bluuebunny/crossref_metadata_2025_split huggingface dataset:
Serial analysis of stable nitrogen and carbon isotopes in hair: monitoring starvation and recovery phases of patients suffering from anorexia nervosa
Authors: Mekota Anna‐Maria , Grupe Gisela , Ufer Sandra , Cuntz Ullrich 
Published: April 2006

AbstractStable nitrogen and carbon isotopic ratios of hair strands of six patients suffering from anorexia nervosa were measured to monitor a dietary change from near starvation to recovery. This paper presents the results of a first‐time study of nitrogen and carbon balance of the patients prior to and after admittance to a hospital and therapy. Sequential analysis of the isotopic ratios of hair strands of all patients could be related to the respective body mass index (BMI) of each patient. Our hypothesis concerning the diachronic change in δ15N and δ13C during therapy was met: The δ15N values were inversely related to the BMI, indicating a slow‐down in catabolism of bodily protein due to the process of gluconeogenesis during the starvation phase. In contrast, the δ13C values and BMI were in phase: an increase in BMI resulted in an increase in the δ13C values. This rise in δ13C ratios is best interpreted by an increased supply of protein in the diet. Furthermore, δ15N and δ13C were inversely related. We conclude that hair, which is easily and non‐traumatically sampled, is an adequate monitor that reflects dietary change and nitrogen balance within days. This isotopic method may also be applied in forensic studies with regard to cases of deprivation, and starvation, and may be a method for investigating starvation in historic populations. Copyright © 2006 John Wiley & Sons, Ltd.
Discovery of fatty acid ester metabolites of spirolide toxins in mussels from Norway using liquid chromatography/tandem mass spectrometry
Authors: Aasen John A. B. , Hardstaff William , Aune Tore , Quilliam Michael A. 
Published: April 2006

AbstractCultured mussels sampled in the spring of 2002 and 2003 from Skjer, a location in the Sognefjord, Norway, tested positive in the mouse bioassay for lipophilic toxins. In a previous report, it was established that a number of spirolides, cyclic imine toxins produced by the phytoplankton Alexandrium ostenfeldii, were present in the mussels and were responsible for the observed toxicity. The main toxin proved to be a new compound named 20‐methyl spirolide G. In subsequent studies, a delayed onset of spirolide‐like symptoms in the mouse bioassay exceeding the usual time limit of 20 min was observed in some samples, with symptoms and death appearing as long as 45–50 min after injection. It is well known that shellfish can extensively metabolize other toxins, such as okadaic acid and the dinophysistoxins, to fatty acid acyl esters and it is also known that a delayed onset of toxic symptoms with such metabolites can occur. Analyses performed with liquid chromatography/tandem mass spectrometry (LC/MS/MS) have revealed a complex mixture of esters of 20‐methyl spirolide G in the contaminated mussels. Precursor ion scanning has delineated the range of fatty acid esters involved, while product ion scanning has provided information on structure. Identity was also supported through reaction of 20‐methyl spirolide G with palmitic anhydride, which produced a derivative with a retention time and spectrum identical with one putative metabolite, 17‐O‐palmitoyl‐20‐methyl spirolide G. Copyright © 2006 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
The influence of structural features on facile McLafferty‐type, even‐electron rearrangements in tandem mass spectra of carboxylate anions
Authors: Grossert J. Stuart , Cook Matthew C. , White Robert L. 
Published: April 2006

AbstractIn contrast to the well‐described McLafferty rearrangement in odd‐electron cations, relatively little has been reported on comparable rearrangements in even‐electron ions, especially negative ions. This work reports a systematic study using tandem mass spectrometry (MS/MS) fragment ion spectra of carboxylate anions having a suitably acidic proton in the γ position. The rearrangement process was studied in both ion trap and triple quadrupole mass spectrometers; characteristic enolate anions and stable neutral products were formed at low collision energies. The process has diagnostic and analytical potential in, for example, the analysis of peptides having C‐terminal serine residues and of 3‐hydroxy‐ or 3‐aminocarboxylic acids in complex mixtures. Copyright © 2006 John Wiley & Sons, Ltd.
The spatial dynamics of invasive species spread
Authors: BenDor Todd K. , Metcalf Sara S. 
Published: April 2006

AbstractThe problem of invasive species spread requires timely analysis of the biological dynamics that lead to spatial dispersion. Here, a spatial dynamic model captures the invasive behavior of the recently introduced emerald ash borer (EAB) (Agrilus planipennis) and its impacts on host ash (Fraxinusspp.) trees. Parasite–host system dynamics are extended spatially using the Spatial Modeling Environment. The resulting model can serve as a repository for changing knowledge about EAB biology and behavior. Studies of the rapid EAB infestation in Michigan are used to inform simulations of its spread in DuPage County, Illinois, USA. We use a geographic information system to create heterogeneous host landscapes and to test alternative policy scenarios. We test the effectiveness of three suppression scenarios: the Michigan eradication strategy, firewood quarantines, and ash tree thinning. Simulations demonstrate that EAB spatial spread accelerates with degraded host capacity, with results pointing to firewood quarantines as the most effective solution. Copyright © 2006 John Wiley & Sons, Ltd.
Spatial dynamics of invasion in sinusoidally varying environments
Authors: Kinezaki Noriko , Kawasaki Kohkichi , Shigesada Nanako 
Published: April 2006

AbstractRange expansions of invading species in homogeneous environments have been extensively studied since the pioneer works by Fisher (Ann Eugen 7:255–369,1937) and Skellam (Biometrika 38:196–218,1951). However, environments for living organisms are often fragmented by natural or artificial habitat destruction. Here we address how such environmental heterogeneity affects the range expansion of invading species. We consider a single‐species invasion in heterogeneous environments whose habitat parameters vary in a sinusoidal or quasi‐sinusoidal manner. Accordingly, Fisher's model is modified to make the intrinsic growth rate and diffusion coefficient spatially variable. By numerically solving the model, we examine the spatio‐temporal pattern of propagating waves, and predict the speed as a function of the amplitude and the wave length of the diffusion coefficient and the intrinsic growth rate. Firstly, the results demonstrate that in the sinusoidally varying environment, if the intrinsic growth rate solely oscillates, the speed increases with increases in the amplitude of oscillation. Conversely, if the diffusion coefficient solely oscillates, the speed decreases with increases in the amplitude of oscillation. When both the intrinsic growth rate and diffusion coefficient oscillate, the speed is synergistically accelerated if the oscillations are in anti‐phase, whereas it is decelerated if the oscillations are in same phase. Secondly, the increase in the wave length in either the intrinsic growth rate or the diffusion coefficient leads to decreases in the speed. Thirdly, in the irregularly varying environment, the irregularity in the amplitude of the intrinsic growth rate enhances the speed, while that of the diffusion coefficient attenuates the speed.
Positive career orientation as an inhibitor of adolescent problem behaviour
Authors: Skorikov Vladimir , Vondracek Fred W. 
Published: April 2006

AbstractThis study tested the hypothesis that positive career orientation can prevent adolescents from engaging in or escalating problem behaviour. A 1‐year, longitudinal study was conducted on a sample of 234 junior‐high and high‐school students, who were 14.8 years old on the average in the beginning of the study. Using structural equation modeling, a developmental, two‐wave, two‐factor empirical model corresponding to the predicted relationships between career orientation and problem behaviour was found to fit the data well. According to the fitted model, positive career orientation had a significant negative longitudinal effect on problem behaviour. In contrast, we found no evidence in support of the assumption that career orientation can be affected by problematic behavioural tendencies.
On the stability and flow reversal of an asymmetrically heated open convection loop
Authors: Bau Haim H. , Torrance K. E. 
Published: April 2006

Experimental results are reported for a U-shaped, free convection loop. The top of the loop is open to an isothermal reservoir. The horizontal leg and one vertical leg are heated at rates Q1 and Q2, respectively. The loop is filled either with water or a water-saturated porous medium. Symmetric heating and asymmetric heating favouring the ascending leg of the loop both yield stable flows. Asymmetric heating favouring the descending leg leads to stable flows when the ratio Q1/Q2 is above a critical value. Below this critical value, the flow is observed to oscillate with increasing amplitude until the direction of flow in the loop undergoes a reversal. A steady flow follows the reversal. Analytical results include a stability analysis and time-dependent, one-dimensional numerical calculations, both of which compare favourably with experiment.The disturbance amplification mechanism is explained in terms of thermal anomalies which move through the loop with the material motion of the fluid. Since the heating and buoyancy generation processes are in phase in the heated, descending leg, a thermal anomaly can amplify as it flows through that leg. As the anomaly moves through the ascending leg, it initiates a subsequent anomaly of opposite sign in the descending leg. The result is an oscillating flow which, under appropriate conditions, can amplify.
Array measurements of atmospheric pressure fluctuations above surface gravity waves
Authors: Snyder R. L. , Dobson F. W. , Elliott J. A. , Long R. B. 
Published: April 2006

A joint experiment to study microscale fluctuations of atmospheric pressure above surface gravity waves was conducted in the Bight of Abaco, Bahamas, during November and December 1974. Field hardware included a three-dimensional array of six wave sensors and seven air-pressure sensors, one of which was mounted on a wave follower. The primary objectives of the study were to resolve differences in previous field measurements by Dobson (1971), Elliott (1972b) and Snyder (1974), and to estimate the vertical profile of wave-induced pressure and the corresponding input of energy and momentum to the wave field.Analysis of a pre-experiment intercalibration of instruments and of 30 h of field data partially removes the discrepancy between the previous measurements of the wave-induced component of the pressure and gives a consistent picture of the profile of this pressure over a limited range of dimensionless height and wind speed. Over this range the pressure decays approximately exponentially without change of phase; the decay is slightly less steep than predicted by potential theory. The corresponding momentum transfer is positive for wind speeds exceeding the phase speed. Extrapolation of present results to higher frequencies suggests that the total transfer is a significant fraction of the wind stress (0·1 to 1·0, depending on dimensionless fetch).Analysis of the turbulent component of the atmospheric pressure shows that the ‘intrinsic’ downwind coherence scale is typically an order-of-magnitude greater than the crosswind scale, consistent with a ‘frozen’ turbulence hypothesis. These and earlier data of Priestley (1965) and Elliott (1972c) suggest a horizontally isotropic ‘intrinsic’ turbulent pressure spectrum which decays ask−νwherekis the (horizontal) wave-number and ν is typically −2 to −3; estimates of this spectrum are computed for the present data. The implications of these findings for Phillips’ (1957) theory of wave growth are examined.
The nonlinear dynamics of baroclinic wave ensembles
Authors: Pedlosky Joseph 
Published: April 2006

A theory is developed to describe the weakly nonlinear dynamics which applies in the simultaneous presence of several, long, baroclinic waves. The geometry is flat (i.e. β = 0) and dissipation is modelled by Ekman friction in the context of the quasi-geostrophic two-layer model. Three main problems are discussed.
For free, unstable waves it is shown that the wave which is realized in finite amplitude is not the linearly most unstable wave. Rather a longer wave, capable of achieving the single largest steady amplitude, is favoured in the competition for the potential energy of the basic state. This result is shown necessary if the end state is steady and numerous numerical calculations indicate the pre-eminence of the same wave if the final state is vacillatory. The notion of conjugate waves, capable of identical final amplitude, is also discussed.If the free waves are subject to time-varying supercriticality so that intervals of stability ensue, the response is asymmetric over the period of the forcing. Sufficiently rapid ‘seasonal’ forcing leads to long-term aperiodic response.If each wave in the spectrum is directly forced a wave hysteresis phenomenon occurs. Sudden jumps in the wave amplitude at critical values of the forcing are intrinsic to the wave response. Again, sufficiently rapid wave forcing produces an aperiodic response.The forced wave problem exhibits multiple equilibria. Each solution branch corresponds to a different dominant wave. The determination of the realized branch depends on the relative stability criteria developed for the free waves.
Some Hele Shaw flows with time-dependent free boundaries
Authors: Richardson S. 
Published: April 2006

We consider a blob of Newtonian fluid sandwiched in the narrow gap between two plane parallel surfaces. At some initial instant, its plan-view occupies a given, simply connected domain, and its growth as further fluid is injected at a number of injection points in its interior is to be determined. It is shown that certain functionals of the domain of a purely geometric character, infinite in number, evolve in a predictable manner, and that these may be exploited in some cases of interest to yield a complete description of the motion.By invoking images, these results may be used to solve certain problems involving the growth of a blob in a gap containing barriers. Injection at a point in a half-plane bounded by a straight line, with an initially empty gap, is shown to lead to a blob whose outline is part of an elliptic lemniscate of Booth for which there is a simple geometrical construction. Injection into a quarter-plane is also considered in some detail when conditions are such that the image domain involved is simply connected.
On the coherent structure of the axisymmetric mixing layer: a flow-visualization study
Authors: Hussain A. K. M. F. , Clark A. R. 
Published: April 2006

In an effort to resolve some controversies regarding the turbulent mixing-layer structure, the near field of a large (18 cm diameter) air jet has been investigated for the jet exit speed of 30 m s−1. The smoke-laden axisymmetric mixing layer has been illuminated by a thin sheet of laser light in an azimuthal plane passing through the jet axis. High-speed visualization films of the mixing layer in the region of its self-preservation (of which a few picture sequences depicting space-time evolutions of the structure of the layer are presented) reveal that most of the time the mixing layer is in a state of disorganization, consisting of relatively smaller scale, random and diffuse turbulent motions; only occasionally are organized distinct large-scale coherent structures formed. The survival distances of the large-scale structures are found to be comparable to their average sizes. The survival time of these structures is about one ‘turnover’ time, each being roughly about five times the local characteristic time scale of the mixing layer. It is seen that tearing is as dominant a mode of large-scale interaction as pairing is; large-scale structures are continually sheared and typically fragmented due to a segment on the high-speed side being torn and swept away from the slower-moving outer portion. Evolution of the large structures occur not primarily through complete pairing as widely believed but quite frequently through ‘fractional pairing’ between segments which have been torn from different upstream large-scale coherent structures or through ‘partial pairing’ when one structure captures only a part of another. The movies show that along with entrainment of non-vortical ambient fluid, radially outward ejection of vortical fluid into the ambient is an important aspect of jet mixing. From aligned displays of ciné film frame sequences, space-time trajectories of identifiable vortical fluid elements have been traced. The convection velocity variation across the shear layer and even the overall structure convection velocity measured from these trajectories agree with those determined from the wave-number-celerity spectra, obtained from double-Fourier transformation of longitudinal velocity space-time correlation measurements with hot-wires.The visualization films do not bear out the two-street vortex ring model recently propounded by Lau. Based on our observations, we propose that tearing, ‘slippage’ and fractional and partial pairings are responsible for the observed radial variation of structure passage frequency, and the causes of the different coherent structures educed by Bruun on the high- and low-speed sides of the mixing layer and for Yule's failure in educing a coherent structure on the low-speed side of the layer.
The interaction between waves and a turbulent current: waves propagating with the current
Authors: Kemp P. H. , Simons R. R. 
Published: April 2006

This paper describes an experimental programme carried out in a laboratory channel with rough and smooth beds, to investigate the interaction between gravity waves and a turbulent current. In particular, changes induced in the mean-velocity profiles, turbulent fluctuations, bed shear stresses and wave attenuation rates are considered for a range of wave heights, keeping the wave period constant. The smooth-boundary tests were carried out as a necessary preliminary to the more-realistic rough-boundary condition.A directionally sensitive laser anemometer was used to measure horizontal, vertical, and 45° velocity components in the oscillating fluid, and an on-line minicomputer was programmed to produce ensemble averages of velocities, Reynolds stresses and wave-elevation data. The cycle was sampled at 200 separate phase positions, with 180 observations at each position. Measurements were made at up to 30 points in the vertical.Preliminary tests were carried out on the unidirectional current and on the waves alone. These show that mean-velocity profiles and turbulence parameters of the current agree satisfactorily with previous experiments, and that the waves are approximated closely by Stokes’ second-order theory.For combined wave and current tests, mean-velocity profiles are generally found to differ from those suggested by a linear superposition of wave and current velocities, a change in boundary-layer thickness being indicated. However, shear stresses at the smooth boundary are found to be described by such a linear addition.
Elastic jumps on fluid-filled elastic tubes
Authors: Cowley S. J. 
Published: April 2006

This paper is concerned with fluid flows through membranous elastic tubes. The tubes are assumed to be either untethered (except at the ends), or to be tethered by axial forces that prevent all axial motion of the tube.First we verify, for axisymmetric deformations that vary slowly in the axial direction, that the elastic balance of the tube can be expressed in terms of a ‘tube law’. In the case of the tethered tubes, the tube law takes the widely used form of a pressure/area relation for both steady and unsteady deformations. However, for untethered tubes, the tube law will generally be time-dependent if the deformations are unsteady. Conditions are then derived between the up- and downstream flows of a turbulent elastic jump. Although it is necessary for the elastic balance to be described by a tube law far up- and far downstream of the jump, we do not assume that the tube law is valid inside the jump. The conditions we derive are believed to hold for both collapsed and expanded tubes.The theory has applications in describing fluid flows within, for example, the airways, blood vessels and the urethra.
Direct numerical simulation of laminar and turbulent Bénard convection
Authors: Grötzbach Günther 
Published: April 2006

The TURBIT-3 computer code has been used for the direct numerical simulation of Bénard convection in an infinite plane channel filled with air. The method is based on the three-dimensional non-steady-state equations for the conservation of mass, momentum and enthalpy. Subgrid-scale models of turbulence are not required, as calculations with different grids show that the spatial resolution of grids with about 322 × 16 nodes provides sufficient accuracy for Rayleigh numbers up to Ra = 3·8 × 105. Hence this simulation model contains no tuning parameters.The simulations start from nearly random initial conditions. This has been found to be essential for calculating flow patterns and statistical data insensitive to grid parameters and agreeing with experimental experience. The numerical results show the theoretically predicted ‘skewed varicose’ instability at Ra = 4000. Warm and cold ‘blobs’ are identified as causing temperature-gradient reversals for all the high Rayleigh numbers under consideration. The calculated wavelengths and the corresponding flow regimes observed in the transition range confirm the stability maps determined theoretically. In the turbulent range the wavelengths agree qualitatively with low-aspect-ratio experiments. Accordingly, the Nusselt numbers lie at the upper end of the scatter band of experimental data, as these also depend on the aspect ratio. Appropriately normalized, the velocity and temperature fluctuation peaks are independent of the Rayleigh number. The vertical profiles agree largely with experimental data and, especially in case of temperature statistics, exhibit comparable or less scatter.
Mass transfer between a plane surface and an impinging turbulent jet: the influence of surface-pressure fluctuations
Authors: Kataoka K. , Kamiyama Y. , Hashimoto S. , Komai T. 
Published: April 2006

Local measurement of the mass-transfer rate and velocity gradient when an axisymmetric jet impinges on a flat plate was carried out using an electrochemical technique. Local measurement of the surface pressure on the flat plate was carried out separately using piezoelectric pressure transducers. The stagnation-point mass-transfer coefficient reaches a maximum when the flat plate is placed at 6 nozzle diameters from a convergent nozzle. It has been confirmed that the mass transfer to the flat plate for a high Schmidt number is greatly enhanced owing to the velocity-gradient disturbances in the wall region of the boundary layer, while the momentum transfer is insensitive to such disturbances. The relative intensity of the velocity-gradient fluctuations on the wall has an extremely large value at and near to the stagnation point, and decreases downstream, approaching a large constant value.These velocity-gradient disturbances are not due to the usual interaction of Reynolds stress with the shear stress of the mean flow, but are due to the interaction with the surface-pressure fluctuations converted from the velocity fluctuations of the oncoming jet.The three co-ordinate dimensions of large-scale eddies are calculated from the auto- and spatial correlations of the surface-pressure fluctuations. It is considered that such large-scale eddies play an important role in the production of a velocity-gradient disturbance in the wall region of the boundary layer from the velocity turbulence of the approaching jet.