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Bees may die out within the next few years, said a group of ecologists from the pages of the British scientific journal Functional Ecology.
This writes the RAMBLER.
In their opinion, the cause of this will be overheating of hives caused by global warming, as the bees will “turn on” to their physiological limits, if the temperature of the planet really will grow as fast as the experts predict.
“That prospect is sobering and frightening to us,” said the scientists.
For the sake of confirmation of his theory about the impact of climate change on the extinction of bees environmentalists painted in black color, increasing thus the temperature, part of the nests of bees osmium in the U.S. state of Arizona. As a result, almost all of their inhabitants died within two years, whereas bees from the pristine scientists of the nests continued to live.
According to environmentalists, the population of bees declining for several years all over the world. For example, wild bees for 5-10 years was less immediately by 25-30%. | <urn:uuid:3644b51b-9b45-47c4-99a8-1896219f89fd> | 3.1875 | 220 | Truncated | Science & Tech. | 54.195929 | 95,571,008 |
However, when he searched the literature he was disappointed to find that there were hardly any studies of this particular behaviour. 'This was a bit surprising given that they are doing this all the time', Sapir says, explaining that the tiny aviators visit flowers to feed once every 2 min.
'I thought that this was an interesting topic to learn how they are doing it and what the consequences are for their metabolism', Sapir says, so he and his postdoc advisor, Robert Dudley, set about measuring the flight movements and metabolism of reversing hummingbirds and they publish their discovery that reversing is much cheaper than hovering flight and no more costly than forward flight for hummingbirds in The Journal of Experimental Biology at http://jeb.biologists.org.
Capturing five Anna's hummingbirds at a feeder located just inside a University of California Berkeley laboratory window, Sapir trained the birds to fly in a wind tunnel by tricking the birds into feeding from a syringe of sucrose disguised as a flower. He then filmed each bird as it hovered to feed before returning to the perch when satisfied.
Knowing that the bird would return to the feeder again soon, Sapir turned on the air flow when the hummingbird arrived, directing the 3 m s flow so that the bird had to fly backwards against the wind to remain stationary at the 'flower'. Then he repeated the experiment with the syringe feeder rotated through 180 deg while the hummingbird flew forward into the wind to stay in place.
Analysing the three flight styles, Sapir recalls that there were clear differences between forward and backward flight. The hummingbirds' body posture became much more upright as they flew backward, forcing them to bend their heads more to insert their beaks into the simulated flower. In addition, the reversing birds reduced the inclination of the plane of the wing beat so that it became more horizontal. And when Sapir analysed the wing beat frequency, he found that the birds were beating their wings at 43.8 Hz, instead of the 39.7 Hz that they use while flying forward. 'That is quite a lot for hummingbirds because they hardly change their wing beat frequency', explains Sapir.
Repeating the experiments while recording the birds' oxygen consumption rates, Sapir says, 'We expected that we would find high or intermediate values for metabolism during backward flight because the bird has an upright body position and this means that they have a higher drag. Also, the birds use backward flight frequently, but not all the time, so we assumed that it would not be more efficient in terms of the flight mechanics compared with forward flight.' However, Sapir was surprised to discover that instead of being more costly, backward flight was as cheap as forward flight and 20% more efficient than hovering. And when Sapir gently increased the wind flow from 0 m s in 1.5 m s steps for a single bird, he found that flight was cheapest at speeds of 3 m s and above, although the bird was unable to fly backwards faster than 4.5 m s.
Describing hummingbirds as insects trapped in a bird's body, Sapir adds that the fluttering flight of hummingbirds has more in common with insects than with their feathered cousins and he is keen to find out whether other hovering animals such as small songbirds and nectar-feeding bats can reverse too.
IF REPORTING ON THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org/content/215/20/3603.abstract
REFERENCE: Sapir, N. and Dudley, R. (2012). Backward flight in hummingbirds employs unique kinematic adjustments and entails low metabolic cost. J. Exp. Biol. 215, 3603-3611.
This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT email@example.com
Kathryn Knight | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:0bc15d9c-58ab-49b1-bec2-8c961b3663e7> | 3.359375 | 1,471 | Truncated | Science & Tech. | 49.098651 | 95,571,010 |
Invisibility may still be the stuff of fictional works like Harry Potter, but researchers in Japan have developed a way to make mice almost totally transparent.
Using a method that almost completely removes colour from tissue — and kills the mouse in the process — researchers say they can now examine individual organs or even whole bodies without slicing into them, offering a “bigger picture” view of the problems they are working on.
The techniques will give scientists a “new understanding of the 3D structure of organs and how certain genes are expressed in various tissues,” said Kazuki Tainaka, the lead author of a research paper published in the US-based Cell magazine.
“We were very surprised that the entire body of infant and adult mice could be made nearly transparent,” he said in a statement issued by Japanese research institute RIKEN and its collaborators
The work, which also involved the University of Tokyo and the Japan Science and Technology Agency, focuses on a compound called haem, the constituent that gives blood its red colour and is found in most tissues of the body.
The process involves pumping a saline solution through the mouse’s heart, pushing the blood out of its circulatory system and killing the creature.
A reagent is then introduced, which works to divorce the haem from the haemoglobin that remains in the animal’s organs.
The dead mouse is skinned and soaked in the reagent for up to two weeks to complete the process.
A sheet of laser light, which can be set to penetrate to a specific level, builds up a complete image of the body, much as a 3D printer creates physical objects in layers.
“Microscopes have so far allowed us to look at things in minute detail, but that has also deprived us of the context of what we are looking at,” Tainaka told AFP.
The new method, which cannot be applied to living things, “will give us details while enabling us to grasp the bigger picture,” he said.
Hiroki Ueda, who led the research team, said in the statement that the method “could be used to study how embryos develop or how cancer and autoimmune diseases develop at the cellular level.
It was hoped the method would lead “to a deeper understanding of such diseases and perhaps to new therapeutic strategies”.
“It could lead to the achievement of one of our great dreams: organism-level systems biology based on whole-body imaging at single-cell resolution.” | <urn:uuid:f7addfec-c6e0-48e7-8072-87d85409573f> | 3.15625 | 524 | News Article | Science & Tech. | 32.777502 | 95,571,012 |
|Mission type||Technology demonstration|
|Operator||The Planetary Society|
|Start of mission|
|Launch date||November 2018|
|Launch site||LC-39A, Kennedy Space Center|
LightSail 2 is a project to demonstrate controlled solar sailing using a CubeSat artificial satellite, developed by The Planetary Society, a global non-profit organization devoted to space exploration. The spacecraft core measures 10 × 10 × 30 cm, and its kite-shaped solar sail deploys into a total area of 32 square meters (340 sq ft).
On May 20, 2015, a nearly identical demonstration spacecraft, LightSail 1 (formerly called LightSail-A), was launched, and deployed its solar sail on June 7, 2015.
In 2005, The Planetary Society attempted to send a larger solar sail named Cosmos 1 into space, but the spacecraft's Russian Volna launch vehicle failed to reach orbit. In 2009, the Society began working on a CubeSat-based solar sail based on NASA's NanoSail-D project, which was lost in August 2008 due to the failure of its Falcon 1 launch vehicle. (A second unit, NanoSail-D2, was successfully deployed in early 2011.)
By 2011, the LightSail project had passed its critical design review, which was conducted by a team including JPL project veterans Bud Schurmeier, Glenn Cunningham, and Viktor Kerzhanovich, as well as Dave Bearden of Aerospace Corporation. The original estimated cost of the LightSail project was US$1.8 million, which was raised from membership dues and private sources. The prototype spacecraft LightSail 1 (or LightSail-A) was built in San Luis Obispo by Stellar Exploration Incorporated, and final integration and testing prior to launch occurred at Ecliptic Enterprises Corporation in Pasadena, California.
In March 2016, The Planetary Society announced they decided to use the convention on naming the spacecraft with the program name followed by a sequential number; the test flight or LightSail-A, became LightSail 1, and the upcoming larger spacecraft is now called LightSail 2.
As a solar sail, LightSail 2's propulsion is dependent on solar radiation alone. Solar photons exert radiation pressure on the sail, producing a small degree of acceleration. Thus, the solar sail will be propelled by pressure from sunlight itself, and not by the charged particles of the solar wind. The Planetary Society expects LightSail 2's orbit to increase by as much as a kilometer per day.
LightSail 2's modular design is based on a modular three-unit CubeSat, a small satellite format created for university-level space projects. One CubeSat-sized module carries the cameras, sensors and control systems, and the other two units will contain and deploy the solar sails.
LightSail 1 flight
A preliminary technology demonstrator spacecraft, LightSail 1 (formerly LightSail-A), was launched as a secondary payload aboard a United Launch Alliance Atlas V rocket at 15:05 UTC on 20 May 2015 from Cape Canaveral Air Force Station, Florida. The mission delivered the satellite to an orbit where atmospheric drag was greater than the force exerted by solar radiation pressure.
Two days after the launch, however, the spacecraft suffered a software malfunction which made it unable to deploy the solar sail or to communicate. On 31 May 2015, The Planetary Society reported having regained contact with LightSail 1. After the solar panels were deployed on 3 June 2015, communications with the spacecraft were lost once more on 4 June. In this case, a fault with the battery system was suspected. Contact was then reestablished on 6 June, and the sail deployment was initiated on 7 June. At a conference on 10 June 2015, after photos of deployment were downloaded, the test flight was declared a success. The spacecraft reentered the atmosphere on 14 June 2015, ending the test flight.
LightSail 2 will demonstrate controlled solar sailing in Earth orbit. By controlling the orientation of the sail relative to the Sun, the flight team will attempt to raise the orbit apogee and increase orbital energy following sail deployment. The flight team will evaluate the evolution of LightSail 2's orbit after the spacecraft is deployed from a partner spacecraft, Prox-1, at an altitude of 720 kilometers. Prox-1 and LightSail 2 are secondary payloads aboard the first operational SpaceX Falcon Heavy launch, which will carry the STP-2 payload for the U.S. Air Force.
- CubeSail (UltraSail)
- IKAROS, a Japanese solar sail, launched in May 2010
- Jupiter Trojan Asteroid Explorer, a large Japanese solar sail proposal
- NanoSail-D2, the successor to NanoSail-D, launched in November 2010
- Near-Earth Asteroid Scout, a solar sail planned to launch in 2019
- Sunjammer, a solar sail that was cancelled before launch in 2014
- Davis, Jason (1 March 2016). "Meet LightSail 2, The Planetary Society's new solar sailing CubeSat". The Planetary Society. Retrieved 2016-03-01.
- Pietrobon, Steven (8 June 2018). "United States Military Manifest". Retrieved 11 June 2018.
- Davis, Jason (March 3, 2017). "Signed, sealed but not delivered: LightSail 2 awaits ship date". The Planetary Society. Retrieved March 29, 2017.
- "LightSail". The Planetary Society. Retrieved 2017-03-29.
- Davis, Jason (May 11, 2018). "LightSail 2 launch slips to Fall". The Planetary Society. Retrieved May 26, 2018.
- Antczak, John (November 9, 2009). "After letdown, solar-sail project rises again". MSNBC. Associated Press.
- Dennis Overbye (November 9, 2009). "Setting Sail Into Space, Propelled by Sunshine". The New York Times.
- "SpaceX's Falcon 1 Falters For a Third Time". Space.com. Retrieved 2017-03-29.
- Louis D. Friedman (June 25, 2010). "LightSail-1 Passes Critical Design Review". The Planetary Society.
- "Planetary Society To Sail Again With LightSail". Space Travel blog. November 10, 2009.
- "A Kilometer Per Day: LightSail Mission Managers Refine Orbit-Raising Plan". www.planetary.org. Retrieved 2017-03-29.
- "LightSail". The Planetary Society. Retrieved 2017-03-29.
- "Frequently Asked Questions". The Planetary Society. Retrieved 2017-03-29.
- "Mission Control Center". The Planetary Society. Retrieved 2015-05-22.
- Wall, Mike (10 May 2015). "Tiny Solar Sail 'Cubesat' Launching with X-37B Space Plane on Wednesday". Space.com. Retrieved 2015-05-20.
- Davis, Jason (April 13, 2015). "LightSail Launch Delayed until at least May 20". The Planetary Society.
- Davis, Jason (January 26, 2015). "It's Official: LightSail Test Flight Scheduled for May 2015". The Planetary Society.
- Wall, Mike (27 May 2015). "LightSail Solar Sail Test Flight Stalled by Software Glitch". Space.com. Retrieved 2015-05-29.
- Fingas, John. "LightSail solar spacecraft gets back in touch with its ground crew". Engadget. Retrieved 2015-05-31.
- "Bill Nye's LightSail spacecraft is back in touch with Earth after rebooting itself". The Verge. 31 May 2015. Retrieved 2015-05-31.
- Davis, Jason (4 June 2015). "LightSail Falls Silent; Battery Glitch Suspected". Planetary Society.
- "LightSail Drama Continues as Spacecraft Wakes for Second Time". The Planetary Society. 2015-06-06. Retrieved 2015-06-06.
- Deployment! LightSail Boom Motor Whirrs to Life. 7 June 2015
- LightSail Test Mission Declared Success; First Image Complete. 9 June 2015.
- LightSail Solar Sail Ends Test Flight with Fall Back to Earth. Leonard David, Space.com. 18 June 2015.
- Molczan, Ted (2015-06-14). "LightSail-A: Post-Sail Deployment Orbital Elements". Retrieved 2015-06-15.
- Nye, Bill. Kickstart LightSail. Event occurs at 3:20. Retrieved 15 May 2015. | <urn:uuid:7bdb2cab-43f4-4095-8ace-d32f249261e1> | 3.015625 | 1,789 | Knowledge Article | Science & Tech. | 60.542872 | 95,571,016 |
Species Detail - Light Emerald (Campaea margaritata) - Species information displayed is based on all datasets.
Terrestrial Map - 10kmDistribution of the number of records recorded within each 10km grid square (ITM).
Marine Map - 50kmDistribution of the number of records recorded within each 50km grid square (WGS84).
insect - moth
3 June (recorded in 2009)
21 September (recorded in 2003)
National Biodiversity Data Centre, Ireland, Light Emerald (Campaea margaritata), accessed 22 July 2018, <https://maps.biodiversityireland.ie/Species/78868> | <urn:uuid:016e6179-932f-4f73-ad83-2073b0f72eaf> | 2.546875 | 141 | Structured Data | Science & Tech. | 35.946 | 95,571,020 |
Science & Health
This discovery was made while on the lookout for massive, distant solar system objects far beyond Pluto.
4 days ago
Pluto is almost always either above the rest of the planets or below, depending on where it is in its long orbit. Only twice every Plutonian year will the planet line up with the rest of the Solar System.
6 days ago
South Pole observatory detects neutrino from supermassive black hole from another galaxy for the first time
This is the same complex where Opportunity, Spirit, and all the Pioneer missions were launched. It was active from the 1950s all the way to 2011.
8 days ago
Ross 128b is more likely than not to have an "equilibrium temperature" 21 degrees C that is neither too hot nor too cold for humans.
8 days ago
1 hour ago
- Do-gooders attract more hatred at workplace, reveals study
- Air pollution is good, smog can do wonders for the planet − that's a govt-funded study from China
- Playing hard to get something? No, it won't work, says this new study
- Bengaluru metro expansion: Over 400 trees in danger; forest dept to translocate younger trees to parks
- SpaceX's rocket fairing-catching boat Mr. Steven just got a major upgrade | <urn:uuid:daa467cd-7f31-4a62-b244-1b3c985b41fa> | 2.875 | 273 | Content Listing | Science & Tech. | 50.959162 | 95,571,025 |
Hey, You Kids! Turn Up That Noise...
October 18, 2007
Bailey Hall 201
Refreshmens will be served in Bailey 204 at 3:45
In some physical and economic systems noise can play a dominant role in the transient behavior of the system. Often times mathematical theories have been developed for the underlying distributions of the solutions for the systems but little theory is available for the transient solutions which is often the primary interest of the scientist/engineer/economist. Compounding this problem the methods used for the numerical treatment of noise are not well developed and are most often focused on additive noise. We discuss some of the background and motivation of the development of mathematical models of noise. We then examine a numerical scheme to approximate proportional noise in stochastic differential equations. Finally, the statistical properties of the numerical approximations of a simple model are examined.
|Union College Math Department Home Page|
Comments to: firstname.lastname@example.org
Created automatically on: Mon Jul 23 03:52:36 EDT 2018 | <urn:uuid:df5a090e-b80d-4ecf-9f00-4a3f9fe21bde> | 2.625 | 208 | News (Org.) | Science & Tech. | 33.706422 | 95,571,032 |
To meet the new DBP rules, ozone doses will have to be minimized to control bromate formation. In some surface water treatment plants, this situation may become of concern, since disinfection will have to be maintained at the current level. Alternative disinfection means such as UV have therefore to be evaluated, and this study was designed to evaluate the impact of MP-UV on water quality parameters such as atrazine, BDOC or nitrites, to determine whether such a treatment step should be inserted before or after the current GAC filtration unit. According to the results shown here, this question is not an issue under conditions needed for Cryptosporidium inactivation.
Optimum location of an ultraviolet step in a surface water treatment plant
C. Lemoine, D. Gatel, J. Cavard; Optimum location of an ultraviolet step in a surface water treatment plant. Water Science and Technology: Water Supply 1 December 2002; 2 (5-6): 381–386. doi: https://doi.org/10.2166/ws.2002.0194
Download citation file: | <urn:uuid:291b161c-eebe-4c6c-bc9d-87c5d685860d> | 2.5625 | 227 | Truncated | Science & Tech. | 49.363217 | 95,571,066 |
MATRIX. CONCEPT OF MATRIX. 1.Definition of matrix Equations. Rectangular number table can be formed from the coefficients. This is a matrix. The rectangular number table with m rows and n columns constructed by m n numbers in a certain order is called a m n
Rectangular number table can be formed
from the coefficients
The rectangular number table
with m rows and n columns
constructed by mn numbers in
a certain order is called a mn
Matrix (briefly matrix).
The horizontals are called the rows of matrix and
the verticals are called the columns of matrix
Is called the element located row i and column j.
The matrix is called real matrix if
its elements are real numbers.From now on,
we only discuss the real matrix.
C and so on. For instance
The matrix is called a square
matrix if its row number
is equal to its column number,
holds for i>j (i<j), and the number of zero before (behind)
the first (last) nonzero element is growing larger (less) as
the rows increase, then we call A a upper (lower)
They are all called trapezoid matrixes.
Are they Trapezoid matrixes?
Please remember the characteristics of trapezoid matrix and follow its definition.
Trapezoid matrix is the most frequently-used matrix.
1.Equality: equality of two matrixes means that
their number of rows and number of columns
are respectively equal and their corresponding
elements are the same. i.e.,
elements are the same
Type is the same
Obviously, A+B=B+A (A+B)+C=A+(B+C)
Negative matrix: the negative matrix of
We write-A, i.e.,
Is called the product of number and matrix，
Briefly number multiple。write：kA
In general，we have
It is the difference
between Matrix and
1.The multiplication of matrixes
does not satisfy commutative law;
2. does not satisfy cancellation law；
3. Has nonzero zero factor.
This is another
notice property 5.
The conclusion does
not hold if the orders of
A and B are not equal.
Transposition of matrix.
Any square matrix can be decomposed
to the sum of a symmetric matrix
and an anti-symmetric matrix.
The determinant of an odd
order anti-symmetric matrix
equals to zero. | <urn:uuid:757778b6-054c-4448-9a14-ea445749c615> | 4.15625 | 552 | Tutorial | Science & Tech. | 57.584775 | 95,571,073 |
NASA's Swift satellite detected the explosion - formally named GRB 080319B - at 2:13 a.m. EDT that morning and pinpointed its position in the constellation Bootes. The event, called a gamma-ray burst, became bright enough for human eyes to see. Observations of the event are giving astronomers the most detailed portrait of a burst ever recorded.
"Swift was designed to find unusual bursts," said Swift principal investigator Neil Gehrels at NASA's Goddard Space Flight Center in Greenbelt, Md. "We really hit the jackpot with this one."
In a paper to appear in Thursday's issue of Nature, Judith Racusin of Penn State University and a team of 92 coauthors report on observations across the spectrum that began 30 minutes before the explosion and followed its afterglow for months. The team concludes the burst's extraordinary brightness arose from a jet that shot material directly toward Earth at 99.99995 percent the speed of light.
At the same moment Swift saw the burst, the Russian KONUS instrument on NASA's Wind satellite also sensed the gamma rays and provided a wide view of their spectral structure. A robotic wide-field optical camera called "Pi of the Sky" in Chile simultaneously captured the burst's first visible light. The system is operated by institutions from Poland.
Within the next 15 seconds, the burst brightened enough to be visible in a dark sky to human eyes. It briefly crested at a magnitude of 5.3 on the astronomical brightness scale. Incredibly, the dying star was 7.5 billion light-years away.
Telescopes around the world already were studying the afterglow of another burst when GRB 080319B exploded just 10 degrees away. TORTORA, a robotic wide-field optical camera operated in Chile with Russian-Italian collaboration, also caught the early light. TORTORA's rapid imaging provided the most detailed look yet at visible light associated with a burst's initial gamma-ray blast.
Immediately after the blast, Swift's UltraViolet and Optical Telescope and X-Ray Telescope indicated they were effectively blinded. Racusin initially thought something was wrong. Within minutes, however, as reports from other observers arrived, it was clear this was a special event.
Gamma-ray bursts are the universe's most luminous explosions. Most occur when massive stars run out of nuclear fuel. As a star's core collapses, it creates a black hole or neutron star that, through processes not fully understood, drive powerful gas jets outward. These jets punch through the collapsing star. As the jets shoot into space, they strike gas previously shed by the star and heat it. That generates bright afterglows.
The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 of a degree across. This core resided within a slightly less energetic jet about 20 times wider.
"It's this wide jet that Swift usually sees from other bursts," Racusin explained. "Maybe every gamma-ray burst contains a narrow jet, too, but astronomers miss them because we don't see them head-on."
Such an alignment occurs by chance only about once a decade, so a GRB 080319B is a rare catch.
J.D. Harrington | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Life Sciences
18.07.2018 | Information Technology | <urn:uuid:b2b64f32-1b77-4675-843c-7858ef994edc> | 3.640625 | 1,312 | Content Listing | Science & Tech. | 48.248827 | 95,571,087 |
Researchers at the University of Edinburgh have discovered that the distinctive species – which has become popular in recent years as a domestic pet – shares with humans the same genetic mechanism that enables embryonic stem cells to divide without limit. This process, which gives embryonic stem cells the capacity to become any of the 200 cell types in the body, is fundamental to all research in the discipline.
Until now, stem cells have been obtained from mice, primates and humans, but never from amphibians. But, because the African clawed frog is easier to study than mice and humans, the Edinburgh team anticipate that it will become an important research tool in their quest to understand and, ultimately, treat disease using stem cells. The results of their study are published in the current edition of the journal Development(*).
The key protein in humans, called Oct4, which governs the process of unlimited division of stem cells, has an equivalent in the African clawed frog, called PouV. This new research shows that the two proteins are not only similar, but perform the same function - both bind to DNA and activate certain genes that keep stem cells dividing. Indeed, embryonic stem cells lacking the Oct4 protein stop dividing and become specialised.
In the study, Dr Gillian Morrison introduced frog PouV proteins into mouse embryonic stem cells lacking Oct4 and found that the frog proteins “rescued” the stem cells – in other words, the cells recovered their ability to divide without limit. Dr Morrison obtained similar effects when she introduced PouV proteins from another amphibian, the axolotl (a type of salamander).
To find out exactly what function PouV proteins perform in frog embryos, Dr Morrison injected special compounds into very young embryos, to inactivate the native PouV proteins. These embryos continued to grow, but had defective heads and tails.
When the scientists looked closely at these embryos, they found that cells had become specialised before they were supposed to – before the embryo was ready for them. Consequently, the structures they make are severely affected.
This suggests that the PouV proteins are holding the cells in an uncommitted state, waiting for the time to come when they will decide what type of cell they are going to be. This is probably what Oct4 is doing in mouse and human embryonic stem cells.
The findings are also interesting because they highlight that the remarkable capacity of embryonic stem cells to divide without limit is at least 300 million years old. “It was very exciting, and humbling, to find that the proteins from such an ancient animal such as the frog can rescue the behaviour of ‘modern’ mouse embryonic stem cells. It told us so much about where this behaviour comes from, and how long ago,” said Dr Morrison.
Dr Josh Brickman, group leader at the Institute for Stem Cell research says, “Our results show that mammals have adopted the function of the amphibian PouV proteins to maintain their embryonic stem cells. These features of dividing without limit and giving rise to many types of cell are thus ancient features of early embryonic cells, crucial for the correct development of both frogs and humans.”
Ana Coutinho | alfa
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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18.07.2018 | Life Sciences
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so x^(1/3) = cuberoot of x
what does x^(2/3) = as a radical?
How would I go about cancelling x^(2/3), or rather what is the opposite function of x^(2/3)?
Turn on thread page Beta
Radicals as exponential fractions watch
- Thread Starter
- 10-09-2015 00:34
- 10-09-2015 01:51
Think about the laws of indices: . Does that help?
By "opposite function", do you mean inverse? In that case, it's the same as for any other function: You want to reflect in the line y = x. In particular, for any function of the form (if you're not comfortable with the notation, pretend I wrote instead of ), the inverse is of the form . | <urn:uuid:daa75857-947b-4c7a-9c3c-b0189ec93bb7> | 2.625 | 178 | Comment Section | Science & Tech. | 85.812314 | 95,571,096 |
Authors: Nainan K. Varghese
Inertia is a property that causes macro bodies to respond sluggishly to external efforts. Since no other entity that can prevent instantaneous action by external efforts on a free macro body or maintain its constant state of motion is known, phenomenon of inertia is usually attributed to matter itself, in negative sense. 3D matter is inert; it has no ability to move, act or oppose external efforts. Property of inertia rightly belongs to universal medium, whose action moves 3D matter-bodies. Property of inertia is due to latticework-structures in universal medium. Only when mechanism of action of external effort and mechanism of motion of 3D matter-bodies, as envisaged in the book ‘MATTER (Re-examined)’, are understood, nature of inertia will be clear.
Comments: 9 Pages. Originally published in General Science Journal
Unique-IP document downloads: 1186 times
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The inch-long spineless fish, called a lancelet, produces a key immune system protein that is similar to but much hardier than the version found in people. The bay waters are a microbial soup teeming with microorganisms, yet the worm-like bottom-feeder is remarkably adept at standing up to the bacterial, viral and chemical threats in its environment. Understanding how it does so could lead to improved biodefense and better immune-boosting drugs to fight cancer and disorders such as rheumatoid arthritis, say scientists at the University of Florida and the University of South Florida, who reported their findings recently in Nature Immunology.
"At a basic level, this sea worm tells us about the evolution of the immune response; specifically, it tells us that primitive organisms have more sophisticated immune systems than we previously thought," said X-ray crystallographer David Ostrov, Ph.D., an assistant professor of pathology, immunology and laboratory medicine at UF's College of Medicine who is affiliated with the UF Shands Cancer Center. "This is the first organism below the level of jawed vertebrates that expresses the type of proteins we use in our own complex adaptive immune system."
The human immune system is constantly at work, on guard to tackle new ills while remembering past offenders. Compared with its predecessors on the evolutionary tree, the lancelet shares genes and proteins remarkably similar to ours that enable it to also skillfully elude attack.
"This influences our therapeutic strategy because we must consider that an organism we are trying to target may have an elaborate defensive system of its own, with features that neutralize what we're trying to do to it," Ostrov said. "For example, if we're trying to create a vaccine against a specific pathogen such as anthrax, smallpox or bird flu, we have to take into account the defensive measures those and other organisms might have."
Organisms such as plants, fungi and primitive animal life are classified as having an innate immune system, which defends against invaders by recognizing predetermined patterns of molecules. About 520 million years ago, a different form of immunity emerged - the adaptive immune system, shared by humans and other organisms with jaws and vertebrae. This type relies on an army of antibodies and other immune system cells to customize its response to an array of pathogens and remember the encounter for future reference.
"We were asking the question why and where did this sharp division occur? What were the most primitive organisms that exhibit the molecules that we use in our adaptive immune systems?" Ostrov said.
"In this study, we have identified the missing link between the innate immune system and the adaptive immune system, and we have found this link just below the level of jawed vertebrates," he said. "We found an intermediate. We found an immune system that is possessing features of both the innate immune system and the adaptive system."
In their most recent study, UF and USF scientists - including geneticist Gary Litman, of USF's Moffitt Cancer Center - bombarded a highly concentrated, crystallized form of an immune system protein isolated from the fish with X-rays, yielding incredibly high-resolution images of its structure. The lancelet also is known as amphioxus, or by the scientific name Branchiostoma floridae.
"We were surprised not only by how similar the molecules are to our immune response proteins but also that the crystals diffracted to a level of resolution that no one has ever been able to achieve studying these adaptive immune response proteins - atomic resolution," Ostrov said.
That means scientists can actually see where individual hydrogen atoms are positioned in the protein's core, providing clues as to which atoms are participating in key stabilizing interactions.
Doctors often use infusions of antibodies to bolster immune systems weakened by cancer or other conditions, but ironically, these proteins are susceptible to enzymes that break them down. A number of such monoclonal antibody-based drugs are in clinical use, such as Herceptin for breast cancer or Avastin for colorectal cancer.
The lancelet's immune response proteins, however, are resilient. Understanding their essential architecture with such precision could lead to new, improved types of antibody-based therapies that are better able to persist in the body, Ostrov said.
"If we could take advantage of the atomic level structural features that we see, particularly those structural features at the stable core of this molecule, then we expect to design and produce more stable monoclonal antibodies for therapy," he said.
Neil S. Greenspan, M.D., Ph.D., a professor of pathology at Case Western Reserve University School of Medicine, called the study "captivating and thorough."
"However, I expect that further research will be required to corroborate some of the key evolutionary interpretations and to place this study in fuller perspective," Greenspan said. "Should the authors' views prove to be basically correct, the study would offer the prospect of enhancing our understanding of the structural requirements for molecules used by the adaptive immune response to recognize and counter components of invading microbes. If so, it would provide an illustration of the potential for studies of diverse species, even those that at first glance may appear to be of no special interest, to yield information of value in understanding human physiology and of use in facilitating medical advances."
Melanie Fridl Ross | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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20.07.2018 | Materials Sciences | <urn:uuid:892680a7-4453-4ad8-84f3-c01015f20d32> | 3.5 | 1,684 | Content Listing | Science & Tech. | 31.01645 | 95,571,113 |
The research of phosphorus of Xiangxi River nearby the Three Gorges, China
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The Xiangxi River is the first middling tributary of the Changjiang River near the Three Gorges Dam. The River is subject to phosphorus pollution mainly from industrial wastewater. As the water quality of the Xiangxi River could directly influence the water quality of the Three Gorges Reservoir, the research on phosphorus levels and its change in the sediment profile of the Xiangxi River could provide useful information in the dynamic changes in the system, thereby offering options for mitigative measures. Water and sediment samples from lower reaches of Xiangxi River were collected and the different forms of phosphorus in sediments of the Xiangxi River were studied. The concentrations of total phosphorus in sediment ranged from 757.67 to 1438.54 mg/kg. Inorganic phosphorus concentrations ranged from 684.63 to 1055.58 mg/kg. Phosphorus contamination was serious in some parts of the Xiangxi River. With an average concentration of 635.17 mg/kg, calcium-bound phosphorus is the main form among different inorganic phosphorus forms. Labile phosphorus and iron/aluminum-bound phosphorus measured 3.40, 0.05and 35.28 mg/kg, respectively. The mobilization potential of phosphorus of sediments was studied through adsorption and release experiments. The equilibrium concentration of phosphorus adsorption and release was around 0.1 mg/L. The initial concentrations of phosphorus in the overlying water and the sediments have obvious effect on phosphorus mobilization potential. In addition, the release rate of phosphorus in sediment increased with water depth.
KeywordsPhosphorus Sediment Adsorption and release Xiangxi River Three Gorges China
This research work was founded by Key Project of Chinese Academy of Sciences (KSCX2-SW-111) and the National Key Project (2002CB412300).
- Berner EK, Berner RA (1987) The global water cycle, geochemistry and environment. Prentice Hall, Englewood Cliffs, NJ, pp 190–191Google Scholar
- Correll DL (1998) The role of phosphorus in the eutrophication of receiving waters: a review. J Environ Qual 27:261–266Google Scholar
- Daniel TC, Sharpley AN, Lemunyon JL (1998) Agricultural phosphorus and eutrophication: a symposium overview. J Environ Qual 27:251–257Google Scholar
- Munn T, Whyte A, Timmerman P (1999) Emerging environmental issues: a global perspective of SCOPE. Ambio 28:464–470Google Scholar
- Tang H (2000) Application of surface coordination principle and modeling on aquatic micro-interfacial processes impacting the water quality. Acta Sci Circumstant 20:2–9Google Scholar
- Thomas EA (1973) Phosphorus and eutrophication. In: Griffith EJ, Beeton A, Spencer JM, Mitchell DT (eds) Environmental phosphorus handbook. Wiley, New York, NY, p 630Google Scholar
- Yu L (2002) Standard methods for examination of water and wastewater, 1st edn. China Environmental Science Press, Beijing (in Chinese)Google Scholar
- Zhong ZC, Qiu YS (1999) Major problems of ecological environment and its strategies in the Three Gorges reservoir of Chongqing. Chongqing Environ Sci 21(2):1–2Google Scholar | <urn:uuid:bc936d49-5ac6-4001-b44a-a51f3d1da152> | 2.71875 | 721 | Academic Writing | Science & Tech. | 45.009857 | 95,571,127 |
Ammonium dihydrogen phosphate
ammonium dihydrogen phosphate
3D model (JSmol)
|Molar mass||115.02 g·mol−1|
|Melting point||190 °C (374 °F; 463 K)|
|40.4 g/100 mL|
|Solubility||soluble in ethanol |
insoluble in acetone
Refractive index (nD)
Std enthalpy of
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|5750 mg/kg (rat, oral)|
Potassium dihydrogen phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Ammonium dihydrogen phosphate (ADP), also and better known as monoammonium phosphate (MAP) in order not to confuse it with adenosine diphosphate (ADP), with formula NH4H2PO4, is formed when a solution of phosphoric acid is added to ammonia until the solution is distinctly acidic. It crystallizes in tetragonal prisms. Monoammonium phosphate is often used in the blending of dry agricultural fertilizers. It supplies soil with the elements nitrogen and phosphorus in a form usable by plants. The compound is also a component of the ABC powder in some dry chemical fire extinguishers. This substance is also supplied in an emerald green, amethyst, or aquamarine crystal growing box kit for children.
Solid monoammonium phosphate shows a dissociation pressure of ammonia of 0.05 mm Hg at 125 °C based on the decomposition reaction as follows:
- NH4H2PO4(s) ⇌ NH3(g) + H3PO4(l)
ADP is a widely used crystal in the field of optics due to its birefringence properties. As a result of its tetragonal crystal structure, this material has negative uniaxial optical symmetry with typical refractive indices no = 1.522 and ne = 1.478 at optical wavelengths.
ADP crystals are piezoelectric, a property required in some active sonar transducers (the alternative being transducers that use magnetostriction). In the 1950s ADP crystals largely replaced the quartz and Rochelle salt crystals in transducers because they are easier to work than Quartz and, unlike Rochelle Salt, are not deliquescent.
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- Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, Florida: CRC Press. pp. 4–40. ISBN 0-8493-0594-2.
- "Monoammonium Phosphate (MAP)" (PDF). www.mosaicco.com. Retrieved 2015-06-05.
- IPNI. "Monoammonium Phosphate (MAP)" (PDF). www.ipni.net. International Plant Nutrition Institute. Retrieved 21 July 2014.
- John R Van Wazer (1958). Phosphorus And Its Compounds - Volume I: Chemistry. New York: Interscience Publishers, Inc. p. 503.
- Amnon Yariv, Pochi Yeh (1984). Optical Waves in Crystals. Wiley, Inc.
- Willem Hackmann (1984). Seek and Strike: Sonar, Anti-Submarine Warfare and the Royal Navy, 1914–1954. Her Majesty's Stationery Office. ISBN 0-11-290423-8. | <urn:uuid:c1cc09ce-3827-4f5d-96ff-38740634fb9b> | 2.578125 | 785 | Knowledge Article | Science & Tech. | 57.629906 | 95,571,139 |
- NGSS (2013) LS
- LS1.C, LS2.A, LS2.B
- AP Biology (2015)
- 2.D.1, 4.B.2, 4.B.3
- AP Environmental Science (2013)
- IB Biology (2016)
- IB Environmental Systems and Societies (2017)
- Vision and Change (2009)
8Film GuideFilm Guide for Termites Digest Wood Thanks to MicrobesThe following classroom-ready resources complement the film Termites Digest Wood Thanks To Microbes. It tells the story of the how termites evolved with the help of microbes passed down through a social behavior which enables them to digest wood.
This Resource is a Part Of
30I Contain Multitudes: The SeriesI Contain Multitudes offers a new lens on life. With an eye on microbes—microscopic single-celled organisms—larger creatures such as ourselves suddenly look very different. Each of us is a more of a society than an individual. Only about half the cells in or on our bodies are human. The rest make up a menagerie of microbes. Microbes produce chemicals and vitamins that we can’t produce on our own, they help digest food, shape development, and influence behavior. | <urn:uuid:0aae54a3-4ed9-4b6d-8d72-96f9cdfa8746> | 3.828125 | 265 | Content Listing | Science & Tech. | 64.079263 | 95,571,156 |
Beargrass is an ecologically, culturally, and economically important plant in the Western United States and, for the first time, landowners, managers, and harvesters now have a comprehensive report about the species.
The report, Natural and Cultural History of Beargrass (Xerophyllum tenax), published by the U.S. Forest Service's Pacific Northwest Research Station, identifies critical knowledge gaps and areas for future research. It also documents how changes in disturbance, including fire, may affect the species across its range.
"Beargrass is emblematic of a web of natural and cultural diversity in the West," said Susan Stevens Hummel, a research forester at the station and lead author of the report. "This means that organisms and processes—like people, plants, and pollinators—are interrelated."
Beargrass is a member of the lily family that, when in bloom, produces a single stalk capped with clusters of white flowers. It grows in a wide variety of habitat types and conditions, but in just two geographic areas—from the mountains of northwestern Washington south into west-central California, and from Canada south into Wyoming along the Rocky Mountains.
The plant provides food, habitat, and raw material for an array of wildlife species—from bees and flies, to rodents, bears, deer, and elk. Beargrass has longstanding cultural value and is harvested by Native Americans for use in basketry and regalia, and for medicinal and decorative purposes. It also is coveted by the commercial floral greens industry, which generates more than $200 million a year in the Pacific Northwest.
Hummel, together with her coauthors at the Xerces Society and the station, found that historical and contemporary land use practices in beargrass habitat, combined with the rise of the commercial floral greens industry, are creating shifts in disturbances within beargrass habitat.
"We found that beargrass is experiencing decreased disturbance from natural and human-caused fire, but increased disturbance from leaf harvest by the floral industry," Hummel said. "Our report looks at each of these different disturbance types and their potential effects on beargrass, its pollinators, and on human gatherers."
Among the report's findings:
- Disturbance effects on pollinators and on beargrass reproduction and abundance are not well understood;
- Traditional and commercial harvesters seek different leaf properties and use different methods to harvest beargrass;
- No coordinated effort exists among landowners to monitor the volume of beargrass being harvested each year.
"This report clarifies for land managers the importance of beargrass and offers researchers a list of knowledge gaps about the plant," Hummel said. "By addressing some of the key issues identified in the report, forest management practices can be developed to help sustain the ecological web of which beargrass is a part."
Natural and Cultural History of Beargrass is available online at http://www.treesearch.fs.fed.us/pubs/42172 and in print by request. Printed copies of the report can be requested by emailing email@example.com or calling (503) 261-1211 and referencing "PNW-GTR-864."
The Pacific Northwest Research Station is headquartered in Portland, Oregon. It has 11 laboratories and centers located in Alaska, Oregon, and Washington and about 400 employees.
Yasmeen Sands | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
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23.07.2018 | Health and Medicine
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An Inconvenient Truth: Few Signs Of Global Warming In Antarctica
Antarctica has confounded scientists, defying the dire predictions of scientists the South Pole would shrink and exacerbate sea level rise in the coming decades.
Climate models predicted Antarctic sea ice would shrink as the world warmed, and that warming would boost snowfall over the southern continent. Neither of those predictions have panned out, and now scientists say “natural variability” is overwhelming human-induced warming.
“Truth is, the science is complex, and that in most places and with most events, natural variability still plays a dominant role, and undoubtedly will continue to do so,” Chip Knappenberger, a climate scientist with the libertarian Cato Institute, told The Daily Caller News Foundation.
“This applies to goings-on in Antarctica as well as in Louisiana,” Knappenberger said, referring to the recent flooding in Louisiana activists have already blamed global warming for.
What recent studies have shown is that natural variability in the climate system plays a big role in the South Pole, and there are few signs of man-made global warming in Antarctica.
Shouldn’t There Be More Snow?
Antarctica is a tricky topic for scientists. It has a long history of chaotic weather and dramatic changes in its ice sheet, and scientists are realizing just how difficult it is to predict future behavior down under.
A recent study seemed to sum up what Knappenberger said should be the “consensus” of mainstream scientists: global warming has exerted little to no detectable influence in Antarctica.
Scientists with Columbia University’s Earth Institute found there’s been little change in Antarctica’s annual snowfall, which flies in the face of what climate models predicted would happen as the planet warmed. They blamed strong “natural variability” for the models’ failures.
“This new paper affirms these other recent findings showing that the expected signal from climate change has been struggling to rise above the noise of natural variability over recent decades, but expects the signal to eventually become noticeable,” Knappenberger said of the study.
Columbia scientists, however, said global warming’s influence on the South Pole should become apparent “by the middle of the current century, thus mitigating future increases in global sea level.”
This is just one of several recent papers suggesting natural variability is still dominant in the South Pole. So why don’t we hear more about supposedly good news?
“When it comes to ‘good’ expectations, such as increase in the surface mass balance of Antarctica, activists prefer to ignore the projections, and instead claim that recent trends indicate the situation is ‘worse than expected,’” Knappenberger said.
The Ice Is Melting … Maybe
Scientists have also been warning for years that, on net, Antarctica has been losing 147 gigatons of ice per year for the last decade or so, mostly from melting on the northern Antarctic Peninsula and its western ice sheet.
There’s seems to be a news story every day about how things are looking worse in the Antarctic. The Washington Post, for example, recently warned a long crack in western Antarctica’ ice was growing. Sounds scary, but sort of obscures what’s happening overall with Antarctica.
A 2015 study by NASA found Antarctica’s ice sheet increased in mass from 1992 to 2008. The study found ice gains in Eastern antarctica more than offset ice loss from melting glaciers in the west.
Zwally’s study was controversial and challenged years of assumptions about what was happening in the South Pole. But months later another study was published showing a “pause” in warming on the Antarctic Peninsula due to a recovering ozone hole and shifting wind patterns.
“The ozone hole contributed to a warming of the Antarctic Peninsula, but has given a small cooling around the rest of the Antarctic,” John Turner, a variability climatologist with the British Antarctic Survey, told The Daily Caller News Foundation.
Turner, one of the paper’s co-authors, found the ozone hole and wind patterns created a cooling trend over the Antarctic Peninsula, masking the warming trend predicted by climate models.
“It’s recently been published that the level of stratospheric ozone has been slowly recovering since the late 1990s, which has played a part in the cessation of the ‘peninsula warming’ that we reported in our recent Nature paper,” said Turner.
“Parts of the ice sheet are certainly melting, but as a result of relatively warm waters getting under the ice shelves and melting the ice from below,” Turner said.
Turner and his colleagues noted that even in a warming world Antarctic temperatures can go up or down in a given year, such is the power of natural variability over the region.
Ice, Ice, Baby!
Climate models predicted Antarctic sea ice would shrink as a result of global warming, but the opposite happened. Antarctic sea ice actually increased in the last two decades.
Chinese scientists compared climate model sea ice predictions to actual observations from 1979 to 2005 and found “the main problem of the [climate] models is their inability to reproduce the observed slight increase of sea ice extent.”
As it turns out, natural variability plays a big role here as well.
“Sea ice extent is strongly influenced by the winds and these have increased from the south over the Ross Sea, contributing to a small increase in total Antarctic sea ice since the late 1970s,” Turner said. “The increase in ice seems to be within the bounds of natural variability.”
Had Chinese researchers gone beyond 2005, they would have found more than just a slight increase. 2014 was the first year on record that Antarctic sea ice coverage rose above 7.72 million square miles. By Sept. 22, 2014, sea ice extent reached its highest level on record — 7.76 million square miles.
Antarctica also had unique ocean currents that keep surface waters cooler than the rest of the world.
A June 2016 study found Antarctica has a unique current pulls cold water from the Southern Ocean’s depths to the surface, causing the surface water to be colder than, say, in the Arctic. Cold water has helped sea ice hit record levels in 2014.
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A study from Northwestern University and the Chicago Botanic Garden has found that climate change may drive local extinction of mason bees in Arizona and other naturally warm climates. This study focused on the blueberry mason bee, a primary pollinator of manzanita shrubs in the wild. Over the course of the two-year study simulating a warmer climate in the bees' nests, 35% of bees died in the first year and 70% died in the second year. The bees in the warmer nests emerged from diapause over a much longer period of time and with smaller bodies and less body fat. This limited their ability to feed and reproduce successfully. "The projected temperatures appear to be pushing this species up against its physiological limits," said Northwestern’s Paul CaraDonna, who led the research. "This is evidence that we might see local extinction in the warmer parts of this species' range, which is pretty sobering."
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Scientists believe mantle plumes are responsible for some of the Earth's most dramatic geological features, such as the Hawaiian islands and Yellowstone National Park. Some plumes may have shallow sources, but a few, such as the one beneath Hawaii, appear to be rooted in the deepest mantle, near Earth's core.
Such deep plumes have long been thought to be so immobile that the motions of continental and oceanic plates were measured against them, but University of Rochester geophysicist John Tarduno and his colleagues at Ludwig-Maximilians, Münster, and Stanford universities have combined magnetic evidence from the Pacific sea floor with computer modeling to show how the plume beneath Hawaii likely bent—its root barely moving while its top moved nearly 1,000 miles across the underside of the Pacific Ocean.
"In 2003, we showed that the hotspot—the plume—that created the Hawaiian chain of islands must have moved. We suggested that mantle motion was involved, but the cause of the change in motion remained a mystery," says Tarduno.
Tarduno cites five possible mechanisms in Science, but one in particular, he says, stands out as a likely explanation for the way the Hawaiian chain of islands and seamounts formed. "We know from theory and from models, including work by Ulrich Hansen and Norm Sleep, that a plume can move slightly near its base, potentially contributing to motion of the Hawaiian hotspot and hotspots elsewhere," says Tarduno. "But a key observation came from a numerical simulation resulting from Hans-Peter Bunge's models, which show how the upper end of the plume, starting at 1500 depth, can drift like a candle flame drawn toward a draft."
The draft in this case, he says, is an ancient oceanic ridge in the Pacific where the seafloor spreads, allowing magma to bubble up through the ocean crust. The ancient ridge is now lost to subduction, but its past presence is recorded by a few magnetic lineations in oceanic crust south of the Bering Sea. The ridge was active around 80 million years ago but extinguished completely by 47 million years ago. Those dates correspond very closely with the motion history Tarduno detected in the Hawaiian hotspot.
In 2001, Tarduno and an international team spent two months aboard the ocean drilling ship JOIDES Resolution, retrieving samples of rock from the Emperor-Hawaiian seamount chain miles beneath the sea's surface. The team started at the northern end of the chain, near Japan, braving cold, foggy days and dodging the occasional typhoon to pull up several long cores of rock as they worked their way south. Using a highly sensitive magnetic device called a SQUID (Superconducting Quantum Interference Device), Tarduno's team discovered that the magnetism of the cores did not fit with the conventional wisdom of fixed hotspots.
The magnetization of the lavas recovered from the northern end of the Emperor-Hawaiian chain suggested these rocks were formed much farther north than the current hotspot, which is forming Hawaii today. As magma forms, magnetite, a magnetically sensitive mineral, records the Earth's magnetic field just like a compass. As the magma cools and becomes solid rock, the "compass" orientation is locked in place, preserving a precise record of the latitude of origin.
If the Hawaiian hot spot had always been fixed at its current location of 19 degrees north, then all the rocks of the entire chain should have formed and cooled there, preserving the magnetic signature of 19 degrees even as the Pacific plate dragged the new stones north-westward. Tarduno's team, however, found that the more northern their samples, the higher the samples' latitude. The northern-most lavas they recovered were formed at over 30 degrees north about 80 million years ago, nearly a thousand miles from where the hot spot currently lies.
"The only way to account for these findings is if the hotspot itself was moving south," says Tarduno. His magnetic readings leveled off at a latitude of nearly 19 degrees, suggesting that the magma plume ceased moving in the area it resides in today.
In addition to the "draft" created by the upwelling of magma into the paleo-ridge, Tarduno says that theory and computer simulations suggest that the most a plume can bend under such conditions would result in about 1,000 miles of movement across the crust—matching what he sees as the distance between the start and stop points of the Hawaiian hotspot. He points out that the bending of a mantle plume helps reconcile the evidence of mobile hotspots on the Earth's crust with the theories that suggest plumes originate in the deepest mantle where high viscosity limits rapid motion. He points out that the plume-ridge capture mechanism may also help explain seemingly anomalous volcanic features on the seafloor, and help geoscientists to use ancient volcanic tracks to understand the past flow of Earth mantle.
This research was funded by the National Science Foundation.About the University of Rochester
Jonathan Sherwood | EurekAlert!
Further reports about: > Ancient African Exodus > Ancient Magnetism > Earth's crust > Emperor-Hawaiian > Magnetism > Pacific Ocean > Pacific sea floor > SQUID > Science TV > Simulations > Superconducting Quantum Interference Device > computer simulation > deep plumes > dramatic geological features > erupting magma > hot mantle > mantle plume > ocean crust > paleomagnetism > plate motion histories
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
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16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
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Heisenberg was a student of Arnold Sommerfeld , an assistant to Max Born , and later a close associate of Niels Bohr . He taught at the universities of Leipzig (1927–41) and Berlin (1942–45). During World War II he headed German efforts in nuclear fission research, which failed to develop a nuclear reactor or atomic bomb. Although he claimed after the war to have had qualms about building nuclear weapons, it seems likely that the reasons Germany failed to do so were technical and logistical.
In 1958 he became director of the Max Planck Institute for Physics and Astrophysics, now located in Munich. His later work concerned the so-called S-matrix approach to nuclear forces and the possibility that space and time are quantized, or granular, in structure. His Physics and Philosophy (1962) and Physics and Beyond (1971) remain popular accounts of the revolutions in modern physics.
See D. C. Cassidy, Uncertainty: The Life and Science of Werner Heisenberg (1993) R. P. Brennan, Heisenberg Probably Slept Here: The Lives, Times and Ideas of the Great Physicists of the 20th Century (1996).
See more Encyclopedia articles on: Physics: Biographies
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- Sports and Everyday Life +- | <urn:uuid:8448ba58-e438-4258-8fa5-bb7d3128ceee> | 2.921875 | 419 | Knowledge Article | Science & Tech. | 35.808766 | 95,571,204 |
The potential of new technologies to reveal insights into the fundamental structure and function of biological systems continues to grow rapidly --but the ability to interpret and merge these datasets lags behind the ability to collect it. In an effort to overcome these limitations, Sven Bergmann, Jan Ihmels, and Naama Barkai, of the Weizmann Institute of Science in Rehovot, Israel, developed a comparative model that integrates gene expression data from microarrays with genomic sequence information to explore genetic networks.
Analyzing the gene expression profiles of six distantly related organisms--bacteria, yeast, plant, nematode, fruitfly, and human--the researchers found that functionally related genes were co-expressed in each species. The most strongly conserved sets of co-expressed genes were associated with core cellular processes or organelles.
Although the regulatory details of individual gene groups varied, the researchers found common ground in the overall landscape of the expression data. The transcription programs exhibit properties typical of dynamically evolving "real-world" networks that are designed to perform in uncertain environments and maintain connections between elements independent of scale. These properties were originally identified in studies of social networks and the World Wide Web, but they aptly describe the real-world challenges of the cell. Studies of dynamically evolving networks show that nodes (i.e., genes and proteins) added at an early stage (much like highly conserved genes) are more likely to develop many connections, acting as a hub. Following these organizational principles, transcription networks would have a relatively small number of highly connected "hub genes"--though a much higher number than one would expect in a random network.
Dr Naama Barkai | PLoS
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine | <urn:uuid:501d63f5-6f8d-4924-8a29-05e7f258cca7> | 3.03125 | 969 | Content Listing | Science & Tech. | 32.609402 | 95,571,205 |
The study used the Hubble Space Telescope and the Very Large Telescope to gauge the mass of the foreground galaxy using both gravitational lensing for its background counterpart as well as the speed of the stars around its edges, using the comparison to see whether the measurements are consistent. The result was an error margin of 9 percent — that sounds like a lot, but it’s both the most precise measurement of relativity to date and demonstrates that the science is valid.
There’s no drama involved, but that’s news in itself. While the test doesn’t conclusively prove that general relativity is the guiding principle of the universe, it saves scientists and companies from having to toss out decades of knowledge. They might not want to rest too easily, though. Scientific American noted that one of the researches, Tom Collett, is planning a follow-up that would check relativity through similar methods. If the theory is off, there’s a chance this would reveal the discrepancies. | <urn:uuid:c5ebf0b9-f03c-4539-b348-f30cf4ebaa80> | 3.46875 | 200 | News Article | Science & Tech. | 40.971429 | 95,571,215 |
Desert ants have adapted to a life in a barren environment which only provides very few landmarks for orientation. Apart from visual cues and odors the ants use the polarized sunlight as a compass and count their steps in order to return safely to their home after searching for food.
Cataglyphis noda ants approaching their nest entrance − a small hole in the ground of an experimental tube. Max Planck Institute for Chemical Ecology/Badeke
In experiments with ants of the genus Cataglyphis in their natural habitats in Tunisia and Turkey, behavioral scientists of the Max Planck Institute for Chemical Ecology in Jena, Germany, have now discovered that ants can also use magnetic and vibrational landmarks in order to find their way back to their nest − a small hole in the desert ground.In addition, carbon dioxide produced by their nestmates’ breathing also helps homing ants to pinpoint their nest entrance. Hence, the ants’ navigational skills prove enormously adaptable to their inhospitable environment.
Dr. Jan-Wolfhard Kellmann | Max-Planck-Institut
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:248f5179-33c4-48fa-9379-b01d665257be> | 3.625 | 801 | Content Listing | Science & Tech. | 36.742877 | 95,571,244 |
In three spatial dimensions, it is a close relative of the quark-gluon plasma, the super-hot state of matter that hasnt existed since the tiniest fraction of a second after the big bang that started the universe. When viewed in 10 dimensions, the minimum number prescribed by what physicists call "string theory," it is a black hole.
No matter what you call it, though, that substance and others similar to it could be the most-perfect fluids in existence because they have ultra-low viscosity, or resistance to flow, said Dam Thanh Son, an associate physics professor in the Institute for Nuclear Theory at the University of Washington.
Son and two colleagues used a string theory method called the gauge/gravity duality to determine that a black hole in 10 dimensions – or the holographic image of a black hole, a quark-gluon plasma, in three spatial dimensions – behaves as if it has a viscosity near zero, the lowest yet measured.
Vince Stricherz | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:99f43c9a-2582-4c91-b9d8-4faf9abdfc27> | 3.140625 | 791 | Content Listing | Science & Tech. | 39.869636 | 95,571,245 |
Scientist develop solar-powered device to help convert urine into beer
The device — developed by researchers from the University of Ghent in Belgium — only uses solar energy to power the machine.
Scientists have created a solar-powered device to extract water and fertiliser from human urine that could be used to grow crops needed to produce beer.
The device, developed by researchers from the University of Ghent in Belgium, uses solar energy to heat the urine that is collected and dumped into a tank.
As the urine evaporates, it is pushed through a “special” membrane that separates and collects water and other material, ‘Techxplore’ reported.
According to researchers, this process removes approximately 95 percent of the ammonia that is present in urine, making it clean enough to drink.
However, realising that many people may not be ready for a sample taste, researchers also have plans to use the water and the fertiliser they make from the other materials extracted (phosphorus, potassium and nitrogen) to grow a crop of hops which will be used to make more beer.
They started their work with the notion of a filtering device and the goal of helping people residing in rural areas where water is meagre.
The device might also be useful in highly trafficked areas such as sports venues, music events and airports, researchers said.
They claim that their device is more energy efficient than other wastewater treatment machines, offering users more immediate benefits. | <urn:uuid:b331ecb6-ed06-4cee-b088-ce2b658bd202> | 3.46875 | 300 | News Article | Science & Tech. | 24.497049 | 95,571,247 |
Microresonator-based optical frequency combs enable highly-precise optical distance ranging at a rate of 100 million measurements per second - publication in Science.
Scientists of Karlsruhe Institute of Technology (KIT) and École polytechnique fédérale de Lausanne (EPFL) have demonstrated the fastest distance measurement so far. The researchers demonstrated on-the-fly sampling of a gun bullet profile with micrometer accuracy.
The experiment relied on a soliton frequency comb generated in a chip-based optical microresonator made from silicon nitride. Potential applications comprise real-time 3D cameras based on highly precise and compact LIDAR systems. DOI: 10.1126/science.aao3924
For decades, distance metrology by means of lasers, also known as LIDAR (laser-based light detection and ranging), has been an established method. Today, optical distance measurement methods are being applied in a wide variety of emerging applications, such as navigation of autonomous objects, e.g. drones or satellites, or process control in smart factories. These applications are associated with very stringent requirements regarding measurement speed and accuracy, as well as size of the optical distance measurement systems.
A team of researchers headed by Professor Christian Koos at KIT's Institute of Photonics and Quantum Electronics (IPQ) together with the team of Professor Tobias Kippenberg at École polytechnique fédérale de Lausanne (EPFL) has started to address this challenge in a joint activity, aiming at a concept for ultra-fast and highly precise LIDAR system that shall fit into a matchbox one day. The basics of this concept have now been published in the scientific journal Science. To demonstrate the viability of their approach, the scientists used a gun bullet flying at a speed of 150 m/s. "We managed to sample the surface structure of the projectile on-the-fly, achieving micrometer accuracy", Professor Koos comments, "To this end, we recorded 100 million distance values per second, corresponding to the fastest distance measurement so far demonstrated."
This demonstration was enabled by a new type of chip-scale light source developed at EPFL, generating optical frequency combs. The combs are generated in optical microresonators, tiny circular structures, which are fed by continuous-wave light from a laser source. Mediated by nonlinear optical processes, the laser light is converted into stable optical pulses - dissipative Kerr solitons - forming regular a pulse train that features a broadband optical spectrum. The concept crucially relies on high-quality silicon nitride microresonsators with ultra-low losses, which were produced at EPFL's Centre of MicroNanotechnology (CMi). "We have developed low-loss optical resonators, in which extremely high optical intensities can be generated - a prerequisite for soliton frequency combs," says Professor Tobias Kippenberg of EPFL, "These so-called Kerr frequency combs have rapidly found their way into new applications over the previous years. "
In their demonstrations, the researchers combined findings from different areas. "In the past years, we have extensively studied methods for ultra-fast communications using chip-scale frequency comb sources," Christian Koos of KIT explains. "We now transfer these results to another research area - optical distance measurements." In 2017, the two teams already published a joint article in Nature, reporting on the potential of chip-scale soliton comb sources in optical telecommunications.
In principle, optical frequency combs consist of light with a multitude of precisely defined wavelengths - the optical spectrum then resembles the teeth of a comb. If the structure of such a comb is known, the inference pattern resulting from superposition of a second frequency comb can be used to determine the distance traveled by the light. The more broadband the frequency combs, the higher is the measurement accuracy. In their experiments, the researchers used two optical microchips to generate a pair of nearly identical frequency combs.
The scientists consider their experiment to be a first demonstration of the measurement technique. Although the demonstrated combination of precision and speed in the ranging experiment is an important milestone in itself, the researchers aim at carrying the work further and at eliminating the remaining obstacles towards technical application. For instance, the range of the method is still limited to typical distances of less than 1 m.
Moreover, today's standard processors do not permit real-time evaluation of the large amount of data generated by the measurement. Future activities will focus on a compact design, enabling highly precise ranging while fitting into the volume of a matchbox. The silicon-nitride microresonators are already commercially available by EPFL's spinoff LiGENTEC SA that has specialized on fabrication of silicon nitride-based photonic integrated circuits (PIC).
The envisaged sensors might serve a wide variety of applications, e.g., for high-throughput in-line control of high-precision mechanical parts in digital factories, replacing state-of-the-art inspection of a small subset of samples by laborious distance metrology. Moreover, the LIDAR concept might pave the path towards high-performance 3D cameras in microchip format, which may find widespread applications in autonomous navigation.
Philipp Trocha, Maxim Karpov, Denis Ganin, Martin H. P. Pfeiffer, Arne Kordts, Stefan Wolf, Jonas Krockenberger, Pablo Marin-Palomo, Claudius Weimann, Sebastian Randel, Wolfgang Freude, Tobias J. Kippenberg, Christian Koos: Ultrafast Optical Ranging Using Microresonator Soliton Frequency Combs. DOI: 10.1126/science.aao3924
Being „The Research University in the Helmholtz Association", KIT creates and imparts knowledge for the society and the environment. It is the objective to make significant contributions to the global challenges in the fields of energy, mobility and information. For this, about 9,300 employees cooperate in a broad range of disciplines in natural sciences, engineering sciences, economics, and the humanities and social sciences. KIT prepares its 26,000 students for responsible tasks in society, industry, and science by offering research-based study programs. Innovation efforts at KIT build a bridge between important scientific findings and their application for the benefit of society, economic prosperity, and the preservation of our natural basis of life. mhe, 23.02.2018
Monika Landgraf | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
23.07.2018 | Health and Medicine
23.07.2018 | Earth Sciences
23.07.2018 | Science Education | <urn:uuid:3ac3c350-03c3-4b81-81a6-c4e203a1e705> | 3.046875 | 1,911 | Content Listing | Science & Tech. | 29.357361 | 95,571,268 |
The proportional counter is a type of gaseous ionization detector device used to measure particles of ionizing radiation. The key feature is its ability to measure the energy of incident radiation, by producing a detector output pulse that is proportional to the radiation energy absorbed by the detector due to an ionising event; hence the detector's name. It is widely used where energy levels of incident radiation must be known, such as in the discrimination between alpha and beta particles, or accurate measurement of X-ray radiation dose.
A proportional counter uses a combination of the mechanisms of a Geiger–Müller tube and an ionization chamber, and operates in an intermediate voltage region between these. The accompanying plot shows the proportional counter operating voltage region for a co-axial cylinder arrangement.
In a proportional counter the fill gas of the chamber is an inert gas which is ionised by incident radiation, and a quench gas to ensure each pulse discharge terminates; a common mixture is 90% argon, 10% methane, known as P-10. An ionising particle entering the gas collides with an atom of the inert gas and ionises it to produce an electron and a positively charged ion, commonly known as an "ion pair". As the ionising particle travels through the chamber it leaves a trail of ion pairs along its trajectory, the number of which is proportional to the energy of the particle if it is fully stopped within the gas. Typically a 1 MeV stopped particle will create about 30,000 ion pairs.
The chamber geometry and the applied voltage is such that in most of the chamber the electric field strength is low and the chamber acts as an ion chamber. However, the field is strong enough to prevent re-combination of the ion pairs and causes positive ions to drift towards the cathode and electrons towards the anode. This is the "ion drift" region. In the immediate vicinity of the anode wire, the field strength becomes large enough to produce Townsend avalanches. This avalanche region occurs only fractions of a millimeter from the anode wire, which itself is of a very small diameter. The purpose of this is to use the multiplication effect of the avalanche produced by each ion pair. This is the "avalanche" region.
A key design goal is that each original ionising event due to incident radiation produces only one avalanche. This is to ensure proportionality between the number of original events and the total ion current. For this reason the applied voltage, the geometry of the chamber and the diameter of the anode wire are critical to ensure proportional operation. If avalanches start to self-multiply due to UV photons as they do in a Geiger–Muller tube, then the counter enters a region of "limited proportionality" until at a higher applied voltage the Geiger discharge mechanism occurs with complete ionisation of the gas enveloping the anode wire and consequent loss of particle energy information.
Therefore, it can be said that the proportional counter has the key design feature of two distinct ionisation regions:
- Ion drift region: in the outer volume of the chamber – creation of number ion pairs proportional to incident radiation energy.
- Avalanche region: in the immediate vicinity of the anode – Charge amplification of ion pair currents, while maintaining localised avalanches.
The process of charge amplification greatly improves the signal-to-noise ratio of the detector and reduces the subsequent electronic amplification required.
In summary, the proportional counter is an ingenious combination of two ionisation mechanisms in one chamber which finds wide practical use.
Signal Amplification by Multiplication
In the case of a cylindrical proportional counter the multiplication, M, of the signal caused by an avalanche can be modeled as follows:
Where a is the anode wire radius, b is the radius of the counter, p is the pressure of the gas, and V is the operating voltage. K is a property of the gas used and relates the energy needed to cause an avalanche to the pressure of the gas. The final term gives the change in voltage caused by an avalanche.
The proportionality between the energy of the charged particle travelling through the chamber and the total charge created makes proportional counters useful for charged particle spectroscopy. By measuring the total charge (time integral of the electric current) between the electrodes, we can determine the particle's kinetic energy because the number of ion pairs created by the incident ionizing charged particle is proportional to its energy. The energy resolution of a proportional counter, however, is limited because both the initial ionization event and the subsequent 'multiplication' event are subject to statistical fluctuations characterised by a standard deviation equal to the square root of the average number formed. However, in practice these are not as great as would be predicted due to the effect of the empirical Fano factor which reduces these fluctuations. In the case of argon, this is experimentally about 0.2.
Proportional counters are also useful for detection of high energy photons, such as gamma-rays, provided these can penetrate the entrance window. They are also used for the detection of X-rays to below 1 Kev energy levels, using thin walled tubes operating at or around atmospheric pressure.
Radioactive contamination detection
Proportional counters in the form of large area planar detectors are used extensively to check for radioactive contamination on personnel, flat surfaces, tools and items of clothing. This is normally in the form of installed instrumentation because of the difficulties of providing portable gas supplies for hand-held devices. They are constructed with a large area detection window made from such as metallised mylar which forms one wall of the detection chamber and is part of the cathode. The anode wire is routed in a convoluted manner within the detector chamber to optimise the detection efficiency. They are normally used to detect alpha and beta particles, and can enable discrimination between them by providing a pulse output proportional to the energy deposited in the chamber by each particle. They have a high efficiency for beta, but lower for alpha. The efficiency reduction for alpha is due to the attenuation effect of the entry window, though distance from the surface being checked also has a significant effect, and ideally a source of alpha radiation should be less than 10mm from the detector due to attenuation in air.
These chambers operate at very slight positive pressure above ambient atmospheric pressure. The gas can be sealed in the chamber, or can be changed continuously, in which case they are known as "gas-flow proportional counters". Gas flow types have the advantage that they will tolerate small holes in the mylar screen which can occur in use, but they do require a continuous gas supply.
Guidance on application use
In the United Kingdom the HSE has issued a user guidance note on selecting the correct radiation measurement instrument for the application concerned . This covers all radiation instrument technologies, and is a useful comparative guide to the use of proportional counters.
- Glenn F Knoll. Radiation Detection and Measurement, third edition 2000. John Wiley and sons, ISBN 0-471-07338-5.
- G.Charpak and F.Sauli; Sauli, F (1984). "High-resolution Electronic Particle Detectors". Annual Review of Nuclear Science. Annual Reviews Inc. 34 (1): 285–350. Bibcode:1984ARNPS..34..285C. doi:10.1146/annurev.ns.34.120184.001441.
- E. Mathieson, Induced charge distributions in proportional detectors, http://www.inst.bnl.gov/programs/gasnobledet/publications/Mathieson's_Book.pdf | <urn:uuid:e9e4ecce-7d23-4f7e-8b86-eda91fef096f> | 3.609375 | 1,568 | Knowledge Article | Science & Tech. | 34.535343 | 95,571,297 |
Have you ever noticed how mathematical ideas are often used in patterns that we see all around us? This article describes the life of Escher who was a passionate believer that maths and art can be. . . .
This article describes the scope for practical exploration of tessellations both in and out of the classroom. It seems a golden opportunity to link art with maths, allowing the creative side of your. . . .
This article looks at the importance in mathematics of representing places and spaces mathematics. Many famous mathematicians have spent time working on problems that involve moving and mapping. . . .
Pythagoras of Samos was a Greek philosopher who lived from about 580 BC to about 500 BC. Find out about the important developments he made in mathematics, astronomy, and the theory of music.
First or two articles about Fibonacci, written for students.
This article gives a taste of the mathematics of Celtic knots.
Second of two articles about Fibonacci, written for students.
Can you identify the mathematicians?
Read this article to find out about the discoveries and inventions of Archimedes.
Read all about Pythagoras' mathematical discoveries in this article written for students.
In the time before the mathematical idea of randomness was discovered, people thought that everything that happened was part of the will of supernatural beings. So have things changed?
The Four Colour Conjecture was first stated just over 150 years ago, and finally proved conclusively in 1976. It is an outstanding example of how old ideas can be combined with new discoveries. prove. . . .
This is the second article in a two part series on the history of Algebra from about 2000 BCE to about 1000 CE.
Dr James Grime takes an Enigma machine in to schools. Here he describes how the code-breaking work of Turing and his contemporaries helped to win the war.
The second of three articles on the History of Trigonometry.
Infinity is not a number, and trying to treat it as one tends to be a pretty bad idea. At best you're likely to come away with a headache, at worse the firm belief that 1 = 0. This article discusses. . . .
This is the first of a two part series of articles on the history of Algebra from about 2000 BCE to about 1000 CE.
Read all about the number pi and the mathematicians who have tried to find out its value as accurately as possible.
Mathematics has always been a powerful tool for studying, measuring and calculating the movements of the planets, and this article gives several examples.
Leonardo who?! Well, Leonardo is better known as Fibonacci and this article will tell you some of fascinating things about his famous sequence.
This article -useful for teachers and learners - gives a short account of the history of negative numbers.
Take a line segment of length 1. Remove the middle third. Remove the middle thirds of what you have left. Repeat infinitely many times, and you have the Cantor Set. Can you find its length?
This article for pupils and teachers looks at a number that even the great mathematician, Pythagoras, found terrifying.
Take a line segment of length 1. Remove the middle third. Remove the middle thirds of what you have left. Repeat infinitely many times, and you have the Cantor Set. Can you picture it?
Most stories about the history of maths seem to be about men. Here are some famous women who contributed to the development of modern maths and prepared the way for generations of female. . . .
Read about David Hilbert who proved that any polygon could be cut up into a certain number of pieces that could be put back together to form any other polygon of equal area.
What would you do if your teacher asked you add all the numbers from 1 to 100? Find out how Carl Gauss responded when he was asked to do just that. | <urn:uuid:d67508f8-23d8-4aba-aa86-b93b7b7f336d> | 3.09375 | 800 | Content Listing | Science & Tech. | 55.873969 | 95,571,298 |
It's well known that the protein calmodulin specifically targets and steers the activities of hundreds of other proteins – mostly kinases – in our cells, thus playing a role in physiologically important processes ranging from gene transcription to nerve growth and muscle contraction But just how it distinguishes between target proteins is not well understood.
Methods developed by biophysicists at the Technische Universitaet Muenchen (TUM) have enabled them to manipulate and observe calmodulin in action, on the single-molecule scale. In recent experiments, as they report in the early edition of PNAS, the Proceedings of the National Academy of Sciences, they compared the sequences of structural and kinetic changes involved in binding two different kinases. The results reveal new details of how calmodulin binds and regulates its target proteins.
A so-called signaling protein and "calcium sensor," calmodulin gives start and stop signals for a great number of intracellular activities by binding and releasing other proteins. Calmodulin can bind up to four calcium ions, and the three-dimensional spatial structure of calmodulin varies with the number of calcium ions bound to it. This structure in turn helps to determine which amino acid chains – peptides and proteins – the calmodulin will bind.
Techniques such as X-ray structural analysis offer snapshots, at best, of steps in this intracellular work flow. But single-molecule atomic-force spectroscopy has opened a new window on such dynamic processes.
Professor Matthias Rief and colleagues at the Technische Universitaet Muenchen had previously shown that they could fix a single calmodulin molecule between a surface and the cantilever tip of a specially built atomic-force microscope, expose it to calcium ions in solution, induce peptide binding and unbinding, and measure changes in the molecule's mechanical properties as it did its work.
"What is special about our technique," Rief says, "is that we can work directly in aqueous solution. We can make our measurements in exactly the conditions under which the protein works in its natural environment. So we can directly observe how the calmodulin snatches the amino acid chain and folds itself, to hold its target fast." Measuring the force needed to bend the calmodulin molecule out of its stable condition at any given moment enables the researchers to compute the energies associated with binding both the calcium ions and the amino acid chains. And by following changes in the molecule's mechanical properties over time, they also can determine how long a protein fragment remains bound.
The results Rief and biophysicist Jan Philipp Junker report in the early edition of PNAS show that their approach also enables detailed comparative studies of binding sequences for different target proteins. The target sequences observed in these experiments are called skMLCK and CaMKK. Rief and Junker used mechanical force – actually pulling on complexes of calmodulin and the target peptides at rates of 1 nanometer per second or less – to slow down the processes to observable time scales and to clearly separate the individual unbinding steps.
"By applying mechanical force," Junker says, "we are able to dismantle the calmodulin-target peptide complex with surgical precision. Using conventional methods, this would be very difficult to do."
Among the detailed insights this approach made accessible are the hierarchy of folding and target binding, the sequence of unbinding events, and target-specific differences in terms of what is called cooperative binding.
Original paper: "Single-molecule force spectroscopy distinguishes target binding modes of calmodulin," by Jan Philipp Junker and Matthias Rief, published in the online Early Edition of PNAS, Proceedings of the National Academy of Sciences for the week of August 10, 2009.Contact:
Patrick Regan | EurekAlert!
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:bde3e7a3-a5b4-4064-b008-f3cf82a8f198> | 3.4375 | 1,447 | Content Listing | Science & Tech. | 33.731929 | 95,571,302 |
The mysterious dark matter that makes up most of the matter in the universe may already have been detected with superconducting circuits, researchers say.
Dark matter is currently one of the greatest mysteries in the cosmos — an invisible substance thought to make up five-sixths of all matter in the universe. The scientific consensus right now is that dark matter is composed of a new type of particle, one that interacts very weakly at best with all the known forces of the universe, except gravity. As such, dark matter is invisible and nearly completely intangible, mostly only detectable via the gravitational pull it exerts.
A number of ongoing experiments based on massive sensor arrays buried underground are attempting to identify the weak signals dark matter is expected to give off when it experiences a rare collision with other particles. So far, none of these studies have detected any dark matter fingerprints.
Now, theoretical physicist Christian Beck at Queen Mary University of London suggests much smaller benchtop detectors might be capable of detecting axions, which are leading theoretical candidates for dark matter particles.
Recent theoretical research suggests axions may condense together, essentially forming super-particles that physicists call Bose-Einstein condensates. "I started thinking not about the behavior of single axions, but [about] the collective behavior of many axions coupled together," Beck said.
Beck noted the equations describing the motion of these axions were very similar to those governing a special kind of circuit known as an S/N/S Josephson junction, a device made of two superconductors separated by a thin layer of metal. (Superconductors are materials in which electricity can flow without any resistance.)
Beck calculated that axions could leave behind a detectable electrical signal when they pass through these devices. "This opens up a new way of searching for axions that people haven't thought about before," he said.
If this notion is true, Beck said that the evidence may already have appeared — in a 2004 experiment exploring noise levels in S/N/S Josephson junctions that revealed a signal of unknown origin. If that signal came from an axion, Beck calculated, it would mean these particles have masses less than four-billionths those of electrons.
To confirm or refute the idea that axions generated the 2004 signal, further experiments are needed, ones paying special focus to shielding from any external radiation, since axions cannot be shielded against.
In addition, the Earth is expected to move faster through the galaxy's halo of dark matter in June and slower in December, so if the signals come from axions, the number of such signals these devices detect should rise and fall over the year.
"I want to now collaborate with my experimental colleagues to do the tests I suggested," Beck said.
Beck detailed his findings online Dec. 2 in the journal Physical Review Letters.
- One 'Oddball' Among 12 Newfound Moons Discovered Orbiting Jupiter
- Image of the Day
- The Best Space Books On Sale for Prime Day
- A Space Fan's Guide to San Diego Comic-Con 2018
This article originally published at Space.com here | <urn:uuid:99726bf8-b15c-4f96-a308-7c1717915483> | 3.765625 | 636 | Truncated | Science & Tech. | 31.057791 | 95,571,311 |
Predicting climate change impacts on biodiversity is a major scientific challenge, but doing so is important for assessing extinction risk, developing conservation action plans, providing guidance for laws and regulations, and identifying the mechanisms and patterns of impact to inform climate change adaptation. In the few decades since the threat of climate change has been recognised, the conservation community has begun assessing vulnerability to climate change.
There is no single ‘correct’ or established way to carry out climate change vulnerability assessments (CCVA) of species. A range of methods have been developed, and a large and burgeoning scientific literature is emerging on this subject. This document aims to ease the challenge that conservation practitioners face in interpreting and using the complex and often inconsistent CCVA literature. The intended target audiences include conservation practitioners (e.g., for CCVA of their focal species or the species in their focal area) and researchers (e.g., for carrying out CCVA to serve conservation, or to evaluate the rigorousness of others’ studies).
These guidelines cover an outline of some of the terms commonly used in CCVA, and describe three dominant CCVA approaches, namely correlative (niche-based), mechanistic and trait-based approaches. This guide is structured to provide readers first with background information on definitions and metrics associated with CCVA. A discussion on identifying CCVA objectives follows, setting the stage for core guidance on selecting and applying appropriate methods. The subsequent sections focus on interpreting and communicating results, as well as suggestions for using results in Red List assessments and addressing the many sources of uncertainty in CCVAs. A final section explores future directions for CCVAs and research needs. The guide ends with ten case studies that provide essentially worked examples of CCVAs that cover the range of methods described.
This guidance document has been developed by a Climate Change Vulnerability Assessment working group convened under the IUCN Species Survival Commission’s Climate Change Specialist Group. The authors’ collective experience covers a broad range of ecosystems, taxonomic groups, conservation sectors and geographic regions, and has been supplemented by an extensive literature review. No guidance on this topic can be exhaustive, but nonetheless, this document should provide a useful reference for those wishing to understand and assess climate change impacts on their focal species, at site, site network and/or at broader spatial scales. | <urn:uuid:e99d9b98-bccd-477d-9c0b-fa71165b9002> | 3.359375 | 470 | Knowledge Article | Science & Tech. | 17.452816 | 95,571,313 |
Metal Deposits Related to Advanced Stages of Rifting
The variability in styles of rifting makes generalization of the more advanced stages of rifting a hazardous exercise. Nevertheless, broad patterns can be recognized. If the rifting is destined to result in creation of a new ocean basin, it will at a certain point produce a narrow seaway similar to that of the present Red Sea (Martinez and Cochran 1988). Other rifts that fail may only do so after they have evolved from an early stage of subaerial and very shallow-marine deposition to deep, starved basin-type environments. Still others may receive sufficient supplies of sediment to build up great thicknesses of sedimentary rocks (< 10 km) without acquiring deep-marine environments.
KeywordsMassive Sulfide Iron Formation Banded Iron Formation Massive Sulfide Deposit Metalliferous Sediment
Unable to display preview. Download preview PDF. | <urn:uuid:9f284791-dfe4-4c1f-9f46-b5e6b1e32f6d> | 2.828125 | 186 | Truncated | Science & Tech. | 24.174964 | 95,571,350 |
Solubility System: Magnesium formate with Boric acid and Water (Original Report)
(2) Boric acid, H3BO3; [10043-35-3] NIST Chemistry WebBook
(3) Water, H2O; [7732-18-5] NIST Chemistry WebBook
|w1||m1 (mol/kg) [Note: $^a]||Phase [Note: ^b]||Phase|
|11.86||5.15||1.25||1||A + B||Liquid|
a) The molality values were calculated by the compilers.
b) The solid phases are: A = Mg(CHO2)2·2H2O; B = H3BO3.
The isothermal method was used. The mixtures were shaken in sealed glass vessels for 5-6 hrs. The boric acid concentration was determined by titration with alkali using mannitol. The Mg2+ content was determined complexometrically using Complexon III. The composition of the solid phases was determined by the Schreinemakers method.
(1) p.a. grade boric acid was recrystallized from water. Magnesium formate dihydrate was obtained by the reaction of Mg(OH) 2 and formic acid. The solid was recrystallized twice from water.
Temperature: The temperature was controlled to within ±0.02°C. | <urn:uuid:72a94ecd-6ebb-43bf-a730-2633a8e7a1de> | 2.5625 | 309 | Academic Writing | Science & Tech. | 62.158156 | 95,571,351 |
The Near Earth Asteroid 2002 NY40 was observed with the William Herschel Telescope on La Palma, Canary Islands, on the night of August 17 to 18, 2002. The asteroid was imaged just before its closest approach to Earth, using the Adaptive Optics system NAOMI. These are the first images of a Near Earth Asteroid obtained with an Adaptive Optics system. During these observations the asteroid was 750,000 kilometres away, twice the distance to the Moon, and moving very rapidly across the sky (crossing a distance similar to the diameter of the Moon in 6 minutes or at 65,000 kilometres per hour). Despite the technical difficulties introduced by this, very high quality images were obtained in the near-infrared with a resolution of 0.11 arcseconds. This resolution is close to the theoretical limit of the telescope, and sets an upper limit to the size of the asteroid: only 400 metres across at the time of the observations.
Measuring the size of asteroids helps astronomers understand their nature and formation history as well as the potential threat they pose.
Near Earth Asteroids are a small population of asteroids that periodically approach or intersect the orbit of our planet, and have the possibility of colliding with the Earth as probably happened 65 million years ago, ending the dinosaur era. However, the probability that such an impact could happen is very low and in particular Near Earth Asteroid 2002 NY40 represents no danger to human live on Earth.
Javier Méndez | AlphaGalileo
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
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Genetic Engineering. Selective breeding – controlled breeding for desired characteristics; takes advantage of naturally occurring genetic variation – Fig. 13 – 1 What are some organisms that are good examples of selective breeding?
Selective breeding – controlled breeding for desired characteristics; takes advantage of naturally occurring genetic variation – Fig. 13 – 1
What are some organisms that are good examples of selective breeding?
1. hybridization – breeding technique that involves crossing dissimilar individuals to bring together the best traits of both organisms
2. inbreeding – mating between organisms that are genetically similar: promotes preservation of desired characteristics; decreases genetic variation
1. Bacteria – radiation or chemicals can cause “beneficial mutations” – Fig. 13-3
2. Plants – chemicals that prevent chromosomal separation lead to polyploidy (What advantages do these plants have?)
3. Induced mutations can also be used to study the function of proteins
Reading the sequence allows the study of specific genes – Fig. 13 -7 (Sanger Sequence)
1. Start with a single strand of DNA with unknown sequence
2. Mix this strand with DNA polymerase and a lot of nucleotides; some of the nucleotides are “tagged” with dye
3. each time a “tagged” nucleotide is added replication stops
4. Using gel electrophoresis complementary DNA strand is “read”
A technique by which any segment of DNA can be quickly amplified (copied many times) – Fig. 13-8
1. DNA is separated and added to a mixture of nucleotides and enzymes
2. New complementary strands are made
3. Cycle is repeated many times
http://www.youtube.com/watch?v=JRAA4C2OPwg&feature=related PCR Animation
PCR Song http://www.youtube.com/watch?v=x5yPkxCLads
Some bacteria can take up naked DNA from the surroundings.
Plasmid – a small, circular, self-replicating DNA molecule separate from the bacterial chromosome
Assimilated foreign DNA is taken up by the plasmid
Offspring of the recipient bacterium will carry a new combination of genes
Genetic marker – a gene that produces a known protein that can be used to “mark” bacteria that have taken up foreign DNA
Plant Transformation – Fig. 13-10
Plasmids that normally infect plant cells can be used as carriers of foreign DNA
Whatever gene is taken up is then expressed by the plant cell
What are some advantages and disadvantages of this technology?
The bacterium can be used to introduce foreign DNA into plant cells. If the transformation is successful, the DNA will be integrated into one of the cell’s chromosomes.
Animal Transformation – Fig. 13-11
Eggs cells are large enough to take up foreign DNA
DNA is inserted manually and enzymes normally present in the cell to repair DNA help to insert the foreign DNA
Technique can be sued to study specific functions of a gene
Transgenic organisms contain genes from another species; possible because of the universal nature of the genetic code – Fig. 13-12
Microorganisms – easy to grow, divide rapidly, can be used to produce human proteins
Animals can be used to improve food supply, or to study effect of human diseases
Plants – genes can be implanted that provide plants with natural insecticides, or resistance to various chemicals
This transgenic tobacco plant, which glows in the dark, was grown from a tobacco cell transformed with the firefly luciferase gene. The plant illustrates how DNA from one organism contains information that can specify traits in another organism.
Cloning – A clone is a lineage of genetically identical individuals or cells
Basic cloning technique – Fig. 13-13 KNOW!!!
The adult sheep is Dolly. The lamb is Dolly’s first offspring., called Bonnie. The fact that dolly was cloned did ot affect her ability to produce a live offspring. Why might it be important for cloned animals to be able to reproduce? | <urn:uuid:76b0e232-0f56-4009-91cf-653e398634e8> | 2.96875 | 847 | Content Listing | Science & Tech. | 40.579205 | 95,571,359 |
Differentiate between the DNI, DHI and GHI?
Direct Normal Irradiance (DNI) is the amount of solar radiation received per unit area by a surface that is always held perpendicular (or normal) to the rays that come in a straight line from the direction of the sun at its current position in the sky. Typically, you can maximize the amount of irradiance annually received by a surface by keeping it normal to incoming radiation. This quantity is of particular interest to concentrating solar thermal installations and installations that track the position of the sun.
Diffuse Horizontal Irradiance (DHI) is the amount of radiation received per unit area by a surface (not subject to any shade or shadow) that does not arrive on a direct path from the sun, but has been scattered by molecules and particles in the atmosphere and comes equally from all directions
Global Horizontal Irradiance (GHI) is the total amount of shortwave radiation received from above by a surface horizontal to the ground. This value is of particular interest to photovoltaic installations and includes both Direct Normal Irradiance (DNI) and Diffuse Horizontal Irradiance (DHI).
Global Horizontal (GHI) = Direct Normal (DNI) X cos(θ) + Diffuse Horizontal (DHI) | <urn:uuid:b23b4553-222b-4c2b-979e-1e7827fafae3> | 3.625 | 270 | Knowledge Article | Science & Tech. | 15.249091 | 95,571,382 |
"Blurb & Contents" Market: Physicists, astronomers, chemists, engineers, and graduate students. "Martin Bailyn's Survey is a marvelous resource for any teacher of thermal physics....The writing is clear; the references are extensive. If the textbook from which you are teaching leaves you dissatisfied with its treatment of a specific topic, Bailyn's compendium is a good place to look for a different or a deeper presentation." American Journal of Physics This work presents the application and theory of thermodynamics, including its formation according to statistical mechanics and its extension into Special Relativity. A unique feature of this book is the addition of the history of thermodynamics, designed to illustrate and emphasize the development of present day concepts. This book provides valuable insights into how these concepts evolved by discussing the pioneering work of Galileo, Clasuius, Kelvin, and others. The inclusion of both a complete survey of the subject, and an historical background (not found in other books) make this a valuable reference for individuals and graduate students. Partial Contents: 1. Temperature and equilibrium. 2. Heat and work. 3. The emergence of thermodynamics. 4. Entropy and the Second Law. 5. Special topics. 6. Equilibrium thermodynamics. 7. Applications. 8. Secondary Effects; the Third Law of Thermodynamics. 9. Phase Transitions. 10. Microscopic Theories. 11. Statistical Mechanics. 12. Thermodynamics in Special Relativity. | <urn:uuid:f8a76338-be08-4f5d-9ee7-9551da682bca> | 3.078125 | 298 | Content Listing | Science & Tech. | 38.686394 | 95,571,384 |
Bose–Einstein condensation of quasiparticles
Bose–Einstein condensation can occur in quasiparticles, particles that are effective descriptions of collective excitations in materials. Some have integer spins and can be expected to obey Bose–Einstein statistics like traditional particles. Conditions for condensation of various quasiparticles have been predicted and observed. The topic continues to be an active field of study.
BECs form when low temperatures cause nearly all particles to occupy the lowest quantum state. Condensation of quasiparticles occurs in ultracold gases and materials. The lower masses of material quasiparticles relative to atoms lead to higher BEC temperatures. An ideal Bose gas has a phase transitions when inter-particle spacing approaches the thermal De-Broglie wavelength: . The critical concentration is then , leading to a critical temperature: . The particles obey the Bose–Einstein distribution and all occupy the ground state:
The Bose gas can be considered in a harmonic trap, , with the ground state occupancy fraction as a function of temperature:
This can be achieved by cooling and magnetic or optical control of the system. Spectroscopy can detect shifts in peaks indicating thermodynamic phases with condensation. Quasiparticle BEC can be superfluids. Signs of such states include spatial and temporal coherence and polarization changes. Observation for excitons in solids was seen in 2005 and for magnons in materials and polaritons in microcavities in 2006. Graphene is another important solid state system for studies of condensed matter including quasi particles; It's a 2D electron gas, similar to other thin films.
Excitons are electron-hole pairs. Similar to helium-4 superfluidity at the -point (2.17K); a condensate was proposed by Böer et al. in 1961. Experimental phenomenon were predicted leading to various pulsed laser searches that failed to produce evidence. Signs were first seen by Fuzukawa et al. in 1990, but definite detection was published later in the 2000s. Condensed excitons are a superfluid and will not interact with phonons. While the normal exciton absorption is broadened by phonons, in the superfluid absorption degenerates to a line.
Excitions results from photons exciting electrons creating holes, which are then attracted and can form bound states. The 1s paraexciton and orthoexciton are possible. The 1s triplet spin state, 12.1meV below the degenerate orthoexciton states(lifetime ~ns), is decoupled and has a long lifetime to an optical decay. Dilute gas densities (n~1014cm−3) are possible, but paraexcition generation scales poorly, so significant heating occurs in creating high densities(1017cm−3) preventing BECs. Assuming a thermodynamic phase occurs when separation reaches the de Broglie wavelength() gives:
Where, is the exciton density, effective mass(of electron mass order) , and , are the Planck and Boltzmann constants. Density depends on the optical generation and lifetime as: . Tuned lasers create excitons which efficiently self-annihilate at a rate: , preventing a high density paraexciton BEC. A potential well limits diffusion, damps exciton decay, and lowers the critical number, yielding an improved critical temperature versus the T3/2 scaling of free particles:
In an ultrapure Cu2O crystal: = 10s. For an achievable T = 0.01K, a manageable optical pumping rate of 105/s should produce a condensate. More detailed calculations by J. Keldysh and later by D. Snoke et al. started a large number of experimental searches into the 1990s that failed to detect signs. Pulse methods led to overheating, preventing condensate states. Helium cooling allows miili-kelvin setups and continuous wave optics improves on pulsed searches. Relaxation explosion of a condensate at lattice temperature 354 mK was seen by Yoshioka et al. in 2011. Recent experiments by Stolz et al. using a potential trap have given more evidence at ultralow temperature 37 mK. In a parabolic trap with exciton temperature 200 mK and lifetime broadened to 650ns, the dependence of luminescence on laser intensity has a kink which indicates condensation. The theory of a Bose gas is extended to a mean field interacting gas by a Bogoliubov approach to predict the exciton spectrum; The kink is considered a sign of transition to BEC. Signs were seen for a dense gas BEC in a GaAs quantum well.
Magnons, electron spin waves, can be controlled by a magnetic field. Densities from the limit of a dilute gas to a strongly interacting Bose liquid are possible. Magnetic ordering is the analog of superfluidity. The condensate appears as the emission of monochromatic microwaves, which are tunable with the applied magnetic field.
In 1999 condensation was demonstrated in antiferromagnetic TlCuCl3, at temperatures as large as 14 K. The high transition temperature (relative to atomic gases) is due to the small mass (near an electron) and greater density. In 2006, condensation in a ferromagnetic Yttrium-iron-garnet thin film was seen even at room temperature with optical pumping. Condensation was reported in gadolinium in 2011. Magnon BECs have been considered as qubits for quantum computing.
Polaritons, caused by light coupling to excitons, occur in optical cavities and condensation of exciton-polaritons in an optical microcavity was first published in Nature in 2006. Semiconductor cavity polariton gases transition to ground state occupation at 19K. Bogoliubov excitations were seen polariton BECs in 2008. The signatures of BEC were observed at room temperature for the first time in 2013, in a large exciton energy semiconductor device and in a polymer microcavity.
Rotons, an elementary excitation in superfluid 4He introduced by Landau, were discussed by Feynman and others. Rotons condense at low temperature. Experiments have been proposed and the expected spectrum has been studied, but roton condensates have not been detected. Phonons were first observed in a condensate in 2004 by ultrashort pulses in a bismuth crystal at 7K.
- Electronic properties of two-dimensional systems, Rev. Mod. Phys. 54, 437, 1 April 1982
- Theory of Bose–Einstein condensation in trapped gases, Rev. Mod. Phys. 71, 463, 1 April 1999
- Many-body physics with ultracold gases, Rev. Mod. Phys. 80, 885,18 July 2008
- On the theory of Bose–Einstein condensation of quasiparticles: On the possibility of condensation of ferromagnons at high temperatures, Low Temp. Phys. 33, 37 (2007)
- Towards Bose–Einstein condensation of excitons in potential traps, Nature 417, 47–52 (2 May 2002)
- Eisenstein, JP; Macdonald, AH (9 December 2004). "Bose–Einstein condensation of excitons in bilayer electron systems". Nature. 432: 691–694. arXiv: . Bibcode:2004Natur.432..691E. doi:10.1038/nature03081. PMID 15592403.
- Berman, OL; Kezerashvili, RY; Lozovik, YE; Snoke, DW (1 November 2010). "Bose–Einstein condensation and superfluidity of trapped polaritons in graphene and quantum wells embedded in a microcavity". Philosophical Transactions of the Royal Society A. 368: 5459–82. Bibcode:2010RSPTA.368.5459B. doi:10.1098/rsta.2010.0208. PMID 21041225.
- London, F (1938). "The -Point of Liquid Helium and the Bose–Einstein Condensation". Nature. 141 (3571): 643–644. Bibcode:1938Natur.141..643L. doi:10.1038/141643a0.
- Einstein, A. (1920) Proc. Berlin Acad. Science
- Kapiza, P (1938). "Viscosity of Liquid Helium below the λ-Point". Nature. 141 (3558): 74. Bibcode:1938Natur.141...74K. doi:10.1038/141074a0.
- Blatt, J.M., K.W. Boer, and W. Brandt, (1962) Bose–Einstein Condensation of excitons, Phys. Rev. 126.5, 1691
- Heinrich Stolz; et al. (10 October 2012). "New Journal of Physics". New Journal of Physics. 14: 105007. arXiv: . Bibcode:2012NJPh...14j5007S. doi:10.1088/1367-2630/14/10/105007.
- Aurora, C.P. (2001) Thermodynamics, McGraw-Hill
- Keldysh, L.V. (1964). Eksp. Teor. Fiz. 47: 1515. Missing or empty
|title=(help); Keldysh, L.V. (1965). Sov. JEPT. 20: 1018. Missing or empty
- Snoke, D.W.; Wolfe, J.P.; Mysyrovicz, A. (1990). "Evidence for Bose-Einstein condensation of excitons inCu2O". Phys. Rev. B. 41: 11171. Bibcode:1990PhRvB..4111171S. doi:10.1103/physrevb.41.11171.
- Naka, N. and Nakasawa, N. (2005) J, Lumin. 112, 11
- Joshioka, K.; Ideguchi, T.; Mysyrovicz, A; Kuwata-Gonokami, M. (2010). "Quantum inelastic collisions between paraexcitons inCu2O". Phys. Rev. B. 82: 041201. Bibcode:2010PhRvB..82d1201Y. doi:10.1103/physrevb.82.041201.
- Stolz, H.; Semkat, D. (2010). "Unique signatures for Bose-Einstein condensation in the decay luminescence lineshape of weakly interacting excitons in a potential trap". Phys. Rev. B. 81: 081302. arXiv: . Bibcode:2010PhRvB..81h1302S. doi:10.1103/physrevb.81.081302.
- "Transition to a Bose–Einstein condensate and relaxation explosion of excitons at sub-Kelvin temperatures". Nature Communications. 2: 328. May 31, 2011. arXiv: . Bibcode:2011NatCo...2E.328Y. doi:10.1038/ncomms1335.
- "Evidence for a Bose–Einstein condensate of excitons". EPL. 107: 10012. July 2014. arXiv: . Bibcode:2014EL....10710012A. doi:10.1209/0295-5075/107/10012.
- Nikuni, T.; Oshikawa, M.; Oosawa, A.; Tanaka, H. (1999). "Bose–Einstein Condensation of Dilute Magnons in TlCuCl3". Physical Review Letters. 84 (25): 5868–71. arXiv: . Bibcode:2000PhRvL..84.5868N. doi:10.1103/PhysRevLett.84.5868. PMID 10991075.
- Demokritov, S.O.; Demidov, VE; Dzyapko, O; Melkov, GA; Serga, AA; Hillebrands, B; Slavin, AN (2006). "Bose–Einstein condensation of quasi-equilibrium magnons at room temperature under pumping". Nature. 443 (7110): 430–433. Bibcode:2006Natur.443..430D. doi:10.1038/nature05117. PMID 17006509.
- Magnon Bose Einstein Condensation made simple. Website of the "Westfählische Wilhelms Universität Münster" Prof.Demokritov. Retrieved 25 June 2012.
- Mathew, SP; Kaul, SN (Jul 6, 2011). "Bose–Einstein condensation of magnons in polycrystalline gadolinium with nano-size grains". J Phys Condens Matter. 23: 266003. Bibcode:2011JPCM...23z6003M. doi:10.1088/0953-8984/23/26/266003. PMID 21673396.
- "Magnon qubit and quantum computing on magnon Bose–Einstein condensates". Phys. Rev. A. 90: 042303. 2 October 2014. Bibcode:2014PhRvA..90d2303A. doi:10.1103/PhysRevA.90.042303.
- Kasprzak, J; Richard, M; Kundermann, S; Baas, A; Jeambrun, P; Keeling, JM; Marchetti, FM; Szymańska, MH; André, R; Staehli, JL; Savona, V; Littlewood, PB; Deveaud, B; Dang (28 September 2006). "Bose–Einstein condensation of exciton polaritons". Nature. 443: 409–414. Bibcode:2006Natur.443..409K. doi:10.1038/nature05131. PMID 17006506.
- "Observation of Bogoliubov excitations in exciton-polariton condensates". Nature Physics. 4: 700–705. 2008. Bibcode:2008NatPh...4..673U. doi:10.1038/nphys1034.
- Das, A; Bhattacharya, P; Heo, J; Banerjee, A; Guo, W (February 19, 2013). "Polariton Bose–Einstein condensate at room temperature in an Al(Ga)N nanowire–dielectric microcavity with a spatial potential trap". Proceedings of the National Academy of Sciences. 110: 2735–2740. arXiv: . Bibcode:2013PNAS..110.2735D. doi:10.1073/pnas.1210842110. PMC . PMID 23382183.
- Francis, Matthew (Feb 6, 2013). "SCIENTIFIC METHOD / SCIENCE & EXPLORATION Bose–Einstein condensate created at room temperature". Ars Technica.
- Plumhof, JD; Stöferle, T; Mai, L; Scherf, U; Mahrt, RF (8 December 2013). "Room-temperature Bose–Einstein condensation of cavity exciton–polaritons in a polymer". Nature Materials. 13: 247–252. Bibcode:2014NatMa..13..247P. doi:10.1038/nmat3825. PMID 24317189.
- L. Landau (1941). J. Phys. USSR. 5: 71. Missing or empty
- "R. P. Feynman". Phys. Rev. 94: 262. 1954. Bibcode:1954PhRv...94..262F. doi:10.1103/PhysRev.94.262.
- "Bose condensation of moving rotons". Soviet Physics Uspekhi. 23: 317–318. 1980. Bibcode:1980SvPhU..23..317I. doi:10.1070/PU1980v023n06ABEH004937.
- L. A. Melnikovsky (22 July 2011). "Bose–Einstein condensation of rotons". Phys. Rev. B. 84: 024525. arXiv: . Bibcode:2011PhRvB..84b4525M. doi:10.1103/PhysRevB.84.024525.
- "Roton spectroscopy in a harmonically trapped dipolar Bose–Einstein condensate". Phys. Rev. A. 86: 021604. 15 August 2012. arXiv: . Bibcode:2012PhRvA..86b1604B. doi:10.1103/PhysRevA.86.021604.
- "Quantum Monte Carlo study of a vortex in superfluid He4 and search for a vortex state in the solid". Phys. Rev. B. 89: 224516. 27 June 2014. arXiv: . Bibcode:2014PhRvB..89v4516G. doi:10.1103/PhysRevB.89.224516.
- "Transient Bose–Einstein condensation of phonons". Physics Letters A. 321: 381–387. 16 February 2004. Bibcode:2004PhLA..321..381M. doi:10.1016/j.physleta.2003.11.063. | <urn:uuid:15811f8d-87d7-42e1-9c30-ad1a59aadf89> | 3.125 | 3,801 | Knowledge Article | Science & Tech. | 65.593829 | 95,571,385 |
Doubts in Physics answered
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The sum of magnitude of two forces acting at a point is 18N an the magnitude of their resultant is 12N.If the resultant makes an angle of 90 degree with the force of smaller magnitude what are magnitude of the two forces?
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26; n = 12) of the ampullar contraction-dilatation cycle concomitant with hemolymph flow in ascidians
(Mukai et al.
Ultrastructure of vegetative and sporulation tages of Haplosporidium ascidiarum from the Ascidian
Ciona intestinalis L.
In this review, we will discuss the gene regulatory network in an ascidian
, Ciona intestinalis.
The amount of carbohydrate recorded in the ascidian
Chemical analysis of polysaccharides from ascidians
reveals sulfate ester, high galactone content and small amounts of glucose and hexosamine in proportions that vary among the different species.
containing phycourobilin and symbiotic with ascidians
Thus, prior to the establishment of man-made substrates (marina floats, pilings, harbor buoys and boat hulls), few shallow-water ascidians
were recorded from the Texas Gulf coast (Van Name 1945; Whitten et al.
greater than] 6 m) assemblages, composed of sponges, bryozoans, brachiopods, cnidarians, and ascidians
(Grange et al.
Third, in sessile organisms, such as ascidians
and plants, there can be no behavioral choice of male gametes; therefore, sperm choice and the postfertilization process of differential abortion may be especially important (Wirtz 1997) and may explain the more obvious nature of these forms of female choice in these taxa (Table 1).
To determine whether the palatability of lecithotrophic larvae from diverse sessile invertebrates varies, and how larval palatability may relate to other life history traits, we examined larval palatability to co-occurring fishes using larvae from sponges (12 species), gorgonians (nine species), corals (three species), hydroids (two species), ascidians
(three species), and a bryozoan (one species).
teleta, along with those of some molluscs, ascidians
, and echinoderms, are inhibited from metamorphosing by endogenously produced nitric oxide (Bishop and Brandhorst, 2001; Pechenik et al.
The stations where interrupted fishing effort was identified presented a higher biomass of sessile, like sponges or ascidians
, and fragile organisms, like little ophiuroids, than the sites continuously disturbed up to 2007.
The colonial ascidians
(Chordata, Tunicata) are marine invertebrates widely distributed in benthic systems.
Modiolarca lateralis (Pteryomorphia: Mytilidae): bivalve associated to six species of ascidians
from Bocas del Toro, Panama
1999) Transmembrane signal transduction for the regulation of sperm motility in fishes and ascidians | <urn:uuid:d9237f9d-ff99-4c24-a262-4a20959f900a> | 2.515625 | 635 | Academic Writing | Science & Tech. | -0.234933 | 95,571,411 |
Spectroscopic Ellipsometry Characterization of Polymers Modified by Atomic Oxygen and Ultraviolet Radiation
Atomic oxygen (AO) and ultraviolet (UV) radiation-induced surface modifications of several space application polymers are investigated with spectroscopic ellipsometry (SE). The polymers studied include Kapton® polyimide, FEP Teflon®, CV-1144-0 silicone and polyarylene ether benzimidazole (PAEBI). Using in situ and ex situ SE covering a large spectral range from 190 nm to 14 μm, various parameters and trends of the polymers are measured as they are exposed to AO and/or UV light.
UV light greater than 200 nm wavelength is used to modify the surface of PAEBI and Kapton. Thickness and index of refraction as a function of depth of the UV-modified surface layers is quantified. The modified layers are optically-modelled assuming an exponentially graded layer, as opposed to standard models that often use either a single homogenous layer or linearly-graded layer. Measurements show that UV light causes a decrease in the index of refraction in both materials. The damaged layer in Kapton is approximately 500 nm into the polymer and approximately 200 nm in the PAEBI.
Two oxide forming polymers, CV-1144-0 silicone and PAEBI, are exposed to AO in an oxygen plasma. Protective oxide layers that form on the polymers are studied using SE. Oxide formation trends, rates of oxidation, amount of porosity, volume percentage of water, and change in optical properties as a function of AO exposure are quantified. Furthermore, studying the change in molecular bond vibrations in the infrared allowed a quasi-chemical analysis of the silicone.
Single wavelength ellipsometry over a large range of incident angles is used to measure changes in potical density of aluminizedFEP Teflon after being exposed to the Low Earth Orbit environment aboard the Hubble Space Telescope. The purpose of the study is to help support physical density measurements acquired by NASA Lewis Research Center. The optical density measurements are in good agreement with physical density measurements. These measurements are in good agreement with excessive heating was a major contributor to increases in density of the FEP returned from the second servicing mission.
KeywordsOptical Constant Oxygen Plasma Hubble Space Telescope Spectroscopic Ellipsometry Service Mission
Unable to display preview. Download preview PDF.
- 1.“US Standard Atmosphere, 1976,” NASA TM-X-74335, (1976).Google Scholar
- 2.J. A. Dever, “Low Earth Orbital Atomic Oxygen and Ultraviolet Radiation Effects on Polymers,” NASA Tech. Memo. 103711, (1991).Google Scholar
- 3.B. A. Banks, K. K. De Groh, S. K. Rutledge, and Frank J. DiFilippo, “Prediction of In-Space Durability of Protected Polymers Based on Ground Laboratory Thermal Energy Atomic Oxygen,” NASA Teck Memo. J07209, (1996).Google Scholar
- 4.R.M.A. Azzam, and N.M. Bashara, Ellipsometry and Polarized Light, North Holland Publishing, New York, (1977).Google Scholar
- 6.J. A. Wooilam, and P. G. Snyder, in Encyclopedia of Material Characterization, Butterworth-Heinemann, Publishers, Boston, 401 (1992).Google Scholar
- 8.F. Wooten, Optical Properties of Solids, Academic Press, New York, (1972).Google Scholar
- 9.S.F. Dyke, AJ. Floyd, M. Sainbury and R.S. Theobald, Organic Spectroscopy, Longman Group Limited, London, 13 (1971).Google Scholar
- 10.S. K. Rutledge, B. A. Banks, et al., “An Evaluation of Candidate Oxidation Resistant Materials for Space Applications in LEO,” NASA Tech. Memo. 100122 (1986).Google Scholar
- 12.B. A. Banks, K. K. de Groh, S. K. Rutledge, and F. J. DiFilippo, “Prediction of In-Space Durability of Protected Polymers Based on Ground Laboratory Thermal Energy Atomic Oxygen,” NASA Tech. Memo. 107209 (1996).Google Scholar
- 13.B. A. Banks, J. A. Dever, L. Gebauer, and C. M. Hill, “Atomic oxygen interactions with FEP Teflon and silicones on LDEF’,” Proceedings of the LDEF First Post-Retrieval Symposium, Kissimmee, FL, June 2–8 1991, NASA CP 3134, Part 2, pg. 801–815.Google Scholar
- 14.T. M. Zuby, K. K. de Groh, and D. C. Smith, “Degradation of FEP Thermal Control Materials Returned from the Hubble Space Telescope,” NASA Tech. Memo. 104627, (1995).Google Scholar
- 15.K. K. de Groh and D. C. Smith, “Investigation of Teflon FEP Embrittlement on Spacecraft in Low Earth Orbit,” Proc. 7th Int. Symp. on Mat. in Space Env., Toulouse, FR, 255 (1997).Google Scholar
- 16.B. A. Banks, T. Stueber, S. K. Rutledge, D. Jaworske, and W. Peters, “Thermal Cycling-caused Degradation of Hubble Space Telescope Aluminized FEP Thermal Insulation,” AIAA #98-0896, (1998)Google Scholar | <urn:uuid:5f2c525c-3e9b-4b26-964b-c3279ace0b43> | 2.671875 | 1,243 | Academic Writing | Science & Tech. | 54.174937 | 95,571,446 |
|< Previous: Making the basic game work: UIButton and CALayer||Next: From outlets to actions: IBAction and string interpolation >|
Our current code chooses the first three items in the countries array, and places them into the three buttons on our view controller. This is fine to begin with, but really we need to choose random countries each time. There are two ways of doing this:
Both approaches are valid, but the former takes a little more work because we need to ensure that all three numbers are different – this game would be even less fun if all three flags were the French flag!
The second approach is easy to do, but there's a catch: we're going to use an iOS framework called GameplayKit. You see, randomness is a complicated thing, and it's easy to write some code that you think randomizes an array perfectly when actually it generates a predictable sequence. As a result, we're going to use an Apple framework called GameplayKit that does all this hard work for us.
Now, you might think, "why would I want to use something called GameplayKit for apps?" But the simple answer is: because it's there, because all devices have it built right in, and because it's available in all your projects, whether games or apps. GameplayKit can do a lot more than just shuffling an array, but we'll get on to that much later.
For now, look at the top of your ViewController.swift file and you'll find a line of code that says
import UIKit. Just before that, add this new line:
With that done, we can start using the functionality given to us by GameplayKit. At the start of the
askQuestion() method, just before you call the first
setImage() method, add this line of code:
countries = GKRandomSource.sharedRandom().arrayByShufflingObjects(in: countries) as! [String]
That will automatically randomize the order of the countries in the array, meaning that
countries will refer to different flags each time the
askQuestion() method is called. To try it out, press Cmd+R to run your program a few times to see different flags each time.
The next step is to track which answer should be the correct one, and to do that we're going to create a new property for our view controller called
correctAnswer. Put this near the top, just above
var score = 0:
var correctAnswer = 0
This gives us a new integer property that will store whether it's flag 0, 1 or 2 that holds the correct answer.
To choose which should be the right answer requires using GameplayKit again, because we need to choose a random number for the correct answer. GameplayKit has a special method for this called
nextInt(upperBound:), which lets you specify a number as your "upper bound" – i.e., the cap for the numbers to generate. GameplayKit will then return a number between 0 and one less than your upper bound, so if you want a number that could be 0, 1 or 2 you specify an upper bound of 3.
Putting all this together, to generate a random number between 0 and 2 inclusive you need to put this line just below the three
setImage() calls in
correctAnswer = GKRandomSource.sharedRandom().nextInt(upperBound: 3)
Now that we have the correct answer, we just need to put its text into the navigation bar. This can be done by using the
title property of our view controller, but we need to add one more thing: we don't want to write "france" or "uk" in the navigation bar, because it looks ugly. We could capitalize the first letter, and that would work great for France, Germany, and so on, but it would look poor for “Us” and “Uk”, which should be “US” and “UK”.
The solution here is simple: uppercase the entire string. This is done using the
uppercased() method of any string, so all we need to do is read the string out from the countries array at the position of
correctAnswer, then uppercase it. Add this to the end of the
askQuestion() method, just after
correctAnswer is set:
title = countries[correctAnswer].uppercased()
With that done, you can run the game and it's now almost playable: you'll get three different flags each time, and the flag the player needs to tap on will have its name shown at the top.
Of course, there's one piece missing: the user can tap on the flag buttons, but they don't actually do anything. Let's fix that…
Take Swift further!
Your Swift skills let you make apps for macOS, watchOS, tvOS, and more, and for one low price you can learn it all with my Swift Platform Pack! | <urn:uuid:0a7d6d7b-af58-4e69-b285-2157da55a274> | 2.671875 | 1,049 | Tutorial | Software Dev. | 59.481895 | 95,571,449 |
The purpose of the list is to increase the speed of the algorithm by
skipping some numbers. This is possible because of the math of Differences
between consecutive primes but i am currently verifying the algorithm if it
works, since the list might be wrong.
2017-02-25 7:44 GMT+01:00 Lindsay John Lawrence <
> Does anyone know the algorithm that is being expressed here?
> I am trying to understand the code... http://picolisp.com/wiki/?99p35
> de prime-factors (N)
> (let (D 2 L (1 2 2 . (4 2 4 2 4 6 2 6 .)) M (sqrt N))
> (while (>= M D)
> (if (=0 (% N D))
> (setq M (sqrt (setq N (/ N (link D)))))
> (inc 'D (pop 'L)) ) )
> (link N) ) ) )
> and having difficulties understanding the purpose of the circular list. | <urn:uuid:ad2d7b1a-2906-467d-8092-1ed09140a277> | 2.859375 | 221 | Comment Section | Software Dev. | 98.522845 | 95,571,451 |
Global Warming and the Greenhouse Effect.
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This easy-to-understand guide explains the basic principles in simple terms, providing insight into the language of organic chemists, the major classes of compounds, and more.
The Elemental Foundation of Chemistry: Atoms, Molecules, Elements, Compounds, Mixtures, and States of Matter.If youre feeling challenged by organic chemistry, fear not!2nd Edition -.Stratospheric Chemistry and the Ozone Layer: A Thin Veil of Protection.Complete with new explanations and example equations, this book will help you ace your organic chemistry class!Chemicals in Our Bodies and Our Environment: Vitamins, Food Additives, Pesticides, and More.Score your highest in your Organic Chemistry I course.The Molecules That Make You What You Are: Nucleic Acids, Proteins, and Hormones.A complete overview of chemical reactions, strategies for solving organic chemistry problems.The book ties every chemistry concept to things familiar to students - nutrition, drugs, the environment, household items.Buy on Amazon, learn to: Grasp the principles of organic chemistry at your own pace.Chemistry in Water: Salts, Acids, and Bases.
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Hydrocarbons dive into hydrocarbons, including a full explanation of alkanes, alkenes, and alkynes. | <urn:uuid:c76de925-b5c5-4f82-adaa-b825bd4d811e> | 3.109375 | 536 | Product Page | Science & Tech. | 47.931538 | 95,571,487 |
Migration has gotten off to a bit of a slow start, but it is in full
swing now! Last week I mentioned that the front moving across the country
was weak, but that if it strengthened it could cause some large fallouts.
Well, that is exactly what happened!
Fallouts in Texas, Louisiana, Alabama, and Florida
cold front brought lots of big storms across much of the country
during the end of last week, and there
were reports of large fallouts all along the Gulf Coast. The main
species all seemed to be the same, regardless of whether the reports came
Texas, Louisiana, Alabama, or Florida (I did not receive any reports
from Mississippi, but I am sure they would have seen the same): Indigo
Buntings, Scarlet Tanagers, Orchard Orioles, Red-eyed Vireos, and
Painted Buntings. One observer on Grand Isle in SE Louisiana saw 105 Indigo
Buntings, 56 Red-eyed Vireos, 49 Scarlet Tanagers, and 30 Orchard
species that were seen included the first Swainson's Thrushes, Gray-cheeked
Thrushes, and Swainson's Warblers, on High Island,Texas, and birders
in Gulf Breeze, Florida saw many Tennessee Warblers, American Redstarts,
and Blue-winged Warblers.
Slows Movement in the Southeast, mid-Atlantic, and Northeast
the Southeast, mid-Atlantic, and Northeast, there haven't been many
new arrivals because, as you can see on the
weather map, yet another cold front is bringing rainy weather and
migrants grounded. In the Midwest, however, winds have already
shifted to the south, so more migrants are starting to arrive. Birders
Ohio are reporting many Hooded Warblers, American Redstarts, Ovenbirds,
and Prairie Warblers, while Indigo Buntings and Orchard Orioles
up in Missouri and Illinois.
Change in Western US
In the Western US, there hasn't been much change, although the
Tucson, AZ area had a big arrival of Hermit Warblers, Orange-crowned
and Hutton's Vireos. Central California saw its first Black-headed
Grosbeaks of the season, along with Anna's hummingbirds, Orange-crowned
and a Hammond's Flycatcher. Swallows (Bar, Tree, Northern Rough-winged)
and warblers (Common Yellowthroats and Yellow-rumped Warblers) have
shown up in Colorado, and the first Vaux's Swifts arrived in
Does This Week Look?
Will there be more fallouts this week? By this point, you should
be able to tell me! Look at the weather map and what do you see? Not much.
the current cold front moves off the east coast by tomorrow, high
pressure will be in place for a couple of days, meaning that all
those birds along the Gulf coast will stick around a little longer.
the weekend, winds will have shifted to the south for much of the
country, which will allow birds to finally start heading north.
I expect to get reports of new arrivals through much of the northern
part of the country, so be ready for them!
in the southern part of the US, from coast to coast, should still
see some good birds, as new migrants arrive from the tropics, but
it doesn't look like there will be any fallouts.
are heading into the peak of spring migration for some areas, while
migration is just starting to kick into high gear in other places;
it is a great time of year all around!
Chickamauga Creek Conservancy | <urn:uuid:35a4d061-33d0-4a36-8e00-df4c5ad3f36a> | 2.53125 | 782 | Personal Blog | Science & Tech. | 52.150495 | 95,571,494 |
There’s more to nitrogen than the letter N. The element and its biogeochemical cycle is the focus of research by Amy Marcarelli, an associate professor of biological sciences. Last year, Marcarelli won a National Science Foundation (NSF) Early Career Award grant to explore two halves of the nitrogen cycle. Her work could flip how we currently think about the nitrogen cycle.
In the nitrogen cycle, the balance of nitrogen fixation and denitrification is not a perfect yin-yang. Unbalanced systems can lead to more than just August pond scum; excess nitrogen is the main driver of the world's dead zones at major river deltas. Marcarelli's research, funded by an NSF CAREER grant, dives into the unexplored side of nitrogen fixation in streams.
Learn more about Marcarelli's research in a few ways:
- Join @mturesearch Thursday March 17 from 1:00 to 2:00 p.m. Eastern for a live chat with @AmyMarcarelli. Follow #mtulive to see the conversation.
- Don’t worry if you missed the live chat—check out the Storify below.
- We also break down the yin and yang of nitrogen fixation and dentrification in an infographic.
- For even more, listen to Marcarelli explain her research with Allison Mills in the video below, with illustrations by Jordan Blahnik and produced by Ben Jaszczak. (Check out the too long; didn't read version up top)
Then, stay tuned this summer as Marcarelli and her research team make their way across North America to measure streams from Puerto Rico to Michigan to Idaho to Alaska. They'll be taking a van that is currently in the shop with a team of mechanical engineering seniors, who transforming it for their senior design project into a transportable ecology lab and classroom. Watch for updates on @mturesearch and #FieldworkFriday.
Nitrogen Fixation Infographic
The infographic below explains how nitrogen fixation and denitrification are like a yin-yang. Most of the time, we think the processes balance each other out. However, Marcarelli's research focuses on the fact that nitrogen fixation is rarely measured in streams; that means we're missing an entire half of that yin-yang. Plus, from other studies on lake environments, we know that nitrogen limitation—a cap on how much nitrogen is available for organisms—is influenced by the availability of other nutrients, notably phosphorus.
Yin-Yang of Nitrogen: #NSFCareer Researcher Amy Marcarelli
The balance of nitrogen fixation and denitrification is not a perfect yin-yang. Unbalanced systems can lead to more than just August pond scum; excess nitrogen is the main driver of the world's dead zones at major river deltas.Amy Marcarelli's research, funded by an NSF CAREER grant, dives into the unexplored side of nitrogen fixation in stream
Over the next summer, @AmyMarcarelli will be leading a team across North America, gathering samples in streams from Puerto Rico to Alaska to get a better sense of nitrogen fixation. Stay tuned on @mturesearch and mtu.edu/unscripted to learn about the team's work. Here's a local stream where they'll sample.This is a recap of a live chat with @AmyMarcarelli and @mturesearch from March 17, 2016.
Meet the Processes
@AmyMarcarelli's work focuses on two processes in the nitrogen cycle: nitrogen fixation and denitrification. In undisturbed natural ecosystems, the processes balance each other out, with each part of the cycle driven by certain microbial communities. In a nutshell: nitrogen gas gets converted (via nitrogen fixation) into a new form of nitrogen (ammonium), which is transformed into another kind (nitrate), and is finally changed again and released back into the atmosphere (via denitrifcation.)
Here is a quick explainer:
The Balancing Act
Within this big global biogeochemical cycle, @AmyMarcarelli is interested in how nitrogen fixation and denitrifcation are balanced.
@mturesearch In lakes, estuaries and rivers, we know that denitrification can increase substantially as N loads increase— Amy Marcarelli (@AmyMarcarelli) March 17, 2016
@mturesearch These are colonies of Nostoc, which are common in our Idaho study streams— Amy Marcarelli (@AmyMarcarelli) March 17, 2016
The Other players
Nitrogen is a major nutrient that organisms need to survive. However, it's not the only nutrient.
@ScottBiogeochem Great q! I don't think we understand well how P changes DNF in streams - planning nutrient enrichment exp in yrs 2-3.— Amy Marcarelli (@AmyMarcarelli) March 17, 2016
Hard to imagine with this picture, but in the summer, the van below will be an ecology powerhouse. Right now a group of @mtuMEEM students are giving the vehicle a make-over to turn it into a transportable lab and classroom.
And all that travel is guaranteed to be better than this:
Michigan Technological University is a public research university, home to more than 7,000 students from 54 countries. Founded in 1885, the University offers more than 120 undergraduate and graduate degree programs in science and technology, engineering, forestry, business and economics, health professions, humanities, mathematics, and social sciences. Our campus in Michigan’s Upper Peninsula overlooks the Keweenaw Waterway and is just a few miles from Lake Superior. | <urn:uuid:8259972d-ac90-4a15-ad57-2b75c6cd88dc> | 2.96875 | 1,172 | News (Org.) | Science & Tech. | 37.73734 | 95,571,502 |
Square is For the lengths of the sides of square are half the lengths of the sides of square two adjacent sides of square are perpendicular bisectors of two adjacent sides of square and the other two sides of square are the perpendicular bisectors of two adjacent sides of square The total area enclosed by at least one of can be written in the form where and are relatively prime positive integers. Find
This problem is copyrighted by the American Mathematics Competitions.
Instructions for entering answers:
For questions or comments, please email firstname.lastname@example.org. | <urn:uuid:5993c183-5227-4ade-b1e3-652da0783db7> | 3 | 115 | Tutorial | Science & Tech. | 31.36575 | 95,571,511 |
A grading implementation written in the Scala languague (https://www.scala-lang.org/index.html)
Scala can be downloaded from their website at https://www.scala-lang.org/download/ and
provides excellent documentation.
Scala uses the Scala IDE that is based on Eclipse. There are also plugins available
on popular IDEs such as IntelliJ and Visual Studio code. The use of these IDEs
requires you to have Java already installed on your machine. The IDE will need to be pointed
to the path of the JDK.
If using Mac OS, Scala can be installed by running
$ brew update $ brew install scala $ brew install sbt
sbt is a build tool commonly used with Scala, as mentioned on Scala's website
Compilation and execution is done by simply navigating to the folder containing the
and running the command | <urn:uuid:2c99e288-f241-4a03-8b5c-9ecf782a7dc7> | 2.78125 | 186 | Product Page | Software Dev. | 53.067765 | 95,571,515 |
New University of Washington research demonstrates that one suggested method, injecting sulfate particles into the stratosphere, would likely achieve only part of the desired effect, and could carry serious, if unintended, consequences.
The lower atmosphere already contains tiny sulfate and sea salt particles, called aerosols, that reflect energy from the sun into space. Some have suggested injecting sulfate particles directly into the stratosphere to enhance the effect, and also to reduce the rate of future warming that would result from continued increases in atmospheric carbon dioxide.
But a UW modeling study shows that sulfate particles in the stratosphere will not necessarily offset all the effects of future increases in atmospheric carbon dioxide.
Additionally, there still is likely to be significant warming in regions where climate change impacts originally prompted a desire for geoengineered solutions, said Kelly McCusker, a UW doctoral student in atmospheric sciences.
The modeling study shows that significant changes would still occur because even increased aerosol levels cannot balance changes in atmospheric and oceanic circulation brought on by higher levels of atmospheric carbon dioxide.
"There is no way to keep the climate the way it is now. Later this century, you would not be able to recreate present-day Earth just by adding sulfate aerosols to the atmosphere," McCusker said.
She is lead author of a paper detailing the findings published online in December in the Journal of Climate. Coauthors are UW atmospheric sciences faculty David Battisti and Cecilia Bitz.
Using the National Center for Atmospheric Research's Community Climate System Model version 3 and working at the Texas Advanced Computing Center, the researchers found that there would, in fact, be less overall warming with a combination of increased atmospheric aerosols and increased carbon dioxide than there would be with just increased carbon dioxide.
They also found that injecting sulfate particles into the atmosphere might even suppress temperature increases in the tropics enough to prevent serious food shortages and limit negative impacts on tropical organisms in the coming decades.
But temperature changes in polar regions could still be significant. Increased winter surface temperatures in northern Eurasia could have serious ramifications for Arctic marine mammals not equipped to adapt quickly to climate change. In Antarctic winters, changes in surface winds would also bring changes in ocean circulation with potentially significant consequences for ice sheets in West Antarctica.Even with geoengineering, there still could be climate emergencies – such as melting ice sheets or loss of polar bear habitat – in the polar regions, the scientists concluded. They added that the odds of a "climate surprise" would be high because the uncertainties about the effects of geoengineering would be added to existing uncertainties about climate change.
For more information, contact McCusker at firstname.lastname@example.org
Vince Stricherz | EurekAlert!
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
Drones survey African wildlife
11.07.2018 | Schweizerischer Nationalfonds SNF
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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12.07.2018 | Event News
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13.07.2018 | Life Sciences | <urn:uuid:8baa2166-c194-4a84-bf2a-beef959d356a> | 3.84375 | 1,177 | Content Listing | Science & Tech. | 30.356952 | 95,571,528 |
Remaining CO2 emission 'quota' may be used up in one generation and more than half of all fossil fuel reserves may need to be left untapped
Carbon dioxide emissions, the main contributor to global warming, are set to rise again in 2014 - reaching a record high of 40 billion tonnes.
The 2.5 per cent projected rise in burning fossil fuels is revealed by the Global Carbon Project, which is co-led in the UK by researchers at the Tyndall Centre for Climate Change Research at the University of East Anglia and the College of Engineering, Mathematics and Physical Sciences at the University of Exeter.
It comes ahead of the New York Climate Summit, where world leaders will seek to catalyse action on climate change.
This latest annual update of the Global Carbon Budget shows that total future CO2 emissions cannot exceed 1,200 billion tonnes – for a likely 66 per cent chance of keeping average global warming under 2°C (since pre-industrial times).
At the current rate of CO2 emissions, this 1,200 billion tonne CO2 'quota' would be used up in around 30 years. This means that there is just one generation before the safeguards to a 2oC limit may be breached.
The international team of climate scientists say that to avoid this, more than half of all fossil fuel reserves may need to be left unexploited.
Prof Corinne Le Quéré, Director of the Tyndall Centre at UEA, said: "The human influence on climate change is clear. We need substantial and sustained reductions in CO2 emissions from burning fossil fuels if we are to limit global climate change. We are nowhere near the commitments necessary to stay below 2°C of climate change, a level that will be already challenging to manage for most countries around the world, even for rich nations.
"Politicians meeting in New York need to think very carefully about their diminishing choices exposed by climate science."
The annual Global Carbon Budget, published today, includes a projection for 2014, as well as figures for 2013 by country and per capita. It is accompanied by a series of papers in Nature Climate Change, Nature Geoscience and Earth System Science Data Discussions.
Lead author of the Nature Geoscience paper, Prof Pierre Friedlingstein, from the University of Exeter said: "The time for a quiet evolution in our attitudes towards climate change is now over. Delaying action is not an option - we need to act together, and act quickly, if we are to stand a chance of avoiding climate change not long into the future, but within many of our own lifetimes.
"We have already used two-thirds of the total amount of carbon we can burn, in order to keep warming below the crucial 2°C level. If we carry on at the current rate we will reach our limit in as little as 30 years' time - and that is without any continued growth in emission levels. The implication of no immediate action is worryingly clear – either we take a collective responsibility to make a difference, and soon, or it will be too late."
Key facts and figures:
The 'Global Carbon Budget 2014', led by UEA Tyndall Centre director Prof Le Quéré is made available in the journal Earth System Science Data Discussions on September 21, 2014.
It is accompanied by a Nature Geoscience paper 'Persistent growth of CO2 emissions and implications for reaching climate targets', led by Prof Friedlingstein from the University of Exeter.
Meanwhile 'Sharing a quota on cumulative carbon emissions' led by Dr Michael Raupach director of the Climate Change Institute at the Australian National University, and a comment article 'Betting on negative emissions', led by Dr Sabine Fuss, at the Mercator Research Institute on Global Commons and Climate Change in Germany, are published in Nature Climate Change.
For more information see the Global Carbon Atlas, which allows users to explore, visualise and interpret data of global, regional and national emissions, visit http://www.globalcarbonatlas.org.
Lisa Horton | Eurek Alert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
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17.07.2018 | Power and Electrical Engineering | <urn:uuid:61769599-e623-4269-b610-a5de8c45a3ca> | 3.40625 | 1,467 | Content Listing | Science & Tech. | 40.850531 | 95,571,564 |
Naming Conventions From Uncle Bob's Clean Code Philosophy
Naming Conventions From Uncle Bob's Clean Code Philosophy
Following this list of rules for naming variables, classes, and methods will help you write cleaner, more professional code.
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This article is the result of reading the book "Clean Code" by Robert C Martin. All the recommendations made here are suggested by Robert C Marin. This article covers the abstract of naming conventions suggested by Clean Code.
The clean code philosophy is seems be to emerged from the fundamentals of Software Craftsmanship. According to many software experts who have signed the Manifesto for Software Craftsmanship, writing well-crafted and self-explanatory software is almost as important as writing working software.
Following are the snippets from the book, show why naming is hard and disputable and the mindset to address this problem:
"The hardest thing about choosing good names is that it requires good descriptive skills and a shared cultural background. This is a teaching issue rather than a technical, business or management issue."
"Focus on whether the code reads like paragraphs and sentences, or at least tables and data structure."
2. Naming Conventions
2.1. Use Intention-Revealing Names
Basically, don't name a variable, class, or method which needs some explanation in comments.
int d; // elapsed time in days int s; // elapsed time in seconds
Can be named as:
int elapsedTimeInDays; int daysSinceCreation; int daysSinceModification; int fileAgeInDays;
2.2. Avoid Disinformation and Encodings
Don't refer to a group of accounts as "accountList," whereas it is actually not a List. Instead, name it "accountGroup," "accounts," or "bunchOfAccounts."
Avoid unnecessary encodings of datatypes along with the variable name.
String nameString; Float salaryFloat;
It may not be necessary where it is very well known to the entire world that in an employee context, the name is going to have a sequence of characters. The same goes for Salary, which is decimal/float.
2.3. Make Meaningful Distinctions
If there are two different things in the same scope, you might be tempted to change one name in an arbitrary way.
What is stored in cust, which is different from customer?
String cust; String customer;
How are these classes different?
class ProductInfo class ProductData
How do you differentiate between these methods in the same class?
void getActiveAccount() void getActiveAccounts() void getActiveAccountsInfo()
So, the suggestion here is to make meaningful distinctions.
2.4. Use Pronounceable Names
Ensure that names are pronounceable. Nobody wants a tongue twister.
Date genymdhms; Date modymdhms; Int pszqint;
Date generationTimeStamp; Date modificationTimestamp; Int publicAccessCount;
2.5. Use Searchable Names
Avoid single letter names and numeric constants, if they are not easy to locate across the body of the text.
grep "MAX_STUDENTS_PER_TEACHER" *.java
grep 15 *.java
Use single letter names only used as local variables in short methods. One important suggestion is that "the length of a name should be correspond to the size of its scope."
2.6. Don't Be Cute/Don't Use Offensive Words
2.7. Pick One Word per Concept
Use the same concept across the codebase.
FetchValue() vs GetValue() vs RetrieveValue()
If you are using fetchValue() to return a value of something, use the same concept; instead of using fetchValue() in all the code, using getValue(), retrieveValue() will confuse the reader.
dataFetcher() vs dataGetter() vs dataFetcher()
If all three methods do the same thing, don't mix and match across the code base. Instead, stick to one.
FeatureManager vs FeatureController
Stick to either Manager or Controller. Again, consistency across the codebase for the same thing.
2.8. Don't Pun
This is exactly opposite of previous rule. Avoid using the same word for two different purposes. Using the same term for two different ideas is essentially pun.
For example, say you have two classes having the same add() method. In one class, it performs addition of two values, in another, it inserts an element into a list. So, choose wisely; in the second class use insert() or append() instead of add().
2.9. Solution Domain Names vs Problem Domain Names
The clean code philosophy suggests using solution domain names such as the name of algorithms or the name of design patterns whenever needed, and use a problem domain name as the second choice.
For example, accountVisitor means a lot to a programmer who is familiar with the Visitor design pattern. A "JobQueue" definitely make more sense to a programmer.
2.10. Add Meaningful Context as a Last Resort
While there are a few names which are meaningful themselves, most are not. Instead, you have to place names in context for your reader by enclosing them in well-named classes, functions, or namespaces. If not possible, prefixing the names may be necessary as a last resort.
For example, the member variable named "state" inside the address class shows what it contains. But the same "state" may be misleading if used to store "Name of The State" without context. So, in this scenario, name it something like "addressState" or "StateName."
The "state" may make more sense in a context where you are coding about addresses when named "addrState."
Robert C. Martin says, "One difference between a smart programmer and a professional programmer is that the professional understands that clarity is king. Professionals use their powers for good and write code that others can understand." I hope this article will help you to be more professional and write clean code, for further reading refer to "Clean Code: A Handbook of Agile Software Craftsmanship."
Manifesto for Agile Craftsmanship
As aspiring Software Craftsmen, we are raising the bar of professional software development by practicing it and helping others learn the craft. Through this work we have come to value:
Not only working software,
but also well-crafted software
Not only responding to change,
but also steadily adding value
Not only individuals and interactions,
but also a community of professionals
Not only customer collaboration,
but also productive partnerships
That is, in pursuit of the items on the left we have found the items on the right to be indispensable.
Published at DZone with permission of Saravanan Subramanian , DZone MVB. See the original article here.
Opinions expressed by DZone contributors are their own. | <urn:uuid:c4bc2b45-9905-4146-8191-746af2413b7c> | 3.015625 | 1,490 | Tutorial | Software Dev. | 43.324003 | 95,571,582 |
1.1.Why are solids rigid?
Ans: The constituent particles in solids have fixed positions and can oscillate about their mean positions. Hence, they are rigid.
1.2.Why do solids have a definite volume?
Ans: The constituent particles of a solid have fixed positions and are not free to move about, i.e., they possess rigidity. That is why they have definite volume.
1.3.Classify the following as amorphous or crystalline solids: Polyurethane, naphthalene, benzoic acid, Teflon, potassium nitrate, cellophane, polyvinyl chloride, fibreglass, copper
Ans: Crystalline solids: Benzoic acid, potassium nitrate, copper Amorphous solids: Polyurethane, Teflon, cellophane, polyvinyl chloride, fibreglass
1.4.Why is glass considered a supercooled liquid?
Ans: Glass is an amorphous solid. Like liquids, it has a tendency to flow, though very slowly. This can be seen from the glass panes of windows or doors of very old buildings which are thickerat the bottom than at the top. Therefore, glass is considered as a supercooled liquid.
1.5.Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show cleavage property?
Ans: As the solid has same value of refractive index along all directions, it is isotropic in nature and hence amorphous. Being amorphous solid, it will not show a clean cleavage and when cut, it will break into pieces with irregular surfaces.
1.6.Classify .the following solids in different categories based on the nature of intermolecular forces operating in them: Potassium sulphate, tin, benzene, urea, ammonia, water, zinc sulphide, graphite, rubidium, argon, silicon carbide
Ans: Potassium sulphate = Ionic Tin=Metallic.
Benzene = Molecular (non-polar)
Water = Molecular (H-bonded)
Zinc sulphide = Ionic Graphite=Covalent Rubidipm Metallic Argon = Molecular (non-polar)
1.7.Solid A is a very hard electrical insulator in. solid as well as in molten state and melts at extremely high temperature. What type of solid is it?
Ans: It is a covalent or network solid.
1.8.Ionic solids conduct electricity in molten state but not in solid state. Explain
Ans: In solid state, the ions cannot move, they are held by strong electrostatic forces of attraction. So, ionic solids do not conduct electricity in solid state. However, in the molten state, they dissociate to give tree ions and hence conduct electricity.
1.9.What type of solids are electrical conductors, malleable and ductile?
Ans: Metallic solids
1.10.Give the significance of a ‘lattice point’.
Ans: Each lattice point represents one constituent particle of the solid. This constituent particle may be an atom, a molecule or an ion.
1.11. Name the parameters that characterise a unit cell.
Ans: A unit cell is characterised by following parameters:
(i)the dimensions of unit cell along three edges: a, b and c.
(ii)the angles between the edges: α (between b and c); β (between a and c) and γ (between a and b)
1.12. Distinguish between
(i) Hexagonal and monoclinic unit cells
(ii) Face-centred and end-centred unit cells.
|Hexagonal unit cell||Monoclinic unit cell|
|α = β = 90°||α = γ = 90°|
|γ = 120°||β ≠ 90°|
|Face-centred unit cell||End-centred unit cell|
|A Face-centred unit cell the constituent particles are present at the corners and one at the centre of each face.||An End-centred unit cell contains particles at the corners and one at the centre of any two opposite faces.|
|Total no of particles in a face centered unit cell= 4||Total no. of particles in an end centered unit cell = 2|
1.13. Explain how much portion of an atom located at
(i)corner and (ii)body centre of a cubic unit cell is part of its neighbouring unit cell.
Ans: (i) An atom at the comer is shared by eight adjacent unit cells. Hence, portion of the atom at the comer that belongs to one unit cell=1/8.
(ii)An atom at the body centre is not shared by any other unit cell. Hence, it belongs fully io unit cell.
1.14. What is the two-dimensional coordination number of a molecule in square close-packed layer?
Ans: In 2D, square close-packed layer, an atom touches 4 nearest neighbouring atoms. Hence, its CN=4
1.15. A compound forms hexagonal close-packed. structure. What is the total number of voids in 0. 5 mol of it? How many of these are tetrahedral voids?
No. of atoms in close packings 0.5 mol =0.5 x 6.022 x 1023 =3.011 x 1023
No. of octahedral voids = No. of atoms in packing =3.011 x 1023
No. of tetrahedral voids = 2 x No. of atoms in packing
= 2 x 3.011 x 1023 = 6.022 x 1023
Total no. of voids = 3.011 x 1023 + 6.022 x 1023
= 9.033 x 1023
1.16. A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy l/3rd of tetrahedral voids. What is the formula of the compound?
Ans: Atoms of N from ccp, therefore, if the lattice points are n, then
No . of atoms of N = n
No. of oct voids = n
No. of td voids = 2n= 2 x 1n/3 = 2n/3
∴ Formula of compound is: M : N
2/3 n : n
1.17. Wh ich of the following lattices has the highest packing efficiency (i) simple cubic (ii) body- centred cubic and (iii) hexagonal close-packed lattice?
Ans: Packing efficiency of:
Simple cubic = 52.4% bcc = 68% hcp = 74%
hcp lattice has the highest packing efficiency.
1.18. An element with molar mass 2.7 x 10-2 kg mol-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7 x 103 kg m-3, what is the nature of the cubic unit cell?
1.19. What type of defect can arise when a solid is heated? Which physical property is affected by it and in what way?
Ans: When a solid is heated, vacancy defect is produced in the crystal. On heating, some atoms or ions leave the lattice site completely, i.e., lattice sites become vacant. As a result-of this defect, density of the substances decreases.
1.20.What type of stoichiometric defect is shown by:
Ans: (i) ZnS shows Frenkel defect
(ii)AgBr shows Frenkel as well as Schottky defect.
1.21. Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it.
Ans: Let us take an example NaCl doped with SrCl, impurity when SrCl2 is added to NaCl solid as an impurity, two Na+ ions will be replaced and one of their sites will be occupied by Sr21- while the other will remain vacant. Thus, we can say that when a cation of higher valence is added as an impurity to an ionic solid, two or more cations of lower valency are replaced by a cation of higher valency to maintain electrical neutrality. Hence, some cationic vacancies are created.
1.22.Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.
Ans: Let us take an example of NaCl. When NaCl crystal is heated in presence of Na vapour, some Cl–ions leave their lattice sites to combine with Na to form NaCl. The e-1 s lost by Na to form Na+ (Na+ + Cl–—> NaCl) then diffuse into the crystal to occupy the anion vacancies. These sites are called F-centres. These e-s absorb energy from visible light, get excited to higher energy level and when they fall back to ground state, they impart yellow colour to NaCl crystal.
1.23.A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity. To which group should this impurity belong?
Ans: Impurity from group 15 should be added to get n-type semiconductor.
1.24.What type of substances would make better permanent magnets, ferromagnetic or ferrimagnetic. Justify your answer.
Ans: Ferromagnetic substances make better permanent magnets. This is because when placed in magnetic field, their domains get oriented in the directions of magnetic field and a strong magnetic field is produced. This ordering of domains persists even when external magnetic field is removed. Hence, the ferromagnetic substance becomes a permanent magnet.
1.1. Define the term ‘amorphous’. Give a few examples of amorphous solids.
Sol. Amorphous solids are those substances, in which there is no regular arrangement of its constituent particles, (i.e., ions, atoms or molecules). The arrangement of the constituting particles has only short range order, i.e., a regular and periodically repeating pattern is observed over short distances only, e.g., glass, rubber and plastics.
1.2. What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass?
Sol. Glass is made up of Si04 tetrahedral units. These constituent particles have short range order only. Quartz is also made up of Si04 tetrahedral units. On heating it softens and melts over a wide range of temperature. It is a crystalline solid having long-range ordered structure. It has a sharp melting point. Quartz can be converted into glass by first melting and then rapidly cooling it.
1.3 Classify each of the following solids as ionic, metallic, modular, network (covalent) or amorphous:
(i) Tetra phosphorus decoxide (P4O10) (ii) Ammonium phosphate, (NH4)3P04 (iii) SiC (iv) I2 (v) P4 (vii) Graphite (viii), Brass (ix) Rb (x) LiBr (xi) Si
1.4 (i) What is meant by the term ‘coordination number’?
(ii) What is the coordination number of atom
(a) in a cubic close-packed structure?
(b) in a body centred cubic structure?
Sol. (i) The number of nearest neighbours of a particle are called its coordination number.
(ii) (a) 12 (b) 8
1.5 How can you determine the atomic mass of an unknown metal if you know its density and the dimensions of its unit cell? Explain.
Sol. Let the edge length of a unit cell = a
Density = d
Molar mass = M
Volume of the unit cell = a3
Mass of the unit cell
= No. of atoms in unit cell x Mass of each atom = Z × m
1.6 ‘Stability of a crystal is reflected in the magnitude of its melting points’. Comment. Collect melting points of solid water, ethyl alcohol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?
Sol. Higher the melting point, greater are the forces holding the constituent particles together and thus greater is the stability of a crystal. Melting points of given substances are following. Water = 273 K, Ethyl alcohol = 155.7 K, Diethylether = 156.8 K, Methane = 90.5 K.
The intermoleoilar forces present in case of water and ethyl alcohol are mainly due to the hydrogen bonding which is responsible for their high melting points. Hydrogen bonding is stronger in case of water than ethyl alcohol and hence water has higher melting point then ethyl alcohol. Dipole-dipole interactions are present in case of diethylether. The only forces present in case of methane is the weak van der Waal’s forces (or London dispersion forces).
1.7 How will you distinguish between the following pairs of terms:
(i) Cubic close packing and hexagonal close packing?
(ii) Crystal lattice and unit cell?
(iii) Tetrahedral void and octahedral void?
Sol. (i) Cubic close packing: When the third layer is placed over the second layer in such a way that the spheres cover the octahedral voids, a layer different from first (A) and second (B) is produced. If we continue packing in this manner, then a packing is obtained where the spheres in every fourth layer will vertically aligned. This pattern of packing spheres is called ABCABC pattern or cubic close packing.
Hexagonal close packing: When a third layer is placed over the second layer in such a manner that the spheres cover the tetrahedral void, a three dimensional close packing is obtained where the spheres in every third or alternate layers are vertically aligned. If we continue packing in this manner, then the packing obtained would be called ABAB pattern or hexagonal close packing.
(ii) Crystal lattice: It is a regular arrangement of the constituent particles (i?.e., ions, atoms or molecules) of a crystal in three dimensional space.
Unit cell: The smallest three dimensional portion of a complete space lattice which when repeated over and over again in different directions produces the complete crystal lattice is called the unit cell.
(iii) Tetrahedral void: A simple) triangular void is a crystal is surrounded by four spheres and is called a tetrahedral void.
Octahedral void: A double triangular void is surrounded by six spheres and is called a octahedral void.
1.8 How many lattice points are there is one unit cell of each of the following lattices?
(i) Face centred cubic (if) Face centred tetragonal (iii) Body centred cubic
(i) The basis of similarities and differences between metallic and ionic crystals.
(ii) Ionic solids are hard and brittle.
Sol. (i) Metallic and ionic crystals
(a) There is electrostatic force of attraction in both metallic and ionic crystals.
(b) Both have high melting points.
(c) Bonds are non-directional in both the cases.
(a) Ionic crystals are bad conductors of electricity in solids state as ions are not free to move. They can conduct electricity only in die molten state or in aqueous solution. Metallic crystals are good conductors of electricity in solid state as electrons are free to move.
(b) Ionic bond is strong due to strong electrostatic forces of attraction.
Metallic bond may be strong or weak depending upon the number of valence electrons and the size of the kernels.
(ii) Ionic solids are hard and brittle.Ionic solids are hard due to the presence of strong electrostatic forces of attraction. The brittleness in ionic crystals is due to the non- directional bonds in them.
1.10 Calculate the efficiency of packing in case of a metal crystal for (i) simple cubic, (ii) body centred cubic, and (iii) face centred cubic (with the assumptions that atoms are touching each other).
Sol. Packing efficiency: It is the percentage of total space filled by the particles.
1.11 Silver crystallises in fcc lattice. If edge length of the cell is 4.07 x 10-8 cm and density is 10.5 g cm-3, calculate the atomic mass of silver.
1.12 A cubic solid is made up of two elements P and Q. Atoms of Q are at the corners of the cube and P at the body centre. What is the formula of the compound? What are the coordination numbers of P and Q?
Sol. As atoms Q are present at the eight comers of the cube, therefore, the contribution of atoms of
Q in the unit cell = 1/8 x 8 = 1.
As atom P is present at the body centre, therefore, the contribution of atoms of P in the unit cell = 1.
.•. Ratio of atoms of P: Q = 1:1
Hence, the formula of the compound = PQ The coordination number of each P and Q = 8 .
1.13 Niobium crystallises in a body centred cubic structure. If density is 8.55 g cm-3, calculate atomic radius of niobium, using its atomic mass 93u.
1.14 If the radius of the octahedral void is r and radius of the atoms in close-packing is R, derive relation between rand R.
Sol. A sphere is fitted into the octahedral void as shown in the diagram.
1.15 Copper crystallises into a fee lattice with edge length 3.61 x 10-8 cm. Show that the calculated density is in agreement with its measured value of 8.92 gcm-3.
This calculated value of density is closely in agreement with its measured value of 8.92 g cm3. | <urn:uuid:54dc6dff-b85b-45c4-806d-94c34192452b> | 3.53125 | 3,927 | Tutorial | Science & Tech. | 65.674216 | 95,571,592 |
Upon publishing his pivotal general theory of relativity, Albert Einstein produced a series of gravitational field equations for the great minds of the time to solve. Little did he know that the solution would predict a phenomenon that would draw in much astonishment, scepticism and confusion.
This was the birth of black hole science – a branch of astronomy that has both propelled our understanding of the universe and captured imaginations. With 2016 marking the centenary of this event, Impact explores the landmark discoveries of the past hundred years. We also delve into the current research, particularly in the University of Nottingham’s black hole laboratory, which could potentially shape the future of science.
In early 1916, just months after the release of his equations, Einstein received an excited correspondence from Karl Schwarzschild. He had cracked it. During his time off from the First World War trenches, the German physicist had become the first to calculate an exact solution to Einstein’s notorious equations. Sadly, Schwarzschild died soon afterwards. However, his findings went on to be published, and they left scientists baffled.
“For such a relatively modern field, scientists have already amassed a wealth of information”
According to Schwarzschild’s solution, certain regions of space and time exist where the gravitational attraction is so extreme that absolutely nothing, not even light, has the ability to escape. Over the following fifty years, it was discovered that these regions – black holes – are typically formed due to massive stars collapsing inwards near the end of their lives.
Through further research during the seventies, astrophysicists at the National Radio Astronomy Observatory discovered that the Milky Way is centred on the highly dense black hole Sagittarius A*. From this, they developed the theory of “supermassive black holes”. Like Sagittarius A*, these cosmic giants lie at the heart of the vast majority of known galaxies.
For such a relatively modern field, scientists have already amassed a wealth of information; and whilst alternative theories should not be dismissed lightly, black hole research has yielded some utterly fascinating results. Nonetheless, plenty still remains to be discovered.
One major advancement was the recent detection of gravitational waves. Until last year these had only been predicted theoretically by Einstein. However, this all changed when in September 2015 gravitational waves were observed for the first time by the LIGO detectors in America.
The waves in question were emitted by two large black holes in a far off galaxy as they spiralled into each other and merged together. Not only did this observation confirm Einstein’s theory of general relativity, it also helped to expand the current understanding of black holes, particularly their behaviour in pairs.
Closer to home, the University of Nottingham Physics & Astronomy department plays host to a cutting edge black hole machine. Fundamentally, this consists of a two thousand-litre tank of water with a small hole in the bottom surrounded by several high-precision cameras.
Similar to water swirling down a plug hole, the hole in the tank creates a vortex in the water which in turn is used by researchers to simulate a black hole. Despite its basic appearance, the machine creates an effective model and has played an integral part in several papers, not forgetting a brief mention on The Big Bang Theory.
Over the past hundred years, our knowledge of the universe has absolutely sky rocketed, and these scientific breakthroughs show no sign of stopping. He may not have realised it at the time but when Schwarzschild calculated his solution to Einstein’s equations he founded one of the most intriguing, most remarkable and most bizarre fields in modern physics. Black-hole science.
https://en.shafaqna.com/wp-content/uploads/2016/12/PIA16695_hires.jpg5601263Yahyahttps://en.shafaqna.com/wp-content/uploads/2018/02/new-logo-s-2.pngYahya2016-12-20 03:12:302016-12-20 03:12:30One Hundred Years Of Black Hole Science | <urn:uuid:cd22f52e-398a-4b7d-ac89-768551140c38> | 4.1875 | 838 | Knowledge Article | Science & Tech. | 38.616359 | 95,571,598 |
The genetic regulation mechanisms of cells are composed of many interacting complex, dynamical networks. The networks that control cell growth, differentiation, maintenance, repair, and many other functions of an adult organism, are essentially nonlinear types of process control. The structure of these networks contains parallel, or intertwining, pathways that have various inputs, outputs, loops, and cross-talks with each other. These levels of nonlinearity of the network guarantee that there are highly consequential, intermittently functioning operations that are only observable while the system experiences a shift in the operating regulatory dynamics in response to particular influences. The traditional reductionist approach that only focuses on a specific regulatory unit fails to capture the full dynamics of the system. Some high-throughput techniques like RNA expression profiling with microarrays can provide a snapshot of an aspect of the system at one time point, but to follow cell responses for an extended period by microarrays, one needs to carefully prepare multiple cell populations under identical conditions and produce the assays at different time points by harvesting cells and extracting analyte from a different cell population at each time point. The whole procedure is technically cumbersome and error-prone, and the cost can be prohibitive if dense temporal sampling is carried out.
Fluorescent reporters have long been used in molecular technology to study cells transcriptional activities, the cellular localization of components, or re-distribution of target proteins, either in a population of cells or a single cell.12.–3 There are two basic types of fluorescent reporters based on the molecular structure: (1) Promoter-reporters that indicate the activity of the promoter for a particular gene. To serve this purpose, a fluorescent reporter can be constructed by fusing the promoter region of a gene of interest with the coding sequence of a fluorescent protein, most commonly a green fluorescent protein (GFP). Then the abundance of the reporter can be used as an indicator of the activity of the promoter. (2) Fusion-reporters that indicate the cellular location of a protein, the stability of a protein, the status of large architectural elements in the cell, or the positioning of small molecules in a cell. This type of fluorescent reporter is made by an in-frame fusion of the coding sequence of either a whole protein or a protein domain to the coding sequence of a fluorescent protein, and then placing that coding sequence under the control of a promoter that will drive the production of that protein at a rate sufficient to produce constant detectable levels of the fusion protein.
The presence of fluorescent molecules can be detected by imaging with an epifluorescent microscope. Because this procedure is non-invasive to the cell, it allows tracking of the same cell population for an extended period of time by imaging the same site repeatedly. The recent introduction of automated digital microscopes allows researchers to use multi-well microtiter plates and sequentially capture the reporter activities in all wells in a high-content fashion.45.–6 To the present day, the majority of approaches that take advantage of such large-scale fluorescent imaging assays limit themselves to the fusion reporters, where the dynamic spatial distributions of such fusion-proteins serve as the indicators of phenotypes of interest. These fusion-reporters can be used in large scale RNAi or small molecules screening, in time-lapse study and/or case-control study.78.9.10.–11 However, to serve as phenotype indicators, only a few key reporters are needed, often less than three. Hence such approaches provide little insights on the mechanism of the cellular regulation network in response to external perturbations.
In this study, we used a batch of promoter reporters to track the transcriptional activities of particular genes. To serve this purpose, we built a library of promoter reporters and designed an experimental protocol. In our experimental protocol, a single assay is carried out by epifluorescent imaging of a site at the bottom of each well in a 384-well plate, producing an image of the cells in that region (∼200 to 300 cells) bearing fluorescent reporters. The imaging speed of automated systems easily accommodates sampling an entire 384-well plate at hourly intervals. If needed, the experiment can be extended to multiple sites/plates to cover more cells with a wider range of cell types and reporters.
Using different wells to test different combinations of cell type, GFP reporter and experimental conditions allows this innovative approach to provide a truly multi-dimensional examination of the cell’s responses to a variety of stimuli. Not only can it follow multiple genes simultaneously, but it can also compare cellular activities under various conditions. Furthermore, it captures the dynamics of transcriptional regulation. The capability to observe a cohort of cell-response behaviors facilitates new possibilities in biological research, e.g., detection of sub-populations with different susceptibilities to the external stimuli, determination of whether the response is continuous or graded, ordering of critical events, and relating different response patterns. To fully realize these possibilities and explore the potential of this method in biological and pharmaceutical applications, we have designed a customized data processing procedure for this experimental protocol. The procedure contains two parts: (1) image processing and transcription quantification, where the fluorescent images are segmented to identify individual nuclei and cells, and the amount of fluorescence each cell is producing is quantified, and (2) data representation, where the extracted time course data are summarized and represented in a way that can facilitate efficient evaluation.
Since the proposed data processing procedure is designed for a high-content fluorescent protein reporter-based experimental protocol, it is necessary to provide some basic information on how the experiment is carried out and the unique challenges associated with the protocol.
The objective of the experimental protocol is to efficiently capture cell process dynamics in response to certain stimuli in order to obtain a deeper understanding of the genetic regulatory mechanisms and constrain the number of possible mechanisms requiring further research. For example, the stimuli applied could be chemicals, biological molecules or environmental alterations. The design and execution of experiments are aimed at understanding the mechanisms invoked in response to a stimulus, and is generally carried out in the three stages: (1) formulate a model of pathways on the processes potentially affected by the stimulus, pick the desired process reporters and cell lines based on the model, and prepare and plate sets of cell line/reporter pairs; (2) perturb the pathways with the stimulus of interest and other stimuli with known effects on components of the pathways of interest, and also include an un-stimulated control; and (3) take fluorescent images periodically for a consecutive time period for all cell populations in the plate. The fluorescent images are taken as two-color image pairs with a blue channel image for the nuclei and a green channel image for the GFP reporters. The imaging rate should be frequent enough to capture any change in the transcription activity, yet not too frequent to induce photobleaching and/or phototoxicity. The transcription itself is a slow, yet dynamic process. It can take 4 to 6 h or more from the time transcription rates change to the time when the new steady-state level of protein product is achieved. Moreover, the protein product is in continuous turnover through translation and proteolysis. The microscope has been fitted with several filters in case that the target cell line is sensitive to light at certain frequency. One can switch to other color channels by using filters in combination with other fluorescent reporters or stains, and avoid or alleviate potential toxic effects. Finally, the computer-controlled shutters used by the automatic imager greatly limit the exposure time of live cells, which further prevents phototoxicity. Thus, we found an hourly sampling rate is sufficient for successful transition tracking, yet low enough not to induce any observable photobleaching and phototoxicity.
In a properly designed plate, each condition will be tested in multiple wells to ensure both adequate coverage and replicates to assess technical variation. In our experiments, every condition is duplicated in three or more wells. There will also be media-only, unperturbed cell population to serve as negative controls and cell-lines with a highly expressed reporter to serve as positive controls. These control wells can serve as a final safeguard to detect any unexpected effects. In the beginning of the experiment, the plate will be imaged for several hours without any stimulants being added. The images taken during this period will provide an estimate on the baseline level of transcriptional activity. Once the stimulants are added, the images will be taken hourly for considerable time, usually over 40 h, to capture any induced response by the chosen reporters. The technical details on how the biological samples were prepared and how the images were taken are available in the Appendix.
Figure 1 shows two typical fluorescent images sampled for the same site in a 48-h drug treatment study. The original images are 16-bit images and are normalized to 8-bit for proper viewing. The full sequence of images is stacked into a video file. The colon cancer cell-line HCT116 is under observation here and the reporter is driven by a 1 kb promoter fragment from MKI67, a nuclear protein whose abundance is tightly correlated with proliferation.12 No drug was added for the first 5 h, then lapatinib, a drug used to treat breast cancer, was added and imaged for 43 h. In Fig. 1, the left image was taken at the beginning of the experiment when no drug has been added, while the right image was taken 43 h after the drug lapatinib was added. There are about 300 cells in the image. The nuclear channel (blue) images the live cell DNA fluorophore, Vybrant Violet, and the promoter reporter activity channel (green) images the GFP reporter protein. For the case shown here, the change in transcriptional activity is significant. In the beginning, gene MKI67 is highly transcribed, indicating strong proliferation activity. At the end of the experiment, most of the GFP fluorescence was reduced to almost unobservable, a likely indicator of reduced transcription followed by apoptotic proteolysis.
Figure 1 shows that fluorescent reporters can help researchers track the cellular activity of the same cohort of cells, in this case, by direct visual evaluation; however, the volume of data that can be handled by visual inspection in a timely manner is very limited, while the volume of data generated by the current approach is always huge. With a 384-well plate there will be 384 videos for evaluation and the number can be much higher if the experiment requires multiple sites being chosen in each well or multiple plates to cover all experimental conditions. Furthermore, visual evaluation is unreliable when one needs to aggregate the results from duplicated wells or when one needs to quantitatively compare different conditions. Hence the high-content nature of the GFP reporter approach calls for a more automatic and quantitative solution to efficiently extract and summarize the captured transcriptional activity.
Objectives of image processing
To facilitate automatic processing of the experiment results, the first step is image processing, where the transcriptional levels of the fluorescent images will be properly extracted, quantified, and saved. When designing the image processing method, several characteristics of cell imaging specific to the experimental protocol must be considered.
• Cell-level activity. Light-based assays have long been used to study cell-level activity. For example, in studies where cell viability is the primary focus, luciferase is often used to help detect cellular ATP level through bioluminescence intensity.13 However, such a measure does not separate individual cells but treats the population as a whole; thus it cannot detect sub-populations. For human cells, cell heterogeneity is very common, especially for cancer, where the carcinoma cells can reside in multiple states in a single tumor, thereby leading to various drug responses and prognosis perspectives.14 By comparison, in GFP reporter based imaging, the transcriptional activity can be extracted at the single cell level. As shown in Fig. 1(b), although the proliferation activity of most cells has been turned off, there is still a small portion of cells whose transcriptional activity remains unchanged, indicating a possible sub-population of cells that is relatively resistant to the applied drug. Thus, a proper image processing method must be able to identify individual cells and extract the transcriptional level of each cell.
• Robustness. The demand for robust performance comes from both the time and space domains. First, it should be noted that each site is being imaged for a period of time and the extracted data will be studied as time-course data rather than independent data. To further complicate the issue, a cell-line could have significantly different responses to different perturbations, so the imaging quality can also vary from well to well and time point to time point. For example, since the cells can possess different morphological shapes in response to the external stimuli, the optimal focus plane will change with both time and condition. The auto-focus mechanism of the scanner will invariably be slightly out of focus from time to time, sometimes even generating unusable images. Hence, the image processing method must be robust enough to produce reliable results for the full time course. Next, as a high-content approach, different stimuli/conditions will be applied to different wells and all wells will be imaged simultaneously. Hence one would expect the cells to experience dramatically different types of perturbation, which will lead to different responses. Actually a well-designed experiment should be able to induce a variety of responses that allows the exploration of certain genetic regulation mechanisms that are only responding to specific stimuli. With such varied responses, one would expect the fluorescent images to experience various changes. For example, in Fig. 1, the cells show morphological changes after application of the drug: the cells now start to form small clusters, and their sizes became smaller. Although, some nuclei became brighter, some nuclei became dimmer. When no drug is applied, the change is not so significant (results not shown). If the method can handle most images with excellent performance but can have very poor results on certain cases, the results will have jarring outliers, lead to misinterpretation of the outcome, and significantly affect the analysis. Ideally, if one can consider consecutive images in time and track the activity of individual cells, the results will be most informative. However, a considerable number of cells will be moving in or out of the imaging area during the experiment and the imaging site itself is not always fixed. These, plus the situations just described, make cell tracking challenging and limit its usefulness. Thus, we utilize single image processing to pursue the activity at a population scale, while making sure that the method is sufficiently robust to produce quality results over all conditions for the whole time course.
• Computation time. The final major issue is the number of images to be processed in each experiment. If the experiment contains a single 384-well plate and the cell cultures are followed for 48 h and imaged every hour with one two-color scan per well, then the outcome will be 18,432 image pairs, which is over 70 GB in storage. The designed method must be able to handle this amount of images in a reasonable time frame.
Image processing procedure
Achieving all of these objectives requires a fast image processing algorithm with good balance between speed and the ability to pick up almost all objects. The most common segmentation methods involve an adaptive-threshold-based approach like the one based on the top-hat transform.15 We have found this approach, with a properly chosen threshold, to be fast and able to identify the foreground objects in general for almost all cases. However, it is difficult to find the optimal threshold for such an approach, which makes it hard to further identify individual nuclei. Level-set-based methods are another popular approach that has been reported to achieve impressive performances, but can be quite complicated and time-consuming.1617.–18 For our experiments, we found that the potential performance gain through this approach does not compensate for the extra computation time and complexity. We decided to build our method using morphological image processing,15 in particular, the watershed transformation,19 another popular and proven approach in cellular image processing. The time-course images are processed independently to maintain process speed and minimize the consequence of unexpected outliers: only one pair of images will be loaded and processed each time, and the results of outlier images can later be discarded without affecting other results.
Figure 2 provides the general flowchart on how a fluorescent image pair is processed: the nuclear channel is first processed to identify all nuclei (top part of Fig. 2) and the reporter channel is then analyzed to extract an individual cell’s expression activity (bottom part of Fig. 2). As a practical example, the critical steps in processing the image in Fig. 1(a) are shown in Fig. 3. In order to show the segmentation details, only a portion of the full image is shown here.
Nuclear channel processing contains two major steps. First, the foreground objects are identified, where an object is either an isolated nucleus or a cluster of nuclei (top left part of Fig. 2). Before segmentation, the nuclear channel image is first pre-processed to remove tiny additive and subtractive noise via a single-stage open-close alternating sequential filter. We apply watershed-based segmentation on the gradient image. It is known that the accuracy of flood holes is critical to the success of the watershed procedure. As is commonly done, we depend on the top-hat transform for marker selection. The local maxima inside the top-hat-identified foreground are filtered by the area open operation20 to form the foreground markers of size no smaller than a designated value based on common nuclei sizes. Similarly, the background markers are found by morphologically thinning the top-hat identified background. Thinning, rather than erosion, is chosen to avoid small and/or narrow passage regions between nuclei being lost. An example of the watershed markers can be viewed in Fig. 3(b).
Overall, the watershed on a gradient image gives a tight boundary on most nuclei; however, if a dim nucleus is attached to a bright nucleus or part of a nucleus is much brighter than other parts, the high gradient of the bright one might overshadow the dim one and the watershed segmentation could miss the dim region. To address this problem, the difference between top-hat transform and watershed results is used to identify and recover large missing objects. To obtain the final identified foreground objects, the segmentation results are sent for post-processing to remove tiny objects that can be artifacts or nuclear debris. An example of the final foreground can be found in Fig. 3(c).
The next step is to identify individual nuclei by de-clumping the clustered nuclei (top right part of Fig. 2). In most cases, nuclei have circular or near-circular shapes, and the tight segmentation boundaries secured by the previous step make it a natural choice to use a shape-based de-clumping method, where we apply watershed segmentation on distance transformed foreground images. The local maxima found through morphological opening are set as markers for flooding holes. For the highly clustered regions, where the boundary shape is not informative enough, shape-based de-clumping might fail to separate some or all of the nuclei. These missed objects usually have a much larger area size and irregular shape than can be detected by the circularity shape factor. Intensity-based watershed segmentation is applied to further de-clump these missed objects, where the markers are found through the area open operator. An example of the watershed markers can be found in Fig. 3(d). To save space, we put both shape-based and intensity-based de-clumping markers in one image. Before passing the identified nuclei to the GFP channel processor, a final post-processing is done by removing the tiny objects generated by the de-clumping procedure. An example of the final segmentation results can be found in Fig. 3(e).
The parameters associated with image processing must be adjusted for each cell-line and experiment because critical factors associated with segmentation, like nuclei size, shape, and intensity range, can vary significantly due to experiment design, biological diversity, or imaging setting. In some extreme cases, the whole de-clumping part might be omitted if the nuclei do not have a round shape. Indeed, for certain cancer cell-lines, it is common to see large cells with large and/or irregularly shaped nuclei. For example, the breakage-fusion-bridge cycles can create very large nuclei or connected nuclei linked through anaphase or chromatin bridges.21 These irregular nuclei cannot be separated by standard criteria like shape or intensity, and can be ambiguous to determine even by experienced biologists. Hence, for such cases, to avoid further complication, it is better to skip the de-clumping step and treat the identified objects as nuclei.
As with the nuclear channel, the processing of the GFP reporter channel can be viewed as a two-step procedure: first, identify the objects; second, identify the cells. Here, both steps are much simpler than their counterparts in nuclear channel. Since the reporters are not bound to any other molecule, one would expect that the fluorescent reporter protein, once produced, should be all over the cytoplasm and quite evenly distributed. Thus, a global threshold can be used to find the objects that have fluorescent intensity over a designated value. The threshold is a fixed value offset by the background intensity, which is largely additive noise that should not be measured as part of the transcriptional activity. The background intensity can be retrieved by finding the mode in the lower part of the intensity histogram. If the cells are at a density where they essentially cover the entire bottom surface of the well, then the mode estimate of the background intensity could be false. In such a case, the imaging site will either be discarded during the quality check or an alternative approach will be used. The reference sites, which have the same media but no cells and are in the same plate, can be used to find the background intensity.* To de-clump the objects into cells, intensity-based watershed segmentation was used. Since the nuclei must be contained in the cells, it is natural to use the identified nuclei as the markers of the presence of a cell for the watershed segmentation. An example of the final GFP reporter channel segmentation results can be found in Fig. 3(f). It should be noted that although we treat the background noise as additive, there exist some multiplicative noise types. Such noise is only prominent when the overall intensity distribution range changes significantly, which can be detected when one observes a large background intensity change. In such cases, rather than trying to normalize such a variance, we discard the site and omit it in the following analysis.
Once the individual cells are identified, the transcriptional activity represented by the reporter is extracted for every cell by summing up the background subtracted pixel intensity of the whole cell area and taking a transform before being exported. The transform is taken because the changes of the chemical reactions prevalent in the cells are multiplicative rather than additive and the -transformed intensity can therefore better represent the dynamics of reporter abundance changes in the cell. The results are exported as a tabular data file for further processing. It should be noted that in our study, the transcription activity is collected from the reporter channel, while the nuclei channel only serves an auxiliary role for better segmentation. However, since the morphological changes of the nuclei can also reveal important information on cellular response, we are working on incorporating such information into our protocol.
The whole image processing procedure is done with MATLAB, with most morphological operators done by the SDC Morphology Toolbox for MATLAB.15 For a standard image pair of size , with about 300 cells, it takes about five minutes to process a 48-time-point series, which is about 6 s per image pair for a standard Windows-based desktop computer (3.3 GHz processor, 4 GB RAM). By splitting the plate into several blocks and running the program in parallel, a single plate can be processed overnight by a multi-core desktop computer.†
Once the images are processed, transcriptional activity extracted, and the results exported, organized data representation is required to help researchers evaluate the quality of the experiment, investigate the outcome, and identify the biologically meaningful relationships.
Before any further processing of the results, their qualities must be thoroughly examined. The experiments require a great deal of handling, dilutions and delivery of cultured cells, media and chemical agents to produce the desired matrix of gene/drug tests. The combination of component complexity per well, the need to move the plate from incubators to biosafety hoods and the scanner can lead to a variety of obstacles. We have observed view-obstructing dust and fiber fragments on the plate bottom, temperature change induced crystallization of marginally soluble perturbants, overly high or low numbers of cells and failure to add DNA binding fluorophore to some sets of cells among other human errors. While imaging is automated, it is not perfect, and either plate fabrication or optical imperfection sometimes leads to images sufficiently out of focus that they cannot be analyzed. For these reasons, any systematic data analysis protocol must incorporate quality control mechanisms to help researchers catch potential errors, exclude problematic imaging sites from later analysis, and improve future experimental design.
Since the purpose of quality control is to help identify potential errors, which in most cases are not independent but clustered in wells closely related in space and/or time, the data should be presented in a way that reflects the original experimental layout. We employ a grey-scale heat map style approach, where each time point is shown as a heat map in a plate layout and all time points are concatenated into a video. The intensity mapping is identical for all time points to facilitate inter-time-point comparison. By viewing the heat map sequence, one can quickly identify most potential errors. Figure 4 shows a typical heat map sequence. The metric evaluated in the heat map is the number of cells identified by the image processing procedure in each well of a 384-well plate. This figure shows the second time point of a 36-time-point experiment. As can be seen in the image, the wells in the lower half of column 24 have almost no cells, which is consistent with the plate layout in which these wells are set as media-only references. However, there are five isolated wells that also have close-to-zero cell counts. A further check on these wells reveals that the DNA fluorophore for the nuclear channel was not correctly applied during the experiment. Thus, few cells were identified, and these wells were excluded from further evaluation. Similarly, other heat map videos can be constructed to evaluate other informative measurements, such as background intensity, foreground size, etc. Once the outliers are identified, the remaining results are analyzed.
Summarize expression profile
As discussed in the Objectives of image processing section, even under the same condition cells can be at different states with different expression levels due to various factors, such as cell cycle status, drug efficiency, heterogeneity of the cell population, etc. Hence, rather than obtain an average expression level, one should aggregate the cell-wise expression levels from all duplicate wells to obtain the expression profile across the whole population. If, for a given gene, the expression state of a cell at a certain time point is viewed as a random distribution, then the expression profile is a density function depending on the cell line, gene, external stimulant, and time. Although, histograms are widely used to visualize the density function, it is cumbersome to put different profiles of different time points and conditions in one plot for comparison, which is critical to the time-course case-control study. Thus, we use a one-dimension kernel density estimation with Gaussian kernel to obtain a density function, which has the properties of being nonnegative and having integral one.22,23 The smoothing parameter is selected by the Sheather-Jones method24 implemented in the Matlab toolbox as discussed by Marron in Ref. 25. Figure 5(a) shows expression profiles in the form of density functions obtained for the cell population imaged in Fig. 1. The profiles of all 48 time points are shown. The lines are coded by grey-scale to indicate time. The two time points corresponding to the two images shown in Fig. 1 are shown in bold lines, with the before-the-drug time point in black, and 43-h time point in light-grey. As a comparison, Fig. 5(b) shows the expression profiles of the un-drugged population of the same reporter and cell line. Note that in this example, since both plots are based on a single imaging site, the density curves are actually not as smooth as pooled results. The -axis is the transcriptional activity level measured by the total fluorescent intensity in scale. The figure clearly shows that the transcription level of target gene MKI67 is relatively high at the beginning of the experiment, with the peak at around 217 (arbitrary camera intensity units). At the end of the experiment, the transcription level of MKI67 has been greatly reduced to around 214, which is a decrease of roughly 8-fold, and is close to the fluorescence level that a cell without GFP would exhibit. The transcription profile also shows that there might be a small portion of cells that remain in a highly proliferative state as their MKI67 levels show no sign of decrease.
The control population shows that without the influence of the drug, the transcription activities remain high in most of cells and only start to decrease in a small portion of cells at the end of the experiment, probably due to the depletion of growth factors in the media. This also confirms that there is little photobleaching in unaffected cells. More revealingly, the bi-modal expression profiles demonstrate beyond any doubt that when turning off, the state transition of MKI68 transcription activity is more of a switch-like procedure, rather than a gradual decrease of transcription level over the whole cell population. Furthermore, the switch-off of the transcription activity among responsive cells is not well synchronized, indicating different latency periods for cells to responding to the drug or even the existence of resistant sub-populations in the cell culture. Such a response dynamic is only observable when individual cell transcription activities, rather than the overall activity, are identifiable.
Viewing expression profiles as density functions allows researchers to compare transcription activities under different conditions in a single plot. In Fig. 5, the transcription activities at different time points are compared. One can also compare the transcription activities under multiple conditions, such as different drugs or cell-lines. One can also put different plots side-by-side and make larger-scale comparisons. While providing a means for direct comparison, a density function does not quantify observed differences. Thus, while this density-based approach can provide straightforward comparison for small-scale studies, where only a few factors are involved and there are few conditions to track and compare, it is less suitable for studies of complex diseases like cancer, where one would like to perturb the cell-line of interest with multiple drugs aiming at different targets and track multiple transcription signatures representing several critically related pathways. To represent the cellular activities at such a large scale in a manageable manner, one needs to further quantify the expression profile while keeping the meaningful responses observable.
From the example shown Fig. 5 as well as other observations, we notice that, for a cell culture at any given time, the distribution of transcription activity is mostly either uni-modal or bi-modal, indicating the cells are in either one or two dominating states most of the time. In the beginning of the experiment, owing to careful preparation, the transcription activity is highly homogeneous and the density function is always uni-modal with a sharp peak. Moreover, when the cell culture reacts to certain stimuli, the response is mostly uni-directional, which can lead to bi-modal distribution during state transition. If one could identify the valid states which the transcription activity can occupy and the percentage of cells in those states for any give time point, then the most informative part of the cellular dynamical system could be captured. However, we have found that such an absolute measure of cellular response is not practical on account of the following reasons: (1) It is hard to determine whether the distribution is uni-modal or bi-modal in many cases, especially when the estimated density functions is not smooth or during the transient period when cell response commences but is not prominent. (2) Assuming the nature of the distribution is correctly identified, then in a bi-modal case, if the two peaks are too close or the minor peak is too small, the state position of the minor peak could be hard to identify. (3) The absolute values of the transcription activity of the case population are of little meaning unless they are benchmarked against a control population. To ensure robustness of the quantified results, rather than using absolute measures, we adopt a relative measure that quantifies the transcription activity changes with respect to a control population.
As a relative measure, our quantification procedure intends to determine the size of the case population that behaves differently from the control population and the magnitude of the difference, which we denoted as pop-shift (PS) and fold-change (FC), respectively. We denote the distributions of the case and control populations as and , respectively, and their corresponding density functions as and , respectively. The control population can represent any condition that makes the comparison meaningful. The most common choice is the unperturbed population at the same time point, although it is also common to choose the same population at the beginning of the experiment. The intuitive idea for PS and FC is shown in Fig. 6. Basically PS measures the non-overlapped areas of the two distributions, as indicated by either grey area in Fig. 6, left and right representing the difference between and where and where , respectively. Because and are density functions, the two grey areas are of same size, i.e.,
Note that PS can be conveniently computed by using the total variation distance.26
For two identical distributions, , while for two totally disjoint distributions, . To evaluate FC, we measure the distance between the mass centers of the two non-overlapped areas, which indicate the extent of the population shifts:
Note that the FC can be conveniently computed as,
The product of PS and FC is given by the difference of mean cell-expression levels,
Although, average expression levels or similar ideas are commonplace in many high-throughput genomic data collection techniques, such as microarrays, the term used here is actually different. The critical difference is that the average here is taken at the cell level over the log-transformed values, whereas the microarray expression level is averaged in the assay during sample preparation and the log transform is taken after the average expression level is retrieved. Thus, the measure used here can improve detection sensitivity by mitigating the distorting impact of over-expressing outliers, which can have concentration levels hundreds of times higher than most of the other cells.
The PS and FC measures assume case population shift in one direction with respect to the control population and are most reliable when the assumption holds. There are cases this assumption is violated. The most common case is when the majority of the cells are shifting towards one direction but there can be a small number of cells shifting in the opposite direction. For example, in the beginning of the experiment, the cell culture is prepared so that the cells are in a quite homogeneous state. However during the on-going experiment, the cells begin to show increased variance in activity even without any external stimulus. The increased variance can be detected as cells shifting to both directions, although there is no meaningful state change. Such a behavior uncertainty could be even higher if the cells are under perturbation. In such cases, PS will report the total cells shifting to both directions while FC will report only small change. The measures hence could be misleading when there is only a small population shift, and affect the detection of the response initiation, which is critical to identifying the order of events. To alleviate this problem, we introduced a modified measure pair by computing both the up-regulation and down-regulation changes.
indicates that any shift to the left is down-regulation, whereas indicates up-regulation. The relationship between the bi-directional PS and FC to the uni-directional pair is straightforward:
Since we assume the state shift is uni-directional, any shift to the opposite direction is only due to noise or some transient activity. Hence, it is worthwhile to combine the measures into one pair according to the following procedure by canceling out the shifts to both directions. We first determine the dominating shifting direction based on and then compute the modified values:
The modified fold change is the FC of the dominating direction, while the modified pop-shift is based on the mean cell-expression level difference and . Rather than cancelling out the PS directly, we choose to use the mean cell-expression level to cancel out the product of PS and FC. This is because the noisy PS terms are usually a slight shift with relatively large PS but small FC. In comparison, a true shift is normally initiated with a far greater FC level but a relatively small percentage of cells. Thus, using the mean cell-expression value can help us identify the initiation of a true state transition. An alternative choice is to use the PS and FC of the dominating direction without canceling out any shift; however, we have noticed that if the PS in the opposite direction is due to noise, say variance, then it usually affects both directions, although the one in the dominating direction is over-shadowed by the true transition and therefore is not detectable. Once the PS and FC values are calculated for all time points of a certain condition, the PS and FC time sequences are separately smoothed with a median filter to remove small irregularities.
To show the transcription activity changes summarized by the PS and FC pair, we use a bar-plot pair as shown in Fig. 7, which refers to the same drugged cell population imaged and processed in Figs. 1 and 5(a). In Fig. 7(a), the initial state of the drugged population was chosen as the control, so for each time point, its current expression profile was compared to its own expression profile at the beginning of the experiment to obtain the PS and FC pair. In Fig. 7(b) the un-drugged population shown in Fig. 5(b) was chosen as the control, so for each time point, drugged population’s current expression profile was compared to the expression profile of the same time point of the control population. In each plot, two bar-plots are put in parallel pairs with common -axis aligned with experiment time points. The top bar-plot represents PS, while the bottom bar-plot, which is drawn downwardly, represents FC. In order to make the whole plot compact for better comparison, the absolute value of the change is shown and different fillings are used to indicate up- or down-regulation: white for increased activity and black for reduced activity. Each tick in the -axis of the PS plots corresponds to a 10% shift. The -axis for FC plots is shown in scale, i.e., two consecutive ticks indicate a twofold difference in concentration. Finally, although the PS and FC pair can reveal most of the cellular response activities, sometimes it’s still helpful to have a measure on the absolute expression levels. Here we chose the initial state, represented by the peak positions in the density functions at the beginning of the experiment, to provide a general idea on the absolute transcriptional level of the target gene. The initial states of both case and control populations are shown at the left of the plot.
Figure 7 shows that under the influence of the drug lapatinib, the transcription of gene MKI67 is turned off, starting from about 10 to 15 h after the drug is added. At the end of the experiment, transcription activities of about 40% of the cells have decreased to to of the no-drug control activity level.
Results and Discussion
To validate use of the proposed data analysis procedure, we have conducted comprehensive experiments to evaluate performance.
Image Processing Performance
The essential performance measure for image processing is nuclei segmentation accuracy. To evaluate nuclei segmentation accuracy, we have randomly selected 4 fluorescent images from 4 different imaging sites that cover over 1000 nuclei. Besides the proposed method, two other methods are used: segmentation by the software CellProfiler27,28 and manual segmentation. CellProfiler is a free open-source cell image analysis software developed by the Broad Institute. We have used Cell Profiler 2.0 (r10997). The nuclei segmentation is conducted through the module Identify Primary Objects, which uses a thresholding-based approach followed by shape-based de-clumping. Since the size of the foreground region in our cell image can vary substantially from image to image and from time to time, based on the suggestions from the software, we choose the two-class Ostu Adaptive segmentation as the thresholding method. The default threshold is too lenient for the cell density observed in our experiment, thus a threshold correction factor of 10 is set to achieve good segmentation of the selected images. For the proposed method, no specific individual parameters are selected for the four images; instead, we used a global parameter setting, which is actually used for all images processed in this paper.
Since there is no ground truth for the segmentation, we use manual segmentation by M. L. Bittner, one of the co-authors, who has three decades experience with cell and nuclear morphology, as a benchmark and compare the other approaches to this manual benchmark for accuracy counts. We also consider another independent manual setting by another experienced biologist. The inconsistency between the manual segmentations provides an idea of how well one could hope to do in comparison to the chosen standard. If two experienced biologists can only agree on 90% of the segmentation results, then it is likely that any claim of above 90% for automatic segmentation is just accidental.
Accuracy counts are divided into three categories: consistent nuclei, under-/over-segmentation, and missed nuclei. Segmentation results are shown in Table 1(a). Performance is comparable for CellProfiler and the proposed method at about 85% accuracy rate. CellProfiler’s performance decreases slightly when the cell density is high or the number of cells is large (over 300). Although the manual segmentation performance is better (relative to the benchmark manual segmentation), it is still below 90% and only 4% better than automatic segmentation methods, reflecting the overall difficulty of the problem and indicating good performance for the automatic methods. It should be noted that the total number of nuclei identified by each method are not the same. For computer-based approach, the most common errors are the over- and under-segmentation, while for manual segmentation, the discrepancy on whether to identify a certain object as cell play a much larger role in accuracy rate.
Accuracy of nuclei segmentation: (a) 4 random selected images from 4 different sites; (b) an image later in the experiment from a site used in (a).
To check the robustness of the image processing, we examine images of the same sites of the four images evaluated in Table 1(a) but at different time points of the experiment. In general, both automatic segmentation methods work pretty well, except for one site, where the nuclei intensity has dropped significantly at the later stage of the experiment. To illuminate the problem, another sample image of that site has been picked out for accuracy counting and the results are listed in Table 1(b), where we see that the segmentation performance has decreased significantly for all methods, with CellProfiler at a paltry 39.3%. The proposed method’s performance at 69% is even better than the manual segmentation, reflecting the great uncertainty even for the experienced biologists. This large discrepancy is due to the extreme condition experienced by the cells under great pressure. Although the dye on the nuclei has become dimmer, the chromosomes have begun to shrink into small yet bright nodes, making it much harder to tell whether an object contains single or multiple nuclei. Moreover, some nuclei have started to break up, a sign of apoptosis, thereby creating small particles that further confuse the segmentation procedure. Overall, the proposed image processing protocol can provide fast and robust image segmentation performance with adequate accuracy for the purpose of the experiment. We didn’t use CellProfiler not due to its general performance, but because of its lack of robustness relative to the kind of image degradation that can occur with our technology—for normal images, both CellProfiler and our approach provide segmentation accuracy close to human performance.
To compare gene expression profiles obtained under the same condition and derive an empirical distribution of profile difference under the identical condition, we measure the variability of duplicated cases. If the experiment and data analysis protocol are highly reproducible, then there should be little difference. In one experiment, we have collected 56 wells of identical condition: cell-line HCT116, reporter for gene MKI67, with no drug applied. Each well contains one imaging site. The experiment lasts 48 h, with images taken at every hour. After image processing and quality check, three time points were removed due to low imaging quality in significant number of imaging sites. The results of the remaining 45 time points are used to compute the profile difference distribution by emulating the standard experimental design, where each condition is covered by three sites. A scheme based on random sampling is used:
1. For a given time point, randomly find three sites to represent the target condition, and obtain the aggregated expression profile via the kernel-density distribution described in Sec. 2.3.2.
2. Randomly find three different sites at the same time point to represent a second sample of the same target condition, and obtain the aggregated expression profile.
3. Compute the pop-shift value between the two profiles.
4. Repeat step 1 to 3 for 1000 times, save the results for this time point.
5. Repeat step 1 to 4 for every time point.
Thus by aggregating all PS values, we have an empirical distribution for profile variation of identical condition based on PS, which is equivalent to total variation, an important distance measure for probability distributions.26 Figure 8(a) shows the distribution of PS values over all time points. For most case pairs, the reproducibility is very high, with PS values between 0.03 and 0.06, and very few PS values over 0.1. Additionally, the empirical distribution of Fig. 8(a) can help researchers identify genuine response differences. Taking identical condition as null hypothesis, the empirical distribution in Fig. 8(a) indicates that a PS value over 0.072 will lead to the rejection of the null hypothesis at significance level 0.05, and a threshold of 0.09 corresponds to the significance level 0.01. Thus if the PS value between the expression profiles of target case and control case is larger than 0.1, one can confidently claim there is a significant difference in the transcriptional response that is worth further investigation. Figure 8(b) shows the thresholds at significance level of 0.05 and 0.01 for each time point, based on the empirical expression distribution of that time point. It can be seen that there is little change in the thresholds at different time points, indicating that the reproducibility is not significantly affected by the time factor for at least 48 h.
Finally, we should point out that the empirical distribution obtained in Fig 8(a) is based on duplicated sites in one plate. Our experience shows that certain experimental factors, like how the sample is prepared, can have direct effects on the outcome, mostly shifts in the expression distribution and/or response dynamics. Thus to ensure reliable comparison, one should carefully prepare the assay so all conditions for direct comparison are in one plate, or in plates that are prepared and imaged as one batch. The tight confidence interval and time-invariance between duplicated cases confirm that the proposed image and data analysis protocol can provide reliable, robust and consistent performance for properly designed experiments.
To evaluate the proposed protocol’s ability to discriminate slight differences in a set of responses, we have designed an experiment where different drug doses are applied to incur different responses. Again, the cell-line HCT116 and the reporter for gene MKI67 are picked. As seen from Fig. 7, HCT116 is sensitive to the drug lapatinib and the transcription of MKI67 will be turned off when the drug is properly applied. In our experiment, six different doses of lapatinib, varying from a very light dose of 1 micromolar (µM) to a higher-than-normal dose of 32 µM are applied to the HCT116 cell-line after the fifth hour and the experiment lasts a total of 48 h. Six duplicates are used to cover each condition.
The bar plots in Fig. 9 show the extracted transcription responses to the drug. To facilitate unbiased evaluation, all corresponding axes across the plots are of the same scale. Since all cases share the same control population, the initial states of all six controls are of the same value. The initial states of all cases are very close to the control state, indicating that the samples are well prepared for the experiment. The effects of different dosing amounts can be clearly seen through direct comparison of the bar-plots. The response magnitudes induced by the drug increase consistently with the dosing amount. The smaller dosing amounts of 1 and 2 µM have observable yet small responses. The 8 µM dose was used in many experiments and has been shown to produce 50% growth inhibition in this cell line. In our experiment, this dose induces a considerable response, and the shift of cells to the reduced expression population is still rising at the end of the experiment. The highest dosing amounts of 16 and 32 µM induce the largest pop-shifts and show signs of saturation at the end of the experiment. Another sign of possible saturation is the relatively smaller extent of fold-change in the highest doses. The difference in the time when responses are initiated can also be readily observed, with the highest doses showing clear responses at five to 10 h after the drug, followed by normal doses at around 15 h, and lowest doses at even later hours. The dose response experiment clearly shows that the proposed protocol is sufficiently sensitive to detect small differences in transcriptional activities.
It is interesting to note that for the response of the lowest dose, if observed alone, its PS values are never high enough to register as a significant response; however, if compared with other cases of related yet non-identical conditions, as the cases shown in Fig. 9, the similarity between this case and other responses can hardly be missed and its contribution to infer the underlying biological mechanism can be rightfully appreciated. Thus, the power of the proposed protocol to detect mechanisms responding to certain perturbation can be further boosted through properly designed experiments.
In previous experiments, we have focused on evaluating specific qualities of the proposed protocol. As a high-content analysis tool, we expect the data analysis should allow researchers to not only follow the transcriptional activities of multiple genes simultaneously but also be able to compare these cellular activities side-by-side for different conditions. In this section, we discuss a full-scale experiment to demonstrate the ability of the data analysis protocol to cover cell process dynamics and reveal hard-to-detect relationships between responses induced by different conditions.
We have further screened the colon cancer cell line HCT116 against a variety of drugs. A total of 17 reporters have been selected to cover the genes for proliferation and survival pathways, two vital pathways in a cancer cell-line, and some other related genes. Figure 10 shows the diagram of two pathways, proliferation on the left and survival on the right. The wiring scheme has been greatly simplified to keep only key components in the diagram. It should be noted that this diagram is based on common knowledge of the two pathways and is not necessarily an accurate description of the cell-line under study. The genes for which reporters are used to assess their transcription are marked by shaded boxes. The drugs used in the experiment are marked in bold text.
Figure 11 shows the bar-plots for the transcriptional responses of all 4 drugs. Each column corresponds to a drug, while each row corresponds to a gene reporter, with the gene name associated with the reporter shown at the right end of that row. Because the experiment is conducted with multiple plates in several runs, whose duration time is different from each other due to various causes, the bar-plots are of different length. To ensure reliable comparison, all conditions associated with the same gene reporter, including the control populations, are contained in the same plate, and thus have been imaged in the same run. The same scale is set to the corresponding axes in all plots to facilitate accurate comparison.
From the bar-plots one can see that all four drugs induce some levels of responses. By showing all reporter responses in one large plot, the patterns in drug response can be more easily detected. Lapatinib induces responses of largest scale, with all but one reporter showing a clear decrease in transcription activity. Specifically, reporters of MYC are down-regulated only in a small portion of cells at the end of the experiment, but in terms of the full transcription profile, it is highly possible that this small shift is no accident. The behavior is consistent with the knowledge in the wiring diagram where lapatinib can inhibit both EGFR in the proliferation pathway and the ERBB2/3 heterodimer in the survival pathway. In comparison, U0126 only induces strong responses in a limited number of reporters, for instance, EGR1, FOS, and MKI67. For the reporters responding with down-regulation, the fold-change is relatively small compared to other drugs that induce similar pop-shifts, and most of these genes are closely related to the proliferation pathway. All of these observations are consistent with knowledge that U0126 is only targeted to a downstream member of the proliferation pathway and the observations confirm the limited scope of U0126’s impact. In comparison, LY 294002 induces a response pattern similar to lapatinib but of smaller degree in HCT116, which is consistent with the fact that LY 294002 targets only the survival pathway.
The most revealing case is Temsirolimus, which exemplifies how the transcription activity bar-plots can uncover subtle and hard-to-discover relationships. Under initial examination, the responses to Temsirolimus are so small that one is likely ignore them if any single reporter is examined alone; however, since all 17 reporters are shown in one plot and 12 of them end at down-regulation states, one is led to consider the overall response pattern. A close examination of the response pattern of LY 294002 shows that out of 17 reporters, 15 are at down-regulation states at the end of the experiment and the two in up-regulation, CDKN1A and MYC, are also up-regulated for Temsirolimus. This similarity reveals that Temsirolimus and LY 294002 are probably targeting the same pathway, but with different drug efficiency. This hypothesis is confirmed through the wiring diagram in Fig. 10, where Temsirolimus targets mTOR, a gene downstream of LY 294002’s target gene PI3KCA. These kinds of observations lead one to reasonably believe that, with careful design, similar procedures can be used to explore relationships between other drug pairs, including compounds of unknown mechanism.
High-content fluorescent protein reporter imaging can be used to track transcriptional activities in parallel. The huge amount of data collected from such an imaging protocol calls for innovative ways to analyze the data. In this paper, we introduced a data processing procedure to extract cell processing dynamics in a reliable and timely manner. The procedure contains two parts: (1) image processing, where the fluorescent images are processed and the transcriptional levels are extracted and quantified; and (2) data representation, where the extracted data are summarized into expression profiles and the transcriptional responses are transformed into informative bar-plots to facilitate efficient evaluation. The proposed data processing procedure provides a systematic solution for examining the experiments at different abstraction levels. Researchers can have a general idea of the whole experiment with bar-plots and further examine the details with expression profiles, or the raw images, if needed. Our experiments showed that the proposed procedure can achieve fast and robust image segmentation with adequate accuracy. The results are highly reproducible, and sensitive enough to detect subtle differences and hidden relationships. The method can help biologists take the advantage of high-content screening technology, accelerate identification of mechanisms underlying potential drug candidates, and in general increase the efficiency of drug discovery and treatment design.
In such case, before the main part of the image processing starts, the reference sites are pre-processed to extract the background intensity and saved in a common file. During the image segmentation, the background will be loaded from the common file, rather than processing the reference sites.
Imaging a 384-well plate requires approximately 43 min when using two color channels and taking two images per well, leaving only a small amount of free time to process images. Like most commercial automated epifluorescence image-acquisition systems, the authors’ systems do not provide simultaneous image capture and image-analysis support.
Although in this study images were taken by IN Cell Analyzer 3000, the general cell-handling and imaging protocol works reliably on another commonly used robotic imager (Molecular Devices, ImageXpress Micro) which has similar autofocus control, a single cooled CCD camera and a Xenon flashlamp excitation source.
Biological Sample Preparation
If a report of the promoter activity level of a specific gene is desired, then a DNA segment of that promoter ( to 2000 base pairs) upstream of the start of transcription for the gene of interest is copied using PCR and cloned into a plasmid pENTR5′ (Life Technologies, K59120), where it is flanked by recombination sites. Such a promoter donor plasmid along with another donor plasmid pENTR11 (A10467) with an eGFP protein coding sequence flanked by recombination sites are used to deliver the promoter and coding sequence via recombination into a recipient lentiviral delivery vector pLenti6.4/R4R2/V5-DEST (A11145) to create a cassette where the promoter of interest will drive the production of eGFP mRNA, which will be translated into fluorescent protein. The lentiviral vector can be transfected into 293FT cells along with helper plasmids that allow RNA copies of the cassette to be produced and encapsulated into particles that are readily taken up by cells, converted into a DNA copy, and integrated into the genome of the that cell, so that the promoter reporter construct resides stably in that cell.
In order to maximize the uniformity of reporter signaling in the population of cells carrying the reporter construct, it is useful to introduce the expression cassette in a uniform way. The lentiviral delivery system allows delivery of cassettes containing the promoter/reporter and blasticidin drug resistant portion of the initial construct in a dose-dependent fashion. These particles can effectively transduce both dividing and non-dividing mammalian cells with the promoter/reporter construct. Cells to receive the reporter are infected at a multiplicity of infection of 0.5 to 0.7, which limits the delivery to one construct per cell to nearly all of the cells that do get infected. The cells are then cultured for three days in the presence of blasticidin, which kills those cells that were not infected, at which point, the cells are ready for use in the assay.
Response dynamics experiments are carried out to determine whether or not a particular drug perturbs a set of processes hypothesized to be altered by the drug. To test the hypothesis, a set of reporters that each evaluates the process activity level at a particular point in the process is required. To allow testing over a wide variety of cellular processes, we have built a GFP library containing over 80 GFP reporters that cover known critical cellular responses. A set of 17 GFP reporters for analysis of proliferation and survival activities in cell line HCT 116 (ATCC #CCL-247) are utilized in this study. HCT 116 reporter-bearing derivative cultures are cultured in DMEM (Life Technologies, 11965118), supplemented with 10% FBS (16000044), 20 mM Hepes (15630080), 20 mM Glutamax (35050061) and 1% Penicillin—Streptomycin (15070963) in T25 flasks. For imaging, a media having low levels of autofluorescence, IM, is prepared. IM contains 70% M-199 (11825015), 30% RPMI-1640 (11875085) supplemented with 10% FBS (16000044), 20 mM Hepes (15630080), 20 mM Glutamax (35050061) and 1% Penicillin—Streptomycin (15070963) and 0.5 µM Vybrant® DyeCycle™ Violet Stain (V35003). The stain is live-cell permeable and produces blue fluorescence () when bound to double-stranded DNA and stimulated with a violet excitation source (). One day prior to an imaging experiment, sub-confluent cells are trypsinized to release them from the flask surface, resuspended in IM and counted in an automated cell counter (Life Technologies C10227) to establish number of cells per milliliter. The concentration of cells is then adjusted to 1500 cells per 30 µl of IM.
A 30 µl aliquot of cells having a particular promoter/reporter construct is delivered to a well in a 384-well microtiter plate (Greiner Bio-One 781 09x) that has black, opaque walls and a thin, UV-transparent well-bottom. The plate wells were previously collagen coated by exposing them to Rat Tail Collagen Type I (BD Biosciences 354249) in 0.02 M acetic acid for 1 to 4 h followed by washing 2 times with 1× PBS (Gibco 14200). The cells were allowed to attach to the plate and equilibrate for 14 to 16 h in a tissue culture chamber prior to beginning imaging. Each condition tested used six replicate wells in reproducibility and sensitivity experiments, and three replicate wells in the full-scale example.
All images examined in this study were taken by an automated scanner (IN Cell Analyzer 3000, General Electric) with a objective.‡ Images were captured using three high-speed cooled CCD cameras for Blue, Green and Red fluorescent channels. Excitation was provided by three separate lasers. Throughout the experiments the focus of the scanner was automatically adjusted using an infrared laser to determine the liquid/well bottom interface and then applying a defined offset per channel. Flat-field correction was determined by imaging wells with slightly fluorescent media prior to the start of the experiment. While imaging, the humidity in the imaging chamber holding the plate is controlled at 70%. The level is controlled at 5% by mixing with ambient air at the proper ratio. The gas mixture is then pumped through a heating and moisturizing chamber to bring it to 37°C. Then the experiment plate was imaged continuously once per hour for 5 h to obtain baseline data. Another 30 µl aliquot of IM was then added which contained perturbants at twice the concentration desired or no additives for control wells and again imaged once per hour for the duration of the whole experiment, which usually lasted up to about 48 h under our experimental settings. After the imaging, the flat-field-corrected images were exported in uncompressed tiff format for image analysis.
Development of these methods was supported in part by a contract from PBS-Bio and a generous grant from the W.M. Keck Foundation. | <urn:uuid:7e9cabab-70ef-4b22-a917-c30866e9c5f6> | 2.9375 | 13,231 | Academic Writing | Science & Tech. | 29.5619 | 95,571,606 |
Comparison of three options for geologic sequestration of CO2 - a case study for California Page: 1 of 8
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COMPARISON OF THREE OPTIONS FOR GEOLOGIC SEQUESTRATION OF CO2
- A CASE STUDY FOR CALIFORNIA -
SALLY M. BENSON
Earth Sciences Division
E.O. Lawrence Berkeley National Laboratory
One Cyclotron Rd., Berkeley, Ca., 94720
Options for sequestration of CO2 are best viewed in light of the regional distribution of CO2
sources and potential sequestration sites. This study examines the distribution of carbon
emissions from fossil fuel power plants in California and their proximity to three types of
reservoirs that may be suitable for sequestration: (1) active or depleted oil fields, (2) active or
depleted gas fields, and (3) brine formations. This paper also presents a preliminary assessment
of the feasibility of sequestering CO2 generated from large fossil-fuel fired power plants in
California and discusses the comparative advantages of three different types of reservoirs for this
purpose. Based on a volumetric analysis of sequestration capacity and current CO2 emission rates
from oil/gas fired power plants, this analysis suggests that oil reservoirs, gas fields and brine
formations can all contribute significantly to sequestration in California. Together they could
offer the opportunity to meet both short and long term needs. In the near term, oil and gas
reservoirs are the most promising because the trapping structures have already stood the test of
time and opportunities for offsetting the cost of sequestration with revenues from enhanced oil
and gas production. In the long term, if the trapping mechanisms are adequately understood and
deemed adequate, brine formations may provide an even larger capacity for geologic
sequestration over much of California.
The State of California, has a population of 34 million people and supports an annual
economy of $1,280 Billion per year, placing it amongst the top 10 economies in the world.
Covering over 411,469 km2, California encompasses a diversity of geologic terrains, from the
volcanoes of the Cascade Mountain range in the north to the deep sedimentary troughs in the
Central and Imperial Valleys in the south, from the Sierra Nevada Mountain range to the east and
the 1500 km coastline to the west (see Figure 1). Rich in natural resources, it has the fourth
largest oil and gas production in the United States, and extensive groundwater and surface water
resources. All of these features make the State of California attractive for a regional case study
for assessing the feasibility of geologic sequestration of CO2.
Current annual CO2 emissions from fossil fuel combustion in California total 380 million
metric tons (MMT); of which 56.5% are from transportation, 16.2% from electrical generation,
14.4% from industrial sources such as refineries and cement kilns, 8.5% from residential heating
and cooking, and 4.4% from commercial uses (California Energy Commission, 1998). Emissions
are expected to increase about 10% by 2010 (California Energy Commission, 1998). Over 95%
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Benson, S.M. Comparison of three options for geologic sequestration of CO2 - a case study for California, article, September 1, 2000; California. (digital.library.unt.edu/ark:/67531/metadc721293/m1/1/: accessed July 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department. | <urn:uuid:19d6289b-fb2b-44a7-840d-4c50e13b8af7> | 2.796875 | 901 | Truncated | Science & Tech. | 35.531759 | 95,571,623 |
Spatiotemporal Change Study for High Altitudes of Pithoragarh District Uttarakhand as an Indicator of Climate Change?Spatiotemporal Change Study for High Altitudes of Pithoragarh District Uttarakhand as an Indicator of Climate Change?
Received Date: Jan 30, 2018 / Accepted Date: Mar 27, 2018 / Published Date: Mar 29, 2018
The spatiotemporal remotely sensed data are extremely valuable for detecting changes in vegetation cover, land use/cover classes, snow, water bodies and other terrestrial features. Mapping of tree line, vegetation line, Snow line and its shift analyses can help in better knowing the trend of climate change scenarios.
The present paper deals with a change analysis pattern in tree line, alpine pastures and snow line for a period of 1972 to 2016. The study was carried out in two block i.e., Munsiyari and Dharchula of Pithoragarh district of Uttarakhand Himalaya using Landsat data of the listed years. The study showed that the from 1972 to 2016 there is mean increase in tree, grassland/pastures and snow line. The mean upward shift of the tree line was highest in Munsyari block (4504 m) and Dharcula block lowest (2856 m). Magnitude of upward shift in terms of elevation range showed that at many places in the Munsyari Block, the upward shift of the tree line crossed 419 m, during 44 years interval. Grassland are found at an elevation of 1400-5754 m interval during 1972, 1523-5780 m interval during 1998 and 1742-6090 m interval during 2016. This included great expanses of pure meadows (grasslands), flowering herbs and scattered miscellaneous vegetation. The vegetation near the snow line and in the proximity of the glaciers was rather thin, scattered, apart from the mosses and lichens. The snowline during 1972 is an elevation of 2939 m, 2991 m for 1998 and 3132 m for 2016.
Keywords: Extraction of individual trees; Tree crown; Dry trees; Remote sensing; Classifiers; Zagros forests; Haft Barm Shiraz
Alpine pasture/grassland, meadows or Bugyals, in higher elevation range between 3,300 m (10,800 ft) and 4,000 m (13,000 ft) of the Himalayas in the Indian state of Uttarakhand, where they are called "nature’s own gardens”. The topography of the terrain is either flat or sloped. The surface of these Bugyals is covered with natural green grass and seasonal flowers. They are used by tribal herdsmen to graze their cattle. During the winter season the alpine meadows remain snowcovered. During summer months, the Bugyals present a riot of beautiful flowers and grass. As Bugyals constitute very fragile ecosystems, particular attention needs to be given for their conservation.
The mountain ranges are karstic, exhibiting fast drainage. Considerations of plant cover and soils are therefore, crucial for water protection . Apart from the potential of climate changes for direct impact on the hydrological cycle , they will very probably also change vegetation properties. Nevertheless, in which way and to what extent such changes will occur remains unclear as yet. An assessment of impacts of climate and land use changes on the vegetation was therefore of high priority as a prerequisite for future strategies of water management. From a management perspective it is particularly important to evaluate changes which might occur at the local scale. In addition to climatic influences, other potential contributing factors also have to be taken into account of which land use may be most important.
Most of the research on alpine tree line shift has primarily been based on field data with a limited geographical extent. Due to its synoptic view and historical records for a wide area, remote sensing is an important tool to study alpine tree line and changes in the recent past. This study confirms that there is an upward shift of vegetation in the alpine zone of the Himalayas. In the Himalayas land above the tree limits is used as alpine pasture for arising cattle during December month.
Temporal remotely sensed data are extremely valuable for detecting changes in vegetation cover, land use/cover classes, snow, water bodies and other terrestrial features. However, the process of change detection involves a number of methodological considerations such as proper ortho-rectification of remotely sensed data, minimizing errors on account of varying phenophases which influence reflectance/ radiometry, and availability of snow/cloud free image .
Remote sensing is an important tool to study alpine treeline and changes in the recent past. This study confirms that there is an upward shift of vegetation in the alpine zone of the Himalayas. In remote sensing studies of vegetation, spectral vegetation indices are normally used. Among all vegetation index (NDVI) is widely used in detecting vegetation change, vegetation greenness and vegetation status, as it has good correlation with canopy cover and leaf area index.
Remote sensing is now recognized as an essential tool for viewing, analyzing and characterizing the alpine treeline ecotone. Mapping of tree line, vegetation line and analysing shift in these using remote sensing data have been reported for a site in NDBR based on the above observation, a study was taken up at the space application center, Ahmedabad, to analyse the change in tree line and alpine vegetation line in the Indian Himalayan region. Here we highlight the results of remote sensing-based observation on tree line changes in Uttarakhand, India.
The present work determiners the extent of such alpine pastures in the eastern and western Himalayas using Landsat-1MSS, Landsat-5TM and Landsat-8 OLI (TIRS) for the period 1972, 1998, 2016. The result of the was changing the tree line snow line and grassland.
The present study proposes the spatiotemporal study of alpine meadows of Pithoragarh district which is one of the district of Uttarakhand state. In this present study two block i.e., Munsiyari and Dharchula were selected. Total area as per availability of remote sensing data scene availability of Munsiyari and Dharchula has 5597.42 km.sq. for this study cover only 4378.528 km.sq. area for 1972, 5182.42 km.sq. 1998 and 5297.30 for 2016. And the remaining area are 1218.892 km.sq. 414.443 km.sq. and 300.12 km.sq. for 1972, 1998 and 2016 respectively (Figure 1).
Climate and Rainfall
Pithoragarh town, being in a valley, is relatively warm during summer and cool during winter. During the coldest months of December and January, the tropical and temperate mountain ridges and high locations receive snowfall and have an average temperature of 5.5-8.0°C (41.9-46.4°F). The temperature rises from mid-March through mid-June. The areas above 3,500 m (11,500 ft) remain in a permanent snow cover. Regions lying at 3,000-3,500 m (9,800-11,500 ft) become snow bound for four to six months. Winter is a time for transhumance–the seasonal migration of the Bhotiya tribe with their herds of livestock to lower, warmer areas.
Materials and Methods
In present Study the Various Landsat series was used for spatiotemporal monitoring like, Landsat 1 MSS data (1972), Landsat 5 TM data (1998), Landsat 8 OLI data (2016) and Cartosat-1 (DEM) data. The methodology involves the Image pre Processing, Digital classification, Unsupervised Classification, Visualization classification, Indices Classification, In present study the use of NDVI, NDSI, NDWI, SAVI based on threshold value for classification for getting better result, then others (Figure 2).
The tree line during 1972 is an average elevation of 3300 m, 3386.5 m for 1998 and 3749 m for 2016. Thus, there is a mean upward shift of the tree line. The difference in the surface distance from the past to the current period is mainly due to the zigzag nature of the ingression along suitable elevational gradients. The mean upward shift of the tree line was highest in Munsyari block (4504 m) and Dharcula block lowest (2856 m). Magnitude of upward shift in terms of elevation range showed that at many places in the Munsyari Block, the upward shift of the tree line crossed 419 m, during 44 years interval.
Grassland are found at an elevation of 1400-5754 m interval during 1972, 1523-5780 m interval during 1998 and 1742-6090 m interval during 2016. This included great expanses of pure meadows (grasslands), flowering herbs and scattered miscellaneous vegetation. The vegetation near the snow line and in the proximity of the glaciers was rather thin, scattered, apart from the mosses and lichens. The snowline during 1972 is an elevation of 2939 m 2991 m for 1998 and 3132 m for 2016 (Table 1).
Table 1: Spatiotemporal Changes.
Previous studies from the tree line zones in the Himalayas had shown that the vegetation has fluctuated in the past in response to long-term climatic changes. In this study had change on the temperature in 1998 was 17.81°C and recent temperature is 18.96°C, was change in 1.15°C. Studies on the impact of ongoing warming under the background influence of greenhouse gases world over have shown that during the past few decades alpine plant species have shifted to higher elevation, though the shifting rate varies with species and their sensitivity to climate. This study confirms that there is an upward shift of vegetation in the alpine zone of the Himalayas. Though there may be some error in the exact elevation gradient in general, there is no doubt that the change is significant. However, any meaningful research to model the vegetation dynamics response to warming requires an effective, long-term ground-observation strategy.
Satellite remote sensing data are the best option in view of the rugged, inaccessible and vast stretch of the Himalayan alpine area. This study has shown the potential of remote sensing data to create and update a database of alpine tree line and vegetation lines.
- Dirnböck T, Grabherr G (2000) GIS assessment of vegetation and hydrological change in a high mountain catchment of the Northern Limestone Alps. Mountain Research and Development 20: 172-179.
- Loaiciga HA, Maidment DR, Valdes JB (2000) Climate-change impacts in a regional karst aquifer, Texas, USA. Journal of Hydrology 227: 173-194.
- Roy DP (2000) The impact of misregistration upon composited wide field of view satellite data and implications for change detection. IEEE Transactions on geoscience and remote sensing 38: 2017-2032.
Citation: Rawat N, Gabriyal R, Kandpal K, Purohit P, Pant D (2018) Spatiotemporal Change Study for High Altitudes of Pithoragarh District Uttarakhand as an Indicator of Climate Change?. J Remote Sensing & GIS 7: 234. Doi: 10.4172/2469-4134.1000234
Copyright: © 2018 Rawat N, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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The 21st-Century Space Race: Will Boeing or SpaceX Be First to Mars?
The aerospace giant aims to beat out Elon Musk by sending the first manned mission to the Red Planet.
The spacesuit gloves are off. It’s not just Elon Musk that wants to take us all to Mars—Boeing has declared its ambition, too. The race to the Red Planet is on.
Speaking at a technology conference in Chicago called What’s Next, Boeing’s CEO Dennis Muilenburg signalled his intention to join this century’s space race. “I'm convinced that the first person to step foot on Mars will arrive there riding on a Boeing rocket," he explained.
Boeing's plans to take people to the Red Planet are nothing new. As Ars Technica points out, the company is already working on a craft that will take humans to Mars, because it’s the primary contractors on NASA's new Space Launch System rocket. That rocket will, eventually, be powerful enough to take up to six astronauts to the planet, but such a mission isn’t expected to take place until the late 2030s.
Muilenburg did, however, hint that Boeing is also interested in space tourism, suggesting that near-Earth recreational trips into orbit would be “blossoming over the next couple of decades into a viable commercial market.” Ambitions to take mere mortals to Mars, then, may also be on the cards.
SpaceX’s Martian offering is as ambitious as you would expect for a company run by Elon Musk. At the International Astronautical Congress in Guadalajara, Mexico, last week, Musk explained that he plans for SpaceX to build as many as 1,000 giant interplanetary spaceships—each larger than NASA’s old Saturn V—to ferry people to Mars. Funding plans remain vague at best, though.
Others have had their eyes on taking humankind to Mars before, but their ambitions seem less likely to be realized. The Netherlands-based nonprofit Mars One, for instance, aims to carry out a one-way manned trip to Mars as soon as 2026. But its plans and schedule have received serious criticism from engineers. The Inspiration Mars Foundation, meanwhile, claimed it would launch a manned mission by 2018 or, failing that, 2021. Its website is no longer live, though, which suggests that plans are on hold.
So for now it least, it’s SpaceX and Boeing that will be competing to get there first.
There are still some nagging concerns over plans to take humankind to Mars, though. As difficult as getting there would be, keeping people alive once there is going to be even harder. Elon Musk has made it quite clear that that’s not his problem. He compares the venture to the Union Pacific Railroad: SpaceX is building the transportation network, not the actual colony. Mars-goers will have to fend for themselves.
Given that fact, the other major concern seems all the more pressing: do many people really want to go?
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:316b2cbf-b750-410f-823b-281170e5fe30> | 2.546875 | 661 | News Article | Science & Tech. | 58.905603 | 95,571,642 |
To better predict tropical cyclone intensity, scientists sponsored by the Office of Naval Research (ONR) recently worked with the National Aeronautics and Space Administration (NASA) and National Oceanic and Atmospheric Administration to gather atmospheric data from storms that formed in the Atlantic Ocean in 2016.
Fully developed tropical cyclones -- variously called hurricanes, typhoons or cyclones, depending on their region--can grow as wide as several hundred miles and sustain winds faster than 150 miles per hour. For example, Typhoon Tip (1979) had 190-mph winds and Hurricane Patricia (2015) whipped up 215-mph winds (the record).
A NASA unmanned Global Hawk plane used to gather atmospheric data from hurricanes that formed in the Atlantic Ocean in 2016. To better predict hurricane intensity, scientists sponsored by the Office of Naval Research are studying this data to design more accurate weather-forecasting systems.
Credit: National Aeronautics and Space Administration
Such storms are notoriously difficult to predict, presenting a volatile meteorological cocktail that can change direction, speed and strength, quickly and unexpectedly. They pose a severe threat to U.S. Navy fleet operations--so accurate forecasting is critical for protecting ships at sea, evacuating vulnerable bases, and performing humanitarian assistance and disaster relief.
"Think about the ships, equipment, people and assets that must be moved to safety before a hurricane hits," said Dr. Ronald Ferek, a program manager in ONR's Ocean Battlespace Sensing Department. "This represents a huge investment of resources. If we can improve the lead time and accuracy of storm forecasts, it would give naval leadership more time and detailed information for preparations, evacuation or shelter-in-place decisions."
The recent research involved flying NASA's unmanned Global Hawk planes above hurricanes -- more than 60,000 feet in the air -- and deploying sensor-laden dropsondes. Dropsondes are parachute- and GPS-equipped devices that measure temperature, humidity, moisture, wind speed and direction, pressure and altitude -- crucial factors in determining the potential strength and destructiveness of a hurricane.
The Global Hawks flew nine missions this year -- dropping 647 dropsondes -- culminating in three flights above Hurricane Matthew, a Category 5 storm that battered the East Coast in October. ONR is sponsoring efforts by the Naval Research Laboratory (NRL) and several universities to analyze and interpret the collected data, and integrate it into computerized prediction models.
"Dropsondes are valuable because they take numerous readings as they descend through the storm to the ocean's surface," said Dr. James Doyle, who works in NRL's Marine Meteorology Division in Monterey, Calif. "This provides in-depth information about internal storm structure, and the environment surrounding the storm."
This year's work builds on the Coupled Ocean/Atmosphere Mesoscale Prediction System-Tropical Cyclone -- COAMPS-TC, for short. This groundbreaking computer-forecasting tool was developed under ONR sponsorship and put into operations at the Fleet Numerical Meteorological and Oceanographic Center in 2013. COAMPS-TC uses complex algorithms to predict hurricane intensity by processing real-time and historical meteorological data, fed by information from satellites and remote-sensing stations.
Although weather forecasters have become better at forecasting a hurricane's path and landfall, they struggle with predicting its strength. But Doyle said this is improving as unmanned planes like the Global Hawk enable data collection from the storm's upper layer, which can rise over 60,000 feet in height. This layer is where tropical cyclones expel the air that ascends rapidly through deep thunderstorms found in the eyewall--where the greatest wind speed and precipitation are found.
Both Ferek and Doyle believe the upper layer dramatically impacts hurricane intensity. They're especially interested in learning how jet streams interact with the upper layer--as well as its effects on the eyewall and secondary circulation (when hot, moist air flows upward from the storm's bottom, fueling greater intensity).
Doyle's team will use this year's data to create an advanced version of COAMPS-TC for the 2017 season -- and will further test this new version by simulating hurricanes that occurred worldwide from 2013-2016. The goal is to see how accurate previous predictions were and use the new information to improve future forecasting.
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For the first time, researchers have detected high concentrations of a popular insecticide in suburban stream sediments, raising concerns about its effects on aquatic life.
Pyrethroids, the active ingredient used in most home and garden insecticides, have been on the market for years. Although the compounds are considered potentially less harmful to humans than other insecticides, surprisingly little information is available about their long-term impact on the environment, according to Donald Weston, Ph.D., an adjunct professor of ecotoxicology at the University of California, Berkeley.
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20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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An intricate new three-dimensional protein structure is providing a detailed look into how brain cells communicate rapidly.
By visualizing how three neural proteins interact with one another, researchers have revealed how they help groups of brain cells release chemical messages at the same time.
The work describes a surprising new cooperation among the three proteins, and could offer insight into other processes where cells secrete molecules, including insulin and airway mucus. Howard Hughes Medical Institute (HHMI) Investigator Axel Brunger and colleagues report the results August 24 in the journal Nature.
When a group of neurons receives an electrical signal, the cells release chemicals called neurotransmitters nearly instantaneously - within less than one thousandth of a second. Neurons hold neurotransmitters in bubble-like structures called synaptic vesicles.
These structures rest inside the end of long, thin projections that point toward neighboring cells. To free neurotransmitters from their bubbles, neurons must fuse vesicle membranes with the outer membrane of the projections. This opens the bubbles and dumps their contents into the space between cells. The chemical signals then float to neighboring cells to relay a message.
Scientists knew that three proteins are involved in spitting out neurons' chemical signals. A group of proteins called SNAREs provides energy for membrane fusion. Another protein, called synaptotagmin, releases neurotransmitters when calcium ions appear following an electrical signal. A third protein, complexin, prevents cells from spontaneously releasing neurotransmitters. Synaptotagmin and complexin each partner with SNARE proteins, but until now, scientists could not explain how these three components worked together.
Brunger's team at Stanford University synthesized portions of each component, allowed them to assemble into a complex, and coaxed the complex to form crystals. Then they determined the structure of the complex by measuring how the crystals diffracted x-ray light.
The crystal structure revealed two ways that the proteins interact. The first interaction - between synaptotagmin and the SNARE proteins - is identical to one Brunger and colleagues described in a 2015 paper in Nature. A second, unexpected, interaction revealed a relationship between all three components in the larger complex.
In this three-component interaction, a curly helix of complexin nestles near a helix in a synaptotagmin protein, arranged so that twists of the helices align like the threads of a screw. These helices also rest atop helices of the SNARE complex.
In collaboration with HHMI Investigator Thomas Südhof, the researchers engineered mouse neurons to produce mutated synaptotagmin proteins, which weakened the attraction between the three proteins. Cells with mutated proteins, or ones that lacked complexin, lost the ability to synchronize neurotransmitter release.
Based on their observations, the researchers propose that the three-part interaction locks down the SNARE proteins, so they cannot perform the membrane fusion required for neurotransmitter release until the right moment. Complexin pins the three proteins together, and synaptotagmin might unlock the SNARE proteins when triggered by calcium ions.
"This tripartite interaction intuitively explains the role of the three components," Brunger says. "Now we can explain the cooperation between complexin, synaptotagmin, and the SNARE complex."
There are more than 60 different SNARE proteins in mammalian cells, which, along with various forms of synaptotagmin, are involved in hormone release and other cellular processes. A similar three-part interaction involving SNARE proteins may be used for other calcium-dependent cellular release processes too, Brunger says.
Qiangjun Zhou et al. "The primed SNARE-complexin-synaptotagmin complex for neuronal exocytosis," Nature 548 (August 24, 2017): 420-425, doi: 10.1038/nature23484.
Meghan Rosen | EurekAlert!
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
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17.07.2018 | Information Technology
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about this item
The volume is intended as an introduction to the physical principles governing the main processes that occur in photosynthesis, with emphasis on the light reactions and electron transport chain. A unique feature of the photosynthetic apparatus is the fact that the molecular structures are known in detail for essentially all of its major components. The availability of this data has allowed their functions to be probed at a very fundamental level to discover the design principles that have guided evolution. Other volumes on photosynthesis have tended to focus on single components or on a specific set of biophysical techniques, and the authors’ goal is to provide new researchers with an introduction to the overall field of photosynthesis.
The book is divided into sections, each dealing with one of the main physical processes in photosynthetic energy conversion. Each section has several chapters each describing the role that a basic physical property, such as charge or spin, plays in governing the process being discussed. The chapters proceed in an orderly fashion from a quantum mechanical description of early processes on an ultrafast timescale to a classical treatment of electron transfer and catalysis on a biochemical timescale culminating in evolutionary principles on a geological timescale. | <urn:uuid:1370ca55-49fe-4de1-b4ba-d250d4618458> | 2.796875 | 235 | Product Page | Science & Tech. | 11.211463 | 95,571,685 |
When sediments are first deposited, they are unconsolidated and are not considered a rock . Lithification is the process of converting unconsolidated sediments into sedimentary rock. Lithification involves primarily the processes of compaction and cementation. Recrystallization is also an important process for some sediments.
Compaction is the rearrangement of sedimentary particles to reduce pore space and squeeze out pore water . Unlithified sediments generally contain some excess space between grains. This is especially true in the case of very fine-grained sediments such as clay and mud. Coarser grained sediments such as sand and gravels are heavy enough to settle with a minimum of pore space. Over time, as sediments accumulate in basins, the thickness and weight of the overlying sediments increases. The pressure on the buried sediments causes all the grains to compress together as tightly as possible. Excess interstitial water is also forced out and the sediments are now compacted.
The next step is cementation. Only after cementation has occurred can the sediments be considered a rock. Although compaction has reduced the pore space within sediments, some space remains. In addition, even though the sediments are compacted to a high degree and have been de-watered, the great pressures and higher temperatures in a sedimentary basin can force hot circulating waters, or basinal brines, to permeate through the sediments. These fluids have the ability to carry dissolved minerals and deposit them within the available pore space of sediments, binding them into rock.
The cement may be derived either from outside sediments or from within the sediments themselves. Externally sourced cementing material is dissolved from some other rock formation or sediments that the fluids permeated prior to entering the sediments to be cemented. Alternatively, a permeating fluid may dissolve the cementing mineral from within the sediments themselves and then redeposit them before exiting.
The most common cementing materials are calcium carbonate, silica, and iron oxides. Calcium carbonate cement is usually in the form of calcite. Silica cement is dominantly quartz but also can be chert or chalcedony. Iron oxide cements occur in the form of hematite or limonite.
Some sediments may become lithified by the recrystallization of mineral constituents rather than by cementation. This is an important process in the formation of limestone and some shales. As the name implies, it involves the in situ recrystallization of the sedimentary grains. In this process, minerals will recrystallize as a response to a change in their chemical environment, such as a rise in the pH . This is because some minerals are more stable than others are in a given set of conditions. Entire grains may reform, or just the rims of minerals. As mineral grains recrystallize, they grow together, forming new interlocking grain boundaries. These interlocking crystals bind the sediments into rock.
See also Sedimentary rocks; Sedimentation
"Lithification." World of Earth Science. . Encyclopedia.com. (July 19, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/lithification
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Many authorities, even at universities, with all due respect, copy each other and don’t check their sources for errors. A lack of knowledge of Einstein’s Relativity? Critical sounds are rare and often not listened to.
For example, Emmy Noether’s well-founded criticism (a century ago) on Einstein’s Relativity was simply ignored. Till today.
Want to see them virtually talking to each other? Check the video. (under construction: sub- and superscript not yet correct)
When you do the checks as we did and then repair Einstein’s Relativity for Noether’s theorem, you get an improved Relativity in which energy and momentum conservation are guaranteed! We hope you get as many “aha” experiences as we did after fifteen years of research.
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Emmy Noether, the ignored scientist
Emmy Noether (1882 – 1935) was a brilliant mathematician, creating one of the pillars of physics: defining reference frames within which energy and momentum conservation can be proven. However, she was at the wrong place at the wrong time.
Albert Einstein, the Pioneer of Space-time
Albert Einstein (1879 – 1955) was a pioneer of space-time. In 1905, he published his theory of Special Relativity, based on the Lorentz transformation.
However, he changed his mind more often than is generally known, leaving paradoxes in his theory of Special Relativity when he changed from the Lorentz transformation to the differential Minkowski formula. He also ignored Noether’s theorem, leaving small errors in the Schwarzschild and Robertson-Walker Solutions.
Time and Repairing the Schwarzschild Solution
In his theory of General Relativity, Einstein replaced the Lorentz transformation by the Minkowski formula. By interpreting time as Karl Schwarzschild did, and using Noether’s theorem with a constant speed of light, we get the Shapiro solution. The relativity principle then leads us to our repaired Schwarzschild Solution, which is simpler and more elegant, with interesting consequences.
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We, therefore, formally designate all of the genera and species listed below as nomina dubia
Two further species were treated as nomina dubia
leleupi Cooreman 1977 from Ecuador were each based on juveniles and were therefore considered nomina dubia
by Platnick & Shadab (1981) and Platnick & Paz (1979), respectively.
Nicolet's entire collection was lost amongst the Museum National d'Histoire Naturelle, Paris, collection and all have long been treated as nomina dubia
The whip spider genus Phrynus Lamarck 1801 currently contains 28 living and two fossil species, with a further 4 species currently listed as nomina dubia
(Quintero 1981; Armas & Gonzalez 2001; Armas & Viquez 2001; Harvey 2002, 2003; Armas & Gadar 2004; Poinar & Brown 2004; Teruel & Armas 2005) and most are distributed from the southern USA to northern South America (Weygoldt 2000; Harvey 2003). | <urn:uuid:fca8eabe-6d75-4f83-99ea-babc356a1097> | 2.53125 | 212 | Structured Data | Science & Tech. | -8.235432 | 95,571,733 |
Primary Style.When the object is serialized out as xml, its qualified name is w:qFormat.
Assembly: DocumentFormat.OpenXml (in DocumentFormat.OpenXml.dll)
'Declaration Public Class PrimaryStyle _ Inherits OnOffOnlyType 'Usage Dim instance As PrimaryStyle
public class PrimaryStyle : OnOffOnlyType
[ISO/IEC 29500-1 1st Edition]
188.8.131.52 qFormat (Primary Style)
This element specifies whether this style shall be treated as a primary style when this document is loaded by an application. If this element is set, then this style has been designated as being particularly important for the current document, and this information can be used by an application in any means desired. [Note: This setting does not imply any behavior for the style, only that the style is of particular significance for this document. end note]
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<w:style … w:styleId="PStyle"> <w:name w:val="PrimaryStyleExample"/> <w:qFormat/> … </w:style>
The qFormat element specifies that this style definition must be treated as a primary style for this document. end example]
This element’s content model is defined by the common boolean property definition in §17.17.4.
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developerWorks: Guide to Python Introspection
Dec 23, 2002, 08:30 (1 Talkback[s])
(Other stories by Patrick K. O'Brien)
How to Help Your Business Become an AI Early Adopter
"In everyday life, introspection is the act of self-examination.
Introspection refers to the examination of one's own thoughts,
feelings, motivations, and actions. The great philosopher Socrates
spent much of his life in self-examination, encouraging his fellow
Athenians to do the same. He even claimed that, for him, 'the
unexamined life is not worth living...'
"In computer programming, introspection refers to the ability to
examine something to determine what it is, what it knows, and what
it is capable of doing. Introspection gives programmers a great
deal of flexibility and control. Once you've worked with a
programming language that supports introspection, you may similarly
feel that "the unexamined object is not worth instantiating."
"This article introduces the introspection capabilities of the
Python programming language. Python's support for introspection
runs deep and wide throughout the language. In fact, it would be
hard to imagine Python without its introspection features. By the
end of this article you should be very comfortable poking inside
the hearts and souls of your own Python objects..." | <urn:uuid:daa11cf8-41f1-4d5f-b1d0-a9c6a2b9bc4b> | 2.84375 | 293 | Content Listing | Software Dev. | 42.526103 | 95,571,764 |
The Water Quality Analysis Simulation Program (WASP 7.2) developed by the USEPA was employed to simulate the transportation and transformation of nitrobenzene, which was spilled due to an industrial accident, in the Songhua River, northeast of China. The model was first calibrated for the concentration of nitrobenzene in the water column with field data, and then applied to systematically expound the transportation and transformation of nitrobenzene in both water and sediment, and predict its distribution and fate in the multimedia of the River. The concentration profiles of the nitrobenzene in water column simulated the field data satisfactorily. Calculated results indicate that the spilled nitrobenzene was mostly either volatilized or biodegraded. Photolysis and sorption of nitrobenzene by suspended particles as well as benthic sediment were insignificant. Overall, results of this study suggested that the residual nitrobenzene would not seriously contaminate the River. Evaluation on the impacts of the spill was used to support the decision on risk assessment and watershed environmental management for the local government.
Modeling the nitrobenzene spill in the Songhua River
N.Q. Ren, A.J. Wang, Z. Li, L.L. Yin, D.J. Lee, F. Wang, L. Xin, L.J. Zhao, Z.Y. He, Y.J. Feng, H.J. Han, You Hong; Modeling the nitrobenzene spill in the Songhua River. Water Science and Technology: Water Supply 1 July 2007; 7 (2): 115–123. doi: https://doi.org/10.2166/ws.2007.046
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The primary reason is that the wetlands prevent a surfeit of nutrients from reaching our oceans and lakes. A study from Halmstad University shows, in addition, that wetlands have contributed to saving several frog and bird species from the “Red List”–a list that shows which species are at risk of dying out in Sweden.
In the latest update, five of the nine red-listed bird species that breed in wetlands–including the little grebe and the little ringed plover–could be taken off the list. Yet another bird species was moved to a lower threat category. As regards batrachians, four species–among them the European tree frog–have been taken off the list, and two species have been moved to a lower threat category.Great effect on biological diversity
During the 19th and 20th centuries, the amount of wetlands in Sweden decreased drastically: almost all original wetlands in agricultural areas have disappeared through drainage and land reclamation. This has affected many of the plants and animals that depend on these types of environments.An inexpensive way to reduce eutrophication
The study shows that creation of wetlands is a cost-effective to catch the nutrients.
“It’s a very effective way of purifying the water. It’s less expensive than constructing treatment plants, and in addition it contributes to biological diversity,” Prof Weisner says.
The research study, which is a compilation of previous studies in the field, was written by Stefan Weisner of Halmstad University and John Strand of the Agricultural Society of Halland, and has been published in Ecological Engineering.
For more information, contact Stefan Weisner, Professor of Biology specialising in environmental science at Halmstad University, tel. 035-16 73 48, e-mail: firstname.lastname@example.org.
Pressofficer Lena Lundén, +46-73 241 74 43, email@example.com"Effects of wetland construction on nitrogen transport and species richness in the agricultural landscape – experiences from Sweden"
link to Reporthttp://www.hh.se/4.70cf2e49129168da015800010489.html
Lena Lundén | idw
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
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The Ministers of the environment from Nigeria and Cameroon have established an agreement to protect the Cross River gorilla, the worlds rarest subspecies of gorilla that totals a mere 280 individuals throughout its entire range, according to the Wildlife Conservation Society (WCS). The Cross River gorilla is only found in Cross River State, Nigeria and western Cameroon and is highly threatened from poaching and habitat fragmentation and loss.
The two countries - represented by Cameroons Minister of Environment and Forestry Chief Tanyi-Mbianyor Clarkson and Nigerias Federal Minister of Environment Col. Bala Mande (Retired)--signed the agreement that will pave the way for a transboundary protected area, in effect combining the Takamanda-Okwangwo complex.
"This is a major conservation victory for Africas rarest great ape, as well as an example of the spirit of transboundary collaboration that has since emerged from Durban," said David Hoyle, WCS conservationist for Cameroon and a delegate at the World Parks Congress. "This is an avenue to diffuse tensions and bring the two countries closer together. This is a major political success."
Stephen Sautner | EurekAlert!
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences | <urn:uuid:8926bc67-3259-49b6-a0c3-ccc1f25e6395> | 3.078125 | 894 | Content Listing | Science & Tech. | 37.0687 | 95,571,811 |
In proteins, some processes require conformational changes involving structural domain diffusion. Among these processes are protein folding, unfolding and enzyme catalysis. During catalysis some enzymes undergo large conformational changes as they progress through the catalytic cycle. According to Kramers theory, solvent viscosity results in friction against proteins in solution, and this should result in decreased motion, inhibiting catalysis in motile enzymes. Solution viscosity was increased by adding increasing concentrations of glycerol, sucrose and trehalose, resulting in a decrease in the reaction rate of the H+-ATPase from the plasma membrane of Kluyveromyces lactis. A direct correlation was found between viscosity (?) and the inhibition of the maximum rate of catalysis (Vmax). The protocol used to measure viscosity by means of a falling ball type viscometer is described, together with the determination of enzyme kinetics and the application of Kramers' equation to evaluate the effect of viscosity on the rate of ATP hydrolysis by the H+-ATPase.
Última actualización: 20/07/2018 | <urn:uuid:0c93dbd3-59cf-445d-8757-badb60d4fe9c> | 2.578125 | 236 | Knowledge Article | Science & Tech. | 8.34625 | 95,571,816 |
Tutorial XML and DOM in PDF
DOM, for Document Object Model, aims to provide a template for a semi-structured document, in other words, an XML document. In particular, it is necessary to define methods of access and modification operating on such a document.
DOM is defined by W3C recommendations, three levels have now been defined. Some parts of these recommendations are dedicated to the processing of XHTML documents; We focus here on the DOM kernel providing valid methods for any XML document.
Download free course Learning basic XML DOM, PDF ebook under 28 pages for beginners.
Table of contents
- Historical Perspective
- Simple Format
- Rules for well-formed XML
- More Rules
- Document Object Model(DOM)
- Tree Structure
- DOM Rules
- Using JDom
- Iterate over children
- Input and output
- Showing Structure Recursively
- The Visitor Pattern
- A DOM Visitor
- Building an Attribute Inventory
- The Inventory Visitor
- Input and Output
- Trimming the Tree
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Take advantage of this course called Tutorial XML and DOM in PDF to improve your Web development skills and better understand DOM.
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All you need to do is download the training document, open it and start learning DOM for free.
HTML5 training guide
This training guide is designated to IT professionals who want to develop with HTML documents such as websites or webapplications. It is assumed that you are familiar with web development,free courses in PDF for download under 681 pages.
HTML5 and CSS3
This tutorial contain a brief overview about HTML5 and CSS3 , a free training document in PDF under 45 pages by Jason Clark.
Document Object Model Tutorial
Download free eBook about DOM, (Document Object Model), learn how to navigate an XML structure.
Python and the XML
Parser of HTML and XML with python and library Python Programming Course Tutorial Computing Learning. | <urn:uuid:e03d1794-2d11-409c-9d83-45629cfbbdce> | 3 | 437 | Product Page | Software Dev. | 42.035397 | 95,571,821 |
A right triangle is a triangle that has one angle equal to 90 degrees. This is often referred to as a right angle. The standard formula for computing the length of the long side of a right triangle has been in use since the days of the ancient Greeks. This formula is based on the simple mathematical concept known as the Pythagorean Theorem. It's named after Pythagoras, the Greek mathematician who first discovered it.
One side of a right triangle is always longer than the other two sides. This long side is known as the hypotenuse and will always be opposite the right angle of the triangle. The other two sides of the triangle are referred to as the legs.
Calculate the square of each leg (that is, multiply the length of each leg by itself).
Add these two values together.
Take the square root of the result of the addition. This is the length of the hypotenuse.
If the legs of the triangle are labeled a and b, and the hypotenuse is labeled c, then the Pythagorean Theorem can be described by this equation, where * represents multiplication: (a * a) + (b * b) = (c * c). In text, this equation can be stated as this formula: “the sum of the squares of the legs of a right triangle are equal to the square of the hypotenuse.”
As an example, consider a right triangle with legs of length 3 and 4. Then (3 * 3) + (4 * 4) = 9 + 16 = 25. The square root of 25 is 5 (that is, 5 * 5 = 25). Therefore, the length of the hypotenuse is 5.
Calculating the square root of the sum may not be obvious. In this case, a calculator should be used to find the value of the square root. Alternatively, the answer can be expressed using the mathematical symbol for square root (i.e., ?25). | <urn:uuid:b7fed4ab-a6e0-473e-a9cf-9208022480ba> | 4.21875 | 406 | Tutorial | Science & Tech. | 69.826519 | 95,571,836 |
the graphene flagship, a coordinated research project established by the european union and consisting of more than 150 academic institutions in 23 countries, announced that it is preparing for a pair of experiments to test graphene in zero-gravity applications this fall.
the graphene flagship will be working with esa to test graphene's impact on loop
heat pipes in space. (graphene flagship)
collaborating with the european space agency (esa), the graphene flagship will launch its experiments between november 6-17 and test graphene’s potential in space applications for light propulsion and for thermal management.
the first experiment will test graphene in solar sails, a project spearheaded by students at tu deelft in the netherlands. as a report from the graphene flagship explained, “by shining laser light on suspended graphene-membranes from flagship partner graphenea, the experiment will test how much thrust can be generated, which could lead to a new way of propelling satellites in space using light from lasers or the sun.”
at the same time, there will also be a test of graphene’s impact on the efficiency of heat transfer in loop heat pipes, which are common cooling solutions used in space applications.
“a significant part of the loop heat pipe is the wick,” the report continued, “typically made of porous metal. in this experiment, the wicks will be coated with different types of graphene-related marerials to improve the efficiency of the heat pipe. the coated wicks will be tested in a low-gravity parabolic flight operated by esa in partnership with novespace, france.”
the test will take place in a series of three-hour flights in a specially modified plane that will perform 30 parabolic assents with 25 seconds of weightlessness in each.
the second test will include coatings of graphene and graphene oxide to test both materials for their impact on the performance of the heat pipes.
andrea ferrari (university of cambridge), science and technology officer of the graphene flagship and chair of its management panel said, "space is the new frontier for the graphene flagship. these initial experiments will test the viability of graphene-enabled devices for space applications. the combined strengths of the graphene flagship, flagship partners and the european space agency as well global leader in aerospace applications leonardo, give a strong basis to reach a high technology readiness level."
learn more about the loop heat pipe team in the video below: | <urn:uuid:83eaecf6-272b-4b99-9b14-15675cb7e609> | 3.4375 | 516 | News Article | Science & Tech. | 28.990205 | 95,571,838 |
Nature builds flawless diamonds, sapphires and other gems. Now a Northwestern University research team is the first to build near-perfect single crystals out of nanoparticles and DNA, using the same structure favored by nature.
"Single crystals are the backbone of many things we rely on -- diamonds for beauty as well as industrial applications, sapphires for lasers and silicon for electronics," said nanoscientist Chad A. Mirkin. "The precise placement of atoms within a well-defined lattice defines these high-quality crystals.
"Now we can do the same with nanomaterials and DNA, the blueprint of life," Mirkin said. "Our method could lead to novel technologies and even enable new industries, much as the ability to grow silicon in perfect crystalline arrangements made possible the multibillion-dollar semiconductor industry."
His research group developed the "recipe" for using nanomaterials as atoms, DNA as bonds and a little heat to form tiny crystals. This single-crystal recipe builds on superlattice techniques Mirkin's lab has been developing for nearly two decades.
In this recent work, Mirkin, an experimentalist, teamed up with Monica Olvera de la Cruz, a theoretician, to evaluate the new technique and develop an understanding of it. Given a set of nanoparticles and a specific type of DNA, Olvera de la Cruz showed they can accurately predict the 3-D structure, or crystal shape, into which the disordered components will self-assemble.
Mirkin is the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences. Olvera de la Cruz is a Lawyer Taylor Professor and professor of materials science and engineering in the McCormick School of Engineering and Applied Science. The two are senior co-authors of the study.
The results will be published Nov. 27 in the journal Nature.
The general set of instructions gives researchers unprecedented control over the type and shape of crystals they can build. The Northwestern team worked with gold nanoparticles, but the recipe can be applied to a variety of materials, with potential applications in the fields of materials science, photonics, electronics and catalysis.
A single crystal has order: its crystal lattice is continuous and unbroken throughout. The absence of defects in the material can give these crystals unique mechanical, optical and electrical properties, making them very desirable.
In the Northwestern study, strands of complementary DNA act as bonds between disordered gold nanoparticles, transforming them into an orderly crystal. The researchers determined that the ratio of the DNA linker's length to the size of the nanoparticle is critical.
"If you get the right ratio it makes a perfect crystal -- isn't that fun?" said Olvera de la Cruz, who also is a professor of chemistry in the Weinberg College of Arts and Sciences. "That's the fascinating thing, that you have to have the right ratio. We are learning so many rules for calculating things that other people cannot compute in atoms, in atomic crystals."
The ratio affects the energy of the faces of the crystals, which determines the final crystal shape. Ratios that don't follow the recipe lead to large fluctuations in energy and result in a sphere, not a faceted crystal, she explained. With the correct ratio, the energies fluctuate less and result in a crystal every time.
"Imagine having a million balls of two colors, some red, some blue, in a container, and you try shaking them until you get alternating red and blue balls," Mirkin explained. "It will never happen.
"But if you attach DNA that is complementary to nanoparticles -- the red has one kind of DNA, say, the blue its complement -- and now you shake, or in our case, just stir in water, all the particles will find one another and link together," he said. "They beautifully assemble into a three-dimensional crystal that we predicted computationally and realized experimentally."
To achieve a self-assembling single crystal in the lab, the research team reports taking two sets of gold nanoparticles outfitted with complementary DNA linker strands. Working with approximately 1 million nanoparticles in water, they heated the solution to a temperature just above the DNA linkers' melting point and then slowly cooled the solution to room temperature, which took two or three days.
The very slow cooling process encouraged the single-stranded DNA to find its complement, resulting in a high-quality single crystal approximately three microns wide. "The process gives the system enough time and energy for all the particles to arrange themselves and find the spots they should be in," Mirkin said.
The researchers determined that the length of DNA connected to each gold nanoparticle can't be much longer than the size of the nanoparticle. In the study, the gold nanoparticles varied from five to 20 nanometers in diameter; for each, the DNA length that led to crystal formation was about 18 base pairs and six single-base "sticky ends."
"There's no reason we can't grow extraordinarily large single crystals in the future using modifications of our technique," said Mirkin, who also is a professor of medicine, chemical and biological engineering, biomedical engineering and materials science and engineering and director of Northwestern's International Institute for Nanotechnology.
The title of the paper is "DNA-mediated nanoparticle crystallization into Wulff polyhedra."
In addition to Mirkin and Olvera de la Cruz, authors of the paper are Evelyn Auyeung (first author), Ting I. N. G. Li, Andrew J. Senesi, Abrin L. Schmucker and Bridget C. Pals, all from Northwestern.
Megan Fellman | EurekAlert!
Colorectal cancer risk factors decrypted
13.07.2018 | Max-Planck-Institut für Stoffwechselforschung
Algae Have Land Genes
13.07.2018 | Julius-Maximilians-Universität Würzburg
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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13.07.2018 | Life Sciences | <urn:uuid:ba387084-39fc-4ef9-8f98-f6a5574d6603> | 3.265625 | 1,823 | Content Listing | Science & Tech. | 40.316215 | 95,571,867 |
Four of nine planetary boundaries have now been crossed as a result of human activity, says an international team of 18 researchers in the journal Science (16 January 2015).
The four are: climate change, loss of biosphere integrity, land-system change, altered biogeochemical cycles (phosphorus and nitrogen).
Two of these, climate change and biosphere integrity, are what the scientists call "core boundaries". Significantly altering either of these "core boundaries" would "drive the Earth System into a new state".
"Transgressing a boundary increases the risk that human activities could inadvertently drive the Earth System into a much less hospitable state, damaging efforts to reduce poverty and leading to a deterioration of human wellbeing in many parts of the world, including wealthy countries," says Lead author, Professor Will Steffen, researcher at the Centre and the Australian National University, Canberra.
"In this new analysis we have improved our quantification of where these risks lie."
The new paper is a development of the Planetary Boundaries concept, which was first published in 2009, identifying nine global priorities relating to human-induced changes to the environment.
"Planetary Boundaries do not dictate how human societies should develop but they can aid decision-makers by defining a safe operating space for humanity"
Katherine Richardson, co-author
The science shows that these nine processes and systems regulate the stability and resilience of the Earth System – the interactions of land, ocean, atmosphere and life that together provide conditions upon which our societies depend.
The research builds on a large number of scientific publications critically assessing and improving the planetary boundaries research since its original publication. It confirms the original set of boundaries and provides updated analysis and quantification for several of them, including phosphorus and nitrogen cycles, land-system change, freshwater use and biosphere integrity.
Though the framework keeps the same processes as in 2009, two of them have been given new names, to better reflect what they represent, and yet others have now also been assessed on a regional level.
"Loss of biodiversity" is now called "Change in biosphere integrity." Biological diversity is vitally important, but the framework now emphasises the impact of humans on ecosystem functioning. Chemical pollution has been given the new name "Introduction of novel entities," to reflect the fact that humans can influence the Earth system through new technologies in many ways.
"Pollution by toxic synthetic substances is an important component, but we also need to be aware of other potential systemic global risks, such as the release of radioactive materials or nanomaterials," says Sarah Cornell, coordinator of the Planetary Boundaries research at the Centre. "We believe that these new names better represent the scale and scope of the boundaries," she continues.
In addition to the globally aggregated Planetary Boundaries, regional-level boundaries have now been developed for biosphere integrity, biogeochemical flows, land-system change and freshwater use. At present only one regional boundary (South Asian Monsoon) can be established for atmospheric aerosol loading.
Nine planetary boundaries
1. Climate change
2. Change in biosphere integrity (biodiversity loss and species extinction)
3. Stratospheric ozone depletion
4. Ocean acidification
5. Biogeochemical flows (phosphorus and nitrogen cycles)
6. Land-system change (for example deforestation)
7. Freshwater use
8. Atmospheric aerosol loading (microscopic particles in the atmosphere that affect climate and living organisms)
9. Introduction of novel entities (e.g. organic pollutants, radioactive materials, nanomaterials, and micro-plastics).
The silver lining
It may seem that the paper puts forward a gloomy message. However, the authors also emphasise the other side of it. This knowledge provides us with a great opportunity to turn things around.
"Planetary Boundaries do not dictate how human societies should develop but they can aid decision-makers by defining a safe operating space for humanity," says co-author Katherine Richardson from the Center for Macroecology, Evolution and Climate, University of Copenhagen.
Johan Rockström, co-author and Centre director, will present the new findings at the World Economic Forum in Davos 21-24 January.
"In the last four years we have worked closely with policymakers, industry and organisations to explore how the planetary boundaries approach can be used as a framework for sectors of societies to reduce risk while developing sustainably," Rockström says.
"It is obvious that different societies over time have contributed very differently to the current state of the earth. The world has a tremendous opportunity this year to address global risks, and do it more equitably. In September, nations will agree the UN's Sustainable Development Goals. With the right ambition, this could create the conditions for long-term human prosperity within planetary boundaries," he continues.
Steffen et al. 2015. Planetary Boundaries: Guiding human development on a changing planet. Science Vol. 347 no. 6223
Planetary Boundaries Q & A (pdf, 129.5 kB)
Planetary Boundaries for Business (pdf, 937.4 kB)
Download high-res illustration (credit: F. Pharand-Deschênes /Globaïa)
Research news | 2018-07-10
The World in 2050 initiative launches new report outlining synergies and benefits that render the goals achievable
Educational news | 2018-07-02
LEAP our leadership programme designed for changemakers that want to lead social-ecological transformations to sustainability. Application deadline is 5 August 2018.
Research news | 2018-06-27
Overfishing, fractured international relationships and political conflicts loom as fish migrate more unpredictably because of climate change. Here is how to deal with it
Research news | 2018-06-26
Profit-maximizing approaches are most likely to produce outcomes that harm people or the environment. But it depends on the circumstances whether a sustainable or a safe approach is most suitable, new study argues
General news | 2018-06-20
Will lead a redesign of the organisational structure at the centre
Research news | 2018-06-20
New book chapter looks into the economic, cultural and ecological reasons why some people leave the fisheries and aquaculture sector, and what could be done to reverse the trend | <urn:uuid:ae40f603-3d4c-4fb2-ad85-88b212ff04b9> | 3.515625 | 1,302 | News (Org.) | Science & Tech. | 25.712308 | 95,571,874 |
Hunt, John M (1975): C4-C7 alkenones in deep sea sediments. PANGAEA, https://doi.org/10.1594/PANGAEA.770334, Supplement to: Hunt, JM (1975): Origin of gasoline range alkanes in the deep sea. Nature, 254(5499), 411-413, https://doi.org/10.1038/254411a0
Always quote above citation when using data! You can download the citation in several formats below.
It is believed that C4 to C7 hydrocarbons in petroleum are formed by the cracking of organic matter at depths generally exceeding 1,000 m at temperatures in excess of 50 °C (Cordel, 1972; Dow, 1974; Tissot et al., 1974)). Also, none of the alkanes in the butane-heptane range are formed biologically as far as is known at present. Consequently, it is thought that they do not occur in shallow, Recent sediments. In 1962, I analysed 22 samples of Recent sediments from 7 different environments and verified that these hydrocarbons were not present at the p.p.m. level (Dunton and Hunt, 1962) although traces of a few hydrocarbons such as butane, isobutane, isopentane and n-heptane have been found (Sokolov, 1957; Veber and Turkeltaub, 1958; Erdman et al., 1958; Emery and Hoggan, 1958). No identification of individual hexanes or heptanes has been reported except when there has been clear evidence of seepage from deeper source sediments (McIver, 1973).
Median Latitude: -5.328226 * Median Longitude: 143.807891 * South-bound Latitude: -48.957300 * West-bound Longitude: 39.369200 * North-bound Latitude: 39.494700 * East-bound Longitude: -92.043300
Date/Time Start: 1968-08-20T00:00:00 * Date/Time End: 1973-07-26T00:00:00
1-3 * Latitude: 23.030000 * Longitude: -92.043300 * Date/Time: 1968-08-20T00:00:00 * Elevation: -3747.0 m * Penetration: 627.9 m * Recovery: 46.6 m * Location: Gulf of Mexico/PLAIN * Campaign: Leg1 * Basis: Glomar Challenger * Device: Drilling/drill rig (DRILL) * Comment: 11 cores; 99.2 m cored; 0 m drilled; 47 % recovery
22-217 * Latitude: 8.926200 * Longitude: 90.538800 * Date/Time: 1972-02-24T00:00:00 * Elevation: -3010.0 m * Penetration: 614.5 m * Recovery: 181.6 m * Location: Indian Ocean//RIDGE * Campaign: Leg22 * Basis: Glomar Challenger * Device: Drilling/drill rig (DRILL) * Comment: 35 cores; 326.5 m cored; 9.5 m drilled; 55.6 % recovery
22-218 * Latitude: 8.007000 * Longitude: 86.282800 * Date/Time: 1972-03-01T00:00:00 * Elevation: -3749.0 m * Penetration: 773 m * Recovery: 59 m * Location: Indian Ocean//FAN * Campaign: Leg22 * Basis: Glomar Challenger * Device: Drilling/drill rig (DRILL) * Comment: 27 cores; 251 m cored; 0 m drilled; 23.5 % recovery | <urn:uuid:a36221c5-c68d-4ddf-91b3-12ca7c43b901> | 2.578125 | 816 | Academic Writing | Science & Tech. | 82.696439 | 95,571,878 |
A surprisingly large number of massive stars have been spotted in regions across the universe, shedding new light on how galaxies near and far evolve, a new study shows.
In the study, astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile investigated intense bouts of star formation in four distant, gas-rich starburst galaxies, where new stars are formed 100 or more times faster than they are in our own galaxy, the Milky Way.
Massive stars in these galaxies produce outflows of gas and create supernova explosions, which release large amounts of energy and stellar material into space. This type of activity can have a significant impact on the area surrounding these stars, according to a statement from the European Southern Observatory (ESO). [Supernova Photos: Great Images of Star Explosions]
Using a new technique similar to radiocarbon dating, the researchers looked for signatures of different types of carbon monoxide to determine the mass distribution of stars in the starburst galaxies. While oxygen isotopes are associated with larger, more massive stars, carbon isotopes are associated with smaller, intermediate-mass stars, Zhi-Yu Zhang, lead researcher and astronomer from the University of Edinburgh, said in the statement. Because carbon and oxygen combine to form carbon monoxide, this means different variations of carbon monoxide form more frequently in larger stars than in smaller ones.
Compared to low-mass stars such as our sun, which can shine for billions of years, massive stars have a much shorter life span. Understanding the distribution of different types of stars provides insight on the formation and evolution of galaxies throughout the history of the universe, according to the statement.
The new study revealed a higher proportion of massive stars within these starburst galaxies than previously expected. Researchers added that similar results were found closer to home in a region of a satellite galaxy of the Milky Way called the Large Magellanic Cloud.
Using ESO's Very Large Telescope, a team of researchers from the University of Oxford detected exceptionally massive stars in 30 Doradus, which is the brightest star-forming region in our galactic neighborhood.
"Our findings lead us to question our understanding of cosmic history," Rob Ivison, co-author of the study and director for science at ESO, said in the statement. "Astronomers building models of the universe must now go back to the drawing board, with yet more sophistication required."
The new work was detailed June 4 in the journal Nature.
Original article on Space.com. | <urn:uuid:03f1d706-ed58-430d-841b-6241197b2f09> | 3.734375 | 511 | News Article | Science & Tech. | 23.013759 | 95,571,906 |
In this tutorial, we are going to learn about the How to write the Selenium Testcases in Python. We are going to cover the how to do Navigation, Locators, Drag and Drop and other Concepts.
We have one demo where we are written the test cases in Python and understand it.
We are going to automate http://demoaut.katalon.com to make an appointment in the system using Selenium Python.
This is a Part 3 of the series Getting Started with Selenium Testcases in Python
Slides – https://docs.google.com/presentation/d/1IIxCaLfqdngWoQ1mi2bb7Sgqlg7LYLLJ0MaBWbhAcj0/edit?usp=sharing
Thanks for reading! 🙂 If you enjoyed it, hit that share button below. Would mean a lot to me and it helps other people see the story.
681 total views, 3 views today | <urn:uuid:5e84bfea-4b8a-4aca-9c94-45570b8cff16> | 2.671875 | 202 | Truncated | Software Dev. | 65.803646 | 95,571,910 |
Washington: A collection of fossil animals discovered off the coast of Florida suggests that present day deep-sea fauna like sea urchins, starfish and sea cucumbers may have evolved earlier than previously believed and survived periods of mass extinctions similar to those that wiped out the dinosaurs.
Ben Thuy and colleagues from the University of Gottingen, Germany published the findings in the open access journal PLOS ONE.
Previously, researchers believed that these present-day animals evolved in the relatively recent past, following at least two periods of mass extinction caused by changes in their oceanic environment.
The new fossil collection described in this study predates the oldest known records of the present-day fauna.
"We were amazed to see that a 114 million year old deep-sea assemblage was so strikingly similar to the modern equivalents", said Thuy, lead author of the study.
According to the authors, this evidence shows that the ancestors of modern deep-sea animals have lived in these deep waters for much longer than previously thought.
That this collection of fossils appears to have survived several drastic changes in oceanic climates also suggests that deep-sea biodiversity may be more resilient than shallow-water life forms, and more resistant to extinction events than previously thought. | <urn:uuid:0b09ff0e-3a76-41eb-a20e-2830376a9df2> | 3.859375 | 256 | News Article | Science & Tech. | 24.735742 | 95,571,923 |
Estimation of the Most Probable Muon Energy at Sea Level Using Two-Paddle Cosmic Ray Detectors
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We present a measurement of the most probable cosmic muon energy at near sea level using a two-paddle cosmic ray detector. Muon rates at two different elevations (27 and 326 m) were measured. Data were collected for 2–3 h for each data set at 1 min intervals in the afternoon of successive days. Muon counts were extracted from a Gaussian fit to the distributions of both sets. Despite the fact that only a limited amount of data were collected and measurements were performed at relatively close altitudes, we observed good agreement between the 2.28 ± 0.21 GeV energy measured in this work and the value of 2 GeV that is reported in the literature.
KeywordsCosmic ray Muon Muon energy Cosmic ray detector
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- 2.Greider P.K.F.: Researcher’s reference manual and data book. Cosmic Rays at Earth. Elsevier, Amsterdam (2001)Google Scholar
- 6.Collier, M.; Wolfley, L.: Assembly Manual for the Berkeley Lab Cosmic Ray Detector. LBNL-51419 (2006)Google Scholar
- 7.Particle Data Group: Cosmic rays. Rev. Particle Phys. (2010). http://pdg.lbl.gov/2010/reviews/rpp2010-rev-cosmic-rays.pdf
- 8.United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR): Sources and Effects of Ionizing Radiation, p. 36. United Nations, New York (1993)Google Scholar
- 9.National Council on Radiation Protection and Measurements: Exposure of the Population in the United States and Canada from Natural Background Radiation. NCRP Report No. 94 (1987)Google Scholar | <urn:uuid:1630d76a-bb81-463c-9338-e6cd120b65fd> | 2.84375 | 393 | Academic Writing | Science & Tech. | 64.27666 | 95,571,947 |
Species Detail - Barred Red (Hylaea fasciaria) - Species information displayed is based on all datasets.
Terrestrial Map - 10kmDistribution of the number of records recorded within each 10km grid square (ITM).
Marine Map - 50kmDistribution of the number of records recorded within each 50km grid square (WGS84).
insect - moth
12 May (recorded in 2008)
5 September (recorded in 2007)
National Biodiversity Data Centre, Ireland, Barred Red (Hylaea fasciaria), accessed 22 July 2018, <https://maps.biodiversityireland.ie/Species/78869> | <urn:uuid:94aa0412-1636-47b2-95e4-72b56f47c6ba> | 2.546875 | 145 | Structured Data | Science & Tech. | 43.842 | 95,571,948 |
1. The advantage of using CNG and LPG are as follows:
a. These are cleaner fuels.
b. These are low cost fuels.
c. These are available easily.
d. These can be supplied through pipes.
2. These days bitumen, a petroleum product is used for surfacing the roads in place of coal tar.
3. Million years ago, earth was having dense forests in low lying wet land areas. Due to earthquakes and volcanic eruptions, these forests got buried under the soil. As more soil deposited over them, they were compressed. The temperature also raised as they sank deeper and deeper. Due to high temperature and lack of oxygen dead plants inside the earth got slowly converted to coal. This process of coal formation is called carbonization.
4. Fill in the blanks.
(a) Fossil fuels are coal, petroleum, and natural gas.
(b) Process of separation of different constituents from petroleum is called refining.
(c) Least polluting fuel for vehicle is CNG.
5. Tick True/False.
6. Fossils fuels are present in nature in limited quantity and are being exhausted
abundantly by us. That is why fossil fuels are called exhaustible natural resources.
7. Coke is a tough porous black substance. It is almost pure form of carbon. It is used in the manufacture of steel and in the extraction of many metals.
8. Petroleum is formed from organism living in the sea. When these organism died, their bodies settled at the bottom of the sea and got covered with layers of the sand and clay. Over millions of years, they were transformed into petroleum oil and natural gas under the absence of air and presence of high temperature and high pressure. | <urn:uuid:907b5d90-dbb4-4133-bb80-49e4bf16a028> | 3.5 | 361 | Q&A Forum | Science & Tech. | 64.033266 | 95,571,952 |
|시간 제한||메모리 제한||제출||정답||맞은 사람||정답 비율|
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You recently acquired a new microwave, and noticed that it provides a large number of buttons to be able to quickly specify the time that the microwave should be running for. There are buttons both for adding time, and for subtracting time. You wonder how efficient you can be when entering cooking times: you want to minimize the number of required button presses.
The microwave can be running for at least 0 seconds, and at most 1 hour. If a button press would result in a cooking time of less than 0 seconds, the microwave will set the cooking time to 0 seconds. If a button press would result in a cooking time of more than 1 hour, the microwave will set the cooking time to 1 hour. Initially, the microwave will run for 0 seconds. There will always be a button adding at least 1 second to the cooking time.
Given the buttons that the microwave provides for entering cooking times, determine the least amount of button presses required to let the microwave run for a certain amount of time. If it is not possible to enter the desired cooking time precisely, determine the smallest achievable cooking time above the target, and the minimum number of button presses required for that cooking time, instead. The microwave does not allow to adjust the cooking time once it has started cooking.
On the first line one positive number: the number of test cases, at most 100. After that per test case:
Per test case:
2 3 50 -10 10 60 1 50 20
2 0 3 10 | <urn:uuid:e9284ac9-e741-4764-ac8f-48204c556d5c> | 2.9375 | 387 | Tutorial | Science & Tech. | 63.471498 | 95,571,967 |
Post Date : 28/03/2017
Scientists from the German Aerospace Centre (DLR) have switched on world’s largest artificial sun – a device developed to help shed light on new ways of making climate-friendly fuels. The artificial sun is giant honeycomb-like set-up of 149 spotlights, officially known as Synlight. It is located in Juelich. It uses xenon short-arc lamps normally found in cinemas to simulate natural sunlight.
Key Facts The aim of Synlight experiment is to develop an optimal setup for concentrating natural sunlight to power a reaction to produce hydrogen fuel. Its goal is to eventually use actual sunlight rather than the artificial light produced using electricity which is costly and requires as much electricity in four hours as a four-person household would use in a year. Using the array, scientists are seeking to produce the equivalent of 10,000 times the amount of solar radiation by focusing the entire array on a single 8×8 in spot (20*20cm). When light from all the lamps is aligned to concentrate on a single spot, it can generate temperatures of around 3,500 degree Celsius i.e. temperature two to three times of a blast furnace.
Hydrogen is the most common element in the universe, but on earth it is relatively rare. One way to manufacture hydrogen is to split water (H2O) into its two elemental components – Hydrogen and oxygen, using electricity in electrolysis process. Synlight experiment will bypass usage of electricity by tapping into the enormous amount of solar energy that reaches Earth from sun. Hydrogen obtained from it will be used to be used in fuel cells, a clean source of energy that does not produce carbon emissions.
Indian Railways has launched India’s first solar powered diesel multiple unit (DEMU) broad gauge t.....Read More
India and the UN Office for South-South Cooperation have launched a partnership fund to promote sust.....Read More | <urn:uuid:b2f09a22-60b5-4a8d-b0d1-f7ce31140ee2> | 3.71875 | 393 | Content Listing | Science & Tech. | 48.833207 | 95,571,977 |
Occurs when the user drags an object over a control.
property OnDragOver: TDragOverEvent;
Use an OnDragOver event to signal that the control can accept a dragged object so the user can drop or dock it.
Within the OnDragOver event handler, change the Accept parameter to false to reject the dragged object. Leave Accept as true to allow the user to drop or dock the dragged object on the control.
To change the shape of the cursor, indicating that the control can accept the dragged object, change the value of the DragCursor property for the control before the OnDragOver event occurs.
The Source is the object being dragged, the Sender is the potential drop target, and X and Y are screen coordinates in pixels. The State parameter specifies how the dragged object is moving over the control.
Note: Within the OnDragOver event handler, the Accept parameter defaults to true. However, if an OnDragOver event handler is not supplied, the control rejects the dragged object, as if the Accept parameter were changed to false. | <urn:uuid:2cc0fb18-dca3-4a3c-b32b-6d7342f6103b> | 2.796875 | 219 | Documentation | Software Dev. | 41.846525 | 95,571,978 |
We investigated habitat variables influencing the species richness and composition of anuran tadpole assemblages in ponds from riparian areas of the Middle Parana´ River. Tadpoles were collected at seven ponds that differed in hydroperiod and 10 habitat variables (water temperature, pH, conductivity, dissolved oxygen, turbidity, depth, size, time of isolation, macrophyte richness, and level of natural or anthropic disturbances) during a 5 year period. The presence/absence of potential tadpole predators was also recorded. Although we did not examine tadpole diets, we categorized anurans into ecomorphological guilds. We found that dissolved oxygen, maximum depth, pond size, macrophyte richness, and disturbances were significantly related to tadpole species richness. We also found that the richness of potential tadpole predator increased with longer pond hydroperiod. Thus, the number of tadpole species was higher in temporary and semi-permanent ponds without potential tadpole predators. The results of our study provide the first quantitative data on the tadpole assemblages in ponds associated with riparian areas of the Middle Parana´ River Floodplain based on multi-year intensive sampling, a finding of both ecological interest and practical significance for future conservation management of anurans of Parana´ River ecosystems.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:b2da2d31-9406-4ef4-8e56-f8ecd493ed04> | 2.8125 | 283 | Academic Writing | Science & Tech. | -1.706386 | 95,571,999 |
Calcite shells of marine organisms such as scallops or clams provide an important archive for the climate reconstructions in previous ages. Climate studies increasingly also use the shell material thrown away near settlements by humans in prehistoric times. Geologist Peter Müller from the Leibniz Centre for Tropical Marine Research (ZMT) has now discovered a considerable potential for error when shells that have been heated for human consumption are used in paleoclimatic studies. His study has just been published in the journal “Scientific Reports”.
What will our climate be like in future? Climate studies from times gone by can help scientists to answer this question. A tried and tested paleoclimatic method is the analysis of oxygen isotopes within the shells of calcifying marine organisms. They can provide insights into the temperature of the oceans or can be employed in reconstructing the rainfall in coastal regions at the time the calcified shells were developed.
For a long time the calcite shells of tiny foraminifers have been used for climate reconstruction. The shells of these aquatic single-cell organisms can be found in almost all sediments. Lately shells such as scallops or clams have also become the focus of climate researchers.
Similar to trees shells grow annual rings when their calcite exterior develops. Their chemical composition mirrors environmental conditions and gives insights into yearly or sometimes even seasonal climate changes. Large amounts of these shells can be found in particular at coastal archaeological sites, which can include deposits of thousands of years.
It is most likely that shells were heated for consumption as far back as the stone ages – even if their exterior does not necessarily show any signs of this cooking process. But are such shells still reliable climate archives?, asks ZMT- geologist Peter Müller.
Together with his colleagues he studied stone-age shell deposits on the coast of Mauretania and compared them to Venus clams from our time, which Müller cooked, grilled or burnt.
Measurements with a mass spectrometer showed that even a small amount of heat changed the composition of isotopes in the shells rendering them unusable for climate reconstructions. By measuring so-called “clumped isotopes”, a relatively new method, the team was able to differentiate precisely between heated and unheated shells.
“The method is so accurate that it even allows us to draw conclusions about the art of cooking in the Stone Age,” says Peter Müller. “We reckon that in order to open them, shells were put on hot stones that had been heated up in the fire.” Previous studies for climate reconstruction that used such prehistoric materials often did not account for that and might have come to the wrong conclusions, says Müller.
In their studies the origin of the Sahara desert was of particular interest for the team. Archaeological deposits could give an insight into the time sequence. Current theories are talking of both abrupt and slow change from lush savannah landscape to desert. Peter Müller’s dataset generated from untreated shells support the theory of a slow climate change in that respect.
Dr. Peter Müller
Mobile: 0032 49 30 299 55
Dr. Susanne Eickhoff
Leibniz Centre for Tropical Marine Research (ZMT)
Tel: 0421 / 23800-37
About the Leibniz Centre for Tropical Marine Research
In research and education the Leibniz Centre for Tropical Marine Research (ZMT) in Bremen is dedicated to the better understanding of tropical coastal ecosystems. As an interdisciplinary Leibniz institute the ZMT conducts research on the structure and functioning of tropical coastal ecosystems and their reaction to natural changes and human interactions. It aims to provide a scientific basis for the protection and sustainable use of these ecosystems. The ZMT works in close cooperation with partners in the tropics, where it supports capacity building and the development of infrastructures in the area of sustainable coastal zone management. The ZMT is a member of the Leibniz Association.
Dr. Susanne Eickhoff | idw - Informationsdienst Wissenschaft
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Life Sciences
18.07.2018 | Information Technology | <urn:uuid:b9dc592b-8a7f-40cc-b97b-3151e209c88a> | 3.6875 | 1,470 | Content Listing | Science & Tech. | 38.415903 | 95,572,006 |
Paintings on rocks in a gorge in the Swiss Alps help monitor erosion rates. Credit: Alexander R. Beer/ETH Zurich In a new feasibility study, a Swiss-German team of scientists with the participation of Jens Turowski, Helmholtz Centre Potsdam—GFZ German Research Centre for Geosciences, shows how erosive processes can be visualized by simple painting on rocks in a mountain gorge in the Swiss Alps. The determination of the spatial distribution of erosive processes is difficult. Especially in rough terrain the installation of measuring devices for a continuous measurement is complicated. This is why to date there are only few data available, especially on millimeter scale. In a new feasibility study, a Swiss-German team of scientists with the participation of Jens Turowski, Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences, shows how erosive processes can be visualized by simple painting.
In a gorge in the Swiss Alps close to Zermatt, the scientists applied horizontal and vertical patterns of paint on an area of thirty times five meters of rock and monitored them for three years via photographs taken from defined positions. Based on these photographs they were able to show the erosive processes in time that become visible by the removal of the paint. They call the new method ”erosion painting”. Erosion painting allows for an analysis of the spatial distribution and intensity of erosive processes in a riverbed. Knowledge on this helps to better understand the physics behind erosion. The study aims at implementing the new method within process research.
Until now, sophisticated techniques like photogrammetry, fixed monitoring stations, laser scanning, or erosion sensors had to be applied to measure and map topographic changes on rock surfaces. But ”why so complicated?” the scientists asked themselves. Erosion painting needs no expensive installation, can be applied fast and on high-resolution even in rough terrain, and only requires visual inspection via photography. Jens Turowski: ”Using paint is a cheap and easy method to analyze the spatial distribution of erosive processes. With this study we would like to show that this method can be applied for science”. By repeated laser scans the scientists did validate their method. This also revealed that laser scanning cannot assess erosion rates on smallest millimeter scale that is, however, made visible by erosion painting.
The scientists only used environmental friendly, water-insoluble latex paint. To minimize the effect on nature the scientists advise to only use the paint sparsely and to avoid sensitive areas. Painting the rocks was a difficult task but the paint helps to determine erosion rates. Credit: Jens Turowski/GFZ Explore further:New mechanism of erosion revealed: Gorges are eradicated by downstream sweep erosion
More information: Alexander R. Beer et al, Graffiti for science – erosion painting reveals spatially variable erosivity of sediment-laden flows, Earth Surface Dynamics (2016). DOI: 10.5194/esurf-4-885-2016
Provided by:Helmholtz Association of German Research Centres | <urn:uuid:4da687f9-7aa3-49ac-ac23-b7c69244553b> | 3.765625 | 644 | Truncated | Science & Tech. | 31.275121 | 95,572,027 |
Authors: Michail Zak
Comments: 28 Pages.
Quantum computing by simulations is based upon similarity between mathematical formalism of quantum mechanics and phenomena to be computed. It exploits a dynamical convergence of several competing phenomena to an attractor which can represent an extrenum of a function, an image, a solution to a system of ODE, or a stochastic process. In this chapter, a quantum version of recurrent nets (QRN) as an analog computing device is discussed. This concept is introduced by incorporating classical feedback loops into conventional quantum networks. It is shown that the dynamical evolution of such networks, which interleave quantum evolution with measurement and reset operations, exhibit novel dynamical properties. Moreover, decoherence in quantum recurrent networks is less problematic than in conventional quantum network architectures due to the modest phase coherence times needed for network operation. It is proven that a hypothetical quantum computer can implement an exponentially larger number of the degrees of freedom within the same
Category: Artificial Intelligence | <urn:uuid:18f10901-2b2b-4e36-a354-b838e0384863> | 2.6875 | 202 | Truncated | Science & Tech. | 4.222778 | 95,572,029 |
|Awuminium suwfate has de chemicaw formuwa Aw2(SO4)3. The form of awuminium suwfate hexadecahydrate is Aw2(SO4)3•16H2O.|
|Structuraw formuwa for n-butane. This is not a chemicaw formuwa. Exampwes of chemicaw formuwas for n-butane are de empiricaw formuwa C2H5, de mowecuwar formuwa C4H10 and de condensed (or semi-structuraw) formuwa CH3CH2CH2CH3.|
A chemicaw formuwa is a way of presenting information about de chemicaw proportions of atoms dat constitute a particuwar chemicaw compound or mowecuwe, using chemicaw ewement symbows, numbers, and sometimes awso oder symbows, such as parendeses, dashes, brackets, commas and pwus (+) and minus (−) signs. These are wimited to a singwe typographic wine of symbows, which may incwude subscripts and superscripts. A chemicaw formuwa is not a chemicaw name, and it contains no words. Awdough a chemicaw formuwa may impwy certain simpwe chemicaw structures, it is not de same as a fuww chemicaw structuraw formuwa. Chemicaw formuwas can fuwwy specify de structure of onwy de simpwest of mowecuwes and chemicaw substances, and are generawwy more wimited in power dan are chemicaw names and structuraw formuwas.
The simpwest types of chemicaw formuwas are cawwed empiricaw formuwas, which use wetters and numbers indicating de numericaw proportions of atoms of each type. Mowecuwar formuwas indicate de simpwe numbers of each type of atom in a mowecuwe, wif no information on structure. For exampwe, de empiricaw formuwa for gwucose is CH2O (twice as many hydrogen atoms as carbon and oxygen), whiwe its mowecuwar formuwa is C6H12O6 (12 hydrogen atoms, six carbon and oxygen atoms).
Sometimes a chemicaw formuwa is compwicated by being written as a condensed formuwa (or condensed mowecuwar formuwa, occasionawwy cawwed a "semi-structuraw formuwa"), which conveys additionaw information about de particuwar ways in which de atoms are chemicawwy bonded togeder, eider in covawent bonds, ionic bonds, or various combinations of dese types. This is possibwe if de rewevant bonding is easy to show in one dimension, uh-hah-hah-hah. An exampwe is de condensed mowecuwar/chemicaw formuwa for edanow, which is CH3-CH2-OH or CH3CH2OH. However, even a condensed chemicaw formuwa is necessariwy wimited in its abiwity to show compwex bonding rewationships between atoms, especiawwy atoms dat have bonds to four or more different substituents.
Since a chemicaw formuwa must be expressed as a singwe wine of chemicaw ewement symbows, it often cannot be as informative as a true structuraw formuwa, which is a graphicaw representation of de spatiaw rewationship between atoms in chemicaw compounds (see for exampwe de figure for butane structuraw and chemicaw formuwas, at right). For reasons of structuraw compwexity, dere is no condensed chemicaw formuwa (or semi-structuraw formuwa) dat specifies gwucose (and dere exist many different mowecuwes, for exampwe fructose and mannose, dat have de same mowecuwar formuwa C6H12O6 as gwucose). Linear eqwivawent chemicaw names exist dat can and do specify any compwex structuraw formuwa (see chemicaw nomencwature), but such names must use many terms (words), rader dan de simpwe ewement symbows, numbers, and simpwe typographicaw symbows dat define a chemicaw formuwa.
Chemicaw formuwas may be used in chemicaw eqwations to describe chemicaw reactions and oder chemicaw transformations, such as de dissowving of ionic compounds into sowution, uh-hah-hah-hah. Whiwe, as noted, chemicaw formuwas do not have de fuww power of structuraw formuwas to show chemicaw rewationships between atoms, dey are sufficient to keep track of numbers of atoms and numbers of ewectricaw charges in chemicaw reactions, dus bawancing chemicaw eqwations so dat dese eqwations can be used in chemicaw probwems invowving conservation of atoms, and conservation of ewectric charge.
- 1 Overview
- 2 Empiricaw formuwa
- 3 Mowecuwar formuwa
- 4 Condensed formuwa
- 5 Law of composition
- 6 Isotopes
- 7 Trapped atoms
- 8 Non-stoichiometric chemicaw formuwas
- 9 Generaw forms for organic compounds
- 10 Hiww system
- 11 See awso
- 12 References
- 13 Externaw winks
A chemicaw formuwa identifies each constituent ewement by its chemicaw symbow and indicates de proportionate number of atoms of each ewement. In empiricaw formuwas, dese proportions begin wif a key ewement and den assign numbers of atoms of de oder ewements in de compound, by ratios to de key ewement. For mowecuwar compounds, dese ratio numbers can aww be expressed as whowe numbers. For exampwe, de empiricaw formuwa of edanow may be written C2H6O because de mowecuwes of edanow aww contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of ionic compounds, however, cannot be written wif entirewy whowe-number empiricaw formuwas. An exampwe is boron carbide, whose formuwa of CBn is a variabwe non-whowe number ratio wif n ranging from over 4 to more dan 6.5.
When de chemicaw compound of de formuwa consists of simpwe mowecuwes, chemicaw formuwas often empwoy ways to suggest de structure of de mowecuwe. These types of formuwas are variouswy known as mowecuwar formuwas and condensed formuwas. A mowecuwar formuwa enumerates de number of atoms to refwect dose in de mowecuwe, so dat de mowecuwar formuwa for gwucose is C6H12O6 rader dan de gwucose empiricaw formuwa, which is CH2O. However, except for very simpwe substances, mowecuwar chemicaw formuwas wack needed structuraw information, and are ambiguous.
For simpwe mowecuwes, a condensed (or semi-structuraw) formuwa is a type of chemicaw formuwa dat may fuwwy impwy a correct structuraw formuwa. For exampwe, edanow may be represented by de condensed chemicaw formuwa CH3CH2OH, and dimedyw eder by de condensed formuwa CH3OCH3. These two mowecuwes have de same empiricaw and mowecuwar formuwas (C2H6O), but may be differentiated by de condensed formuwas shown, which are sufficient to represent de fuww structure of dese simpwe organic compounds.
Condensed chemicaw formuwas may awso be used to represent ionic compounds dat do not exist as discrete mowecuwes, but nonedewess do contain covawentwy bound cwusters widin dem. These powyatomic ions are groups of atoms dat are covawentwy bound togeder and have an overaww ionic charge, such as de suwfate [SO
ion, uh-hah-hah-hah. Each powyatomic ion in a compound is written individuawwy in order to iwwustrate de separate groupings. For exampwe, de compound dichworine hexoxide has an empiricaw formuwa CwO
3, and mowecuwar formuwa Cw
6, but in wiqwid or sowid forms, dis compound is more correctwy shown by an ionic condensed formuwa [CwO
, which iwwustrates dat dis compound consists of [CwO
ions and [CwO
ions. In such cases, de condensed formuwa onwy need be compwex enough to show at weast one of each ionic species.
Chemicaw formuwas as described here are distinct from de far more compwex chemicaw systematic names dat are used in various systems of chemicaw nomencwature. For exampwe, one systematic name for gwucose is (2R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanaw. This name, interpreted by de ruwes behind it, fuwwy specifies gwucose's structuraw formuwa, but de name is not a chemicaw formuwa as usuawwy understood, and uses terms and words not used in chemicaw formuwas. Such names, unwike basic formuwas, may be abwe to represent fuww structuraw formuwas widout graphs.
In chemistry, de empiricaw formuwa of a chemicaw is a simpwe expression of de rewative number of each type of atom or ratio of de ewements in de compound. Empiricaw formuwas are de standard for ionic compounds, such as CaCw
2, and for macromowecuwes, such as SiO
2. An empiricaw formuwa makes no reference to isomerism, structure, or absowute number of atoms. The term empiricaw refers to de process of ewementaw anawysis, a techniqwe of anawyticaw chemistry used to determine de rewative percent composition of a pure chemicaw substance by ewement.
For exampwe, hexane has a mowecuwar formuwa of C
14, or structurawwy CH
3, impwying dat it has a chain structure of 6 carbon atoms, and 14 hydrogen atoms. However, de empiricaw formuwa for hexane is C
7. Likewise de empiricaw formuwa for hydrogen peroxide, H
2, is simpwy HO expressing de 1:1 ratio of component ewements. Formawdehyde and acetic acid have de same empiricaw formuwa, CH
2O. This is de actuaw chemicaw formuwa for formawdehyde, but acetic acid has doubwe de number of atoms.
Mowecuwar formuwas indicate de simpwe numbers of each type of atom in a mowecuwe of a mowecuwar substance. They are de same as empiricaw formuwas for mowecuwes dat onwy have one atom of a particuwar type, but oderwise may have warger numbers. An exampwe of de difference is de empiricaw formuwa for gwucose, which is CH2O (ratio 1:2:1), whiwe its mowecuwar formuwa is C6H12O6 (number of atoms 6:12:6). For water, bof formuwas are H2O. A mowecuwar formuwa provides more information about a mowecuwe dan its empiricaw formuwa, but is more difficuwt to estabwish.
In organic chemistry impwying mowecuwar geometry and structuraw formuwas
The connectivity of a mowecuwe often has a strong infwuence on its physicaw and chemicaw properties and behavior. Two mowecuwes composed of de same numbers of de same types of atoms (i.e. a pair of isomers) might have compwetewy different chemicaw and/or physicaw properties if de atoms are connected differentwy or in different positions. In such cases, a structuraw formuwa is usefuw, as it iwwustrates which atoms are bonded to which oder ones. From de connectivity, it is often possibwe to deduce de approximate shape of de mowecuwe.
A condensed chemicaw formuwa may represent de types and spatiaw arrangement of bonds in a simpwe chemicaw substance, dough it does not necessariwy specify isomers or compwex structures. For exampwe, edane consists of two carbon atoms singwe-bonded to each oder, wif each carbon atom having dree hydrogen atoms bonded to it. Its chemicaw formuwa can be rendered as CH3CH3. In edywene dere is a doubwe bond between de carbon atoms (and dus each carbon onwy has two hydrogens), derefore de chemicaw formuwa may be written: CH2CH2, and de fact dat dere is a doubwe bond between de carbons is impwicit because carbon has a vawence of four. However, a more expwicit medod is to write H2C=CH2 or wess commonwy H2C::CH2. The two wines (or two pairs of dots) indicate dat a doubwe bond connects de atoms on eider side of dem.
A tripwe bond may be expressed wif dree wines (HC≡CH) or dree pairs of dots (HC:::CH), and if dere may be ambiguity, a singwe wine or pair of dots may be used to indicate a singwe bond.
Mowecuwes wif muwtipwe functionaw groups dat are de same may be expressed by encwosing de repeated group in round brackets. For exampwe, isobutane may be written (CH3)3CH. This condensed structuraw formuwa impwies a different connectivity from oder mowecuwes dat can be formed using de same atoms in de same proportions (isomers). The formuwa (CH3)3CH impwies a centraw carbon atom connected to one hydrogen atom and dree CH3 groups. The same number of atoms of each ewement (10 hydrogens and 4 carbons, or C4H10) may be used to make a straight chain mowecuwe, n-butane: CH3CH2CH2CH3.
Law of composition
In any given chemicaw compound, de ewements awways combine in de same proportion wif each oder. This is de waw of constant composition.
The waw of constant composition says dat, in any particuwar chemicaw compound, aww sampwes of dat compound wiww be made up of de same ewements in de same proportion or ratio. For exampwe, any water mowecuwe is awways made up of two hydrogen atoms and one oxygen atom in a 2:1 ratio. If we wook at de rewative masses of oxygen and hydrogen in a water mowecuwe, we see dat 94% of de mass of a water mowecuwe is accounted for by oxygen and de remaining 6% is de mass of hydrogen, uh-hah-hah-hah. This mass proportion wiww be de same for any water mowecuwe.
Chemicaw names in answer to wimitations of chemicaw formuwas
The awkene cawwed but-2-ene has two isomers, which de chemicaw formuwa CH3CH=CHCH3 does not identify. The rewative position of de two medyw groups must be indicated by additionaw notation denoting wheder de medyw groups are on de same side of de doubwe bond (cis or Z) or on de opposite sides from each oder (trans or E). Such extra symbows viowate de ruwes for chemicaw formuwas, and begin to enter de territory of more compwex naming systems.
As noted above, in order to represent de fuww structuraw formuwas of many compwex organic and inorganic compounds, chemicaw nomencwature may be needed which goes weww beyond de avaiwabwe resources used above in simpwe condensed formuwas. See IUPAC nomencwature of organic chemistry and IUPAC nomencwature of inorganic chemistry 2005 for exampwes. In addition, winear naming systems such as Internationaw Chemicaw Identifier (InChI) awwow a computer to construct a structuraw formuwa, and simpwified mowecuwar-input wine-entry system (SMILES) awwows a more human-readabwe ASCII input. However, aww dese nomencwature systems go beyond de standards of chemicaw formuwas, and technicawwy are chemicaw naming systems, not formuwa systems.
Powymers in condensed formuwas
For powymers in condensed chemicaw formuwas, parendeses are pwaced around de repeating unit. For exampwe, a hydrocarbon mowecuwe dat is described as CH3(CH2)50CH3, is a mowecuwe wif fifty repeating units. If de number of repeating units is unknown or variabwe, de wetter n may be used to indicate dis formuwa: CH3(CH2)nCH3.
Ions in condensed formuwas
For ions, de charge on a particuwar atom may be denoted wif a right-hand superscript. For exampwe, Na+, or Cu2+. The totaw charge on a charged mowecuwe or a powyatomic ion may awso be shown in dis way. For exampwe: H3O+ or SO42−. Note dat + and - are used in pwace of +1 and -1, respectivewy.
For more compwex ions, brackets [ ] are often used to encwose de ionic formuwa, as in [B12H12]2−, which is found in compounds such as Cs2[B12H12]. Parendeses ( ) can be nested inside brackets to indicate a repeating unit, as in [Co(NH3)6]3+Cw3−. Here, (NH3)6 indicates dat de ion contains six NH3 groups bonded to cobawt, and [ ] encwoses de entire formuwa of de ion wif charge +3.[furder expwanation needed]
This is strictwy optionaw; a chemicaw formuwa is vawid wif or widout ionization information, and Hexamminecobawt(III) chworide may be written as [Co(NH3)6]3+Cw3− or [Co(NH3)6]Cw3. Brackets, wike parendeses, behave in chemistry as dey do in madematics, grouping terms togeder - dey are not specificawwy empwoyed onwy for ionization states. In de watter case here, de parendeses indicate 6 groups aww of de same shape, bonded to anoder group of size 1 (de cobawt atom), and den de entire bundwe, as a group, is bonded to 3 Chworine atoms. In de former case, it is cwearer dat de bond connecting de chworines is ionic, rader dan covawent.
Awdough isotopes are more rewevant to nucwear chemistry or stabwe isotope chemistry dan to conventionaw chemistry, different isotopes may be indicated wif a prefixed superscript in a chemicaw formuwa. For exampwe, de phosphate ion containing radioactive phosphorus-32 is 32PO43−. Awso a study invowving stabwe isotope ratios might incwude de mowecuwe 18O16O.
A weft-hand subscript is sometimes used redundantwy to indicate de atomic number. For exampwe, 8O2 for dioxygen, and 168O2 for de most abundant isotopic species of dioxygen, uh-hah-hah-hah. This is convenient when writing eqwations for nucwear reactions, in order to show de bawance of charge more cwearwy.
The @ symbow (at sign) indicates an atom or mowecuwe trapped inside a cage but not chemicawwy bound to it. For exampwe, a buckminsterfuwwerene (C60) wif an atom (M) wouwd simpwy be represented as MC60 regardwess of wheder M was inside de fuwwerene widout chemicaw bonding or outside, bound to one of de carbon atoms. Using de @ symbow, dis wouwd be denoted M@C60 if M was inside de carbon network. A non-fuwwerene exampwe is [As@Ni12As20]3−, an ion in which one As atom is trapped in a cage formed by de oder 32 atoms.
This notation was proposed in 1991 wif de discovery of fuwwerene cages (endohedraw fuwwerenes), which can trap atoms such as La to form, for exampwe, La@C60 or La@C82. The choice of de symbow has been expwained by de audors as being concise, readiwy printed and transmitted ewectronicawwy (de at sign is incwuded in ASCII, which most modern character encoding schemes are based on), and de visuaw aspects suggesting de structure of an endohedraw fuwwerene.
Non-stoichiometric chemicaw formuwas
Chemicaw formuwas most often use integers for each ewement. However, dere is a cwass of compounds, cawwed non-stoichiometric compounds, dat cannot be represented by smaww integers. Such a formuwa might be written using decimaw fractions, as in Fe0.95O, or it might incwude a variabwe part represented by a wetter, as in Fe1–xO, where x is normawwy much wess dan 1.
Generaw forms for organic compounds
A chemicaw formuwa used for a series of compounds dat differ from each oder by a constant unit is cawwed a generaw formuwa. It generates a homowogous series of chemicaw formuwas. For exampwe, awcohows may be represented by de formuwa CnH(2n + 1)OH (n ≥ 1), giving de homowogs medanow, edanow, propanow for n=1–3.
The Hiww system (or Hiww notation) is a system of writing empiricaw chemicaw formuwas, mowecuwar chemicaw formuwas and components of a condensed formuwa such dat de number of carbon atoms in a mowecuwe is indicated first, de number of hydrogen atoms next, and den de number of aww oder chemicaw ewements subseqwentwy, in awphabeticaw order of de chemicaw symbows. When de formuwa contains no carbon, aww de ewements, incwuding hydrogen, are wisted awphabeticawwy.
By sorting formuwas according to de number of atoms of each ewement present in de formuwa according to dese ruwes, wif differences in earwier ewements or numbers being treated as more significant dan differences in any water ewement or number—wike sorting text strings into wexicographicaw order—it is possibwe to cowwate chemicaw formuwas into what is known as Hiww system order.
The Hiww system was first pubwished by Edwin A. Hiww of de United States Patent and Trademark Office in 1900. It is de most commonwy used system in chemicaw databases and printed indexes to sort wists of compounds.
A wist of formuwas in Hiww system order is arranged awphabeticawwy, as above, wif singwe-wetter ewements coming before two-wetter symbows when de symbows begin wif de same wetter (so "B" comes before "Be", which comes before "Br").
The fowwowing exampwe formuwae are written using de Hiww system, and wisted in Hiww order:
- Dictionary of chemicaw formuwas
- Ewement symbow
- Nucwear notation
- Periodic tabwe
- IUPAC nomencwature of inorganic chemistry
- Formuwa unit
|Wikidata has de property:
- "Law of Constant Composition". Everyding Maf and Science. SIYAVULA. Retrieved 31 March 2016. This materiaw is avaiwabwe under a Creative Commons Attribution-Share Awike 3.0 wicense.
- Chai, Yan; Guo, Ting; Jin, Changming; Haufwer, Robert E.; Chibante, L. P. Fewipe; Fure, Jan; Wang, Lihong; Awford, J. Michaew; Smawwey, Richard E. (1991). "Fuwwerenes wwf Metaws Inside". Journaw of Physicaw Chemistry. 95 (20): 7564–7568. doi:10.1021/j100173a002.
- Edwin A. Hiww (1900). "On a system of indexing chemicaw witerature; Adopted by de Cwassification Division of de U.S. Patent Office". J. Am. Chem. Soc. 22 (8): 478–494. doi:10.1021/ja02046a005.
- Wiggins, Gary. (1991). Chemicaw Information Sources. New York: McGraw Hiww. p. 120.
- Rawph S. Petrucci; Wiwwiam S. Harwood; F. Geoffrey Herring (2002). "3". Generaw Chemistry: Principwes and Modern Appwications (8f ed.). Prentice-Haww. ISBN 0-13-198825-5. OCLC 46872308.
- Hiww notation exampwe, from de University of Massachusetts Loweww wibraries, incwuding how to sort into Hiww system order
- Mowecuwar formuwa cawcuwation appwying Hiww notation. The wibrary cawcuwating Hiww notation is avaiwabwe on npm. | <urn:uuid:5d0f05fa-1574-48f8-80ec-2601cf26a60b> | 2.578125 | 6,042 | Knowledge Article | Science & Tech. | 33.895566 | 95,572,055 |
Mass spectrometry plays a unique and important role in lipid biochemistry, serving as a tool to elucidate lipid structure while offering a method of analysis that relies on ion chemistry, an intrinsic property of lipid substances, rather than physical properties.
In this comprehensive reference, Robert C. Murphy provides readers with an understanding of the general physical concepts of mass spectrometry and its use in the analysis of specific lipid substances. Opening the text with a description of the fundamentals of mass spectrometry, Dr. Murphy discusses currently used mass analyzers and ancillary techniques, including high-resolution mass spectrometry, selected ion recording, tandem mass spectrometry, and database generation, and details specific examples of their use. He then examines state-of-the-art desorption ionization techniques - including electron ionization, chemical ionization, fast atom bombardment, and electron capture ionization techniques - which can supply vital structural information when coupled with tandem mass spectrometry. Subsequent chapters focus on the ion chemistry of specific lipids, with coverage ranging from fatty acids and their derivatives to glycosphingolipids. Dr. Murphy presents over 80 complete mass spectra of these lipid substances and more than 120 detailed mechanistic schemes describing the fragmentation pathways observed in these mass spectra. The author also demonstrates the use of mass spectrometry for quantitative assays of the lipids discussed and the application of specific ion measurement as a strategy to enhance sensitivity and specificity.
Mass Spectrometry of Lipids is a fundamental resource on fatty acyl-type lipids for both experienced mass spectroscopists and graduate-level students.
|Introduction and Mass Spectrometers|
|Eicosanoid Mass Spectrometry|
|Triaclyglycerols, Diaclyglycerols, and Monoacylglycerols|
|Table of Contents provided by Publisher. All Rights Reserved.|
Series: Handbook of Lipid Research
Number Of Pages: 290
Published: 30th April 1993
Publisher: Springer Science+Business Media
Country of Publication: US
Dimensions (cm): 25.4 x 17.8 x 2.54
Weight (kg): 1.36 | <urn:uuid:fa2d0db5-04e7-4a80-ab71-c4a9ec6568aa> | 2.671875 | 447 | Truncated | Science & Tech. | 15.770882 | 95,572,059 |
Stellar rotation is a well-known quantity for tens of thousands of stars. In contrast, differential rotation (DR) is only known for a handful of stars because DR cannot be measured directly. We present rotation periods for more than 24,000 active stars in the Kepler field. Thereof, more than 18,000 stars show a second period, which we attribute to surface differential rotation. Our rotation periods are consistent with previous measurements and the theory of magnetic braking. Our results on DR paint a rather different picture: The temperature dependence of the absolute shear δΩ is split into two groups separated around 6000 K. For the cooler stars δΩ only slightly increases with temperature, whereas stars hotter than 6000 K show large scatter. This is the first time that DR has been measured for such a large number of stars.
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Choose a citation style from the tabs below | <urn:uuid:29744916-9b8a-462b-a970-e4447d78e63e> | 3.5 | 188 | Academic Writing | Science & Tech. | 50.380962 | 95,572,061 |
The microscopic flexibility of DNA is a key ingredient for understanding its interaction with proteins and drugs but is still poorly understood and technically challenging to measure. Several experimental methods probe very long DNA samples, but these miss local flexibility details. Others mechanically disturb or modify short molecules and therefore do not obtain flexibility properties of unperturbed and pristine DNA. Here, we show that it is possible to extract very detailed flexibility information about unmodified DNA from melting temperatures with statistical physics models. We were able to retrieve, from published melting temperatures, several established flexibility properties such as the presence of highly flexible TATA regions of genomic DNA and support recent findings that DNA is very flexible at short length scales. New information about the nanoscale Na+ concentration dependence of DNA flexibility was determined and we show the key role of ApT and TpA steps when it comes to ion-dependent flexibility and melting temperatures.
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Choose a citation style from the tabs below | <urn:uuid:591a2582-8849-4efc-a8fd-d63b360d3669> | 2.5625 | 196 | Academic Writing | Science & Tech. | 3.265395 | 95,572,081 |
Whale sharks, the largest fish in the world, actively travel through the water, overcoming thousands of kilometers. But scientists have noticed that in the world there are about 20 places where they prefer to gather in flocks sometimes exceeding 50 individuals. For a long time experts did not know why sharks prefer specific locations off the coast of Australia, Belize, Mildew and Mexico, reported My planet with the link to ScienceAlert.
Experts from the universities of Salford and York have compared the underlying indices are popular meeting places for whale sharks, reports ScienceAlert.
It turned out that they all have similar characteristics: this is the shallows, adjacent to sharp breaks (drops from 200 to 1000 m). For a space sharks have two main reasons: they are rich in food and plankton, in which the heat and you can warm up after diving to a depth where the water is very cold. | <urn:uuid:8f6c785c-5a6b-4e4b-88fe-b9d49ec6e93f> | 2.8125 | 181 | Truncated | Science & Tech. | 46.266992 | 95,572,093 |
All organic compounds contain carbon as their primary constituent. Carbon atoms form the backbone that bonds to other atoms including hydrogen, nitrogen, oxygen and sulfur. Carbon also bonds to the halogens: florine, chlorine, bromine and iodine. Carbon atoms are the basic building blocks of life, and energy-rich organic compounds are important in all life processes.
The most abundant organic compound in the terrestrial environment is cellulose. A type of carbohydrate, cellulose contains chains of glucose rings. Providing strength and rigidity, cellulose forms the cell walls of plants. Cellulose is the primary constituent of wood, making this organic compound the most abundant one on the surface of the Earth. Cellulose is difficult to digest but holds promise for advancing the development of biofuels.
The most abundant organic compound in the Earth’s atmosphere is methane, a greenhouse gas implicated in climate change. Sources of atmospheric methane include enteric fermentation (digestion in livestock), wetlands, rice paddies, burning of biomass (forest fires), termites, landfills, the ocean, freshwater ecosystems, gas hydrates, coal mining and gas drilling -- venting and transmission. In 1988, the total annual production of methane was estimated at about 540 teragrams (595 million tons).
Phytoplankton are the primary producers of organic compounds in the ocean. These tiny, single-celled organisms live near the surface of the water and undergo photosynthesis, transforming inorganic carbon into organic compounds. Taking up carbon dioxide, they release as much oxygen into the atmosphere as terrestrial plants. An important component of the Earth’s carbon cycle and climate system, when phytoplankton dies it sinks, carrying carbon to the bottom of the sea.
Soils are composed of organic compounds important for biological processes. Only making up a fraction of the outermost layer of the Earth's surface, or pedosphere, organic compounds form the basis for life in the terrestrial environment. Organic compounds hold soil particles together to reduce erosion and minimize compaction, improve the storage and transport of air, nutrients and water that supports plant growth and growth of decomposing organisms within the soil. Organic compounds also reduce the toxic effects of pollutants and retain atmospheric carbon. | <urn:uuid:d97b46ab-bfa4-4b54-950a-bd8e86afc126> | 4.21875 | 458 | Knowledge Article | Science & Tech. | 25.741015 | 95,572,126 |
Igor Stagljar, Professor in the Faculty of Medicine's Donnelly Centre for Cellular and Biomolecular Research, and his team developed the first roadmap for ATP-binding cassette (ABC) transporter proteins. These proteins are crucial components of every cell, and are also involved in tumor resistance.
Scientists have struggled with understanding how ABC transporter proteins work and communicate with other proteins. Stagljar and his team, including first author Dr. Jamie Snider, have solved the mystery by using Membrane Yeast Two-Hybrid ('MYTH') technology to see how these transporter proteins interact with other vital components in the cell.
"Cell systems are complex and we need to have a solid grasp of how the individual pieces fit together in order to understand why certain diseases occur and how to best treat them," says Stagljar, who is also cross-appointed to the Departments of Biochemistry and Molecular Genetics.
ABC transporter proteins act as cellular gatekeepers by retaining nutrients and expelling toxins from the cell. If these proteins are not working properly, it can cause a number of diseases including: cystic fibrosis, age-related macular degeneration, Tangier disease, and Dubin-Johnson syndrome. ABC proteins can also cause cancer cells to reject chemotherapy drugs which makes treatment less effective.
"Our discovery shows how ABC transporter proteins effect cancer and other diseases, and this knowledge can help us develop better, more targeted drugs. This is truly momentous," said Stagljar.
The study was published today in Nature Chemical Biology.
Suniya Kukaswadia | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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19.07.2018 | Life Sciences | <urn:uuid:8b112a4e-a702-4e92-bdc8-5fb8e72de5b5> | 3.0625 | 971 | Content Listing | Science & Tech. | 37.655028 | 95,572,129 |
A wet climatic period was responsible for the phenomenon. According to climate scenarios, the climate may become wetter in this area, potentially giving rise again to a period of oxygen-free bottom-water. These results are published in the September issue of Nature Geoscience.
Alternating organic-rich and organic-poor beds have been deposited on the floor of the Eastern Mediterranean. These deposits coincide with the alternation of wet and dry climatic periods. Researchers believe that the organic-rich beds, called sapropels, can originate in two ways: 1. More organisms live in the surface water because, for example, rivers introduce more nutrients. As a result, more organisms sink to the bottom when they die. 2. The organic material is better preserved. If dead organisms sink to an oxygen-free bottom, the organic material breaks down less well.Sapropel
This research shows that there is a high chance of finding organic-rich deposits in an environment devoid of oxygen. Climate change may contribute to the formation of organic-rich beds. Besides sequestering large quantities of CO2, these separated beds can also be converted into oil over the course of time.
This research forms part of the PASS project, a marine programme in the Eastern Mediterranean. NWO Earth and Life Sciences financed the necessary logistics, such as ship and equipment lease via the National Research Cruise Programme.
Kim van den Wijngaard | alfa
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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WHAT'S THE MEANING?
An integrated development environment, or IDE, is a software that compiles the necessary tools used by developers for writing and testing software. IDEs usually have a code editor, compiler, interpreter, and a debugger, which are all accessible through a single graphical user interface. The first IDE was a part of the Dartmouth Time Sharing System and was command-based, unlike the current versions of IDEs where developers see menu-type of capabilities and options. IDEs like IntelliJ IDEA and Visual Studio Code are not coding software but are tools to help developers manage their work.
DID YOU KNOW?
Did you know that Python, the general-purpose programming language, was named after a 1970s British surreal comedy group? Guido Van Rossum said in a tutorial that the language he invented was named after Monty Python, the British comedy group that first aired on BBC. He also said that references to Python's skits are encouraged when using the language like he did when he used the words "spam and eggs" in the program instead of the more accepted terms "foo and bar". Python is the fourth most highly rated programming language according to the TIOBE index as of June, since it has a 5.76% rating, just three percent below third-placer C++, but it is far away from C (14.94%) and Java (15.37%). | <urn:uuid:d06fa6a9-0f00-447c-9b67-b886401ea824> | 2.984375 | 344 | Product Page | Software Dev. | 48.231567 | 95,572,182 |