bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective strength eccentricity concept for inelastic analysis of asymmetric structures
Authors: Mittal A. K. , Jain Ashok K.
Published: April 2007

A large number of parameters affect the inelastic response of an eccentric system. The centre of resistance no longer remains constant due to continuous loading and unloading of various elements of the system in and out of the inelastic region. The objective of this study is to develop the concept of strength eccentricity for asymmetrical structures excited well into the inelastic region in the event of a severe earthquake. A single mass monosymmetric three‐element system is selected. The torsional flexibility parameter is varied so as to obtain nine eccentric configurations covering the entire spectrum of such systems. These models were subjected to S00E component of the El Centro earthquake of 1940 which is considered to be a very severe earthquake. The concept of effective strength eccentricity is introduced which is defined as strength eccentricity at the point of intersection of ductility ratio curves of REE and FEE. It is proposed to provide additional strength in the elements of a torsionally unbalanced system independent of the design eccentricity. Empirical equations are proposed to account for design eccentricity and additional strength as well as distribution of the design strength. The proposed formulation is compared with the torsional provisions of UBC 1991, NBCC 1990 and NZC 1992. It is concluded that additional ductility demand on the REE and FEE designed based on the proposed formulation is almost nil as compared to that given by the three codes. The NZC and UBC require maximum ductility on the REE. The increase in overall strength of the system is least for the proposed formulation as compared to that given by the three codes. NBCC consistently requires the maximum total strength ratio.
Boundary element method with exterior collocation in two‐dimensional elastodynamic problems
Authors: Fu T. M. , Xiong J. G. , Cheung Y. K.
Published: April 2007

In the present paper, the boundary element method with exterior collocation was applied to two‐dimensional elastodynamic problems. The stability of the numerical solution was discussed and the collocation rule of source points outside the region being studied was investigated in the frequency domain by means of the computed error in the boundary displacement and the condition number of the coefficient matrix for two typical wave propagation problems. The achieved results are helpful to the practical application of this method to earthquake ground motion analysis.
Modal equations of linear structures with viscoelastic dampers
Authors: Inaudi José A. , Kelly James M.
Published: April 2007

Several types of energy dissipation devices using viscoelastic materials have been proposed to reduce vibration in structures subjected to wind and earthquake excitations. At constant temperature and small strain levels, the mechanical behaviour of Viscoelastic (VE) materials can be described using linear operators. In general, the stiffness and damping matrices of structures using VE devices are frequency dependent; this implies that the classical second‐order differential equations for the modal co‐ordinates are not a complete model for this type of structures. In this paper, the concept of modal coupling in the frequency domain is addressed, expressions for diagonalizable frequency‐dependent stiffness and damping matrices are given, and an iterative technique for the computation of the response of viscoelastic structures is studied. Necessary and sufficient conditions for convergence of the technique are given and numerical examples are developed to illustrate the application of the method.
An application of damage mechanics for seismic analysis of concrete gravity dams
Authors: Ghrib Faouzi , Tinawi René
Published: April 2007

This paper discusses the local approach of fracture using damage mechanics concepts to evaluate the seismic response of concrete gravity dams. A constitutive model for plain concrete, subjected to tensile stresses, is presented. The mesh‐dependent hardening technique is adopted such that the fracture energy dissipated is not affected by the finite element mesh size. The model is implemented in conjunction with the Hilber, Hughes Taylor alpha algorithm for time marching. Koyna dam is utilized to validate the proposed formulation. The importance of initial damage prior to the advent of an earthquake is also investigated. A 60 m concrete gravity dam is therefore selected and subjected to ground motion typical of eastern North America. Five scenarios of initial damage are presented and the results confirm the importance of accounting for the initial state for the seismic safety evaluation of an existing dam.
Impulse‐momentum and resistance analysis of reinforced concrete structures
Authors: Selna Lawrence G. , Chow Hoong‐Leong
Published: April 2007

The viability of most analytical approaches developed to predict the inelastic response of Reinforced Concrete (RC) structures requires the load‐deformation relationship to have a positive slope. In many realistic cases the slope is not positive. When this happens, most analytical approaches consider the maximum point as the failure point or use unrealistic material laws, e.g., the assumption of a positive slope when it really is negative. Hence, there is a need to develop a new analytical approach which recognizes load‐deflection relationships which have ascending and descending branches. A method based on the impulse momentum principle and the resistance force (IMR) of an RC structure is developed. The resistance force vector {R(t)} is used in place of the stiffness approach. The material non‐linearity of RC systems can be elegantly accounted for in the {R(t)} vector. An examination of numerical properties of the IMR method shows that stability and convergence are dependent on a time step length ratio. Applications of the IMR method which predict the inelastic seismic response of RC structures are performed.
Passive seismic control of cable‐stayed bridges with damped resonant appendages
Authors: Villaverde Roberto , Martin Scott C.
Published: April 2007

A study is conducted to investigate the effectiveness of attaching to cable‐stayed bridges resonant appendages with a relatively small mass and a high damping ratio as a means to reduce their response to earthquake excitations. The study is based on a previously developed formulation that shows that the use of these appendages may increase the inherent damping of building structures and, as a result, may reduce their response to seismic disturbances. It includes numerical and experimental tests that are conducted to assess the validity of such a formulation for the case of cable‐stayed bridges and the extent to which such appendages can reduce their seismic response. In the numerical study, an actual cable‐stayed bridge is modelled with finite elements and analysed with and without the proposed appendages under different earthquake ground motions. Appendages with damping ratios of 10, 15, 20 and 30 per cent and masses that, respectively, represent 0.67, 1.5, 2.7 and 6.0 per cent of the total mass of the bridge are considered. In the experimental test, a 3.7 m long cable‐stayed bridge and an appendage consisting of a small mass, a small spring and a small viscous damper are built and the bridge tested, without and with the appendage, on a pair of shaking tables which are set to reproduce ground acceleration records from past earthquakes. The damping ratio of the appendage in this test is 32 per cent and its mass represents about 8 per cent of the total mass of the bridge model. In the numerical test, it is found that the appendages reduce the longitudinal response of the bridge deck up to 88 per cent. Similarly, in the experimental test it is found that the appendage reduces the longitudinal bridge deck response by about 41 per cent. From these studies, it is concluded that the suggested appendages may indeed be effective in reducing the seismic response of cable‐stayed bridges as they are for building structures.
Continuous pulse control of structures with material non‐linearity
Authors: Pantelides Chris P. , Nelson Paul A.
Published: April 2007

A control method is presented for reducing the dynamic response of structures in the inelastic material range using a control force from an active bracing system. Recent full‐scale experiments have verified the feasibility of implementing active control systems for control of seismic structures with existing technology. The proposed method of continuous pulse control uses closed‐loop feedback control as a combination of two algorithms. The first is the instantaneous optimal algorithm which was derived assuming linear material behaviour, and the second is pulse control which applies a corrective pulse when a prespecified structural displacement, velocity, or acceleration threshold is exceeded. The three criteria of displacement, velocity, and acceleration lead to three pulse control schemes. Each of the three schemes is used in conjunction with the instantaneous optimal control to yield three continuous pulse algorithms, the displacement continuous pulse, velocity continuous pulse and acceleration continuous pulse. Comparisons between the three continuous pulse algorithms and the pulse control for seismic structures in the inelastic range show that the continuous pulse algorithms use less control energy and reduce the response better than pulse control. A comparison between the velocity continuous pulse and the non‐linear optimal algorithm shows that the velocity continuous pulse uses a larger control force but is more adaptable than the non‐linear optimal algorithm, in the sense that it can reduce the response of a given structure to various probable earthquakes. The non‐linear optimal algorithm is more effective than the velocity continuous pulse for a single specific earthquake but is not as effective for other earthquakes which may occur in the life of the structure.
Dynamic interaction between 3‐D rigid surface foundations and comparison with the ATC‐3 provisions
Authors: Qian J. , Beskos D. E.
Published: April 2007

The dynamic behaviour of a system of three‐dimensional, massless, rigid, surface foundations of arbitrary shape perfectly bonded to the elastic half‐space is numerically studied with the frequency domain boundary element method. This method employs the dynamic Green's function for the surface of the half‐space and this results in a discretization of only the soil‐foundation interfaces. In addition, use of isoparametric quadratic quadrilateral boundary elements increases the accuracy of the method, which is confirmed by comparison with other known numerical solutions. Externally applied loads, harmonically varying with time, are considered. The through the soil coupling effect between the foundations as a function of distance and frequency is assessed through extensive parametric studies involving two and four rigid foundations being isolated or interconnected. It is found that the assertion of ATC‐3 regulations that omission of coupling effects leads to conservative results is not always correct for all frequencies.
The prediction of earthquake peak ground acceleration in europe
Authors: Ambraseys N. N.
Published: April 2007

The paper presents predictive relations for peak horizontal and vertical ground accelerations generated by earthquakes in the European area.
Application of microtremor measurements to the estimation of earthquake ground motions in Kushiro city during the Kushiro‐Oki earthquake of 15 january 1993
Authors: Suzuki Takeyasu , Adachi Yoshitaka , Tanaka Minato
Published: April 2007

Microtremor measurements were conducted in Kushiro City, Hokkaido Island of Japan. The thickness of alluvial deposits in the central area of Kushiro City abruptly changes from 0 to 80 m. Predominant ground motion at a microtremor measuring site is represented by the spectral ratio, the ratio of Fourier amplitude spectrum of microtremor in the horizontal direction to that in the vertical direction. The peak frequency of the spectral ratio corresponds well to the predominant frequency estimated from the thickness of alluvial layer at each site. Based on a hypothesis that the spectral ratio can be regarded identical with a half of the amplification factor from diluvial bed rock to the ground surface, the strong ground motion due to the Kushiro‐oki earthquake at each site is estimated. The method of estimation is verified by the comparison of the synthesized accelerogram with the recorded one at West Port of Kushiro. The results satisfactorily explain major damages and vibrations felt in Kushiro City during the earthquake.
CQC and SRSS methods for non‐classically damped structures
Authors: Sinha R. , Igusa T.
Published: April 2007

Two mode combination methods are presented for structures with non‐classical (non‐proportional) damping. They are of the same level of complexity as the well‐known SRSS and CQC methods. They require only a single, real‐valued participation factor for each mode, a single correlation coefficient, and standard relative displacement response spectra. A base‐isolation study shows that the standard SRSS and CQC methods for classically damped structures give under‐conservative response predictions, and that the proposed methods give accurate predictions.
Earthquake analysis of concrete gravity dams including base sliding
Authors: Chávez Juan W. , Fenves Gregory L.
Published: April 2007

A numerical method, the hybrid frequency‐time domain (HFTD) procedure, is used to compute the earthquake response of concrete gravity dams, including sliding along the interface between the dam base and the foundation rock. The solution procedure accounts for the non‐linear base sliding behaviour and the frequency‐dependent response of the impounded water and flexible foundation rock. A Coulomb friction model represents the force‐displacement relationship for sliding at the base interface. Using the solution procedure, an analysis of a typical dam (122 m high) shows that base sliding will occur during a moderate earthquake but the sliding displacement will be a tolerable amount when dam‐foundation rock interaction is considered.
Dynamic response of a multi‐layered poroelastic medium
Authors: Rajapakse R. K. N. D. , Senjuntichai T.
Published: April 2007

An exact stiffness matrix method is presented to evaluate the dynamic response of a multi‐layered poroelastic medium due to time‐harmonic loads and fluid sources applied in the interior of the layered medium. The system under consideration consists of N layers of different properties and thickness overlying a homogeneous half‐plane or a rigid base. Fourier integral transform is used with respect to the x‐co‐ordinate and the formulation is presented in the frequency domain. Fourier transforms of average displacements of the solid matrix and pore pressure at layer interfaces are considered as the basic unknowns. Exact stiffness (impedance) matrices describing the relationship between generalized displacement and force vectors of a layer of finite thickness and a half‐plane are derived explicitly in the Fourier‐frequency space by using rigorous analytical solutions for Biot's elastodynamic theory for porous media. The global stiffness matrix and the force vector of a layered system is assembled by considering the continuity of tractions and fluid flow at layer interfaces. The numerical solution of the global equation system for discrete values of Fourier transform parameter together with the application of numerical quadrature to evaluate inverse Fourier transform integrals yield the solutions for poroelastic fields. Numerical results for displacements and stresses of a few layered systems and vertical impedance of a rigid strip bonded to layered poroelastic media are presented. The advantages of the present method when compared to existing approximate stiffness methods and other methods based on the determination of layer arbitrary coefficients are discussed.
Seismic torsional response and design procedures for a class of setback frame buildings
Authors: Duan X. N. , Chandler A. M.
Published: April 2007

This paper presents results of an analytical study of the inelastic earthquake torsional response of a class of setback frame buildings. In the first part of the study, the modal response spectrum analysis procedure is utilized to determine the yielding strengths of structural members in an idealized but representative setback frame building model. Results are then presented for the inelastic dynamic response of this setback building model subjected to an ensemble of six earthquake ground motions. The results indicate that the modal response spectrum analysis procedure is inadequate for preventing excessive response leading to concentration of damage in vulnerable structural members, such as those in the tower near the notch and those in the base (the part of the structure below the tower) near the perimeter at the opposite side of the tower. The second part of the study develops a modified equivalent static force procedure for strength design of such setback frame buildings. Response analyses show that the proposed procedure results in improved and satisfactory inelastic performance of the selected class of setback frame buildings, having a wide range of realistic configurations.
Duration of earthquake fault motion in California
Authors: Trifunac M. D. , Novikova E. I.
Published: April 2007

Duration of high frequency (5–25 Hz) radiation of energy from earthquake sources in California is consistent with the estimates of fault length and with dislocation velocity estimates of 2–3 km/sec. This duration can be described by an exponential function of magnitude for 2·5 < M < 7·5. It is related to the times it takes the dislocation to spread over the fault width (1/f2), and the fault length (∼ 1/f1), and to reach its ultimate amplitude (T0).

The results in this paper can be used to estimate the range of amplitudes and the duration of long period pulses of strong ground motion near faults, as these long period pulses can be related to the properties of high‐frequency radiation from the source. Such pulses must be considered in the analyses of yielding structures, when the average peak acceleration of the pulse exceeds the yield resistance seismic coefficient of the structure.
Semi‐analytical techniques for the determination of the dynamic response of equipment in structures supported on coulomb friction elements
Authors: Hernried Alan G. , Lei Kai‐Ming
Published: April 2007

Techniques for the analysis of equipment in structures supported on a Coulomb friction type support that is subjected to harmonic and earthquake ground motion are presented. The behaviour is governed by two phases—a sliding phase and a non‐sliding phase. Since the behaviour in each of the phases is linear, an analytical expression for equipment response can be obtained in terms of the roots of an appropriate characteristic polynomial. The times of phase transition are determined by an iterative scheme. The methodology is accurate, less computationally intensive, and avoids the difficulties that can be encountered with standard numerical integration techniques for highly non‐linear systems.
Earthquake simulator testing of pounding between adjacent buildings
Authors: Papadrakakis Manolis , Mouzakis Harris P.
Published: April 2007

Two‐storey‐building frames have been designed and built in an effort to investigate the pounding phenomenon of adjacent buildings during earthquakes. Static tests have been first performed to determine the static characteristics and the support conditions of the test structures. Sinusoidal and random acceleration signal tests have been subsequently performed to determine the dynamic characteristics of the test structures. Two series of tests were carried out using the shaking table simulator. In the first case, the dynamic response has been recorded without pounding, while in the second case, the test structures have been placed with zero‐gap separation and pounding was induced. Input energy time histories were correlated and compared with and without pounding. The experimental results were compared with analytical ones based on a formulation of the contact impact problem by the Lagrange multiplier method. Good agreement between the experimental and the analytical results was achieved.
Numerical technique for dynamic analysis of structures with friction devices
Authors: Dimova S. , Meskouris K. , Krätzig W. B.
Published: April 2007

In recent years a number of studies on employing friction elements for the seismic protection of buildings has demonstrated conclusively that such devices can markedly reduce earthquake‐induced vibrations. Any numerical estimate of the effectiveness of such isolation systems implies a correct solution of the pertinent nonlinear equations of motion. In direct integration algorithms, the phase transitions between adherence and sliding, or the sliding phase may be accompanied by marked high‐frequency oscillation of the relative velocity difference.

The paper presents a numerical technique for overcoming these problems, thus leading to increased accuracy of the solutions of equations of motions with Coulomb damping. Since only the damping matrix and the loading vector are involved, the procedure is also computationally efficient. In order to validate the proposed numerical technique, an experimental study of a friction system has been carried out. The dynamic response of a four‐storey braced frame with friction devices is presented as an example for the practical application of the proposed numerical technique.
Seismic interaction at separation joints of an instrumented concrete bridge
Authors: Malhotra Praveen K. , Huang Moh J. , Shakal Anthony F.
Published: April 2007

A multi‐span, curved, concrete box‐girder bridge has been extensively instrumented by the California Strong Motion Instrumentation Program (CSMIP) in cooperation with the California Department of Transportation (Caltrans). On 28 June 1992, the bridge was shaken by the magnitude 7–5 Landers and magnitude 6–6 Big Bear earthquakes in southern California. The epicentres of these earthquakes were 50 and 29 miles (81 and 46 km) from the bridge, respectively. All 34 strong‐motion sensors installed on the bridge recorded the response to these earthquakes and provided an insightful set of data. A striking aspect of the response is the presence of intermittent sharp spikes in nearly all of the acceleration records from sensors at the deck of the bridge. Among these the highest spike was 0.8g for the Landers and 1.0g for the Big Bear earthquake. The peak ground acceleration at the bridge site was only about 0.1g for both these earthquakes. With the aid of visual examination and simple analysis it is deduced that (1) the spikes were caused by forces generated at separation joints by impacts and stretching of the cable restrainers between adjacent bridge segments; (2) the forces of impacts and cable stretching are directly proportional to the size of the spikes and can be estimated by the use of a simple formula; and (3) the spikes travelled from their source to other locations on the bridge with the velocity of a compression wave propagating through concrete.
Basin effects analysis from a dense strong motion observation network
Authors: Wen Kuo‐Liang , Peng Han‐Yih , Liu Liang‐Fang , Shin Tzay‐Chyn
Published: April 2007

The strong ground motion observation network began to operate in the Taipei Basin area as part of the Taiwan Strong Motion Instrumentation Program (TSMIP). It is operated by the Seismological Observation Centre of the Central Weather Bureau. Forty‐three free‐field accelerometers have been installed in the Taipei Basin, and several earthquakes have been recorded by this network since its installation. Three events with magnitudes of 5–7, 5–4 and 6–2 that triggered more than ten stations are used here to study the characteristics of the basin effects on ground motions both in the time and frequency domains. From this study, it is clear that vibrations of different frequencies have different amplifications in the Taipei Basin. In fact, the frequency responses show the variation can even be up to about 7 times. The horizontal peak ground acceleration (PGA) and spectral ratio contours in the low‐frequency band are closely correlated with the geological structure in the Taipei Basin. The analysis of the response spectra also shows this correlation phenomenon and the relation between the damage from an earthquake and the basin effects.
Strong‐motion instrumentation of dams
Authors: Darbre G. R.
Published: April 2007

Strong‐motion instrumentation schemes are developed for dams. Emphasis is put on the observation of the free‐field motions at the dam sites, of the effective motions at the abutments and of the global dam responses from which the dynamic properties of the dams are also obtained. Array configurations that are compatible with these observation goals are developed for arch, gravity and embankment dams. The associated accelerograph and array specifications are also presented.
Response of non‐classically damped structures in the modal subspace
Authors: D'Aveni Antonino , Muscolino Giuseppe
Published: April 2007

The evaluation of the dynamic response of non‐classically damped linear structures requires the solution of an eigenproblem with complex eigenvalues and modal shapes. Since in practice only a small number of complex modes are needed, the complex eigenvalue problem is solved in the modal subspace in which the generalized damping matrix is not uncoupled by classical real modes. It follows that the evaluation of the structural response requires in both cases the determination of complex modes by numerical techniques, which are not as robust as techniques currently used for the solution of the real eigenvalue problem, and the use of complex algebra. In the present paper an unconditionally stable step‐by‐step procedure is presented for the response of non‐classically damped structures in the modal subspace without using complex quantities. The method is based on the evaluation of the fundamental operator in approximated form of the numerical procedure. In addition, the method can be easily modified to incorporate the modal superposition pseudo‐static correction terms.
Dynamic subscales in the finite element approximation of thermally coupled incompressible flows
Authors: Codina Ramon , Principe Javier
Published: April 2007

In this paper, we propose a variational multiscale finite‐element approximation for the incompressible Navier–Stokes equations using the Boussinesq approximation to model thermal coupling. The main feature of the formulation in contrast to other stabilized methods is that we consider the subscales as transient. They are solution of a differential equation in time that needs to be integrated. Likewise, we keep the effect of the subscales both in the nonlinear convective terms of the momentum and temperature equations and, if required, in the thermal coupling term of the momentum equation. Apart from presenting the main properties of the formulation, we also discuss some computational aspects such as the linearization strategy or the way to integrate in time the equation for the subscales. Copyright © 2007 John Wiley & Sons, Ltd.
Comparing density forecast models
Authors: Bao Yong , Lee Tae‐Hwy , Saltoğlu Burak
Published: April 2007

In this paper we discuss how to compare various (possibly misspecified) density forecast models using the Kullback–Leibler information criterion (KLIC) of a candidate density forecast model with respect to the true density. The KLIC differential between a pair of competing models is the (predictive) log‐likelihood ratio (LR) between the two models. Even though the true density is unknown, using the LR statistic amounts to comparing models with the KLIC as a loss function and thus enables us to assess which density forecast model can approximate the true density more closely. We also discuss how this KLIC is related to the KLIC based on the probability integral transform (PIT) in the framework of Diebold et al. (1998). While they are asymptotically equivalent, the PIT‐based KLIC is best suited for evaluating the adequacy of each density forecast model and the original KLIC is best suited for comparing competing models. In an empirical study with the S&P500 and NASDAQ daily return series, we find strong evidence for rejecting the normal‐GARCH benchmark model, in favor of the models that can capture skewness in the conditional distribution and asymmetry and long memory in the conditional variance.  Copyright © 2007 John Wiley & Sons, Ltd.
The hidden martingale restriction in Gram‐Charlier option prices
Authors: Corrado Charles
Published: April 2007

A hidden martingale restriction is developed for option pricing models based on Gram–Charlier expansions of the normal density function. The restriction is hidden behind a reduction in parameter space for the Gram–Charlier expansion coefficients. The resulting restriction is invisible in the option price. © 2007 Wiley Periodicals, Inc. Jrl Fut Mark 27: 517–534, 2007
A simplified approach to modeling the co‐movement of asset returns
Authors: Harris Richard D. F. , Stoja Evarist , Tucker Jon
Published: April 2007

The authors propose a simplified multivariate GARCH (generalized autoregressive conditional heteroscedasticity) model (the S‐GARCH model), which involves the estimation of only univariate GARCH models, both for the individual return series and for the sum and difference of each pair of series. The covariance between each pair of return series is then imputed from these variance estimates. The proposed model is considerably easier to estimate than existing multivariate GARCH models and does not suffer from the convergence problems that characterize many of these models. Moreover, the model can be easily extended to include more complex dynamics or alternative forms of the GARCH specification. The S‐GARCH model is used to estimate the minimum‐variance hedge ratio for the FTSE (Financial Times and the London Stock Exchange) 100 Index portfolio, hedged using index futures, and compared to four of the most widely used multivariate GARCH models. Using both statistical and economic evaluation criteria, it was found that the S‐GARCH model performs at least as well as the other models that were considered, and in some cases it was better. © 2007 Wiley Periodicals, Inc. Jrl Fut Mark 27:575–598, 2007
Testing association between disease and multiple SNPs in a candidate gene
Authors: Gauderman W. James , Murcray Cassandra , Gilliland Frank , Conti David V.
Published: April 2007

Current technology allows investigators to obtain genotypes at multiple single nucleotide polymorphism (SNPs) within a candidate locus. Many approaches have been developed for using such data in a test of association with disease, ranging from genotype‐based to haplotype‐based tests. We develop a new approach that involves two basic steps. In the first step, we use principal components (PCs) analysis to compute combinations of SNPs that capture the underlying correlation structure within the locus. The second step uses the PCs directly in a test of disease association. The PC approach captures linkage‐disequilibrium information within a candidate region, but does not require the difficult computing implicit in a haplotype analysis. We demonstrate by simulation that the PC approach is typically as or more powerful than both genotype‐ and haplotype‐based approaches. We also analyze association between respiratory symptoms in children and four SNPs in the Glutathione‐S‐Transferase P1 locus, based on data from the Children's Health Study. We observe stronger evidence of an association using the PC approach (p = 0.044) than using either a genotype‐based (p = 0.13) or haplotype‐based (p = 0.052) approach. Genet. Epidemiol. 2007. © 2007 Wiley‐Liss, Inc.
The effect of chronic benzodiazepine use on cognitive functioning in older persons: good, bad or indifferent?
Authors: Bierman E. J. M. , Comijs H. C. , Gundy C. M. , Sonnenberg C. , Jonker C. , Beekman A. T. F.
Published: April 2007

Objective

This study investigates the effects of benzodiazepine (BZ) use on cognitive performance in elderly persons in a longitudinal design.

Study design and setting

Data were obtained from the Longitudinal Aging Study Amsterdam (LASA), in the Netherlands. 2,105 respondents (≥62 years of age) were included and had repeated measurements over a period of 9 years. For all BZs the type, dosage, frequency and duration of use was measured. The equivalent of a dose of diazepam was determined with regard to type and dosage and a cumulative dosage was calculated. General cognitive functioning was measured with the Mini‐Mental State Examination, information processing speed was measured with the coding task, fluid intelligence with Raven's Coloured Progressive Matrices and episodic memory with the Auditory Verbal Learning Test. Multilevel analyses were used to investigate the relationship between BZ use and cognitive decline.

Results

A negative effect of BZ use on cognitive performance was found. However, the effect sizes were very small.

Conclusion

This study suggests that both duration and cumulative exposure to BZ has a small negative effect on the long‐term cognitive functioning of elderly people in the community. Copyright © 2007 John Wiley & Sons, Ltd.
Caffeine and 35% carbon dioxide challenge tests in panic disorder
Authors: Nardi Antonio E. , Valença Alexandre M. , Lopes Fabiana L. , de‐Melo‐Neto Valfrido L. , Freire Rafael C. , Veras Andre B. , Nascimento Isabella , King Anna Lucia , Soares‐Filho Gastão L. , Mezzasalma Marco A. , Zin Walter A.
Published: April 2007

Our aim was to compare the demographic and clinical features of panic disorder (PD) patients with agoraphobia—DSM‐IV—who had a panic attack after both an oral caffeine and the 35% carbon dioxide (CO2) challenge tests (responsive group) and compare them with PD patients who did not have a panic attack after both tests (non‐responsive group). We examined 83 PD patients submitted to a 35% CO2test and to an oral caffeine (480 mg) intake within 1 week interval. A panic attack was induced in 51 (61.4%) patients during the CO2test (χ2 = 31.67, df = 1,p < 0.001) and in 38 (45.8%) patients during the caffeine test (χ2 = 18.28, df = 1,p = 0.023). All patients who had a panic attack during the caffeine test also had a panic attack during the CO2test (n = 38)—responsive group. The responsive had more (χ2 = 24.55, df = 1,p = 0.008) respiratory PD subtype, disorder started earlier (Mann‐Whitney,p < 0.001) had a higher familial prevalence of PD (χ2 = 20.34, df = 1,p = 0.019), less previous alcohol abuse (χ2 = 23.42, df = 1,p < 0.001), and had more previous depressive episodes (χ2 = 27.35, df = 1,p < 0.001). Our data suggest that there is an association between respiratory PD subtype and hyperreactivity to challenge tests: CO2and oral caffeine. Copyright © 2007 John Wiley & Sons, Ltd.
Comparison of gene expression data from human and mouse breast cancers: Identification of a conserved breast tumor gene set
Authors: Klein Andreas , Wessel Ralf , Graessmann Monika , Jürgens Martin , Petersen Iver , Schmutzler Rita , Niederacher Dieter , Arnold Norbert , Meindl Alfons , Scherneck Siegfried , Seitz Susanne , Graessmann Adolf
Published: April 2007

The aim of our work was to establish a database for breast cancer gene expression data in order to compare human and mouse breast cancer. We identified human and mouse homologues genes and compared the expression profile of 24 human breast tumors with 6 WAP‐SVT/t breast tumors (WAP‐SVT/t animals, line 8). Our studies confirmed the heterogeneity in gene expression of human as well as mouse breast cancer cells. However, 63 genes were found to be differentially expressed (upregulated: 40; downregulated: 23 genes) in at least 75% of the breast tumors of both species. To differentiate between early and late events in tumor formation, we compared the 63 differentially expressed genes with a mouse data set obtained from hyperplastic mammary glands. This revealed that the majority of the early deregulated genes are cell proliferation specific. These early changes seem to be necessary although not sufficient for breast cancer formation. Late alterations concern mainly genes belonging to the category of cell communication and metabolism. Interestingly, most of the 63 conserved genes are commonly associated with tumorigenesis. © 2007 Wiley‐Liss, Inc.
Preparation and properties of biodegradable polymeric blends from poly(propylene carbonate) and poly(ethylene‐co‐vinyl alcohol)
Authors: Wang X. L. , Du F. G. , Jiao J. , Meng Y. Z. , Li R. K. Y.
Published: April 2007

Biodegradable blends of poly(propylene carbonate)/ethylene–vinyl alcohol copolymers (PPC/EVOH) were melt prepared. The mechanical strength, crystallization and melting behavior, morphologies, and thermal properties of these blends were fully investigated using tensile tester, modulated differential scanning calorimetry, scanning electron microscopy, and thermogravimetric analysis, respectively. The results indicated that the thermal stability of blends could be enhanced by increasing EVOH content. No change was observed for the tensile strength when EVOH content was lower than 30 wt %. The tensile strength, however, increased obviously with increasing EVOH content when EVOH content was higher than 30 wt %. The crystallization behavior of the PPC/EVOH blends was studied accordingly. The degradability test showed that the weight loss of PPC/EVOH blends increased with increasing EVOH content because of the strong moisture sorption of EVOH. Morphology observation indicated that the PPC/EVOH blends exhibited a two‐phase microstructure. The blends with EVOH contents ranging from 40 to 60 wt % showed the best comprehensive properties as biodegradable thermoplastic for many applications. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
Comparison of amorphous TCP nanoparticles to micron‐sized α‐TCP as starting materials for calcium phosphate cements
Authors: Brunner Tobias J. , Bohner Marc , Dora Claudio , Gerber Christian , Stark Wendelin J.
Published: April 2007

The development of degradable bone cements with a mineral composition similar to natural bone was investigated using highly reactive calcium phosphate phases as starting materials. Mixtures of XRD‐amorphous, glassy tricalcium phosphate (amorphous‐TCP) nanoparticles of 25–60 nm size and micron sized, milled α‐TCP were set by hydration with sodium phosphate buffer and investigated for possible application as single component calcium phosphate cements (CPCs). Isothermal calorimetry allowed a precise tracking of the setting process. Amorphous‐TCP nanoparticles converted into calcium deficient hydroxyapatite with cement setting times below 12 min. The total energy release by the material during hardening corroborated the importance of high specific surface area and phase composition, that is, amorphous state of the nanometric starting material as repeatedly suggested earlier. The phase composition of the resulting CPCs was characterized by X‐ray diffraction before and after setting. The morphology was investigated by nitrogen adsorption, scanning, and transmission electron microscopy and revealed the formation of highly porous calcium deficient hydroxyapatite with specific surface areas of up to 160 m2 g−1 after setting. In contrast to the very fast reaction time and highest specific surface area, the mechanical stability of the resulting CPC is still insufficient and requires further improvement. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2007
Severe form of congenital cerebral and cerebellar atrophy: A neurodegenerative disorder of fetal onset
Authors: Phadke Shubha , Puri Ratna , Phadke Rajendra
Published: April 2007

Infantile olivopontocerebellar atrophy (OPCA) is a rare congenital disorder likely due to an intrauterine neurodegenerative condition. Characteristic presentations are failure to thrive, cerebellar ataxia, respiratory insufficiency, and hypotonia or hypertonia. A few cases with severe manifestations (eg, the Pena‐Shokeir phenotype) presenting in the neonatal period have also been reported. We present a case of infantile OPCA with the Pena‐Shokeir II phenotype and severe atrophy of the cerebellum and cerebral hemispheres. Comparison of prenatal sonographic findings of the fetal brain at 30 weeks' menstrual age and CT findings during the neonatal period indicated prenatal onset of the neurodegenerative process, which progressed rapidly during the last trimester. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
The dynamic fetal brain
Authors: Towner Dena , McGahan John , Rhee‐Morris Laila , Gerscovich Eugenio
Published: April 2007

Purpose.

To evaluate fetuses with normal intracranial anatomy in the second trimester that became abnormal in the third trimester.

Methods.

We sonographically examined 6 fetuses with a normal second‐trimester head sonogram that presented later in pregnancy with an abnormal head sonogram.

Results.

Four categories of intracranial pathology were depicted: obstructive hydrocephalus, intraventricular intracranial hemorrhage, non‐intraventricular intracranial hemorrhage, and porencephaly.

Conclusions.

Despite a normal midtrimester intracranial examination, evaluation of the fetal intracranial contents should be undertaken in subsequent sonographic examinations, because significant pathology can develop spontaneously. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
Acromioclavicular joint injury: Enhanced technique of examination with dynamic maneuver
Authors: Peetrons Philippe , Bédard Justine P.
Published: April 2007

Acromioclavicular (AC) sprains can be graded in 3 to 6 different types according to Tossy or Rockwell, respectively. In mild sprains (Tossy and Rockwell I), movements in the AC joint are minimal, because the coraco‐clavicular ligaments are intact. In these patients, stress radiography is usually normal, and sonographic examination at rest can be normal as well, showing minimal or no displacement between the 2 extremities of the bones. We present a simple dynamic maneuver to enhance the diagnosis of these mild sprains known as the cross‐arm maneuver, in which the hand is placed on the opposite shoulder. The dynamic sonographic examination during this maneuver clearly shows abnormal movements in the clavicle's extremity, which “falls down” to the acromion in the cross‐arm position and is raised and pulled from the acromion at rest. The maneuver is very easy to perform and may be useful when a mild AC joint sprain is suspected. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
FAIR‐TrueFISP imaging of cerebral perfusion in areas of high magnetic susceptibility differences at 1.5 and 3 Tesla
Authors: Boss Andreas , Martirosian Petros , Klose Uwe , Nägele Thomas , Claussen Claus D. , Schick Fritz
Published: April 2007

Purpose

To estimate cerebral blood perfusion in areas of strong magnetic susceptibility changes with high spatial and temporal resolution using a flow‐sensitive alternating inversion recovery (FAIR) arterial spin labeling (ASL) method.

Materials and Methods

We implemented an ASL method that is capable of imaging perfusion in areas of high magnetic susceptibility changes by combining a FAIR spin preparation with a true fast imaging in steady precession (TrueFISP) data acquisition strategy. A TrueFISP readout sequence was applied especially in regions with magnetic field inhomogeneities and compared with corresponding FAIR measurements obtained with a standard echo‐planar imaging (EPI) readout. Quantitative perfusion images were obtained at 1.5 Tesla (1.5T) from eight healthy volunteers (24–42 years old) and one patient (23 years old). FAIR‐TrueFISP perfusion images were compared with FAIR echo‐planar images. T1 maps, which are necessary for quantitative perfusion estimation, were obtained with inversion recovery (IR) TrueFISP and IR EPI. Additionally, high‐resolution perfusion measurements were performed on four volunteers at 3T.

Results

The two ASL perfusion imaging modalities yielded comparable diagnostic image quality in brain areas with low susceptibility differences at 1.5T. Cerebral perfusion of gray matter (GM) areas was 105.7 ± 5.2 mL/100 g/minute for FAIR‐TrueFISP and 88.8 ± 14.6 mL/100 g/minute for FAIR‐EPI at 1.5T, and 70.4 ± 7.1 mL/100 g/minute for FAIR‐TrueFISP and 63.5 ± 6.9 mL/100 g/minute for FAIR‐EPI at 3.0T. Higher perfusion values at 1.5T were due to more pronounced partial‐volume effects from fast moving spins at lower spatial resolution. The FAIR‐TrueFISP sequence showed no significant distortions and markedly reduced signal void artifacts in areas of high susceptibility changes (e.g., near brain–bone transitions and close to metallic clips) compared to FAIR‐EPI. At 3T, highly resolved FAIR‐TrueFISP perfusion images were acquired with an in‐plane resolution of up to 1.3 mm.

Conclusion

FAIR‐TrueFISP allows for assessment of cerebral perfusion in areas of critically high susceptibility changes with conventional ASL methods. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Quadrature coil design for high‐resolution carotid artery imaging scores better than a dual phased‐array coil design with the same volume coverage
Authors: Ouhlous Mohamed , Moelker Adriaan , Flick Herman J. , Wielopolski Piotr A. , de Weert Thomas T. , Pattynama Peter M.T. , van der Lugt Aad
Published: April 2007

Purpose

To evaluate the ability of a custom‐built coil design to provide improved signal‐to‐noise ratio (SNR) and less signal drop with increasing depth at the carotid artery.

Materials and Methods

Phased‐array surface coils can provide a high SNR to image the carotid vessel wall. However, given the required field‐of‐view (FOV) and penetration depth, these coils show either a fast signal drop with increasing depth or a moderate SNR at increased coil size. A quadrature surface coil (a butterfly coil in conjunction with a linear single‐loop coil) was compared with a phased‐array coil in phantom and human studies.

Results

The phantom studies showed that the quadrature coil has better SNR over the required FOV than a standard phased‐array coil (26% at 3 cm depth).

Conclusion

The quadrature coil enables better image quality to be achieved. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Lactate, choline, and creatine levels measured by vitro 1H‐MRS as prognostic parameters in patients with non‐small‐cell lung cancer
Authors: Yokota Hajime , Guo Jianfei , Matoba Munetaka , Higashi Kotaro , Tonami Hisao , Nagao Yosinobu
Published: April 2007

Purpose

To determine the biochemical characteristics of lung cancer tissue using in vitro 1H‐MRS, and investigate the correlation between survival probabilities and lactate (Lac), creatine (Cr), and choline (Cho) concentrations measured by in vitro 1H‐MRS.

Materials and Methods

A total of 21 patients with lung cancer were included in this retrospective study. 1H‐MRS spectra measurements were performed at 6.35T using a JNM‐EX270, high‐resolution FT‐NMR spectrometer.

Results

When normal lung tissue was compared with lung cancer tissue, significant differences were noted most consistently in the levels of Lac and Cho, with lung cancer tissue showing higher values than normal lung tissue. Lac concentrations of lung cancer tissue were significantly higher in patients with recurrence compared to patients without recurrence (0.285 ± 0.096 μmol/g). The mean overall survival of patients in the low‐Lac group was 50.28 ± 6.47 months, which is significantly higher compared to the high‐Lac group, which had a mean survival time of only 30.49 ± 5.41 months.

Conclusion

Kaplan‐Meier analysis of the data showed that the overall and disease‐free survival probabilities were significantly higher in patients with low tumor Lac values than in those with high tumor Lac concentrations. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.