bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study of the Rotational Distribution Function of Nitrogen in a Shock Wave
Authors: Robben F. , Talbot L.
Published: December 2004

The electron beam fluorescence technique has been used to measure the rotational energy distribution through shock waves in nitrogen. At Mach 1.7 the deviation from thermodynamic equilibrium was found to be small, and the rotational temperature profile followed the density profile. Comparison with theoretical calculations yielded the rotational relaxation collision number ZR = 5, in satisfactory agreement with other determinations. At high Mach numbers the measured rotational distribution function within the shock wave could not be represented by a single temperature, but was found to be representable approximately by the merging of two rotational distribution functions corresponding to temperatures upstream and downstream of the shock wave. The profile of the average local ``temperature,'' defined by the ratio of the total measured rotational energy to the gas density, was found to precede the density profile through the shock wave by an amount which increased with Mach number.
Hypersonic Adiabatic Impact Pressure of a Rarefied Gas
Authors: Edwards R. H. , Quan Victor
Published: December 2004

A solution to the Boltzmann equation for the Pitot tube problem is formulated. The distribution function is taken as a sum of two separate distribution functions, one of which is characteristic of the molecules coming from the free stream and the other of the molecules emerging from the tube wall. Each distribution function is further divided into quadrants in the velocity space. The local variables are the number densities in these quadrants and are determined by taking appropriate moments of the Boltzmann equation. Governing equations for the flow of a rarefied gas in an impact tube under hypersonic and adiabatic conditions are derived. Approximate closed form solution to these equations is obtained. The results are in close agreement with other theories for the free molecule limit and with experimental data for finite mean free paths.
Thermal Conductivity of Gaseous Ammonia at Different Temperatures
Authors: Srivastava B. N. , Gupta A. Das
Published: December 2004

Thermal conductivity of the polar gas ammonia at a pressure of 18 cm of Hg has been measured over the temperature range 38–200°C by the hot-wire method. With the help of a theory recently put forward by Mason and Monchick, the collision numbers for rotational relaxation Zrot have been determined from the experimental data. The values thus obtained show that Zrot increases with rise of temperature.
Flute Instability at Low Density
Authors: Simon Albert , Rosenbluth Marshall N.
Published: December 2004

Some of the results of a previous paper [M. N. Rosenbluth and A. Simon, Phys. Fluids 8, 1300 (1965)] are extended to low plasma densities. The proper macroscopic equations for use with a weakly unstable plasma are listed, and the differential equation for stability analysis is derived. In the moderate density regime, this leads to a variational principle and a sufficiency condition. In a special case, this becomes a minimization principle analogous to the δW one. At very low densities, the effect of a nonuniform electric field on a marginally stable system is considered, and it is shown that stabilization depends only on the second spatial derivative of E, a result which has a simple drift interpretation, and which may have some relevance to observations in ``OGRA'' and ``Phoenix.''
Pressure Wave Generation in a Fissioning Gas, III: Amplification of the Pressure Pulse with Helium 3 as Driver
Authors: Busch C. W. , Oppenheim A. K. , Smith H. P.
Published: December 2004

Use of He3 is associated with highest specific energy released in gaseous fission, but amplitude of resulting pressure wave is small. This can be ameliorated by use of heavier gases in driven section, yielding interesting means for amplification of pressure pulse.
Size of Ice Crystals Formed during Rapid Expansion of Humid Air
Authors: Thomann H.
Published: December 2004

The size of the ice crystals formed during the expansion of humid air in a supersonic nozzle is determined by analyzing samples sucked into Pitot probes. Small probes read a higher humidity than is present in the free stream. This increase is a measure of the inertia of the crystals, and thus of their size. For spherical crystals, a radius of 15 Å (1.5 × 10−9m) is predicted which means that a crystal contains about 360 molecules. This result is confirmed by measuring the evaporation rate of crystals behind normal shocks. It is further found that the particles are of fairly uniform size. No variation of the size with humidity was found for water concentrations below 2 × 10−3.
Hall Currents in Magnetohydrodynamic Shock Waves
Authors: Leonard B. P.
Published: December 2004

The steady-state structure of magnetohydrodynamic shock waves in a slightly ionized gas is discussed. Both scalar and tensor conductivity cases are considered, and the magnetic diffusivity is taken to be much greater than both the viscous and thermal diffusivities. These properties lead naturally to the application of a singular perturbation technique for finding the structure of the magnetic layer, in which imbedded viscous and thermal sublayers may appear in the form of discontinuities. Numerical solutions are obtained for a variety of typical cases. Hall currents are found to give rise to a spiraling magnetic field component, whereas in scalar conductivity shocks the magnetic field remains in a single plane.
Flow around a Nonconducting Sphere in a Current-Carrying Fluid
Authors: Chow Chuen-Yen
Published: December 2004

The creeping flow caused by a nonconducting sphere in an incompressible, viscous fluid carrying an otherwise uniform electric current is investigated analytically. For a stationary sphere the fluid motion is found to be induced from the upstream and downstream directions of the current toward a plane which passes through the center of the sphere and is perpendicular to the current at infinity. For a sphere moving slowly in a direction parallel to the current far away, a reverse-flow region is formed behind the body. It is also found that the electromagnetic field does not affect the drag of a moving sphere.
Prekinetic Equations for a Plasma
Authors: Özizmir Ercüment , Imre Kaya
Published: December 2004

Bogoliubov theory for a multicomponent plasma is generalized through relaxation of his assumptions regarding the functional dependence and the ``initial condition'' to obtain a theory within which the approach to the kinetic regime can be studied. It is assumed that the correlations Gl(l > s) are functionals of G1,…, Gs and eτHGl(e−τHG1,…, e−τHGs) → 0 as τ → ∞, where H is the Poisson bracket operator corresponding to the kinetic energy and s(≥ 1) is a fixed but otherwise arbitrary integer. It is shown that the analytic solution of the resulting functional chain with respect to the parameters α = nλ1/s, β = λ1/s (where n is the density and λ is the interaction strength) is of order βl−s provided G1,…, Gs are of order β0. This property enables one to break the hierarchy in the expansion with respect to β only. The time and length scales for which the treatment is valid for a given s are discussed. The case s = 2 which leads to the ``prekinetic'' equations is considered in some detail. The closed coupled set of equations for G1 and G2 obtained in this case differ from those studied in the literature through appearance of the double pair correlations in the equation for G2, which makes the latter equation non-linear.
Stability of the Poiseuille Plasma Arc in an Axial Magnetic Field
Authors: Yuen Man Chuen
Published: December 2004

The instability of the positive column of an atmospheric argon Poiseuille plasma arc in an axial magnetic field of the order of 100 G was studied both experimentally and theoretically. The instability was manifest as a helical oscillation of the conducting core. The neutral stability curves of frequency versus applied magnetic field for various arc currents and flow rates were obtained by studying the growth or decay of artificially created helical disturbances. The wavelengths of the helix at neutral stability were measured. The critical magnetic fields for the naturally excited oscillation were measured and found to be higher than that at neutral stability. A linearized stability analysis was developed. The theoretical results predict well the frequency and the shape of the neutral stability curves. From both the experiment and the theory, it was found that the destabilizing force is the J × B force and the stabilizing mechanisms are the viscous and the thermal effects.
Reflection of a Shock Wave at a Surface
Authors: Scala Sinclaire M. , Gordon Paul
Published: December 2004

A new finite difference method is employed in obtaining numerical solutions for the complete Navier-Stokes equations. The physical problem treated is the time-dependent propagation of a one-dimensional disturbance, which is produced by the forward motion of a piston through a compressible, viscous, thermally conducting, perfect diatomic gas and its subsequent reflection at a material surface. Two values of disturbance strength are considered, including weak and strong shock waves. The quantities determined include the variation of gas velocity, pressure, density, and temperature as a function of time and distance. In addition, the heat transfer rate and the pressure, which are of considerable interest in the interpretation of shock tube phenomena, are determined at the surface during the period of reflection of the shock wave.
Excluded Volume in a Fluid of Particles with Rigid Cores
Authors: De Rocco Andrew G.
Published: December 2004

A simple model for excluded volume in a fluid of hard spheres is employed to study the relationship of the van der Waals and Bragg-Williams equations of state. The set of phase states {Ṽ} defined by Ṽj = V − (j − 1)ω (j = 1, 2, …, N), where ω is twice the usual covolume, is used to evaluate the configurational partition function in two distinct ways. It is observed that a product over {Ṽ} leads to the Bragg-Williams result while a sum over {Ṽ} corresponds to the answer of van der Waals. These observations are discussed in connection with the applicability of the results to fluids and solids. Additional material on a gas of hard-(lines, squares, cubes) is presented in terms of a density expansion of the configurational partition function. This expansion is found to be no easier to interpret than the conventional cluster integrals themselves.
Interaction Models, Negative Energy Waves, and Electrostatic Instabilities
Authors: Hall Laurence S. , Heckrotte Warren
Published: December 2004

It has been possible to introduce certain physical interpretations for the various contributions which a given species may make to the total dispersion relation for electrostatic instabilities of an anisotropic magnetized plasma. These interpretations are helpful in developing one's physical intuition regarding such instabilities. One appropriate specialization is the use of a physical model of the interaction of a distribution of particles with an imposed wave for the case in which the wave is set up primarily by a species other than that which drives the instability. Conversely, when the cooperative nature of the driver species is dominant, it is natural to describe its properties in terms of negative energy waves. The discussion shows the connection between these viewpoints as special cases of our more general description.
Transmission and Reflection of Electromagnetic Waves Normally Incident on a Warm Plasma
Authors: Comstock Craig
Published: December 2004

The solution for an electric field normally incident onto a warm, semi-infinite plasma is obtained by means of a modified Wiener-Hopf technique. The warm plasma is taken into account by means of the relativistic Vlasov equation. It is found that the previously obtained solution of Taylor gives the correct term for the wavenumber in the plasma, but not the correct answer for the field. It is shown that the method of considering an ``equivalent'' fully infinite plasma corresponds to a physically unrealistic matching of the plasma to the vacuum. The field inside the plasma is found. The field just inside the plasma is discussed, and the nonuniform limit from warm to cold plasma found by Taylor is not found in our solution.
Propagation and Damping of Ion Waves in a Plasma with Negative Ions
Authors: D'Angelo N. , Goeler S. v. , Ohe T.
Published: December 2004

The ion waves split up into two modes of propagation; if the fraction of negative ions is large, the collisionless damping of the faster mode is weak.
Plasma Wave Propagation in Hot Inhomogeneous Media
Authors: Berk H. L. , Rosenbluth M. N. , Sudan R. N.
Published: December 2004

The WKB solution for plasma wave propagation is obtained for the one-dimensional Vlasov equation. In principle, a solution can be obtained to all orders in the smallness parameter.
Orthogonal Polynomial Solution of the Boltzmann Equation for a Strong Shock Wave
Authors: Radin Shelden H. , Mintzer David
Published: December 2004

The structure of a strong shock wave in a neutral, monatomic gas is studied here using the generalized orthogonal polynomial method of solution of the Boltzmann equation suggested by Mintzer. Mott-Smith's bimodal distribution function, with the shock thickness X(M) left arbitrary, is used as the weight function to generate the orthogonal polynomials of the expansion. This automatically makes Mott-Smith's distribution function the zeroth- and first-approximation distribution functions without specification of X(M). In the second approximation a particular choice of X(M) must be made in order that the equations have a unique solution which represents a shock wave and, with that choice of X(M), predictions are made only for Mach numbers above 2.14. The X(M) thus determined is the same as obtained by Mott-Smith by transporting cx2, but with the restriction to Mach numbers above 2.14.
A Mott-Smith Distribution to Describe the Structure of a Plane Shock Wave in a Binary Mixture
Authors: Oberai M. M.
Published: December 2004

The problem of the shock wave structure in a binary mixture is restudied in view of an inconsistency in the postulates of an earlier paper. Assuming a bimodal distribution—a supersonic and a subsonic mode—for each component gas, it is observed that, for consistency, the flow velocity and temperature of the subsonic mode must be postulated as functions of position. Explicit calculations are given for the case when the initial mixture contains only a small fraction of the second gas. The results for this case are found not to differ much from earlier results.
Electron Beam Studies of the Diffusive Separation of Helium-Argon Mixtures
Authors: Rothe Dietmar E.
Published: December 2004

A narrow electron beam was used to selectively determine the component densities in rarefied helium-argon flows by spectrally analyzing the beam's luminescence. After a systematic study of the electron beam fluorescence in helium and argon had been made in a series of preliminary experiments, point-by-point measurements were made along and off the axes of underexpanded free jets and through normal shock waves produced by shock holders placed in the jets. Various argon mole fractions were used, and the jet Reynolds numbers ranged from 100 to 10 000. The argon enrichment found along the jet axis agrees well with a theory recently proposed by Sherman. Off-axis tests show an argon deficiency near the jet boundary. The experimental shock profiles agree only qualitatively with one-dimensional theories. Radial diffusion destroyed the otherwise approximate one-dimensionality of the shock waves, resulting in a significant argon enrichment inside the partially stagnated shock holder.
Cold-Plasma Effects in Finite-Length Plasmas
Authors: Guest G. E. , Beasley C. O.
Published: December 2004

Criteria are derived for the relative cold-plasma density necessary to stabilize the grad B drift waves in finite-length energetic plasmas separated from grounded conducting end plates by a cold plasma. For a dense (ω2pi≫ω2ci) hot-electron plasma in which the electron precession frequency, ωge≪ωci, the ion gyrofrequency, it is found that (Ncold/Nhot)critical ∼ 2l2(ωge/ωci)(LhLc/2R2p)m/M, where k⊥ = l/Rp. If lωge ∼ ωci, the corresponding criterion is very roughly given by (Ncold/Nhot)critical∼(l2/δ)(LhLc/2Rp2)(m/M),where 0 < δ = 1 − (lωge/ωci) < 1. For hot-ion plasmas, a two-dimensional stability diagram is given which predicts a high-density stable regime for small ratios of Ncold/Nhot. A tentative comparison with thresholds observed in several experiments is made.
Computer Experiment of Anomalous Diffusion
Authors: Hockney R. W.
Published: December 2004

A computer model of the diffusion of a fully ionized plasma across a constant magnetic field is described. The two-dimensional motion of one thousand charged rods is followed as they move according to Newtons law of motion under the action of their mutual electrostatic forces. A square region is considered which is perpendicular to a constant magnetic field. Plasma rods are injected thermally from one side of the square, and the transport of rods to the opposite side is observed. The model is virtually collisionless, and the observed diffusion can be attributed to the effect of the coherent electric field arising from the spontaneous growth of plasma instabilities. The magnitude of the diffusion is given by the Bohm drain diffusion formula. The dominant instability is an m = 1 drift wave which occurs when the electron drift motion is in synchronism with an electrostatic ion wave. The results of the calculation have been displayed in a short two-minute movie which shows the time variation of the potential surface.
The U
L
41 protein of herpes simplex virus mediates selective stabilization or degradation of cellular mRNAs
Authors: Esclatine Audrey , Taddeo Brunella , Roizman Bernard
Published: December 2004

The U
L
41 protein of herpes simplex virus 1 has been reported to mediate the degradation of both viral and cellular mRNAs. Extensive studies on β-actin and some viral mRNAs were consonant with this conclusion. In earlier studies, we reported that the U
L
41-dependent degradation of cellular mRNAs up-regulated after infection was selective. One class of the up-regulated mRNAs, exemplified by the stress-inducible immediate-early 1 mRNA, is deadenylated, 3′ to 5′ degraded and is not translated. Another class of up-regulated mRNAs, exemplified by GADD45β, does not undergo this pattern of degradation and is translated. A puzzling feature of the earlier results is that the amounts of up-regulated mRNAs accumulating in the cytoplasm of ΔU
L
41 mutant virus-infected cells was lower than in WT virus-infected cells, a contradiction, inasmuch as if the rates of accumulation were identical and degradation of the mRNAs were higher in WT virus-infected cells, the steady-state levels should have been higher in ΔU
L
41 mutant virus-infected cells. In this report, we show that in ΔU
L
41 mutant virus-infected cells, the rates of degradation of the stress-inducible immediate-early response gene 1 and other up-regulated mRNAs are approximately the same as those observed in mock-infected cells and are faster than in WT virus-infected cells. This is contrary to the observed U
L
41-dependent degradation of β-actin and other mRNAs. The U
L
41 protein thus mediates two functions, i.e., it mediates rapid degradation of some mRNAs exemplified by β-actin and stabilizes or delays the degradation of other mRNAs exemplified by GADD45β, tristetraprolin, etc. A model unifying both activities of the U
L
41 protein is presented.
The Audit Commission: guiding, steering and regulating local government
Authors: Kelly Josie
Published: December 2004

How does the non‐executant state ensure that its agents are fulfilling their obligations to deliver nationally determined policies? In the case of elected local government in England and Wales, this function is carried out by the Audit Commission (AC) for Local Authorities and the Health Service for England and Wales. Since being established in 1983, it is the means by which local authorities are held to account by central government, both for its own purposes and on behalf of other interested stakeholders.

Although the primary function of the AC is to ensure that local authorities are fulfilling their obligations, it does so by using different methods. By acting as a regulator, an independent expert, an opinion former and a mediator, the AC steers local authorities to ensure that they are compliant with the regulatory regime and are implementing legislation properly.
On Quantum Statistical Inference
Authors: Barndorff-Nielsen Ole E. , Gill Richard D. , Jupp Peter E.
Published: December 2004

Interest in problems of statistical inference connected to measurements of quantum systems has recently increased substantially, in step with dramatic new developments in experimental techniques for studying small quantum systems. Furthermore, developments in the theory of quantum measurements have brought the basic mathematical framework for the probability calculations much closer to that of classical probability theory. The present paper reviews this field and proposes and interrelates some new concepts for an extension of classical statistical inference to the quantum context.
Accommodating Stochastic Departures from Percentile Invariance in Causal Models
Authors: Dobbin Kevin K. , Louis Thomas A.
Published: December 2004

Consider a clinical trial in which participants are randomized to a single-dose treatment or a placebo control and assume that the adherence level is accurately recorded. If the treatment is effective, then good adherers in the treatment group should do better than poor adherers because they received more drug; the treatment group data follow a dose–response curve. But, good adherers to the placebo often do better than poor adherers, so the observed adherence–response in the treatment group cannot be completely attributed to the treatment. Efron and Feldman proposed an adjustment to the observed adherence–response in the treatment group by using the adherence–response in the control group. It relies on a percentile invariance assumption under which each participant’s adherence percentile within their assigned treatment group does not depend on the assigned group (active drug or placebo). The Efron and Feldman approach is valid under percentile invariance, but not necessarily under departures from it. We propose an analysis based on a generalization of percentile invariance that allows adherence percentiles to be stochastically permuted across treatment groups, using a broad class of stochastic permutation models. We show that approximate maximum likelihood estimates of the underlying dose–response curve perform well when the stochastic permutation process is correctly specified and are quite robust to model misspecification.
Monopolistic Competition, Increasing Returns and International Coordination of Entry Policy
Authors: Ohyama Michihiro
Published: December 2004

This paper presents a new model of monopolistic competition in which firms produce differentiated products under decreasing costs. This model is used to confirm and illustrate the limitations of the excess entry hypothesis, well known in the literature on industrial organization. The validity of the theorem is limited in the sense that it fails to hold in the present model if the properly defined degree of love for variety is sufficiently large. The model is extended to allow for intraindustry trade and to examine the conditions for gains (or losses) from trade in a two‐country framework. It is shown how the degree of love for variety affects them. The significance and nature of international coordination of competition policy in the present setting is considered. The degree of love for variety is again shown to be of crucial importance in the characterization of the optimal policy coordination.
Six Weeks at Hawkspur Green: A Pacifist Episode during the Battle of Britain
Authors: Brock Peter
Published: December 2004

In early summer 1940 a small group of pacifist undergraduates from the universities of Oxford and Cambridge had formed a Universities Ambulance Unit. They started training for medical work in June as the Battle of Britain got under way; their training camp, situated at Hawkspur Green near London, lasted for about six weeks. The intellectual caliber of the group was indeed extremely high, though this did not entail necessarily medical efficiency! The unit aimed at providing a service alternative for “unchurched” pacifists liable for military service. Among the campers was Canadian George Grant, later a prominent philosopher, and his letters home provide insight into life at Hawkspur Camp. No camp records exist, but in their old age several ex‐campers have reflected on this “remarkable episode” in their careers. In fact, however, the unit never became a reality. Some ex‐campers eventually joined the armed forces; others engaged in relief work in the London Blitz or some other form of alternative service. The author perceives three significant aspects in the Hawkspur experience: youthful rebellion against war, vanished fellowship, and lost innocence.
Der Markt für Venture Capital: Anreizprobleme, Governance Strukturen und staatliche Interventionen
Authors: Gebhardt Georg , Schmidt Klaus M.
Published: December 2004

In this paper we give an overview, with special emphasis on Germany, of the recent development of the market for venture capital. We analyse the financial contracting problems that arise when entrepreneurs need capital from outside investors, and demonstrate how these problems are addressed by the institutions and contracts observed in the market for venture capital. Finally, we discuss the arguments in favour of government subsidies for private R&D, and argue that there are positive incentive effects if these subsidies are given to venture capital financed projects, rather than to established firms.
The contralateral organization of visual memory: A theoretical concept and a research tool
Authors: Gratton Gabriele
Published: December 2004

Contralateral‐control methods can be applied to psychophysiology and in particular to the study of visual memory. Visual memory possesses some degree of hemispheric organization, so that visual memory traces for laterally presented stimuli are stronger or more durable in the hemisphere contralateral to the hemifield where the stimuli were first presented. I first introduce the concept of hemispheric organization of function. Then I discuss how hemispheric organization can be exploited for obtaining information about the time course and brain localization of psychological processes, using a contralateral‐control method. Behavioral and event‐related brain potential data support the hemispheric organization view of visual memory, and the contralateral‐control method, in conjunction with the recording of the event‐related optical signal, can be used to reveal the existence of memory‐driven processes in early stations of the visual system.
Psychophysiological measures of (dis)inhibition as liability indicators for schizophrenia
Authors: Clementz Brett A.
Published: December 2004

Two psychophysiological measures, poor suppression of midlatency auditory‐evoked responses in a paired stimulus paradigm and ocular motor abnormalities, may index genetic liability for schizophrenia. An important feature of these measures is that both patients and their nonpsychotic relatives exhibit basically the same performance. These measures may be successful endophenotypes for schizophrenia because they assess poor response inhibition associated with dysfunction of dorsolateral prefrontal cortex circuitry. Data bearing on this hypothesis are reviewed, and it is posited that assessment of the auditory‐evoked gamma band response and saccade measures of inhibitory abilities are the most valid behavioral measures of schizophrenia's neuropathological correlates. The extant data suggest that psychophysiological studies of schizophrenia can provide consistent and theoretically meaningful information for localizing neuropathology and for assessing the genetics of this complex disorder.
Effects of dual task demands on the accuracy of smooth pursuit eye movements
Authors: Kathmann Norbert , Hochrein Andrea , Uwer Ruth
Published: December 2004

The effect of attention allocation on smooth pursuit eye movements (SPEM) was investigated. Eye movements were electrooculographically recorded in 27 healthy subjects who tracked a visual target that moved horizontally with constant or unpredictably varying velocity. In some trials, subjects performed additional auditory discrimination tasks varying in difficulty. Pursuit error decreased when attention was divided between both tasks. The pattern of results is incompatible with the assumption made in previous research that attention enhancement improves SPEM accuracy. Rather, ocular smooth pursuit appears to be executed in the automatic mode, although intentional and selective processes must contribute. Moreover, controlled attention directed to the tracking task interfered with smooth pursuit. A reinterpretation of earlier studies in which visual monitoring tasks were used to improve eye tracking is needed.
Individual differences in electrodermal responsivity to predictable aversive stimuli and substance dependence
Authors: Taylor Jeanette , Carlson Scott R. , Iacono William G. , Lykken David T. , McGue Matt
Published: December 2004

To determine if the inability to take advantage of the predictability of an aversive stimulus to diminish its psychological impact reflects a deficit in inhibitory control related to the development of substance dependence, we recorded skin conductance responses (SCRs), heart rate (HR), and anticipatory electrodermal nonspecific fluctuations (NSFs) from 175 16–18‐year‐old boys when a white noise blast was either unpredictable or temporally predictable. Compared with boys who had moderately reduced or augmented SCRs to predictable blasts (moderate and poor modulators, respectively), boys whose SCRs were greatly reduced (good modulators) had fewer symptoms of alcohol and nicotine dependence and more anticipatory NSFs. HR appeared to index an active coping response for good and moderate modulators. The autonomic response pattern evident for good modulators may index an inhibitory control mechanism protecting them from developing substance dependence.
Event‐related potential correlates of proactive interference in schizophrenic patients and controls
Authors: Rößner Patricia , Rockstroh Brigitte , Cohen Rudolf , Wagner Michael , Elbert Thomas
Published: December 2004

Performance and event‐related potentials (ERPs) were examined in a proactive interference (PI) task with 15 male schizophrenic patients and 15 matched healthy controls. Within a paired‐associate task, 30 pairs of semantically unrelated words (A‐B) were presented twice, followed by cued recall, in which the paired‐associate B had to be named upon cue A. Subsequently, 50% of the A‐words were paired with new words (A‐C) and presented in random order together with 15 novel pairings (D‐E). Slower responses and poorer recall of C‐ than of E‐words in the final recall indicated PI in both groups. During acquisition, the paired‐associates (C/E) evoked larger P3 and positive slow wave in controls than in patients. During recall, cues (A/D) evoked a slow wave with predominating anterior negativity in controls and posterior positivity in patients. The group‐specific ERP pattern suggests deviant encoding and retrieval processes in schizophrenic individuals.
A distinction between the initiation and the continuation of response preparation
Authors: Ilan Aaron B. , Miller Jeff
Published: December 2004

Previous findings suggest that motoric response preparation cannot be initiated in parallel with memory scanning. In the present study, response preparation was initiated with the aid of a precue to examine whether such preparation can be maintained or continued while memory scanning is active. In Experiment 1, each trial began with a colored square indicating which hand might be needed to respond. A probe letter's memory set membership determined whether the primed response should be made or withheld. Lateralized readiness potentials were initiated by the square precue and continued to increase after letter presentation, suggesting that once response preparation had been initiated it was continued in parallel with memory scanning. Experiment 2 suggested that the difficulty of the concurrent memory search had little effect on the continuation of response preparation. The results support the view that motoric response preparation consists of at least two qualitatively distinct phases—initiation and continuation.
Contrasting patterns of brain activity in anxious apprehension and anxious arousal
Authors: Nitschke Jack B. , Heller Wendy , Palmieri Patrick A. , Miller Gregory A.
Published: December 2004

Evidence suggests that a distinction between anxious apprehension (worry) and anxious arousal (somatic anxiety) might account for some discrepancies in the literature examining brain activity in anxiety. In the current study, we compared the regional brain activity of groups of anxious apprehension and anxious arousal participants, selected on the basis of self‐report measures previously shown to be psychometrically distinct from each other and from a specific measure of depression. Patterns of hemispheric asymmetry in electroencephalogram alpha distinguished the two types of anxiety, with the anxious arousal group showing more right than left activity. No significant asymmetry was found for the anxious apprehension group. The results provide further support for contrasting patterns of brain activity in distinct types of anxiety. Research is needed to specify further the topography and functional significance of this distinction.
An electrophysiological analysis of modality‐specific aspects of word repetition
Authors: Joyce Carrie A. , Paller Ken A. , Schwartz Tanya J. , Kutas Marta
Published: December 2004

Priming effects to words are reduced when modality changes from study to test. This change was examined here using behavioral and electrophysiological measures of priming. During the study, half of the words were presented visually and half auditorally; during a subsequent lexical decision test, all words were presented visually. Lexical decisions were faster for within‐ than cross‐modality repetitions. In contrast, modality influenced recognition only for low‐frequency words. During lexical decision, event‐related brain potentials were more positive to studied than unstudied words (200–500 ms). A larger and shorter duration effect was observed for within‐ than cross‐modality repetitions (300–400 ms). This latter effect is viewed as an electrophysiological index of modality‐specific processing associated with priming. Results suggest that multiple events—both modality‐specific and modality‐nonspecific—underlie perceptual priming phenomena.
Temporal stability of the emotion‐modulated startle response
Authors: Larson Christine L. , Ruffalo Dante , Nietert Jennifer Y. , Davidson Richard J.
Published: December 2004

In the present study, we examined the stability of one measure of emotion, the emotion‐modulated acoustic startle response, in an undergraduate sample. Using the acoustic startle paradigm on two different occasions, we measured stability of affective modulation of the startle response during and following the presentation of pictures selected to be of positive, negative, or neutral emotional valence. The two assessments were separated by 4 weeks. Two groups of subjects were compared: one group that viewed the same pictures at each assessment and a second group that viewed different pictures at the second assessment. We found that viewing different pictures at two assessments separated by 4 weeks yielded moderate stability of the emotion modulation of startle magnitude, whereas subjects who viewed the same pictures at both assessments showed poor stability. Furthermore, this difference was due to the stability of responses to high versus low arousal pictures, not to differences in valence.
Vagal changes following cancer chemotherapy: Implications for the development of nausea
Authors: Morrow Gary R. , Andrews Paul L.R. , Hickok Jane T. , Stern Robert
Published: December 2004

Many physiological changes that occur contemporaneously with nausea are mediated by the autonomic nervous system, but the specific autonomic changes associated with nausea have not been characterized. Cardiac parasympathetic (vagal) activity as indicated by heart rate variability, measured as the standard deviation of successive differences (SDSD) in beat‐to‐beat intervals, was assessed in 24 women with ovarian cancer immediately prior to and accompanying nausea that occurred following anticancer chemotherapy. A progressive increase in SDSD followed infusion of the chemotherapy agent, indicating a rise in cardiac parasympathetic (vagal) activity, with onset of nausea consistently occurring after the peak activity had been reached, at a time when SDSD was decreasing. An increase in parasympathetic activity seems to set the stage for the expression of nausea but an additional stimulus is apparently needed to finally trigger the event.
On the search for the neurophysiological manifestation of recollective experience
Authors: Spencer Kevin M. , Abad Enrique Vila , Donchin Emanuel
Published: December 2004

M.E. Smith (1993) obtained event‐related brain potentials (ERPs) from subjects performing a recognition memory task using “remember” (R) and “know” (K) judgments, and reported observing in the ERP a “neurophysiological manifestation of recollective experience” as a difference between the positive waveforms elicited by stimuli that yielded R and K judgments. We replicated his experiment and examined the componential structure of the R>K effect in two ways. First, we found that correction for P300 latency jitter eliminated the effect reported by Smith. Second, the application of principal component analysis indicated that the positive waveform elicited by the words in the test list was a P300. These analyses do not support the hypothesis that there is a new component (the “memory‐evoked shift”) that is a specific manifestation of recollection.
Hierarchical processing and level‐repetition effect as indexed by early brain potentials
Authors: Han Shihui , He Xun , Woods David L.
Published: December 2004

Event‐related potentials were recorded to investigate the mechanisms of hierarchical processing and level‐repetition effect. Participants identified targets that appeared at global, local, or both levels of hierarchical patterns. Reaction times showed global precedence and level‐repetition effects. An occipital P1 wave was enhanced to local relative to global targets. The P1 to local targets was also larger when preceded by global than local targets. Global and both‐level target selections were indexed by two posterior negativities peaking at 130 and 190 ms poststimulus, whereas local target selection was indexed by a broad occipitotemporal negativity. A late selection positivity was observed over the left occipitotemporal site for global targets but over the central site for local targets. The findings suggest that sensory‐perceptual mechanisms contribute to global precedence and level‐repetition effects in hierarchical processing.
The relationship between respiratory‐related evoked potentials and the perception of inspiratory resistive loads
Authors: Webster Kate E. , Colrain Ian M.
Published: December 2004

This study investigated the relationship between resistive load magnitude, load magnitude estimation, and the respiratory‐related evoked potential. In Part 1, 10 healthy subjects estimated the magnitude of five inspiratory resistive loads. Two subjects were shown to have a markedly reduced slope of the magnitude estimation‐resistive load relationship and were suggested to be “poor perceivers” of respiratory stimuli. In Part 2, evoked potentials were recorded from the same 10 subjects using the same resistive loads as Part 1. A log‐log plot of the group averaged P1 amplitudes showed a linear relationship with resistive load. Aberrant P3 components were seen in the 2 poor perceiving subjects and one of the 2 showed no late response. In the other 8 subjects, P3 varied as a function of resistive load, being augmented to larger loads. These results provide evidence that P3 may be a key index of the perception of respiratory sensitivity and effort.
Neural sources involved in auditory target detection and novelty processing: An event‐related fMRI study
Authors: Kiehl Kent A. , Laurens Kristin R. , Duty Timothy L. , Forster Bruce B. , Liddle Peter F.
Published: December 2004

We used event‐related functional magnetic resonance imaging (erfMRI) techniques to examine the cerebral sites involved with target detection and novelty processing of auditory stimuli. Consistent with the results from a recent erfMRI study in the visual modality, target processing was associated with activation bilaterally in the anterior superior temporal gyrus, inferior and middle frontal gyrus, inferior and superior parietal lobules, anterior and posterior cingulate, thalamus, caudate, and the amygdala/hippocampal complex. Analyses of the novel stimuli revealed activation bilaterally in the inferior frontal gyrus, insula, inferior parietal lobule, and in the inferior, middle, and superior temporal gyri. These data suggest that the scalp recorded event‐related potentials (e.g., N2 and P3) elicited during similar tasks reflect an ensemble of neural generators located in spatially remote cortical areas.
Constraints for emotion specificity in fear and anger: The context counts
Authors: Stemmler Gerhard , Heldmann Marcus , Pauls Cornelia A. , Scherer Thomas
Published: December 2004

We investigated psychophysiological responses to fear and anger inductions during real‐life and imagination. Female participants (N= 158) were assigned to a fear‐treatment, fear‐control, anger‐treatment, or anger‐control group. Context (real‐life, imagination) was varied in two sessions of fixed order. Eleven self‐report and 29 somatovisceral variables were registered. Results showed that (a) except during anger imagination, control groups were emotionless; (b) in control groups, contexts prompted diverging somatovisceral responses, but similar emotion self‐reports; except during fear imagination, the emotion inductions (c) were successful and (d) produced specific emotion reports; (e) during real‐life, somatovisceral fear and anger responses exhibited a marked cardiovascular defense reflex; (f) in addition, real‐life fear showed an adrenaline‐like specific response pattern, whereas real‐life anger showed specific forehead temperature and EMG extensor increases, accompanied by an elevated DBP during imagination. A Component Model of Somatovisceral Response Organization is proposed.
Time‐of‐day variations in different measures of sleepiness (MSLT, pupillography, and SSS) and their interrelations
Authors: Danker‐Hopfe Heidi , Kraemer Susanne , Dorn Hans , Schmidt Andrea , Ehlert Ingrid , Herrmann Werner M.
Published: December 2004

The aim of the present study is to analyze how well physiological measures of sleepiness derived from pupillography and the Multiple Sleep Latency Test correlate with a subjective measure, the Stanford Sleepiness Scale (SSS) score. The results are based on data from 12 healthy participants, who underwent these tests every 2 hr from 7:00 a.m. until 11:00 p.m. Sleep latencies were correlated with four different variables derived from pupillography and the SSS score. The results indicate that the physiologically based variables correspond very well. This is reflected by similar patterns of time‐of‐day variations, a good agreement at the group level, and correlations at the individual level, whereas the SSS shows a quite different pattern of variation. The two physiological measures of sleepiness seem to reflect the same aspect of the level of tonic central nervous activation, which is not correlated with the subjective feeling of sleepiness.
Differential effects of active versus passive coping on secretory immunity
Authors: Bosch Jos A. , de Geus Eco J.C. , Kelder Angele , Veerman Enno C.I. , Hoogstraten Johan , Amerongen Arie V. Nieuw
Published: December 2004

This study examined the acute immunological effects of two laboratory stressors, expected to evoke distinct patterns of cardiac autonomic activity; namely an “active coping” time‐paced memory test, and a “passive coping” stressful video showing surgical operations. We measured salivary S‐IgA, IgA‐subclasses (IgA1, IgA2), and secretory component (SC). SC is responsible for the transport of S‐IgA across the epithelium, and thus a rate‐determining step in S‐IgA secretion. Thirty‐two male undergraduates were subjected to both stressors and a control video (a didactic television program). The memory test induced a typical “fight‐flight” response, characterized by increases in heart rate and blood pressure in association with a decrease in cardiac preejection period (PEP) and vagal tone. The surgical video produced a “conservation‐withdrawal”‐like response, characterized by an enhanced vagal tone, a decrease in heart rate, and a moderate sympathetic coactivation (as indicated by a shortened PEP and an increased systolic pressure). The memory test induced an increase in the concentration and, to a lesser extent, in the output of S‐IgA, IgA1, and SC. The output of IgA2 was not significantly affected. For the surgical video, a different pattern emerged: During stressor exposure S‐IgA remained unaffected, against the background of a small increase in SC output. However, 10 min after the surgical video S‐IgA levels had decreased. This decrease in S‐IgA was paralleled by a decrease in IgA1, but not IgA2. We conclude that acute stress can have both enhancing and suppressive effects on secretory immunity, the IgA1 subclass in particular. The mechanisms that underlie these divergent responses may include stressor‐specific patterns of autonomic activation.
Consolidation of psychophysiology as a scientific discipline, 1930–1964: A historical note
Authors: Holguín Socorro Rodríguez , Cadaveira Fernando
Published: December 2004

The ground covered by psychophysiology throughout the decades prior to its constitution as an independent discipline has not been well documented, despite its historical interest. A bibliometric study of the research published in scientific journals by 66 of the most relevant psychophysiologists from 1930 to 1964, analyzing the contents of the records indexed in the PsycINFO database, gives us an image of the state of the emergent discipline during that period. This study reveals that this was a period of consolidation, marked by the refinement of instruments and procedures, the characterization of measurements, and the establishment of the basic relationships between physiological and psychological variables, the development and validation of basic constructs such as activation, or interest in the study of psychopathology. In these years the foundations of psychophysiology were laid, leading to the formalization of the discipline at the end of the period.
Effects of perceptual context on event‐related brain potentials during auditory spatial attention
Authors: Arnott Stephen R. , Alain Claude
Published: December 2004

The effects of auditory spatial attention on event‐related brain potentials (ERPs) were examined in situations that promoted stream segregation. Short and long noise bursts were presented at three azimuth locations and listeners were asked to respond to the longer sounds occurring at either the right‐ or left‐most location. In the baseline condition, the three sound sources were evenly spaced apart. In the distractor clustering conditions, middle and far sounds were clustered. In the attended clustering conditions, middle and attended sounds were clustered. ERP indices of attention, isolated as negative difference (Nd) waves, were greater over the hemisphere contralateral to the attended location. Nd waves were also larger when the middle sounds were moved toward the far distractors, consistent with an object‐based gradient of auditory attention in which higher order information provided by the perceptual context influences selective processing.