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Electrostatic Field (electrostatic + field)
Kinds of Electrostatic Field Selected AbstractsEffect of Thawing and Cold Storage on Frozen Chicken Thigh Meat Quality by High-Voltage Electrostatic FieldJOURNAL OF FOOD SCIENCE, Issue 4 2010Chang-Wei Hsieh ABSTRACT:, One of the most popular issues in electrostatic biology is the effects of a high-voltage electrostatic field (HVEF) on the thawing of chicken thigh meat. In this study, chicken thigh meat was treated with HVEF (E-group), and compared to samples stored in a common refrigerator (R-group), to investigate how HVEF affects chicken thigh meat quality after thawing at low temperature storage (,3 and 4 °C). The results showed that there were no significant differences in biochemical and microorganism indices at ,3 °C. However, the HVEF can significantly shorten thawing time for frozen chicken thigh meat at ,3 °C. After thawing chicken thigh meat and storing at 4 °C, the total viable counts reached the Intl. Commission on Microbiological Specification for Foods limit of 107 CFU/g on the 6 and 8 d for the R- and E-group, respectively. On the 8th d, the volatile basic nitrogen had increased from 11.24 mg/100 g to 21.9 mg/100 g for the E-group and 39.9 mg/100 g for the R-group, respectively. The biochemical and microorganism indices also indicated that the E-group treatment yielded better results on thawing than the R-group treatment. The application of this model has the potential to keep products fresh. [source] Giant Electric Field Tuning of Magnetic Properties in Multiferroic Ferrite/Ferroelectric HeterostructuresADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Ming Liu Abstract Multiferroic heterostructures of Fe3O4/PZT (lead zirconium titanate), Fe3O4/PMN-PT (lead magnesium niobate-lead titanate) and Fe3O4/PZN-PT (lead zinc niobate-lead titanate) are prepared by spin-spray depositing Fe3O4 ferrite film on ferroelectric PZT, PMN-PT and PZN-PT substrates at a low temperature of 90,°C. Strong magnetoelectric coupling (ME) and giant microwave tunability are demonstrated by a electrostatic field induced magnetic anisotropic field change in these heterostructures. A high electrostatically tunable ferromagnetic resonance (FMR) field shift up to 600,Oe, corresponding to a large microwave ME coefficient of 67,Oe cm kV,1, is observed in Fe3O4/PMN-PT heterostructures. A record-high electrostatically tunable FMR field range of 860 Oe with a linewidth of 330,380,Oe is demonstrated in Fe3O4/PZN-PT heterostructure, corresponding to a ME coefficient of 108,Oe cm kV,1. Static ME interaction is also investigated and a maximum electric field induced squareness ratio change of 40% is observed in Fe3O4/PZN-PT. In addition, a new concept that the external magnetic orientation and the electric field cooperate to determine microwave magnetic tunability is brought forth to significantly enhance the microwave tunable range up to 1000,Oe. These low temperature synthesized multiferroic heterostructures exhibiting giant electrostatically induced tunable magnetic resonance field at microwave frequencies provide great opportunities for electrostatically tunable microwave multiferroic devices. [source] Auxiliary functions for molecular integrals with Slater-type orbitals.INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2008Abstract The Gauss transform of Slater-type orbitals is used to express several types of molecular integrals involving these functions in terms of simple auxiliary functions. After reviewing this transform and the way it can be combined with the shift operator technique, a master formula for overlap integrals is derived and used to obtain multipolar moments associated to fragments of two-center distributions and overlaps of derivatives of Slater functions. Moreover, it is proved that integrals involving two-center distributions and irregular harmonics placed at arbitrary points (which determine the electrostatic potential, field and field gradient, as well as higher order derivatives of the potential) can be expressed in terms of auxiliary functions of the same type as those appearing in the overlap. The recurrence relations and series expansions of these functions are thoroughly studied, and algorithms for their calculation are presented. The usefulness and efficiency of this procedure are tested by developing two independent codes: one for the derivatives of the overlap integrals with respect to the centers of the functions, and another for derivatives of the potential (electrostatic field, field gradient, and so forth) at arbitrary points. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Adsorption of water in mordenite,An ab initio studyINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2001Th. Demuth Abstract The adsorption of water in mordenite has been investigated using density functional theory using gradient corrections to the exchange,correlation functional. In the neutral complex water is strongly physisorbed through two different hydrogen bonds, the stronger between the acid site and the water oxygen atom, the weaker between a hydrogen atom of the adsorbed molecule and a framework oxygen atom. Strong polarizations and structural distortions of both the acid site and the molecule have been observed. To elucidate the question if a chemisorbed complex (creation of a hydroxonium ion) is possible, ab initio molecular dynamics have been performed, indicating that a protonation of water occurs even for the low coverage of one water molecule per unit cell. However, this ionic configuration cannot be stabilized by the electrostatic field of the zeolite framework and is therefore not a minimum of the potential energy surface. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 110,116, 2001 [source] Proton Transfer on the Molecular Surface of Proteins and Model SystemsISRAEL JOURNAL OF CHEMISTRY, Issue 2 2009Ran Friedman Proton transfer (PT) reactions take place on the molecular surface of proteins, membranes, ionic polymers, and other molecules. The rates of the reactions can be followed experimentally, while the atomistic details can be elucidated by molecular modeling. This manuscript gives a brief overview of the use of computer simulations and molecular modeling, in conjuction with experiments, to study PT reactions on the surface of solvated molecules. An integrative approach is discussed, where molecular dynamics simulations are performed with a protein, and quantum-mechanics-based calculations are performed on a small molecule. The simulation results allow the identification of the necessary conditions that yield PT reactions on the molecular surface. The reactions are efficient when they involve a donor and acceptor located a few Å apart and under the influence of a negative electrostatic field. In proton-pumping proteins, it is possible to identify such conditions a priori and locate proton-attracting antenna domains without the need to mutate each potential donor and acceptor. Based on density functional theory calculations, the arrangement of water molecules that interconnect the donor and acceptor moieties is suggested as the rate-limiting step for proton transfer on the molecular surface. [source] Charge and Mass Transfer Across the Metal/Solution InterfaceISRAEL JOURNAL OF CHEMISTRY, Issue 3-4 2008Eliezer Gileadi Electrode reactions are characterized by charge transfer across the interface. The charge can be carried by electrons or by ions. It is shown here that when both mass and charge cross the interface, the charge must be carried by the ionic species, not by the electrons, as a result of the very large difference in the time scale for electron and ion transfer. A prime example of charge transfer by ions is metal deposition. It is proposed that ion transfer occurs by migration of the ions across the interface, under the influence of the high electrostatic field in the double layer. The rate constants observed for metal deposition are comparable to those for outer-sphere charge transfer. These unexpectedly high rate constants for metal deposition are explained by a model in which removal of the solvation shell and reduction of the effective charge on the metal ion occur in many small steps, and a make-before-break mechanism exists, which lowers the total Gibbs energy of the system as it moves along the reaction coordinate from the initial to the final state. [source] Encapsulation efficiency and release behaviors of bovine serum albumin loaded in alginate microspheres prepared by sprayingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Jie Zhang Abstract Spraying and spraying with an electrostatic field (SEF) were employed to prepare alginate microspheres for delivering proteins, especially for intestinal digestive enzymes and cytokines. The encapsulation efficiency (EE) of a model protein [bovine serum albumin (BSA)] at a pH value lower than the isoelectric point was 20% higher than that at a natural pH. Moreover, for the microspheres prepared by SEF, EE improved significantly with increasing electric voltage. The interactions between BSA and the alginate microspheres were identified with Fourier transform infrared spectroscopy. The release profiles in vitro showed a controlled and pH-responsive release manner for the encapsulated BSA. A first-order release equation was postulated and modified to describe the release kinetics with an obviously initial burst release related to the eroded porous matrix. The equation fit the release data well when the pH value and composition of the release media were changed. The analysis of the release kinetics indicated that the drug release rate was in an inverse ratio to the diameter of the microspheres. Increasing the gas flow rate or electric voltage decreased both the mean diameter and size distribution of the microspheres significantly and enhanced the release rate of loaded drugs from alginate microspheres. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis analysis revealed that BSA kept its structural integrity during the encapsulation and release process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effect of Thawing and Cold Storage on Frozen Chicken Thigh Meat Quality by High-Voltage Electrostatic FieldJOURNAL OF FOOD SCIENCE, Issue 4 2010Chang-Wei Hsieh ABSTRACT:, One of the most popular issues in electrostatic biology is the effects of a high-voltage electrostatic field (HVEF) on the thawing of chicken thigh meat. In this study, chicken thigh meat was treated with HVEF (E-group), and compared to samples stored in a common refrigerator (R-group), to investigate how HVEF affects chicken thigh meat quality after thawing at low temperature storage (,3 and 4 °C). The results showed that there were no significant differences in biochemical and microorganism indices at ,3 °C. However, the HVEF can significantly shorten thawing time for frozen chicken thigh meat at ,3 °C. After thawing chicken thigh meat and storing at 4 °C, the total viable counts reached the Intl. Commission on Microbiological Specification for Foods limit of 107 CFU/g on the 6 and 8 d for the R- and E-group, respectively. On the 8th d, the volatile basic nitrogen had increased from 11.24 mg/100 g to 21.9 mg/100 g for the E-group and 39.9 mg/100 g for the R-group, respectively. The biochemical and microorganism indices also indicated that the E-group treatment yielded better results on thawing than the R-group treatment. The application of this model has the potential to keep products fresh. [source] Keeping quality of tomato fruit by high electrostatic field pretreatment during storageJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2008Yu Wang Abstract BACKGROUND: High electrostatic field, as a feasible and non-chemical technique, applied to food preservation is a new area of study. The present article intensively investigated this new preservation method, together with its effects on post-harvest physiology and quality of tomato. RESULTS: Green mature tomatoes were exposed to negative (or positive) high electrostatic field for 2 h at 20 °C and then stored for 30 days at 13 ± 1 °C, 85,90% RH. Our results indicated that negative high electrostatic field (,2 kV cm,1) could delay the decline of firmness and the change in color, total soluble sugar and titratable acidity of tomato fruit during storage. The peak of respiration and ethylene production of tomato fruit during storage were delayed by negative high electrostatic field treatment for 6 days and 3 days, respectively. Increases of malondialdehyde content and electrical conductivity in tomato fruit were inhibited significantly by negative high electrostatic field treatment during storage (P < 0.05). CONCLUSION: A high electrostatic field of , 2 kV cm,1 can be used to keep the qualities and extend the shelf-life of tomato fruit. Further research should be highly recommended to understand the mechanisms improving the storability of tomato fruit by negative high electrostatic field. Copyright © 2007 Society of Chemical Industry [source] A 3-D QSAR Study of Catechol- O -Methyltransferase Inhibitors Using CoMFA and CoMSIAMOLECULAR INFORMATICS, Issue 10 2008Chunzhi Ai Abstract Inhibitors of Catechol- O -Methyltransferase (COMT) play an important role in the treatment of Parkinson's Disease (PD). A new Three-Dimensional Quantitative Structure,Activity Relationship (3-D QSAR) analysis was performed on 36 previously reported COMT inhibitors employing Comparative Molecular Field Analysis (CoMFA) and Comparative Molecular Similarity Indices Analysis (CoMSIA) methodologies to correlate the molecular fields and percent inhibition values and three predictive models were derived. The CoMFA and CoMSIA models with steric and electrostatic field yielded cross-validated rs of 0.585 and 0.528, respectively whereas the conventional rs were 0.979 and 0.891, respectively. The CoMSIA model with hydrophobic field exhibited a r of 0.544 and a r of 0.930. The individual inspection of 3-D contours generated from these models helps in understanding the possible region for structural modification of molecules to improve the inhibitory bioactivity. These 3-D QSAR models are also useful for designing and predicting novel COMT inhibitors. [source] Conceptual DFT properties-based 3D QSAR: Analysis of inhibitors of the nicotine metabolizing CYP2A6 enzymeJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 12 2009Sofie Van Damme Abstract Structure-activity relationships of 46 P450 2A6 inhibitors were analyzed using the 3D-QSAR methodology. The analysis was carried out to confront the use of traditional steric and electrostatic fields with that of a number of fields reflecting conceptual DFT properties: electron density, HOMO, LUMO, and Fukui f, function as 3D fields. The most predictive models were obtained by combining the information of the electron density with the Fukui f, function (r2 = 0.82, q2 = 0.72), yielding a statistically significant and predictive model. The generated model was able to predict the inhibition potencies of an external test set of five chemicals. The result of the analysis indicates that conceptual DFT-based molecular fields can be useful as 3D QSAR molecular interaction fields. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009 [source] Dynamic Charge Equilibration-Morse stretch force field: Application to energetics of pure silica zeolitesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2002Jan Sefcik Abstract We present the Dynamic Charge Equilibration (DQEq) method for a self-consistent treatment of charge transfer in force field modeling, where atomic charges are designed to reproduce electrostatic potentials calculated quantum mechanically. Force fields coupled with DQEq allow charges to readjust as geometry changes in classical simulations, using appropriate algorithms for periodic boundary conditions. The full electrostatic energy functional is used to derive the corresponding forces and the second derivatives (hessian) for vibrational calculations. Using DQEq electrostatics, we develop a simple nonbond force field for simulation of silica molecular sieves, where nonelectrostatic interactions are described by two-body Morse stretch terms. Energy minimization calculations with the new force field yield accurate unit cell geometries for siliceous zeolites. Relative enthalpies with respect to quartz and third-law entropies calculated from harmonic vibrational analysis agree very well with available calorimetric data: calculated SiO2 enthalpies relative to ,-quartz are within 2 kJ/mol and entropies at 298 K are within 3 J/mol K of the respective experimental values. Contributions from the zero point energy and vibrational degrees of freedom were found to be only about 1 kJ/mol for the free energy of mutual transformations between microporous silica polymorphs. The approach presented here can be applied to interfaces and other oxides as well and it is suitable for development of force fields for accurate modeling of geometry and energetics of microporous and mesoporous materials, while providing a realistic description of electrostatic fields near surfaces and inside pores of adsorbents and catalysts. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 1507,1514, 2002 [source] Observation of interfacial electrostatic field-induced changes in the silicon dielectric function using spectroscopic ellipsometryPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008J. Price Abstract This work investigates the capability of spectroscopic ellipsometry to measure charge trapping centers in thin dielectric films. Specific interfacial electrostatic fields, induced by electrons injected into charge trapping states at the interface, have been identified that directly affect the underlying silicon substrate critical points. The effect of a field-induced change in the silicon fundamental absorption edge due to different processing conditions affecting the oxygen vacancy defects at the interface is presented. Measuring the field-induced change in the silicon dielectric function between a sample with a 2 nm HfO2 film as-deposited and the same sample after a 1000 °C anneal in an N2 ambient reveals that a stronger interfacial field is present for the as-deposited HfO2 film. These results are consistent with the understanding that high temperature anneals work well to passivate oxygen vacancy defects at the silicon/HfO2 interface. Finally, we compare our results with Second Harmonic Generation where specific resonant features are identifiable with electric field enhancements at the same interface. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Theory of Ion Transport in Electrochemically Switchable Nanoporous Metallized MembranesCHEMPHYSCHEM, Issue 1 2009Christian Amatore Dr. Abstract A physicomathematical model of ion transport through a synthetic electrochemically switchable membrane with nanometric metal-plated pores is presented. Due to the extremely small size of the cylindrical pores, electrical double layers formed inside overlap, and thus, strong electrostatic fields whose intensities vary across the cross-sections of the nanopores are created. Based on the proposed model a relationship between the relative electrostatic energies experienced by ions in the nanopores and the potential applied to the membrane is established. This allows the prediction of transference numbers and explains quantitatively the ion-transport switching capability of such synthetic membranes. The predictions of this model agree satisfactorily with previous experimental data obtained for this type of devices by Martin and co-workers. [source] | |||||||||||||