Summer is around the corner-time for cookouts and sunbathing.But too mach sun can result in sunburn, which is the main cause of skin cancer.
To help people stay safe, researchers report in ACS Sensors the development of a paper-based sensor for monitoring sun exposure given different skin tones and sunscreen levels
Borizii sunt printre substanțele cele mai rezistente și cele mai rezistente la căldură de pe planetă, dar căldura lui Achilles, ca și atâtea materiale „, este că ele se oxidează la temperaturi ridicate.
Adezivul natural al iederii englezești ar putea să dețină cheia unor noi abordări pentru vindecarea rănilor, armuri puternice pentru armată și poate chiar produse cosmetice cu o putere de ședere mai bună.este interesat în special de bioadezive care ar putea ajuta la vindecarea rănilor după intervenții chirurgicale sau intervenții chirurgicale. Alții, în special militarii americani, sunt interesați de aplicațiile de acoperire a suprafețelor pentru scopuri care includ consolidarea sistemelor de armură, a spus el
| Posted: May 24, 2016 | |
Ivy’s powerful grasp could lead to better medical adhesives, stronger battle armor(Nanowerk News) English ivy’s natural glue might hold the key to new approaches to wound healing, stronger armor for the military and maybe even cosmetics with better staying power. |
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| New research from The Ohio State University illuminates the tiny particles responsible for ivy’s ability to latch on so tight to trees and buildings that it can withstand hurricanes and tornadoes. (Not to mention infuriate those trying to rid their homes of the vigorous green climber.) | |
| The researchers pinpointed the spherical particles within English ivy’s adhesive and identified the primary protein within them. | |
| „By understanding the proteins that give rise to ivy’s strength, we can give rise to approaches to engineer new bio-inspired adhesives for medical and industry products,” said Mingjun Zhang, the biomedical engineering professor who led the work. | |
| „It’s a milestone to resolve this mystery. We now know the secret of this adhesive and the underlying molecular mechanism,” said Zhang, who focuses his work on finding answers in nature for vexing problems in medicine. | |
| The study appears today in the journal Proceedings of the National Academy of Sciences(„Nanospherical arabinogalactan proteins are a key component of the high-strength adhesive secreted by English ivy”). | |
| Like many scientists before him, Charles Darwin among them, Zhang found himself captivated by English ivy – the physics of it, the sheer strength of it. | |
| „Ivy has these very tiny hairy structures that have a wonderful interaction with the surface as the plant climbs. One day I was looking at the ivy in the backyard and I was amazed at the force,” Zhang said. | |
| „It’s very difficult to tear down, even in a natural disaster. It’s one of the strongest adhesive forces in nature.” | |
| When he and his team took a look at the ivy’s glue with a powerful atomic-force microscope, they were able to identify a previously unknown element in its adhesive. | |
| The tiny particles inside the glue on their laboratory slides turned out to be primarily made up of arabinogalactan proteins. And when the scientists investigated further, they discovered that the driving force behind the curing of the glue was a calcium-mediated interaction between the proteins and pectin in the gelatinous liquid that oozes from ivy as it climbs. | |
| Zhang said particles rich in those proteins have exceptional adhesive abilities – abilities that could be used to the advantage of many, from biomedical engineers to paint makers. | |
| Zhang, a member of Ohio State’s Davis Heart and Lung Research Institute, is particularly interested in bioadhesives that could aid in wound healing after injury or surgeries. Others, notably the U.S. military, are interested in surface-coating applications for purposes that include strengthening armor systems, he said. | |
| Many plants are excellent climbers, but scientists have had limited information about the adhesives that enable those plants to affix themselves to walls, fences and just about anything in their way, he said. | |
| „When climbing, ivy secretes these tiny nanoparticles which make initial surface contact. Due to their high uniformity and low viscosity, they can attach to large areas on various surfaces,” Zhang said. | |
| After the water evaporates, a chemical bond forms, Zhang said. | |
| „It’s really a nature-made amazing mechanism for high-strength adhesion,” he said. | |
| The glue doesn’t just sit on the surface of the object that the ivy is clinging to, he said. It finds its way into openings invisible to the naked eye, further solidifying its bond. | |
| To confirm what they found, Zhang and his collaborators used the nanoparticles to reconstruct a simple glue that mimics ivy adhesive. Advanced bioadhesives based on this research will take more time and research. | |
| In addition to its strength, ivy adhesive has other properties that make it appealing to scientists looking for answers to engineering quandaries, Zhang said. | |
| „Under moisture or high or low temperatures, it’s not easily damaged,” he said. „Ivy is very resistant to various environmental conditions, which makes the adhesive a particularly interesting candidate for the development of armor coatings.” | |
| Ivy also is considered a pest because it can be destructive to buildings and bridges. Knowing what’s at the heart of its sticking ability could help scientists unearth approaches to resist the plant, Zhang said. |
| Source: Ohio State University |
O familie de compuși cunoscuți sub numele de perovskites, care pot fi transformate în filme subțiri cu multe proprietăți electronice și optice promițătoare, a fost un subiect de cercetare fierbinte în ultimii ani. Dar, deși aceste materiale ar putea fi extrem de utile în aplicații precum celulele solare, unele limitări încă îngreunează eficiența și coerența acestora.
| Posted: May 24, 2016 | |
Light can ‘heal’ defects in some solar cells(Nanowerk News) A family of compounds known as perovskites, which can be made into thin films with many promising electronic and optical properties, has been a hot research topic in recent years. But although these materials could potentially be highly useful in applications such as solar cells, some limitations still hamper their efficiency and consistency. |
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| Now, a team of researchers at MIT and elsewhere say they have made significant inroads toward understanding a process for improving perovskites’ performance, by modifying the material using intense light. The new findings are being reported in the journal Nature Communications („Photo-induced halide redistribution in organic-inorganic perovskite films”), in a paper by Samuel Stranks, a researcher at MIT; Vladimir Bulovic, the Fariborz Maseeh (1990) Professor of Emerging Technology and associate dean for innovation; and eight colleagues at other institutions in the U.S. and the U.K. The work is part of a major research effort on perovskite materials being led by Stranks, within MIT’s Organic and Nanostructured Electronics Laboratory. | |
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| A sample of the mineral perovskite is shown in the foreground, while behind it is an image the researchers used to prove the effects of intense light on a thin film of perovskite. Fluorescence imaging shows that areas that received more light became more purified, as revealed by brighter fluorescence from those regions. | |
| Tiny defects in perovskite’s crystalline structure can hamper the conversion of light into electricity in a solar cell, but “what we’re finding is that there are some defects that can be healed under light,” says Stranks, who is a Marie Curie Fellow jointly at MIT and Cambridge University in the U.K. The tiny defects, called traps, can cause electrons to recombine with atoms before the electrons can reach a place in the crystal where their motion can be harnessed. | |
| Under intense illumination, the researchers found that iodide ions — atoms stripped of an electron so they carry an electric charge — migrated away from the illuminated region, and in the process apparently swept away most of the defects in that region along with them. | |
| “This is the first time this has been shown,” Stranks says, “where just under illumination, where no [electric or magnetic] field has been applied, we see this ion migration that helps to clean the film. It reduces the defect density.” While the effect had been observed before, this work is the first to show that the improvement was caused by the ions moving as a result of the illumination. | |
| This work is focused on particular types of the material, known as organic-inorganic metal halide perovskites, which are considered promising for applications including solar cells, light-emitting diodes (LEDs), lasers, and light detectors. They excel in a property called the photoluminescence quantum efficiency, which is key to maximizing the efficiency of solar cells. But in practice, the performance of different batches of these materials, or even different spots on the same film, has been highly variable and unpredictable. The new work was aimed at figuring out what caused these discrepancies and how to reduce or eliminate them. | |
| Stranks explains that “the ultimate aim is to make defect-free films,” and the resulting improvements in efficiency could also be useful for applications in light emission as well as light capture. | |
| Previous work reducing defects in thin-film perovskite materials has focused on electrical or chemical treatments, but “we find we can do the same with light,” Stranks says. One advantage of that is that the same technique used to improve the material’s properties can at the same time be used as a sensitive probe to observe and better understand the behavior of these promising materials. | |
| Another advantage of this light-based processing is it doesn’t require anything to come in physical contact with the film being treated — for example, there is no need to attach electrical contacts or to bathe the material in a chemical solution. Instead, the treatment can simply be applied by turning on the source of illumination. The process, which they call photo-induced cleaning, could be “a way forward” for the development of useful perovskite-based devices, Stranks says. | |
| The effects of the illumination tend to diminish over time, Stranks says, so “the challenge now is to maintain the effect” long enough to make it practical. Some forms of perovskites are already “looking to be commercialized by next year,” he says, and this research “raises questions that need to be addressed, but it also shows there are ways to address” the phenomena that have been limiting this material’s performance. | |
| “I think the paper provides valuable insight that is likely to help people make more efficient solar cells by figuring out how to reduce the number of iodine vacancies,” says Michael McGehee, a professor of materials science and engineering at Stanford University, who was not involved in this research. “I think it is fascinating that illuminating the perovskites improves their photoluminescence efficiency by enabling iodine to move around and eliminate iodine vacancies. … This research does not make solar cells better, but it does greatly increase our understanding of how these complex materials function in solar cells.” |
| Source: By David L. Chandler, MIT |
dezvoltat de-icerul pe bază de grafen pentru a servi un scop dublu. Noul material încă mai topeste gheața din aripi și fire atunci când condițiile sunt prea reci. Dar dacă aerul este peste 7 grade Fahrenheit, gheața nu se va forma deloc.Filmul dur, care se formează atunci când pulverizatorul este pulverizat pe o suprafață, este realizat din nanoparticule de grafen subțire atomice care sunt conductive, astfel că materialul poate fi de asemenea încălzit cu electricitate pentru a topi gheața și zăpada în condiții mai reci.
Materialul poate fi acoperit cu spray, făcându-l potrivit pentru aplicații de mari dimensiuni, cum ar fi aeronave, linii electrice, cupole radar și nave, potrivit cercetătorilo
| Posted: May 24, 2016 | |
Dual-function, graphene-based material good for aircraft, extreme environments(Nanowerk News) Rice University scientists have advanced their graphene-based de-icer to serve a dual purpose. The new material still melts ice from wings and wires when conditions get too cold. But if the air is above 7 degrees Fahrenheit, ice won’t form at all. |
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| The Rice lab of chemist James Tour gave its de-icer superhydrophobic (water-repelling) capabilities that passively prevent water from freezing above 7 degrees. The tough film that forms when the de-icer is sprayed on a surface is made of atom-thin graphene nanoribbons that are conductive, so the material can also be heated with electricity to melt ice and snow in colder conditions. | |
| The material can be spray-coated, making it suitable for large applications like aircraft, power lines, radar domes and ships, according to the researchers. The study was published this month in the American Chemical Society journal ACS Applied Materials and Interfaces („Passive Anti-icing and Active Deicing Films”). | |
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| Rice University scientists have modified their graphene-based de-icer to resist the formation of ice well below the freezing point and added superhydrophobic capabilities. The robust film is intended for use in extreme environments as well as on aircraft, power lines and ships. (Image: Tour Group/Rice University) | |
| „We’ve learned to make an ice-resistant material for milder conditions in which heating isn’t even necessary, but having the option is useful,” Tour said. „What we now have is a very thin, robust coating that can keep large areas free of ice and snow in a wide range of conditions.” | |
| Tour, lead authors Tuo Wang, a Rice graduate student, and Yonghao Zheng, a Rice postdoctoral researcher, and their colleagues tested the film on glass and plastic. | |
| Materials are superhydrophobic if they have a water-contact angle larger than 150 degrees. The term refers to the angle at which the surface of the water meets the surface of the material. The greater the beading, the higher the angle. An angle of 0 degrees is basically a puddle, while a maximum angle of 180 degrees defines a sphere just touching the surface. | |
| The Rice films use graphene nanoribbons modified with a fluorine compound to enhance their hydrophobicity. They found that nanoribbons modified with longer perfluorinated chains resulted in films with a higher contact angle, suggesting that the films are tunable for particular conditions, Tour said. | |
| Warming test surfaces to room temperature and cooling again had no effect on the film’s properties, he said. | |
| The researchers discovered that below 7 degrees, water would condense within the structure’s pores, causing the surface to lose both its superhydrophobic and ice-phobic properties. At that point, applying at least 12 volts of electricity warmed them enough to retain its repellant properties. | |
| Applying 40 volts to the film brought it to room temperature, even if the ambient temperature was 25 degrees below zero. Ice allowed to form at that temperature melted after 90 seconds of resistive heating. | |
| The researchers found that while effective, the de-icing mode did not remove water completely, as some remained trapped in the pores between linked nanoribbon bundles. Adding a lubricant with a low melting point (minus 61 degrees F) to the film made the surface slippery, sped de-icing and saved energy. |
| Source: Rice University |
Inelele naturale ale iederei ar putea să dețină cheia unor noi abordări pentru vindecarea rănilor, armuri mai puternice pentru armată și poate chiar produse cosmetice cu o putere de ședere mai bună.iluminează particulele mici responsabile pentru capacitatea iederii de a se fixa atât de strâns pe copaci și clădiri încât poate rezista uraganelor și tornadelor.Zhang a spus ca particule bogate in aceste proteine au abilitati exceptionale de adeziv -abilitati care ar putea fi folosite in avantajul multor, de la ingineri biomedicale la producatorii de vopsea
un nou tip de material metalic extrem de puternic, dar ductil.Materialele metalice din forjarea materialelor de la Düsseldorf ar putea fi prelucrate la fel de ușor și în mod rentabil ca oțelul ductil în mod special și vor absorbi cât mai multă energie de impact într-un accident atunci când sunt încorporate în caroseria unei mașini. În același timp, materialul ar fi suficient de puternic încât foile de metal subțiri și, deci, ieftine și care economisesc resursele, să nu renunțe când sunt supuse unei forțe slabe.
| Posted: May 24, 2016 | |
Strength and ductility for alloys(Nanowerk News) For the steel industry, there may be a way out of the dilemma that has existed since people began processing metal. Scientists from the Max-Planck-Institut für Eisenforschung in Düsseldorf (Germany) are presenting a new type of metallic material that is extremely strong, but simultaneously ductile. |
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| Up until now, one material property could only be improved at the expense of the other – something that is being changed by the Düsseldorf-based researchers, who are entering new terrain in the development of metallic materials. | |
| Their work (Nature, „Metastable high-entropy dual-phase alloys overcome the strength–ductility trade-off”) is thus contributing to the future design of metallic components with thinner sheets, and thereby helping to save resources. | |
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| A strong alloy made of iron, manganese, cobalt and chrome becomes ductile because it can have two coexisting crystal structures, and one structure can transform into the other. The two crystal structures can be identified by the two different colours in this cross section of the material, which was produced with the aid of electron backscatter diffraction. | |
| Ideally, steels and steel-related alloys should be capable of both properties: they should not fragment, for example during processing in a mill or as car bodies involved in an accident. In other words, they must be “ductile”, as materials scientists refer to it. However, they also need to be strong so that they do not warp or break when subjected to weak forces. A team headed by Dierk Raabe, director at the Max-Planck-Institut für Eisenforschung, and Cemal Cem Tasan, formerly head of a research group at this Institute and now professor at the Massachusetts Institute of Technology in the US, has now succeeded in combining both properties in one material. To date, extremely ductile metallic materials were not particularly strong and vice versa. | |
| “We pursued a new strategy in the development of this material, which generally opens up new possibilities for the design of metallic materials,” says Dierk Raabe. | |
| The team began at a type of material that has been the subject of extensive testing by materials scientists in recent years, but which was too brittle for many applications up until now: alloys in which metallurgists combine similar quantities of typically five or more different metals. | |
| Atomic disorder enables high-strength alloys | |
| As the atoms of the different elements are distributed along the positions in the crystal lattices of these materials without any identifiable order and the entropy is, to a certain extent, a measure for the disorder, the materials are called high-entropy alloys. Such materials can be particularly strong because the disorder of the numerous different atoms in a structure makes it difficult for dislocations to move. | |
| Dislocations are defects in the crystal lattice that move through a crystal when a material becomes deformed. However, there has been one disadvantage to the high strength of the alloys with atomic disorder till now: when such a material gives way under pressure, it is usually brittle. | |
| Steels that mainly contain iron, usually another main component and small quantities of other elements like carbon, vanadium or chrome, are, on the other hand, often ductile. They are not brittle; however, up until now they have not been strong enough to enable, for example, the construction of car bodies with thinner sheets. In the crystals of steels, the atoms are more or less regularly arranged. | |
| Steels become particularly ductile though if they can switch from one structure to another. This is because this process swallows energy, which can then no longer initiate any damage in the material. In a car body or other steel components, tiny areas then alternate with the two different atom arrangements. | |
| The change in the crystal structure makes the material ductile | |
| It was precisely this coexistence of the different crystal structures that was detrimental to the high-entropy alloys – thus far. | |
| “We have now turned this conception on its head, as recent studies have shown that this is not the important factor,” says Zhiming Li, who made this scientific turnaround the topic of his project. | |
| Together with his colleagues, Li searched for a material that is, on the one hand, as strong as a high-entropy alloy, but, like particularly ductile steels, has two coexisting crystal structures. The search produced an alloy made from 50 per cent iron, 30 per cent manganese and 10 per cent respectively of cobalt and chrome. | |
| “With this alloy, we have shown that our concept works,” says Raabe. “If we further improve the microstructure and the composition, we can even further enhance the strength and ductility.” | |
| This is precisely the area the researchers are now working on. This means that they could, once and for all, solve the metal-processing industry’s dilemma of having to choose between strong or ductile materials. The metallic materials from the Düsseldorf-based materials forge could be processed just as easily and cost-efficiently as a particularly ductile steel and absorb as much impact energy in an accident when incorporated in the body of a car. At the same time, the material would be strong enough that thin and thus low-cost and resource-conserving metal sheets do not give way when subjected to a weak force. |
| Source: Max-Planck-Institut für Eisenforschung |
a inventat o metodă pentru identificarea rapidă a veninelor care lovește o țintă specifică în organism și optimizarea acestor venine pentru utilizare terapeutică
Dispozitivele infraroșii sunt utilizate pentru o vizibilitate îmbunătățită prin ceață și pentru vizibilitate nocturnă și pentru observații care nu sunt posibile cu lumină vizibilă
au dezvoltat de-icerul pe bază de grafen pentru a servi un scop dublu. Materialul nou încă mai topeste gheața din aripi și fire atunci când condițiile sunt prea reci.
prezintă un nou tip de material metalic extrem de puternic, dar ductil;
contribuie astfel la proiectarea viitoare a componentelor metalice cu foi mai subțiri, ajutând astfel la economisirea resurselor
