bluuebunny/crossref_metadata_2025 huggingface dataset:
Oncologic Outcome of Intersphincteric Resection for Very Low Rectal Cancer
Authors: Saito Norio , Sugito Masanori , Ito Masaaki , Kobayashi Akihiro , Nishizawa Yusuke , Yoneyama Yasuo , Nishizawa Yuji , Minagawa Nozomi
Published: June 2009

Background

In 2000 we launched a prospective program of intersphincteric resection (ISR) for very low rectal cancer. In this study we compared the oncologic outcome of patients who underwent ISR with the outcome of patients who underwent abdominoperineal resection (APR).

Methods

The data of 202 patients with very low rectal cancer who underwent curative ISR (n = 132) or curative APR (n = 70) between 1995 and 2006 were analyzed. Patients were divided into ISR and APR groups. Survival and local recurrence were investigated in both groups.

Results

The median follow‐up was 40 months in the ISR group and 57 months in the APR group. The 5‐year local relapse‐free survival rate was 83% in the ISR group and 80% in the APR group (p = 0.364), and the 5‐year disease‐free survival rate was 69% in the ISR group and 63% in the APR group (p = 0.714).

Conclusions

For very low rectal cancers, ISR appears to be oncologically acceptable and can reduce the number of APRs.
Pattern of Lymph Node Involvement in Proximal Gastric Cancer
Authors: Ishikawa Shinji , Shimada Shinya , Miyanari Nobutomo , Hirota Masahiko , Takamori Hiroshi , Baba Hideo
Published: June 2009

Background

The operative methods for proximal gastric cancer differ depending on the institution, thus there is no optimal therapeutic strategy. A splenic hilum lymph node (No. 10) dissection is necessary for D2 operation for proximal gastric cancer, which means it requires splenectomy. However, unnecessary splenectomy should be avoided.

Methods

A total of 127 proximal gastric cancer cases from our institution were studied retrospectively. In addition, 1,569 cases were collected from the literature and were used as pooled data for further analysis. All cases were examined for the depth of tumor invasion and lymph node metastasis.

Results

A retrospective analysis revealed that proximal gastric cancer within submucosa (40 cases) had no N2 lymph node metastasis in our study. The 5‐year overall survival of all cases was 25.2% and the disease‐free survival was 23.6%. From the pooled data analysis, No. 10 lymph node metastasis was observed in 0.9% of the patients with submucosa proximal gastric cancer. Furthermore, there was no No. 4d lymph node metastasis when the depth of cancer was limited to within the subserosa.

Conclusions

Although a randomized, controlled trial concerning survival is necessary, according to this study, there is a possibility that limited resection might be accepted for proximal gastric cancer according to the depth of wall invasion.
Parents’ Perceptions of Autism Spectrum Disorder Etiology and Recurrence Risk and Effects of their Perceptions on Family Planning: Recommendations for Genetic Counselors
Authors: Selkirk Christina G. , McCarthy Veach Patricia , Lian Fengqin , Schimmenti Lisa , LeRoy Bonnie S.
Published: June 2009

Knowledge about the etiology of Autism Spectrum Disorders (ASDs) is increasing, but causes remain elusive for most cases. Genetic counselors are positioned to help families that have children with ASDs despite uncertainty regarding etiology. To determine how genetic counselors might best provide services, an anonymous survey was conducted with 255 parents whose children were diagnosed on the autism spectrum. Questions concerned: 1) their perceptions of ASD cause(s) and 2) recurrence risk, 3) whether perceived risk affected family planning decisions, 4) whether parents had received genetic services, and 5) how genetic counselors might assist families. The most prevalent perceived cause was genetic influences (72.6%). Most parents’ recurrence risk perceptions were inaccurately high and significantly affected family planning. Only 10% had seen a genetic professional related to an ASD. Parents provided several suggestions for genetic counselor best practices. Findings indicate the importance of genetic counselor awareness of parent perceptions in order to best help families who have children with ASDs.
Spatial distribution of bryophytes along a moisture gradient: an approach using photosynthetic pigments as indicators of stress
Authors: Spitale Daniel
Published: June 2009

Height above water table in aquatic habitats has long been recognized as the key factor for determining the spatial structure of bryophyte assemblages. Using photosynthetic pigments as indicators of stress along a wet‐to‐dry gradient, I tested whether different habitat preferences were revealed. A field experiment was set up to obtain a semi‐natural hydrological gradient. The spatial distribution of species was quantified by determining the pigment content in natural assemblages and by applying the regression equations derived from the experimental manipulation. The species were able to move water in quantities that were statistically significantly different from each other, which was in agreement with the species characteristics and the colony architectures. Photosynthetic pigments responded in a complex way to the water gradient and, for each species, one or more stress indicators were reliable. A wide overlapping of spatial distribution exists in natural conditions, especially in complex habitats like springs. Although in this study a restricted selection of species has been examined, the method proposed to evaluate the theoretical height above water table is coherent with the broad spatial pattern observed. This approach may be particularly useful for understanding both the coexistence of similar species and the spatial distributions of bryophytes in spring habitats in relation to water stress tolerance.
Synthesis and Application of Perfluoroalkyl Quaternary Ammonium Salts in Protein‐Based Fire‐Fighting Foam Concentrates
Authors: Zaggia Alessandro , Conte Lino , Padoan Gennifer , Bertani Roberta
Published: June 2009

Nine perfluoroalkyl quaternary ammonium salts containing a perfluorinated tail were synthesized in order to evaluate their properties as additives in protein‐based fire‐fighting foam concentrates. They were obtained in high yield starting from (perfluoro‐n‐octyl)methyl oxirane via a two‐step reaction scheme. Their structures were identified by Fourier‐transform infrared spectroscopy and elemental analysis. Surface tension, interfacial tension, critical micellar concentration, and spreading coefficient of aqueous solutions of the synthesized compounds were first determined. Synthetic perfluoroalkyl quaternary ammonium salts were then added at reduced concentration (0.5 wt.%) to a commercial protein‐based fire‐fighting foam concentrate and their effects on foam spreading properties were further investigated via five specific laboratory tests: sealing time test, burn back time test, foam expansion test, drain time test, and foam flowing test. Results showed that the perfluoroalkyl quaternary ammonium salts strongly influence surface and extinguishing properties of protein‐based fire‐fighting foam concentrates, producing stable foams able to spread spontaneously over hydrocarbons and forming aqueous films with enhanced organic‐vapor sealing properties.
Antiretroviral therapy with or without protease inhibitors impairs postprandial TAG hydrolysis in HIV-infected men
Authors: Ware Lisa J. , Jackson Akil G. A. , Wootton Stephen A. , Burdge Graham C. , Morlese John F. , Moyle Graeme J. , Jackson Alan A. , Gazzard Brian G.
Published: June 2009

Mechanisms underlying the lipodystrophy syndrome associated with antiretroviral therapy (ART) for HIV infection are not completely understood. We investigated the effect of ART on blood lipid concentrations in the fasting state and after consumption of a meal containing [1-13C]palmitic acid in HIV-positive men receiving nucleoside reverse transcriptase inhibitors (NRTI,n7), NRTI combined with protease inhibitors (PI; NRTIPI,n6), in HIV-positive but therapy-naïve men (noART,n5) and in HIV-seronegative men (controls,n6). HIV-positive subjects had higher fasting TAG concentrations and resting energy expenditure than controls. Subjects receiving NRTIPI therapy had higher fasting NEFA concentrations than the other groups. There were no significant differences in postprandial lipid metabolism between noART subjects and controls. NRTI therapy impaired hydrolysis of meal-derived TAG, most evidently when combined with PI (the NRTIPI group). Accumulation of13C-label in the NEFA fraction was not different between groups. In the NRTIPI group, fasting and postprandial NEFA concentrations were significantly higher than other groups. Postprandial glucose and insulin responses in HIV-positive subjects did not differ from controls. These findings suggest that ART dyslipidaemia is associated with impaired postprandial TAG clearance, which is exacerbated by NRTIPI therapy. If dyslipidaemia is to be minimised in ART, the specific adverse effects of particular combinations during the fed state should be considered.
Soya isoflavone supplementation enhances spatial working memory in men
Authors: Thorp Alicia A. , Sinn Natalie , Buckley Jonathan D. , Coates Alison M. , Howe Peter R. C.
Published: June 2009

Females perform better in certain memory-related tasks than males. Sex differences in cognitive performance may be attributable to differences in circulating oestrogen acting on oestrogen β receptors (ERβ) which are prevalent in brain regions such as the hippocampus, frontal lobe and cortex that mediate cognitive functions. Since soya isoflavones are known to activate ERβ, chronic isoflavone supplementation in males may improve cognitive performance in memory-related tasks. A 12-week double-blind, placebo-controlled cross-over trial was conducted in thirty-four healthy men to investigate the effect of isoflavone supplementation on cognitive function. Volunteers were randomised to take four capsules/d containing soya isoflavones (116 mg isoflavone equivalents/d: 68 mg daidzein, 12 mg genistein, 36 mg glycitin) or placebo for 6 weeks, and the alternate treatment during the following 6 weeks. Assessments of memory (verbal episodic, auditory and working), executive function (planning, attention, mental flexibility) and visual-spatial processing were performed at baseline and after each treatment period. Isoflavone supplementation significantly improved spatial working memory (P = 0·01), a test in which females consistently perform better than males. Compared with placebo supplementation, there were 18 % fewer attempts (P = 0·01), 23 % fewer errors (P = 0·02) and 17 % less time (P = 0·03) required to correctly identify the requisite information. Isoflavones did not affect auditory and episodic memory (Paired Associate Learning, Rey's Auditory Verbal Learning Task, Backward Digit Span and Letter-Number Sequencing), executive function (Trail Making and Initial Letter Fluency Task) or visual-spatial processing (Mental Rotation Task). Isoflavone supplementation in healthy males may enhance cognitive processes which appear dependent on oestrogen activation.
Comparative effect of orally administered sodium butyrate before or after weaning on growth and several indices of gastrointestinal biology of piglets
Authors: Le Gall Maud , Gallois Mélanie , Sève Bernard , Louveau Isabelle , Holst Jens J. , Oswald Isabelle P. , Lallès Jean-Paul , Guilloteau Paul
Published: June 2009

Sodium butyrate (SB) provided orally favours body growth and maturation of the gastrointestinal tract (GIT) in milk-fed pigs. In weaned pigs, conflicting results have been obtained. Therefore, we hypothesised that the effects of SB (3 g/kg DM intake) depend on the period (before v. after weaning) of its oral administration. From the age of 5 d, thirty-two pigs, blocked in quadruplicates within litters, were assigned to one of four treatments: no SB (control), SB before (for 24 d), or after (for 11–12 d) weaning and SB before and after weaning (for 35–36 d). Growth performance, feed intake and various end-point indices of GIT anatomy and physiology were investigated at slaughter. The pigs supplemented with SB before weaning grew faster after weaning than the controls (P < 0·05). The feed intake was higher in pigs supplemented with SB before or after weaning (P < 0·05). SB provided before weaning improved post-weaning faecal digestibility (P < 0·05) while SB after weaning decreased ileal and faecal digestibilities (P < 0·05). Gastric digesta retention was higher when SB was provided before weaning (P < 0·05). Post-weaning administration of SB decreased the activity of three pancreatic enzymes and five intestinal enzymes (P < 0·05). IL-18 gene expression tended to be lower in the mid-jejunum in SB-supplemented pigs. The small-intestinal mucosa was thinner and jejunal villous height lower in all SB groups (P < 0·05). In conclusion, the pre-weaning SB supplementation was the most efficient to stimulate body growth and feed intake after weaning, by reducing gastric emptying and intestinal mucosa weight and by increasing feed digestibility.
Vitamin E status and quality of life in the elderly: influence of inflammatory processes
Authors: Capuron Lucile , Moranis Aurélie , Combe Nicole , Cousson-Gélie Florence , Fuchs Dietmar , De Smedt-Peyrusse Véronique , Barberger-Gateau Pascale , Layé Sophie
Published: June 2009

Chronic low-grade inflammation is a characteristic of ageing that may lead to alterations in health status and quality of life. In addition to intrinsic biological factors, recent data suggest that poor nutritional habits may largely contribute to this condition. The present study aimed at assessing mental and physical components of quality of life and at determining their relationship to vitamin E status, inflammation and tryptophan (TRP) metabolism in the elderly. Sixty-nine elderly subjects recruited from the Three-City cohort study participated in the study. Quality of life was assessed using the medical outcomes study thirty-six-item short-form health survey (SF-36). Biological assays included the measurement of plasma vitamin E (α-tocopherol), inflammatory markers, including IL-6 and C-reactive protein, and TRP metabolism. Results showed that participants with poor physical health status, as assessed by the SF-36, exhibited lower circulating concentrations of α-tocopherol together with increased concentrations of inflammatory markers. Similarly, poor mental health scores on the SF-36 were associated with lower concentrations of α-tocopherol, but also with decreased concentrations of TRP. These findings indicate that nutritional status, notably as it relates to vitamin E, is associated with immune function and quality of life in the elderly.
Adaptation of a non-ruminant nutrient-based growth model to rainbow trout (Oncorhynchus mykiss Walbaum)
Authors: HUA K. , BIRKETT S. , DE LANGE C. F. M. , BUREAU D. P.
Published: June 2009

Models that accurately describe and predict growth and nutrient utilization of fish can be useful in developing strategies to improve the economic and environmental sustainability of aquaculture operations. Current bioenergetics models are not sufficiently flexible to be applied to the wide range of conditions encountered in aquaculture. There is a need to move from bioenergetics approaches to more mechanistic approaches based on nutrient utilization by fish. A non-ruminant nutrient-based growth model has been successfully used in pig production. The model explicitly describes the utilization of energy-yielding nutrients and metabolites for body protein deposition (Pd) and body lipid deposition (Ld) at the whole animal level. Partitioning of intake of energy-yielding nutrients between Pd and Ld is governed by a minimum ratio (minLP) of the body lipid mass (L) to protein mass (P), a maximum daily rate of Pd (PdMax), or maximum efficiency of using intake of the first limiting dietary essential amino acid (AA) for body Pd. The growth model was adapted to rainbow trout (Oncorhynchus mykiss (Walbaum 1792)) through parameterization and various modifications consistent with its framework. The fish nutrient-based model was evaluated by comparing model simulations with data from various experiments carried out with rainbow trout. Significant discrepancies between model predictions and experimental observations were observed. The model predicted energy retention well but did not always accurately predict growth rate, nor Pd and Ld. Overall, the model underestimated growth rate (expressed as thermal-unit growth coefficient (TGC)) by 37% and Pd by 15% and overestimated Ld by 13%. These discrepancies are probably attributable to differences in nutrient utilization and partitioning mechanisms between fish and pigs. The development of more reliable models requires better understanding of the nutritional and endogenous determinants of fish growth.
The changing role of agriculture in Dutch society
Authors: MEERBURG B. G. , KOREVAAR H. , HAUBENHOFER D. K. , BLOM-ZANDSTRA M. , VAN KEULEN H.
Published: June 2009

Dutch agriculture has undergone significant changes in the past century, similar to many countries in the European Union. Due to economies of scale and in order to remain economically profitable, it became necessary for farmers to increase farm size, efficiency and external inputs, while minimizing labour use per hectare. The latter has resulted in fewer people working in the agricultural sector. Consequently, Dutch society gradually lost its connection to agricultural production. This divergence resulted in a poor image for the agricultural sector, because of environmental pollution, homogenization of the landscape, outbreaks of contagious animal diseases and reduced animal welfare. Although the general attitude towards agriculture seems to have improved slightly in recent years, there is still a long way to go in regaining this trust.

In order to keep the Dutch countryside viable, farmers are considered indispensable. However, their methods of production should match the demands of society in terms of sustainability. This applies both to farming systems that are used in a monofunctional way (production only) and to multifunctional farming systems. For researchers involved in development of these farming systems, this requires new capabilities; contrary to the situation in the past, citizens and stakeholder groups now demand involvement in the design of farming systems. In the current paper, it is suggested that, besides traditional mainstream agriculture, other alternative farming systems should be developed and implemented. Hence, Dutch agricultural research should remain focused on the cutting edge of economy and society. Despite all efforts, not all of these newly developed systems will acquire a position within the agricultural spectrum. However, some of the successful ones may prove extremely valuable.
Reversal of the lift force on an oblate bubble in a weakly viscous linear shear flow
Authors: ADOUA RICHARD , LEGENDRE DOMINIQUE , MAGNAUDET JACQUES
Published: June 2009

We compute the flow about an oblate spheroidal bubble of prescribed shape set fixed in a viscous linear shear flow in the range of moderate to high Reynolds numbers. In contrast to predictions based on inviscid theory, the numerical results reveal that for weak enough shear rates, the lift force and torque change sign in an intermediate range of Reynolds numbers when the bubble oblateness exceeds a critical value that depends on the relative shear rate. This effect is found to be due to the vorticity generated at the bubble surface which, combined with the velocity gradient associated with the upstream shear, results in a system of two counter-rotating streamwise vortices whose sign is opposite to that induced by the classical inviscid tilting of the upstream vorticity around the bubble. We show that this lift reversal mechanism is closely related to the wake instability mechanism experienced by a spheroidal bubble rising in a stagnant liquid.
Turbulence and mixing in unsteady breaking surface waves
Authors: DRAZEN DAVID A. , MELVILLE W. KENDALL
Published: June 2009

Laboratory measurements of the post-breaking velocity field due to unsteady deep-water breaking are presented. Digital particle image velocimetry (DPIV) is used to measure the entire post-breaking turbulent cloud with high-resolution imagery permitting the measurement of scales fromO(1m) down toO(1mm). Ensemble-averaged quantities including mean velocity, turbulent kinetic energy (TKE) density and Reynolds stress are presented and compare favourably with the results of Melville, Veron & White (J. Fluid Mech., vol. 454, 2002, pp. 203–233; MVW). However, due to limited resolution, MVW's measurements were not spatially coherent across the turbulent cloud, and this restricted their ability to compute turbulent wavenumber spectra. Statistical spatial quantities including the integral length scaleL11, Taylor microscale λfand the Taylor microscale Reynolds numberReλare presented. Estimation of an eddy viscosity for the breaking event is also given based on analysis of the image data. Turbulent wavenumber spectra are computed and within 12 wave periods after breaking exhibit what have been termed ‘spectral bumps’ in the turbulence literature. These local maxima in the spectra are thought to be caused by an imbalance between the transport of energy from large scales and the dissipation at small scales. Estimates of the dissipation rate per unit mass are computed using both direct and indirect methods. Horizontally averaged terms in the TKE budget are also presented up to 27 wave periods after breaking and are discussed with regard to the dynamics of the post-breaking flow. Comparisons of the TKE density in the streamwise and cross-stream planes with the three-dimensional full TKE density are given in an appendix.
Acoustic resonances and trapped modes in annular plate cascades
Authors: KOCH WERNER
Published: June 2009

As a stepping stone towards understanding acoustic resonances in axial flow compressors, acoustic resonances are computed numerically in fixed single and tandem plate cascades in an infinitely long annular duct. Applying perfectly matched layer absorbing boundary conditions in the form of the complex scaling method of atomic and molecular physics to approximate the radiation condition the resonance problem is transformed into an eigenvalue problem. Of particular interest are resonances with zero radiation damping (trapped modes) or very small radiation damping (nearly trapped modes). Such resonances can be excited by wakes from compressor cascades or struts. If the shedding frequency is sufficiently close to an acoustic resonant frequency, the latter may control the vortex shedding causing high-intensity tonal noise or occasionally even blade failure. All resonances are computed for zero mean flow approximating low-Mach-number flows. The influence of various cascade parameters on the resonant frequencies is studied and, whenever possible, our numerical results are compared with published experimental findings.
Experimental and numerical study of miscible Faraday
instability
Authors: ZOUESHTIAGH F. , AMIROUDINE S. , NARAYANAN R.
Published: June 2009

A study of the Faraday instability of diffuse interfaces between pairs of
miscible liquids of different densities, by means of experiments and by a
nonlinear numerical model, is presented. The experimental set-up consisted of a
rectangular cell in which the lighter liquid was placed above the denser one.
The cell in this initially stable configuration was then subjected to vertical
vibrations. The subsequent behaviour of the ‘interface’ between
the two liquids was observed with a high-speed camera. This study shows that
above a certain acceleration threshold an instability developed at the
interface. The amplitude of the instability grew during the experiments which
then led to the mixing of the liquids. The instability finally disappeared once
the two liquids were fully mixed over a volume, considerably larger than the
initial diffuse region. The results of a companion two-dimensional nonlinear
numerical model that employs a finite volume method show very good agreement
with the experiments. A physical explanation of the instability and the
observations are advanced.
A study of two-dimensional flow past regular polygons via conformal mapping
Authors: TIAN ZHONG WEI , WU ZI NIU
Published: June 2009

In this paper we study two-dimensional flow around regular polygons with an arbitrary but even number of edges N and one apex pointing to the free stream, with comparison to circular-cylinder flow. Both inviscid flow and low-Reynolds-number viscous flow are addressed. For inviscid flow, we obtained the exact solution for pure potential flow through Schwarz–Christoffel transformation, with the emphasis on the role of edge number, N, on the flow details. We also studied the behaviour, stationary lines and stability of vortex pair and found new stationary lines compared to circular cylinder. For viscous flow we derived the equation of stream function in the mapped (circle) domain, based on which approximate expressions for the critical Reynolds numbers and Strouhal number, as functions of the edge number, are obtained. The Reynolds number is based on the diameter of the circumscribed circle. For the steady flow, the first critical Reynolds number is a monotonically decreasing function of N, while N → ∞ corresponds to that for circular cylinder. The bifurcation point is ahead of the bifurcation point for circular cylinder. For unsteady flow, the critical Reynolds number for vortex shedding and the Strouhal number are both monotonically decreasing functions of N.
A comprehensive probability density function formalism for multiphase flows
Authors: PAI MADHUSUDAN G. , SUBRAMANIAM SHANKAR
Published: June 2009

A theoretical foundation for two widely used statistical representations of multiphase flows, namely the Eulerian–Eulerian (EE) and Lagrangian–Eulerian (LE) representations, is established in the framework of the probability density function (p.d.f.) formalism. Consistency relationships between fundamental statistical quantities in the EE and LE representations are rigorously established. It is shown that fundamental quantities in the two statistical representations bear an exact relationship to each other only under conditions of spatial homogeneity. Transport equations for the probability densities in each statistical representation are derived. Exact governing equations for the mean mass, mean momentum and second moment of velocity corresponding to the two statistical representations are derived from these transport equations. In particular, for the EE representation, the p.d.f. formalism is shown to naturally lead to the widely used ensemble-averaged equations for two-phase flows. Galilean-invariant combinations of unclosed terms in the governing equations that need to be modelled are clearly identified. The correspondence between unclosed terms in each statistical representation is established. Hybrid EE–LE computations can benefit from this correspondence, which serves in consistently transferring information from one representation to the other. Advantages and limitations of each statistical representation are identified. The results of this work can also serve as a guiding framework for direct numerical simulations of two-phase flows, which can now be exploited to precisely quantify unclosed terms in the governing equations in the two statistical representations.
Analogy between velocity and scalar fields in a turbulent channel flow
Authors: ANTONIA ROBERT ANTHONY , ABE HIROYUKI , KAWAMURA HIROSHI
Published: June 2009

The relationship between the fluctuating velocity vector and the temperature fluctuation has been examined using direct numerical simulation databases of a turbulent channel flow with passive scalar transport using a constant time-averaged heat flux at each wall for h+ = 180, 395, 640 and 1020 (where h is the channel half-width with the superscript denoting normalization by wall variables) at Prandtl number Pr=0.71. The analogy between spectra corresponding to the kinetic energy and scalar variance is reasonable in both inner and outer regions irrespective of whether the spectra are plotted in terms of kx or kz, the wavenumbers in the streamwise and spanwise directions respectively. Whereas all three velocity fluctuations contribute to the energy spectrum when kx is used, the longitudinal velocity fluctuation is the major contributor when kz is used. The quality of the analogy in the spectral domain is confirmed by visualizations in physical space and reflects differences between spatial organizations in the velocity and scalar fields. The similarity between the spectra corresponding to the enstrophy and scalar dissipation rate is not as good as that between the kinetic energy and scalar variance, emphasizing the prominence of the scalar sheets as the centre of the channel is approached. The ratio R between the characteristic time scales of the velocity and scalar fluctuations is approximately constant over a major part of the channel and independent of h+, when the latter is sufficiently large. This constancy, which is not observed in quantities such as the turbulent Prandtl number, follows from the spectral similarities discussed in this paper and has implications for turbulent heat transport models.
Centrifugal effects in rotating convection: nonlinear
dynamics
Authors: LOPEZ J. M. , MARQUES F.
Published: June 2009

Rotating convection in cylindrical containers is a canonical problem in fluid
dynamics, in which a variety of simplifying assumptions have been used in order
to allow for low-dimensional models or linear stability analysis from trivial
basic states. An aspect of the problem that has received only limited attention
is the influence of the centrifugal force, because it makes it difficult or even
impossible to implement the aforementioned approaches. In this study, the mutual
interplay between the three forces of the problem, Coriolis, gravitational and
centrifugal buoyancy, is examined via direct numerical simulation of the
Navier–Stokes equations in a parameter regime where the three forces are
of comparable strengths in a cylindrical container with the radius equal to the
depth so that wall effects are also of order one. Two steady axisymmetric basic
states exist in this regime, and the nonlinear dynamics of the solutions
bifurcating from them is explored in detail. A variety of bifurcated solutions
and several codimension-two bifurcation points acting as organizing centres for
the dynamics have been found. A main result is that the flow has simple dynamics
for either weak heating or large centrifugal buoyancy. Reducing the strength of
centrifugal buoyancy leads to subcritical bifurcations, and as a result linear
stability is of limited utility, and direct numerical simulations or laboratory
experiments are the only way to establish the connections between the different
solutions and their organizing centres, which result from the competition
between the three forces. Centrifugal effects primarily lead to the
axisymmetrization of the flow and a reduction in the heat flux.
Effects of axisymmetric strain on a passive scalar field: modelling and experiment
Authors: GYLFASON A. , WARHAFT Z.
Published: June 2009

Homogeneous, approximately isotropic turbulence at two Taylor-scale Reynolds numbers,Rλ=50, 190, with a mean transverse temperature gradient is passed through an axisymmetric contraction. The effects of the straining on the velocity field, and on the passive scalar field, are investigated within the contraction as are the effects of releasing the strain in the post-contraction region. Components of the fluctuating velocity and scalar gradient covariance are measured in order to understand their relation to the large-scale anisotropy of the flow. The scale-dependent spectral evolution of the scalar is also determined. A tensor model is constructed to predict the evolution of the fluctuating scalar gradient covariance. The model constants are determined in the post-contraction relaxation region, where the flow geometry does not vary. The model is shown to perform well throughout the flow, even in the contraction in which the geometry varies. Rapid distortion theory is applied to the scalar field in the contraction, and its solutions are compared to the experimental results.
Linear instability analysis of low-pressure turbine flows
Authors: ABDESSEMED N. , SHERWIN S. J. , THEOFILIS V.
Published: June 2009

Three-dimensional linear BiGlobal instability of two-dimensional states over a periodic array of T-106/300 low-pressure turbine (LPT) blades is investigated for Reynolds numbers below 5000. The analyses are based on a high-order spectral/hpelement discretization using a hybrid mesh. Steady basic states are investigated by solution of the partial-derivative eigenvalue problem, while Floquet theory is used to analyse time-periodic flow set-up past the first bifurcation. The leading mode is associated with the wake and long-wavelength perturbations, while a second short-wavelength mode can be associated with the separation bubble at the trailing edge. The leading eigenvalues and Floquet multipliers of the LPT flow have been obtained in a range of spanwise wavenumbers. For the most general configuration all secondary modes were observed to be stable in the Reynolds number regime considered. When a single LPT blade with top to bottom periodicity is considered as a base flow, the imposed periodicity forces the wakes of adjacent blades to be synchronized. This enforced synchronization can produce a linear instability due to long-wavelength disturbances. However, relaxing the periodic restrictions is shown to remove this instability. A pseudo-spectrum analysis shows that the eigenvalues can become unstable due to the non-orthogonal properties of the eigenmodes. Three-dimensional direct numerical simulations confirm all perturbations identified herein. An optimum growth analysis based on singular-value decomposition identifies perturbations with energy growthsO(105).
Combined effects of flow curvature and rotation on uniformly sheared turbulence
Authors: ROACH D. C. , HOLLOWAY A. G. L.
Published: June 2009

This paper describes an experiment in which a uniformly sheared turbulence was subjected to simultaneous streamwise flow curvature and rotation about the streamwise axis. The distortion of the turbulence is complex but well defined and may serve as a test case for turbulence model development. The uniformly sheared turbulence was developed in a straight wind tunnel and then passed into a curved tunnel section. At the start of the curved section the plane of the mean shear was normal to the plane of curvature so as to create a three-dimensional or ‘out of plane’ curvature configuration. On entering the curved tunnel, the flow developed a streamwise mean vorticity that rotated the mean shear about the tunnel centreline through approximately 70°, so that the shear was nearly in the plane of curvature and oriented so as to have a stabilizing effect on the turbulence. Hot wire measurements of the mean velocity, mean vorticity, mean rate of strain and Reynolds stress anisotropy development along the wind tunnel centreline are reported. The observed effect of the mean shear rotation on the turbulence was to diminish the shear stress in the plane normal to the plane of curvature while generating non-zero values of the shear stress in the plane of curvature. A rotating frame was identified for which the measured mean velocity field took the form of a simple shear flow. The turbulence anisotropy was transformed to this frame to estimate the effects of frame rotation on the structure of sheared turbulence.
Inside the moving layer of a sheared granular bed
Authors: MOUILLERON H. , CHARRU F. , EIFF O.
Published: June 2009

The moving layer at the surface of a granular bed sheared by a viscous flow has been investigated experimentally. The fluid and particle velocities have been measured using particle imaging velocimetry (PIV) and particle tracking, respectively, with a technique of matched index of refraction. The mean velocity profiles are found to be parabolic. The models of Bagnold (Phil. Trans. R. Soc. Lond. A, vol. 249, 1956, pp. 235–297) and Leighton & Acrivos (Chem. Engng Sci., vol. 41, 1986, pp. 1377–1384) fail to account for the observations. A simplified model assuming uniform particle concentration provides good agreement close to the threshold.
Origin of transonic buffet on aerofoils
Authors: CROUCH J. D. , GARBARUK A. , MAGIDOV D. , TRAVIN A.
Published: June 2009

Buffeting flow on transonic aerofoils serves as a model problem for the more complex three-dimensional flows responsible for aeroplane buffet. The origins of transonic aerofoil buffet are linked to a global instability, which leads to shock oscillations and dramatic lift fluctuations. The problem is analysed using the Reynolds-averaged Navier–Stokes equations, which for the foreseeable future are a necessary approximation to cover the high Reynolds numbers at which transonic buffet occurs. These equations have been shown to reproduce the key physics of transonic aerofoil flows. Results from global-stability analysis are shown to be in good agreement with experiments and numerical simulations. The stability boundary, as a function of the Mach number and angle of attack, consists of an upper and a lower branch – the lower branch shows features consistent with a supercritical bifurcation. The unstable modes provide insight into the basic character of buffeting flow at near-critical conditions and are consistent with fully nonlinear simulations. The results provide further evidence linking the transonic buffet onset to a global instability.
Large-scale amplitude modulation of the small-scale structures in turbulent boundary layers
Authors: MATHIS ROMAIN , HUTCHINS NICHOLAS , MARUSIC IVAN
Published: June 2009

In this paper we investigate the relationship between the large- and small-scale energy-containing motions in wall turbulence. Recent studies in a high-Reynolds-number turbulent boundary layer (Hutchins & Marusic, Phil. Trans. R. Soc. Lond. A, vol. 365, 2007a, pp. 647–664) have revealed a possible influence of the large-scale boundary-layer motions on the small-scale near-wall cycle, akin to a pure amplitude modulation. In the present study we build upon these observations, using the Hilbert transformation applied to the spectrally filtered small-scale component of fluctuating velocity signals, in order to quantify the interaction. In addition to the large-scale log-region structures superimposing a footprint (or mean shift) on the near-wall fluctuations (Townsend, The Structure of Turbulent Shear Flow, 2nd edn., 1976, Cambridge University Press; Metzger & Klewicki, Phys. Fluids, vol. 13, 2001, pp. 692–701.), we find strong supporting evidence that the small-scale structures are subject to a high degree of amplitude modulation seemingly originating from the much larger scales that inhabit the log region. An analysis of the Reynolds number dependence reveals that the amplitude modulation effect becomes progressively stronger as the Reynolds number increases. This is demonstrated through three orders of magnitude in Reynolds number, from laboratory experiments at Reτ ~ 103–104 to atmospheric surface layer measurements at Reτ ~ 106.
Magnetohydrodynamic stability of plasmas with ideal and relaxed regions
Authors: MILLS R. L. , HOLE M. J. , DEWAR R. L.
Published: June 2009

A unified energy principle approach is presented for analysing the magnetohydrodynamic (MHD) stability of plasmas consisting of multiple ideal and relaxed regions. The gauge a = ξ × B for the vector potential, a, of linearized perturbations is used, with the equilibrium magnetic field B obeying a Beltrami equation, ∇ × B = αB, in relaxed regions. In a region with such a force-free equilibrium Beltrami field we show that ξ obeys the same Euler–Lagrange equation whether ideal or relaxed MHD is used for perturbations, except in the neighbourhood of the magnetic surfaces where B · ∇ is singular. The difference at singular surfaces is analysed in cylindrical geometry: in ideal MHD only Newcomb's small solutions are allowed, whereas in relaxed MHD only the odd-parity large solution and even-parity small solution are allowed. A procedure for constructing global multi-region solutions in cylindrical geometry is presented. Focusing on the limit where the two interfaces approach each other arbitrarily closely, it is shown that the singular-limit problem encountered previously by Hole et al. in multi-region relaxed MHD is stabilized if the relaxed-MHD region between the coalescing interfaces is replaced by an ideal-MHD region. We then present a stable (k, pressure) phase-space plot, which allows us to determine the form a stable pressure and field profile must take in the region between the interfaces. From this knowledge, we conclude that there exists a class of single-interface plasmas that were found to be stable by Kaiser and Uecker, but are shown to be unstable when the interface is resolved.
A length-scale formula for confined quasi-two-dimensional plasmas
Authors: ANDERSEN TIMOTHY D. , LIM CHJAN C.
Published: June 2009

Typically a magnetohydrodynamical model for neutral plasmas must take into account both the ionic and the electron fluids and their interaction. However, at short time scales, the ionic fluid appears to be stationary compared to the electron fluid. On these scales, we need consider only the electron motion and associated field dynamics, and a single fluid model called the electron magnetohydrodynamical model which treats the ionic fluid as a uniform neutralizing background applies. Using Maxwell's equations, the vorticity of the electron fluid and the magnetic field can be combined to give a generalized vorticity field, and one can show that Euler's equations govern its behavior. When the vorticity is concentrated into slender, periodic, and nearly parallel (but slightly three-dimensional) filaments, one can also show that Euler's equations simplify into a Hamiltonian system and treat the system in statistical equilibrium, where the filaments act as interacting particles. In this paper, we show that, under a mean-field approximation, as the number of filaments becomes infinite (with appropriate scaling to keep the vorticity constant) and given that angular momentum is conserved, the statistical length scale, R, of this system in the Gibbs canonical ensemble follows an explicit formula, which we derive. This formula shows how the most critical statistic of an electron plasma of this type, its size, varies with angular momentum, kinetic energy, and filament elasticity (a measure of the interior structure of each filament) and in particular it shows how three-dimensional effects cause significant increases in the system size from a perfectly parallel, two-dimensional, one-component Coulomb gas.
Streptococcus pyogenes emmand T types within a decade, 1996–2005: implications for epidemiology and future vaccines
Authors: NIR-PAZ R. , KORENMAN Z. , RON M. , MICHAEL-GAYEGO A. , COHEN-PORADOSU R. , VALINSKY L. , BEALL B. , MOSES A. E.
Published: June 2009

Streptococcus pyogenesgroup A (GAS) is a primary human pathogen. We performed geneticemmsequence and serological T-antigen typing of 819 mostly invasive GAS isolates recovered in Israel during 1996–2005. Of the 72emmtypes found, the six most prevalent types (1, 81, 89, 14, 28, 5) comprised 30·2% of all isolates, andemm-type changes were observed over the years. The predicted coverage of the 26-valentS. pyogenesvaccine formulated for usage in the USA was predicted to be only ~60%. On the basis of differentemm–T antigen type associations, some Israeli strains are probably different clonal types than those found in USA. About 2% of GAS hademmtypes that were originally associated withS. dysgalactiaesubsp.equisimilis emmgenes. Therefore, routineemmtyping allows meaningful GAS strain surveillance, and provides data relevant to better vaccine coverage.
Characterization and epidemiological relationships of SpanishBrachyspira hyodysenteriaefield isolates
Authors: HIDALGO Á. , CARVAJAL A. , PRINGLE M. , RUBIO P. , FELLSTRÖM C.
Published: June 2009

This research aimed to describe the genetic and phenotypic diversity of 74 SpanishBrachyspira hyodysenteriaefield isolates, to establish epidemiological relationships between the isolates and to confirm the presence of tiamulin-resistant isolates in Spain. For these purposes, we performed biochemical tests in combination with diagnostic PCR analysis for the identification ofBrachyspiraspp. and for detection of thesmpA/smpBgene. We also used antimicrobial susceptibility tests, random amplified polymorphic DNA (RAPD) and a new pulsed-field gel electrophoresis (PFGE) protocol. The combination of RAPD and PFGE allowed the study of epidemiological relationships. Both indole-negative and tiamulin-resistant isolates ofB. hyodysenteriaeare reported in Spain for the first time. The genetic analyses indicated a relationship between these Spanish isolates and indole-negative isolates previously obtained from Germany and Belgium.
Critical parameters for modelling the spread of foot-and-mouth disease in wildlife
Authors: HIGHFIELD L. D. , WARD M. P. , LAFFAN S. W. , NORBY B. , WAGNER G. G.
Published: June 2009

A series of simulation experiments was conducted to determine how estimates of the latent and infectious periods, number of neighbours (contacts) and population size impact on the predicted magnitude and distribution of foot-and-mouth disease (FMD) outbreaks in white-tailed deer in southern Texas. Outbreaks were simulated using a previously developed and applied susceptible–latent–infected–recovered geographic automata model. There were substantial differences in the estimated predicted number of deer and locations infected, based on the model parameters used (3779–119 879 deer infected and 227–6526 locations affected). There were also substantial differences in the spatial risk of infection based on the model parameters used. The predicted spread of FMD was found to be most sensitive to the assumed latent period and the assumed number of contacts. How these parameters are estimated is likely to be critical in studies on the impact of FMD spread in situations in which wildlife reservoirs might potentially exist.
Coxiella burnetii(Q fever) seroprevalence in cattle
Authors: McCAUGHEY C. , MURRAY L. J. , McKENNA J. P. , MENZIES F. D. , McCULLOUGH S. J. , O'NEILL H. J. , WYATT D. E. , CARDWELL C. R. , COYLE P. V.
Published: June 2009

Human cases of Q fever appear to be common in Northern Ireland compared to the rest of the British Isles. The purpose of this study was to describe the seroepidemiology ofCoxiella burnetiiinfection in cattle in Northern Ireland in terms of seroprevalence and determinants of infection. A total of 5182 animals (from a stratified systematic random sample of 273 herds) were tested with a commercialC. burnetiiphase 2 IgG ELISA. A total of 6·2% of animals and 48·4% of herds tested positively. Results from a multilevel logistic regression model indicated that the odds of cattle being infected with Q fever increased with age, Friesian breed, being from large herds and from dairy herds. Large dairy herd animal prevalence was 12·5% compared to 2·1% for small beef herds. Preliminary seroprevalence in sheep (12·3%), goats (9·3%), pigs (0%) rats (9·7%) and mice (3·2%) using indirect immunofluorescence is reported.