Simplified multiplet pattern HSQC-TOCSY experiment for accurate determination of long-range heteronuclear coupling constants

A new two-dimensional pulse sequence for accurately determining heteronuclear coupling constants is presented. It is derived from HSQC and HECADE techniques with B0 gradient coherence selection. The main feature of the proposed method is spectra with only one component of the IS doublet; i.e., the final result is equivalent to a selective broadband excitation of either Salpha or Sbeta spin states and a preservation of these states during the entire experiment. The effect is obtained by an appropriate combination of in- and antiphase coherences. It is demonstrated that heteronuclear single-bond as well as long-range coupling constants and their relative signs are readily evaluated. The proposed sequence is equally or less sensitive to a variation of heteronuclear one-bond couplings than previously published, closely related sequences. The new method is applied to a peptide sample for determination of 3JN, Hbeta.     

Excited atomic state of Li

An optical transition of 3489 A has been shown to arise from Li using beam foil spectroscopic technique. The mean life of the state emitting this radiation has been measured to be 2.23 ä 0.08 n sec.     

Metal-enhanced fluorescence using anisotropic silver nanostructures: critical progress to date

In this critical and timely review, the effects of anisotropic silver nanostructures on the emission intensity and photostability of a key fluorophore that is frequently used in many biological assays is examined. The silver nanostructures consist of triangular, rod-like, and fractal-like nanoparticles of silver deposited on conventional glass substrates. The close proximity to silver nanostructures results in greater intensity and photostability of the fluorophore than for fluorophores solely deposited on glass substrates. These new anisotropic silver nanostructure-coated surfaces show much more favorable effects than silver island films or silver colloid-coated substrates. Subsequently, the use of metal-enhanced fluorescence (MEF) for biosensing applications is discussed.     

An analog of the fundamental theorem of arithmetic in ordered groupoids

In the note we consider ordered groupoids with the Riesz interpolation property, that is, ifa _i ≤b _j (i, j=1,2), then there exists ac such thata _i ≤c≤b _j (i, j=1,2). For such groupoids possessing the descending chain condition for the positive cone and the property

激振面积对低应变动测法影响的数值研究

利用ABAQUS有限元软件建模, 分析了基桩横向尺寸对低应变检测的影响. 结果表明: (1)在建模过程中, 当桩端土厚度及桩周土半径达到桩长的1/2以上时, 计算所得数值解可以收敛稳定; (2)基桩横向尺寸对低应变法检测有显著影响, 具体与施加激振面积相关, 当激振面积较大时, 横向尺寸影响能有效弱化; (3)通过实测曲线与数值解比较, 二者较为吻合, 本文所述规律和方法对工程实践具有一定指导意义.     

低温下ZnSe－ZnS多量子阱的光致发光光谱和喇曼散射谱

本文报导了２Ｋ下，在ＧａＡｓ（１００）衬底上用ＭＯＣＶＤ方法生长的ＺｎＳｅ－ＺｎＳ多量子阱材料的光致发光光谱和喇曼散射谱．用共振激发、共振喇曼和共振瑞利散射等方法对各发光谱带和喇曼散射峰的来源和机制进行了鉴别．     

通过破裂反应研究轻丰中子核的集团结构

概括介绍了关于轻丰中子同位素链集团结构的理论模型和通过破裂反应研究该结构的实验方法、 实验装置及物理分析。 The theoretical models of the cluster structures of the light neutron rich nuclei as well as the corresponding physical mechanism and experimental approaches by breakup reaction have been introduced, which may serve as references for possible experimental studies of the cluster structure of light neutron rich nuclei.      

Dynamical quantum phase transition in XY chains with the Dzyaloshinskii-Moriya and XZY-YZX three-site interactions

We study the dynamical quantum phase transitions (DQPTs) in the $XY$ chains with the Dzyaloshinskii-Moriya interaction and the $XZY$-$YZX$ type of three-site interaction after a sudden quench. Both the models can be mapped to the spinless free fermion models by the Jordan-Wigner and Bogoliubov transformations with the form $H=\sum_{k}ǎrepsilon_{k}(\eta^{†}_{k}\eta_{k}-\frac{1}{2})$, where the quasiparticle excitation spectra $ǎrepsilon_{k}$ may be smaller than 0 for some $k$ and are asymmetrical ($ǎrepsilon_{k}\neqǎrepsilon_{-k}$). It is found that the factors of Loschmidt echo equal 1 for some $k$ corresponding to the quasiparticle excitation spectra of the pre-quench Hamiltonian satisfying $ǎrepsilon_{k}\cdotǎrepsilon_{-k}<0$, when the quench is from the gapless phase. By considering the quench from different ground states, we obtain the conditions for the occurrence of DQPTs for the general $XY$ chains with gapless phase, and find that the DQPTs may not occur in the quench across the quantum phase transitions regardless of whether the quench is from the gapless phase to gapped phase or from the gapped phase to gapless phase. This is different from the DQPTs in the case of quench from the gapped phase to gapped phase, in which the DQPTs will always appear. Moreover, we analyze the different reasons for the absence of DQPTs in the quench from the gapless phase and the gapped phase. The conclusion can also be extended to the general quantum spin chains.     

XRD与SEM的钢渣尾渣物理激发机理研究

钢渣是冶金工业中产生的主要固体废弃物,其产量约为每年粗钢产量的15%~20%。由于技术的局限,导致我国钢渣利用率较低,仅为年钢渣产量的10%;同时加之管理制度的不健全,导致钢渣大量露天堆放,对土地资源、地下水源,以及空气质量造成严重影响。固体废弃物再利用是资源可持续发展的重要途径之一,由于钢渣的主要化学成分(CaO,SiO₂,A1₂O₃,MgO,Fe₂O₃,MnO,f-CaO等)、主要矿物组成(硅酸三钙、硅酸二钙、钙镁橄榄石、钙镁蔷薇辉石、铁酸二钙等)与水泥熟料的主要化学成分、主要矿物组成极为相似,是一种具有潜在胶凝活性的胶凝材料。以钢渣尾渣作为研究对象,采用机械研磨的方式对钢渣尾渣处理,即物理激发,获得不同粒径钢渣尾渣微粉。依据《用于水泥和混凝土中的钢渣粉》(GB/T 20491-2006)与《水泥胶砂强度检验方法(ISO法)》(GB/T 17671-1999)制备一系列钢渣尾渣胶砂试块(分别标记为A₄₀,A₆₀,A₈₀,A₁₀₀和A₁₂₀)。研究对钢渣尾渣胶凝活性的影响,以及不同水化时间对钢渣尾渣胶凝活性的影响,即3 d钢渣尾渣胶砂强度、7 d钢渣尾渣胶砂强度与28 d钢渣尾渣胶砂强度。利用激光粒度分析仪(LPSA)对钢渣尾渣微粉的粒径分布进行测试与分析,X射线衍射仪(XRD)对钢渣尾渣微粉与钢渣尾渣胶砂的矿物组成进行测试与分析,扫描电子显微镜(SEM)进行微观形貌测试与分析,从而获得钢渣尾渣的物理激发机理。结果表明,随着钢渣尾渣微粉粒径的减小,其胶凝活性呈现先增加后降低的趋势,当研磨时间为80 min时,A₈₀钢渣尾渣微粉的胶凝活性最高,即3 d活性指数为67.55%、7 d活性指数为71.96%和28 d活性指数为73.61%。随着钢渣尾渣微粉粒径的减小,钢渣尾渣微粉中RO相的XRD特征峰强度稳定,Ca₂SiO₄与Ca₃SiO₅的XRD特征峰强度呈现先增加后降低的趋势,Ca₃SiO₅与Ca₂SiO₄参与水化反应,生成一定量的Ca(OH)₂与C-S-H凝胶,具有良好的胶凝活性。A₈₀钢渣尾渣微粉中Ca₂SiO₄含量较少,而Ca₃SiO₅含量较多,均可以生成一定量的Ca(OH)₂与C-S-H凝胶,小幅提高A₈₀钢渣尾渣胶砂的早期(3~7 d)力学性能,大幅提高A₈₀钢渣尾渣胶砂的中、后期(7 d~28 d)力学性能。当水化时间3 d时,A₈₀钢渣尾渣胶砂中存在少量水化产物且大量分散小颗粒;当水化时间7 d时,A₈₀钢渣尾渣胶砂中水化产物大幅增加且形成较大颗粒;当水化时间28 d时,A₈₀钢渣尾渣胶砂中形成大量水化产物且几乎不存在分散小颗粒。从而进一步实现固体废弃物的资源化再利用,达到钢铁企业增加效益,环境缓解压力的目的。     

Exact projective solutions of generalized nonlinear Schrödinger system with variable parameters

A direct self-similarity mapping approach is successfully applied to a generalized nonlinear Schrödinger (NLS) system. Based on the known exact solutions of a self-similarity mapping equation, a few types of significant localized excitation with novel properties are obtained by selecting appropriate system parameters. The integrable constraint condition for the generalized NLS system derived naturally here is consistent with the known compatibility condition generated via the Painlev? analysis.