633 research outputs found
Hydrogenation and Hydro-Carbonation and Etching of Single-Walled Carbon Nanotubes
We present a systematic experimental investigation of the reactions between
hydrogen plasma and single-walled carbon nanotubes (SWNTs) at various
temperatures. Microscopy, infrared (IR) and Raman spectroscopy and electrical
transport measurements are carried out to investigate the properties of SWNTs
after hydrogenation. Structural deformations, drastically reduced electrical
conductance and increased semiconducting nature of SWNTs upon sidewall
hydrogenation are observed. These changes are reversible upon thermal annealing
at 500C via dehydrogenation. Harsh plasma or high temperature reactions lead to
etching of nanotube likely via hydro-carbonation. Smaller SWNTs are markedly
less stable against hydro-carbonation than larger tubes. The results are
fundamental and may have implications to basic and practical applications
including hydrogen storage, sensing, band-gap engineering for novel electronics
and new methods of manipulation, functionalization and etching of nanotubes.Comment: 3 pages, 4 figure
Long Range Intrinsic Ferromagnetism in Two Dimensional Materials and Dissipationless Future Technologies
The inherent susceptibility of low-dimensional materials to thermal
fluctuations has long been expected to poses a major challenge to achieving
intrinsic long-range ferromagnetic order in two-dimensional materials. The
recent explosion of interest in atomically thin materials and their assembly
into van der Waals heterostructures has renewed interest in two-dimensional
ferromagnetism, which is interesting from a fundamental scientific point of
view and also offers a missing ingredient necessary for the realization of
spintronic functionality in van der Waals heterostructures. Recently several
atomically thin materials have been shown to be robust ferromagnets. Such
ferromagnetism is thought to be enabled by magneto crystalline anisotropy which
suppresses thermal fluctuations. In this article, we review recent progress in
two-dimensional ferromagnetism in detail and predict new possible
two-dimensional ferromagnetic materials. We also discuss the prospects for
applications of atomically thin ferromagnets in novel dissipationless
electronics, spintronics, and other conventional magnetic technologies.
Particularly atomically thin ferromagnets are promising to realize time
reversal symmetry breaking in two-dimensional topological systems, providing a
platform for electronic devices based on the quantum anomalous Hall Effect
showing dissipationless transport. Our proposed directions will assist the
scientific community to explore novel two-dimensional ferromagnetic families
which can spawn new technologies and further improve the fundamental
understanding of this fascinating area.Comment: To be appear in Applied Physics Review
Impact of North Korean nuclear weapons test on 3 September, 2017 on inland China traced by C-14 and I-129
Environmental impact of North Korea nuclear weapons testing on 3 Sept, 2017, is of key concern. In order to investigate whether there is radioactive leakage and whether it can be transported to inland China, C-14 and I-129 are determined in aerosol samples collected in a Chinese inland city before and after the test. Aerosol Delta C-14 values before and after the test do not show any significant difference. In contrast, a four-fold increase of I-129/I-127 ratios was found after the test. The possible sources of I-129 in these atmospheric samples and the impact of the North Korea nuclear test are discussed
Rapid determination of long-lived radionuclides using accelerator mass spectrometry measurement without chemical preparation
Spin in the abstracts of randomized controlled trials in periodontology and oral implantology: A cross‐sectional analysis
Accelerator Mass Spectrometry Analysis of Ultra-Low-Level <sup>129</sup>I in Carrier-Free AgI-AgCl Sputter Targets
Separation of carrier-free iodine from low-level iodine samples and accurate measurement of ultra-low-level I-129 in microgram iodine target are essential but a bottleneck in geology and environment research using naturally produced I-129. This article presents a detection technique of accelerator mass spectrometry (AMS) for accurate determination of ultra-low-level I-129 in carrier-free AgI-AgCl sputter targets. Copper instead of aluminum was selected as the suitable sample holder material to avoid the reaction of AgI-AgCl powder with aluminum. Niobium powder was selected as thermally and electrically conductive matrix to be mixed with AgI-AgCl powder, in order to obtain and maintain a stable and high iodine ion current intensity, as well as less memory effect and low background level of I-129. The most optimal ratio of the Nb matrix to the AgI-AgCl powder was found to be 5:1 by mass. The typical current of I-127(5+) using AgI-AgCl targets with iodine content from 5 to 80 mu g was measured to be 5 to 100 nA. Four-year AMS measurements of the I-129/I-127 ratios in standards of low iodine content and the machine blanks showed a good repeatability and stability.</p
Antioxidant and anti-dyslipidemic effects of polysaccharidic extract from sea cucumber processing liquor
Sea cucumber is a seafood of high nutritional value. During its processing, sea cucumber processing liquor is routinely produced, which is usually discarded as waste. The chemical composition of this processing liquor is similar to sea cucumbers themselves. Hence, valuable ingredients, such as functional polysaccharides, could be obtained from them. Results Biologically active polysaccharides from sea cucumber processing liquor were extracted through protease hydrolysis and electroosmosis. The analysis revealed that the polysaccharide extract from sea cucumber processing liquor (PESCPL) is predominantly composed of mannose, in addition to some glucose and fucose. The antioxidant activity of PESCPL was analyzed using in vitro. It was demonstrated that PESCPL could effectively scavenge 1,1-diphenyl-2-picrylhydrazyl radicals, hydroxyl radicals, and superoxide anion radicals. The effect of PESCPL was investigated in vivo by using mice model fed with high-fat diets with/without PESCPL supplement. It was shown that PESCPL could increase the catalase and superoxide dismutase activity in the serum and decrease serum malonaldehyde content. Furthermore, mice fed with PESCPL diet showed a considerable decrease in the serum cholesterol and triglyceride levels and an increase in high-density lipoprotein cholesterol levels. Conclusions Our research highlights that PESCPL is a natural antioxidant and could be utilized as a therapeutic supplement for dyslipidemia
Optimization Design of IGV Profile in Centrifugal Compressor
Variable inlet guide vane (IGV) is used to control the mass flow and generate prewhirl in centrifugal compressors. The efficient operation of IGV is limited to the range of aerodynamic characteristics of their vane profiles. In order to find out the best vane profile for IGV regulation, the modern optimization method was adopted to optimize the inlet guide vane profile. The main methodology idea was to use artificial neural network for continuous fitness evaluation and use genetic algorithm for global optimization. After optimization, the regulating performance of IGV has improved significantly, the prewhirl ability has been enhanced greatly, and the pressure loss has been reduced. The mass flow and power of compressor reduced by using the optimized guide vane at large setting angles, and the efficiency increased significantly; the flow field distribution has been improved obviously, since the nonuniform distribution of flow and flow separation phenomenon greatly weakened or even completely disappeared. The achievement of this research can effectively improve the regulation ability of IGV and the performance of compressor
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