Search

In this work, we provide a unified theoretical framework describing how drug molecules can permeate across membranes in neutral and ionized forms for unstirred in vitro systems. The analysis provides a self-consistent basis for the origin of the unstirred water layer (UWL) within the Nernst-Planck framework in the fully unstirred limit and further provides an accounting mechanism based simply on the bulk aqueous solvent diffusion constant of the drug molecule. Our framework makes no new assumptions about the underlying physics of molecular permeation. We hold simply that Nernst-Planck is a reasonable approximation at low concentrations and all physical systems must conserve mass. The applicability of the derived framework has been examined both with respect to the effect of stirring and externally applied voltages to measured permeability. The analysis contains data for 9 compounds extracted from the literature representing a range of permeabilities and aqueous diffusion coefficients. Applicability with respect to ionized permeation is examined using literature data for the permanently charged cation, crystal violet, providing a basis for the underlying mechanism for ionized drug permeation for this molecule as being due to mobile counter-current flow.

The stokes shift in Co-doped ZnO nanorods are investigated through optical emission and absorption spectroscopic study. High resolution x-ray diffraction and transmission electron microscopic study reveal that well crystalline as well as rod-like nanostructures. The red shifts in UV emission due to strong exciton-phonon coupling with enhanced defect emission are employed by photoluminescence spectroscopy. The optical absorption spectroscopy indicates the blue shifting of absorption edge owing to potential fluctuation of carrier density through incorporation of Co in ZnO host. Thus the exhibited a red shift in energy for band-edge emission relative to the absorption edge, could be significant for tailoring the optical behavior of nanocrystals for specific applications by controlling their size and structure.

Our successful synthesis of the first examples of Sn(IV) complexes of meso-aryl dipyrrins is reported. Sn(IV) dipyrrins are synthesized by treating meso-aryl dipyrrins with readily available SnCl2 center dot 2H(2)O in pyridine at reflux temperature and isolated as pure complexes by recrystallization. The X-ray structure revealed that the complex is hexa-coordinated and the Sn(IV) ion is coordinated to two dipyrrin units and two chlorides with overall appearance of a butterfly like structure. The complexes are stable in solution and characterized by spectral and electrochemical techniques.

The oxidation behavior of Ti-25Al, Ti-24Al-15Nb, and Ti-25Al-11Nb (at. pct) titanium aluminides was studied in dry oxygen at atmospheric pressure in the temperature range 1000 to 1300 K for 4 to 6 hours by thermogravimetry. The oxidation products were characterized by X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray (EDX) analysis. Although some departures from the parabolic rate law were found, the analysis of data revealed that the parabolic rate law was a more reliable basis for interpretation of results as compared to the empirical power law. Parabolic rate constants (k p ) for Ti-24Al-15Nb and Ti-25Al-11Nb were almost the same at the same temperature. However, k p values for Ti-25Al were 2 to 8 times larger than niobium-containing alloys except at 1000 K, where k p values for all three alloys were approximately the same. The effective activation energy (Q eff) was 289 kJ/mole for Ti-25Al in the range of 1000 to 1300 K, while in the case of Ti-24Al-15Nb and Ti-25Al-11Nb,Q eff values were 329 and 330 kJ/mole, respectively, in the range of 1100 to 1300 K. In general, the scales on Ti-25Al were porous and exhibited significant spallation above 1100 K. The scales were thinner, compact, and adherent for niobium-containing alloys. The scales formed on these alloys were predominantly composed of TiO2, while Al2O3 was also present as a minor constituent. The superior oxidation resistance of the niobium-containing alloys has been attributed to the doping effect of niobium in TiO2.

Significant subscale hardening was observed in Ti-25Al and Ti-24Al-15Nb after exposure in O{sub 2}, N{sub 2} and 20O{sub 2}-80N{sub 2} at 1,300 K. The diffusivities of nitrogen and oxygen were determined from the microhardness profiles. The diffusivities of nitrogen in Ti-25Al and Ti-24Al-15Nb are comparable to that reported for {alpha}-Ti. No data could be located in literature on these or similar alloys. Diffusivity of oxygen in Ti-24Al-15Nb determined in the present study is close to that reported for Ti-25Al-11Nb.

Treatment of six-coordinate (5,10,15-triphenylcorrole)dihydroxyphosphorus(V) [P(TPC)(OH)2] with trifluoroacetic acid (TFA) in CH2Cl2 for 30 min at room temperature followed by recrystallization gave stable five-coordinate (5,10,15-triphenylcorrole)oxophosphorus(V) [P(TPC)O] in quantitative yield. The formation of [P(TPC)O] from [P(TPC)(OH)2] in the presence of TFA was also monitored by NMR, absorption and fluorescence spectroscopic titration studies. The structure of the isolated [P(TPC)O] was confirmed by X-ray crystallography. In [P(TPC)O], the corrole ring is distorted, and the PV ion is displaced by 0.456 angstrom from the N4 plane towards the axial oxygen atom. This is unlike six-coordinate (5,10,15-triphenylcorrole)dimethoxyphosphorus(V) [P(TPC)(OCH3)2], in which the PV ion lies in the porphyrin plane. NMR, absorption and fluorescence spectroscopy and electrochemical studies indicate that [P(TPC)O] exhibits interesting and distinct properties, which differ from the six-coordinate [P(TPC)(OCH3)2]. Attempts to reduce the PV complex [P(TPC)O] to its corresponding PIII complex by treating it with LiAlH4 resulted in the formation of six-coordinate (5,10,15-triphenylcorrole)dihydridophosphorus(V) [P(TPC)H2].

The hexa-coordinated rhenium(I) tricarbonyl complexes of 5,10,15,20-tetraphenyl-21-thiaporphyrin 1 and 5,10,15,20-tetraphenyl-21-oxaporphyrin 2 have been synthesized by thermal reaction of corresponding free base porphyrin with Re(2)(CO)(10). The compounds 1 and 2 are characterized by HR-MS mass, (1)H, and (13)C NMR, FTIR, UV-vis, and electrochemical techniques and the structures are determined by X-ray single crystal analysis. The X-ray analysis revealed different coordination behavior of Re(CO)(3) with 21-thiaporphyrin and 21-oxaporphyrin. Interestingly, the Re(CO)(3) coordinates to two of the three inner nitrogens and one sulfur instead of three inner nitrogens as generally expected to produce unique compound 1 whereas it coordinates to three inner nitrogens but not with furan oxygen to form compound 2. The 21-thiaporphyrin ring is more distorted in compound 1 compared to 21-oxaporphyrin ring in compound 2 on complexation with Re(CO)(3). The presence of three carbonyl groups in compounds 1 and 2 are verified by (13)C NMR and IR spectroscopy. The absorption spectra of compounds 1 and 2 showed ill-defined Q-bands along with broad Soret band and the extinction coefficients are much lower than their corresponding free base porphyrins. The compounds 1 and 2 showed two reversible porphyrin ring based reductions supporting their electron deficient nature. The compound 1 is very stable under protonation conditions, and the protonation occurs at the uncoordinated pyrrole ring whereas the compound 2 undergoes decomplexation under same conditions. Furthermore, compound 1 showed the fluxional behavior in coordination mode of binding in solution.

We investigate the nature of competitive equilibrium for brands competing in a multi-attribute product space when consumer preferences for product attributes follow nonuniform distributions. We establish subgame-perfect equilibria in a two-stage game, where firms choose positions in the first stage and prices in the second stage. Two types of entry scenarios are investigated. In the first, the number of brands is given exogenously, and all of them choose positions simultaneously. In the second scenario, firms enter in sequence, and the early entrants can choose strategies to deter the entry of later entrants. We find the equilibria for two, three, and four brands for consumer preferences that follow a beta distribution. Nonuniform distributions result in equilibrium configurations that are substantially different from those obtained for uniform consumer distributions. In the two brands case, for sufficiently concentrated distributions we find asymmetric position equilibria with one firm at the corner of the market and one firm at an interior position. In the case of three brands, for sufficiently concentrated preferences we find symmetric equilibria that do not yield maximal differentiation. We also establish an equilibrium for the case of four competing brands. In addition we characterize entry deterring positioning strategies and examine how they vary with the distribution of consumer preferences.

In the transverse sections of low carbon continuously cast steel billets, samples for analyses of carbon and sulphur were collected by drilling at the billet centres as well as at the columnar-equiaxed transition (CET) boundaries, as revealed in etched macrostructures. Correlation of degrees of segregation for carbon (rc) with those for sulphur (rs) agreed closely with that predicted by Scheil's or modified Scheil's equation at the CET boundaries, but not at the billet centres. Variations of rc and rs with fractional solidification, although did not agree with predictions of the above equations, were in qualitative agreement with actual macrosegragation data reported in literature. Attempts were also made to correlated the experimental macrostructural and macrosegragation data with predictions based on conjugate fluid flow-heat transfer model developed earlier. Results of this exercise demonstrated close agreement of the predicted locations of CET boundaries with the measured values. This is being taken as additional confirmation of the reliability of the conjugate fluid flow-heat transfer model. Also, it seems that this model may be employed to estimate the size of equiaxed zone in continuous casting of steel.

The synthesis, spectroscopic, and electrochemical properties of seven new P(V)-meso-triarylcorroles (1-7) are reported. Compounds 1-7 were prepared by heating the corresponding free-base corroles with POCl(3) at reflux in pyridine. Hexacoordinate P(V) complexes of meso-triarylcorroles were isolated that contained two axial hydroxy groups, unlike the P(V) complex of 8,12-diethyl-2,3,7,13,17,18-hexamethylcorrole, which was pentacoordinate, or the P(V) complex of meso-tetraphenylporphyrin, which was hexacoordinate with two axial chloro groups. (1)H and (31)P NMR spectroscopy in CDCl(3) indicated that the hexacoordinated P(V)-meso-triarylcorroles were prone to axial-ligand dissociation to form pentacoordinated P(V)-meso-triarylcorroles. However, in the presence of strongly coordinating solvents, such as CH(3)OH, THF, and DMSO, the P(V)-meso-triarylcorroles preferred to exist in a hexacoordinated geometry in which the corresponding solvent molecules acted as axial ligands. X-ray diffraction of two complexes confirmed the hexacoordination environment for P(V)-meso-triarylcorroles. Their absorption spectra in two coordinating solvents revealed that P(V)-meso-triarylcorroles showed a strong band at about 600 nm together with other bands, in contrast to P(V)-porphyrins, which showed weak bands in the visible region. These compounds were easier to oxidize and more difficult to reduce compared to P(V)-porphyrins. These compounds were brightly fluorescent, unlike the weakly fluorescent P(V)-porphyrins, and the quantum yields for selected P(V)-corroles were as high as Al(III) and Ga(III) corroles, which are the best known fluorescent compounds among oligopyrrolic macrocycles.

Composite bipolar plates for polymer electrolyte membrane fuel cell (PEMFC) were developed by compression molding technique using vinyl ester resin as a binder and natural graphite, carbon black, and carbon fiber as conductive reinforcements. The developed bipolar plates were characterized for electrical conductivity, flexural strength, deflection at mid-span, hydrogen permeability, and morphology. The in-plane and through-plane electrical conductivities of the composite bipolar plate (VER:25%;CB:5%;CF:5%;NG:65%) were 355.05 and 95.96 S·cm−1 , respectively. The flexural strength of the same bipolar plate was 53.50 MPa with a deflection of 5.37%. The hydrogen permeability of the bipolar plate was in the order of 10−9 cm3 ·cm−1 ·s−1 at 50°C. The overall properties of the composite bipolar plate were found to achieve the benchmark set by USA-Department of Energy. However, the through-plane electrical conductivity of the above composite was edge below the target value. Therefore, graphene, being one of the most electrical conductive materials, has been reinforced into the composite bipolar plate. The results were very encouraging as 1% graphene reinforcement increased the in-plane and through-plane electrical conductivities of the bipolar plate by around 6 and 35%, respectively. The performance of a PEMFC was evaluated using the developed bipolar plate in in-situ condition.Copyright © 2011 by ASME

The metal derivatives (Co(II), Ni(II), Cu(II), Zn(II) and Sn(IV)) of hexaporphyrinato cyclotriphosphazene systems were prepared by treating the hexaporphyrin assembly on cyclotriphosphazene ring with the appropriate metal salt under standard metallation conditions. The complete metallation of all six porphyrin units in hexaporphyrin assembly required 10-12 h reflux as judged by the absorption spectroscopy. The metal derivatives were confirmed by molecular ion peak in mass spectra for all compounds. (31)P and (1)H NMR spectra for Ni(II), Zn(II) and Sn(IV) derivatives and ESR spectra for Cu(II) derivative also confirmed the complete metallation of all six porphyrin units. The hexametalloporphyrin assemblies are freely soluble in common organic solvents. The spectral, electrochemical and fluorescence studies indicate that the six porphyrin units in assemblies interact very weakly and retain their individual characteristic features in the ground and excited states. (C) 2011 Elsevier B.V. All rights reserved.

Based on an analysis of playing statistics for two different seasons, NBA players can be classified as filling distinct roles, such as scorers, bangers, dishers, inner court members, and walls. These roles have a great deal of face validity and correspond to distinct offensive and defensive playing styles. In addition, the roles players fill are not necessarily tied to unique positions. The nature of the game may be subtly changing. NBA teams no longer rely on a physically dominant center. The roles of the big men have become more varied over time. Teams can improve their performance by having a balanced role structure. Analysis of a team's role structure provides useful guidelines for selecting draft choices and executing trades.

A steady-state three-dimensional heat flow model based on the concept of artificial effective thermal conductivity has been developed. On the basis of available literature information, boundary conditions to the governing heat flow equation have been applied, and the equation was solved via the control-volume based finite difference procedure. The model is sufficiently general and can be applied to various geometrical shapes of relevance to continuous casting of steel. Sensitivity of the predicted results to various numerical approximation including grid configurations, as well as to other modelling parameters such as axial conduction, mushy zone modelling procedure, choice of value of Keff have been extensively studied. It has been shown that assumptions and numerical procedures influence the computed results significantly. Finally, numerical predictions have been compared with three sets of experimental measurements reported in literature on shell thickness in industrial casters. In contrast to some earlier claims, these indicated only poor to moderate agreement between model predictions and experimental results.

Molecular dynamics trajectories of large biological molecules are restricted to nanoseconds. We describe a computational method, based on optimization of a functional, to extend the time of molecular simulations by orders of magnitude. Variants of our technique have already produced microsecond and millisecond trajectories. The large steps enable feasible computations of atomically detailed approximate trajectories. Numerical examples are provided: (i) a conformational change in blocked glycine peptide and (ii) helix formation of an alanine-rich peptide.

An examination of the timing of consumers' purchases for coffee reveals that consumers vary a great deal in terms of the regularity of their purchasing behavior. Some consumers make purchases at seemingly random time intervals, while others purchase at highly regular intervals. The measurement of regularity in purchase timing, as well as the identification of its covariates, is important in many contexts such as modeling purchase incidence and sales forecasting. We measure the degree of regularity among a sample of coffee purchasers and identify several consumer characteristics that vary with the degree of regularity in purchase timing. Results show that regularity in purchase timing is related to brand loyalty, store loyalty and deal proneness, as well as to certain pattern of routinization by the households, and that regularity may be used, along with other aspects of purchase behavior, to provide a basis for market segmentation.

The non-resonant elastic scattering of low-energy photons by the bound valence electron in the ground state 3s of atomic sodium confined in quantum plasmas is investigated theoretically. The incident photon energy is assumed to be much smaller than the 3s-3p excitation energy. The alkali atom sodium is first formulated as an effective one-electron problem in which the attractive interaction between the valence electron and the atomic ion core is simulated by a spherically symmetric model potential. The Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential model is then used to mimic the effective two-body (valence-core) interaction within quantum plasmas. Non-relativistic calculations performed within the electric dipole approximation indicate that the non-resonant elastic photon scattering cross-section undergoes a dramatic growth by several orders of magnitude as the quantum wave number increases. A qualitative explanation of this phenomenon is presented. In the absence of the oscillatory cosine screening term, a similar growth is observed at larger values of the quantum wave number. Our computed relevant atomic data are in very good agreement with the experimental as well as the previous theoretical data for the zero-screening (free atom) case, and with the very limited, accurate theoretical results available for the case of exponential screened-Coulomb two-body interaction, without the cosine screening term.

This prospective, observational study was carried out in a teaching hospital in Calcutta, India. The aim of the study was to evaluate the prevalence of anti-phospholipid syndrome (APS) among women with recurrent miscarriages/late pregnancy loss when no other apparent causes were identified, in the study population. The women were put through a variety of investigations to determine the cause of miscarriage/pregnancy loss. Only those women who had a normal result for all the investigation went for the anti-phospholipid antibodies (APLA) test. The expelled products of conception/placenta were also sent for histopathological confirmation. A total of 445 women were studied over a 4-year period. A total of 155 women were offered a screening for APLA antibodies. Out of them, 43 women (27.7%) tested positive for APLA. Histopathological evidence was present in all the specimens. Interestingly, one woman had histopathological evidence of thrombosis, but her blood tests for the antibody were negative.

The liver X receptors (LXRs) alpha and beta are responsible for the transcriptional regulation of a number of genes involved in cholesterol efflux from cells and therefore may be molecular targets for the treatment of cardiovascular disease. However, the effects of LXR ligands on cholesterol turnover in cells has not been examined comprehensively. In this study, cellular cholesterol handling (e.g., synthesis, catabolism, influx, and efflux) was examined using a stable isotope labeling study and a two-compartment modeling scheme. In HepG2 cells, the incorporation of 13C into cholesterol from [1-13C]acetate was analyzed by mass isotopomer distribution analysis in conjunction with nonsteady state, multicompartment kinetic analysis to calculate the cholesterol fluxes. Incubation with synthetic, nonsteroidal LXR agonists (GW3965, T0901317, and SB742881) increased cholesterol synthesis (approximately 10-fold), decreased cellular cholesterol influx (71-82%), and increased cellular cholesterol efflux (1.7- to 1.9-fold) by 96 h. As a consequence of these altered cholesterol fluxes, cellular cholesterol decreased (36-39%) by 96 h. The increased cellular cholesterol turnover was associated with increased expression of the LXR-activated genes ABCA1, ABCG1, FAS, and sterol-regulatory element binding protein 1c. In summary, the mathematical model presented allows time-dependent calculations of cellular cholesterol fluxes. These data demonstrate that all of the cellular cholesterol fluxes were altered by LXR activation and that the increase in cholesterol synthesis did not compensate for the increased cellular cholesterol efflux, resulting in a net cellular cholesterol loss.

The two types of protein folding problems (theoretical predictions of protein structure and folding pathways) are discussed. Most of the effort in our laboratory has been devoted to computing three-dimensional structures of proteins from amino acid sequence, using either an all-atom or a united-residue force field. More recently, folding pathways have been computed with a stochastic difference equation method, and folding trajectories have been simulated by molecular dynamics with the united-residue force field.

Computational and theoretical considerations for the extension of systems biology into the spatiotemporal realm will be discussed. Both limitations and extensions of current approaches within the research community will be investigated, along with the approach taken by our group in a newly developed software package, CellSim. Application of all computational aspects described rely on cellular assays imaged by fluorescence confocal microscopy. Taken together, this extension to systems biology may answer questions about complex protein networks and the role spatial heterogeneity may play in such processes.

Activation of the extracellular signal-regulated kinases (ERK1/2; p42/p44 mitogen-activated protein kinase (MAPK)) is one of the most extensively studied signaling pathways not least because it occurs downstream of oncogenic RAS. Here, we take advantage of the wealth of experimental data available on the canonical RAS/RAF/MEK/ERK pathway of Bhalla et al. to test the utility of a newly developed nonlinear analysis algorithm designed to predict likelihood of cellular transformation. By using ERK phosphorylation as an “output signal”, the method analyzes experimentally determined kinetic data and predicts putative oncogenes and tumor suppressor gene products impacting the RAS/MAPK module using a purely theoretical approach. This analysis identified several modifiers of ERK/MAPK activation described previously. In addition, several novel enzymes are identified which are not previously described to affect ERK/MAPK phosphorylation. Importantly, the nonlinear analysis enables a ranking of modifiers of MAPK activation predicting their relative importance in RAS-dependent oncogenesis. The results are compared with a linearized analysis based on sensitivity analysis about the steady state or metabolic control analysis (MCA). The results are favorable, pointing to the utility of first-order sensitivity analysis and MCA in the analysis of complex signaling networks for oncogenes.

Interest centers here on whether a polyproline II helix can propagate through adjacent non-proline residues, and on shedding light on recent experimental observations suggesting the presence of significant PP(II) structure in a short alanine-based peptide with no proline in the sequence. For this purpose, we explored the formation of polyproline II helices in proline-rich peptides with the sequences Ac-(Pro)(3)-X-(Pro)(3)-Gly-Tyr-NH(2), with X = Pro (PPP), Ala (PAP), Gln (PQP), Gly (PGP), and Val (PVP), and Ac-(Pro)(3)-Ala-Ala-(Pro)(3)-Gly-Tyr-NH(2) (PAAP), by using a theoretical approach that includes a solvent effect as well as cis trans isomerization of the peptide groups and puckering conformations of the pyrrolidine ring of the proline residues. Since (13)C chemical shifts have proven to be useful for identifying secondary-structure preferences in proteins and peptides, and because values of the dihedral angles (phi,psi) are the main determinants of their magnitudes, we have, therefore, computed the Boltzmann-averaged (13)C chemical shifts for the guest residues in the PXP peptide (X = Pro, Ala, Gln, Gly, and Val) with a combination of approaches, involving molecular mechanics, statistical mechanics, and quantum mechanics. In addition, an improved procedure was used to carry out the conformational searches and to compute the solvent polarization effects faster and more accurately than in previous work. The current theoretical work and additional experimental evidence show that, in short proline-rich peptides, alanine decreases the polyproline II helix content. In particular, the theoretical evidence accumulated in this work calls into question the proposal that alanine has a strong preference to adopt conformations in the polyproline II region of the Ramachandran map.

This paper describes previous work on decision fusion in audio-visual speech recognition. A novel approach is proposed to combine audio and video channel information in audio-visual speech recognition scenario. We have considered frame-level phonetic classification problem using two single-stream Gaussian mixture models. Audio and video streams are adaptively weighted using a cumulative mean of the sample confidence values over past frames in addition to the present sample confidence value. The confidence values for audio and video decisions are computed using an L-statistics (linear combination of order-statistics) of log-likelihoods against phone models. It is shown through various experiments, on a database of about 15000 sentences from large vocabulary continuous speech, that the proposed approach results in better classification accuracy as compared to other approaches.

Molecular dynamics trajectories of large biological molecules are restricted to nanoseconds. We describe a computational method, based on optimization of a functional, to extend the time of molecular simulations by orders of magnitude. Variants of our technique have already produced microsecond and millisecond trajectories. The large steps enable feasible computations of atomically detailed approximate trajectories. Numerical examples are provided: (i) a conformational change in blocked glycine peptide and (ii) helix formation of an alanine-rich peptide.

Molecular Dynamics (MD) simulations provide an atomically detailed description of complex systems on a wide range of temporal and spatial scales. Despite numerous successes and many insightful observations, a clear limitation of the MD approach is its short time scales. Routine simulations of complex and large molecular systems at the atomically level of detail are restricted to nanoseconds. This time scale is far too short to address many interesting processes in biophysics, such as conformational transitions, transport phenomena and reactions.

Molecules of the title macrocycle, C36H22N4O4, are located on an inversion center. The porphyrin ring shows a wave-like conformation with adjacent pyrrole rings tilted above the porphyrin plane and the interporphyrin distance is 3.584 (3) Å. The dihedral angles between the meso-furyl groups and the porphyrin plane are 38.87 (7) and 48.29 (7)°; these are much smaller than those observed for meso-tetraphenylporphyrin, indicating that the meso-furyl groups are more inclined towards the porphyrin plane. The decrease in the dihedral angle is due to the presence of intramolecular hydroden bonding between the meso-fury O atom and the β-pyrrole CH group. Intramolecular N—H...N hydrogen bonds are also present.

Synthesis and first structural characterization of hexa coordinated rhenium(I)tricarbonyl complex of 5,20-bis( p-tolyl)-10,15-bis(p-methoxyphenyl)-21-selenaporphyrin 3 are described. The Re(I)complex of 21-selenaporphyrin 3 was synthesized by treating free base 21-selenaporphyrin in 1,2-dichlorobenzene with Re(CO)(5)Cl at reflux for 7 h and analyzed using mass, NMR, FT-IR, UV-vis and electrochemical techniques. The first structure of metal complex of 21-selenaporphyrin was determined by X-ray single crystal analysis. The crystal structure revealed that the Re(CO)(3) coordinates to two of the three inner nitrogens and one selenium to produce compound 3. The selenophene ring bent towards the Re(I)ion and the selenium is displaced by 0.41 angstrom from the mean plane of 24-atoms to coordinate with Re(I)ion in eta(1)-fashion. The 21-selenaporphyrin is distorted in compound 3 compared to free base 21-selenaporphyrin. H-1 and C-13 NMR studies indicated that compound 3 exhibits fluxional behaviour in coordination mode of binding in solution. The compound 3 is highly stable and does not undergo decomplexation under acidic conditions. The absorption spectra showed three broad Q-bands and splitted Soret band and electrochemical studies indicated that compound 3 is stable under redox conditions.

In this work, the compatibility studies of silicon and its different multilayer structures with hydrazine for possible applications to MEMS have been reported. Grazing incidence x-ray diffraction patterns of the r.f. sputtered Si/SiO2/Si3N4 stack layer show preferably oriented crystalline structure after hydrazine treatment at different temperatures. The Fourier transform infrared spectroscopic measurement reveals that local bonding of the constituent atoms of the surface layers, where Si–O bond is replaced partially by Si–N bond while treated. Further, the surface morphology carried out by atomic force microscopy exhibits the tendency of reducing surface roughness with the increase in temperature during hydrazine treatment. From the axisymmetric drop shape analysis (ADSA), it is observed that static contact angle changes slightly for different wettability nature of solid surface due to aggregation of crystallites in the valley of the surface fluctuation and anisotropic modification in preferred orientation of the film surface. On the basis of equation of state theory with approximation of solid surface–liquid, interfacial energy was applied to determine the solid surface free energy providing the limited variation in different stack layers. Lastly, the J–V characteristic of the stack layer treated by hydrazine at different temperatures shows multiple current conduction regions with the same current density for varying electric field. Therefore, among various single or multilayer silicon-based thin film combinations, the Si/SiO2/Si3N4 stack layer is the most promising passivation layer for hydrazine-based MEMS applications.

Four axial-bonding type Al(III) porphyrin based dyads, containing thiaporphyrins with N3S 1 and N2S2 2 cores and expanded thaiporphyrins with N2S3 3 and N2S4 4 cores, were synthesised by treating [(TPP)A1(III)OH] with the corresponding mono-functionalised meso-4-hydroxyphenyl thiaporphyrin or expanded thiaporphyrin building blocks in benzene at refluxing temperature. The stable dyads 1-4 are freely soluble in common organic solvents and characterized by mass, ID and 2D NMR, absorption, electrochemical and fluorescence techniques. ID and 2D NMR studies unambiguously confirmed the dyads. The absorption and electrochemical studies show weak interaction between the two macrocycles in dyads and the constituted macrocycles in dyads mostly retain their characteristic individual features. The steady state fluorescence studies indicate a decrease in the quantum yield of Al(m) porphyrin unit in dyads 1-4 and invoked the possibility of singlet-singlet energy transfer from the Al(m) porphyrin unit to the N3S porphyrin unit in dyad 1 and N2S2 porphyrin unit in dyad 2. Structural information of these dyads in their ground (S-0) state are generated by applying density functional theory (DFT) based quantum chemical calculations. Excited state calculations are carried out following time dependent density functional theory (TD-DFT) and UV-Vis spectra of these dyads are simulated in the Soret band region.

Zn embedded ZnO nanostructure thin films were prepared using a cost-effective novel vacuum-carbon-arc combined with the vacuum annealing technique. The photoluminescence spectra of the samples exhibit a strong near-band-edge emission around 377 nm and a weak defect band in the visible range accompanied by some multiphonon peaks at a higher energy. The shift in the optical absorption band arises due to potential fluctuation of the carrier density. Surface optical phonon mode predominant Raman spectra are observed, which is attributed to the surface potential (due to defects) present in the system. The predicted surface phonon frequency based on the dielectric continuum approach is in good agreement with that observed experimentally.

This paper discusses the problems in interpreting the correlation coefficient as a measure of geographical accessibility to public services by income groups. As an alternative a relative index is proposed which incorporates the unique limits to the correlation coefficient in any area and thus allows meaningful comparison of results between areas and services. To illustrate the use and interpretation of the relative index an empirical analysis of differential access is presented.

The optical and electrical properties of evaporated amorphous silicon with hydrogen have been studied under various deposition conditions. Infrared measurements indicate that the hydrogen content of the films are comparable to a‐Si : H films produced by other techniques. The optical‐absorption coefficient below the band gap of ∼1.55 eV was measured to be ∼100 cm−1 for samples made at deposition temperatures of ∼275–325 °C. For these samples the photoresponse at room temperature and the temperature dependence of the conductivities were studied. Dark conductivities were found to be thermally activated for T≳300 K with activation energies of ∼0.75 eV. We found type‐1 photoconductivity and investigated its dependence on the light intensity. When samples were heated to ∼175 °C in a vacuum and then exposed to air, they exhibited time‐dependent increases in the dark conductivity and photoconductivity. This effect was reversible by a reanneal in a vacuum. High‐temperature anneals to ∼450 °C increased the optical absorption below 1.4 eV and decreased the photoresponse significantly.

In COMPLOC, an interactive computer game, students apply their knowledge of store location models to a realistic scenario. The competitive framework instills student interest and appreciation for long-term planning in a competitive environment. The article discusses the structure of the game, its learning objectives and our experience with its use.

The authors compare market share models differing in terms of functional form, estimation procedure, and level of parameterization. They evaluate the models by testing the accuracy of predicted shares as well as the validity of the estimated parameters. The tests indicate that valid parameter estimates and similar forecasts are obtained with linear, multiplicative, and attraction models. Better share forecasts generally are obtained from models with brand-specific parameterization and OLS estimation. Most of these conclusions are contrary to previous findings. Several implications for researchers are discussed.

The question of spatial nonstationarity in retail choice models generally has been ignored in the literature. This paper discusses why such nonstationarity might arise and presents an empirical test of nonstationarity in grocery choice data collected from a midwestern city. Based on these findings a nonstationarity retail choice model is proposed. The nonstationary model predicts data from a hold-out sample better than the stationary model.

Designing a network of service centers involves a tradeoff between the revenue likely to be generated by providing a high level of service and the cost of operating the service network. The authors develop a procedure for determining the location and design strategies for new services using a modified maximal covering location-allocation model. The network optimization procedure relies on direct assessment of consumer sensitivity to distance and nondistance factors through conjoint analysis and simultaneously determines the network size, location of outlets, price, and operating characteristics.

The spatiotemporal pattern of periodic market places depends upon the function of the marketing system in a region. Market places that facilitate local exchange would be located differently from those that facilitate interregional trade or provide urban goods to rural areas. The effects of changes in transport infrastructure and consumer behavior on market location patterns also depend upon the organization of the marketing system. The process of market organization implicit in the “consumer hypothesis'’is in contradiction with the theoretical models of periodic markets.

Reduction of porous and dense pellets of ferric oxide were carried out with methane in the temperature range of 1073 to 1298K. The reduction pattern was, broadly speaking, topochemical. Volume of pellets increased upon reduction except at 1298K. Extent of carbon deposition in pellets increased linearly with increasing temperature. Rate of reduction with CH4 was approximately 41/2 times slower as compared to that with H2 at 1223K. The overall reaction may be considered to consist of decomposition of CH4 into C and H2, and reduction of pellet by the resulting H2. The decomposition reaction was found to control the overall rate primarily. The reduction of pellet by H2 seems to be controlled by counter diffusion of H2 and H2O in the gas boundary layer.