bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Turbulence in the Tip Region of a Waterjet Pump Rotor
Authors: Wu Huixuan , Miorini Rinaldo L. , Katz Joseph
Published: March 2011

A series of high resolution planar particle image velocimetry measurements performed in a waterjet pump rotor reveal the inner structure of the tip leakage vortex (TLV) which dominates the entire flow field in the tip region. Turbulence generated by interactions among the TLV, the shear layer that develops as the backward leakage flow emerges from the tip clearance as a “wall jet”, the passage flow, and the endwall is highly inhomogeneous and anisotropic. We examine this turbulence in both RANS and LES modelling contexts. Spatially non-uniform distributions of Reynolds stress components are explained in terms of the local mean strain field and associated turbulence production. Characteristic length scales are also inferred from spectral analysis. Spatial filtering of instantaneous data enables the calculation of subgrid scale (SGS) stresses, along with the SGS energy flux (dissipation). The data show that the SGS energy flux differs from the turbulence production rate both in trends and magnitude. The latter is dominated by energy flux from the mean flow to the large scale turbulence, which is resolved in LES, whereas the former is dominated by energy flux from the mean flow to the SGS turbulence. The SGS dissipation rate is also used for calculating the static and dynamic Smagorinsky coefficients, the latter involving filtering at multiple scales; both vary substantially in the tip region, and neither is equal to values obtained in isotropic turbulence.
Quasi-Periodic Structure of Vortical Flows Produced in the Wake of Finite Bluff Bodies Partially Immersed in a Boundary Layer
Authors: Bourgeois Jason A. , Sattari Pooria , Martinuzzi Robert J.
Published: March 2011

The quasi-periodic vortex shedding structure in the wake of finite surface-mounted square- and circular-cross-section cylinders is investigated for several aspect ratios. Complex continuous wavelet transforms (CWT’s) are used to obtain a phase function φ(t) from hot-wire measurements. Mean relative phases and phase averaged particle image velocimetry (PIV) measurements indicate an upstream bending of the initially vertical shed vortex structures for all obstacles investigated. This upstream bending mechanism reorients vorticity streamwise and is described in terms of Biot-Savart induction that occurs at the junction of the tip and side shear layers. This mechanism of vorticity concentration/reorientation is inherently three-dimensional and interacts with the nominally two-dimensional mechanism of alternate vortex sheet roll-up from the opposing obstacle side faces. This mechanism typically acts higher along the height for square-as opposed to circular-cross section cylinders and plays a more dominant role for smaller aspect ratios.
Viscosity Studies of Aqueous Solutions of Hafnium Oxide Particles and Polystyrene Nanospheres
Authors: Pitts Katie Lieg , Shedd Timothy
Published: March 2011

Nanoparticle colloidal system rheology has long been researched, without many concrete conclusions. Literature has been devoted to the viscosity and shear properties of these systems since Einstein’s PhD thesis. However, most models are based on molecular dynamics which are not necessarily applicable to real systems, and most real systems are modeled by empiricism. This report looks to unify these approaches through rheological testing and mathematical analysis in order to achieve several goals using a system composed of hafnium oxide particles suspended in water. The first goal is to have a viscosity model that fits not only empirical data, but also the relevant theory and first principles. By employing the modern techniques of a rhoemeter-on-a-chip to nano-scale particles, the limitations of traditional rheometry are bypassed. The molecular dynamics approaches are converted to zero-shear and infinite-shear viscosities which can be applied to traditional models. A modern model was then derived, applied to new data, and agreement was found to a satisfactory degree. No significant change in viscosity with shear rate was found experimentally or analytically. Traditional research is done with spherical particles, such as polystyrene nanopsheres, as which we are approximating hafnium oxide (HfOx) to be. Polystyrene nanospheres are nominally spherical and commercially available at relatively inexpensive costs. Actual spherical data was required for appropriate comparison, and the findings show that the spherical particles have distinct properties.
Solid/Water Interface of Functionalized Silica Surfaces Studied by Dynamic Force Measurements
Authors: Wu Yan , Karacor M. Basar , Prakash Shaurya , Shannon Mark A.
Published: March 2011

In this study, silica surfaces were chemically modified yielding dissimilar surfaces with –Br, –NH2, and –CH3 functional group terminations. The dynamic response of an oscillating micro-cantilever with a gold-coated tip interacting with the functionalized silica surfaces was studied in electrolyte solutions with pH ranging from 4 to 9. The amplitude and phase of the cantilever oscillation were monitored and used to calculate the effective stiffness of the AFM cantilever, which relates to the double layer interactions and the hydrodynamic damping at the solid/water interface. The data for the dynamic response of the AFM over silica surfaces as a function of chemical functionalization and electrolyte pH show that the effective stiffness has distinctive dependence on the surface charge of functionalized silica surfaces. The hydrodynamic damping also correlates strongly with the relative hydrophobicity of the surface, suggesting a dependence on interfacial characteristics including effective slip lengths. It is hoped that the experimental data reported here will provide insights for development of more theoretical models explaining the underlying mechanisms.
Experimental Measurement of Pressure Pulses From a Pulp Screen Rotor
Authors: Delfel Sean , Olson James , Ollivier-Gooch Carl , Wallace Phil
Published: March 2011

Pressure screens are the most industrially effective way to remove contaminants from a pulp stream, improving the strength, smoothness, and optical qualities of both new and recycled paper. Pressure screens are comprised of two main components: a screen cylinder with narrow slots or small holes and a rotor. The main function of the rotor is to prevent the narrow cylinder apertures from becoming plugged by pulp and debris. In this study, the pressure pulses generated by a novel multi-element foil (MEF) and a single-element foil rotor in a pressure screen were measured at various foil configurations, rotor speeds, and flow rates. The experimental measurements were compared to the results from a computational fluid dynamics model (CFD). Experimental measurements showed that increasing both the angle-of-attack and the flap angle of the MEF increases the magnitude of the negative pressure pulse and reduce the magnitude of the maximum pressure pulse generated by the rotor. At the optimum configurations, the MEF was shown to produce a 126% higher magnitude negative pressure pulse and a 39% lower magnitude positive pressure pulse. It was also found that at higher tip speeds the magnitude of the pressure pulse varies with tip speed squared and the non-dimensional pressure coefficient is Reynolds number independent. Similarly, at higher tip speeds increasing the velocity of the flow through the slots had no effect on the pressure pulse generated by the rotor. At lower rotor speeds, however, the dimensionless pressure was increasingly depending on Reynolds number as slot flow velocity was increased. This is likely due to the increase in slot flow velocity causing the onset of flow separation over the foil. Finally, the numerical model was shown to accurately predict the pressure pulses generated by the MEF at low angles-of-attack and flap angles. However, the model predicted that the foil would stall at lower angles than what was shown experimentally. This is probably because the CFD model used a solid wall boundary condition rather than modeling the slots in the cylinder, preventing low momentum fluid from re-entering the domain.
Prediction of the Stress-Strain Response of the Ultrafine-Grained Materials Using Multi-Scale Analysis
Authors: Banu Mihaela , Afteni Mitica , Epureanu Alexandru , Tabacaru Valentin
Published: March 2011

There are several severe plastic deformation processes that transform the material from microsized grains to the nanosized grains under large deformations. The grain size of a macrostructure is generally 300 μm. Following severe plastic deformation it can be reached a grain size of 200 nm and even less up to 50 nm. These structures are called ultrafine grained materials with nanostructured organization of the grains. There are severe plastic deformation processes like equal angular channel, high pressure torsion which lead to a 200 nm grain size, respectively 100 nm grain size. Basically, these processes have a common point namely to act on the original sized material so that an extreme deformation to be produced. The severe plastic deformation processes developed until now are empirically-based and the modeling of them requires more understanding of how the materials deform. The macrostructural material models do not fit the behavior of the nanostructured materials exhibiting simultaneously high strength and ductility. The existent material laws need developments which consider multi-scale analysis. In this context, the present paper presents a laboratory method to obtain ultrafine grains of an aluminum alloy (Al-Mg) that allows the microstructure observations and furthermore the identification of the stress–strain response under loadings. The work is divided into (i) processing of the ultrafine-grained aluminum alloy using a laboratory-scale process named in-plane controlled multidirectional shearing process, (ii) crystallographic analysis of the obtained material structure, (iii) tensile testing of the ultrafine-grained aluminum specimens for obtaining the true stress-strain behavior. Thus, the microscale phenomena are explained with respect to the external loads applied to the aluminum alloy. The proposed multi-scale analysis gives an accurate prediction of the mechanical behavior of the ultrafine-grained materials that can be further applied to finite element modeling of the microforming processes.
Interaction Between Two Opposing Turbulent Round Jets
Authors: Alkandry Hind , Stegeman Koen , Higuchi Hiroshi
Published: March 2011

Two jets are placed opposed to each other and their interaction process is studied in water using particle image velocimetry (PIV). A fully developed pipe flow exists at the exit. Averaged in time the radial jet will go in the direction perpendicular to the direction of the jets. However, the instantaneous velocity field of the radial jet for both angles is highly unstable. A comparison between the two angles and a single jet is also conducted. The results are compared to the laboratory experiment that simulates a personal ventilation system with two opposing jets supplying fresh air to the occupant.
Two Target Parameters, the Heat Transfer Qmix/B and the Drag Force Fdmix/C are Susceptible to the Molar Gas Composition W of the Six Gas–Gas Mixtures in the W-Domain [0, 1]
Authors: Mobinipouya Mohammad Reza
Published: March 2011

This paper addresses the laminar boundary layer flow of selected binary gas mixtures along a heated flat plate. To form the binary gas mixtures, light helium (He) is the primary gas and the heavier secondary gases are nitrogen (N2), oxygen (O2), xenon (Xe), carbon dioxide (CO2), methane (CH4), tetrafluoromethane (CF4) and sulfur hexafluoride (SF6). The central objective in the work is to investigate the potential of this group of binary gas mixtures for heat transfer intensification. From fluid physics, two thermophysical properties: viscosity η and density ρ influence the fluid flow, whereas four thermophysical properties: viscosity η, thermal conductivity λ, density ρ, and heat capacity at constant pressure Cp affect the forced convective heat transfer. The heat transfer augmentation from the flat plate is pursued by stimulating the forced convection mode as a whole. In this regard, it became necessary to construct a specific correlation equation to handle binary gas mixtures owing Prandtl number Pr ∈ (0.1, 1). The rate of heat transfer Q between a heated plate and a cold fluid is calculated with: Qmix/B=λmix0.623ρmix0.500Cp,mix0.377ηmix0.123(1) If the surface area of the plate A and the temperature difference Tw–T∞ are specified, the only possible way for intensifying the rate of heat transfer Q is by enlarging the magnitude of the average heat transfer coefficient h. This is precisely the main goal to be pursued in the present paper. The average heat transfer coefficient h in laminar boundary layer flows of incompressible, viscous fluids along heated flat plates depends on the dimensionless fluid temperature gradient at the plate θ′(0). It is given by the Prandtl number function f (Pr).
Effect of Diffuser Contraction for a Centrifugal Compressor
Authors: Kang Kyung-Jun , Shin You-Hwan , Kim Kwang-Ho , Lee Yoon-Pyo
Published: March 2011

This study will be described details on influence of movable diffuser such as local reverse flow patterns and pressure fluctuation in a vaneless diffuser during unstable operation of a centrifugal compressor. The experimental study is carried out in centrifugal compressor immersed into a water reservoir. Particle Image Velocity (PIV) is used to observe a secondary flow pattern and pressure transducer is used for investigating the onset and development of rotating stall inside vaneless diffuser. The reverse flow zone observes near hub wall of impeller exit at relatively low flow rate. This reverse flow on hub side wall brings about the rotating stall. This paper be simultaneously discussed on the effects of diffuser contraction to remove local reverse flow zone near hub wall, which are including variation of flow field in a vaneless diffuser and the influence on the pressure fluctuation. A contraction due to movable diffuser three cases (40%, 53% and 86% of diffuser width) was inserted into vaneless diffuser from a shroud wall. According to the results, the rotating stall involving single and two cells is enveloped by the outer lobe of the Rossby wave. Under the rotating stall onset, the stall propagation rate is 1.25Hz, 25% of the impeller speed in the same direction as the impeller in case of no contraction. In case of 40% contraction, onset of rotating stall is not delayed. In contrast of that, onset of rotating stall is delayed in case of 53%, 87% contraction. There exist several secondary vortices inside vaneless diffuser under onset of rotating stall. The size and location of them vary as flow rate decreases.
The Effect of Material Properties on the Efficiency of Valve-Less Rectification Micropumps
Authors: Fadl Ahmed , Demming Stefanie , Zhang Zongqin , Hoxhold Bjo¨rn , Bu¨ttgenbach Stephanus , Krafczyk Manfred , Meyer Donna M. L.
Published: March 2011

High efficiency valve-less rectification micropumps are essential in developing effective microfluidic systems. Many parameters have been reported in the literature to have an effect on the efficiency of valve-less rectification micropumps. These parameters are related to the dynamics of fluid flow (such as Reynolds number), rectifying geometries, or actuators (such as actuator frequency). In this work, we studied the effect of the material properties on the efficiency of valve-less rectification micropumps. Two valve-less rectification micropumps based on the same rectifying geometry, bifurcation, are fabricated using two different materials, Polydimethylsiloxane (PDMS) and SU-8 photoresist. The pumps are tested and results are compared. Experimental results suggest that the material properties have an apparent effect on the pumping performance of valve less rectification micropumps. The results are presented in terms of flow rates and maximum back pressures.
Heat and Mass Transfer in the Corner Flow Region of Vertical Microgrooves
Authors: Nie Xuelei , Hu Xuegong , Garimella Suresh V. , Tang Dawei
Published: March 2011

Evaporation of the thin film formed in microgrooves is associated with high heat transfer rates. One of the factors that limits this heat transfer is the capacity of the microgroove to drive fluid into the thin film. The mass flow rate and mass flux in the corner flow region of a microgroove is experimentally and theoretically investigated in this work. The experiments yield the speed at which wetting occurs in vertical microgrooves. The wetting speed reflects the balance between the gravitational, viscous and capillary forces acting on the film. A force balance is also conducted on the liquid in the corner flow region of the microgrooves. This analysis allows a calculation of the maximum amount of liquid that the microgrooves can drive to the evaporating surface in the corner flow region, which in turn determines the maximum evaporation rate in this localized area.
Transient Response of Submerged Elastic Structures Subject to Underwater Shock Waves
Authors: Liu Zhanke , Young Yin L.
Published: March 2011

This paper presents the transient response of submerged elastic structures subject to underwater shock waves. Two fundamental effects are investigated, namely, the inertial and elastic effects, characterized by two non-dimensional parameters, namely, the inertial parameter M and the elastic parameter K. Case studies are provided with physical and mathematical interpretations of the results.
Numerical Analysis of Thermal Conductivity of Non-Charring Material Ablation Carbon-Carbon and Graphite With Considering Chemical Reaction Effects, Mass Transfer and Surface Heat Transfer
Authors: Kianifar Ali , Mohammadiun Hamid
Published: March 2011

Nowadays, there is little information, concerning the heat shield systems, and this information is not completely reliable to use in so many cases. For example, the precise calculation can not be done for various materials. In addition, the real scale test has two disadvantages: high cost and low flexibility, and for each case, we must perform a new test. Hence, using a numerical modeling program that calculates the surface recession rate and interior temperature distribution is necessary. Also, the numerical solution of governing equation for non-charring material ablation is presented in order to anticipate the recession rate and the heat response of non-charring heatshields. The governing equation is nonlinear and the Newton-Rafson method along with TDMA algorithm is used to solve this nonlinear equation system. Using Newton-Rafson method for solving the governing equation is one of the advantages of the solving method because this method is simple and it can be easily generalized to more difficult problems. The obtained results are compared with reliable sources in order to examine the accuracy of compiling code.
New Lab-on-a-Chip System for Infectious Disease Analysis
Authors: Ritzi-Lehnert Marion , Claussen Jan , Schaeffer Eva , Wiborg Ole , Wick Isabell , Drese Klaus S. , Himmelreich Ralf , Attig Hans , Dahlke Rainer , Grosshauser Gerd , Jeziorski Markus , Wende Andy , Rothmann Thomas
Published: March 2011

Early diagnosis followed by personalised efficient therapy of infectious diseases (e.g. respiratory diseases, meningitis, sepsis) can lead to considerable reduction of costs in health care. Point-of-care testing (POCT) can provide early detection since this kind of decentralised analysis can be done by unskilled personnel at any time. Other advantages of automated miniaturised Lab-on-a-Chip systems (LoC) are reduction of time and reagents, elimination of cross-contamination and enhanced reproducibility due to enhanced process control. Such Lab-on-a-Chip systems will establish themselves on market only when sensitivity and specificity meet clinical requirements. An integrated cost-efficient lab-on-a-chip system is presented which allows performing all diagnostic process steps for pathogen analysis of respiratory viruses from nasopharyngeal samples. The microfluidic disposable chip comprises structures for lysis of nasopharyngeal swab samples, preparation of total nucleic acids using magnetic silica beads, reverse transcription followed by QIAplex PCR technology and labelling of the nucleic acids by hybridisation with LiquiChip Beads and streptavidin-R-phycoerythrin. Labelled target sequences are transferred for analysis into a QIAGEN LiquiChip 200 workstation. The core of the instrument is a construction based on rotating heating bars allowing for fast cycling. All chemicals needed for performing of 24 analyses are either stored freeze-dried on the single-use disposable microfluidic chip (processing cartridge) or as liquids in a separate reagent cartridge. After introducing the sample into the lysis chamber of the microfluidic chip and inserting the chip into the device all steps are done automatically. To realise these steps, fluidic control in terms of light barriers and turning valves are integrated into the injection moulded disposable chip. This includes metering structures as well as magnetic stir bars for mixing. The functionality was proven by direct comparison of samples processed manually vs. automatically using the “ResPlex Panel II” for detection of respiratory viruses from nasopharyngeal samples. The efficiency of the automated LoC system yields at about 30–60% as compared to the manually performed reference experiments. Comparing the performance of the instrument with commercially available kits and nucleic acid preparation devices showed slightly weaker but clearly positive final signal intensities obtained from the prototype device even without protocol optimization.
Simulation of Heat Transfer in Nanoscale Flow Using Molecular Dynamics
Authors: Darbandi Masoud , Abbasi Hossein Reza , Sabouri Moslem , Khaledi-Alidusti Rasool
Published: March 2011

We investigate heat transfer between parallel plates separated by liquid argon using two-dimensional molecular dynamics (MD) simulations incorporating with 6–12 Lennard-Jones potential between molecule pairs. In molecular dynamics simulation of nanoscale flows through nanochannels, it is customary to fix the wall molecules. However, this approach cannot suitably model the heat transfer between the fluid molecules and wall molecules. Alternatively, we use thermal walls constructed from the oscillating molecules, which are connected to their original positions using linear spring forces. This approach is much more effective than the one which uses a fixed lattice wall modeling to simulate the heat transfer between wall and fluid. We implement this idea in analyzing the heat transfer in a few cases, including the shear driven and poiseuille flow with specified heat flux boundary conditions. In this method, the work done by the viscous stress (in case of shear driven flow) and the force applied to the fluid molecules (in case of poiseuille flow) produce heat in the fluid, which is dissipated from the nanochannel walls. We present the velocity profiles and temperature distributions for the both chosen test cases. As a result of interaction between the fluid molecules and their adjacent wall molecules, we can clearly observe the velocity slip in the velocity profiles and the temperature jump in the cross-sectional temperature distributions.
Modeling Laminar Fluid Flows in Rectangular Vapor Grooves of Evaporators Used in Loop Heat Pipes
Authors: Jesuthasan Nirmalakanth , Baliga B. Rabi
Published: March 2011

Loop heat pipes (LHPs) are devices in which capillary forces in a wick and liquid-vapor phase-change phenomena are used to achieve continuous and relatively high rates of transfer of thermal energy from a heat source to a heat sink. Quasi one-dimensional models of the fluid flow and heat transfer within LHPs, with empirical correlations as inputs, are commonly used as the basis of cost-effective computer simulations for the design and optimization of these devices for specific applications. The focus in this work is on laminar fluid flows in straight rectangular vapor grooves of flat evaporators used in LHPs. The pressure drops for such fluid flows are computed in available quasi one-dimensional models of LHPs using correlations for a friction factor that applies strictly only in the fully-developed region of flows in straight rectangular ducts with impermeable walls. The resulting errors can become serious if the pressure drop in the vapor grooves is a significant contributor to the overall pressure drop in the LHP. Thus, to enhance the capabilities of current quasi one-dimensional models of LHPs, more accurate correlations for predicting the aforementioned pressure drop are needed. In this work, a three-dimensional parabolic finite volume method is used to simulate laminar Newtonian fluid flows in straight rectangular vapor grooves of flat evaporators, for a representative range of LHP operating conditions. The mathematical model, computational methodology, results, and suitable correlations for the pressure drops are presented and discussed in this paper.
PIV Study of the Near-Field Region of a Turbulent Round Jet
Authors: Milanovic Ivana M. , Hammad Khaled J.
Published: March 2011

Turbulent jets have been extensively studied in the past due to their fundamental importance and wide spread usage in numerous industrial processes to enhance momentum, heat and mass transfer. Most previous work focused on the far-field or self-similar region of the flow. However, the initial development region, where the flow is dominated by streamwise and large-scale, Kelvin-Helmholtz-type, structures, received far less attention. In the current study, Particle Image Velocimetry (PIV) was used to obtain reliable statistics in the near-field region of a turbulent submerged jet. The jet issued from an 84 diameter, D, long pipe which ensured fully-developed turbulent flow conditions at the outlet. The two-dimensional flow field in the plane containing the jet axis was measured in the initial 8D region, for three Reynolds numbers: 14,602, 19,135, and 24,685. The selected Reynolds numbers overlap with the previously identified critical Reynolds number range, 10,000–20,000, where flow characteristics of a jet undergo a dramatic transition to a much more chaotic and well-mixed state or fully developed turbulence.
Non-Newtonian Effects on Blood Flow Dynamics in Stented Coronary Artery Bifurcations
Authors: Zarandi Marjan Molavi , Mongrain Rosaire , Bertrand Olivier F. , Bonakdar Ali
Published: March 2011

From clinical practice, it is known that coronary artery bifurcations are regions where the flow is strongly perturbed, and is prone to the development of atherosclerotic lesions. Bifurcation lesions have always represented a major challenge for placement of stents for treatment of stenosis. Conventional bare metal stents are mostly used in clinical practice of bifurcation lesion treatments since there is no specific commercially available stent dedicated for treating bifurcations. Stent design is strongly influenced by the specific hemodynamic conditions in a given vessel. Therefore, in principal, what was previously assessed for standard stent design, should be re-assessed for stenting bifurcations. In this paper a blood flow model for stented coronary artery bifurcation is presented. The non-Newtonian approach incorporating blood rheology under low shear rates is presented by employing Carreau model. Computational fluid dynamics modeling is used to adapt the model and characterize the non-Newtonian flow patterns and identify the hemodynamic factors that may influence the stent design. The results shows that the flow conditions and particularly shear stress distribution in the vicinity of stent struts and near arterial wall are significantly different compared to the usually assumed Newtonian flow conditions.
Flow Patterns and CHF in a Locally Heated Liquid Film Shear-Driven in a Minichannel
Authors: Zaitsev D. V. , Kabov O. A.
Published: March 2011

Thin and very thin (less than 10 μm) liquid films driven by a forced gas/vapor flow (stratified or annular flows), i.e. shear-driven liquid films in a narrow channel is a promising candidate for the thermal management of advanced semiconductor devices in earth and space applications. Development of such technology requires significant advances in fundamental research, since the stability of joint flow of locally heated liquid film and gas is a rather complex problem. The paper focuses on the recent progress that has been achieved by the authors through conducting experiments. Experiments with water in flat channels with height of H = 1.2–2.0 mm (mini-scale) show that a liquid film driven by the action of a gas flow is stable in a wide range of liquid/gas flow rates. Map of isothermal flow regime was plotted and the length of smooth region was measured. Even for sufficiently high gas flow rates an important thermocapillary effect on film dynamics occurs. Scenario of film rupture differs widely for different flow regimes. It is found that the critical heat flux for a shear driven film can be 10 times higher than that for a falling liquid film, and exceeds 400 W/cm2 in experiments with water for moderate liquid flow rates. This fact makes use of shear-driven liquid films promising in high heat flux chip cooling applications.
Role of Thermocapillary Convection in Rupture of a Falling Liquid Film Heated From Below
Authors: Gatapova Elizaveta , Zaitsev Dmitry , Kabov Oleg
Published: March 2011

The present work is aimed to describe and explain the physical mechanism of the rupture of a liquid film of moderate thickness falling down a heated substrate. Our investigations are based on the experimental data obtained using IR thermography, fiber optical technique as well as theoretical estimation of critical values. We show that thermocapillary convection may be responsible for critical film thickness. By investigating the instability of thermocapillary cells we demonstrate that thermocapillary forces play a dominant role in the first and the second stages of the dry patch formation process.
Experimental and Numerical Investigation of Two-Phase Patterns in a Cross-Junction Microfluidic Chip
Authors: Sur Aritra , Yang Lixin , Liu Dong
Published: March 2011

Two-phase microfluidic systems have been found in a wide range of engineering applications. Accurate determination of the two-phase flow patterns in microchannels is crucial to selecting appropriate predictive tools for pressure drop, heat and mass transfer in the microfluidic devices. Most of the prevailing two-phase flow maps developed using visualization techniques are unable to reveal the fundamental mechanisms responsible for the formation of specific flow pattern under given flow conditions. In this work, the high-speed photographic method is employed to study the liquid-gas two-phase flow in a cross-junction microfluidic chip with a rectangular cross section of 300 μm by 100 μm. The dynamics of bubbly, slug and annular flows are investigated. Numerical models using the VOF approach are developed to simulate the two-phase mixing and flow pattern formation in the microfluidic device. The roles of the inertia, viscous shear and surface tension forces in forming various two-phase flow patterns are discussed. The experimental results and the simulation data together provide a comprehensive phenomenological description of the key parameters and processes that govern the two-phase flow pattern formation in microfluidic devices.
Frequency Response of Gas-Filled Tube With Minor Losses
Authors: West Brian M. , Smith Barton L. , Liu Fei , Cattafesta Lou
Published: March 2011

The results of a study of the frequency response of a pneumatic system designed to provide pulsed flow for flow control applications are presented. The system consists of a high pressure air source, a high-frequency solenoid valve, a length of tube and a minor loss. The experiment mimics the pneumatic drive for our Coanda-Assisted Spray Manipulation actuator and applies to many flow control applications involving pulsed flow. Square wave signals of various frequency were fed to the solenoid valve. The flow at the exit of the flow system was measured with a single hot wire and compared to steady flow through the same geometry. The effect of the inlet pressure, tube length and the size and position of the minor loss were tested. These data are modeled using a Transmission Matrix Model in.
Innovation
Authors: Riendeau Diane
Published: March 2011

Special thanks to Danielle Campanella, Shannon Mandel, Jaime Stasiorowski and Bryan Musolf for their ideas for this column.
How to Grow a Mind: Statistics, Structure, and Abstraction
Authors: Tenenbaum Joshua B. , Kemp Charles , Griffiths Thomas L. , Goodman Noah D.
Published: March 2011

In coming to understand the world—in learning concepts, acquiring language, and grasping causal relations—our minds make inferences that appear to go far beyond the data available. How do we do it? This review describes recent approaches to reverse-engineering human learning and cognitive development and, in parallel, engineering more humanlike machine learning systems. Computational models that perform probabilistic inference over hierarchies of flexibly structured representations can address some of the deepest questions about the nature and origins of human thought: How does abstract knowledge guide learning and reasoning from sparse data? What forms does our knowledge take, across different domains and tasks? And how is that abstract knowledge itself acquired?
A Circadian Rhythm Orchestrated by Histone Deacetylase 3 Controls Hepatic Lipid Metabolism
Authors: Feng Dan , Liu Tao , Sun Zheng , Bugge Anne , Mullican Shannon E. , Alenghat Theresa , Liu X. Shirley , Lazar Mitchell A.
Published: March 2011

Circadian control of liver metabolism is mediated by cycles of recruitment of the histone deacetylase HDAC3.
Ordered and Dynamic Assembly of Single Spliceosomes
Authors: Hoskins Aaron A. , Friedman Larry J. , Gallagher Sarah S. , Crawford Daniel J. , Anderson Eric G. , Wombacher Richard , Ramirez Nicholas , Cornish Virginia W. , Gelles Jeff , Moore Melissa J.
Published: March 2011

Fluorescently labeled yeast spliceosome proteins reveal the events of intron splicing as it happens.
Role of Cathepsin A and Lysosomes in the Intracellular Activation of Novel Antipapillomavirus Agent GS-9191
Authors: Birkus Gabriel , Kutty Nilima , Frey Christian R. , Shribata Riri , Chou Tsuifen , Wagner Carston , McDermott Martin , Cihlar Tomas
Published: March 2011

GS-9191, a bis-amidate prodrug of the nucleotide analog 9-(2-phosphonylmethoxyethyl)-N
6
-cyclopropyl-2,6-diaminopurine (cPrPMEDAP), was designed as a topical agent for the treatment of papillomavirus-associated proliferative disorders, such as genital warts. In this study, we investigated the mechanism of conversion of GS-9191 to cPrPMEDAP. We observed that GS-9191 is hydrolyzed in the presence of the lysosomal carboxypeptidase cathepsin A (CatA)
in vitro
and is less efficiently metabolized in CatA-deficient fibroblasts than in control cells. In addition, knockdown of CatA by small interfering RNA (siRNA) reduced the intracellular accumulation of GS-9191 metabolites. However, intracellular CatA levels did not correlate with the susceptibility of tested cell lines to GS-9191, indicating that the CatA step is unlikely to be rate limiting for the activation of GS-9191. Further analysis showed that upon the hydrolysis of the carboxylester bond in one of the GS-9191 amidate moieties, the unmasked carboxyl group displaces
l
-phenylalanine 2-methylpropyl ester from the other amidate moiety. The cPrPMEDAP–
l
-phenylalanine conjugate (cPrPMEDAP-Phe) formed is not metabolized by Hint1 (histidine triad nucleotide binding protein 1) phosphoramidase but undergoes spontaneous degradation to cPrPMEDAP in acidic pH that can be significantly enhanced by the addition of SiHa cell extract. Pretreatment of SiHa cells with bafilomycin A or chloroquine resulted in an 8-fold increase in the intracellular concentration of cPrPMEDAP-Phe metabolite and the accumulation of GS-9191 metabolites in the lysosomal/endosomal fraction. Together, these observations indicate that the conversion of GS-9191 to cPrPMEDAP occurs in lysosomes via CatA-mediated ester cleavage, followed by the release of cPrPMEDAP, most likely through the combination of enzyme-driven and spontaneous pH-driven hydrolysis of a cPrPMEDAP-Phe intermediate.
Noninvasive Molecular Diagnosis of Human Visceral Leishmaniasis
Authors: Vaish Manisha , Mehrotra Sanjana , Chakravarty Jaya , Sundar Shyam
Published: March 2011

Previously developed methods for noninvasive PCR diagnosis of visceral leishmaniasis (VL) have significant limitations. Diagnosis of VL using PCR and buccal swabs was evaluated in 307 subjects, including 148 patients confirmed to have VL. This method is simple and well tolerated and has good potential for development, showing 83% sensitivity with 90.56% specificity in control groups.
Lyssavirus Detection and Typing Using Pyrosequencing
Authors: De Benedictis Paola , De Battisti Cristian , Dacheux Laurent , Marciano Sabrina , Ormelli Silvia , Salomoni Angela , Caenazzo Silvia Tiozzo , Lepelletier Anthony , Bourhy Hervé , Capua Ilaria , Cattoli Giovanni
Published: March 2011

Rabies is a fatal zoonosis caused by a nonsegmented negative-strand RNA virus, namely, rabies virus (RABV). Apart from RABV, at least 10 additional species are known as rabies-related lyssaviruses (RRVs), and some of them are responsible for occasional spillovers into humans. More lyssaviruses have also been detected recently in different bat ecosystems, thanks to the application of molecular diagnostic methods. Due to the variety of the members of the genus
Lyssavirus
, there is the necessity to develop a reliable molecular assay for rabies diagnosis able to detect and differentiate among the existing rabies and rabies-related viruses. In the present study, a pyrosequencing protocol targeting the 3′ terminus of the nucleoprotein (N) gene was applied for the rapid characterization of lyssaviruses. Correct identification of species was achieved for each sample tested. Results from the pyrosequencing assay were also confirmed by those obtained using the Sanger sequencing method. A pan-lyssavirus one-step reverse transcription (RT)-PCR was developed within the framework of the pyrosequencing procedure. The sensitivity (Se) of the one-step RT-PCR assay was determined by using
in vitro
-transcribed RNA and serial dilutions of titrated viruses. The assay demonstrated high analytical and relative specificity (Sp) (98.94%) and sensitivity (99.71%). To date, this is the first case in which pyrosequencing has been applied for lyssavirus identification using a cheaper diagnostic approach than the one for all the other protocols for rapid typing that we are acquainted with. Results from this study indicate that this procedure is suitable for lyssavirus detection in samples of both human and animal origin.
The rs8099917 Polymorphism, When Determined by a Suitable Genotyping Method, Is a Better Predictor for Response to Pegylated Alpha Interferon/Ribavirin Therapy in Japanese Patients than Other Single Nucleotide Polymorphisms Associated with Interleukin-28B
Authors: Ito Kiyoaki , Higami Katsuya , Masaki Naohiko , Sugiyama Masaya , Mukaide Motokazu , Saito Hiroaki , Aoki Yoshihiko , Sato Yo , Imamura Masatoshi , Murata Kazumoto , Nomura Hideyuki , Hige Shuhei , Adachi Hiroshi , Hino Keisuke , Yatsuhashi Hiroshi , Orito Etsuro , Kani Satomi , Tanaka Yasuhito , Mizokami Masashi
Published: March 2011

We focused on determining the most accurate and convenient genotyping methods and most appropriate single nucleotide polymorphism (SNP) among four such polymorphisms associated with interleukin-28B (IL-28B) in order to design tailor-made therapy for patients with chronic hepatitis C virus (HCV) patients. First, five different methods (direct sequencing, high-resolution melting analysis [HRM], hybridization probe [HP], the InvaderPlus assay [Invader], and the TaqMan SNP genotyping assay [TaqMan]) were developed for genotyping four SNPs (rs11881222, rs8103142, rs8099917, and rs12979860) associated with IL-28B, and their accuracies were compared for 292 Japanese patients. Next, the four SNPs associated with IL-28B were genotyped by Invader for 416 additional Japanese patients, and the response to pegylated interferon/ribavirin (PEG-IFN/RBV) treatment was evaluated when the four SNPs were not in linkage disequilibrium (LD). HRM failed to genotype one of the four SNPs in five patients. In 2 of 287 patients, the results of genotyping rs8099917 by direct sequencing differed from the results of the other three methods. The HP, TaqMan, and Invader methods were accurate for determination of the SNPs associated with IL-28B. In 10 of the 708 (1.4%) patients, the four SNPs were not in LD. Eight of nine (88.9%) patients whose rs8099917 was homozygous for the major allele were virological responders, even though one or more of the other SNPs were heterozygous. The HP, TaqMan, and Invader methods were suitable to determine the SNPs associated with IL-28B. The rs8099917 polymorphism should be the best predictor for the response to the PEG-IFN/RBV treatment among Japanese chronic hepatitis C patients.
Recurrent Community-Acquired Methicillin-Resistant Staphylococcus aureus Infections in an HIV-Infected Person
Authors: Vyas Kartavya , Hospenthal Duane R. , Mende Katrin , Crum-Cianflone Nancy F.
Published: March 2011

HIV-infected persons are at heightened risk for recurrent community-acquired methicillin-resistantStaphylococcus aureus(CA-MRSA) infections, but there are limited data regarding the molecular characterization of these events. We describe an HIV-infected patient with 24 soft tissue infections and multiple colonization events. Molecular genotyping from 33 nonduplicate isolates showed all strains were USA300, Panton-Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME) positive, and genetically related.
Ribosome Binding to a 5′ Translational Enhancer Is Altered in the Presence of the 3′ Untranslated Region in Cap-Independent Translation of Turnip Crinkle Virus
Authors: Stupina Vera A. , Yuan Xuefeng , Meskauskas Arturas , Dinman Jonathan D. , Simon Anne E.
Published: March 2011

Plus-strand RNA viruses without 5′ caps require noncanonical mechanisms for ribosome recruitment. A translational enhancer in the 3′ untranslated region (UTR) of
Turnip crinkle virus
(TCV) contains an internal T-shaped structure (TSS) that binds to 60S ribosomal subunits. We now report that the 63-nucleotide (nt) 5′ UTR of TCV contains a 19-nt pyrimidine-rich element near the initiation codon that supports translation of an internal open reading frame (ORF) independent of upstream 5′ UTR sequences. Addition of 80S ribosomes to the 5′ UTR reduced the flexibility of the polypyrimidine residues and generated a toeprint consistent with binding to this region. Binding of salt-washed 40S ribosomal subunits was reduced 6-fold when the pyrimidine-rich sequence was mutated. 40S subunit binding generated the same toeprint as 80S ribosomes but also additional ones near the 5′ end. Generation of out-of-frame AUGs upstream of the polypyrimidine region reduced translation, which suggests that 5′-terminal entry of 40S subunits is followed by scanning and that the polypyrimidine region is needed for an alternative function that requires ribosome binding. No evidence for RNA-RNA interactions between 5′ and 3′ sequences was found, suggesting that TCV utilizes an alternative means for circularizing its genome. Combining 5′ and 3′ UTR fragments
in vitro
had no discernible effect on the structures of the RNAs. In contrast, when 80S ribosomes were added to both fragments, structural changes were found in the 5′ UTR polypyrimidine tract that were not evident when ribosomes interacted with the individual fragments. This suggests that ribosomes can promote an interaction between the 5′ and 3′ UTRs of TCV.
U
L
31 of Herpes Simplex Virus 1 Is Necessary for Optimal NF-κB Activation and Expression of Viral Gene Products
Authors: Roberts Kari L. , Baines Joel D.
Published: March 2011

Previous results suggested that the U
L
31 gene of herpes simplex virus 1 (HSV-1) is required for envelopment of nucleocapsids at the inner nuclear membrane and optimal viral DNA synthesis and DNA packaging. In the current study, viral gene expression and NF-κB and c-Jun N-terminal kinase (JNK) activation of a herpes simplex virus mutant lacking the U
L
31 gene, designated ΔU
L
31, and its genetic repair construct, designated ΔU
L
31-R, were studied in various cell lines. In Hep2 and Vero cells infected with ΔU
L
31, expression of the immediate-early protein ICP4, early protein ICP8, and late protein glycoprotein C (gC) were delayed significantly. In Hep2 cells, expression of these proteins failed to reach levels seen in cells infected with ΔU
L
31-R or wild-type HSV-1(F) even after 18 h. The defect in protein accumulation correlated with poor or no activation of NF-κB and JNK upon infection with ΔU
L
31 compared to wild-type virus infection. The protein expression defects of the U
L
31 deletion mutant were not explainable by a failure to enter nonpermissive cells and were not complemented in an ICP27-expressing cell line. These data suggest that pU
L
31 facilitates initiation of infection and/or accelerates the onset of viral gene expression in a manner that correlates with NF-κB activation and is independent of the transactivator ICP27. The effects on very early events in expression are surprising in light of the fact that U
L
31 is designated a late gene and pU
L
31 is not a virion component. We show herein that while most pUL31 is expressed late in infection, low levels of pU
L
31 are detectable as early as 2 h postinfection, consistent with an early role in HSV-1 infection.
Isolation and identification of by-products of gas phase catalytic oxidation of anthracene to 9,10-anthraquinone
Authors: Chvátal Ivan , Vymětal Jan , Pecha Jaroslav , Šimánek Vilím , Dolejš Ladislav , Bartoň Josef , Fryčka Josef
Published: March 2011

A total of 29 associate components were identified in technical 9,10-anthraquinone. The product contained all the prominent impurities present in the starting anthracene except for 9,10-dihydroanthracene and fluorene. 9-(9'-Anthryl)-carbazole and Diels-Alder type adducts of anthracene with maleic anhydride and with maleinimide were also detected. The isolated and identified by-products of oxidation of anthracene were 1,4-anthraquinone, 4,4'-dioxo-1,1'-bianthrylidene, 4,10'-dioxo-1,9'-bianthrylidene, 1-(4'-oxy-1'-naphthylidene)-4-oxyanthracene, 2,3-naphthalenedicarboxylic acid and anhydride, and 5,7,12,14-tetrahydro-5,14;7,12-di(o-benzeno)pentacene-6,13-dione. Of the compounds formed by oxidation of the anthracene impurities, isolated and identified were dibenzo[b,d]pyrone, xanthone, 1,8-naphthalenedicarboxylic acid anhydride,9-fluorenone, and naphthol[2,3-b]thiophene-4,9-dione. As products of a deeper oxidation of the starting compounds, phthalic anhydride, maleic anhydride, maleinimide, phthalic acid, and maleic acid were found. Four additional components whose structure could not be determined were also isolated. The pathway of the anthracene oxidation is suggested.
Synthesis of 2-fluoropropenoic acid derivatives
Authors: Tolman Vladimír , Špronglová Pavla
Published: March 2011

A method is described for the synthesis of 2-fluoropropenoic acid esters, amides, and nitrile from the corresponding derivatives of 2-fluoro-3-(4-toluenesulfonyloxy)propanoic acid by heating with potassium phthalimide in vacuo. The free acid Ia and its chloride have also been synthesized. The reactivity of esters and nitrile of acid Ia has been verified by the Michael addition of diethyl acetamidomalonate to these compounds.
On bonding, stability and surface states in ordered alloys: FeTi and FeAl
Authors: Tomášek Mojmír , Pick Štěpán , Šob Mojmír
Published: March 2011

Partial wave analysis together with the qualitative analysis of hybridization has been performed for two ordered alloys with CsCl structure, FeTi and FeAl. Relation to the theory of crystal superstructures and surface states is mentioned. Relative importance of covalency and ionocity in the cohesion of these compounds is treated in simple terms with the aim to better understand the nature of their stability.