bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of a Strong Shock Wave as Approximated by a Collisionless Shock with Polynomial Corrections
Authors: Kovitz A. A. , Mintzer D.
Published: December 2004

The structure of a strong shock wave is investigated from the point of view of kinetic theory. An approximate solution of the Boltzmann equation is developed in the form of an infinite series of generalized orthogonal polynomials in velocity space; the leading term of the series is taken to be the velocity distribution function for a ``collisionless shock wave''; higher-order terms are computed in terms of the orthogonal polynomials with the collisionless distribution acting as the weight function. Number density and temperature distributions are obtained and compared with the results of several other kinetic theory descriptions of strong shock waves based on modifications of the Mott-Smith distribution function. The agreement with the present treatment is good enough to support the ``collisionless'' interaction proposed as the dominating physical process.
Cross-Field Diffusion of Quiescent Potassium Magnetoplasmas
Authors: Wolf N. S. , Rogers K. C.
Published: December 2004

Plasma loss in a single-ended Q-device was measured as a function of magnetic field strength by a technique giving D⊥ directly. When fluctuations in the plasma are small compared to kT, D⊥ agrees with the classical result.
Effects of Turbulence on Laminar Skin Friction and Heat Transfer
Authors: Smith Mahlon C. , Kuethe Arnold M.
Published: December 2004

Experiments were performed in two low-turbulence wind tunnels (u∞′ < 0.1%) to determine the effects of turbulence on heat transfer from plates and circular cylinders in incompressible flow. Grid turbulence up to 6% was imposed. Heat transfer was increased about 30% in the laminar region of a flat plate and up to 70% on a circular cylinder; smaller though still significant increases in shearing stress at the wall were measured by hot wires near the surface. A phenomenological theory is given which shows good agreement with the experiment.
Weakly Radiative Acoustic Flow Induced by Radiation from a Stationary Wall
Authors: Solan Alexander , Cohen Ira M.
Published: December 2004

The radiative wave flow induced by radiation from a stationary solid wall is treated for large ratio of photon mean free path to molecular mean free path, lph/λmfp ≫ 1, and large Boltzmann number, 1 ≪ Bo ≤ (lph/λmfp)½ (weak radiation). For times within the range (λmpf/lph)½ ≪ ta∞/lph ≪ Bo, where a∞ is the isentropic speed of sound, the problem is split into a radiationless heat-conducting boundary layer and a radiation-induced acoustic outer region. The representations of the two regions are reduced to a heat-conduction equation and an inhomogeneous linear wave equation, respectively, and these are solved in closed form. The flow in the acoustic region differs from ordinary acoustic flow in that it is induced throughout the flow field instantaneously, rather than progressively. The wavelike behavior manifests itself in a weak discontinuity (in the second derivatives of the flow variables) which propagates outwards from the plate at the isentropic speed of sound.
Asymptotic Law of Decay of Homogeneous Magnetoturbulence
Authors: Nihoul Jacques C. J.
Published: December 2004

Solutions of the magnetohydrodynamic equations for the spectral energy tensors are obtained by assuming that the turbulent field is homogeneous and weak enough for triple correlations to be negligible. The total turbulent magnetic and kinetic energies are derived by integrating over all wave number space. The asymptotic law of decay (for times larger than the ``inhibition time'') is obtained in an analytical form by the method of steepest descent, and it is shown that there are two important contributions to the total energy, one which decays as t−5/2, as in ordinary turbulence and corresponds to equipartition between magnetic and kinetic modes, and one which decays as t−3 and leads to the partition of energy between the two modes in the inverse ratio of their respective diffusivities. In the course of the decay, the latter becomes negligible, but the time at which the t−5/2 component dominates depends upon the ratio n = ν/λ of the two diffusivities and is found to fall beyond any reasonable time of observation if n is much less or much larger than one; in which cases, equipartition is not approached before the turbulence is damped out or has attained such a large scale that, in experimental situations, the limit of validity of the homogeneity hypothesis is reached.
Ionization Phenomena in a Gas-Particle Plasma
Authors: Gibson Edward G.
Published: December 2004

Particles in a plasma can appreciably change the electron density from the value it would assume if the particles were not present. The case of pure particle ionization, in which there is only thermionic emission from the particles and no gas ionization, is first considered. It is established that the potential and the charge distributions can be divided into a strong shielding regime, in which most of the free electrons are packed close to the particle surfaces in regions of high potential, and its direct opposite, a weak shielding regime. In both regimes, the free-electron content of the plasma is most readily altered by variations in the particle size, rather than in the work function or particle temperature. The suppression of one form of ionization by the other when both particle and gas contribution to the electron density are comparable is next investigated. In the case of gaseous ionization enhancement it is shown that, if the thermionically emitting particles are hotter than the gas, the electron temperature will also be higher than that of the gas and the gaseous ionization thereby enhanced. Lastly, it is shown that in some transient situations, the particles are able to control the time rate of change of the electron density.
Kinetic Equation for an Unstable Plasma in Parallel Electric and Magnetic Fields
Authors: Fried Burton D. , Ossakow Sidney L.
Published: December 2004

The response of a homogeneous plasma, in a strong uniform magnetic field, B0, to the sudden application of a strong, uniform electric field is studied in a self-consistent formulation which treats the coupled equations for the one-particle and two-particle distribution functions resulting from neglect of three-particle correlations. As in earlier work on the case B0 = 0, the electric field is assumed to be large compared to that which produces a ``runaway current,'' so that particle-wave interactions should dominate. In the limit of strong magnetic field, use of the Bernstein-Kulsrud expansion in k⊥Ric makes the problem effectively one-dimensional, eliminating the need for factorization assumptions of the form f(v) = f∥(v∥)f⊥ (v⊥) used in the B0 = 0 case. Only the dominant contributions to the diffusion in velocity space, arising from the fastest growing waves, are retained. Other simplifications result from the assumption of unequal electron and ion temperatures, but it proves necessary to specify the ratio Te/Ti, rather than simply assuming it to be large. In sharp contrast to the case B0 = 0, it is found that the diffusion affects only those electrons which have, in the ion rest frame, velocities of order (m/M)½ of the electron thermal speed. No appreciable ``quasi-linear'' effects, such as the current limitation found in the B0 = 0 case, are therefore to be expected; the results of numerical calculations confirming this are summarized.
Scattering of Energetic Particles by Laboratory Plasmas
Authors: Montgomery David , Roqúe Celso , Alexeff Igor
Published: December 2004

Possible experiments on the scattering of energetic particles by laboratory plasmas are discussed. Expressions for scattering coefficients in terms of the electric field autocorrelation function are derived. Sample situations are considered. Whereas incoherent scattering of electromagnetic waves is governed by the charge density autocorrelation function, energetic particle scattering is governed by the electric field autocorrelation function.
End Losses from a Linear θ Pinch
Authors: Morse Richard L.
Published: December 2004

End losses from a linear θ pinch are estimated from a self-consistent calculation of the structure of the plasma and the confining magnetic field.
Transient Coupling between Motions of Plasma and Neutrals in the F Region
Authors: Barthel James R.
Published: December 2004

In a weakly ionized plasma, the motion of the neutrals causes induced electric fields, which result in a transient plasma drift at approximately the neutral velocity if the flow field dimension exceeds the decay length for Alfvén waves.
Axisymmetric Plasmasphere Resonances: Toroidal Mode
Authors: Radoski Henry R. , Carovillano Robert L.
Published: December 2004

The usual magnetohydromagnetic approach is used to investigate axisymmetric perturbations in a plasma permeated by a static dipole field. The model plasmasphere used has stationary, perfectly reflecting boundaries concentric with the dipole, and the plasma density is assumed to be spherically symmetric. The poloidal wave equation is reduced to a hierarchy of coupled differential equations in the radial variable. The toroidal wave equation is solved exactly using a density law which gives a good order of magnitude fit to recent whistler data. Because the extent of the plasma is finite, the eigenperiods are everywhere finite, including the poles. The stretched string model of vibrating lines of force is derived using the Wentzel-Kramers-Brillouin approximation, which fortuitously gives the exact periods for the density law utilized. Two unusual results are the prediction of shorter periods in the polar zones than at some high middle latitudes and discontinuous eigenperiods across the line of force which just grazes the outer plasma boundary. A general discussion of the results and the special significance of the toroidal and poloidal modes because of their symmetry is provided.
Linearized Rayleigh's Problem in Magnetogasdynamics
Authors: Cercignani Carlo , Tironi Gino
Published: December 2004

Rayleigh's problem for a viscous, compressible, conducting fluid is studied. Linearization yields a solution which is equal, in first approximation, to the one for the incompressible, viscous, conducting fluid. Compressibility effects are then taken into account by evaluating the solution of the pressure equation. This equation contains a complicated source term depending upon the previously found expressions for the velocity parallel to the plate and the induced magnetic field. Due to the complicated expression of the source term, an operational solution of the equation is quite intractable. Thus, numerical techniques are used. The equation is solved by a finite-differences method which is shown to be numerically stable. Comparisons are made between the pressure profile and Hanin's graphs.
Alfvén Wave Generation in a Spherical System
Authors: Motz Robin O.
Published: December 2004

Magnetohydrodynamic waves were generated by small amplitude oscillation of a dielectric sphere in a mercury-filled spherical shell in a longitudinal magnetic field. The velocity of the waves was determined by creating a standing wave resonance. The waves were moving with Alfvén velocity.
Normal Ionizing Shock Waves with Equilibrium Chemistry in Hydrogen
Authors: Taussig Robert T.
Published: December 2004

The steady-state jump equations for normal ionizing shock waves in hydrogen are solved numerically assuming the upstream and downstream states are at chemical equilibrium. Accurate thermodynamic functions are used to include changes due to dissociation and ionization of the gas. The results show that the solutions with chemistry are qualitatively like the ideal gas normal ionizing shock wave solutions, the number and type of possible downstream states being the same. The analysis for the switch-on shock with chemistry is presented here for the first time. Inclusion of chemical effects can extend the switch-on shock velocity range above the classical limit for an ideal gas. The problem of a steady, current-driven shock traveling in an electromagnetic shock tube is solved. The results agree well with recent experimental evidence and confirm the analytic approximations made by Kunkel and Gross.
Laminar Boundary Layers with Surface Catalyzed Reactions
Authors: Libby Paul A. , Liu Tsong-mou
Published: December 2004

There is presented a theoretical analysis of the properties of a laminar boundary layer undergoing surface catalysis with two reactants and two products according to a one-step, unidirectional reaction following a Langmuir-Hinshelwood mechanism. The boundary condition at the catalytic surface is rather general and leads to a variety of reaction orders; indeed, the effective order may change with position along the surface. The solution for the concentration field is given by an integral equation which is readily solved by numerical iteration. Application of the analysis is made to the hydrogenation of ethylene on a nickel film. The values of the flow parameters required by the numerical analysis are selected to correspond to a possible laboratory experiment which would not only permit comparison with the present theory but which might also provide a tool for obtaining physiochemical data relative to surface catalysis.
Flow of a Second-Order Fluid past a Symmetrical Cylinder
Authors: Srivastava A. C. , Maiti M. K.
Published: December 2004

The velocity profile within the boundary layer region for the flow of a second-order fluid past a symmetrical cylinder has been determined for various values of a nondimensional parameter formed out of the velocity and material constants. As an example, the flow past a circular cylinder has been discussed in detail, and the separation point has been calculated for different values of the above mentioned parameter. It is found that the increase in second-order effect shifts the point of separation towards the forward stagnation point.
Equivalence between two Formalisms of Plasma Fluctuations
Authors: Weinstock Jerome
Published: December 2004

The expression for auto-correlation functions given in terms of the two-time distribution function is related by a trivial identity to the expression for auto-correlation functions, which is given in terms of the usual distribution function.
Measurement of Shock Wave Thickness by the Electron Beam Fluorescence Method
Authors: Robben F. , Talbot L.
Published: December 2004

Shock wave thicknesses and density ratios have been measured in helium, argon, and nitrogen by means of the electron beam fluorescence method, over the range 1.5 < M < 17.4, in a low density wind tunnel. The shock thicknesses in argon and helium agreed well with Mott-Smith theory at the higher Mach numbers and were between Navier-Stokes and Mott-Smith theories at the lowest Mach number. In nitrogen the measured shock thicknesses were considerably greater than the predictions of Navier-Stokes theory. Measured density ratios across the shock wave were in good agreement with theory, in the lower density flow. Poorer agreement was found at higher flow densities, leading to estimates of upper bounds for the range of linear variation of fluorescence intensity with gas density. Density ratios for shocks produced in divergent free-jet flows were found to be in better agreement with theory after a viscous curvature correction was applied. An anomalous dip in the fluorescence intensity was found ahead of helium shock waves produced in the free-jet flows. Some preliminary measurements were made of the fluorescence lifetimes in helium, argon, and nitrogen, and the presence of a halo surrounding the electron beam was investigated briefly.
Measurements of Rotational Temperatures in a Low Density Wind Tunnel
Authors: Robben F. , Talbot L.
Published: December 2004

The fluorescence of a 30-kV electron beam has been used as a probe to measure the rotational distribution function of flowing nitrogen in a low-density wind tunnel. The fluorescence consists predominantly of the so-called first negative system of nitrogen, a series of bands originating from the B2Σ+ state of N2+. Measurements of the intensities of the rotational structure of the (0–0) vibrational band have been used to calculate, through a theoretical model, the original rotational distribution function of N2 before excitation. This technique was originally proposed by Muntz, who also carried out a series of experiments demonstrating the validity of the theoretical model. A series of measurements was performed in the undisturbed flows of a subsonic nozzle, a Mach 4 nozzle, and free-jet expansions from sonic orifices at Mach numbers ranging up to 19. The rotational temperature measurements are shown to be about 3% high at 280 °K, with a progressively increasing error at lower temperatures. These measurements also indicated no measurable lag in rotational temperature in the free-jet expansions.
Slanting of a Magnetically Stabilized Electric Arc in Transverse Supersonic Flow
Authors: Bond Charles E.
Published: December 2004

Experimental observations are presented which indicate the existence of a convective interaction mechanism affecting the direction and stability of electric current in a flowing gas. The observations were made of an electric arc confined in transverse supersonic flow by means of a nonuniform magnetic field mutually orthogonal with the freestream velocity field and the applied electric field. The positive column exhibits remarkable stability when allowed to slant across the applied electric field, approximately parallel to the freestream Mach line. The direction of slant is the Hall direction, cathode root downstream, but the magnitude of the slant angle does not appear to vary with the Hall parameter ωeτe. At the Mach numbers investigated, 2.0, 2.5, and 3.5, the inclination of the stable arc to the freestream is near the Mach angle, which is near the angle corresponding to a maximum in the discharge parameter E∥/Ps, the ratio of parallel component of electric field to pressure at the upstream boundary of the arc. Under conditions where the column could not assume its characteristic slant angle, a highly unstable discharge was observed.
Oscillating Instabilities in Multicomponent Diffusion
Authors: Miller L. , Mason E. A.
Published: December 2004

An apparently new oscillatory phenomenon in gaseous multicomponent diffusion is studied experimentally and theoretically. The interdiffusion of two gases can ``drag along'' a third gas; if the third gas is heavy enough and abundant enough, the upper layers of the mixture can become more dense than the lower layers. The resulting density inversion may cause convection, and irregular oscillations result. A diffusion theory is developed which predicts fairly well the concentrations of the third gas for which the system just becomes unstable. The criterion for the onset of convection if a density inversion exists in a diffusing gas mixture is discussed by analogy with Rayleigh's treatment of convection in a heat-conducting gas having a temperature inversion. Some multicomponent systems may have several density reversals and will be unstable for any orientation in a gravitational field. It is suggested that diffusion instabilities are quite common and may play a role in some natural and engineering processes.
Stability of a Tangential Discontinuity in an Incompressible Conducting Fluid
Authors: Todd Leonard
Published: December 2004

A simple physical prescription is given for the stability criterion on the tangential discontinuity in an incompressible conducting fluid.
Relation between the Kelvin-Helmholtz Instability and the Resistive Drift Instabilities
Authors: Von Goeler S.
Published: December 2004

The Kelvin-Helmholtz instability and the resistive drift instabilities both lie on the same branch of the dispersion relation, the Kelvin-Helmholtz instability traveling at a somewhat smaller angle with respect to the magnetic field.
Nonlinear Diffusion with Recombination in an Electron Beam Excited Plasma
Authors: Mosburg Earl R.
Published: December 2004

The radial distributions of electron density and light intensity are calculated from the nonlinear diffusion equations with a recombination term added. Two-body and three-body recombination mechanisms are considered in addition to the intermediate case of collisional-radiative recombination.
Kinetic Theory of Source Flow Expansion with Application to the Free Jet
Authors: Hamel Bernard B. , Willis D. Roger
Published: December 2004

A systematic approximation has been constructed for the moment equations of kinetic theory which describe source flow expansion. For small source Knudsen number, the moments are expanded and solutions are obtained near the source. These solutions are nonuniformly valid far from the source, breaking down when transition flow is encountered. To analyze the rarefied regime, the equations are rescaled taking account that the flow is hypersonic in the transition regime. This allows us to apply a hypersonic approximation to the moment equations in the rarefied regime and subsequently match this to the inviscid solution. For spherical expansion we resolve the problem to a relaxation process with two translation temperatures, one along streamlines T∥, and the other transverse to streamlines T⊥. We obtain expressions for the terminal Mach number in terms of source Knudsen number and intermolecular force law, and a simple rarefaction criteria is found which states that transition flow is encountered when T∥ − T⊥ ≅ Tisentropic.
Experimental Determination of the Thermal Conductivity of Atmospheric Argon Plasma
Authors: Knopp C. F. , Cambel Ali Bulent
Published: December 2004

The radial temperature distribution within a cylindrically symmetric argon plasma column was determined by spectroscopic analysis for arc currents of 30 to 60 A. Temperatures obtained from absolute line and absolute continuum radiation were found to be in excellent agreement. An empirical expression, based on the Kramers-Unsöld theoretical model, was obtained for the radiated power, as a function of temperature. Using the measured temperature profiles, the calculated radiated power, and an analytical expression for the electrical conductivity, the thermal conductivity of argon was determined for the temperature range of 8500 to 12 000°K. The data were in good agreement with theoretically predicted results.
Anomalous Electron Diffusion and Ion Acceleration in a Low-Density Plasma
Authors: Janes G. S. , Lowder R. S.
Published: December 2004

Ion and electron transport properties have been measured in a steady state, weakly turbulent plasma that was subjected to crossed E and B fields. The geometry permits quantitative measurements of electron and ion currents. The ion gyro radius is large compared to the apparatus dimensions. Measurements of the potential gradients, Hall currents, and ion velocity show that the ions are freely accelerated through the plasma by electrostatic forces. However, an ``anomalous diffusion'' of electrons is observed since the electron current across the magnetic field is much too large to be due to collisional diffusion. The plasma is weakly turbulent, consisting of a slowly rotating density concentration on which higher frequency fluctuations are superimposed. Electric field fluctuations are found that are correlated with the density variations so as to produce the ``anomalous diffusion'' via adiabatic E × B drifts. The magnitudes of these electric field and density variations are used to predict a net electron current that agrees with the direct measurements of this current. Reasonable agreement with the turbulent diffusion theory of Yoshikawa and Rose is obtained.
Viscous Instability of an Incompressible Fluid Half-Jet Flow
Authors: Lessen Martin , Ko Sung-Hwan
Published: December 2004

The instability of the free laminar boundary layer between parallel streams is investigated for an incompressible fluid. It is found that the minimum critical Reynolds number for instability is 3.6 based on the assumption of parallel unperturbed flow. However, when the parallel flow theory is corrected for the nonparallelism that actually exists at low Reynolds numbers, the minimum critical Reynolds number for instability becomes 12.
Rotating Couette Flow of a Binary Liquid Mixture
Authors: Kulinski E. S.
Published: December 2004

Impulsively started, rotating Couette flow of a binary, perfect solution is discussed for the purpose of exhibiting possible multifluid phenomena. It is shown that inhomogeneity due to baro-diffusion can give rise to phenomena which are commonly thought of as rheological effects.
Establishment of Concentration Profile for the Flow of a Binary Fluid Mixture
Authors: Kao Timothy W.
Published: December 2004

A study is made of the establishment of concentration profile of the heavy species for a binary fluid mixture under a body force from a uniformly mixed upstream condition. An inviscid hydrodynamical model is adopted. Two cases are considered. In the first case the flow is a swirling motion and the body force is provided by the centrifugal action of the swirl. In the second case the flow is a duct flow confined between two parallel walls with potential body force. Use is made of a perturbation procedure in terms of an expansion of the reciprocal of a diffusive Péclet number to obtain a closed form zeroth-order solution. The orders of the higher-order correction terms are explicitly given. The interplay between Fickian and baro-diffusion is brought out, and asymptotic solutions far downstream of the inlet are explicitly calculated for a class of swirling flows. The problem bears on various phenomena where a knowledge of the concentration of the heavier component is important, such as in gaseous nuclear cavity reactor propulsion devices.
Landau Damping in Inhomogeneous Plasmas
Authors: Jackson E. A. , Raether M.
Published: December 2004

Solutions of the Vlasov equation for a bounded, one-dimensional, inhomogeneous plasma are presented. The results indicate that the high-frequency modes of oscillation (Tonks-Dattner resonances) can exhibit a very large Landau damping even in the long-wavelength regime.
Propagation of Ion Acoustic Waves along Cylindrical Plasma Columns
Authors: Wong A. Y.
Published: December 2004

A theoretical analysis shows the boundary effects on ion acoustic waves propagating along the magnetic field to be unimportant if the ion Larmor radius is much smaller than the plasma radius. Results are supported by experiments.
Instability of Laminar Flow of a Perfect Magnetofluid
Authors: Kent Arthur
Published: December 2004

A simple sufficient condition is given for instability against small oscillations of symmetric laminar flows of an inviscid incompressible perfectly conducting magnetofluid, flowing between parallel walls in the presence of a symmetric magnetic field parallel to the flow. The condition is interesting because it shows that any such flow that is stable in the absence of a magnetic field can be made unstable by the superposition of a suitable magnetic field parallel to the flow.
Interaction of Oblique Detonation Waves with Iron
Authors: Sternberg H. M. , Piacesi D.
Published: December 2004

Impacts of oblique detonations in pentolite on iron are treated by the methods of plane, steady, compressible flow. Regular reflection, three-shock Mach reflection, and expansion are discussed. The maximum transmitted pressure, 452 kbar, is shown to occur at an impact angle of 63.4°, at the onset of Mach reflection. The steady double plastic wave structure in iron, which appears at impact angles between 71.3° and 90°, is calculated. Results for two colliding detonation waves are obtained as a special case.
Harmonic Generation in an Ionized Gas
Authors: Desloge Edward A. , Coleman Donald J.
Published: December 2004

The effect of collisions on harmonic generation in an ionized gas through which an electromagnetic wave is passing is considered. A set of equations is obtained from which it is possible, knowing the various collision cross sections, to obtain the dependence of the third-harmonic power generation on the molecular temperature, the magnitude of the field, the frequency of the field, and the various particle densities. The analysis is valid for large and small fields, elastic and inelastic cross sections, and arbitrary degree of ionization, provided (1) the frequency of the field is much greater than both the plasma frequency and the collision frequency for electron energy relaxation; (2) the magnitude of the electron drift velocity is small compared to the electron thermal speed; (3) the interaction of the electrons with electrons, ions, and molecules can be treated as binary collisions; (4) spatial variations in the density, drift velocity, pressure, electron temperature, electric field, etc., can be neglected; and (5) the electron density is constant in time.
Anomalous Bremsstrahlung and Renormalized Kinetic Equation
Authors: Baus M.
Published: December 2004

The anomalous term found recently in the collision integral for bremsstrahlung is eliminated through a redefinition of the distribution function leading to dynamically dressed field oscillators.
Reflection-Absorption Properties of Walls and Sheaths in the Propagation of Ion-Acoustic Waves
Authors: Bertotti B. , Brambilla M. , Sestero A.
Published: December 2004

The Van Kampen-Case normal mode theory is applied to the solution of a boundary value problem for the propagation of ion-acoustic waves in collisionless plasmas, the boundary condition being provided by the nature of the charge sheath near the walls.
Higher-Order Corrections to the Chew-Goldberger-Low Theory
Authors: Frieman Edward , Davidson Ronald , Langdon Bruce
Published: December 2004

A complete higher-order set of equations of the Chew-Goldberger-Low theory has been derived. A slight modification of these equations produces the finite Larmor-radius hydromagnetic theory of Kennel and Greene. Some comments on the properties of these equations are given.
Measurement of Thermal Conductivity of Gases using Thermal Diffusion Columns
Authors: Saksena M. P. , Saxena S. C.
Published: December 2004

A discussion of the method of determining thermal conductivity of a gas employing a thermal diffusion column is presented along with its theory and various corrections. This method has been earlier employed by Blais and Mann, who were also the first to suggest it. However, this work posed certain doubts about the suitability of the method, which is convenient and preferable for high-temperature measurements. An apparatus of this type is employed to determine the thermal conductivity of air and helium. The maximum temperature investigated is 140°C only, and the success achieved has encouraged to extend the scope of these measurements to still higher temperatures.
Neutral Point in the Geomagnetic Field
Authors: Grad Harold , Hu Pung Nien
Published: December 2004

The neutral point on the boundary of the geomagnetic cavity in the solar wind is discussed. From the equilibrium and stability conditions it is shown that the correct geometry of the neutral point is a cusp.
Isotropic Turbulence and Inertial-Range Structure
Authors: Kraichnan Robert H.
Published: December 2004

The abridged Lagrangian-History Direct Interaction closure approximation is interpreted physically and used to analyze energy transfer, effective eddy viscosities, and Lagrangian spacetime statistics in stationary and decaying isotropic turbulence. The results are then specialized to the inertial range. Numerical values are predicted for the Kolmogorov constant, the asymptotic eddy viscosities due to inertial-range wavenumbers, and the dimensionless constant in Inoue's formula for the mean-square change of Lagrangian velocity with time. Computed curves are presented for the localness of energy transfer, for Lagrangian spacetime structure functions, and for Lagrangian spacetime acceleration-acceleration and velocity-acceleration covariances. The Kolmogorov dissipation spectrum is computed, and the predicted spectra for the inertial and dissipation ranges are compared with experiment.
Analysis of the Dielectric Constant of a Two-Temperature Plasma
Authors: Klevans E. H. , Primack J. R.
Published: December 2004

The dielectric constant of a homogeneous, fully ionized two-temperature plasma is investigated to determine: (1) the conditions under which ion waves will be found; (2) accurate values for the phase velocity and damping rate of the ion waves; (3) the validity of approximate expressions for the ion wave phase velocity and damping; (4) the behavior of the dynamic shielding factor when ion waves are possible.
Turbulent Diffusion in a Penning-Type Discharge
Authors: Thomassen K. I.
Published: December 2004

Anomalous diffusion arising from a low-frequency flute instability is investigated in a Penning discharge. Theory and experiment on the instability are compared, and measurements of the turbulent fields are used to determine statistical transport rates. Finally, a small magnetic well is created with Ioffe bars to suppress the instability and lower the loss rate.
Sound Propagation in Rarefied Gases
Authors: Kahn David
Published: December 2004

The attenuation and dispersion of sound in nearly collisionless gases is studied as a function of the sound to particle path ratio. Numerical calculations appropriate to two highly rarefied atmospheres are given.
Future Directions in Cancer Research: Impact of the Completion of the Human Genome
Authors: Zoon Kathryn C.
Published: December 2004

The sequencing of the human genome will have a major impact on the prevention, diagnosis, treatment, monitoring, and outcome of cancer. Progress will most likely occur in a stepwise fashion with the biggest initial impact in diagnosis and molecular targeting of new medicines. Advances in genomics and proteomics have already resulted in major findings that are facilitating earlier cancer diagnosis and disease stratification. New treatments that target specific pathways are well underway for many cancers and likewise, molecular analyses aimed at finding medicines with reduced toxicities are being conducted. Close interaction with the Food and Drug Administration will be very important to integrate these new technologies into product development and the approval of new medicines and diagnostics. Clearly, we are now approaching the era of personalized medicines in which one has the opportunity to maximize the efficacy and minimize the side effects of the cancer treatments. The ability to translate this new technology into improving cancer patient care and outcomes will require that scientists from academia, industry, and government work together closely to develop the framework and standards necessary to maximize the benefit of the human genome project.
Cancer Therapeutics: Understanding the Mechanism of Action
Authors: Cattley Russell C. , Radinsky Bert R.
Published: December 2004

An intended consequence of the significant investment to characterize the mammalian genome, and its alterations in neoplastic diseases, has been the discovery and commercialization of new approaches to anticancer therapy. As a result, the list of available targets, formerly directed against the processes of DNA replication and mitosis, or in hormonal regulation of growth of tissue, has been dramatically extended. Many of the newer targets represent normal or aberrant signaling pathways, and are present within the cancer cell as second messengers, on its surface (as receptors), or in the external milieu (as ligands). These targets are, therefore, important to the cancer cell phenotype, and affect proliferation, differentiation, and death options for the cell. Another group of targets encompass the cancer cell's relationship to the tissue environment (both stroma and nonneoplastic cells). These targets involve interactions with blood supply (angiogenesis), immune function (evasion), and matrix (invasion and metastasis). Thus, most targets are directly or indirectly critical to some aspect of cancer cell physiology, although a few additional targets are being approached as localization signals for the delivery of otherwise less specific chemotherapeutic or radiotherapeutic agents. The development of new therapeutic approaches has expanded the scope of research required to characterize the mechanism of action for anticancer agents in preclinical models and in clinical trials. In preclinical research, mechanism of action studies have supported the selection of therapeutic agents, appropriate models of efficacy, and experimental design, as well as rational characterization and prediction of nontumor (host) effects. In clinical research, mechanism of action studies have supported the identification of surrogate markers of efficacy (critical for determining adequacy of dose and latency of response), and the selection of patient subpopulations and tumor subtypes most likely to exhibit clinical responses. Finally, information on mechanism of action may suggest strategies for combination therapies and predict potential mechanisms of disease resistance to therapy.
Consumer Labels can Convey Polyphenolic Content: Implications for Public Health
Authors: Waterhouse Andrew L.
Published: December 2004

Polyphenolics are a large group of related substances. Many of these, in
fact much of that found in food, is composed of processing‐derived substances
too complex for complete identification. Recent studies have suggested likely
benefits for diets high in polyphenols, particular in reducing heart disease mortality,
but other benefits have also been suggested. A consumer label based on
the major polyphenolic classes is both manageable and fairly informative as
most foods do not contain all possible classes. Differences between class
member can be significant, but data on individual substances is impractical
and no data is certainly less informative. Equivalency scales may be useful but
may skew content of many foods towards the high‐equivalency substances, even
while the full beneficial effects of each individual substance is poorly described.
'New Wave' Student Voice and the Renewal of Civic Society
Authors: Fielding Michael
Published: December 2004

The re-emerging field of 'student voice' has the potential to offer an important contribution to education for civic society. An exploration of what 'student voice' aspires to and what it actually does suggests quite different sets of possibilities for educational and civic renewal.
A new intellectual framework is offered in the hope that it might contribute further to democratic aspirations and emergent realities.
Autoimmune Epilepsy: Some Epilepsy Patients Harbor Autoantibodies to Glutamate Receptors and dsDNA on both Sides of the Blood‐brain Barrier, which may Kill Neurons and Decrease in Brain Fluids after Hemispherotomy
Authors: Ganor Yonatan , Goldberg-Stern Hadassa , Amrom Dina , Lerman-Sagie Tally , Teichberg Vivian I. , Pelled Dori , Futerman Anthony H. , Ben Zeev Bruria , Freilinger Michael , Verheulpen Denis , Van Bogaert Patrick , Levite Mia
Published: December 2004

Purpose: Elucidating the potential contribution of specific autoantibodies (Ab′s)
to the etiology and/or pathology of some human epilepsies. Methods: Six epilepsy
patients with Rasmussen′s encephalitis (RE) and 71 patients with other epilepsies
were tested for Ab′s to the –B— peptide (amino acids 372‐395) of the glutamate/AMPA
subtype 3 receptor (GluR3B peptide), double‐stranded DNA (dsDNA), and
additional autoimmune disease‐associated autoantigens, and for the ability of their
serum and cerebrospinal‐fluid (CSF) to kill neurons. Results: Elevated anti‐GluR3B
Ab′s were found in serum and CSF of most RE patients, and in serum of 17/71
(24%) patients with other epilepsies. In two RE patients, anti‐GluR3B Ab′s
decreased drastically in CSF following functional‐hemispherotomy, in association
with seizure cessation and neurological improvement. Serum and CSF of two RE
patients, and serum of 12/71 (17%) patients with other epilepsies, contained
elevated anti‐dsDNA Ab′s, the hallmark of systemic‐lupus‐erythematosus. The sera
(but not the CSF) of some RE patients contained also clinically elevated levels of
–classical— autoimmune Ab′s to glutamic‐acid‐decarboxylase,
cardiolipin,
β2‐glycoprotein‐I and nuclear‐antigens SS‐A and RNP‐70. Sera and CSF of some
RE patients caused substantial death of hippocampal neurons. Conclusions: Some
epilepsy patients harbor Ab′s to GluR3 and dsDNA on both sides of the blood‐brain
barrier, and additional autoimmune Ab′s only in serum. Since all these Ab′s may
be detrimental to the nervous system and/or peripheral organs, we recommend
testing
for their presence in epilepsy, and silencing their activity in Ab‐positive patients.
Virus‐induced Systemic Vasculitides: New Therapeutic Approaches
Authors: Guillevin Loïc
Published: December 2004

The best therapeutic strategy in virus‐induced vasculitides should take
into account the etiology of the disease and be adapted to the pathogenesis. The
combination of antiviral treatments and plasma exchanges has been proven
effective in polyarteritis nodosa (PAN). In human immunodeficiency virus
(HIV)‐related vasculitis this strategy is also effective and does not jeopardize, like
cytotoxic agents, the outcome of AIDS. In vasculitis related to HCV‐associated
cryoglobulinemia, plasma exchanges improve the outcome but the poor
effectiveness of antiviral drugs is not able to favor,
usually, a definite recovery of the patients and relapses are frequent.
Inflammatory Bowel Disease: Autoimmune or Immune‐mediated Pathogenesis?
Authors: Wen Zhonghui , Fiocchi Claudio
Published: December 2004

The pathogenesis of Crohn′s disease (CD) and ulcerative colitis (UC), the two
main forms of inflammatory bowel disease (IBD), is still unclear, but both
autoimmune and immune‐mediated phenomena are involved. Autoimmune
phenomena include the presence of serum and mucosal autoantibodies against
intestinal epithelial cells in either form of IBD, and against human tropomyosin
fraction five selectively in UC. In addition, perinuclear antineutrophil cytoplasmic
antibodies (pANCA) are common in UC, whereas antibodies against Saccharomyces
cerevisiae (ASCA) are frequently found in CD. Immune‐mediate phenomena
include a variety of abnormalities of humoral and cell‐mediated immunity, and
a generalized enhanced reactivity against intestinal bacterial antigens in both CD
and UC. It is currently believed that loss of tolerance against the indigenous enteric
flora is the central event in IBD pathogenesis. Various complementary factors
probably contribute to the loss of tolerance to commensal bacteria in IBD. They
include defects in regulatory T‐cell function, excessive stimulation of mucosal
dendritic cells, infections or variants of proteins critically involved in bacterial
antigen recognition, such as the products of CD‐associated
NOD2/CARD15 mutations.
Intra‐uterine Growth Restriction Downregulates the Hepatic Toll Like Receptor‐4 Expression and Function
Authors: Equils Ozlem , Singh Sapna , Karaburun Semra , Lu Daning , Thamotharan Manikkavasagar , Devaskar Sherin U.
Published: December 2004

Maternal starvation is a significant cause of intrauterine growth restriction
(IUGR) in the world and increases the risk of infection in the neonate. We examined
the effect of maternal starvation on Toll like receptor (TLR)4 expression in hepatic,
splenic and intestinal tissues obtained from the adult IUGR offspring of prenatal
calorie restricted rats. The hepatic TLR4 protein concentration was undetectable in
the IUGR rats that had restricted milk intake during the suckling period
(SM/SP; n = 4, p < 0.05) as compared to the normal
growth controls (CM/CP; n=4),
and access to ad lib milk intake during the sucking period partially corrected the
hepatic TLR4 expression (SM/CP; n = 4). IUGR had no effect
on the splenic (n = 4) or
intestinal (n = 4) TLR4 mRNA levels. In the liver, IUGR
led to a 20% increase in
baseline tumor necrosis factor (TNF)‐α mRNA expression ( p < 0.03) and a 70%
increase in interleukin‐1β (IL‐1β) mRNA expression ( p < 0.008) as compared to
the control rats (CM/CP; n = 7). LPS‐induced hepatic
TNF‐α release was significantly
higher in SM/SP as compared to CM/CP. We propose that IUGR dysregulates
TLR4 expression and function in the offspring, which may help explain
the increased risk of Gram‐negative sepsis and inflammatory diseases in this
population.
Surveying In Switzerland
Authors: Flotron A.
Published: December 2004

The author traces the development of the Swiss official surveying system from its origins according to the federal law in 1912 until the system of the renewed cadastre 93, standards for which were recently issued. He summarizes the techniques applied today in the official surveying system and describes the commercial situation of the private surveyors and surveying companies.
United Grain Growers: Enterprise Risk Management and Weather Risk
Authors: Harrington Scott , Niehaus Greg
Published: December 2004

Abstract

In August of 1999, Mike McAndless, the risk manager of United Grain Growers (UGG), was preparing for a meeting with the firm's chief financial officer, Peter Cox. Mike and Peter had spent considerable time over the past three years with representatives of the Willis Group Ltd., a large international insurance broker, identifying and measuring UGG's major sources of risk. The risk assessment process indicated that, although UGG hedged most of its currency and commodity price risk and purchased insurance against property and liability losses, the firm's earnings still exhibited substantial volatility. This volatility was, in large part, due to the weather. Mike and Peter had to decide whether to retain the risk or shift it to another party using one of two innovative contractual arrangements: weather derivatives or a new type of insurance contract.
Legitimacy Problems in Deliberative Democracy
Authors: Parkinson John
Published: December 2004

The classic accounts of deliberative democracy are also accounts of legitimacy: ‘that outcomes are legitimate to the extent they receive reflective assent through participation in authentic deliberation by all those subject to the decision in question’ ( Dryzek, 2001, p. 651 ). And yet, in complex societies deliberative participation by all those affected by collective decision-making is extremely implausible. There are also legitimacy problems with the demanding procedural requirements which deliberation imposes on participants. Given these problems, deliberative democracy seems unable to deliver legitimate outcomes as it defines them.

Focusing on the problem of scale, this paper offers a tentative solution using representation, a concept which is itself problematic. Along the way, the paper highlights issues with the legitimate role of experts, the different legitimate uses of statistical and electoral representation, and differences between the research and democratic imperatives driving current attempts to put deliberative principles into practice, illustrated with a case from a Leicester health policy debate. While much work remains to be done on exactly how the principles arrived at might be transformed into working institutions, they do offer a means of criticising existing deliberative practice.
A Prospective Study of Memory for Child Sexual Abuse
Authors: Goodman Gail S. , Ghetti Simona , Quas Jodi A. , Edelstein Robin S. , Alexander Kristen Weede , Redlich Allison D. , Cordon Ingrid M. , Jones David P.H.
Published: December 2004

Previous research indicates that many adults (nearly 40%) fail to report their own documented child sexual abuse (CSA) when asked about their childhood experiences. These controversial results could reflect lack of consciously accessible recollection, thus bolstering claims that traumatic memories may be repressed. In the present study, 175 individuals with documented CSA histories were interviewed regarding their childhood trauma. Unlike in previous studies, the majority of participants (81%) in our study reported the documented abuse. Older age when the abuse ended, maternal support following disclosure of the abuse, and more severe abuse were associated with an increased likelihood of disclosure. Ethnicity and dissociation also played a role. Failure to report CSA should not necessarily be interpreted as evidence that the abuse is inaccessible to memory, although inaccessibility or forgetting cannot be ruled out in a subset of cases.