Os(VIII)-catalysed oxidation of sulfides by sodium salt of N-chlorobenzenesulfonamide

Catalytic activity of Os(VIII) in the oxidation of some twenty organic sulfides with sodium salt of N-chlorobenzenesulfonamide (CAB) has been investigated in alkaline (pH8.7) t-butanol–water (1:1 v/v) medium. Significant retarding influence of [OH⁻] on the reactivity is exhibited. The catalysed reaction is strongly accelerated in the presence of Hg(II). Imperfections are observed in the linear Hammett relationship in the case of –NO₂ substituents.     

On the transverse compression response of Kevlar KM2 using fiber-level finite element model

Flexible textile composites like woven Kevlar fabrics are widely used in high velocity impact (HVI) applications. Upon HVI they are subjected to both longitudinal tensile and transverse compressive loads. To understand the role of transverse properties, the single fiber and tow transverse compression response (SFTCR and TTCR) of Kevlar KM2 fibers are numerically analyzed using plane strain finite element (FE) models. A finite strain formulation with a minimum number of 84 finite elements is determined to be required for the fiber cross section to capture the finite strain SFTCR through a mesh convergence study. Comparison of converged numerical solution to the experimental results indicates the dominant role of geometric stiffening at finite strains due to growth in contact width. The TTCR is studied using a fiber length scale FE model of a single tow comprised of 400 fibers transversely loaded between rigid platens. This study along with micrographs of yarn after mechanical compaction illustrates fiber spreading and fiber–fiber contact friction interactions are important deformation mechanisms at finite strains. The TTCR is also studied using homogenized yarn level models with properties from the literature. Comparison of TTCR between fiber length scale and homogenized yarn length scale models indicate the need for a nonlinear material model for homogenized approaches to accurately predict the transverse compression response of the fabrics.     

Experimental and theoretical investigation of the molecular and electronic structure of anticancer drug camptothecin

The Fourier Transform Infrared spectrum of (S)-4 ethyl-4-hydroxy-1H-pyrano [3',4':6,7]-indolizino-[1,2-b-quinoline-3,14-(4H,12H)-dione] [camptothecin] was recorded in the region 4000-400 cm(-1). The Fourier Transform Raman spectrum of camptothecin (CPT) was also recorded in the region 3500-50 cm(-1). Quantum chemical calculations of geometrical structural parameters and vibrational frequencies of CPT were carried out by MP2/6-31G(d,p) and density functional theory DFT/B3LYP/6-311++G(d,p) methods. The assignment of each normal mode has been made using the observed and calculated frequencies, their IR and Raman intensities. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. Most of the computed frequencies were found to be in good agreement with the experimental observations. The isotropic chemical shifts computed by (13)C and (1)H NMR analysis also show good agreement with experimental observations. Comparison of calculated spectra with the experimental spectra provides important information about the ability of computational method to describe the vibrational modes of large sized organic molecule.     

A parallel multi-configuration self-consistent field algorithm

A scalable multi-configuration self-consistent field (MCSCF) algorithm is described. The method for optimizing the orbital and configurational parameters is based upon the two-step Newton–Raphson approach with an augmented orbital Hessian matrix. A single copy of the two-electron integrals in the molecular orbital basis is distributed over the memory of all processors. Storage of the augmented Hessian is avoided by re-computing its elements as needed. A replicated data approach is used to parallelize the configuration interaction step. Scalability to 1024 processors is demonstrated.