bluuebunny/crossref_metadata_2025 huggingface dataset:
Munc13‐2−/− baseline secretion defect reveals source of oligomeric mucins in mouse airways
Authors: Zhu Yunxiang , Ehre Camille , Abdullah Lubna H. , Sheehan John K. , Roy Michelle , Evans Christopher M. , Dickey Burton F. , Davis C. William
Published: February 2008

Since the airways of control mouse lungs contain few alcian blue/periodic acid–Schiff's (AB/PAS)+ staining ‘goblet’ cells in the absence of an inflammatory stimulus such as allergen sensitization, it was surprising to find that the lungs of mice deficient for the exocytic priming protein Munc13‐2 stain prominently with AB/PAS under control conditions. Purinergic agonists (ATP/UTP) stimulated release of accumulated mucins in the Munc13‐2‐deficient airways, suggesting that the other airway isoform, Munc13‐4, supports agonist‐regulated secretion. Notably, however, not all of the mucins in Munc13‐2‐deficient airways were secreted, suggesting a strict Munc13‐2 priming requirement for a population of secretory granules. AB/PAS+ staining of Munc13‐2‐deficient airways was not caused by an inflammatory, metaplastic‐like response: bronchial–alveolar lavage leucocyte numbers, Muc5ac and Muc5b mRNA levels, and Clara cell ultrastructure (except for increased secretory granule numbers) were all normal. A Muc5b‐specific antibody indicated the presence of this mucin in Clara cells of wildtype (WT) control mice, and increased amounts in Munc13‐2‐deficient mice. Munc13‐2 therefore appears to prime a regulated, baseline secretory pathway, such that Clara cell Muc5b, normally secreted soon after synthesis, accumulates in the gene‐deficient animals, making them stain AB/PAS+. The defective priming phenotype is widespread, as goblet cells of several mucosal tissues appear engorged and Clara cells accumulated Clara cell secretory protein (CCSP) in Munc13‐2‐deficient mice. Additionally, because in the human airways, MUC5AC localizes to the surface epithelium and MUC5B to submucosal glands, the finding that Muc5b is secreted by Clara cells under control conditions may indicate that it is also secreted tonically from human bronchiolar Clara cells.
4‐Aminopyridine‐sensitive outward currents in preBötzinger complex neurons influence respiratory rhythm generation in neonatal mice
Authors: Hayes John A. , Mendenhall Jeffrey L. , Brush Benjamin R. , Del Negro Christopher A.
Published: February 2008

We measured a low‐threshold, inactivating K+ current, i.e. A‐current (IA), in respiratory neurons of the preBötzinger complex (preBötC) in rhythmically active slice preparations from neonatal C57BL/6 mice. The majority of inspiratory neurons (21/34 = 61.8%), but not expiratory neurons (1/8 = 12.5%), expressed IA. In whole‐cell and somatic outside‐out patches IA activated at −60 mV (half‐activation voltage measured −16.3 mV) and only fully inactivated above −40 mV (half‐inactivation voltage measured −85.6 mV), indicating that IA can influence membrane trajectory at baseline voltages during respiratory rhythm generation in vitro. 4‐Aminopyridine (4‐AP, 2 mm) attenuated IA in both whole‐cell and somatic outside‐out patches. In the context of rhythmic network activity, 4‐AP caused irregular respiratory‐related motor output on XII nerves and disrupted rhythmogenesis as detected with whole‐cell and field recordings in the preBötC. Whole‐cell current‐clamp recordings showed that 4‐AP changed the envelope of depolarization underlying inspiratory bursts (i.e. inspiratory drive potentials) from an incrementing pattern to a decrementing pattern during rhythm generation and abolished current pulse‐induced delayed excitation. These data suggest that IA opposes excitatory synaptic depolarizations at baseline voltages of approximately −60 mV and influences the inspiratory burst pattern. We propose that IA promotes orderly recruitment of constituent rhythmogenic neurons by minimizing the activity of these neurons until they receive massive coincident synaptic input, which reduces the periodic fluctuations of inspiratory activity.
Dynamic Substructuring Based on a Double Modal Analysis
Authors: Besset S. , Jézéquel L.
Published: February 2008

Modal synthesis methods have long been studied because the use of generalized coordinates makes it possible to reduce calculation costs. Our approach uses modes to describe each part of the assembly of several substructures. This method, called “Double Modal Synthesis,” is presented through primal and dual formulations. As modal truncation usually introduces a lack of precision, we will use an ω2 development if necessary. These formulations will first be explained using a continuous formulation. A finite element method will then be proposed. Another aim of the paper is to introduce formulations needed to understand the multimodal analysis methods that will be presented in a forthcoming paper.
Rain Ingestion in Axial Flow Compressors at Part Speed
Authors: Day Ivor , Williams John , Freeman Christopher
Published: February 2008

New experimental work is reported on the effects of water ingestion on the performance of an axial flow compressor. The background to the work is the effect that heavy rain has on an aeroengine compressor when operating in a “descent idle” mode, i.e., when the compressor is operating at part speed and when the aeromechanical effects of water ingestion are more important than the thermodynamic effects. Most of our existing knowledge in this field comes from whole engine tests. The current work provides the first known results from direct measurements on a stand-alone compressor. The influence of droplet size on path trajectory is considered both computationally and experimentally to show that most rain droplets will collide with the first row of rotor blades. The water on the blades is then centrifuged toward the casing where the normal airflow patterns in the vicinity of the rotor tips are disrupted. The result of this disruption is a reduction in compressor delivery pressure and an increase in the torque required to keep the compressor speed constant. Both effects reduce the efficiency of the machine. The behavior of the water in the blade rows is examined in detail, and simple models are proposed to explain the loss of pressure rise and the increase in torque. The measurements were obtained in a low speed compressor, making it possible to study the mechanical (increase in torque) and aerodynamic (reduction in pressure rise) effects of water ingestion without the added complication of thermodynamic effects.
PIV Maps of Tip Leakage and Secondary Flow Fields on a Low-Speed Turbine Blade Cascade With Moving End Wall
Authors: Palafox P. , Oldfield M. L. G. , LaGraff J. E. , Jones T. V.
Published: February 2008

New, detailed flow field measurements are presented for a very large low-speed cascade representative of a high-pressure turbine rotor blade with turning of 110deg and blade chord of 1.0m. Data were obtained for tip leakage and passage secondary flow at a Reynolds number of 4.0×105, based on exit velocity and blade axial chord. Tip clearance levels ranged from 0% to 1.68% of blade span (0% to 3% of blade chord). Particle image velocimetry was used to obtain flow field maps of several planes parallel to the tip surface within the tip gap, and adjacent passage flow. Vector maps were also obtained for planes normal to the tip surface in the direction of the tip leakage flow. Secondary flow was measured at planes normal to the blade exit angle at locations upstream and downstream of the trailing edge. The interaction between the tip leakage vortex and passage vortex is clearly defined, revealing the dominant effect of the tip leakage flow on the tip end-wall secondary flow. The relative motion between the casing and the blade tip was simulated using a motor-driven moving belt system. A reduction in the magnitude of the undertip flow near the end wall due to the moving wall is observed and the effect on the tip leakage vortex examined.
Large Eddy Simulation of Flow and Heat Transfer in the Developing Flow Region of a Rotating Gas Turbine Blade Internal Cooling Duct With Coriolis and Buoyancy Forces
Authors: Sewall Evan A. , Tafti Danesh K.
Published: February 2008

The problem of accurately predicting the flow and heat transfer in the ribbed internal cooling duct of a rotating gas turbine blade is addressed with the use of large eddy simulations (LES). Four calculations of the developing flow region of a rotating duct with ribs on opposite walls are used to study changes in the buoyancy parameter at a constant rotation rate. The Reynolds number is 20,000, the rotation number is 0.3, and the buoyancy parameter is varied between 0.00, 0.25, 0.45, and 0.65. Previous experimental studies have noted that leading wall heat transfer augmentation decreases as the buoyancy parameter increases with low buoyancy, but heat transfer then increases with high buoyancy. However, no consistent physical explanation has been given in the literature. The LES results from this study show that the initial decrease in augmentation with buoyancy is a result of larger separated regions at the leading wall. However, as the separated region spans the full pitch between ribs with an increase in buoyancy parameter, it leads to increased turbulence and increased entrainment of mainstream fluid, which is redirected toward the leading wall by the presence of a rib. The impinging mainstream fluid results in heat transfer augmentation in the region immediately upstream of a rib. The results obtained from this study are in very good agreement with previous experimental results.
Fully Automated Model-Based Performance Analysis Procedure for On-Line and Off-Line Applications
Authors: Bauer Michael , Staudacher Stephan
Published: February 2008

The development of modern gas turbines is accompanied by an extensive prototype testing. To evaluate performance, the engines are fitted with a substantial number of sensors measuring pressures, temperatures, shaft speeds, etc. The test data are analyzed by procedures calculating data that are not directly measured, e.g., component efficiencies and turbine temperatures. Engine manufacturers usually apply such procedures for a detailed analysis after the test (off-line) as well as to ensure a safe and efficient engine operation during the test (on-line). Especially for the latter application, a fast and reliable assessment of the performance of the engine and its components as well as a fast and reliable detection of measurement faults are required. The paper describes a fully automated performance analysis procedure for off-line as well as on-line applications. The basis of the procedure is a full thermodynamic model representing the expected behavior of the engine to be tested. By such a model-based analysis procedure, a comparison between test data and the expected engine behavior is performed. The way the comparison is done allows detecting and isolating measurement faults and component malfunctions. In case of a detected measurement fault, the measurement will be excluded automatically from the analysis. At MTU Aero Engines GmbH the procedure is regularly applied for on-line and off-line test data analysis of different engine types. Compared to the procedures used thus far, many measurement faults can be detected quickly and reliably.
Control of Three-Dimensional Separations in Axial Compressors by Tailored Boundary Layer Suction
Authors: Gbadebo Semiu A. , Cumpsty Nicholas A. , Hynes Tom P.
Published: February 2008

One of the important ways of improving turbomachinery compressor performance is to control three-dimensional (3D) separations, which form over the suction surface and end wall corner of the blade passage. Based on the insights gained into the formation of these separations, this paper illustrates how an appropriately applied boundary layer suction of up to 0.7% of inlet mass flow can control and eliminate typical compressor stator hub corner 3D separation over a range of operating incidence. The paper describes, using computational fluid dynamics, the application of suction on the blade suction surface and end wall boundary layers and exemplifies the influence of end wall dividing streamline in initiating 3D separation in the blade passage. The removal of the separated region from the blade suction surface is confirmed by an experimental investigation in a compressor cascade involving surface flow visualization, surface static pressure, and exit loss measurements. The ensuing passage flow field is characterized by increased blade loading (static pressure difference between pressure and suction surface), enhanced average static pressure rise, significant loss removal, and a uniform exit flow. This result also enables the contribution of the 3D separation to the overall loss and passage blockage to be assessed.
Criteria for Spike Initiated Rotating Stall
Authors: Vo Huu Duc , Tan Choon S. , Greitzer Edward M.
Published: February 2008

A computational study to define the phenomena that lead to the onset of short length-scale (spike) rotating stall disturbances has been carried out. Based on unsteady simulations, we hypothesize there are two conditions necessary for the formation of spike disturbances, both of which are linked to the tip clearance flow. One is that the interface between the tip clearance and oncoming flows becomes parallel to the leading-edge plane. The second is the initiation of backflow, stemming from the fluid in adjacent passages, at the trailing-edge plane. The two criteria also imply a circumferential length scale for spike disturbances. The hypothesis and scenario developed are consistent with numerical simulations and experimental observations of axial compressor stall inception. A comparison of calculations for multiple blades with those for single passages also allows statements to be made about the utility of single passage computations as a descriptor of compressor stall.
A New Dynamic Model of High-Speed Railway Vehicle Moving on Curved Tracks
Authors: Lee Sen-Yung , Cheng Yung-Chang
Published: February 2008

A new dynamic model of railway vehicle moving on curved tracks is proposed. In the new model, the motion of the car body is considered and the motion of the truck frame is not restricted by a virtual boundary. Based on the heuristic nonlinear creep model, the nonlinear coupled differential equations of the motion of an eight degrees of freedom car system—considering the lateral displacement and the yaw angle of each wheelset, the truck frame, and the half car body—moving on curved tracks are derived completely. To illustrate the accuracy of the analysis, the limiting cases are examined. It is shown that the influence of the gyroscopic moment of the wheelsets on the critical hunting speed is negligible. In addition, the influences of the suspension parameters, including those losing in the six degrees of freedom system, on the critical hunting speeds evaluated via the linear and the nonlinear creep models are studied and compared.
Dynamic Modeling of Satellite Tether Systems Using Newton’s Laws and Hamilton’s Principle
Authors: Mankala Kalyan K. , Agrawal Sunil K.
Published: February 2008

The objective of this paper is to derive the dynamic equations of a tether as it is deployed or retrieved by a winch on a satellite orbiting around Earth using Newton’s laws and Hamilton’s principle and show the equivalence of the two methods. The main feature of this continuous system is the presence of a variable length domain with discontinuities. Discontinuity is present at the boundary of deployment because of the assumption that the stowed part of the cable is unstretched and the deployed part is not. Developing equations for this variable domain system with discontinuities, specially using Hamilton’s principle, is a nontrivial task and we believe that it has not been adequately addressed in the literature.
Film Cooling and Heat Transfer on Two Cutback Trailing Edge Models
With Internal Perforated Blockages
Authors: Choi Jung-ho , Mhetras Shantanu , Han Je-Chin , Lau Sai C. , Rudolph Ron
Published: February 2008

Experiments to study heat transfer and film cooling on the cutback trailing edge of a turbine blade with slot ejection were performed. Heat transfer from two rows of perforated blockage inserts for lateral impingement on the coolant channel walls prior to coolant ejection into the freestream was also investigated. The internal test geometry is similar to the crossover impingement hole design used in modern gas turbine blades for trailing edge cooling. A liquid crystal technique based on hue value detection was used to measure the heat transfer coefficient on a trailing edge film-cooling model with slot ejection and an internal model with perforated blockage inserts. It was also used to determine the film effectiveness on the cutback trailing edge. For the internal model with the perforated blockage inserts, Reynolds numbers based on the hydraulic diameter of the slot and exit velocity were 5000, 10,000, 20,000, and 30,000 and corresponding coolant-to-freestream velocity ratios ranged from 0.26 to 1.83 for the external model with slot ejection, respectively. The experiments were performed for two different designs, 1 and 2, with Design 1 incorporating two different configurations with a staggered/inline slot exit arrangement and Design 2 with a staggered slot exit arrangement. Both designs utilized a 90deg flow turn into the blockage inserts as an entrance to the test section to simulate a realistic blade passage design. Results show that the internal design geometry of the trailing edge and Reynolds numbers can affect heat transfer in an internal model with perforated blockage inserts. Design 2 with a wider entrance channel and a sloped land near the ejection slots provided low heat transfer coefficients in the internal as well as external model but gave higher film-cooling effectiveness from slot ejection.
Moving Boundary-Moving Mesh Analysis of Freezing Process in Water-Saturated Porous Media Using a Combined Transfinite Interpolation and PDE Mapping Methods
Authors: Rattanadecho P. , Wongwises S.
Published: February 2008

This paper couples the grid generation algorithm with the heat transport equations and applies them to simulate the thermal behavior of freezing process in water-saturated porous media. Focus is placed on establishing a computationally efficient approach for solving moving boundary heat transfer problem, in two-dimensional structured grids, with specific application to an undirectional solidification problem. Preliminary grids are first generated by an algebraic method, based on a transfinite interpolation method, with subsequent refinement using a partial differential equation (PDE) mapping (parabolic grid generation) method. A preliminary case study indicates successful implementation of the numerical procedure. A two-dimensional solidification model is then validated against available analytical solution and experimental results and subsequently used as a tool for efficient computational prototyping. The results of the problem are in good agreement with available analytical solution and experimental results.
Subcooled Boiling Flow Heat Transfer From Plain and Enhanced Surfaces in Automotive Applications
Authors: Ramstorfer Franz , Steiner Helfried , Brenn Günter , Kormann Claudius , Rammer Franz
Published: February 2008

The requirement for the highest possible heat transfer rates in compact, efficient cooling systems can often only be met by providing for a transition to subcooled boiling flow in strongly heated wall regions. The significantly higher heat transfer rates achievable with boiling can help keep the temperatures of the structure on an acceptable level. It has been shown in many experimental studies that special surface finish or porous coatings on the heated surfaces can intensify the nucleate boiling process markedly. Most of those experiments were carried out with water or refrigerants. The present work investigates the potential of this method to enhance the subcooled boiling heat transfer in automotive cooling systems using a mixture of ethylene-glycol and de-ionized water as the coolant. Subcooled boiling flow experiments were carried out in a vertical test channel considering two different types of coated surfaces and one uncoated surface as a reference. The experimental results of the present work clearly demonstrate that the concept of enhancing boiling by modifying the microstructure of the heated surface can be successfully applied to automotive cooling systems. The observed increase in the heat transfer rates differ markedly for the two considered porous coatings, though. Based on the experimental data, a heat transfer model for subcooled boiling flow using a power-additive superposition approach is proposed. The model assumes the total wall heat flux as a nonlinear combination of a convective and a nucleate boiling contribution, both obtained from well-established semiempirical correlations. The wall heat fluxes predicted by the proposed model are in very good agreement with the experimental data for all considered flow conditions and surface types.
Genetic Algorithm Based Optimization of PCM Based Heat Sinks and Effect of Heat Sink Parameters on Operational Time
Authors: Nagose Atul , Somani Ankit , Shrot Aviral , Narasimhan Arunn
Published: February 2008

Using an approach that couples genetic algorithm (GA) with conventional numerical simulations, optimization of the geometric configuration of a phase-change material based heat sink (PBHS) is performed in this paper. The optimization is done to maximize the sink operational time (SOT), which is the time for the top surface temperature of the PBHS to reach the critical electronics temperature (CET). An optimal solution for this complex multiparameter problem is sought using GA, with the standard numerical simulation seeking the SOT forming a crucial step in the algorithm. For constant heat dissipation from the electronics (constant heat flux) and for three typical PBHS depths (A), predictive empirical relations are deduced from the GA based simulation results. These correlations relate the SOT to the amount of phase change material to be used in the PBHS (φ), the PBHS depth (A), and the heat-spreader thickness (s), a hitherto unconsidered variable in such designs, to the best of the authors’ knowledge. The results show that for all of the typical PBHS depths considered, the optimal heat-spreader thickness is 2.5% of the PBHS depth. The developed correlations predict the simulated results within 4.6% for SOT and 0.32% for ϕ and empowers one to design a PBHS configuration with maximum SOT for a given space restriction or the most compact PBHS design for a given SOT.
Discussion of Boundary Conditions of Transpiration Cooling Problems Using Analytical Solution of LTNE Model
Authors: Wang Jianhua , Shi Junxiang
Published: February 2008

To compare five kinds of different boundary conditions (BCs), an analytical solution of a steady and one-dimensional problem of transpiration cooling described by a local thermal nonequilibrium (LTNE) model is presented in this work. The influence of the five BCs on temperature field and thermal effectiveness is discussed using the analytical solution. Two physical criteria, if the analytical solution of coolant temperature may be higher than hot gas temperature at steady state and if the variation trend of thermal effectiveness with coolant mass flow rate at hot surface is reasonable, are used to estimate the five BCs. Through the discussions, it is confirmed which BCs at all conditions are usable, which BCs under certain conditions are usable, and which BCs are thoroughly unreasonable.
Chaotic Synchronization in Ultra-Wide-Band Communication and Positioning Systems
Authors: Chedjou J. C. , Kyamakya K. , Mathis W. , Moussa I. , Fomethe A. , Fono V. A.
Published: February 2008

This paper investigates synchronization transitions in a system of coupled Rössler type nonidentical self-sustained chaotic oscillators. The interest in Rössler oscillators is due to their chaotic behavior at very high frequencies. Both phase synchronization and lag synchronization are analyzed numerically considering coupling parameters. It is shown that both types of synchronization can be achieved by monitoring the coupling parameters. The advantage of using one parameter to ensure both types of synchronization is found in practice. Another advantage of monitoring only one resistor is found in the accuracy of results. One resistor is used to predict the boundaries of the control resistor for the occurrence of each type of synchronization. An experimental study of the synchronization is carried out in this paper. An appropriate electronic circuit describing the coupled oscillators is designed and realized. Experimental wave forms in the drive and response systems are obtained and their comparison done to confirm the achievement of synchronization. The analog simulation is advantageous to analyze the behavior of the coupled system at very high frequencies at appropriate time scaling and offers the possibility of using our coupled system for ultra-wide-band applications.
The Maternal Nucleolus Is Essential for Early Embryonic Development in Mammals
Authors: Ogushi Sugako , Palmieri Chiara , Fulka Helena , Saitou Mitinori , Miyano Takashi , Fulka Josef
Published: February 2008

With fertilization, the paternal and maternal contributions to the zygote are not equal. The oocyte and spermatozoon are equipped with complementary arsenals of cellular structures and molecules necessary for the creation of a developmentally competent embryo. We show that the nucleolus is exclusively of maternal origin. The maternal nucleolus is not necessary for oocyte maturation; however, it is necessary for the formation of pronuclear nucleoli after fertilization or parthenogenetic activation and is essential for further embryonic development. In addition, the nucleolus in the embryo produced by somatic cell nuclear transfer originates from the oocyte, demonstrating that the maternal nucleolus supports successful embryonic development.
TOPLESS Mediates Auxin-Dependent Transcriptional Repression During
Arabidopsis
Embryogenesis
Authors: Szemenyei Heidi , Hannon Mike , Long Jeff A.
Published: February 2008

The transcriptional response to auxin is critical for root and vascular development during
Arabidopsis
embryogenesis. Auxin induces the degradation of AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) transcriptional repressors, freeing their binding partners, the AUXIN RESPONSE FACTOR (ARF) proteins, which can activate transcription of auxin response genes. We show that TOPLESS (TPL) can physically interact with IAA12/BODENLOS (IAA12/BDL) through an ETHYLENE RESPONSE FACTOR (ERF)–associated amphiphilic repression (EAR) motif. TPL can repress transcription in vivo and is required for IAA12/BDL repressive activity. In addition,
tpl-1
can suppress the patterning defects of the
bdl-1
mutant. Direct interaction between TPL and ARF5/MONOPTEROS, which is regulated by IAA12/BDL, results in a loss-of-function
arf5
/
mp
phenotype. These observations show that TPL is a transcriptional co-repressor and further our understanding of how auxin regulates transcription during plant development.
Antiretroviral Therapy with a Twice-Daily Regimen Containing 400 Milligrams of Indinavir and 100 Milligrams of Ritonavir in Human Immunodeficiency Virus Type 1-Infected Women during Pregnancy
Authors: Ghosn Jade , De Montgolfier Ines , Cornélie Chantal , Dominguez Stéphanie , Pérot Claire , Peytavin Gilles , Marcelin Anne-Geneviève , Pauchard Michèle , Ouagari Zineb , Bonmarchand Manuela , Agher Rachid , Calvez Vincent , Bricaire François , Dommergues Marc , Katlama Christine , Tubiana Roland
Published: February 2008

We evaluated the safety and efficacy of a twice daily regimen containing 400 mg of indinavir and 100 mg of ritonavir in 32 human immunodeficiency virus (HIV)-infected women during pregnancy. The median indinavir trough concentration was 208 ng/ml during the third trimester. At delivery, 26 of 28 women on indinavir-ritonavir had HIV RNA levels of <200 copies/ml. No infant was HIV infected. These data are encouraging for the use of this combination for prevention of mother-to-child transmission of HIV.
Affinity of Doripenem and Comparators to Penicillin-Binding Proteins in
Escherichia coli
and
Pseudomonas aeruginosa
Authors: Davies Todd A. , Shang Wenchi , Bush Karen , Flamm Robert K.
Published: February 2008

Doripenem, a parenteral carbapenem, exhibited high affinity for penicillin-binding protein 2 (PBP2) and PBP3 in
Pseudomonas aeruginosa
and PBP2 in
Escherichia coli
, the primary PBPs whose inhibition leads to cell death. This PBP affinity profile correlates with the broad-spectrum gram-negative activity observed with doripenem.
Microfilariae of the Filarial NematodeLitomosoides sigmodontisExacerbate the Course of Lipopolysaccharide-Induced Sepsis in Mice
Authors: Hübner Marc P. , Pasche Bastian , Kalaydjiev Svetoslav , Soboslay Peter T. , Lengeling Andreas , Schulz-Key Hartwig , Mitre Edward , Hoffmann Wolfgang H.
Published: February 2008

Helminths facilitate their own survival by actively modulating the immune systems of their hosts. We investigated the impacts that different life cycle stages of the rodent filariaLitomosoides sigmodontishave on the inflammatory responses of mice injected with sublethal doses of lipopolysaccharide (LPS). Mice infected with female adult worms from prepatent infections, worms which have not yet started to release microfilariae, developed lower levels of proinflammatory cytokines in the peripheral blood after LPS challenge than sham-treated controls, demonstrating that female adult worms can mitigate the innate immune response. The presence of microfilariae in mice, however, through either direct injection or implantation of microfilaria-releasing adult female worms, turned the LPS challenge fatal. This lethal outcome was characterized by increased plasma levels of gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), interleukin 12 (IL-12), and IL-6, greater numbers of macrophages and granulocytes in the peripheral blood, and decreased body temperatures in microfilaria-infected mice. Microfilaria-infected mice deficient in IFN-γ receptor and TNF receptor 1 had increased survival rates after LPS challenge compared to immune-competent mice, suggesting that microfilariae worsen LPS-induced sepsis through actions of IFN-γ and TNF-α. In summary, we have demonstrated that infection of mice withL. sigmodontisfemale adult worms from prepatent infections protects mice injected with LPS whereas microfilariae worsen LPS-induced sepsis through the induction of proinflammatory cytokines and upregulation of granulocytes, NK cells, and monocytes in the peripheral blood.
Differences in Human Antibody Reactivity to
Plasmodium falciparum
Variant Surface Antigens Are Dependent on Age and Malaria Transmission Intensity in Northeastern Tanzania
Authors: Vestergaard Lasse S. , Lusingu John P. , Nielsen Morten A. , Mmbando Bruno P. , Dodoo Daniel , Akanmori Bartholomew D. , Alifrangis Michael , Bygbjerg Ib C. , Lemnge Martha M. , Staalsoe Trine , Hviid Lars , Theander Thor G.
Published: February 2008

Plasmodium falciparum
variant surface antigens (VSA) are involved in the pathogenesis of malaria. Immunoglobulin G (IgG) with specificity for VSA (anti-VSA IgG) is therefore considered important for acquired immunity. To better understand the nature and dynamics of variant-specific IgG responses at population level, we conducted an immunoepidemiological study in nearby communities in northeastern Tanzania, situated at different altitudes and therefore exposed to different levels of
P. falciparum
transmission intensity. Samples of plasma and infected red blood cells (IRBC) were collected from 759 individuals aged 0 to 19 years. Plasma levels of IgG with specificity for VSA expressed by a panel of different parasite isolates were measured by flow cytometry, while the ability of plasma to inhibit IRBC adhesion to CD36 was examined in cellular assays. The level and repertoire of the heterologous anti-VSA IgG response developed dramatically in individuals at 1 to 2 years of age in the high-transmission area, reaching a maximum level at around 10 years of age; only a modest further increase was observed among older children and adults. In contrast, at lower levels of malaria transmission, anti-VSA IgG levels were lower and the repertoire was more narrow, and similar age- and transmission-dependent differences were observed with regard to the ability of the plasma samples to inhibit adhesion of IRBC to CD36. These differences indicate a strong and dynamic relationship between malaria exposure and functional characteristics of the variant-specific antibody response, which is likely to be important for protection against malaria.
TWO REMARKS ON SUBVARIETIES OF MODULI SPACES
Authors: JOSHI KIRTI
Published: February 2008

We study two natural questions about subvarieties of moduli spaces. In the first section, we study the locus of curves equipped with F-nilpotent bundles and its relationship to the p-rank zero locus of the moduli space of curves of genus g. In the second section, we study subvarieties of moduli spaces of vector bundles on curves. We prove an analogue of a result of F. Oort about proper subvarieties of moduli of abelian varieties.
FORCES BETWEEN ELECTRIC CHARGES IN MOTION: RUTHERFORD SCATTERING, CIRCULAR KEPLERIAN ORBITS, ACTION-AT-A-DISTANCE AND NEWTON'S THIRD LAW IN RELATIVISTIC CLASSICAL ELECTRODYNAMICS
Authors: FIELD J. H.
Published: February 2008

Standard formulae of classical electromagnetism for the forces between electric charges in motion derived from retarded potentials are compared with those obtained from a recently developed relativistic classical electrodynamic theory with an instantaneous intercharge force. Problems discussed include small angle Rutherford scattering, Jackson's recent "torque paradox" and circular Keplerian orbits. Results consistent with special relativity are obtained only with an instantaneous interaction. The impossibility of stable circular motion with retarded fields in either classical electromagnetism or Newtonian gravitation is demonstrated.
A NOTE ON THE EXACT SOLUTION OF THE SPECIAL MODIFIED KdV EQUATION
Authors: WANG HONGLEI , XIANG CHUNHUAN
Published: February 2008

The modified KdV (Korteweg–de Vries) equation with two different variable coefficients can be employed in many different physical fields with time changing. In the present work, by using the truncated expansion, some new exact solutions of the equation are obtained. The general equation may change into lots of other forms KdV equation if we select different parameters.
APPLICATIONS OF LEFT CIRCULANT MATRICES IN SIGNAL AND IMAGE PROCESSING
Authors: ANDRECUT M.
Published: February 2008

We show numerically that the orthogonal transformation corresponding to the eigenvectors of (random) left circulant matrices, has similar performance in signal/image processing like the discrete cosine transform.
A HYBRID FINITE ELEMENT CALCULATION OF COMPLEX ELECTROMAGNETIC FIELDS
Authors: LIU NIAN , XIE CHI
Published: February 2008

In order to increase to a greater extent the calculation accuracy for complex electromagnetic fields in the modern physics, a hybrid finite element method (HFEM) is presented for analysis and simulation of complex electromagnetic fields. In the paper, the hybrid finite element method (HFEM) with high accuracy is introduced, and the complex electromagnetic field in an electromagnetic device has been calculated successfully by the hybrid finite element method (HFEM) and the electromagnetic properties of the electromagnetic device under the specific work condition is evaluated. It is shown that the method can provide a much more accurate calculation and good agreement between the computed values and the experimental values.
Effectiveness of augmented-reality visualization versus cognitive mediation for learning actions in near space
Authors: Klatzky Roberta L. , Wu Bing , Shelton Damion , Stetten George
Published: February 2008

The present study examined the impact of augmented-reality visualization, in comparison to conventional ultrasound (CUS), on the learning of ultrasound-guided needle insertion. Whereas CUS requires cognitive processes for localizing targets, our augmented-reality device, called the “sonic flashlight” (SF) enables direct perceptual guidance. Participants guided a needle to an ultrasound-localized target within opaque fluid. In three experiments, the SF showed higher accuracy and lower variability in aiming and endpoint placements than did CUS. The SF, but not CUS, readily transferred to new targets and starting points for action. These effects were evident in visually guided action (needle and target continuously visible) and visually directed action (target alone visible). The results have application to learning to visualize surgical targets through ultrasound.
Controlled physical random functions and applications
Authors: Gassend Blaise , Dijk Marten Van , Clarke Dwaine , Torlak Emina , Devadas Srinivas , Tuyls Pim
Published: February 2008

The cryptographic protocols that we use in everyday life rely on the secure storage of keys in consumer devices. Protecting these keys from invasive attackers, who open a device to steal its key, is a challenging problem. We propose controlled physical random functions (CPUFs) as an alternative to storing keys and describe the core protocols that are needed to use CPUFs. A physical random functions (PUF) is a physical system with an input and output. The functional relationship between input and output looks like that of a random function. The particular relationship is unique to a specific instance of a PUF, hence, one needs access to a particular PUF instance to evaluate the function it embodies. The cryptographic applications of a PUF are quite limited unless the PUF is combined with an algorithm that limits the ways in which the PUF can be evaluated; this is a CPUF. A major difficulty in using CPUFs is that you can only know a small set of outputs of the PUF—the unknown outputs being unrelated to the known ones. We present protocols that get around this difficulty and allow a chain of trust to be established between the CPUF manufacturer and a party that wishes to interact securely with the PUF device. We also present some elementary applications, such as certified execution.
On predictive models and user-drawn graphical passwords
Authors: Oorschot P. C. van , Thorpe Julie
Published: February 2008

In commonplace text-based password schemes, users typically choose passwords that are easy to recall, exhibit patterns, and are thus vulnerable to brute-force dictionary attacks. This leads us to ask whether other types of passwords (e.g., graphical) are also vulnerable to dictionary attack because of users tending to choose memorable passwords. We suggest a method to predict and model a number of such classes for systems where passwords are created solely from a user's memory. We hypothesize that these classes define weak password subspaces suitable for an attack dictionary. For user-drawn graphical passwords, we apply this method with cognitive studies on visual recall. These cognitive studies motivate us to define a set of
password complexity factors
(e.g., reflective symmetry and stroke count), which define a set of classes. To better understand the size of these classes and, thus, how weak the password subspaces they define might be, we use the “Draw-A-Secret” (DAS) graphical password scheme of Jermyn et al. [1999] as an example. We analyze the size of these classes for DAS under convenient parameter choices and show that they can be combined to define apparently popular subspaces that have bit sizes ranging from 31 to 41—a surprisingly small proportion of the full password space (58 bits). Our results quantitatively support suggestions that user-drawn graphical password systems employ measures, such as graphical password rules or guidelines and proactive password checking.
ODSBR
Authors: Awerbuch Baruch , Curtmola Reza , Holmer David , Nita-Rotaru Cristina , Rubens Herbert
Published: February 2008

Ah hoc networks offer increased coverage by using multihop communication. This architecture makes services more vulnerable to internal attacks coming from compromised nodes that behave arbitrarily to disrupt the network, also referred to as Byzantine attacks. In this work, we examine the impact of several Byzantine attacks performed by individual or colluding attackers. We propose ODSBR, the first on-demand routing protocol for ad hoc wireless networks that provides resilience to Byzantine attacks caused by individual or colluding nodes. The protocol uses an adaptive probing technique that detects a malicious link after log
n
faults have occurred, where
n
is the length of the path. Problematic links are avoided by using a route discovery mechanism that relies on a new metric that captures adversarial behavior. Our protocol never partitions the network and bounds the amount of damage caused by attackers. We demonstrate through simulations ODSBR's effectiveness in mitigating Byzantine attacks. Our analysis of the impact of these attacks versus the adversary's effort gives insights into their relative strengths, their interaction, and their importance when designing multihop wireless routing protocols.
Metaphors of human thinking for usability inspection and design
Authors: Frøkjær Erik , Hornbæk Kasper
Published: February 2008

Usability inspection techniques are widely used, but few focus on users' thinking and many are appropriate only for particular devices and use contexts. We present a new technique (MOT) that guides inspection by metaphors of human thinking. The metaphors concern habit, the stream of thought, awareness and associations, the relation between utterances and thought, and knowing. The main novelty of MOT is its psychological basis combined with its use of metaphors to stimulate inspection. The first of three experiments shows that usability problems uncovered with MOT are more serious and more complex to repair than problems found with heuristic evaluation. Problems found with MOT are also judged more likely to persist for expert users. The second experiment shows that MOT finds more problems than cognitive walkthrough, and has a wider coverage of a reference collection of usability problems. Participants prefer using MOT over cognitive walkthrough; an important reason being the wider scope of MOT. The third experiment compares MOT, cognitive walkthrough, and think aloud testing, in the context of nontraditional user interfaces. Participants prefer using think aloud testing, but identify few problems with that technique that are not found also with MOT or cognitive walkthrough. MOT identifies more problems than the other techniques. Across experiments and measures of usability problems' utility in systems design, MOT performs better than existing inspection techniques and is comparable to think aloud testing.
Understanding changes in mental workload during execution of goal-directed tasks and its application for interruption management
Authors: Bailey Brian P. , Iqbal Shamsi T.
Published: February 2008

Notifications can have reduced interruption cost if delivered at moments of lower mental workload during task execution. Cognitive theorists have speculated that these moments occur at subtask boundaries. In this article, we empirically test this speculation by examining how workload changes during execution of goal-directed tasks, focusing on regions between adjacent chunks within the tasks, that is, the subtask boundaries. In a controlled experiment, users performed several interactive tasks while their pupil dilation, a reliable measure of workload, was continuously measured using an eye tracking system. The workload data was extracted from the pupil data, precisely aligned to the corresponding task models, and analyzed. Our principal findings include (i) workload changes throughout the execution of goal-directed tasks; (ii) workload exhibits transient decreases at subtask boundaries relative to the preceding subtasks; (iii) the amount of decrease tends to be greater at boundaries corresponding to the completion of larger chunks of the task; and (iv) different types of subtasks induce different amounts of workload. We situate these findings within resource theories of attention and discuss important implications for interruption management systems.
A grid-free abstraction of the Navier-Stokes equations in Fortran 95/2003
Authors: Rouson Damian W. I. , Rosenberg Robert , Xu Xiaofeng , Moulitsas Irene , Kassinos Stavros C.
Published: February 2008

Computational complexity theory inspires a grid-free abstraction of the Navier-Stokes equations in Fortran 95/2003. A novel complexity analysis estimates that structured programming time grows at least quadratically with the number of program lines. Further analysis demonstrates how an object-oriented strategy focused on mathematical objects renders the quadratic estimate scale-invariant, so the time required for the limiting factor in program development (debugging) no longer grows as the code grows. Compared to the coordinate-free C++ programming of Grant et al. [2000], grid-free Fortran programming eliminates a layer of procedure calls, eliminates a related need for the C++ template construct, and offers a shorter migration path for Fortran programmers. The grid-free strategy is demonstrated by constructing a physical-space driver for a Fourier-space Navier-Stokes solver. Separating the expression of the continuous mathematical model from the discrete numerics clarifies issues that are otherwise easily conflated. A run-time profile suggests that grid-free design substantially reduces the fraction of the procedures that significantly impact runtime, freeing more code to be structured in ways that reduce development time. Applying Amdahl's law to the total solution time (development time plus run time) leads to a strategy that negligibly impacts development time but achieves 58% of the maximum possible speedup.
Computing sparse Hessians with automatic differentiation
Authors: Walther Andrea
Published: February 2008

A new approach for computing a sparsity pattern for a Hessian is presented: nonlinearity information is propagated through the function evaluation yielding the nonzero structure. A complexity analysis of the proposed algorithm is given. Once the sparsity pattern is available, coloring algorithms can be applied to compute a seed matrix. To evaluate the product of the Hessian and the seed matrix, a vector version for evaluating second order adjoints is analysed. New drivers of ADOL-C are provided implementing the presented algorithms. Runtime analyses are given for some problems of the CUTE collection.
Algorithm 870
Authors: Linardakis Leonidas , Chrisochoides Nikos
Published: February 2008

We present a geometric domain decomposition method and its implementation, which produces good domain decompositions in terms of three basic criteria: (1) The boundary of the subdomains create good angles, that is, angles no smaller than a given tolerance Φ
0
, where the value of Φ
0
is determined by the application which will use the domain decomposition. (2) The size of the separator should be relatively small compared to the area of the subdomains. (3) The maximum area of the subdomains should be close to the average subdomain area. The domain decomposition method uses an approximation of a Medial Axis as an auxiliary structure for constructing the boundary of the subdomains (separators). The
N
-way decomposition is based on the “divide and conquer” algorithmic paradigm and on a smoothing procedure that eliminates the creation of any new artifacts in the subdomains. This approach produces well shaped uniform and graded domain decompositions, which are suitable for parallel mesh generation.