bluuebunny/crossref_metadata_2025 huggingface dataset:
Tumor necrosis factor–α contributes to below‐level neuropathic pain after spinal cord injury
Authors: Peng Xiang‐min , Zhou Zhi‐gang , Glorioso Joseph C. , Fink David J. , Mata Marina
Published: April 2006

Objective

Our objective was to elucidate the mechanisms responsible for below‐level pain after partial spinal cord injury (SCI).

Methods

We used lateral hemisection to model central neuropathic pain and herpes simplex viral (HSV) vector–mediated transfer of the cleaved soluble receptor for tumor necrosis factor–α (TNF‐α) to evaluate the role of TNF‐α in the pathogenesis of below‐level pain.

Results

We found activation of microglia and increased expression of TNF‐α below the level of the lesion in the lumbar spinal cord after T13 lateral hemisection that correlated with emergence of mechanical allodynia in the hind limbs of rats. Lumbar TNF‐α had an apparent molecular weight of 27kDa, consistent with the full‐length transmembrane form of the protein (mTNF‐α). Expression of the p55 TNF soluble receptor (sTNFRs) by HSV‐mediated gene transfer resulted in reduced pain behavior and a decreased number of ED1‐positive cells, as well as decreased phosphorylation of the p38 MAP kinase (p‐p38) and diminished expression of mTNF‐α in the dorsal horn.

Interpretation

These results suggest that expression of mTNF‐α after injury is related to development of pain, and that reverse signaling through mTNF‐α by sTNFR at that level reduces cellular markers of inflammatory response and pain‐related behavior. Ann Neurol 2006;59:843–851
Completing Latin squares: Critical sets II
Authors: Horak Peter , Dejter Italo J.
Published: April 2006

It is shown that each critical set in a Latin square of order n > 6 has to have at least $\left\lfloor {7n-\sqrt{n}-20}\over{2}\right\rfloor$ empty cells. © 2006 Wiley Periodicals, Inc. J Combin Designs 15: 77–83, 2007
Low‐temperature structural phase transitions in crystalline bromo and iodo 9‐hydroxyphenalenone derivatives: Quantum chemistry employment
Authors: Dolin S. P. , Khrulev A. A. , Polyakov E. V. , Mikhailova T. Yu. , Levin A. A.
Published: April 2006

The model approaches and quantum chemical calculations are employed to explain the peculiarities of the ferroelectric behavior of new “zero‐dimensional” H‐bonded materials, i.e., 5‐bromo and 5‐iodo derivatives of 9‐hydroxyphenalenone (9HPO) and its deuteroxy analogue (9DPO). The tunneling parameters Ω (H/D) and the Ising model coupling parameters Jij are evaluated and discussed. Analysis of these parameters for the hydroxy and deuteroxy species demonstrates the quantum paraelectric behavior of both Br and I 9HPO derivatives due to the large values of the Ω(H)/J0 relation, where J0 is the molecular field parameter describing the coupling of any given H‐bond proton with all rest ones. In contrast, small values Ω(D)/J0 for their 9DPO analogues favor the low‐temperature structural phase transition into an ordered phase, which has a rather antiferroelectric than ferroelectric character. The estimates obtained and the resulting conclusions are in line with the overall observed trends in behavior of the substances under examination that emerge from the available experimental data. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
The Effects of Retinoic Acid on the Insulin‐like Growth Factor Axis in Primary Tissue Culture from Hyperparathyroidism
Authors: Wong Chris K.M. , Lai Teresa , Holly Jeffrey M.P. , Wheeler Malcolm H. , Stewart Claire E.H. , Farndon John R.
Published: April 2006

Background

The importance of the IGF system in HPT has been previously demonstrated. Additionally, the role of vitamin A in HPT has been reported. Retinoic acid (RA), a derivative of vitamin A, is a ligand for the IGF II receptor (IGF2R). We have evaluated the interactions of RA with the IGF system in a primary parathyroid cell culture model.

Materials and Methods

Primary cell cultures were prepared from nine patients. Following adhesion, the cells were transferred to serum‐free medium and dosed once with growth factors ± RA for 96 hours. Proliferation was assessed by measuring tritiated thymidine incorporation.

Results

Compared with the control group (100%), both IGF I and II increased DNA synthesis significantly. Retinoic acid significantly reduced the basal DNA synthesis to 82.2% ± 4.2% compared with control (P < 0.05). Retinoic acid ×10−5 M completely abrogated the proliferative actions of IGF II (70.2% ± 9.7%, P < 0.05) but had no significant effect on the IGF I response (P > 0.05). To evaluate the role of IGF2R or IGFBPs in mediating the actions of RA, the IGF II analogs [Leu27]IGF II (10–20‐fold reduced IGF I receptor affinity) and des(1–6) IGF II (lower IGFBP binding affinity) were used. The IGF II inhibitory effect of RA was enhanced in the presence of analogs [Leu27]IGF II (P = 0.052) but not with des(1–6)IGF II (P > 0.05), compared with wild‐type IGF II.

Conclusions

These data implicate a novel antiproliferative role for RA in enhancing the pericellular clearance of IGF II via the IGF2R preventing ligand activation of the IGF I receptor. This may have broader implications for RA effects in other tumors.
Experimental study of the two-dimensional inverse energy cascade in a square box
Authors: Sommeria J.
Published: April 2006

A quantitative experimental study of the two-dimensional inverse energy cascade is presented. The flow is electrically driven in a horizontal layer of mercury and three-dimensional perturbations are suppressed by means of a uniform magnetic field, so that the flow can be well approximated by a two-dimensional Navier–Stokes equation with a steady forcing term and a linear friction due to the Hartmann layer. Turbulence is produced by the instability of a periodic square network of 36 electrically driven alternating vortices. The inverse cascade is limited at large scales, either by the linear friction or by the finite size of the domain, depending on the experimental parameters. In the first case, $k^{-\frac{5}{3}$ spectra are measured and the corresponding two-dimensional Kolmogorov constant is in the range 3–7. In the second case, a condensation of the turbulent energy in the lowest mode, corresponding to a spontaneous mean global rotation, is observed. Such a condensation was predicted by Kraichnan (1967) from statistical thermodynamics arguments, but without the symmetry breaking. Random reversals of the rotation sense, owing to turbulent fluctuations, are more and more sparse as friction is decreased. The lowest mode fluctuations and the small scales are statistically independent.
Experimental study of secondary flow in a magnetohydrodynamic channel
Authors: Girshick S. L. , Kruger C. H.
Published: April 2006

The Hall effect in the magnetohydrodynamic (MHD) channel flow of a plasma leads to the presence of transverse Lorentz forces. The non-uniform distribution of these body forces may cause secondary flows to develop; these can exert a significant influence on the plasma momentum, thermal and electrical behaviour. The effect is predicted to be large for envisioned large-scale MHD devices. An experimental study of this phenomenon is described. The apparatus consisted of a laboratory-scale MHD channel in which a controlled net axial current was applied. Plasma velocities were measured using laser-Doppler anemometry. The results demonstrate that transverse Lorentz forces can drive intense secondary flows at a value of the magnetic interaction parameter based on the Hall current of approximately one. The peak measured transverse velocities were 15% of the bulk velocity. Qualitatively, the basic character of the large-scale secondary flow structure was in accord with a simple model based on a first-order distribution of the axial current density. Measurements were also made under a variety of conditions of the profiles of mean axial velocity and of the axial and transverse components of turbulence intensity, of electrode surface temperatures and of plasma voltage distributions. These results all support the conclusion that convective transport by MHD secondary flow caused significant asymmetries to develop in the cross-plane distribution of scalar quantities.
An experimental investigation of a turbulent shear flow with separation, reverse flow, and reattachment
Authors: Ruderich R. , Fernholz H. H.
Published: April 2006

Experiments were performed in the highly turbulent and disturbed flow over a bluff plate with a long splitter plate in its plane of symmetry. The flow separates at the sharp bevelled edge of the bluff plate, forms a free shear layer on top of the reverse-flow region which is bounded on its other side by the splitter plate, and reattaches on the splitter plate over a narrow region curved in spanwise direction. Downstream of reattachment the shear flow adjusts slowly to the wall boundary conditions.

Measurements of mean velocity, Reynolds-shear-stress and Reynolds-normal-stress distributions were carried out by hot-wire and pulsed-wire anemometry. The latter technique was used in those regions of the flow where reverse flow occurred or where the flow was highly turbulent. Spectra and integral lengthscales were measured to investigate the state and structure of the flow. The large-eddy structure in the inner region of the flow had lengthscales in the two cross-stream directions which were approximately equal, indicating a fast break-up of spanwise structures just downstream from separation.

Mean and fluctuating quantities showed a self-similar behaviour in a short region upstream of reattachment and ‘profile similarity’ in the separated shear layer and along the splitter plate downstream from reattachment. Probability-density distributions of skin friction were measured and used to calculate mean and fluctuating values. No flapping of the reattaching shear layer could be observed. Pulsed-wire measurements revealed that the logarithmic law of the wall does not hold either in the reverse-flow region or in a region about half the length of the bubble downstream from reattachment.
Nonlinear interactions between convection, rotation and flows with vertical shear
Authors: Hathaway David H. , Somerville Richard C. J.
Published: April 2006

A three-dimensional and time-dependent numerical model is used to study the nonlinear interactions between thermal convective motions, rotation, and imposed flows with vertical shear. All cases have Rayleigh numbers of 104 and Prandtl numbers of 1.0. Rotating cases have Taylor numbers of 104.

For the non-rotating cases, the effects of the shear on the convection produce longitudinal rolls aligned with the shear flow and a downgradient flux of momentum. The interaction between the convection and the shear flow decreases the shear in the interior of the fluid layer while adding kinetic energy to the convective motions. For unit Prandtl number the dimensionless flux of momentum is equal to the dimensionless flux of heat.

For rotating cases with vertical rotation vectors, the shear flow favours rolls aligned with the shear and produces a downgradient flux of momentum. However, the Coriolis force turns the flow induced by the convection to produce a more complicated shear that changes direction with height. As in the non-rotating cases, the convective motions become more energetic by extracting energy from the mean flow. For Richardson numbers larger than about − 1.0, the dominant source of eddy kinetic energy is the shear flow rather than buoyancy.

For rotating cases with tilted rotation vectors the results depend upon the direction of the shear. For weak shear, convective rolls aligned with the rotation vector are favoured. When the shear flow is directed to the east along the top, the rolls become broader and the convection weaker. For large shear in this direction, the convective motions are quenched by the competition between the shear flow and the tilted rotation vector. When the shear flow is directed to the west along the top, strong shear produces rolls aligned with the shear. The heat and momentum fluxes become large and can exceed those found in the absence of a tilted rotation vector. Countergradient fluxes of momentum can also be produced.
On the sheared density interface of an entraining stratified fluid
Authors: Narimousa Siavash , Fernando Harindra J. S.
Published: April 2006

This paper deals with the nature of the entrainment interface of a two-layer fluid subjected to interfacial velocity shear. The shear flow was generated by driving the mixed layer over the dense layer by a disk pump such that there is no stress at the top of the mixed layer. During the entrainment process a sharp, thin-density interfacial layer developed; its thickness δ was found to increase linearly with the mixed-layer depth h, independent of the Richardson number Riu. The shear layer thickness δs was found to be much larger than δ and the ratio δs/h is also found to be constant, irrespective of Riu. At the entrainment interface, the estimated buoyancy flux and the dissipation of turbulent kinetic-energy appear to be of the same order. This result supports an entrainment law of the form E ∼ Riu−1, where E is the entrainment coefficient. The interfacial layer showed sporadic large-amplitude wave oscillations whose amplitudes scaled well with the estimated size of the undulations caused by the impingement of large eddies (of size h) on the density interface. The density-interfacial layer was found to be ‘topped’ by a layer of partially mixed fluid which had not yet incroporated into the well-mixed region.
The scattering of light by a chaotically convecting fluid
Authors: Ryrie Susan C.
Published: April 2006

The way in which light, scattered by a thin layer of fluid, may be used to obtain quantitative information about the temperature field in the fluid is investigated. Expressions for the phase shift imposed by the fluid, and the intensity of the scattered light are derived in terms of the Fourier representation of the temperature field, under the assumption of small variations in the refractive index. The method is applied to the particular case of chaotic convection, with a view to studying the connection between strange attractors and turbulence. Two simple mathematical models of chaotic convection are studied; particular emphasis is attached to the statistical properties of the flow and of the scattered light field, which are calculated numerically.
Heat-flow experiments in liquid 4He with a variable cylindrical geometry
Authors: Gao H. , Metcalfe G. , Jung T. , Behringer R. P.
Published: April 2006

This paper first describes an apparatus for measuring the Nusselt number N versus the Rayleigh number R of convecting normal liquid 4He layers. The most important feature of the apparatus is its ability to provide layers of different heights d, and hence different aspect ratios [Gcy ]. The horizontal cross-section of each layer is circular, and [Gcy ] is defined by [Gcy ] = D/2d where D is the diameter of the layer. We report results for 2.4 [les ] [Gcy ] [les ] 16 and for Prandtl numbers Pr spanning 0.5 [lsim ] Pr [lsim ] 0.9 These results are presented in terms of the slope N1 = RcdN/dR evaluated just above the onset of convection at Rc. We find that N1 is only a slowly increasing function of [Gcy ] in the range 6 [lsim ] [Gcy ] [lsim ] 16, and that it has a value there which is quite close to 0.72. This value of N1 is in good agreement with variational calcuations by Ahlers et al. (1981) pertinent to parallel convection rolls in cylindrical geometry. Particularly for [Gcy ] [lsim ] 6, we find additional small-scale structure in N1 associated with changes in the number of convection rolls with changing [Gcy ]. An additional test of the linearzied hydrodynamics is given by measurements of Rc. We find good agreement between theory and our data for Rc.
Steady entry flow in a curved pipe
Authors: Bovendeerd P. H. M. , Steenhoven A. A. Van , Vosse F. N. Van De , Vossers G.
Published: April 2006

Laser-Doppler velocity measurements were performed on the entry flow in a 90° bend of circular cross-section with a curvature ratio a/R = 1/6. The steady entry velocity profile was parabolic, having a Reynolds number Re = 700, with a corresponding Dean number κ = 286. Both axial and secondary velocities were measured, enabling a detailed description of the complete flow field. The secondary flow at the entrance of the bend was measured to be directed completely towards the inner bend. Significant disturbance of the axial velocity field was not measured until a downstream distance (aR)½. Maximum secondary velocities were measured at 1.7 (aR)½ downstream from the inlet. The development of the axial flow field can be quite well explained from the secondary velocity field.
On the linear stability of the inviscid Kármán vortex street
Authors: Jimenez Javier
Published: April 2006

The classical point-vortex model for a Kármán vortex street is linearly stable only for an isolated case. This property has been shown numerically to hold for other, more complicated, models of the same flow. It is shown here that it is a consequence of the Hamiltonian structure of the model, related to the codimension of the set of matrices with a particular Jordan block structure in the space of Hamiltonian matrices, and that it can be expected to hold generically for any two-dimensional inviscid array of vortices that has back-to-fore symmetry, and that is ‘close enough’ to the point-vortex model.
Calculation of the effect of polymer additive in a converging flow
Authors: Ryskin G.
Published: April 2006

The conical-channel flow of a dilute polymer solution is investigated theoretically. The stress field due to polymer additive is calculated using a new molecular model, based on the physical picture of the polymer molecules unravelling in strong flows and Batchelor's theory for the stress in a suspension of elongated particles. Good agreement is obtained with the experimental results of James & Saringer (1980). The absence of a significant polymer effect in a two-dimensional case (the wedge-channel flow), observed by the same authors (James & Saringer 1982a), is also explained. The fundamental differences between the proposed model and the elastic-dumbbell models are discussed.
Nonlinear binary-mode interactions in a developing mixing layer
Authors: Nikitopoulos D. E. , Liu J. T. C.
Published: April 2006

In this paper we present the formulation and results of two-wave interactions in a spatially developing shear layer, directed at understanding and interpreting the physical mechanisms that underlie the results of quantitative observation. Our study confirms the existence of Kelly's mechanism that augments the growth of a subharmonic disturbance by extracting energy from its fundamental or vice versa. This mechanism is shown to be strongest in the region where the fundamental begins to return energy to the mean flow and the two wave modes are of comparable energy levels. It is found that the initial conditions and especially the initial phase angle between the two disturbances play a very significant role in the modal development and that of the shear layer itself. A doubling of the shear-layer thickness is shown to take place; the two successive plateaux in its growth are attributed to the peaking in the energy production rates of the fundamental and subharmonic fluctuations.
Transition of transient vertical natural-convection flows in water
Authors: Joshi Yogendra , Gebhart Benjamin
Published: April 2006

Experimental results and interpretations are given for transient natural convection adjacent to a suddenly heated flat vertical surface in quiescent water. The 1.24 m high surface resulted in laminar, transition and turbulent regimes downstream, in transients and in steady state, over a wide range of surface-energy input rates. Flows were visualized and velocity and temperature measurements made at various downstream locations, after imposing a uniform internal-energy generation rate within the very thin surface. Upflow development from quiescence to steady state was found to depend strongly on the downstream location x and imposed input heat flux. Laminar flow persisted into steady state, for short downstream distances. Further downstream, the flow became turbulent during the transient. Relaminarization at later time occurred only for lower flux inputs. Local measurements across the fluid layer show that the transient disturbances close to the leading edge of the surface are confined to within the final steady boundary layer. Downstream, they extend much further into the ambient. First disturbances always arose before the leading-edge-effect propagation estimates. The trend of data was in agreement with theory for a non-dimensional time τ < 85. For larger τ, turbulence instead terminated the one-dimensional transport regime simultaneously, at all downstream locations. This single value of τ also amounts to a single value of the non-dimensional thermal energy of the flow, ETT = 19.7. Disturbance frequency data early in the transient suggest the presence of a strongly selective amplification mechanism, very similar to that found in steady flows. The non-dimensional times at which local steady state was achieved were best correlated by a Fourier number, over a wide range of energy input conditions. Turbulence arising during the transient enhances the thermal transport significantly. Local convection coefficients then were found to be as much as 40% higher than the eventual steady values.
Third-order resonance effects and the nonlinear stability of drop oscillations
Authors: Natarajan Ramesh , Brown Robert A.
Published: April 2006

The three-dimensional nonlinear oscillations of an isolated, inviscid drop with surface tension are studied by a multiple timescale analysis and pre-averaging applied to the variational principle for the appropriate Lagrangian. Amplitude equations are derived which describe the generic cubic resonance caused by the spatial degeneracy of the eigenfrequencies of the linear normal modes. This resonant coupling leads to the instability of the finite amplitude axisymmetric oscillations to small non-axisymmetric perturbations, as is demonstrated here for the three-and four-lobed normal modes. Solutions to the interaction equations that describe finite amplitude, non-axisymmetric travelling-wave solutions are also obtained and their stability is investigated. A non-generic cubic resonance between the two-lobed and four-lobed oscillatory modes leads to quasi-periodic motions.
Simulation of flow between concentric rotating spheres. Part 1. Steady states
Authors: Marcus Philip S. , Tuckerman Laurette S.
Published: April 2006

Axisymmetric spherical Couette flow between two concentric differentially rotating spheres is computed numerically as an initial-value problem. The time-independent spherical Couette flows with zero, one and two Taylor vortices computed in our simulations are found to be reflection-symmetric about the equator despite the fact that our pseudospectral numerical method did not impose these properties. Our solutions are examined for self-consistency, compared with other numerical calculations, and tested against laboratory experiments. At present, the most precise laboratory measurements are those that measure Taylor-vortex size as a function of Reynolds number, and our agreement with these results is within a few per cent. We analyse our flows by plotting their meridional circulations, azimuthal angular velocities, and energy spectra. At Reynolds numbers just less than the critical value for the onset of Taylor vortices, we find that pinches develop in the flow in which the meridional velocity redistributes the angular momentum. Taylor vortices are easily differentiated from pinches because the fluid in a Taylor vortex is isolated from the rest of the fluid by a streamline that extends from the inner to the outer sphere, whereas the fluid in a pinch mixes with the rest of the flow.
Excitation of instability waves in free shear layers. Part 1. Theory
Authors: Bechert D. W.
Published: April 2006

The generation of instability waves in free shear layers is investigated theoretically. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. For this model the forced instability waves are calculated. The shear-layer excitation by a source farther away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. Any type of source farther away from the plate edge produces a parabolic pressure field near the edge. For this latter, fairly general case, a reference quantity is found for the magnitude of the excited instability waves. The theory is then extended to two streams, one on each side of the shear layer, having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. The limitations to the theory and some aspects related to experiments are discussed. In particular, for a comparison with measurements, numerical computations of the velocity field outside the shear layer have been carried out.
Unsteady lifting-line theory by the method of matched asymptotic expansions
Authors: Wilmott P.
Published: April 2006

An unsteady lifting-line theory is presented for a general motion of a wing of high aspect ratio. Our matched-asymptotic-expansions analysis parallels that of Van Dyke (1964) in his solution for the steady lifting line, but is complicated by the shedding of transverse vortices associated with variation of circulation with time. The principal result is an expression for the downwash due to three-dimensional effects. Numerical calculations are presented for a wing of elliptic planform following a curved path.
Linear internal waves generated by density and velocity perturbations in a linearly stratified fluid
Authors: Meng James C. S. , Rottman James W.
Published: April 2006

A generalized theoretical analysis and finite-difference solutions of the Navier-Stokes equations of the initial-value problem are applied to obtain the linear internal wave fields generated by a density perturbation and two rotational velocity perturbations in an inviscid linearly stratified fluid. The velocity perturbations are those due to an axisymmetric swirl and a vortex pair. Solutions obtained correspond to the strong stratification limit.

The theoretical results of the rotational perturbation cases show an oscillating non-propagating disturbance, which is absent in the density-perturbation case. The swirl-flow solution shows an oscillatory behaviour in both the angular momentum deposited in the fluid and in the torque exerted by the external gravitational force field. The vortex-flow solution shows a vertical ray pattern.

The equi-partitioning of energy is reached at about 0.4 of a Brunt-Väisälä (B.V.) period. The potential energy-kinetic energy conversion, or vice versa, takes place between 0.15 and 0.3 B.V. periods.
Subharmonic resonance, pairing and shredding in the mixing layer
Authors: Monkewitz Peter A.
Published: April 2006

An instability-wave analysis is presented to describe the spatial evolution of a fundamental mode and its subharmonic on an inviscid parallel mixing layer. It incorporates explicitly the weakly nonlinear interaction between the two modes. The computational finding that the development of the subharmonic, leading eventually to pairing or shredding, crucially depends on its phase relation with the fundamental is fully confirmed. Furthermore it is shown that a critical fundamental amplitude has to be reached before the (spatial) subharmonic becomes phase locked with the fundamental and exhibits a modified growth rate. Then the analysis is exploited to explain the occurrence of amplitude modulations in ‘natural’ mixing layers and to estimate the width of the subharmonic spectral peaks. Also, the case of oblique subharmonic waves is briefly touched upon. In the last part, ways are explored to model non-parallel effects, i.e. to handle the saturation of the rapidly growing subharmonic. Using this wave description, the role of mode interaction in the ‘vortex pairing’ and ‘shredding’ process is assessed.
Longitudinal vortices imbedded in turbulent boundary layers Part 2. Vortex pair with ‘common flow’ upwards
Authors: Mehta R. D. , Bradshaw P.
Published: April 2006

Detailed mean flow and turbulence measurements have been made in a low-speed turbulent boundary layer in zero pressure gradient with an isolated, artificially generated vortex pair imbedded in it. The vortices, generated by two half-delta wings on the floor of the wind-tunnel settling chamber, rotate in opposite directions such that the ‘common flow’ between the vortices is away from the surface, and the vortex pair draws boundary-layer fluid upwards. The distance of the vortex cores above the surface grows downstream, and is roughly twice the local boundary-layer thickness. The cancellation of circulation by mixing of fluid from the two vortices is slow, and the vortices are identifiable down the full length of the test section. As in the case of the single vortex investigated in Part 1 of this series, large changes in structural parameters of the turbulence occur.
Turbulent mixing at a shear-free density interface
Authors: Hannoun Imad A. , List E. John
Published: April 2006

The interaction of a sharp density interface with oscillating-grid-induced shear-free turbulence was experimentally investigated. A linear photodiode array was used in conjunction with laser-induced fluorescence to measure the concentration of dye that was initially only in the less dense layer. A laser-Doppler velocimeter was used to measure the vertical velocity in and above the density interface at a point where the dye concentration was also measured. Potential refractive-index-fluctuation problems were avoided using solutes that provided a homogeneous optical environment across the density interface. Internal wave spectra, amplitudes and velocities, as well as the vertical mass flux were measured. The results indicate that mixing occurs in intermittent bursts and that the gradient (local) Richardson number remains constant for a certain range of the overall Richardson number Rj, defined in terms of an integral lengthscale, buoyancy jump and turbulence intensity. The spectra of the internal waves decay as f−3 at frequencies below the maximum Brunt-Väisälä frequency. These findings give support to a model for oceanic mixing proposed by Phillips (1977) in which the internal waves are limited in their spectral density by sporadic local instabilities and breakdown to turbulence. The results also indicate that, for a certain Rj range, the thickness of the interfacial layer (normalized by the integral lengthscale of the turbulence) is a decreasing function of Rj. At sufficiently high Rj the interfacial thickness becomes limited by diffusive effects. Finally, we discuss a simple model for entrainment at a density interface in the presence of shear-free turbulence.
Plane simple shear of smooth inelastic circular disks: the anisotropy of the second moment in the dilute and dense limits
Authors: Jenkins J. T. , Richman M. W.
Published: April 2006

We consider a plane, steady, homogeneous flow of circular disks. The disks are identical, smooth, and inelastic. We adopt the assumption of molecular chaos and introduce an anisotropic Maxwellian velocity distribution function based on the full second moment of the velocity fluctuations. In the limits of dilute and dense flows, we determine approximate analytic solutions of the balance law for the second moment that result in stresses whose qualitative behaviour and magnitudes are in good agreement with numerical simulations.
Phenomena of vortex shedding and flow interference of three cylinders in different equilateral arrangements
Authors: Lam K. , Cheung W. C.
Published: April 2006

This paper describes how the flows around three equal circular cylinders arranged in an equilateral-triangular manner interact at different angles of incidence α and spacing ratios l/d. Some vortex-shedding-frequency data evaluated from flow visualization experiments conducted at Reynolds numbers of 2.1 × 103 and 3.5 × 103, based on the diameter of a single cylinder, using a dye -injection technique, are presented. In order to provide additional insight to the understanding of the flow structure around this particular cylinder array, some photographs indicating the typical flow patterns for various arrangements are also presented. The investigation indicates that the flows interact in a complex fashion for spacing ratios smaller than 2.29 and it also reveals that, at this range of spacing ratios and at α = 0°, bistable flow characteristic exists. Moreover, for l/d approximately smaller than 4.65 there always exists an angle at which the vortex shedding behind an upstream cylinder is suppressed by a nearest downstream cylinder. This angle is found not to remain constant but increases as the spacing ratio increases. For illustration and comparisons, some numerical results obtained from the application of the surface-vorticity method have also been presented.
Equilibrium shapes and stability of captive annular menisci
Authors: Tsamopoulos J. A. , Poslinski A. J. , Ryan M. E.
Published: April 2006

Equilibrium shapes and stability of annular fluid menisci held together by surface tension are analysed by applying asymptotic and computer-aided techniques from bifurcation theory. The shapes and locations of the menisci are governed by the Young–Laplace equation. These shapes are grouped together into families of like symmetry that branch from the basic family of annular shapes at specific values of the aspect ratio, α. Multiple equilibrium shapes exist over certain values of α. The inner, outer or both the inner and outer interfaces may possess either a cylindrical or sinusoidal equilibrium shape. Changes in applied pressure, fluid volume, or gravitational Bond number break families of the same symmetry which now develop limit points. Numerical calculations rely on a finite-element representation of the interfaces and the results compare very well with asymptotic analysis which is valid for small deformations. The results are important for the blow moulding process and are invaluable in understanding its dynamics. These dynamics are expected to be considerably different from the dynamics of a liquid jet first analysed by Rayleigh.
Verses quite like cwen to gebeddan in The Metres of Boethius
Authors: Griffith M. S.
Published: April 2006

The metrical grammar of Beo 665a cwen to gebeddan is, for that poem, strikingly irregular: the verse is of Sievers Type A with a preposition and prefix in the first dip and yet displays single - rather than the expected double - alliteration. The Metres of Boethius, a text whose metrical grammar (unlike that of Beowulf) generates a number of similar examples of this licence, allows a better understanding of the structure and rhetoric of the Beowulf verse. In particular, these analogous exceptions show that the absence of the expected alliteration accentuates the semantic contrast of the two stressed elements of the verse.
Homogeneous nucleation rate measurements of 1-propanol in helium: The effect of carrier gas pressure
Authors: Brus David , Ždímal Vladimír , Stratmann Frank
Published: April 2006

Kinetics of homogeneous nucleation in supersaturated vapor of 1-propanol was studied using an upward thermal diffusion cloud chamber. Helium was used as a noncondensable carrier gas and the influence of its pressure on observed nucleation rates was investigated. The isothermal nucleation rates were determined by a photographic method that is independent on any nucleation theory. In this method, the trajectories of growing droplets are recorded using a charge coupled device camera and the distribution of local nucleation rates is determined by image analysis. The nucleation rate measurements of 1-propanol were carried out at four isotherms 260, 270, 280, and 290K. In addition, the pressure dependence was investigated on the isotherms 290K (50, 120, and 180kPa) and 280K (50 and 120kPa). The isotherm 270K was measured at 25kPa and the isotherm 260K at 20kPa. The experiments confirm the earlier observations from several thermal diffusion chamber investigations that the homogeneous nucleation rate of 1-propanol tends to increase with decreasing total pressure in the chamber. In order to reduce the possibility that the observed phenomenon is an experimental artifact, connected with the generally used one-dimensional description of transfer processes in the chamber, a recently developed two-dimensional model of coupled heat, mass, and momentum transfer inside the chamber was used and results of both models were compared. It can be concluded that the implementation of the two-dimensional model does not explain the observed effect. Furthermore the obtained results were compared both to the predictions of the classical theory and to the results of other investigators using different experimental devices. Plotting the experimental data on the so-called Hale plot shows that our data seem to be consistent both internally and also with the data of others. Using the nucleation theorem the critical cluster sizes were obtained from the slopes of the individual isotherms and compared with the Kelvin prediction. The influence of total pressure on the observed isothermal nucleation rate was studied in another experiment, where not only temperature but also supersaturation was kept constant as the total pressure was changed. It was shown that the dependence of the nucleation rate on pressure gets stronger as pressure decreases.
Homodimerization of the G protein SRβ in the nucleotide-free state involves proline cis/trans isomerization in the switch II region
Authors: Schwartz Thomas U. , Schmidt Daniel , Brohawn Stephen G. , Blobel Günter
Published: April 2006

Protein translocation across and insertion into membranes is essential to all life forms. Signal peptide-bearing nascent polypeptide chains emerging from the ribosome are first sampled by the signal-recognition particle (SRP), then targeted to the membrane via the SRP receptor (SR), and, finally, transferred to the protein-conducting channel. In eukaryotes, this process is tightly controlled by the concerted action of three G proteins, the 54-kD subunit of SRP and the α- and β-subunits of SR. We have determined the 2.2-Å crystal structure of the nucleotide-free SRβ domain. Unexpectedly, the structure is a homodimer with a highly intertwined interface made up of residues from the switch regions of the G domain. The remodeling of the switch regions does not resemble any of the known G protein switch mechanisms. Biochemical analysis confirms homodimerization
in vitro
, which is incompatible with SRα binding. The switch mechanism involves cis/trans isomerization of a strictly conserved proline, potentially implying a new layer of regulation of cotranslational transport.
Medium‐term results of percutaneous vertebroplasty in multiple myeloma
Authors: Ramos Luis , De Las Heras José Antonio , Sánchez Sergio , González‐Porras José Ramón , González Rafael , Mateos Maria Victoria , San Miguel Jesús F.
Published: April 2006

Abstract:  Vertebral compression fractures (VCFs) are common in multiple myeloma (MM). Percutaneous vertebroplasty (PVP) is used to stabilize vertebral collapse and treat the pain. Few studies have been carried out on PVP in MM and follow‐up has tended to be short. We have prospectively evaluated the safety and efficacy of PVP in the VCFs resulting from MM or plasmacytomas. Nineteen PVP were performed in 12 consecutive patients. We monitored their pain and functional status using visual analog (VAS) and Eastern Cooperative Oncology Group (ECOG) scale, respectively. For a subjective assessment, every patient was asked about his/her degree of satisfaction. The mean age of the participants was 66 yr. Significant improvement occurred 1 d after PVP according to the VAS score (7.5 pre‐PVP to 3.7, P < 0.0001) and ECOG assessment (3.1 to 2.5, P = 0.002). This significant improvement was maintained after 3.2 yr of follow‐up. Sixty‐three percent of patients were highly satisfied with the result of the PVP and 37% were satisfied. The peri‐operative mortality was 0%. Leakage of the cement outside of the vertebral body was noted in 16 of 19 injected vertebrae (84%) but none of the patients developed any clinical or neurological symptoms. At the last follow‐up, no further collapse in the treated or neighboring vertebrae was noted. VCFs caused by MM or plasmacytomas can be effectively treated by vertebroplasty. PVP is associated with early clinical improvement of pain and function and can be maintained after a long follow‐up without major procedure‐related complications.
Construction and evaluation of a web‐based interactive prescribing curriculum for senior medical students
Authors: Smith Anthony , Tasioulas Tina , Cockayne Nicole , Misan Gary , Walker Graham , Quick Gary
Published: April 2006

Aims

To develop and evaluate for the National Prescribing Service (NPS) a web‐based interactive prescribing curriculum for Australian senior medical students based on the World Health Organization’s Guide to Good Prescribing.

Methods

Teachers of prescribing from all Australian medical schools in 2000 wrote 12 case‐based modules which were converted to on‐line format. Objective evidence was provided for selecting first‐line medicines from available alternatives by comparing efficacy, safety, convenience and cost. The curriculum was made available to final year students in 2001 and was evaluated by measuring use from web statistics and by semistructured interviews with 15 teachers (2003) and on‐line surveys of 363 students over 2003 and 2004.

Results

By 2004 the curriculum was used by nine of 11 possible medical schools. Uptake increased each year from 2001 and all 12 modules were accessed consistently. Student access was significantly (P < 0.001) greater when prescribing was an assessable part of their course. Teachers’ evaluations were uniformly supportive and the curriculum is seen as a valuable resource. Student responses came from a small proportion of those with password access but were also supportive. Over half of student respondents had created their own evidence‐based formulary.

Conclusions

A collaborative venture initiated by the NPS with Australian medical schools has been successfully implemented in most courses. Teachers find the resource of high quality. Student respondents find the curriculum valuable in developing their own prescribing skills. It is best delivered by self‐directed study followed by tutorial discussion of prescribing decisions.
Gamma knife radiosurgery for acromegaly – long‐term experience
Authors: Ježková Jana , Marek Josef , Hána Václav , Kršek Michal , Weiss Vladimír , Vladyka Vilibald , Lišák Roman , Vymazal Josef , Pecen Ladislav
Published: April 2006

Objective  The Leksell gamma knife (LGK) is one of the treatment options for pituitary adenomas. We report on our long‐term experience treating acromegaly using LGK.

Design   Since 1993 we have followed 96 acromegaly patients through periods of from 12 to 120 months. The mean follow‐up period was 53·7 ± 26·8 months. Seventy‐two patients were treated with neurosurgery prior to LGK; for 24 LGK was the primary treatment. Thirteen patients were irradiated twice, due to persistent activity of the adenoma or its residue. Pituitary functions were tested at 6‐month intervals, post‐irradiation. The target tumour volume for radiosurgery was between 93·3 and 12 700 mm3 (median 1350 mm3).

Results  Fifty per cent of the patients achieved mean GH < 2·5 µg/l within 42 months, normalized their IGF‐I within 54 months, and achieved GH suppression in the oral glucose tolerance test (oGTT) < 1 µg/l with normal IGF‐I within 66 months. LGK effectiveness was dependent on initial adenoma hormonal activity (GH and IGF‐I serum levels), not on the size of the adenoma. Patients with primary neurosurgery followed by LGK irradiation had better outcomes than those with LGK alone. Irradiation arrested all adenoma growth, causing tumour shrinkage in 62·3% of patients. Twenty‐six developed hypopituitarism when irradiated by 15 Gy (or more) on functional peritumoral pituitary tissue. No hypopituitarism appeared using lower doses.

Conclusions  In acromegaly, LGK is a useful adjunct to primary neurosurgery when treating post‐surgical residues because it can limit the duration of medical therapy. It can be used as a primary therapy when neurosurgery is not possible.
Complex intervention development for diabetes self‐management
Authors: Sturt Jackie , Whitlock Sandra , Hearnshaw Hilary
Published: April 2006

Aim.  The aim of this paper is to present the development and evaluation of the Self‐Efficacy Goal Achievement nursing intervention for type 2 diabetes.

Background.  Systematic reviews support the clinical effectiveness of diabetes self‐management programmes that are collaborative, involve biomedical feedback and are goal focussed.

Method.  The self‐efficacy goal achievement intervention comprises patient goal‐setting consultations with practice nurses using the Diabetes Management Self‐Efficacy Scale. The United Kingdom Medical Research Council framework for the evaluation of complex interventions by randomized controlled trial was used to develop and evaluate the intervention. The ‘preclinical’ study included literature analysis and findings from parallel studies. The ‘phase I’ study, carried out in spring 2003, was a small trial of the intervention, evaluation of its feasibility, identification of appropriate outcome measures for future trials and improvement of the components, with two nurses and eight patients.

Findings.  The ‘preclinical’ study supported continued intervention development. The ‘phase I’ intervention resulted in a mean reduction in participants’ glycosylated haemoglobin of 0·93% between baseline and 3‐months postintervention. It showed an increase in patient self‐efficacy and some decline in patient diabetes treatment satisfaction. Qualitative data recorded therapeutically desirable behavioural changes in all participants. Follow‐up consultations and goal evaluation were found to be important to patients. Nurses reported (i) reservations about the repeated use of components of the intervention, which were felt to be repetitive and restrictive; and (ii) the time commitment required to deliver the educational sessions.

Conclusions.  Most phase I components were effective in delivering a feasible nursing intervention. The intervention has been adjusted to remove the less effective components and enhance the more effective. The outcome measures were appropriate for the intervention. A phase II trial is being developed to further test both the intervention and research protocol for comparing the intervention to an alternative.