bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charged Rotating Black Hole from Five Dimensional Point of View
Authors: Frolov V. P. , Zelnikov A. I. , Bleyer U. 
Published: May 2007

AbstractIt is shown that the usual characteristics of a black hole and of the physical fields produced by it obtain a unified geometrical meaning in the five‐dimensional framework. Especially, it is demonstrated that a solution for a rotating black hole with electric and scalar charges can be generated by a boost transformation of the fifth coordinate from the Kerr solution.
Bergauf‐Diffusion des Phosphors im Silizium
Authors: Maser K. 
Published: May 2007

AbstractBei der Tiefendiffusion des Phosphors im Silizium bei 1523 K (1250°C) unter O2− rein aus einer vorgebildeten Diffusionszone werden durch Neutronenaktivierungsanalysen zwei Besonderheiten beobachtet:
In der Nähe der SiO2 – Si‐Phasengrenze findet im Si‐Kristall eine Bergauf‐Diffusion des Phosphors statt.
Die gesamte in der Diffusionzone des Si‐Kristalls integrierte Phosphormenge ist unabhängig von der Dauer der Tiefendiffusion. Eine Ausdiffusion des Phosphors vom Si‐Kristall in die SiO2− Schicht hinein findet nicht statt.
Als Ursache für die Bergauf‐Diffusion werden inhomogen verteilte Punktdefekte (z. B. Vakanzen) betrachtet, die eine nichtficksche Dotandenflußkomponente hervorrufen. Dies bedeutet, daß für diesen Fall der Festkörperdiffusion Einsteins Annahme einer symmetrischen Wahrscheinlichkeits‐funktion für die Dotandensprünge [21] nicht gilt.
Ionic Interactions in a Polarizable Dipolar Hard‐Sphere Solvent
Authors: Krienke Hartmut , Weigl Gisbert 
Published: May 2007

AbstractPotentials of mean forces of ions in infinitely diluted solutions are calculated by means of a general virial expansion for systems with short and long range interactions. The screened potentials are calculated by the MSA‐approximation for the chain sum in the mixture model.
Electrons in a strong magnetic field on a disk
Authors: Kasner M. , Apel W. 
Published: May 2007

AbstractThe problem of interacting electrons moving under the influence of a strong magnetic field in two dimensions on a finite disk is reconsidered. First, the results of exact diagonalizations for up to N = 9 electrons for Coulomb as well as for a short‐range interaction are used in the search for a peculiar ground state corresponding to filling factor 1/3. Not for the Coulomb, but only for the short‐range interaction, can the 1/3‐state be safely identified amongst the spectra of various filling factors close to 1/3. Second, the propositions of the concept of quasiparticles, as used in the hierarchical theory, are examined in view of the exact results for the disk geometry. Whereas the theory for the quasiholes is in complete accordance with the spectra, for the quasielectrons, finite size corrections make an analysis difficult. For the quasielectron energy, an extrapolation to N→ ∞ is given and compared with the corresponding extrapolations of three different proposals for trial wave functions. While the limiting value for the best trial wave function is very close to the limit of the exact results, the behavior of the finite size corrections of the exact energies and of the trial wave functions, respectively, is qualitatively rather different.
Quantum fluctuations of vacuum stress tensors and spacetime curvatures
Authors: Jaekel Marc‐Thierry , Reynaud Serge 
Published: May 2007

AbstractWe analyze the quantum fluctuations of vacuum stress tensors and spacetime curvatures, using the framework of linear response theory which connects these fluctuations to dissipation mechanisms arising when stress tensors and spacetime metric are coupled. Vacuum fluctuations of spacetime curvatures are shown to be a sum of two contributions at lowest orders; the first one corresponds to vacuum gravitational waves and is restricted to light‐like wavevectors and vanishing Einstein curvature, while the second one arises from gravity of vacuum stress tensors. From these fluctuations, we deduce noise spectra for geodesic deviations registered by probe fields which determine ultimate limits in length or time measurements. In particular, a relation between noise spectra characterizing spacetime fluctuations and the number of massless neutrino fields is obtained.
Analytical results for the electronic shell structure in mesoscopic systems: Balian‐Bloch type theory for spheres, discs, rings and anti‐dot lattices
Authors: Tatievski B. , Stampfli P. , Bennemann K. H. 
Published: May 2007

AbstractThe electronic shell structure resulting from the interference of closed orbital paths is determined for mesoscopic systems like spherical clusters, discs and rings by extending the semiclassical theory of Balian and Bloch. Analytical results for the shell structure in the density of states are obtained. Thus, the dependence of the shell structure on dimension, size and geometry and potential of the mesoscopic system and on an external magnetic field can be studied systematically. Comparison of the semiclassical results and those of quantum mechanical calculations permits analysis of typical quantum mechanical effects and shows the validity of the semiclassical theory. Our results should stimulate new experiments, can be used to calculate oscillations in the binding‐energy, ionization‐potential, and can be applied to analyze oscillations in the electronic density of states of quantum dot systems like anti‐dot lattices.
Simulations of single polymer chains in the dense limit
Authors: Grassberger Peter , Hegger Rainer 
Published: May 2007

AbstractWe present simulation results for single α‐thermal chain polymers in finite volumes. For this we use a recently proposed recursive implementation of the enrichment method. In 3 dimensions it allows the simulation of extremely long chains (up to N = 300000). It is much less efficient for d = 2, but we can also there extend considerably the previously accessible range of chain lengths and densities. We verify most tested scaling laws, and we point out similarities with complex optimization problems.
New field equations in the 5‐dimensional projective unified field theory
Authors: Schmutzer E. 
Published: May 2007

AbstractNew field equations of the Projective Unified Field Theory are presented which avoid potential difficulties of former versions with respect to the equivalence principle. The physical interpretation of this new version remains unchanged: constancy of the “gravitational constant”, electromagnetic polarization of the vacuum, definiteness of the energy of the stationary scalaric field, etc. Furthermore, the Klein‐Gordon field and the Dirac field are treated.
Maximum entropy approach to Schrödinger's radial equation
Authors: Garcias F. , Casas M. , Plastino A. 
Published: May 2007

AbstractFrom the sole knowledge (at a finite number of points) of the numerical values of the potential V(r) corresponding to Schrödinger's radial equation, it is found that recourse to Information Theory (IT) concepts allows one to infer the pertinent wave functions (and eigenvalues) without attempting to solve the concomitant differential equation. Moreover, the underlying IT ideas allow for an analytical treatment that yields exact wave functions of the maximum (quantal) entropy form in a number of cases of interest.
Preparation and pyroelectrical investigation of bimorph polymer layers
Authors: Bauer‐Gogonea S. , Bauer S. , Wirges W. , Gerhard‐Multhaupt R. 
Published: May 2007

AbstractTwo different procedures for the preparation of bimorph structures within nonlinear optical polymer layers are reported. One technique consists of thermally assisted poling above the glass‐transition temperature followed by photo‐induced poling below the glass‐transition temperature. In this poling scheme, the second step is based on the photoisomerization of the dipole molecules. The other method comprises two consecutive thermally assisted poling steps with opposite field polarity in a double layer of two nonlinear optical polymers with different glass‐transition temperatures. Pyroelectric thermal analysis is employed for analyzing the stability of the resulting bimorph structures, while pyroelectric depth profiling allows for a non‐destructive qualitative analysis of their polarization distributions.
Topological investigation of the fractionally quantized Hall conductivity
Authors: Asselmeyer T. , Keiper R. 
Published: May 2007

AbstractUsing the fiber bundle concept developed in geometry and topology, the fractionally quantized Hall conductivity is discussed in the relevant many‐particle configuration space. Electronmagnetic field and electron‐electron interactions under FQHE conditions are treated as functional connections over the torus, the torus being the underlying two‐dimensional manifold. Relations to the (2 + 1)‐dimensional Chern‐Simons theory are indicated. The conductivity being a topological invariant is given as e2/h times a linking number which is the quotient of the winding numbers of the self‐consistent field and the magnetic field, respectively. Odd denominators are explained by the two spin structures which have been considered for the FQHE correlated electron system.
Zero and finite temperature phase diagram of the spinless fermion model in infinite dimensions
Authors: Uhrig G. S. , Vlaming R. 
Published: May 2007

AbstractThe phase diagram of the model of spinless fermions with repulsive nearest neighbour interaction is calculated analytically on a hypercubic lattice in infinite dimensions (d → ∞). In spite of its simplicity the model displays a rich phase diagram depending on the doping δ, the interaction U and the temperature T. The system can be in the homogeneous phase (HOM), the nonsegregated AB charge density wave (AB‐CDW), the AB phase separation region (PS‐AB/HOM; coexistence of AB‐CDW and HOM), the incommensurate phase (IP) or the IP phase separation region (PS‐AB/IP; coexistence of AB‐CDW and IP). We identify three important values of the interaction UIPL = 0.572 < UIPH = 1.914 < UIP/PS = 4.212 which distinguish four intervals of U. These imply four different types of phase diagrams. In all the three phase diagrams with U below UIP/PS the IP appears. We propose a new general ansatz for the order parameter of this phase. A competition between the IP, the PS‐AB/IP and the PS‐AB/HOM is found. The relevance of our findings for the phase scenario of the Hubbard model is shown.
Generation of burst noise by nonlinear autoregression
Authors: Kumičák J. 
Published: May 2007

AbstractNonlinear generalization of autoregressive sequence of first order is used as basis for construction of mathematical model of bistable burst noise. It is proved that the noise generated using such a model has Lorentzian spectrum after clipping the white noise component. In passing it is demonstrated that random telegraph signal is obtainable by simple iteration.The proposed model suggests that one should expect to observe temperature dependence of frequency of transitions between the two levels of burst noise waveform.
Crystallization of electrons confined to a lattice
Authors: Fulde P. 
Published: May 2007

AbstractA necessary condition for electron crystallization is the dominance of the electronic Coulomb repulsion as compared with the kinetic energy. We show that 4f systems are good candidates for electron or hole crystallization to occur since the small radius of the 4f shell leads to small hybridizations and hence kinetic energy of the f electrons. Crystallization may take place in lattices with several equivalent 4f sites per unit cell when the electron or hole number is less than the number of sites. We give evidence that charge ordering in Yb4As3 is an example of the mechanism considered here. We also compare it with those considered by Wigner, Verwey, Mott and Hubbard.
The antispermatogenic activity of some phenylbismuth(III) O,O′‐dialkyldithiophosphates
Authors: Sharma Pankaj K. , Rehwani H. , Gupta R. S. , Singh Y. P. 
Published: May 2007

AbstractTen dialkyldithiophosphate derivatives of phenylbismuth(III) of the type, Ph(3–n)Bi[S(S)P(OR)2]n [where n = 1; R = Me(1), Et(2), Pri(3), Prn(4) and Bun(5); n = 2; R = Me(6), Et(7), Pri(8), Prn(9) and Bun(10)] have been synthesized by the reactions of triphenylbismuth(III) with corresponding dialkyldithiophosphoric acids in 1:1 and 1:2 stoichiometric ratios, respectively, in stirred benzene solution. The newly synthesized brown colored compounds, 1–10 have been characterized by elemental analyses, molecular weight measurements, IR and NMR (1H, 13C and 31P) spectral studies. The ligand diethyldithiophosphoric acid, [(C2H5O)2P(S)SH], and its organobismuth(III) derivatives, compounds 2 and 7 were administered to adult male rats by oral gavage at the dose of 25 mg per kg body weight per day, for 60 days, and their effects were evaluated and compared for changes in testicular morphology, circulatory concentrations of testosterone, FSH and LH, sperm dynamics, fertility index and testicular cell population dynamics. Copyright © 2007 John Wiley & Sons, Ltd.
Hydrosilylation of unsaturated fatty acid N‐phenyl amides
Authors: El Kadib A. , Katir N. , Castel A. , Delpech F. , Rivière P. 
Published: May 2007

AbstractThe synthesis and the characterization of new silylated fatty acid N‐phenyl amides as novel precursors for structured materials are described. Hydrosilylation of vinylic groups in terminal N‐phenyl unsaturated fatty amides was efficiently catalyzed by Karstedt's catalyst. Radical initiators have been found to be active for both terminal and internal double bonds of unsaturated fatty N‐phenyl amides at the necessary condition to suppress initially the conjugation in the amide function, the anilide moiety acting as a radical inhibitor. Copyright © 2007 John Wiley & Sons, Ltd.
Palladium chloride anchored on organic functionalized MCM‐41 as a catalyst for the Heck reaction
Authors: Fan Guo‐zhi , Cheng Si‐qing , Zhu Ming‐fang , Gao Xin‐lei 
Published: May 2007

AbstractPalladium chloride was grafted to amino‐functionalized MCM‐41 to prepare heterogeneous catalysts. XRD, N2 adsorption–desorption isotherms, IR, 13C and 29Si cross‐polarization magic‐angle spinning NMR spectroscopy and XPS techniques were employed to characterize the catalytic materials. The heterogeneous palladium catalyst exhibited excellent catalytic activity for the Heck vinylation of iodobenzene with methyl acrylate, giving 92% yield of methyl cinnamate in the presence of N‐methylpyrrolidone (NMP) and triethylamine (Et3N). The stability of the heterogeneous catalyst was also studied in detail. The catalytic tests showed that the palladium leaching correlated to solvent, base and palladium loading. The heterogeneous catalyst exhibited excellent stability towards loss of activity and palladium leaching was not observed during six recycles in the presence of toluene and Na2CO3. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and characterization of α, ω‐bis [tri ‐ (w ‐ triphenylstannyl) butylstannyl] alkanes as starting materials for organotin dendrimers
Authors: Aksu Yilmaz , Aksu Sevil , Schumann Herbert 
Published: May 2007

AbstractPh3Sn(CH2)mCH2 [m = 2 (1a), 3 (1b)] reacts with Ph3SnH, yielding Ph3Sn(CH2)nSnPh3 [n = 4 (2a), 5 (2b)], which in turn reacts with CH3COOH or HCl, producing (CH3CO2)3Sn(CH2)nSn(O2CCH3)3 (3a, b) and Cl3Sn(CH2)nSnCl3 (4a, b), respectively. Alkylation of compounds 4 with BrMg(CH2)2CH2 affords (CH22CH2)3Sn(CH2)nSn(CH2CH2CH2)3 (5a,b). Hydro‐ stannylation of 5a, b with Ph3SnH results in the formation of [Ph3Sn(CH2)4]3Sn(CH2)nSn[(CH2)4 SnPh3]3 (6a, b) which on agitation with HCl gives [ClPh2Sn(CH2)4]3Sn(CH2)nSn[(CH2)4SnPh2Cl]3 (7a, b). Hydrogenation of 7a and 7b with LiAlH4 leads to [HPh2Sn(CH2)4]3Sn(CH2)nSn[(CH2)4SnPh2H]3 (8a, b), which on further reaction with CH22OH yields [HO(CH2)3Ph2Sn(CH2)4]3Sn(CH2)n Sn[(CH2)4SnPh2(CH2)3OH]3 (9a, b). All compounds were characterized by multinuclear NMR studies (1H, 13C, 119Sn), mass spectrometry (MALDI‐TOF, EI) and elemental analyses. Copyright © 2007 John Wiley & Sons, Ltd.
New stable germylenes, stannylenes, and related compounds. 8. Amidogermanium(II) and ‐tin(II) chlorides R2N‐E14‐Cl (E14 = Ge, R = Et; E14 = Sn, R = Me) revealing new structural motifs
Authors: Khrustalev Victor N. , Glukhov Ivan V. , Borisova Irina V. , Zemlyansky Nikolay N. 
Published: May 2007

AbstractNew stable amidogermanium(II) and ‐tin(II) chlorides R2NE14Cl [E14 = Ge, R = Et (1), E14 = Sn, R = Me (2)] have been synthesized and their crystal structures have been determined by X‐ray diffraction analysis. Both 1 and 2 are dimers formed via the two intermolecular E14← N dative interactions, with the bridged amido ligands and the terminal chloro ligands. The central E142N2 four‐membered ring has a butterfly conformation in the germanium derivative 1 and a planar conformation in the tin derivative 2. The chloride atoms are disposed in the trans‐configuration relative to the four‐membered ring. Both structures 1 and 2 reveal new previously unobserved structural motifs for amidogermanium(II) and ‐tin(II) chlorides, respectively. The electronic structures of 1 and 2 were studied by quantum chemistry within the DFT approach. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis of novel stereodefined vinylgermanes bearing an allyl group or an allenyl group: (E)‐2‐aryl‐1‐germylalka‐1,4‐dienes and (E)‐4‐aryl‐5‐germylpenta‐1,2,4‐trienes
Authors: Kato Kotaro , Senda Yoshiya , Makihara Yoshiaki , Kojima Takeshi , Kurihara Hiroyuki , Takahashi Yutaka , Nakano Taichi 
Published: May 2007

AbstractStereodefined synthesis of an unprecedented family of vinylgermanes bearing an allyl group, (E)‐2‐aryl‐1‐germylalka‐1,4‐dienes, or an allenyl group, (E)‐4‐aryl‐5‐germylpenta‐1,2,4‐trienes, via a cross‐coupling reaction of (Z)‐germyl(stannyl)ethenes with the respective allyl halide (Br, Cl) and propargyl bromide is described. In the reaction with allyl halides, either a Pd(dba)2–CuI combination (dba: dibenzylideneacetone) or CuI alone readily catalyzes or mediates the coupling reaction of (Z)‐germyl(stannyl)ethenes, producing the novel vinylgermanes bearing an allyl group. The thienyl group or hydroxy group of the (Z)‐germyl(stannyl)ethene survives the reaction. Copper(I) iodide alone readily mediates the reaction with allyl chloride or methallyl chloride upon addition of sodium bromide to produce the respective cross‐coupled product in good yield. In contrast, crotyl halides (Br, Cl) or prenyl chloride couple with/without allylic transposition in the bromide or the chloride. In the reaction with propargyl bromide, a Pd(dba)2 and CuI combination efficiently drives the coupling reaction of (Z)‐germyl(stannyl)ethenes in NMP (N‐methylpyrrolidone), providing the stereochemically defined allenyl vinylgermanes, (E)‐4‐aryl‐5‐germylpenta‐1,2,4‐trienes, in good yields. Copyright © 2007 John Wiley & Sons, Ltd.
Prediction of polycyclic aromatic hydrocarbon solubilities in benzene
Authors: Muthukumarasamy Thenmozhi , Thiruganam Karunanithi 
Published: May 2007

AbstractSolubilities of polycyclic aromatic hydrocarbon (PAH) solutes; naphthalene, fluorene, acenaphthene, fluoranthene, anthracene, phenanthrene, pyrene, chrysene and triphenylene in benzene are predicted using UNIFAC, modified UNIFAC (Dortmund), and combination of Flory‐Huggins and Scatchard‐Hildebrand (FH‐SH) methods. Applicability of the R‐UNIFAC method to the binary PAHs in benzene systems is studied. Exponent R of the R‐UNIFAC method is used in the modified UNIFAC (Dortmund) model to get a new expression for combinatorial activity coefficient. It is shown that the group contribution models using exponent R in combinatorial part of the equation perform much better than the original ones but none of the models considered satisfactorily predicts solid‐liquid equilibria (SLE) of all PAHs studied (FH‐SH model gives a prediction error of 98.08% for chrysene + benzene system). It is also shown that accounting the heat capacity change on melting terms makes considerable difference with ideal solubility in the case of higher melting PAHs in benzene. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.
Research on the slagging characteristics of Shenhua coal
Authors: Weijuan Yang , Junhu Zhaou , Xinyu Cao , Xiaohu Zhao , Zequan Lan , Jianzhong Liu , Kefa Cen 
Published: May 2007

AbstractShenhua coal is one of high‐quality power coals of high calorific value that has large reserves in China. But the low fusion point of its ash poses some problems for its application in thermal power plants. The experiments were carried out in a 0.25 MW combustion facility to make a comparative study of the ash deposition and slagging process of Shenhua coal and XinWen coal. The results show that the ash deposition process of Shenhua coal lasts longer than that of Xinwen, and self‐cleaning of the slag does not take place with the Shenhua coal. Also, the ash deposition of Shenhua coal decreases the heat transfer of the furnace wall severely. The three slag or ash specimens, sampled in the furnace, near the furnace wall and in the flue duct, were tested and analyzed. It was indicated that the furnace wall slag is rich in iron while in the fly ash calcium content is higher. The slag near furnace wall had a larger ratio of silicon to aluminum, more glassy matter and smaller crystal characteristic peaks in the X‐ray diffraction (XRD) pattern. The crystalline matter is mostly quartz in the furnace wall slag. The crystal characteristic peaks in XRD in the fly ash are larger than those of the furnace wall slag. The crystalline matter of the fly ash are quartz, andalusite and hematite. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.
Study on the submicron and micron morphology and the properties of poor bituminous coal burnout
Authors: Fu Pei‐Fang , Zhou Huai‐Chun , Fang Qing‐Yan , Yao Hai , Qiu Jianrong , Xu Minghou 
Published: May 2007

AbstractCarbon burnout and its reaction mechanism have been widely focused on in the past decades. The properties of burnout, submicron and micron morphology and the reaction mechanism of poor bituminous coal/char (PBC) in a W‐shaped power plant boiler was studied and was compared with those in DTF and in TGA, which showed that the degree of PBC burnout in TGA at 1450 °C was greater than or approximately equal to that in a W‐shaped boiler, and that the complexity of the reactions among residual char, oxygen and SiO2 did not apparently result in mass loss in TGA, although the weight percentage of the residual char in ash decreased from 33% ad (air dry basis) at 900 °C to 9% ad at 1450 °C. According to the distribution of pores and the properties of the char burnout, the char can be simply categorized into three classes: char burnout easy, char burnout difficult and char burnout very difficult. The differences of the reaction mechanism must be considered while predicting the burning rate and degree of char burnout in a full‐scale boiler by making use of experimental results from TGA and DTF. A different char particle contains markedly different amount of carbons, but for a special char particle, the ratio of carbon to ash is generally constant, and an ash shell does not exist on the char surface. The fusion mineral matter composing of C‐O‐Si‐Al is amorphous, not in the form of Al2O3 and SiO2 above 1450 °C. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.