bluuebunny/crossref_metadata_2025 huggingface dataset:
An initial investigation on torsional properties of nickel‐titanium instruments produced with a new manufacturing method
Authors: Gambarini Gianluca , Pompa Giorgio , Di Carlo Stefano , De Luca Massimo , Testarelli Luca
Published: November 2008

A new manufacturing process involving twisting of a ground blank combined with heat treatment has been recently developed to produce nickel‐titanium rotary files for root canal preparation. The aim of this study was to compare torsional resistance of prototype instruments produced using the new manufacturing method versus traditional nickel‐titanium instruments produced by the customary grinding process. Twenty prototypes instruments of the same design and dimensions were divided in two groups of 10 each, according to the different manufacturing method. A file‐testing apparatus specifically designed to perform torsional testing was used in accordance with the International Organization for Standardization 3630‐1. The results indicated that instruments manufactured by the new manufacturing process demonstrated significantly higher average maximum torque levels than those manufactured by the existing grinding process (P < 0.05). Since instruments design and dimensions of the instruments were the same, the different manufacturing process could be the only explanation for this improvement in torsional resistance.
Factors associated with low vitamin D status of Australian alpacas
Authors: Judson GJ , McGregor BA , Partington DL
Published: November 2008

Objective To investigate factors associated with low vitamin D status of alpacas at pasture in southern Australia.

Design A 2‐year survey of alpacas from two farms in South Australia and three in Victoria. Blood samples were collected from 20 to 30 alpacas on each farm on five occasions each year. Breed, gender, age and fleece colour of animals were recorded.

Method Blood samples were assayed for plasma 2.5‐hydroxycholecalciferol (25‐OH D3) and plasma inorganic phosphorus (Pi). Data sets from 802 animal samples were analysed by multiple regression to determine variables associated with low vitamin D status of alpacas. The relationship between plasma 25‐OH D3and plasma Pi was also investigated.

Results Vitamin D status was significantly affected by month of sampling, with low values in late winter and high values in summer. Plasma vitamin D concentrations increased with age, were higher in alpacas with light fleeces than in those with dark fleeces and were also higher in the Suri than in the Huacaya breed. Plasma Pi concentrations were generally lower in alpacas with plasma 25‐OH D3values < 25 nmol/L.

Conclusions Young alpacas with dark fleeces are most at risk from vitamin D insufficiency in late winter in southern Australia. The present study indicates that plasma Pi values are not a reliable indicator of vitamin D status of alpacas as assessed by plasma 25‐OH D3concentrations.
Human flora‐associated rodents – does the data support the assumptions?
Authors: Silley Peter
Published: November 2008

There is little direct literature detailing exhaustive bacteriological studies comparing human donor faecal flora, human flora‐associated (HFA) mouse models and conventional rodent faecal flora. While there is a premise that the implanted donor faecal flora from humans is established in the rodent model the evidence is incomplete and indeed for groups such as Bifidobacterium spp. it is lacking. The reviewed bacteriology studies are generally lacking in detail with the exception of one study from which the data have mostly been overlooked when cited by other workers. While there are studies that suggest that the HFA rodent model is more relevant to man than studies with conventional rodents, the hypothesis remains to be proven. This review concludes that the established microbial flora in the HFA rodent model is different to that of donor human faecal flora, and this clearly raises the question as to whether this matters, after all a model is a model and as such models can be useful even should they fail to be a true representation of, in this case, the gastrointestinal tract. What matters is that there is a proper understanding of the limitations of the model as we attempt to unravel the significance of the components of the gastrointestinal flora in health and disease; examples of why such an analysis is important are provided with regard to obesity and nutritional studies. The data do unsurprisingly suggest that diet is an extremely influential variable when interpreting HFA and conventional rodent data. The microbiology data from direct bacteriology and indirect enzyme studies show that the established microbial flora in the HFA rodent model is different to that of donor human faecal flora. The significance of this conclusion remains to be established.
Guidelines for forensic assessment of natural unexpected cardiovascular death
Authors: Yang Kyung‐Moo , Lee Sang‐Yong , Kim Yoon‐Shin , Seo Joong‐Seok , Lee Yoon Seong , Seo Jeong‐Wook
Published: November 2008

Sudden unexpected deaths due to cardiovascular diseases make up almost half of all natural deaths. Practical guidelines are needed for forensic autopsy practice in cases of natural unexpected deaths due to ischemic heart disease or other cardiovascular diseases in Korea. An evaluation of the clinical history is the first step, including the collection of all available information on the subject. As a standard autopsy procedure, every subsystem of the heart and vessels should be thoroughly studied including the coronary arteries, the myocardium, the cardiac valves, and the conducting system. In addition, histological, toxicological, biochemical and molecular analysis need to be applied to the detection of myocardial infarction from the medico‐legal point of view. Also important is the assessment of risk factors for natural unexpected cardiac death (NUCD) in order to establish a cause–effect relationship. There are three groups of ischemic conditions of heart leading to NUCD, those being acute myocardial infarction, atherosclerotic heart disease and critical coronary atherosclerosis. Additionally, there are practical concerns on formulating the report. Pathologists may use sudden cardiac death or NUCD as a main diagnosis when there is no alternative diagnosis, though they would do better to comment on conditions contributing to the death. Finally, pathologists should be encouraged to suspect unexplained causes of death in order to find clearer answers.
Film-Cooling on a Gas Turbine Blade Pressure Side or Suction Side With Compound Angle Shaped Holes
Authors: Gao Zhihong , Narzary Diganta P. , Han Je-Chin
Published: November 2008

The film-cooling effectiveness on the surface of a high pressure turbine blade is measured using the pressure sensitive paint technique. Compound angle laidback fan-shaped holes are used to cool the blade surface with four rows on the pressure side and two rows on the suction side. The coolant injects to one side of the blade, either pressure side or suction side. The presence of wake due to the upstream vanes is simulated by placing a periodic set of rods upstream of the test blade. The wake rods can be clocked by changing their stationary positions to simulate progressing wakes. The effect of wakes is recorded at four phase locations along the pitchwise direction. The freestream Reynolds number, based on the axial chord length and the exit velocity, is 750,000. The inlet and exit Mach numbers are 0.27 and 0.44, respectively, resulting in a pressure ratio of 1.14. Five average blowing ratios ranging from 0.4 to 1.5 are tested. Results reveal that the tip-leakage vortices and endwall vortices sweep the coolant on the suction side to the midspan region. The compound angle laidback fan-shaped holes produce a good film coverage on the suction side except for the regions affected by the secondary vortices. Due to the concave surface, the coolant trace is short and the effectiveness level is low on the pressure surface. However, the pressure side acquires a relatively uniform film coverage with the multiple rows of cooling holes. The film-cooling effectiveness increases with the increasing average blowing ratio for either side of coolant ejection. The presence of stationary upstream wake results in lower film-cooling effectiveness on the blade surface. The compound angle shaped holes outperform the compound angle cylindrical holes by the elevated film-cooling effectiveness, particularly at higher blowing ratios.
Numerical Investigations of the Coupled Flow Through a Subsonic Compressor Rotor and Axial Skewed Slot
Authors: Lu Xingen , Chu Wuli , Zhu Junqiang , Zhang Yangfeng
Published: November 2008

In order to advance the understanding of the fundamental mechanisms of axial skewed slot casing treatment and their effects on the subsonic axial-flow compressor flow field, the coupled unsteady flow through a subsonic compressor rotor and the axial skewed slot was simulated with a state-of-the-art multiblock flow solver. The computational results were first compared with available measured data, that showed the numerical procedure calculates the overall effect of the axial skewed slot correctly. Then, the numerically obtained flow fields were interrogated to identify the physical mechanism responsible for improvement in stall margin of a modern subsonic axial-flow compressor rotor due to the discrete skewed slots. It was found that the axial skewed slot casing treatment can increase the stall margin of subsonic compressor by repositioning of the tip clearance flow trajectory further toward the trailing of the blade passage and retarding the movement of the incoming∕tip clearance flow interface toward the rotor leading edge plane.
Interstage Flow Interactions and Loss Generation in a Two-Stage Shrouded Axial Turbine
Authors: Porreca L. , Kalfas A. I. , Abhari R. S. , Yun Y. I. , Song S. J.
Published: November 2008

The aerodynamics and kinematics of flow structures, including the loss generation mechanisms, in the interstage region of a two-stage partially shrouded axial turbine are examined. The nonaxisymmetric partial shroud introduces highly three-dimensional unsteady interactions, the details of which must be understood in order to optimize the design of the blade/shroud. Detailed measurements of the steady and unsteady pressure and velocity fields are obtained using a two-sensor fast response aerodynamic probe and stereoscopic particle image velocimetry. These intrusive and nonintrusive measurement techniques yield a unique data set that describes the details of the flow in the interstage region. The measurements show that a highly three-dimensional interaction occurs between the passage vortex and a vortex caused by the recessed shroud platform design. Flow coming from the blade passage suddenly expands and migrates radially upward in the cavity region, causing a localized relative total pressure drop. Interactions of vortex and wake structures with the second stator row are analyzed by means of the combination of the measured relative total pressure and nondeterministic pressure unsteadiness. The analysis of the data gives insight on unsteady loss mechanisms. This study provides improved flow understanding and suggests that the design of the blade/shroud and second stator leading edge may be further improved to reduce unsteady loss contribution.
Effects of Obstructions and Surface Roughness on Film Cooling Effectiveness With and Without a Transverse Trench
Authors: Somawardhana Ruwan P. , Bogard David G.
Published: November 2008

Recent studies have shown that film cooling with holes embedded in a shallow trench significantly improves cooling performance. In this study, the performance of shallow trench configurations was investigated for simulated deteriorated surface conditions, i.e., increased surface roughness and near-hole obstructions. Experiments were conducted on the suction side of a scaled-up simulated turbine vane. Results from the study indicated that as much as 50% degradation occurred with upstream obstructions, but downstream obstructions actually enhanced film cooling effectiveness. However, the transverse trench configuration performed significantly better than the traditional cylindrical holes, both with and without obstructions and almost eliminated the effects of both surface roughness and obstructions.
Aerothermal Investigations of Tip Leakage Flow in Axial Flow Turbines—Part II: Effect of Relative Casing Motion
Authors: Krishnababu S. K. , Dawes W. N. , Hodson H. P. , Lock G. D. , Hannis J. , Whitney C.
Published: November 2008

A numerical study has been performed to investigate the effect of casing motion on the tip leakage flow and heat transfer characteristics in unshrouded axial flow turbines. The relative motion between the blade tip and the casing was simulated by moving the casing in a direction from the suction side to the pressure side of the stationary blade. Base line flat tip geometry and squealer type geometries, namely, double squealer or cavity and suction side squealer, were considered at a clearance gap of 1.6%C. The computations were performed using a single blade with periodic boundary conditions imposed along the boundaries in the pitchwise direction. Turbulence was modeled using the shear stress transport k-ω model. The flow conditions correspond to an exit Reynolds number of 2.3×105. The results were compared to those obtained without the relative casing motion reported in Part I of this paper. In general, the effect of relative casing motion was to decrease the tip leakage mass flow and the average heat transfer to the tip due to the decrease in leakage flow velocity caused by a drop in driving pressure difference. Compared to the computations with stationary casing, in the case of all the three geometries considered, the average heat transfer to the suction surface of the blade was found to be larger in the case of the computations with relative casing motion. At a larger clearance gap of 2.8%C, in case of a flat tip, while the tip leakage mass flow decreased due to relative casing motion, only a smaller change in the average heat transfer to the tip and the suction surface of the blade was noticed.
Hamiltonian Chaos in a Model Alveolus
Authors: Henry F. S. , Laine-Pearson F. E. , Tsuda A.
Published: November 2008

In the pulmonary acinus, the airflow Reynolds number is usually much less than unity and hence the flow might be expected to be reversible. However, this does not appear to be the case as a significant portion of the fine particles that reach the acinus remains there after exhalation. We believe that this irreversibility is at large a result of chaotic mixing in the alveoli of the acinar airways. To test this hypothesis, we solved numerically the equations for incompressible, pulsatile, flow in a rigid alveolated duct and tracked numerous fluid particles over many breathing cycles. The resulting Poincaré sections exhibit chains of islands on which particles travel. In the region between these chains of islands, some particles move chaotically. The presence of chaos is supported by the results of an estimate of the maximal Lyapunov exponent. It is shown that the streamfunction equation for this flow may be written in the form of a Hamiltonian system and that an expansion of this equation captures all the essential features of the Poincaré sections. Elements of Kolmogorov–Arnol’d–Moser theory, the Poincaré–Birkhoff fixed-point theorem, and associated Hamiltonian dynamics theory are then employed to confirm the existence of chaos in the flow in a rigid alveolated duct.
LSM Cathodes Infiltrated With Er2O3 Stabilized Bi2O3
Authors: Zhang Q. S. , Hirano A. , Imanishi N. , Takeda Y. , Yamahara K.
Published: November 2008

The La0.8Sr0.2MnO3 perovskite oxide (LSM) electrode was infiltrated with Er2O3 stabilized Bi2O3 (ESB) to improve the cathode performance of intermediate temperature solid oxide fuel cells. ESB infiltration was carried out by dropping the nitrate solution of Bi(NO3)3 and Er(NO3)3 (80:20mol ratio) on the LSM electrode surface prepared on yttria stabilized zirconia by screen-printing technique. The electrode performance of the infiltrated LSM electrode was studied by electrochemical impedance spectroscopy (EIS) analysis in open air. The EIS results showed that the electrode resistance was drastically decreased by the infiltration of Bi(NO3)3–Er(NO3)3 solution into the LSM electrode; the electrode resistance was as low as 2.31Ωcm2 for the infiltration LSM cathode at 600°C, which was compared with ∼380Ωcm2 for the noninfiltrated LSM cathode. The low electrode resistance could be explained by the formation of high oxide ion conductivity Er2O3-doped Bi2O3 on the LSM particles.
Characterization of Anode-Supported Solid Oxide Fuel Cells With PSCF Cathode
Authors: Haanappel V. A. C. , Mai A. , Uhlenbruck S. , Tietz F.
Published: November 2008

A systematic study was initiated of anode-supported single cells with Pr0.58Sr0.4Co0.2Fe0.8O3−δ (PSCF) cathode. These solid oxide fuel cells (SOFCs) were characterized by electrochemical and diffusion and permeation measurements. In particular, the influence of various sintering temperatures of the cathode and various types of Ce0.8Gd0.2O2−δ (CGO) interlayer was investigated in more detail. Results from electrochemical measurements performed between 650°C and 800°C showed that the performance of anode-supported SOFCs with screen-printed porous CGO interlayer and a PSCF cathode was excellent. Even at 650°C, the area-specific resistance was lower than 0.5Ωcm2. The microstructure of the cathode and the performance of this type of SOFC were not obviously affected by variations in the sintering temperature of the cathode. Higher electrochemical performance, in particular, in the temperature range 650–750°C, was achieved by applying a thin and dense CGO interlayer using reactive sputtering or electron beam physical vapor deposition.
Thermofluid-Dynamic Analysis of Circular-Planar Type Intermediate-Temperature Solid Oxide Fuel Cells
Authors: Campanari Stefano , Iora Paolo , Lucchini Andrea , Romano Matteo
Published: November 2008

This work presents a computational thermofluid-dynamic analysis of circular-planar type intermediate-temperature solid oxide fuel cells (SOFCs), based on the Hexis design. A single cell, representative of the average conditions of a real stack, is simulated in detail considering the real anode and cathode channel design, featuring an array of square pegs supporting the interconnection layers. The analysis is developed starting from cell operating data assumed from real test experimental information for an anode-supported SOFC with a 100cm2 active area, fed with pure hydrogen, and is extended to different reactant flow rates and generated heat flux power densities to evidence a generalized correlation for the thermofluid-dynamic behavior of the fuel cell under variable operating conditions. Aiming to provide a set of general results for the calculation of the heat transfer coefficient, which is applicable for the purpose of a complete thermal and electrochemical finite volume analysis, the simulation calculates local temperature distributions depending on radial and angular positions. The fluid-dynamic analysis evidences the existence of preferential flow paths and nonuniformity issues of the gas flow field, which may affect significantly the cell performances, and indicates possible cell design improvements.
A Full Scale Microcontroller Based Direct Methanol Fuel Cell Test Station
Authors: Shakeri M. , Imen J. , Rostami M. R.
Published: November 2008

The development of a direct methanol fuel cell requires a fully automatic test station for understanding its characteristic and behavior. A unique design of test station for operation of a cell or stack among 0.5W and 1.5kW has been designed and fabricated at Fuel Cell Research Technology Group in Babol University of Technology. The control unit of the test station is based on a microcontroller. The control unit is designed and fabricated for the test station to perform the test standalone. This control unit is programed to control the test station completely and independently. For data acquisitions in long time, manual control of the test, input initial set point and controllable parameter values, drawing desired curve, and microcontroller calibration, a computer software with graphical user interface is added to the system in order to drive the test station. The test station has been in operation approximately 1200h. The dynamic and stationary behaviors of the cell and/or stack dependent on the process parameters were controlled and measured by the test station.
La
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Sr
0.2

Co
0.8

Fe
0.2

O
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Nanoparticles Formed in Micropores of La0.8Sr0.2MnO3–Yttria Stabilized Zirconia Cathodes
Authors: Zhang Q. S. , Hirano A. , Matsumura T. , Imanishi N. , Takeda Y. , Yamahara K.
Published: November 2008

La 0.8 Sr 0.2 Co 0.8 Fe 0.2 O 3 (LSCF) nanoparticles are formed in micropores of La0.8Sr0.2MnO2(LSM)-yttria stabilized zirconia (YSZ) cathodes by reaction-infiltration method. Bismuth nitrate is added in the precursor nitrate solution for LSCF as the reaction promoter. The LSCF phase is observed at 600°C by the addition of bismuth nitrate, and about 100nm particle size LSCF(Bi) is homogenously distributed on the LSM-YSZ surface. The electrode impedance of LSM-YSZ/YSZ/LSM-YSZ cells is examined and has found that the electrode polarization resistance is extremely reduced by the LSCF(Bi) infiltration in LSM-YSZ. The performance of the anode support fuel cell of Ni-YSZ/YSZ/LSM-YSZ is examined at 700°C. The LSCF(Bi) infiltrated LSM-YSZ cathode significantly enhanced the cell performance with a 97%H2-3%H2 fuel at 700°C. The maximum power density of 0.35W∕cm2 is attended.
Experimental Investigation on the Process-Induced Damage of a Direct Methanol Fuel Cell Assembled by the Printed Circuit Board Technique
Authors: Kuan Yean-Der , Chang Chia-Hao
Published: November 2008

The printed circuit board (PCB)-based direct methanol fuel cell (DMFC) package is a novel manufacturing and assembly process, which is full potential in mass production, and very limited literatures make study on the effects of the related process parameters. The hot press is a necessary and key process to make the PCB package, i.e., the key component of a DMFC, membrane electrode assemblies (MEA), needs to sustain a severe test. In order to minimize the process-induced damage of the MEAs, it is important to make a good control on the process parameters. Therefore, the objective of this paper is to present a methodology to explore a good combination of hot-press parameters. The considered parameters include the compression ratio of the MEA, heating time, heating temperature, and hot pressing pressure acting on the MEA. During the experimental investigation, a series of experiments was made first to discuss the effect of the individual parameter of the hot-press process on the MEA performance, wherein a reasonable range of each process parameter condition was able to be well defined. Moreover, the Taguchi experimental method was adopted to explore the parameter effects on the DMFC performance during the digital packaging process and to determine the best combination of parameter conditions. At the end, a MEA was made a hot press under the best parameter combination, which could verify the result obtained from Taguchi’s experiments. The result is able to be an important reference for the future manufacturing design guideline of PCB-based DMFC package.
Influence of Flow Channel Design on the Flow Pressure Drop and the Performance of Direct Methanol Fuel Cells
Authors: Hwang Yong-Sheen , Cha Suk-Won , Choi Hoon , Lee Dae-Young , Kim Seo Young
Published: November 2008

We investigated the optimum flow channel design for direct methanol fuel cells (DMFCs). Especially, we explored the effect of the pressure drop across the inlet and outlet on the performance of the DMFCs with various flow channel designs. In DMFC systems, the optimization of such parameters are critical to minimize the power usage by the auxiliary devices, such as fuel pump and blowers. In this paper, we present how the pressure drop control may determine the optimal driving point of the DMFC stack. Also, we show how the optimal fuel utilization ratio may be achieved, without degrading the performance of DMFC stacks. Overall, we discuss how the flow channel design affects the selection of the balance of plant (BOP) components, the design of the DMFC system, and the efficiency of the entire system.
Registration Using Multiplanar Structures for Augmented Reality Systems
Authors: Tao Guan , Lijun Li , Cheng Wang
Published: November 2008

This paper illustrates a novel registration method for augmented reality systems based on multiplanar structures and natural feature tracking. Our method distinguishes itself from other methods in the following ways: First, our method can use arbitrary multiple planes without any information on the physical relationship of the planes. Second, we put forward a new method to establish the world coordinate system. Compared with the traditional method, our approach needs only three noncollinear points of the real world and really enhances the usability of our system. Third, we propose novel classification based local and global tracking strategies to match features between reference images and the current frame directly. Our method casts off the requirement that the initial camera position should be close to the reference images while overcoming the problem of error accumulation. Some experiments have been carried out to demonstrate the validity of the proposed approach.
Operational Space Calibration for Remote Welding Based on Surface Tracking With Shared Force Control
Authors: Wei Xiuquan , Li Haichao , Gao Hongming , Wu Lin
Published: November 2008

This paper presents a novel operational space calibration approach for robotic remote welding based on surface tracking with shared force control. A human-machine shared force controller is designed to combine manual control with local force control. A position-based force control strategy for surface tracking on the constrained motion plane is adopted. A precise method to measure the contact point’s spatial location during the surface tracking process is proposed. The operational space calibration for the L-pipe part is solved by direct least-squares fitting algorithm of elliptic tracking trajectory and L-pipe part calibration algorithm. The experimental results show that the proposed calibration method can make the operational space model error less than 1mm, which meets the requirements of carrying out assembling contact tasks during the remote welding process with passive compliance.
A Simple Mass-Spring Model With Roller Feet Can Induce the Ground Reactions Observed in Human Walking
Authors: Whittington Ben R. , Thelen Darryl G.
Published: November 2008

It has previously been shown that a bipedal model consisting of a point mass supported by spring limbs can be tuned to simulate periodic human walking. In this study, we incorporated roller feet into the spring-mass model and evaluated the effect of roller radius, impact angle, and limb stiffness on spatiotemporal gait characteristics, ground reactions, and center-of-pressure excursions. We also evaluated the potential of the improved model to predict speed-dependent changes in ground reaction forces and center-of-pressure excursions observed during normal human walking. We were able to find limit cycles that exhibited gait-like motion across a wide spectrum of model parameters. Incorporation of the roller foot (R=0.3m) reduced the magnitude of peak ground reaction forces and allowed for forward center-of-pressure progression, making the model more consistent with human walking. At a fixed walking speed, increasing the limb impact angle reduced the cadence and prolonged stance duration. Increases in either limb stiffness or impact angle tended to result in more oscillatory vertical ground reactions. Simultaneous modulation of the limb impact angle and limb stiffness was needed to induce speed-related changes in ground reactions that were consistent with those measured during normal human walking, with better quantitative agreement achieved at slower speeds. We conclude that a simple mass-spring model with roller feet can well describe ground reaction forces, and hence center of mass motion, observed during normal human walking.
Stress Analyses Coupled With Damage Laws to Determine Biomechanical Risk Factors for Deep Tissue Injury During Sitting
Authors: Linder-Ganz Eran , Gefen Amit
Published: November 2008

Deep tissue injury (DTI) is a potentially life-threatening form of pressure ulcer that onsets in muscle tissue overlying bony prominences and progresses unnoticeably to more superficial tissues. To minimize DTI, the efficacy of wheelchair cushions should be evaluated not only based on their performance in redistributing interface pressures but also according to their effects on stress concentrations in deep tissues, particularly muscles. However, a standard bioengineering approach for such analyses is missing in literature. The goals of this study were to develop an algorithm to couple finite element (FE) modeling of the buttocks with an injury threshold for skeletal muscle and with a damage-stiffening law for injured muscle tissue, from previous animal experiments, to predict DTI onset and progression for different patient anatomies and wheelchair cushions. The algorithm was also employed for identifying intrinsic (anatomical) biomechanical risk factors for DTI onset. A set of three-dimensional FE models of seated human buttocks was developed, representing different severities of pathoanatomical changes observed in chronically sitting patients: muscle atrophy and “flattening” of the ischial tuberosity (IT). These models were then tested with cushions of different stiffnesses representing products available on the market and semirigid supports. Outcome measures were the percentage of damaged muscle tissue volumes after 90min and 110min of simulated continuous immobilized sitting as well as muscle injury rates post-60min, -90min, and -110min of continuous sitting. Damaged muscle volumes grew exponentially with the level of muscle atrophy. For example, simulation of a subject with 70% muscle atrophy sitting on a soft cushion showed damage to 33% of the muscle volume after 90min of immobilized sitting, whereas a comparable simulation with a nonatrophied muscle yielded only 0.4% damaged tissue volume. The rates of DTI progression also increased substantially with increasing severities of muscle atrophy, e.g., 70% atrophy resulted in 8.9, 2.7, and 1.6 times greater injury rates compared with the “reference” muscle thickness cases, after 60min, 90min, and 110min of sitting, respectively. Across all simulation cases, muscle injury rate was higher when a “flatter” IT was simulated. Stiffer cushions increased both the extent and rate of DTI at times shorter than 90min of continuous sitting, but after 110min, volumes and rates of tissue damage converged to approximately similar values across the different cushion materials. The present methodology is a practical tool for evaluating the performances of cushions in reducing the risk for DTI in a manner that goes far beyond the commonly accepted measurements of sitting pressures.
Development of a Dual-Handed Haptic Assembly System: SHARP
Authors: Seth Abhishek , Su Hai-Jun , Vance Judy M.
Published: November 2008

Virtual reality (VR) technology holds promise as a virtual prototyping (VP) tool for mechanical assembly; however, several developmental challenges still need to be addressed before VP applications can successfully be integrated into the product realization process. This paper describes the development of System for Haptic Assembly and Realistic Prototyping (SHARP), a portable virtual assembly system. SHARP uses physics-based modeling for simulating realistic part-to-part and hand-to-part interactions in virtual environments. A dual-handed haptic interface for a realistic part interaction using the PHANToM® haptic devices is presented. The capability of creating subassemblies enhances the application’s ability to handle a wide variety of assembly scenarios at the part level as well as at the subassembly level. Swept volumes are implemented for addressing maintainability issues, and a network module is added for communicating with different VR systems at dispersed geographic locations. Support for various types of VR systems allows an easy integration of SHARP into the product realization process, resulting in faster product development, faster identification of assembly and design issues, and a more efficient and less costly product design process.
Association and Feeding Relationships Between Eogammarus confervicolus (Amphipoda, Gammaridae) and Benthic Algae on Sturgeon and Roberts Banks, Fraser River Estuary
Authors: Pomeroy W. M. , Levings C. D.
Published: November 2008

Field and laboratory studies of the feeding and association of the gammarid amphipod Eogammarus confervicolus with algae and vascular plant debris were conducted on jetties, marshes, and sandflats at the Fraser River Estuary. Associations with Prasiola meridionalis (alga), and debris from Carex lyngbyei (vascular plant) were statistically significant. Vascular plant debris was more widespread in winter (January) compared to a summer survey (August). Laboratory growth rates and survival varied with food types, which were ranked (best to worst) as follows: Enteromorpha linza, Pylaiella littoralis, Porphyra spp., Navicula grevillei, Carex lyngbyei debris and Ulva lactuca. Assimilation efficiencies, measured with gravimetric and radioisotope techniques (14C) ranged from about 78% with P. littoralis to 62% with U. lactuca. Construction of jetties could increase the surface area for algal growth, but there would be no appreciable enhancement of primary production compared to a natural marsh/sandflat ecosystem.Key words: Crustacea, Eogammarus confervicolus, benthic algae, Fraser Estuary, intertidal distribution, feeding, ecological associations, engineering structures
Production of Nonviable Oocytes by Pacific Hake (Merluccius productus)
Authors: Foucher R. P. , Beamish R. J.
Published: November 2008

Ripening ovaries of Pacific hake from the Strait of Georgia contained several size-classes of oocytes. Only those from the group of the largest yolked oocytes became hydrated and were eventually released to be fertilized. Examination of ovaries from recently spawned fish showed that smaller, residual yolked oocytes were being resorbed. Yolked oocytes not released at spawning may represent a potential for an increase in fecundity of Pacific hake in the Strait of Georgia. The failure of some developing oocytes to be released suggests that traditional methods of estimating fecundity will not accurately estimate the number of gametes produced by each female. Cytological observations suggested that the number of potential oocytes is not fixed at first maturity.Key words: Pacific hake, fecundity, oocytes, spawning, Strait of Georgia
Leaf Litter Processing in a Regulated Rocky Mountain Stream
Authors: Short Robert A. , Ward James V.
Published: November 2008

Processing of alder (Alnus tenuifolia) was investigated during autumn and winter to determine the influence of stream regulation on leaf litter processing. Study sites were the Colorado River below Granby Dam and the Fraser River, an unregulated tributary. Alder leaves (5-g units) were attached to bricks and placed in riffles. Leaching controls were retrieved after 48 h; thereafter five replicates were collected from each site after 17, 38, 52, and 66 d. There were significant differences (P < 0.05) in processing rates between sites. The loss rate coefficient (k) was much higher (k = 0.0462) for leaves incubated in the regulated section of the Colorado River than for those in the unregulated tributary (k = 0.0235). The hypothesis that reductions in macroinvertebrate shredders would decrease processing rates of leaf litter in regulated streams was not supported by the results. The "winter warm" thermal regime below the reservoir seems to compensate for the virtual absence of shredder species apparently by enhanced microbial processing.Key words: Colorado River, leaf litter, macroinvertebrates, Rocky Mountains, stream regulation, temperature
Estimating the Population Dynamics of Coho Salmon (Oncorhynchus kisutch) Using Pooled Time-Series and Cross-Sectional Data
Authors: Anderson James L. , Wilen James E.
Published: November 2008

The population dynamics of natural and hatchery coho salmon (Oncorhynchus kisutch) were estimated for three regions, (1) Washington coastal, (2) Columbia River region, and (3) Oregon/California coastal, using pooled time-series and cross-sectional data. Two functional forms were compared: the Beverton–Holt and Ricker models. Both models yielded very similar results. In both cases, we found that the natural coho stock recruitment is significantly affected by parent stock level (positive), parent stock density (negative), river flow (positive), and hatchery smolt release (negative). The significant factors affecting hatchery coho salmon were smolt release level (positive), smolt release density (negative), and upwelling (positive).
A Conceptual Genetic Fitness Model for Fisheries Management
Authors: Kapuscinski Anne R. D. , Lannan James E.
Published: November 2008

A generalized model for managing fisheries to maintain reproductive fitness is proposed. The fitness of an individual within a stock is its number of successful progeny, where successful means survival to the reproductive stage. The fitness of a stock is a probability distribution (W) described by its mean [Formula: see text] and variance (Vw). An example of equations, derived from a variance effective number, expresses the distribution as a function of phenotypic variables (including abundance, immigration and age structure) which could be estimated in fishery surveys. Management of a stock as a self-perpetuating system requires maintenance of its probability distribution at a sufficiently broad level, estimated from reference generations, to allow it to perpetuate in the face of fishing and natural mortality in a changing environment. Modification of the distribution by exploitation or management actions imposes the risk of reduction of genotypic diversity in the stock. Selection of appropriate reference generations requires careful attention to biological detail. Application of the model is illustrated by computing the effective number for fictitious stocks with different life histories.
Vertical Distribution and Habitat Partitioning Between Different Size Classes of Vendace, Coregonus albula, in Thermally Stratified Lakes
Authors: Hamrin Stellan F.
Published: November 2008

Diel vertical distribution of juvenile and adult vendace, Coregonus albula, was studied acoustically and by gill netting during summer in thermally stratified lakes in southern Sweden. Daytime distribution of adult vendace was restricted to hypolimnion (minimum 5 °C). During nocturnal vertical migrations, adults moved into the metalimnion, but temperatures greater than 18 °C were avoided. In contrast, juvenile vendace were often found in the warmer and more shallow water of the metalimnion during the day. At night, the juveniles experienced a temperature change of 10° as they migrated into the epilimnion. All age classes had a nocturnal/crepescular diel rhythm. The diel vertical distribution of vendace is interpreted as a response to temperature stratification and to diel changes in light intensities. The different responses of the age classes are influenced by ontogenetic changes in temperature and light preferences as well as by size-related intraspecific interactions.
Transmission of Diphyllobothrium ditremum to Arctic Char (Salvelinus alpinus) in Two Subarctic Quebec lakes
Authors: Bérubé Michel , Curtis Mark A.
Published: November 2008

Diphyllobothrium ditremum (Cestoda: Pseudophyllidea) transmission to arctic char (Salvelinus alpinus) was investigated at two small (<10 ha) lakes in northern Quebec, where the char populations exhibit a marked difference in plerocercoid prevalence (78 vs. 18%) and abundance (27.7 vs. 1.2 plerocercoids/fish). The highly infected char population was characterized by slow growth and poor feeding conditions. Feeding behavior of char in the two lakes differed principally in the fall, when consumption of benthos significantly decreased in the highly infected population as char fed more on copepods or sticklebacks (Gasterosteus aculeatus). Presence of these two food items in char stomachs was associated with high abundance of D. ditremum. The availability of alternative foods, such as larval insects and amphipods, appears to prevent char from acquiring heavy infections of D. ditremum, even in circumstances where all potential hosts are present.
Fitting and Comparing Several Growth Curves of the Generalized von Bertalanffy Type
Authors: Misra R. K.
Published: November 2008

The earlier version of the von Bertalanffy growth formula (VBGF) has three parameters and is a special case of the "generalized" VBGF which has four parameters. The special VBGF can easily lead to erroneous results whereas the large flexibility built into the generalized VBGF enables it to provide a biologically realistic fit to the data. I present a statistical method and a computer program in Fortran (1) to fit the generalized VBGF to a sample (a sample comprises several age groups, with one or more observations in an age group), (2) to examine statistically the fit to a sample, and (3) to compare statistically these curves (and their individual parameters) fitted to several samples. An example is provided, which also compares the fit of the generalized VBGF with the special VBGF.
TRPA1 in bradykinin-induced mechanical hypersensitivity of vagal C fibers in guinea pig esophagus
Authors: Yu Shaoyong , Ouyang Ann
Published: November 2008

Bradykinin (BK) activates sensory nerves and causes hyperalgesia. Transient receptor potential A1 (TRPA1) is expressed in sensory nerves and mediates cold, mechanical, and chemical nociception. TRPA1 can be activated by BK. TRPA1 knockout mice show impaired responses to BK and mechanical nociception. However, direct evidence from sensory nerve terminals is lacking. This study aims to determine the role of TRPA1 in BK-induced visceral mechanical hypersensitivity. Extracellular recordings of action potentials from vagal nodose and jugular neurons are performed in an ex vivo guinea pig esophageal-vagal preparation. Peak frequencies of action potentials of afferent nerves evoked by esophageal distension and chemical perfusion are recorded and compared. BK activates most nodose and all jugular C fibers. This activation is repeatable and associated with a significant increase in response to esophageal distension, which can be prevented by the B2 receptor antagonist WIN64338. TRPA1 agonist allyl isothiocyanate (AITC) activates most BK-positive nodose and jugular C fibers. This is associated with a transient loss of response to mechanical distensions and desensitization to a second AITC perfusion. Desensitization with AITC and pretreatment with TRPA1 inhibitor HC-030031 both inhibit BK-induced mechanical hypersensitivity but do not affect BK-evoked activation in nodose and jugular C fibers. In contrast, esophageal vagal afferent Aδ fibers do not respond to BK or AITC and fail to show mechanical hypersensitivity after BK perfusion. This provides the first evidence directly from visceral sensory afferent nerve terminals that TRPA1 mediates BK-induced mechanical hypersensitivity. This reveals a novel mechanism of visceral peripheral sensitization.
Effect of a chloride channel activator, lubiprostone, on colonic sensory and motor functions in healthy subjects
Authors: Sweetser Seth , Busciglio Irene A. , Camilleri Michael , Bharucha Adil E. , Szarka Lawrence A. , Papathanasopoulos Athanasios , Burton Duane D. , Eckert Deborah J. , Zinsmeister Alan R.
Published: November 2008

Lubiprostone, a bicyclic fatty acid chloride channel activator, is efficacious in treatment of chronic constipation and constipation-predominant irritable bowel syndrome. The study aim was to compare effects of lubiprostone and placebo on colonic sensory and motor functions in humans. In double-blind, randomized fashion, 60 healthy adults received three oral doses of placebo or 24 μg lubiprostone per day in a parallel-group, placebo-controlled trial. A barostat-manometry tube was placed in the left colon by flexible sigmoidoscopy and fluoroscopy. We measured treatment effects on colonic sensation and motility with validated methods, with the following end points: colonic compliance, fasting and postprandial tone and motility indexes, pain thresholds, and sensory ratings to distensions. Among participants receiving lubiprostone or placebo, 26 of 30 and 28 of 30, respectively, completed the study. There were no overall effects of lubiprostone on compliance, fasting tone, motility indexes, or sensation. However, there was a treatment-by-sex interaction effect for compliance ( P = 0.02), with lubiprostone inducing decreased fasting compliance in women ( P = 0.06) and an overall decreased colonic tone contraction after a standard meal relative to fasting tone ( P = 0.014), with greater effect in women ( P < 0.01). Numerical differences of first sensation and pain thresholds ( P = 0.11 in women) in the two groups were not significant. We concluded that oral lubiprostone 24 μg does not increase colonic motor function. The findings of decreased colonic compliance and decreased postprandial colonic tone in women suggest that motor effects are unlikely to cause accelerated colonic transit with lubiprostone, although they may facilitate laxation. Effects of lubiprostone on sensitivity deserve further study.
Parameter estimation for mathematical models of NKCC2 cotransporter isoforms
Authors: Marcano Mariano , Yang Hun-Mo , Nieves-González Aniel , Clausen Chris , Moore Leon C.
Published: November 2008

An optimization problem, formulated using a nonlinear least-squares approach, was used to estimate parameters for kinetic models of the three isoforms of the kidney-specific Na-K-2Cl (NKCC2) cotransporter. Specifically, the optimization problem estimates the magnitude of model parameters (i.e., off-binding and translocation rate constants) by minimizing the distance between model unidirectional fluxes and published unidirectional 86Rb+ uptake curves for the A, B, and F isoforms of the NKCC2 cotransporter obtained in transfected Xenopus oocytes. By using different symmetry assumptions, NKCC2 models with five, six, seven, or eight parameters were evaluated. The optimization method identified parameter sets that yielded computed unidirectional fluxes consistent with the uptake data. However, the parameter values were not unique, in that systematic exploration of the parameter space revealed alternative parameter sets that fit the data with similar accuracy. Finally, we demonstrate that the optimization method can identify parameter sets for the three transporter isoforms that differ only in ion binding affinities, a result that is consistent with a published mutagenesis analysis of the molecular and structural bases for the differences in 86Rb+ uptake among the A, B, and F isoforms. These NKCC2 cotransporter models will facilitate the development of larger scale models of ion transport by thick ascending limb cells.