bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic isolation of buildings with sliding concave foundation (SCF)
Authors: Hamidi M. , El Naggar M. H. , Vafai A. , Ahmadi G.
Published: November 2002

In this paper, a new base isolation system, namely the sliding concave foundation (SCF), is introduced and the behaviour of the buildings using such a system is theoretically investigated. A building supported on the new system behaves like a compound pendulum during seismic excitation. The pendulum behaviour accompanied by the large radius of foundation curvature shifts the fundamental period of the system to a high value (e.g. more than 8sec), in a frequency range where none of the previously recorded earthquakes had considerable energy. This results in a large decrease in the structural responses. Since small friction forces are essential on the contact surfaces, PTFE sheets can be used as sliding surfaces. Although the pure frictional sliding systems have the same efficiency as the SCF, in reducing the responses of the superstructure, the main advantage of the new system is a significant decrease in sliding displacement. The performance of the SCF subjected to a number of harmonic and non‐harmonic base excitations is studied and its ability to reduce the structural responses is examined. Some numerical examples are solved for a single‐degree‐of‐freedom (SDOF) structure and the responses are compared with the responses of the same SDOF structure on a fixed base or a pure frictional sliding support system. The comparisons confirm the effectiveness of the new system. Copyright © 2002 John Wiley & Sons, Ltd.
The pseudo‐viscous frictional energy dissipator: a new device for mitigating seismic effects
Authors: Wu Bin , Ou Jinping
Published: November 2002

Viscous energy dissipators (EDORs) have good suppressing effects on acceleration or base shear and they do not add axial pressure to the column when peak moment in the column occurs at peak displacement. Pall frictional EDORs can dissipate energy even when the compression brace buckles due to a special frictional damping mechanism. Retaining the advantages of viscous and Pall EDORs and overcoming their disadvantages, a pseudo‐viscous frictional energy dissipator (PVEDOR) is developed. PVEDORs use the frictional damping mechanism of Pall EDORs, but the slip force of PVEDORs is made variable so that the slip force reduces with increasing displacement. Behaviour testing of PVEDORs shows that they possess the important hysteretic feature of viscous EDORs, i.e. the restoring force of PVEDORs are out‐of‐phase with displacement. Earthquake simulation tests of a 16‐storey frame structure incorporating PVEDORs and ordinary steel braces and bare frame are carried out. The test results show that PVEDORs have good vibration‐suppressing effects. An analytical hysteretic model of PVEDORs basically agrees with the behaviour testing results. Finally, the parameter influence of PVEDORs on suppressive effectiveness of structural vibration under earthquake conditions is studied. Numerical analyses show that PVEDORs have good control effects on both seismic displacement and acceleration, and that control effects of PVEDORs on base shear are much better than Coulomb‐type frictional EDORs or metallic EDORs. Copyright © 2002 John Wiley & Sons, Ltd.
Influence of free field variability on linear soil–structure interaction (SSI) by indirect integral representation
Authors: Savin E.
Published: November 2002

An integral equation for the representation of the response of a structure impinged by an incident wave field including soil–structure interaction is proposed. It requires the knowledge of the fundamental solution for the overall soil–structure domain when a unit load is applied to the structure. This fundamental solution is obtained by means of a substructuring technique and boundary integral equations using the Green tensors for homogeneous or horizontally stratified soil media. The effects of a non‐stationary modulated random incident field are addressed in terms of the instantaneous power spectral density of the structural response of interest for a given coherency function of the free field. Several applications of the proposed procedure are presented. The first one considers kinematic interaction of a rigid circular foundation and is used to validate the numerical implementation. The second one considers a complex structure on a stiff stratified soil and the last one considers the pounding effect between two adjacent, identical structures resting on a thin soft soil layer. Copyright © 2002 John Wiley & Sons, Ltd.
Sliding fragility of block‐type non‐structural components. Part 1: Unrestrained components
Authors: Lopez Garcia D. , Soong T. T.
Published: November 2002

Motivated by the development of performance‐based design guidelines with emphasis on both structural and non‐structural systems, this paper focuses on seismic vulnerability assessment of block‐type unrestrained non‐structural components under sliding response on the basis of seismic inputs specified by current seismic codes. Two sliding‐related failure modes are considered: excessive relative displacement and excessive absolute acceleration. It is shown that an upper bound for the absolute acceleration response can be assessed deterministically, for which a simple yet completely general equation is proposed. In contrast, fragility curves are proposed as an appropriate tool to evaluate the excessive relative displacement failure mode. Sample fragility curves developed through Monte‐Carlo simulations show that fragility estimates obtained without taking into account vertical base accelerations can be significantly unconservative, especially for relatively large values of the coefficient of friction. It is also found that reasonable estimates of relative displacement response at stories other than the ground in multistorey buildings cannot in general be obtained by simply scaling the ground acceleration to the peak acceleration at the corresponding storey. Failure modes considered in this study are found to be essentially independent of each other, a property that greatly simplifies assessment of conditional limit states. Copyright © 2002 John Wiley & Sons, Ltd.
Sliding fragility of block‐type non‐structural components. Part 2: Restrained components
Authors: Lopez Garcia D. , Soong T. T.
Published: November 2002

This paper focuses on seismic vulnerability assessment of restrained block‐type non‐structural components under sliding response on the basis of seismic inputs specified by current seismic codes. The general representation of restrained equipment considered in this study consists of a rigid block restrained by four post‐tensioned, symmetrically arranged cables. Two sliding‐related failure modes are considered: restraint breakage and excessive absolute acceleration. Fragility analysis is proposed as an appropriate tool to evaluate these failure modes. Sample fragility curves developed through Monte‐Carlo simulations show that the restraint breakage limit state is sensitive to the parameters of the equation of motion. For instance, fragility estimates obtained without taking into account vertical base accelerations can be significantly unconservative for relatively large values of the coefficient of friction. In contrast, the excessive absolute acceleration limit state exhibits little sensitivity to the parameters of the equation of motion. Peak absolute acceleration response is almost always equal to or greater than the horizontal peak base acceleration. Representative results suggest that reasonable response estimates for blocks located at stories other than the ground in multistorey buildings can in general be obtained by simply scaling the ground acceleration to the peak acceleration at the corresponding storey. Copyright © 2002 John Wiley & Sons, Ltd.
Comparative study of the inelastic response of base isolated buildings
Authors: Ordoñez Daniel , Foti Dora , Bozzo Luis
Published: November 2002

This article presents a numeric comparative study of the inelastic structural response of base isolated buildings. The comparative study includes the following isolation systems: laminated rubber bearings, New Zealand one, pure friction and the frictional pendulum ones. The study is based on obtaining non‐linear response spectra for various design parameters using six earthquake records. Usually the base isolation of a new building seeks to maintain the structure in the linear elastic range. The response of old weak buildings or the response of new ones subjected to extreme earthquakes may not be, necessarily, in the aforementioned ideal elastic range. Consequently, it is important to characterize the response of isolated buildings responding inelastically. A conclusion from this research is that the isolators affect significantly the structural response of weak systems. Rubber isolators seem slightly less sensitive to plastification that may occur in the structure compared to friction isolators. Ductility demands in the structure are affected significantly by friction and neoprene protected systems, in particular sliding ones where larger demands are obtained. Copyright © 2002 John Wiley & Sons, Ltd.
Interactive effects of personality and organizational politics on contextual performance
Authors: Witt L. A. , Kacmar K. Michele , Carlson Dawn S. , Zivnuska Suzanne
Published: November 2002

The authors explored the process of evaluating contextual performance in the context of a politically charged atmosphere. They hypothesized that the negative relationship between perceptions of organizational politics and contextual performance is weaker among workers high in three of the Big Five model of personality dimensions—agreeableness, extraversion, and conscientiousness. Data were collected from a matched sample of 540 supervisors and subordinates employed in the private sector. Results indicated that the interaction of politics and the personality dimension of agreeableness explained a significant incremental amount of variance in the interpersonal facilitation facet of contextual performance. These findings demonstrate the need to consider both the situation and the person as antecedents of contextual performance. Copyright © 2002 John Wiley & Sons, Ltd.
A longitudinal analysis of the association between emotion regulation, job satisfaction, and intentions to quit
Authors: Côté Stéphane , Morgan Laura M.
Published: November 2002

The present longitudinal study explored the association between emotion regulation, defined as the conscious manipulation of one's public displays of emotion, and job satisfaction and intentions to quit. We predicted, based on an emotional dissonance model, that the suppression of unpleasant emotions decreases job satisfaction and increases intentions to quit. We propose a social interaction model that predicts that the amplification of pleasant emotions increases job satisfaction and decreases intentions to quit by improving the quality of interpersonal encounters at work. Data from 111 workers were gathered at two time points separated by four weeks. Advantages of the design included the use of longitudinal data and the statistical control for several personality, job, and demographic factors. Longitudinal regression analyses and tests of mediation revealed that, as predicted, (a) the suppression of unpleasant emotions decreases job satisfaction, which in turn increases intentions to quit, and (b) the amplification of pleasant emotions increases job satisfaction. Applied implications are discussed and suggestions for future research are offered. Copyright © 2002 John Wiley & Sons, Ltd.
Insider or outsider? how employee perceptions of insider status affect their work behavior
Authors: Stamper Christina L. , Masterson Suzanne S.
Published: November 2002

Many researchers have used the insider–outsider distinction when discussing employment relationships (e.g., Graen & Scandura, 1987; Pfeffer & Baron, 1988). However, there is no known empirical research directly assessing employees' perceptions of their status as organizational insiders. This article is intended as an initial step to theoretically and empirically explore the concept of perceived insider status (PIS). First, we build theoretical arguments describing how organizations may differentiate between insider and outsider employees, leading to differences in perceptions of insider status. We then hypothesize and show empirical evidence that contrasts, but relates, actual inclusion and perceived organizational support to PIS. We subsequently examine two types of discretionary employee behavior, altruism and production deviance, as potential consequences of PIS. Our results suggest that both actual inclusion, as well as perceived insider status, have implications for organizational functioning via discretionary employee behaviors. Copyright © 2002 John Wiley & Sons, Ltd.
A general non‐linear optimization algorithm for lower bound limit analysis
Authors: Krabbenhoft Kristian , Damkilde Lars
Published: November 2002

The non‐linear programming problem associated with the discrete lower bound limit analysis problem is treated by means of an algorithm where the need to linearize the yield criteria is avoided. The algorithm is an interior point method and is completely general in the sense that no particular finite element discretization or yield criterion is required. As with interior point methods for linear programming the number of iterations is affected only little by the problem size.

Some practical implementation issues are discussed with reference to the special structure of the common lower bound load optimization problem, and finally the efficiency and accuracy of the method is demonstrated by means of examples of plate and slab structures obeying different non‐linear yield criteria. Copyright © 2002 John Wiley & Sons, Ltd.
Volume‐dependent pressure loading and its influence on the stability of structures
Authors: Rumpel T. , Schweizerhof K.
Published: November 2002

Deformation‐dependent pressure loading on solid structures is created by the interaction of gas with the deformable surface of a structure. Such fairly simple load models are valid for static and quasi‐static analyses and they are a very efficient tool to represent the influence of gas on the behaviour of structures. Completing previous studies on the deformation dependence of the loading with the assumption of infinite gas volumes, the current contribution is focusing on the influence of modifications of the size and shape of a finite volume containing the gas in particular on the stability of structures. The linearization of the corresponding virtual work expression necessary for a Newton‐type solution leads to additional terms for the volume dependence. Investigating these terms the conservativeness of the problem can be proven by the symmetry of the linearized form. The discretization with finite elements leads to standard stiffness matrix forms plus the so‐called load stiffness matrices and a rank‐one update for each enclosed volume part, if the loaded surface segments are identical with element surfaces. Some numerical examples show first the effectiveness of the approach and the necessity to take the corresponding terms in the variational expression and in the following linearization into account, and second the particular influence of this term on the stability of structures is shown with some specific examples. Copyright © 2002 John Wiley & Sons, Ltd.
Stable isotope (13C, 15N and 34S) analysis of the hair of modern humans and their domestic animals
Authors: Bol Roland , Pflieger Christian
Published: November 2002

Relationships between dietary status and recent migration were examined by δ13C, δ15N and δ34S analysis of hair samples from 43 modern humans living in a rural community in SW England. The isotopic content of 38 ‘local’ hair samples was compared with that of five recently arrived individuals (from Canada, Chile, Germany and the USA). Hair samples from domestic animals (i.e. mainly cats, dogs, cows and horses) were analysed to examine the difference in δ13C, δ15N and δ34S values between herbivores and carnivores. Generally, modern human hair data from the triple stable isotope (δ13C, δ15N and δ34S) provided enough information to confirm the dietary status and origin of the individual subjects. The dietary intake was generally reflected in the animal hair δ15N and δ13C values, i.e. highest in the carnivores (cats). However, a non‐local origin of food sources given to domesticated omnivores (i.e. dogs) was suggested by their hair δ34S values. Copyright © 2002 John Wiley & Sons, Ltd.
Evolution of the δ13C signature related to total carbon contents and carbon decomposition rate constants in a soil profile under grassland
Authors: Accoe Frederik , Boeckx Pascal , Cleemput Oswald Van , Hofman Georges , Zhang Ying , Li Rong hua , Guanxiong Chen
Published: November 2002

Evolution of the total carbon (C) content and the 13C enrichment (δ13C signature) of soil organic matter (SOM) with increasing depth in a soil profile under permanent grassland (C3 vegetation) were investigated. The relationship between the total C content and the δ13C signature at different depths in the upper 30 cm of the soil profile could be well fitted by the Rayleigh equation (y = −29.8 − 2.3x, R2 = 0.95, p < 0.001), describing the enrichment in 13C as resulting from isotopic fractionation associated with C mineralization (isotope enrichment factor ε = −2.3‰). Potential C dynamics of SOM in four depth intervals of the profile (0–10, 10–20, 20–30 and 30–40 cm depth) were investigated through an incubation study. The C decomposition rate constants decreased with increasing sampling depth from 0.0479 yr−1 (0–10 cm sampling depth) to 0.0256 yr−1 (30–40 cm sampling depth) and were highly correlated (y = 0.02 + 0.13x, R2 = 0.93, p < 0.05) with the corresponding Δδ13C values (average change of the δ13C signature per depth increment). These results suggest that changes of the δ13C signature of SOM in undisturbed soil profiles under continuous C3 vegetation may serve as an indicator of the variation of SOM quality with increasing depth. Copyright © 2002 John Wiley & Sons, Ltd.
Technical considerations for RNA‐based stable isotope probing: an approach to associating microbial diversity with microbial community function
Authors: Manefield Mike , Whiteley Andrew S. , Ostle Nick , Ineson Philip , Bailey Mark J.
Published: November 2002

An ongoing challenge within microbial ecology is the development of methodologies that attribute microbial community functions to microbial diversity. One approach, involving the incorporation of stable isotopes from labelled tracer compounds into biological signature molecules (biomarkers), may overcome this current limitation. To examine the potential of RNA as the biomarker in stable isotope probing we have generated a series of atom % 13C‐enriched RNA samples through exploitation of the anabolic abilities of a phenol‐degrading environmental isolate. Isotope ratio mass spectrometry was used to determine the atom % 13C of each RNA sample (ca. 1–100%). The corresponding buoyant density (1.755–1.795 g mL−1) was determined by equilibrium density gradient centrifugation and agarose gel electrophoresis. This empirically defined relationship between the atom % 13C of RNA and its buoyant density suggests ribonucleic acids with atom % 13C enrichments greater than 10% can be isolated by equilibrium density centrifugation. The processing and analysis of isolated RNA by reverse transcription polymerase chain reaction, denaturing gradient gel electrophoresis, cloning and sequencing are discussed. The RNA‐based stable isotope probing protocol presented here will find particular utility in assessing the roles of microbial community members in the biodegradation of natural and anthropogenic xenobiotic compounds. Copyright © 2002 John Wiley & Sons, Ltd.
Use of the international system of units (SI) in isotope ratio mass spectrometry
Authors: Milton Martin J. T. , Wielgosz Robert I.
Published: November 2002

In this communication, we show how the established principles of the International System of Units (SI) can be used to develop a basis for stable, comparable and coherent measurements of isotope ratios by mass spectrometry. We show that there are no important differences in the traceability of quantities that represent ratios of the abundance of isotopes and those that represent fractions. However, it is important to distinguish between results expressed in ‘absolute’ terms and those expressed relative to stated references such as those expressed in terms of the commonly used quantity ‘delta’. © Crown copyright 2002. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.
Making an honest measurement scale out of the oxygen isotope δ‐values
Authors: Gat Joel R. , DeBievre Paul
Published: November 2002

The differential measurement of the abundance of oxygen isotopes based on reference materials, such as VSMOW for the case of water, was used because the precision of the absolute mass‐spectrometric determination of the abundance fell short of the differences to be measured. Since then these measurements have been much improved, so that a calibration scheme of the oxygen isotope abundance in water, carbonates, silica, phosphates, sulfates, nitrates and organic materials is suggested, based on an accredited primary standard of oxygen in air and using standard fluorination and O2 to CO2 conversion techniques. Copyright © 2002 John Wiley & Sons, Ltd.
Rhetoric and reality in the allocation of water to the environment: a case study of the Goulburn River, Victoria, Australia
Authors: Ladson Anthony , Finlayson Brian
Published: November 2002

In the Goulburn River, located in Victoria (Australia), dams and diversions for irrigation have modified streamflows and water temperature, and contributed to environmental degradation that includes declining native fish populations.

With the passage of a new Water Act in 1989, the Victorian Government proposed to address environmental and water allocation issues through the development of tradeable water entitlements. Initially, these had a strong environmental focus and were to be allocated within an adaptive management framework that involved monitoring and evaluation to refine the total allowable diversion to sustainable levels. The actual specification of tradeable water entitlements for the Goulburn River, undertaken in 1995, differed substantially from those early proposals. Entitlements were largely based on historical use with limited and ineffective allocation of water to the environment because water temperature was not considered. A water market has been established but market failure is likely to result in an under‐allocation of water to the environment. Access to the market is restricted except to irrigation authorities and water users, and transaction costs and uncertainties in environmental requirements reinforce the status quo in water allocation which is dominated by production values. Copyright © 2002 John Wiley & Sons, Ltd.
Von Willebrand Factor Expression in a Shiga Toxin-mediated Primate Model of Hemolytic Uremic Syndrome
Authors: Pysher Theodore J. , Siegler Richard L. , Tesh Vernon L. , Taylor Fletcher B.
Published: November 2002

von Willebrand Factor (vWF) is stored and released from activated or damaged endothelial cells and platelets, and its multimers have considerable prothrombotic properties. To investigate the role of vWF in the pathogenesis of post-diarrheal (D+) hemolytic uremic syndrome (HUS), we used a baboon model to study vWF expression following the intravenous administration of 100 ng/kg of Shiga toxin 1 (Stx 1), given either as a single dose, or as four divided doses, with and without lipopolysaccharide (LPS). vWF antigen was measured in plasma and urine obtained at 0, 12, 24, 36, 48, and 60 h by enzyme-linked immunosorbent assay (ELISA), and immunohistochemical expression of vWF in renal tissue obtained at autopsy was quantified by image analysis. Animals that received the single dose of Stx 1, or the four divided doses of Stx 1 plus LPS uniformly developed HUS, but those that received divided doses of Stx 1 without LPS, or LPS alone did not. Plasma vWF levels rose significantly in animals that received LPS, with or without Stx 1; but not in those that received Stx 1 alone. Urine vWF levels were generally undetectable. vWF expression was greater in renal tissue of animals that developed HUS than in those that did not, and was seen in both glomeruli, and, especially, peritubular capillaries. Since HUS developed in animals that did not experience a rise in plasma vWF levels, it does not appear that LPS-mediated systemic vWF release is essential to the pathogenesis of HUS in our model. The renal tissue findings, however, suggest a role for Stx-mediated intrarenal vWF release in the acute nephropathy of D+ HUS.
Tuberous Sclerosis in a 19-Week Fetus: Immunohistochemical and Molecular Study of Hamartin and Tuberin
Authors: Wei Jianjun , Li Peng , Chiriboga Luis , Mizuguchi Masashi , Yee Herman , Miller Douglas C. , Greco M. Alba
Published: November 2002

Tuberous sclerosis complex (TSC) is a genetically heterogeneous disease caused by mutations of TSC1 or TSC2 genes. It involves multiple organ systems resulting in mild to lethal hamartoma formation due to gene mutation in the germ line and loss of heterozygosity (LOH) in somatic cells. Hamartin ( TSC1) and tuberin ( TSC2) are expressed broadly. However, little is known about tissue susceptibility to hamartomas when equal or similar amounts of TSC gene expression are present. In this study, we present a 19-week gestational age fetus with pathological features of TSC, which was confirmed by finding LOH of TSC2 in a cardiac rhabdomyoma. Developmental expression of hamartin and tuberin in the TSC fetus, an age-matched non-TSC fetus, and a 26-week gestational age non-TSC fetus were analyzed by immunohistochemistry. We found that in addition to the differential expression of the TSC genes in some normal tissues compared with that in the TSC-affected fetus, the cellular localization and distribution of hamartin and tuberin were dramatically different in different tissues. In general, hamartin and tuberin are mainly expressed in epithelial cells, myocytes, and neural tissues. By comparing the incidence of the hamartomas in early childhood and gene expression in tissues, it appears that tissues with co-expression of hamartin and tuberin are prone to a higher incidence of hamartomas than those expressing only one protein, or two proteins but in different patterns of cellular localization.
Value of the Perinatal Autopsy: Critique
Authors: Gordijn Sanne J. , Erwich Jan Jaap H. M. , Khong T. Yee
Published: November 2002

In consenting to a perinatal autopsy, the primary motive of parents may be to find the exact cause of death. A critical review on the value of perinatal autopsies was performed to see whether parents could be counseled regarding their main motive. A literature search was performed in MEDLINE, EXCERPTA MEDICA, and the Cochrane library. We evaluated the value of the autopsy by comparing the clinical and autopsy diagnoses in stillbirths, neonatal deaths, and therapeutic terminations. Clinicopathologic concordance was divided into four categories: (1) change in diagnosis, (2) additional findings, (3) complete confirmation, and (4) inconclusive. We sought information on factors that may influence the value of perinatal autopsies: the type and definitions of perinatal loss; autopsy rate; level of hospital; expertise of pathologists; autopsy protocol used; whether patients were inborn or referred; and antenatal diagnosis. From the 27 articles that met our review criteria, the autopsy revealed a change in diagnosis or additional findings in 22% to 76% of cases. If confirmation of clinical findings is included, then the value of the perinatal autopsy was as high as up to 100%. Factors that could influence this rate were reported variably by investigators. When centers report their experience of the value of the perinatal autopsy, information on the factors that may influence their reports should be provided as well. Clinicians can confidently advise parents of the usefulness of the perinatal autopsy in ascertaining the cause of death or for counseling their future pregnancies.
Expression of Apoptosis-related Antigens, Fas, bcl-2, p53, and Mib-1 Proliferation Index in the Hypoplastic Thymus of DiGeorge Syndrome
Authors: Zhou Holly , Perkins Sherrie L. , Tripp Sheryl , Hussong Jerry W. , Coffin Cheryl M.
Published: November 2002

Apoptosis, along with cellular proliferation, plays a major role in normal developmental processes and tissue homeostasis. We hypothesized that altered apoptosis-related pathways and/or reduced cell proliferation might play a role in the thymic hypoplasia or aplasia in Di-George syndrome (DG). We used immunohistochemistry to evaluate the apoptosis-related antigens Fas (CD95), bcl-2, and p53, as well as Mib-1 proliferation index in the thymuses from six patients with DG. The results were compared with those from the thymuses from six patients with non-DG congenital heart disease. All DG patients (age 32 weeks GA to 4 months) had hypoplastic thymuses ranging from microscopic foci to 2.7 g in weight (expected for age, 4.7 ± 3.6 g to 10 ± 6 g). The thymic weights from the patients with non-DG congenital heart disease (age 37 weeks GA to 1 month) ranged from 3 to 5.6 g and were at the lower range of expected weight by age (expected for age, 8.4 ± 5.6 g to 12 ± 7 g). All thymuses showed histologic features of stress-induced involution. In both groups, a ≥ 50% Mib-1 proliferation index was found in the cortical thymocytes, whereas < 5% Mib-1 labeling was seen in the medullary thymocytes; Fas stained medullary epithelial cells (3+) and cortical epithelial cells (1 +); bcl-2 stained medullary thymocytes (3+) and cortical thymocytes (1+); p53 stained less than 1% of nuclei in all sections. No significantly altered Mib-1 proliferation index or expression of Fas, bcl-2, and p53 was observed in the hypoplastic thymuses in DG, compared to these same measures in non-DG. These results suggest that thymic hypoplasia in DG may be mediated by mechanisms other than reduced cellular proliferation and/or altered Fas, bcl-2, and p53 apoptotic pathways.
Cortisol and cardiovascular reactions to mental stress and antibody status following hepatitis B vaccination: A preliminary study
Authors: Burns Victoria E. , Ring Christopher , Drayson Mark , Carroll Douglas
Published: November 2002

This study examined possible neuroendocrine mechanisms underlying the association between stress and antibody response to vaccination. Hepatitis B antibody titers were obtained, and salivary cortisol and cardiovascular activity measured during baseline, mental arithmetic, and recovery in 30 undergraduates. It was hypothesised that higher reactivity would be associated with poorer antibody status. Compared to individuals with high antibody titers, those with low titers had significantly lower cortisol levels throughout, exhibited a significantly attenuated end‐of‐task reduction in cortisol relative to resting baseline, and had larger cardiac output and inotropic reactions, but smaller increases in total peripheral resistance, to mental arithmetic. In sum, variations in indices of both hypothalamic pituitary adrenocortical axis and sympathetic nervous system activity were associated with individual differences in immune response to vaccination.
The role of psychophysiology in clinical assessment: ERPs in the evaluation of memory
Authors: Allen John J.B.
Published: November 2002

Psychophysiological measures hold great potential for informing clinical assessments. The challenge, before such measures can be widely used, is to develop test procedures and analysis strategies that allow for statistically reliable and valid decisions to be made for any particular examinee, despite large individual differences in psychophysiological responding. Focusing on the evaluation of memory in clinical, criminal, and experimental contexts, this paper reviews the rationale for and development of ERP‐based memory assessment procedures, with a focus on methods that allow for statistically supported decisions to be made in the case of a single examinee. The application of one such procedure to the study of amnesia in Dissociative Identity Disorder is highlighted. To facilitate the development of other psychophysiological assessment tools, psychophysiological researchers are encouraged to report the sensitivity and specificity of their measures where possible.
Cardiovascular patterns associated with threat and challenge appraisals: A within‐subjects analysis
Authors: Quigley Karen S. , Barrett Lisa Feldman , Weinstein Suzanne
Published: November 2002

Previous studies demonstrated distinct cardiovascular patterns associated with threat and challenge appraisals for groups of participants. We extend these results by assessing whether appraisals continue to be associated with these cardiovascular response patterns within an individual as appraisals change. Participants completed four verbal mental arithmetic tasks for which they made appraisals before and after each task. Cardiac reactivity and total peripheral resistance (TPR) were calculated for the first and last minutes of each task, and the number of responses and percent correct were measured for each task. In line with our prediction, pretask appraisals were related to some task‐related cardiac responses across the four tasks. In addition, task‐related cardiovascular reactivity and behaviors both influenced appraisals following the task. Our findings suggest that an idiographic analysis of appraisals, cardiovascular physiology, and task‐related behaviors provides a richer understanding of the appraisal process and reveals sex differences deserving further assessment.
The relationship of age and cardiovascular fitness to cognitive and motor processes
Authors: Hillman Charles H. , Weiss Edward P. , Hagberg James M. , Hatfield Bradley D.
Published: November 2002

Older and younger aerobically trained and sedentary adults participated in an S1‐S2‐S3 paradigm designed to elicit event‐related potential (ERP) and behavioral responses to determine the influence of cardiovascular fitness on cognitive and motor processes. The paradigm provided warning (S1) as to the difficulty level of an upcoming decision task (S2). Participants had to decide the taller of two bars on presentation of S2 but hold their response until S3, to which they indicated their choice motorically. Results revealed age‐related differences for ERP measures as older participants showed increased amplitude of the stimulus preceding negativity (SPN) prior to S2, and longer latencies and equipotentiality of P3 in response to S2. Fitness effects were also observed for the contingent negative variation (CNV) with decreased amplitude for fit relative to sedentary individuals. Age interacted with fitness for P3 latency to S2 as older sedentary individuals showed the longest latency followed by older fit and both younger groups. No significant group differences were observed for reaction time (RT) to S3. Therefore, physical fitness is associated with attenuation of cognitive decline in older individuals and greater economy of motor preparation for both young and older participants.
Attentional modification of short‐lead prepulse inhibition and long‐lead prepulse facilitation of acoustic startle among preadolescent boys
Authors: Hawk Larry W. , Pelham William E. , Yartz Andrew R.
Published: November 2002

In adults, short‐lead prepulse inhibition and long‐lead prepulse facilitation of startle are greater during attended than ignored prestimuli. To examine these phenomena in children, fourteen 9‐ to 12‐year‐old boys completed a tone discrimination task in two sessions separated by 1 week. During each tone series, participants attended to one pitch and ignored the other. Startle probes (102 dB) were presented 120, 240, 2,000 or 4,500 ms following the onset of two‐thirds of tones, and during one‐third of intertrial intervals. Eyeblink EMG startle was recorded. Percent prepulse inhibition at 120 ms was greater for attended than ignored stimuli in Session 1 but not Session 2. Long‐lead prepulse facilitation was marginally greater for attended than ignored tones and did not vary across sessions. Test–retest reliability was moderate during attended prestimuli but was modest during ignored prestimuli. Reliability of attentional modification was poorest at 120 ms and strongest at 4,500 ms. Overall, this study extended prior work in adults and provided a basis for further study of controlled attentional modification of startle in children.
Covariations of EEG asymmetries and emotional states indicate that activity at frontopolar locations is particularly affected by state factors
Authors: Papousek Ilona , Schulter Günter
Published: November 2002

To test the hypothesis that activation asymmetries of the most anterior parts of the prefrontal cortex may be related to state‐dependent regulation of emotion, spontaneous changes of cortical activation asymmetries from one session to a second one were related to spontaneous mood changes in two large samples (ns = 56 and 128). The interval between sessions was 2 to 4 weeks. Results show that mood changes specifically covary with changes of EEG asymmetry at the frontopolar electrode positions, but not with changes at other locations (dorsolateral frontal, temporal, and parietal). Anxiety, tension, and depression were found to decrease when frontopolar activation asymmetry shifted to the right. Taking the new findings into account may contribute to the refinement and extension of theories on EEG laterality and emotion.
Driver fatigue: Electroencephalography and psychological assessment
Authors: Lal Saroj K.L. , Craig Ashley
Published: November 2002

Fatigue has major implications for transportation system safety; therefore, investigating the psychophysiological links to fatigue could enhance our understanding and management of fatigue in the transport industry. This study examined the psychophysiological changes that occurred during a driver simulator task in 35 randomly selected subjects. Results showed that significant electroencephalographic changes occur during fatigue. Delta and theta activity were found to increase significantly during fatigue. Heart rate was significantly lower after the driving task. Blink rate also changed during the fatigue task. Increased trait anxiety, tension–anxiety, fatigue–inertia and reduced vigor–activity were shown to be associated with neurophysiological indicators of fatigue such as increased delta and theta activity. The results are discussed in light of directions for future studies and for the development of a fatigue countermeasure device.
Difficulty does not account for emotion‐specific heart rate changes in the directed facial action task
Authors: Levenson Robert W. , Ekman Paul
Published: November 2002

Boiten (1996) used the Directed Facial Action task (a task we developed in which participants follow instructions, based on theory about how emotion is expressed in the face, to move facial muscles deliberately to produce different facial configurations) to investigate heart rate differences among six emotional configurations. Boiten's findings closely replicated ours (Levenson, Ekman, & Friesen, 1990) in terms of heart rate change, self‐reported emotion, and rated difficulty during the configurations. Boiten concluded that differences in difficulty were responsible for found differences in heart rate; in contrast, we had concluded that heart rate findings could not be explained in this manner. In this paper, we argue that neither Boiten nor we did the critical analyses needed to determine whether heart rate changes were mediated in this way. Performing these analyses, we conclude that neither reported difficulty nor two other potential mediators (time required to make the facial configurations; activity of nonfacial muscles) mediated the heart rate differences that we found between emotional configurations in the Directed Facial Action task.
Temporary and longer term retention of acoustic information
Authors: Winkler István , Korzyukov Oleg , Gumenyuk Valentina , Cowan Nelson , Linkenkaer‐Hansen Klaus , Ilmoniemi Risto J. , Alho Kimmo , Näätänen Risto
Published: November 2002

Though many studies suggest that fine acoustic details fade from memory after 15 s or even less, everyday experience tells us that the voice of a person or a musical instrument can be recognized long after it was last heard. We wished to determine whether tones leave a lasting memory trace using an experimental model of implicit recognition and testing whether exact pitch information can be retrieved even after 30 s. Event‐related brain potentials demonstrated the survival of an accurate representation of tone pitch in the auditory cortex. This result provides a link between short‐duration buffering and permanent storage of acoustic information.
Affective imagery and the startle response: Probing mechanisms of modulation during pleasant scenes, personal experiences, and discrete negative emotions
Authors: Miller Mark W. , Patrick Christopher J. , Levenston Gary K.
Published: November 2002

Two experiments addressed the following issues concerning modulation of the acoustic startle reflex during emotional imagery: (1) Is startle inhibited or potentiated during imagery of pleasurable events? (2) Does startle modulation differ for personal versus standard imagery scenes? (3) Is startle modulated differently during anger versus fear? For standard scenes, startle was greater during aversive than pleasant imagery, with both exceeding neutral. Blink potentiation was greater during imagery of personal pleasant than nonpersonal pleasant scenes. Startle potentiation did not differ for anger versus fear material, but differences were found in self‐report, corrugator EMG, and HR response. These results suggest that in addition to the emotional valence of imagined material, startle reactivity is influenced by the degree of engagement or active disengagement from the sensory environment. The findings also indicate that fear and anger are differentiable in terms of affective report, cardiac mobilization, and expressive behavior, but not at the primary motivational level at which reflex priming occurs.
The magneto-Rayleigh–Taylor instability in dynamic
z pinches
Authors: DOUGLAS M.R. , DE GROOT J.S. , SPIELMAN R.B.
Published: November 2002

The magneto-Rayleigh–Taylor (MRT) instability limits
the performance of dynamic z pinches. This instability
develops at the plasma-vacuum/field interface, growing in amplitude
throughout the implosion, thereby reducing the peak plasma velocity
and spatial uniformity at stagnation. MRT instabilities are
believed to play a dominant role in the case of high wire number
arrays, gas puffs and foils. In this article, the MRT instability
is discussed in terms of initial seeding, linear and nonlinear
growth, experimental evidence, radiation magnetohydrodynamic
simulations, and mitigating schemes. A number of experimental
results are presented, where the mitigating schemes have been
realized. In general, the problem is inherently three dimensional,
but two-dimensional simulations together with theory and experiment
enhance our physical understanding and provide insight into
future load design.
Electromagnetically induced transparency in plasma
Authors: ERSFELD B. , JAROSZYNSKI D.A.
Published: November 2002

The coupled propagation of two electromagnetic waves in plasma
is studied to establish the conditions for induced transparency.
Induced transparency refers to the situation where both waves
propagate unattenuated, although the frequency of one (or both)
of them is below the plasma frequency so that it could not
propagate in the absence of the other. The effect is due to
the interaction of the waves through their beat, which modulates
both the electron mass and, by exciting longitudinal plasma
oscillations, their number density, and thus the plasma frequency.
Starting from a relativistic fluid description, a dispersion
relation for plane waves of weakly relativistic intensities
is derived, which takes into account the polarization of the
waves and the nonlinearities with respect to both their amplitudes.
This serves as a basis for the exploration of the conditions
for induced transparency and the modes of propagation.
All-optical devices based on three-wave mixing for logic
and information processing
Authors: YAHALOMI EREZ.M.
Published: November 2002

A method of creating all-optical devices for logic information
processing is presented. The mechanism is based on virtual photon
interaction in quantum field description, or dipole moment
interaction in classical description. The device consists of
two optical information bits channels and one optical bits channel
of logic commands like AND, NOT, OR. A variety of logic operations
can be achieved on one optical setup by polarization change
of the logic bits which determines the logic commands. I present
another application for the method as an information channels
selector.
Laser wakefield acceleration in narrow plasma-filled channels
Authors: LOTOV K.V.
Published: November 2002

The wakefield acceleration driven by a single laser pulse in
a narrow plasma-filled solid waveguide is considered. Parameters
of the waveguide which provide the maximum energy gain of
accelerated particles at a given length and peak power of the
driver are found in the approximation of a relativistically
weak driver. The obtained formulas are illustrated by calculating
the electron energy gain achievable with the terawatt laser
of Utsunomiya University.
Brillouin backscattering instability in inhomogeneous
collisional plasma
Authors: SHALABI BASSAM , AL-KHATEEB AHMED
Published: November 2002

Brillouin backscattering instability is investigated in
inhomogeneous collisional plasma. The slow-coupling equations
for the instability in a medium with linear density ramp are
obtained. For large inhomogeneity scale length, the homogeneous
growth rate is found to be modified by a factor of

[1/square root(2) times square root(ω02/
(ω02 + νe2) +
ω0/square root(ω02 +
νe2))]

For the convective instability, the amplification factor is found to
be

[Λ = (|γB0|2/2β)(ω02/ω02 + νe2)]

The presence of collisions leads to a reduction in both the growth
rate and the amplification factor, where the threshold intensity for the
instability to occur increases.
Accurate timing of a particle beam using laser ablation
Authors: BALLARD A. , BONIN K.
Published: November 2002

We report on a new technique that we used to accurately time
the velocity of a cluster beam. It involves deflecting particles
away from their usual beam path by scattering with an ablation
plume. We were able to time the occurrence of a C60
cluster beam to better than 0.2%. This technique was critical
in recent light-force polarizabilities experiments.
Angular distribution of X-ray line radiation from
laser-irradiated planar targets
Authors: ARORA V. , CHAKERA J.A. , KUMBHARE S.R. , NAIK P.A. , GUPTA N.K. , GUPTA P.D.
Published: November 2002

A study of angular distribution of X-ray line radiation emitted
from a laser-produced plasma is presented. Plasma was produced
by irradiating a planar magnesium target using single laser
pulses of 6 J, 4.5 ns (FWHM) from an Nd:glass laser system.
Angular distribution of X-ray emission in the spectral range
of 7–10 Å was recorded using a single X-ray crystal
spectrograph. X-ray emission intensity for different resonance
lines is observed to decrease up to an angle of ∼45°
with respect to target normal, followed by a significant increase
at higher angles. The observed departure of angular distribution
from a monotonically decreasing behavior is broadly in agreement
with the calculations of the escape factor of the radiation
at different angles from a thick disk-shaped plasma using a
spectroscopic code RATION.