bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerothermal Performance of a Winglet at Engine Representative Mach and Reynolds Numbers
Authors: O’Dowd D. O. , Zhang Q. , He L. , Oldfield M. L. G. , Ligrani P. M. , Cheong B. C. Y. , Tibbott I.
Published: April 2011

This paper presents an experimental and numerical investigation of the aerothermal performance of an uncooled winglet tip, under transonic conditions. Spatially resolved heat transfer data, including winglet tip surface and near-tip side-walls, are obtained using the transient infrared thermography technique within the Oxford high speed linear cascade test facility. Computational fluid dynamics (CFD) predictions are also conducted using the Rolls-Royce HYDRA suite. Most of the spatial heat transfer variations on the tip surface are well-captured by the CFD solver. The transonic flow pattern and its influence on heat transfer are analyzed, which shows that the turbine blade tip heat transfer is greatly influenced by the shock wave structure inside the tip gap. The effect of the casing relative motion is also numerically investigated. The CFD results indicate that the local heat transfer distribution on the tip is affected by the relative casing motion but the tip flow choking and shock wave structure within the tip gap still exist in the aft region of the blade.
Transient Thermal Response of Turbulent Compressible Boundary Layers
Authors: Li Hongwei , Nalim M. Razi , Merkle Charles L.
Published: April 2011

A numerical method is developed with the capability to predict transient thermal boundary layer response under various flow and thermal conditions. The transient thermal boundary layer variation due to a moving compressible turbulent fluid of varying temperature was numerically studied on a two-dimensional semi-infinite flat plate. The compressible Reynolds-averaged boundary layer equations are transformed into incompressible form through the Dorodnitsyn–Howarth transformation and then solved with similarity transformations. Turbulence is modeled using a two-layer eddy viscosity model developed by Cebeci and Smith, and the turbulent Prandtl number formulation originally developed by Kays and Crawford. The governing differential equations are discretized with the Keller-box method. The numerical accuracy is validated through grid-independence studies and comparison with the steady state solution. In turbulent flow as in laminar, the transient heat transfer rates are very different from that obtained from quasi-steady analysis. It is found that the time scale for response of the turbulent boundary layer to far-field temperature changes is 40% less than for laminar flow, and the turbulent local Nusselt number is approximately 4 times that of laminar flow at the final steady state.
Atomic-scale modeling of InxGa1−xN quantum dot self-assembly
Authors: Zhang Zhenli , Chatterjee Alok , Grein Christoph , Ciani Anthony J. , Chung Peter W.
Published: April 2011

The authors simulate in three dimensions the molecular beam epitaxial growth of InxGa1−xN with classical molecular dynamics. Atomic interactions are simulated with Stillinger–Weber potentials. Both homoepitaxial and heteroepitaxial growths are studied. The effects of substrate temperature and indium concentration on quantum dot morphology, concentration profiles, and the thickness of wetting layers qualitatively agree with experimental findings. The authors’ simulations support earlier suggestions that quantum dot formation in the InGaN/GaN system is governed by a stress-driven phase separation mechanism.
Thioredoxin Mediates Oxidation-Dependent Phosphorylation of CRMP2 and Growth Cone Collapse
Authors: Morinaka Akifumi , Yamada Mayumi , Itofusa Rurika , Funato Yosuke , Yoshimura Yuta , Nakamura Fumio , Yoshimura Takeshi , Kaibuchi Kozo , Goshima Yoshio , Hoshino Mikio , Kamiguchi Hiroyuki , Miki Hiroaki
Published: April 2011

Repulsive guidance signaling triggers the collapse of neuronal growth cones through a mechanism involving oxidation and phosphorylation.
PI3K and Chemotaxis: A Priming Issue?
Authors: Afonso Philippe V. , Parent Carole A.
Published: April 2011

The differentiation or “priming” status of cells may explain contradictory findings for the role of phosphoinositide 3-kinases in chemotaxis.
Science Signaling
Podcast: 26 April 2011
Authors: Liu Chuan-ju , VanHook Annalisa M.
Published: April 2011

A growth factor that antagonizes signaling by tumor necrosis factor–α relieves symptoms of inflammatory arthritis.
Stressing Out Your Neighbors
Authors: Adler Elizabeth M.
Published: April 2011

Tumor cells transmit endoplasmic reticulum stress to macrophages to promote an inflammatory microenvironment.
Glutamate Receptors in Pollen
Authors: Hines Pamela J.
Published: April 2011

Amino acid modulation of Ca
2+
signaling guides growth of plant pollen tubes.
Progranulin Protects
Authors: Mueller Kristen L.
Published: April 2011

A growth factor protects against arthritis in mice by blocking tumor necrosis factor–dependent signaling.
Cell Cycle Fertilization Trigger
Authors: Ray L. Bryan
Published: April 2011

Cyclin degradation is not the only mechanism that controls the exit of mouse oocytes from meiosis.
In Vivo
Efficacy of a Human-Simulated Regimen of Ceftaroline Combined with NXL104 against Extended-Spectrum-β-Lactamase (ESBL)-Producing and Non-ESBL-Producing Enterobacteriaceae
Authors: Wiskirchen Dora E. , Crandon Jared L. , Furtado Guilherme H. , Williams Gregory , Nicolau David P.
Published: April 2011

Ceftaroline exhibits
in vitro
activity against extended-spectrum β-lactamase (ESBL)-, AmpC-, and KPC-producing
Enterobacteriaceae
when combined with the novel β-lactamase inhibitor NXL104. The purpose of this study was to evaluate the efficacy of a human-simulated regimen of ceftaroline plus NXL104 against
Enterobacteriaceae
in a murine thigh infection model.

IMPORTANCE
Twelve
Enterobacteriaceae
isolates were tested with neutropenic ICR mice. Seven of these isolates were also tested with immunocompetent mice. Doses were given to simulate human free-drug exposures of ceftaroline (600 mg) plus NXL104 (600 mg) every 8 h over 24 h by targeting the percentage of time that free drug concentrations remain above the MIC, ƒ
T
>MIC. The change in log
10
CFU/ml compared with 0 h controls was observed after 24 h. Human-simulated exposures were achieved against all isolates (MICs of ≤0.015 to 1 μg/ml) in both the neutropenic and the immunocompetent host models, which was equivalent to a ƒ
T
>MIC of 100%. A 0.5 to ≥2 log CFU reduction was observed in the neutropenic thigh infection model. Furthermore, significantly greater reductions in bacterial density were observed for five of seven isolates studied in an immunocompetent model than in the neutropenic-host model. Regardless of immune status, ceftaroline (600 mg) combined with NXL104 (600 mg) every 8 h provided predictable efficacy against ESBL-, non-ESBL-, and KPC-producing isolates with an MIC of ≤1 μg/ml and could be useful in combating the growing threat of resistant
Enterobacteriaceae
.
Use of the NP-40 Detergent-Mediated Assay in Discovery of Inhibitors of β-Hematin Crystallization
Authors: Sandlin Rebecca D. , Carter Melissa D. , Lee Patricia J. , Auschwitz Jennifer M. , Leed Susan E. , Johnson Jacob D. , Wright David W.
Published: April 2011

The protozoan parasite responsible for malaria affects over 500 million people each year. Current antimalarials have experienced decreased efficacy due to the development of drug-resistant strains of
Plasmodium
spp., resulting in a critical need for the discovery of new antimalarials. Hemozoin, a crystalline by-product of heme detoxification that is necessary for parasite survival, serves as an important drug target. The quinoline antimalarials, including amodiaquine and chloroquine, act by inhibiting the formation of hemozoin. The formation of this crystal does not occur spontaneously, and recent evidence suggests crystallization occurs in the presence of neutral lipid particles located in the acidic digestive vacuole of the parasite. To mimic these conditions, the lipophilic detergent NP-40 has previously been shown to successfully mediate the formation of β-hematin, synthetic hemozoin. Here, an NP-40 detergent-based assay was successfully adapted for use as a high-throughput screen to identify inhibitors of β-hematin formation. The resulting assay exhibited a favorable
Z
′ of 0.82 and maximal drift of less than 4%. The assay was used in a pilot screen of 38,400 diverse compounds at a screening concentration of 19.3 μM, resulting in the identification of 161 previously unreported β-hematin inhibitors. Of these, 48 also exhibited ≥90% inhibition of parasitemia in a
Plasmodium falciparum
whole-cell assay at a screening concentration of 23 μM. Eight of these compounds were identified to have nanomolar 50% inhibitory concentration values near that of chloroquine in this assay.
Selective Membrane Disruption: Mode of Action of C16G2, a Specifically Targeted Antimicrobial Peptide
Authors: Kaplan Christopher W. , Sim Jee Hyun , Shah Kevin R. , Kolesnikova-Kaplan Aida , Shi Wenyuan , Eckert Randal
Published: April 2011

The specifically targeted antimicrobial peptide (STAMP) C16G2 was developed to target the cariogenic oral pathogen
Streptococcus mutans
. Because the design of this peptide was novel, we sought to better understand the mechanism through which it functioned. Compared to antimicrobial peptides (AMPs) with wide spectra of activity, the STAMP C16G2 has demonstrated specificity for
S. mutans
in a mixed-culture environment, resulting in the complete killing of
S. mutans
while having minimal effect on the other streptococci. In the current study, we sought to further confirm the selectivity of C16G2 and also compare its membrane activity to that of melittin B, a classical toxic AMP, in order to determine the STAMP's mechanism of cell killing. Disruption of
S. mutans
cell membranes by C16G2 was demonstrated by increased SYTOX green uptake and ATP efflux from the cells similar to those of melittin B. Treatment with C16G2 also resulted in a loss of membrane potential as measured by DiSC(3)5 fluorescence. In comparison, the individual moieties of C16G2 demonstrated no specificity and limited antimicrobial activity compared to those of the STAMP C16G2. The data suggest that C16G2 has a mechanism of action similar to that of traditional AMPs and kills
S. mutans
through disruption of the cell membrane, allowing small molecules to leak out of the cell, which is followed by a loss of membrane potential and cell death. Interestingly, this membrane activity is rapid and potent against
S. mutans
, but not other noncariogenic oral streptococci.
Fungicidal Monoclonal Antibody C7 Interferes with Iron Acquisition in Candida albicans
Authors: Brena Sonia , Cabezas-Olcoz Jonathan , Moragues María D. , Fernández de Larrinoa Iñigo , Domínguez Angel , Quindós Guillermo , Pontón José
Published: April 2011

We have developed a monoclonal antibody (MAb), C7, that reacts with the Als3p and enolase present in the
Candida albicans
cell wall and exerts three anti-
Candida
activities: candidacidal activity and inhibition of both adhesion and filamentation. To investigate the mode of action of MAb C7 on fungal viability, we examined changes in the genome-wide gene expression profile of
C. albicans
grown in the presence of a subinhibitory concentration of MAb C7 (12.5 μg/ml) by using microarrays. A total of 49 genes were found to be differentially expressed upon treatment with MAb C7. Of these, 28 were found to be upregulated and 21 were found to be downregulated. The categories of upregulated genes with the largest number of variations were those involved in iron uptake or related to iron homeostasis (42.86%), while the energy-related group accounted for 38.10% of the downregulated genes (8/21). Results were validated by real-time PCR. Since these effects resembled those found under iron-limited conditions, the activity of MAb C7 on
C. albicans
mutants with deletions in key genes implicated in the three iron acquisition systems described in this yeast was also assessed. Only mutants lacking the
TPK1
gene and, to a lesser extent, the
TPK2
gene were less sensitive to the candidacidal effect of MAb C7. FeCl
3
or hemin at concentrations of ≥7.8 μM reversed the candidacidal effect of MAb C7 on
C. albicans
in a concentration-dependent manner. The results presented in this study provide evidence that the candidacidal effect of MAb C7 is related to the blockage of the reductive iron uptake pathway of
C. albicans
.
Modest but Variable Effect of Rifampin on Steady-State Plasma Pharmacokinetics of Efavirenz in Healthy African-American and Caucasian Volunteers
Authors: Kwara Awewura , Tashima Karen T. , Dumond Julie B. , Poethke Pamela , Kurpewski Jaclyn , Kashuba Angela D. M. , Court Michael H. , Greenblatt David J.
Published: April 2011

Efavirenz-based antiretroviral regimen is preferred during rifampin-containing tuberculosis therapy. However, current pharmacokinetic data are insufficient to guide optimized concurrent dosing. This study aimed to better characterize the effects of rifampin on efavirenz pharmacokinetics. Subjects were randomized to receive 600 mg efavirenz/day or 600 mg efavirenz with 600 mg rifampin/day for 8 days, with plasma samples collected for pharmacokinetic analysis over 24 h on day 8. Treatments were then crossed over after at least a 2-week washout period, and procedures were repeated. Efavirenz concentrations were determined by high-performance liquid chromatography (HPLC), and pharmacokinetic parameters were estimated by noncompartmental analysis. Efavirenz pharmacokinetic differences between treatment periods were evaluated by pairedttest. The coefficients of variation in efavirenz plasma AUC0-24(area under the concentration-time curve from 0 to 24 h) were 50% and 56% in the absence and presence of rifampin, respectively. Of the 11 evaluable subjects (6 white, 5 black; 6 women, 5 men), the geometric mean AUC0-24ratio on/off rifampin (90% confidence interval) was 0.82 (0.72, 0.92), with individual AUC0-24ratios varying from 0.55 to 1.18. Five subjects had a 24-hour efavirenz concentration (C24) of <1,000 ng/ml on rifampin. They were more likely to have received a lower dose in milligrams/kilogram of body weight and to have lower efavirenz AUC0-24values in the basal state. Although rifampin resulted in a modest reduction in efavirenz plasma exposure in subjects as a whole, there was high variability in responses between subjects, suggesting that efavirenz dose adjustment with rifampin may need to be individualized. Body weight and genetic factors will be important covariates in dosing algorithms.
Transcriptional Profiling of Azole-Resistant Candida parapsilosis Strains
Authors: Silva A. P. , Miranda I. M. , Guida A. , Synnott J. , Rocha R. , Silva R. , Amorim A. , Pina-Vaz C. , Butler G. , Rodrigues A. G.
Published: April 2011

Herein we describe the changes in the gene expression profile ofCandida parapsilosisassociated with the acquisition of experimentally induced resistance to azole antifungal drugs. Three resistant strains ofC. parapsilosiswere obtained following prolongedin vitroexposure of a susceptible clinical isolate to constant concentrations of fluconazole, voriconazole, or posaconazole. We found that after incubation with fluconazole or voriconazole, strains became resistant to both azoles but not to posaconazole, although susceptibility to this azole decreased, whereas the strain incubated with posaconazole displayed resistance to the three azoles. The resistant strains obtained after exposure to fluconazole and to voriconazole have increased expression of the transcription factorMRR1, the major facilitator transporterMDR1, and several reductases and oxidoreductases. Interestingly, and similarly to what has been described inC. albicans, upregulation ofMRR1andMDR1is correlated with point mutations inMRR1in the resistant strains. The resistant strain obtained after exposure to posaconazole shows upregulation of two transcription factors (UPC2andNDT80) and increased expression of 13 genes involved in ergosterol biosynthesis. This is the first study addressing global molecular mechanisms underlying azole resistance inC. parapsilosis; the results suggest that similarly toC. albicans, tolerance to azoles involves the activation of efflux pumps and/or increased ergosterol synthesis.
Efficacy of Caspofungin in a Juvenile Mouse Model of Central Nervous System Candidiasis
Authors: Flattery Amy M. , Hickey Emily , Gill Charles J. , Powles Mary Ann , Misura Andrew S. , Galgoci Andrew M. , Ellis Joan D. , Zhang Rena , Sandhu Punam , Ronan John , Abruzzo George K.
Published: April 2011

Neonatal candidiasis is an increasingly common occurrence causing significant morbidity and mortality and a higher risk of dissemination to the central nervous system (CNS) than that seen with older patients. The current understanding of optimal antifungal therapy in this setting is limited. We have developed a model of disseminated candidiasis with CNS involvement in juvenile mice to assess the efficacy of the echinocandin caspofungin relative to amphotericin B (AmB). Juvenile mice were inoculated intravenously with 5.64 × 104CFU ofCandida albicansMY1055. Treatment with caspofungin at 1, 2, 4, and 8 mg/kg of body weight/day, AmB at 1 mg/kg/day, or a vehicle control (VC) was initiated 30 h after infection and continued for 7 days. Pharmacokinetic parameters for caspofungin were also determined. Culture and histology showed evidence of disseminated candidiasis with multifocal encephalitis at the start of antifungal therapy. Survival was 100% in all treated groups, while mortality was 100% in the VC by day 11 after infection. By day 5, all mice in the caspofungin treatment (four doses) groups showed reductions in kidney and brain burden relative to the VC, while AmB treatment reduced kidney burden but gave no reduction of brain fungal burden. Systemic levels of caspofungin were similar in infected and uninfected mice, while brain levels were higher in infected animals. In this juvenile mouse model, caspofungin demonstrated dose-dependent activity, equivalent to or better than that of AmB at 1 mg/kg, against disseminated candidiasis with CNS involvement.
Pharmacokinetics of Intravenous and Oral Linezolid in Adults with Cystic Fibrosis
Authors: Keel Rebecca A. , Schaeftlein Andre , Kloft Charlotte , Pope J. Samuel , Knauft R. Frederic , Muhlebach Marianne , Nicolau David P. , Kuti Joseph L.
Published: April 2011

Linezolid is a treatment option for methicillin-resistant
Staphylococcus aureus
(MRSA) infections in cystic fibrosis (CF) patients. Little is known, however, about its pharmacokinetics in this population. Eight adults with CF were randomized to receive intravenous (i.v.) and oral linezolid at 600 mg twice daily for 9 doses in a crossover design with a 9-day washout. Plasma samples were collected after the first and ninth doses of each phase. Population pharmacokinetic analyses were performed by nonlinear mixed-effects modeling using a previously described 2-compartment model with time-dependent clearance inhibition. Monte Carlo simulation was performed to assess the activities of the linezolid dosing regimens against 42 contemporary MRSA isolates recovered from CF patients. The following pharmacokinetic parameter estimates were observed for the population: absorption rate constant, 1.91 h
−1
; clearance, 9.54 liters/h; volume of central compartment, 26.8 liters; volume of peripheral compartment, 17.3 liters; and intercompartmental clearance, 104 liters/h. Linezolid demonstrated nonlinear clearance after 9 doses, which was reduced by a mean of 38.9% (range, 28.8 to 59.9%). Mean bioavailability was 85% (range, 47 to 131%). At steady state, 600 mg given twice daily produced 93.0% and 87.2% probabilities of obtaining the target pharmacodynamic exposure against the MRSA isolates for the i.v. and oral formulations, respectively. Thrice-daily dosing increased the probabilities to 97.0% and 95.6%, respectively. Linezolid pharmacokinetics in these adults with CF were well described by a 2-compartment model with time-dependent clearance inhibition. Standard i.v. and oral dosing regimens should be sufficient to reliably attain pharmacodynamic targets against most MRSA isolates; however, more frequent dosing may be required for isolates with MICs of ≥2 μg/ml.
Leishmania-Infected Macrophages Are Targets of NK Cell-Derived Cytokines but Not of NK Cell Cytotoxicity
Authors: Prajeeth Chittappen K. , Haeberlein Simone , Sebald Heidi , Schleicher Ulrike , Bogdan Christian
Published: April 2011

Natural killer (NK) cells are important components of a protective immune response against intracellular pathogens such asLeishmaniaparasites, which reside within myeloid cells. Previousin vivostudies in murine cutaneous or visceral leishmaniasis showed that NK cells are activated by conventional dendritic cells in a Toll-like receptor 9-, interleukin-12 (IL-12)-, and IL-18-dependent manner during the early phase of infection and help to restrict the tissue parasite burden by unknown mechanisms. Here, we tested whether NK cells contribute to the control ofLeishmaniainfections by lysing or by activating infected host cells. Coculture experiments revealed that activated NK cells from poly(I:C)-treated mice readily killed tumor target cells, whereasLeishmania infantum- orL. major-infected macrophages or dendritic cells remained viable. Infection withLeishmaniadid not significantly alter the expression of NK cell-activating molecules (retinoic acid early transcript alpha [Rae-1α], mouse UL16-binding protein-like transcript 1 [MULT-1], CD48) or inhibitory molecules (major histocompatibility complex [MHC] class I, nonclassical MHC class 1b molecule Qa-1) on the surface of myeloid cells, which offers an explanation for their protection from NK cell cytotoxicity. Consistent with thesein vitrodata,in vivocytotoxicity assays revealed poor cytolytic activity of NK cells against adoptively transferred infected wild-type macrophages, whereas MHC class I-deficient macrophages were efficiently eliminated. NK cells activated by IL-12 and IL-18 stimulated macrophages to kill intracellularLeishmaniain a cell contact-independent but gamma interferon-, tumor necrosis factor-, and inducible nitric oxide synthase-dependent manner. We conclude thatLeishmaniaparasites, unlike viruses, do not render infected myeloid cells susceptible to the cytotoxicity of NK cells. Instead, soluble products of NK cells trigger the leishmanicidal activity of macrophages.
Role of Src Kinases in Mobilization of Glycosylphosphatidylinositol-Anchored Decay-Accelerating Factor by Dr Fimbria-Positive Adhering Bacteria
Authors: Queval Christophe J. , Nicolas Valérie , Beau Isabelle
Published: April 2011

Afa/Dr fimbriae constitute the major virulence factor of diffusely adheringEscherichia coli(Afa/Dr DAEC). After recognizing membrane-bound signaling receptors, they trigger cell responses. One of these receptors is the human decay-accelerating factor (hDAF). It has previously been reported that the binding of Afa/Dr fimbriae to hDAF quickly induces recruitment of hDAF around adhering bacteria. The aim of our study is to analyze the role of Src kinases in the Dr fimbria-induced recruitment of hDAF. Using biochemical methods and confocal microscopy followed by 3-dimensional (3D) analysis, we have shown that the activation and cell membrane targeting of Src kinases are necessary for the recruitment and organization of hDAF around adhering bacteria. We identified c-Src to be the specific kinase involved in this process. Using a set of Src-green fluorescent protein mutants, we showed that the catalytic activity and the Src homology 2 (SH2) and SH3 domains of the Src kinases are necessary for Dr fimbria-induced hDAF mobilization to occur. In addition, using mutated Dr fimbriae and a set of mutated hDAFs in which each of the complement control protein (CCP) domains had successively been deleted, we found that the aspartic acids at position 54 in the Dr fimbriae and in CCP domain 4 of hDAF played pivotal roles in the mobilization of the Src kinases and hDAF, respectively.
Toll-Like Receptors Participate in Macrophage Activation and Intracellular Control of Leishmania (Viannia) panamensis
Authors: Gallego Carolina , Golenbock Douglas , Gomez Maria Adelaida , Saravia Nancy Gore
Published: April 2011

Toll-like receptors (TLRs) play a central role in macrophage activation and control of parasitic infections. Their contribution to the outcome ofLeishmaniainfection is just beginning to be deciphered. We examined the interaction ofLeishmania panamensiswith TLRs in the activation of host macrophages.L. panamensisinfection resulted in upregulation of TLR1, TLR2, TLR3, and TLR4 expression and induced tumor necrosis factor alpha (TNF-α) secretion by human primary macrophages at comparable levels and kinetics to those of specific TLR ligands. The TLR dependence of the host cell response was substantiated by the absence of TNF-α production in MyD88/TRIF−/−murine bone marrow-derived macrophages and mouse macrophage cell lines in response to promastigotes and amastigotes. Systematic screening of TLR-deficient macrophages revealed that TNF-α production was completely abrogated in TLR4−/−macrophages, consistent with the increased intracellular parasite survival at early time points of infection. TNF-α secretion was significantly reduced in macrophages lacking endosomal TLRs but was unaltered by a lack of TLR2 or MD-2. Together, these findings support the participation of TLR4 and endosomal TLRs in the activation of host macrophages byL. panamensisand in the early control of infection.
Geochemical signature of Ordovician Mn-rich sedimentary rocks on the Avalonian shelf
Authors: Romer Rolf L. , Kirsch Moritz , Kroner Uwe
Published: April 2011

Mn-rich (3.26–15.6 wt.% MnO) sedimentary layers (coticules, Strohschiefer) occur in Ordovician siliciclastic sedimentary rocks that were deposited on the Avalonian shelf and subsequently metamorphosed between 340 and 380 Ma. The Mn-rich layers formed during periods of restricted clastic input, when Mn concentrated by a redox-controlled dissolution–precipitation process near the sediment–water interface, comparable to recent Mn-crusts in the boreal settings of the Baltic Sea, the Barents Sea, and the Kara Sea. Enhanced clastic sedimentation brought the process to a halt and buried the Mn-rich layers. Formation of Mn-rich layers resumed upon renewed reduction in clastic input. Nd and Sr isotope data exclude a volcanic or hydrothermal derivation of Mn. Instead, Mn input occurred via rivers from the continental crust. The Nd isotopic composition and geochemical fingerprints of Mn-rich and hosting Mn-poor sedimentary rocks suggests that the clastic input was dominated by material derived from Gondwana rather than from Avalonia. The occurrence of coticules, however, seems to be restricted to the Avalonian shelf.
Nearshore articulate crinoid from the Albian of Alberta, Canada (Early Cretaceous, Echinodermata)
Authors: Ausich William I. , Buckley Robin A. , Plint A. Guy
Published: April 2011

During the middle Albian, a southward incursion of the Boreal Ocean flooded northern Alberta and adjacent British Columbia, forming a large embayment known as the Hulcross Sea. Marine mudstones of the Hulcross Formation and Harmon Member of the Peace River Formation record transgression, whereas sandstones of the Cadotte Member of the Peace River Formation record shoreline regression to the north. Abundant hummocky and swaley lamination in the Cadotte sandstone attest to the influence of storms on a shallow shelf. The Cadotte sandstone undergoes a lateral facies change from mud-free shoreface sandstone in the south to heterolithic offshore facies in the north. An articulated crinoid was found within a hummocky sandstone bed about 15 km seaward (north) of the shoreface-shelf facies transition. The articulated state of the crinoid indicates that it was buried very rapidly, and never exhumed. The arms through 20 mm of the column are preserved, but because the details of the aboral cup are not well preserved, this specimen must be left in open nomenclature. The elliptical columnals with a concave latus in the distal portion of the preserved column ally this specimen to the Bourgueticrinida, although with details of the aboral cup lacking and other characters atypical for Mesozoic bourgueticrinids, the Canadian specimen is placed in Bathycrinidae indeterminate. The oldest previously recorded bathycrinids were from the Upper Cretaceous (Maastrichtian), thus this report extends their range to the Lower Cretaceous (Albian).
Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 2. Origin, geochemistry, and geochronology 1This article is a companion paper to Ross et al. 2011. Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 1. Mode of emplacement in three areas. Canadian Journal of Earth Sciences, 48: this issue.2Ministère des Ressources naturelles et de la Faune (MRNF) Contribution BEGQ 8439-2010/2011-2. Natural Resources Canada, Earth Science Sector Contribution 20100252.
Authors: Ross P.-S. , McNicoll V. , Goutier J. , Mercier-Langevin P. , Dubé B.
Published: April 2011

In the Archean Blake River Group, mafic to intermediate fragmental units have controversially been proposed to have formed during the collapse of a giant submarine caldera. This paper describes and interprets these rocks, summarizing their physical characteristics, inferred origins, age relationships, and geochemical signatures. The widespread Stadacona member, south of Rouyn-Noranda, consists of several hundred metres of bedded volcaniclastic rocks interpreted to have been mostly deposited from aqueous density currents fed directly by explosive eruptions. The magmas involved in these eruptions were plagioclase-phyric, tholeiitic to transitional basalts. The similarly widespread D’Alembert tuff, in the northern part of the Blake River Group, shares many physical characteristics with the Stadacona member and is thought to have a similar origin. However, the D’Alembert tuff is approximately six million years younger than the Stadacona member. It is composed mostly of transitional to calc-alkaline andesites and basaltic andesites with very distinct trace element profiles. Volcaniclastic rocks from other areas, such as Tannahill Township in Ontario and the Monsabrais area in Quebec, are interpreted to represent mostly in situ to remobilized hyaloclastite, with no explosive eruptions involved in their genesis. Our observations and interpretations are not compatible with models in which the volcaniclastic units are emplaced during a catastrophic event in relation with the collapse of a giant caldera. Instead, the fragmental rocks were produced by various mechanisms at many distinct times during the evolution of the Blake River Group.
Life history variation in upper Columbia River Chinook salmon (Oncorhynchus tshawytscha): a comparison using modern and ~500-year-old archaeological otoliths
Authors: Miller Jessica A. , Butler Virginia L. , Simenstad Charles A. , Backus David H. , Kent Adam J.R.
Published: April 2011

Conservation planning often occurs only after a species has been extirpated from portions of its historical range and limited information is available on life history diversity prior to development. To provide information on Chinook salmon ( Oncorhynchus tshawytscha ) life history before and after local extirpation, we examined the chemical (87Sr:86Sr, Sr:Ca) and structural composition of modern and archaeological otoliths from the upper Columbia River. We compared otoliths from modern spring (yearling migrant, n = 15) and summer–fall (yearling (n = 7) and subyearling (n = 12) migrants) runs with those from extirpated runs (n = 8) to estimate the number of and similarity among natal environments and reconstruct aspects of the migratory history. Presumptive natal sources were most similar between the archaeological collections and the modern summer–fall run. Chinook salmon represented by the archaeological otoliths also displayed life history traits, including size at freshwater emigration and adult size at return to fresh water, most similar to the summer–fall subyearling run. These data indicate that there is the potential to maintain aspects of predevelopment Chinook salmon life histories in the Columbia River, and strategies that promote maintenance of that life history diversity may be warranted.
Recent evidence of biological recovery from acidification in the Adirondacks (New York, USA): a multiproxy paleolimnological investigation of Big Moose Lake
Authors: Arseneau Kristina M.A. , Driscoll Charles T. , Brager Lindsay M. , Ross Karen A. , Cumming Brian F.
Published: April 2011

This investigation provides evidence of biological recovery from acidification in an acid-impacted Adirondack (New York, USA) lake. Water chemistry measurements collected monthly since 1982 show that Big Moose Lake is undergoing chemical recovery from acid deposition. To assess possible biological recovery, changes in chrysophyte, diatom, and cladoceran assemblages are analyzed in a sediment core. Three questions are addressed: (i) is there a significant shift in species composition after the 1995 implementation of the US Acid Rain Program? (ii) Are post-1995 changes in species composition consistent with chemical recovery from acidification or, rather, other changing chemical/climatic factors? (iii) Are the species assemblages returning to their pre-acidification state? Post-1995 declines in the relative abundance of diatom and chrysophyte taxa with low pH-optima and increases in taxa with higher pH-optima indicate biological recovery from acidification. In contrast, the cladocera remain unresponsive to post-1995 increases in pH. No species group has returned to its pre-disturbance state and post-ca. 1995 increases in certain taxa (e.g., Synura echinulata ) may be related to recent climate warming in the Adirondacks.
A fisheries perspective of behavioural variability: differences in movement behaviour and extraction rate of an exploited sparid, snapper (Pagrus auratus)
Authors: Parsons Darren M. , Morrison Mark A. , McKenzie Jeremy R. , Hartill Bruce W. , Bian Richard , Francis R.I.C. Chris
Published: April 2011

Intraspecific variation in movement patterns are well established for many species, but poorly appreciated in fisheries management. In this study we dart-tagged snapper ( Pagrus auratus ), an important fishery species, across different areas and habitats in the Hauraki Gulf, New Zealand. Tag returns were used to quantify movement behaviour and extraction rates using a maximum likelihood model that corrected for spatial variability in population size and fishing effort. Residency was high (~90%) in two strata and lower (75%) in the remaining stratum. The stratum with the highest residency also appeared to experience the highest extraction rate (likely due to a lower population size). These results confirm the existence of differences in movement behaviour within the snapper population, suggesting that localized areas may become depleted regardless of the status of the overall stock. This has consequences for the scale of fisheries management and the size of marine reserves implemented in different regions. Understanding why variation in movement behaviour exists (i.e., genetic vs. environmental) is the next step in addressing the influence of animal behaviour on fisheries management.
Climate change modulates structural and functional lake ecosystem responses to introduced anadromous salmon
Authors: Selbie Daniel T. , Sweetman Jon N. , Etherton Peter , Hyatt Kim D. , Rankin D. Paul , Finney Bruce P. , Smol John P.
Published: April 2011

We integrated limnological, paleolimnological, and fisheries analyses in Tuya Lake, British Columbia, Canada, to explore the effects and interactions of climate warming and sockeye salmon introductions on northern lake ecology. We tracked millennially unprecedented, climate-correlated changes in inferred lake production, stratification, and trophic structure since the mid-1800s, most likely resulting from declining ice cover and enhanced stratification. Post-1970s algal (diatom) species turnover, coeval across several remote northern Cordilleran lakes, marked an apparent increase in warming and the induction of inferred nitrogen deficiencies in Tuya Lake. Lower post-stocking phosphorus (P) and nitrogen (N) concentrations and a strong P-modeled salmon biomass correlation (r2 = 0.87) indicated salmon production reduced epilimnetic nutrient availability. Post-stocking chlorophyll reductions, late-summer algal dominance by heterocystous cyanobacteria and low-N-tolerant diatoms, and a strong chlorophyll-modeled salmon biomass correlation (r2 = 0.87) indicated that salmon influenced lake productivity, most likely by enhancing climate-induced N-deficiencies. Predicted smolt-biomass nutrient exports were minimal, with post-introduction nutrient reductions likely related to planktivory and enhanced sedimentation losses. Our study highlights how climate warming changes northern lake ecosystem structure and functioning, influencing responses to subsequent stresses.
The consequences of short-term cortisol elevation on individual physiology and growth rate in wild largemouth bass (Micropterus salmoides)
Authors: O’Connor Constance M. , Gilmour Kathleen M. , Arlinghaus Robert , Matsumura Shuichi , Suski Cory D. , Philipp David P. , Cooke Steven J.
Published: April 2011

In this study, we explored the growth, survival, and potential population-level effects of short-term experimentally induced stress in largemouth bass ( Micropterus salmoides ). Cortisol implants [50 mg·(kg body mass)–1] were used to increase circulating stress hormones in a group of wild fish in a research lake for ∼6 d in June 2007. Through mark-and-recapture, we compared survival, growth, and plasma biochemistry of cortisol-treated, sham-treated, and control fish at liberty until October 2007. Cortisol-treated fish displayed persistent growth rate depression compared with other groups. However, neither plasma biochemistry nor mortality rates differed among treatments. In a complementary study, we found that the standard metabolic rates (SMR) of cortisol-treated fish were higher than control fish ∼56 h following treatment. Bioenergetics modelling revealed that a transient elevation in SMR alone was insufficient to explain the observed growth depression. Finally, we constructed a simple population model to explore the potential consequences of growth depression. We found that a 10% reduction in population growth rate is conceivable when 39% of the population experiences a stress causing the growth rate depression documented in this study. Our study is novel in highlighting that individual and potentially population-level growth depression can result from a single stress event of short duration.
The cumulative impacts of climate change on Fraser River sockeye salmon (Oncorhynchus nerka) and implications for management
Authors: Healey Michael
Published: April 2011

Anadromous Pacific salmon ( Oncorhynchus spp.) are vulnerable to climate change in both freshwater and marine habitats. I use a qualitative model to assess the cumulative effects of climate change across life stages and generations of Fraser River sockeye salmon ( Oncorhynchus nerka ) and other salmon species. The effects of climate change most relevant to Fraser River sockeye include warming of freshwater and marine habitats, altered hydrology in spawning rivers, reduced productivity in nursery habitats, and changed distribution and phenology of predator and prey species. The weight of evidence indicates that these changes will negatively affect growth and survival of Fraser River sockeye at all life stages. Effects on one life stage will also carry forward to heighten adverse effects at subsequent life stages and across generations so that the cumulative impact is greater than the impact on individual stages. Salmon can adapt to climate change but probably not enough to sustain productivity. In the south, focus of policy and management on conserving and enhancing resilience is needed to retain some salmon production. At the same time, Arctic habitats are becoming accessible to salmon. Management in the Arctic should protect potentially productive habitats from development and facilitate their colonization by Pacific salmon.
Do juvenile Atlantic salmon (Salmo salar) use chemosensory cues to detect and avoid risky habitats in the wild?
Authors: Kim Jae-Woo , Grant James W.A. , Brown Grant E.
Published: April 2011

We examined whether juvenile Atlantic salmon ( Salmo salar ) in the wild adjust their behaviour in response to chemical cues of predator activity during a 4-week period after emergence from gravel nests. In each of seven 75 m2 sites in Catamaran Brook, New Brunswick, Canada, we established three contiguous sections differing in perceived predator activity by releasing stream water in control sections, conspecific alarm cues in risky sections, and nothing in buffer sections in both 2006 and 2007. As predicted, the density of young-of-the-year (YOY) salmon tended to decrease in alarm cue sections, while it increased in control and buffer sections. After the 2-week manipulation in 2006, we switched treatments so that buffer sections became alarm cue sections and alarm cue sections became buffer sections for an additional 2-week period. After the switch, the number of YOY increased least in the new alarm cue sections and most in control and new buffer sections. In contrast with YOY, the density of age 1+ parr was not affected by the experimental treatments. Our results suggest that YOY salmon can use chemical alarm cues to assess the predator activity of habitats in the wild.
Energetic costs and benefits of cyclic habitat switching: a bioenergetics model analysis of diel vertical migration in coregonids
Authors: Busch Susan , Johnson Brett M. , Mehner Thomas
Published: April 2011

Recent studies on diel vertical migration (DVM) of two coregonid species ( Coregonus spp.) in Lake Stechlin (Germany) have suggested that the nocturnal distribution of fish is linked with metabolic benefits. We used a spatially explicit bioenergetics-based foraging model to test whether energetic constraints contribute to explain DVM of both species. The newly parameterized model was compared with independent data from Lake Stechlin that covered a 9 month period. Predicted growth rates matched observed growth rates of each fish species reasonably well. The simulation of different migration scenarios showed that even slight changes in night-time depths modified growth rates, primarily owing to temperature-dependent respiration. Fish that performed DVM grew faster than nonmigratory fish that occupied deep hypolimnetic water over a diel cycle. However, the most energy-efficient strategy simulated had fish remaining within the metalimnion. Here, energetic benefits (foraging) clearly outweighed higher energetic costs (respiration) in the warmer waters. Although DVM can be energetically beneficial, it is not the most efficient strategy performed by coregonids in Lake Stechlin. We suggest that multiple factors, rather than bioenergetics efficiency alone, are the evolutionary basis for DVM of many freshwater fish species.
OPTIMAL PATENT LENGTH IN A NORTH-SOUTH FRAMEWORK: A COMMENT
Authors: BANERJEE SWAPNENDU , KABIRAJ TARUN
Published: April 2011

We show that under some conditions, it is optimal for the non-innovating south to give patent protection for a longer period than the innovating north. However, a cooperative patent agreement involves a larger protection by each country compared to the non-cooperative situation.
SUBCONTRACTING, RENEGOTIATION OF CONTRACT AND QUALITY PROVISION
Authors: BANERJEE CHATTERJEE TANMOYEE , RAYCHAUDHURI AJITAVA
Published: April 2011

In a principal-agent framework under moral hazard, when the monopolist can pass on the liability of any defect of the product to the subcontractors, and cannot credibly commit to a high level of investment, he actually chooses a low investment level and supplies a low quality product if the product replacement cost is below a critical level. However, under contract renegotiation, when the monopolist is taking the entire risk of replacing the defective product, he will profitably choose high investment level and serves high quality product. But the results show that the monopolist will choose to renegotiate the contract only for limited values of product replacement cost, even if renegotiation is socially optimal.
CLAMPING LOSSES OF FOLDED- AND STRAIGHT-BEAM MEMS RESONATORS MADE FROM POLYCRYSTALLINE 3C-SiC FILMS
Authors: CHANG WEN-TENG
Published: April 2011

This paper presents an analysis of clamping losses in microelectromechanical systems (MEMS)-based, flexural mode silicon carbide (SiC) lateral resonators. The study includes folded- and straight-beam resonators made from (111) polycrystalline 3 C - SiC side by side. The device testing was conducted at 30 μTorr using a transimpedance-amplifier-based circuit to measure the total quality factor. It was found that thermoelastic damping (TED) in SiC MEMS-based lateral resonators has minimal contributions to overall energy dissipation in the aforementioned devices. Moreover, the difference in material losses of these devices is negligible due to their similar microstructure. In this case, clamping losses are responsible when one is comparing the energy dissipation mechanism of these two types of resonators. The findings showed that the total losses for a folded-beam resonator were reduced by more than 10 times that for a straight-beam resonator when the beam lengths were set at 150 μm and operated at the same level of resonant frequency. The clamping coefficient of the folded-beam resonator was between 0.7 and 1.8, suggesting that the effective dimension of a folded-beam resonator should include part of the proof mass.
ROBUST SYNCHRONIZATION OF A CLASS OF COUPLED DELAYED NETWORKS WITH MULTIPLE STOCHASTIC DISTURBANCES: THE CONTINUOUS-TIME CASE
Authors: LIANG JINLING , WANG ZIDONG , LIU XIAOHUI
Published: April 2011

In this paper, the robust synchronization problem is investigated for a new class of continuous-time complex networks that involve parameter uncertainties, time-varying delays, constant and delayed couplings, as well as multiple stochastic disturbances. The norm-bounded uncertainties exist in all the network parameters after decoupling, and the stochastic disturbances are assumed to be Brownian motions that act on the constant coupling term, the delayed coupling term as well as the overall network dynamics. Such multiple stochastic disturbances could reflect more realistic dynamical behaviors of the coupled complex network presented within a noisy environment. By using a combination of the Lyapunov functional method, the robust analysis tool, the stochastic analysis techniques and the properties of Kronecker product, we derive several delay-dependent sufficient conditions that ensure the coupled complex network to be globally robustly synchronized in the mean square for all admissible parameter uncertainties. The criteria obtained in this paper are in the form of linear matrix inequalities whose solution can be easily calculated by using the standard numerical software. The main results are shown to be general enough to cover many existing ones reported in the literature. Simulation examples are presented to demonstrate the feasibility and applicability of the proposed results.
INITIAL RECTIFIED ATTRACTORS FOR PERFECT GS AND Q-S SYNCHRONIZATION OF CHAOTIC SYSTEMS
Authors: ALIBEAKI SMAIL , HAERI MOHAMMAD , TAVAZOEI MOHAMMAD SALEH
Published: April 2011

The controlled attractor with initial rectifying action, referred to as initial rectified attractor (IRA) in this paper, is introduced for the purpose of generalized and Q-S chaos synchronization. The IRA is designed to make the states of drive and response systems synchronized in the form of generalized and Q-S within a finite time interval. The reaching time is shown to be independent of the initial conditions and dynamics of the chaotic systems, and can be determined in advance. With numerical experiments it is demonstrated that perfect synchronization can be achieved between the modified Lorenz and the hyperchaotic Rössler systems in different configurations.