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Xijun Wang, Zhaowu Wang, Guozhen Zhang, Jun Jiang
Oxygen vacancy defect in monoclinic VO2 has been shown to modulate the metal-insulator transition (MIT) at room temperature. However, as the electronic and structural reorganizations occur simultaneously, the origin of MIT is still unclear. Here we performed first-principles calculations to examine electronic variations separately from structural reorganizations during MIT. It is found that oxygen defect induces electronic reorganization by creating polarized 3d-orbitial electrons, while structure reorganization makes the conduction band edge states available for occupation...
June 21, 2017: Journal of Physical Chemistry Letters
Hong Zhang, Jie Jiang, Na Li, Ming Li, Yingying Wang, Jing He, Hong You
A variant of dielectric-barrier discharge named surface desorption dielectric-barrier discharge ionization (SDDBDI) mass spectrometry was developed for high-efficiency ion transmission and high spatial resolution imaging. In SDDBDI, a tungsten nanotip and the inlet of the mass spectrometer are used as electrodes, and a piece of cover slip is used as a sample plate as well as an insulating dielectric barrier, which simplifies the configuration of instrument and thus the operation. Different from volume dielectric-barrier discharge (VDBD), the microdischarges are generated on the surface at SDDBDI, and therefore the plasma density is extremely high...
June 21, 2017: Analytical Chemistry
Michael J Klein, Gabriel M Veith, Arumugam Manthiram
Rational design of conductive carbon hosts for high energy density lithium-sulfur batteries requires an understanding of the fundamental limitations to insulating active material loading. In this work, we investigate the electrochemistry of lithium sulfide films ranging in thickness from 30 to 3500 nm. We show that films thicker than approximately 40 nm cannot be charged at local charge densities above 1 μA cm-2, and by implication, the maximum useful pore diameter is near 60 nm in a practical cathode. 'Activation' overpotentials for Li2S are identified in thicker films, resulting from polysulfide generation, but are shown not to improve the fundamental areal charge limitations...
June 21, 2017: Journal of the American Chemical Society
K T Law, Patrick A Lee
1T-TaS2 is unique among transition metal dichalcogenides in that it is understood to be a correlation-driven insulator, where the unpaired electron in a 13-site cluster experiences enough correlation to form a Mott insulator. We argue, based on existing data, that this well-known material should be considered as a quantum spin liquid, either a fully gapped [Formula: see text] spin liquid or a Dirac spin liquid. We discuss the exotic states that emerge upon doping and propose further experimental probes.
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
Tao Du, Yue-Xun Li, Yan Li, He-Lin Lu, Hui Zhang
The dimerized Kane-Mele model with/without the strong interaction is studied using analytical methods. The boundary of the topological phase transition of the model without strong interaction is obtained. Our results show that the occurrence of the transition only depends on dimerized parameter α . From the one-particle spectrum, we obtain the completed phase diagram including the quantum spin Hall (QSH) state and the topologically trivial insulator. Then, using different mean-field methods, we investigate the Mott transition and the magnetic transition of the strongly correlated dimerized Kane-Mele model...
June 20, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Fatemeh Behrouznejad, Cheng-Min Tsai, Sudhakar Narra, Eric W-G Diau, Nima Taghavinia
Solar cells with high-efficiency, low-cost and high-stability are the target for the new generation of solar cells. A fully printable perovskite (CH3NH3PbI3) solar cell (PSC) with device architecture FTO/TiO2/Al2O3/NiOx/C is fabricated in the current research as a low-cost and relatively stable structure and is investigated to determine how different fabrication factors such as the thickness of the insulating spacer layer (Al2O3) or treatments such as heat and UV-O3 treatments can affect the interfacial properties of this multi-layer mesoporous structure...
June 20, 2017: ACS Applied Materials & Interfaces
Haolun Wang, Xuan Zhang, Ning Wang, Yan Li, Xue Feng, Ya Huang, Chunsong Zhao, Zhenglian Liu, Minghao Fang, Gang Ou, Huajian Gao, Xiaoyan Li, Hui Wu
Ultralight and resilient porous nanostructures have been fabricated in various material forms, including carbon, polymers, and metals. However, the development of ultralight and high-temperature resilient structures still remains extremely challenging. Ceramics exhibit good mechanical and chemical stability at high temperatures, but their brittleness and sensitivity to flaws significantly complicate the fabrication of resilient porous ceramic nanostructures. We report the manufacturing of large-scale, lightweight, high-temperature resilient, three-dimensional sponges based on a variety of oxide ceramic (for example, TiO2, ZrO2, yttria-stabilized ZrO2, and BaTiO3) nanofibers through an efficient solution blow-spinning process...
June 2017: Science Advances
S Faezeh Mousavi, Rahman Nouroozi, Giuseppe Vallone, Paolo Villoresi
Recent studies demonstrated that the optical channels encoded by Orbital Angular Momentum (OAM) are capable candidates for improving the next generation of communication systems. OAM states can enhance the capacity and security of high-dimensional communication channels in both classical and quantum regimes based on optical fibre and free space. Hence, fast and precise control of the beams encoded by OAM can provide their commercial applications in the compatible communication networks. Integrated optical devices are good miniaturized options to perform this issue...
June 19, 2017: Scientific Reports
Kanako Kumamoto, Tokuichi Iguchi, Ryuichi Ishida, Takuya Uemura, Makoto Sato, Shinji Hirotsune
The robust axonal growth and regenerative capacities of young neurons decrease substantially with age. This developmental downregulation of axonal growth may facilitate axonal pruning and neural circuit formation but limits functional recovery following nerve damage. While external factors influencing axonal growth have been extensively investigated, relatively little is known about the intrinsic molecular changes underlying the age-dependent reduction in regeneration capacity. We report that developmental downregulation of LIS1 is responsible for the decreased axonal extension capacity of mature dorsal root ganglion (DRG) neurons...
June 19, 2017: Biology Open
M Canillas, B Moreno, E Chinarro, A M Rajnicek
TiO2 is proposed here for the first time as a substrate for neural prostheses that involve electrical stimulation. Several characteristics make TiO2 an attractive material: Its electrochemical behaviour as an insulator prevents surface changes during stimulation. Hydration creates -OH groups at the surface, which aid cell adhesion by interaction with inorganic ions and macromolecules in cell membranes. Its ability to neutralize reactive oxygen and nitrogen species that trigger inflammatory processes confers biocompatibility properties in dark conditions...
October 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Lizhi Zhang, Feng Zhai, Kyung-Hwan Jin, Bin Cui, Bing Huang, Zhiming Wang, JunQiang Lu, Feng Liu
Tunable spin transport in nano devices is highly desirable to spintronics. Here, we predict existence of quantum spin Hall effects and tunable spin transport in As-graphane, based on first-principle density functional theory and tight binding calculations. Monolayer As-graphane is constituted by using As adsorbing on graphane with honeycomb H vacancies. Owing to the surface strain, monolayer As-graphane nanoribbons will self-bend toward the graphane side. The naturally curved As-graphane nanoribbons then exhibit unique spin transport properties, distinctively different from the flat ones, which is a two-dimensional topological insulator...
June 19, 2017: Nano Letters
Michael Parizh, Yuri Lvovsky, Michael Sumption
Magnetic Resonance Imaging (MRI), a powerful medical diagnostic tool, is the largest commercial application of superconductivity. The superconducting magnet is the largest and most expensive component of an MRI system. The magnet configuration is determined by competing requirements including optimized functional performance, patient comfort, ease of siting in a hospital environment, minimum acquisition and lifecycle cost including service. In this paper, we analyze conductor requirements for commercial MRI magnets beyond traditional NbTi conductors, while avoiding links to a particular magnet configuration or design decisions...
January 2017: Superconductor Science & Technology
Greta Smedje, Juan Wang, Dan Norbäck, Håkan Nilsson, Karin Engvall
PURPOSE: To investigate the relationships between symptoms compatible with the sick building syndrome (SBS) in adults and building dampness and ventilation in single-family houses. METHODS: Within the Swedish BETSI study, a national sample of single-family houses were inspected by professional building experts, and adults living in the houses answered a questionnaire on SBS. Relationships between building factors and SBS were analysed using logistic regression. RESULTS: Of the respondents, 23% reported having had weekly SBS symptoms during the last three months...
June 17, 2017: International Archives of Occupational and Environmental Health
H Geng, W Luo, W Y Deng, L Sheng, R Shen, D Y Xing
The surface states of three-dimensional topological insulators possess the unique property of spin-momentum interlocking. This property gives rise to the interesting inverse Edelstein effect (IEE), in which an applied spin bias μ is converted to a measurable charge voltage difference V. We develop a semiclassical theory for the IEE of the surface states of Bi2Se3 thin films, which is applicable from the ballistic regime to diffusive regime. We find that the efficiency of the spin-charge conversion, defined as γ = V/μ, exhibits a universal dependence on the ratio between sample size and electron mean free path...
June 16, 2017: Scientific Reports
Alexandros Vegiopoulos, Maria Rohm, Stephan Herzig
Adipose tissue represents a critical component in healthy energy homeostasis. It fulfills important roles in whole-body lipid handling, serves as the body's major energy storage compartment and insulation barrier, and secretes numerous endocrine mediators such as adipokines or lipokines. As a consequence, dysfunction of these processes in adipose tissue compartments is tightly linked to severe metabolic disorders, including obesity, metabolic syndrome, lipodystrophy, and cachexia. While numerous studies have addressed causes and consequences of obesity-related adipose tissue hypertrophy and hyperplasia for health, critical pathways and mechanisms in (involuntary) adipose tissue loss as well as its systemic metabolic consequences are far less understood...
June 16, 2017: EMBO Journal
Agnes Lewden, Manfred R Enstipp, Baptiste Picard, Tessa van Walsum, Yves Handrich
Marine endotherms living in cold water face an energetically challenging situation. Unless properly insulated these animals will lose heat rapidly. The field metabolic rate of king penguins at sea is about twice that on land. However, when at sea, their metabolic rate is higher during extended resting periods at the surface than during foraging, when birds descend to great depth in pursuit of their prey. This is most likely explained by differences in thermal status. During foraging peripheral vasoconstriction leads to a hypothermic shell, which is rewarmed during extended resting bouts at the surface...
June 16, 2017: Journal of Experimental Biology
Jing Kong, Emil Proynov, Jianguo Yu, Ruth Pachter
The linear chain of hydrogen atoms, a basic prototype for the transition from metal to Mott insulator, is studied with a recent density functional theory model functional for nondynamic and strong correlation. The computed cohesive energy curve for the transition agrees well with accurate literature results. The variation of the electronic structure in this transition is characterized with a density-functional descriptor that yields atomic population of effectively localized electrons. These new methods are also applied to the study of the Peierls dimerization of the stretched even-spaced Mott insulator to a chain of H2 molecules, a different insulator...
June 16, 2017: Journal of Physical Chemistry Letters
Bitan Roy, Yahya Alavirad, Jay D Sau
We investigate the phase diagram of a three-dimensional, time-reversal symmetric topological superconductor in the presence of charge impurities and random s-wave pairing. Combining complimentary field theoretic and numerical methods, we show that the quantum phase transition between two topologically distinct paired states (or thermal insulators), described by thermal Dirac semimetal, remains unaffected in the presence of sufficiently weak generic randomness. At stronger disorder, however, these two phases are separated by an intervening thermal metallic phase of diffusive Majorana fermions...
June 2, 2017: Physical Review Letters
Siddhardh C Morampudi, Ari M Turner, Frank Pollmann, Frank Wilczek
We show that neutral anyonic excitations have a signature in spectroscopic measurements of materials: The low-energy onset of spectral functions near the threshold follows universal power laws with an exponent that depends only on the statistics of the anyons. This provides a route, using experimental techniques such as neutron scattering and tunneling spectroscopy, for detecting anyonic statistics in topologically ordered states such as gapped quantum spin liquids and hypothesized fractional Chern insulators...
June 2, 2017: Physical Review Letters
Jamo Momand, Ruining Wang, Jos E Boschker, Marcel A Verheijen, Raffaella Calarco, Bart J Kooi
Phase-change materials based on GeSbTe show unique switchable optoelectronic properties and are an important contender for next-generation non-volatile memories. Moreover, they recently received considerable scientific interest, because it is found that a vacancy ordering process is responsible for both an electronic metal-insulator transition and a structural cubic-to-trigonal transition. GeTe-Sb2Te3 based superlattices, or specifically their interfaces, provide an interesting platform for the study of GeSbTe alloys...
June 16, 2017: Nanoscale
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