Yury Gogotsi

Bio: Yury Gogotsi is an academic researcher from Drexel University. The author has contributed to research in topics: MXenes & Carbon. The author has an hindex of 171, co-authored 956 publications receiving 144520 citations. Previous affiliations of Yury Gogotsi include Qatar Airways & Clemson University.

Materials science: Energy storage wrapped up

Abstract: Cables and wires are used to conduct electricity, but can they also store energy? The answer is a resounding 'yes', if they are encased by a supercapacitor device — a finding that might open up many applications.

Raman microspectroscopy of nanocrystalline and amorphous phases in hardness indentations

Abstract: During hardness indentation, materials are subjected to highly l highly localized stresses. These stresses not only cause crack formation and plastic deformation by dislocation gliding, but a complete change of the crystal structure and formation of amorphous phases or high-pressure polymorphs can occur in the zone of maximum contact stresses. Such contact-induced phase transformations were observed in hard and brittle materials including semiconductors (Si, Ge, GaAs and InSb) and common ceramic materials such as SiC and SiO2 (α-quartz and silica glass). A prime tool for their investigation is the Raman microspectroscopy of hardness indentations. In Si and Ge, there is an initial transformation to metallic high-pressure phases upon hardness indentation and a subsequent formation of crystalline, nanocrystalline, or amorphous phases depending on the conditions of the hardness test, in particular the unloading rate. A phase transformation occurs also in InSb, whereas the results for GaAs do not give sufficient evidence for phase transformations. Indentation-induced amorphization has been observed in SiC and quartz. Even diamond has been shown to undergo amorphization and phase transformation under nonhydrostatic stress conditions imposed by indentation tests. Copyright © 1999 John Wiley & Sons, Ltd.

Transformation of diamond to graphite

Abstract: Despite almost forty years of trying, no one has managed to transform diamond into graphite under pressure1, or find out what the pressure limit for diamond might be2. If diamond were to behave like other group IV elements, such as silicon, germanium or tin, it would transform under compressive indentation to the β-tin structure3, but it does not2,4. Here we use micro-Raman spectroscopy to determine what happens to diamond when it is subjected to high contact compression as a result of pressing a sharp diamond indenter against its surface4. We find that, under this non-hydrostatic compression, diamond at the point of indentation is transformed into disordered graphite. This discovery may eventually lead to the more efficient machining of diamond.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Materials for electrochemical capacitors

Abstract: Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.