bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical Approach to Mechanosensation of Bone Tissue based on a Micromechanical Analysis of a Single Osteon
Authors: Lenz Christian , Nackenhorst Udo
Published: December 2004

The subject of this work is to study the mechanosensation of bone tissue using a numerical approach. Therefore a finite element analysis of a single osteon was carried out. The calculated strains at the lacuna leads to a deeper insight into the mechanical conditions the osteocytes are exposed to. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An H‐matrix Type Preconditioner For Frictional Contact Problems
Authors: Abdelhakim Lotfi
Published: December 2004

The bilateral or unilateral contact problem with Coulomb friction between two elastic bodies is considered [1]. An algorithm is introduced to solve the resulting finite element system by a non‐overlapping domain decomposition method [2, 3]. The global problem is transformed to a independant local problems posed in each bodie and a problem posed on the contact surface (the interface problem). The solution is obtained by using a successive approximation method, in each step of this algorithm we solve two intermediate problems the first with prescribed tangential pressure and the second with prescribed normal pressure [8]. Our preconditioner construction is based on the application of the H‐matrix technique [6, 7] together with the representation of the H1/2 seminorm by a sum of partial seminorms [4]. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient finite element formulation based on the strong discontinuity approach for the modeling of material failure
Authors: Mosler J. , Bruhns O. T.
Published: December 2004

A new finite element formulation based on the strong discontinuity approach is proposed. Following [1], localized inelastic deformations are represented as surfaces of discontinuous displacements within the respective finite element by applying the Enhanced Assumed Strain (EAS) concept. However, and in contrast to previous publications, the jump part of the displacement field is not condensed out at the element level by employing static condensation. Instead, the L2‐orthogonality condition is reformulated resulting in an equation which is formally identical to the necessary condition of yielding known from standard plasticity theory. Hence, it is possible to apply the return‐mapping algorithm to the numerical implementation. Only slight modifications of this by now classical algorithm are necessary. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Mixed Finite Element Method for Fourth Order Eigenvalue Problems
Authors: Nataraj Neela
Published: December 2004

A new mixed finite element method for approximating eigenpairs of IV order elliptic eigenvalue problems with Dirichlet boundary conditions has been given. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fast Numerical Simulation of 3D Steady‐State Hot Rolling Processes by Utilizing Diffpack and Deform
Authors: Obereder Andreas , Kainz Alexander
Published: December 2004

In hot rolling of steel a precise determination of strip spread, lateral flow, profile and flatness can be considered as key points to produce top quality strips satisfying the most demanding tolerances. Typical 3D‐effects like broadening and relative strip profile changes can only be predicted precisely by 3D‐numerical simulations. Commercial finite element packages, however, are very time consuming, especially when based on (updated) Lagrangian concepts and one is merely interested in the stationary process behaviour. Therefore, a fast quasi‐stationary description in Eulerian coordinates with deformationupdates via the streamline technique was developed and implemented numerically [1, 6]. The underlying rigid‐viscoplastic constitutive law for the strip or slab was implemented according to a non‐linear Newtonian fluid [2]. The solution of the free boundary value or contact problem including friction leads to a non‐linear variational inequality (cf. [3, 6]), which is solved iteratively in Eulerian coordinates. The self‐developed simulation code (written in C++, cf. [4]) can handle non‐linear plastic materials, contact and friction between the deformed work roll and the slab, including also grid adaptations. In this report simulation results for both edger and flat passes are presented. These results were calibrated with real mill process data and also validated against the commercial software package DEFORM [5] and yields satisfactory correspondence [6, 7]. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the simulation of a moving discontinuity by boundary element methods
Authors: Oberste‐Brandenburg Claus , Jovanović Lidija
Published: December 2004

The movement of a discontinuity in a continuum can usually be expressed in terms of the state in its direct vicinity. Thus, the knowledge of the local state around the discontinuity is vitally important in order to adequately describe its movement. Numerical schemes local to the discontinuity, as e.g. moving finite element methods, are appropriate approaches to describe its motion. However, for a large number of problems, the local state not only depends on measures of the discontinuity plane itself but also on measures related to the bulk behavior of the material, such as temperature or stress. For a complete description, the bulk behavior of the material has to be numerically modeled as well. In this contribution, the interface and its propagation is modeled explicitly by a two‐dimensional discretization of the interface. The same discretization is utilized to describe the behavior of the bulk material employing the boundary element method. As an example, the movement of a phase transition front in a single crystal is presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison between the material point method and the finite element method in view of extrusion problems
Authors: Schilling O. , Reese S.
Published: December 2004

An appropriate method for the simulation of continuous forming processes is the material point method (MPM) [1],[2] which combines the viewpoints of fluid dynamics and solid mechanics. The MPM and related methods [3] are derived from the particle‐in‐cell methods [4]. Bodies are discretised by Lagragian particles with pointwise mass distributions. The differential equations in their weak form are solved on temporary meshes built of standard finite elements. At the end of each time step the particle positions are updated and the mesh is replaced by a new mesh with a regular shape. The state variables at the nodes of the new mesh are extracted from the state variables at the particles by a transfer algorithm. When particles pass element boundaries, numerical difficulties might be observed. These are eliminated by a smooth approximation of nodal data from material point data. The modified MPM has been implemented together with the FEM in one programme because the similarities of the methods outbalance the differences. On the basis of numerical examples the results of both methods are compared. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New approach in Stochastic Finite Element Method
Authors: Sniady P. , Zielichowski‐Haber W.
Published: December 2004

In the paper, the new methodology for Stochastic Finite Element Method (SFEM) as the means to analyze structure in the probabilistic framework is presented. The concept of random influence vector is introduced and used to develop the universal formulas in the framework of SFEM that can work effectively for a wide variety of random loads. Furthermore, the derived formulas enable to separate the structural uncertain properties from random parameters of load resulting in the hybrid formulation of SFEM and to analyze the structure in probabilistic framework subject to any stochastic space load. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contour integration and “mixed–variables–technique” applied to an infinite plate on the halfspace
Authors: Trinks Carolin , Ruge Peter
Published: December 2004

An infinite plate on the halfspace is treated as a typical soil–structure interaction problem. Based on an analytical solution in the wavenumber– and frequency domain the dynamic flexibility is obtained using contour integration. The force–displacement relationship is transformed into the time domain by means of a rational approximation technique and the fractional calculus. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Weakly coupled analysis of a blade in multiphase mixing vessel
Authors: Vesenjak Matej , Ren Zoran , Hriberšek Matjaž
Published: December 2004

Two or more physical systems frequently interact with each other, where the independent solution of one system is impossible without a simultaneous solution of the others. An obvious coupled system is that of a dynamic fluid‐structure interaction. [8] In this paper a computational analysis of the fluid‐structure interaction in a mixing vessel is presented. In mixing vessels the fluid can have a significant influence on the deformation of blades during mixing, depending on speed of mixing blades and fluid viscosity. For this purpose a computational weakly coupled analysis has been performed to determine the multiphase fluid influences on the mixing vessel structure. The multiphase fluid field in the mixing vessel was first analyzed with the computational fluid dynamics (CFD) code CFX. The results in the form of pressure were then applied to the blade model, which was the analysed with the structural code MSC.visualNastran forWindows, which is based on the finite element method (FEM). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FE‐formulation for plate and beam elements to simulate onset and propagation of discrete cracks in solid structures
Authors: Wackerfuß Jens , Gruttmann Friedrich
Published: December 2004

The aim of this paper is to present some numerical aspects related to the modeling both the formation and the propagation of discrete cracks in solid structures. The presented formulation corresponds to the concept of embedded discontinuities [1], and will be applied to a plate and to a beam element.

The failure of solid structures is often triggered by a highly localized pattern of inelastic deformation in the form of narrow bands. Characteristic examples are shear bands in metals and soils, or localized bands of cracking in brittle materials, like concrete or rocks. A well known difficulty associated with classical (local, rate‐independent) continuum theories with strain softening attributes is that numerical solutions are found to lack invariance with respect to the choice of spatial discretization. For quasi‐static boundary problems, this mathematical inconsistency causes the loss of ellipticity for the governing equations (material instability). To regularize this inconsistency, several strategies have been applied. In the presented formulation, additional degrees of freedom are considered. Within the concept of embedded discontinuities, the regular displacements are enriched by discontinuities. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of Yield‐line Geometries for Arbitrary Simply Supported Slabs
Authors: Wüst Jochen
Published: December 2004

The calculation of limit loads of slabs using the yield‐line theory requires the assumption of a kinematical collapse mechanism. In recent years several approaches concerning the optimization of predefined mechanisms have been introduced. Usually they contain semi‐automatic procedures which depend on user‐defined yield‐line predictions. This paper presents a systematic approach and a numerical procedure to find yield‐line predictions for arbitrary all‐side supported slabs. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Advanced Shell Element Formulations for Coupled Electromechanical Systems
Authors: Yang Fan , Lammering Rolf , Mesecke‐Rischmann Simone
Published: December 2004

With the significantly increasing applications of smart structures, piezoelectric material is widely used in branches of engineering sciences. Normally, the Finite Element Method is employed in the numerical analysis of these structures [2]. In this contribution, in order to avoid the locking effects and zero energy modes, the Assumed Natural Strain (ANS) Method [4] is implemented into four‐node piezoelectric shallow shell elements, by using the two‐field variational formulation in which displacements and electric potentials serve as independent variables and the three‐field variational formulation in which the dielectric displacement is taken as an independent variable additionally [3]. Moreover, a quadratic variation of the electric potential through the thickness direction is applied in the two‐field formulation. Numerical examples of piezoelectric sensors and actuators are presented, showing the behaviour of the shell elements by using different hybrid finite element formulations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ethylene polymerization with iron‐based diimine catalyst supported on MCM‐41
Authors: Zhang Mingge , Xu Hong , Guo Cunyue , Ma Zhi , Dong Jinxiang , Ke Yucai , Hu Youliang
Published: December 2004

A mesoporous molecular sieve MCM‐41 supported iron‐based diimine catalyst (MC) was prepared for the first time. The kinetic behavior of ethylene polymerization with MC was studied. The effects of Al/Fe molar ratio and various cocatalysts on the catalytic activity and properties of the polyethylene obtained were investigated. The results showed that good catalytic activities can be reached with cocatalyst methylaluminoxane (MAO) and triethylaluminium (TEA). Ethylene polymerization with MC gave polymers with higher molecular weight, melting temperature and onset temperatures of decomposition (Tonset) and better morphology than those obtained with the corresponding homogeneous catalyst. Copyright © 2004 Society of Chemical Industry
Further studies on styrene/styrene derivative copolymerizations using combined diphenylzinc‐additive initiator systems
Authors: Rabagliati Franco M , Pérez Mónica A , Rodríguez Francisco J , Caro Carlos J , Crispel Nicolás
Published: December 2004

A combination of diphenylzinc, a metallocene and methylaluminoxane (Ph2Zn‐metallocene‐MAO) is a suitable initiator system for the polymerization of styrene and for its copolymerization with para‐alkyl substituted styrenes. This paper reports new experimental results which reinforce our previous findings indicating that polymerization processes are initiated by monomer coordination to active species resulting from these particular combined systems. Polymerization propagates by a cationic pathway. Further to our previous observation that the I+ inductive effect of para‐substituents in styrene improves conversion to polymer, we now find that methyl substitution on the vinyl double bond of styrene, in spite of the I+ inductive effect and as a result of increased steric hindrance, makes the polymerization process difficult. On the other hand, the replacement of titanocenes by zirconocenes or hafnocenes generates Ph2Zn‐metallocene‐MAO initiator systems which are also able to induce homo‐ and copolymerization, but with lower yields and producing practically amorphous polymers. The efficiency of our Ph2Zn‐metallocene‐MAO initiator systems follows the order titanocene > zirconocene > hafnocene, at least for the studied metallocenes. Copyright © 2004 Society of Chemical Industry
In situ polymerization of ethylene with bis(imino)pyridine iron(II) catalysts supported on clay: The synthesis and characterization of polyethylene–clay nanocomposites
Authors: Ray Saptarshi , Galgali Girish , Lele Ashish , Sivaram S.
Published: December 2004

Polyethylene–clay nanocomposites were synthesized by in situ polymerization with 2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl] pyridine iron(II) dichloride supported on a modified montmorillonite clay pretreated with methylaluminoxane (MAO). The catalysts and the obtained nanocomposites were examined with wide‐angle X‐ray scattering. The exfoliation of the clay was further established by transmission electron microscopy. Upon the treatment of the clay with MAO, there was an increase in the d‐spacing of the clay galleries. No further increase in the d‐spacing of the galleries was observed with the iron catalyst supported on the MAO‐treated clay. The catalyst activity for ethylene polymerization was independent of the Al/Fe ratio. The exfoliation of the clay inside the polymer matrix depended on various parameters, such as the clay content, catalyst content, and Al/Fe ratio. The crystallinity percentage and crystallite size of the nanocomposites were affected by the degree of exfoliation of the clay. Moreover, when ethylene was polymerized with a mixture of the homogeneous iron(II) catalyst and clay, the degree of exfoliation was significantly lower than when the polymerization was performed with a preformed clay‐supported catalyst. This observation suggested that in the supported catalyst, at least some of the active centers resided within the galleries of the clay. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 304–318, 2005
Arenesulfonyl bromides: The second universal class of functional initiators for the metal‐catalyzed living radical polymerization of methacrylates, acrylates, and styrenes
Authors: Grigoras Cristian , Percec Virgil
Published: December 2004

The metal‐catalyzed living radical polymerization of methyl methacrylate,n‐butyl acrylate, and styrene, initiated withp‐toluenesulfonyl bromide and phenoxybenzene‐4,4′‐disulfonyl bromide and catalyzed with CuBr/2,2′‐bipyridine (bpy) and various self‐regulated Cu‐based catalytic systems such as Cu2O/bpy, Cu2S/bpy, Cu2Se/bpy, and Cu2Te/bpy, is reported. Similarities and differences between the arenesulfonyl chloride and arenesulfonyl bromide initiators are discussed. The arenesulfonyl bromide initiators require reduced reaction times to produce polymers in high conversions under milder reaction conditions than the corresponding arenesulfonyl chloride initiators. At the same time, they exhibit 100% initiator efficiency and generate polymers with narrow molecular weight distributions and functional chain ends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 319–330, 2005
Synthesis and properties of silica/polystyrene/polyaniline conductive composite particles
Authors: Lee Chia‐Fen , Tsai Hung‐Hsin , Wang Lee‐Yih , Chen Chia‐Fu , Chiu Wen‐Yen
Published: December 2004

In this study, silica/polystyrene/polyaniline (SiO2/PS/PANI) conductive composite particles were synthesized by four sequential reactions. The nanosized SiO2 particles were synthesized from tetraethoxysilane (TEOS) by a sol–gel process with water as the solvent medium, followed by a surface modification with triethoxyvinylsilane; then the surface modified SiO2 particles were used as seeds to synthesize SiO2/PS composite particles with soapless seeded emulsion polymerization. Finally, the SiO2/PS particles were used as seeds to synthesize the SiO2/PS/PANI conductive composite particles. The sol–gel process of SiO2, the effect of surface modification, and several other factors that influenced polymerization of styrene in the soapless seeded emulsion polymerization will be discussed. Either potassium persulfate (KPS) or 2,2′‐azobis(isobutyramidine) dihydrochloride (AIBA) was used as the initiator to synthesize the uniform SiO2/PS particles successfully, and the cross‐section morphology of the SiO2/PS particles was found to be of a core–shell structure, with SiO2 as the core, and PS as the shell. The SiO2/PS particles were well dispersed in many organic solvents. In the following step to synthesize SiO2/PS/PANI conductive composite particles, sodium dodecyl sulfate (SDS) played an important role, specifically, to absorb aniline onto the surfaces of the SiO2/PS particles to carry out the polymerization of aniline over the entire surface of the particles. The conductivity of the SiO2/PS/PANI composite particles approached that of semiconductive materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 342–354, 2005
Peeling of polydimethylsiloxane adhesives at low velocities: Cohesive failure
Authors: Piau J.‐M. , Ravilly G. , Verdier C.
Published: December 2004

This work presents results obtained in 90‐degree peeling tests at low velocities in the case of Newtonian adhesives, when failure is cohesive. Peeling experiments are described and consider the influence of the thickness, viscosity, and surface tension of the adhesive, as well as the backing rigidity. A simple model, based on lubrication effects in thin films, is considered and compared with the measurements, when peeling is a two‐dimensional phenomenon. Furthermore, a criterion for predicting the transition between the two‐dimensional regime and the three‐dimensional regime at higher velocities is proposed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 145–157, 2005
The study of the phase diagram and internal energy of the mixed spin‐3/2 and spin‐5/2 ferrimagnetic Ising system with interlayer coupling by effective‐field theory; a simple approach of calculating internal energy
Authors: Zhang Qi , Wei Guozhu , Gu Yongwei
Published: December 2004

Phase diagrams and internal energies of a layered Ising system were studied using the effective‐field theory (EFT) with correlations. The results show that the critical temperature becomes larger, while the compensation temperature and the internal energy become smaller with the increase in the interlayer coupling and the crystal‐field. The traditional method to calculate the internal energy of the Ising system by the EFT is based on a differential of its differential operator identity. So an additional differential procedure must be carried out when calculating the internal energy. In this paper, a new function on which the differential operator acts is introduced to solve this problem, without performing the additional differential procedure. The results obtained by the two methods are exactly the same. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dislocation mechanism of quantum dot formation in heteroepitaxial structures
Authors: Vengrenovich R. D. , Gudyma Yu. V. , Yarema S. V.
Published: December 2004

Quantum dot formation during heteroepitaxial growth of 3D islands in Stranski–Krastanow mode is described. The island size distribution function is shown to become narrower, and the dispersion decreases markedly for dislocation growth mechanism with subsequent separation of dislocations from the island base. Probable reasons for slowing down of Ostwald ripening are also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polaron effect on the binding energy of hydrogenic impurities in a cylindrical quantum dot
Authors: Wang Rui‐Qiang , Xie Hong‐Jing , Yu You‐Bin
Published: December 2004

The binding energy of a shallow hydrogenic impurity in a cylindrical quantum dot (QD) is investigated by using a variational method, where a two‐parameter trial wave function is introduced to consider the anisotropic nature of the QD system. We have taken into consideration the influence of the confined longitudinal optical (LO) phonons as well as the side‐surface (SSO) and top‐surface (TSO) optical phonons. Our calculations are performed within the effective‐mass approximation for an infinitely deep confinement potential system model. Numerical calculation shows that the binding energy of an impurity is greatly modified by the electron–phonon interactions and the phonon contribution to the impurity binding energy is dependent on the QD sizes (radius and height). It is noted that we obtain about a 4% higher impurity binding energy than that based on a one‐parameter trial wave function. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photon echo studies of biexcitons and coherences in colloidal CdSe quantum dots
Authors: Colonna Anne E. , Yang Xiujuan , Scholes Gregory D.
Published: December 2004

Nonlinear optical properties of colloidal quantum dots are studied to elucidate the significance and nature of many‐body effects. Two‐pulse photon echo studies of nanocrystalline CdSe quantum dots are reported for samples dispersed in a poly(butylmethacrylate) film (4.4 K). Oscillations are observed in the experimental data that are attributed to 1S3/21Se–2S3/21Se biexciton cohererences. Signals are simulated using a phenomenological model based on the many‐body description of the dynamics (the average polarization model). It is found that the electronic coherences and the nonlinear response originating from biexciton source terms are important, but their manifestation in the photon echo signals is strongly influenced by the interplay between homogeneous and inhomogeneous line broadening. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comment on “Orbital ordering and orbital fluctuations in transition metal oxides” [phys. stat. sol. (b) 236, No. 2, 281–288 (2003)]
Authors: Radwanski R. J. , Ropka Z.
Published: December 2004

We argue that the 3A2 state considered by Oleś in phys. stat. sol. (b) 236, 281 (2003) for the d2 system occurring in the V3+ ion in V2O3 and LaVO3 as well as in the Ti2+ ion in TiO and in many other oxides is wrong. The proper ground state is 3T1g – its 9‐fold degeneracy is further split in a crystal by intra‐atomic spin–orbit interactions and lattice distortions. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scaling behavior of ground‐state energy cluster expansion for linear polyenes
Authors: Griffin L. L. , Wu Jian , Klein D. J. , Schmalz T. G. , Bytautas L.
Published: December 2004

Ground‐state energies for linear‐chain polyenes are additively expanded in a sequence of terms for chemically relevant conjugated substructures of increasing size. The asymptotic behavior of the large‐substructure limit (i.e., high‐polymer limit) is investigated as a means of characterizing the rapidity of convergence and consequent utility of this energy cluster expansion. Consideration is directed to computations via: simple Hückel theory, a refined Hückel scheme with geometry optimization, restricted Hartree–Fock self‐consistent field (RHF‐SCF) solutions of fixed bond‐length Parisier–Parr–Pople (PPP)/Hubbard models, and ab initio SCF approaches with and without geometry optimization. The cluster expansion in what might be described as the more “refined” approaches appears to lead to qualitatively more rapid convergence: exponentially fast as opposed to an inverse power at the simple Hückel or SCF–Hubbard levels. The substructural energy cluster expansion then seems to merit special attention. Its possible utility in making accurate extrapolations from finite systems to extended polymers is noted. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Effect of hindered piperidine light stabilizer molecular structure and UV absorber addition on the oxidation of HDPE. Part 2: Mechanistic aspects—molecular modeling and electron spin resonance spectroscopy study
Authors: Liauw Christopher M. , Quadir Angela , Allen Norman S. , Edge Michele , Wagner Alan
Published: December 2004

The first in this series of papers explored the effect of the structural characteristics of 2,2,6,6‐tetramethylpiperidine‐based hindered amine light stabilizers (HALS) on the thermal and photostabilization of high‐density polyethylene. In the second part, the energies (stabilities) of the nitroxyl radicals and various intermediate species have been predicted using AccuModel® and related to stabilization performance and electron spin resonance (ESR) spectral data. Nitroxyl radicals with low predicted stability generally afforded improved thermal and photostabilization. ESR spectra were used to obtain values of nitroxyl radical concentration ([>NO·]) and g‐factor as a function of pre‐aging time for combinations of pre‐aged HDPE and >NH HALS. Demethylation reactions of > N‐methyl HALS resulted in uselessly weak ESR spectra. The HALS that afforded poor thermal oxidative stabilization gave rise to pronounced minima in [>NO·] that coincided with a maximum in hydroperoxide concentration. The g‐factor values indicated that a predominant nitroxyl canonical form generally promoted superior thermal oxidative stabilization, whereas a predominance of the dipolar N·+O− form promoted superior photo‐oxidative stabilization. These trends may be related to greater radical‐scavenging and peroxide‐trapping effects, respectively. Molecular modeling and ESR spectra can therefore provide valuable insight into the effectiveness of HALS and stabilization mechanisms. J. Vinyl Addit. Technol. 10:159–167, 2004. © 2004 Society of Plastics Engineers.
Pathoarchitectonic pattern of iso‐ and allocortical lesions in juvenile and adult neuronal ceroid‐lipofuscinosis
Authors: Braak H. , Braak E.
Published: December 2004

Conclusion

Juvenile and adult forms of NCL reveal a pronounced and specific involvement of nerve cells generating isocortico‐isocortical projections and isocortico‐entorhinal connections. They also show a specific destruction of the nerve cells generating the perforant path. Additional changes are seen in a deep entorhinal layer receiving a feedback projection from the hippocampus. Within the hippocampal formation, the CA4/CA3 projection cells necessary for intrahippocampal processing of the data are markedly changed. This lesion pattern leads to a partial or complete interruption of the flow of information from the isocortex to the hippocampal formation. It is assumed that the pathoarchitectonic pattern contributes to the development of personality changes and cognitive impairment, both frequently seen even in early stages of NCL.
Linkage analysis of late‐infantile neuronal ceroid‐lipofuscinosis (CLN2) using markers on chromosome 16p
Authors: Williams R. , Mitchison H. , McKay T. , Järvelä I. , Gardiner R. M.
Published: December 2004

Conclusion

These results provide further evidence of non‐allelic genetic heterogeneity within the disorders grouped together as the neuronal ceroid‐lipofuscinoses. There are at least three mutations at different loci involved in the pathogenesis of these disorders. The discrepancy in the extent of the regions excluded using data from the families with classical CLN2 and families with Finnish variant late‐infantile NCL is due to the smaller number of families segregating for Finnish variant late‐infantile NCL.
Novel glycine conjugates in medium‐chain acyl‐CoA dehydrogenase deficiency
Authors: Pitt J. J.
Published: December 2004

The glycine conjugates of isocaproic, 4‐methylhexanoic, 7‐hydroxyoctanoic and 8‐hydroxyoctanoic acids have been identified in the urine of children with medium‐chain acyl‐CoA dehydrogenase (MCAD) deficiency using gas chromatography‐mass spectrometry of the trimethylsilyl derivatives. A quantitative study showed that the glycine conjugates of isocaproic and 4‐methylhexanoic acids were excreted during acute episodes and in smaller amounts when subjects were asymptomatic. The glycine conjugates of 7‐hydroxyoctanoic and 8‐hydroxyoctanoic acids were detectable during acute episodes. None of the conjugates was detected in controls or controls receiving a diet containing medium‐chain triglycerides. It is suggested that the glycine conjugates of isocaproic acid and 4‐methylhexanoic acid are metabolites of branched‐chain fatty acids and that they are specific for MCAD deficiency.
Improved identification of heterozygotes for phenylketonuria using blood neopterin and biopterin
Authors: Alós T. , Bel Y. , Cabello M. L. , Catalá J. L. , Dalmau J. , Ferré J. , García A. M. , Ruiz‐Vázquez P.
Published: December 2004

A novel approach that combines information provided by the metabolism of pteridines and that of phenylalanine has been applied to the detection of heterozygotes for phenylketonuria. Phenylalanine, tyrosine, biopterin and neopterin have been measured in serum from normal controls and heterozygotes for classical phenylketonuria, before and after a phenylalanine oral load. Significant differences in neopterin and biopterin mean values in fasting serum and in the mean increase of biopterin induced by the phenylalanine load were found between groups. Inclusion of pteridine data in the discriminant analysis significantly improved the resolution of the classical phenylalanine loading test for the detection of heterozygotes for phenylketonuria.
Juvenile metachromatic leukodystrophy: neurological outcome two years after bone marrow transplantation
Authors: Guffon N. , Souillet G. , Maire I. , Dorche C. , Mathieu M. , Guibaud P.
Published: December 2004

Conclusion

Our patient was not an ideal candidate since she was not clinically completely asymptomatic and presented with abnormal MRI and decreased nerve conduction when the metachromatic leukodystrophy was diagnosed in her older sibling. Nevertheless, 2 years after graft the deterioration did not progress and the MRI improved, while her brother became bed‐ridden within few months after the same initial symptoms.

These favourable results need further confirmation after several years since significant differences in course have been observed in siblings (Clarke et al 1989).
Maple syrup urine disease (MSUD): Screening for known mutations in Italian patients
Authors: Parrella T. , Surrey S. , Iolascon A. , Sartore M. , Heidenreich R. , Diamond G. , Ponzone A. , Guardamagna O. , Burlina A. B. , Cerone R. , Parini R. , Dionisi‐Vici C. , Rappaport E. , Fortina P.
Published: December 2004

Maple syrup urine disease (MSUD) is an autosomal recessive disease due to deficiency of the branched‐chain α‐ketoacid dehydrogenase (BCKDH) caused by a large number of mutations. In the present study, DNA from Italian patients and their relatives was examined for three point mutations (Y393N in the E1α gene, T841G and G1031A in the E2 gene) and two deletions (−G at the intron/exon border of exon 8 in the E2 gene and an 11 bp deletion in exon 1 of the E1β gene) using the polymerase chain reaction (PCR) followed by allele‐specific oligonucleotide (ASO) hybridization, gene‐scanning size analysis of fluorescent‐tagged PCR products and/or automated DNA sequence analysis. Our results show that two different mutations account for 7 of the 20 mutant MSUD alleles. Two unrelated affected children, two of their parents and one sibling were carriers for the 11 bp deletion in the E1β gene, one patient and her mother were heterozygous for Y393N in E1α, while T841G, G1031A and the −G deletion in E2 were not detected. This study is the first attempt to characterize at a nucleic acid level MSUD mutations in Italy. Our results indicate that additional defects are present in the Italian population and that, unlike the Mennonites, a number of different MSUD mutations exist in Italians.
Prenatal detection of Canavan disease (aspartoacylase deficiency) by DNA analysis
Authors: Elpeleg O. N. , Shaag A. , Anikster Y. , Jakobs C.
Published: December 2004

Amniocentesis was performed in four pregnancies at risk for Canavan disease (CD). In all families both parents were of Ashkenazi‐Jewish origin and harboured the C854 mutation in the cDNA of the aspartoacylase gene. Using DNA analysis of the amniotic cells, three fetuses were predicted to be non‐affected and one fetus was predicted to be affected. The concentration ofN‐acetylaspartic acid (NAA) in the amniotic fluid was in agreement with these results. In urine samples of the three newborns predicted to be non‐affected, the concentration of NAA was normal. Tissues of the aborted fetus were not available. We conclude that DNA analysis is probably a reliable method for prenatal diagnosis of CD.
Further studies on erythrocyte thiamin transport and phosphorylation in seven patients with thiamin‐responsive megaloblastic anaemia
Authors: Rindi G. , Patrini C. , Laforenza U. , Mandel H. , Berant M. , Viana M. B. , Poggi V. , Zarra A. N. F.
Published: December 2004

Erythrocyte thiamin metabolism and transport were investigated in 7 patients from Brazil, Israel and Italy suffering from thiamin‐responsive megaloblastic anaemia (TRMA) associated with diabetes mellitus and sensorineural deafness. All patients discontinued thiamin therapy for 4–7 days before the investigation. TRMA patients showed invariably reduced total thiamin levels in erythrocytes (percentage reduction compared with healthy controls, −46.8±3%; mean±SEM). The proportions of individual thiamin compounds, expressed as a percentage of total thiamin content, were within the normal range, whereas their absolute amounts were significantly decreased in the following order: thiamin monophosphate > thiamin pyrophosphate > thiamin. Thiamin pyrophosphokinase activity was also reduced as compared with controls (mean reduction±SEM, −25.9±1%). The saturable, specific component of thiamin uptake, which normally prevails at physiological concentrations of thiamin (<2µmol/L), was absent in erythrocytes obtained from TRMA patients, while the non‐saturable (diffusive) component of uptake was normally present.

These results confirm observations made previously in two patients and demonstrate that TRMA is consistently associated with a state of thiamin deficiency, which is presumably secondary to reduced thiamin cellular transport and absorption (caused by lack of a membrane‐specific carrier), and to impaired intracellular pyrophosphorylation.
Polyunsaturated fatty acid status in patients with phenylketonuria
Authors: Sanjurjo P. , Perteagudo L. , Soriano J. Rodríguez , Vilaseca A. , Campistol J.
Published: December 2004

To determine whether then−6 andn−3 polyunsaturated fatty acid levels can be affected by the PKU diet, fatty acid composition was studied in PKU subjects and controls together with their lipid intake. The study population consisted of 40 PKU patients treated with a phenylalanine‐restricted diet. Controls were 50 children on whom preoperative tests had been carried out for minor surgery. Methyl esters were obtained from plasma and red blood‐cells and separated by gas chromatography. PKU patients showed lower docosahexaenoic acid levels (22:6n−3) (p<0.001) and highern−6 series levels in plasma (18:2n−6) (p<0.001) and in red blood‐cells (20:4n−6) (p<0.001) than the control population. Since docosahexaenoic and arachidonic acids are fundamental structural components for normal brain development, it seems necessary to consider a dietary adjustment in these patients.
PKU‐related dysgammaglobulinaemia: The effect of diet therapy on IgE and allergic sensitization
Authors: Riva E. , Fiocchi A. , Agostoni C. , Biasucci G. , Sala M. , Banderali G. , Luotti D. , Giovannini M.
Published: December 2004

The effect of diet on the development of immunoallergic signs and symptoms in children with phenylketonuria (PKU) was evaluated. Immunological indices of 58 children with PKU treated with diets were compared to the immunological indices of 58 healthy (non‐PKU) children. In the PKU group, 39 children had been placed on diet therapy within the first month of life; 19 children had been placed on diet therapy after 6 months of age. Total circulating lymphocytes; CD3+, CD4+, CD8+ circulating lymphocytes; and serum IgA, IgM, IgG and total IgE levels were measured for each child. Skin prick tests were performed for common inhalant and food allergens. Every 3 months over the 2‐year period of this study, the signs and symptoms of eczema, allergic rhinitis and asthma were recorded.

The PKU group had lower IgG levels (p=0.004) and higher total IgE levels (p=0.0001) than the control group. Significantly lower IgE levels were found in children started on diet therapy within the first month of life compared with those started on diet therapy after 6 months of age (p=0.0001). Allergic sensitization was significantly more frequent in the PKU group (24/58 vs 13/58,z=2.00,p<0.05), but no significant difference in the incidence of eczema and allergic rhinitis was found. Asthma was less frequent in the PKU group than in the control group (5/58 vs 14/58,z=2.09,p<0.05). Thus, diet appeared to prevent the development of immunoallergic signs and symptoms.
Type C Niemann‐Pick disease fibroblasts and their transformed cell lines are hypersensitive to HMG‐CoA reductase inhibitors
Authors: Yamamoto T. , Ohashi T. , Tokoro T. , Maekawa K. , Eto Y.
Published: December 2004

The deficiency of exogenous cholesterol transport within fibroblasts of Niemann‐Pick disease type C (NPC) has been addressed. In this Report we confirmed that the endogenous synthesis of cholesterol within cells was markedly increased in NPC fibroblasts and those transformed by origin‐defective simian virus 40. The transformed fibroblasts and those of the primary culture were hypersensitive to 3‐hydroxy‐3‐methylglutaryl‐coenzyme A reductase inhibitors as a consequence of their dependence on endogenous cholesterol biosynthesis. The transformed fibroblasts should help further biochemical and genetic research in this condition.
Surface Temperature Trend for the Northern Hemisphere-Updated
Authors: Brinkmann Waltraud A.R.
Published: December 2004

The surface temperature curve for the Northern Hemisphere was extended to include the years 1969 through 1973 following the same procedure used by H. C. Willett, J. M. Mitchell, Jr., and C. H. Reitan. The analysis showed a slight warming of 0.02°C between the periods 1965–1969 and 1970–1973, and a significant decrease in the number of negative temperature changes at individual stations (indicating a decrease in the total area experiencing temperature decrease).
The Bishop Ash Bed, a Pleistocene Marker Bed in the Western United States
Authors: Izett G. A. , Wilcox Ray E. , Powers H. A. , Desborough G. A.
Published: December 2004

Biotite-bearing chalky-white rhyolitic ash, here called the Bishop ash bed, occurs in-middle Pleistocene alluvial and lacustrine deposits at eight localities scattered from California to Nebraska and is correlated with the basal air-fall lapilli of the Bishop Tuff, an ash flow of eastern California, radiometrically dated about 0.7 million years. Correlation of the Bishop ash bed with the air-fall lapilli is made on the basis of similar petrography and on chemistry as determined by electron microprobe, atomic absorption, and emission spectrographic analyses. At five localities the Bishop ash bed lies stratigraphically below a Pearlette-like ash. As more occurrences of the Bishop ash bed are found, it should become an increasingly important dated stratigraphic marker relating middle Pleistocene deposits and events across several geomorphic provinces.

Another biotite-bearing chalky-white ash, here called the ash of Green Mountain Reservoir, occurs at three other localities and is distinguishable from the Bishop ash bed by small differences in chemical composition of the glass. The ash of Green Mountain Reservoir is younger than the Bishop ash bed, as shown by the fact that at one locality it lies stratigraphically above the aforementioned bed of Pearlette-like ash.
The Pleistocene Prehistory of Siberia
Authors: Klein Richard G.
Published: December 2004

Very little is known about the prehistory of Siberia prior to the Sartan (“Main Würm” = “Main Wisconsin”) Stadial of the Last Glacial. It is not yet clear whether this is result of the inadequacy of investigations so far or of the fact that human occupation was relatively limited in pre-Sartan times. The Sartan occupation of Siberia has been well documented by the discovery of a relatively large number of open-air sites in the major river valleys of the region. The large numbers of broken-up animal bones found at many of these sites, in combination with rich inventories of bone and stone artifacts and remains of structures, hearths, ect., show that the Sartan inhabitants of Siberia were comparable in level of cultural development to their European (Upper Paleolithic) contemporaries. More particularly, they seem to have been effective big-game hunters, fully capable of exploiting the comparatively rich game resources of their open country environment. As in Europe, evidence from Siberia suggests that the environmental change (especially reforestation) which took place at the end of the Last Glacial led to decreased reliance on big-game hunting and increased emphasis on other modes of subsistence, especially fishing.
The Cape Deceit Fauna—Early Pleistocene Mammalian Assemblage from the Alaskan Arctic
Authors: Guthrie R. D. , Matthews John V.
Published: December 2004

Pleistocene exposures located near Cape Deceit on the south shore of Kotzebue Sound (Alaska) contain a complex sequence of organic sediments which have yielded fossil vertebrates of taxonomic, evolutionary, and zoogeographic significance. Cape Deceit Local Fauna from the Cape Deceit Formation, lowermost of three major stratigraphic units recognized at the site, contains representatives of the genera Canis, Rangifer, Cervus, Ochotona, Lemmus, Microtus, Pliomys, and a newly described genus and species, Predicrostonyx hopkinsi-predecessor of the extant genus Dicrostonyx. In addition to P. hopkinsi, new species of Ochotona, Pliomys, and Microtus are described from the Cape Deceit Local Fauna. the stage of evolution of Microtus deceitensis sp. n. and P. hopkinsi sp. n. indicate that the Cape Deceit Formation is at least of pre-Cromerian age. This assumption is substantiated by the stratigraphy of the overlying Inmachuk and Deering formations, fossils from these units (including Dicrostonyx torquatus and D. henseli), and C-14 dates. The Cape Deceit Local Fauna, therefore, contains the earliest North American record of several of the included genera in addition to the only North American record of Pliomys.

Stratigraphic features at the exposure indicate that the Cape Deceit Local Fauna mammals lived in a treeless (tundra) environment showing that the contemporary tundra mammalian fauna has a lengthy arctic-adapted evolutionary history. We postulate the existence in northeastern Eurasia and Alaska of a Pleistocene-Recent “Beringian” mammalian realm which has at times contributed to the fauna of more southern regions of the Palaerctic and Nearctic. The fact that this southern movement of arctic-adapted or arctic-derived Beringian mammals occurred at different times in Europe and North America (interpreted by some as indicating the existence of a “Beringian filter-bridge”) is, we think, due largely to differences of continental physiography and Pleistocene geography south of the Beringian area.
Quaternary History of Northern Cumberland Peninsula, Baffin Island, N.W.T.: Part V: Factors Affecting Corrie Glacierization in Okoa Bay
Authors: Andrews J. T. , Dugdale R. E.
Published: December 2004

Corries in Okoa Bay contain glaciers, ice patches or are empty. Each of 165 corries is described by 17 variables that describe shape, location and geometry and also have some relationship to the glaciological conditions in each basin. Analyses of these data in terms of “explaining” the factors controlling glacierization (using information and graph-theoretic methods and multiple stepwise discriminant analysis) all emphasize the importance of elevation on the current pattern. Orientation is also significant as virtually all glaciers and ice patches are contained in north-facing corries. Residual elevations from a linear trend surface on corrie lip altitudes indicate that empty corries lie, on average, only 200 m below those currently ice-filled, thus the area is extremely sensitive to the effects of climatic change. Empty corries also lie at the same elevations, on average, in north- and south-facing locations. The orientation of glacierized corries toward the north is a reflection of the variations in insolation between north- and south-facing slopes at latitude 67°30′N. Calculations indicate a difference under clear skies of 25% for global radiation and ∼50% for absorbed short-wave radiation. The 200-m lowering of local snowline implied by the corrie lip data is equivalent to a 1.2°C temperature decrease—this is the same as estimates based on changes in the earth's orbital parameters for this latitude. A lowering of temperature results in an increase in the ratio: sublimation/melting which leads to a reduction in the amount of ablation. It is suggested that glacierization of much of Baffin Island is possible with a lowering of snowline by 200 m, this could then trigger other areas such as Labrador and Keewatin.