Highly efficient parallel algorithm for finite difference solution to Navier–Stoke''s equation on a hypercube

It has been shown in [Nuclear Science and Engineering 93 (1986) 6799] that the finite difference discretization of Navier–Stoke's equation leads to the solution of N×N system written in the matrix form as My=B, where M is a quasi-tridiagonal having non-zero elements at the top right and bottom left corners. We present an efficient parallel algorithm on a p-processor hypercube implemented in two phases. In phase I a generalization of an algorithm due to Kowalik [High Speed Computation, Springer, New York] is developed which decomposes the above matrix system into smaller quasi-tridiagonal (p+1)×(p+1) subsystem, which is then solved in Phase II using an odd–even reduction method.     

A new symmetric five-diagonal finite difference method for computing eigenvalues of fourth-order two-point boundary value problems

We present a new symmetric five-diagonal finite difference method for computing eigenvalues of two-point boundary value problems involving a fourth-order differential equation.     

Altered phase model for polymer clay nanocomposites

This paper describes a multiscale approach used to model polymer clay nanocomposites (PCNs) based on a new altered phase concept. Constant-force steered molecular dynamics (SMD) is used to evaluate nanomechanical properties of the constituents of intercalated clay units in PCNs, which were used in the finite element model. Atomic force microscopy and nanoindentation techniques provided additional input to the finite element method (FEM) model. FEM is used to construct a representative PCN model that simulates the composite response of intercalated clay units and the surrounding polymer matrix. From our simulations we conclude that, in order to accurately predict mechanical response of PCNs, it is necessary to take into account the molecular-level interactions between constituents of PCN, which are responsible for the enhanced nanomechanical properties of PCNs. This conclusion is supported by our previous finding that there is a change in crystallinity of polymeric phase due to the influence of intercalated clay units. The extent of altered polymeric phase is obtained from observations of a zone of the altered polymeric phase surrounding intercalated clay units in the "phase image" of PCN surface, obtained using an atomic force microscope (AFM). An accurate FEM model of PCN is constructed that incorporates the zone of the altered polymer. This model is used to estimate elastic modulus of the altered polymer. The estimated elastic modulus for the altered polymer is 4 to 5 times greater than that of pure polymer. This study indicates that it is necessary to take into account molecular interactions between constituents in nanocomposites due to the presence of altered phases, and furthermore provides us with a new direction for the modeling and design of nanocomposites.     

Drug binding and order-order and order-disorder transitions in DNA triple helices

The Zimm and Bragg theory for helix-to-coil transitions has been suitably amended and applied to explain the two-step transition in the DNA triplex. The experimental measurements reported elsewhere have been successfully interpre- ted. The order-order and order-disorder transitions associated with the melting of the DNA triple helix, with and without netropsin binding, were characterized by the nucleation parameter, enthalpy change, sharpness of transition, and heat capacity. The destabilization of the triplex and stabilization of the duplex on netropsin binding are reflected in these characteristic parameters.     

Crystallization and structural studies of n‐benzyloxycarbonyl‐L‐tyrosine‐L‐glycine‐ethyl ester (Z‐Tyr‐Gly‐OEt)

It is axiomatic that efficient crystal production reflects upon the quality of structure. An empirical relation for mass proportions of two solvents in crystallization of Z‐Tyr‐Gly‐OEt shows a linear relationship. The dipeptide crystallizes in orthorhombic space group P2₁2₁2_1, with cell parameters a = 5.0680(1) Å, b = 13.8650(1) Å and c = 28.2630(1) Å, Z = 4, D_calc= 1.339Mg/m³, μ=0.820mm^‐1, F₀₀₀=848, CuKα = 1.5418 Å. The structure was solved by direct methods and final R1 and wR2 are 0.444 and 0.1276, respectively. The structure analysis reveals the trans conformation of the peptide unit with ω = ‐178.2(5)°, implying only a slight deviation from planarity. The torsion angles at glycine [ϕ, ψ = ‐84.4(7)°, 179.9(5)°] are characteristic of left‐handed poly glycine II helices. A number of N‐H…O, O‐H…O and C‐H…O hydrogen bondings play a role in stabilizing the molecules within unit cell. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nonlinear chromatography Recent theoretical and experimental results

The theory of nonlinear chromatography has been advanced by the incorporation of recent results obtained by the theory of partial differential equations. The system of equations of the ideal model has been solved analytically in the case of a single component for which the equilibrium isotherm between the mobile and the stationary phases is given by a Langmuir equation. A series of computer programs has been written which permits the calculation of numerical solutions of the semi-ideal model. The properties of the solutions obtained are described and discussed for a one-component system (profile of high concentration bands of a pure compound eluted by a pure solvent), several two-component systems (elution of a pure compound band by a binary mobile phase, separation of a binary mixture eluted by a pure mobile phase), and three-component systems (separation of a binary mixture eluted by a binary solvent, displacement and separation of a binary mixture). Experimental results are reported which validate the conclusions derived from the numerical integration of the model. The conclusions of the work apply to all high-performance chromatographic procedures, i.e., to those where the kinetics of mass transfer are fast enough for the mobile and stationary phases always to be near equilibrium. More specifically, the contribution from the kinetics of the retention mechanism to the mass transfer resistance must itself be negligible. This clearly excludes affinity chromatography.     

Role of coordinated metal ions on the orientation of phthalocyanine based coatings

In the present work, we have investigated the molecular orientation of phthalocyanine films deposited on polycrystalline gold. Three films built from the following molecules are investigated: phthalocyanine (H(2)Pc), cobalt phthalocyanine (CoPc) and copper phthalocyanine (CuPc). The films are prepared by spin coating and drop casting methods. Orientation analysis has been performed using polarization dependent Fourier transform infrared (FTIR) spectroscopy using transmission and grazing angle reflectance mode. The FTIR study suggests that each phthalocyanine film contains both alpha- and beta-phases. H(2)Pc based films demonstrate deposition method dependence on the molecular orientation, while the CuPc and CoPc films preserve their molecular orientation independent of deposition method. Grazing angle analysis also suggests that CoPc films show negligible preferred orientation irrespective of film deposition methods. In literature, the band at 878cm(-1) in CuPc has been assigned to out-of-plane bending of C-H. Our grazing angle experiments suggest that this band cannot be assigned to out-of-plane bending vibrations of C-H. Accurate band assignments are also described here for the phthalocyanine system.