bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypoxia reduces the hypothalamic thermogenic threshold and thermosensitivity
Authors: Tattersall Glenn J. , Milsom William K.
Published: September 2009

Hypoxia is well known to reduce the body temperature (Tb) of mammals, although the neural origins of this response remain uncertain. Short‐term hypoxic exposure causes a reduction in the lower critical temperature of the thermal neutral zone and a reduction in whole body thermal conductance of rodents, providing indirect support that hypoxia lowers Tb in a regulated manner. In this study, we examined directly the potential for changes in central thermosensitivity to evoke the hypoxic metabolic response by heating and cooling the preoptic area of the hypothalamus (the area which integrates thermoreceptor input and regulates thermoeffector outputs) using chronic, indwelling thermodes in ground squirrels during normoxia and hypoxia (7, 10 and 12% O2). We found that the threshold hypothalamic temperature for the metabolic response to cooling (Tth) of ∼38°C in normoxia was proportionately reduced in hypoxia (down to 28–31°C at 7% O2) and that the metabolic thermosensitivity (α; the change in metabolic rate for any given change in hypothalamic temperature below the lower critical temperature) was comparatively reduced by 5 to 9 times. This provides strong support for the hypothesis that the fall in temperature that occurs during hypoxia is the result of a reduction in the activation of thermogenic mechanisms. The decrease in the central thermosensitivity in hypoxia, however, appears to be a critical factor in the alteration of mammalian Tb. We suggest, therefore, that an altered central thermosensitivity may provide a proximate explanation of how low oxygen and similar stressors reduce normal fluctuations in Tb (i.e. circadian), in addition to the depression in regulated Tb.
Frequency‐dependent disynaptic inhibition in the pyramidal network: a ubiquitous pathway in the developing rat neocortex
Authors: Berger Thomas K. , Perin Rodrigo , Silberberg Gilad , Markram Henry
Published: September 2009

The general structure of the mammalian neocortex is remarkably similar across different cortical areas. Despite certain cytoarchitectural specializations and deviations from the general blueprint, the principal organization of the neocortex is relatively uniform. It is not known, however, to what extent stereotypic synaptic pathways resemble each other between cortical areas, and how far they might reflect possible functional uniformity or specialization. Here, we show that frequency‐dependent disynaptic inhibition (FDDI) is a generic circuit motif that is present in all neocortical areas we investigated (primary somatosensory, auditory and motor cortex, secondary visual cortex and medial prefrontal cortex of the developing rat). We did find, however, area‐specific differences in occurrence and kinetics of FDDI and the short‐term dynamics of monosynaptic connections between pyramidal cells (PCs). Connectivity between PCs, both monosynaptic and via FDDI, is higher in primary cortices. The long‐term effectiveness of FDDI is likely to be limited by an activity‐dependent attenuation of the PC–interneuron synaptic transmission. Our results suggest that the basic construction of neocortical synaptic pathways follows principles that are independent of modality or hierarchical order within the neocortex.
Inhibition of Herpesvirus Replication by 5-Substituted 4′-Thiopyrimidine Nucleosides
Authors: Prichard Mark N. , Quenelle Debra C. , Hartline Caroll B. , Harden Emma A. , Jefferson Geraldine , Frederick Samuel L. , Daily Shannon L. , Whitley Richard J. , Tiwari Kamal N. , Maddry Joseph A. , Secrist John A. , Kern Earl R.
Published: September 2009

A series of 4′-thionucleosides were synthesized and evaluated for activities against orthopoxviruses and herpesviruses. We reported previously that one analog, 5-iodo-4′-thio-2′-deoxyuridine (4′-thioIDU), exhibits good activity both in vitro and in vivo against two orthopoxviruses. This compound also has good activity in cell culture against many of the herpesviruses. It inhibited the replication of herpes simplex virus type 1 (HSV-1), HSV-2, and varicella-zoster virus with 50% effective concentrations (EC50s) of 0.1, 0.5, and 2 μM, respectively. It also inhibited the replication of human cytomegalovirus (HCMV) with an EC50of 5.9 μM but did not selectively inhibit Epstein-Barr virus, human herpesvirus 6, or human herpesvirus 8. While acyclovir-resistant strains of HSV-1 and HSV-2 were comparatively resistant to 4′-thioIDU, it retained modest activity (EC50s of 4 to 12 μM) against these strains. Some ganciclovir-resistant strains of HCMV also exhibited reduced susceptibilities to the compound, which appeared to be related to the specific mutations in the DNA polymerase, consistent with the observed incorporation of the compound into viral DNA. The activity of 4′-thioIDU was also evaluated using mice infected intranasally with the MS strain of HSV-2. Although there was no decrease in final mortality rates, the mean length of survival after inoculation increased significantly (P< 0.05) for all animals receiving 4′-thioIDU. The findings from the studies presented here suggest that 4′-thioIDU is a good inhibitor of some herpesviruses, as well as orthopoxviruses, and this class of compounds warrants further study as a therapy for infections with these viruses.
OXA-143, a Novel Carbapenem-Hydrolyzing Class D β-Lactamase in
Acinetobacter baumannii
Authors: Higgins Paul G. , Poirel Laurent , Lehmann Marlene , Nordmann Patrice , Seifert Harald
Published: September 2009

A carbapenem-resistant
Acinetobacter baumannii
strain was isolated in Brazil in 2004 in which no known carbapenemase gene was detected by PCR. Cloning experiments, followed by expression in
Escherichia coli
, gave an
E. coli
recombinant strain expressing a novel carbapenem-hydrolyzing class D β-lactamase (CHDL). OXA-143 showed 88% amino acid sequence identity with OXA-40, 63% identity with OXA-23, and 52% identity with OXA-58. It hydrolyzed penicillins, oxacillin, meropenem, and imipenem but not expanded-spectrum cephalosporins. The
bla
OXA-143
gene was located on a ca. 30-kb plasmid. After transformation into reference strain
A. baumannii
ATCC 19606, it conferred resistance to carbapenems. Analysis of the genetic environment of
bla
OXA-143
revealed that it was associated with neither insertion sequences nor integron structures. However, it was bracketed by similar replicase-encoding genes at both ends, suggesting acquisition through a homologous recombination process. This study identified a novel class D β-lactamase involved in carbapenem resistance in
A. baumannii
. This enzyme is the first member of a novel subgroup of CHDLs whose prevalence remains to be determined.
Bronchopulmonary Disposition of Intravenous Voriconazole and Anidulafungin Given in Combination to Healthy Adults
Authors: Crandon Jared L. , Banevicius Mary Anne , Fang Annie F. , Crownover Penelope H. , Knauft R. Fredrick , Pope J. Samuel , Russomanno John H. , Shore Eric , Nicolau David P. , Kuti Joseph L.
Published: September 2009

Voriconazole and anidulafungin in combination are being investigated for use for the treatment of pulmonary aspergillosis. We determined the pulmonary disposition of these agents. Twenty healthy participants received intravenous voriconazole (at 6 mg/kg of body weight every 12 h [q12h] on day 1 and then at 4 mg/kg q12h) and anidulafungin (200 mg on day 1 and then 100 mg every 24 h) for 3 days. Five participants each were randomized for collection of bronchoalveolar lavage samples at times of 4, 8, 12, and 24 h. Drug penetration was determined by the ratio of the total drug area under the concentration-time curve during the dosing interval (AUC
0-τ
) for epithelial lining fluid (ELF) and alveolar macrophages (AM) to the total drug AUC
0-τ
in plasma. The mean (standard deviation) half-life and AUC
0-τ
were 6.9 (2.1) h and 39.5 (19.8) μg·h/ml, respectively, for voriconazole and 20.8 (3.1) h and 101 (21.8) μg·h/ml, respectively, for anidulafungin. The AUC
0-τ
values for ELF and AM were 282 and 178 μg·h/ml, respectively, for voriconazole, and 21.9 and 1,430 μg·h/ml, respectively, for anidulafungin. This resulted in penetration ratios into ELF and AM of 7.1 and 4.5, respectively, for voriconazole and 0.22 and 14.2, respectively, for anidulafungin. The mean total concentrations of both drugs in ELF and AM at 4, 8, 12, and 24 h remained above the MIC
90
/90% minimum effective concentration for most
Aspergillus
species. In healthy adult volunteers, voriconazole achieved high levels of exposure in both ELF and AM, while anidulafungin predominantly concentrated in AM.
Proteomic Analysis of
Rickettsia parkeri
Strain Portsmouth
Authors: Pornwiroon Walairat , Bourchookarn Apichai , Paddock Christopher D. , Macaluso Kevin R.
Published: September 2009

Rickettsia parkeri
, a recently recognized pathogen of human, is one of several
Rickettsia
spp. in the United States that causes a spotted fever rickettsiosis. To gain insights into its biology and pathogenesis, we applied the proteomics approach to establish a two-dimensional gel proteome reference map and combined this technique with cell surface biotinylation to identify surface-exposed proteins of a low-passage isolate of
R. parkeri
obtained from a patient. We identified 91 proteins by matrix-assisted laser desorption ionization-tandem time of flight mass spectrometry. Of these, 28 were characterized as surface proteins, including virulence-related proteins (e.g., outer membrane protein A [OmpA], OmpB, β-peptide, and RickA). Two-dimensional immunoblotting with serum from the
R. parkeri
-infected index patient was utilized to identify the immunoreactive proteins as potential targets for diagnosis and vaccine development. In addition to the known rickettsial antigens, OmpA and OmpB, we identified translation initiation factor 2, cell division protein FtsZ, and cysteinyl-tRNA synthetase as immunoreactive proteins. The proteome map with corresponding cell surface protein analysis and antigen detection will facilitate a better understanding of the mechanisms of rickettsial pathogenesis.
Dissolved Phosphorus Dynamics in Headwater Streams
Authors: Prairie Yves T. , Kalff Jacob
Published: September 2009

A comparative study of seven headwater streams was undertaken to evaluate the relative importance of land use, water discharge, water temperature, solar irradiance, and stream sediment resuspension on levels of dissolved phosphorus (DP). In six of the streams, [DP] increased from early spring to late summer. Nutrient-rich streams are temporally more variable than nutrient-poor ones. Average DP concentrations were not related to the proportion of forest cover but showed a correspondence with underlying geology. Despite the restricted geographical area, relationships between [DP] and water discharge varied in magnitude and in direction among the streams. Simple hydrological models treating the catchments as two-reservoir systems accounted for the different behaviors and performed satisfactorily when the effect of temperature was considered. The residual variance showed no seasonal trends but was significantly correlated with daily solar irradiance for one of the seven streams. Finally, the hypothesis that resuspension of stream sediments affects soluble phosphorus concentration was experimentally rejected.
Influence of Molecular Weight and Molecular Volume on Dietary Absorption Efficiency of Chemicals by Fishes
Authors: Niimi A. J. , Oliver B. G.
Published: September 2009

Rainbow trout (Salmo gairdneri) were exposed to 17 halogenated organic chemicals to examine the influence of molecular weight (MW) and molecular volume (MV) on dietary absorption efficiency. The results of this and other studies indicated that organic chemicals with MWs greater than 600 were poorly absorbed although some chemicals with lower MWs were also poorly absorbed. A better trend was suggested when efficiences were examined in relation to MV where chemicals with MVs over 0.3 nm3were poorly absorbed. Neither index provided a relationship that would consistently estimate the absorption efficiency of chemicals that were moderately to well absorbed by salmonids.
Growth Rate Responses of Lotic Periphytic Diatoms to Experimental Phosphorus Enrichment: The Influence of Temperature and Light
Authors: Bothwell Max L.
Published: September 2009

Phosphate enrichment experiments were conducted year-round at the experimental troughs research apparatus (EXTRA) on the South Thompson River in British Columbia to determine the relationship between external concentration of orthophosphate and the growth rates of lotic periphytic diatom communities. Growth rate saturation always occurred at a phosphate concentration of approximately 0.3–0.6 μg P∙L−1. The maximum growth rate (μmax-P) with phosphorus enrichment varied seasonally with temperature. The relative specific growth rates (μ:μmax-P) as a function of external phosphate were constant. Seasonal changes in solar insolation (PAR) had no effect on the autotrophic community growth rates in unamended river water. Temperature exerted the most dominant influence on phosphorus-replete growth rates.
Influence of pH on the Acute Lethality of Fenitrothion, 2,4-D, and Aminocarb and Some pH-Altered Sublethal Effects of Aminocarb on Rainbow Trout (Salmo gairdneri)
Authors: Doe K. G. , Ernst W. R. , Parker W. R. , Julien G. R. J. , Hennigar P. A.
Published: September 2009

Three pesticides, fenitrothion, 2,4-D, and aminocarb, were tested in static 96-h acute lethal toxicity tests using fingerling rainbow trout (Salmo gairdneri) at pH 4.6, 5.6, 6.9, and 8.5. The toxicity of aminocarb, a base, increased significantly with increasing pH. Conversely, the toxicity of the acidic pesticide 2,4-D increased with decreasing pH. The toxicity of the neutral pesticide fenitrothion did not change significantly with changing pH. Subsequent tests were performed on trout fingerlings with aminocarb to determine the effect of two exposure pH's on brain acetylcholinesterase activity and whole-body aminocarb residue. Brain acetylcholinesterase was found to be inversely proportional to whole-body aminocarb content of fish. In fish exposed at pH 4.6, brain acetylcholinesterase was maximally depressed at 6 h, after which it recovered to within the control range. Whole-body aminocarb concentrations rose to a maximum within 6 h and subsequently declined to low levels. In fish exposed at pH 8.2, brain acetylcholinesterase dropped below the control range by 1 h and remained low until all fish died by 72 h. A maximum whole-body aminocarb concentration was reached within 1 h and remained elevated until the fish died. Several explanations for the observed results are presented.
A Maximum Likelihood Methodology for Estimating Length-at-Maturity with Application to Pacific Cod (Gadus macrocephalus) Population Dynamics
Authors: Welch D. W. , Foucher R. P.
Published: September 2009

A maximum likelihood methodology for the analysis of maturity-at-length data is presented, and illustrated with data for female Pacific cod (Gadus macrocephalus) from Hecate Strait, British Columbia. Our approach explicitly accounts for the binomial nature of maturity data. Estimated maturity–length relationships show substantial differences for females sampled from different grounds within Hecate Strait, as well as large between-year differences in the maturity–length relationships for individual grounds. However, the maturity–length characteristics for a single ground are stable thoughout the spawning season, and we argue that the observed temporal variability is unlikely to be a sampling artefact. Assuming constant somatic growth rates, these differences correspond to shifts of slightly more than 1 yr in the median age-at-maturity; this shift implies that the instantaneous population growth rate rm, for Pacific cod can increase by up to 0.25 yr−1 in years when maturation occurs at smaller body size. This corresponds to an increase of over 50% in the sustainable fishing mortality rate, independent of other factors. Our results suggest that more attention should be focussed on assessing the reproductive dynamics of adult fish.
Fish in the Structure and Function of Freshwater Ecosystems: A "Top-down" View
Authors: Northcote T. G.
Published: September 2009

The role of fish in regulation of the structure and function of freshwater ecosystems (lakes and streams) is examined with respect to effects resulting directly from their feeding activity, indirectly from size or other forms of prey selectivity, and from influences on nutrient cycling and transport. That fish have long had a legitimate place in limnological research is documented by a review of limnological books, texts, and journals. Recognition of their "top-down" effects, started largely from Czechoslovakian research (Hrbáček and others) in the mid-1950's, was popularized by American and German research (Brooks, Jacobs, and others) in the mid-1960's and has enjoyed a remarkable upsurge in the 1970's, continuing into the 1980's. Although size-selective predation has been an important phenomenon in stimulating widespread research on effects of fish on freshwater communities and their function, the importance of other mechanisms in such regulation is considered.
Structure and Interannual Variability of the Plankton and its Environment off Southwest Nova Scotia in Late Spring and Early Summer
Authors: Koslow J. Anthony , Perry R. Ian , Hurley Peter C. F. , Fournier Robert O.
Published: September 2009

Consistent alongshore and/or onshore–offshore gradients in temperature, salinity, and inorganic nutrient were observed off southwest Nova Scotia in June/July, 1981–85. The distributions were established primarily by mixing of relatively warm, high-salinity, nutrient-rich Slope Water with the cold, low-salinity, nutrient-poor water of the Nova Scotia Current. Tidal mixing and frontal dynamics were of secondary importance. Consistent with the distribution of nutrient and the earlier onset of stratification offshore, chlorophyll a concentrations were generally highest offshore and lowest inshore, and the distributions of Zooplankton displacement volume and of dominant copepod species were similar. Salinity, nutrient, and chlorophyll a concentrations and the abundance of zoo-plankton were all generally higher throughout the spring of 1985 than in 1983–84. In 1985, there was greater upwelling and Slope Water influence and decreased flow of the shelf current. This was associated with a reversal of the North Atlantic atmospheric pressure anomaly field, which led to predominantly offshore and southwest alongshore winds in winter and spring, 1985. Correlations of recruitment to northwest Atlantic cod (Gadus morhua) stocks with wind and North Atlantic atmospheric pressure anomalies (Koslow et al. 1987) may be based upon the wind's influence on nutrient availability and plankton abundance.
A Drift–Retention Dichotomy for Larval Haddock (Melanogrammus aeglefinus) Spawned on Browns Bank
Authors: Campana Steven E. , Smith Stephen J. , Hurley Peter C. F.
Published: September 2009

This study was designed to assess the dispersal of haddock (Melanogrammus aeglefinus) larvae from their Browns Bank spawning site in terms of either drift or retention mechanisms. Larvae were collected in comprehensive surveys of southwestern Nova Scotia conducted at monthly intervals through the winter–spring of 1985. To avoid any confounding of larval displacement patterns by the numerically dominant young larvae, all spatial analyses were structured by age through otolith microstructure techniques. The results of a trend surface analysis indicated that both drift and retention processes operated in concert to split and disperse the larval population. Retention was probably physically based, through the action of a "leaky" gyre around Browns Bank. Although similar processes are believed to have influenced the distribution of Browns Bank cod (Gadus morhua) larvae, the interspecific difference in spawning time, coupled with the apparent instability of the gyre, produced a different balance between transported and retained larvae. A drift–retention dichotomy for Browns Bank ichthyoplankton has implications for both recruitment and stock structure studies.
Distribution of Potentially Harmful Phytoplankton Species in the Northern Strait of Georgia, British Columbia
Authors: Haigh R. , Taylor F. J. R.
Published: September 2009

Spatial and temporal distributions of Chaetoceros convolutum (including C. concavicorne), Heterosigma akashiwo, Protogonyaulax (= Alexandrium) catenella, and Dinophysis are presented for the northern Strait of Georgia from March to September, 1986. In spring C. convolutum was found on the slightly stratified eastern side in concentrations just below those leading to kills of caged salmon (4-5000 cells∙L−1). The northern Strait became thermally stratified in summer. At this time the population centre of C. convolutum shifted to mid-Strait near the edge of the Discovery Passage tidal jet where it was maintained near the pycnocline (10–15 m) in concentrations up to 35,000 cells∙L−1. Heterosigma akashiwo, another fish killer, was the pbotosynthetic dominant in June and reached 200 000 cells∙L−1 in the northwest at 5 m. Protogonyaulax catenella, a source of paralytic shellfish poison (PSP), was also most abundant in the north and west, where dangerous levels of PSP often occur, particularly near Comox. Collectively, Dinophysis species exceeded the critical concentration for diarrheic shellfish poisoning (200 cells∙L−) on the western side during summer. All the potentially harmful flagellated species seem to be introduced from the northern passageways. Sheltered bays to the north are possible seed beds for cyst-forming species whereas C. convolutum remains in the Strait year-round.
Tidal Influence on Spawning Time of Pacific Herring (Clupea harengus pallasi
Authors: Hay D. E.
Published: September 2009

Dates of over 17 000 records of Pacific herring (Clupea harengus pallasi) spawns from 1951 to 1986 in British Columbia were examined by tidal or lunar phases. The frequency of spawns was significantly higher during neap tides following a new moon. The effect was greatest in spawning areas close to the open Pacific and least in the inside waters of the Strait of Georgia. The mechanism of tidal influence on spawning is uncertain but may involve inhibition of spawning during periods of strong spring tides corresponding to periods of full and new moons. An association between spawning time and tidal phases requires that the annual calendar dates of spawning times change between years. A tidal cycle (or a synodic month) is about 29.6 d, and 12 synodic mo equals 355.4 d, whereas a calendar year is about 365.2 d. Therefore, the dates of tidal phases, such as the springtide, are either about 10 d earlier or 5 d later relative to the previous year. Other possible consequences of tidal influence include the timing of spawning waves and differences in size composition and egg size between waves.
Responses of Plasma Electrolytes, Thyroid Hormones, and Gill Histology in Atlantic Salmon (Salmo salar) to Acid and Limed River Waters
Authors: Brown S. B. , Evans R. E. , Majewski H. S. , Sangalang G. B. , Klaverkamp J. F.
Published: September 2009

Sexually maturing Atlantic salmon, Salmo salar, were held, in the acidic (pH range 4.7–5.2) Westfield River, Nova Scotia and in the nearby, less acidic (pH range 5.2–5.6) Medway River. Exposure to Westfield River water in 1985 (149 d) and 1986 (126 d) reduced plasma osmolality, Na+, Cl−, and Ca++(in females only) concentrations of post-spawning fish compared to those in fish held in the Medway River. There were coincidental increases in plasma K+, glucose, and unidentified osmotic fraction (UOF). Gill tissue showed hyperplasia of primary lamellae epithelium. Together, these findings indicate compromised ionoregulatory ability. Decreased plasma T3(3,5,3′-triiodo-L-thyronine) suggests altered thyroid function. Westfield River water did not affect plasma T4(L-thyroxine) or protein concentrations. An unintentional handling stress caused even more severely depressed plasma ions and more elevated plasma glucose in Westfield fish in 1985 relative to 1986; Medway fish largely recovered from this stress. These observations indicate that acid-exposed fish may be more sensitive to additional stressors. Limestone treatment of Westfield River water (elevating its pH to Medway values) ameliorated ionoregulatory ability but did not affect plasma T3and Ca++(female). A high salt diet (3% NaCl) failed to protect salmon from the effects of acidic water.
Bacteria as Biocontrol Agents for Rearing Larvae of the Crab Portunus trituberculatus
Authors: Nogami Kinya , Maeda Masachika
Published: September 2009

Bacterial strain PM-4, isolated from a crustacean culturing pond, improved the growth of crab (Portunus trituberculatus) larvae and repressed the growth of Vibrio anguillarum in seawater. PM-4 was cultured in a large quantity and was added daily for 6 d to 200 m3 of seawater used for culturing crab larvae. Initial bacterial density in the crustacean culture water was 106 cells/mL When bacteria increased to more than 107 cells/mL (at crab larval growth stage zoea II), the protozoan population, primarily flagellates, grew rapidly and reduced bacterial numbers to 106 cells/mL Among the bacterial assemblages monitored, added PM-4 dominated the bacterial populations, i.e. Vibrio spp. numbers decreased or even became undetectable in seawater. Production of crab larvae was greatly increased by adding bacterial strain PM-4 to their culture water.
Bacterial Productivity in Forested and Open Streams in Southern Ontario
Authors: Hudson J. J. , Roff J. C. , Burnison B. K.
Published: September 2009

Bacterial abundance, biomass, and heterotrophic production were measured in the water, sediment, and epilithon of forested and open streams in southern Ontario in summer 1988. Relationships of environmental variables to production were examined. The time course of nucleoside incorporation, recovery efficiency of bacterial DNA, isotope dilution, and disturbance artifacts were examined to compare bacterial production rates and to determine the appropriateness of the rate of [3H]thymidine incorporation into bacterial DNA as an estimate of bacterial production in these habitats. Water column bacterial biomass (12–97 μg C∙L−1) and heterotrophic production (0.21–67 μg C∙L−1∙h−1) were greater in open streams than in forested streams. Differences between open and forested stream sediment bacterial biomass (0.30–1.1 g C∙m−2) and heterotrophic production (18–140 mg C∙m−2∙h−1) were not as pronounced as they were in the water column. A methodological disturbance artifact may have introduced a minor bias in sediment production measurements. Epilithic bacterial biomass was 35–150 mg C∙m−2, and heterotroph production was 1.3–51 mg C∙m−2∙h−1, significantly greater (P < 0.05) in open streams than in forested streams. Epilithic production and stream water temperature were positively correlated (P < 0.05). Heterotrophic bacterial production exceeded net primary production in forested streams, but not in open streams.
EXISTENCE OF STRONG SOLUTIONS AND UNIQUENESS IN LAW FOR STOCHASTIC DIFFERENTIAL EQUATIONS DRIVEN BY FRACTIONAL BROWNIAN MOTION
Authors: DUNCAN TYRONE , NUALART DAVID
Published: September 2009

In this paper we establish the existence of pathwise solutions and the uniqueness in law for multidimensional stochastic differential equations driven by a multi-dimensional fractional Brownian motion with Hurst parameter H > 1/2.
A NUMERICAL STUDY OF PULSATILE POWER LAW FLUID FLOW IN A POROUS CHANNEL
Authors: RATHISH KUMAR B. V. , SHALINI  , NIGAM MOHIT , SANGWAN VIVEK , KRISHNA MURTHY S. V. S. S. N. V. G.
Published: September 2009

The pulsatile flow characteristics of a power law fluid in a channel filled with a homogeneous porous medium are investigated by employing the Darcy–Brinkman–Forchheimer model. Finite element method in conjunction with β-family of time discretization schemes for parabolic equation have been used to numerically solve the model for analyzing the flow. Influence of various parameters, such as power law index (n), Darcy number (Da*), Forchheimer coefficient (Γ), pulsatile amplitude parameter (A), and Womerseley parameter (α), on the flow properties have been analyzed. Increasing Γ or decreasing Da* leads to decrease in velocities and shear stress for all values of n.
NUMERICAL STUDY ON NATURAL CONVECTION OF A GROWING CRYSTAL IN SOLUTION LAYER CAVITY
Authors: TORII SHUICHI , YANG WEN-JEI
Published: September 2009

Numerical study is performed on the thermal fluid-flow transport phenomena in a disk-shape cavity. Consideration is given to the movement and growth of the crystal in solution layer. Here the lysozyme is employed as the crystal. The mechanism is numerically investigated by solving the two-dimensional governing equations through discretization by means of a finite-difference technique and simultaneously the crystal movement is predicted by the Basset–Boussinesq–Oseen (BBO) equation. It is found that (i) the crystal circulates in the cavity with fluid current and shows the circulation pattern of a donut shape, like the flow in a typical Benard cell, (ii) when the particle makes the second circulation with a larger loop, it falls on to the bottom near the vertical side-wall, and (iii) the size of the falling particle becomes larger as the Rayleigh number, i.e. the temperature difference between the heat sink and the vertical side-wall is increased.
ORTHOGONALITY PRESERVERS REVISITED
Authors: Burgos María , Fernández-Polo Francisco J. , Garcés Jorge J. , Peralta Antonio M.
Published: September 2009

We obtain a complete characterization of all orthogonality preserving operators from a JB *-algebra to a JB *-triple. If T : J → E is a bounded linear operator from a JB *-algebra (respectively, a C *-algebra) to a JB *-triple and h denotes the element T**(1), then T is orthogonality preserving, if and only if, T preserves zero-triple-products, if and only if, there exists a Jordan *-homomorphism [Formula: see text] such that S(x) and h operator commute and T(x) = h•r(h) S(x), for every x ∈ J, where r(h) is the range tripotent of h, [Formula: see text] is the Peirce-2 subspace associated to r(h) and •r(h) is the natural product making [Formula: see text] a JB *-algebra.

This characterization culminates the description of all orthogonality preserving operators between C *-algebras and JB *-algebras and generalizes all the previously known results in this line of study.
JORDAN SYMMETRIC SPACES
Authors: Chu Cho-Ho
Published: September 2009

We introduce a class of Riemannian symmetric spaces, called Jordan symmetric spaces, which correspond to real Jordan triple systems and may be infinite dimensional. This class includes the symmetric R-spaces as well as the Hermitian symmetric spaces.
HYPERMEASURE THEORY
Authors: Wright J. D. Maitland
Published: September 2009

Much of classical vector measure theory can be interpreted as the study of weakly compact operators on commutative function algebras. Non-commutative measure theory can be thought of as a similar study, where the domain algebras are replaced by non-commutative operator algebras. Hypermeasure theory is something beyond this, where we replace operator algebras by more general classes of Banach space.
Can direct manipulation lower the barriers to computer programming and promote transfer of training?
Authors: Hundhausen Christopher D. , Farley Sean F. , Brown Jonathan L.
Published: September 2009

Novices face many barriers when learning to program a computer, including the need to learn both a new syntax and a model of computation. By constraining syntax and providing concrete visual representations on which to operate, direct manipulation programming environments can potentially lower these barriers. However, what if the ultimate learning goal of the novice is to be able to program in conventional textual languages, as is the case for introductory computer science students? Can direct manipulation programming environments lower the initial barriers to programming, and, at the same time, facilitate positive transfer to textual programming? To address this question, we designed a new direct manipulation programming interface for novices, and conducted an experimental study to compare the programming processes and outcomes promoted by the direct manipulation interface against those promoted by a textual programming interface. We found that the direct manipulation interface promoted significantly better initial programming outcomes, positive transfer to the textual interface, and significant differences in programming processes. Our results show that direct manipulation interfaces can provide novices with a “way in” to traditional textual programming.
The ModelCraft framework
Authors: Song Hyunyoung , Guimbretière François , Lipson Hod
Published: September 2009

Recent advancements in rapid prototyping techniques such as 3D printing and laser cutting are changing the perception of physical 3D models in architecture and industrial design. Physical models are frequently created not only to finalize a project but also to demonstrate an idea in early design stages. For such tasks, models can easily be annotated to capture comments, edits, and other forms of feedback. Unfortunately, these annotations remain in the physical world and cannot easily be transferred back to the digital world. Our system, ModelCraft, addresses this problem by augmenting the surface of a model with a traceable pattern. Any sketch drawn on the surface of the model using a digital pen is recovered as part of a digital representation. Sketches can also be interpreted as edit marks that trigger the corresponding operations on the CAD model. ModelCraft supports a wide range of operations on complex models, from editing a model to assembling multiple models, and offers physical tools to capture free-space input. Several interviews and a formal study with the potential users of our system proved the ModelCraft system useful. Our system is inexpensive, requires no tracking infrastructure or per object calibration, and we show how it could be extended seamlessly to use current 3D printing technology.
Emergence of consensus and shared vocabularies in collaborative tagging systems
Authors: Robu Valentin , Halpin Harry , Shepherd Hana
Published: September 2009

This article uses data from the social bookmarking site del.icio.us to empirically examine the dynamics of collaborative tagging systems and to study how coherent categorization schemes emerge from unsupervised tagging by individual users.

First, we study the formation of stable distributions in tagging systems, seen as an implicit form of “consensus” reached by the users of the system around the tags that best describe a resource. We show that final tag frequencies for most resources converge to power law distributions and we propose an empirical method to examine the dynamics of the convergence process, based on the Kullback-Leibler divergence measure. The convergence analysis is performed for both the most utilized tags at the top of tag distributions and the so-called long tail.

Second, we study the information structures that emerge from collaborative tagging, namely tag correlation (or folksonomy) graphs. We show how community-based network techniques can be used to extract simple tag vocabularies from the tag correlation graphs by partitioning them into subsets of related tags. Furthermore, we also show, for a specialized domain, that shared vocabularies produced by collaborative tagging are richer than the vocabularies which can be extracted from large-scale query logs provided by a major search engine.

Although the empirical analysis presented in this article is based on a set of tagging data obtained from del.icio.us, the methods developed are general, and the conclusions should be applicable across other websites that employ tagging.
A lock-free, concurrent, and incremental stack scanning mechanism for garbage collectors
Authors: Kliot Gabriel , Petrank Erez , Steensgaard Bjarne
Published: September 2009

Two major efficiency parameters for garbage collectors are the throughput overheads and the pause times that they introduce. Highly responsive systems need to use collectors with as short as possible pause times. Pause times have decreased significantly over the years, especially through the use of concurrent garbage collectors. For modern concurrent collectors, the longest pause is typically created by the need to atomically scan the runtime stack. All practical concurrent collectors that we are aware of must obtain a snapshot of the pointers on each thread's runtime stack, in order to reclaim objects correctly. To further reduce the duration of the collector pauses, incremental stack scans were proposed. However, previous such methods employ locks to stop the mutator from accessing a stack frame while it is being scanned. Thus, these methods introduce potentially long and unpredictable pauses for a mutator thread. In this work we propose the first concurrent, incremental, and lock-free stack scanning mechanism for garbage collectors, that allows high responsiveness and support for programs that employ fine-grain synchronization to avoid locks. Our solution can be employed by all concurrent collectors that we are aware of, it is lock-free, it imposes a negligible overhead on the program execution, and it supports intra-stack references as found in languages like C#.
Post-copy live migration of virtual machines
Authors: Hines Michael R. , Deshpande Umesh , Gopalan Kartik
Published: September 2009

We present the design, implementation, and evaluation of post-copy based live migration for virtual machines (VMs) across a Gigabit LAN. Post-copy migration defers the transfer of a VM's memory contents until after its processor state has been sent to the target host. This deferral is in contrast to the traditional pre-copy approach, which first copies the memory state over multiple iterations followed by a final transfer of the processor state. The post-copy strategy can provide a "win-win" by reducing total migration time while maintaining the liveness of the VM during migration. We compare post-copy extensively against the traditional pre-copy approach on the Xen Hypervisor. Using a range of VM workloads we show that post-copy improves several metrics including pages transferred, total migration time, and network overhead. We facilitate the use of post-copy with adaptive prepaging techniques to minimize the number of page faults across the network. We propose different prepaging strategies and quantitatively compare their effectiveness in reducing network-bound page faults. Finally, we eliminate the transfer of free memory pages in both pre-copy and post-copy through a dynamic self-ballooning (DSB) mechanism. DSB periodically reclaims free pages from a VM and significantly speeds up migration with negligible performance impact on VM workload.
Memory buddies
Authors: Wood Timothy , Tarasuk-Levin Gabriel , Shenoy Prashant , Desnoyers Peter , Cecchet Emmanuel , Corner Mark D.
Published: September 2009

Many data center virtualization solutions, such as VMware ESX, employ content-based page sharing to consolidate the resources of multiple servers. Page sharing identifies virtual machine memory pages with identical content and consolidates them into a single shared page. This technique, implemented at the host level, applies only between VMs placed on a given physical host. In a multiserver data center, opportunities for sharing may be lost because the VMs holding identical pages are resident on different hosts. In order to obtain the full benefit of content-based page sharing it is necessary to place virtual machines such that VMs with similar memory content are located on the same hosts.

In this paper we present Memory Buddies, a memory sharingaware placement system for virtual machines. This system includes a memory fingerprinting system to efficiently determine the sharing potential among a set of VMs, and compute more efficient placements. In addition it makes use of live migration to optimize VM placement as workloads change.We have implemented a prototype Memory Buddies system with VMware ESX Server and present experimental results on our testbed, as well as an analysis of an extensive memory trace study. Evaluation of our prototype using a mix of enterprise and e-commerce applications demonstrates an increase of data center capacity (i.e. number of VMs supported) of 17%, while imposing low overhead and scaling to as many as a thousand servers.
GPU virtualization on VMware's hosted I/O architecture
Authors: Dowty Micah , Sugerman Jeremy
Published: September 2009

Modern graphics co-processors (GPUs) can produce high fidelity images several orders of magnitude faster than general purpose CPUs, and this performance expectation is rapidly becoming ubiquitous in personal computers. Despite this, GPU virtualization is a nascent field of research. This paper introduces a taxonomy of strategies for GPU virtualization and describes in detail the specific GPU virtualization architecture developed for VMware's hosted products (VMware Workstation and VMware Fusion).

We analyze the performance of our GPU virtualization with a combination of applications and microbenchmarks. We also compare against software rendering, the GPU virtualization in Parallels Desktop 3.0, and the native GPU. We find that taking advantage of hardware acceleration significantly closes the gap between pure emulation and native, but that different implementations and host graphics stacks show distinct variation. The microbenchmarks show that our architecture amplifies the overheads in the traditional graphics API bottlenecks: draw calls, downloading buffers, and batch sizes.

Our virtual GPU architecture runs modern graphics-intensive games and applications at interactive frame rates while preserving virtual machine portability. The applications we tested achieve from 86% to 12% of native rates and 43 to 18 frames per second with VMware Fusion 2.0.
Towards better performance per watt in virtual environments on asymmetric single-ISA multi-core systems
Authors: Kumar Viren , Fedorova Alexandra
Published: September 2009

Single-ISA heterogeneous multicore architectures promise to deliver plenty of cores with varying complexity, speed and performance in the near future. Virtualization enables multiple operating systems to run concurrently as distinct, independent guest domains, thereby reducing core idle time and maximizing throughput. This paper seeks to identify a heuristic that can aid in intelligently scheduling these virtualized workloads to maximize performance while reducing power consumption.

We propose that the controlling domain in a Virtual MachineMonitor or hypervisor is relatively insensitive to changes in core frequency, and thus scheduling it on a slower core saves power while only slightly affecting guest domain performance. We test and validate our hypothesis and further propose a metric, the Combined Usage of a domain, to assist in future energy-efficient scheduling. Our preliminary findings show that the Combined Usage metric can be used as a starting point to gauge the sensitivity of a guest domain to variations in the controlling domain's frequency.
Dynamic Analysis of a Unified Multivariate Counting Process and Its Asymptotic Behavior
Authors: Sumita Ushio , Huang Jia-Ping
Published: September 2009

The class of counting processes constitutes a significant part of applied probability. The classic counting processes include Poisson processes, nonhomogeneous
Poisson processes, and renewal processes. More sophisticated counting processes,
including Markov renewal processes, Markov modulated Poisson processes, age‐dependent counting processes, and the like, have been developed for accommodating
a wider range of applications. These counting processes seem to be quite different
on the surface, forcing one to understand each of them separately. The purpose
of this paper is to develop a unified multivariate counting process, enabling one to
express all of the above examples using its components, and to introduce new counting processes. The dynamic behavior of the unified multivariate counting process is
analyzed, and its asymptotic behavior as t → ∞ is established. As an application,
a manufacturing system with certain maintenance policies is considered, where the
optimal maintenance policy for minimizing the total cost is obtained numerically.
Total Ponderomotive Force on an Extended Test Body
Authors: Langemann D.
Published: September 2009

Droplets on insulating material suffer a nonvanishing total ponderomotive force because of the inhomogeneity of the surrounding electric field. A series expansion of this total force is proven in a two‐dimensional setting by determining the line charge density at the boundary of the test body via a Fredholm integral equation, which is solved by Fourier techniques. The influence of electric charges in the neighborhood of the test body can be estimated as well as the convergence speed of the series expansion. In all realistic applications the series converges very fast. The numerical effort in the simulation of the motion of rainwater droplets on outdoor insulators reduces considerably.
Model and Variable Selection Procedures for Semiparametric Time Series Regression
Authors: Kato Risa , Shiohama Takayuki
Published: September 2009

Semiparametric regression models are very useful for time series analysis. They facilitate the detection of features resulting from external interventions. The complexity of semiparametric models poses new challenges for issues of nonparametric and parametric inference and model selection that frequently arise from time series data analysis. In this paper, we propose penalized least squares estimators which can simultaneously select significant variables and estimate unknown parameters. An innovative class of variable selection procedure is proposed to select significant variables and basis functions in a semiparametric model. The asymptotic normality of the resulting estimators is established. Information criteria for model selection are also proposed. We illustrate the effectiveness of the proposed procedures with numerical simulations.
Universal Forms for One‐Dimensional Quantum Hamiltonians: A Comparison of the SUSY and the De La Peña Factorization Approaches
Authors: Canderle L. , Plastino A. , Casas M. , Plastino A. R.
Published: September 2009

We show that by linking two factorization techniques often employed
to solve Schroedinger′s equation one can give any one‐dimensional hamiltonian
the same form in terms of quantities typical of these approaches.
These are the supersymmetric technique (SUSY) and the one of De La
Peña′s. It is shown that the linkage between them exhibits interesting
peculiarities, that are illustrated in the case of a very important family of
quantum potentials, namely, reflection‐less ones.
Learning Classifier Systems: A Complete Introduction, Review, and Roadmap
Authors: Urbanowicz Ryan J. , Moore Jason H.
Published: September 2009

If complexity is your problem, learning classifier systems
(LCSs) may offer a solution. These rule-based, multifaceted,
machine learning algorithms originated and have evolved in
the cradle of evolutionary biology and artificial intelligence.
The LCS concept has inspired a multitude of implementations
adapted to manage the different problem domains to
which it has been applied (e.g., autonomous robotics, classification,
knowledge discovery, and modeling). One field that
is taking increasing notice of LCS is epidemiology, where
there is a growing demand for powerful tools to facilitate
etiological discovery. Unfortunately, implementation optimization
is nontrivial, and a cohesive encapsulation of implementation
alternatives seems to be lacking. This paper
aims to provide an accessible foundation for researchers of
different backgrounds interested in selecting or developing
their own LCS. Included is a simple yet thorough introduction,
a historical review, and a roadmap of algorithmic components,
emphasizing differences in alternative LCS implementations.