bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of the Transition Between Lean Conventional Diesel Combustion and Lean, Premixed, Low-Temperature Diesel Combustion
Authors: Busch Stephen , Bohac Stanislav V. , Assanis Dennis N.
Published: March 2009

New diesel combustion modes face difficult challenges with respect to engine-out emissions and transient behavior. Transitions between lean conventional diesel combustion and lean, premixed, low-temperature diesel combustion are investigated with an automotive diesel engine. Effects of fuel pressure on transitional cycles are investigated. Cycle-by-cycle heat release analysis is performed and an exhaust mass flow model is used to obtain cycle-averaged NO concentrations. The behavior of combustion progression and NO emissions during the transitions are discussed. Observed cool-flame separation behavior is identified and explained.
Optical Diagnostics of a Late Injection Low-Temperature Combustion in a Heavy Duty Diesel Engine
Authors: Lachaux Thierry , Musculus Mark P. B. , Singh Satbir , Reitz Rolf D.
Published: March 2009

A late injection, high exhaust-gas recirculation (EGR)-rate, low-temperature combustion strategy was investigated in a heavy-duty diesel engine using a suite of optical diagnostics: chemiluminescence for visualization of ignition and combustion, laser Mie scattering for liquid fuel imaging, planar laser-induced fluorescence (PLIF) for both OH and vapor-fuel imaging, and laser-induced incandescence (LII) for soot imaging. Fuel is injected at top dead center when the in-cylinder gases are hot and dense. Consequently, the maximum liquid fuel penetration is 27 mm, which is short enough to avoid wall impingement. The cool flame starts 4.5 crank angle degrees (CAD) after the start of injection (ASI), midway between the injector and bowl-rim, and likely helps fuel to vaporize. Within a few CAD, the cool-flame combustion reaches the bowl-rim. A large premixed combustion occurs near 9 CAD ASI, close to the bowl rim. Soot is visible shortly afterwards along the walls, typically between two adjacent jets at the head vortex location. OH PLIF indicates that premixed combustion first occurs within the jet and then spreads along the bowl rim in a thin layer, surrounding soot pockets at the start of the mixing-controlled combustion phase near 17 CAD ASI. During the mixing-controlled phase, soot is not fully oxidized and is still present near the bowl-rim late in the cycle. At the end of combustion near 27 CAD ASI, averaged PLIF images indicate two separate zones. OH PLIF appears near the bowl rim, while broadband PLIF persists late in the cycle near the injector. The most likely source of broadband PLIF is unburned fuel, which indicates that the near-injector region is a potential source of unburned hydrocarbons.
Investigation of Soot Concentration and Particle Size Distribution on a Single Cylinder Diesel Engine
Authors: Stumpf Markus , Merkel Sascha , Eckert Peter , Wagner Uwe , Velji Amin , Spicher Ulrich , Moehler Ottmar
Published: March 2009

The purpose of this study was the characterization of the size distribution and the concentration of the particles emitted by diesel engines under various speed and load points, and different injection pressures. Fine and ultrafine particles emitted by modern diesel engines, in particular those with sizes below 100 nm, are of significant importance for the human health, since the latter are respirable and may have therefore negative effects. The investigations described in this paper provide an insight into the formation of soot particles in the combustion chamber and their number concentration and size distribution in the exhaust gas pipe. The experiments were performed on a single cylinder diesel engine. For the purpose of comparability to multi cylinder engines, the crankshaft drive, the liner, the piston and the cylinder head were based on a heavy duty production engine. The engine was operated with a common rail injection system which was controlled by an electronic control device that offered several degrees of freedom regarding number, duration and timing of the single injections. During the investigations the engine was operated at several speed and load points with and without pilot injection. The in-cylinder soot concentration was measured crank angle resolved with the two-color-method. The Filter-Smoke-Number (FSN) and the NOx concentration were determined in the exhaust gas. Furthermore the particle number and the particle size distribution were measured by means of a Scanning Mobility Particle Sizer (SMPS). The main focus of the experiments was on the investigation of the in-cylinder soot concentration and the particle size distribution running the engine at several injection pressures during different engine speed/load configurations. In order to obtain a potential correlation to common exhaust gas quantification methods, the Filter-Smoke-Number was measured simultaneously. The results of the experiments provide knowledge which is of eminent importance with respect to further diesel combustion development with regard to both the soot concentration and the soot particle properties.
On the Pressure Relief Valve for the Lubrication System of an Internal Combustion Engine
Authors: Giuffrida Antonio , Lanzafame Rosario
Published: March 2009

The lubrication system for automotive internal combustion engines consists of several components. Oil flow rate for lubrication is generated by a positive displacement pump equipped with a pressure relief valve, usually present in the casing of the pump to prevent high oil pressures building up in the system and to deliver to the sump the exceeding generated flow rate. This study focuses on the static and dynamic characteristics of the pressure relief valve with considerations about the stability of the overall system, according to design parameters of both the valve and the system itself.
Spatial and Temporal Stress Distributions in Spark Ignition Engine Pistons at Wide Open Throttle
Authors: Kubicki Maciej , Watson Harry , Williams John , Stryker Peter
Published: March 2009

Spatial and temporal stress distributions in two piston geometries for a sinusoidal piston motion engine with different rigid piston-connecting rod attachments were investigated; one was a homogeneous, all-aluminum piston with a bolted connection located remote to the piston crown, and the second was a composite piston structure in which a steel connecting rod is imbedded into the aluminum piston crown. The piston stress response to the applied thermo-mechanical loads was predicted using LUSAS (London University Stress Analysis System). A dynamic finite element analysis of the homogeneous piston was performed for the duration of one complete combustion cycle and a static analysis modeled the two component piston with loads estimated at the time when stress was highest. Two types of thermo-mechanical fatigue were analyzed: low cycle high stress and high cycle low stress. Nodal stress histories at 2000 rpm are presented for equivalent Huber (stress fields equivalent to the three dimensional stress state), radial, hoop, longitudinal, and shear stresses. Specific locations of the maximum compressive and tensile stresses were identified and show that maximum stress occurs at different times for different locations. At nodal locations where mechanical loads counteract thermal expansion forces, stress levels peak at the time when gas pressure is low. Stresses peak at the time of maximum pressure where thermal and mechanical loads have the same sense. The principle of superposition was used to differentiate the thermal and mechanical stress contributions in the piston and, most notably, in the piston crown region. The maximum amplitude and frequency of the thermal and mechanical-thermal stresses indicated high cycle fatigue failure was not likely. However, high compressive stress developed in material weakened by high temperatures is the most likely cause of failure. The two component piston is formed with a steel cone insert cast into the piston. The static results show high local Huber (von Mises) stresses at the dissimilar material interface and the highest value of hoop stress and, consequently, the main cause of large equivalent stress levels is in the steel cone insert. A modified flexible tripod shaped cone resulted in significant reduction of hoop stress in the region of contact with the aluminum. However, the peak equivalent stress present in the aluminum crown of this model was too high for the material to withstand. The last results presented are for the homogeneous piston modified to lower stress concentrations and with boundary conditions modified to represent enhanced cooling of the piston underside. The peak piston temperatures were significantly reduced and consequently the Huber stress levels were reduced. Analysis of the dynamic stresses indicated a low probability for fatigue failure. These results indicated that a homogeneous aluminum piston could become a feasible concept, provided additional piston cooling mechanisms are installed.
Optimization of Injector Spray Configurations for an HSDI Diesel Engine at High Load
Authors: Bergin Michael J. , Reitz Rolf D.
Published: March 2009

CFD simulations were conducted with the KIVA-3v code with improved spray and combustion sub-models. Combustion analysis was performed using micro-genetic optimizations for a 1.9L HSDI diesel engine at a high load operating conditions (∼15 bar imep). The study explored injector spray configurations, including the number of injector nozzle holes, the hole diameters, and their orientations. The engine swirl ratio and start-of-injection timing were also varied. The optimizations considered injector nozzles with 14, 12, 10 and 8 injector holes. Each configuration included consideration of a pair of injector holes. Variations in the orientation angle of the first hole were explored. For the second hole, both the orientation angle and the azimuthal spacing relative to the first hole were varied. The chosen parameters allowed the holes to be symmetrically spaced or coincident azimuthally. The performance of each simulation was based on a merit function which accounts for fuel economy, NOx and soot emissions. For the test conditions chosen, an 8-hole injector configuration was found to be the best. This is explained by the improved fuel spray penetration and mixing associated with a smaller number of large diameter nozzle holes. For all injector configurations, the optima selected groups of holes where the total angular spacing between holes was less than eight degrees. The optimum swirl ratio found was approximately that of the baseline engine design.
Feasibility of Pulsed Microwave Plasma Ignition for Use in SI-Engines
Authors: Pertl Franz A. , Smith James E.
Published: March 2009

Ignition of the fuel-air mixture through compression and spark ignition are the two basic methods for igniting combustion mixtures in modern internal combustion (IC) engines. A significant environmental and economic benefit could be obtained if spark ignited (SI) engines were to be made more efficient. Higher thermal efficiencies could be obtained through operation with leaner fuel-air mixtures and through operations at higher power densities and pressures. These types of mixtures are often more difficult to ignite with traditional spark plugs. In pursuit of better ignition sources, this paper investigates a microwave plasma alternative to the traditional spark plug. Additionally, measurements of a novel pulsed microwave induced plasma ignition concept are presented. Measurements at atmospheric pressures show promising results with respect to energy and plasma formation delay. With some refinement, it is possible to produce sufficiently energetic microwave discharges, in a short enough time frame to make them feasible for ignition of SI engines in an automotive setting. These results justify further investigation to quantify the advantages such an ignition source may have to offer.
An Advanced Turbocharging System for Improved Fuel Efficiency
Authors: VanDyne Edward A. , Riley Michael B.
Published: March 2009

Turbochargers provide an efficient method of utilizing exhaust energy to boost intake air pressure for improved engine performance and efficiency. However transient operation requires increased air delivery (via quicker compressor response) to allow more rapid fueling for acceleration in both diesel and natural gas engines. In diesel engines rapid boosting will avoid increased particulates caused by excessive fueling during acceleration. Further, in applications that use either a wastegate, inlet bypass or variable vanes in the turbine to limit boost pressures, the excess energy in the exhaust is thrown away. The SuperTurbo™ (or superturbocharger) can recover much of the wasted energy and return it to the crankshaft, increasing overall efficiency. Woodward has developed a mechanical geartrain connected to the turbine shaft that transmits power through a variable speed hydraulic transmission to the crankshaft of an engine. This combination, a superturbocharger, provides the needed characteristics of (a) recovery of energy at high speed/load operating points (turbocompounding), (b) very rapid acceleration of the turbine shaft during transients (supercharging), (c) elimination of boost limitation devices, and (d) a variable speed hydraulic transmission that will be lower cost than a high-speed, high-power electrical system. While the air requirements are different for diesel and natural gas engines, both have sufficient exhaust energy to drive a turbine beyond the needs of the compressor for much of the performance map. Part load operation may be different as natural gas engines are usually throttled. The choice of a diesel or natural gas application was influenced by the availability of a suitable engine. The first prototype superturbocharger was built and tested on a Mack E7G natural gas engine, replacing the wastegated turbocharger of the stock engine. Preliminary results show fuel economy improvements of almost 6% at high speeds and high loads. In addition the load response of the engine was greatly increased due to the ability to accelerate turbine shaft speed, increasing boost. However there was a peak power output drop due to limitations in boost and imperfect sizing.
Chromosomal Integration of the Extended-Spectrum β-Lactamase Gene
bla
CTX-M-15
in
Salmonella enterica
Serotype Concord Isolates from Internationally Adopted Children
Authors: Fabre Laëtitia , Delauné Aurélia , Espié Emmanuelle , Nygard Karin , Pardos Maria , Polomack Lucette , Guesnier Françoise , Galimand Marc , Lassen Jørgen , Weill François-Xavier
Published: March 2009

We report the emergence of
Salmonella enterica
isolates of serotype Concord (and its monophasic variant 6,7:l,v:-) producing the extended-spectrum β-lactamases (ESBLs) SHV-12 and CTX-M-15 in France and Norway between 2001 and 2006 (43 in France and 26 in Norway). The majority of these isolates were from adopted children from Ethiopia, most of whom were healthy carriers. Several symptomatic secondary cases were found in the adoptive families and health care facilities in France. Serotype Concord isolates collected before 2003 produced SHV-12 encoded on a 340-kb conjugative plasmid of replicon IncI1. Isolates collected after 2003 produced CTX-M-15. We detected two conjugative plasmids carrying
bla
CTX-M-15
. One plasmid, approximately 300 kb in size, was positive for the IncHI2 replicon and the plasmid-mediated quinolone resistance gene
qnrA1
. The other plasmid, from one of the earliest CTX-M-15-producing isolates collected, was a fusion plasmid with IncY and IncA/C
2
replicons and was 200 kb in size. However, we showed, using Southern hybridization of I-CeuI-digested chromosomal DNA and S1 nuclease analysis of plasmid DNA, that most isolates had a
bla
CTX-M-15
gene located on chromosomal DNA. Analysis of the flanking regions of the chromosomally located
bla
CTX-M-15
gene by cloning revealed an IS
Ecp1
truncated by an intact IS
26
upstream from the
bla
CTX-M-15
gene and a truncated
orf477
gene downstream from
bla
CTX-M-15
. We found regions beyond the IS
26
and the
orf477
genes that were derived from IncA/C
2
plasmids, suggesting the chromosomal integration of part of the
bla
CTX-M-15
-carrying IncY and IncA/C
2
fusion plasmid from early CTX-M-15-producing isolates.
Violacein Extracted from
Chromobacterium violaceum
Inhibits
Plasmodium
Growth In Vitro and In Vivo
Authors: Lopes Stefanie C. P. , Blanco Yara C. , Justo Giselle Z. , Nogueira Paulo A. , Rodrigues Francisco L. S. , Goelnitz Uta , Wunderlich Gerhard , Facchini Gustavo , Brocchi Marcelo , Duran Nelson , Costa Fabio T. M.
Published: March 2009

Violacein is a violet pigment extracted from the gram-negative bacterium
Chromobacterium violaceum
. It presents bactericidal, tumoricidal, trypanocidal, and antileishmanial activities. We show that micromolar concentrations efficiently killed chloroquine-sensitive and -resistant
Plasmodium falciparum
strains in vitro; inhibited parasitemia in vivo, even after parasite establishment; and protected
Plasmodium chabaudi chabaudi
-infected mice from a lethal challenge.
Pharmacokinetics and Safety of Famciclovir in Children with Herpes Simplex or Varicella-Zoster Virus Infection
Authors: Sáez-Llorens X. , Yogev R. , Arguedas A. , Rodriguez A. , Spigarelli M. G. , De León Castrejón T. , Bomgaars L. , Roberts M. , Abrams B. , Zhou W. , Looby M. , Kaiser G. , Hamed K.
Published: March 2009

Two multicenter, open-label, single-arm, two-phase studies evaluated single-dose pharmacokinetics and single- and multiple-dose safety of a pediatric oral famciclovir formulation (prodrug of penciclovir) in children aged 1 to 12 years with suspicion or evidence of herpes simplex virus (HSV) or varicella-zoster virus (VZV) infection. Pooled pharmacokinetic data were generated after single doses in 51 participants (∼12.5 mg/kg of body weight [BW] for children weighing <40 kg and 500 mg for children weighing ≥40 kg). The average systemic exposure to penciclovir was similar (6- to 12-year-olds) or slightly lower (1- to <6-year-olds) than that in adults receiving a 500-mg dose of famciclovir (historical data). The apparent clearance of penciclovir increased with BW in a nonlinear manner, proportional to BW
0.696
. An eight-step weight-based dosing regimen was developed to optimize exposure in smaller children and was used in the 7-day multiple-dose safety phases of both studies, which enrolled 100 patients with confirmed/suspected viral infections. Twenty-six of 47 (55.3%) HSV-infected patients who received famciclovir twice a day and 24 of 53 (45.3%) VZV-infected patients who received famciclovir three times a day experienced at least one adverse event. Most adverse events were gastrointestinal in nature. Exploratory analysis following 7-day famciclovir dosing regimen showed resolution of symptoms in most children with active HSV (19/21 [90.5%]) or VZV disease (49/53 [92.5%]). Famciclovir formulation (sprinkle capsules in OraSweet) was acceptable to participants/caregivers. In summary, we present a weight-adjusted dosing schedule for children that achieves systemic exposures similar to those for adults given the 500-mg dose.
Plasmodium falciparumNa+/H+Exchanger 1 Transporter Is Involved in Reduced Susceptibility to Quinine
Authors: Henry Maud , Briolant Sébastien , Zettor Agnès , Pelleau Stéphane , Baragatti Meili , Baret Eric , Mosnier Joel , Amalvict Rémy , Fusai Thierry , Rogier Christophe , Pradines Bruno
Published: March 2009

Polymorphisms in thePlasmodium falciparum crt(Pfcrt), Pfmdr1, and Pfmrpgenes were not significantly associated with quinine (QN) 50% inhibitory concentrations (IC50s) in 23 strains ofPlasmodium falciparum. An increased number of DNNND repeats in Pfnhe-1microsatellite ms4760 was associated with an increased IC50of QN (P= 0.0007). Strains with only one DNNND repeat were more susceptible to QN (mean IC50of 154 nM). Strains with two DNNND repeats had intermediate susceptibility to QN (mean IC50of 548 nM). Strains with three DNNND repeats had reduced susceptibility to QN (mean IC50of 764 nM). Increased numbers of NHNDNHNNDDD repeats were associated with a decreased IC50of QN (P= 0.0020). Strains with profile 7 for Pfnhe-1ms4760 (ms4760-7) were significantly associated with reduced QN susceptibility (mean IC50of 764 nM). The determination of DNNND and NHNDNHNNDDD repeats in Pfnhe-1ms4760 could be a good marker of QN resistance and provide an attractive surveillance method to monitor temporal trends inP. falciparumsusceptibility to QN. The validity of the markers should be further supported by analyzing more isolates.
Gene Expression and Evolution of Antifungal Drug Resistance
Authors: Anderson James B. , Sirjusingh Caroline , Syed Nazia , Lafayette Shantelle
Published: March 2009

Permanent changes in gene expression result from certain forms of antifungal resistance. In this study, we asked whether any changes in gene expression are required for the evolution of a drug-resistant phenotype in populations. We examined the changes in gene expression resulting from the evolution of resistance in experimental populations of the yeast
Saccharomyces cerevisiae
with two antifungal drugs, fluconazole (FLC) in a previous study and amphotericin B (AmB) in this study, in which five populations were subjected to increasing concentrations of AmB, from 0.25 to 128 μg/ml in twofold increments. Six genes, YGR035C,
YOR1
,
ICT1
,
GRE2
,
PDR16
, and YPLO88W, were consistently overexpressed with resistance to AmB reported here and with resistance to FLC involving a mechanism of increased efflux reported previously. We then asked if the deletion of these genes impaired the ability of populations to evolve resistance to FLC over 108 generations of asexual reproduction in 32 and 128 μg/ml FLC, the same conditions under which FLC-resistant types evolved originally. For each of three deletion strains,
YOR1
,
ICT1
, and
PDR16
strains, extinctions occurred in one of two replicate populations growing in 128 μg/ml FLC. Each of these three deletion strains was mixed 1:1 with a marked version of the wild type to measure the relative ability of the deletion strain to adapt over 108 generations. In these assays, only the
PDR16
deletion strain consistently became extinct both at 32 and at 128 μg/ml FLC. The deletion of
PDR16
reduces the capacity of a population to evolve to resistance to FLC.
An ABC Transporter of
Streptococcus pneumoniae
Involved in Susceptibility to Vancoresmycin and Bacitracin
Authors: Becker Petra , Hakenbeck Regine , Henrich Bernhard
Published: March 2009

Vancoresmycin is a novel tetramic acid antibiotic, probably interfering with functions of the cytoplasmic membrane. To investigate its mode of action, mutants of
Streptococcus pneumoniae
exhibiting reduced susceptibility to vancoresmycin were isolated at a low frequency. Four of them were further examined and showed similar pleiotropic phenotypes, including reduced growth rate, early autolysis, and chain formation. In one mutant, the level of transcripts from a single locus encoding the potential ABC transporter Spr0812-Spr0813 was increased sixfold. The corresponding DNA sequence revealed a nonsense mutation (C1744T) in spr0813, leading to the formation of a truncated permease lacking 2 of the 10 predicted transmembrane helices. As demonstrated by deletion and transformation analysis and reconstructing the spr0813
C1744T
mutation in the wild-type background, this nucleotide exchange was sufficient to cause reduced susceptibility to vancoresmycin and higher amounts of spr0812-spr0813 mRNA. Mapping and reporter assays of the cognate promoter P

abc

showed that spr0812 and spr0813 are cotranscribed with a preceding small gene and that the spr0813
C1744T
mutation does not affect the activity of P

abc

. Due to the similarity of Spr0812-Spr0813 to bacitracin transporters of
Streptococcus mutans
and
Bacillus
spp., the bacitracin susceptibility of spr0813 mutants was examined. Both the spr0813
C1744T
nonsense mutation and the deletion of the transporter genes led to a clearly increased sensitivity to bacitracin. Thus, the intact transporter is required for intrinsic resistance to bacitracin, whereas reduced vancoresmycin susceptibility is mediated by the truncated permease.
Distinct Patterns of Dendritic Cell Cytokine Release Stimulated by Fungal β-Glucans and Toll-Like Receptor Agonists
Authors: Huang Haibin , Ostroff Gary R. , Lee Chrono K. , Wang Jennifer P. , Specht Charles A. , Levitz Stuart M.
Published: March 2009

β-Glucans derived from fungal cell walls have potential uses as immunomodulating agents and vaccine adjuvants. Yeast glucan particles (YGPs) are highly purifiedSaccharomyces cerevisiaecell walls composed of β1,6-branched β1,3-d-glucan and free of mannans. YGPs stimulated secretion of the proinflammatory cytokine tumor necrosis factor alpha (TNF-α) in wild-type murine bone marrow-derived myeloid dendritic cells (BMDCs) but did not stimulate interleukin-12p70 (IL-12p70) production. A purified soluble β1,6-branched β1,3-d-glucan, scleroglucan, also stimulated TNF-α in BMDCs. These two β-glucans failed to stimulate TNF-α in Dectin-1 (β-glucan receptor) knockout BMDCs. Costimulation of wild-type BMDCs with β-glucans and specific Toll-like receptor (TLR) ligands resulted in greatly enhanced TNF-α production but decreased IL-12p70 production compared with TLR agonists alone. The upregulation of TNF-α and downregulation of IL-12p70 required Dectin-1, but not IL-10. Gamma interferon (IFN-γ) priming did not overcome IL-12p70 reduction by β-glucans. Similar patterns of cytokine regulation were observed in human monocyte-derived dendritic cells (DCs) costimulated with YGPs and the TLR4 ligand lipopolysaccharide. Finally, costimulation of BMDCs with YGPs and either the TLR9 ligand, CpG, or the TLR2/1 ligand, Pam3CSK4, resulted in upregulated secretion of IL-1α and IL-10 and downregulated secretion of IL-1β, IL-6, and IFN-γ-inducible protein 10 but had no significant effects on IL-12p40, keratinocyte-derived chemokine, monocyte chemotactic protein 1, or macrophage inflammatory protein α, compared with the TLR ligand alone. Thus, β-glucans have distinct effects on cytokine responses following DC stimulation with different TLR agonists. These patterns of response might contribute to the skewing of immune responses during mycotic infections and have implications for the design of immunomodulators and vaccines containing β-glucans.
B- and T-Cell Responses in Group A Streptococcus M-Protein- or Peptide-Induced Experimental Carditis
Authors: Gorton Davina , Govan Brenda , Olive Colleen , Ketheesan Natkunam
Published: March 2009

The etiology of rheumatic fever and rheumatic heart disease (RF/RHD) is believed to be autoimmune, involving immune responses initiated between streptococcal and host tissue proteins through a molecular mimicry mechanism(s). We sought to investigate the humoral and cellular responses elicited in a Lewis rat model of group A streptococcus M-protein- or peptide-induced experimental valvulitis/carditis, a recently developed animal model which may, in part, represent human rheumatic carditis. Recombinant streptococcal M5 protein elicited opsonic antibodies in Lewis rats, and anti-M5 antisera recognized epitopes within the B- and C-repeat regions of M5. One peptide from the streptococcal M5 protein B-repeat region (M5-B.6, amino acids 161 to 180) induced lymphocytes that responded to both recombinant M5 and cardiac myosin. Rats immunized with streptococcal M5 protein developed valvular lesions, distinguished by infiltration of CD3+, CD4+, and CD68+cells into valve tissue, consistent with human studies that suggest that RF/RHD are mediated by inflammatory CD4+T cells and CD68+macrophages. The current study provides additional information that supports the use of the rat autoimmune valvulitis model for investigating RF/RHD.
Functional Comparison of the Binding of Factor H Short Consensus Repeat 6 (SCR 6) to Factor H Binding Protein fromNeisseria meningitidisand the Binding of Factor H SCR 18 to 20 toNeisseria gonorrhoeaePorin
Authors: Shaughnessy Jutamas , Lewis Lisa A. , Jarva Hanna , Ram Sanjay
Published: March 2009

BothNeisseria meningitidisandNeisseria gonorrhoeaerecruit the alternative pathway complement inhibitory protein factor H (fH) to their surfaces to evade complement-dependent killing. Meningococci bind fH via fH binding protein (fHbp), a surface-exposed lipoprotein that is subdivided into three variant families based on one classification scheme. Chimeric proteins that comprise contiguous domains of fH fused to murine Fc were used to localize the binding site for all three fHbp variants on fH to short consensus repeat 6 (SCR 6). As expected, fH-like protein 1 (FHL-1), which contains fH SCR 6, also bound to fHbp-expressing meningococci. Using site-directed mutagenesis, we identified histidine 337 and histidine 371 in SCR 6 as important for binding to fHbp. These findings may provide the molecular basis for recent observations that demonstrated human-specific fH binding to meningococci. Differences in the interactions of fHbp variants with SCR 6 were evident. Gonococci bind fH via their porin (Por) molecules (PorB.1A or PorB.1B); sialylation of lipooligosaccharide enhances fH binding. Both sialylated PorB.1B- and (unsialylated) PorB.1A-bearing gonococci bind fH through SCR 18 to 20; PorB.1A can also bind SCR 6, but only weakly, as evidenced by a low level of binding of FHL-1 relative to that of fH. Using isogenic strains expressing either meningococcal fHbp or gonococcal PorB.1B, we discovered that strains expressing gonococcal PorB.1B in the presence of sialylated lipooligosaccharide bound more fH, more effectively limited C3 deposition, and were more serum resistant than their isogenic counterparts expressing fHbp. Differences in fH binding to these two related pathogens may be important for modulating their individual responses to host immune attack.
Children with the Le(a+b−) Blood Group Have Increased Susceptibility to Diarrhea Caused by Enterotoxigenic
Escherichia coli
Expressing Colonization Factor I Group Fimbriae
Authors: Ahmed Tanvir , Lundgren Anna , Arifuzzaman Mohammad , Qadri Firdausi , Teneberg Susann , Svennerholm Ann-Mari
Published: March 2009

Recent studies have shown that children with blood group A have increased susceptibility to enterotoxigenic
Escherichia coli
(ETEC) diarrhea and that Lewis blood group “a” antigen (Le
a
) may be a candidate receptor for ETEC colonization factor (CF) antigen I (CFA/I) fimbriae. Based on these findings, we have attempted to determine if children with the Le(a+b−) phenotype may be more susceptible to diarrhea caused by ETEC, in particular ETEC expressing CFA/I and related fimbriae of the CFA/I group, than Le(a−b+) children. To test this hypothesis, we have determined the Lewis antigen expression in 179 Bangladeshi children from a prospective birth cohort study in urban Dhaka in which ETEC expressing major CFs such as CFA/I, CS3, CS5, and CS6 was the most commonly isolated diarrhea pathogen during the first 2 years of life. The Lewis blood group phenotypes were determined by a dot blot immunoassay using saliva samples and by a tube agglutination test using fresh red blood cells. The results indicate that Le(a+b−) children more often had symptomatic than asymptomatic ETEC infections (
P
< 0.001), whereas symptomatic and asymptomatic ETEC infections were equally frequent in Le(a−b+) children. We also show that children with the Le(a+b−) blood type had significantly higher incidences of diarrhea caused by ETEC expressing fimbriae of the CFA/I group than Le(a−b+) children (
P
< 0.001). In contrast, we did not find any association between the Lewis blood group phenotype and diarrhea caused by ETEC expressing CS6 or rotavirus.
ToeHold Artisans Collaborative: Building Entrepreneurial Capabilities to Tackle Poverty
Authors: Shanmugam Sindhu , Ramakrishna Velamuri S.
Published: March 2009

Toehold Artisans Collaborative (TAC) is a project launched by the Asian Center for Entrepreneurship Initiatives (ASCENT), a non-profit organization based in Bangalore, to build entrepreneurial capacity in a community of footwear artisans of the small southern Indian town of Athani. Prior to ASCENT's involvement, which began in 1998, the artisans of Athani were making a subsistence wage, which did not even guarantee them two square meals a day. They could not send their children to school and were thus suffering from economic stagnation.

TAC is an established Group Enterprise of 14 women Self Help Groups (SHG). Even though women's SHGs are the direct stakeholders, the men are not left out — they are treated as co-preneurs for all inputs, exposure to international fairs and production purposes. The front end of TAC is a customer-centric business enterprise that has taken the exquisite footwear brand 'ToeHold™' to challenging international mainstream markets. The backend is an artisan-centric social enterprise striving for improvement in the quality of life of about 400 artisans' families. The case documents how TAC was set up and evolved during the 1998–2006 period, the challenges it faced and continues to face, and the impact it has had on the artisan community. It is useful for examining the effective organization and running of social enterprises.
ATOMIC FORCE MICROSCOPY MEASUREMENTS OF BOVINE SERUM ALBUMIN ADHESION FORCES ON SURFACES
Authors: LAI CHUN-CHIH , MOTTA NUNZIO , BELL JOHN M.
Published: March 2009

A novel, direct technique has been developed to measure the interactions of bovine serum albumin (BSA) on surfaces by using atomic force microscopy (AFM) in a liquid environment. We have been able to measure adhesion forces between proteins and substrate surfaces in phosphate-buffered saline (PBS) solution directly, without any modification to the substrate and the AFM tip. Two different surfaces have been used in the measurements: mica (hydrophilic surface) and polystyrene (hydrophobic surface). The results show that a polystyrene surface has larger adhesion forces to BSA than a mica surface. This is consistent with previous research, which demonstrated that hydrophobic surfaces enhance protein adhesion but hydrophilic surfaces do not.
Moving sounds enhance the visually-induced self-motion illusion (circular vection) in virtual reality
Authors: Riecke Bernhard E. , Väljamäe Aleksander , Schulte-Pelkum Jörg
Published: March 2009

While rotating visual and auditory stimuli have long been known to elicit self-motion illusions (“circular vection”), audiovisual interactions have hardly been investigated. Here, two experiments investigated whether visually induced circular vection can be enhanced by concurrently rotating auditory cues that match visual landmarks (e.g., a fountain sound). Participants sat behind a curved projection screen displaying rotating panoramic renderings of a market place. Apart from a no-sound condition, headphone-based auditory stimuli consisted of mono sound, ambient sound, or low-/high-spatial resolution auralizations using generic head-related transfer functions (HRTFs). While merely adding nonrotating (mono or ambient) sound showed no effects, moving sound stimuli facilitated both vection and presence in the virtual environment. This spatialization benefit was maximal for a medium (20° × 15°) FOV, reduced for a larger (54° × 45°) FOV and unexpectedly absent for the smallest (10° × 7.5°) FOV. Increasing auralization spatial fidelity (from low, comparable to five-channel home theatre systems, to high, 5° resolution) provided no further benefit, suggesting a ceiling effect. In conclusion, both self-motion perception and presence can benefit from adding moving auditory stimuli. This has important implications both for multimodal cue integration theories and the applied challenge of building affordable yet effective motion simulators.
The effects of head-mounted display mechanical properties and field of view on distance judgments in virtual environments
Authors: Willemsen Peter , Colton Mark B. , Creem-Regehr Sarah H. , Thompson William B.
Published: March 2009

Research has shown that people are able to judge distances accurately in full-cue, real-world environments using visually directed actions. However, in virtual environments viewed with head-mounted display (HMD) systems, there is evidence that people act as though the virtual space is smaller than intended. This is a surprising result given how well people act in real environments. The behavior in the virtual setting may be linked to distortions in the available visual cues or to a person's ability to locomote without vision. Either could result from issues related to added mass, moments of inertia, and restricted field of view in HMDs. This article describes an experiment in which distance judgments based on normal real-world and HMD viewing are compared with judgments based on real-world viewing while wearing two specialized devices. One is a mock HMD, which replicated the mass, moments of inertia, and field of view of the HMD and the other an inertial headband designed to replicate the mass and moments of inertia of the HMD, but constructed to not restrict the field of view of the observer or otherwise feel like wearing a helmet. Distance judgments using the mock HMD showed a statistically significant underestimation relative to the no restriction condition but not of a magnitude sufficient to account for all the distance compression seen in the HMD. Indicated distances with the inertial headband were not significantly smaller than those made with no restrictions.
On spatiochromatic visual sensitivity and peripheral color LOD management
Authors: Duchowski Andrew T. , Bate David , Stringfellow Paris , Thakur Kaveri , Melloy Brian J. , Gramopadhye Anand K.
Published: March 2009

Empirical findings from a gaze-contingent color degradation study report the effects of artificial reduction of the human visual system's sensitivity to peripheral chromaticity on visual search performance. To our knowledge, this is the first such investigation of peripheral color reduction. For unimpeded performance, results suggest that, unlike spatiotemporal content, peripheral chromaticity cannot be reduced within the central 20° visual angle. Somewhat analogous to dark adaptation, reduction of peripheral color tends to simulate scotopic viewing conditions. This holds significant implications for chromatic Level Of Detail management. Specifically, while peripheral spatiotemporal detail can be attenuated without affecting visual search, often dramatically (e.g., spatial detail can be so reduced up to 50% at about 5°), peripheral chromatic reduction is likely to be noticed much sooner. Therefore, color LOD reduction (e.g., via compression), should be maintained isotropically across the central 20° visual field.
Toward a definition of visual complexity as an implicit measure of cognitive load
Authors: Harper Simon , Michailidou Eleni , Stevens Robert
Published: March 2009

The visual complexity of Web pages is much talked about; “complex Web pages are difficult to use,” but often regarded as a subjective decision by the user. This subjective decision is of limited use if we wish to understand the importance of visual complexity, what it means, and how it can be used. We theorize that by understanding a user's visual perception of Web page complexity, we can understand the cognitive effort required for interaction with that page. This is important because by using an easily identifiable measure, such as visual complexity, as an implicit marker of cognitive load, we can design Web pages which are easier to interact with. We have devised an initial empirical experiment, using card sorting and triadic elicitation, to test our theories and assumptions, and have built an initial baseline sequence of 20 Web pages along with a library of qualitative and anecdotal feedback. Using this library, we define visual complexity, ergo perceived interaction complexity, and by taking these pages as “prototypes” and ranking them into a sequence of complexity, we are able to group them into: simple, neutral, and complex. This means we can now work toward a definition of visual complexity as an implicit measure of cognitive load.
Real-world vision
Authors: Canosa Roxanne L.
Published: March 2009

Visual perception is an inherently selective process. To understand when and why a particular region of a scene is selected, it is imperative to observe and describe the eye movements of individuals as they go about performing specific tasks. In this sense, vision is an active process that integrates scene properties with specific, goal-oriented oculomotor behavior. This study is an investigation of how task influences the visual selection of stimuli from a scene. Four eye tracking experiments were designed and conducted to determine how everyday tasks affect oculomotor behavior. A portable eyetracker was created for the specific purpose of bringing the experiments out of the laboratory and into the real world, where natural behavior is most likely to occur. The experiments provide evidence that the human visual system is not a passive collector of salient environemental stimuli, nor is vision general-purpose. Rather, vision is active and specific, tightly coupled to the requirements of a task and a plan of action. The experiments support the hypothesis that the purpose of selective attention is to maximize task efficiency by fixating relevant objects in the scene. A computational model of visual attention is presented that imposes a high-level constraint on the bottom-up salient properties of a scene for the purpose of locating regions that are likely to correspond to foreground objects rather than background or other salient nonobject stimuli. In addition to improving the correlation to human subject fixation densities over a strictly bottom-up model [Itti et al. 1998; Parkhurst et al. 2002], this model predicts a central fixation tendency when that tendency is warranted, and not as an artificially primed location bias.
ASSURE
Authors: Sidiroglou Stelios , Laadan Oren , Perez Carlos , Viennot Nicolas , Nieh Jason , Keromytis Angelos D.
Published: March 2009

Software failures in server applications are a significant problem for preserving system availability. We present ASSURE, a system that introduces rescue points that recover software from unknown faults while maintaining both system integrity and availability, by mimicking system behavior under known error conditions. Rescue points are locations in existing application code for handling a given set of programmer-anticipated failures, which are automatically repurposed and tested for safely enabling fault recovery from a larger class of (unanticipated) faults. When a fault occurs at an arbitrary location in the program, ASSURE restores execution to an appropriate rescue point and induces the program to recover execution by virtualizing the program's existing error-handling facilities. Rescue points are identified using fuzzing, implemented using a fast coordinated checkpoint-restart mechanism that handles multi-process and multi-threaded applications, and, after testing, are injected into production code using binary patching. We have implemented an ASSURE Linux prototype that operates without application source code and without base operating system kernel changes. Our experimental results on a set of real-world server applications and bugs show that ASSURE enabled recovery for all of the bugs tested with fast recovery times, has modest performance overhead, and provides automatic self-healing orders of magnitude faster than current human-driven patch deployment methods.
Maximum benefit from a minimal HTM
Authors: Hofmann Owen S. , Rossbach Christopher J. , Witchel Emmett
Published: March 2009

A minimal, bounded hardware transactional memory implementation significantly improves synchronization performance when used in an operating system kernel. We add HTM to Linux 2.4, a kernel with a simple, coarse-grained synchronization structure. The transactional Linux 2.4 kernel can improve performance of user programs by as much as 40% over the non-transactional 2.4 kernel. It closes 68% of the performance gap with the Linux 2.6 kernel, which has had significant engineering effort applied to improve scalability.

We then extend our minimal HTM to a fast, unbounded transactional memory with a novel technique for coordinating hardware transactions and software synchronization. Overflowed transactions run in software, with only a minimal coupling between hardware and software systems. There is no performance penalty for overflow rates of less than 1%. In one instance, at 16 processors and an overflow rate of 4%, performance degrades from an ideal 4.3x to 3.6x.
Gordon
Authors: Caulfield Adrian M. , Grupp Laura M. , Swanson Steven
Published: March 2009

As our society becomes more information-driven, we have begun to amass data at an astounding and accelerating rate. At the same time, power concerns have made it difficult to bring the necessary processing power to bear on querying, processing, and understanding this data. We describe Gordon, a system architecture for data-centric applications that combines low-power processors, flash memory, and data-centric programming systems to improve performance for data-centric applications while reducing power consumption. The paper presents an exhaustive analysis of the design space of Gordon systems, focusing on the trade-offs between power, energy, and performance that Gordon must make. It analyzes the impact of flash-storage and the Gordon architecture on the performance and power efficiency of data-centric applications. It also describes a novel flash translation layer tailored to data intensive workloads and large flash storage arrays. Our data show that, using technologies available in the near future, Gordon systems can out-perform disk-based clusters by 1.5× and deliver up to 2.5× more performance per Watt.
Accelerating critical section execution with asymmetric multi-core architectures
Authors: Suleman M. Aater , Mutlu Onur , Qureshi Moinuddin K. , Patt Yale N.
Published: March 2009

To improve the performance of a single application on Chip Multiprocessors (CMPs), the application must be split into threads which execute concurrently on multiple cores. In multi-threaded applications, critical sections are used to ensure that only one thread accesses shared data at any given time. Critical sections can serialize the execution of threads, which significantly reduces performance and scalability.

This paper proposes Accelerated Critical Sections (ACS), a technique that leverages the high-performance core(s) of an Asymmetric Chip Multiprocessor (ACMP) to accelerate the execution of critical sections. In ACS, selected critical sections are executed by a high-performance core, which can execute the critical section faster than the other, smaller cores. As a result, ACS reduces serialization: it lowers the likelihood of threads waiting for a critical section to finish. Our evaluation on a set of 12 critical-section-intensive workloads shows that ACS reduces the average execution time by 34% compared to an equal-area 32T-core symmetric CMP and by 23% compared to an equal-area ACMP. Moreover, for 7 out of the 12 workloads, ACS improves scalability by increasing the number of threads at which performance saturates.