bluuebunny/crossref_metadata_2025 huggingface dataset:
Aeroelastic Instability in Labyrinth Seals
Authors: Ehrich F.
Published: March 2013

Labyrinth seals and associated structural elements have been noted to sustain fatigue failure in high powered, high speed rotating machinery under circumstances that preclude blaming standing wave resonances or “stick-slip” excitation from rotor/stator rubs. Alford [2] has hypothesized that such failures may be caused by self-excited aeroelastic vibration of the seal. A model is defined in which a pressure perturbation in the seal internal volume between the high and low pressure teeth can cause an elastic rotation of the seal rotor or stator element about a virtual pivot point located on the high or low pressure side of the seal. This rotation, in turn, causes a nonuniform opening and closing of the high and low pressure clearances which can give rise to the hypothesized pressure perturbation. A stability parameter is then derived in terms of the high pressure and low pressure tooth clearances, the supply pressure to the seal, the seal width and height, and two parameters indicative of the elastic properties of the seal—its stiffness to radial motion and the location of its virtual pivot point. The stability criterion is applied to a pair of actual labyrinth seal rotors which differ from each other only slightly and are known, from actual practice, to straddle the stability boundary. That is, the larger diameter unit is known to be unstable and the smaller diameter unit known to be stable. On the basis of an instability incident simulated on component test, the stiffness used in evaluating the stability parameter is modified to be representative of the least stiff vibratory mode, and the stability parameter is shown to give reasonable indication of the stability problem in labyrinth seals.
Film Cooling With Injection Through Holes: Adiabatic Wall Temperatures Downstream of a Circular Hole
Authors: Goldstein R. J. , Eckert E. R. G. , Ramsey J. W.
Published: March 2013

An experimental investigation has been conducted to determine the film cooling effectiveness with injection of air through a discrete hole into a turbulent boundary layer of air on a flat plate. The secondary air enters at either an angle of 35 deg or an angle of 90 deg to the main flow. The film cooling effectiveness is found to be considerably different from that obtained in previous studies in which the secondary fluid was introduced through a continuous slot.
The Single-Blow Transient Testing Technique for Compact Heat Exchanger Surfaces
Authors: Pucci P. F. , Howard C. P. , Piersall C. H.
Published: March 2013

The single-blow, transient testing technique for determining the heat transfer characteristics of heat exchanger surfaces, with a summary of the underlying theory, a description of an experimental facility, and comments on the applicability of the technique, are presented. Heat transfer and flow friction data are presented for plate-fin type surfaces fabricated of perforated nickel plate. The data indicate that perforations increase heat transfer performance without a large frictional power penalty.
The Evolution of Compressor and Turbine Bladings in Gas Turbine Design
Authors: Seippel C.
Published: March 2013

The author, having been associated with the construction of gas turbines from the first 4000-kw unit delivered in 1939 to the city of Neuchaˆtel to the present time, gives some personal views on the evolution of the axial compressor and turbine bladings which are the key elements to the gas turbines. The axial compressor was created to supply air efficiently for the supercharged “Velox” boiler. It made the evolution to the modern gas turbine possible. The main problems encountered were related to the stability of flow. An enormous increase of volume capacity was achieved in the course of time. The increase of pressure ratio made special measures necessary to overcome instability at starting. The expansion turbine started on the basis of steam turbine practice and underwent a parallel evolution to large capacities. Its particular problems are related to the high temperatures of the gases.
The Energy Exchanger, a New Concept for High-Efficiency Gas Turbine Cycles
Authors: Weatherston R. C. , Hertzberg A.
Published: March 2013

A method of circumventing the turbine inlet temperature limitation of present-day gas turbines is presented. This method is based on a direct fluid-to-fluid energy exchanger whereby the available energy of expansion of the hot combustion gas in a gas turbine cycle is transferred directly to a colder gas. The aerodynamic wave processes in several possible modes of operation are examined to determine the inherent limitations in efficiency of direct fluid-to-fluid energy exchange processes. In particular, it is demonstrated that, by using a system of isentropic compression waves to avoid shock losses and by carefully choosing the molecular weights of the fluids utilized in the energy exchanger, perfect energy exchange is possible in principle. When allowances are made for losses due to mixing, leakage, and viscous effects, an energy exchanger utilizing heated combustion air at 3240 deg F to drive steam at 1500 deg F with a potential energy exchange efficiency of 85 percent is feasible. Applications of the air-steam energy exchanger operating in gas turbine cycles utilizing a conservative choice of component efficiencies indicate that thermal efficiencies of gas turbine power cycles of 50–60 percent may be possible.
Methods of Turbocharging With Special Reference to Large Two-Stroke Diesel Engines
Authors: Gyssler G.
Published: March 2013

In view of the steady increase in the mean pressures, the systems employed for turbo-charging diesel engines have been progressively developed. A number of methods have been applied, both to four-stroke and particularly to two-stroke engines. This paper compares the various systems with one another. Trends for future developments are outlined.
Basic Problems in the Formation of Sulfates in Boiler Furnaces
Authors: Reid William T.
Published: March 2013

Reactions involving the formation of sulfates are responsible for most of the problems with external corrosion in boiler furnaces. This paper reviews what is known today about these materials and how they are formed in combustion systems.
High-Temperature Corrosion Studies in an Oil-Fired Laboratory Combustor
Authors: Barrett Richard E.
Published: March 2013

Interaction of sulfur oxides in the combustion gas with furnace elements has been recognized as the major contributor to corrosion and deposits in boilers and gas turbines. These interactions are of two kinds: (a) Catalysis, whereby furnace elements serve as catalytic surfaces to speed the formation of SO3 from SO2 and molecular oxygen, and (b) chemical reaction, whereby the sulfur oxides react chemically with the furnace elements or with deposits on the furnace elements. Catalysis was studied under boiler furnace conditions and the effects of metal composition, temperature, and various coating materials were examined. Some information was also obtained on chemical reactions of sulfur with bare and coated specimens.
Proven Practices in Chemical Control for Steam Power Plants
Authors: Straub F. G.
Published: March 2013

The author has conducted research on boiler water treatment at the University of Illinois and in many steam power plants during the last forty-three years. This research covered the cause and prevention of water soluble and silica deposits in steam turbine, metal losses in the wet steam areas of the steam turbine, metal pickup in the preboiler feedwater cycle, internal corrosion in boiler tubes including oxygen embrittlement. The author reports that with proper control of the water treatment these difficulties can be prevented. He outlines the water treatments used and reports the favorable results obtained in boilers, many of which have operated for over twenty years (600–2600 psi). He also reports on the operation of a large number of boilers which have operated for a similar number of years without requiring internal acid cleaning. These results only cover the operation of conventional boilers with natural and controlled circulation.
Setting the Popping Point of Safety Valves While at Reduced Boiler Pressures
Authors: Nurmi H.
Published: March 2013

This paper discusses a method of setting the popping point of safety valves using a hydraulic cylinder to aid the steam pressure in popping the safety valve. This method has been successfully tested on various boilers ranging in operating pressure from 1500–2700 psig. The ASME Boiler and Pressure Vessel Committee have agreed that this method meets the intent of the Code. Use of the hydraulic cylinder, while at reduced boiler pressures, to set safety valve popping points produces significant economic gains and improves community relations.
Optimization of Contact Grid Spacing for High Solar Flux Photovoltaic Cells
Authors: Beckman W. A.
Published: March 2013

A method for obtaining the optimum gridline spacing for photovoltaic cells operating at high solar fluxes is presented. Using a distributed resistance and diode model of a photovoltaic cell, a differential equation is obtained which relates voltage to position on the cell surface. This equation was solved numerically to obtain the maximum power point efficiency. The maximum power point efficiency is shown to depend upon five dimensionless groups which are combinations of basic cell parameters, geometric parameters, and the solar flux level. The results are presented in graphical form from which the optimum gridline spacing can be obtained for any desired incident solar flux. In addition, the variation in the performance of any specified cell can be obtained from the graphs as a function of the solar flux level.
Coupled Blade-Disk-Shroud Flutter Instabilities in Turbojet Engine Rotors
Authors: Carta F. O.
Published: March 2013

An energy method is used to investigate a flutter instability of turbojet engine rotors which is caused by the interactions between unsteady air loading and the coupled vibration modes of the rotating blade-disk-shroud system. It is shown, analytically, in this parametric study that under certain circumstances the coupling between blade modes permits the transfer of energy from the air to the blade-disk-shroud system, giving rise to a self-excited instability. Both unsteady potential flow theory and empirical data for oscillating airfoils at high incidence are used.
Some Experiments at Low Speed on Compressor Cascades
Authors: Pollard D. , Gostelow J. P.
Published: March 2013

Some results of recent work on low-speed cascade tunnels are described. Preliminary investigations, directed toward the analysis and improvement of the airflow and testing techniques, revealed that, when porous sidewall suction was employed, almost all change in axial velocity occurred within the blade row. Variation of axial velocity ratio, aspect ratio, Reynolds number, and turbulence level for one particular cascade facilitated an explanation of differences between the results of early British and American cascade tests. More recently, work has involved cascade tests on an analytically derived cascade. Good agreement was obtained between theoretical and experimental pressure distributions and profile boundary layers.
Streamline Curvature Computing Procedures for Fluid-Flow Problems
Authors: Novak R. A.
Published: March 2013

An attempt is made in this paper to develop forms of the equation of motion, the continuity equation, and the equations which define the fluid which are amenable to a solution by what has come to be termed “the streamline curvature approach.” The techniques were developed in their present form specifically as a result of the comparatively recent interest in the axial compressor for jet engines. Fluid fields, in general, can be considered to have different energy levels on differing surfaces, to be subject to boundary conditions which impose significant curvature accelerations, and to be rotational. An intelligent exploitation of the possibilities inherent in these degrees of flexibility can very significantly modify and improve the turbomachine; the techniques thereby become adaptable to other situations. It is part of the purpose of this paper to suggest that the technique has become sufficiently mature so that a careful appraisal of its relevance to areas other than turbomachinery is in order.
Summary of Experimental Investigation of Three Axial-Flow Pump Rotors Tested in Water
Authors: Miller M. J. , Crouse J. E. , Sandercock D. M.
Published: March 2013

Three rotors were tested, to study flow and performance across loaded axial-flow blade rows. Principal design parameters varied were flow coefficient (0.29 < φ < 0.45), blade loading parameter at tip (0.25 < Dt < 0.66), and hub-tip radius ratio (0.4 < rh/rt < 0.8). Overall and blade element performances under noncavitating flow conditions are discussed in detail. Comparisons between the measured, three-dimensional design parameters and those computed from two-dimensional cascade correlations are made. A limited amount of performance obtained during operation of the rotors in unstable flow and cavitating flow conditions is presented.
Hydraulic Transients Caused by Reciprocating Pumps
Authors: Streeter V. L. , Wylie E. B.
Published: March 2013

Steady-oscillatory flow, such as that produced by reciprocating pumps, can be analyzed using impedance methods including friction. The actual pulsating flow produced by the pump is combined with the elastic and geometric characteristics of the piping system in the analysis. Fluid compressibility is included in both the pump and pipe system analysis. Experimental confirmation of the theory is given.
Bond Behavior of CFRP Cured Laminates: Experimental and Numerical Investigation
Authors: Naser M. , Hawileh R. , Abdalla J. A. , Al-Tamimi A.
Published: March 2013

The use of externally bonded carbon fiber-reinforced polymers (CFRPs) as strengthening systems to improve the condition and overall capacity of existing reinforced concrete structural members is found to be a promising scheme. This field has drawn the attention of many researchers in the past two decades through the implementation of much theoretical work as well as experimental studies. It was evident through many experimental investigations conducted by a number of researchers that the bond action between fiber-reinforced polymers and reinforced concrete members is considered one of the main factors affecting the performance and reliability of external strengthening systems and warrants further investigation. Debonding failure is a brittle mode of failure that may occur prematurely before strengthened members develop their full composite and expected capacities. This paper aims to investigate the bond behavior between the CFRP-concrete interface via experimental work and finite element (FE) simulations. The experimental study consisted in testing nine concrete prisms with different bonded lengths of the CFRP plates that vary between 25% (60 mm), 50% (120 mm), and 75% (180 mm) of the total length of the concrete prisms and instrumented with strain gauges. A FE simulation model was created and validated using the experimental results of the tested specimens, and a parametric study was carried out to investigate the effect of several parameters on the bond behavior between CFRP and concrete surfaces. The trend of the FE simulation results shows a good agreement with the experimental results and those available in the literature. It was observed that the optimum length of the CFRP plate is in the range between 150 mm and 160 mm when bonded to concrete surfaces. Other conclusions and observations were drawn based on the experimental and numerical results.
Unsteady Conjugate Heat Transfer Analysis of an Immersed Particle Innovative Heat Exchanger
Authors: Nettis Leonardo , De Bellis Fabio , Catalano Luciano A. , Verzicco Roberto
Published: March 2013

The improvement of both heat recovery Joule-Brayton cycles and closed cycle (externally fired) gas turbine plants is strongly limited by the availability of high efficiency heat exchangers. In such a scenario, a nonconventional heat exchanger was recently proposed; this device employs falling solid particles to perform heat transfer between two separate gas flows and was designed with a 1D model neglecting conduction within the particles. Although the experimental reliability of this assumption was already obtained for one particle size, there is no proof available of the quantitative effect introduced by the above mentioned simplification and, more importantly, no indication of when this assumption becomes unacceptable. In this work, direct numerical simulation (DNS) of a solid particle immersed in a gas flow has been performed in order to further validate the hypothesis of negligible conduction and to enhance the design of the proposed heat exchanger. Unsteady conjugate heat transfer has been used to predict the final temperature of the solid sphere for Reynolds numbers ranging from 30 to nearly 300, the computational grid being generated with the immersed boundary (IB) technique. A validation of the study is presented, together with grid independence and boundary independence assessment. The results fully confirmed the worthiness of the initial assumption, with a 1.4% maximum error for high Reynolds conditions (large diameter particles) with respect to the 1D model. Additionally, the code has been employed to explore the influence of the wake in the case of aligned particles, namely, the worst possible situation in terms of efficiency of the heat transfer mechanism. Finally, the discrepancy between the results obtained with an axisymmetric domain and a 3D domain, in terms of final temperature of the particle, have been investigated for the highest Reynolds number, when the flow is supposed to lose its axial symmetry.
Analytical Computation of the Actuator and Cartesian Workspace Boundaries for a Planar 2-Degree-of-Freedom Translational Tensegrity Mechanism
Authors: Chen Samuel , Arsenault Marc
Published: March 2013

Tensegrity mechanisms are interesting candidates for high-acceleration robotic applications since their use of cables allows for a reduction in the weight and inertia of their mobile parts. In this work, a planar two-degree-of-freedom translational tensegrity mechanism that could be used for pick and place applications is introduced. The mechanism uses a strategic actuation scheme to generate the translational motion as well as to ensure that the cables remain taut at all times. Analytical solutions to the direct and inverse kinematic problems are developed, and the mechanism’s workspace boundaries are computed in both the actuator and Cartesian spaces. The influence of the mechanism’s geometry on the size and shape of the Cartesian workspace are then studied. Based on workspace size only, it is found that the optimal mechanism geometry corresponds to a relatively large ratio between the length of the struts and the width of the base and end-effector.
Parametric Investigations of Direct Methanol Fuel Cell Electrodes Manufactured by Spraying
Authors: Koraishy Babar M. , Solomon Sam , Meyers Jeremy P. , Wood Kristin L.
Published: March 2013

Key processing steps in the thin-film process of manufacturing catalyst layers for direct methanol fuel cells are catalyst ink formulation and its application. The catalyst ink is typically composed of supported or unsupported catalysts, binder (ionomer), solvents, and additives. Rheological properties of the ink, amount of binder, and choice of solvents are tuned to match the particular ink application process used to fabricate the electrode, as each coating process has its own unique requirements. Besides affecting the coating process, the choice and ratios of these components can significantly affect the electrochemical performance of the electrode. In this study, catalyst inks are designed and investigated for the spraying process, for utilization in the continuous fabrication of DMFC electrodes. For this purpose, the effect of the binder (ionomer) content on the performance of the electrodes is studied in detail. Decal-transfer electrodes are fabricated on a custom-built automated spraying apparatus with individually specified anode and cathode binder contents, and assembled to form a catalyst coated membrane (CCM) type membrane electrode assembly (MEA). These electrodes are rigorously tested to specifically identify their electrochemical performance, catalyst utilization and electrode morphology.
Optimization of Enclosed Aisle Data Centers Using Bypass Recirculation
Authors: Demetriou Dustin W. , Khalifa H. Ezzat
Published: March 2013

The work presented in this paper describes a simplified thermodynamic model that can be used for exploring optimization possibilities in air-cooled data centers. The model is used to evaluate parametrically the total energy consumption of the data center cooling infrastructure for data centers that utilize aisle containment. The analysis highlights the importance of reducing the total power required for moving the air within the computer room air conditioners (CRACs), the plenum, and the servers, rather than focusing primarily or exclusively on reducing the refrigeration system’s power consumption. In addition, the benefits of introducing a bypass recirculation branch in enclosed aisle configurations are shown. The analysis shows a potential for as much as a 60% savings in cooling infrastructure energy consumption by utilizing an optimized enclosed aisle configuration with bypass recirculation, instead of a traditional enclosed aisle in which all the data center exhaust is forced to flow through the CRACs. Furthermore, computational fluid dynamics is used to evaluate practical arrangements for implementing bypass recirculation in raised floor data centers. A configuration where bypass tiles, with controllable low-lift fans, are placed close to the discharge of CRACs results in increased mixing and is shown to be a suitable method for providing nearly thermally uniform conditions to the inlet of the servers in an enclosed cold aisle. Other configurations of bypass implementation are also discussed and explored.
Thermal Stresses of Through Silicon Vias and Si Chips in Three Dimensional System in Package
Authors: Kinoshita Takahiro , Kawakami Takashi , Hori Tatsuhiro , Matsumoto Keiji , Kohara Sayuri , Orii Yasumitsu , Yamada Fumiaki , Kada Morihiro
Published: March 2013

Thermal conduction and mechanical stresses in through silicon via (TSV) structures in three dimensional system in package (3D SiP) under device operation condition were discussed. A large scale simulator, ADVENTURECluster® based on finite element method (FEM) was used to simulate the effects of voids formed inside Cu TSVs on the thermal conduction and mechanical stresses in the TSV structure. The thermal performance that was required in 3D SiP was estimated to ensure the reliability. Simulations for thermal stresses in the TSV structure in 3D SiP were carried out under thermal condition due to power ON/OFF of device. In case that void was not present inside the TSV, the stresses in TSV were close to the hydrostatic pressure and the magnitude of the equivalent stress was lower than the yield stress of copper. Maximum principal stress of the Si chip in the TSV structure for the case without voids was lower than that of the bending strength of silicon. However, the level of the stresses in the Si chips should not be negligible for damages to Si chips. In case that void was present inside the TSV, stress concentration was occurred around the void in the TSV. The magnitude of the equivalent stress in the TSV was lower than the yield stress of copper. The magnitude of the maximum principal stress of the Si chip was lower than that of the bending strength of silicon. However, its level should not be negligible for damages to TSVs and Si chips. The stress on inner surfaces of Si chip was slightly reduced due to the presence of a void in the TSV.
Numerical Simulations of Electromigration and Stressmigration Driven Void Evolution in Solder Interconnects
Authors: Sadasiva Subramanya , Subbarayan Ganesh , Jiang Lei , Pantuso Daniel
Published: March 2013

Understanding the effect of high current density on void formation and growth and relating the size of the void to the resulting electrical/mechanical failure is a critical need at the present time to ensure reliable functioning of flip-chip packages. In general, toward this end, the modeling and simulation of geometrical evolution of current induced voids have been relatively few. Simulations considering the coupled effects of mass transport through mechanisms of surface and bulk diffusion under the influence of electrical, thermal, and stress fields in solder joints leading to eventual electromigration failure do not appear to be common. In this study, we develop a phase field model for the evolution of voids under electrical, thermal, and stress fields in a flip-chip solder interconnect. We derive the equations of motion for the void accounting for energetic contributions from the active factors of surface energy, stress, and electric potential, considering both surface diffusion and transfer of the material through the bulk of the material. We describe the implementation of this model using a finite element code written in the PYTHON language, coupled with a commercial finite element solver from which we obtain the electrical, thermal, and stress fields driving the void motion. We demonstrate the implemented methodology through simulations of void evolution in flip-chip solder joints under the effects of mechanical/electrical fields and surface/bulk diffusion.
In-rich InGaN thin films: Progress on growth, compositional uniformity, and doping for device applications
Authors: Hoffbauer Mark A. , Williamson Todd L. , Williams Joshua J. , Fordham Julia L. , Yu Kin M. , Walukiewicz Wladek , Reichertz Lothar A.
Published: March 2013

A number of In-rich InGaN films with In contents in the 20–40% range have been grown at moderately low temperatures on sapphire and silicon substrates at high growth rates using a versatile molecular beam epitaxy-type technology that utilizes an energetic beam of N atoms called energetic neutral atom beam lithography and epitaxy to overcome reaction barriers in the group III-nitride system. Extensive characterization results on the crystalline, optical, and electrical properties of the In-rich InGaN materials are reported. It was found that N-rich growth conditions are required to produce materials that have excellent crystallinity, uniform compositions, and bright band edge photoluminescence. For In-rich InGaN growth on sapphire, electrical transport measurements show reasonably low carrier concentrations and high mobilities. Successful p-type doping of In-rich InGaN with ∼20% and ∼40% In contents is demonstrated, and preliminary results on the formation of a p–n junction are reported. For In-rich InGaN growth on Si, the film structural properties are somewhat degraded and carrier concentrations are considerably higher.
Proton beam scattering system optimization for clinical and research applications
Authors: Wroe A. J. , Schulte R. W. , Barnes S. , McAuley G. , Slater J. D. , Slater J. M.
Published: March 2013

Purpose:

To develop and test a method for optimizing and constructing a dual scattering system in passively scattered proton therapy.

Methods:

A beam optics optimization algorithm was developed to optimize the thickness of the first scatterer (S1) and the profile (of both the high‐Z material and Lexan) of the second scatterer (S2) to deliver a proton beam matching a given set of parameters, including field diameter, fluence, flatness, and symmetry. A new manufacturing process was also tested that allows the contoured second scattering foil to be created much more economically and quickly using Cerrobend casting. Two application‐specific scattering systems were developed and tested using both experimental and Monte Carlo techniques to validate the optimization process described.

Results:

A scattering system was optimized and constructed to deliver large uniform irradiations of radiobiology samples at low dose rates. This system was successfully built and tested using film and ionization chambers. The system delivered a uniform radiation field of 50 cm diameter (to a dose of ±7% of the central axis) while the depth dose profile could be tuned to match the specifications of the particular investigator using modulator wheels and range shifters. A second scattering system for intermediate field size (4 cm < diameter < 10 cm) stereotactic radiosurgery and radiation therapy (SRS and SRT) treatments was also developed and tested using GEANT4. This system improved beam efficiency by over 70% compared with existing scattering systems while maintaining field flatness and depth dose profile. In both cases the proton range uniformity across the radiation field was maintained, further indicating the accuracy of the energy loss formalism in the optimization algorithm.

Conclusions:

The methods described allow for rapid prototyping of scattering foils to meet the demands of both research and clinical beam delivery applications in proton therapy.
Draft Genome Sequence of the Actinomycete
Rhodococcus
sp. Strain AW25M09, Isolated from the Hadsel Fjord, Northern Norway
Authors: Hjerde Erik , Pierechod Marcin M. , Williamson Adele K. , Bjerga Gro E. K. , Willassen Nils P. , Smalås Arne O. , Altermark Bjørn
Published: March 2013

The cold-adapted
Rhodococcus
sp. strain AW25M09 was isolated from an Atlantic hagfish caught off the shore of northern Norway as part of an ongoing bioprospecting project that aims to identify novel bacteria with biotechnological potential. Here, we present the 5.8-Mb draft genome sequence, together with details regarding the origin of the strain and its sequence assembly.
Complete Genome Sequence of Clostridium stercorarium subsp.
stercorarium
Strain DSM 8532, a Thermophilic Degrader of Plant Cell Wall Fibers
Authors: Poehlein Anja , Zverlov Vladimir V. , Daniel Rolf , Schwarz Wolfgang H. , Liebl Wolfgang
Published: March 2013

Clostridium stercorarium
strain DSM 8532 is a thermophilic bacterium capable of efficiently degrading polysaccharides in plant biomass and converting the resulting sugars to ethanol and acetate. The complete genome sequence of 2.96 Mbp reveals a multitude of genes for hydrolytic enzymes and enables further study of the organism and its enzymes, and their exploitation for biotechnological processes.
Intellectual disability and mental health problems: a qualitative study of general practitioners’ views
Authors: Fredheim Terje , Haavet Ole Rikard , Danbolt Lars Johan , Kjønsberg Kari , Lien Lars
Published: March 2013

Objectives

To investigate general practitioners’ (GPs) experiences in managing patients with intellectual disabilities (ID) and mental and behavioural problems (MBP).

Design

Qualitative study using in-depth interviews.

Setting

General practice in Hedmark county, Norway.

Participants

10 GPs were qualitatively interviewed about their professional experience regarding patients with ID and MBP. Data were analysed by all authors using systematic text condensation.

Results

The participants’ knowledge was primarily experience-based and collaboration with specialists seemed to be individual rather than systemic. The GPs provided divergent attitudes to referral, treatment, collaboration, regular health checks and home visits.

Conclusions

GPs are in a position to provide evidence-based and individual treatment for both psychological and somatic problems among patients with ID. However, they do not appear to be making use of evidence-based treatment decisions. The GPs feel that they are left alone in decision-making, and find it difficult to find trustworthy collaborative partners. The findings in this study provide useful information for further research in the field.
Cadmium exposure, intercellular adhesion molecule-1 and peripheral artery disease: a cohort and an experimental study
Authors: Fagerberg Björn , Bergström Göran , Borén Jan , Barregard Lars
Published: March 2013

Objectives

Cadmium exposure has been found to be associated with atherosclerotic plaques in the carotid arteries and with circulating levels of the proatherogenic intercellular adhesion molecule-1 (ICAM-1). The research questions were (1) if blood and urinary cadmium levels are associated with low ankle-brachial index (ABI) as a measure of peripheral artery disease in a longitudinal study and (2) if ICAM-1 mediates proatherogenic effects of cadmium exposure.

Design

A prospective, observational cohort study with a 5-year follow-up and an experimental study of cultured human aortic endothelial cells exposed to cadmium.

Setting

Research unit at a university hospital.

Participants

A cohort of 64-year-old women (n=489) recruited by stratified sampling of similarly sized groups with normal, impaired and diabetic glucose tolerance as assessed in a population-based screening examination.

Primary and secondary outcome measures

ABI (ratio of the systolic blood pressures in the tibial and brachial arteries ≤0.9 in any artery) in relation to cadmium exposure; ICAM-1 concentrations in the cell culture medium after cadmium incubation.

Results

High (tertile 3 vs 1) concentrations of blood (B-Cd) or creatine-adjusted urinary cadmium (U-Cd) at baseline were found to predict low ABI after adjustment for smoking and other cardiovascular risk factors at baseline. For U-Cd the OR was 2.5 (95% CI 1.1 to 5.8). After exclusion of participants with ultrasound-assessed femoral atherosclerosis at baseline the OR for U-Cd was unchanged, and for B-Cd it was 3.7 (95% CI 1.05 to 13.3). Inclusion of serum ICAM-1 levels did not affect the cadmium-related ORs in multivariate analyses. The experimental study did not show any cadmium-induced increase of the production of ICAM-1 from human endothelial cells.

Conclusions

Cadmium exposure was associated with future peripheral artery disease, supporting the concept that cadmium exposure in the population has proatherogenic effects, although ICAM-1 mediated effects do not seem to be involved.
Protease inhibitors and cardiac autonomic function in HIV-infected patients: a cross-sectional analysis from the Strategies for Management of Antiretroviral Therapy (SMART) Trial
Authors: Soliman Elsayed Z , Roediger Mollie P , Duprez Daniel A , Knobel Hernando , Elion Richard , Neaton James D ,   for the INSIGHT SMART Study Group
Published: March 2013

Objective

To compare cardiac autonomic function as measured by heart rate variability for HIV-infected participants taking protease inhibitors (PIs) with those taking a non-nucleoside reverse transcriptase inhibitor without a PI (NNRTI-no PI) regimen.

Design

Cross-sectional analysis.

Setting

Multicentre study.

Participants

2998 participants (average age 44 years, 28% females) enrolled in the Strategies for Management of Antiretroviral Therapy (SMART) trial.

Primary outcome measures

Heart rate and two heart rate variability measures (the SD of all filtered RR intervals over the length of the recording (SDNN) and the root mean square of successive differences in normal RR intervals (rMSSD)).

Results

At study entry, 869 participants were taking a boosted PI (PI/r), 579 a non-boosted PI and 1550 an NNRTI-no PI. Median values (IQR) of heart rate, SDNN and rMSSD were: 68 (60–75) beats/min (bpm), 21 (13–33) ms, 22 (13–35) ms in the PI/r group, 68 (60–75) bpm, 21 (13–33) ms and 21 (14–33) ms in the non-boosted PI group and 69 (62–77) bpm, 20 (13–31) ms and 21(13–33) ms in the NNRTI-no PI group. After adjustment for baseline factors, for those given PI/r and non-boosted PI, heart rate was 2.2 and 2.8 bpm, respectively, lower than the NNRTI-no PI group (p<0.001 for both). On the other hand, compared with the NNRTI-no PI group, log SDNN and log rMSSD were significantly greater for those in the non-boosted PI (p values for baseline adjusted differences in log-transformed SDNN and rMSSD were 0.004 and 0.001) but not for those in the PI/r group at the 0.01 α-level.

Conclusions

Compared to an NNRTI-no PI regimen, heart rate was lower for those taking a PI/r or non-boosted PI and heart rate variability was greater, reflecting better cardiac autonomic function, for those taking a non-boosted PI regimen but not PI/r.
Emergency department diagnosis and treatment of traumatic hip dislocations in children under the age of 7 years: a 10-year review
Authors: Bressan Silvia , Steiner Ivan Peter , Shavit Itai
Published: March 2013

Background and aims

Traumatic hip dislocations (THD) are uncommon in children. They constitute true emergencies because unrecognised THD leads to avascular necrosis (AVN) of the femoral head. This review presents the evidence for best practice for the diagnosis and treatment of THD in the emergency department (ED) of children under the age of 7 years.

Methods

Searches for the period 2002–2012 were performed in PubMED, Cochrane database, EMBASE, Google Scholar and hand search.

Results

Twenty-five case reports and case series articles were identified, 53 described children with acute and 23 with neglected THD. Overall, 42 (55%) were male and 73 (96%) sustained a posterior dislocation. Forty-eight (63%) had THD following a low-energy trauma. Eight (11%) reported associated injuries. Twenty-one (39.6%) acute dislocations were reduced in the ED without complications. AVN was identified in 3 (5.7%) children, who underwent reduction ≥10 h after dislocation. Redislocation occurred in 3 (5.7%) children and coxa magna developed in 5 (9.4%). Long-term functional outcome of 42 patients resulted in full recovery, and it was fair to good in 3 (including 2 children with AVN). All neglected cases (≥4 weeks from trauma) needed open reduction in the operating room (OR). AVN was identified in 11 children (47.8%). Hip function was completely recovered in 16 (70%) patients.

Conclusions

THD in this age group mainly occurs with low-energy trauma and leads to posterior dislocations. Urgent closed reduction of acute cases are done in the OR, or the ED. ED reduction appears to be safe. Neglected THDs need open reduction.
Balloon-assisted guide catheter positioning to overcome extreme cervical carotid tortuosity: technique and case experience
Authors: Peeling Lissa , Fiorella David
Published: March 2013

Background and significance

We describe a method by which to efficiently and atraumatically achieve distal positioning of a flexible guiding catheter beyond extreme cervical tortuosity using a hypercompliant temporary occlusion balloon.

Methods

A retrospective review of a prospective neuroendovascular database was used to identify cases in which a hypercompliant balloon catheter (Hyperform or Hyperglide, ev3/Covidien, Irvine, California, USA; Scepter or Scepter XC, Alisa Viejo, California, USA) was used to achieve distal positioning of a flexible guiding catheter (Navion, ev3/Covidien, Irvine, California, USA; Neuron, Penumbra Inc, Alameda, California, USA). After achieving a stable guiding sheath position within the proximal cervical carotid artery, a hypercompliant balloon catheter was manipulated beyond the tortuous cervical internal carotid segment into the distal carotid artery. The balloon was then inflated to anchor it distally within an intracranial (cavernous or petrous) segment of the internal carotid artery. The guiding catheter was then advanced beyond the tortuous cervical segment, over the balloon catheter, as gentle counter traction was applied to the balloon.

Results

Balloon-assisted guiding catheter placement was used to perform endovascular treatments of 12 anterior circulation aneurysms. One patient underwent coiling alone. Five patients underwent balloon-assisted coiling. One patient underwent balloon and stent assisted coil embolization. Four patients with five carotid aneurysms (one with bilateral carotid aneurysms) underwent vascular reconstruction with the pipeline embolization device. All patients had severe tortuosity of the extracranial carotid system. Three patients had findings consistent with cervical carotid fibromuscular dysplasia. The technique was successful each time it was attempted. No parent artery dissections or catheter induced vasospam were noted in any case.

Discussion

Hypercompliant balloon catheters can be reliably used to facilitate safe and rapid distal positioning of flexible guiding catheters beyond severe cervical tortuosity.
Effect of particle fabric on the coefficient of lateral earth pressure observed during one-dimensional compression of sand
Authors: Northcutt Sheri , Wijewickreme Dharma
Published: March 2013

The effect of initial particle fabric on the one-dimensional compression response of Fraser River sand was investigated. One-dimensional compression with lateral stress measurement was carried out on reconstituted Fraser River sand specimens using an instrumented oedometer. Laboratory specimens were reconstituted by air pluviation, tamping, and vibration and were prepared with an initial relative density ranging from medium loose to very dense. For Fraser River sand in one-dimensional compression, air-pluviated specimens yielded the highest values for the coefficient of lateral earth pressure at rest (Ko), tamped specimens produced the lowest Kovalues, and vibrated specimens produced intermediate Kovalues. The results from the present study demonstrate that specimens resulting from different laboratory reconstitution methods (i.e., different initial particle fabrics) exhibit different one-dimensional compression responses and produce different Kovalues. A “fabric factor” was introduced to account for the effect of the initial particle fabric on the measured coefficient of lateral earth pressure at rest. Using the fabric factor, the constant volume friction angle, and the specimen relative density, a new empirical equation defining the coefficient of lateral earth pressure at rest during normally consolidated loading is proposed.
Comparative analysis of multiplicity of target fragments in a few A GeV 4He–emulsion interactions
Authors: Abdelsalam A. , Metwalli N. , Kamel S. , Aboullela M. , Badawy B.M. , Abdallah N.
Published: March 2013

We report an experimental measurement on the multiplicity of slow target-associated particles in the forward and backward hemispheres in the interactions of 4He ions with emulsion nuclei at 2.1A and 3.7A GeV. The results indicate that the target fragment multiplicity does not depend on the incident kinetic energy. The dominant feature characterizing the multiplicity distributions of black and grey particles, in both forward and backward hemispheres, is exponential decay shaped curves, with the exception of the most central collisions and heavy target sizes. The results favor the nuclear limiting fragmentation hypothesis in the energy range beyond 1 GeV.
From likes to dislikes: conditioned taste aversion in the great pond snail (Lymnaeastagnalis)
Authors: Ito E. , Kojima S. , Lukowiak K. , Sakakibara M.
Published: March 2013

The neural circuitry comprising the central pattern generator (CPG) that drives feeding behavior in the great pond snail (Lymnaea stagnalis (L., 1758)) has been worked out. Because the feeding behavior undergoes associative learning and long-term memory (LTM) formation, it provides an excellent opportunity to study the causal neuronal mechanisms of these two processes. In this review, we explore some of the possible causal neuronal mechanisms of associative learning of conditioned taste aversion (CTA) and its subsequent consolidation processes into LTM in L. stagnalis. In the CTA training procedure, a sucrose solution, which evokes a feeding response, is used as the conditioned stimulus (CS) and a potassium chloride solution, which causes a withdrawal response, is used as the unconditioned stimulus (US). The pairing of the CS–US alters both the feeding response of the snail and the function of a pair of higher order interneurons in the cerebral ganglia. Following the acquisition of CTA, the polysynaptic inhibitory synaptic input from the higher order interneurons onto the feeding CPG neurons is enhanced, resulting in suppression of the feeding response. These changes in synaptic efficacy are thought to constitute a “memory trace” for CTA in L. stagnalis.
A first exploration of genome size diversity in sponges
Authors: Jeffery Nicholas W. , Jardine Catherine B. , Gregory T. Ryan
Published: March 2013

The phyla known as early-branching lineages of animals have become the subject of increasing interest from the perspectives of genomics and evolutionary biology. Unfortunately, data on even the most fundamental properties of their genomes, such as genome size, remain very scarce. In this study, genome size estimates are reported for 75 species of sponges (phylum Porifera) representing 33 families and 12 orders, marking the first large survey of genome size diversity for an early-branching phylum. Sponge genome sizes averaged around 0.2 pg but exhibited a 17-fold range overall (0.04–0.63 pg). In addition, the results of comparisons of two methods of genome size quantification (flow cytometry and Feulgen image analysis densitometry) are presented, thereby facilitating future work on these animals. Some particularly promising avenues for future investigation are highlighted.
Miniature inverted-repeat transposable elements: discovery, distribution, and activity
Authors: Fattash Isam , Rooke Rebecca , Wong Amy , Hui Caleb , Luu Tina , Bhardwaj Priyanka , Yang Guojun
Published: March 2013

Eukaryotic organisms have dynamic genomes, with transposable elements (TEs) as a major contributing factor. Although the large autonomous TEs can significantly shape genomic structures during evolution, genomes often harbor more miniature nonautonomous TEs that can infest genomic niches where large TEs are rare. In spite of their cut-and-paste transposition mechanisms that do not inherently favor copy number increase, miniature inverted-repeat transposable elements (MITEs) are abundant in eukaryotic genomes and exist in high copy numbers. Based on the large number of MITE families revealed in previous studies, accurate annotation of MITEs, particularly in newly sequenced genomes, will identify more genomes highly rich in these elements. Novel families identified from these analyses, together with the currently known families, will further deepen our understanding of the origins, transposase sources, and dramatic amplification of these elements.
QUANTUM COSMOLOGY: SUSY'S STAGE
Authors: MONIZ PAULO VARGAS
Published: March 2013

This report comprises two parts. On the one hand, I will, based on the talks at the CM4 parallel session "Quantum Cosmology and Quantum Effects in the Early Universe" which I chaired, point to interesting recent developments in quantum cosmology. On the other hand, some of the basics of supersymmetric quantum cosmology are briefly reviewed, pointing to promising lines of research to explore. I will start with the latter, finishing the report with the former.
RADO'S CONJECTURE IMPLIES THAT ALL STATIONARY SET PRESERVING FORCINGS ARE SEMIPROPER
Authors: DOEBLER PHILIPP
Published: March 2013

Todorčević showed that Rado's Conjecture (RC) implies CC*, a strengthening of Chang's Conjecture. We generalize this by showing that also CC**, a global version of CC*, follows from RC. As a corollary we obtain that RC implies Semistationary Reflection and (†), i.e. the statement that all forcings that preserve the stationarity of subsets of ω1 are semiproper.
Developing our world views
Authors: Pearson Jennifer , Robinson Simon
Published: March 2013

This forum looks at how the fields of interaction design and HCI can extend to cover "developing" communities around the world, ones that are gaining access to digital technology for the first time.

Gary Marsden, Editor