bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficiency Enhancement of a Small Scale Closed Solar Thermal Brayton Cycle by a Combined Simple Organic Rankine Cycle
Authors: Riazi H. , Ahmed N. A.
Published: October 2013

In this paper efficiency enhancement of a small scale closed solar thermal Brayton cycle is investigated by combining it to a simple organic Rankine cycle. Brayton power cycles are generally known as the enabling technology for high temperature solar power towers due to their higher efficiencies compared to other power cycles. Unlike conventional solar-thermal plants, which concentrate the sun’s energy to generate steam for driving a turbine, the Brayton thermodynamic does not use water. Instead, the concentrated solar energy is used to heat compressed air, which then expands through a gas turbine to generate power. Irreversible loss in compressor and turbine, the operating temperature of solar collector and recuperator effectiveness are the main features that limit the net power output of the system which should be considered and analyzed. The exhaust of the gas turbine is still at high temperature that should be cooled down before entering the compressor. Thus, this heat can be utilized to operate a low temperature Rankine cycle and increase the system efficiency and power generation.

Operating points of off the shelf micro-turbines and steam turbine with parabolic solar dish concentrator of various concentrating ratios are considered. Thermodynamic analysis is applied, by using the first and second law of thermodynamics, to obtain the optimum temperature of solar collector, minimum irreversibility rates to maximize the efficiency and net power output of the system at various steady-state conditions.

Results show that for the closed solar thermal Brayton cycle the maximum overall first law efficiency of the system can be increased of more than 5% by combining a simple Rankine cycle to recover the exhaust heat and a significant 20% increase in the second law efficicency. The system efficiency is related to the solar concentration ratio with an optimum operating temperature and the choice of micro-turbine. On this basis, both the overall efficiency and the total output power may reach their maximum value by optimizing the pressure ratio. In a small scale closed solar thermal Brayton cycle combined by a Rankine cycle with a micro turbine operating at its highest compressor efficiency, the operating conditions can be optimized in such a way that the system produces maximum net power output or having the highest overall efficiency.
Noise Measurements and Reduction for High-Frequency Vibrating Devices in the Application of Cooling Electronics
Authors: Huang Longzhong , Simon Terrence , Zhang Min , Yeom Taiho , North Mark , Cui Tianhong
Published: October 2013

Traditional heat sinks for electronics cooling have become ever more difficult to design to meet the high dissipation rate of modern high-heat-flux electronics. Active devices, especially devices operating at a high frequency, show promise toward enhancing heat transfer performance. However, active devices generate noise that may not be acceptable to personnel. The present work studies acoustic characteristics of piezoelectrically-driven synthetic jets and oscillating plate agitators operating at high frequency (around 1000 Hz) employed in an electronics cooling module for heat transfer enhancement purposes. The A-weighted noise level from such actuators is measured and found to increase with increases of driving voltage and operational frequency. The measured sound pressure level of the active devices used in our present enhanced heat transfer module can be as high as 100 dB. Through a power spectrum analysis, we find that most acoustic energy is in a narrow frequency band close to the operating frequency of the active device. To decrease the noise level, a muffler, which also allows cooling air to recirculate through the equipment cabinet, has been designed and tested. An analytical model is employed to select the geometry of the muffler for optimal performance based on acoustic characteristics of the active devices and the through-flow pressure drop. The muffler having this optimal design is fabricated and tested and found to be able to decrease the noise level generated by two actuators from 83 dB to 64 dB.
Micro-Power Generators Employing Commercially Available Piezoelectric Materials
Authors: Roa-Prada Sebastian
Published: October 2013

Piezoelectric devices are among the most efficient and reliable solutions for power harvesting from environment vibrations. Considerable effort has been devoted recently in the engineering community towards reducing the size and increasing the power density of these generators at the micro level. The objectives of this paper are to identify commercially available materials and to determine the geometrical configuration best suited for energy harvesting applications by assessing their performance when used in a cantilever beam micro-generator with a fixed volume. To achieve this objective, a comprehensive database with properties of commercially available piezoelectric materials is first established. Then electro-mechanical simulation is carried out to study the changes in device performance with respect to variations in the geometrical configuration for a vibrating beam with a fixed end and a mass attached at the free tip. Once the materials and geometrical configuration providing the highest power output are identified, other aspects important to system implementation are discussed such as feasibility of fabrication at the desired scale and integration with the electronic circuitry. The results obtained provide guidelines for designing and realizing reduced scale cantilever-beam piezoelectric harvesters employing high performance, commercially available materials.
Compact Modeling of 3D Stacked Die Inter-Tier Microfluidic Cooling Under Non-Uniform Heat Flux
Authors: Wan Zhimin , Kim Yoon Jo , Joshi Yogendra K.
Published: October 2013

Three-dimensional (3D) stacking is an emerging trend for future high performance microsystems. The stacking of chips increases the power density significantly, with associated thermal concerns. For interior tiers in a 3D stack, the surface area for the heat removal is further reduced. Also, realistic power maps on active tiers produce highly non-uniform patterns, with maximum heat fluxes 5–10 times the average values. Conventional air-cooled heat sinks cannot meet these thermal requirements. In this paper, a compact thermal model of a multi-layer chip stack subjected to the realistic power map was developed. Interlayer pin fins were modeled on the back of the chips, with water as the coolant. It was found that the compact model ran ten times faster than the full computational fluid dynamics/heat transfer (CFD/HT) model, with errors within 5%. The compact model was then used to analyze the thermal characteristics of 4 layer stacked dual core Penryn microprocessors, with a total power of 172.4 W. The non-uniform power map produced maximum heat flux of 300 W/cm2 in the hot spots. The results show that at a pressure drop of 20 kPa and inlet water temperature of 20 °C, the temperature of the bottom tier is higher than the other three tiers and the maximum temperature of the bottom layer is 56 °C. This is because the bottom layer thermal management only depends on one-sided pin fin cooling, while the other layers have double-sided cooling. A dual pass channel configuration reduced the maximum temperature to 50 °C. Overall, the interlayer pin fin cooling was found to be a very effective thermal management method for 3D stacked die packaging.
A Sensitivity Based Approach to Determining Non-Cooperative Solutions in Nash and Stackelberg Games
Authors: Ghotbi Ehsan , Otieno Wilkistar A. , Dhingra Anoop K.
Published: October 2013

A sensitivity based approach is presented to determine Nash solution(s) in multiobjective problems modeled as a non-cooperative game. The proposed approach provides an approximation to the rational reaction set (RRS) for each player. An intersection of these sets yields the Nash solution for the game. An alternate approach for generating the RRS based on design of experiments (DOE) combined with response surface methodology (RSM) is also explored. The two approaches for generating RRS are compared on three example problems to find Nash and Stackelberg solutions. It is seen that the proposed sensitivity based approach (i) requires less computational effort than a RSM-DOE approach, (ii) is less prone to numerical errors than the RSM-DOE approach, (iii) is able to find all Nash solutions when the Nash solution is not a singleton, (iv) is able to approximate non linear RRS, and (v) is able to find better a Nash solution on an example problem than the one reported in the literature.
Development of a Materials for Energy Storage Course for Engineering Students
Authors: Corneal Lindsay M.
Published: October 2013

The advanced energy storage industry is a rapidly growing field. This industry is looking for engineering graduates with the skills and training to work in the area of energy storage. The School of Engineering at Grand Valley State University is developing a three-course certificate in advanced energy to address this need. The objective of the certificate is to prepare students with a sound engineering and science education which is augmented with knowledge of energy as applied to advanced energy storage for electrified vehicles and power management.

As part of the certificate in advanced energy, a course is being developed in Materials for Energy Storage. This course will study the components of electrochemical cells and the various materials used for these components. The focus will be on the properties of the different materials, the benefits and drawbacks of each one, and the selection of materials for specific applications. The interaction between the materials of the individual components within the cells will be examined. Finally, the electrochemical energy storage system will be considered as a whole and the testing and performance of the cells will be studied.

This paper will present a description and overview of the course, and the topics that will be covered. As the course is in the development stage, the plans for assessment after its pilot offering will be discussed.
Full Field Measurements of the Dynamic Response of AA6061-T6 Aluminum Alloy Under High Strain Rate Compression and Torsion Loads
Authors: Owolabi Gbadebo , Odoh Daniel , Odeshi Akindele , Whitworth Horace
Published: October 2013

Aluminum alloys exhibit an attractive combination of mechanical and physical properties such as high stiffness and low density, which favors their utilization in many structural applications. Thus, increasing the structural applications of aluminum alloy is the driving force for the need to adequately understand its deformation and failure mechanisms under various types of dynamic loading conditions. In this study, full field plastic deformation of AA6061-T6 aluminum alloy at high strain-rates under compressive and torsion loads are measured using split Hopkinson compression and torsion bars and a high speed digital image correlation system. The stress-strain curves obtained using the high speed digital cameras are compared with results obtained from the elastic waves in the compression and torsion bars. A post deformation analysis of the specimen also shows strain localization along narrow adiabatic shear bands in the AA6061-T6 alloy.
New Fabrication Method for High-Q MEMS Inductors
Authors: Kuo Wen-Cheng , Hsu Chao-Yang , Yang Yao-Joe
Published: October 2013

This study presents a novel fabrication method to enhance the quality of flexible MEMS inductors for wireless energy and data transmission applications. The fabrication process used parylene C as a polymeric substrate material with a thickness of 50 μm and patterned by a picosecond laser. We modeled the test device in a simulation and then verified its feasibility through experimentation. We computed the projected Q-factor enhancement to be approximately 8.9x the 2 μm metal thickness of traditional evaporation methods at a 1 MHz operation frequency. The thickness of the metal, integrated with picosecond laser-cutting technology, resulted in an enhanced Q-factor compared to traditional multilayer or fold-and-bond methods. The production process was simple and did not require a bonding process. The research indicated that such Q-enhanced MEMS inductors could be integrated with biomedical implants for wireless energy and data transmission applications.
Acoustic Emission Monitoring of Composite Plates Under Buckling Loads
Authors: Abazary S. , Refahi Oskouei A.
Published: October 2013

Delamination and Fracture are the most common failure modes in composite materials, since they will result in the reduction of stiffness and can grow throughout other layers. Buckling is consisted of two main stages including delamination and fracture. Delamination is too consisted of two main stages including initiation and propagation. AE is a suitable method for in situ monitoring of damage in composite materials. In this study, by using AE monitoring, an experimental analysis on different sets of glass/polyester under buckling loading has been carried out. Scanning electron microscope (SEM) was used in thistest to show behavior of the initiation delamination damage.
Analysis of Propeller Design Methods and Validation With the CFD Computation of a Propeller-Pump
Authors: Albert Sven , Epple Philipp , Delgado Antonio
Published: October 2013

There is a large variety of axial propellers available, ranging from very small devices with only millimeters in diameter to ship propellers being several meters in size. Also they are applicable in several different ways, from low pressure propellers when actually used as fans or high pressure differences when used for propulsion purposes. Several theories have been developed to calculate and predict propeller performance. The basic theory is the linear momentum theory which takes only the axial motion into account. The theory can be refined taking the rotational motion and hence the angular momentum into account and also segmenting the propeller into several blade elements, to which classical airfoil theory can be applied. However, common literature does not include any precise verification of these theories. The present work shows with CFD computations the validation and hence accuracy of the blade element theory and its predecessors on a specific axial machine, namely the blood assist Reitan catheter propeller-pump. The propeller-pump is evaluated in a large operational range, using a commercial CFD code. The theory is then applied to the CFD results calculating the stream tube, in which all the necessary parameters, like interference factors, are evaluated. Those will deliver the machine characteristics thrust, torque and efficiency according to these theories. Comparison of this data to the CFD values shows good agreement, especially when segmenting the propeller and therefore using multiple stream tubes. Thus, the validity of these theories and its range of applicability was verified showing in detail how these theories can be employed as reliable design tools coupled with CFD verification.
Tire-Force Based Holistic Corner Control
Authors: Chen Shih-Ken , Ghoneim Youssef , Moshchuk Nikolai , Litkouhi Bakhtiar , Pylypchuk Valery
Published: October 2013

This paper describes an analytical methodology and the related algorithms for controlling the vehicle tire forces. The purpose of the control is to provide the driver with a normal driving feel and keep the vehicle on a target path even under demanding road conditions. All the control variables are calculated in real time by minimizing a weighted cost function of the errors between actual and target CG forces and moments. Such real time optimization is possible due to the availability of analytical solutions for the tire force adjustments. A key ingredient of the approach is the idea of making the weights in the cost function dependent on tire states after the optimal linear solution is obtained. When the tire reserve approaches its upper limit, the corresponding weighted element increases exponentially. As a result, the stability element in the cost function dominates the gradient of the target function regardless of CG force error magnitudes. Once the tire state becomes normal then the CG force error correction becomes the dominant component in the control solutions.
Micro-Scale Part Manipulation on a Liquid Interface Through Interface Curvature Effects
Authors: Carballo Jose , Ni Qi , Vasquez Jose , Chatzisavas Sotirios , Crane Nathan
Published: October 2013

Microscale assembly has many factors that limit assembly rates [1]. At this scale, capillary interactions between particles and nearby substrates are significant, and can be utilized for controlling assembly processes [2,3]. Typically these assembly processes involve direct capillary bonding, but lateral capillary forces can also be applied to floating parts by changing the local curvature of the fluid interface [4]. In this work, we introduce some basic concepts of a microscale component integration system that utilizes local changes in the fluid interface curvature to manipulate floating prismatic parts. Two approaches for achieving fluidic micro-integration, on a water-oil interface, are proposed. The first technique is intended to individually acquire, re-position and release floating parts. It has the capability of short distance part translation/orientation. The second technique provides long-distance part conveying.
Finite Element Based Evaluation of Abrasive Waterjet Peening With Elastic Prestress: Effect of Prestress Loading
Authors: Sadasivam Balaji , Arola Dwayne
Published: October 2013

Abrasive Waterjet (AWJ) peening has emerged as a potential surface treatment process for components subjected to high–cycle fatigue loading and that require a “rough” surface. Conducting treatments while subjecting the surface to tensile elastic prestress has resulted in an increase in the magnitude and depth of residual stress. Recent finite element based studies have revealed that the residual stress field in AWJ peening is influenced by the boundary conditions and whether the prestress is administered by load or displacement control. However, previous investigations concerned with AWJ peening have been limited to a flexural loading arrangement to achieve tensile prestress of the treated surface. In the present investigation, a finite element based study is conducted to evaluate the effect of prestress loading configurations and a comparison of flexural vs axial loading on the residual stress fields resulting from peening surface treatments. Results show that the prestress loading influences the depth of residual stress and axial prestress results in a greater depth than that achieved with flexure prestress.
Extending Blind Modal Identification to the Underdetermined Case for Ambient Vibration
Authors: McNeill Scot
Published: October 2013

The modal identification framework known as Blind Modal Identification (BMID) has recently been developed, drawing on techniques from Blind Source Separation (BSS). Therein, a BSS algorithm known as Second Order Blind Identification (SOBI) was adapted to solve the Modal IDentification (MID) problem. One of the drawbacks of the technique is that the number of modes identified must be less than the number of sensors used to measure the vibration of the equipment or structure.

In this paper, an extension of the BMID method is presented for the underdetermined case, where the number of sensors is less than the number of modes to be identified. The analytic signal formed from measured vibration data is formed and the Second Order Blind Identification of Underdetermined Mixtures (SOBIUM) algorithm is applied to estimate the complex-valued modes and modal response autocorrelation functions. The natural frequencies and modal damping ratios are then estimated from the corresponding modal auto spectral density functions using a simple Single Degree Of Freedom (SDOF), frequency-domain method. Theoretical limitations on the number of modes identified given the number of sensors are provided.

The method is demonstrated using a simulated six DOF mass-spring-dashpot system excited by white noise, where displacement at four of the six DOF is measured. All six modes are successfully identified using data from only four sensors. The method is also applied to a more realistic simulation of ambient building vibration. Seven modes in the bandwidth of interest are successfully identified using acceleration data from only five DOF. In both examples, the identified modal parameters (natural frequencies, mode shapes, modal damping ratios) are compared to the analytical parameters and are demonstrated to be of good quality.
Study of the Thermal-Structural Behavior of a Piston Diesel With Gallery Through Finite Element Method
Authors: Avila Aguilar José Manuel , Lesso Arroyo Raul , Martínez Cruz Jorge
Published: October 2013

The finite element analysis is a useful tool to investigate the behavior of a body subjected to different loads. The objective of this work was the analysis of an aluminum diesel piston provided with a cooling gallery, Cu-Zn bushings, and a Ni-resist insert. This piston is used in 1.9 L turbodiesel engines. The investigation was undertaken in order to observe the mechanical behavior of the piston at the operating temperatures and pressures and thus to study the performance of the different parts of the piston.

The analysis was performed using a finite element software, taking into account a coupled field analysis and involving a fluid passing through the cooling gallery, temperature and pressure at the piston head which resulted in heat flow and thermo-mechanical stresses in the piston.

According to the obtained results, it is worth noting the important role of Cu-Zn bushings in the piston as they support the highest stress of about 359 MPa and protect the piston against failure, and these bushings are able to support more stress that the body of the piston (aluminum yield stress limit 290 MPa). Also it is observed that the cooling gallery acts as a thermal barrier by preventing the heat flow from the head piston (approximately 213 ° C) toward the piston body (approximately 80 ° C). Another important aspect is the structural thermal interaction analysis and it can be observed the influence of high temperatures in the piston, increasing stress up to 100%. Finally it was concluded that the piston is able to withstand the operating pressures and temperatures.
An Adaptive Hybrid Force/Motion Control Design for Robot Manipulators Interacting in Constrained Motion With Unknown Non-Rigid Environments
Authors: Jafari Aghil , Rezaei Mehdi , Talebi Ali , Ghidary Saeed Shiry , Monfaredi Reza
Published: October 2013

In the present paper, the objective of hybrid control is specified and an adaptive hybrid force/motion control approach is proposed. Based on the concept of hybrid control, the task space is decomposed into position and force controlled subspaces. An adaptive scheme is presented which makes the controller robust when the robot is in interaction with an unknown non-rigid environment. By using the classical Lyapunov method, it is demonstrated that the proposed control law ensures the tracking of the unconstrained components of the desired end-effector trajectories, with regulation of the desired contact force along the constrained direction. Simulation results verify the effectiveness of our prosperous adaptive hybrid control in robot-environment interaction.
The Mechanisms of the Phenomenon of Tornado-Like Jets Self-Organization in the Flow Along the Dimples on the Initially Flat Surface
Authors: Kiknadze G. I. , Gachechiladze I. A. , Barnaveli T. T.
Published: October 2013

The mechanisms of the phenomenon of the tornado-like jets self-organization are described. Tornado-like jets are incorporated into a continuous medium stream and induced by three-dimensional reliefs of double curvature indented on surfaces.
X-ray photoelectron spectroscopy study of para-substituted benzoic acids chemisorbed to aluminum oxide thin films
Authors: Kreil Justin , Ellingsworth Edward , Szulczewski Greg
Published: October 2013

A series of para-substituted, halogenated (F, Cl, Br, and I) benzoic acid monolayers were prepared on the native oxide of aluminum surfaces by solution self-assembly and spin-coating techniques. The monolayers were characterized by x-ray photoelectron spectroscopy (XPS) and water contact angles. Several general trends are apparent. First, the polarity of the solvent is critical to monolayer formation. Protic polar solvents produced low coverage monolayers; in contrast, nonpolar solvents produced higher coverage monolayers. Second, solution deposition yields a higher surface coverage than spin coating. Third, the thickness of the monolayers determined from XPS suggests the plane of the aromatic ring is perpendicular to the surface with the carboxylate functional group most likely binding in a bidentate chelating geometry. Fourth, the saturation coverage (∼2.7 × 1014 molecules cm−2) is independent of the para-substituent.
I'll Tell You What You Think: An Exercise in Pseudoscience Debunking in an Introductory Astronomy Course
Authors: Caton Dan
Published: October 2013

At Appalachian State University students have to take just two semesters of a physical or biological science to satisfy the general education requirements. Most non-science major students have little time in their crowded schedules to take additional science courses, whether they want to or not, and in fact face a surcharge when taking more courses than needed to graduate. Given this environment, it is essential that we cover more than just the basics of one particular discipline, like astronomy in my case. We should teach something about the overall philosophy of science, the scientific method, and the importance of science in our lives.
Seeing Earth's Orbit in the Stars: Parallax and Aberration
Authors: Timberlake Todd K.
Published: October 2013

During the 17th century the idea of an orbiting and rotating Earth became increasingly popular, but opponents of this view continued to point out that the theory had observable consequences that had never, in fact, been observed.1 Why, for instance, had astronomers failed to detect the annual parallax of the stars that must occur if Earth orbits the Sun? To address this problem, astronomers of the 17th and 18th centuries sought to measure the annual parallax of stars using telescopes. None of them succeeded. Annual stellar parallax was not successfully measured until 1838, when Friedrich Bessel detected the parallax of the star 61 Cygni.2 But the early failures to detect annual stellar parallax led to the discovery of a new (and entirely unexpected) phenomenon: the aberration of starlight. This paper recounts the story of the discovery of stellar aberration. It is accompanied by a set of activities and computer simulations that allow students to explore this fascinating historical episode and learn important lessons about the nature of science.3
On the Intensity Profile of Electric Lamps and Light Bulbs
Authors: Bacalla Xavier , Salumbides Edcel John
Published: October 2013

We demonstrate that the time profile of the light intensity from domestic lighting sources exhibits simple yet interesting properties that foster lively student discussions. We monitor the light intensity of an industrial fluorescent lamp (also known as TL) and an incandescent bulb using a photodetector connected to an oscilloscope. The light intensity of these sources displays modulation at twice the ac power supply frequency. The familiarity of ac line power supply, commonplace light sources, and simplicity of the setup encourage student confidence, allowing them to think deeper and continually reassess their notions, and if managed can lead to a satisfactory explanation of the observations.
Smartphone-aided measurements of the speed of sound in different gaseous mixtures
Authors: Parolin Sara Orsola , Pezzi Giovanni
Published: October 2013

Here we describe classroom-based procedures aiming at the estimation of the speed of sound in different gas mixtures with the help of a plastic drain pipe and two iPhones or iPod touches. The procedures were conceived to be performed with simple and readily available tools.
Megalin Contributes to Kidney Accumulation and Nephrotoxicity of Colistin
Authors: Suzuki Takahiro , Yamaguchi Hiroaki , Ogura Jiro , Kobayashi Masaki , Yamada Takehiro , Iseki Ken
Published: October 2013

Interest has recently been shown again in colistin because of the increased prevalence of infections caused by multidrug-resistant Gram-negative bacteria. Although the potential for nephrotoxicity is a major dose-limiting factor in colistin use, little is known about the mechanisms that underlie colistin-induced nephrotoxicity. In this study, we focused on an endocytosis receptor, megalin, that is expressed in renal proximal tubules, with the aim of clarifying the role of megalin in the kidney accumulation and nephrotoxicity of colistin. We examined the binding of colistin to megalin by using a vesicle assay. The kidney accumulation, urinary excretion, and concentrations in plasma of colistin in megalin-shedding rats were also evaluated. Furthermore, we examined the effect of megalin ligands and a microtubule-depolymerizing agent on colistin-induced nephrotoxicity. We found that cytochromec, a typical megalin ligand, inhibited the binding of colistin to megalin competitively. In megalin-shedding rats, renal proximal tubule colistin accumulation was decreased (13.5 ± 1.6 and 21.3 ± 2.6 μg in megalin-shedding and control rats, respectively). Coadministration of colistin and cytochromecor albumin fragments resulted in a significant decrease in urinaryN-acetyl-β-d-glucosaminidase (NAG) excretion, a marker of renal tubular damage (717.1 ± 183.9 mU/day for colistin alone, 500.8 ± 102.4 mU/day for cytochromecwith colistin, and 406.7 ± 156.7 mU/day for albumin fragments with colistin). Moreover, coadministration of colistin and colchicine, a microtubule-depolymerizing agent, resulted in a significant decrease in urinary NAG excretion. In conclusion, our results indicate that colistin acts as a megalin ligand and that megalin plays a key role in the accumulation in the kidney and nephrotoxicity of colistin. Megalin ligands may be new targets for the prevention of colistin-induced nephrotoxicity.
Sensititre MYCOTB MIC Plate for Testing Mycobacterium tuberculosis Susceptibility to First- and Second-Line Drugs
Authors: Lee Jongseok , Armstrong Derek T. , Ssengooba Willy , Park Jeong-ae , Yu Yeuni , Mumbowa Francis , Namaganda Carolyn , Mboowa Gerald , Nakayita Germine , Armakovitch Sandra , Chien Gina , Cho Sang-Nae , Via Laura E. , Barry Clifton E. , Ellner Jerrold J. , Alland David , Dorman Susan E. , Joloba Moses L.
Published: October 2013

For
Mycobacterium tuberculosis
, phenotypic methods for drug susceptibility testing of second-line drugs are poorly standardized and technically challenging. The Sensititre MYCOTB MIC plate (MYCOTB) is a microtiter plate containing lyophilized antibiotics and configured for determination of MICs to first- and second-line antituberculosis drugs. To evaluate the performance of MYCOTB for
M. tuberculosis
drug susceptibility testing using the Middlebrook 7H10 agar proportion method (APM) as the comparator, we conducted a two-site study using archived
M. tuberculosis
isolates from Uganda and the Republic of Korea. Thawed isolates were subcultured, and dilutions were inoculated into MYCOTB wells and onto 7H10 agar. MYCOTB results were read at days 7, 10, 14, and 21; APM results were read at 21 days. A total of 222 isolates provided results on both platforms. By APM, 106/222 (47.7%) of isolates were resistant to at least isoniazid and rifampin. Agreement between MYCOTB and APM with respect to susceptibility or resistance was ≥92% for 7 of 12 drugs when a strict definition was used and ≥96% for 10 of 12 drugs when agreement was defined by allowing a ± one-well range of dilutions around the APM critical concentration. For ethambutol, agreement was 80% to 81%. For moxifloxacin, agreement was 83% to 85%; incorporating existing DNA sequencing information for discrepant analysis raised agreement to 91% to 96%. For MYCOTB, the median time to plate interpretation was 10 days and interreader agreement was ≥95% for all drugs. MYCOTB provided reliable results for
M. tuberculosis
susceptibility testing of first- and second-line drugs except ethambutol, and results were available sooner than those determined by APM.
Differential Susceptibilities to Azithromycin Treatment of Chlamydial Infection in the Gastrointestinal Tract and Cervix
Authors: Yeruva Laxmi , Melnyk Stepan , Spencer Nicole , Bowlin Anne , Rank Roger G.
Published: October 2013

Evidence from animal studies suggests that chlamydiae may persist in the gastrointestinal tract (GI) and be a reservoir for reinfection of the genital tract. We hypothesize that there may be a differential susceptibility of organisms in the GI and genital tracts. To determine the effect of azithromycin on persistent chlamydial gut infection, C57BL/6 and BALB/c mice were infected orally and genitally and treated with azithromycin (Az) orally (20, 40, or 80 mg/kg of body weight), and the numbers of chlamydiae were determined from cervix and cecal tissues. The Az concentration in the cecum and cervix was measured by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Az treatment cleared genital infection in both C57BL/6 and BALB/c mice; however, GI infection was not cleared with the same doses. HPLC data showed the presence of Az at both sites of infection, and significant amounts of Az were measured in treatment groups. However, no significant difference in Az levels between the cecum and the cervix was observed, indicating similar levels of Az reaching both sites of infection. These data indicate that antibiotic levels that are sufficient to cure genital infection are ineffectual against GI infection. The results suggest a reevaluation of antibiotic therapy for chlamydial infection.
Evaluation of the Efficacies of Amphotericin B, Posaconazole, Voriconazole, and Anidulafungin in a Murine Disseminated Infection by the Emerging Opportunistic Fungus Sarocladium (Acremonium)
kiliense
Authors: Fernández-Silva Fabiola , Capilla Javier , Mayayo Emilio , Sutton Deanna A. , Hernández Pilar , Guarro Josep
Published: October 2013

We evaluated and compared the efficacies of different antifungal drugs against
Sarocladium kiliense
(formerly
Acremonium kiliense
), a clinically relevant opportunistic fungus, in a murine model of systemic infection. Three clinical strains of this fungus were tested, and the therapy administered was as follows: posaconazole at 20 mg/kg of body weight (twice daily), voriconazole at 40 mg/kg, anidulafungin at 10 mg/kg, or amphotericin B at 0.8 mg/kg. The efficacy was evaluated by prolonged animal survival, tissue burden reduction, and (1→3)-β-
d
-glucan serum levels. In general, the four antifungal drugs showed high MICs and poor
in vitro
activity. The efficacy of the different treatments was only modest, since survival rates were never higher than 40% and no drug was able to reduce fungal load in all the organs for the three strains tested. Posaconazole, in spite of its high MICs (≥16 μg/ml), showed the highest efficacy. The (1→3)-β-
d
-glucan serum levels were equally reduced by all drugs evaluated.
Epidemiology of Bloodstream Infections Caused by Acinetobacter baumannii and Impact of Drug Resistance to both Carbapenems and Ampicillin-Sulbactam on Clinical Outcomes
Authors: Chopra Teena , Marchaim Dror , Awali Reda A. , Krishna Amar , Johnson Paul , Tansek Ryan , Chaudary Khawar , Lephart Paul , Slim Jessica , Hothi Jatinder , Ahmed Harris , Pogue Jason M. , Zhao Jing J. , Kaye Keith S.
Published: October 2013

Acinetobacter baumannii
has become a leading cause of bloodstream infections (BSI) in health care settings. Although the incidence of infection with carbapenem- and ampicillin-sulbactam-resistant (CASR)
A. baumannii
has increased, there is a scarcity of studies which investigate BSI caused by CASR
A. baumannii
. A retrospective cohort study was conducted on adult patients with BSI caused by
A. baumannii
and who were admitted to the Detroit Medical Center between January 2006 and April 2009. Medical records were queried for patients' demographics, antimicrobial exposures, comorbidities, hospital stay, and clinical outcomes. Bivariate analyses and logistic regression were employed in the study. Two hundred seventy-four patients with BSI caused by
A. baumannii
were included in the study: 68 (25%) caused by CASR
A. baumannii
and 206 (75%) caused by non-CASR
A. baumannii
. In multivariate analysis, factors associated with BSI caused by CASR
A. baumannii
included admission with a rapidly fatal condition (odds ratio [OR] = 2.83, 95% confidence interval [CI] = 1.27 to 6.32,
P
value = 0.01) and prior use of antimicrobials (OR = 2.83, 95% CI = 1.18 to 6.78,
P
value = 0.02). In-hospital mortality rates for BSI caused by CASR
A. baumannii
were significantly higher than those for non-CASR
A. baumannii
-induced BSI (43% versus 20%; OR = 3.0, 95% CI = 1.60 to 5.23,
P
value < 0.001). However, after adjusting for potential confounders, the association between BSI caused by CASR
A. baumannii
and increased risk of in-hospital mortality was not significant (OR = 1.15, 95% CI = 0.51 to 2.63,
P
value = 0.74). This study demonstrated that CASR
A. baumannii
had a distinct epidemiology compared to more susceptible
A. baumannii
strains; however, clinical outcomes were similar for the two groups. Admission with a rapidly fatal condition was an independent predictor for both CASR
A. baumannii
and in-hospital mortality.
Exoenzyme S ADP-Ribosylates Rab5 Effector Sites To Uncouple Intracellular Trafficking
Authors: Simon Nathan C. , Barbieri Joseph T.
Published: October 2013

Pseudomonas aeruginosa
exoenzyme S (ExoS) ADP-ribosylates multiple eukaryotic targets to promote cytopathology and bacterial colonization. ADP-ribosylation of the small GTPase Rab5 has previously been shown to block fluid-phase endocytosis and trafficking of plasma membrane receptors to the early endosomes as well as inhibit phagocytosis of the bacterium. In this study, ExoS is shown to be capable of ADP-ribosylating 6 candidate arginine residues that are located in the effector binding region or in the C terminus of Rab5. Two Rab5 derivatives were engineered, which contained Arg→Ala mutations at four Arg residues within the effector binding region (EF) or two Arg residues within the C-terminal tail (TL). Expression of Rab5(TL) does not affect the ability of ExoS to modify intracellular trafficking, while expression of Rab5(EF) rescued the ability of ExoS to inhibit intracellular trafficking. ADP-ribosylation of effector arginines likely uncouples Rab5 signaling to downstream effectors. This is a different mechanism for inhibition than observed for the ADP-ribosylation of Ras by ExoS, where ADP-ribosylated Ras loses the ability to bind guanine nucleotide exchange factor (GEF). Other experiments showed that expression of dominant negative Rab5(Ser34Asn) does not inhibit ExoS trafficking to the perinuclear region of intoxicated cells. This study provides insight into a mechanism for how ExoS ADP-ribosylation of Rab5 inhibits Rab5 function.
Sternoclavicular joint septic arthritis: an interesting lesson in clinical anatomy
Authors: Fry Damian , Boyle Stephen
Published: October 2013

An otherwise healthy 45-year-old man presented to our emergency department holding his left arm in abduction and external rotation. He reported pain in his left shoulder and chest for the preceding 10 days that had become much worse over the last 48 h and was eased only by holding his arm in this position. The CT of the chest revealed soft tissue swelling around the left sternoclavicular joint consistent with sternoclavicular joint septic arthritis with significant inflammatory involvement of the medial component of the left pectoralis major muscle. The patient was taken to theatre for washout of the left sternoclavicular joint and is currently recovering well at home on intravenous antibiotics.
Laparoscopic cholecystectomy in a patient with situs inversus totalis: case report with review of literature
Authors: Ali Mohammed Sulaiman , Attash Saad Muwafaq
Published: October 2013

Situs inversus totalis is a rare autosomal recessive disorder which can cause diagnostic confusion in a lot of clinical conditions including calculous cholecystitis due to the reversed anatomical positions of abdominal viscera. Laparoscopic cholecystectomy is much more challenging in the presence of this disorder due to loss of usual orientation. We present a case of a 43-year-old woman who was diagnosed at our centre to have calculous cholecystitis in the presence of situs inversus totalis. Laparoscopic cholecystectomy was performed safely after adjustment of the positions of the team inside the operative theatre and of the port sites. The patient tolerated the operation very well and was discharged home after 24h. On follow-up visit the patient was doing very well and completely free of symptoms.
The role of proximal dynamic joint stability in the development of exertional medial tibial pain: a prospective study
Authors: Verrelst Ruth , De Clercq Dirk , Vanrenterghem Jos , Willems Tine , Palmans Tanneke , Witvrouw Erik
Published: October 2013

Objective

To prospectively determine risk factors contributing to the development of exertional medial tibial pain (EMTP).

Methods

Data were prospectively collected on healthy female students in physical education, who were freshmen in 2010–2011 and 2011–2012. Eighty-six female students aged 19.38±0.85 years, were tested at the beginning of their first academic year. Kinematic parameters in the frontal and transverse plane were measured during a single-leg drop jump (SLDJ). For further analysis, the SLDJ task was divided in two phases: touchdown until maximal knee flexion (MKF) and then MKF until take-off, representing landing and push-off phase, respectively. The injury follow-up of the students was assessed using a weekly online questionnaire and a 3-monthly retrospective control questionnaire. EMTP was diagnosed by an experienced medical doctor. Cox regression analysis was used to identify the potential risk factors for the development of EMTP.

Results

During injury follow-up (1–2 years), 22 participants were diagnosed with EMTP. The results of this study identified that increased range of motion (ROM) in the transverse plane of hip and thorax during landing (p=0.010 and 0.026, respectively) and during push off (p=0.019 and 0.045, respectively) are predictive parameters for the development of EMTP in women.

Conclusions

Increased ROM values of hip and thorax in the transverse plane, which can be interpreted as impaired ability to maintain dynamic joint stability resulting in increased accessory movements, are significant contributors to the development of EMTP in women.
Influence of soil nail orientations on stabilizing mechanisms of loose fill slopes
Authors: Cheuk C.Y. , Ho K.K.S. , Lam A.Y.T.
Published: October 2013

Soil nailing has been used to upgrade substandard loose fill slopes in Hong Kong. Due to the possibility of static liquefaction failure, a typical design arrangement comprises a structural slope facing anchored by a grid of soil nails bonded into the in situ ground. Numerical analyses have been conducted to examine the influence of soil nail orientations on the behaviour of the ground nail–facing system. The results suggest that the use of steeply inclined nails throughout the entire slope could avoid global instability, but could lead to significant slope movement especially when sliding failure prevails, for instance, due to interface liquefaction. The numerical analyses also demonstrate that if only subhorizontal nails are used, the earth pressure exerted on the slope facing may cause uplift failure of the slope cover. To overcome the shortcomings of using soil nails at a single orientation, a hybrid nail arrangement comprising nails at two different orientations is proposed. The numerical analyses illustrate that the hybrid nail arrangement would limit slope movement and enhance the robustness of the system.
Potential future climate effects on mountain hydrology, stream temperature, and native salmonid life history
Authors: MacDonald Ryan J. , Boon Sarah , Byrne James M. , Robinson Mike D. , Rasmussen Joseph B.
Published: October 2013

Native salmonids of western North America are subject to many environmental pressures, most notably the effects of introduced species and environmental degradation. To better understand how native salmonids on the eastern slopes of the Canadian Rocky Mountains may respond to future changes in climate, we applied a process-based approach to hydrologic and stream temperature modelling. This study demonstrates that stream thermal regimes in western Alberta, Canada, may only warm during the summer period, while colder thermal regimes during spring, fall, and winter could result from response to earlier onset of spring freshet. Model results of future climate impacts on hydrology and stream temperature are corroborated by an intercatchment comparison of stream temperature, air temperature, and hydrological conditions. Earlier fry emergence as a result of altered hydrological and thermal regimes may favour native westslope cutthroat trout (Oncorhynchus clarkii lewisii) in isolated headwater streams. Colder winter stream temperatures could result in longer incubation periods for native bull trout (Salvelinus confluentus) and limit threatened westslope cutthroat trout habitat.
On a path integral representation of the Nekrasov instanton partition function and its Nekrasov–Shatashvili limit
Authors: Ferrari Franco , Piątek Marcin
Published: October 2013

In this work we study the Nekrasov–Shatashvili limit of the Nekrasov instanton partition function of Yang–Mills field theories with 𝒩 = 2 supersymmetry and gauge group SU(N). The theories are coupled with fundamental matter. A path integral expression of the full instanton partition function is derived. It is checked that in the Nekrasov–Shatashvili (thermodynamic) limit the action of the field theory obtained in this way reproduces exactly the equation of motion used in the saddle-point calculations.
LIMIT AND SHAKEDOWN ANALYSIS UNDER UNCERTAINTY
Authors: STAAT MANFRED
Published: October 2013

Structural reliability analysis is based on the concept of a limit state function separating failure from safe states of a structure. Upper and lower bound theorems of limit and shakedown analysis are used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. Shakedown describes an asymptotic and therefore time invariant structural behavior under time variant loading. The limit state function and its gradient are obtained from a mathematical optimization problem. The method is implemented into a general purpose finite element model (FEM) code. Combined with first-order methods/second-order methods (FORM/SORM) robust and precise analyses can be performed for structures with high reliability. This approach is particularly effective because the sensitivities which are needed by FORM/SORM are derived from the solution of the deterministic problem.