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Hello guys, Thank you for your help on my last question. I have another very simple question. I have been trying to figure this out for a while, and since my professor doesn't help me in the class I have to turn to you guys. Here is the assignment:
Write a C++ program that inputs a number from the keyboard between 0 and 49 and then uses a for or while loop to display every integer that follows the integer that is input and that is evenly divisible by 4. The last number that will be displayed is 100. In other words, if the number you input from the keyboard is 45, your program will output
48 52 56 60 … 92 96 100
Or if your input is 40, your program will output
44 48 52 56 … 92 96 100
Your program does not have to run multiple times. One line of numbers per a.out is sufficient.
Place an error trap in your program that will reject any keyboard inputs < 0 or > 49. Use any wording you wish for the input prompt.
Now here is what I have come up with so far. I am pretty close to getting it, I am just missing one thing I think.
using namespace std;
int main ()
cout << "Input a number between 0 and 49." << endl;
cin >> n;
while (n < 100)
n = n + 4;
cout << n << ", ";
if (n < 0 || n > 49 )
cout << "The number you entered is less than 0. Invalid entry.";
When I compile this program and run it it works but not as I want it to.
When I enter a number, any number at all, it will list all the numbers that follow it up to 100 - which is correct; but it also outputs "the number you have entered is less than 0. Invalid entry". I have been trying to figure this out and i know it is a simple fix, I just can't figure it out.
You're performing the input range check after the loop which is wrong in the first place: The loop isn't supposed to even be executed at all in case of invalid input, and that can't be accomplished when you do the check at a point when the loop has finished already.
Also, when the loop is done, n will always have the value 100, since the code in the loop has modified it, and of course that will always trigger your error message.
I was thrown out of college for cheating on the metaphysics exam; I looked into the soul of the boy sitting next to me.
This is a snakeskin jacket! And for me it's a symbol of my individuality, and my belief... in personal freedom. | <urn:uuid:e61f74d7-385a-4722-afe8-86941eaf6894> | 3.1875 | 566 | Comment Section | Software Dev. | 80.281961 |
ANSI Common Lisp 15 Arrays 15.1 Array Concepts
15.1.2 Specialized Arrays
An array can be a general array,
meaning each element may be any object,
or it may be a specialized array,
meaning that each element must be of a restricted type.
The phrasing "an array specialized to type <<type>>"
is sometimes used to emphasize the element type of an array.
This phrasing is tolerated even when the <<type>> is t,
even though an array specialized to type t
is a general array, not a specialized array.
The next figure lists some defined names that are applicable to array
creation, access, and information operations.
General Purpose Array-Related Defined Names
18.104.22.168 Array Upgrading
22.214.171.124 Required Kinds of Specialized Arrays | <urn:uuid:f09a5a67-2681-4751-a004-b407755a2562> | 3.21875 | 181 | Documentation | Software Dev. | 54.739591 |
Agile development model is also a type of Incremental model. Software is developed in incremental, rapid cycles. This results in small incremental releases with each release building on previous functionality. Each release is thoroughly tested to ensure software quality is maintained. It is used for time critical applications. Extreme Programming (XP) is currently one of the most well known agile development life cycle model.
Diagram of Agile model:
Advantages of Agile model:
- Customer satisfaction by rapid, continuous delivery of useful software.
- People and interactions are emphasized rather than process and tools. Customers, developers and testers constantly interact with each other.
- Working software is delivered frequently (weeks rather than months).
- Face-to-face conversation is the best form of communication.
- Close, daily cooperation between business people and developers.
- Continuous attention to technical excellence and good design.
- Regular adaptation to changing circumstances.
- Even late changes in requirements are welcomed
Disadvantages of Agile model:
- In case of some software deliverables, especially the large ones, it is difficult to assess the effort required at the beginning of the software development life cycle.
- There is lack of emphasis on necessary designing and documentation.
- The project can easily get taken off track if the customer representative is not clear what final outcome that they want.
- Only senior programmers are capable of taking the kind of decisions required during the development process. Hence it has no place for newbie programmers, unless combined with experienced resources.
When to use Agile model:
- When new changes are needed to be implemented. The freedom agile gives to change is very important. New changes can be implemented at very little cost because of the frequency of new increments that are produced.
- To implement a new feature the developers need to lose only the work of a few days, or even only hours, to roll back and implement it.
- Unlike the waterfall model in agile model very limited planning is required to get started with the project. Agile assumes that the end users’ needs are ever changing in a dynamic business and IT world. Changes can be discussed and features can be newly effected or removed based on feedback. This effectively gives the customer the finished system they want or need.
- Both system developers and stakeholders alike, find they also get more freedom of time and options than if the software was developed in a more rigid sequential way. Having options gives them the ability to leave important decisions until more or better data or even entire hosting programs are available; meaning the project can continue to move forward without fear of reaching a sudden standstill. | <urn:uuid:70aa8ed1-0116-425b-8bcf-d17aa8959afc> | 2.8125 | 536 | Knowledge Article | Software Dev. | 25.410716 |
Update! I’ve added a few more experiments for your Mad Scientist’s laboratory. Here’s an new post of 10 spooky Halloween Science experiments (including those below) posted this Oct. (2012) : Click here to check them out.
Since lots of people are looking for fun science experiments to do for Halloween, I compiled some of mine so that they’re easy to find. Just click on the name of the experiment to go to the instructions, see photos of what to do, and learn a little science. Some of them also have links to my videos or TV segments where I demonstrate how to do the experiments. They’re all really easy and lots of fun!
Goblin Goo (All you need is cornstarch and water. Here’s a video on how to make the goo. You can add a little food coloring to the water if you want, but it may stain your hands!)
Bag of Blood (If you have ziplock baggies, water, red food coloring and skewers, you can do this experiment!)
Fizzy Balloon Monster Heads (After we made Goblin Goo, I demonstrated how to make Fizzy Balloon Monster heads. Click here to watch.)
Magic Potion (Bubbly, stinky Halloween fun: I made a short video on how to make magic potion. Click here to watch it.
Mad Scientist’s Green Slime (To see a TV segment where we made Mad Scientist’s Green Slime, click here!)
Apple Mummies (Here’s a link to a TV segment where the kids and I demonstrated how to make Apple Mummies. Click here.)
Alien Monster Eggs (These make a great centerpiece for a Halloween party, when you’re done playing with them.) I demonstrated how to make them on Kare 11 this week! Click here to watch the video.
Frankenworms Gummyworms soaked in baking soda and water come to “life” when you drop them into vinegar! Click here for directions and a video.
Here’s a video of Halloween science experiments you can find on KidScience app for iPhones and iPod Touch. Kids will love watching how-to videos of all the experiments on KidScience Premium!
Next week, I’m headed to Goddard Space Flight Center in Maryland to learn more about climate change for my role as an Earth Ambassador for NASA! When I return, I’ll talk about my trip and demonstrate an all-new Halloween science experiment on Kare11′s Sunrise News on Oct. 19th.
- Halloween Science for Kids of All Ages Halloween brings out the kid in everyone, and there’s no...
- Halloween Science: Creepy Critter Slingshots If you love marshmallows, you’ll love this physics experiment for...
- Halloween Science: Mad Scientist’s Green Slime What could be more fun than creating your own green...
- Halloween Science: Magic Bag of Blood You’ll be amazed when you fill a plastic zip-lock bag...
Related posts brought to you by Yet Another Related Posts Plugin. | <urn:uuid:b1b67b9d-59b9-4c11-904c-a7b4ab04d5dc> | 2.765625 | 646 | Personal Blog | Science & Tech. | 68.538148 |
On the tail of my post about planetary snowballs, the Faint Young Sun Paradox has raised its head again. Three to four billion years ago the Sun was only about 70% as luminous as it is today - it was young and its core temperature was a little lower, so the output of radiation was somewhat less. This has long been a vexing issue for the early Earth. The geological record firmly points to a warm world with plenty of nice liquid water, but if the Sun was heating the planet so much less then something must have offset this to prevent a global freeze. A long postulated solution, and a seemingly good one, has been that the young Earth must have had more atmospheric carbon dioxide, and possibly methane to boost the greenhouse effect and keep things warm.
However, a new study of ancient marine sediments (banded iron formations) by Rosing et al. (and a great discussion by Jim Kasting) adds significantly to other geological evidence that atmospheric carbon dioxide in that young Earth was at about the same level it is today. So how do we solve the paradox ?
Rosing et al. bring up an idea that has been around before - that the young Earth just absorbed more of the sunlight hitting it, by virtue of being less reflective. One way to do this is to alter the amount and type of cloud cover. Because we think a lot of modern clouds are 'seeded' by the muck that life itself (not just us) dumps into the atmosphere, then a young Earth - with a different biosphere - could have have less reflective cloud cover. This is by no means a done deal, but it's certainly interesting to reconsider, and the paradox of the faint young Sun continues to intrigue. | <urn:uuid:204ead74-db23-4a4a-b165-547780642286> | 3.484375 | 351 | Comment Section | Science & Tech. | 52.204381 |
Arrange your fences to make the largest rectangular space you can. Try with four fences, then five, then six etc.
An activity making various patterns with 2 x 1 rectangular tiles.
A hallway floor is tiled and each tile is one foot square. Given
that the number of tiles around the perimeter is EXACTLY half the
total number of tiles, find the possible dimensions of the hallway.
By adding another $2$ pebbles in line you double the area to $2$, like this:
The rule that's developing is that you keep the pebbles that are down already (not moving them to any new positions) and add as FEW pebbles as necessary to DOUBLE the PREVIOUS area, using RECTANGLES ONLY!
So, to continue, we add another three pebbles to get an area of $4$:
You could have doubled the area by doing:
But this would not obey the rule that you must add as FEW pebbles as possible each time. So this one is not allowed.
Number 6 would look like this:
Well, now it's time for you to have a go.
"It's easy,'' I hear you say. Well, that's good. But what questions can we ask about the arrangements that we are getting?
We could make a start by saying "Stand back and look at the shapes you are getting. What do you see?'' I guess you may see quite a lot of different things.
It would be good for you to do some more of this pattern. See how far you can go. You may run out of pebbles, paper or whatever you may be using. (Multilink, pegboard, elastic bands with a nail board, etc.)
Well now, what about some questions to explore?
Here are some I've thought of that look interesting:
Try to answer these, and any other questions you come up with, and perhaps put them in a kind of table/graph/spreadsheet etc.
Do let me see what you get - I'll be most interested.
Don't forget the all-important question to ask - "I wonder what would happen if I ...?'' | <urn:uuid:36d2e25c-ac65-4409-833d-88199b5cd926> | 2.96875 | 462 | Tutorial | Science & Tech. | 74.673614 |
How many loops of string have been used to make these patterns?
I've made some cubes and some cubes with holes in. This challenge
invites you to explore the difference in the number of small cubes
I've used. Can you see any patterns?
Create a pattern on the left-hand grid. How could you extend your pattern on the right-hand grid?
Here is your chance to investigate the number 28 using shapes,
cubes ... in fact anything at all.
There are nine teddies in Teddy Town - three red, three blue and three yellow. There are also nine houses, three of each colour. Can you put them on the map of Teddy Town according to the rules?
Take 5 cubes of one colour and 2 of another colour. How many
different ways can you join them if the 5 must touch the table and
the 2 must not touch the table?
These caterpillars have 16 parts. What different shapes do they make if each part lies in the small squares of a 4 by 4 square? | <urn:uuid:e1cb3180-8f5c-4e06-96cb-243bcfa941f8> | 3.0625 | 215 | Content Listing | Science & Tech. | 76.775533 |
Three beads are threaded on a circular wire and are coloured either red or blue. Can you find all four different combinations?
Find out how we can describe the "symmetries" of this triangle and
investigate some combinations of rotating and flipping it.
There are nine teddies in Teddy Town - three red, three blue and three yellow. There are also nine houses, three of each colour. Can you put them on the map of Teddy Town according to the rules?
Choose the size of your pegboard and the shapes you can make. Can
you work out the strategies needed to block your opponent?
You have 4 red and 5 blue counters. How many ways can they be
placed on a 3 by 3 grid so that all the rows columns and diagonals
have an even number of red counters?
A tetromino is made up of four squares joined edge to edge. Can
this tetromino, together with 15 copies of itself, be used to cover
an eight by eight chessboard?
Ahmed has some wooden planks to use for three sides of a rabbit run
against the shed. What quadrilaterals would he be able to make with
the planks of different lengths?
Use the Cuisenaire rods environment to investigate ratio. Can you
find pairs of rods in the ratio 3:2? How about 9:6?
How many different triangles can you make on a circular pegboard
that has nine pegs?
Use the sightings of the lion to guess the location of its lair.
Can you find all the different ways of lining up these Cuisenaire
Our 2008 Advent Calendar has a 'Making Maths' activity for every
day in the run-up to Christmas.
Can you put the 25 coloured tiles into the 5 x 5 square so that no
column, no row and no diagonal line have tiles of the same colour
A card pairing game involving knowledge of simple ratio.
A game for 2 people that everybody knows. You can play with a
friend or online. If you play correctly you never lose!
What shaped overlaps can you make with two circles which are the
same size? What shapes are 'left over'? What shapes can you make
when the circles are different sizes?
Hover your mouse over the counters to see which ones will be
removed. Click to remover them. The winner is the last one to
remove a counter. How you can make sure you win?
Work out the fractions to match the cards with the same amount of
Is it possible to place 2 counters on the 3 by 3 grid so that there
is an even number of counters in every row and every column? How
about if you have 3 counters or 4 counters or....?
Try to stop your opponent from being able to split the piles of counters into unequal numbers. Can you find a strategy?
An interactive game to be played on your own or with friends.
Imagine you are having a party. Each person takes it in turns to
stand behind the chair where they will get the most chocolate.
A game for 1 or 2 people. Use the interactive version, or play with friends. Try to round up as many counters as possible.
An interactive activity for one to experiment with a tricky tessellation
This was a problem for our birthday website. Can you use four of these pieces to form a square? How about making a square with all five pieces?
An interactive game for 1 person. You are given a rectangle with 50 squares on it. Roll the dice to get a percentage between 2 and 100. How many squares is this? Keep going until you get 100. . . .
A game to be played against the computer, or in groups. Pick a 7-digit number. A random digit is generated. What must you subract to remove the digit from your number? the first to zero wins.
A game for 2 people that can be played on line or with pens and paper. Combine your knowledege of coordinates with your skills of strategic thinking.
What are the coordinates of the coloured dots that mark out the
tangram? Try changing the position of the origin. What happens to
the coordinates now?
A train building game for 2 players.
NRICH December 2006 advent calendar - a new tangram for each day in
the run-up to Christmas.
Choose 13 spots on the grid. Can you work out the scoring system? What is the maximum possible score?
How have the numbers been placed in this Carroll diagram? Which labels would you put on each row and column?
Can you make the green spot travel through the tube by moving the
yellow spot? Could you draw a tube that both spots would follow?
Use the blue spot to help you move the yellow spot from one star to
the other. How are the trails of the blue and yellow spots related?
Cut four triangles from a square as shown in the picture. How many
different shapes can you make by fitting the four triangles back
A simulation of target archery practice
Using angular.js to bind inputs to outputs
Can you put the numbers from 1 to 15 on the circles so that no
consecutive numbers lie anywhere along a continuous straight line?
Can you fit the tangram pieces into the outline of Little Ming playing the board game?
Can you see why 2 by 2 could be 5? Can you predict what 2 by 10
Try out the lottery that is played in a far-away land. What is the
chance of winning?
Starting with the number 180, take away 9 again and again, joining up the dots as you go. Watch out - don't join all the dots!
Can you work out what is wrong with the cogs on a UK 2 pound coin?
Use the interactivity to find all the different right-angled
triangles you can make by just moving one corner of the starting
How can the same pieces of the tangram make this bowl before and after it was chipped? Use the interactivity to try and work out what is going on!
Can you fit the tangram pieces into the outlines of the watering can and man in a boat?
Investigate how the four L-shapes fit together to make an enlarged
L-shape. You could explore this idea with other shapes too.
Can you fit the tangram pieces into the outlines of Mai Ling and Chi Wing?
Use the interactivity or play this dice game yourself. How could
you make it fair? | <urn:uuid:a0b6b308-da61-4706-82e5-07493ff0e896> | 2.8125 | 1,354 | Content Listing | Science & Tech. | 73.081224 |
This photomosaic is a careful compilation of multiple images of a mussel bed at the Atwater Valley 340 site. The images were taken with a downward-looking still camera in 2006. Click image for larger view and image credit.
The sea-floor community of tubeworms, mussels, shrimp, and a crab in the Green Canyon 852 (GC 852) site. Click image for larger view and image credit.
Penn State University
The Expedition to the Deep Slope 2007 mission includes two types of activities, which together will advance our understanding of the sea floor communities that live in association with hydrocarbon seepage and hardgrounds in the deep Gulf of Mexico. We will revisit about half of the sites we discovered in 2006, complete our characterization of these impressive sites, and also collect time series data that will provide important information on how fast seep animals grow and how the deep communities change over time. The second objective will be to explore three to five new areas and to characterize any new sites and communities we discover. We have identified likely sites for these exploratory dives and will use them to fill in key pieces to the puzzle of the seep animal and coral distribution patterns in the deep Gulf of Mexico. All of the sites we will study are in areas where energy companies could soon begin to drill for oil and gas. Our mission will provide essential information on the ecology and biodiversity of these deep-sea communities to regulatory agencies and energy companies as the quest for oil moves into deeper and deeper water.
The largest oil reserves in the continental United States are found in the Gulf of Mexico. The Minerals Management Service (MMS) of the U.S. Department of the Interior oversees the responsible extraction of these natural resources and has been supporting the study of the hydrocarbon seep communities since the early 1980s. Up until a few years ago, these studies were focused on communities found between 500 and 1,000 meter (m) depth.
Meanwhile, energy companies have continued to develop the technology for extraction of oil and gas from deeper and deeper water, and now have the capability to drill oil wells in all water depths in the Gulf of Mexico. This is one of the reasons that the MMS and NOAA have funded our study. It is also one of the reasons that our project received a Cooperative Conservation Award from the Department of the Interior this year for this project.
On June 4, our plan is to depart Fort Lauderdale, Florida, on the NOAA ship Ronald H. Brown, beginning our two-day transit to our first dive site. We will begin our operations at one of the lushest sites we discovered last year, which we call AT 340 — which is short for "Atwater Valley lease area, block 340," the MMS lease block where the site is located. When we first arrive, we will deploy an array of navigational transponders that will allow us to make detailed maps of the sea floor and to always know where we are (within a meter or two). The Jason II remotely operated vehicle (ROV), designed by the Woods Hole Oceanographic Institution’s Deep Submergence Laboratory, can work around the clock. As soon as our transponders are ready to go, we will launch the ROV and begin our bottom operations. We do not want to stop the bottom operations just to retrieve collections so we will be using an “elevator” to send our collections back to the surface (without recovering the ROV). On board the ship, teams of scientists will be working on these valuable collections: analyzing the chemistry and geology, identifying the animals, and studying the microbial communities.
A red gorgonian from the Coral Garden area in GC 852. The eight tiny tentacles on each polyp place this coral in the Octocorallia sub class. You can also see an anemone attached to the coral and a small galatheid crab in the background. Click image for larger view and image credit.
The next site we will visit will be GC 852 (located in the Green Canyon lease area, block 852). In addition to lush communities of tubeworms and mussels, we also discovered a beautiful coral community at this site. We have several studies to complete at GC 852, but when we are finished we will change the types of equipment we have on the ROV and begin the most exploratory phase of the expedition. We will dive on at least three new sites, and perhaps as many as five. What we do and how long we spend working on each site will depend on what we find. These are sites never before seen by human eyes, and we will have to adapt our plans as we go.
About halfway through the expedition we will have an at-sea exchange of personnel. Six new scientists will board a transfer ship in Florida and meet us about 150 miles off the coast of Louisiana. Six other scientists will disembark our research ship, take the “taxi” in to a port in Texas, and fly back to their home laboratories. Meanwhile, the rest of us will continue our exploration and study of the deep seep sites. Our plan is to finish up with the sites offshore of Mississippi and Louisiana by about our third week at sea, and then move 200 miles further to the west and make a series of dives at three different sites in the Alaminos Canyon lease blocks, off the coast of Texas.
A few of the hard and soft corals in the Coral Garden area in GC 852. Click image for larger view and image credit.
A large aggregation of tubeworms (mostly Escarpia laminata) attached to carbonate blocks at 2,200-meter depth in Alaminos Canyon lease block 645. In the foreground is the Bushmaster collection device, which is attached to the front of the Alvin submersible. Click image for larger view and image credit.
At Alaminos Canyon (AC) 818, in 2,800m water, we have a tubeworm growth study underway and have also seen, but not collected, what is almost certainly a new species of clam with sulfur-oxidizing symbionts. Another site, AC 645, was the first deep water hydrocarbon seep community discovered in the Gulf of Mexico, and where we banded some tubeworms and mapped mussel communities way back in 1992. We found our 1992 study area during the last dive of the 2006 expedition, so we will return here and document the changes in the communities and growth of the worms that has occurred over the last 16 years!
Another site, in AC 601, hosts a large lake of brine that covers about 17,000 square meters of the sea floor. The sediments here had some of the most extreme chemistry and strange microbial activity of any site we visited, and the chemists and microbiologists are excited for another set of samples from this site.
By the end of this expedition, we will have a very good understanding of the biodiversity of the communities on the deep hard grounds and seeps in the Gulf of Mexico, and their relation to the complex geology and geochemistry of the region. We will have the samples needed to begin unraveling the relationships among the populations at different sites and the data to estimate growth rates and calculate ages of some of the key species. We will also have collected a large quantity of “ground-truth” information, relating what can be detected by remote sensing to what is actually present on the sea floor. This will provide us with a vastly improved ability to predict the occurrence of seep and coral communities in the deep sea, based on geophysical, geochemical, and satellite data collected from both on and above the surface of the ocean. | <urn:uuid:6975013b-2096-4563-8a36-7864e29e13b4> | 3.046875 | 1,585 | Knowledge Article | Science & Tech. | 44.386013 |
This is about simple random walk (as defined in theory). Uses the cairo library. A ball walks randomly on the screen and leaves a trace behind.
Defined probability for the next step to walk is 0.5. Probabilities for left step and other parameters are pre-defined however someone can change them from inside the constructor at will. Accepted probabilities are from 0 to 1, also -1 is accepted, this indicates that the program choses on its own the probability for the next step to walk. The purpose of this is to show the the usage of cairo library!
The one direction use red color, the other blue color, and black color is used when the walk comes at the starting position. Predifined is 1000 steps and speed 400ms, after this a summary of the steps like a graph is shown on the screen. Other information are displayed on the screen like total count of steps, the current height (how far away is from the starting height), maximum, minimum height, statistical probability from walk history etc. | <urn:uuid:398eb132-e8e0-4b20-8b66-2a81c1432176> | 3.1875 | 211 | Documentation | Software Dev. | 56.004091 |
|Ada 95 Quality and Style Guide||Chapter 3|
Make reserved words and other elements of the program visually distinct from each other.
Use lowercase for all reserved words (when used as reserved words).
- Use mixed case for all other identifiers, a capital letter beginning every word separated by underscores.
- Use uppercase for abbreviations and acronyms (see automation notes).
example... type Second_Of_Day is range 0 .. 86_400; type Noon_Relative_Time is (Before_Noon, After_Noon, High_Noon); subtype Morning is Second_Of_Day range 0 .. 86_400 / 2 - 1; subtype Afternoon is Second_Of_Day range Morning'Last + 2 .. 86_400; ... Current_Time := Second_Of_Day(Calendar.Seconds(Calendar.Clock)); if Current_Time in Morning then Time_Of_Day := Before_Noon; elsif Current_Time in Afternoon then Time_Of_Day := After_Noon; else Time_Of_Day := High_Noon; end if; case Time_Of_Day is when Before_Noon => Get_Ready_For_Lunch; when High_Noon => Eat_Lunch; when After_Noon => Get_To_Work; end case; ...
Visually distinguishing reserved words allows you to focus on program structure alone, if desired, and also aids scanning for particular identifiers.
The instantiation chosen here is meant to be more readable for the experienced Ada programmer, who does not need reserved words to leap off the page. Beginners to any language often find that reserved words should be emphasized to help them find the control structures more easily. Because of this, instructors in the classroom and books introducing the Ada language may want to consider an alternative instantiation. The Ada Reference Manual (1995) chose bold lowercase for all reserved words.
Ada names are not case sensitive. Therefore, the names max_limit, MAX_LIMIT, and Max_Limit denote the same object or entity. A good code formatter should be able to automatically convert from one style to another as long as the words are delimited by underscores.
As recommended in Guideline 3.1.4, abbreviations should be project-wide. An automated tool should allow a project to specify those abbreviations and format them accordingly.
|< Previous Page||Search||Contents||Index||Next Page >| | <urn:uuid:7062308c-4a40-4938-b009-8e32dad0b52b> | 3.078125 | 520 | Documentation | Software Dev. | 29.640825 |
Saturday 15 June
Common cockchafer (Melolontha melolontha)
Common cockchafer fact file
- Find out more
- Print factsheet
Common cockchafer description
This common, large beetle often crashes into lighted windows at night during early summer (3). It is a familiar beetle that belongs to the same family as dung beetles (Scarabaeidae) (4). As it flies it produces an alarming loud buzzing noise, but it is harmless to humans (3). The ribbed wing cases or ‘elytra’ are reddish-brown in colour, and the head and the pronotum are blackish and covered in short hairs. The fan-like antennae are longer in males than females (5). The larvae are fat white grubs that typically have a curved body shape and live in the soil. They can grown up to 40 to 46 mm in length (5). ‘Chafer’ is a Middle English word which is thought to mean ‘to gnaw’. The prefix ‘cock’ is often used to signal maleness, but it may be a simple term of familiarity (6). The larvae are often called rook-worms, as rooks are said to have a particular love of both adult and larval cockchafers (3).
- Also known as
- May beetle, Maybug.
- Adult beetle length: 20 – 30 mm (2)
- Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- In insects, the hardened cuticle on the upper surface of the first thoracic segment (the part of the body nearest the head).
- National Biodiversity Network Species Dictionary (January 2004): http://www.nhm.ac.uk/nbn
- Harde, K.W. (2000) Beetles. Silverdale Books, Leicester.
- Chinery. M. (1993) Insects of Britain and Northern Europe. Harper Collins Publishers Ltd, London.
- Kendall Bioresearch Services (January 2004): http://www.kendall-bioresearch.co.uk/chafer.htm
- HYPP Zoology (January 2004): http://www.inra.fr/Internet/Produits/HYPPZ/RAVAGEUR/6melmel.htm
- Buczaki, S. (2002) Fauna Britannica. Hamlyn, London.
- view the contents of, and Material on, the website;
- download and retain copies of the Material on their personal systems in digital form in low resolution for their own personal use;
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Common cockchafer biology
Adult cockchafers eat leaves and flowers of a range of deciduous trees, plants and shrubs but do not tend to be serious pests in Britain. The larvae, on the other hand, can be serious pests of grasses and cereals, as they live in the soil feeding on roots. They can be serious pests in gardens, nurseries and pastures, causing brown patches of grass to appear. They also attack other garden plants and vegetables (4).
Adults appear in April or May. They feed for a time, and females become mature at 10 to 15 days after emergence. After mating, females lay around 20 eggs in soft soil. A large number of females die after egg-laying, but some return to feeding and may then go on to lay a second or even third batch of eggs (5). After 4-6 weeks the larvae hatches out. It takes 3-4 years for the larvae to become fully developed, and they burrow deeper into the soil each winter to hibernate (5).Top
Common cockchafer range
Widespread and common throughout much of Britain, but less common in the north (1).Top
Common cockchafer habitat
Occurs in a range of habitats including gardens and agricultural land (5).Top
Common cockchafer status
Not threatened (2).Top
Common cockchafer threats
Although this species is not threatened at present, it has declined significantly and is no longer the serious pest it once was. This is thought to be due to mechanical cultivation, which kills the larvae(5).Top
Common cockchafer conservation
Conservation action is not required for this species (4).Top
Find out more
For more on invertebrates and their conservation see Buglife- the invertebrate conservation trust:
AuthenticationThis information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact: email@example.comTop
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Botany online 1996-2004. No further update, only historical document of botanical science!
Phototropismis a growth movement induced by a light stimulus. Growth towards a source of light is called positive phototropism, that away from the source is termed negative phototropism. The tips of shoots are usually positively, that of roots negatively phototropic.
Originally (with J. v. SACHS, for example) was phototropism called heliotropism, because the plant grows towards the sun. The name was altered when it became clear that plants react also towards artificial sources of light (W. PFEFFER). Before proceeding further shall another problem be outlined shortly: Does the plant react to light or to the air? Here is a citation from A. de CANDOLLE ( 1834/38).
"Gardeners and farmers tell usually that plants are attracted by the air and only TESSIER proved this to be false by a simple experiment: He placed living plants in a basement with two openings, on one side spent a glass window light but no air, on the other brought an airhole leading through a spacious and dark room air but not light. All plants grew towards the glass window."
A.de CANDOLLE noticed as soon as 1809 that the growth towards light is caused by an unequal growth of the opposite parts of an organ. The part exposed to light grows slower than the one that is not exposed. J. v. SACHS discovered the importance of the light quality (the dependence on the wave length) for the phototropic reaction. Blue, violet and ultraviolet light together have the same effect as very strong white light. The effect remains even after the UV part is taken away. Red, yellow , and green light has no effect on most plants. Red light causes a phototropic reaction in some fern prothalliums, though.
The amount of light and the phototropic reaction are linked. This connection is known in literature under the terms Bunsen-Roscoe law, product law or reciprocity theorem (FRÖSCHEL and BLAAUW, 1908, BLAAUW, 1909). The Bunsen-Roscoe law states that the product of time and intensity, and thus the energy amount of the used light, is the measure of the stimulus strength. It is thus of no importance whether a light stimulus of low intensity is applied for a longer period of time or whether a stimulus of high intensity is applied for a short time. We know today that the Bunsen-Roscoe law applies only in a very limited sense, since a certain minimal amount of light has to be present in order to trigger the reaction (threshold value), and an increase in light intensity does not always cause an increase in the phototropic reaction, but may in contrast suppress the positive reaction. A continuous increase causes a second positive reaction with a new maximum, that decreases again and rises once more (= 1., 2., and 3. positive phototropic bending).
The dose-effect curve of the phototropism of etiolated Avena coleoptiles (schematic depiction). The amount of white light is given in lux seconds, the ordinate gives the positive or negative bending. The reaction spheres of the 1., 2., and 3. positive, as well as that of the negative phototropic bending are shown (according to H. MOHR and P. SCHOPFER, 1978, and H. G. duBUY and E. NUERNBERGK, 1943).
Positive and negative phototropism within the same tissue are characteristic not only for Avena coleoptiles. It can also be observed under natural light conditions with germinating plants of the tropic Aracea Monstera gigantea. At low amounts of light (a low flow of photons) does it react positively, at too high amounts negatively phototropic. It differs from Avena primarily in the stimulus thresholds at which one reaction becomes the opposite.
Phototropic reactions are characteristic for growing tissues, and are less easily detected in fully differentiated ones. This is on one hand caused by the cellsí loss of plasticity, and on the other hand by the development of mostly inflexible strengthening elements that set a mechanic resistance against each deformation of the tissue. In the shoot axis are they arranged in the periphery thus bringing about an especially high stability.
These facts show that we have stimulus perception, stimulus forwarding, the mechanism of the bending, and experimental data for all three reaction parts, but it is still not understood how these parts are linked. We do not know how the synthesis of the information molecules (the phytohormone auxine) is influenced by the light receptor after stimulation. We do not know either how the decision for a negative or a positive phototropic reaction is made, and we have only rudimentary knowledge about the way in which auxine could stimulate the elongation of the cell walls in the growth zone.
A further example of literature is the phototropic bending of the sporangium of Phycomyces: Indeed is its mechanism better understood than that of the Avena coleoptile, since the problem of intracellular forwarding of information does not occur. The question how opposite walls of the same cell can grow with differing velocity remains. Changes of the turgor cannot explain it. | <urn:uuid:8bcdfc42-4978-4516-97dd-a1521d437d1a> | 3.609375 | 1,096 | Knowledge Article | Science & Tech. | 45.684797 |
Set your doomsday clock now: Earth will be ripped from the sun just before universe blows up (.... but only in 16.7 billion years)
By Rob Waugh
This is the way the world ends: Two months before doomsday, the Earth will be ripped from the Sun, and five days before the moon will be torn from the earth
A doomsday timetable predicts what will happen to our universe if mysterious 'dark energy' rips our universe to shreds.
Dark energy is thought to make up around 70% of the universe - and physicists have explored an idea called 'the big rip' where the energy destroys the entire universe.
Two months before doomsday, the Earth will be ripped from the Sun, and five days before the moon will be torn from the earth.
The Sun will be destroyed 28 minutes before the end of time and 16 minutes before the final curtain the Earth will explode.
The rather gloomy prediction was made by Chinese theoretical physicists exploring one possible idea of 'dark energy' - a theoretical, mysterious energy thought to be everywhere in the universe.
The academics worked out one possible 'future' - a doomsday scenario triggered by dark energy.
The 'big rip' theory - where dark energy destroys all in its path - will see the Milky Way torn apart 32.9 million years before the end of the universe, they say.
The good news is even in the worst case scenario we have 16.7 billion years to say our goodbyes.
Dark energy is believed to make up about 70 per cent of the current content of the universe, and provides one explanation of how galaxies may meet their end.
In the 'big rip' theory, if the ratio
of pressure and density of dark energy falls below -1, it will grow to
infinity in a finite period of time.
And because it repels gravity, this is bad news for the universe.
Burnt to a crisp: The good news is even in the worst case scenario we have 16.7 billion years to say our goodbyes
Scientists from the University of Science and Technology of China, the Institute of Theoretical Physics at the Chinese Academy of Sciences, Northeastern University, and Peking University met to discuss the worse case scenario for the 'big rip' theory.
‘We wanted to infer from the current data what the worst fate would be for the Universe’, they said.
But they add: ‘At worst, the time remaining before the Universe ends in a big rip is 16.7 billion years.’ | <urn:uuid:d8a60844-0800-49cc-a3a2-f0b7563bc122> | 3.109375 | 526 | Truncated | Science & Tech. | 55.6191 |
int getresuid(uid_t *ruid, uid_t *euid, uid_t *suid); int getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid);
returns the real UID, the effective UID, and the saved set-user-ID
of the calling process, in the arguments
performs the analogous task for the process's group IDs.
On success, zero is returned.
On error, -1 is returned, and
is set appropriately.
One of the arguments specified an address outside the calling program's
These system calls appeared on Linux starting with kernel 2.1.44.
The prototypes are given by glibc since version 2.3.2,
These calls are nonstandard;
they also appear on HP-UX and some of the BSDs. | <urn:uuid:bb6b71d2-a1bf-45c9-8858-1d5263aa4b14> | 2.71875 | 191 | Documentation | Software Dev. | 70.605808 |
Degradation of Natural Resources
The disappearance of natural resources damages an area and limits its ability to sustain a population. The population could be trees, sea grass, animals, or even people. Often, this damage is the result of beneficial activities performed irresponsibly. Wastewater discharged into an estuary can alter the salinity, affecting the lifecycle of sea grass and fish nurseries. If fishing is a source of income for a community, not only will improper treatment and disposal of wastewater damage natural resources, but it will harm the local economy as well.
On a larger scale, natural resources can be impacted to a point that they can no longer be repaired. Species cannot be brought back and populations can no longer survive on the land. Damage from deforestation impacts biodiversity, causes soil erosion, and limits the farming of an area.
Degradation of natural resources often has a chain effect. For example, consider the impact that clearing acres of rain forest for farming has on the environment — both local and global. The soil cannot support crops that are harvested on a yearly basis and its productivity quickly diminishes.
As income decreases along with the crop yield, farmers abandon the land in search of more fertile fields, increasing pressure on local resources. The deforested land does not absorb rainwater as before, so rainfall causes more water to flow into nearby rivers all at once, flooding downstream villages and cities. However, drought is also an outcome of deforestation.
Part of the reason rain forests are so wet is that trees play a vital role in supplying water to the atmosphere through transpiration; without trees, the water to produce rain simply isn't there. Haphazard deforestation results in patches of remaining forest separated by cleared land. Plants and animals are effectively marooned, isolated from their species. Fewer options can result in inbreeding, weakening the gene pool.
Larger species, usually predators, are especially vulnerable to population loss simply because there are so few of them. A bad breeding year, a natural disaster, or a disease can wipe them out. On a global scale, deforestation contributes to a buildup of greenhouse gases; fewer trees mean more carbon dioxide is left in the atmosphere.
However, people are gaining a better understanding that one system cannot operate at the expense of another. Conservation of natural resources has become a priority for businesses and governments, which tout sustainability as a way to strike a balance between helping the environment and preventing economic or personal hardship. | <urn:uuid:f0137c01-8d76-4f4a-99a1-165e5b7ef466> | 4.0625 | 500 | Knowledge Article | Science & Tech. | 27.271231 |
Apache has fast become one of the most commonly used web server solutions today. With its use comes the ability to manipulate the behaviour of your site in certain ways (server-side) from a type of file called .htaccess. This guide covers the various commands, and possibilities of using such a file.
Firstly, in order to use this, mod_rewrite must be enabled in httpd.conf. It is also recommended that the .htaccess file created is CHMOD'd to 644 so that the server can use it, but the browser cannot; preventing any sort of security hole from a user getting access to it.
A htaccess file acts from where it created, typically the root of the webserver, down to all the subfolders. Any folders that should not be affected by a htaccess above it should have it's own htaccess file that negates any rules that should not take affect.
Probably one of the most useful commands (otherwise known as a directive) available in a htaccess file, is that of
RewriteRule - it is this that can be used rewrite one URL into another. For this to work,
RewriteEngine On must be used first, as with any other Rewrite command.
RewriteEngine On RewriteRule old.* new$1
The above example will redirect any urls that start with old to one where old has been replaced by new. For example, a request to /oldnews.php would change to /newnews.php by using the rule. As it uses a regular expression for the pattern, the
.* tells Apache that multiple characters of any type should be matched - whatever is matched is assigned to $1 in the substitution. The syntax for this is as follows:
RewriteRule pattern substitution
Note: patterns use extended regular expressions
Using this methodology, it is easy to produce a rewrite rule for making friendly URLs for dynamic pages. For example, if you visit www.newearthonline/article/68 you will be automatically redirected to www.newearthonline.co.uk/index.php?page=article&article=68 - this is done using a rewrite rule.
RewriteEngine On RewriteRule ^article/([0-9]+)/? article.php&article=$1 [R=301, L]
The rule itself will look for "article/" followed by 1 or more integers, and an optional forward slash. When this is matched it will take the integer and use it in the rewrite of the URL. The usage of the flags on the end of the RewriteRule is to signal that it is a permanent redirect (so absolute URLs are not needed), and to say it is the last rule to run for the request. These flags are covered in more detail later on. | <urn:uuid:19b64e06-2208-4506-9890-98740f368c16> | 2.6875 | 578 | Tutorial | Software Dev. | 52.649937 |
Carbon-neutrality has never been more highly prized. Half of New Zealand's greenhouse gas emissions come from the guts of sheep and cows; Norway spews ever more gases from its North Sea oil platforms; Iceland has soaring emissions thanks to its aluminium smelters. But all have promised to cut their emissions to zero by becoming founding members of the Climate Neutral Network, set up by the UN Environment Programme at a meeting in Monaco last week.
This is a big turnaround for Iceland, which negotiated a 10 per cent rise in its emissions under the Kyoto protocol, but now plans to become the world's first economy run on hydrogen manufactured using clean geothermal energy. Despite its rising emissions, Norway is promising to be carbon-neutral by 2030, partly by capturing emissions and burying them under the North Sea. New Zealand has big plans for renewable power generation and electric cars.
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:24284db1-3c1f-455b-867a-df3ada762ea3> | 3.21875 | 201 | Truncated | Science & Tech. | 41.881105 |
Chip Somodevilla/Getty Images
The Rotating Service Structure (L) swings back to reveal the space shuttle Atlantis at Kennedy Space Center, Cape Canaveral, Florida, on July 7, 2011. The U.S. space program has served as a source of inspiration to generations of Americans.
The Rotating Service Structure (L) swings back to reveal the space shuttle Atlantis at Kennedy Space Center, Cape Canaveral, Florida, on July 7, 2011. The U.S. space program has served as a source of inspiration to generations of Americans. Chip Somodevilla/Getty Images
Back in 1972 the library in my hometown wasn't very big. But its size didn't matter much to my 10-year-old sensibilities. That was the year I discovered their collection on the U.S. space program. Those few books where big enough to help change my life.
I spent the whole summer poring over images taken by NASA astronauts and space probes. I decided one day, no matter what, I was going to be a scientist too.
That experience turns out to be almost universal for the last three generations of U.S. scientists.
Recently, I've been asking astronomers what inspired them as kids. The answers they give me are all the same. From graduate students to full professors, their first scientific inspiration was the U.S. space program.
If the researchers are older, their eyes light up with memories of watching John Glenn stuffed into a tiny Mercury capsule getting blown into Earth-orbit or seeing the first grainy close up images of Mars beamed back from Mariner 4's 1965 flyby of the red planet. If they are younger, their voices quicken with memories of shuttle astronauts on heroically long spacewalks repairing the wounded Hubble Space Telescope. Always it was the U.S. space program that lit a fire in their kid imaginations and launched them onto scientific trajectories.
This effect isn't limited to astronomers. Dig below the surface of many scientifically trained American adults and you'll find a bunch of kids who caught the science bug from the U.S. Space Program.
So what happens now? Today is the last shuttle launch. We're facing a years-long gap before NASA can put its own astronauts into space. Without the roar of space shuttle launches, are we facing an "Inspiration Gap" too? What's going inspire the next generation of students to a life in science?
Reorienting a space program drifting from lack of clear direction and a lack of funds is the right thing to do. So is supporting the fledging private space industry. But with this gap we could easily forget our larger ambitions for the rest of the solar system. Real-world budget pressures might defer the truly thrilling goals — like seeing human beings clamor over the red hills of Mars — forever.
The loss of that dream would feel terrible for the 10-year-old I was all those years ago. More importantly, it would be a terrible loss for all the 10-year-olds dreaming now of exploration and science. And for a nation that needs science and scientists to survive, it would the most terrible loss of all.
Inspiration is difficult to measure and even more difficult to price. But, as I have seen, it's the root of our excellence in science.
Right now there is frozen moon called Europa orbiting Jupiter. It has a surface of ice that is miles thick. Below the ice is a liquid ocean that goes even deeper. Who knows what unimagined ecosystems might live in those oceans. Someday, somebody who was inspired now as kid is going to wander those frozen plains and drill down to explore those oceans. If we are smart in our choices then those kids could still be our own. | <urn:uuid:d15a824d-28ec-4928-a4a6-aa42e8577af2> | 3 | 766 | Nonfiction Writing | Science & Tech. | 61.196813 |
May 28, 2010
Science Scene - Jurassic Park Looms?
For now, the team plans to study Australian marsupials like the extinct thylacine, a small tiger, and endangered Tasmanian Devil.
The team's method for re-creating the blood was a breakthrough in itself. Researchers used DNA that had been extracted from Siberian mammoth specimens, between 25,000 and 43,000 years old. (Mammoth DNA has already been sequenced.)
They converted the blood DNA sequences into RNA, and inserted them into E. coli bacteria. The bacteria acted as RNA factories, manufacturing authentic mammoth protein.
The resulting hemoglobin molecules are no different than taking a blood sample from a real woolly mammoth, Cooper said.
The concept could conceivably be used for any extinct species, as long as scientists have DNA samples.
"(This) opens the way to being able to study all sorts of proteins from the past, and to study many physiological characteristics," Cooper said. "It's really paleobiology; you're studying how extinct species function, and how they adapted to climate change and other past environmental conditions that we can't get at in the fossil record." | <urn:uuid:2056a3c3-9ba4-441e-97ed-0ade420be9e5> | 3.890625 | 241 | Personal Blog | Science & Tech. | 51.25411 |
ANSI Common Lisp 3 Evaluation and Compilation 3.2 Compilation
3.2.1 Compiler TerminologyThe following terminology is used in this section.
The compiler is a utility that translates code into an implementation-dependent form that might be represented or executed efficiently. The term compiler refers to both of the functions compile and compile-file.
The term coalesce is defined as follows. Suppose A and B are two literal constants in the source code, and that A' and B' are the corresponding objects in the compiled code. If A' and B' are eql but A and B are not eql, then it is said that A and B have been coalesced by the compiler.
The term further compilation refers to implementation-dependent compilation beyond minimal compilation. That is, processing does not imply complete compilation. Block compilation and generation of machine-specific instructions are examples of further compilation. Further compilation is permitted to take place at run time.
The compilation environment is maintained by the compiler and is used to hold definitions and declarations to be used internally by the compiler. Only those parts of a definition needed for correct compilation are saved. The compilation environment is used as the environment argument to macro expanders called by the compiler. It is unspecified whether a definition available in the compilation environment can be used in an evaluation initiated in the startup environment or evaluation environment.
The evaluation environment is a run-time environment in which macro expanders and code specified by eval-when to be evaluated are evaluated. All evaluations initiated by the compiler take place in the evaluation environment.
The run-time environment is the environment in which the program being compiled will be executed.
The compilation environment inherits from the evaluation environment, and the compilation environment and evaluation environment might be identical. The evaluation environment inherits from the startup environment, and the startup environment and evaluation environment might be identical.
The term compile-time definition refers to a definition in the compilation environment. For example, when compiling a file, the definition of a function might be retained in the compilation environment if it is declared inline. This definition might not be available in the evaluation environment.
The term run time refers to the duration of time that the loader is loading compiled code or compiled code is being executed. At run time, only the run-time environment is available.
The term run-time definition refers to a definition in the run-time environment.
The term run-time compiler refers to the function compile or implicit compilation, for which the compilation and run-time environments are maintained in the same Lisp image. Note that when the run-time compiler is used, the run-time environment and startup environment are the same. | <urn:uuid:10e26b50-fbb8-4363-a647-bd3ade90591d> | 3.203125 | 545 | Documentation | Software Dev. | 23.910797 |
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Sub Resize ( Width As Float, Height As Float )
Changes the size of a PDF surface for the current (and subsequent) pages.
- Width : the width of the page in millimeters.
- Height : the height of the page in millimeters.
This function should only be called before any drawing operations have been performed on the current page. The simplest way to do this is to call this function immediately after creating the surface or immediately after completing a page with either Cairo.ShowPage | <urn:uuid:020b976c-5d1a-4b21-ba18-dc2f713cff04> | 2.796875 | 144 | Tutorial | Software Dev. | 58.870552 |
Java Assertion or assert keyword in java is little unknown and not many programmer is familiar with this and it's been rarely used specially if you have not writing unit test using JUnit which extensively uses Java assertion to compare test result. Junit itself is the biggest manifestation of what assertion in Java can do and believe me by using assertion along with Exception you can write robust code. Assertion not only improve stability of code but also help you to become better programmer by forcing you to think about different scenario while writing production quality code and improving your think through ability.
Java Assertion tutorial - How Assertion works in Java
What is assert keyword in Java
assert keyword is used to implement assertion in java. we can use assert keyword in two format
assert booleanExpression : errorMessage;
(here errorMessage can not be an invocation to a method with return type void)
How Assertion works in Java
As shown above assert keyword in java has two form first form "assert booleanExpression " is used to test the boolean expression and if boolean expression is false then java throws AssertionError and your program terminates. you can use assert here to validate input or assumption for example for a method which calculates stock price for trading , name of stock should not be null or empty, but as java recommends we should not use assertion to check arguments of public method instead public method should always check its argument and throw appropriate exception e.g. IllegalArgumentException.
Second form of assert keyword "assert booleanExpression : errorMessage" is more useful and provides a mechanism to pass additional data when Java assertion fails and java throws AssertionError.
Benefit of using Assertion in Java
Assertion in Java offers several benefits to programmer if it used properly. even many of seasoned programmer has recommended using assertion in Java as good programming practice and good to add this point on your code review checklist ? let's figure out why using assert keyword is desired and what benefit assertion offers :
1) assertion is simply great for data validation. In my opinion there is no better way then using java assert keyword to validate data passed to method, classic example is a method which calculates interest rates here we know that amount, time can not be less than zero by using assert keyword in java we can validate this data at run-time and if by any chance your function is getting incorrect data your program will fail with AssertionError.
2) Assertion in Java guarantees that at a certain point on function your assumption or certain condition is true otherwise it would not have come to that point and would have been terminated with AssertionError, this makes debugging in Java lot easier.
3) Using Java assert keyword helps to detect bug early in development cycle which is very cost effective. Assertion in Java also makes debugging easier to me AssertionError is a best kind of error while debugging because its clearly tell source and reason of error. Also code written using assert keyword fails close to source of error and require less time to find out the cause as compared to code without assert keyword.
4) assert statement in java is similar to unit test directly integrated into your code and have more chances to test your code with real word data than Junit test case, so it always complement your Junit tests or integration test suite.
5) writing code with assert statement will help you to be better programmer and improve quality of code, yes this is true based on my experience when we write code using assert statement we think through hard, we think about possible input to a function, we think about boundary condition which eventually result in better discipline and quality code.
6) assertion in java gives you lot of confident while maintaining or refactoring code, you can create new code and use assertion to compare output with old method if your program works well then you can simply comment out your old method.
1) Assertion is introduced in JDK 1.4 and implemented using assert keyword in java.
2) assertion can be enable and disable at run time by using switch -da or -disableassertion
3) Always remember Assertion does not replace Exception but compliments it.
4) Another important point is Assertion also doesn't replace need of unit testing instead if you see JUnit it shows how assertion can be useful to validate conditions.
5) do not use assertion to validate arguments or parameters of public method.
6) you can compile java code where assert is a legal identifier instead of keyword because by passing -source 1.3 during compilation. if you are working in java version 1.2 you can compile your code with assertion as below "
javac -source 1.4 OnlineStockTradingDemo.java
That’s all on Java Assertion, benefits of assertion in Java and where to use assertion in Java. Key point is Assertion should be thought as replacement of unit testing or Exception rather it compliments both of them , with Java assertion you can have more real world data for testing than unit testing. | <urn:uuid:59126911-d3cd-49d4-8cad-d27b9ad1a4f8> | 3.921875 | 1,032 | Personal Blog | Software Dev. | 31.070782 |
The concept of dark matter arose as a solution to a problem that has been puzzling astronomers for decades. Galaxies, when observed, rotate at a much faster rate than is expected for the estimated mass they contain. Astronomers and physicists have suggested that the extra mass may be accounted for by dim objects that our instruments cannot detect, or that the laws of gravitation are different over large distances. The most convincing argument, however, is that a previously unknown type of matter—dark matter—is clumped throughout the universe. We did not know about dark matter before now because it rarely interacts with regular (what physicists call baryonic) matter or with light other than through gravitation. | <urn:uuid:0cadb9b9-209c-47bd-a3c1-168469283640> | 3.921875 | 137 | Knowledge Article | Science & Tech. | 32.319759 |
The sum of the internal angles of a triangle on a sphere is greater than 180°, and related to the area of the triangle
The area of a spherical triangle with interior angles α, β, γ is S = r2 (α + β + γ - π), a remarkable formula because it does not contain the lengths of the sides. This formula is most easily found by using diangles (translation of the German Zweieck). It is axiomatic in the plane that two straight lines cannot contain an area. On the sphere, however, two straight lines -- that is, great circles -- define an area, which we shall call a diangle. The two sides of a diangle are half-circumferences of the sphere, and its two angles are also equal. The area of a diangle is the area of the sphere times the ratio of the angle of the diangle to 2π radians, or S = 2r2θ, where θ is the angle of the diangle. A diangle is the figure enclosed by two equal straight lines, which is what great circles are, on the sphere.
Now sketch a sphere and a spherical triangle upon it. Extend each side of the triangle completely around the sphere, noting that an equal triangle is formed on the diametrically opposite side of the sphere from the original triangle. What one really needs to draw diagrams for spherical geometry is a sphere one can draw upon, and a hemispherical base to make the drawing and measuring of great circles easy. If we had one of these, what is about to be described would be very easy to picture. The sketch will just do, with an effort to understand what is going on in three dimensions.
Consider any pair of sides. The extended sides form two diangles, covering part of the sphere. Now take another pair of sides. When extended, these form two more diangles that do not overlap the first two, except within the triangle and its doppelganger on the other side of the sphere. The final pair of sides make two diangles that complete the covering of the sphere, and again overlap the two triangles. Therefore, the sum of the areas of the six diangles is equal to the area of the sphere, plus the four triangle areas extra: 4r2 (α + β + γ) = 4πr2 + 4S. Hence, S = r2(α + β + γ - π), which was to be proved.
Imagine walking around the triangle on its sides. When you come to the corner with internal angle α, you must turn through an angle of π - α. By the time you return to your starting place, you have had to turn through a total angle of Δ = 3π - α - β - γ. The area of the triangle can easily be expressed in terms of this angle: S = r2(2π - Δ). The area of the triangle can, therefore, be expressed solely in terms of how far you turn in circumambulating it. For a triangle in a plane, Δ is always 2π radians, as you may find obvious, giving S = 0 in the limit, which is perfectly appropriate when you think about it, since we have 0·∞.
On the sphere, you do not have to turn through 2π radians in following a path that leads back to where you started. As Magellan proved, you only have to go far enough in a straight line to return to your starting point. In this case, Δ = 0, and S = 2πr2, the area of a hemisphere, which is indeed the area enclosed by your path. If you proceed a distance s along a path of curvature k (the reciprocal of the radius of curvature), you turn through an angle ks. Using integral calculus, this means that Δ = ∫ kds, or S = r2(2π - ∫ kds), which is the celebrated formula of Gauss and Bonnet. k is the geodesic curvature of the path, which is zero for a great circle, since a great circle is a straight line on a sphere. The case of abrupt corners can be handled by including an explicit term for them, or by adding (π - α)δ(sα - s), where δ(x) is the Dirac delta function, for a corner of internal angle α at position sα.
Composed by J. B. Calvert
Put into HTML 19 November 2000 | <urn:uuid:92c786a7-77c4-492b-a7b8-8585097c79cb> | 4.25 | 934 | Academic Writing | Science & Tech. | 67.77815 |
A relatively large turtle with a brown carapace with yellow or orange streaks or highlights, and a yellow plastron with black markings on each scute. The skin of the neck and limbs is orange, brighter in spring and autumn. Adults measure 5.5 to 7.5 inches (14 to 19 cm) in total length. An older common name for this turtle was “red legs.”
Mating occurs before and after hibernation. Nesting in late May to early June. Clutches of 4 to 12 eggs are laid in shallow nests. The eggs hatch in 60 to 70 days. Adults do not reproduce until the age of at least 11 or 12.
Woodland or open field habitats in flood plains. Hibernates in streams, either wedged in root tangles, under overhanging banks, or sitting on the bottom in low flow areas.
Feeds on a wide variety of foods, including algae, moss, leaves, berries, insects, slugs and other mollusks, earthworms, tadpoles, crayfish and carrion. Young in captivity have been observed eating terrestrial isopods.
Found in eastern North America from Nova Scotia south to northern Virginia; westward to northern Michigan (appears to be absent from Ohio). Its range includes all New England states. Within Connecticut it is known from several sites, mostly in the eastern portions of the state.
Not federally protected, but protected from international trade by the Convention on International Trade in Endangered Species (CITES). A species of special concern in Connecticut. Possession is prohibited without permits. Protected in most northeastern states. In decline from habitat loss, nest predation, collection and road mortality.
Conant, R. and J.T. Collins. 1991. A Field Guide to Reptiles and Amphibians: Eastern/Central North America. Boston: Houghton Mifflin. 450 pp.
Klemens, M.W. 1993a. Amphibians and Reptiles of Connecticut and Adjacent Regions. Hartford, CT: State Geological and Natural History Survey of Connecticut Bulletin 112. 318 pp.
——1993b. Amphibians and Reptiles in Connecticut. Hartford, CT: State Geological and Natural History Survey of Connecticut Bulletin 32. 96 pp.
Tyning, Thomas F., editor, 1997. Status and Conservation of Turtles of the Northeastern United States. Lanesboro, MN: Serpent’s Tale Publishers. 53 pp.
Text by Richard Haley and Gregory J. Watkins-Colwell.
Photographs © Twan Leenders. All rights reserved. Used by permission. Animal featured in photographs on this page is from Connecticut. | <urn:uuid:23d75416-eac0-4f32-907e-10cd56a9f58d> | 2.75 | 555 | Knowledge Article | Science & Tech. | 58.809243 |
condition. The condition system was influenced by the Common Lisp error system [? ] and the Standard ML exception mechanism. It is a simplification of the former and an extension of the latter. Following standard practice, this text defines the actions of functions in terms of their normal behaviour. Where an exceptional behaviour might arise, this has been defined in terms of a condition. However, not all exceptional situations are errors. Following Pitman, we use condition to be a kind of occasion in a program when an exceptional situation has been signalled. An error is a kind of condition|error and condition are also used as terms for the objects that represent exceptional situations. A condition can be signalled continuably by passing a continuation for the resumption to signal. If a continuation is not supplied then the condition cannot be continued. These two categories are characterized as follows:
defcondition(see Section ). The definition of a condition causes the creation of a new class of condition. A condition is signalled using the function
signal, which has two required arguments and one optional argument: an instance of a condition, a resume continuation or the empty list, the latter signifying a non-continuable signal, and a thread. A condition can be handled using the special form
with-handler, which takes a function, the handler function, and a sequence of forms to be protected. The initial condition class hierarchy is as follows:
(), the superclass is taken to be
<condition>. Otherwise superclass-name must be
<condition>or the name of one of its subclasses.
call-next-methodto carry out initialization specified by superclasses then does the condition specific initialization.
signalif the given condition is not an instance of the condition class
signal, otherwise, thread indicates the thread on which condition is to be signalled.
signalcalls the nearest enclosing handler with condition. If the second argument is supplied,
signalregisters the specified condition to be signalled on thread. The condition must be an instance of the condition class
<thread-condition>, otherwise an error is signalled (condition class:
<wrong-condition-class>) on the thread calling
signalon a determined thread has no effect on either the signalled or signalling thread except in the case of the above error.
call-next-handlerspecial form calls the next enclosing handler. It is an error to evaluate this form other than within an established handler function. The
call-next-handlerspecial form is normally used when a handler function does not know how to deal with the class of condition. However, it may also be used to combine handler function behaviour in a similar but orthogonal way to
call-next-method(assuming a generic handler function).
signalas its first argument. The resume continuation is the continuation (or
()) that was given to
signalas its second argument.
with-handlerform is evaluated in three steps:
with-handler. The exceptional behaviour of
with-handlerhappens when there is a call to
signalduring the evaluation of protected-form.
signalcalls the nearest enclosing handler-function passing on the first two arguments given to
signal. The handler-function is executed in the dynamic extent of the call to
signal. However, any calls to
signals occurring during the execution of handler-function are dealt with by the nearest enclosing handler outside the extent of the form which established handler-function. It is an error if there is no enclosing handler. In this circumstance the identified error is delivered to the configuration to be dealt with in an implementation-defined way. Errors arising in the dynamic extent of the handler function are signalled in the dynamic extent of the original
signalbut are handled in the enclosing dynamic extent of the handler.
signalreturns with the result passed back from the handler function. | <urn:uuid:a7070e4c-bf78-4a31-97b1-c42352079ac2> | 3.21875 | 808 | Documentation | Software Dev. | 36.721127 |
I was clearing out a bunch of pictures I took on my old cell phone, and I had forgotten that I snapped these photos last winter …
Now there are some people who believe that things such as crop-circles are the handy work of extra-terrestrials. They are likely to say: “Who or what else could create such perfect patterns?” Some of those severely confused people might look at these pictures and draw similar conclusions. But unless someone can offer up a better explanation, they appear to me to be four separate vapor trails (a.k.a. contrails) that have formed a close-to-geometrically-perfect double cross. Having never seen a convergence of vapor trails like this before, I started wondering what the odds might be of me witnessing such an occurrence. There are several factors to consider, and probably some factors that I’m not even aware of, but I’ll give it my best shot.
First, I have concluded that these are four distinct trails caused by four different airplanes. The space between each set of parallel trails is very wide, so that would rule out that a single craft caused either pair of trails. Were each set of parallel trails much closer to each other, we might be talking about as few as two planes, but this is definitely four separate aircraft at work.
Second, these four planes must have traveled close to the epicenter within a few hours of each other, for that is how long vapor trails can last according to the folks at contrailscience.com (your one-stop shop for all things contrail related). Yet they also say that some contrails can last just a few seconds, based on a variety of environmental factors. A few seconds to several hours is a pretty big range to time. The apparent “thickness” of each vapor trail is a fairly good indication of the order in which the planes left their marks. The oldest trail looks like it is about 33% as thick as the most recent trail. If I assume that each vapor trail lasted for a total of 120 minutes (and that’s probably being generous) from my vantage point, then the oldest trail should be no older that 80 minutes. Jumping ahead to the thickest contrail, that one appears to me as if it passed 20 minutes prior to my taking the photos. So that means that the four planes converged on the epicenter within 60 minutes of each other. Each of the four trails show various degrees of decay, so that means I snapped the photos somewhere in the near middle of those 60 minutes, so lets call it the 30 minute mark. To summarize, my best guess is that I caught this 60-minute long event within 30 minutes of the last plane leaving its trail.
Third, I’d like to try and determine the relative altitude of each trail to one another. These pictures make is appear as if these trails actually make contact at the crossings. That would be about as rare an occurrence as you could possibly get for four separate planes. So chances are much more likely that these contrails are occurring at different altitudes. How can that be calculated? Unfortunately, not very accurately with just one set of photos. The vapor trails in relation to my position on the ground are about a 30 degree angle above the horizon. But what if the relative position were 45 degrees? Or directly overhead at 90 degrees? Would they still appear to be crossed lines? I think it is impossible to say without any other photos taken from other vantage points.
Fourth, I need to try to determine just how close to “parallel” these pairs of vapor trails actually are. Most likely, these are only “apparently parallel” trails. If you look at the right side lower pair of trails, as they fade out of sight they appear to be closer to each other than at the epicenter of the rendezvous with the other pair of trails. Following the same trails beyond the point of exchanges, the pair continue to the upper left side of the photo and appear to be slightly wider still. However, this is what I would expect to occur if I were looking at a highway in the desert heading off to the horizon, and these lines do fall into that kind of pattern. Another point that argues in favor of parallel lines (and any pilots or air traffic controllers can correct me if I’m mistaken) is that that planes are likely to be instructed to fly on similar headings over any given part of the sky, kind of like traffic lanes for airplanes. Taking all this into consideration, I think the photos reveal actual near-parallel vapor trails.
And finally, a question: where are the most likely places to see uncommon patterns of vapor trails? The answer is wherever there are military activities occurring. Check out these photos. The photos I snapped were taken in North Haven, CT, and the closest military aircraft to there is stationed at Bradley Airport in Windsor, CT, about 45 miles to the north. So it is unlikely, though not impossible, that this was some sort of formation being flown by four military aircraft. It is much more plausible that these were commercial jetliners cruising at 30,000 feet or higher. Plus, Connecticut is fly-over territory for major airports in Boston, New York, and New Jersey, so Connecticut regularly has multiple vapor trails in the sky at any given moment.
(As a side note, one of the eeriest things for me about 9/11 was going outside that morning, looking at that perfect cloudless blue sky and seeing no vapor trails at all, anywhere. All flights in the country were grounded. It was so unusual for me to see a Connecticut sky without contrails that I was taken aback at the sight of that pure blue sky.)
Anyway, back to the calculations. At 39, this is the first time in my life I have ever seen this kind of vapor trail pattern. While my eyes are not glued to the sky at all times, I do look up at the daytime sky probably more often than the average person (hence my observation about 9/11). So I’ll say that on average, I’ve looked at a clear Connecticut sky for half of my days since I was 8 years old. 39 years, minus 8 years equals 31 years, divided by 2, equals 15.5 years, which equals about 5,660 days (counting for leap days and such.) On any given day of those 5,660 fair weather days, I would say that I’ve personally witnessed 4 vapor trails per day (which is probably a very modest estimate, I’ve spent time in the back yard with my daughter and we’ve counted a dozen trails over the course of 30 minutes). But sticking with 4 trails per day, that turns out to be no fewer than 22,640 contrails I have seen in my life over the Connecticut skies. Going back to my earlier calculations that this occurrence lasted for 60 minutes, that means that I only had one hour on any given clear day to have witnessed it. I’ll call that a 1-in-24 chance that I was at the right place at the right time. If I multiply 22,640 times 24, that equals 543,360. Factoring in the relative altitudes of the four trails, I have to assume that these are four different altitudes and not actual convergences of any of the lines, only apparent convergences, so there should be no need to invoke a “rarity” multiplier based on relative altitudes. However, to the best of my estimates, we are talking about 2 sets of near parallel trails, and the rarity of that occurring should be factored. But by how much? If we were talking about just one set of parallel lines, I don’t think we’d come up with a multiplier much more than 1, but since it is a pair of parallel lines that forming a double cross at my vantage point, I think I would need to, at a minimum, apply a multiplier of 3 (again, probably a low estimate). So 543,360 times 3 equals 1,630,080. And finally, the fact that rare vapor trail patterns are more likely to occur in the vicinity of military actions (such as a war or at least an armed forces base) probably account for a small multiplier to be figured in here, and I’ll call that 1.25.
So to the best of my calculations, the odds that I would witness a double crossing of parallel vapor trails once in my life (to date) are 2,037,600-to-1. I could have applied more data to the calculation (such as, what were the chances that I had a cell phone with a camera handy in time to take the shots?) and I am sure that my rough calculations are less-than-ideal in the world of statistics, but it’s about as good a guess as I can muster. This is not to say that there is a millions-to-one chance that this could have occurred. Quite the contrary, given the amount of planes in the skies at any moment, these kinds of patters must occur more frequently than can ever be witnessed. I am only trying to figure out the odds in relation to one specific person, namely me.
Any way you look at it, you have to admit, these are some pretty cool and rare photos, unless I’ve somehow been double-crossed, and alien spaceships are actually responsible. | <urn:uuid:5056a56c-a258-4a38-9093-65ac0432c486> | 2.765625 | 1,958 | Personal Blog | Science & Tech. | 57.568675 |
This is a post by Sarah Opfer, NOAA Marine Debris Program Great Lakes Regional Coordinator.
The “Great Pacific Garbage Patch“—a purported island of trash twice the size of Texas floating in the Pacific Ocean—receives a lot of media attention. Recent reports suggest that a similar garbage patch may be developing in the Great Lakes as well.
However, based on research we know that the name “garbage patch” is misleading and that there is no island of trash forming in the middle of the ocean. We also know that there is no blanket of marine trash that is visible using current satellite or aerial photography.
Yet, there are places in the ocean where currents bring together lots and lots of floatable materials, such as plastics and other trash. While the types of litter gathering in these areas can vary greatly, from derelict fishing nets to balloons, the kind that is capturing the most attention right now are microplastics. These are small bits of plastic often not immediately evident to the naked eye.
While we know about the so-called “garbage patches” in the Pacific Ocean, could there be a similar phenomenon in other parts of the world, including the Great Lakes? Recent research on the distribution of plastics in the Great Lakes has people now asking that very question.
The Great Lakes are no mere group of puddles. They contain nearly 20% of the world’s surface freshwater and have a coastline longer than the East Coast of the United States. Within the Great Lakes system, water flows from Lake Superior and Lake Michigan, the lakes furthest west and highest in elevation, east into Lake Huron. From there, it travels through Lake St. Clair and the Detroit River into Lake Erie. Then, some 6 million cubic feet of water pass over Niagara Falls each minute and into Lake Ontario before flowing through the St. Lawrence River and into the Atlantic Ocean.
This water flow influences circulation patterns within and between each of the lakes. Currents within the Great Lakes also are powered by wind, waves, energy from the sun, water density differences, the shape of the lakebed, and the shoreline. These circulation currents have the tendency to create aggregations of garbage and debris in certain areas, just like in the oceans. But, just as in the Pacific Ocean, this doesn’t mean the Great Lakes have floating trash islands either.
In an effort to better identify and understand how plastic debris is spread throughout the Great Lakes, researchers at the University of Waterloo in Canada have partnered with COM DEV on an exploratory research project. COM DEV is a designer and manufacturer of space and remote sensing technology. Researchers are working with this industry partner to develop and test the ability of different remote sensors to detect plastics in the Great Lakes.
If they find the task is feasible and the trial runs prove to be effective, this work could be applied beyond the Great Lakes and across the United States. The NOAA Marine Debris Program, part of the Office of Response and Restoration, is engaged with and following the project. We plan to participate in the next steps of this promising effort. You can learn more about the project and a related workshop on plastic pollution in the Great Lakes.
Sarah Opfer received her bachelor’s and master’s degrees in biology from Bowling Green State University and was a Knauss Sea Grant fellow with NOAA in 2009. She is based in Ohio and enjoys having Lake Erie in her back yard! While away from work she enjoys cooking, reading, kayaking, dreaming of places she wants to travel to, and spending time with her family. | <urn:uuid:b48487f2-56ac-4d6c-b992-7f4ed891f938> | 3.765625 | 737 | Personal Blog | Science & Tech. | 45.953161 |
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...for more than 300 years, until the perfection of mechanical calculating machines in the late 19th century and computers in the 20th century rendered them obsolete for large-scale computations. The natural, or Napierian, logarithm (with base e ≅ 2.71828 and written ln n), however, continues to be one of the most useful functions in mathematics, with...
Scottish mathematician and theological writer who originated the concept of logarithms as a mathematical device to aid in calculations.
What made you want to look up "natural logarithm"? Please share what surprised you most... | <urn:uuid:d36f028b-ad0b-4d03-a470-06e0ba687509> | 3.09375 | 164 | Knowledge Article | Science & Tech. | 46.715732 |
Distributed programming has several basic common architectures: client-server, peer-to-peer, distributed objects, clustering, and grid computing. These architectures are not all mutually exclusive, and particular implementations may be combinations of these architectures.
- In the client-server scheme, client code requests data from the server, and input to the client is sent back to the server when the client makes any changes. This is the most common architecture.
- In the peer-to-peer scheme, there is no particular machine providing a service or managing the network resources. All responsibilities are uniformly distributed among the machines on the network.
- Distributed objects are software modules that exist on multiple computers throughout the network but are designed to work together. A program running on one machine sends a message to an object on a remote machine to perform some processing. The results are sent back to the calling machine. There are no distinctions between clients and servers with distributed objects, although logically it is still a client-server system and any machine may be both a client and a server at the same time.
- Clustering refers to a set of tightly integrated computers that run the same processes in parallel. Tasks are subdivided and the subdivisions are run on individual machines. The individual results are then assembled to produce the final result. Clustering differs from other kinds of distributed computing in that clustered computers are usually much more tightly coupled. Clustering is a way to construct a kind of "supercomputer" from a group of similar machines over a LAN. Clusters are centrally controlled and often the node machines don't even have keyboards or monitors. These nodes exist strictly to share their resources for the processes allocated by the server.
- A computer grid utilizes the resources of many separate machines connected by a large network to solve process-intensive problems. Where a cluster is a logical client-server model, a grid is more like a peer-to-peer model that shares resources as well as files. This scheme often uses the Internet to access many widely dispersed computers to solve problems that would normally require the use of a supercomputer. An example of this is the SETI@home project (setiathome.berkeley.edu) that uses idle time on thousands of computers throughout the world to help analyze data from radio telescopes as part of an effort to search for extraterrestrial life.
There are three common strategies for implementing a communications scheme in client-server architectures (Table 2). These are presented in the order of oldest and most standard to newest and most modular. Berkeley sockets (or just "sockets") are the earliest version we discuss, followed by RPC, and then RMI. The latter two strategies are both based upon sockets yet remove some of the management overhead normally required by sockets.
|Brief Comparison of Communication Strategies|
|Sockets||The "Standard" for network application communication.||Data is sent as bytes and must be reconstructed into something useful at the receiving end of the connection.|
|Remote Procedure Calls (RPC)||Sends complete data structures instead of just bytes. Offers reliability in the form of an acknowledgment message that the data has been successfully transferred. Eliminates socket management overhead.||Complex Interface Description Language needed to allow various platforms to call the RPC.|
|Remote Method Invocation (RMI)||Passes objects instead of straight bytes or data structures. Eliminates socket management overhead. Access to rich Java library tools.||Java only (unless JNI is used). Need JVM 1.5 or newer to use latest features.|
Sockets are defined as endpoints for communication, with one socket at each endpoint of the communications channel. A socket works with Internet Protocol (IP) and either Transmission Control Protocol (TCP) or UDP (User Datagram Protocol). The difference between TCP and UDP is that TCP provides error checking and is bidirectional. UDP is unidirectional and provides no error checking. In this project, we needed TCP because it provides feedback that a connection has actually been established. With sockets the client has to manage the socket connection by opening it, closing it, and establishing an input stream to read from the socket. The server employs a "listener" to monitor a specific port. When a client sends a request for a connection, the server will accept the request and the connection will be established. With sockets each connection is unique. The client needs to know the address of the server, but the server does not need to know the address of the client prior to the connection being established. Once a connection is established, both sides can send and receive information.
The main disadvantage of plain sockets is the overhead of creating and managing the connections. There are newer communications strategies such as RPC and RMI that simplify these connection maintenance details.
When a process calls a procedure on a remote application in a distributed system, it is known as an RPC. With RPCs, an ordinary data structure is used in passing data to a remote procedure. The essential concept of RPC is hiding all the network code within "stub" procedures. The goal of RPC is to simplify writing distributed applications by making the networking code transparent. With RPC, a daemon or "stub" runs on a port of a remote system and listens for messages addressed to it. These stubs locate the appropriate port on the client or server and package the parameters into a form that can be transmitted over the network. This is known as "marshaling." The main drawbacks of RPC are that in passing parameters, true pass-by-reference is not permitted, it is difficult to send and make sense of complex data types such as user-defined types, exception handling is more difficult, and there can be issues with data representation (www.wikipedia.org/wiki/Remote_procedure_call). There is a selection of standardized RPC systems available such as Microsoft's .NET Remoting and Java's Remote Method Invocation.
For reasons of portability and tool availability, we decided to use RMI. With RMI, objects are passed using remote method calls known as "callbacks" instead of data structures. RMI simplifies the design of the client because all it does is get a proxy for the remote object from entries in the RMI registry. It then simply calls the method in the same way it would call a local method. Since RMI is Java specific, it doesn't provide a direct connection between objects implemented in different languages. Using Java's Native Interface (JNI) API, however, it is possible to wrap existing C or C++ code such as the CodeMatch DLL with a Java interface, then export this interface remotely through RMI (see Figure 1). The JNI lets Java code that runs inside a Java Virtual Machine (JVM) interoperate with applications and libraries written in other programming languages. | <urn:uuid:3f7b6a64-3649-43e7-8f52-40253108ae97> | 3.8125 | 1,394 | Documentation | Software Dev. | 37.43777 |
Schematic three dimensional cross section of a cell membrane. There are two major components of this dynamic, fluid, structure: lipids and proteins. A lipid bilayer provides the basic structure within which proteins are free to diffuse. Sugar moieties can be present as part of either proteins (glycoproteins) or lipids (glycolipids). A further important component shown is cholesterol; which intercalates between lipid molecules and affects membrane fluidity/stability.
Essential Biological Functions:
Cell growth and differentiation
Potential Commercial Applications
Drug response monitoring
Source: NIST: These World Wide Web pages are provided as a public service by the National Institute of Standards and Technology (NIST). With the exception of material marked as copyrighted, information presented on these pages is considered public information and may be distributed or copied. Use of appropriate byline/photo/image credits is requested.
The drawing was made by Dana Burns, and can also be found in Scientific American, 1985, 253(4), pages 86-90, in the article The molecules of the cell membrane by M.S. Bretscher.
· Date: Sun October 22, 2006 · Views: 117730 · Filesize:41.0kb, 60.3kb · Dimensions: 702 x 371 · | <urn:uuid:4ec8dc9d-d733-4e80-b01f-48ff36004d12> | 2.953125 | 264 | Truncated | Science & Tech. | 36.142759 |
Robert Andrews Millikan
The American physicist Robert Andrews Millikan, b. Morrison,
Ill., Mar. 22, 1868, d. Dec. 19, 1953, determined through an
oil-drop experiment the value of the charge on an electron and
demonstrated that the charge was a discrete constant rather than
a statistical average. For this work, as well as for his work on
the photoelectric effect, he received the Nobel Prize for physics
in 1923. Millikan was affiliated with the University of Chicago
(1896-1921) and the California Institute of Technology (1921-53).
His First Course in Physics (1906), written with Henry Gale, was
a standard textbook for many years. | <urn:uuid:a494b508-265e-411d-b05c-9e4441642251> | 3.3125 | 151 | Knowledge Article | Science & Tech. | 58.444573 |
Microscopy is the science of producing and observing images of objects that cannot be seen by the unaided eye. A microscope is an instrument which produces the image. The primary function of a microscope is to resolve, that is distinguish, two closely spaced objects as separate. The secondary function of a microscope is to magnify. Microscopy has developed into an exciting field with numerous applications in biology, geology, chemistry, physics, and technology.
The light microscope
The most common, inexpensive, and easy to use microscope is the light microscope, which produces a magnified image of the object by bending and focusing light rays. The light microscope uses a variety of glass lenses to produce a magnified image that is focused before the eye. The magnifying properties of a converging lens, like
that which is used in a typical magnifying glass or camera. Light from the object is bent, or refracted, as it passes through the lens producing an image which is inverted and magnified. In the simplest compound microscope, two converging lenses are used. The image from the first lens (objective) becomes the object for the second lens (eyepiece). The final image is much larger than either lens could produce independently. With a little effort, you can reproduce this effect yourself by using two magnifying glasses.
The wavelength of visible light ultimately limits the resolving power of the light microscope. Therefore, two objects separated by distances significantly less than about 0.4 micrometers (the smallest wavelength of visible light) cannot be distinguished as separate. This is because the light microscope produces its images by reflecting from or transmitting visible light through a specimen. An analogy can be made to ocean waves at the beach, with wavelengths of a few meters. If two people were wading into the surf only a few inches apart (a separation much less than the wavelength of the ocean waves), it would be impossible to distinguish them as separate by analyzing the ocean waves that reflected from them. Despite these limitations, the resolution of the light microscope is sufficient to produce excellent images of many of the important cell structures and organelles, and consequently still has many applications, chiefly in biology.
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The just Chemical. Electron microscopes get better magnification and also resolving power compared to light microscopes however the sample needs to be murdered and put into vacuum pressure ch
Appears like the actual DAPI and also GFP emissions overpower to some degree.
Wish this can help.
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This podcast is part of the series: forces
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This podcast was designed to cover the force of gravity. The purpose of this particular podcast is to compare weight on the various planets as a result of the force of gravity on a mass.
Content Areas: Science
Alabama Course of Study Alignments and/or Professional Development Standard Alignments:
[S1] PHS (9-12) 6: Identify characteristics of gravitational, electromagnetic, and nuclear forces.
[S1] PHS (9-12) 7: Relate velocity, acceleration, and kinetic energy to mass, distance, force, and time.
[S1] PHS (9-12) 12: Identify metric units for mass, distance, time, temperature, velocity, acceleration, density, force, energy, and power.
[S1] E&S (9-12) 1: Describe sources of energy, including solar, gravitational, geothermal, and nuclear. | <urn:uuid:92aa931b-3085-4f98-9dd8-dde71b5d7c52> | 3.40625 | 213 | Truncated | Science & Tech. | 41.195427 |
A chemical element, often called simply an element, is a substance that cannot be decomposed or transformed into other chemical substances by ordinary chemical processes. All matter consists of these elements and as of 2006, 117 unique elements have been discovered or artificially created. The smallest particle of such an element is an atom, which consists of electrons centered about a nucleus of protons and neutrons.
Chemistry terminology Edit
Earlier an element or pure element was defined as a substance which "can't be further broken down into another compound with different chemical properties"—which should be taken to mean it consists of atoms of one element. However, because of allotropy, the isotope effect, and the confusion with the more useful term referring to the general class of atoms (irrespective of what compound it may be in), this usage is in disfavor amongst contemporary chemists, and sees restricted, mostly historical, use. This definition was motivated by the observation that these elements could not be dissociated by chemical means into other compounds. For example, water could be converted into hydrogen and oxygen, but hydrogen and oxygen could not be further decomposed, thus "elemental". There are also many counterexamples (for example "elemental oxygen" (O2) can be decomposed by solely chemical means into oxygen ions and atoms which have drastically different chemical properties). This article will concern itself with the latter definition.
The lightest elements are hydrogen and helium. All the heavier elements are made, both naturally and artificially, through various methods of nucleosynthesis. As of 2006, there are 117 known elements: 94 occur naturally on Earth (six in trace quantities: technetium, atomic number 43; promethium, atomic number 61; astatine, atomic number 85; francium, atomic number 87; neptunium, atomic number 93; and plutonium, atomic number 94) and 95 (including californium) have been detected in the universe at large. The 23 elements not found on earth are derived artificially; technetium was the first purportedly non-naturally occurring element to be synthesized, in 1937, although trace amounts of technetium have since been found in nature, and the element may have been discovered naturally in 1925. All artificially derived elements are radioactive with short half-lives, so if any atoms of these elements were present at the formation of Earth they are extremely likely to have already decayed.
Lists of the elements by name, by symbol, by atomic number, by density, by melting point, and by boiling point as well as Ionization energies of the elements are available. The most convenient presentation of the elements is in the periodic table, which groups elements with similar chemical properties together.
Atomic number Edit
The atomic number of an element, Z, is equal to the number of protons which defines the element. For example, all carbon atoms contain 6 protons in their nucleus, so for carbon Z=6. These atoms may have different numbers of neutrons, which are known as isotopes of the element.
Atomic mass Edit
The atomic mass of an element, A, as measured in unified atomic mass units (u) is the average mass of all the atoms of the element in an environment of interest (usually the earth's crust and atmosphere). Since electrons are of negligible mass, and neutrons are barely more than the mass of the proton, for lighter elements this often corresponds to the sum of the protons and neutrons in the nucleus of the most abundant isotope. However, particularly with heavier elements, more than one stable isotopes contributes significantly to the average atomic mass. An example is chlorine, which is about three-quarters 35Cl and a quarter 37Cl.
The atomic masses that are given on the periodic table are actually the mean abundance-corrected atomic masses for natural samples of the element, which are calculated by the following method. As an example, assume there naturally exist two isotopes of chlorine with respective atomic masses 35 and 37 AMU. Assume that 75% of the atoms in natural chlorine happen to be the 35 AMU version and 25% of the total number of atoms (particles) happen to be about 37 AMU in mass. Multiplying these gives 35 * 0.75 = 26.25 AMU and 37 * 0.25= 9.25 AMU, and the fraction-weighted atomic mass that results is the sum of these numbers, which is 35.5 AMU. For an element with three naturally occurring isotopes the method is the same: sum the masses of the isotopes weighted by atom-fraction. This method of calculating the average mass takes into account the relative abundance of all of the isotopes of an element, so that this mass number always gives the same total number of atoms, for a natural sample of any element. This allows for approximate counting of atoms in a natural element sample, by simply weighing the sample. There are many instances in nature (particularly with light and volitile elements) where isotope ratios are slightly affected by natural sorting processes, but in most cases the atomic masses given may be used to estimate number of atoms in a natural sample to four or more significant figures.
Some isotopes are radioactive and decay into other elements upon radiating an alpha or beta particle. Certain elements have no nonradioactive isotopes: specifically the elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), and all observed elements with atomic numbers greater than 82.
The naming of elements precedes the atomic theory of matter, although at the time it was not known which chemicals were elements and which compounds. When it was learned, existing names (e.g., gold, mercury, iron) were kept in most countries, and national differences emerged over the names of elements either for convenience, linguistic niceties, or nationalism. For example, the Germans use "Wasserstoff" for "hydrogen" and "Sauerstoff" for "oxygen," while English and some romance languages use "sodium" for "natrium" and "potassium" for "kalium," and the French, Greeks and Poles prefer "azote/azot" for "nitrogen."
But for international trade, the official names of the chemical elements both ancient and recent are decided by the International Union of Pure and Applied Chemistry, which has decided on a sort of international English language. That organization has recently prescribed that "aluminium" and "caesium" take the place of the US spellings "aluminum" and "cesium," while the US "sulfur" takes the place of the British "sulphur." But chemicals which are practicable to be sold in bulk within many countries, however, still have national names, and those which do not use the Latin alphabet cannot be expected to use the IUPAC name. According to IUPAC, the full name of an element is not capitalized, even if it is derived from a proper noun such as the elements californium or einsteinium (unless it would be capitalized by some other rule, for instance if it begins a sentence, or an article or subsection title in a Wikipedia article). Isotopes of chemical elements are also uncapitalized if written out: carbon-12 or uranium-235.
In the second half of the twentieth century physics laboratories became able to produce nuclei of chemical elements that have a half life too short for them to remain in any appreciable amounts. These are also named by IUPAC, which generally adopts the name chosen by the discoverer. This can lead to the controversial question of which research group actually discovered an element, a question which delayed the naming of elements with atomic number of 104 and higher for a considerable time. (See element naming controversy).
Precursors of such controversies involved the nationalistic namings of elements in the late nineteenth century. For example, lutetium was named in reference to Paris, France. The Germans were reluctant to relinquish naming rights to the French, often calling it cassiopeium. The British discoverer of niobium originally named it columbium, in reference to the New World. It was used extensively as such by American publications prior to international standardization.
- For the listing of current and not used Chemical symbols, and other symbols that look like chemical symbols, please see List of elements by symbol.
Specific chemical elementsEdit
Before chemistry became a science, alchemists had designed arcane symbols for both metals and common compounds. These were however used as abbreviations in diagrams or procedures; there was no concept of atoms combining to form molecules. With his advances in the atomic theory of matter, John Dalton devised his own simpler symbols, based on circles, which were to be used to depict molecules.
The current system of chemical notation was invented by Berzelius. In this typographical system chemical symbols are not used as mere abbreviations - though each consists of letters of the Latin alphabet - they are symbols intended to be used by peoples of all languages and alphabets. The first of these symbols were intended to be fully universal; since Latin was the common language of science at that time, they were abbreviations based on the Latin names of metals - Fe comes from Ferrum, Ag from Argentum. The symbols were not followed by a period (full stop) as abbreviations were. Later chemical elements were also assigned unique chemical symbols, based on the name of the element, but not necessarily in English. For example, sodium has the chemical symbol 'Na' after the Latin natrium. The same applies to "W" (wolfram) for tungsten, "Hg" (hydrargyrum) for mercury, "K" (kalium) for potassium, "Au" (aurum) for gold, and "Sb" (stibium) for antimony.
Chemical symbols are understood internationally when element names might need to be translated. There are sometimes differences; for example, the Germans have used "J" instead of "I" for iodine, so the character would not be confused with a roman numeral.
The first letter of a chemical symbol is always capitalized, as in the preceding examples, and the subsequent letters, if any, are always lower case (small letters).
General chemical symbolsEdit
There are also symbols for series of chemical elements, for comparative formulas. These are one capital letter in length, and the letters are reserved so they are not permitted to be given for the names of specific elements. For example, an "X" is used to indicate a variable group amongst a class of compounds (though usually a halogen), while "R" is used for a radical, meaning a compound structure such as a hydrocarbon chain. The letter "Q" is reserved for "heat" in a chemical reaction. "Y" is also often used as a general chemical symbol, although it is also the symbol of yttrium. "Z" is also frequently used as a general variable group. "L" is used to represent a general ligand in inorganic and organometallic chemistry. "M" is also often used in place of a general metal.
Although not officially used, in nuclear physics the three main isotopes of the element hydrogen are often written as H for protium, D for deuterium and T for tritium. This is in order to make it easier to use them in chemical equations, as it replaces the need to write out the AMU for each isotope. It is written like this:
D2O (heavy water)
Instead of writing it like this:
Most common elements in the UniverseEdit
These are the ten most common elements in the Universe as measured in parts per million, by mass:
|Element||Parts per million|
Recently discovered elementsEdit
The first transuranium element (element with atomic number greater than 92) discovered was Neptunium in 1940. The heaviest element that has been found to date is element 118, Ununoctium, which was successfully synthesized on October 9, 2006, by the Flerov Laboratory of Nuclear Reactions in Dubna, Russia
Element 117, Ununseptium, is yet to be created or discovered, although its place in the periodic table is preestablished, and likewise for possible elements beyond 118.
- Abundance of the chemical elements
- Chemical elements named after people
- Chemical elements named after places
- Chemical symbol
- Discovery of the chemical elements
- Elements song
- Fictional element
- Periodic table
- Systematic element name
- List of elements by atomic number
- Island of stability
Chemical information Edit
|This page received some of its content from Wikipedia. The source article was at Wikipedia:Chemical element. The list of authors can be seen in the page history. As with Chemistry, the text of Wikipedia is available under the GNU Free Documentation License.| | <urn:uuid:74fecbd0-4d10-430f-b850-24c02bf060d8> | 3.796875 | 2,676 | Knowledge Article | Science & Tech. | 26.053012 |
- This target means to open the URL in the current buffer.
- This target means to open the URL in a new buffer, and to switch to that buffer.
- This target means to open the URL in a new buffer, but not to switch to that buffer.
- This target means to open the URL in a new buffer, in a new window.
- This is like OPEN_CURRENT_BUFFER, except that for hyperlinks, the intent of the hyperlink itself will be obeyed.
- In an HTML Frameset document, this target represents the focused frame. When not in a Frameset, it behaves like OPEN_CURRENT_BUFFER.
When web content calls window.open to try to load an URL in a new window, the actual place that the URL will get loaded in is controlled by the variable browser_default_open_target.
From the Command Line
When Conkeror is called from the OS level, and one or more URLs or webjumps are given on the command line, this is called remoting. The target of URLs loaded by remoting is controlled by setting the value of url_remoting_fn to one of several pre-defined handler functions, or to a function of your own creation. | <urn:uuid:12fd49e7-c131-42ec-bf13-b7f3b515ce1e> | 3.015625 | 261 | Documentation | Software Dev. | 58.841077 |
|This article is a stub. You can help out by.|
Introduced as an ARB extension to the OpenGL Specification as of version OpenGL 1.4 and promoted to a 'Core' function in OpenGL 2.0, GLSL is a high level language used to define vertex, fragment, and with the new DX10 class of hardware geometry shaders.
GLSL (a.k.a. glslang) is the OpenGL Shading Language. It's a C-like high level language to create OpenGL fragment (pixel) and vertex shaders. A shader is a program that is loaded on the GPU and called for every vertex or pixel: this gives programmers the possibility to implement techniques and visual effects and execute them faster. In modern games lots of shaders are used: lights, water, skinning, reflections and much more.
To really understand shaders, you should have a knowledge about the rendering pipeline; this helps to understand where and when the shaders act in the rendering process. In general, you must know that vertex are collected, processed by vertex shaders, primitives are built, then are applied colors, textures and are also called fragment shaders; finally it comes to the rasterization and the frame is put on the buffer.
The GLSL has a C-Like syntax. It introduces several new data types, and has support for branching and looping constructs like if/else, for, do-while, etc. It has support for user defined functions, but comes with many built in functions that focus mostly on graphics programming.
Using a shader
A shader is a program, to be run it must be loaded, compiled and linked. Each vertex and fragment shader must have one entry point (the main function) each, but one can create and link more shader source files into a single shader program, much like the C compilation model. | <urn:uuid:e8bf96eb-6b83-4f72-b9ee-5911e8b29ba5> | 3.765625 | 387 | Knowledge Article | Software Dev. | 55.332339 |
Solar and Heliospheric Observatory
|Organization||ESA / NASA|
|Launch date||December 2, 1995|
|Launch vehicle||Atlas IIAS|
|Mission length||17 years, 5 months, and 20 days elapsed|
|Mass||1,850 kg (610 kg payload)|
|Orbit height||1.5×106 km (heliocentric)|
|Orbit period||1 Earth year|
|Wavelength||optical through UV, also magnetic information|
|GOLF||solar core oscillations
|MDI||oscillations and magnetic fields (Doppler imager)|
|EIT||low corona and photosphere
|UVCS||solar wind acceleration
|LASCO||low to outer corona
(two visible light cameras,
one imaging Fabry–Pérot interferometer)
|SWAN||solar wind density (UV camera)|
|solar wind ions (material samplers)|
The Solar and Heliospheric Observatory (SOHO) is a spacecraft built by a European industrial consortium led by Matra Marconi Space (now Astrium) that was launched on a Lockheed Martin Atlas IIAS launch vehicle on December 2, 1995 to study the Sun, and has discovered over 2400 comets. It began normal operations in May 1996. It is a joint project of international cooperation between the European Space Agency (ESA) and NASA. Originally planned as a two-year mission, SOHO currently continues to operate after over seventeen years in space. In November 2012, a mission extension lasting until December 2014 was approved.
In addition to its scientific mission, it is currently the main source of near-real-time solar data for space weather prediction. Along with the GGS Wind and Advanced Composition Explorer (ACE), SOHO is one of three spacecraft currently in the vicinity of the Earth–Sun L1 point, a point of gravitational balance located approximately 0.99 astronomical unit (AU)s from the Sun and 0.01 AU from the Earth. In addition to its scientific contributions, SOHO is distinguished by being the first three-axis-stabilized spacecraft to use its reaction wheels as a kind of virtual gyroscope; the technique was adopted after an on-board emergency in 1998 that nearly resulted in the loss of the spacecraft.
The SOHO spacecraft is in a halo orbit around the Sun–Earth L1 point, the point between the Earth and the Sun where the balance of the (larger) Sun's gravity and the (smaller) Earth's gravity is equal to the centripetal force needed for an object to have the same orbital period in its orbit around the Sun as the Earth, with the result that the object will stay in that relative position.
Although sometimes described as being at L1, the SOHO spacecraft is not exactly at L1 as this would make communication difficult due to radio interference generated by the Sun, and because this would not be a stable orbit. Rather it lies in the (constantly moving) plane which passes through L1 and is perpendicular to the line connecting the sun and the Earth. It stays in this plane, tracing out an elliptical lissajous orbit centered about L1. It orbits L1 once every six months, while L1 itself orbits the sun every 12 months as it is coupled with the motion of the Earth. This keeps SOHO at a good position for communication with Earth at all times.
Communication with Earth
In normal operation the spacecraft transmits a continuous 200 kbit/s data stream of photographs and other measurements via the NASA Deep Space Network of ground stations. SOHO's data about solar activity are used to predict solar flares, so electrical grids and satellites can be protected from their damaging effects (mainly, solar flares may produce geomagnetic storms, which in turn produce geomagnetically induced current creating black-outs, etc.).
In 2003 ESA reported the failure of the antenna Y-axis stepper motor, necessary for pointing the high-gain antenna and allowing the downlink of high-rate data. At the time, it was thought that the antenna anomaly might cause two to three week data-blackouts every three months. However, ESA and NASA engineers managed to use SOHO's low-gain antennas together with the larger 34 and 70 meter DSN ground stations and judicious use of SOHO's Solid State Recorder (SSR) to prevent total data loss, with only a slightly reduced data flow every three months.
Near loss of SOHO
The SOHO Mission Interruption sequence of events began on June 24, 1998, while the SOHO Team was conducting a series of spacecraft gyroscope calibrations and maneuvers. Operations proceeded until 23:16 UTC when SOHO lost lock on the Sun, and entered an emergency attitude control mode called Emergency Sun Reacquisition (ESR). The SOHO Team attempted to recover the observatory, but SOHO entered the emergency mode again on June 25 02:35 UTC. Recovery efforts continued, but SOHO entered the emergency mode for the last time at 04:38 UTC. All contact with SOHO was lost, and the mission interruption had begun. SOHO was spinning, losing electrical power, and no longer pointing at the Sun.
Expert ESA personnel were immediately dispatched from Europe to the United States to direct operations. Days passed without contact from SOHO. On July 23, the Arecibo Observatory and DSN antennas were used to locate SOHO with radar, and to determine its location and attitude. SOHO was close to its predicted position, oriented with its side versus the usual front Optical Surface Reflector panel pointing toward the Sun, and was rotating at one RPM. Once SOHO was located, plans for contacting SOHO were formed. On August 3 a carrier was detected from SOHO, the first signal since June 25. After days of charging the battery, a successful attempt was made to modulate the carrier and downlink telemetry on August 8. After instrument temperatures were downlinked on August 9, data analysis was performed, and planning for the SOHO recovery began in earnest.
The SOHO Recovery Team began by allocating the limited electrical power. After this, SOHO's anomalous orientation in space was determined. Thawing the frozen hydrazine fuel tank using SOHO's thermal control heaters began on August 12. Thawing pipes and the thrusters was next, and SOHO was re-oriented towards the Sun on September 16. After nearly a week of spacecraft bus recovery activities and an orbital correction maneuver, the SOHO spacecraft (bus) returned to normal mode on September 25 at 19:52 UTC. Recovery of the instruments began on October 5 with SUMER, and ended on October 24, 1998 with CELIAS.
Only one gyro remained operational after this recovery, and on December 21 that gyro failed. Attitude control was accomplished with manual thruster firings that consumed 7 kg of fuel weekly, while ESA developed a new gyroless operations mode that was successfully implemented on February 1, 1999.
Additional references
- "SOHO's Recovery - An Unprecedented Success Story" (PDF). Retrieved 2006-03-11. -PDF
- "SOHO Mission Interruption Preliminary Status and Background Report - July 15, 1998". Retrieved 2006-03-11.
- "SOHO Mission Interruption Joint NASA/ESA Investigation Board Final Report - August 31, 1998". Retrieved 2006-03-11.
- "SOHO Recovery Team". Retrieved 2006-03-11. Image
- "The SOHO Mission [[Lagrangian point#L1|L1]] Halo Orbit Recovery From the Attitude Control Anomalies of 1998" (PDF). Retrieved 2007-07-25. Wikilink embedded in URL title (help)
- Weiss, K. A.; Leveson, N.; Lundqvist, K.; Farid, N.; Stringfellow, M. (2006-01-09). "An analysis of causation in aerospace accidents". Digital Avionics Systems, 2001. DASC. The 20th Conference Vol. 1.
- Leveson, N. G. (July 2004). "The Role of Software in Spacecraft Accidents". AIAA Journal of Spacecraft and Rockets 41 (4).
- Neumann, Peter G. (January 1999). "Risks to the Public in Computers and Related Systems". Software Engineering Notes 24 (1): 31–35. doi:10.1145/308769.308773.
Scientific objectives
The three main scientific objectives of SOHO are:
- Investigation of the outer layer of the Sun, which consists of the chromosphere, transition region, and the corona. CDS, EIT, LASCO, SUMER, SWAN, and UVCS are used for this solar atmosphere remote sensing.
- Making observations of solar wind and associated phenomena in the vicinity of L1. CELIAS and CEPAC are used for "in situ" solar wind observations.
- Probing the interior structure of the Sun. GOLF, MDI, and VIRGO are used for helioseismology.
The SOHO Payload Module (PLM) consists of twelve instruments, each capable of independent or coordinated observation of the Sun or parts of the Sun, and some spacecraft components. The instruments are:
- Coronal Diagnostic Spectrometer (CDS) which measures density, temperature and flows in the corona.
- Charge ELement and Isotope Analysis System (CELIAS) which studies the ion composition of the solar wind.
- Comprehensive SupraThermal and Energetic Particle analyser collaboration (COSTEP) which studies the ion and electron composition of the solar wind. COSTEP and ERNE are sometimes referred to together as the COSTEP-ERNE Particle Analyzer Collaboration (CEPAC).
- Extreme ultraviolet Imaging Telescope (EIT) which studies the low coronal structure and activity.
- Energetic and Relativistic Nuclei and Electron experiment (ERNE) which studies the ion and electron composition of the solar wind. (See note above in COSTEP entry.)
- Global Oscillations at Low Frequencies (GOLF) which measures velocity variations of the whole solar disk to explore the core of the sun.
- Large Angle and Spectrometric Coronagraph (LASCO) which studies the structure and evolution of the corona by creating an artificial solar eclipse.
- Michelson Doppler Imager (MDI) which measures velocity and magnetic fields in the photosphere to learn about the convection zone which forms the outer layer of the interior of the sun and about the magnetic fields which control the structure of the corona. The MDI is the biggest producer of data by far on SOHO. In fact, two of SOHO's virtual channels are named after MDI, VC2 (MDI-M) carries MDI magnetogram data, and VC3 (MDI-H) carries MDI Helioseismology data.
- Solar Ultraviolet Measurement of Emitted Radiation (SUMER) which measures plasma flows, temperature and density in the corona.
- Solar Wind ANisotropies (SWAN) which uses telescopes sensitive to a characteristic wavelength of hydrogen to measure the solar wind mass flux, map the density of the heliosphere, and observe the large-scale structure of the solar wind streams.
- UltraViolet Coronagraph Spectrometer (UVCS) which measures density and temperature in the corona.
- Variability of solar IRradiance and Gravity Oscillations (VIRGO) which measures oscillations and solar constant both of the whole solar disk and at low resolution, again exploring the core of the sun.
Public availability of images
Observations from some of the instruments can be formatted as images, most of which are also readily available on the internet for either public or research use (see the official website). Others such as spectra and measurements of particles in the solar wind do not lend themselves so readily to this. These images range in wavelength or frequency from optical (Hα) to extreme ultraviolet (UV). Images taken partly or exclusively with non-visible wavelengths are shown on the SOHO page and elsewhere in false color.
Unlike many space-based and ground telescopes, there is no time formally allocated by the SOHO program for observing proposals on individual instruments: interested parties can contact the instrument teams directly via e-mail and the SOHO web site to request time via that instrument team's internal processes (some of which are quite informal, provided that the ongoing reference observations are not disturbed). A formal process (the "JOP" program) does exist for using multiple SOHO instruments collaboratively on a single observation. JOP proposals are reviewed at the quarterly Science Working Team ("SWT") meetings, and JOP time is allocated at monthly meetings of the Science Planning Working Group. First results have been presented in Solar Physics, volumes 170 and 175 (1997), edited by B. Fleck and Z. Švestka.
Comet discovery
As a consequence of its observing the Sun, SOHO (specifically the LASCO instrument) has inadvertently allowed the discovery of comets by blocking out the Sun's glare. Approximately one-half of all known comets have been spotted by SOHO, discovered over the last 15 years by over 70 people representing 18 different countries searching through the publicly available SOHO images online. Michał Kusiak of the Polish Jagiellonian University (Uniwersytet Jagielloński) discovered SOHO's 1999th and 2000th comets on 26 December 2010. As of 2013[update], SOHO has discovered over 2400 comets, with an average discovery rate of every 2.59 days.
Amateur astronomer Mike Oates' discovery of over 140 comets in the SOHO data resulted in the minor planet "68948 Mikeoates" being named after him; this was used by lexicographer Erin McKean in her TED talk as an example of how Internet users can contribute to collections.
Instrument contributors
The Max Planck Institute for Solar System Research contributed to SUMER, LASCO and CELIAS instruments. The Smithsonian Astrophysical Observatory built the UVCS instrument. The Lockheed Martin Solar and Astrophysics Laboratory (LMSAL) built the MDI instrument in collaboration with the solar group at Stanford University.
See also
- Solar Dynamics Observatory (SDO), launched 2010, still operational.
- STEREO (Solar TErrestrial RElations Observatory), launched 2006, still operational.
- Transition Region and Coronal Explorer (TRACE), launched 1998, decommissioned 2010.
- Triana, satellite intended for L1
- High Resolution Coronal Imager (Hi-C), launched 2012, sub-orbital telescope.
- Mission extensions approved for science missions, ESA, 29 November 2012
- "Antenna anomaly may affect SOHO scientific data transmission". ESA news. Retrieved 14 March 2005.
- "SOHO's antenna anomaly: things are much better than expected". ESA news. Retrieved 14 March 2005.
- Domingo, V., Fleck, B., Poland, A. I., Solar Physics 162, 1--37 (1995)
- Fleck B (1997). "First Results from SOHO". Rev Modern Astron. 10: 273–96. Bibcode:1997RvMA...10..273F.
- Karl Battams on Twitter (2 Jan 2013). "SOHO comet discovery rate for 2010-2012". Retrieved 2013-01-02.
- SOHO's 2000th Comet Spotted By Student, SOHO Hotshots, 28 December 2010
- Sungrazing Comets (Karl Battams) on Twitter (19 Oct 2012). "has discovered a new comet every 2.59-days on average". Retrieved 2012-10-20.
- Mike's SOHO Comet Hunt
- http://www.ted.com/talks/erin_mckean_redefines_the_dictionary.html video time 12:36-13:06
|Wikimedia Commons has media related to: Solar and Heliospheric Observatory|
- ESA SOHO webpage
- SOHO Homepage
- "A Description of the SOHO Mission". NASA's SOHO website. Retrieved 24 October 2005.
- "Latest SOHO Images". NASA's SOHO website. Retrieved 24 October 2005., free to use for educational and non-commercial purposes.
- SOHO Mission Profile by NASA's Solar System Exploration
- "Space Weather Now". National Weather Service - Space Environment Center. Retrieved 24 October 2005.
- "The SOHO Mission L1 Halo Orbit Recovery From the Attitude Control Anomalies of 1998" (PDF). Retrieved 24 October 2005. - PDF
- Sun trek website A useful resource about the Sun and its effect on the Earth
- Coordinating with SOHO (Stein Vidar Hagfors Haugan. COSPAR Published by Elsevier Ltd. 2004)
- SOHO Spots 2000th Comet
- Transits of Objects through the LASCO/C3 field of view (FOV) in 2013 (Giuseppe Pappa)
- Noteable objects in LASCO C3 and LASCO Star Maps (identify objects in the field of view for any day of the year)
- You can discover the next comet…from your couch! (science for citizens 18 Oct 2011) | <urn:uuid:9f77c61d-16f0-437b-813c-b57b8607b559> | 2.984375 | 3,719 | Knowledge Article | Science & Tech. | 42.75099 |
I thought case statement is like if statement. So in my example, when i is 4 and it meets case 1, then case 1 is not going to be entered. Why am I wrong? Thanks.
Larry, don't you see your reasoning is faulty?
OK, so what does break do? What purpose does it serve if, by your reasoning, once a case condition is met, the switch is exited as soon as the next case condition is met? If that's your conclusion, then why not just remove the break statements from case 1, case 2, and case 3? It's just unnecessary typing, according to your conclusion.
The answer is as GCDEF mentioned -- break does mean something in a case statement, and that is to ensure that the condition doesn't "fall through" to the next case condition. | <urn:uuid:2395adc0-1d56-41e4-812e-09fa7af5ba50> | 2.796875 | 168 | Comment Section | Software Dev. | 75.868946 |
Most species of organisms are unrecognized for their unique, versatile abilities, appearance and existence. When we think of organisms we often think of the typical dog, cat and other household pets. When we think of wild organisms, we think of zebras, lions, monkeys and other animals seen in habitats that are known for housing wild animals, like zoos. When thinking of aquatic organisms we think of jellyfish, goldfish, and sharks. We have become accustomed to a stereotype of the organisms that form each label of organisms; people are becoming ignorant to the variety and eccentricity of organisms we have among us today. This following list is of 10 eccentric organisms, showing the plethora of organisms within each species. | <urn:uuid:cd332afc-5fcc-42e0-962c-7cdc043acb89> | 2.765625 | 142 | Listicle | Science & Tech. | 34.163164 |
Fungi are not plants.
Living things are organized for study into large, basic groups called kingdoms. Fungi were listed in the Plant Kingdom for many years. Then scientists learned that fungi show a closer relation to animals, but are unique and separate life forms. Now, Fungi are placed in their own Kingdom.
It is a hidden kingdom. The part of the fungus that we see is only the fruit of the organism. The living body of the fungus is a mycelium made out of a web of tiny filaments called hyphae. The mycelium is usually hidden in the soil, in wood, or another food source. A mycelium may fill a single ant, or cover many acres. The branching hyphae can add over a half mile (1 km) of total length to the mycelium each day. These webs live unseen until they develop mushrooms, puffballs, truffles, brackets, cups, birds nests, corals or other fruiting bodies. If the mycelium produces microscopic fruiting bodies, people may never notice the fungus.
Most fungi build their cell walls out of chitin. This is the same
material as the hard outer shells of insects and other arthropods. Plants do
not make chitin.
Fungi feed by absorbing nutrients from the organic material in which they live. Fungi do not have stomachs. They must digest their food before it can pass through the cell wall into the hyphae. Hyphae secrete acids and enzymes that break the surrounding organic material down into simple molecules they can easily absorb.
Fungi have evolved to use a lot of different items for food. Some are decomposers living on dead organic material like leaves. Some fungi cause diseases by using living organisms for food. These fungi infect plants, animals and even other fungi. Athletes foot and ringworm are two fungal diseases in humans. The mycorrhizal fungi live as partners with plants. They provide mineral nutrients to the plant in exchange for carbohydrates or other chemicals fungi cannot manufacture.
You probably use fungal products every day without being aware of it. People eat mushrooms of all shapes, sizes and colors. Yeasts are used in making bread, wine, beer and solvents. Drugs made from fungi cure diseases and stop the rejection of transplanted hearts and other organs. Fungi are also grown in large vats to produce flavorings for cooking, vitamins and enzymes for removing stains.
BACK TO CATALOG
Last update: 15 Nov 06. © 1995, Robert Fogel, Ivins, UT 84738. Edited by Patricia Rogers. Pilobolus photograph couresty of M.J. Wynne. Geastrum, Amanita, and Morchella photographs courtesy of R. L. Shaffer. | <urn:uuid:dc1d45fe-92cc-4a00-a106-c410620ceb76> | 3.359375 | 583 | Knowledge Article | Science & Tech. | 53.9866 |
In this example the stereochemistry is given by up/down-bonds except at position 4 (C-6 within the drawing) where the two methylgroups are located. From the drawing it is unspecified which methylgroup is in axial or equatorial position respectively, therefore the methylgroups can't be distinguished resulting in a predicted value of 26.5ppm for both of them with a fairly large expectation range of 15.6-34.5ppm. (the methylgroups are numbered C-16 and C-17 within the drawing)
In the second example the missing piece of information is inserted by
defining the axial methylgroup using an up-bond. The other methylgroup
is automatically assigned to the equatorial position leading to a dramatic
improvement of the prediction quality. The estimated values for these methylgroups
differ now by ca. 12ppm caused by 1,3-diaxial interaction as to be expected. | <urn:uuid:d09ce6c4-8bdf-4b3b-b29a-e4e69ebaafcb> | 3.046875 | 197 | Documentation | Science & Tech. | 47.538547 |
How to parse xml file in Java or how to read xml file in java is one of common need of a Java Developer working with enterprise Java application which uses XML for data representation, messaging and data transfer. Java has good support to handle XML files and XML Documents and you can read XML File in Java, create or write to XML file in Java by using various XML parsers available. Reading XML file is little bit different than reading text or binary file in Java but it uses same concept of File class.
Universal acceptability of XML and Java has helped them to grow together and they have lot of things common in between just like Java is platform independence, XML provides data which is also platform independent. You can use XML to transfer data between a legacy application written in C or C++ and Java.
What is important to work with XML in Java is correct understanding of XML Parser, Basic knowledge of XML document etc. In this Java XML Tutorial we will see how to parse and XML File by using both DOM XML Parser. We will also see difference between DOM and SAX parser in XML and other basics related to XML parsing in Java. I thought about this article after sharing my xpath notes in Java.
How to read XML File in Java
JAXP - Java API for XML Parsing
Java provides extensive support for reading XML file, writing XML file and accessing any element from
XML file. All XML parsing related classes and methods are inside JAXP. Though DOM related code comes from org.w3c.dom package. All XML parsers are in javax.xml.parsers package.we will see example of parsing xml files using JAXP API in next section.
Parse XML File in Java using DOM Parser
In this section we will see how to parse xml files or how to read xml file using DOM XML Parser.DOM is quick and easy way to parse xml files in Java and if you are doing it for testing its way to go. Only thing to concern is that XML files which need to be parsed must not be too large. You can also create xml file by using DOM parser and DocumentFactory Class in Java.
XML file for parsing in Java
Here is xml file Stocks.xml which contains some stocks and there price, quantity we will use this in our xml parsing example in Java.
Code Example of Parsing XML File in Java using DOM Parser
Here is a code example of parsing above xml file in Java using DOM parser: | <urn:uuid:b7f6f565-2455-45b4-ae32-aa38ce071236> | 2.84375 | 513 | Tutorial | Software Dev. | 62.621578 |
Fundamental Concepts of Force
When we push or pull on a body, we are said to exert a force on it. Forces can also be exerted by inanimate objects. For example, a locomotive exerts a force on a train it is pulling or pushing. Similarly, compressed air in a container exerts a force on the wall of the container.The force may produce motion of the body or may cause the body to deform. Energy may be expended in the process, or the applied force may be balanced by an opposing force so that no energy is expended.
The distortion or the displacement that occurs when a body is subjected to a force occurs in accordance with Hooke's and Newton's laws governing the behavior of elastic and non-elastic bodies.
Sir Isaac Newton (1642-1727) was the first to state the basic laws of motion of bodies. He postulated three fundamental principles:
- First Law: A body remains at rest or continues to move in a straight line with uniform velocity if there is no unbalanced force acting on it.
- Second Law: An unbalanced force acting on a body will cause that body to accelerate in the direction of the force with an acceleration inversely proportional to the mass of the body.
- Third Law: For every action there is an equal and opposite reaction.
During the same era, Robert Hooke (1635-1703) observed that when an elastic body is subjected to stress its dimension or shape changes in proportion to the applied stress over a range of stresses. This led to Hooke's law which states that strain, the relative change in dimension, is proportional to stress. If the stress applied to a body goes beyond a certain value known as the elastic limit , the body does not return to its original state once the stress is removed. Hooke's law applies only in the region below the elastic limit.
Because measurement of distortion or of motion provides the means of determining the magnitude of a force, Newton's and Hooke's laws are key concepts in force measurements.
Unit of Force
The unit of force is derived from a fundamental quantity, mass. The fundamental unit of mass is the kilogram (kg). The kilogram itself is defined as the mass of a platinum-iridium cylinder kept at the International Bureau of Weights and Measures at Sevres, near Paris, France. A replica of this cylinder is kept at the National Institute of Standards and Technology in Gaithersburg, MD. It serves as the standard of mass for the US.
The unit of force is the Newton (N). By definition, the newton is the force required to give a one-kilogram mass an acceleration of one meter per second squared. | <urn:uuid:2dd1f420-b6af-4d2d-8f93-492e32742083> | 4.40625 | 552 | Knowledge Article | Science & Tech. | 46.423698 |
A question which has been vexing astronomers for a long time is whether the forces of attraction between stars and galaxies will eventually result in the universe collapsing back into a single point, or whether it will expand forever with the distances between stars and galaxies growing ever larger. Toby O'Neil describes how the mathematical theory of dimension gives us a way of
approaching the question.
Knots crop up all over the place, from tying a shoelace to molecular structure, but they are also elegant mathematical objects. Colin Adams asks when is a molecule knot a molecule? and what happens if you try to build a knot out of sticks?
"As Obi-Wan Kenobi said about the Light Sabre in Star Wars IV, a slide-rule is an ancient weapon from a more civilised age," state Chris Budd and Chris Sangwin in their book, Mathematics Galore, soon to released by Oxford University Press. The book digs up the slide-rule and a few more historical artefacts, as well as the art of country dancing, to present a pick-and-mix bag of mathematical ideas for the aspiring mathematician or the mathematically inclined general reader. | <urn:uuid:1de4f68e-658a-475b-8064-b70673deb7f4> | 2.765625 | 233 | Truncated | Science & Tech. | 34.523077 |
(E27) Electro-Magnetic Waves, at last!
James Clerk MaxwellJames Clerk Maxwell was born in Edinburgh, Scotland, in 1831 when Faraday also discovered electromagnetic induction. His father was a well-to-do attorney, but his mother died when he was young leaving him the only surviving child in the family. He studied in the Edinburgh Academy, a bright lad with interest and talent not only in mathematics and sciences, but also in drawing and poetry. Later he attended the Universities of Edinburgh and Cambridge, and from early age did original research and published articles. In 1856 he joined the faculty at Marischal (later the University of Aberdeen) and in 1860 moved to Kings College in London, where he got to know Faraday and appreciate his work.
Faraday's grasp of physics was intuitive, without higher math. Maxwell had both math and the intuition, and he therefore tried to understand Faraday's vision and translate it into mathematical terms.
He did much more in his short career (he died of cancer at 48), such as investigation into the theory of color and in particular the theory of gases. An ideal gas may be viewed as a collection of individual molecules moving randomly, with an average speed that increases with temperature, colliding elastically and frequently. Because of these collisions, some molecules gain energy above the average, others lose it, creating an average distribution found by Maxwell and still named the Maxwellian. From his theory he deduced viscosity, mean path between collisions and many other properties. He even worked out the theory of the radiometer, a vertical "windmill" with vanes black on one side and white on the other, spun up in an evacuated glass bulb by a beam of light. The spin is often attributed to light pressure, but the effect is much more complex.
Electric and Magnetic Fields, and Maxwell's EquationsHis greatest success, though, were "Maxwell's Equations" a set of rigorous mathematical relations confirming Faraday's guess that a transverse electro-magnetic wave could exist, and that light was probably such a wave. He assembled the equations of electricity and magnetism--the basic ones which did not depend on properties of materials, but held even in a vacuum:
Maxwell expressed each of these statements in a suitable mathematical form, but we skip that since it would require tools of differential calculus of three-dimensional quantities and of vectors. Number #2 is true even though we do observe magnetic poles on bar magnets; however, the existence of such paired poles can also be explained by a suitable distribution of currents. It was Ampére who originally pointed out that if each atom included a small circulating current ("Ampére current"), lining up the axes of those currents would produce the same bulk magnetism as is observed in bar magnets and lodestones.
When #2 is formulated mathematically, its alternative interpretation is that magnetic field lines behave like streamlines in an incompressible fluid (like water, in practice; see discussion of magnetic flux).
There remains a certain vagueness in all this: which here are "real" objects and which just mathematical abstractions? Electric charges and electric currents are presumably real, associated with the matter in which they reside--and if isolated magnetic poles existed, they might be deemed "real" too.
On the other hand the "electric force" and the "magnetic force" at a point in empty space seem somewhat abstract: unless an electric charge or electric current are actually located at such a point, it did not seem any different from any point in empty space. And yet Maxwell ultimately held that they were not quite empty. A point associated with a possible electric force was endowed with an "electric field E," a vector with strength and direction, implying that if a charge q was placed there, it would sense a force qE. Similarly, an otherwise empty point would be endowed with a magnetic field B if a force mB would be sensed by a magnetic pole m there, if such poles existed--or a force I(dlxB) on a current I in a short length of conductor dl (a vector), as explained at the end of
The Displacement Current
Waves in general are associated with a periodic interchange of energy:
The two were linked, but a gap seemed to exist. By equation (4), varying the magnetic field B changed the magnetic flux, producing a changing electric field E. If a transformer coil is placed around the changing flux, this E will create a changing current I, which may create more of the variable magnetic field B.
But you need a changing current I: if no coil is placed in that space--no current is expected. And current is what creates a magnetic field B. A changing electric field E was not a source of magnetism.
Except..... for that strange way an AC current can flow across a capacitor, even if the space between the plates is empty. Given two parallel plates A and B, if the voltage at A changes, for the short interval before the charge (and energy) of the capacitor can change, the voltage at B follows the one on A. At least for that very short time, a voltage change does propagate across the gap. That may be generalized to an AC current, provides it changes fast enough. if the input is an AC voltage with angular frequency ω, the current flowing across the gap is proportional to ω, too.
The frequency f associated with a light wave can be calculated from its wavelength λ in optical experiments and from the velocity of light c: f=c/λ One gets quite high frequencies, at which this unusual AC current might cross empty space quite easily. Maxwell named it the displacement current.
Does the displacement current have the same properties as current conducted by a wire--in particular, the ability to create a magnetic field B? Maxwell guessed it did, and so a high frequency AC electric field E could drive a high frequency AC magnetic field B across empty space. Equations could then be written in which a wave of E and one of B alternate, perpendicular to each other and (for both) to the direction in which the wave advances ("the ray of light"), with a velocity which in vacuum equals c. In ordinary light E can be in any direction perpendicular to the ray, but polarized waves, where (say) E is always in the same direction (and B perpendicular to it) are also possible
In 1884 John Henry Poynting proved that if electro-magnetic waves existed, they would be able to transmit both energy and momentum to material which intercepted it, which seemed a valid test of their reality. The energy is evident in any object heated by bright sunlight, and the momentum showed itself in the pressure of sunlight measured in 1902 by Lebedev in Russia. It is now considered for solar sails in deep space.
Maxwell died of stomach cancer in 1879, and who knows what else he may have contributed, had he lived to a ripe old age. One important question remained: how could an electromagnetic wave be generated? Its details occupied many scientists in the 50-60 years that followed and led to an entire new insight on physics at the atomic scale, now known as quantum theory. Hot solid substances radiated a continuous spectrum whose frequency rose with energy--from cherry-red hot iron in a smith's forge, to the bright yellow light of the filaments of Edison and Welsbach--to the even hotter electric arc of Humphry Davy, whose light contained a lot of ultra-violet (the reason arc welders wear special masks). The hotter the source, the shorter the wavelength, but for a while scientists did not understand why.
Glowing gases (e.g. in fluorescent lights) behaved differently. When excited by high voltages, they preferred to emit light at selected frequencies ("line spectrum"), accurately defined and characteristic of the emitting substance. Here was clearly a lot of information, and it took a complete overhaul of physics to figure it out; see here, here and here for some details.
All these involved processes on an atomic scale, where electro-magnetic circuitry does not exist and where (as it turned out) laws of physics are markedly modified. But how to create electromagnetic waves using known electrical equipment in the laboratory? Heinrich Hertz in Germany proved mathematically and confirmed by experiment in 1886 that the high-frequency AC in a loop antenna (generating a magnetic field) or an antenna composed of two opposing rods (a "dipole antenna," with the circuit closed by the displacement current) could generate an E-M wave.
It was already known that lightning and sparks produced currents which oscillated very rapidly, a mixture of high-frequency AC (even now, on an AM radio during a thunderstorm, you can hear the crackling of "static" due to lightning, regardless of the station you are tuned to).
Hertz created a high frequency spark discharge by generating a high voltage by transformer and discharging it through an "antenna" (he tried both kinds) with a spark gap in the middle (see also here). The oscillations between a charged capacitor and an inductor can also broadcast an E-M wave.
Hertz was mainly interested in proving the generation of electromagnetic waves; little did he suspect that by 1903 Marconi would send radio signals across the Atlantic ocean, or that in 1912 the sinking "Titanic" would radio for help after colliding (at full speed) with a drifting iceberg.
Next Stop: E28. Communication |
Author and Curator: Dr. David P. Stern | <urn:uuid:8c211478-d846-48e3-9c66-0f4d5bf9011c> | 3.265625 | 1,964 | Knowledge Article | Science & Tech. | 39.502772 |
A chlorobenzene (phenyl chloride) is formed if benzene is treated with chlorine in the presence of ferric chloride but the absence of water.
The reaction is driven to completion by the gentle heating of the reaction mixture. The overall equation of the reaction is:
Firstly, it is necessary for there to be an electrophile to attack the regions of high electron density within the benzene ring. This is achieved by the splitting of the single bond within the chlorine molecule, accompanied by the creation of a chloronium ion. It is this chloronium ion which acts as the electrophile in the reaction.
The pi electrons in the benzene ring are attacked by the chloronium ion and a proton is lost from the benzene molecule intermediate due to resonance stabilisation. The proton (which is chemically a hydrogen ion) regenerates the ferric chloride catalyst and the reaction continues for as long as there are reactants present.
The progress of the reaction can be tested by wet blue litmus paper. The hydrogen chloride fumes given off turn it red. This reaction can be summed up by the stoichiometric equation:
You may be interested in reading: | <urn:uuid:38c21e03-029a-49cc-813c-27cb919a0a55> | 3.671875 | 242 | Knowledge Article | Science & Tech. | 36.026382 |
1207 Pine Leaf-mining Moth Clavigesta purdeyi
(Durrant, 1911)Wingspan 10-12 mm.
Quite a small Tortricid, this moth, in common with some other coniferous-feeding species, has expanded its range during the last century. Earlier only occurring in southern England, it is now widely distributed in England and Wales.
The larvae feed internally on the needles of pine (Pinus), overwintering in this stage.
Flying from July to September, the adults are attracted to light. | <urn:uuid:dd8b9d26-cc95-4380-af07-d1b5b89db31c> | 3.234375 | 114 | Knowledge Article | Science & Tech. | 48.354 |
And they wonder why the weather has changed...
Climate Progress / By Joe Romm
Global CO2 Emissions Hit New Record in 2011, Keeping World on Track for 'Devastating' 11°F Warming
The scientific literature now makes clear that even 7°F warming would destroy the livable climate 7 billion people have come to depend upon.
May 29, 2012 | First the bad news from the International Energy Agency (IEA). Thanks to a huge jump in Chinese emissions, “global carbon-dioxide (CO2) emissions from fossil-fuel combustion reached a record high of 31.6 gigatonnes (Gt) in 2011.”
The worse news is that, “The new data provide further evidence that the door to a 2°C trajectory is about to close,” according to IEA Chief Economist Fatih Birol. Why does that matter? As Reuters reported:
Scientists say ensuring global average temperatures this century do not rise more than 2 degrees Celsius above pre-industrial levels is needed to limit devastating climate effects like crop failure and melting glaciers.Darn you truth-telling scientists, always ruining the party (see “James Hansen Is Correct About Catastrophic Projections For U.S. Drought If We Don’t Act Now“).
And the worst news, as Birol told Reuters, is that:“When I look at this data, the trend is perfectly in line with a temperature increase of 6 degrees Celsius [11°F], which would have devastating consequences for the planet.”As Birol said of 11°F warming late last year, “Even School Children Know This Will Have Catastrophic Implications for All of Us.” If only school children ran the country.
In fact, the scientific literature now makes clear that even 4°C (7°F) warming would destroy the livable climate 7 billion people have come to depend upon (see “An Illustrated Guide to the Science of Global Warming Impacts: How We Know Inaction Is the Gravest Threat Humanity Faces“).
So what is the ‘good’ news? We have has been reducing our emissions:
CO2 emissions in the United States in 2011 fell by 92 Mt, or 1.7%, primarily due to ongoing switching from coal to natural gas in power generation and an exceptionally mild winter, which reduced the demand for space heating. US emissions have now fallen by 430 Mt (7.7%) since 2006, the largest reduction of all countries or regions. This development has arisen from lower oil use in the transport sector (linked to efficiency improvements, higher oil prices and the economic downturn which has cut vehicle miles travelled) and a substantial shift from coal to gas in the power sector.
Actually, the change in vehicle miles traveled (VMT) predated the downturn. VMT “began to plateau as far back as 2004 and dropped in 2007 for the first time since 1980,” as Brookings has reported. Indeed, per capita driving saw “flat-lining growth after 2000 and falling rates since 2005.”
The point is that given Obama’s strong new fuel economy standards and the reality of peak oil (that high oil prices are here to stay absent a global depression), the U.S. could meet its Copenhagen target of a 17% reduction in CO2 from 2005 levels with a pretty modest carbon tax (see “Bipartisan Support Grows for Carbon Price as Part of Debt Deal“). And that is the prerequisite for a global deal that would take us off the 6C path and give us a fighting chance at 2C.
T-Cat - "Conservation of momentum applies to a system closed in kinetic energy, not a thermodynamically closed system."
T-Cat on Potential Energy: "Which means that you aren't converting it all at any point until you reach the ground."
Two months ago, James Lovelock, the godfather of global warming, gave a startling interview to msnbc.com in which he acknowledged he had been unduly “alarmist” about climate change.
The implications were extraordinary.
Lovelock is a world-renowned scientist and environmentalist whose Gaia theory — that the Earth operates as a single, living organism — has had a profound impact on the development of global warming theory.
Unlike many “environmentalists,” who have degrees in political science, Lovelock, until his recent retirement at age 92, was a much-honoured working scientist and academic.
His inventions have been used by NASA, among many other scientific organizations.
Lovelock’s invention of the electron capture detector in 1957 first enabled scientists to measure CFCs (chlorofluorocarbons) and other pollutants in the atmosphere, leading, in many ways, to the birth of the modern environmental movement.
Having observed that global temperatures since the turn of the millennium have not gone up in the way computer-based climate models predicted, Lovelock acknowledged, “the problem is we don’t know what the climate is doing. We thought we knew 20 years ago.” Now, Lovelock has given a follow-up interview to the UK’s Guardian newspaper in which he delivers more bombshells sure to anger the global green movement, which for years worshipped his Gaia theory and apocalyptic predictions that billions would die from man-made climate change by the end of this century.
Lovelock still believes anthropogenic global warming is occurring and that mankind must lower its greenhouse gas emissions, but says it’s now clear the doomsday predictions, including his own (and Al Gore’s) were incorrect.
He responds to attacks on his revised views by noting that, unlike many climate scientists who fear a loss of government funding if they admit error, as a freelance scientist, he’s never been afraid to revise his theories in the face of new evidence. Indeed, that’s how science advances.
Among his observations to the Guardian:
(1) A long-time supporter of nuclear power as a way to lower greenhouse gas emissions, which has made him unpopular with environmentalists, Lovelock has now come out in favour of natural gas fracking (which environmentalists also oppose), as a low-polluting alternative to coal.
As Lovelock observes, “Gas is almost a give-away in the U.S. at the moment. They’ve gone for fracking in a big way. This is what makes me very cross with the greens for trying to knock it … Let’s be pragmatic and sensible and get Britain to switch everything to methane. We should be going mad on it.” (Kandeh Yumkella, co-head of a major United Nations program on sustainable energy, made similar arguments last week at a UN environmental conference in Rio de Janeiro, advocating the development of conventional and unconventional natural gas resources as a way to reduce deforestation and save millions of lives in the Third World.)
(2) Lovelock blasted greens for treating global warming like a religion.
“It just so happens that the green religion is now taking over from the Christian religion,” Lovelock observed. “I don’t think people have noticed that, but it’s got all the sort of terms that religions use … The greens use guilt. That just shows how religious greens are. You can’t win people round by saying they are guilty for putting (carbon dioxide) in the air.”
(3) Lovelock mocks the idea modern economies can be powered by wind turbines.
As he puts it, “so-called ‘sustainable development’ … is meaningless drivel … We rushed into renewable energy without any thought. The schemes are largely hopelessly inefficient and unpleasant. I personally can’t stand windmills at any price.”
(4) Finally, about claims “the science is settled” on global warming: “One thing that being a scientist has taught me is that you can never be certain about anything. You never know the truth. You can only approach it and hope to get a bit nearer to it each time. You iterate towards the truth. You don’t know it.”
They can deny deny deny all they want to...
Facts are facts.
Record high heats
Sea levels rising
Polar cap melting
Deny? Do you know who James Lovelock is? Try reading the article.
What research has Lovelock published related to climate change? Say over the last 20 years.Originally Posted by Sailor
A lot of cats can't be wrong!
His last published paper about global warming was in 2007. He had written a couple of books in in the early 2000's I believe also.
That should have been articles, not books.
And the name of that paper was? And it was published in what journal?Originally Posted by Sailor
As they say, anyone can write a book.He had written a couple of books in in the early 2000's I believe also.
A lot of cats can't be wrong!
And what are the names of those articles and the journals he published them in?Originally Posted by Sailor
A lot of cats can't be wrong! | <urn:uuid:a4282700-43da-4645-9774-9bd67604ab23> | 2.71875 | 1,932 | Comment Section | Science & Tech. | 54.768943 |
Regional trends of wind storm occurrence in Europe are investigated using the 20th Century Reanalysis (20CR). While based on surface observations only, this dataset produces storm events in good agreement with the traditional ERA40 and NCEP reanalyses. Time series display decadal-scale variability in the occurrence of wind storms since 1871, including a period of enhanced storm activity during the early 20th century. Still, significant upward trends are found in central, northern and western Europe, related to unprecedented high values of the storminess measures towards the end of the 20th century, particularly in the North Sea and Baltic Sea regions.
This way you can cut your water consumption by a third! Pause the water flow when soaping and avoid long showers. A shower uses about 30 to 80 litres, while a bath uses 150 to 200 litres of precious water. Install low-flow shower heads and think before buying a power shower.
More green tips | <urn:uuid:6e2119c5-aaf6-433d-8ffb-5692e0c184ce> | 3.015625 | 191 | Knowledge Article | Science & Tech. | 41.984859 |
Climate change is a reality. Today, our world is hotter than it has been in two thousand years. By the end of the century, if current trends continue, the global temperature will likely climb higher than at any time in the past two million years.
Temperature change 1765-2100: Graph excerpted from the IPCC's Third Assessment Report showing past and predicted changes to global temperature.
While the end of the 20th century may not necessarily be the warmest time in Earth's history, what is unique is that the warmth is global and cannot be explained by the natural mechanisms that explain previous warm periods. There is a broad scientific consensus that humanity is in large part responsible for this change, and that choices we make today will decide the climate of the future.
How we are changing the climate
For more than a century, people have relied on fossil fuels such as oil, coal and gas for their energy needs. Burning these fossil fuels releases the greenhouse gas (GHG) carbon dioxide into the atmosphere. Other, even more potent greenhouse gases are also playing a role, as well as massive deforestation.
The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action.
Joint statement by 11 national science academies to world leaders (full text)
What we know
While there are still uncertainties, particularly related to the timing, extent and regional variations of climate change, there is mainstream scientific agreement on the key facts:
Certain gasses in the atmosphere, such as carbon dioxide, create a "greenhouse effect", trapping heat and keeping the Earth warm enough to sustain life as we know it.
Burning fossil fuels (coal, oil, etc.) releases more carbon dioxide into the atmosphere. Although not the most potent greenhouse gas, carbon dioxide is the most significant in terms of human effects because of the large quantities emitted.
Carbon dioxide concentrations in the atmosphere are now the highest in 150,000 years.
The 1990's was most likely the warmest decade in history, and 1998 the warmest year.
There is also widespread agreement that:
A certain amount of additional warming - about 1.3 degrees Celsius (2.3 degrees Fahrenheit) compared to pre-industrial levels - is probably inevitable because of emissions so far. Limiting warming to under 2 degrees Celsius (3.6 degrees Fahrenheit) is considered vital to preventing the worst effects of climate change.
If our greenhouse gas emissions are not brought under control, the speed of climate change over the next hundred years will be faster than anything known since before the dawn of civilization.
There is a very real possibility that climate feedback mechanisms will result in a sudden and irreversible climate shift. No one knows how much global warming it would take to trigger such a "doomsday scenario."
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Physics- PLEASE HELP
A luggage carousel at an airport has the form of a section of a large cone, steadily rotating about its vertical axis. Its metallic surface slopes downward toward the outside, making an angle of 21.0° with the horizontal. A 37.0 kg piece of luggage is placed on the carouse...
3. A 2000 kg sports car moves in a horizontal circular path of 150 m\radius at a constant speed of 80 m\s. a. magnitude of centripetal acceleration b. magnitude of centripetal force
A cannon ball is fired with a velocity of 200 m\s2 at an < of 25° above ground. The total flight time is 45.6 seconds. (Neglect air resistance.) a. Calculate the initial horizontal\vertical components of the velocity b. Calculate maximum height of the cannon ball above ...
1. A rescue plane flying horizontally at an altitude of 500 m and velocity of 300 m\s east drops a food supply packet to plane crash survivors on the ground. The packet falls freely to the ground without a parachute. Assume that the weather is perfect. a. Calculate the time it...
18. Balance sheet and income statement data indicate the following: Bonds payable, 6% (issued 2000, due 2020) $1,200,000 Preferred 8% stock, $100 par (no change during the year) 200,000 Common stock, $50 par (no change during the year) 1,000,000 Income before income tax for ye...
Science 8R - Homework Check
2000m= 200000cm The rest are correct!
Math 8R - Help!!!!
Hours x pay per hour= total pay 6 2/3 x 27=v 180 dollars
A diver springs upward from a board that is 4.40 m above the water. At the instant she contacts the water her speed is 14.0 m/s and her body makes an angle of 68.8 ° with respect to the horizontal surface of the water. Determine her initial velocity, both (a) magnitude and...
The drawing shows an exaggerated view of a rifle that has been sighted in' for a 91.4-meter target. If the muzzle speed of the bullet is v0 = 392 m/s, there are the two possible angles θ1 and θ2 between the rifle barrel and the horizontal such that the bull...
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Bignum Euler's Totient
Sorry, this page is not working for certain browsers, and I'm not sure why. If it doesn't work for you, my apologies.
Euler's Totient, for some positive integer n, is how many positive integers there are less than n which share no common factors with it. (In math-speak, numbers with no common factors are called relatively prime, or coprime, to each other.) | <urn:uuid:77b66d25-e7db-428c-a885-706590fb2b9a> | 2.90625 | 94 | Personal Blog | Science & Tech. | 58.546786 |
How Would Nuclear War Affect The Climate?
"I'm drawn to extreme scenarios," said Luke Oman, a climate scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. Perhaps the most extreme scenario in his portfolio is nuclear conflict. Using a NASA computer simulation, Oman and colleagues model the climate's response to the smoke from fires brought about by regional nuclear war. His work, performed with colleagues at Rutgers University prior to joining NASA, is part of a larger panel discussing the issue on Feb. 18 at the meeting of the American Association for the Advancement of Science (AAAS) in Washington.
NASA: How were you turned on to this line of research?
Oman: The idea was spawned at a 2005 meeting of the American Geophysical Union, where I presented my research from Rutgers University on the subject of volcanoes.
Specifically, that work used computer simulations to model how sulphur dioxide gas ejected from volcanoes is converted into solid sulfate particles and then circulated in the upper atmosphere where it can impact climate.
While we were at the conference, some colleagues asked if the model could be modified to simulate black carbon aerosols emitted during a nuclear conflict, to illustrate the resulting impact on climate.
NASA: Has this been attempted before?
Oman: Yes, researchers started in the 1980s to look at the impacts from large-scale nuclear conflict scenarios.
More recently, with the emergence of smaller nuclear states, we wanted to make estimates of regional-scale conflicts. What kind of climate anomalies would we see? How would growing seasons change? My talk at the AAAS meeting, for example, is geared toward regional war and the potential impacts on global temperature and precipitation.
But it wasn't until about 10 years ago that the models became comprehensive enough to tackle these questions in a fully coupled way.
NASA: How do you go about simulating climate impacts of nuclear conflict?
Oman: With modeling we can find out some interesting aspects about the impact of aerosols on the underlying atmospheric dynamics and what's controlling their transport and removal.
We used a general circulation model, ModelE, from NASA's Goddard Institute for Space Studies in New York. ModelE is a coupled ocean-atmosphere model that shows how various inputs — in our case black carbon — would affect global climate.
Without this model the work wouldn't be possible. That's because it was one of the very few models that had a coupled atmosphere and ocean along with interactive aerosols, to be able to more fully address this issue then ever before.
NASA: What did the model reveal?
Oman: Instead of sulfate particles, like you get from a volcanic eruption, a nuclear event produces soot, and that results in very different climate impacts. Whereas sulfate particles from a volcano might warm the air of the upper atmosphere by a couple degrees, black carbon absorbs heat from the sun and can lead to much more atmospheric warming.
Sulfate and soot also vary in their impact on temperature at Earth's surface. That's because the particles differ in the amount of solar energy that they prevent from reaching the ground.
NASA: How does surface temperature change?
Oman: We studied the scenario of using 100 Hiroshima-size bombs, the fires from which would inject upward of 5 teragrams (megatons) of black carbon particles into Earth's upper troposphere. Observations of forest fires have shown this to occur on much smaller scales.
On the ground, global temperatures would fall by a little over 1 degree Celsius (C) (1.8 Fahrenheit (F)) over first three years. In contrast, aerosols from the 1991 eruption of Mount Pinatubo contributed to about 3/10 of a degree C (~ 0.5 F) of cooling over one year. Black carbon particles are smaller than sulfate particles and can be lofted much higher by solar heating, where their influence on climate can last up to a decade.
We also saw that two to four years after the event, rainfall would decrease globally by an average of about 10 percent.
As my colleagues Michael Mills [National Center for Atmospheric Research in Boulder, Colo.] and Brian Toon [University of Colorado at Boulder] are discussing at AAAS, the scenario also drives global stratospheric ozone loss and influences communities far away from the conflict. Agriculture, for example, would likely be disrupted from the combination of cooler temperatures, less precipitation and decreases in solar radiation reaching the surface. This would cause widespread interruptions to growing seasons by producing more frequent frosts.
NASA: How do you think this information is relevant for decision makers?
Oman: A primary goal of this work is to get the information revealed by our study into the hands of decision makers as well as to get other groups interested in this problem and to be aware of the potential impacts. Before we did this study, we didn't know what the climate anomalies would be or how long they would last. This is critical information that needs to be known in advance along with knowledge that the consequences of such a scenario would be global.
NASA's Earth Science News Team | <urn:uuid:22d02821-a175-4ca8-a219-3bacd7329be4> | 3.578125 | 1,041 | Audio Transcript | Science & Tech. | 41.601972 |
Ray Optics: Refraction and Lenses
Refraction and Lenses: Audio Guided Solution
A light ray is traveling through crown glass (n = 1.52) and approaching the boundary with water (n = 1.33) as shown in the diagram at the right.
a. Use a protractor to measure the angle of incidence of the light ray in the crown glass.
b. Calculate the angle of refraction of the light ray as it enters into the water.
Audio Guided Solution
Click to show or hide the answer!
Habits of an Effective Problem Solver
- Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
- Identify the known and unknown quantities and record them in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., do = 24,8 cm; di = 16.7 cm; f = ???.
- Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
- Identify the appropriate formula(s) to use.
- Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.
Read About It!
Get more information on the topic of Refraction and Lenses at The Physics Classroom Tutorial.
Return to Problem Set
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stellar evolution, life history of a star, beginning with its condensation out of the interstellar gas (see interstellar matter) and ending, sometimes catastrophically, when the star has exhausted its nuclear fuel or can no longer adjust itself to a stable configuration. Because a star's total energy reserve is finite, a star shining today cannot continue to produce its present luminosity steadily into the indefinite future, nor can it have done so from the indefinite past. Thus, stellar evolution is a necessary consequence of the physical theory of stellar structure, which requires that the luminosity, temperature, and size of a star must change as its chemical composition changes because of thermonuclear reactions.
Phases of Stellar Evolution
Contraction of the Protostar
The initial phase of stellar evolution is contraction of the protostar from the interstellar gas, which consists of mostly hydrogen, some helium, and traces of heavier elements. In this stage, which typically lasts millions of years, half the gravitational potential energy released by the collapsing protostar is radiated away and half goes into increasing the temperature of the forming star. Eventually the temperature becomes high enough for thermonuclear reactions to begin; if the mass of the protostar is too small to raise the temperature to the ignition point for the thermonuclear reaction, the result is a brown dwarf, or "failed star." In these thermonuclear reactions, loosely called "hydrogen burning," four hydrogen nuclei are fused to form a helium nucleus (see nucleosynthesis). This point in time is conventionally called age zero.
Many protostar contractions have been observed in isolated gas clouds; that is, where one cloud contracted to form one star. However, in 1995, the first example of a star-forming region was found in the Eagle Nebula, some 7,000 light-years from the earth. In this region, stars are being formed at the tips of long, fingerlike columns stretching from a huge cloud of interstellar gas and dust; the columns are being eroded by radiation (a process called photoevaporation) from stars in the vicinity, leaving scattered knots of matter that contract into stars.
Mature Stars and the Main Sequence
Once formed, a star settles into a long "middle age" during which it shines steadily as it converts its hydrogen supply into helium. For stars of a given chemical composition, the mass alone determines the luminosity, surface temperature, and size of the star. The luminosity increases very sharply with an increase in the mass; doubling the mass (which is proportional to the energy supply) increases the luminosity (which is proportional to the rate of using energy) more than 10 times. Hence the more massive and luminous a star is, the faster it depletes its hydrogen and the faster it evolves.
Because the middle age of a star is the longest period in stellar evolution, one would expect most of the observed stars to be at this stage and to show a strong correlation of luminosity with color (color is a measure of stellar temperature). This prediction is confirmed by plotting stars on a Hertzsprung-Russell diagram, in which the majority of stars fall along a diagonal line called the main sequence. The main sequence is most heavily populated at the low luminosity end; these are the stars that evolve most slowly and so remain longest on the main sequence.
As a star's hydrogen is converted into helium, its chemical composition becomes inhomogeneous: helium-rich in the core, where the nuclear reactions occur, and more nearly pure hydrogen in the surrounding envelope. The hydrogen near the center of the core is consumed first. As this is depleted, the site of the nuclear reactions moves out from the center of the core and fusion occurs in successive concentric shells. Finally fusion occurs only in a thin, outer shell of the core, the only place where both the hydrogen content and the temperature are high enough to sustain the reactions.
Old Stars and Death
As the helium content of the star's core builds up, the core contracts and releases gravitational energy, which heats up the core and actually increases the rates of the nuclear reactions. Thus the rate of hydrogen consumption rises as the hydrogen is used up. To accommodate the higher luminosity resulting from the increased reaction rates, the envelope must expand to allow an increased flow of energy to the surface of the star. As the outer regions of the star expand, they cool.
The star now consists of a dense, helium rich core surrounded by a huge, tenuous envelope of relatively cool gas; the star has become a red giant. Eventually, the contracting stellar core will reach temperatures in excess of 100 million degrees Kelvin. At this point, helium burning sets in. With the ignition of that process, the expansion of the envelope is halted and then reversed; the star retreats from the red giant phase, shrinking in size and luminosity, and reapproaches the main sequence. The exact course of evolution is uncertain, but as the star recrosses the main sequence, it will probably become unstable. The star may eject some of its mass or become an exploding nova or supernova star; at the very least, it will become a pulsating variable star, possibly a Cepheid variable.
In the later stages of evolution, further contraction and elevation of temperature open up new thermonuclear reactions. It is believed that the heavier elements in the universe, up to iron, were synthesized in the interiors of stars by a variety of intricate nuclear reactions, many involving neutron absorption. Elements heavier than iron are made in supernova explosions. As a result of the nuclear reactions, the chemical composition of the late-stage star becomes highly inhomogeneous; its structure is fractionated into a number of concentric shells consisting of different elements around an iron core.
The final outcome of stellar evolution depends critically on the remaining mass of the old star. The vast majority of stars do not develop iron cores. If the mass is not greater than the Chandrasekhar mass limit (1.5 times the sun's mass), the star will become a white dwarf, glowing feebly for billions of years by radiating away its remaining heat energy until it becomes a black dwarf, a totally dead star. If the star is too massive to become a stable white dwarf, contraction will continue until the temperature reaches about 5 billion degrees Kelvin. At this temperature the iron nuclei in the core begin to absorb electrons; this creates neutron-rich isotopes and simultaneously deprives the core of its pressure. With further collapse and increase in density, the core becomes a special kind of rigid solid. At still higher density, the solid "evaporates" as the nuclei break up into free neutrons. The resulting neutron fluid forms the core of a new astrophysical body, called a neutron star, of which pulsars are examples. If the stellar mass is too great to be stable even as a neutron star, complete gravitational collapse will ensue and a black hole will form.
Validating the Theory of Stellar Evolution
Because the computed lifetimes of stars range from millions to billions of years, one cannot follow an individual star through its life history observationally, or even observe significant changes in the whole span of human history, except from the violent events of nova and supernova explosions. However, new stars are continually being formed and hence stars of all ages exist at the present epoch; examples of the various stages of stellar evolution can be found in different stars. The age of a star is not a directly observable characteristic but must be inferred from the very evolutionary theory one is trying to validate. Confidence in this circular reasoning results from its self-consistency and its ability to draw together into a unified picture a wide variety of observational data on individual stars, clusters of stars, and galaxies.
See cosmology; star clusters.
See I. S. Shklovsky, Stars: Their Birth, Life, and Death (1978); D. A. Cooke, The Life and Death of Stars (1985); A. Harpaz, Stellar Evolution (1994); I. Asimov, Star Cycles: The Life and Death of Stars (1995).
Questia, a part of Gale, Cengage Learning. www.questia.com
Publication information: Article title: stellar evolution. Encyclopedia title: The Columbia Encyclopedia, 6th ed.. © 2012 The Columbia Electronic Encyclopedia © 2012, Columbia University Press. Licensed from Columbia University Press. Used with the permission of Columbia University Press. All Rights Reserved. Publisher: The Columbia University Press. Place of publication: Not available. Publication year: 2013.
This material is protected by copyright and, with the exception of fair use, may not be further copied, distributed or transmitted in any form or by any means. | <urn:uuid:0a6c0f0c-3cdd-4ddb-b8ed-246e6e541774> | 3.640625 | 1,781 | Knowledge Article | Science & Tech. | 34.450361 |
define-structure form introduces a binding of a name to a
structure. A structure is a view on an underlying package which is
created according to the clauses of the define-structure form.
Each structure has an interface that specifies which bindings in the
structure's underlying package can be seen via that structure in other
An open clause specifies which structures will be opened up for use inside the new package. At least one structure must be specified or else it will be impossible to write any useful programs inside the package, since define, lambda, cons, etc. will be unavailable. Packages typically include scheme, which exports all bindings appropriate to Revised5 Scheme, in an open clause. For building structures that export structures, there is a defpackage package that exports the operators of the configuration language. Many other structures, such as record and hash table facilities, are also available in the Scheme 48 implementation.
prefix forms produce new
views on existing structures by renaming or hiding exported names.
Subset returns a new structure that exports only the listed names
from its <structure> argument.
With-prefix returns a new structure that adds <prefix>
to each of the names exported by the <structure> argument.
For example, if structure
exports only(subset s (a))
exports(with-prefix s p/)
with-prefix are simple macros that
expand into uses of
modify, a more general renaming form.
modify structure specification the <command>s are applied to
the names exported
by <structure> to produce a new set of names for the <structure>'s
Expose makes only the listed names visible.
Hide makes all but the listed names visible.
Rename makes each <name>0 visible as <name>1
name and not visible as <name>0 , while
alias makes each <name>0 visible as both <name>0
Prefix adds <name> to the beginning of each exported name.
The modifiers are applied from right to left. Thus
makes(modify scheme (prefix foo/) (rename (car bus))))
The package's body is specified by begin and/or files clauses. begin and files have the same semantics, except that for begin the text is given directly in the package definition, while for files the text is stored somewhere in the file system. The body consists of a Scheme program, that is, a sequence of definitions and expressions to be evaluated in order. In practice, we always use files in preference to begin; begin exists mainly for expository purposes.
A name's imported binding may be lexically overridden or shadowed by defining the name using a defining form such as define or define-syntax. This will create a new binding without having any effect on the binding in the opened package. For example, one can do (define car 'chevy) without affecting the binding of the name car in the scheme package.
Assignments (using set!) to imported and undefined variables are not allowed. In order to set! a top-level variable, the package body must contain a define form defining that variable. Applied to bindings from the scheme structure, this restriction is compatible with the requirements of the Revised5 Scheme report.
It is an error for two of a package's opened structures to export two different bindings for the same name. However, the current implementation does not check for this situation; a name's binding is always taken from the structure that is listed first within the open clause. This may be fixed in the future.
File names in a files clause can be symbols, strings, or lists (Maclisp-style "namelists"). A ".scm" file type suffix is assumed. Symbols are converted to file names by converting to upper or lower case as appropriate for the host operating system. A namelist is an operating-system-independent way to specify a file obtained from a subdirectory. For example, the namelist (rts record) specifies the file record.scm in the rts subdirectory.
If the define-structure form was itself obtained from a file, then file names in files clauses are interpreted relative to the directory in which the file containing the define-structure form was found. You can't at present put an absolute path name in the files list.
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Table of contents
The specific three dimensional arrangement of atoms in molecules is referred to as molecular geometry. We also define molecular geometry as the positions of the atomic nuclei in a molecule. There are various instrumental techniques such as X-Ray crystallography and other experimental techniques which can be used to tell us where the atoms are located in a molecule. Using advanced techniques, very complicated structures for proteins, enzymes, DNA, and RNA have been determined. Molecular geometry is associated with the chemistry of vision, smell and odors, taste, drug reactions and enzyme controlled reactions to name a few.
Molecular geometry is associated with the specific orientation of bonding atoms. A careful analysis of electron distributions in orbitals will usually result in correct molecular geometry determinations. In addition, the simple writing of Lewis diagrams can also provide important clues for the determination of molecular geometry. Click on a picture to link to a page with the GIF file and a short discussion of the molecule.
Valence Shell Electron Pair Repulsion (VSEPR) theory
Electron pairs around a central atom arrange themselves so that they can be as far apart as possible from each other. The valence shell is the outermost electron-occupied shell of an atom that holds the electrons involved in bonding. In a covalent bond, a pair of electrons is shared between two atoms. In a polyatomic molecule, several atoms are bonded to a central atom using two or more electron pairs. The repulsion between negatively charged electron pairs in bonds or as lone pairs causes them to spread apart as much as possible.
The idea of "electron pair repulsion can be demonstrated by tying several inflated balloons together at their necks. Each balloon represents an electron pair. The balloons will try to minimize the crowding and will spread as far apart as possible. According to VSEPR theory, molecular geometry can be predicted by starting with the electron pair geometry about the central atom and adding atoms to some or all of the electron pairs. This model produces good agreement with experimental determinations for simple molecules. With this model in mind, the molecular geometry can be determined in a systematic way.
Molecules can then be divided into two groups:
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I am asking for help in basic Prolog, a language whose paradigms are difficult for me to grasp. I am very familiar with other languages (C++, Lisp, Java, Assembly, etc.) but am a complete novice with Prolog.
What needs to be solved - in basic English: given 2 parameters, find a corresponding number in a 2D Array.
The problem is a brainlessly easy puzzle on the web which asks you to pick a number, choose that number's color and then pick the house that contains your given number. The puzzle is set up such that there is only one number for each corresponding color/house combination.
What is currently in place:
function guess(Color, Houses) :- <--Need what goes here --> green(1, 15, 23, 24). pink(2, 6, 10, 18). etc... houseA(2, 4, 7, 14). etc...
The code must match the colors and houses to pick out the correct number. So for example, given
"?- guess(pink, houseA)" should return
"Your number is 2."
I have been writing down ideas on how to implement this in prolog and none of them get me any further. I do not know how I would implement if/else statements to check which color I should search, or how to check which numbers would correspond between house and color, or even how to "return" values!
It seems to me that I am missing a key point or...way of thinking about the language.
Any help would be appreciated. Thank you! | <urn:uuid:3277479c-8fca-4640-a8c1-4bf388f8cf71> | 2.921875 | 329 | Q&A Forum | Software Dev. | 78.830577 |
A BK-Tree is a really cool data structure for building a “dictionary” of similar words. It can be used to guess that you meant “cat” when you wrote “cta”. It works by building a tree with words from a dictionary by using the first word as a root node and then attaching subsequent words with a branch of length d(root_word, new_word) where d is a function for finding the “distance” between two words. This is usually the Levenshtein_ distance, i.e. the minimum number of edits needed to transform one string into the other.
If the branch is “taken”, i.e. there is already another word connected along a branch of length d(root_word, new_word), the insert operation is done on this word instead. That is the whole algorithm for constructing the BK-tree.
So if we have the following list of words:
["cat", "cut", "hat", "man", "hit"], we will start by creating a “cat” node with no children. To add “cut” we calculate the Levensteinh distance to be one and insert it under the “cat” node.
The query algorithm is also simple: We find the distance d from the query word to the root node. If this is less than the maximum distance we allow, n, we include this word in the result. We then find all the child nodes connected by branches of length (d-n) ≤ l ≤ (d+n) and recursively query these nodes and add to the result. The result is a list of words satisfying d(query_word, word) ≤ n.
The following code is a Haskell implementation of BK-Trees.
import qualified Data.Map as M import Control.Applicative import Data.Maybe (mapMaybe) -- A BK-Tree is has a root word and more trees connected to it with branches of -- lengths equal to the Levenshtein distance between their root words (i.e. an -- n-ary tree). data BKTree s = BKTree s (M.Map Int (BKTree s)) | Empty deriving (Show) -- Inserting a word is done by inserting it along a branch of lenght -- [Levenshtein distance] between the word to be inserted and the root. If -- there is a child node there, change focus to that child and continue the -- operation. insertWord :: BKTree String -> String -> BKTree String insertWord Empty newWord = BKTree newWord M.empty insertWord (BKTree rootWord ts) newWord = case M.lookup d ts of Nothing -> BKTree rootWord (M.insert d (BKTree newWord M.empty) ts) Just c -> BKTree rootWord (M.adjust (flip insertWord $ newWord) d ts) where d = levenshtein rootWord newWord -- Querying the tree consists of checking the Levenshtein distance for the -- current node, then recursively checking all child nodes connected with a -- branch of length [(d-n),(d+n)] query :: Int -> String -> BKTree String -> [String] query n queryWord (BKTree rootWord ts) = if d <= n then rootWord:ms else ms where -- Levenshtein distance from query word to this node's word d = levenshtein rootWord queryWord -- find child nodes in the range [(d-n),(d+n)] ... cs = mapMaybe (`M.lookup` ts) [(d-n)..(d+n)] -- ... recursively query these child nodes and concatenate the results ms = concatMap (query n queryWord) cs -- Levenshtein distance calculation function taken from -- en.wikibooks.org/wiki/Algorithm_Implementation/Strings/Levenshtein_distance levenshtein :: (Eq t) => [t] -> [t] -> Int levenshtein sa sb = last $ foldl transform [0..length sa] sb where transform xs@(x:xs') c = scanl compute (x+1) (zip3 sa xs xs') where compute z (c', x, y) = minimum [y+1, z+1, x + fromEnum (c' /= c)] ask :: BKTree String -> IO () ask bk_tree = do putStrLn "Enter query word: " queryWord <- getLine putStrLn "Enter max distance: " dist <- read <$> getLine print $ query dist queryWord bk_tree ask bk_tree main :: IO () main = do -- read dictionary file, skipping comments dic <- (filter (not . comment) . lines) <$> readFile "dictionary.txt" -- build BK-Tree let bk_tree = foldl (insertWord) Empty dic ask bk_tree where comment = True comment ('#':_) = True comment _ = False
It even works! Here are a few examples where I used a dictionary of ~5800 words:
λ> query 1 "thie" bk_tree ["tie","the","this","thief"] λ> query 1 "catt" bk_tree ["cat","cart"] | <urn:uuid:dc997d4a-7ee9-449c-97cb-7fed755871b1> | 3.59375 | 1,164 | Documentation | Software Dev. | 75.153218 |
Algae biofuel is something that is currently receiving lot of attention and many consider this as one of the most promising biofuel technologies that should in years to come significantly reduce our dependence on fossil fuels.
It is not very difficult to spot the advantages of using algae biofuel. Algae biofuel can decrease the need for fossil fuels, and expensive foreign oil, it can reduce our carbon footprint, and make our environment healthier by decreasing the climate change impact. Also, with the future development of renewable energy sources such as algae biofuel, air pollution resulting from fossil fuels burning and (upcoming) energy crisis resulting from the exhaustion of natural resources would no longer present such an imminent threat. However this would require using algae biofuel on massive scale.
Harvesting algae to manufacture algae biofuel can be a rather challenging process. Collecting algae involves the process of separating it from its growing medium which alone is connected with some difficulties. Afterwards, the algae must be dried and only then we can transform them into biofuel. Also, there are many different algae species, meaning that some species require different conditions that need to be developed prior to harvesting. The drying of algae is vital component in the harvesting process, and this also requires special conditions.
Oil extraction from algae is a much debated topic because it is currently connected with significant costs. In theory this process could not be easier, just harvest the algae and remove the oil from it, but the reality gets much more complicated once you include costs of this process. The mechanical method and the chemical method are the two most common methods used to extract oil from algae.
Like with any other energy source we also need to discuss possible environmental impact of algae biofuel, whether it is a positive or negative. The environmental effects of extracting oil from algae are also quite controversial topic because some environmentalists do not think they are environmentally friendly source of energy. These negative opinions are mostly connected with solvents used to extract oil as they can if not treated properly harm not only our environment, but can also have negative impact on human health. This is the main reason why science is working hard to come up with the environmentally friendly extraction processes but so far the possible solutions have not been acceptable from the economic point of view, because of the high costs, which does not support commercial component of mass production.
What this means is that although algae biofuel is one of the most promising biofuel alternatives currently being researched, it is still far from reaching a level where it will be both economically viable, as well as environmentally friendly source of energy. This means that science still needs to provide answers to these issues, and improve environmental as well as economic component of algae biofuel.
Those are serious setbacks but these setbacks should serve as a great motivation for us to work harder, and devote our resources and expertise to overcome these challenges, and create algae biofuel that would not be connected with negative environmental impact, and in the same time making extraction less costly. The need for renewable energy sources is more than obvious, and each renewable energy source with big enough potential needs more attention, Algae biofuel is definitely one of the potential answers to cut our dependence on fossil fuels.
You can read the following article if you want to learn more about algae biofuel: Biofuel production from algae. | <urn:uuid:36354d91-4836-42fa-aeb2-63e44aef4d6b> | 3.53125 | 665 | Personal Blog | Science & Tech. | 24.528304 |
Grismer organized this summer’s multi-nation animal-sleuthing trip and departed for Cambodia’s jungles determined to lead the group despite suffering an excruciating back fracture during a weight-lifting exercise a few weeks prior to the journey.
His sacrifices were rewarded and his push for jungle preservation bolstered. The trek produced 58 frog, toad, lizard and snake species and data that indicated an extended range for an amazing frog with green blood and turquoise bones as well as for a legless, blind lizard species. “This adds a huge body of data to the conservation efforts in the Phnom Samkos Wildlife Sanctuary,” Grismer said. “This will help the Ministry of the Environment generate funds to support efforts to keep out the loggers. It adds to the reasoning of why the area needs to be protected.”
Grismer will return to Cambodia in March to collect the specimens from the Natural History Museum at the Royal University of Phnom Penh. He and his students will analyze the specimens at La Sierra and publish their findings in the Cambodian Journal of Natural History. During that trip he plans to explore islands off the southern coast of Cambodia, a region formerly utilized by the Khmer Rouge and so remote no scientists have been there, Grismer said. It took three years to acquire the government’s permission to enter the area, he said.
Why save the lizard?
Grismer’s hazardous field research supports his calling and cause, his reason for enduring the danger, dirt, fatigue and pain involved in discovering new creatures and new behavioral patterns; he uses the species documentation to help save pristine portions of Planet Earth from ever-encroaching development, and to educate the public on the importance of preserving the chain of life.
“The issue is, if we knowingly let some little lizard go extinct, we’re sending an unmistakable message to governments and lay people that letting some species go extinct is acceptable,” he said. If certain key species are allowed to die out, it could disrupt major ecosystems and in so doing, destroy communities, said Grismer. “The general public has real concerns about extinction and unfortunately some scientists are giving only party-line answers.”
Grismer lays out the argument in the March 2011 edition of the Malaysian Naturalist in an article titled “Reptiles Go Extinct …Does it Affect Us?” Grismer writes, “Species, any species (and some more than others), are worth protecting at least on principle alone. …If we allow the extinction of selected species then where do we draw the line? Who decides which species stay and which are expendable? What criteria are used to decide this?”
Conservation in Southeast Asia is still emerging and is reliant on scientific data for its advancement. “We’re at the front line right now discovering new species and earmarking new locations that will need to be afforded protection soon,” said Quah. “I cannot stress enough the importance of the data that Dr. Grismer and his other colleagues are collecting in the field. We’re only beginning to find out what is out there and this is all invaluable data that will help us build baseline data for future work for the conservation of these species.” | <urn:uuid:15256ce9-ae81-4c7e-9026-a91c46babcf2> | 2.78125 | 688 | Knowledge Article | Science & Tech. | 41.847458 |
The principle of the Three-Way-Alignment is to build up a multiple alignment by
constructing a tree and aligning sequences and pre-aligned
groups of sequences simultaneously:
Given N sequences and assume, that there is a tree topology for sequences and a multiple alignment for n sequences coupled to the tree, i.e n=5:
Each edge of the tree is tested for an insertion of a new sequence, i.e. test edge e:
For an insertion of a sequence in edge e, a three-way-alignment between
the following groups of sequences is computed
- The aligned sequences on the left of e
- The aligned sequences on the right of e
- the new sequence
The three-way alignment implies new edge weights and therefore a new path length
for the complete tree:
In order to keep the amount of evolution as small as possible,
one chooses the topology resulting in the smallest path length.
In the example an alignment of n+1 sequences now is coupled with a tree
topology for six sequences:
and a new sequence may be inserted...
When constructing a multiple alignment iteratively in this way,
a correction of positions in the profile alignments is possible.
For a more detailed view on the subject, have a look at the paper
of Vingron and v. Haeseler. | <urn:uuid:60c89eae-5fae-4a75-8c11-1d7750035d6e> | 3.015625 | 284 | Tutorial | Science & Tech. | 48.242116 |
The reasons for the design of RTLinux can be understood by examining the working of the standard Linux kernel. The Linux kernel separates the hardware from the user-level tasks. The kernel uses scheduling algorithms and assigns priority to each task for providing good average performances or throughput. Thus the kernel has the ability to suspend any user-level task, once that task has outrun the time-slice allotted to it by the CPU. This scheduling algorithms along with device drivers, uninterruptible system calls, the use of interrupt disabling and virtual memory operations are sources of unpredictability. That is to say, these sources cause hindrance to the realtime performance of a task.
You might already be familiar with the non-realtime performance, say, when you are listening to the music played using 'mpg123' or any other player. After executing this process for a pre-determined time-slice, the standard Linux kernel could preempt the task and give the CPU to another one (e.g. one that boots up the X server or Netscape). Consequently, the continuity of the music is lost. Thus, in trying to ensure fair distribution of CPU time among all processes, the kernel can prevent other events from occurring.
A realtime kernel should be able to guarantee the timing requirements of the processes under it. The RTLinux kernel accomplishes realtime performances by removing such sources of unpredictability as discussed above. We can consider the RTLinux kernel as sitting between the standard Linux kernel and the hardware. The Linux kernel sees the realtime layer as the actual hardware. Now, the user can both introduce and set priorities to each and every task. The user can achieve correct timing for the processes by deciding on the scheduling algorithms, priorities, frequency of execution etc. The RTLinux kernel assigns lowest priority to the standard Linux kernel. Thus the user-task will be executed in realtime.
The actual realtime performance is obtained by intercepting all hardware interrupts. Only for those interrupts that are related to the RTLinux, the appropriate interrupt service routine is run. All other interrupts are held and passed to the Linux kernel as software interrupts when the RTLinux kernel is idle and then the standard Linux kernel runs. The RTLinux executive is itself nonpreemptible.
Realtime tasks are privileged (that is, they have direct access to hardware), and they do not use virtual memory. Realtime tasks are written as special Linux modules that can be dynamically loaded into memory. The initialization code for a realtime tasks initializes the realtime task structure and informs RTLinux kernel of its deadline, period, and release-time constraints.
RTLinux co-exists along with the Linux kernel since it leaves the Linux kernel untouched. Via a set of relatively simple modifications, it manages to convert the existing Linux kernel into a hard realtime environment without hindering future Linux development. | <urn:uuid:5008b5c0-4d71-4fe4-b252-9e85b0663d0e> | 3.796875 | 579 | Tutorial | Software Dev. | 33.06351 |
I walk 1km up the hill at 4km/h and 1km down the hill at 6km/h.
What is my mean speed?
Average speed (ie mean speed) is defined as "total distance travelled" divided by "time to travel the distance." (It is a common error to find two speeds and take a geometric average.) We know the distance, we need to find the time.Originally Posted by Natasha1
So the average speed for the round trip will be: | <urn:uuid:26066222-c8d5-464c-bd96-780e4370d9c7> | 3.03125 | 101 | Q&A Forum | Science & Tech. | 72.777923 |
Helm and Gwinner searched for signs of migratory behavior in two subspecies of stonechats, Saxicola torquata, comparing a migrant that breeds in Austria, S. t. rubicola, and its equatorial resident relative, S. t. axillaris. European stonechats are short-distance, nocturnal migrators that begin their journey when daylight lasts just over 12 hours. Since they would otherwise be sleeping at night, nocturnal activity can serve as a proxy for Zugunruhe. African stonechats are sedentary species that do not abandon their breeding grounds in Kenya. To investigate the presence of Zugunruhe in a resident species, the researchers raised and bred the offspring of Kenyan stonechats in their lab in Germany. One group of these birds was held for the duration of a migratory period under the nearly equal light and dark conditions of their native habitat, and a subset remained under these conditions for a year and a half. A control group was exposed to the natural seasonal light fluctuations of southern Germany. Helm and Gwinner recorded the birds' nocturnal movements with infrared motion sensors, and counted the number of movements within ten-minute intervals. If 20 or more movements were noted, the interval was considered "active."
Even though the African stonechats experienced no temporal cues--light levels remained constant--their nocturnal activity roughly tracked the season. The
Contact: Paul Ocampo
Public Library of Science | <urn:uuid:f464db8a-a5e0-4410-a6e7-bd90e2a4f38c> | 3.9375 | 303 | Truncated | Science & Tech. | 34.366155 |
Siple Dome Ice Core Age-Depth Scales
This data set is part of the WAISCORES project, an NSF-funded project to understand the influence of the West Antarctic ice sheet on climate and sea level change. WAISCORES researchers acquired and analyzed ice cores from the Siple Dome, in the Siple Coast region, West Antarctica.
Nereson's 'Age Versus Depth' plot shows the results of the calculations published in her paper on predicted age-depth scales (Nereson, N.A., E.D. Waddington, C.F. Raymond, and H.P. Jacobson. 1996. Predicted Age-Depth Scales for Siple Dome and Inland WAIS Ice Cores in West Antarctica.Geophys. Res. Let., 23(22): 3163-3166.).
The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.
Nadine Nereson. 2003. Siple Dome Ice Core Age-Depth Scales. [indicate subset used]. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5T151KD. | <urn:uuid:9c12db18-2aa8-4c4d-8c8f-e98a6a39a3c8> | 3.046875 | 262 | Knowledge Article | Science & Tech. | 65.461145 |
Klotzbach, P. J., R. A. Pielke, Sr., R. A. Pielke, Jr., J. R. Christy, and R. T. McNider (2009), An alternative explanation for differential temperature trends at the surface and in the lower troposphere, J. Geophys. Res., 114, D21102, doi:10.1029/2009JD011841. Link
This paper investigates surface and satellite temperature trends over the period from 1979 to 2008. Surface temperature data sets from the National Climate Data Center and the Hadley Center show larger trends over the 30-year period than the lower-tropospheric data from the University of Alabama in Huntsville and Remote Sensing Systems data sets. The differences between trends observed in the surface and lower-tropospheric satellite data sets are statistically significant in most comparisons, with much greater differences over land areas than over ocean areas. These findings strongly suggest that there remain important inconsistencies between surface and satellite records. | <urn:uuid:c74f3217-9055-408f-95f5-ea02a9bfed74> | 2.78125 | 205 | Academic Writing | Science & Tech. | 48.3 |
Montage: Neptune and Triton
NASA – This computer generated montage shows Neptune as it would appear from a spacecraft approaching Triton, Neptune’s largest moon. The wind and sublimation eroded south polar cap of Triton is shown at the bottom of the Triton image, a cryovolcanic terrain at the upper right, and the enigmatic “cantaloupe terrain” at the upper left. Voyager 2 flew by Triton and Neptune on Aug. 29, 1989.
- Amazon River exhales virtually all carbon taken up by rain forest
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- How Dreamworks, LinkedIn and Google Build Intrapreneurial Cultures
- Updates from Congressman Sandy Levin
- 2010 April
- 10 things you may not know about Ethernet
- Space Shuttle Update (45)
- Updates from Congressman Jim Jordan
- China’s cyberwar
- Single-photon emitter for quantum cryptography | <urn:uuid:a196c7cb-6df2-47e6-89d8-cbbf7e554bc5> | 2.890625 | 210 | Content Listing | Science & Tech. | 33.645053 |
Web Servers and Python
Python-based Web servers have been available in the standard library for many years (see the BaseHTTPServer, SimpleHTTPServer and CGIHTTPServer modules). To address various issues of scalability, robustness and convenience with such existing servers, other server frameworks and solutions have been developed since that time.
Web Servers written in Python
Twisted includes a very scalable web server written in Python.
Rocket - a pure python HTTP server for WSGI applications and static files which runs on cPython 2.5-3.x and Jython 2.5
Spawning - a WSGI server which supports multiple processes, multiple threads, green threads, non-blocking HTTP io, and automatic graceful upgrading of code.
Web Servers embedding Python
In addition to the above, some non-Python-based Web servers support Python-based applications by embedding the Python virtual machine for improved performance:
mod_wsgi embeds Python in the Apache HTTP server
ModPython embeds Python in the Apache HTTP server
PyWX embeds Python in AOLServer
Nginx WSGI support module for Nginx HTTP server
Modjy embeds a jython interpreter in Java Servlet containers, e.g. Tomcat, Glassfish, Websphere, etc, and supports WSGI. Distributed with jython since March 2009.
Standard Library Technologies
BaseHTTPServer (along with successors such as DocXmlRpcServer) can be considered as the original Python Web framework, but it really just provides the ability to process HTTP requests and to generate responses using a relatively primitive API. Some WebFrameworks use it as the basis for serving content, however. | <urn:uuid:1a6e35bf-66a4-4e9d-99bd-d1ba78d383f0> | 2.71875 | 351 | Knowledge Article | Software Dev. | 32.508918 |
Events in August 1945 and thereafter have revealed that mathematics holds one of the most important keys to the future of the human race. The common man is curious to know how and why the science of numbers plays this basic role. The Main Stream of Mathematics attempts to appease this curiosity.
Modern Mathematics with its ramifications into every conceivable area of thought is like a tree. We shall mount, climb out on a few sturdy limbs, return to the trunk, ascend a little higher, then branch out once more. Most of our time will be spent exploring the branches, which will support us between the periodic intervals of rising on the trunk. Since we are not climbing on a dare or running a race, but are engaged in our activities for pleasure, we shall, in human fashion, look outside and beyond. We shall not attempt to reach the summit or to venture out to every twig and leaf, for that would require a profound and monumental treatise.
Answers to questions like the following are simple and will be found in this volume:
A special feature of the book is the historical or legendary material, which has been included both to show the evolution of science, and because the facts are so full of surprises. There are few who do not know Einstein as a mathematician, but how many have heard of Hilbert? Again, most laymen have never read a word about the Hindu mathematicians whose influence on our daily lives is probably greater than that of Henry VIII or Napoleon. In a few instances we have combined fiction with fact in narrating biographical incidents. The men of mathematics come alive in association with their surroundings. It is surprising that they have almost never figured in historical fiction.
We shall, of course, discuss ordinary arithmetic and algebra. Our objective, however, will be to examine their relationship to other systems of numeration and symbolism, systems that have some factors in common with the everyday species but diverge in ways rendering them more suitable for certain scientific applications. Geometry will be considered at first in relation to art and the inspiration of art—nature itself—leaving the notion of pure geometry for a later chapter. Trigonometry as a tool can stand some de-emphasis in favor of its characteristic of mirroring the eternal periodicity of nature. Statistics is no longer glorified bookkeeping but a means of testing hypotheses, controlling industrial processes, and describing the nature of matter. Calculus concepts, freed of manipulative detail, are within the reach of all.
Relativity is a natural climax to mathematical discussions. Today a comprehensible outline of this subject can be offered to the layman—yet less than fifty years ago it had been mastered by only a handful of savants. The man in the street can even gain some understanding of the objectives of Einstein's new unified field theory. Finally, we must touch on a major issue of mathematical philosophy—the infinite, with is intriguing paradoxes and its inevitable association with the most profound problems of modern mathematics.
At this point, I should like to express my gratitude to the late John A. Swenson for being the first to stimulate in me a love of mathematics and a desire to undertake a mathematical career. Throughout his lifetime he acted as a source of inspiration.
Table of Contents | <urn:uuid:02501c97-c513-481b-856e-a9afc9763da3> | 3.234375 | 652 | Academic Writing | Science & Tech. | 36.679493 |
As mentioned in the introduction to this chapter, the themes that are discussed as relevant for the development of ecosystem based management can be of three different types:
- Instances where impact of human activities on the ecosystem has been demonstrated or is likely
- Instances where there is a risk for such impact from future activities
- Instances where there is no significant impact in the ecosystem but it has been shown or might be expected that the situation deviates from goals that we can expect that an ecosystem based management plan will have
Examples of such goals are listed in the introduction of this chapter.
It should be emphasized that although the summary given below covers many of the most relevant themes, it should not be considered a complete list. Rather, the highlighted themes should be looked upon as both a significant part of the basis for ecosystem-based management in the Barents Sea as well as important examples that illustrate how the contents of this report may be used to further ecosystem-based management in the area. Some issues that are clearly relevant have not been discussed, such as the concept of vulnerable and valuable areas, which is important in the management plan for the Norwegian part of the Barents Sea. The need for specific attention to risks for the loss of biodiversity and needs for protective measures for threatened species of arctic endemics within the region are examples of other relevant issues that have not been discussed in this chapter.
The themes are sorted to the categories listed above. Some of the themes may not be easily classified to one of the categories. This is commented where it is relevant. | <urn:uuid:e1a91dcc-febb-41c5-84bf-9900fbc8c1d9> | 3.1875 | 317 | Content Listing | Science & Tech. | 20.34825 |
Simply begin typing or use the editing tools above to add to this article.
Once you are finished and click submit, your modifications will be sent to our editors for review.
characteristics of flow
Mafic (ferromagnesian, dark-coloured) lavas such as basalt characteristically form flows known by the Hawaiian names pahoehoe and aa (or a’a). Pahoehoe lava flows are characterized by smooth, gently undulating, or broadly hummocky surfaces. The liquid lava flowing beneath a thin, still-plastic crust drags and wrinkles it into tapestry-like folds and rolls resembling twisted...
...common products of the Earth’s volcanoes. There are two major types of lava flow, referred to around the world by their Hawaiian names: pahoehoe, a more fluid flow with a smooth to ropy surface; and aa (or a’a), a more viscous flow whose surface is covered by thick, jumbled piles of loose, sharp blocks. Both types have the same chemical composition; the difference seems to be in the eruptive...
...important in determining the character of lava flows. For example, hot basaltic lava produces flows with smooth to ropy surfaces. These flows, known as pahoehoe, tend to flow farther than the cooler aa flows of the same chemical composition that have rough, broken surfaces.
What made you want to look up "aa"? Please share what surprised you most... | <urn:uuid:9e4ef7ac-450f-48d9-90ff-1b331bd20d54> | 3.375 | 314 | Knowledge Article | Science & Tech. | 53.313909 |
1/4x - 5/12x = x - 4/3 Please show steps and answer. Thanks.
If g(x)= -2^2 and h(x)=x-2/5. Find the indicated value. h(g(5)) I got -5.4. is that right?
How many grams are in one milliliter?
How do you solve this problem? 3/5k - (k + 1/3) = 1/15 (k + 3) Please show me the steps. Thanks.
In my book the anser for D is 2.68 x 10^4 mg/L as CaCO3, my first thought was to do what you did but i cant get to the answer in the book, am I missing something very obvious here? Im getting like 5.4 x 10^4
4(3)+4(3) *4 *4 --------- 12+12=24
A museum curator moves artifacts into place on many different display surfaces. Use the values in Table 4-2 in the textbook to find Fs,max and Fk if you were to move a 157 kg aluminum sculpture across a horizontal steel platform. Fs,max: Fk:
Are (1/2 x 3) x 8 and 3 x (1/2 x 8) equal? Explain how this can help in finding the area of a triangle
I need to variables would equal 180 by being divided by 1/2
For Further Reading | <urn:uuid:eb5663ba-52b2-4ecd-9f17-5518532d4c93> | 3.25 | 308 | Comment Section | Science & Tech. | 111.759166 |
Treasure Hunting on the Moon: LRO and the Search for Water
A bottle of one of the most expensive brands of water costs $40, and is presented in a frosted glass container decorated with crystal. On the moon, a bottle of water would run about $50,000, and forget about that heavy crystal glass. That's because it costs around $50,000 per pound to launch anything to the moon. Discovering water on the moon would be like finding a gold mine.
In fact, scientists have discovered evidence for water or hydrogen, a component of water, in special places on the moon. Since the moon is not tilted much from its rotation axis, the depths of certain craters in the lunar poles may not have seen the sun for billions of years. The long night over these areas, called Permanently Shaded Regions (PSRs), will have made them very cold, and able to trap hydrogen or water molecules as ice.
However, with almost no atmosphere, most of the moon is drier than the driest terrestrial desert. How could water get on the moon in the first place? Some scientists believe water vapor from past comet impacts has migrated across the lunar surface to the poles to become embedded in the soil at the bottom of these dark craters. Others believe hydrogen was also embedded in the lunar soil in these polar cold traps over time. The hydrogen comes from the sun and is carried to the moon by the solar wind, a thin gas that's continuously blowing off of the solar surface and fills the entire solar system. Most of the solar wind is hydrogen.
"Both methods may have contributed to polar hydrogen or ice deposits," said Dr. Richard Vondrak of NASA's Goddard Space Flight Center in Greenbelt, Md. Vondrak is project scientist for NASA's Lunar Reconnaissance Orbiter, or LRO. Among its many missions, the spacecraft will help identify the most likely places to find hydrogen or ice deposits on the moon.
Lunar water could be used for more than just drinking. It could be broken down into hydrogen and oxygen for use as rocket fuel and breathable air. Even sufficient concentrations of hydrogen by itself would be valuable because it could be used as fuel or combined with oxygen from the soil to make water.
With launch costs so high, it will be much cheaper to mine the moon for hydrogen or ice than to haul water up from Earth. Naturally, this assumes there's enough of this resource there, and it's technically feasible to mine. As useful as lunar water deposits would be, without evidence that they exist, they are just wishful thinking by mission planners.
Clementine, a small probe launched by NASA and the U.S. Department of Defense in 1994, gave the first piece of evidence. The probe directed a radio transmitter toward the lunar polar regions, and antennas at Earth picked up the reflections. "The Clementine scientists said the signal indicated the presence of ice, but others questioned that interpretation, claiming rough ground could give the same signal," said Vondrak.
More evidence came in 1998 from NASA's Lunar Prospector mission. The measurement used the presence of hydrogen as a sign of potential ice deposits. The moon is constantly hit by cosmic rays, particles moving at almost the speed of light that come from explosions on the sun and in space. These particles strike the lunar soil and, like the break at the start of a pool game, create a shower of other particles. Neutrons, a component of the center of atoms, are among these particles, and some fly back out into space.
These neutrons were detected by an instrument on Lunar Prospector. The neutrons scattered back into space normally have a wide range of speeds. However, if the neutrons hit hydrogen atoms in the lunar soil before being ejected into space, the impact will quickly slow them down.
"A neutron has about the same mass as a hydrogen atom, so when they collide, the neutron loses most of its speed instantly, just as the collision between a speeding cue ball and another billiard ball often leaves the cue ball standing still," explains Vondrak.
As Lunar Prospector scanned the lunar surface, its neutron counters recorded the number of neutrons moving at speeds in the middle of the range. Over the polar regions, the counters detected a decrease in the number of neutrons moving at mid-range speeds. This meant that many neutrons were being suddenly slowed by impacts with hydrogen, so there is probably a concentration of hydrogen or even water ice somewhere in the lunar poles.
However, the measurements could not tell whether the deposits were hydrogen or ice, nor did they have the resolution to accurately locate the deposits within the polar zones. LRO will be able to do both.
LRO has a camera system with both wide-angle and high-resolution cameras, called the Lunar Reconnaissance Orbiter Camera (LROC). As LRO orbits over the poles, the moon rotates beneath the spacecraft, and the cameras will gradually build up a detailed picture of the region. Scientists using LROC will combine the images it takes during a year in orbit to make a movie that reveals the regions in permanent shadow (PSRs). These areas will be the most promising places to search for hydrogen or ice.
The spacecraft also has a neutron detector with much better resolution than Lunar Prospector's, called the Lunar Exploration Neutron Detector (LEND). The detector can locate hydrogen deposits to an area about 10 kilometers (about 6.2 miles) across. This is smaller than the estimated size of most PSRs.
LEND will be able to detect hydrogen or ice that's buried up to about a meter (3.2 feet) below the surface. The deposits are expected to be gradually buried by material thrown out from tiny micrometeorite impacts that constantly bombard the moon.
"This burial, called gardening, actually preserves the deposits, because otherwise they would be slowly liberated back into space by cosmic ray hits and ultraviolet light from stars," said Vondrak. "Of course, the deposits directly hit by the micrometeorite are vaporized, but the impact zone is a very tiny area -- deposits are more likely to be covered by impact material."
LRO's Diviner instrument measures temperature. It will be directed at the PSRs to see if they are really cold enough to trap hydrogen or water molecules for billions of years.
PSR temperature depends on the shape and depth of the craters. Although the bottoms may be in permanent shadow, the sun is likely to rise high enough to appear over the rims and illuminate the sides. Sunlight reflected from the sides could strike the bottom and warm it enough so that any ice would evaporate before it can be buried.
LRO includes a laser ranging system that will build an elevation map to show the contours of the polar craters. The instrument, called the Lunar Orbiter Laser Altimeter (LOLA), records the time it takes for a laser pulse to travel from the spacecraft to the lunar surface and back to calculate the height of the lunar terrain. After a year in orbit aboard LRO, LOLA will have created an elevation map of the polar regions that is accurate to within a half-meter (20 inches) vertically and 50 meters (about 160 feet) horizontally. It will be used to rule out craters with the wrong shape to store hydrogen or ice.
PSRs will, of course, be dark. The job of LRO's Lyman Alpha Mapping Project (LAMP) is to see in the dark. It is sensitive enough to make pictures of the crater depths using reflected light from stars and glowing interstellar gas (actually a specific type of ultraviolet light, called Lyman Alpha, which like all ultraviolet light is invisible to the human eye). Also, any ice on the surface of the PSRs will leave a distinct imprint in the reflected light, definitively revealing its presence.
An experimental radio transmitter and receiver on board LRO, called Mini-RF, also could detect ice deposits on the surface and beneath it as well. Ice deposits will change the reflected radio signal in a specific way, revealing their presence.
Finally, LRO has a companion spacecraft, called the Lunar Crater Observation and Sensing Satellite (LCROSS), which will be deliberately crashed into a polar crater. The resulting plume of material from the impact will be observed by LRO and telescopes on Earth for evidence of hydrogen or water.
There will actually be two chances to test for water this way, because there will be two impacts -- the first from the upper stage of the rocket that carried LRO and LCROSS to the moon, which also will be observed by LCROSS, and the second from LCROSS itself.
"Multiple instruments and spacecraft are the power of the LRO mission -- we can verify that water or hydrogen is there with several independent techniques," said Vondrak.
NASA's Goddard Space Flight Center | <urn:uuid:ea51f8c4-5d58-46a8-b971-c06862bedc6a> | 3.65625 | 1,826 | Knowledge Article | Science & Tech. | 46.219476 |
11:12 17 February 2010
From the tiny Anchiornis huxleyi to a feathered ancestor of Tyrannosaurus rex and the huge Gigantoraptor, Xu Xing's fossil finds have helped to unearth the evolutionary link between dinosaurs and birds.
Image 1 of 11
One of the first feathered dinosaurs ever uncovered, Beipiaosaurus was unearthed in 1997 by Xu Xing and colleagues near the city of Beipaio in Liaoning province, China. This “unexpected” find gave support to the theory that feathers were widespread in dinosaurs and that dinosaurs were the ancestors of modern birds.
(Image: Zhao Chuang and Xing Lida) | <urn:uuid:7a8bfeed-033c-4ebe-9991-c80dc553c56a> | 3.296875 | 143 | Truncated | Science & Tech. | 30.10945 |
The high-temperature superconductors known as Perovskites are a mixture of metal oxides which display the mechanical and physical properties of ceramics. YBaCuOx, (YBCO) is a very common Type II superconductor. A key element to the behavior of these materials is the presence of planes containing copper and oxygen atoms chemically bonded to each other. The special nature of the copper-oxygen chemical bond permits materials to conduct electricity very well in some directions. See Figure (15), a drawing of the molecular cell structure in YBaCuO.
Most ceramic materials are considered good electrical insulators. YBCO compounds, also known as 1-2-3 compounds, are very sensitive to oxygen content. They change from semiconductors at YBaCuO to superconductors at YBaCuO without losing their crystalline structure. The high sensitivity of superconductors to oxygen content is due to the apparent ease to which oxygen can move in and out of the molecular lattice. Using the standard valance charges for the metallic elements, one would expect a formula of YBaCuO. However, it has been found that these superconductors usually have more oxygen atoms than predicted. According to the formula, YBaCuO, the metals are in a mole ratio of 1-2-3.
YBaCuO was the first material found to be superconducting above liquid nitrogen temperature. It exhibits a very interesting and complex relationship between its chemistry, crystal structure and physical properties. A very subtle electronic charge balance exists between the one dimensional copper-oxygen chains, which have variable oxygen content, and the two dimensional copper-oxygen pyramidal planes, where superconductivity originates.
In oxygen deficient YBaCuO, oxygen is removed from the CuO chains. A 90 K superconductor is obtained for 0<× <0.2, a 60 K superconductor for 0.3<× <0.55, and an antiferromagnetic semiconductor for 0.55<× <1.0. These changes in T as a function of x are shown in Figure (16), a graph of T versus oxygen content.
Since perovskites are ceramics, the procedure for making them is very similar to making other ceramics. All that is needed is a mortal and pestle, a die cast mold,a well-ventilated kiln or furnace and the necessary chemicals. Oxides, carbonates, and nitrates are good sources for the metals needed to make YBCO. The following recipe for making YBCO superconductors allows ambitious and outstandingly competant readers to make their own superconductors. Excellent quality commercially produced superconductors may be purchased at very reasonable cost through various vendors.
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Standing on your tiptoes is hard enough, but imagine trying to do it while staying balanced on top of someone else's head. Or, just as difficult, imagine staying upright with someone standing on your head. To keep balanced, the Nanjing acrobats must be aware of their centers of mass, and the various forces—called torques—that might cause them to rotate and fall out of balance. In this unit, you'll learn how these two concepts make it possible for the acrobats to achieve their amazing acts of balance.
Watch the Video
Circus Physics: Center of Mass
Watch Jessica and Anan perform an acrobatic form of ballet. Such feats would be impossible without a strong understanding of center of mass.
Questions to Consider While Watching the Video
- How is the woman able to balance on the man?
- How is her balancing like a seesaw?
- Where is her center of mass as she balances?
- What happens when she becomes unbalanced?
- Why does the man move beneath her?
Here's a diagram of Jessica and Anan balancing:
To stay balanced, as in figure A, both acrobats must keep their centers of mass—CoM—above their points of support. For Jessica, the point of support is Anan's head. In Figure B, you can see what happens if her center of mass is not over Anan's head...she falls!
Figure C shows what happens if Anan's center of mass is no longer over his own point of support, his foot on the ground. If this happens, both acrobats fall.
When the center of mass is not over the point of support, a torque results. You can think of torque as similar to force, except that instead of causing linear acceleration, it causes rotational acceleration. In other words, torques cause objects to turn.
Just like for normal forces, there's a simple law that tells you how much effect a torque will have on an object's rotation:
T = Iα
T is the torque, I is the object's moment of inertia, a quantity that incorporates both mass, and distance from the pivot point. Finally, α is the rotational acceleration that results from the torque.
The reason Jessica keeps her arms outstretched and leg kicked back is that these extended limbs act as lever arms, generating balancing torques that keep her from tipping over. A good way to visualize how this works is to think about a seesaw.
Torque in these scenarios can be found by multiplying:
mass x gravity x distance to the pivot
In scenario A, the torque on both sides is mgL, so the people are balanced. In scenario B, the mass on the left side is the same as the right side but it is at half the distance, therefore the torque is greater on the right side and it rotates in that direction. In scenario C, the torque on the left side is 2mgL and mgL on the right. Now the torques are unbalanced in the opposite direction, so the see saw rotates the other way. In D, the mass on the left side is again doubled, but is only half as far from the pivot, so the torque is half that in C, thus the seesaw balances with no rotation.
Jessica and Anan sit on opposite sides of a 3 meter-long seesaw. If Jessica sits on the end of the seesaw and her mass is 55 kg, where must Anan, whose mass is 70 kg, sit to perfectly balance Jessica?
Answer: Anan must sit ≈1.18 meters from the pivot
Jessica creates a torque of 55kg x 1.5 meters—half the length of the seesaw. To balance, Anan must create an equivalent torque, but since he weighs more, he must sit at some distance, d, that is closer than 1.5 meters from the pivot.
Setting these two torques equal to each other gives:
(55kg) x (1.5m) = (70kg) x (d)
Solving for d, we get:
d = (55kg) x (1.5m) / (70kg) ≈ 1.18 meters)
If you'd like to learn more about balancing acts and center of mass, check out these links:
- scienceworld.wolfrom.com: Center of Mass
- Circopedia.org: Chinese Acrobatic Theater
- Circopedia.org: Nanjing Troup | <urn:uuid:335c3ec0-456d-4350-9582-51f517a7a1a1> | 3.625 | 941 | Tutorial | Science & Tech. | 68.506345 |
Nov. 13, 2010 Over the next century, recruitment of new corals could drop by 73 percent, as rising carbon dioxide levels turn the oceans more acidic, suggests a new study led by scientists at the University of Miami Rosenstiel School of Marine and Atmospheric Science. The research findings reveal a new danger to the already threatened Caribbean and Florida reef Elkhorn corals.
"Ocean acidification is widely viewed as an emerging threat to coral reefs," said Rosenstiel School graduate student Rebecca Albright. "Our study is one of the first to document the impacts of ocean acidification on coral recruitment."
Albright and colleagues report that ocean acidification could compromise the successful fertilization, larval settlement and survivorship of Elkhorn corals. The research results suggest that ocean acidification could severely impact the ability of coral reefs to recover from disturbance, said the authors.
Elkhorn coral, known as Acropora palmata, is recognized as a critical reef-building species that once dominated tropical coral reef ecosystems. In 2006, Elkhorn was included on the U.S. Endangered Species List largely due to severe population declines over the past several decades.
The absorption of carbon dioxide by seawater, which results in a decline in pH level, is termed ocean acidification. The increased acidity in the seawater is felt throughout the marine food web as calcifying organisms, such as corals, oysters and sea urchins, find it more difficult to build their shells and skeletons making them more susceptible to predation and damage.
Recent studies, such as this one conducted by Albright and colleagues, are beginning to reveal how ocean acidification affects non-calcifying stages of marine organisms, such as reproduction.
"Reproductive failure of young coral species is an increasing concern since reefs are already highly stressed from bleaching, hurricanes, disease and poor water quality," said Chris Langdon, associate professor at the Rosenstiel School and co-author of the study, published in the Proceedings of the National Academy of Sciences.
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The above story is reprinted from materials provided by University of Miami Rosenstiel School of Marine & Atmospheric Science.
- Rebecca Albright, Benjamin Mason, Margaret Miller, Chris Langdon. Ocean acidification compromises recruitment success of the threatened Caribbean coral Acropora palmata. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1007273107
Note: If no author is given, the source is cited instead. | <urn:uuid:f3cc73de-846b-43cc-a442-599e06daf1bc> | 3.453125 | 521 | Truncated | Science & Tech. | 24.550739 |
We are in the midst of a global extinction crisis. Biodiversity is in decline as species after species disappear. Some estimates predict that up to 50% of species will be committed to extinction by 2050. Other estimates claim the current rate of extinction may be 10,000 times the background rate. Many ecologists and conservationists have declared the current species decline the sixth great mass extinction.
A recent paper published in the journal Nature argues that our current estimates of species loss are based on a flawed model and tend to overestimate the magnitude of species decline. The paper has received plenty of attention, and has been heavily criticized by ecologists and conservation biologists. The paper is wrong, but it is wrong for the right reasons, and the criticisms it has garnered point to a gaping hole in our understanding of population dynamics. | <urn:uuid:39672ef8-44f1-4f4b-b2a8-e25fbda5ea75> | 3.3125 | 163 | Personal Blog | Science & Tech. | 37.240127 |
"Lost World" Yeti Crab Swarm
A camera-equipped submersible robot filmed species such as barnacles, crabs, anemones, and even an octopus, all of which are mostly colorless and live in utter darkness at depths of 7,875 feet (2,400 meters), according to a new study.
About 2,000 miles (3,200 kilometers) east of the southern tip of South America, "this is a new province of deep-sea life, something like a new continent, and it's a place we've been trying to [reach] for a long time," said study co-author Jon Copley, a marine biologist at the University of Southampton in the United Kingdom.
"It harbors some of the lushest abundance of life I have ever seen in the deep ocean," he said.
Jockeying for Position
Male yeti crabs (such as the one at right) are larger and stay closest to the vents to feed communities of bacteria on their hair-lined bellies.
Female yeti crabs stray farther away, into the vent field's cooler water, to protect tiny embryos lining their bellies.
"Unlike the other few species of yeti crab, which wave their arms or dance, these were mostly stationary, but did jockey for position in the warm water," Copley said.
The temperature of the water near the vents is on par with that of the warm tropics, he added.
Antarctic "Car Wash" Barnacles
Snake-like barnacles protrude from rocks in cooler waters near the yeti crab swarms.
At the barnacles' tips are diamond-like heads that appear to filter-feed organic matter floating through the deep-sea oasis.
"We nicknamed one mineral spire covered with these barnacles 'Car Wash,' because it looked like those spinning cylinders you see in a car wash," Copley said.
Black Smokers of the Lost World
These openings in the Earth's crust, called black smoker chimneys, can spew mineral-rich water as hot as 720 degrees Fahrenheit (382 degrees Celsius).
The minerals, including hydrogen sulfide, provide food for the bottom of the ecosystem's sunless food chain.
Surprisingly, the researchers did not find any shrimp, tubeworms, mussels, or other creatures typically found near hydrothermal vents.
"The new life we're seeing here gives us insights into how animals disperse and evolve in deep ocean," Copley said.
"We can say, OK, the same species here is found elsewhere, while these are missing, so what are the reasons? We can now ask those questions and test ideas."
Antarctic Anemones in the Pink
These pink anemones (pictured) likely represent a new species, and some are surprisingly large for anemones—roughly the size of a person's palm.
Like other anemones, the animals probably feed by capturing bits of food drifting through the water.
A more diverse array of animals was found along the southern end of the East Scotia Ridge, while the northern end was "rather stygian," Copley said.
"It's more rugged and quite challenging to navigate around," he said. "It's a mystery right now as to why the northern end isn't as lush as the southern."
One Tough Anemone
An unnamed long-tentacled anemone manages to eke out an existence at the fringes of the warm vents.
The average temperature of Antarctica oceans hovers around 29 degrees Fahrenheit (-1.5 degrees Celsius).
"When food is really scarce, animals evolve some remarkable adaptations for finding and catching a meal"-such as these long tentacles, Copley said.
All That Glitters
A slice of a hydrothermal vent chimney glitters with flecks of pyrite—also called fool's gold, a crystallized form of iron sulfide.
In addition to surveying marine life, researchers cut out pieces of the chimneys and hauled them back to the surface.
"It's important for us as biologists to know the chemistry of these vents," Copley said. "It can help explain why we see some species around particular areas and not others."
One of the rarest finds the team encountered was a 2-foot-long (0.6-meter-long) octopus.
Copley isn't sure what the octopus eats. But the team did manage to film the animals walking around on the sea floor in a weird fashion.
"The back four tentacles sort of shuffle like the treads of a tank, while the front four feel in front of the octopus," Copley said.
"We weren't able to collect any specimens—they were quick and rare—but they're quite possibly a new species." | <urn:uuid:aba5f487-81d1-40af-b335-d39b0062c37e> | 2.984375 | 1,006 | Knowledge Article | Science & Tech. | 51.195918 |
||It has been suggested that Ecoacoustics be merged into this article. (Discuss) Proposed since July 2012.|
Acoustic ecology, sometimes called ecoacoustics or soundscape studies, is the relationship, mediated through sound, between living beings and their environment. Acoustic ecology studies started in the late 1960s with R. Murray Schafer and his team at Simon Fraser University (Vancouver, Canada) as part of the World Soundscape Project. The original WSP team included Barry Truax and Hildegard Westerkamp, Bruce Davies and Peter Huse, among others. The first study produced by the WSP was titled The Vancouver Soundscape. The interest in this area grew enormously after this pioneer and innovative study and the area of acoustic ecology raised the interest of researchers and artists all over the world. In 1993, the members of the by now large and active international acoustic ecology community formed the World Forum of Acoustic Ecology.
Every three years since the WFAE's founding at Banff, Canada in 1993, an international symposium has taken place. Stockholm, Amsterdam, Devon, Peterborough, and Melbourne followed. In November 2006, the WFAE meeting took place in Hirosaki, Japan. Koli, Finland, was the meeting place of the latest WFAE world conference.
From its roots in the sonic sociology and radio art of Schafer and his colleagues, acoustic ecology has found expression in many different fields. While most have taken some inspiration from Schafer's writings, in recent years there have also been healthy divergences from the initial ideas. Among the expanded expressions of acoustic ecology are increasing attention to the sonic impacts of road and airport construction, widespread networks of "phonographers" exploring the world through sound, the broadening of bioacoustics (the use of sound by animals) to consider the subjective and objective responses of animals to human noise, including increasing use of the idea of "acoustic ecology" in the literature, and a popular in the effects of human noise on animals, with ocean noise capturing the most attention. Another important outcome of the evolution of acoustic ecology studies is soundscape composition.
List of works
"Dominion" by Barry Truax
"Dominion" takes listeners on an acoustic journey across Canada. The work begins with the firing of the Noon Gun in St. John's harbour in Newfoundland and continues westward, recording sounds such as the Peace Tower bell in Ottawa and the O Canada Horn in Vancouver, along the way. A 12-piece orchestra, representing the 10 provinces and then two territories, carries listeners through the work, along with the whistle of a Canadian Pacific Railway train, representing the railroad that first connected Canada over a century ago. Source: "Science of Sound", Canadian Geographic Online.
Acoustic Ecological Archeology
Marc E. Moglen (2007) recreated pre-historical Soundscapes (Acoustic Ecology) at University of California, Berkeley's Department of Anthropology, combining compositional techniques with site recordings for a non-diegetic piece in the virtual world of Second Life, on "Okapi Island". At the Center for New Media the acoustic ecological setting of the former jazz scene in Oakland, CA was developed for a virtual world setting.
"Soundmarks of Canada" by Peter Huse
"A composition recreating the acoustic profile of community sounds unique to Canadian locales, coast to coast". Source: Soundscapes of Canada.
See also
- Bernie Krause
- Lombard effect
- Marine mammals and sonar
- Fisheries acoustics
- Noise map
- "World Forum for Acoustic Ecology". Archived from the original on 11 December 2008. Retrieved 2008-12-17.
- "World Forum for Acoustic Ecology 2006, in Hirosaki, Aomori, Japan". November 2006. Retrieved 2008-12-17.
- "phonography.org". Archived from the original on 20 December 2008. Retrieved 2008-12-17.
- "Acoustic Ecology Institute" Online
- Acoustic Ecology and the Soundscape Bibliography compiled by Maksymilian Kapelanski for Leonardo/ISAST
- Bazilchuk, Nancy. 2007. Choral Reefs: An inexpensive device monitors ocean health through sound. Conservation 8(1).
- "An Introduction to Acoustic Ecology" written by Kendall Wrightson Online
- "Midwest Society for Acoustic Ecology" Online
- "New York Society for Acoustic Ecology" Online
- "Science of sound" Canadian Geographic Online
- Soundscape: The Journal of Acoustic Ecology, published by the WFAE Online
- "World Forum for Acoustic Ecology" Online
- "World Listening Project" Online | <urn:uuid:7bf2dee1-5e02-420c-99e0-005c4a9f587f> | 3.171875 | 975 | Knowledge Article | Science & Tech. | 27.510848 |
A typical galaxy contains much more matter than what we can actually see. In fact, the visible portion of a galaxy represents only about 5 to 10% of total mass of the galaxy. Many studies lead us to define the conclusion that the Universe abounds in matter that we cannot see. This unseen matter is called Dark Matter because either it does not emit light or its light emission is too dim for us to detect.
Normal matter, such as STARS, PLANETS, DUST and MOLECULES , is often called Baryonic Matter because its mass is primarily due to the combined mass of the protons and neutrons, which are combinedly called Baryons, it contains. The mass of electrons is neglected because the mass of an electron is so small relative to the mass of a proton or neutron. Some of the normal matter such as burned out stars and dim interstellar gas, is part of the dark matter in a galaxy.
However, according to various calculations, this dark normal matter is only a small part of the total dark matter. The rest is called Non Baryonic Dark Matter because it does not contain proton and neutrons. What it contains? We know only one member of this type of dark matter…..the neutrinos. | <urn:uuid:ad916a21-731a-4ca3-a4dd-d47b356f7e9a> | 4.0625 | 257 | Personal Blog | Science & Tech. | 56.690275 |
For an RC circuit (Vout across capacitor), the impulse response is:
h(t) = 1/RC * exp[-t/RC] * u(t), where u(t) is the unit step.
The transfer function of the circuit is:
H(s) = 1/RC * 1/(s + 1/RC)
Here, the the pole is at Re(s) = -1/RC, and Im(s) = 0. The location of the pole is dictated by the physical parameters of the circuit, namely the size of R and C.
What I don't follow is the validity of obtaining the frequency response:
We set Re(s) = 0, and Im(s) = jw
That way, we get:
H(jw) = 1/RC * 1/(jw + 1/RC)
1. It was Re(s) of the pole which told us about the physical parameters of the system (R and C) - how can we just set it to zero?
2. When we set s = jw, what is it that makes the sinusoid be applied to the input of the RC circuit, rather than be applied to some other node like in between R and C? | <urn:uuid:0fe0eb3d-cd3e-4024-a4d4-749d6a0f4dd5> | 3.390625 | 265 | Q&A Forum | Science & Tech. | 89.504773 |
A student web page designed by Sarah Redding and Jody Shields
The Minke whale, a member of the rorqual
whale family, is the smallest of all the baleen whales. Minke
whales grow up to 9 meters long and at full size weigh approximately
6 to 7 tonnes. Females are typically 1.5 meters longer than the males.
Minke whales are stocky, yet streamlined and slender looking,
dark gray on their back side and lighter shades underneath. They
have a distinctively triangular, narrow and pointed head, and
hence are often referred to as "sharp-headed finner and
little piked whale". Minkes have two long flippers which
grow to about 1/8 of their body size. A white band on each flipper
distinguishes them from other whales in the rorqual family. Minke
whales can live up to 50 years in the wild.
Minkes are carnivorous seasonal feeders
and share the same diet as blue whales. The minke whale has about
300 pairs of short, smooth baleen plates, approximately 30 cm
in length and 13 cm in width. Using their fine, creamy baleen
bristles, minke whales sieve through the ocean water to filter
out polar zooplankton and small fish. Sometimes minkes will chase
schools of sardines, anchovies, cod herring, and capelin, coming
up from underneath with their mouth gaping to catch a big meal.
In order to let in all these fish at once, minke whales have
50 -70 grooves in their throat to allow for this expansion.
Minkes are for the most part solitary
animals, but are sometimes seen travelling in pods of 2 to 3.
When food is plentiful, the minke whales will often gather in
groups of 200 to 300. Minkes breath air at the surface of the
water through two blow holes near the top of the head, but when
they dive minke whales hold their breath for 20 to 25 minutes.
The blow of a minke whale is relatively small compared to many
of the great whale sin the ocean, as it only reaches a height
of two meters.
Minkes usually swim between 5 and 24
km/hour. Minkes are known to approach moving vessels without
warning, but are careful not to bowride ships. Some minkes have
been seen keeping up with speed boats that move about 29-34 km/hour,
however they only travel this speed when they are in danger!
Minkes are very vocal animals, that
produce a series of grunts and thuds to communicate with other
minke whales and to echolocate objects in their surroundings.
The loudness of minke whale sounds has been compared to a jet
plane taking off!
Minke whales exist in every one of
the world's oceans with the exception of the polar oceans as
they are only covered in a few centimetres of blubber. We don't
blame them, wouldn't you rather be in the Caribbean than in the
Minke whales breed while they are in
warm waters in the late winter and early spring. The gestation
period of minke calves is about 10 months, and the birth takes
place near the surface of the ocean in shallow waters. A newborn
calf usually surfaces to take it's first breath within the first
10 seconds of its life. New born calves are usually 2.8 meters
long and weigh close to 1000 pounds. The baby will stay with
its mother for 1 to 2 years or until the mother has another calf.
Most minke whales reach puberty at 2 years of age.
Minkes whales are listed on the endangered
species list as a threatened species as there remains only approximately
800,000 minkes in the world. Some Japanese and Russian vessels
are still known to hunt minke whales. Minke whales have been
protected by international law since 1986, which will hopefully
help to stop these countries from hunting these magnificent animals.
Check out this website for more information on Minke whales
Minke Whale Research in Australia
American Cetacean Society, Minke whale page
The Mammal Society, hear the Minke whale song
and Answers about toothed whales
to Marine Biodiversity index | <urn:uuid:63a85ac3-0dc9-4282-bb49-fc1fdd802ae2> | 3.75 | 923 | Knowledge Article | Science & Tech. | 56.275882 |
Sent in by:
Michael of GA and Kyle of MI
Have a blast-off! Pop a cork!
- tomato juice
- lime juice
- grapefruit juice
- 3 large clear glasses
- baking soda
- 3 1/2 liter water bottles
- corks that tightly fit the opening of the water bottles
- safety goggles
- paper and pencil
- Check with a grown-up before you begin.
- If you've ever made a Lemon Juice Rocket, you'll remember that lemon juice and baking soda combine to form bubbles of carbon dioxide gas. But it's not just lemon juice that can make bubbles and pop a cork. Test out three different acidic juices to find out which can shoot a cork rocket the farthest. The ZOOMers tested lime juice, grapefruit juice and tomato juice.
- The ZOOMers charted their results. To make your own chart, write the liquids you test in rows on the left side of your page and write the results you want to track in columns at the top of your page. The ZOOMers recorded Height of the Bubbles, Reaction Time in Cup, Height of Rockets and Reaction Time of Rockets.
- Predict which liquid will be fastest and slowest. Predict which will go highest and lowest. Write your predictions on your chart so that you can compare them later to your results.
- To start the activity, put one teaspoon of baking soda in each of three clear glasses.
- Add one cup of each liquid you are testing to each of the glasses.
- Observe and chart the reactions of each of your liquids to the baking soda. Which liquid bubbled the highest? Which reacted the slowest? Write your results on your chart and compare them to your predictions.
- Now, test these liquids as rocket fuel. Make sure you do this part outside, because these rockets make a mess when they blast off.
- Based on your results from testing the liquids in glasses, make predictions about how well each rocket will perform. How high will it go? How quickly will it blast off?
- Write your predictions on your chart to compare to your results later.
- To build your rockets, pour one cup of each liquid you are testing into each of your water bottles.
- Make three fuel cells out of one teaspoon of baking soda wrapped in a square of toilet paper.
- Test one rocket at a time. Just drop the packet of baking soda into the bottle, put the cork in the top of the bottle and wait.
- Time how long it takes to fizz up and launch the rocket. Compare how high the rockets fly.
- Once you have launched each of your rockets, record your results on your chart.
Compare your results to your predictions. Were you spot on or way off? Why do you think the liquids reacted they way they did? Make sure you send your results to ZOOM!
Guetchine, age 13 of New York wrote:
it was cool did it for science fair at school
Mike, age 10 of Beverly wrote:
lime juice worked the best
Max, age 10 of Beverly, MA wrote:
I made a godzilla sized rocket with 5 table sponns and 9 cups of lime juice
Dylan, age 8 of Tacoma, WA wrote:
the lemon juice fizzed up a lot and then it blew up too the ceiling. then we mixed the lemon juice with orange juice and baking soda and it went even higher! it was cool.
Dedrek, age 11 of Miami wrote:
My results is when I put the lemon juice and baking soda in to the bottle it created a chemical reaction pushed the cork in out of the bottle.
Zac, age 11 of Germantown, TN wrote:
The vinegar and the lemon juice reacted in about average 2 1/2 seconds. When the orange juice and coke just fizzed, so it worked.
Robert, age 4 of Collierville, HI wrote:
It went really high. And it almost it me so I had to jump away.
Blake, age 4 of Collierville, TN wrote:
It blew up about what I think was 30 ft.
Jasmine, age 11 of Tampa wrote:
this was totaly awesome I loved the idea it was not only something that you work with but it was extremly fun!!! ttyl ~jazzie~
Diera, age 10 of Memphis, TN wrote:
when I did it it shot up in the air it went s high I didnt see it until it fell back down it was so great thx
Nerlie, age 7 of Sunrise, FL wrote:
it blow up in the air!
Kellie, age 13 of Sacramento, CA wrote:
Mine went so high that I couldn't even tell about how much it was.
Olga, age 10 of Brooklyn, NY wrote:
myn went so high that it touched the ceeling
Duniya, age 10 of Canada, AB wrote:
what happend is it needed some baking soda and lime or lemon to do it. so frist we put a bottle in the middle of the table next we put the lemon jucies in side the bottle. then we put the baking soda inside and hrey and put the cork inside the bottle. then you waent for five min and its started to blow up and the cork flys in the air.
Olivia, age 8 of San Diego, CA wrote:
When I did it the lime was the only one that bubbled in the bottle and cup. This was a fun experiment to do. I want to do it again. I predicted that the lime was the only one that will shoot and I was right. This is a good experiment to do for a progect, science progect ect, and at home you will have alot of fun doing this progect.
Ryan, age 12 of Fontana, CA wrote:
i did a lemon juice rocket and it went atleast 35ft
Chris, age 8 of New York wrote:
It went 30 feet high
David, age 11 of CA wrote:
i made a big rocket dat was 5 feet high and I poured in 3/4 of the bottle with vinegar and a lot of vinegar n I went 55 feet n blew up.
Emily, age 6 of NC wrote:
it was flying 13 feet
Sean, age 11 of Edinburg, TX wrote:
my lemon juice rocket was 40 to 50 feet in the air it was so cool when it happened I said my fav. thing to "oh my god"
Yessenia, age 14 of Miami, FL wrote:
wow... my rocket went 18 feet high. But t was awesome I liked it. You should keep on making more rockets but with different liquids.
Kenzie, age 11 of New York, NY wrote:
It went crazy and it went ten feet high!
Jennifer, age 11 of Cape Town wrote:
I mixed lemon and grape juice and flew twice the height of plain lemon juice It was awsome!!!
Teri, age 9 of Houston, TX wrote:
We didn't have tomato juice but we used vinegar, lemon juice, and baking soda. But we did it 3 times and the vinegar won every time.
Stanly, age 10 of Sacramento, CA wrote:
The lime juice work but the other one didn't!!!
Taylor, age 11 of O'Burg, SC wrote:
The cork flew 25 feet in the air! T tried coke, lemon juice, and orange juice. It was awseome!!!
Tre, age 12 of Louisville, KY wrote:
First I tried the lemon juice it worked ok but the vinger worked way better.
Adeza, age 9 of Yonkers, NY wrote:
The lemon juice rocket flew about 23ft. in the air I was surprised.
Shantel, age 9 of Mount Vernon, NY wrote:
The lemon juice bottle fell on its side and still shot straight back, and the cork flu and I couldnot find it. | <urn:uuid:03154ec4-8dbb-4d7b-89f1-6aa2c35f3a04> | 3.421875 | 1,691 | Comment Section | Science & Tech. | 75.458181 |
The size or magnitude of earthquakes and other seismic events is measured using the Richter scale. Several thousand earthquakes larger than magnitude 4 on the Richter scale occur each year around the globe. A magnitude 4 earthquake is a fairly light earthquake which can cause windows and doors to rattle, but which does not result in significant damages.
A seismic event generates two types of seismic waves: body waves and surface waves. The faster body waves travel through the interior of the Earth while the slower surface waves – as the name suggests – travel along its surface. Both types of wave are looked at during analysis to collect specific information on a particular event.
The instruments employed to measure seismic waves are seismometers, which are sensors converting ground motion into electrical voltage.
The objective of seismic monitoring is to detect and locate underground nuclear explosions.
Objectives of seismic monitoring
Seismic monitoring is one of the three waveform technologies used by the Comprehensive Nuclear-Test-Ban Treaty (CTBT) verification regime to monitor compliance with the Treaty. The objective of seismic monitoring is to detect and locate underground nuclear explosions. Data resulting from seismic monitoring are used to distinguish between an underground nuclear explosion and the numerous natural and man-made seismic events that occur every day, such as earthquakes and mining explosions.
Underground nuclear testing began in the 1950s and provoked growing concern. It was, however, soon recognized that seismic observations could provide a method of verifying the strength and location of these events.
Seismic technology is a very efficient means of detecting a suspected nuclear explosion. Seismic waves travel so fast that an event creating these waves can be registered by seismic stations distributed worldwide in a time span ranging from a few seconds to about ten minutes.
Seismic technology is very efficient at detecting a suspected nuclear explosion as seismic waves travel very fast and can be registered within seconds.
A seismic event generates body waves and surface waves. Both are of crucial importance for the analysis of a suspicious event. They provide essential information on the location, the strength and the nature of an event.
There are two types of body waves emanating from a seismic event, P-waves and S-waves. P-waves are primary or compressional waves that alternately compress and expand the ground in the direction of the wave’s propagation. These waves can move through any material.
S-waves are secondary or shear waves in the ground that move perpendicular to the direction of the wave’s propagation. S-waves can only move through solids as this kind of movement is impossible in liquid or gaseous materials. | <urn:uuid:5a25a5a7-fe90-43de-82f5-912f040550c6> | 4.1875 | 524 | Knowledge Article | Science & Tech. | 29.086427 |
Trash that cannot be recycled always ends up in a pile. Then, it decomposes very slowly until it finally turns to soil. Under natural circumstances, however, this takes far too long. The range of biodegradation is 4 weeks for a cardboard box to 5,000 years for Styrofoam.
The amount of trash produced by one person, in a day, may not seem significant, but it is when multiplied by a population of 7 billion. It does not take anyone special to realize that even with the natural process of decay; this has, and will, create a huge stockpile of garbage. This outpacing is why landfills exist.
Fortunately, something can be done. And it can be done now. There is a machine – a Plasma Converter that can eat landfills and turn them into what a thriving industrial nations needs the most, and that is oil. Joseph Longo’s Plasma Converter turns our most vile and toxic trash into clean energy, and promises to make a relic of the landfill. Garbage put into this machine is obliterated into its molecular parts by superheated electric plasma. Once in the plasma chamber, the molecular parts mix with air and carbon dioxide to become oil and glass for road asphalt.
A Plasma Converter is already in operation in Long Island, New York. Upstart is expensive, but the machine will pay for itself, with its own byproducts, in about 10 years. After that, the machine will generate pure profit and provide obvious economic multipliers. The best part about it is that the more garbage it eats, the more oil it makes, the better our roads become, and the smaller our landfills become. Who knows, one day, it may even eat The Great Pacific Garbage Patch.
Revolutionary machines of such type come around rarely, and this one in particular, offers a way to clean up our landfills and turn garbage into a somewhat “renewable resource.”
If we were given the opportunity to turn our accumulating 7 billion-population trash pile into a usable resource, would you take it? What are some of the known downfalls or cons of using plasma conversion? | <urn:uuid:45f5acde-34d9-48db-9831-0d1e616d2e78> | 3 | 447 | Personal Blog | Science & Tech. | 49.202966 |
Dirty Hydro: Dams and Greenhouse Gas Emissions
Hydropower is often believed to be an inherently "climate-friendly" technology. But scientific studies indicate that the rotting of organic matter in reservoirs produces significant amounts of the greenhouse gases carbon dioxide, methane and nitrous oxide. The warming impact of tropical reservoirs can be much higher than even the dirtiest fossil-fuel power plants.
- Download the factsheet to learn more about the different types of greenhouse gases that are being emitted, how reservoirs produce them, and how key regions and hydropower projects are contributing to global warming.
- Read the fact sheet in Spanish. | <urn:uuid:3e1243e4-bf85-4d23-97f7-c1cb7c88d8dd> | 3.53125 | 129 | Tutorial | Science & Tech. | 25.795 |
Fieldwork: Darwin’s Frogs in Chile
PROFILE: Dr. Claudio Soto-Azat
SPECIES: Darwin’s frog
I work in a vast area of central, south and southern Chile and Argentina. The area I work over covers 1,250 km in length. Therefore transportation and long driving sessions are a rule. Central and Northern areas are not tough, and they were characterized naturally by a temperate beech forest, however nowadays this area has had a huge impact from cities, agriculture and the forestry industry, which has drastically modified the environment. South of Valdivia (Southern Chile), the forest gets very humid and cold, roads get very dirty and natural environments still dominate.
Especially in Southern Chile, there are the most beautiful landscapes. If you have a sunny day (very exceptionally), you may begin to think everything makes sense.
The vast majority of the time, conditions in Southern Chile are very tough. Lots of rain, sometimes spending a long time in tents, not having regular access to showers, toilets or comfortable place to sleep after a long days work.
If you have a sunny day (very exceptionally), you may begin to think everything makes sense.
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I work on the conservation of Darwin’s frog. They are infact two species, the Northern Darwin’s frog (R. rufum) and the Southern Darwin’s frog (R. darwinii). The first lives in the coastal range of Central and South Chile. The second inhabits the South and Argentina in both coastal areas and in the Andes. These are poorly known species and their populations have dramatically fallen in the last decades. Even worse, R. rufum has not been seen since 1978 and habitat destruction has been the most obvious cause of this possible extinction. Some populations of R. darwinii still persist in Southern Chile, where environment conditions are tough. Therefore, in our spirit to understand and conserve these species, we undertake expeditions to record and monitor surviving populations.
Share this article to support Claudio’s work: | <urn:uuid:c6a08909-6ea4-498e-bed8-b98c5a0b46c7> | 2.984375 | 452 | Personal Blog | Science & Tech. | 48.430985 |
strtol(3) BSD Library Functions Manual strtol(3)
strtoimax, strtol, strtoll, strtoq -- convert a string value to a long, long long, intmax_t or quad_t integer
Standard C Library (libc, -lc)
#include <inttypes.h> intmax_t strtoimax(const char *restrict str, char **restrict endptr, int base); #include <stdlib.h> long strtol(const char *restrict str, char **restrict endptr, int base); long long strtoll(const char *restrict str, char **restrict endptr, int base); #include <sys/types.h> #include <stdlib.h> #include <limits.h> quad_t strtoq(const char *str, char **endptr, int base);
The strtol() function converts the string in str to a long value. The strtoll() function converts the string in str to a long long value. The strtoimax() function converts the string in str to an intmax_t value. The strtoq() function converts the string in str to a quad_t value. The conversion is done according to the given base, which must be between 2 and 36 inclusive, or be the special value 0. The string may begin with an arbitrary amount of white space (as deter- mined by isspace(3)) followed by a single optional `+' or `-' sign. If base is zero or 16, the string may then include a ``0x'' prefix, and the number will be read in base 16; otherwise, a zero base is taken as 10 (decimal) unless the next character is `0', in which case it is taken as 8 (octal). The remainder of the string is converted to a long, long long, intmax_t or quad_t value in the obvious manner, stopping at the first character which is not a valid digit in the given base. (In bases above 10, the letter `A' in either upper or lower case represents 10, `B' represents 11, and so forth, with `Z' representing 35.) If endptr is not NULL, strtol() stores the address of the first invalid character in *endptr. If there were no digits at all, however, strtol() stores the original value of str in *endptr. (Thus, if *str is not `\0' but **endptr is `\0' on return, the entire string was valid.) Extended locale versions of these functions are documented in strtol_l(3). See xlocale(3) for more information.
The strtol(), strtoll(), strtoimax(), and strtoq() functions return the result of the conversion, unless the value would underflow or overflow. If no conversion could be performed, 0 is returned and the global vari- able errno is set to EINVAL (the last feature is not portable across all platforms). If an overflow or underflow occurs, errno is set to ERANGE and the function return value is clamped according to the following ta- ble. Function underflow overflow strtol() LONG_MIN LONG_MAX strtoll() LLONG_MIN LLONG_MAX strtoimax() INTMAX_MIN INTMAX_MAX strtoq() LLONG_MIN LLONG_MAX
[EINVAL] The value of base is not supported or no conversion could be performed (the last feature is not portable across all platforms). [ERANGE] The given string was out of range; the value converted has been clamped.
#include <stdlib.h> #include <limits.h> <limits.h> is necessary for the strtol() and strtoll() functions.
The strtol() function conforms to ISO/IEC 9899:1990 (``ISO C90''). The strtoll() and strtoimax() functions conform to ISO/IEC 9899:1999 (``ISO C99''). The BSD strtoq() function is deprecated. BSD November 28, 2001 BSD
Mac OS X 10.8 - Generated Fri Aug 31 15:31:58 CDT 2012 | <urn:uuid:19a692d3-53c4-4ec4-ac4b-f536b4cb8420> | 3.34375 | 915 | Documentation | Software Dev. | 71.19838 |
The center of the Sun
The center of the sun is very hot (about 15 million degrees Celsius) and the pressure is immense (about 100 billion times the airpressure here on Earth).
Because of that, atoms come so close to eachother that they fuse.
In every second, the Sun spends 700 billion tons of protons (or: Hydrogen) in this way. And only a small fraction (0.7 percent) is turned into light.
Right now, about half of the amount of Hydrogen in the core of the Sun has been fused into Helium. This took the sun about 4,5 billion years. | <urn:uuid:7756180a-bf16-4c49-8912-b3c994c56079> | 3.53125 | 130 | Knowledge Article | Science & Tech. | 73.247426 |
Sanjayan, Conservancy lead scientist
I am standing in the depths of a bunker-like building that sprawls beneath the farmland just outside of Sioux Falls, South Dakota.
Aboveground, the building is nondescript, Wal-Mart-like — except for the giant dish antennae that point to the skies and the United Nations flag that flutters alongside the Stars and Stripes, hinting at the global significance of this monolith.
This is the center for Earth Resources Observation and Science (EROS), run by the U.S. Geological Survey. EROS is the place to which Earth-imaging satellites transmit their data.
As a conservationist, I use these images all the time.
Satellites have been taking pictures of us from God's perspective since the 1960s. Though satellites were first controlled by the military, more recent ones — like Landsat, Terra and Aqua — have been launched for scientific and public-use purposes.
Sweeping north to south in polar orbits, they image the globe in huge swaths; over a few days, nearly every corner of the planet is exposed. EROS holds the largest collection of such images. Eric Clemons, the center's director, calls it the "family photo album of planet Earth."
And I'm here to flip through the pictures. But where to start?
When asked to choose, I pick not my home in Missoula, Montana, or my country of birth — Sri Lanka — or even my favorite fishing spot (it's a secret), but rather a place I've visited in northern Tanzania: Laetoli.
From space, it turns out, Laetoli is not much to look at — a smudge of green and gold. To be honest, it's also disappointing from the ground, just scrubby savanna, thorny acacias and rocks, unremarkable but for one thing: At Laetoli, two pairs of fossilized footprints, some 3.7 million years old, mark the time when our ancestors first stood upright — and walked.
It takes imagination to work out the scene. Two individuals — the larger, male — move leisurely on parallel paths on a drizzly day. The tilt of the smaller prints may indicate a female, carrying an infant on her hip.
What were these humanlike primates looking for? Opportunity perhaps in the form of a recent animal kill. Or maybe approaching danger. Stand on your hind feet and you get an advantage over quadrupeds. You know a bit sooner what the future holds.
Now, here in Sioux Falls, looking at an image of Laetoli, it occurs to me that for a few million years, human experience was limited to a 2-mile radius. That's about as far as we can see before the ground falls away with the curvature of the Earth.
Then, in virtually one human generation, we overcame this limitation. Now we can see the entire planet at once.
Scientists of my generation have grown up using satellite imagery. It is the most essential applied tool for conservation because it allows us to see a landscape — and the threats to it — at the proper scale.
If you are working to reduce deforestation of the Amazon or estimate carbon emissions from forest fires or design protected areas, satellite images are indispensible.
We have entered a new period of human understanding, one in which extrapolating our understanding of what's beyond our sight has given way to whole-Earth analysis. We know what's coming around the corner.
Now we must find bold solutions to what we see — to realize the full potential of our upright stance first begun in East Africa and culminating here in this planetary library.
The opinions expressed in "Wild Life" are the author's. They should not be construed as the position of The Nature Conservancy.March 11, 2013 | <urn:uuid:76fe5972-2a8a-432d-82ac-d5abd6602304> | 2.9375 | 788 | Nonfiction Writing | Science & Tech. | 51.623601 |
Kaku's Parallel Worlds is out soon (Penguin). It considers the possibility of travelling from our universe to other universes through wormholes and black holes.
He is reading about supermassive black holes in The Edge of Infinity by Fulvio Melia (Cambridge, 2003). "It is truly remarkable that, before our eyes, just in the past decade or so, thousands of black holes have been tentatively or conclusively identified in the universe. Eventually, astronomers hope to find the holy grail of black hole physics - a sensor reading indicating the presence of the event horizon itself. Perhaps then one may begin to ask the deep questions about black holes: do they emit radiation? Is information truly lost?"
Important books? Science and Ultimate Reality, edited by John Barrow, Paul Davies and Charles Harper (Cambridge, 2004), looks at the great unsolved problems in quantum theory, including the famous Schrödinger's cat problem: can the cat be ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:82aa2832-d1d2-464b-a569-d30548cc5472> | 2.75 | 223 | Truncated | Science & Tech. | 42.589109 |
SOMETIMES it pays to give underlings a treat. Dominant male chacma baboons allow lower-ranking males to mate with their females as a way to protect the dominant male's own offspring in their absence.
That's the conclusion reached by Louise Barrett at the University of Lethbridge in Alberta, Canada, who studied 11 years of observations from a baboon troop in De Hoop Nature Reserve, South Africa. Subordinate males in the troop fathered 23 of 64 offspring during that time.
Barrett reckons that giving mating rights to subordinates makes them more likely to protect the young once the alpha male dies or wanders off. When this happens, new alpha males - usually from an outside group - move in, and tend to try to kill infants from the previous regime.
Barrett found that subordinates that had fathered offspring stayed ... | <urn:uuid:aeb0399b-2744-4ba3-89f3-c830dc64a17d> | 3.21875 | 175 | Truncated | Science & Tech. | 49.658623 |
Back in the later years of the 19th century, physicists had put together an incredibly successful synthesis of electricity and magnetism, topped by the work of James Clerk Maxwell. They had managed to show that these two apparently distinct phenomena were different manifestations of a single underlying "electromagnetism." One of Maxwell's personal triumphs was to show that this new theory implied the existence of waves traveling at the speed of light -- indeed, these waves are light, not to mention radio waves and X-rays and the rest of the electromagnetic radiation spectrum.
The puzzle was that waves were supposed to represent oscillations in some underlying substance, like water waves on an ocean. If light was an electromagnetic wave, what was "waving"? The proposed answer was the aether, sometimes called the "luminiferous aether" to distinguish it from the classical element. This idea had a direct implication: that Maxwell's description of electromagnetism would be appropriate as long as we were at rest with respect to the aether, but that its predictions (for the speed of light, for example) would change as we moved through the aether. The hunt was to find experimental evidence for this idea, but attempts came up short. The Michelson-Morley experiment, in particular, implied that the speed of light did not change as the Earth moved through space, in apparent contradiction with the aether idea.
So the aether was a theoretical idea that never found experimental support. In 1905 Einstein pointed out how to preserve the symmetries of Maxwell's equations without referring to aether at all, in the special theory of relativity, and the idea was relegated to the trash bin of scientific history.
Aether was a concept introduced by physicists for theoretical reasons, which died because its experimental predictions were ruled out by observation. Dark matter and dark energy are the opposite: they are concepts that theoretical physicists never wanted, but which are forced on us by the observations.
Dark matter, in particular, is nothing at all like the aether. It's something that seems to behave exactly like an ordinary particle of matter, just one with no electric charge or strong interaction with known matter particles. Those aren't hard to invent; particle physicists have approximately a billion different candidate ideas, and experiments are making great progress in trying to detect them directly. But the idea didn't come along because theorists had all sorts of irresistible ideas; we were dragged kicking and screaming into accepting dark matter after decades of observations of galaxies and clusters convinced people that regular matter simply wasn't enough. And once that idea is accepted, you can go out and make new predictions based on the dark matter model, and they keep coming true -- for example in studies of
Dark energy is conceptually closer to the aether idea -- like the aether, it's not a particle, it's a smooth component that fills space. Unlike the aether, it does not have a "frame of rest" (as far as we can tell); the dark energy looks the same no matter how you move through it. (Not to mention that it has nothing to do with electromagnetic radiation -- it's dark!) And of course, it was forced on us by observations, especially the 1998 discovery that the universe
is accelerating, which ended up winning the Nobel Prize in 2011. That discovery took theoretical physicists around the world by surprise -- we knew it was possible in principle, but almost nobody actually believed it was true. But when the data speak, a smart scientist listens. Subsequent to that amazing finding, cosmologists have made other predictions based on the dark energy idea, which (as with dark matter) keep coming true: for the cosmic microwave background again, as well as for the distribution of large-scale structure in the universe.
There is still much we don't know about dark matter and dark energy; in particular, we certainly haven't nailed down what exactly they are (although we have many plausible ideas), and the only way we've detected them is indirectly, through their effects on gravitational fields in the universe. But they are not arbitrary; both ideas make very specific predictions for what those gravitational effects should be, which astronomers have tested and verified. Unlike the aether, which shrunk and eventually disappeared under experimental scrutiny, the case for dark matter and dark energy continues to grow stronger. | <urn:uuid:6c59b302-5d87-45e1-bbaf-ac8d56e5d451> | 3.3125 | 874 | Nonfiction Writing | Science & Tech. | 31.413424 |
Objects in the Sky
On any dark night you watch the sky, if you see a light travelling really fast, then that can be a Meteor or perhaps shooting star. It really is not just a star but only a small speck from the dust entering very own Earth's environment at a very higher speed, approximately 150 thousand kilometers per hour. at this speed the dirt is vaporized through the heat and the encompassing air can also be heated and lights up just like a florescent light.
You can find two forms of Meteor, the very first are considered to originate in the large distensions of rock left over of some planet, referred to as Asteroids which orbit a Sun in between Jupiter and Mars. Hardly ever two asteroids engagement with each other and when they do clash, chips of Iron and Rock tend to be thrown off and sometimes head in the direction of Earth. These could be a few mm across or approximately hundreds of yards around. They may be quite unusual and are known as individual 'fireballs' occasionally impacting the bottom as Meteorites and when they are big, they might even result in craters.
The second sorts of meteors created from comets and they are a lot more common. Like a comet approaches the Sun, the frozen gas and water cut up off and therefore are blown away from the radiation through the Sun. Dirt particles released from the melt down are more substantial and consequently stay more or even less around the same orbit.
You can find many incompetent substantial methods and activities related to deep sky objects. A few of these objects tend to be bright enough to locate and see by small telescopes and binoculars. However the fainter things require the light-accumulating energy of telescopes with huge objectives and simply because they are invisible towards the naked eye, could be difficult to find. This has improved popularity within telescopes which can locate D SOs instantly and huge reflecting telescopes, for example Dob-son Ian design telescopes, with extensive fields of see well suitable for such noticing. Observing weak objects will need dark skies, therefore these relatively transportable types of telescopes. | <urn:uuid:3c1a526c-813e-4391-b9fc-bc8513cbb0de> | 3.140625 | 425 | Knowledge Article | Science & Tech. | 41.240188 |
Figure 2: Sequence of longitude-depth cross-sections of mean temperature
in the equatorial Pacific Ocean for the months of December 1996, and April,
August, and December of 1997. Also shown are corresponding temperature
anomalies which represent departures of temperatures from long-term
means for the given month. The sequence is more fully described in the
text of this article. (Image source: NOAA)
Back to Children of the Tropics:
El Niño and La Niña. | <urn:uuid:34270ee8-a441-4f5a-9683-668afdc254ef> | 2.9375 | 103 | Knowledge Article | Science & Tech. | 37.149392 |
It is thought that AMF played significant role on the adaptation of plants from aquatic to terrestrial ecosystems. Fossil records indicate arbuscular mycorrhizal-like symbiosis developed some 450 millions of years ago (early Devonian). In this sense, AMF became a obligate symbionts in order to complete all their ontogenic cycle. Glomites rhyniensis is the ancestor of AMF. This fungus was found in preserved roots of Aglaophyton major, Rhynia, and Nothia.
Ectomycorrhizal fungi are thought to have evolved from saprotroph fungi in the Paleozoic Era. Fossil records for Ascomycetes and Basidiomycetes start in the Silurian and Permian Periods, respectively. | <urn:uuid:a7dca074-a4c0-4a5e-a618-9c0b7a637f94> | 3.484375 | 166 | Knowledge Article | Science & Tech. | 21.698469 |