Mathematically speaking a cup has the same topology as a doughnut. glass is topologically the same as an appleexplains Professor Klaus Ensslin who led the research detailed in two papers published in Physical Review Letters.
Changing the topology of an object can improve its usefulness for example by transforming a beaker into a cup with handle.
The Lifshitz transition does not apply to objects in our normal environment; rather the physicists are researching an abstract topology of surfaces with
which the energy state of electrons is described with electronic materials. In particular the researchers examined surfaces of constant energy as these determine the conductivity of the material and its application potential.
Ensslin makes another comparison to demonstrate the mathematical concept behind these energy surfaces: magine a hilly landscape in which the valleys fill up with electrical charges
just as the water level rises between the hills when it rains. his is how a conductive material is formed from an initial isolator
when it stops raining the water has formed a lake from which the individual hilltops emerge like islands.
When the water level increases the three lakes join to form a large ocean. he topology has changed altogethervarlet concludes.
Metals are not suitable and initially the ETH team was had unaware it found the material that others had been looking for. e observed something strange in our measurements with the graphene sandwich construction that we were not able to explainsays Varlet.
To produce the sandwich construction Varlet enclosed the double layer of graphene in two layers of boron nitride a material otherwise used for lubrication
Although both materials are cheap a lot of work is required in the cleanroom the carbon flakes must be exceptionally clean to produce a functioning component. significant part of my work consists of cleaning the graphenesays Varlet.
The topology of quantum states for example offers a way of decoupling them from their environment
which comprises groups from the universities of Basel Lausanne Geneva and ETH Zurich and representatives from IBM.
#Plants can t run from stress, but they can adapt Scientists have discoveredâ a key molecular cog in a plant s biological clock.
Transcription factors known as genetic switches drive gene expression in plants based on external stresses such as light rain soil quality
while keeping it on a consistent track. emperature helps keep the hands of the biological clock in the right placesays Steve A. Kay dean of the USC Dornsife College of Letters Arts
and Sciences and the corresponding author of the study. ow we know more about how that works. ay worked with lead author Dawn Nagel a postdoctoral researcher and coauthor Jose Pruneda-Paz an assistant professor at the University of California
and the transcriptional network work could allow scientists to breed plants that are better able to deal with stressful environments#crucial in a world where farmers attempt to feed an increasing population amid urban development of arable land
and a rising global temperature. lobal climate change suggests that it s going to get warmer and since plants cannot run away from the heat they re going to have to adapt to a changing environmentnagel says. his study suggests one mechanism for us to understand how this interaction works. oth plants
and animals have transcription factors but plants have on average six times as many likely because they lack the ability to get up
and the fact that now all of its genome has been sequenced. The Ruth L. Kirschstein National Research Service Award and the National institutes of health National Institute of General Medical supported the work e
#New polymer makes solar cells more efficient Solar cells made from polymers have the potential to be cheap and lightweight
but scientists are struggling to make them generate electricity efficiently. A polymer is a type of large molecule that forms plastics
and other familiar materials. he field is rather immature it s in the infancy stagesays Luping Yu a professor in chemistry at the University of Chicago.
Now a team of researchers led by Yu has identified a new polymer that allows electrical charges to move more easily through the cell boosting electricity production. olymer solar cells have great potential to provide low-cost lightweight
and flexible electronic devices to harvest solar energysays Luyao Lu a graduate student in chemistry and lead author of a paper in the journal Nature Photonics that describes the result.
The active regions of such solar cells are composed of a mixture of polymers that give and receive electrons to generate electrical current
when exposed to light. The new polymer developed by Yu s group called PID2 improves the efficiency of electrical power generation by 15 percent
when added to a standard polymer-fullerene mixture. ullerene a small carbon molecule is one of the standard materials used in polymer solar cellslu says. asically in polymer solar cells we have a polymer as electron donor
and fullerene as electron acceptor to allow charge separation. n their work the researchers added another polymer into the device resulting in solar cells with two polymers and one fullerene.
The group achieved an efficiency of 8. 2 percent when an optimal amount of PID2 was added the highest ever for solar cells made up of two types of polymers with fullerene
and the result implies that even higher efficiencies could be possible with further work. The group which includes researchers at the Argonne National Laboratory is now working to push efficiencies toward 10 percent a benchmark necessary for polymer solar cells to be viable for commercial application.
The result was remarkable not only because of the advance in technical capabilities Yu notes but also because PID2 enhanced the efficiency via a new method.
The standard mechanism for improving efficiency with a third polymer is by increasing the absorption of light in the device.
But in addition to that effect the team found that when PID2 was added charges were transported more easily between polymers and throughout the cell.
In order for a current to be generated by the solar cell electrons must be transferred from polymer to fullerene within the device.
But the difference between electron energy levels for the standard polymer-fullerene is large enough that electron transfer between them is difficult.
PID2 has energy levels in between the other two and acts as an intermediary in the process. t s like a stepyu says. hen it s too high it s hard to climb up
but if you put in the middle another step then you can easily walk up. he addition of PID2 caused the polymer blend to form fibers
which improve the mobility of electrons throughout the material. The fibers serve as a pathway to allow electrons to travel to the electrodes on the sides of the solar cell. t s like you re generating a street
and somebody that s traveling along the street can find a way to go from this end to anotheryu explains.
To reveal this structure Wei Chen of the Materials science Division at Argonne National Laboratory and the Institute for Molecular Engineering performed X-ray scattering studies using the Advanced Photon Source at Argonne
and the Advanced Light source at Lawrence Berkeley. ithout that it s hard to get insight about the structureyu says. hat benefits us tremendously. his knowledge will serve as a foundation from
which to develop high-efficiency organic photovoltaic devices to meet the nation s future energy needschen adds.
The National Science Foundation Air force Office of Scientific research and US Department of energy funded the research e
#Scientists use light to make mice asocial California Institute of technology rightoriginal Studyposted by Jessica Stoller-Conrad-Caltech on September 19 2014scientists have discovered antagonistic neuron populations in the mouse amygdala that control
whether the animal engages in social behaviors or asocial repetitive self-grooming. This discovery may have implications for understanding neural circuit dysfunctions that underlie autism in humans.
Humans with autism often show a reduced frequency of social interactions and an increased tendency to engage in repetitive solitary behaviors.
Autism has also been linked to dysfunction of the amygdala a brain structure involved in processing emotions.
This discovery which is like a eesaw circuitwas led by postdoctoral scholar Weizhe Hong in the laboratory of David J. Anderson biology professor at Caltech and an investigator with the Howard hughes medical institute.
The work appears online in the journal Cell. e know that there is some hierarchy of behaviors
and they interact with each other because the animal can t exhibit both social and asocial behaviors at the same time.
and their associated behaviors the researchers used a technique called optogenetics. In optogenetics neurons are altered genetically
so that they express light-sensitive proteins from microbial organisms. Then by shining a light on these modified neurons via a tiny fiber optic cable inserted into the brain researchers can control the activity of the cells as well as their associated behaviors.
Using this optogenetic approach Anderson s team was able to selectively switch on the neurons associated with social behaviors
That is when high-intensity light was used the mice became aggressive in the presence of an intruder mouse.
When the neurons associated with asocial behavior were turned on the mouse began self-grooming behaviors such as paw licking
For example if a lone mouse began spontaneously self-grooming the researchers could halt this behavior through the optogenetic activation of the social neurons.
and the activation stopped the mouse would return to its self-grooming behavior. Surprisingly these two groups of neurons appear to interfere with each other s function:
and his colleagues say may have some relevance to human behavioral disorders such as autism. n autismanderson says here is a decrease in social interactions
and promoting these perseverative persistent behaviors. tudies from other laboratories have shown that disruptions in genes implicated in autism show a similar decrease in social interaction and increase in repetitive
and social behaviors nd if you don t understand the circuitry you are never going to understand how the gene mutation affects the behavior. oing forward he says such a complete understanding will be necessary for the development of future therapies.
but if you found the right population of neurons it might be possible to override the genetic component of a behavioral disorder like autism by just changing the activity of the circuits#tipping the balance of the seesaw in the other directionhe says.
The Simons Foundation the National institutes of health and the Howard hughes medical institute supported the work. Source: Caltechyou are free to share this article under the Creative Commons Attribution-Noderivs 3. 0 Unported license i
#How to make carbon thread without clumps Made into fibers single-walled carbon nanotubesâ line up like a fistful of raw spaghetti noodles thanks to a new process.
The tricky bit according to Rice university chemist Angel Martã is keeping the densely packed nanotubes apart before they re drawn together into a fiber.
Left to their own devices carbon nanotubes form clumps that are perfectly wrong for turning into the kind of strong conductive fibers needed for projects ranging from nanoscale electronics to macro-scale power grids.
Earlier research at Rice by chemist and chemical engineer Matteo Pasquali a coauthor of the new paper used an acid dissolution process to keep the nanotubes separated until they could be spun into fibers.
and lead authors Chengmin Jiang a graduate student and Avishek Saha a Rice alumnus starts with negatively charging carbon nanotubes by infusing them with potassium a metal and turning them into a kind of salt known as a polyelectrolyte.
otherwise dampen the nanotubes ability to repel one another. Put enough nanotubes into such a solution and they re caught between the repellant forces
and an inability to move in a crowded environment Martã says. They re forced to align a defining property of liquid crystals
and this makes them more manageable. The tubes are forced ultimately together into fibers when they are extruded through the tip of a needle.
At that point the strong Van der waals force takes over and tightly binds the nanotubes together says Martã an assistant professor of chemistry and bioengineering and of materials science and nanoengineering.
But to make macroscopic materials Martã s team needed to pack many more nanotubes into the solution than in previous experiments. s you start increasing the concentration the number of nanotubes in the liquid crystalline phase becomes more abundant than those in the isotropic (disordered) phase
and that s exactly what we neededmartã says. The researchers discovered that 40 milligrams of nanotubes per milliliter gave them a thick gel after mixing at high speed
and filtering out whatever large clumps remained. t s like a centrifuge together with a rotary drummartã says of the mixing gear. t produces unconventional forces in the solution. eeding this dense nanotube gel through a narrow needle-like opening produced
continuous fiber on the Pasquali lab s equipment. The strength and stiffness of the neat fibers also approached that of the fibers previously produced with Pasquali s acid-based process. e didn t make any modifications to his system
and it worked perfectlymartã says. The hair-width fibers can be woven into thicker cables and the team is investigating ways to improve their electrical properties through doping the nanotubes with iodide. he research is basically analogous to
what Matteo doesmartã says. e used his tools but gave the process a spin with a different preparation so now we re the first to make neat fibers of pure carbon nanotube electrolytes.
That s very cool. asquali says that the spinning system worked with little need for adaptation
because the setup is sealed. he nanotube electrolyte solution could be protected from oxygen and water which would have caused precipitation of the nanotubeshe says. t turns out that this is not a showstopper
because we want the nanotubes to precipitate and stick to each other as soon as they exit the sealed system through the needle.
The process was not hard to control adapt and scale up once we figured out the basic science. he Welch Foundation supported the research
which appears in ACS Nano T
#Color display designed for squid skin camo Rice university rightoriginal Studyposted by Jade Boyd-Rice on September 16 2014scientists have developed a new full-color display technology that once refined could be a critical component for creating artificial
quid skin camouflaging metamaterials that can eecolors and automatically blend into the background. The technology uses aluminum nanoparticles to create the vivid red blue and green hues found in today s top-of-the-line LCD televisions and monitors.
The breakthrough is the latest in a string of recent discoveries by a research team working to develop materials that mimic the camouflage abilities of cephalopods the family of marine creatures that includes squid octopus
and cuttlefish. ur goal is to learn from these amazing animals so that we could create new materials with the same kind of distributed light-sensing
The color display technology delivers bright red blue and green hues from five-micron-square pixels that each contains several hundred aluminum nanorods.
By varying the length of the nanorods and the spacing between them researchers Stephan Link and Jana Olson showed they could create pixels that produced dozens of colors including rich tones of red green
and blue that are comparable to those found in high-definition LCD displays. luminum is useful
because it s compatible with microelectronic production methods but until now the tones produced by plasmonic aluminum nanorods have been muted
and washed outsays Link associate professor of chemistry at Rice and the lead researcher on the PNAS study. he key advancement here was to place the nanorods in an ordered array. lson says the array setup allowed her to tune the pixel s color in two
ways first by varying the length of the nanorods and second by adjusting the length of the spaces between nanorods. his arrangement allowed us to narrow the output spectrum to one individual color instead of the typical muted shades that are produced usually by aluminum nanoparticlesshe adds.
Olson s five-micron-square pixels are about 40 times smaller than the pixels used in commercial LCD displays.
To make the pixels she used aluminum nanorods that each measured about 100 nanometers long by 40 nanometers wide.
She used electron-beam deposition to create arrays regular arrangements of nanorods in each pixel.
She was able to fine-tune the color produced by each pixel by using theoretical calculations by Rice physicists Alejandro Manjavacas a postdoctoral researcher
and Peter Nordlander professor of physics and astronomy. lejandro created a detailed model of the far-field plasmonic interactions between the nanorodsolson says. hat proved very important
because we could use that to dial in the colors very precisely. alas and Link say the research team hopes to create an LCD display that uses many of the same components found in today s displays including liquid crystals polarizers and individually addressable pixels.
The photonic aluminum arrays would be used in place of the colored dyes that are found in most commercial displays.
Unlike dyes the arrays won t fade or bleach after prolonged exposure to light and the inherent directionality of the nanorods provides another advantage. ecause the nanorods in each array are aligned in the same direction our pixels produce polarized lighthe says. his means we can do away with one polarizer in our setup
and it also gives us an extra knob that we can use to tune the output from these arrays.
It could be useful in a number of ways. hey hope to further develop the display technology
and eventually to combine it with other new technologies that the squid skin team has developed both for sensing light
and for displaying patterns on large polymer sheets. For example Halas and colleagues published a study in Advanced Materials in August about an aluminum-based CMOS-compatible photodetector technology for color sensing.
In addition University of Illinois at Urbana-Champaign co-principal investigator John Rogers and colleagues published a proof-of-concept study in PNAS in August about new methods for creating flexible black-and-white polymer displays
In earlier research microbiologist Gemma Reguera of Michigan State university identified that Geobacter bacteria s tiny conductive hairlike appendages
By increasing the strength of the pili nanowires she improved their ability to clean up uranium and other toxic wastes.
and Environmental microbiology Reguera has added an additional layer of armor to her enhanced microbes. The microbes also use the pili to stick to each other
The Geobacter biofilm encased by a network of nanowires and slime gives the bacteria a shield
and increases their ability to neutralize even more uranium. The improvement also allows the bacteria to survive longer even when exposed to higher concentrations of the radioactive material.
and turn it into a mineral which prevents the toxic material from leaching into groundwater.
As the biofilm concentrates many nanowires around the Geobacter cells more uranium can be mineralized bound
which surrounds the biofilm cells and boosts the Geobacter s pili armor so the biofilm now can pull double duty by helping mineralize uranium.
The shield keeps the uranium from penetrating deep into the Geobacter biofilm. By keeping this process on the surface of the film the bacteria are exposed not to uranium
and as a community they are able to clean up more toxic waste. he results surpassed our most optimistic predictionsreguera says. ven thin biofilms immobilized uranium like sponges.
They reduced it to a mineral all while not suffering any damage to themselves for prolonged periods of time. ven
when exposed to extremely high and toxic concentrations of uranium levels that would destroy individual Geobacter cells the biofilms didn t just survive they thrived she adds.
Additional researchers from Michigan State and EXAFS Analysis also contributed to the study. Reguera s future research will focus on deciphering how the biofilm matrix that encases the cells shields them so effectively
and how to improve its properties further. She has patented the microbe. Source: Michigan State Universityyou are free to share this article under the Creative Commons Attribution-Noderivs 3. 0 Unported license o
#o-seeums harbor virus that makes cows sick A virus that causes a serious disease in cows
and sheep is able to survive the winter by reproducing in the biting bugs that transmit it.
and is particularly significant as climate change brings more moderate winter temperatures. In the United states alone the disease costs the cattle and sheep industry an estimate $125 million annually. y conducting this epidemiological study on a commercial dairy farm in Northern California we were able to demonstrate that the virus overwinters
in female midges that had fed on an infected animal during the previous seasonsays lead author Christie Mayo a veterinarian
and postdoctoral researcher in the School of veterinary medicine at University of California Davis. his discovery has important ramifications for predicting the occurrence of bluetongue in livestock
and we hope for eventually developing controls for the diseasesays coauthor James Maclachlan veterinary professor and viral disease expert.
Bluetongue disease first identified during the 1800s in southern Africa is transmitted by the Culicoides biting midge a tiny gnat sometimes referred to as a o-seeum. he disease mostly sickens sheep
but also infects cattle and goats and deer and other wild ruminants. In the US the virus greatest economic impact is in the cattle industry
because it is bigger than the domestic sheep industry and most adversely impacted by international trade barriers related to bluetongue.
The disease doesn t pose a threat to human health. The name bluetongue derives from the swollen lips and tongue of affected sheep
which may turn blue in the late stages of the disease. The virus that causes bluetongue was isolated first
and identified in the Western hemisphere in the early 1950s. In California bluetongue is most prevalent
For the new study published in PLOS ONE researchers monitored cows and midges on a Northern California dairy farm for more than a year.
They documented for the first time the presence of genetic material for the bluetongue virus in female midges that were collected during two consecutive winter seasons.
There was no sign of infection in the dairy cattle being studied. The researchers concluded that those long-lived female midges had been infected with the bluetongue virus during the previous warm-weather season.
and would later in the season once again transmit it to cows on the dairy. The bluetongue virus may also have other yet-to-be discovered modes of overwintering in temperate regions the researchers say.
Other researchers from UC Davis UC Riverside University of Florida Gainesville and the Atlantic Veterinary College Charlottetown Prince edward island Canada contributed to the study.
The US Department of agriculture s National Institute of Food and Agriculture and the UC Davis School of veterinary medicine s Center for Food Animal health provided funding r
#These LEGO-inspired ceramics won t shatter California Institute of technology rightoriginal Studyposted by Brian Bell-Caltech on September 12 2014scientists are on the way to developing the perfect ceramic material:
Caltech materials scientist Julia Greer and her colleagues have developed a method for constructing new structural materials by taking advantage of the unusual properties that solids can have at the nanometer scale where features are measured in billionths of meters.
In a paper published in the journal Science the researchers explain how they used the method to produce a ceramic (e g. a piece of chalk
or a brick) that contains about 99.9 percent air yet is incredibly strong and that can recover its original shape after being smashed by more than 50 percent. eramics have always been thought to be heavy
and brittlesays Greer a professor of materials science and mechanics. e re showing that in fact they don t have to be
if you use the concept of the nanoscale to create structures and then use those nanostructures like LEGO to construct larger materials you can obtain nearly any set of properties you want.
You can create materials by design. he researchers use a direct laser writing method called two-photon lithography to ritea three-dimensional pattern in a polymer by allowing a laser beam to crosslink
and harden the polymer wherever it is focused. The parts of the polymer that were exposed to the laser remain intact
while the rest is dissolved away revealing a three-dimensional scaffold. That structure can then be coated with a thin layer of just about any kind of material#a metal an alloy a glass a semiconductor etc.
Then the researchers use another method to etch out the polymer from within the structure leaving a hollow architecture.
The applications of this technique are practically limitless Greer says. Since pretty much any material can be deposited on the scaffolds the method could be particularly useful for applications in optics energy efficiency and biomedicine.
For example it could be used to reproduce complex structures such as bone producing a scaffold out of biocompatible materials on
which cells could proliferate. In the latest work Greer and her students used the technique to produce
what they call three-dimensional nanolattices that are formed by a repeating nanoscale pattern. After the patterning step they coated the polymer scaffold with a ceramic called alumina
(i e. aluminum oxide) producing hollow-tube alumina structures with walls ranging in thickness from 5 to 60 nanometers and tubes from 450 to 1380 nanometers in diameter.
Greer s team next wanted to test the mechanical properties of the various nanolattices they created.
Using two different devices for poking and prodding materials on the nanoscale they squished stretched
and otherwise tried to deform the samples to see how they held up. They found that the alumina structures with a wall thickness of 50 nanometers and a tube diameter of about 1 micron shattered when compressed.
That was not surprising given that ceramics especially those that are porous are brittle. However compressing lattices with a lower ratio of wall thickness to tube diameter#where the wall thickness was only 10 nanometers#produced a very different result. ou deform it
and all of a sudden it springs backgreer says. n some cases we were able to deform these samples by as much as 85 percent
and they could still recover. o understand why consider that most brittle materials such as ceramics silicon
and glass shatter because they are filled with flaws#imperfections such as small voids and inclusions. The more perfect the material the less likely you are to find a weak spot where it will fail.
Therefore the researchers hypothesize when you reduce these structures down to the point where individual walls are only 10 nanometers thick both the number of flaws
and the size of any flaws are kept to a minimum making the whole structure much less likely to fail. ne of the benefits of using nanolattices is that you significantly improve the quality of the material
and you get the added benefit of needing only a very small amount of material in making them. he Greer lab is now aggressively pursuing various ways of scaling up the production of these so-called metamaterials.
and the Institute for Collaborative Biotechnologies supported the work. Source: Caltechyou are free to share this article under the Creative Commons Attribution-Noderivs 3. 0 Unported license t
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