Isobaric analogue resonances in71As through proton elastic scattering on70Ge

The analogues of the low-lying levels in⁷¹Ge have been observed as resonances in the compound nucleus⁷¹As through proton elastic scattering on⁷⁰Ge in the energy rangeE _p=3.5 to 5.3 MeV. The excitation functions cover the analogue resonances corresponding to states upto 2.3 MeV excitation in⁷¹Ge. The sub-structures in the 5.06 MeV resonance, first observed by Temmer and co-workers have been confirmed in the present experiment. The present investigation reveals similar sub-structures in the 4.13 MeV resonance lending further support to the existence of intermediate structure near an isobaric analogue resonance. The resonance parameters and the spectroscopic factors (for the corresponding parent states) have been extracted. The results are compared with the information available from the⁷⁰Ge(d, p)⁷¹Ge reaction.     

Neutron scattering by anharmonic crystals and the effect of sublattice displacements

A theory has been given for the scattering of neutrons by anharmonic crystals, for which terms of the typeV ⁽³⁾ (k _1j1; —k _1j1;o _j) which contribute to the sublattice displacements are not neglected. Using the standard perturbation theory in the interaction picture or Green’s function method, an expression has been derived for the differential scattering cross-section which brings in the shift and the width of the phonons in one-phonon energy exchange processes. It is shown that the sublattice displacements will modify the phase factor arising from the scattering by any atom in the unit cell, and the Debye-Waller factor also gets altered both by the sublattice displacements as well as by higher order terms arising from anharmonicity. It is shown that the differential scattering cross-section contains a term linearly depending on the third order anharmonicity coefficientV ⁽³⁾ (k _1j1;k _2j2;k _3j3) and neutron scattering by crystals should provide a useful method for evaluating the third order anharmonicity coefficients.     

显微动态图像分析技术及其在生物物理中的应用

介绍了一种可实时监测细胞生命活动的显微动态图像分析技术。该技术把显微光学成像技术、数字处理技术和动态图像分析技术结合为一体,可实现对活细胞的结构功能、生长过程和环境变化的影响等进行非侵入性连续监测。通过在细胞膜弹性模量测量中的应用表明,该技术不仅原理可靠,实现容易,应用方便,而且检测速度快,测量精度高,稳定性能好。此项技术可望在生物物理学的实验研究中获得广泛的应用。     

First-principles investigations on the mechanical,thermal,electronic,and optical properties of the defect perovskites Cs_2SnX_6(X= Cl,Br, I)

The mechanical properties, thermal properties, electronic structures, and optical properties of the defect perovskites Cs_2SnX_6(X = Cl, Br, I) were investigated by first-principles calculation using PBE and HSE06 hybrid functional. The optic band gaps based on HSE06 are 3.83 eV for Cs_2SnCl_6, 2.36 eV for Cs_2SnBr_6, and 0.92 eV for Cs_2SnI_6, which agree with the experimental results. The Cs_2SnCl_6, Cs_2SnBr_6, and Cs_2SnI_6 are mechanically stable and they are all anisotropic and ductile in nature. Electronic structures calculations show that the conduction band consists mainly of hybridization between the halogen p orbitals and Sn 5s orbitals, whereas the valence band is composed of the halogen p orbitals. Optic properties indicate that these three compounds exhibit good optical absorption in the ultraviolet region, and the absorption spectra red shift with the increase in the number of halogen atoms. The defect perovskites are good candidates for probing the lead-free and high power conversion efficiency of solar cells.     

Mechanical,elastic, anisotropy,and electronic properties of monoclinic phase of m-Si_xGe_(3-x)N_4

The structural,mechanical,elastic anisotropic,and electronic properties of the monoclinic phase of m-Si_3N_4,mSi_2GeN_4,m-SiGe_2N_4,and m-Ge_3N_4are systematically investigated in this work.The calculated results of lattice parameters,elastic constants and elastic moduli of m-Si_3N_4and m-Ge_3N_4are in good agreement with previous theoretical results.Using the Voigt–Reuss–Hill method,elastic properties such as bulk modulus B and shear modulus G are investigated.The calculated ratio of B/G and Poisson’s ratio v show that only m-SiGe_2N_4should belong to a ductile material in nature.In addition,m-SiGe_2N_4possesses the largest anisotropic shear modulus,Young’s modulus,Poisson’s ratio,and percentage of elastic anisotropies for bulk modulus ABand shear modulus AG,and universal anisotropic index AUamong m-Si_xGe_(3-x)N_4(x=0,1,2,3.)The results of electronic band gap reveal that m-Si_3N_4,m-Si_2GeN_4,m-SiGe_2N_4,and m-Ge_3N_4 are all direct and wide band gap semiconducting materials.     

Singular variation property of elastic constants of piezoelectric ceramics shunted to negative capacitance

Piezoelectric shunt damping has been widely used in vibration suppression, sound absorption, noise elimination, etc.In such applications, the variant elastic constants of piezoelectric materials are the essential parameters that determine the performances of the systems, when piezoelectric materials are shunted to normal electrical elements, i.e., resistance,inductance and capacitance, as well as their combinations. In recent years, many researches have demonstrated that the wideband sound absorption or vibration suppression can be realized with piezoelectric materials shunted to negative capacitance. However, most systems using the negative-capacitance shunt circuits show their instabilities in the optimal condition, which are essentially caused by the singular variation properties of elastic constants of piezoelectric materials when shunted to negative capacitance. This paper aims at investigating the effects of negative-capacitance shunt circuits on elastic constants of a piezoelectric ceramic plate through theoretical analyses and experiments, which gives an rational explanation for why negative capacitance shunt circuit is prone to make structure instable. First, the relationships between the elastic constants c_(11), c_(33), c_(55) of the piezoelectric ceramic and the shunt negative capacitance are derived with the piezoelectric constitutive law theoretically. Then, an experimental setup is established to verify the theoretical results through observing the change of elastic constant c_(55) of the shunted piezoelectric plate with the variation of negative capacitance.The experimental results are in good agreement with the theoretical analyses, which reveals that the instability of the shunt damping system is essentially caused by the singular variation property of the elastic constants of piezoelectric material shunted to negative capacitance.     

InOOH压致氢键对称化及其弹性性质

利用第一性原理研究了InOOH在高压下的氢键对称化行为及其对InOOH弹性等性质的影响.结果表明约在18 GPa时InOOH中的氢键发生了对称化转变,导致轴比率b/c对压力的斜率由负值变为正值;压缩弹性常数、非对角弹性常数、体积模量和纵波波速出现异常增加,如体积模量增加了20%—40%.高压下InOOH弹性性质呈现出更加明显的各向异性.常压下InOOH呈现韧性,且伴随着氢键对称化韧性异常增加.对畸变金红石型MOOH(M=Al,In,Ga,Fe,Cr)化合物在高压下的弹性性质转变与氢键性质转变的耦合规律进行了初探.     

First-principles investigation of the effects of strain on elastic thermal,and optical properties of CuGaTe_2

Based on the density functional theory, the influences of strain on structural, elastic, thermal and optical properties of CuGaTe_2 are discussed in detail. It is found that the tensile strain on CuGaTe_2 is beneficial to the decrease of lattice thermal conductivity by reducing the mean sound velocity and Debye temperature. Moreover, all strained and unstrained CuGaTe_2 exhibit rather similar optical characters. But the tensile strain improves the ability to absorb sunlight in the visible range.These research findings can give hints for designing thermoelectric and photovoltaic devices.     

Elastic,vibrational, and thermodynamic properties of Sr_(10)(PO_4)_6F_2 and Ca_(10)(PO_4)_6F_2 from first principles

The electronic, elastic, vibrational, and thermodynamic properties of Sr_(10)(PO_4)_6F_2(Sr-FAP) and Ca_(10)(PO_4)_6F_2(CaFAP) are systematically investigated by the first-principles calculations. The calculated electronic band structure indicates that the Sr-FAP and Ca-FAP are insulator materials with the indirect band gap of 5.273 eV and 5.592 eV, respectively. The elastic constants are obtained by the "stress–strain" method, and elastic modulus are further evaluated and discussed. The vibrational properties, including the phonon dispersion curves, the phonon density of states, the Born effective charge, and associated longitudinal optical and transverse optical(LO–TO) splitting of optical modes, as well as the phonon frequencies at zone-center are obtained within the linear-response approach. Substitution of Ca by Sr causes phonon frequencies to shift to lower values as expected due to the mass effect. Additionally, some phonon-related thermodynamic properties, such as Helmholtz free energy F, internal energy E, entropy S, and specific heat C_V of Sr-FAP and Ca-FAP are predicted with the harmonic approximation. The present calculated results of two apatites are consistent with the reported experimental and theoretical results.     

After-Effects of Electrolytically diffused hydrogen in the second-order elastic coefficient of poynting’s effect in nickel and steel

Summary If hydrogen is diffused electrolytically in a metal, it subsequently escapes out if the metal is left to itself. However this hydrogen-treated metal does not totally regain the original magnitudes of its various physical properties,e. g., thermo e.m.f., electrical resistivity, elastic modulii etc. This effect has also been observed in the second-order elastic effect (the Poynting effect) in nickel and two varieties of steel. Measurements were carried out first before hydrogen diffusion. The samples were electrolytically diffused with hydrogen and the left to themselves for a few days and the measurements were repeated. The changed values of the coefficient of Poynting effect are discussed in terms of the dislocations created by in-and out-going hydrogen. Now retired