bluuebunny/crossref_metadata_2025 huggingface dataset:
Wave Propagation in Hot Plasma Waveguides with Infinite Magnetostatic Fields
Authors: Kuehl H. H. , Stewart G. E. , Yeh C.
Published: December 2004

Solutions of the ``dispersion relation'' for an unbounded Maxwellian electron plasma, 2k2/kD2 = Z′(ω/kvth) for ω real are given. Solutions of the corresponding relation for a circular waveguide filled with a hot plasma with an infinite magnetostatic field are also presented. It is shown that these solutions are of importance in evaluating the fields in such waveguides since they determine the poles of the integrands which arise in the integral formulation of the problem. The integral solution for the field in the waveguide due to a general symmetric excitation at the wall of the waveguide is given.
Plasma Depolarization and Heating in the Collision of Polarized Plasmas
Authors: Beckner Everet H.
Published: December 2004

A study has been conducted of the deceleration and depolarization phenomena which occurred when oppositely-directed plasma streams were caused to collide in the presence of a transverse magnetic field. The depolarization which followed collision of these oppositely-polarized plasmas resulted primarily from plasma deceleration through j × B forces. Translational kinetic energy was found to be efficiently converted to thermal energy in such processes. In addition, Ohmic heating effects were quite important, particularly late in time. Ohmic potential drops were found to be unimportant, even for these highly tensor plasmas. The presence of the transverse magnetic field during collision resulted in significant increase in the assembled plasma temperature, density, and ``lifetime,'' compared to those which occurred when the field was absent.
Charge Separation Effects in the Ferraro-Rosenbluth Cold Plasma Sheath Model
Authors: Sestero Arrigo
Published: December 2004

An exact treatment is given of the Ferraro-Rosenbluth cold plasma sheath model, to improve on the charge neutral approximation considered previously in the literature. It is found that the turning points of the ion stream and of the electron stream are actually separated in space. It is found also, somewhat unexpectedly, that there exists a certain range of parameters for which the ions are turned back sooner than the electrons, due to the combined effect of the electric and magnetic forces in the sheath. The change of behavior in the solution occurs discontinuously, allowing for no intermediate case with the two species of particles turning together. Finally, it is found that the sheath is not, in general, over-all charge-neutral, and that the excess charge can actually be of either sign, depending on the values of the parameters.
Drag of a Sphere Oscillating in a Conducting Viscous Medium
Authors: Singh M. P.
Published: December 2004

The effects of rotation, magnetic field and compressibility on the disturbances engendered by the slow oscillations of a conducting sphere in a viscous medium are considered. It is shown that the magnetic field tends to increase the resistance and to decrease the apparent mass of the fluid, whereas the rotation makes no contribution to the drag. The magnetic field and the rotation generate vorticity and the electric current. The viscosity tends to contract the lines of magnetic force, while the streamlines are stretched by the effect of the magnetic field and the viscosity. The nature of the wave propagation remains essentially similar in both rotating and nonrotating cases, as well as in hydromagnetics and in the nonmagnetic case. When the fluid is compressible, sound waves in addition to the other waves are found.
Observations of the Structure of Spinning Detonation
Authors: Schott Garry L.
Published: December 2004

Spinning detonation waves in acetylene-oxygen mixtures highly diluted with argon have been studied in circular tubes by a variety of simple photographic, electrical, and mechanical (soot inscription) techniques. The combined results of these experiments permit the deduction of a fairly detailed description of the system of shock waves, reaction zones, and contact zones which exists at the front of the spinning detonation. The outstanding feature of the observed structure is that about half of the gas near the tube wall is burned in a wave which propagates in a nearly circumferential direction through shocked, unburned gas behind the nonplanar primary shock front. The relation of this structure to that of White's ``laminar detonations'' in rectangular nozzles and to spinning detonation wave structures recently proposed by certain Russian workers is discussed.
Round Laminar Jet in an Axial Magnetic Field
Authors: Hoult D. P.
Published: December 2004

The flow of an axisymmetric jet of a conducting liquid in a uniform axial magnetic field is studied. The magnetic Reynolds number is low, and the viscous Reynolds number, R, is high. The first terms of an asymptotic expansion of the solution are obtained. The momentum in the jet is not constant but decays linearly with the distance downstream of the orifice. The flow is confined by the magnetic field to a tube of diameter R−1/4 which lies on the axis of the jet.
Wave Motion in a Plasma Based on a Fokker-Planck Equation
Authors: Oppenheim Alan
Published: December 2004

An isotropic Fokker-Planck collision model is introduced in Boltzmann's equations in order to study the small amplitude wave motion of an unbounded, fully ionized, neutral, two-component plasma in a uniform applied magnetic field. In the Laplace and Fourier transformed space the linearized Boltzmann's equations with Maxwell's equations are solved and the dispersion relation is constructed. Because the isotropic Fokker-Planck operators describe a diffusion process in velocity space while the previously considered Krook relaxation models do not, an infinite number of new Larmor resonance modes is found at arbitrary directions of propagation with respect to the applied magnetic field. These new resonances remain in the limit of long macroscopic wavelengths and small collision frequencies. At propagation parallel to the applied magnetic field new resonances are found for wavelengths large and small with respect to the mean free path. In other macroscopic ranges such as the cold plasma regime and the long wavelength magnetohydrodynamic regime the Krook and the isotropic Fokker-Planck models give the same results to lowest order.
Quasi-Linear Theory for Small Larmor Radius Universal Instabilities
Authors: Hoh F. C.
Published: December 2004

A class of universal instabilities is discussed. The basic physical mechanism of these instabilities is illustrated with a simple physical picture, and the large amount of energy available to drive these instabilities is pointed out. A small Larmor radius quasi-linear theory is developed for a class of unstable ion waves whose phase velocities along the magnetic field lie between the thermal velocities of ions and electrons. In the approximation of localized perturbations, the final state quantities of the plasma are given without specifying the detailed instability mechanism. An essential feature is that the quasi-linear theory predicts an anomalous ``displacement'' of a group of resonant particles rather than any anomalous diffusion. The theory is applied to a special type of the current-driven universal instability. Its quasi-linear consequences are explored.
Motion and Decay of a Vortex in a Nonuniform Stream
Authors: Ting L. , Tung C.
Published: December 2004

The motion of a vortex in a two-dimensional incompressible nonuniform stream is studied by including the viscous effects in the inner core of the vortex. A systematic procedure is presented by the introduction of two different sets of length and time scales with the larger scales identified with the typical scales of the outer nonuniform flow. The ratios of the scales are powers of the small parameter ε which is inversely proportional to the square root of the Reynolds number of the vortex. It is shown that the leading term of the solution to the Navier-Stokes equations are composed of the classical inviscid solution matched with the solution of a decaying axially symmetric vortex. Thus the singularity in the center of the vortex associated with the classical inviscid theory is removed. The next-order solution shows that the time average of the velocity of the center of the vortex over a period of the order of the larger time scale should agree at least to the order of ε2 with the local space mean of the velocity of the outer inviscid flow which has been assumed to be the velocity of the center of the vortex in the classical inviscid theory of vortex motion. The nonuniformity of the outer flow will induce a nonaxially symmetric solution for the inner viscous region of the order ε2 or higher, which in turn will introduce an additional term to the outer flow of the order of ε4 or higher.
Interpretation of Time Spectra Measured in High-Intensity Shear Flows
Authors: Lumley J. L.
Published: December 2004

Fisher and Davies have suggested several mechanisms which can prevent the direct interpretation of time spectra as space spectra by the frozen pattern hypothesis. It is shown that, when various criteria such as that of Lin are satisfied, all but one of these mechanisms, the fluctuation of convection velocity, can be disregarded at high frequencies. An analytical model of this mechanism is constructed and several of its properties examined. On the basis of this model, a correction formula is obtained for the high-frequency part of the one-dimensional streamwise spectrum. This is applied to experimental data taken in a curved turbulent mixing layer. It is found that even under extreme circumstances corrections from this source are not likely to exceed 30%.
Generalized Orthogonal Polynomial Solutions of the Boltzmann Equation
Authors: Mintzer David
Published: December 2004

Solutions of the Boltzmann equation of the form f(r, v, t) = f(0)(r, v, t) Σ ap(r, t)Mp(v; r, t) are considered, where f(0) is some zero-order approximation to f. It is shown that, to obtain reasonable equations for the ap and to relate them to the moments of f, the Mp should be a polynomial set in velocity-space, orthogonalized with f(0) as the weighting factor. It is shown how the Burnett method and the Grad method are derivable when the problem is a near-equilibrium one; and how the half-range polynomial method results when particular symmetry conditions are imposed. An illustration of the method is given for the case of the equilibration of a two-temperature gas mixture.
Temperature and Power Measurements in a Plasma Heated by Absorption of Ion Cyclotron Waves
Authors: Hooke W. M. , Rothman M. A. , Sinnis J. , Adam J.
Published: December 2004

A plasma in a magnetic mirror field is heated by means of an induction coil which generates plasma waves at a frequency near the gyrofrequency of the ions. Several hundred kilowatts of power are transmitted to the plasma. Ion energies in the neighborhood of 1 keV are observed in a small volume within the plasma. These energies are believed to be associated with ions trapped within a small magnetic mirror region following their acceleration by ion cyclotron damping of the waves. In a deuterium plasma production of neutrons is observed in association with these trapped ions. Ion energies of 200–300 eV are found throughout the total 10-liter plasma volume. The electron temperature is approximately 10 eV. Energy is lost from the plasma in times ranging from 30–50 μsec. This loss rate appears to result from particle losses as well as radiation from impurities. To explain the loss of energy it is not necessary to invoke an instability mechanism.
Plasma End Losses and Heating in the ``Low-Pressure'' Regime of a Theta Pinch
Authors: Little E. M. , Quinn W. E. , Sawyer G. A.
Published: December 2004

A neutron-producing plasma with ion energy ∼3–4 keV has been produced at filling densities 10–50 μHg without negative bias magnetic fields in a 570-kJ theta pinch. Axial interferograms, taken with a ruby-laser-illuminated Mach—Zehnder interferometer show that a stable compressed plasma core exists throughout the magnetic half cycle with no ionized impurities outside the core, and no drift toward the wall. The interferograms give peak plasma densities of 2 to 5 × 1016 cm-3, and also indicate a loss of particles as a function of time. Plasma containment times (e-folding times of N) before peak compression are 6 to 30 μsec. The observed loss rates are approximately in agreement with predictions of free flow through an orifice whose radius is equal to an ion Larmor radius. Soft x-ray measurements yield ∼300 eV electron temperature for all filling pressures. Absolute intensities of the soft x-ray emissions show the impurity level to be <0.1%. The ion energy for the low-pressure regime deduced from pressure balance between plasma and magnetic field (assuming β = 1) is about a factor two higher than the ion energy deduced from the measured neutron yield for a Maxwell distribution. The discrepancy suggests that the distribution is more nearly monoenergetic than Maxwellian.
Effect of a Cylindrical Boundary on the Added Mass of Two Cylinders in Liquid Helium
Authors: Hussey R. G. , Reynolds J. M.
Published: December 2004

An expression is derived for the added mass of two equal circular cylinders (radius a) moving normal to the line of centers in an ideal fluid enclosed by a fixed cylindrical boundary (radius b). The two moving cylinders, with centers 2c apart, have velocities equal in magnitude but opposite in direction. Except for extreme cases, the added mass per unit length of each cylinder is given by M=πa2ρ[1−12γ2+8β4γ2(β4−γ4)2], where ρ is the fluid density, β = b/a, and γ = c/a. This expression is compared with the results of a torsion pendulum experiment in liquid helium II. For γ = 4.9 and 8.6 < β < 11, the predicted change in moment of inertia is in good agreement with that observed in liquid helium between 2.15° and 1.3°K. The observed damping is independent of boundary radius.
Parameter of Discontinuity and Differential-Operator Expansion of the Linear Boltzmann or Master Operator
Authors: Siegel Armand , Akama Hachiro
Published: December 2004

The ratio of the average microscopic agitation interval to the macroscopic relaxation time is proposed as the expansion parameter of linear Boltzmann or master operators. This parameter is interpretable physically both as a measure of the discontinuity of the random process, and as an inverse measure of the size of the fluctuating system. In the limit when the expansion parameter is zero, the process becomes continuous and is described by the Fokker-Planck equation. When the parameter is nonvanishing, the expansion of the master operator in terms of it is, in three representative cases, a ``CD expansion'' in products of creation and destruction operators for Hermite functions; the dominant term is usually the Fokker-Planck operator. These results are considered in relation to van Kampen's hypothesis for small-parameter expansions of the same operators. It is found that the CD expansion fits the available model processes exactly, and that these processes do not satisfy van Kampen's hypothesis. As a new application, the explicit CD series is given for the density fluctuation model. Special cases of the model include the density fluctuations studied by van Kampen and the Ehrenfest urn model.
Unsteady Flows in an Unsteady Environment
Authors: Lee T. S.
Published: December 2004

This theoretical study treats flows behind a shock or sound wavefront propagating into an environment which is itself allowed to be undergoing some generally unsteady (i.e., nonstationary, nonuniform, and thus nonisentropic) motion. Interest is with centrally symmetric geometries. Considerations regarding self-similarity are investigated and conditions for its existence are arrived at in terms of four constancy relations. The nature of flow singularities is discussed in general terms and relevant examples exhibiting certain of their respective features are given. It is found also that known similarity solutions of the nonisentropic flow family and certain centered-wave solutions of the isentropic flow family are identifiable as special cases of the present theory. The formulation is general enough to apply to implosive as well as explosive problems.
Low-Frequency Instability of Partially Ionized Plasma
Authors: Morse David L.
Published: December 2004

The stability of a partially ionized plasma in a magnetic field is investigated. The electron and ion flow equations and continuity equations are used to describe low-frequency, macroscopic variations of plasma density and space potential. The solutions to the linearized forms of these equations consist of a set of eigenfunctions of perturbed density, and a complex frequency eigenvalue corresponding to each perturbed density eigenfunction. It is found that rotating ``flutelike'' density perturbations may grow when a steady radial electric field is present, either parallel or antiparallel to the unperturbed density gradient. The growth rate is proportional to a ``corrected'' electric field, which includes the time-invariant gradients of both density and space potential. The stabilizing effects of diffusion, parallel and perpendicular to the magnetic field, are considered.
Vaporization Waves as a General Property of High Temperature Matter
Authors: Bennett F. D.
Published: December 2004

Electrical data on exploding wires suggest strongly that vaporization waves can occur in all metals. If a vapor pressure function capable of representing the data for metals is assumed, the thermodynamic, vaporization wave velocity can be expressed in terms of a general function and a characteristic velocity. Values of this velocity have been calculated for several metals and show a spread of four orders of magnitude. Necessary conditions are proposed under which any substance can exhibit vaporization waves at high temperatures.
Kinetic-Theoretic Description of Shock Wave Formation. II.
Authors: Chu C. K.
Published: December 2004

The method and results previously obtained [C. K. Chu, Phys. Fluids 8, 12 (1965)] for a one-dimensional gas (γ = 3) is extended to a monatomic three-dimensional gas (γ = 5/3). The classical Riemann problem—the flow of a gas in a shock tube—is treated as an initial value problem for the Krook equation, after the Krook equation is first reduced to two simultaneous Krook equations each for a one-dimensional gas. The numerical scheme used is the same as that previously proposed. Results are obtained on the formation of shocks corresponding to Mach numbers of 1.27, 1.5, and 1.75. It is seen that the stronger the shock, the shorter the formation time. The short-time behavior of the flow agrees with free flow, while the long-time behavior agrees with fluid dynamics. The shocks formed agree very closely with the results of Liepmann, Narasimha, and Chahine.
Effect of an Axial Magnetic Field on the Stability of an Axisymmetric Jet or Wake
Authors: Hoult David P.
Published: December 2004

Theoretical calculations on the effect of a uniform axial magnetic field on the sinuous unstable mode of an axisymmetric jet or wake are presented. The fluid is incompressible. The viscous Reynolds number is assumed infinite, and the magnetic Reynolds number is low. The profile studied is trapezoidal with thin shear layers. The calculations are done for small axial wavenumber, α. In the nonmagnetic case, the approximate amplification rate as a function of α agrees with numerical calculations up to the α for maximum amplification rate, when properly scaled. In the magnetic case, a new effect occurs. Due to the helical nature of the instability, the electric field must be nonzero to make the electric current source-free. It is shown that the magnetic field always decreases the amplification rate. The effect is small, of order α2, because the electric field for small α cancels the current generated by fluid crossing field lines.
Hydromagnetic Waves in a Shear Flow
Authors: Koppel Donald
Published: December 2004

Small disturbances superimposed upon the basic flow of parallel magnetic lines of force stretched by a shear flow of the associated fluid are considered. The resulting system of equations is reduced to an ordinary linear second order differential equation. This equation is solved for various asymptotic limits of a parameter it contains, and in the general case, by numerical integration. The resulting magnetic and flow fields of the small disturbance are described.
Harmonic Generation in a Microwave Discharge
Authors: Murphy Brian
Published: December 2004

The first two harmonics generated in a microwave discharge in which a weak dc field is present are calculated. The mechanism by which harmonics are generated is assumed to be a modulation of the electron collision frequency by the microwave field. The second harmonic is strongest at a pressure for which the collision frequency is well below the frequency of the perturbing microwave field. The third harmonic is strongest when the collision frequency is approximately equal to the frequency of the microwave field. These results are found to be in reasonable agreement with the observations of Uenohara.
Determination and Assessment of Morse Potential Functions for some Nonpolar Gases
Authors: Konowalow Daniel D. , Carrá Sergio
Published: December 2004

Morse potential functions for Ar, Kr, Xe, N2, and CH4 are determined from the experimental viscosity, η(T), and second virial coefficient, B(T). These potentials afford only conditionally compatible (and not very accurate) descriptions of these two properties, although they compare favorably with high-energy repulsive potentials. In these respects, they are superior to those based largely on crystal data. The Morse and the Kihara spherical-core potentials for Ar are compared. Neither is able to reproduce the known B(T), η(T) as well as the repulsive potentials within acceptable limits.
Magnetospheric Free-Boundary Problem in Axial Symmetry
Authors: Blum Ronald
Published: December 2004

An approximate solution for the steady-state interaction between a field-free streaming plasma and a magnetic dipole parallel to the stream is obtained. The free boundary (magnetopause) between the magnetic field region (magnetosphere) and the plasma is determined by the conditions that the plasma be field-free and that its kinetic pressure on the boundary balances the pressure of the magnetic field inside the boundary. The solution was derived by a combination of analytic and numerical (relaxation) methods, with an error of approximately 1% or less in the dimensions of the magnetosphere.
Differential Effects of Cast Shadows on Perception and Action
Authors: Bonfiglioli Claudia , Pavani Francesco , Castiello Umberto
Published: December 2004

In two experiments we investigated the effects of cast shadows on different real-life tasks. In experiment 1, participants were required to make a speeded verbal identification of the target object (perceptual task), whereas in experiment 2 participants were required to reach for and grasp the target object (motor task). In both experiments real three-dimensional (3-D) objects were presented, one at a time, either with their own natural cast shadow (congruent condition) or with the cast shadow of a different object (incongruent condition). Shadows were cast either to the left or to the right of the object. We asked whether the features of the shadow (ie whether it is congruent or incongruent with the object, and whether it is cast to the left or to the right of the object) could influence perception and action differently. Results showed that cast shadows did not influence identification of real 3-D objects (experiment 1), but they affected movement kinematics, producing distractor-like interference, particularly on movement trajectory (experiment 2). These findings suggest a task-dependent influence of cast shadows on human performance. In the case of object-oriented actions, cast shadows may represent further affordances of the object, and as such compete for the control of the action.
A Two-Point Visual Control Model of Steering
Authors: Salvucci Dario D , Gray Rob
Published: December 2004

When steering down a winding road, drivers have been shown to use both near and far regions of the road for guidance during steering. We propose a model of steering that explicitly embodies this idea, using both a ‘near point’ to maintain a central lane position and a ‘far point’ to account for the upcoming roadway. Unlike control models that integrate near and far information to compute curvature or more complex features, our model relies solely on one perceptually plausible feature of the near and far points, namely the visual direction to each point. The resulting parsimonious model can be run in simulation within a realistic highway environment to facilitate direct comparison between model and human behavior. Using such simulations, we demonstrate that the proposed two-point model is able to account for four interesting aspects of steering behavior: curve negotiation with occluded visual regions, corrective steering after a lateral drift, lane changing, and individual differences.
Vascular cambium necrosis in forest fires: using hyperbolic temperature regimes to estimate parameters of a tissue-response model
Authors: Dickinson M. B. , Jolliff J. , Bova A. S.
Published: December 2004

Hyperbolic temperature exposures (in which the rate of temperature rise increases with time) and an analytical solution to a rate-process model were used to characterise the impairment of respiration in samples containing both phloem (live bark) and vascular-cambium tissue during exposures to temperatures such as those experienced by the vascular cambium in tree stems heated by forest fires. Tissue impairment was characterised for red maple (Acer rubrum), chestnut oak (Quercus prinus), Douglas fir (Pseudotsuga menziesii), and ponderosa pine (Pinus ponderosa) samples. The estimated temperature dependence of the model’s rate parameter (described by the Arrhenius equation) was a function of the temperature regime to which tissues were exposed. Temperatures rising hyperbolically from near ambient (30°C) to 65°C produced rate parameters for the deciduous species that were similar at 60°C to those from the literature, estimated by using fixed temperature exposures. In contrast, samples from all species showed low rates of impairment, conifer samples more so than deciduous, after exposure to regimes in which temperatures rose hyperbolically between 50 and 60°C. A hypersensitive response could explain an early lag in tissue-impairment rates that apparently caused the differences among heating regimes. A simulation based on stem vascular-cambium temperature regimes measured during fires shows how temperature-dependent impairment rates can be used to predict tissue necrosis in fires. To our knowledge, hyperbolic temperature exposures have not been used to characterise plant tissue thermal tolerance and, given certain caveats, could provide more realistic data more efficiently than fixed-temperature exposures.
gerbil: Genotype resolution and block identification using likelihood
Authors: Kimmel Gad , Shamir Ron
Published: December 2004

The abundance of genotype data generated by individual and international efforts carries the promise of revolutionizing disease studies and the association of phenotypes with individual polymorphisms. A key challenge is providing an accurate resolution (phasing) of the genotypes into haplotypes. We present here results on a method for genotype phasing in the presence of recombination. Our analysis is based on a stochastic model for recombination-poor regions (”blocks”), in which haplotypes are generated from a small number of core haplotypes, allowing for mutations, rare recombinations, and errors. We formulate genotype resolution and block partitioning as a maximum-likelihood problem and solve it by an expectation-maximization algorithm. The algorithm was implemented in a software package calledgerbil(genotype resolution and block identification using likelihood), which is efficient and simple to use. We testedgerbilon four large-scale sets of genotypes. It outperformed two state-of-the-art phasing algorithms. Thephasealgorithm was slightly more accurate thangerbilwhen allowed to run with default parameters, but required two orders of magnitude more time. When using comparable running times,gerbilwas consistently more accurate. For data sets with hundreds of genotypes, the time required byphasebecomes prohibitive. We conclude thatgerbilhas a clear advantage for studies that include many hundreds of genotypes and, in particular, for large-scale disease studies.
Proteinase-activated receptors 1 and 4 counter-regulate endostatin and VEGF release from human platelets
Authors: Ma Li , Perini Rafael , McKnight Webb , Dicay Michael , Klein Andre , Hollenberg Morley D. , Wallace John L.
Published: December 2004

The roles of proteinase-activated receptors (PARs) in platelet functions other than aggregation are not well understood. Among these is the release of factors that regulate the process of angiogenesis, such as endostatin and VEGF, which, respectively, inhibit and promote angiogenesis. PAR1 and PAR4 are expressed on the surface of human platelets and can be activated by thrombin. In the present study, we have attempted to determine the roles of PAR1 and PAR4 in regulating release of endostatin and VEGF from human platelets. Aggregation and endostatin release could be elicited by a specific PAR4 agonist (AYPGKF-NH
2
). The PAR4 agonist concentration dependently suppressed VEGF release. A selective PAR1 agonist (TFLLR-NH
2
) induced platelet aggregation and VEGF release but suppressed endostatin release. Thrombin did not affect endostatin or VEGF release. However, in the presence of a selective PAR1 antagonist (SCH79797), thrombin stimulated endostatin release and suppressed VEGF release. Conversely, in the presence of a selective PAR4 antagonist (transcinnamoyl-YPGKF-NH
2
), thrombin stimulated VEGF release.
In vivo
, treatment of rats with established gastric ulcers with a PAR1 antagonist each day for 1 wk resulted in a significant retardation of healing. We conclude that PAR1 and PAR4 counter-regulate the release of endostatin and VEGF from platelets. These protease-activated receptors could therefore play a crucial role in regulating angiogenesis and in turn could regulate the processes of wound healing and tumor growth.
Identification and Functional Characterization of Ankyrin-Repeat Family Protein ANKRA as a Protein Interacting with BKCaChannel
Authors: Lim Hyun-Ho , Park Chul-Seung
Published: December 2004

Ankyrin-repeat family A protein (ANKRA) was originally cloned in mouse as an interacting protein to megalin, a member of low-density lipoprotein receptor superfamily. Here, we report that the isolation of rat ANKRA as a new binding partner for the α-subunit of rat large-conductance Ca2+-activated K+channel (rSlo). We mapped the binding region of each protein by using yeast two-hybrid and in vitro binding assays. ANKRA expressed together with rSlo channels were colocalized near the plasma membrane and coimmunoprecipitated in transfected cells. We also showed that BKCachannel in rat cerebral cortex coprecipitated with rANKRA and colocalized in cultured rat hippocampal neuron. Although the coexpression of ANKRA did not affect the surface expression of rSlo, the gating kinetics of rSlo channel was significantly altered and the effects were highly dependent on the intracellular calcium. These results indicate that ANKRA could modulate the excitability of neurons by binding directly to endogenous BKCachannel and altering its gating kinetics in a calcium-dependent manner.
TheFLA3KAP Subunit Is Required for Localization of Kinesin-2 to the Site of Flagellar Assembly and Processive Anterograde Intraflagellar Transport
Authors: Mueller Joshua , Perrone Catherine A. , Bower Raqual , Cole Douglas G. , Porter Mary E.
Published: December 2004

Intraflagellar transport (IFT) is a bidirectional process required for assembly and maintenance of cilia and flagella. Kinesin-2 is the anterograde IFT motor, and Dhc1b/Dhc2 drives retrograde IFT. To understand how either motor interacts with the IFT particle or how their activities might be coordinated, we characterized a ts mutation in the Chlamydomonas gene encoding KAP, the nonmotor subunit of Kinesin-2. The fla3-1 mutation is an amino acid substitution in a conserved C-terminal domain. fla3-1 strains assemble flagella at 21°C, but cannot maintain them at 33°C. Although the Kinesin-2 complex is present at both 21 and 33°C, the fla3-1 Kinesin-2 complex is not efficiently targeted to or retained in the basal body region or flagella. Video-enhanced DIC microscopy of fla3-1 cells shows that the frequency of anterograde IFT particles is significantly reduced. Anterograde particles move at near wild-type velocities, but appear larger and pause more frequently in fla3-1. Transformation with an epitope-tagged KAP gene rescues all of the fla3-1 defects and results in preferential incorporation of tagged KAP complexes into flagella. KAP is therefore required for the localization of Kinesin-2 at the site of flagellar assembly and the efficient transport of anterograde IFT particles within flagella.
Evaluation of Seldinger Technique Emergency Cricothyroidotomy versus Standard Surgical Cricothyroidotomy in 200 Cadavers
Authors: Schaumann Nikolaus , Lorenz Veit , Schellongowski Peter , Staudinger Thomas , Locker Gottfried J. , Burgmann Heinz , Pikula Branko , Hofbauer Roland , Schuster Ernst , Frass Michael
Published: December 2004

Background

Percutaneous cricothyroidotomy is a lifesaving procedure for airway obstruction in trauma victims who need airway establishment and cannot be intubated or in whom intubation has failed.

Methods

The purpose of this study was to examine whether there is a training effect using Seldinger technique emergency cricothyroidotomy (group 1; Arndt Emergency Cricothyroidotomy Catheter Set; Cook Critical Care, Bloomington, IN) versus standard surgical cricothyroidotomy (group 2). Twenty emergency physicians performed five cricothyroidotomies with each method in a total of 200 human cadavers, comparing efficacy and safety (speed, success rate, and injuries).

Results

Seven attempts in group 1 and six in group 2 had to be aborted. Time intervals from the start of the procedure to location of the cricothyroid membrane were not significantly different between the groups. However, time to tracheal puncture (P < 0.01) and time to first ventilation (P < 0.001) were significantly longer in group 2. No time effect could be observed in both groups. The airway was accurately placed into the trachea through the cricothyroid membrane in 88.2% (82 of 93) of the cadavers in group 1 and in 84.0% (79 of 94) in group 2 (not significant). No injuries were observed in group 1, whereas there were six punctures of the thyroid vessels in group 2 (P < 0.05).

Conclusions

With respect to time needed for the procedure, the participants performed Seldinger technique emergency cricothyroidotomy significantly faster as compared with standard surgical cricothyroidotomy. Even if no training effect had been observed, the authors believe that it is important to train residents in different methods of cricothyroidotomy in cadavers in addition to training in mannequins to achieve a higher level of efficacy in real-life situations. The shorter time to first ventilation and the fact that no injuries could be observed favor the Seldinger technique.
Propofol and Thiopental Do Not Interfere with Regional Cerebral Blood Flow Response at Sedative Concentrations
Authors: Veselis Robert A. , Feshchenko Vladimir A. , Reinsel Ruth A. , Beattie Bradley , Akhurst Timothy J.
Published: December 2004

Background

Anesthetics may affect the regional cerebral blood flow (rCBF) response associated with increased brain activity in humans. rCBF was measured as auditory stimulus rate was increased during propofol and thiopental administration.

Methods

After informed consent, 10 right-handed male volunteer participants (aged 33.5 +/- 10.4 yr, weighing 74.5 +/- 8.4 kg) received thiopental (n = 4) or propofol (n = 6) intravenously at stepwise target concentrations of propofol 1.2 and 2.5-3, or thiopental 4 and 7-9 microg/ml, representing sedative and hypnotic drug concentrations. The latter made volunteers unresponsive to voice or mild stimulation. Quantitative positron emission tomographic brain images were obtained at 0, 20, and 40 auditory words per minute at each drug concentration. Using SPM99 analysis, 10-mm spherical regions of interest were identified by peak covariation of word rate with rCBF across all conditions and drug concentrations. Individual mean rCBF responses in these and primary auditory cortex (Heschl's gyri) were obtained.

Results

Significant increases in rCBF with auditory word rate occurred in temporal lobes bilaterally at baseline (significance, T = 4.95). There was no change in this response during sedation (T = 5.60). During unresponsiveness seven of 10 participants had a diminished response in the left temporal lobe (T = 3.18). Global CBF, corrected for changes in PCO2 (3% .mmHg PCO2), was reduced 15% by sedation and 27% during unresponsiveness.

Conclusion

The presence of propofol or thiopental does not affect the rCBF response to increasing stimulus rate during consciousness. Thus, changes in rCBF activation patterns with sedative concentrations of these drugs represent effects on brain activity itself. The neuroanatomical targets of drug effect on memory and attention may be revealed by changes in rCBF patterns associated with these cognitive activities.
Succinylcholine Dosage and Apnea-induced Hemoglobin Desaturation in Patients
Authors: Naguib Mohamed , Samarkandi Abdulhamid H. , Abdullah Khaled , Riad Waleed , Alharby Saleh W.
Published: December 2004

Background

The authors examined the notion that a reduction in succinylcholine dose from 1 mg/kg to approximately 0.6 mg/kg would allow a faster recovery of spontaneous ventilation and reduction in the incidence of hemoglobin desaturation during the period of apnea in simulated complete upper airway obstruction situations.

Methods

This prospective, randomized, double-blind study involved 60 patients. After preoxygenation to an end-tidal oxygen concentration >90%, patients were anesthetized with 2 microg/kg fentanyl and 2 mg/kg propofol. After loss of consciousness, patients were randomly allocated to receive 0.56 or 1.0 mg/kg succinylcholine or saline (control group). Oxygen saturation was monitored continuously at the index finger. When the patient became apneic, the face mask was removed and the patient's airway was left unsupported. If the oxygen saturation decreased to 90%, the face mask was reapplied, and ventilation was assisted until the patient was awake. Time from injection of the study drug to the first visible spontaneous diaphragmatic movements was noted.

Results

Oxygen saturation decreased <90% in 45%, 65%, and 85% of patients in the control, 0.56 mg/kg, and 1.0 mg/kg succinylcholine groups, respectively (P = 0.03). Corresponding times (mean +/- SD) to spontaneous of diaphragmatic movements were 2.7 +/- 1.2, 4.8 +/- 2.5, and 4.7 +/- 1.3 min, respectively. These times were longer (P < 0.001) after either dose of succinylcholine compared with controls.

Conclusions

Reduction in succinylcholine dose from 1.0 mg/kg to 0.56 mg/kg decreased the incidence of hemoglobin saturation <90% from 85% to 65% but did not shorten the time to spontaneous diaphragmatic movements. A significant fraction of patients would be at risk if there were failure to intubate and ventilate whether succinylcholine is administered or not and regardless of the dose of succinylcholine administered.
No Evidence of Memory Function during Anesthesia with Propofol or Isoflurane with Close Control of Hypnotic State
Authors: Kerssens Chantal , Ouchi Takashi , Sebel Peter S.
Published: December 2004

Background

The authors previously demonstrated memory function during apparently adequate general anesthesia in trauma patients. Hypnotic state fluctuations, stress, and variable amnesic qualities of commonly used anesthetics could account for this effect.

Methods

The authors replicated the trauma investigation in 90 elective surgical patients to enable anesthetic titration to a bispectral index value of 50-55 during auditory presentation of word stimuli. Patients were randomly assigned to maintenance with propofol (n = 48) or isoflurane (n = 42). Before surgery, state anxiety and trait anxiety were assessed using self-report measures. Postoperative memory assessment relied on the process dissociation procedure using a word stem completion task.

Results

There were no differences between groups for relevant demographic, preoperative, or supplemental drug variables. Ninety-eight percent of words were presented within a bispectral index range of 40-60, with values averaging 48.8 (SD = 5.7) during word presentation. Neither the process dissociation procedure nor standard measures of conscious recall and recognition memory showed evidence of explicit or implicit memory. Preoperative stress levels did not correlate with postoperative memory test scores in either study group.

Conclusions

In contrast to the results of their previous study, the authors found no evidence of memory function with close control of hypnotic state. This suggests that hypnotic state fluctuations are important to memory activation under anesthesia. Other variables may contribute to preserved memory function as well. Propofol and isoflurane block memory equally well during adequate anesthesia.
Electronic Nose Prediction of a Clinical Pneumonia Score: Biosensors and Microbes
Authors: Hanson C William , Thaler Erica R.
Published: December 2004

Background

The authors performed a prospective study to determine whether breath test analysis using an electronic nose correlates with a clinical pneumonia score.

Methods

Exhaled gas was sampled from the expiratory limb of the ventilator in mechanically ventilated surgical intensive care patients and assayed with the electronic nose. Components of a clinical pneumonia score were recorded concurrently.

Results

The score predicted by the electronic nose showed good correlation with the actual pneumonia score (r = 0.81). Bland Altman analysis showed a mean bias of 0.0 (limits +/- 2.6).

Conclusions

The electronic nose is a new biosensor technology that correlates with a clinical pneumonia score.
Isoflurane Modulation of Neuronal Nicotinic Acetylcholine Receptors Expressed in Human Embryonic Kidney Cells
Authors: Yamashita Megumi , Mori Takashi , Nagata Keiichi , Yeh Jay Z. , Narahashi Toshio
Published: December 2004

Background

It is well established that neuronal nicotinic acetylcholine receptors (nAChRs) are sensitive to inhalational anesthetics. The authors previously reported that halothane potently blocked alpha4beta2-type nAChRs of rat cortical neurons. However, the effect of isoflurane, which is widely used clinically, on nAChRs largely remains to be seen. The authors studied the effects of isoflurane as compared with sevoflurane and halothane on the human alpha4beta2 nAChRs expressed in human embryonic kidney cells.

Methods

The whole-cell and single-channel patch clamp techniques were used to record currents induced by acetylcholine.

Results

Isoflurane, sevoflurane, and halothane suppressed the acetylcholine-induced currents in a concentration-dependent manner with 50% inhibitory concentrations of 67.1, 183.3, and 39.8 microM, respectively, which correspond to 0.5 minimum alveolar concentration or less. When anesthetics were coapplied with acetylcholine, isoflurane and sevoflurane decreased the apparent affinity of receptor for acetylcholine, but halothane, in addition, decreased the maximum acetylcholine current. When isoflurane was preapplied and coapplied, its inhibitory action was independent of acetylcholine concentration. Isoflurane blocked the nAChR in both resting and activated states. Single-channel analyses revealed that isoflurane at 84 microM decreased the mean open time and burst duration without inducing "flickering" during channel openings. Isoflurane increased the mean closed time. As a result, the open probability of single channels was greatly reduced by isoflurane.

Conclusions

Isoflurane, sevoflurane, and halothane potently blocked the alpha4beta2 nAChR. Isoflurane suppression of whole-cell acetylcholine currents was a result of decreases in the open time, burst duration, and open probability and an increase in the closed time of single channels. The high sensitivity of neuronal nAChRs to inhalational anesthetics is expected to play an important role in several stages of anesthesia.
Changes in Properties of Spinal Dorsal Horn Neurons and Their Sensitivity to Morphine after Spinal Cord Injury in the Rat
Authors: Wang Jungang , Kawamata Mikito , Namiki Akiyoshi
Published: December 2004

Background

To gain a better understanding of spinal cord injury (SCI)-induced central neuropathic pain, the authors investigated changes in properties of spinal dorsal horn neurons located rostrally and caudally to the lesion and their sensitivity to morphine in rats after SCI.

Methods

The right spinal cord of Sprague-Dawley rats was hemisected at the level of L2. At 10 to 14 days after the SCI, when mechanical hyperalgesia/allodynia had fully developed, spontaneous activity and evoked responses to mechanical stimuli of wide-dynamic-range (WDR) and high-threshold neurons rostral and caudal to the lesion were recorded. Effects of cumulative doses of systemic (0.1-3 mg/kg) and spinal (0.1-5 microg) administration of morphine on spontaneous activity and evoked responses to the stimuli of the neurons were evaluated.

Results

Spontaneous activity significantly increased in WDR neurons both rostral and caudal to the SCI site, but high-frequency background discharges with burst patterns were only observed in neurons rostral to the SCI site. Significant increases in responses to the mechanical stimuli were seen both in WDR and high-threshold neurons located both rostrally and caudally to the lesion. The responses to nonnoxious and noxious stimuli were significantly greater in caudal WDR neurons than in rostral WDR neurons. In contrast, the responses to pinch stimuli were significantly higher in rostral high-threshold neurons than those in caudal high-threshold neurons. Systemically administered morphine had a greater effect on responses to nonnoxious and noxious stimuli of rostral WDR neurons than those of caudal WDR neurons. Spinally administered morphine significantly suppressed responses of WDR neurons in SCI animals to nonnoxious stimuli compared with those in sham-operated control animals.

Conclusions

The findings suggest that changes in properties of spinal dorsal horn neurons after SCI are caused by different mechanisms, depending on the classification of the neurons and their segmental locations.