bluuebunny/crossref_metadata_2025 huggingface dataset:
CQC modal combination rule for high‐frequency modes
Authors: Kiureghian Armen Der , Nakamura Yutaka
Published: April 2007

The CQC rule for modal combination is extended to include the quasi‐static contribution of truncated modes and the effects of input narrow‐bandedness and cut‐off frequency. A simple measure of the error in approximating a high‐frequency modal response by its quasi‐static contribution is derived. The extended rule is applicable to structures with high‐frequency modes and to seismic inputs which may not be regarded as wide band. Numerical examples demonstrate the significance of input bandwidth and cut‐off frequency on modal cross‐correlation coefficients, and on the error resulting from truncation of high‐freqeuncy modes.
Seismic cracking and energy dissipation in concrete gravity dams
Authors: Bhattacharjee S. S. , Léger P.
Published: April 2007

A finite element method for seismic fracture analysis of concrete gravity dams is presented. The proposed smeared crack analysis model is based on the non‐linear fracture behaviour of concrete. The following features have been considered in the development of the model: (i) the strain softening of concrete due to microcracking; (ii) the rotation of the fracture band with the progressive evolution of microcrack damage in finite elements; (iii) the conservation of fracture energy; (iv) the strain‐rate sensitivity of concrete fracture parameters; (v) the softening initiation criterion under biaxial loading conditions; (vi) the closing‐reopening of cracks under cyclic loading conditions. The seismic fracture and energy response of dams and the significance of viscous damping models to take account of non‐cracking structural energy dissipation mechanisms are discussed. The influences of global or local degradation of the material fracture resistance on the seismic cracking response of concrete dams were also studied. Two‐dimensional seismic response analyses of Koyna Dam were performed to demonstrate the application of the proposed non‐linear fracture mechanics model.
Maximum response of asymmetric structures subject to A multicomponent earthquake
Authors: Li B. , Al‐Bermani F. G. A. , Kitipornchai S.
Published: April 2007

A simple and general technique to obtain a six‐component earthquake input motion of a rigid foundation using three‐linear‐components earthquake record is presented. Using the multicomponent input, the maximum structural response to an arbitrarily oriented earthquake is derived. The method is applied to determine the response spectrum for a two‐d.o.f. laterally and torsionally coupled linear system. The effects of foundation geometry, structural properties and apparent wave velocity on the structural response are investigated. It is found that increasing the foundation size reduces the peak values of the input motion; this reduction is more pronounced for a square foundation than for a circular one.
Theoretical and experimental studies on rectangular liquid dampers under arbitrary excitations
Authors: Koh C. G. , Mahatma S. , Wang C. M.
Published: April 2007

This paper presents a study on the behaviour of rectangular liquid dampers under a horizontal excitation of arbitrary time history. The theoretical model to predict motion of a shallow liquid in a rectangular tank is adapted from a previous researchers' model which was developed for sinusoidal excitations. The model includes an energy dissipation term arising from liquid viscosity. In the present consideration of arbitrary excitations, the energy dissipation term is derived in a straightforward way, without resorting to the equivalent linearization method or assumption of harmonic response as used by earlier researchers. The up‐crossing rate of wave height is used in furnishing the Reynolds number required for the evaluation of shear stress in the boundary layer. Since there was no known precedent study involving arbitrary excitations, experiments have been performed accordingly to verify the model. Generally, the theoretical model furnishes results which are found to be in close agreement with the experimental ones. The results also illustrate the strong dependency of liquid motion upon the natural frequency of the damper, amplitude and frequency content of the excitation spectrum. The model is then applied to study the effectiveness of tuned liquid dampers in vibration control of a single‐degree‐of‐freedom structure subjected to earthquake excitations. Significant suppression of structural vibration can be achieved using tuned liquid dampers.
Response analysis of reinforced concrete structures under seismic excitation
Authors: Mørk K. J.
Published: April 2007

The theoretical background and capabilities of a program for response analysis of reinforced concrete structures under seismic excitation are presented. The emphasis is on the analysis of stiffness and strength degradation due to severe plastic deformations.

An extended version of the model of Roufaiel–Meyer is utilized as the constitutive moment–curvature relation. This takes into account the transition from uncracked to cracked sections, including a mechanism for strength deterioration. The finite length of plastic end zones is taken into account by controlling the plasticity in certain sections and at internal cross sections of the members. Incremental bending stiffness corresponding to the local bending axes of the elements between these control sections is determined by linear interpolation.

The stochastic earthquake excitation may be specified either as a standardized acceleration time‐series applied at the earth surface and scaled with stochastically varying maximum acceleration and duration, or as an intensity modulated Gaussian white noise process filtered through a Kanai–Tajimi filter. Based on Monte‐Carlo simulation, the program calculates the mean values and standard deviations of storey displacements, bending moments in critical sections and maximum softening damage indicators, defined from the lower time‐averaged eigenperiods.

An adaptive system reduction scheme has been implemented based on a truncated expansion of external nodal point degrees‐of‐freedom in the linear eigenmodes of the initial undamaged structure. A full description of the internal degrees‐of‐freedom controlling the hysteresis is maintained.

In order to demonstrate the ability of the program to predict the actual seismic response of reinforced concrete structures, computed results were compared to the experimentally recorded results of a 10‐storey 4‐bay reinforced concrete model.
Iterative methods for non‐classically damped dynamic systems
Authors: Udwadia Firdaus E. , Kumar Ravi
Published: April 2007

Non‐classically damped structural systems do not easily lend themselves to the modal superposition method because these systems yield coupled second‐order differential equations. In this paper, a variety of new computationally efficient iterative methods for determining the response of such systems are developed. The iterative approaches presented here differ from those presented earlier in that they are computationally superior and/or are applicable to the determination of the responses of broader classes of structural systems. Numerical examples, which are designed to evaluate the efficacy of these schemes, show the vastly improved rates of convergence when compared to earlier iterative schemes.
Dynamic stiffness of unbounded medium based on damping‐solvent extraction
Authors: Song Chongmin , Wolf John P.
Published: April 2007

In the damping‐solvent extraction method, to calculate the dynamic‐stiffness matrix of an unbounded medium, a finite region of the medium, adjacent to the structure is analysed in the first step, whereby hysteretic material damping is introduced artificially as a solvent. This leads to the dynamic‐stiffness matrix of the damped bounded medium, which is assumed in the second step to be equal to that of the damped unbounded medium. In the third step, the effect of the material damping on the dynamic‐stiffness matrix is eliminated, i.e. the damping solvent is extracted, resulting in the dynamic‐stiffness matrix of the unbounded medium. The damping‐solvent extraction method permits an efficient calculation of the dynamic‐stiffness matrix of an unbounded medium by analysing the adjacent bounded medium only, which exhibits the same dynamic characteristics as the (bounded) structure. The familiar standard finite‐element method is sufficient for the analysis and the hysteretic damping is introduced by multiplying the elastic moduli by 1 + 2i£. The introduced hysteretic material damping, the solvent, is extracted at the end of the analysis for each coefficient of the dynamic‐stiffness matrix and for each frequency independently of the others by a very concise equation based on a Taylor expansion.

The method is evaluated thoroughly for dynamic soil‐structure interaction and for seismic reservoir‐dam interaction using stringent simple cases with analytical solutions available and is also applied to practical examples, by calculating the dynamic‐stiffness matrix of a semi‐infinite wedge and an embedded foundation.
Neural network for earthquake selection in structural time history analysis
Authors: Cheng M. , Popplewell N.
Published: April 2007

A neural network is employed to select earthquake waves in a time history approach for structural dynamics. The neural network is a preferable alternative to an expert system because knowledge can easily be renewed. It involves a back propagation model having three layers (one input, one hidden and one output layer) and is used to avoid inappropriate earthquake input prior to practical numerical computations. Knowledge to categorize the earthquake waves is acquired through network training with earthquake response spectra and structural responses. The trained network is tested by categorizing the responses of three types of unknown structures caused by 50 previously recorded earthquakes. Comparisons are made with analogous data from the traditional site dominant period method. Results demonstrate that, unlike the latter method, a neural network is generally more successful as the number of training patterns increases.
Attenuation of earthquake‐induced ground displacements
Authors: Ambraseys N. N. , Srbulov M.
Published: April 2007

Attenuation laws predicting induced displacements generated by earthquakes of different magnitude at different distances as a function of the critical acceleration ratio of the foundation materials have been derived from a substantial data set of strong‐motion records obtained worldwide.
Seismic response of a cylindrical shell embedded in a layered viscoelastic half‐space. I: Formulation
Authors: Luco J. E. , de Barros F. C. P.
Published: April 2007

A method to obtain the three‐dimensional harmonic response of a infinitely long cylindrical shell of circular cross‐section embedded in a layered viscoelastic half‐space and subjected to harmonic plane waves impinging at an oblique angle with respect to the axis of the shell is presented. The procedure combines an indirect integral representation for the field in the exterior half‐space with a model of the pipeline or tunnel based on Donnell shell theory. The integral representation for the soil is based on the use of moving Green's functions for the layered viscoelastic half‐space. The accuracy of the formulation is tested by comparison of results obtained by using different discretizations. Extensive comparisons with previous two‐ and three‐dimensional results for the case of a shell embedded in a uniform half‐space and some new numerical results for a shell embedded in a multilayered half‐space are presented in a companion paper.
Dynamic soil pressures on rigid cylindrical vaults
Authors: Veletsos A. S. , Younan A. H.
Published: April 2007

A critical evaluation is made of the dynamic pressures and the associated forces induced by ground shaking on an upright, circular, rigid vault that is embedded in a uniform viscoelastic stratum of constant thickness and infinite extent in the horizontal plane. Both the vault and the stratum are presumed to be supported on a non‐deformable base undergoing a space‐invariant, uniform horizontal motion. The effects of both harmonic and earthquake‐induced excitations are examined. Simple approximate expressions for the responses of the system are formulated, and comprehensive numerical data are presented which elucidate the underlying response mechanisms and the effects and relative importance of the various parameters involved. The parameters investigated include the height to radius ratio for the vault, the conditions at the vault‐medium interface, and the material properties of the stratum. In addition to valuable insights into the response of the particular system being examined, the results presented provide a conceptual framework for the analysis and interpretation of solutions for more involved systems as well.
Formulation of hydrodynamic pressures in cracks due to earthquakes in concrete dams
Authors: Tinawi René , Guizani Lotfi
Published: April 2007

A new analytical development of the seismic hydrodynamic pressure inside pre‐existing cracks on the upstream face of concrete dams is presented. The finite control volume approach is utilized to derive an expression for the seismic hydrodynamic pressure using the continuity principle and the linear momentum theorem for the fluid inside the crack. The derived pressure expression is a function of the relative crack‐opening acceleration and velocity. The acceleration and velocity terms are then recast in the form of added mass and damping matrices which can then be included at the nodes inside the discrete crack of a finite element model. This procedure linearizes the solution of the problem. A dam, 55 m high and having an initial crack opening of 2 mm at the base or near the crest and subjected to two different accelerograms, is analysed. For high‐frequency ground motion, the seismic hydrodynamic pressure inside the crack, at the base of the dam, appears to be 50 per cent higher than the corresponding hydrostatic pressure.
Performance of a high damping rubber bearing base isolation system for a shear beam structure
Authors: Chen Yu , Ahmadi Goodarz
Published: April 2007

Performance of High Damping Laminated Rubber Bearing (HD‐LRB) base isolation system in protecting the structure and the structural content is studied. A non‐uniform shear beam structural model is considered, and the generalized non‐stationary Kanai–Tajimi model for the El Centro 1940 earthquake is used as excitation. The technique of equivalent linearization is utilized and the mean‐square response statistics of secondary systems and primary structure are evaluated. Statistically estimated peak responses of the secondary system and the primary structure are evaluated and the results are compared with the response spectra for the actual earthquake accelerogram. Comparison of the stochastic responses for base‐isolated structures with the HD‐LRB and the linear Laminated Rubber Bearing (LRB) and the fixed‐base structure is also carried out. It is shown that the HD‐LRB system significantly reduces the mean‐square, as well as the peak acceleration and deflection responses without generating large base displacements. Furthermore, the non‐linear behaviour of the HD‐LRB somewhat improves the performance of the bearing in reducing the peak responses of the secondary system and the primary structure when compared with the linear LRB model.
Dynamic characterization of multiple tuned mass dampers and some design formulas
Authors: Abé Masato , Fujino Yozo
Published: April 2007

Multiple Tuned Mass Dampers (MTMD) consist of a large number of small oscillators with natural frequencies distributed around the natural frequency of a controlled mode of the structure. In the present paper, the modal characteristics and efficiency of the MTMD are studied analytically. Perturbation solutions for the modal properties of the MTMD–structure system are obtained and the modal characteristics are discussed. An explicit formula to estimate the effectiveness of the MTMD subjected to harmonic forces is also derived. It is shown that the MTMD is efficient when at least one of the oscillators is strongly coupled with the structure in any mode. Based on this observation, a critical bandwidth of the natural frequencies of the MTMD to make the system multiply tuned is derived in a simple form, and furthermore a robustness criterion for the frequency tuning under a given bandwidth is proposed. It is shown that, when properly designed, the MTMD can be much more stable (robust) than a conventional single TMD while maintaining more or less the same efficiency. Numerical studies verify the accuracy of the perturbation solutions and the proposed formulas.
Site response analysis in the valley of Mexico: Selection of input motion and extent of non‐linear soil behaviour
Authors: Ordaz M. , Faccioli E.
Published: April 2007

It is well known that seismic waves in the lake‐bed zone of Mexico city are dramatically amplified, and that the soft clays in this region exhibit an unusually large elastic range. New field and laboratory data show that clays in certain areas within the Valley of Mexico have lower elastic thresholds and, hence, non‐linear soil behaviour would be more likely to take place. In this paper, we analyse geotechnical and strong‐motion data to model, using a one‐dimensional (1‐D) approach, the non‐linear soil response at two sites in Mexico City during the September 19, 1985 (Ms = 8.1) Michoacán earthquake. Results suggest that, even for motions as large as those recorded during the 1985 Michoacán event, a linear viscoelastic behaviour must be assumed for the examined area, although, as far as it is presently known, the clays from this area show the greatest modulus reduction among the Mexico City clays. Thus, a linear 1‐D propagation analysis continues to be a suitable engineering option in computing expected ground motions at soft sites for the Valley of Mexico. Caution, however, is warranted when selecting input motions, since, as shown in this paper, large differences can result depending on the choice of outcrop motions.
Dynamic‐stiffness matrix in time domain of unbounded medium by infinitesimal finite element cell method
Authors: Wolf John P. , Song Chongmin
Published: April 2007

To calculate the dynamic‐stiffness matrix in the time domain (unit‐impulse response functions) of the unbounded medium, the infinitesimal finite element cell method based solely on the finite element formulation and working exclusively in the time domain is developed. As in the cloning algorithm, the approach is based on similarity of the unbounded media corresponding to the interior and exterior boundaries of the infinitesimal finite element cell. The derivation can be performed exclusively in the time domain, or alternatively in the frequency domain. At each time station a linear system of equations is solved. The consistent‐boundary method to analyse a layered medium in the frequency domain and the viscous‐dashpot boundary method are special cases of the infinitesimal finite element cell method. The error is governed by the finite element discretization in the circumferential direction, as the width of the finite‐element cell in the radial direction is infinitesimal. The infinitesimal finite element cell method is thus ‘exact in the finite‐element sense’. This method leads to highly accurate results for a vast class of problems, ranging from a one‐dimensional spherical cavity to a rectangular foundation embedded in a half‐plane.
Discussion on a paper by X. N. Duan and A. M. Chandler
Authors: Nakamura Tsuneyoshi , Nakamura Yutaka
Published: April 2007

The authors have presented the results of inelastic earthquake response analysis of a class of asymmetric building models and concluded that regularly asymmetric buildings excited well into the inelastic range may not be conservatively designed via modal analysis of their elastic models. The purpose of this short communication is to refer to the results in contrast to the authors' and to make some comments on their paper.
Scattering of plane SH waves by a cylindrical alluvial valley of circular‐arc cross‐section
Authors: Yuan Xiaoming , Liao Zheng‐Peng
Published: April 2007

A closed‐form solution of two‐dimensional scattering of plane SH waves by a cylindrical alluvial valley of circular‐arc cross‐section in a half‐space is presented using the wave functions expansion. The solution is reduced to solving a set of infinite linear algebraic equations using the exterior region form of Graf's addition theorem. Numerical solutions are obtained by truncation of the infinite equations and their accuracies are demonstrated by convergence of the numerical results to the exact boundary condition with the increasing of the truncation order. The present solution is compared with the existing one presented by Todorovska and Lee for the same problem and their differences are analysed. Complicated effects of the depth‐to‐width ratio of the alluvial valley on surface ground motion are finally illustrated.
A mass penalty technique to control the critical time increment in explicit dynamic finite element analyses
Authors: Macek Richard W. , Aubert Brian H.
Published: April 2007

The applicability of explicit time integration in structural dynamics is often limited by a restrictively small solution time increment. This paper presents a mass penalty technique whereby the highest natural frequencies of a dynamic system can be preferentially lowered with only a minimal effect on the structural modes. Because the critical time increment is inversely proportional to the highest natural frequency, a dramatic increase in the solution time increment may be achieved. An expression is developed for the frequency shift and a number of useful properties of this technique are derived analytically for linear systems. Its utility in non‐linear analyses is demonstrated with several examples.
A probabilistic assessment of seismic damage in ductile structures
Authors: Basu Biswajit , Gupta Vinay K.
Published: April 2007

The current practices in ductility‐based earthquake design ignore the damage caused by the repeated random inelastic excursions. A ductile structure may however suffer different degrees of damage depending on the number and amplitudes of these inelastic excursions. The information about the largest response peak as available from the response spectra may not thus be enough as the higher‐order peaks are likely to play an important role in the progressing damage. A probabilistic model is proposed here to estimate the damage in a structure with a given amount of ductility by using the order statistics of the higher‐order peaks. The proposed formulation relates damage to the entire response process, not just to the largest response. It thus accounts for the different roles played by the total number of peaks in the process, the relative amplitudes and number of excursions, and frequency content of the response process.
When the doorbell rings–a case of building response to a long distance earthquake
Authors: Pan Tso‐Chien
Published: April 2007

Responding to ground tremors caused by the magnitude 7–0 Liwa earthquake in Sumatra on 16 February 1994, a doorbell system on the 15th floor of a 17‐storey building in Singapore rang repeatedly at an epicentral distance of more than 750 km. This paper first reviews briefly the regional seismicity, surface geology and effects of local soil amplification for Singapore. It then estimates the building response through the linear and non‐linear analyses of impact conditions for the double‐pendulum doorbell system. Based on the impact analysis results, it is shown that the acceleration response at the 15th floor reached at least 0–02 g and that the base shear coefficient was no less than 1–0 per cent. The response was comparable to the notional horizontal load which usually governs the design of most buildings in Singapore. In view of the fast growing economy and the rapid urbanization of Singapore, it is prudent to re‐evaluate systematically the effects of a long distance, large Sumatra earthquake on Singapore.
Seismic displacements of torsionally unbalanced buildings
Authors: Tso W. K. , Wong C. M.
Published: April 2007

A parametric study is carried out to evaluate the seismic displacements at the flexible edge of torsionally unbalanced (TU) structural systems. Guidelines are provided to estimate these displacements so that they can be incorporated in the formulation of the displacement‐based seismic design approach for the design of TU buildings. The ability of three code procedures to estimate the flexible‐edge displacement is examined to show that not all procedures lead to conservative estimates. Finally, it is shown that elastic spectrum analysis incorporating accidental torsion effect is a viable means to estimate the flexible‐edge displacements.
Response of rigid body assemblies to dynamic excitation
Authors: Winkler Tibor , Meguro Kimiro , Yamazaki Fumio
Published: April 2007

Shaking table tests were conducted to investigate the response of rectangular wooden blocks and block assemblies of various sizes and slenderness to harmonic and earthquake base excitation. The shaking tests were followed by an analytical and a numerical study of response of single blocks and block assemblies. The analytical study was aimed at establishing criteria for the initiation of rocking and of overturning in response to harmonic base motion and consisted of solving numerically the differential equations of motion of a rigid block on a rigid foundation. The numerical study, in the course of which the response of both single blocks and block assemblies was examined, was implemented by means of the Distinct Element Method (DEM). Prior to the DE simulation of actual shaking tests, preliminary analyses were conducted to confirm numerical stability and to evaluate material and damping parameters. Comparing the recorded time histories with those given by the analytical study and the DE simulation, good agreement was found. The distinct element model in use appeared to follow the highly non‐linear motion of rigid body assemblies faithfully to reality. On the basis of the results, provided that the necessary parameters are carefully estimated, the employed DE model can be regarded as an appropriate tool to simulate response of rigid body assemblies to dynamic base excitation.
Hybrid control of seismic‐excited bridge structures
Authors: Yang J. N. , Wu J. C. , Kawashima K. , Unjoh S.
Published: April 2007

Recently, several hybrid protective systems have been explored for applications to seismic‐excited bridge structures. In particular, two types of aseismic hybrid protective systems have been shown to be quite effective: (i) rubber bearings and variable dampers (or actuators), and (ii) sliding bearings and actuators. In this paper, control methods are presented for these hybrid protective systems. The control methods are based on the theory of variable structure system (VSS) or sliding mode control (SMC). Emphasis is placed on the static (direct) output feedback controllers using only the information measured from a few sensors without an observer. Simulation results demonstrate that the control methods presented are robust with respect to system parametric uncertainties and the performance is quite remarkable. Sensitivity studies are conducted to evaluate the effectiveness of hybrid protective systems and passive sliding isolators for reducing the response of seismic‐excited bridge structures. The advantages of each protective system are demonstrated by simulation results for a wide range of earthquake intensities.
Statistical analysis of peaks and directivity of earthquake ground motion
Authors: Ansary Mehedi A. , Yamazaki Fumio , Katayama Tsuneo
Published: April 2007

Conversion factors are useful for attenuation and damage estimation relationships. These factors among different definitions of peaks (i.e. larger, average and resultant) for peak ground motion indices and acceleration response spectrum were investigated. A large number of horizontal acceleration records recorded at 76 free‐field sites of the Japan Meteorological Agency were used in this study. Two orthogonal horizontal components were combined in the time domain to get the maximum resultant peak ground motion indices and acceleration response spectrum in the horizontal plane. From the analysis, the means of the larger/resultant ratio were found to be 0·934 for acceleration, 0·926 for velocity, and 0·913 for displacement. A similar decreasing trend was observed for the means of the average/resultant ratio of the ground motion indices and acceleration response spectrum. The directivity of peak ground motion indices was also examined. It was found that the peak ground motion is more likely to occur in the transverse direction than in other directions. This trend is more prominent in the long‐period contents of ground motion.
Strength enhancement in particulate solids under high loading rates
Authors: Chandra Dipankar , Krauthammer Theodor
Published: April 2007

The so‐called ‘strain‐rate effect’ in any material has been investigated here from a structural dynamics point of view. Starting with lumped‐mass models (SDOF and 2‐DOF) and assuming a rate‐independent failure criterion, it is shown here how a high loading rate produces an effect of strength enhancement in any massive elastic material and how failure takes place in a stronger component of a system as the loading rate increases. Extrapolating the concept of an equivalent elastic modulus as introduced in lumped‐mass models and extending the analysis to a semi‐infinite elastic continuum, an algorithm has been schematized to evaluate an overall equivalent elastic modulus of a concrete body under the influence of high loading rate treating the concrete as a two‐component solid mixture consisting of cement paste matrix and aggregates.
Factors affecting solid phase microextraction (SPME) to concentrate the odorants of Chinese white salted noodles for GC–MS analysis
Authors: Lin Li‐Yun , Peng Chiung‐Huei , Wang Hui‐Er , Wu Tsung‐Han , Chen Cheng‐Chang , Yu Tung‐Hsi , Wu Cheung‐May , Peng Robert Y.
Published: April 2007

Over 0.4 billion people consume Chinese white salted noodles (CWSN) as their daily main diet. Rapid flavour and taste control of CWSN has consequently attracted much attention from noodle processors and distributors. In this study, the conventional solid‐phase microextraction (SPME) technique plus GC and GC–MS was used to concentrate the odorants in CWSN and examine its potential for improving the related quality control (QC) technology. The results indicated that the optimum adsorption time and temperature are 160 min and 30 °C, respectively. Higher temperatures are not suggested for SPME because of thermal leakage and desorption possibilities. Moreover, dry adsorption is more stable than wet adsorption regarding the amount adsorbed and the operational stability, and CAR/PDMS was found to be superior to PDMS/DVB in this regard. In this investigation, a total of 25 odorant species were identified; corresponding regains of 55.11 and 31.25 p.p.m. were obtained for dry and wet adsorption, respectively, among which hexanal was the most abundant (37.10 p.p.m. dry adsorption vs. 20.79 p.p.m. wet adsorption), while 2‐heptenal (4.24 p.p.m.), 2‐octenal (2.01 p.p.m.), 2‐pentylfuran (1.91 p.p.m.), 2‐nonenal (1.41 p.p.m.) and 2‐butyl‐2‐octenal (1.35 p.p.m.) were the next in order of decreasing amount. Interestingly, dry adsorption with CAR/PDMS was specifically more efficient for quantification of total aldehydes (52 p.p.m. vs. 28 p.p.m. for wet adsorption). It is concluded that for flavour quality control of CWSN during both processing and storage, such an analytical technology can be very feasible and satisfactory. Copyright © 2007 John Wiley & Sons, Ltd.
Composition and chemical variability of the twig oil of Abies alba Miller from Corsica
Authors: Duquesnoy Emilie , Castola Vincent , Casanova Joseph
Published: April 2007

The composition of the essential oil of twigs of individual trees of Abies alba Miller from Corsica was investigated by CC, GC (RI), GC–MS and 13C‐NMR. Among the 65 identified compounds, limonene, β‐phellandrene, α‐pinene, camphene and β‐pinene were found to be the major components. Fifty‐three oil samples were analysed and the results were submitted to chemometric analysis (K‐means clustering and principal component analysis). Two groups were distinguished within the essential oils. Samples belonging to the first group (64% of the samples) were characterized by a very high content of limonene (mean value 46.1%). Conversely, the mean composition of the samples of the second group (36% of the samples) was dominated by camphene, α‐pinene and limonene. Such a chemical composition is reported for the first time within A. alba essential oils. Copyright © 2007 John Wiley & Sons, Ltd.
External validation of a risk group defined by recursive partitioning analysis in patients with head and neck carcinoma treated with surgery and postoperative radiotherapy
Authors: León Xavier , López Montserrat , Piñeiro Zenaida , Langendijk Johannes A. , Leemans Charles R. , Quer Miquel
Published: April 2007

Background:

Several clinical trials have proved that concurrent chemoradiotherapy is more efficacious than radiotherapy alone among high‐risk patients with head and neck squamous cell carcinoma (HNSCC) who undergo surgery. A risk‐group classification defined according to a recursive partitioning analysis (RPA) for these patients has been recently proposed. The objective of the present study was to carry out an external validation of this RPA‐derived classification system.

Methods:

A retrospective study of 442 HNSCC patients treated with surgery and postoperative radiotherapy was conducted. The external validity of the RPA‐derived classification system was assessed, and its ability to stage patients and to predict locoregional control of the disease was compared with the TNM system.

Results:

The RPA‐derived classification system succeeded in obtaining a monotonic prognosis gradient in locoregional control of the disease with increasing stage, and achieved greater differences in survival between stages than the TNM and pTNM classifications. Besides, the RPA method had a better homogeneity of the categories included in each stage, and in the heterogeneity between stages.

Conclusions:

The RPA‐derived classification system allowed for the clear definition of prognostic groups in surgically treated HNSCC patients, improving the prognostic capacity of the TNM and pTNM classifications. The RPA‐derived classification system is a useful tool in the definition of patients who, given a poor prognosis, should be considered candidates to adjuvant chemoradiotherapy. © 2007 Wiley Periodicals, Inc. Head Neck, 2007
Phasic cholinergic signaling in the hippocampus: Functional homology with the neocortex?
Authors: Gulledge Allan T. , Kawaguchi Yasuo
Published: April 2007

Acetylcholine (ACh) acts as a neurotransmitter in both the hippocampus and neocortex to facilitate learning, memory, and cognitive function. Here we show that transient muscarinic ACh receptor (mAChR) activation inhibits action potential generation in CA1, but not in CA3, pyramidal neurons via activation of an SK‐type calcium‐activated potassium conductance. Hyperpolarizing responses generated by focal ACh application near the somata of CA1 pyramidal neurons were blocked by atropine or the M1‐like mAChR antagonist pirenzepine, but not by the M2‐like mAChR antagonist methoctramine. Inhibitory cholinergic responses required intracellular calcium signaling, as evidenced by their sensitivity to depletion of internal calcium stores or internal calcium chelation. Cholinergic inhibition did not require GABAergic synaptic transmission, but was blocked by apamin, an SK channel antagonist. In contrast to inhibitory effects in CA1 neurons, ACh was primarily depolarizing, and enhanced action potential firing in CA3 pyramidal neurons. These results, when combined with recent data in neocortical neurons, suggest a functional homology in phasic cholinergic signaling in the hippocampus and neocortex whereby ACh preferentially inhibits those neurons in the lower cortical layers (CA1 and layer 5 neurons) that provide the majority of extracortical efferent projections. © 2007 Wiley‐Liss, Inc.
Expression of cyclin D3 through Sp1 sites by histone deacetylase inhibitors is mediated with protein kinase C‐δ (PKC‐δ) signal pathway
Authors: Kim Young‐Ho , Lim Jun Hee , Lee Tae‐Jin , Park Jong‐Wook , Kwon Taeg Kyu
Published: April 2007

The histone deacetylase (HDAC) inhibitors are an exciting new class of drugs that are targeted as anti‐cancer agents. These compounds can induce growth arrest, apoptosis, and/or terminal differentiation in a variety of cancers. The inhibition of HDACs shifts toward hyper‐acetylation, thereby driving transcriptional activation. In present study, HDAC inhibitor apicidin was used to elucidate the effect on expression of cell cycle related proteins and the molecular mechanism for transcriptional regulation of cyclin D3 in response to HDAC inhibitors in human colon cancer cells. We found that apicidin increases the transcriptional activity of cyclin D3 gene, which results in accumulation of cyclin D3 mRNA and protein. Apicidin‐induced cyclin D3 expression is mediated by Sp1 sites within the cyclin D3 promoter. Apicidin‐mediated cyclin D3 expression is attenuated by rottlerin, a specific protein kinase C‐δ (PKC‐δ) inhibitor, but not mitogen‐activated protein kinases (MAPKs) inhibitors. Furthermore, suppression of PKC‐δ expression by transfection with its siRNA prominently attenuated apicidin‐induced cyclin D3 expression. These results indicate that the cyclin D3 induction caused by apicidin was associated with PKC‐δ signaling pathway not MAPKs signaling pathways. Taken together, these results suggest that the activation of cyclin D3 transcription by HDAC inhibitor apicidin was mediated through Sp1 sites and pointed to the possible participation of PKC‐δ. J. Cell. Biochem. 101: 987–995, 2007. © 2007 Wiley‐Liss, Inc.
Age‐dependent telomere‐shortening is repressed by phosphorylated α‐tocopherol together with cellular longevity and intracellular oxidative‐stress reduction in human brain microvascular endotheliocytes
Authors: Tanaka Yasufumi , Moritoh Yusuke , Miwa Nobuhiko
Published: April 2007

Cellular life‐span of neonatal human brain microvascular endotheliocytes (HBME) was estimated by population doubling levels (PDLs) for serial subcultivations until spontaneous proliferation stoppage, and was 2.4‐fold longer for continuous administration with the 6‐O‐phosphorylated derivative (TocP) of α‐tocopherol (Toc), being bio‐available owing to its water‐solubility, or TocP plus 2‐O‐phosphorylated ascorbate (Asc2P), and 1.3‐fold longer with Asc2P, at a dose of 150 µM, than for the non‐administered control. Enlarged cell diameters indicative of cellular aging were repressed for TocP‐administered cells as analyzed with a channelizer. Age‐dependent shortening of telomeric DNA length (291 bp/PDL) was slowed markedly for TocP (165 bp/PDL) or TocP plus Asc2P, but slightly for Asc2P. Telomerase activity as assessed by the PCR‐based TRAP method was detectable slightly at younger ages but no longer at middle ages for the non‐administered cells, but, for TocP‐administered cells, was intensely detected at younger ages and appreciably until middle ages. Intracellular TocP amounts were not changed age‐dependently in contrast to a marked decrease in Toc which accrued from TocP esterolysis. This may be partly attributed to age‐dependent changes in the lipid peroxidation product acrolein (ACR), which was abundant at older ages in non‐administered cells, but scarcely in TocP‐administered cells. Furthermore, intracellular reactive oxygen species (ROS) such as H2O2 and hydroperoxides as detected using the redox indicator CDCFH‐DA was less abundant in TocP‐administered cells than in non‐administered cells. Thus the telomeric‐DNA retention, concurrently with retained telomerase activity, was shown to be correlated with cellular longevity, and may be supported by diminished oxidative stress, in hydrophobic microenvironment, which can be achieved by TocP rather than AscP. J. Cell. Biochem. 102: 689–703, 2007. © 2007 Wiley‐Liss, Inc.
Evaluation of relative DNA binding affinities of anthrapyrazoles by electrospray ionization mass spectrometry
Authors: Smith Suncerae I. , Guziec Lynn J. , Guziec Frank S. , Hasinoff Brian B. , Brodbelt Jennifer S.
Published: April 2007

Binding interactions of a new series of anthrapyrazoles (APs) with DNA were evaluated by electrospray ionization mass spectrometry (ESI‐MS). Relative binding affinities were estimated from the ESI‐MS data based on the fraction of bound DNA for DNA/anthrapyrazole mixtures, and they show a correlation to the shift in melting point of the DNA measured from a previous study. Minimal sequence specificity was observed for the series of anthrapyrazoles. Upon collisionally activated dissociation of the duplex/anthrapyrazole complexes, typically ejection of the ligand was the dominant pathway for most of the complexes. However, for complexes containing AP2 or mitoxantrone, strand separation with the ligand remaining on one of the single strands was observed, indicative of a different binding mode or stronger binding. Copyright © 2007 John Wiley & Sons, Ltd.
Protein content and gluten quality of durum wheat (Triticum turgidum subsp. durum) as affected by sowing date
Authors: Motzo Rosella , Fois Simonetta , Giunta Francesco
Published: April 2007

The end use quality of durum wheat is sensitive to the environmental conditions pertaining before and during grain filling, and can therefore be modified by manipulation of cultivar and sowing date. A field trial was carried out to study the effect on protein content and gluten quality of varying both sowing date (October, December and March) and cultivar (Simeto, Colosseo and Creso). A delay in sowing date was associated with a decrease in mean grain weight, but not in grain nitrogen content, thus leading to an overall increase from 10.7 to 14.7% in grain protein percentage. Independent of sowing date, over 78% of the grain nitrogen was derived from re‐translocation from vegetative tissue. The similar amounts of nitrogen accumulated in each grain at maturity were set by the similarity in the amount of nitrogen available at anthesis. The observed increase in protein percentage partly explained the greater dough strength (alveographic W) observed in material harvested from the latest sowing. The gluten index, on the other hand, decreased as sowing was delayed. Given the parallel increase in glutenin percentage, we propose that temperatures above 30 °C at the end of the grain filling period have a negative effect on the gluten polymerisation process. Copyright © 2007 Society of Chemical Industry
A practical method for calculating the corrosion rate of uniformly depassivated reinforcing bars in concrete
Authors: Ghods P. , Isgor O.B. , Pour‐Ghaz M.
Published: April 2007

The quantification of active corrosion rate of steel in concrete structures through nondestructive methods is a crucial task for scheduling maintenance/repair operations and for achieving accurate service life predictions. Measuring the polarization resistance of corroding systems and using the Stern‐Geary equation to calculate the corrosion current density of active steel is a widely‐used method for this purpose. However, these measurements are greatly influenced by environmental factors; therefore, accurate monitoring of corrosion requires integrating the instantaneous corrosion rates over time. Although advanced numerical models are helpful in research settings, they remain to be computationally expensive and complex to be adopted by general engineering community. In this paper, a practical numerical model for predicting corrosion rate of uniformly depassivated steel in concrete is developed. The model is built on Stern's earlier work that an optimum anode‐to‐cathode ratio exists for which the corrosion current on the metal surface reaches a maximum value. The developed model, which represents the corrosion rate as a function of concrete resistivity and oxygen concentration, is validated using experimental data obtained from the literature.
Very high‐resolution three‐dimensional functional MRI of the human visual cortex with elimination of large venous vessels
Authors: Barth M. , Norris D. G.
Published: April 2007

We propose a very high‐resolution, three‐dimensional (3D) gradient‐echo technique with a twofold parallel imaging acceleration using a specialized occipital receiver coil at 3 T to perform functional MRI (fMRI) of the visual cortex. This configuration makes it possible to acquire 3D fMRI data within a timescale compatible with a block design. Without further processing, the functional maps at an isotropic 3D resolution of 0.42 µL (0.75 mm voxel size) and near‐isotropic resolution of 1.2 µL (1 mm voxel size) show very robust activation in visual areas, but with clear contamination from larger veins. As this technique allows direct identification of veins in the functional scan, it permits removal of their effect from the activation maps. In our study, elimination of veins qualitatively improves the spatial specificity of activation maps, while reducing the activated volume by about 25%. The proposed technique provides functional information at the resolution of anatomical scans, is localized to gray matter, and facilitates functional to anatomical co‐registration because of minimal distortions. Copyright © 2007 John Wiley & Sons, Ltd.
Eikonal equation‐based front propagation for arbitrary complex configurations
Authors: Wang Y. , Guibault F. , Camarero R.
Published: April 2007

This paper presents a front propagation method using the Eikonal equation, ∇ϕ ⋅ ∇ϕ = 1, in which, ϕ represents the smallest Euclidean distance field to the front to be propagated. The offset capturing approach consists in first calculating the ϕ field over a uniform Cartesian grid fully covering the front to be propagated, and then constructing the iso‐ϕ curves or surfaces as the propagated result. The calculation of ϕ uses a 3D numerical scheme, the Fast Sweeping Scheme. Validation for accuracy of the method is presented using academic test cases. A real 3D industry application, draft tube with two piers, is successfully propagated and demonstrated using special boundary conditions to cope with inlet and outlet planes during front propagtion. This application involves the propagation of a front that exhibits both concave and convex shape regions, sharp corners, and local tangent plane surface discontinuities as well as a multi‐connected domain. Copyright © 2007 John Wiley & Sons, Ltd.