bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-calorie cranberry juice supplementation reduces plasma oxidized LDL and cell adhesion molecule concentrations in men
Authors: Ruel Guillaume , Pomerleau Sonia , Couture Patrick , Lemieux Simone , Lamarche Benoît , Couillard Charles
Published: August 2007

Elevated circulating concentrations of oxidized LDL (OxLDL) and cell adhesion molecules are considered to be relevant markers of oxidative stress and endothelial activation which are implicated in the development of CVD. On the other hand, it has been suggested that dietary flavonoid consumption may be cardioprotective through possible favourable impacts on LDL particle oxidation and endothelial activation. The present study was undertaken to determine the effect of the daily consumption of low-calorie cranberry juice cocktail on plasma OxLDL, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin concentrations in men. Thirty men (mean age 51 (sd10) years) were recruited and asked to consume increasing daily doses of cranberry juice cocktail (125, 250 and 500 ml/d) over three successive periods of 4 weeks. Plasma OxLDL and adhesion molecule concentrations were measured by ELISA before and after each phase. We noted a significant decrease in plasma OxLDL concentrations following the intervention (P < 0·0001). We also found that plasma ICAM-1 (P < 0·0001) and VCAM-1 (P < 0·05) concentrations decreased significantly during the course of the study. In summary, the present results show that daily cranberry juice cocktail consumption is associated with decreases in plasma OxLDL, ICAM-1 and VCAM-1 concentrations in men.
Vitamin B12deficiency results in the abnormal regulation of serine dehydratase and tyrosine aminotransferase activities correlated with impairment of the adenylyl cyclase system in rat liver
Authors: Ebara Shuhei , Nakao Motoyuki , Tomoda Mayuko , Yamaji Ryoichi , Watanabe Fumio , Inui Hiroshi , Nakano Yoshihisa
Published: August 2007

The aim of the present study was to elucidate the mechanism of the vitamin B12deficiency-induced changes of the serine dehydratase (SDH) and tyrosine aminotransferase (TAT) activities in the rat liver. When rats were maintained on a vitamin B12-deficient diet, the activities of these two enzymes in the liver were significantly reduced compared with those in the B12-sufficient control rats (SDH 2·8 (sd0·56)v.17·5 (sd6·22) nmol/mg protein per min (n5);P < 0·05) (TAT 25·2 (sd5·22)v.41·3 (sd8·11) nmol/mg protein per min (n5);P < 0·05). In the B12-deficient rats, the level of SDH induction in response to the administration of glucagon and dexamethasone was significantly lower than in the B12-sufficient controls. Dexamethasone induced a significant increase in TAT activity in the primary culture of the hepatocytes prepared from the deficient rats, as well as in the cells from the control rats. However, a further increase in TAT activity was not observed in the hepatocytes from the deficient rats, in contrast to the cells from the controls, when glucagon was added simultaneously with dexamethasone. The glucagon-stimulated production of cAMP was significantly reduced in the hepatocytes from the deficient rats relative to the cells from the control rats. Furthermore, the glucagon-stimulated adenylyl cyclase activity in the liver was significantly lower in the deficient rats than in the controls. These results suggest that vitamin B12deficiency results in decreases in SDH and TAT activities correlated with the impairment of the glucagon signal transduction through the activation of the adenylyl cyclase system in the liver.
Macronutrient intake and discrepancy with nutritional recommendations in a group of elderly diabetic subjects
Authors: Helmer Catherine , Bricout Hélène , Gin Henri , Barberger-Gateau Pascale
Published: August 2007

Diet is a major aspect of glycaemic control in type 2 diabetes, particularly among the elderly. The objective of this study was to describe the food habits of elderly diabetic subjects compared with non-diabetic ones and to examine the difference between their nutritional behaviour and nutritional recommendations. This study was based on the Three City (3C) community-based cohort. The food habits of 1336 participants aged 65 or over, including 149 diabetic subjects, were evaluated using a FFQ and a 24 h recall of food consumption. For both sexes, intake of carbohydrates was lower for diabetic compared to non-diabetic subjects, essentially due to a lower intake of mono-/disaccharides. For diabetic men, this was compensated for by a higher intake of protein whereas women had a lower energy intake overall. Fibre intake was also higher in diabetic men. There was no absolute increase in fats intake, neither for men nor for women, and distribution of subtypes of fats (saturated, monounsaturated and polyunsaturated) did not differ between diabetic and non-diabetic subjects. Carbohydrates provided 40·5 % of energy intake in diabetic men and 43·9 % in diabetic women. Contrary to nutritional recommendations for diabetic subjects, for approximately two-thirds of the diabetic subjects carbohydrates represented less than 45 % of daily energy intake. Although food habits of elderly diabetic subjects differed from those of non-diabetic ones, these habits are not totally in line with nutritional recommendations. These results should be taken into account to adapt nutritional advice given to the diabetic population.
Chicory increases acetate turnover, but not propionate and butyrate peripheral turnovers in rats
Authors: Pouteau Etienne , Rochat Florence , Jann Alfred , Meirim Isabelle , Sanchez-Garcia Jose-Luis , Ornstein Kurt , German Bruce , Ballèvre Olivier
Published: August 2007

Chicory roots are rich in inulin that is degraded into SCFA in the caecum and colon. Whole-body SCFA metabolism was investigated in rats during food deprivation and postprandial states. After 22 h of food deprivation, sixteen rats received an IV injection of radioactive14C-labelled SCFA. The volume of distribution and the fractional clearance rate of SCFA were 0·25–0·27 litres/kg and 5·4–5·9 %/min, respectively. The half-life in the first extracellular rapidly decaying compartment was between 0·9 and 1·4 min. After 22 h of food deprivation, another seventeen rats received a primed continuous IV infusion of13C-labelled SCFA for 2 h. Isotope enrichment (13C) of SCFA was determined in peripheral arterial blood by MS. Peripheral acetate, propionate and butyrate turnover rates were 29, 4 and 0·3 μmol/kg per min respectively. Following 4 weeks of treatment with chicory root or control diets, eighteen fed rats received a primed continuous IV infusion of13C-labelled SCFA for 2 h. Intestinal degradation of dietary chicory lowered caecal pH, enhanced caecal and colonic weights, caecal SCFA concentrations and breath H2.The diet with chicory supplementation enhanced peripheral acetate turnover by 25 % (P = 0·017) concomitant with an increase in plasma acetate concentration. There were no changes in propionate or butyrate turnovers. In conclusion, by setting up a multi-tracer approach to simultaneously assess the turnovers of acetate, propionate and butyrate it was demonstrated that a chronic chicory-rich diet significantly increases peripheral acetate turnover but not that of propionate or butyrate in rats.
Consumption of organic foods and risk of atopic disease during the first 2 years of life in the Netherlands
Authors: Kummeling Ischa , Thijs Carel , Huber Machteld , van de Vijver Lucy P. L. , Snijders Bianca E. P. , Penders John , Stelma Foekje , van Ree Ronald , van den Brandt Piet A. , Dagnelie Pieter C.
Published: August 2007

We prospectively investigated whether organic food consumption by infants was associated with developing atopic manifestations in the first 2 years of life. The KOALA Birth Cohort Study in the Netherlands (n 2764) measured organic food consumption, eczema and wheeze in infants until age 2 years using repeated questionnaires. Diet was defined as conventional ( < 50 % organic), moderately organic (50–90 % organic) and strictly organic (>90 % organic). Venous blood samples taken from 815 infants at 2 years of age were analysed for total and specific IgE. Multivariate logistic regression models were fitted to control for potential confounding factors. Eczema was present in 32 % of infants, recurrent wheeze in 11 % and prolonged wheezing in 5 %. At 2 years of age, 27 % of children were sensitised against at least one allergen. Of all the children, 10 % had consumed a moderately organic diet and 6 % a strictly organic diet. Consumption of organic dairy products was associated with lower eczema risk (OR 0·64 (95 % CI 0·44, 0·93)), but there was no association of organic meat, fruit, vegetables or eggs, or the proportion of organic products within the total diet with the development of eczema, wheeze or atopic sensitisation. Further studies to substantiate these results are warranted.
Response of a compressible laminar boundary layer to free-stream vortical disturbances
Authors: RICCO PIERRE , WU XUESONG
Published: August 2007

As a first step towards understanding the role of free-stream turbulence in laminar–turbulent transition, we calculate the fluctuations induced by free-stream vortical disturbances in a compressible laminar boundary layer. As with the incompressible case investigated by Leibet al. (J. Fluid Mech. vol. 380, 1999, p. 169), attention is focused on components with long streamwise wavelength. The boundary-layer response is governed by the linearized unsteady boundary-region equations in the typical streamwise region where the local boundary-layer thickness δ* iscomparable with the spanwise length scale Λ of the disturbances. The compressible boundary-region equations are solved numerically for a single Fourier component to obtain the boundary-layer signature. The root-mean-square of the velocity and mass-flux fluctuations induced by a continuous spectrum of free-stream disturbances are computed by an appropriate superposition of the individual Fourier components.

Low-frequency vortical disturbances penetrate into the boundary layer to form slowly modulating streamwise-elongated velocity streaks. In the compressible regime, vortical disturbances are found to induce substantial temperature fluctuations so that ‘thermalstreaks’ also form. They may have a significant effect on the secondary instability. The calculations indicate that for a vortical disturbance with a relatively large Λ, the induced boundary-layer fluctuation ultimately evolves into an amplifying wave. This is due to a receptivity mechanism, in which a vortical disturbance first excites a decaying quasi-three-dimensional Lam–Rott eigensolution. The latter then undergoes wavelength shortening to generate a spanwise pressure gradient, which eventually converts the Lam–Rott mode into an exponentially growing mode. The latter is recognized to bea highly oblique Tollmien–Schlichting wave. A parametric study suggests that this receptivity mechanism could be significant when the free-stream Mach number is larger than 0.8.
Direct numerical simulations of dense suspensions: wave instabilities in liquid-fluidized beds
Authors: DERKSEN J. J. , SUNDARESAN S.
Published: August 2007

We present results of direct numerical simulations of travelling waves in dense assemblies of monodisperse spherical particles fluidized by a liquid. The cases we study have been derived from the experimental work of others. In these simulations, the flow of interstitial fluid is solved by the lattice-Boltzmann method (LBM) and the particles move under the influence of gravity, hydrodynamic forces stemming from the LBM, subgrid-scale lubrication forces and hard-sphere collisions. We first show that the propagating inhomogeneous structures seen in the simulations are in agreement with those observed experimentally. We then use the detailed information contained in the simulation results to assess aspects of two-fluid model closures, namely, fluid–particle drag, and the various contributions to the effective stresses. We show that the rates of compaction and dilation of the particle phase in the travelling waves are comparable to the rate at which the microstructure relaxes, and that there is a pronounced effect of the rate of compaction on the average collisional normal stress. Although this effect can be expressed as an effective bulk viscosity term, this approach would require the use of a path-dependent bulk viscosity. We also find that the effective fluid–particle drag coefficient can be described well with the often-used closure motivated by the experiments of Richardson & Zaki (Trans. Inst. Chem. Engng vol. 32, 1954, p. 35). In this respect, the effect of the system size for determining the drag requires specific care. The shear viscosity of the particle phase manifests small, but clearly noticeable dependence on the rate of compaction/dilation of the particle phase. Our observations point to the need for higher-order closures that recognize the slow evolution of the microstructure in these flows and account for the effects of non-equilibrium microstructure on the stresses.
Attenuation of long interfacial waves over a randomly rough seabed
Authors: ALAM MOHAMMAD-REZA , MEI CHIANG C.
Published: August 2007

The effects of randomly irregular bathymetry on the propagation of interfacial gravity waves are studied. Modelling sea water by a two-layer fluid of different densities, weakly nonlinear waves much longer than the sea depth but comparable to the horizontal scale of bathymetry are treated by Boussinesq approximation and multiple-scale analysis. For transient wave pulses, the governing equation for the pulse profile is shown to be an integro-differential equation combining KdV and Burgers terms. Quantitative and qualitative effect of disorder on the attenuation of wave amplitude, reduction of wave speed and change of wave profile are examined numerically and analytically based on the asymptotic approximation. For time-harmonic waves, mode-coupling equations are derived and examined for the competition between diffusion by random scattering, steepening by nonlinearityand frequency dispersion for a broad range of depth ratios.
Quasi-static rheology of foams. Part 1. Oscillating strain
Authors: KABLA ALEXANDRE , DEBREGEAS GEORGES
Published: August 2007

A quasi-static simulation is used to study the mechanical response of a disordered bidimensional aqueous foam submitted to an oscillating shear strain. The application of shear progressively extends the elastic domain, i.e. the strain range within which no plastic process occurs. It is associated with the development of an irreversible normal stress difference, and a decrease in the shear modulus, which are both signatures of the appearance of anisotropy in the film network. Beyond this mechanical measurement, the evolutionof the structural properties of the foam is investigated. We focus in particular on the energy E0 defined as the minimum line-length energy under zero shear stress. For strainamplitude less than ~0.5, this quantity is found to decay with the number of applied cycles as a result of the curing of topological defects. However, for higher strain amplitude, plastic events appear to increase the structural disorder and tend to gather near the shearing walls. This process is a precursor of the shear-banding transition observed in fully developed flows, which will be studied in the companion paper. Movies are available with the online version of the paper.
Quasi-static rheology of foams. Part 2. Continuous shear flow
Authors: KABLA ALEXANDRE , SCHEIBERT JULIEN , DEBREGEAS GEORGES
Published: August 2007

The evolution of a bidimensional foam submitted to continuous quasi-static shearing isinvestigated both experimentally and numerically. We extract, from the images of the sheared foam, the plastic flow profiles as well as the local statistical properties of the stress field. When the imposed strain becomes larger than the yield strain, the plastic events develop large spatial and temporal correlations, and the plastic flow becomes confined to a narrow shear band. This transition and the steady-state regime of flow are investigated by first focusing on the elastic deformation produced by an elementary plastic event. This allows us to understand (i) the appearance of long-lived spatial heterogeneities of the stress field, which we believe are at the origin of the shear-banding transition, and (ii) the statistics of the dynamic fluctuations of the stress field induced by plastic rearrangements in the steady-state regime. Movies are available with the online versionof the paper.
Sound generated by instability wave/shock-cell interaction in supersonic jets
Authors: RAY PRASUN K. , LELE SANJIVA K.
Published: August 2007

Broadband shock-associated noise is an important component of the overall noise generated by modern airplanes. In this study, sound generated by the weakly nonlinear interaction between linear instability waves and the shock-cell structure in supersonic jets is investigated numerically in order to gain insight into the broadband shock-noise problem. The model formulation decomposes the overall flow into a mean flow, linear instability waves, the shock-cell structure and shock-noise. The mean flow is obtained by solving RANSequations with a k-ε model. Locally parallel stability equations are solved for the shock structure, and linear parabolized stability equations are solved for the instability waves. Then, source terms representing the instability wave/shock-cell interaction are assembled and the inhomogeneous linearized Euler equations are solved for the shock-noise.Three cases are considered, a cold under-expanded Mj = 1.22 jet, a hot under-expanded Mj = 1.22 jet, and a cold over-expanded Mj = 1.36 jet.

Shock-noise computations are used to identify and understand significant trends in peak sound amplitudes and radiation angles. The peak sound radiation angles are explained well with the Mach wave model of Tam & Tanna J. Sound Vib. Vol. 81, 1982, p. 337). The observed reduction of peak sound amplitudes with frequency correlates well with the corresponding reduction of instability wave growth with frequency. However, in order to account for variation of sound amplitude for different azimuthal modes, the radial structure of the instability waves must be considered in additionto streamwise growth. The effect of heating on the Mj = 1.22 jet is shown to enhance the sound radiated due to the axisymmetric instability waves while the other modesare relatively unaffected. Solutions to a Lilley–Goldstein equation show that soundgenerated by ‘thermodynamic’ source terms is small relative to sound from ‘momentum’ sources though heating does increase the relative importance of the thermodynamic source. Furthermore, heating preferentially amplifies sound associated with the axisymmetric modes owing to constructive interference between sound from the momentumand thermodynamic sources. However, higher modes show destructive interference between these two sources and are relatively unaffected by heating.
Viscous flow past a flexible fibre tethered at its centre point: vortex shedding
Authors: ZHU LUODING
Published: August 2007

Motivated by a laboratory experiment reported in Alben, Shelley & Zhang (Nature, vol. 420, 2002, p. 479), we performed simulations of an elastic fibre anchored at its centre point and immersed in a flowing viscous incompressible fluid by the immersed boundary (IB) method. We focus on the influence of some dimensionless parameters on vortex shedding from the fibre for Re in the range [30, 800]. Three sets of simulationswere designed to investigate the influence of Reynolds number Re, dimensionless fibre flexure modulus b, and dimensionless fibre length on vortex shedding. According to the simulation results, Re, b, and each has a significant influence on the structure of shed vortices. However, Re has little influence on the vortex shedding frequency. With the increase of dimensionless bending modulus, the dimensionless vortex shedding frequency (fvs) and the critical Reynolds number (Rec) decrease approximately as power-law functions. Both fvs and Rec increase approximately linearly as dimensionless fibre length increases.
Generation of solitary waves by transcritical flow over a step
Authors: GRIMSHAW R. H. J. , ZHANG D.-H. , CHOW K. W.
Published: August 2007

It is well-known that transcritical flow over a localized obstacle generates upstream and downstream nonlinear wavetrains. The flow has been successfully modelled in the framework of the forced Korteweg–de Vries equation, where numerical and asymptotic analytical solutions have shown that the upstream and downstream nonlinear wavetrains have the structure of unsteady undular bores, connected by a locally steady solution over the obstacle, which is elevated on the upstream side and depressed on the downstream side. Inthispaper we consider the analogous transcritical flow over a step, primarily in the context of water waves. We use numerical and asymptotic analytical solutions of the forced Korteweg–de Vries equation, together with numerical solutions of the full Eulerequations, to demonstrate that a positive step generates only an upstream-propagating undular bore, and a negative step generates only a downstream-propagating undular bore.
Vortex interaction with a moving sphere
Authors: ALLEN J. J. , JOUANNE Y. , SHASHIKANTH B. N.
Published: August 2007

This paper details the experimental results of the axisymmetric collision of a vortex ring with a sphere. The experiments were conducted in water and a neutrally buoyant sphere was free to move in response to the impulse delivered by the vortex ring during the interaction. Good agreement has been achieved between kinematic data for the sphere speed and acceleration and the behaviour of the moment and rate of change of the moment of vorticity, measured using particle image velocimetry (PIV). The interaction of the vortex ring with the sphere creates secondary vorticity on the sphere surface. This initially results in a reduction of the fluid impulse and an acceleration of the sphere. However, within the measurement window of the interaction, the rate of increase of the positive moment of vorticity is slightly larger than the rate of increase of the negative moment of vorticityand the sphere gradually slows. A movie is available with the online version of the paper.
Motion of a sphere normal to a wall in a second-order fluid
Authors: ARDEKANI A. M. , RANGEL R. H. , JOSEPH D. D.
Published: August 2007

The motion of a sphere normal to a wall is investigated. The normal stress at the surface of the sphere is calculated and the viscoelastic effects on the normal stress for different separation distances are analysed. For small separation distances, when the particle is moving away from the wall, a tensile normal stress exists at the trailing edge if the fluid is Newtonian, while for a second-order fluid a larger tensile stress is observed. When the particle is moving towards the wall, the stress is compressive at the leading edge for a Newtonian fluid whereas a large tensile stress is observed for a second-orderfluid. The contribution of the second-order fluid to the overall force applied to the particle is towards the wall in both situations. Results are obtained using Stokes equationswhen α1+α2=0. In addition, a perturbation method has been utilized for a sphere very close to a wall and the effect of non-zero α1+α2 is discussed. Finally, viscoelastic potential flow is used and the results are compared with the other methods.
Molecular epidemiology with subtype analysis ofCryptosporidiumin calves in Belgium
Authors: GEURDEN T. , BERKVENS D. , MARTENS C. , CASAERT S. , VERCRUYSSE J. , CLAEREBOUT E.
Published: August 2007

The prevalence ofCryptosporidiumin calves younger than 10 weeks was estimated in a cross-sectional epidemiological study on 100 dairy (n=499) and 50 beef (n=333) farms in East Flanders (Belgium), using a previously evaluated immunofluorescence assay (Merifluor®). The calf prevalence was 37% (95% Probability Interval (PI): 7–70%) in dairy calves and 12% (95% PI: 1–30%) in beef calves. To elucidate the genetic diversity, theCryptosporidium18S ribosomal DNA and the 70 kDa heat shock protein gene were targeted. In the majority of the samplesC. parvumwas present, althoughC. boviswas also identified, all but one in calves older than 1 month. The porcine-specificC. suiswas identified in 1 beef calf. Subtyping ofC. parvumpositive isolates by sequence analysis of the 60 kDa glycoprotein gene indicated the presence of 4 allele IIa subtypes, along with 1 subtype IIdA22G1. The subtype IIaA15G2R1 was most prevalent, next to subtype IIaA13G2R1 and IIaA16G2R1, and a new subtype IIaA14G2R1. The results of the present study indicate a high prevalence ofCryptosporidiuminfections in calves in Belgium and confirm that these calves should be considered as a potential zoonotic reservoir for human infections.
Genetic fingerprinting and identification of differentially expressed genes in isolates ofLeishmania donovanifrom Indian patients of post-kala-azar dermal leishmaniasis
Authors: SUBBA RAJU B. V. , SINGH R. , SREENIVAS G. , SINGH S. , SALOTRA P.
Published: August 2007

Post-kala-azar dermal leishmaniasis (PKDL) is an unusual dermatosis that develops as a sequel in 5–15% of cured cases of kala-azar (KA) after months or years of treatment in India. Molecular differences are reported to exist between the KA and PKDL isolates which may underlie the diversity in clinical manifestations of the disease. Here, arbitrary primed-PCR (AP-PCR) has been used for genetic fingerprinting of parasite isolates from dermal lesions of PKDL patients (n=14) and compared with bone-marrow derived parasites from KA patients (n=3). All isolates showed an identical AP-PCR pattern with 4 arbitrary primers. Further, AP-PCR was exploited to identify the stage regulated genes of the parasite. Six polymorphic fragments were identified in PKDL in comparison with KA isolates, and were subjected to Northern blot analysis. Five polymorphic fragments represented transcribed sequences; 4 out of 5 drew differential expression in pro- and amastigote stages, although the expression was comparable between PKDL and KA isolates. The study led to the identification of genes, which exhibit stage-regulated expression inLeishmania donovaniderived from PKDL or KA patients, including a putative phosphodiesterase, DEAD box RNA helicase, iron superoxide dismutase b (fesodb) and a hypothetical protein. Demonstration of transcripts of DEAD box RNA helicase in PKDL and KA diseased tissues implicates its role in disease pathogenesis.
Life in the Atacama: Searching for life with rovers (science overview)
Authors: Cabrol Nathalie A. , Wettergreen David , Warren‐Rhodes Kim , Grin Edmond A. , Moersch Jeffrey , Diaz Guillermo Chong , Cockell Charles S. , Coppin Peter , Demergasso Cecilia , Dohm James M. , Ernst Lauren , Fisher Gregory , Glasgow Justin , Hardgrove Craig , Hock Andrew N. , Jonak Dominic , Marinangeli Lucia , Minkley Edwin , Ori Gian Gabriele , Piatek Jennifer , Pudenz Erin , Smith Trey , Stubbs Kristen , Thomas Geb , Thompson David , Waggoner Alan , Wagner Michael , Weinstein Shmuel , Wyatt Michael
Published: August 2007

The Life in the Atacama project investigated the regional distribution of life and habitats in the Atacama Desert of Chile. We sought to create biogeologic maps through survey traverses across the desert using a rover carrying biologic and geologic instruments. Elements of our science approach were to: Perform ecological transects from the relatively wet coastal range to the arid core of the desert; use converging evidence from science instruments to reach conclusions about microbial abundance; and develop and test exploration strategies adapted to the search of scattered surface and shallow subsurface microbial oases. Understanding the ability of science teams to detect and characterize microbial life signatures remotely using a rover became central to the project. Traverses were accomplished using an autonomous rover in a method that is technologically relevant to Mars exploration. We present an overview of the results of the 2003, 2004, and 2005 field investigations. They include: The confirmed identification of microbial habitats in daylight by detecting fluorescence signals from chlorophyll and dye probes; the characterization of geology by imaging and spectral measurement; the mapping of life along transects; the characterization of environmental conditions; the development of mapping techniques including homogeneous biological scoring and predictive models of habitat location; the development of exploration strategies adapted to the search for life with an autonomous rover capable of up to 10 km of daily traverse; and the autonomous detection of life by the rover as it interprets observations on‐the‐fly and decides which targets to pursue with further analysis.
Little River Experimental Watershed database
Authors: Bosch D. D. , Sheridan J. M. , Lowrance R. R. , Hubbard R. K. , Strickland T. C. , Feyereisen G. W. , Sullivan D. G.
Published: August 2007

The U.S. Department of Agriculture Agricultural Research Service Southeast Watershed Research Laboratory (SEWRL) initiated a hydrologic research program on the Little River Experimental Watershed in south‐central Georgia, United States, in 1967. The primary intent of the program was to develop an improved understanding of basic hydrologic and water quality processes on Coastal Plain watersheds and to evaluate the effects of agricultural management practices on the region's natural resources and environment. Long‐term (up to 37 years), research‐quality streamflow data have been collected for up to eight flow measurement sites within the Gulf‐Atlantic Coastal Plain physiographic region, an important agricultural production area in the southeastern United States. Forty‐six precipitation gauges and three climate stations are currently in operation to collect data in support of the hydrologic network. Over the past 20 years, sediment and agrichemical concentrations in streamflow have also been monitored to permit evaluation of the impacts of agriculture on regional surface and groundwater quality. Along with the hydrologic and water quality data, geographic spatial data layers for terrain, soils, geology, vegetation, and land management have also been developed. These databases, described in five accompanying data reports, can be accessed via an ftp site supported by the SEWRL (ftp://www.tiftonars.org/).
Storm tracks and annular modes
Authors: Luo Dehai , Gong Tingting , Diao Yina , Zhou Wen
Published: August 2007

In this paper, it is demonstrated by using a weakly nonlinear model that low‐frequency annular modes with a dipole meridional structure can be excited by the eddy fluxes from synoptic‐scale eddies. If the storm track organized by synoptic‐ scale eddies is zonally confined in a narrow localized region as observed in the Northern Hemisphere (NH), the eddy‐driven dipolar pattern will exhibit both a relatively short zonal scale and a zonal asymmetry during its life cycle, which is attributed to the strong downstream energy dispersion of Rossby waves. Such a zonal asymmetry is found to be sensitive to the relative position between the preexisting storm track and dipole mode. However, if the preexisting storm track is zonally confined in a rather wide localized region, as observed in the Southern Hemisphere (SH), the Rossby wave dispersion almost disappears. In this case, the eddy‐driven dipole mode with a relatively large zonal scale exhibits a zonal symmetry, which is almost insensitive to its position relative to the preexisting storm track. This sheds light on why eddy‐driven dipole modes in the SH are more likely to be annular modes.
Trends in tropical tropospheric column ozone from satellite data and MOZART model
Authors: Beig Gufran , Singh Vikas
Published: August 2007

Trend analysis of tropical (30°S–30°N) tropospheric columnar ozone (TCO) has been done using Nimbus7 and Earth Probe satellite ‐Total Ozone Mapping Spectrometer (TOMS) data for the period of 1979–2005 using multifunctional regression model. Results indicate highest increasing trend (7–9% per decade) over some parts of south Asian continental region which is attributed to increasingly high emissions of ozone precursors over the region. Among different marine regions, Ozone trend is found to be highest (4–6% per decade) over the Bay of Bengal which is largely be explained by the large scale wind systems causing massive transport of continental pollutants over this region. The study also includes the comparison of the satellite results with those obtained from a 3‐D chemistry transport model. In some cases, the magnitude of observed trends is consistent with the model trends. However, in some cases like East Asia and area around Philippines differences are inevitable.
Impact of model physics on estimating the surface mass balance of the Greenland ice sheet
Authors: Bougamont Marion , Bamber Jonathan L. , Ridley Jeff K. , Gladstone Rupert M. , Greuell Wouter , Hanna Edward , Payne Anthony J. , Rutt Ian
Published: August 2007

Long‐term predictions of sea level rise from increased Greenland ice sheet melting have been derived using Positive Degree Day models only. It is, however, unknown precisely what uncertainties are associated with applying this simple surface melt parameterization for future climate. We compare the behavior of a Positive Degree Day and Energy Balance/Snowpack model for estimating the surface mass balance of the Greenland ice sheet under a warming climate. Both models were first tuned to give similar values for present‐day mass balance using 10 years of ERA‐40 climatology and were then run for 300 years, forced with the output of a GCM in which atmospheric CO2 increased to 4 times preindustrial levels. Results indicate that the Positive Degree Day model is more sensitive to climate warming than the Energy Balance model, generating annual runoff rates almost twice as large for a fixed ice sheet geometry. Roughly half of this difference was due to differences in the volume of melt generated and half was due to differences in refreezing rates in the snowpack. Our results indicate that the modeled snowpack properties evolve on a multidecadal timescale to changing climate, with a potentially large impact on the mass balance of the ice sheet; an evolution that was absent from the Positive Degree Day model.
Seasonal variation in the correlation of airglow temperature and emission rate
Authors: Espy P. J. , Stegman J. , Forkman P. , Murtagh D.
Published: August 2007

The hydroxyl (OH) rotational temperature and band emission rate have been derived using year‐round, ground‐based measurements of the infrared OH nightglow from Sweden from 1991 to 2002. Recent work has suggested that, during the winter, all scales of dynamical variations of radiance and temperature arise from vertical motions, implying that the effective source concentrations of atomic oxygen are constant. The present data show correlations between temperature and radiance both during winter and summer that are consistent with those observed in that previous work. However, during the transition to summer there is a rapid decrease in the temperature and its variation that is not reflected in the band radiance, suggesting that only the shorter‐scale variations are accompanied by significant vertical motion. This indicates that the shorter‐scale dynamical variations occur against an independent, seasonally changing background temperature profile in a way that is consistent with that predicted by gravity‐wave models.
Thermal convection of water filled in a tall vessel at or near the center of a solenoidal magnet
Authors: Maki Syou , Ataka Mitsuo , Tagawa Toshio , Ozoe Hiroyuki
Published: August 2007

Three-dimensional computation is carried out on the convection of water in a tall, cylindrical vessel heated from below and cooled from above at or near the center of a bore of a solenoidal magnet. The computation results indicate that the flow localization is realized by the distribution of the magnetic force. Furthermore, due to inclination of the vessel and small off-centered replacement from the magnet center, flow direction control over the localized convection roll is achieved. The results presented include promotion of convection without mechanical stirring, local suppression of convection, and induction of a large roll with a fixed direction. Thus, it is discussed that control over convective flows is potentially possible in a tall vessel with the aid of magnetic force.
Comparison of direct numerical simulations and particle-image velocimetry data of turbulent channel flow rotating about the streamwise axis
Authors: Recktenwald I. , Weller T. , Schröder W. , Oberlack M.
Published: August 2007

The influence of rotation about the streamwise axis on a turbulent channel flow is discussed by analyzing and comparing numerical and experimental data. The numerical study uses direct numerical simulations (DNS), while the experiments were based on particle-image velocimetry (PIV). The flow properties in the numerical and experimental analyses were maintained as similar as possible. For comparability with data from the literature the nonrotating channel flow at a Reynolds number Reτ=180 serves as a reference problem. Depending on the rotation rate of the channel the development of a secondary flow perpendicular to the main flow has been found in both investigations. The rotation primarily influences those components of the Reynolds shear stresses, which contain the spanwise velocity component. The size of the correlation areas and thus the length scales of the flow increase in all three coordinate directions, leading to longer structures. The increased momentum exchange can be deducted from the behavior of the mean main velocity profile, which shows a decreased centerline velocity and an increased velocity near the wall at growing rotation rates. The qualitative development of the mean flow and the statistical flow properties is similar for the simulation and the experiment. The growth of the coherent turbulent structures with the rotation rate is confirmed by both investigations.
Metastable cluster intermediates in the condensation of charged macromolecule solutions
Authors: Hutchens Shelby B. , Wang Zhen-Gang
Published: August 2007

The authors examine the possibility of a two-step nucleation to the bulk condensation transition that proceeds via a metastable liquid cluster intermediate having some preferred size. The metastable intermediate is stabilized by electrostatic repulsion, which becomes screened by small mobile ions at sufficiently large cluster sizes, thus allowing the eventual condensation to a bulk phase. Our calculation employs a capillary model for the cluster and the electrostatic interactions are treated using the Poisson-Boltzmann approach. Condensation via this metastable intermediate may be a very general phenomenon which applies not only to solutions of charged particles (e.g., proteins, colloidal particles, and polyelectrolytes) but to any system involving short-range attraction and long-range repulsion undergoing macrophase separation in which a metastable microphase separation is also possible.
Charge transmission through a molecular wire: The role of terminal sites for the current-voltage behavior
Authors: Petrov E. G. , Zelinskyy Ya. R. , May V. , Hänggi P.
Published: August 2007

The current-voltage and the conductance-voltage characteristics are analyzed for a particular type of molecular wire embedded between two electrodes. The wire is characterized by internal molecular units where the lowest occupied molecular orbital (LUMO) levels are positioned much above the Fermi energy of the electrodes, as well as above the LUMO levels of the terminal wire units. The latter act as specific intermediate donor and acceptor sites which in turn control the current formation via the superexchange and sequential electron transfer mechanisms. According to the chosen wire structure, intramolecular multiphonon processes may block the superexchange component of the interelectrode current, resulting in a negative differential resistance of the molecular wire. A pronounced current rectification appears if (i) the superexchange component dominates the electron transfer between the terminal sites and if (ii) the multiphonon suppression of distant superexchange charge hopping events between those sites is nonsymmetric.
Sensitive ultrasonic vibrometer for very low frequency applications
Authors: Cretin B. , Vairac P. , Jachez N. , Pergaud J.
Published: August 2007

Ultrasonic measurement of distance is a well-known low cost method but only a few vibrometers have been developed because sensitivity, spatial resolution, and bandwidth are not high or wide enough for standard laboratory applications. Nevertheless, compared to optical vibrometers, two interesting properties should be considered: very low frequency noise (0.1Hzto1kHz) is reduced and the long wavelength enables rough surfaces to be investigated. Moreover, the ultrasonic probe is a differential sensor, without being a mechanical load for the vibrating structure as usual accelerometers based on contacting transducers are. The main specificity of the presented probe is its ultralow noise electronics including a 3∕2 order phase locked loop which extracts the phase modulation related to the amplitude of the detected vibration. This article presents the main useful physical aspects and details of the actual probe. The given application is the measurement of the vibration of an isolated optical bench excited at very low frequency with an electromagnetic transducer.
Digital-signal-processor-based dynamic imaging system for optical tomography
Authors: Lasker Joseph M. , Masciotti James M. , Schoenecker Matthew , Schmitz Christoph H. , Hielscher Andreas H.
Published: August 2007

In this article, we introduce a dynamic optical tomography system that is, unlike currently available analog instrumentation, based on digital data acquisition and filtering techniques. At the core of this continuous wave instrument is a digital signal processor (DSP) that collects, collates, processes, and filters the digitized data set. The processor is also responsible for managing system timing and the imaging routines which can acquire real-time data at rates as high as 150Hz. Many of the synchronously timed processes are controlled by a complex programable logic device that is also used in conjunction with the DSP to orchestrate data flow. The operation of the system is implemented through a comprehensive graphical user interface designed with LABVIEW software which integrates automated calibration, data acquisition, data organization, and signal postprocessing. Performance analysis demonstrates very low system noise (∼1pW rms noise equivalent power), excellent signal precision (<0.04%–0.2%) and long term system stability (<1% over 40min). A large dynamic range (∼190dB) accommodates a wide scope of measurement geometries and tissue types. First experiments on tissue phantoms show that dynamic behavior is accurately captured and spatial location can be correctly tracked using this system.
Nanosecond x-Ray diffraction from polycrystalline and amorphous materials in a pinhole camera geometry suitable for laser shock compression experiments
Authors: Hawreliak J. , Lorenzana H. E. , Remington B. A. , Lukezic S. , Wark J. S.
Published: August 2007

Nanosecond pulses of quasimonochromatic x-rays emitted from the K shell of ions within a laser-produced plasma are of sufficient spectral brightness to allow single-shot recording of powder diffraction patterns from thin foils of order millimeter diameter. Strong diffraction signals have been observed in a cylindrical pinhole camera arrangement from both polycrystalline and amorphous foils, and the experimental arrangement and foil dimensions are such that they allow for laser shocking or quasi-isentropic loading of the foil during the diffraction process.
Elastic and thermal properties of Zr2Al3C4: Experimental investigations and ab initio calculations
Authors: He L. F. , Wang J. Y. , Bao Y. W. , Zhou Y. C.
Published: August 2007

This article presents the results of combined experimental and theoretical studies of elastic and thermal properties of Zr2Al3C4 carbide. The full set of second order elastic constants, bulk modulus, shear modulus, and Young’s modulus of Zr2Al3C4 were calculated and compared with those of Zr3Al3C5 and ZrC. The experimentally measured Young’s modulus and shear modulus are in good agreement with theoretical ones. The calculated Debye temperature from elastic constants of Zr2Al3C4 is 830 K, which is slightly higher than that of Zr3Al3C5, and exhibits pronounced enhancement in comparison with that of ZrC. The highest Debye temperature of Zr2Al3C4 is related with its highest specific stiffness, i.e., the stiffness-to-weight ratio. The heat capacity and thermal conductivity of Zr2Al3C4 were measured by means of the flash method. The thermal conductivity of Zr2Al3C4 decreases with increasing temperature, for instance the values at room temperature and 1600 K are 15.5 and 10.1 W/m K, respectively. The investigations provide information on elastic and thermal properties of Zr2Al3C4 with promising high temperature applications.
Modeling of low energy-high dose arsenic diffusion in silicon in the presence of clustering-induced interstitial generation
Authors: Skarlatos D. , Tsamis C.
Published: August 2007

In this work we develop a simple macroscopic model for the prediction of arsenic diffusion in silicon under low energy-high dose implantation conditions. Under these conditions, As-enhanced diffusion is attributed mainly to interstitial injection due to the formation of As-vacancy clusters. The basis of the model is the introduction of a bulk interstitial generation source from the entire As distribution, taking into account the difference between the chemical and active profiles of the dopant during drive-in annealing. The model has been introduced to the SYNOPSYS-TAURUS process simulator in order to simulate the results of an experiment especially designed for this purpose. Very satisfactory simulation results have been obtained, taking into account the simplicity of the model. Moreover, the model predicts, at least for short annealing times, the initial stage (trend) of the well-known arsenic uphill diffusion phenomenon at the native oxide/silicon interface.
Optical manipulation and rotation of liquid crystal drops using high-index fiber-optic tweezers
Authors: Abedin Kazi Sarwar , Kerbage Charles , Fernandez-Nieves Alberto , Weitz David A.
Published: August 2007

We report an optical fiber tweezer based on high-index material for trapping and optical manipulation of microscale particles in water. The use of a high-index material increases the trapping force with respect to the more common silica, through tighter focusing of light. We demonstrate the potential of this simple and versatile device by trapping and rotating nematic liquid crystal drops. We monitor the rotation of the drop by detecting light modulation observed with the same fiber using backscattered light, which exhibits modulation in intensity due to the rotation of the drop; this further extends the capabilities of the fiber tweezers.
On the structural and energetic properties of the hydrogen absorber Li2Mg(NH)2
Authors: Moysés Araújo C. , Scheicher Ralph H. , Jena Puru , Ahuja Rajeev
Published: August 2007

The authors have performed density functional theory based calculations of several possible conformations for the crystal structure of Li2Mg(NH)2 and they confirm the α phase, resolved from both x-ray and neutron diffraction data, as the ground-state configuration. It is also found that although the N–H bond is stronger in Li2Mg(NH)2 than in Li2NH, hydrogen release from Li2Mg(NH)2∕LiH mixture displays more favorable thermodynamics than that from the Li2NH∕LiH mixture. The insights gained from this seemingly counterintuitive result should prove helpful in the search for promising hydrogen storage materials.