Determination of the spin axis in quantum spin Hall insulator monolayer WTe2

Evidence for the quantum spin Hall (QSH) effect has been reported in several experimental systems in the form of approximately quantized edge conductance. However, the most fundamental feature of the QSH effect, spin-momentum locking in the edge channels, has never been demonstrated experimentally. Here, we report clear evidence for spin-momentum locking in the edge channels of monolayer WTe2, thought to be a two-dimensional topological insulator (2D TI). We observe that the edge conductance is controlled by the component of an applied magnetic field perpendicular to a particular axis, which we identify as the spin axis. The axis is the same for all edges, situated in the mirror plane perpendicular to the tungsten chains at 40$\pm$2{\deg} to the layer normal, implying that the spin-orbit coupling is inherited from the bulk band structure. We show that this finding is consistent with theory if the band-edge orbitals are taken to have like parity. We conclude that this parity assignment is correct and that both edge states and bulk bands in monolayer WTe2 share the same simple spin structure. Combined with other known features of the edge states this establishes spin-momentum locking, and therefore that monolayer WTe2 is truly a natural 2D TI

Mitochondrial DNA Evidence for a Diversified Origin of Workers Building Mausoleum for First Emperor of China

Variant studies on ancient DNA have attempted to reveal individual origin. Here, based on cloning sequencing and polymerase chain reaction-restriction fragment length polymorphisms, we analyzed polymorphisms in the first hypervariable region and coding regions of mitochondrial DNA of 19 human bone remains which were excavated from a tomb near the Terra Cotta Warriors and dated some 2,200 years before present. With the aim of shedding light on origins of these samples who were supposed to be workers building the mausoleum for the First Emperor of China, we compared them with 2,164 mtDNA profiles from 32 contemporary Chinese populations at both population and individual levels. Our results showed that mausoleum-building workers may be derived from very diverse sources of origin

BTX from the gas-phase hydrodeoxygenation and transmethylation of guaiacol at room pressure

Biosourced aromatics (benzene toluene xylene (BTX) and phenols) could be obtained by catalytic hydrodeoxygenation (HDO) coupled with transmethylation at atmospheric pressure in a fixed-bed reactor. We choose guaiacol as a model compound to investigate the catalytic HDO over Fe/Ni/HBeta catalyst. The active amount (5%-15%), temperature (250-400 degrees C), and 1/WHSV (1.5-4.0) significantly influenced the hydrogenolysis of the C-aromatic-O bond and transmethylation. The mechanism showed that feed and intermediate products formed the "surface pool" on the catalyst surface, which enabled the HDO reaction by the reduced intermediate species (Z-FeH2+ and Z-NiH+). Fe/Ni/HBeta exhibited good activity for both methyl transfer and HDO. Moreover, the aromatic ring did not undergo catalytic hydrogenation, and most methyl or methoxyl molecules transferred onto the phenolic or benzene ring and remained after deoxygenation. Consequently, carbon loss was minimized, and hydrogen consumption was reduced. (C) 2016 Elsevier Ltd. All rights reserved

Efficient upgrading process for production of low quality fuel from bio-oil

To improve the quality of fast pyrolysis bio-oil, an efficient catalytic upgrading process is proposed with pristine Ni/MgO catalyst and ethanol. Esterification, hydrogenation, alkylation of aromatic ring and depolymerization of lignin -derived pyrolytic oligomers simultaneously occurred in the upgrading process. Esters, ketones and alkyl -substituted aromatic compounds were found to be the main components in the volatile fraction of the upgraded bio-oil. Under the optimal conditions, pH value and HHV (high heating value) of the upgraded bio-oil were 5.01 and 24.9 MJ kg(-1), respectively. This result suggested that the properties of bio-oil could be effectively improved by the catalytic upgrading process. Moreover, carbon efficiency of this upgrading process was relatively high because that formation of coke is suppressed in the upgrading process. (C) 2016 Elsevier Ltd. All rights reserved

Comparison of characterization and adsorption of biochars produced from hydrothermal carbonization and pyrolysis

Two types of rice-husk biochars, hydrothermally produced hydrochar and slow-pyrolysis pyrochar, were produced at different temperatures and were characterized and used as adsorbent material for the removal of methylene blue, iodine, and copper ions from aqueous solution. The characterization results showed that the hydrochars contained higher heating value, volatile matter content, carbon content and oxygen functional groups, and retained lower oxygen content and ash content than the pyrochars. Although the hydrochar retained relatively lower surface area, its adsorption capacity for methylene blue, iodine, and copper ions was much higher than pyrochar due to its ion-exchange and complexation. The adsorption isotherms of copper ions by two types of biochars were well described by the Langmuir and Freundlich models. (C) 2018 Elsevier B.V. All rights reserved

Research and Hardware Implementation of a Reduced-Latency Quadruple-Precision Floating-Point Arctangent Algorithm

In the field of digital signal processing, such as in navigation and radar, a significant number of high-precision arctangent function calculations are required. Lookup tables, polynomial approximation, and single/double-precision floating-point Coordinate Rotation Digital Computer (CORDIC) algorithms are insufficient to meet the demands of practical applications, where both high precision and low latency are essential. In this paper, based on the concept of trading area for speed, a four-step parallel branch iteration CORDIC algorithm is proposed. Using this improved algorithm, a 128-bit quad-precision floating-point arctangent function is designed, and the hardware circuit implementation of the arctangent algorithm is realized. The results demonstrate that the improved algorithm can achieve 128-bit floating-point arctangent calculations in just 32 cycles, with a maximum error not exceeding 2×10−34 rad. It possesses exceptionally high computational accuracy and efficiency. Furthermore, the hardware area of the arithmetic unit is approximately 0.6317 mm2, and the power consumption is about 40.6483 mW under the TSMC 65 nm process at a working frequency of 500 MHz. This design can be well suited for dedicated CORDIC processor chip applications. The research presented in this paper holds significant value for high-precision and rapid arctangent function calculations in radar, navigation, meteorology, and other fields

Highly stable monolithic titanium silicalite-1 catalyst for 1-butene epoxidation

A monolithic titanium silicalite-1 (TS-1) catalyst was prepared by coating TS-1 onto a specially designed stainless-steel support. The catalyst was used in 1-butene epoxidation, a strong exothermic reaction, to produce butene oxide in a fixed-bed reactor. Compared with the traditional extruded TS-1, the monolithic catalyst demonstrates excellent catalytic stability and reusability. To understand the reason for this performance, heat conduction behaviors of the monolithic and extruded catalysts were studied and compared. This was accomplished by firstly developing a kinetic model to determine reaction kinetic parameters, and then simulating the temperature distribution within the reactor. It revealed a much lower temperature-rise over the monolithic catalyst than over the extruded catalyst. This study demonstrates that the stainless-steel support of the monolithic catalyst is effective in dissipating high reaction heat of 1-butene epoxidation, thus limits local temperature-rise within the reactor. This inhibits the formation of channel-blocking byproducts and improves the catalytic stability

Highly stable monolithic titanium silicalite-1 catalyst for 1-butene epoxidation

A monolithic titanium silicalite-1 (TS-1) catalyst was prepared by coating TS-1 onto a specially designed stainless-steel support. The catalyst was used in 1-butene epoxidation, a strong exothermic reaction, to produce butene oxide in a fixed-bed reactor. Compared with the traditional extruded TS-1, the monolithic catalyst demonstrates excellent catalytic stability and reusability. To understand the reason for this performance, heat conduction behaviors of the monolithic and extruded catalysts were studied and compared. This was accomplished by firstly developing a kinetic model to determine reaction kinetic parameters, and then simulating the temperature distribution within the reactor. It revealed a much lower temperature-rise over the monolithic catalyst than over the extruded catalyst. This study demonstrates that the stainless-steel support of the monolithic catalyst is effective in dissipating high reaction heat of 1-butene epoxidation, thus limits local temperature-rise within the reactor. This inhibits the formation of channel-blocking byproducts and improves the catalytic stability