bluuebunny/crossref_metadata_2025 huggingface dataset:
Resource Letter NSM-1: New insights into the nuclear shell model
Authors: Dean David J. , Hamilton Joseph H.
Published: January 2011

This Resource Letter provides a guide to the literature on the spherical shell model as applied to nuclei. The nuclear shell model describes the structure of nuclei starting with a nuclear core developed by the classical neutron and proton magic numbers N,Z=2,8,20,28,50,82,126, where gaps occur in the single-particle energies as a shell is filled, and the interactions of valence nucleons that reside beyond that core. Various modern extensions of this model for spherical nuclei are likewise described. Significant extensions of the nuclear shell model include new magic numbers for spherical nuclei and now for deformed nuclei as well. When both protons and neutrons have shell gaps at the same spherical or deformed shapes, they can reinforce each other to give added stability to that shape and lead to new magic numbers. The vanishings of the classical spherical shell model energy gaps and magic numbers in new neutron-rich nuclei are described. Spherical and deformed shell gaps are seen to be critical for the existence of elements with Z>100.
Ice rafts not sails: Floating the rocks at Racetrack Playa
Authors: Lorenz Ralph D. , Jackson Brian K. , Barnes Jason W. , Spitale Joe , Keller John M.
Published: January 2011

We suggest that the existence of many of the rock-carved trails at Racetrack Playa in Death Valley National Park is predominantly due to the effect of arbitrarily weak winds on rocks that are floated off the soft bed by small rafts of ice, as also occurs in arctic tidal beaches to form boulder barricades. These ice cakes need not have a particularly large surface area if the ice is adequately thick—the ice cakes allow the rocks to move by buoyantly reducing the reaction and friction forces at the bed, not by increasing the wind drag. The parameter space of ice thickness and extent versus rock size for flotation is calculated and found to be reasonable. We demonstrate the effect with a simple experiment.
Relaxing gap capacitor models of electrified interfaces
Authors: Partenskii M. B. , Jordan P. C.
Published: January 2011

Relaxing gap capacitor models emphasize the charge-induced variation of the effective gap of electric double layer capacitors. The first such model, the elastic capacitor, resolved the theoretical puzzle of negative differential capacitance by linking its origin to the charge-induced contraction of the effective gap. It also revealed the importance of treating the electrode charge density as a self-adjustable equilibrium quantity rather than as an independently fixed variable. We show that negative differential capacitance for fixed electrode charge density leads to a charging instability for fixed applied voltage. The “squishy capacitor” model, which allows for lateral variation of the effective gap, relates negative differential capacitance to instabilities in isolated systems, with a resultant lateral redistribution of surface charge. We review the origin of negative differential capacitance, discuss charging instabilities, and explore the analogy between the critical behavior of the squishy capacitor and first-order phase transitions.
Experiments on buoyancy and surface tension following Galileo Galilei
Authors: Straulino S. , Gambi C. M. C. , Righini A.
Published: January 2011

We analyze passages of Galileo’s writings on aspects of floating. Galileo encountered peculiar effects such as the “floating” of light objects made of dense material and the creation of large drops of water that were difficult to explain because they are related to our current understanding of surface tension. Even though Galileo could not understand the phenomenon, his proposed explanations and experiments are interesting from an educational point of view. We replicate the experiment on water and wine that was described by Galileo in his Two New Sciences.
Visualizing circular motion around a Schwarzschild black hole
Authors: Müller Thomas , Boblest Sebastian
Published: January 2011

An observer who moves on a circular orbit around a Schwarzschild black hole with a constant but arbitrary velocity must compensate for the gravitational and centrifugal acceleration to stay on this orbit. The local reference frame of the observer undergoes a geodesic precession, which depends on the radius of the orbit and the velocity. We describe the details of this circular motion and an interactive program that shows what the observer would see.
Science Signaling
Podcast: 4 January 2011
Authors: Yaffe Michael B. , VanHook Annalisa M.
Published: January 2011

Chief Scientific Editor Michael Yaffe reviews the past year in
Science Signaling
.
Confined to Quarters?
Authors: Adler Elizabeth M.
Published: January 2011

Canonical Wnt signaling involves sequestration of glycogen synthase kinase 3.
Memory-Stealing Caspase
Authors: Wong Wei
Published: January 2011

Caspase-3 plays an apoptosis-independent role in the early pathogenesis of Alzheimer’s disease.
Beyond Cell Cycle Control
Authors: VanHook Annalisa M.
Published: January 2011

A phosphatase normally associated with cell cycle control is required for ciliogenesis in zebrafish.
A Safety Catch on Immune Response
Authors: Vinson Valda
Published: January 2011

A double safety-catch mechanism controls amplification of the complement cascade during immune responses.
Dextromethorphan Efficiently Increases Bactericidal Activity, Attenuates Inflammatory Responses, and Prevents Group A Streptococcal Sepsis
Authors: Li Ming-Han , Luo Yueh-Hsia , Lin Chiou-Feng , Chang Yu-Tzu , Lu Shiou-Ling , Kuo Chih-Feng , Hong Jau-Shyong , Lin Yee-Shin
Published: January 2011

Group A streptococcus (GAS) is an important human pathogen that causes a wide spectrum of diseases, ranging from mild throat and skin infections to severe invasive diseases such as necrotizing fasciitis and streptococcal toxic shock syndrome. Dextromethorphan (DM), a dextrorotatory morphinan and a widely used antitussive drug, has recently been reported to possess anti-inflammatory properties. In this study, we investigated the potential protective effect of DM in GAS infection using an air pouch infection mouse model. Our results showed that DM treatment increased the survival rate of GAS-infected mice. Bacterial numbers in the air pouch were lower in mice treated with DM than in those infected with GAS alone. The bacterial elimination efficacy was associated with increased cell viability and bactericidal activity of air-pouch-infiltrating cells. Moreover, DM treatment prevented bacterial dissemination in the blood and reduced serum levels of the proinflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and IL-1β and the chemokines monocyte chemotactic protein 1 (MCP-1), macrophage inflammatory protein 2 (MIP-2), and RANTES. In addition, GAS-induced mouse liver injury was reduced by DM treatment. Taken together, DM can increase bacterial killing and reduce inflammatory responses to prevent sepsis in GAS infection. The consideration of DM as an adjunct treatment in combination with antibiotics against bacterial infection warrants further study.
Antimicrobial Susceptibility ofBrucella melitensisIsolates in Peru
Authors: Maves Ryan C. , Castillo Rosa , Guillen Alfredo , Espinosa Benjamin , Meza Rina , Espinoza Nereyda , Núñez Gladys , Sánchez Luis , Chacaltana Jesús , Cepeda David , González Sofía , Hall Eric R.
Published: January 2011

Brucellosis is an important public health problem in Peru. We evaluated 48 humanBrucella melitensisbiotype 1 strains from Peru between 2000 and 2006. MICs of isolates to doxycycline, azithromycin, gentamicin, rifampin, ciprofloxacin, and trimethoprim-sulfamethoxazole were determined by the Etest method. All isolates were sensitive to tested drugs during the periods of testing. Relapses did not appear to be related to drug resistance.
First Identification and Characterization of an AdeABC-Like Efflux Pump in
Acinetobacter
Genomospecies 13TU
Authors: Roca Ignasi , Espinal Paula , Martí Sara , Vila Jordi
Published: January 2011

Non-
Acinetobacter baumannii
spp. are emerging among clinical
Acinetobacter
isolates causing nosocomial infections, and some (such as genomospecies 13TU) appear to be multidrug resistant. The prevalence of non-
Acinetobacter baumannii
spp. in the hospital setting is likely understated due to poor identification techniques. We report the first identification of an AdeABC-type efflux pump in an
Acinetobacter
genomospecies 13TU clinical isolate, its contribution to multidrug resistance, and the coexistence of three Ade-type efflux pumps in this strain.
Antimicrobial Resistance among Invasive Nontyphoidal
Salmonella enterica
Isolates in the United States: National Antimicrobial Resistance Monitoring System, 1996 to 2007
Authors: Crump John A. , Medalla Felicita M. , Joyce Kevin W. , Krueger Amy L. , Hoekstra R. Michael , Whichard Jean M. , Barzilay Ezra J.
Published: January 2011

Nontyphoidal salmonellae (NTS) are important causes of community-acquired bloodstream infection. We describe patterns of antimicrobial resistance among invasive NTS in the United States. We compared bloodstream NTS isolates with those from stool submitted to the National Antimicrobial Resistance Monitoring System (NARMS) from 1996 to 2007. We describe antimicrobial resistance among invasive strains by serogroup and serotype. Of the 19,302 NTS isolates, 17,804 (92.2%) were from stool or blood. Of these, 1,050 (5.9%) were bloodstream isolates. The median ages (ranges) of patients with and without bacteremia were 36 (<1 to 97) years and 20 (<1 to 105) years, respectively (
P
< 0.001). Males (odds ratio [OR], 1.21; 95% confidence interval [CI], 1.06 to 1.38) and those ≥65 years of age were at greater risk for invasive disease.
Salmonella enterica
serotypes Enteritidis, Typhimurium, and Heidelberg were the most common serotypes isolated from blood;
S. enterica
serotypes Dublin, Sandiego, and Schwarzengrund were associated with the greatest risk for bloodstream isolation. Of invasive isolates, 208 (19.8%) were resistant to ampicillin, 117 (11.1%) to chloramphenicol, and 26 (2.5%) to trimethoprim-sulfamethoxazole; 28 (2.7%) isolates were resistant to nalidixic acid and 26 (2.5%) to ceftriaxone. Antimicrobial resistance to traditional agents is common. However, the occurrence of nalidixic acid and ceftriaxone resistance among invasive NTS is cause for clinical and public health vigilance.
Paraoxonases as Potential Antibiofilm Agents: Their Relationship with Quorum-Sensing Signals in Gram-Negative Bacteria
Authors: Camps Jordi , Pujol Isabel , Ballester Frederic , Joven Jorge , Simó Josep M.
Published: January 2011

The property of many bacteria to form biofilms constitutes a major health problem. Bacteria living in biofilms have a very high resistance to antibiotics. Biofilms may develop at a certain locations with the participation of secreted molecules, termed quorum-sensing signals, when a sufficient density of bacterial growth occurs. In Gram-negative bacteria, acyl homoserine lactones (AHL) have been identified as major quorum-sensing signals. The paraoxonases (PONs) constitute a family of enzymes comprising 3 members (PON1, PON2, and PON3) that have lactonase activity and are able to hydrolyze AHL. In this minireview, we summarize some existing basic knowledge on PON genetics, biochemistry, and function and describe recent research that reports evidence of the important roles that they may play in the organism's defense against biofilm formation. Finally, we propose some lines of future research that could be very productive.
Increased Glycolytic ATP Synthesis Is Associated with Tafenoquine Resistance inLeishmania major
Authors: Manzano José Ignacio , Carvalho Luis , Pérez-Victoria José M. , Castanys Santiago , Gamarro Francisco
Published: January 2011

Tafenoquine (TFQ), an 8-aminoquinoline used to treat and preventPlasmodiuminfections, could represent an alternative therapy for leishmaniasis. Indeed, TFQ has shown significant leishmanicidal activity bothin vitroandin vivo, where it targetsLeishmaniamitochondria and activates a final apoptosis-like process. In order not to jeopardize the life span of this potential antileishmania drug, it is important to determine the likelihood thatLeishmaniawill develop resistance to TFQ and the mechanisms of resistance induced. To address this issue, a TFQ-resistantLeishmania majorpromastigote line (R4) was selected. This resistance, which is unstable in a drug-free medium (revertant line), was maintained in intramacrophage amastigote forms, and R4 promastigotes were found to be cross-resistant to other 8-aminoquinolines. A decreased TFQ uptake, which is probably associated with an alkalinization of the intracellular pH rather than drug efflux, was observed for both the R4 and revertant lines. TFQ induces a decrease in ATP synthesis in allLeishmanialines, although total ATP levels were maintained at higher values in R4 parasites. In contrast, ATP synthesis by glycolysis was significantly increased in R4 parasites, whereas mitochondrial ATP synthesis was similar to that in wild-type parasites. We therefore conclude that increased glycolytic ATP synthesis is the main mechanism underlying TFQ resistance inLeishmania.
Dispensability of Surfactant Proteins A and D in Immune Control ofMycobacterium tuberculosisInfection following Aerosol Challenge of Mice
Authors: Lemos Maria P. , McKinney John , Rhee Kyu Y.
Published: January 2011

Surfactant proteins A and D (SP-A and -D) play a role in many acute bacterial, viral, and fungal infections and in acute allergic responses.In vitro, human SPs bindMycobacterium tuberculosisand alter human and rat macrophage-mediated functions. Here we report the roles of SP-A and SP-D inM. tuberculosisinfection following aerosol challenge of SP-A-, SP-D-, and SP-A/-D-deficient mice. These studies surprisingly identified no gross defects in uptake or immune control ofM. tuberculosisin SP-A-, SP-D-, and SP-A/-D-deficient mice. While both SP-A- and SP-D-deficient mice exhibited evidence of immunopathologic defects, the CD11bhighCD11chighdendritic cell populations and the gamma interferon (IFN-γ)-dependent CD4+T cell response toM. tuberculosiswere unaltered in all genotypes tested. Together, these data indicate that SP-A and SP-D are dispensable for immune control ofM. tuberculosisin a low-dose, aerosol challenge, murine model of tuberculosis (TB).
TcsL Is an Essential Virulence Factor inClostridium sordelliiATCC 9714
Authors: Carter Glen P. , Awad Milena M. , Hao Yibai , Thelen Tennille , Bergin Ingrid L. , Howarth Pauline M. , Seemann Torsten , Rood Julian I. , Aronoff David M. , Lyras Dena
Published: January 2011

Clostridium sordelliiis an important pathogen of humans and animals, causing a range of diseases, including myonecrosis, sepsis, and shock. Although relatively rare in humans, the incidence of disease is increasing, and it is associated with high mortality rates, approaching 70%. Currently, very little is known about the pathogenesis ofC. sordelliiinfections or disease. Previous work suggested that the lethal large clostridial glucosylating toxin TcsL is the major virulence factor, but a lack of genetic tools has hindered our ability to conclusively assign a role for TcsL or, indeed, any of the other putative virulence factors produced by this organism. In this study, we have developed methods for the introduction of plasmids intoC. sordelliiusing RP4-mediated conjugation fromEscherichia coliand have successfully used these techniques to insertionally inactivate thetcsLgene in the reference strain ATCC 9714, using targetron technology. Virulence testing revealed that the production of TcsL is essential for the development of lethal infections byC. sordelliiATCC 9714 and also contributes significantly to edema seen during uterine infection. This study represents the first definitive identification of a virulence factor inC. sordelliiand opens the way for in-depth studies of this important human pathogen at the molecular level.
Genotype Is Correlated with but Does Not Predict Virulence of
Vibrio
vulnificus
Biotype 1 in Subcutaneously Inoculated, Iron Dextran-Treated Mice
Authors: Thiaville Patrick C. , Bourdage Keri L. , Wright Anita C. , Farrell-Evans Melissa , Garvan Cynthia Wilson , Gulig Paul A.
Published: January 2011

Vibrio
vulnificus
is the leading cause of reported deaths from infections related to consumption of seafood in the United States. Affected predisposed individuals frequently die rapidly from sepsis. Otherwise healthy people can experience severe wound infection, which can lead to sepsis and death. A question is why, with so many people consuming contaminated raw oysters, the incidence of severe
V
.
vulnificus
disease is low. Molecular typing systems have shown associations of
V
.
vulnificus
genotypes and the environmental or clinical source of the strains, suggesting that different genotypes possess different virulence potentials. We examined 69
V
.
vulnificus
biotype 1 strains that were genotyped by several methods and evaluated them for virulence in a subcutaneously inoculated iron dextran-treated mouse model. By examining the relationships between skin infection, systemic liver infection, and presumptive death (a decrease in body temperature), we determined that liver infection is predicated on severe skin infection and that death requires significant liver infection. Although most strains caused severe skin infection, not every strain caused systemic infection and death. Strains with polymorphisms at multiple loci (
rrn
,
vcg
, housekeeping genes, and repetitive DNA) designated profile 2 were more likely to cause lethal systemic infection with more severe indicators of virulence than were profile 1 strains with different polymorphisms at these loci. However, some profile 1 strains were lethal and some profile 2 strains did not cause systemic infection. Therefore, current genotyping schemes cannot strictly predict the virulence of
V
.
vulnificus
strains and further investigation is needed to identify virulence genes as markers of virulence.
Shiga Toxin Subtypes Display Dramatic Differences in Potency
Authors: Fuller Cynthia A. , Pellino Christine A. , Flagler Michael J. , Strasser Jane E. , Weiss Alison A.
Published: January 2011

Purified Shiga toxin (Stx) alone is capable of producing systemic complications, including hemolytic-uremic syndrome (HUS), in animal models of disease. Stx includes two major antigenic forms (Stx1 and Stx2), with minor variants of Stx2 (Stx2a to -h). Stx2a is more potent than Stx1. Epidemiologic studies suggest that Stx2 subtypes also differ in potency, but these differences have not been well documented for purified toxin. The relative potencies of five purified Stx2 subtypes, Stx2a, Stx2b, Stx2c, Stx2d, and activated (elastase-cleaved) Stx2d, were studiedin vitroby examining protein synthesis inhibition using Vero monkey kidney cells and inhibition of metabolic activity (reduction of resazurin to fluorescent resorufin) using primary human renal proximal tubule epithelial cells (RPTECs). In both RPTECs and Vero cells, Stx2a, Stx2d, and elastase-cleaved Stx2d were at least 25 times more potent than Stx2b and Stx2c.In vivopotency in mice was also assessed. Stx2b and Stx2c had potencies similar to that of Stx1, while Stx2a, Stx2d, and elastase-cleaved Stx2d were 40 to 400 times more potent than Stx1.
Responses of Cod (Gadus morhua) and Haddock (Melanogrammus aeglefinus) to Baited Hooks in the Natural Environment
Authors: Løkkeborg Svein , Bjordal Åsmund , Fernö Anders
Published: January 2011

The behaviour of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) towards baited hooks was observed in the sea with underwater television. Both species exhibited a diel rhythm of feeding activity most pronounced in cod, with an increase at dawn and a decrease at dusk. The activity rhythm of cod changed from bimodal with peaks in the morning and afternoon in September, to unimodal in December. Haddock showed a less clear activity rhythm during daytime. Activity of fish decreased at high current velocities. Both cod and haddock swam upstream towards baited hooks. More haddock responded to the bait than cod, but haddock showed a less intense response characterized by biting repeatedly at parts of the bait, whereas cod completely ingested the bait and thereby increased the probability of getting hooked. The observed difference in hooking behaviour between cod and haddock explains differences between the species found in longline fishing trials with different bait sizes and hook designs.
Upstream Transport of Mirex by Migrating Salmonids
Authors: Scrudato Ronald J. , McDowell William H.
Published: January 2011

Mirex is a persistent chlorinated hydrocarbon found in appreciable concentrations in sediments and pelagic organisms of Lake Ontario. Concentrations are particularly high in introduced salmonids, which spawn in considerable numbers in tributaries of the Lake. We sampled the sediments and biota of several tributary streams in the Salmon River drainage basin. Greater concentrations of mirex were found in the resident brown trout (Salmo trutta) of tributaries accessible to migrating salmonids than in a nearby reference tributary inaccessible to migration. No significant differences in mirex concentrations were found in lower trophic levels (crayfish and stoneflies) or sediments, although mirex was detected in all samples. Because point sources of mirex are distant from these tributaries we conclude that migrating salmonids make a significant contribution to the upstream transport of mirex from Lake Ontario. Ingestion of salmonid eggs by brown trout, decomposition of salmonid carcasses by blowfly larvae, and ingestion of carcasses by aquatic and terrestrial scavengers are all means by which the contaminant is introduced to upstream environments.
Extrapolation of Laboratory pH Dose–Response Data to Fluctuating Environments: Comparisons with a Null Model
Authors: Haefner James W. , Abbott Linda C.
Published: January 2011

A simple model was developed to extrapolate laboratory dose–response data to randomly varying conditions. We fit published data of dose–response experiments for the effects of low pH stress on survival rates of stream macro-invertebrates to a modification of the Weibull distribution. Using the resulting parameter estimates and Monte Carlo simulation, we compared the values obtained in constant laboratory conditions with the expected survival rates obtained in fluctuating environments. For each of three species, we performed 108 Monte Carlo experiments in a full factorial design that varied the mean pH, the standard deviation of pH fluctuations, the distribution from which pH values were drawn, the distributions of runs of constant pH, and the presence of episodic events. Fluctuating environments decreased the survival rates of resistant species, but increased survivorship of sensitive species. No one exposure duration under laboratory conditions could consistently be extrapolated to the suite of variable environments we examined. Probit analyses performed on the observed and simulated data indicated that LC-50s of different observed exposure durations were similar to each other and to the LC-50s of the simulated data assuming an exposure of 24 h. Based on these results, we recommend that toxicity studies incorporate temporal variability directly by using varying dose levels in laboratory tests.
Among-Population Variability of Fish Growth: III. Influence of Fish Community
Authors: Boisclair D. , Leggett W. C.
Published: January 2011

We assessed the relationship between in situ fish growth and fish community descriptors in 12 yellow perch (Perca flavescens) populations that exhibited a 1.8 to 10-fold range in growth rates depending on age class. Data on the quantity and quality of food consumed were used to assess the mechanisms by which fish community composition influences in situ growth rates. Among-population variability in growth rates of the 12 perch populations was most strongly and consistently explained by the average density of the total fish community and/or the average density of cyprinids. A multivariate model involving fish average density and perch feeding levels explained 90% of the variance in perch growth. Perch growth rates decreased as fish average density increased (r2 = 0.60) and increased as feeding levels increased (r2 = 0.30). We found no significant relationship between the quantity of food consumed by perch and fish average density. The percent contribution of prey taxonomic groups to perch diet was not related to fish average density. We suggest that nonexploitative interactions (operating through increased activity costs) provides a more credible explanation for the negative relationship between perch growth and fish average density than does exploitative competition (decreased total quantities of food consumed or prey quality).
Effects of Heterogeneity in the Spatial and Temporal Pattern of Juvenile Alewife (Alosa pseudoharengus) and Blueback Herring (A. aestivalis) Density on Estimation of an Index of Abondance
Authors: Jessop B. M. , Anderson W. E.
Published: January 2011

Significant heterogeneity occurred in the spatial and temporal pattern of the nocturnal, near-surface (0 to 1.5 m depth) density of juvenile anadromous alewife (Alosa pseudoharengus) and blueback herring (A. aestivalis) in the Mactaquac Dam headpond, Saint John River, New Brunswick. Juvenile alewife were less available to a pushnet than were blueback herring. Patches of higher density persisted for up to 4 wk for both species. Estimates of patch size depended upon the sampling scale, with larger patches (16 to 58 km long) composed of smaller patches (0.5 to 2.2 km long). The index of aggregation of Taylor's power law was similar for both species pooled value 2.20) Lloyd's index of patchiness varied significantly, for both species, spatially but not temporally, and tended to be higher for blueback herring than for alewife. Density and patchiness differed for both species within and between an upriver, lotic zone and downriver, lentic zone. Mean densities were more precisely estimated at high than at low densities and for alewife than for blueback herring (n = 61). Stratification increased the precision, relative to simple random sampling, of estimates of mean density, particularly at high densities of the more patchily dispersed blueback herring. Autocorrelation occurred in the spatial density pattern of both species at coarse (1–100 km) and medium (0.1–4 km) sampling scales. Variations in the intensity and grain of patchiness may affect the choice of survey design, sample and sample unit size, and frequency of sampling required for a desired precision of density estimates.
Influence of Rainbow Trout (Oncothynchus mykiss) on Density and Feeding Behaviour of a Perlid Stonefly
Authors: Feltmate Blair W. , Williams D. Dudley
Published: January 2011

Stonefly (Paragnetina media) density was reduced in a rainbow trout (Oncorhynchus mykiss) enclosure by approximately 35%, whereas in a trout exclosure no significant changes in density occurred. Of the 35% reduction, approximately two-fifths and three-fifths were attributable, respectively to direct consumption of stoneflies by trout, and emigration by stoneflies from the predator-stressed section of stream. With trout present in laboratory aquaria, predator avoidance behaviour resulted in stoneflies remaining significantly more on dark substrate on which they were less vulnerable to trout predators. Stoneflies consumed significantly fewer prey (enchytraeid whiteworms) over 24 h, in the presence of both small (2.0–4.0 cm) and large (10.0–12.0 cm) rainbow trout in aquaria, compared with stoneflies feeding in trout-free aquaria. Feeding rate and substrate selection did not differ between well-fed and starved (5 d) nymphs.
Relationship of Condition of Walleye (Stizostedion vitreum) and Northern Pike (Esox lucius) to Water Clarity, with Special Reference to Dauphin Lake, Manitoba
Authors: Craig J. F. , Babaluk J. A.
Published: January 2011

An examination of 37 lakes in the central region of Canada revealed that the summer condition of northern pike, Esox lucius, was correlated with Secchi depth but there was no such correlation for walleye, Stizostedion vitreum. A study of the diets of the two predatory fish coexisting in a prairie lake, showed overlap in the food items selected in July. Food density did not appear to be limited. Walleye food consumption rose from about 1% bodyweight in the spring to 2% in late summer and was less than 1% in the late autumn and early winter. Pike food consumption was similar except it rose to over 3% in the early winter when the lake froze over and the water cleared. High turbidity in the prairie lake during the open water period may have reduced the ability of pike to feed.
Ecological and Genetic Studies onDreissena polymorpha(Pallas): a New Mollusc in the Great Lakes
Authors: Hebert Paul D. N. , Muncaster B. W. , Mackie G. L.
Published: January 2011

Dreissena polymorpha, a bivalve mollusc endemic to Europe, has established a population in Lakes St. Clair and Erie, likely as a result of ballast water discharge. Allozyme studies showed that the Lake St. Clair population was polymorphic at 73.9% of the loci examined and that individual heterozygosities averaged 31.6%. This high level of genotypic diversity indicated that the population was founded from a substantial number of individuals and did not undergo a bottleneck subsequent to founding. The population is reproducing with peak densities in excess of 200 individuals∙m−2. Juvenile settlement occurs in late July and August with veliger larvae preferentially settling on the shells of live mussels. The species appears likely to become a dominant member of the shallow water benthos throughout the lower Great Lakes.
Uptake and Elimination of Coliform Bacteria by Four Marine Bivalve Mollusks
Authors: Bernard F. R.
Published: January 2011

Bivalve filter feeding mollusks remove suspended bacteria from the ambient water and either sediment them with the pseudofaeces, or ingest and digest them. On the basis of bacterial contamination of water and known pumping rate, accumulations usually exceed expected levels by an order of magnitude. This does not reflect high uptake efficiency of the bivalve, but is a function of the digestive process separating bacterial clusters, thereby increasing inoculative loci both for multiple tube estimates and plate counts. Uptake rates are species specific and temperature dependent and show little correlation with the ambient bacterial loading. Elimination is also species specific and variable.
Analysis of Otolith Microstructure to Determine Growth Histories in Larval Cohorts of a Tropical Herring (Herklotsichthys castelnaui)
Authors: Thorrold Simon R. , Williams David McB.
Published: January 2011

Otolith microstructure was used to characterize growth in five cohorts of larval Herklotsichthys castelnaui from Townsville, north eastern tropical Australia in spring/summer of 1987. Ontogenetic development of larval H. castelnaui is described, and is correlated with changes in otolith microstructure. Development of fin rays coincided with a period of rapid otolith and somatic growth. Otolith increment width and water temperature series were modelled for each cohort using time series analysis. Cross-correlation functions showed no detectable dependencies between increment widths and temperature. Length-at-age relationships were significantly different among cohorts. Repeated-measures analysis of variance was used to establish differences in increment spacing among cohorts. Measurement of otolith radii allowed back-calculation of absolute growth rates of cohorts over the first 30 d of larval life. Significant differences in growth trajectories were detected among cohorts. Data presented here suggest that growth may vary among cohorts separated by as little as 2 wk, and that these differences are detectable by otolith increment analysis.
Event Analysis Applied to Timing in Marine Fish Ontogeny
Authors: Chambers R. Christopher , Leggett William C.
Published: January 2011

We illustrate the utility of event analysis for characterizing timing in marine fish life histories, comparing event series among experimental groups, and predicting event timing in untested environments. Two examples using early life history traits are given, in example (1) we analyzed parental influence on metamorphosis timing in experimental laboratory populations of winter flounder (Pseudopleuronectes americanus). We fit a Weibull distribution to right-censored observations of age at metamorphosis and then estimated the fraction of individuals from each of two families that had become juveniles by a predetermined day. Offspring of one family were 1.25 times more likely than the second to enter the juvenile period under the applied time constraint. In example (2) we evaluated temperature effects on age at death of unfed capelin hatchlings (Mallotus villosus). Using an accelerated failure time model we predicted age at death at an untested temperature and, assuming a patchy distribution of prey, estimated the number of days available to a cohort to encounter a suitable food patch and still maintain the potential for generating an above average year-class. These examples demonstrate the utility of event analysis for more thorough use of observations on ontogenetic timing in experimental and natural populations.
Larval Mosquitoes as Vulnerable Prey: Chaoborus Predation
Authors: Helgen J. C.
Published: January 2011

The vulnerability of instar I and II larvae of the mosquito Aedes vexans as prey for Chaoborus americanus is much greater than that of the small coexisting prey, Daphnia pulex. Predation on Aedes larvae could reduce Aedes populations in overlapping habitats, and be a selective force in driving Aedes to lay eggs in muds of more temporary wetlands. Predation rates are great (7–25∙d−1) and ingestion times are rapid (0.8–6 s) on Aedes instars I and II. In prey choice experiments, Chaoborus strongly prefers Aedes I over small Daphnia. An Aedes diet promotes growth of Chaoborus at least as well as a Daphnia diet. Larval Aedes behaviors show a distinct difference between the first two and last two instars. Aedes swimming speeds and swimming distances increase with each instar, but when disturbed, the first two instars significantly reduce their swimming distances. Calculated prey vulnerabilities, based on swimming speeds and reciprocal ingestion times, suggest a much greater vulnerability for Aedes I and II than that for small (0.8 mm) Daphnia or for Aedes III and IV (4.6–6.2 mm).
HIGH PRECISION INTEGER ADDITION, SUBTRACTION AND MULTIPLICATION WITH A GRAPHICS PROCESSING UNIT
Authors: EMMART NIALL , WEEMS CHARLES
Published: January 2011

In this paper we evaluate the potential for using an NVIDIA graphics processing unit (GPU) to accelerate high precision integer multiplication, addition, and subtraction. The reported peak vector performance for a typical GPU appears to offer good potential for accelerating such a computation. Because of limitations in the on-chip memory, the high cost of kernel launches, and the nature of the architecture's support for parallelism, we used a hybrid algorithmic approach to obtain good performance on multiplication. On the GPU itself we adapt the Strassen FFT algorithm to multiply 32KB chunks, while on the CPU we adapt the Karatsuba divide-and-conquer approach to optimize application of the GPU's partial multiplies, which are viewed as "digits" by our implementation of Karatsuba. Even with this approach, the result is at best a factor of three increase in performance, compared with using the GMP package on a 64-bit CPU at a comparable technology node. Our implementations of addition and subtraction achieve up to a factor of eight improvement. We identify the issues that limit performance and discuss the likely impact of planned advances in GPU architecture.
NEIGHBORHOOD STRUCTURES FOR GPU-BASED LOCAL SEARCH ALGORITHMS
Authors: LUONG THÉ VAN , MELAB NOUREDINE , TALBI EL-GHAZALI
Published: January 2011

Local search algorithms are powerful heuristics for solving computationally hard problems in science and industry. In these methods, designing neighborhood operators to explore large promising regions of the search space may improve the quality of the obtained solutions at the expense of a high-cost computation process. As a consequence, the use of GPU computing provides an efficient way to speed up the search. However, designing applications on a GPU is still complex and many issues have to be faced. We provide a methodology to design and implement different neighborhood structures for LS algorithms on a GPU. The work has been evaluated for binary problems and the obtained results are convincing both in terms of efficiency, quality and robustness of the provided solutions at run time.
SOME GPU ALGORITHMS FOR GRAPH CONNECTED COMPONENTS AND SPANNING TREE
Authors: SOMAN JYOTHISH , KOTHAPALLI KISHORE , NARAYANAN P J
Published: January 2011

Graphics Processing Units (GPU) are application specific accelerators which provide high performance to cost ratio and are widely available and used, hence places them as a ubiquitous accelerator. A computing paradigm based on the same is the general purpose computing on the GPU (GPGPU) model. The GPU due to its graphics lineage is better suited for the data-parallel, data-regular algorithms. The hardware architecture of the GPU is not suitable for the data parallel but data irregular algorithms such as graph connected components and list ranking.

In this paper, we present results that show how to use GPUs efficiently for graph algorithms which are known to have irregular data access patterns. We consider two fundamental graph problems: finding the connected components and finding a spanning tree. These two problems find applications in several graph theoretical problems. In this paper we arrive at efficient GPU implementations for the above two problems. The algorithms focus on minimising irregularity at both algorithmic and implementation level. Our implementation achieves a speedup of 11-16 times over a corresponding best sequential implementation.
ON THE PERFORMANCE AND TECHNOLOGICAL IMPACT OF ADDING MEMORY CONTROLLERS IN MULTI-CORE PROCESSORS
Authors: SANCHO JOSE CARLOS , KERBYSON DARREN J. , LANG MICHAEL
Published: January 2011

The increasing core-count on current and future processors is posing critical challenges to the memory subsystem to efficiently handle concurrent memory requests. The current trend is to increase the number of memory channels available to the processor's memory controller. In this paper we investigate the advantages and disadvantages of this approach from both a technological and an application performance viewpoint. In particular, we explore the trade-off between employing multiple memory channels per memory controller and the use of multiple memory controllers with fewer memory channels. Experiments conducted on two current state-of-the-art multi-core processors, a 6-core AMD Istanbul and a 4-core Intel Nehalem-EP, using the STREAM benchmark and a wide range of production applications. An analytical model of the STREAM performance is used to illustrate the diminishing return obtained when increasing the number of memory channels per memory controller whose effect is also seen in the application performance. In addition, we show that this performance degradation can be efficiently addressed by increasing the ratio of memory controllers to channels while keeping the number of memory channels constant. Significant performance improvements can be achieved in this scheme, up to 28%, in the case of using two memory controllers each with one channel compared with one controller with two memory channels.
LEVERAGING SHARED CACHES FOR PARALLEL TEMPORAL BLOCKING OF STENCIL CODES ON MULTICORE PROCESSORS AND CLUSTERS
Authors: WITTMANN MARKUS , HAGER GEORG , TREIBIG JAN , WELLEIN GERHARD
Published: January 2011

Bandwidth-starved multicore chips have become ubiquitous. It is well known that the performance of stencil codes can be improved by temporal blocking, lessening the pressure on the memory interface. We introduce a new pipelined approach that makes explicit use of shared caches in multicore environments and minimizes synchronization and boundary overhead. Benchmark results are presented for three current x86-based microprocessors, showing clearly that our optimization works best on designs with high-speed shared caches and low memory bandwidth per core. We furthermore demonstrate that simple bandwidth-based performance models are inaccurate for this kind of algorithm and employ a more elaborate, synthetic modeling procedure. Finally we show that temporal blocking can be employed successfully in a hybrid shared/distributed-memory environment, albeit with limited benefit at strong scaling.
LARGE-SCALE PERFORMANCE ANALYSIS OF SWEEP3D WITH THE SCALASCA TOOLSET
Authors: WYLIE BRIAN J. N. , GEIMER MARKUS , MOHR BERND , BÖHME DAVID , SZEBENYI ZOLTÁN , WOLF FELIX
Published: January 2011

Cray XT and IBM Blue Gene systems present current alternative approaches to constructing leadership computer systems relying on applications being able to exploit very large configurations of processor cores, and associated analysis tools must also scale commensurately to isolate and quantify performance issues that manifest at the largest scales. In studying the scalability of the Scalasca performance analysis toolset to several hundred thousand MPI processes on XT5 and BG/P systems, we investigated a progressive execution performance deterioration of the well-known ASCI Sweep3D compact application. Scalasca runtime summarization analysis quantified MPI communication time that correlated with computational imbalance, and automated trace analysis confirmed growing amounts of MPI waiting times. Further instrumentation, measurement and analyses pinpointed a conditional section of highly imbalanced computation which amplified waiting times inherent in the associated wavefront communication that seriously degraded overall execution efficiency at very large scales. By employing effective data collation, management and graphical presentation, in a portable and straightforward to use toolset, Scalasca was thereby able to demonstrate performance measurements and analyses with 294,912 processes.
SPACETIME VARIATION OF α AND THE CMB POWER SPECTRA AFTER THE RECOMBINATION
Authors: WANG XIULIAN , LI MINGZHE
Published: January 2011

The possible variation of the fine structure constant may be due to the non-minimal coupling of the electromagnetic field to a light scalar field which can be the candidate of dark energy. Its dynamical nature renders the fine structure constant varies with time as well as space. In this paper we point out that the spatial fluctuation of the fine structure will modify the power spectra of the temperature and the polarization of the cosmic microwave background. We show explicitly that the fluctuations of the coupled scalar field generate new temperature anisotropies at the linear order and induce a B mode to the polarization at higher order in general.
QUANTUM PROPERTIES OF PERIODIC INSTANTONS ON A CIRCLE
Authors: SHURGAIA A. V.
Published: January 2011

Quantum properties of a (1+1)-dimensional scalar theory on a cylinder with a compact spatial part, namely, 0 ≤ x ≤ L, are considered. In particular, quantum theory around the classical periodic field configurations is studied and the lifetime of a quantum periodic instanton is estimated.
"BIG" DIVISOR D3/D7 SWISS-CHEESE PHENOMENOLOGY
Authors: MISRA AALOK
Published: January 2011

We review progress made over the past couple of years in the field of Swiss-Cheese Phenomenology involving a mobile spacetime filling D3-brane and stack(s) of fluxed D7-branes wrapping the "big" (as opposed to the "small") divisor in (the orientifold of (a) Swiss-Cheese Calabi–Yau. The topics reviewed include reconciliation of large volume cosmology and phenomenology, evaluation of soft supersymmetry breaking parameters, one-loop RG-flow equations' solutions for scalar masses, obtaining fermionic (possibly first two generations' quarks/leptons) mass scales in the [Formula: see text]-regime as well as (first two generations') neutrino masses (and their one-loop RG flow) of around an eV. The heavy sparticles and the light fermions indicate the possibility of "split SUSY" large volume scenario.
PARETO ENVELOPES IN SIMPLE POLYGONS
Authors: CHEPOI VICTOR , NOUIOUA KARIM , THIEL EDOUARD , VAXÈS YANN
Published: January 2011

For a set T of n points in a metric space (X, d), a point y ∈ X is dominated by a point x ∈ X if d(x, t) ≤ d(y, t) for all t ∈ T and there exists t′ ∈ T such that d(x, t′) < d(y, t′). The set of non-dominated points of X is called the Pareto envelope of T. H. Kuhn (1973) established that in Euclidean spaces, the Pareto envelopes and the convex hulls coincide. Chalmet et al. (1981) characterized the Pareto envelopes in the rectilinear plane (ℝ2, d1) and constructed them in O(n log n) time. In this note, we investigate the Pareto envelopes of point-sets in simple polygons P endowed with geodesic d2- or d1-metrics (i.e., Euclidean and Manhattan metrics). We show that Kuhn's characterization extends to Pareto envelopes in simple polygons with d2-metric, while that of Chalmet et al. extends to simple rectilinear polygons with d1-metric. These characterizations provide efficient algorithms for construction of these Pareto envelopes.
MODELLING STUDENT INTERACTIONS IN INTELLIGENT LEARNING ENVIRONMENTS: CONSTRUCTING BAYESIAN NETWORKS FROM DATA
Authors: MAVRIKIS MANOLIS
Published: January 2011

Human-Computer Interaction modelling can benefit from machine learning. This paper presents a case study of the use of machine learning for the development of two interrelated Bayesian Networks for the purposes of modelling student interactions within Intelligent Learning Environments. The models predict (a) whether a given student's interaction is effective in terms of learning and (b) whether a student can answer correctly questions in an intelligent learning environment without requesting help. After discussing the requirements for these models, the paper presents the particular techniques used to pre-process and learn from the data. The case study discusses the models learned based on data collected from student interactions on their own time and location. The paper concludes by discussing the application of the models and directions for future work.
EVALUATING SUBJECTIVE ASPECTS OF HCI ON AN EXAMPLE OF A NON-TASK ORIENTED CONVERSATIONAL SYSTEM
Authors: DYBALA PAWEL , PTASZYNSKI MICHAL , RZEPKA RAFAL , ARAKI KENJI
Published: January 2011

The evaluation of subjective aspects of HCI, such as human-likeness, likeability or users' emotions towards computers is still quite a neglected issue, especially in the field of non-task oriented conversational systems (chatterbots). In this paper we try to bridge this gap by proposing a new methodology of evaluation. The methods presented were tested in our research on humor-equipped chatterbots. We describe them in details, discuss their drawbacks and usability. In one of the presented methods we used an emotiveness analysis system, which itself can be considered an AI tool, as it was used to detect users' emotions towards conversational systems, and to perform their automatic evaluation. We also propose some methods that we have not used yet, which, however, seem applicable in this field, such as brain scanning techniques. Finally, we give some ideas that should be addressed in the future.
EFFECTS OF DEUTERIUM–LITHIUM FUSION REACTION ON INTERNAL TRITIUM BREEDING
Authors: MAHDAVI M. , JALALY B.
Published: January 2011

The optimal usage of designed fuel pellets is one of the very important parameters in inertial confinement fusion (ICF) systems. In this research, time-dependent dynamical equations for D/D fuel are written by considering impurity of 6 Li . Then dependency of gain on temperature, density and pellet radius is studied using Runge–Kutta method. The obtained results show that the energy gain will be maximized at the initial temperature 35 keV, density, 5000 g/cm3 and ratio impurity of 6 Li , 0.05.