bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigations of Laser Micromachining of Nickel Using Thin Film Micro Thermocouples
Authors: Choi Hongseok , Li Xiaochun
Published: April 2008

Laser-material interactions during laser micromachining are extremely complicated. In order to improve the fundamental understanding of the laser micromachining process, it is essential to investigate the complex phenomena and mechanisms of the physical processes within and close to the region of the interaction. Moreover, C-type micro thin film thermocouples with a junction size of 2×2μm2 were fabricated to increase the maximum operation temperature and spatial resolution of sensors. Surface temperature distribution around the laser spot was obtained in the range from 45μmto85μm away from the center of laser spot. The result showed that there was a steep gradient of temperature in the radial direction and a superheated area around the laser spot. Topographical characterizations of laser micromachining with various laser energy fluences were undertaken to correlate the resulting geometry changes with surface temperature measurements. Possible changes of surface chemical composition induced by the laser micromachining process, in particular, oxide formation, were also investigated around the laser spot.
Selective Ultrasonic Foaming of Polymer for Biomedical Applications
Authors: Wang Hai , Li Wei
Published: April 2008

Biocompatible polymeric material with well-defined, interconnected porous structure plays an important role in many biomedical applications, such as tissue engineering, controlled drug release, biochemical sensing, and 3D cell culture for drug discovery. In this study, a novel fabrication process for porous polymer is developed using high intensity focused ultrasound. This acoustic method is solvent-free and capable of creating interconnected porous structures with varying topographical features at designed locations. An experimental study on the selective ultrasonic foaming technique is presented in this paper. We investigated the effects of major process variables, including ultrasound power, scanning speed, and gas concentration. Both pore size and interconnectivity of the created porous structures were examined. It was found that the pore size could be controlled with the scanning speed of the ultrasound insonation and that interconnected porous structures could be obtained using a partial saturation procedure. A concentration-dependent gas diffusion model was developed to predict the gas concentration profiles for partially saturated samples. A cell culture study was conducted to examine cell growth behavior in the fabricated porous structures.
Improving Discharge Characteristics of Indirect Integral Collector Storage Systems With Multielement Storage
Authors: Boies A. M. , Homan K. O.
Published: April 2008

The desired performance of unpressurized integral collector storage systems hinges on the appropriate selection of storage volume and the immersed heat exchanger. This paper presents analytical results expressing the relation between storage volume, number of heat exchanger transfer units, and temperature-limited performance. For a system composed of a single storage element, the limiting behavior of a perfectly stratified storage element is shown to be superior to a fully mixed storage element, consistent with a more general analysis of thermal storage. Since, however, only the fully mixed limit is readily obtainable in a physical system, the present paper also examines a division of the storage volume into separate compartments. This multielement storage system shows significantly improved discharge characteristics as a result of improved elemental area utilization and temperature variation between elements, comparable in many cases to a single perfectly stratified storage element. In addition, the multielement system shows increased robustness with respect to variations in heat exchanger effectiveness and initial storage temperature.
Thermoeconomic Optimization of a Solar Chimney Power Plant
Authors: Pretorius Johannes P. , Kröger Detlev G.
Published: April 2008

No physical optimum solar chimney power plant exists when only regarding the dimensions of such a plant. However, if construction costs are introduced, thermoeconomically optimal plant configurations may be established. This paper investigates the thermoeconomic optimization of a large-scale solar chimney power plant. Initially, relevant dimensions are selected, which are to be optimized. An approximated cost model is then developed, giving the capacity for finding optimum plant dimensions for different cost structures. Multiple computer simulations are performed and results are compared to the approximated cost of each specific plant. Thermoeconomically optimal plant configurations are obtained.
Thermal Stress Analysis/Life Prediction of Concentrating Photovoltaic Module
Authors: Cao M. , Butler S. , Benoit J. T. , Jiang Y. , Radhakrishnan R. , Chen Y. , Bendapudi S. , Horne Steve
Published: April 2008

Aiming at understanding the structural integrity of two representative concentrating photovoltaic (CPV) module configurations, finite element thermal stress analysis is carried out in this investigation. This study covers the nominal and extreme operating conditions, including system startup and shutdown. While the first CPV module is bonded by epoxy-type material, the bonding material for the second CPV module is lead-free solder. The analysis of the first module confirms that this CPV module can endure the thermal stress under steady-state operation. However, residual stress analysis shows that the epoxy holding together the PV cell/aluminum nitride and aluminum nitride/heat sink pairs will likely break, first at some sporadic spots, and then in a good part of the bond causing the failure of the CPV module, as the cell temperature drops from 100°Cto0°C. Nonlinear viscoplastic analysis using the temperature profile of CPV cell fatigue test ongoing at United Technologies Research Center (UTRC) is performed to evaluate the structure strength and subsequently predict the life of the second CPV module. The result reveals that the maximum characteristic stresses of the PV cell components and heat sink are below the strength allowable for the corresponding materials under both the steady-state and overnight idle conditions. Critical locations on the solder that are potentially susceptible to structural failure after a few thousand thermal cycles due to the excessive shear stress are identified. A rough estimation of the module life is provided and compared with the fatigue test. This investigation provides firsthand understanding of the structural integrity of CPV modules and is thus beneficial for the solar energy community.
Impact of Solar Model Selection on Building Energy Analysis for Kuwait
Authors: Al-Anzi Adnan , Seo Donghyun , Krarti Moncef
Published: April 2008

This paper summarizes the results of a comparative analysis for four models utilized to predict solar radiation in Kuwait City, Kuwait. The four models include the Kasten model, Zhang and Huang model, Muneer model, and neural network based model. The analysis was based on hourly measured solar data for Kuwait City. The measured hourly solar radiation data are obtained for the year 1994 and include global, direct, and diffuse solar radiations. Nonsolar weather data for the same year and site are obtained from the US National Climatic Data Center (NCDC). Weather files suitable for building energy simulation are developed using measuered data as well as predictions from the four solar models. A series of simulation analysis to determine the impact of solar model selection for the weather file on the energy uses predictions from a whole-building simulation program using office buildings in Kuwait. The results of the validation analysis and the simulation evaluation indicate that Zhang and Huang model is suitable for the predicting hourly solar radiation suitable for energy analysis of buildings in Kuwait.
High Flux Central Receivers of Molten Salts for the New Generation of Commercial Stand-Alone Solar Power Plants
Authors: Lata Jesús M. , Rodríguez Manuel , de Lara Mónica Álvarez
Published: April 2008

Molten salt technology represents nowadays the most cost-effective technology for electricity generation for stand-alone solar power plants. Although this technology can be applied to both concentrating technologies, parabolic through and central receiver systems (CRSs), CRS technology can take advantages from its higher concentration, allowing to work at higher temperatures and therefore with a reduction in the size and cost of the storage system. The receiver system is the “door” for which the energy passes from the field collector to the thermal-electric cycle; it represents, therefore, the core of the CRS and its performance directly affects plant production. Starting from the published lessons from SOLAR TWO receiver technology, the validation of an improved receiver for molten salt technology was assumed as part of the SOLAR TRES solar thermal power commercial plant development. Main challenges for the new receiver were to increase its allowable peak flux up to 1MW∕m2 in order to maximize the thermal efficiency of the CRS solar power plant, and to improve its safe life without limiting the incident fluxes that the field of heliostats is able to deliver with an optimized pointing strategy. Several advanced features in geometric and thermodynamic aspects and in its material selection have been implemented on the receiver. With the results of a sensitivity analysis carried out with an own code developed by SENER (SENREC), a prototype receiver panel was designed, fabricated, and installed in a proper test bed at the PSA. Test validation on this panel was carried out in 2007. The initial test results show a very good behavior of the prototype receiver, which allows to anticipate that the objectives of its design can be fulfilled. SENER and CIEMAT have joined forces to face up the challenge of sizing and designing a new molten salt receiver of high thermal efficiency, able to operate at high fluxes without compromising its durability (at least 25years). Main challenges for the new receiver design were to optimize the receiver dimensions and receiver tube sizes and material selection to surpass the operating conditions in the new plants with respect to SOLAR TWO.
Development of Three-Dimensional Alginate Encapsulated Chondrocyte Hybrid Scaffold Using Microstereolithography
Authors: Lee Seung-Jae , Rhie Jong-Won , Cho Dong-Woo
Published: April 2008

Hydrogels are useful materials because of their chemical similarity to extracellular matrix and their ability to rapidly diffuse hydrophilic nutrients and metabolites. Using rapid prototyping methods, we fabricated freeform three-dimensional (3D) scaffolds with chondrocytes encapsulated in an alginate hydrogel. The 3D hybrid scaffold was developed as combination of two components, a trimethylene carbonate (TMC)/trimethylolpropane (TMP) framework and an alginate hydrogel within an encapsulation of chondrocytes. To develop 3D hybrid scaffolds, we employed a microstereolithography system. The biodegradable, photopolymerizable liquid prepolymer was prepared by the polymerization of TMC with TMP and subsequently end capped with an acrylate group. The meshed framework of scaffolds withstood mechanical loading effectively. The line depth and linewidth could be controlled by varying laser power, scan path, and scan speed. Results of cell culture indicate that the biomimetic nature of these encapsulated chondrocyte scaffolds effectively retain the phenotypic function of chondrocytes within the scaffold structure. The proposed 3D hybrid scaffolds can be used for cartilage regeneration.
A Feasibility Study of LENS® Deposition of CoCrMo Coating on a Titanium Substrate
Authors: Ram G. D. Janaki , Stucker B. E.
Published: April 2008

Titanium- and cobalt-base alloys are the most widely used orthopedic implant materials. As there are specific advantages and disadvantages with both of them, one approach to fabricate superior implants is to combine these two material systems. The current work examines the feasibility of depositing CoCrMo coatings on Ti substrates using Laser Engineered Net Shaping®. Studies show that deposition of CoCrMo coating on a Ti substrate is very challenging, cracking and delamination being the major observations. Several alternative strategies, which may lead to satisfactory coatings, are presented.
High-Throughput Production of Single-Cell Microparticles Using an Inkjet Printing Technology
Authors: Xu Tao , Kincaid Helen , Atala Anthony , Yoo James J.
Published: April 2008

In this study, a novel biocompatible and inexpensive method for the rapid production of single-cell based microparticles is described. Using an HP DeskJet 550C printer, alginate microparticles containing one to several insulin-producing cells (beta-TC6) were fabricated by coprinting the cells and sodium alginate suspension into a CaCl2 solution. This method is able to generate microparticles of 30–60μm in diameter at a rate as high as 55,000particles∕s. Cell survival assays showed that more than 89% of printed cells survived the fabrication process. The printed beta-TC6 cells demonstrated continuous insulin secretion over a 6day period, which suggests that the printed cells are able to maintain normal cellular function within the microparticles. We show that the printing conditions, such as cell number, alginate concentration, and ionic strengths of CaCl2, influence cellular distribution and geometry of the printed particles. This study presents a simple and high-throughput method to encapsulate single cells, and this technique may be applied in various research investigations, including single-cell analysis, high-throughput drug screening, and stem cell differentiation at the single-cell level.
Temperature Sensing by an Olfactory Neuron in a Circuit Controlling Behavior of
C. elegans
Authors: Kuhara Atsushi , Okumura Masatoshi , Kimata Tsubasa , Tanizawa Yoshinori , Takano Ryo , Kimura Koutarou D. , Inada Hitoshi , Matsumoto Kunihiro , Mori Ikue
Published: April 2008

Temperature is an unavoidable environmental cue that affects the metabolism and behavior of any creature on Earth, yet how animals perceive temperature is poorly understood. The nematode
Caenorhabditis elegans
“memorizes” temperatures, and this stored information modifies its subsequent migration along a temperature gradient. We show that the olfactory neuron designated AWC senses temperature. Calcium imaging revealed that AWC responds to temperature changes and that response thresholds differ depending on the temperature to which the animal was previously exposed. In the mutant with impaired heterotrimeric guanine nucleotide–binding protein (G protein)–mediated signaling, AWC was hyperresponsive to temperature, whereas the AIY interneuron (which is postsynaptic to AWC) was hyporesponsive to temperature. Thus, temperature sensation exhibits a robust influence on a neural circuit controlling a memory-regulated behavior.
Post-exercise hypotension and cardiovascular responses to moderate orthostatic stress in endurance-trained males
Authors: Scott Jessica M. , Esch Ben T.A. , Lusina Sarah-Jane C. , McKenzie Donald C. , Koehle Michael S. , Sheel A. William , Warburton Darren E.R.
Published: April 2008

We tested the hypothesis that following an acute bout of exercise cardiovascular and cerebrovascular responses to lower-body negative pressure (LBNP) would be altered due to post-exercise hypotension (PEH). Ten healthy, male, endurance-trained athletes (mean age ± SD = 29.6 ± 5) were assessed for cardiovascular and cerebrovascular responses to LBNP following acute bouts of interval and continuous exercise. Mean arterial pressure (MAP), cardiac output, total peripheral resistance, heart rate variability, and total cerebral oxygen index were determined during a baseline LBNP session. These indices were also determined during two other LBNP sessions: following an acute bout of interval exercise, and following an acute bout of continuous exercise. Compared with baseline, MAP was reduced after both exercise conditions, similar to values previously reported (10 mmHg; p < 0.05 vs. pre-exercise). Total peripheral resistance was significantly reduced following both exercise bouts, and heart rate was significantly increased post-exercise (rest: 59.6 ± 11.2; interval: 77.8 ± 12.8; continuous: 80.3 ± 15.2 beats·min–1). Both cardiac output and stroke volume responses to LBNP following exercise were not altered when compared with baseline measurements. Tissue oxygenation during –40 mmHg (interval: 74.31% ± 7.82% vs. continuous: 69.13% ± 5.23%) was significantly lower than during normobaric pressure (interval: 77.14% ± 1.30% vs. continuous: 74.41% ± 0.94%). It appears from these observations that although young, endurance-trained males experience PEH following acute bouts of interval or continuous exercise, this hypotension does not alter the cardiovascular and cerebrovascular responses to a moderate orthostatic stress.
Children’s thermoregulation during exercise in the heat — a revisit
Authors: Falk Bareket , Dotan Raffy
Published: April 2008

The review revisits some child–adult differences relevant to thermoregulation and offers alternatives to accepted interpretations. Morphologically, children have a higher body surface area to mass ratio — a major factor in “dry” heat dissipation and effective sweat evaporation. Locomotion-wise, children are less economical than adults, producing more heat per unit body mass. Additionally, children need to divert a greater proportion of their cardiac output to the skin under heat stress. Thus, a larger proportion of their cardiac output is shunted away from the body’s core and working muscles — particularly in hot conditions. Finally, under all environmental conditions and allometric comparisons, children's sweating rates are lower than those of adults. The differences appear to suggest thermoregulatory inferiority, but no epidemiological data show higher heat-injury rates in children, even during heat waves. We suggest that children employ a different thermoregulatory strategy. In extreme temperatures, they may indeed be more vulnerable, but under most ambient conditions they are not necessarily inferior to adults. Children rely more on dry heat dissipation by their larger relative skin surface area than on evaporative heat loss. This also enables them to evaporate sweat more efficiently with the added bonus of conserving water better than adults.
Plasma lipoprotein (a), homocysteine, and other cardiovascular disease (CVD) risk factors in Nigerians with CVD
Authors: Ebesunun M.O. , Agbedana E.O. , Taylor G.O.L. , Oladapo O.O.
Published: April 2008

Elevated plasma lipoprotein (a) (Lp(a)) and total homocysteine (tHcy) concentrations, as well as fat distributions, are associated with cardiovascular disease (CVD) risk. The purpose of this study was to evaluate plasma Lp(a), tHcy, percentage body fat, anthropometric indices, and blood pressure (BP) and their relationships with each other in well-defined, hospital-based, CVD patients in a Nigerian African community. One hundred seventy patients suffering from hypertensive heart disease, hypertension, ischaemic heart disease, and myocardial infraction with the mean age of 45.3 ± 1.3 years and 58 apparently healthy volunteers with the mean age of 44.8 ±1.2 years were selected. Anthropometric indices and BP were measured. Percentage body fat, body mass index, and waist-to-hip ratio (WHR) were calculated. Plasma Lp(a) and tHcy concentrations were determined. The results showed significant increases in BP, skinfold thickness (SFT) variables, and WHR in all of the CVD patients. Plasma Lp(a) was also significantly increased (p < 0.001), whereas the slight increase in the mean tHcy was not statistically significant. Positive significant correlations were found between systolic BP, triceps, SFT, and percentage body fat (p < 0.01), whereas significant correlations were found between some body composition variables, tHcy, and systolic BP (p < 0.05). Our findings provide supportive evidence for altered plasma Lp(a) concentration in addition to some other traditional CVD risk factors in Nigerians. The role of homocysteine is not well defined.
Relationship between the metabolic syndrome and physical activity energy expenditure: a MONET study
Authors: Karelis Antony D. , Lavoie Marie-Ève , Messier Virginie , Mignault Diane , Garrel Dominique , Prud’homme Denis , Rabasa-Lhoret Rémi
Published: April 2008

The purpose of this cross-sectional study was to examine the association between the metabolic syndrome (MetS) and physical activity energy expenditure (PAEE) in overweight and obese sedentary postmenopausal women. The study population consisted of 137 overweight and obese sedentary postmenopausal women (age, 57.7 ± 4.8 years; BMI, 32.4 ± 4.6 kg·m–2). Subjects had the MetS if 3 out of the following 5 criteria were met: visceral fat > 130 cm2, high-density lipoprotein (HDL) cholesterol < 1.29 mmol·L–1, fasting triglycerides ≥ 1.7 mmol·L–1, blood pressure ≥ 130/85 mmHg, and fasting glucose ≥5.6 mmol·L–1. We measured (i) body composition (by dual-energy X-ray absorptiometry); (ii) visceral fat (by computed tomography); (iii) insulin sensitivity (using the hyperinsulinemic-euglycemic clamp); (iv) plasma lipids, fasting glucose, and insulin, as well as 2 h glucose during an oral glucose tolerance test; (v) resting blood pressure; (vi) peak oxygen consumption (VO2 peak); (vii) PAEE (using doubly labeled water); and (viii) lower-body muscle strength (using weight-training equipment). Forty-two women (30.7%) had the MetS in our cohort. Individuals without the MetS had significantly higher levels of PAEE (962 ± 296 vs. 837 ± 271 kcal·d–1; p < 0.05), VO2 peak (18.2 ± 3.0 vs. 16.7 ± 3.2 mL·min–1·kg–1; p < 0.05), and insulin sensitivity, as well as significantly lower levels of 2 h glucose and central lean body mass. No differences in total energy expenditure, resting metabolic rate, and muscle strength between groups were observed. Logistic regression analysis showed that 2 h glucose (odds ratio (OR): 1.50 (95% CI 1.17–1.92)), central lean body mass (OR: 1.17 (95% CI 1.05–1.31)), and PAEE (OR: 0.998 (95% CI 0.997–1.000)), but not VO2 peak and (or) muscle strength, were independent predictors of the MetS. Lower levels of PAEE and higher levels of 2 h glucose, as well as central lean body mass, are independent determinants of the MetS in our cohort of overweight and obese postmenopausal women.
eIF4E, the mRNA cap-binding protein: from basic discovery to translational researchThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Systems and Chemical Biology, and has undergone the Journal's usual peer review process.
Authors: Sonenberg Nahum
Published: April 2008

Translational control is an important strategy by which eukaryotic cells regulate gene expression. Translation is the last step in the flow of genetic information, and regulation at this level allows an immediate and rapid response to changes under physiological conditions. Because the processes of mRNA biogenesis, including transcription, splicing, and export to the cytoplasm, are time consuming, the use of pre-existing mRNAs via the control of translation is advantageous in many circumstances. A prime target of translational control is the initiation factor eIF4E, which recognizes the m7GpppN cap structure present at the 5′ end of all nuclear transcribed eukaryotic mRNAs. In this article I describe the discovery of eIF4E, its mechanism of action in translation initiation, and its role in the control of cancer and innate immunity.
Effect of soil microstructure on the compressibility of natural Singapore marine clay
Authors: Low Han-Eng , Phoon Kok-Kwang , Tan Thiam-Soon , Leroueil Serge
Published: April 2008

The effect of soil microstructure on the compressibility of natural Singapore marine clay is studied in this paper. It was found that natural Singapore marine clay can sustain higher void ratio than reconstituted Singapore marine clay at the same effective stress in one-dimensional compression. This difference is most noticeable between yield stress and two times the yield stress. This void ratio difference is commonly attributed to soil microstructure, and the decrease in this difference at higher stresses is attributed to progressive destructuration. As a consequence of progressive destructuration, the virgin compression curve is nonlinear and the compression index along the virgin compression range is variable, which is only noticeable during the constant rate of strain consolidation test on high-quality samples. In the absence of high-quality samples and constant rate of strain consolidation tests, an empirical method is proposed to obtain a first-order estimation of a nonlinear virgin compression curve using index properties and yield stress. This paper demonstrates that the proposed method works reasonably well with natural Singapore marine clay. The error bound for the predicted compression indices is approximately ±20% of the compression indices measured with constant rate of strain test on high-quality samples.
A decision analysis framework for the assessment of likely post-failure velocity of translational and compound natural rock slope landslides
Authors: Glastonbury James , Fell Robin
Published: April 2008

An integral component of the assessment of hazard and risk for landslides from large natural rock slopes is the examination of the likely consequences associated with failure. This in turn is inherently related to the post-failure velocity of the slide mass. This paper presents a decision analysis framework for assessment of the post-failure velocity of such slopes. The paper includes discussion of characteristics that influence the post-failure velocity and presents decision trees and supporting matrices to allow assessment of the likely post-failure velocity of translational and internally sheared compound landslides. These represent the most common classes of large rock landslides. The framework is based on data gathered from a large number of landslides from natural rock slopes and incorporates information from a study of excavated rock slopes. These landslides have been studied to determine the factors and characteristics of rock slope failures that influence the post-failure velocity. The framework provides an ability to semiquantitatively assess the uncertainty in prediction of the likely post-failure velocity and identify critical areas of investigation, which would allow for reduction of this uncertainty. The method is expected to be of most use in a quantitative or qualitative risk-based analysis for landslide safety management.
Design of geosynthetic reinforcements for platforms subjected to localized sinkholes
Authors: Villard Pascal , Briançon Laurent
Published: April 2008

Construction of road and railway platforms in areas subject to localized sinkholes requires the use of specific reinforcements, for example, geosynthetics. The current design method for these structures is based on the assumption that there is no displacement of the geosynthetic in the anchorage areas on either side of the cavity. A new analytical method is proposed that takes into account the displacements and deformation of the geosynthetic reinforcement in the anchorage areas and the increase in stress at the edge of the cavity. To validate this new analytical method, a full-scale experiment was carried out; the use of optical fibre sensors integrated into the geosynthetic sheet made it possible to accurately measure the strain of the geosynthetic reinforcement. Comparison of the results obtained by this new analytical method with measurements of a full-scale experiment and the results of a finite element model confirmed the relevance of these new developments.
Clogging: bridge formation and vibration-based destabilization
Authors: Valdes Julio R. , Santamarina J. Carlos
Published: April 2008

The migration of mobile particles through porous networks is restricted when the size of the migrating particles approaches the size of pore throats. In this case, single particle retention or entrapment by bridge formation takes place. Experimental results show that bridge formation and stability are controlled by particle shape, relative throat-to-particle size, and skeletal forces. Forced-vibration studies provide additional insight into bridge stability and the potential for vibration-based unclogging, and show that it is easier to prevent bridge formation than to destabilize already formed bridges. Results from these pore-scale studies are relevant to filter clogging and unclogging, water and oil extraction, sand production in oil wells, and in food grain, aggregate and powder handling operations.
Performance of gravity caisson on sand compaction piles
Authors: Leung Chun Fai , Shen Rui Fu
Published: April 2008

Gravity caissons were employed as part of the wharf front structures for a container port terminal in Singapore. This paper reports the movements of eight consecutive gravity caissons supported on sand compaction piles (SCPs) with highly variable lengths of penetration. It is established that the caisson movements increase with an increase in the length of the SCP, as longer SCPs are necessary when hard strata are at greater depth. The large caisson movements observed during caisson infilling and backfilling do not pose a concern because the wharf deck beams connecting adjacent caissons can be adjusted. However, the caisson movements under service loads would affect the operation of the overlying quay cranes on top of the caissons. The present field study reveals that preloading the caissons is effective in reducing the caisson movements under service loads because the observed caisson movements are insignificant during subsequent unloading–reloading of the caissons. Back-analysis using the finite element method (FEM) shows that the observed caisson movements at different construction stages can be reasonably replicated. The numerical results are also used to evaluate the caisson tilt angle, which could not be measured in the present field study. The caisson tilt is found to be independent of the length of SCPs underneath a caisson.
Two-scale modeling of unsaturated water flow in a double-porosity medium under axisymmetric conditions
Authors: Szymkiewicz Adam , Lewandowska Jolanta , Angulo-Jaramillo Rafael , Butlańska Joanna
Published: April 2008

In this paper the development and experimental validation of a numerical model of two-dimensional unsaturated flow in a double-porosity medium is presented. The model is based on the coupled formulation for flow in macro- and micropores obtained by homogenization. It was applied to simulate the axisymmetrical tension disk infiltration experiments that were carried out in a double-porosity medium. The physical model was a three-dimensional periodic structure, composed of porous spheres made of sintered clay and embedded in Hostun fine sand HN38. The hydraulic parameters of both porous materials were determined by inverse analysis of independent infiltration experiments performed on sand and sintered clay. The effective parameters of the double-porosity medium were calculated from the solution of the local boundary value problem, obtained from the homogenization procedure. The cumulative infiltration curve and the global dimensions of the humidified zone obtained from the numerical solution are in good agreement with the observations. Moreover, numerical simulations showed the existence of a narrow zone of local nonequilibrium that moves with the infiltration front. Upstream of this zone, the infiltration bulb is in the local equilibrium conditions.
Anisotropic shear strength of a residual soil of sandstone
Authors: Bica Adriano Virgilio Damiani , Bressani Luiz Antônio , Vendramin Diego , Martins Flávia Burmeister , Ferreira Pedro Miguel Vaz , Gobbi Felipe
Published: April 2008

This paper discusses results of laboratory tests carried out with a residual soil originated from the weathering of eolian sandstone from southern Brazil. Parent rock features, like microfabric and particle bonding, are remarkably well preserved within this residual soil. Stiffness and shear strength properties were evaluated with consolidated drained (CID) and consolidated undrained (CIU) triaxial compression tests. Undisturbed specimens were tested with two different orientations between the specimen axis and bedding surfaces (i.e., parallel (δ = 0°) or perpendicular (δ = 90°)) to investigate the effect of anisotropy. When CID triaxial tests were performed with δ = 0°, the yield surface associated with the structure was much larger than when tests were performed with δ = 90°. Coincidently, CIU tests with δ = 0° showed peak shear strengths much greater than for δ = 90° at comparable test conditions. Once the peak shear strength was surpassed, CIU tests followed collapse-type effective stress paths not shown by corresponding tests with remolded specimens. A near coincidence was observed between the yield surface determined with CID tests and the envelope of collapse-type effective stress paths for δ = 0° and δ = 90°.
Compression testing and analysis of drilled concrete tapered piles in cohesive-frictional soil
Authors: Khan M. Kamran , El Naggar M. Hesham , Elkasabgy Mohamed
Published: April 2008

When pile driving is difficult and (or) economically not viable, cast-in-place piles are indispensable. Tapered piles, which have top cross-sections larger than the bottom cross-sections, have the potential for substantial advantages over conventional straight-sided piles. This paper investigates the construction and performance of innovative drilled concrete tapered piles. A full-scale pile load-testing program was conducted to evaluate the axial compressive capacity of drilled concrete tapered piles in frictional soil. One straight and three tapered augers were designed and manufactured to produce six piles. The piles that were constructed and tested included four tapered and two straight piles. The testing results showed that tapered piles with a taper angle varying between 0.95° and 1.91° had a load carrying capacity up to 50% higher than the straight-sided piles with equal volume. It should be noted, however, that the experimental results are site specific. Moreover, an analytical expression was developed to evaluate the pile taper effect on its shaft capacity in terms of a taper coefficient, Kt. The value of Ktevaluated from the analytical expression compared well with experimentally measured values. Finally, a two dimensional nonlinear finite element analysis was conducted to simulate the load test conditions, and it proved to be successful.
Seepage force in a drained circular tunnel: An analytical approach
Authors: Park Kyung-Ho , Lee Joo-Gong , Owatsiriwong Adisorn
Published: April 2008

This study deals with the investigation of analytical solutions for the seepage forces acting on the lining in a drained circular tunnel under the steady-state groundwater flow condition. Two different boundary conditions (one for zero water pressure and the other for a constant total head) along the tunnel circumference are mentioned. Simple closed-form analytical solutions for seepage force along the tunnel circumference are derived in a theoretically consistent way for two different boundary conditions by using the conformal mapping technique. The seepage force predictions are compared to investigate the differences among the solutions. It is shown that the seepage forces acting on the lining should be considered for a drained tunnel and that the seepage forces greatly increase for a very deep tunnel.
Influence de l’interaction de la température et de l’activité de l’eau sur la croissance et la production de l’ochratoxine A parAspergillus niger,Aspergillus carbonariusetAspergillus ochraceussur un milieu de base café
Authors: Kouadio Ahou Irène , Lebrihi Ahmed , Agbo Georges N’ zi , Mathieu Florence , Pfohl-Leszkowiz Annie , Dosso Mireille Bretin
Published: April 2008

Dans cette étude, l’influence de l’interaction de la température et de l’activité de l’eau sur la croissance fongique et la production de l’ochratoxine A sur un milieu de base café a été évaluée. La croissance optimale des trois souches d’ Aspergillus a été observée dans les mêmes conditions écologiques à savoir, 30 °C pour la température et 0,99 pour l’activité de l’eau. Les croissances journalières maximales sont 11,2, 6,92 et 7,22 mm/jour respectivement pour la souche d’Aspergillus niger, d’Aspergillus carbonarius et d’Aspergillus ochraceus. Cependant, les conditions écologiques de production optimale d'ochratoxine A varient selon la souche toxinogène avec comme facteur limitant, l’activité de l’eau. Cette production d’ochratoxine A est inhibée à la température de 42 °C et à l’activité de l’eau de 0,75. La correspondance établie entre les valeurs d’activité de l’eau testées en laboratoire et celles mesurées sur un lot de cerises mûres mis à sécher au soleil montre que les 5 premiers jours de séchage constituent la phase critique de multiplication fongique et de production de l’ochratoxine A. Ainsi, un séchage artificiel des cerises à une température supérieure à 42 °C évitera non seulement la multiplication fongique mais également la contamination de ce produit par l’ochratoxine A.
Effect of soil composition, temperature, indigenous microflora, and environmental conditions on the survival ofEscherichia coliO157:H7
Authors: Vidovic Sinisa , Block Hushton C. , Korber Darren R.
Published: April 2008

The survival of Escherichia coli O157:H7 in replicate soil microcosms was quantified in 2 types of silty clay loam soil (high carbon and low carbon) under either sterile or nonsterile conditions. Microcosms were held at –21, 4, and 22 °C under constant soil moisture content. Differences existed (P < 0.05) in survival of E. coli O157:H7 in low- and high-carbon soil at all temperatures, indicating an important role of soil composition on the survival of this pathogen. The highest death rate of E. coli O157:H7 in sterile soil occurred in the low-carbon soil at 4 °C, whereas in nonsterile soil the highest death rate was observed in the low-carbon soil at 22 °C. These results suggest that the most lethal effects on E. coli O157:H7 in the sterile system occurred via the synergy of nutrient limitation and cold stress, whereas in the nonsterile system lethality was owing to inhibition by indigenous soil microorganisms and starvation. Results obtained from an in situ field survival experiment demonstrated the apparent sensitivity of E. coli O157:H7 cells to dehydration, information that may be used to reduce environmental spread of this pathogen as well as formulate appropriate waste management strategies.
Pulsed-light system as a novel food decontamination technology: a review
Authors: Elmnasser N. , Guillou S. , Leroi F. , Orange N. , Bakhrouf A. , Federighi M.
Published: April 2008

In response to consumer preferences for high quality foods that are as close as possible to fresh products, athermal technologies are being developed to obtain products with high levels of organoleptic and nutritional quality but free of any health risks. Pulsed light is a novel technology that rapidly inactivates pathogenic and food spoilage microorganisms. It appears to constitute a good alternative or a complement to conventional thermal or chemical decontamination processes. This food preservation method involves the use of intense, short-duration pulses of broad-spectrum light. The germicidal effect appears to be due to both photochemical and photothermal effects. Several high intensity flashes of broad spectrum light pulsed per second can inactivate microbes rapidly and effectively. However, the efficacy of pulsed light may be limited by its low degree of penetration, as microorganisms are only inactivated on the surface of foods or in transparent media such as water. Examples of applications to foods are presented, including microbial inactivation and effects on food matrices.
Comparative study of the hemagglutinin and neuraminidase genes of influenza A virus H3N2, H9N2, and H5N1 subtypes using bioinformatics techniques
Authors: Ahn Insung , Son Hyeon S.
Published: April 2008

To investigate the genomic patterns of influenza A virus subtypes, such as H3N2, H9N2, and H5N1, we collected 1842 sequences of the hemagglutinin and neuraminidase genes from the NCBI database and parsed them into 7 categories: accession number, host species, sampling year, country, subtype, gene name, and sequence. The sequences that were isolated from the human, avian, and swine populations were extracted and stored in a MySQL®database for intensive analysis. The GC content and relative synonymous codon usage (RSCU) values were calculated using JAVA codes. As a result, correspondence analysis of the RSCU values yielded the unique codon usage pattern (CUP) of each subtype and revealed no extreme differences among the human, avian, and swine isolates. H5N1 subtype viruses exhibited little variation in CUPs compared with other subtypes, suggesting that the H5N1 CUP has not yet undergone significant changes within each host species. Moreover, some observations may be relevant to CUP variation that has occurred over time among the H3N2 subtype viruses isolated from humans. All the sequences were divided into 3 groups over time, and each group seemed to have preferred synonymous codon patterns for each amino acid, especially for arginine, glycine, leucine, and valine. The bioinformatics technique we introduce in this study may be useful in predicting the evolutionary patterns of pandemic viruses.
Chromosomal model for analysis of a long CTG/CAG tract stability in wild-type Escherichia coli and its nucleotide excision repair mutants
Authors: Szwarocka Sylwia T. , Stączek Paweł , Parniewski Paweł
Published: April 2008

Many human hereditary neurological diseases, including fragile X syndrome, myotonic dystrophy, and Friedreich’s ataxia, are associated with expansions of the triplet repeat sequences (TRS) (CGG/CCG, CTG/CAG, and GAA/TTC) within or near specific genes. Mechanisms that mediate mutations of TRS include DNA replication, repair, and gene conversion and (or) recombination. The involvement of the repair systems in TRS instability was investigated in Escherichia coli on plasmid models, and the results showed that the deficiency of some nucleotide excision repair (NER) functions dramatically affects the stability of long CTG inserts. In such models in which there are tens or hundreds of plasmid molecules in each bacterial cell, repetitive sequences may interact between themselves and according to a recombination hypothesis, which may lead to expansions and deletions within such repeated tracts. Since one cannot control interaction between plasmids, it is also sometimes difficult to give precise interpretation of the results. Therefore, using modified lambda phage (λInCh), we have constructed a chromosomal model to study the instability of trinucleotide repeat sequences in E. coli. We have shown that the stability of (CTG/CAG)68tracts in the bacterial chromosome is influenced by mutations in NER genes in E. coli. The absence of the uvrC or uvrD gene products greatly enhances the instability of the TRS in the chromosome, whereas the lack of the functional UvrA or UvrB proteins causes substantial stabilization of (CTG/CAG) tracts.
Thiosulfate oxidation and mixotrophic growth of Methylobacterium oryzae
Authors: Anandham R. , Indiragandhi P. , Madhaiyan M. , Kim Kyounga , Yim Woojong , Saravanan V.S. , Chung Jongbae , Sa Tongmin
Published: April 2008

Thiosulfate oxidation and mixotrophic growth with succinate or methanol plus thiosulfate was examined in nutrient-limited mixotrophic condition for Methylobacterium oryzae CBMB20, which was recently characterized and reported as a novel species isolated from rice. Methylobacterium oryzae was able to utilize thiosulfate in the presence of sulfate. Thiosulfate oxidation increased the protein yield by 25% in mixotrophic medium containing 18.5 mmol·L–1of sodium succinate and 20 mmol·L–1of sodium thiosulfate on day 5. The respirometric study revealed that thiosulfate was the most preferable reduced inorganic sulfur source, followed by sulfur and sulfite. Thiosulfate was predominantly oxidized to sulfate and intermediate products of thiosulfate oxidation, such as tetrathionate, trithionate, polythionate, and sulfur, were not detected in spent medium. It indicated that bacterium use the non-S4intermediate sulfur oxidation pathway for thiosulfate oxidation. Thiosulfate oxidation enzymes, such as rhodanese and sulfite oxidase activities appeared to be constitutively expressed, but activity increased during growth on thiosulfate. No thiosulfate oxidase (tetrathionate synthase) activity was detected.
LINEAR RELATIONS FOR COEFFICIENTS OF DRINFELD MODULAR FORMS
Authors: KAZALICKI MATIJA
Published: April 2008

Choie, Kohnen and Ono have recently classified the linear relations among the initial Fourier coefficients of weight k modular forms on SL2(ℤ), and they employed these results to obtain particular p-divisibility properties of some p-power Fourier coefficients that are common to all modular forms of certain weights. Using this, they reproduced some famous results of Hida on non-ordinary primes. Here we generalize these results to Drinfeld modular forms.
THETA FUNCTION IDENTITIES AND REPRESENTATIONS BY CERTAIN QUATERNARY QUADRATIC FORMS
Authors: ALACA AYŞE , ALACA ŞABAN , LEMIRE MATHIEU F. , WILLIAMS KENNETH S.
Published: April 2008

Some new theta function identities are proved and used to determine the number of representations of a positive integer n by certain quaternary quadratic forms.
ARITHMETIC OF ℓ-REGULAR PARTITION FUNCTIONS
Authors: PENNISTON DAVID
Published: April 2008

Let bℓ(n) denote the number of ℓ-regular partitions of n, where ℓ is prime and 3 ≤ ℓ ≤ 23. In this paper we prove results on the distribution of bℓ(n) modulo m for any odd integer m > 1 with 3 ∤ m if ℓ ≠ 3.
ALGEBRAIC QUANTUM PERMUTATION GROUPS
Authors: Bichon Julien
Published: April 2008

We discuss some algebraic aspects of quantum permutation groups, working over arbitrary fields. If 𝕂 is any characteristic zero field, we show that there exists a universal cosemisimple Hopf algebra coacting on the diagonal algebra 𝕂n: this is a refinement of Wang's universality theorem for the (compact) quantum permutation group. We also prove a structural result for Hopf algebras having a non-ergodic coaction on the diagonal algebra 𝕂n, on which we determine the possible group gradings when 𝕂 is algebraically closed and has characteristic zero.
HOMOMORPHISMS OF DIRECTED POSETS
Authors: Chajda Ivan
Published: April 2008

We modify the concept of SL-homomorphism introduced by K.P. Shum, P. Zhu and N. Kehayopulu [7] for directed posets. Since every directed poset can be converted into an algebra called a directoid, we investigate the relationship between our homomorphisms and these of directoids. We point out that no modification of SL-congruences is necessary since congruences induced by our homomorphisms are just that of directoids.
UNARILY EXTENDED SEMILATTICES
Authors: Marczak Adam W. , Płonka Jerzy
Published: April 2008

In this paper we give equational and structural characterizations of all algebras representing the sequence (0, 3,1,1,…). In the first part of the paper we prove that an algebra without constants has exactly three distinct essentially unary term operations and exactly one essentially n-ary term operation for every n > 1 if and only if it is clone equivalent to a generic of one of three varieties of algebras defined in Section 2. The second part of the paper is devoted to the representations of algebras from these three varieties by means of semilattice ordered systems of algebras.
ON AN INEQUALITY FOR DIVIDED DIFFERENCES
Authors: Pečarić J. , Lipanović M. Rodić
Published: April 2008

The main purpose of this paper is to give the generalization and improvement of the result given in [2] on the inequality of the difference of two integral means which can also be represented as the difference of two divided differences.