bluuebunny/crossref_metadata_2025 huggingface dataset:
Do Substance Use, Psychosocial Adjustment, and Sexual Experiences Vary for Dating Violence Victims Based on Type of Violent Relationships?
Authors: Zweig Janine M. , Yahner Jennifer , Dank Meredith , Lachman Pamela
Published: November 2016

ABSTRACT

BACKGROUND

We examined whether substance use, psychosocial adjustment, and sexual experiences vary for teen dating violence victims by the type of violence in their relationships. We compared dating youth who reported no victimization in their relationships to those who reported being victims of intimate terrorism (dating violence involving one physically violent and controlling perpetrator) and those who reported experiencing situational couple violence (physical dating violence absent the dynamics of power and control).

METHODS

This was a cross‐sectional survey of 3745 dating youth from 10 middle and high schools in the northeastern United States, one third of whom reported physical dating violence.

RESULTS

In general, teens experiencing no dating violence reported less frequent substance use, higher psychosocial adjustment, and less sexual activity than victims of either intimate terrorism or situational couple violence. In addition, victims of intimate terrorism reported higher levels of depression, anxiety, and anger/hostility compared to situational couple violence victims; they also were more likely to report having sex, and earlier sexual initiation.

CONCLUSIONS

Youth who experienced physical violence in their dating relationships, coupled with controlling behaviors from their partner/perpetrator, reported the most psychosocial adjustment issues and the earliest sexual activity.
Hand Hygiene Program Decreases School Absenteeism Due to Upper Respiratory Infections
Authors: Azor‐Martinez Ernestina , Cobos‐Carrascosa Elena , Seijas‐Vazquez Maria Luisa , Fernández‐Sánchez Carmen , Strizzi Jenna M. , Torres‐Alegre Pilar , Santisteban‐Martínez Joaquin , Gimenez‐Sanchez Francisco
Published: November 2016

ABSTRACT

BACKGROUND

We assessed the effectiveness of a handwashing program using hand sanitizer to prevent school absenteeism due to upper respiratory infections (URIs).

METHODS

This was a randomized, controlled, and open study on a sample of 1341 children 4‐12 years old, attending 5 state schools in Almería (Spain), with an 8‐month follow‐up. The experimental group (EG) washed their hands with soap and water, together with using hand sanitizer, and the control group followed their usual handwashing procedures. Absenteeism rates due to URIs were compared between the 2 groups through a multivariate Poisson regression analysis. The percent of days missed in both groups were compared with a z test.

RESULTS

Overall, 1271 cases of school absenteeism due to URIs were registered. Schoolchildren from the EG had a 38% lower risk of absenteeism due to URIs, incidence rate ratio: 0.62, 95% confidence interval: 0.55‐0.70, and a decrease in absenteeism of 0.45 episodes/child/academic year, p < .001. Pupils missed 2734 school days due to URIs and the percentage of days absent was significantly lower in the EG, p < .001.

CONCLUSIONS

Use of hand sanitizer plus handwashing with soap accompanied by educational support is an effective measure to reduce absenteeism due to URIs
Perceptions of Peer Sexual Behavior: Do Adolescents Believe in a Sexual Double Standard?
Authors: Young Michael , Cardenas Susan , Donnelly Joseph , J. Kittleson Mark
Published: November 2016

BACKGROUND

The purpose of the study was to (1) examine attitudes of adolescents toward peer models having sex or choosing abstinence, and (2) determine whether a “double standard” in perception existed concerning adolescent abstinence and sexual behavior.

METHODS

Adolescents (N = 173) completed questionnaires that included 1 of 6 randomly assigned vignettes that described male and female peer models 3 ways: (1) no information about model's sexual behavior, (2) model in love but choosing abstinence, and (3) model in love and having sex. Participants read the vignette to which they had been assigned and responded to statements about the peer model. Data were analyzed using multivariate analysis of variance.

RESULTS

Results did not show evidence of a sexual double standard among male participants, but did show some evidence of a sexual double standard among female participants. Additionally, both male and female participants evaluated more harshly peer models that were having sex than peer models that chose abstinence.

CONCLUSIONS

Findings provide insight concerning the lack of a sexual double standard among male participants, the existence, to some degree, of a sexual double standard among female participants, and demonstrate the existence of a social cost to both young men and young women for choosing to have sex.
Pan‐genotypic treatment regimens for hepatitis C virus: Advantages and disadvantages in high‐ and low‐income regions
Authors: Hézode C.
Published: November 2016

During the last 5 years, the availability of direct‐acting antiviral (DAA) agents has revolutionized the treatment of hepatitis C virus (HCV). Compared with interferon/ribavirin—the previous standard of care—DAA combination regimens offer improved sustained virological response (SVR) rates, shorter treatment durations of 8‐24 weeks, convenient once‐daily single‐tablet formulations and more favourable tolerability profiles. HCV treatment is complex, and the choice of therapy must consider a complex range of factors, including baseline viral load, fibrosis stage, the HCV genotype and subgenotype, and the presence of resistance‐associated substitutions at baseline. Globally, HCV genotype 1 predominates, and there are extensive data and various treatment options available for this genotype. Genotypes 2–6 are prevalent and may even predominate in different geographical regions, reflecting diverse factors including human migration patterns and unsafe use of injection drugs and blood products. Such factors are themselves influenced by socio‐economic factors, and poor regions often have the greatest unmet need for effective HCV therapies. The latest pan‐genotypic DAA combination regimens provide the potential to eradicate HCV around the globe, regardless of genotype, hence minimizing the need for virological testing services, which often are unavailable in poorer regions. Economics inevitably remain a barrier to access, and extensive cooperation will be required between clinical organisations and pharmaceutical manufacturers to agree appropriate pricing policies, especially in poorer economic regions. This review considers key data and treatment guidelines for DAA therapies, including pan‐genotypic combination regimens, in the context of regional differences in HCV genotype and socio‐economic factors.
Growth Performance and Body Composition of Aspikutum: A New Hybrid of Asp, Leuciscus aspius ♀, × Caspian Kutum, Rutilus frisii ♂, Cultured under Different Stocking Densities in Circular Concrete Tanks
Authors: Bagheri Mohaddeseh , Falahatkar Bahram , Efatpanah Iraj
Published: November 2016

The first step for rearing the newly produced hybrid of Asp, Leuciscus aspius ♀, × Caspian Kutum, Rutilus frisii ♂ (so‐called “Aspikutum”) is to understand essential production requirements such as stocking density. For this purpose, fish (60.4 g) were held at five stocking densities of 2, 4, 6, 8, and 10 kg/m3 in circular concrete tanks (603 L) for a period of 56 d. The culture system was maintained at natural temperature and photoperiod. Fish were fed thrice a day using a commercial diet. At the end of the trial, growth indices, including final mean weight, weight gain, and specific growth rate, were significantly higher at the density of 10 kg/m3 compared with 2 kg/m3 (P< 0.05). Feed intake was significantly greater at 10 kg/m3 compared with 2 kg/m3 (P< 0.05); however, feed efficiency, protein efficiency ratio, protein productive value, and hepatosomatic index remained unchanged among the stocking densities (P> 0.05). Increased stocking density caused significant increase in body protein and fat contents (P< 0.05). Condition factor in higher densities (8 and 10 kg/m3) was significantly higher compared with 2 kg/m3 (P< 0.05). The results indicated that rearing this hybrid in the studied weight range at high density of 10 kg/m3 or more is possible without negative impacts on growth performance and body composition.
Indeterminacy, Angst and Conflicting Values
Authors: Williams J. Robert G.
Published: November 2016

How should we make choices where the values we subscribe to give conflicting recommendations? I will be defending a reduction of decision making under conflict to decision making under indeterminacy, in the spirit of Broome. To defend this, I set out and endorse the basic features of decision making under conflict that Ruth Chang identifies. I show that we find exactly those features in cases of decision making under indeterminacy not involving conflicting values. Further, my theory of decision making under indeterminacy predicts and explains these features. Particular attention will be paid to the aspect that Chang emphasizes as the decisive problem for the Broomean reduction: the resolutional residue, or angst, that decision making under conflict evinces.
Effective Exchange Rates, Current Accounts and Global Imbalances
Authors: Beckmann Joscha , Czudaj Robert
Published: November 2016

This study analyzes the dynamics between real effective exchange rates and current accounts from a novel perspective. We start by dissecting long‐run and time‐varying short‐run dynamics as well as causalities between both variables. Following this, we extend our framework by including short‐term interest rates. Finally, we examine common exchange rate and current account dynamics across countries based on common factors. Our results show that a real appreciation coincides with a worsening of the current account in most cases. The adjustment pattern is time varying but suggests that the causality mainly runs from effective exchange rates to current accounts. However, an extension of our framework based on monthly data shows that trade balance adjustment is observed less frequently, suggesting that valuation effects play an important role for the relationship between current accounts and exchange rates. From a global point of view, cross‐country trends that drive exchange rates and current accounts also share similar dynamics over the long run, which is an important finding in the context of global imbalances.
Efficacy and duration of action of oral fluralaner and spot‐on moxidectin/imidacloprid in cats infested with Lynxacarus radovskyi
Authors: Han Hock Siew , Noli Chiara , Cena Tiziana
Published: November 2016

Background

Lynxacarus radovskyi has been observed in cats in Malaysia; previously treatment with fipronil and moxidectin/imidacloprid spot‐on has been described.

Objectives

To compare the efficacy of two spot‐on treatments of moxidectin/imidacloprid, two weeks apart to a single oral dose of fluralaner against Lynxacarus radovskyi and evaluate time to re‐infestation.

Methods

Thirty cats were assigned to three groups of ten cats each. Group 1 received one 250 mg fluralaner tablet. Group 2 received two doses of moxidectin/imidacloprid spot‐on two weeks apart. Group 3 consisted of untreated controls. For each cat, three plucks of about 50 hairs each were collected from three sites (dorsal neck, lateral thigh and perineal/tail region) for a total of nine pluckings every two weeks. Severity of infestation was scored from 0 (no parasite), to 1 (only nonhatched eggs), 2 (both hatched and nonhatched eggs), 3 (<50 mites) and 4 (>50 mites). Efficacy was compared between treatment groups and over time in the same group, and results analysed statistically. Re‐infestation was defined as the identification of new eggs or mites on hair pluckings.

Results

Moxidectin/imidacloprid spot‐on and oral fluralaner achieved 100% eradication within 28 days. No significant difference was observed between groups 1 and 2; re‐infestation occurred by Day 56 in both treatment groups.

Conclusion

A single dose of oral fluralaner or two moxidectin/imidacloprid spot‐on treatments two weeks apart are efficacious in the eradication of L. radovskyi in cats and able to prevent re‐infestation for at least 42 days post‐treatment.
Self-Assembly of Monolayers of Mixtures of Particles
Authors: Amah Edison C. , Musunuri Naga , Fischer Ian S. , Singh Pushpendra , Hossain Md. Shahadat
Published: November 2016

We have numerically studied the self-assembly process of particle mixtures on fluid-liquid interfaces when an electric field is applied in the direction normal to the interface. The electric and capillary forces on the particles causes them to self-assemble into molecular-like hierarchical arrangements consisting of composite particles arranged in a pattern. As in experiments, the structure of a composite particle depends on factors such as the relative sizes of the particles and their polarizibilities, and the electric field intensity. If the particles sizes differ by a factor of two or more, the composite particle has a larger particle at its core and several smaller particles forming a ring around it. The number of particles in the ring and the spacing between the composite particles depends on their relative polarizibilities, the size of the smaller particles and the electric field intensity. Approximately same sized particles, on the other hand, form chains (analogous to polymeric molecules) in which positively and negatively polarized particles alternate.
Nonlinear Study of Convective Heat Transfer in Tightly Curved Rectangular Microchannels
Authors: Liu Fang
Published: November 2016

To address the effects of curvature, initial conditions and disturbances, a numerical study is made on the fully-developed bifurcation structure and stability of the forced convection in tightly curved rectangular microchannels of aspect ratio 10 and curvature ratio 0.5 at Prandtl number 7.0. Eleven solution branches (seven symmetric and four asymmetric) are found with 10 bifurcation points and 27 limit points. The flows on these branches are with 2, 4, 6, 7, 8, 9 or 10-cell structures. The flow structures change along the branch because of the flow instability. The average friction factor and Nusselt Number are different on different solution branches. It is found that more than 22.33% increase in Nu can be achieved with less than 9.34% increase in fRe at Dk of 2000. As Dean number increases, finite random disturbances lead the flows from a stable steady state to another stable steady state, a periodic oscillation, an intermittent oscillation, another periodic oscillation and a chaotic oscillation. The mean friction factor and mean Nusselt Number are obtained for all physically realizable flows. A significant enhancement of heat transfer can be obtained at the expense of a slightly increase of flow friction in tightly coiled rectangular ducts.
Velocity Slip and Temperature Jump for Gas Flows Past Anisotropic Surfaces: Analytical Derivation and Numerical Simulation
Authors: To Quy-Dong , Vu Van-Huyen , Lauriat Guy , Leonard Celine
Published: November 2016

In this paper, we present a development on the theory and simulation method for gas flows inside a micro/nano-channel confined between anisotropic walls. Typical examples of those structures are orthorhombic crystal surfaces, unequally strained crystals, surfaces containing parallel stripes at atomic scale or even randomly rough surfaces whose profile distributions are anisotropic, etc... As a result, the gas-wall collision behavior depends strongly on the direction and cannot be captured by traditional isotropic models, e.g Maxwell or Cercignani-Lampis (CL) [1, 2]. These effects have been shown by our previous work based on MD simulations of beam scattering experiments. In particular, the tangential accommodation coefficient varies with the projection direction of the gas atom onto the solid wall surface [3].
Modeling and Simulation of Multistage Microcompressor With Passive Microvalves for Micro Coolers
Authors: Le Shawn T. , Hegab Hisham
Published: November 2016

A cascaded multistage (2-stage) micro gas compressor in series is investigated through a lump model simulation to determine its feasibility in increasing compressor performance. A dynamic model of the micro gas compressor which consists of a unimorph piezoelectric diaphragm and passive micro check valves is presented and simulated with a Matlab Simulink® tool. Simulation is implemented for a 1 and 2-stage microcompressor design. Finite element analysis (FEA) is used to determine the lump model parameters from the fluid-structure interaction (FSI) between the microvalve and gas flow dynamics. FSI model parameters are extracted and developed as a lump model equation for Simulink® numerical computation. Dynamic simulations confirm that there is an increase in pressure ratio for a multistage microcompressor when compared to a single stage, which is achievable with passive microvalves. However, there are negative effects of using passive microvalves at high frequency. Frequency response results gathered from simulation shows that mass flow rate through the microvalve decreases above the frequency threshold ∼1 kHz for our design. This is in two parts due to a smaller gap height opening of the microvalve plate at high frequency and the reverse flow leakage. Both losses in mass flow rate from the microvalves decrease the total flow rate of the microcompressor above ∼1 kHz. Increasing actuation frequency below the ∼1 kHz threshold increases the flow rate of the microcompressor in the design. Therefore, it is concluded that the maximum flow rate of the microcompressor increases with increasing operation frequency, but becomes limited by the negative effect of the microvalve at a high frequency threshold due to the attenuation of the microvalve gap height. Although flow rate is affected, maximum pressure ratio of the microcompressor is still achievable at various frequency range, assuming the stroke volume of the pump chamber is constant throughout all frequency ranges. Multistage simulations show that the operation frequency ratio between each stage can have some negative effect in achieving the maximum theoretical pressure ratio.
Towards the Understanding of Transformation of Annular to Droplet-Annular Gas-Liquid Flow
Authors: Kumar Parmod , Mitra Sushanta K. , Das Arup Kumar
Published: November 2016

Annular flow and its deviations due to change of phase velocities in parallel and counter flows are very common in many adiabatic and non-adiabatic applications of two phase flow. The transformation from annular flow to its counterpart droplet-annular flow is often poorly understood as it needs to handle multi scale interfaces experimentally or numerically. In the present work, attempts have been made to capture both wavy annular interface and dynamics of tiny droplets throughout its life cycle using grid based volume of fluid framework. 3-D simulation domain with length (L)/diameter (D) ratio as 6 is considered under the effect of gravitational acceleration and phase inertial field. Wavy interface is observed numerically between the phases using phase fraction contours along with the occurrence of three very interesting phenomena, which include rolling, undercutting and orificing. At low liquid and gas velocities orificing has been observed which restricts the path of gaseous phase. Departure from the orificing phenomenon has been seen at higher gas phase velocities which transforms to other phenomenon called rolling. Rolling is the folding of liquid film by the high velocity gaseous phase towards the radially outward direction. Further, increase in liquid phase velocities above gaseous phase velocities results in undercutting of liquid film by the gas phase. Moreover the liquid droplets can be seen in the entire phenomenon through the gas phase in the core of the tube. We presented a regime map of gas liquid velocities to segregate clear understanding of annular to droplet-annular flow due to orificing, rolling and undercutting. The present study will enrich the knowledge of multiphase flow transportation in process plants, chemical reactors, nuclear reactors and refineries where gas-liquid annular flow is most widely used flow pattern.
Numerical Investigation of the Effect of Micro Channel Bends Angle
Authors: Rovenskaya Olga , Croce Giulio
Published: November 2016

A pressure driven compressible gas flow through three-dimensional microchannel with bend of various angles is investigated using Navier–Stokes equations coupled with the first-order Maxwell slip boundary condition along with Smoluchowski temperature jump definition. A wide range of bend angles from 60° to 180° is considered. The details of the flow structures near the corner are analyzed, investigating the competing effects of rarefaction, compressibility and geometry on the channel performances. The bent results are compared to those from the equivalent straight micro-channel geometry in terms of mass flow rate and Poiseuille number. The analysis of the flow structure shows that the channel geometry is important in microfluidic applications. In particular, it is found that a micro-channel with bend angle less than 90 degrees produces an increase in mass flow with respect to the straight one, while obtuse angle bends produce a mass flux reduction. For the sharp angle the flow separation and recirculation occur in the corner of the bend and this becomes more critical as the bend angle decreases. The rarefaction alleviates the geometry effect, while compressibility enhances it.
Conjugate Heat Transfer in a Hexagonal Micro Channel Using Hybrid Nano Fluids
Authors: Hegde Shreyas S. , Ganesan Narendran , Gnanasekaran N.
Published: November 2016

Research is being focused on the use of micro channels with nano fluids as the heat sinks. This requires fundamental understanding of the heat transfer phenomenon in micro channels. The objective of this paper is to present results from a numerical study on laminar forced convection in a Hexagonal Micro Channel (HMC) heat sink. In particular, the numerical study is carried out using a single phase model. The fluid considered is Alumina-Copper hybrid Nano fluid. The performance of Al2O3+Cu+water is compared with Al2O3+water nano fluid and pure water with different volume fractions. The solid region of the channel is assumed as aluminum with a hydraulic diameter of 175μm. The solid and fluid regions of the micro channel are discretized using finite volume method by combining Navier Stokes equation and energy equation for conjugate heat transfer. The thermo physical properties for alumina nanoparticles are calculated by considering it as a spherical particle of 45nm diameter. The effect of surface roughness on convective heat transfer coefficient and pressure drop for the case of nano fluids is also considered. The analysis is further extended by adding pulsating input and by varying the velocity sinusoidally. The Brownian motion of nano particles is increased to study the efficiency of the heat sink. This ensures all the nano particles are in suspension and the randomness increases the micro convection in the fluid. Incorporating the pulsating flow increases the dispersion of the heat in the nano fluid at a faster rate and also decreases particle settlement in laminar flow. The combined effect of surface roughness and pulsating flow accounts for the change in the velocity profile and thermal boundary layer of the channel. Also the effect of surface roughness ranging from 0.2–0.6 is attempted and the variations in pressure drop, Nusselt number, and heat transfer coefficient are studied. The influence of hexagonal geometry and its interaction with alumina nano fluids is intensively studied by evaluating a three dimensional conjugate heat transfer model. The effect of side wall angle of 45°, 50° and 55° are computed to relate the velocity function with pressure drop, surface roughness and local heat transfer coefficient. The variation of Nusselt number with very low volume fraction of nano particles with a minimal amount of pressure drop is also presented.
Comparative Studies on Water Self-Diffusivity Confined in Graphene Nanogap: Molecular Dynamics Simulation
Authors: Moulod Mohammad , Hwang Gisuk
Published: November 2016

Fundamental understanding of the water in graphene is crucial to optimally design and operate the sustainable energy, water desalination, and bio-medical systems. A numerous atomic-scale studies have been reported, primarily articulating the surface interactions (interatomic potentials) between the water and graphene. However, a systematic comparative study among the various interatomic potentials is rare, especially for the water transport confined in the graphene nanostructure. In this study, the effects of different interatomic potentials and gap sizes on water self-diffusivity are investigated using the molecular dynamics simulation at T = 300 K. The water is confined in the rigid graphene nanogap with the various gap sizes Lz = 0.7 to 4.17 nm, using SPC/E and TIP3P water models. The water self-diffusivity is calculated using the mean squared displacement approach. It is found that the water self-diffusivity in the confined region is lower than that of the bulk water, and it decreases as the gap size decreases and the surface energy increases. Also, the water self-diffusivity nearly linearly decreases with the increasing surface energy to reach the bulk water self-diffusivity at zero surface energy. The obtained results provide a roadmap to fundamentally understand the water transport properties in the graphene geometries and surface interactions.
Dip Coating of Electrochemically Generated Graphene and Graphene Oxide Coatings to Enhance Pool Boiling Performance
Authors: Jaikumar Arvind , Kandlikar Satish G. , Gupta Anju
Published: November 2016

Passive pool boiling enhancements offer attractive cooling possibilities to address the demand for effective thermal management in high powered electronic systems. Enhancements in pool boiling have been achieved through area augmentation, providing additional nucleation sites or by inducing liquid wettability changes. Graphene, a two-dimensional material, has garnered significant attention of researchers due to its excellent thermal properties. In this study, heat transfer surfaces are dip coated with an electrochemically generated solution consisting of graphene oxide (GO) and graphene and its pool boiling performance with distilled water at atmospheric pressure was obtained. The surfaces were characterized using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The static contact angles of the engineered surfaces are measured. The underlying wettability mechanisms are supported by high speed imaging of the nucleating bubbles. A maximum Critical Heat Flux (CHF) of 182 W/cm2 and a Heat Transfer Coefficient (HTC) of 96 kW/m2°C was obtained with the thinnest coating which translated to an enhancement of 42% in CHF and 47% in HTC when compared to a plain uncoated surface.
Oscillating Heat Pipe Performance With Modified Evaporator Geometries
Authors: Hoesing Mitchell P. , Michna Gregory J.
Published: November 2016

An oscillating heat pipe (OHP) is a heat transfer device that is capable of transferring large amounts of thermal energy with low thermal resistances. These characteristics make it a potentially viable option for high-heat flux cooling requirements. OHPs have several key advantages over other cooling technologies: passive operation, simplicity, low cost, and low mass. OHPs consist of an evaporator, adiabatic, and condenser sections joined by multiple interconnected meandering channels. A two-phase working fluid, in this study acetone, fills the channels and acts as the heat transfer medium. The focus of this study is to investigate OHP performance with enhancements in the evaporator section. Four evaporator geometry variations were studied: wavy channel, straight channel, recessed cavity, and pin and cavity. It was found that the wavy-channel and recessed-cavity geometries have superior performance when compared to the traditional straight channel, with 40% and 27% lower thermal resistances, respectively. The pin-and-cavity OHP performed 22% worse in terms of thermal resistance, than the straight-channel OHP. The wavy-channel OHP uniquely showed excellent operating characteristics in the horizontal orientation (0° inclination angle). Both the wavy-channel and recessed-cavity OHPs also showed the ability to transfer larger amounts of thermal energy (up to 400 W) before drying out. The reduction in performance of the pin-and-cavity OHP relative to the straight-channel OHP indicates that a reduction in performance and results when the pressure drop between the evaporator and condenser sections is increased.
Three-Dimensional VOF Simulations of Laminar Fluid Flows in Micro-Pipes Containing Superhydrophobic Walls With Micro-Posts and Micro-Ridges
Authors: Eleshaky Mohamed E.
Published: November 2016

This paper investigates water flowfield characteristics inside micro-pipes containing superhydrophobic walls under laminar flow conditions. It also investigates the effects of solid fraction, wall pattern, and Reynolds number on both skin friction drag and flow field characteristics. A transient, incompressible, three-dimensional, volume-of-fluid (VOF) methodology has been employed to continuously track the air–water interface and to visualize the dynamic behavior of the complex flows inside micro-pipes containing different superhydrophobic wall features (square micro-posts and longitudinal micro-ridges). The results of the present simulations show that micro-pipes containing superhydrophobic walls with longitudinal micro-ridges features have a better frictional performance than those having square posts features. The predicted results also show that the frictional performance of micro-pipes is a monotonically decreasing function of Reynolds number for both patterns examined in the present study. In addition, as the solid fraction decreases, the flow enhancement of superhydrophobic micro-pipes increases and it seems, based on the studied cases, to reach an asymptotic value. However, a further study is needed to confirm this latter issue.
Hydrodynamic and Thermal Characteristics of the Flow Inside a Rectangular Microchannel With Different Cylindrical Micro Pin Fins
Authors: Mohammadi Ali , Koşar Ali
Published: November 2016

This article presents a computational study to investigate the hydrodynamic and thermal characteristics of the flow inside a rectangular microchannel with the dimensions of 5000 × 1500 × 100 μm3 (l × w × h’) with different inline arrangements of cylindrical micro pin fins. A parametric study is performed on the effect of different geometrical specifications of micro pin fins on the wake-pin fin interaction. Three values of (50, 100 and 200 μm) are considered for the pin fin diameters (D) while the overall height (H) of the system is set to be constant (100 μm). For the first two cases, two longitudinal and vertical pitch ratios (SL/D and ST/D) of 1.5 and 3 are considered while for H/D ratio of 0.5, only ST/D ratio of 1.5 and SL/D ratios of 1.5 and 3 are considered. As a result, a total number of ten different geometries are analyzed in five different Reynolds numbers of 20, 40, 80, 120 and 160. A constant heat flux is applied through the bottom surface of the microchannel as well as the micro pin fins surfaces. All other surfaces are assumed to be thermally isolated. Thermodynamic properties of water are set to vary with temperature and it is assumed that the working flow remains in the liquid form in all operating conditions. ANSYS commercial package v14.5 with an academic license is utilized to generate the 3D models, applying the appropriate grid networks and simulating the flow fields for each configuration. Results show major dependencies of pressure drops, friction factors, Nusselt numbers and Thermal Performance Index values on ST/D ratio and Reynolds number while minor dependencies of these parameters on SL/D and H/D ratios are observed.
Design of Anode Flow Channels and Headers for a Large PEMFC Operating at Ultra-Low Stoichiometric Flow Conditions at the Anode Exit
Authors: Rizvandi Omid B. , Yesilyurt Serhat
Published: November 2016

High utilization of hydrogen is desired in operation of PEM fuel cells. Typically, additional devices for hydrogen recovery at the anode exit are necessary. Alternatively, dead-ended anode (DEA) operation may be considered, however this mode causes severe voltage transients and loss of catalyst support in hydrogen-depleted regions of the active area. Here. ultra-low stoichiometric (ULS) flow conditions that deliver very high hydrogen utilization is considered, however uniform flow distribution is necessary in this case. In order to obtain the flow distribution in the channels and in the inlet and exhaust headers in the anode, a three-dimensional CFD model is developed based on the finite-element method to solve Stokes equations subject to no-slip boundary conditions on the walls, specified pressure at the inlet and specified flow rate at the exit, which is set to a very low value comparable to the typical rate of nitrogen accumulation in the anode side in order to simulate the ULS flow. Uniformity of the flow distribution between the channels is quantified by means of two performance metrics: (i) the root-mean-square (rms) of the channel average velocities; (ii) the ratio of maximum and minimum values of the channel averages. Effects of geometric parameters, such as the widths of the channels and ribs and the position and lengths of the baffles in the inlet and exhaust headers are studied. The final design has less than 5% rms, and less than 1.2 for maximum to minimum average channel velocity ratio.
Vortex Laden Flows in a Micro-Gap for Enhanced Direct Chip Cooling
Authors: Gorodetsky Amir , Haustein Herman D.
Published: November 2016

Heat dissipation in modern high-power electronics require high performance cooling, which traditional air-based systems cannot provide. Rather, novel systems using liquids, which have inherently better heat transfer characteristics, must be used. Therefore, these have recently been extensively examined. The present study aims to identify the liquid flow patterns which significantly increase heat transfer, examine them through simulation (transient 2D laminar DNS) and experimentally realize the most promising configuration. Any such flow patterns should target a major inhibitor of heat transfer, namely, the development of the thermal boundary layer. From the literature, it was seen that traveling vortices should meet this demand, due to generation of perpendicular unsteady or periodic flows, and consequently significant disruption of the boundary layer. Traditionally, micro-channels have been widely employed for micro-electronics cooling. However, the generation and persistence of the desired vortices over longer distances, as well as a desired lower pressure drop can be obtained in micro-gaps, which have inherently overall lower wall-fluid friction. The desired vortices can be further enhanced by active methods such as inlet flow pulsation. In the present study, based on numerical simulations (grid-independent and validated against an analytical solution) a suitable micro-gap geometrical configuration was chosen, while the flow rate (Re) and excitation frequency (Strouhal number around the well-known resonance, St = 0.3) with low amplitude, were examined over a wide range. Further examination led to the choice of two methods for vortex generation. The first is a use of bluff bodies as flow obstructers in the micro-gap, whereby vortex shedding (von Karman street) occurs already at low Reynolds numbers (Re>50). A preliminary experimental device was constructed with side and top view capabilities, for flow visualization, as well as the possibility of wall temperature measurement by IR thermography. Preliminary simulations and experiments showed that Vortex shedding onset was only mildly affected in the micro-scale (200 micron obstruction in 600 micron channel), while heat transfer was seen to increase three-fold over obstruction-free gap, with only mild pressure drop increase. The second method has additional advantage of imposed perpendicular flow. The model consists of a row of slot-jets in a micro-gap with cross-flow. Recent experimental and numerical studies employing a similar hybrid cooling scheme, showed significant heat flux dissipation (305 W/cm2). Here too, significant increase of the heat transfer was found, with additional increase associated with flow pulsation. In future experimental work, the intention is to include MEMS based actuators for individual control of the jets’ excitation ability and effective slot width.
Age equivalence in the benefit of repetition for speech understanding
Authors: Helfer Karen S. , Freyman Richard L.
Published: November 2016

Although repetition is the most commonly used conversational repair strategy, little is known about its relative effectiveness among listeners spanning the adult age range. The purpose of this study was to identify differences in how younger, middle-aged, and older adults were able to use immediate repetition to improve speech recognition in the presence of different kinds of maskers. Results suggest that all groups received approximately the same amount of benefit from repetition. Repetition benefit was largest when the masker was fluctuating noise and smallest when it was competing speech.
Papers of note in
Science
Authors: VanHook Annalisa M.
Published: November 2016

This week’s articles highlight a growth factor that promotes spinal cord regeneration in fish, an insecticidal peptide from bacteria that can protect plants from pests, and a transcription factor network downstream of the plant hormone abscisic acid.
Four additional genes in the sigB operon of Bacillus subtilis that control activity of the general stress factor sigma B in response to environmental signals
Authors: Wise A A , Price C W
Published: November 2016

sigma B of the gram-positive bacterium Bacillus subtilis is an alternative transcription factor activated by a variety of environmental stresses, including the stress imposed upon entry into the stationary growth phase. Previous reports have shown that this stationary-phase activation is enhanced when cells are grown in rich medium containing glucose and glutamine. The sigma B structural gene, sigB, lies in an operon with three other genes whose products have been shown to control sigma B activity in response to environmental stress. However, none of these is sufficient to explain the enhanced stationary-phase activation of sigma B in response to glucose. We show here that the four genes previously identified in the sigB operon constitute the downstream half of an eight-gene operon. The complete sigB operon is preceded by a sigma A-like promoter (PA) and has the order PA-orfR-orfS-orfT-orfU-PB-rsbV-rsbW-sig B-rsbX, where rsb stands for regulator of sigma-B and the previously identified sigma B-dependent promoter (PB) is an internal promoter preceding the downstream four-gene cluster. Although the genes downstream of PB were also transcribed by polymerase activity originating at PA, this transcription into the downstream cluster was not essential for normal induction of a sigma B-dependent ctc-lacZ fusion. However, deletion of all four upstream open reading frames was found to interfere with induction of the ctc-lacZ fusion in response to glucose. Additional deletion analysis and complementation studies showed that orfU was required for full glucose induction of sigma B-dependent genes. orfU encodes a trans-acting, positive factor with significant sequence identity to the RsbX negative regulator of sigma B. On the basis of these results, we rename orfU as rsbU to symbolize the regulatory role of its product.
The pcsA gene is identical to dinD in Escherichia coli
Authors: Ohmori H , Saito M , Yasuda T , Nagata T , Fujii T , Wachi M , Nagai K
Published: November 2016

The pcsA68 mutant of Escherichia coli is a cold-sensitive mutant which forms long filaments with a large nucleoid in the central region at 20 degrees C. We here show that (i) the coding region for the pcsA gene is identical with orfY located upstream of pyrE and can be deleted without loss of viability; (ii) pcsA is also identical to dinD, a DNA damage-inducible gene, whose expression is regulated by the LexA-RecA system; (iii) the cold-sensitive phenotype of the pcsA68 mutation is suppressed by delta recA or lexA1 (Ind-) mutation, but not by sulA inactivation; (iv) overproduction of PcsA68 leads to inhibition of cell growth in recA+ and delta recA strains at 20 and 37 degrees C, but PcsA+ does not show such an effect at any temperature; (v) SOS response is induced in the pcsA68 mutant cells at 20 degrees C. We discuss the possible function of the pcsA gene, comparing it with the sulA or the dif-xerCD function. We also describe a new method for gene disruption with positive and negative selection.
In vitro studies of the domains of the nitrogen fixation regulatory protein NIFA
Authors: Berger D K , Narberhaus F , Lee H S , Kustu S
Published: November 2016

The prokaryotic enhancer-binding protein NIFA is a multidomain transcriptional activator that catalyzes the formation of open complexes at nitrogen fixation (nif) promoters by a specialized form of RNA polymerase containing sigma 54. The NIFA protein from Klebsiella pneumoniae consists of three domains: the N-terminal domain of unknown function; the central catalytic domain, which is sufficient for transcriptional activation; and the C-terminal DNA-binding domain. Purified fusion proteins between maltose-binding protein (MBP) and NIFA deleted of its N-terminal domain (MBP-delta N-NIFA) or its C-terminal domain (MBP-NIFA-delta C) activated transcription from the K. pneumoniae nifH promoter both in vitro and in vivo. We previously showed that the same was true for a fusion between MBP and the central domain of NIFA. These results indicate that NIFA is sufficiently modular for all fusions carrying its catalytic domain to be active. Unexpectedly, however, simple predictions regarding the location of determinants of the heat lability and insolubility of NIFA, which were based on previous studies of its isolated central and C-terminal domains, were not borne out. Contrary to a previous report from this laboratory, we found that the in vitro start site of transcription for the K. pneumoniae nifH operon could be either of two adjacent G residues, as others had reported in vivo. This was true independent of the activator, i.e., with MBP-NIFA and MBP-delta N-NIFA and with the homologous activator NTRC. When open complexes were formed with GTP as the activating nucleotide, the upstream G residue was probably as a consequence of initiation of transcription.
Inositol monophosphatase activity from the Escherichia coli suhB gene product
Authors: Matsuhisa A , Suzuki N , Noda T , Shiba K
Published: November 2016

The suhB gene is located at 55 min on the Escherichia coli chromosome and encodes a protein of 268 amino acids. Mutant alleles of suhB have been isolated as extragenic suppressors for the protein secretion mutation (secY24), the heat shock response mutation (rpoH15), and the DNA synthesis mutation (dnaB121) (K. Shiba, K. Ito, and T. Yura, J. Bacteriol. 160:696-701, 1984; R. Yano, H. Nagai, K. Shiba, and T. Yura, J. Bacteriol. 172:2124-2130, 1990; S. Chang, D. Ng, L. Baird, and C. Georgopoulos, J. Biol. Chem. 266:3654-3660, 1991). These mutant alleles of suhB cause cold-sensitive cell growth, indicating that the suhB gene is essential at low temperatures. Little work has been done, however, to elucidate the role of the product of suhB in a normal cell and the suppression mechanisms of the suhB mutations in the aforementioned mutants. The sequence similarity shared between the suhB gene product and mammalian inositol monophosphatase has prompted us to test the inositol monophosphatase activity of the suhB gene product. We report here that the purified SuhB protein showed inositol monophosphatase activity. The kinetic parameters of SuhB inositol monophosphatase (Km = 0.071 mM; Vmax = 12.3 mumol/min per mg) are similar to those of mammalian inositol monophosphatase. The ssyA3 and suhB2 mutations, which were isolated as extragenic suppressors for secY24 and rpoH15, respectively, had a DNA insertion at the 5' proximal region of the suhB gene, and the amount of SuhB protein within mutant cells decreased. The possible role of suhB in E. coli is discussed.
Physical mapping of the Mycoplasma gallisepticum S6 genome with localization of selected genes
Authors: Gorton T S , Goh M S , Geary S J
Published: November 2016

We report the construction of a physical map of the Mycoplasma gallisepticum S6 genome by field-inversion gel electrophoresis of DNA fragments generated by digestion of genomic DNA with rare-cutting restriction endonucleases. The size of the M. gallisepticum S6 genome was calculated to be approximately 1,054 kb. The loci of several genes have been assigned to the map by Southern hybridization utilizing specific gene probes.
Agrobacterium tumefaciens VirB11 protein requires a consensus nucleotide-binding site for function in virulence
Authors: Stephens K M , Roush C , Nester E
Published: November 2016

virB11, one of the 11 genes of the virB operon, is absolutely required for transport of T-DNA from Agrobacterium tumefaciens into plant cells. Previous studies reported that VirB11 is an ATPase with autophosphorylation activity and localizes to the inner membrane even though the protein does not contain the consensus N-terminal export sequence. In this report, we show that VirB11 localizes to the inner membrane even in the absence of other tumor-inducing (Ti) plasmid-encoded proteins. To facilitate the further characterization of VirB11, we purified this protein from the soluble fraction of an Escherichia coli extract by fusing VirB11 to the maltose-binding protein. The maltose-binding protein-VirB11 fusion was able to complement a virB11 deletion mutant of A. tumefaciens for tumor formation and also localized properly to the inner membrane of A. tumefaciens. The 72-kDa protein, purified from E. coli, exhibited no autophosphorylation, ATPase activity, or ATP-binding activity. To study the importance of the Walker nucleotide-binding site present in VirB11, mutations were generated to replace the conserved lysine residue with either alanine or arginine. Expression of the virB11K175A mutant gene resulted in an avirulent phenotype, and expression of the virB11K175R mutant gene gave rise to an attenuated virulence phenotype. Both mutant proteins were present at levels three to four times higher than that of VirB11 in the wild-type strain. The mutant genes did not exhibit a transdominant phenotype on tumor formation in bacteria that were expressing wild-type virB11. The mutant proteins also localized properly to the inner membrane of A. tumefaciens, but the VirB11K175R protein appeared to be unstable after lysis of the cells.