Conformational landscape of platinum(II)-tetraamine complexes: DFT and NBO studies

The potential energy surfaces of chiral tetraamine Pt(II) coordination complexes were computed at the B3LYP/LANL2DZ level of theory by a systematic variation of two dihedral angles: C12–C15–C34–C37 (θ) and C24–C17–C31–C48 (ψ) employing a grid resolution of 30°. Potential energy surfaces calculated using density functional theory methods and Boltzmann-derived populations revealed strong preference for one diasteromer of each series studied. In addition, natural bond orbital analysis show that the minima are stabilized predominantly by a combination of electronic interactions between two phenyl groups, the phenyl groups and the Pt²⁺ ion, as well as with the amine groups. Additional experimental characterization of the diasteroisomers studied here is in progress and will permit further molecular modeling studies with the appropriate stereochemistry.     

Media Preparation Using Tuna-Processing Wastes for Improved Lipase Production by Shrimp Gut Isolate Staphylococcus epidermidis CMST Pi 2

Extracellular lipase production by Staphylococcus epidermidis CMST Pi 2 isolated from the intestine of shrimp Penaeus indicus has been investigated in shake-flask experiment using different preparations of tuna-processing waste such as raw fish meat, defatted fish meat, alkali hydrolysate, and acid hydrolysate as nitrogen source. Among the tested tuna preparations, defatted fish meat supported the maximum lipase production, and 2.5% concentration of the same was found to be optimum for maximizing the lipase production. The effect of carbon sources on lipase production revealed that glucose aided the higher lipase production than any other tested carbon source and a concentration of 2% glucose registered as optimum to enhance the lipase production. The halotolerancy of S. epidermidis CMST Pi 2 for lipase production indicated that 4% of sodium chloride was optimum to yield maximum lipase. Among the surfactants tested, lipase production was high in Tween 20 added medium when compared to other surfactants, and its optimum concentration recorded was 0.8%. Partial characterization of crude enzyme revealed that pH 7 and 55 °C temperature were optimum for maximum lipase activity.     

Synchronization of impulsively coupled complex systems with delay

This paper investigates the synchronization of complex systems with delay that are impulsively coupled at discrete instants only. Based on the comparison theorem of impulsive differential system, a distributed impulsive control scheme is proposed to achieve the synchronization for systems with delay. In the control strategy, the influence of all nodes to network synchronization relies on its weight. The proposed control scheme is applied to the chaotic delayed Hopfield neural networks and numerical simulations are presented to demonstrate the effectiveness of the proposed scheme.     

11B and constraints on neutrino oscillations and spectra from neutrino nucleosynthesis

We study the sensitivity to variations in the triple-alpha and 12C(α,γ)16O reaction rates, of the yield of the neutrino-process isotopes 7Li, 11B, 19F, 138La, and 180Ta in core-collapse supernovae. Compared to solar abundances, less than 15% of 7Li, about 25%-80% of 19F, and about half of 138La is produced in these stars. Over a range of ±2σ for each helium-burning rate, 11B is overproduced and the yield varies by an amount larger than the variation caused by the effects of neutrino oscillations. The total 11B yield, however, may eventually provide constraints on supernova neutrino spectra.     

Evidence for shape coexistence at medium spin in Rb

Four previously known rotational bands in ⁷⁶Rb have been extended to moderate spins using the Gammasphere and Microball γ ray and charged particle detector arrays and the ⁴⁰Ca(⁴⁰Ca, 3pn) reaction at a beam energy of 165 MeV. The properties of two of the negative-parity bands can only readily be interpreted in terms of the highly successful Cranked Nilsson-Strutinsky model calculations if they have the same configuration in terms of the number of g9/2 particles, but they result from different nuclear shapes (one near-oblate and the other near-prolate). These data appear to constitute a unique example of shape coexisting structures at medium spins.     

On connected dominating sets of restricted diameter

A connected dominating set (CDS) is commonly used to model a virtual backbone of a wireless network. To bound the distance that information must travel through the network, we explicitly restrict the diameter of a CDS to be no more than s leading to the concept of a dominating s-club. We prove that for any fixed positive integer s it is NP-complete to determine if a graph has a dominating s  -club, even when the graph has diameter s+1$s+1$. As a special case it is NP-complete to determine if a graph of diameter two has a dominating clique. We then propose a compact integer programming formulation for the related minimization problem, enhance the approach with variable fixing rules and valid inequalities, and present computational results.     

Solving maximum clique in sparse graphs: an O(nm+n2^{d/4}) algorithm for d-degenerate graphs

We describe an algorithm for the maximum clique problem that is parameterized by the graph’s degeneracy \(d\) . The algorithm runs in \(O\left( nm+n T_d \right) \) time, where \(T_d\) is the time to solve the maximum clique problem in an arbitrary graph on \(d\) vertices. The best bound as of now is \(T_d=O(2^{d/4})\) by Robson. This shows that the maximum clique problem is solvable in \(O(nm)\) time in graphs for which \(d \le 4 \log _2 m + O(1)\) . The analysis of the algorithm’s runtime is simple; the algorithm is easy to implement when given a subroutine for solving maximum clique in small graphs; it is easy to parallelize. In the case of Bianconi-Marsili power-law random graphs, it runs in \(2^{O(\sqrt{n})}\) time with high probability. We extend the approach for a graph invariant based on common neighbors, generating a second algorithm that has a smaller exponent at the cost of a larger polynomial factor.     

An improved error bound for a finite element approximation of a model for phase separation of a multi-component alloy

Using the approach of Rulla (1996 SIAM J. Numer. Anal. 33, 68-87)for analysing the time discretization error and assuming moreregularity on the initial data, we improve on the error boundderived by Barrett and Blowey (1996 IMA J. Numer. Anal. 16,257-287) for a fully practical piecewise linear finite elementapproximation with a backward Euler time discretization of amodel for phase separation of a multi-component alloy.     

Ionic conductivity in hydrogels for contact lens applications

Biphasic hydrogel polymers are in the forefront of new extended wear contact lens development. In the biphasic hydrogel the objective is to produce co-continuous domains of siloxane units for high oxygen permeability, coupled with hydrophilic units forming aqueous channels for hydraulic and ion mobility. These are distributed in phase separated nano-scale regions such that the material is optically clear while achieving the required properties to maintain corneal health and lens movement. This paper describes how Impedance Spectroscopy permits a rapid measurement of ion conductivity in a range of silicone and non-silicone hydrogel materials with water contents ranging from 18% to 75% equilibrium water content. For non-silicone hydrogels relative sodium ion conductivity follows a typical percolation curve. However, for silicone hydrogels ion mobility is three orders of magnitude higher than conventional hydrogels of the same equilibrium water content. The influence of electrolyte concentration, interfacial electrode sample contact pressure and temperature are also reported. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.     

Molecular structural analysis of 55mol% CuI-45mol% Ag2MoO4 solid electrolyte using XPS and laser raman techniques

The solid electrolyte 55 mol% CuI - 45 mol% Ag₂MoO₄ has been analyzed structurally by employing X-ray photoelectron spectroscopic (XPS) and laser Raman studies. The core level Ag 3d, Cu 2p, Mo 3d, I 3d and O1s XPS spectra of the constituent elements were recorded. The presence of both bridging (BO) and non-bridging (NBO) oxygen atoms in the oxyanion framework has been identified through the deconvolution of the O 1s spectrum. Laser Raman spectroscopic studies tend to reveal that the oxyanion framework is constructed with [MoO ₄ ²⁻ ]-tetrahedral and [MoO₆]-octahedral units as in the case of CuI - Cu₂MoO₄ and AgI - Ag₂O - MoO₃ glasses.