bluuebunny/crossref_metadata_2025_split huggingface dataset:
Easy‐to‐clean Schichten – spezielle Anwendungen
Authors: Frick D. , Pulker H. K. 
Published: March 2006

AbstractEs kann festgehalten werden, dass auf Hohlnadeln aus Stahl transparente Nanokomposit‐Schichten auf den Innen‐ und Außenoberflächen der Nadeln oder teflonartige Fluorpolymer‐Schichten auf den Aussenoberflächen sowie eine Kombination einer Innenbeschichtung mit einem Nanokomposit‐System und einer Aussenbeschichtung mit Fluorpolymeren aufgebracht werden können.Diese Innovation bringt in der medizinischen Diagnostik und chemischen Analytik in Forschung und Laborpraxis wesentliche Vorteile: starke Reduzierung von Verschleppungen (carry‐over), Reinigung mit geringerem Verbrauch an Waschflüssigkeiten, die Schicht wirkt als Diffusionsbarriere gegen Ionen, die aus dem Metall austreten, es besteht eine wesentlich längere Gebrauchsdauer der Nadeln und ein höherer Durchsatz der Tests.Es ist geplant, nächstens auch bakterizid wirkende Ag+ abgebende Nano‐Silber‐Komposit‐Lackschichten als Überzüge für medizinische Geräte und andere keimfrei zu machende Gegenstände einzusetzen.
Energy recovery using vapour recompression
Authors: Bethge D. 
Published: March 2006

AbstractThe multiple‐effect principle can be used to reduce thermal energy requirements in thermal processes. According to this principle the energy is used several times over, according to the number of effects. Another possibility consists in increasing the pressure of the heat emitted by the process in the form of vapours to such a level so as to reuse it in the process. Jet pumps or mechanical recompressors, which are frequently operated in the rough vacuum range, are used for this purpose. This principle is explained in examples of thermal separation technology.
Species‐specific features affect the ability of census‐derived models to map winter avian distribution
Authors: Carrascal Luis M. , Seoane Javier , Palomino David , Alonso César L. , Lobo Jorge M. 
Published: March 2006

AbstractWe identify autoecological traits of bird species that influence the accuracy of predictive models of species distribution based on census data obtained from stratified sampling. These models would serve as a complementary approach to the development of regional bird atlases. We model the winter bird abundance of 64 terrestrial bird species in 77 census plots in Central Spain (Madrid province), using regression tree analyses. The predicted distribution of species density derived from statistical models (birds/10 ha) was compared with the published relative abundances depicted by a very accurate regional atlas of wintering birds (birds observed per 10 h). Statistical models explained an average of 41.7% of the original deviance observed in the local bird distribution (range 19.6–79.3%). Significant associations between observed relative abundances (atlas data) and predicted average densities in 1×1 km squares within 10×10 km UTMs were attained for 44 out of 64 species. Interspecific discrepancies between predicted and observed distribution maps decreased with between‐year constancy in regional bird distribution and the degree of ecological specialization of species. Therefore, statistical modeling using census localities allowed us to depict geographical variations in bird abundance that were similar to those in the quantitative atlas maps. Nevertheless, bird distributions derived from statistical models are less reproducible in some species than in others, depending on their autoecological traits.
Expression of the α7, α4 and α3 nicotinic receptor subtype in the brain and adrenal medulla of transgenic mice carrying genes coding for human AChE and β‐amyloid
Authors: Mousavi Malahat , Nordberg Agneta 
Published: March 2006

AbstractHuman AChE‐enzyme (hAChE) enhances the over‐expression of β‐amyloid (Aβ) containing plaques in the brain of transgenic mice (APPSWE/hAChE‐Tg) carrying mutated genes for human amyloid precursor protein (APPSWE) and hAChE. In this study, we showed that interaction of hAChE with Aβ affects the plasticity of the α7 nicotinic acetylcholine receptors (nAChRs) both in the brain and adrenal medulla. An age‐related increase in the 125I‐αbungarotoxin (125I‐αBTX) binding (specific to α7 nAChRs) was observed in the adrenal medulla of 3, 7 and 10 months old control mice. In contrast, a significant decrease in 125I‐αBTX binding was detected in the adrenal medulla of 10 months old APPSWE/hAChE‐Tg.A significantly higher α7 nAChR mRNA level was observed in the brain of APPSWE/hAChE‐Tg at 3 and 7 months of age and in the adrenal medulla at 3 and 10 months of age compared to those of the control mice. The α3 nAChR mRNA level was significantly higher in the brain of APPSWE/hAChE‐Tg at 3 months of age and in the adrenal medulla at 10 months of age. The α4 nAChR mRNA level remained unchanged in the brain and adrenal medulla of APPSWE/hAChE‐Tg for all age groups.Based on these observations, we conclude that a high load of Aβ and an over‐expression of hAChE induce differences in the expression of the nAChR subtypes at various ages in the brain and in the adrenal medulla of hAChE/APPSWETg mice. The findings may have implications for a better understanding the underlying mechanism for AD‐related pathogenesis.
Hypersonic weak-interaction solutions for flow past a very slender axisymmetric body
Authors: Cross Arthur K. , Bush William B. 
Published: March 2006

The Navier–Stokes hypersonic weak-interaction theory is presented for the flow of a viscous, heat-conducting, compressible fluid past a very slender axisymmetric body, when the ratio of the radius of the body to the radial thickness of the viscous region, produced and supported by the body, is much less than unity. The fluid is assumed to be a perfect gas having constant specific heats, a constant Prandtl number of order unity, and viscosity coefficients varying as a power of the absolute temperature. Solutions are studied for the free-stream Mach number, the free-stream Reynolds number based on the axial length of the body, and the reciprocal of the weak-interaction parameter much greater than unity.It is shown that, for the viscosity-temperature exponent ω less than 1, seven distinct layers span the region between the shock wave and the body, which is of arbitrary shape. The leading approximations for the behaviour of the flow in these seven layers are analyzed, and the restrictions imposed on the theory are obtained.
Non-linear wave propagation in a relaxing gas
Authors: Blythe P. A. 
Published: March 2006

An outline of the classical far-and near-field solutions for small-amplitude one-dimensional unsteady flows in a general inviscid relaxing gas is given. The structure of the complete flow field, including a non-linear near-frozen (high frequency) region at the front, is obtained by matching techniques when the relaxation time is ‘large’.If the energy in the relaxing mode is small compared with the total internal energy, the solution in the far field is, in general, more complex than that predicted by classical theory. In this case the rate process is not necessarily able to diffuse all convective steepening. An equation valid in this limit is derived and discussed. In particular, a sufficient condition for the flow to be shock-free is established. For an impulsively withdrawn piston it is shown that the solution is single-valued both within and downstream of the fan. Some useful similarity rules are pointed out.The corresponding formulation for two-dimensional steady flows is also noted in the small energy limit.
On the trapping of long-period waves round islands
Authors: Longuet-Higgins M. S. 
Published: March 2006

The trapping of short-period gravity waves by islands and seamounts has been studied by Chambers (1965) and by Longuet-Higgins (1967). It was shown by the latter that in the absence of rotation, or when the wave frequency σ is large compared with the Coriolis parameter f, these waves cannot be perfectly trapped; some energy must always leak away to infinity. Very long-period oscillations in the presence of a sloping shelf surrounding an island, with σ [Lt ] f, have been studied by Mysak (1967) and Rhines (1967, 1969). Here perfect trapping is possible. However, as pointed out in Longuet-Higgins (1968), the rotation itself exerts a strong trapping effect not only when |σ| [Lt ] f, but also whenever a |σ| < f. It seems not to have been noticed that this effect is capable of trapping waves round an island in an ocean of uniform depth, in the absence of any shelf or sloping region offshore.The existence of such waves is demonstrated for a circular island in § 1 of the present paper. It is shown that the waves exist only when the azimuthal wave-number n is at least 1. The waves always progress round the island in a clockwise sense in the northern hemisphere. At large distances r from the island, the wave amplitude decays exponentially, but this exponential trapping occurs only if the radius a of the island exceeds the critical value (n(n − 1)gh)½/f. When n = 1, this critical radius is zero, so that in theory the waves exist for any island of non-zero radius.The application of these results to the ocean is discussed in § 2. Except possibly for baroclinic motions, it appears that only the waves corresponding to n = 1 could exist in fact, and that their frequency would be nearly equal to the inertial frequency f. It is unlikely that f could be regarded as constant over a sufficiently wide area for the model to apply without qualification. Nevertheless, the oscillations may be regarded as the local adjustment of the pressure field to inertial currents in the neighbourhood of the island. It is possible that the peak at about 0·73 c.p.d. in the spectrum of sea-level at Oahu, as found by Miyata & Groves (1968), can be interpreted in this way.
Steady free convection above a point heat source and a horizontal line heat source in a vertical magnetic field
Authors: Soward A. M. 
Published: March 2006

An electrically conducting fluid is contained above a horizontal plane. A uniform vertical magnetic field is applied externally and the plane is maintained at a uniform temperature except for a point or a line heat source. Density variations are ignored except where they give rise to buoyancy forces.(i) The point heat source. Non-linear effects are small sufficiently far from the source. The resulting buoyancy forces interact with the magnetic forces to maintain a radial inflow towards the heat source. This fluid then escapes vertically as a jet, its structure now depending on the additional influence of viscosity. The perturbations of the temperature distribution and the magnetic field due to the motion are obtained. Finally, the effects of these perturbations back on to the fluid velocity are considered. The most striking features of the perturbations are (a) the action of the jet as a line source of heat for the fluid in the outer regions, (b) the large (compared to other perturbations) eddy in the jet.(ii) The line heat source. The temperature distribution and magnetic field are weakly perturbed only if the thermal and electrical conductivities are sufficiently small. Similar results are obtained, as in (i) above, provided ε (a dimensionless number characterising the strength of thermal convection: see (1.32), (3.24)) is less than ¼. However, even for small ε, the effects of thermal convection cannot be ignored. Hence, superimposed on the jet is an eddy (driven by buoyancy forces) whose flux of fluid increases indefinitely with its height above the plane. When ε > ¼, the results suggest that numerous eddies will be formed.
A transient flow problem in magnetohydrodynamics
Authors: Soward A. M. 
Published: March 2006

A flat plate x = 0, |y| < L is initially at rest in an electrically conducting, inviscid, incompressible fluid permeated by a uniform magnetic field (B0, 0, 0). The plate is impulsively accelerated to a small velocity (— U, 0, 0) which is then kept constant. It is assumed that LV/λ 1 and U/V [Lt ] 1, where V is the Alfven velocity, and λ is the magnetic diffusivity.Four stages in the development of the flow are distinguished, the last three being:
(ii) L [Lt ] Vt [Lt ] (λ)½. During this stage the initial potential flow is being disturbed by propagation of electric current and vorticity from the plate. The initial discontinuity on the plate has only propagated a small distance away compared to L, but a large distance compared to the length scale of diffusion (λt)½. Exact solutions to the flow are found in the neighbourhood of y = — L and y = 0 (x = 0).(iii) Vt [Lt ] L [Lt ] (λt)½. The asymptotic behaviour of the electric current and vorticity on the plate are determined showing that a column of fluid of length Vt moves with the plate, aligned to the magnetic field. The transverse diffusion of the current sheets bounding the column accelerates the fluid in layers of thickness O(λt)½.(iv) (λt)½ [Lt ] L. Unlike stages (ii) and (iii), where the motion is dominated by the propagation of vorticity and electric current as Alfven waves from the plate, diffusive mechanisms completely dominate the motion. ‘Slug’ flow is maintained. The nature of the flow, including the structure of the layers bounding the column are determined for |x| [Lt ] (λt)½.
The laminar flow of dilute polymer solutions around circular cylinders
Authors: James David F. , Acosta Allan J. 
Published: March 2006

This paper describes the measurements of heat transfer and drag for the flow of dilute polymer solutions around very small cylinders. The thermal experiments were carried out at Reynolds numbers less than 50, and the results establish the dependence of the heat transfer on fluid velocity, cylinder diameter, solution concentration, and polymer molecular weight. The drag measurements were conducted with the same type of solutions and in the same Reynolds-number range. To complement the heat-transfer and drag measurements, the flows around a cylinder and through an orifice were examined visually. These flow-visualization studies showed that the streamline pattern with dilute polymer solutions can be significantly different from that with Newtonian fluids because of viscoelastic effects.An analysis of Rouse's theory of macromolecules shows that for low accelerations a dilute polymer solution behaves mechanically like a Maxwell model. The analysis thereby produces a relaxation time, a single parameter representing the elasticity of the fluid, which can be related to the properties of the solute and solvent. This relaxation time is contained in a new dimensionless group which governs dynamic similarity when induced elastic stresses dominate viscous stresses in the flow around a circular cylinder. The dimensionless group is shown to correlate the thermal data when the heat transfer does not depend on the free stream velocity.
On edge effects in rheometry
Authors: Griffiths D. F. , Walters K. 
Published: March 2006

Consideration is given to the influence of edge effects on rheological measurements. To facilitate this, we discuss theoretically the flow generated by the slow steady rotation of a solid of revolution in an elastico-viscous liquid confined by convenient bath surfaces. The relevant linear partial differential equations are solved numerically. The simple problem of a rotating sphere and a concentric spherical container, for which an exact analytic solution is available, is first discussed to justify the method employed, and to indicate the necessary conditions to obtain a given accuracy. The numerical method is then applied to the case of a cone of finite dimensions rotating in a bath of elastico-viscous liquid. The predicted flow is shown to be in good agreement with experimental observations.Application of the theory to rheogoniometric situations indicates that edge effects are not likely to be as significant as has been conjectured in the past.
The constitutive equation for a dilute emulsion
Authors: Frankel N. A. , Acrivos Andreas 
Published: March 2006

A constitutive equation for dilute emulsions is developed by considering the deformations, assumed infinitesimal, of a small droplet freely suspended in a time-dependent shearing flow. This equation is non-linear in the kinematic variables and gives rise to ‘fluid memory’ effects attributable to the droplet surface dynamics. Furthermore, it has the same form as the corresponding expression for a dilute suspension of Hookean elastic spheres (Goddard & Miller 1967), and reduces to a relation previously proposed by Schowalter, Chaffey & Brenner (1968) when time-dependent effects become small.Numerical solutions are also presented for the case of a small bubble in a steady extensional flow for the purpose of estimating the range of validity of the small deformation analysis. It is shown that, unlike the drag of a bubble which, in creeping motion, is known to be relatively insensitive to its exact shape, the macroscopic stress field in an emulsion is not well described by the present analysis unless the shapes of the deformed bubbles agree closely with those given by the first-order theory. Thus, the present rheological equation should prove of value in a qualitative rather than a quantitative sense.
The diffraction of tides by a narrow channel
Authors: Buchwald V. T. 
Published: March 2006

A Green's function for a semi-infinite rotating ocean of uniform depth is obtained, and the resulting near and far fields are estimated asymptotically.Given a tide of uniform height at the mouth of a narrow channel on a semiinfinite ocean, the Green's function is used to calculate the diffracted Kelvin and Poincaré waves propagating up the channel and into the ocean.
Entry flow in a channel. Part 2
Authors: Wilson S. D. R. 
Published: March 2006

This paper complements an earlier paper by Van Dyke which has appeared under the same title. The problem of channel entry flow is re-examined and the early work is found to be formally incorrect. The techniques of modern boundary-layer theory are used to examine the region near the entrance. Various inlet conditions are considered and it is found that the usual condition of uniform entry velocity causes the intrusion of fractional powers of the Reynolds number into the expansions. The most satisfactory model is that of uniform flow into an infinite cascade of parallel plates.The non-uniformity of the expansions at large downstream distances was studied in Van Dyke's paper and is not dealt with here, except to show that it may be treated separately.
Turbulent air flow over the dominant component of wind-generated water waves
Authors: Chang P. C. , Plate E. J. , Hidy G. M. 
Published: March 2006

This paper presents a laboratory study of the dynamic properties of air flow over small wind-generated water waves. On the basis of measurements of mean velocity profiles, turbulent intensity profiles and energy spectra, the detailed structure of turbulent wind immediately above and between the crests of progressive water waves has been examined.The velocity sensor (a hot-wire anemometer) was fastened to a self-adjusting positioner to measure instantaneous air velocities at a fixed distance from a moving water surface. The waves had a dominant frequency, 2·4 Hz, and a ratio of wave celerity and air friction velocity close to one. With the aid of a digital computer, the desired parameters of air flow were obtained by a statistical technique which was developed to sample and average simultaneous recordings of water surface displacements and instantaneous air velocities.The results of the wind field measurements over representative waves indicate that, on the average, the air flow separates from the wavy water surface just behind crests, and reattaches somewhere on the windward face of the next wave. The measured turbulent quantities consistently show the characteristics of separated air flow. The separation phenomenon suggests that, without some modification, the Benjamin-Miles shearing flow mechanism is inapplicable to the growth of fully-developed small water waves, at least when the ratio of the phase speed to air friction velocity is of order unity. The observed flow configuration tends to support the separation mechanism of energy transfer originally outlined by Jeffreys and later explored further by Stewart and Deardorff.Mean properties of the turbulent air flow referred to the mean water level were obtained by continuous sampling of the air flow over many waves with a sensing probe, either at a fixed distance from the mean water level (fixed probe measurement) or at a constant distance from the moving water surface (moving probe measurement). It was found that for continuously averaged measurements, the fixed probe yielded results which deviate less from the local mean than the moving probe results. This holds for the mean velocity distributions and especially for the turbulent quantities.
The breakdown of electrical insulation in a plane layer of insulating fluid by electrocapillary instability
Authors: Michael D. H. , O'Neill M. E. , Zuercher J. C. 
Published: March 2006

A theoretical and experimental study is made of the failure of electrical insulation in a layer of dielectric fluid filling a circular hole in a horizontal solid dielectric sheet. A potential difference is applied between conducting fluids which bound the fluid and solid dielectric layer above and below. It is observed that a critical potential difference is reached at which the fluid dielectric becomes statically unstable under the action of surface tension and normal electrical stresses at its interfaces. When this potential is reached the dielectric fluid insulation fails.The critical potential difference is calculated by both an approximate and an exact theory. The approximate theory ignores the changes in the electrostatic field within the solid dielectric by allowing a charge distribution at the curved surface of the hole. Comparison with the results of an exact theory shows that such an approximation introduces only small errors in the calculated points of transition to instability.It is shown that failure may take the form of a symmetric (sausage) mode of displacement, or an antisymmetric (kink) mode, depending on whether the radius of the hole is greater or less than approximately the depth of the layer respectively. The two forms of failure were indicated in the experiments, and the observed critical voltages are in good agreement with those predicted by the theory.
On the initial-value problem in the kinetic theory of gases
Authors: Baum Howard R. 
Published: March 2006

The relaxation of an initially non-uniform gas to equilibrium is studied within the framework of the kinetic theory of gases. The macroscopic gas properties are taken to depend on one spatial dimension as well as the time. The amplitude of the non-uniformity is assumed to be small with a length scale large compared with the mean free path, and the Krook model of the Boltzmann collision integral is employed.By applying multi-time scale perturbation methods to this reduced problem, uniformly valid analytical solutions for the macroscopic velocity, density and temperature are obtained. The macroscopic equations appropriate to each stage of the relaxation process are obtained in a straightforward and unambiguous manner. The distribution function obtained is shown to be a re-expansion of the Chapman–Enskog solution of the Krook equation, with additional terms accounting for the relaxation of the initial conditions to a near equilibrium form. The results indicate that the uniformly valid frst approximation to the macroscopic velocity, density and temperature can be obtained from the Navier–Stokes equations, but that no purely macroscopic set of equations will suffice for the determination of higher approximations.