bluuebunny/crossref_metadata_2025 huggingface dataset:
Acute and Long‐Term Effects of Atrioventricular Junction Ablation and VVIR Pacemaker in Symptomatic Patients with Chronic Lone Atrial Fibrillation and Normal Ventricular Response
Authors: UENG KWO‐CHANG , TSAI TSUNG‐PO , TSAI CHIN‐FENG , WU DER‐JINN , LIN CHUNG‐SHENG , LEE SHIH‐HUANG , CHEN SHIH‐ANN
Published: December 2004

AV Junction Ablation and Pacing.
Introduction: The precise role of irregular ventricular response in atrial fibrillation (AF) has not been fully elucidated. This study examined the independent effects of rhythm regularity in patients with chronic AF.

Methods and Results: This study included 50 patients who had chronic lone AF and a normal ventricular rate. Among these patients, 21 who underwent AV junction ablation and implantation of a VVIR pacemaker constituted the ablation group; the other 29 patients were the medical group. Acute hemodynamic findings were measured in 21 ablation patients before ablation (during AF, baseline) and 15 minutes after ablation (during right ventricular pacing). Compared with baseline data, ablation and pacing therapy increased cardiac output (4.7 ± 0.8 vs 5.2 ± 0.9 L/min; P = 0.05), decreased pulmonary capillary wedge pressure (16 ± 5 vs 13 ± 4 mmHg; P = 0.001), and decreased left ventricular end‐diastolic pressure (14 ± 4 vs 11 ± 3 mmHg; P < 0.05). After 12 months, the ablation group patients showed lower scores in general quality of life (−20%; P < 0.001), overall symptoms (−24%; P < 0.001), overall activity scale (−23%; P = 0.004), and significant increase of left ventricular ejection fraction (44% ± 6% vs 49% ± 5%; P = 0.02) by echocardiographic examination.

Conclusion: AV junction ablation and pacing in patients with chronic AF and normal ventricular response may confer acute and long‐term benefits beyond rate control by eliminating rhythm irregularity.
Phased‐Array Intracardiac Echocardiography to Guide Radiofrequency Ablation in the Left Atrium and at the Pulmonary Vein Ostium
Authors: MORTON JOSEPH B. , SANDERS PRASHANTHAN , BYRNE MELISSA J. , POWER JOHN , MOW CHRISTOPHER , EDWARDS GLENN A. , KALMAN JONATHAN M.
Published: December 2004

Echocardiography and Pulmonary Vein Ablation. Introduction: We sought to evaluate the utility of a phased‐array intracardiac echocardiography (ICE) device to identify left atrial (LA) and pulmonary vein (PV) anatomy; accurately guide radiofrequency ablation (RFA) to the right or left PV ostium and LA appendage (LAA); and evaluate PV blood flow before and after RFA using Doppler parameters.

Methods and Results: Twelve adult sheep were anesthetized and an Acuson 10–French, 7–MHz ICE transducer introduced via the internal jugular vein into the right atrium. The LA was imaged and PV anatomy and blood flow documented using two‐dimensional and pulsed‐wave Doppler. Mean LA dimensions were 4.6 ± 0.4 × 3.5 ± 0.5 cm; mean single right and left main PV ostium diameters were 1.5 ± 0.2 and 1.3 ± 0.3 cm; and mean right and left PV first‐order branch diameters were 0.8 ± 0.2 and 0.6 ± 0.1 cm. Mean PV maximum inflow velocity for the right PV were 0.30 ± 0.05 m/sec and for the left PV were 0.35 ± 0.04 m/sec. The PV ostia and LAA could be targeted accurately for RFA using ICE guidance. At pathologic evaluation, the mean distance of the lesion center to the right or left PV‐LA junction was 3.0 ± 2.0 mm. The mean distance of the lesion center to the posterior margin of the LAA was < 4 mm in all cases. There was no significant increase in PV maximum inflow velocity or decrease in PV diameter following RFA at the PV ostium. Absence of PV obstruction was confirmed at pathology.

Conclusion: Phased‐array ICE allows detailed assessment of LA and PV anatomy when imaged from the right atrium; accurate guidance of RFA to the PV ostium and LAA; and immediate evaluation of PV patency after RFA.
Post Systolic Shortening in Nonobstructive Hypertrophic Cardiomyopathy With Delayed Emptying of the Apex: A Doppler Flow, Tissue Doppler and Strain Rate Imaging Case Study
Authors: Støylen Asbjørn , Sletvold Olav , Skjaerpe Terje
Published: December 2004

We report a case of a 92‐year‐old woman with syncope and exertional dyspnea, who on echocardiographic examination proved to have hypertrophic cardiomyopathy. Doppler flow revealed delayed emptying of the apex, extending into the early filling phase. Tissue Doppler and strain rate imaging illustrated postsystolic shortening corresponding to the apical ejection, demonstrating that the apical flow was due to wall thickening resulting in active ejection. The imaging methods and mechanics of post‐systolic shortening are discussed. (ECHOCARDIOGRAPHY, Volume 20, May 2003)
Effects of conspecific and heterospecific competitors on feeding and oviposition of a predatory ladybird: a laboratory study
Authors: Agarwala B. K. , Bardhanroy P. , Yasuda H. , Takizawa T.
Published: December 2004

Abstract There are several examples of intraguild interactions among insect predators of aphids, but little is known regarding the effects of interactions on feeding and oviposition of individual competitors in a guild. In the laboratory, we determined the feeding and oviposition responses of a ladybird predator to its conspecific and heterospecific competitors in an aphidophagous guild. Gravid females of Menochilus sexmaculatus (Fabricius) (Coleoptera, Coccinellidae) reduced oviposition, but not feeding, when exposed to immobilised conspecific or Coccinella transversalis (Fabricius) (Coleoptera, Coccinellidae) individuals in the short‐term (3 h) and long‐term (24 h). Feeding and oviposition responses were not affected when M. sexmaculatus females were exposed to larvae or adults of Scymnus pyrocheilus Mulsant (Coleoptera, Coccinellidae) beetles or larvae of the syrphid fly Ischiodon scutellaris (Fabricius) (Diptera: Syrphidae). The ratio of eggs laid to numbers of aphids consumed by M. sexmaculatus females was also affected by the presence of conspecific or C. transversalis larvae. The results suggest that fecundity of this predator may be affected by both conspecific and heterospecific competitors in a patchy resource.
Conspecific thistle plant selection by a herbivorous ladybird beetle, Epilachna pustulosa
Authors: Fujiyama Naoyuki , Koizumi Tatsuya , Katakura Haruo
Published: December 2004

Host selection by Epilachna pustulosa Kôno (Coleoptera: Coccinellidae) was surveyed in an area of about 130 ares, focusing on the role of the spatial distribution pattern of the host plant, thistle Cirsium kamtschaticum Ledeb. (Asteraceae) and the environmental conditions of habitats where thistle plants were growing. A total of 198 thistle clones were found in the area studied, and approximately 40% showed some degree of E. pustulosa infestation by July. Eggs were only oviposited on thistle clones that were fed on by adults. Adult beetles and egg masses of E. pustulosa showed an aggregated distribution in the earlier season (June) among thistle clones. The distribution of adults became more random (but still aggregated) by the later season (July), along with an increase in the number of infested clones. Multiple logistic regression analyses revealed that clone size and soil moisture were consistently important for the beetle's choice of clones to feed on. The other logistic regression analyses indicated that thistle‐clone size and sunlight condition influenced egg distribution. Thistle clone selection by E. pustulosa changed with season from a rather strict selection in June to a more obscure one in July, expanding the range of thistle clones used as feeding and oviposition substrate.
Spatial organisation of European eel (Anguilla anguilla L.) in a small catchment
Authors: Laffaille P , Feunteun E , Baisez A , Robinet T , Acou A , Legault A , Lek S
Published: December 2004

Abstract –  Modelling‐governing patterns of European eel (Anguilla anguilla L.) distribution of four eel size classes (<150, 150–300, 300–450 and >450 mm) in the Frémur basin (northwest France) was done using artificial neural network (ANN) techniques and ecological profiles. Our results demonstrate the high predictive power of the ANN models. Some macro‐ and microscale factors, such as distance from the sea, depth and flow velocity, have the most significant influence on the models. Influence of distance from the sea appears to be very different from the spatial organisation usually described in river systems. In fact, the general tendencies of total eel densities according to the distance from the sea showed that densities increase weakly upstream. Another outcome was the variations in habitat preference according to the eel size, even if this species is spread over practically every type of microhabitat. Small eels were mainly found in shallow habitats with strong abundance of aquatic vegetation, whereas large eels tend to be found in intermediate to high depth with small to intermediate abundance of aquatic vegetation. Finally, we hypothesise that European eels change behaviour and microhabitat characteristic preference around a size of 300 mm.
Intentional replantation – a ‘last resort’ treatment or a conventional treatment procedure? Nine case reports
Authors: Peer Michael
Published: December 2004

Abstract –  Intentional replantation is an accepted endodontic treatment procedure in which a tooth is extracted and treated outside the oral cavity and then inserted into its socket to correct an obvious radiographic or clinical endodontic failure. This article reviews nine cases of intentional replantation (IR) that show the feasibility of the procedure in a variety of indications. Only one case of replantation showed evidence of pathosis that reflected root resorption or ankylosis. This report suggests that IR is a reliable and predictable procedure and should be more often considered as a treatment modality in our efforts to maintain the natural dentition.
Evaluation of pulpal blood flow after tooth splinting of luxated permanent maxillary incisors
Authors: Strobl Heinrich , Haas Markus , Norer Burghard , Gerhard Stefan , Emshoff Rüdiger
Published: December 2004

Abstract –  Laser Doppler flowmetry (LDF) is a non‐invasive method to assess pulpal blood flow (PBF). Dental injury has been associated with losses of pulpal sensibility. The purpose of this study was to assess whether LDF could be used to detect short‐ and long‐term changes of PBF values of luxated permanent maxillary central incisors after repositioning and splinting. In 18 trauma patients, a single maxillary incisor treated by repositioning and splinting, and the respective contralateral homologous tooth were investigated by LDF to assess local PBF values. Perfusion units (PU) were taken in four sessions: on the day of splint removal, and 12, 24, and 36 weeks after splint removal. Analysis of the luxation type‐related PBF measurements revealed intrusion type‐related PBF values to be associated with a significant decrease in PBF values (P < 0.05), while lateral luxation and extrusion type‐related PBF values showed no significant difference between the session‐related values (P > 0.05). PBF measurements did not change over time for the contralateral incisors (P > 0.05). Teeth affected by an intrusion‐type luxation injury remained unresponsive to sensitivity testing at follow up, while 3 (60%) developed grey discoloration of the crown. LDF may become useful in the detection of ischemic episodes of luxated maxillary central incisors after repositioning and splinting. Further studies are warranted to assess the validity of post‐traumatic ‘ischemic episodes’ by comparing it to histological tooth pulp changes.
Some Stable Hydromagnetic Equilibria
Authors: Johnson J. L. , Oberman C. R. , Kulsrud R. M. , Frieman E. A.
Published: December 2004

Hydromagnetic equilibria are obtained for a variety of situations which differ little from that of a zero pressure uniform axial magnetic field. Criteria for ascertaining the stability of these equilibria are found by means of an energy principle. In particular, if helically invariant fields are present, stable equilibria with nonzero pressure and net axial current can be found.
Generation and Thermalization of Plasma Waves
Authors: Stix Thomas H.
Published: December 2004

Generation of hydromagnetic and ion cyclotron waves by an induction coil is considered for a cylindrical plasma in a uniform confining magnetic field. Resonance widths are calculated and power absorption is calculated and compared to ohmic losses in the induction coil. Rapid thermalization of transverse plasma waves occurs when appreciable numbers of ions stream through the periodic perturbation with velocities such that, in their own rest frames, these ions ``feel'' the perturbation at their own cyclotron frequency. This effect, termed cyclotron damping, makes possible an efficient plasma heating scheme for thermonuclear reactors. Radio-frequency power can be transferred from an induction coil into ion cyclotron waves with an efficiency typically greater than 65%. The wave energy can be quickly transformed into energy of effectively random transverse ion motion by causing the ion cyclotron wave to travel along a magnetic field which decreases slowly with distance.
Dissipation of Energy due to Solid Particles Suspended in a Viscous Liquid
Authors: Brenner Howard
Published: December 2004

A general method is developed for calculating the additional mechanical energy dissipation incurred by the presence of solid particles suspended in an incompressible viscous fluid in laminar flow. The development is applicable to flow in any apparatus within which the steady motion of a homogeneous fluid can be described by omitting the inertial terms in the Navier-Stokes equations or in which the motion occurs in concentric circles. The validity of the results obtained is limited to situations in which the particle dimensions are small compared to those of the apparatus in which the motion is occurring.

The technique, based largely upon a reciprocal theorem for the inertialess flow of viscous fluids, is employed to calculate the permanent pressure drop accompanying the passage of liquid through a bed of fluidized solids. When the particles are uniformly distributed throughout the bed, this pressure diminution is equal to the bed weight (corrected for buoyancy) per unit area of duct—in agreement with experimental data on systems in a state of particulate fluidization. Calculations are also presented for the permanent pressure arising from the passage of fluid past an immobilized spherical particle within a cylindrical duct.

Einstein's formula for the apparent viscosity of a dilute suspension of spherical particles is also deduced. By means of a new definition of suspension viscosity the heretofore different points of view advanced by Einstein, Jeffery, and Burgers are seen to be consistent with one another. Einstein's result is shown to be independent of the type of viscometer employed provided that the motion of a homogeneous fluid within the device fulfills the previous criteria.

In the case of nonspherical particles it is demonstrated that the constant in Einstein's viscosity equation (which has a value of 2.5 for spheres) can never be less than unity, whatever the shape of the rigid particles or their orientation with respect to the axes of the apparatus.
Optical Refractivity of High-Temperature Gases. II. Effects Resulting from Ionization of Monatomic Gases
Authors: Alpher Ralph A. , White Donald R.
Published: December 2004

This paper describes shock-tube studies of the optical index of refraction of ionized argon in which observed optical effects have been related to the ionization of the shocked argon. The plasma dispersion formula has been applied to the measured refractivities to determine values of equilibrium electron concentrations on the order of 1017 cm−3. Good agreement is found between experimental and calculated values of the degree of ionization. The ionization relaxation process is strikingly portrayed in the interferograms and may be studied in some detail. Some questions concerning proposed kinetics for the relaxation behind strong shock waves in monatomic gases are discussed.
On the Second Virial Coefficient
Authors: Goldberger M. L.
Published: December 2004

The second virial coefficient is calculated by a new method which exploits certain results known from formal scattering theory. In particular it is shown that the essential quantity may be expressed as the determinant of the S matrix at a given energy. The present approach suggests several approximation techniques and also seems applicable to many-body problems.
Two-Dimensional Gaseous Detonations: Velocity Deficit
Authors: Fay James A.
Published: December 2004

The measured velocity of gaseous detonation waves is less than that predicted by the Chapman-Jouguet plane wave theory. The velocity deficit (difference between theoretical and measured velocities) has been found earlier to vary inversely with the tube diameter and initial pressure. A quantitative explanation of this effect is advanced by determining the growth of the viscous boundary layer on the tube wall and its effect upon the flow in the reaction zone of the detonation front. It is proposed that the boundary layer displacement effect within the reaction zone produces a uniform flow divergence throughout the detonation front. The velocity deficit due to this two-dimensional flow is determined, using measured values of reaction zone thickness. The agreement of the velocity deficit with measured values is within a factor of two for the five hydrogen-oxygen-inert gas mixtures and one acetylene-oxygen mixture for which sufficient data are available.
Theory of the Flow in the Magnetic Annular Shock Tube
Authors: Kemp Nelson H. , Petschek Harry E.
Published: December 2004

The magnetic annular shock tube uses a magnetic field to drive a shock wave through an annular region, producing a very high-temperature plasma [cf. R. M. Patrick, Phys. Fluids 2, 589 (1959)]. It is shown that this particular configuration allows a fairly precise calculation of the flow parameters. Numerical calculations of the significant flow properties for a complete range of the initial field strength and orientation have been made and are presented graphically.
Test Particles in a Completely Ionized Plasma
Authors: Rostoker Norman , Rosenbluth M. N.
Published: December 2004

Starting from the Liouville equation, a chain of equations is obtained by integrating out the coordinates of all but one, two, etc., particles. One ``test'' particle is singled out initially. All other ``field'' particles are assumed to be initially in thermal equilibrium. In the absence of external fields, the chain of equations is solved by expanding in terms of the parameter g = 1/nLD3. For the time evolution of the distribution function of the test particle, an equation is obtained whose asymptotic form is of the usual Fokker-Planck type. It is characterized by a frictional-drag force that decelerates the particle, and a fluctuation tensor that produces acceleration and diffusion in velocity space. The expressions for these quantities contain contributions from Coulomb collisions and the emission and absorption of plasma waves. By consideration of a Maxwell distribution of test particles, the total plasma-wave emission is determined. It is related to Landau's damping by Kirchoff's law. When there is a constant external magnetic field, the problem is characterized by the parameter g, and also the parameter λ = ωc/ωp. The calculation is made by expanding in terms of g, but all orders of λ are retained. To the lowest order in g, the frictional drag and fluctuation tensor are slowly varying functions of λ.

When λ ≪ 1, the modification of the collisional-drag force due to the magnetic field, is negligible. There is a significant change in the properties of plasma waves of wavelength greater than the Larmor radius which modifies the force due to plasma-wave emission. When λ ≫ 1, the force due to plasma-wave emission disappears. The collisional force is altered to the extent that the maximum impact parameter is sometimes the Larmor radius instead of the Debye length, or something in between. In the case of a slow ion moving perpendicular to the field, the collisional force is of a qualitatively different form. In addition to the drag force antiparallel to the velocity of the particle, there is a collisional force antiparallel to the Lorentz force. The force arises because the particle and its shield cloud are spiralling about field lines. The force on the particle is equal and opposite to the centripetal force acting on the ``shield cloud.'' It is much smaller than the Lorentz force.
Remark on Dilute Bose Systems
Authors: Peretti J.
Published: December 2004

Some results are given on the connection existing between the Lee-Huang-Yang theory for the interacting Bose systems, and the Bogoliubov theory.
Flow and Stress Near an Interface between Stratified Liquids
Authors: Lofquist Karl
Published: December 2004

Observations are made of a density current system in which salt water flows turbulently under a pool of fresh water. The density and rate of flow of the salt water are varied, resulting in varying degrees of agitation of the interface. Measurements include the interface slope, the velocity and density profiles, and the rate of mixing. Profiles of stress and effective viscosity are developed from the observations and the equation of motion. In the zone of stable stratification the effective viscosity has a minimum equal to or greater than the molecular viscosity depending upon whether the interface is laminar or agitated. Dimensionless relationships between the observed or computed quantities and the given fluid properties and flow characteristics are investigated. The principal independent variables are a Reynolds number and a Froude number. An interfacial stress coefficient is found to depend upon both. With fair accuracy, the velocity profile can be related to the interfacial stress in a manner analogous to that for turbulent flow near a rigid boundary.
Entropy Production and Pressure Waves
Authors: Rosen Gerald
Published: December 2004

Neglecting thermal conduction and viscous dissipation, the velocity-free equations of one-dimensional flow are derived with the inclusion of general fluid thermodynamics. The strength of finite amplitude pressure waves is introduced into the theory. This quantity is conserved if the entropy of each fluid particle remains constant with time. The growth or decay of the strength is examined for a perfect gas which produces entropy.
Shock Hugoniots for Liquid Argon
Authors: Fickett W. , Wood W. W.
Published: December 2004

Shock Hugoniots for liquid argon are calculated using equations-of-state obtained from the Monte Carlo method and the Lennard-Jones-Devonshire cell theory, using an experimentally determined pair potential. Agreement with presently available experimental data is poor.
Propagation of Flames Supported by a Zeroeth-Order Chemical Reaction
Authors: Hirschfelder Joseph O. , Van Domelen Sarah S.
Published: December 2004

Flames supported by zeroeth-order chemical reactions have two very useful unique properties. Their characteristics are independent of diffusion, and the chemical reactions are completed at a finite point in space. These properties should make zeroeth-order flames ideally suited to serve as ``global'' reactions for complicated flame systems involving either three-dimensional geometry or time-dependent phenomena. Extensive tables are given for the properties of steady-state one-dimensional zeroeth-order flames. Good agreement with the numerical calculations is obtained by using a simple approximation (based upon the Adams and Wilde approach) which results in simple closed-form expressions for the flame variables.
Coherent and Incoherent Radiation from a Plasma
Authors: Harris E. G. , Simon Albert
Published: December 2004

The Vlasov equations have been derived previously by Harris by starting from the Liouville equation and treating both plasma particles and electromagnetic field statistically. A byproduct of this derivation was an equation for fλ(qλ,pλ), the probability density in the phase space of one of the radiation field oscillators. These functions are now used to define an entropy for the electromagnetic field. If the phases and amplitudes of all electromagnetic waves are precisely defined (coherent radiation), the field entropy is negatively infinite. Any incoherence increases the entropy. A direct consequence of the fλ equation is that the field entropy is a constant of the motion. This is analogous to Newcomb's proof that the particle entropy is constant. It follows that incoherent radiation cannot be calculated from the Vlasov equations.
Nonequilibrium Distribution Functions in a Fluid
Authors: Lebowitz J. L. , Frisch H. L. , Helfand E.
Published: December 2004

The behavior of a nonequilibrium fluid is analyzed on a level intermediate between that of hydrodynamics, where microstructure is totally ignored, and a phase space description, where the complete N-body problem must be solved. The study of the fluid at this level generally involves solving an appropriate transport equation. For liquids, the primary subject of this investigation, the Fokker-Planck equation of Kirkwood is accepted as a working model and solutions are found by the methods of Chapman and Enskog and of Grad to terms linear in deviations from local equilibrium. (It is argued, however, for a different form of the pair space force than that suggested by Kirkwood and co-workers.) The results are similar in form to distributions found with other kinetic models. Variational principles are also considered. It is shown that the one- and two- particle distribution functions have the property of maximizing the entropy subject to the constraints of given densities and fluxes. Alternatively, these distributions maximize the entropy plus entropy productions in appropriate characteristic times. These variational principles do not depend on the use of the Fokker-Planck equation but appear to possess general validity.
Molecular Distribution Functions Involving Two Times
Authors: Vineyard George H.
Published: December 2004

A kinetic theory of distribution functions for the condition of subsets of molecules in a classical fluid at two distinct times is developed. The treatment is a natural generalization of the kinetic theories of Yvon, Kirkwood, and Born and Green, and leads to differentio-integral equations linking distributions for q molecules and distributions for q + 1 molecules. A generalization of the usual superposition approximation is suggested to truncate this infinite system of equations. Symmetries and other simple properties of the two-time distribution functions are explored, and it is shown that the pair correlation that determines inelastic scattering is a reduced form of the two-body positional distribution function. Explicit distributions are not calculated.
Virial Coefficients and Intermolecular Forces of Hydrocarbons
Authors: Connolly J. F. , Kandalic G. A.
Published: December 2004

The second virial coefficient of the gaseous equation of state is not very sensitive to molecular shape. Therefore, its temperature dependence is not usually a good criterion for distinguishing between intermolecular potentials. However, if the molecules are highly asymmetric and if the temperature range is broad, the effect of asymmetry should become apparent. By measuring 2nd virial coefficients of benzene and n-octane at high temperatures, and combining these results with low temperature values from the literature, the Kihara potential is shown to be superior to that of Lennard-Jones, for nonspherical molecules. The Kihara potential is also applied to the normal paraffins from propane through heptane.
Loss of Charged Particles in a Stellarator During Ohmic Heating
Authors: Ellis R. A. , Goldberg L. P. , Gorman J. G.
Published: December 2004

The average charged particle confinement times τ0 in hydrogen and deuterium plasmas during Ohmic heating in the B-3 stellarator have been determined. The observed values of τ0 are approximately proportional to the square root of the magnetic confining field and were less than the values expected on the basis of classical collisional diffusion. The low values of τ0 persisted when the system was, in theory, made hydromagnetically stable by the addition of helical stabilizing winding. It is inferred that the observed low confinement times are not due to a known hydromagnetic instability.
Intermolecular Forces from Diffusion and Thermal Diffusion Measurements
Authors: Weissman S. , Saxena S. C. , Mason E. A.
Published: December 2004

Experimental values of the diffusion coefficient and the thermal diffusion factor for the systems He–Ar, He–CO2, and H2–CO2, over a temperature range of about −78° to 325°C, are analyzed for the purpose of testing the Lennard-Jones (12−6) and the exp-6 intermolecular potentials, as well as the combination rules usually used in conjunction with these potentials. The exp-6 potential gives excellent results for He–Ar, but the 12−6 potential is not satisfactory. This system affords no opportunity to choose between the various combination rules. The 12−6 potential works fairly well for He–CO2 and H2CO2. On the whole, the combination rules are surprisingly good, being no worse than the potentials themselves. The importance of considering the higher theoretical approximations for the thermal diffusion factor is emphasized. An expression interrelating the transport properties and independent of any particular intermolecular potential is proposed, which can be used to test how well a mixture conforms to the basic assumptions of the Chapman-Enskog theory or to indicate the consistency of the experimental measurements.
Turbulence Theory and Functional Integration. II.
Authors: Rosen Gerald
Published: December 2004

Proofs are given which show that the integral representations for the Navier-Stokes spatial correlation functions satisfy the reality conditions, the continuity conditions, and the Navier-Stokes condition. With the aid of the integral representations for the correlation functions an analysis of the decay of homogeneous turbulence is developed. For the initial period of decay the theory predicts the empirical law u2 α ν(t″ − t′)−1, as well as a universal and shape-preserving two-point correlation tensor.
Optical Study of Boundary-Layer Transition Processes in a Supersonic Air Stream
Authors: Spangenberg W. G. , Rowland W. R.
Published: December 2004

A sequential-spark schlieren system with cylindrical-lens camera was used to trace the history of transition from laminar to turbulent flow on a cylindrical model in a Mach number 1.96 air stream. Both smooth and rough models were tested at several Reynolds numbers per unit length. The results showed that transition in a supersonic stream starts with high-frequency disturbances in the laminar boundary layer which degenerate into areas of turbulent flow. These spots erupt independently near the trailing face of the turbulent-flow region which is always moving downstream. The addition of the newly turbulent areas of finite size to the trailing face of the turbulent-flow region causes it to jump upstream discontinuously. Spots are traveling at a very low velocity when they first become visible and accelerate to continue downstream at a velocity of about 0.7 times free-stream speed at their trailing face. The origin of the fresh areas of breakdown to turbulence is apparently in amplified Tollmien-Schlichting waves. The frequency of spot production lies within the region where stability theory predicts that disturbances within the boundary layer will be amplified. It is concluded that transition mechanisms in supersonic flow are similar to those in a subsonic air stream.
Plasma Injection into a Magnetic Field of Cusped Geometry
Authors: Coensgen F. H. , Sherman A. E. , Nexsen W. E. , Cummins W. F.
Published: December 2004

A plasma stream was directed from a field-free region along the axis of symmetry into a magnetic field of biconical cusped geometry. No evidence was found to support the hypothesis that a directed plasma stream can not penetrate a magnetic field whose value exceeds Bc2 = 12πρv2, where ρ is the plasma density and v its directed velocity. As the plasma penetrated the magnetic field, the plasma and field were found to intermix. Large quantities of the plasma which entered the containment region through one point cusp were found to leave promptly through the second point cusp and through the line cusp. Bombardment of the vacuum chamber walls in the vicinity of the line cusp generated sufficient secondary ions to mask any small scale plasma trapping. However, there was no evidence of gross trapping of the injected plasma.
Some Variational Theorems for Non-Newtonian Flow
Authors: Johnson M. W.
Published: December 2004

A new variational theorem is formulated which has as its Euler equations and natural boundary conditions all of the differential equations and boundary conditions of the boundary value problem under consideration. Other variational theorems, including the classical theorems of Helmholtz, follow from this fundamental theorem. Conditions under which the theorems obtained are minimum or maximum principles are discussed and application to non-Newtonian flow in a tube is made.
Solutions of Concentration-Dependent Diffusion Equation
Authors: Paul Ranjit
Published: December 2004

The concentration of a gas in a chamber of Ney and Armistead type, as a function of time, has been calculated for two simple cases of concentration dependence of the diffusion coefficient viz., (i) D = D0(1 + αc), and (ii) D = D0[1 + αc/(1 + c)]. The correction due to the nonattainment of a quasi-stationary state has also been calculated.
Screw Instability of a Plasma Column
Authors: Hoh F. C.
Published: December 2004

It is known that the positive column is unstable in a strong longitudinal magnetic field. The correct explanation of this phenomenon has been given by Kadomtsev and Nedospasov. However, the instability mechanism is not fully interpreted in their work. In this contribution, the main features of Kadomtsev and Nedospasov's stability criterion are derived from simple physical arguments, and the mechanism responsible for instability is thus shown in a quantitative way. In particular, the perturbed radial potential distribution can be related to the perturbed density distribution, and hence need not be assumed. It turns out that this screw instability is a new and important type of instability hitherto not considered. The instability mechanism is not very sensitive to the degree of ionization, and hence may also be expected to be operative in highly ionized plasma columns. Possible connections with the instabilities observed in the Stellarator and the Zeta machine are discussed. An attempt is also made to explain regular oscillations observed in a toroidal discharge in terms of the present theory.
Kinetic-Theory Description of Conductive Heat Transfer from a Fine Wire
Authors: Lees Lester , Liu Chung-Yen
Published: December 2004

The Maxwell moment method utilizing the two-sided Maxwellian distribution function is applied to the problem of conductive heat transfer between two concentric cylinders at rest. Analytical solutions are obtained for small temperature differences between the cylinders. The predicted heat transfer agrees very well with experiments performed on the heat loss from a fine wire by Bomelburg and Schäfer, Rating, and Eucken. Comparison with results given by Grad's thirteen-moment equations, and with those given by Fourier's ``law'' plus the Maxwell—Smoluchowski temperature-jump boundary condition, shows that the two-sided character of the distribution function is a crucial factor in problems involving surface curvature.
Stability of Step Shocks
Authors: Erpenbeck Jerome J.
Published: December 2004

The hydrodynamic stability of a steady, plane, step shock through a fluid medium with arbitrary equation of state is investigated through consideration of the initial-value problem for the time-dependent hydrodynamic equations, linearized in perturbations from the steady flow. If the stability function, Fs = 1 + κ - κ2(v1 - v) pS/T (with κ the Mach number, v the specific volume, T the absolute temperature, pS the entropy derivative of pressure at constant volume, and subscript 1 referring to the preshock state) is negative, disturbances grow exponentially with time and the shock is unstable. The character of the shock Hugoniot with respect to stability is discussed.
Laminar Hydromagnetic Flow in an Annulus with Porous Walls
Authors: Jain R. K. , Mehta K. N.
Published: December 2004

The exact solution in a closed form of the hydromagnetic equations for an incompressible, viscous, and electrically conducting fluid flow through an annulus with porous walls in the presence of a radial transverse magnetic field is obtained. The solution is reduced to a simpler form with the use of the plausible condition v/vH ≪ 1 which holds for most of the fluids used in hydromagnetic experiments. The pressure distribution is discussed for this form of the solution. The problem is also extended to include parallel Couette flow.
Second Virial Coefficient of Polar Gases
Authors: Saxena S. C. , Joshi K. M.
Published: December 2004

The theoretical expressions for the second virial coefficient, B(T), are derived for the (18–6-3) Stockmayer potential Φ(r)=4ε[(σr)18−(σr)6]−μ2r3g(θ1,θ2,φ),where g(θ1, θ2, φ) = 2 cos θ1 cos θ2 − sin θ1 sin θ2 cos φ, and also according to the (28–7-3) potential. Tables of the reduced virial coefficient are given as a function of the reduced temperature for the (18–6-3) potential, and experimental B(T) data are interpreted for a number of gases. The potential parameters are reasonable and reproduce the B(T) data within the limits of experimental errors. The point dipole polarizable model is also considered.
Interaction between a Radio Wave and a High-Temperature Plasma
Authors: Koga Toyoki
Published: December 2004

The effect of the temperature of a fully ionized plasma on its conductivity to a radio wave is investigated, taking into consideration the finite wavelength of the radio wave. The order of the effect is kT/(ma2), where T is the temperature of the gas, m the mass of an electron, k the Boltzmann constant, a the phase velocity of the wave. The relativistic effect is not considered.
Correspondence between Normal-Shock and Blunt-Body Flows
Authors: Gibson W. E. , Marrone P. V.
Published: December 2004

An approximate solution for coupled, nonequilibrium chemistry along streamlines of inviscid, blunt-body airflows is described. The solution is derived from a correspondence between the chemical relaxation zone along a streamline and that behind a normal shock. This correspondence applies in general for Newtonian flows with binary kinetics. Along the stagnation streamline, binary kinetics are not required. The approximate solution is compared with exact numerical solutions of the blunt-body problem and is found to be accurate for the high enthalpies corresponding to hypersonic flight.
Perturbed One-Dimensional Unsteady Flows Including Transverse Magnetic-Field Effects
Authors: Mirels Harold , Braun Willis H.
Published: December 2004

The effect of small unsteady mass, momentum, and heat addition in a uniform (or piecewise uniform) basic flow is discussed. A general solution is given. A method for obtaining closed-form solutions, in cases where the disturbed flow is self-similar, is also presented. These solutions are applied to find the interaction between a flow, due to a piston starting impulsively from rest, and a transverse magnetic field. It is assumed that Rm « 1 and RmRh « 1, where Rm and Rh are the flow magnetic Reynolds and pressure numbers, respectively. The electrical potential is assumed to be uniform in the channel. Both a narrow (in the streamwise direction) intense magnetic field and a wide, less intense, field are treated. In the latter case it is found that the shock, generated by the motion of the piston, is decelerated by the magnetic field when the shock Mach number Ms is near 1 but is accelerated by the magnetic field when Ms is high. This behavior is due to the electromagnetic body forces dominating at Ms near 1 and the Joule heating dominating at large Ms. These numerical results also apply to the hot-gas region of a shock tube employing strong shocks.
Heat and Mass Transfer from Single Spheres in Stokes Flow
Authors: Acrivos Andreas , Taylor Thomas D.
Published: December 2004

The classical problem of heat and mass transfer from single spheres at low values of the Reynolds number, where the velocity field is given by Stokes' formula, is considered. It is shown, by the use of a singular perturbation technique, how an expansion may be derived for the Nusselt number Nu in terms of the Péclet number Pe which yields an accurate expression for the rate of transfer of energy or matter in the range 0 ≦ Pe ≦ 1. It is also established, by studying both the Pe → 0 and Pe → ∞ asymptotes, that the functional relation between Nu and Pe as obtained with the Stokes velocity profile is less sensitive to an increase in the Reynolds number than the familiar Stokes law for the drag coefficient.
Nonlinearized Theory of Transverse Plasma Oscillations
Authors: Enoch Jacob
Published: December 2004

Exact, nonlinearized, solutions of the Vlasov equation for a homogeneous, neutral plasma with infinitely heavy ions in the presence of transverse electromagnetic waves are found. The dispersion relation is developed both for stationary waves and for the general initial value problem. For stationary waves the result is analogous to that obtained by Van Kampen in his linearized treatment of the longitudinal plasma oscillations. The initial-value problem approach yields results similar to those of Landau but, for nonrelativistic plasmas, damping exists only for phase velocities much smaller than the velocity of light. It is proved that no growing-wave solutions exist. A distribution function which is consistent with a single-wave-packet solution of the wave equation, and which propagates subject to an arbitrary root of the dispersion relation, is constructed. The intimate relationship between the initial electron distribution function and the dispersion relation is discussed.
High-Frequency Conductivity and the Emission and Absorption Coefficients of a Fully Ionized Plasma
Authors: Dawson John , Oberman Carl
Published: December 2004

The problem of the ac conductivity of a fully ionized plasma is investigated for frequencies embracing the plasma frequency. The finite duration of encounters is taken into account in a self-consistent fashion which includes collective effects. The concomitant processes of absorption and emission of electromagnetic radiation are investigated and in particular the bremsstrahlung emission and absorption coefficients near the plasma frequency are given. The conversion of longitudinal to transverse waves by scattering from ions is discussed.
Heat Transfer to Cold Electrodes in a Flowing Ionized Gas
Authors: Fay J. A. , Hogan W. T.
Published: December 2004

A slightly ionized gas was formed in the wake of a detonation wave in a shock tube by seeding with a potassium salt. Wire electrodes were placed with axes normal to the shock-tube axis and separated by a variable distance along the tube axis. The heating of each electrode was measured by determining the rate of change of electrical resistance of the electrode. Electrode heating in excess of that due to aerodynamic heat transfer was only observable in the range of 102 to 103 A/cm2 and was found to be proportional to the current. The excess heating rate divided by the total current was measured to be 4.9 V for the anode and 3.2 V for the cathode. By varying the spacing of the electrodes, it was found that the gas resistance could be accounted for by the geometric effects alone in combination with the gas conductivity as measured by Basu for this mixture.
Pressure Analysis of Conduction in Liquids
Authors: Stuetzer Otmar M.
Published: December 2004

Manometric measurements of the electrohydrostatic pressure distribution in dielectric liquids permit determination of space charge and field distribution, and of carrier generation rate.
Nonlinear Effects from Vlasov's Equation
Authors: Engelmann F. , Feix M. , Minardi E. , Oxenius J.
Published: December 2004

Nonlinear effects from Vlasov's equation are studied for a one-dimensional electron gas with fixed neutralizing background. The electron distribution function is expanded in Hermite polynomials and a closure condition is introduced to cut off the resulting infinite system of differential equations for the expansion coefficients. Then a nonlinear partial differential equation can be derived for the electric field. The consequences of some different closure conditions are studied. It turns out that their use implies severe restrictions on the physical situations described. In the discussed closed polynomial approximations no nonlinear instabilities are found. In particular, it results that with vanishing heat flux one has only stable linear or nonlinear oscillations showing that unstable situations are necessarily nonadiabatic. In an analogous manner, the condition that the plasma follows a state law with pressure proportional to density, like a perfect gas, eliminates unstable modes.
Stability of Liquid Flow down an Inclined Plane
Authors: Yih Chia-Shun
Published: December 2004

The stability of a liquid layer flowing down an inclined plane is investigated. A new perturbation method is used to furnish information regarding stability of surface waves for three cases: the case of small wavenumbers, of small Reynolds numbers, and of large wavenumbers. The results for small wavenumbers agree with Benjamin's result obtained by the use of power series expansion, and the results for the two other cases are new. The results for large wavenumbers, zero surface tension, and vertical plate contradict the tentative assertion of Benjamin. The three cases are then re-examined for shear-wave stability, and the results compared with those for confined plane Poiseuille flow. The comparison serves to indicate the vestiges of shear waves in the free-surface flow, and to give a sense of unity in the understanding of the stability of both flows. The case of large wavenumbers also serves as a new example of the dual role of viscosity in stability phenomena.

The topological features of the ci curves for four cases (surface tension = 0 or ≠ 0 and angle of plate inclination = or <½π) are depicted. The effect of variability of surface tension is briefly assessed.
Plasma Resonance Interaction with a Spatially Rotating Static Magnetic Field
Authors: Karr H. , Knapp E. , Riesenfeld W.
Published: December 2004

The ion cyclotron resonance interaction of plasma with a rotating transverse magnetic perturbation on a longitudinal magnetic field is investigated experimentally and theoretically. The plasma is injected axially from a coaxial hydromagnetic gun along a longitudinal magnetic field on which there is superimposed a transverse spatially rotating perturbation field. A resonance transfer of ion energy from the longitudinal to the transverse direction is observed when the spatial period or wavelength of the perturbation field and the plasma velocity and ion cyclotron frequency satisfy the relation λz = 2πvz/ΩB. Measurements of plasma diamagnetism and transit time show an increase of up to a factor of two in diamagnetism coupled with a decrease in axial velocity corresponding to a reduction to half the initial longitudinal energy. Resonance may be observed over a range of longitudinal energies by varying the parameters of the system. For the plasma gun and perturbation field helix used in the experiment, optimum resonance was obtained with plasmas of longitudinal energy of ∼ 2.5 keV and particle densities of ∼ 1015cm−3(β ≳ 0.8). A theoretical account of the effect is given which considers the excitation by the perturbation field of circularly polarized electromagnetic waves in the plasma at ion cyclotron frequency and the transfer of longitudinal ion energy into transverse motion through the intermediate action of the waves.