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Electric Charges (electric + charge)
Selected AbstractsCa for Er substitution in tetragonal ErPO4 · H2O crystallised from phosphoric acid solutionCRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2004R. Kijkowska Abstract Erbium phosphate monohydrate with limited Ca for Er substitution, obtained through crystallisation from boiling phosphoric acid solution has been characterised by X-ray diffraction, Ir-spectroscopy and thermal analysis (TGA-DTA) methods. The difference in the electric charge between di-valent calcium and tri-valent erbium in the solid crystallised was compensated by simultaneous substitution of HPO42- for PO43- . Ca incorporation in erbium phosphate made expansion of tetragonal ErPO4 · H2O unit cell. After ignition at 900 °C the tetragonal crystal modification was maintained but the unit cell parameters of all the investigated phosphates, whether Ca-substituted or Ca-free, contracted to the same level. The unique contraction of the unit cell was resulted from recrystallisation of Ca-substituted into Ca-free erbium phosphate, while Ca was transferred into Ca(PO3)2 formed as a separate phase. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural and functional studies of cinnamomin, a new type II ribosome-inactivating protein isolated from the seeds of the camphor treeFEBS JOURNAL, Issue 22 2001Liang Xie Cinnamomin is a new type II ribosome-inactivating protein (RIP). Its A-chain exhibits RNA N -glycosidase activity to inactivate the ribosome and thus inhibit protein synthesis, whereas the glycosylated B-chain is a lectin. The primary structure of cinnamomin, which exhibits approximately 55% identity with those of ricin and abrin, was deduced from the nucleotide sequences of cDNAs of cinnamomin A- and B-chains. It is composed of a total of 549 amino-acid residues: 271 residues in the A-chain, a 14-residue linker and 264 residues in the B-chain. To explore its biological function, the cinnamomin A-chain was expressed in Escherichia coli with a yield of 100 mg per L of culture, and purified through two-step column chromatography. After renaturation, the recovery of the enzyme activity of the expressed A-chain was 80% of that of native A-chain. Based on the modeling of the three-dimensional structure of the A-chain, the functional roles of five amino acids and the only cysteine residues were investigated by site-directed mutagenesis or chemical modification. The conserved single mutation of the five amino-acid residues led to 8,50-fold losses of enzymatic activity, suggesting that these residues were crucial for maintaining the RNA N -glycosidase activity of the A-chain. Most interestingly, the strong electric charge introduced at the position of the single cysteine in A-chain seemed to play a role in enzyme/substrate binding. [source] Theoretical studies on effects of hydrogen bonds attaching to cysteine ligands on 4Fe-4S clustersINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2008Y. Kitagawa Abstract The effect of hydrogen bonds attaching to sulfur atoms of cysteine ligands on 4Fe-4S cluster is examined by using UB3LYP method. Calculated results indicate that an existence of the hydrogen bonds scarcely changes SOMO-SUMO gap, shapes of Kohn-Sham orbitals, and magnetic interactions between Fe ions, although it stabilizes Kohn-Sham orbital energies of SOMO and SUMO about 1.0 eV. And they also make a reduced state stable in comparison with an oxidized state. In addition, the point charges of +0.1e (e: elementary electric charge) at the position of the hydrogen atoms give almost same results to the hydrogen bonds quantitatively. The results suggest that a positive environment from the hydrogen bonds around the clusters is important for a redox potential of 4Fe-4S clusters. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Cooling Device for Bradycardia Based on Peltier Element for Accurate Anastomosis of Off-Pump Coronary Artery Bypass GraftingARTIFICIAL ORGANS, Issue 10 2002Yukio Kuniyoshi Abstract: Upon introducing off-pump coronary artery bypass grafting (CABG), the indications for CABG were expanded to include patients who previously had no operative indications. For accurate anastomosis, various devices and methods have been developed. Bradycardia is easily induced by drug administration. However, this method of achieving bradycardia also has adverse effects on cardiac function. We have developed a new device to decrease the heart rate by regional cooling of the sino-atrial node. The new device is incorporated with Peltier's element, which uses an electric charge to create a temperature gradient on both of its surfaces. In terms of the cooling ability of this device, its cooling surface is chilled from 25°C to 0°C within 30 s. During in vivo animal experiments, this device has been shown to decrease the myocardial temperature around the sino-atrial node to 15°C and suppress sino-atrial node activity, resulting in bradycardia to 60 beats/min level. In summary, the simple and easily applicable device for local cooling in combination with the application of diltiazem for effective heart rate reduction may be very helpful for the surgeon and may avoid disadvantages for critically ill patients. [source] A detailed analysis of hotspots and insulation breakdown phenomena in power inductor windings at high frequency regimes: overcurrents and overvoltagesEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2008J. A. Brandão Faria Abstract This research paper is the last of a group of three papers dedicated to the analysis and computation of the high-frequency electromagnetic behaviour of inductor windings where a multiconductor transmission line approach is used. The present work is essentially concerned with application aspects linked up with the important engineering problem of windings insulation damage, which can occur either because of excessive temperature (winding hotspots) or because of excessive electric field strength (dielectric breakdown). For single and multilayer windings we present here a wealth of information in graphical and tabular form concerning the distribution of voltages, currents, electric charges, charge densities, electric field components and power losses along the inductor winding turns, operating at the critical resonance frequencies characteristic of the structure (which is the worst possible scenario). This information is analysed and processed in order to allow for a detection of the winding zones where breakdown phenomena and hotspots could most probably occur. Copyright © 2007 John Wiley & Sons, Ltd. [source] Multidrug resistance modulator interactions with neutral and anionic liposomes: membrane binding affinity and membrane perturbing activityJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2005Madeleine Castaing A variety of cationic lipophilic compounds (modulators) have been found to reverse the multidrug resistance of cancer cells. In order to determine the membrane perturbing efficacy and the binding affinity of such drugs in neutral and anionic liposomes, the leakage of Sulfan blue induced by five modulators bearing different electric charges was quantified using liposomes with and without phosphatidic acid (xEPA = 0 and 0.1), at four lipid concentrations. The binding isotherms were drawn up using the indirect method based on the dependency of the leakage rate on the modulator and the lipid concentrations. Upon inclusion of negatively charged lipids in the liposomes: (i) the binding of cationic drugs was favoured, except in a case where modulator aggregation occurred in the lipid phase; (ii) the drugs with a net electric charge greater than 1.1 displayed a greater enhancement in their potency to produce membrane perturbation; and (iii) the EPA effect on membrane permeation was due mainly to that on membrane perturbation (,50%) and, to a lesser extent, to that on the binding affinity (,50%). The present study provides evidence that drug-membrane interactions are the result of a complex interplay between the structural and electrical characteristics of the drugs and those of the membranes. [source] Factors that prevent learning in electrochemistryJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 2 2007Hans-Jürgen Schmidt Electrochemistry plays an important role in curricula, textbooks, and in everyday life. The purpose of the present study was to identify and understand secondary-school students' problems in learning electrochemistry at an introductory chemistry level. The investigation covered four areas: (a) electrolytes, (b) transport of electric charges in electrolyte solutions, (c) the anode and the cathode, and (d) the minus and plus poles. Written tests were given to high-school students in five cycles. The population from which random samples were drawn totalled 15,700 subjects. Students were asked to select the correct answers and to justify their choices. It was found that students based their reasoning on four alternative concepts: (a) During electrolysis, the electric current produces ions; (b) electrons migrate through the solution from one electrode to the other; (c) the cathode is always the minus pole, the anode the plus pole; and (d) the plus and minus poles carry charges. The results suggest a teaching strategy in which students first experience and learn about electrochemistry concepts. In the second step, appropriate concept terms are added, and students then are confronted with the alternative concepts described in this article. © 2006 Wiley Periodicals, Inc. J Res Sci Teach 44: 258,283, 2007 [source] Liouville and Fokker,Planck dynamics for classical plasmas and radiationANNALEN DER PHYSIK, Issue 6 2006R.F. Alvarez-Estrada Abstract We consider a nonequilibrium statistical system formed by many classical non-relativistic particles of opposite electric charges (plasma) and by the classical dynamical electromagnetic (EM) field. The charges interact with one another directly through instantaneous Coulomb potentials and with the dynamical degrees of freedom of the transverse EM field. The system may also be subject to external influences of: i) either static, but spatially inhomogeneous, electric and magnetic fields (case 1)), or ii) weak distributions of electric charges and currents (case 2)). The particles and the dynamical EM field are described, for any time t > 0, by the classical phase-space probability distribution functional (CPSPDF) f and, at the initial time (t = 0), by the initial CPSPDF fin. The CPSPDF f and fin, multiplied by suitable Hermite polynomials (for particles and field) and integrated over all canonical momenta, yield new moments. The Liouville equation and fin imply a new nonequilibrium linear infinite hierarchy for the moments. In case 1), fin describes local equilibrium but global nonequilibrium, and we propose a long-time approximation in the hierarchy, which introduces irreversibility and relaxation towards global thermal equilibrium. In case 2), the statistical system, having been at global thermal equilibrium, without external influences, for t , 0, is subject to weak external charge-current distributions: then, new hierarchies for moments and their long-time behaviours are discussed in outline. As examples, approximate mean-field (Vlasov) approximations are treated for both cases 1) and 2). [source] | ||||||||||||||||