bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamically Available Volume: A Novel Order Parameter for Dense and Nearly Arrested Systems
Authors: Dawson Kenneth A. , Lynch Iseult , Lawlor Aonghus , de Gregorio Paolo
Published: August 2006

Summary: Many common materials ‘solidify’ upon a small change in their surroundings (such as temperature or pH), and the underlying phenomenon is the collective slowing of the motion of the constituent molecules. Examples include gels, polymers, proteins, and other soft matter systems. It has been known for some time that ‘arrest’ is related to some concept of ‘free volume’. However, it has emerged more recently that the important parameter is the volume usable in the long‐ranged reorganisation of the system (the dynamically available volume, DAV) as this determines mobility in these systems. The DAV diminishes as systems arrest, and this is the canonical order parameter for understanding the arrest of complex systems. This idea has been taken a step further here, wherein it is clearly indicated that thermal fluctuation effects can be accommodated within the DAV scenario.

Dynamically available volume (DAV) i.e, the empty space that is available to promote long‐ranged motion, and hence diffusion is shown here (the shaded polygonal volume, overemphasized for clarity) to allow the red particle to pass into a neighbouring cage. Repeat of this process is needed for long‐ranged transport (diffusion), and only some DAV is ultimately useful, and therefore termed ‘connected’ DAV.

magnified image

Dynamically available volume (DAV) i.e, the empty space that is available to promote long‐ranged motion, and hence diffusion is shown here (the shaded polygonal volume, overemphasized for clarity) to allow the red particle to pass into a neighbouring cage. Repeat of this process is needed for long‐ranged transport (diffusion), and only some DAV is ultimately useful, and therefore termed ‘connected’ DAV.
Kinetic Study of Ethylene Polymerization Over Supported Bis(imino)pyridine Iron (II) Catalysts
Authors: Barabanov Artem A. , Bukatov Gennady D. , Zakharov Vladimir A. , Semikolenova Nina V. , Mikenas Tatiana B. , Echevskaja Ljudmila G. , Matsko Michail A.
Published: August 2006

Summary: The number of active centers (CP) and propagation rate constants (kP) for polymerization of ethylene with supported catalysts LFeCl2/SiO2, LFeCl2/Al2O3 and LFeCl2/MgCl2 (L = 2,6‐(2,6‐(Me)2C6H3NCMe)2C5H3N), activated by an Al(i‐Bu)3 co‐catalyst, were determined by a method of polymerization inhibition with radioactive 14CO. In contrast to homogeneous systems based on LFeCl2, the supported catalysts are highly active and stable in ethylene polymerization at 70–80 °C. In the presence of hydrogen, the activity of the supported catalysts substantially increases (2–4 fold). The data obtained on the effect of hydrogen on the calculated CP and kP values suggests that for ethylene polymerization without hydrogen, the “dormant” active centers are formed in the catalytic systems. A scheme for the formation of these “dormant” centers and their reactivation in presence of hydrogen is suggested. For the investigated supported catalysts the CP values were found to be only 2 to 4% of the total iron complex content in the catalysts. The kP value for the catalysts prepared using different supports (SiO2, Al2O3 and MgCl2) were close (3.2 × 104 to 4.5 × 104 L · (mol · s)−1 at 70 °C). The support composition affects neither the molecular mass (MM) nor the molecular mass distribution (MMD) of the polymers produced. The obtained CP and kP values and data on the polymer MM and MMD lead to conclusion that the nature of the support has almost no effect on the structure of the active centers and the distribution of their reactivity.

Effect of support on the MMD of PE produced over supported LFeCl2 catalysts.

magnified image

Effect of support on the MMD of PE produced over supported LFeCl2 catalysts.
Single Radiation‐Induced Grafting Method for the Preparation of Two Proton‐ and Lithium Ion‐Conducting Membranes
Authors: Nasef Mohamed Mahmoud , Saidi Hamdani
Published: August 2006

Summary: Two distinct types of polymer electrolyte membranes for conducting protons and lithium ions have been prepared by a radiation‐induced grafting method. The polymer electrolyte precursor (PVDF‐g‐PS) is obtained by the simultaneous grafting of styrene onto poly(vinylidene fluoride) (PVDF) followed by one of two specific treatments. This includes sulfonation with a chlorosulfonic acid/dichloromethane mixture to obtain proton (H+)‐conducting membranes, or activation with LiPF6/EC/DC liquid electrolyte to obtain lithium ion (Li+)‐conducting membranes. The chemical structure of the obtained electrolyte membranes is verified by FT‐IR spectroscopy. Differential scanning calorimetry is used to examine the changes in the crystallinity and the thermal properties of both electrolyte membranes during the preparation process. The thermal stability of both electrolyte membranes is also evaluated using thermal gravimetrical analysis. The obtained polymer electrolyte membranes achieve superior conductivity values: 1.61 × 10−3 S · cm−1 for Li+ and 5.95 × 10−2 S · cm−1 for H+ at room temperature at a polystyrene content of 50%. The results of this work suggest that high quality H+‐ and Li+‐conducting membranes can be obtained using a single radiation‐induced grafting method.

Schematic representation of the single root for preparation of Li+‐ and H+‐conducting membranes started by radiation‐induced grafting of styrene onto a PVDF film followed by chemical treatment.

magnified image

Schematic representation of the single root for preparation of Li+‐ and H+‐conducting membranes started by radiation‐induced grafting of styrene onto a PVDF film followed by chemical treatment.
Preparation and Characterization of Trialkoxysilane‐Containing Acrylic Resin/Alumina Hybrid Materials
Authors: Li Mingqi , Zhou Shuxue , You Bo , Wu Limin
Published: August 2006

Summary: In the present study (3‐methacryloxypropyl)trimethoxysilane (MPMS) containing acrylic resin/alumina hybrid materials with various alumina contents were prepared. The effects of ethylacetoacetate (EAA) content, catalyst type, and water content during sol–gel process for alumina sols on the microstructure and properties of the hybrid materials were investigated by SAXS, AFM, DSC, TGA, and nano‐indentation tester, respectively. It was found that the hybrid materials exhibited a homogeneity and the alumina phase of the hybrids had mass fractal dimension and open structure. The thermal and mechanical properties of the hybrid materials were obviously improved when alumina was incorporated. The EAA contents, catalyst type, and water content during sol–gel process for alumina sols had obvious effects on the microstructure and properties of the hybrid materials.

Typical load–displacement curves of the pure acrylic resin and hybrid materials with increasing alumina content.

magnified image

Typical load–displacement curves of the pure acrylic resin and hybrid materials with increasing alumina content.
Slice‐selected LED and BPPLED: application of slice selection to DOSY
Authors: Park Ki D. , Lee Young J.
Published: August 2006

High‐resolution DOSY (Diffusion‐ordered spectroscopy) is a series of 2‐dimensional and 3‐dimensional NMR techniques based on the differing diffusivity of constituent molecules in the solution state, with which the individual NMR spectrum of each component in a chemical mixture can be observed. All of the DOSY pulse sequences are derived from the spin‐echo or stimulated‐echo techniques under the effect of PFG (pulsed field gradient). One of the requirements for successful DOSY experiments and data fitting is that PFG must be uniform across the active sample volume. However, PFG, in general, is not uniform across the active sample volume in commercial high‐resolution NMR probes and this nonuniformity of PFG is known to produce systematic errors in DOSY experiments. In fact, a strong and uniform gradient field can be realized only in the central region of the gradient coil and the slice‐selection technique, widely used in Magnetic Resonance (MR) imaging, can be employed in resolving problems associated with the nonuniformity of PFG. We have developed a slice‐selection pulse block, which can be generally applied to any DOSY pulse sequence with proper care of the phase cycling and experimental parameters. We applied the slice‐selection technique to LED and BPPLED pulse sequences, which are among the most popular DOSY pulse sequences, and obtained good experimental results for a chemical mixture. Copyright © 2006 John Wiley & Sons, Ltd.
Algorithms to calculate the distribution of the longest path length of a stochastic activity network with continuous activity durations
Authors: Leemis Lawrence M. , Duggan Matthew J. , Drew John H. , Mallozzi Jeffrey A. , Connell Kerry W.
Published: August 2006

We develop algorithms to calculate the probability distribution of the longest path of an arbitrary stochastic activity network with continuous activity durations by three techniques: recursive Monte Carlo simulation, series‐parallel reduction, and conditioning. Examples illustrate the use of the three techniques. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(3), 143–165 2006
Hyper hamiltonian laceability of Cayley graphs generated by transpositions
Authors: Araki Toru
Published: August 2006

Suppose thatG(V0∪V1,E) is a bipartite graph with partite sets of equal size.Gis calledhyper hamiltonian laceableif (1) it has a hamiltonian path between any pair of vertices in different partite sets, and (2) for any vertexv∈Vi, there is a hamiltonian path inG−vbetween any two vertices inV1 −i. Star and bubble‐sort graphs have been considered as interconnection networks for parallel and distributed systems, and these graphs are known to be hyper hamiltonian laceable. Furthermore, it is well known that these graphs belong to the class of Cayley graphs on symmetric groups generated by a set of transpositions. In this article, we generalize those results by showing that any Cayley graph generated by transpositions is hyper hamiltonian laceable. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(3), 121–124 2006
Solution methods for the p‐median problem: An annotated bibliography
Authors: Reese J.
Published: August 2006

The p‐median problem is a network problem that was originally designed for, and has been extensively applied to, facility location. In this bibliography, we summarize the literature on solution methods for the uncapacitated and capacitated p‐median problem on a network. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(3), 125–142 2006
The marketing profession: evolution and future
Authors: Enright Michael
Published: August 2006

Marketing claims professional status and presents to the broader community as professional. The paper draws on previous contributions to the broader issue of professionalism and uses the examples from law, medicine and accounting to argue that the attempt has been neither completely successful nor easily demonstrable. Five criteria common to well‐known and accepted professions are developed. The paper concludes that marketing is yet to achieve professional status and asks whether such status is essential for marketers.

Copyright © 2006 John Wiley & Sons, Ltd.
Treatment for children with severe aplastic anemia and sickle cell disease in low income countries in Latin America: A report on the recent meetings of the Monza International School of Pediatric Hematology/Oncology (MISPHO): Part III
Authors: Howard Scott C. , Wilimas Judy A. , Flores Andronica , Pacheco C. , de Reyes Gladis , Machin Sergio , Svarch Eva , Navarrete Marta , Nieves Rosa , Rodriguez Hilze , Masera Giuseppe ,   The MISPHO Consortium Writing Committee
Published: August 2006

Treatment of hematologic disorders in low‐income countries (LIC) is difficult. This report summarizes treatment of sickle cell disease and aplastic anemia by pediatric hematologists from 15 LIC who participate in the Monza International School of Pediatric Hematology/Oncology (MISPHO). Patients with severe sickle cell disease were treated with low dose hydroxyurea, which safely reduced vaso‐occlusive crises. Patients with severe aplastic anemia fared poorly due to lack of availability and high cost of anti‐thymocyte globulin and cyclosporine and lack of access to stem cell transplantation. Appropriate therapy was most likely to occur in MISPHO centers with an active twinning program with a center in a high‐income country. Pediatr Blood Cancer 2007;48:598–599. © 2006 Wiley‐Liss, Inc.
Two‐dimensional Bose‐Einstein condensates in a CO2‐laser optical lattice
Authors: Cennini G. , Geckeler C. , Ritt G. , Salger T. , Weitz M.
Published: August 2006

We report on experiments with all‐optically produced Bose‐Einstein condensates in a mesoscopic optical lattice. By retroreflecting the radiation of a CO2‐laser operating near 10.6 μm, a lattice with spacing between sites of λ/2 ≃ 5.3 μm is realized, for which atom tunneling is negligible. Once cooled to quantum degeneracy by direct evaporative cooling in the lattice, the properties of the trapped microclouds can be studied with far field interference experiments. The microscopic atom clouds are shown to be in the two‐dimensional regime for small atom filling. The realized system has extremely long coherence times, and holds fascinating prospects for both quantum logic and the study of novel collective phenomena.
Implementation of generalized measurements with minimal disturbance on a quantum computer
Authors: Decker T. , Grassl M.
Published: August 2006

We consider the problem of efficiently implementing a generalized measurement on a quantum computer. Using methods from representation theory, we exploit symmetries of the states we want to identify respectively symmetries of the measurement operators. In order to allow the information to be extracted sequentially, the disturbance of the quantum state due to the measurement should be minimal.
Continuous variable entanglement between frequency modes
Authors: Glöckl O. , Andersen U.L. , Leuchs G.
Published: August 2006

The pairwise production of photons in nonlinear optical processes ensures entanglement to occur between two photons. E.g. when the Kerr effect is exploited, the photons are produced in different frequency modes, which are symmetric with respect to the pump frequency. Since these photons are produced into the same spatial mode, the quadrature entanglement can be witnessed only by the use of a frequency selective device which transforms the adjacent frequency modes into two different spatial modes. We use a Mach‐Zehnder interferometer with a large path length difference to separate symmetric frequency modes located 10.25 MHz from the carrier. We measure correlations of the quadrature components of 1.6 ± 0.1dB below the shot noise in the amplitude and 1.4 ± 0.1dB in the phase.
Implementation complexity of physical processes as a natural extension of computational complexity
Authors: Janzing D.
Published: August 2006

The theory of computational complexity in computer science investigates the time and space resources required to solve a computational problem. We show that an analogous complexity theory can be developed for quantum control problems which do not stem from computational problems. First we use the same mathematical concept to show similar lower bounds on the complexity of the following tasks:

(1) Computing the boolean function “Majority”,

(1) Optimal algorithmic cooling on n> two‐level systems,

(2) Optimal work extraction by a heat engine acting on 2n> hot and 1 cold two‐level system,

(3) Preparing appropriate n‐qubit entanglement for improving frequency standards in Ramsey spectroscopy,

(4) Implementing a von‐Neumann measurement that is strongly incompatible with macroscopic observables.

We describe furthermore instances of the problems “optimal heat engines” and “precise measurements” which are likely to be complex since NP‐ or even PSPACE‐complete computational problems can be reduced to them.

In order to define implementation complexity also for other systems than n qubit registers we rephrase some approaches to define complexity measures using a set of available interactions and explore the complexity of analogue to digital conversion using a Jaynes Cumming interaction as an example.

Furthermore we argue that, from a physical perspective of complexity, operations should only considered to be simple if there is a physically reasonable Hamiltonian that can implement them by its autonomous time evolution within a short time interval. Therefore we discuss a Hamiltonian whose natural time evolution can implement computation processes.
How to distill entanglement from a finite amount of qubits?
Authors: Probst‐Schendzielorz S. , Bschorr T. , Freyberger M.
Published: August 2006

We discuss a specific entanglement distillation scheme [D. Deutsch et al., Phys. Rev. Lett. 77, 2818 (1996)] under the constraint of finite samples of entangled qubit pairs. It is shown that an iterative process based on this method can be explicitly formulated. The average fidelity of this process can be strongly enhanced by introducing a conditional storing of entangled qubit pairs in each step of the iteration. We investigate the corresponding limitations on the size and the initial fidelity of the sample.
Transport dynamics of single ions in segmented microstructured Paul trap arrays
Authors: Reichle R. , Leibfried D. , Blakestad R.B. , Britton J. , Jost J.D. , Knill E. , Langer C. , Ozeri R. , Seidelin S. , Wineland D.J.
Published: August 2006

It was recently proposed to use small groups of trapped ions as qubit carriers in miniaturized electrode arrays that comprise a large number of individual trapping zones, between which ions could be moved [1,2] This approach might be scalable for quantum information processing with a large numbers of qubits. Processing of quantum information is achieved by transporting ions to and from separate memory and qubit manipulation zones in between quantum logic operations. The transport of ion groups in this scheme plays a major role and requires precise experimental control and fast transport times. In this paper we introduce a theoretical framework to study ion transport in external potentials that might be created by typical miniaturized Paul trap electrode arrays. In particular we discuss the relationship between classical and quantum descriptions of the transport and study the energy transfer to the oscillatory motion during near‐adiabatic transport. Based on our findings we suggest a numerical method to find electrode potentials as a function of time to optimize the local potential an ion experiences during transport. We demonstrate this method for one specific electrode geometry that should closely represent the situation encountered in realistic trap arrays.
Polymer electrolyte with ionic liquid for DSSC application
Authors: Singh Pramod K. , Kim Ki‐Il , Lee Jae‐Wook , Rhee Hee‐Woo
Published: August 2006

We have investigated the structural and ionic conductivity properties of the polymer electrolyte PEO:KI/I2 doped with an ionic liquid 1‐ethyl 3‐methylimidazolium thio‐cyanate (EMImSCN). Incorporation of the ionic liquid (IL) reduced the crystallinity, and enhanced the ionic conductivity. Optimized conductivity was found at 80 wt% of ionic liquid composition. This high electrical conductivity was suitable for dye sensitized solar cell (DSSC) application. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Encoding Type and Position in Peptide QSAR: Application to Peptides Binding to Class I MHC Molecule HLA‐A*0201
Authors: Pissurlenkar Raghuvir R. S. , Malde Alpeshkumar K. , Khedkar Santosh A. , Coutinho Evans C.
Published: August 2006

Various QSAR approaches have evolved over time to find a relationship between chemical structure and biological response by translating the information in the chemical structure into a quantitative (Hansch approach) or qualitative (Free–Wilson approach) description followed by a statistical modeling. The nature and position of every amino acid in the peptide sequence dictate its binding to the receptor. We have investigated an approach to peptide QSAR where the position and type of every amino acid in the sequence are encoded in the QSAR paradigm, and along with the principles of the Hansch (descriptor QSAR) and the Free–Wilson (binary QSAR) methodologies we were able to arrive at the optimal sequence of amino acids in the peptide. As an example, we illustrate the procedure on two datasets of nonamer peptides that bind to the class I major histocompatibility complex molecule HLA‐A*0201. The models generated have statistically significant co‐relation coefficient (r2) and predictive r2 (r2pred). The cross‐validated r2 (q2) for “descriptor QSAR” approach and the “binary QSAR” approach are in an acceptable range. The QSAR analysis is able to identify the preferential and detrimental amino acids at every position of the nonamer peptide. This QSAR formalism as applied to peptides is a simple and effective way to explain structure–activity relationships as well as to optimize the binding affinity.
Quantitative Structure–Activity Relationship Study of Some Aspartic Acid Analogues to Correlate and Predict their Sweetness Potency
Authors: Vepuri Suresh B. , Tawari Nilesh R. , Degani Mariam S.
Published: August 2006

A series of aspartame analogues and chemically modified derivatives was evaluated for their structure–activity relationship, as artificial sweeteners using Three Dimensional Quantitative Structure–Activity Relationship (3D‐QSAR) with Genetic Functional Algorithm (GFA). A four‐term equation was developed with conventional and cross‐validated coefficients of 0.753 and 0.660, respectively. 3D‐QSAR studies of the same series were also performed by Comparative Molecular Field Analysis (CoMFA) and Comparative Molecular Similarity Indices Analysis (CoMSIA). The CoMFA model produced modest statistical significance with conventional and cross‐validated correlation coefficients of 0.768 and 0.390, respectively. The combination of steric, electrostatic, hydrophobic, and H‐bond acceptor fields in CoMSIA gave better results with conventional and cross‐validated correlation coefficients of 0.927 and 0.585, respectively. The predictive ability of 3D‐QSAR with GFA, CoMFA, and CoMSIA were determined using a test set of ten molecules giving predictive correlation coefficients of 0.375, 0.535, and 0.596, respectively, indicating better predictivity of CoMSIA compared to the other methods. Based on this information, some key features that may be used to design new sweeteners and predict their sweetness value have been identified.
QSAR Analysis of the Anticancer Activity of 2,5‐Disubstituted 9‐Aza‐Anthrapyrazoles
Authors: Slavov Svetoslav , Atanassova Mariyana , Galabov Boris
Published: August 2006

The anticancer activity of 35 2,5‐disubstituted 9‐Aza‐Anthrapyrazoles (9‐aza‐APs) was analyzed employing the Best Multiple Linear Regression (BMLR) as well as a heuristic method for selection of the best descriptors implemented in the CODESSA software to provide a reliable 2D‐QSAR model from a set of nearly 500 descriptors. The Chem‐X (version 2000) software was used to develop a corresponding 3D‐QSAR model. The steric and electrostatic interactions between a probe atom (H+) and a set of aligned molecules were assessed using the comparative molecular field analysis method. The results from 2D‐ and 3D‐QSAR analyses show that the anticancer activity of the studied series of 9‐aza‐APs is strongly dependent on electrostatic interactions. A binding of these derivatives to DNA has been discussed as a key factor determining the cytotoxic activity against tumor cell. The value of the maximum sum partial negative charge at the nitrogen atoms in 9‐aza‐APs influences strongly the activity of the compounds. The magnitude of these charges define the hydrogen‐bond acceptor properties of the 9‐aza‐APs. The hydrogen‐bond donor properties of the NH and OH groups in the studied series of compounds also play a key role in the binding process. The stable ring structure of the 9‐aza‐APs also appears to be an important factor for the antitumor activity of the compounds.
Fluorous TEMPO: An Efficient Mediator for the Aerobic Oxidation of Alcohols to Carbonyl Compounds
Authors: Holczknecht Orsolya , Pozzi Gianluca , Quici Silvio
Published: August 2006

The aerobic oxidation of alcohols to aldehydes and ketones mediated by a fluorous derivative of the stable nitroxyl radical 2,2,6,6‐Tetramethylpiperidine‐1‐oxyl (TEMPO) has been investigated. The applicability of literature protocols originally developed for TEMPO‐mediated reactions was assessed. Best results were obtained using molecular oxygen and a catalytic system combining the fluorous nitroxyl radical with Co(NO3)2/Mn(NO3)2 (Minisci's conditions). Primary and benzylic alcohols were smoothly oxidized to the corresponding aldehydes under both homogeneous and fluorous biphasic conditions, whereas the oxidation of secondary aliphatic alcohols to ketones proved more challenging, in line with the behavior of similar catalytic systems based on polymer‐supported TEMPO derivatives. The fluorous radical and related byproducts were easily removed from the reaction mixture by simple phase separation or fluorous liquid–liquid extraction, thus greatly simplifying the purification of the products. Recycling of the fluorous radical was also attempted with good results in the case of oxidation reactions requiring mild conditions.
Theoretical study of thermal rearrangements of α‐silylalcohols: Effects of substituents attached to the silicon atom on the reactions
Authors: Yu Yongming , Feng Shengyu
Published: August 2006

To investigate the effects of substituents attached to the silicon atom on the thermal rearrangement reactions of α‐silyl alcohols, the thermal rearrangement reactions of dimethylsilyl methanol (CH3)2SiHCH2OH and vinylsilyl methanol CH2CHSiH2CH2OH were studied by ab initio calculations at the G3 level. Geometries of various stationary points were fully optimized at the MP2(full)/6‐31G(d) and MP2(full)/6‐311G(d,p) levels, and harmonic vibrational frequencies were calculated at the same levels. The reaction paths were investigated and confirmed by intrinsic reaction coordinate (IRC) calculations at the MP2(full)/6‐31G(d) level. The results show that two dyotropic reactions could occur when (CH3)2SiHCH2OH or CH2CHSiH2CH2OH is heated. One is Brook rearrangement reaction (reaction A), and the dimethylsilyl or vinylsilyl groups migrates from carbon atom to oxygen atom coupled with a simultaneous migration of a hydrogen atom from oxygen atom to carbon atom passing through a double three‐membered ring transition state, forming dimethylmethoxylsilane (CH3)2SiHOCH3 or methoxylvinylsilane CH2CHSiH2OCH3; the other is a hydroxyl group migration (reaction B) from carbon atom to silicon atom, coupled with a simultaneous migration of a hydrogen atom from silicon atom to carbon atom, via a double three‐membered ring transition state, forming trimethylsilanol (CH3)3SiOH or methylvinylsilanol CH3SiH(OH)CHCH2. The G3 barriers of the reactions A and B were computed to be 312.8 and 241.4 kJ/mol for (CH3)2SiHCH2OH, and 317.6 and 233.7 kJ/mol for CH2CHSiH2CH2OH, respectively. On the basis of the MP2(full)/6‐31G(d) optimized parameters, vibrational frequencies, and G3 energies, the reaction rate constants k(T) and equilibrium constants K(T) were calculated using canonical variational transition state theory (CVT) with centrifugal‐dominant small‐curvature tunneling (SCT) approximation over a temperature range of 400–1800 K. The influences of methyl and vinyl groups attached to the silicon atom on reactions are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Trigonal pyramidal carbon geometry as model for electrophilic addition–substitution and elimination reactions and its significance in enzymatic processes
Authors: Buck Henk M.
Published: August 2006

Various examples are given in which compounds are characterized as products or intermediates in a (distorted) trigonal pyramidal (TP) geometry. These observations have taken place mainly in the field of carbocation chemistry. Special attention is given to carbenium ions formed by halogen addition to 1,1‐diarylsubstituted ethylenes focused on the electronic effects of the C‐halogen bond as axial bond in a TP geometry with regard to the π‐distribution in the rest of the molecular system. The experimental verification is accompanied by quantum chemical calculations. We also used the TP structure as a reactive model for specific enzymatic reactions. The relevance of this geometry is shown for the dehalogenation reaction of the nucleophilic displacement in dichloroethane catalyzed by haloalkane dehalogenase and for the decarboxylation of L‐ornithine with ornithine decarboxylase under loss of carbon dioxide. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Molecular dynamics simulations of polarizable DNA in crystal environment
Authors: Babin Volodymyr , Baucom Jason , Darden Thomas A. , Sagui Celeste
Published: August 2006

We have investigated the role of the electrostatic description and cell environment in molecular dynamics (MD) simulations of DNA. Multiple unrestrained MD simulations of the DNA duplex d(CCAACGTTGG)2 have been carried out using two different force fields: a traditional description based on atomic point charges and a polarizable force field. For the time scales probed, and given the “right” distribution of divalent ions, the latter performs better than the nonpolarizable force field. In particular, by imposing the experimental unit cell environment, an initial configuration with ideal B‐DNA duplexes in the unit cell acquires sequence‐dependent features that very closely resemble the crystallographic ones. Simultaneously, the all‐atom root‐mean‐square coordinates deviation (RMSD) with respect to the crystallographic structure is seen to decay. At later times, the polarizable force field is able to maintain this lower RMSD, while the nonpolarizable force field starts to drift away. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Die Gustav‐Heinemann‐Brücke über die Spree im neuen Zentrum Berlins – Moderne Lösungen der schwingungstechnischen Probleme eines schlanken Überbaus
Authors: Zimmer Eva‐Marie , Mündecke Michael
Published: August 2006

Im neuen Zentrum Berlins, dem Spreebogen zwischen Regierungs‐ und Parlamentsbereich und dem neuen Bahnkreuzungspunkt Berlin Hauptbahnhof, wurde als kurze Verbindung die Gustav‐Heinemann‐Fußgängerbrücke über die Spree errichtet. Der im Ergebnis eines Gutachterverfahrens ausgewählte Entwurf eines sehr schlanken Vierendeelträgers war von vornherein als schwingungsanfällig, sowohl für fußgängerinduzierte als möglicherweise auch für windinduzierte Schwingungen anzusehen.

Es wird nach der Beschreibung des Bauwerks und der städtebaulichen Situation über die Berechnungen zur Ermittlung des Schwingungsverhaltens bei Anregung durch Fußgänger bzw. zur Abschätzung des Schwingungsverhaltens bei Anregung durch Wind und über die Berechnungen zur Konfektionierung von Schwingungstilgern/‐dämpfern berichtet. Abschließend werden die notwendigen Versuche zur Absicherung der Rechenergebnisse und zum Nachweis der Wirksamkeit der Tilger vorgestellt.
Erdbebenbemessung von Stahlbauten nach neuer DIN 4149‐1
Authors: Akkermann Jan , Constantinescu Dan
Published: August 2006

Die neue deutsche, seit April 2005 im Weißdruck vorliegende Erdbeben‐Bemessungsnorm gibt gegenüber ihrer Vorgängerin auch für Stahlbauten eine Vielzahl neuer Bemessungs‐ und Konstruktionsregeln vor. Im vorliegenden Beitrag werden die wesentlichen Bemessungsmethoden und die Besonderheiten für den Stahlbau vor dem Hintergrund der Praxisanwendung vorgestellt.
GABAA receptor regulation of voluntary ethanol drinking requires PKCϵ
Authors: Besheer Joyce , Lepoutre Veronique , Mole Beth , Hodge Clyde W.
Published: August 2006

Protein kinase C (PKC) regulates a variety of neural functions, including ion channel activity, neurotransmitter release, receptor desensitization and differentiation. We have shown previously that mice lacking the ε‐isoform of PKC (PKCε) self‐administer 75% less ethanol and exhibit supersensitivity to acute ethanol and allosteric positive modulators of GABAA receptors when compared with wild‐type controls. The purpose of the present study was to examine involvement of PKCε in GABAA receptor regulation of voluntary ethanol drinking. To address this question, PKCε null‐mutant and wild‐type control mice were allowed to drink ethanol (10% v/v) vs. water on a two‐bottle continuous access protocol. The effects of diazepam (nonselective GABAA BZ positive modulator), zolpidem (GABAA α1 agonist), L‐655,708 (BZ‐sensitive GABAA α5 inverse agonist), and flumazenil (BZ antagonist) were then tested on ethanol drinking. Ethanol intake (grams/kg/day) by wild‐type mice decreased significantly after diazepam or zolpidem but increased after L‐655,708 administration. Flumazenil antagonized diazepam‐induced reductions in ethanol drinking in wild‐type mice. However, ethanol intake by PKCε null mice was not altered by any of the GABAergic compounds even though effects were seen on water drinking in these mice. Increased acute sensitivity to ethanol and diazepam, which was previously reported, was confirmed in PKCε null mice. Thus, results of the present study show that PKCε null mice do not respond to doses of GABAA BZ receptor ligands that regulate ethanol drinking by wild‐type control mice. This suggests that PKCε may be required for GABAA receptor regulation of chronic ethanol drinking. Synapse 60:411–419, 2006. © 2006 Wiley‐Liss, Inc.
Macroscopic properties of spontaneous mutations in slow‐channel syndrome: Correlation by domain and disease severity
Authors: Zayas Roberto , Lasalde‐Dominicci Jose , Gomez Christopher M.
Published: August 2006

The slow‐channel syndrome (SCS) is a neuromuscular disorder characterized by fatigability, progressive weakness, and degeneration of the neuromuscular junction. The SCS is caused by missense mutations in the four subunits of the skeletal muscle acetylcholine receptor (AChR), which leads to altered channel gating, prolonged neuromuscular postsynaptic currents, and impaired neuromuscular transmission. Although a diverse set of mutations in different functional domains of the AChR appear to be associated with symptoms of widely ranging severity, there is as yet no mutant channel property or combination that explains the variations in disease severity. By observing the recovery time of AChR from desensitization, the authors determined that this process is significantly enhanced in SCS channels. In addition, as expected, the authors found that SCS macroscopic decay currents in transfected HEK293 cells are slower than wild type currents. While slight differences in relative Ca2+ permeability between some SCS mutations were identified, they did not correlate with apparent disease severity. These results suggest that of the different AChR kinetic features studied, only recovery from desensitization and slow postsynaptic currents correlate with the severity observed in the different mutations of this syndrome. Synapse 60:441–449, 2006. © 2006 Wiley‐Liss, Inc.
Dielectric properties of graphite nanocomposites
Authors: Wong Shing‐Chung , Wouterson Erwin M. , Sutherland Eric M.
Published: August 2006

Polymer nanocomposites are an emerging class of multifunctional materials that have not been optimized for their functional potential. In this study, the dielectric properties of graphite polymer nanocomposites were evaluated. The objective was to develop for composite applications, an alternative cost‐effective nanoscale carbon material with properties comparable to those of carbon nanotubes. J. VINYL. ADDIT. TECHNOL., 12:127–130, 2006. © 2006 Society of Plastics Engineers
Effect of high molecular weight acrylic copolymers on the viscoelastic properties of engineering resins
Authors: Mekhilef Nafaa , Hong Sheng , Carrington Courtney , Davis Benjamin
Published: August 2006

In this work, the viscoelastic properties of acrylic‐based copolymer blends with poly(methyl methacrylate) (PMMA) and polycarbonate were investigated in the molten and solid states. High molecular weight copolymers of methyl methacrylate with butyl acrylate (MMA‐co‐BA) having varying molecular weight and composition were used to enhance the rheological properties in shear and extension. Blends containing up to 15 wt% of copolymer were prepared at 200°C and 150 rpm by using a DSM micro‐compounder. The samples were characterized by size exclusion chromatography (SEC), dynamic mechanical analysis (DMA), and rheology. The rheological properties were determined by using small amplitude oscillatory measurements (SAOM) in shear and a Rheotens™ device for melt strength determination. For PMMA, the effects of high molecular weight PMMA copolymer on the matrix were related to the molecular weight, the tacticity of the copolymer, and the individual components. The rheological properties in shear showed enhanced storage and loss moduli at low frequency, while no change was observed at high frequency. In addition, extensional viscosity measurements made by using the filament stretching technique showed a significant increase in melt strength compared to that of the base PMMA with the blend containing the highest molecular weight copolymer showing the maximum force and a reduced drawdown ratio. For polycarbonate, its blends with acrylic copolymer were found to be immiscible. Similar enhancement in the moduli at low frequencies was observed, but a significant increase in the viscosity was obtained as well, resulting from the response of the two‐phase system. This change in the rheological properties was further increased at 15 wt% loading. Owing to the formation of a phase‐separated morphology, the melt strength was found to increase only slightly. J. VINYL. ADDIT. TECHNOL., 12:143–150, 2006. © 2006 Society of Plastics Engineers
An inquiry into the causes for the multiple goals of the United States Antitrust Law from a historical perspective
Authors: Tie Han
Published: August 2006

It is not the case as Robert Bork claims that the U. S. antitrust law had only one goal—maximization of consumer welfare of efficiency—at the very beginning and should have been kept that way for its later development. Partly because of the fighting among different interest groups as well as spokesmen of different regions at the 51st Congress, the Sherman Antitrust Act came out as a legislation with multiple goals, which were also taking shape under the influence of the Republican idea of balance of power, the liberal belief in property rights, the freedom of contract of classic economics, and the price theory of neoclassic economics. In more than a hundred years after that, the U.S. antitrust law has shifted the center of its goals as a result of the change of regulatory regimes with different emphases such as market function, economic stabilization, social concern, and economic efficiency during different periods. From a historical perspective, it is beyond dispute that the U.S. antitrust law has had multiple goals instead of only one.
Conflict and mutual support between local consciousness and national consciousness disturbance on Chuanxing suoji in 1936
Authors: Dongjie Wang
Published: August 2006

From the late Qing Dynasty to the Republican period, there was a transition on the understanding of the relationship between China as a state and its localities. Local and national consciousness generally supported each other but were in conflict at times. In this essay the author intends to explore the reasons and influences of the Sichuan people’s criticism of the Chuanxing suoji (Rambling Notes on Sichuan) letter written by Chen Hengzhe, and analyze the interplay between local and national consciousness in the early days when the Nanjing government controlled Sichuan. The uproar caused by the article also showed the gap between mainstream intellectuals and peripheral intellectuals.
Dissatisfied Hand Surgeons: What Causes Them to Change Jobs?
Authors: Smith Anthony A. , Craft Randall O. , Rebecca Alanna M. , Duncan Scott F. M.
Published: August 2006

Because physician turnover, especially during the first 5 years after joining a practice group, has been reported to be as high as 54%, we sought to identify and quantify the factors that lead hand surgeons to leave their practices. An eight-question practice survey was administered to 10 hand surgeons, all of whom had left their practices under various circumstances. All respondents were men (mean age, 43.2 years). Nine surgeons were in their first practice and one was in his second. Time in the practice ranged from 4 months to 6.5 years (mean time, 3.4 years). Questions about surgical practice issues were asked of all survey participants, who were then asked to quantify the influence of the issue on their decision to leave their own surgical practice with a Likert scale ranging from 1 (no influence) to 5 (greatly influenced the decision to leave). The strongest influences on the decision to leave a practice were interpersonal conflict (mean, 4.7 points) and lack of decision-making ability within the practice (mean, 4.2 points). The influence of partnership determination (mean, 3.3 points) was mixed, whereas staff support (mean, 2.9 points), salary agreements (mean, 2.4 points), employment contracts (mean, 1.6 points), and retirement benefits (mean, 1.0 points) played a lesser role in the surgeons' decisions to leave their practices.
Systolic and diastolic heart failure: Different phenotypes of the same disease?
Authors: De Keulenaer Gilles W. , Brutsaert Dirk L.
Published: August 2006

Traditional pathophysiological concepts of chronic heart failure have largely focused on the haemodynamic consequences of ventricular systolic dysfunction. How these concepts relate to the pathophysiology of diastolic heart failure, i.e., heart failure with a preserved ejection fraction is, however, unclear, causing uncertainty about pathophysiology, diagnosis and management.

Recent measurements of regional myocardial systolic function in patients with diastolic heart failure indicate that systolic and diastolic heart failure may be more closely related than previously anticipated. Rather than being considered as separate diseases with a distinct pathophysiology, systolic and diastolic heart failure may be merely different clinical presentations within a phenotypic spectrum of one and the same disease. In this review, we will interpret these new insights in a broader conceptual context of chronic heart failure and design novel paradigms in which systolic and diastolic heart failure jointly progress in a pathophysiological time trajectory of only one disease.
Thyroid pathology and the globus symptom: are they related? A two year prospective trial
Authors: Burns P , Timon C
Published: August 2006

Introduction: The globus sensation is a constant feeling of a lump in the throat and may be associated with thyroid enlargement. A two year prospective study was set up to ascertain the relationship between thyroid pathology and globus symptoms.

Materials and methods: All patients undergoing thyroid surgery over a two year period were included. Patients were questioned pre- and post-operatively. Globus symptom scores were recorded using a visual analogue scale. The size, weight and histological features of the removed specimens were correlated and statistical analysis performed.

Results: Two hundred patients were included in the study; 58 were symptomatic for globus pharyngeus pre-operatively, and 80 per cent of these patients' symptoms resolved post-operatively (p≤0.0001). Patients with histological features of inflammation showed the greatest improvement (p≤0.0001).

Conclusion: As many as one-third of patients with a thyroid mass will complain of a globus-like symptom. Patients undergoing thyroid surgery, who are symptomatic for globus pharyngeus, can expect that their symptoms will improve following surgery.
Indigenous-state relations in the UN: establishing the indigenous forum
Authors: Lindroth Marjo
Published: August 2006

The UN Permanent Forum on Indigenous Issues (PFII) was established on 31 July 2000 and held its first session at UN Headquarters in New York in May 2002. The result of decades of development, the forum signified an official opening of the UN to indigenous peoples' participation alongside that of states. This article analyses the discussions on the establishment of the PFII and the role of indigenous peoples as political actors in those discussions. A focus of particular interest is the contradiction between state sovereignty and indigenous self-determination. In examining the establishment process, the analysis draws on scholarship dealing with norms, institutions, organisation and legitimacy. The themes and frames used by indigenous peoples that are significant in state-indigenous relations and that have had an effect on the forum are indigenousness, self-determination, rights and recognition. These show how the relationship between state sovereignty and indigenous self-determination underlay the establishment discussions and their outcome. The materials for the article comprise the transcripts of the establishment negotiations, interventions of state and indigenous representatives, as well as literature on the political participation of indigenous peoples, international law and the UN system and indigenous peoples. The discussions are analysed textually. The article claims that, although the UN is a state-dominated organisation, indigenous peoples are nevertheless able to affect international cooperation. This is an INDIPO project paper (Tennberg 2006).
The International Polar Heritage Committee
Authors: Chaplin Paul
Published: August 2006

The International Polar Heritage Committee (IPHC) was formed to serve as a resource for professionals who often work in isolation on heritage protection projects in Arctic and Antarctic regions. Its credibility has now been established in a number of areas of the wider polar infrastructure and its networks continue to expand. With such an international structure it is also able to act as an independent advocate to promote polar heritage protection issues in professional, public and political arenas.
Between elderly parents and adult children: a new look at the intergenerational care provided by the ‘sandwich generation’
Authors: GRUNDY EMILY , HENRETTA JOHN C.
Published: August 2006

The ‘sandwich generation’ has been conceptualised as those mid-life adults who simultaneously raise dependent children and care for frail elderly parents. Such a combination of dependants is in fact very unusual, and the more common situation is when adults in late mid-life or early old age have one or more surviving parents and adult but still partly dependent children. It can be hypothesised that for parents in this pivotal position, the demands from adult children and from elderly parents compete, with the result that those who provide help to one are less likely to provide help to the other. An alternative hypothesis, however, is that family solidarity has an important influence but is not universal, so that some pivotal-generation parents engage in intergenerational exchange in both directions, and there is a positive association between helping parents and helping children. To investigate this question, the paper presents an analysis of data from two broadly comparable national surveys, in Great Britain and the United States, on the care provided by women aged 55–69 years to their descendent and ascendent relatives. The results show that around one-third of the women reported providing help to members of both generations, and that around one-fifth provided support to neither. They broadly support the solidarity hypothesis, but provide some evidence that having three or more children is associated with a reduced likelihood of providing help to a parent.