bluuebunny/crossref_metadata_2025 huggingface dataset:
INHIBITION OF SOME FOODBORNE BACTERIA BY ALCOHOL EXTRACT OF SUMAC (RHUS CORIARIA L.)
Authors: NASAR‐ABBAS S.M. , HALKMAN A. KADIR , Al‐HAQ M.I.
Published: February 2005

The inhibitory effect of alcohol extract of sumac (Rhus coriaria L.) was investigated at concentrations of 0.1, 0.5, 1.0, 2.5 and 5.0% (w/v) on the growth of 12 bacterial strains (6 Gram positives and 6 Gram negatives), mostly foodborne including pathogens. Minimal inhibitory concentration of the spice for each test organism was also studied by observing their growth on Nutrient Agar containing the spice extract at various incremental levels equivalent to 100–5000 mg/L of spice. Alcohol extract of sumac was found to be effective against all the test organisms, Gram positives being more sensitive than Gram negatives. Among the Gram positives, Bacillus species (B. cereus, B. megaterium, B. subtilis and B. thuringiensis) were found to be the most sensitive, surviving up to only 500 mg/L of the spice, followed by Staphylococcus aureus (1000 mg/L), whereas Listeria monocytogenes was found to be the most resistant, surviving up to 1500 mg/L. Of the Gram negative bacteria, Salmonella enteritidis and Escherichia coli type I were found to be more resistant, surviving up to 3000 mg/L of the spice, followed by E. coli O157:H7 (2500 mg/L), Hafnia alvei (2000 mg/L), Proteus vulgaris (1500 mg/L) and Citrobacter freundii (1000 mg/L). Significant differences (P < 0.01) were found among bacterial strains and between the extracts of unripened and ripened sumac samples, with ripened being more effective against all of the bacteria tested.
GROWTH OF ESCHERICHIA COLI O157:H7 AND SALMONELLA SEROVARS ON RAW BEEF, PORK, CHICKEN, BRATWURST AND CURED CORNED BEEF: IMPLICATIONS FOR HACCP PLAN CRITICAL LIMITS
Authors: INGHAM STEVEN C. , LOSINSKI JILL A. , BECKER KATIE L. , BUEGE DENNIS R.
Published: February 2005

Small amounts (10–25 g; 6.3–20.8 cm2 inoculated area) of raw ground beef, intact beef, pork and chicken (dark and white meat),and bratwurst and cured corned beef were inoculated with Salmonella serovars and Escherichia coli O157:H7, refrigerated 24 h at 5C, and then held either at 10C (± 1C) for up to 8 h or at room temperature (22C ± 2C) for up to 2 h. Except for a 0.2 log CFU increase in Salmonella serovars in ground beef during 2 h at room temperature, pathogens did not grow. Results of trials with commercial amounts of beef, pork, chicken, ground beef and bratwurst exposed to 10C for 8 h or 22C for 2 h also showed no pathogen growth. Potential critical limits for processing of previously refrigerated raw meat products are exposure temperatures between 5 and 10C for not more than 8 h or between 5 and 22C for not more than 2 h.
ANTIMICROBIAL SCREENING OF DECALEPIS HAMILTONII WIGHT AND ARN. (ASCLEPIADACEAE) ROOT EXTRACTS AGAINST FOOD‐RELATED MICROORGANISMS
Authors: THANGADURAI D. , MURTHY K.S.R. , PRASAD P.J.N. , PULLAIAH T.
Published: February 2005

The antimicrobial activity of petroleum ether, benzene, chloroform, ethyl acetate and methanol extracts of Decalepis hamiltonii Wight and Arn. (Asclepiadaceae) against 15 different food‐related microorganisms was evaluated. Among the solvent extracts, methanolic and petroleum ether extracts are the most active exhibiting growth inhibition of 11 and nine of the 15 organisms, respectively. The inhibitory activity was comparable with the respective standards. The results suggest that methanolic and petroleum ether extracts can be used for the bioactivity‐guided isolation of novel antimicrobials which prevents food spoilage.
Modulation of sarcoplasmic reticulum Ca2+ release by glycolysis in cat atrial myocytes
Authors: Kockskämper Jens , Zima Aleksey V. , Blatter Lothar A.
Published: February 2005

In cardiac myocytes, glycolysis and excitation–contraction (E–C) coupling are functionally coupled. We studied the effects of inhibitors (2‐deoxy‐d‐glucose (2‐DG), iodoacetate (IAA)), intermediates (glucose‐6‐phosphate (G6P), fructose‐6‐phosphate (F6P), fructose‐1,6‐bisphosphate (FBP), phosphoenolpyruvate (PEP)) and products (pyruvate, l‐lactate) of glycolysis on sarcoplasmic reticulum (SR) Ca2+ release and uptake in intact and permeabilized cat atrial myocytes. In field‐stimulated (0.5–0.7 Hz) intact myocytes, 2‐DG (10 mm) and IAA (1 mm) caused elevation of diastolic [Ca2+]i and [Ca2+]i transient alternans (Ca2+ alternans) followed by a decrease of the amplitude of the [Ca2+]i transient. Focal application of 2‐DG resulted in local Ca2+ alternans that was confined to the region of exposure. 2‐DG and IAA slowed the decay kinetics of the [Ca2+]i transient and delayed its recovery (positive staircase) after complete SR depletion, suggesting impaired activity of the SR Ca2+‐ATPase (SERCA). 2‐DG and IAA reduced the rate of reuptake of Ca2+ into the SR which was accompanied by a 15–20% decrease of SR Ca2+ load. Major changes of mitochondrial redox state (measured as FAD autofluorescence) were not observed after inhibition of glycolysis. Pyruvate (10 mm) and l‐lactate (10 mm) elicited similar changes of the [Ca2+]i transient. Pyruvate, l‐lactate and IAA – but not 2‐DG – induced intracellular acidosis. Recording of single channel activity of ryanodine receptors (RyRs) incorporated into lipid bilayers revealed complex modulation by glycolytic intermediates and products (1 mm each): some were without effect (G6P, PEP, l‐lactate) while others either increased (F6P, +40%; FBP, +265%) or decreased (pyruvate, −58%) the open probability of the RyR. Consistent with these findings, spontaneous SR Ca2+ release (Ca2+ sparks) in permeabilized myocytes was facilitated by FBP and inhibited by pyruvate. The results indicate that in atrial myocytes glycolysis regulates Ca2+ release from the SR by multiple mechanisms including direct modulation of RyR activity by intermediates and products of glycolysis and modulation of SERCA activity through local changes of glycolytically derived ATP.
Post‐tetanic potentiation in the rat calyx of Held synapse
Authors: Habets Ron L. P. , Borst J. Gerard G.
Published: February 2005

We studied synaptic plasticity in the calyx of Held synapse, an axosomatic synapse in the auditory brainstem, by making whole‐cell patch clamp recordings of the principal cells innervated by the calyces in a slice preparation of 7‐ to 10‐day‐old rats. A 5 min 20 Hz stimulus train increased the amplitude of excitatory postsynaptic currents (EPSCs) on average more than twofold. The amplitude of the synaptic currents took several minutes to return to control values. The post‐tetanic potentiation (PTP) was accompanied by a clear increase in the frequency, but not the amplitude, of spontaneous EPSCs, which returned to baseline more rapidly than the potentiation of evoked release. The size of the readily releasable pool of vesicles was increased by about 30%. In experiments in which presynaptic measurements of the intracellular calcium concentration were combined with postsynaptic voltage clamp recordings, PTP was accompanied by an increase in the presynaptic calcium concentration to about 210 nm. The decay of the PTP matched the decay of this increase. When the decay of the calcium transient was shortened by dialysing the terminal with EGTA, the PTP decay sped up in parallel. Our experiments suggest that PTP at the calyx of Held synapse is due to a long‐lasting increase in the presynaptic calcium concentration following a tetanus, which results in an increase in the release probability of the vesicles of the readily releasable pool. Although part of the PTP can be explained by a direct activation of the calcium sensor for phasic release, other mechanisms are likely to contribute as well.
Experimental models of developmental programming: consequences of exposure to an energy rich diet during development
Authors: Armitage James A. , Taylor Paul D. , Poston Lucilla
Published: February 2005

Studies in both humans and experimental animals addressing the ‘Fetal Origins of Adult Disease’ hypothesis have established a relationship between an adverse intrauterine environment and offspring disease in adult life. This phenomenon, termed ‘fetal programming’ describes a process whereby a stimulus in utero establishes a permanent response in the fetus leading to enhanced susceptibility to later disease. However, the environment, during periods of developmental plasticity in postnatal life, can also ‘programme’ function. Thus, the terms ‘developmental programming’ and the ‘Developmental Origins of Adult Health and Disease’ are preferentially utilized. The ‘Thrifty Phenotype’ hypothesis explained the association between insufficient in utero nutrition and the later development of Type 2 diabetes. Most recently the ‘Predictive Adaptive Response’ hypothesis proposes that the degree of mismatch between the pre‐ and postnatal environments is an important determinant of subsequent disease. Epidemiological studies have indicated that fetal growth restriction correlates with later disease, implying that fetal nutritional deprivation is a strong programming stimulus. This prompted the development of experimental animal models using controlled maternal calorie, protein or macronutrient deficiency during key periods of gestation. However, in many societies, maternal and postnatal nutrition are either sufficient or excessive. Here, we examine findings from a range of nutritional studies examining maternal and/or postnatal nutritional excess. There is supportive evidence from a limited number of studies to test the ‘Predictive Adaptive Response’ hypothesis. These suggest that maternal over‐nutrition is deleterious to the health of offspring and can result in a phenotype of the offspring that is characteristic of metabolic syndrome.
Oleoylethanolamide excites vagal sensory neurones, induces visceral pain and reduces short‐term food intake in mice via capsaicin receptor TRPV1
Authors: Wang Xiangbin , Miyares Rosa Linda , Ahern Gerard P.
Published: February 2005

Oleoylethanolamide (OEA) is an endogenous lipid that regulates feeding and body weight. Although the effects of OEA are believed to depend on activation of vagal sensory afferent neurones, the mechanisms involved in exciting these neurones are unclear. Here we show that OEA directly excited nodose ganglion neurones, the cell bodies of vagal afferents. OEA depolarized these neurones and evoked inward currents that were restricted to capsaicin‐sensitive cells. These currents were fully blocked by the TRPV1 inhibitor, capsazepine, and no responses to OEA were observed in neurones cultured from TRPV1‐null mice. Similarly, OEA induced a rise in Ca+ concentration in wild‐type but not TRPV1‐deficient neurones, and responses to OEA were greater at 37°C compared to room temperature. Significantly, OEA administration in mice induced visceral pain‐related behaviours that were inhibited by capsazepine and absent in TRPV1‐null animals. Further, OEA reduced 30‐min food intake in wild‐type but not in TRPV1‐null mice. Thus, the acute behavioural effects of OEA may result from visceral malaise via the activation of TRPV1.
The effect of sleep onset on upper airway muscle activity in patients with sleep apnoea versus controls
Authors: Fogel Robert B. , Trinder John , White David P. , Malhotra Atul , Raneri Jill , Schory Karen , Kleverlaan Darci , Pierce Robert J.
Published: February 2005

Pharyngeal dilator muscles are important in the pathophysiology of obstructive sleep apnoea syndrome (OSA). We have previously shown that during wakefulness, the activity of both the genioglossus (GGEMG) and tensor palatini (TPEMG) is greater in patients with OSA compared with controls. Further, EMG activity decreases at sleep onset, and the decrement is greater in apnoea patients than in healthy controls. In addition, it is known that the prevalence of OSA is greater in middle‐aged compared with younger men. Thus, we had two goals in this study. First we compared upper airway muscle activity between young and middle‐aged healthy men compared with men with OSA. We also explored the mechanisms responsible for the decrement in muscle activity at sleep onset in these groups. We investigated muscle activity, ventilation , and upper airway resistance (UAR) during wakefulness and sleep onset (transition from α to θ EEG activity) in all three groups. Measurements were obtained during basal breathing (BB) and nasal continuous positive airway pressure (CPAP) was applied to reduce negative pressure‐mediated muscle activation). We found that during wakefulness there was a gradation of GGEMG and UAR (younger < older < OSA) and that muscle activity was reduced by the application of nasal CPAP (to a greater degree in the OSA patients). Although CPAP eliminated differences in UAR during wakefulness and sleep, GGEMG remained greater in the OSA patients. During sleep onset, a greater initial fall in GGEMG was seen in the OSA patients followed by subsequent muscle recruitment in the third to fifth breaths following the α to θ transition. On the CPAP night, and GGEMG still fell further in the OSA patients compared with control subjects. CPAP prevented the rise in UAR at sleep onset along with the associated recruitment in GGEMG. Differences in TPEMG among the groups were not significant. These data suggest that the middle‐aged men had upper airway function midway between that of young normal men and the abnormal airway of those with OSA. Furthermore it suggests that the initial sleep onset reduction in upper airway muscle activity is due to loss of a ‘wakefulness’ stimulus, rather than to loss of responsiveness to negative pressure, and that this wakefulness stimulus may be greater in the OSA patient than in healthy controls.
The Modified Super-Ellipsoid Yield Criterion for Human Trabecular Bone
Authors: Bayraktar Harun H. , Gupta Atul , Kwon Ron Y. , Papadopoulos Panayiotis , Keaveny Tony M.
Published: February 2005

Despite the importance of multiaxial failure of trabecular bone in many biomechanical applications, to date no complete multiaxial failure criterion for human trabecular bone has been developed. By using experimentally validated nonlinear high-resolution, micro-mechanical finite-element models as a surrogate for multiaxial loading experiments, we determined the three-dimensional normal strain yield surface and all combinations of the two-dimensional normal-shear strain yield envelope. High-resolution finite-element models of three human femoral neck trabecular bone specimens obtained through micro-computed tomography were used. In total, 889 multiaxial-loading cases were analyzed, requiring over 41,000 CPU hours on parallel supercomputers. Our results indicated that the multiaxial yield behavior of trabecular bone in strain space was homogeneous across the specimens and nearly isotropic. Analysis of stress-strain curves along each axis in the 3-D normal strain space indicated uncoupled yield behavior, whereas substantial coupling was seen for normal-shear loading. A modified super-ellipsoid surface with only four parameters fit the normal strain yield data very well with an arithmetic error±SD less than −0.04±5.1%. Furthermore, the principal strains associated with normal-shear loading showed excellent agreement with the yield surface obtained for normal strain loading (arithmetic error±SD<2.5±6.5%). We conclude that the four-parameter “Modified Super-Ellipsoid” yield surface presented here describes the multiaxial failure behavior of human femoral neck trabecular bone very well.
Mechanical Approach to Nanomachining of Silicon Using Oxide Characteristics Based on Tribo Nanolithography (TNL) in KOH Solution
Authors: Park Jeong Woo , Kawasegi Noritaka , Morita Noboru , Lee Deug Woo
Published: February 2005

The TNL (Tribo Nanolithography) method in aqueous solution uses the atomic force microscopy as a machining tool for the nanoscale fabrication of silicon. A specially designed cantilever with a diamond tip allows the formation of oxide patterns easily by a simple scratching process. A rectangular structure with a slope can be fabricated by a process in which a thin oxide layer rapidly forms in the substrate at the diamond-tip sample junction along the scanning path of the tip, and, simultaneously, the area uncovered with the oxide layer is being etched. Etching in KOH and HF is conducted to verify corrosion characteristics of oxide.
Systematical Characterization of Material Response to Microscale Laser Shock Peening
Authors: Chen Hongqiang , Wang Youneng , Kysar Jeffrey W. , Yao Y. Lawrence
Published: February 2005

The response of materials after microscale laser shock peening (μLSP) was experimentally characterized and compared with the theoretical prediction from FEM analysis in microlength level. Since μLSP is predominantly a mechanical process instead of a thermal process, the characterization focuses on mechanical properties and associated microstructures. An X-ray microdiffraction technique was applied on the postpeened single crystal aluminum of (001) and (110) orientations, and an X-ray profile was analyzed by subprofiling and Fourier analysis method. Spatially resolved residual stress and strain deviation was quantified and explained in terms of the heterogeneous dislocation cell structure. In-plane crystal lattice rotation induced by μLSP were measured by electron backscatter diffraction (EBSD) and compared with the FEM simulation. Average mosaic size was evaluated from X-ray profile Fourier analysis and compared with the result from EBSD. Surface strength increase and dislocation cell structure formation were studied. The systematical characterization helps develop more realistic simulation models and obtain better understanding in microlength level.
Development of an Assembly-free Process Based on Virtual Environment for Fabricating 3D Microfluidic Systems Using Microstereolithography Technology
Authors: Kang Hyun-Wook , Lee In Hwan , Cho Dong-Woo
Published: February 2005

As it is difficult to construct a microfluidic system composed of micromixers, microchannels, and/or microchambers in a single process, an assembly process is typically used. Using microstereolithography technology, however, the complex microfluidic system can be made in a single process, provided that the fabrication information of the microfluidic system is available. In this work, an assembly-free process based on a virtual environment was developed. The assembly-free process can be used to design various microfluidic systems before actual fabrication commences and then to generate the information required for the microstereolithography process. Using the developed process, various microfluidic systems can be fabricated without any additional assembling process.
Scanning Grating Microinterferometer for MEMS Metrology
Authors: Kim Byungki , Schmittdiel Michael C. , Degertekin F. Levent , Kurfess Thomas R.
Published: February 2005

Quality control and metrology are critical to improved productivity and yield in MEMS design and production. This paper presents a micrograting interferometer for use in measuring MEMS devices. The sensor is also capable of making dynamic measurements, qualifying the functionality of the MEMS devices. The system employs a phase sensitive diffraction grating for interferometric axial resolution and a microfabricated lens for improved lateral resolution. The microinterferometer is capable of array implementation and can be used to increase the yield of MEMS manufacturing processes. The results generated by a single microinterferometer show good correlation with both analytic models and measurements of the MEMS devices by other metrology tools. The microinterferometer enables measurement of steady state vibration of MEMS devices as well as the development of surface vibration profiles. Initial results presented in this paper also demonstrate the ability to measure quantities such as part surface curvature, as well as reduce low frequency vibrational noise. The use of a deformable diffraction grating is proposed to further enhance the sensor’s capabilities.
Development of Ultrafine Piercing By SiC Fiber Punch
Authors: Mori Toshihiko
Published: February 2005

An integrated micropress was developed for ultrafine piercing of metallic foils by a SiC fiber punch. The fiber punch was produced by a series of processes that use buffing and electrolysis operations. The technology incorporates unique tooling and fixturing techniques to handle delicate pinholes, apertures, collimators, and air slits to allow a repeatable manufacturing process with minimal part handling. Since the diagnostic pinholes may be very thin or small in size, it is critical that there is minimal human intervention from the start to the final process of the piercing operation. Selection of materials, design of the integrated micropress, and performance of the system are discussed in detail. The performance of the technique was tested on three kinds of metal foils that have various thickness and strength. A 17-μm-thick aluminum foil was tested as an example of a high aspect ratio and low strength, a 15-μm-thick beryllium copper for a high strength, and an 8 μm stainless steel for a hard-to-form materials. Observations of the scanning electron microscope show that every hole was truly round with the sheared surface being smooth and burr free. Based on the measurements of the punch force and punch stroke, the material behavior in the ultrafine piercing process resembled that of the normal punching process, with a strong dependence on the material properties and the aspect ratio. The SiC fiber was found to be a secure ultrafine punch, with sufficient strength that can produce truly round holes particularly in smaller sizes.
Microforming: Experimental Investigation of the Extrusion Process for Micropins and its Numerical Simulation Using RKEM
Authors: Cao Jian , Krishnan Neil , Wang Zhong , Lu Hongsheng , Liu Wing K. , Swanson Anthony
Published: February 2005

Microforming using a small machine (or so-called desktop machine) is an alternative new approach to those using full-size heavy equipment for manufacturing microparts. Microparts are commonly defined as parts or structures with at least two dimensions in the submillimeter range, which are used extensively in electronics and micromechanical products. However, when scaling down a conventional forming process to microscale, the influence of the so-called size effect needs to be considered. The individual microstructure (size, shape, and orientation of grains) and the interfacial conditions show a significant effect on the process characteristics. In this paper, the process of extrusion is investigated to establish it as a viable process for microforming. A forming assembly is fabricated and used in conjunction with a loading substage to extrude micropins with a final diameter of 1 mm. The effect of grain size is investigated by using workpieces heat treated to produce grain sizes varying from 32 μm up to 211 μm. Two extrusion dies with different roughness are used to study the effect of surface finish. While experiments lead to interesting questions and new discoveries, theoretical or numerical solutions are necessary tools for process optimization. Here, knowing the limits of the current widely used numerical simulation tools [i.e., the Finite Element Method (FEM)], a new method, the Reproducing Kernel Element Method (RKEM), has recently been developed to address the limitations of the FEM (for example, remeshing issue), while maintaining FEM’s advantages, e.g., the polynomial reproducing property and function interpolation property. The new RKEM method is used to simulate the microextrusion problem. Its results are compared with that obtained from the FEM and the experiment result. Satisfactory results were obtained. Future directions on the experimental and simulation work are addressed.
On the Modeling and Analysis of Machining Performance in Micro-Endmilling, Part I: Surface Generation
Authors: Vogler Michael P. , DeVor Richard E. , Kapoor Shiv G.
Published: February 2005

This paper examines the surface generation process in the micro-endmilling of both single-phase and multiphase workpiece materials. We used 508 μm dia endmills with edge radii of 2 and 5 μm to machine slots in ferrite, pearlite, and two ductile iron materials at feed rates ranging from 0.25 to 3.0 μm/flute. A surface generation model to predict the surface roughness for the slot floor centerline is then developed based on the minimum chip thickness concept. The minimum chip thickness values were found through finite element simulations for the ferrite and pearlite materials. The model is shown to accurately predict the surface roughness for single-phase materials, viz., ferrite and pearlite. Two phenomena were found to combine to generate an optimal feed rate for the surface generation of single-phase materials: (i) the geometric effect of the tool and process geometry and (ii) the minimum chip thickness effect. The surface roughness measurements for the ductile iron workpieces indicate that the micromilling surface generation process for multiphase workpiece materials is also affected by the interrupted chip-formation process as the cutting edge moves between phases resulting in burrs at the phase boundaries and the associated increases in surface roughness.
On the Modeling and Analysis of Machining Performance in Micro-Endmilling, Part II: Cutting Force Prediction
Authors: Vogler Michael P. , Kapoor Shiv G. , DeVor Richard E.
Published: February 2005

In Part II of this paper, a cutting force model for the micro-endmilling process is developed. This model incorporates the minimum chip thickness concept in order to predict the effects of the cutter edge radius on the cutting forces. A new chip thickness computation algorithm is developed to include the minimum chip thickness effect. A slip-line plasticity force model is used to predict the force when the chip thickness is greater than the minimum chip thickness, and an elastic deformation force model is employed when the chip thickness is less than the minimum chip thickness. Orthogonal, microstructure-level finite element simulations are used to calibrate the parameters of the force models for the primary metallurgical phases, ferrite and pearlite, of multiphase ductile iron workpieces. The model is able to predict the magnitudes of the forces for both the ferrite and pearlite workpieces as well as for the ductile iron workpieces within 20%.
Nanosurface Fabrication of Hard Brittle Materials by Structured Tool Imprinting
Authors: Yoshino Masahiko , Aravindan Sivanandam
Published: February 2005

This paper reports on nanosurface fabrication of hard brittle materials by structured diamond tool imprinting. Ultrafine structured surfaces were fabricated on soda glass, firelite glass, quartz glass, quartz wafer, and silicon. A specially designed and developed nanoindentation tester and a structured diamond tool machined by Focused Ion Beam (FIB) are used for the generation of such surfaces. Imprinted marks and the ultrafine structures are analyzed for their geometrical shape and accuracy. Load-depth analysis on the formed surfaces was carried out. Critical depth, at which ductile-to-brittle transition in deformation occurs, was assessed for the hard brittle materials. Limits of ductile mode indentation for hard brittle materials were discussed in detail. Variation in the depth of structures in an imprinted mark was studied.
Effects of Spherical Targets on Capacitive Displacement Measurements
Authors: Vallance R. Ryan , Marsh Eric R. , Smith Philip T.
Published: February 2005

Capacitive displacement sensors are widely used in precision manufacturing and metrology because they measure displacements with nanometer resolution. Prior literature usually treats capacitive sensors consisting of electrodes arranged as parallel plates. In this work, the target electrode is spherical, which is common in machine tool metrology, spindle metrology, and the measurement of sphericity. The capacitance due to a gap between flat and spherical electrodes is less than that of two flat electrodes, which causes four effects. As the diameter of the target electrode is reduced, the sensitivity increases, the sensing range decreases, the sensing range shifts toward the target, and the sensor becomes nonlinear. This paper demonstrates and quantifies these effects for a representative capacitive sensor, using finite element analysis and experimental testing. For larger spheres, the effects are correctible with apparent sensitivities, but measurements with the smallest spheres become increasingly nonlinear and inaccurate.
Three-Dimensional Velocity Field Reconstruction
Authors: Frakes David , Smith Mark , de Ze´licourt Diane , Pekkan Kerem , Yoganathan Ajit
Published: February 2005

The problem of inter-slice magnetic resonance (MR) image reconstruction is encountered often in medical imaging applications. In such scenarios, there is a need to approximate information not captured in contiguously acquired MR images due to hardware sampling limitations. In the context of velocity field reconstruction, these data are required for visualization and computational analyses of flow fields to be effective. To provide more complete velocity information, a method has been developed for the reconstruction of flow fields based on adaptive control grid interpolation (ACGI). In this study, data for reconstruction were acquired via MRI from in vitro models of surgically corrected pediatric cardiac vasculatures. Reconstructed velocity fields showed strong qualitative agreement with those obtained via other acquisition techniques. Quantitatively, reconstruction was shown to produce data of comparable quality to accepted velocity data acquisition methods. Results indicate that ACGI-based velocity field reconstruction is capable of producing information suitable for a variety of applications demanding three-dimensional in vivo velocity data.
Age Dependency of the Biaxial Biomechanical Behavior of Human Abdominal Aorta
Authors: Geest Jonathan P. Vande , Sacks Michael S. , Vorp David A.
Published: February 2005

Background: The biomechanical behavior of the human abdominal aorta has been studied with great interest primarily due to its propensity to develop such maladies as atherosclerotic occlusive disease, dissections, and aneurysms. The purpose of this study was to investigate the age-related biaxial biomechanical behavior of human infrarenal aortic tissue. Methods of Approach: A total of 18 samples (13 autopsy, 5 organ donor) were harvested from patients in each of three age groups: Group 1 (<30years old, n=5), Group 2 (between 30 and 60 years old, n=7), and Group 3 (>60years old, n=6). Each specimen was tested biaxially using a tension-controlled protocol which spanned a large portion of the strain plane. Response functions fit to experimental data were used as a tool to guide the appropriate choice of the strain energy function W. Results: Under an equibiaxial tension of 120 N/m, the average peak stretch values in the circumferential direction for Groups 1, 2, and 3 were mean±SD1.46±0.07,1.15±0.07, and 1.11±0.06, respectively, while the peak stretch values in the longitudinal direction were 1.41±0.03,1.19±0.11, and 1.10±0.04, respectively. There were no significant differences between the average longitudinal and circumferential peak stretch within each group p>0.1, but both of these values were significantly less p<0.001 for Groups 2 and 3 when compared to Group 1. Patients in Group 1 were modeled using a polynomial strain energy function W, while patients in Groups 2 and 3 were modeled using an exponential form of W, suggesting an age-dependent shift in the mechanical response of this tissue. Conclusion: The biaxial tensile testing results reported here are, to our knowledge, the first given for the human infrarenal aorta and reinforce the importance of determining the functional form of W from experimental data. Such information may be useful for the clinician or researcher in identifying key changes in the biomechanical response of abdominal aorta in the presence of an aneurysm.
Pre-Impact Lower Extremity Posture and Brake Pedal Force Predict Foot and Ankle Forces During an Automobile Collision
Authors: Hardin E. C. , Su A. , van den Bogert A. J.
Published: February 2005

Background: The purpose of this study was to determine how a driver’s foot and ankle forces during a frontal vehicle collision depend on initial lower extremity posture and brake pedal force. Method of Approach: A 2D musculoskeletal model with seven segments and six right-side muscle groups was used. A simulation of a three-second braking task found 3647 sets of muscle activation levels that resulted in stable braking postures with realistic pedal force. These activation patterns were then used in impact simulations where vehicle deceleration was applied and driver movements and foot and ankle forces were simulated. Peak rearfoot ground reaction force FRF, peak Achilles tendon force FAT, peak calcaneal force FCF and peak ankle joint force FAJ were calculated. Results: Peak forces during the impact simulation were 476±687NFRF, 2934±944 N FCF and 2449±918 N FAJ. Many simulations resulted in force levels that could cause fractures. Multivariate quadratic regression determined that the pre-impact brake pedal force (PF), knee angle (KA) and heel distance (HD) explained 72% of the variance in peak FRF, 62% in peak FCF and 73% in peak FAJ. Conclusions: Foot and ankle forces during a collision depend on initial posture and pedal force. Braking postures with increased knee flexion, while keeping the seat position fixed, are associated with higher foot and ankle forces during a collision.
Time-Resolved DPIV Analysis of Vortex Dynamics in a Left Ventricular Model Through Bileaflet Mechanical and Porcine Heart Valve Prostheses
Authors: Pierrakos Olga , Vlachos Pavlos P. , Telionis Demetri P.
Published: February 2005

The performance of the heart after a mitral valve replacement operation greatly depends on the flow character downstream of the valve. The design and implanting orientation of valves may considerably affect the flow development. A study of the hemodynamics of two orientations, anatomical and anti-anatomical, of the St. Jude Medical (SJM) bileaflet valve are presented and compared with those of the SJM Biocor porcine valve, which served also to represent the natural valve. We document the velocity field in a flexible, transparent (LV) using time-resolved digital particle image velocimetry (TRDPIV). Vortex formation and vortex interaction are two important physical phenomena that dominate the filling and emptying of the ventricle. For the three configurations, the following effects were examined: mitral valve inlet jet asymmetry, survival of vortical structures upstream of the aortic valve, vortex-induced velocities and redirection of the flow in abidance of the Biot–Savart law, domain segmentation, resonant times of vortical structures, and regions of stagnant flow. The presence of three distinct flow patterns, for the three configurations, was identified by the location of vortical structures and level of coherence corresponding to a significant variation in the turbulence level distribution inside the LV. The adverse effect of these observations could potentially compromise the efficiency of the LV and result in flow patterns that deviate from those in the natural heart.
Cross-Sectional Profiles and Volume Reconstructions of Soft Tissues Using Laser Beam Measurements
Authors: Langelier Eve , Dupuis Daniel , Guillot Michel , Goulet Francine , Rancourt Denis
Published: February 2005

Precise geometric reconstruction is a valuable tool in the study of soft tissues biomechanics. Optical methods have been developed to determine the tissue cross section without mechanical contact with the specimen. An adaptation of the laser micrometer developed by Lee and Woo [ASME J. Biomech. Eng., 110 (2), pp. 110–114]. is proposed in which the laser-collimated beam rotates around and moves along a fixed specimen to reconstruct its cross sections and volume. Beam motion is computer controlled to accelerate data acquisition and improve beam positioning accuracy. It minimizes time-dependent shape modifications and increases global reconstruction precision. The technique is also competent for the measurement of immersed collagen matrices.
The Effect of Incorporating Vessel Compliance in a Computational Model of Blood Flow in a Total Cavopulmonary Connection (TCPC) with Caval Centerline Offset
Authors: Masters J. C. , Ketner M. , Bleiweis M. S. , Mill M. , Yoganathan A. , Lucas C. L.
Published: February 2005

Background—The total cavopulmonary connection (TCPC), a palliative correction for congenital defects of the right heart, is based on the corrective technique developed by Fontan and Baudet. Research into the TCPC has primarily focused on reducing power loss through the connection as a means to improve patient longevity and quality of life. The goal of our study is to investigate the efficacy of including a caval offset on the hemodynamics and, ultimately, power loss of a connection. As well, we will quantify the effect of vessel wall compliance on these factors and, in addition, the distribution of hepatic blood to the lungs. Methods—We employed a computational fluid dynamic model of blood flow in the TCPC that includes both the non-Newtonian shear thinning characteristics of blood and the nonlinear compliance of vessel tissue. Results—Power loss in the rigid-walled simulations decayed exponentially as caval offset increased. The compliant-walled results, however, showed that after an initial substantial decrease in power loss for offsets up to half the caval diameter, power loss increased slightly again. We also found only minimal mixing in both simulations of all offset models. Conclusions—The increase in power loss beyond an offset of half the caval diameter was due to an increase in the kinetic contribution. Reduced caval flow mixing, on the other hand, was due to the formation of a pressure head in the offset region which acts as a barrier to flow.
Material Properties and Residual Stress in the Stage 12 Chick Heart During Cardiac Looping
Authors: Zamir Evan A. , Taber Larry A.
Published: February 2005

During the morphogenetic process of cardiac looping, the initially straight cardiac tube bends and twists into a curved tube. The biophysical mechanisms that drive looping remain unknown, but the process clearly involves mechanical forces. Hence, it is important to determine mechanical properties of the early heart, which is a muscle-wrapped tube consisting primarily of a thin outer layer of myocardium surrounding a thick extracellular matrix compartment known as cardiac jelly. In this work, we used microindentation experiments and finite element modeling, combined with an inverse computational method, to determine constitutive relations for the myocardium and cardiac jelly at the outer curvature of stage 12 chick hearts. Material coefficients for exponential strain-energy density functions were found by fitting force-displacement and surface displacement data near the indenter. Residual stress in the myocardium also was estimated. These results should be useful for computational models of the looping heart.
The Effect of Overshooting the Target Strain on Estimating Viscoelastic Properties From Stress Relaxation Experiments
Authors: Gimbel Jonathan A. , Sarver Joseph J. , Soslowsky Louis J.
Published: February 2005

Background: Tendon’s mechanical behaviors have frequently been quantified using the quasi-linear viscoelastic (QLV) model. The QLV parameters are typically estimated by fitting the model to a single-step stress relaxation experiment. Unfortunately, overshoot of the target strain occurs to some degree in most experiments. This has never been formally investigated even though failing to measure, minimize, or compensate for overshoot may cause large errors in the estimation of parameters. Therefore, the objective of this study was to investigate the effect of overshoot on the estimation of QLV parameters. Method of approach: A simulated experiment was first performed to quantify the effect of different amounts of overshoot on the estimated QLV parameters. Experimental data from tendon was then used to determine if the errors associated with overshoot could be reduced when a direct fit is used (i.e., the actual strain history was used in the curve fit). Results: We found that both the elastic and viscous QLV parameters were incorrectly estimated if overshoot was not properly accounted for in the fit. Furthermore, the errors associated with overshoot were partially reduced when overshoot was accounted for using a direct fit. Conclusions: A slow ramp rate is recommended to limit the amount of overshoot and a direct fit is recommended to limit the errors associated with overshoot, although other approaches such as adjusting the control system to limit overshoot could also be utilized.
Modeling of Advanced Melting Zone for Manufacturing of Optical Fibers*
Authors: Wei Zhiyong , Lee Kok-Meng , Zhou Zhi , Hong Siu-Ping
Published: February 2005

Optical fibers are drawn from preforms (fused silica glass rods) typically made up of two concentric cylinders (the core rod and the clad tube), which are usually joined in a separate fusion process. The setup time and hence manufacturing cost can be significantly reduced if the two cylinders can be joined in the same furnace in which the fiber is drawn. A good understanding of the transient temperature distribution is needed for controlling the feed rate to avoid thermally induced cracks. Since direct measurement of the temperature fields is often impossible, the geometrical design of the preform and the control of the feed rate have largely been accomplished by trials-and-errors. The ability to predict the transient temperature distribution and the thermally induced stresses will provide a rational basis to design optimization and feed rate control of the process. In this paper, we present an analytical model to predict the transient conductive-radiative transfer as two partially joined, concentric glass cylinders with specular surfaces are fed into the furnace. Finite volume method (FVM) is used to solve the radiative transfer equation (RTE). The specular surface reflectivity is obtained by the Fresnel’s law and the Snell’s law. The boundary intensities are obtained through the coupling of the interior glass radiative transfer and the exterior furnace enclosure analysis. The model has been used to numerically study the transient conductive-radiative transfer in the advanced melting zone (AMZ) of an optic fiber drawing process. This problem is of both theoretical and practical interest in the manufacture of optical fibers. The computational method for the radiation transfer developed in this paper can also be applied to the simulation of the fiber drawing process and other glass-related manufacturing processes.
Insertion- and Deletion-Associated Genetic Diversity of
Mycobacterium tuberculosis
Phospholipase C-Encoding Genes among 106 Clinical Isolates from Turkey
Authors: Talarico Sarah , Durmaz Riza , Yang Zhenhua
Published: February 2005

Bacterial phospholipase C has been reported to play a role in the pathogenesis of many bacteria. In order to gain a better understanding of the potential role of
Mycobacterium tuberculosis
phospholipase C in the pathogenesis of human tuberculosis, we investigated the genetic diversity of the four
M. tuberculosis
phospholipase C-encoding genes (
plcA
,
plcB
,
plcC
, and
plcD
) resulting from the IS
6110
insertion and associated deletion, among 106 clinical isolates obtained from Turkey, by using PCR, Southern hybridization, and DNA sequencing. Two sequenced
M. tuberculosis
strains, H37Rv and CDC1551, were used as the references in the comparison. Sixty-six (62.3%) of the 106 isolates had an intact
plcD
gene, and 40 (37.7%) showed an interruption of the gene. Of the latter 40 isolates, 19 (47.5%) had an IS
6110
insertion with no associated deletion in the
plcD
gene, 2 (5%) had an IS
6110
insertion and an associated deletion within the
plcD
gene, 15 (37.5%) had an IS
6110
insertion in the
plcD
gene that was associated with a partial deletion of the
plcD
gene and its right forward adjacent region, and 4 (10%) had a complete deletion of the
plcD
gene. The proportions of the isolates with an interrupted
plcA
,
plcB
, or
plcC
gene were 3.8, 1.9, and 3.8%, respectively. The data indicate that there is a much higher frequency of IS
6110
insertion and deletion in the
plcD
gene than in the
plcA
,
plcB
, and
plcC
genes of
M. tuberculosis
.
Identification of Variable-Number Tandem-Repeat Loci in
Leptospira interrogans
Sensu Stricto
Authors: Majed Z. , Bellenger E. , Postic D. , Pourcel C. , Baranton G. , Picardeau M.
Published: February 2005

Leptospira interrogans
sensu stricto is responsible for the most frequent and severe cases of human leptospirosis. The epidemiology and clinical features of leptospirosis are usually associated with the serovars and serogroups of
Leptospira
. Because of the difficulties associated with serological identification of
Leptospira
strains, we evaluated a novel PCR-based method for typing
L. interrogans
serovars. Based upon the genome sequence of
L. interrogans
serovar Lai type strain 5660, 44 loci were analyzed by PCR for their variability in size due to the presence of variable-number tandem repeats (VNTR). Seven VNTR loci were found to be powerful markers for serovar identification, epidemiology, and phylogenetic studies of
L. interrogans
. This rapid and easy method should greatly contribute to a better knowledge of the epidemiology of
Leptospira
.
Distribution of the Urease Gene Cluster among and Urease Activities of Enterohemorrhagic
Escherichia coli
O157 Isolates from Humans
Authors: Friedrich Alexander W. , Köck Robin , Bielaszewska Martina , Zhang Wenlan , Karch Helge , Mathys Werner
Published: February 2005

Enterohemorrhagic
Escherichia coli
(EHEC) O157 strains belong to two closely related major groups, which are differentiated by their sorbitol fermentation phenotypes. Here we studied the conservation of urease genes and their expression in sorbitol-fermenting (SF) and non-SF EHEC O157 isolates. PCR targeting
ure
genes (
ureA
, -
B
, -
C
, -
D
, -
E
, -
F
, and -
G
) demonstrated that each of these genes was present in 58 of 59 EHEC O157:H7 isolates. In contrast, none of 82 SF EHEC O157:NM (nonmotile) isolates contained any of the
ure
genes. Hence, the absence of the urease genes distinguishes SF EHEC O157:NM strains from EHEC O157:H7, but this absence demonstrates that the urease genes are not useful genetic targets for the detection of EHEC strains, because SF EHEC O157:NM strains are missed by such a strategy. When examined for urease activity on Christensen agar and in the API 20E system, only one O157:H7 strain displayed urease activity and produced elevated levels of ammonia, which was subsequently confirmed by ammonia electrode measurement. Because the
ure
genes were absent from each of nine strains of
E. coli
O55:H7, the proposed progenitor of EHEC O157, we hypothesize that EHEC O157:H7 diverged from the evolutionary pathway at an early stage and then acquired the O islands carrying the
ure
gene cluster.