Maleimide‐based thiol reactive multiarm star polymers via Diels‐Alder/retro Diels‐Alder strategy

Multiarm star polymers containing thiol‐reactive maleimide groups at their core have been synthesized by utilization of atom transfer radical polymerization (ATRP) of various methacrylates using a masked maleimide containing multiarm initiator. One end of the initiator contains multiple halogen groups that produce the star architecture upon polymerization and the other end contains a masked maleimide functional group. Unmasking of the maleimide group after the polymerization provides the thiol reactive maleimide core that is widely used in bioconjugation. Functionalization of the core maleimide group with a thiol containing tripeptide was used to demonstrate facile reactivity of the core of these multiarm polymers under reagent‐free conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2546–2556, 2010     

An efficient fluctuating charge model for transition metal complexes

A fluctuating charge model for transition metal complexes, based on the Hirshfeld partitioning scheme, spectroscopic energy data from the NIST Atomic Spectroscopy Database and the electronegativity equalization approach, has been developed and parameterized for organic ligands and their high‐ and low‐spin Fe^II and Fe^III, low‐spin Co^III and Cu^II complexes, using atom types defined in the Momec force field. Based on large training sets comprising a variety of transition metal complexes, a general parameter set has been developed and independently validated which allows the efficient computation of geometry‐dependent charge distributions in the field of transition metal coordination compounds. © 2013 Wiley Periodicals, Inc.     

Unteady heat flow and temperature variation in human SST regions

The temperature distribution in human skin and subdermal tissue layer is presented using bioheat transfer equation. The body temperature is determined by the balance between heat produced and heat lost by our body. The time-dependent solutions have been found to be affected by the metabolic heat genaration rate, blood mass flow, the rate of evaporation of perspiration and also by the atmospheric temperature. The analytic solutions for different layers have been calculated numerically and are also shown graphically.     

Phonon properties of rare earth ytterbium pnictides

We report for the first time the complete phonon dispersion curves for the ytterbium pnictide compounds (YbN, YbP and YbAs) using a breathing shell model to establish their predominant ionic nature. The calculated results also show that this group of rare earth compounds does not show any elastic and phonon anomalies which are the characteristic features of other rare earth compounds. We emphasize the need for further Raman and neutron scattering measurements.     

A three-body force shell model calculation of Schottky defect formation energies of ionic crystals with CsCl structure

A three-body force shell model (TSM) for the calculation of Schottky defect formation energies in solids with cesium chloride structure has been developed by incorporating the effects of long-range three-body interactions (TBI) in the shell model. These TBI in the defect lattice arise from the deformation of electron shells when the nearest neighbour ions get relaxed from their equilibrium position. This model has been used to calculate the cation and anion extraction and Schottky defect formation energies of CsCl, CsBr, CsI, TlCl, TlBr and NH₄Cl crystals. The calculated values of these defect properties agree reasonably well with their measured values.     

Nonlinear lattice dynamical theory for valence transition in rare earth compounds

A nonlinear lattice dynamical theory is proposed to explain the mode softening in intermediate valence compound Sm_0.75 Y_0.25 S. In this theory we consider the breathing motion of the electron shells of Sm-ion to be nonlinear, and depend on temperature, resulting in strong electron-ion coupling. We calculate the salient features of the nonlinear breathing potential, which resembles theφ ⁴ potential for second order ferro-electric transitions. We also calculate the temperature dependence of LO(L) frequency for this compound, showing that at transition temperature (about 200 K) this mode freezes.     

Sensitivity analysis methods for a crop-mix problem in linear programming

Summary Four different methods of analyzing the sensitivity of the optimal solution of a crop-mix problem in linear programming, e. g., (a) variability analysis for second-best and third-best solutions, (b) perturbation analysis around a specific optimal basis, (c) the sensitivity coefficient approach, and (d) the method of fractile criterion by which a specified fractile of the distribution of profits is maximized, are investigated here. The objective is to compare the different operational methods of sensitivity analysis applied to an empirical economic problem.

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Zusammenfassung Die vorliegende Arbeit behandelt vier Methoden zur Untersuchung der Sensitivität der optimalen Lösung eines crop-mix-Problems der linearen Programmierung: a) variability analysis für zweit- und drittbeste Lösungen, b) perturbation analysis der optimalen Basis, c) das sensitivity-coefficient-Verfahren und d) die fractile-criterion-Methode, durch die ein bestimmter Teil der Gewinnverteilung maximiert wird. Ziel der Arbeit ist ein Vergleich der Methoden bezüglich ihrer Anwendung auf empirische ökonomische Probleme.

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Work done under the NSF Projects 420-21-17 and 420-04-62 at the Department of Economics, Iowa State University, Ames, Iowa. Other research work closely related to this paper may be found inSengupta; Sengupta-Portillo-Campbell; Sengupta-Tintner.     

Adsorption of water on TiN (1 0 0), (1 1 0) and (1 1 1) surfaces: A first-principles study

We use first-principles density functional theory-based calculations in the analysis of the interaction of H₂O with (1 0 0), (1 1 0) and (1 1 1) surfaces of TiN, and develop understanding in terms of surface energies, polarity of the surface and chemistry of the cation, through comparison with H₂O adsorption on ZrN. While water molecule physisorbs preferentially at Ti site of (1 0 0) and (1 1 1) surfaces, it adsorbs dissociatively on (1 1 0) surface of TiN with binding stronger than almost 1.32 eV/molecule. Our analysis reveals the following general trends: (a) surfaces with higher energies typically lead to stronger adsorption, (b) dissociative adsorption of H₂O necessarily occurs on a charge neutral high energy surface and (c) lower symmetry of the (1 1 0) plane results in many configurations of comparable stability, as opposed to the higher symmetry (1 0 0) and (1 1 1) surfaces, which also consistently explain the results of H₂O adsorption on MgO available in literature. Finally, weaker adsorption of H₂O on TiN than on ZrN can be rationalized in terms of greater chemical stability of Ti arising from its ability to be in mixed valence.