bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Empirical Correction Term to Density Functional Theory for the Description of the TiCl4‐Lewis Base Complexes
Authors: Cavallo Luigi , Fedele Rosalisa , Morini Giampiero , Ducéré Jean‐Marie , Melchior Andrea , Correa Andrea , Piemontesi Fabrizio , Tolazzi Marilena 
Published: January 2008

AbstractCalorimetric and computational investigation on the interaction of TiCl4 with some Lewis bases (esters and ethers) is presented. The bases were chosen for their relevance in heterogeneous Ziegler‐Natta polymerization of propene. Comparison of the theoretical data with the calorimetric data indicates that calculations consistently underestimate the experimental binding energies. In light of this consistency, we propose that an empirical correction term added to the theoretical binding energies could represent an empirical solution for the prediction of the TiCl4/donor binding energies with reasonable accuracy.
Synthesis of Titanatranes Containing Bis(aryloxo)‐(alkoxo)amines and their Use in Catalysis for Ethylene Polymerization
Authors: Padmanabhan Sudhakar , Wang Wei , Katao Shohei , Nomura Kotohiro 
Published: January 2008

AbstractSyntheses of titanatranes containing [(O‐2,4‐Me2C6H2‐6‐CH2)2‐{O(CH2)nCH2}]N3− (n = 1,2) have been explored. Catalytic activity for ethylene polymerization by Ti2(OiPr)2{[(O‐2,4‐Me2C6H2‐6‐CH2)2(µ2‐OCH2‐CH2)]N}2 (1a) ‐ MAO catalyst increased at high temperature; the activity also increased upon addition of AlMe3. Ti(O‐ 2,6‐iPr2C6H3){[(O‐2,4‐Me2C6H2‐6‐CH2)2(OCH2CH2)]N} (1c) showed higher activity than 1a under the same conditions. Ti{[(O‐2,4‐Me2C6H2‐6‐CH2)2(HOCH2CH2CH2)]N}2 was isolated from the reaction of Ti(OiPr)4 with bis(2‐hydroxy‐3,5‐dimethylbenzyl)‐propanolamine; the structure was determined by X‐ray crystallography.
A Flat Model Approach to Tethered Bis(imino)pyridyl Iron Ethylene Polymerization Catalysts
Authors: Han Wei , Niemantsverdriet Hans (J.W.) , Thune Peter C. 
Published: January 2008

AbstractA surface science model for a silica supported bis(imino)pyridyl iron complexes is applied to reveal the surface chemistry of these heterogeneous polymerization catalysts. The polymerization activity of these models and the molecular weight distribution of the resulting polymer are comparable to similar catalysts supported on amorphous silica. The catalyst deactivates partially during the first hour of ethylene polymerization. Based on photoelectron spectroscopy (XPS) we attribute this deactivation to iron extrusion by the aluminium alkyl activator.
Octahedral Complexes in the Polymerization of α‐Olefins
Authors: Aharonovich Sinai , Volkis Victoria , Eisen Moris S. 
Published: January 2008

AbstractSummary: A series of dimethyl titanium benzamidinate complexes has been prepared containing various functional groups at the aromatic ring. These functional groups were selected to study their electronic or steric effects at the cationic metal center in the polymerization of propylene. Quantitative structure activity relationship (QSAR) studies showed that a linear relationship is observed only for the Taft Parameter (Es). Mono‐ and bis‐benzamidinate complexes were found to produce similar polymers indicating that alike active species are obtained regardless of the starting complex. Deuterium labeled 2‐D‐propene showed that a new epimerization mechanism for this type of complexes is operative.
Hydrogen Effects for Propylene Polymerization with Ultra Low TiCl3 Loading MgCl2‐Supported Catalyst
Authors: Kouzai Iku , Wada Tooru , Taniike Toshiaki , Terano Minoru 
Published: January 2008

AbstractHydrogen effects for propylene polymerization were investigated with ultra low TiCl3 loading MgCl2‐supported catalysts in which the electric states of Ti species can be almost uniform. Hydrogen did not affect the catalyst activity, while the efficiency of hydrogen as a chain transfer agent was found to depend on the Ti content of the catalyst and the stereospecificity of the polymerization sites: Hydrogen was effective for isospecific sites independent of Ti contents, but inert for aspecific sites only at the extremely low Ti content. These results were explained within the island model, where isospecific sites may be located in the islands with other Ti species in their surroundings acting, as a steric hindrance for isospecific polymerization and as hydrogen dissociation sites after deactivation. Most of the aspecific sites should be isolated only at the extremely low Ti content. These isolated sites have no other Ti species in their surroundings, i.e. no hydrogen dissociation sites, and are inert to hydrogen.
Huntington's disease phenocopies are clinically and genetically heterogeneous
Authors: Wild Edward J. , Mudanohwo Ese E. , Sweeney Mary G. , Schneider Susanne A. , Beck Jon , Bhatia Kailash P. , Rossor Martin N. , Davis Mary B. , Tabrizi Sarah J. 
Published: January 2008

AbstractHuntington's disease (HD) classically presents with movement disorder, cognitive dysfunction and behavioral problems but is phenotypically variable. One percent of patients with HD‐like symptoms lack the causative mutation and are considered HD phenocopies. Genetic diseases known to cause HD phenocopies include HD‐like syndromes HDL1, HDL2, and HDL4 (SCA17). HD has phenotypic overlap with dentatorubral‐pallidoluysian atrophy, the spinocerebellar ataxias and neuroferritinopathy. Identifying the genetic basis of HD phenocopies is important for diagnosis and may inform the search for HD genetic modifiers. We sought to identify neurogenetic diagnoses in the largest reported cohort of HD phenocopy patients. Two hundred eighty‐five patients with syndromes consistent with HD, who were HD expansion‐negative, were screened for mutations in PRNP, JPH3, TBP, DRPLA, SCA1, SCA2, SCA3, FTL and FRDA. Genetic diagnoses were made in 8 subjects: we identified 5 cases of HDL4, 1 of HDL1 and 1 of HDL2. One patient had Friedreich's ataxia. There were no cases of DRPLA, SCA1, SCA2, SCA3, or neuroferritinopathy. HD phenocopies are clinically and genetically diverse and a definitive genetic diagnosis is currently possible in only a minority of cases. When undertaken, it should be clinically directed and patients and clinicians should be prepared for the low probability of reaching a genetic diagnosis in this group of patients. © 2008 Movement Disorder Society
Perceived imbalance and risk of Parkinson's disease
Authors: Gao Xiang , Chen Honglei , Schwarzschild Michael A. , Logroscino Giancarlo , Ascherio Alberto 
Published: January 2008

AbstractWe prospectively examined associations between perceived imbalance and Parkinson's disease (PD) risk in the Health Professional Follow‐up Study (HPFS), and Nurses' Health Study (NHS). We included 39,087 men and 82,299 women free of PD at baseline (1990) in the current analyses. We documented 449 incident PD cases during 12 years follow‐up. Subjects who reported difficulty with balance before 1990 (baseline) were 1.8 more times likely to develop PD, relative to those who reported no balance difficulty (pooled multivariate RR = 1.8; 95% CI: 1.3, 2.5; P < 0.0001). When we further examined associations between perceived imbalance at baseline and PD onset during different time periods, we found a significant elevation of PD risk only during the first 4 years of follow‐up. This result suggests that the imbalance may in some cases be an early sign of PD, and may represent the onset of motor symptoms although they have not been clinically recognized. © 2008 Movement Disorder Society
Domain decomposition preconditioners for elliptic equations with jump coefficients
Authors: Zhu Yunrong 
Published: January 2008

AbstractThis paper provides a proof of the robustness of the overlapping domain decomposition preconditioners for the linear finite element approximation of second‐order elliptic boundary value problems with strongly discontinuous coefficients. By analyzing the eigenvalue distribution of the domain decomposition preconditioned system, we prove that only a small number of eigenvalues may deteriorate with respect to the discontinuous jump or mesh size, and all the other eigenvalues are bounded below and above nearly uniformly with respect to the jump and mesh size. As a result, we prove that the convergence rate of the preconditioned conjugate gradient methods is nearly uniform with respect to the large jump and mesh size. Copyright © 2008 John Wiley & Sons, Ltd.
Plasma oscillations in nanotransistors for room temperature detection and emission of terahertz radiation
Authors: El Fatimy A. , Tauk R. , Boubanga S. , Teppe F. , Dyakonova N. , Knap W. , Lyonnet J. , Meziani Y. M. , Otsuji T. , Poisson M.‐A. , Morvan E. , Bollaert S. , Shchepetov A. , Roelens Y. , Gaquiere Ch. , Theron D. , Cappy A. 
Published: January 2008

AbstractIn this work we present experimental results on room temperature terahertz (THz) detection/emission from nanotransistors as well as double grating gates structures. It shows that the emission spectra from GaN/AlGaN HEMT transistor can be successfully interpreted in the frame of the Dyakonov‐Shur model which predicts that by heating/accelerating the electrons up to velocities comparable with plasma wave velocity can lead to instability and generation of plasma waves in the transistor channel. Studies of the current dependence of THz detection by InGaAs based HEMT is also presented. It is shown that in realistic transistor structures the room temperature resonant THz detection can be observed only upon applying a current high enough to produce fast/hot electrons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The correlation effect of carrierinduced magnetic solitons in diluted magnetic semiconductors
Authors: Kanazawa I. 
Published: January 2008

AbstractWe have discussed the localization mechanism in the transport property in the random potentials due to the alloy potential fluctuations in diluted magnetic semiconductors, taking into account the long‐range interactions among magnetic solitons, by using the effective Lagrangian of diffusion modes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of easy magnetization axis orientation on magnetization reversal in permalloy strips
Authors: Kim Dong Ho , Hwang Tae‐Jong , Ryu Kwang‐Su , Shin Sung‐Chul 
Published: January 2008

AbstractWe studied the effect of easy magnetization axis orientation with respect to the strip direction on magnetization reversal process in permalloy strips by measuring the magnetoresistance (MR), the magneto‐optic Kerr effect (MOKE), and the real‐time domain evolution. The three strips were patterned on a single chip with the easy‐axis orientation of each strip relative to the longitudinal direction by around 0, 30, and 60°, respectively. The overall shape of field‐dependent MR was mostly governed by the anisotropic magnetoresistance. The longitudinal MR ratio was significantly increased with increasing angle between the easy axis and the bar direction. Several MR steps were observed during the magnetization reversal in 0 and 30° bars, and the simultaneous measurement of the MOKE and the domain images identified that the MR steps were associated with evolution of the magnetic domains. In addition a resistance contribution from the domain walls was also observed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ring signatures for benzenoids with up to seven rings, Part 1: Catacondensed systems
Authors: Randić Milan , Balaban Alexandru T. 
Published: January 2008

AbstractWe revisited the π‐electron ring partitions in catacondensed benzenoids and re‐examined structural regularities reported for the ring partitions in these compounds, seeking the origin of the observed regularities. We examined the distribution of the π‐electron ring partitions by counting the contributions arising from benzene rings having different assigned numbers of π‐electrons. This has led to a better insight into the underlying structure of the π‐electron ring partitions and also to a novel and unique π‐electron “signature” of individual rings in benzenoid hydrocarbons. The physical interpretation of the local π‐electron ring partition represents the local π‐electron density of benzenoid molecules, and is not an alternative index of local aromaticity as one may erroneously assume. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Plasma chemical reactions of thin nickel films
Authors: Quaas M. , Wulff H. , Ivanova O. , Helm C. A. 
Published: January 2008

AbstractNickel clusters of about 20 nm in diameter were treated in a microwave plasma (SLAN, 2.45 GHz) using different gas compositions. The Ni films were exposed to argon/oxygen and argon/hydrogen plasma to study oxidation and reductions reactions, especially the oxidation kinetics. The films were investigated by grazing incidence X‐ray diffractometry (GIXD) to control the phase formation. Thickness and density were determined by X‐ray reflectometry (XR); sample topology was studied by atomic force microscopy (AFM). A combination of these techniques allowed a detailed analysis of the plasma chemical processes.Oxygen plasma treatment results in the formation of NiO on the Ni particles. The effect of hydrogen plasma depends on the used negative substrate voltage. Metallic Ni is formed without an external voltage. The oxidation kinetics can be described using the ‘shrinking core’ model. The oxide formation rate depends on the sample history, i.e. on the number of oxidation/reduction cycles carried out. While the first oxidation process is clearly found to be diffusion controlled, the kinetics of the subsequent cycles is obviously more reaction controlled. Copyright © 2008 John Wiley & Sons, Ltd.
Tribological testing and optimisation of electroless Ni‐P coatings based on Taguchi method and grey relational analysis
Authors: Sahoo Prasanta , Pal Sujan Kumar 
Published: January 2008

AbstractThis paper presents an experimental study of tribological characteristics of electroless Ni‐P (EN) coatings and optimisation of coating process parameters based on Taguchi method coupled with grey relational analysis. A grey relational grade obtained from the grey relational analysis is used as performance index to study the deposition of EN coating with multiple tribological performance characteristics. Experiments are carried out by utilising the combination of process parameters based on L27 Taguchi orthogonal design with four process parameters, namely, bath temperature, concentration of nickel source solution, concentration of reducing agent and annealing temperature. It has been observed that concentrations of nickel source solution and bath temperature are the most significant parameters for controlling the friction and wear behaviour of EN coating. The surface morphology, composition and wear mechanism of coatings are also studied with the help of scanning electron microscopy, energy dispersed X‐ray analysis and X‐ray diffraction analysis. Copyright © 2008 John Wiley & Sons, Ltd.
iPTT: peer‐to‐peer push‐to‐talk for VoIP
Authors: Lin Jiun‐Ren , Pang Ai‐Chun , Wang Yung‐Chi 
Published: January 2008

AbstractThis paper proposes iPTT, a peer‐to‐peer (P2P) Push‐to‐Talk (PTT) service for Voice over IP (VoIP). In iPTT, a distributed and mobile‐operator independent network architecture is presented to accelerate the deployment of the PTT service. Based on the serverless architecture, we develop two mechanisms, that is, flooding‐based floor control mechanism (FFC) and tree‐based floor control mechanism (TFC), for real‐time talk‐burst determination. The determination algorithms and the corresponding message flows for these two mechanisms are designed to show the feasibility of FFC and TFC. The performance of FFC and TFC is investigated through our analytical and simulation models in terms of the determination latency and the number of floor‐control message exchanges. Copyright © 2008 John Wiley & Sons, Ltd.
HAWT near‐wake aerodynamics, Part I: axial flow conditions
Authors: Haans Wouter , Sant Tonio , van Kuik Gijs , van Bussel Gerard 
Published: January 2008

AbstractAn improved physical understanding of the rotor aerodynamics of a horizontal axis wind turbine (HAWT) is required to reduce the uncertainties associated with today's design codes. Wind tunnel experiments contribute to increased knowledge and enable validation and construction of models. The present study focuses on the near‐wake of a model HAWT in both axial and yawed flow conditions. At three downstream planes parallel to the rotor plane, single‐sensor hot‐film traverses are made. The phase‐locked unsteady three‐dimensional flow velocity vector is determined by a novel data reduction method. A series of two papers discusses the near‐wake aerodynamics of a model HAWT. The main goals are to obtain a detailed understanding of the near‐wake development and to arrive at a base for model construction and validation. The first paper presents the experimental setup, data reduction and the results for the baseline case (axial flow conditions). In the second paper, the results for the yawed flow cases are presented and the effect of yaw misalignment on the near‐wake development is discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Graph transformations for object-oriented refinement
Authors: Zhao Liang , Liu Xiaojian , Liu Zhiming , Qiu Zongyan 
Published: January 2008

Abstract

An object-oriented program consists of a section of
class declarations
and a
main method
. The class declaration section represents the structure of an object-oriented program, that is the data, the classes and relations among them. The execution of the main method realizes the application by invoking methods of objects of the classes defined in the class declarations. Class declarations define the general properties of objects and how they collaborate with each other in realizing the application task programmed as the main method. Note that for one class declaration section, different main methods can be programmed for different applications, and this is an important feature of reuse in object-oriented programming. On the other hand, different class declaration sections may support the same applications, but these different class declaration sections can make significant difference with regards to understanding, reuse and maintainability of the applications. With a UML-like modeling language, the class declaration section of a program is represented as a
class diagram
, and the instances of the class diagram are represented by
object diagrams
, that form the
state space
of the program. In this paper, we define a class diagram and its object diagrams as
directed labeled graphs
, and investigate what changes in the class structure maintain the capability of providing
functionalities
(or
services
). We formalize such a structure change by the notion of
structure refinement
. A structure refinement is a transformation from one graph to another that preserves the
capability
of providing services, that is, the resulting class graph should be able to provide at least as many, and as good, services (in terms of functional refinement) as the original graph. We then develop a
calculus of object-oriented refinement
, as an extension to the classical
theory of data refinement
, in which the refinement rules are classified into four categories according to their natures and uses in object-oriented software design. The soundness of the calculus is proved and the completeness of the refinement rules of each category is established with regard to normal forms defined for object-oriented programs. These completeness results show the power of the simple refinement rules. The normal forms and the completeness results together capture the essence of polymorphism, dynamic method binding and object sharing by references in object-oriented computation.
Pulmonary artery hypertension in a child with MELAS due to a point mutation of the mitochondrial tRNA(Leu) gene (m.3243A>G)
Authors: Sproule D. M. , Dyme J. , Coku J. , de Vinck D. , Rosenzweig E. , Chung W. K. , De Vivo D. C. 
Published: January 2008

SummaryAlthough linked with cardiac dysfunction, the association of MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke‐like episodes) and pulmonary artery hypertension (PAH) has not been previously described. PAH and right ventricular heart failure were identified by echocardiography in a 3‐year‐old boy with a history of hypotonia, microcephaly and developmental delay. He initially presented with a 10‐day history of dyspnoea, dependent oedema and reduced oral intake. Lactic acidosis was noted on serial arterial blood sampling and cerebrospinal fluid. Muscle biopsy demonstrated cytochrome‐c oxidase‐positive ‘ragged‐red’ fibres consistent with MELAS; subsequent analyses revealed the m.3243A>G point mutation most commonly associated with MELAS. The mutation was heteroplasmic, representing 92% of the total mtDNA from a lung sample. Nitric oxide and epoprostenol were administered without significant clinical or echocardiographic improvement of his PAH. A ‘mitochondrial cocktail’ including biotin, riboflavin, carnitine and coenzyme Q10 also was provided. Five months after presentation, he developed seizures; MRI imaging of his brain demonstrated multiple focal lesions. His clinical status worsened with increasing cardiopulmonary failure. He died two months later. Although therapy for both MELAS and PAH remains limited, recent investigations suggest a beneficial role for l‐arginine in both conditions, implying a possible common pathophysiology. Mitochondrial diseases such as MELAS should be considered in cases of idiopathic PAH, particularly when associated with multisystem involvement including short stature, hearing loss, renal dysfunction, retinopathy, diabetes mellitus, migraines, seizures, ophthalmoplegia, fatigability and weakness.
Amnionless (AMN) mutations in Imerslund–Gräsbeck syndrome may be associated with disturbed vitamin B12 transport into the CNS
Authors: Luder A. S. , Tanner S. M. , de la Chapelle A. , Walter J. H. 
Published: January 2008

SummaryFamilial selective vitamin B12 (cobalamin, Cbl) malabsorption (Imerslund–Gräsbeck syndrome, IGS, OMIM 261100) is a group of autosomal recessive disorders characterized by selective malabsorption of Cbl from the terminal ileum in the presence of normal histology. Mutations in the amnionless (AMN) and cubilin (CUBN) genes are known to be causes of IGS. Their gene products combine to form a receptor complex (cubam), which is instrumental in the binding and transport of Cbl in the gut. As opposed to Cbl transport in the terminal ileum, normal transport of Cbl into the CNS is poorly understood and little is known regarding its molecular basis. Studies in adults with neuropsychiatric disease have suggested the presence of an active transport mechanism into the central nervous system constituting a blood–brain barrier (BBB) for Cbl. A child with IGS, compound heterozygous for a missense and a nonsense mutation in the amnionless (AMN) protein gene, was noted to have a high daily cobalamin (Cbl) requirement for neuropsychiatric, but not for systemic metabolic and haematological, remission. Measurements of CSF Cbl revealed evidence that the transport of Cbl into the central nervous system was impaired, and a standard Schilling test was consistent with a dose response of cobalamin transport across the terminal ileum. Amnionless protein is known to be expressed in the fetal and postnatal central nervous system, and is known to be involved in Cbl transport in other tissues such as kidney as well as the gut. It is possible that an active Cbl transport mechanism at the BBB exists, and that the amnionless (AMN) protein may be part of this mechanism, as it is in cobalamin transport in the terminal ileum.