bluuebunny/crossref_metadata_2025 huggingface dataset:
Interleukin‐4 Induces Coxiella burnetii Replication in Human Monocytes but not in Macrophages
Authors: GHIGO ERIC , IMBERT GUENIÈVRE , CAPO CHRISTIAN , RAOULT DIDIER , MEGE JEAN‐LOUIS
Published: July 2009

Abstract: Coxiella burnetii, an obligate intracellular bacterium, is the agent of Q fever. The chronic disease is characterized by impaired cell‐mediated immune response and microbicidal activity of monocytes. We hypothesized that interleukin(IL)‐4, a Th2 cytokine, interferes with the fate of C. burnetii inside monocytes. C. burnetii survived without multiplication in resting monocytes, but replicated in IL‐4‐treated monocytes. The effect of IL‐4 is specific for monocytes since IL‐4 did not stimulate C. burnetii replication in monocyte‐derived macrophages. The effects of IL‐4 on bacterial replication and on tumor necrosis factor (TNF) production in monocytes were apparently not related. Although IL‐4 inhibited C. burnetii‐stimulated release of TNF, the addition of recombinant TNF to IL‐4‐treated monocytes did not prevent the IL‐4 effect. These results suggest that IL‐4 enables monocytes to support C. burnetii replication and a Th2 polarization of immune response that may interfere with immune control of Q fever.
Fusogenicity of the Coxiella burnetii Parasitophorous Vacuole
Authors: HOWE DALE , MELNIČÁKOVA JANA , BARÁK IMRICH , HEINZEN ROBERT A.
Published: July 2009

Abstract: This study investigated whether C. burnetii protein synthesis and replication is required for maintenance of the fusogenic character of the Coxiella parasitophorous vacuole (PV). Vero cells were infected with C. burnetii, (Nine Mile strain in phase II) at a multiplicity of infection of approximately 10 and simultaneously treated with bacteriostatic concentrations of chloramphenicol or carbenicillin. At 96 h post‐infection, cells were viewed by phase contrast microscopy for PV maturation. Mature, spacious PV containing multiple nonreplicating C. burnetii were clearly visible in infected Vero cells treated with the cell wall inhibitor carbenicillin. Conversely, mature, spacious PV did not form in cells treated with the protein synthesis inhibitor chloramphenicol. Rather, immunofluorescence microscopy revealed individual C. burnetii in small, tight PV scattered throughout the cytoplasm. Like mature PV, these PV localized with the lysosomal glycoprotein LAMP‐1, but not the early endosome protein EEA.1. This result suggests that de novo C. burnetii protein synthesis, but not replication, is required for homotypic fusion and maturation of nascent C. burnetii PV. We next examined whether sustained C. burnetii protein synthesis is necessary for maintenance of PV fusogenicity. J774A.1 murine macrophage‐like cells with mature C. burnetii PV were incubated with latex beads and the trafficking of beads to PV was quantified. Fusion of PV with bead‐laden vacuoles was severely inhibited in cells treated with chloramphenicol. These results suggest that sustained C. burnetii protein synthesis is required for PV fusion with other vacuoles of the endocytic pathway.
Interactions between Rickettsiae andDermacentor variabilisTicks
Authors: MACALUSO KEVIN R. , MULENGA ALBERT , SIMSER JASON A. , AZAD ABDU F.
Published: July 2009

Abstract:Tick‐borne spotted fever group rickettsiae are maintained in nature primarily through transstadial and transovarial transmission in their vector. In the tick,Dermacentor variabilis, the infection of, and persistence within, the ovaries are critical steps in the transmission cycle of rickettsiae from one generation to the next. Although ixodid ticks can experimentally maintain several species of rickettsiae, often only a single species is maintained transovarially. The molecular mechanisms underlying exclusion processes are unknown. In this study, an attempt to identify the molecules that may be involved in rickettsial adhesion to tick cells was carried out. Monoclonal antibodies to mammalian alpha and beta subunits of integrins were used to screen a lambda phage library, constructed from uninfected tick ovarian tissues. Positive plaques for both alpha and beta integrins were identified. For one integrin, β3, the plaque was isolated and the insert sequenced. The role of these molecules, identified by library screening, in rickettsial infection and survival are discussed.
Molecular Pathogenesis of Coxiella burnetii in a Genomics Era
Authors: SAMUEL J. E. , KISS K. , VARGHEES S.
Published: July 2009

Abstract: The agent of acute and chronic Q fever, Coxiella burnetii, occupies a unique niche among intracellular pathogens. The mechanisms the organism employs to cause disease are unclear but involve persistence in a parasitophorous vacuole and the subsequent host response. Studies designed to model molecular mechanisms of pathogenesis have relied upon indirect evidence for testing the role of virulence factors since methods for generation of defined mutations have not been developed. Evidence suggests replication involving a developmental lifecycle is critical for intra‐ and extracellular survival but this cycle is incompletely defined. It has been proposed that survival in the phagolysosomal‐like parasitophorous vacuole requires specific iron uptake systems, secretion of enzymes to detoxify the compartment (catalase and SOD), and down‐regulation of an oxidative burst (acid phosphatase). Studies to test these potential virulence mechanisms can be accelerated with the recent development of the complete genome sequence for the prototype acute disease isolate, Nine Mile. Proteins differentially expressed during the developmental cycle can more readily be identified with MALDI‐TOF description of proteomic profiles. Genes encoding secreted Cu/Zn SOD, catalase, and acid phosphatase are predicted and can be tested for function and expression. An iron regulon is predicted based upon Fur‐regulated open reading frames. The specific role the iron‐regulated genes play in iron acquisition can be tested. Confirmation of the iron regulon and others can be tested using microarrays based upon the genomic ORF predictions. These are examples of how we are rapidly changing the experimental approaches used to investigate C. burnetii to improve our understanding of the biology of this unusual and highly adapted organism.
Analysis of 16S rRNA Gene Sequences of Ehrlichia canis, Anaplasma platys, and Wolbachia Species from Canine Blood in Japan
Authors: UNVER AHMET , RIKIHISA YASUKO , KAWAHARA MAKOTO , YAMAMOTO SHIZUO
Published: July 2009

Abstract: In the present study, three canine blood samples from Japan, that were suspected to be ehrlichia positive were examined. After sequencing the 16S rRNA genes, each dog was found to be infected either with Ehrlichia canis (Kagoshima 1), Anaplasma platys (Okinawa 1), or Wolbachia sp. (Okinawa 2). Phylogenic analysis was performed on these sequences. The nearly entire 16S rRNA sequence of Kagoshima 1 was found to be most similar to the sequences from Oklahoma and Venezuela E. canis strains (1 base pair difference out of 1,387, 99.9% sequence identity). The 16S rRNA gene sequence of Okinawa 1 showed the closest DNA identity to the French strain of A. platys (1 base deletion out of 1,385 bp, 99.6% sequence identity). The 16S rRNA gene sequence of Okinawa 2 illustrated the closest DNA identity to that of a Wolbachia sp. from Dirofilaria immitis (98.9% sequence similarity). These data imply a low diversity within E. canis strains and within A. platys strains, including those strains reported in this study. This is also the first demonstration of Wolbachia DNA in dog blood, suggesting the involvement of Wolbachia sp. in canine febrile illnesses.
Genetic Analysis of Isolates of Rickettsia rickettsii That Differ in Virulence
Authors: EREMEEVA MARINA E. , KLEMT RYAN M. , SANTUCCI‐DOMOTOR LISA A. , SILVERMAN DAVID J. , DASCH GREGORY A.
Published: July 2009

Abstract: We examined the degree of intraspecies genetic polymorphisms present among 13 R. rickettsii strains isolated from the blood of patients and ixodid ticks from North and South America. Preliminary confirmation of these isolates as R. rickettsii was done by evaluating RsaI and PstI restriction fragment length polymorphic (RFLP) sites in a 631 bp fragment of the rOmpA gene amplified with primers encompassing the Rr190.70‐701 nt region. All isolates had the same profile, which was identical to that previously described for strain Bitterroot. The AluI RFLP analysis of the rOmpA fragment differentiated only Hlp#2 isolate from the other strains. Two types of RFLP patterns were obtained for a 381 bp gltA fragment. Strains Bitterroot, Sheila Smith, Lost Horse Canyon, and Morgan contained an additional AluI fragment of 40 bp, compared to the four‐band profile of 122, 87, 81, and 43 bp determined for other isolates. These differences correlated with the absence of a CGC insert in the former isolates as determined by comparative DNA sequence analysis. To measure the levels of deletion/mutation events among isolates of R. rickettsii, DNA sequence analysis was performed on a portion of a 2,672 bp region spanning the 3′‐end of polA to the 5′‐end of dnaE. Except for Hlp#2 strain these isolates were highly conserved in the regions sequenced.
Probabilistic Evaluation of Aspirating Doses of a Q Fever Pathogen
Authors: VOROBEYCHIKOV E. V. , KURTZER G. M. , VASILENKO A. Z. , MISNIKOV O. P.
Published: July 2009

Abstract: The process of biological aerosol penetration into respiratory organs is connected with the estimation of the amount of an aspiration dose of microorganisms (D) a human gets in the center of infection. Here we submit a probabilistic model describing the process of hits of a Q fever pathogen in a human respiratory tract. This approach makes it possible to get qualitatively different probabilistic estimations of doses received and corresponding values of critical time intervals of exposure at which the amount accumulated in the respiratory tract turns into an infecting dose. This permits one to approach the explanation of the infection process in the context of the absence of its absolute nature, which is connected both with the immune system responses and the irregularity with which the recipient receives aspiration doses under conditions of artificial distribution of the microbe‐bearing aerosol.
Problems and Perspectives of Molecular Epidemiology of Infectious Diseases
Authors: TARASEVICH I. V. , SHAGINYAN I. A. , MEDIANNIKOV O. Y.
Published: July 2009

Abstract: Current tendencies and problems of molecular biology and its application in infectious diseases are discussed. Basic stages of the development of molecular epidemiology as a leading tool for epidemiological studies are reviewed. More than 30 years ago, molecular epidemiology was first used to study nosocomial infections. Special attention is given to the achievements of Russian scientists, especially in the discovery of Astrakhan spotted fever Rickettsia, noncultured forms of Vibrio cholerae, and the microorganism “Montezuma.” Also, the development of PCR‐based methods of identification and typing of Mycobacterium tuberculosis by Russian specialists and its significant role in strategies for diagnosing and treatment of tuberculosis are discussed. Now, the most important field of application of molecular biology methods is bacterial evolution, especially with regard to pathogenic microorganisms and emerging infections. Searching for the novel pathogenic agents, establishment of the infectious nature of diseases with unclear origin, and determining the precise mechanisms of pathogenicity are most intriguing issues. So, molecular biology should play a major role both in clinical and research fields.
Antiepileptic Drugs and Apoptosis in the Developing Brain
Authors: BITTIGAU PETRA , SIFRINGER MARCO , IKONOMIDOU CHRYSANTHY
Published: July 2009

Abstract:Epilepsy is the most common neurologic disorder in young humans. Antiepileptic drugs (AEDs), used to treat seizures in children, infants, and pregnant women, cause cognitive impairment, microcephaly, and birth defects by unknown mechanisms. We tested whether common AEDs cause neurodegeneration in the developing rat brain. Rats aged 3‐30 days received phenytoin, phenobarbital, diazepam, clonazepam, vigabatrin, or valproic acid. Histologic examination of the brains revealed that these drugs cause widespread and dose‐dependent apoptotic neurodegeneration in the developing rat brain during the brain growth spurt period. Apoptotic neurodegeneration was triggered at plasma drug levels relevant for seizure control in humans. Antiepileptic drugs lead to reduced expression of neurotrophins and decreased concentrations of the active forms of ERK1/2, RAF, and AKT. β‐Estradiol, which stimulates pathways that are activated by neurotrophins, ameliorated AEDs‐induced apoptotic neurodegeneration. Our findings present one possible mechanism to explain cognitive impairment and reduced brain mass associated with pre‐ or postnatal exposure of humans to antiepileptic therapy.
Hypoxic Preconditioning Prevents Cortical Infarction by Transient Focal Ischemia‐Reperfusion
Authors: LIN ANYA M.Y. , DUNG SHIANG‐WEN , CHEN CHAU‐FONG , CHEN WEN‐HAN , HO LOW‐TONE
Published: July 2009

Abstract: One of the proposed pathologic actions underlying brain infarction is excess free radicals resulting from reoxygenation. In this paper we report an investigation of the neuroprotective effect of hypoxic preconditioning on transient focal ischemia‐reperfusion injuries in rat brain. Female Wistar rats were subjected to 380 mmHg in an altitude chamber for 15 hours/day. Our ex vivo studies showed that auto‐oxidation and iron‐induced lipid peroxidation of brain homogenates of the four‐week hypoxia‐preconditioned rats were significantly lower than those of the normoxic rats. A focal infarction in the cerebral cortex of normoxic rats was consistently observed 24 hours after a 60‐minute transient ischemic occlusion of the right middle cerebral artery and bilateral common carotid arteries. Hypoxic preconditioning in fact attenuated cortical infarction in a duration‐dependent manner. Induction of the neuroprotection required two weeks of hypoxic preconditioning. Four weeks of hypoxic preconditioning significantly reduced the cortical infarcted area, the elevated lipid peroxidation, and resulted in an acute increase in cytosolic cytochrome c in the infarcted cortex of normoxic rats. The protective effect of four weeks of hypoxic preconditioning lasted seven days under a renormoxic condition. Our data suggest that oxidative stress may result in apoptosis in the transient focal ischemia‐reperfusion injuries. Furthermore, hypoxic preconditioning attenuated cortical infarction in the rat brain. Although supplementation of antioxidants may encounter difficulty at the blood‐brain barrier, hypoxic preconditioning is very likely to protect CNS targets from oxidative injuries without any barrier.
Environmental Conditions Unexpectedly Affect the Long‐Term Extent of Cell Death Following an Hypoxic Episode
Authors: ISAACSON ROBERT L. , FAHEY JEANNE M. , MUGHAIRBI FADWA AL
Published: July 2009

Abstract: Previously we reported delayed cell death, defined by clear‐cut cell loss 60 days after a nitrite‐induced hypoxic episode. The loss of cells was not apparent two weeks after the treatment, although some changes in cellular appearance were observed at that time. A similar delayed loss of neurons in the hippocampus after hypoxia induced by blood vessel occlusion has also been found. In addition, we reported that the amount of methemoglobinemia induced by the sodium nitrite can be reduced by the stress produced by handling and the injection of saline 2 or 24 h before the nitrite administration. The degree of methemoglobin formed is directly related to cell death in certain areas of the brain, including regions within the hippocampus. Considering the many effects that can be produced by chronic and acute stress of several kinds and the length of time during which these effects manifest themselves, we undertook to determine the histologic effects of the stresses of transport on the neuroanatomic effects of sodium nitrite administration 60 days post administration. Comparisons were made of the effects of two methods of transport from the laboratory in which the animals (male CD‐1 mice) were injected with the sodium nitrite or saline (Tufts Medical School) to the laboratory in which the histologic evaluations were made (Binghamton University). The animals began their travel several hours after the injections. One transport method was by commuter airline and the other was by automobile. All animals had the same transport from the supplier to the Boston location (truck). Thus, the stress of experimental interest occurred after the nitrite administration. Upon arrival at Binghamton University, the animals were housed at the University in their own colony room for 60 days before sacrifice. After sacrifice, sections from their brains were subjected to a number of histologic staining procedures, including PTAH, the Bielschowsky silver method, GFAP, and the standard Nissl procedure. Although special attention was paid to hippocampal areas, changes in cells in the habenulæ and the linings of ventricular areas were also prominent. Surprisingly, the nitrite treatment before transport to Binghamton offered partial protection against the very substantial and lasting effects of the injections, transport, and handling found in the control animals. Differential effects caused by the two methods of transport were also noted.
The Acute Effects of Acrylamide on Astrocyte Functions
Authors: ASCHNER MICHAEL , CAO CHENG‐CHEN , WU QI , FRIEDMAN MARVIN A.
Published: July 2009

Abstract: We assessed biochemical endpoints indicative of acute toxicity in neonatal rat primary astrocyte cultures exposed to acrylamide. Metallothionein (MT), glutamine synthetase (GS), glutamate/aspartate transporter (GLAST), and taurine transporter (tau‐T) mRNA expression levels as well as cell volume were determined in astrocytes acutely treated with 0.1 and 1.0 mM acrylamide. Statistically significant changes in acrylamide treated astrocytes were noted for GS (0.1 mM) and GLAST (1.0 mM) mRNA expression levels. All other measurements were insignificant in comparison with controls, suggesting that astrocytic function is minimally compromised even at exceedingly high levels of acute acrylamide exposure.
Mathematical Modeling of Skin Bioheat Transfer
Authors: Xu F. , Lu T. J. , Seffen K. A. , Ng E. Y. K.
Published: July 2009

Advances in laser, microwave, and similar technologies have led to recent developments of thermal treatments for disease and injury involving skin tissue. In spite of the widespread use of heating therapies in dermatology, they do not draw upon the detailed understanding of the biothermomechanics of behavior, for none exists to date, even though each behavioral facet is well established and understood. It is proposed that a detailed understanding of the coupled biological-mechanical response under thermal agitation will contribute to the design, characterization, and optimization of strategies for delivering better treatment. For a comprehensive understanding on the underlying mechanisms of thermomechanical behavior of skin tissue, recent progress on bioheat transfer, thermal damage, thermomechanics, and thermal pain should be systematically reviewed. This article focuses on the transfer of heat through skin tissue. Experimental study, theoretical analysis, and numerical modeling of skin thermal behavior are reviewed, with theoretical analysis carried out and closed-form solutions obtained for simple one-layer Fourier theory based model. Non-Fourier bioheat transfer models for skin tissue are discussed, and various skin cooling technologies summarized. Finally, the predictive capacity of various heat transfer models is demonstrated with selected case studies.
Assessment of the Ocular Response Analyzer as a Tool for Intraocular Pressure Measurement
Authors: Elsheikh Ahmed , Alhasso Daad , Kotecha Aachal , Garway-Heath David
Published: July 2009

The ocular response analyzer (ORA) is a new indentation tonometer that subjects the cornea to an increasing then decreasing air pulse, and uses the corresponding two applanation pressures P1 and P2 to estimate the intraocular pressure (IOP). The present study aims to improve the accuracy of IOP estimation through representative numerical simulation of the ORA procedure. A parametric study has been carried out to consider the effect of corneal thickness, curvature, age, and true IOP on the P1 and P2 measurements. Based on the obtained database of input and output parameters, an equation has been suggested relating the P1 and P2 measurements to the value of IOP. The equation is intended to make IOP estimates independent of corneal stiffness, which varies with size and age. The equation has been tested against a clinical data set obtained at Moorfields Eye Hospital involving 144 subjects, and found to produce IOP estimates that are less dependent on corneal size and age than published equations.
Convergence Properties of a Computational Learning Model for Unknown Markov Chains
Authors: Malikopoulos Andreas A.
Published: July 2009

The increasing complexity of engineering systems has motivated continuing research on computational learning methods towards making autonomous intelligent systems that can learn how to improve their performance over time while interacting with their environment. These systems need not only to be able to sense their environment, but should also integrate information from the environment into all decision making. The evolution of such systems is modeled as an unknown controlled Markov chain. In previous research, the predictive optimal decision-making (POD) model was developed that aims to learn in real time the unknown transition probabilities and associated costs over a varying finite time horizon. In this paper, the convergence of POD to the stationary distribution of a Markov chain is proven, thus establishing POD as a robust model for making autonomous intelligent systems. The paper provides the conditions that POD can be valid, and an interpretation of its underlying structure.
Mobile Agent Technology for Distributed Sensing and Actuation Systems
Authors: Chen Bo
Published: July 2009

Distributed sensing and actuation systems research has drawn a great attention in recent years from various research communities. These systems are usually deployed in wild fields using a wireless network for the communication. Due to the shortage of power supply and bandwidth, the less communication between system components is desired since it consumes much more power comparing with local computation and uses network bandwidth. In addition, the dynamics of the deployed environments requires distributed sensing and actuation systems being self-organized, scalable, and adaptable. To achieve these desirable characteristics, this paper proposes a mobile agent approach to reduce raw data transmission over a network and increase the flexibility of a distributed sensing and actuation system. The basic ideas of the proposed mobile agent method and the framework based on a mobile agent system called Mobile-C are introduced. Mobile-C is embedded into sensor nodes consisting of an embedded computer and several expansion boards for analog/digital signal input/output and wireless communication. The advantages of using mobile agent based wireless sensor networks for intelligent structure health monitoring are discussed, and a data analysis mobile agent example is given to demonstrate the capability of such a network to dynamically deploy data analysis algorithms and reduce raw data transmission.
Application of Extended Kalman Filter in a Forced-Feedback Metering Poppet Valve System
Authors: Li Chang , Fales Roger
Published: July 2009

This work focuses on an accurate Extended Kalman Filter (EKF) estimator, which is applied in a forced-feedback metering poppet valve system (FFMPVS). The EKF estimator is used to estimate the position and velocity of the main poppet valve, the pilot poppet valve and the piston through using the control volume pressure, the load pressure and the pressure between the pilot poppet and the actuator housing, which are all disturbed by noise. The EKF estimator takes advantage of its recursive optimal state estimation to estimate the states of this metering poppet valve, which is a non-linear, time-variant dynamical system in real time. The EKF estimator has robustness to parameter variations and ability to filter measurement noises. It is shown that the EKF estimator tracks the states confidently and promptly for both the steady-state and transient performance, at the same time, the EKF estimator also filters the noise of the measured pressures.
Theoretical and Practical Aspects About Bio-Lubrication of Synovial Joints by Radioactive Molecular Treatment
Authors: Ungur Petru , Patcas Elisabeta , Pop Petru A. , Corbu Silviu , Marcu Florin M.
Published: July 2009

The paper has presented the result of tests and researches realized at our university and Oncology Clinical Hospital from Oradea, Radiotherapy Section, about improving of biolubrication between cartilages in relative moving of synovial joints with osteoarthritis, having slow evolution under non-conventional treatment of irradiation with gamma ray. By radioactive molecular treatment of synovial joints with gamma ray, type hinge of knee and spheres of disorder hip (gon-arthrosis and cox-arthrosis), changed molecular structures of porous cartilages and of synovial fluid in contact. All these due to partial recovering of mechanical-elastic and damper system that was spoiling, with a great reducer of pains, altering some orthopedic and non-conventional treatments at overweight patients, which are been impossible by surgery. This paper has presented a theoretical model of human body subjected the applied and conjunction forces, which explained the damping of vibrations and shocks inside of synovial joints by elastic modulus-E of bone cartilages in contact and variation of dynamic viscosity-η of synovial fluid. This work had proposed to promoted osteoarthritis therapy by using irradiation with gamma ray, being ones of the most modern active molecular treatments by using irradiation with particles in radiotherapy from neurological field.
On the Prediction of the Strain Rate Intensity Factor in Metal Forming Processes
Authors: Lyamina Elena
Published: July 2009

The strain rate intensity factor is the coefficient of the principal singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. Such singular behaviour occurs in the case of several rigid plastic models (rigid perfectly plastic solids, the double-shearing model, the double slip and rotation model, some of viscoplastic models). Since it is only possible to introduce the strain rate intensity factor for singular velocity fields, it is obvious that standard finite element codes cannot be used to calculate it. The currently available distributions of the strain rate intensity factor have been found from closed form solutions or with the use of simple approximate solutions (for instance upper bound solutions). Closed form solutions are available for boundary value problems with simple geometry (flow through infinite rough channels, compression of infinite layers between rough plates and so on) and, therefore, are mostly of academic interest. Simple approximate solutions can predict general tendencies in the distribution of the strain rate intensity factor but cannot predict its distribution with a sufficient accuracy for industrial applications. For, the strain rate intensity factor reflects a very local effect inherent in the velocity field whereas simple approximate methods, such as the upper bound method, estimate global parameters, such as the limit load. The purpose of the present research is to propose a special numerical technique for calculating the strain rate intensity factor in the case of plane strain deformation of rigid perfectly plastic materials and to verify it by means of comparison with an analytical solution. The technique is based on the method of Riemann.
Educating Children in Manufacturing and Mechanical Concepts
Authors: Hill Rodney
Published: July 2009

A multilevel, multifaceted learning environment has been designed at the NSF Engineering Research Center for Reconfigurable Manufacturing Systems (ERC/RMS) to help young children (ages 5 to 10 years) understand the basic concepts of manufacturing industry and to appreciate why manufacturing is important to their lives. The design of this environment is grounded on observed interactions of children and technology, research literature on pupil’s understanding of mechanics and on the concepts of a rich learning environment. The components of this environment include stories, cartoon characters, puzzles, games, and solitary and group activities. The activities require easily available household objects and common toys. These materials are targeted for families with early-elementary and home-schooled children.
Development of an Integrated Design System (IDS) for Hydraulic Machinery
Authors: Schmalhorst C. , Fluri B. , Schilling R.
Published: July 2009

An integrated computer-aided system for the initial design and optimisation of hydraulic machinery components, i.e. bladings of centrifugal pumps and fans as well as of water turbines, is presented. The IDS developed at the Institute of Fluidmechanics consists of an artificial neural network (ANN) for the initial design of components, a finite volume CFD-code based on the Reynolds-averaged Navier-Stokes equations and a finite element based computational structural analysis (CSA) code, as well as of an efficient module for the interactive modification of geometry of components. The design and optimisation process is demonstrated for a Francis turbine runner blading. The process starts with an initial design taken from the ANN which is in the next step analysed by means of our inhouse Navier-Stokes solver NS3D with respect to the performances to be guaranteed. The turbine stage is modelled as a single blade passage of the rotor and a stator blading. The CFD-results may be analysed by tailor-made post-processing. Based on the numerical simulation results the initial design may be interactively improved in an iterative process. The design targets in this stage of the process are efficiency and cavitation behaviour of the runner. Finally, the CFD-results are used as boundary conditions for a steady state CSA simulation yielding the distribution and magnitude of stresses within the runner, especially between the blades and the runner band (shroud). In addition to the time-independant CFD- and CSA-simulations a transient Fluid-Structur-Interaction (FSI) analysis may be simulated taking into account all blade passages in the rotor as well as in the stator. This simulation model yields a much more accurate loading of the structure due to unsteady pressure distributions. In this step the design can be scrutinised with respect to its fatigue resistance. After generating a design satisfying all requirements and boundary conditions the optimised geometry is fed back into the ANN to be used for similar applications. After having carried out design and optimisation processes for a number of characteristic hydraulic machinery a higher level of efficiency and cavitation behaviour may be reached.
The Design of a Computational Framework for Multiphysics Simulation and Optimization of MEMS
Authors: Guo Jian , Querin Osvaldo M.
Published: July 2009

This paper presented the “Top-Down” design of a computational framework for multiphysics simulation and optimization of MEMS devices. This framework couples various existing phenomena-specific single-physics tools-each specialized for a most appropriate physical domain-into an integrated architecture, which allows MEMS designers to predict the behavior of a novel MEMS device and optimize it more exactly and more quickly. The most distinctive feature of the framework is its flexibility on implementing variant coupling strategies, which enables the framework perform the multiphysics simulation much more effective than others. The details of the framework and its implementation are described in this paper.
Lost Work in an Ecosystem Used as an Environmental Impact Index
Authors: Diaz-Mendez Sosimo E. , Rodriguez-Lelis Jose Maria , Hernandez-Guerrero Abel , Chavez Rosa Hilda
Published: July 2009

The work that an ecosystem can carry out decreases as a function of lost work, when some natural or anthropogenic alterations exist; the extinction of the ecosystem depends on how much lost work it can support. Lost work assessment in an ecosystem can be determined and then used as an indicator of the environmental impact. If the ecosystem is divided in subsystems and each subsystem is interrelated with the other ones, an ideal work can be obtained to revoke all the damage from each alteration in the ecosystem (being the subsystems the water, the soil, the atmosphere, the organisms and the society). Thus, the global index could be determined by adding the partial indexing of each subsystem, and could be used to determine the trend that an ecosystem will follow due to alterations.
Life Prediction of Electrical Power Transmission Towers
Authors: Salazar Juan E. , Mendoza Jesus A.
Published: July 2009

This paper presents a study conducted to estimate the remaining theoretical life of one type of 400 kV latticed steel towers installed on a power transmission line in Venezuela. The study focused on determining the structural behavior and vibration characteristics of suspension towers on the fore mentioned line, considering material loss of their structural members due to atmospheric corrosion, in different design conditions. For this purpose, a commercially available FEM code was used to build models to perform structural and modal analysis of the chosen type of tower, in order to determine load effects in the structure (stress and deformation), natural frequencies and mode shapes in each of the different design states. Then, a simple methodology engineered as part of this study leads to prediction of the tower’s service life based on an allowable state of stress and deformation in the tower (direct and vibration-induced) affected by different reliability factors and taking into account corrosion effects and corrosion rates in a particular environment along the transmission line.
Evaluation of Numerical Methods for Simulation of Weak Impact
Authors: Kochavi Eytan , Shafir Itay , Gruntman Shimon , deBotton Gal
Published: July 2009

An elastic cantilever beam subjected to weak impact is investigated with focus on its ability to absorb the impact energy. It was found that the location of impact along the beam has a significant influence on the kinetic energy absorbed. It was established in both, using an experimental setup and numerical computations. A reduced degrees of freedom analytical model of this simple continuous system is analyzed in order to explain its quite complicated behavior. The same impact spot, at which the maximum impact energy was absorbed, was predicted by the analytical model. At this location 90% of the kinetic energy is absorbed in the form of elastic beam vibrations. The results of this demonstration may be used for designing an elastic kinetic energy absorbing system.
Electrohydrodynamic Gas Pump in a Vertical Tube
Authors: Brown N. M. , Lai F. C.
Published: July 2009

The characteristics of an electrohydrodynamic (EHD) gas pump were experimentally evaluated in this study. Experiments were conducted using positive DC voltage (13.0 kV – 30.0 kV), applied to a thin corona wire of diameter 0.51 mm. The ground plate used in the study was mounted on the inner surface of a cylinder and had a width of 12.7 mm and a total exposed surface area of 1.52 × 10−3 m2. The pumps tested were identical except for their spacing between the emitting electrode and the ground plate, which varied from 0.66D to 1.33D. The results show that the current on the ground plate increases as the applied voltage increases. It is also observed that the applied voltage at which flow was first detected in the cylinder correlates well with the electrode spacing. It appears that the four electrodes placed along the surface of the pipe were able to disturb the boundary layer enough to create a uniform flow profile within the pipe. As a result, flow as high as 2.5 m/s was observed in the cylinder with an electrode spacing of L/D = 1.33. The results also show that the ionic wind velocity increases with an increasing EHD Reynolds number for L/D = 0.66 and 1.0, but decreases with the EHD Reynolds number for L/D > 1.
Numerical Investigations of Model Propeller Turbine Performance Under Different Guide Vane Opening
Authors: Daqing Zhou , Qu Bo , Yuan Zheng
Published: July 2009

In the paper, CFD method is applied to investigate model propeller turbine performance under different guide vane opening. First, the whole passage geometric models of model propeller turbine have been built with 0° runner blade under five kinds of guide vane opening, and subdivided with about 1.78 million cells of unstructured mesh. Then, three dimensional turbulent flow computations are made at the water head of H = 1m and the runner speed of n = 217.4 r/min, with the two turbulent models, RNG k-ε and Spalart-Allmadas. Furthermore, the curves of moment value and axial hydraulic thrust value are plotted and compared with experimental curves, which shows that numerical results agree well with experimental data, and Spalart-Allmadas model has better precision than RNG k-ε model. Finally, the flow fields of different parts in the turbine passage are displayed and analyzed respectively under the large, normal and small guide vane opening, which shows the fact that the rotating direction of vortex in the axial diffuse of draft tube is opposite by comparing the large opening with the small opening, and the flow field is in disorder and unsteady especially under the small opening. On the whole, CFD method has many unique advantages and has played more and more important roles on the investigations of hydro turbine performance.
Gas-Liquid Flows in Flow Cells and Fracture Models
Authors: Ahmadi G. , Crandall D. , Smith D. H.
Published: July 2009

Gas-liquid multiphase flows in porous media and fractured rock is of importance when carbon-dioxide displaces brine within geological reservoirs during CO2 sequestration activities. In this paper, experimental and computational modeling of multiphase flows in a porous flow cell and a modeled fracture are described. The experiments performed with the laboratory-scale flow models are described in detail. Experimental data concerning the displacement of two immiscible fluids in the lattice-like flow cell are presented. The flow pattern and the residual saturation of the displaced fluid during the displacement are discussed. It was shown that the gas-liquid flows generate fractal interfaces, with lower fractal dimensions and higher residual saturations at low injection rates. This phenomenon corresponds to viscous and capillary fingering, and is discussed. Numerical simulations of the experimental flow cell are also presented. These are shown to be similar to the experimental results, and then varied to included different surface-fluid interactions not easily studied with the experimental equipment. Numerical simulation results for single and multiphase flows through rock fractures are also presented. A fracture geometry was obtained from a series of CT scans of fractured sandstone and used to construct a laboratory scale model and a computational domain. Computational results showed that the major losses occur in the regions with smallest apertures. These computational results are compared to flows through the experimental model. An empirical expression for the fracture friction factor was also described.
Estimation of Average Void Fraction for Gas-Liquid, Two-Phase Flow in an Industrial Nozzle Assembly Using a Quick-Closing-Valve
Authors: Rahman Mohammad A. , Gomez Johana , Heidrick Ted , Fleck Brian A. , McMillan Jennifer
Published: July 2009

Experimentally accurate void fraction measurements are a challenge in an air/water, two-phase flows through an industrial nozzle assembly, as a highly non-uniform void fraction exists in the feeding conduit prior to the nozzle. In this study, average void fractions were measured by isolating a section in the feeding conduit of a horizontal nozzle assembly, termed as the quick-closing-valve (QCV) technique. A high-speed video camera was utilized to capture the asynchronization closing time, tac. The average closing time and asynchronization for the pneumatically controlled valves were 200 ms and 2 ms, respectively. Based on the equation of 100umtac (1−α)/αlc, the synchronization error between the two valves was 1.12%, 1.26%, and 1.79% for the 1%, 2% and 4% ALR cases, respectively; here um is the mixture velocity, α is the void faction, and lc is the closing length. Higher synchronization error at 4% ALR occurs due to enhanced momentum in the flow regime. Experimental results indicate that the average α over the 33.4 cm feeding conduit (6.25 mm ID) was 76% (αtheoretical = 75%) for the 2% ALR, and 85% (αtheoretical = 83%) for the 3.3% ALR. In the two-phase, two-component flow the α affects the drop size and stability of the spray produced from an industrial nozzle assembly. Learning from this study will yield insights and conceptual understanding of two-phase flow phenomena in conduit, which would affect stability, pulsation tendency, and possibly atomization performance of the nozzle downstream. Two-phase flow nozzles have wide applications in the industries, e.g. petrochemical, pharmaceutical, and others.
Applied Pulsed Flow for Single-Phase Convective Heat Transfer Enhancement in a Laminar Flow Cooling System
Authors: Olayiwola Bolaji O. , Schaldach Gerhard , Walzel Peter
Published: July 2009

Experimental and CFD studies were performed to investigate the enhancement of convective heat transfer in a laminar cooling system using flow pulsation in a flat channel with series of regular spaced fins. Glycerol-water mixtures with dynamic viscosities in the range of 0.001 kg/ms–0.01 kg/ms were used. A steady flow Reynolds number in the laminar range of 10 < Re < 1200 was studied. The amplitudes of the applied pulsations are in the range of 0.25 < A < 0.55 mm and the frequency range is 10 < f < 60 Hz. Two different cooling devices with active length L = 450 mm and 900 mm were investigated. CFD simulations were performed on a parallel-computer (Linux-cluster) using the software suit CFX11 from ANSYS GmbH, Germany. The rate of cooling was found to be significant at moderate low net flow rates. In general, no significant heat transfer enhancement at very low and high flow rates was obtained in compliance with the experimental data. The heat transfer coefficient was found to increase with increasing Prandtl number Pr at constant oscillation Reynolds number Reosc whereas the ratio of the hydraulic diameter to the length of the channel dh/L has insignificant effect on the heat transfer coefficient. This is due to enhanced fluid mixing. CFD results allow for performance predictions of different geometries and flow conditions.
Optimization of Thermoelectric Modules for Computer System Thermal Management and Infrastructure Energy Efficiency
Authors: Shah Amip J. , Rogacs Anita , Patel Chandrakant D.
Published: July 2009

With the proliferation of multiple cores on a single processor and the integration of numerous stacked die in chip packages, the resulting non-uniformity in power dissipation necessitates spatially and temporally localized control of temperature in the package. Thermoelectric (TE) devices can potentially provide one mechanism to achieve such control. Unfortunately, at typical junction-to-ambient temperatures, the coefficient-of-performance (COP) of existing bulk TE devices tends to be quite low. As a result, for many high-power systems, the additional power input required to operate a TE cooling module can lead to an increase in the overall system cost-of-ownership, causing TE cooling solutions to be excluded from cost-sensitive thermal management solutions in high-volume computer systems. However, recent trends of compaction and consolidation of computer servers in high-density data centers have resulted in a dramatic increase in the burdened cost-of-ownership of mission-critical IT facilities. For example, the energy consumption of the cooling infrastructure for many high-density data centers can equal or exceed the power consumption of the compute equipment. Thus, for the growing enterprise thermal management segment, the appropriate metric is no longer the COP of the thermal solution but rather the COP of the cooling ensemble, which takes into account the energy efficiency of cooling solutions in the chip, system, rack, data center and facility. To examine the effects of chip-level COP on the ensemble-level COP, this paper explores a case study comparing two ensemble solutions. In one case, local hotspots on a chip in a three-dimensional package are mitigated by increasing fan power at the system level (and subsequently, in the computer room and the rest of the ensemble). In another case, local hotspots at the chip are mitigated through spot-cooling via TE cooling modules. For each of these cases, the COP of the ensemble is evaluated. The model suggests that while feasible, the benefit of using TEs at current performance levels is limited. However, ongoing research that may improve TE performance in the future has the potential to enhance infrastructure energy efficiency.
Experimental and Computational Study of Nanoparticle Transport in Agarose Gel
Authors: Su Di , Salloum Maher , Ma Ronghui , Zhu Liang
Published: July 2009

In magnetic nanoparticle hyperthermia for cancer treatment, controlling heat deposition and temperature elevations is an immense challenge in clinical applications. In this study, we evaluate magnetic nanofluid transport using agarose gel that has porous structures similar to human tissue by injecting magnetic nanoparticle solution into the extracellular space of gel. The nanofluid distribution in the gel is examined via digital images of the nanofluid spreading in the gel. By adjusting the gel concentration and injection flow rate, the results have demonstrated that a relatively low injection rate leads to a spherically shaped nanofluid distribution in the gels which is desirable for controlling temperature elevations. In parallel to the experimental study, a particle tracking model is developed to study the migration and deposition of nanoparticles in the porous structure under multiple forces including Brownian motion, London-Van der Waals attraction, electrostatic forces, gravitational body force, viscous force, and inertial force. This model allows for the determination of the rate of nanoparticle deposition on the porous structure for various particle sizes, surface potentials, and local fluid velocity. In the future, the information obtained in this study can be used with continuous porous medium theory to predict the evolution of the concentration and deposition profiles of nanoparticles in porous structure during infusion process.
Transient Natural Convection Slip Flow in a Vertical Microchannel Heated at Uniform Heat Flux
Authors: Buonomo Bernardo , Manca Oronzio
Published: July 2009

Miniaturization of devices has received a rapid expansion in the last years and a great attention of research activities is given to microflow due to its new applications of microfluidic systems and components. In the present paper a transient investigation on natural convection in parallel-plate vertical microchannels is carried out numerically. The vertical microchannel is considered asymmetrically or symmetrically heated at uniform heat flux. The first-order model for slip velocity and jump temperature is assumed in microscale conditions. The analysis is performed in laminar boundary layer assumption for different values for different values of Knudsen number, Rayleigh number and the ratio of wall heat flux in order to evaluate their effects on wall temperatures, mass flow rate and Nusselt number. Wall temperature overshoots are detected for the different conditions. These values increase increasing the Knudsen number, Kn, at high Rayleigh number, Ra, whereas for lower Ra the lowest wall temperature are obtained for Kn = 0.05. Mass flow rate increases increasing Kn whereas Nusselt number decreases increasing Kn.