bluuebunny/crossref_metadata_2025 huggingface dataset:
A Fast Method for Electronic Band Structure Calculations
Authors: Guo Qiong , Bilal Osama R. , Hussein Mahmoud I.
Published: August 2012

Band structure calculation provides a basis for the study of thermal, optical and magnetic properties of crystals. The reduced Bloch mode expansion (RBME) method is a model reduction method in which a selected set of Bloch eigenvectors within the irreducible Brillouin zone at high symmetry points are used to expand the unit cell problem at hand. In this method, a major reduction in computational cost is achieved with minimum loss of accuracy. The method applies to both classical and ab inito band structure calculations of periodic media, and to any type of wave propagation problem: phononic, photonic, electronic, etc. In this work, the applicability of RBME in calculating the three-dimensional (3D) electronic band structure for crystal structures with different symmetries is demonstrated. Using the Kronig-Penney fixed potential, a high-symmetry cubic model and a low-symmetry triclinic model are considered. For both cases, the energy (eigenvalues) and wave functions (eigenvectors) demonstrate very good convergence performance with the number of expansion points.
Modeling and Validation of a Prototype Thermally-Enhanced Polymer Heat Exchanger
Authors: Robinson Frank , Cevallos Juan G. , Bar-Cohen Avram , Bruck Hugh
Published: August 2012

Polymer heat exchangers (PHXs) have received considerable attention since their invention more than 40 years ago due to their corrosion resistance, low density and low manufacturing cost. New polymer composites with higher strengths, thermal conductivities and thermal stability promise to bridge the performance gap between polymers and corrosion resistant metals. In the present study, PHX components were injection molded using thermally enhanced polyamide 12 resin and assembled into a crossflow finned-plate heat exchanger prototype. The prototype was implemented in an air-to-water experimental test apparatus and the heat transfer results were compared to an analytical model. This comparison confirmed that a polymer composite heat exchanger (PCHX) can offer significantly enhanced heat transfer relative to a pure polymer. A thermomechanical finite element model of the PCHX was developed and validated using experimental results. At fluid pressures near ambient, the heat transfer rate of the PCHX was 28% less than could be attained with an identical titanium heat exchanger. As fluid pressures increased, the through wall conduction resistance had a larger effect on heat transfer rate, reducing the performance of the PCHX relative to the titanium heat exchanger. Stress analysis of the thermally enhanced PCHX revealed that the stresses due to pressure loading were more sensitive to heat exchanger geometry, while the stresses due to thermal loading were more sensitive to material property anisotropy.
Flexural Toughness as an Attribute for Impact Damage Evaluation of Composite Laminates
Authors: Alemi-Ardakani Mohammad , Milani Abbas S. , Yannacopoulos Spiro , Trudel-Boucher David , Shokouhi Golnaz
Published: August 2012

Popularity and application of composite materials are increasing in several industries including transportation, construction and aerospace. The mechanical properties of these materials should be known to engineers to be able to design/select new products. Impact resistance is one of the properties which have been studied extensively over the past years and still is an ongoing topic in composites research. Since analytical solutions have not been fully developed for the impact characterization of anisotropic materials, researchers often perform mechanical testing in conjunction with visual inspection methods to investigate the impact behavior of composite materials. The present study shows that flexural toughness can be used as a parameter in the design/material selection stage in the evaluation of pre- and post-impact damage of composite laminates. A series of drop-weight impact tests, using a 200J energy level, were performed on specimens made of four different stacking configurations of TWINTEX® and unidirectional laminates (polypropylene and glass fiber commingled composites) according to ASTM D7136. The damaged areas of the impacted specimens were measured using image analysis. Four-point flexural testing was then carried out, based on ASTM D7264, on both non-impacted and impacted specimens. Damaged area and flexural toughness, along with a set of other commonly used mechanical properties, were selected as measures for damage evaluation. Comparison of results before and after impact and under different criteria showed that in the present case study, visual inspection is not sufficient in predicting the post-impact properties of the tested specimens and can be misleading. On the other hand, flexural toughness could give a much clearer perspective on the extent of post-impact resistance of the specimens.
Impact/Debonding Tolerant Sandwich Panel With Aluminum Tube Reinforced Foam Core
Authors: Ji Gefu , Ouyang Zhenyu , Li Guoqiang , Pang Su-Seng
Published: August 2012

Sandwich construction has been extensively used in various fields. However, sandwich panels have not been fully exploited in critical structural applications due to damage tolerance and safety concern. A major problem of sandwich panels is the debonding at or near the core/face sheet interface, especially under impact loading, which can lead to a sudden loss of structural integrity and cause catastrophic consequences. In order to improve the debonding resistance and energy absorption of sandwich panel under impact loadings, a new foam core is proposed which is a hybrid core consisting of hollow metallic microtubes reinforced polymer matrix. The objective of this study was to characterize its static and dynamic performances. Two types of new hybrid cores were investigated in this work. One consisted of polymer resin reinforced by transversely aligned continuous metallic militubes, denoted as type-I sandwich panel. The other was made of polymer resin reinforced by aligned continuous in-plane metallic militubes, denoted as type-II sandwich panel. Additionally, the traditional sandwich panels with polymeric syntactic foam core were also prepared for comparisons. Static and impact tests demonstrated that interface debonding and subsequent shear failure in the core could be largely excluded from the type-II panel. Meanwhile, a significant transition to ductile failure was observed in type-II sandwich panel with dramatically enhanced load capacity and impact energy dissipation. The results indicated that type-II panel may be considered a promising option for critical structural applications featured by debonding and impact tolerance.
Experimental Testing of Micro-Scale Self Assembly Process Model
Authors: Carballo Jose M. , Hollis Sean , Crane Nathan
Published: August 2012

Self assembly holds potential as a more efficient mass-production tool for integration of micro and nano-scaled devices, than traditional pick-and-place methods. While there has been significant innovation in self-assembly demonstrations, less progress has been made on models to predict the relationship between process rates and yields and key process parameters. This work is meant to gather experimental data on capillary self assembly process for micrometer scaled devices, using a controlled experimental assembly system. The purpose is to identify appropriate process variables that can be used to characterize self-assembly processes. Candidate process variables include kinetic energy, angle of impact, surface binding energy, shape and size of surfaces, and fraction area of assembly. Significant improvements to the previously reported self assembly test system are shown. While the experimental techniques continue to be refined, empirical relations are shown for various angles of impact, with fixed kinetic and binding energy values.
Far-Infrared Imaging Method for Non-Contact Monitoring of Micromixer
Authors: Yang Yang , Liu Jing
Published: August 2012

For many Lap-on-a-Chip applications, rapid and homogenous mixing of two or more fluid species is inevitable. However, it is also of great importance to developing a quick and convenient method for monitoring the mixture processing, as well as the entire working process of the Lab-on-a-chip. In order to develop a quick and convenient method, this paper is dedicated to establish a non-contact image way for monitoring not only the liquid flow behavior, but also the mixability between each reactant. The far-infrared thermal imaging system was adopted to detect and map the surface temperature distribution of the micromixer, which consequently could help achieve the non-contact monitoring of the mixing process.
Evaluation of the Power-Generation Capacity of Implantable Thermoelectric Power Generator Driven by Radioisotope Fuel
Authors: Yang Yang , Liu Jing
Published: August 2012

The unique merit of the implantable thermoelectric generator lies in its direct utilization of the temperature difference intrinsically existing throughout the whole biological body. Therefore, it can resolve the service life mismatch between the IMD and its battery. In order to promoting the TEG maximum power, a piece of radioisotope fuel was fixed on the TEG hot junction. Recurring to the thermal energy released during disintegration of radioactive isotope, it can guarantee a marked promotion in the temperature difference across the implanted TEG; consequently apply enough power for the IMDs.
Experimental Verification of Model Pressurized Thick-Walled Cylinder With Numerical and Theoretical Methods
Authors: Macwan Sunilbhai P. , Hu Zhong , Delfanian Fereidoon
Published: August 2012

Pressurized thick-walled cylinders undergo repeated cycles of high stress and temperatures that may severely shorten the life of the component. Testing pressurized cylinder can help to evaluate the strength of the cylinder. This research seeks to determine the pressure to which the component is subjected by instrumenting the outside of the cylinder, and to evaluate hoop strain and hoop stress of the internal and external surface of the pressurized thick-walled cylinder. This study provides experimental results and then compares them with theoretical and numerical data for the cylinder under investigation. Using the experimental method, an axial load up to 15,000 lb is applied to the cylinder using a Landmark 370 MTS unit to generate pressure inside the cylinder wall. Lame´ equations are used to calculate hoop stress theoretically. The numerical data is obtained using finite element simulation (ANSYS) to calculate hoop stress and hoop strain at the internal and external surfaces of the cylinder. This work provides useful information for evaluating the strength of thick-walled cylindrical structures in a laboratory setting.
Hollow Cathode With Low Work Function Electride Insert
Authors: Rand Lauren P. , Waggoner Ryne M. , Williams John D.
Published: August 2012

Hollow cathodes are critical devices in the successful operation of electric propulsion thrusters. Cathodes featuring C12A7:electride as an ultra-low work function thermionic emitter are hypothesized to have faster start-up times and lower operating temperatures than conventional hollow cathodes. C12A7:electride is a crystalline ceramic in which electrons clathrated in sub-nanometer sized cages act as a conductive medium. Due to its unique atomic structure and large size, C12A7:electride has a predicted work function of 0.6 eV. As a result, C12A7:electride is an attractive option for a thermionic emission material in a hollow cathode. Calculations predict equivalent levels of current emission as LaB6 or CeB6, but at much lower temperature. C12A7:electride is stable at temperatures below its re-crystallization temperature (∼1000 °C) and is not consumed during operation. C12A7:electride has been fabricated at CSU using a simplified, one-step approach that results in a more conductive material than previously reported. The material has been integrated into a novel hollow cathode design that takes advantage of its unique properties to decrease start-up time and power consumption. Our paper will discuss preliminary results obtained with several cathode configurations. In addition, results from the experimental determination of basic material properties such as conductivity and work function will be presented. Strategies to further enhance electron emission through surface modifications will also be discussed.
Coupled Non-Equilibrium Green’s Function (NEGF) Electron-Phonon Interaction in Thermoelectric Materials
Authors: Musho T. D. , Walker D. G.
Published: August 2012

Over the last decade, nano-structured materials have shown a promising avenue for enhancement of the thermoelectric figure of merit. These performance enhancements in most cases have been a direct result of selectively modifying certain geometric attributes that alter the thermal or electrical transport in a desirable fashion. More often, models used to study the electrical and/or thermal transport are calculated independent of each other. However, studies have suggested electrical and thermal transport are intimately linked at the nanoscale. This provides an argument for a more rigorous treatment of the physics in an effort to capture the response of both electrons and phonons simultaneously. A simulation method has been formulated to capture the electron-phonon interaction of nanoscale electronics through a coupled non-equilibrium Greens function (NEGF) method. This approach is unique because the NEGF electron solution and NEGF phonon solution have only been solved independently and have never been coupled to capture a self-consistent inelastic electron-phonon scattering. One key aspect of this formalism is that the electron and phonon description is derived from a quantum point of view and no correction terms are necessary to account for the probabilistic nature of the transport. Additionally, because the complete phonon description is solved, scattering rates of individual phonon frequencies can be investigated to determine how electron-phonon scattering of particular frequencies influences the transport. This computational method is applied to the study of Si/Ge nanostructured superlattice thermoelectric materials.
Microassembly via Coordinated Manipulation of Objects Using a Multifingered Micromanipulator
Authors: Pelzmann Christopher , Saggere Laxman
Published: August 2012

This paper presents a novel approach to manipulation and assembly of micro-scale objects using a chip-scale multi-fingered micromanipulator, in which multiple, independently controlled compliant fingers coordinate with each other to grasp and manipulate multiple objects simultaneously on-chip. The structural and functional advantages of this multi-fingered micromanipulator in achieving high dexterity in a compact form as compared to other state-of-the-art manipulation tools are discussed. A formulation of the kinematics of the manipulator’s compliant fingers along with two different control strategies including an operator-driven closed-loop control and a semi-autonomous open-loop control for coordinated manipulation and on-chip assembly of micro-scale objects are introduced. Finally, the details of implementation of both control strategies and successful experimental demonstration of manipulations and assembly of two interlocking micro-scale parts with sub-micron mating clearance using the multifingered manipulator are presented.
Virtual Height Aided Solar Chimney: A New Design
Authors: Ahmed Khaled I. E. , Abdel-Rahman Ali K. , Ahmed Mahmoud , Khairaldien Wael M.
Published: August 2012

Renewable energy source deployment is growing rapidly as it reduces CO2 emissions and increases diversity and security of supply. Solar chimney (SC) is a promising large-scale power technology, which absorbs solar radiation and converts parts of solar energy into electric power free of CO2 emissions. A major problem of Solar Chimney Power Plant (SCPP) is its low conversion efficiency as determined by the thermal performance of the system. However, the conversion efficiency of SCPP significantly increases with the SC height increase. The current paper proposes a new design of a virtual height aided solar chimney. In this new system the solar chimney is aided with a passive cooling system at the top of the chimney and a passive solar heater at its base to virtually mimic larger heights of the chimney. The new design has been simulated numerically for development and optimization. The numerical study is done in two stages to examine this concept. In the first stage, numerical results are obtained for the effect of the chimney height on the inside air flow speed. Then, in the second stage, the effect of decreasing the temperature at the chimney exit and the effect of increasing the temperature at the chimney base on the air flow speed are examined separately for small chimney heights. Then the combined effect of the two actions is investigated at a wide range of chimney heights. The numerical results have shown that the localized base heating and exit cooling have significantly enhanced the chimney performance for chimney heights up to 500m. A chimney with height of 300m gains an increase in the air velocity more than 25% due to the heating and cooling actions. Virtual height aided Chimney with original height of 300m acts similarly to a conventional chimney with height of 500m due to the effect of base heating and exit cooling actions. This air flow velocity increase reflects 100% increase in the expected generated electric power. Further detailed results are presented and discussed.
Initial Impact of Liquid Jets and Entrainment of Air Bubbles: A Numerical Study
Authors: Qu Xiaoliang , Khezzar Lyes , Li Zhenlin
Published: August 2012

This paper presents a three-dimensional unsteady numerical simulation of a turbulent plunging liquid jet without artificial surface disturbance impinging on a quiecent liquid pool. The focal point of the study is the initial impact and air entrainment process. The multiphase, Volume of Fluid Model is used in combination with the Reynolds Averaged k-ε turbulence model. The process of the initial impact of the jet on the free surface, the subsequent formation of an air cavity and the subsequent break-down of the cavity into small bubbles are captued and analyzed. These simulations show clearly and in detail the process of air carryunder by the liquid-liquid jet. The air cavity caused by the intial jet impact stretches deeply under the pool surface untill break down due to the shear created by a torroidal vortex. The predicted maximum height of the developing air cavity shows very good agreement with existing semi-empirical correlations from the literature and experiments. The velocity of the front of the air cavity is equal to about half the jet valocity at impact as shown by previous works and the predicted penetration depth shows acceptable agreement with previous correlations. The VOF model shows a strong capability of tracking the interface between two phases.
Large Eddy Simulation of Multiple Round Impinging Jets
Authors: Kharoua N. , Khezzar L. , Nemouchi Z.
Published: August 2012

Large eddy simulation of flow and heat transfer of multiple turbulent round jets in an in-line array impinging on a flat plate is conducted. The full geometry is used in the simulation of the 9 jets. To capture the interactions between the jets the full geometry is meshed in this work. The Reynolds number based on the nozzle diameter of 13 mm, jet initial average velocity of 23.88 m/s and properties of air at room temperature was equal to 20,000. The computations of the mean vertical and horizontal component of the velocity vector in selected planes show very good agreement with experiments. The flow behavior of the jets agrees with experimental findings in terms of vortices surrounding the jets and the appearance of the asymmetry on and close to the flat impingement plane. The predicted mean surface Nusselt number on the flat heated plate shows also excellent agreement with experiments and a relative maximum between the jets in the region of the upwash fountain flow where the wall jets collide, not seen in the experiments, is captured by the numerics.
A New Method to Analyze Three-Dimensional Non-Repetitive Run-Out (3D-NRRO) of Angular Contact Ball Bearings
Authors: Yang Zhaohui , Hong Jun , Zhang Jinhua , Wang Micheal Yu , Li Baotong
Published: August 2012

As ultra-precision index of high-precision ball bearings, the value of three-dimensional non-repetitive run-out (3D-NRRO) directly influences the rotation accuracy in complex mechanical system. Reducing 3D-NRRO contributes to improve the quality of manufacturing in machining tools. This paper develops five-freedom model to analyze the 3D-NRRO of an angular contact ball bearing caused by geometrical errors of the rings raceways and the balls. In the model, the variation of contact angle caused by centrifugal force of balls is taken into consideration, and the geometrical errors of rings raceway and balls are described by Fourier series. Meanwhile, based on Hertzian contact theory and the solution method of dimensional chains, the 3D-NRRO analytical program has been developed, the value of 3D-NRRO analysis is shown. From the results, the relationship between the 3D-NRRO and the geometrical errors of rings raceway and balls are analyzed quantitatively. Findings of this paper provide theoretical supports to reduce or control the 3D-NRRO by optimizing manufacturing process of bearing components.
A Numerical Study of Air-Side Heat Transfer Enhancement Using V-Formation Delta-Winglet Vortex Generators in Heat Exchangers
Authors: Xie Junling , Liu Liping
Published: August 2012

The numerical study proposed is to investigate the effectiveness of delta-winglet vortex generators (VGs) used for heat-transfer enhancement in a horizontal rectangular channel as a typical air passage for fin-and-tube heat exchangers. The effects of four different configurations of vortex generators have been investigated: (1) single pair VGs with a 30 degree attack angle; (2) 2-pair VG array with a 30 degree attack angle; (3) single pair VGs with a 45 attack angle; (4) 2-pair VG array with a 45 attack angle. The numerical results indicate that average Nusselt number increase is 31%–38% and 51%–71% for the channel mounted with VGs with a 30 degree attack angle and a 45 degree attack angle, respectively. The enhancement for single large pair of VGs is higher than that for a V-formation array with 2 small pairs. However, VGs also introduce extra pressure drop penalties to the channel flow, and higher heat-transfer performance is also accompanied by a larger pressure drop penalty. According to the results, a single large pair of VGs with 45 attack angle shows the best overall performance among all the configurations investigated.
Numerical Study of Slip Factor Model: Effect of Inlet Total Pressure and Gas Composition on the Performance Curve of Centrifugal Compressor
Authors: Aligoodarz M. R. , Moshrefi A. M. H. , Karrabi H. , Tehrani M. R. Soleimani
Published: August 2012

Development of hardware and CFD codes, especially in turbulence model and optimization of numerical codes has led to increment in usage of CFD which is capable of simulating different experimental situations take place at laboratory. Particularly in issues related to turbo machinery, two-dimensional test of blades, three-dimensional investigation of different stages and studying the effect of different parameters are very costly. By means of CFD modeling all these issues are accessible. Actual flow within the compressor is three dimensional and fully turbulent due to geometry complexity, flow velocity and viscosity. For this reason it has become more and more popular to perform 3D numerical studies. In this study three-dimensional analysis of flow in a two stage centrifugal compressor is performed. Since no experimental data is available to evaluate the results of the present numerical analysis, validation is done by using experimental data of the gas turbine set up at Sharif University of Technology Laboratory. Numerical results are used for the evaluation of the slip factor models and finally, the effects of inlet gas composition and inlet total pressure on characteristic map are investigated.
Experimental Investigation of Subcooled Flashing Flow in Simulated Cracks
Authors: Wolf Brian , Revankar Shripad T. , Riznic Jovica R.
Published: August 2012

In this study an experimental program was developed to measure the choking flow rate of subcooled water through simulated tube crack geometries (L/D<10 L< 5mm) and results are compared with models in literature. A test facility was designed and built to measure leak rates of subcooled water from through-wall simulated tube cracks up to 6.8 MPa. Two types of test specimens were used in the experimental program. One, a round orifice like hole is created to simulate a pitting type flaw. The others are laser cut slits representing axial cracks. Flow discharge tests were carried out with water at room temperature to determine the flow characteristics for each test specimen. Also, subcooled flashing discharge tests with heated water were carried out up to a vessel pressure of 6.8 MPa at various subcoolings. A modified Burnell correlation was developed using upstream saturation and subcooled temperature conditions and the predictions of the correlation agreed well with the present experimental data.
Reliability Based Design Optimization Using Automatic Differentiation
Authors: Pugazhendhi K. , Dhingra A. K.
Published: August 2012

Typically, a reliability based design optimization (RBDO) problem is solved as a nested optimization problem because an evaluation of the probabilistic constraint(s) involves solving a minimization problem. Over the years, a number of algorithms have been developed to solve the RBDO problem efficiently. All of these approaches involve an evaluation of derivatives of the responses. In this paper, a decoupled approach using automatic differentiation (AD) is presented to solve the RBDO problem. The proposed approach employs AD to evaluate the reliability, as well as to evaluate the sensitivity of the most probable point (MPP) with respect to the design variables. Since these evaluations involve a computation of the Jacobian and the Hessian, a use of AD improves the accuracy while simultaneously reducing the required number of response evaluations. The applicability of the proposed approach is shown through examples of increasing complexity ranging from problems where closed form solutions are available for evaluation of response to situations where finite element analysis is needed to compute the system response.
An Energy Appetite of U.S. Water Systems: How Much Energy Does It Take to Supply Our Water?
Authors: Vorum Martin
Published: August 2012

This paper reports a new method to estimate energy used in water supply and return phases of the water cycle. An example is a composite case for energy used in water systems of the United States (U.S.) using data from the U.S. Geological Survey (USGS). The new method is innovatively simple: it avoids complexities of data-intensive, bottom-up models, often used to map water networks. This method helps to prioritize how to improve energy efficiency in water systems. The method uses a top-down approach requiring limited system data, and relying on a transparent computation of energy. The method applies to standalone or composite systems. It applies to small-scale, single-user systems, to large water supply/return networks, or to summations of data for classes of systems whether simple or complex, and whether interconnected or not. The reported example shows transport could account for about 95 percent of U.S. water systems’ energy use. Energy use for transport among different water-sectors ranged from roughly 80 percent to nearly 100 percent of total sectoral energy demand. Contrasting that generalization, specific data for standalone systems would show when energy demand depends, for example, more on treatment needed to meet quality standards.
Energy Efficient Strategies and Renewable Energy Technologies for Desalination
Authors: Jacangelo Joseph G. , Oppenheimer Joan A. , Subramani Arun , Badruzzman Mohammad
Published: August 2012

Energy is often the most significant factor in the affordability and sustainability of treating various different source waters with reverse osmosis membrane facilities. More than 33% of the cost to produce water using reverse osmosis (RO) technology is attributed to electrical demands. The largest energy-consuming component of the overall treatment are the high pressure pumps required to feed water to the process. Because of the high energy burden and production of greenhouse gas (GHG) emissions, renewable energy is being increasingly considered for desalination projects. The selection of the appropriate renewable energy resource depends on several factors, including plant size, feed water salinity, remoteness, availability of grid electricity, technical infrastructure, and the type and potential of the local renewable energy resource. The cost of desalination with renewable energy resources, as opposed to desalination with conventional energy sources, can be an important alternative to consider when reduced environmental impact and lower gas emissions are required. Considering the proposed climate protection targets that have been set and the strong environmental drivers for lowered energy usage, future water desalination and advanced water treatment systems around the world could be increasingly powered by renewable energy resources. In addition to renewables, energy optimization/minimization is deemed critical to desalting resource management. Methods employed include enhanced system design, high efficiency pumping, energy recovery devices and use of advanced membrane materials.
Raising Global Human Capitals and Engineers From the East
Authors: Honda Hiroshi
Published: August 2012

The global human capitals (GHCs) are sometimes meant in Japan to be those that can produce higher (economic) value than ordinary human resources in the global arena. For discussion purposes, they are grouped into specialists and generalists in a relative sense, and further into several categories of professions, including global engineers in charge of power plants (or global power engineer), in the current paper. Issues of raising GHCs from the East, such as various gaps and barriers typically seen in raising them from Japan, are discussed and compared with those typically raised in the West. It is shown that personal language/knowledge structures, which are formed through education of one’s infancy to entire life, and relevant skills are key factors in raising various GHCs. Further, types of Japanese universities and students are classified into several categories, for which educational issues are addressed and summarized for betterment of the education for the subject purposes.
Experimental Investigation of Selective Withdrawal and Light Layer Entrainment of Stratified Immiscible Liquids
Authors: Hartenberger Joel D. , O’Hern Timothy J.
Published: August 2012

The withdrawal of fluid from only one layer of a vertically stratified immiscible fluid system is often referred to as selective withdrawal. For a given withdrawal location, the ability to predict the maximum flow rate at which fluid from one layer can be withdrawn before an adjacent layer of fluid is also entrained is critical for many applications. The Strategic Petroleum Reserve (SPR) offers one such example where oil is stored above an underlying brine layer in large underground caverns. When oil is added to a cavern, a corresponding volume of brine must be withdrawn through a hanging string that extends through the oil into the brine layer. If the depth of the string below the oil-brine interface is insufficient for a given flow rate, oil may be inadvertently withdrawn along with the expected brine — potentially introducing oil into the brine handling system and leading to costly cleanup to prevent environmental contamination. Laboratory experiments with two immiscible liquids (silicone oil and water or brine) have been conducted to investigate this behavior for typical SPR cavern conditions. In these experiments the higher density fluid is withdrawn through a tube below the liquid-liquid interface. As the withdrawal point is raised closer to the interface for a given flow rate, or the flow rate is increased for a given submergence, the overlying lower density layer begins to entrain along with the higher density liquid. The critical withdrawal depth at which transition to light layer entrainment occurs is measured for a given flow rate of the lower liquid, and the process is repeated for different flow rates. Most prior literature concerning the transition from selective withdrawal has examined removal of the lower density fluid and the transition to entraining the higher density fluid, whereas this work focuses on the inverse. Experiments were performed for a range of different light layer silicone oils and heavy layer water or brine, covering a range of density and viscosity ratios. Three separate withdrawal tubes of differing diameter were placed in two orientations to establish the depth at which selective withdrawal began as a function of fluid properties. The data show that, at the highest flow rates, the transition to light layer entrainment can occur when the withdrawal point is up to two diameters below the liquid-liquid interface, depending on the lower fluid density. Particle Image Velocimetry (PIV) was performed to map the instantaneous velocity field. The strength of the velocity vectors increased dramatically near the withdrawal tube opening showing the region in which inertial forces dominated the flow pattern.
Circadian Rhythm of Redox State Regulates Excitability in Suprachiasmatic Nucleus Neurons
Authors: Wang Tongfei A. , Yu Yanxun V. , Govindaiah Gubbi , Ye Xiaoying , Artinian Liana , Coleman Todd P. , Sweedler Jonathan V. , Cox Charles L. , Gillette Martha U.
Published: August 2012

Diurnal metabolic changes in circadian clock neurons are coupled to changes in potassium channel activity.
Mycobacterial Disease and Impaired IFN-γ Immunity in Humans with Inherited ISG15 Deficiency
Authors: Bogunovic Dusan , Byun Minji , Durfee Larissa A. , Abhyankar Avinash , Sanal Ozden , Mansouri Davood , Salem Sandra , Radovanovic Irena , Grant Audrey V. , Adimi Parisa , Mansouri Nahal , Okada Satoshi , Bryant Vanessa L. , Kong Xiao-Fei , Kreins Alexandra , Velez Marcela Moncada , Boisson Bertrand , Khalilzadeh Soheila , Ozcelik Ugur , Darazam Ilad Alavi , Schoggins John W. , Rice Charles M. , Al-Muhsen Saleh , Behr Marcel , Vogt Guillaume , Puel Anne , Bustamante Jacinta , Gros Philippe , Huibregtse Jon M. , Abel Laurent , Boisson-Dupuis Stéphanie , Casanova Jean-Laurent
Published: August 2012

Tuberculosis Vaccine Conundrum

Some children experience severe clinical disease when they are vaccinated against tuberculosis, an attenuated live vaccine that is normally innocuous in humans. Several germline mutations have been identified that account for this susceptibility, and now

Bogunovic
et al.

(p.
1684
, published online 2 August) add another to the list—
ISG15
. Uncovering this mutation, which is inherited in an autosomal recessive manner, was a surprise because studies with mice deficient in
ISG15
showed enhanced susceptibility to some viral, but not bacterial, infections. Nevertheless, patients lacking
ISG15
were not able to produce adequate amounts of interferon-γ, a cytokine critical for clearance of the bacteria.
Neuroretinitis following bull ant sting
Authors: Ullrich Katja , Saha Niladri , Lake Stewart
Published: August 2012

Cat scratch disease causes the majority of cases of neuroretinitis. Neuroretinitis is characterised by clinical features of papillitis, macular oedema and macular star. We report a case study of infection withBartonella henselaemost likely transmitted by a bull ant sting. The patient presented with blurred vision and reduced visual acuity after being stung by an ant in her garden some 7 days earlier. Further testing revealed positive serology toB henselaeand the patient improved with appropriate treatment.
Palm oil thorn-induced squamous cell carcinoma with underlying burns scar
Authors: Qi Qi Choo , Ajit Singh Vivek
Published: August 2012

Marjolin's ulcers are malignancies that arise from previously traumatised, chronically inflamed or scarred skin. We present a case with childhood burns, who had repeated irritation of his forearm skin with palm oil thorns that eventually led to malignant change.
Another case of chest pain on the acute medical take!: Figure 1
Authors: White Sarah
Published: August 2012

A physiologically fit 91-year-old gentleman presented with sudden onset chest pain, breathlessness and cardiovascular compromise associated with vomiting. He was treated for renal colic, community-acquired pneumonia and pulmonary embolism before a formal diagnosis of Boerhaave's syndrome was made. The patient was prepared for emergency surgery, unfortunately his condition deteriorated rapidly and he was subsequently managed conservatively. He died 2 days later. Diagnosis and treatment of Boerhaave's syndrome are often delayed. Treatment options for Boerhaave's syndrome include conservative measures, endoscopic interventions and surgery. Chest pain is a common presentation on the acute medical take. Boerhaave's syndrome is a rare cause of chest pain, which may mimic other conditions but should not be missed due a high death rate.
Spontaneous mesenteric haematoma; diagnosis and management: Figure 1
Authors: Parker Sam G , Thompson Jeremy N
Published: August 2012

Spontaneous mesenteric haematomas are rare. They have been reported to be associated with coagulopathies, connective tissue disorders, past trauma, arteriopathy and pancreatitis. However, some cases have been reported in which there is no apparent underlying aetiology. Here we report such a case and we review the literature that discusses optimal diagnosis and management. In this case, spontaneous haemostasis occurred by intra-abdominal tamponade and the regression of the haematoma was monitored with regular imaging.
Psychological consequences of false-positive screening mammograms in the UK
Authors: Bond Mary , Pavey Toby , Welch Karen , Cooper Chris , Garside Ruth , Dean Sarah , Hyde Christopher J
Published: August 2012

Objectives

To identify the psychological effects of false-positive screening mammograms in the UK.

Methods

Systematic review of all controlled studies and qualitative studies of women with a false-positive screening mammogram. The control group participants had normal mammograms. All psychological outcomes including returning for routine screening were permitted. All studies had a narrative synthesis.

Results

The searches returned seven includable studies (7/4423). Heterogeneity was such that meta-analysis was not possible. Studies using disease-specific measures found that, compared to normal results, there could be enduring psychological distress that lasted up to 3 years; the level of distress was related to the degree of invasiveness of the assessment. At 3 years the relative risks were, further mammography, 1.28 (95% CI 0.82 to 2.00), fine needle aspiration 1.80 (95% CI 1.17 to 2.77), biopsy 2.07 (95% CI 1.22 to 3.52) and early recall 1.82 (95% CI 1.22 to 2.72). Studies that used generic measures of anxiety and depression found no such impact up to 3 months after screening. Evidence suggests that women with false-positive mammograms have an increased likelihood of failing to reattend for routine screening, relative risk 0.97 (95% CI 0.96 to 0.98) compared with women with normal mammograms.

Conclusions

Having a false-positive screening mammogram can cause breast cancer-specific distress for up to 3 years. The degree of distress is related to the invasiveness of the assessment. Women with false-positive mammograms are less likely to return for routine assessment than those with normal ones.
Predictive risk algorithms in a population setting: an overview
Authors: Manuel Douglas G , Rosella Laura C , Hennessy Deirdre , Sanmartin Claudia , Wilson Kumanan
Published: August 2012

Background

The widespread use of risk algorithms in clinical medicine is testimony to how they have helped transform clinical decision-making. Risk algorithms have a similar but underdeveloped potential to support decision-making for population health.

Objective

To describe the role of predictive risk algorithms in a population setting.

Methods

First, predictive risk algorithms and how clinicians use them are described. Second, the population uses of risk algorithms are described, highlighting the strengths of risk algorithms for health planning. Lastly, the way in which predictive risk algorithms are developed is discussed briefly and a guide for algorithm assessment in population health presented.

Conclusion

For the past 20 years, absolute and baseline risk has been a cornerstone of population health planning. The most accurate and discriminating method to generate such estimates is the use of multivariable risk algorithms. Routinely collected data can be used to develop algorithms with characteristics that are well suited to health planning and such data are increasingly available. The widespread use of risk algorithms in clinical medicine is testimony to how they have helped transform clinical decision-making. Risk algorithms have a similar but underdeveloped potential to support decision-making for population health.
Anomalous origin of the right vertebral artery from the right common carotid artery associated with an aberrant right subclavian artery
Authors: Nalamada Keerthana , Chitravanshi Nitya , Duffis Ennis Jesus , Prestigiacomo Charles J , Gandhi Chirag D
Published: August 2012

Vertebral artery origin anomalies are typically incidental findings during angiography or post mortem examination. We present two cases of vertebral origin from the right common carotid artery in association with an aberrant right subclavian artery. We also review the embryonic development and the clinical significance of this anomaly.
Early clinical implications of microalbuminuria in patients with acute ischaemic stroke
Authors: Cho Bang-Hoon , Kim Joon-Tae , Chang Jane , Choi Kang-Ho , Nam Tai-Seung , Choi Seong-Min , Lee Seung-Han , Park Man-Seok , Kim Byeong-Chae , Kim Myeong-Kyu , Cho Ki-Hyun
Published: August 2012

Background

Microalbuminuria is thought to be independently associated with an increased risk of, and mortality from, stroke. However, no studies have shown whether microalbuminuria is associated with the early clinical outcomes of acute ischaemic stroke. Therefore we investigated whether this. We also looked at radiological outcomes in stroke patients with microalbuminuria.

Methods

This was a retrospective study of patients with ischaemic stroke (within 72 h of symptom onset) who had been consecutively admitted to the Cerebrovascular Center at Chonnam National University Hospital between May 2010 and February 2011. Early clinical outcomes were assessed by early neurological deterioration (END) and modified Rankin Scale score >2 at discharge. In addition, early radiological outcomes were assessed from haemorrhagic transformation (HT) and lesion changes on follow-up diffusion-weighted imaging. We categorised a urine albumin/creatinine ratio of ≤30 mg albumin/g creatinine as normal and 30–300 mg albumin/g creatinine as microalbuminuria.

Results

139 of 361 patients (38.5%) had microalbuminuria. In multivariate analysis, microalbuminuria was independently associated with END and HT. Furthermore, there were significant relationships between urinary albumin/creatinine ratio and white matter hyperintensity (WMH) grades (31.78 mg albumin/g creatinine for no WMH, 48.41 for grade 1, 64.29 for grade 2, and 44.16 for grade 3; p=0.004) and the types of HT (37.43 mg albumin/g creatinine for no HT, 71.41 for HI, and 131.63 for PH; p<0.001).

Conclusion

In the early phase of ischaemic stroke, patients with microalbuminuria were associated with worse clinical and radiological outcomes (END, HT and lesion changes on follow-up diffusion-weighted imaging) than those without.
Incidence of acute hepatitis C virus infection among men who have sex with men with and without HIV infection: a systematic review
Authors: Yaphe Sean , Bozinoff Nikki , Kyle Rachel , Shivkumar Sushmita , Pai Nitika Pant , Klein Marina
Published: August 2012

Background

A recent increase in reports of acute hepatitis C virus infection (HCV) in HIV-infected and HIV-uninfected men who have sex with men (MSM), with the sole risk factor being sexual exposure, has led to routine screening and targeted prevention requests for this population; current evidence for this necessity is unclear.

Objective

A systematic review was conducted to assess the incidence of HCV infection among studies conducted in HIV-positive and/or HIV-negative MSM to explore the implications for routine HCV screening.

Data sources

The MEDLINE, EMBASE and BIOSYS databases were searched for the period January 2000 to May 2012, yielding 21 studies. Six conferences were hand-searched for the same period yielding four abstracts.

Study selection

Only studies in English presenting incidence rates of HCV and specifying HIV status were included.

Data abstraction

Data were abstracted by two authors using predefined data fields. The STROBE checklist was used to assess study quality.

Data synthesis

Data were divided into HIV-negative MSM and HIV-positive MSM subgroups, and HCV incidence density measurements were pooled. Using a DerSimonian–Laird random effects model, pooled incidence was 1.48/1000 person-years (95% CI 0.75 to 2.21) for the HIV-negative MSM subgroup. The HIV-positive MSM subgroup was at 4.1 times higher risk of acquiring HCV at 6.08/1000 person-years (95% CI 5.18 to 6.99). Studies directly comparing subgroups estimated a pooled risk difference of 3.45/1000 person-years (95% CI 1.63 to 5.27).

Conclusion

HIV-positive MSM were at higher risk for acute HCV infection than HIV-negative MSM, substantiating the need for routine screening initiatives. Insufficient evidence exists to warrant routine screening of HIV-negative MSM, except on a case-by-case basis, such as high-risk sexual behaviour.
Serum and urinary adiponectin in dogs with renal disease from leishmaniasis
Authors: Tvarijonaviciute A. , Ceron J. J. , García‐Martinez J. D.
Published: August 2012

The objective of this study was to perform an analytical validation of a commercially available ELISA kit (human adiponectin) for urinary adiponectin determination in dogs, and to evaluate urinary adiponectin in dogs with glomerular injury. For this purpose, urine samples from three healthy dogs and three dogs with diagnosed kidney disease were used for analytical validation of the method. In order to evaluate possible influence of kidney damage on urinary adiponectin, serum and urine samples from six healthy and 58 dogs with leishmaniasis were included. The diseased dogs were allocated to three groups according to their urine protein/creatinine (UPC) ratio as non‐proteinuric (NP), borderline proteinuric (BP), and proteinuric (P). Intra‐ and inter‐assay coefficients of variation (CV) were lower than 10 per cent and 12 per cent, respectively. Dilutions of canine urine samples resulted in linear regression equations close to 1. Mean recovery was of 112 per cent. The detection limit was 0.75 ng/ml. Urinary adiponectin and urinary adiponectin/creatinine (UAC) ratio showed significantly higher values in urine of P group dogs compared with healthy, NP and BP dogs. In conclusion, an ELISA kit can be used for precise and accurate urinary adiponectin measurement in dogs. Urinary adiponectin is increased in dogs with proteinuria suggesting its possible use as a marker of kidney damage.