bluuebunny/crossref_metadata_2025 huggingface dataset:
Heritability of dispersal in the great reed warbler
Authors: Hansson B. , Bensch S. , Hasselquist D.
Published: December 2004

Dispersal is commonly considered to be a condition‐dependent behaviour with no or low heritability. Here, we show that dispersal in the great reed warbler (Acrocephalus arundinaceus) has a high heritability. Analyses of capture–recapture data of male great reed warblers gathered from the species’ whole Swedish breeding range revealed a remarkable offspring–parent resemblance in dispersal behaviour (philopatry vs. inter‐population dispersal). Also, the degree of dispersal differed between cohorts, which shows that dispersal was partly conditionally dependent. The offspring to mid‐parent estimate of heritability was 0.50. In a previous study of the same data set of male offspring, we did not detect associations between dispersal and several relevant environmental, parental and offspring condition factors. Thus, our results indicate that variation in dispersal partly has a genetic basis in great reed warblers.
Regional warming‐induced species shift in north‐west Mediterranean marine caves
Authors: Chevaldonné P. , Lejeusne C.
Published: December 2004

The north‐western Mediterranean Sea's high biodiversity originates from a mixture of temperate and subtropical species. Large‐scale warming has been detected through northward range shifts of ‘warm‐water’ species, and mass‐mortality events for ‘cold‐water’ invertebrates. Marine caves are affected in a more subtle way. By monitoring endemic species of cave mysids (Crustacea) and comparing our results with data in the literature, we observed a strong decline in one species, coupled with the success of another. Near Marseille (France), this phenomenon began while two major thermal anomalies were reported. Different tolerances to temperature were demonstrated by both the species distribution ranges and laboratory experimentation. We provide a possible physiological explanation for populations of cold stenothermal species of endemic cave mysids being replaced by congeners of warmer affinities, with a high risk of extinction. We also found strong support for the view that Mediterranean marine biodiversity is already under the threat of global warming.
Different male morphs of Otitesella pseudoserrata fig wasps have equal fitness but are not determined by different alleles
Authors: Pienaar Jason , Greeff Jaco M.
Published: December 2004

The extreme male dimorphisms exhibited by some non‐pollinating fig wasps have often been thought to be a consequence of a genetic polymorphism, and have been cited as an example of how frequency‐dependent selection can maintain alternative alleles in a population. If true, then the proportions of each morph in one generation should reflect their mating success in previous generations. Here, we test the genetic polymorphism assumption in the male dimorphic species Otitesella pseudoserrata, and demonstrate that it is impossible for such a mechanism to generate alternative morphs in the highly variable proportions observed. These results suggest that male dimorphism is not a classic case of alternative strategies attributable to alternative alleles at a single locus. Rather, it would seem that although the fitnesses of the alternative morphologies are frequency dependent, their actual proportions in a generation are determined through a facultative decision.
The mycorrhizal dependence of subordinates determines the effect of arbuscular mycorrhizal fungi on plant diversity
Authors: Urcelay Carlos , Díaz Sandra
Published: December 2004

It is widely recognized that arbuscular mycorrhizal fungi (AMF) influence plant community structure. Several studies in the past few years have focused on the effect of AMF on plant diversity, showing contradictory results. On the basis of studies carried out in grasslands, it has been proposed that these results may not be in conflict but rather depend on mycorrhizal dependence of dominant and subordinate species in the plant community. Here, we propose a simple conceptual model to explain the effect of AMF on plant diversity and dominance hierarchy. Our model suggests that the effect of AMF on plant diversity can be explained mainly by mycorrhizal dependence of subordinates. It also gives predictions for a wider range of community types, and helps in identifying the systems in which empirical data are most critically needed.
Serial analysis of ribosomal sequence tags (SARST): a high‐throughput method for profiling complex microbial communities
Authors: Neufeld Josh D. , Yu Zhongtang , Lam Wan , Mohn William W.
Published: December 2004

Two decades of culture‐independent studies have confirmed that microbial communities represent the most complex and concentrated pool of phylogenetic diversity on the planet. There remains a need for innovative molecular tools that can further our knowledge of microbial diversity and its functional implications. We present the method and application of serial analysis of ribosomal sequence tags (SARST) as a novel tool for elucidating complex microbial communities, such as those found in soils and sediments. Serial analysis of ribosomal sequence tags uses a series of enzymatic reactions to amplify and ligate ribosomal sequence tags (RSTs) from bacterial small subunit rRNA gene (SSU rDNA) V1‐regions into concatemers that are cloned and sequenced. This approach offers a significant increase in throughput over traditional SSU rDNA clone libraries, as up to 20 RSTs are obtained from each sequencing reaction. To test SARST and measure the bias associated with this approach, RST libraries were prepared from a defined mixture of pure cultures and from duplicate arctic soil DNA samples. The actual RST distribution reflected the theoretical composition of the original defined mixture. Data from duplicate soil libraries (1345 and 1217 RSTs, with 525 and 505 unique RSTs, respectively) indicated that replication provides a strongly correlated RST profile (r2 = 0.80) and division‐level distribution of RSTs (r2 = 0.99). Using sequence data from abundant soil RSTs, we designed specific primers that successfully amplified a larger portion of the SSU rDNA for further phylogenetic analysis. These results suggest that SARST is a powerful approach for reproducible high‐throughput profiling of microbial diversity amenable to medical, industrial or environmental microbiology applications.
Genomic polymorphism in symbiotic populations of Photobacterium leiognathi
Authors: Dunlap Paul V. , Jiemjit Anchalee , Ast Jennifer C. , Pearce Meghan M. , Marques Ryan R. , Lavilla‐Pitogo Celia R.
Published: December 2004

Photobacterium leiognathi forms a bioluminescent symbiosis with leiognathid fishes, colonizing the internal light organ of the fish and providing its host with light used in bioluminescence displays. Strains symbiotic with different species of the fish exhibit substantial phenotypic differences in symbiosis and in culture, including differences in 2‐D PAGE protein patterns and profiles of indigenous plasmids. To determine if such differences might reflect a genetically based symbiont‐strain/host‐species specificity, we profiled the genomes of P. leiognathi strains from leiognathid fishes using PFGE. Individual strains from 10 species of leiognathid fishes exhibited substantial genomic polymorphism, with no obvious similarity among strains; these strains were nonetheless identified as P. leiognathi by 16S rDNA sequence analysis. Profiling of multiple strains from individual host specimens revealed an oligoclonal structure to the symbiont populations; typically one or two genomotypes dominated each population. However, analysis of multiple strains from multiple specimens of the same host species, to determine if the same strain types consistently colonize a host species, demonstrated substantial heterogeneity, with the same genomotype only rarely observed among the symbiont populations of different specimens of the same host species. Colonization of the leiognathid light organ to initiate the symbiosis therefore is likely to be oliogoclonal, and specificity of the P. leiognathi/leiognathid fish symbiosis apparently is maintained at the bacterial species level rather than at the level of individual, genomotypically defined strain types.
Design of 16S rRNA‐targeted oligonucleotide probes for detecting cultured and uncultured archaeal lineages in high‐temperature environments
Authors: Nercessian Olivier , Prokofeva Maria , Lebedinski Alexander , L’Haridon Stéphane , Cary Craig , Prieur Daniel , Jeanthon Christian
Published: December 2004

In order to facilitate the evaluation of archaeal community diversity and distribution in high‐temperature environments, 14 16S rRNA oligonucleotide probes were designed. Adequate hybridization and wash conditions of the probes encompassing most known hyperthermophilic Archaea, members of the orders Thermococcales, Desulfurococcales and Sulfolobales, of the families Methanocaldococcaceae, Pyrodictiaceae and Thermoproteaceae, of the genera Archaeoglobus, Methanopyrus and Ignicoccus, and of the as yet uncultured lineages Korarchaeota, Crenarchaeota marine group I, deep‐sea hydrothermal vent euryarchaeotic group 2 (DHVE 2), and deep‐sea hydrothermal vent euryarchaeotic group 8 (DHVE 8) were determined by dot‐blot hybridization from target and non‐target reference organisms and environmental clones. The oligonucleotide probes were also used to evaluate the archaeal community composition in nine deep‐sea hydrothermal vent samples. All probes, except those targeting members of Sulfolobales, Thermoproteaceae, Pyrodictiaceae and Korarchaeota, gave positive hybridization signals when hybridized against 16S rDNA amplification products obtained from hydrothermal DNA extracts. The results confirmed the widespread occurrence of Thermococcales, Desulfurococcales, Methanocaldococcaceae and Archaeoglobus in deep‐sea hydrothermal vents, and extended the known ecological habitats of uncultured lineages. Despite their wide coverage, the probes were unable to resolve the archaeal communities associated with hydrothermally influenced sediments, suggesting that these samples may contain novel lineages. This suite of oligonucleotide probes may represent an efficient tool for rapid qualitative and quantitative characterization of archaeal communities. Their application would help to provide new insights in the future into the composition, distribution and abundance of Archaea in high‐temperature environments.
Memory deficits and retrieval processes in ALS1
Authors: Mantovan M. C. , Baggio L. , Barba G. Dalla , Smith P. , Pegoraro E. , Soraru' G. , Bonometto P. , Angelini C.
Published: December 2004

Subtle neuropsychological deficits have been described in patients affected by amyotrophic lateral sclerosis (ALS) without dementia. Overall, selective impairment in memory function has been reported, but the source of memory impairment in ALS has yet to be defined. We performed neuropsychological screening in 20 ALS patients. Semantic encoding and post‐encoding cue effects on the retrieval of word lists were investigated in the ALS patients and normal controls. Severity of memory impairment was correlated to cerebral blood perfusion detected by single photon emission computed tomography (SPECT). ALS patients showed moderate impairments in frontal and memory tests. Short‐term memory was normal, while serial position retrieval of word lists with normal recency effect but poor primacy effect showed long‐term memory deficit. ALS patients performed better in cued encoding than in cued post‐encoding recall condition. In the cued post‐encoding condition, the primacy effect in word list recall improved significantly in controls, but not in ALS patients, as compared with both the free recall and cued encoding conditions. SPECT hypoperfusion was observed in frontal and temporal areas in ALS patients. ALS patients showed a long‐term memory deficit which did not improve in cued post‐encoding condition as it does for controls. We hypothesize abnormal retrieval processes related to frontal lobe dysfunction which entails difficulties in generating stable long‐memory traces at encoding.
Interaction between GSTM1‐null and CYP2D6‐deficient alleles in the pathogenesis of Parkinson's disease
Authors: Santt O. , Baranova H. , Albuisson E. , Bignon Y.‐J. , Lucotte G.
Published: December 2004

The present study was conducted to examine the interaction between cytochrome P450 2D6: CYP2D6 (phase I) poor metabolizer (PM) and glutathione S‐transferase M1: GSTM1 (phase II) null genotypes, among 103 unrelated French Parkinson's disease (PD) patients. Both genes are involved in the biotransformation process, and the main objective of that work is to assess synergic effect between CYP2D6 PM and GSTM1 null genotypes in PD patients. Patients with both GSTM1 null genotype and poor metabolizer CYP2D6 have shown a strong dependency of multiplicative interaction (9.50; P = 0.016); this have also been observed when combining GSTM1 null with CYP2D6*4 deficient alleles, but were at the limit of significance (2.18; P = 0.076). Such a combination of polymorphic peculiarities in studied metabolic genes might represent additional risk factor for development of sporadic PD.
Prevention of Epilepsy After Head Trauma: Do We Need New Drugs or a New Approach?
Authors: Benardo Larry S.
Published: December 2004

Summary:  Annually in the U.S. about 500,000 head injuries are severe enough to require hospitalization. Past studies of severe head trauma estimate the risk of late seizures, which are synonymous with epilepsy, to be from 26 to 53%. Furthermore, head trauma accounts for 5% of all epilepsy cases and 20% of symptomatic epilepsy. Although potentially preventable, no effective prophylaxis for posttraumatic epilepsy currently exists. Prior attempts to prevent posttraumatic epileptogenesis used various anticonvulsants, usually given many hours after injury. Generally these studies showed these agents suppressed seizures in the first week after trauma, but had no effect on the incidence of late posttraumatic seizures. Brain trauma engages a rapid excitotoxic process triggered by glutamate release, similar to that seen with ischemia. For ischemic cell damage early and rapid delivery of agents has been a key to rescuing or protecting neurons. Yet, no study has addressed whether the rapidity of drug delivery is critical in the prophylaxis of late seizures. Perhaps excitotoxicity proximate to the brain injury also leads to the neurological deficits seen after severe trauma, initiating and promoting epileptogenesis, and that disrupting this process may prevent epilepsy. While experimental models of epileptogenesis have shown that GABAergic drugs, including valproate (VPA), may be antiepileptogenic, the timing of treatment with putative prophylactic drugs has not been studied. Recent laboratory work explored this issue using an in vitro model of posttraumatic epileptogenesis. The data suggest that a limited time domain exists for VPA to intervene in the epileptogenic process, requiring the earliest possible intervention. We contend that protection from posttraumatic epileptogenesis can be conferred only if agents are given soon after trauma. A pilot study is proposed to begin to translate these findings to explore the feasibility of early VPA delivery to severe head trauma patients admitted to Kings County Hospital Center in Brooklyn, NY, a Level 1 trauma center.
Passive Current Redistribution in the Heart
Authors: GIROUARD STEVE , IDEKER RAYMOND
Published: December 2004

Passive Stimulation of Myocardium. Introduction: Electrical stimuli produce a spatial distribution of voltage across the heart. We hypothesized that the potential difference between tissue near a stimulating electrode and a remote site could cause sufficient current to flow through a highly conductive wire connecting the two sites to directly stimulate the remote tissue.

Methods and Results: In six open chest pigs, we inserted a catheter with right ventricular (RV) and superior vena cava (SVC) coil electrodes. A wire was placed with one end contacting the epicardium 10 ± 2 mm away from the RV electrode and the other end on left ventricular (LV) epicardium 56 ± 14 mm from the RV end of the wire. Stimuli of 10 to 100 V were delivered to the RV and SVC electrodes. Potentials were recorded from two 252–electrode arrays placed over the RV and LV ends of the passive wire. The current induced in the wire was measured. A minimum stimulus of 15 ± 6 V was needed between RV SVC electrodes to not only pace the RV but also to pace the LV through the passive wire as detected by the electrode array recordings. Current in the wire varied linearly with RV‐SVC stimulus strength.

Conclusion: Coupling RV and LV epicardium with a passive wire while stimulating the RV endocardium induced sufficient current in the wire to synchronously pace the LV.
On the Approach of Electrons to Equilibrium
Authors: Kahalas S. L. , Kashian H. C.
Published: December 2004

The relaxation of electrons to equilibrium in the absence of an external field is discussed for a slightly ionized gas in which elastic collisions predominate. The gas consists of electrons and neutral molecules having a Maxwellian interaction. Spatial diffusion is neglected as well as electron-electron interaction. The change of the electronic distribution function from a simple nonequilibrium distribution to a Maxwellian distribution is followed in time. Electron attachment to neutral molecules is briefly considered.
Oscillations of a Finite Cold Plasma in a Strong Magnetic Field
Authors: Dawson John , Oberman Carl
Published: December 2004

Of prime concern in plasma investigations is the coupling of a bounded plasma with external electromagnetic fields. In the present paper the properties of the normal modes of a cold plasma slab, and cylinder, situated in a strong magnetic field are derived, and then used to discuss the transmission and reflection of radiation, the scattering by a plasma cylinder, the response to driving sources in the vicinity of the plasma, and the radiation due to plasma oscillations.
Laminar Boundary Layer with Suction and Injection
Authors: Gribben R. J.
Published: December 2004

With the assumptions of a heat insulated body, a Prandtl number of unity and a linear temperature-viscosity relation the axisymmetric equations governing a given high-speed compressible flow are reduced to the equations describing an incompressible two-dimensional flow past a flat plate with a determinable main stream and normal wall velocity distribution. The results are applied to the supersonic flows over a cone with wall velocities proportional (i) to the first power and (ii) to the inverse-half-power of distance along a generator when the resulting incompressible flows are known. Also the flow near the tip of a general slender body of revolution in supersonic flow with constant wall velocity is obtained by solving numerically the equations of the correlated incompressible flow. It is also shown that, if the assumption of an insulated body is discarded, a given high-speed compressible flow may still be correlated with a determinable low-speed compressible flow.
Fluid Mechanics of Copper
Authors: Allen William A. , Morrison Harvey L. , Ray Daniel B. , Rogers James W.
Published: December 2004

Under pressure of sufficient magnitude, a metal such as copper can be considered to be an inviscid compressible fluid specified by an experimentally determined Hugoniot curve. This paper indicates the calculations necessary to solve the elementary problem of flow of an arbitrary fluid around an infinite wedge. The results are displayed in the form of graphs. A graphical solution is indicated for a problem involving impact of a conical projectile with a target. Agreement has been obtained between the theoretical and experimental results.
Laminar Flow in the Entrance Region of a Porous Pipe
Authors: Weissberg Harold L.
Published: December 2004

The equation of motion for steady, incompressible, axially symmetric flow in a pipe with uniform wall suction or injection is expressed in terms of a ``dimensionless stream function,'' F(ζ, η) = ψ(x, r)/ψ(x, a), where ψ is the usual stream function, x and r are cylindrical polar coordinates, a is the radius of the pipe, ζ = 1 − [2Rx/(aN)], η = (r/a)2. R and N are Reynolds numbers which specify the flows through the pipe wall and through the inlet, respectively. This equation, which includes as a special case the equation previously obtained by Yuan and Finkelstein for similar (affine) velocity profiles, is greatly simplified by passing to the limit which is approached as N increases. Nonsimilar, ζ-dependent solutions are approximated by a generalization of the method applied by Morduchow to the ζ-independent equation of Yuan and Finkelstein. The results show the manner in which the condition of similarity of the velocity profiles is approached for a prescribed (e.g., parabolic) inlet profile. They also indicate the development of reverse flow at the wall of the pipe in the range of R values for which no similar solutions exist.
Supersonic Flow in a Tube with Longitudinal Slots
Authors: Wachtell G. P. , Carfagno S. P.
Published: December 2004

A differential equation is derived for the pressure along the axis of a longitudinally slotted tube through which there is supersonic gas flow, for the general case in which both the tube cross section and the slot width vary with axial position. An approximate method of solution for the special case, in which the tube cross section and slot width are constant, is then found in closed form and confirmed experimentally to within a constant factor. This factor is attributed to the formation of a boundary layer along the slot walls.
Transverse Compression Waves in a Stabilized Discharge
Authors: Reagan Daryl
Published: December 2004

An electric discharge which is compressed by its own magnetic field, and ``stabilized'' by means of an axial magnetic field, can have transverse wave motions which cause its periodic compression and expansion. This kind of motion can cause the heating of the ions in the discharge. The simplest of these wave modes are described and an estimate is given of the power available to the waves as a result of the interaction of the electrons in the discharge with an axial electric field. This interaction can cause the attenuation or spontaneous growth of the waves, depending upon the circumstances. It is likely that in high current gas discharge experiments there are examples of growing and decaying waves of this type.
Cyclotron Radiation from a Hot Plasma
Authors: Drummond W. E. , Rosenbluth M. N.
Published: December 2004

In their Geneva paper, Trubnikov and Kudryavtsev calculated the cyclotron radiation from a hot plasma. In doing this, the assumption was made that the individual particles radiated as though they were in a vacuum. We have investigated this approximation by calculating the absorption length directly from the Boltzmann equation, and we find that indeed this assumption is correct whenever (ωp/ωe)2 ≪ m2, where m is the harmonic number of the radiation in question, ωp is the plasma frequency, and ωe is the cyclotron frequency. For a contained plasma, the left hand side of this inequality is of the order of magnitude of one, and thus the inequality is well satisfied for the dominant radiation from a plasma at high temperature.

The angular independence of the absorption coefficient has been calculated, and this together with a more careful examination of the mechanism of thermonuclear energy transfer to the electrons, leads to a modification of the results presented by Trubnikov and Kudryavtsev at Geneva. In addition, it is shown that by the use of reflectors the critical size can be reduced by two orders of magnitude.
Heat Transport by Convection
Authors: Nakagawa Yoshinari
Published: December 2004

The character of heat transport by cellular convection, which arises beyond the marginal state of stability in a layer of fluid bound between two constant temperature surfaces is examined. It is shown that a simple equation characterizes the heat transport in the neighborhood of the marginal state of stability when the convection is steady, and its cellular pattern of motion is represented by the solutions of the linear theory. The results of the study include all three cases of boundary conditions, namely, when the bounding surfaces of the layer are both free, are both rigid, or one is free and the other is rigid.
Heat Transport by Convection in Presence of an Impressed Magnetic Field
Authors: Nakagawa Yoshinari
Published: December 2004

The effect of an impressed magnetic field on heat transport by convection, which arises from instability in a layer of an electrically conducting fluid, bounded between two constant temperature surfaces, is examined. It is shown that such a field reduces the amount of heat transported by convection, and that when the strength of the magnetic field is increased, such reduction becomes proportional to (π2Q)−1, where Q = σμ2 cos2ϑH2 d2/ρν, d is the depth of the layer, ρ the density, H the strength of magnetic field, ϑ the inclination of the direction of H to the vertical, and σ, μ and ν are the coefficients of electrical conductivity, magnetic permeability, and kinematic viscosity, respectively, for all types of the boundary conditions. It is also shown that in the neighborhood of the marginal state of stability, a simple formula characterizes the heat transport by convection.
On the Electrical Behavior of an Ideal Plasma
Authors: Gambirasio Giorgio
Published: December 2004

The solution of the equation for the current in an ideal plasma, when the electric field, in a direction perpendicular to a constant magnetic field, is abruptly increased from zero to a constant value, is obtained using Laplace transforms. An exact solution and approximate solutions for some simple cases are obtained and discussed. An expression and the corresponding RLC network are found for the specific impedance of the plasma.
Equivalence of the Landau and Fokker-Planck Collision Terms
Authors: Enoch Jacob
Published: December 2004

It is shown that the Landau collision term is equivalent to the Fokker-Planck type collision term as derived on the basis of the assumption that binary collisions predominate.
Thermal Conductivities of Rare Gas Mixtures
Authors: Mason Edward A. , Von Ubisch Hans
Published: December 2004

Recent measurements of the thermal conductivities of all ten possible binary mixtures of the rare gases and of the ternary mixture He–Kr–Xe at 29° and 520°C are compared with theoretical calculations. Three calculations are carried out, based on: (1) rigorous kinetic theory, (2) an approximate formula which uses only conductivities of the pure components, and (3) a new semiempirical formula which also requires knowledge of the conductivity of one composition of binary mixture. The agreement is generally satisfactory and furnishes support for the usefulness and accuracy of the formulas used.
Boundary-Layer Formation in the Pinch
Authors: Killeen John , Gibson Gordon , Colgate S. A.
Published: December 2004

A study is made of various processes that occur prior to the pinch effect when an electric field is applied to a deuterium gas. The variables of the problem are the percentage of ionization, the electron and ion temperatures, the resistivity of the gas, and the current density. A one-dimensional problem is considered in which the above variables are determined as functions of one-space dimension and the time. The equations determining these variables are: the heat developed as the current flows through the gas equals the rate of increase of the internal energy of the plasma, the equation describing the rate of ionization, the equation describing the rate of transfer of energy from electrons to ions and the electromagnetic field equations. These equations are a generalization of the plasma equations solved by Wyld and Watson in that spatial dependence is included, i.e., a current layer is calculated instead of assuming a constant current. The equations are solved numerically using an IBM 704 computer.
Scattering of Electromagnetic Waves by Longitudinal Plasma Waves
Authors: Rosen Philip
Published: December 2004

It is shown that Bragg reflection of electromagnetic waves from plasma oscillations is possible. The wave equation for the electromagnetic field passing through a medium of plasma waves is derived, and it is found to be similar to that of Brillouin for a wave in a medium of variable dielectric constant.
Resonance in a Plasma with Two Ion Species
Authors: Buchsbaum S. J.
Published: December 2004

When a high-density plasma column in an axial magnetic field possesses two (or more) in species of different charge-to-mass ratios, there exists a plasma resonance condition which involves only the ion cyclotron frequencies. At reasonance, the two ion clouds oscillate transversely to the static magnetic field and 180 deg out of phase with each other, while the electrons remain relatively motionless. The ratio of the ion oscillatory energy to that of the electrons is of the order of the ratio of the ion-to-electron masses. Collisions between the two ion clouds randomize the large ordered velocities of the ions with great efficiency. Thus, by exciting this resonance, considerable ion heating may be realized. The effect of varying the relative concentration of the two ions is discussed.
Passage of Shock Waves Through Ducts of Variable Cross Section
Authors: Rudinger George
Published: December 2004

If shock waves strong enough to produce supersonic flow pass through a duct of variable cross section, the shape of which is approximated by a single discontinuous area change, a variety of wave patterns may be found. These are unique for particular conditions except for a range of area convergence for which it was recently shown that three solutions exist. Examination of the transient processes that precede the establishment of the final flow suggests, and a general proof confirms, that only one of these solutions can actually be realized if the duct converges monotonically. For more general duct configurations, the other solutions may also be found, but the correct wave pattern may have to be established with the aid of a wave diagram in which area changes are properly taken into account. For configurations with a throat, additional wave patterns may appear both within and outside of the region of ambiguity which then loses its significance.
Turbulence Theory and Functional Integration. I.
Authors: Rosen Gerald
Published: December 2004

An integral representation of the general solution to the Hopf φ equation is reported. Integral representations for the spatial correlation functions are derived from the characteristic functional φ. These exact results are applied to Navier-Stokes fluid turbulence.
Energy Transfer in a Turbulent Fluid
Authors: Tanenbaum B. Samuel , Mintzer David
Published: December 2004

A method is introduced by which experimental measurements of two- and three-velocity correlation functions can be used to provide a direct test of energy transfer hypotheses in a turbulent fluid. By using this method, the optimal values for the three empirical parameters m, n, and γ, which appear in the general transfer function proposed by T. von Kármán, are determined from the correlation function data of R. W. Stewart and A. A. Townsend. This optimal transfer function is found to be: Toptimal(k)=1.2 [k−5/2E1/4∫ 0k k′ 3E5/4(k′)dk′−k3E5/4∫ k∞ k′−5/2E1/4(k′)dk′],and a comparison, based on the data, is made between this transfer function and transfer functions proposed by W. Heisenberg and L. Kovasznay.
Blunt Body Viscous Layer with and without a Magnetic Field
Authors: Oguchi Hakuro
Published: December 2004

The present paper is mainly concerned with the solution for the viscous flow in the shock layer about the stagnation region of a sphere in hypersonic flow. The Reynolds numbers considered are in a range too low to apply usual boundary layer theory within the shock layer, but are large enough that the shock wave may be regarded as a discontinuous surface. This viscous layer problem has been studied previously by Probstein. With the assumption of constant density in the shock layer an analytic solution is applied to this problem both with and without an applied magnetic field. This solution makes use of the fact that the ratio of the density ahead of the shock to that behind the shock (ε) is small. The solution has been found in analytic form to first order in ε. In the nonmagnetic case numerical results for both the shock wave detachment distance and skin friction are presented for a value of ε = 0.1 and they are shown to be in good agreement with the exact numerical calculations of Probstein and Kemp. Numerical results are also presented on the effect of an applied magnetic field on both the shock wave detachment distance and skin friction. It is found that for a fixed value of ε and Reynolds number the skin friction decreases and the detachment distance increases for increasing values of the magnetic field parameter S which is proportional to the magnetic pressure divided by the total pressure.
Possibility of an Electrostatic Instability in a Stellarator
Authors: Ellis R. A. , Goldberg L. P. , Gorman J. G.
Published: December 2004

At certain times during Ohmic heating in hydrogen and deuterium discharges in the B-3 stellarator, it was observed that over a wide range of experimental conditions the plasma current decreased abruptly (current inhibition) following a period of increasing current and decreasing charged particle density. It is suggested that this may be a manifestation of an electrostatic instability.
Hydromagnetic Resonators
Authors: Gajewski Ryszard , Mawardi O. K.
Published: December 2004

The behavior of hydromagnetic waves in a cylindrical resonator of arbitrary cross section is examined. The conducting fluid inside the resonator is permeated with a steady uniform magnetic field parallel to the generators of the cylinder. The equation describing the eigenfrequency spectrum is derived for all possible modes and types of waves. It is shown that a TLA (transverse longitudinal acoustic) type wave when reflected from a rigid conducting termination generates an accompanying TLM (transverse longitudinal magnetohydrodynamic) type wave and vice versa. Energy losses due to the finite viscosity and electrical conductivity of the fluid as well as to the finite conductivity of the walls are then estimated for the case of T (purely transverse) type waves. A Q factor for T type waves is subsequently calculated.
Some Unexpected Results of Shock-Heating Xenon
Authors: Gloersen Per
Published: December 2004

Results from a detailed experimental study of the structure of pressure-driven incident shock waves in very pure xenon contained in a thoroughly pumped Pyrex shock tube are presented and discussed. As a result of some optical studies of the luminous structure of the shocks, the following features of the luminosity delay time were discovered: independence of the pressure in the undisturbed xenon in the range 0.75 to 4.0 mm Hg, dependence on shock velocity in a way not explainable on the basis of reasonable volume processes alone, and dependence on shock tube diameter. The visible luminosity from the shock was found to terminate well in advance of the measured position of the xenon-driver interface. This is indicative of severe radiation cooling. The visible luminosity was also found to be profoundly altered by the addition of impurities either in the xenon itself or in the driver. The spectrum of the delayed luminosity in the region from 3000 to 10 000 A was studied with an electronic-recording time-resolving spectrometer and found to consist of xenon atom lines superimposed on a strong continuum. The continuum may reasonably be attributed to dissociative transitions from bound excited states of the Xe2 molecule related to the xenon atom levels 7 pKJ and above to unbound Xe2 states related to the atomic levels 6s11 and 6s12. Positive electrical signals, observed during the passage of the shock through external metal rings, are attributed to ejection of electrons from the shock tube walls by photoelectric action and/or metastable atoms. In addition, two different types of electrical precursors were observed. The first was observed under the usual conditions, namely that the shock was sufficiently strong to cause the delayed luminosity. The second was observed in some experiments in which the shock was too weak to cause the delayed luminosity. Both could be due to a photoelectric effect on the shock tube walls, but the precursor observed in the absence of the delayed luminosity may be also due to diffusion of electrons ahead of the shock front. The present experiments strongly indicate that shock tube experiments of others may need reinterpretation.
Fluid Flow through a Porous Channel
Authors: Wageman W. E. , Guevara F. A.
Published: December 2004

Approximate solutions of the equations of motions governing laminar incompressible fluid flow through a cylindrical channel with a porous wall are derived. The invalidity of an approximation in the solution of these equations under certain circumstances is pointed out, and the results of a numerical integration in the region where the approximation is invalid are indicated. A brief description is given of an experiment to verify the calculations, and some interesting results are noted.
On Complete Blast Scaling
Authors: Ericsson Ulf , Edin Kjell
Published: December 2004

Experimental evidence is presented for the ability of Sachs' complete energy scaling to account for the influence of ambient pressure and temperature at not too small distances from the charge.
Kinetic Equation with a Constant Magnetic Field
Authors: Rostoker Norman
Published: December 2004

The collision operator is derived for the case of a spatially homogeneous plasma subject to a constant external magnetic field. A generalization of Lenard's method is employed.
Ion Wave Instabilities
Authors: Bernstein Ira B. , Kulsrud Russell M.
Published: December 2004

The dispersion relation for electrostatic oscillations in a magnetic field is derived on the basis of the Boltzmann equation for arbitrary velocity distributions and for propagation in an arbitrary direction under the following restrictions: (1) The thermal velocities of the particles and the phase velocity of the wave are small compared to those of light; (2) the component of the wave vector k perpendicular to the magnetic field is small compared to the reciprocal of the gyration radius of an ion at the larger of the mean ion, and electron thermal, energies; (3) the magnetic field B is uniform. The dispersion relation is formally identical with that for electrostatic oscillations in the absence of a magnetic field. The dispersion relation is examined for stability under the further restrictions that: (4) The mean thermal energy of the ions is small compared to that of the electrons; (5) the electron distribution function for the component of the velocity v along B has a single maximum. It is found that a very small shift along B of this maximum relative to the ions leads to an unstable ion oscillation. The growth rates and frequencies of these oscillations are determined; their possible applications are discussed. Some further results on the ``two stream'' instability are given.
Plasma Motion Across Magnetic Fields
Authors: Schmidt George
Published: December 2004

The analysis of plasma flow problems in magnetic fields is usually based on a hydromagnetic fluid model. In low-density collisionless plasmas, however, the limitations of the applicability of this method are not clearly understood. In this paper a simplified self-consistent field method is used, with particle motion considered in the guiding center approximation. In this case the high ``dielectric constant'' of the magneto-plasma plays the role of the infinite conductivity of the fluid model. Several experiments are analyzed on the basis of this model, and the limitations and shortcomings of the hydromagnetic treatment discussed.
Sufficient Conditions for Hydromagnetic Stability of a Diffuse Linear Pinch
Authors: Furth Harold P.
Published: December 2004

From the energy principle a sufficient stability condition can be derived that involves a disposable function. The existence of some choice of the disposable function such as to satisfy the sufficient condition is a necessary condition for stability. The disposable function may also be chosen so as to yield sufficient conditions that are not necessary, but that may be useful from the points of view of simplicity and generality. This technique is illustrated for ``maximal-force configurations,'' where the current density is everywhere orthogonal to the magnetic field.
Magnetic Annular Arc
Authors: Powers William E. , Patrick Richard M.
Published: December 2004

The performance characteristics of an annular-arc configuration under the influence of a magnetic field have been experimentally analyzed, particularly with respect to the effects of tensor conductivity and j × B body forces. In this device the plasma conditions are such that the electrical conductivity is insufficient to prevent the diffusion of the plasma through the magnetic field, i.e., the magnetic Reynolds number was small. Experiments were conducted with this device using helium and argon at power levels up to 50 kW, magnetic field strengths to 10 000 G, and particle densities of the order of 1016/cm3 to 1017/cm3. The electron gyroradius was smaller than the electron mean free path, i.e., ωeτe > 1, where ωe is the gyrofrequency, and τe is the time between collisions for electrons. The impedance of the arc in helium was found to vary linearly with ωeτe. The existence of a circulating azimuthal Hall current was also demonstrated. A yaw probe was employed to measure the angle of the flow due to the j × B Lorentz forces. A good agreement was found between the measured rotation in argon and the predicted value obtained from momentum considerations.
Theory of Higher-Order Effects in Fluids
Authors: Storer R. G. , Green H. S.
Published: December 2004

A method is presented which, in principle, enables one to calculate higher-order coefficients for transport in fluids. To illustrate this theory the second-order terms in the pressure tensor which depend on the mass velocity are presented and evaluated approximately in terms of a microscopic relaxation time. Under certain approximations it is found that it is possible to sum the higher-order terms to every order.
Electrical Conductivity of a Turbulent Plasma
Authors: Yoshikawa Shoichi
Published: December 2004

The conductivity of a turbulent plasma parallel to a magnetic field is determined. The plasma is assumed to be homogeneous and the motion of ions is neglected. The ordinary magnetohydrodynamic equations are used. The nonlinear contribution of the product of density and the electric field to the dc conductivity is expressed in terms of the density fluctuations of the plasma. Both weakly ionized and fully ionized plasmas are considered. The nonlinear effect is present either in a weakly ionized plasma or in a fully ionized plasma with adiabatic waves. For example, in a weakly ionized plasma, the conductivity is reduced by the factor 1 - ⅓ S without a magnetic field, and is reduced by the factor 1 - S with a strong magnetic field where S½ is the ratio of ac rms value of the density to the dc density. The noise electric fields are found to increase with external dc electric field, especially for a high magnetic field.
Current-Layer Diffusion in a One-Dimensional Pinch
Authors: Falk Theodore J. , Turcotte Donald L.
Published: December 2004

Diffusion of the current layer at the surface of a compressible electrically conducting gas in a one-dimensional pinch is analyzed in the limit of large time. Magnetohydrodynamic equations including finite scalar electrical and thermal conductivities are used, and the degree of ionization is taken to be constant. A parameter, which is proportional to the diffusion speed divided by the sound speed, is used to show that the inertia terms may be discarded in large-time high-electrical-conductivity problems. Some numerical results for the temperature, velocity, and magnetic field within the current layer are presented in terms of a similarity variable. In the cases analyzed the gas boundary is displaced from its infinite conductivity position by an amount which is of the order of magnitude of the current-layer thickness. Comparison of constant conductivity with temperature-dependent conductivity results shows that Joule heating at the gas boundary improves confinement if the initial conductivities are low.
Anomalous Diffusion Arising from Microinstabilities in a Plasma
Authors: Drummond William E. , Rosenbluth Marshall N.
Published: December 2004

A plasma is considered in which a Maxwellian distribution of electrons with thermal velocity ve and drift velocity vD is drifting relative to a Maxwellian distribution of ions with thermal velocity vi. For vD ≲ ve the usual ion acoustic waves are stable, however, electrostatic ion cyclotron waves with ω ≅ Ωi are unstable for vD ≳ 5vi. In the case when 5vi ≲ vD ≲ ve, and Te/Ti < 2 the electrostatic ion cyclotron waves grow to a nonlinear equilibrium spectrum. This spectrum of waves leads to a diffusion of electrons across the field lines with a diffusion coefficient D = αρ2eΩe, where ρe is the electron Larmor radius and Ωe is the electron Larmor frequency. α, the ratio of the resulting diffusion coefficient to the Bohm diffusion coefficient, is given by a constant × (vD/ve)5(Te/Ti)2.
Formation of Drift Instabilities by Collisional Relaxation of High-Energy Particles
Authors: Dreicer H. , Mjolsness R.
Published: December 2004

The relaxation of a small group of fast test electrons as a result of two-body Coulomb encounters with slow field electrons and ions orbiting in a magnetic field is investigated. The analysis is based upon an asymptotic form of the Fokker-Planck equation which includes the slowing down in speed as well as the angular scattering of the test electrons. The derivation as well as the analytic solution of this equation is presented, and is used to illustrate a case where collisional relaxation of the test electrons alone is responsible for the formation of a second peak in the one-dimensional electron velocity distribution. The maximum growth rate for the resulting electrostatic drift instability is calculated in the limit when the second peak is much smaller than the main peak, and is found to be proportional to the ratio of test to field particle density. The results are used to suggest an explanation of the several unstable current steps observed in the stellarator during its crowbarred relaxation phase.
Descent of Particles and Molecules through the Upper Atmosphere
Authors: Banister John R. , Davis H. L.
Published: December 2004

The descent of small particles or heavy molecules through a stagnant exponential atmosphere has been studied by numerical analysis. Both gravitational fall and molecular diffusion are taken into account. It is found that material injected in an arbitrary but horizontally uniform configuration assumes a constant profile which descends through the atmosphere at the fall rate of particles located at the maximum concentration. Analytic expressions are given which describe the profile descent rate, the constant-profile shape, and the constant-profile assemblage criterion. The material retention of an intervening turbulent layer in the atmosphere is examined; it is found that the later history of material is little affected by such a layer.