bluuebunny/crossref_metadata_2025 huggingface dataset:
Does Chronic Daily Headache Arise De Novo in Association With Regular Use of Analgesics?
Authors: Bahra Anish , Walsh Maggie , Menon Sanjeev , Goadsby Peter J.
Published: December 2004

Background.—The prevalence of chronic daily headache in association with regular use of analgesics is about 2%. Whether regular use of analgesics has a causal or consequential relationship to daily headache has not been established. A causal relationship has been suggested consequent to the observation of improvement or resolution of headache following analgesic withdrawal in patients attending headache clinics, but this observation has not been validated by controlled trials.

Purpose.—The aim of our investigation was to determine whether regular use of analgesics is associated with the development of chronic daily headache de novo and to characterize the clinical phenotype of those headaches by carefully studying chronic daily headache in patients with regular use of analgesics for a nonheadache indication.

Methods.—Patients attending a rheumatology‐monitoring clinic of second‐line agents were interviewed by a training neurologist with regard to their analgesic and headache history. Headache classification was according to the criteria of the International Headache Society. Daily headache characteristics were surveyed via a standardized questionnaire, and headache features were further explored by a trained medical interviewer.

Results.—Of 110 patients presenting to a rheumatology‐monitoring clinic, 73% had a diagnosis of rheumatoid arthritis, 23% had seronegative arthritis, and 4% comprised a miscellaneous group. One hundred three were using one or more analgesics regularly for their arthritis. Of this group, 8 (7.6%) reported a history of chronic daily headache, each of whom reported a history of migraine. The onset of migraine occurred before the onset of chronic daily headache in 7 patients and at about the same time as the chronic daily headache in 1 patient. In those with onset of migraine prior to chronic daily headache, the mean interval before the onset of headache was 30 years (range, 10 to 50 years). Regular use of analgesics preceded the onset of daily headache in 5 patients by a mean of 5.4 years (range, 2 to 10 years). In 1 patient, analgesic use and the development of daily headache occurred at about the same time. In 1 patient, the onset of daily headache preceded regular use of analgesics by almost 30 years. Five of those with regular use of analgesics had been taking an opiate‐based preparation in combination with a nonsteroidal anti‐inflammatory agent in 4. Two had been on a combination of acetaminophen (paracetamol) and a nonsteroidal anti‐inflammatory drug. The minimum number of tablets per week was 7, and the mean was 48 (range, 7 to 87). Of those patients who did not have daily headache, 41% had a history of migraine and 27% reported a history of tension‐type headache.

Conclusion.—These findings suggest that individuals with primary headache, specifically migraine, are predisposed to developing chronic daily headache in association with regular use of analgesics.
Comparative Efficacy of Eletriptan 40 mg Versus Sumatriptan 100 mg
Authors: Mathew Ninan T. , Schoenen Jean , Winner Paul , Muirhead Nancy , Sikes Carolyn R.
Published: December 2004

Objective.—To confirm the efficacy advantage of eletriptan 40 mg over sumatriptan 100 mg.

Background.—Eletriptan 80 mg has demonstrated significantly greater efficacy when compared to both sumatriptan 50 mg and 100 mg in two studies. Eletriptan 40 mg demonstrated significantly greater efficacy than sumatriptan 100 mg in one previous trial.

Methods.—Two thousand one hundred thirteen patients with a diagnosis of migraine according to International Headache Society criteria were randomized using a double‐blind, double‐dummy, parallel‐group design, and treated for a single migraine attack with either eletriptan 40 mg, sumatriptan 100 mg, or placebo. The primary endpoint was 2‐hour headache response. Secondary endpoints included headache response rates at 1 hour, pain‐free rates, absence of associated symptoms, functional response at 1 and 2 hours, and sustained headache response.

Results.—Headache response rates at 2 hours postdose were significantly higher for eletriptan 40 mg (67%) than for sumatriptan 100 mg (59%; P  <  .001) and placebo (26%; P  <  .0001). Eletriptan 40 mg consistently showed significant (P  <  .01) efficacy over sumatriptan 100 mg across secondary clinical outcomes, including 1‐hour headache response; 2‐hour pain‐free response; absence of nausea, photophobia, and phonophobia; functional improvement; use of rescue medication; treatment acceptability; and sustained headache response (P  <  .05). Overall, treatment‐related adverse events were low, nausea being the only adverse event with an incidence of 2% or higher (4.9% with eletriptan, 4.2% sumatriptan, 2.8% placebo).

Conclusion.—This trial confirmed that eletriptan 40 mg offers superior efficacy in treating migraine pain and associated symptoms and in restoring patient functioning when compared with sumatriptan 100 mg.
Effect of Autogenic Training on Drug Consumption in Patients With Primary Headache: An 8‐Month Follow‐up Study
Authors: Zsombok Terezia , Juhasz Gabriella , Budavari Agota , Vitrai Jozsef , Bagdy Gyorgy
Published: December 2004

Objective.—To examine the effects of Schultz‐type autogenic training on headache‐related drug consumption and headache frequency in patients with migraine, tension‐type, or mixed (migraine plus tension‐type) headache over an 8‐month period.

Background.—Behavioral treatments often are used alone or adjunctively for different types of headache. There are, however, only a few studies that have compared the efficacy and durability of the same treatment in different types of primary headache, and the effects of treatment on headache‐related drug consumption rarely have been assessed even in these studies.

Methods.—Twenty‐five women with primary headache (11 with mixed headache, 8 with migraine, and 6 with tension‐type headache) were evaluated via an open‐label, self‐controlled, 8‐month, follow‐up study design. After an initial 4 months of observation, patients began learning Schultz‐type autogenic training as modified for patients with headache. They practiced autogenic training on a regular basis for 4 months. Based on data from headache diaries and daily medication records, headache frequencies and the amounts of analgesics, “migraine‐specific” drugs (ergots and triptans), and anxiolytics taken by the patients were compared in the three subgroups over the 8‐month period.

Results.—From the first month of implementation of autogenic training, headache frequencies were significantly reduced in patients with tension‐type and mixed headache. Significant reduction in frequency was achieved in patients with migraine only from the third month of autogenic training. Decreases in headache frequencies were accompanied by decreases in consumption of migraine drugs and analgesics resulting in significant correlations among these parameters. Reduction in consumption of anxiolytic drugs was more rapid and robust in patients with tension‐type headache compared to patients with migraine, and this outcome failed to show any correlation with change in headache frequency.

Conclusion.—Schultz‐type autogenic training is an effective therapeutic approach that may lead to a reduction in both headache frequency and the use of headache medication.
Postcraniotomy Headache
Authors: Gee Joey R. , Ishaq Y. , Vijayan Nazhiyath
Published: December 2004

Background.—Persistent headache following craniotomy has been reported in the past, but the clinical features of this condition have not been well described.

Objective.—This study was undertaken to evaluate the incidence and clinical features of postcraniotomy headache.

Methods.—The medical records of 107 patients who had undergone surgery for brain tumor or intractable epilepsy were reviewed. The clinical features of preoperative and postoperative headache and any headache therapy initiated were obtained from the medical records. The surgical site and the underlying pathology were documented. The subsequent course of the headache also was recorded.

Results.—We evaluated 102 patients who underwent surgery: 76 for an underlying brain tumor, 21 for intractable epilepsy, and 5 for intracranial hemorrhage. Five patients were disqualified because of inadequate documentation. Fifty‐eight patients did not complain of headache preoperatively. Eleven patients who did not have preoperative headache experienced headache postoperatively. Eight had undergone surgery for intractable epilepsy and 3 for brain tumor. Eighty‐two percent of these patients experienced gradual resolution of their headaches over time, and most did not require major medical intervention for controlling their headache. No cases of debilitating headaches were identified. The majority of the headaches were located over the surgical site.

Conclusions.—The pathogenesis of postoperative headache remains unclear. The clinical characteristics of the headache following craniotomy suggest a combination of tension‐type and “site‐of‐injury headache” overlying the surgical site. These headaches are similar to the headaches described following head trauma.
Visual cortex excitability in migraine before and after valproate prophylaxis: a pilot study using TMS.
Authors: Mulleners WM , Chronicle EP , Vredeveld JW , Koehler PJ
Published: December 2004

Eur J Neurol. 2002 Jan;9(1):35‐40

We examined the effect of standard migraine prophylaxis with sodium valproate on repeated measures of occipital excitability using transcranial magnetic stimulation (TMS). We predicted that, comparing pre‐ and post‐treatment assessments, a reduction in clinical migraine parameters would be paralleled by a decrease in excitability measurements.A total of 31 migraine patients enrolled in the study, for assessment prior to and 1 month after commencement of sodium valproate prophylaxis. At each assessment, we used a standardized protocol to stimulate the occipital cortex with a 90‐mm circular (coil A) and 70 mm figure‐of‐eight (coil B) coil. We recorded the threshold stimulation intensity at which subjects just perceived phosphenes. Subjects kept detailed records of headache parameters 1 month before and also during the study period.Valproate therapy significantly improved headache indexes, as expected. In MA subjects assessed with coil B, phosphene thresholds were significantly higher post‐treatment than pre‐treatment, but those for MO did not change. Modest correlations were observed in MA patients between increase in phosphene threshold and decrease in headache index. Although preliminary, the findings with coil B lend some support to the notion that effective migraine prophylaxis may be achieved through lowering cortical excitability by gamma‐aminobutyric acid (GABA)‐ergic intervention. Further investigation of the effect of sodium valproate or other similarly acting substances on cortical excitability in migraine is warranted.

Comment: This paper provides a useful noninvasive human model in which to study the potential development of prophylactic treatments for migraine with aura. It will be important to standardize experimental conditions and to establish a rigorous experimental protocol for simulation parameters. However, this promises to be an important technique for use in future drug development. DSM
Practical approaches to migraine management.
Authors: Diamond S , Wenzel R
Published: December 2004

CNS Drugs. 2002;16(6):385‐403

Migraine is a recurrent clinical syndrome characterised by combinations of neurological, gastrointestinal and autonomic manifestations. The exact pathophysiological disturbances that occur with migraine have yet to be elucidated; however, cervico‐trigemino‐vascular dysfunctions appear to be the primary cause. Despite advances in the understanding of the pathophysiology of migraine and new effective treatment options, migraine remains an under‐diagnosed, under‐treated and poorly treated health condition. Most patients will unsuccessfully attempt to treat their headaches with over‐the‐counter medications. Few well designed, placebo‐controlled studies are available to guide physicians in medication selection. Recently published evidence‐based guidelines advocate migraine‐specific drugs, such as serotonin 5‐HT(1B/1D) agonists (the Ätriptans') and dihydroergotamine mesylate, for patients experiencing moderate to severe migraine attacks. Additional headache attack therapy options include other ergotamine derivatives, phenothiazines, nonsteroidal anti‐inflammatory agents and opioids. Preventative medication therapy is indicated for patients experiencing frequent and/or refractory attacks.

Comment: A nicely written, practical review article which I recommend for medical students, residents, and primary care physicians. SJT
Cluster headache: aetiology, diagnosis and management.
Authors: Ekbom K , Hardebo JE
Published: December 2004

Drugs. 2002;62(1):61‐69

Cluster headache is characterised by repeated attacks of strictly unilateral pain in the orbital region associated with local autonomic symptoms or signs. The attacks are brief but of a very severe, almost excruciating intensity. For unknown reasons males are affected more often than females. Recent studies suggest that an autosomal dominant gene has a role in some families with cluster headache. Hormonal studies indicate a dysfunction in the central nervous system. Neuroimaging has revealed primary defects in the hypothalamic grey matter. Local homolateral dilatation in the intracranial segment of the internal carotid and ophthalmic arteries during attacks is the result of a generic neurovascular activation, probably mediated by trigeminal parasympathetic reflexes. Sumatriptan 6mg subcutaneously is the drug of choice in the treatment of acute attacks. Inhalation of 100% oxygen can also be recommended. In the prophylactic treatment, verapamil is the first option. Other drugs that can be considered are corticosteroids, which may induce a remission of frequent, severe attacks, and lithium. Oral ergotamine tartrate may be sufficient for patients with night attacks and/or short, rather mild to moderately severe cluster headache periods. Third line drugs are serotonin inhibitors (methysergide and pizotifen) and valproic acid. Patients should be encouraged to keep headache diaries and be carefully instructed about the nature and treatment of the headaches. Alcohol can bring on extra attacks and should not be consumed during active periods of cluster headache.

Comment: A useful review of clinical options. Given the effectiveness of injectable sumatriptan and the prophylactic use of ergotamine mentioned, one might speculate that the new intranasal formulations of triptans (eg, zolmitriptan) and triptans with a longer half‐life (eg, frovatriptan) may prove to be effective in the treatment of cluster headache. DSM
Sumatriptan challenge in bipolar patients with and without migraine: a neuroendocrine study of 5‐HT1D receptor function.
Authors: Mahmood T , Silverstone T , Connor R , Herbison P
Published: December 2004

Int Clin Psychopharmacol. 2002 Jan;17(1):33‐36

An association between bipolar disorder and migraine has been lately recognized and an abnormality of central serotonergic function is suggested as the underlying neurophysiological disturbance. To examine the role of serotonin in bipolar disorder and migraine, we used the neuroendocrine challenge paradigm, and we chose sumatriptan, a 5HT1D agonist, as the pharmacological probe. We studied nine bipolar patients with migraine, nine bipolar patients without it, seven migraine patients, and nine matched normal controls. A post‐hoc analysis showed subsensitivity of serotonergic function, reflected in a blunted growth hormone response to sumatriptan challenge in bipolar patients who also suffered from migraine.

Comment: Given regulatory and labelling concerns about the potential for triptans to provoke serotonin syndrome, the apparent down‐regulation of serotonergic function in patients with bipolar disorder may suggest cause for cautious optimism and encourage future study of triptans in these patients to establish true causality or otherwise.

A prospective trial of sumatriptan injectable identified 1700 patients who repetitively used the triptan and were concomitantly on selective serotonin reuptake inhibitor (SSRI) medication. No serotonin syndrome was reported in any patient (Putnam GP, O'Quinn S, Bolden‐Watson CP, Davis RL, Gutterman DL, Fox AW. Migraine polypharmacy and the tolerability of sumatriptan: a large‐scale, prospective study. Cephalalgia. 1999;19:668‐675). Since SSRIs can rarely induce serotonin syndrome alone, there is a significant difficulty in establishing a risk of coadministration. DSM and SJT
Soil organic carbon content and composition of 130‐year crop, pasture and forest land‐use managements
Authors: Martens Dean A. , Reedy Thomas E. , Lewis David T.
Published: December 2004

Conversion of former agricultural land to grassland and forest ecosystems is a suggested option for mitigation of increased atmospheric CO2. A Sharpsburg prairie loess soil (fine, smectitic, mesic Typic Argiudoll) provided treatments to study the impact of long‐term land use on soil organic carbon (SOC) content and composition for a 130‐year‐old cropped, pasture and forest comparison. The forest and pasture land use significantly retained more SOC, 46% and 25%, respectively, compared with cropped land use, and forest land use increased soil C content by 29% compared with the pasture. Organic C retained in the soils was a function of the soil N content (r=0.98,P<0.001) and the soil carbohydrate (CH) concentration (r=0.96,P<0.001). Statistical analyses found that soil aggregation processes increased as organic C content increased in the forest and pasture soils, but not in the cropped soil. SOC was composed of similar percentages of CHs (49%, 42% and 51%), amino acids (22%, 15% and 18%), lipids (2.3%, 2.3% and 2.9%) and unidentified C (21%, 29% and 27%), but differed for phenolic acids (PAs) (5.7%, 11.6% and 1.0%) for the pasture, forest and cropped soils, respectively. The results suggested that the majority of the surface soil C sequestered in the long‐term pasture and forest soils was identified as C of plant origin through the use of CH and PA biomarkers, although the increase in amino sugar concentration of microbial origin indicates a greater increase in microbial inputs in the three subsoils. The practice of permanent pastures and afforestation of agricultural land showed long‐term potential for potential mitigation of atmospheric CO2.
Energy Coupling at a Two-Fluid Plasma Density Discontinuity
Authors: Dunphy Katherine Haynes , Kahn David , Mintzer David
Published: December 2004

The coupling of energy among electron-acoustic, ion-acoustic, and transverse electromagnetic waves at a density discontinuity in a two-fluid fully ionized plasma is studied by means of the plane wave solutions of the linearized equations of hydrodynamics and Maxwell's equations. An expression for energy conservation in a two-fluid plasma is discussed and applied to energy coupling among the three allowed modes. Numerical results for all types of wave coupling illustrate the influence of the plasma parameters on the efficiency of energy conversion.
Turbulent Spots and Wall Roughness Effects in Shock Tube Boundary Layer Transition
Authors: Thompson W. Paul , Emrich Raymond J.
Published: December 2004

Turbulent spots have been identified as a transition mechanism in shock tube boundary layer flows for a range of weak shocks at initial pressures near one atmosphere in air, using thin-film wall temperature gauges. The shape and growth rate of the spots is consistent with that found by other investigators in sub- and supersonic steady flows. A study of naturally occurring and artificially generated turbulent spots, and of flow tripping by two- and three-dimensional roughness elements, has shown the existence of an unconditionally stable region behind the shock, in which finite disturbances will not cause flow breakdown or transition to turbulence. The limit of this stable region is given by Reδ = 1.7 ± 0.3 × 103, based on boundary layer thickness at 99% of free-stream velocity. In the absence of artifical perturbations, laminar flow is seen to persist for times as much as a factor 5 longer than those seen by previous investigators. These maximum transition times were limited by flow tripping at wall discontinuities, and hence represent only a lower bound on the ultimate duration of laminar flow attainable in shock tubes.
Nonlinear Plasma Waves II. Nonlinear Effects near the Upper Hybrid Resonance
Authors: Freidberg Jeffrey P.
Published: December 2004

The problem of calculating the amount of energy which can be stored in a plasma near the upper hybrid resonance is treated by considering a macroscopic plasma model in which all nonlinear terms are maintained. For frequencies sufficiently close to the hybrid frequency, and for low temperatures, application of the traveling wave hypothesis reduces the macroscopic equations to an ordinary nonlinear differential equation with an additional small nonlinear term. The solution of this equation, by the perturbation procedure described in Pt. I, indicates that nonlinear effects (overtaking and trapping) become more important at lower energy levels as the frequency approaches the hybrid frequency. Explicit expressions are given for the maximum allowable stored energy at hybrid frequency in both a cold and warm plasma.
Fluctuations in the Plasma of the Model Stellarator
Authors: Young K. M.
Published: December 2004

Low m-number fluctuations of floating potential, density, and magnetic fields have been investigated in Ohmically heated discharges in the C stellarator. The azimuthal velocity of the perturbations reverses direction near vD/vi = 1 (vD is the electron drift velocity due to current and vi is the ion thermal velocity). For vD/vi ≳ 1, the wave moves at about the electron diamagnetic drift velocity and detailed probe measurements are consistent with the mode being the current-driven universal instability: the amplitude and relative phasing of the fluctuations indicate that the low-m fluctuations can cause the plasma loss. For vD/vi ≲ 1, the wave moves close to the plasma Er × B0 velocity and measurements are consistent with the resistive-g mode: measurement accuracy prevents a definite statement on the relationship between the fluctuations and the plasma loss.
Latitude-Dependent Plasmasphere Oscillations
Authors: Carovillano Robert L. , Radoski Henry R.
Published: December 2004

For a perfectly conducting plasma magnetized by a dipole field, the magnetohydrodynamic toroidal mode describes waves which propagate energy along the field lines. This characteristic causes the resonance oscillations of this mode to be strongly latitude-dependent. The periods of these oscillations are determined for a generalized plasma density of the form ρ = ρ0(a/r)sD(φ) and compared with previously obtained results for the poloidal or isotropic mode. A discussion is provided of the validity of the model plasmasphere and the conditions for experimental observation.
Restricted Variational Principle Methods for Boundary Value Problems of Kinetic Theory
Authors: Ortloff Charles R.
Published: December 2004

The surface integral term resulting from application of Rosen's restricted variational principle to kinetic theory boundary value problems in a three-dimensional physical space is shown to lead to a natural boundary condition equivalent to surface flux conservation.
Modified Quasi-Linear Equations and the Approach to Thermal Equilibrium
Authors: Harris E. G.
Published: December 2004

Modified quasi-linear equations have been derived which predict that the particle velocity distribution function approaches the Maxwell-Boltzmann distribution and the energy distribution of plasma oscillations approaches the Raleigh-Jeans distribution.
Kinetic Theory of Polyatomic Gases: Models for the Collision Processes
Authors: Brau Charles A.
Published: December 2004

Models are developed for the collision term in the kinetic equation for polyatomic gases. Assumptions are made which imply that the translational degrees of freedom undergo violent changes in collisions, while the internal degrees of freedom undergo relatively small transitions. The models consist of a term for the translational degrees of freedom which is closely related to the Krook models for monatomic gases and a term for the internal degrees of freedom which has the character of a diffusion expression. An explicit model is constructed for a gas of eccentrically loaded spherical molecules. Disposable parameters appearing in the model are evaluated in the limits of impulsive and adiabatic collisions. The existence of characteristic rotational energy relaxation times in these limits is briefly examined.
Theory of Axisymmetric Thermal Convection in a Rotating Fluid Annulus
Authors: Hide R.
Published: December 2004

A simplified theoretical model is presented of axisymmetric thermal convection in an annulus of liquid of kinematical viscosity ν, thermal diffusivity κ, and thermal coefficient of cubical expansion α, which rotates at Ω rad/sec about a vertical axis and is subject to a horizontal temperature contrast of |ΔT| C°. Ω is such that although Coriolis forces are in (geostrophic) balance with horizontal pressure gradients throughout most (though not all) parts of the fluid, centripetal acceleration is everywhere much less than that due to gravity, g. When an appropriate Péclét number, proportional to X=gα|ΔT|ν12/8κΩ32, is very small, heat conduction dominates the temperature field and the governing equations can be linearized. Otherwise the governing equations are essentially nonlinear, and when X is very large the temperature field is dominated by heat advection. The expressions obtained for the mean thermal structure and heat transfer agree satisfactorily with an analytical treatment of the small X case and with laboratory and numerical studies of the large X case. The expression obtained for the Brunt-Väisälä frequency, when combined with baroclinic instability theory, predicts that the axisymmetric flow should give rise to a definite type of nonaxisymmetric flow under conditions that agree remarkably well with laboratory studies.
Stability of Helmholtz Flow in an Unstable Atmosphere
Authors: Eisler Thomas J.
Published: December 2004

The stability of the Helmholtz profile in an atmosphere with an unstable density gradient has been studied. It is found that the convective and shear instabilities are essentially separate. It is noted that the shear gives rise to an amplified mode at right angles to the direction of the mean flow.
Entrainment Models for Laminar Jets, Plumes, and Wakes
Authors: Morton B. R.
Published: December 2004

Entrainment models are developed for laminar axisymmetric flow in viscous jets, plumes, and wakes, and an application is made to the ascent of laminar plumes in a stably stratified environment. The entrainment flux scale is obtained using order-of-magnitude arguments, and in each case is shown to be proportional to the kinematic viscosity ν with the exception of thermal plumes at Prandtl numbers less than unity when it is proportional to the thermometric conductivity κ.
Charge-to-Mass Relationships for Electrohydrodynamically Sprayed Liquid Droplets
Authors: Pfeifer Robert J. , Hendricks Charles D.
Published: December 2004

From a mathematical model suggested by Vonnegut and Neubauer, relationships between droplet radius and charge to mass ratio are developed for electrohydrodynamically sprayed liquid particles. Under the assumption that an unstable liquid mass disrupts into equally sized and charged particles so that the system energy tends toward a minimum value, probability distributions of the charge-to-mass ratio and the droplet radius are derived as modified Maxwell—Boltzmann functions; such functions explain certain features of experimentally observed distributions. That charged droplet systems tend toward a minimum energy configuration is verfied by experimental evidence for Wood's metal, octoil, and glycerine.
Hydromagnetic Surface Waves in a Conducting Liquid Surrounded by a Compressible Gas
Authors: Gerwin Richard
Published: December 2004

Those surface waves are studied that can propagate along a plane interface separating a conducting (incompressible) liquid from a nonconducting, compressible gas, when there is a static magnetic field parallel to the interface. For any given direction of propagation along the surface (except exactly perpendicular to the magnetic lines), and with the gas mass density small compared to that of the liquid, we find an approximate critical magnetic field strength above which the usual surface Alfvén waves cannot exist. Instead, at these strong magnetic fields, there are surface sound waves in the gas. The critical magnetic field at which the (actually smooth) transition from Alfvén-type to sound-type surface waves takes place is practically independent of the gas density, depending essentially only on its temperature.
Condensation and Electrical Conduction in Metallic Vapors
Authors: Solbes Albert , Kerrebrock Jack L.
Published: December 2004

A first-order theory of the bulk properties of condensing metallic plasmas is proposed. The theory accounts for the effects of ionization on the condensation process, and of the liquid phase on the electrical properties of the plasma. It indicates that there should be an increase in the effective supersaturation, due to impact of ions on droplets, if the electron density is high. It also predicts the existence of a critical electron temperature, such that for larger temperatures, a nonequilibrium state of high electron density can be maintained, while for lower temperatures the electron density approaches that in equilibrium with the droplet's surface. Experiments carried out in wet potassium vapor qualitatively confirm the existence of the critical temperature. The electrical conductivity of dry potassium plasma agrees quantitatively with that predicted by the two-temperature theory, with an electron collision cross section of 250 Å2.
Transverse Electromagnetic Waves in the Cosmic Ray Gas
Authors: Lerche I.
Published: December 2004

Under the assumption that the galactic magnetic field can be taken to be homogeneous, linearized equations are set up to describe the effect of a transverse electromagnetic wave on a gas composed of cold electrons and protons and relativistic protons embedded in the magnetic field. The system is assumed to be stable against electrostatic disturbances and the wave is taken to propagate normal to the unperturbed magnetic field direction. It is shown that if the perpendicular cosmic ray pressure exceeds the parallel cosmic ray pressure an unstable situation will result. It is also shown that the e-folding time is too long for the process to be physically significant.
Electrical Conductivity of a Multi-Ion Species Plasma
Authors: Dawson J. M.
Published: December 2004

A small number of highly ionized impurities have a large effect on plasma conductivity. Temperatures computed from measured conductivities may be in error unless these are properly taken into account. It is shown how this should be done.
Optical Determination of Barium Plasma Density
Authors: Motz Robin O.
Published: December 2004

It is shown theoretically that a measurement of just the scattering of resonance radiation from a barium plasma column can underestimate the total ion density by as much as 30%.
Laminar Elasticoviscous Flow in an Annulus with Porous Walls
Authors: Mishra Shankar Prasad , Roy Jyotirmoy Sinha
Published: December 2004

The problem of steady incompressible laminar flow of elasticoviscous liquids through a cylindrical annulus in the presence of suction and injection is considered. The rate of suction at one wall is taken to be equal to the rate of injection at the other wall of the annulus. Perturbation method is used for the axial velocity regarding S = R Rc as the perturbation parameter. For rapid convergence of the series solution, S is taken to be equal to 0.1. The effects of cross-flow Reynolds number R and elastic number Rc on the components of velocity and the pressure fields are shown graphically.
Electrohydrodynamically Induced Spatially Periodic Cellular Stokes-Flow
Authors: Smith C. V. , Melcher J. R.
Published: December 2004

An experiment is described in which a spatially periodic, time-invariant electric field is used to create a spatially periodic cellular flow by the action of an electric shear stress in the region of a fluid-fluid interface. The cellular motion is closely related to large-amplitude interfacial deformations observed when an electric field stresses the interface between two fluids having nearly the same electrical conductivity. A simple theoretical model is developed for the cell streamlines, flow velocity, and distribution of electric potential, and this model is shown to be in agreement with the experimental observations.
Shock and Current Layer Structure in an Electromagnetic Shock Tube
Authors: Vlases George C.
Published: December 2004

The problem of separation of the shock wave and current sheet in magnetically driven shock tubes is examined. Experiments were performed in cold, unmagnetized hydrogen in a large, fast inverse pinch shock tube in which the simple ``skin-depth criterion'' for obtaining separation was satisfied. Direct measurements of the shock by piezoelectric gauges, and the current sheet by magnetic probes, show that separation nevertheless did not occur. Although the shock wave was located at the very front of the current layer, the layer became much thicker at low pressures than predicted by the skin depth theory. Various mechanisms involved in the emergence of a shock from a current layer, and in the thickening of this layer, are discussed.
Effect of Resonant Charge Exchange Collisions on Unipolar Ion Streams
Authors: Sajben Miklos
Published: December 2004

The effect of resonant charge exchange collisions between an initially monoenergetic unipolar ion stream and a uniform neutral background gas is investigated by postulating a simplified collision mechanism. First-order approximation to the velocity distribution function for distances small compared to the mean free path and an asymptotic distribution function for large distances are obtained; both are found to be highly anisotropic. The results are valid if the ion energy gained between subsequent collisions is large compared with the thermal energy of the neutral gas. Errors introduced by the physical assumptions are discussed.
Collisionless Absorption and Emission of Electromagnetic Waves by a Bounded Plasma
Authors: Hinton F. L.
Published: December 2004

The absorption and emission properties of a hot bounded plasma can be greatly influenced by collective behavior in the plasma. A homogeneous slab model of a collisionless plasma is used in a theoretical study of these collective effects. Peaks in the absorptivity occur at the resonance frequencies of longitudinal standing waves in the plasma. Power can be absorbed from an incident electromagnetic wave by Landau damping of the plasma waves which it couples to. Radiation is emitted from a collisionless bounded plasma because plasma waves excited in the wakes of fast electrons are partially converted to electromagnetic waves at the plasma boundaries. The radiation has peaks at the same frequencies as the absorption because of the collective reinforcement of the plasma waves at their resonance frequencies. In thermal equilibrium the collisionless absorption and emission obey Kirchhoff's law. The emission may be enhanced if many nonthermal electrons are present.
Stochastic Electron Heating and Hydromagnetic Wave Damping
Authors: Barnes Aaron
Published: December 2004

Physical processes involved in collisionless damping of the fast hydromagnetic mode are investigated by considering the stochastic heating of electrons by a random spectrum of fast waves. We take as a model a weakly damped fast wave, propagating in a direction such that the damping is mainly due to electron heating; allowance is made for the possibility of a small component of electric field parallel to the unperturbed field. To estimate the damping we consider an ensemble of electrons accelerated (1) by magnetic-moment magnetic-field-gradient interaction and (2) by the parallel electric field. Electron heating is calculated from a Fokker—Planck type of equation; the damping decrement is obtained by equating the electron heating rate to the wave energy loss rate, and agrees with the damping decrement obtained from the appropriate asymptotic limit of the general dispersion relation. Some general aspects of this method for obtaining wave-damping decrements are discussed.
One-Dimensional Static Pinch Solutions
Authors: Lam S. H.
Published: December 2004

Exact (quasi-neutral) one-dimensional static pinch solutions are obtained when the distributions functions are allowed to have two perpendicular temperatures. The solutions can simulate plasma-magnetic field interfaces, single sheet pinches, and periodic pinches.
An Ultra-Fast Thetatron Pinch Experiment
Authors: Adlam J. H. , Burcham J. N.
Published: December 2004

A power supply consisting entirely of coaxial lines was used to produce a current pulse of 100 nsec duration in a thetatron coil, the plasma inside the coil being preionized. Measurements were made of the magnetic field, using magnetic probes, and of x rays produced. These measurements showed that, under suitable conditions, shock waves were produced and the electrons were heated to a temperature of several thousand electron volts. A necessary condition for producing an electron temperature approaching that required by shock theory was that the magnetic field outside the plasma should be in the opposite direction to the magnetic field inside the plasma.
Anisotropic Compression of a Relativistic Plasma
Authors: Noerdlinger Peter D. , Yui Alexander Ko-Min
Published: December 2004

The momentum distribution is calculated for a relativistic plasma originally in thermal equilibrium which has been subjected to a slow anisotropic compression.
Transport Properties of a Nonequilibrium Partially Ionized Gas in a Magnetic Field
Authors: Chmieleski Robert M. , Ferziger Joel H.
Published: December 2004

A modified Chapman—Enskog technique developed for a partially ionized gas in an electric field is generalized to include the effects of a magnetic field. The method allows the electron and heavy particle temperatures to differ while requiring all species to have the same macroscopic velocity to zero order. Expressions are obtained for the transport properties of such a gas and a complete set of self-contained magnetohydrodynamic equations is given. As an example, the transport properties of a fully ionized gas containing a single ion species are evaluated using the cutoff Coulomb potential. In the limit of equal electron and ion temperatures, the results are in agreement with previous results.
Stability of Laminar Boundary Layers at Separation
Authors: Wazzan Ahmed R. , Okamura T. T. , Smith A. M. O.
Published: December 2004

The stability of laminar boundary layers at separation is considered. The velocity distribution is represented by (1) a Pohlhausen fourth-degree polynomial P4, and (2) by a Falkner—Skan similarity profile at separation, Hartree β = − 0. 1988. The Orr—Sommerfeld equation is integrated using Runge—Kutta with Gram—Schmidt orthonormalization. Using single precision arithmetic, the method leads to satisfactory answers at Reynolds numbers R1 = 100 000 and larger. In either case the minimum critical Reynolds number is found to be of the order of 100. It is found that the neutral curves for the P4 profile obtained by solving the Orr—Sommerfeld equation, whether exactly (numerically) or within the framework of the asymptotic approximations, approach along the upper branch the same asymptotic value, namely α1 = 0.8028 (in the case of the β = − 0. 1988 profile, however, the corresponding values is α1 = 1.240). It is also found that the asymptotes to the lower branch in both cases vary with α1 according to R11/3∼α1 −7/9 (in the case of the β = − 0. 1988 profile however, the corresponding variation is R11/3 ∼ α1 - 0. 477).
Application of a Microwave Technique to the Measurement of Electron Density and Ionization Time
Authors: Lederman Samuel , Dawson Edward F.
Published: December 2004

The measurement of ionization rates, electron density, and ionization time in thermally ionized gases, by means of a microwave technique, is discussed. The technique used in this work utilizes a so-called ``end-wall'' microwave resonant cavity. It is essentially a microwave cavity operated in the TE011 mode with a plasma forming one end wall. Since the resonant frequency of such a cavity is a function of the axial length of the cavity, a variable density plasma with its corresponding variable conductivity is utilized to tune the cavity to different resonant frequencies. It is shown that by applying two frequencies to the cavity separated from each other by a known Δf, which is small compared to the resonant frequency of the closed cavity, a simple method is arrived at to measure electron density, ionization rate, and ionization time.
Plasma Wind Tunnel Studies of Collision-Free Flows and Shocks
Authors: Pugh E. , Patrick R.
Published: December 2004

A plasma wind tunnel has been constructed and the super-Alfvénic flow over a magnetic obstacle studied. The wind tunnel produces a steady (10−3 sec) flow of high enthalpy (∼100 eV), high density (1014) plasma. The flow of this high conductivity plasma has been studied using magnetic field probes. The interface and shock wave produced in front of a magnetic obstacle in the flow have been studied. The shock wave is shown to satisfy the usual magnetohydrodynamic Rankine—Hugoniot relations.
Functional Integration Theory for Incompressible Fluid Turbulence
Authors: Rosen Gerald
Published: December 2004

A purely deductive approximation theory for incompressible fluid turbulence is presented, based exclusively on the Hopf characteristic functional space-time formulation and without any additive statistical postulate. Certain real symmetric solenoidal tensors called ``stationary functionalities'' are defined in terms of the characteristic functional by functional integration, quantities which vanish in the neighborhood of an exact physical characteristic functional, hence, for an approximate physical characteristic functional. By explicit functional integration, the first and second tensorial rank stationary functionalities are evaluated with a zero-mean velocity field Gaussian approximation for the characteristic functional. Equating the resulting expressions to zero produces a subsidiary equation and a dynamical equation for the two-point velocity correlation tensor, equations which are identical to the Navier-Stokes expectation value equation for a zero-mean velocity field and to a specific two-point Navier-Stokes expectation value equation with a zero-mean velocity field probability distribution such that the fourth-order velocity field product expectation values are related to lower-order product expectation values in the same way as for a zero-mean Gaussian probability distribution. Specialized forms of the nonlinear integrodifferential dynamical equation are worked out for the cases of homogeneous and isotropic homogeneous turbulence.
Macroscopic Quasi-Linear Theory of the Two-Stream Instability
Authors: Völk Heinrich J.
Published: December 2004

The quasi-linear development of the instability of two counter-streaming electron beams is discussed from a hydrodynamic point of view. While it turns out that the closure assumptions for the system of moment equations have an appreciable influence on the time asymptotic result, the nonresonant diffusion mechanism allows a number of interesting interpretations in the fluid picture.
Plasma Heating by the Fast Hydromagnetic Wave
Authors: Chung K. , Rothman M. A.
Published: December 2004

The fast (right-handed) hydromagnetic wave is generated by a Stix coil installed on the Model C stellarator. Maximum wave generation and heating occurs, as expected, under conditions such that the wavelength of the propagating wave equals the wavelength of the coil structure. Measurements of diamagnetic pressure determine the efficiency for conversion of rf power into thermal energy. Theoretical calculations of heating rates shows that plasma resistivity and Landau damping are insufficient to account for the observed heating rates if only the body wave is considered. Introduction of surface waves associated with finite electron mass results in increased Ez fields which enhance the heating rate.
Observation of a Ballooning-Type Instability in a Plasma Confined by a Quadrupole Magnetic Field
Authors: Meade D. M. , Yoshikawa S.
Published: December 2004

Instabilities of a ballooning type were observed in the ∮ dl/B stable region of a linear quadrupole device. The amplitude distribution of the fluctuation along a field line behaved like a standing wave that had a node where ▿B2 · ▿p < 0 and was peaked where ▿B2 · ▿p > 0. The quantity k∥λmfpe was typically 5–10. The observed fluctuation is in qualitative agreement with the theory of collisionless drift waves modified to take into account the change of field curvature and field strength along the field line. The threshold for the instability appears to be strongly dependent on the ratio of the plasma radius to connection length. The plasma confinement was not sensitive to the presence of the ballooning instability.
Single Particle Motion in Toroidal Stellarator Fields
Authors: Gibson A. , Taylor J. B.
Published: December 2004

The discussion of the motion of single particles in stellarators is simplified by identifying three distinct groups of particles. The drift equations are used to treat these groups by analytical and numerical methods. It is shown that, unlike an axisymmetric system the region of a stellarator with surfaces closed about a magnetic axis need not form a perfect trap. In fact, unless the toroidal curvature is very small, particles in one of the groups, those mirrored between maxima in a single period of the helical field, will drift out beyond the separatrix no matter how large the magnetic field strength.
Direct Measurement of Mass Pickup in a Low-Energy Theta Pinch
Authors: Harris Robert W.
Published: December 2004

A balanced magnetic probe technique has been used to determine the drive force acting on the plasma sheath during the first pinch. The sheath motion was studied with the probe technique, and with image converter framing pictures. The sheath mass was determined from the velocity and the time integral of the drive force. The results indicate an average pickup coefficient of 0.82 ± 0.06 for the first half of the pinch. Electron density and temperature were determined during the first half of the pinch by measurement of the Hβ line profile. Combination of the spectroscopic and mass data indicates an average sheath ionization lower than predicted by theory, but the experimental error in the ionization determination precludes a definite conclusion to this effect.
Propagation of Longitudinal Waves into a Nonuniform Plasma
Authors: Leavens William M.
Published: December 2004

Numerical solutions of the Vlasov equation for plasma wave propagation through a sheath into a nonuniform plasma have been obtained. A strong wave is excited for frequencies slightly above the plasma frequency at the sheath edge.
New Mechanism for Low-Frequency Oscillations in Partially Ionized Gases
Authors: Roth J. Reece
Published: December 2004

An outline is given of the theory underlying a class of low-frequency oscillations in partially ionized gases that are described by the operation of the plasma continuity equations.