Lună: martie 2018

Oamenii de stiinta creeaza filme multifunctionale de proteine-polimer(

„Noi credem că filmele proteine-dendrimer sunt materiale promițătoare pentru crearea biosenzorilor și pot fi, de asemenea, folosite în medicină ca material de îmbrăcare bioactiv”

Posted: Mar 05, 2018
Scientists create multifunctional protein-polymer films

(Nanowerk News) A team from Lomonosov Moscow State University (MSU) together with foreign and Russian colleagues found that when mixing dendrimers (tree-like polymers) and proteins, multilayer films are spontaneously formed. They are easily formed and retain the activity and function of protein enzymes, which determines their potential as a material for creating biosensors and medical products. The results of the study are published in the journal Polymer(„Spontaneous formation of nanofilms under interaction of 4th generation pyrydylphenylene dendrimer with proteins”).
Dendrimer molecule is marked yellow. The surface of the protein molecule is color-coded in accordance with the chemical properties of amino acid residues (red – positive charge, blue – negative charge, green – polarized, and white – hydrophobic). (Image: Vladimir Muronetz)
Today a huge number of polymers is known, with different structure, composition, and properties. One of the most interesting examples are dendrimers – tree-like macromolecules. They are arranged as follows: three chemical groups are attached to the central core, each one branches into two same groups, and so on, and so on. Such a structure is achieved by a multistage synthesis.
The number of branching points determines generation number of the dendrimer: the first generation polymer has one branching point, the second one has two, the third has three, and so on. The further, the denser and more spherical becomes the structure, and its physical and chemical properties are preset by the functional groups on the outer layer. Dendrimers are able to form surface cavities into which molecules can be enveloped, and this property was the main prerequisite for the active study of these polymers. However, MSU scientists have found a completely different application for dendrimers.
„We found that upon mixing of proteins with fourth generation dendrimers the self-assembly of multilayer nanofilms 200-700 nm thick occurs. They can be adjacent to glass or plastic surfaces, as well as be formed at the liquid-air interface,” says Vladimir Muronetz, professor of the Faculty of Bioengineering and Bioinformatics and the Faculty of Biology, MSU, and Head of the Animal Cell Biochemistry Department in A.N. Belozersky Institute of Physico-Chemical Biology, MSU.
Scientists have conducted experiments on the incorporation of various enzymes into the composition of nanofilms: lysozyme, which destroys the bacterial cell walls, and several types of proteinases break down proteins. It was concluded that in the composition of nanofilms these proteins are able to preserve activity for about two weeks. This two-component system is resistant to the action of cleaning agents (detergents), to changes in the medium acidity, and is generally stable during storage. However, the main advantage of the produced films is the simplicity of their formation process due to self-assembly.
„We believe that protein-dendrimer films are promising materials for creating biosensors, and can also be used in medicine as bioactive dressing material,” concludes Vladimir Muronetz.

Source: Lomonosov Moscow State University

Atlasul celular (The Cell Atlas )

Următorul mega-proiect al Biologiei va afla de ce suntem cu adevărat făcuți. Obiectivul este de a construi primul „atlas celular” cuprinzător sau o hartă a celulelor umane, o minune tehnologică care ar trebui să dezvăluie, pentru prima dată, ce corpuri umane sunt de fapt făcute și să ofere oamenilor de știință un nou model sofisticat de biologie care ar putea accelera căutarea de droguri.

The Cell Altas

Materiale avansate Morgan, compozite și sisteme de apărare pentru a închide Coventry Factory-coausing masive Layoffs(Morgan Advanced Materials, Composites&Defense Systems to Close its Coventry Factory-Coausing Massive Layoffs)

Compania care produce vehicule blindate specializate și armuri de corp pentru Ministerul Apărării intenționează să închidă fabrica din Coventry.Au început consultări cu lucrătorii din fabrica Foleshill Road despre disponibilizări

Morgan

Axionul izolator prezintă o magnetorezistență gigantică la câmpuri magnetice scăzute(Axion insulator exhibits giant magnetoresistance at low magnetic fields)

Un material cuantic care prezintă o schimbare uriașă de rezistență la câmpurile magnetice relativ scăzute a fost fabricat de cercetători de la RIKEN, Universitatea din Tokyo și alte institute ( Science Advances , „Croitorie structură tricoloră de izolație topologică magnetică pentru izolator axion robust ” ). Materialul este promițător pentru realizarea circuitelor electronice în care curentul curge fără pierderi.Un material cuantic care a generat foarte mult entuziasm recent este izolatoarele topologice, care au proprietatea curioasă de a conduce electricitatea pe suprafețele lor, dar nu și în interiorul lor.

Posted: Mar 02, 2018

Axion insulator exhibits giant magnetoresistance at low magnetic fields

(Nanowerk News) A quantum material that exhibits a huge change in resistance at relatively low magnetic fields has been fabricated by researchers at RIKEN, the University of Tokyo and other institutes (Science Advances, „Tailoring tricolor structure of magnetic topological insulator for robust axion insulator”). The material is promising for realizing electronic circuits in which current flows without loss.
molecular beam epitaxy system
The molecular beam epitaxy system used to make an axion insulator device whose resistance varies greatly with applied magnetic field. (Image: RIKEN Center for Emergent Matter Science)Quantum effects usually manifest themselves on an atomic or molecular scale, but they are observable on much larger scales in a special class of materials known as quantum materials. One quantum material that has been generating a lot of excitement recently is topological insulators, which have the curious property of conducting electricity on their surfaces but not in their interiors. Devices based on topological insulators will be more robust against internal defects and external conditions than conventional devices. Topological insulators also promise an array of exotic new carrier phenomena when symmetry rules are relaxed.

One such phenomenon is the topological magnetoelectric effect, in which the interior of a topological insulator is magnetized by a quantized current circulating on its surface. This effect has been difficult to observe experimentally because it has been challenging to find a suitable material system.

Masataka Mogi at the University of Tokyo and his collaborators had previously made a suitable system known as an axion insulator, but they observed axion insulator behavior only in a narrow range of magnetic fields.

Now, Mogi, with colleagues at the RIKEN Center for Emergent Matter Science and other institutions in Japan, has succeeded in making the axion insulator state more robust and useful by doping one magnetic ion into the bottom surface of their device and a different one into the top. This allowed them to individually reverse one surface magnetization at a time and observe how the axion insulator responds to a wider range of magnetic fields, electric fields and temperatures.

As a result, the researchers were able to observe a whopping change in the resistance of the system—over 10,000,000 per cent—with a small change in the applied magnetic field. While effects like this have been observed in other topological materials, they have usually required a much larger swing in the magnetic field.
This novel behavior may lead to new kinds of electronic devices, Mogi says. “Using contemporary spintronic techniques may enable us to construct dissipationless electronic circuits in which the edge current runs in parallel magnetization regions, but not in anti-parallel regions.”
Making practical devices will require increasing operating temperatures, which are currently capped below 1 kelvin. Mogi is confident that this can be accomplished by growing higher quality films.
Source: RIKEN

Materialul grafenic întărește semnalul nervos în creier(Graphene material strengthens nerve signaling in the brain)

Mai puțin de 20 de ani dupa ce a fost dezvoltat, o foaie subțire, elastică de atomi de carbon cu proprietăți remarcabile , cunoscut sub numele de grafen transforma domenii biomedicale în măsura flung ca ingineria tesuturilor, neuroprosthetics si descoperirea de droguri.
Deoarece conduce cu ușurință căldură și electricitate, grafenul poate fi de asemenea un bun biosenzor.

Posted: Mar 02, 2018

Graphene material strengthens nerve signaling in the brain

(Nanowerk News) Less than 20 years after it was developed, a thin, resilient sheet of carbon atoms with remarkable properties known as graphene is transforming biomedical fields as far flung as tissue engineering, neuroprosthetics and drug discovery.
Because it readily conducts heat and electricity, graphene also may be a good biosensor. But it’s not neutral. When Vanderbilt University scientists tried to use graphene to measure electrical activity in the brain, they found that it actually enhanced nerve cell signaling.
It did so by enabling nerve cell membranes to pull in more cholesterol. The fatty substance was used to make more of the vesicles that package neurotransmitters, the chemical messengers that relay signals between nerve cells. More vesicles and more neurotransmitter meant stronger signals.
These findings, reported in the journal Nature Communications („Membrane cholesterol mediates the cellular effects of monolayer graphene substrates”), came as a complete surprise to the investigators. They raise the possibility that graphene may enable researchers to change how cells communicate with each other by manipulating the cholesterol content in the cell membrane.
Qi Zhang, PhD, Kristina Kitko
Qi Zhang, PhD, Kristina Kitko and colleagues are studying the way graphene impacts nerve cell signaling in the brain.
Graphene “not only may be a very good vehicle to deliver drugs but also a way to potentiate the drug effect,” said the paper’s senior author, Qi Zhang, PhD, assistant professor of Pharmacology in the Vanderbilt University School of Medicine.
The researchers began their experiment by growing neurons — nerve cells — on a sheet of graphene.
The paper’s first author, Kristina Kitko, a graduate student in interdisciplinary material science, picks up the story from there in an invited column she wrote for a Nature Chemistry blog: “We observed an increase in neuronal firing frequency on graphene,” she wrote. “This was substantial and our curiosity was piqued. When we began to look at more targeted measurements of presynaptic activity, what consistently emerged was surprising: synaptic potentiation on graphene.”
Realizing that graphene was likely acting at the nerve cell membrane, which consists primarily of cholesterol, the next question was: “Might cholesterol somehow be involved?”
“This led us to the idea of manipulating membrane cholesterol levels,” Kitko continued. “Cholesterol plays important and fundamental roles to cells in a variety of ways, but with particular relevance to drug discovery we demonstrated the effect of graphene on G protein-coupled receptors, whose activity are mediated by cholesterol.”
Half of all drugs target these receptors.
Source: By Bill Snyder, Vanderbilt University

Lampă indicatoare(Pointing light)

echipa UCSB încearcă să difuzeze sau să direcționeze undele optice (cu frecvență în infraroșu) într-o anumită direcție, cu un grad ridicat de control la o frecvență extrem de ridicată. În mod tradițional, antenele au funcționat în domeniul gigahertz sau megahertz; Grupul lui Schuller lucrează la scară de zeci de terahertzi sau 1 triliu de cicluri pe secundă în gama de frecvențe optice.Sensibilizarea mediului în mod mai rapid și mai eficient ar fi un beneficiu în domenii precum teledetecția, vehiculele autonome și afișajele holografice.

Posted: Mar 01, 2018

Pointing light

(Nanowerk News) Without the vast, nearly infinite web of crisscrossing electromagnetic waves that travel invisibly through the air, the modern world would cease to exist. Transmitting digital data and sensing and returning information about the environment at the speed of light, these waves are important in many emerging applications, including autonomous vehicles, Lidar and holographic displays, where the ability to direct and steer light beams over time is crucial to mapping surroundings or to immersion in an augmented reality.
UC Santa Barbara engineer Jon Schuller aims to manipulate specialized semiconductor materials and devices to control light without using mechanically moving parts — an achievement that could have wide-ranging applications. He is pursuing ways to use sub-wavelength interactions involving any element smaller than the wavelength of light (about one micron) to not only steer light, but also to enable faster, more efficient sensing. He also hopes to shrink the size of the system and improve its performance — all at a lower cost.
remote sensing
Sensing the environment more quickly and efficiently would be a benefit in such areas as remote sensing, autonomous vehicles and holographic displays. (Image: Peter Allen)
In a paper in the journal Nature Communications („Ultrawide thermal free-carrier tuning of dielectric antennas coupled to epsilon-near-zero substrates”), Schuller, an assistant professor, and his UCSB collaborators — Chris Palmstrøm, a professor of electrical and computer engineering and of materials, and graduate students Mihir Pendharkar and Prasad P. Iyer — describe a technique for applying heat to the semiconductor indium antimonide (InSb) to form an ideal material for controlling the phase of light necessary to achieve tunability.
“Sub-wavelength elements are essentially active mirrors, reflecting light with a controllable phase, and are able to generate and modulate the light when it interacts with matter,” said Schuller, a faculty member in UCSB’s Department of Electrical and Computer Engineering. “Our focus is on steering the beam. When multiple objects emit light, the different phases cause them to add up constructively in certain directions and destructively in others.”
One way to encode digital data is to turn a laser on and off rapidly, which can be achieved by splitting the laser into two waves, shifting the phase of one 180 degrees and recombining them. As the parallel beams travel through space, the waves align as mirror images of each other. The peaks of one wave line up with the troughs of the other, canceling out the signal. By switching the phase between 0 degrees (on) and 180 degrees (off) millions of times per second, information is encoded into the ones and zeroes of a digital data sequence.
To cause such phase shifts at the micron scale of light is much more difficult than doing so at the millimeter or centimeter scale. “At that scale, the phase-shifting device is so small that the light travels very little distance and therefore has very little time to interact with the material,” Schuller explained. “We need to find a much larger and more extreme light-matter interaction that can occur over such a small distance and time.”
For example, a material’s refractive index can be changed from 10-3 to 10-4 — one-tenth of a percent to one-hundredth of a percent — a significant increment in scientific terms. However, this research investigates effects that are one to 10,000 times bigger. The refractive index tells a lot about how light behaves in a material, such as its speed, its effective wavelength and the angle at which light rays bend as they enter or exit the material.
One type of modulation involves changing the number of mobile electrons in the material to alter its optical properties, which in turn affects the phases. It is possible to change electron density simply by changing the temperature of InSb without having to run a current through it.
Ultimately, the UCSB team is trying to broadcast or direct optical (infrared-frequency) waves in a particular direction with a high degree of control at an extremely high frequency. Traditionally, antennas have operated in the domain of gigahertz or megahertz; Schuller’s group is working at the scale of tens of terahertz, or 1 trillion cycles per second in the optical frequency range.
For now, the researchers are using their new thermal free-carrier method — employing heat to tune the number of electrons — to solve the challenges of optical tuning. Eventually, their goal is to activate InSb electrically, which — while faster and offering more benefits — poses another complex challenge. That makes the thermal approach even more valuable, permitting the researchers to experiment with the material without having to create an electrical system to activate it.
“Our temperature technique is a clever way to look at the basic physics of this problem — the basic optical materials science questions — and get all the complexities of the ultimate application that will use electricity,” said Schuller.
Source: UC Santa Barbara

Forma lucrurilor care urmează să vină pentru materialele cuantice?(The shape of things to come for quantum materials?)

Materialele pentagonale 2-D pot permite un nou grad de libertate pentru proiectarea noilor dispozitive optoelectronice și electronice conceptuale, care nu sunt posibile utilizând alte materiale 2-D. Mai mult decât atât, materialul este stabil în aer, ceea ce nu este valabil pentru multe alte semiconductori 2-D. De exemplu, este mai puțin susceptibil la oxidare decât fosforul negru, un alt material promițător 2-D cu un decalaj de bandă reglabil.
Descoperirea blocurilor adiționale pentagonale suplimentare poate avansa aplicații în optoelectronica cu energie scăzută, piezoelectrică, termoelectrică și spintronică.

Posted: Mar 01, 2018

The shape of things to come for quantum materials?

(Nanowerk News) For the first time, researchers isolated and characterized atomically thin 2-D crystals of pentagons bonded together in palladium diselenide (PdSe2). The research confirmed predictions that the puckered structure would be stable.
composed of pentagonal tiles
Theory predicted the existence of materials composed of pentagonal “tiles” (purple, teal, green, and pink). Now, researchers have proven these materials exist. Scientists made and characterized the first-ever sheets composed of pentagons of palladium diselenide. Rather than being flat, the material is puckered. The top image shows this puckered structure with blue palladium atoms and gold selenium atoms. The puckered structure leads to interesting electronic properties. These tiles are promising building blocks for air-stable electronics, photonics, and other technologies. (Image: Oak Ridge National Laboratory)
The unique structure of the material results in beneficial properties. It has fast-moving electrons. Also, it is stable in air. Other 2-D semiconductors are not stable in air. These properties may enable advanced uses in detectors, solar cells, and transistors. Further, this material could advance superconductivity for electrical flow without losses, piezoelectric sensors, and energy-efficient computing.
Most 2-D crystals studied to date are a lattice of hexagons—for example, graphene, transition metal dichalcogenides, and black phosphorus—and the lattice layers may be planar or puckered. Theory predicted a family of 2-D crystalline materials with lattices made of pentagonal “tiles.” Sheets of pentagons are unusual even in nature.
Now, a team led by Oak Ridge National Laboratory has proven experimentally the existence of one member of this family (Journal of the American Chemical Society, „PdSe2: Pentagonal 2D layers with high air stability for electronics”).
The researchers used bulk crystals made by a group from Nanyang Technological University; they exfoliated the crystals to obtain puckered layers of PdSe2. Using high-resolution scanning transmission electron microscopy, they characterized layers having different thicknesses. Micro-absorption optical spectroscopy, Raman spectroscopy, and first-principles calculations showed layer thickness changed the band gap.
The band gap is the energy range in a solid at which electronic states cannot exist. The thickness changed the band gap from 0 in the bulk (multiple layers) to 1.3 electron volts in single monolayers.
That finding paves the way for pentagonal 2-D materials with tunable band gaps, which may bring new capabilities to electronics and photonics. Most 2-D materials have highly symmetric lattices and, as a result, exhibit isotropic behavior—that is, a physical property has the same value when measured in different directions. In contrast, pentagonal 2-D PdSe2 is anisotropic—meaning property values differ when measured in different directions.
Pentagonal 2-D materials may allow a new degree of freedom for designing conceptually new optoelectronic and electronic devices not possible using other 2-D materials. Moreover, the material is stable in air, which is not true of many other 2-D semiconductors. For example, it is less susceptible to oxidation than black phosphorus, another promising 2-D material with a tunable band gap.
The discovery of additional puckered pentagonal building blocks may advance applications in low-energy optoelectronics, piezoelectrics, thermoelectrics, and spintronics.
Source: U.S. Department of Energy, Office of Science

Buretele de carbon durabil din lemn ar putea fi viitorul senzorilor care pot fi purtați, tratamentul poluant(Durable wood carbon sponge could be the future of wearable sensors, pollutant treatment)

au demonstrat pentru prima data ca lemnul poate fi transformat direct intr-un burete de carbon capabil sa reziste la compresia repetata si alte conditii mecanice extreme;Procesul nostru de a crea burete de carbon din lemn este unic pentru că păstrăm structura lemnului, ceea ce face ca buretele să fie foarte compresibil și rezistent la stres, ceea ce înseamnă că performanța buretului de lemn este unul dintre cele mai bune dintre toate materialele ușoare și comprimabile materiale carbonice raportate vreodată

Posted: Mar 01, 2018

Durable wood carbon sponge could be the future of wearable sensors, pollutant treatment

(Nanowerk News) Engineers at the University of Maryland, College Park (UMD) have for the first time demonstrated that wood can be directly converted into a carbon sponge capable of enduring repeated compression and other extreme mechanical conditions. The UMD engineers’ wood carbon sponge overcomes several limiting factors of other lightweight, compressible carbon sponges because it is simpler, less expensive, and more sustainable to produce. The new sponge can be used in various applications such as energy storage (e.g., batteries), pollutant treatment, and electronic devices and sensors.
A peer-reviewed paper about the research was published March 1 in the journal Chem („Scalable and Sustainable Approach toward Highly Compressible, Anisotropic, Lamellar Carbon Sponge”).
text
Most lightweight, compressible carbon sponges are made from raw materials that are usually unrenewable fossil resources–such as graphene–and by a complicated fabrication process that involves multiple steps and environmentally unfriendly chemicals. In contrast, the UMD researchers use a simple chemical process to transform balsa wood, a choice biomass-based material that is both renewable and abundant.
„Our results reveal that rigid and incompressible balsa can be made highly compressible by a chemical treatment and carbonization process, yielding a wood carbon sponge with mechanical compressibility and fatigue resistance and electrical response sensitivity surpassing those of most reported compressible carbonaceous materials,” says corresponding author Liangbing Hu, associate professor of materials science and engineering at UMD’s A. James Clark School of Engineering.
Hu and colleagues achieved the bendable yet resilient architecture of the wood carbon sponge by using common chemicals to destroy the stiff hemicellulose and lignin fibers that maintain the normal cell-wall structure of balsa wood, then heating the treated wood to 1,000C in order to turn the organic material into carbon alone. The net effect of the process was to collapse the repeated, regular, rectangular pockets typical of the microstructure of balsa and other woods and replace them with a stack of wavy, interlocking, arch-like carbon sheets, likened by Hu to a cross between a coiled spring and a honeycomb.
Normal carbonized wood–obtained from only the heating step without any chemical modifications–is so fragile that any reasonable applied force pulverizes it irreversibly into ash and dust. However, the wood carbon sponge withstood and rebounded from substantial compression for up to 10,000 consecutive trials before deformation set in. Such a performance initially surprised the research team.
„Our process for creating the wood carbon sponge is unique because we preserve the structure of the wood. This makes the sponge highly compressible and resistant to stress. This means the performance of our wood carbon sponge is one of the best among all lightweight and compressible carbonaceous materials ever reported,” says lead author Chaoji Chen, postdoctoral researcher at UMD’s A. James Clark School of Engineering.
After conducting further mechanical and electrical tests on the sponge, the researchers were able to incorporate a slice of it into a strain sensor prototype suitable for attachment to a human finger, a quality desirable for use in wearable fitness or health-monitoring electronics.
The researchers believe that the wood carbon sponge could also be incorporated into water purification devices and energy storage and conversation technologies, such as supercapacitors and rechargeable batteries. „The abundant applications illustrate the value of a strategy that explores the hidden potentials of natural materials, such as trees, by drawing inspiration from other natural structures and sources,” Hu says.
Source: University of Maryland