Revolutionary solar cells double as lasers

Latest research finds that the trailblazing ‘perovskite’ material used in solar cells can double up as a laser, strongly suggesting the astonishing efficiency levels already achieved in these cells is only part of the journey.Commercial silicon-based solar cells — such as those seen on the roofs of houses across the country — operate at about 20% efficiency for converting the Sun’s rays into electrical energy. It’s taken over 20 years to achieve that rate of efficiency.A relatively new type of solar cell based on a perovskite material — named for scientist Lev Perovski, who first discovered materials with this structure in the Ural Mountains in the 19th century — was recently pioneered by an Oxford research team led by Professor Henry Snaith.Perovskite solar cells, the source of huge excitement in the research community, already lie just a fraction behind commercial silicon, having reached a remarkable 17% efficiency after a mere two years of research — transforming prospects for cheap large-area solar energy generation.Now, researchers from Professor Sir Richard Friend’s group at Cambridge’s Cavendish Laboratory — working with Snaith’s Oxford group — have demonstrated that perovskite cells excel not just at absorbing light but also at emitting it. The new findings, recently published online in the Journal of Physical Chemistry Letters, show that these ‘wonder cells’ can also produce cheap lasers.By sandwiching a thin layer of the lead halide perovskite between two mirrors, the team produced an optically driven laser which proves these cells “show very efficient luminescence” — with up to 70% of absorbed light re-emitted.The researchers point to the fundamental relationship, first established by Shockley and Queisser in 1961, between the generation of electrical charges following light absorption and the process of ‘recombination’ of these charges to emit light.Essentially, if a material is good at converting light to electricity, then it will be good at converting electricity to light. The lasing properties in these materials raise expectations for even higher solar cell efficiencies, say the Oxbridge team, which — given that perovskite cells are about to overtake commercial cells in terms of efficiency after just two years of development — is a thrilling prospect.”This first demonstration of lasing in these cheap solution-processed semiconductors opens up a range of new applications,” said lead author Dr Felix Deschler of the Cavendish Laboratory. “Our findings demonstrate potential uses for this material in telecommunications and for light emitting devices.”Most commercial solar cell materials need expensive processing to achieve a very low level of impurities before they show good luminescence and performance. Surprisingly these new materials work well even when very simply prepared as thin films using cheap scalable solution processing.The researchers found that upon light absorption in the perovskite two charges (electron and hole) are formed very quickly — within 1 picosecond — but then take anywhere up to a few microseconds to recombine. This is long enough for chemical defects to have ceased the light emission in most other semiconductors, such as silicon or gallium arsenide. “These long carrier lifetimes together with exceptionally high luminescence are unprecedented in such simply prepared inorganic semiconductors,” said Dr Sam Stranks, co-author from the Oxford University team.”We were surprised to find such high luminescence efficiency in such easily prepared materials. This has great implications for improvements in solar cell efficiency,” said Michael Price, co-author from the group in Cambridge.Added Snaith: “This luminescent behaviour is an excellent test for solar cell performance — poorer luminescence (as in amorphous silicon solar cells) reduces both the quantum efficiency (current collected) and also the cell voltage.”Scientists say that this new paper sets expectations for yet higher solar cell performance from this class of perovskite semiconductors. Solar cells are being scaled up for commercial deployment by the Oxford spin-out, Oxford PV Ltd. …

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Cancer researchers find key protein link

A new understanding of proteins at the nexus of a cell’s decision to survive or die has implications for researchers who study cancer and age-related diseases, according to biophysicists at the Rice University-based Center for Theoretical Biological Physics (CTBP).Experiments and computer analysis of two key proteins revealed a previously unknown binding interface that could be addressed by medication. Results of the research appear this week in an open-source paper in the Proceedings of the National Academy of Sciences.The proteins are Bcl-2, well-known for its role in programmed cell death, and NAF-1, a member of the NEET family that binds toxic clusters of iron and sulfur. How the two interact is now known as a major determinant in the cell processes of autophagy and apoptosis — literally, life and death. An ability to uncover binding sites on the proteins that send the cell one way or the other opens a path toward the regulation of those processes, according to Jos Onuchic, Rice’s the Harry C. and Olga K. Wiess Chair of Physics and professor of physics and astronomy.Pockets and folds in proteins exist to bind to other molecules and catalyze actions in a cell in signaling pathways. The ability to block a specific binding site or to enhance a desired interaction is critical to drug design, Onuchic said.”In our early work we have shown the link between NEET proteins and cancer. Now we can understand the molecular details of how these interactions are governed,” Onuchic said. “Others have shown that NAF-1 is up-regulated in cancer cells, which leads us to believe that cancer may hijack control over the expression of this protein. This affects the cell’s system of checks and balances. …

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Million suns shed light on fossilized plant

Scientists have used one of the brightest lights in the Universe to expose the biochemical structure of a 50 million-year-old fossil plant to stunning visual effect.The team of palaeontologists, geochemists and physicists investigated the chemistry of exceptionally preserved fossil leaves from the Eocene-aged ‘Green River Formation’ of the western United States by bombarding the fossils with X-rays brighter than a million suns produced by synchrotron particle accelerators.Researchers from Britain’s University of Manchester and Diamond Light Source and the Stanford Synchrotron Radiation Lightsource in the US have published their findings, along with amazing images, in Metallomics; one of the images is featured on the cover of the latest edition of the Royal Society of Chemistry journal.Lead author Dr Nicholas Edwards, a postdoctoral researcher at The University of Manchester, said: “The synchrotron has already shown its potential in teasing new information from fossils, in particular our group’s previous work on pigmentation in fossil animals. With this study, we wanted to use the same techniques to see whether we could extract a similar level of biochemical information from a completely different part of the tree of life.”To do this we needed to test the chemistry of the fossil plants to see if the fossil material was derived directly from the living organisms or degraded and replaced by the fossilisation process.”We know that plant chemistry can be preserved over hundreds of millions of years — this preserved chemistry powers our society today in the form of fossil fuels. However, this is just the ‘combustible’ part; until now no one has completed this type of study of the other biochemical components of fossil plants, such as metals.”By combining the unique capabilities of two synchrotron facilities, the team were able to produce detailed images of where the various elements of the periodic table were located within both living and fossil leaves, as well as being able to show how these elements were combined with other elements.The work shows that the distribution of copper, zinc and nickel in the fossil leaves was almost identical to that in modern leaves. Each element was concentrated in distinct biological structures, such as the veins and the edges of the leaves, and the way these trace elements and sulphur were attached to other elements was very similar to that seen in modern leaves and plant matter in soils.Co-author Professor Roy Wogelius, from Manchester’s School of Earth, Atmospheric and Environmental Sciences, said: “This type of chemical mapping and the ability to determine the atomic arrangement of biologically important elements, such as copper and sulphur, can only be accomplished by using a synchrotron particle accelerator.”In one beautiful specimen, the leaf has been partially eaten by prehistoric caterpillars — just as modern caterpillars feed — and their feeding tubes are preserved on the leaf. The chemistry of these fossil tubes remarkably still matches that of the leaf on which the caterpillars fed.”The data from a suite of other techniques has led the team to conclude that the chemistry of the fossil leaves is not wholly sourced from the surrounding environment, as has previously been suggested, but represents that of the living leaves. Another modern-day connection suggests a way in which these specimens are so beautifully preserved over millions of years.Manchester palaeontologist and co-author Dr Phil Manning said: “We think that copper may have aided preservation by acting as a ‘natural’ biocide, slowing down the usual microbial breakdown that would destroy delicate leaf tissues. This property of copper is used today in the same wood preservatives that you paint on your garden fence before winter approaches.”Story Source:The above story is based on materials provided by Manchester University. Note: Materials may be edited for content and length.

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Roomy cages built from DNA could one day deliver drugs, devices

Move over, nanotechnologists, and make room for the biggest of the small. Scientists at the Harvard’s Wyss Institute have built a set of self-assembling DNA cages one-tenth as wide as a bacterium. The structures are some of the largest and most complex structures ever constructed solely from DNA, they report today’s online edition of Science.Moreover, the scientists visualized them using a DNA-based super-resolution microscopy method — and obtained the first sharp 3D optical images of intact synthetic DNA nanostructures in solution.In the future, scientists could potentially coat the DNA cages to enclose their contents, packaging drugs for delivery to tissues. And, like a roomy closet, the cage could be modified with chemical hooks that could be used to hang other components such as proteins or gold nanoparticles. This could help scientists build a variety of technologies, including tiny power plants, miniscule factories that produce specialty chemicals, or high-sensitivity photonic sensors that diagnose disease by detecting molecules produced by abnormal tissue.”I see exciting possibilities for this technology,” said Peng Yin, Ph.D., a Core Faculty member at the Wyss Institute and Assistant Professor of Systems Biology at Harvard Medical School, and senior author of the paper.Building with DNADNA is best known as a keeper of genetic information. But scientists in the emerging field of DNA nanotechnology are exploring ways to use it to build tiny structures for a variety of applications. These structures are programmable, in that scientists can specify the sequence of letters, or bases, in the DNA, and those sequences then determine the structure it creates.So far most researchers in the field have used a method called DNA origami, in which short strands of DNA staple two or three separate segments of a much longer strand together, causing that strand to fold into a precise shape. DNA origami was pioneered in part by Wyss Institute Core Faculty member William Shih, Ph.D., who is also an Associate Professor in the Department of Biological Chemistry and Molecular Pharmacology at Harvard Medical School and the Department of Cancer Biology at the Dana-Farber Cancer Institute.Yin’s team has built different types of DNA structures, including a modular set of parts called single-stranded DNA tiles or DNA bricks. Like LEGO bricks, these parts can be added or removed independently. Unlike LEGO bricks, they spontaneously self-assemble.But for some applications, scientists might need to build much larger DNA structures than anyone has built so far. …

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BPA linked to breast cancer tumor growth

UT Arlington biochemists say their newly published study brings researchers a step closer to understanding how the commonly used synthetic compound bisphenol-A, or BPA, may promote breast cancer growth.Subhrangsu Mandal, associate professor of chemistry/biochemistry, and Arunoday Bhan, a PhD student in Mandal’s lab, looked at a molecule called RNA HOTAIR. HOTAIR is an abbreviation for long, non-coding RNA, a part of DNA in humans and other vertebrates. HOTAIR does not produce a protein on its own but, when it is being expressed or functioning, it can suppress genes that would normally slow tumor growth or cause cancer cell death.High levels of HOTAIR expression have been linked to breast tumors, pancreatic and colorectal cancers, sarcoma and others.UT Arlington researchers found that when breast cancer and mammary gland cells were exposed to BPA in lab tests, the BPA worked together with naturally present molecules, including estrogen, to create abnormal amounts of HOTAIR expression. Their results were published online in February by the Journal of Steroid Biochemistry and Molecular Biology.”We can’t immediately say BPA causes cancer growth, but it could well contribute because it is disrupting the genes that defend against that growth,” said Mandal, who is corresponding author on the paper.”Understanding the developmental impact of these synthetic hormones is an important way to protect ourselves and could be important for treatment,” he said.Bhan is lead author on the new paper. Co-authors include Mandal lab members Imran Hussain and Khairul I Ansari, as well as Linda I. Perrotti, a UT Arlington psychology assistant professor, and Samara A.M. Bobzean, a member of Perrotti’s lab.”We were surprised to find that BPA not only increased HOTAIR in tumor cells but also in normal breast tissue,” said Bhan. He said further research is needed, but the results beg the question — are BPA and HOTAIR involved in tumor genesis in addition to tumor growth?BPA has been widely used in plastics, such as food storage containers, the lining of canned goods and, until recently, baby bottles. It belongs to a class of endocrine disrupting chemicals, or EDCs, which have been shown to mimic natural hormones. These endocrine disruptors interfere with hormone regulation and proper function of human cells, glands and tissue. …

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Don’t throw out old, sprouting garlic — it has heart-healthy antioxidants

“Sprouted” garlic — old garlic bulbs with bright green shoots emerging from the cloves — is considered to be past its prime and usually ends up in the garbage can. But scientists are reporting in ACS’ Journal of Agricultural and Food Chemistry that this type of garlic has even more heart-healthy antioxidant activity than its fresher counterparts.Jong-Sang Kim and colleagues note that people have used garlic for medicinal purposes for thousands of years. Today, people still celebrate its healthful benefits. Eating garlic or taking garlic supplements is touted as a natural way to reduce cholesterol levels, blood pressure and heart disease risk. It even may boost the immune system and help fight cancer. But those benefits are for fresh, raw garlic. Sprouted garlic has received much less attention. When seedlings grow into green plants, they make many new compounds, including those that protect the young plant against pathogens. Kim’s group reasoned that the same thing might be happening when green shoots grow from old heads of garlic. Other studies have shown that sprouted beans and grains have increased antioxidant activity, so the team set out to see if the same is true for garlic.They found that garlic sprouted for five days had higher antioxidant activity than fresher, younger bulbs, and it had different metabolites, suggesting that it also makes different substances. …

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From surf to turf: Archaeologists and chemists trace ancient British diets

The change by our ancestors from hunter-gathers to farmers is one of the most intensively researched aspects of archaeology. Now a large-scale investigation of British archaeological sites dating from around 4,600 BC to 1,400 AD has examined millions of fragments of bone and analysed over 1,000 cooking pots.The team, led by Professor Richard Evershed of the University of Bristol’s School of Chemistry, developed new techniques in an effort to identify fish oils in the pots. Remarkably, they showed that more than 99 per cent of the earliest farmer’s cooking pots lacked sea food residues.Other clues to ancient diets lie within human bones themselves, explored by the Cardiff group led by Dr Jacqui Mulville. The sea passes on a unique chemical signature to the skeletons of those eating seafood; while the early fisher folk possessed this signature it was lacking in the later farmers.Lead author of the study, Dr Lucy Cramp said: “The absence of lipid residues of marine foods in hundreds of cooking pots is really significant. It certainly stacks up with the skeletal isotope evidence to provide a clear picture that seafood was of little importance in the diets of the Neolithic farmers of the region.”Returning to the pots, the Bristol team used a compound-specific carbon isotope technique they have developed to identify the actual fats preserved in the cooking pots, showing that dairy products dominated the menu right across Britain and Ireland as soon as cattle and sheep arrived.The ability to milk animals was a revolution in food production as, for the first time humans did not have to kill animals to obtain food. As every farmer knows, milking stock requires a high level of skill and knowledge.In view of this, team member, Alison Sheridan from the National Museum of Scotland concludes that: “The use of cattle for dairy products from the earliest Neolithic confirms the view that farming was introduced by experienced immigrants.”Viewed together the findings show that Early British hunters feasted on venison and wild boar and ate large quantities of sea food, including seals and shellfish. With the introduction of domestic animals some 6,000 years ago they quickly gave up wild foods and fishing was largely abandoned, and people adopted a new diet based around dairying.Dr Cramp continued: “Amazingly, it was another 4,000 years before sea food remains appeared in pots again, during the Iron Age, and it was only with the arrival of the Vikings that fish became a significant part of our diet.”Dr Mulville said: “Whilst we like to think of ourselves as a nation of fish eaters, with fish and chips as our national dish, it seems that early British farmers preferred beef, mutton and milk.”Why people changed so abruptly from a seafood to farming diet remains a mystery. Professor Evershed said: “Since such a clear transition is not seen in the Baltic region, perhaps the hazardous North Atlantic waters were simply too difficult to fish effectively until new technologies arrived, making dairying the only sustainable option.”Story Source:The above story is based on materials provided by University of Bristol. Note: Materials may be edited for content and length.

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Primitive artificial cell turned into complex biological materials

Imagine starting from scratch with simple artificial microscopic building blocks and ending up with something much more complex: living systems, novel computers or every-day materials. For decades scientists have pursued the dream of creating artificial building blocks that can self-assemble in large numbers and reassemble to take on new tasks or to remedy defects. Now researchers have taken a step forward to make this dream into a reality.”The potential of such new human-made systems is almost limitless, and many expect these novel materials to become the foundation of future technologies,” says Dr. Maik Hadorn from Department of Chemistry and Applied Biosciences at ETH Zrich, who conducted the research as a postdoctoral research fellow at University of Southern Denmark (SDU).Over the last three years he and the colleagues Eva Boenzli, Kristian T. Srensen and Martin M. Hanczyc from the Center for Fundamental Living Technology (FLinT) at SDU have worked on the challenges of making primitive building blocks assemble and turn into something functional.”We used short DNA strands as smart glue to link preliminary stages of artificial cells (called artificial vesicles) to engineer novel tissue-like structures,” says Dr. Maik Hadorn.As part of the EU-sponsored project MATCHIT (MATrix for CHemical Information Technology) Dr. Maik Hadorn and coworkers have earlier showed that short DNA strands can guide the self-assembly process of artificial vesicles; that two types of artificial vesicles can be linked in a way predefined by the person conducting the experiment, and that assembled structures can be reassembled, when triggered externally.In their most recent scientific article, published in Langmuir in December 2013, the researchers from SDU, in collaboration with colleagues from Italy and Japan, not only increased the complexity of the self-assembled structures that are now composed of several types of artificial vesicles — they also loaded one vesicle type with a basic cellular machinery derived from bacterial cells. This enabled these vesicles to translate an encapsulated genetic blueprint into a functional protein.Put together the researchers have managed to engineer controlled assemblies that are visible to the naked eye and that resemble natural tissues in their architecture as well as in their functionalities.Methods of constructing simple artificial structures have been known for decades, but only the use of DNA strands that act as a smart glue has allowed the researchers to overcome shortcomings of precedent methods and to engineer higher-order structures of predefined and programmable architecture.”As the artificial vesicles resemble natural cells both in size and composition, they are an ideal starting point for a multitude of applications. One application can be a temporal support for wound healing: A wound may be covered with assemblies of vesicles that are tailored in a patient specific manner. …

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Puzzling question in bacterial immune system answered

A central question has been answered regarding a protein that plays an essential role in the bacterial immune system and is fast becoming a valuable tool for genetic engineering. A team of researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have determined how the bacterial enzyme known as Cas9, guided by RNA, is able to identify and degrade foreign DNA during viral infections, as well as induce site-specific genetic changes in animal and plant cells. Through a combination of single-molecule imaging and bulk biochemical experiments, the research team has shown that the genome-editing ability of Cas9 is made possible by the presence of short DNA sequences known as “PAM,” for protospacer adjacent motif.”Our results reveal two major functions of the PAM that explain why it is so critical to the ability of Cas9 to target and cleave DNA sequences matching the guide RNA,” says Jennifer Doudna, the biochemist who led this study. “The presence of the PAM adjacent to target sites in foreign DNA and its absence from those targets in the host genome enables Cas9 to precisely discriminate between non-self DNA that must be degraded and self DNA that may be almost identical. The presence of the PAM is also required to activate the Cas9 enzyme.”With genetically engineered microorganisms, such as bacteria and fungi, playing an increasing role in the green chemistry production of valuable chemical products including therapeutic drugs, advanced biofuels and biodegradable plastics from renewables, Cas9 is emerging as an important genome-editing tool for practitioners of synthetic biology.”Understanding how Cas9 is able to locate specific 20-base-pair target sequences within genomes that are millions to billions of base pairs long may enable improvements to gene targeting and genome editing efforts in bacteria and other types of cells,” says Doudna who holds joint appointments with Berkeley Lab’s Physical Biosciences Division and UC Berkeley’s Department of Molecular and Cell Biology and Department of Chemistry, and is also an investigator with the Howard Hughes Medical Institute (HHMI).Doudna is one of two corresponding authors of a paper describing this research in the journal Nature. The paper is titled “DNA interrogation by the CRISPR RNA-guided endonuclease Cas9.” The other corresponding author is Eric Greene of Columbia University. Co-authoring this paper were Samuel Sternberg, Sy Redding and Martin Jinek.Bacterial microbes face a never-ending onslaught from viruses and invasive snippets of nucleic acid known as plasmids. To survive, the microbes deploy an adaptive nucleic acid-based immune system that revolves around a genetic element known as CRISPR, which stands for Clustered Regularly Interspaced Short Palindromic Repeats. Through the combination of CRISPRs and RNA-guided endonucleases, such as Cas9, (“Cas” stands for CRISPR-associated), bacteria are able to utilize small customized crRNA molecules (for CRISPR RNA) to guide the targeting and degradation of matching DNA sequences in invading viruses and plasmids to prevent them from replicating. There are three distinct types of CRISPR-Cas immunity systems. …

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Diagnosis just a breath away with new laser that advances breath analysis for disease diagnosis

University of Adelaide physics researchers have developed a new type of laser that will enable exciting new advances in areas as diverse as breath analysis for disease diagnosis and remote sensing of critical greenhouse gases.Published in the journal Optics Letters, the researchers from the University’s Institute for Photonics and Advanced Sensing and the School of Chemistry and Physics describe how they have been able to produce 25 times more light emission than other lasers operating at a similar wavelength — opening the way for detection of very low concentrations of gases.”This laser has significantly more power and is much more efficient than other lasers operating in this frequency range,” says Ori Henderson-Sapir, PhD researcher. “Using a novel approach, we’ve been able to overcome the significant technical hurdles that have prevented fiber lasers from producing sufficient power in the mid-infrared.”The new laser operates in the mid-infrared frequency range — the same wavelength band where many important hydrocarbon gases absorb light.”Probing this region of the electromagnetic spectrum, with the high power we’ve achieved, means we will be able to detect these gases with a high degree of sensitivity,” says Project Leader Dr David Ottaway. “For instance, it should enable the possibility of analysing trace gases in exhaled breath in the doctors’ surgery.”Research has shown that with various diseases, minute amounts of gases not normally exhaled can be detected in the breath; for example, acetone can be detected in the breath when someone has diabetes.Other potential applications include detection in the atmosphere of methane and ethane which are important gases in global warming.”The main limitation to date with laser detection of these gases has been the lack of suitable light sources that can produce enough energy in this part of the spectrum,” says Dr Ottaway. “The few available sources are generally expensive and bulky and, therefore, not suitable for widespread use.”The new laser uses an optical fiber which is easier to work with, less bulky and more portable, and much more cost effective to produce than other types of laser.The researchers, who also include Jesper Munch, Emeritus Professor of Experimental Physics, reported light emission at 3.6 microns — the deepest mid-infrared emission from a fiber laser operating at room temperature. They have also shown that the laser has the promise of efficient emission across a large wavelength spectrum from 3.3-3.8 micron.”This means it has incredible potential for scanning for a range of gases with a high level of sensitivity, with great promise as a very useful diagnostic and sensing tool,” says Dr Ottaway.This research was supported by the State Government through the Premiers Science Research Foundation (PSRF).Story Source:The above story is based on materials provided by University of Adelaide. Note: Materials may be edited for content and length.

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Hempseed oil packed with health-promoting compounds, study finds

Long stigmatized because of its “high”-inducing cousins, hemp — derived from low-hallucinogenic varieties of cannabis — is making a comeback, not just as a source of fiber for textiles, but also as a crop packed with oils that have potential health benefits. A new study, which appears in ACS’ Journal of Agricultural and Food Chemistry, details just how many healthful compounds hempseed oil contains.Maria Angeles Fernndez-Arche and colleagues note that for millennia, people around the world cultivated cannabis for textiles, medicine and food. Hemp has high levels of vitamins A, C and E and beta carotene, and it is rich in protein, carbohydrates, minerals and fiber. In the early 20th century, many countries banned cannabis because some varieties contain large amounts of the high-inducing compound THC. And although Colorado recently legalized recreational marijuana use — and some states have passed medical marijuana laws — the drug remains illegal according to U.S. federal law. But the European Union has legalized growing low-THC versions of hemp, and it’s making its way back into fabrics and paper. With increasing interest in plant oils as a source of healthful compounds, Fernndez-Arche’s team wanted to investigate hempseed oil’s potential.They did a detailed analysis of a portion of hempseed oil. They found it has a variety of interesting substances, such as sterols, aliphatic alcohols and linolenic acids, that research suggests promote good health. For example, it contains α-linolenic acid, which is an omega-3 fatty acid that some studies suggest helps prevent coronary heart disease. …

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Breakthrough in rechargeable batteries: New twist to sodium-ion battery technology

A Kansas State University engineer has made a breakthrough in rechargeable battery applications.Gurpreet Singh, assistant professor of mechanical and nuclear engineering, and his student researchers are the first to demonstrate that a composite paper — made of interleaved molybdenum disulfide and graphene nanosheets — can be both an active material to efficiently store sodium atoms and a flexible current collector. The newly developed composite paper can be used as a negative electrode in sodium-ion batteries.”Most negative electrodes for sodium-ion batteries use materials that undergo an ‘alloying’ reaction with sodium,” Singh said. “These materials can swell as much as 400 to 500 percent as the battery is charged and discharged, which may result in mechanical damage and loss of electrical contact with the current collector.””Molybdenum disulfide, the major constituent of the paper electrode, offers a new kind of chemistry with sodium ions, which is a combination of intercalation and a conversion-type reaction,” Singh said. “The paper electrode offers stable charge capacity of 230 mAh.g-1, with respect to total electrode weight. Further, the interleaved and porous structure of the paper electrode offers smooth channels for sodium to diffuse in and out as the cell is charged and discharged quickly. This design also eliminates the polymeric binders and copper current collector foil used in a traditional battery electrode.”The research appears in the latest issue of the journal ACS Nanoin the article “MoS2/graphene composite paper for sodium-ion battery electrodes.”For the last two years the researchers have been developing new methods for quick and cost-effective synthesis of atomically thin two-dimensional materials — graphene, molybdenum and tungsten disulfide — in gram quantities, particularly for rechargeable battery applications.For the latest research, the engineers created a large-area composite paper that consisted of acid-treated layered molybdenum disulfide and chemically modified graphene in an interleaved structured. The research marks the first time that such a flexible paper electrode was used in a sodium-ion battery as an anode that operates at room temperature. Most commercial sodium-sulfur batteries operate close to 300 degrees Celsius, Singh said.Singh said the research is important for two reasons:1. Synthesis of large quantities of single or few-layer-thick 2-D materials is crucial to understanding the true commercial potential of materials such as transition metal dichalcogenides, or TMD, and graphene.2. Fundamental understanding of how sodium is stored in a layered material through mechanisms other than the conventional intercalation and alloying reaction. …

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Are banana farms contaminating Costa Rica’s crocs?

Sep. 19, 2013 — Shoppers spend over £10 billion on bananas annually and now this demand is being linked to the contamination of Central America’s crocodilians. New research, published in Environmental Toxicology and Chemistry, analyses blood samples from spectacled caiman in Costa Rica and finds that intensive pesticide use in plantations leads to contaminated species in protected conservation areas.”Banana plantations are big business in Costa Rica, which exports an estimated 1.8 million tonnes per year; 10% of the global total,” said author Paul Grant from Stellenbosch University, South Africa. “The climate of the country’s North East is ideal for bananas; however, the Rio Suerte, which flows through this major banana producing area, drains into the Tortuguero Conservation Area.”Tortuguero is home to the spectacled caiman (Caiman crocodilus), one of the most common species of crocodilian in Central America. This freshwater predator is known to be highly adaptive, feeding on fish, crustaceans and in the case of larger specimens, wild pigs.Due to the increased global demand for fruit, pesticide use has more than doubled across Central America in the past twenty years. In Costa Rica, which ranks second in the world for intensity of pesticide use, the problem of contamination is compounded by environmental conditions and lax enforcement of regulations.”Frequent heavy rains can wash pesticides from plantation areas, leading to contamination and the reapplication of sprays to the crops,” said Grant. “Without adequate enforcement of regulations dangerous practices such as aerial spraying close to streams or washing application equipment in rivers also contributes to contamination downstream.”The team collected blood samples from 14 adult caiman and analyzed them for traces of 70 types of pesticide. Caiman within the high intensity banana crop watershed of Rio Suerte had higher pesticide burdens relative to other more remote locations.The nine pesticides detected in the caiman blood were identified as insecticides. Of these seven were listed as Persistent Organic Pollutants (POPS), banned under the 2011 Stockholm Convention.”Caiman near banana plantations had higher pesticide burdens and lower body condition,” said Grant. “This suggests that either pesticides pose a health risk to caiman, or that pesticides harm the habitat and food supply of caiman, thereby reducing the health of this predator.”As long-lived species atop the food chain crocodilians provide an integrated assessment of the fate of pesticides in tropical areas and can be indicative of pesticide damage throughout the ecosystem.”Caiman and other aquatic species have been exposed to pesticides from upstream banana plantations, even in remote areas of a national wilderness area,” concluded Grant. …

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New device harnesses sun and sewage to produce hydrogen fuel

Oct. 10, 2013 — A novel device that uses only sunlight and wastewater to produce hydrogen gas could provide a sustainable energy source while improving the efficiency of wastewater treatment.A research team led by Yat Li, associate professor of chemistry at the University of California, Santa Cruz, developed the solar-microbial device and reported their results in a paper published in the American Chemical Society journal ACS Nano. The hybrid device combines a microbial fuel cell (MFC) and a type of solar cell called a photoelectrochemical cell (PEC). In the MFC component, bacteria degrade organic matter in the wastewater, generating electricity in the process. The biologically generated electricity is delivered to the PEC component to assist the solar-powered splitting of water (electrolysis) that generates hydrogen and oxygen.Either a PEC or MFC device can be used alone to produce hydrogen gas. Both, however, require a small additional voltage (an “external bias”) to overcome the thermodynamic energy barrier for proton reduction into hydrogen gas. The need to incorporate an additional electric power element adds significantly to the cost and complication of these types of energy conversion devices, especially at large scales. In comparison, Li’s hybrid solar-microbial device is self-driven and self-sustained, because the combined energy from the organic matter (harvested by the MFC) and sunlight (captured by the PEC) is sufficient to drive electrolysis of water.In effect, the MFC component can be regarded as a self-sustained “bio-battery” that provides extra voltage and energy to the PEC for hydrogen gas generation. “The only energy sources are wastewater and sunlight,” Li said. “The successful demonstration of such a self-biased, sustainable microbial device for hydrogen generation could provide a new solution that can simultaneously address the need for wastewater treatment and the increasing demand for clean energy.”Microbial fuel cells rely on unusual bacteria, known as electrogenic bacteria, that are able to generate electricity by transferring metabolically-generated electrons across their cell membranes to an external electrode. …

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Unregulated, agricultural ammonia threatens U.S. national parks’ ecology

Oct. 10, 2013 — Thirty-eight U.S. national parks are experiencing “accidental fertilization” at or above a critical threshold for ecological damage, according to a study published in the journal Atmospheric Chemistry and Physicsand led by Harvard University researchers. Unless significant controls on ammonia emissions are introduced at a national level, they say, little improvement is likely between now and 2050.The environmental scientists, experts in air quality, atmospheric chemistry, and ecology, have been studying the fate of nitrogen-based compounds that are blown into natural areas from power plants, automobile exhaust, and — increasingly — industrial agriculture. Nitrogen that finds its way into natural ecosystems can disrupt the cycling of nutrients in soil, promote algal overgrowth and lower the pH of water in aquatic environments, and ultimately decrease the number of species that can survive.”The vast majority, 85 percent, of nitrogen deposition originates with human activities,” explains principal investigator Daniel J. Jacob, Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at the Harvard School of Engineering and Applied Sciences (SEAS). “It is fully within our power as a nation to reduce our impact.”Existing air quality regulations and trends in clean energy technology are expected to reduce the amount of harmful nitrogen oxides (NOx) emitted by coal plants and cars over time. However, no government regulations currently limit the amount of ammonia (NH3) that enters the atmosphere through agricultural fertilization or manure from animal husbandry, which are now responsible for one-third of the anthropogenic nitrogen carried on air currents and deposited on land.”Ammonia’s pretty volatile,” says Jacob. “When we apply fertilizer in the United States, only about 10 percent of the nitrogen makes it into the food. All the rest escapes, and most of it escapes through the atmosphere.”The team of scientists — comprising researchers from Harvard SEAS, the National Park Service, the USDA Forest Service, the U.S. …

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Bismuth-carrying nanotubes show promise for CT scans

Sep. 4, 2013 — Scientists at Rice University have trapped bismuth in a nanotube cage to tag stem cells for X-ray tracking.Bismuth is probably best known as the active element in a popular stomach-settling elixir and is also used in cosmetics and medical applications. Rice chemist Lon Wilson and his colleagues are inserting bismuth compounds into single-walled carbon nanotubes to make a more effective contrast agent for computed tomography (CT) scanners.Details of the work by Wilson’s Rice team and collaborators at the University of Houston, St. Luke’s Episcopal Hospital, and the Texas Heart Institute appear in the Journal of Materials Chemistry B.This is not the first time bismuth has been tested for CT scans, and Wilson’s lab has been experimenting for years with nanotube-based contrast agents for magnetic resonance imaging (MRI) scanners. But this is the first time anyone has combined bismuth with nanotubes to image individual cells, he said.”At some point, we realized no one has ever tracked stem cells, or any other cells that we can find, by CT,” Wilson said. “CT is much faster, cheaper and more convenient, and the instrumentation is much more widespread (than MRI). So we thought if we put bismuth inside the nanotubes and the nanotubes inside stem cells, we might be able to track them in vivo in real time.”Experiments to date confirm their theory. In tests using pig bone marrow-derived mesenchymal stem cells, Wilson and lead author Eladio Rivera, a former postdoctoral researcher at Rice, found that the bismuth-filled nanotubes, which they call Bi@US-tubes, produce CT images far brighter than those from common iodine-based contrast agents.”Bismuth has been thought of before as a CT contrast agent, but putting it in nanotube capsules allows us to get them inside cells in high concentrations,” Wilson said. “That lets us take an X-ray image of the cell.”The capsules are made from a chemical process that cuts and purifies the nanotubes. When the tubes and bismuth chloride are mixed in a solution, they combine over time to form Bi@US-tubes.The nanotube capsules are between 20 and 80 nanometers long and about 1.4 nanometers in diameter. …

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New laser-based tool could dramatically improve the accuracy of brain tumor surgery

Sep. 4, 2013 — A new laser-based technology may make brain tumor surgery much more accurate, allowing surgeons to tell cancer tissue from normal brain at the microscopic level while they are operating, and avoid leaving behind cells that could spawn a new tumor.In a new paper, featured on the cover of the journal Science Translational Medicine, a team of University of Michigan Medical School and Harvard University researchers describes how the technique allows them to “see” the tiniest areas of tumor cells in brain tissue.They used this technique to distinguish tumor from healthy tissue in the brains of living mice — and then showed that the same was possible in tissue removed from a patient with glioblastoma multiforme, one of the most deadly brain tumors.Now, the team is working to develop the approach, called SRS microscopy, for use during an operation to guide them in removing tissue, and test it in a clinical trial at U-M. The work was funded by the National Institutes of Health.A need for improvement in tumor removalOn average, patients diagnosed with glioblastoma multiforme live only 18 months after diagnosis. Surgery is one of the most effective treatments for such tumors, but less than a quarter of patients’ operations achieve the best possible results, according to a study published last fall in the Journal of Neurosurgery.”Though brain tumor surgery has advanced in many ways, survival for many patients is still poor, in part because surgeons can’t be sure that they’ve removed all tumor tissue before the operation is over,” says co-lead author Daniel Orringer, M.D., a lecturer in the U-M Department of Neurosurgery who has worked with the Harvard team since a chance meeting with a team member during his U-M residency.”We need better tools for visualizing tumor during surgery, and SRS microscopy is highly promising,” he continues. “With SRS we can see something that’s invisible through conventional surgical microscopy.”The SRS in the technique’s name stands for stimulated Raman scattering. Named for C.V. Raman, one of the Indian scientists who co-discovered the effect and shared a 1930 Nobel Prize in physics for it, Raman scattering involves allows researchers to measure the unique chemical signature of materials.In the SRS technique, they can detect a weak light signal that comes out of a material after it’s hit with light from a non-invasive laser. By carefully analyzing the spectrum of colors in the light signal, the researchers can tell a lot about the chemical makeup of the sample.Over the past 15 years, Sunney Xie, Ph.D., of the Department of Chemistry and Chemical Biology at Harvard University — the senior author of the new paper — has advanced the technique for high-speed chemical imaging. By amplifying the weak Raman signal by more than 10,000 times, it is now possible to make multicolor SRS images of living tissue or other materials. The team can even make 30 new images every second — the rate needed to create videos of the tissue in real time.Seeing the brain’s microscopic architectureA multidisciplinary team of chemists, neurosurgeons, pathologists and others worked to develop and test the tool. …

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Promising new angle for drugs to prevent stroke and heart attack

Aug. 30, 2013 — Platelets, which allow blood to clot, are at the heart of numerous cardiovascular problems, including heart attacks and stroke. New research has uncovered a key platelet protein that could offer a new angle for developing drugs to prevent thrombosis, or dangerous blood clots, in patients who are at high risk such as those with atherosclerosis or a history of heart problems.”I think we’re at the start of an exciting journey of drug discovery for a new class of antithrombotic therapies,” said lead study author Stephen Holly, PhD, assistant professor of biochemistry and biophysics at the University of North Carolina School of Medicine. This work was performed in collaboration with senior authors Leslie Parise, PhD, at UNC and Benjamin Cravatt, PhD, at The Scripps Research Institute.The study was published online August 29 ahead of print in the journal Chemistry & Biology and funded by grants from the American Heart Association and the National Institutes of Health.In the human circulatory system, platelets are something of a double-edged sword. Without their clotting abilities, even a minor injury could result in potentially fatal bleeding. But during a heart attack or stroke, platelets form a clot that can potentially block blood flow through our veins and arteries, a dangerous condition called thrombosis, which can deprive tissues of oxygen and lead to death.Several antithrombotic drugs are available, but some have been found to cause bleeding — a side effect that is particularly troublesome when these drugs are used to prevent thrombosis in people undergoing heart surgery. “There’s still room for improvement, in terms of making an ideal drug that can block platelet function without initiating bleeding,” said Dr. Holly.Dr. Holly and his colleagues uncovered several potential drug targets using a screening technique that has never before been applied to the cardiovascular system. The technique, called activity-based protein profiling, has been used in cancer research and allows researchers to track the actual activities of proteins operating within a cell. …

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Mosquitoes smell you better at night

Aug. 30, 2013 — In work published this week in Nature: Scientific Reports, a team of researchers from the University of Notre Dame’s Eck Institute for Global Health, led by Associate Professor Giles Duffield and Assistant Professor Zain Syed of the Department of Biological Sciences, revealed that the major malaria vector in Africa, the Anopheles gambiae mosquito, is able to smell major human host odorants better at night.The study reports an integrative approach to examine the mosquito’s ability to smell across the 24-hour day and involved proteomic, sensory physiological, and behavioral techniques. The researchers examined the role for a major chemosensory family of mosquito proteins, odorant-binding proteins (OBPs), in the daily regulation of olfactory sensitivities in the malarial mosquito. It is thought that OBPs in the insect antennae and mouth parts function to concentrate odorant molecules and assist in their transport to the actual olfactory receptors, thereby allowing for odorant detection. The team revealed daily rhythmic protein abundance of OBPs, having higher concentrations in the mosquito’s sensory organs at night than during the day. This discovery could change the way we look at protecting ourselves from these disease-carrying pests.The team also included Matthew M. Champion, Eck Institute for Global Health Research Assistant Professor in the Department of Chemistry and Biochemistry, who specializes in proteomics.This study utilized mass spectrometry to quantify protein abundance in mosquito sensory organs, and electroantennograms to determine the response induced by host odorants at different times of the day. The coincident times of peak protein abundance, olfactory sensitivity and biting behavior reflect the extraordinarily fine-tuned control of mosquito physiology. Olfactory protein abundance and olfactory sensitivity are high when needed (at night) and low when not required (daytime).Samuel Rund, a doctoral candidate in the laboratory of Duffield and a former Eck Institute for Global Health Fellow, and Nicolle Bonar, a visiting undergraduate student from Queens University of Ontario, Canada, were the lead authors on this research. The Notre Dame team also included then-undergraduate student John Ghazi, Class of 2012; undergraduate Cameron Houk, Class of ’14; and graduate student Matthew Leming.Rund noted, “This was an exciting opportunity to bring many people and techniques together to make some really fascinating findings on the mosquito’s ability to smell humans, its host. …

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Botany and health: Very small chemical changes to dietary flavonoids cause very large effects on human immune system

Aug. 30, 2013 — Scientists at the University of York have discovered that very small chemical changes to dietary flavonoids cause very large effects when the plant natural products are tested for their impact on the human immune system.Plants are capable of making tens of thousands of different small molecules — an average leaf for example, produces around 20,000. Many of these are found in a typical diet and some are already known to have medicinal properties with effects on health, diseases and general well-being.Now plant biologists and immunologists at York have joined forces to examine a very closely related family of these small molecules (flavonoids) to establish how tiny changes to their chemical structures affect their bio-activity.The research, published in The Journal of Biological Chemistry, has important implications for diet and in the development of new pharmaceuticals from plant natural products.Researchers from the Centre for Novel Agricultural Products (CNAP) and the Centre for Immunology and Infection (CII) in the University’s Department of Biology designed experiments to test the bioactivity of plant-derived flavonoids.Professor Dianna Bowles, a plant biochemist and founding Director of CNAP, led the research with Professor Paul Kaye, the Director of CII, who developed the robust assay system involving human cells to assess the impacts of the different structures.Professor Bowles, who referred to the research in a panel discussion on ‘Nature’s Marvellous Medicines’ at the recent Royal Society Summer Science Exhibition, said: “We were measuring how flavonoids affected the production of inflammatory mediators by cells stimulated by microbial products. We found that the way in which a flavonoid scaffold was decorated had massive effects on how the cells responded. If a methyl group was attached at one site, there would be no effect; methylate another site, and the cells would produce far greater amounts of these inflammatory mediators. Therefore, the site of attachment on the structural scaffold was all-important in determining the bioactivity of the small molecule.”Plant products in our diet have immense molecular diversity and consequently also have a huge potential for affecting our health and well being. We are only at the beginning of discovering the multitude of their effects.”Professor Kaye added: “The research demonstrates the level of control that the shape of a molecule can have on its recognition by our immune system cells. This is really important since we can use information such as this to design new drugs for clinical use, as novel immunomodulators, for example.”

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