蝶状铁硒簇合物双(μ-P-甲苯硒基)六羰基二铁双膦取代衍生物的~1H和~(13)CNMR谱的归属研究

测得并解析了2个蝶状铁硒取代衍生物（μ-p-MeC6H4Se）2Fe2（CO）。（PH2PCH2CH2PPH2）（A）和（μ-P-MeC6H4Se）2Fe2（CO）4（cis-Ph2PCH=CHPPh2）（B）的1H-1HCOSY谱和1H-13CCOSY谱以及A的1H－1HNOESY谱，从而进一步确证了它们的结构．     

A new component mode synthesis method: Quasi-static mode compensation

A new component mode synthesis method is presented in this paper that combines the computational efficiency of the well-known constraint mode approach with the dynamic compensation accuracy obtained by higher-order expansion methods. Instead of employing static constraint modes, quasi-static modes are used to capture inertial effects of the truncated modes. The method is ideally suited for mid-band frequency analysis in which both high-frequency and low-frequency modes may be omitted. A tuning parameter, designated as the centering frequency, controls the dynamic range of the quasi-static modes. Numerical examples are provided which demonstrate the improved accuracy of the proposed method.     

Automated site-directed drug design: Searches of the Cambridge Structural Database for bond lengths in molecular fragments to be used for automated structure assembly

Summary In this paper a database of small frequently occurring molecular fragments is used for the determination of fragment bond lengths from the Cambridge Structural Database. A large number of bond types are described that have not been reported previously.     

Minimax approach to structural optimization problems

The problem of determining the shape of an elastic body which is optimal for a whole class of loads is formulated. Its general solution scheme, based on a minimax approach, is indicated. The optimization problem of an elastic beam is studied for both the simply supported case and the cantilevered case, and some specific properties of the optimal shape are determined.The author is grateful to Professor A. I. Lurie, Professor F. L. Chernousko, and Professor G. S. Shapiro for useful discussions of the results.     

Interaction of Lamb mode (A(o)) with structural discontinuity and generation of "Turning modes" in a T-joint

In the present work, the interaction of the fundamental anti-symmetric guided Lamb mode (A_o) with a structural discontinuity in a composite structure was studied through Finite Element numerical simulations and experiments. The structural component selected for this study was a T-joint section made from glass/epoxy material. This co-cured composite structure is made-up of an upper shell (skin) and a spar as the sub-components. It was observed that when A_o mode interacts with the junction (structural discontinuity) of these sub-components, a mode-converted S_o mode is generated. Experiments were conducted using air-coupled ultrasound to validate the numerical simulations. The back-propagating “Turning modes”, which propagate from the thin region to the spar web and vice versa, were also numerically simulated and experimentally verified.     

Structural, optical and electrical studies on amino acid based new GBC crystals having non linear optical response

Transparent crystals of α-glycine with barium nitrate and calcium nitrate (GBC) have been grown from aqueous solution by slow evaporation technique at room temperature. Crystals of size 22 × 25 × 4 mm³ have been obtained in 3-4 weeks time. The solubility of GBC has been determined in water. The grown crystal belongs to orthorhombic system with cell parameters a = 12.7321 A.U, b = 13.7752 A.U and c = 8.6002 A.U with unit cell volume of 1508.36 (A.U)³. Comparative IR and Raman studies indicate a molecule with a lack of center of symmetry. A wide transparency window useful for optoelectronic applications is indicated by the UV Studies. Using Nd:YAG laser (1064 nm), the optical second harmonic generation (SHG) conversion efficiency of GBC is found to be 0.702 times than that of standard KDP. On exposure to light the GBC crystals exhibit positive photoconductivity. I-V characteristics, dielectrics studies, electrical and Vickers micro hardness measurement have been carried out. The GBC crystal exhibits more mechanical strength compared to the reported GSN crystals.     

A new conceptual approach to assigning biomass combustion-derived methoxyphenol structures by using a gas chromatographic retention index model

A new conceptual approach towards iteratively constructing chromatographic retention time/index models is presented. The approach is applicable where there is potential structural uncertainty in a number of members of the dataset used in constructing the model, and where limited spectroscopic information is available to guide the process. The model is demonstrated on a suite of biomass combustion-derived methoxyphenols for which gas chromatographic polydimethylsiloxane retention index data was available in the literature, but where there was ambiguity regarding the identity of several members of the dataset. The retention property model is populated by sequentially screening a series of candidate structures that meet basic mass spectrometric requirements by using a multiple linear regression model containing molecular and physicochemical properties that have been previously shown to yield reliable predictions of chromatographic behaviour within a compound class. The criteria for deciding on the likely structure(s) out of a suite of candidate structures is based upon the improved quality of fit the most probable structure gives the regression model relative to other candidate structures. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Evidence for a cubic-to-icosahedral transition of quasi-free Pd-H-clusters controlled by the hydrogen content

An in situ synchrotron radiation study of quasi-free five nanometer-sized palladium clusters during hydrogen absorption is combined with molecular dynamics simulations to investigate the structural development. In the diffraction patterns, strong intensity changes are found that provide evidence for a structural phase transformation that is significantly different from the α--Pd-H bulk phase transition. The structural transition is reversible and driven by the hydrogen concentration. The intensity changes are consistent with a cubic-to-icosahedral structural phase transition obtained in molecular dynamical simulations using embedded-atom-method potentials. Received 15 October 2001 and Received in final form 7 February 2002     

Ionic conduction properties of layer-type oxides NaxMx/2Ti1−x/2O2 (M=Ni, Co; 0.60≤x≤1.0)

Layer-type oxide Na_xM_x/2^IITi_1−x/2^IVO₂ (M=Co, Ni; 0.60≤x≤1.0) has been prepared by solid state reactions. In both series, two structural variants of type -NaFeO₂ (O3) and β-RbScO₂ (P2) have been obtained consecutively as x decreases with a borderline composition around x_c0.7. With the decrease of x, the ionic conductivity has been found to increase up to 8.4×10⁻² S cm⁻¹ at 770 K (Na_0.67Co_0.33Ti_0.67O₂). Compositions of P2 have been found to exhibit the conductivity values two to five times greater than those of O3, primarily due to the larger rectangular threshold available for the diffusion of Na⁺ ions. Such a structural effect has also been considered to depend on the polarizability of alkali ion. HT-XRD and ²³Na-NMR data of Na_0.67Co_0.33Ti_0.67O₂ strongly suggest that the diffusion of Na⁺ ion is deeply related with the local distortion of trigonal prismatic sites, leading to the change of activation energy around 430 K.     

Replacing suffix trees with enhanced suffix arrays

The suffix tree is one of the most important data structures in string processing and comparative genomics. However, the space consumption of the suffix tree is a bottleneck in large scale applications such as genome analysis. In this article, we will overcome this obstacle. We will show how every algorithm that uses a suffix tree as data structure can systematically be replaced with an algorithm that uses an enhanced suffix array and solves the same problem in the same time complexity. The generic name enhanced suffix array stands for data structures consisting of the suffix array and additional tables. Our new algorithms are not only more space efficient than previous ones, but they are also faster and easier to implement.