bluuebunny/crossref_metadata_2025 huggingface dataset:
Lichtschwächung durch Interferenz und damit verbundenes Herausheben quantenmechanischer Eigenschaften von Lichtwellen
Authors: Bandilla A.
Published: May 2007

In Fortführung von Untersuchungen des Jubilars und seiner Mitarbeiter in den 60er Jahren zu den Eigenschaften der kohärenten Zustände wird die Veränderung eines kohärenten Feldes unter der Wirkung von Zwei‐Photonen‐Absorption betrachtet.

Dazu wird die vereinfachte Beschreibung dieses Absorptionsvorganges benutzt. Diese Beschreibung gewinnt man durch Summierung der Kurzzeitnäherung. Sie liefert eine enorme analytische Vereinfachung und eine anschauliche physikalische Interpretation. Wegen der zu einer merklichen Zwei‐Photonen‐Absorption nötigen hohen Intensität sind die durch diese Absorption verursachten quantenmechanischen Veränderungen ohne klassisches Analogon relativ klein. Überlagert man das so gewonnene Feld mit einem kohärenten, so kann die resultierende Photonenzahl stark reduziert werden. Diese Schwächung ist völlig verschieden von der durch Ein‐Photonen‐Absorption, weil hierbei das antibunching effektiv verstärkt wird. Dazu ist ein gleichzeitig vorhandenes squeezing notwendig. Dieses wird diskutiert, ohne aber auf die tiefere Problematik des squeezing einzugehen.
Microscopic Structure of Semimagic Nuclei with 82 Neutrons or 50 Protons
Authors: Enghardt W. , Prade H. , Jäger H. U. , Käubler L. , Keller H.‐J. , Stary F. , Kostov L. K.
Published: May 2007

Excited states of the semimagic nuclei 138Ba, 140Ce, 141Pr, 143Pm, 144Sm, 109Sn and 111Sn have been investigated by means of in‐beam γ‐spectroscopic methods. Levels in the vicinity of the yrast line having energies up to about 5 MeV have been identified and spin and parity could be determined for most of them. Several nanosecond and subnanosecond isomers have been found in the level schemes of the nuclei investigated. The g‐factors of three nanosecond isomers have been measured. The large amount of experimental information has been compared with the results of a comprehensive analysis of the excited states of N = 82 and Z = 50 semimagic nuclei in the framework of the shell model with configuration mixing. This reveals that the majority of the observed excited states of N = 82 isotones or Z = 50 isotopes can be understood as few‐particle excitations outside the doubly magic cores 132Sn and 100Sn, respectively.
On Adiabatic and Non‐Adiabatic Improvements of the Mean‐Field Approximation for Fermion‐ or (Pseudo‐)Spin‐Boson Interaction
Authors: Enders P.
Published: May 2007

Starting at the tight‐binding electron‐phonon Hamiltonian for a linear diatomic chain (half‐filled Peierls chain with extrinsic gap), being a special realization of the fermion‐ or (pseudo)spin‐boson interaction, we examine some improvements of the usual MFA: an improved phonon trial function with (anti‐)symmetrized coherent states; a generalized Hartree‐Fock decoupling with anomalous averages after transforming the electron‐phonon interaction to an effective electron‐electron one; a pure bosonic treatment using the Holstein‐Primakoff transformation. Systematic improvements at the ground state are obtained. But for finite temperatures the formalism soon becomes quite elaborate. Nevertheless, these different approaches provide valuable insights into various aspects of this interaction problem. Furthermore, the unifying features of various particle‐particle interactions are emphasized and the connection between solid‐state (physics) and (molecular) quantum chemistry is mentioned.
Oxidationskinetik von Schwefel auf einer Palladium(111)‐Oberfläche
Authors: Kölzer J. G. , Wassmuth H.‐W.
Published: May 2007

Die Reaktionskinetik für die Oxidation von Schwefel auf einer Pd(111)‐Oberfläche wurde mittels massenspektrometrischer Analyse der Desorptionsprodukte und Augerelektronenspektroskopie (AES) für Schwefelbedeckungsgrade bis maximal Θs = 3/7 untersucht. Neben umfangreichem empirischen Material über die unter stationären äußeren Bedingungen ablaufende S‐Oxidation (T = 520…1075 K, po2 = 2 · 10−7…2 · 10−5 mbar) konnte Einblick in den Reaktionsmechanismus gewonnen werden. Dieser läßt sich weder als reiner Langmuir‐Hinshelwood‐ noch als reiner Eley‐Rideal‐Mechanismus klassifizieren, sondern läuft unter dem Einfluß eines Precursors ab.
Der Irrtum als Wegbereiter des Fortschritts
Authors: Schöpf Hans‐Georg
Published: May 2007

Die Geschichte der Physik lehrt uns, daß einige ihrer großen Errungenschaften falschen, z. T. ganz abwegigen Vorstellungen entstammen. Diese Auffassung soll durch die Entdeckungsgeschichte der Keplerschen Gesetze, der Maxwellschen Gleichungen und des Planckschen Strahlungsgesetzes belegt werden. Die genannten Geschehnisse geben zu einer Typologie des wissenschaftlich fruchtbaren Irrtums Anlaß.
Charged Rotating Black Hole from Five Dimensional Point of View
Authors: Frolov V. P. , Zelnikov A. I. , Bleyer U.
Published: May 2007

It 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

Bei 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

Potentials 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

The 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

We 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

The 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

We 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

New 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

From 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

Two 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

Using 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

The 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

Nonlinear 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

A 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

Ten 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

The 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

Palladium 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

Ph3Sn(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

New 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

Stereodefined 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

Solubilities 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

Shenhua 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

Carbon 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.
A computational fluid dynamic study of a low‐humidity co‐current spray dryer
Authors: Huang Li Xin , Mujumdar A. S.
Published: May 2007

Because spray drying uses high‐temperature gas as the drying medium and the deposits on the wall cannot be avoided in practical spray dryers, the products are subject to degradation by overheating. In order to reduce the degradation of the active components in the dried powder, a low‐dew‐point (LDP) spray dryer is proposed and evaluated via a computational fluid dynamic (CFD) model. A cylinder‐on‐cone spray dryer with pressure nozzle is investigated numerically with a commercial CFD code. The effects of low inlet air humidity and temperature on the gas flow patterns, droplet trajectories and overall dryer performance are investigated. The volumetric evaporation rate values, volumetric heat transfer intensity and thermal energy consumption per unit evaporation of water were computed and compared for evaporation of pure water in a spray chamber 2.215 m in diameter with a cylindrical top section 2.0 m high and a bottom cone 1.725 m high. Although a smaller product capacity is obtained compared with the normal spray dryer, it has advantages for drying heat‐sensitive materials. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.
Through drying characteristic of oil palm empty fruit bunch (EFB) fibers using superheated steam
Authors: Hasibuan Rosdanelli , Wan Daud Wan Ramli
Published: May 2007

Empty fruit bunches (EFB) of the oil palm have great potential to be used as industrial fibers in various industries, such as fiber board, mattress and cushion, erosion controller, thermoplastic filler, paper, acoustics control, sound insulator, and animal feed industries. A rotary drum dryer with a flue gas drying medium has been conventionally used to dry EFB fibers. However, this drying system tends to produce highly entangled and blackened fiber. Furthermore, the uneven contact between the flue gas and fiber in the rotary dryer may cause nonuniformity in the moisture content of the product. To overcome this problem, the present work uses superheated steam as the drying medium for EFB fiber drying. The drying experiments were carried out at the following conditions: atmospheric pressure; temperature range 112–172 °C; steam superficial velocity in the range 0.14‐4.3 m/s, distance from steam nozzle to EFB in the range 50–200 mm; and size of holes on plate in the range 10–200 mesh. The initial fiber moisture content was in the range 0.96‐1.46 kg/kg dry basis. The mass loss of EFB fiber during the drying process was periodically measured using an analytical balance connected directly to the wire mesh plate when the steam was diverted momentarily so that the effect of momentum transfer between the steam and the sample holder is minimized. In the temperature range 112–172 °C and at atmospheric pressure, the equilibrium moisture content isotherm is found to follow an exponential equation with coefficient ke = 15.365 kg/kg, ne = —0.001 °C−me and power index me = 1.869. It was found that for maximum moisture removal, the temperature and steam superficial velocity was 142 °C and 0.39 m/s, respectively. The effect of steam velocity is greater than that of steam temperature in decreasing the moisture content. The drying rate initially increases to a maximum and then falls off exponentially thereafter. A new drying model was developed for superheated steam for drying of EFB fiber, which is given by MR = 1 − atnexp(−ktm). The increasing drying rate is largely described by the exponential term with the coefficient k having values ranging from 1.945 to 5.351 s−n and the index m having values ranging from − 0.843 to 1.198. The falling drying rate is largely described by the power law term with the coefficient a ranging in value from 0.453 to 1.027 s−m and the power index n ranging in value from 0.0415 to 0.317. The drying is best carried out with the plate at a distance of 150 mm from the sample holder containing a 50 mesh plate. The superheated steam through the drying system can successfully reduce the moisture content by almost 100% in 15 min without steam condensation during the drying process. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.
Acid rock drainage formation and treatment: a review
Authors: Egiebor Nosa O. , Oni Ben
Published: May 2007

The exploitation of coal and metallic mineral resources worldwide invariably results in the production of large quantities of overburden, gangue, and tailings materials containing significant amounts of sulfide minerals. These sulfide minerals, which include sphalerite, chalcopyrite, galena, and other complex sulfides, are often disseminated in pyrite, which is the most abundant sulfide mineral in the earth's crust. Once exposed to water and oxygen through mining and mineral processing operations, these sulfides become immediately susceptible to chemical and biochemical oxidation with the consequent production of highly acidic, metal‐laden leachates, which are generally referred to as acid rock drainage (ARD) or acid mine drainage (AMD). This ARD production, which can be sustained for hundreds of years, has become the single biggest environmental problem facing the mining and mineral industry. Untreated acid rock drainage leads to serious contamination of large areas of land, as well as surface and ground water resources. The seriousness of the problem has led to major research efforts to find solutions. However, effective ARD treatment and prevention solutions have eluded the scientific community over the past decades. This paper presents a detailed review of the current state of scientific knowledge with regard to the magnitude of the problem, the chemistry and mechanism of sulfide mineral oxidation and ARD formation, the role of microorganisms in ARD formation process, and the proposed approaches for the treatment, control, and prevention of ARD formation. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.
Grafting of poly (methyl acrylate) onto sulfite pulp fibers and its effect on water absorbance
Authors: Jain Vaibhav , Xiao Huining , Ni Yonghao
Published: May 2007

To prepare super water absorbent hydrogels of wood cellulose fibers, poly (methyl acrylate) (PMA) was copolymerized onto softwood sulfite pulp fibers using free radical initiator followed by alkaline hydrolysis. Ceric ammonium nitrate (CAN) was used as the free radical initiator. Effects of various parameters such as fiber concentration, monomer/pulp (M/pulp) ratio, CAN concentration, and reaction time on the grafting yield and on other grafting parameters were investigated. The graft conversion was the same from low to medium fiber concentration. The amount of initiator required was found to be independent of fiber concentration to achieve maximum grafting yield. Different fiber fractions (classified based on their length) have no effect on the grafting yield. The evidence of graft copolymerization was determined by using ATR‐IR spectroscopy. The X‐ray diffraction (XRD) analysis shows that grafting takes place both in amorphous and crystalline regions of cellulose fibers and the decrease in crystallinity of the grafted fibers with an increase in grafting yield was confirmed. The surface morphology of the PMA‐g‐cellulose was characterized by scanning electron microscopy (SEM). The water retention value of the hydrolyzed grafted pulp was determined based on a centrifugation technique. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
High performance liquid chromatography study of water‐soluble complexes and covalent conjugates of polyacrylic acid with bovine serum albumin
Authors: Akkiliç Namık , Mustafaeva Zeynep , Mustafaev Mamed
Published: May 2007

Polycomplex formation of bovine serum albumin (BSA) and polyacrylic acid (PAA) was studied by pH titration, fluorescence, and HPLC methods in water solutions. It was shown that the complex formation and the solubility (phase state) of the polycomplexes depended on pH of the solutions and ratio of the components. The stability of PAA‐BSA complexes was negligibly weak when pH = 6.0–7.0 [pH > pI (isoelectric pH)]. Stable water‐soluble polycomplexes formed at pH = pI (pH 5.0) in a wide range of nBSA/nPAA ratios (0.05–50) and coexisted with free protein molecules at the higher ratios of components. Existence of water‐soluble and insoluble PAA‐BSA complexes has been observed at pH ≤ 4.5. The soluble to insoluble state transition of polycomplexes has been confirmed and binding mode of polyelectrolytes to proteins was assumed dependent on the ratio of components as a result of formation of soluble polycomplexes, complex coacervation, or amorphous precipitates. Soluble complexes were formed as fully homogenized mixtures. Fraction composition of the mixtures and insoluble complexes depended on the protein/polymer ratio and over the critical protein/polymer ratio, the soluble polycomplexes coexisted with free BSA molecules. On the other hand, the comparision of covalent conjugate formation and complexation of PAA with BSA has been revealed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Lanthanide triflates as curing initiators for solid DGEBA resin: Thermal and mechanical characterization
Authors: García S. J. , Serra A. , Suay J.
Published: May 2007

A new class of cationic initiators, lanthanide triflates, has been studied in the curing of diglycidyl ether of bisphenol‐A (DGEBA). Two metal salts (Erbium and Ytterbium (III) trifluoromethanesulfonate) in various proportions (0.5, 1, and 2 parts per hundred of resin) have been used and the thermal and mechanical properties of the thermosets compared to a common solid epoxy system (crosslinked with o‐tolylbiguanide). The kinetics of these processes has been evaluated by the isoconversional method that has been proved to be an excellent tool to predict the principal curing parameters (conversion/time/temperature). Their mechanical properties have been evaluated by dynamic mechanical thermal analysis (DMTA), stress‐strain curves, impact resistances and adhesion to metallic substrates, and the thermal characteristics were measured by calorimetry (DSC) and thermogravimetry (TGA). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
A novel approach to the interpretation and prediction of solvent effects in the synthesis of macroporous polymers
Authors: Scheler Stefan
Published: May 2007

A trivariate interpolation technique, the modified Shepard's method, was applied for the first time to explain and predict various properties of macroporous polymers from the Hansen solubility parameters of the porogens employed for polymerization. Highly crosslinked polymers and copolymers were prepared from ethylene glycol dimethacrylate and methacrylic acid by free‐radical polymerization with 30 different porogenic solvents. Instead of the spherical model used by Hansen, detailed three‐dimensional maps were computed to represent the measured properties in a δd–δp–δh diagram (where δd, δp, and δh are the Hansen solubility parameters according to the three types of bonding forces: dispersion, polar, and hydrogen‐bonding, respectively). This method was able to detect unapparent correlations between the different polymer properties, thus providing a better understanding of the pore‐formation process. An important finding was the crucial role of the initiator solubility and its partitioning between the solution and the polymer surface, which proved to be key factors for the explanation of many contradictory solvent effects. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Preparation and characterization of 2‐hydroxyethyl methacrylate‐based porous copolymeric particles
Authors: Fang Dongyu , Pan Qinmin , Rempel Garry L.
Published: May 2007

2‐Hydroxyethyl methacrylate was copolymerized with three different comonomers, methyl methacrylate (MMA), styrene (St), and N‐vinyl‐2‐pyrrolidone (NVP), respectively, to prepare porous particles crosslinked using ethylene glycol dimethacrylate (EGDMA) in the presence of an organic solvent, 1‐octanol (porogen), by means of suspension copolymerization in an aqueous phase initiated by 2,2‐azobisisobutyronitrile. Nano‐pores were observed in the particles. The pore size and the swelling properties of these particles can be controlled by changing comonomers or adjusting the crosslinker or porogen concentration. A lower crosslinker or porogen concentration favors generating smaller pores, whereas a higher concentration of a hydrophilic comonomer, higher concentration of crosslinker, and higher porogen volume ratio promote the generation of larger pores. In addition, the effects of the porous characteristics on the swelling properties were explored. The swelling capacity of the porous particles is reduced with the increase in the crosslinker concentration; however, there is a critical porogen volume ratio, in which the maximal swelling capacity is reached. Higher porosity in the particles and higher amount of hydrophilic comonomer favor a higher swelling capacity of the particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Preparation and pervaporation performances of fumed‐silica‐filled polydimethylsiloxane–polyamide (PA) composite membranes
Authors: Tang Xiaoyu , Wang Ren , Xiao Zeyi , Shi Er , Yang Jing
Published: May 2007

Fumed‐silica‐filled polydimethylsiloxane (PDMS)–polyamide (PA) composite membranes were prepared by the introduction of hydrophobic fumed silica into a PDMS skin layer. The cross‐sectional morphology of these filled composite membranes was observed with scanning electron microscopy. Their pervaporation performances were tested with aqueous ethanol solutions at 30, 35, and 40°C. Increasing the amount of the fumed silica resulted in significantly enhanced ethanol permeability of the membranes. When the content of the fumed silica in the PDMS skin layer was 20 wt %, the ethanol permeability increased to nearly twice that of the unfilled PDMS–PA composite membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Facile synthesis of dendronized polyamides with chloromethyl groups in the periphery and some properties
Authors: Liu Meihua , Xu Weijian , Xu Xiaocong , Lu Yanbing
Published: May 2007

A novel dendronized aromatic polyamide with a polyamide backbone and chloromethylene‐end‐functionalized polyamide dendrons is reported for the first time. An attempt at a one‐pot synthesis of end‐functionalized dendronized polymers with a macromonomer strategy without protection and deprotection procedures is also reported for the first time. The results from Fourier transform infrared and NMR spectral analysis indicated that perfect coverage of the chloromethyl groups in the periphery of the resulting polymers was obtained. Data from gel permeation chromatography analysis showed a typical weight‐average molecular weight (Mw) of 76,678 and a polydispersity of 2.44 for the first‐generation polymers and an Mw of 41,554 and a polydispersity of 2.74 for the second‐generation polymers. The solubility in solvents for the resulting polymers was improved remarkably because of the introduction of the dendritic fragments and the existence of the periphery functional groups. Both the glass‐transition temperature and onset decomposition temperature decreased versus those of the linear aromatic polyamides, but the 50% weight loss temperature was still up to 723°C. The X‐ray diffractograms indicated only an amorphous peak in the wide‐angle region of 24–25°. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Fe(II) adsorption onto natural polymers derived from low‐grade lignites
Authors: Tarlan Esra , Ahmetli Gulnare
Published: May 2007

In comparison with conventional chemical treatment methods for Fe(II) ions, adsorption and ion exchange are considered more easily applicable and economical, depending on the material used. Polymeric materials are the examples used in these commonly applied removal processes. In this study, the adsorption of Fe(II) ions from aqueous solutions onto two different natural polymers, insoluble humic acids (IHAs) extracted from low‐grade lignites from Beysehir and Ermenek (in the central Anatolia region, Konya, Turkey), was investigated. The IHAs were synthesized through a series of acid–base reactions, and the obtained precipitates were chemically stable and had about 40% humic matter together with functional carboxyl and hydroxyl groups. The effects of the time and initial metal concentration on the effectiveness of the IHAs for Fe(II) adsorption were determined through batch experiments; the adsorption isotherms and capacities were calculated. The IHAs were effective, with capacities of 59 mg/g for the Beysehir IHA and 57 mg/g for the Ermenek IHA, for Fe removal under neutral pH conditions. The adsorption followed mainly a Freundlich isotherm for both IHAs, and the calculated adsorption rates were 0.86 for the Beysehir IHA and 0.81 for the Ermenek IHA. This indicated that the effectiveness of the Beysehir IHA was slightly higher than that of the Ermenek IHA. The results confirmed the real possibility of the practical application of IHAs for the separation of Fe(II) in aqueous systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Effect of an organic dicarboxylic acid salt on fractionated crystallization of polypropylene droplets
Authors: Jin Y. , Hiltner A. , Baer E.
Published: May 2007

The effect of a particulate nucleating agent on fractionated crystallization of polypropylene (PP) was studied. A novel method utilizing breakup of PP nanolayers was used to obtain a dispersion of PP droplets in a polystyrene (PS) matrix. An assembly with hundreds of PP nanolayers alternating with thicker PS layers was fabricated by layer‐multiplying coextusion. The concentration of an organic dicarboxylic acid salt (HPN) nucleating agent in the coextruded PP nanolayers was varied up to 2 wt %. When the assembly was heated into the melt, interfacial driven breakup of the thin PP layers produced a dispersion of PP particles in a PS matrix. Analysis of optical microscope images and atomic force microscope images indicated that layer breakup produced a bimodal particle size distribution of submicron particles and large, micron‐sized particles. Almost entirely submicron particles were obtained from breakup of 12 nm PP layers. The fraction of PP as submicron particles dropped dramatically as the PP nanolayer thickness increased to 40 nm. Only large, micron‐sized particles were obtained from 200 nm PP nanolayers. The crystallization behavior of the particle dispersions was characterized by thermal analysis and wide angle X‐ray diffraction. Only part of the PP was nucleated by HPN. It was found that HPN was not effective in nucleating the population of submicron particles. The particulate HPN was too large to be accommodated in the submicron PP particles. On the other hand, the amount of nucleated crystallization qualitatively paralleled the fraction of PP in the form of large, micron‐sized particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Effect of cavitation on the plastic deformation and failure of isotactic polypropylene
Authors: Na Bing , Lv Ruihua
Published: May 2007

To clarify the effect of cavitation, which is mostly induced by crystalline phase, on the plastic deformation and failure of isotactic polypropylene, solid‐state annealing at 160°C for 1.5 h is adopted to change the crystalline phase only while the amorphous phase keeps nearly intact. With aid of a special video setup, the relation of true stress and strain as well as the evolution of volume strain with axial strain has been derived. Enhancing crystalline phase due to annealing increases the yield stress and volume strain simultaneously. Moreover, the strain corresponding to steep increasing of volume strain is comparable with that related to yield, indicating that cavitation at early stage is accompanied with process of yield. With knowledge of toughness derived from impact tensile stretching and essential work of fracture (EWF), respectively, the relationship between cavitation and toughness has been correlated to some degree. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007