bluuebunny/crossref_metadata_2025 huggingface dataset:
Navier-Stokes Simulation of the Flow Around an Airfoil in Darrieus Motion
Authors: Tchon Ko-Foa , Paraschivoiu Ion
Published: May 2008

In order to study the dynamic stall phenomenon on a Darrieus wind turbine, the incompressible flow field around a moving airfoil is simulated using a noninertial stream function-vorticity formulation of the two-dimensional unsteady Navier-Stokes equations. Spatial discretization is achieved by the streamline upwind Petrov-Galerkin finite element method on a hybrid mesh composed of a structured region of quadrilateral elements in the vicinity of solid boundaries, an unstructured region of triangular elements elsewhere, and a layer of infinite elements surrounding the domain and projecting the external boundary to infinity. Temporal discretization is achieved by an implicit second order finite difference scheme. At each time step, a nonlinear algebraic system is solved by a Newton method. To accelerate computations, the generalized minimum residual method with an incomplete triangular factorization preconditioning is used to solve the linearized Newton systems. The solver is applied to simulate the flow around a NACA 0015 airfoil in Darrieus motion and the results are compared to experimental observations. To the authors’ knowledge, it is the first time that the simulation of such a motion has been performed using the Navier-Stokes equations.
Closed-Form Analytical Solutions of High-Temperature Heat Pipe Startup and Frozen Startup Limitation
Authors: Cao Y. , Faghri A.
Published: May 2008

Previous numerical and experimental studies indicate that the high-temperature heat pipe startup process is characterized by a moving hot zone with relatively sharp fronts. Based on the above observation, a flat-front model for an approximate analytical solution is proposed. A closed-form solution related to the temperature distribution in the hot zone and the hot zone length as a function of time are obtained. The analytical results agree well with the corresponding experimental data, and provide a quick prediction method for the heat pipe startup performance. Finally, a heat pipe limitation related to the frozen startup process is identified, and an explicit criterion for the high-temperature heat pipe startup is derived. The frozen startup limit identified in this paper provides a fundamental guidance for high-temperature heat pipe design.
Freezing Flow in a Subcooled Permeable Medium
Authors: Griffiths S. K. , Nilson R. H.
Published: May 2008

Analytical similarity solutions are derived for the problem of transient one-dimensional flow and freezing of a liquid in an initially dry permeable half-space. The structure of the flow consists of three regions: a liquid zone in which the temperature decreases to the freezing temperature, a central two-phase zone where the temperature is at the freezing point, and a leading gas-filled region in which the temperature is nearly undisturbed. The propagation velocity of this intrusion is determined as a function of the subcooling, latent heat, and other process parameters. As the inlet temperature approaches the freezing temperature, the governing equations admit a pair of solutions having propagation velocities that sometimes differ by more than an order of magnitude.
Heat Transfer With Very High Free-Stream Turbulence: Part II—Analysis of Results
Authors: Maciejewski P. K. , Moffat R. J.
Published: May 2008

Correlations describing the effect of free-stream turbulence on heat transfer have been offered by Simonich and Bradshaw (1978), Pedisius et al. (1983), and Blair (1983a), but they fail to describe the present data. The present data can be represented by a function of St, St/St0, ReΔ2Tu, and Λ/Δ2 within ±20 percent, but equally well by a simple correlation relating the rms fluctuating velocity in the free stream, u′, to the heat transfer coefficient, h. A new Stanton number, St′, based on u′max, the maximum standard deviation in the streamwise component of velocity found in the wall affected region, collects the data of Blair (1983b), Pedisius et al. (1983), Vogel (1984), MacArthur (1986), and Hollingsworth et al. (1989), as well as the data from the present experiment, all within ± 15 percent. The fact that h can be expressed as a function of local u′ alone suggests the possibility of geometry-independent correlations for turbulent heat transfer.
Turbulent Heat Transport in a Boundary Layer Behind a Junction of a Streamlined Cylinder and a Wall
Authors: Wroblewski D. E. , Eibeck P. A.
Published: May 2008

Measurements of the turbulent velocity and temperature fields were made in a heated boundary layer 14 diameters downstream of a junction of a tapered cylinder and a wall (ReD = 24,700). The boundary layer is strongly affected by the presence of large-scale unsteadiness arising from vortex shedding, which appears in the measurements as “turbulence” with a strong spectral component at the shedding frequency. The boundary layer exhibits three distinct spanwise regions: (1) the innerwake region, z/D<0.8, where vortex shedding effects are observed only in the spanwise component of the fluctuations; (2) the middle-wake region, 0.8<z/D<1.6, where strong vortex shedding is seen in all three components of the fluctuations; and (3) the outer-wake region, z/D>1.6, where the flow is approaching a two-dimensional boundary-layer flow. Cross-spectra of νθ indicate that vortex shedding increases the turbulent heat flux in the middle-wake region. However, peak values of the Stanton number and the eddy diffusivity are observed in the inner-wake region, where the cross-spectra of turbulent heat flux do not exhibit a peak near the shedding frequency, but do show an increase compared to a two-dimensional boundary layer over a much broader frequency range.
Effect of Uneven Wall Temperature on Local Heat Transfer in a Rotating Square Channel With Smooth Walls and Radial Outward Flow
Authors: Han J.-C. , Zhang Y. M.
Published: May 2008

The influence of uneven wall temperature on the local heat transfer coefficient in a rotating square channel with smooth walls and radial outward flow was investigated for Reynolds numbers from 2500 to 25,000 and rotation numbers from 0 to 0.352. The square channel, composed of six isolated copper sections, has a length-to-hydraulic diameter ratio of 12. The mean rotating radius to the channel hydraulic diameter ratio is kept at a constant value of 30. Three cases of thermal boundary conditions were studied: (A) four walls uniform temperature, (B) four walls uniform heat flux, and (C) leading and trailing walls hot and two side walls cold. The results show that the heat transfer coefficients on the leading surface are much lower than that of the trailing surface due to rotation. For case A of four walls uniform temperature, the leading surface heat transfer coefficient decreases and then increases with increasing rotation numbers, and the trailing surface heat transfer coefficient increases monotonically with rotation numbers. The decreased (or increased) heat transfer coefficients on the leading (or trailing) surface are due to the cross-stream and centrifugal buoyancy-induced flows from rotations. However, the trailing surface heat transfer coefficients, as well as those for the side walls, for case B are higher than for case A and the leading surface heat transfer coefficients for cases B and C are significantly higher than for case A. The results suggest that the local uneven wall temperature creates the local buoyancy forces, which change the effect of the rotation. Therefore, the local heat transfer coefficients on the leading, trailing, and side surfaces are altered by the uneven wall temperature.
Hot Wire/Film Behavior in Low-Temperature Gases
Authors: Kwack E. Y. , Shakkottai P. , Luchik T. S. , Aaron K. M. , Fabris G. , Back L. H.
Published: May 2008

Commercially available hot wires/films were used to measure the velocities of evaporated hydrogen or helium gas during cryogenic mixing experiments. Hot wires were found to be too delicate to use in this harsh environment. Hot films were rugged enough to use at cryogenic temperatures even though they failed after a number of thermal cycles. Since the hot films have small aspect ratios, 13.4 and 20, they are quite sensitive to the thermal loading, Tw/Tg, even with a correction for the conduction end loss. In general, although the increase of the Nusselt number with Reynolds number at low temperatures was similar to that at room temperature, there was also a pronounced variation with Tw/Tg over the large range of 1.2 to 12 investigated.
Heat and Momentum Transport in Self-Sustained Oscillatory Viscous Flows
Authors: Majumdar D. , Amon C. H.
Published: May 2008

Heat and momentum transport in-self-sustained oscillatory viscous flows is investigated by direct numerical simulation using the spectral element method. Above a critical Reynolds number, these flows bifurcate to a time-periodic, self-sustained oscillatory state. Traveling waves are observed, even at moderately low Reynolds numbers, inducing self-sustained oscillations that result in very well-mixed flows, which, in turn, lead to convective heat transfer augmentation. These oscillatory states are investigated and correlations between the time- and space-averaged Nusselt and Reynolds numbers are obtained. The transport phenomena of heat and momentum due to the oscillatory components of the flow are analyzed by looking at the phase portraits of velocity and temperature, investigating the behavior of the terms involving their fluctuations, as well as considering the correlation coefficients between the fluctuating components. Results are presented for laminar and transitional incompressible flows in communicating channels, composed of interrupted surfaces, leading to relatively thin thermal boundary layers that further contribute to heat transfer augmentation.
Effect of Nozzle Configuration on Transport in the Stagnation Zone of Axisymmetric, Impinging Free-Surface Liquid Jets: Part 1—Turbulent Flow Structure
Authors: Stevens J. , Pan Y. , Webb B. W.
Published: May 2008

This study characterized the mean and fluctuating parts of the radial component of the local velocity in the stagnation region of an impinging, free-surface liquid jet striking a smooth flat plate. Four different nozzle exit conditions were studied, including fully developed pipe flow, a contoured nozzle, and turbulence-damped and -undamped sharp-edged orifices. Liquid jet Reynolds numbers in the range 30,000 to 55,000 were investigated. Velocities were measured using laser-Doppler velocimetry. Mean velocities were found to vary nearly linearly with radial location, with the slope of the line being a function of distance from the impingement plate. Dimensionless mean velocity gradients, of relevance to the heat transfer, were found to be a strong function of nozzle type, but roughly independent of jet Reynolds number for a given nozzle type. Turbulence levels were also found to be strongly influenced by the nozzle exit condition. Local heat transfer data corresponding to the flow structure measurements presented here are reported in Part 2 of this study.
Effect of Nozzle Configuration on Transport in the Stagnation Zone of Axisymmetric, Impinging Free-Surface Liquid Jets: Part 2—Local Heat Transfer
Authors: Pan Y. , Stevens J. , Webb B. W.
Published: May 2008

This is the second of a two-part study on the flow structure and heat transfer characteristics of turbulent, free-surface liquid jets. Part 2 deals with the effect of selected nozzle configurations on the local heat transfer in the stagnation zone. Infrared techniques have been used to characterize the local heat transfer for the four nozzle configurations whose mean and turbulent flow structure was detailed in Part 1. The results show that for identical jet Reynolds numbers, significant differences exist in the magnitudes of the local Nusselt number for the nozzle types studied. Differences of approximately 40 percent were observed. Local heat transfer results reveal that for already turbulent jets, the mean radial velocity gradient appears to be more influential in determining the heat transfer than incremental changes in the level of turbulence (as measured by the radial component of the fluctuations). An empirical correlation of the experimental data supports this conclusion, and reveals that the stagnation Nusselt number is affected independently by the jet Reynolds number and the dimensionless mean radial velocity gradient.
Experiment on Spatio-Temporal Turbulent Structures of a Natural Convection Boundary Layer
Authors: Tsuji T. , Nagano Y. , Tagawa M.
Published: May 2008

The spatio-temporal structures of a turbulent natural convection boundary layer along a vertical flat plate in air have been examined using a thermocouple rake and a pair of hot-wire/cold-wire arrangements. The instantaneous temperature profile clearly indicates the evolution of a large-scale motion originating in the outer region of the boundary layer. However, the space-time correlation measurements did not suggest the existence of any quasi-coherent structures such as low-speed streaks and bursts. The convection (or advection) velocity and characteristic length scales of turbulence were also investigated. The convection velocity exceeds the local mean velocity in the near-wall and outermost regions. The microscale of the thermal field shows a strongly anisotropic structure, and the integral scale indicates a large-scale structure normal to the wall.
Linearization of Natural Convection From a Vertical Plate With Arbitrary Heat-Flux Distributions
Authors: Lee S. , Yovanovich M. M.
Published: May 2008

A simple model is developed to predict the heat transfer characteristics of a vertical plate with arbitrarily prescribed surface heat-flux variations under a buoyancy-driven flow. The analysis is based on the linearized approximations to the boundary layer form of the conservation equations. Explicit, closed-form solutions for the surface temperature of the plate and fluid temperature distributions are obtained for the full range of Prandtl numbers. Surface heat-flux variations of discontinuous as well as continuous types are examined, and the results are compared with air data obtained by using various solution methods including numerical simulations. It is shown that the present predictions are in excellent agreement with those of other methods that are capable of producing exact solutions.
Natural Convection Heat Transfer From an Isothermal Vertical Surface to a Stable Thermally Stratified Fluid
Authors: Angirasa D. , Srinivasan J.
Published: May 2008

Natural convection from an isothermal vertical surface to a thermally stratified fluid is studied numerically. A wide range of stratification levels is considered. It is shown that at high levels of ambient thermal stratification, a portion at the top of the plate absorbs heat, while a horizontal plume forms around a location where the plate temperature equals the ambient temperature. The plume is shown to be inherently unsteady, and its transient nature is investigated in detail. The effect of the temperature defect in striating the plume is discussed. Average Nusselt number data are presented for Pr=6.0 and 0.7.
Reversed Flow Structure and Heat Transfer Measurements for Buoyancy-Assisted Convection in a Heated Vertical Duct
Authors: Gau C. , Yih K. A. , Aung W.
Published: May 2008

Buoyancy-assisted convection flow and heat transfer processes in a heated vertical channel are studied experimentally for situations where the buoyancy parameter Gr/Re2 is relatively large. The channel wall is made of two parallel plates, with one wall heated uniformly and the opposite wall insulated. A uniform air flow is made to enter the channel from the bottom. The reversed flow is visualized, which occurs initially near the channel exit for the case when Gr/Re2 is greater than a threshold value. The cold reversed flow enters the channel from the outside and forms a V-shaped recirculating flow region in the downstream part of the duct. This region gradually propagates upstream as the buoyancy parameter Gr/Re2 increases. The counterflow motion, leading to mixing between the heated buoyant fluid and the V-shaped recirculation, is shown to be highly unstable and characterized by generation of eddies and vortices when the value of Gr/Re2 is large. An increase in Re has the effect of pushing the reversed flow downstream and making the recirculating region wider. Temperature fluctuations are measured to provide insight into the complex phenomena being studied. The penetration depth of the reversed flow is measured and compared with prediction based on a simple model. Local and average Nusselt numbers are also measured and presented.
Effects of Buoyancy on Laminar Flow in Curved Elliptic Ducts
Authors: Dong Z. F. , Ebadian M. A.
Published: May 2008

This paper numerically investigates the effects of buoyancy on fully developed laminar flow in a curved duct with an elliptic cross section. The flow of Newtonian fluids is assumed steady in terms of Boussinesq approximation. The curved elliptic duct is subjected to thermal boundary conditions of axially uniform heat flux and peripherally uniform wall temperature. The numerically generated boundary-fitted coordinate system is applied to discretize the solution domain of the elliptic duct, and the Navier-Stokes equations and the energy equation, including the curvature ratio, are solved by use of the control volume-based finite difference method. The solution covers a wide range of curvature ratios, and Dean and Grashof numbers. The results presented are displayed graphically and in tabular form to illustrate the buoyancy effect. It is further shown that buoyancy acts to increase both the Nusselt number and the friction factor and changes the distribution of the velocity and the temperature. The results for the curved circular duct with and without buoyancy are compared with the data available in the open literature for all cases. Also compared with the published data are the results of laminar flow in a curved elliptic duct, and very good agreement is obtained.
Radiative Properties of Interacting Particles
Authors: Al-Nimr M. A. , Arpaci V. S.
Published: May 2008

Two statistical models for the radial distribution function are proposed. In terms of these models, analytical expressions for the radiation efficiency factors of random homogeneous systems are derived. The Planck and Rosseland mean absorption coefficients are evaluated and the ratio of dependent over independent mean absorption coefficients is given. The role of the far-field and the near-field effects on radiation is investigated. The near-field effect on the scattered radiation is found to be negligible compared to the far-field effect. The effect of particle interaction is demonstrated by a simple transport problem.
Evaporation of Single Drops of n-Pentane/n-Hexane Mixtures in Water
Authors: Shimaoka H. , Mori Y. H.
Published: May 2008

The evaporation of isolated drops (2.1−3.0 mm diameter) of nonazeotropic n-pentane/n-hexane mixtures in the medium of water was observed under pressures of 0.11−0.46 MPa and temperature differences up to 27 K. The mole fractions of n-pentane, x, in the mixtures were set at 0.9, 0.5, 0.1, and 0, to be completed by the condition x = 1 set in a preceding work (Shimaoka and Mori, 1990). Experimental results are presented in terms of the instantaneous rise velocity of, and an expression of instantaneous heat transfer to, each drop evaporating and thereby transforming into a liquid/vapor two-phase bubble and finally into a vapor bubble. The dependencies of the heat transfer characteristics on the pressure, the temperature difference, and x are discussed.
Modeling of Transient Stratified Flow in Vertical Tube Assemblies
Authors: Peterson P. F. , Akbarzadeh A.
Published: May 2008

This study considers a case of uniform flow into the bottom of a rectangular vertical tube array, with outflow from a point sink in one bottom corner. Experimental results show that, upon a step change to a higher density, a clearly defined density interface forms, and buoyancy forces cause channeling of the dense fluid. The tube array geometry permits an analytic solution, which agrees well with the experiments. Standard control-volume numerical methods, however, predict a diffuse, thick, and viscous density interface, in contrast to the thin interface seen in the experiment. This viscous effect can be attributed to numerical diffusion, and a Lagrangian interface tracking procedure is shown to reduce the diffusion effect greatly.
Transient Natural Convection in a Horizontal Concentric Annulus Filled With a Porous Medium
Authors: Pop I. , Ingham D. B. , Cheng P.
Published: May 2008

The method of matched asymptotic expansions is applied to study the problem of transient natural convection in a horizontal concentric porous annulus with inner and outer cylinders maintained at uniform temperatures. Asymptotic solutions for the inner layer, the outer layer, and the core are obtained for small times. A uniformly valid solution for stream function, tangential velocity, and temperature, which is valid for the whole domain, is constructed.
A Two-Wavelength Holographic Interferometry Study on the Solidification of a Binary Alloy Around a Horizontal Pipe
Authors: Spatz T. L. , Poulikakos D.
Published: May 2008

An experimental study on the transient outward solidification of a transparent binary alloy from an internally cooled horizontal pipe is reported in this paper. Two-wavelength holographic interferometry was used to visualize the density field in the liquid phase and to measure the local heat and mass transfer rates at the mush/liquid interface at characteristic times, Stefan numbers, and initial concentrations. The presence of double diffusive convection in the liquid phase greatly affected the local Nusselt and Sherwood numbers. The dependence of the pipe wall temperature, the solidified volume fraction, and the shape of the solid/mush and mush/liquid interfaces on the Stefan number, time, and initial concentration were also determined. The flow field in the liquid phase was visualized with the help of shadowgraphs. Interface photographs presented in this paper demonstrate the effect of the initial concentration on the structure of the mush/liquid interface, which varies from rather smooth to highly dendritic.
Characterization of the Carbapenem-Hydrolyzing Oxacillinase Oxa-58 in an
Acinetobacter
Genospecies 3 Clinical Isolate
Authors: Marti Sara , Sánchez-Céspedes Javier , Blasco M. Dolores , Ruiz Marc , Espinal Paula , Alba Verónica , Fernández-Cuenca Felipe , Pascual Alvaro , Vila Jordi
Published: May 2008

Based on imipenem resistance in an
Acinetobacter
genospecies 3 clinical isolate, we were able to identify, for the first time in this genomic species, a plasmid-encoded
bla
OXA-58
gene that was 100% homologous to the same gene in
Acinetobacter baumannii
.
Alteration of GyrA Amino Acid Required for Ciprofloxacin Resistance in
Klebsiella pneumoniae
Isolates in China
Authors: Fu Yingmei , Guo Lishuang , Xu Yan , Zhang Wenli , Gu Jiaao , Xu Jianfeng , Chen Xiaobei , Zhao Yuehui , Ma Jiayu , Liu Xinghan , Zhang Fengmin
Published: May 2008

Resistance to ciprofloxacin was detected in 111 (48.1%) isolates of
Klebsiella pneumoniae
from China. GyrA alterations were identified in the ciprofloxacin-resistant and ciprofloxacin-susceptible isolates. The results, including previously published data, indicate that the single substitution Ser83→Ile and three types of double mutations at Ser83 and Asp87 were required for ciprofloxacin resistance (
P
< 0.05).
Comparative Study of the Susceptibilities of Major Epidemic Clones of Methicillin-Resistant
Staphylococcus aureus
to Oxacillin and to the New Broad-Spectrum Cephalosporin Ceftobiprole
Authors: Chung Marilyn , Antignac Aude , Kim Choonkeun , Tomasz Alexander
Published: May 2008

Multidrug-resistant strains of
Staphylococcus aureus
continue to increase in frequency worldwide, both in hospitals and in the community, raising serious problems for the chemotherapy of staphylococcal disease. Ceftobiprole (BPR; BAL9141), the active constituent of the prodrug ceftobiprole medocaril (BAL5788), is a new cephalosporin which was already shown to have powerful activity against a number of bacterial pathogens, including
S. aureus
. In an effort to test possible limits to the antibacterial spectrum and efficacy of BPR, we examined the susceptibilities of the relatively few pandemic methicillin-resistant
S. aureus
(MRSA) clones that are responsible for the great majority of cases of staphylococcal disease worldwide. We also included in the tests the highly oxacillin-resistant subpopulations that are present with low frequencies in the cultures of these clones. Such subpopulations may represent a natural reservoir from which MRSA strains with decreased susceptibility to BPR may emerge in the future. We also tested the efficacy of BPR against MRSA strains with reduced susceptibility to vancomycin and against MRSA strains carrying the enterococcal vancomycin resistance gene complex. BPR was shown to be uniformly effective against all these resistant MRSA strains, and the mechanism of superb antimicrobial activity correlated with the strikingly increased affinity of the cephalosporin against penicillin-binding protein 2A, the protein product of the antibiotic resistance determinant
mecA
.
Early Bactericidal Activity and Pharmacokinetics of the Diarylquinoline TMC207 in Treatment of Pulmonary Tuberculosis
Authors: Rustomjee R. , Diacon A. H. , Allen J. , Venter A. , Reddy C. , Patientia R. F. , Mthiyane T. C. P. , De Marez T. , van Heeswijk R. , Kerstens R. , Koul A. , De Beule K. , Donald P. R. , McNeeley D. F.
Published: May 2008

Tibotec Medicinal Compound 207 (TMC207) is a novel diarylquinoline with a unique mode of action that targets mycobacterial ATP synthase. TMC207 exhibits high in vitro activity against mycobacterial strains either susceptible or resistant to all first-line and many second-line drugs, including fluoroquinolones, and has shown exceptional in vivo activity against several mycobacterial species in different animal models. In this early bactericidal activity study, 75 treatment-naïve patients with smear-positive pulmonary tuberculosis were randomized to once-daily oral TMC207 (25 mg, 100 mg, or 400 mg), 600 mg rifampin (RIF), or 300 mg isoniazid (INH) for 7 days. Sixteen-hour overnight sputum collected at baseline and on each treatment day was plated in serial dilutions on selective agar plates. The bactericidal activity was expressed as the log
10
decrease in CFU/ml sputum/day. Pharmacokinetic sampling was performed on day 7 of TMC207 administration up to 24 h postdose. The decreases in log
10
CFU counts (± standard deviation) from baseline to day 7 were 0.04 ± 0.46 for 25 mg TMC207 (
n
= 14), 0.26 ± 0.64 for 100 mg TMC207 (
n
= 14), 0.77 ± 0.58 for 400 mg TMC207 (
n
= 14), 1.88 ± 0.74 for INH (
n
= 11), and 1.70 ± 0.71 for RIF (
n
= 14). Significant bactericidal activity of 400 mg TMC207 was observed from day 4 onward and was similar in magnitude to those of INH and RIF over the same period. The pharmacokinetics of TMC207 were linear across the dose range. In summary, TMC207 demonstrated bactericidal activity with a delayed onset and was well tolerated, and no study drug-related serious adverse events occurred.
Role of Cj1211 in Natural Transformation and Transfer of Antibiotic Resistance Determinants inCampylobacter jejuni
Authors: Jeon Byeonghwa , Muraoka Wayne , Sahin Orhan , Zhang Qijing
Published: May 2008

Campylobacter jejuni, an important food-borne human pathogen, is increasingly resistant to antimicrobials. Natural transformation is considered to be a main mechanism for mediating the transfer of genetic materials encoding antibiotic resistance determinants inC. jejuni, but direct evidence for this notion is still lacking. In this study, we determined the role of Cj1211 in natural transformation and in the development of antibiotic resistance inC. jejuni. Insertional mutagenesis of Cj1211, aHelicobacter pyloriComH3 homolog, abolished natural transformation inC. jejuni. In vitro coculture ofC. jejunistrains carrying either kanamycin or tetracycline resistance markers demonstrated the development of progenies that were resistant to both antibiotics, indicating that the horizontal transfer of antibiotic resistance determinants actively occurs in mixedCampylobacterpopulations. A mutation of Cj1211 or the addition of DNase I in culture media completely inhibited the formation of progenies that were resistant to both antibiotics, indicating that the horizontal transfer of the resistance determinants is mediated by natural transformation. Interestingly, the mutation of Cj1211 also reduced the frequency of emergence of spontaneous mutants that were resistant to fluoroquinolone (FQ) and streptomycin but did not affect the outcome of FQ resistance development under FQ treatment, suggesting that natural transformation does not play a major role in the emergence of FQ-resistantCampylobacterstrains during treatment with FQ antimicrobials. These results define Cj1211 as a competence factor inCampylobacter, prove the role of natural transformation in the horizontal transfer of antibiotic resistance determinants inCampylobacter, and provide new insights into the mechanism underlying the development of FQ-resistantCampylobacterstrains.
Inhibition of Cell-to-Cell Transmission of Human T-Cell Lymphotropic Virus Type 1 In Vitro by Carbohydrate-Binding Agents
Authors: Balestrieri Emanuela , Ascolani Arianna , Igarashi Yasuhiro , Oki Toshikazu , Mastino Antonio , Balzarini Jan , Macchi Beatrice
Published: May 2008

Peripheral blood mononuclear cells (PBMCs) from healthy individuals can be infected by human T-lymphotropic virus type 1 (HTLV-1) upon cocultivation of the PBMCs with irradiated HTLV-1-transformed human MT-2 cells. This model system closely mimics HTLV-1 transmission through cell-to-cell contact. Carbohydrate-binding agents (CBAs) such as the α(1,3)/α(1,6)mannose-specific
Hippeastrum hybrid
agglutinin and the GlcNAc-specific
Urtica dioica
agglutinin, and also the small, nonpeptidic α(1,2)-mannose-specific antibiotic pradimicin A, were able to efficiently prevent cell-to-cell HTLV-1 transmission at nontoxic concentrations, as evidenced by the lack of appearance of virus-specific mRNA and of the viral protein Tax in the acceptor cells. Consistently, antivirally active doses of CBAs fully prevented HTLV-1-induced stimulation of PBMC growth. The inhibitory effects of CBAs on HTLV-1 transmission were also evident when HTLV-1-infected C5MJ cells were used in place of MT-2 cells as a virus donor cell line. The anti-HTLV-1 properties of the CBAs highlight the importance of the envelope glycans in events underlying HTLV-1 passage from cell to cell and indicate that CBAs should be further investigated for their potential to prevent HTLV-1 infection, including mother-to-child virus transmission by cell-to-cell contact through breast milk feeding.
Hookworm-Induced Persistent Changes to the Immunological Environment of the Lung
Authors: Reece Joshua J. , Siracusa Mark C. , Southard Teresa L. , Brayton Cory F. , Urban Joseph F. , Scott Alan L.
Published: May 2008

A number of important helminth parasites of humans have incorporated short-term residence in the lungs as an obligate phase of their life cycles. The significance of this transient pulmonary exposure to the infection and immunity is not clear. Employing a rodent model of infection with hookworm (Nippostrongylus brasiliensis), we characterized the long-term changes in the immunological status of the lungs induced by parasite infection. At 36 days after infection, alterations included a sustained increase in the transcription of both Th2 and Th1 cytokines as well as a significant increase in the number and frequency of alveolar macrophages displaying an alternatively activated phenotype. WhileN. brasiliensisdid not induce alternate activation of lung macrophages in STAT6−/−animals, the parasite did induce a robust Th17 response in the pulmonary environment, suggesting that STAT6 signaling plays a role in modulating Th17 immunity and pathology in the lungs. In the context of the cellular and molecular changes induced byN. brasiliensisinfection, there was a significant reduction in overall airway responsiveness and lung inflammation in response to allergen. In addition, theN. brasiliensis-altered pulmonary environment showed dramatic alterations in the nature and number of genes that were up- and downregulated in the lung in response to allergen challenge. The results demonstrate that even a transient exposure to a helminth parasite can effect significant and protracted changes in the immunological environment of the lung and that these complex molecular and cellular changes are likely to play a role in modulating a subsequent allergen-induced inflammatory response.
Native Outer Membrane Proteins Protect Mice against Pulmonary Challenge with Virulent Type AFrancisella tularensis
Authors: Huntley Jason F. , Conley Patrick G. , Rasko David A. , Hagman Kayla E. , Apicella Michael A. , Norgard Michael V.
Published: May 2008

Francisella tularensisis a gram-negative intracellular bacterium and the causative agent of the zoonotic disease tularemia.F. tularensisis a category A select agent and thus a potential agent of bioterrorism. Whereas anF. tularensislive, attenuated vaccine strain (LVS) is the basis of an investigational vaccine, this vaccine is not licensed for human use because of efficacy and safety concerns. In the present study, we immunized mice with isolated native outer membrane proteins (OMPs), ethanol-inactivated LVS (iLVS), or purified LVS lipopolysaccharide (LPS) and assessed the ability of each vaccine preparation to protect mice against pulmonary challenge with the virulent type AF. tularensisstrain SchuS4. Antibody isotyping indicated that both Th1 and Th2 antibody responses were generated in mice after immunization with OMPs or iLVS, whereas LPS immunization resulted in only immunoglobulin A production. In survival studies, OMP immunization provided the greatest level of protection (50% survival at 20 days after infection with SchuS4), and there were associated 3-log reductions in the spleen and liver bacterial burdens (compared to nonvaccinated mice). Cytokine quantitation for the sera of SchuS4-challenged mice indicated that OMP and iLVS immunizations induced high levels of tumor necrosis factor alpha and interleukin-2 (IL-2) production, whereas only OMP immunization induced high levels of IL-10 production. By comparison, high levels of proinflammatory cytokines, including RANTES, granulocyte colony-stimulating factor, IL-6, IL-1α, IL-12p40, and KC, in nonvaccinated mice indicated that these cytokines may facilitate disease progression. Taken together, the results of this study demonstrate the potential utility of an OMP subunit (acellular) vaccine for protecting mammals against type AF. tularensis.
Distinct Isoforms of Phospholipase A2Mediate the Ability ofSalmonella entericaSerotype Typhimurium andShigella flexneriTo Induce the Transepithelial Migration of Neutrophils
Authors: Mumy Karen L. , Bien Jeffrey D. , Pazos Michael A. , Gronert Karsten , Hurley Bryan P. , McCormick Beth A.
Published: May 2008

Salmonellaspp. andShigellaspp. are responsible for millions of cases of enteric disease each year worldwide. While these pathogens have evolved distinct strategies for interacting with the human intestinal epithelium, they both induce significant proinflammatory responses that result in massive transepithelial migration of neutrophils across the intestinal mucosa. It has previously been shown withSalmonella entericaserotype Typhimurium that the process of neutrophil transmigration is mediated in part by the secretion of hepoxilin A3(HXA3; 8-hydroxy-11,12-epoxy-eicosatetraenoic acid), a potent neutrophil chemoattractant, from the apical surface of infected model intestinal epithelium. This study confirms that HXA3is also secreted in response to infection byShigella flexneri, that it is produced by a pathway involving 12/15-lipoxygenase (12/15-LOX), and thatS. entericaserovar Typhimurium andS. flexnerishare certain elements in the mechanism(s) that underlies the otherwise separate signal transduction pathways that are engaged to induce polymorphonuclear leukocyte (PMN) transepithelial migration (protein kinase C and extracellular signal-regulated kinases 1 and 2, respectively). PMN transepithelial migration in response to infection withS. flexneriwas dependent on 12/15-LOX activity, the enzyme responsible for the initial metabolism of arachidonic acid to HXA3. Probing further into this pathway, we also found thatS. entericaserovar Typhimurium andS. flexneriactivate different subtypes of phospholipase A2, a critical enzyme involved in the liberation of arachidonic acid from cellular membranes. Thus, althoughS. entericaserovar Typhimurium andS. flexneriutilize different mechanisms for triggering the induction of PMN transepithelial migration, we found that their reliance on 12/15-LOX is conserved, suggesting that enteric pathogens may ultimately stimulate similar pathways for the synthesis and release of HXA3.
The prevalence and effects of adult attention-deficit/hyperactivity disorder (ADHD) on the performance of workers: results from the WHO World Mental Health Survey Initiative
Authors: de Graaf R , Kessler R C , Fayyad J , ten Have M , Alonso J , Angermeyer M , Borges G , Demyttenaere K , Gasquet I , de Girolamo G , Haro J M , Jin R , Karam E G , Ormel J , Posada-Villa J
Published: May 2008

Objectives:

To estimate the prevalence and workplace consequences of adult attention-deficit/hyperactivity disorder (ADHD).

Methods:

An ADHD screen was administered to 18–44-year-old respondents in 10 national surveys in the WHO World Mental Health (WMH) Survey Initiative (n = 7075 in paid or self-employment; response rate 45.9–87.7% across countries). Blinded clinical reappraisal interviews were administered in the USA to calibrate the screen. Days out of role were measured using the WHO Disability Assessment Schedule (WHO-DAS). Questions were also asked about ADHD treatment.

Results:

An average of 3.5% of workers in the 10 countries were estimated to meet DSM-IV criteria for adult ADHD (inter-quartile range: 1.3–4.9%). ADHD was more common among males than females and less common among professionals than other workers. ADHD was associated with a statistically significant 22.1 annual days of excess lost role performance compared to otherwise similar respondents without ADHD. No difference in the magnitude of this effect was found by occupation, education, age, gender or partner status. This effect was most pronounced in Colombia, Italy, Lebanon and the USA. Although only a small minority of workers with ADHD ever received treatment for this condition, higher proportions were treated for comorbid mental/substance disorders.

Conclusions:

ADHD is a relatively common condition among working people in the countries studied and is associated with high work impairment in these countries. This impairment, in conjunction with the low treatment rate and the availability of cost-effective therapies, suggests that ADHD would be a good candidate for targeted workplace screening and treatment programs.
Chemoprevention and screening in primary sclerosing cholangitis
Authors: Kitiyakara T , Chapman R W
Published: May 2008

Primary sclerosing cholangitis (PSC) is a chronic inflammatory disease that causes fibrosis of the biliary tree. Life expectancy of patients is reduced by liver failure and a high incidence of malignancy. It is closely associated with inflammatory bowel disease, particularly ulcerative colitis, which coexists in approximately three-quarters of northern European patients. Cancers include cholangiocarcinoma, gallbladder cancer, hepatocellular carcinoma, pancreatic cancer and colorectal cancer. Ursodeoxycholic acid appears to reduce the incidence of colorectal neoplasia in patients with PSC, and there is some suggestion that it may also reduce the incidence of cholangiocarcinoma. A chemoprotective benefit of 5-aminosalicylates has not been confirmed in patients with PSC with associated inflammatory bowel disease. There is no accepted screening programme for cholangiocarcinoma, but methods for detecting early disease using biochemical markers, scanning using positron emission tomography or MRI, and endoscopic procedures such as endosonography and endoscopic retrograde cholangiopancreatography are discussed. A combination of techniques is often used in an attempt to diagnose early cholangiocarcinoma. Cholecystectomy should be performed for gallbladder polyps, as many are malignant, and ultrasonography and α-fetoprotein testing are suggested for screening for hepatocellular carcinoma. Colorectal carcinoma screening should be performed after the diagnosis of PSC, and surveillance colonoscopy should be performed annually if there is concomitant colitis.
Stroke in pregnancy and the puerperium
Authors: Treadwell S D , Thanvi B , Robinson T G
Published: May 2008

Stroke is a recognised complication of pregnancy, contributing to more than 12% of all maternal deaths. Estimated incidence rates vary considerably from 4.3 to 210 strokes per 100 000 deliveries. Atherosclerosis is rare in young adults, and so other causes of stroke become increasingly likely. Aetiological factors important in pregnancy include hypercoagulability due to maternal physiological changes, pre-eclampsia and eclampsia, cerebral venous thrombosis, paradoxical embolism, postpartum cerebral angiopathy and peripartum cardiomyopathy. Management of patients with pregnancy-related stroke should generally proceed as for non-pregnant patients, although there are a number of important areas specific to pregnancy which will be considered here.
Non-Hodgkin's lymphoma and tuberculosis coexistence in the same organs: a report of two cases
Authors: Fanourgiakis P , Mylona E , Androulakis I I , Eftychiou C , Vryonis E , Georgala A , Skoutelis A , Aoun M
Published: May 2008

Non-Hodgkin's lymphoma (NHL) may be preceded by chronic inflammatory diseases and furthermore has been related to immune deficiency. Tuberculosis (TB), on the other hand, is a chronic infectious disease whose presentation and reactivation is known to be promoted by cell mediated immunodeficiency. The coexistence of NHL and TB in the same organ is rare. We report two cases of NHL and TB coexistence in two different organs: cervical lymph nodes and kidney. The cases illustrate how misleading the concurrence of NHL and TB infection can be, delaying the diagnosis and treatment of either disease.
Progression of early warning scores (EWS) in patients with acute pancreatitis: a re-evaluation of a retrospective cohort of patients
Authors: Garcea G , Jackson B , Pattenden C J , Ong S L , Neal C P , Dennison A R , Berry D P
Published: May 2008

Introduction

Early warning scores (EWS) is a physiological scoring system measured hourly. This study determined how progression of EWS affected outcome in acute pancreatitis.

Methods

The single worst EWS score for each 24 h period following admission was recorded for 110 patients with acute pancreatitis. Scores falling below 3 were defined as improving; scores which remained at 3 or rising were considered deteriorating.

Results

Deteriorating EWS values were associated with a greatly increased risk of mortality (p<0.001). All patients within the groups, who died, had an adverse outcome or had severe pancreatitis, demonstrated a failure to improve on a median admission EWS of ⩾3 or a deterioration of their median EWS to above this. This progression occurred within 48 h of admission. Evaluating the progression of EWS (that is, improving or deteriorating scores) resulted in an improvement in the sensitivity and specificity in predicting adverse outcome, mortality or severe pancreatitis when compared to previously published data on EWS scores alone, on days 1 to 3 following admission.

Conclusion

Deteriorating EWS values within the 48 h from admission are associated with adverse outcome or death in acute pancreatitis. Measuring progression of EWS over 72 h from admission can further improve accuracy of this monitoring system for acute pancreatitis.
Clinical applications and advances of positron emission tomography with fluorine-18-fluorodeoxyglucose (18F-FDG) in the diagnosis of liver neoplasms
Authors: He Y-x , Guo Q-y
Published: May 2008

Positron emission tomography (PET) using 18F-fluorodeoxyglucose (18F-FDG) has been widely used not only for detecting and staging malignant tumours but also for monitoring therapy response and for differentiating malignant lesions from benign lesions. However, the sensitivity of 18F-FDG PET for hepatocellular carcinoma (HCC) is low. Recent research about the novel drug shows that the sensitivity of 11C-acetate PET for HCC is higher than that of 18F-FDG PET and 11C-acetate also indicates tumour cell differentiation. 18F-FDG PET proved to be highly sensitive in detecting hepatic metastases from different primaries. 18F-FDG PET has also been shown to be useful and more accurate than conventional imaging modalities in demonstrating the effect of local treatments in liver tumours. With the development of small animal imaging, animal research about 18F-FDG PET is increasing.
Age at First Maturity and the Early Expression of Oocyte Recruitment Processes in Two Forms of Atlantic Salmon (Salmo salar)and Their Hybrids
Authors: Sutterlin A. M. , MacLean D.
Published: May 2008

The two pure lines and the reciprocal hybrids between an early maturing dwarf form of landlocked Atlantic salmon (Salmo salar) and a later maturing anadromous form were reared in captivity for a minimum period of 2.5 yr. Despite similar growth rates, 90% of female parr of the dwarf landlocked strain matured at age 2+ yr (fork length 15 cm), while no females of the anadromous form matured at this time. The weight of the ovary differed in the two pure forms at age 0+ and the numbers, size, and stages of previtellogenic oocytes also differed at age1+. Ovarian patterns of development and the time of onset of sexual maturation in the hybrid forms appeared intermediate to that of the parental forms. The implications of genetically controlled factors influencing rates of sexual maturation, growth, smoltification, and subsequent fecundity are discussed.
Responses of Pacific Herring, Clupea harengus pallasi, to Some Underwater Sounds
Authors: Schwarz Abby L. , Greer Galen L.
Published: May 2008

We describe the behavioral responses of net-penned Pacific herring (Clupea harengus pallasi) to a variety of tape-recorded sounds. Sounds recorded in the field from a herring fishing fleet included moving and stationary (idling) vessels, sonar, echo sounder, and deck gear. Natural sounds included rain on the water surface, gull (Larus spp.) cries, killer whale (Orcinus orca) vocalizations, barks of Steller's sea lions (Eumetopias jubatus), and sounds made by herring themselves. Sounds of more uniform structure were created with an electronic synthesizer and played back to herring to determine the relative effectiveness of various combinations (triads) of amplitude and frequency (increasing, decreasing, constant) and temporal pattern (continuous, regularly, or irregularly pulsed tones). Herring did not respond visibly to any of the taped sounds of natural origin or to sonar or echo sounders. There were three categories of negative response given to other sounds. Avoidance responses were elicited by sounds of large vessels approaching at constant speed, by smaller vessels but only when on accelerated approach, and by 11 different triads of the electronically synthesized sounds. Alarm, and less frequently Startle, were both elicited by those electronic sounds with an essentially instantaneous rise time in amplitude. Herring produced Chirps and Whistles in addition to feeding and hydrodynamic noises. Chirps consisted of one or several bursts of pulses in the range 1800–3200 Hz and occurred in bouts. Whistles were narrow-band continuous (unpulsed) sounds of 1600–2000 Hz. Captive herring showed no response to playbacks of these sounds.