Type B epitaxy of Ge on CaF2(111) surface

It was known experimentally that type B orientation, which is rotated 180° about the [111] axis, dominated the heteroepitaxial growth of Ge(111) on a CaF₂(111) substrate at an elevated temperature. We performed first principles calculations using density functional theory to determine the energetics of the Ge(111)/CaF₂(111) interface and found that the type B orientation of the Ge film is most likely a result of a direct bonding between Ge atoms and Ca²⁺ at the CaF₂ surface with the top F^? layer depleted. Our theoretical prediction is supported by our X-ray diffraction experiments on {111} < 121> biaxially textured Ge/CaF₂ samples.     

Synthesis and Properties of Thermotropic Poly(oxybenzoate-co-oxynaphthoate) Copolyester Modified by a Third AB Type Monomer

Abstract

The synthesis and modification of high performance thermotropic liquid crystal polyesters (TLCP) are still being investigated due to their excellent properties. In this study modification of poly(oxybenzoate-co-oxynaphthoate) (P-HBA/HNA), a random copolymer of 4-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA), by 5?mol% of one of three AB type monomers (AB type monomers are those who have hydroxy and carboxylic end groups), vanillic acid (VA), 4-hydroxyphenylacetic acid (HPA) and 4-hydroxycinnamic acid (HCA), was conducted. The influence of the AB type third monomer on the liquid crystal properties, melting behavior, thermal stability, microstructure and fiber morphology of the resulting modified terpolyesters was comparatively studied relative to the parent copolymer. When 5?mol% of the HBA units were replaced, the resulting terpolyesters had much lower melting temperatures and could be easily melt processed, while the modified terpolyesters exhibited higher melting and glass transition temperatures when 5?mol% of the HNA units were replaced. Weaker melting peaks and larger melting ranges were observed for the modified terpolyesters, attributed to the existence of nonperiodic layer crystallites caused by the modifiers. The obtained terpolyesters showed good thermal stability and could be melt processed in a broad nematic phase temperature region. The molecular chain packing of the modified terpolyesters was almost destroyed by the third AB type reactants. Fibers prepared from the resulting terpolyesters exhibited well developed fibrillar structure and higher orientation factors, indicating that modification of the P-HBA/HNA by using the AB type monomers to improve its properties would be useful.     

Spatially Homogeneous Conformally Stäckel Spaces of Type (3.1)

Russian Physics Journal - In this work, we have obtained all spatially homogeneous space-time models related to the intersection of the set of Stäckel spaces of type (2.1) and the set of...     

Vibrational Spectra of Arsenates and Phosphates of the Type Kcaln(XO4)2

The infrared and Raman spectra of polycrystal-line samples of different compounds of the types KCaLn(AsO₄)₂ and KCaLn(PO₄)₂, belonging to the hexagonal LaPO₄, structural modification, were recorded and discussed. A complete vibrational assignment, based on a factor group analysis, is proposed. The influence of the different lanthanide cations on the internal vibrations of the XO₄ groups is briefly discussed and some comparisons with related compounds are also made.

It is well known that simple lanthanide arsenates, phosphates, vanadates and cnromates (V) of the type LnXO₄ belong to two different structural types.     

Charge/orbital ordering structure of Pr(1-x)Ca(x)MnO(3)(x = 3/8) examined by low-temperature transmission electron microscopy

The structural phase transition of Pr(1-x)Ca(x)MnO(3)(x = 3/8) was investigated by means of low-temperature transmission electron microscopy. Superlattice reflection spots with a modulation wave vector q(1) = (0,1/2,0) appeared below 230 K, indicating formation of the d(3x(2-r(2))/d(3y(2)-r(2)) type of charge/orbital ordering. Below 150 K, a new series of superlattice reflection spots with a modulation wave vector q(2) = (1/4,1/4,1/2) appeared, suggesting an additional ordering of excess 1/8 Mn(3+), necessary due to the deviation of x from 1/2, with the occupation of the d(3z(2-r(2)) type of e(g) orbital.     

Stäckel electrovacuum spaces that admit full separation of variables in a diagonalized Dirac equation. Type (2.1)

We list all electrovacuum Stäckel spaces of the type (2.1) that admit diagonalization and full separation of variables in the Dirac equation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 116–120, February, 1992.     

Reanalysis of the Z_c(4020), Z_c(4025), Z(4050) and Z(4250) as Tetraquark States with QCD Sum Rules

In this article, we calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and study the C γμ- Cγνtype scalar, axial-vector and tensor tetraquark states in details with the QCD sum rules. In calculations, we use the formula μ = (M 2X/ Y /Z-(2Mc)2)~(1/2) to determine the energy scales of the QCD spectral densities. The predictions MJ =2=(4.02+0.09-0.09) GeV, MJ =1=(4.02+0.07-0.08) GeV favor assigning the Zc(4020) and Zc(4025) as the JP C= 1+-or 2++diquark-antidiquark type tetraquark states, while the prediction M++J =0=(3.85+0.15-0.09) GeV disfavors assigning the Z(4050) and Z(4250) as the JP C= 0diquark-antidiquark type tetraquark states. Furthermore, we discuss the strong decays of the 0++, 1+-, 2++diquark-antidiquark type tetraquark states in details.     

Spin-triplet superconductivity in UNi(2)Al(3) revealed by the (27)Al Knight shift measurement

We report (27)Al Knight shift ( (27)K) measurement on a single-crystal UNi(2)Al(3) that reveals a coexistence of superconductivity and a spin-density-wave (SDW) type of magnetic ordering ( T(SDW) = 4.5 K). The spin part of (27)K, (27)K(s), does not change down to 50 mK across the superconducting (SC) transition temperature T(c) approximately 0.9 K. In contrast with the isostructural compound UPd(2)Al(3) ( T(c) approximately 2 K), which was identified to be a spin-singlet d-wave superconductor, the behavior of (27)K strongly supports that UNi(2)Al(3) , like UPt(3) and Sr(2)RuO(4), belongs to a class of spin-triplet SC pairing state superconductors.     

Luminescence of the Derivatives of Boranes and Adducts of Decaborane(14) of the B10H12[Py(X)]2 Type

The luminescence properties of a series of derivatives of boranes of the type of B₁₀H₁₂[Py(X)]₂, C₂B₉H₁₁Py(X), and C₂B₉H₁₀BrPy(X) and of the salts of klozo-hydroborate anions B₁₀H₁₀ ^2– and B₁₂H₁₂ ^2– with the cations of quaternary pyridine bases (Py(X) is the pyridine and its derivatives) were investigated. The derivatives of decaborane(14) 6,9-bis(pyridine)-nido-decaborane(12) and 6,9-bis(3,4-dimethylpyridine)-nido decaborane(12) are proposed as a base of luminescent materials for recording and visualizing synchrotron radiation within the energy range 10–40 eV. They possess a number of advantages over the base material, namely, sodium salicylate.     

A New Type of Detuning System of RF Compressors (SLED)

In our SLAC type of RF pulse compressor (SLED), the detuning device works not as well as expected. It happend that the detuning needles sticked to the sleeves when working at detuning mode. Due to this reason, we can not measure its energy multiplication factor. To solve the sticking problem of SLED needles, a prototype of the new SLED detuning system has been developed and it has been operated with high power successfully on BEPC Linac.     

一种新型的能量倍增器解调谐系统

在北京正负电子对撞机(BEPC)直线加速器工程中,参考美国SLAC微波脉冲压缩技术,成功地研制了能量倍增器(SLED).该装置自1988年运行以来,一直存在一个隐患,解调谐系统设计有问题,不能随便解谐.BEPCⅡ经常需要长脉冲束流,这就要求能量倍增器能够方便地进行解调谐.为此,参考日本KEK的资料,对目前能量倍增器解调谐系统进行了彻底的改进,完成了新的SLED解调谐系统的研制任务,并在加速器上成功地进行了高功率试运行.     

Second-harmonic generation in quasi-periodically domain-inverted Sr(0.6) Ba(0.4) Nb(2)O(6) optical superlattices

One-dimensional Fibonacci-type quasi-periodically domain-inverted structures have been successfully fabricated in a strontium barium niobate crystal by electric field poling. With a single such structure, type I phase-matched second-harmonic generation (SHG) has been demonstrated at several wavelengths from red to near ultraviolet. The spectral positions of the observed SHG peaks are in good agreement with theoretical predictions. The range of measured conversion efficiencies is 2-10%.     

On Nested Bethe Ansatz for RTT Algebra of o(2n) Type

We study the highest weight representations of the RTT algebras for the R matrix of o(2n) type by the nested algebraic Bethe ansatz. We show how auxiliary RTT algebra à can be used to find Bethe vectors and Bethe conditions. For special representations, in which representation of RTT algebra à is trivial, the problem was solved by Reshetikhin.

     

Variable Separation and Exact Separable Solutions for Equations of Type uxt=A(u,ux)uxx+B(u,ux)

The generalized conditional symmetry is developed to study the variable separation for equations of type u_xt=A(u,u_x)u_xx+B(u,u_x). Complete classification of those equations which admit derivative-dependent functional separable solutions is obtained and some of their exact separable solutions are constructed.     

Application of 2,4-bis(halomethyl)quinoline: synthesis and biological activities of 2,4-bis(benzofuran-2-yl)- and 2,4-bis(aroxymethyl)quinolines

Molecular Diversity - In the present investigation, the synthesis of a new type of halomethylquinoline building block, i.e., ethyl 4-(bromomethyl)-2-(chloromethyl)quinoline-3-carboxylate, and its...     

High-Resolution FTIR Spectrum of the nu(12) Band of trans-d(2)-Ethylene

The nu(12) band of trans-d(2)-ethylene (trans-C(2)H(2)D(2)) has been recorded with an unapodized resolution of 0.0024 cm(-1) in the frequency range of 1240-1360 cm(-1) by Fourier transform infrared (FTIR) spectroscopy. This band was found to be relatively free from any local frequency perturbations. By fitting a total of 1185 infrared transitions of nu(12) with a standard deviation of 0.00043 cm(-1) using a Watson's A-reduced Hamiltonian in the I(r) representation, a set of accurate rovibrational constants for v(12) = 1 state was derived. The nu(12) band is A type with a band center at 1298.03797 +/- 0.00004 cm(-1). Copyright 2000 Academic Press.     

Magnetic-field induced quantum critical point in YbRh(2)Si(2)

We report low-temperature calorimetric, magnetic, and resistivity measurements on the antiferromagnetic (AF) heavy-fermion metal YbRh(2)Si(2) ( T(N)=70 mK) as a function of magnetic field B. While for fields exceeding the critical value B(c0) at which T(N)-->0 the low-temperature resistivity shows an AT2 dependence, a 1/(B-B(c0)) divergence of A(B) upon reducing B to B(c0) suggests singular scattering at the whole Fermi surface and a divergence of the heavy quasiparticle mass. The observations are interpreted in terms of a new type of quantum critical point separating a weakly AF ordered from a weakly polarized heavy Landau-Fermi liquid state.     

Clebsch-Gordan Coefficients,Racah Coefficients and Braiding Fusion of Quantum sl(2) Enveloping Algebra (I)

Quantum Clebsch-Gordan coefficients and the first type quantum Racah coefficients of quantum sl(2) enveloping algebra are given explicitly. The quantum 3-j and 6-j symbols, similar to those in the theory of angular momentum are abo introduced. The solution R_q^j1j2 of quantum Yang-Baxter equaton is expressed in terms of the quantum Clebsch-Gordan coefficients. It is shown that when j1=j2, R_q^jj is just the same as R_AW^j matrix obtained by Akutsu and Wadati for the representation of the braid group. The second type quantum Racah coefficients, which are the solutions of the face models, are also computed explicitly and related to the first type quantum Racah coefficients. The famous pentagonal relation is proved from the formula between two quantum Racah coefficients. The graphical representation of those formulas is discussed.     

新型Sr（NO3）2的水热合成及其晶体结构

本文以Sr（NO₃）₂和水为原料,采用水热法合成了一种新型的Sr（NO₃）₂结构。利用X-射线单晶衍射对其结构进行了测定,结果表明:该晶体属于立方晶系,Pa-3空间群,α=b=c=0.77402（7）nm,α=β=γ=90.00°,V=0.46372（7）nm³,Z=4,Dc=3.031g/cm³,F（000）=400,R_gt（F）=0.0287,wR_ref（F²）=0.0888。     

Tree-level breaking of SU(2)×U(1) in general SUGRA theories

It is shown that SU(2)×U(1) can be broken at the tree level, without the occurrence of global potential minima that break U(1)_e.m., in supergravity models that are more general than those proposed by Nilles, Srednicki and Wyler. The study comprises an analysis of models with a general soft supersymmetry-breaking structure as well as those of the Hall-Lykken-Weinberg type.