bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scattering of obliquely incident seismic waves by a cylindrical valley in a layered half‐space
Authors: Liu S. W. , Datta S. K. , Bouden M. , Shah A. H. 
Published: April 2007

AbstractThree‐dimensional scattering of seismic waves by a cylindrical alluvial valley embedded in a layered half‐space is investigated by using the combination of the boundary integral representation and the finite element method. The surface displacements due to incident plane harmonic body waves (P, SV and SH) propagating at an arbitrary angle to the axis of the cylindrical valley are evaluated numerically for two semi‐elliptical alluvial valleys. The presence of the layer is found to have a strong effect on the amplification of the surface displacements in some cases. The three‐dimensional motion seems to be quite critical and may cause large amplification. The surface ground motion becomes significant when compared with corresponding free‐field motion as the wavelengths become comparable to the characteristic length of the valley. The maximum amplification always occurs atop the valley. Numerical results show that the amplitude and the amplification pattern of the surface displacement strongly depend upon the frequency, the angle and the type of the incident waves.
A simple error estimator and adaptive time stepping procedure for dynamic analysis
Authors: Zienkiewicz O. C. , Xie Y. M. 
Published: April 2007

AbstractA simple local error estimator is presented for time integration schemes in dynamic analysis. This error estimator involves only a small computational cost. The time step size is adaptively adjusted so that the local error at each time step is within a prescribed accuracy. It is found that the estimator performs well under various circumstances and provides an economical adaptive process. Attempts to estimate the global time integration error are also reported.
Three‐dimensional analysis of spatially varying ground motions around a uniform canyon in a homogeneous half‐space
Authors: Zhang Liping , Chopra Anil K. 
Published: April 2007

AbstractDepartment of Civil Engineering, University of California, Berkeley, CA 94720, U.S.A.A direct boundary element method to determine the three‐dimensional seismic response of an infinitely‐long canyon of arbitrary but uniform cross‐section cut in a homogeneous viscoelastic half‐space is presented. The seismic excitation is represented by P, SV, SH or Rayleigh waves at arbitrary angles with respect to the axis of the canyon. The accuracy of the procedure and implementing computer program is demonstrated by comparison with previous solutions for the limiting case of two‐dimensional response, recently obtained three‐dimensional response results for infinitely‐long canyons, and three‐dimensional boundary method solutions presented in this paper for finite canyons.
Dynamics of rigid strip foundations embedded in orthotropic elastic soils
Authors: Wang Y. , Rajapakse R. K. N. D. 
Published: April 2007

AbstractThis study is concerned with the dynamic response of an arbitrary shaped rigid strip foundation embedded in an orthotropic elastic soil. The foundation is subjected to time‐harmonic vertical, horizontal and moment loadings. The boundary‐value problem related to an embedded foundation is analysed by using the indirect boundary integral equation method. The kernel functions of the integral equations are displacement and traction Green's functions of an anisotropic elastic half plane. Exact analytical solutions are used for the Green's functions. The boundary integral equation is solved by using numerical techniques. Selected numerical results are presented for the impedances of rectangular and semi‐circular rigid strip foundations embedded in four types of anisotropic soils. A discussion on the influence of soil anisotropy and frequency of excitation on the impedances is presented. The versatility of the analysis is demonstrated by considering the through soil interaction between two semi‐circular strip foundations.
Response variability in structural dynamics
Authors: Jensen H. , Iwan W. D. 
Published: April 2007

AbstractThis paper presents a technique for treating uncertainties in the dynamic models of a structural system. The formulation of the method is presented for a simple case of a single‐degree‐of‐freedom linear oscillator. The uncertainties are modelled as random variables and are assumed to be time‐independent. The solution is expanded as a series involving the random terms, and a system of linear ordinary differential equations for the unknowns of the problem is derived using the weighted residual method. The system of equations is then integrated in time and the response variability is computed. Validation calculations show that the results from the method agree well with those obtained by other solution techniques. Finally, some possible applications and extensions of the present work are discussed.
Spatially coupled vibrations of a suspension bridge under random highway traffic
Authors: Bryja D. , Śrniady P. 
Published: April 2007

AbstractThe problem of spatial dynamic response of a suspension bridge to the passage of trains of concentrated forces with random values is considered. The arrival of forces at the bridge is assumed to constitute a Poisson process of events. Such an excitation process is an appropriate model of vehicular traffic loads acting on the bridge. The bridge is idealized by a single‐span thin‐walled beam underslung to two cables. The response of the bridge in the space‐time domain is described by a coupled system of non‐linear, integro‐differential equations. The dynamic influence functions of vertical and horizontal deflections at each cross‐section point are obtained for the linear case. Cumulants and probability density functions of response are determined. Numerical methods have been used to develop a computer‐oriented algorithm aimed at the numerical solution of the problem. As examples, numerical results for a particular bridge with some practical load cases are presented and illustrated by graphs.
Impedance functions for three‐dimensional foundations supported on an infinitely‐long canyon of uniform cross‐section in a homogeneous half‐space
Authors: Zhang Liping , Chopra Anil K. 
Published: April 2007

AbstractA direct boundary element procedure is presented to determine the impedance matrix for a three‐dimensional foundation supported on an infinitely‐long canyon of uniform cross‐section cut in a homogeneous half‐space. The uniform cross‐section of the canyon permits analytical integration along the canyon axis leading to a series of two‐dimensional boundary problems involving Fourier transforms of the full‐space Green's functions. Solution of these two‐dimensional boundary problems leads to a dynamic flexibility influence matrix which is inverted to determine the impedance matrix. The accuracy of the procedure is demonstrated by comparison with previous solutions for a surface‐supported, square foundation and results obtained by a three‐dimensional boundary element method (BEM) for a foundation of finite‐width supported on an infinitely‐long canyon. Compared with the three‐dimensional BEM, the present method requires less computer storage and is more accurate and efficient. The foundation impedance matrix determined by this procedure can be incorporated in a substructure method for earthquake analysis of arch dams.
A case study of mimo system identification applied to building seismic records
Authors: Li Yi , Mau S. T. 
Published: April 2007

AbstractA large number of high quality strong‐motion records of building response are obtained from recent earthquake events in California. The accelerometers are typically deployed at several levels from the basement up. In order to learn as much as possible about the building behaviour from these records, a multiple input‐multiple output (MIMO) system identification procedure is implemented to analyse these records in a systematic way. The procedure is an extension of the least‐square‐output‐error method applied to a classically damped linear second order system. The time varying behaviour is modelled through a time window approach. The procedure includes (i) preliminary record analysis, (ii) input and model selection, (iii) parameter identification and (iv) drift analysis.The records of a 15‐storey reinforced concrete building obtained during the Whittier earthquake are analysed. It is found that the fundamental period is much longer than that of a regular building. The torsional response is significant and is caused by both the translational and the torsional motions at the ground level. The maximum drift occurs at the ground storey. The second and the third translational modes in each direction are as important as the first modes in making up the ground storey drift. When the maximum drift occurs in one direction the corresponding drift in the orthogonal direction can be as high as 30 per cent of the maximum drift.
Vibration of three‐dimensional rigid raft foundation on viscoelastic medium
Authors: Zhao Chongbin , Valliappan S. 
Published: April 2007

AbstractUsing the coupled model of finite and infinite elements, the compliance of a rigid raft (plate) on a viscoelastic medium is calculated in this paper. Further, the effects of different proportions of radiation damping and material damping in the total damping and the distribution of wave motion in the near field are also investigated. From the numerical results, it can be concluded that: (1) the radiation damping plays an important role in the total damping, compared to the material damping; (2) the material damping has some effect on the compliance of the raft; (3) under the action of harmonic concentrated loads, the displacement amplitudes in the near field gradually decrease with the increase in the distance from the raft and the material damping; (4) the strata characteristics of the soil medium have considerable influence on the compliance of the raft and the distribution of wave motion in the near field.
Ambient vibration survey of the fatih sultan mehmet (second Bosporus) suspension bridge
Authors: Brownjohn J. M. W. , Dumanoglu A. A. , Severn R. T. 
Published: April 2007

AbstractAmbient accelerations due to dynamic excitation by wind and traffic were measured on the deck, towers, cables and hangers of the Fatih suspension bridge. From these measurements it was possible to obtain natural frequencies, mode shapes and damping ratios for vertical, lateral, torsional and associated modes in the deck and tower up to a maximum of 2 Hz.The objective of the test was to validate the mathematical modelling used in seismic analyses of the bridge. The agreement between the experimental and theoretical modes was acceptable for vertical modes below 1 Hz, and for torsional modes, but it was difficult to identify the lateral modes due to low levels of response.The dynamic behaviour of this bridge and two other major European suspension bridges is discussed in relation to the differences in loading and structural design.
The Effect of the Anode Loading and Method of MEA Fabrication on DMFC Performance
Authors: Reshetenko T. V. , Kim H.‐T. , Krewer U. , Kweon H.‐J. 
Published: April 2007

AbstractThe influence of the Pt‐Ru anode loading and MEA preparation techniques on direct methanol fuel cell (DMFC) performance is studied. Two different anode catalyst layer preparation techniques are employed. One is the direct coating of anode catalyst ink on a membrane to form a catalyst coated membrane, CCManode, and the other is the coating of the ink on the diffusion layers, which generates a catalyst coated substrate, CCSanode. The power density of a combined CCManode/CCScathodeMEA is higher than for a CCSanode/CCScathodeMEA. The main difference in the performance is observed in the high current density region, where two‐phase flow is present and mass transfer processes govern the performance. The CCManodeand CCSanodehave different macroscopic structures, while showing the same microscopic morphology. Based on their morphological differences, it is expected that the combination of the CCManodeand carbon paper provides the more homogeneous removal of CO2at high currents. The authors suggest that the application of the CCManodewith an optimal anode loading improves anode mass transfer, reduces methanol crossover, and enhances the electrochemical reactions.
Graphite Electrodes Modified with Platinum‐Nickel Nano‐Particles for Methanol Oxidation
Authors: Abdel Rahim M. A. , Hassan H. B. , Abdel Hameed R. M. 
Published: April 2007

AbstractMethanol electro‐oxidation is investigated at graphite electrodes modified with various platinum and nickel nano‐particle deposits using cyclic voltammetry. The modified electrodes are prepared by the simultaneous electrodeposition of metals from their salt solutions using potentiostatic and galvanostatic techniques. They show enhanced catalytic activity towards methanol oxidation in KOH solution. The catalytic activity of platinum nano‐particles is found to be significantly affected by the presence of relatively small amounts of nickel deposits. A comparison is made between the electrocatalytic activity of Pt/C and (Pt‐Ni)/C electrodes. The results show that the methanol electro‐oxidation current increases with an increase in the nickel content. In particular, the highest catalytic activity is achieved for platinum to nickel deposits of 95%:5% (wt.‐%), in other cases the catalytic activity decreases. It is found that Ni enhances the catalytic activity of Pt by increasing the number of active sites, as well as through an electron donation process from Ni to Pt. This process takes place once the nickel hydroxide (Ni(OH)2)/nickel oxy‐hydroxide (NiOOH) transformation begins. The effect of the methanol concentration on the methanol oxidation reaction is investigated. The order of reaction, with respect to methanol, at the modified (Pt‐Ni)/C electrode is found to be 0.5.
Expression of a functional metabotropic glutamate receptor 5 on enteric glia is altered in states of inflammation
Authors: Nasser Yasmin , Keenan Catherine M. , Ma Adrienne C. , McCafferty Donna‐Marie , Sharkey Keith A. 
Published: April 2007

AbstractThe metabotropic glutamate receptor 5 (mGluR5) is expressed by astrocytes and its expression is modulated by inflammation. Enteric glia have many similarities to astrocytes and are the most numerous cell in the enteric nervous system (ENS). We investigated whether enteric glia express a functional mGluR5 and whether expression of this receptor was altered in colitis. In both enteric plexuses of the ileum and colon of guinea pigs and mice, we observed widespread glial mGluR5 expression. Incubation of isolated segments of the guinea pig ileum with the mGluR5 specific agonist RS‐2‐chloro‐5‐hydroxyphenylglycine (CHPG) caused a dose‐dependent increase in the glial expression of c‐Fos and the phosphorylated form of the extracellular signal‐regulated kinase 1/2. Preincubation of tissues with the group I metabotropic glutamate receptor antagonist, S‐4‐carboxyphenylglycine, abolished the effects of CHPG. We examined mGluR5 expression in the guinea pig trinitrobenzene sulfonic acid and the IL‐10 gene‐deficient (IL‐10−/−) mouse models of colitis. In guinea pigs, mGluR5 immunoreactivity became diffusely localized over the colonic myenteric ganglia, suggesting a change in receptor distribution. In contrast, glial mGluR5 expression was significantly reduced in the colonic myenteric plexus of IL‐10−/− mice, as assessed with both real‐time quantitative RT‐PCR as well as immunohistochemistry and image analysis. These changes occurred without concomitant changes to enteric ganglia or glial fibrillary acidic protein expression in the IL‐10−/− mouse. Our data suggest that enteric glia are a functional target of the glutamatergic neurotransmitter system in the ENS and that changes in mGluR5 expression may be of physiological significance during colitis. © 2007 Wiley‐Liss, Inc.
Purines induce directed migration and rapid homing of microglia to injured pyramidal neurons in developing hippocampus
Authors: Kurpius Dana , Nolley Eric P. , Dailey Michael E. 
Published: April 2007

AbstractTraumatic CNS injury activates and mobilizes resident parenchymal microglia (MG), which rapidly accumulate near injured neurons where they transform into phagocytes. The mechanisms underlying this rapid ‘homing’in situare unknown. Using time‐lapse confocal imaging in acutely excised neonatal hippocampal slices, we show that rapid accumulation of MG near somata of injured pyramidal neurons in the stratum pyramidale (SP) results from directed migration from tissue regions immediately adjacent to (<200 μm from) the SP. Time‐lapse sequences also reveal a ‘spreading activation wave’ wherein MG situated progressively farther from the SP begin to migrate later and exhibit less directional migration toward the SP. Because purines have been implicated in MG activation and chemotaxis, we tested whether ATP/ADP released from injured pyramidal neurons might account for these patterns of MG behavior. Indeed, application of apyrase, which degrades extracellular ATP/ADP, inhibits MG motility and homing to injured neurons in the SP. Moreover, bath application of exogenous ATP/ADP disrupts MG homing by inducing directional migration toward the slice exterior and away from injured neurons. These results indicate that extracellular ATP/ADP is both necessary and sufficient to induce directional migration and rapid homing of neonatal MG to injured neuronsin situ. Rapid, ATP/ADP‐dependent MG homing may promote clearance of dead and dying cells and help limit secondary damage during the critical first few hours after neuronal injury. © 2007 Wiley‐Liss, Inc.
Olfactory ensheathing cells promote migration of Schwann cells by secreted nerve growth factor
Authors: Cao Li , Zhu Yan‐Ling , Su Zhida , Lv Baolai , Huang Zhihui , Mu Lifang , He Cheng 
Published: April 2007

AbstractTransplantation of Schwann cells (SCs) and olfactory ensheathing cells (OECs) have emerged as very promising therapies for spinal cord repair. The important features of interaction between SCs and OECs are beginning to be appreciated, although the underlying mechanism remains unclear. In the present study, we tested the effects of OECs on SCs migration using a range of in vitro migration assays. We found that SCs migrated abundantly upon OECs monolayer, and the migration‐promoting effects were identified to be due to the secreted diffusible factors in OEC‐derived conditioned medium (OEC‐CM). Furthermore, neutralizing nerve growth factor (NGF) in OEC‐CM with NGF antibody could block this effect. Moreover, we found that NGF promotes SCs migration even on astrocyte monolayer. Taken together, these findings provide the first evidence that OECs can promote SCs migration in astrocytic environment by secreted NGF. © 2007 Wiley‐Liss, Inc.
Cardiovascular effects of high dose venlafaxine XL in patients with major depressive disorder
Authors: Mbaya Patrick , Alam Faouzi , Ashim Sindhu , Bennett David 
Published: April 2007

AbstractObjectiveTo assess cardiovascular safety profile of high dose Venlafaxine XL in patients with major depression.MethodEffects of high dose venlafaxine (mean 346.15 mg;) on the cardiovascular system in 37 patients with major depressive disorder were evaluated: BP, ECG (PR, QT, QRSD and QTc intervals) and heart rate.Results12.5% of patients developed hypertension after starting treatment with venlafaxine. There was an association between heart rate and the dose of venlafaxine although not statistically significant. There was no association between dose of venlafaxine and PR, QT, QRSD and QTc intervals. One patient on 300 mg who was hypertensive and on other medications that may prolong QTc, had mildly prolonged QTc. However this was not clinically significant.ConclusionThis study of subjects on high dose venlafaxine (mean 346.15 mg; range 225–525 mg) did not demonstrate any clinical or statistically significant effects on electrocardiogram (ECG) parameters including PR, QT, QRSD and QTc interval. Copyright © 2007 John Wiley & Sons, Ltd.
Human papillomavirus type distribution in invasive cervical cancer and high‐grade cervical lesions: A meta‐analysis update
Authors: Smith Jennifer S. , Lindsay Lisa , Hoots Brooke , Keys Jessica , Franceschi Silvia , Winer Rachel , Clifford Gary M. 
Published: April 2007

AbstractData on human papillomavirus (HPV) type distribution in invasive and pre‐invasive cervical cancer is essential to predict the future impact of HPV16/18 vaccines and HPV‐based screening tests. A meta‐analyses of HPV type distribution in invasive cervical cancer (ICC) and high‐grade squamous intraepithelial lesions (HSIL) identified a total of 14,595 and 7,094 cases, respectively. In ICC, HPV16 was the most common, and HPV18 the second most common, type in all continents. Combined HPV16/18 prevalence among ICC cases was slightly higher in Europe, North America and Australia (74–77%) than in Africa, Asia and South/Central America (65–70%). The next most common HPV types were the same in each continent, namely HPV31, 33, 35, 45, 52 and 58, although their relative importance differed somewhat by region. HPV18 was significantly more prevalent in adeno/adenosquamous carcinoma than in squamous cell carcinoma, with the reverse being true for HPV16, 31, 33, 52 and 58. Among HSIL cases, HPV16/18 prevalence was 52%. However, HPV 16, 18 and 45 were significantly under‐represented, and other high‐risk HPV types significantly over‐represented in HSIL compared to ICC, suggesting differences in type‐specific risks for progression. Data on HPV‐typed ICC and HSIL cases were particularly scarce from large regions of Africa and Central Asia. © 2007 Wiley‐Liss, Inc.
Serial transplantation of NMU‐induced rat mammary tumors: A model of human breast cancer progression
Authors: Chan Maren M. , Lu Xin , Merchant Faisal M. , Dirk Iglehart James , Miron Penelope L. 
Published: April 2007

AbstractHuman breast cancer is a heterogeneous disease that appears to progress from an in situ tumor to invasive cancer. Little is known about the molecular events driving this progression. Although microarray technology has helped us understand the genetic heterogeneity of breast cancer, its application to studying the transition from in situ to invasive disease is limited by the inability to follow the progression of a single patient's tumor. We previously used rat specific microarrays to show that N‐methyl‐N‐nitrosourea induced tumors are similar to low‐grade estrogen‐receptor positive human breast cancer. Here, we transplanted these tumors through 5 generations of syngeneic hosts, and studied 65 resulting tumors. Most transplanted tumors gradually progressed from a noninvasive, low‐grade cancer to a higher‐grade invasive disease, losing p63 localization and basement membrane integrity. Invasive cancers frequently demonstrated a more mesenchymal phenotype with increased vimentin expression. Additionally, a unique transplant series is described with a phenotype similar to human basal‐like breast cancer. Rat‐specific Affymetrix gene arrays containing 15,866 gene probes identified genes that differentiated highly invasive tumors from those of low invasive potential. A linear regression analysis was used to find genes whose change in expression paralleled increasing invasive features independent of the transplant lineage of origin. Genes identified were assigned membership in cell adhesion, signal transduction, cell cycle and extracellular matrix groups, among others. This animal model overcomes the difficulty in studying human breast cancer progression. Our data support a gradual and continuous alteration in programs of gene expression during breast cancer invasion. © 2007 Wiley‐Liss, Inc.