most Violent Hurricane
"Camille, which swept through coastal Mississippi and Louisiana in August 1969, was the storm that inspired the five-level scale currently used to predict the damage inflicted by hurricanes, and remains the only Category 5 storm-the strongest-to make landfall in modern American history." -- Publishers Weekly
(DVD) QC945.H83945 2004x
Presenting film-footage, first-hand accounts, and commentary by experts, this program examines a number of the hurricanes that have had devastated U.S. coasts over the last few decades, including Hurricane Andrew, Hurricane Gilbert, and Hurricane Camille.
Browse the Catalog
For additional titles, browse the library catalog under the subjects:
National Hurricane Center (hurricanes.gov)
This is NOAA's National Weather service hurricane center. It reports on both the Atlantic - Caribbean Sea - Gulf of Mexico region and the Eastern Pacific region.
Learn what you should do if you are in the path of a hurricane.
- Hurricane Preparedness
Weather updates and hurricane facts and history.
This site has lots of satellite images without much text but if you go to their blog, you can see updated commentary with a lot of explanatory text.
NASA Hurricanes/Tropical Cyclones
Latest storm images and data from the National Aeronautics and Space Administration.
NOLA Hurricane News and Storm Tracking
From the publishers of the Times-Picayune newspaper, here are updates to any existing hurricanes in the Caribbean region.
Information on how to prepare for a hurricane and what to do during one.
Last updated January 16, 2013 | <urn:uuid:6b465c4f-eb6e-4962-912e-34bb7bbdc320> | 2.953125 | 825 | Content Listing | Science & Tech. | 39.991272 |
Library Home || Primary || Math Fundamentals || Pre-Algebra ||
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|Math Fundamentals, difficulty level 3. Use this exploration problem to discover the relation between circumference and diameter.|
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Clearly we can't have three collinear points on a sphere. Look at the "on a sphere" case and assume there is a configuration where they do not all lie on a single sphere.
Any three points define a plane. The locus of points equidistant from these three is a line perpendicular to the plane (through the circumcentre). There are at most two points on such a line which are unit distance from the original three, $P$ and $Q$ say. These are the centres of two unit circles, and one of the remaining two points must lie on each sphere.
Note that $P$ and $Q$ are related by a reflection in the original plane. There are five sets of four points in the original configuration. Each set defines a unit sphere, and if two spheres are the same, then all are. So there are five spheres and the centres are related by reflections in the planes defined by triangles.
[From here is a bathtime intuition which, per comments doesn't work. However note that each pair of centres is related by a reflection, which may not map other centres to centres, and therefore creates an infinite group. I thought I could see the group acting on the centres, but I can't make it work - thanks for comments to put me right]
There is just one group of order 5 - cyclic - and this would imply that the centres of the five spheres formed a regular pentagon. Since this does not provide a suitable configuration, none exists. [Would need three points in each of five planes meeting in a single line, no three collinear] | <urn:uuid:63047dc9-1b46-419b-9dcc-fe54222616fc> | 3.09375 | 331 | Q&A Forum | Science & Tech. | 56.888654 |
A total order on a set is a way of ordering its elements to say that some elements precede others, with the understanding that any two elements can be compared one way or the other.
A toset is a set equipped with a total order.
The category of finite nonempty totally ordered sets and order-preserving maps is called , the simplex category.
The category of all finite totally ordered sets and order-preserving maps is called , the augmented simplex category.
A linear order is much like a total order, except that it is based on an irreflexive relation .
Using excluded middle, one can move between linear orders and total orders using negation; that is, the negation of a total order is a linear order and vice versa. Actually one usually swaps the order too, as follows:
One often sees defined as but ; this is equivalent, but doesn't show the duality explicitly. Similarly, one often sees defined as or ; this is not even equivalent constructively, although it is classically.
In classical mathematics, the distinction between total orders and linear orders is merely a terminological technicality, which is not always observed; more precisely, there is a natural bijection between the set of total orders on a given set and the set of linear orders on , and one distinguishes them by their notation. In constructive mathematics, however, they are irreducibly different.
For more, including why linear orders are more often useful in constructive mathematics, see linear order. | <urn:uuid:99c442d3-3303-4909-b184-6f81b950ea17> | 2.75 | 310 | Knowledge Article | Science & Tech. | 24.696753 |
C got stuck right in, marvelling at how the little objects immediately stuck to the bottom of the giant magnets. She spent a lot of time testing out which ones would stick and was perplexed by the fact that some wouldn’t. We talked about what materials they were made of and she soon picked up that only the metal items worked.
I had some small, powerful craft magnets in the tin and they were fantastic and creating a dramatic result! She held them flat in the palm of her hand, lowered the giant magnet and watched them literally jump up to catch it! This was a real moment of “awe and wonder” (to quote an Early Years government target!) and was repeated many, many times.
It was great fun to see how items would dangle off the bottom and soon she found that the smaller, lighter things could hold onto each other, sharing and transferring magnetism from the original source.
This piece of metal picked up a magnetic force from the original magnet and was able to suspend all these items below it! There were a lot of “wows!” and “”oooos!”
As she picked up the small nails they naturally formed a magnetic chain and this totally fascinated her.
She experimented with adding more nails, one by one to the bottom of the chain to see if they would “stick”, which they did until they got too heavy! This process was repeated for a long time and with a huge amount of concentration, determination and satisfaction.
- knowledge & understanding of the world (includes Science): investigate the world using a range of materials and techniques, ask questions such as who? where? why? when?, experiment with new concepts and seek to answer questions, learn new vocabulary related to science: force, magnet, magnetism
- phse: sustain concentration on self-chosen tasks for extended periods of time | <urn:uuid:721499af-38fc-4a49-a754-98ef1de3dfb4> | 3.46875 | 390 | Personal Blog | Science & Tech. | 57.460897 |
The double star, Porrima, is a double star system located about 40 light-years away, relatively close to the Sun in the grand scheme of things. The two stars orbit each other about every 170 years, and as they do so, the apparent distance that separates them changes (from our Earth-bound point of view). Right now, the two are well separated, meaning that with a telescope pointed at Saturn you will see the two stars as distinct objects. Only a few years ago, their alignment was such that you would have needed a very powerful telescope to see the two stars in the Porrima system as individual stars. Right now, if you put Saturn into view in a small to medium telescope, you will also get the Porrima system in your field of view as well.
The diagram (above) illustrates where to find Saturn and Porrima over the next few days, and this article from Space.com also provides insight and additional diagrams to help you see this sight.
So seize the moment and be an amateur astronomer for a night, making a fun discovery for yourself. | <urn:uuid:9c4011d5-a178-4f2e-a7ef-8df1d1554b5b> | 3.328125 | 223 | Personal Blog | Science & Tech. | 53.3825 |
In the absence of public funded science education and projects, did conflict and climatic uncertainty drive human evolution? http://www.bbc.co.uk/news/science-environment-19598980
What explains the extraordinarily fast rate of evolution in the human lineage over the past two million years?
A leading human origins researcher has come up with a new idea that involves aggression between groups and the boom-bust cycles that have punctuated our spread into new environments.
Speaking at this year's Calpe conference Prof Ian Tatersall said "I think it's fair to say that our species Homo sapiens and its antecedents have come much farther, much faster than any other mammalian group that has been documented in this very tight time-frame."
This phenomenon of accelerated evolution is known as "tachytely".
Among our ancestors, brain size doubled between two million and one million years ago. Then it has almost doubled again between one million years and the present day.
Along with the increase in brain size came a reduction in the size of the teeth and face along with other changes in the skull.
Such fast change is not seen among apes, and … the move our ancestors made from a tree-dwelling, to a ground-dwelling existence … is not enough to explain what is observed.
Certain evolutionary psychologists have popularised a model in which culture and brain complexity spurred each other on to greater heights in humans…But Prof Tatersall said …
Aggression between small, distinct human groups in the past is one of the major remaining agents of such changes. … He said, "Inter-group conflict would certainly have placed a premium on such correlates of neural function as planning and throwing. If we were somehow able to implicate conflict among groups as a selective agent for increasing intelligence within groups, this might explain the otherwise quite mystifying independent increases in brain size that we see in several different lineages within the genus Homo."
Such conflict could be seen as a form of predation. And, predation is regarded as a classic example of the "Red Queen" hypothesis whereby prey and predator become faster or more cunning in a self-reinforcing way.
Indeed, there are hints of such conflict from the sparse fossil record. A paper published this month in the Journal of Human Evolution http://www.sciencedirect.com/science/article/pii/S0047248412001406 suggested that ancient humans in northern Spain were engaged in predatory cannibalism against another band of people.
Prof Tatersall refers to the phenomenon as the "ratchet effect" and pointed to the large variation in human fossils from the early Pleistocene in Africa as an example, which may support his hypothesis.
At the conference, Richard Wrangham from Harvard University offered an alternative view, questioning the role of conflict as a driver. He pointed out that human hunter-gatherers had similar rates of inter-group aggression to chimpanzees. | <urn:uuid:63820689-46b3-417d-9f65-481a56e1e411> | 3.328125 | 608 | Comment Section | Science & Tech. | 39.631686 |
Science Fair Project Encyclopedia
The trachea (IPA /'treikiə/), or windpipe, is a tube extending from the larynx to the bronchi in mammals, and from the pharynx to the syrinx in birds, carrying air to the lungs. It is lined with ciliated cells which push particles out and reinforced with cartilage rings.
In ill or injured persons, the natural airway formed by the trachea may be damaged or closed off. Intubation is the medical procedure of inserting an artificial tube into the trachea to permit breathing. See also choking.
Diseases of the trachea include:
Many terrestrial arthropods have evolved a closed respiratory system composed of spiracles, tracheae, and tracheoles to transport metabolic gasses to and from tissue. The distribution of spiracles can vary greatly among the many orders of insects, but in general each segment of the body may have a pair of spiracles, each of which connects to an atrium and has a relatively large tracheal tube behind it. The tracheae are invaginations of the cuticular exoskeleton that branch throughout the body with diameters ranging from 200 micrometers to 0.1 micrometers. The smallest tubes, tracheoles, penetrate tissue cells and serve as sites of diffusion for water, oxygen, and carbon dioxide. Gas may be conducted through the respiratory system by means of active ventilation or passive diffusion. Insects do not carry oxygen in their blood, as do vertebrates; this limits their size.
A tracheal tube may contain ridge-like circumferential rings of taenidia in various geometries such as loops or helixes.
In the head, thorax, or abdomen, tracheae may also be connected to air sacs. Many insects, such as grasshoppers, which actively pump the air sacs in their abdomen, are able to control the flow of air through their body.
- Westneat, Mark W.; Betz, Oliver; Blob, Richard W.; Fezzaa, Kamel; Cooper, James W.; Lee, Wah-Keat (January 2003) "Tracheal Respiration in Insects Visualized with Synchrotron X-ray Imaging". Science 299, 558-560.
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:fd051a88-af45-4e67-893f-3edd2013cd2a> | 3.640625 | 513 | Knowledge Article | Science & Tech. | 44.534911 |
Plants producing Oxygen at Night
e.heim at bluewin.ch
Sat Oct 21 13:32:05 EST 2000
No, I dont think, that plants can produce oxygen at night. For oxygen
production they need light. It might be possible, that some kind of plants
produce oxygen during the time you have put on the lights in your bedroom.
But when it is dark...? I think, it is a mission impossible.
Storage of oxygen is done by Crassulaceae. They absorb oxygen at night und
produce sugar during the day. It is an adaptation to the hot temperatures at
daylight. But i think, that you are searching for the other way. Store
oxygen during the day and release it at night. I never heard of something
Riki Clarke <rikiclarke at parisgroup.freeserve.co.uk> schrieb in im
Newsbeitrag: 8ssgou$rqr$1 at news6.svr.pol.co.uk...
> Hi all
> Can anyone answer my dilemma regarding plants as I was led to believe that
> certain types of plant were more suitable for the bedroom than others
> because they produced or released Oxygen at night. Is this true - can
> produce oxygen at night or can they store oxygen they have produced during
> the day to release at night ???
> If they do please give plant examples.
> Many Thanks
More information about the Plantbio | <urn:uuid:122ffef2-3f74-4a2f-9a7e-13e5fe4fc6a7> | 3.015625 | 316 | Comment Section | Science & Tech. | 70.618966 |
Since when are evolutionary biologists supposed to be experts in physics?
1/12/2007 3:05:33 AM
Because electrons in a potential well can only exist in a limited number of quantized states, none of which can be described as \"stuck to the nucleus\".
Here's the \"can't be arsed to learn physics beyond 8th grade\" version: electrons are not spitballs.
1/12/2007 3:12:08 AM
Don't a proton and an electron become a neutron when they collide? I read that neutrons have a slightly higher mass than protons, so I figure that's how they form.
1/12/2007 5:14:13 AM
Yankee: Such a reaction, if it ever occurred, would emit no energy. If it happened, how would we know?
1/12/2007 6:59:19 PM
The reaction does emit something. A proton and electron combine to produce a neutron and a neutrino. Though, neutrinos are extremely hard to detect.
Luckily, protons and electrons combine most often (I believe) in a process called electron capture. This happens when a large atom has too many protons but not enough energy to radiate properly. The path of least resistance for such things is for a proton and electron pair to combine, forming a new element. This lighter element's inner electron orbit is now missing an electron (an excited state!). As electrons cascade to fill, an x-ray photon is emitted. This x-ray photon can be detected.
/Or somebody that actually knows physics could comment. We pretend to know everything, but I'm just CS.
1/12/2007 11:44:28 PM
Two words: Neutron stars.
1/13/2007 12:02:57 AM
"that in 15 billion years has never gotten attached to the nucleus."
Gentlemen, I give you:
By combining a Proton and an Electron...
2/20/2008 6:40:59 PM
Failed physics again.
During electron capture, an electron in an atom's inner shell is drawn into the nucleus where it combines with a proton, forming a neutron and a neutrino. The neutrino is ejected from the atom's nucleus.
2/20/2008 7:17:01 PM
2/20/2008 7:49:15 PM
You shame your village.
5/21/2008 1:52:33 PM | <urn:uuid:6777bdee-7943-493a-8eb1-3de67e56e4d8> | 2.875 | 523 | Comment Section | Science & Tech. | 80.255 |
What is Photosynthesis?
by Govindjee and Rajni Govindjee
Photosynthesis converts massive amount of Sunlight into electrical and then chemical energy. The input is carbon dioxide (CO2), water (H
2O), minerals and light, and the output is carbohydrates (food) that we need for our nourishment, and oxygen that we need to breathe [Ref. 1] This oxygenic photosynthesis occurs in higher plants (e.g., rice, maize, wheat, mosses, ferns, forest trees, shrubs, etc); in green, red, brown and yellow algae, and even blue-green cyanobacteria. There are photosynthetic bacteria (e.g., purple and green bacteria; and heliobacteria) that can produce carbohydrate (food), but no oxygen. They are called anoxygenic photosynthesizers. Instead of the all-abundant water, they use H2S or even organic matter. Oxygenic photosynthesizers use the green pigment Chlorophyll a, located in protein complexes in photosynthetic membranes, to run the photochemistry of the process, whereas the anoxygenic photosynthesizers use Bacteriochlorophyll instead. The set of photosynthetic reactions are arbitrarily divided into (1) the light phase (that produces the reducing power and ATP, the energy currency of life); and (2) the dark phase (where the products of light phase are used to convert CO2 to carbohydrates).
Photosynthesis is the most important biological process on Earth. It serves as the World's largest solar battery. The primary reactions have close to 100% quantum efficiency (i.e., one quantum of light leads toone electron transfer); and under most ideal conditions, the overall energy efficiency can reach 35%. Due to losses at all steps in biochemistry, one has been able to get only about 1 to 2% energy efficiency in most crop plants. Sugarcane is an exception as it can have almost 8% efficiency. However, many plants in Nature often have only 0.1 % energy efficiency. Due to massive vegetation, the total productivity is very high indeed. (Deforestation is a bad deal for all of us because it would add to the already increasing CO2 in the atmosphere and its attendant consequences, such as global warming.) The photosynthesis of the past is what had stored the Sun's energy that ultimately produced coal; natural gas; and the petroleum (called petrol in India and gas in USA). Photosynthesis also provides us with the fiber, the clothing, and indirectly all the building materials including our Macs and PCs. In the villages in India, firewood, used for cooking and heating, also owes its existence to Photosynthesis. We cannot leave out the dried "cowdung" (gobar) from the scene. The cow that produced it clearly ate hay that was the dried form of what photosynthesis had produced for her. Thus, we depend upon the process for our existence in more ways than is often considered. Perhaps, the Earth is the only hospitable planet for our lives. In short, our Sun God (Suraj Devta) has given us this life through Photosynthesis.
The major problem is that increasing population pressures may cause havoc in our Society if the future Photosynthesis cannot support it. Thus, it is essential to understand the intricacies of the process and exploit it to our benefit. We need to learn how to improve crop productivity; how to go after sustainable agriculture; and how to invent means such that plant biotechnology becomes our friend, not our enemy; and how to mold plants by genetic engineering to provide us with cheap vaccines and medicines. Finally, the impact of global climate change on Photosynthesis and of Photosynthesis on global climate change needs to be understood [Refs. 2 and 3]. Thus, it is necessary to train scientists who will exploit the molecular and cellular aspects of photosynthesis, and also those who will go after integrating the information at a systems level. Both must go on hand in hand in order for the future to be bright for our grand children and great grand children.
Applications. Several photosynthesis-based (and, some distant) opportunities for the human race are highly promising.
As mentioned earlier, the primary reaction of photosynthesis is highly efficient. Thus, attempts are being made to produce artificial systems to just do that and to produce chemical energy in artificial systems (e.g., in membrane vesicles, the liposomes). A research group at Arizona State University has succeeded in producing ATP (the energy currency of life) in such systems [Ref. 4].
Since water is available in huge quantities on our Earth, and since hydrogen is a clean fuel, another effort is being made at Golden (Colorado) and Berkeley (California) to use the green alga Chlamydomonas reinhardtii to trick it in converting water into oxygen and hydrogen. The problem is that hydrogen production machinery is sensitive to oxygen. Thus, researchers are attempting to separate in time the two processes. We await results of such research.
Genetic Engineering is another powerful approach that is being used to produce plants that are, for example, resistant to frost; insects; drought and pathogens (disease causing organisms), etc. A specific example is the development of a cotton variety that would be resistant to caterpillars that are eating the leaves and destroying the crops. The best hope for the developing countries is, of course, the increased yield of plants under marginal lands (such as in dry and saline soils).
Another exciting approach, also by genetic engineering, is to construct plants that have added nutritional values (such as plants that make lots of Vitamin E; crop plants that are rich in specific proteins; rice containing iron in the form of ferritin; and canola plants that produce palm oil). Such engineering approaches [Ref. 5] can increase quality and quantity of food to meet the needs of the increasing World population.
A highly exciting new application is constructing plants that produce medicines (plants have been doing it since they came to be on our Earth, but now we can direct them to make what we need and in quantities we need). In particular, efforts at Boyce Thompson Institute aim to produce vaccines in bananas that will revolutionize their delivery to children in developing countries [Ref. 6]. It will be affordable and would increase the life expectancy and health of millions. What a delightful thought! .
Sun shines each day and does not charge us any money for the light it gives us. The light falling on Earth is very clean and will be there for a very long time as long as the Sun lasts. In addition to the current applications, mentioned above, Photosynthesis-based technology could also include (1) using the concept of efficient "energy capture" to our artificial systems just as plants have been doing: thousands of chlorophyll a molecules (antenna) serving one center where the process occurs efficiently; (2) the use of compounds, produced by plants, in triggering reactions that kill cancer cells; and (3) the use of photosynthetic organisms in cleaning of aqueous surface environments (lakes, etc). An excellent example is in the use of cyanobacteria that literally eat up the nitrates from ground water and clear it for us. The opportunities that photosynthesis-based technology provides us are enormous. The success, however, requires a concerted effort on the part of biophysicists, biochemists, molecular biologists, plant physiologists, microbiologists, geneticists, agronomists, physicists, chemists, bio-technologists and engineers to come together and ask what they can do for the World, not what the World can do for them.
Hall, D.O. and K.K. Rao (1999) Photosynthesis. 6th Edition,Cambridge University Press, Cambridge, UK. (ISBN 0-521-64497 6, paperback), 214 pages
Walker, D. (1992) Energy, Plants and Man. Oxygraphics, Sheffield, U.K. (ISBN 1 870232 05 4, paperback), 277 pages.
Falkowski, P. G. and J.A. Raven (1997) Aquatic Photosynthesis. Blackwell, Oxford, UK (ISBN 0-86542-387-3, paperback), 375 pages.
Steinberg-Yfrach, G., J.-L. Rigaud, E.N. Durantini, A.L. Moore, and T. Moore (1998) Light-driven production of ATP catalysed by FoF1-ATP Synthase in an artificial membrane. Nature 392: 479-482.
Shintani, D. and DellaPenna, D. (1998) Elevating the Vitamin E content of plants through metabolic engineering. Science 282: 2098-2100.
Langridge, W.H. (2000) Edible Vaccines. Scientific American 283: 66-71.
For further reading, see the following four selected URLs:
http://www.life.uiuc.edu/govindjee contains sites for a brief presentation on the basics of photosynthesis; a full description of the "Photosynthesis Process"; a program "Photosynthesis and Time"; an article on "Photosynthesis and the World Wide Web", and a chapter on "Milestones in Photosynthesis", among other items.
http://esg-www.mit.edu:8001/esgbio/ps/psdir.html has a good hypertext on Photosynthesis at MIT's experimental study group; it covers both the "light" and the "dark" reactions of photosynthesis.
http://www.biotech-resource.com is a great portal to biotech resources.
http://photoscience.la.asu.edu/photosyn/ is the most visited site; it has several basic articles; list of books at all levels on photosynthesis including the Series "Advances in Photosynthesis". In particular, an excellent source of information on "Genetic Engineering and Society" can be found at this site. For a direct access, go to http://photoscience.la.asu.edu/photosyn/courses/BIO_343/default.html | <urn:uuid:3b126f4c-4cbb-426b-930f-0aff1a317a84> | 3.6875 | 2,096 | Knowledge Article | Science & Tech. | 46.619574 |
There is no guarantee that your questions here will ever be answered. You can be published anonymously - just let us know!
From Meltem YAGLI
Answered By Ben Okopnik
Hello, I am the researh assistant in Eastern Mediterranean University, and i am doing master in computer engineering department. About the adaptation of linux with other operating systems, i have a problem. if you can help me, i will be very happy.
I have a program that is written in C and my operating system is linux now. This program has been done before on dos operating system, (it includes stdio.h, stdlib.h, conio.h, etc..). so, if i want to run this program, linux can not find conio.h. (there is no such library file in linux) Could you help me for this. i wonder, is there any corresponding file in linux that can do the functions of conio.h? The only chance is to include this corresponding file to my program.
[Ben] <Smile> I certainly hope that it's not the only chance. If you take a look at the very top of "conio.h" on a DOS machine, you'll probably see something like the following (this is from the "conio.h" that came with the old Borland Turbo-C):
/* conio.h Direct MSDOS console input/output. Copyright (c) Borland International 1987,1988,1990 All Rights Reserved. */
That's why there's none in the standard C 'include's for Linux: it's a DOS-specific library! Now, I've done very little C programming in the last few years - mostly just little quick things - so I haven't had to deal with any fancy console stuff, and no need for anything like "conio.h". If I did, the library that is commonly used in Linux for console I/O is "curses.h". Take a look at libncurses5-dev; you'll have to do a bit of rewriting, since Linux handles console I/O differently from DOS, but it shouldn't be too bad.
|1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29| | <urn:uuid:9bae0574-2c1f-4f0b-8408-e386d537fc57> | 2.71875 | 479 | Q&A Forum | Software Dev. | 79.522546 |
A SPECIES of African monkey has added charcoal to its diet, apparently to help it overcome the chemical defences of the plants it eats. The monkeys can now tolerate a wider range of plants and, as a result, their population has soared.
Scientists working on the east African island of Zanzibar observed that in one part of the island, red colobus monkeys (
Struhsaker says that the monkeys get the charcoal from burned tree and palm stumps in fields, out of abandoned kilns, and even steal it from villagers' hearths. His observations, published in the current issue of the
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:bf75b47a-15a2-4bbb-89e2-152468bcfcd0> | 3.6875 | 151 | Truncated | Science & Tech. | 44.509814 |
Saturday, 1 February 1997
Why don't penguins' feet freeze?
Why do Antarctic penguins' feet not freeze in winter when they are in constant contact with the ice and snow? Years ago I heard on the radio that scientists had discovered that penguins had colateral circulation in their feet that prevented them from freezing but I have seen no further information or explanation of this. Despite asking scientists studying penguins about this, none could give an answer.
Susan Pate, Enoggera, Queensland | <urn:uuid:afa701ba-44ff-45d0-ad82-2150df66256e> | 2.71875 | 103 | Personal Blog | Science & Tech. | 47.370139 |
TOM BEARDEN: A decade ago, Camille Parmesan was spending months in the California back country doing scientific research on the biology of butterflies. She found something she wasn't looking for.
CAMILLE PARMESAN: I was really working on more basic questions of their evolution of diet and their behavior and looking for food plants and what-not, and it was over the years as I was doing this, it became very obvious that they're extremely sensitive to climate, particularly temperature.
They can only fly at very certain times of the day where you've got sunshine and the right air temperatures. If they get too hot, they stop flying. If they get too cold, they stop flying.
TOM BEARDEN: She learned those things in the early 1990s, about the time the global warming debate first began. That debate continues to this day -- if it's real, if it's caused by humans, and whether humans can do anything about it.
With her studies on butterflies, Parmesan became was one of the first scientists to study how changing climate might effect wildlife populations. When she studied one species, the Edith's Checkerspot Butterfly, up and down the West Coast, a pattern emerged.
States where the butterflies had once been but were now extinct were grouped toward the south. When she looked at places where the butterflies still lived, there was a subtle but noticeable shift to the North.
After factoring out other causes, Parmesan tentatively concluded the butterflies were gradually and almost imperceptibly moving north in response to a slight rise in global temperature.
CAMILLE PARMESAN: If something accidentally gets blown out of its normal range, the normal range for the species, it just dies. But with climate warming now, you get those same events happening, and when that female plops down and lays her eggs, now it has a chance of surviving.
And so over a five or ten-year period, you can get several populations starting. Once you get that, you've got the whole species' range having shifted.
TOM BEARDEN: A few years later, when Parmesan and her associates looked at hundreds of studies of butterflies, the same pattern showed up.
In England, the speckled wood butterfly had lived mostly in the south in the mid-20th century. By the end of the century, most had moved to the English midlands. In Sweden and Finland, the silver-washed fritillary used to live here. Now it lives here as well.
Not all the butterfly species followed that pattern. Some moved south; some didn't move at all. A clear majority, though, had moved north, and that raises questions about the negative impacts of global warming.
CAMILLE PARMESAN: The question is, how many species are going to be able to just move north and live perfectly happily, and how many are going to be obstructed, either because they are such habitat specialists that there just isn't any food for them to the North or they're being delayed because they are dependent on some plant; the plant has a slower rate of change, therefore, they can't move north.
TOM BEARDEN: Early this year, an international team of ecologists completed a computer study that went much further in predicting the consequences of global warming.
Their study made headlines around the world. It estimated that by the year 2050 as many as one million species could be on their way to extinction due to global warming.
Lee Hannah, a senior fellow at Conservation International, was one of the authors. The team looked at 1,500 plants and animals and mapped the precise areas where each could live in the present climate. Then they estimated how the climate might change by 2050.
LEE HANNAH: All species depend on climate for their survival, and each species has climatic conditions that it prefers. You'll see that this is the preferred climate of this species, and we use the climate projections to project where it might go in the future, and that's this dark yellow area.
And you can see it's both contracting and moving up slope. We're strongly seeing the up-slope movement as things go from a lower elevation where it's warm now to trying to maintain that same temperature envelope and maintain the other climate variables that it prefers in the future.
TOM BEARDEN: And at some point, it can't go... there's no place to go, there's no place to go higher.
LEE HANNAH: Right.
TOM BEARDEN: The researchers matched that reduced living space to a well-known ecological law -- The bigger the piece of land, the more different species live on it. And the corollary -- less land area means fewer species.
They concluded that hundreds of thousands of species would lose so much living space that many stood a much greater chance of eventually going extinct. How much greater? The number varied, depending on how much the climate changed.
LEE HANNAH: Species risk of extinction was quite significant with climate change-- in double digits in almost all regions and with the mid-range scenario extinction risk of about 25 to 30 percent.
TOM BEARDEN: Which is an enormous number?
LEE HANNAH: It's a very large number. It's important to notice that that number isn't expected by 2050. It's the climate changes that would occur by 2050 that would eventually lead to that level of extinction.
TOM BEARDEN: Still, as big as the number is, it's only the product of number crunching. The researchers did no new fieldwork and made no new observations. The authors admit they don't know exactly how many species might go extinct or when. What they do find is that the overall trend of the numbers is disturbing.
LEE HANNAH: We've called them a first pass or a first run "look at this" issue. And that means the early projections are a reasonable first guess at what this might mean for species on the planet.
TOM BEARDEN: Daniel Botkin thinks the computer modeling used in the study was too simplistic.
DANIEL BOTKIN: Quantitatively not useful, and based on a false premise which is not useful.
TOM BEARDEN: Botkin taught environmental science at the University of California, Santa Barbara , wrote a book about forest ecology, and even developed a computer program to predict growth patterns in forests over many years.
He says species are adaptable and the study doesn't prove plants and animals will go extinct if their living space shrinks.
DANIEL BOTKIN: Shrinking area will have an effect, but having a small area or a smaller area of a certain size doesn't necessarily mean you have by necessity dropped an exact number of species.
That's not to say that there isn't going to be an effect on species of global warming or that as you reduce area and reduce habitat there won't be problems. But as a prediction, in terms of the number of species, this paper is, I believe, misleading.
TOM BEARDEN: Some have argued that this is essentially a computer modeling study and that the computer models themselves don't really accurately reflect the ecosystem itself.
LEE HANNAH: We're trying to look at what happens in the future, and of course those efforts can never be perfect. These models are some of the most sophisticated tools we have to address this issue. That's why we think it's important to take their results very seriously.
TOM BEARDEN: Botkin says he does take the impact of global warming on species seriously, but he thinks the right approach is to work it out slowly, one species at a time.
DANIEL BOTKIN: Well, the approach I like is the approach that I've used myself, where you look at individual species and use them and for themselves or as types of species and then look at specific effects of global warming.
My concern is that we haven't looked enough at the effects on living things. This has been a very small part of any funding and any effort, and yet effects on life is what really matters about global warming.
TOM BEARDEN: Camille Parmesan is continuing her studies in the lab, not the field. She says biologists spent a lot of the 20th century worrying about a different threat to wildlife -- the loss of habitat caused by advancing civilization. So they were slow, she says, to respond to climate as a different threat.
CAMILLE PARMESAN: People have shifted from thinking of habitat loss as being the major problem. Well, it's the major problem right now, but if you're trying to save something for your grandchildren, something over the next 100 years, then climate change turns out to be a bigger problem.
TOM BEARDEN: Parmesan and other scientists hope their findings can help guide policy-makers on the best response to a changing climate in the future. | <urn:uuid:e67f5c3d-79a0-44be-8369-6787affabbc8> | 3.25 | 1,866 | Audio Transcript | Science & Tech. | 54.321557 |
- The brain contains neural machinery for recognizing errors, correcting them, and optimizing behavior.
- The neurotransmitter dopamine plays a major role in our ability to learn from our mistakes. Genetic variants that affect dopamine signaling may partly explain differences between people in the extent to which they learn from errors or negative consequences.
- Certain patterns of cerebral activity often foreshadow errors, opening up the possibility of preventing blunders with portable devices that can detect error-prone brain states.
April 26, 1986: During routine testing, reactor number 4 of the Chernobyl nuclear power plant explodes, triggering the worst catastrophe in the history of the civilian use of nuclear energy.
September 22, 2006: On a trial run, experimental maglev train Transrapid 08 plows into a maintenance vehicle at 125 mph near Lathen, Germany, spewing wreckage over hundreds of yards, killing 23 passengers and severely injuring 10 others.
This article was originally published with the title Minding Mistakes. | <urn:uuid:0c215f3a-3e1e-4f57-b984-87788ac5bfe3> | 3.328125 | 195 | Truncated | Science & Tech. | 21.347857 |
Wilson Bentley, an early 20th century farmer from Jehrico, Vermont, is best remembered as the "Snowflake Man" for his thousands of marvelous snowflake photographs. But Bentley also was a student of the rain. Hi, I'm Dave Thurlow and this is The Weather Notebook.
While photographing snowflakes was his life's work, for six summers Bentley turned his interest to examining and sizing raindrops. His contributions to the science of meteorology are legendary, especially since his exhaustive study, was just a hobby.
Bentley's apparatus for gathering raindrops - a shallow pan of wheat flour - was a marvel of simplicity. While photographing rain splash patterns, Bentley found them to be just about the same size as the falling drops. He divided his raindrop "fossils" into five size categories to determine their size distribution.
He then determined that different kinds of storms produce different size raindrops. Bentley found few rainfall events had uniform drop sizes, but those that did were composed of either all small drops or all large drops. He concluded that the size of drops and flakes tells a lot about the vertical structure of the storm, which before airplanes was a true find. Low clouds he found, produced small drops mostly. The largest drops, around a quarter inch in diameter, fell from miles-high clouds: those of thunderstorms.
Unfortunately, Bentley was so far ahead of his time that he wasnt fully appreciated by contemporary scientists. They didnt take this farmer seriously. It was 40 years before his work was uncovered, work that set up even the current understanding of snowflake, and raindrop, formation.
Thanks to contributing writer Keith Heidorn. Find out more about snowflake Bentley at mountwashington.org | <urn:uuid:736fd959-2068-45ba-8700-9199ccb33046> | 3.28125 | 358 | Audio Transcript | Science & Tech. | 46.46379 |
Recipe for the Perfect James Webb Space Telescope Mirror
Mirrors are a critical part of any space telescope, and the James Webb Space Telescope's mirrors are made of a special element that will enable it to withstand the rigors of space and see farther back in time/distance than any other telescope now in operation.
Space telescope mirrors must endure the extremely frigid temperatures in space, be highly reflective, lightweight and tough. Those are exactly the qualities that make up the 18 mirrors being developed for the Webb Telescope.
To collect as much light as possible to see galaxies from 13 billion light-years away, the Webb Telescope needs a large mirror but also needs to be lightweight enough to not weigh down the rocket carrying it into space. The answer was to make it out of beryllium.
Mirror History and Make-up
By definition, a mirror is an object with a surface that is smooth enough to form an image, such as a "plane mirror," which has a flat surface. Curved mirrors produce magnified or reduced images or focus light or simply distort the reflected image. Most mirrors are designed for visible light. There are, however, mirrors that work at other wavelengths of electromagnetic radiation, "such as X-ray, infrared, microwave, or even radio wavelengths.
Mirrors on Earth have been made from many things. Europeans during the Renaissance coated glass with a tin-mercury amalgam. The silvered-glass mirror invented in 1835 involved the deposition of a thin layer of metallic silver onto glass through the chemical reduction of silver nitrate. Today, mirrors are often produced by the vacuum deposition of aluminum (or sometimes silver) directly onto the glass substrate.
Space Mirrors: What is Beryllium?
Mirrors for space telescopes require special materials. That's where beryllium comes in. Beryllium is a light metal (atomic symbol: Be) with many features that make it desirable to be used for the Webb Telescope's mirrors.
Beryllium is steel-gray in color, very strong for its weight and good at holding its shape across a range of temperatures, which is just what it would encounter in space. Beryllium is also a good conductor of electricity and heat and is not magnetic. It also has one of the highest melting points of the light metals.
What's also interesting is that beryllium is a relatively rare element in both the Earth and the universe, because stable forms of beryllium are not formed either in the atomic reactions inside stars or in the Big Bang. Instead, when carbon and oxygen atoms in the gas between the stars collide with each other or are struck by other particles, the nucleus of the atoms will occasionally break into up into the lighter elements lithium, beryllium and boron.
Here on Earth, most of the beryllium exists in minerals such as beryl and bertrandite. It is also a component of the precious gems aquamarine, red beryl and emerald. Currently, most industrial production of beryllium is accomplished by a chemical reaction between beryllium fluoride and magnesium metal.
Beryllium is used to develop parts for supersonic (faster-than-the-speed-of-sound) airplanes and the Space Shuttle, because it is both lightweight and strong. It is also used in gyroscopes, computer equipment, watch springs and instruments where light weight, rigidity and dimensional stability are needed.
Beryllium is actually highly toxic to plants, animals and humans. It's not necessary or useful for life. In fact, it has no known role in living organisms. So, during the manufacturing and handling, special care has to be taken when working with it, because it is unhealthy to breathe in or swallow beryllium dust.
How and Where the Beryllium Mirror is Made
The beryllium being used to make the Webb Telescope's mirrors was mined in Utah and then purified. The particular type of beryllium used in the Webb mirrors is called "O-30" and is a fine powder of high purity. The powder is then placed into a stainless steel canister and pressed into a flat shape. The steel canister is then removed and the resulting chunk of beryllium is cut in half to make two mirror blanks about 1.3 meters (4 feet) across. Each mirror blank will be used to make one mirror segment; the full Webb mirror will be made from 18 hexagonal (six-sided) segments.
Once the mirror blanks pass inspection, they are molded into their final shape, polished and temperature tested to ensure they can withstand the frigid temperatures of space.
Beryllium is much more capable than glass to handle the frigid cold of space. The James Webb Space Telescope will face a temperature of -240 degrees Celsius (33 Kelvin). Beryllium contracts and deforms less than glass -- and remains more uniform -- in such temperatures. For the same reason, the optics of the Spitzer Space Telescope were entirely built of beryllium metal. It is thanks to beryllium that the James Webb Space Telescope will be able to see further back into the universe and back in time than any other space telescope operating today.
The James Webb Space Telescope is expected to launch in 2013. NASA's Goddard Space Flight Center in Greenbelt, Md., is managing the overall development effort for the Webb Telescope. The telescope, being built by Northrop Grumman, is a joint project of NASA and many U.S. partners, the European Space Agency and the Canadian Space Agency.
NASA's Goddard Space Flight Center | <urn:uuid:29c6b6a0-2aad-4fa8-ae93-9ed03bd6fe54> | 4.21875 | 1,163 | Knowledge Article | Science & Tech. | 42.305724 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2001 January 17
Explanation: Why is NGC 3310 bursting with young stars? The brightest of these new stars are so hot that they light up this spiral galaxy not only in blue light, but in light so blue humans can't see it: ultraviolet. The Hubble Space Telescope took the above photograph in different bands of ultraviolet light. Speculation holds that NGC 3310 collided with one of its own dwarf companion galaxies only about 50 million years previously. This merger sent density waves rippling around the spiral disk, causing many gas clouds to condense into star forming regions. Imaging nearby galaxies in ultraviolet light allows astronomers to better understand the images of distant highly redshifted galaxies in visible light, and so to understand why many of these distant galaxies appear relatively fragmented. The unusually smooth NGC 3310 spans over 20 thousand light years and lies about 50 million light years away towards the constellation of Ursa Major.
Authors & editors:
Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
& Michigan Tech. U. | <urn:uuid:19f5abd0-3fac-4351-8f8d-54f4fb9c1338> | 3.765625 | 261 | Knowledge Article | Science & Tech. | 47.340777 |
The equation for respiration is C6H12O6+6O2→6CO2+6H2O+36ATP. The chemical formula for ATP is C10H16N5O13P3. How is this possible, since it violates the law of conservation of mass because it is ...
When a human being exhales $CO_2$, what is, by the numbers, the main source of carbon atoms exiting the body in this way? I mean what class of cells, or which tissues are the biggest on a pie chart of ...
I was wondering what oxygen actually does in the body. I have seen a few answers to other questions that involve the electron chain and I am really not sure what that is. So I was wondering what ...
I know NADH is used in cellular respiration and NADPH is used in photosynthesis. What difference does the phosphate group make that the same one isn't or can't be used for both? Is there a greater ...
What does the human body use oxygen for besides the final electron acceptor in the electron transport chain?
My biology teachers never explained why animals need to breathe oxygen, just that we organisms die if we don't get oxygen for too long. Maybe one of them happened to mention that its used to make ATP. ... | <urn:uuid:ee45d6ba-49a6-45f5-8eeb-4ef4e32386fb> | 3.171875 | 268 | Q&A Forum | Science & Tech. | 69.754927 |
(3 quadrocopters = 12 rotors)
To toss the ball, the quadrocopters accelerate rapidly outward to stretch the net tight between them and launch the ball up. Notice in the video that the quadrocopters are then pulled forcefully inward by the tension in the elastic net, and must rapidly stabilize in order to avoid a collision. Once recovered, the quadrotors cooperatively position the net below the ball in order to catch it.
Because they are coupled to each other by the net, the quadrocopters experience complex forces that push the vehicles to the limits of their dynamic capabilities. | <urn:uuid:42ad6a2b-3942-4a4e-b313-87c24475c07d> | 3.359375 | 125 | Tutorial | Science & Tech. | 32.6625 |
Summary: Solid carbon dioxide is added to a large beaker of water containing universal indicator. As the CO2 dissolves, the indicator changes from neutral (green) to acidic (orange).
Dry Ice is extemely cold, use gloves or tongs when handling.
Chemicals and Solutions:
universal indicator solution
2 lbs. dry ice
25 mL of 0.l M NaOH solution
6 M NaOH solution
4 liter beaker of water
Add univeral indicator solution to the water and make the solution purple by adding some 0.1 M NaOH solution. Then just start adding dry ice to the solution. The dry ice will sublime causing the solution to bubble and it will also dissolve in the water forming carbonic acid causing the indicator to change colors as the solution becomes more and more acidic. The solution will change from purple to blue to green to yellow to orange and finally to red. Once the red color is reached 6M NaOH can be added to take the color back up to purple and the cycle can begin again. | <urn:uuid:73777b8a-a85d-4e25-ab02-50b328ce28c8> | 3.109375 | 216 | Tutorial | Science & Tech. | 51.990893 |
Index of dispersion
In probability theory and statistics, the index of dispersion, dispersion index, coefficient of dispersion, or variance-to-mean ratio (VMR), like the coefficient of variation, is a normalized measure of the dispersion of a probability distribution: it is a measure used to quantify whether a set of observed occurrences are clustered or dispersed compared to a standard statistical model.
It is also known as the Fano factor, though this term is sometimes reserved for windowed data (the mean and variance are computed over a subpopulation), where the index of dispersion is the special case where the window is infinite. Windowing data is frequently done: the VMR is frequently computed over various intervals in time or small regions in space, which may be called "windows", and the resulting statistic called the Fano factor.
It is only defined when the mean μ is non-zero, and is generally only used for positive statistics, such as count data or time between events, or where the underlying distribution is assumed to be the exponential distribution or Poisson distribution.
In this context, the observed dataset may consist of the times of occurrence of predefined events, such as earthquakes in a given region over a given magnitude, or of the locations in geographical space of plants of a given species. Details of such occurrences are first converted into counts of the numbers of events or occurrences in each of a set of equal-sized time- or space-regions.
The above defines a dispersion index for counts. A different definition applies for a dispersion index for intervals, where the quantities treated are the lengths of the time-intervals between the events, and where the index is equivalent to the square of the coefficient of variation of the interval lengths. Common usage is that "index of dispersion" means the dispersion index for counts.
Some distributions, most notably the Poisson distribution, have equal variance and mean, giving them a VMR = 1. The geometric distribution and the negative binomial distribution have VMR > 1, while the binomial distribution has VMR < 1, and the constant random variable has VMR = 0. This yields the following table:
|constant random variable||VMR = 0||not dispersed|
|binomial distribution||0 < VMR < 1||under-dispersed|
|Poisson distribution||VMR = 1|
|negative binomial distribution||VMR > 1||over-dispersed|
When the coefficient of dispersion is less than 1, a dataset is said to be "under-dispersed": this condition can relate to patterns of occurrence that are more regular than the randomness associated with a Poisson process. For instance, points spread uniformly in space or regular, periodic events will be under-dispersed.
If the index of dispersion is larger than 1, a dataset is said to be over-dispersed: this can correspond to the existence of clusters of occurrences. Clumped, concentrated data is over-dispersed.
In terms of the interval-counts, over-dispersion corresponds to there being more intervals with low counts and more intervals with high counts, compared to a Poisson distribution: in contrast, under-dispersion is characterised by there being more intervals having counts close to the mean count, compared to a Poisson distribution.
The relevance of the index of dispersion is that it has a value of one when the probability distribution of the number of occurrences in an interval is a Poisson distribution. Thus the measure can be used to assess whether observed data can be modeled using a Poisson process.
A sample-based estimate of the dispersion index can be used to construct a formal statistical hypothesis test for the adequacy of the model that a series of counts follow a Poisson distribution.
The VMR is a good measure of the degree of randomness of a given phenomenon. This technique is also commonly used in currency management.
For randomly diffusing particles (Brownian motion), the distribution of the number of particle inside a given volume is poissonian, i.e. VMR=1. Therefore, to assess if a given spatial pattern (assuming you have a way to measure it) is due purely to diffusion or if some particle-particle interaction is involved : divide the space into patches, Quadrats or Sample Units (SU), count the number of individuals in each patch or SU, and compute the VMR. VMRs significantly higher than 1 denote a clustered distribution, where random walk is not enough to smother the attractive inter-particle potential.
The first to discuss the use of a test to detect deviations from a Poisson or binomial distribution appears to have been Lexis in 1877. One of the tests he developed was the Lexis ratio.
This index was first used in botany by Clapham in 1936.
If the variates are Poisson distributed then ihe index of dispersion is distributed as a χ2 statistic with n - 1 degrees of freedom when n is large and is μ > 3. For many cases of interest this approximation is accurate and Fisher in 1950 derived an exact test for it.
Hoel studied the first four moments of its distribution He found that the approximation to the χ2 statistic is reasonable if μ > 5.
See also
Similar ratios
- Coefficient of variation,
- Standardized moment,
- Fano factor, (windowed VMR)
- Signal to noise ratio, (in signal processing)
- Cox &Lewis (1966)
- Cox & Lewis (1966), p72
- Cox & Lewis (1966), p71
- Cox & Lewis (1966), p158
- Upton&Cook(2006), under index of dispersion
- Frome EL (1982) Algorithm AS 171: Fisher's exact variance test for the Poisson distribution. J Roy Stat Soc Series C (Applied Statistics) 31(1) (1982) 67-71
- Hoel PG (1943) On indices of dispersion. Annals Math Stat 14(2) 155-162
- Cox, D. R., and Lewis, P.A.W. (1966) The Statistical Analysis of Series of Events Methuen, London
- Upton, G., and Cook, I. (2006) Oxford Dictionary of Statistics (2nd edition). OUP. ISBN 978-0-19-954145-4 | <urn:uuid:11a73c91-edca-42f5-a7c2-ab2e0c733b8c> | 3.734375 | 1,330 | Knowledge Article | Science & Tech. | 40.392554 |
Meet the Tiniest Wing-Propelled Diver
Most wing-propelled diving birds are fairly large, ocean-going fellows. Not so for the smallest species to adapt this strategy. Cinclidae are a very special group of songbirds that hunt underwater for insect prey in freshwater streams. These marvelous little birds are capable of both “walking” along the bottom by gripping the substrate and of propelling themselves through the water column with their wings. Today, five species can be found. As a group these species have spread throughout much of the world including North America, Europe, Asia and Africa.
Dippers look rather unassuming when on land, and it would be easy to mistake them for catbirds or other garden variety songbirds at a glance. However, detailed studies have revealed many evolutionary novelties associated with more efficient waterproofing of the feathers, modified wing musculature to assist in the underwater “flight” stroke, and physiological properties of blood haemoglobin that make them very efficient at employing their unique feeding strategy. DNA studies indicate that the closest relatives of the dippers are thrushes and Old World flycatchers, but these groups show no particular affinities for water.
Our team is studying the dipper to learn what it can tell us about the earliest stages of wing-propelled diving. Since dippers make only shallow dives, are very small, and spend much time on land, they may provide clues about which evolutionary changes happen first during the transitions from a non-diving, volant bird body plan to a flightless diving bird body plan (like that of penguins). | <urn:uuid:3f231796-937d-4da4-88ae-13470872cbfc> | 3.75 | 330 | Personal Blog | Science & Tech. | 34.330248 |
close closes stream.
Closing a stream means
that it may no longer be used in input or output operations.
The act of closing a file stream
ends the association between the stream and its associated file;
the transaction with the file system is terminated,
and input/output may no longer be performed on the stream.
If abort is true, an attempt is made to clean up any side
effects of having created stream.
If stream performs output to a file
that was created when the stream was created, the
file is deleted and any previously existing file is not superseded.
It is permissible to close an already closed stream,
but in that case the result is implementation-dependent.
After stream is closed, it is still possible to perform
the following query operations upon it:
streamp, pathname, truename,
merge-pathnames, pathname-host, pathname-device,
pathname-type, pathname-version, namestring,
host-namestring, enough-namestring, open,
probe-file, and directory.
The effect of close on a constructed stream is
to close the argument stream only.
There is no effect on the constituents of composite streams.
For a stream created with make-string-output-stream,
the result of get-output-stream-string is unspecified after close. | <urn:uuid:315c56fe-61e1-4416-aaab-c5612e2864a4> | 2.796875 | 293 | Documentation | Software Dev. | 42.679525 |
Project Title: Evaluating Tsunami Hazards to the Atlantic and Caribbean Coasts
Mendenhall Fellow: Alberto Lopez-Venegas, email@example.com
Duty Station: Woods Hole, MA
Start Date: October 1, 2006
Education: Ph.D. 2006, Northwestern University, Geophysics
Research Advisors: Uri ten Brink, (508) 457-2396, firstname.lastname@example.org; Eric Geist, (650) 329-5457, email@example.com; Homa Lee, (650) 329-5485, firstname.lastname@example.org
Project Description: Tsunamis, resulting from either tectonic events or subaerial/submarine landslides, have been historically recorded in the Caribbean region since the 16th century (Lander and others, 2002). At least 91 reported tsunamis have occurred in the Caribbean basin since colonization by Europeans, and of these events, at least 27 have been well documented. In 1918, an earthquake occurring on the western wall of the Mona Canyon (M 7.5) between Hispaniola and Puerto Rico (Mercado and McCann, 1998) generated a tsunami that reached the western coast of Puerto Rico and caused extensive damage along the coast and hundred of meters inland. More recently, in 1946, the northern portion of Hispaniola experienced a major earthquake (M 8.1). The death toll of the 1918 Mona Canyon and the 1946 Dominican Republic tsunamis are estimated at 42 and 1,800, respectively. The tsunami that followed within a few minutes of an earthquake in the Anegada Trough in 1867 created 6-9 meter high waves in St. Thomas's Charlotte Amalie and St. Croix's Christiansted Harbors. Although the Atlantic Ocean is primarily surrounded by passive margins, regional tectonics nearby the Iberian peninsula are prone to cause tsunamis, as is the case of the great Lisbon earthquake of 1755, which reached the Caribbean and Eastern United States with considerable wave heights.
The number of casualties in these events exceeds those from the U.S. West Coast, Hawaii, and Alaska combined during that time. Today, a repeat of any of these events could potentially yield similar destruction for the area, given the increase in population since then. Large tourism cruise ships, petroleum carriers,
hotels, marinas, condominiums, schools, petrochemicals and power plants and others are at risk. The devastation from the tsunami and resulting effects could
cost several billion dollars in damage and cost associated with fire control, rescue efforts, clean-up, and reconstruction.
The Atlantic coast, although not at a risk of a near-field tsunami by thrust earthquakes, is at risk from far-field tsunamis and locally generated landslides,
such as the one triggered by the 1929 Grand Banks earthquake (M 7.2) that affected the U.S. and Canadian Atlantic coasts (e.g. Piper et al., 1999). In
addition, the continental slope of the U.S. shows evidence for many past slides, and the adjacent abyssal plains show giant sedimentation events, possibly from large submarine slides (Pilkey, 1988), whose recurrence interval has not been estimated so far.
These and other factors reflect the potential catastrophic events to which the Caribbean and the Atlantic are prone. Hence, knowledge of potential tsunami
genesis locations and their outcome must be evaluated a priori, in order to be prepared for their occurrence. To assess the risks and estimate with a higher degree of accuracy which areas are vulnerable and the likely damage extent, a detailed study of the bathymetry is to be obtained and updated. Proposed work includes detailed multibeam bathymetry surveys along the northeastern coast of the Caribbean plate, with emphasis on northeastern Hispaniola, the Mona Canal and the northern Lesser Antilles. These data, in conjunction to single-channel seismic reflection/refraction profiles and re-location of microearthquake activity will be used to identify active faults in the area and evaluate whether those faults are capable of generating tsunamis. Once candidate faults are examined, a range of fault geometries and parameters will be used to forecast and examine near and far fields effects.
Lander, J.F., Whiteside, L.S., and Lockridge, P.A., 2002, A brief history of tsunamis in the Caribbean Sea: Science of Tsunami Hazards, v. 20, p. 57–94.
Mercado, A., and McCann, W., 1998, Numerical simulation of the 1918 Puerto Rico tsunami: Natural Hazards, v. 18, p. 57–76.
Pilkey, O.H., 1988, Basin plains: Giant sedimentation events, in Clifton, H.E., ed., Sedimentologic consequences of convulsive geologic events,
Geological Society of America Special Paper 229, p. 93–99,.
Piper, D.J.W., Cochonat, P., and Morrison, M.L., 1999, The sequence of events around the epicentre of the 1929 Grand Banks earthquake; initiation of debris flows and turbidity current inferred from sidescan sonar: Sedimentology, v. 46, p. 79–97.
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Interleaving the binary encodings of the two numbers a and b seems to be the best solution:
For example the encoding of
a = 20d = 10100b
b = 5d = 101b
We interleave the bits starting with the least significant bits (we pad shorter numbers with 0's so they are the same length).
The two original numbers resulting paired number is 0100110010b = 306d
This pairing function can be easily decoded in computed and reversed by a constant time.depth (see http://mathworld.wolfram.com/PairingFunction.html, depth 1?) circuit and so is in FAC0.
- Pigeon, P. Contributions à la compression de données. Ph.D. thesis. Montreal, Université de Montréal, 2001. (page 115) | <urn:uuid:5d9ba81a-817d-49a6-aab7-48fa07a69008> | 3.078125 | 177 | Knowledge Article | Science & Tech. | 78.268357 |
Imagine a space faring civilization hurtling between galaxies at speeds fast enough to travel from Earth to the moon in seven minutes! They are being propelled by the gravitational energy of a black hole. And, their "spaceship" has resources for supporting a population of several billion.
This sounds like far out science fiction fantasy, but it's within the realm of plausibility.
It turns out that the supermassive black hole in the center of our Milky Way galaxy hits a star "out of the ballpark" about every 100,000 years. Astronomers have clocked these runaway stars as having enough velocity to escape the galaxy.
Though as yet there is no definitive evidence that traces their trajectories straight back to the central black hole, there is no other conceivable mechanism for imparting so much kinetic energy onto a star — not a supernova blast, nor a gravitational "billiard ball" game among multiple star systems.
That is, unless the central 4 million solar mass black hole becomes one of the players. The theory is that a star could be slingshot out of a binary star system if the stellar duo swung close to the central black hole. The hole's gravitational tidal forces would break apart the pair's gravitational embrace.
The companion star orbiting in the direction of the black hole would pick up momentum and plunge toward the black hole. In accordance with Newton's third law of motion — action-reaction — the other binary companion would go whizzing off with the same velocity but opposite direction away from the black hole.
In just a few thousand years the star would ascend out of the galactic plane and hurtle deep into intergalactic space. The persistent tug of our Milky Way's dark matter halo would slow it down but the star would never fall back into the Galaxy.
So far at least 16 of these so-called hypervelocity stars are known. They were first hypothesized in 1988. But the first one wasn’t detected until 2005. Hot and bright blue short-lived stellar runaways have been picked out because they are not native to the old stellar galactic halo population, they had to travel there. Also, the torturous Milky Way core — a stellar Monster Truck assembly plant — favors making massive stars in binary pairs.
However, it is not impossible that a sun-like star in a binary system could get the boot too. It would carry along any planetary system.
Now imagine an intelligent civilization arises on the surface a habitable planet in the runaway system. Their astronomers would gaze out into an inky black starless sky. True, there are stars in the Milky Way’s halo, but they are so faint that only a chance nearby passing star would become visible. Globular star clusters in the Milky Way’s halo would pepper the sky, looking like tiny cotton balls.
The bright nucleus of the Milky Way would look like a fuzzy headlamp. The ghostly faint tentacles of the spiral arms could be seen winding out from the nucleus. They would sprawl across a huge swath of sky.
Alien sky lore would have no constellations in the absence of stars. All mythology would be built around the nighttime wispy pinwheel with its cycloptic "glowing eye." Alien sky watchers would duly note the appearance of brilliant star-like novae and supernovae in the spiral disk. These might as first be construed as omens or messages from the gods, or fuel other superstitions. But fireworks in the galactic disk would be dutifully recorded.
The development of telescopic astronomy would allow star clusters and nebulae to be resolved. It would be as big a revelation as when Galileo first observed the Milky Way in 1609. Bright blue stars would be seen sprinkled across in the Milky Way’s spiral arms. Spectroscopy would show that the pinpoints are made of the same stuff the alien’s parent star is. But it would take a great leap of imagination to connect the tiny pinpoints to the brilliant glowing orb of their star.
Only the alien equivalent of an Einstein, Newton, and Galileo rolled together might have the conceptual breakthrough that their system is the oddball outcast in a universe of myriad stars. This might get the scientist burned at the stake as a heretic.
Inevitably larger telescopes would yield a view of the universe that revealed myriad other pinwheel structures. Spectroscopy would show they are racing away too. Still the aliens literally wouldn’t know if they’re coming or going. A long-lived civilization’s science archive would note the shrinking and dimming of the Milky Way over geologic time. They might conclude that the eerie pinwheel is speeding away from them. And without a cosmological or stellar framework, they would have no idea of cosmic evolution. They would not even be able to calibrate the vast distance to the Galaxy.
It would be easy for them to conclude that their great yellow star was the center of the universe. Ironically, the alien scientists would remain pre-Copernican even though they had a panoramic view of the Galaxy that any earthbound astronomers would envy.
Photo Illustration: Ray Villard | <urn:uuid:89abc3a7-70aa-4a3f-bf1e-b432b3cf41cf> | 3.703125 | 1,061 | Nonfiction Writing | Science & Tech. | 49.811304 |
Jupiter is the largest planet in the solar system, and claims one of its most enigmatic satellites. In 1979, heavy volcanic activity was discovered on Io - the first such instance confirmed outside of planet Earth. The gases emitted during Io's volcanic eruptions are the foundation for research into a variety of space phenomena occurring around Jupiter, and Nikon products are proving most vital to the study.
We asked Dr. Shoichi Okano, head of the project and Professor at the Planetary Plasma and Atmospheric Research Center (PPARC), Graduate School of Science, Tohoku University, for details regarding the research.
Volcanoes created by Jupiter's incredible gravitational forces
First of all, please tell us what kind of work is done at PPARC.
Well, the purposes of the observations we perform here are to attempt to shed light on the nature of space phenomena occurring on all of the planets in our solar system, and to gain a clearer understanding of the evolution and current state of the planets. At PPARC, we are conducting remote observation of various planets using optical methods and radio techniques. I work in the planetary spectroscopy section and my primary responsibility is to carry out observations using optical instruments.
The solar system comprises nine planets, Earth being the third. Its size and atmospheric characteristics are considered "average". The planets vary greatly in these respects - from Jupiter, which is far, far larger than Earth, to Mercury, which is extremely small and barely even has an atmosphere. What drives me to continue researching is the belief that the observation of physical phenomena on each of the planets may one day lead to a greater understanding of the entire solar system. Currently my time and energy are focused on a study of Jupiter.
What is it that has you so interested in Jupiter ?
In terms of size and power, Jupiter is unrivalled in our solar system. Its diameter is 11 times that of the earth, and its gravitational pull 2.4 times greater. As the Earth, Jupiter has a magnetic field, and the strength of the magnet is an almost incomprehensible 20,000 times that of our planet. What's more, the monstrous planet performs a complete rotation in only ten hours - more than twice as quickly as Earth. It's easy to see how Jupiter got its name, from the supreme deity in Greco-Roman mythology.
Of course, there is more to Jupiter than its immense size and force. It has 61 moons in constant orbit around it - including one called "Io", one of the four Galilean moons and the one physically closest to the big planet. Io, about the same size as the moon that orbits Earth, was found to have numerous volcanoes - volcanic activity was confirmed during the U.S.'s Voyager mission of the late 1970s. Other than Earth, Io is the only body in the solar system on which the existence of volcanoes has been proven.
Hadn't the existence of volcanoes been observed from Earth until then ?
Attempts to view other planets from the earth are complicated by the characteristic sway of the earth's atmosphere, called "seeing" - these factors tend to make the view somewhat blurry. It's comparable to trying to view pebble stones on a river bed as the water flows over them. However, thanks to rapid development in Adaptive Optics to negate the effects of seeing, we have succeeded in actually locating volcanoes on Io, though the smoke from their eruptions remains beyond viewability.
Volcanic activity was initiated by fluctuations in Jupiter's powerful gravitational pull. It's the same tidal effect our moon has on the earth. Just as our moon's movement helps dictate the ebb and flow of our seas, the solid surface of Io underwent violent, repeated expansion and contraction, causing friction which heated the satellite, resulting in volcanic activity.
Io is transformed by the astounding power of Jupiter. Is the same phenomenon occurring on any of Jupiter's other moons ?
Currently Io is the only satellite that we know has volcanoes. It is most likely due to the fact that Io is the closest of the four Galilean moons to Jupiter. The balance between Jupiter's gravitational forces and the speed at which Io orbits the planet keep the satellite from being drawn closer to Jupiter. Should its orbiting speed decrease and Io move closer, the planet's gravitational pull would break Io into pieces.
Does the volcanic activity on Io influence Jupiter in any way ?
Io's volcano emits enormous quantities of gas higher than 100km above its surface. As the gas is ionized, either due to illumination by solar ultraviolet radiation or by collision with surrounding plasma, it becomes what is known as "Jupiter plasma". Jupiter is surrounded by an extremely strong magnetic field and rotates at very high speeds. Once the gas has been ionized, it is captured by the magnetic field and begins a high-speed orbit of the planet along the line of the field.
Io emits huge volumes of gas during its 42-hour full orbit of Jupiter. Total mass of emitted gas can reach as much as 1,000 kilograms per second. Once the gas is ionized, the ions and electrons are trapped by the magnetic field of Jupiter and they accumulate along the orbit of Io. This results in, among other things, a large, doughnut-shaped mass of ions - a "plasma torus" - that is glowing and visible from the earth using a telescope. The majority of the plasma in the planet's magnetosphere comes from the volcanoes of Io.
How can observation of volcanic gas and its distribution be performed from the earth ?
During our observation we pay close attention to sodium atoms and sulfur ions, as they are relatively easy to see. Sodium atoms are distributed tens of millions of kilometers away from Jupiter. We refer to it as a "sodium nebula" as that's the form it takes when distributed. We believe that some sodium ions, however, are caught in the planet's magnetic field, and again they become neutralized, reverting to atoms with the velocity to escape the gravitational pull of Jupiter. This explains why sodium atoms spread so far from Jupiter. As shown in the figure, neutral sodium atoms glow as they are illuminated by solar radiation.
The figure has been scaled based on the radius of Jupiter (RJ, 71,000km). As you can see, the sodium atoms are sent as far as 450RJ (32 million kilometers) from the planet. To break free from Jupiter's magnetosphere and travel such distances, the atoms would have to be moving at least 60 kilometers per second - over five times the speed required in the case of Earth. The generation of this amazing speed is one of the key targets of our research.
We can observe plasma torus by tracking sulfur ions - these ions emit light when they collide with electrons, making them viewable via optical instruments.
Influenced by the magnetic force of Jupiter, the plasma torus orbits the planet at great speeds, syncing itself with the planet's rotation cycle. As we observe a plasma torus at a fixed point, we see the sulfur ions either come closer to or go farther away from the earth. Considering the principles of the Doppler effect as they apply here, the wavelength of light when the ions move closer to Earth is shorter than that of the light when the ions are moving farther away. We can estimate the difference in wavelength using the rotational speed of Jupiter.
However, there is a small discrepancy between the estimated difference in wavelengths and the actual difference. The reason for this is the delay between the ionization of the ions emitted from Io's volcanoes and the point in time where the ions' movement matches the speed of the magnetic field. In other words, carefully observing this delay will teach us a great deal about the ionization process, which leads us to another one of Jupiter's many phenomena - the aurora. | <urn:uuid:ab6a3334-de9e-46fa-96ae-57e0813def48> | 3.234375 | 1,594 | Audio Transcript | Science & Tech. | 45.232515 |
File:Glacier Mass Balance.png
From Global Warming Art
This figure shows the change in average thickness of mountain glaciers around the world. This information, known as the glaciological mass balance, is found by measuring the annual snow accumulation and subtracting surface ablation driven by melting, sublimation, or wind erosion. These measurements do not account for thinning associated with iceberg calving, flow related thinning, or subglacial erosion. All values are corrected for variations in snow and firn density and expressed in meters of water equivalent (Dyurgerov 2002).
Measurements are shown as both the annual average thickness change and the accumulated change during the fifty years of measurements presented. Years with a net increase in glacier thickness are plotted upwards and in red; years with a net decrease in glacier thickness (i.e. positive thinning) are plotted downward and in blue. Only three years in the last 50 have experienced thickening in the average.
Systematic measurements of glacier thinning began in the 1940s, but fewer than 15 sites had been measured each year until the late 1950s. Since then more than 100 sites have contributed to the average in some years (Dyurgerov 2002, Dyurgerov and Meier 2005). The percentage of measurement sites at which net thinning has been observed averages two-thirds over this interval, and reached a maximum of 96% in 2003 (Dyurgerov 2005). Error bars indicate the standard error in the mean.
Other observations, based on glacier length records, suggest that glacier retreat has occurred nearly continuously since the early 1800s and the end of the little ice age, but variations in rate have occurred, including a significant acceleration during the twentieth century that is believed to have been a response to global warming (Oerlemans 2005).
- Further information: Retreat of glaciers since 1850
This figure was prepared by Robert A. Rohde from published data.
- [abstract] [ Dyurgerov, Mark B. (2002). Glacier Mass Balance and Regime: Data of Measurements and Analysis. Occasional Paper 55.
- [abstract] [ Dyurgerov, Mark B. and Mark F. Meier (2005). Glaciers and the Changing Earth System: A 2004 Snapshot. Institute of Arctic and Alpine Research. Occasional Paper 58.
- [abstract] [ Oerlemans, J.H. (2005). "Extracting a Climate Signal from 169 Glacier Records". Science 308: 675-677.
GWArt images and pages linking to this file
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Click on a date/time to view the file as it appeared at that time.
|current||10:06, 29 July 2006||658×500 (24 KB)||Robert A. Rohde||(invert scales, more intelligible)|
|09:09, 29 July 2006||650×499 (23 KB)||Robert A. Rohde| | <urn:uuid:3b188253-1e67-4d0d-8cba-625148b0e4e0> | 3.765625 | 613 | Knowledge Article | Science & Tech. | 52.791578 |
In this tutorial, we will introduce you the DOCTYPE of HTML5. DOCTYPE stands for document type declaration. It is an instruction not a tag that informs the web browser about the version of the page in which it is written. It is essential information for rendering the program as after recognizing the version, the web browser behaves in the same manner.
Each HTML document must be start with DOCTYPE even before defining the <html> tag. <!Doctype > is a singular tag.
Declaration syntax of DOCTYPE in HTML5.
The declaration of DOCTYPE is case_ insensitive.
DTD does not required by the doctype in HTML5. Because SGML( Standard
Generalized Markup language) does not support HTML5. But in html4.01 DTD is
compulsory. Because HTML4.01 is based on SGML.
HTML5 have only one type of DOCTYPE. But in HTML4.01 have three different type of DOCTYPE.
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:23881a9a-f9a2-4e46-b137-a438f8de288e> | 3.4375 | 260 | Documentation | Software Dev. | 62.5798 |
A massive lightning flash that extends from the top of a thundercloud up to the ionosphere.
Han-Tzong Su of National Cheng Kung University of Taiwan and his colleagues report in the June 25 Nature that they've observed another new type of lightning "gigantic jets." The researchers used low-light cameras to capture images of the gargantuan electrical discharges shooting upward from the tops of thunderclouds over the south china sea. The jets ascend to the ionosphere the charged portion of the upper atmosphere to form vast 50-mile-tall shapes resembling carrots or trees that last less than a second. By feeding negative charge from the thundercloud to the ionosphere, the researchers believe such jets may have a strong influence on what they call "earth's global electric circuit."
Agnieszk A. Biskup, "New Lightning Discovered," The Boston Globe, July 1, 2003
Su noted that while the other types of jets seem to occur over most parts of the world, the six gigantic optical jets observed so far have all been connected to thunderstorms over the open sea.
"It is likely that the gigantic jets are a special feature of oceanic thunderstorms," he said.
In addition to the images, Su's team used data from monitoring stations in Antarctica and Japan to show that the discharges also produced extremely low frequency radio waves that could interfere with global radio communications.
Victor Pasko, an electrical engineer at Pennsylvania State University who pioneered study of blue jets, noted in an accompanying Nature commentary that in addition to causing significant disturbances of long-range radio signals, "the ionization created by a gigantic jet is likely to have a significant chemical effect on that part of the atmosphere," although no studies have been done on such changes.
Lee Bowman, "Some lightning jets shoot up high into atmosphere," Scripps Howard News Service, June 25, 2003
Here we report observations of five gigantic jets that establish a direct link between a thundercloud (altitude 16 km) and the ionosphere at 90 km elevation. Extremely-low-frequency radio waves in four events were detected, while no cloud-to-ground lightning was observed to trigger these events. Our result indicates that the extremely-low-frequency waves were generated by negative cloud-to-ionosphere discharges, which would reduce the electrical potential between ionosphere and ground. Therefore, the conventional picture of the global electric circuit needs to be modified to include the contributions of gigantic jets and possibly sprites.
H. T. Su et al., Gigantic jets between a thundercloud and the ionosphere," Nature, June 26, 2003
A gigantic jet is an example of a superbolt, a lightning flash that extends for tens of miles. Another example is the sprite mentioned in the example citation, which is usually called a red sprite. Both are forms of upward lightning that starts from the cloud tops and extends into the upper atmosphere. Other lightning types have equally whimsical names: carrot sprites, angel sprites, blue jets, elves, and trolls. Scientists group all of these lightning types under the heading of Transient Luminous Events (TLEs) because they appear and disappear in a few hundredths or thousandths of a second. | <urn:uuid:6b571f65-9687-49f2-a0c7-9070b12a7ca4> | 3.515625 | 658 | Knowledge Article | Science & Tech. | 34.286645 |
The Origin of Matter
The question of how matter triumphed over antimatter in the formation of the universe still awaits a satisfactory answer
One of the first questions for cosmologists, posed most elegantly by the Russian dissident physicist Andrei Sakharov, is: Why is there stuff? In the first moments after the big bang, it's thought that the universe was utterly empty. Shortly thereafter, matter was created—and necessarily more matter than antimatter, because otherwise the stuff and the antistuff would have annihilated each other. Cline lays out the candidates for a theory of how the fundamental particles called baryons—components of the atomic nucleus—came about. It's possible that leptons—electrons and their particle cousins—arose first, creating an asymmetry that led to the predominance of matter over antimatter.
Go to Article | <urn:uuid:c0aebb9e-5008-4bed-b048-a3f7b73b9f8e> | 3.1875 | 180 | Truncated | Science & Tech. | 21.797179 |
Clues from hurricane 'fingerprints'
Scientists decode hurricane 'records' left in trees and rocks to try to predict the strength of future storms.
(Page 2 of 2)
To gather that information, scientists first turned to sediment cores taken from marshes, lagoons, and lakes behind barrier beaches. This "is the most useful and proven technique to date," says Kam-biu Liu, a Louisiana State University paleoclimatologist who first applied the approach to the hurricane problem in 1989. As a tropical cyclone makes landfall, the storm surge washes beach sand into these bodies of water. The sand settles to the bottom, then gets covered with organic material that forms most of the muck at the bottom. The sand layers show up in the cores. Scientists can find out when the storm or storms struck by using radiocarbon dating techniques on the organic material above and below the sandy layer. Dr. Liu and Jeffrey Donnelly of the Woods Hole (Mass.) Oceanographic Institution have pioneered this approach along the Gulf Coast and in the Northeast and Puerto Rico.Skip to next paragraph
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Scientists have been able to trace storm histories back at least 5,000 years. After looking at data from four sites along the Gulf Coast, for example, Liu notes that hurricane activity in the region was fairly low during the first 1,200 years in the samples and the past 1,000 years or so. But for 2,800 years in between, activity was relatively high; a major hurricane struck each site as often as once every 200 years.
Researchers are now trying to figure out the atmospheric and oceanic drivers for such long-term swings.
Clues written in stone
Where some researchers hunt for hurricanes in the muck, others are turning to the record written in stone and wood. Both approaches take advantage of changes that severe storms bring to the ratio of oxygen isotopes in water they drop. Rain from tropical cyclones carries more of the lighter oxygen isotopes than rain from ordinary storms. University of Houston researcher James Lawrence – who had been working on the isotopic content of storm water – saw that the approach could be applied to hurricane studies and offered the idea up in a paper he published in 1998. That sent Boston College's Dr. Frappier and researchers at the University of Tennessee, among others, off to caves and forests.
By 2001, researchers were bringing tree-ring samples and stalagmite samples in for analysis. But, notes University of Tennessee tree-ring expert Henri Grissino-Mayer, the work was a lot harder than it looked. Sometimes the best specimens are underwater stumps. Then it's time to date the entire ring, each with a light portion representing early-season growth, and a dark portion representing late-season growth. Because the hurricane season is most intense from August on, this late-season growth is the main target. Then each of those segments gets a once-over for the oxygen-isotope content. The work is painstaking and requires a steady hand to extract the samples.
The stalagmite work is similar. Frappier says this summer's effort in Mexico has been largely a reconnaissance trip to find stalagmites in caves that may hold the information they seek.
In both cases the results from their samples, gathered in 2001, only hit the streets in the past year. The tree-ring results from the work by Tennessee's Claudia Mora and Dr. Grissino-Mayer, and colleagues from the University of South Carolina and the University of New Mexico, appeared last September.
Frappier's results appeared last February. The tree rings tracked hurricanes back some 220 years. And while the record from the stalagmite Frappier selected stretched back 23 years, it records storms by week and month, not just by season. Beyond these approaches, "we are also experimenting with the application of corals to this line of research, although it's not as far along as tree rings and cave deposits," Liu notes.
Still, "by putting together this team of people and tackling the problem from different angles using different techniques and looking at different time scales we will have a better understanding of the spatial and temporal variations in hurricane activity across the entire Caribbean Basin." | <urn:uuid:33895f57-d715-4c5d-9ba6-2507527b02f7> | 3.671875 | 869 | Truncated | Science & Tech. | 48.444194 |
How to add a ReadOnly property in C#?
Property - A property is an entity that describes the features of an object.
A property is a piece of data contained within a class that has an exposed interface
for reading/writing. Looking at that definition, you might think you could declare a
public variable in a class and call it a property. While this assumption is somewhat
valid, the true technical term for a public variable in a class is a field. The key
difference between a field and a property is in the inclusion of an interface.
We make use of Get and Set keywords while working with
properties. We prefix the variables used within this code block with an underscore.
Value is a keyword, that holds the value
which is being retrieved or set. See code below to set a property as ReadOnly. If
a property does not have a set accessor, it becomes a ReadOnly property.
Default Values of Types
Const - ReadOnly
Interface Reference, is, as
public class ClassA
private int length = 0;
public ClassA(int propVal)
length = propVal;
public int length
More Interview Questions... | <urn:uuid:7e909691-79d8-4aa4-a977-d58f5af7daea> | 3.1875 | 245 | Tutorial | Software Dev. | 53.483917 |
There are thousands of species of insects that begin life as caterpillars. It is nearly impossible to identify them without seeing them, and even then it can be quite difficult. Features to note are whether they are smooth, hairy, bristled, or spiny; presence or absence of knobs, bumps, a rear horn, fleshy filaments, or tufts; sluglike or more typical caterpillar form; and host plant.
Here are some resources that may help:
We hope this helps,eNature Naturalists | <urn:uuid:4e2745d3-402f-4afd-85bf-0bb235c3f174> | 3 | 107 | Q&A Forum | Science & Tech. | 32.458658 |
A brief digression into other DTDs may help make clear what parts of the previous section were specific to DocBook and what parts are general to all structural-markup languages.
TEI (Text Encoding Initiative) is a large, elaborate DTD used primarily in academia for computer transcription of literary texts. TEI's Unix-based toolchains use many of the same tools that are involved with DocBook, but with different stylesheets and (of course) a different DTD.
XHTML, the latest version of HTML, is also an XML application described by a DTD, which explains the family resemblance between XHTML and DocBook tags. The XHTML toolchain consists of web browsers and a number of ad-hoc HTML-to-print utilities.
Many other XML DTDs are maintained to help people exchange structured information in fields as diverse as bioinformatics and banking. You can look at a list of repositories to get some idea of the variety out there. | <urn:uuid:0072514b-e2bf-4bab-be88-4a35dd9a3a07> | 2.703125 | 204 | Knowledge Article | Software Dev. | 45.519286 |
Research Aims to Develop Fishery-independent Methods for Assessing Coral Reef Fish Populations in the Main Hawaiian Islands
During September 1-13, 2012, the NOAA Ship Oscar Elton Sette is conducting a research cruise to improve assessments of reef fish populations in the main Hawaiian Islands. The focus is on reef habitats around Oahu and the Maui-nui complex of Maui, Lanai and Molokai. A primary cruise objective is to compare fishery-independent methods for assessing fish populations on coral reefs. The data gathered will also supplement accumulated information on reef fishes gathered by the NOAA Pacific Islands Fisheries Science Center (PIFSC) as part of NOAA's Pacific Reef Assessment and Monitoring Program.
The 13-day research expedition is led by PIFSC associates Dr. Jill Zamzow and Kevin Lino of the Joint Institute for Marine and Atmospheric Research of the University of Hawaii (JIMAR). The research team includes scientists from PIFSC, JIMAR, and collaborators from Hawaii Division of Aquatic Resources.
During the expedition, 2 methods will be used to assess the abundance of reef fish. At about 200 selected survey sites in hardbottom habitats in waters < 30 m deep, SCUBA divers will conduct a stationary point count survey. The sampling locations are selected using a stratified-random survey design. At a subset of the selected sites, the survey team will place stationary stereo-video cameras (BRUVS) on the seafloor. Data collected in the shallow-water habitats where both methods are used will be compared to help in the development of a diver-independent capability for reef fish assessment.
The BRUVS will also be deployed at additional survey sites in 30-100 m deep habitats, waters too deep for safe SCUBA operations. Together, the survey operations will enable documentation of reef fish assemblages across the spectrum of reef fish habitats. These and other related survey efforts are designed to improve the ability of PIFSC and partners to generate an accurate picture of the status and trends of coral reef fishes around the Hawaiian Islands.
Stationary Point Counts
The stationary point count (SPC) method involves a pair of SCUBA divers conducting simultaneous counts in adjacent visually-estimated 15 m-diameter plots extending from the substrate to the limits of vertical visibility. Prior to beginning each SPC survey operation, the divers lay out a 30 m line across the seafloor. Markings on the line at 7.5 m, 15 m and 22.5 m enable the divers to locate the mid-point (7.5 m or 22.5 m) and two edges (0 m and 15 m; or 15 m and 30 m) of the survey plots. Each diver conducts the SPC survey in 2 steps. The first is a 5-minute species enumeration period in which the diver records all species observed within their cylinder. Following that is a tallying step, in which the diver systematically works through their list of species, and for each species counts and records the number of fish in the survey plot, along with an estimated size (total length, TL, to nearest cm) of each fish seen. The tallying step is conducted as a series of rapid visual sweeps of the plot, with one species-grouping counted per sweep. To the extent possible, divers remain at the center of their cylinder throughout the counts. In cases where a species is observed during the species enumeration step but not seen during the tally sweeps, the diver records their best estimates of the size and number of fish observed during the species enumeration step and marks the data record as 'non-instantaneous'.
During the 2-step SPC procedure, small and cryptic species will tend to be underrepresented in the counts made by an observer remaining in the center of the cylinder. So to estimate the abundance of these species, after the tallies are done the diver leaves the center observation position and swims through the plot, carefully searching for small and cryptic species and counting them.
BRUVS are baited, remote, underwater video stations. The non-destructive stereo video samplers can provide scientifically rigorous estimates of fish abundance and size structure. BRUVS were originally developed in the laboratory of Dr. Euan Harvey at the University of Western Australia. The use of stereo cameras allows scientists to obtain accurate estimates of the number and size of fish attracted to the station and enables an understanding of each species' local length frequency distribution and biomass density. Each of a group of up to 8 BRUVS units is deployed for approximately 15 minutes, then recovered and placed at a different sampling location; in this manner, the units are deployed in a "leap frog" fashion throughout the day. This allows for considerable sampling replication in space and time throughout the cruise.
BRUVS are termed 'remote' because the systems are deployed on the seafloor and function independently of an operator or observer. Each BRUVS system uses 2 off-the-shelf high-definition video cameras mounted 0.7 m apart on a base bar that is inwardly converged at 8 degrees to gain an optimized field of view (with a forward-viewing range of ~10 m). The cameras are placed within PVC pipe housings with acrylic front and rear ports and mounted within a galvanized roll-bar frame. Stabilizing arms and bait arms (20 mm plastic conduit) are attached and then detached during and after deployment.
Each BRUVS can be left unbaited or can accommodate up to 1 kg of bait. The bait is placed in a plastic-coated wire basket suspended on a bait arm 1.2 m in front of the unit. Various types of bait may be used, depending on supply/local availability. At predefined GPS locations, each BRUVS is deployed from the vessel by hand (each unit weighs ~ 50kg) with a rope and floats attached. The BRUVS is left in place for 15 to 60 minutes (depending on survey design), after which vessel crew members can retrieve them by grappling surface floats and hauling the attached lines aboard with the aid of a hand-powered or electric winch or pot-hauler. Video footage collected by the BRUVS can be reviewed as soon as the camera is retrieved to the vessel and can be archived for later analysis. | <urn:uuid:3a729037-7a82-4b57-9578-30798779f6f6> | 3.015625 | 1,291 | Knowledge Article | Science & Tech. | 45.621801 |
The LNP_TEST function computes the Lomb Normalized Periodogram of two sample populations X and Y and tests the hypothesis that the populations represent a significant periodic signal against the hypothesis that they represent random noise.
LNP_TEST is based on the routine
fasper described in section 13.8 of Numerical Recipes in C: The Art of Scientific Computing (Second Edition), published by Cambridge University Press, and is used by permission.
Result = LNP_TEST( X, Y [, /DOUBLE] [, HIFAC=scale_factor] [, JMAX=variable] [, OFAC=value] [, WK1=variable] [, WK2=variable] )
The result is a two-element vector containing the maximum peak in the Lomb Normalized Periodogram and its significance. The significance is a value in the interval [0.0, 1.0]; a small value indicates that a significant periodic signal is present.
An n-element integer, single-, or double-precision floating-point vector containing equally or unequally spaced time samples.
An n-element integer, single-, or double-precision floating-point vector containing amplitudes corresponding to Xi.
Set this keyword to force the computation to be done in double-precision arithmetic.
Use this keyword to specify the scale factor of the average Nyquist frequency. The default value is 1.
Use this keyword to specify a named variable that will contain the index of the maximum peak in the Lomb Normalized Periodogram.
Use this keyword to specify the oversampling factor. The default value is 4.
Use this keyword to specify a named variable that will contain a vector of increasing linear frequencies.
Use this keyword to specify a named variable that will contain a vector of values from the Lomb Normalized Periodogram corresponding to the frequencies in WK1.
This example tests the hypothesis that two sample, n-element populations X and Y represent a significant periodic signal against the hypothesis that they represent random noise:
; Define two n-element sample populations: X = [ 1.0, 2.0, 5.0, 7.0, 8.0, 9.0, $ 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, $ 16.0, 17.0, 18.0, 19.0, 20.0, 22.0, $ 23.0, 24.0, 25.0, 26.0, 27.0, 28.0] Y = [ 0.69502, -0.70425, 0.20632, 0.77206, -2.08339, 0.97806, $ 1.77324, 2.34086, 0.91354, 2.04189, 0.53560, -2.05348, $ -0.76308, -0.84501, -0.06507, -0.12260, 1.83075, 1.41403, $ -0.26438, -0.48142, -0.50929, 0.01942, -1.29268, 0.29697] ; Test the hypothesis that X and Y represent a significant periodic ; signal against the hypothesis that they represent random noise: result = LNP_TEST(X, Y, WK1 = wk1, WK2 = wk2, JMAX = jmax) PRINT, result
The small value of the significance represents the possibility of a significant periodic signal. A larger number of samples for X and Y would produce a more conclusive result. WK1 and WK2 are both 48-element vectors containing linear frequencies and corresponding Lomb values, respectively. JMAX is the indexed location of the maximum Lomb value in WK2.
CTI_TEST, FV_TEST, KW_TEST, MD_TEST, R_TEST, RS_TEST, S_TEST, TM_TEST, XSQ_TEST | <urn:uuid:59846aae-46c1-428e-ab19-29bf1130f25e> | 3.3125 | 857 | Documentation | Science & Tech. | 77.256962 |
Welcome to PhysLink.com - Your physics and astronomy online portal. Stay a while! Check out our extensive library of educational and reference materials. Also, check out our fun section!
What are some examples of cohesion and adhesion?
Asked by: Leroy
Cohesion is the term for molecules of a substance sticking together. One of the most common examples is water beading up on a hydrophobic surface.
Water molecules are what are called dipoles: they have an electric 'pole' at each end of the molecule with opposite charges because the electrons in the molecule tend to congregate near the oxygen atom and away from the hydrogen atoms. Thus the negative part of one water molecule will attract the positive parts of other, nearby molecules. This is why water falls from the sky as raindrops, and not individual molecules, or why water tends to bead up on the hood of your freshly waxed car, or why you can cause water to bulge out over the rim of a glass if you fill it carefully; the molecules are all pulling together.
Water molecules are not only attracted to each other, but to any molecule with positive or negative charges. When a molecule attracts to a different substance, this is termed adhesion. Think about what happens when you dip one end of a piece of paper towel into a glass of water. The water will climb up the fibers of the paper, getting it wet above the level of the water in the glass. We know gravity is pulling down on the water, so why do they move up? Because the water molecules' positive and negative charges are attracted to the positive and negative charges in the cellulose molecules in the paper.
Note that both the examples above have both cohesion and adhesion occuring but one is stronger than the other. If the water molecules are more strongly attracted to each other than to the surrounding material, they bead up and try to get as close to each other as possible. If there is a stronger attraction to some other material, they spread out and try to get close to the other material.
Erector 20 Model Set
Today's Price: $39.00
Great Erector starter set that allows you to build 20 cool models. Buy it now! Deal ends at midnight!
Here are our physics & astronomy bestsellers:
Solar Science Kit
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Ultimate Chemistry Set CHEM C3000 v2.0
Worlds Strongest Magnets
Blue Fiber Optic Light | <urn:uuid:da1d0c5a-9a7d-460e-9951-2c187a4becbf> | 3.9375 | 543 | Q&A Forum | Science & Tech. | 43.399967 |
from the urls-we-dig-up dept
The search for intelligent life might be more fruitful if we started looking more closely at other animals right here on Earth. The progress of artificial intelligence in computers might also be surpassed by breeding a few hyper-intelligent pets someday. Some zoo animals are already playing around with iPads, so maybe we'll have some super smart cyborgs... In any case, here are just a few examples of projects that are studying how smart our fellow vertebrates might be.
- DARPA is scanning dog brains with MRI machines to figure out which dogs are best suited for military dog training. The FIDOS (Functional Imaging to Develop Outstanding Service-Dogs) project could help train dogs more effectively for all kinds of tasks -- from detecting drugs to being better therapy companions. [url]
- PBS has a great documentary that follows how raccoons are adapting to urban living. Anyone who has tried to protect their garbage cans knows how wily raccoons are. [url]
- What animal would you use to model the cognitive development of human babies? If you said piglets, then maybe you should try being a neuroscientist at the Beckman Institute at the University of Illinois. [url]
- The problem-solving capabilities of captive hyenas appear to be a bit better than their wild cousins. The tests administered to these hyenas were admittedly a bit biased.... [url] | <urn:uuid:7b60eb44-7b07-4c8a-81cf-216851008c4e> | 2.84375 | 297 | Listicle | Science & Tech. | 48.179169 |
from the urls-we-dig-up dept
Neil Armstrong's recent passing has reminded lots of folks about the first manned mission to the moon. The whole idea that "we could put a man on the moon" seemed incredible in the 1960's, and the feat is still remarkably difficult -- even if kids today can't fully appreciate the accomplishment. Maybe someday, we'll go back to the moon (and this XKCD will have to be adjusted), but in the meantime, here are just a few links about that historic first moonwalk.
- Neil Armstrong's first words as he stepped on the moon were slightly misheard by everyone on Earth, and audio analysis of the recordings suggests that Armstrong didn't just mis-speak. "That's one small step for *A* man, one giant leap for mankind." [url]
- In 2006, NASA realized that it had lost its original Apollo 11 moon landing videos, but fortunately, archived footage of the moonwalk was found in Australia in 2010. The tapes were restored and digitized -- and hopefully we won't lose them again when nobody remembers what MP4 is. [url]
- President Nixon was prepared for an Apollo 11 disaster with a speech that he thankfully never read to the American public. The "moon disaster" speech is a creepy reminder that space exploration is an inherently risky venture... [url] [page2] | <urn:uuid:dc07227c-54d3-46be-b221-b709a6c8411d> | 2.796875 | 283 | Content Listing | Science & Tech. | 58.332691 |
A total solar eclipse occurred over the northeastern Australian coast early in the morning of November 14 local time.
Clueless about this spectacular astronomical event? No worries, we've got you covered. We're here to explain what causes this remarkable act of nature, what skygazers see and how those outside of Australia can join in the experience.
What exactly is a total solar eclipse?
A solar eclipse happens when the moon, as it orbits Earth, passes directly in front of the sun, obscuring its rays and casting a shadow on Earth's surface. Sometimes referred to as a "happy accident of nature," a total solar eclipse occurs when the moon is perfectly aligned with both the sun and Earth, so it appears from our perspective that the sun is completely blocked.
When is this happening and who can see it?
The total solar eclipse became visible in the far north of Australia about an hour after sunrise local time on November 14 (afternoon of November 13 in the United States and evening of November 13 in Europe).
A total eclipse of the sun can only be seen from within what's known as the path of totality, a narrow path the moon's inner shadow travels as it glides across the Earth. The most populated areas within that path are in the Cairns and Great Barrier Reef region.
It estimated to take about three hours for the moon's shadow to travel the entire path of totality. What time total darkness occurred, and how long it lasted, depended on location. Totality was expected to begin in Cairns at 0638 local time and was to last nearly two minutes. By contrast, totality was estimated to only last just about 20 seconds in the small town of Innisfail.
What's all the fuss about? Don't these happen frequently?
According to NASA, a full solar eclipse happens, on average, every 18 months. The last one happened in July 2010, crossing Chile's Easter Island, and one will occur over equatorial Africa in November 2014. But for any given region, a total solar eclipse only happens, on average, once every 375 years. | <urn:uuid:da0c3aff-7508-4cfe-90a7-7f2e45768adc> | 3.421875 | 427 | Knowledge Article | Science & Tech. | 50.385 |
As if we needed further evidence for the intelligence of corvids, researchers studying New Caledonian Crows have found them using mirrors to solve problems.
Scientists captured 10 wild birds and placed them in large cages in order to record their behaviour in response to mirrors.Further tests ruled out the possibility that crows were using a sense of smell to find the food. Other animals that can interpret images in mirrors include African grey parrots, great apes, dolphins, monkeys and Asian elephants, but apparently these New Caledonian Crows were the first to do so without extensive prior contact with humans.
All the crows reacted to seeing their reflections as if they were encountering another crow; the birds made rapid head movements, raised their tails and even attacked the reflection.
Lead researcher Felipe S Medina Rodriguez said the crows' antagonistic reaction to their mirror image "was not surprising". He explained that an animal usually had extensive exposure to mirrors before it began to display an understanding that the image it was seeing was itself....
The second part of the experiment, though, revealed some surprising findings.
The scientists devised a task to test whether the crows could use mirrors to locate cubes of meat that were hidden from direct view.
All of the crows tested appeaed to understand how the meat's reflection correlated to its location.
"We were surprised by how quickly the crows learnt to use a mirror reflection to locate hidden food," said Mr Medina.
"Usually, it takes longer for an animal to start using the properties of mirrors to have access to otherwise non-visible objects."
The linked article also contains a summary of a study on the problem-solving skills of Great Tits and Blue Tits. | <urn:uuid:f823385a-b873-4c13-a076-465b4a089b24> | 3.546875 | 349 | Personal Blog | Science & Tech. | 43.598448 |
Mud, marine snow and coral reefs
Wolanski, Eric, Richmond, Robert, McCook, Laurence, and Sweatman, Hugh (2003) Mud, marine snow and coral reefs. American Scientist, 91 (1). pp. 44-51.
|PDF - Repository staff only - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader|
View at Publisher Website: http://dx.doi.org/10.1511/2003.1.44
Worldwide degradation of coral reefs is widely recognized, but the exact causes have proved elusive. The authors have studied reefs in Australia and Guam for 10 to 20 years, amassing data about threats to reef welfare and developing computer models from those data to predict the effectiveness of remedial actions. Their findings suggest that control of runoff from adjoining land areas, which affects reef health in several ways, may be key to reef recovery.
|Item Type:||Article (Refereed Research - C1)|
|Deposited On:||09 Jul 2009 15:04|
|Last Modified:||15 Apr 2013 11:23|
Last 12 Months: 0
Repository Staff Only: item control page | <urn:uuid:cd6498a4-1b19-4516-a45a-d2a1d505fb98> | 2.8125 | 249 | Academic Writing | Science & Tech. | 64.665833 |
|Ivars Peterson's MathTrek|
April 1, 1996
Euclid's Elements, which presented the state of the art in geometry around 300 B.C., has been extraordinarily influential. This massive, 13-volume compendium set the standard for precise mathematical exposition and discourse for many centuries. More than 2,000 editions have been published, and new, interactive versions now appear on the World Wide Web.
But that's not all. Now there exists compelling evidence that Euclid had a fourteenth book in mind.
Officials of the Foundation for Old Occidental Languages announced today that, after a year devoted to authentication and analysis, they are prepared to release the text of a manuscript that appears to be a Latin translation of research notes jotted down by Euclid in preparation for writing a fourteenth volume of Elements.
"This is truly an astonishing document," says Duncan D. Umber of St. Patrick's College of Medieval Studies, who examined the manuscript last month. "Euclid went much farther in his investigations than anyone had previously suspected.
"People continually underestimate what the ancients were able to do," he adds. "We will need to reassess Greek mathematics in its entirety."
The parchment manuscript was found by 12-year-old William Kelly, who was exploring a rocky cave on an island off the west coast of Ireland. At first, Kelly thought that he had discovered a treasure map. But the Latin words stymied him and the fanciful decorations reminded him of things he had seen in church. Kelly brought the packet to Seamus Donne, a local priest who happened to have an interest in illuminated manuscripts. Donne quickly appreciated the value of Kelly's find and contacted the foundation.
The newly found work lacks the highly organized, compact structure of Elements. Its text refers to the definitions, axioms, and propositions contained in the first 13 books, but without the clarity and rigor of the preceding volumes. Obviously a work in progress, these pages document Euclid's efforts to settle several important mathematical issues.
It's clear that Euclid was uncomfortable with the fifth and most complicated of the five postulates that begin Elements. This postulate states that "if a straight line falling on two straight lines makes the interior angles on the same side less than two right angles, the two straight lines, if produced indefinitely, meet on that side on which the angles are less than two right angles."
Euclid's newly discovered notes propose an alternative way of expressing this notion: Through any given point can be drawn exactly one straight line parallel to a given straight line. He goes on to consider two other cases: One in which no parallel line can be drawn through the point and another in which more than one parallel can be drawn. In these two situations, he says, the sum of the interior angles of a triangle is no longer exactly equal to two right angles.
On the surface of a sphere, for example, a triangle's angle sum is greater than two right angles, Euclid notes. Such a geometry has no parallel lines, yet it obeys his first four postulates.
The manuscript hints that Euclid also explored the curious geometry that arises from the existence of multiple parallels. "I have discovered things so wonderful that I was astounded," he writes at one point. "Out of nothing I have created a strange, new world." Unfortunately, much of this section of the manuscript has deteriorated beyond repair, so only tantalizing fragments remain.
In one brief passage, Euclid mentions a problem that he had with determining the length of the coastline of a rugged island in the Aegean owned by one of his former students. He observes that the answer obtained by a man pacing the island's perimeter would differ from that of an ant making the same journey. The ant would take many more steps, following the shoreline's ragged edge much more closely than the man. A creature smaller than an ant would get an even larger estimate of the coastline's length.
Euclid also shows how it's possible to build a star-like figure out of triangles. He starts with a large equilateral triangle, then breaks up each side with a protruding equilateral triangle one-third as large. Then he repeats the procedure with each new side, adding successively smaller triangles. He calls the resulting shape an "asteroid."
Euclid goes on to speculate about how such "meriton" forms may be useful for describing natural objects. "Clouds are not spheres, mountains are not cones, coastlines are not circles, and bark is not smooth, nor does lightning travel in a straight line," he comments.
One highly cryptic section of Euclid's notes refers to a massive computational project. He apparently had hundreds of students over a period of many years computing the squares of numbers, taking differences, and obtaining answers that served as starting points for successive steps in some kind of procedure for creating fanciful mosaics.
Euclid also spent time looking at extensions of the Pythagorean relationship (Proposition I.47). In his notes, he presents an ingenious argument to prove that the area of a right-angle triangle whose sides are all whole numbers cannot be a square of a whole number. Furthermore, he notes that it is impossible for a cube to be written as the sum of two cubes or a fourth power to be written as the sum of two fourth powers. Then he makes a giant leap in conjecturing that the same thing holds for all powers greater than 2.
Euclid leaves an intriguing note: "I have a truly marvellous demonstration of this proposition which this page is too small to contain."
The remarkable material described in these long-lost writings reinforces the impression that, in Euclid's time, the library at Alexandria in Egypt was much more than a reference institution or a school. It was also a major research center. Euclid's Elements was intended not so much as a textbook but as a comprehensive accounting of what was known to date. It was meant to serve as a stepping stone toward new research in mathematics.
There are some skeptics. "Euclid was not a particularly brilliant mathematician," says Bartholomew Cubbins of Banana State University. "It's wrong to credit him with these insights. I'm sure they were common knowledge in Euclid's time, and he merely wrote them down."
Nonetheless, the astonishingly wide range of these investigations and speculations means that our use of the term "non-Euclidean geometry" is clearly misleading. We can now honestly say that it's all Euclidean geometry.
Copyright © 1996 by Ivars Peterson.
Cahill, Thomas. How the Irish Saved Civilization: The Untold Story of Ireland's Heroic Role from the Fall of Rome to the Rise of Medieval Europe. Nan A. Talese/Doubleday, 1995.
Devlin, Keith. Mathematics: The Science of Patterns. Scientific American Library, 1994.
Mandelbrot, Benoit B. The Fractal Geometry of Nature. W.H. Freeman, 1982.
Peterson, Ivars. The Mathematical Tourist: Snapshots of Modern Mathematics. W.H. Freeman, 1988.
Todhunter, Isaac (ed.). Euclid's Elements, Books I-VI, XI and XII. Dent, 1933.
Biographical and other information on Euclid is available at http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Euclid.html.
Comments are welcome. Please send messages to Ivars Peterson at firstname.lastname@example.org. | <urn:uuid:dfa5652b-3be8-48d6-b1de-80f74fd2f602> | 3.671875 | 1,566 | Knowledge Article | Science & Tech. | 50.813503 |
SCICEX: The Science Ice Exercise
The Science Ice Exercise (SCICEX) program is a collaboration between the U.S. Navy and the marine research community to utilize nuclear-powered submarines for the study of the Arctic Ocean. Unlike surface ships, submarines have the unique and valuable ability to operate and take measurements regardless of sea ice cover and weather conditions. The goal of the program is to acquire comprehensive data about Arctic sea ice, water properties, and bathymetry.
SCICEX is important because it adds critical pieces to the overall information needed to analyze sea ice and ocean dynamics - ice thickness and bathymetry data in particular but also chemical, biological, and physical oceanographic data. With the success of the initial project in 1993, the U.S. Navy and the National Science Foundation (NSF) signed a Memorandum of Agreement (MOA) in 1994 that called for five more dedicated SCICEX missions. The dedicated SCICEX cruises occurred in 1995, 1996, 1997, 1998, and 1999.
In October of 1998, due in large part to a drastic reduction in the size of the nuclear submarine fleet, the U.S. Navy announced that they could no longer facilitate the dedicated missions. In an effort to try and continue the SCICEX program, the Navy and the science community agreed upon shorter duration missions that included data collection for science but did not include civilian scientists on board the submarines. These were coined Science Accommodation Missions (SAMs). To date, four SAMs have been completed in 2000, 2001, 2003, and 2005. More routine opportunities to collect SCICEX data during SAMs are expected. | <urn:uuid:35731472-1dcc-46bf-b0fe-af2221e9d855> | 3.3125 | 336 | Knowledge Article | Science & Tech. | 35.017282 |
It actually is providing an image, you just cannot see it because of contrast. The light you have in the picture is flooding the room with enough ambient light that the image that is actually formed has no contrast.
- Pinhole camera image quality heavily depends on the pinhole size.
However, the smaller the pinhole, the "dimmer" the image will be,
this is the problem that you have.
- In order to be able to view the image you will need to make the
pinhole basically in a box. The box could be an entire room (e.g.
cover all windows in a room with aluminum foil so it is very dark,
then prick a pinhole in the foil on one of the windows) or a smaller
box with a "viewing screen." The key think is that whatever "box"
that you use needs to be relatively dark inside.
A viewing screen can be something clear but diffuse, like parchment paper or privacy glass. Even with the viewing screen, you need to somehow make it dark enough so that your eyes can see it.
You could also make an enclosure large enough for you head to fit into, but still maintain a good level of darkness.
If you have an old webcam, this might work inside of an enclosed box, then you can view the image on your computer.
This is one of the things that makes using pinhole cameras in demonstrations difficult, you want the object being imaged to be well lit, but you need the viewing screen to be dark. | <urn:uuid:6601f20f-3519-457a-ab29-6b647fc5d749> | 3.046875 | 316 | Q&A Forum | Science & Tech. | 60.667539 |
If we are travelling with the speed of light, can we see whats behind us(like if we are moving away from earth can we able see the earth)? And how we see the things that we are approaching with speed of light? Does the things look like fast forwarding because we are moving and the source also sending photons with the same light speed.
closed as not a real question by Ϛѓăʑɏ βµԂԃϔ, Manishearth♦ Feb 6 at 15:28
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, see the FAQ.
Remember that there are no preferred frames in special relativity, so your question "If we are travelling with the speed of light, can we see whats behind us?" is exactly equivalent to asking "If something is travelling away from us at the speed of light can we see it?".
We know the answer to this because Nature has kindly done the experiment for us. You probably know that the universe is expanding so galaxies distant from us are moving away, and the speed they move away is dependent on their distance from us. This means there is a distance at which the galaxies are moving away from us at the speed of light. Subject to a few assumptions about the universe, the red shift of light from those galaxies will be infinite and this means we can't see them.
So the answer to your question is no!
I know you don't realize it, but you're actually asking the wrong question. You're making an assumption (massive objects can go at the speed of light) that is unphysical. Still, thinking about this very question (and why it is wrong) is how Einstein came up with his Theory of Special Relativity, so it is worth thinking about.
One way to think about this is to imagine that you send out two photons, say one second apart. They're separated by a distance of one light-second, and assuming they never bounce off of something, they will never collide in the history of the universe.
However, photons don't experience time the way that massive objects do. Their creation and destruction occur at the same instant (as they would experience it); for things traveling at slightly below the speed of light, their creation & destruction occur rapidly (relative to the at-rest reference frame we're using to define their speed), but never quite instantly (as they never go quite at the speed of light).
In short, in order to think about how this works, you want to think about Special Relativity. I recommend reading Mr. Tompkins in Paperback. It does a lot better than I will, at helping you to get a sense of how things work when dealing with special relativity and things that move close to the speed of light. The book imagines that the speed of light were relatively slow, a few tens of miles per hour, and what happens when you take a train trip. It's a fun read. | <urn:uuid:eb755ffb-3005-4196-b72f-f26e0f3e063d> | 3.09375 | 641 | Q&A Forum | Science & Tech. | 60.299174 |
Regular Expressions, Part 2
September 18, 2009
In the previous exercise, we decided on an intermediate representation for regular expressions and wrote a parser that produces the intermediate representation corresponding to a regular expression given as input.
Your task today is to write the corresponding matcher that takes an intermediate representation and a target string and returns a boolean indicating whether or not the regular expression matches the target string, using the same conventions as the prior exercise. Your matcher will be similar to Rob Pike’s matcher that we studied previously. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.
Pages: 1 2 | <urn:uuid:64f98322-d1c0-46b0-9472-2d18e9a017c7> | 2.96875 | 144 | Personal Blog | Software Dev. | 21.555457 |
One-way ticket to Mars
Posted on Aug 22, 2012 in Science
Amid the commotion and celebration of the successful landing of NASA’s Curiosity rover on Mars last week, a small group of entrepreneurs outside of the United States is already planning for the next giant leap — sending humans to Mars.
The Dutch-based Mars One project, with a projected cost of about $6 billion for the first four astronauts involved, intends to put a man on the Red Planet by 2023 well before the United States does. In contrast, NASA projects its first manned mission to Mars to be in the 2030s, almost a decade later. After the first group of astronauts land, more would be sent periodically to create a sizeable and sustainable colony.
Sounds good, doesn’t it? But there’s a catch. Everyone who leaves Earth will be spending the rest of his or her life on Mars, never to return. The one-way program makes perfect logistical sense.
The fuel requirement would be halved, and a return spacecraft would not be necessary. The reduced weight makes getting to Mars much, much easier than a two-way trip.
What sounds good on paper may not work in real life, however. The psychological effects of such a mission upon the astronauts must be thoroughly considered. These brave souls would never see other humans again. They will live and die in another world, quite literally millions of miles away from civilization.
But haven’t humans done this before? The fearless colonists who settled the Americas surely knew that they would never see their home again. They surely understood that they will have only themselves for company. A one-way mission to Mars isn’t too different, is it?
Yet, the colonists of the Mayflower only journeyed across a single ocean. They were still within the embrace of Mother Earth. It wasn’t too different; fewer people, perhaps, and a few new plants and animals. The colonists of Mars, on the other hand, will have left their cradle. They will be stripped of all the comforts of home — no more birds chirping; no more cloudless days on a golden beach; no more crisp sea breezes.
These colonists will live in a metal can in an arid wasteland frequented by planet-wide dust storms. Risks include suffocation from lack of oxygen and decompression sickness from breathing in too much nitrogen. The only thing that separates them from certain death from these ailments is a thin layer of metal and plastics. One can only imagine the psychological strain such an environment would put upon the astronauts. I cringe even at the thought of being in such a place for a month, much less the rest of my life.
Though the mission of Mars One is noble, it is very rash. Columbus didn’t come to settle the New World; he came and returned to the Old World. In the 1960s and 1970s, we did not simply put a man on the moon; we also returned him safely to Earth. Our exploration of Mars should follow the examples of Columbus and the moon missions.
The first astronauts to step on Mars should also have the opportunity to return to Earth. Only when we are capable of sustained interplanetary flight should there be a permanent colony on Mars. By then, we will have improved the technologies for spaceflight, and astronauts will be able to come and go as they please. | <urn:uuid:1d2e21c0-4ba7-4e32-90ca-8eab7aab58a0> | 3.109375 | 697 | Truncated | Science & Tech. | 59.367464 |
This is an introduction to developing Jython, just to get someone started. It doesn't cover the source code in any depth or discuss the design behind Jython. It's purely aimed at getting a development environment set up. It's definitely not complete so feel free to make it better!
Check out a copy of the Jython source with Mercurial, available on most *nix systems or with Cygwin on Windows.
You can use the command line tool hg, or GUI clients are available on most platforms.
To obtain the a copy of the current development source, clone the repo via:
hg clone http://hg.python.org/jython
Attach patches to issues in the Jython bug tracker.
Also, you can upload them to http://codereview.appspot.com (the Jython repository is already registered).
When Jython first followed CPython into use of Mercurial as the repository, it continued to reference a part of the CPython source at https://svn.python.org as a "sub-repository". This meant you still needed Subversion installed. As of 20 March 2012, the Jython Mercurial repository contains a snapshot of CPython libs in the 2.2, 2.5, and default branches.
You therefore only need the following advice if you are somehow working with an old repository.
The following advice is based on experience using Mercurial 1.9, Slik Subversion and Windows 7 (AMDx64). Other tools and operating systems exist. An installation that gives you the command 'svn' on your path is sufficient.
If you do not have Subversion installed (and on the PATH) the Mercurial hg clone command will terminate with the message:
abort: The system cannot find the file specified
at the point where it attempts to read the sub-repository, specified in the files .hgsub and .hgsubstate .
A second requirement is that Subversion should accept the SSL certificate from the site svn.python.org. If you have not used Subversion already to access the site, you may find that the hg clone command hangs at the point where it attempts to read the sub-repository. A simple solution is to visit the site once from the command line as follows:
svn info https://svn.python.org/projects/python/branches/release26-maint/Lib/
Subversion will issue a warning about the certificate, and you will be able to "accept permanently" the site's certificate. The Mercurial clone operation should not now hang.
If you see the sub-directory CPythonLib created in your local repository, then the call to Subversion by Mercurial was a success. (It can take a few minutes to complete.)
Ant is a Java-based tool used to build Jython from source.
Eclipse users, see Eclipse Ant notes
Download the latest version (Jython requires Ant 1.7 or later to build) and install it so Ant's bin directory is somewhere in your path.
To build Jython, run ant in the top-level Jython directory (which contains the Ant file build.xml).
The results of the build appear in the dist subdirectory.
The Jython build process generates an executable Bash script, dist/bin/jython, to make it easy to launch your build of Jython. It works on Unix-like platforms (including Mac OS X and Cygwin).
If you're using Windows without Cygwin, use the batch file dist/bin/jython.bat instead.
Now you're ready to run tests...
- There are a couple different places to find test cases
Jython's dist/Lib/test (populated by the build process)
Jython's bugtests subdirectory (included with the development sources)
Run a particular test, or the whole Python test suite with ant regrtest.
See TestingJython for some more details.
Note the following describes the current trunk/jython. If you are working from an older tag, src doesn't exist and src/com and src/org are moved up a level.
src/org : top level package for python
src/com : zxJDBC related sources
src/shell : launcher scripts
src/templates: java source generator & related templates, used to update portions of java classes elsewhere in the source tree
Demo : demo sources for the website and such
Lib : the python source files for Jython standard library implementations
Lib/test : test cases
Misc : random scripts which are not all used; some generate source
Tools : JythonC and Freeze
CPythonLib : Lib directory from the corresponding version of cpython, via svn:externals
bugtests : additional test cases covering bug reports
JythonDeveloperGuide/PortingPythonModulesToJython : A good starting task for a Jython developer
CodingStandards : The standards for writing Java code for Jython
PatchGuidelines : How to make a patch for submission to the tracker
How things work
ImplementNewType : Implementing a new type (a beginner's notes)
ImplementSequenceType : Implementing a new sequence type
JythonModulesInJava : How to write a Jython module in Java
PythonTypesInJava : How to make a Jython type in Java (2.5 and later), mostly about the type exposer
JythonClassesInJava : How to make a Jython class in Java (pre-2.2, deprecated)
JythonDeveloperGuide/ImplementingStrAndRepr : Tips for implementation of __str__ and __unicode__ in Java.
JythonDeveloperGuide/UsingPyNewStringFromPythonCode : On the corner case of converting a Java String to a Python String.
GeneratedDerivedClasses : gderived.py, a tool used when implementing new types
BufferProtocol : Design of a Jython equivalent to the CPython buffer protocol (buffer API)
MethodDispatch : An explanation of Jython method dispatch mechanism.
WebsiteBuilderSetup : How to get the pieces setup to edit and build the Jython website
VersionTransition : Why some tests are excluded in going to a new version and how to go about fixing them
JythonDeveloperGuide/RegressionTestNotes : Some notes the regression tests
JythonDeveloperGuide/PleaseAdoptMe : Tasks looking for volunteers
HowToReleaseJython : Checklist for building a release and updating the website
SvnToHgMigration : Notes on the migration to Mercurial
PerformanceEnhancements : Ideas on how to speedup Jython
CodebaseCleanup : Tasks/general guidelines on keeping the codebase clean | <urn:uuid:1b3b4824-f0c0-4344-98cf-6f39322ae096> | 2.6875 | 1,433 | Documentation | Software Dev. | 42.135325 |
Satellite View Selection
11:30 AEST on Friday 24 May 2013 | Cloud/surface composite, Australia
Images from Japan Meteorological Agency satellite MTSAT via Bureau of Meteorology.
Australian Government Bureau of Meteorology
National Meteorological and Oceanographic Centre
Satellite Notes for the 1800UTC chart on 24 May 2013
Issued at 5:45 am EST Saturday on 25 May 2013
A complex low pressure system, off the north coast of New South Wales, is pushing low cloud along the northern New South Wales and southeast Queensland coast. A significant cloud band, associated with this low and an upper trough, extends from the Coral Sea down to the North Island of New Zealand.
A broad area of convective cloud lies over waters to the north of Western Australia. Patchy low cloud off the Western Australian west coast is due to a surface trough, which is located offshore.
While patchy low cloud over the Bight and adjacent coast is the result of a strong slow moving high pressure system. Cloud to the south of the continent is associated with a series of cold fronts. | <urn:uuid:8954f803-3083-458a-b9d0-92930ef47c9e> | 2.984375 | 221 | Knowledge Article | Science & Tech. | 46.181676 |
These documents are part of a technical report series on conservation projects funded by the Critical Ecosystem Partnership Fund (CEPF) and the Conservation International Pacific Islands Program (CI-Pacific). The main purpose of this series is to disseminate project findings and successes to a broader audience of conservation professionals in the Pacific, along with interested members of the public and students. The reports are being prepared on an ad-hoc basis as projects are completed and written up.
In most cases the reports are composed of two parts, the first part is a detailed technical report on the project which gives details on the methodology used, the results and any recommendations. The second part is a brief project completion report written for the donor and focused on conservation impacts and lessons learned.
The CEPF fund in the Polynesia-Micronesia region was launched in September 2008 and will be active until 2013. It is being managed as a partnership between CI Pacific and CEPF. The purpose of the fund is to engage and build the capacity of non-governmental organizations to achieve terrestrial conservation. The total grant envelope is approximately US$6 million, and focuses on three main elements: the prevention, control and eradication of invasive species in key biodiversity areas (KBAs); strengthening the conservation status and management of a prioritized set of 60 KBAs and building the awareness and participation of local leaders and community members in the implementation of threatened species recovery plans.
Since the launch of the fund, a number of calls for proposals have been completed for 14 eligible Pacific Island Countries and Territories (Samoa, Tonga, Kiribati, Fiji, Niue, Cook Islands, Palau, FSM, Marshall Islands, French Polynesia, Wallis and Futuna, Eastern Island, Pitcairn and Tokelau). By late 2010 more than 35 projects in 9 countries and territories were being funded.
The Polynesia-Micronesia Biodiversity Hotspot is one of the most threatened of Earth's 34 biodiversity hotspots, with only 21 percent of the region's original vegetation remaining in pristine condition. The Hotspot faces a large number of severe threats including invasive species, alteration or destruction of native habitat and over exploitation of natural resources. The limited land area exacerbates these threats and to date there have been more recorded bird extinctions in this Hotspot than any other. In the future climate change is likely to become a major threat especially for low lying islands and atolls which could disappear completely.
For more information on Conservation International’s work in the Pacific please visit:
www.conservation.org/Pacific_Islands or e-mail us at email@example.com | <urn:uuid:dd56e1b5-6546-447e-870b-dfd70cfd0a89> | 3.171875 | 541 | Knowledge Article | Science & Tech. | 23.698712 |
Specifications have become essential reading for anyone who wants to develop front-end
web sites properly using the newest and most brilliant features available to them
today. This article will hopefully give you a clue as to which one (of several)
to look at when learning about HTML5 and why it should help you; One of the main
problems is that the W3C specifications are often written for implementors not authors
("implementors" are browser and tool makers, and "authors" are web developers) and
they seem dry and hard to digest.
1. The Main Specs
HTML - Living Standard by WHATWG
This HTML spec on WHATWG is a superset of the HTML5 spec, the difference is that
it includes post-HTML5 features that have been put into separate specs such as
Web Video Text Tracks, but importantly are still apart of HTML5.
I personally would use this specification if, as a developer, I wanted to be involved
in the future development of the spec. It frequently changes, which is a good thing
if you like to keep on top of what's new with the standard and of browser changes,
and you'll be able to keep track of new features that are not in the official HTML5
HTML5 A vocabulary and associated APIs for HTML and XHTML by W3C
This specification is the HTML5 spec on the W3C site and is the spec being prepared
for "last Call" at the moment (May 2011). I'd advise using this specification if
you're not bothered about keeping up to date with the constant HTML5 developments,
the spec is alot smaller than other specifications available because it doesnt include
the areas that have been turned into their own specifications - like
Canvas 2D API and Microdata.
Web Applications 1.0
With a photo of a Kitchen Sink on the home page to give an indication of it's work,
this specification houses everything that the WHATWG is currently working on. This
specification is useful to find out information about
Web Sockets API and
Server-sent Events. The disadvantage of this spec is that it doesnt
have the ability to hide the implementor details (the dry bits, if you're a developer!).
2. Cut Down Specifications
HTML5 for Web Authors
The HTML5 for Web Authors specification removes the implementation details intended
for browser makers and adds some stlying, making it more accessible to a developer
and easier to read. It has recently been updated and is especially useful for finding
HTML5: The Markup Language Reference
This is a really excellent quick reference for authors, it describes the syntax,
structure and semantics of HTML5 with the idea that it's easy to read, concise and
to the point. This is really useful when you want to quickly remind yourself of
the essentials of HTML5 or perhaps learn about things you didnt already know, and
it provides useful links back to HTML5 for Web
Developers which provides more detailed information.
HTML5 for Web Developers
This specification removes the implementation details intended for browser makers,
and includes things that the W3C's HTML5 spec doesnt like Microdata, the site has
really easy to use functionality like instant searching and the design is really
well thought out. This spec will keep on getting better and better hopefully and
is my recommendation as a developer. Another great feature is that it's on
GitHub, making it the only specification one can easily contribute to.
Huge credits go out to Ben Schwarz
and WHATWG because it's ace.
Personally I like to use a combination of specifications, this helps me to keep
up to date with what's changing and removes the problem of using features of HTML5
that have changed or are likely to change. HTML - A Living standard, HTML5: The
Markup Language Reference and HTML5 for Web Developers provide a great base and
house more than enough information to keep well in-the-know as it were. All of the
specifications are useful but as a developer the most valuable to me is the HTML5
for Web Developers.
The Next Step
The next step is to get involved and find out as much as you can about the HTML5
specification, learn from it and contribute in the following ways: | <urn:uuid:693ed578-6191-4c63-9bad-c3fed926a3d3> | 2.90625 | 899 | Tutorial | Software Dev. | 40.738166 |