bluuebunny/crossref_metadata_2025 huggingface dataset:
Planning and Implementing a Reintroduction of Wolves to Yellowstone National Park and Central Idaho
Authors: Fritts Steven H. , Bangs Edward E. , Fontaine Joseph A. , Johnson Mark R. , Phillips Michael K. , Koch Edward D. , Gunson John R.
Published: December 2004

The Northern Rocky Mountain Wolf Recovery plan proposed reintroduction ofCanis lupus(gray wolf) to Yellowstone National Park and central Idaho as part of a wolf restoration plan for the northern Rocky Mountains of the United States. Strong opposition from some factions within the region forestalled the action for two decades. An environmental impact statement, conducted in 1992–1994 with extensive public input, culminated in a proposal to reintroduce wolves designated as “non‐essential—experimental” under Section 10 (j) of the federal Endangered Species Act. This approach, approved by the Secretary of the Interior in 1994, provided for wolf restoration while allowing management flexibility to deal with concerns of the local public. A reintroduction plan was developed in the summer and fall of 1994. Acquiring, holding, transporting, and releasing suitable wolves for reintroduction presented a myriad of technical and logistical challenges that required effective planning and coordination by all participants. In January 1995, 29 wolves were captured in Alberta and transported to Yellowstone National Park (14) and central Idaho (15). Idaho wolves were freed immediately upon arrival; Yellowstone wolves (three family groups) were held in acclimation pens in the park until late March. Most Idaho wolves traveled extensively within the area intended for them, averaging 82 km net distance away from release sites after 5 months (range = 30–220 km), and three male‐female pairs formed by July. After 5 months in the wild, at least 13 of 15 Idaho‐released wolves were alive within the intended area, as were 13 of 14 Yellowstone wolves; one wolf was known to have been illegally killed in each area. No livestock were killed. Wolves released into Yellowstone Park continued to live as packs, stayed closer to their release sites (x = 22 km at end of June), and settled into home ranges; two packs produced a total of nine pups. The progress of the reintroduction program in its first year far exceeded expectations. Reintroductions of about 15 wolves to each area for 2–4 more years are scheduled, but the project may be shortened because of early successes. Future reintroduction planners can expect sociocultural issues to pervade the effort, but they can be optimistic that, from a biological standpoint, reintroduction of wolves has strong potential as a restoration technique.
Woodland Restoration in the Western Australian Wheatbelt: A Conceptual Framework Using a State and Transition Model
Authors: Yates Colin J. , Hobbs Richard J.
Published: December 2004

Woodlands dominated by Eucalyptus spp. in temperate southeastern and southwestern Australia have been extensively cleared for agriculture and are often badly degraded by livestock grazing. This has resulted in the loss of biodiversity and widespread land degradation. The continuing decline of these woodlands has become a concern for the conservation of biodiversity, and there is a growing interest among farmers, land managers, and researchers in developing techniques for restoring them. Currently few scientific guidelines exist for undertaking woodland restoration programs. We use a state and transition model to develop hypotheses on restoration strategies for salmon gum (Eucalyptus salmonophloia) woodlands. We consider that this approach provides a suitable framework for organizing knowledge and identifying areas where further information is needed, and hence provides a useful starting point for a restoration program. The model has the potential to provide a tool for land managers with which they can assess the action and effort needed to undertake woodland restoration in agricultural landscapes.
Biomass and Nutrient Accumulation During Natural Afforestation of Iron‐Smelting Slag
Authors: Smith Frances C. , Johnson Arthur H. , Dranoff Martin , Wibiralske Anne
Published: December 2004

This paper summarizes the accumulation of nutrient capital during the natural afforestation of iron‐smelting slag. The study site was the Beckley Furnace (North Caanan, Connecticut, U.S.A.) slag dump, which was abandoned around 1918. Currently, a Pinus strobus (white pine)‐dominated forest occupies the site. Our primary objective was to determine the relationships among stand development and belowground nutrient pools to evaluate controls on the rates at which nitrogen, calcium, magnesium, and potassium accumulate in the developing forest. Along a developmental gradient of increasing stand basal area, we measured (1) aboveground biomass, (2) root biomass, (3) above‐ground nutrient capital, (4) belowground nutrient capital, (5) soil weight, (6) soil organic carbon weight, (7) soil moisture, and (8) understory richness and density. Regression analysis suggests, as expected, that the addition of organic matter controls the accumulation of above‐ and belowground nutrients, soil water, and understory plant composition and distribution. The rather rapid rate of nitrogen accumulation suggests that allochthonous as well as autochthonous organic matter is an important source of nutrients for the developing forest soil and vegetation. Compared to those of other northeastern forests, soils in the most developed areas at the Beckley site have accumulated more than enough labile nutrient capital in 75 years to support a forest typical of the region. In the most developed stands, understory composition indicates mesic soil conditions, and that within the next 75 years or so the Beckley slag dump will be floristically very similar to the surrounding forest.
The Flora and Invertebrate Fauna of Abandoned Limestone Quarries in Derbyshire, United Kingdom
Authors: Wheater C. Philip , Cullen W. Rod
Published: December 2004

Abandoned limestone quarries are hostile environments for plant and invertebrate colonization and establishment. The length of time taken for successful establishment by natural processes may be unacceptable for reclamation purposes; several techniques are used to reduce the time scales involved. A new technique, restoration blasting, aims to replicate natural daleside landforms by selective blasting of modern production quarry faces. We compare the flora and invertebrate fauna of restoration‐blasted sites, hydro‐seeded with daleside species, with naturally regenerating disused quarries and a natural daleside. Restoration‐blasted sites were found to have less plant cover, more bare ground, fewer orders of invertebrates, and generally fewer animals within each order than the other two types of site. The disused quarries tended to have intermediate characteristics between the restoration‐blasted sites and the natural daleside. The age of the site may be important in determining the plants and invertebrates occurring there. This may be related to the time available for establishment or a greater degree of settlement or stability within the biotic and abiotic components of the site. Although most of the results indicate that time since establishment may be important, some variations occur. In particular, the development of vegetation cover in areas grazed by rabbits is problematic. These results are important in the assessment of successful reclamation because the invertebrate fauna may contribute greatly to the overall system. Both plant and animal communities appear to be establishing well on the sites reclaimed by restoration blasting. Further monitoring will identify the speed at which such environments achieve the desired aim of replicating daleside communities and the communities best able to be sustained following this technique.
Expression of THR1, a 1,3,8‐Trihydroxynaphthalene Reductase Gene Involved in Melanin Biosynthesis in the Phytopathogenic Fungus Bipolaris oryzae, is Enhanced by Near‐Ultraviolet Radiation
Authors: Kihara Junichi , Moriwaki Akihiro , Ito Machiko , Arase Sakae , Honda Yuichi
Published: December 2004

1,3,8‐Trihydroxynaphthalene (1,3,8‐THN) reductase is involved in the production of fungal dihydroxynaphthalene (DHN) melanin. We isolated and characterized THR1, a gene encoding 1,3,8‐THN reductase, from the phytopathogenic fungus Bipolaris oryzae. Sequence analysis showed that THR1 encodes a putative protein of 267 amino acids having a molecular weight of 28.5 kDa and 68–98% sequence identity to other fungal 1,3,8‐THN reductases. Targeted disruption of the THR1 gene showed that it is essential for melanin biosynthesis in B. oryzae. Northern blot analysis showed that THR1 transcripts are constitutively expressed during normal growth but are specifically enhanced by near‐ultraviolet (NUV) radiation in a dose‐dependent manner. These results indicate that THR1 expression is transcriptionally enhanced by NUV radiation in B. oryzae.
Association of Angiotensin Converting Enzyme Gene I/D Polymorphism of Vitiligo in Korean Population
Authors: Jin Sheng‐Yu , Park Hyun‐Ho , Li Guang‐Zhe , Lee Hee‐Jae , Hong Mee‐Suk , Hong Seung‐Jae , Park Hun‐Kuk , Chung Joo‐Ho , Lee Mu‐Hyoung
Published: December 2004

Vitiligo (leukoderma) is an acquired idiopathic hypomelanotic disorder characterized by the circumscribed depigmented patches. Vitiligo is a polygenic disease. The exact pathogenesis is not yet known. The angiotensin converting enzyme (ACE) gene was selected as a candidate gene as ACE plays an important role in the physiology of the vasculature, blood pressure and inflammation, and its relationship with various diseases, including autoimmune diseases, has been widely investigated. The I/D polymorphism of ACE gene in vitiligo patients has not been reported. In this study, we investigated ACE gene polymorphism in 120 vitiligo patients and in 429 healthy volunteers in Korea. The ACE gene genotype distribution (P = 0.032) and allele frequency (P = 0.012) were significantly different between vitiligo patients and healthy controls. This study suggests that the ACE gene polymorphism has a strong association with the development of vitiligo in Korean patients.
Comparison of Long‐Term Survival of Pigmented Epidermal Reconstructs Cultured In Vitro vs. Xenografted on Nude Mice
Authors: Casoli Vincent , Cario‐André Muriel , Costet Pierre , Pain Catherine , Taïeb Alain
Published: December 2004

Epidermal reconstructs incorporating pigment cells have been used in vitro over the last decade to study the physiology of the epidermal melanin unit. However, the major limitation of this technology is the duration of the assays, which need to be completed within 2–3 weeks to obviate the problem of epidermal senescence and excessive terminal differentiation. This becomes a major problem for studying long‐term biological phenomena in photoprotection and epidermal skin cancers. We report here a simplified surgical technique in immunotolerant mice allowing long‐term studies. The creation of a vascularized mouse skin flap is the key point of the surgical procedure. Long‐term pigmentation of the xenografts seemed macroscopically successful, but surprisingly microscopy at 11 and 16 weeks postgrafting showed mostly dermal pigment aggregates and rare Melan‐A positive dermal and epidermal pigment cells. In the same reconstructs maintained in vitro, dermal pigment and dermal pigment cells were never noted. It could be speculated that in our model, the colonization of the xenografted dead human dermis by murine cells influences melanocyte survival.
Hepatocyte Growth Factor Controls the Proliferation of Cultured Epidermal Melanoblasts and Melanocytes from Newborn Mice
Authors: Hirobe Tomohisa , Osawa Masatake , Nishikawa Shin‐Ichi
Published: December 2004

Mouse epidermal melanoblasts and melanocytes preferentially proliferated from disaggregated epidermal cell suspensions derived from newborn mouse skin in a serum‐free melanocyte‐proliferation medium (MDMD) and melanoblast‐proliferation medium (MDMDF) supplemented with dibutyryl adenosine 3′:5′‐cyclic monophosphate (DBcAMP) and/or basic fibroblast growth factor (bFGF). Pure cultured primary melanoblasts and melanocytes were further cultured with MDMD/MDMDF supplemented with hepatocyte growth factor (HGF) from 14 days (keratinocyte depletion). The HGF increased the number of melanoblasts and melanocytes, but not the percentage of differentiated melanocytes in the melanoblast–melanocyte population in the absence of keratinocytes. Flow cytometry analysis showed that melanoblasts and melanocytes in the S and/or G2/M phases of the cell cycle were increased by the treatment with HGF. Moreover, an anti‐HGF antibody supplemented to MDMD/MDMDF from the initiation of the primary culture (in the presence of keratinocytes) inhibited the proliferation of melanoblasts and melanocytes, but not the differentiation of melanocytes. These results suggest that HGF is a keratinocyte‐derived factor involved in regulating the proliferation of epidermal melanoblasts and melanocytes from newborn mice in cooperation with cAMP elevators and/or bFGF.
In Situ Hybridization: An Informative Technique for Pigment Cell Researchers
Authors: Suzuki Itaru , Motokawa Tomonori
Published: December 2004

Many cellular events are regulated at the transcriptional level. Recent technical advances such as DNA microarray have made it possible to determine mRNA profiles of cultured cells or tissues. However, since it is still impossible to completely simulate the in vivo environment in culture conditions, mRNA profiles of cultured cells are not perfect representatives of original cells. Furthermore, for cells that exist at lower densities, mRNA profiling using tissue samples would be difficult. By using tissue in situ hybridization, mRNA levels of genes in tissues can be determined at cellular resolution. Although throughput of tissue in situ hybridization is not high enough for mRNA profiling, it may be sufficient to investigate temporal/spatial expression profiles of genes that are known to be important or found to be interesting in high‐throughput transcriptome/proteome analyses. Recent technical advances have made it easier for everybody to perform tissue in situ hybridization using normal experimental instruments with sufficient sensitivity to detect most genes. Although this technique has been utilized mainly in developmental biology, it will be fully advantageous when combined with high‐throughput comprehensive transcriptome/proteome analyses.
Quercetin Enhances Melanogenesis By Increasing the Activity and Synthesis of Tyrosinase in Human Melanoma Cells and in Normal Human Melanocytes
Authors: Nagata Hidetaka , Takekoshi Susumu , Takeyama Reiko , Homma Takao , Yoshiyuki Osamura R.
Published: December 2004

Quercetin (3,3′,4′,5,7‐pentahydroxyflavone) is a diphenyl propanoid widely distributed in edible plants. In this study, we examined the effect of quercetin on melanogenesis in human HMVII melanoma cells and in normal human epidermal melanocytes (NHEM) in the absence of ultraviolet radiation. Upon the addition of quercetin to the culture medium, the melanin content in melanoma cells (HMVII) increased remarkably in time‐ and dose‐dependent manners. In addition, quercetin induced melanogenesis in cultured NHEM. As compared with controls, melanin content was increased about sevenfold by treatment with 20 μM (HMVII) or 1 μM (NHEM) quercetin for 7 d. Tyrosinase activity was also increased, to 61.8‐fold higher than the control. The expression of tyrosinase protein was slightly increased by the addition of quercetin. However, quercetin did not affect the expression of tyrosinase mRNA. Tyrosinase activation by quercetin was blocked by actinomycin‐D or by cycloheximide demonstrating that its actions in stimulating melanogenesis may involve both transcriptional and translational events. Tyrosinase activity was increased dramatically whereas the level of melanogenic inhibitor was remarkably decreased following quercetin treatment. Taken together, these results demonstrate that in human melanoma cells and in NHEM, quercetin stimulates melanogenesis by increasing tyrosinase activity and decreasing other factors such as melanogenic inhibitors.
Effects of Ultraviolet Light on Melanocyte Differentiation: Studies with Mouse Neural Crest Cells and Neural Crest‐derived Cell Lines
Authors: Hosaka Eri , Soma Yoshinao , Kawa Yoko , Kaminaga Hiroko , Osumi Kayoko , Ooka Shiho , Watabe Hidenori , Ito Masaru , Murakami Fumiko , Mizoguchi Masako
Published: December 2004

To evaluate the etiologic role of ultraviolet (UV) radiation in acquired dermal melanocytosis (ADM), we investigated the effects of UVA and UVB irradiation on the development and differentiation of melanocytes in primary cultures of mouse neural crest cells (NCC) by counting the numbers of cells positive for KIT (the receptor for stem cell factor) and for the L‐3,4‐dihydroxyphenylalanine (DOPA) oxidase reaction. No significant differences were found in the number of KIT‐ or DOPA‐positive cells between the UV‐irradiated cultures and the non‐irradiated cultures. We then examined the effects of UV light on KIT‐positive cell lines derived from mouse NCC cultures. Irradiation with UVA but not with UVB inhibited the tyrosinase activity in a tyrosinase‐positive cell line (NCCmelan5). Tyrosinase activity in the cells was markedly enhanced by treatment with α‐melanocyte‐stimulating hormone (α‐MSH), but that stimulation was inhibited by UVA or by UVB irradiation. Irradiation with UVA or UVB did not induce tyrosinase activity in a tyrosinase‐negative cell line (NCCmelb4). Levels of KIT expression in NCCmelan5 cells and in NCCmelb4 cells were significantly decreased after UV irradiation. Phosphorylation levels of extracellular signal‐regulated kinase 1/2 in cells stimulated with stem cell factor were also diminished after UV irradiation. These results suggest that UV irradiation does not stimulate but rather suppresses mouse NCC. Thus if UV irradiation is a causative factor for ADM lesions, it would not act directly on dermal melanocytes but may act in indirect manners, for instance, via the overproduction of melanogenic cytokines such as α‐MSH and/or endothelin‐1.
Enhanced Interaction in the Positive Column
Authors: Ecker G.
Published: December 2004

Recent theoretical work has shown that under certain conditions enhanced electron-ion interaction may be present in a plasma. This paper investigates the influence of such enhanced interaction on the characteristics of the positive column in a longitudinal magnetic field. The calculations are based on the Boltzmann transport equations, using an effective interaction parameter. Enhanced interaction has several consequences: It causes enhanced diffusion and with that an increase in electron temperature (T−) due to increased particle wall losses. This influence on T− is in general small and may be negligible for nonuniform enhancement. It also has a pronounced influence on the radial distribution depending on the type of diffusion. Finally, for a given electron temperature, enhanced interaction results in an increase of the ion (T+)—and gas (T0) temperatures due to increased energy exchange between electrons and ions. The same effect also changes the relation Xz(T−), Xz being the longitudinal electric field. Consequently, enhanced interaction influences the field Xz in two ways, namely through the increased particle loss (T−) and the energy exchange Xz(T−). The results suggest measurement of the radial potential distribution as a means for experimental investigation of enhanced interaction in the discharge.
Self-Induced Velocity on a Curved Vortex
Authors: Hama Francis R. , Nutant John
Published: December 2004

By means of examples the distribution of self-induced velocity along a curved vortex is investigated analytically as well as by means of an analog experiment of the magnetic field of a current-carrying cable. Results verify, at least for these examples, a theorem which was intuitively introduced by Hama in his study of detailed process of boundary-layer transition; the induced velocity on a curved vortex is largest in the region where the curvature is largest.
Optical Refractivity of High-Temperature Gases. III. The Hydroxyl Radical
Authors: White Donald R.
Published: December 2004

The optical refractive index has been measured interferometrically behind Mach 6 to 9 shock waves advancing into nearly equimolal hydrogen and oxygen at pressures of 0.01, 0.015, and 0.02 atm. Pressure measurements in these experiments together with other data on similar systems show the shocked gas to be in an equilibrium state. The refractivity to be expected from all species present, except the hydroxyl radical, is computed, and the difference between this and the observed refractivity is attributed to hydroxyl radical present at the equilibrium density. The resultant specific refractivity in the blue is K = 0.35 ± 0.04 cm3/g, corresponding to a polarizability of ᾱ = 1.5 ± 0.2A3 and a refractivity of μ − 1 = (2.5 ± 0.3) × 10−4.
Existence of Detonations for Small Values of the Rate Parameter
Authors: Wood W. W.
Published: December 2004

The simplified, one-dimensional, steady-state Navier-Stokes detonation problem formulated by Hirschfelder, Curtiss, et al. is examined with respect to the existence of solutions when the reaction rate is small compared to the molecular collision rate. The latter condition is necessary for the assumed unimolecular mechanism to be valid, but is also the condition where these authors were unable to find solutions by numerical integration of the differential equations. It is shown that solutions indeed exist for arbitrarily small values of the reaction rate, and that these solutions approach the von Neumann model of a shock preceding a deflagration. An asymptotic approximation to the solution is given which should be adequate for such small reaction rates.

In order to make the steady-state problem mathematically well defined, the usual difficulty of the very small reaction rate in the initial state is removed by imposing an ignition temperature. It is shown that if the reaction rate and Mach number are held fixed while the ignition temperature is raised slightly above the von Neumann spike temperature, the solution changes to a flame having the same hot boundary state, but with the detonation von Neumann spike state as its initial state.
Slowly Reacting Gas Mixture in a Heat Conductivity Cell
Authors: Secrest Don , Hirschfelder Joseph O.
Published: December 2004

A hypothetical gas mixture composed of A2, B2, and AB which reacts bimolecularly, 2AB ⇌ A2 + B2, is placed in a thermal conductivity cell. The heat flux as well as the chemical and thermal profiles are calculated numerically for fast, slow, and intermediate reaction rates. Since the chemical composition is not in equilibrium with the local temperature, considerable calculational difficulties are encountered. An approximation scheme is given for estimating the behavior of such systems. It is found that for fast reactions, local equilibrium applies. If the rate of the chemical reactions is slow compared to the rate of diffusion (an exact criterion is given), the chemical composition within the cell becomes homogeneous throughout the cell. This composition is determined by the set of equations ∫ T CT HλRi dT=0,where λ is the coefficient of heat conductivity and ℛi is the net rate of production of molecules of the ith species. Conversely, from a knowledge of the steady-state chemical composition we may determine the chemical reaction rates. Calculations are made for a mixture of H2, I2, and HI. This system should be easy to study experimentally since the I2 concentration can be determined from optical absorption and the HI concentration can be determined from infrared absorption.
Motion of a Viscous Compressible Gas Adjacent to a Sliding Plate
Authors: Harlow Francis H. , Meixner Billy D.
Published: December 2004

Numerical calculations were made of the motion of a viscous compressible gas adjacent to a flat plate moving rapidly in its own plane. The analytical solutions given by Stewartson were checked and good agreement obtained after a slight modification was made in the results of his solution-matching technique. The computer results illustrate the detailed flow profiles which should be useful in the generation of improved analytical solutions. In addition, computations were performed to show the effects of variations of Prandtl number, viscosity ratio, and plate acceleration history.
Effect of Collisions on the Landau Damping of Plasma Oscillations
Authors: Platzman P. M. , Buchsbaum S. J.
Published: December 2004

The effect of collisions on the Landau damping of a one-dimensional longitudinal plasma oscillation in the absence of a magnetic field is analyzed. It is found that in a steady state, collisions (no matter how few in number) affect the velocity distribution of the trapped electrons and thus play a major role in determining the Landau damping. When the damping is small (Im k « Re k), it is reduced from its collisionless value by a factor νc2/(νc2 + Ω2) where νc is the electron collision frequency for momentum transfer and Ω2 = eEk/m is the frequency of oscillation of a trapped electron in the approximately parabolic potential trough of the wave.
Collisionless Plasma Shock Waves
Authors: Yoshihara Hideo
Published: December 2004

A solution for the profile of a collisionless plasma shock wave in the absence of magnetic fields has been determined using the nonlinear Vlasov equations. The uniform shock speed is taken to be much less than the electron thermal speed of the ambient plasma. Under these conditions a solution is found for a given Mach number of the shock only for a definite ratio of the electron to positive ion temperatures in the quiescent plasma. Profiles of the macroscopic state variables are calculated for a Mach number of 20½.
Effect of Boundary-Layer Growth in a Shock Tube on Shock Reflection from a Closed End
Authors: Rudinger George
Published: December 2004

The pressure behind a shock wave propagating in a constant-area duct increases slightly with time as a result of the growing boundary layer. This rise is considerably magnified by the shock reflection from the closed end of the duct. Analysis of the local interaction of the reflected shock with the boundary layer yields information on the shock configuration, but the combined effects of the waves produced by the growing boundary layer along the entire shock tube must be considered to obtain the state of the gas behind the reflected shock. The theory of the flow field behind the incident shock is modified to allow for effects in addition to boundary-layer growth which cause deviations from an ideal shock-tube flow. Experimental observations of the pressure rise behind the reflected shock, obtained for shock pressure ratios up to about 4.5 are in satisfactory agreement with the computed results, and estimates for stronger shock waves are presented.
Energy Loss from a Toroidal Pinch Discharge
Authors: Karr H. J. , Knapp E. A. , Osher J. E.
Published: December 2004

Most high-temperature plasma devices, and in particular pinch discharges, have energy-loss rates much larger than can be accounted for in terms of hydrogenic bremsstrahlung or quiescent plasma diffusion. This loss has been investigated for a toroidal pinch discharge machine with longitudinal stabilizing magnetic field, Perhapsatron S-4. It is found that the major energy dissipation is due to vacuum ultraviolet emission from partially stripped impurity ions. The impurity is predominantly oxygen liberated from the walls of the tube into the discharge after the pinch has been formed. Characteristics of this radiation are discussed, as well as a possible mechanism for the release of the impurity into the discharge. Comparisons between experimental results and theoretical predictions on the rate of radiation loss are given.
Turbulent Structure of Gaseous Detonation
Authors: White Donald R.
Published: December 2004

Self-sustaining and overdriven detonations in 2H2 + O2 + 2CO have been studied in a shock tube at initial pressures from 0.01 to 1.4 atm. Measurements have included pressure, density obtained interferometrically, and luminosity whose intensity is shown to be proportional to [CO][O]. Strongly overdriven waves are one dimensional and are followed by the calculated equilibrium state. Self-sustaining detonations are followed by a state in which the pressure and density are lower than calculated according to the usual C-J hypothesis, and in which the flow is supersonic with respect to the wave front. Furthermore, the flow in and behind the reaction zone invariably appears to be turbulent. In an examination of the implications of this turbulence, a Chapman-Jouguet detonation is considered to be one with the minimum velocity of propagation which will satisfy the conservation relations for turbulent flow at the rear of reaction zone. It is shown that this minimum (C-J) velocity is slightly greater than that calculated assuming turbulence is not present, and that the final state attained following the decay of turbulence can lie either on the ``strong'' or ``weak'' detonation branch of the Hugoniot curve. Intermediate states, including the conventionally calculated C-J state, in general do not represent stable solutions. The self-sustaining detonation, which must correspond to the weak detonation solution, appears as a special case of a C-J detonation.
Two-Reaction Steady Detonations
Authors: Erpenbeck Jerome J.
Published: December 2004

Steady, one-dimensional detonations in an idealized, three-component, gaseous medium with reactions A ⇋ B, A ⇋ C, proceeding with Arrhenius unimolecular kinetics are investigated by way of exemplification of the Wood-Salsburg analysis as well as delineation of the behavior at the trouble-some ``pathological'' locus for this special case. The analysis is detailed for the exothermic parallel-reaction case with large disparity in the heats of reaction but results for other cases are mentioned. Stability conditions for a pathological detonation are reformulated as conditions on the parameters of the system which, though necessary, are by no means sufficient. For both the exothermic parallel-reaction case and the consecutive-reaction case, with the second reaction endothermic, it appears that the stability conditions are not inconsistent with the existence of a pathological solution. Numerical results for several systems at the equilibrium Chapman-Jouguet detonation velocity are presented, including one in which the equilibrium CJ condition is inapplicable.
Shock Initiation of Solid Explosives
Authors: Campbell A. W. , Davis W. C. , Ramsay J. B. , Travis J. R.
Published: December 2004

Initiation phenomena in solid explosives produced by strong shock waves are described. Shock pressures in the explosive are between 20 and 200 kbar. It is demonstrated that in the usual case the shock wave travels not as an inert shock, but as a shock to which the explosive contributes energy, probably from reaction at voids and defects. This slightly reacting shock travels at increasing velocity for some distance, typically 1 cm in the experiments described, and then in a travel of perhaps 0.01 cm becomes full detonation, moving at full velocity. The increase to full detonation velocity occurs without overshoot. Experiments demonstrating the variation of sensitivity to shock with density, grain size, and other properties are discussed. The explosives studied are cyclotol B, TNT, plastic-bonded HMX, and nitromethane-carborundum mixtures.
Density Field for Rarefied Flow through an Orifice
Authors: Howard Weston M.
Published: December 2004

A theoretical investigation is made of the density field for rarefied flow through an orifice. Within the assumptions of Maxwellian velocity distribution of the gas and of diffuse reflection from the reservoir walls, exact expressions are found for the density at the center line of the effusing stream for a circular orifice and for all regions of the field for square and rectangular orifices. The density field is found to be most affected by orifice geometry in the near region. For narrow slits the effect is felt further from the orifice than for nearly square or circular geometries.
Viscous Magnetohydrodynamic Boundary Layer
Authors: Sherman A.
Published: December 2004

The behavior of the Blasius boundary layer, for a fluid of constant electrical conductivity, in the presence of a non-uniform magnetic field is studied. Distortion of the applied field due to currents flowing in the fluid is neglected; that is, the magnetic Reynolds number is assumed to be zero. Since the fluid is of uniform conductivity, the influence of the pressure distribution, caused by the interaction between the magnetic field and the inviscid flow, on the boundary layer is taken into account along with the Lorentz body force within the layer itself. The nonlinear boundary layer equations are solved by the method of power series expansion utilizing the Görtler variables. Particular attention is given to the case in which the nonuniform field is established in a constant height channel. The boundary layer, then, is assumed to begin at some position along one wall, and grow in the downstream direction. For purposes of computation, the problem is further specialized to treat the case in which the nonuniform field is generated by a current-carrying wire imbedded in one wall of the channel and aligned normal to the flow. The results of a calculation, for one choice of the relevant nondimensional parameters, show that the reduction in skin friction is sufficient to separate the boundary layer.
Synchrotron Radiation from Mirror Machine Geometries
Authors: Beard David B. , Baker John C.
Published: December 2004

The radiation due to the orbiting of electrons in a confining magnetic field has been numerically integrated over a thermal velocity distribution perpendicular to the magnetic field as a function of frequency of emitted radiation and the angle the radiation propagation vector makes with the magnetic field. The general dependence of the emission on angle and frequency has been examined by the use of various approximations and is shown to agree with the numerical calculations. Our result for a velocity distribution perpendicular to the magnetic field more nearly corresponds to Drummond and Rosenbluth's previous angular dependence than with Trubnikov's result for an isotropic velocity distribution.
Intermolecular Potential Functions for Nonpolar Molecules
Authors: Konowalow Daniel D. , Hirschfelder J. O.
Published: December 2004

The Morse potential function is used to represent the intermolecular potential for several nonpolar substances. The potential constants are determined from a combination of crystal structure and second virial coefficient data for Ne, Ar, Kr, Xe, CH4, and N2. Over a wide temperature range the theoretical second virial coefficients determined from the Morse potential for these substances agree very well with experimental data and are quite comparable with calculations using the Buckingham (exp−-6) or the Lennard-Jones (12–6) potentials. For Kr, it is found that the agreement with the experimental second virial coefficients is greatly improved by dividing the intermolecular potential into two separate Morse functions, one applicable where the potential is negative and the other applicable where the potential is positive.
Theory of the Molecular Friction Constant
Authors: Helfand Eugene
Published: December 2004

The molecular friction tensor, as given by a time integral of an autocorrelation of forces, is calculated with the assumption that the trajectories of the particles are linear and unaccelerated for the times of interest. Such trajectories are appropriate to lowest order in the force on a particle. Application is made to particles interacting via a Coulombic potential. The result previously derived by Chandrasekhar is obtained without the introduction of a cutoff for large distances. In order to handle molecular systems we treat the ``soft'' part of the potential by the linear trajectory technique, and add a small term to account for hard-core collisions.
Wakes in Liquid-Liquid Systems
Authors: Magarvey R. H. , Bishop Roy L.
Published: December 2004

Evidence is presented to support a stable drop wake configuration consisting of a double row of vortex rings. This wake pattern is observed to be characteristic of liquid drops moving through a disperse liquid phase with Reynolds numbers appropriate to a range of nonoscillating drops. The wake configuration displays a high degree of symmetry and periodicity in the shedding of vortices. The wakes are rendered visible by the scrubbing of an aniline dye from the drop as it passes through the continuous phase. The larger oscillating drops leave wakes in which many rings are present, but the symmetry of the smaller drops is lacking.
Electrostatic Instabilities in Slightly Inhomogeneous Plasmas
Authors: Frieman E. , Pytte A.
Published: December 2004

Two approximate methods are presented for studying electrostatic instabilities in a spatially inhomogeneous plasma with no applied external magnetic field. The first is a perturbation procedure to be applied when the deviations from uniformity are small. The second is similar to a W. K. B. procedure to be applied when the density is a slowly varying function of position. Stability criteria are derived for both methods.
Theory of an Electrostatic Probe in a Strong Magnetic Field
Authors: Bertotti Bruno
Published: December 2004

If the magnetic field is so strong as to impair collective transverse drifts, all the charges supplied to the probe come mainly from a long tube of force, whose section is about one Larmor radius larger than the probe; while a diffusion process, more efficient than ordinary drifts, continuously exchanges particles between the inside and the rest of the plasma. A one-dimensional model of this process is proposed, leading to an integro-differential Poisson's equation, which has been studied for the case in which the collected particles are very fast. The solution consists of a chargeless, slowly decaying potential which describes the geometrical screening effect of the probe; while in the sheath an approximate boundary-layer solution matches with the probe's potential.
Configuration of a Plasma in an Axially Symmetric Magnetic Field
Authors: Katz Sylvan
Published: December 2004

Closed form analytic solutions are obtained for the static configuration of a fully ionized low β density adiabatic plasma immersed in an externally applied axially symmetric magnetic field. There is introduced first a special orthogonal curvilinear coordinate system, one of whose coordinate curves coincides with the externally applied magnetic field. Then, by performing a perturbation expansion for a low β adiabatic plasma, a system of zero-order equations is obtained. Although this system of equations is incomplete, in that there are more unknowns than equations serving for their determination, a determinate integrable system of equations is obtained by specifying that the diagonal elements of the divergence of the zero-order heat flux tensor vanish. This system of equations is integrated to yield analytic results dependent on the boundary conditions imposed upon the plasma. Finally, it is shown that if a trapping criterion is to be satisfied, the boundary conditions imposed upon the plasma must satisfy certain inequalities.
Distribution of Density in a Planetary Exosphere. II
Authors: Öpik E. J. , Singer S. F.
Published: December 2004

In an isolated neutral exosphere three components can be distinguished: (1) elliptic-ballistic; (2) hyperbolic-ballistic; (3) bound-elliptic. Component (2) forms the escape flux which cannot be defined simply. The velocity distribution of all components is calculated as a function of altitude in the exosphere; one can thereby assess the importance of the bound orbits. Even with the bound orbits completely filled, according to detailed balancing, the velocity distribution is non-Maxwellian; hence the barometric formula cannot be applied to determine the distribution of density. The absence of a Maxwellian distribution is shown to exist at all levels above the reference level (base of the exosphere) and the effective kinetic temperature of the gas is shown to decrease with altitude. The ``base of the exosphere'' forms the dividing level between the barosphere and exosphere; its conventional definition has been re-examined and it is redefined to correspond to the level from which one-half of the escaping molecules may escape without suffering any collisions. Numerical results for all components versus altitude are given for neutral hydrogen and oxygen, applicable to the terrestrial exosphere. The contribution of bound orbits is estimated and shown to be minor at all levels. Bound orbits may be important for the exospheres of the outer planets. The interplanetary gas may be considered as an extension of the solar atmosphere; however caution must be exercised in treating it as an exosphere.
Effect of Chemical Reaction Order on Flame Propagation
Authors: Hirschfelder Joseph O.
Published: December 2004

The properties of flames supported by one-step exothermal chemical reactions of orders zero through third are compared. New calculations are made for flames supported by second- and third-order reactions. The Adams and Wilde type of approximate solutions are obtained. The ignition temperature approximation is developed for zero- and second-order flames. Neither the Adams and Wilde nor the ignition temperature approximation is suitable for flames supported by high-order or complex systems of chemical reactions.
Kinetic Equation for a Warm Plasma
Authors: Woollett E. L.
Published: December 2004

A generalized Balescu-Lenard kinetic equation is derived for a fully ionized, zero-external-field, homogeneous, unbounded plasma which includes relativistic corrections to the thermal motion through terms of order (kT/mc2). The kinetic equation is constructed in the space of coordinates and relativistic mechanical momenta. The calculation, based on the Darwin Lagrangian, makes use of the multiple time-scale perturbation theory of Frieman and Sandri. Part of the collision integral is expressed in terms of a shielded Lorentz force. The three-body Lorentz force, which appears when the acceleration of a source particle is expressed in terms of the coordinates and velocities of all other particles, does not contribute in the approximation considered.
Loss Rates of Charged Particles from Ohmically-Heated Discharges in the C-Stellarator
Authors: Hinnov E. , Bishop A. S.
Published: December 2004

Ionization rates in the C-Stellarator discharges of helium and hydrogen, with Ohmic heating, are deduced from measured electron densities, temperatures, and the intensities of certain spectrum lines. Particle loss rates are obtained from the difference between the ionization rates and the observed changes in electron densities. It is shown that the average charged particle confinement time varies linearly with the confining field and the aperture of the current channel and inversely with the electron temperature. The confinement time is the same for helium and hydrogen and is not explicitly dependent on ohmic heating current or particle density.
Kernel of the Linearized Wang Chang-Uhlenbeck Collision Operator
Authors: Finkelstein Leib , Harris S.
Published: December 2004

An explicit form of the kernel of the linearized Wang Chang-Uhlenbeck collision operator is derived. This kernel is shown to be nonsymmetric in the arguments in which the kernel of the linearized Boltzmann collision operator is symmetric. Knowledge of the kernel reduces the dimension of the integral over the distribution function from 5 to 3.
Departures from Local Thermal Equilibrium in a Magnetically-Driven Shock Wave
Authors: Eckerle K. L. , McWhirter R. W. P.
Published: December 2004

An experimental study is reported of the time-resolved spectrum of the plasma produced by the magnetically-driven shock wave in a T-tube. It is shown that the population densities of the excited levels of helium ions in the plasma depart from the values they would have in local thermal equilibrium. On the other hand if local thermal equilibrium is assumed and the electron temperature estimated for the intensity ratio of He II (4686Å) to He I (5876Å) then in the conditions of the experiment an error of a factor of two in the electron temperature arises. The reason for the departure from local thermal equilibrium was shown to be the rapid rate of change of the plasma conditions (especially the electron temperature). This is so great that the ionization and recombination rates, being slower, cause certain population densities to lag behind the electron density and electron temperature. These rates were found to be consistent with the rates calculated by Bates et al. in their collisional-radiative model for the ionization and recombination of hydrogen-like ions.
Structure of a Perpendicular Shock Wave in a Plasma
Authors: Hu Pung Nien
Published: December 2004

Based on the Boltzmann equations for fully ionized gases, analytic solutions of weak perpendicular shock waves are obtained. The result shows that all weak shock waves (in ionized gases as well as in nonionized gases) have similar profiles given by the hyperbolic-tangent function of the distance. The shock thickness is found to depend on four basic parameters, namely, the mean free path of the gas, the length of penetration, the Larmor radius based on thermal speed, and the mass ratio of electron and ion. From the explicit expression of the shock thickness, various significant cases are derived and discussed. The most interesting case occurs when the mean free path is larger than the electron length of penetration, which is in turn larger than the electron Larmor radius; it is found that both the scaled and the actual shock thickness can be smaller than the length of penetration—a result contrary to that obtained for collisionless plasmas.
Dispersion of Particle Pairs in Homogeneous Turbulence
Authors: Kraichnan Robert H.
Published: December 2004

The relative dispersion of particle pairs in homogeneous turbulence is treated by the Lagrangian-History Direct-Interaction closure approximation for a convected scalar field. Richardson's diffusion equation emerges, with the sole difference that the eddy diffusivity depends on the duration of the dispersion as well as on particle separation. The diffusivity tensor is evaluated in the inertial range, and the probability distribution for the separation distance of a particle pair is computed for longtime, inertial-range dispersion. From this solution, numerical values are obtained for the dimensionless constants in Richardson's law for mean-square separation distance and Oboukhov's scalar-field inertial-range spectrum law. An inequality relating these two constants is inferred from qualitative considerations, without use of the closure approximation.
Formation and Penetration of High-Speed Collapse Jets
Authors: Harlow Francis H. , Pracht William E.
Published: December 2004

The explosively driven oblique collapse of two metal plates has been studied numerically in order to deduce the interaction region structural details. Emphasis was placed upon circumstances leading to high-speed jet formation. It is shown that many of the features of metallic jets can be estimated easily from readily accessible data on metal properties. The inclusion of viscosity has only a small effect for stress coefficients of reasonable magnitude, but is sufficient to explain the discrepancy between experiments and simple theory near the critical angle for jet formation. The penetration of a metallic jet was also calculated in order to show the detailed interaction with a target. The calculations were performed on high-speed computer with the Particle-in-Cell method.