8,092 research outputs found

    Liquid Crystal-Solid Interface Structure at the Antiferroelectric-Ferroelectric Phase Transition

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    Total Internal Reflection (TIR) is used to probe the molecular organization at the surface of a tilted chiral smectic liquid crystal at temperatures in the vicinity of the bulk antiferroelectric-ferroelectric phase transition. Data are interpreted using an exact analytical solution of a real model for ferroelectric order at the surface. In the mixture T3, ferroelectric surface order is expelled with the bulk ferroelectric-antiferroelectric transition. The conditions for ferroelectric order at the surface of an antiferroelectric bulk are presented

    The 7-channel FIR HCN Interferometer on J-TEXT Tokamak

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    A seven-channel far-infrared hydrogen cyanide (HCN) laser interferometer has been established aiming to provide the line integrated plasma density for the J-TEXT experimental scenarios. A continuous wave glow discharge HCN laser designed with a cavity length 3.4 m is used as the laser source with a wavelength of 337 {\mu}m and an output power up to 100 mW. The system is configured as a Mach-Zehnder type interferometer. Phase modulation is achieved by a rotating grating, with a modulation frequency of 10 kHz which corresponds to the temporal resolution of 0.1 ms. The beat signal is detected by TGS detector. The phase shift induced by the plasma is derived by the comparator with a phase sensitivity of 0.06 fringe. The experimental results measured by the J-TEXT interferometer are presented in details. In addition, the inversed electron density profile done by a conventional approach is also given. The kinematic viscosity of dimethyl silicone and vibration control is key issues for the system performance. The laser power stability under different kinematic viscosity of silicone oil is presented. A visible improvement of measured result on vibration reduction is shown in the paper.Comment: conference (15th-International Symposium on Laser-Aided Plasma Diagnostics

    Ultrathin MgB2 films fabricated on Al2O3 substrate by hybrid physical-chemical vapor deposition with high Tc and Jc

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    Ultrathin MgB2 superconducting films with a thickness down to 7.5 nm are epitaxially grown on (0001) Al2O3 substrate by hybrid physical-chemical vapor deposition method. The films are phase-pure, oxidation-free and continuous. The 7.5 nm thin film shows a Tc(0) of 34 K, which is so far the highest Tc(0) reported in MgB2 with the same thickness. The critical current density of ultrathin MgB2 films below 10 nm is demonstrated for the first time as Jc ~ 10^6 A cm^{-2} for the above 7.5 nm sample at 16 K. Our results reveal the excellent superconducting properties of ultrathin MgB2 films with thicknesses between 7.5 and 40 nm on Al2O3 substrate.Comment: 7 pages, 4 figures, 2 table

    New radiocarbon evidence on early rice consumption and farming in South China

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    While the possibility of indigenous rice cultivation cannot be entirely ruled out, there is increasing evidence suggesting that rice farming was introduced to South China during the late-Holocene. However, determination of the exact timing of the spread of rice farming to South China is fraught with the lack of reliable radiocarbon dates. In this article, we present 15 new AMS 14C dates of charred plant remains recovered from late-Holocene sites of Shixia and Guye in Guangdong Province of South China. Our new AMS 14C dates suggest a later arrival of rice farming in the Pearl River Delta than previously thought. These new AMS 14C dates will shed new lights to an improved understanding of the environmental background and ecology of the southward spread of rice farming

    Microstructure of Injection Moulding Machine Mould Clamping Mechanism: Design and Motion Simulation

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    With the advent of intelligence technologies, more and more machines and devices are involved in the creation of complex structures. In the intelligent manufacturing industries, mouldings including injection moulding, blow moulding, compression moulding, and others play critical roles in manufacturing highly precise parts required for building intelligent machines (such as computers, cell phones, robots etc.). The performance of the clamping mechanism directly affects the quality of the microstructure of injection products. The design of the injection moulding mould clamping mechanism is based on the microstructure characteristics of the trip of the toggle lever mechanism ratio, speed ratio, and force amplification ratio. These are used to study the main performance parameters, such as analysis, as well as for the establishment of the physical model of the clamping mechanism. The model is based on the microstructure of injection of hyperbolic elbow clamping mechanism kinematics simulation. Simulation results and theoretical calculation contrast analysis show that the maximum dynamic template speed is 215.34 mm/s. The dynamic templates and cross-head speed ratio is 2.15; therefore, the design of the injection moulding mould clamping mechanism for the microstructure provides favourable technical support. The method described here is important to build complicated moulds required to build highly precise parts to build intelligent machineries

    Mapping QTLs for mineral element contents in brown and milled rice using an Oryza sativa × O. rufipogon backcross inbred line population

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    Biofortifying food crops with essential minerals would help to alleviate mineral deficiencies in humans. Detection of quantitative trait loci (QTLs) for mineral nutrient contents in rice was conducted using backcross inbred lines derived from an interspecific cross of Oryza sativa × O. rufipogon. The population was grown in Hangzhou and Lingshui, with the contents of Mg, Zn, Fe, Mn, Cu and Se in brown rice measured in both trials and that in milled rice tested in Hangzhou only. A total of 24 QTLs for mineral element contents were identified, including two for both the brown and milled rice, 17 for brown rice only, and five for milled rice only. All the seven QTLs detected for the mineral contents in milled rice and 13 of the 19 QTLs for the contents in brown rice had the enhancing alleles derived from O. rufipogon. Fifteen QTLs were clustered in seven chromosomal regions, indicating that common genetic-physiological mechanisms were involved for different mineral nutrients and the beneficial alleles could be utilized to improve grain nutritional quality by markerassisted selection

    Enhancement of Transition Temperature in FexSe0.5Te0.5 Film via Iron Vacancies

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    The effects of iron deficiency in FexSe0.5Te0.5 thin films (0.8<x<1) on superconductivity and electronic properties have been studied. A significant enhancement of the superconducting transition temperature (TC) up to 21K was observed in the most Fe deficient film (x=0.8). Based on the observed and simulated structural variation results, there is a high possibility that Fe vacancies can be formed in the FexSe0.5Te0.5 films. The enhancement of TC shows a strong relationship with the lattice strain effect induced by Fe vacancies. Importantly, the presence of Fe vacancies alters the charge carrier population by introducing electron charge carriers, with the Fe deficient film showing more metallic behavior than the defect-free film. Our study provides a means to enhance the superconductivity and tune the charge carriers via Fe vacancy, with no reliance on chemical doping.Comment: 15 pages, 4 figure

    Genetic diversity and relationships among cabbage (Brassica oleracea var. capitata) landraces in China revealed by AFLP markers

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    Genetic diversity and relationships among Chinese traditional cabbage landraces have not yet been well investigated. To explore the diversity, 83 landraces originating in Northern China, Southern China, Eastern Europe, Western Europe as well as other countries were evaluated by using AFLP markers. Results indicated that cabbage landraces exhibited a relatively low level of diversity. Among the 575 markers, 41.9% were polymorphic with an average PIC value of 0.354. Unweighted pair group method with arithmetic averages (UPGMA) cluster and population structure analysis consistently divided all landraces into two major groups reflecting geographic origins. Group 1 was a distinct group comprised of Northern China landraces and Eastern European landraces, whereas Group 2 was comprised of populations of Southern China landraces, Western European populations and other countries. Landraces with varied maturing times or head types could not be distinguished based on molecular data. The Northern China population was closely allied to the Eastern Europe population (D = 0.037). The integration of our data with historical documents confirmed that traditional cabbage landraces cultivated in North of China were first introduced from Russia.Key words: Amplified fragment length polymorphism (AFLP), genetic diversity, cabbage (Brassica oleracea var. capitata), landraces, population structure

    Effects of the sintering atmosphere on the superconductivity of SmFeAsO1-xFx compounds

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    A series of SmFeAsO1-xFx samples were sintered in quartz tubes filled with air of different pressures. The effects of the sintering atmosphere on the superconductivity were systematically investigated. The SmFeAsO1-xFx system maintains a transition temperature (Tc) near 50 K until the concentration of oxygen in quartz tubes increases to a certain threshold, after which Tc decreases dramatically. Fluorine losses, whether due to vaporization, reactions with starting materials, and reactions with oxygen, proved to be detrimental to the superconductivity of this material. The deleterious effects of the oxygen in the sintering atmosphere were also discussed in detail.Comment: 9 pages, 5 figure
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