bluuebunny/crossref_metadata_2025 huggingface dataset:
Targeting the Skin for Genetic Immunization
Authors: Falo, Jr. Louis D.
Published: December 2004

One of the most promising applications of recent advances in gene therapy is the development of immunization strategies based on the delivery of antigen‐encoding DNA. DNA‐based vaccination, also referred to as genetic vaccination or polynucleotide vaccination, offers considerable promise for improvement over existing immunization strategies, and the skin offers unique potential as a target tissue for genetic vaccines. The expression of genetically introduced antigens in a cutaneous microenvironment rich in both professional antigen‐presenting cells and accessory cells, which are capable of producing immunostimulatory cytokines, has the potential to overcome the historical limitations of vaccinology and immunotherapy. Though the precise molecular mechanisms of genetic immunization remain unclear, a general working model of the events through which antigen‐encoding plasmids introduced into the skin initiate an immune response can be constructed. The finding that Langerhans cells can be transfected in vivo raises the exciting possibility that these migrating professional antigen‐presenting cells can be genetically engineered in vivo. By designing strategies to codeliver genes encoding antigens with genes encoding immunoregulatory molecules to the same antigen‐presenting cell, it may be possible to either induce or suppress antigen‐specific immune responses in the host. Though many aspects of the biology of cutaneous DNA immunization remain unknown, the skin appears to offer unique potential for the application of advances in gene therapy to vaccination and genetic engineering of the immune response.
Public Health Nursing: The Generalist in a Specialized Environment
Authors: May Kathleen M. , Phillips Linda R. , Ferketich Sandra L. , Verran Joyce A.
Published: December 2004

Abstract  In implementing a generalist model of public health nursing (the Comprehensive Multi‐level Nursing Practice Model) in a rural county health department, a research team encountered critical challenges. The framework for the model was a philosophy of public health nursing practice and action research to support the public health nurse generalist role. Challenges in implementing the model stemmed from conflicts between the research team and the health department that were rooted in philosophical differences about how to implement care and the nature of nursing and the public health nursing role. Key factors were the subtle forces operating in the public health environment that constrain the public health nurse generalist role. Based on conflicts that arose in implementing the model, implications for public health nursing practice are in opportunities to influence policy at health department and other levels and responsibility for assuring professional practice.
Two Hundred Ninety‐Six Cases of Onychomycosis in Children and Teenagers: A 10‐Year Laboratory Survey
Authors: Lateur N. , Mortaki A. , André J.
Published: December 2004

Abstract: There is still little data available about the epidemiology of childhood onychomycosis. Looking at our laboratory figures over a 10‐year period provided us with some useful information. Nail keratin samples were taken by dermatologists from 21,557 patients with nail conditions, mainly in the Brussels region. The specimens were examined by direct microscopy and/or histology, and cultured on Sabouraud medium agar. Only patients less than 17 years of age were considered as children. Clinical information was gathered about age, sex, and the location of the infected nail. Nine hundred sixty‐three of the samples were from children, and 296 of those children had proven onychomycosis. More than three‐fourths of the cases were found in children more than 6 years old, and boys were more frequently affected than girls. Toenails were the predominant location of infection. Trichophyton rubrum was the main pathogen, followed by Candida spp. and Trichophyton interdigitale. One case was caused by Scopulariopsis spp. As in adults, onychomycosis is probably the main nail disease in children. After the age of 6 years, the presentation is very similar to that in adults: toenails are mostly involved, and T. rubrum, the main pathogen, is responsible for distal and lateral subungual onychomycosis.
Frequency and Clinical Role of Staphylococcus aureus Overinfection in Atopic Dermatitis in Children
Authors: Ricci Giampaolo , Patrizi Annalisa , Neri Iria , Bendandi Barbara , Masi Massimo
Published: December 2004

Abstract: The goal of this study was to evaluate the frequency and role of Staphylococcus aureus infection in patients with atopic dermatitis (AD). In 81 children, ages 2 months to 9 years, affected with moderate to severe AD, 308 samples from the cutaneous lesions were obtained and analyzed. S. aureus was isolated in 52 children (64.2%). Five of these were also colonized by Streptococcus pyogenes and one by Candida albicans. In 61 patients, total IgE serum level and specific IgE were tested to evaluate their allergic status: in 43 children a diagnosis of extrinsic AD was made, while 18 were affected by intrinsic AD. A higher presence of the bacterium was observed in allergic (71%) versus nonallergic children (49%). Our data demonstrate the importance of S. aureus in the clinical manifestation of AD and, in particular, its role in worsening the eczematous lesions of the face, neck, and perineum in children less than 1 year of age.
Leg Ulcer in Hereditary Spherocytosis
Authors: Giraldi Susana , Abbage Kerstin T. , Marinoni Leide P. , Oliveira Vania , Pianowski Mara A. , Lehmkuhl Adelina E. , Neto José Fillus
Published: December 2004

Abstract: Indolent leg ulcers are a rare complication found in patients with hereditary spherocytosis. We report a 13‐year‐old girl with hereditary spherocytosis who developed a chronic painful ulcer on the medial malleolus. All other etiologies were ruled out. Nine months after splenectomy the ulcer healed completely and the symptoms disappeared. We discuss and review this unusual entity in children.
Intractable Diarrhea of Infancy with Facial Dysmorphism, Trichorrhexis Nodosa, and Cirrhosis
Authors: Landers Maeran C. , Schroeder Theresa L.
Published: December 2004

Abstract: A 3‐year‐old girl had severe intractable diarrhea with trichorrhexis nodosa and cirrhosis. This patient was referred to the pediatric dermatology clinic for lifelong brittle hair. The brittle hair microscopically demonstrated trichorrhexis nodosa. The girl also had facial dysmorphism, with a prominent forehead and cheeks, broad flat nose, and hypertelorism. She had a history of severe intractable diarrhea since 2 weeks of age and failure to thrive requiring lifelong total parenteral nutrition (TPN). Hepatomegaly was noted and prompted liver biopsy which demonstrated cirrhosis. Mental retardation and developmental delay was also found upon examination. This child may be included in the syndrome of intractable infant diarrhea, an entity known in the gastroenterology literature but yet not reported in the dermatologic literature. Dermatologists should be aware of this syndrome in which trichorrhexis nodosa is commonly seen.
Imiquimod is Highly Effective for Extensive, Hyperproliferative Condyloma in Children
Authors: Majewski Slawomir , Pniewski Tomasz , Malejczyk Magdalena , Jablonska Stefania
Published: December 2004

Abstract: We describe a dramatic response to imiquimod of long‐lasting, highly proliferative extensive perianal condylomas involving the anal canal in a 19‐month‐old girl. Her mother was free of condyloma and allegedly had no human papillomavirus (HPV) infection during pregnancy. There was no evidence of sexual abuse. Application of 5% imiquimod cream to the child every other day for 3 weeks resulted in almost complete resolution of the warts, with total clearance within another 2 weeks. The inflammatory reaction was moderate. Since there is still discussion of whether imiquimod may be prescribed for small children, this case of very extensive condyloma provides evidence that the compound is safe and highly effective.
Melanogenic Response of the Kupffer Cells of Rana Esculenta L. to Melanocyte Stimulating Hormone
Authors: Guida Gabriella , Zanna Paola , Gallone Anna , Argenzio Elisabetta , Cicero Rosa
Published: December 2004

We have previously shown that Kupffer cells (KCs) of Rana esculenta L. possess melanogenic ability. The melanogenic enzyme activities in these cells are different from those described in skin melanocytes, and very little is known about their regulation by extracellular signalling molecules. In order to study this regulation, we analysed the effects of NDP‐MSH on the levels of expression of the tyrosinase gene and on dopa‐oxidase activity, using primary cultures of KCs. Incubation of the cells with NDP‐MSH increases tyrosinase gene transcription, within the first 24 h of stimulation. To gain insight into the signalling mechanism involved in the cell response to the hormone, KCs in culture were incubated with IBMX or forskolin. These agents mimic the effects of α‐MSH on melanocytes by increasing the intracellular level of cAMP. The experimental results showed that while the hormonal treatment always activated the KC tyrosinase system, treatment with IBMX or forskolin never did. Therefore, in KCs the tyrosinase‐stimulating action of NDP‐MSH was not mimicked by cAMP elevating agents. Assays of cAMP levels in cells stimulated with NDP‐MSH demonstrated that the hormone does not produce significant increases in intracellular cAMP. On the contrary, forskolin produced significant increases in cAMP starting from 30 min of incubation. These results suggest that tyrosinase induction by melanocortins in KCs is not mediated by the cAMP pathway, and highlight the existence of substantial differences in the hormone signal transduction mechanisms between amphibian KCs and melanocytes or melanoma cells.
Induced Oscillations in a Rarefied Plasma in a Magnetic Field
Authors: Greifinger P. S.
Published: December 2004

The excitation of collective plasma motion by a small charged object moving through a low-density unbounded plasma in an external uniform, static magnetic field is considered. The energy loss per unit path length due to the excitation of collective plasma motion is found as a function of magnetic field strength for an arbitrary angle between the velocity of the object and the field direction. It is assumed throughout this paper that the ion temperature is zero and the velocity of the charged object is small compared to the mean thermal electron speed.
Motion of a Viscous Liquid Past an Ellipsoid
Authors: Venkates H. G.
Published: December 2004

A symmetrical flow pattern due to the motion of a viscous liquid past an ellipsoidal body is determined. A unitary treatment of the flow problem is possible in which the pure potential flow, the slow viscous flow and the type of flow postulated in the Prandtl theory are seen to be limiting cases of an exact solution. The flow pattern for the case of the sphere and of the elliptic cylinder have been derived as special cases. The method consists in extending the equations of hydrodynamics by the introduction of certain fictitious body forces which are eventually made to vanish in the limit.
Approach to Equilibrium of a Quantum Plasma
Authors: Balescu R.
Published: December 2004

The treatment of irreversible processes in a classical plasma [R. Balescu, Phys. Fluids 3, 62 (1960)] is extended to a gas of charged particles obeying quantum statistics. The various contributions to the equation of evolution for the reduced one-particle Wigner function are written in a form analogous to the classical formalism. The summation is then performed in a straightforward manner. The resulting equation describes collisions between particles ``dressed'' by their polarization clouds, exactly as in the classical situation.
Validity of the Nonlinear Poisson-Boltzmann Equation
Authors: Balazs Nandor L.
Published: December 2004

The validity of the nonlinear and linearized Poisson-Boltzmann equation is analyzed by comparing analytically and numerically the correct equation of state of a one-dimensional plasma with the approximate ones following from the Poisson-Boltzmann equation.
Particle Surfaces for High-Energy Electrons in a Stellarator
Authors: Meservey E. B. , Goldberg L. P.
Published: December 2004

A simple theory of high-energy (``runaway'') electron surfaces in a stellarator is presented. X-ray intensity measurements qualitatively confirm the prediction of the simple theory, namely that, in a machine whose figure-eight twist is negative (i.e., each U bend rotated counterclockwise as seen from beyond that U bend) runaway surfaces drift toward the center of curvature (inside) of the stellarator loop for accelerating field E parallel to confining field B and toward the outside for E antiparallel to B. The time behavior of x-ray intensity indicates that the actual runaway surfaces do not have the predicted circular cross section but have, superposed on this, perturbations of m-fold azimuthal symmetry at values of plasma current corresponding to the predicted ranges for various modes of the ``kink'' instability.
Variational Principles in Plasma Dynamics
Authors: Su Chau-Hsing
Published: December 2004

A Lagrangian density is constructed for a multifluid system. Maxwell's equations and flow equations for inviscid, barotropic, and infinitely electrical conducting fluid are obtained from the Lagrangian density through the use of the well-known Lagrange-Euler equations. Flow equations for plasma consisting of electrons and ions are derived from the equations of different species. In this way, in addition to the usual equations of momentum and continuity, a generalized Ohm's law is also obtained.
Effect of Coulomb Scattering on Two-Stream Instabilities in a Plasma
Authors: Tidman D. A.
Published: December 2004

The effect is investigated of a small amount of two-body scattering on the two-stream instability that occurs in a plasma of contrastreaming electrons and ions. This is done by assuming the electronion collision frequency is small and making a perturbation expansion in this quantity. The Fokker-Planck scattering formula for the Coulomb interaction is used. It is found that, as the ordered streaming energy of the electrons is thermalized, enhanced Landau damping competes with the growth of the instability.
Unstable Cyclotron Oscillations in a Cylindrical Plasma Shell
Authors: Burt P. , Harris Edward G.
Published: December 2004

Longitudinal oscillations of a finite, cylindrical shell of plasma in a uniform axial magnetic field have been investigated. The ions are assumed to move initially in concentric Larmor orbits while the electrons are stationary. By neglecting random velocities, it is possible to obtain a dispersion relation for longitudinal (electrostatic) waves which is solved in the limit of short wavelength perturbations. The real parts of the frequencies of the disturbances are found to be integral multiples of the ion cyclotron frequency. Conditions for instability similar to those of the infinite plasma are also found which depend upon the thickness of the shell.
Testing Time and Contact-Zone Phenomena in Shock-Tube Flows
Authors: Hooker William J.
Published: December 2004

Measurements have been made in a shock tube of the hot-flow duration, the structure of the contact front, and the nature of the mixing zone. The flow duration was obtained by spectroscopically detecting the first arrival of the driver gas, and is observed to become vanishingly small with decreasing initial driven gas pressure. These data and the data of Roshko and Duff are compared with predictions of Roshko's (laminar) theory and the numerical example of Anderson's (turbulent) theory. Agreement with the one point of Anderson's prediction is surprisingly good, while the agreement with Roshko's theory ranges from excellent to unsatisfactory. Approximations in Roshko's treatment which contribute to the lack of correlation with the data obtained in the smaller diameter shock tubes of Duff and the present work are emphasized and a formulation of the flow model is developed which better predicts the actual shock-tube flow durations.
Kirkendall Effect in Gaseous Diffusion. II. Absolute Determination of Diffusion Coefficients
Authors: Mason E. A.
Published: December 2004

It is shown how the Kirkendall effect in gaseous diffusion can be used to determine absolute values of diffusion coefficients, rather than only relative values, by extrapolation of the observed marker motion to zero capillary diameter. In this way the diffusion coefficient of He-Ar at 30°C and 1 atm is found to be 0.761 cm2/sec, in agreement with a directly measured value of 0.762 cm2/sec.
Existence of Solutions of One-Dimensional Flow of a Real Gas
Authors: Menkes J.
Published: December 2004

Formal solutions to the equations of motion of the one-dimensional, unsteady flow of a viscous, compressible, heat-conducting gas are presented. The relationship between the existence of these solutions and the problem of hydrodynamic stability is discussed.
Magnetically Insulated Shock Tube
Authors: Fowler Richard G. , Turner Eugene B.
Published: December 2004

Experiments were carried out in a small (1 in. diameter) electrically driven shock tube with a homogeneous longitudinal magnetic field of up to 20 000 gauss in both the discharge and expansion chambers. A 1600-joule capacitor bank was used with deuterium pressures of 150 μ Hg or more, giving shock velocities of up to 8 cm/μsec. At magnetic field strengths of 7500 gauss and higher, several effects were found. The shock velocity was substantially increased. An interface, such as seen in diaphragm-type shock tubes was clearly defined in the wave-speed photographs. The reflected shock velocities were abnormally high, indicating a γ of more than 5/3. The shock fronts were observed to be convex.
Plasma Injection into a Vacuum Magnetic Field
Authors: Scott F. R. , Voorhies H. G.
Published: December 2004

Experimental measurements have been made on the axial injection of dense, highly directed plasmas of deuterium, hydrogen, and helium into a cusp magnetic field. Magnetic probe measurements show that during injection a diamagnetic region forms over a radius which varies inversely with the axial field strength for each type plasma. Axial velocities of the dense plasma are measured with a movable loop-permanent magnet assembly. For deuterium the mean axial velocity was v0 = 8.7 ± 0.5 × 106 cm/sec, for helium v0 = 1.08 ± 0.5 × 107 cm/sec and for hydrogen 1.4 ± 0.1 × 107 cm/sec. Optical emission line shapes for helium show a Doppler width equal to 118 ± 11 ev in the peak axial field region during injection. Deuterium emission lines gave both ion kinetic temperature and ion densities after injection which indicate reasonable containment with high β. A simple hydrodynamic model of a supersonic diffuser compares favorably with the experimental observations during injection for both deuterium and helium.
Linked-Diagram Expansion for the Equation of State of a Gas of Molecules
Authors: Kaufman Allan N. , Watson Kenneth M.
Published: December 2004

The method of the linked-diagram expansion is applied to the equilibrium statistical mechanics of a nondegenerate gas of molecules, taking into account the structure of the molecules, and using the Pauli principle for all the electrons. The equation of state is obtained in the form of a virial expansion analogous to that of Ursell and Mayer.
Viscosity of Two-Component Gaseous Mixtures
Authors: Hirschfelder Joseph O. , Taylor Marion H. , Kihara Taro , Rutherford Reginald
Published: December 2004

The conditions are found where the viscosity of a binary mixture of dilute gases either has a maximum or minimum with respect to variations in the composition. A maximum in the viscosity is most likely to occur for a mixture of a polar and nonpolar gas in which the viscosities of the pure components are nearly equal and their molecular weights are quite different. A minimum should occur for a mixture of two nonpolar gases in which both the viscosities and molecular weights of the pure components are nearly equal. There are 17 experimental examples of maxima (and three additional mixtures with predicted maxima) in the viscosity but up to the present time no cases have been discovered where the viscosity has a minimum. A comparison between theory and experiment shows excellent agreement for the viscosity of binary mixtures.
Dynamics of Ionized Gases
Authors: Dupree Thomas H.
Published: December 2004

Ionized gas dynamics is discussed in terms of two coupled equations for the one- and two-particle distribution functions. The equations have been obtained previously by multiple integration of the Liouville equation and a formal expansion in the specific volume. The two-particle equation is solved for a multicomponent plasma in terms of two operators which depend on the one-particle functions. It is shown that these operators have a simple interpretation and lend an easy insight into the correlation mechanism. If one neglects the time dependence of the one-particle functions which occur in the operators, then the operators can be obtained explicitly. This procedure is shown to be valid for plasmas with ``smooth'' velocity distributions and no large inhomogeneities. When velocity instabilities exist, the correlation function is subject to growing oscillation. The ultimate effect of this instability is not clear.
Convective Circulation in Water Induced by Evaporative Cooling
Authors: Spangenberg W. G. , Rowland W. R.
Published: December 2004

Schlieren photographs taken simultaneously from the top and side of a tank of water are here used to study convection currents induced by evaporative cooling. It is found that water from the cooled surface layer collects along lines producing thickened regions which become unstable and plunge in vertical sheets. Surface water then continues to flow downward through the sheets, reducing the cooled surface layer to a thin film. In top schlieren views the plunging regions sometimes appear straight, sometimes curved, and branched or terminated with no fixed pattern. The number of lines per unit area is a function of the cooling rate rather than the depth of the container. Reticulated surface patterns were observed only at particular cooling rates and columnar plunging occurred only on rare occasions. No distinctly different combination of conditions to differentiate between the causes of these different modes was evident. Numerical integration of the nonlinear temperature distribution in the cooled layer showed a critical Rayleigh number of 1193 when convective circulation started, and a Rayleigh number of 102 for maintaining an established uniform circulation.
Generalizations of the Saha Equation
Authors: Dewan Edmond M.
Published: December 2004

The Saha equation, which relates temperature to ion densities, is sometimes used under circumstances that do not justify the assumptions of thermodynamic equilibrium upon which it is based. Astronomers have therefore made generalizations of this equation but have unfortunately assumed thermodynamic equilibrium energy distributions for the particles and the radiation field even though these may be at different temperatures. It is therefore interesting to know how the nonequilibrium steady-state energy distributions affect the ionization densities. In the present treatment a general expression relating ion densities to the radiation and particle energy distributions is obtained. This equation reduces to Saha's equation in the limit of thermal equilibrium and gives numerical results in good agreement with other work based on entirely different considerations, thus providing a good check. We find that under certain conditions one would expect results that differ enormously from those predicted by the Saha equation.
Propagation of A ⇌ B → C Flames
Authors: Curtiss C. F. , Hirschfelder Joseph O. , Taylor Marion H.
Published: December 2004

The equations describing a flame supported by the chemical reaction A ⇌ B → C are solved by an iterative procedure using the Arrhenius temperature dependence of the reaction rate constants. It is found that an excellent approximation to a solution is obtained by setting the net rate of production of B to zero. This approximation is a form of the pseudostationary state approximation although B is not necessarily in near equilibrium with the reactant A. In addition, explicit solutions are obtained for the temperature and concentration profiles using the ignition temperature approximation for the temperature dependence of the reaction rate constants.
Shock-Wave Curvature at Low Initial Pressure
Authors: Duff Russell E. , Young James L.
Published: December 2004

The shape of the primary shock wave in a shock tube has been measured by recording the time of arrival of the shock in argon at an array of piezoelectric detectors located along a diameter of a 28.6-mm i.d. shock tube operated at an initial expansion chamber pressure of 0.34 mm Hg. The following conclusions were drawn from the results: (1) Shock-wave tilt was negligibly small under the conditions of these experiments; (2) shock-wave curvature is independent of shock strength for shock Mach numbers from 1.8 to 6.3; (3) the shock-front shape is nearly spherical; (4) the axial extent or the bulge of the curved shock is approximately 1 mm. The axial extent of a shock in argon was also measured over the range of initial pressure from 0.1 to 20 mm Hg. It varies approximately as the inverse square root of the initial pressure.
Transport Phenomena in a Fully Ionized Gas Confined in a Strong Magnetic Field
Authors: Koga Toyoki
Published: December 2004

The distributions of ions and of electrons in the presence of a strong magnetic field in the z direction are not assumed as being almost Maxwellian. Instead, f(0)(cx2 + cy2, cz, x ± r cy/c) is taken for the distributions in the zeroth approximation with respect to the ratio (Larmor radius r)/(free path length λ), and an iteration method is developed for solving the Boltzmann equation. First, defining the density of guiding centers of particles, f(0) is expanded into powers of (r ∂ f(0) / ∂ x)/f(0). By coarse-graining the Boltzmann equation over one cycle of Larmor's gyration, equations of moments in the first approximation with respect to r/λ are derived. The simple mode of collision proposed by Bhatnagar et al. is assumed. A special case is studied in detail in order to compare the present theory with those of other authors who assume distributions to be almost Maxwellian. The agreement is good. The effects of drifts of guiding centers caused by the spatial nonuniformity of a magnetic field and/or by a static electric field in the presence of a uniform magnetic field are investigated.
Interaction of a Streaming Plasma with the Magnetic Field of a Two-Dimensional Dipole
Authors: Hurley James
Published: December 2004

The interaction of a rarefied plasma stream and the magnetic field of a two-dimensional dipole has been investigated assuming that the domain of interaction between the field and plasma stream is small. The dipole field is found to be confined to a cavity in the plasma, with the plasma constituents being specularly reflected from the cavity wall. The shape of the cavity wall and the magnetic field inside have been determined. The interest of this problem lies in the analogous three-dimensional problem: the interaction between the solar wind and the earth magnetic dipole field.
Radiation by a Large-Amplitude Plasma Oscillation
Authors: Tidman D. A. , Weiss George H.
Published: December 2004

A plasma oscillation which is initially purely longitudinal in a plasma of zero temperature is considered and the amount of electromagnetic radiation produced by the wave is then determined using second-order perturbation theory.
Shock Curvature due to Boundary-Layer Effects in a Shock Tube
Authors: Hartunian R. A.
Published: December 2004

A two-dimensional, linearized treatment, including real gas effects, of shock curvature in a shock tube is presented. An expression for shock shape as a function of shock Mach number and initial pressure of the test gas is presented. The results are compared with the available experimental data obtained in argon at low shock strengths and in air at high shock Mach numbers. Within the scatter of the data in the latter experiments, there is relatively good agreement with theory, while theory falls approximately 30 ± 10% above the data in argon. Some of this disagreement is attributed to application of the two-dimensional theoretical result to axisymmetric shock tubes of finite dimensions used in the experiments.
Time Lag in the Thermalization of a Fast Ion in a Plasma
Authors: Frisch H. L.
Published: December 2004

The time lag in the thermalization of the spherical mean speed of a fast ion injected into a plasma is defined and computed without solving the Fokker-Planck equation governing the distribution in speed. The time lag and certain related, recursively computable, time moments can serve as local measures of the rate of evolution of the Maxwellian distribution from an initial one, particularly for large values of the speed. Numerical computations of the time lag are presented for a fully ionized deuterium plasma for two initial conditions. Certain natural extensions of the time lag are briefly mentioned.
Stability of a Slightly Inhomogenous Plasma
Authors: Krall Nicholas A. , Rosenbluth M. N.
Published: December 2004

Slightly inhomogeneous plasmas are studied to determine their stability against growing longitudinal electrostatic oscillations. The procedure is to expand Maxwell's equations and the collisionless Boltzmann equation about ε = 0, corresponding to a uniform plasma, where the expansion parameter ε characterizes the particle density gradient. It is found that the shift in the eigenfrequency of the oscillation is of order ε2; this shift is a real number to order ε2 if the eigenfrequency for the corresponding uniform plasma, ε = 0, is a real number. Transverse modes are also examined for some special directions of propagation, with similar results. It is observed that this expansion procedure would not reproduce instabilities associated with particle drifts.
Two-Fluid Hydrodynamic Equations for a Neutral, Disparate-Mass, Binary Mixture
Authors: Hamel Bernard B.
Published: December 2004

In gas mixtures with roughly equal masses, self-collisions and cross-collisions between species are of equal importance in the approach of the mixture to a Maxwellian distribution about a single temperature and velocity and the usual Chapman-Enskog transport theory obtains. In a disparate-mass mixture, however, the effects of self- and cross-collisions are not equal and one has an epochal relaxation, with the temperature relaxation occurring on the longest time scale. The clear distinction between a single molecular relaxation time and a hydrodynamic time scale which makes the usual Chapman-Enskog theory possible is absent for the disparate-mass case, and a more complex ordering of time scales is necessary to obtain hydrodynamic solutions. In the present work, for neutral, disparate-mass mixtures, the Boltzmann collision integrals are replaced by relaxation-type kinetic models and terms in the model equation are ordered according to mass ratio. A set of two-fluid transport equations is then derived by obtaining normal solutions of these model equations. The derived transport equations and coefficients are discussed, and their correspondence to the usual Chapman-Enskog results is shown.
Decaying Second-Order Isothermal Reaction in Final Period Turbulence
Authors: O'Brien Edward E.
Published: December 2004

It is shown that for a decaying second-order, isothermal reaction in final period turbulence the asymptotic decay rate of the mean square fluctuations is as t−11/2.
Further Results on Hydromagnetic Instability of Fluid between Two Coaxial Cylinders
Authors: Chow Chuen-Yen , Uberoi Mahinder S.
Published: December 2004

Characteristic values are found for the stability of a current-carrying fluid between two concentric cylinders with radii ratio 0.05–0.9. The wavenumber and the characteristic value decrease with this ratio indicating that experimental verification is possible.
Approximate Solution of a Plane Radiating ``Piston Problem''
Authors: Wang K. C.
Published: December 2004

A thermally radiating and absorbing plane ``piston problem'' is investigated. The zeroth-order approximation in a series expansion in the density ratio across the shock is carried out for both the similar and nonsimilar cases. Simple analytical results exhibit a clear picture of the radiation effects to a shock layer structure. Accuracy is demonstrated for certain similar cases through direct comparison with the exact numerical results. The method of approach established can be applied to the multi-dimensional steady radiating shock layer problems with minor modifications.
Stability of Magnetohydrodynamic Half-Jet Part I. Magnetohydrodynamic Half-Jet
Authors: Lessen Martin , Deshpande Narayan V.
Published: December 2004

A boundary-layer-type theory for a compressible half-jet with an aligned magnetic field is formulated. The electrical conductivity of the fluid is assumed to be infinite. It is known in the incompressible case that for a meaningful solution the ratio of the magnetic pressure and the dynamic pressure cannot exceed unity. This ratio has a further limitation in the compressible case.
Exact Inversion of Dispersion Relations
Authors: McCune James E.
Published: December 2004

A method is proposed for explicitly determining the complex roots of dispersion relations involving transcendental analytic functions. A simple consequence of Cauchy's theorem, the method has application in many fields, including current plasma problems.
Statistical Initial-Value Problem for Burgers' Model Equation of Turbulence
Authors: Jeng D. T. , Foerster R. , Haaland S. , Meecham W. C.
Published: December 2004

Some statistical characteristics of the Burgers' model equation are studied using a high-speed computer. With the initial turbulent velocity field given, the closed form solution is used to find the fluid velocity field at later time. The velocity correlation functions, energy spectra, and other statistical properties are examined. The energy spectrum falls off like the inverse second power of the wave number (agreeing with earlier Wiener-Hermite expansion results). Calculations based on the use of the quasi-normal assumption are also presented. It is found, as is known for the Navier-Stokes equation, that for general initial values of the energy spectrum function the function becomes (unacceptably) negative at later times. However, it is found that the calculation yields positive spectra (though not those of the ``experiment'' above) at least for moderate times, if the spectrum found from the numerical experiment is used at initial times. This suggests that for real fluids the quasi-normal assumption may at least be stable if the initial condition is not too far from the correct one.
Electric Fields Caused by the Diffusion of Charged Particles across a Magnetic Field
Authors: Schwirzke Fred
Published: December 2004

Plasma density, electron temperature, and potential distribution were measured across and along the magnetic field for a determination of the effective ion and electron-diffusion coefficients in a cylindrical plasma column of finite length which is given by conducting end walls. Ion and electron flux to the end walls were measured. The potential across the magnetic field was recorded as a function of magnetic induction B, pressure P, and length L. The observed radial electric field, Er, is opposite in sign to the density gradient and is related to the electron temperature gradient. When a plasma contacts a wall, a potential drop proportional to the electron temperature, Te, is present over the sheath which impresses on the plasma a positive potential in relation to the grounded end walls. When Te gradually decreases perpendicular to B owing to electron collisions with cold gas particles, the plasma potential decreases proportionately and an outward directed Er is built up, which enhances the plasma loss across the magnetic field.
``Minimum-B'' Suppression of Oscillations in a Q-Device
Authors: Decker John A.
Published: December 2004

The ``minimum-B'' magnetic field geometry provided by the combination of a transverse quadrupole-cusp field with a uniform axial field suppresses certain of the low-frequency oscillations spontaneously present in the cesium plasma of the ``Topsy'' Q-device with a uniform magnetic field.
Mixtures of Maxwell Molecules
Authors: Sirovich Lawrence
Published: December 2004

The linearized collision integrals for mixtures of Maxwell molecules are considered. A simple proof of the eigentheory is given. Relations for and amongst eigenvalues are obtained. A brief discussion of the corresponding relaxation theory is also included.
Wave-Excited Anomalous Diffusion in a Fully Ionized Magnetoplasma
Authors: Eastlund B. J. , Josephy K. , Leheny R. F. , Marshall T. C.
Published: December 2004

The transverse diffusion coefficient D⊥ of a fully ionized plasma in a Q machine was observed to depend on the frequency and amplitude of low-frequency (kilocycle) waves. These waves, observed with a floating Langmuir probe and spectrum analyzer, could be impressed on the plasma (1) by a weak electron beam injected along the plasma axis, (2) by applying an ac signal of appropriate frequency to a plate at one end of the plasma, or (3) were found to occur naturally. D⊥ was determined from the radial profile of potassium plasma pulses. In all cases, D⊥ was strongly influenced by the amplitude of the low-frequency components of the spectrum and was observed to be proportional to the rms power of the fluctuations. The impedance of the plasma as a function of the impressed ac signal showed minima at frequencies close to that of the ``drift instability,'' where the value of D⊥ exhibited strong maxima.
Particle Loss in a Three-Dimensional Cusp
Authors: Grossmann William
Published: December 2004

The loss of particles through an axisymmetric cusped magnetic field containment geometry is considered. An appropiate adiabatic invariant is derived for the plasma considered to be a high β, collisionless collection of particles contained within a field-free region bounded by a mathematically sharp interface. The particles are allowed to undergo soft collisions with the interface thus giving rise to a boundary layer. A velocity space loss cone criterion analogous to the loss cone criterion in magnetic mirror machines is derived. Particle loss rates are calculated for a special form of the particle distribution function, and the results are compared with relevant experimental data. A previous treatment of the present problem considering two-dimensional geometry is re-examined in view of the present work concerning adiabatic invariance.
Moment Methods and ``Restricted Variation'' in Kinetic Theory
Authors: Narasimha Roddam
Published: December 2004

It is shown that there is a strict one-to-one correspondence between results obtained by the use of ``restricted'' variational principles and those obtained by a moment method of the Mott-Smith type for shock structure.
Extension of the Newcomb Entropy Method of Stability Analysis
Authors: Rowlands G.
Published: December 2004

It is shown that a plasma in zero magnetic field whose distribution function is any function of the kinetic energy is stable to longitudinal and transverse disturbances.
Variational Principle for a Guiding-Center Plasma
Authors: Grad Harold
Published: December 2004

A new variational formulation is presented for the equilibrium and stability of a guiding-center plasma with emphasis on open-ended systems confined by mirrors. In contrast to all earlier formulations, this is a classical one in which equilibria arise as stationary states of a certain potential and stable equilibria minimize the same potential. The formulation is more general than earlier ones in that it includes nonlinear perturbations, a variety of boundary conditions (lines tied or not), multiple turning points, and a correct treatment of electric fields along the lines. In addition, a number of ambiguous procedures and incorrect statements which are found in earlier stability analyses are corrected.
Ion Waves in Bounded Plasma
Authors: Bertotti B. , Cavaliere A. , Giupponi P.
Published: December 2004

The role of the charge sheath at the wall of a discharge in determining the appropriate boundary conditions for a low frequency wave in a low pressure discharge is discussed by means of a hydrodynamical model. It is found that Bohm's condition for the mean ion velocity holds even when oscillations are present. The electron dynamics is neglected and the dispersion relation shows the existence of a principal mode which propagates along the tube just as in an infinite medium; all other modes are damped. Analysis of the dynamics of the oscillating sheath shows that it behaves like a battery, transferring the electrostatic oscillation to the wall with no distortion and no impedance.
Integral Method in Compressible Laminar Boundary Layers and its Application
Authors: Chan Yat-Yung
Published: December 2004

A method is developed for calculating the properties of compressible boundary layers with heat transfer and arbitrary pressure gradients. The method is based on the integral relations and one-parameter correlation concept. The energy integral equation is also considered with the momentum integral equation such that the variation of the ratio of the energy defect thickness to the momentum defect thickness, which has a strong effect on the computation of heat transfer, is taken into account. Thus high accuracy is obtained in predicting heat transfer. The method is then applied to calculate the self-induced pressure interaction problem in hypersonic flows. The solutions cover the complete range of interaction and show good agreement with other more exact theoretical results as well as experimental data. With the present method and the local similarity concept, closed form solutions to the pressure interaction problem can be obtained.
Time-Dependent Correlations in a Maxwell Gas
Authors: Ranganathan S. , Yip Sidney
Published: December 2004

The Fourier transform of the time-dependent density-density correlation function is calculated from the linearized Boltzmann equation for Maxwell molecules. The initial value problem is solved numerically for a small density disturbance. The results are compared with relaxation-time kinetic models, and it is found that the triple-relaxation time model with eigenvalue ordering gives good agreement for all wavelengths and frequencies. Similar macroscopic responses can also be calculated with appropriate changes in the initial conditions. The heat-heat correlation function is considered as a specific example.
Steady Motion of a Disk in a Viscous Fluid
Authors: Michael Paul
Published: December 2004

A difference approximation to the Navier-Stokes equation has been solved by numerical iteration for the steady motion of a disk. As has been indicated by experiments, it was assumed that the flow is axially symmetric. The solution obtained is in terms of the stream function and vorticity. It was found necessary to use a relatively fine mesh and, in order to satisfy boundary conditions, to consider a fluid region ∼30 disk radii downstream; the latter was accomplished by using an irregular mesh. Solutions were obtained for Reynolds numbers (based upon disk diameter) from 1.5 to 50; calculated drag coefficients were found to be in good agreement with the experiments of Schmiedel and of Wilmarth, Hawk, and Harvey.
Blast Waves from an Inverse Pinch Machine
Authors: Vlases George C. , Jones Donald L.
Published: December 2004

Cylindrical blast waves are produced in an inverse pinch machine operating in the mode where the energy deposition time is short compared to the time required for the wave to traverse the chamber. Advantages of this method over conventional explosive and exploding wire methods are discussed. A simple formula is developed which predicts the shock trajectory over the entire range of strong shocks to the weak shock limit.
Harmonics of the Electron Gyro-Frequency in Plasmas
Authors: Canobbio E. , Croci R.
Published: December 2004

Intense radiation emitted by plasmas at harmonics of the electron gyrofrequency is discussed. The nonrelativistic dispersion relation for propagation vectors nearly perpendicular to the external magnetic field is studied for an unperturbed Maxwellian distribution function. The real and complex wavenumbers of ordinary and extraordinary waves are given when Landau and collisional damping are negligible. Their behavior near the harmonics, the upper hybrid frequency, and cutoffs is considered in detail. When damping is present, the wave propagation undergoes a deep change. In typical experimental conditions no ordinary and no transverse extraordinary waves exist in the very neighborhood of the harmonics with a large index of refraction, while there are sets of short quasi-electrostatic waves which are of interest in explaining the experiments. Near the hybrid frequency the relatively fast quasi-electrostatic waves are substituted for elliptically polarized waves (still predominantly longitudinal) which originate from the coupling between the cold-plasma and the electrostatic modes. The equation for the electrostatic waves is also discussed in plasmas with electron streams and temperature anisotropies.
Dielectric Tensor in Vlasov Plasmas near Cyclotron Harmonics
Authors: Shkarofsky I. P.
Published: December 2004

The relativistic expression for the dielectric tensor obtained by Trubnikov is simplified in the very weakly relativistic limit at and near electron cyclotron harmonics. Wavenumbers parallel to magnetic field are included, leading to relativistic damping when this wavenumber is minute and to cyclotron damping when it is sufficiently large. The transition to the nonrelativistic Z function is shown and the regions of validity of the various functions are indicated. Collisional damping is neglected. The dielectric elements given here are also applicable to cases of complex ω and real k. An example of such a situation arises in Alouette cyclotron harmonic reception when one is concerned with an initial time value problem. For this application the analytic continuation of a complicated function is provided, and the tracks where it is real for complex ω are investigated.
Dispersion of Waves in Cyclotron Harmonic Resonance Regions in Plasmas
Authors: Shkarofsky I. P.
Published: December 2004

The dispersion of waves near electron cyclotron harmonics is investigated including to first order wavenumbers parallel to the magnetic field. The proper relativistic form for the dielectric tensor elements is applied. The relativistic formulation is compared with the nonrelativistic one applicable for larger wavenumbers parallel to magnetic field and the differences are noted. In either analysis, different behaviors result depending on whether the wavenumber or frequency is taken to be complex. In the former case, the waves near the Appleton-Hartree values are localized and a gap exists between them and the higher-order cyclotron harmonic plasma waves. In the latter case, this gap does not occur but the relativistic analysis shows a rapid rise in frequency above the harmonic as one tends to zero wavenumber perpendicular to magnetic field. It is also shown that the large argument expansion in terms of inverse argument of the nonrelativistic Z function produces incorrect dispersion results in certain regions.