bluuebunny/crossref_metadata_2025 huggingface dataset:
The Biochemical, Molecular, and Genomic Aspects of Leukotriene C4 Synthase
Authors: Penrose John F. , Austen K. Frank
Published: December 2004

Leukotriene C4 (LTC4) synthase is an 18 kD integral membrane enzyme of the 5‐lipoxygenase/LTC4 synthase pathway and is positioned as the pivotal and only committed enzyme for the formation of the cysteinyl leukotrienes. Although its function is to conjugate catalytically LTA4 to reduced glutathione, LTC4 synthase is differentiated from other glutathione S‐transferase family members by its lack of amino acid homology, substrate specificity, and kinetics. LTC4 synthase (LTC4S) protein is present in the perinuclear membranes of a limited number of hematopoietic cells involved in allergic inflammation, including mast cells, eosinophils, basophils, and macrophages. The cDNA encodes a monomeric protein of 150 amino acids with three hydrophobic domains interspersed with two hydrophilic loops. Site‐directed mutagenic studies reveal that the enzyme functions as a homodimer and that arginine‐51 in the first hydrophilic loop, and tyrosine‐93 in the second hydrophilic loop, are involved in the acid and base catalysis of LTA4 and glutathione, respectively. Homology and secondary structural predictions indicate that LTC4S is a novel member of a new gene superfamily of integral membrane proteins, each with the capacity to participate in leukotriene biosynthesis. The gene for LTC4S is 2.5 kb in length and is localized on chromosome 5q35, distal to that of the genes for cytokines and receptors important in the development and perpetuation of allergic inflammation. Immunohistochemical studies of mucosal biopsies from the bronchi of aspirin‐intolerant asthmatics show that LTC4S is overrepresented in individuals with this phenotype, and this finding correlates with overproduction of cysteinyl leukotrienes and lysine‐aspirin bronchial hyperreactivity.
Activation of the Plasma Kallikrein / Kinin System on Endothelial Cells
Authors: Røjkjær Rasmus , Schmaier Alvin H.
Published: December 2004

For more than two decades, it has been known that activation of the plasma kallikrein/kinin system only occurs when it is exposed to artificial, negatively charged surfaces. The existence of physiological, negatively charged surfaces has, however, never been demonstrated in vivo. In this report, we describe current knowledge about how the proteins of the plasma kallikrein/kinin system interact with and become activated on cell membranes. In this model, activation of the plasma kallikrein/kinin system on endothelial cells is not initiated by factor XII autoactivation, as seen on artificial surfaces. On endothelial cells, plasma prekallikrein is activated by a membrane‐associated cysteine protease. This activation is dependent on the presence of high molecular weight kininogen and an optimal zinc (Zn2+) concentration. Although the initiation of activation of plasma prekallikrein is independent of factor XII, kallikrein‐mediated factor XIIa generation, in turn, accelerates the activation of the system. Further kallikrein formed on endothelial cell membranes is capable of cleaving its receptor and native substrate, high molecular weight kininogen, liberating bradykinin and terminating activation. In addition, the kallikrein formed on the surface of endothelial cells results in kinetically favorable activation of prourokinase and, subsequently, plasminogen. Activation of the plasma kallikrein/kinin system on endothelial cells proceeds by a physiological mechanism to initiate cellular fibrinolysis independent of plasmin, fibrin, and tissue‐type plasminogen activator.
Novel Mechanisms of Calcium Handling by the Osteoclast: A Review–Hypothesis
Authors: Zaidi Mone , Moonga Baljit S. , Adebanjo Olugbenga A.
Published: December 2004

The osteoclast is a cell that is unique in its ability to resorb bone and, in doing so, becomes exposed to unusually high millimolar Ca2+ concentrations. It is generally accepted that, during resorption, osteoclasts can “sense” changes in their ambient Ca2+ concentration. This triggers a sharp cytosolic Ca2+ increase through both Ca2+ release and Ca2+ influx. The change in cytosolic Ca2+ is transduced finally into inhibition of bone resorption. It has been shown that a type 2 ryanodine receptor isoform, expressed uniquely in the plasma membrane, functions as a Ca2+ influx channel and possibly as a Ca2+ sensor. Ryanodine receptors are ordinarily Ca2+ release channels that have a microsomal membrane location in a wide variety of eukaryotic cells, including the osteoclasts. However, only recently has it become obvious that ryanodine receptors are also expressed in osteoclast nuclear membranes, at which site they probably gate nucleoplasmic Ca2+ influx. Nucleoplasmic Ca2+ in turn regulates key nuclear processes, including gene expression and apoptosis. Here, we review the potential mechanisms underlying the recognition, movement, and effects of Ca2+ in the osteoclast. We will also speculate on the general biological significance of the unique processes used by the osteoclast to handle high Ca2+ loads during bone resorption.
Thalassemia and Malaria: New Insights into an Old Problem
Authors: Clegg John B. , Weatherall David J.
Published: December 2004

The hemoglobinopathies are probably the world’s most common genetic diseases: The World Health Organization has estimated that at least 5% of the population are carriers for one or other of the most serious forms, the α‐ and β‐thalassemias and the structural variant hemoglobins S, C, and E, which are found at polymorphic frequencies in many countries. All these hemoglobinopathies are believed to provide protection against malaria, and it is thought that, in malarial regions of the world, natural selection has been responsible for elevating and maintaining their gene frequencies, an idea first proposed 50 years ago by J.B.S. Haldane.

Epidemiological studies undertaken in the 1950s on hemoglobin S in Africa provided support for the “malaria hypothesis,” but until recently it has proved extremely difficult to verify it for the thalassemias. The application of molecular methods has, however, provided new opportunities to address this old question. Population and molecular genetic analysis of thalassemia variants, and microepidemiological studies of the relationship between α‐thalassemia and malaria in the southwest Pacific, have provided unequivocal evidence for protection. Surprisingly, some of this protection appears to derive from enhanced susceptibility in very young thalassemic children to both Plasmodium falciparum and, especially, P. vivax, and this early exposure appears to provide the basis for better protection in later life.
Genetic Determinants of HIV‐1 Infection and Its Manifestations
Authors: Kaslow Richard A. , McNicholl Janet M.
Published: December 2004

The human immunodeficiency virus type 1 (HIV‐1), which has become pandemic within a single generation, has encountered an immune system in which genetically encoded elements have evolved gradually under different environmental pressures in diverse populations. Important heritable differences in genes that alter susceptibility to HIV‐1 infection or the rate of deterioration of immunity, or both, have been discovered in cohorts carefully defined for intensity of exposure to the virus, viral subtype characteristics, and onset and course of infection. For the highly polymorphic human leukocyte antigen (HLA) antigen processing and presenting system, the principle that small contributions of multiple interactive HLA marker combinations (primarily in the class I pathway) significantly modulate the course of HIV‐1 infection has now been confirmed in several independently evaluated groups of patients. Variants of HLA genes probably also play some role in the acquisition of infection by the various routes of transmission. Genes for an elaborate set of circulating chemokine molecules and their cell‐surface receptors clearly regulate cell attachment and penetration of HIV. Certain allelic forms of one, the CCR5 gene, alter susceptibility to infection and the rate of progression of disease; in the homozygous state, a deleted form (Δ32 CCR5) strongly protects against infection, and in infected heterozygotes, it slows the disease process somewhat. Mutants in genes of other chemokine system components further differentiate the response to infection, and frequencies of these forms vary between and within races. Work relating additional genetic markers to HIV infection or disease is at earlier stages. Dissecting the effects of multiple variants in complex gene systems will clearly require organized comprehensive approaches in considerably larger populations than have typically been assembled.
Aboriginal Nurses' Perception of Facilitators and Barriers for Taking a Sexual History in Taiwan
Authors: Tsai Yun‐Fang , Hsiung Ping‐Chuan
Published: December 2004

Abstract  The potential for risky sexual behaviors and adolescent unplanned pregnancy has become a main concern in the health care system for aborigines in eastern Taiwan. Using aboriginal nurses to provide information on sexual behaviors may have potential as a means of promoting healthy sexual practices among aborigines. This study explored aboriginal nurses' perceptions of facilitators and barriers for taking a sexual history. Several health centers in eastern Taiwan were randomly selected to recruit subjects in 2000. A self‐report questionnaire was administered to 206 female nurses (age = 28.4, SD = 7.4) who worked in various clinical units. These aboriginal nurses perceive the major facilitators in taking a sexual history to be having attended a communication training course and experiencing a needle stick accident; they want to prevent themselves or colleagues from becoming infected. The major perceived barriers to taking sexual history result from patients' feeling embarrassed and not knowing how to answer the questions and patients' purposely concealing information. Decreasing these barriers and reinforcing facilitators about taking a sexual history is an important task for nursing education, and nurses can play an important role in promoting aborigines' sexual health and decreasing the prevalence of sexually transmitted diseases in this population.
Proceedings of the 1998 Meeting of the Society for Pediatric Dermatology
Authors: Duarte Ana M. , LAUDE TERESITA A.
Published: December 2004

The Society for Pediatric Dermatology held its annual meeting in Cambridge, Massachusetts, on July 23–26, 1998. Selected summaries of presentations at the meeting follow.
Proceedings of the 1998 Meeting of the Society for Pediatric Dermatology
Authors: Duarte Ana M. , TAÏEB ALAIN
Published: December 2004

The Society for Pediatric Dermatology held its annual meeting in Cambridge, Massachusetts, on July 23–26, 1998. Selected summaries of presentations at the meeting follow.
Two Cases of Lymphomatoid Papulosis in Children
Authors: Aoki Eri , Aoki Mikako , Kono Minori , Kawana Seiji
Published: December 2004

Abstract: An 8‐year‐old Japanese boy had a 4‐month history of self‐healing crops of violaceous, scaling papules and several small indurated areas of erythema on his limbs, buttocks, and trunk. Histologically there was an infiltration of small lymphocytic cells with scattered large atypical cells expressing CD30. Characterization of T‐cell receptor gene rearrangement showed monoclonality of the infiltrating cells. The second patient, a 15‐year‐old Japanese girl, had a 2‐week history of self‐healing papulovesicular eruptions on her face and limbs. Large CD30+ atypical cells were also noted in the perivascular lymphocytic infiltration. Immunohistochemical studies revealed CD8 expression on almost all CD30+ cells in the second case. In the literature, there have been two reports of children with large CD30+ atypical cells expressing CD8 and two cases expressing CD4, whereas all adult cases reported have had cells expressing only CD4.
Granular Parakeratosis in Children: Case Report and Review of the Literature
Authors: Pimentel Dalva Regina Neto , Michalany Nilceo , Morgado de Abreu Marilda Aparecida Milanêz , Petlik Beno , Alchorne Maurício Mota de Avelar
Published: December 2004

Abstract: Granular parakeratosis is a cutaneous eruption with erythematous and/or brownish hyperkeratotic papules and plaques which are exclusively localized to intertriginous areas and show histopathologic features of an unusual form of parakeratosis. The etiology is unknown, but the excessive use of various topical preparations (e.g., ointments and deodorants) has been associated with this disease. It has heretofore been reported only in adults. We report two children, ages 3 and 5 months, with characteristic lesions in the groin associated with topical pomades used to prevent diaper rash. This is the first report associating the clinical presentation and the histopathologic diagnosis of granular parakeratosis in children. The literature on this entity is also reviewed and all case reports are summarized.
A Case of Congenital Mucinous Nevus: A Connective Tissue Nevus of the Proteoglycan Type
Authors: Chang Sung‐Eun , Kang Sook‐Kyoung , Kim Eun‐Sung , Lee Mi‐Woo , Choi Jee‐Ho , Sung Kyung‐Jeh , Moon Kee‐Chan , Koh Jai‐Kyoung
Published: December 2004

Abstract: Mucinous nevus is a very rare entity and can be classified as both a cutaneous mucinosis (CM) and a connective tissue nevus (CTN). We describe the clinicopathologic features of an unusual case of mucinous nevus in a 14‐year‐old Korean boy who presented with zosteriform plaques of congenital onset.
Cutaneous Pustular Leukemoid Reactions in Trisomy 21
Authors: Burch Joanna M. , Weston William L. , Rogers Maureen , Morelli Joseph G.
Published: December 2004

Abstract: We report two neonates with Down syndrome and postnatal leukemoid reactions who developed acute widespread pustular eruptions. The white blood cell (WBC) counts on the first day of life were markedly elevated, with blasts seen on examination of the peripheral blood smear. The skin eruptions progressed and became pustular. Viral and bacterial cultures were negative. Skin examination revealed pustules on an erythematous base on the cheeks, shoulders, trunk, and proximal extremities. Skin biopsy specimens showed an intraepidermal pustule with an inflammatory infiltrate including neutrophils, eosinophils, and mononuclear cells. The mononuclear cells had atypical, immature‐appearing nuclei. In patient 1, these cells were strongly myeloperoxidase positive on immunohistochemistry, indicating myeloid lineage. In patient 2, these cells were CD3‐positive T cells. Patient 1 received a 5‐day infusion of continuous cytarabine (ara‐C) secondary to high WBC counts and symptomatic hyperviscosity. During therapy, the high WBC count and the pustules resolved. The lesions of patient 2 improved with topical mometasone furoate and resolved as her WBC count decreased. Recently, similar cases have been reported. Transient myeloproliferative disorders, or leukemoid reactions, should always be considered when newborns with Down syndrome or trisomy 21 mosaicism develop a pustular eruption.
Dystrophic Epidermolysis Bullosa Inversa with COL7A1 Mutations and Absence of GDA‐J/F3 Protein
Authors: Kahofer Peter , Bruckner‐Tuderman Leena , Metze Dieter , Lemmink Henny , Scheffer Hans , Smolle Josef
Published: December 2004

Abstract: Epidermolysis bullosa dystrophica inversa (DEB‐I) is a very rare disease characterized by autosomal recessive inheritance that causes blistering and erosions on the trunk and extremities occurring in early infancy with a predilection for flexural and mucosal areas thereafter. Ultrastructural findings show dermolytic blistering and absent or rudimentary anchoring fibrils as in generalized forms of dystrophic epidermolysis bullosa. Immunoreactivity for type VII collagen, however, is preserved. We present two patients with DEB‐I with compound heterozygosity for the two different COL7A1 mutations, one of them (Arg2069Cys in exon 74) carried by the heterozygous mother, the other one (Lys142Arg in exon 3) carried by the heterozygous father, accompanied by absence of the associated anchoring fibrils protein GDA‐J/F3.
Immunotherapy for Recalcitrant Warts in Children Using Intralesional Mumps or Candida Antigens
Authors: Clifton Missy M. , Johnson Sandra Marchese , Roberson Paula K. , Kincannon Jay , Horn Thomas D.
Published: December 2004

Abstract: Intralesional injection of mumps and Candida skin test antigens has been shown to be effective in the treatment of warts. Warts are generally difficult to treat in children. To determine the efficacy of intralesional skin test antigen injection for the treatment of resistant warts in children, we treated 47 pediatric patients with one or more warts with intralesional injection of mumps or Candida skin test antigen into one wart. Twenty‐two patients (47%) with resistant warts experienced complete resolution of treated warts. An average of 3.78 treatments were necessary. An additional 34% of children had a greater than 25% improvement in their warts. Sixty‐eight percent of subjects with more than one wart also noted at least partial resolution (greater than 25% resolution) of untreated warts at distant sites, with 34% experiencing complete resolution. We concluded that intralesional injection of skin test antigens is an effective therapy for children who have recalcitrant, nongenital, cutaneous warts.
Ken and Katie Caterpillar: Helpful Props for Treatment of Molluscum Contagiosum
Authors: Silverman Robert A. , Lucky Anne
Published: December 2004

Abstract: A hand‐made prop that aids in the efficient treatment of molluscum contagiosum with curettage or cantharidin is described. Small bandages or pieces of tape are affixed to a tongue depressor prior to the procedure so that they may be placed quickly over the treated molluscum. This improves time management and helps to reduce patient anxiety.
Isotretinoin Treatment of Acne in a Patient with Apert Syndrome
Authors: Gilaberte Montserrat , Puig Lluis , Alomar Agustín
Published: December 2004

Abstract: Apert syndrome is an autosomal dominant disease caused by mutations in fibroblast growth factor receptor (FGFR‐2) and characterized by premature fusion of the cranial sutures and early epiphyseal closure. The development of widespread, severe, pustular acne around puberty is a characteristic feature in these patients. The FGFR‐2 mutation of Apert syndrome has been described in localized nevoid acne lesions, which have been attributed to somatic mosaicism. Isotretinoin has been reported to be useful in controlling this acne. We report the successful treatment of acne with isotretinoin in a teenager with Apert syndrome and review the pathophysiology of acne in this syndrome.
Clinical and Histopathological Characterization of Cutaneous Melanomas in the Melanoblastoma‐Bearing Libechov Minipig Model
Authors: Vincent‐Naulleau Silvia , Le Chalony Catherine , Leplat Jean‐Jacques , Bouet Stéphan , Bailly Christiane , Spatz Alain , Vielh Philippe , Avril Marie‐Françoise , Tricaud Yves , Gruand Joseph , Horak Vratislav , Frelat Gérard , Geffrotin Claudine
Published: December 2004

Spontaneous animal tumors appear to be highly suitable models to study human oncology and cancer therapy. The aim of this study was to characterize the clinical and histological features of hereditary melanocytic lesions found in the French herd of melanoblastoma‐bearing Libechov minipigs (MeLiM) and their Duroc crossbreeds. Clinically, we discriminated between three types of melanocytic skin lesions, which offer a lesion continuum from lentigo to metastatic melanomas. More than 70% of these lesions appear on piglets before they are 3 months old and preferentially on homogeneous black coat piglets. The incidence of melanoma reaches 50% in MeLiM. Most of the highly invasive melanomas regressed spontaneously in the first year of the piglet's life and the regression was followed by hair, skin and iris depigmentation. A histopathological study was conducted according to the human melanoma classification. Except for lentigo maligna, we observed the three main types of human melanoma in swine [superficial spreading melanoma (SSM), nodular or unclassified melanoma] with an excess of SSM (59–67%). The histological events leading to total spontaneous regression are chronologically described. The genetic predisposition, the high incidence of melanoma, the clinical and histopathological features similar to the human disease and the high rate of spontaneous regression offer an opportunity to use this model for studying genetic events controlling melanoma development and regression and the biological mechanisms involved in oncogenesis and anti‐cancerous self‐defense.
The Spleen Pigment Cells in Some Amphibia
Authors: Scalia Marina , Pietro Cinzia Di , Poma Mariangela , Ragusa Marco , Sichel Giovanni , Corsaro Concetta
Published: December 2004

It was demonstrated that the spleen pigment cells of Amphibia are macrophages: they show an ultrastructurally distinctive morphology, are able to phagocytose and react positively for non‐specific esterases. These pigmented macrophages express mRNA for tyrosinase and also they show dopa oxidase activity; therefore they are able to synthesize melanins, as Kupffer cells do.
Interaction of a Streaming Plasma with the Magnetic Field of a Line Current
Authors: Hurley James
Published: December 2004

The interaction between the magnetic field of a line current and a rare plasma streaming toward it is investigated. It is assumed that the field of the line current is confined to a cavity with the plasma particles specularly reflected in a thin layer of the cavity wall. The shape of the cavity wall and the field in the cavity are calculated.
Pinch with Rotating Plasma
Authors: Gerjuoy E. , Rosenbluth M. N.
Published: December 2004

The magnetohydrodynamic stability of an infinitely conducting incompressible plasma, in the shape of an infinitely long circular cylinder within an external conductor, compressed by external Bθ and Bz against internal Bz, is investigated in the circumstance that the plasma has an angular velocity about the z axis of the cylinder. Two different cases are examined in detail: (i) arbitrarily large constant angular velocity, in which case the differential equation for the perturbed total (magnetic plus hydrodynamic) pressure inside the plasma is solved exactly in terms of Bessel functions; (ii) nonconstant but small angular velocity, in which event perturbation theory can be employed. For both these cases the rotating plasma is less stable than the nonrotating plasma.
Relativistic Theory of the Propagation of Plane Electromagnetic Waves
Authors: Tang C. L. , Meixner J.
Published: December 2004

Based on the complete set of equations of thermodynamics of irreversible processes of a fluid in electromagnetic fields, a relativistic theory of the influence of electromagnetic waves on a simple fluid is developed. In particular, the oscillations of the fluid induced by a plane electromagnetic wave are evaluated, and the energy-momentum tensor is determined. It is further conjectured that Minkowski's tensor and Abraham's tensor lead to the same result when matter is properly taken into account. The irreversible processes of heat conduction and viscosity accompanying the oscillations of matter are briefly discussed.
Escape of Planetary Atmospheres. I. Escape Layer
Authors: Gilvarry J. J.
Published: December 2004

The critical layer for thermal escape of a planetary atmosphere is treated on a model in which an isothermal exosphere at high temperature merges within a narrow zone (the endopause) of varying temperature into the remainder (the endosphere) of the atmosphere, isothermal above the level at which mixing stops. Only one major constituent of the atmosphere is considered, and constant scale heights are assumed for the exosphere and for the endosphere above the level at which diffusion sets in. The height of the escape layer is evaluated analytically by considering the pressure balance at the base of the exosphere. The result permits one to determine explicitly the amount (the concentration or the number of molecules above unit area) of a minor constituent at the critical level, taking thermal diffusion across the endopause into account. The predicted height of the escape layer as determined from a model atmosphere of Nicolet shows essential agreement with the height inferred directly by means of the number density, scale height, and collision diameter.
Density Fluctuations and Heat Conduction in a Pure Liquid
Authors: Nettleton R. E.
Published: December 2004

Two components of the heat flux in a pure liquid are identified—one carried by sound waves and the other by diffusing molecules. Coupled relaxation equations are obtained for these components, both depending on the density gradient ∇ρ, and this dependence is interpreted thermodynamically as a further coupling of these equations with the equation determining (∂/∂t)(∇ρ). The latter can be immediately written down with the aid of Onsager's theorem and an inertial principle developed in a previous paper. The thermodynamic interpretation of these rate equations also leads to an explicit expression for the coefficient of (∇ρ)2 in a Taylor expansion, about equilibrium, of the Helmholtz free energy. This result is compared with similar free-energy terms assumed to exist by other authors.
Chemical Reaction and Diffusion in a Catalytic Tubular Reactor
Authors: Walker R. E.
Published: December 2004

The general solution to the axially symmetric problem of diffusion, reaction, and convection of a trace reactant in a catalytic tubular flow reactor is presented. First-order heterogeneous and homogeneous reaction kinetics are assumed as well as a nonaccelerating Poiseuille flow. The decay of reactant upstream and downstream of the source is examined. Machine calculations have been used to study in detail the characteristics of the asymptotic solution which is shown to be similar to the solution for the one-dimensional model frequently used in analysis of experimental reactor data. This study has resulted in a guide that can be used for judging the error introduced through using a one-dimensional interpretation of a practical system. In addition, it is further pointed out that, for those conditions where the reaction is controlled by both convection and diffusion, flow reactor techniques can be used to measure the diffusion coefficients of labile chemical species.
Limiting Velocity for a Rotating Plasma
Authors: Lin Shao-Chi
Published: December 2004

A quasi-steady state solution has been obtained for a homogeneous plasma undergoing simultaneous ionization and rotation in a crossed electric-magnetic field. It was found that the ordinary electron-impact ionization process, when supported by the full rate of energy transfer from the ions to the electrons via Coulomb collisions, will be sufficiently rapid to provide a close coupling between the kinetic energy of the ions and the ionization energy of the neutrals under a wide range of conditions. The results can be used to interpret the limiting velocity observed by Alfvén and Fahleson in some recent rotating plasma experiments. The same results can also be used to predict the occurrence of similar limiting velocity in some rectilinear plasma accelerators.
Thermal Diffusion in Some Mixtures of Inert Gases
Authors: Grew K. E. , Mundy J. N.
Published: December 2004

Thermal diffusion has been investigated experimentally in several binary mixtures of inert gases, especially at low ``reduced'' temperatures, and the results compared with theoretical values based on the Lennard-Jones and exponential-six molecular models. The thermal diffusion factor for krypton-argon mixtures is found to pass through a positive minimum value; this behavior, theoretically possible, has not previously been observed. Other mixtures examined are xenon-krypton and krypton-nitrogen; the mixtures of radon with neon, argon, and krypton; and the isotopic mixture 22Ne−20Ne.
Effect of Neutral Particles on the Transport Properties of a Plasma in a Uniform Magnetic Field
Authors: Wright James P.
Published: December 2004

The effect of neutral particles on viscosity, heat flow, current, and drift in an ionized plasma is derived. The effect of neutrons in a hydrogen plasma in a strong uniform magnetic field is calculated. The effect begins to be significant at a temperature of approximately 10 kev, depending on the values of other variables.
Boundary Layer between a Plasma and a Magnetic Field
Authors: Grad Harold
Published: December 2004

The problem of a steady boundary layer or sheath between a plasma and a magnetic field is considered. A self-consistent transition layer is found which joins a uniform magnetic field at plus infinity with a collisionless field-free plasma region with arbitrary velocity distribution at minus infinity; i.e., a magnetic field profile is found such that the exact particle orbits in this field produce a current which gives rise to the field. An interesting mathematical feature of the ``thinnest'' such solution is that, with any nonsingular velocity distribution at minus infinity, the magnetic field penetrates only a finite distance into the plasma although the plasma extends to infinity, exponentially attenuated, into the magnetic field region. The scale of length is the ratio of the speed of light to the plasma frequency or, equivalently, the Larmor radius of a representative particle. Electric fields arising from charge separation in the case of particles of different mass are ignored.
Plasma Motion in a Curved Magnetic Field
Authors: Eubank Harold P. , Wilkerson Thomas D.
Published: December 2004

A parametric study has been made of the transmission of a burst of plasma through a 90° sector of magnetic field. Polarization fields are inhibited during the early phase of plasma entry into the bend, allowing complete transmission of the fast part of the plasma (densities ∼ 1011/cm3). As the input density exceeds that for which the polarization field is inhibited, drifts occur which rapidly reduce the plasma transmission to zero. This transition appears to depend only upon the input density and magnetic field of the bend.
Interaction between a Magnetic Field and an Electrically Produced Shock Wave
Authors: Barach John Paul
Published: December 2004

Shock flows of speeds up to 1 cm/μsec in krypton have been observed to interact with a magnetic field of 5700 gauss. A reflected shock is observed and deceleration of the flow is measured. Gas flows of up to Mach 63 are produced by an annular electric shock tube powered by a capacitor discharge of long time constant. A radial magnetic field geometry provides closed paths within the gas flow for the induced currents. The speed of the wave reflected off the magnetic field is found to increase slightly with interaction strength. The flow momentum lost per particle as the flow traverses the field region is calculated and is compared to the impulse delivered each particle by the magnetic field. Approximate agreement is found over a wide range of experimental conditions, validating the magnetohydrodynamic picture of the interaction and the use of the scalar gas conductivity.
Rotating Plasma Experiments. II. Energy Measurements and the Velocity Limiting Effect
Authors: Baker D. A. , Hammel J. E.
Published: December 2004

The total rotational energy and energy loss rate in Ixion III, the Los Alamos rotating plasma experiment, have been measured as functions of time. As the radial electric field is increased, a limiting velocity of rotation of approximately 1.3 × 107 cm/sec is observed. Measurements indicate the presence of a region of fully ionized plasma whose contaminants radiate large amounts of energy in the form of line radiation in the vacuum ultraviolet. Mechanisms that have been proposed to explain the velocity limit are discussed in relation to the experimental results.
Motion of an Impurity Particle in a Boson Superfluid
Authors: Girardeau M.
Published: December 2004

The problem of the low-lying spectrum of a system of many bosons and one impurity particle interacting by repulsive, central, two-body forces is treated by first eliminating the dynamical variables of the impurity in terms of an added effective boson-boson interaction, and then treating the boson system by an extension of Bogolubov's method. In this way various physical properties of the clothed impurity particle, including its dispersion relation and effective mass, are obtained; singularities associated with the onset of acoustical wave drag as the impurity speed reaches the speed of sound in the boson medium are predicted. The parameters measuring the smallness of the corrections to the above results are shown to be the dimensionless boson-boson interaction, the dimensionless boson-impurity interaction, and the boson-impurity mass ratio. The treatment is then adapted to the case of hard spheres at low density by employing the Huang-Yang-Lee pseudopotential method; the results are valid if the dimensionless boson density and the boson-impurity mass ratio are small. A few remarks are made concerning the connection of the models treated with experimentally accessible results.
Hydromagnetic Stability of a Tubular Pinch
Authors: Newcomb William A. , Kaufman Allan N.
Published: December 2004

Necessary and sufficient conditions are derived for the hydromagnetic stability of a tubular pinch with a very thin current layer. The derivation is based on the energy principle, according to which a system is stable if and only if the energy integral is positive for every virtual displacement. The virtual displacements are divided into two types, depending on whether their radial components are continuous or discontinuous in the limit of an infinitely thin layer. Separate stability criteria are given for each type, and stability diagrams are constructed on the basis of numerical calculations. The tubular-pinch results are supplemented with a brief discussion of the columnar pinch, and it is concluded that the tubular pinch is easier to stabilize.
Propagation of Electromagnetic Waves in a Plasma with Strong Magnetic Field
Authors: Poeverlein H.
Published: December 2004

Formulations describing the propagation of electromagnetic waves in a cold plasma in the presence of a constant magnetic field H0 become particularly simple in a limit case that corresponds to a high longitudinal conductivity component (component parallel to H0) and negligible transverse conductivity components. In this case, perfect guidance along the magnetic force lines is found for one propagation mode and propagation independent of direction for the other, characteristics known to appear in hydromagnetic waves. In the present case, however, no ion effects need be taken into consideration and the phase velocity is high, equaling vacuum velocity. Propagation of plane waves is treated and a wave-theoretical formulation is derived, valid for any wave field under the assumed conditions with a uniform magnetic field. A section on propagation in force line tubes includes some physical discussion. Comparisons are made between our limit case and other limit cases of waves in plasmas, which have been thoroughly studied previously—hydromagnetic waves (without compressional forces) and ionospheric whistlers.
Stability of Laminar Flames
Authors: Petersen Russell E. , Emmons Howard W.
Published: December 2004

Markstein theory of stability of laminar flames is shown to be supported by experimental results on oscillated laminar propane-air flames. Disturbances in appropriate wavelength ranges grow and distort while for other ranges disturbances are damped. These facts imply important restrictions on the nature of a turbulent flame and its interaction with the surrounding flow field.
On Cylindrical Magnetohydrodynamic Shock Waves
Authors: Greifinger Carl , Cole Julian D.
Published: December 2004

If an axial rod is surrounded by an ionized gas, an expanding cylindrical shock wave can be produced by passing through the gas a current which returns along the rod. The azimuthal magnetic field of the current acts like a piston, pushing the plasma away from the rod and leaving behind a cylindrical vacuum region. The case considered is that where a uniform magnetic field parallel to the axis is initially present in the gas; in this case a transverse magnetohydrodynamic shock wave results from the current discharge. The flow is analyzed under the assumptions that the plasma is a nonviscous, nonheat-conducting, ideal gas of infinite electrical conductivity, and that the discharge current increases linearly with time. The analysis is made first on the basis of the ``snowplow'' theory of Rosenbluth, and then from a similarity solution of the full magnetohydrodynamic equations. The results of the two solutions are compared for the case γ = 7/5. It is found that the speed predicted by the snowplow theory is in very good agreement with the speed of the contact front obtained from the solution of the full equations over the entire range of shock strength, but that the snowplow speed is a good approximation to the shock speed only in the limit of strong shocks. The effect on the flow of varying the axial field is discussed.
Hydrodynamic Drag on Spheres Moving in Liquid Helium
Authors: Laing R. A. , Rorschach H. E.
Published: December 2004

The drag coefficient of spheres falling in liquid helium I and II and in some ordinary fluids for Reynolds numbers between 104 and 3 × 106 has been measured. The values of the drag coefficient and the size of the wall corrections for helium I agree with the helium II results and with the results obtained for ordinary fluids. The drag crisis in liquid helium is postponed, but this can be explained by the small value of its kinematic viscosity and the dynamics of boundary layer formation. This agreement suggests that helium I and helium II can be described at high Reynolds numbers by a single velocity field satisfying a Navier-Stokes equation.
Influence of Wave Reflections on the Development of Detonation
Authors: Laderman A. J. , Oppenheim A. K.
Published: December 2004

One of the most significant features of the transition from deflagration to detonation is the dynamics of wave interactions occurring in the course of the process. Of particular interest is the effect of waves reflected from the closed end. The present study was based on a streak self-light photograph of a stoichiometric hydrogen-oxygen flame accelerating to detonation, and a simultaneous pressure transducer record taken at the closed end of the tube in the vicinity of the source of ignition. The photograph revealed considerable information on the flow field behind the flame, so that with the additional pressure measurement it was possible to deduce specific data on the changes of state in the gas, and the dynamic effects of wave reflections on the initiation of the process. The results were rationalized by means of a gas wave dynamic analysis yielding sufficiently complete wave diagrams of the phenomena to assess their importance with respect to the transition from deflagration to detonation.
Capillary Instability of a Liquid Jet
Authors: Alterman Z.
Published: December 2004

The capillary instability of a liquid cylindrical jet is studied both in the case of a static jet or a jet in pure axial motion, with additional rotation and with a superposed magnetic field. The static jet, which is unstable for axisymmetric perturbations of wavelengths exceeding its circumference, is stabilized by a sufficiently strong magnetic field. Rotation causes stability or instability according to the relative angular velocities of jet and surroundings. A jet in axial motion is unstable even in a magnetic field. For a given velocity, the jet is stable only for such perturbations which have wave numbers exceeding a given value.
Expansion and Contraction of Capillary Jets of Viscoelastic Liquids
Authors: Middleman S. , Gavis J.
Published: December 2004

The increase of diameter, or expansion which occurs when viscoelastic liquids are ejected into air from a capillary nozzle is investigated. For low ejection velocities the jet expands; the expansion reaches a maximum with increasing velocity then decreases; at high velocity the jet contracts. An analysis based upon the momentum equation for the jet shows the phenomenon to be dependent upon the Weber number, the rheological properties of the fluid, and the ratio of the tension in the jet to twice the kinetic energy of ejection. The origin of the tension is thought to lie in three different effects: a nonlinear normal stress developed in the capillary, a viscous normal stress developed outside the capillary as a result of relaxation of the original velocity profile in the capillary, and a normal stress developed outside the capillary as a result of elastic reaction to profile relaxation.
On the Propagation of Sound in a Liquid Containing Gas Bubbles
Authors: Hsieh Din-Yu , Plesset Milton S.
Published: December 2004

The theory of the propagation of sound in a homogeneous gas including the effect of heat conduction is presented for the purpose of clarifying the underlying thermodynamic process. The propagation of sound in a liquid with a homogeneous and isotropic distribution of gas bubbles is then considered. The bubbles are assumed to be sufficiently small and numerous so that the mixture can be taken to be a uniform medium. The effect of heat conduction is included. If f is the ratio of gas volume in the mixture to liquid volume, it is shown for the range of f of general interest that the acoustic condensations and rarefactions of the gaseous portion of the medium are essentially isothermal. It is also found that the attenuation of an acoustic disturbance by heat conduction is quite small.
Scalar Formulation of Ideal Charged Gas Flow
Authors: Schmid Lawrence A.
Published: December 2004

In the case of adiabatic flow of an ideal electron or ion gas in the presence of gravitational and electromagnetic fields, it is possible to derive a system of scalar equations of motion for the gas that provides an alternative to the Euler formulation. The new dynamical variables that replace the velocity are three scalars, one of which is a generalization of the flow potential and satisfies a generalized Hamilton-Jacobi equation. The other two are constants of motion that specify the intrinsic vorticity, which is that part of the total vorticity that is not produced by the external fields, but rather is simply a residue of the initial conditions of the gas. It is this intrinsic vorticity that satisfies the generalization of the simple vorticity conservation theorem. The same formalism can be adapted to the case of constant-temperature flow and to the flow of an arbitrary barotropic fluid.
Analogy for the Laboratory Simulation of Hydromagnetic Phenomena in Astrophysics
Authors: Pneuman G. W.
Published: December 2004

An analogy involving convective diffusion of a dye in a moving fluid is described which permits the laboratory simulation of many hydromagnetic phenomena believed to occur on a cosmic scale.
Stability of One-Dimensional Laminar Flames with Distributed Heat Losses
Authors: Kennerley J. A. , Adler J.
Published: December 2004

The time-dependent stability of one-dimensional laminar flames with distributed heat losses has been investigated. It is shown that, when heat losses are predominantly by conduction, all small disturbances from a steady state decay with increasing time or lead to a uniform displacement of the flame in the direction of propagation. With the assumptions of the present analysis, flame stability limits are thus solely determined by the existence of steady-state solutions.
Transient Phenomena in Dissociative Reactions
Authors: Brau Charles A. , Keck James C. , Carrier George F.
Published: December 2004

The ``diffusion theory'' of dissociation is used to analyze vibration-dissociation coupling in the early phases of dissociation behind a shock wave. It is shown that deviations from vibrational equilibrium introduce ``incubation times'' into the long-time behavior of macroscopic molecular observables, such as the number density. For example, if Q(t) is some macroscopic observable whose value is Q0 in vibrational equilibrium behind the shock wave with no dissociation, then at long times Q(t) = Q0 exp [−(t − τQ)/τDiss], where τDiss is the dissociation time and τQ is the incubation time for the observable Q. The incubation times are experimentally observable quantities and may be positive or negative, depending on the observable, Q. Approximate methods are used to calculate incubation times according to a simplified Morse oscillator model. The results agree well with experimental measurements made by Wray in O2-argon mixtures. Incubation effects are found to increase rapidly in importance as the temperature increases, with |τQ/τDiss| ≳ 10% when kT ≳ 15% of the dissociation energy.
Wave Propagation in One-Dimensional Reactive Flows
Authors: Barthel Harold O. , Strehlow Roger A.
Published: December 2004

The theories of characteristic surfaces and of acoustics are used to examine the nature of transverse waves in steady, one-dimensional reactive flows in the Mach number range 0 < M < ∞. Ray refraction and reflection at a normal shock wave and flow matching between adjacent reactive and non-reactive regions are investigated. For certain different Mach number ranges, a shock wave followed by either an endothermic or exothermic reaction will contain a region which is bounded by a specific ray that travels purely normal to the flow at the location having M = (γ + 2)−½ irrespective of the reactions occurring in the flow. In this region trapped rays produce a transverse wave front with many shock front contacts. An example of the development of such a complex transverse wave structure behind a detonation is given using a specific model for the detonation and the initial wave front shape.
Ionization Rate of Air behind High-Speed Shock Waves
Authors: Wilson J.
Published: December 2004

Measurements have been made of the ionization rate of air behind strong shock waves for shock velocities between 9 and 12.5 mm/μsec. The electron density behind the shock was determined from the infrared emission around 6 μ, this radiation being predominantly free-free bremsstrahlung. It was concluded that at shock speeds below 9.5 mm/μsec the predominant ionization mechanism is the reaction, N + O → NO+ + e, as postulated by Lin and Teare for slower shock speeds. However, for shock speeds above 9.5 mm/μsec, electron impact becomes the predominant ionization mechanism.
Solitary Waves in an Atmosphere with Arbitrary Wind and Density Profiles
Authors: Shen M. C.
Published: December 2004

Solitary waves in a compressible atmosphere of finite or infinite height with arbitrary wind and density profiles are studied. Explicit expressions for the critical speed and the first-order solution of the internal solitary waves are obtained by a perturbation scheme applied to the nonlinear equations and are expressed in terms of simple integrals of velocity and density profiles of the atmosphere in the state of equilibrium. The slope of the density profile at the bottom surface plays an important role in determining the signature of the wave, and solitary waves do not appear when the parameters involved in the solitary wave solution assume certain critical values. The results obtained cover many of the existing solitary wave solutions as special cases.
Stability of Magnetohydrodynamic Half-Jet Part II. Inviscid Stability of Incompressible Magnetohydrodynamic Half-Jet
Authors: Lessen Martin , Deshpande Narayan V.
Published: December 2004

Inviscid stability of an incompressible half-jet in the presence of an aligned magnetic field has been investigated, and the neutrally stable eigenvalues are determined. It is shown that the magnetic field has a stabilizing effect on this boundary-layer type flow, but it does not stabilize the flow completely.
Suddenly Pressurized Elastomagnetohydrodynamic Channel Flow
Authors: Farn Charles L. S. , Arpaci Vedat S.
Published: December 2004

The channel flow of a suddenly pressurized visco-elastic and electrically conducting fluid under the influence of a constant and transversal magnetic field is given analytic treatment. Flow oscillations resulting from the elasticity of the fluid and damping effect of the magnetic field on these oscillations are shown in terms of three parameters.