bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unsteady disturbances of streaming motions around bodies
Authors: Atassi H. M. , Grzedzinski J. 
Published: April 2006

For small-amplitude vortical and entropic unsteady disturbances of potential flows, Goldstein proposed a partial splitting of the velocity field into a vortical part u(I) that is a known function of the imposed upstream disturbance and a potential part ∇ϕ satisfying a linear inhomogeneous wave equation with a dipole-type source term. The present paper deals with flows around bodies with a stagnation point. It is shown that for such flows u(I) becomes singular along the entire body surface and its wake and as a result ∇ϕ will also be singular along the entire body surface. The paper proposes a modified splitting of the velocity field into a vortical part u(R) that has zero streamwise and normal components along the body surface, an entropy-dependent part and a regular part ∇ϕ* that satisfies a linear inhomogeneous wave equation with a modified source term.For periodic disturbances, explicit expressions for u(R) are given for three-dimensional flows past a single obstacle and for two-dimensional mean flows past a linear cascade. For weakly sheared flows, it is shown that if the mean flow has only a finite number of isolated stagnation points, u(R) will be finite along the body surface. On the other hand, if the mean flow has a stagnation line along the body surface such as in two-dimensional flows then the component of u(R) in this direction will have a logarithmic singularity.For incompressible flows, the boundary-value problem for ϕ* is formulated in terms of an integral equation of the Fredholm type. The theory is applied to a typical bluff body. Detailed calculations are carried out to show the velocity and pressure fields in response to incident harmonic disturbances.
Growth and translation of a liquid-vapour compound drop in a second liquid. Part 1. Fluid mechanics
Authors: Vuong S. T. , Sadhal S. S. 
Published: April 2006

The fluid dynamics associated with a compound drop consisting of a vapour bubble, partly surrounded by its own liquid in another immiscible liquid is considered. The fluid motion is analysed in the limit of Stokes flow and at the same time the surface tension forces are considered to be large enough to allow the interfaces to have uniform curvature. The flow field consists of translation and growth that can arise from change of phase.An exact analytical solution for the axisymmetric flow field is obtained. The important results of physical interest are the drag force and the flow behaviour. In the case without growth, the drag force lies between the bubble and the solid-sphere limits for a sphere of the same volume as the total liquid and vapour dispersed phase. The maximum drag force is observed when the liquid and vapour volumes are nearly the same. This is the effect of weak circulation due to the smaller available space as compared with a spherical drop. With growth this effect appears to be enhanced. The flow streamlines exhibit secondary vortices in the dispersed phase when there is growth. The velocity field and the drag results here are applied to the heat transfer problem for the compound drop in Part 2 of this two-part series.
Axisymmetric draining of a cylindrical tank with a free surface
Authors: Zhou Qiao-Nian , Graebel W. P. 
Published: April 2006

The withdrawal of layered fluids from an open tank through a hole centred on the bottom is investigated numerically under the assumption of potential flow. A fully cubic-spline nonlinear axisymmetric boundary-integral-method scheme with the built-in boundary conditions, which effectively reduces the numerical errors at the intersection lines where the tank wall and the density interfaces meet, is used. Two cases are studied: (i) the tank contains only one fluid with a free surface; (ii) the tank contains two fluids having different densities with a distinct interface and a free surfaceThe numerical results show two different phenomena, depending upon the drain rate and initial conditions. When the tank is rapidly drained, a dip forms at the centre of the lower interface and extends into the hole very quickly, as observed by Lubin & Springer (1967). For a slowly draining tank, a jet forms in the centre of the depression region. This jet can either shoot up or move down, depending on the initial conditions.
Locally axisymmetric turbulence
Authors: George William K. , Hussein Hussein J. 
Published: April 2006

The failure of local isotropy to describe the experimentally obtained derivative moments in turbulent shear flows has previously been well-documented, but is briefly reviewed. The same data are then used to evaluate the hypothesis that the turbulence is locally axisymmetric. Locally axisymmetric turbulence is defined herein as turbulence which is locally invariant to rotations about a preferred axis.The derivative moment relations are derived from the general form of the two-point velocity correlation tensor near the origin for axisymmetric turbulence. These are used to derive relations for the rate of dissipation of kinetic energy, the mean-square vorticity, and the components of each. Almost all of the experimental derivative moment data are shown to be consistent with these equations, and thus with local axisymmetry.
Resonance in nonlinear bubble oscillations
Authors: Longuet-Higgins Michael S. 
Published: April 2006

In two recent papers (Longuet-Higgins 1989a,b) the author showed that the shape oscillations of bubbles can emit sound like a monopole source, at second order in the distortion parameter ε. In the second paper (LH2) it was predicted that the emission would be amplified when the second harmonic frequency 2σn of the shape oscillation approaches the frequency ω of the breathing mode. This ‘resonance’ would however be drastically limited by damping due to acoustic radiation and thermal diffusion. The predictions were confirmed by further numerical calculations in Longuet-Higgins (1990a).Ffowcs Williams & Guo (1991) have questioned the conclusions of LH2 on the grounds that near resonance there is a slow (secular) transfer of energy between the shape oscillation and the volumetric mode which tends to diminish the amplitude of the shape oscillation and hence falsify the perturbation analysis. They have also argued that the volumetric mode never grows sufficiently to produce sound of the stated order of magnitude. In the present paper we show that these assertions are unfounded. Ffowcs Williams & Guo considered only undamped oscillations. Here we show that when the appropriate damping is included in their analysis the secular transfer of energy becomes completely insignificant. The resulting pressure pulse (figure 5 below) is found to be essentially identical to that calculated in LH2, figure 3. Moreover, in the initial-value problem considered in LH2, the excitation of the volumetric mode takes place not by a secular energy transfer but by a resonance during the first few cycles of the shape oscillation. This accounts for the amplification near resonance found in Longuet-Higgins (1990a). Finally, it is pointed out that the initial energy of the shape oscillations is far greater than is required to produce the O(ε2) volume pulsations that were studied in LH2, and which were used for a comparison with field data. This acoustic radiation was not calculated by Ffowcs Williams & Guo.
Turbulence in a separated boundary layer
Authors: Dianat M. , Castro Ian P. 
Published: April 2006

This paper presents and discusses the results of an extensive experimental investigation of a flat-plate turbulent boundary subjected to an adverse pressure gradient sufficiently strong to lead to the formation of a large separated region. The pressure gradient was produced by applying strong suction through a porous cylinder fitted with a rear flap and mounted above the boundary layer and with its axis in the spanwise direction. Attention is concentrated on the structure of the turbulent flow within the separated region and it is shown that many features are similar to those that occur in separated regions produced in a very dissimilar manner. These include the fact that structure parameters, like Reynolds stress ratios, respond markedly to the re-entrainment of turbulent fluid transported upstream from the reattachment region, the absence of any logarithmic region in the thin wall boundary layer beneath the recirculation zone and the lack of any effective viscous scaling in this wall region, and the presence of a significant low-frequency motion having timescales much longer than those of the large-eddy structures around reattachment.Similarities with boundary layers separating under the action of much weaker pressure gradients are also found, despite the fact that the nature of the flow around separation is quite different. These similarities and also some noticeable differences are discussed in the paper, which concludes with some inferences concerning the application of turbulence models to separated flows.
Unsteady entrance flow in a 90° curved tube
Authors: Rindt C. C. M. , van Steenhoven A. A. , Janssen J. D. , Vossers G. 
Published: April 2006

A numerical model enabling the prediction of the axial and secondary velocity fields in three-dimensional configurations at moderate Reynolds numbers and Womersley parameters is presented. Steady and unsteady entrance flows in a 90° curve tube (δ = ⅙) under various flow conditions are analysed. The good quality agreement between axial and secondary velocities for a sinusoidally varying flow rate at a Womersley parameter of α = 7.8, obtained from a finite-element calculation, and those obtained from laser-Doppler measurements justify the use of the numerical model.Halfway into the deceleration phase for a sinusoidally varying flow rate (200 < Re < 800, α = 7.8) a strong resemblance is found to the steady flow case (Re = 700). In contrast with steady flow, near the inner wall reversed axial flow regions are found halfway into and at the end of the deceleration phase. Throughout the flow cycle the Dean-type secondary flow field highly influences axial flow resulting in a shift of the maximal axial velocity towards the outer wall, C-shaped axial isovelocity lines and an axial velocity plateau near the inner wall. Further downstream in the curved tube the Dean-type secondary vortex near the plane of symmetry is deflected towards the sidewall (’tail’–formation), as is also found for steady flow. An increase of the Womersley parameter (α = 24.7) results in a constant secondary flow field which is probably mainly determined by the steady component of the flow rate. A study on the flow phenomena occurring for a physiologically varying flow rate suggests that the diastolic phase is only of minor importance for the flow phenomena occurring in the systolic phase. Elimination of the steady flow component (− 300 < Re < 300) results in a pure Dean-type secondary flow field (no ‘tail’-formation) for α = 7.8 and in a Lyne-type secondary flow field for α = 24.7. The magnitude of the secondary velocities for α = 24.7 are of O(10−2) as compared to the secondary velocities for α = 7.8.
Treatment of Oesophageal Bile Reflux in Children
Authors: Orel Rok , Brecelj Jernej , Homan Matjaž , Heuschkel Robert 
Published: April 2006

ABSTRACTObjectives:Reflux of duodenal juice into the oesophagus has a role in the pathogenesis of both oesophageal and laryngopharyngeal inflammatory and neoplastic lesions. As little is known about effective therapy, we studied the effect of proton pump inhibitor therapy on oesophageal bile reflux in children.Methods:Twenty‐nine children with moderate to severe erosive oesophagitis and abnormal oesophageal bile reflux were studied before and after treatment with omeprazole 1 mg/kg per day. Outcomes included a clinical symptom score, oesophageal acid and bile reflux (simultaneous 24‐hour pH and Bilitec 2000 monitoring), and mucosal healing.Results:After 8 weeks of therapy, 17 (59%) of the patients were symptom‐free, and 5 (17%) had minimal symptoms. Mucosal healing or reduction to low‐grade oesophagitis was achieved in 25 children (86%; P < 0.0005). Mean percentages of total, upright, and supine time with oesophageal pH less than 4 were reduced from 17.0%, 16.8%, and 19.2% before treatment, to 2.83%, 3.17%, and 2.07%, respectively, after treatment (all P < 0.00001). Similarly, mean percentages of total, upright, and supine time with bile reflux were reduced from 16.96%, 12.67%, and 22.0%, to 2.27%, 1.91%, and 2.23%, respectively (P < 0.000001, P < 0.0001, and P < 0.000001, respectively).Conclusions:Omeprazole 1 mg/kg per day is an effective therapy for the majority of children with severe erosive oesophagitis due to abnormal isolated bile reflux or combined acid and bile reflux. It remains unclear how patients with treatment‐resistant bile reflux should be managed.
Tunnel plasticity and quaternary structural integrity of a pentameric protein ring
Authors: Woycechowsky Kenneth J. , Seebeck Florian P. , Hilvert Donald 
Published: April 2006

AbstractCyclic protein oligomers are common in cells. However, the importance of the residues that line the central tunnel of protein rings for overall architectural integrity is not well understood. To investigate the role of tunnel positions in protein assembly and stability, we prepared variants of the homo‐pentameric lumazine synthase (LS) from Saccharomyces cerevisiae in which the three residues that line the middle of the tunnel were simultaneously changed. As a consequence of symmetry, these mutations cause a total of 15 changes in the structure of the pentameric complex. Detailed characterization of the variants indicates that they retain quaternary structural integrity, even in cases where the mutations induce considerable secondary structure alterations. The tunnels of symmetric ring‐shaped proteins, such as LS, may consequently represent an overlooked site for protein engineering.
Crystal structure of human peptidoglycan recognition protein Iα bound to a muramyl pentapeptide from Gram‐positive bacteria
Authors: Guan Rongjin , Brown Patrick H. , Swaminathan Chittoor P. , Roychowdhury Abhijit , Boons Geert‐Jan , Mariuzza Roy A. 
Published: April 2006

AbstractPeptidoglycan recognition proteins (PGRPs) are pattern recognition receptors of the innate immune system that bind bacterial peptidoglycans (PGNs). We determined the crystal structure, to 2.1 Å resolution, of the C‐terminal PGN‐binding domain of human PGRP‐Iα in complex with a muramyl pentapeptide (MPP) from Gram‐positive bacteria containing a complete peptide stem (L‐Ala‐D‐isoGln‐L‐Lys‐D‐Ala‐D‐Ala). The structure reveals important features not observed previously in the complex between PGRP‐Iα and a muramyl tripeptide lacking D‐Ala at stem positions 4 and 5. Most notable are ligand‐induced structural rearrangements in the PGN‐binding site that are essential for entry of the C‐terminal portion of the peptide stem and for locking MPP in the binding groove. We propose that similar structural rearrangements to accommodate the PGN stem likely characterize many PGRPs, both mammalian and insect.
A comparison of the steady‐state pharmacokinetics of nevirapine in men, nonpregnant women and women in late pregnancy
Authors: Von Hentig Nils , Carlebach Amina , Gute Peter , Knecht Gaby , Klauke Stefan , Rohrbacher Maren , Stocker Hartmut , Kurowski Michael , Harder Sebastian , Staszewski Schlomo , Haberl Annette 
Published: April 2006

AimsTo evaluate the pharmacokinetics of nevirapine and any possible influencing factors in pregnant women (n = 16), nonpregnant women (n = 13) and men (n = 14), who received nevirapine 200 mg twice daily together with nucleoside reverse transcriptase inhibitors.MethodsBlood samples were taken for 12 h at steady state. Nevirapine concentrations were measured by liquid chromatography‐tandem mass spectrometry. The influence of gender, age, body weight and comedication on minimum and maximum concentrations (Cmin, Cmax), area under the concentration‐time curve (AUC), total clearance (CLtot), half‐life (t1/2) and volume of distribution (Vd) was analysed by multivariate techniques.ResultsMean [95% confidence interval (CI)]Cmax, AUCss and clearance were 5221 ng ml−1 (4267, 6175), 50 789 ng −1h ml−1 (43 453, 58 125) and 69.9 ml min−1 for men, 5871 ng ml−1 (4848, 6895), 57 045 ng h−1 ml−1 (45 997, 68 093) and 65.6 ml min−1 for nonpregnant women and 4505 ng ml−1 (3644, 5366), 44 579 ng h−1 ml−1 (36 564, 52 594) and 82.1 ml min−1 for pregnant women. The differences between pregnant and nonpregnant women (% difference, 95% CI) in Cmax (−30.3; −28.5, −33.0), AUCss (−28.0; − 25.8, − 29.5) and clearance (20.2; 26.6, 15.6) reached statistical significance (P = 0.010, P = 0.028 and P = 0.028, respectively). The multivariate analysis underscored the influence of bodyweight on the plasma exposure to nevirapine.ConclusionsPregnant women exhibited an increased nevirapine clearance and comparably low plasma concentrations, whereas women with a low bodyweight achieved high plasma nevirapine concentrations. The large variability in nevirapine concentrations in women may lead to loss of efficacy and viral resistance, or drug toxicity, and therefore these patients should be monitored frequently.
Cost‐effectiveness analysis in glaucoma: what drives utility? Results from a pilot study in Sweden
Authors: Kobelt Gisela , Jonsson Björn , Bergström Anders , Chen Enping , Lindén Christina , Alm Albert 
Published: April 2006

Abstract.Purpose:  To investigate the effect of different levels of visual field defect in glaucoma on utilities and to test if utilities could be assessed using a general questionnaire such as the EQ‐5D. Methods:  A cross‐sectional study in 199 patients with ocular hypertension or open‐angle glaucoma grouped into 5 severity stages according to visual field defects was performed in 4 specialized ophthalmic centres. Descriptive analysis was performed for the sample and by stage, and the effect of vision loss on utility was investigated with multiple step‐wise regression analysis. Results:  The mean age of the sample was 70 and the mean MD in the worse eye was −13.1 dB (SD 10.2). Visual acuity (VA) was 0.63 and 0.87 in the worse and better eye, respectively, and the mean utility was 0.80 (SD 0.23). Utility decreased with increasing glaucomatous damage, ranging from 0.84 for mild disease to 0.72 for severe damage (MD −2.5 to −28.1), but the difference between the groups was not statistically significant when controlling for co‐morbidity, except for the most severe stage (p < 0.01). In multiple regression analysis, visual field in the better eye was significantly correlated with utility, and there was an indirect correlation between visual field in the worse eye and utility: the effect of total VA on utility was significant, and MD in the worse eye was correlated with total VA. Conclusions:  Utility is strongly correlated with overall vision. Our results suggest a relationship between glaucomatous damage and utility, and patients with severe damage have a significantly lower utility. However, this should be further investigated in larger samples that include more patients with moderate‐severe bilateral damage.
Financial Spread Betting
Authors: Buik David 
Published: April 2006

Abstract
Traditional betting has two outcomes: you win or you lose. Spread betting has many more possibilities: you can win a lot or a little; you can lose or lose much, much more than you imagined. Spread betting, say its fans, brings a whole new level of uncertainty—and excitement. It has been described as the crack cocaine of gambling. Spread bets can be laid on almost any sporting or other result, but in the field of finance it is making particular inroads. David Buik, of the City spread betting company Cantor Index Ltd, explains.
Dettori Day
Authors: Docherty Jenny 
Published: April 2006

Abstract
It was the day at the races the bookies want to forget. September 28th, 1996, was the one day that dreams came true for punters—they made a killing and, for once, went home richer than the bookmakers. It was the day that Frankie Dettori rode all seven winners at Ascot. Jenny Docherty describes the day's events.
Transcriptome Analysis Reveals Mechanisms by Which
Lactococcus lactis
Acquires Nisin Resistance
Authors: Kramer Naomi E. , van Hijum Sacha A. F. T. , Knol Jan , Kok Jan , Kuipers Oscar P. 
Published: April 2006

ABSTRACT

Nisin, a posttranslationally modified antimicrobial peptide produced by
Lactococcus lactis
, is widely used as a food preservative. Yet, the mechanisms leading to the development of nisin resistance in bacteria are poorly understood. We used whole-genome DNA microarrays of
L. lactis
IL1403 to identify the factors underlying acquired nisin resistance mechanisms. The transcriptomes of
L. lactis
IL1403 and
L. lactis
IL1403 Nis
r
, which reached a 75-fold higher nisin resistance level, were compared. Differential expression was observed in genes encoding proteins that are involved in cell wall biosynthesis, energy metabolism, fatty acid and phospholipid metabolism, regulatory functions, and metal and/or peptide transport and binding. These results were further substantiated by showing that several knockout and overexpression mutants of these genes had strongly altered nisin resistance levels and that some knockout strains could no longer become resistant to the same level of nisin as that of the wild-type strain. The acquired nisin resistance mechanism in
L. lactis
is complex, involving various different mechanisms. The four major mechanisms are (i) preventing nisin from reaching the cytoplasmic membrane, (ii) reducing the acidity of the extracellular medium, thereby stimulating the binding of nisin to the cell wall, (iii) preventing the insertion of nisin into the membrane, and (iv) possibly transporting nisin across the membrane or extruding nisin out of the membrane.
Minocycline Impedes African Trypanosome Invasion of the Brain in a Murine Model
Authors: Masocha Willias , Rottenberg Martin E. , Kristensson Krister 
Published: April 2006

ABSTRACT

Passage of
Trypanosoma brucei
across the blood-brain barrier (BBB) is a hallmark of late-stage human African trypanosomiasis. In the present study we found that daily administration of minocycline, a tetracycline antibiotic, impedes the penetration of leukocytes and trypanosomes into the brain parenchyma of
T. brucei brucei
-infected C57BL/6 mice. The trypanosome-induced astrocytic and microglial reactions were reduced in the minocycline-treated mice, as were the levels in the brain of transcripts encoding adhesion molecules intercellular adhesion molecule 1 (ICAM-1) and endothelial-leukocyte adhesion molecule 1 (E-selectin); the inflammatory cytokines tumor necrosis factor alpha, interleukin-1α (IL-1α), IL-1β, IL-6, and gamma interferon; and matrix metalloprotease 3 (MMP-3), MMP-8, and MMP-12. Loss of weight occurring during infection with
T. b. brucei
was not observed after treatment of the mice with minocycline; these mice also survived longer than nontreated mice. Invasion of trypanosomes and leukocytes into the brain parenchyma most likely triggered the loss of weight and death of infected animals, since minocycline did not affect the growth of
T. b. brucei
either in vitro or in vivo or the levels of the transcripts encoding the cytokines and MMPs in the spleen. In conclusion, our data show that
T. b. brucei
invasion of the brain is related to that of leukocytes and that minocycline can ameliorate the disease in trypanosome-infected mice.