An ab-initio study of silicon adsorption on metallic surfaces (Au/Ag): Novel perspective to explore chemical bonding

We analyzed localized charge time evolution in the system of two interacting quantum dots (QD) (artificial molecule) coupled with the continuous spectrum states. We demonstrated that Coulomb interaction modifies relaxation rates and is responsible for non-monotonic time evolution of the localized charge. We suggested new mechanism of this non-monotonic charge time evolution connected with charge redistribution between different relaxation channels in each QD.     

Synthesis of some novel and complex thiopyrano indole derivatives from simple oxindole via intramolecular domino hetero Diels–Alder reactions

Some novel polycyclic thiopyrano[2,3-b]indole derivatives 7 were synthesized from simple oxindole 1 by exploring intramolecular domino hetero Diels–Alder reactions strategy.     

Measurement of radon concentrations and their annual effective doses in soils and rocks of Jaintiapur and its adjacent areas,Sylhet, North-east Bangladesh

Journal of Radioanalytical and Nuclear Chemistry - The study investigates the measurement of radon concentration in soils and rocks as a natural tracer for exploring uranium mineralization, first...     

Mechanical breakdown of trabecular bone: Dependence on microstructure

Experiment on mechanical strength of porous trabecular bone shows power law dependence on the density of the structure. Physical structure and mechanical properties of the trabecular network are modelled here with a fractal lattice network of elastic springs having a strain based fracture criteria. An analysis of the model system supports the power law and shows that lacunarity is an important parameter in differentiating the mechanical strength of trabecular bones of same density.     

Performance analysis for an all-optical wavelength converter using four-wave mixing (FWM) in a single mode fiber

An analytical approach is presented to determine the performance of a tunable wavelength converter based on four wave mixing (FWM) in a single mode fiber (SMF) with two pump lasers. The analysis is carried out for an intensity modulated (IM) signal taking into considerations the effects of spectral broadening due to FWM and laser phase noise. The results evaluated at a bit rate of 10 Gb/s show that the signal power is substantially higher at lower values of wavelength separation. For example, for input powers of 10 mW each, wavelength separation of 4 nm between the pump-2 and the input signal, the output converted power is found to be –10 dBm corresponding to wavelength separation of 2 nm between pump-1 and converter signal. The corresponding crosstalk power is found to be –25 dBm at a channel separation of 3 times bit rate.     

Bimetallic Ag‐Pt Sub‐nanometer Supported Clusters as Highly Efficient and Robust Oxidation Catalysts

A combined experimental and theoretical investigation of Ag‐Pt sub‐nanometer clusters as heterogeneous catalysts in the CO→CO₂ reaction (COox) is presented. Ag₉Pt₂ and Ag₉Pt₃ clusters are size‐selected in the gas phase, deposited on an ultrathin amorphous alumina support, and tested as catalysts experimentally under realistic conditions and by first‐principles simulations at realistic coverage. In situ GISAXS/TPRx demonstrates that the clusters do not sinter or deactivate even after prolonged exposure to reactants at high temperature, and present comparable, extremely high COox catalytic efficiency. Such high activity and stability are ascribed to a synergic role of Ag and Pt in ultranano‐aggregates, in which Pt anchors the clusters to the support and binds and activates two CO molecules, while Ag binds and activates O₂, and Ag/Pt surface proximity disfavors poisoning by CO or oxidized species.     

Structure d'alcaloïdes indoliques doubles d'un type nouveau

The Structure of bis-indoline alkaloids of a novel type The structure of folicangine 4 , a bis-indoline alkaloid from the leaves of Voacanga africana, is obtained by correlation with voafolidine 3a and isovoafolidine 3b . It requires an ether bridge between the two parts of the molecule, as in subsessiline (amataine 5a ). Subsessiline-lactone, from the leaves of Voacanga thouarsii has structure 5b proved by correlation with 5a . The CD. curves of double-indole alkaloids of vobtusine type are given (Table 3).     

Embedding in higher dimensions causes ambiguity in determining equations from data

A linear system of dimension D can be embedded by D time-delay vectors. However, a nonlinear system often requires more vectors, almost always not more than 2D+1. This paper is regarding the consequence of such an embedding. We encountered this problem in an attempt to obtain a set of equations from the observed data. Our goal was to generate a system which is topologically conjugate to the original system. We found that many a times our efforts led to highly unstable systems. Now, we have an explanation. Embedding in higher dimensions causes a topological foliation and this foliation has a D-dimensional “leaf”. All the data were on this leaf and therefore we were unable to distinguish this foliated system from those where the foliation had collapsed. We illustrate the phenomenon by examples from numerically generated data and suggest possible remedies.     

A lipase catalyzed condensation reaction with a tricyclic diketone: yet another example of biocatalytic promiscuity

Novozym 435 (a commercially available immobilized form of Candida antarctica lipase B) was found to catalyze a condensation reaction of 5-hydroxy-endo-tricyclo[5.2.1.0^2,6]deca-4,8-dien-3-one with acetaldehyde (enzymatically produced from vinyl acetate in situ) under low water conditions, in presence of 10% organic co-solvent (N,N-dimethyl formamide or pyridine), to form a bis-adduct. Even though the condensation reaction occurred with pyridine (acting as a base catalyst) in the presence of acetaldehyde and in the absence of enzyme, the reaction was very slow as compared to the enzymatic process. Thus, while the non-enzymatic process took 4 days to achieve 100% conversion; in presence of enzyme it was possible within 4 h.     

Explicitly correlated MRCI-F12 potential energy surfaces for methane fit with several permutation invariant schemes and full-dimensional vibrational calculations

A data-set of nearly 100,000 symmetry unique multi-configurational ab initio points for methane were generated at the (AE)-MRCI-F12(Q)/CVQZ-F12 level, including energies beyond 30,000 cm^?1 above the minimum and fit into potential energy surfaces (PESs) by several permutation invariant schemes. A multi-expansion interpolative fit combining interpolating moving least squares (IMLS) fitting and permutation invariant polynomials (PIP) was able to fit the complete data-set to a root-mean-square deviation of 1.0 cm^?1 and thus was used to benchmark the other fitting methods. The other fitting methods include a single PIP expansion and two neural network (NN) based approaches, one of which combines NN with PIP. Full-dimensional variational vibrational calculations using a contracted-iterative method (and a Lanczos eigensolver) were used to assess the spectroscopic accuracy of the electronic structure method. The results show that the NN-based fitting approaches are able to fit the data-set remarkably accurately with the PIP–NN method producing levels in remarkably close agreement with the PIP–IMLS benchmark. The (AE)-MRCI-F12(Q)/CVQZ-F12 electronic structure method produces vibrational levels of near spectroscopic accuracy and a superb equilibrium geometry. The levels are systematically slightly too high, beginning at ～ 1–2 cm^?1 above the fundamentals and becoming correspondingly higher for overtones. The PES is therefore suitable for small ab initio or empirical corrections and since it is based on a multi-reference method, can be extended to represent dynamically relevant dissociation channels.