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MFM and Related Techniques
Magnetic force microscopy is commonly understood as a scanning force microscopy technique that is devoted to the measurement of tip-sample forces mediated by a magnetic field. In fact, every scanning force microscope can be used as a magnetic force microscope, if a tip with a magnetic moment is used. Then the SFM becomes sensitive to magnetic fields emanating from the surface of a sample. However, other types of tips that are sensitive to magnetic fields may also be used. Examples are microfabricated Hall probes, magnetoresistive sensors, and superconductive quantum interference devices (SQUIDS).
KeywordsDomain Wall Magnetic Force Microscopy Magnetic Image Stray Field Bloch Wall
Unable to display preview. Download preview PDF. | <urn:uuid:8cf085a7-95ad-4039-a06b-fb68e250acb1> | 2.921875 | 154 | Truncated | Science & Tech. | 18.017391 | 95,487,155 |
We never were.
Shows how useful commas can be.
Thank you for the plots. Visuals always appreciated in a physics discussion.
If the universe is expanding a constant rate, as can be seen from nearly the entire history of the expansion, then the expansion is not slowing down. If you viewed a galaxy moving away from you at say 6 Gy and then again at 10 Gy it would be receding from you at the same rate. A galaxy twice as far away would still be receding at twice that velocity. This would also be true of the event horizon. A better way to understand this is to consider the perimeter of the circle. The observable universe exists along that perimeter. The perimeter of the circle scales linearly with the radius. The co-moving coordinates describe the expansion in this manner.
No, that's not what is seen from the entire history of the expansion. The entire history of the expansion shows change in the rate of expansion--it was decelerating in the early universe, then a few billion years ago it started accelerating.
A wrong quote
>"Now we are not in the center of the universe ...."
- that was the quote from the original post not (not mine).
Actually, I'm in the center of universe; any other observer may make the same claim...
Ooops sorry, don't know how I did that.
but yes everyone is at the center of what is observable for them.
The whole Universe may or may not be infinite, and need not have a center anywhere,
just as there is no place on the surface of a sphere which could be called a center.
We dont even know the universe is sphere. I dont think theres any meaning calling "center of the universe", in this sense its just meaningless
Absolutely false. You are in the center of the Observable Universe, NOT "the universe"
EDIT: OOPS ... I see rootone beat me to it.
Actually, we know that is is NOT a sphere. If it were, it would have a center and it does not.
Well, it is not false; in fact, the existence of "the universe" if it is not an observable one (in broad information sense) is matter of fate and believe...
Only in the sense that we can't directly observe it. But if you want to reject the belief that there is universe beyond the part we can observe, you have to claim that the laws of physics suddenly change at the boundary of our observable universe, for no apparent reason. Because if they don't, then the universe beyond what we can observe must be there, since that's what the laws of physics that we see in our observable universe imply.
Well, if it is not provable then it is matter of assumption what is totally fine to make, pretty much the same as with different kind of multiverses if such assumptions help some brains to construct theories with better predictive power then it definitely has its merits...
Yes, but saying that the universe just stops at the boundary of our observable universe is also an assumption--and one which violates Occam's Razor. That's why the assumption that the universe continues past the boundary of our observable universe seems preferable--because it doesn't require claiming that something changes at that particular boundary for no apparent reason.
>"but saying that the universe just stops at the boundary of our observable universe"
Pls quote where I made such silly assertion ;o)
You made it implicitly here:
It's only a matter of "faith and belief" if you start with the assumption that the universe stops at the boundary of our observable universe, for no apparent reason. If instead you start with the assumption that the laws of physics don't stop at a particular point for no apparent reason, just because that point happens to be the boundary of our observable universe--i.e., if you start with Occam's Razor--then it doesn't take any "faith and belief" to see that there must be universe beyond the boundary of our observable universe.
I've made an explicit explanation of my point:
SB>“if it is not provable then it is matter of assumption what is totally fine to make, pretty much the same as with different kind of multiverses if such assumptions help some brains to construct theories with better predictive power then it definitely has its merits... ”
You are definitely free to make your “implicit” interpretations I just see no relation to my point to discuss.
What is "provable" depends on what assumptions you start with. You start with the assumption "anything we can't observe we have to take on faith"--but that requires you to also assume that the laws of physics suddenly change at the boundary of our observable universe, for no apparent reason. Only with that additional assumption--which violates Occam's Razor as well as common sense--can you say it isn't "provable" that there is more to the universe than the part we can directly observe.
Whereas I start from the assumption "the laws of physics stay the same everywhere", which allows me to prove immediately that they don't change at the boundary of our observable universe for no apparent reason, and therefore there is more to the universe than the part we can directly observe.
In other words, your apparent belief that only I have to make "assumptions" and you don't, in order to support our respective viewpoints, is not correct.
Perhaps the above will help to explain its relevance.
Thanks, That is what I thought.
Some of the other answers were confusing, at least to me.
Separate names with a comma. | <urn:uuid:548fc3d5-8e4a-40c0-8995-3b1fcbd9d785> | 3.078125 | 1,160 | Comment Section | Science & Tech. | 53.527232 | 95,487,159 |
Geneva: In 20 years' time, most of the Caribbean coral reefs may disappear, since what is left of them currently does not exceed one-sixth of the original coral cover, according to a report published by the United Nations Environment Program (UNEP) on Wednesday.
The report lists the population explosion along the coast lines, overfishing, the pollution of coastal areas, global warming and invasive species among the main reasons that have put Caribbean coral reefs in danger of extinction.
The report was prepared in cooperation between the UNEP, Global Coral Reef Monitoring Network (GCRMN) and the International Union for Conservation of Nature (IUCN).
It is the result of the work of 90 experts who studied corals, seaweeds, grazing sea urchins and fish.
The experts agreed that 50 percent of the Caribbean sea coral cover has disappeared since the 1960's.
"The rate at which the Caribbean corals have been declining is truly alarming," said Carl Gustaf Lundin, Director of IUCN's Global Marine and Polar Programme.
"But this study brings some very encouraging news: The fate of Caribbean corals is not beyond our control and there are some very concrete steps that we can take to help them recover," he added.
According to the report published in the UNEP website, "restoring parrotfish populations and improving other management strategies such as protection from overfishing and excessive coastal pollution could help the reefs recover and make them more resilient to future climate change impacts."
Parrotfish were brought to the brink of extinction due to overfishing throughout the 20th century, something which the experts find as a reason which led to coral decline in the region.
The disappearance of parrotfish broke the natural balance of coral reefs when algae, the species' food, were allowed to smother the reefs.
It is necessary to take action to address overfishing and pollution, with the aim of contributing to the restoration of these reefs and making them more able to adapt to climate change caused by the high temperature of the sea water, said the report.
Climate change is the most prominent threat to coral reefs, as it raises the level of acidic ocean waters that cause coral bleaching.
The report is based on an analysis of 35,000 surveys taken from 90 different locations in the Caribbean.
The study concluded that the corals which have suffered the most tragic declines are those in Jamaica, along the shores of the US state of Florida, as well as the US Virgin Islands.
The Caribbean region is home to nine percent of the world's coral reefs, which can be found in the waters of 38 countries, generating vital revenues for local economies. | <urn:uuid:af35cb6c-c59a-4750-a6e7-8eaa745224cc> | 3.53125 | 548 | News Article | Science & Tech. | 31.980189 | 95,487,225 |
"Synthesizing Pure Graphene, a ‘Miracle Material’" Topic
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|Tango01 ||31 Aug 2017 12:52 p.m. PST|
"Formed deep within the earth, stronger than steel, and thinner than a human hair. These comparisons aren't describing a new super hero. They're describing graphene, a substance that some experts have called "the most amazing and versatile" known to mankind.
UConn chemistry professor Doug Adamson, a member of the Polymer Program in UConn's Institute of Materials Science, has patented a one-of-a-kind process for exfoliating this wonder material in its pure (unoxidized) form, as well as manufacturing innovative graphene nanocomposites that have potential uses in a variety of applications.
If you think of graphite like a deck of cards, each individual card would be a sheet of graphene. Comprised of a single layer of carbon atoms arranged in a hexagonal lattice, graphene is a two-dimensional crystal that is at least 100 times stronger than steel. Aerogels made from graphene are some of the lightest materials known to man, and the graphene sheets are one of the thinnest, at only one atom thick – that is approximately one million times thinner than a human hair. Graphene is also even more thermally and electrically conductive than copper, with minimal electrical charge…"
|Great War Ace ||31 Aug 2017 2:40 p.m. PST|
Never heard of the stuff before. That's not surprising, since I am not by nature a "science guy". But from what I just read, this process could revolutionize desalinization (making the planet virtually independent of water worries), and also create incredibly light and enormously tough surfaces: armor? Aircraft that weigh a fraction of what they do now, but are ten times tougher to penetrate? | <urn:uuid:683dbfcc-f143-4533-9ed4-32c6e5754bc0> | 2.921875 | 448 | Comment Section | Science & Tech. | 43.886178 | 95,487,231 |
Berkeley Lab researchers successfully use distributed acoustic sensing for seismic monitoring
Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have shown for the first time that dark fiber – the vast network of unused fiber-optic cables installed throughout the country and the world – can be used as sensors for detecting earthquakes, the presence of groundwater, changes in permafrost conditions, and a variety of other subsurface activity.
In a pair of recently published papers, a team led by Berkeley Lab researcher Jonathan Ajo-Franklin announced they had successfully combined a technology called “distributed acoustic sensing,” which measures seismic waves using fiber-optic cables, with novel processing techniques to allow reliable seismic monitoring, achieving results comparable to what conventional seismometers can measure.
“This has huge potential because you can just imagine long stretches of fibers being turned into a massive seismic network,” said Shan Dou, a Berkeley Lab postdoctoral fellow. “The idea is that by using fiber that can be buried underground for a long time, we can transform traffic noise or other ambient vibrations into usable seismic signals that can help us to monitor near-surface changes such as permafrost thaw and groundwater-level fluctuations.”
Dou is the lead author of “Distributed Acoustic Sensing for Seismic Monitoring of the Near Surface: A Traffic-Noise Interferometry Case Study,” which was published in September in Nature’s Scientific Reports and verified the technique for monitoring the Earth’s near surface. More recently, Ajo-Franklin’s group published a follow-up study led by UC Berkeley graduate student Nate Lindsey, “Fiber-Optic Network Observations of Earthquake Wavefields,” in Geophysical Research Letters (GRL), which demonstrates the viability of using fiber-optic cables for earthquake detection.
What is dark fiber?
Dark fiber refers to unused fiber-optic cable, of which there is a glut thanks to a huge rush to install the cable in the early 1990s by telecommunications companies. Just as the cables were buried underground, the technology for transmitting data improved significantly so that fewer cables were needed. There are now dense corridors of dark fiber crisscrossing the entire country.
Distributed acoustic sensing (DAS) is a novel technology that measures seismic wavefields by shooting short laser pulses across the length of the fiber. “The basic idea is, the laser light gets scattered by tiny impurities in the fiber,” said Ajo-Franklin. “When fiber is deformed, we will see distortions in the backscattered light, and from these distortions, we can measure how the fiber itself is being squeezed or pulled.”
Using a test array they installed in Richmond, California – with fiber-optic cable placed in a shallow L-shaped trench, one leg of about 100 meters parallel to the road and another perpendicular – the researchers verified that they could use seismic waves generated by urban traffic, such as cars and trains, to image and monitor the mechanical properties of shallow soil layers.
The measurements give information on how “squishy” the soil is at any given point, making it possible to infer a great deal of information about the soil properties, such as its water content or texture. “Imagine a slinky – it can compress or wiggle,” Ajo-Franklin said. “Those correspond to different ways you can squeeze the soil, and how much energy it takes to reduce its volume or shear it.”
He added: “The neat thing about it is that you’re making measurements across each little unit of fiber. All the reflections come back to you. By knowing all of them and knowing how long it takes for a laser light to travel back and forth on the fiber you can back out what’s happening at each location. So it’s a truly distributed measurement.”
Having proven the concept under controlled conditions, the team said they expect the technique to work on a variety of existing telecommunications networks, and they are currently conducting follow-up experiments across California to demonstrate this. Ongoing research in Alaska is also exploring the same technique for monitoring the stability of Arctic permafrost.
Added Dou: “We can monitor the near surface really well by using nothing but traffic noise. It could be fluctuations in groundwater levels, or changes that could provide early warnings for a variety of geohazards such as permafrost thaw, sinkhole formation, and landslides.”
Using fiber for quake detection
Building on five years of Berkeley Lab-led research exploring the use of DAS for subsurface monitoring using non-earthquake seismic sources, Ajo-Franklin’s group has now pushed the envelope and has shown that DAS is a powerful tool for earthquake monitoring as well.
In the GRL study led by Lindsey in collaboration with Stanford graduate student Eileen Martin, the research team took measurements using the DAS technique on fiber-optic arrays in three locations – two in California and one in Alaska. In all cases, DAS proved to be comparably sensitive to earthquakes as conventional seismometers, despite its higher noise levels. Using the DAS arrays, they assembled a catalog of local, regional, and distant earthquakes and showed that processing techniques could take advantage of DAS’ many channels to help understand where earthquakes originate from.
Ajo-Franklin said that dark fiber has the advantage of being nearly ubiquitous, whereas traditional seismometers, because they are expensive, are sparsely installed, and subsea installations are particularly scarce. Additionally, fiber allows for dense spatial sampling, meaning data points are only meters apart, whereas seismometers typically are separated by many kilometers.
Lindsey added: “Fiber has a lot of implications for earthquake detection, location, and early warning. Fiber goes out in the ocean, and it’s all over the land, so this technology increases the likelihood that a sensor is near the rupture when an earthquake happens, which translates into finding small events, improved earthquake locations, and extra time for early warning.”
The GRL paper notes other potential applications of using the dark fiber, including urban seismic hazard analysis, global seismic imaging, offshore submarine volcano detection, nuclear explosion monitoring, and microearthquake characterization.
The Latest on: Dark fiber
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via Google News and Bing News | <urn:uuid:2a63aea3-44d6-4839-871b-e2506cdd407a> | 2.765625 | 2,041 | News Article | Science & Tech. | 40.44702 | 95,487,234 |
- When she did different analysis of different corn with different phenotypes in
corn kernel, she saw two types of observations. The first type is shown in a)
and there is a second type down a bit.
- We’re looking at cells with the chromosomes so two copies of the
chromosome you would expect to see. On these particular chromosomes, you
see 2 different alleles, one which has a big C and one with a small c. The big C
in this example means wild type and the small c means recessive or the
nonfunctional. The C gene happens to code for colour so C determines a
purple colour, if you have a big C then you have a purple colour in the cell and
for Sh, the wild type, the big S with the h is shrunken so if you have a big Sh
then it is nice and plump like a regular corn you see, so that is Sh so that is a
nice plump kernel and the Wx is for shiny. If you have the wild type then you
have a purple colour that is nice and plump and shiny in appearance.
- As the kernel grows, in some of the cells, what happens is, because in this
region the Ds region, if it was present (located in the slide), as the kernel
grows, some of the cells get a break at the Ds so wherever that Ds is located
you lose that part of the chromosome. That part becomes nonfunctional and
gets destroyed. Cells with this particular genotype, they take on a different
phenotype – they are colourless so the cells that have this DNA will be
colourless, shrunken and not shiny (dull).
- This would be happening during the development of the kernel so you have a
region that is colourless, shrunken and not shiny and then you have the normal
pigmented plump and shiny.
- In other cases, there was another type of allele at the C locus so in other
words, at the position where the colour gene was, that was a different allele
(different sequence). In this case, the cells would inherit a different
combination of genes & alleles so you would have dominant ones & you have
the recessive ones. The deal with this c-Ds is that the Ds is inserted into that C
gene, the big C gene and therefore notice how it has a small c there, it means it
would be colorless so not normally allowing the purple colour to show. The
reason is because the DS has been inserted into the normal C gene. What
happens is the cells initially have this genotype and as they develop, some of
the cells have a situation where the Ds actually moves out of that region where
the C gene is and when that Ds chunk moves away, you now return to the
normal wild type gene. Therefore what you end up with are regions where the
cell has gone back to the regular phenotype with purple & spots.
- This is what Barbara McClintock figured out, that there were parts of the
DNA that were moving around, that this Ds had the ability to move out of a
region of a chromosome and therefore change the phenotype.
- Over time with experiments, people realized that the C gene would look like
this, and it would code for purple pigment. Or if you had a situation where you
had a copy of this, you would have a purple pigment.
- In the case of a mutant with a cm mutant, or the c-Ds mutant shown on the
other slide. In this case the C gene is interrupted by this Ds element it is called
a transposable element. This interrupts the coding sequence of the gene &
therefore in this case providing this stays sable (?), you get a colourless
- If people figured out that you had the Ac gene which is a completely
different gene and it was present with the cm-DS gene, so the same one as up
there then in certain circumstances in certain cells, the Ds could move out so it
would move out of this locus where the C gene was and then you’d have these
spotted kernels. But you need the Ac present, if you don’t have the Ac present
then you always have colourless and as well there was another mutant that had
Ac present in the same region in the C gene and Ac on its own was able to | <urn:uuid:1565e448-c487-4156-8fd4-845064686949> | 4.0625 | 940 | Audio Transcript | Science & Tech. | 52.042387 | 95,487,239 |
A National Aeronautics and Space Administration (NASA) study has predicted that certain cities face the most threat due to rising sea levels due to melting ice caps that is triggered by climate change and global warming. The NASA tool has warned that Mumbai, New York, London, and Mangalore face danger due to floods as ice caps keep melting and lead to rising sea levels.
NASA’s predictions seems to be correct as heavy rainfall has been lashing Mumbai and Mangalore frequently, resulting in flooding of several pockets of the area. According to the NASA study, the southeastern coast of India in Tamil Nadu has seen a shocking 550 mm or 21.7 inches of rain, whereas the total rainfall in that region has been about 200 mm or 7.9 inches.
‘As countries and cities try to mitigate flooding, they have to think about 100 years in future, and they want to assess the risk in the same way as insurance companies do,” says Erik Ivins, a senior researcher at the Jet Propulsion Laboratory run by NASA in the USA.
NASA says low-pressure produced rain in Tamil Nadu and south coastal Andhra Pradesh. The study, published in the journal Science Advances, also helps climate researchers determine vulnerable ice caps that are in particular danger of melting away and that climate change experts should be ‘most worried about’. It also details the catastrophic effect that the melting could have on the world’s coastal cities. The scientists point out that as land ice melts and is taken in by the oceans, the Earth’s gravitational as well as rotational potentials get disturbed. This results in strong patterns of rising sea levels (SLR).
In the coming century, glacial melt and rising sea levels could potentially rise so much that it could pose a threat to Mangalore (sea levels rise by 15.98 cm), Mumbai (15.26 cm), New York (10.65 cm), the study added. The predictions are based on the analysis conducted and data gathered by a tool that has been developed by NASA to predict cities that are most prone to inundation due to melting of ice caps and a warmer climate.
‘This provides, for each city, a picture of which glaciers, ice sheets and ice caps are of importance,” scientists said to media.
There has been a consensus among Earth and climate change scientists and researchers that the melting of land ice as well as those at the poles significantly lead to sea-level rise (SLR). They also agree that greater global warming would accelerate the risks to human civilizations. As land ice continues to be lost to the oceans, the disturbance in the Earth’s gravitational as well as rotational indices can lead to strong overall impact. There has been a dearth of reliable forecasting models mapping clearly future ice changes.
The NASA tool tries to correctly link and predict rising sea levels (LSL) changes. The tool uses advanced mathematical models to determine the gradient of rising sea levels keeping in mind local variations in ice thickness of the important ice drainage systems of the world. Exhaustive mapping of the gradients has lead to the new diagnostic tool called gradient fingerprint mapping (GFM). The tool helps one with more accurate assessment of rising sea levels and coastal inundation in the future. There could be major consequences for Antarctica and Greenland, leading to flooding of major port cities, depend on their location with respect to the drainage system. For instance, London is affected by changes in the western part of Greenland Ice Sheet (GrIS), while New York is affected by changes in northeastern portions of GrIS.
The study has applied the NASA tool GFM to 293 big port cities in order to help coastal planners to calculate rising sea levels and prepare for the future.
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London: Some of the first large organisms on the Earth formed ecosystems that were much more complex than previously thought, an analysis of the feeding habits of a 555-million-year-old organism revealed.
An international team of researchers from Canada, Britain and the US studied fossils of an extinct organism called Tribrachidium, which lived in the oceans some 555 million years ago.
Using a computer modelling approach, they were able to show that Tribrachidium fed by collecting particles suspended in water. This is called suspension feeding and it had not previously been documented in organisms from this period of time.
Tribrachidium lived during a period of time called the Ediacaran, which ranged from 635 million to 541 million years ago.
This period was characterised by a variety of large, complex organisms, most of which are difficult to link to any modern species.
It was previously thought that these organisms formed simple ecosystems characterised by only a few feeding modes, but the new study suggests they were capable of more types of feeding than previously appreciated.
“Our study has shown that Tribrachidium and perhaps other species were capable of suspension feeding. This demonstrates that, contrary to our expectations, some of the first ecosystems were actually quite complex,” said Simon Darroch from Vanderbilt University, US.
“The computer simulations we ran allowed us to test competing theories for feeding in Tribrachidium. This approach has great potential for improving our understanding of many extinct organisms,” said Imran Rahman from University of Bristol, England.
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Since the end of the 1960s West Africa has continuously been suffering hard drought. The rainfall deficit for the 1970s and 1980s, calculated to compare with the 1950s and 1960s, thus reached as high as 50% over the northern part of the Sahel. The hydrological cycle as a whole is affected by this drought, which results in serious consequences for agriculture and food security.
IRD researchers, aiming to understand the mechanisms behind this situation, examined rainfall data from 1950 to 1990. Two sub-periods emerge : a wet one (1951-1969), followed by a dry one (1970-1990). This finding led them to modify drastically the classic model which presents the monsoon as a process that unfurls in a continuous sweep from South to North. Two rainfall dynamics regimes are in evidence, distinct in time and in space, separated by a sharp transition. The mean date for this, a jump heralding the monsoon onset, is around 22 June, which proved to be highly constant for both the wet and the dry sub-periods.
The proposed model predicts that the first monsoon phase starts off from the Atlantic coast in February and propagates steadily northwards. By May it has reached the central Sahel (13°N longitude, Niamey). After a period of stabilization, rainfall abruptly becomes much heavier. It touches the whole Sahel zone simultaneously. A short dry season then appears on the coast before a second rainy season arises there from September, linked to the retreat of the monsoon towards the South.
Marie-Lise Sabrie | alfa
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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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Modeling Volcanic Processes: The Physics and Mathematics of Volcanism (BOK)
Sendes vanligvis innen 7-15 dager
Understanding the physical behavior of volcanoes is key to mitigating the hazards active volcanoes pose to the ever-increasing populations living nearby. The processes involved in volcanic eruptions are driven by a series of interlinked physical phenomena, and to fully understand these, volcanologists must employ various physics subdisciplines. This book provides the first advanced-level, one-stop resource examining the physics of volcanic behavior and reviewing the state-of-the-art in modeling volcanic processes. Each chapter begins by explaining simple modeling formulations and progresses to present cutting-edge research illustrated by case studies. Individual chapters cover subsurface magmatic processes through to eruption in various environments and conclude with the application of modeling to understanding the other volcanic planets of our Solar System. Providing an accessible and practical text for graduate students of physical volcanology, this book is also an important resource for researchers and professionals in the fields of volcanology, geophysics, geochemistry, petrology and natural hazards.
CAMBRIDGE UNIVERSITY PRESS
|Dimensjoner||18,9cm x 24,6cm x 2,4cm||Vekt||1090 gram|
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Last updated on May 23rd, 2018
Perl (nicknamed “the Swiss Army chainsaw of scripting languages”) is a family of high-level, general-purpose, interpreted, dynamic programming languages, including Perl 5 and Perl 6. It was developed by Larry Wall in 1987. Perl 5 is used for scripting, system administration, network programming, finance, bioinformatics, GUIs, etc. Here’s a list of some of the best Perl tutorials, Perl books and Perl courses to help you learn Perl in 2018.
Learn Perl 5 By Doing It by John Purcell will help you learn how to use Perl for a variety of common tasks. This Perl tutorial will help you learn how to use regular expressions.
Some of the Perl programs you will learn to include downloading text and images, reformatting data, importing and exporting data to and from databases, sysadmin-type tasks like renaming or moving files, fixing even huge amounts of data quickly and even creating web CGI scripts. This is the best Perl tutorial in 2018.
Perl Programming for Beginners by Stone River eLearning is a crash course that will get you up to speed in Perl. This Perl tutorial will help you learn the Perl fundamentals and design a Perl application. You will learn various Perl fundamentals like scalar data, arrays and lists, subroutines, input and output, hashes, and regular expressions. This Perl tutorial will teach you to work with different data types including strings, numbers, variables and user input. You will create and use array, subroutines, hashes, and regular expressions in Perl. This is the best Perl tutorial for beginners in 2018.
Perl for Beginners: Learn A to Z of Perl Scripting Hands-on by AkaSkills! will help you learn Perl. This Perl tutorial covers all relevant Perl concepts. You will understand Strings, Variables, Hashes, Arrays and all other important Perl topics and features. This Perl course is made for beginners. You will get a certification of completion that validates your skills at the end of this Perl tutorial.
Learning Perl: Making Easy Things Easy and Hard Things Possible by Randal L. Schwartz, Brian D Foy and Tom Phoenix teaches you the basics and shows you how to write programs. Each chapter in this book includes exercises to help you practice what you’ve just learned. This is the best Perl book for beginners in 2018.
Effective Perl Programming: Ways to Write Better, More Idiomatic Perl by Joseph N. Hall, Joshua A. McAdams and Brian D Foy is the classic Perl guide. You will learn to solve real-world problems with Perl. The book contains with idioms, techniques, and examples. It teaches you everything needed to write more powerful, expressive, and succinct Perl code. You will learn strings, lists, arrays, structures, namespaces, regular expressions, subroutines, and more. This is one of the best Perl books in 2018.
Perl One-Liners: 130 Programs That Get Things Done by Peteris Krumins is a cookbook of useful, customizable, and fun scripts will even help hone your Perl coding skills. This Perl book contains more than 100 one-liners that do all sorts tasks. You’ll find one-liners Perl programs that generate random passwords, check to see if a number is prime with a regular expression and much more.
Perl Cookbook by Tom Christiansen and Nathan Torkington is a comprehensive collection of problems, solutions, and practical examples. This book contains hundreds of rigorously reviewed Perl recipes. It also has thousands of examples ranging from brief one-liners to complete applications. Perl users of all levels can make use of the practical answers and code examples.
Amazon Associates Disclosure: We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites. | <urn:uuid:72ccabe6-744d-4f94-a1a6-dcf4b675822c> | 3.078125 | 813 | Listicle | Software Dev. | 55.475801 | 95,487,340 |
The rate of the SN2 reaction is second order overall due to the reaction being bimolecular (i.e. there are two molecular species involved in the rate-determining step). The reaction does not have any intermediate steps, only a transition state. This means that all the bond making and bond breaking takes place in a single step. In order for the reaction to occur both molecules must be situated correctly. | <urn:uuid:af6339c0-dd17-44c1-8006-861c41bf4b8f> | 2.59375 | 85 | Knowledge Article | Science & Tech. | 52.381905 | 95,487,341 |
The Global Ocean Science Report (GOSR) assesses for the first time the status and trends in ocean science capacity around the world. The report offers a global record of who, how, and where ocean science is conducted: generating knowledge, helping to protect ocean health, and empowering society to support sustainable ocean management in the framework of the United Nations Agenda 2030.
The GOSR identifies and quantifies the key elements of ocean science at the national, regional and global scales, including workforce, infrastructure and publications. This is the first collective attempt to systematically highlight opportunities as well as capacity gaps to advance international collaboration in ocean science and technology. This report is a resource for policy makers, academics and other stakeholders seeking to harness the potential of ocean science to address global challenges.
A comprehensive view of ocean science capacities at the national and global levels takes us closer to developing the global ocean science knowledge needed to ensure a healthy, sustainable ocean.
Read the report | <urn:uuid:d233a375-f20c-491e-8978-ea42cebb0255> | 2.703125 | 192 | News (Org.) | Science & Tech. | 10.747955 | 95,487,410 |
In the current issue of the journal Environmental Science & Technology, they reveal that introduction of the compound tributyltin (TBT) as a biocide in boat paint in the 1960s resulted in a dramatic and sudden loss of aquatic vegetation from most of the 50 or so Norfolk Broads lakes.
At the time, scientists pointed the finger at contamination from sewage works and fertiliser run-off from farmland, despite suggestions from the local community that the burgeoning leisure boating industry might be to blame.
Though the use of TBT was banned in freshwater systems in the UK in 1987, the researchers say 40 years on from TBT's introduction the fragile ecosystem remains shattered despite expensive attempts to restore it.
Dr Carl Sayer, of the UCL Environmental Change Research Centre, who co-led the study, says: "For too long TBT has been neglected as a driver of environmental destruction in freshwater wetlands and even though it is no longer in use in UK inland waterways, TBT contamination and its negative effects are still being reported all over the world.
"Real concerns have been raised about TBT derived from industrial and ship breaking activities in several major river systems including the Ganges, Brahmaputra and Yangtze – all of which are connected to shallow lakes. In the case of the Yangtze, the linked shallow lakes are some of the largest in the world and, like the Broads, have experienced problems with plant loss on a large scale."
TBT was originally designed for use on the hulls of large ocean-going ships to reduce the build-up of barnacles. Since the 1970s it has been linked to a host of negative effects in the marine environment including mutations in shellfish. An aggressive marketing programme in the 1960s saw its use fashionably worldwide on much smaller craft both in the oceans and within inland waterways.
"TBT is extremely toxic and highly persistent in the environment, earning it the controversial title as the most toxic substance ever introduced deliberately by man into the aquatic environment," explains Dr Sayer.
"In freshwaters, once TBT is released from an antifouling coating it is rapidly absorbed by bacteria and algae, and eventually works its way up the food chain. Within a short period of time after the paint's introduction to the Broads, it knocked out many of the small invertebrates which are a part of the life support system for water plants – turning the waters of the Broads green with algae."
To investigate levels of TBT in the Broads the researchers took sediment cores from two lakes, one close to the centre of the boating industry and the other half a kilometre away. Results show an abrupt decline in plant and invertebrate populations at the precise time that a strong TBT signature was detected.
"The irony of the tale is that the paint was designed to stop barnacles attaching to boats – which you don't get in freshwater. By simply lifting boats out of the water once a year and using a bit of elbow grease, one of Britain's areas of outstanding natural beauty might still be intact rather than on the long road to recovery."
Judith H Moore | 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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20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
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I f we were transported forward in time, to an Earth ravaged by catastrophic climate change, we might see long, delicate strands of fire hose stretching into the sky, like spaghetti, attached to zeppelins hovering 65,000 feet in the air. Factories on the ground would pump 10 kilos of sulfur dioxide up through those hoses every second. And at the top, the hoses would cough a sulfurous pall into the sky. At sunset on some parts of the planet, these puffs of aerosolized pollutant would glow a dramatic red, like the skies in Blade Runner. During the day, they would shield the planet from the sun’s full force, keeping temperatures cool—as long as the puffing never ceased.
Technology that could redden the skies and chill the planet is available right now. Within a few years we could cool the Earth to temperatures not regularly seen since James Watt’s steam engine belched its first smoky plume in the late 18th century. And we could do it cheaply: $100 billion could reverse anthropogenic climate change entirely, and some experts suspect that a hundredth of that sum could suffice. To stop global warming the old-fashioned way, by cutting carbon emissions, would cost on the order of $1 trillion yearly. If this idea sounds unlikely, consider that President Obama’s science adviser, John Holdren, said in April that he thought the administration would consider it, “if we get desperate enough.” And if it sounds dystopian or futuristic, consider that Blade Runner was set in 2019, not long after Obama would complete a second term.
Humans have been aggressively transforming the planet for more than 200 years. The Nobel Prize–winning atmospheric scientist Paul Crutzen—one of the first cheerleaders for investigating the gas-the-planet strategy—recently argued that geologists should refer to the past two centuries as the “anthropocene” period. In that time, humans have reshaped about half of the Earth’s surface. We have dictated what plants grow and where. We’ve pocked and deformed the Earth’s crust with mines and wells, and we’ve commandeered a huge fraction of its freshwater supply for our own purposes. What is new is the idea that we might want to deform the Earth intentionally, as a way to engineer the planet either back into its pre-industrial state, or into some improved third state. Large-scale projects that aim to accomplish this go by the name “geo-engineering,” and they constitute some of the most innovative and dangerous ideas being considered today to combat climate change. Some scientists see geo-engineering as a last-ditch option to prevent us from cooking the planet to death. Others fear that it could have unforeseen—and possibly catastrophic—consequences. What many agree on, however, is that the technology necessary to reshape the climate is so powerful, and so easily implemented, that the world must decide how to govern its use before the wrong nation—or even the wrong individual—starts to change the climate all on its own.
I f geo-engineers have a natural enemy, it is the sun. Their first impulse is to try to block it out. Stephen Salter, a Scottish engineer, has mocked up a strategy that would cool the planet by painting the skies above the oceans white. Salter’s designs—based on an idea developed by John Latham at the National Center for Atmospheric Research—call for a permanent fleet of up to 1,500 ships dragging propellers that churn up seawater and spray it high enough for the wind to carry it into the clouds. The spray would add moisture to the clouds and make them whiter and fluffier, and therefore better at bouncing sunlight back harmlessly into space. Salter, who has investigated the technical feasibility of this idea minutely (down to the question of whether ship owners would mind affixing spray nozzles to their hulls with magnets), estimates the cost to build the first 300 ships—enough to turn back the climatological clock to James Watt’s era—to be $600 million, plus another $100 million per year to keep the project going.
Roger Angel, an astronomy and optics professor at the University of Arizona, would block the sun by building a giant visor in space. He proposes constructing 20 electromagnetic guns, each more than a mile long and positioned at high altitudes, that would shoot Frisbee-size ceramic disks. Each gun would launch 800,000 disks every five minutes—day and night, weekends and holidays—for 10 years. The guns would aim at the gravitational midpoint between the Earth and the sun, so that the disks would hang in space, providing a huge array of sunshades that would block and scatter sunlight and put the Earth in a permanent state of annular eclipse. Angel’s scheme relies on launch technology that doesn’t yet exist (no one has ever wanted to shoot Frisbees at the sun before), and would cost several trillion dollars. “I know it sounds like mad science,” he says. “But unfortunately we have a mad planet.”
Of all the ideas circulating for blocking solar heat, however, sulfur-aerosol injection—the Blade Runner scenario—may actually be the least mad. And it provides an illustrative example of the trade-offs that all geo-engineering projects of its scale must confront. The approach is already known to work. When Mount Tambora erupted in Indonesia in 1815 and spewed sulfur dioxide into the stratosphere, farmers in New England recorded a summer so chilly that their fields frosted over in July. The Mount Pinatubo eruption in the Philippines in 1991 cooled global temperatures by about half a degree Celsius for the next few years. A sulfur-aerosol project could produce a Pinatubo of sulfur dioxide every four years.
The aerosol plan is also cheap—so cheap that it completely overturns conventional analysis of how to mitigate climate change. Thomas C. Schelling, who won the 2005 Nobel Prize in economics, has pointed out how difficult it is to get vast international agreements—such as the Kyoto Protocol—to stick. But a geo-engineering strategy like sulfur aerosol “changes everything,” he says. Suddenly, instead of a situation where any one country can foil efforts to curb global warming, any one country can curb global warming all on its own. Pumping sulfur into the atmosphere is a lot easier than trying to orchestrate the actions of 200 countries—or, for that matter, 7 billion individuals—each of whom has strong incentives to cheat.
But, as with nearly every geo-engineering plan, there are substantial drawbacks to the gas-the-planet strategy. Opponents say it might produce acid rain and decimate plant and fish life. Perhaps more disturbing, it’s likely to trigger radical shifts in the climate that would hit the globe unevenly. “Plausibly, 6 billion people would benefit and 1 billion would be hurt,” says Martin Bunzl, a Rutgers climate-change policy expert. The billion negatively affected would include many in Africa, who would, perversely, live in a climate even hotter and drier than before. In India, rainfall levels might severely decline; the monsoons rely on temperature differences between the Asian landmass and the ocean, and sulfur aerosols could diminish those differences substantially.
Worst of all is what Raymond Pierrehumbert, a geophysicist at the University of Chicago, calls the “Sword of Damocles” scenario. In Greek legend, Dionysius II, the ruler of Syracuse, used a single hair to suspend a sword over Damocles’ head, ostensibly to show him how precarious the life of a powerful ruler can be. According to Pierrehumbert, sulfur aerosols would cool the planet, but we’d risk calamity the moment we stopped pumping: the aerosols would rain down and years’ worth of accumulated carbon would make temperatures surge. Everything would be fine, in other words, until the hair snapped, and then the world would experience the full force of postponed warming in just a couple of catastrophic years. Pierrehumbert imagines another possibility in which sun-blocking technology works but has unforeseen consequences, such as rapid ozone destruction. If a future generation discovered that a geo-engineering program had such a disastrous side effect, it couldn’t easily shut things down. He notes that sulfur-aerosol injection, like many geo-engineering ideas, would be easy to implement. But if it failed, he says, it would fail horribly. “It’s scary because it actually could be done,” he says. “And it’s like taking aspirin for cancer.”
I n 1977, the physicist Freeman Dyson published the first of a series of articles about how plants affect the planet’s carbon-dioxide concentrations. Every summer, plants absorb about a tenth of the carbon dioxide in the atmosphere. In the fall, when they stop growing or shed their leaves, they release most of it back into the air. Dyson proposed creating forests of “carbon-eating trees,” engineered to suck carbon more ravenously from the air, and to keep it tied up in thick roots that would decay into topsoil, trapping the carbon. He now estimates that by annually increasing topsoil by just a tenth of an inch over land that supports vegetation, we could offset all human carbon emissions.
Dyson’s early geo-engineering vision addressed a central, and still daunting, problem: neither sulfur-aerosol injection nor an armada of cloud whiteners nor an array of space-shades would do much to reduce carbon-dioxide levels. As long as carbon emissions remain constant, the atmosphere will fill with more and more greenhouse gases. Blocking the sun does nothing to stop the buildup. It is not even like fighting obesity with liposuction: it’s like fighting obesity with a corset, and a diet of lard and doughnuts. Should the corset ever come off, the flab would burst out as if the corset had never been there at all. For this reason, nearly every climate scientist who spoke with me unhesitatingly advocated cutting carbon emissions over geo-engineering.
But past international efforts to reduce emissions offer little cause for optimism, and time may be quickly running out. That’s why a few scientists are following Dyson’s lead and attacking global warming at its source. David Keith, an energy-technology expert at the University of Calgary, hopes to capture carbon from the air. He proposes erecting vented building-size structures that contain grids coated with a chemical solution. As air flows through the vents, the solution would bind to the carbon-dioxide molecules and trap them. Capturing carbon in these structures, which might resemble industrial cooling towers, would allow us to manage emissions cheaply from central sites, rather than from the dispersed places from which they were emitted, such as cars, planes, and home furnaces. The grids would have to be scrubbed chemically to separate the carbon. If chemists could engineer ways to wash the carbon out that didn’t require too much energy, Keith imagines that these structures could effectively make our carbon-spewing conveniences carbon-neutral.
The question then becomes where to put all that carbon once it’s captured. Keith has investigated one elegant solution: put it back underground, where much of it originated as oil. The technology for stashing carbon beneath the earth already exists, and is routinely exploited by oil-well drillers. When oil wells stop producing in large quantities, drillers inject carbon dioxide into the ground to push out the last drops. If they inject it into the right kind of geological structure, and deep enough below the surface, it stays there.
We might also store carbon dioxide in the oceans. Already, on the oceans’ surface, clouds of blooming plankton ingest amounts of carbon dioxide comparable to those taken in by trees. Climos, a geo-engineering start-up based in San Francisco, is trying to cultivate ever-bigger plankton blooms that would suck in huge supplies of carbon. When the plankton died, the carbon would end up on the sea floor. Climos began with the observation that plankton bloom in the ocean only when they have adequate supplies of iron. In the 1980s, the oceanographer John Martin hypothesized that large amounts of oceanic iron may have produced giant plankton blooms in the past, and therefore chilled the atmosphere by removing carbon dioxide. Spread powdered iron over the surface of the ocean, and in very little time a massive bloom of plankton will grow, he predicted. “Give me half a tanker of iron,” Martin said, “and I’ll give you the next Ice Age.” If Martin’s ideas are sound, Climos could in effect become the world’s gardener by seeding Antarctic waters with iron and creating vast, rapidly growing offshore forests to replace the ones that no longer exist on land. But this solution, too, could have terrible downsides. Alan Robock, an environmental scientist at Rutgers, notes that when the dead algae degrades, it could emit methane—a greenhouse gas 20 times stronger than carbon dioxide.
Just a decade ago, every one of these schemes was considered outlandish. Some still seem that way. But what sounded crankish only 10 years ago is now becoming mainstream thinking. Although using geo-engineering to combat climate change was first considered (and dismissed) by President Johnson’s administration, sustained political interest began on the business-friendly right, which remains excited about any solution that doesn’t get in the way of the oil companies. The American Enterprise Institute, a conservative think tank historically inimical to emission-reduction measures, has sponsored panels on the sulfur-aerosol plan.
By now, even staunch environmentalists and eminent scientists with long records of climate-change concern are discussing geo-engineering openly. Paul Crutzen, who earned his Nobel Prize by figuring out how human activity punched a hole in the ozone layer, has for years urged research on sulfur-aerosol solutions, bringing vast credibility to geo-engineering as a result.
With that growing acceptance, however, come some grave dangers. If geo-engineering is publicly considered a “solution” to climate change, governments may reduce their efforts to restrict the carbon emissions that caused global warming in the first place. If you promise that in a future emergency you can chill the Earth in a matter of months, cutting emissions today will seem far less urgent. “Geo-engineering needs some government funding, but the most disastrous thing that could happen would be for Barack Obama to stand up tomorrow and announce the creation of a geo-engineering task force with hundreds of millions in funds,” says David Keith.
Ken Caldeira, of the Carnegie Institution for Science, thinks we ought to test the technology gradually. He suggests that we imagine the suite of geo-engineering projects like a knob that we can turn. “You can turn it gently or violently. The more gently it gets turned, the less disruptive the changes will be. Environmentally, the least risky thing to do is to slowly scale up small field experiments,” he says. “But politically that’s the riskiest thing to do.”
Such small-scale experimentation, however, could be the first step on a very slippery slope. Raymond Pierrehumbert likens geo-engineering to building strategic nuclear weapons. “It’s like the dilemma faced by scientists in the Manhattan Project, who had to decide whether that work was necessary or reprehensible,” he says. “Geo-engineering makes the problem of ballistic-missile defense look easy. It has to work the first time, and just right. People quite rightly see it as a scary thing.”
T he scariest thing about geo-engineering, as it happens, is also the thing that makes it such a game-changer in the global-warming debate: it’s incredibly cheap. Many scientists, in fact, prefer not to mention just how cheap it is. Nearly everyone I spoke to agreed that the worst-case scenario would be the rise of what David Victor, a Stanford law professor, calls a “Greenfinger”—a rich madman, as obsessed with the environment as James Bond’s nemesis Auric Goldfinger was with gold. There are now 38 people in the world with $10 billion or more in private assets, according to the latest Forbes list; theoretically, one of these people could reverse climate change all alone. “I don’t think we really want to empower the Richard Bransons of the world to try solutions like this,” says Jay Michaelson, an environmental-law expert, who predicted many of these debates 10 years ago.
Even if Richard Branson behaves, a single rogue nation could have the resources to change the climate. Most of Bangladesh’s population lives in low-elevation coastal zones that would wash away if sea levels rose. For a fraction of its GDP, Bangladesh could refreeze the ice caps using sulfur aerosols (though, in a typical trade-off, this might affect its monsoons). If refreezing them would save the lives of millions of Bangladeshis, who could blame their government for acting? Such a scenario is unlikely; most countries would hesitate to violate international law and become a pariah. But it illustrates the political and regulatory complications that large-scale climate-changing schemes would trigger.
Michaelson—along with many others—has called for public research on some possible legal responses to geo-engineering. “It would be a classic situation where the problem should be handled in an official capacity,” he says. In practice, that would likely mean industrialized governments’ regulating geo-engineering directly, in a way that lets them monopolize the technology and prevent others from deploying it, through diplomatic and military means, or perhaps by just bribing Bangladesh not to puff out its own aerosols. Such a system might resemble the way the International Atomic Energy Agency now regulates nuclear technology.
And since geo-engineering—like nuclear weapons—would most likely be deployed during a moment of duress, legal experts like Victor have urged establishing preliminary regulations well in advance. “Suppose the U.S. or Brazil decided it needed some combination of emissions-cutting and geo-engineering in a sudden catastrophe,” Victor says. “How would the rest of us respond? There’s been no serious research on the topic. It has to be done right now, and not in a crisis situation.” An outright ban on geo-engineering could lead other countries to try out dangerous ideas on their own, just as a ban on cloning in the United States has sent research to Korea and Singapore; it would constrain all but the least responsible countries.
Victor doesn’t believe geo-engineering will solve anything by itself, but he expects that ultimately we will have a cocktail of solutions. Perhaps we could start with a few puffs of sulfur in the atmosphere to buy time, then forests of plankton in the ocean, and then genetically engineered carbon-hungry trees. What isn’t an option, Victor says, is refusing to fund more research, in the hope that geo-engineering won’t be needed.
Thomas Schelling, who won his Nobel Prize for using game theory to explain nuclear strategy and the behavior of states in arms races, shares Victor’s frustration about the way geo-engineering has been ignored. Multinational agreements to cut emissions amount to a game of chicken that tends to end unhappily in Schelling’s models. The ideal outcome would be a technology that changes the game. “We just have to consider that we may need this kind of project, and might need it in a hurry,” he says. “If the president has to go by boat from the White House to the Capitol, we should be ready scientifically—but also diplomatically—to do something about it.”
We should keep such images in mind. And they should remind us that, one way or another, a prolonged love affair with carbon dioxide will end disastrously. A pessimist might judge geo-engineering so risky that the cure would be worse than the disease. But a sober optimist might see it as the biggest and most terrifying insurance policy humanity might buy—one that pays out so meagerly, and in such foul currency, that we’d better ensure we never need it. In other words, we should keep investigating geo-engineering solutions, but make quite clear to the public that most of them are so dreadful that they should scare the living daylights out of even a Greenfinger. In this way, the colossal dangers inherent in geo-engineering could become its chief advantage. A premonition of a future that looks like Blade Runner, with skies dominated by a ruddy smog that’s our only defense against mass flooding and famine, with sunshades in space and a frothy bloom of plankton wreathing the Antarctic, could finally horrify the public into greener living. Perhaps a Prius doesn’t sound so bad, when a zeppelin is the alternative.
We want to hear what you think. Submit a letter to the editor or write to firstname.lastname@example.org. | <urn:uuid:7e2b1cc0-9ae9-494c-8f87-12da6d2de779> | 3.671875 | 4,466 | Nonfiction Writing | Science & Tech. | 42.720407 | 95,487,433 |
Land water, including groundwater extraction, contributes far less to sea level rise than previously thought, according to a new study.
Groundwater extraction and other land water contribute about three times less to sea level rise than previous estimates, according to a new study published in the journal Nature Climate Change. The study does not change the overall picture of future sea level rise, but provides a much more accurate understanding of the interactions between water on land, in the atmosphere, and the oceans, which could help to improve future models of sea level rise.
© haveseen | Adobe Stock Photo
“Projecting accurate sea level rise is important, because rising sea level is a threat to people who live near the ocean and in small islands,” explains IIASA researcher Yoshihide Wada, who led the study. “Some low-lying areas will have more frequent flooding, and very low-lying land could be submerged completely. This could also damage substantially coastal infrastructure.”
Sea level has risen 1.7 mm per year over the 20th and the early 21st century, a trend that is expected to continue as climate change further warms the planet. Researchers have attributed the rising seas to a combination of factors including melting ice caps and glaciers, thermal expansion (water expands as it gets warmer), and the extraction of groundwater for human use.
Land water contributions are small in comparison to the contribution of ice melt and thermal expansion, yet they have been increasing, leading to concerns that this could exacerbate the problem of sea level rise caused by climate change.
However, much uncertainty remains about how much different sources contribute to sea level rise. In fact, sea level has actually risen more than researchers could account for from the known sources, leading to a gap between observed and modeled global sea-level budget.
Previous studies, including estimates used in the IPCC Fifth Assessment Report, had assumed that nearly 100% of extracted groundwater ended up in the ocean. The new study improves on previous estimates by accounting for feedbacks between the land, ocean, and atmosphere. It finds that number is closer to 80%. That means that the gap between modeled and observed sea level rise is even wider, suggesting that other processes are contributing more water than previously estimated.
“During the 20th century and early 21st century, cumulative groundwater contribution to global sea level was overestimated by at least 10 mm,” says Wada. In fact, the new study shows that from 1971 to 2010, the contribution of land water to global sea level rise was actually slightly negative – meaning that more water was stored in groundwater and also due to reservoir impoundment behind dams. From 1993 to 2010, the study estimates terrestrial water as contributing positive 0.12 mm per year to sea level rise.
The study does not change the fact that future groundwater contribution to sea level will increase as groundwater extraction increases. And the increasing trend in groundwater depletion has impacts beyond sea level rise. Wada explains, “The water stored in the ground can be compared to money in the bank. If you withdraw money at a faster rate than you deposit it, you will eventually start having account-supply problems. If we use groundwater unsustainably, in the future there might not be enough groundwater to use for food production. Groundwater depletion can also cause severe environmental problems like reduction of water in streams and lakes, deterioration of water quality, increased pumping costs, and land subsidence.”
Wada Y, Lo MH, Yeh PJF, Reager JT, Famiglietti JS, Wu RJ, Tseng YH (2016). Fate of water pumped from underground and contributions to sea-level rise. Nature Climate Change. doi:10.1038/NCLIMATE3001
The International Institute for Applied Systems Analysis (IIASA) is an international scientific institute that conducts research into the critical issues of global environmental, economic, technological, and social change that we face in the twenty-first century. Our findings provide valuable options to policymakers to shape the future of our changing world. IIASA is independent and funded by prestigious research funding agencies in Africa, the Americas, Asia, Europe, and Oceania. www.iiasa.ac.at
Katherine Leitzell | idw - Informationsdienst Wissenschaft
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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
13.07.2018 | Life Sciences | <urn:uuid:bce12dc1-c6ae-4817-ab16-59b7d3c382a8> | 3.671875 | 1,500 | Content Listing | Science & Tech. | 39.043246 | 95,487,464 |
Testing Drugs with Stem Cells
Researchers are using human embryonic stem cells to determine the toxicity of potential pharmaceuticals.
Testing the toxicity of pharmaceutical candidates in lab rats before the compounds are judged safe enough for human clinical trials is notoriously unreliable. Often compounds that appear safe in the rodents prove to be toxic in humans.
To come up with a better way of predicting toxicity, Gabriela Cezar, assistant professor of animal science at the University of Wisconsin-Madison, is turning to human embryonic stem cells. In the current issue of Stem Cells and Development, Cezar and her colleagues reveal a novel way to test drug toxicity: by monitoring the behavior of embryonic stem cells exposed to a drug-candidate compound. Studying how potential drugs affect embryonic stem cells could provide a far more accurate prediction of a drug’s potential toxicity than conventional animal models can.
During normal development, embryonic stem cells produce molecules that direct cellular metabolism and differentiation. Cezar hypothesized that exposure to a toxic drug may skew concentrations of these molecules, disrupting cell-to-cell interactions and causing a biological cascade resulting in potential developmental disorders.
As a proof of concept, Cezar’s group looked at human embryonic stem cells’ response to valproate, an anti-epileptic drug that has been linked with cases of autism and spina bifida in the offspring of mothers treated with the drug. “Developmental disorders and birth defects start in utero during pregnancy, and we have no way to measure or look at mechanisms that could be participating in the onset of these diseases,” says Cezar. “With human embryonic stem cells, we can recapitulate development of the human brain and measure concrete changes of chemicals to drugs like valproate.”
In the experiment, Cezar introduced various dosages of valproate, from very low to high, into three sets of embryonic stem-cell cultures, altering the dosages over different lengths of time. Control groups contained stem cells not exposed to the drug. Cezar then ran each sample through a mass spectrometer, which measured concentrations of the molecules present in culture.
Compared with the control group, samples with valproate exhibited significant changes in the concentrations of two key molecules: glutamate and kynurenin. Both molecules are heavily involved in early brain development, and Cezar found that exposure to valproate caused spikes in each molecule’s concentrations, indicating that such molecules may serve as biomarkers for a drug’s potential toxicity.
“We’re predicting toxicity to humans in human cells,” says Cezar. “Discovering these measurable molecules of toxicity, we hope to present other serious adverse reactions that are caused by testing drugs in animals, with the hope of bringing safer drugs to patients.”
However, using embryonic stem cells as testing grounds for drug safety is still a relatively new concept, and according to some scientists, much more research is needed before it can be determined that the method is viable. Steven Tannenbaum, professor of chemistry and toxicology at MIT, says that drug metabolism in the body is a complex process. In particular, drugs taken into the body are processed first in the liver, taking on different forms before traveling through the rest of the body, and into the womb. “More than 90 percent of drugs are metabolized in the liver to other forms of the drug, some of which might be toxic,” says Tannenbaum. “This group has taken valproic acid, which is normally extensively metabolized in the body, and exposed it under unrealistic conditions.”
Cezar says that a possible solution may be to direct embryonic stem cells to grow into liver cells before exposing them to drugs–a project that she may take up in the future. “As long as we can make the cells from human embryonic stem cells, then once we have the mature cells in a dish, we could discover biomarkers in liver toxicity,” says Cezar.
“It’s a very versatile platform.”
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:65fc410a-2c7a-492b-a8bd-7276fefab797> | 3.359375 | 875 | News Article | Science & Tech. | 26.976349 | 95,487,477 |
- 18.01 (released) ...
The object tool is a debugging tool that displays extended dynamic information about runtime objects while debugging an application. This information includes the values of attributes, as well as the values of
once functions that have already been called.
By default the Object tool display is composed of one grid, which gives information about the current stack element. Specifically, it provides the Current object value, the arguments' values of the current stack element's feature call, the values of the local variables, as well as the value of the
Result (if this feature is a function).
When an exception occurs (for instance, an assertion violation), the object tool will also display the exception information:
All objects can be expanded to see the values of their attributes. They are also pickable, so that it is possible to drop them onto the Object tool, an expression evaluator tool (also know as Watch tool), or an editor.
The toolbar buttons:
- the remove object command
- the set slice size command .
- the button can give an expanded display of the string relative to an object, by dropping the object onto the button (or pressing Ctrl+E on the selected value). Use it if an object has a very long string representation or a string representation that contains carriage returns, for example.
- the button switches the display of integer values between decimal and hexadecimal format.
- and the button controls the remote object storage . | <urn:uuid:3849ddea-0a37-4519-bf05-c9c28870332a> | 2.84375 | 300 | Documentation | Software Dev. | 42.8975 | 95,487,488 |
The properties of dwarf galaxies have presented many challenges. «Ten years ago, my team at the University of Washington found that our cosmological model predicts 30-50 times as many small objects as we see. If the numbers had been nearly equal, that would have been an easy success for the model. If there were none, we might figure out a way to keep any from forming» says lead author George Lake «but at the risk of confusing fairy tales, having 30-50 times fewer dwarfs than predicted presents a ‹Goldilock’s problem›. How do we keep most of them from forming, but not all?»
The main theory to prevent the formation of luminous dwarfs has been that events in the early Universe remove the gas that might have formed stars. The first of these events is the global heating and reionization of the Universe that happens within a billion years after the big bang. In this theory, the small fraction of dwarfs that form quickly enough escape destruction. «While this is an interesting idea, it doesn’t explain why most of the dwarfs have stars that form much later than this» says Lake.
There is also the odd grouping of dwarfs. «Like those of the correct fairy tale, the dwarfs that we have are ‹friendly›, they group together both within our galaxy and in nearby associations» continues co-author Elena D’Onghia. «One might even think they’ve seen the movie as seven of them are associated with The Magellanic Clouds, the largest satellites of the Milky Way that are easily seen if you are lucky enough to view the sky from the Southern Hemisphere».
In the past, other researchers have noticed that as galaxies form hierarchically in the Universe, that many of the pieces come in as groups of small objects. «The critical element of these groups of dwarfs isn’t that they are a club, but rather they have a ‹dwarf leader› or ‹parent›. When events in the early Universe expels the gas in the smallest object, the dwarf leader shepherds this gas and allows its small companions to recapture it at later times» says D’Onghia.
Lake and D’Onghia have put all these puzzle pieces together to propose that the Magellanic Clouds were the largest members of a group of dwarf galaxies that entered the Milky Way dark halo not long ago. Seven of the eleven brightest satellite galaxies of our Milky Way were part of this group. New simulations performed at the University of Zurich show that it is typical for dwarf galaxies to form in groups and enter large galaxies at late times. The group is then disrupted by tidal forces, spreading the small population of luminous dwarfs around the Milky Way making the satellite galaxies we observe today.
New measurements by scientists at Harvard University including Nitya Kallivayalil and Gurtina Besla indicate that the Magellanic Clouds are moving faster than previously believed and may have entered the Milky Way recently. «The scenario proposed by D’Onghia and Lake fits in well with these observational determinations and may account for many facets of the satellite population of the Milky Way», according to Lars Hernquist of Harvard University.
As well as wrapping up several problems in galaxy formation, their theory makes clear predictions that will be tested rapidly. One such prediction is that isolated dwarf and satellite galaxies will be found to have companions. Since their theory was first circulated, the dwarf galaxy Leo IV was found to have another little Leo V companion in July. The existence of nearby dwarf associations also supports this new theory.
Lake and D’Onghia are located in the Institute of Theoretical Physics at the University of Zurich. This Institute is known for the pioneering work in relativity and cosmology. Most recently, they have been leaders in predicting the distribution and properties of dark matter in the Universe.
Beat Mueller | alfa
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | 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
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:fb781e4a-d3e9-42cf-8ce9-f0411c578a28> | 3.40625 | 1,454 | Content Listing | Science & Tech. | 44.043903 | 95,487,489 |
posted by missy
I really need help on this problem.
A sector has area of 15 in^2 and central angle of 0.2 radians. Find the radius of the circle and arc length of the sector
area of whole circle /15 = 2π/.2
area of whole circle = 30π/.2 = 150π
then πr^2 = 150π
r^2 = 150
r = √150 = 5√6
arclength = rØ = 5√6(.2) = √6
or if you don't know that formula .....
arc /(2π(5√6) = .2/(2π)
arc = 2π(5√6)(.2)/(2π) = √6 | <urn:uuid:158ba264-e59f-4495-8888-5e9ba5651e5b> | 3.03125 | 170 | Q&A Forum | Science & Tech. | 130.495143 | 95,487,490 |
Natur & Miljø i Costa Rica: Månedsrapport
- Ankomst til destinationen
- Fleksible Startdatoer
- Støtte & Sikkerhed
- Praktisk Information
Conservation in Costa Rica - Monthly - Update January - February 2015
With the beginning of the year came new goals and opportunities for the Costa Rica team. We continued with the hard work of saving the scarlet macaws, we started compiling a guide to the different butterfly species that have been found in the park over the last years and we also started with environmental education in schools.
Scarlet Macaw Nest Site Protection
Around 1,000 scarlet macaws live in Costa Rica. Although there are already protected areas dedicated to the protection of this species, the number still decreases. The most serious threat to the scarlet macaw is poaching – because of poverty (and greed) farmers are forced to steal to save money for their family. Athough this trade is illegal, there are still people who want to buy the birds and as such, the macaws remain at risk.
For this reason, we have had this project running for three years in an effort to save this beautiful species and their habitat. This is the “Return of the Macaw Project”. The scarlet macaw (Ara macao) is a large bird of bright colours and can grow to about 79 inches, weighing about 900 grams. Most of their feathers are red, except for the wings, which are blue and yellow. The scarlet macaw has no feathers around the eyes and is characterised by its long blue tail. There is no visible difference between the sexes, although juvenile birds have black eyes, while the older birds’ eyes are yellow. The scarlet macaw’s beak is hooked and very sharp, which allows it to open the hard seeds that it feeds on.
We had a successful start to the year when we found a couple in the same nest. Last year when we climbed this tree, we found four eggs. Unfortunately, these eggs did not hatch. This could be for many reasons, one of which is climate change. We will now start new research in the macaw nests using a “datalogger” to record the temperature and the humidity. Every macaw nest will have a device that tells us the conditions of the nest, so that we can compare it with the success of the hatch.
We started this year with an ambitious project – to plant more than 4000 trees around the National Park. We will do this together with the people who are in charge of the “water services” for every village. They take the water from the river source, so it is in this river source that we will plant the trees using only native species, such as:
- Cocobolo (Dalbergia retusa)
- Guanacaste (Enterolobium ciclocarpum)
- Espavel (Anacardium excelcium)
We have also been in several meetings with the people of the village and we have visited the places where we will be planting the trees. We have a big job ahead but we are excited to be a part of the conservation of the water source around the village.
We have once again started the butterfly project in the Barra Honda National Park. One of the changes has been the sampling site. Last year we worked in different transects, using two methodologies. One of them was the use of the hand traps, and the other using aerial traps tied in trees.
We are now doing the butterfly project on the trails using hand traps, and in the sampling areas we are using the aerial traps.
Education is the best way to make a change in the world and this is why we have started environmental education this year. We are currently working in five different schools teaching the children about different conservation topics. We cover subjects such as: biodiversity, flora and fauna, forest fires, conservation and protection and ecosystems.
Until next time,
Conservation Manager, Costa Rica | <urn:uuid:cbd3e508-0386-402c-810e-37faa755f47a> | 2.671875 | 842 | News (Org.) | Science & Tech. | 49.737768 | 95,487,492 |
Slideshow: Fossil Hunting in the Andes
Central Chile's rugged Andes mountains preserve some of South America's best mammal fossils. But finding them requires endurance, persistence--and a willingness to climb.
view the slideshow Credits: TRYSTAN HERRIOTT
Even on days our fossil hunting turns up nothing new, we revel in the splendor of landscape all around us--such as this striking view of Antuco volcano from one of our localities in the Lake Laja region...
Rocky outcrops above the El Pino River in the Lake Laja region also turned out to contain ancient mammal fossils.
This precipitous site in the Cachapoal River drainage is where we discovered a five-centimeter-long skull of New World monkey we named Chilecebus carrascoensis. Note the person (inside white ellipse) for scale.
ANDR? R. WYSS
More often than not, fossil sites are far from even the most primitive of roads. Here some of our team is backpacking into a site a site about 100 kilometers north of Tinguiririca , in the drainage basin of the Cachapoal River . This locality produced one of our best fossils--the most complete skull of an early New World monkey ever discovered. ANDR? R. WYSS Advertisement
LOST IN LAJA:
Here we are somewhere in Estero Trapa Trapa (nearly Lake Laja) trying to figure out where we are. I (Wyss) consult the GPS while John Flynn (middle) and Darin Croft study the maps.
WALKING TO THE OUTCROP:
Even for areas that we can approach by truck, such as this one near Lake Laja, it is usually a fair hike to the outcrop for a day’s fossil hunting.
EASIER WAY AROUND:
Sometimes we can actually get a pickup truck within a few kilometers of a fossil site. Here are some of our crew members below fossiliferous outcrop we call Cerro Los Pinos near Lake Laja, which is about 300 kilometers south of the Tinguiririca valley.
NO HORSING AROUND:
Riding cross-country on horseback is another way we get around central Chile’s rugged terrain. On the day this photograph was taken, we had spent most of a day trying to find a suitable camping spot for exploring a promising locality near the Teno River. The guy on horseback on the far right is me (Wyss). The other people in the picture are Chilean geologist Reynaldo Charrier (standing) and two Chilean cowboys. The photographer was geologist Philip Gans, one of my fellow faculty members from the University of California, Santa Barbara. He recalls this day as being “fairly odd from a culinary standpoint.” Gans writes, “Andy and I set off on foot to explore, and everyone else and all the horses (and unfortunately all of the food) went back down to the drainage to find a different way up to our target site, so we did not see them again for about 6 or 7 hours. All we had had to eat that day was a little coffee (with milk from one of the mares!) and a little piece of empanada, so by the time we finally hooked up [with the group] again, I think Andy and I were pretty hungry. Actually, I was a little better off, because in my pack I was carrying two dozen fresh eggs. Along about mid-afternoon, I suddenly remembered I had these, and in desperation I ate a couple warm, raw eggs to tide me over.”
PHILIP GANS Advertisement
In the spring of 1994, reconstruction of the small road leading into the Tinguiririca valley was especially slow, but we did not learn of this impediment until arriving on the scene. Turning frustration into an opportunity, we began explorations outside the Tinguiririca valley. We soon found more fossiliferous localities, and most of them were quite remote and only accessible by long approaches by helicopter or other means.
Here is team member Franyo Zapatta, a Chilean geology student, having just reached the fossil-bearing outcrop we call Tapado. Some of our best fossils come from this perch—Andy’s Rule strikes again! Tapado lies just a few kilometers west of our first discovery site in the Tinguiririca valley, but the mammal remains we found there are several million years older. This view is looking east, up the valley toward the town of Termas del Flaco, which is visible in valley floor (
white oval). ANDR? R. WYSS
TRICKY RIVER CROSSING:
We had to ford the raging Tinguiririca River without a bridge to reach the second major cache of mammal fossils we found in the Tinguiririca Valley. This photograph yet again encapsulates “Andy’s Rule,” which says that the harder an outcrop is to reach, the likelier it is to contain fossils. (The yellow box indicates the location from which following photo was taken, and the yellow arrow shows the direction of that view.)
ANDR? R. WYSS
This view--due east, with the skyline marking the border with Argentina--leaves no doubt about the incline of the slopes flanking the Tinguriririca River. For a sense of scale, look closely for our team’s cluster of half a dozen camping tents (inside the white circle), near the edge of the purplish-brown, fossil-bearing rocks. During three full field seasons prospecting this locality, we turned up at least 25 species of 32-million-year-old mammals--most of which are new to science.
ANDR? R. WYSS Advertisement
FOSSIL DISCOVERY TREK
After several hours of trudging up the steep southern slopes of the Tinguiririca valley near Termas del Flaco (which is visible in the valley floor), the two of us reached the highest ridge in the late afternoon. A bit disappointed about not finding any fossils on the way up, we looked for a milder route down. Not long after, we crossed a patch of volcanic sediments that turned out to contain remains of an amazing variety of ancient mammals, including an early sloth and a chinchillalike rodent.
ANDR? R. WYSS
Our first fossil reconnaissance trip to central Chile culminated here at the summer resort village of Termas del Flaco. On the last day of that expedition, we split up to prospect the precipitous slopes flanking each side of the Tinguriririca River, which flows briskly along the southern edge of the town’s hot spring pools. That afternoon, another team member and I discovered the first cache of mammal fossils in a layer of purplish-brown volcanic sediments nearly 1,000 meters above the valley floor.
ANDR? R. WYSS
Rocks exposed above central Chile’s Lake Teno contain fossil mammals buried in mudflows from one of this volcano’s ancient predecessors.
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You may want to have a look at Help with the concept of closures.
and Closure on Closures
. A closure is basically a piece of code that can be executed outside of the scope it was defined, but can still remembers things from that scope. I know you were asking specific questions but I feel those two links will help give you a broader and deeper understanding of the concept.
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Group 3 element
|Group 3 in the periodic table|
21 Transition metal
39 Transition metal
* Whether the elements lutetium (Lu) and lawrencium (Lr), in period 6 and 7, are in group 3 is disputed. The grouping used in this article places La and Ac in group 3, which is the most common form. For other groupings, see group 3 borders.
Group 3 is a group of elements in the periodic table. This group, like other d-block groups, should contain four elements, but it is not agreed what elements belong in the group. Scandium (Sc) and yttrium (Y) are always included, but the other two spaces are usually occupied by lanthanum (La) and actinium (Ac), or by lutetium (Lu) and lawrencium (Lr); less frequently, it is considered the group should be expanded to 32 elements (with all the lanthanides and actinides included) or contracted to contain only scandium and yttrium. When the group is understood to contain all of the lanthanides, its trivial name is the rare-earth metals.
Three group 3 elements occur naturally, scandium, yttrium, and either lanthanum or lutetium. Lanthanum continues the trend started by two lighter members in general chemical behavior, while lutetium behaves more similarly to yttrium. While the choice of lutetium would be in accordance with the trend for period 6 transition metals to behave more similarly to their upper periodic table neighbors, the choice of lanthanum is in accordance with the trends in the s-block, which the group 3 elements are chemically more similar to. They all are silvery-white metals under standard conditions. The fourth element, either actinium or lawrencium, has only radioactive isotopes. Actinium, which occurs only in trace amounts, continues the trend in chemical behavior for metals that form tripositive ions with a noble gas configuration; synthetic lawrencium is calculated and partially shown to be more similar to lutetium and yttrium. So far, no experiments have been conducted to synthesize any element that could be the next group 3 element. Unbiunium (Ubu), which could be considered a group 3 element if preceded by lanthanum and actinium, might be synthesized in the near future, it being only three spaces away from the current heaviest element known, oganesson.
In 1787, Swedish part-time chemist Carl Axel Arrhenius found a heavy black rock near the Swedish village of Ytterby, Sweden (part of the Stockholm Archipelago). Thinking that it was an unknown mineral containing the newly discovered element tungsten, he named it ytterbite.[note 1] Finnish scientist Johan Gadolin identified a new oxide or "earth" in Arrhenius' sample in 1789, and published his completed analysis in 1794; in 1797, the new oxide was named yttria. In the decades after French scientist Antoine Lavoisier developed the first modern definition of chemical elements, it was believed that earths could be reduced to their elements, meaning that the discovery of a new earth was equivalent to the discovery of the element within, which in this case would have been yttrium.[note 2] Until the early 1920s, the chemical symbol "Yt" was used for the element, after which "Y" came into common use. Yttrium metal was first isolated in 1828 when Friedrich Wöhler heated anhydrous yttrium(III) chloride with potassium to form metallic yttrium and potassium chloride.
In 1869, Russian chemist Dmitri Mendeleev published his periodic table, which had empty spaces for elements directly above and under yttrium. Mendeleev made several predictions on the upper neighbor of yttrium, which he called eka-boron. Swedish chemist Lars Fredrik Nilson and his team discovered the missing element in the minerals euxenite and gadolinite and prepared 2 grams of scandium(III) oxide of high purity. He named it scandium, from the Latin Scandia meaning "Scandinavia". Chemical experiments on the element proved that Mendeleev's suggestions were correct; along with discovery and characterization of gallium and germanium this proved the correctness of the whole periodic table and periodic law. Nilson was apparently unaware of Mendeleev's prediction, but Per Teodor Cleve recognized the correspondence and notified Mendeleev. Metallic scandium was produced for the first time in 1937 by electrolysis of a eutectic mixture, at 700–800 °C, of potassium, lithium, and scandium chlorides.
In 1751, the Swedish mineralogist Axel Fredrik Cronstedt discovered a heavy mineral from the mine at Bastnäs, later named cerite. Thirty years later, the fifteen-year-old Vilhelm Hisinger, from the family owning the mine, sent a sample of it to Carl Scheele, who did not find any new elements within. In 1803, after Hisinger had become an ironmaster, he returned to the mineral with Jöns Jacob Berzelius and isolated a new oxide which they named ceria after the dwarf planet Ceres, which had been discovered two years earlier. Ceria was simultaneously independently isolated in Germany by Martin Heinrich Klaproth. Between 1839 and 1843, ceria was shown to be a mixture of oxides by the Swedish surgeon and chemist Carl Gustaf Mosander, who lived in the same house as Berzelius: he separated out two other oxides which he named lanthana and didymia. He partially decomposed a sample of cerium nitrate by roasting it in air and then treating the resulting oxide with dilute nitric acid. Since lanthanum's properties differed only slightly from those of cerium, and occurred along with it in its salts, he named it from the Ancient Greek λανθάνειν [lanthanein] (lit. to lie hidden). Relatively pure lanthanum metal was first isolated in 1923.
Lutetium was independently discovered in 1907 by French scientist Georges Urbain, Austrian mineralogist Baron Carl Auer von Welsbach, and American chemist Charles James as an impurity in the mineral ytterbia, which was thought by most chemists to consist entirely of ytterbium. Welsbach proposed the names cassiopeium for element 71 (after the constellation Cassiopeia) and aldebaranium (after the star Aldebaran) for the new name of ytterbium but these naming proposals were rejected, although many German scientists in the 1950s called the element 71 cassiopeium. Urbain chose the names neoytterbium (Latin for "new ytterbium") for ytterbium and lutecium (from Latin Lutetia, for Paris) for the new element. The dispute on the priority of the discovery is documented in two articles in which Urbain and von Welsbach accuse each other of publishing results influenced by the published research of the other. The Commission on Atomic Mass, which was responsible for the attribution of the names for the new elements, settled the dispute in 1909 by granting priority to Urbain and adopting his names as official ones. An obvious problem with this decision was that Urbain was one of the four members of the commission. The separation of lutetium from ytterbium was first described by Urbain and the naming honor therefore went to him, but neoytterbium was eventually reverted to ytterbium and in 1949, the spelling of element 71 was changed to lutetium. Ironically, Charles James, who had modestly stayed out of the argument as to priority, worked on a much larger scale than the others, and undoubtedly possessed the largest supply of lutetium at the time.
André-Louis Debierne, a French chemist, announced the discovery of actinium in 1899. He separated it from pitchblende residues left by Marie and Pierre Curie after they had extracted radium. In 1899, Debierne described the substance as similar to titanium and (in 1900) as similar to thorium. Friedrich Oskar Giesel independently discovered actinium in 1902 as a substance being similar to lanthanum and called it "emanium" in 1904. After a comparison of the substances half-lives determined by Debierne, Hariett Brooks in 1904, and Otto Hahn and Otto Sackur in 1905, Debierne's chosen name for the new element was retained because it had seniority, despite the contradicting chemical properties he claimed for the element at different times.
Lawrencium was first synthesized by Albert Ghiorso and his team on February 14, 1961, at the Lawrence Radiation Laboratory (now called the Lawrence Berkeley National Laboratory) at the University of California in Berkeley, California, United States. The first atoms of lawrencium were produced by bombarding a three-milligram target consisting of three isotopes of the element californium with boron-10 and boron-11 nuclei from the Heavy Ion Linear Accelerator (HILAC). The nuclide 257103 was originally reported, but then this was reassigned to 258103. The team at the University of California suggested the name lawrencium (after Ernest O. Lawrence, the inventor of cyclotron particle accelerator) and the symbol "Lw", for the new element, but "Lw" was not adopted, and "Lr" was officially accepted instead. Nuclear-physics researchers in Dubna, Soviet Union (now Russia), reported in 1967 that they were not able to confirm American scientists' data on 257103. Two years earlier, the Dubna team reported 256103. In 1992, the IUPAC Trans-fermium Working Group officially recognized element 103, confirmed its naming as lawrencium, with symbol "Lr", and named the nuclear physics teams at Dubna and Berkeley as the co-discoverers of lawrencium.
So far, no experiments were conducted to synthesize any element that could be the next group 3 element; if lutetium and lawrencium are considered to be group 3 elements, then the next element in the group should be element 153, unpenttrium (Upt). However, after element 120, filling electronic configurations stops obeying Aufbau principle. According to the principle, unpenttrium should have an electronic configuration of [Og]8s25g186f147d1[note 3] and filling the 5g-subshell should be stopped at element 138. However, the 7d-orbitals are calculated to start being filled on element 137, while the 5g-subshell closes only at element 144, after filling of 7d-subshell begins. Therefore, it is hard to calculate which element should be the next group 3 element. Calculations suggest that unpentpentium (Upp, element 155) could also be the next group 3 element. If lanthanum and actinium are considered group 3 elements, then element 121, unbiunium (Ubu), should be the fifth group 3 element. The element is calculated have electronic configuration of [Og]8s28p1/21, which is not associated with transition metals, without having a partially filled d-subshell. No experiments have been performed to create unpenttrium, unbiunium or any element that could be considered the next group 3 element; however, unbiunium is the element with the lowest atomic number that has not been tried to be created and thus has chances to be, while unpenttrium, unpentpentium or any other element considered if preceded by lawrencium is very unlikely to be created due to drip instabilities that imply that the periodic table ends soon after the island of stability at unbihexium.
|21||scandium||2, 8, 9, 2|
|39||yttrium||2, 8, 18, 9, 2|
|57||lanthanum||2, 8, 18, 18, 9, 2|
|89||actinium||2, 8, 18, 32, 18, 9, 2|
Like other groups, the members of this family show patterns in their electron configurations, especially the outermost shells, resulting in trends in chemical behavior. However, lawrencium is an exception, since its last electron is transferred to the 7p1/2 subshell due to relativistic effects.
Most of the chemistry has been observed only for the first three members of the group; chemical properties of both actinium and especially lawrencium are not well-characterized. The remaining elements of the group (scandium, yttrium, lutetium) are reactive metals with high melting points (1541 °C, 1526 °C, 1652 °C respectively). They are usually oxidized to the +3 oxidation state, even though scandium, yttrium and lanthanum can form lower oxidation states. The reactivity of the elements, especially yttrium, is not always obvious due to the formation of a stable oxide layer, which prevents further reactions. Scandium(III) oxide, yttrium(III) oxide, lanthanum(III) oxide and lutetium(III) oxide are white high-temperature-melting solids. Yttrium(III) oxide and lutetium(III) oxide exhibit weak basic character, but scandium(III) oxide is amphoteric. Lanthanum(III) oxide is strongly basic.
Elements that show tripositive ions with electronic configuration of a noble gas (scandium, yttrium, lanthanum, actinium) show a clear trend in their physical properties, such as hardness. At the same time, if group 3 is continued with lutetium and lawrencium, several trends are broken. For example, scandium and yttrium are both soft metals. Lanthanum is soft as well; all these elements have their outermost electrons quite far from the nucleus compared to the nuclei charges. Due to the lanthanide contraction, lutetium, the last in the lanthanide series, has a significantly smaller atomic radius and a higher nucleus charge, thus making the extraction of the electrons from the atom to form metallic bonding more difficult, and thus making the metal harder. However, lutetium suits the previous elements better in several other properties, such as melting and boiling points. Very little is known about lawrencium, and none of its physical properties have been confirmed.
|Melting point||1814 K, 1541 °C||1799 K, 1526 °C||1193 K, 920 °C||1323 K, 1050 °C|
|Boiling point||3109 K, 2836 °C||3609 K, 3336 °C||3737 K, 3464 °C||3471 K, 3198 °C|
|Density||2.99 g·cm−3||4.47 g·cm−3||6.162 g·cm−3||10 g·cm−3|
|Appearance||silver metallic||silver white||gray||silvery|
|Atomic radius||162 pm||180 pm||187 pm||215 pm|
Composition of group 3
It is disputed whether lanthanum and actinium should be included in group 3, rather than lutetium and lawrencium. Other d-block groups are composed of four transition metals,[note 6] and group 3 is sometimes considered to follow suit. Scandium and yttrium are always classified as group 3 elements, but it is controversial which elements should follow them in group 3, lanthanum and actinium or lutetium and lawrencium. Scerri has proposed a resolution to this debate on the basis of moving to a 32-column table and consideration of which option results in a continuous sequence of atomic number increase. He thereby finds that group 3 should consist of Sc, Y, Lu, Lr. The current IUPAC definition of the term "lanthanoid" includes fifteen elements including both lanthanum and lutetium, and that of "transition element" applies to lanthanum and actinium, as well as lutetium but not lawrencium, since it does not correctly follow the Aufbau principle. Normally, the 103rd electron would enter the d-subshell, but quantum mechanical research has found that the configuration is actually [Rn]7s25f147p1[note 7] due to relativistic effects. IUPAC thus has not recommended a specific format for the in-line-f-block periodic table, leaving the dispute open.
- Lanthanum and actinium are sometimes considered the remaining members of group 3. In their most commonly encountered tripositive ion forms, these elements do not possess any partially filled f-orbitals, thus continuing the scandium—yttrium—lanthanum—actinium trend, in which all the elements have relationship similar to that of elements of the calcium—strontium—barium—radium series, the elements' left neighbors in s-block. However, different behavior is observed in other d-block groups, especially in group 4, in which zirconium, hafnium and rutherfordium share similar chemical properties lacking a clear trend. It has however been argued that this is irrelevant because the principle of increasing basicity down the table is more fundamental, and because the behavior of the group 3 elements is more similar to their s-block neighbors than their d-block neighbors.
- In other tables, lutetium and lawrencium are classified as the remaining members of group 3. In these tables, lutetium and lawrencium end (or sometimes succeed) the lanthanide and actinide series, respectively. Since the f-shell is nominally full in the ground state electron configuration for both of these metals, they behave most similarly to other period 6 and period 7 transition metals compared to the other lanthanides and actinides, and thus logically exhibit properties similar to those of scandium and yttrium. However, this resemblance in not unique to lutetium and lawrencium, but is common among all the late lanthanides and actinides.
- Some tables, including the one published by IUPAC refer to all lanthanides and actinides as being in group 3: 30 lanthanide and actinide elements together with scandium and yttrium. Lanthanides, as electropositive trivalent metals, all have a closely related chemistry, and all show many similarities to scandium and yttrium, but they also show additional properties characteristic of their partially filled f-orbitals which are not common to scandium and yttrium.
- Exclusion of all elements is based on properties of earlier actinides, which show a much wider variety of chemistry (for instance, in range of oxidation states) within their series than the lanthanides, and comparisons to scandium and yttrium are even less useful. However, these elements are destabilized, and if they were stabilized to more closely match chemistry laws, they would be similar to lanthanides as well. Also, the later actinides from californium onwards behave more like the corresponding lanthanides, with only the valence +3 (and sometimes +2) shown.
- In 2015, IUPAC initiated a project to decide
... group 3 of the periodic table as consisting either of
the elements Sc, Y, Lu and Lr, or
the elements Sc, Y, La and Ac.— IUPAC,
- The project is led by Eric Scerri. Apparently, group 3 comprising 32 elements (as older periodic tables show) is not considered.
The La and Ac variant remains the most common in the literature, despite some calls for a change to the Lu and Lr variant. In terms of chemical behaviour, and trends going down group 3 for properties such as melting point, electronegativity and ionic radius, scandium, yttrium, lanthanum and actinium are similar to their group 1–2 counterparts. In this variant, the number of f electrons in the most common (trivalent) ions of the f-block elements consistently matches their position in the f-block. For example, the f-electron counts for the trivalent ions of the first three f-block elements are Ce 1, Pr 2 and Nd 3.
Scandium, yttrium, lanthanum, and lutetium tend to occur together with the other lanthanides (except promethium) in the Earth's crust, and are often harder to extract from their ores. The abundance of elements in Earth's crust for group 3 is quite low — all the elements in the group are uncommon, the most abundant being yttrium with abundance of approximately 30 parts per million (ppm); the abundance of scandium is 16 ppm, while that of lutetium is about 0.5 ppm. The abundance of lanthanum is greater, being about 35 ppm. For comparison, the abundance of copper is 50 ppm, that of chromium is 160 ppm, and that of molybdenum is 1.5 ppm.
Scandium is distributed sparsely and occurs in trace amounts in many minerals. Rare minerals from Scandinavia and Madagascar such as gadolinite, euxenite, and thortveitite are the only known concentrated sources of this element, the latter containing up to 45% of scandium in the form of scandium(III) oxide. Yttrium has the same trend in occurrence places; it is found in lunar rock samples collected during the American Apollo Project in a relatively high content as well.
The principal commercially viable ore of lutetium is the rare-earth phosphate mineral monazite, (Ce,La,etc.)PO4, which contains 0.003% of the element. The main mining areas are China, United States, Brazil, India, Sri Lanka and Australia. Pure lutetium metal is one of the rarest and most expensive of the rare-earth metals with the price about 10,000 USD/kg, or about one-fourth that of gold. Lanthanum is much more common, being the second most abundant rare earth, and in addition to monazite can also be extracted economically from bastnäsite.
The most available element in group 3 is yttrium, with annual production of 8,900 tonnes in 2010. Yttrium is mostly produced as oxide, by a single country, China (99%). Lutetium and scandium are also mostly obtained as oxides, and their annual production by 2001 was about 10 and 2 tonnes, respectively.
Group 3 elements are mined only as a byproduct from the extraction of other elements. The metallic elements are extremely rare; the production of metallic yttrium is about a few tonnes, and that of scandium is in the order of 10 kg per year; production of lutetium is not calculated, but it is certainly small. The elements, after purification from other rare-earth metals, are isolated as oxides; the oxides are converted to fluorides during reactions with hydrofluoric acid. The resulting fluorides are reduced with alkaline earth metals or alloys of the metals; metallic calcium is used most frequently. For example:
- Sc2O3 + 3 HF → 2 ScF3 + 3 H2O
- 2 ScF3 + 3 Ca → 3 CaF2 + 2 Sc
Group 3 elements are generally hard metals with low aqueous solubility, and have low availability to the biosphere. No group 3 element has any documented biological role in living organisms. The radioactivity of the actinides generally makes them highly toxic to living cells, causing radiation poisoning.
Scandium has no biological role, but it is found in living organisms. Once reached a human, scandium concentrates in the liver and is a threat to it; some its compounds are possibly carcinogenic, even through in general scandium is not toxic. Scandium is known to have reached the food chain, but in trace amounts only; a typical human takes in less than 0.1 micrograms per day. Once released into the environment, scandium gradually accumulates in soils, which leads to increased concentrations in soil particles, animals and humans. Scandium is mostly dangerous in the working environment, due to the fact that damps and gases can be inhaled with air. This can cause lung embolisms, especially during long-term exposure. The element is known to damage cell membranes of water animals, causing several negative influences on reproduction and on the functions of the nervous system.
Yttrium has no known biological role, though it is found in most, if not all, organisms and tends to concentrate in the liver, kidney, spleen, lungs, and bones of humans. There is normally as little as 0.5 milligrams found within the entire human body; human breast milk contains 4 ppm. Yttrium can be found in edible plants in concentrations between 20 ppm and 100 ppm (fresh weight), with cabbage having the largest amount. With up to 700 ppm, the seeds of woody plants have the highest known concentrations.
Lutetium has no biological role as well, but it is found even in the highest known organism, the humans, concentrating in bones, and to a lesser extent in the liver and kidneys. Lutetium salts are known to cause metabolism and they occur together with other lanthanide salts in nature; the element is the least abundant in the human body of all lanthanides. Human diets have not been monitored for lutetium content, so it is not known how much the average human takes in, but estimations show the amount is only about several micrograms per year, all coming from tiny amounts taken by plants. Soluble lutetium salts are mildly toxic, but insoluble ones are not. Lanthanum is not essential for humans and has a low to moderate level of toxicity. However, it is essential for the methanotrophic bacterium Methylacidiphilum fumariolicum SolV, although the general similarity of the rare earths means that it may be substituted by some of the other early lanthanides with no ill effects.
The high radioactivity of lawrencium would make it highly toxic to living cells, causing radiation poisoning. The same is true for actinium.
The Scandium sub-group comprises Scandium (sc),yttrium (Y) Lanthanum (La) and Actinium (Ac). In addition, the element of the cerium and thorium families are also included in the sub-group. the main characteristics of scandium and its analogous are summarised below: Atomic No. ( Sc)21 ( Y)39 ( La )57 Atomic wt. (44.95) (88A^9) (138;9) Valency electron. (3d'4s2) Scandium and its analogous are the first d-elements of thair period i.e.they are the first whose d-subs-hell of the penultimate shell being to be filled the presency of just one electron in the d-state accounts for the stabiliry oxidation state of III in scandium and its analogous. the stable co-ordonationv number increases in the transition from scandium to yttrium and
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- Kang, Weekyung; Bernstein, E. R. (2005). "Formation of Yttrium Oxide Clusters Using Pulsed Laser Vaporization". Bull. Korean Chem. Soc. 26 (2): 345–348. doi:10.5012/bkcs.2005.26.2.345.
- Cotton, S. A. (1994). "Scandium, Yttrium and the Lanthanides: Inorganic and Coordination Chemistry". Encyclopedia of Inorganic Chemistry. John Wiley & Sons. ISBN 0-471-93620-0.
- Dean, John A. (1999). Lange's handbook of chemistry (Fifteenth edition). McGraw-Hill, Inc. pp. 589–592. ISBN 0-07-016190-9.
- Barbalace, Kenneth. "Periodic Table of Elements Sorted by Melting Point". Environmental Chemistry.com. Retrieved 2011-05-18.
- Barbalace, Kenneth. "Periodic Table of Elements Sorted by Boiling Point". Environmental Chemistry.com. Retrieved 2011-05-18.
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- Barbalace, Kenneth. "Scandium". Chemical Book. Retrieved 2011-05-18.
- Barbalace, Kenneth. "Yttrium". Chemical Book. Retrieved 2011-05-18.
- Scerri, Eric (2012). "Mendeleev's Periodic Table Is Finally Completed and What To Do about Group ?". Chem. Int. 34 (4): 28–31. doi:10.1515/ci.2012.34.4.28.
- IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "transition element".
- Barbalace, Kenneth. "Periodic Table of Elements". Environmental Chemistry.com. Retrieved 2007-04-14.
- "WebElements Periodic Table of the Elements". Webelements.com. Retrieved 2010-04-03.
- "Periodic Table of the Elements". International Union of Pure and Applied Chemistry (IUPAC). Retrieved 2010-04-03.
- "Visual Elements". Royal Society of Chemistry. Retrieved 4 July 2011.
- Dolg, Michael. "Lanthanides and Actinides" (PDF). Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany. CLA01. Retrieved 4 July 2011.
- IUPAC (2015). "The constitution of group 3 of the periodic table". Retrieved 2016-11-10.
- Greenwood, N. N.; Harrington, T. J. (1973). The chemistry of the transition elements. Oxford: Clarendon Press. p. 50. ISBN 0-19-855435-4.
- Aylward, G.; Findlay, T. (2008). SI chemical data (6th ed.). Milton, Queensland: John Wiley & Sons. ISBN 978-0-470-81638-7.
- Wiberg, N. (2001). Inorganic Chemistry. San Diego: Academic Press. p. 119. ISBN 0-12-352651-5.
- Wulfsberg, G. (2006). "Periodic table: Trends in the properties of the elements". Encyclopedia of Inorganic Chemistry. New York: John Wiley & Sons. p. 3. ISBN 978-0-470-86210-0.
- Cotton, S. (2007). Lanthanide and Actinide Chemistry. Chichester: John Wiley & Sons. p. 150. ISBN 978-0-470-01006-8.
- Bernhard, F. (2001). "Scandium mineralization associated with hydrothermal lazurite-quartz veins in the Lower Austroalpie Grobgneis complex, East Alps, Austria". Mineral Deposits in the Beginning of the 21st Century. Lisse: Balkema. ISBN 90-265-1846-3.
- Kristiansen, Roy (2003). "Scandium – Mineraler I Norge" (PDF). Stein (in Norwegian): 14–23. Archived from the original (PDF) on October 8, 2010.
- von Knorring, O.; Condliffe, E. (1987). "Mineralized pegmatites in Africa". Geological Journal. 22: 253. doi:10.1002/gj.3350220619.
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- Pol, Arjan; Barends, Thomas R. M.; Dietl, Andreas; Khadem, Ahmad F.; Eygensteyn, Jelle; Jetten, Mike S. M.; Op Den Camp, Huub J. M. (2013). "Rare earth metals are essential for methanotrophic life in volcanic mudpots". Environmental Microbiology. 16 (1): 255–64. doi:10.1111/1462-2920.12249. PMID 24034209.
- Ytterbite was named after the village it was discovered near, plus the -ite ending to indicate it was a mineral.
- Earths were given an -a ending and new elements are normally given an -ium ending.
- Unpenttrium, according to calculations, should have an electronic configuration of [Og]8s25g186f117d28p1/22.
- If lutetium and lawrencium are included instead, the table ends with the following lines:
- If lutetium and lawrencium are included instead, the table ends with the following lines (the data for lawrencium is approximate):
Properties of the group 3 elements Name Lutetium Lawrencium Melting point 1925 K, 1652 °C ? 1900 K, ? 1627 °C Boiling point 3675 K, 3402 °C ? Density 9.84 g·cm−3 ? 16 g·cm−3 Appearance silver gray ? Atomic radius 174 pm ?
- However, the group 12 elements are not always considered to be transition metals.
- The expected configuration of lawrencium if it did obey the Aufbau principle would be [Rn]7s25f146d1, with the normal incomplete 6d-subshell in the neutral state.
- Emsley, John (2001). Nature's building blocks: an A-Z guide to the elements. US: Oxford University Press. ISBN 0-19-850341-5. | <urn:uuid:df7c17d3-906c-4ff7-b698-ea5c596c7feb> | 3.640625 | 10,674 | Knowledge Article | Science & Tech. | 64.049047 | 95,487,536 |
|MLA Citation:||Bloomfield, Louis A. "Question 1558: What becomes of a log's gravitational energy when you burn it?"|
How Everything Works 16 Jul 2018. 16 Jul 2018 <http://howeverythingworks.org/print1.php?QNum=1558>.
But appearances can be deceiving. Since energy is a conserved quantity, the energy that you invest in the firewood can't disappear. It simply becomes difficult to find because it is dispersed in the burned gases that were once the wood.
To find that energy, imagine compressing the burned gases into a small container to make their weight more noticeable and reduces buoyant effects due to the atmosphere. You could then carry those burned gases, which include all of the firewood's atoms, back down the hill. As you descended, the container of burned gases would transfer its gravitational potential energy to you.
I've swept a number of details under the rug, such as the fact that many of the oxygen atoms in your container were originally part of the atmosphere rather than the log. But even when all those details are taken into account, the answer is the same: the firewood's gravitational energy doesn't disappear, it just gets more difficult to find. | <urn:uuid:be6a1629-fab8-4eae-8b28-886dfed7b5d3> | 2.796875 | 255 | Q&A Forum | Science & Tech. | 55.601164 | 95,487,577 |
HTML/CGI Web Server Interface
Chapter Updated 2/1/99
The main objective of this chapter is to provide information regarding the
basic concepts of utlilizing the HTML/CGI interface with Xbase.
The HTML/CGI interface is designed to work with web server technologies such
as the Apache Web Server. The HTML class is a user interface
included with Xbase DBMS.
Utilizing this technolgy leverages on the ability to generate code which is
useable on a wide variety of client platforms. Any platform which runs a
browser program can access Xbase DBMS applications running on a web
Before using this class, it would be helpful to have an
understanding of how HTML works, which is beyond the scope of this chapter.
The HTML class is relatively simple. When the class initializes, the
class constructor creates an internal two dimensional array with field
names and data. The array
is accessed by the GetData, GetArraryNo and GetDataForField methods.
There is one sample form testhtml.html
and one sample program testhtml.cpp
which demonstrate the use of the HTML class.
Apache Install Hints
To run cgi scripts with apache, the recommended approach is to compile
programs with a .cgi extension. If the executable programs are not kept
int the cgi-bin directory, then you will need to add a handler
to your Apache configuration script.
Addtionally, in the Directory stanzas, add ExecCGI to the Options clause.
Additional handler statement:
AddHandler cgi-script .cgi
< Directory /usr/local/myproject >
Options ExecCGI Indexes
allow from all
< /Directory >
Send me mail - firstname.lastname@example.org | <urn:uuid:dc591901-d208-451d-a206-f4fce66181d7> | 2.875 | 385 | Documentation | Software Dev. | 46.368062 | 95,487,604 |
Cleaning to corallivory: ontogenetic shifts in feeding ecology of tubelip wrasse
- 205 Downloads
Cleaning and corallivory are two prevalent feeding modes among coral reef fishes. Some fishes exhibit ontogenetic shifts between cleaning behaviour and corallivory, suggesting some common physiological or morphological adaptations suited to these highly contrasting feeding habits. This study investigated ontogenetic changes in feeding behaviour for three species of coral-feeding wrasses (F: Labridae). All three species (Labrichthys unilineatus, Labropsis alleni and Diproctacanthus xanthurus) exhibited substantial changes in feeding behaviour from juvenile to adult size classes. While L. unilineatus was corallivorous throughout its entire life, the coral taxa consumed varied greatly with ontogeny. Labropsis alleni and D. xanthurus exhibited pronounced changes, with juveniles cleaning before a switch to obligate corallivory at approximately 3.5–5 cm. The ability of L. alleni and D. xanthurus to adopt a cleaning strategy may be a consequence and their close relationship to the obligate cleaner wrasses (Genus: Labroides).
KeywordsOntogeny Labridae Coral-feeding Cleaning behaviour Specialisation
This study was completed in partial fulfilment of an honours degree in Marine Biology at James Cook University. The author greatly appreciates the assistance of T. Petray who helped collect field data. Thanks to M. Pratchett, G. Jones and two anonymous reviewers for helpful comments on earlier versions of this manuscript.
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- Choat JH (1991) Biology of herbivorous fishes on coral reefs. In: Sale PF (ed) The ecology of fishes on coral reefs. Academic Press, San Diego, California, pp 120–155Google Scholar
- Cole AJ, Pratchett MS, Jones JP (2008) Diversity and functional importance of coral-feeding fishes on tropical coral reefs. Fish Fish 9:286–307Google Scholar
- Cole AJ, Pratchett MS, Jones JP (2009) Corallivory in tubelip wrasses: diet, feeding and trophic importance. J Fish Biol (in press)Google Scholar
- Côté IM (2000) Evolution and ecology of cleaning symbiosis in the sea. Oceanogr Mar Biol Annu Rev 38:311–355Google Scholar
- Hughes TP, Baird AH, Bellwood DR, Card M, Connolly SR, Folke C, Grosberg R, Hoegh-Guldberg O, Jackson JBC, Kleypas J, Lough JM, Marshall P, Nystrom M, Palumbi SR, Pandolfi JM, Rosen B, Roughgarden J (2003) Climate change, human impacts, and the resilience of coral reefs. Science 301:929–933CrossRefPubMedGoogle Scholar
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- Wainwright PC, Bellwood DR (2002) Ecomorphology of feeding in coral reef fishes. In: Sale PF (ed) Coral reef fishes: Dynamics and diversity in a complex ecosystem. Academic Press, San Diego, pp 33–55Google Scholar
- Youngbluth MJ (1968) Aspects of the ecology and ethnology of the cleaning fish Labroides phthirophagus Randall. Z Tierpsychol 25:915–932Google Scholar | <urn:uuid:7738b150-3443-4289-b43e-311418d37f88> | 2.734375 | 864 | Academic Writing | Science & Tech. | 37.65564 | 95,487,616 |
The California condor was one of the first species to be listed under the Endangered Species Preservation Act in 1966 when the population was reduced to a handful of birds.
Through a massive collaborative effort that included fieldwork and breeding in zoos, the condor population has grown to more than 400 birds, more than half of which are now free-flying in the wild.
Unfortunately, there is overwhelming evidence that lead poisoning from accidental ingestion of spent ammunition is the leading cause of death in the wild population, and this may prevent the establishment of self-sustaining populations.
"After reviewing nearly 20 years of our mortality data on the free-ranging birds, it became clear that lead poisoning is the primary problem for the birds in the wild. And this is not just a problem for California condors.
We can view them as an indicator species, warning us about the hazards of widespread lead contamination in the environment." said Bruce Rideout, director of the wildlife disease laboratories for San Diego Zoo Global.
Our collaborators at the Wildlife Health Center at the School of Veterinary Medicine, University of California at Davis recently published a review of the impact of lead in ammunition on scavenging birds and what it means for the health of our shared environment. The review article can be found in the January edition of the journal EcoHealth.
Bringing species back from the brink of extinction is the goal of San Diego Zoo Global. As a leader in conservation, the work of San Diego Zoo Global includes onsite wildlife conservation efforts (representing both plants and animals) at the San Diego Zoo, San Diego Zoo Safari Park, and San Diego Zoo Institute for Conservation Research, as well as international field programs on six continents.
The important conservation and science work of these entities is made possible by the San Diego Zoo Global Wildlife Conservancy and is supported in part by the Foundation of San Diego Zoo Global.
Christina Simmons | 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:41832aa7-f106-4fa9-a301-8d0e8cdc908e> | 3.671875 | 1,046 | Content Listing | Science & Tech. | 40.398209 | 95,487,637 |
Breaking News Emails
For decades, NASA has relied on an efficient but highly toxic fuel known as hydrazine to power satellites and manned spacecraft. Now the agency is laying the groundwork to replace that propellant with a safer, cleaner alternative.
NASA's Green Propellant Infusion Mission, or GPIM, has passed its first thruster pulsing test, a major milestone that paves the way for a planned test flight in 2015, agency officials said. NASA unveiled the rocket thruster success Tuesday in Washington, D.C., during a briefing with aerospace industry officials and Colorado Sen. Mark Udall, D-Colo.
The GPIM initiative aims to demonstrate that a green fuel with nearly 50 percent better performance than hydrazine could power Earth-circling satellites and eventually deep space missions. [Images: Superfast Spacecraft Propulsion Concepts]
Hydrazine has powered satellites and manned spacecraft for years, but it is highly flammable and corrosive, making it dangerous and expensive to transport. Since the fuel can be extremely harmful if it is inhaled or touches the skin, it is handled by workers wearing inflatable suits.
The new rocket fuel, dubbed AF-M315E, is far more benign; it is stored in glass jars and has been described as less toxic than caffeine.
The propellant is an energetic ionic liquid that evaporates more slowly and requires more heat to ignite than hydrazine, making it more stable and much less flammable.Its main ingredient is hydroxyl ammonium nitrate, and when it burns, it gives off nontoxic gasses like water vapor, hydrogen and carbon dioxide.
Importantly, M315E is safe enough to be loaded into a spacecraft before it goes to the launch pad, which would cut the time and cost of ground processing for a vehicle headed for space.
"In today's world you cannot and do not want to load a spacecraft with hydrazine and ship it," said Michael Gazarik, associate administrator for NASA's Space Technology Mission Directorate (STMD).
Udall said the new propellant will cause less harm to the environment, boost fuel efficiency and pave the way for more complex launches.
"I don't know what there isn't to like in there," he told reporters Tuesday.
A company based in Udall's home state, Ball Aerospace, has been working with subcontractor Aerojet Rocketdyne and NASA scientists to develop a propulsion system that can handle the new environmentally friendly fuel. The project is getting support from NASA's Space Technology Mission Directorate, a new office charged with injecting money into vital technologies the space agency needs to fulfill its deep-space exploration goals.
Ball and Aerojet officials said that they successfully completed a test of the new fuel using a 22 Newton, (5 pound force) thruster, achieving an 11-hour continuous burn. In the planned 2015 demonstration flight, this thruster would fire simultaneously with four smaller 1 Newton thrusters to maneuver in space, making orbit and altitude changes.
Right now, the team working on GPIM is in the preliminary design review phase. They hope to pass a critical design review by the end of the year, which would set the stage for the green propulsion system to launch in early 2015 aboard a fly aboard a boxy satellite, the Ball Configurable Platform 100 spacecraft bus.
NASA's GPIM budget is about $42.3 million, including a contract with Ball for about $35.3 million, according to a space agency spokesperson. Ball is developing the software to fly the spacecraft and the fundamental thruster technology is being provided by Aerojet Rocketdyne. The Edwards Air Force Research Laboratory, meanwhile, is contributing all propellant required for the mission.
M315E is just one new propulsion technology NASA is exploring to make its future missions more efficient. Some options wouldn't even require propellant fuel, such as solar sails that harness energy from the sun to send a vehicle through space.
- NASA's Quest for Green Rocket Fuel | Video
- Images: Cross-Country Flight in a Solar-Powered Plane
- Rocket Science in Your Car: 7 Aerospace Technologies On the Road | <urn:uuid:3010053a-40fb-4f55-ac3f-82536cc9e890> | 2.90625 | 850 | News Article | Science & Tech. | 38.867859 | 95,487,638 |
Sclerosponges: Potential High-Resolution Recorders of Marine Paleotemperatures
Gary B. Hughes, Charles W. Thayer, 2001. "Sclerosponges: Potential High-Resolution Recorders of Marine Paleotemperatures", Geological Perspectives of Global Climate Change, Lee C. Gerhard, William E. Harrison, Bernold M. Hanson
Download citation file:
Sclerosponges have great potential as seawater temperature recorders. These animals precipitate their skeletons in carbon and oxygen isotopic equilibrium with the surrounding seawater (Druffel and Benavides, 1986). Their skeletons also display chemical properties that vary directly with changes in environmental conditions. Lack of photosynthetic symbionts allows sclerosponges to live below the photic zone, providing the potential to investigate past marine conditions beyond the range of corals. Individual sponges live for several centuries, preserving archives of pre- and postindustrial seawater variations within single specimens (Hartman and Reiswig, 1980). Crosscorrelation of successively older specimens could yield up to 2000 years of marine history. Extracting environmental information can be accomplished by determining elemental characteristics preserved in skeletal growth bands. A method is presented here that utilizes energy dispersive spectroscopy (EDS) to provide inexpensive assessment of magnesium (Mg): calcium (Ca) and chlorine (Cl): calcium (Ca) ratios at high spatial resolution, yielding environmental data with correspondingly high temporal resolution. The relationship between environmental conditions and skeletal characteristics is defined by a spectral transfer function, which can then be applied to skeletal carbonate data from ancient sponges to reconstruct past environmental conditions. Accurate reconstruction of seawater temperature and salinity variations is demonstrated here at submonthly resolution. The technique’s efficiency is ideal for documenting long, high-resolution records of marine paleoenvironments. | <urn:uuid:3ca9e394-68ca-4ced-91d1-7dbcf4c690ab> | 2.59375 | 385 | Academic Writing | Science & Tech. | -2.765331 | 95,487,641 |
Showing results for: Carbon sinks and sequestration
This book, by Klaus Lorenz and Rattan Lal, discusses the present state of knowledge on soil carbon dynamics in different types of agricultural systems, including croplands, grasslands, wetlands and agroforestry systems. It also discusses bioenergy and biochar.
A recent paper assesses the carbon implications of converting Indonesian rainforests to oil palm monocultures, rubber monocultures or rubber agroforestry systems (known as “jungle rubber”). It finds that carbon losses are greatest from oil palm plantations and lowest from jungle rubber systems, in all cases being mainly from loss of aboveground carbon stocks. The paper points out that, “Thorough assessments of land-use impacts on resources such as biodiversity, nutrients, and water must complement this synthesis on C but are still not available.”
The Hoffmann Centre at UK think tank Chatham House has produced a summary of a workshop held in January 2018 on policy implications of widespread deployment of negative emissions technologies. The workshop concluded that bioenergy with carbon capture and storage (BECCS) cannot be used at the scale assumed in emissions pathways compliant with the Paris agreement, because it would cause large land use change in regions of high biodiversity and compete with food production for land. Nevertheless, some BECCS may be needed. Direct air capture would use less land than BECCS, but there are economic and technical barriers.
The FCRN’s Tara Garnett is featured in this video by UK climate website Carbon Brief, which discusses how farmers could reduce the carbon footprint of beef production. Tara points out that production-side measures only go so far, and that consumption changes are needed as well.
The electronic Rothamsted Archive provides data on agricultural experiments (starting in 1843) and weather records (since 1853). A recent paper gives an official account of the history of the archive. The archive includes results of experiments on wheat, permanent grassland, barley, woodland and rotational systems.
A report from the National Academies of Sciences, Engineering, and Medicine summarises a webinar and workshop that addressed the current state of knowledge on managing land to remove carbon dioxide from the atmosphere, the research needed for predicting the relevant impacts of land use change and management practices and the state of knowledge on policies, incentives, and socio-economic constraints on terrestrial carbon sequestration activities.
A new paper finds that a range of “ambitious but not unrealistic” climate mitigation options could, together, mean that using bioenergy with carbon capture and storage (BECCS) is not necessary for staying within 1.5°C of warming. Mitigation options considered include limiting population, lower meat consumption and use of lab-grown meat, lifestyle changes such as lower car use, electrification of energy end-use sectors, high efficiency manufacturing, agricultural intensification and mitigation of non-CO2 greenhouse gases.
This article evaluates the “4 per 1000” initiative’s potential to increase soil organic carbon (SOC) by assessing 16 long-term soil experiments conducted by the UK based Rothamsted Research, involving 114 different soil treatments (including addition of farmyard manure (FYM), nitrogen fertilisers, pasture leys, conversion of arable land into woodland and residue incorporation) over 7–157 years.
In this paper, researchers from the Joint Research Centre of the European Commission investigate the extent to which variation in nitrous oxide (N2O) emissions may offset or enhance the mitigation effects of carbon sequestration in arable European soils. They employ a biogeochemical model with input data from ~8000 soil sampling locations to quantify CO2 and N2O flux associated with different agricultural practices aimed at carbon (C) mitigation.
This report by the Meridian Institute brings together existing information about climate change impacts and opportunities for climate adaptation and mitigation into a food systems framework.
This study, undertaken by researchers at Michigan State University and the Union of Concerned Scientists, compares the net greenhouse gas (GHG) balance of two different beef finishing systems in the Upper Midwest, of the United States: a feedlot system; and a grazing system based on adaptive multi-paddock (AMP) grazing principles.
The FAO has just published a briefing paper which proposes three ways to substantially reduce emissions from livestock production.
Using volcanic rock dust as a fertiliser on farms could offset around one tenth of global greenhouse gas emissions, according to preliminary estimates.
Scotland’s soils contain over half of the UK’s soil carbon stock, making it important to know how to avoid soil carbon loss. The Scottish landscape is currently a net sink for carbon (mainly due to forestry). A recent report assesses current knowledge on soil carbon and land use in Scotland.
A report by the European Academies’ Science Advisory Council finds that negative emissions technologies (NETs) have ‘limited realistic potential’ and cannot be relied upon to remove carbon at the rate envisaged in the Intergovernmental Panel on Climate Change (IPCC) scenarios for avoiding dangerous climate change.
This paper, by researchers from the US and the Netherlands, presents the findings of a model analysis that estimates how much soil organic carbon (SOC) has been lost, and from where, as a result of land use and land cover change (LU-LCC) associated with human agricultural activities. | <urn:uuid:336c2fd4-2d4a-4d9d-bb36-83d3c2eb8841> | 3 | 1,105 | Content Listing | Science & Tech. | 17.480111 | 95,487,644 |
The findings, published in the prestigious peer-reviewed journal Nature Materials, form part of ongoing efforts to develop new materials for gas storage applications and could have an impact in the advancement of new carbon capture products for reducing emissions from fossil fuel processes.
It focuses on the metal organic framework NOTT-202a, which has a unique honeycomb-like structural arrangement and can be considered to represent an entirely new class of porous material.
Most importantly, the material structure allows selective adsorption of carbon dioxide — while other gases such as nitrogen, methane and hydrogen can pass back through, the carbon dioxide remains trapped in the materials nanopores, even at low temperatures.
Lead researcher Professor Martin Schröder, in the University’s School of Chemistry, said: “The unique defect structure that this new material shows can be correlated directly to its gas adsorption properties. Detailed analyses via structure determination and computational modelling have been critical in determining and rationalising the structure and function of this material.”
The research team — which is included Dr Sihai Yang, Professor Alexander Blake, Professor Neil Champness and Dr Elena Bichoutskaia at Nottingham — collaborated on the project with colleagues at the University of Newcastle and Diamond Light Source and STFC Daresbury Laboratory.
NOTT-202a consists of a tetra-carboxylate ligands — a honeycomb like structure made of a series of molecules or ions bound to a central metal atom — and filled with indium metal centres. This forms a novel structure consisting of two interlocked frameworks.
State-of-the-art X-ray powder diffraction measurements at Diamond Light Source and advanced computer modelling were used to probe and gain insight into the unique carbon dioxide capturing properties of the material.
The study has been funded by the ERC Advanced Grant COORDSPACE and by an EPSRC Programme Grant ChemEnSus aimed at applying coordination chemistry to the generation of new multi-functional porous materials that could provide innovative solutions for key issues around environmental and chemical sustainability.
These projects incorporate multi-disciplinary collaborations across chemistry, physics and materials science, and aim to develop new materials that could have application in gas storage, sieving and purification, carbon capture, chemical reactivity and sensing.
Emma Thorne | EurekAlert!
Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern
20.07.2018 | Princeton University
Relax, just break it
20.07.2018 | DOE/Argonne National Laboratory
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
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The shallow habitable region of cratonal crust deforms with a strain rate on the order of approximately 10(19) s(1). This is rapid enough that small seismic events are expected on one-kilometer spatial scales and one-million-year timescales. Rock faulting has the potential to release batches of biological substrate, such as dissolved H(2), permitting transient blooms. In addition, the steady-state deformation of the brittle crust causes numerous small faults to be permeable enough (on the order of approximately 10(15) m(2)) for water to flow on a kilometer scale over relatively short geological times ( approximately 10(5) yr). Hence, active faults act as concentrated niches capable of episodically tapping resources in the bulk volume of the rock. Radiolysis and ferrous iron are potentially bases of sustainable hard-rock niches.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:95444afd-144b-4c0c-bb6e-75e7eabc27a4> | 3.375 | 200 | Academic Writing | Science & Tech. | 27.778251 | 95,487,646 |
This is an online periodic table that presents the 103 elements in a visual manner. The elements are presented along with information on thier history, chemical, and physical properties. A unique image or animation associated with these properties is also given.
4D (6-8) #1. All matter is made up of atoms, which are far too small to see directly through a microscope. The atoms of any element are alike but are different from atoms of other elements. Atoms may stick together in well-defined molecules or may be packed together in large arrays. Different arrangements of atoms into groups compose all substances.
4D (6-8) #5. Scientific ideas about elements were borrowed from some Greek philosophers of 2,000 years earlier, who believed that everything was made from four basic substances: air, earth, fire, and water. It was the combinations of these "elements" in different proportions that gave other substances their observable properties. The Greeks were wrong about those four, but now over 100 different elements have been identified, some rare and some plentiful, out of which everything is made. Because most elements tend to combine with others, few elements are found in their pure form.
4D (6-8) #6. There are groups of elements that have similar properties, including highly reactive metals, less-reactive metals, highly reactive nonmetals (such as chlorine, fluorine, and oxygen), and some almost completely nonreactive gases (such as helium and neon). An especially important kind of reaction between substances involves combination of oxygen with something elseÑas in burning or rusting. Some elements don't fit into any of the categories; among them are carbon and hydrogen, essential elements of living matter.
4D (9-12) #1. Atoms are made of a positive nucleus surrounded by negative electrons. An atom's electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. Atoms form bonds to other atoms by transferring or sharing electrons.
%0 Electronic Source %D 2011 %T Visual Elements Periodic Table %I The Royal Society of Chemistry %V 2018 %N 23 July 2018 %9 application/flash %U http://www.rsc.org/periodic-table
Disclaimer: ComPADRE offers citation styles as a guide only. We cannot offer interpretations about citations as this is an automated procedure. Please refer to the style manuals in the Citation Source Information area for clarifications. | <urn:uuid:c894db0e-f958-4ce6-9ef8-88c50ab2b875> | 3.765625 | 505 | Structured Data | Science & Tech. | 38.187046 | 95,487,679 |
Astronomers reveal a new high resolution map of the magnetic field lines in gas and dust swirling around the supermassive black hole at the centre of our Galaxy, published in a new paper in Monthly Notices of the Royal Astronomical Society. The team, led by Professor Pat Roche of the University of Oxford, created the map, which is the first of its kind, using the CanariCam infrared camera attached to the Gran Telescopio Canarias sited on the island of La Palma.
Black holes are objects with gravitational fields so strong that not even light can escape their grasp. The centre of almost every galaxy appears to host a black hole, and the one we live in, the Milky Way, is no exception. Stars move around the black hole at speeds of up to 30 million kilometres an hour, indicating that it has a mass of more than a million times our Sun.
The colour scale in the image shows the amount of infrared (heat) radiation coming from warm dust particles in the filaments and luminous stars within a light year of the Galactic centre. The position of the black hole is indicated by an asterisk. The lines trace the magnetic field directions and reveal the complex interactions between the stars and the dusty filaments, and the impact that they and the gravitational force has on them. The observations were made with the largest telescope in Europe, which allowed details of the fine structure in the magnetic fields to be revealed for the first time.
Credit: E. Lopez-Rodriguez / NASA Ames / University of Texas at San Antonio
Visible light from sources in the centre of the Milky Way is blocked by clouds of gas and dust. Infrared light, as well as X-rays and radio waves, passes through this obscuring material, so astronomers use this to see the region more clearly. CanariCam combines infrared imaging with a polarising device, which preferentially filters light with the particular characteristics associated with magnetic fields.
The new map covers a region about one light year on each side of the supermassive black hole. The map shows the intensity of infrared light, and traces magnetic field lines within filaments of warm dust grains and hot gas, which appear as thin lines reminiscent of brush strokes in a painting.
The filaments, several light years long, appear to meet close to the black hole (at a point below centre in the map), and may indicate where orbits of streams of gas and dust converge. One prominent feature links some of the brightest stars in the centre of the Galaxy. Despite the strong winds flowing from these stars, the filaments remain in place, bound by the magnetic field within them. Elsewhere the magnetic field is less clearly aligned with the filaments. Depending on how the material flows, some of it may eventually be captured and engulfed by the black hole.
The new observations give astronomers more detailed information on the relationship between the bright stars and the dusty filaments. The origin of the magnetic field in this region is not understood, but it is likely that a smaller magnetic field is stretched out as the filaments are elongated by the gravitational influence of the black hole and stars in the galactic centre.
Roche praises the new technique and the result: "Big telescopes like GTC, and instruments like CanariCam, deliver real results. We're now able to watch material race around a black hole 25,000 light years away, and for the first time see magnetic fields there in detail."
The team are using CanariCam to probe magnetic fields in dusty regions in our galaxy. They hope to obtain further observations of the Galactic Centre to investigate the larger scale magnetic field and how it links to the clouds of gas and dust orbiting the black hole further out at distances of several light years.
Helen Klus | 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:bc177b7e-b163-4648-b8f7-7110712ea1ac> | 4.125 | 1,345 | Content Listing | Science & Tech. | 42.78279 | 95,487,681 |
The following content is the second chapter of my new e-book titled “Laravel: my first framework“. This writing is copyright by Maksim Surguy. Unauthorized copy and distribution of this material is prohibited.
Chapter 2. Getting started for Development with Laravel
This chapter covers
Installing Laravel with Composer
Meeting Artisan: the command line interface
Understanding structure of a Laravel application
Creating a website with Laravel
Getting started with some PHP frameworks could be a hard and painstaking process with a steep learning curve. Fortunately this is not the case with Laravel. Laravel is beginner-friendly, easy to install and configure, and even somebody who never used another framework before could get started quickly. This chapter will first give you an idea of how development with Laravel looks like in general. Then you will meet a tool underlying Laravel called “Composer” and you will learn how to install Laravel using it. You will meet Laravel’s helper tool called “Artisan” and after that you will learn in detail about Laravel application structure. Finally, you will build a complete and functional website with Laravel. While building the site you will see the following Laravel’s features in action: routing, templating, database operations, sending mail and more. Let’s get started by taking a high level look at the process of developing an application with Laravel.
This chapter assumes that you have Apache, PHP 5.3.7 or greater with MCrypt extension installed and database engine like MySQL already installed and set up.
2.5 Development overview
In the previous chapter you have learned that Laravel comes pre-configured to work out of the box. When you have Laravel installed you can get into developing your application right away. The development process for most web applications built with Laravel generally looks like this:
Configuring database, cache, mail and other settings if necessary
Creating the end points (routes) of your application
Creating the models and the database structure for the data
Creating the controllers and integrating them with the routes and the views
Creating the view templates that will make up the user-facing side of the application
Testing the application
Refining the code of the application
Don’t worry if some of these terms are not familiar to you yet, we will be giving proper attention to all of them throughout the book. In fact, you will get to meet most of these concepts in this very chapter!
A note on design patterns
While there are many specific software development methodologies such as BDD (Behavior Driven Development), TDD (Test Driven Development), DDD (Domain Driven Design) and more, this book will try to stay neutral and follow a general simplified development model as described above
Now that you are aware of how the development process of Laravel applications looks like in general, let’s get familiar with a very important tool that Laravel uses for its architecture.
2.6 Meeting Composer
Laravel framework consists of many separate components that are downloaded and put together automatically into a framework through a special tool called “Composer”. This tool could be downloaded from http://getcomposer.org/, it is the holy grail of dependency management for PHP.
In the old days to install a PHP library or a PHP framework you could just download it as a Zip archive from a website. If those PHP libraries or frameworks were to implement third-party libraries or classes, eventually it would get hard or impossible to keep track of dependencies (due to large number of components, new versions, bug fixes or patches coming out). There were a few attempts at solving the dependency management problem in PHP community in the past. Maybe such things as PEAR or PECL sound familiar to you? Those are some of the popular PHP dependency managers but due to their shortcomings they are failing at delivering the promised efficiency when it comes to publishing new dependencies or managing already existing ones inside a library or a framework. Learning from past mistakes and from other software development ecosystems, PHP community eventually came up with a tool that is flexible, powerful and easy to use – Composer.
Being a tool like “npm” for NodeJS or “RubyGems” for Ruby, Composer allows PHP developers, including those who develop with Laravel, to easily specify which other PHP libraries are used in their code or initiate installation and update of those dependencies through the command line. Composer has been around since 2011 but just like Laravel, matured very quickly into a solution that many developers love to use. Before creating your own library be sure to check Composer’s website for existing solutions because there are thousands of packages to choose from.
Making Composer as the tool of choice for installing Laravel and managing its components allows for great flexibility and extendibility of Laravel applications.
2.7 Installing Laravel
When you have Composer configured (see Appendix for instructions on that), you can install and start using Laravel by just executing one command in the command line replacing “companySite” with the name of your project:
After executing this command from the command line Composer will download all components that Laravel is comprised of and weave them together into a framework ready to become your next web application.
You will need to run this command for every new Laravel project unless you create some base template that you could use for all of your applications
2.8 Meeting Artisan: Laravel’s command line interface
Laravel comes pre-packaged with a powerful command line interface (CLI) called “Artisan”. Many repetitive tasks like model creation, running database migrations, launching development server and more can be executed with Artisan. Besides over 30 built-in commands Laravel allows for creation of custom commands.
Artisan Command Line Tool, or Artisan CLI, is a helper tool that comes with Laravel and could be used through operating system’s command line to accelerate development of a web application.
You can run Artisan commands through your system’s command line (ex. Terminal on Mac OS X). Navigate to your Laravel application’s root and run the following command:
You should see the version of the framework your application uses and a list of all commands available trough Artisan CLI. Executing commands through Artisan affects only the application that you navigated to in the command line, not all Laravel applications system-wide. You will get to use many of Artisan’s commands throughout this book to accelerate development. Now that you have learned about installation and have met the Artisan CLI, let’s take a look at the general structure of a web application built with Laravel.
2.9 Application structure overview
A web application built with Laravel consists of certain components that work together to make up a product that functions as the developer intended. Some of these components the developer will need to create: Model-View-Controller code of the application, definition of application’s endpoints (routes), database structure (migrations, models), and unit tests. Others, the developer needs to adjust and configure: various application settings, environment settings and third party packages. Figure 2.1 illustrates which components a Laravel web application consists of:
Figure 2.1 Components that make up a Laravel web application
Even though that might look like a lot of parts to an application, don’t worry, as you will see throughout this chapter not all of them need to be created or modified by you for each and every application.
All these parts of the application will need to be located in specific places inside of a folder that is created after installation of Laravel following instructions in the “Installing Laravel” section. Let’s start discovering the directory structure of a typical Laravel application by looking at the root level of the application.
2.9.1 Files and folders in the root level of the application
The root folder of Laravel application contains Composer configuration, condensed information about the framework, folders containing environment settings, public-facing files, application code and folder with all installed packages including packages that make up Laravel framework itself. Table 2.1 shows a list of all files and folders in application’s root directory when Laravel is installed through Composer’s “create-project” command:
Table 2.1 List of root-level files and folders of a Laravel application
Folder or file
Contains your application’s code
Contains Laravel framework’s directory paths, compiled Laravel framework file and application environment settings
Third party packages and packages making up Laravel are installed into this folder.
This Composer configuration file contains a list of packages that the application is using, version settings for each package and stability settings
Contains instructions on how to contribute to Laravel PHP Framework.
Provides general information about Laravel and links to documentation, pull requests and the license of the application. If you are making an open source project on top of Laravel be sure to update this file to reflect the purpose and description of your application
Laravel has a special command that launches the current application on the system’s PHP server. This file is a helper file for that functionality
Provides the built-in command line interface for Laravel,so that a developer can accelerate certain tasks
Configuration file for PHPUnit unit testing tool
There will be times when you won’t have to touch all of these files and folders during development of your application. For example “vendor” folder is managed by Composer tool so you don’t need to modify anything in that folder, you would go into “bootstrap” folder only when you want to add a new environment setting, “phpunit.xml” file will only be modified when you will be using PHPUnit unit testing tool, etc. On the other hand there is one very special folder inside of the root, it is called “app” and it will contain the actual code of your application. Let’s take a look inside of that most important folder.
2.9.2 Contents of the “app” folder
When building applications with Laravel, this folder will be the center of your attention. The routes, route filters, various configuration settings and database migrations for your application will reside in this folder. Because Laravel uses Model-View-Controller pattern for your application, you will notice “models”, “views” and “controllers” folders among other folders in the “app” folder. These folders store your application’s data models, view templates and application controllers respectively. Table below (table 2.2) shows a list of all files and folders inside of the “app” directory:
Table 2.2 Contents of the “app” directory
Folder or file
Classes that represent the data models
Templates for views and view layouts
Application-specific settings such as database credentials, session and cache driver settings
Database seeds (sample data) and database migrations
Language strings for validation, pagination and email reminders
Custom classes containing Artisan commands
Cache, temporary sessions and compiled views
Files that help you adjust an error handler and,application maintenance mode behavior
Application’s unit tests
Logic and definition of filters used in the application
List of all registered endpoints of the application (routes)
Knowing the file and folder structure of a Laravel application will help you put things in right places so please take a closer look at each file and folder created after installing Laravel.
2.9.3 Configuration settings
Configuring a Laravel application is pretty simple comparing to other frameworks or hand made code. Configuration files in a Laravel application are stored inside directory “app/config” and have file names corresponding to what settings they affect. In table 2.3 let’s explore responsibilities of each configuration settings file and folder:
Table 2.3 Configuration settings inside of the “app/config” directory
Folder or file
Contains settings for
Packages that the application is using
Application key, timezone and locale, debugger settings, service providers and aliases for classes
Authentication driver, model and table used to represent users, password reminder settings
Cache driver, cache database connection and table
Classes that will be included when application is optimized
Database connection for MySQL, Sqlite, Postgres, SQLServer and Redis
Email driver, SMTP settings, “From” address and name
Queue driver and connection
Session driver and connection, session lifetime and name of the cookie
Creation of new packages using Laravel’s Workbench tool
By default the configuration settings are set so that you can use Laravel right away:
The session driver is set to save sessions on the disk inside of “app/storage/sessions” directory.
The cache driver is set to save the cache on the disk inside of “app/storage/cache” directory.
The time zone is set to UTC.
The language is set to English.
The database driver is set to MySQL (you only need to provide connection settings).
The provided settings are enough to get started but most likely your application will use a database or have your own time zone, and some settings will have to be different than the provided defaults. The comments inside of each configuration settings file make it easy to understand what the options are for each setting. Besides the default configuration stored in “app/config” folder, Laravel uses a concept called “environments” to manage application settings depending on where the application is being accessed from – a local machine or by going to a URL on the web. We will learn about environments a bit later, but meanwhile let’s apply the knowledge we learned in this chapter to create a fully functional Laravel application, a company website!
2.10 Tutorial: building a website with Laravel
Let’s imagine that you are running a marketing/development company and you would like to build a simple website for your company. The company website will consist of three simple pages: home page with a welcome message, a page that lists all services offered by the company and a contact page with company’s contact information and a functional contact form. The sketches (wireframes) for the company website follow in figure 2.2:
Figure 2.2 A wireframe of company website’s pages
Following the development of an application from start to finish will give you an idea of how the development with Laravel looks like in practice. When you finish building the application you will be familiar with the way Laravel applications are structured and you will see how Laravel makes it easy for you to modify your applications in the future. In the process of meeting Laravel’s methods you will understand how the Laravel framework alleviates common web development problems and you will experience its advantages over plain PHP code first hand.
So that there is a concrete goal, let’s define some specifications for the site’s individual pages. These pages will have the following functionality:
Home page – a page with information about the company and a menu for navigation
Services page – contains a list of the services that the company offers, this list will be retrieved from the database and embedded into the output HTML of the page
Contact page – contains a contact form with two fields, the subject and the body of the message. This message will be sent as an HTML email to the site’s administrator by using Laravel’s mail functions.
While keeping in mind these basic requirements we will create a site that will work according to the specifications. Before we get into development let’s first take a high level look at how building a real website with Laravel looks like.
2.10.1 The big picture – development overview
The development of the company website will consist of 9 steps in the following sequence, starting with installing Laravel (figure 2.3):
Figure 2.3 Overview of the development steps necessary to build an application
Installing Laravel by creating a new Laravel project.
Configuring application settings for the DB and for sending of emails
Defining application’s endpoints (routes)
Creating the HTML templates for each of the site’s pages
Create the DB structure and the data model for the services offered by the company
Filling the DB with data that represents the services offered by the company
Connecting the HTML templates to the endpoints (routes) of the application
Adding validation to the contact form to prevent empty submissions
Adding ability to send emails from the application
At the end of the development process you will have a fully functional company website that will work according to the specifications we defined in the introduction to this section. Let’s start the development of the company site by installing Laravel!
2.10.2 Creating a new Laravel project
To download and install Laravel we will use Composer command described in section 2.3 of this chapter. Open up your command line and navigate to where you would like the company website created, then execute “create-project” command that will create a new Laravel project:
After Laravel’s components are downloaded and put together by Composer, you should see a new folder called “companySite” appear in the current directory. Navigate to the new folder, in particular switch to the “app” folder because the “app” folder will be the heart of your application. You will see a folder structure described in section 2.5.2. Open up your favorite code editor and get ready to write some code.
2.10.3 Configuring application settings
In case with our example website there are only two things to configure, database settings and email driver settings (figure 2.4):
Figure 2.4 Overview of application settings configuration
Since the application will use a database to store the data for the services that the company offers, you will need to create a database first and then tell the Laravel application what settings to use for the database connection. To change the database connection settings open up “database.php” file in the “app/config” folder and set the settings to match your database connection, for example listing 2.1 shows settings for MySQL database engine:
Listing 2.1 Adjusting MySQL database connection settings in app/config/database.php
This book will use MySQL as the database engine of choice but you are free to use any of the four database engines that Laravel supports: MySQL, Postgres, SQLite, or SQL Server.
Now that the database settings are configured let’s configure the settings for sending email. Laravel supports three different email drivers: PHP’s built in “mail” driver, “smtp” driver and the “sendmail” driver. For this tutorial we will use the “mail” driver that comes with PHP because it needs minimal setup. The mail settings for the Laravel application are located in “app/config/mail.php” file so let’s open it and edit the following lines (listing 2.2), saving the file afterwards:
Listing 2.2 Adjusting email driver settings in app/config/mail.php
That’s it! Thanks to adjusting these settings we will be able to send email through the contact form in the application. This concludes configuration of the application, the rest of the settings are set to reasonable defaults (as specified in section 2.5.3). Next up, you will be defining the routes for the application.
2.10.4 Specifying endpoints (routes) of the website
Each website and web application has certain endpoints that are reachable by typing a URL in the browser’s address bar. These endpoints are called “routes” (we will look more into the concept of routes in chapter 3). Our example website will have routes for the following URLs, along with descriptions of what they will do:
“/” – root route, will show the index page of the company site
“services” – will show the services page
“contact” – will show the contact page, also route is used to submit the contact form
In Laravel applications, the routing is defined in “app/routes.php” file. Open that file up, you should see the following default code (listing 2.3) that comes with a new Laravel application:
Listing 2.3 Initial contents of app/routes.php file
We will specify the application’s routes by replacing the default route with the following definitions for the application’s routes (listing 2.4):
Listing 2.4 Modifying routes in the app/routes.php file
Having defined these routes we can now test the application in the browser and see the routes working. Let’s start Laravel’s development server by using an Artisan command in the command line:
This command will launch system’s PHP server on port 8000 and will make the application reachable by typing the following URL in the browser:
Go ahead and try the three new routes in the browser, the root route, the services page route and the contact page route. You should see the text output according to what we specified in the “routes.php” file (figure 2.5):
Figure 2.5 The basic routes for three pages set up and displaying text when you visit them
Later in this chapter we will come back to these routes and add ability to display a template file instead of just text strings.
2.10.5 Creating the database structure and the model for the data
Next step in the development of the application will be adding application’s models and specifying the structure of the data in the database (figure 2.6):
Figure 2.6 When the routes are set up, create the database structure and data model
As we defined in the specifications, the database will be used only for one purpose – to retrieve the list of services that the company offers. Each service offered by the company will have a title and description and a list of these services will be shown on the “services” page of the site. What could the structure be for the table that will store the company’s services? Let’s think this through. First, a unique id is needed; we can use an auto-incrementing integer for that and just call it “id” for simplicity. Second, we will give the title to each service, and third, some text description. Last, let’s give this table a name “services” since that perfectly describes what data it will store. That is all we need for this simple application’s database. Please take a look at the resulting table structure in figure 2.7:
Figure 2.7 Database structure for table “services” that will store company’s services
With this database structure in mind, we could create the “services” table through various means, by using PHPMyAdmin, the command line or by using Laravel’s database migrations. What are migrations? Migrations are like blueprints for a database. Migrations allow developers to have an easy way to keep track of changes in database structure; they are very much like version control for a database structure. For the purpose of seeing more of Laravel’s capabilities, let’s use a migration to create our table with Laravel. We will use Laravel’s helper tool Artisan to create the skeleton for the migration, so go back to the command line and execute the following command (make sure you are in application’s root directory):
After the migration skeleton is created, it will appear in “app/database/migrations” folder, the file will have a name that starts with the current date/time and ends with “create_services_table.php”. Open this file in the code editor. You will need to fill the contents of the “up” and “down” functions of the migration file with the following schema definitions (listing 2.5):
Listing 2.5 Migration schema for “services” table
The migration definition has been created but to translate the above migration into a “services” table in the database you need to run the migration by executing artisan’s migrate command from the command line:
Keep in mind that the operations with the database will use the database connection settings you have provided in the database.php settings file. If those settings were set correctly you should see a success message in the terminal, something like “Migration table created successfully. Migrated: timestamp_create_services_table”. Now if you check your database you will see that Laravel created the table “services” with the fields you specified in the migration file.
To use the “services” table in the application we need to make Laravel aware of what DB tables are available for use and the way to do that is to define data models for each separate kind of data that the application will be working with. Laravel comes with a powerful Object-relational mapping called “Eloquent ORM” that makes working with the data in databases very easy. Eloquent ORM has a few conventions that we will make use of.
The first convention is that Laravel uses an auto-incrementing integer with the name “id” as the primary key for the records in tables. Although this could be easily changed if needed, this is exactly what we have already so we won’t have to modify our existing table.
Another convention is that Laravel likes your tables to be plural but the data models for the tables to be singular (this too is flexible). As an example if you have a table called “products” in the database, your model should be named “product”, if you have table called “users” your model for that table would be named “user”. For this particular application we need to create a data model that will make Eloquent ORM aware of the “services” table and the way to do that is to create a model called “Service” in the “app/models” directory, create a new file called Service.php with the contents of listing 2.6 and place it into “app/models” folder:
Listing 2.6 Data model for services offered by the company
This is all that is needed to tell Laravel about the “services” table in your database. You do not need to specify the name of the “services” table anywhere in the application. Laravel will assume that there is a table named as a plural of the class “Service” in the “app/models” folder. Now when you need to access the data from the “services” table throughout the application you will be able to use Eloquent’s powerful methods of accessing and managing data.
2.10.6 Filling the database with data
You have the “services” table structure ready but the table is empty and there is no “services” that we can show on the “services” page. You should fill the “services” table with information about the services that the company offers. This can be done in many ways. For example you can use PHPMyAdmin tool or the command line to create the rows for “services” table. But for the purpose of exposing you to Laravel’s power and might we will use one of Laravel’s tools to fill the data. Laravel has a built-in way to populate the data in the database. Populating a database is called “seeding” the database.
We will seed the database by creating a class called “ServiceTableSeeder” with a single function “run” that will simply create three different services that will be later displayed on the site. Please create “ServiceTableSeeder.php” in the “app/database/seeds” folder of the application and place the code from listing 2.7 in it:
Listing 2.7 Database seed for “services” table
After creating the seed class it needs to be executed in order for the data to appear in the database. Laravel’s DatabaseSeeder class located in “app/database/seeds” folder is the right place to call the execution of the new ServiceTableSeeder class. Let’s open up the “DatabaseSeeder.php” and add a single line to it’s run function (listing 2.8):
Listing 2.8 Contents of modified app/database/seeds/DatabaseSeeder.php file
Now that we have the seed defined and the DatabaseSeeder configured to run it, we need to execute Laravel’s seed command in the command line and it will create the data in the database:
If you see a message that says “Database seeded!” then all is well and the content you have defined in the “ServiceTableSeeder” class will be translated into the data in the “services” table. Check your database to make sure the seeding went well and if it did, let’s continue developing our application and start showing the data in the browser!
2.10.7 Creating HTML and Blade views
While we have our application’s internals mostly finished, the application so far doesn’t have any face to it. Right now all we show to the user is the blank screen with a line of text coming from the application’s routes. Let’s improve that by creating HTML templates for displaying information on each page and for presenting the navigational menu of the site. Then when we have the view templates all ready we will get routes to display these templates in the browser (figure 2.8):
Figure 2.8 Create HTML templates
Laravel comes with a simple yet powerful templating engine called “Blade”. The templates made with Blade look much like plain HTML but with sprinkles of some special statements that make it possible to output PHP data, looping over it, inject other templates, use different layouts and more. Using Blade can definitely save you time and spare from headache when it comes to creating the application’s pages and maintaining the visual aspect of the application.
Application’s view templates are located in the “app/views” directory and files that use Blade syntax end with “.blade.php” in the file name. One of the most useful features of Blade is ability to use a common layout for desired templates of the site and we will make a simple layout that all of the pages of the site will share. Let’s again look at the desired look of the company site in figure 2.9:
Figure 2.9 A wireframe of company website’s pages
184.108.40.206 Building the layout
From this approximate sketch we see that the navigational menu is common to all three pages and the content that goes below the menu is different between the pages. We will build a layout that will allow us to keep the common elements, in this case the site’s navigation in one place and the part that changes, the content, in another. Let’s create the application layout by making a new file in the “app/views” directory, call it “layout.blade.php” and the contents of it will be as follows in listing 2.9:
Listing 2.9 Blade Layout for the company website (layout.blade.php)
220.127.116.11 Building the template for the home page
We have the layout for the site ready. Now let’s create the templates that will be inserted into this layout. These templates will also go into “app/views” directory and they will be used to display content onto the page. First, let’s create the template for the home page as in listing 2.10 and place it in “home.blade.php” file:
Listing 2.10 Blade template for the home page (home.blade.php)
18.104.22.168 Building the template for the services page
As we specified before, the services page will display the data from the database so the template for this page will need a bit more explanation. One of the best practices of web development is to never do calls to the database from the view templates. Therefore we will do the database calls elsewhere and then pass the retrieved data as objects to the view template. We can then display the data using Blade’s clean and easy to read syntax. Let’s create “services.blade.php” file in the “app/views” directory and have the contents of listing 2.11 in it:
Listing 2.11 Blade template for the services page (services.blade.php)
That’s it for the services page! No messy PHP, no database calls from the view template, this looks nice and clean. Let’s build the template for the last page of the site, the contact page!
22.214.171.124 Building the template for the contact page
The contact page will feature the form that will consist of three inputs, the text input for the subject of the message, the text area for the body of the message, and the submit button. While we could hand code the HTML form, it could be faster to use some of the Laravel’s built-in methods for building the forms in the templates. As a demonstration, the complete HTML for the form page would look like listing 2.12:
Listing 2.12 HTML code of the contact page without using Blade
This is quite a bit of code. Let’s see how Laravel can make it easier for you to create a form for the contact page. Laravel provides multiple shortcuts for opening and closing forms, creating labels, text inputs, buttons, selects and much more. Using these shortcuts will make the code cleaner and easier to modify. Let’s look at this aspect of Laravel in action by creating a template, “contact.blade.php” in “app/views” folder, and by putting the following contents in it (listing 2.13):
Listing 2.13 Blade template for the contact page (contact.blade.php)
As you can see we have achieved the same HTML output with a lot less code by using Laravel’s Blade templating engine. At this point the view templates are complete and we would like to display them in the browser by adjusting our routes to show the templates instead of text strings. Let’s do that in the next section!
2.10.8 Displaying view templates from the routes
In section 2.6.4 we left the routes in a state where they are just displaying simple text strings. Of course the time of the blank pages with a single string is now over and we will connect the routes and the view templates together. For simplicity, we can use Laravel’s “View::make()” functionality to render the templates when the pages are requested in the browser.
126.96.36.199 Connecting the home page route to the view template
Let’s start with the index route, as it is the most basic one, the route for showing the site’s homepage. Since all this route is doing is showing a view template, we can call Laravel’s “View::make()” function providing it with the name of our view template and it will render the template upon request. This is how it will look like in the “app/routes.php” file after replacing the text string output (listing 2.14):
Listing 2.14 Index route modified to display template for the home page
Returning a rendered view from a route will simply display it in the browser. Now if you visit the homepage of the application in the browser you should see a page that looks similar to figure 2.10:
Figure 2.10 Content of the site’s homepage displaying from the Blade template
This looks good! Even though there is no CSS to make the pages look pretty, we have a functional home page for the site now. Two pages of the site are left to be made functional, the services page and the contact page. Let’s finish up the services page.
188.8.131.52 Connecting the services page route to the view template
As you remember the services that the company offers are stored in the database and we have even created the view template for the services page. That page expects to receive an array of objects that it can then iterate through to get the title and description of each service. We will use Eloquent ORM to retrieve all services from the database and then we will pass the result to the services template. Please look at the listing 2.15 to see how this looks like in action inside of a route and modify your existing “services” route to match this one:
Listing 2.15 Services route modified to display data from services table
With these changes the services route should now be fully functional and it should display the page containing the services that we previously inserted into the database (figure 2.11):
Figure 2.11 Content of the services page displaying the list of services from the database
This was easy, wasn’t it? In other frameworks or using PDO in plain PHP retrieving records and getting various data attributes would be a bit more involved but Laravel makes development enjoyable by providing logical methods and by forcing solid yet flexible conventions.
184.108.40.206 Connecting the contact page route to the view template
The only page left for us to be developed is the contact form and we are ready to modify the route that leads to it so that it displays the template we created earlier. Replace the existing “contact” route with this one (listing 2.16):
Listing 2.16 Modified route for the contact page
Laravel will convert the Blade template we created for the contact page into HTML along with form we crafted using the “Form” methods. Now going to the “contact” URL in the browser should show a page similar to figure 2.12:
Figure 2.12 Contact page with the form rendered from the view template
We are almost there. The form is on the contact page but what happens when we try to submit it? We will receive an error stating that the requested page is not found. That is because when the form is submitted it is POSTed to the “contact” route and currently we do not have the route definition for the POST method of “contact” route. Let’s create that. We will add one more route in the “app/routes.php” file, as in listing 2.17:
Listing 2.17 Adding a POST route for the contact page at the end of routes
Voila! Now when we submit the form on the contact page we will get a message that says “Message sent”. That is kind of a lie because we don’t send anything yet, but we are optimistic. We would like to receive the values submitted by the form and email the contact request to the administrator of the company site. One problem with that is that the values provided by the user could be empty. How can we prevent submittal of an empty form or a form with invalid values? Dear reader, enter validation!
2.10.9 Adding validation to the contact form
Validation of input tells us if the data entered by the user is valid or not valid. Applying validation to form data is very easy in Laravel. We will discuss it in detail in later chapters but for now we will do the following process to verify that the submitted form data is valid:
Gather the user’s input
Define some validation rules for the input fields
Validate the input according to the validation rules
If the data is valid, proceed doing something useful, otherwise come back to the form displaying what validation errors have occurred and also preserving user’s input
With this process flow implemented and with validation in action, the “contact” route will look like the code following in listing 2.18:
Listing 2.18 Adding validation to the form input in the “contact” route
When the validation of the input data fails, the application will redirect the user back to the contact page remembering the user’s input and also storing validation errors in the session. One small thing that we now need in our view template is to add the display of the error messages that arise when the validation does not pass. We can just display the errors in a string but another way is to loop through the errors using Laravel’s HTML helpers, open up the “contact.blade.php” template file from “app/views” folder and add this line above the form methods:
Please see the listing 2.19 to verify that it is in the right place:
Listing 2.19 Addition of the validation error messages (contact.blade.php)
Validating user’s input and showing error messages will prevent an empty form to be submitted and thus will decrease the number of empty emails the site administrator will be getting. Speaking of emails, as of right now we are not sending anything even when the user has filled the input fields properly. Why don’t we fix that right away? Let’s learn how to send emails from our application!
2.10.10 Sending HTML email with Laravel
Laravel makes sending HTML emails almost too simple. Let’s first look at how we could send an email using plain PHP using the built-in “mail” function and then we will build the same functionality using Laravel’s methods to see what benefits there are to using Laravel’s email features.
We will send the contact request email to the site admin after the validation of the contact form passes. To do that in plain PHP we could add it to the POST route of the “contact” route as follows in listing 2.20:
Listing 2.20 Sending email in the “contact” POST route using plain PHP
This is good enough but the code is pretty messy and not easy to maintain. If you need to change the content of the email, recipients, add CC and BCC to the email it will not be an easy task. Laravel alleviates these problems by separating the presentation of the email from the functional part (sending it, specifying recipients, etc). Let’s achieve the same functionality but using Laravel’s easy to read methods.
We already configured the email driver to use PHP’s built in “mail” function and specified the “from” address and name (refer to section 2.6.2 to see how we did that). Now all we need is to specify which HTML template will be used for the emails and what data it will contain. Let’s create a basic view template in “app/views/emails” and call it “contact.blade.php”, the content of it will be as follows in listing 2.21:
Listing 2.21 Template for the HTML email (contact.blade.php in app/views/emails)
This template will be sent out when the contact form is submitted and when the form input passes validation. We will use Laravel’s “Mail” functionality to send the HTML email, | <urn:uuid:e93be8b5-5bea-4240-bf26-fffc01b6d06e> | 2.65625 | 9,283 | Truncated | Software Dev. | 49.684959 | 95,487,692 |
The use of nitrogen in an explosive is ironic because a molecule of nitrogen gas (N2) represents one of the most stable bonds we have ever discovered. If nitrogen is explosive, why hasn’t the atmosphere, which is mostly nitrogen, ever succumbed to devastating explosions?
Still, if it weren’t for nitrogen, TNT or dynamites would have been about as explosive as cheese or sand. So, what then makes nitrogen the magic ingredient?
How do explosives work?
At the heart of any explosive are chemicals mixed in a perfect ratio participating in what is called an exothermic redox or a reduction-oxidation reaction. A redox reaction is a type of chemical reaction that requires its reactants to exchange electrons. The reactant losing its electrons is said to be ’oxidized’, while the reactant that gains these very electrons is said to be ‘reduced’. In the case of an explosive, this transaction is exothermic, meaning that it releases heat upon completion.
For instance, the mixture of potassium nitrate, carbon and sulfur in the perfect ratio constitutes what is popularly known as gunpowder. A chemical reaction is triggered when the mixture is exposed to heat or even a mere spark. The oxidized species are carbon and sulfur, while the potassium nitrate is reduced. The reaction, being exothermic, also releases a burst of energy in the form of heat and light.
However, an exothermic reaction does not guarantee an explosion. The rusting of iron is also caused by an exothermic redox reaction, but I have yet to see a corroded nail abruptly explode. The key to causing an explosion is not just any exothermic reaction, but a very quick one. Rusting does not cause iron to explode because it is an extremely slow and prolonged process.
When a detonator triggers the reaction either physically, chemically or electronically, the mixture undergoes a phase transition from solid or liquid to gas. The heat released in the reaction increases the temperature of this gas. However, the quick nature of this reaction means that the transition and consequently the expansion of this gas is tremendously rapid.
A single gram of TNT produces almost one liter of gas in seconds, which is a thousand-fold increase in volume! Therefore, the energy and pressure that is released, almost instantaneously, propagate outwards as a swift shock wave that is powerful enough to sweep people, trees and cars right along with it.
Nitrogen is a crucial constituent of an explosive for the simple reason that its highly unstable compounds, when incited, will rapidly decompose into nitrogen gas, a ridiculously stable compound. However, why should the production of a stable compound from an unstable compound release such a staggering amount of energy?
Well, before synthesizing nitrogen compounds such as nitroglycerine, the major ingredient of dynamite, or trinitrotoluene, popularly known by its initials TNT, we must first break the nitrogen compound into individual nitrogen atoms. Separating a stable compound such as nitrogen into its constituents is like separating two wet pages that have gotten stuck together: it requires a lot of energy to do so. Thus, when the process occurs in reverse, that is, when the atoms recombine to form nitrogen gas, the same amount of energy is produced.
Before a compound can be formed, these bonds must be broken. This process requires 950 kJ mol−1—
Thus, a reaction is more exothermic when it produces more stable compounds. This is why, while oxygen is obviously necessary for combustion, explosives are replete with it because its compounds, like nitrogen’s, rapidly decompose to form oxygen molecules, an equally stable molecule. Another explosive favorite is carbon.
Even though gasoline, which also fosters these elements, boasts more potential energy than TNT, the latter explodes because, first of all, it is highly unstable, and second, as mentioned, because of the reaction’s rapidity, because of the high velocity with which the energy and gases are released.
In fact, to witness nitrogen’s rage, simply pour some liquid nitrogen into a bottle and subject it to room temperature. The formidably dense, unstable compound will rapidly convert into nitrogen gas. A bottle not strong enough to stifle this expansion will easily blow apart. However, a bottle strong enough to stifle the explosion would actually pressurize it, thereby setting it ablaze. The seemingly innocuous act will eventually culminate in a sudden Kaboom! | <urn:uuid:551a2394-3fec-455b-9316-ae182a9bf7c7> | 3.71875 | 925 | Knowledge Article | Science & Tech. | 31.303853 | 95,487,714 |
By Robert A. Andersen
Algal Culturing Techniques is a finished reference on all points of the isolation and cultivation of marine and freshwater algae, together with seaweeds. it really is divided into seven elements that disguise background, media instruction, isolation and purification ideas, mass culturing options, mobile counting and development dimension strategies, and experiences on subject matters and functions of algal tradition strategies for environmental investigations.
Algal Culturing Techniques used to be built to function either a brand new textbook and key reference for phycologists and others learning aquatic platforms, aquaculture and environmental sciences. scholars of algal ecology, marine botany, marine phycology, and microbial ecology will benefit from the hands-on technique for culturing various algae from clean and marine waters. Researchers in undefined, resembling aquaculture, pharmaceutical, foodstuffs, and biotechnology businesses will locate an authoritative and entire reference.
- Sponsored by means of the Phycological Society of America
- Features colour photos and illustrations throughout
- Describes culturing tools starting from the attempt tube to open air ponds and coastal seaweed farms
- Details isolation suggestions starting from conventional micropipette to automatic move cytometeric methods
- Includes purification, development, upkeep, and cryopreservation techniques
- Highlights equipment for estimating algal populations, progress premiums, setting apart and measuring algal pigments, and detecting and culturing algal viruses
- Features a accomplished appendix of approximately 50 algal tradition medium recipes
- Includes a thesaurus of phycological terms
Read Online or Download Algal Culturing Techniques PDF
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Extra resources for Algal Culturing Techniques
G. 1986. Biological and ecological characterization of the marine unicellular cyanobacterium Synechococcus. , and Li, W. K. , eds. Photosynthetic Picoplankton. Can. Bull. Fish. Aquatic Sci. 214:71–120. Chapter 3 Marine Culture Media Paul J. Harrison AMCE Program, Hong Kong University of Science and Technology John A. 0. 0. 1. 0. 1. 2. 3. 0. 1. 2. 3. 4. 5. 6. 7. 0. 1. 2. 0. 1. 2. 0. 0. References Natural seawater (NW) is a complex medium containing more than 50 known elements and a large and variable number of organic compounds.
2001). Although such comparisons are rarely done quantitatively, assessing media on the basis of the length of time a culture can remain at a stationary biomass is a criterion that is probably quite relevant to culture collections. Another criterion for media evaluation is whether the original morphology of the cells is maintained, but this is seldom evaluated (Harrison et al. 1980) and can be impractical for small species. Many recipes that include soil water extract justify the addition on the basis that it maintains the original cell morphology during longterm culturing.
The modifications were the omission of Tris (the pH buffer) and the addition of silicate. The omission of Tris was compensated for by adding equimolar amounts of NaHCO3 and HCl to prevent precipitation during autoclaving. During autoclaving CO2 is lost, and CO2 can be added indirectly before autoclaving by adding NaHCO3 or by directly bubbling CO2 through the medium. 3 : 1 chelator to trace metal ratio, compared to 1 : 1 in ‘f’ medium (Guillard and Ryther 1962), which may reduce the tendency to form metal precipitates and metal toxicity (Harrison et al.
Algal Culturing Techniques by Robert A. Andersen | <urn:uuid:f34c47e5-1660-462d-a82a-bc657e3372a4> | 2.75 | 1,168 | Product Page | Science & Tech. | 27.852312 | 95,487,716 |
A ‘sun shield’ made from an ultra-thin surface film is showing promise as a potential weapon in the fight to protect the Great Barrier Reef from the impacts of coral bleaching.
Great Barrier Reef Foundation Managing Director Anna Marsden said the results from a small-scale research trial led by the scientist who also developed Australia’s polymer bank notes were very encouraging.
The project was supported by The Tiffany & Co. Foundation, made possible through a grant to the University of Melbourne USA Foundation.
“We’ve partnered with scientists from the University of Melbourne and the Australian Institute of Marine Science to develop sun protection for the Reef,” Ms Marsden said.
“The ‘sun shield’ is 50,000 times thinner than a human hair and completely biodegradable, containing the same ingredient corals use to make their hard skeletons – calcium carbonate. It’s designed to sit on the surface of the water above the corals, rather than directly on the corals, to provide an effective barrier against the sun.
“While it’s still early days, and the trials have been on a small scale, the testing shows the film reduced light by up to 30%.
“Scientists tested the effectiveness of the one molecule thick film on seven different coral species in simulated coral bleaching event conditions at the Australian Institute of Marine Science’s National Sea Simulator (SeaSim).
“The surface film provided protection and reduced the level of bleaching in most species.”
With the surface film containing the same ingredient that corals use to make their skeletons, the research also showed the film had no harmful effects on the corals during the trials.
“This is a great example of developing and testing out-of-the-box solutions that harness expertise from different areas. In this case, we had chemical engineers and experts in polymer science working with marine ecologists and coral experts to bring this innovation to life,” Ms Marsden said.
“The project set out to explore new ways to help reduce the impact of coral bleaching affecting the Great Barrier Reef and coral reefs globally and it created an opportunity to test the idea that by reducing the amount of sunlight from reaching the corals in the first place, we can prevent them from becoming stressed which leads to bleaching.
“It’s important to note that this is not intended to be a solution that can be applied over the whole 348,000 square kilometres of Great Barrier Reef – that would never be practical. But it could be deployed on a smaller, local level to protect high value or high-risk areas of reef.
“The concept needs more work and testing before it gets to that stage, but it’s an exciting development at a time when we need to explore all possible options to ensure we have a Great Barrier Reef for future generations.”
The Latest on: Coral bleaching
via Google News
The Latest on: Coral bleaching
The Great Barrier Reef Is Losing Its Ability to Recover from Bleaching Events
on July 18, 2018 at 12:05 pm
If you hadn’t heard, things aren’t looking too rosy for the world’s reefs. Warmer oceans have led to an uptick in global coral bleaching events, ocean acidification is decreasing the amount of free ca... […]
Reef scientists consider floating film to stop coral bleaching
on July 18, 2018 at 7:08 am
A floating film that sits on top of the ocean and shields coral from the sun is just one of the ideas being discussed at the Great Barrier Reef Restoration Symposium in Cairns. ABC NewsRadio's Steve C... […]
Can we save the coral reefs?
on July 18, 2018 at 2:25 am
According to Science, the latest global coral bleaching from 2015-2017 is finally over. However, Unesco says 21 of 29 World Heritage reefs have been damaged through heat stress and bleaching. Bleachin... […]
"Cloud Brightening" Shows How Weird Plans to Save Coral Reefs Have Become
on July 16, 2018 at 2:50 pm
This, he says, could help keep the water around the reef from warming quickly and bleaching the coral. To achieve this inconceivably huge task, Harrison proposes spraying seawater up at the clouds, wh... […]
Florida’s coral disease outbreak is most “extensive” ever: scientist
on July 16, 2018 at 11:50 am
Even before this disease outbreak, corals in Florida were under so much pressure from different stressors like nutrient pollution from runoff, dredging, which created a lot of sediment and heat stress ... […]
Can We Create Sunscreen That Protects Both Humans and Coral Reefs?
on July 16, 2018 at 8:31 am
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The Coral Reefs We Depend On Most May Fall First
on July 12, 2018 at 10:43 am
In the Indian Ocean, however, Perry said low accretion rates are largely driven by coral bleaching. Corals turn bone white when seawater temperatures rise too high and will die if the bleaching event ... […]
Island of Coral Resilience Shows Hope – and Limits – for Reefs’ Future
on July 12, 2018 at 10:38 am
And that was before the most recent global coral-bleaching crisis hit the region hard in 2015. As the Caribbean’s reefs were dying, some 1,000 miles to the north in the middle of the Atlantic Ocean, s... […]
Half of the World’s Coral Reefs Are Dead, but a Scientist May Know How to Save the Rest
on July 10, 2018 at 7:16 am
This phenomenon, called coral bleaching, has decimated half the Great Barrier Reef—more than 67,000 miles of dead coral. Reefs that have stronger microorganism presences have a higher damage threshold ... […]
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If observers can influence the outcomes of measurements, then do these observes need to be conscious? Does consciousness play a special role in physics at all?
A brief introduction to the strange theory of quantum mechanics and how it appears to afford a special role to observers.
Can the very act of observing something change what's being observed? This series of articles and videos explores some basic questions about the role of the observers in physics.
Has the future already already been written? Is time just an illusion? Take a step outside of spacetime with cosmologist Marina Cortês to discover the block universe.
Fundamental physics says time is symmetric - so why does time move forwards for us in a block universe?
Is time real? Are we just puppets living out a future already written? Marina Cortês explains why she thinks time is fundamental and that we don't live in a block universe.
Marina Cortês is one of a growing number of physicists who believe time is fundamental. We ask her about the alternatives theories to the block universe, where time comes first.
Physics tells us that we live in a block universe, containing all of the past and all of the future. What does this perspective mean for our understanding of time, events, and free will?
The possibility that there might be many parallel worlds has just become a little more likely.
In these two short videos the legendary Andrew Wiles talks about what it was like to prove Fermat's Last Theorem, and what it feels like to do maths.
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The Rome lab at UCLA has collaborated with a number of groups to use the baculovirus system to produce large quantities of vaults. When the major vault protein (MVP) is expressed in insect cells, vault particles are assembled on polyribosomes in the cytoplasm. By using molecular genetic techniques to modify the gene encoding the major vault protein, vault particles have been produced with chemically active peptides attached to their sequence. These modified proteins are incorporated into the inside of the vault particle without altering its basic structure. Proteins and peptides can also be packaged into vaults by attachment of a packaging domain derived from the VPARP protein. A number of modified vault particles have been produced in order to test the concept that vaults can be bio-engineered to allow their use in a wide variety of biological applications including drug delivery , biological sensors, enzyme delivery, controlled release , and environmental remediation .
Lysosomes are microscopic, sac-like structures suspended in the cytosol of the cell's plasma membrane. The digestive enzymes contained within these organelles are called acid hydrolases. Aside from the breakdown of food particles, the enzymes also digest damaged membranes, aiding in recycling wornout parts of the cell. Another important function of the lysosomes is the prevention of microorganisms from invading the cell. Harmful bacteria and viruses are usually targeted and digested by lysosomes found in white blood cells. Due to their digestive properties, acid hydrolases are isolated from the rest of the cell by the membrane that envelopes the lysosomes. Otherwise, the enzymes will digest all cellular components. | <urn:uuid:5d8731c1-12a0-46a5-9925-2101da5c531f> | 3.421875 | 337 | Knowledge Article | Science & Tech. | 16.684231 | 95,487,732 |
Global composite temp.: +0.10 C (about 0.18 degrees Fahrenheit) above 30-year average for April.
The University of Alabama in Huntsville
April 2013 map
Northern Hemisphere: +0.12 C (about 0.22 degrees Fahrenheit) above 30-year average for April.
Southern Hemisphere: +0.09 C (about 0.16 degrees Fahrenheit) above 30-year average for April.
Tropics: +0.17 C (about 0.31 degrees Fahrenheit) above 30-year average for April.
March temperatures (revised):
Global Composite: +0.18 C above 30-year average
Northern Hemisphere: +0.33 C above 30-year average
Southern Hemisphere: +0.04 C above 30-year average
Tropics: +0.23 C above 30-year average
(All temperature anomalies are based on a 30-year average (1981-2010) for the month reported.)
Notes on data released May 6, 2013:
Compared to seasonal norms, during April the coldest area on the globe was in the southeastern portion of Saskatchewan, Canada, where the average temperature was as much as 4.82 C (about 8.7 degrees Fahrenheit) cooler than seasonal norms. Compared to seasonal norms, the “warmest” area on the globe in April was on the northeastern Russian coast near the Bering Sea. Temperatures there averaged 4.51 C (about 8.1 degrees Fahrenheit) warmer than seasonal norms for April.Archived color maps of local temperature anomalies are available on-line at:
The satellite-based instruments measure the temperature of the atmosphere from the surface up to an altitude of about eight kilometers above sea level. Once the monthly temperature data is collected and processed, it is placed in a "public" computer file for immediate access by atmospheric scientists in the U.S. and abroad.
Neither Christy nor Spencer receives any research support or funding from oil, coal or industrial companies or organizations, or from any private or special interest groups. All of their climate research funding comes from federal and state grants or contracts.
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science 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...
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
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The Hubble Space Telescope has its big eye pointed deep into space, where the remains of a massive supernova star dubbed Supernova 1987A are drifting. And the scientists behind it are studying the site in the hopes of learning more about the role star guts play in the evolution of galaxies.
New studies led by Kevin France, a research associate at the Center for Astrophysics and Space Astronomy at the University of Colorado in Boulder, have detected significant brightening of the emissions from the former star, writes the Daily Camera.
Those emanations “allow us to accurately measure the velocity and composition of the ejected” guts, which provide a kind of blueprint regarding what elements are being recycled in the Large Magellanic Cloud and how it changes its environment on human time scales.
Hubble is the world’s only observatory that can examine the brightening of the String of Pearls (pictured), as the remains are known, in ultraviolet light, says France.
Photo via colorado.edu (courtesy NASA). | <urn:uuid:59b69dcc-17d7-43ef-bc19-940dda0c2c3d> | 3.890625 | 209 | Truncated | Science & Tech. | 26.815602 | 95,487,772 |
Hubble Space Telescope: Discoveries
Publisher: NASA 2012
Number of pages: 128
The book takes the reader on a tour of Hubble's most significant science successes, combined with some of the telescope's technology and history. The book details Hubble's work in cosmology, planetary science and galactic science. Interactive elements include a gallery of images taken by Hubble's different instruments, an interactive showing how astronomers measure distance in space, and a short movie on the discovery of planet Fomalhaut b.
Home page url
Download or read it online for free here:
by Andrew Fraknoi, David Morrison, Sidney C. Wolff - Unglue.it
This book is designed to meet the scope and sequence requirements of one- or two-semester introductory astronomy courses. It begins with relevant fundamentals and progresses through an exploration of the solar system, stars, galaxies and cosmology.
by Charles J. White - J. Wiley
I present the main principles of Astronomy in a form adapted to the elementary course of instruction which is commonly given at colleges and the higher grades of academies. I selected those topics which seemed to me to be the most important.
by Martin V. Zombeck - Cambridge University Press
This handbook is an essential reference for space astronomy and astrophysics. It covers topics such as atomic physics, nuclear physics, relativity, plasma physics, electromagnetism, mathematics, probability and statistics, and geophysics.
by Forest Ray Moulton - The MacMillan Company
It has been assumed that the reader has an interest in the wonderful universe which surrounds him, and that he has arrived at such a stage of intellectual development that he demands the reasons for whatever conclusions he is asked to accept. | <urn:uuid:190bdd30-8c9b-43bf-b6fa-94304d09a3d7> | 3.453125 | 358 | Product Page | Science & Tech. | 29.283384 | 95,487,778 |
Open graph description entity tag
The Open Graph protocol enables any web page to become a rich object in a social graph, a open protocol supported by Facebook
Meta Keywords are a specific type of meta tag that appear in the HTML code of a Web page and help tell search engines what the topic of the page is.
This page contains a meta robots tag which tells search engines and robots to index or not index the page.
Sites who has this tag are verfied by google to use WebMaster tools
The http-equiv attribute provides an HTTP header for the information/value of the content attribute. The http-equiv attribute can be used to simulate an HTTP response header. | <urn:uuid:4f083b35-932c-4aaa-8604-ec45b1ca4cf1> | 2.6875 | 141 | Documentation | Software Dev. | 39.093233 | 95,487,793 |
The lithosphere and asthenosphere form the upper two layers of the earth. The lithosphere, Greek for "stone," is composed of brittle rock. Below the lithosphere, the asthenosphere, Greek for "weak," is composed of ductile and semi-fluid rock. The lithosphere rides atop the slowly flowing asthensophere. The differences between these two layers include locations, physical properties, chemical properties and roles in plate tectonics.
The lithosphere represents the earth’s top layer, consisting of the crust and the upper reaches of the mantle. The depth of this layer is between 49 and 62 miles. The upper lithosphere is composed of both oceanic crust, about 4.5 miles thick, and continental crust, about 22 miles thick. The lithosphere plunges into and through the asthenosphere in tectonic subduction zones. The lithospheric layer is also deeper under mountain ranges. The asthenosphere is below the lithosphere, composed of the upper mantle. The thickness of this layer ranges between 62 and 217 miles. The asthenosphere rises to the surface at mid-oceanic ridges.
The lithosphere is composed of relatively cool, rigid rocks. These rocks behave elastically, although they are brittle and can break, fracture or fault. At its lower limit, the lithosphere contains mantle rock. This rock is similar in composition to the asthenosphere, but it is cooler and less fluid. The asthenosphere is a semi-fluid layer of partly molten rock. A balance between temperature and pressure maintains a consistency similar to that of warm tar. This ductile material consists of solid particles, with liquid filling the space between them. This state causes asthenospheric rock to behave like a plastic, capable of gradual flow.
The slush-like rock material of the asthenosphere is composed of iron-magnesium silicates. This chemical composition is nearly identical to the lower mesospheric layer. In contrast, lithospheric rocks contain more silica, but less aluminum, sodium and potassium. Within the lithosphere, composition varies between oceanic crust and continental crust. Oceanic crust contains less silica than continental crust, producing a darker color. Oceanic crust also contains more magnesium and iron than continental crust, making it much denser.
Roles in Plate Tectonics
The lithosphere, being rigid, is broken into pieces called tectonic plates. These plates ride on top of the semi-fluid asthenosphere. The asthenospheric flow is driven by convection, caused by heat deep within the earth. As this layer slowly flows, the lithosphere’s tectonic plates are moved laterally, as if on a conveyor belt. The asthenosphere is also responsible for the creation of new crust. This occurs at mid-ocean ridges where convection forces the asthenosphere to the surface. As the partly molten material extrudes, it cools and forms new crust. The convection also forces the lithospheric plates to move apart at these ridges, called divergent boundaries, or zones. | <urn:uuid:a72f7a45-b9ee-4bd2-9058-f7f94485248c> | 4.53125 | 640 | Knowledge Article | Science & Tech. | 38.39094 | 95,487,804 |
Geologists, archeologists, anthropologists, ecologists, engineers, and natural resource managers routinely use National Cooperative Soil Survey (NCSS) data across field sciences.
Researchers at Iowa State University decided to test the reliability of this data as applied in geology, and sought to create the best possible Quaternary geology map of the Des Moines Lobe solely using NCSS data. Their broader goal was to create the map to explore how the rich level of detail in the Soil Survey Geographic (SSURGO) database can be used to serve many other areas of study.
Bradley A. Miller (Environmental Programs, Iowa State University), C. Lee Burras (Dep. of Agronomy, Iowa State University), and William G. Crumpton (Dep. of Ecology, Evolution, and Organismal Biology, Iowa State University) categorized soil map units with respect to geologic units and successfully created a detailed Quaternary geologic map for the Des Moines Lobe. Their map showed strong agreement with existing Quaternary geologic maps while adding a user-controlled level of scale. The results are published in the Winter 2008 issue of Soil Survey Horizons.
Digital county soil maps were obtained from the USDA-NRCS Soil Survey Geographic (SSURGO) Database, and a database was constructed that categorized each soil series that appeared in the selected counties for surface geologic attributes. The database key was based on terms found in the online Official Series Descriptions, and the database was then linked to the SSURGO shapefile in ESRI’s ArcGIS 9.2 software. The soils were displayed by grouping categorized soil into 15 geologic units. Quaternary geologic maps that were available in a GIS format were used to compare the new Quaternary geologic map for level of agreement and detail.
The resulting map communicates many of the spatial intricacies of the Des Moines Lobe landform with the 15 map units based on geologic units. The display of these map units shows detailed features of ground moraine, stagnation moraine, glacial lakes, outwash, and loess deposits.
The researchers envision widespread use of the method, given the generally good agreement with the existing Quaternary geologic maps and the inclusion of finer detail and user-controllable scale. The development of keys that relate soil survey terminology to information of geologic interest will allow soil survey to be a quick and easy reference for geologic inquiry. The same concept can be applied to any discipline affected by soil properties.
Soil Survey Horizons, https://www.soils.org/soil_survey_horizons/, is a medium for expressing ideas, problems, and philosophies concerning the study of soils in the field. Articles include research updates, soil news, history of soil survey, and personal essays from the lives of soil scientists. Soil Survey Horizons is published by the Soil Science Society of America.
The Soil Science Society of America (SSSA) is a progressive, international scientific society that fosters the transfer of knowledge and practices to sustain global soils. Based in Madison, WI, and founded in 1936, SSSA is the professional home for 6,000+ members dedicated to advancing the field of soil science. It provides information about soils in relation to crop production, environmental quality, ecosystem sustainability, bioremediation, waste management, recycling, and wise land use.
SSSA supports its members by providing quality research-based publications, educational programs, certifications, and science policy initiatives via a Washington, DC, office. For more information, visit www.soils.org.
SSSA is the founding sponsor of an approximately 5,000-square foot exhibition, Dig It! The Secrets of Soil, which opened on July 19, 2008 at the Smithsonian's Natural History Museum in Washington, DC.
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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Transportation and Logistics
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The stratosphere (/
Ozone and temperature
The mechanism describing the formation of the ozone layer was described by British mathematician Sydney Chapman in 1930. Molecular oxygen absorbs high energy sunlight in the UV-C region, at wavelengths shorter than about 240 nm. The oxygen atoms produced combine with molecular oxygen to form ozone. Ozone in turn is photolysed much more rapidly than molecular oxygen as it has a stronger absorption that occurs at longer wavelengths, where the solar emission is more intense. Ozone (O3) photolysis produces O and O2. The oxygen atom product combines with atmospheric molecular oxygen to reform O3, releasing heat. The rapid photolysis and reformation of ozone heats the stratosphere resulting in a temperature inversion. This increase of temperature with altitude is characteristic of the stratosphere; its resistance to vertical mixing means that it is stratified. Within the stratosphere temperatures increase with altitude (see temperature inversion); the top of the stratosphere has a temperature of about 270 K (−3°C or 26.6°F). This vertical stratification, with warmer layers above and cooler layers below, makes the stratosphere dynamically stable: there is no regular convection and associated turbulence in this part of the atmosphere. However, exceptionally energetic convection processes, such as volcanic eruption columns and overshooting tops in severe supercell thunderstorms, may carry convection into the stratosphere on a very local and temporary basis. Overall the attenuation of solar UV at wavelengths that damage DNA by the ozone layer allows life to exist on the surface of the planet outside of the ocean. All air entering the stratosphere must pass through the tropopause, the temperature minimum that divides the troposphere and stratosphere. The rising air is literally freeze dried; the stratosphere is a very dry place. The top of the stratosphere is called the stratopause, above which the temperature decreases with height.
Sydney Chapman gave a correct description of the source of stratospheric ozone and its ability to generate heat within the stratosphere; he also wrote that ozone may be destroyed by reacting with atomic oxygen, making two molecules of molecular oxygen. We now know that there are additional ozone loss mechanisms, and that these mechanisms are catalytic meaning that a small amount of the catalyst can destroy a great number of ozone molecules. The first is due to the reaction of hydroxyl radicals OH· with ozone. OH is formed by the reaction of electronically excited oxygen atoms produced by ozone photolysis, with water vapor. While the stratosphere is dry, additional water vapor is produced in situ by the photochemical oxidation of methane (CH4). The HO2 radical produced by the reaction of OH with O3 is recycled to OH by reaction with oxygen atoms or ozone. In addition, solar proton events can significantly effect ozone levels via Radiolysis with the subsequent formation of OH . Laughing gas or Nitrous oxide (N2O) is produced by biological activity at the surface and is oxidised to NO in the stratosphere; the so-called NOx radical cycles also deplete stratospheric ozone. Finally, chlorofluorocarbon molecules are photolysed in the stratosphere releasing chlorine atoms that react with ozone giving ClO and O2. The chlorine atoms are recycled when ClO reacts with O in the upper stratosphere, or when ClO reacts with itself in the chemistry of the Antarctic ozone hole. Paul J. Crutzen, Mario J. Molina and F. Sherwood Rowland were awarded the Nobel Prize in Chemistry in 1995 for their work describing the formation and decomposition of stratospheric ozone.
Commercial airliners typically cruise at altitudes of 9–12 km (30,000–39,000 ft) which is in the lower reaches of the stratosphere in temperate latitudes. This optimizes fuel efficiency, mostly due to the low temperatures encountered near the tropopause and low air density, reducing parasitic drag on the airframe. Stated another way, it allows the airliner to fly faster while maintaining lift equal to the weight of the plane. (The fuel consumption depends on the drag, which is related to the lift by the lift-to-drag ratio.) It also allows them to stay above the turbulent weather of the troposphere.
Because the temperature in the tropopause and lower stratosphere is largely constant with increasing altitude, very little convection and its resultant turbulence occurs there. Most turbulence at this altitude is caused by variations in the jet stream and other local wind shears, although areas of significant convective activity (thunderstorms) in the troposphere below may produce turbulence as a result of convective overshoot.
On October 24, 2014, Alan Eustace became the record holder for reaching the altitude record for a manned balloon at 135,890 ft (41,419 m). Dr Eustace also broke the world records for vertical speed skydiving, reached with a peak velocity of 1,321 km/h (822 mph) and total freefall distance of 123,414 ft (37,617 m) – lasting four minutes and 27 seconds.
Circulation and mixing
The stratosphere is a region of intense interactions among radiative, dynamical, and chemical processes, in which the horizontal mixing of gaseous components proceeds much more rapidly than does vertical mixing. The overall circulation of the stratosphere is termed as Brewer-Dobson circulation, which is a single celled circulation, spanning from the tropics up to the poles, consisting of the tropical upwelling of air from the tropical troposphere and the extra-tropical downwelling of air. Stratospheric Circulation is a pre-dominantly wave-driven circulation in that the tropical upwelling is induced by the wave force by the westward propagating Rossby Waves, in a phenomenon called Rossby-Wave pumping.
An interesting feature of stratospheric circulation is the QBO in the tropical latitudes, which is driven by gravity waves that are convectively generated in the troposphere. The QBO induces a secondary circulation that is important for the global stratospheric transport of tracers, such as ozone or water vapor.
Another large-scale feature that significantly influences Stratospheric Circulation is the breaking planetary waves resulting in intense quasi-horizontal mixing in the midlatitudes. This breaking is much more pronounced in the winter hemisphere where this region is called the surf zone. This breaking is caused due to a highly non-linear interaction between the vertically propagating planetary waves and the isolated high potential vorticity region known as Polar Vortex. The resultant breaking causes large scale mixing of air and other trace gases throughout the midlatitude surf zone. The timescale of this rapid mixing is much smaller than the much slower timescales of upwelling in the tropics and downwelling in the extratropics.
During northern hemispheric winters, sudden stratospheric warmings, caused by the absorption of Rossby waves in the stratosphere, can be observed in approximately half of winters when easterly winds develop in the stratosphere. These events often precede unusual winter weather and may even be responsible for the cold European winters of the 1960s.
Stratospheric warming of the polar vortex results in its weakening. When the vortex is strong, it keeps the cold, high pressure air masses contained in the arctic; when the vortex weakens, air masses move equatorward, and results in rapid changes of weather in the mid latitudes.
Bacterial life survives in the stratosphere, making it a part of the biosphere. In 2001 an Indian experiment, involving a high-altitude balloon, was carried out at a height of 41 kilometres and a sample of dust was collected with bacterial material inside.
Some bird species have been reported to fly at the lower levels of the stratosphere. On November 29, 1973, a Rüppell's vulture (Gyps rueppelli) was ingested into a jet engine 11,278 m (37,000 ft) above the Ivory Coast, and bar-headed geese (Anser indicus) reportedly overfly Mount Everest's summit, which is 8,848 m (29,029 ft).
Léon Teisserenc de Bort from France and Richard Assmann from Germany, in separate publications and following years of observations, announced the discovery of an isothermal layer at around 11–14 km, which is the base of the lower stratosphere. This was based on temperature profiles from unmanned instrumented balloons.
- Le Grand Saut
- Lockheed U-2
- Paris Gun (projectile was the first artificial object to reach stratosphere)
- Red Bull Stratos
- RQ-4 Global Hawk
- Service ceiling
- "ISS022-E-062672 caption". NASA. Archived from the original on 19 November 2012. Retrieved 21 September 2012.
- "Atmospheric Temperature Trends, 1979–2005". NASA/Earth Observatory. 6 July 2007. Archived from the original on 5 September 2015. Retrieved 24 August 2015.
- Jones, Daniel (2003) , Peter Roach, James Hartmann and Jane Setter, eds., English Pronouncing Dictionary, Cambridge: Cambridge University Press, ISBN 3-12-539683-2
- "Stratosphere". Merriam-Webster Dictionary.
- Seinfeld, J. H., and S. N.(2006), Atmospheric Chemistry and Physics: From Air Pollution to Climate Change 2nd ed, Wiley, New Jersey
- "Altitude of a Commercial Jet". Hypertextbook.com. Archived from the original on 2011-10-31. Retrieved 2011-11-08.
- "Google's Alan Eustace beats Baumgartner's skydiving record". BBC News. Archived from the original on 2014-10-25.
- N.Butchart, A.A. Scaife, J. Austin, S.H.E. Hare, J.R. Knight. Quasi-biennial oscillation in ozone in a coupled chemistry-climate model Archived 2014-05-18 at the Wayback Machine., Journal of Geophysical Research.
- M.E. McIntyre, T.N. Palmer. Breaking planetary waves in the stratosphere Archived 2017-03-17 at the Wayback Machine., Nature.
- M.P. Baldwin and T.J. Dunkerton. 'Stratospheric Harbingers of Anomalous Weather Regimes Archived 2014-01-12 at the Wayback Machine., Science Magazine.
- A.A. Scaife, J.R. Knight, G.K. Vallis, C.K. Folland. A stratospheric influence on the winter NAO and North Atlantic surface climate Archived 2014-05-18 at the Wayback Machine., Geophysical Research Letters.
- S. Shivaji et al, "Isolation of three novel bacterial strains, Janibacter hoylei sp. nov., Bacillus isronensis sp. nov. and Bacillus aryabhattai sp. nov. from cryotubes used for collecting air from upper atmosphere.", Int J Syst Evol Microbiol, 2009.
- M. M. Woolfson. Time, Space, Stars & Man: The Story of the Big Bang. World Scientific; 2013. ISBN 978-1-84816-933-3. p. 388.
- Laybourne, Roxie C. (December 1974). "Collision between a Vulture and an Aircraft at an Altitude of 37,000 Feet" (PDF). The Wilson Bulletin. Wilson Ornithological Society. 86 (4): 461–462. ISSN 0043-5643. JSTOR 4160546. OCLC 46381512. Archived (PDF) from the original on 2014-02-22.
- "Audubon: Birds". Audubonmagazine.org. Archived from the original on 2011-09-14. Retrieved 2011-11-08.
- Thomas Alerstam, David A. Christie, Astrid Ulfstrand. Bird Migration (1990). Page 276.
- The dictionary definition of stratosphere at Wiktionary
- Current map of global winds and temperatures at the 10 hPa level. | <urn:uuid:6636fe85-fb16-4133-b756-fc554853680c> | 4.46875 | 2,580 | Knowledge Article | Science & Tech. | 44.221283 | 95,487,819 |
Drag and Drop in Java - This section is going to illustrates you how to create a program to drag and drop the tree item in Java .
In SWT, the class DND provides all the constants to drag the source and drop. The class DragSource defines the source for drag transfer. The method setTransfer() sets the text to be transferred by the DragSource. The class TextTransfer converts the plain text into a specific representation of data. The method getInstance() returns the instance of TextTransfer class. The method addDragListener() notifies when a drag and drop operation is in progress by calling the class DragSourceAdapter.
The class Tree allows to create the hierarchy of items. We have create a tree to drag the tree item and drop it into the text. The method getSelection() returns an array of selected tree items.
The class DropTarget defines the target to drop the text. The method setTransfer() specifies the text that can be transferred to the DropTarget. The method addDropListener() notifies when a drag and drop operation is in progress by calling the class DropTargetAdapter.
Following code sets the data to be the first selected item's text:
|event.data = tree.getSelection().getText();|
Following code sets the text field to get the dropped text.
Here is the code of DragAndDropExample.java
Output will be displayed as: | <urn:uuid:a4770738-6f57-4adc-896c-a76d8cae38a4> | 3.328125 | 289 | Tutorial | Software Dev. | 57.915808 | 95,487,826 |
Was there ever life on Mars? That's a question the European Space Agency hopes to answer through the ExoMars mission, which will fly to the red planet in 2013. As the New Scientist reports, one crucial element of the mission—the Urey instrument—has received $2 million in funding from NASA, and it will probe Martian soil two meters (6.6 feet) below the surface in order to seek out amino acids.
Chemical signs of life can be ambiguous, but scientists are hoping that Urey will be able to tell whether any amino acids on Mars were made by living organisms or some other process.
The key is to measure the symmetry, or "chirality" of each amino acid, which can be in either of two mirror-image configurations, labelled L and D. . . . "Life on Earth is based on chiral molecules, so our underlying assumption is that this is a central feature of biochemistry," says instrument team leader Jeffrey Bada of the University of California, San Diego, US.
The lesson from Earth is that biology will use only one of the two possible chiral forms. All amino acids in terrestrial life are of the L form, whereas synthetic amino acids come in equal mixtures of L and D.
In order to distinguish between L and D variants, Urey will see how the amino acids react to a chiral molecule dubbed g-cyclodextrin, the New Scientist says. Researchers behind the Urey instrument are counting on the device's very high sensitivity, which is high enough to detect "a few cells per gram," according to Bada. | <urn:uuid:52336309-4947-4104-9fcb-f43d96291eee> | 3.90625 | 328 | News Article | Science & Tech. | 51.181364 | 95,487,840 |
NASA announced that any future missions to the moon will be done in metric. This will simplify communications with companies and organizations from other countries, and it will allow things like metric hand tools — used by the Russian space agency — to be used on the NASA missions.
Besides simplifying tools and making communication easier between countries, it also avoids a particular form of disaster. NASA has used the metric system since 1990, but to make it easier for American contractors they used a dual system, with both metric and imperial units in play. This had disastrous consequences in 1999. The Mars Climate Orbiter was destroyed on insertion into Mars orbit because of a metric conversion error. A thruster contractor gave NASA thrust data in imperial measurements (pounds of thrust per second, or pound-seconds). Most of the data was in metric, since the programs came from the Mars Global Surveyor. There was a conversion factor for converting pound-seconds to newton-seconds, but it was buried in a formula... and was left out of the Mars Climate Orbiter's software.
A pound-second is the amount of force produced by a thruster in pounds of force per second. The metric equivalent is a newton-second. A newton is the amount of force it takes to accelerate a kilogram at 1 metre per second per second (or metre/second2. There are 4.45 pounds in a newton.
When the Mars Climate Orbiter had to make an engine thrust to put it into Mars orbit, it was told to fire its thrusters for a certain length of time. The program thought that the thrusters were less powerful than they were. Instead of putting the robotic orbiter at an altitude of between 140 and 150 kilometres, the orbiter was thrown into an orbit 57 km high. Before it had a chance to slow down. Friction and forces tore the orbiter apart.
NASA also says they will use standard Internet protocols for communicating with moon missions. This will make it easier for private companies and smaller organizations to get involved.
This is assuming that a moon mission actually happens in my lifetime. There's some question as to whether or not a moon mission will get off the ground, or if it was just thrown out there for the sake of politics, or for the sake of the current administration's legacy.
Here's the story about NASA and the metric system: http://www.space.com/news/070108_moon_metric.html
4 Good Years
1 year ago | <urn:uuid:24d81973-62a1-4933-830e-762c548c8e62> | 3.65625 | 508 | Personal Blog | Science & Tech. | 57.26247 | 95,487,858 |
Examine an executing Power Query mashup under a microscope and what to you see? Data pulsing down pathways between expressions. Increase your microscope’s magnifying power. As you zoom in on one of the flows, what you’re viewing transforms from a blurred stream of data into the individual data items that make up that flow.
As you study what you see, you notice that the data items flowing by fit into groupings based on the kind of value they contain: some hold text, others are made up of a date, a time or a datetime; yet others are true/false values, then there are numbers…and it looks like there are even more categories beyond these!
In this post, we’ll begin exploring these categories—we’ll begin exploring the kinds of values supported by the M language. In programming parlance, these kinds of values” are called types.
Types can have special behaviors associated with them. For example, date and time have a special rule around addition: add a date and a time together and you get back a datetime! We’ll investigate these special rules.
Also, we’ll discuss the literal syntax associated with each type. In this context, ”literal” implies that you literally want to write out a value in code. You might, for example, literally want to set variable rate to the hand-selected value of 100. The syntax you use to code up the expression that produces the literal value you want is called literal syntax. Different types have different literal syntax rules. We’ll talk about these rules, as well.
There’s a lot to cover. In this post, we’ll explore the specifics of text (strings). If we explored all of the types in this post, it would get mighty long, so we’ll save the others for later.
- Introduction, Simple Expressions &
- Functions: Defining (part 2)
- Functions: Function Values, Passing, Returning, Defining Inline, Recursion (part 3)
- Variables & Identifiers (part 4)
- Paradigm (part 5)
- Power Query M Primer (Part 6): Types—Intro & Text (Strings) [this post]
In M code, to type up text, you have one choice. Unlike some programming languages, M’s literal strings come in only one flavor. No single-quoted vs. double quoted. No heredocs. No interpolated strings. Plain and simple—just double-quoted Unicode strings.
If the string itself needs to contain the double-quote character, the simplest way to accommodate that need is to escape each double quote by doubling it:
"He said ""run"" and so I did." // evaluates to the string: He said "run" and so I did.
Strings can also span multiple lines.
However, at times (perhaps often), you may find it more convenient to code multi-line strings using a single line of source code. To do this, use an escape sequence. These sequences start with “#(“, contain an escape code (or several codes, as we’ll see in a moment) and end with “)”.
Power Query supports three special control character escape codes:
Below, a line feed character is encoded into a string using an escape sequence.
Multiple escape codes can be combined inside an escape sequence by separating them with commas. However, no extra whitespace is allowed (interesting—this is one of the few places in Power Query where whitespace between language elements is relevant).
"Hello#(cr,lf)World" "Hello#(cr)#(lf)World" // evaluates to the same string as the preceding
Short and long hexadecimal Unicode values can also be used. This ability comes in handy when you need a string to contain a character that’s not easy to type on your keyboard—or when you want to show a simple example, like the below which demonstrates using both short and long hexadecimal syntax to insert a total of two spaces between the two words.
"Hello#(0020,00000020)World" // evaluates to: Hello World
The escape sequence’s syntax raises a question: What happens if you want
#( to literally be in a string? You’re not trying to use it as an escape sequence. Instead, you want those characters to literally be included in the string.
The answer? You escape it by…drumroll please…using an escape sequence! Below, the “#” symbol inside the escape sequence is a special escape code called an escape escape.
"Part Code #(#)(2501)" // becomes string: Part Code #(2150)
Once you have a value of type text—whether you hand-coded it using a string literal or received it as the output value from another expression, you can work with it using several operators.
Text support standard comparison operators (=, <>, >=, >, <=, <). Using them is straightforward.
"a" = "a" // evaluates to true "a" > "b" // evaluates to false
Comparison are case-sensitive. To compare in a case-insensitive way, you’ll need to fall back to a library function. For example:
Comparer.Equals(Comparer.OrdinalIgnoreCase, "A", "a") // evaluates to true
Text values can be combined (concatenated) using the combination operator (&):
"Good" & " " & "Morning!" // evaluates to: Good Morning!
However, Power Query does not implicitly convert non-text values to text when they are concatenated with text. The below isn’t allowed. Text and numbers can’t be directly concatenated together.
"You have " & 5 & " left."
Don’t worry, though! It’s easy to adapt the above so it works. Simply use a library function to convert the number to text.
"You have " & Text.From(0.5) & " left." // evaluates to: You have 0.5 left. "You have " & Number.ToText(0.5, "P") & " left." // evaluates to: You have 50.00% left.
Combining text with null produces null.
"Something Profound" & null // evaluates to null null & "Something Profound" // evaluates to null
Hopefully, you already know this, but Power Query’s library includes a number of functions related to type text. Unfortunately, at least as of the present, regular expression support isn’t a part of that list of functions.
There are many more types to cover. Maybe we should look at type numeric next.
Until then, happy coding! | <urn:uuid:0da7e253-6411-45a5-a827-c2188f1cd0c0> | 2.75 | 1,448 | Personal Blog | Software Dev. | 53.076799 | 95,487,894 |
factorial of a number calculator - formula, step by step calculation & solved example problems online to calculate the factorial of a given number (positive integer) n. Factorial often written with the exclamation sign: n!, is the result of series consecutive numbers product less than or equal to n (i.e) from given number to 1 as examples given below. 0! = 1 1! = 1 2! = 2 x 1 = 2 3! = 3 x 2 x 1 = 6 4! = 4 x 3 x 2 x 1 = 24 5! = 5 x 4 x 3 x 2 x 1 = 120 and so on.
In mathematics, the product of all positive integers less than or equal to n (i.e) n! = n x (n-1) x (n-2) x .... x 1. The value of 0! = 1. The factorial function is extensively used in permutaions (nPr) & combinations (nCr), probability & statistics, calculus, algebra & other advanced mathematical analysis.
The below mathematical formula is used in this calculator to find the factorial of a given positive number n!
The below solved example may be useful to understand how the values are being used in the mathematical formulas to determine the factorial of a number. Example Problem : Find the factorial for the integer 7? Solution : Data given n = 7 Step by step calculation formula to find n! = n x (n-1) x (n-2) x .... x 1 substitute the values n! = 7 x 6 x 5 x 4 x 3 x 2 x 1 n! = 5040
The factorial is an important function in the field of statistics & probability. The above formulas, step by step calculation & solved example may be useful to understand how to determine the factorial of a number but for fast computation, when it comes to online this factorial calculator may be useful to perform & verify your such calculations online.
|Math Worksheet to find n Factorial value|
|Worksheet for Octal Number Conversion|
|Trapezium Area Calculation|
|Exponential Distribution Formula, Example| | <urn:uuid:fc7fc9a8-76c9-4dbe-be61-8c45f070cd23> | 3.734375 | 443 | Product Page | Science & Tech. | 73.968788 | 95,487,897 |
Following a heart attack, cells die, causing lasting damage to the heart.
Keith Jones, PhD, a researcher in the department of pharmacology and cell biophysics, and colleagues are trying to reduce post-heart attack damage by studying the way cells die in the heart—a process controlled by transcription factors.
Transcription factors are proteins that bind to specific parts of DNA and are part of a system that controls the transfer of genetic information from DNA to RNA and then to protein. Transfer of genetic information also plays a role in controlling the cycle of cells—from cell growth to cell death.
"We call it 'gene regulatory therapy,'" says Jones.
So far, studies have identified the role for an important group of interacting transcription factors and the genes they regulate to determine whether cells in the heart survive or die after blood flow restriction occurs.
Often, scientists use virus-like mechanisms to transfer DNA and other nucleic acids inside the body.
The "virus" takes over other healthy cells by injecting them with its DNA. The cells, then transformed, begin reproducing the virus' DNA. Eventually they swell and burst, sending multiple replicas of the virus out to conquer other cells and repeat the process.
Now, UC researchers are further investigating new, non-viral delivery mechanisms for this transfer of DNA.
"We can use non-viral delivery vehicles to transfer nucleic acids, including transcription factor decoys, to repress activation of specific transcription factors in the heart," Jones says, adding that the researchers have made this successfully work within live animal models. "This means we can block the activity of most transcription factors in the heart without having to make genetically engineered mice."
Jones will be presenting these results at the International Society for Heart Research in Cincinnati, June 17-20.
He says this delivery mechanism involves flooding the cells with "decoys" which trick the transcription factors into binding to the decoys rather than to target genes, preventing them from activating those genes.
"We can use this technology to identify the target genes and then investigate the action of these genes in the biological process," Jones says.
He says that this delivery has limitations and advantages.
"It can be used to block a factor at any point in time and is reversible," he says. "However, right now, a specific delivery route must be used to target the tissue or cell."
Jones and other researchers are hoping that this new technology will allow them to directly address the effects of gene regulation in disease, as opposed to using classical drugs that treat symptoms or have significant adverse outcomes.
"So far, this seems to cause no adverse effects in animals," he says. "We are hopeful and are working toward pre-clinical studies."
Katie Pence | EurekAlert!
O2 stable hydrogenases for applications
23.07.2018 | Max-Planck-Institut für Chemische Energiekonversion
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
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 | Science Education
23.07.2018 | Health and Medicine
23.07.2018 | Life Sciences | <urn:uuid:bcacc0e1-cb15-4f1f-8256-6123cf6fa0a8> | 3.609375 | 1,152 | Content Listing | Science & Tech. | 39.655649 | 95,487,913 |
An exception is an event that occurs when an error arises within a program.
Ruby exceptions are packaged into objects of class Exception or one of Exception's many subclasses.
Ruby has about 30 main predefined exception classes, such as NoMemoryError, RuntimeError, SecurityError, ZeroDivisionError, and NoMethodError.
One of the standard exception classes is ArgumentError, which is used when the arguments provided to a method are fatally flawed.
You can use this class as an exception if bad data is supplied to a method of your own:
class Person def initialize(name) raise ArgumentError, "No name present" if name.empty? end # w w w .j a va 2s. c o m end fred = Person.new('')
You can call raise with no arguments at all, and a generic RuntimeError exception will be raised. | <urn:uuid:3a7910d4-ad75-45af-979e-224c666ac05e> | 4.125 | 181 | Documentation | Software Dev. | 46.295752 | 95,487,938 |
You must have used createsuperuser command in your django application at one or other time. If not then I am sure you must have used makemigrations or migrate commands in your project. Yes? Yes. So these commands, also called as management commands are used to execute some piece of code from command line. In this article I will tell you how to create your own command.
myapp |-management | |-commands | |-__init__.py | |-mycommand.py |-__init__.py- Inside commands directory create a file with name of your command. Lets say mycommand.py. - Add below code to this file.
from django.core.management.base import BaseCommand, CommandError class Command(BaseCommand): help = 'Command to do........' def add_argument(self, parser): pass def handle(self, *args, **options): try: # your logic here print("I am here") except Exception as e: CommandError(repr(e))- We must define a class with name Command which extends BaseCommand . - Here add_argument function is used to add the arguments to command on command line. - Write whatever login you want to execute in handle function. Pro tip here : If your logic is very lengthy, you can write it as a separate service and call that service function in your handle function. - Save the files and on terminal execute your command. You will see the output on the screen.
$ python manage.py mycommand
def add_arguments(self, parser): parser.add_argument('msg', nargs='+', type=str)Now you may use this variable msg in your command.
def handle(self, *args, **options): try: # your logic here msg = options["msg"] print(msg) print("I am here") except Exception as e: CommandError(repr(e))You can use this command in crontab to execute is periodically. Read this article on how to schedule a task on pythonanywhere.com server. | <urn:uuid:4757eaff-1817-44e9-b32e-647ae05ff7ff> | 2.625 | 434 | Tutorial | Software Dev. | 55.188491 | 95,487,945 |
Two MIT researchers have developed a thin-film material whose phase and electrical properties can be switched between metallic and semiconducting simply by applying a small voltage. The material then stays in its new configuration until switched back by another voltage. The discovery could pave the way for a new kind of “nonvolatile” computer memory chip that retains information when the power is switched off, and for energy conversion and catalytic applications.
The findings, reported in the journal Nano Letters in a paper by MIT materials science graduate student Qiyang Lu and associate professor Bilge Yildiz, involve a thin-film material called a strontium cobaltite, or SrCoOx.
Usually, Yildiz says, the structural phase of a material is controlled by its composition, temperature, and pressure. “Here for the first time,” she says, “we demonstrate that electrical bias can induce a phase transition in the material. And in fact we achieved this by changing the oxygen content in SrCoOx.”
“It has two different structures that depend on how many oxygen atoms per unit cell it contains, and these two structures have quite different properties,” Lu explains.
One of these configurations of the molecular structure is called perovskite, and the other is called brownmillerite. When more oxygen is present, it forms the tightly-enclosed, cage-like crystal structure of perovskite, whereas a lower concentration of oxygen produces the more open structure of brownmillerite.
The two forms have very different chemical, electrical, magnetic, and physical properties, and Lu and Yildiz found that the material can be flipped between the two forms with the application of a very tiny amount of voltage — just 30 millivolts (0.03 volts). And, once changed, the new configuration remains stable until it is flipped back by a second application of voltage.
Strontium cobaltites are just one example of a class of materials known as transition metal oxides, which is considered promising for a variety of applications including electrodes in fuel cells, membranes that allow oxygen to pass through for gas separation, and electronic devices such as memristors — a form of nonvolatile, ultrafast, and energy-efficient memory device. The ability to trigger such a phase change through the use of just a tiny voltage could open up many uses for these materials, the researchers say.
Previous work with strontium cobaltites relied on changes in the oxygen concentration in the surrounding gas atmosphere to control which of the two forms the material would take, but that is inherently a much slower and more difficult process to control, Lu says. “So our idea was, don’t change the atmosphere, just apply a voltage.”
“Voltage modifies the effective oxygen pressure that the material faces,” Yildiz adds. To make that possible, the researchers deposited a very thin film of the material (the brownmillerite phase) onto a substrate, for which they used yttrium-stabilized zirconia.
In that setup, applying a voltage drives oxygen atoms into the material. Applying the opposite voltage has the reverse effect. To observe and demonstrate that the material did indeed go through this phase transition when the voltage was applied, the team used a technique called in-situ X-ray diffraction at MIT’s Center for Materials Science and Engineering.
The basic principle of switching this material between the two phases by altering the gas pressure and temperature in the environment was developed within the last year by scientists at Oak Ridge National Laboratory. “While interesting, this is not a practical means for controlling device properties in use,” says Yildiz. With their current work, the MIT researchers have enabled the control of the phase and electrical properties of this class of materials in a practical way, by applying an electrical charge.
In addition to memory devices, the material could ultimately find applications in fuel cells and electrodes for lithium ion batteries, Lu says.
“Our work has fundamental contributions by introducing electrical bias as a way to control the phase of an active material, and by laying the basic scientific groundwork for such novel energy and information processing devices,” Yildiz adds.
In ongoing research, the team is working to better understand the electronic properties of the material in its different structures, and to extend this approach to other oxides of interest for memory and energy applications, in collaboration with MIT professor Harry Tuller.
José Santiso, the nanomaterials growth division leader at the Catalan Institute of Nanoscience and Nanotechnology in Barcelona, Spain, who was not involved in this research, calls it “a very significant contribution” to the study of this interesting class of materials, and says “it paves the way for the application of these materials both in solid state electrochemical devices for the efficient conversion of energy or oxygen storage, as well as in possible applications in a new kind of memory devices.”
The work was supported by the National Science Foundation.
Subscribe to energy news & events: (See past editions) | <urn:uuid:e00938fb-26f8-48b5-82da-e41da1c92ea6> | 3.484375 | 1,057 | News (Org.) | Science & Tech. | 21.186776 | 95,487,948 |
Scientists at the Department of Energy's Oak Ridge National Laboratory have performed neutron structural analysis of a vitamin B6-dependent protein, potentially opening avenues for new antibiotics and drugs to battle diseases such as drug-resistant tuberculosis, malaria and diabetes.
Specifically, the team used neutron crystallography to study the location of hydrogen atoms in aspartate aminotransferase, or AAT, an enzyme vital to the metabolism of certain amino acids.
An ORNL-led team used neutrons to observe the AAT enzyme, a vitamin B6-dependent protein, and found that the chemical reaction occurred only in one active site. Nuclear scattering length density maps (colored mesh) highlight the positions of critical hydrogen atoms, including a low-barrier hydrogen bond (magenta mesh) not thought to exist in AAT, which may be crucial for catalysis.
Credit: Jill Hemman and Andrey Kovalevsky /Oak Ridge National Laboratory, US Dept. of Energy
"We visualized the first neutron structure of a vitamin B6 enzyme that belongs to a large protein family with hundreds of members that exist in nature," said ORNL's Andrey Kovalevsky, a senior co-author of the study, which was published in Nature Communications.
Vitamin B6-dependent proteins are part of a diverse group of enzymes that conduct over a hundred different chemical reactions in cells. The enzymes are of interest to biomedical, as well as bioenergy, researchers because of their role in metabolizing amino acids and other cell nutrients.
"These enzymes are unique in that each one performs a specific chemical reaction with exquisite accuracy, while suppressing other viable chemical transformations," Kovalevsky said. "How they accomplish this is not well understood, but it is of great significance for drug design."
The team's previous research predicted that hydrogen atoms move in and around the enzyme's active site, where the chemical reaction takes place, indicating that the hydrogen atoms' positioning controls the reaction type. Knowing the precise location of hydrogen atoms can explain why the behavior of these enzymes is so specific, but hydrogen is hard to detect with standard methods such as X-ray crystallography.
To directly determine the positions of hydrogen atoms within AAT, the ORNL-led team turned to neutron diffraction techniques. The researchers exposed delicate protein crystals to neutrons using the IMAGINE beamline at ORNL's High Flux Isotope Reactor and the LADI-III beamline at the Institut Laue-Langevin in Grenoble, France.
Surprisingly, the team observed a reaction within one AAT protein biomolecule while another AAT biomolecule was unchanged, providing a before-and-after perspective of the enzyme-catalyzed chemical reaction.
"The data revealed that in one of the enzyme's biomolecular structures the covalent bonds reorganized after a chemical reaction occurred in the active site and, in another, the reaction had not taken place," Kovalevsky said. "Essentially, we were able to obtain two structures in one crystal, which has never been done before for any protein using neutrons."
With this knowledge, the team will run molecular simulations to determine the hydrogen atoms' specific behavior when interacting with the enzyme. The results could be useful in guiding the future design of novel medicines against multidrug-resistant tuberculosis, malaria, diabetes and antibiotic-resistant bacteria.
"This study highlights how neutrons are an unrivaled probe for identifying the location of hydrogen atoms in biological systems, providing us with an unprecedented level of structural detail for this important enzyme," LADI-III beamline scientist Matthew Blakeley said.
The neutron crystallography study, titled "Direct visualization of critical hydrogen atoms in a pyridoxal 5'- phosphate enzyme," included co-authors Steven Dajnowicz of ORNL and the University of Toledo; ORNL's Andrey Kovalevsky, Jerry Parks, Ryne C. Johnston and Kevin L. Weiss; Matthew P. Blakeley of the Institut Laue Langevin; David A. Keen of Rutherford Appleton Laboratory; Oksana Gerlits of the University of Tennessee, and Timothy C. Mueser of the University of Toledo.
Steven Dajnowicz, the paper's lead co-author and a doctoral student at the University of Toledo, works in ORNL's Biology and Soft Matter Division as part of ORNL's Graduate Opportunities (GO!) student program. Mueser is Dajnowicz' advisor and a senior co-author of the paper.
This project was funded by DOE's Office of Science and used resources at ORNL's Center for Structural Molecular Biology. Neutron crystallography work was performed at ORNL's HFIR, a DOE Office of Science User Facility, and at the Institut Laue-Langevin. This work also used ORNL's Compute and Data Environment for Science for quantum mechanical calculations. This project was also supported in part by the Center for the Advancement of Science in Space and the National Aeronautics and Space Administration.
ORNL is managed by UT-Battelle for the Department of Energy's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. DOE's Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit http://science.
Sara Shoemaker | 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...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Materials Sciences
19.07.2018 | Earth Sciences
19.07.2018 | Life Sciences | <urn:uuid:59cfd645-7411-4cba-9b6c-f0f7ead4a29e> | 3.390625 | 1,759 | Content Listing | Science & Tech. | 31.409592 | 95,487,978 |
Concept: Batesian mimicry
- Proceedings of the National Academy of Sciences of the United States of America
- Published over 5 years ago
A near-perfect mimetic association between a mecopteran insect species and a ginkgoalean plant species from the late Middle Jurassic of northeastern China recently has been discovered. The association stems from a case of mixed identity between a particular plant and an insect in the laboratory and the field. This confusion is explained as a case of leaf mimesis, wherein the appearance of the multilobed leaf of Yimaia capituliformis (the ginkgoalean model) was accurately replicated by the wings and abdomen of the cimbrophlebiid Juracimbrophlebia ginkgofolia (the hangingfly mimic). Our results suggest that hangingflies developed leaf mimesis either as an antipredator avoidance device or possibly as a predatory strategy to provide an antiherbivore function for its plant hosts, thus gaining mutual benefit for both the hangingfly and the ginkgo species. This documentation of mimesis is a rare occasion whereby exquisitely preserved, co-occurring fossils occupy a narrow spatiotemporal window that reveal likely reciprocal mechanisms which plants and insects provide mutual defensive support during their preangiospermous evolutionary histories.
- Proceedings. Biological sciences / The Royal Society
- Published about 5 years ago
The great majority of plant species in the tropics require animals to achieve pollination, but the exact role of floral signals in attraction of animal pollinators is often debated. Many plants provide a floral reward to attract a guild of pollinators, and it has been proposed that floral signals of non-rewarding species may converge on those of rewarding species to exploit the relationship of the latter with their pollinators. In the orchid family (Orchidaceae), pollination is almost universally animal-mediated, but a third of species provide no floral reward, which suggests that deceptive pollination mechanisms are prevalent. Here, we examine floral colour and shape convergence in Neotropical plant communities, focusing on certain food-deceptive Oncidiinae orchids (e.g. Trichocentrum ascendens and Oncidium nebulosum) and rewarding species of Malpighiaceae. We show that the species from these two distantly related families are often more similar in floral colour and shape than expected by chance and propose that a system of multifarious floral mimicry-a form of Batesian mimicry that involves multiple models and is more complex than a simple one model-one mimic system-operates in these orchids. The same mimetic pollination system has evolved at least 14 times within the species-rich Oncidiinae throughout the Neotropics. These results help explain the extraordinary diversification of Neotropical orchids and highlight the complexity of plant-animal interactions.
Venom systems have evolved on multiple occasions across the animal kingdom, and they can act as key adaptations to protect animals from predators . Consequently, venomous animals serve as models for a rich source of mimicry types, as non-venomous species benefit from reductions in predation risk by mimicking the coloration, body shape, and/or movement of toxic counterparts [2-5]. The frequent evolution of such deceitful imitations provides notable examples of phenotypic convergence and are often invoked as classic exemplars of evolution by natural selection. Here, we investigate the evolution of fangs, venom, and mimetic relationships in reef fishes from the tribe Nemophini (fangblennies). Comparative morphological analyses reveal that enlarged canine teeth (fangs) originated at the base of the Nemophini radiation and have enabled a micropredatory feeding strategy in non-venomous Plagiotremus spp. Subsequently, the evolution of deep anterior grooves and their coupling to venom secretory tissue provide Meiacanthus spp. with toxic venom that they effectively employ for defense. We find that fangblenny venom contains a number of toxic components that have been independently recruited into other animal venoms, some of which cause toxicity via interactions with opioid receptors, and result in a multifunctional biochemical phenotype that exerts potent hypotensive effects. The evolution of fangblenny venom has seemingly led to phenotypic convergence via the formation of a diverse array of mimetic relationships that provide protective (Batesian mimicry) and predatory (aggressive mimicry) benefits to other fishes [2, 6]. Our results further our understanding of how novel morphological and biochemical adaptations stimulate ecological interactions in the natural world.
Mimicry is one of the oldest concepts in biology, but it still presents many puzzles and continues to be widely debated. Simulation of wasps with a yellow-black abdominal pattern by other insects (commonly called “wasp mimicry”) is traditionally considered a case of resemblance of unprofitable by profitable prey causing educated predators to avoid models and mimics to the advantage of both (Figure 1a). However, as wasps themselves are predators of insects, wasp mimicry can also be seen as a case of resemblance to one’s own potential antagonist. We here propose an additional hypothesis to Batesian and Müllerian mimicry (both typically involving selection by learning vertebrate predators; cf. Table 1) that reflects another possible scenario for the evolution of multifold and in particular very accurate resemblances to wasps: an innate, visual inhibition of aggression among look-alike wasps, based on their social organization and high abundance. We argue that wasp species resembling each other need not only be Müllerian mutualists and that other insects resembling wasps need not only be Batesian mimics, but an innate ability of wasps to recognize each other during hunting is the driver in the evolution of a distinct kind of masquerade, in which model, mimic, and selecting agent belong to one or several species (Figure 1b). Wasp mimics resemble wasps not (only) to be mistaken by educated predators but rather, or in addition, to escape attack from their wasp models. Within a given ecosystem, there will be selection pressures leading to masquerade driven by wasps and/or to mimicry driven by other predators that have to learn to avoid them. Different pressures by guilds of these two types of selective agents could explain the widely differing fidelity with respect to the models in assemblages of yellow jackets and yellow jacket look-alikes.
Abstract Because predation is the main cause of avian nest failure, selection should favor strategies that reduce the probability of nest predation. We describe apparent Batesian mimicry in the morphology and behavior of a Laniocera hypopyrra nestling. On hatching, the nestling had a distinctive bright orange color and modified feathers all over its body, and 6 days after hatching, it started to move its head very slowly from side to side (in a “caterpillar” movement) when disturbed. These traits gave it a resemblance to a hairy, aposematic caterpillar. This species has a long nestling period for its size (20 days), perhaps due to slow provisioning rates (about one feeding per hour). We argue that the slow growth rate, combined with high nest predation, favors the evolution of antipredation mechanisms such as the unique morphological and behavioral characteristics of L. hypopyrra nestlings.
Batesian mimicry, a phenomenon in which harmless organisms resemble harmful or unpalatable species, has been extensively studied in evolutionary biology. Model species may differ from population to population of a single mimetic species, so different predation pressures might have driven micro-evolution towards better mimicry among regions. However, there is scant direct evidence of micro-evolutionary change over time in mimicry traits. Papilio polytes shows female-limited Batesian mimicry. On Okinawa, one mimicry model is Pachliopta aristolochiae, which was not present on the island until 1993. In P. polytes, the size of the hind-wing white spot, a mimetic trait, is maternally heritable. Among specimens collected between 1961 and 2016, the average white spot size was unchanged before the model’s arrival but has rapidly increased since then. However, white spot size showed greater variance after the model’s establishment than before. This suggests that before 1993, white spot size in this population was not selectively neutral but was an adaptive trait for mimicking an unpalatable native, Byasa alcinous, which looks like P. aristolochiae apart from the latter’s hind-wing white spot. Thus, some females switched their model to the new one after its arrival.
Although the forces behind the evolution of imperfect mimicry remain poorly studied, recent hypotheses suggest that relaxed selection on small-bodied individuals leads to imperfect mimicry. While evolutionary history undoubtedly affects the development of imperfect mimicry, ecological community context has largely been ignored and may be an important driver of imperfect mimicry. Here we investigate how evolutionary and ecological contexts might influence mimetic fidelity in Müllerian and Batesian mimicry systems. In Batesian hoverfly systems we find that body size is not a strong predictor of mimetic fidelity. However, in Müllerian velvet ants we find a weak positive relationship between body size and mimetic fidelity when evolutionary context is controlled for and a much stronger relationship between community diversity and mimetic fidelity. These results suggest that reduced selection on small-bodied individuals may not be a major driver of the evolution of imperfect mimicry and that other factors, such as ecological community context, should be considered when studying the evolution of imperfect mimicry.
Warning signals are an effective defence strategy for aposematic prey, but only if they are recognized by potential predators. If predators must eat prey to associate novel warning signals with unpalatability, how can aposematic prey ever evolve? Using experiments with great tits (Parus major) as predators, we show that social transmission enhances the acquisition of avoidance by a predator population. Observing another predator’s disgust towards tasting one novel conspicuous prey item led to fewer aposematic than cryptic prey being eaten for the predator population to learn. Despite reduced personal encounters with unpalatable prey, avoidance persisted and increased over subsequent trials. Next we use a mathematical model to show that social transmission can shift the evolutionary trajectory of prey populations from fixation of crypsis to fixation of aposematism more easily than was previously thought. Therefore, social information use by predators has the potential to have evolutionary consequences across ecological communities.
Animal communication is often deceptive; however, such dishonesty can become ineffective if it is used too often, is used out of context, or is too easy to detect [1-3]. Mimicry is a common form of deception, and most mimics gain the greatest fitness benefits when they are rare compared to their models [3, 4]. If mimics are encountered too frequently or if their model is absent, avoidance learning of noxious models is disrupted (Batesian mimicry ), or receivers become more vigilant and learn to avoid perilous mimics (aggressive mimicry ). Mimics can moderate this selective constraint by imperfectly resembling multiple models , through polymorphisms , or by opportunistically deploying mimetic signals [1, 7]. Here we uncover a novel mechanism to escape the constraints of deceptive signaling: phenotypic plasticity allows mimics to deceive targets using multiple guises. Using a combination of behavioral, cell histological, and molecular methods, we show that a coral reef fish, the dusky dottyback (Pseudochromis fuscus), flexibly adapts its body coloration to mimic differently colored reef fishes and in doing so gains multiple fitness benefits. We find that by matching the color of other reef fish, dottybacks increase their success of predation upon juvenile fish prey and are therefore able to deceive their victims by resembling multiple models. Furthermore, we demonstrate that changing color also increases habitat-associated crypsis that decreases the risk of being detected by predators. Hence, when mimics and models share common selective pressures, flexible imitation of models might inherently confer secondary benefits to mimics. Our results show that phenotypic plasticity can act as a mechanism to ease constraints that are typically associated with deception. VIDEO ABSTRACT.
- Proceedings of the National Academy of Sciences of the United States of America
- Published over 3 years ago
Understanding the evolutionary transition from interspecific exploitation to cooperation is a major challenge in evolutionary biology. Ant-aphid relationships represent an ideal system to this end because they encompass a coevolutionary continuum of interactions ranging from mutualism to antagonism. In this study, we report an unprecedented interaction along this continuum: aggressive mimicry in aphids. We show that two morphs clonally produced by the aphid Paracletus cimiciformis during its root-dwelling phase establish relationships with ants at opposite sides of the mutualism-antagonism continuum. Although one of these morphs exhibits the conventional trophobiotic (mutualistic) relationship with ants of the genus Tetramorium, aphids of the alternative morph are transported by the ants to their brood chamber and cared for as if they were true ant larvae. Gas chromatography-mass spectrometry analyses reveal that the innate cuticular hydrocarbon profile of the mimic morph resembles the profile of ant larvae more than that of the alternative, genetically identical nonmimic morph. Furthermore, we show that, once in the brood chamber, mimic aphids suck on ant larva hemolymph. These results not only add aphids to the limited list of arthropods known to biosynthesize the cuticular chemicals of their deceived hosts to exploit their resources but describe a remarkable case of plastic aggressive mimicry. The present work adds a previously unidentified dimension to the classical textbook paradigm of aphid-ant relationships by showcasing a complex system at the evolutionary interface between cooperation and exploitation. | <urn:uuid:2e1e6ccc-cbe5-44cc-9f4b-6ccd6f89b4fc> | 2.71875 | 2,880 | Academic Writing | Science & Tech. | 8.335088 | 95,487,987 |
Concept: Honey bee
Neonicotinoid clothianidin adversely affects insect immunity and promotes replication of a viral pathogen in honey bees
- Proceedings of the National Academy of Sciences of the United States of America
- Published over 4 years ago
Large-scale losses of honey bee colonies represent a poorly understood problem of global importance. Both biotic and abiotic factors are involved in this phenomenon that is often associated with high loads of parasites and pathogens. A stronger impact of pathogens in honey bees exposed to neonicotinoid insecticides has been reported, but the causal link between insecticide exposure and the possible immune alteration of honey bees remains elusive. Here, we demonstrate that the neonicotinoid insecticide clothianidin negatively modulates NF-κB immune signaling in insects and adversely affects honey bee antiviral defenses controlled by this transcription factor. We have identified in insects a negative modulator of NF-κB activation, which is a leucine-rich repeat protein. Exposure to clothianidin, by enhancing the transcription of the gene encoding this inhibitor, reduces immune defenses and promotes the replication of the deformed wing virus in honey bees bearing covert infections. This honey bee immunosuppression is similarly induced by a different neonicotinoid, imidacloprid, but not by the organophosphate chlorpyriphos, which does not affect NF-κB signaling. The occurrence at sublethal doses of this insecticide-induced viral proliferation suggests that the studied neonicotinoids might have a negative effect at the field level. Our experiments uncover a further level of regulation of the immune response in insects and set the stage for studies on neural modulation of immunity in animals. Furthermore, this study has implications for the conservation of bees, as it will contribute to the definition of more appropriate guidelines for testing chronic or sublethal effects of pesticides used in agriculture.
This study measured part of the in-hive pesticide exposome by analyzing residues from live in-hive bees, stored pollen, and wax in migratory colonies over time and compared exposure to colony health. We summarized the pesticide burden using three different additive methods: (1) the hazard quotient (HQ), an estimate of pesticide exposure risk, (2) the total number of pesticide residues, and (3) the number of relevant residues. Despite being simplistic, these models attempt to summarize potential risk from multiple contaminations in real-world contexts. Colonies performing pollination services were subject to increased pesticide exposure compared to honey-production and holding yards. We found clear links between an increase in the total number of products in wax and colony mortality. In particular, we found that fungicides with particular modes of action increased disproportionally in wax within colonies that died. The occurrence of queen events, a significant risk factor for colony health and productivity, was positively associated with all three proxies of pesticide exposure. While our exposome summation models do not fully capture the complexities of pesticide exposure, they nonetheless help elucidate their risks to colony health. Implementing and improving such models can help identify potential pesticide risks, permitting preventative actions to improve pollinator health.
Visual abilities of the honey bee have been studied for more than 100 years, recently revealing unexpectedly sophisticated cognitive skills rivalling those of vertebrates. However, the physiological limits of the honey bee eye have been largely unaddressed and only studied in an unnatural, dark state. Using a bright display and intracellular recordings, we here systematically investigated the angular sensitivity across the light adapted eye of honey bee foragers. Angular sensitivity is a measure of photoreceptor receptive field size and thus small values indicate higher visual acuity. Our recordings reveal a fronto-ventral acute zone in which angular sensitivity falls below 1.9°, some 30% smaller than previously reported. By measuring receptor noise and responses to moving dark objects, we also obtained direct measures of the smallest features detectable by the retina. In the frontal eye, single photoreceptors respond to objects as small as 0.6° × 0.6°, with >99% reliability. This indicates that honey bee foragers possess significantly better resolution than previously reported or estimated behaviourally, and commonly assumed in modelling of bee acuity.
Alarm communication is a key adaptation that helps social groups resist predation and rally defenses. In Asia, the world’s largest hornet, Vespa mandarinia, and the smaller hornet, Vespa velutina, prey upon foragers and nests of the Asian honey bee, Apis cerana. We attacked foragers and colony nest entrances with these predators and provide the first evidence, in social insects, of an alarm signal that encodes graded danger and attack context. We show that, like Apis mellifera, A. cerana possesses a vibrational “stop signal,” which can be triggered by predator attacks upon foragers and inhibits waggle dancing. Large hornet attacks were more dangerous and resulted in higher bee mortality. Per attack at the colony level, large hornets elicited more stop signals than small hornets. Unexpectedly, stop signals elicited by large hornets (SS large hornet) had a significantly higher vibrational fundamental frequency than those elicited by small hornets (SS small hornet) and were more effective at inhibiting waggle dancing. Stop signals resulting from attacks upon the nest entrance (SS nest) were produced by foragers and guards and were significantly longer in pulse duration than stop signals elicited by attacks upon foragers (SS forager). Unlike SS forager, SS nest were targeted at dancing and non-dancing foragers and had the common effect, tuned to hornet threat level, of inhibiting bee departures from the safe interior of the nest. Meanwhile, nest defenders were triggered by the bee alarm pheromone and live hornet presence to heat-ball the hornet. In A. cerana, sophisticated recruitment communication that encodes food location, the waggle dance, is therefore matched with an inhibitory/alarm signal that encodes information about the context of danger and its threat level.
The causes of bee declines remain hotly debated, particularly the contribution of neonicotinoid insecticides. In 2013 the UK’s Food & Environment Research Agency made public a study of the impacts of exposure of bumblebee colonies to neonicotinoids. The study concluded that there was no clear relationship between colony performance and pesticide exposure, and the study was subsequently cited by the UK government in a policy paper in support of their vote against a proposed moratorium on some uses of neonicotinoids. Here I present a simple re-analysis of this data set. It demonstrates that these data in fact do show a negative relationship between both colony growth and queen production and the levels of neonicotinoids in the food stores collected by the bees. Indeed, this is the first study describing substantial negative impacts of neonicotinoids on colony performance of any bee species with free-flying bees in a field realistic situation where pesticide exposure is provided only as part of normal farming practices. It strongly suggests that wild bumblebee colonies in farmland can be expected to be adversely affected by exposure to neonicotinoids.
- Proceedings of the National Academy of Sciences of the United States of America
- Published about 2 years ago
Bumblebees (Bombus terrestris) use information from surrounding electric fields to make foraging decisions. Electroreception in air, a nonconductive medium, is a recently discovered sensory capacity of insects, yet the sensory mechanisms remain elusive. Here, we investigate two putative electric field sensors: antennae and mechanosensory hairs. Examining their mechanical and neural response, we show that electric fields cause deflections in both antennae and hairs. Hairs respond with a greater median velocity, displacement, and angular displacement than antennae. Extracellular recordings from the antennae do not show any electrophysiological correlates to these mechanical deflections. In contrast, hair deflections in response to an electric field elicited neural activity. Mechanical deflections of both hairs and antennae increase with the electric charge carried by the bumblebee. From this evidence, we conclude that sensory hairs are a site of electroreception in the bumblebee.
Recently, the widespread distribution of pesticides detected in the hive has raised serious concerns about pesticide exposure on honey bee (Apis mellifera L.) health. A larval rearing method was adapted to assess the chronic oral toxicity to honey bee larvae of the four most common pesticides detected in pollen and wax - fluvalinate, coumaphos, chlorothalonil, and chloropyrifos - tested alone and in all combinations. All pesticides at hive-residue levels triggered a significant increase in larval mortality compared to untreated larvae by over two fold, with a strong increase after 3 days of exposure. Among these four pesticides, honey bee larvae were most sensitive to chlorothalonil compared to adults. Synergistic toxicity was observed in the binary mixture of chlorothalonil with fluvalinate at the concentrations of 34 mg/L and 3 mg/L, respectively; whereas, when diluted by 10 fold, the interaction switched to antagonism. Chlorothalonil at 34 mg/L was also found to synergize the miticide coumaphos at 8 mg/L. The addition of coumaphos significantly reduced the toxicity of the fluvalinate and chlorothalonil mixture, the only significant non-additive effect in all tested ternary mixtures. We also tested the common ‘inert’ ingredient N-methyl-2-pyrrolidone at seven concentrations, and documented its high toxicity to larval bees. We have shown that chronic dietary exposure to a fungicide, pesticide mixtures, and a formulation solvent have the potential to impact honey bee populations, and warrants further investigation. We suggest that pesticide mixtures in pollen be evaluated by adding their toxicities together, until complete data on interactions can be accumulated.
Central place foragers, such as pollinating bees, typically develop circuits (traplines) to visit multiple foraging sites in a manner that minimizes overall travel distance. Despite being taxonomically widespread, these routing behaviours remain poorly understood due to the difficulty of tracking the foraging history of animals in the wild. Here we examine how bumblebees (Bombus terrestris) develop and optimise traplines over large spatial scales by setting up an array of five artificial flowers arranged in a regular pentagon (50 m side length) and fitted with motion-sensitive video cameras to determine the sequence of visitation. Stable traplines that linked together all the flowers in an optimal sequence were typically established after a bee made 26 foraging bouts, during which time only about 20 of the 120 possible routes were tried. Radar tracking of selected flights revealed a dramatic decrease by 80% (ca. 1500 m) of the total travel distance between the first and the last foraging bout. When a flower was removed and replaced by a more distant one, bees engaged in localised search flights, a strategy that can facilitate the discovery of a new flower and its integration into a novel optimal trapline. Based on these observations, we developed and tested an iterative improvement heuristic to capture how bees could learn and refine their routes each time a shorter route is found. Our findings suggest that complex dynamic routing problems can be solved by small-brained animals using simple learning heuristics, without the need for a cognitive map.
Honey bee pollination is a key ecosystem service to nature and agriculture. However, biosafety research on genetically modified crops rarely considers effects on nurse bees from intact colonies, even though they receive and primarily process the largest amount of pollen. The objective of this study was to analyze the response of nurse bees and their gut bacteria to pollen from Bt maize expressing three different insecticidal Cry proteins (Cry1A.105, Cry2Ab2, and Cry3Bb1). Naturally Cry proteins are produced by bacteria (Bacillus thuringiensis). Colonies of Apis mellifera carnica were kept during anthesis in flight cages on field plots with the Bt maize, two different conventionally bred maize varieties, and without cages, 1-km outside of the experimental maize field to allow ad libitum foraging to mixed pollen sources. During their 10-days life span, the consumption of Bt maize pollen had no effect on their survival rate, body weight and rates of pollen digestion compared to the conventional maize varieties. As indicated by ELISA-quantification of Cry1A.105 and Cry3Bb1, more than 98% of the recombinant proteins were degraded. Bacterial population sizes in the gut were not affected by the genetic modification. Bt-maize, conventional varieties and mixed pollen sources selected for significantly different bacterial communities which were, however, composed of the same dominant members, including Proteobacteria in the midgut and Lactobacillus sp. and Bifidobacterium sp. in the hindgut. Surprisingly, Cry proteins from natural sources, most likely B. thuringiensis, were detected in bees with no exposure to Bt maize. The natural occurrence of Cry proteins and the lack of detectable effects on nurse bees and their gut bacteria give no indication for harmful effects of this Bt maize on nurse honey bees.
Spray adjuvants are often applied to crops in conjunction with agricultural pesticides in order to boost the efficacy of the active ingredient(s). The adjuvants themselves are largely assumed to be biologically inert and are therefore subject to minimal scrutiny and toxicological testing by regulatory agencies. Honey bees are exposed to a wide array of pesticides as they conduct normal foraging operations, meaning that they are likely exposed to spray adjuvants as well. It was previously unknown whether these agrochemicals have any deleterious effects on honey bee behavior. | <urn:uuid:7adadee5-185a-4f2e-b194-3709dc7c8221> | 2.625 | 2,851 | Academic Writing | Science & Tech. | 14.098744 | 95,487,988 |
Sunlight is earth’s most ubiquitous form of energy. It is clean, inexhaustible, and the United States boasts one of the largest solar resources of any industrialized country. In the last decade, both distributed generation (small-scale installations located close to where the energy is ultimately used) and utility-scale generation have grown rapidly, and this expansion has brought solar energy into new realms of competitiveness. With effective support, solar energy can help to address some of the United States’ most pressing energy concerns, including energy security and climate change.
Solar energy is often classified as either active or passive. Active solar technology refers to electric or mechanical devices that draw on the energy of the sun to produce electricity and/or provide heating or cooling. Passive solar energy involves intelligent building design to leverage the sun’s power to light, heat, and even cool.
Photovoltaic (PV) solar technology generates electricity by converting solar radiation into direct electrical current, and photovoltaic panels have achieved success in residential, non-residential, utility-scale, and off-grid applications.
Solar Thermal Electric (STE), or concentrating solar power (CSP), technologies use mirrors and lenses to focus a large area of sunlight into a concentrated beam. The beam heats a source, most commonly water, thereby producing steam to rotate a turbine. STE systems are often utility-scale, and through efficient storage of thermal energy, a plant can continue to generate electricity after dark. STE technologies exist in four common forms, including parabolic troughs, solar power towers, parabolic dishes, and Fresnel reflectors.
Concentrating Photovoltaic (CPV) technology also uses mirrors and lenses to concentrate sunlight. However, instead of using the sunlight’s thermal energy to produce steam, the concentrated beam is directed at high-efficiency photovoltaic cells.
Solar Heating and Cooling (SHC) technology traps and stores the sun’s energy for controlled use in homes, offices, pools, and other spaces. Solar water heating is an example of a SHC technology.
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- UK Research Uncovers Cheap Way to Recycle Carbon Fiber - July 10, 2018 | <urn:uuid:246d904f-4319-49f3-b051-24bb4301217d> | 3.34375 | 483 | Knowledge Article | Science & Tech. | 18.160102 | 95,487,993 |
The replicas possess natural adhesion properties inherited from the spiky pollen particles while gaining magnetic behavior, allowing for tailored adhesion to surfaces.
These scanning electron microscope images show a pollen particle (left) that has been coated with iron oxide and a replica of the same particle (right) after firing at 600 C to remove the organic material and crystallize the iron oxide. Arrows point to features that were preserved by the process.
Credit: Courtesy of Brandon Goodwin and Ken Sandhage
By taking advantage of the native pollen grain shape and a non-natural oxide chemistry, this work provides a unique demonstration of tunable, bio-enabled multimodal adhesion. The spikes inherited from the sunflower pollen provide short range adhesion – over nanoscale distances – while the oxide chemistry provides an adhesion mode that operates over much longer distances – up to one millimeter.
The work was supported by the Air Force Office of Scientific Research, and has been accepted for publication in the journal Chemistry of Materials. A "just-accepted" version of the manuscript has appeared online.
"Pollen grains are inexpensive and sustainable templates that are readily available in large quantities," said Ken Sandhage, a professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. "Because pollen grains are already designed by nature for adhesion, we thought that it would be interesting to try to augment such natural behavior with an additional, non-natural mode of adhesion."
Sandhage and graduate student Brandon Goodwin began by examining the microscopic shapes of several types of pollen – including ragweed, pecan and dandelion – before choosing particles from the sunflower (Helianthus annuus). The sunflower pollen grains are nearly spherical, but covered with spikes that can entangle with the hairs on bees' legs, or adhere to surfaces via van der Waals forces at nanometer-scale distances, Sandhage explained.
The researchers washed the burr-like pollen particles with chloroform, methanol, hydrochloric acid and water to clean the surfaces and expose hydroxyl groups for chemically attaching their coating. They then applied iron oxide using an automated, layer-by-layer surface sol-gel process they had developed earlier for coating diatom shells made of silica. Reaction of the iron oxide precursor with the hydroxyl groups on the surface of the pollen particles resulted in a highly-conformal coatings.
The sol-gel process used alternating cycles of exposure to an iron (III) isopropoxide precursor solution and water to apply 30 thin layers of hematite (Fe2O3) onto the pollen. Heating the particles to 600 degrees Celsius then burned out the organic material from the original pollen grains and crystallized the iron oxide, leaving hollow 3D particles. The shells were then heated again in a controlled oxygen atmosphere to convert the hematite into magnetite (Fe3O4), which is more strongly magnetic.
"We examined individual pollen grains before and after firing, and we could see that the shape and surface features were well preserved," said Sandhage, who is the B. Mifflin Hood Professor in the School of Materials Science and Engineering. "The conformal nature of the coating process allowed us to generate ceramic replicas that retained even tiny surface features on the starting pollen grains."
The adhesion properties of the magnetic pollen-shaped particles were then analyzed by graduate student Ismael Gomez and professor Carson Meredith, both from Georgia Tech's School of Chemical and Biomolecular Engineering. Gomez and Meredith used an atomic force microscope (AFM) tip to press the replicas onto a variety of surfaces, then measured the force required to remove them from the surfaces. They studied replica pollen adhesion to polyvinyl alcohol, polyvinyl acetate, polystyrene, silicon, nickel and neodymium-iron-boron – and compared the adhesion properties to those of the original sunflower pollen grains.
"We found that we achieved multimodal adhesion by retaining short-range van der Waals attraction, as exhibited by the native pollen, and gaining magnetic adhesion," Sandhage said.
The layer-by-layer nature of the coating process allowed for control of the amount of magnetic material, and the magnetic properties of the pollen replicas. The researchers chose to apply 30 layers to achieve sufficient long-range magnetic behavior while retaining high-aspect-ratio, sharp spikes that provide for short-range van der Waals forces.
"Reproducibly generating large quantities of such cheap microparticles possessing high-aspect surface features over their entire particle surfaces would be quite challenging using synthetic top-down methods," Sandhage said.
The Air Force Multidisciplinary University Research Initiative (MURI) that funded the work is aimed at both understanding adhesion in natural systems and controllably tailoring such adhesion. In future research supported by the MURI, Sandhage and Meredith plan to study other oxide materials and explore the variety of shapes available in pollen particles.
"Now that we know how to generate such particle replicas, there is certainly more chemical tailoring that we can explore for adhesion," said Sandhage, who also holds an adjunct position in Georgia Tech's School of Chemistry and Biochemistry. "Through the proper combination of pollen shape, synthetic chemistry and thermal treatments, we can significantly expand the range of properties of these pollen replicas."
This research was supported by the U.S. Air Force Office of Scientific Research through award number FA9550-10-1-0555. Any conclusions are those of the authors and do not necessarily represent the official views of the U.S. Air Force.
CITATION: William Brandon Goodwin, Ismael J. Gomez, Carson Meredith and Kenneth H. Sandhage, "Conversion of Pollen Particles into Three-Dimensional Ceramic Replicas Tailored for Multimodal Adhesion." (Chemistry of Materials, 2013): http://dx.doi.org/10.1021/cm402226w
John Toon | EurekAlert!
Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern
20.07.2018 | Princeton University
Relax, just break it
20.07.2018 | DOE/Argonne National Laboratory
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 | Power and Electrical Engineering
20.07.2018 | Information Technology
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Alkanes are referred to as saturated hydrocarbons that is, hydrocarbons having all carbon atoms bonded to other carbon atoms or hydrogen atoms with sigma bonds only. As the alkanes posses weak Van Der Waals forces, the first four members, \(C_1\)
Structures of Alkanes: All the carbon atoms present in alkane are \(sp^3\)
Solubility of alkanes: Due to very little difference of electronegativity between carbon and hydrogen and covalent nature of C-C bond or C-H bond alkanes are generally non-polar molecules. As we generally observe, polar molecules are soluble in polar solvents whereas non-polar molecules are soluble in non-polar solvents. Hence, alkanes are hydrophobic in nature that is, alkanes are insoluble in water. However, they are soluble in organic solvents as the energy required to overcome the existing Van Der Waals forces and generate new Van Der Waals forces is quite comparable.
Boiling point of alkanes: As the intermolecular Van Der Waals forces increase with the increase of the molecular size or the surface area of the molecule we observe:
• Boiling point of alkanes increases with increasing molecular weight,
• The straight chain alkanes are observed to have higher boiling point in comparison to their structural isomers.
Melting point of alkanes: Melting point of alkanes follow the same trend as their boiling point that is, it increases with increase in molecular weight. This is attributed to the fact that higher alkanes are solids and it’s difficult to overcome intermolecular forces of attraction between them. It is generally observed that even numbered alkanes have higher trend in melting point in comparison to odd numbered alkanes as the even numbered alkanes pack well in solid phase, forming a well organized structure which is difficult to break.
Know more about the Pyrolysis of Hydrocarbons: Alkanes‘
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Java Data Mining
Java Data Mining (JDM) is a standard Java API for developing data mining applications and tools. JDM defines an object model and Java API for data mining objects and processes. JDM enables applications to integrate data mining technology for developing predictive analytics applications and tools. The JDM 1.0 standard was developed under the Java Community Process as JSR 73. In 2006, the JDM 2.0 specification was being developed under JSR 247, but has been withdrawn in 2011 without standardization.
Various data mining functions and techniques like statistical classification and association, regression analysis, data clustering, and attribute importance are covered by the 1.0 release of this standard.
It never received wide acceptance, and there is no known implementation.
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This article has moved to brucesherwood.net
generaly we consider that E=hv (v=frequency of light)
what I mean is there any loss in energy of light when it travel via glass or other material having heigher optical density .if it does then how?
When light travels through air, then through glass, and then reemerges into air, the final frequency is the same as before it entered the glass (and the color is unchanged). Hence the photon energy has not changed. I’m not sure what the proper description is for the photon when inside the glass, but clearly there is no energy change.
if there is no variation in energy
there will be defect in Einstine
because,we have so far consider that speed of light does not hold constant for different medium of different optical density,so by above equation there will be variation in energy E
in other case,speed of light will be same for every medium.
Please read my blog article again. Its subject is that the speed of light is always c = 3e8 m/s. Also, note that in E = hf, the frequency f is the same in the air and in the glass. As for E = mc^2, that famous equation is not a general one: it just describes the energy content of an object of nonzero mass m that is at rest, and a photon is never at rest. For objects with mass, the correct relationship between mass and energy is E = gamma*mc^2, where gamma is 1/sqrt(1-v^2/c^2), and even this more general equation is irrelevant for massless particles (m=0) such as the photon, for which the most one can say is that E = pc, where p is the momentum. For particles with nonzero mass, one can say E^2 – (pc)^2 = (mc^2)^2.
thank u sir for your kind information.if you don’t mind,can you please discribe me about the phenomina change and about permitivity of a particular substance wrt light speed
No, sorry; I haven’t the time to reply, as this is a very complex subject. See an advanced E&M textbook for such discussions.
The latest issue (March 2013) of the American Journal of Physics has a very good article that has tangential bearing on this topic. “There are no particles, there are only fields”, is about as accessible a description I’ve seen that outlines the lessons of quantum field theory on the question of field/particle duality. The title almost says it all, but in the above discussion it fits with the field descriptors of the situation implying that thinking of this propagation in terms of photons may be a bit of a red herring.
Thanks much for your comment, Joel. I found the AJP article to be very interesting indeed.
It puzzles me that you don’t mention the group velocity of light when discussing such a fundamental topic. It can be equal to the phase velocity if the medium is not dispersive. So it is c/n , in this case, which means the energy of the light pulse is delayed compared to the free space propagation case. And, clearly, the measurement of the time delay in the experiment you proposed must prove that. So it seems “the speed of light in a medium with refractive index n is 3e8/n m/s” is true or pretty close to that. Correct me if I’m wrong.
If you suddenly turn on a single-frequency sine wave, downstream of the material you will first see light arrive at the speed of c = 3e8 m/s. It is only after many cycles that a steady state is established in which there is a phase shift at the observation location that is consistent with what would happen if light moved through the material at a speed of c/n. The speed of light is everywhere and always 3e8 m/s, but the superposition of all the fields produced by all the accelerated charges, the original ones and those in the material, makes in the steady state a situation in which the phase advances through the material with a speed of c/n. The first energy to arrive downstream, before the steady state is established, arrives at the speed of 3e8 m/s.
Well I agree with you on the question of phase speed. But it is still unclear what you mean by the the first energy to arrive downstream. If we have a short pulse which is convinient to use for measuring time delay, then it has a certain shape, an envelope of the wave which propagates through space at a group velocity. And this velocity can easily be equal to c/n or close to that, which means the slab of glass actually delays the light pulse comparing with its propagation in free space. Sorry, I still cannot see where I’m wrong.
Consider a very detailed mechanistic view. You want to make a short pulse, which we can do by accelerating a point charge upwards from rest and then decelerate it to rest. This pulse will propagate downstream where it encounters a slab of glass, placed so that a normal to the glass passes through the source charge location. The electric field accelerates charges in the glass, mainly the electrons, because the nuclei are very massive. These accelerated electrons (re)radiate. At an observation location downstream (along a line to the source charge that is perpendicular to the slab) we observe an electric field that is the superposition of the radiation from the original source charge and the radiation from the electrons in the glass. With the exception of the small number of electrons lying exactly on the line connecting source and observation locations, all re-radiation from electrons in the glass is retarded compared to the original radiation, because the distance from source to off-axis electron in the glass to the observation location is longer than the direct path. This means that the first nonzero electric field is observed at a time determined by 3e8 m/s.
Continuing to observe after first noting a nonzero electric field, the shape of the pulse will be different from the original pulse because there is a transient behavior of the bound electrons in the glass which is often modeled by an electron bound to the atom by a spring-like force, with damping. Of course the usual term for this is dispersion, that the phase velocity depends on the frequency.
I’ve deliberately avoided using the terms “phase velocity” or “group velocity” to make the point as clearly as I know how. This doesn’t mean that these concepts aren’t useful, but the fundamental physics of the situation is that the speed of light is 3e8 m/s.
Thanks for your extensive reply. I think I begin to understand your point. Theses are just two different ways to look at the same situation. One way is to say that a light pulse travels at a group velocity an is therefore slowed down by a slab of glass, because this velocity is less than c in the glass. This is the conception I had in mind initially. But your point is that light always travels at 3e8 m/s and the reason why we observe the delay after it passed through a slab of glass is that at the observation location we have a superposition of the original wave and the wave from the accelerated charges in the glass. These two waves interfere destructively or constructively at different moments so that it appears to us that the light pulse was delayed.
In order for these two approaches to give the same result we must suppose that the original and the secondary wave are in antiphase at the first moment when they arrive at the observation location. And they stop canceling out each other after a delay which corresponds to the delay we can obtain from the group velocity conception. Makes sense to me. Is this what you meant?
No, that’s definitely not what I meant. I say again that in the case of the momentarily accelerated/decelerated charge, the first appearance of a nonzero field at the observation location takes place at a time that is d/3e8 seconds after the start of the acceleration, where d is the distance between source charge and observation location, for the reasons I gave. There is NO delay in the first appearance of a nonzero field. With or without the glass slab, the time when you first notice a field is d/3e8 seconds. What the glass slab does is to change E(t) at the observation location (the pulse shape), due to reradiation, to be different from what it would be without the slab.
In the case of turning on pure sinusoidal acceleration of the source charge, after a transient, in the steady state, the timing of maxima of E at the observation location is the same that you would get if light traveled at a speed c/n through the glass, and this effect is due to the superposition of the field you would get without the glass and the field due to reradiation.
All right. I see your point. Many thanks for finding time to explain! 🙂
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Материал из Антэкология /// Anthecology
Relationships between Flowering Phenology and Fruit-Set of Dwarf Shrubs in Alpine Fellfields in Northern Japan: a Comparison with a Subarctic Heathland in Northern Sweden
Relationships between flowering phenology and fruit-set of 10 ericaceous species were studied in three alpine fellfields in the Taisetsu Mountains, northern Japan. Flowering season varied from late May to early August among species. There was a positive correlation between flowering time and fruit-set under natural conditions. Pollinator exclusion by net-bagging and hand-pollination revealed that very low fruit-set in early-flowering species was caused by severe pollen limitation, while late-flowering species tended to have high fruit-set with slight pollen limitation. Such seasonal patterns reflect the changes in seasonal activity of pollinating insects, which are highly influenced by ambient temperature. A similar research program was conducted in a subarctic heathland in northern Sweden with almost similar species composition. In Sweden, however, there was no positive correlation between flowering time and fruit-set. The difference between the alpine fellfields and the subarctic heathland may be caused by the specific seasonal pattern of temperature change in either region. A steep increase in air temperature from early to mid-summer in the alpine fellfields in Japan may cause an increase in pollinator availability with progress of season. | <urn:uuid:dde698bc-26c0-4779-ba4a-1226ab087e2d> | 2.609375 | 311 | Academic Writing | Science & Tech. | 17.318252 | 95,488,077 |
In organic chemistry, transesterfication is the process of exchanging the organic group R? of an ester with the organic group R? of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst. The reaction can also be accomplished with the help of enzymes (biocatalysts) particularly lipases (E.C.184.108.40.206).
Strong acids catalyse the reaction by donating a proton to the carbonyl group, thus making it a more potent electrophile, whereas bases catalyse the reaction by removing a proton from the alcohol, thus making it more nucleophilic. Esters with larger alkoxy groups can be made from methyl or ethyl esters in high purity by heating the mixture of ester, acid/base, and large alcohol and evaporating the small alcohol to drive equilibrium.
In the transesterification mechanism, the carbonyl carbon of the starting ester react to give a tetrahedral intermediate, which either reverts to the starting material, or proceeds to the transesterified product (RCOOR2). The various species exist in equilibrium, and the product distribution depends on the relative energies of the reactant and product.
The largest scale application of transesterification is in the synthesis of polyesters. In this application diesters undergo transesterification with diols to form macromolecules. For example, dimethyl terephthalate and ethylene glycol react to form polyethylene terephthalate and methanol, which is evaporated to drive the reaction forward.
The reverse reaction, methanolysis, is also an example of transesterification. This process has been used to recycle polyesters into individual monomers (see plastic recycling). It is also used to convert fats (triglycerides) into biodiesel. This conversion was one of the first uses. Transesterified vegetable oil (biodiesel) was used to power heavy-duty vehicles in South Africa before World War II.
It was patented in the US in the 1950s by Colgate, though biolipid transesterification may have been discovered much earlier. In the 1940s, researchers were looking for a method to more readily produce glycerol, which was used to produce explosives for World War II. Many of the methods used today by producers have their origin in the original 1940s research.
Biolipid transesterification has also been recently shown by Japanese researchers to be possible using a super-critical methanol methodology, whereby high temperature, high-pressure vessels are used to physically catalyze the biolipid/methanol reaction into fatty-acid methyl esters.
Base-catalyzed transesterification is characterized by a negative activation volume (approx. -12 cm3/mol) and therefore it proceeds faster under high-pressure conditions. It has been shown that amine-catalyzed alcoholysis of sterically hindered esters (e.g. protecting groups, chiral auxiliaries) proceeds rapidly at room temperature under 10 kbar pressure, giving quantitative yields. | <urn:uuid:7ae26b65-5f21-44aa-b3b7-b6a1b1e18be9> | 3.6875 | 644 | Knowledge Article | Science & Tech. | 22.328279 | 95,488,128 |
After the sun sets over the desert, pocket mice start shaking their little tails – really shaking them. And shaking their entire rear ends. I first noticed the strange behavior while going through footage from wildlife cameras while researching a different question. I soon realized how few mammologists had seen the dancing.
Recently, India has come under scrutiny for its failure to improve food and nutrition security (FNS). Prominent governmental and nongovernmental strategies addressing FNS include promoting horticultural crops to increase incomes, distributing food, and providing nutritional education. Analyzing qualitative data collected in the summer of 2013, I examine programs in Uttarakhand, India where hunger has been eradicated, yet malnutrition persists.
Recognizing the interdecadal changes in the dispersion of yearly hurricane activity, a new statistical model is developed to more realistically predict (by June 1 of each year) the number of seasonal hurricanes over the North Atlantic. It is based on a Poisson regression using the Multivariate ENSO Index (MEI) conditioned upon the Atlantic Multidecadal Oscillation (AMO) index, the zonal psuedo stress, and average March, April, and May (MAM) Atlantic sea surface temperatures (SSTs).
Frozen ground (i.e. permafrost) contains a huge reservoir of carbon and as the climate warms the ground thaws making old carbon accessible for microbial decomposition. Permafrost accounts for half of the world’s soil carbon (~1700 Pg) and microbes can transform this carbon into CO2 and CH4.
In January 2014 a new wastewater treatment plant (WWTP) – Agua Nueva was commissioned in Tucson Arizona. This WWTP is unique within the U.S. that it has: i) dissolved air flotation instead of conventional primary sedimentation; and ii) a 5 stage Bardenpho process for nutrient removal. In this presentation we show the efficacy of this 21st Century WWTP plant for removal of nitrogen and phosphate, and for the removal of 7 model viruses.
In the American Southwest, the current prolonged warm drought is similar to the predicted future climate change scenarios for the region. This study aimed to determine patterns in vegetation response to the early 21st century drought across ecosystem types.
Dengue fever is a mosquito-borne virus that is quickly spreading geographically, with several recent outbreaks occurring in the US. Climate change may fuel this spread because of the close relationships between climate, and the dengue vector and virus. This research examines the impact of present and future climate data on Ae. aegypti and dengue fever transmission in 32 locations across the southern United States.
Atmospheric rivers (ARs) are understood to be the cause of nearly all extreme precipitation events leading to flooding in the western United States. These narrow channels of high moisture and strong winds draw moisture from the tropics to the west coast during the winter. The floods associated with ARs have been some of the most significant in the area. Furthermore, in the context of climate change, IPCC AR4 projections show increases in frequency of ARs and longer flood-hazard seasons in California. | <urn:uuid:0b326807-06ef-49da-8bba-c02e4de16d4a> | 2.515625 | 648 | Content Listing | Science & Tech. | 31.785561 | 95,488,130 |
A technique for measuring wavefront errors in an optical system that receives light from a spatially extended, arbitrarily structured, incoherent source is described. If we place a suitable transparent mask at an image plane of the system, the structure in the light source serves as a tracer for wavefront errors. The slope of the wavefront error can be detected in the form of intensity variations in a pupil image that follows the mask. One-dimensional numerical simulations of the method as well as the analytical treatment of the proposed principle are presented. The application of the technique as a wavefront sensor in an adaptive optical system for solar observations, in which aberrations are caused by atmospheric turbulence in the light path, is discussed as an example.
O. von der Luhe,
"Wavefront Error Measurement Technique Using Extended, Incoherent Light Sources," Optical Engineering 27(12), 121078 (1 December 1988). https://doi.org/10.1117/12.7978681 | <urn:uuid:4f24b0eb-0b79-4eb9-b02f-bc1f6a52a9a4> | 2.65625 | 201 | Academic Writing | Science & Tech. | 35.737766 | 95,488,148 |
Tropical Pacific Drifting Buoys
Rick Lumpkin / Mayra Pazos, AOML, Miami
During June 2018, 262 satellite-tracked surface drifting buoys were reporting
from the tropical Pacific. The drifter array indicated that large-scale
currents were close to their climatological June strengths.
a) Top: Movements of drifting buoys in the tropical Pacific Ocean.
The linear segments of each trajectory represent a one week displacement.
Trajectories of buoys which have lost their subsurface drogues are gray; those with
drogues are blue.
b) Middle: Monthly mean currents calculated from all buoys 1993-2010 (gray),
and currents measured by the drogued buoys this month (black) smoothed by an
c) Bottom: Anomalies from the climatological monthly mean currents for this month. | <urn:uuid:3a6682ab-707c-41c7-ab91-36f5d6f513ab> | 2.90625 | 186 | Knowledge Article | Science & Tech. | 38.043442 | 95,488,157 |
Tropical cyclones are also referred to as hurricanes. They are formed when heat is released as moist air rises, during evaporation. The resultant; condensation of water vapor, fuels the formation of cyclonic windstorms and polar lows. This phenomenon leads to the formation of a warm-core storm system.
Hurricanes are commonly observed along the equator doldrums and tropical regions of the planet. The counterclockwise rotation observed in the Northern Hemisphere and clockwise rotation of winds recorded in the Southern Hemisphere, differ in strength according to location and surge.
Hurricane Formation and Characteristics
The movement of warm air, within the hurricane, from the tropics to the temperate latitudes, makes them a major air circulation mechanism. The other advantages of hurricanes include their role in relieving drought and maintaining the troposphere's equilibrium.
Tropical hurricanes have a core of 'sinking' air, also referred to as the 'eye of the hurricane'. Interestingly, the weather in this core region is calm and cloud free. The spherical formation may range in size from 2.5 kms to 370 kms in diameter! The 'stadium effect' refers to the outward curving of the eye-wall, to resemble a stadium.
The hurricane also has a CDO or Central Dense Overcast. This region is the concentrated thunderstorm bearing region near the center or eye of the hurricane. The size of a hurricane is usually determined on the basis of the measurement from the 'center of circulation' to the outermost 'isobar'.
Interesting Facts about Hurricanes
Storms over the North Atlantic or the Caribbean are termed as hurricanes. Storms occurring in the western Pacific Ocean, are known as typhoons. Whereas storms or hurricanes forming over the Indian Ocean are termed as cyclones.
In the 19th century an Australian weatherman named Clement Wragge, came up with the idea of naming hurricanes. Since then all hurricane names were women's names. In 1979, men's names were added to the list.
A detailed study of the tropical water temperature variations, rapid cooling with altitude, high humidity, low wind shear, and the presence of a previously existent disturbance in weather, is very important to understand the phenomenon.
Hurricane activity is most commonly observed in late summer. This is mainly due to the striking difference between sea temperatures and seasonal basin patterns, within each identified temperature zone. While May is observed as the least active hurricane month, September is considered the most active, worldwide.
The six Regional Specialized Meteorological Centers worldwide are responsible for tracking hurricanes. These laboratories also issue warnings and advisories about hurricane formations in the designated areas. They function alongside six Tropical Cyclone/Hurricane Warning Centers, that ensure awareness in smaller regions. | <urn:uuid:f66b3845-5d00-4d31-991e-c297d30a3676> | 4.03125 | 565 | Knowledge Article | Science & Tech. | 26.657273 | 95,488,206 |
Drag the jigsaw pieces onto the frame so that the Roman numerals are in order from smallest to largest.
Level 1 - 6 by 5 grid starting at 1
Level 2 - 6 by 6 grid starting at a number between 3 and 9
Level 3 - 7 by 7 grid starting at a number between 33 and 49
Level 4 - 8 by 7 grid starting at a number between 70 and 88
Level 5 - 8 by 8 grid starting at a number between 450 and 470
See alse the Roman Numerals Quiz.
If you aren't an expert on Roman numerals here is an explanation:
Numbers are formed by combining symbols together. So II is two ones, i.e. 2, and XIII is a ten and three ones, i.e. 13. There is no zero in this system, so 207, for example, is CCVII, using the symbols for two hundreds, a five and two ones. 1066 is MLXVI, one thousand, fifty and ten, a five and a one.
Symbols are placed from left to right in order of value, starting with the largest. However, in a few specific cases, to avoid four characters being repeated in succession (such as IIII or XXXX) these can be reduced using subtractive notation as follows:
Explanation adapted from the Wikepedia article on Roman numerals.
This web site contains over a thousand free mathematical activities for teachers and pupils. Click here to go to the main page which links to all of the resources available.
Please contact me if you have any suggestions or questions.
Mathematicians are not the people who find Maths easy; they are the people who enjoy how mystifying, puzzling and hard it is. Are you a mathematician?
Comment recorded on the 2 May 'Starter of the Day' page by Angela Lowry, :
"I think these are great! So useful and handy, the children love them.
Comment recorded on the 18 September 'Starter of the Day' page by Mrs. Peacock, Downe House School and Kennet School:
"My year 8's absolutely loved the "Separated Twins" starter. I set it as an optional piece of work for my year 11's over a weekend and one girl came up with 3 independant solutions."
"Numeracy is a proficiency which is developed mainly in Mathematics but also in other subjects. It is more than an ability to do basic arithmetic. It involves developing confidence and competence with numbers and measures. It requires understanding of the number system, a repertoire of mathematical techniques, and an inclination and ability to solve quantitative or spatial problems in a range of contexts. Numeracy also demands understanding of the ways in which data are gathered by counting and measuring, and presented in graphs, diagrams, charts and tables."
Secondary National Strategy, Mathematics at key stage 3
Learning and understanding Mathematics, at every level, requires learner engagement. Mathematics is not a spectator sport. Sometimes traditional teaching fails to actively involve students. One way to address the problem is through the use of interactive activities and this web site provides many of those. The Go Maths main page links to more activities designed for students in upper Secondary/High school.
If you found this activity useful don't forget to record it in your scheme of work or learning management system. The short URL, ready to be copied and pasted, is as follows:
Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for those learning Mathematics anywhere in the world. Click here to enter your comments. | <urn:uuid:714f780c-b3d3-403f-83db-0ede1de5cfdf> | 3.984375 | 743 | Tutorial | Science & Tech. | 53.240511 | 95,488,219 |
Herschel was launched on 14 May 2009, and progress since launch with various webreleases can be followed on the Herschel Science Centre Latest News webpage at http://herschel.esac.esa.int/latest_news.shtml.
Herschel has a 3.5m diameter, passively cooled Cassegrain telescope and a complement of three science instruments, whose focal plane units are cryogenically cooled inside a superfluid helium cryostat. The PACS and SPIRE instruments provide broadband imaging photometry in six bands centred on 75, 100, 160, 250, 350, and 500 µm and imaging spectroscopy over the range 55-672 µm. The HIFI instrument provides very high-resolution heterodyne spectroscopy over the ranges 157-212 and 240-625 µm.
Beginning in October 2009 Herschel gradually - as more and more observing modes were validated and released for use - started to perform observations from the various approved science programmes using the PACS and SPIRE instruments. Owing to an anomaly, the HIFI instrument was unavailable from August 2009 to January 2010, and science using HIFI only started in earnest in February 2010.
This volume of Astronomy & Astrophysics contains 152 papers that were submitted by end of March 2010 highlighting Herschel's first science results. A few papers describe the observatory and its instruments, and the rest are dedicated to observations of many astronomical targets from bodies in the Solar System to distant galaxies.
The prime science objectives of Herschel are intimately connected to the physics of and processes in the interstellar medium (ISM) in the widest sense: near and far in both space and time, stretching from Solar System objects and the relics of the formation of the Sun and our Solar System, through star formation in and feedback by evolved stars to the ISM, to the star formation history of the Universe, galaxy evolution, and cosmology. The very first observational results from Herschel already show that it will have strong impact on research in these fields as exemplified by the following three observational results.
The 'Great Observatory Origins Deep Survey' (GOODS), is a field that has been observed by many telescopes in a range of wavelengths, seen now by Herschel/SPIRE in submillimetre wavelengths (Fig. 1). This area of sky is devoid of foreground objects, such as stars within our Galaxy or any other nearby galaxies, which makes it ideal for observing deeper into space. Each fuzzy blob is a very distant galaxy seen as they were three to ten billion years ago when star formation was very more widespread throughout the Universe. The image is made from the three SPIRE bands, with blue, green, and red, corresponding to 250, 350, and 500 ìm, respectively.
Herschel has imaged (Fig. 2) a stellar nursery around 1000 light-years away in the constellation Aquila (the Eagle). This cloud, 65 light-years across, is so shrouded by dust that no infrared satellite has been able to see into it, until now. Thanks to Herschel's greater sensitivity at the longest infrared wavelengths, astronomers have their first picture inside this cloud. Using Herschel's PACS and SPIRE instruments at the same time, the image shows two bright regions where large newborn stars are causing hydrogen gas to shine. Embedded in the dusty filaments are 700 condensations of dust and gas that will eventually become stars. Astronomers estimate that about 100 are 'protostars', that is, celestial objects in the final stages of formation. Each one just needs to ignite nuclear fusion in its core to become a true star. The other 600 objects are not developed enough to be called protostars, but eventually they will become another generation of stars. Observing these stellar nurseries is a key programme for Herschel, which aims to uncover the demographics of star formation and its origins, or in other words, the quantities of stars that can form and the range of masses for these newborn stars.
A part of a Herschel/HIFI spectral scan is shown in Fig. 3. The observation is towards the Orion Nebula, a relatively nearby star-forming region, the 'sword' in the constellation of Orion. A characteristic feature is the spectral richness: among the organic molecules identified in this spectrum are water, carbon monoxide, formaldehyde, methanol, dimethyl ether, hydrogen cyanide, sulphur oxide, sulphur dioxide, and their isotope analogues. It is expected that new molecules will also be identified. This spectrum is the first glimpse of the spectral richness of regions of star and planet formation. It harbours the promise of a deep understanding of the chemistry of space once the complete spectral surveys are available.
These three examples are but the tip of the iceberg of what has been achieved in only a few months of science observing. The current best estimate of the total mission lifetime - from the launch onward - is in the range 3.5-4 years. Although the initial science results from Herschel are just appearing and are very exciting, they represent only a very small fraction of what is still to come.
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....
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Scarce metals are found in a wide range of everyday objects around us. They are complicated to extract, difficult to recycle and so rare that several of them have become "conflict minerals" which can promote conflicts and oppression. A survey at Chalmers University of Technology now shows that there are potential technology-based solutions that can replace many of the metals with carbon nanomaterials, such as graphene.
They can be found in your computer, in your mobile phone, in almost all other electronic equipment and in many of the plastics around you. Society is highly dependent on scarce metals, and this dependence has many disadvantages.
Scarce metals such as tin, silver, tungsten and indium are both rare and difficult to extract since the workable concentrations are very small. This ensures the metals are highly sought after - and their extraction is a breeding ground for conflicts, such as in the Democratic Republic of the Congo where they fund armed conflicts.
In addition, they are difficult to recycle profitably since they are often present in small quantities in various components such as electronics.
Rickard Arvidsson and Björn Sandén, researchers in environmental systems analysis at Chalmers University of Technology, have now examined an alternative solution: substituting carbon nanomaterials for the scarce metals. These substances - the best known of which is graphene - are strong materials with good conductivity, like scarce metals.
"Now technology development has allowed us to make greater use of the common element carbon," says Sandén. "Today there are many new carbon nanomaterials with similar properties to metals. It's a welcome new track, and it's important to invest in both the recycling and substitution of scarce metals from now on."
The Chalmers researchers have studied the main applications of 14 different metals, and by reviewing patents and scientific literature have investigated the potential for replacing them by carbon nanomaterials. The results provide a unique overview of research and technology development in the field.
According to Arvidsson and Sandén the summary shows that a shift away from the use of scarce metals to carbon nanomaterials is already taking place.
"There are potential technology-based solutions for replacing 13 out of the 14 metals by carbon nanomaterials in their most common applications. The technology development is at different stages for different metals and applications, but in some cases such as indium and gallium, the results are very promising," Arvidsson says.
"This offers hope," says Sandén. "In the debate on resource constraints, circular economy and society's handling of materials, the focus has long been on recycling and reuse. Substitution is a potential alternative that has not been explored to the same extent and as the resource issues become more pressing, we now have more tools to work with."
The research findings were recently published in the Journal of Cleaner Production. Arvidsson and Sandén stress that there are significant potential benefits from reducing the use of scarce metals, and they hope to be able to strengthen the case for more research and development in the field.
"Imagine being able to replace scarce metals with carbon," Sandén says. "Extracting the carbon from biomass would create a natural cycle."
"Since carbon is such a common and readily available material, it would also be possible to reduce the conflicts and geopolitical problems associated with these metals," Arvidsson says.
At the same time they point out that more research is needed in the field in order to deal with any new problems that may arise if the scarce metals are replaced.
"Carbon nanomaterials are only a relatively recent discovery, and so far knowledge is limited about their environmental impact from a life-cycle perspective. But generally there seems to be a potential for a low environmental impact," Arvidsson says.
Carbon nanomaterials consist solely or mainly of carbon, and are strong materials with good conductivity. Several scarce metals have similar properties. The metals are found, for example, in cables, thin screens, flame-retardants, corrosion protection and capacitors.
Rickard Arvidsson and Björn Sandén at Chalmers University of Technology have investigated whether the carbon nanomaterials graphene, fullerenes and carbon nanotubes have the potential to replace 14 scarce metals in their main areas of application (see table in attached image). They found potential technology-based solutions to replace the metals with carbon nanomaterials for all applications except for gold in jewellery. The metals which we are closest to being able to substitute are indium, gallium, beryllium and silver.
Johanna Wilde | EurekAlert!
Research finds new molecular structures in boron-based nanoclusters
13.07.2018 | Brown University
3D-Printing: Support structures to prevent vibrations in post-processing of thin-walled parts
12.07.2018 | Fraunhofer-Institut für Produktionstechnologie IPT
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
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When surveys are conducted in the Southwest, the discovery of new species (i.e., not yet scientifically named and recognized) of arthropods is not uncommon, especially in areas with unique environments. Not only do arthropods dominate the taxonomic composition and biomass of terrestrial biological communities, but they also represent key ecological functional groups such as detritivores, herbivores, predators, pollinators, and they serve as important food resources to vertebrate predators. In order to understand park natural resources and ecosystem processes, arthropod inventory studies are needed. Knowing what species of arthropods occur at particular parks will enable resource managers to better plan and implement management of the park’s species and their habitats, especially endemic (geographically restricted to that area) species that are dependent upon proper management of their habitats within those parks for their existence.
Arthropod Inventory Survey in White Sands National Monument and Cuatrocienegas in Mexico
Arthropods are the largest group of animals on earth, and parks such as White Sands National Monument (NM) support thousands of species of arthropods compared to tens or hundreds of species of vertebrate animals and vascular plants respectively. The vertebrate animals and vascular plants of the Chihuahuan Desert have been named and studied by scientists for many years, yet we know relatively little about the arthropods.
The purpose of this research is to survey the arthropods of White Sands National Monument, New Mexico, USA, and Cuatrociénegas Protected Area, Coahuila, Mexico, specifically to discover new unnamed and potentially endemic species. Both areas are located within the Chihuahuan Desert, and both areas are desert basins with gypsum deposits, including gypsum flats, gypsum outcrops, gypsum dunes, and surface waters in the form of springs, ponds, and streams. This project is a U.S. National Park Service, Sister Parks Program-funded study, awarded to White Sands NM, and to the Biology Department, University of New Mexico, Museum of Southwestern Biology, Division of Arthropods. This arthropod survey began in 2010 and will end in 2014.
Prior to this survey, only two species of crickets that were named in 1947, and two species of moths that were named in 2009, were known to be endemic to White Sands NM. A similar survey of the moths of White Sands NM, concurrent with this study, has resulted in the discovery of even more new moth species.
From the 1960s through the 1980s, 14 arthropod species were discovered and described from Cuatrocienegas protected area in Coahila, Mexico by various researchers working independently, and all 14 appear to be endemic there. However, no comprehensive survey for arthropods has ever been conducted at Cuatrocienegas prior to this study. Arthropod species that are endemic to the gypsum dunes and soils at both White Sands and Cuatrocienegas are adapted to live specifically on or in those gypsum substrates. Most are white or pale in color for camouflage, and species that live in the sand have modified legs and body shapes to enhance their ability to burrow through the sand.
This survey focuses only on certain arthropod groups (orders, families, and genera) for which we could find taxonomic experts willing to perform specimen identifications to the species level. This involved approximately 20 experts for approximately 70 taxonomic groups of arthropods, representing hundreds of species in those groups. A variety of common arthropod sampling or collecting methods are being used to survey arthropods in the two parks, including active search and capture, sweep nets for arthropods on vegetation, dip nets for aquatic arthropods, pitfall traps for arthropods on the ground surface, aerial nets for flying insects, and ultraviolet and mercury vapor lights and light traps for night-flying insects. Field surveys were designed to target arthropods of those groups, and to target the principal terrestrial and aquatic habitats present in both parks. Different arthropod species are active at different seasons and at different times of day or night, so surveys are being conducted throughout the spring, summer, and fall months and at different times of day and night.
All specimens collected on survey trips were taken to the Museum of Southwestern Biology at the University of New Mexico (UNM), and prepared as museum specimens. Most insects were mounted on insect specimen pins and allowed to dry, while soft-bodied arthropods such as spiders, scorpions, crustaceans, crickets, and insect larvae were field collected into ethanol and transferred to museum storage containers where they remain preserved in ethanol. All specimens were provided with a specimen data label containing information on where and when they were collected, as well as any habitat information, collection method, and who collected each specimen. Those museum specimens were then sent to the appropriate taxonomic experts for identification. The taxonomic experts provide identifications to the species level for already named species, and report any specimens that appear to be new, unnamed species. The taxonomic experts may proceed with formal scientific species descriptions, or in most cases, species will be formally named at a later time. Once taxonomic identifications of named species and determinations of unnamed species have been made, the specimens are returned to UNM, and all information is entered into an electronic database. All specimens remain housed in the Division of Arthropods unless taxonomic experts request the loan of specimens to describe new species.
Results and Discussion
© David Lightfoot
Most of the field survey work is completed as of 2013 and lab work and taxonomic expert identifications are in progress. Thus far, we have found five species of arthropods from White Sands NM that were previously unknown, and likely endemic, including three grasshoppers, one fly, and one moth. We have found 11 species of arthropods from Cuatrocienegas that appear to be new and possibly endemic, including one sand cockroach, three grasshoppers, three katydids, one darkling beetle, one moth, and one spider. More new species may be discovered as taxonomic experts evaluate specimens collected from this study over the next year or so.
We have not attempted to survey or evaluate other taxonomic groups of arthropods, and once this particular inventory survey is completed, additional arthropod species are likely to be discovered at both parks. Additional future arthropod surveys should be conducted when taxonomic experts are available for those other groups. Our findings of several new and endemic species of arthropods at both White Sands NM and Cuatrocienegas now provide both parks with more information on the biota of their parks and knowledge of additional special status species to include in natural resource management plans. These newly found arthropod species will likely be further studied by scientists conducting research on animal adaptations to gypsum and desert environments, biological evolution and speciation, and biogeography.
For more information, contact:
David C. Lightfoot, email@example.com
Kelly B. Miller, firstname.lastname@example.org
Museum of Southwestern Biology
Department of Biology
University of New Mexico
Prepared by Chihuahuan Desert Network Inventory and Monitoring Program, 2013. | <urn:uuid:b69ac525-9e26-44af-a14d-7bbbf50cabf8> | 3.96875 | 1,496 | Knowledge Article | Science & Tech. | 21.575584 | 95,488,284 |
Digging Deeper: What is Dendrogeomorphology?
Note: This is the first part in a series in dendrogeomorphology.
The rate at which streambanks are eroding, and the total annual quantity of sediment being entrained from those eroding streambanks are of a primary concern for ecological, water quality, and sediment studies.
The U.S. Environmental Protection Agency recently determined that streambank erosion constitutes as high as 90 percent of the annual sediment yield found in rivers.
With strong regulatory pressure to reduce sediment in our nation’s rivers, as well as associated pollutants such as bacteria that may be bound-up in the sediments, the industry is in need of a method to quickly calculate erosion rates at specific locations.
While methods such as bank pins and direct measurement provide accurate tracking of erosion rates over time, they require several years’ worth of data to provide meaningful results, which limits the ability of local agencies, governments and other groups to understand local erosion rates.
Freese and Nichols ecological engineer Bryan Dick along with colleague Ian Jewell, have developed a method using the exposed roots of trees along riverbanks to provide an accurate and quick method of determining local erosion.
What exactly is dendrogeomorphology?
By using the tree rings of a root sample, it is possible to identify dates of change in land surface along riverbanks, hillsides, lakeshores etc. Tree anatomy changes in response to environmental factors such as being buried in the ground, or exposed to the elements.
When a root becomes exposed on a riverbank, the change in anatomy (cells, vessels, etc.) is reflected in the growth rings of the tree. This change can be observed by taking an exposed root sample from a streambank or hillslope and examining a cross-section of the root. Within the cross-section, an anatomical change can be seen (such as the one shown at right) indicating the year in which the root became exposed. From there, by taking the distance away from the riverbank to the exposed root and dividing it by the number of years of exposure (growth rings on the root sample starting at the indicator and continuing outward), the annual erosion rate is determined. With this basic approach, any number of samples of exposed roots can be collected along a stream or river reach and used to determine local erosion rates. | <urn:uuid:b8a3f7a2-027c-4aea-9733-219e67f83553> | 3.84375 | 485 | Knowledge Article | Science & Tech. | 31.793295 | 95,488,298 |
Climate and Ecosystem Change in the Mediterranean
Since the opening of the Suez Canal in 1869 many hundreds of marine animal and plant species from the Red Sea have invaded the eastern Mediterranean, leading to significant changes in the native flora and fauna of the Mediterranean.
An international team of researchers reported in a recent issue of the international journal Plos One that warming in the Mediterranean caused by climate change could promote the invasion of tiny marine animals called foraminifera.
The foraminifera Pararotalia is a very unimpressive animal at first glance. It is unicellular and very small. Despite this, foraminifera play an important role in the stabilization of ecosystems in the coastal zone. The calcite shells of dead animals form the foundation for many reef ecosystems and have a fundamental importance as so called-ecosystem engineers.
Foraminiferal specialists such as Dr. Christiane Schmidt can identify foraminifera by the shape of their calcite shells. Together with her future MARUM colleagues the geo-ecologist, who will return to Bremen after completing a short-term fellowship in Japan, collected samples of living foraminifera at the Nachscholim National Park, south of Haifa, from the spring of 2012 to autumn 2013.
One object of their search was the newly described Foraminifera Pararotalia, which was first discovered in 1994 in the eastern Mediterranean and has multiplied explosively there since then.
“To date there is no evidence of the occurrence of this species in the Red Sea,” says Dr. Schmidt. MARUM researcher Dr. Raphael Morard, who conducted the molecular identification on this species adds: “With these methods we can show that Pararotalia is indeed an invasive species that originates from the Indian Ocean and the Pacific.”
The success of the genus Pararotalia in the Mediterranean can be attributed to its ecology. This foraminifer lives in symbiosis with tiny microalgae. This symbiosis provides two advantages: foremost, the algae provide food for the Pararotalia through photosynthesis, and this also promotes the growth of the calcite shell of its host.
“Basically it is the temperature regime in the eastern Mediterranean that dictates whether species such as Pararotalia can survive or not,” Dr. Schmidt says. “We have cultured this species in the laboratory and shown that its thermal optimum is around 28°C, but below 20°C and above 35°C it has extreme difficulty surviving.
Next, the team developed a computer model to determine which regions in the eastern Mediterranean are especially well suited for Pararotalia. The model takes into account all occurrence records of this species published to date and, based on the light regime and sea-water turbidity in these locations, both important factors for the survival of the species, models where it is likely to occur now and in the future. The model gives clear results: the coastal ecosystems of Israel and Lebanon are currently the best-suited habitats for this species, but the species currently also lives in Syria and southeastern Turkey.
The model also suggests that in the future Pararotalia will likely expand to areas in the Mediterranean that are still too cold for its survival today. Increasing sea-water temperatures will lead to migration of the species into the western Mediterranean. Co-author Dr. Anna Weinmann, researcher at the University of Bonn says: “Our model clearly shows that by 2100 Pararotalia will likely be found in the Aegean, the Ionic Sea, in Greece, and in Libya due to transport by the prevailing currents.”
Christiane Schmidt, Raphael Morard, Ahuva Almogi-Labin, Anna E. Weinmann, Danna Titelboim, Sigal Abramovich, Michal Kucera
Recent Invasion of the Symbiont-Bearing Foraminifera Pararotalia into the Eastern Mediterranean Facilitated by the Ongoing Warming Trend
In: PLOS One online, 13th August 2015, http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0132917
More information / interview requests / photos:
MARUM Science Communication
Phone ++49 - 421 - 218-65541
MARUM aims at understanding the role of the oceans in the Earth’s system by employing state-of-the-art methods. It examines the significance of the oceans within the framework of global change, quantifies interactions between the marine geosphere and biosphere, and provides information for sustainable use of the ocean.
MARUM comprises the DFG research center and the cluster of excellence "The Ocean in the Earth System".
Albert Gerdes | idw - Informationsdienst Wissenschaft
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
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This project is a tutorial project for how to create shaders in UE4 (4.7). Most material effects can be created in-editor using the excellent tools that Epic has provided us with. There are some times though, where you simply want to use a pixel or compute shader to do some work but you don't want this work to end up in a material surface or post process material, but simply have access to it in a render target, a Cpp texture object or a struct. This is where basic HLSL shaders really shine. And while it is possible to use normal HLSL shaders in UE4, there doesn't seem to be any tutorials for it yet, and there are some complications that make it necessary to take a few detours before you can actually create and run your shader. It is worth to note that this is not a tutorial on how to program shaders in general, or how to write HLSL, but rather how to get shaders working in UE4. For learning how to program shaders or HLSL, I recommend other resources, such as MSDN: https://msdn.microsoft.com/en-us/library/bb509561(v=VS.85).aspx or instructional books for more advanced users such as "GPU Pro" by Wolfgang Engel.
The HLSL: There is no simply way to compile a shader and have it work properly like you can in a simple project. I haven't investigated it much, but compiling your shader from an inline string or loading a file and compiling your shader code does not seem like it is an easy task in UE4. Instead the recommended way is to place your shader code in so called *.usf files under your engine's Engine/Shaders/ directory. Depending on if you are using a binary or source build of the engine, this will obviously change which Engine/Shaders/ folder you actually have to use.
The shader compilation: When you have placed your shader code in the correct folder, you need to compile it. This is done using a macro in your Cpp source called IMPLEMENT_SHADER_TYPE. One problem with this though is that if you simply place this and your other code in your main project, you are going to have problems since this macro must be available and run during an early phase of engine start up, and in addition to this cannot be rerun if you decide to recompile your code in-editor. Ignoring this will actually crash the engine :). The solution is to put the shader declaration and initialization into a plugin and override the load phase of the plugin in question to "PostConfigInit".
Shader parameters: Shaders take their input from the generic ParameterMap system in UE4. You can program this from your shader declarations using a combination of macros and code calls. The macros are generally used to declare structures to be used in the shaders, such as uniform / constant buffers etc. And the code parts are to bind runtime instances of these buffers to the ParameterMap. You can also bind resources like textures to the shaders if you want to.
Shader invocation: When you have declared your shader in the appropriate plugin, you can now start up your project and start using it. Shaders in UE4 have to be invoked on the rendering thread, to hopefully nobody's surprise. To make sure we get our code to run on this thread, Epic has given us another handy macro called ENQUEUE_UNIQUE_RENDER_COMMAND_ONEPARAMETER. There are variations of this macro that let you send more than one parameter too, but since we only want to send ourselves, one parameter does fine. We simply instruct the render thread to take a pointer to our shader consumer object and call a function on it. It is inside this function that we can do all the appropriate calls to set rendering states, buffers, shaders etc. as well as dispatch rendering calls. All rendering functions are accessible through an abstraction layer called the RHI "Rendering Hardware Interface", which as the name suggests is a way for our code to be platform independent. Most function names on the RHI seem to be inspired by directx rather than any other API though, which might be good to know. If you are having trouble finding a particular function, the best way is therefore to check MSDN before any OpenGL resources or otherwise.
Shader output: After you have run your shader it is of course time to harvest your output. There is no special UE4 magic to this step as it uses the normal SetRenderTarget RHI functions for pixel shader output and your UAVs for compute shader output.
How to run this project: To get the project to run, you first need to bind it to an engine, you do this like any other project by right clicking the uproject file and switching version if needed, and then doing Generate Project. You then need to open up the solution file and build the source code.
How to use this project: I would recommend checking out the example project supplied in this repository to understand how to best use the project code. All the relevant files in the repository are:
- Everything under the Plugins/ folder (For declaring the shaders)
- Everything under the CopyToEngineShaders/ folder (For copying into the Engine/Shaders/ folder, these are the actual HLSL shaders)
- Source/ShaderPluginDemo/ShaderPluginDemoCharacter.cpp/.h (These are changes and additions to the main character class in the demo project to allow for the shader's use. I have removed all non-related comments in these files to make it easy to see where I have made changes)
- Everything under the Content/ShaderPluginDemo/ folder (These are the editor objects that I use to set up the shader use in the scene)
- The project settings file (I have created some new input bindings)
Project controls: W/A/S/D - Movement Space - Jump Move mouse - Look around Left mouse button - Paint the object you are aiming at with the output of the compute shader/pixel shader chain Q/E - Change the blend amount on the pixel shader. Q moves the blend closer to the pixel shader simple gradient, while E moves the blend closer to the compute shader output.
General comments on the demo project: The demo project demonstrates how to use both pixel and compute shaders using the method I have explained. In the tick function, I first run a compute shader that generates a cool visualization of a galaxy entirely within the shader. This is then packed into a R32_UINT format to allow for usage within the pixel shader which is then run that simply generates a gradient and then blends with the compute shader output. The user can shoot objects in the demo scene to apply a dynamic material instance to the object hit that is then loaded with the rendertarget containing the pixel shader output. You can also modify the amount of blending that the pixel shader does by holding the Q and E buttons.
I hope someone finds this useful :)
Best regards, Temaran
Some people have had problems with the shadercopyhelper and are getting shader related errors such as: Assertion failed: ShaderRef != NULL && *ShaderRef != NULL [File:Runtime/ShaderCore/Public/Shader.h] [Line: 926] Failed to find shader type FComputeShaderDeclaration
Basically, the plugin defines its shaders in *.usf files. These *.usf files can only be read by the engine if they reside in the Engine/Shaders folder.
This is of course a problem, since you cannot define these on the project level, and if you want to leverage the system, you have to change your engine setup.
The way I tried to solve this problem with the plugin was to create a different plugin that basically just copies the shader files to the correct location early in the editor launch process.
This seems to work for most people, but sometimes, it fails for some setups it seems.
I can think of a few things you can try to fix this: *I've only tested this tutorial with 4.7, so if you happen to run a different engine version, it might not work because of that.
*Ensure that the Project/Shaders folder actually contains the *.usf files and those have not been corrupted or deleted or something silly like that.
*If the files are there, you can try to remove the ShaderCopyHelper plugin (under plugins) and manually copy the usf files to your Engine/Shaders folder. | <urn:uuid:e916ea63-db47-4ff9-9ad1-68354af76238> | 2.890625 | 1,789 | Documentation | Software Dev. | 47.280231 | 95,488,309 |
The climate is warming in the arctic at twice the rate of the rest of the globe creating a longer growing season and increased plant growth, which captures atmospheric carbon, and thawing permafrost, which releases carbon into the atmosphere.
Woods Hole Research Center (WHRC) Assistant Scientist Sue Natali and colleagues engineered first-of-a-kind warming experiments in the field to determine net gains or losses in carbon emissions. The study entitled “Permafrost degradation stimulates carbon loss from experimentally warmed tundra,” published in the journal Ecology found that growing season gains do not offset carbon emissions from permafrost thaw.
Summer warming experiment
Winter warming experiment
According to Dr. Natali, “Our results show that while permafrost degradation increased carbon uptake during the growing season, in line with decadal trends of ‘greening’ tundra, warming and permafrost thaw also enhanced winter respiration, which doubled annual carbon losses.”
Permafrost contains three to seven times the amount of carbon sequestered in tropical forests. The warming climate threatens to thaw permafrost, which will result in the release of carbon dioxide and methane into the atmosphere creating feedbacks to climate change – more warming and greater permafrost thaw. Prior to this study, “the understanding of permafrost feedbacks to climate change had been limited by a lack of data examining warming effects on both vegetation and permafrost carbon simultaneously,” said Dr. Natali.
This study measured CO2 emissions from permafrost thaw and its impact on the carbon balance on an ecosystem level. According to Dr. Natali, “There is 100 times more carbon stored belowground than aboveground in the arctic, so observed changes in plant productivity are only a very small component of the story. Given the amount of carbon stored belowground in the arctic, it is very unlikely that plant growth can ever fully offset C losses from permafrost thaw.”
The three year long Carbon in Permafrost Experimental Heating Research (CiPEHR) project warmed air and soil and thawed permafrost using two warming experiments. The “winter warming” treatment consisted of snow packs, which functioned like down comforters insulating the ground during the winter until the snow was removed at the start of the growing season. The “summer warming” treatment consisted of open-topped greenhouses that warmed the air during the summer. The team measured warming effects on CO2 uptake by plants and release by plants and microbes.
Scientists estimate that within the next century permafrost will have declined 30% to 70% and there is limited accounting of how much carbon is stored in these frozen soils or the rate at which it will be released. For Dr. Natali:
“The only way we can accurately project future climate is to understand the responses of both plants and microbes to a warming climate. This study was the first to simulate whole ecosystem warming in the arctic, including permafrost degradation, similar to what is projected to happen as a result of climate change. There is a strong potential for significant global carbon emissions if rates calculated here become typical for permafrost ecosystems in a warmer world.”
WHRC is an independent research institute where scientists collaborate to examine the drivers and impacts of climate change and identify opportunities for conservation around the globe.
Contact: Eunice Youmans, Director of External Affairs 508-444-1509
Email Eunice Youmans
Eunice Youmans | EurekAlert!
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 | Materials Sciences
18.07.2018 | Life Sciences
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Heat exchanger surface area calculations
David Wells says:
My "Dave's Heat Transfer Rules of Thumbs" are:
For natural air circulation, figure around 10 Watts per square meter [of surface area] per degree C heat transfer, and for forced air, f gure up to about three times this value.
For water natural circulation, figure around 200 Watts per square meter per degree C heat transfer, and again for forced circulation, figure up to three times this.
For oil or organic materials such as non-oxygenated oils, like pure hydrocarbons, for non-boiling heat transfer, figure about one fifth the water values. For pure oxygenated materials for stuff like alcohols or glycols, figur e about one third of the water circulation values.
For boiling or condensation heat transfer of organics, figure around 1000 Watts per square meter per degree C. Assumes vapor is at atmospheric pressure.
For boiling heat transfer of polar oxygenated materials like water or methanol, figure about triple the value or about 3000 Watts per square meter per degree C. Again, assumes fluids condense or evaporate at near atmospheri c pressure.
For calculating the effect of the pressure of the boiler or condenser, figure the heat transfer will go as roughly the cube of the absolute pressure. So, for example, if your boiler operates at sub-atmospheric pressure of , say, 1/8 atmospheres, the heat transfer will be reduced by the cube root of one eigth, which is about 0.5. So the heat transfer rate is reduced by half.
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Practical uses of carbon dating
Let's look closely at how the half-life affects an isotope. Therefore, after one half-life, you would have 5 grams of Barium-139, and 5 grams of Lanthanum-139.After another 86 minutes, half of the 5 grams of Barium-139 would decay into Lanthanum-139; you would now have 2.5 grams of Barium-139 and 7.5 grams of Lanthanum-139.
If you could watch a single atom of a radioactive isotope, U-238, for example, you wouldn’t be able to predict when that particular atom might decay.As we have mentioned before each radioactive isotope has its own decay pattern.Not only does it decay by giving off energy and matter, but it also decays at a rate that is characteristic to itself.It is confusing when the maximum date for Carbon 14 is listed as 60,000 years and 80,000 years in the same article (Chapter 4 Dating Methods by Roger Patterson and the reference article summary 4.2 by Riddle.) and as 50,000 years in another (The Answers Book) as well as 95,000 years in the Creation College lecture by Dr. This is why there is the disparity in the quoted limits to radiocarbon dating, as highlighted by this inquirer. This is due to the fact that the AMS instrument has to be calibrated, and yet the organic materials used for calibration (that are supposed to be so old they shouldn't have any detectable radiocarbon left in them) all contain so much radiocarbon that it means samples of unknown age can't yield dates above this radiocarbon barrier.But the radiocarbon detected in diamonds is equivalent to ages of up to 80,000 years.
So you can see why the various age limits have appeared in different publications of ours.
Levels of carbon-14 become difficult to measure and compare after about 50,000 years (between 8 and 9 half lives; where 1% of the original carbon-14 would remain undecayed).
The question should be whether or not carbon-14 can be used to date any artifacts at all? There are a few categories of artifacts that can be dated using carbon-14; however, they cannot be more 50,000 years old.
This technique is not restricted to bones; it can also be used on cloth, wood and plant fibers.
Carbon-14 dating has been used successfully on the Dead Sea Scrolls, Minoan ruins and tombs of the pharaohs among other things. The half-life of carbon-14 is approximately 5,730 years. dinosaurs the evolution alleges lived millions of years ago.
This decay is an example of an exponential decay, shown in the figure below. | <urn:uuid:f7bed731-1302-4427-93ed-c7b2ac7a397e> | 3.640625 | 570 | Knowledge Article | Science & Tech. | 60.224045 | 95,488,350 |
Friction as a Function of Velocity (Negative Viscous Friction Revealed)
The control engineer often assumes a viscous friction model. To describe dry rubbing the tribologist rarely includes any velocity dependence at all, and when he does it is as likely to be negative as positive. Based on the experimental work presented here, the kinetic plus viscous friction model seems very accurate at velocities above a minimum velocity. Below the this velocity, decreasing friction with increasing velocity, or negative viscous friction, is observed.
KeywordsViscous Friction Kinetic Friction Apply Torque Compliant Motion Lorentzian Model
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Can you put the numbers from 1 to 15 on the circles so that no consecutive numbers lie anywhere along a continuous straight line?
Place six toy ladybirds into the box so that there are two ladybirds in every column and every row.
Can you put the numbers 1 to 8 into the circles so that the four calculations are correct?
Use the numbers and symbols to make this number sentence correct. How many different ways can you find?
This task, written for the National Young Mathematicians' Award 2016, involves open-topped boxes made with interlocking cubes. Explore the number of units of paint that are needed to cover the boxes. . . .
Make a pair of cubes that can be moved to show all the days of the month from the 1st to the 31st.
Alice and Brian are snails who live on a wall and can only travel along the cracks. Alice wants to go to see Brian. How far is the shortest route along the cracks? Is there more than one way to go?
Tim's class collected data about all their pets. Can you put the animal names under each column in the block graph using the information?
Can you fill in this table square? The numbers 2 -12 were used to generate it with just one number used twice.
There are 44 people coming to a dinner party. There are 15 square tables that seat 4 people. Find a way to seat the 44 people using all 15 tables, with no empty places.
These are the faces of Will, Lil, Bill, Phil and Jill. Use the clues to work out which name goes with each face.
If we had 16 light bars which digital numbers could we make? How will you know you've found them all?
The ancient Egyptians were said to make right-angled triangles using a rope with twelve equal sections divided by knots. What other triangles could you make if you had a rope like this?
Lolla bought a balloon at the circus. She gave the clown six coins to pay for it. What could Lolla have paid for the balloon?
Using the statements, can you work out how many of each type of rabbit there are in these pens?
The Vikings communicated in writing by making simple scratches on wood or stones called runes. Can you work out how their code works using the table of the alphabet?
A magician took a suit of thirteen cards and held them in his hand face down. Every card he revealed had the same value as the one he had just finished spelling. How did this work?
An activity making various patterns with 2 x 1 rectangular tiles.
Use the clues to find out who's who in the family, to fill in the family tree and to find out which of the family members are mathematicians and which are not.
Hover your mouse over the counters to see which ones will be removed. Click to remover them. The winner is the last one to remove a counter. How you can make sure you win?
I was in my car when I noticed a line of four cars on the lane next to me with number plates starting and ending with J, K, L and M. What order were they in?
Can you put plus signs in so this is true? 1 2 3 4 5 6 7 8 9 = 99 How many ways can you do it?
How can you arrange the 5 cubes so that you need the smallest number of Brush Loads of paint to cover them? Try with other numbers of cubes as well.
Let's say you can only use two different lengths - 2 units and 4 units. Using just these 2 lengths as the edges how many different cuboids can you make?
How many triangles can you make on the 3 by 3 pegboard?
Systematically explore the range of symmetric designs that can be created by shading parts of the motif below. Use normal square lattice paper to record your results.
There are seven pots of plants in a greenhouse. They have lost their labels. Perhaps you can help re-label them.
How could you put eight beanbags in the hoops so that there are four in the blue hoop, five in the red and six in the yellow? Can you find all the ways of doing this?
This problem is based on a code using two different prime numbers less than 10. You'll need to multiply them together and shift the alphabet forwards by the result. Can you decipher the code?
Ten cards are put into five envelopes so that there are two cards in each envelope. The sum of the numbers inside it is written on each envelope. What numbers could be inside the envelopes?
This problem is based on the story of the Pied Piper of Hamelin. Investigate the different numbers of people and rats there could have been if you know how many legs there are altogether!
In the planet system of Octa the planets are arranged in the shape of an octahedron. How many different routes could be taken to get from Planet A to Planet Zargon?
What is the greatest number of counters you can place on the grid below without four of them lying at the corners of a square?
Find the product of the numbers on the routes from A to B. Which route has the smallest product? Which the largest?
The planet of Vuvv has seven moons. Can you work out how long it is between each super-eclipse?
Take a rectangle of paper and fold it in half, and half again, to make four smaller rectangles. How many different ways can you fold it up?
Kate has eight multilink cubes. She has two red ones, two yellow, two green and two blue. She wants to fit them together to make a cube so that each colour shows on each face just once.
How many DIFFERENT quadrilaterals can be made by joining the dots on the 8-point circle?
There are 4 jugs which hold 9 litres, 7 litres, 4 litres and 2 litres. Find a way to pour 9 litres of drink from one jug to another until you are left with exactly 3 litres in three of the jugs.
You cannot choose a selection of ice cream flavours that includes totally what someone has already chosen. Have a go and find all the different ways in which seven children can have ice cream.
Nina must cook some pasta for 15 minutes but she only has a 7-minute sand-timer and an 11-minute sand-timer. How can she use these timers to measure exactly 15 minutes?
A dog is looking for a good place to bury his bone. Can you work out where he started and ended in each case? What possible routes could he have taken?
A merchant brings four bars of gold to a jeweller. How can the jeweller use the scales just twice to identify the lighter, fake bar?
Suppose we allow ourselves to use three numbers less than 10 and multiply them together. How many different products can you find? How do you know you've got them all?
Investigate the different ways you could split up these rooms so that you have double the number.
Place eight queens on an chessboard (an 8 by 8 grid) so that none can capture any of the others.
Place the numbers 1 to 8 in the circles so that no consecutive numbers are joined by a line.
Take 5 cubes of one colour and 2 of another colour. How many different ways can you join them if the 5 must touch the table and the 2 must not touch the table?
This magic square has operations written in it, to make it into a maze. Start wherever you like, go through every cell and go out a total of 15!
Zumf makes spectacles for the residents of the planet Zargon, who have either 3 eyes or 4 eyes. How many lenses will Zumf need to make all the different orders for 9 families? | <urn:uuid:a5b14e38-218a-4538-a735-02eabd22b2a4> | 3.375 | 1,615 | Content Listing | Science & Tech. | 74.020617 | 95,488,378 |
Astronomers find giant planet around very young star
In contradiction to the long-standing idea that larger planets take longer to form, U.S. astronomers today announced the discovery of a giant planet in close orbit around a star so young that it still retains a disk of circumstellar gas and dust.
"For decades, conventional wisdom held that large Jupiter-mass planets take a minimum of 10 million years to form," said Christopher Johns-Krull, the lead author of a new study about the planet, CI Tau b, that will be published in the Astrophysical Journal. "That's been called into question over the past decade, and many new ideas have been offered, but the bottom line is that we need to identify a number of newly formed planets around young stars if we hope to fully understand planet formation."
CI Tau b is at least eight times larger than Jupiter and orbits a 2 million-year-old star about 450 light years from Earth in the constellation Taurus. Johns-Krull and a dozen co-authors from Rice, Lowell Observatory, the University of Texas at Austin, NASA and Northern Arizona University made the peer-reviewed study available online this week.
Earth and the sun are more than 4 billion years old, and while the 3,300-plus catalog of exoplanets includes some older and some younger than Earth, the obstacles to finding planets around newly formed stars are varied and daunting, Johns-Krull said. There are relatively few candidate stars that are young enough, bright enough to view in sufficient detail with existing telescopes and still retain circumstellar disks of gas and dust from which planets form. Stars so young also are often active, with visual outbursts and dimmings, strong magnetic fields and enormous starspots that can make it appear that planets exist where they do not.
CI Tau b orbits the star CI Tau once every nine days. The planet was found with the radial velocity method, a planet-hunting technique that relies upon slight variations in the velocity of a star to determine the gravitational pull exerted by nearby planets that are too faint to observe directly with a telescope. The discovery resulted from a survey begun in 2004 of 140 candidate stars in the star-forming region Taurus-Auriga.
"This result is unique because it demonstrates that a giant planet can form so rapidly that the remnant gas and dust from which the young star formed, surrounding the system in a Frisbee-like disk, is still present," said Lisa Prato of Lowell Observatory, co-leader of the young planet survey and a co-author on the paper. "Giant planet formation in the inner part of this disk, where CI Tau b is located, will have a profound impact on the region where smaller terrestrial planets are also potentially forming."
Additional team members were Patrick Hartigan, Naved Mahmud, Wei Chen, Wilson Cauley and Joshua Jones, all of Rice; Christopher Crockett and Brian Skiff of Lowell Observatory; Daniel Jaffe, Jacob McLane and Gregory Mace of the University of Texas at Austin; and Charles Beichman of NASA's Jet Propulsion Laboratory. Cauley is currently a postdoctoral researcher at Wesleyan University, and Crockett now writes for Science News.
The team observed CI Tau dozens of times from the University of Texas at Austin's McDonald Observatory near Fort Davis, Texas; the Lowell Observatory in Flagstaff, Ariz.; the NASA Infrared Telescope Facility and the Keck II telescopes on Mauna Kea, Hawaii; and the Kitt Peak National Observatory's 2.1- and 4-meter telescopes in southern Arizona.
Initial optical radial velocity data from McDonald Observatory confirmed that a planet might be present, and the team added photometry measurements from Lowell and five years of infrared observations from Hawaii, Kitt Peak and McDonald to rule out the possibility that the optical signal resulted from starspots or another masking phenomenon.
Johns-Krull said the team has examined about half of the young stars in the Taurus-Auriga survey sample, and the data from several of these suggest that more planets may be found.
"Ours isn't the only group looking for planets around young stars, and my hope is that astronomers can find enough of them to shed light on some of the nagging questions about planet formation," Johns-Krull said. "For instance, the 'brown dwarf desert,' an unexplained paucity of objects that are larger than giant planets but smaller than stars. If close investigation of young stars reveals more brown dwarfs in short-period orbits than elsewhere, that could confirm the theory that they tend to merge with their central stars within a few million years of forming."
NASA, the National Science Foundation and the Arizona Space Grant consortium supported the research.
The study and research data are available at: http://arxiv.org/abs/1605.07917
This release can be found online at news.rice.edu.
Follow Rice News and Media Relations on Twitter @RiceUNews.
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for best quality of life and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview. | <urn:uuid:3a738d17-06bd-46df-a6b5-e77339f1626c> | 3.59375 | 1,214 | News (Org.) | Science & Tech. | 40.981192 | 95,488,396 |
Journal of Environmental Science and Public Health
Review ArticleOpen Access
An Exploration into Wind Turbines, Their Impacts and Potential Solutions
Hiwa Mohammad Qadr*
Department of Physics, College of Science, Raparin University, Sulaimanyah, Iraqi Kurdistan, Iraq
*Corresponding Author: Hiwa Mohammad Qadr, Department of Physics, College of Science, Raparin University, Sulaimanyah, Iraqi Kurdistan, Iraq, E-mail: firstname.lastname@example.org
Received: 08 February 2018; Accepted: 22 February 2018; Published: 28 February 2018
This review considers some environmental problems and solutions associated with turbines and their impact on humans and birds. The objective is to explore the relationship between noise pollution, electromagnetic interference and visual impact problems that how wind farm create stress for nearby residents and will refer to problems of avian collision with wind turbines. Furthermore, it will be shown that it includes result of solutions for reducing these problems.
Noise pollution, Avian collision, Disturbed sleep, Visual impact, Birdlife
Over the past few years, we have been able to see noticeably higher costs for electricity needs. Electricity prices have been climbing rapidly because the number of people in the world has increased, along with machines they buy for their homes that consume electricity. There has been a dramatic rise in capacity for electricity generation from wind energy. Therefore, the experts have developed wind power as a renewable energy resource that is constantly recycled in nature. Nevertheless, despite all the work in this area, it seems that, as well as benefits, wind power can also have disadvantages for humans and wildlife.
Environmental impacts associated with wind energy can be both positive and negative. On the positive side, wind turbines can be more environmentally friendly than other fuels. Other sources of energy, such as fossil fuels and nuclear power, are particularly known to produce pollution. On the negative side, wind turbines can create problems uch as fossil fuels and nuclear power, are particularly known to produce pollution. On the negative side, wind turbines can create problems for people who are living in the vicinity, such as disturbed sleep and stress because of noise, visual impact and electromagnetic interference . Additionally, according to ?some negative environmental aspects have been shown to be especially important in populated or scenic areas.?
Accordingly, this review will explain wind energy and demonstrate the complex relationship between wind turbines and humans and nature, specifically birds. Furthermore, it will be shown that it includes result of solutions for reducing these problems.
1.1 Stress effect and wind turbines
Stress has been defined as reaction with human?s body to a change, which requires a mental, physical or responses to the stressors. It has been demonstrated that stressors can be having the difference between people that located on a person compared with other people. There is no doubt that wind turbines have developed swiftly in the world and there appear to be some drawbacks, which may cause stress or suffering to people in the vicinity, especially with large wind farms. This can unfortunately result in mental health and sleep problems, when wind turbines produce a combination of noise pollution and electromagnetic interruptions. Furthermore, increased stress can damage the human brain and cause anxiety, anger and high blood pressure.
2.1 Noise pollution caused by wind turbines Noise pollution problems, associated with stress, have undoubtedly been particularly studied in respect of environmental issues and wind energy. Noise levels are usually measured in a unit that is called decibel (dB), weighted by the sensitivity of the human ear. In contrast, loud music might be heavy that may be relaxing and desirable for people. Normally, most of the human population can hear sounds which have frequencies in-between approximately 20 Hz infrasound to 20000 Hz ultrasound. As result of this, not all of us can hear sounds with frequency outside of this range . Some frequencies cause unpleasant emotions for humans, as with some wind turbines (like unwanted sounds such as a car horn and an alarm clock); different levels of frequency, intensity, and frequency distribution affect concerns about noise .
It has been claimed by WHO cited in that environmental noise can mainly have different mental impacts due to machines as wind turbines, for instance emotional stress, headache, anxiousness and social conflicts. Plenty of wind turbines have been put into rural areas where there is a lower population, as this reduces the impact and stress caused .
Furthermore, the noise pollution produced by wind turbines can disturb sleep in various ways. For example, people living near to the wind farms, maybe awake overnight, difficulty to sleep very well and felling very tired in the morning. This resultant sleep disturbance leads to biological effects, for instance the level of stress hormone change, unwanted movement of the people during sleep. Such effects may not be very noticeable at first, but do affect health in the long term .
Despite the increase in the number of wind turbines caused by increasing in the rate of heart beat and blood pressure due to massive noise. It is clear that it is important to explore solutions to decrease the problem.
2.2 Visual effects caused by wind turbines It seems that constructing new artificial wind farms in the countryside land can have an extraordinary consequence on these regions and make anxiety for their residents. In fact, the components of nature are likely to be organized appealingly in a balance condition. It is probable that the attractiveness of the environment and countryside may be devastated where wind turbines have been built in these areas. One of wind power?s observed difficult environmental impact issues, as well as a major important matter from the general public, is visibility. Although, when compared with other environmental impact related to wind power, the visual impact could be the least serious .
For instance, the optical impacts and countryside observations have been considered as key natural problems in establishing the applications of wind farm related to wind energy improvement as visual impacts and landscape are by nature subjective and altering over period and place. The countryside?s and optical effects such as features like substation constructions, grid connection, access and place tracks, turbines (size, height, number, material and colour), communication lines and anemometer masts .
According to , wind turbines have an extremely noticeable structure in any countryside due to their high capacity. In general, the people who are resident near wind turbines are more affected compared to those citizens who live far away. In contrast, many people believe that this can be changed when the huge numbers of turbines lead to breaking the optic impact of the countryside, as people will simply be used to them. For example, larger turbines can be more suitable than small turbines. Additionally, the larger turbines don?t appear as noticeable to human eyes, because their rotational speed is slower than small turbines.
On the other hand, disagree that turbines have an attractive beautification, and they can appeal to travellers, encouraging them to visit those areas containing some wind turbines. Generally, the people most anxious about the environment are the ones who are likely to be the most stressed by its visual impact. Thus, this issue can mainly be solved by reducing stressful implications on the population.
2.3 Electromagnetic interference effects of wind turbines Wind turbines create electromagnetic interference (EMI) problems involving X-Rays and ultra violet rays. EMI can be defined as disturbance that affects an electrical field. Typically, any kind of big structure, whether moving or stationary, stationary, might degrade and interfere with the transmission of electromagnetic signals. It is likely that their vertical structure can reflect portions of the electromagnetic radiation in a way that interferes with the original signal arriving at the receiver. Several people have suggested that wind turbines could lead to interference and impact on radio transmissions and TV when they rotate blades that can disrupt the signals .
In addition, effects of electromagnetic interference, including scattering of signals and blocking, might affect household TV and other electronic devices, which causes stress to people, additionally to any long-term health implications.
2.4 Avian collisions with wind turbines Wind turbines can also affect birds and other flying animals such as bats, when they interact with rotor blades. As the result of this, they are being killed and injury by wind turbines because they fly around offshore or in rural areas. In general, there are two significant categories of impact. Firstly, it can directly impact, for example, via serious risks to birds and bats flying into the machines, due to the huge pressure around the turbines. Secondly, there is also indirect impact, including disturbance of breeding and staging, consequently affecting migration and travelling birds disturbing effect on migrating as well as travelling birds [2, 5].
It has been claimed by when the turbine is blended with the skyline, this may cause more birds to be killed. However, according to a study by BUND in Germany cited in , ?there is statistically one bird death per year for two turbines, or 8000 bird deaths per year. 5-10 million birds die in road traffic and the same number again in power lines?.
In conclusion, wind turbines are not benefit and suitable for birds but it may not be a huge problem, and there are solutions to ease the problem
3.1 Solutions to the noise pollution of wind turbines Noise from wind turbines is generated by moving blades, but reduction of wind turbines noise has to occur by one of two main ways. Firstly, the moving components such as gearbox and generator produce mechanical noise. Secondly, aerodynamic noise is created by interaction of the blades of a turbine with wind . Data that has been collected when wind farms are developed, suggest that modern wind turbines designs appear to reduce noise pollution when compared with older models . According to mechanical noise can be reduced power, which generated by wind turbines during mid-night and impacts on nearby residents therefore putting a long distance between wind farms and the occupants. Moreover, aerodynamic noise maybe decreases by limiting the number of cycle blades per a minute.
In summary, it is believed that noise pollution from wind turbines does create some problems, but it can be solved using some patterns of action, outlined above Furthermore, Impact on people reduces according to distance, so the fewer people close to the turbines, the better.
3.2 Solutions to the visual impact from wind turbines The second area for solutions, is regarding visual impact of turbines. Although many people believe that wind turbines look attractive, but a majority of the population consider wind turbines unattractive, so the main solution is to minimise their visual impact. According to , the equipment quality of wind energy generators can create a substantial contribution to this issue. Features that help to minimize visual impact include their colour, size of wind turbine, the number of blades and distance between the residences and wind turbines.
First of all, the colour of wind turbines should be designed using colours suitable for the reduction of the visual impact . Secondly, the distance from dwellings has been recognized as a significant attributing factor in minimizing wind turbines pressure on people. From further away, the rotational blades appear lower, not attracting people?s eyes when they are moving . Therefore, ideally they need to be built high up to catch the most wind, but far away to lessen the impact.
3.3 Solutions to the electromagnetic interference from wind turbines The third factor that can create stress is electromagnetic interference and there are some solutions to this. Modern blades are produced using synthetic materials, which when substituted for metal blades reduce interference to mobile and TV signals and have a lower effect on the electromagnetic radiation transmission. Electrical systems, which are maintained well, should not suffer too much interference. Overall, when wind turbines are sited close to residents, interference can prove very difficult to rule out .
3.4 Solutions to the avian collisions from wind turbines Thinking about solutions to avian collisions, there are three potential ways to reduce the danger to flying creatures with turbines, and thus reduce the associated environmental impact. Firstly, an increase in the visibility of rotor blades. Secondly, use turbines that have white flashing lights, not red ones. Thirdly, protect migration paths when birds fly in large numbers. Using these three patterns, birds could be helped to avoid collision with wind turbines Thus, in three patters, birds may be avoiding interaction. Process of the world by wind turbines is causes of killing the average number of birds and other flying animals, but as can be seen from the above solutions that cause declining impacts on them.
4. Conclusion This work has looked at the context and background to wind turbines, and some of the problem areas they can create, in terms of noise, visual impact, interference and the risk of collision in the bird population. Following this, some approaches to limit the negative impact and stresses they can produce, were outlined.
As this report has demonstrated, the environmental impacts of wind turbines can create significant stress for residents who are living the vicinity. Such stress could potentially lead to psychological distress and various physical health and well-being problems. It appears that these symptoms could be directly linked to pollution, visual impact and electromagnetic interference associated with wind turbines. The work has also outlined ways in which wind turbines can impact on birdlife.
It has been suggested that if wind turbines are planned and designed carefully, many of these negative impacts may be eliminated or reduced in terms of the amount of stress on people . Ways to do this, which have been discussed, include altering colour, design, construction material, taking care over planning sites and selecting exact locations with care and attention to the potential problems. For example, there is still disagreement about whether wind turbines should be located onshore or offshore, and which location creates the most impact. There is no doubt that when wind turbines have been built far from inhabitants, an amount of electrical energy may be lost due to using electric resistance wire for transferring the generated electricity from turbines to houses. Therefore, inventors suggest the best solution to discover this problem.
Finally, despite the negative impacts, solutions are being found, as has been discussed, and it seems clear that wind turbines have a lot of potential to be a cleaner energy source, with lower impact than many other fuels, and may be part of a future global strategy to address climate change issues.
- Saidur R, Rahim N, Islam M, et al. Renewable and sustainable energy reviews 15 (2011): 2423-2430.
- Manwell JF, McGowan JG, Rogers AL. Wind energy explained: theory design and application John Wiley and Sons (2010).
- Bowdler D, Leventhall G, Raspet R. Journal of the Acoustical Society of America 132 (2012): 1233.
- Association E.W.E. Wind energy-the facts: a guide to the technology economics and future of wind power Routledge (2012).
- Energy G. R. http://www.greenrhinoenergy.com/renewable/wind/wind_environment.php. 2013.
- Müller DK, Jansson B. Tourism in peripheries: perspectives from the far north and south Cabi (2006)
- Citation: Hiwa Mohammad Qadr. An Exploration into Wind Turbines, their Impacts and Potential
Solutions. Journal of Environmental Science and Public Health 2 (2018): 64-69. | <urn:uuid:f78d1522-d6f5-424d-a67b-fdd257118eef> | 2.921875 | 3,078 | Academic Writing | Science & Tech. | 32.790694 | 95,488,403 |
The motor of a ski boat generates an average power of 6.90 x 10^4 W when the boat is moving at a constant speed of 15 m/s. When the boat is pulling a skier at the same speed, the engine must generate an average power of 8.70 x10^4 W. What is the tension in the tow rope that is pulling the skier?
The drawing shows the force-versus-displacement graph for two different bows. These graphs give the force that an archer must apply to draw the bowstring.
(a) For which bow is more work required to draw the bow fully from s = 0 to s = 0.50 m?
(b) Estimate the additional work required for the bow identified in part (a) compared to the other bow.
A net external force is applied to a 7.58-kg object that is initially at rest. The net force component along the displacement of the object varies with the magnitude of the displacement as shown in the drawing. What is the speed of the object at s = 20.0 m?
Two pole-vaulters just clear the bar at the same height. The first lands at a speed of 8.60 m/s, and the second lands at a speed of 8.90 m/s. The first vaulter clears the bar at a speed of 1.00 m/s. Ignore air resistance and friction and determine the speed at which the second vaulter clears the bar.
(Please refer to the attachment for detailed problems with figs.)© BrainMass Inc. brainmass.com July 17, 2018, 9:20 pm ad1c9bdddf
The work, energy and power in physics are analyzed.Net external force is applied to an object. | <urn:uuid:f1fdced8-ffc4-49c3-abbf-a8bc7ddf6161> | 3.453125 | 371 | Tutorial | Science & Tech. | 89.298204 | 95,488,406 |
September 19 2015 Astronomy Newsletter
Here's the latest article from the Astronomy site at BellaOnline.com.
Hyperion – Saturn's Weird Wobbly Moon
Saturn has lots of moons – more than five dozen of them with confirmed orbits. They are remarkable in many ways, but perhaps the strangest one is the misshapen and unpredictable Hyperion.
By the way, Hyperion was first spotted by the Bonds on September 16, 1848. Mimas was discovered by William Herschel on September 17, 1789.
I have a particular fondness for Hyperion the Titan. I'm surprised the astronomy community hasn't adopted him! He was one of the twelve offspring of Uranus and Gaia, himself fathering Helios (Sun), Selene (Moon) and Eos (Dawn). He represented light and observation. Indeed the Greek historian Diodorus Siculus (90 BCE - 30 BCE) wrote of Hyperion: “[He] was the first to understand, by diligent attention and observation, the movement of both the sun and the moon and the other stars, and the seasons as well, in that they are caused by these bodies, and to make these facts known to others.”
*Astronomy Photographer of the Year 2015*
The winners of the competition were announced in Greenwich on Thursday night, and the exhibition is now open. I'll be writing more about this later, but here's the overall winning picture: http://www.rmg.co.uk/sites/default/files/s05_lj_1300.jpg It's entitled “Eclipse Totality over Sassendalen”, by Luc Jamet of France. He took it on the island of Svalbard in the far north of Norway, one of the few places where the March eclipse was visible in its totality.
Here's where you can find out about seeing the exhibition in Greenwich or see the online exhibition: http://www.rmg.co.uk/whats-on/exhibitions/astronomy-photographer-of-the-year. This page also includes the winning images for previous years of the competition.
*Reminder of the lunar eclipse*
September 27-28 is the date. In order to find out whether you can see the eclipse - and how much of it - here is a map: http://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2015Sep28T.pdf The times given are UTC, which is Greenwich Mean Time. That means the greatest eclipse in Britain is about four in the morning. Ugh! The timing is better in the Americas where many people will be able to see it on the night of the 27th.
Please visit http://astronomy.bellaonline.com/Site.asp for even more great content about Astronomy.
I hope to hear from you sometime soon, either in the forum http://forums.bellaonline.com/ubbthreads.php/forums/323/1/Astronomy or in response to this email message. I welcome your feedback!
Do pass this message along to family and friends who might also be interested. Remember it's free and without obligation.
I wish you clear skies.
Mona Evans, Astronomy Editor
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The Hayashi track is a luminosity–temperature relationship obeyed by infant stars of less than 3 M☉ in the pre-main-sequence phase (PMS phase) of stellar evolution. It is named after Japanese astrophysicist Chushiro Hayashi. On the Hertzsprung–Russell diagram, which plots luminosity against temperature, the track is a nearly vertical curve. After a protostar ends its phase of rapid contraction and becomes a T Tauri star, it is extremely luminous. The star continues to contract, but much more slowly. While slowly contracting, the star follows the Hayashi track downwards, becoming several times less luminous but staying at roughly the same surface temperature, until either a radiative zone develops, at which point the star starts following the Henyey track, or nuclear fusion begins, marking its entry onto the main sequence.
The shape and position of the Hayashi track on the Hertzsprung–Russell diagram depends on the star's mass and chemical composition. For solar-mass stars, the track lies at a temperature of roughly 4000 K. Stars on the track are nearly fully convective and have their opacity dominated by hydrogen ions. Stars less than 0.5 M☉ are fully convective even on the main sequence, but their opacity begins to be dominated by Kramers' opacity law after nuclear fusion begins, thus moving them off the Hayashi track. Stars between 0.5 and 3 M☉ develop a radiative zone prior to reaching the main sequence. Stars between 3 and 10 M☉ are fully radiative at the beginning of the pre-main-sequence. Even heavier stars are born onto the main sequence, with no PMS evolution.
At an end of a low- or intermediate-mass star's life, the star follows an analogue of the Hayashi track, but in reverse—it increases in luminosity, expands, and stays at roughly the same temperature, eventually becoming a red giant.
In 1961, Professor Chushiro Hayashi published two papers that led to the concept of the pre-main-sequence and form the basis of the modern understanding of early stellar evolution. Hayashi realized that the existing model, in which stars are assumed to be in radiative equilibrium with no substantial convection zone, cannot explain the shape of the red giant branch. He therefore replaced the model by including the effects of thick convection zones on a star's interior.
A few years prior, Osterbrock proposed deep convection zones with efficient convection, analyzing them using the opacity of H- ions (the dominant opacity source in cool atmospheres) in temperatures below 5000K. However, the earliest numerical models of Sun-like stars did not follow up on this work and continued to assume radiative equilibrium.
In his 1961 papers, Hayashi showed that the convective envelope of a star is determined by:
where E is unitless, and not the energy. Modelling stars as polytropes with index 3/2—in other words, assuming they follow a pressure-density relationship of —he found that E=45 is the maximum for a quasistatic star. If a star is not contracting rapidly, E=45 defines a curve on the HR diagram, to the right of which the star cannot exist. He then computed the evolutionary tracks and isochrones (luminosity-temperature distributions of stars at a given age) for a variety of stellar masses and noted that NGC2264, a very young star cluster, fits the isochrones well. In particular, he calculated much lower ages for solar-type stars in NGC2264 and predicted that these stars were rapidly contracting T Tauri stars.
In 1962, Hayashi published a 183-page review of stellar evolution. Here, he discussed the evolution of stars born in the forbidden region. These stars rapidly contract due to gravity before settling to a quasistatic, fully convective state on the Hayashi tracks.
In 1965, numerical models by Iben and Ezer & Cameron realistically simulated pre-main-sequence evolution, including the Henyey track that stars follow after leaving the Hayashi track. These standard PMS tracks can still be found in textbooks on stellar evolution.
The forbidden zone is the region on the HR diagram to the right of the Hayashi track where no star can be in hydrostatic equilibrium, even those that are partially or fully radiative. Newborn protostars start out in this zone, but are not in hydrostatic equilibrium and will rapidly move towards the Hayashi track.
The star's luminosity is therefore given by:
For a given L, a lower temperature implies a larger radius, and vice versa. Thus, the Hayashi track separates the HR diagram into two regions: the allowed region to the left, with high temperatures and smaller radii for each luminosity, and the forbidden region to the right, with lower temperatures and correspondingly higher radii. The Hayashi limit can refer to either the lower bound in temperature or the upper bound on radius defined by the Hayashi track.
The region to the right is forbidden because it can be shown that a star in the region must have a temperature gradient of:
where for a monatomic ideal gas undergoing adiabatic expansion or contraction. A temperature gradient greater than 0.4 is therefore called superadiabatic.
Consider a star with a superadiabatic gradient. Imagine a parcel of gas that starts at radial position r, but moves upwards to r+dr in a sufficiently short time that it exchanges negligible heat with its surroundings—in other words, the process is adiabatic. The pressure of the surroundings, as well as that of the parcel, decreases by some amount dP. The parcel's temperature changes by . The temperature of the surroundings also decreases, but by some amount dT' that is greater than dT. The parcel therefore ends up being hotter than its surroundings. Since the ideal gas law can be written , a higher temperature implies a lower density at the same pressure. The parcel is therefore also less dense than its surroundings. This will cause it to rise even more, and the parcel will become even less dense than its new surroundings.
Clearly, this situation is not stable. In fact, a superadiabatic gradient causes convection. Convection tends to lower the temperature gradient because the rising parcel of gas will eventually be dispersed, dumping its excess thermal and kinetic energy into its surroundings and heating up said surroundings. In stars, the convection process is known to be highly efficient, with a typical that only exceeds the adiabatic gradient by 1 part in 10 million.
If a star is placed in the forbidden zone, with a temperature gradient much greater than 0.4, it will experience rapid convection that brings the gradient down. Since this convection will drastically change the star's pressure and temperature distribution, the star is not in hydrostatic equilibrium, and will contract until it is.
A star far to the left of the Hayashi track has a temperature gradient smaller than adiabatic. This means that if a parcel of gas rises a tiny bit, it will be more dense than its surroundings and sink back to where it came from. Convection therefore does not occur, and almost all energy output is carried radiatively.
Stars form when small regions of a giant molecular cloud collapse under their own gravity, becoming protostars. The collapse releases gravitational energy, which heats up the protostar. This process occurs on the free-fall timescale, which is roughly 100,000 years for solar-mass protostars, and ends when the protostar reaches approximately 4000 K. This is known as the Hayashi boundary, and at this point, the protostar is on the Hayashi track. At this point, they are known as T Tauri stars and continue to contract, but much more slowly. As they contract, they decrease in luminosity because less surface area becomes available for emitting light. The Hayashi track gives the resulting change in temperature, which will be minimal compared to the change in luminosity because the Hayashi track is nearly vertical. In other words, on the HR diagram, a T Tauri star starts out on the Hayashi track with a high luminosity and moves downward along the track as time passes.
The Hayashi track describes a fully convective star. This is a good approximation for very young pre-main-sequence stars they are still cool and highly opaque, so that radiative transport is insufficient to carry away the generated energy and convection must occur. Stars less massive than 0.5 M☉ remain fully convective, and therefore remain on the Hayashi track, throughout their pre-main-sequence stage, joining the main sequence at the bottom of the Hayashi track. Stars heavier than 0.5 M☉ have higher interior temperatures, which decreases their central opacity and allows radiation to carry away large amounts of energy. This allows a radiative zone to develop around the star's core. The star is then no longer on the Hayashi track, and experiences a period of rapidly increasing temperature at nearly constant luminosity. This is called the Henyey track, and ends when temperatures are high enough to ignite hydrogen fusion in the core. The star is then on the main sequence.
Lower-mass stars follow the Hayashi track until the track intersects with the main sequence, at which point hydrogen fusion begins and the star follows the main sequence. Even lower-mass 'stars' never achieve the conditions necessary to fuse hydrogen and become brown dwarfs.
The exact shape and position of the Hayashi track can only be computed numerically using computer models. Nevertheless, we can make an extremely crude analytical argument that captures most of the track's properties. The following derivation loosely follows that of Kippenhahn, Weigert, and Weiss in Stellar Structure and Evolution.
In our simple model, a star is assumed to consist of a fully convective interior inside of a fully radiative atmosphere.
The convective interior is assumed to be an ideal monatomic gas with a perfectly adiabatic temperature gradient:
This quantity is sometimes labelled . The following adiabatic equation therefore holds true for the entire interior:
where is the adiabatic gamma, which is 5/3 for an ideal monatomic gas. The ideal gas law says:
where is the molecular weight per particle and H is (to a very good approximation) the mass of a hydrogen atom. This equation represents a polytrope of index 1.5, since a polytrope is defined by , where n=1.5 is the polytropic index. Applying the equation to the center of the star gives: We can solve for C:
But for any polytrope, , , and . and K are all constants independent of pressure and density, and the average density is defined as . Plugging all 3 equations into the equation for C, we have:
where all multiplicative constants have been ignored. Recall that our original definition of C was:
We therefore have, for any star of mass M and radius R:
We need another relationship between P, T, M, and R, in order to eliminate P. This relationship will come from the atmosphere model.
The atmosphere is assumed to be thin, with average opacity k. Opacity is defined to be optical depth divided by density. Thus, by definition, the optical depth of the stellar surface, also called the photosphere, is:
where R is the stellar radius, also known as the position of the photosphere. The pressure at the surface is:
The optical depth at the photosphere turns out to be . By definition, the temperature of the photosphere is where effective temperature is given by . Therefore, the pressure is:
We can approximate the opacity to be:
where a=1, b=3. Plugging this into the pressure equation, we get:
Finally, we need to eliminate R and introduce L, the luminosity. This can be done with the equation:
In cool stellar atmospheres (T < 5000 K) like those of newborn stars, the dominant source of opacity is the H- ion, for which and , we get and .
Since A is much smaller than 1, the Hayashi track is extremely steep: if the luminosity changes by a factor of 2, the temperature only changes by 4 percent. The fact that B is positive indicates that the Hayashi track shifts left on the HR diagram, towards higher temperatures, as mass increases. Although this model is extremely crude, these qualitative observations are fully supported by numerical simulations.
At high temperatures, the atmosphere's opacity begins to be dominated by Kramers' opacity law instead of the H- ion, with a=1 and b=-4.5 In that case, A=0.2 in our crude model, far higher than 0.05, and the star is no longer on the Hayashi track.
In Stellar Interiors, Hansen, Kawaler, and Trimble go through a similar derivation without neglecting multiplicative constants, and arrived at:
where is the molecular weight per particle. The authors note that the coefficient of 2600K is too low—it should be around 4000K—but this equation nevertheless shows that temperature is nearly independent of luminosity.
The diagram at the top of this article shows numerically computed stellar evolution tracks for various masses. The vertical portions of each track is the Hayashi track. The endpoints of each track lie on the main sequence. The horizontal segments for higher-mass stars show the Henyey track.
It is approximately true that:
The diagram to the right shows how Hayashi tracks change with changes in chemical composition. Z is the star's metallicity, the mass fraction not accounted for by hydrogen or helium. For any given hydrogen mass fraction, increasing Z leads to increasing molecular weight. The dependence of temperature on molecular weight is extremely steep—it is approximately
Decreasing Z by a factor of 10 shifts the track right, changing by about 0.05.
Chemical composition affects the Hayashi track in a few ways. The track depends strongly on the atmosphere's opacity, and this opacity is dominated by the H- ion. The abundance of the H- ion is proportional to the density of free electrons, which, in turn, is higher if there are more metals because metals are easier to ionize than hydrogen or helium.
Observational evidence of the Hayashi track comes from color-magnitude plots—the observational equivalent of HR diagrams—of young star clusters. For Hayashi, NGC 2264 provided the first evidence of a population of contracting stars. In 2012, data from NGC 2264 was re-analyzed to account for dust reddening and extinction. The resulting color-magnitude plot is shown at right.
In the upper diagram, the isochrones are curves along which stars of a certain age are expected to lie, assuming that all stars evolve along the Hayashi track. An isochrone is created by taking stars of every conceivable mass, evolving them forwards to the same age, and plotting all of them on the color-magnitude diagram. Most of the stars in NGC 2264 are already on the main sequence (black line), but a substantial population lies between the isochrones for 3.2 million and 5 million years, indicating that the cluster is 3.2-5 million years old and a large population of T Tauri stars is still on their respective Hayashi tracks. Similar results have been obtained for NGC 6530, IC 5146, and NGC 6611.
The lower diagram shows Hayashi tracks for various masses, along with T Tauri observations collected from a variety of sources. Note the bold curve to the right, representing a stellar birthline. Even though some Hayashi tracks theoretically extend above the birthline, few stars are above it. In effect, stars are 'born' onto the birthline before evolving downwards along their respective Hayashi tracks.
The birthline exists because stars formed from overdense cores of giant molecular clouds in an inside-out manner. That is, a small central region first collapses in on itself while the outer shell is still nearly static. The outer envelope then accretes onto the central protostar. Before the accretion is over, the protostar is hidden from view, and therefore not plotted on the color-magnitude diagram. When the envelope finishes accreting, the star is revealed and appears on the birthline. | <urn:uuid:37caa18d-1acf-40c7-abe7-dfa03667311e> | 3.125 | 3,400 | Knowledge Article | Science & Tech. | 43.431602 | 95,488,419 |
While working with elliptic curves for cryptography reasons, I found the notion of a primitive point, but no definition.
For example, $P(0,6)$ is a primitive point on the elliptic curve $y^2\equiv x^3+2x+2 \mod 17$.
What does that mean? How can I tell if a point is primitive or not?
The points on an elliptic curve (plus a ‘point at infinity’) form a group under a certain addition law, explained in this Wikipedia article. (You probably know this already.) A primitive point $P$ is simply a generator of this group: all elements of the group can be expressed as $P+P+…+P$ ($k$ times) for some $k$. If the elliptic curve has a prime number of points, then all its points (except the point at infinity) are primitive; but in general, the elliptic curve may or may not have a primitive point.
Yes, primitive point means the group is cyclic and that P is a generator.
Let E be an elliptic curve over a finite field F_q. The group E( F_q ) is cyclic if gcd( #E( F_q ), q-1 ) = 1. To test whether a point P generates E( F_q ) it is necessary to factorise #E( F_q ). The case when #E( F_q ) is prime is an easy special case.
If M = gcd( #E( F_q ), q-1 ) > 1 then one can determine whether E( F_q ) is cyclic or not (both cases can arise) in expected (randomised) polynomial time using the Weil pairing. This algorithm is due to Victor Miller and is explained in his paper in the Journal of Cryptology, volume 17 (2004). | <urn:uuid:4341a935-3004-48b5-bad3-8f3a5616c18a> | 2.921875 | 397 | Q&A Forum | Science & Tech. | 69.314067 | 95,488,428 |
Methanogenic bacteria of 108g SS-1in the activated sludges from an aeration tank treating sewage and from a secondary sedimentation tank of an activated sludge plant treating textile dyeing wastewater were enumerated by the Most Probable Number (MPN) technique. By using the two activated sludges as the seed material, anaerobic granular sludges were obtained at 35°C in two lab-UASB reactors having volumes of 29 and 481, and treating a glucose molasses solution of 1000-3500 mg COD 1-1and citrate wastewater of 20,000-36,000 mg COD 1-1respectively. The characteristics of granulation using the activated sludge as the seed were similar to those using digested sewage sludge as the seed. It is shown that activated sludge is readily available seed material for an anaerobic reactor. The growth of methanogenic bacteria in the activated sludge can be attributed to the existence of some anaerobic nuclei in the activated sludge flocs. The factors for the cultivation of granular sludge by using the activated sludge are also discussed. © 1987.
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Quantity: 115 available
2011. 28cm. Pp.650. Hardbound.
Among all vertebrates, gobies are second in diversity only to the teleost family Cyprinidae. The Gobiidae consists of more than 200 genera and nearly 2,000 species and make up the largest family of marine fishes.
Gobies account for as much as 50% of the energy flow in coral reef communities. Their small size, ability to adapt to numerous ecological niches and to be bred in aquaria has led to numerous studies both in the field and laboratory. Gobies are found from above the high tide line to depths of over 1,100 m. Some species are found only within caves, others deep inside sponges, and some others climb waterfalls to return to their native streams. They vary reproductively from gonochoric to hermaphrodite, monogamy to polygyny and promiscuity, some have short life spans and reproduce only once while others have longer life spans reproducing one or more times per year.
The Biology of Gobies written by over 30 experts from 15 countries summarizes what is known about the systematics, ecology, zoogeography, and general biology of the Gobiiformes. This foundation will provide the basic information necessary for future studies.
Title: The Biology of Gobies
Categories: Marine Fishes,
ISBN 13: 9781578084364
Weight: 1.00 Item
Inventory number: 979219
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A differential equation is a mathematical equation that relates some function with its derivatives. In applications, the functions usually represent physical quantities, the derivatives represent their rates of change, and the equation defines a relationship between the two. Because such relations are extremely common, differential equations play a prominent role in many disciplines including engineering, physics, economics, and biology.
In pure mathematics, differential equations are studied from several different perspectives, mostly concerned with their solutions—the set of functions that satisfy the equation. Only the simplest differential equations are solvable by explicit formulas; however, some properties of solutions of a given differential equation may be determined without finding their exact form.
If a self-contained formula for the solution is not available, the solution may be numerically approximated using computers. The theory of dynamical systems puts emphasis on qualitative analysis of systems described by differential equations, while many numerical methods have been developed to determine solutions with a given degree of accuracy.
Differential equations first came into existence with the invention of calculus by Newton and Leibniz. In Chapter 2 of his 1671 work "Methodus fluxionum et Serierum Infinitarum", Isaac Newton listed three kinds of differential equations:
He solves these examples and others using infinite series and discusses the non-uniqueness of solutions.
for which the following year Leibniz obtained solutions by simplifying it.
Historically, the problem of a vibrating string such as that of a musical instrument was studied by Jean le Rond d'Alembert, Leonhard Euler, Daniel Bernoulli, and Joseph-Louis Lagrange. In 1746, d’Alembert discovered the one-dimensional wave equation, and within ten years Euler discovered the three-dimensional wave equation.
The Euler–Lagrange equation was developed in the 1750s by Euler and Lagrange in connection with their studies of the tautochrone problem. This is the problem of determining a curve on which a weighted particle will fall to a fixed point in a fixed amount of time, independent of the starting point.
In 1822, Fourier published his work on heat flow in Théorie analytique de la chaleur (The Analytic Theory of Heat), in which he based his reasoning on Newton's law of cooling, namely, that the flow of heat between two adjacent molecules is proportional to the extremely small difference of their temperatures. Contained in this book was Fourier's proposal of his heat equation for conductive diffusion of heat. This partial differential equation is now taught to every student of mathematical physics.
For example, in classical mechanics, the motion of a body is described by its position and velocity as the time value varies. Newton's laws allow these variables to be expressed dynamically (given the position, velocity, acceleration and various forces acting on the body) as a differential equation for the unknown position of the body as a function of time.
In some cases, this differential equation (called an equation of motion) may be solved explicitly.
An example of modelling a real world problem using differential equations is the determination of the velocity of a ball falling through the air, considering only gravity and air resistance. The ball's acceleration towards the ground is the acceleration due to gravity minus the acceleration due to air resistance. Gravity is considered constant, and air resistance may be modeled as proportional to the ball's velocity. This means that the ball's acceleration, which is a derivative of its velocity, depends on the velocity (and the velocity depends on time). Finding the velocity as a function of time involves solving a differential equation and verifying its validity.
Differential equations can be divided into several types. Apart from describing the properties of the equation itself, these classes of differential equations can help inform the choice of approach to a solution. Commonly used distinctions include whether the equation is: Ordinary/Partial, Linear/Non-linear, and Homogeneous/Inhomogeneous. This list is far from exhaustive; there are many other properties and subclasses of differential equations which can be very useful in specific contexts.
Ordinary differential equationsEdit
An ordinary differential equation (ODE) is an equation containing an unknown function of one real or complex variable x, its derivatives, and some given functions of x. The unknown function is generally represented by a variable (often denoted y), which, therefore, depends on x. Thus x is often called the independent variable of the equation. The term "ordinary" is used in contrast with the term partial differential equation, which may be with respect to more than one independent variable.
Linear differential equations are the differential equations that are linear in the unknown function and its derivatives. Their theory is well developed, and, in many cases, one may express their solutions in terms of integrals.
Partial differential equationsEdit
A partial differential equation (PDE) is a differential equation that contains unknown multivariable functions and their partial derivatives. (This is in contrast to ordinary differential equations, which deal with functions of a single variable and their derivatives.) PDEs are used to formulate problems involving functions of several variables, and are either solved in closed form, or used to create a relevant computer model.
PDEs can be used to describe a wide variety of phenomena in nature such as sound, heat, electrostatics, electrodynamics, fluid flow, elasticity, or quantum mechanics. These seemingly distinct physical phenomena can be formalised similarly in terms of PDEs. Just as ordinary differential equations often model one-dimensional dynamical systems, partial differential equations often model multidimensional systems. PDEs find their generalisation in stochastic partial differential equations.
Non-linear differential equationsEdit
Non-linear differential equations are formed by the products of the unknown function and its derivatives are allowed and its degree is > 1. There are very few methods of solving nonlinear differential equations exactly; those that are known typically depend on the equation having particular symmetries. Nonlinear differential equations can exhibit very complicated behavior over extended time intervals, characteristic of chaos. Even the fundamental questions of existence, uniqueness, and extendability of solutions for nonlinear differential equations, and well-posedness of initial and boundary value problems for nonlinear PDEs are hard problems and their resolution in special cases is considered to be a significant advance in the mathematical theory (cf. Navier–Stokes existence and smoothness). However, if the differential equation is a correctly formulated representation of a meaningful physical process, then one expects it to have a solution.
Linear differential equations frequently appear as approximations to nonlinear equations. These approximations are only valid under restricted conditions. For example, the harmonic oscillator equation is an approximation to the nonlinear pendulum equation that is valid for small amplitude oscillations (see below).
Differential equations are described by their order, determined by the term with the highest derivatives. An equation containing only first derivatives is a first-order differential equation, an equation containing the second derivative is a second-order differential equation, and so on. Differential equations that describe natural phenomena almost always have only first and second order derivatives in them, but there are some exceptions, such as the thin film equation, which is a fourth order partial differential equation.
In the first group of examples, let u be an unknown function of x, and let c & ω be known constants. Note both ordinary and partial differential equations are broadly classified as linear and nonlinear.
- Inhomogeneous first-order linear constant coefficient ordinary differential equation:
- Homogeneous second-order linear ordinary differential equation:
- Homogeneous second-order linear constant coefficient ordinary differential equation describing the harmonic oscillator:
- Inhomogeneous first-order nonlinear ordinary differential equation:
- Second-order nonlinear (due to sine function) ordinary differential equation describing the motion of a pendulum of length L:
In the next group of examples, the unknown function u depends on two variables x and t or x and y.
- Homogeneous first-order linear partial differential equation:
- Homogeneous second-order linear constant coefficient partial differential equation of elliptic type, the Laplace equation:
Existence of solutionsEdit
Solving differential equations is not like solving algebraic equations. Not only are their solutions often unclear, but whether solutions are unique or exist at all are also notable subjects of interest.
For first order initial value problems, the Peano existence theorem gives one set of circumstances in which a solution exists. Given any point in the xy-plane, define some rectangular region , such that and is in the interior of . If we are given a differential equation and the condition that when , then there is locally a solution to this problem if and are both continuous on . This solution exists on some interval with its center at . The solution may not be unique. (See Ordinary differential equation for other results.)
However, this only helps us with first order initial value problems. Suppose we had a linear initial value problem of the nth order:
For any nonzero , if and are continuous on some interval containing , is unique and exists.
- A delay differential equation (DDE) is an equation for a function of a single variable, usually called time, in which the derivative of the function at a certain time is given in terms of the values of the function at earlier times.
- A stochastic differential equation (SDE) is an equation in which the unknown quantity is a stochastic process and the equation involves some known stochastic processes, for example, the Wiener process in the case of diffusion equations.
- A differential algebraic equation (DAE) is a differential equation comprising differential and algebraic terms, given in implicit form.
Connection to difference equationsEdit
The theory of differential equations is closely related to the theory of difference equations, in which the coordinates assume only discrete values, and the relationship involves values of the unknown function or functions and values at nearby coordinates. Many methods to compute numerical solutions of differential equations or study the properties of differential equations involve the approximation of the solution of a differential equation by the solution of a corresponding difference equation.
The study of differential equations is a wide field in pure and applied mathematics, physics, and engineering. All of these disciplines are concerned with the properties of differential equations of various types. Pure mathematics focuses on the existence and uniqueness of solutions, while applied mathematics emphasizes the rigorous justification of the methods for approximating solutions. Differential equations play an important role in modelling virtually every physical, technical, or biological process, from celestial motion, to bridge design, to interactions between neurons. Differential equations such as those used to solve real-life problems may not necessarily be directly solvable, i.e. do not have closed form solutions. Instead, solutions can be approximated using numerical methods.
Many fundamental laws of physics and chemistry can be formulated as differential equations. In biology and economics, differential equations are used to model the behavior of complex systems. The mathematical theory of differential equations first developed together with the sciences where the equations had originated and where the results found application. However, diverse problems, sometimes originating in quite distinct scientific fields, may give rise to identical differential equations. Whenever this happens, mathematical theory behind the equations can be viewed as a unifying principle behind diverse phenomena. As an example, consider the propagation of light and sound in the atmosphere, and of waves on the surface of a pond. All of them may be described by the same second-order partial differential equation, the wave equation, which allows us to think of light and sound as forms of waves, much like familiar waves in the water. Conduction of heat, the theory of which was developed by Joseph Fourier, is governed by another second-order partial differential equation, the heat equation. It turns out that many diffusion processes, while seemingly different, are described by the same equation; the Black–Scholes equation in finance is, for instance, related to the heat equation.
- Euler–Lagrange equation in classical mechanics
- Hamilton's equations in classical mechanics
- Radioactive decay in nuclear physics
- Newton's law of cooling in thermodynamics
- The wave equation
- The heat equation in thermodynamics
- Laplace's equation, which defines harmonic functions
- Poisson's equation
- The geodesic equation
- The Navier–Stokes equations in fluid dynamics
- The Diffusion equation in stochastic processes
- The Convection–diffusion equation in fluid dynamics
- The Cauchy–Riemann equations in complex analysis
- The Poisson–Boltzmann equation in molecular dynamics
- The shallow water equations
- Universal differential equation
- The Lorenz equations whose solutions exhibit chaotic flow.
So long as the force acting on a particle is known, Newton's second law is sufficient to describe the motion of a particle. Once independent relations for each force acting on a particle are available, they can be substituted into Newton's second law to obtain an ordinary differential equation, which is called the equation of motion.
Maxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents. They are named after the Scottish physicist and mathematician James Clerk Maxwell, who published an early form of those equations between 1861 and 1862.
The Einstein field equations (EFE; also known as "Einstein's equations") are a set of ten partial differential equations in Albert Einstein's general theory of relativity which describe the fundamental interaction of gravitation as a result of spacetime being curved by matter and energy. First published by Einstein in 1915 as a tensor equation, the EFE equate local spacetime curvature (expressed by the Einstein tensor) with the local energy and momentum within that spacetime (expressed by the stress–energy tensor).
In quantum mechanics, the analogue of Newton's law is Schrödinger's equation (a partial differential equation) for a quantum system (usually atoms, molecules, and subatomic particles whether free, bound, or localized). It is not a simple algebraic equation, but in general a linear partial differential equation, describing the time-evolution of the system's wave function (also called a "state function").
- Verhulst equation – biological population growth
- von Bertalanffy model – biological individual growth
- Replicator dynamics – found in theoretical biology
- Hodgkin–Huxley model – neural action potentials
The Lotka–Volterra equations, also known as the predator–prey equations, are a pair of first-order, non-linear, differential equations frequently used to describe the population dynamics of two species that interact, one as a predator and the other as prey.
The rate law or rate equation for a chemical reaction is a differential equation that links the reaction rate with concentrations or pressures of reactants and constant parameters (normally rate coefficients and partial reaction orders). To determine the rate equation for a particular system one combines the reaction rate with a mass balance for the system. In addition, a range of differential equations are present in the study of thermodynamics and quantum mechanics.
- Complex differential equation
- Exact differential equation
- Functional differential equation
- Initial condition
- Integral equations
- Numerical methods for solving differential equations
- Picard–Lindelöf theorem on existence and uniqueness of solutions
- Recurrence relation, also known as 'difference equation'
- Abstract differential equation
- Newton, Isaac. (c.1671). Methodus Fluxionum et Serierum Infinitarum (The Method of Fluxions and Infinite Series), published in 1736 [Opuscula, 1744, Vol. I. p. 66].
- Bernoulli, Jacob (1695), "Explicationes, Annotationes & Additiones ad ea, quae in Actis sup. de Curva Elastica, Isochrona Paracentrica, & Velaria, hinc inde memorata, & paratim controversa legundur; ubi de Linea mediarum directionum, alliisque novis", Acta Eruditorum
- Hairer, Ernst; Nørsett, Syvert Paul; Wanner, Gerhard (1993), Solving ordinary differential equations I: Nonstiff problems, Berlin, New York: Springer-Verlag, ISBN 978-3-540-56670-0
- Cannon, John T.; Dostrovsky, Sigalia (1981). "The evolution of dynamics, vibration theory from 1687 to 1742". Studies in the History of Mathematics and Physical Sciences. 6. New York: Springer-Verlag: ix + 184 pp. ISBN 0-3879-0626-6. GRAY, JW (July 1983). "BOOK REVIEWS". Bulletin (New Series) of the American Mathematical Society. 9 (1). (retrieved 13 Nov 2012).
- Wheeler, Gerard F.; Crummett, William P. (1987). "The Vibrating String Controversy". Am. J. Phys. 55 (1): 33–37. Bibcode:1987AmJPh..55...33W. doi:10.1119/1.15311.
- For a special collection of the 9 groundbreaking papers by the three authors, see First Appearance of the wave equation: D'Alembert, Leonhard Euler, Daniel Bernoulli. - the controversy about vibrating strings (retrieved 13 Nov 2012). Herman HJ Lynge and Son.
- For de Lagrange's contributions to the acoustic wave equation, can consult Acoustics: An Introduction to Its Physical Principles and Applications Allan D. Pierce, Acoustical Soc of America, 1989; page 18.(retrieved 9 Dec 2012)
- Speiser, David. Discovering the Principles of Mechanics 1600-1800, p. 191 (Basel: Birkhäuser, 2008).
- Fourier, Joseph (1822). Théorie analytique de la chaleur (in French). Paris: Firmin Didot Père et Fils. OCLC 2688081.
- Boyce, William E.; DiPrima, Richard C. (1967). Elementary Differential Equations and Boundary Value Problems (4th ed.). John Wiley & Sons. p. 3.
- Weisstein, Eric W. "Ordinary Differential Equation Order." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/OrdinaryDifferentialEquationOrder.html
- Order and degree of a differential equation, accessed Dec 2015.
- Zill, Dennis G. A First Course in Differential Equations (5th ed.). Brooks/Cole. ISBN 0-534-37388-7.
- Einstein, Albert (1916). "The Foundation of the General Theory of Relativity". Annalen der Physik. 354 (7): 769. Bibcode:1916AnP...354..769E. doi:10.1002/andp.19163540702. Archived from the original (PDF) on 2006-08-29.
- Einstein, Albert (November 25, 1915). "Die Feldgleichungen der Gravitation". Sitzungsberichte der Preussischen Akademie der Wissenschaften zu Berlin: 844–847. Retrieved 2006-09-12.
- Misner, Charles W.; Thorne, Kip S.; Wheeler, John Archibald (1973). Gravitation. San Francisco: W. H. Freeman. ISBN 978-0-7167-0344-0 Chapter 34, p. 916.
- Griffiths, David J. (2004), Introduction to Quantum Mechanics (2nd ed.), Prentice Hall, pp. 1–2, ISBN 0-13-111892-7
- IUPAC Gold Book definition of rate law. See also: According to IUPAC Compendium of Chemical Terminology.
- Kenneth A. Connors Chemical Kinetics, the study of reaction rates in solution, 1991, VCH Publishers.
- Abbott, P.; Neill, H. (2003). Teach Yourself Calculus. pp. 266–277.
- Blanchard, P.; Devaney, R. L.; Hall, G. R. (2006). Differential Equations. Thompson.
- Coddington, E. A.; Levinson, N. (1955). Theory of Ordinary Differential Equations. McGraw-Hill.
- Ince, E. L. (1956). Ordinary Differential Equations. Dover.
- Johnson,, W. (1913). A Treatise on Ordinary and Partial Differential Equations. John Wiley and Sons. In University of Michigan Historical Math Collection
- Polyanin, A. D.; Zaitsev, V. F. (2003). Handbook of Exact Solutions for Ordinary Differential Equations (2nd ed.). Boca Raton: Chapman & Hall/CRC Press. ISBN 1-58488-297-2.
- Porter, R. I. (1978). "XIX Differential Equations". Further Elementary Analysis.
- Teschl, Gerald (2012). Ordinary Differential Equations and Dynamical Systems. Providence: American Mathematical Society. ISBN 978-0-8218-8328-0.
- Zwillinger, D. (1997). Handbook of Differential Equations (3rd ed.). Boston: Academic Press.
|Wikiquote has quotations related to: Differential equation|
|Wikibooks has a book on the topic of: Ordinary Differential Equations|
|Wikiversity has learning resources about Differential equations|
|Wikisource has the text of the 1911 Encyclopædia Britannica article Differential Equation.|
- Lectures on Differential Equations MIT Open CourseWare Videos
- Online Notes / Differential Equations Paul Dawkins, Lamar University
- Differential Equations, S.O.S. Mathematics
- Introduction to modeling via differential equations Introduction to modeling by means of differential equations, with critical remarks.
- Mathematical Assistant on Web Symbolic ODE tool, using Maxima
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- Collection of ODE and DAE models of physical systems MATLAB models
- Notes on Diffy Qs: Differential Equations for Engineers An introductory textbook on differential equations by Jiri Lebl of UIUC
- Khan Academy Video playlist on differential equations Topics covered in a first year course in differential equations.
- MathDiscuss Video playlist on differential equations [dead link] | <urn:uuid:329844b3-45ff-4ec1-84b0-6637a243e087> | 3.3125 | 4,796 | Knowledge Article | Science & Tech. | 29.000307 | 95,488,481 |
In the enormous living space provided by the sea, there are plankton (drifters), nekton (swimmers), and benthos (bottom-living organisms). Much of the benthos releases eggs and larvae into the plankton — this is the meroplankton, abundant in coastal waters. The larvae are dispersed by currents; they settle when their time has come, and start growing on the appropriate solid subtrate. The meroplankton feeds planktonic and nektonic predators. Conversely, the plankton feeds the benthos. Thus there is an intimate ecologic relationship between free-swimming and bottom-living organisms. Ultimately, of course, benthic organisms rely on food produced in surface waters in the sunlit zone (Fig. 6.1). The notable exception is the deep-sea benthic community at the hot vents of the Mid-Ocean Ridge (see Sect. 6.9).
Weitere Kapitel dieses Buchs durch Wischen aufrufen
- Productivity and Benthic Organisms — Distribution, Activity, and Environmental Reconstruction
Prof. Dr. Dr. h.c. mult. Eugen Seibold
Ph.D. Prof. Wolfgang H. Berger
- Springer Berlin Heidelberg
Fallstudie Überschwemmungskarten/© Thaut Images | Fotolia | <urn:uuid:ce1287a3-7ddc-416b-aac3-3694481abaa9> | 3.625 | 290 | Knowledge Article | Science & Tech. | 45.26552 | 95,488,526 |
This unusual phenomenon, predicted by the theory of General Relativity, was discovered by chance by a doctoral student at the Instituto de Astrofísica de Canarias while analysing images of the Sculptor dwarf galaxy
The PhD student Margherita Bettinelli, of the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), together with an international team of astrophysicists has recently discovered an unusual astronomical object: an Einstein ring. These phenomena, predicted by Einstein's theory of General Relativity, are quite rare but scientifically interesting.
This is an image of the "Canarias Einstein ring". In the centre of the picture, we can see how the source galaxy (the greenish-blue circle), which is further away "surrounds" the lens galaxy (red dot) almost completely. This phenomenon is produced because the strong gravitational field of the lens galaxy distorts the space-time in its neighborhood, bending the paths of the light rays which come from the source galaxy. As they are almost perfectly aligned, the resulting image of the source galaxy is almost circular.
Credit: Image made up from several images taken with the DECam camera on the Blanco 4m telescope at the Cerro Tololo Observatory in Chile.
The interest is sufficiently strong that this object has been given its own name: the "The Canarias Einstein ring". The research was carried out by the Stellar Populations group at the IAC, led by Antonio Aparicio and Sebastian Hidalgo. The results were published in the international journal Monthly Notices of the Royal Astronomical Society.
An Einstein ring is a distorted image of a very distant galaxy, which is termed "the source". The distortion is produced by the bending of the light rays from the source due to a massive galaxy, termed "the lens", lying between it and the observer.
The strong gravitational field produced by the lens galaxy distorts the structure of space-time in its neighbourhood, and this does not only attract objects which have a mass, but also bends the paths of light. When the two galaxies are exactly aligned, the image of the more distant galaxy is converted into an almost perfect circle which surrounds the lens galaxy. The irregularities in the circle are due to asymmetries in the source galaxy.
Confirmation using the GTC
The chance discovery was made by Margherita Bettinelli when she was examining data taken through the "Dark Energy Camera" (DECam) of the 4m Blanco Telescope at the Cerro Tololo Observatory, in Chile. While working on her doctoral thesis, she was analyzing the stellar population of the Sculptor dwarf galaxy and noticed the peculiar morphology of the Einstein ring.
This quickly raised the attention of the members of the group and they started to observe and analyze its physical properties with the OSIRIS spectrograph on the Gran Telescopio CANARIAS (GTC).
This "Canarias Einstein ring" is one of the most symmetrical discovered until now and is almost circular, showing that the two galaxies are almost perfectly aligned, with a separation on the sky of only 0.2 arcseconds. The source galaxy is 10,000 million light years away from us.
Due to the expansion of the Universe, this distance was smaller when its light started on its journey to us, and has taken 8,500 million years to reach us. We observe it as it was then: a blue galaxy which is beginning to evolve, populated by young stars which are forming at a high rate. The lens galaxy is nearer to us, 6,000 million light years away, and is more evolved. Its stars have almost stopped forming, and its population is old.
"Studying these phenomena -says Antonio Aparicio, one of the IAC astrophysicts who is leading the resarch-, gives us especially relevant information about the composition of the source galaxy, and also about the structure of the gravitational field and of the dark matter in the lens galaxy".
Elena Mora | 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...
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18.07.2018 | Health and Medicine | <urn:uuid:067be51c-17f7-4c40-a45f-cbe3bc01281b> | 3.796875 | 1,471 | Content Listing | Science & Tech. | 38.422462 | 95,488,536 |
May 2018 On the year-at-a-glance plots, (e.g. this one you can now click the list of missions to go to the mission segment views (as well as the rectangles on the map and calendar). Click the glider ID for the standard view, or the mission name for a new series of plots that inform piloting decisions during missions by showing potential future trajectories depending on the heading chosen for the glider to fly. For the 4, 12, and 30-day views the trajectories go 1, 2 and 3 days ahead (with constant heading), or double that (in a 2-stage process) for selected missions. For example, our system predicted that a glider off Jervis Bay could either 1) possibly get back to the deployment location 70km away by fighting the current for 6 days, or 2) go 250km out to, and around, a cyclonic eddy.
April 2018: Added surface current vectors from altimetry to the mission segment views, and annotated the tracks by the date. (29 May: fixed a bug with the annotation. It now correctly annotates the first position of each UTC day)
22 March, 2017: Implemented 3 improvements (before re-plotting all missions) in order to address users' desire to 1) quickly see how glider observations compare with 'normal', 2) see more data at once than shown in the 12d segment pages, and 3) navigate between available images. At present, the best(/only?) available estimate of what is 'normal' in terms of temperature and salinity, for all of Australia's regional seas, is the 2009 version of the CSIRO Atlas of Regional Seas (CARS2009). Our T/S plots of the glider data have always shown this for reference, in part to help identify potential calibration issues. What we have now added is the option to see all glider T and S observations as anomalies, defined as the difference from the CARS2009 estimate for the day-of-year and location of the glider observations. When interpreting these plots of anomaly, users should bear in mind that CARS estimates are smoothed in both space and time, and that these 'average' values may not be ones that are often observed (who has 2.5 children?). Temperature and salinity anomaly are now shown in the all-mission, year-at-a-glance plots as well as the (new) 30d-segment single-mission plots.
23 February, 2016: Replotted all delayed-mode glider data, showing only data with QC flags 1 or 2 ('good' or 'probably good'). The near-real time plots (with no QC screening) are replotted at '_nrt' URLs (rather than being over-written by delayed-mode, leading to ambiguity of source). The index page now lists the processing version of the data. Mission count and time and distance totals are given.
17 February, 2016: Replotted all glider data with the Dissolved Oxygen shown as percent saturation instead of concentration.
3 March, 2015: Replotted all glider data and fixed an error that was preventing the 2015 data from being shown.
28 November, 2014: Slocum glider data also updating continuously. Erroneous GPS positions are now screened out at the plotting stage. ANFOG are working to improve the position QC and error flags. Both Seagliders and Slocum positions are now added in near-real time to the SST plots and animations.
20 November, 2014: Seaglider data updating continuously, index page re-designed for easier navigation, 12-day data segments added, several other minor improvements to the plotting.
17 October, 2014: First mostly-complete release, mostly free of errors.
IMOS operates two types of glider; Seagliders for blue-water missions sampling to 1000m, and Slocum gliders for continental shelf missions. Both types, like Argo profilers, can change their buoyancy, allowing them to sink to a chosen depth then rise back up again. Unlike Argo profilers, however, they have wings so they can glide through the water in a chosen direction. The forward velocity is only about 0.25m/s, which is faster than ocean currents in many places but much slower than strong ocean currents. Glider piloting, consequently, is quite a challenge so missions do not always achieve the planned trajectory. The relative motion of the glider with respect to the water should also be borne in mind when analysing the data. This is why the graphics presented here have a map showing the glider trajectory alongside section views of the sensor data.
There are still several issues to be resolved or documented but both will probably have to wait until some time in November 2014 or later, sorry. The main issue is that salinity from some glider missions is mis-calibrated. Lesser issues are things like un-trapped GPS wobbles (i.e. mid-dive excursions to inland Australia not flagged by LATITUDE_quality_control). Velocity and heading data are missing from the 2014 real-time Slocum glider files. Please note that when we read the data, we are striding through the sensor data, but over-sampling the velocity data, in order to show both on the same page at similar intervals.
|Year at a glance||Mission TS||4- and 12-day mission segments|
|Map and timeline showing locations and times of the missions, and the depth-range of temperature, salinity, fluorescence and dissolved oxygen data. Anomalies (i.e. the difference from climatology) of the temperature and salinity can be seen by selecting [tempa] or [psala] links. These plots also serve as links to the plots of 4-day, 12-day and 30-day mission segments. Choose between Seaglider and Slocum Gliders, 4, 12d or 30d segments, and the year (delayed-mode or near-real-time for the present year), using the row of links along the top, then click a red box (or the name of the mission listed in central Australia) to see the chosen mission.||Temperature-salinity plots of mission data, colour-coded by depth. These plots are just a quick-look at the mission data compared with the climatological (CARS2009) estimate for the mid-time and point of the mission, to reveal any possible gross calibration errors.||Frames at 12h intervals, each showing 4, 12 or 30 days of mission data (tip: the animation provided is the best way to view these). Left panel: Track of the glider showing 4 velocity vectors along the track: Red: this is the glider's recorded heading shown as a velocity by assuming the speed through the water is 0.25m/s (which is about right when the glider is flying well). Magenta: GPS-based estimates of the water velocity when the glider is at the surface (and therefore not gliding, but possibly subject to breaking waves knocking it through the water). Blue: estimates by the glider's software of the dive-average (i.e. depth-average) water velocity, dead-reckoned from the dive angle and heading data, and GPS positions at the start and end of each dive. Black: velocity over ground estimated from the GPS positions before and after the dive. This velocity is shown as vectors at the beginning and end of the trajectory, and as a colour for the magnitude (i.e. the speed) along the trajectory.Right panels, from top: magnitudes of the velocities, then time-depth sections of sensor data. The dissolved oxygen concentration measurements made by the glider are shown here as % saturation (100 * DO/DOsaturation(t,s)).|
Editor's Choices of glider observations of various oceanographic phenomena (more examples will be added - nominations are welcome):
|Kimberley tidal spiral slocum glider making progress northwards while influenced by strong circular tidal currents||Hyper-saline waters in Spencer's Gulf| | <urn:uuid:0d14eb01-9f58-439c-b39a-5ed74f19d305> | 2.53125 | 1,701 | Documentation | Science & Tech. | 50.415372 | 95,488,561 |
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[A] mathematical model for data types where a data type is defined by its behavior. all of the datastructures we’ll look at in this series are containers. The Java.
There are mainly two types of error in java. 1-compile time error. 2-runtime error. How many types or kinds of errors can occur in a Java programming language, and how can we modify those errors? What is data type in Java.
Large applications developed by large teams can benefit from static type. an error message. Flow is a client-server program. A Flow server must be running, and. | <urn:uuid:c9922fe5-e190-41fa-bdcc-725164bab2ce> | 2.546875 | 920 | Content Listing | Software Dev. | 58.993205 | 95,488,565 |
The ninth anneal of Pile No.1 was due in early October 1957. Formerly anneals had been carried out after 30 000 megawatt days of irradiation, but the Windscale Technical Committee had recently decided to extend the interval to 50 000 megawatt days. However, the pile group manager, Ron Gausden, had asked for the change to be made in two steps, to 40 000 megawatt days on this occasion and to 50 000 later. So the ninth anneal was taking place after a longer irradiation period than before. Some small pockets of graphite, mainly in the front lower part of the pile, had apparently failed to release Wigner energy in the previous anneal and in these areas the irradiation probably amounted to 80 000 megawatt days.
KeywordsFuel Element Pile Group Nuclear Accident Friday Afternoon Friday Morning
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Module::LocalBuild - Support routines for setting up perltools area
Module::LocalBuild::need ( dest_dir => "obj_foobar", # Areas we don't need to build, but need to add libraries for libs => ["some_path/ModuleFoo/lib", "some_path/ModuleBar/lib", ], # Packages we need to build # It is important to include Module-LocalBuild in its own list # otherwise changes in the build process won't be detected as changes! packages => ['some_path/Module-LocalBuild', 'some_path/ModuleBaz', ], # Additional build dependencies deps => , );
Module::LocalBuild is used to call 'perl Makefile.PL' and friends on packages in a local working copy of a source code repository. This allows people to have local copies of Perl modules, and edit them at will without having to worry about when to compile them.
It also allows the same sources to be simultaneously built and maintained under different operating systems.
Specify needed submodules. Checks the specified modules's date stamps, and if needed run make on them, and install them into a local directory.
Setup the 'use lib' and PERL5LIB path appropriately to find the modules, and so any programs called under a new shell (with the same environment) will also find them.
Requires named parameters as specified below.
- dest_dir => directory
Directory name to write the blib library tree under. This directory should be absolute, and should include the Perl version number; otherwise builds on different OSes may collide.
- deps => [ directories... ]
Additional directory names which if change will request a rebuild. This is useful for local files, such as scripts which wrap mlbuilder.
- libs => [ directories... ]
Add the specified perl library directories, as if using 'use lib'. However, in addition to doing a 'use lib' they will be added to PERL5LIB such that subprocesses may see the libraries specified.
- locker_module => package_name
If specified, when a rebuild is required this package will be used for lock services. This prevent multiple processes from building at once, even when run under NFS on different machines. IPC::Locker is compatible with the API required.
- packages => [ packages... ]
List of packages. Future versions will support an array of hash references, where each hash may specify an action associated with the package.
This environment variable is set automatically when the packages are built. When set calling Module::LocalBuild will skip the build process. This accelerates subprocesses, as only the parent process needs to complete the up-to-date check.
The requested libraries are appended to the standard Perl PERL5LIB variable.
Copyright 2000-2010 by Wilson Snyder. This program is free software; you can redistribute it and/or modify it under the terms of either the GNU Lesser General Public License Version 3 or the Perl Artistic License Version 2.0.
Wilson Snyder <email@example.com> | <urn:uuid:ab96da6e-d35c-4ae6-95c2-e01afc5ba591> | 2.6875 | 646 | Documentation | Software Dev. | 40.630679 | 95,488,583 |
To orient ourselves in space, our brain generates an internal coordinate system. Heidelberg researchers now refute the current model on how nerve cells generate this mental map.
The food pellet must be further away—a mouse is foraging for food. To estimate distances and to orient itself in space, the brain forms an internal spatial map. So-called grid neurons take on an important role in this process. They fire when the mouse happens to be at decisive positions.
From a bird's perspective, the activity pattern of a grid cell forms a hexagonal pattern in space—very reminiscent of a coordinate system on a map (see figure). But how is this abstract activity pattern generated that is not based on sensory input from the environment?
To find answers, researchers investigated neuronal connections by means of theoretical models. The currently most promising model is now refuted by scientists from the Bernstein Center Heidelberg/Mannheim and the Department of Clinical Neurobiology at the Medical Faculty of Heidelberg University and The German Cancer Research Center (DKFZ), who put the model to test in animal experiments.
"In our study, we measured the nerve cell activity in freely moving mice," explains Christina Buetfering, first author of the study. "We were interested in grid cells as well as nerve cells that interconnect the grid cells: so-called interneurons".
The crucial trick: the activity of interneurons could be selectively switched on and off by light signals in genetically modified mice. While the mice moved around during foraging, the researchers activated the cells now and then. This helped them to identify and closely observe the interneurons in the measured data stream. Also, they were able to analyze how grid cells responded to the activity of interneurons—giving a hint on how the neurons must be connected.
The scientists discovered that interneurons show no spatial activity patterns like grid cells do. In addition, individual interneurons are not exclusively connected to grid cells with similar activity patterns. Instead, they get their input signals from very different grid cells and send their output information to diverse nerve cells.
"With these results we were able to refute two basic predictions of the current theoretical network model," Buetfering discusses. "The model assumes that for generating the inner mental map, grid cells of the same spatial orientation must be very closely connected—which was thought to be realized via spatially active interneurons."
However, interneurons seem to have a different main task. The cells send inhibitory signals to quite different neurons in their environment. Therefore, they possibly rather take over a modulating function by ensuring a balance between excitation and inhibition in the brain area during excessive nerve cell activity.
In this way they could prevent epileptic seizures. How grid cells manage to fire at the right time at the right place—thereby generating the abstract mental coordinate system—has, once again, become more mysterious.
The Bernstein Center Heidelberg/Mannheim is part of the National Bernstein Network Computational Neuroscience in Germany. With this funding initiative, the German Federal Ministry of Education and Research (BMBF) has supported the new discipline of Computational Neuroscience since 2004 with over 180 million Euros. The network is named after the German physiologist Julius Bernstein (1835-1917).
Prof. Dr. Hannah Monyer
Clinical Neurobiology (A230)
German Cancer Research Center
Im Neuenheimer Feld 280
Tel: +49 (0)6221 42 3100
C. Buetfering, K. Allen & H. Monyer (2014): Parvalbumin interneurons provide grid cell-driven recurrent inhibition in the medial entorhinal cortex. Nature Neuroscience, advanced online publication
http://www.dkfz.de/de/klinische-neurobiologie Lab Hannah Monyer
http://www.uni-heidelberg.de Heidelberg University
http://www.klinikum.uni-heidelberg.de Heidelberg University Hospital
http://www.dkfz.de German Cancer Research Center
http://www.bccn-heidelberg-mannheim.de Bernstein Center Heidelberg/Mannheim
http://www.nncn.de National Bernstein Network Computational Neuroscience
Mareike Kardinal | idw - Informationsdienst Wissenschaft
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