bluuebunny/crossref_metadata_2025 huggingface dataset:
High diversity of fungi associated with living parts of boreal forest bryophytes
Authors: Kauserud Håvard , Mathiesen Cecilie , Ohlson Mikael
Published: October 2008

Bryophytes are a dominant and functionally important component of the forest floor vegetation in boreal forests, yet little is known about the fungal diversity associated with these abundant plants. Using molecular identification, we document an ecologically and phylogenetically diverse array of fungi associated with the living parts of three widespread and abundant boreal forest bryophytes, i.e., Hylocomium splendens (Hedw.) Schimp. in B.S.G., Pleurozium schreberi (Brid.) Mitt., and Polytrichum commune Hedw. From 376 cloned ITS sequences, 158 operational taxonomic units (OTUs), roughly corresponding to the number of species, were defined based on sequence similarity searches (Fasta) and phylogenetic analyses. A main portion (62.8%) of the OTUs belonged to Ascomycota, 32.0% to Basidiomycota, 3.9% to Chytridiomycota, and 1.3% to Glomeromycota. The most common orders were Helotiales (18.6%), Agaricales (11.5%), Chaetothyriales (9.6%), and Tremellales (9.0%). Frequently detected OTUs of potentially high ecologic importance included two with high sequence similarity (>99%) to the agaric Entoloma conferendum (Britzelm.) Noordel and the endophyte Lophodermium piceae (Fckl.) Hoehn., and various OTUs with affinity to the Helotian genus Hyphodiscus. Several ectomycorrhiza-forming basidiomycetes were also detected. Most OTUs (77.2%) were only detected once and a very small overlap in composition of OTUs was observed among the three bryophytes, indicating the occurrence of an immense fungal diversity associated with boreal forest bryophytes that deserves further study.
Hypolimnion Injection of Nutrient Effluents as a Method for Reducing Eutrophication
Authors: Schindler D. W. , Ruszczynski T. , Fee E. J.
Published: October 2008

Injection of nutrients into the anoxic hypolimnion of a small Precambrian Shield lake for 5 yr caused less of a eutrophication problem than discharging nutrients into surface waters. Phytoplankton standing crop and production in the whole lake averaged only 10–21% of values in a nearby lake fertilized at the surface. Five-year averages for the epilimnion only were still lower: 5–8% of those in the surface-fertilized lake. Analysis of long-term trends in chlorophyll and nutrient concentrations revealed much slower rates of increase than in surface-fertilized lakes.Key words: eutrophication, hypolimnion injection, sediment–water interaction, nutrients, experimental lakes
Analysis of the Response of Hypolimnetic Phytoplankton in Continuous Culture to Increased Light or Phosphorus Using Track Autoradiography
Authors: Knoechel R. , deNoyelles Jr. F.
Published: October 2008

Phytoplankton from the hypolimnetic biomass peak in Lake 266SW (Experimental Lakes Area, northwestern Ontario) was subjected to conditions of increased light or phosphorus in continuous culture. Phosphorus enrichment increased total carbon fixation 16% relative to the control; however, the particulate fraction was initially depressed and the phytoplankton biomass was less than 2% greater after 10 d. The high light culture displayed 21% higher final biomass despite a 13% decline in total carbon fixation which was primarily due to reduced extracellular release. The 21 most common species demonstrated a wide range of positive and negative biomass responses to the experimental perturbations; however, the three dominant chrysophyte species all responded positively to higher light. Detection of population biomass changes provided a direct and accurate means of quantifying perturbation effects provided the species response was stable over several days. Measurement of carbon uptake rates of species through track autoradiography provided the additional sensitivity and temporal resolution needed to monitor low level or variable responses. Synedra radians exhibited a lengthy lag period before demonstrating a strong positive response to phosphorus enrichment, while Dinobryon sertularia shifted from neutral to strongly negative and then strongly positive within a 3-d period. These results illustrate the inadequacy of short-term bioassays for the prediction of long-term perturbation effects.Key words: growth rate, primary production, Ankistrodesmus falcatus, Dinobryon sertularia, Synedra radians
Physiological Indicators of Nutrient Deficiency in Lake Phytoplankton
Authors: Healey F. P. , Hendzel L. L.
Published: October 2008

Physiological indicators of N and P deficiency were measured in summer populations of several central Canadian lakes. Measurements included six composition ratios (P/C, N/C, N/P, ATP/C, chlorophyll a/C, and protein/carbohydrate) and three metabolic indicators (alkaline phosphatase activity and P and N debts expressed per unit particulate ATP). Overall results show P deficiency is generally greater than N deficiency in all the small lakes studied, embracing a wide range of maximum chlorophyll concentrations and N/P loading ratios. In two larger, very turbid lakes, neither P nor N deficiency appeared important, and light limitation is suggested. In a series of lakes of known N and P loading rates, indicators of P deficiency increased but those of N deficiency showed little trend with increasing N/P loading ratio. Some indicators of P deficiency appeared to provide a sensitive means of following the movement of river water, and loss of P from it, through a large lake. Some comparisons of net phytoplankton with total seston showed surprisingly little interference from detritus in these measurements.Key words: deficiency, nitrogen, phosphorus, physiological indicators, phytoplankton
Errors in Molybdenum Blue Methods for Determining Orthophosphate in Freshwater
Authors: Stainton M. P.
Published: October 2008

Whole lakewater was spiked with carrier free 32PO4, filtered through a 0.45-μm membrane filter and the filtrate fractionated using G-25 Sephadex. Three molecular weight fractions incorcorporated 32P labeling, one of which was colloidal. This labeled filtrate was treated with several variations of the molybdenum blue method for measuring orthophosphate followed by molecular weight fractionation. All variations in the molybdenum blue method caused a significant loss of phosphorus from the colloidal fraction. Phosphorus originating from the colloidal fraction tested as orthophosphate giving an overestimate of the true orthophosphate present.Key words: orthophosphate, analytical errors, freshwater
Radiochemical Analysis of Orthophosphate Concentrations and Seasonal Changes in the Flux of Orthophosphate to Seston in Two Canadian Shield Lakes
Authors: Levine S. N. , Schindler D. W.
Published: October 2008

Seasonal changes in the concentration and dynamics of phosphate–phosphorus were studied in two small lakes, one oligotrophic and one artificially eutrophied. Because the molybdate blue phosphate technique frequently overestimates phosphate concentrations, three radiochemical assays were used. One, involving sephadex fractionation, was unsatisfactory because of the long period required for high molecular weight phosphorus fractions to reach isotopic equilibrium. The second method was unusable both for epilimnion waters within the Experimental Lakes Area, because of its low sensitivity, and for hypolimnion waters, due to interference from nonphosphate compounds. The third method, Rigler's bioassay, indicated that PO4-P in both lakes seldom exceeded 0.1 μg∙L−1, even under anoxic conditions. Organisms, and not mineral reactions, appeared to regulate the phosphate concentration at all depths in the lakes.Key words: phosphorus dynamics, orthophosphate
Nitrogen Fixation in Canadian Precambrian Shield Lakes
Authors: Flett Robert J. , Schindler David W. , Hamilton Robert D. , Campbell Norman E. R.
Published: October 2008

Acetylene reduction assays in the water columns of several artificially eutrophied lakes in the Experimental Lakes Area revealed that nitrogen fixation by planktonic blue-green algae could supply a significant portion of the nitrogen income to these lakes. In situ 15N2 uptake experiments in one lake indicated that nitrogen fixation was proceeding at a slow rate in the low oxygen region of the thermocline, probably via methane oxidizing bacteria. Other 15N2 uptake experiments in the littoral sediments of an oligotrophic lake failed to detect nitrogen fixation. Generally, algal nitrogen fixation occurred in Shield lakes that were subject to total N:total P loading ratios (wt/wt) of less than approximately 10. This suggests that in these lakes phosphorus removal from loading is the best technique for eutrophication abatement and that nitrogen removal, when applied by itself, may be detrimental because it could encourage bloom formation of nitrogen fixing blue-green algae.Key words: nitrogen fixation, eutrophication, blue-green algae, acetylene reduction, nitrogen-15
Important Factors for Estimating Annual Phytoplankton Production in the Experimental Lakes Area
Authors: Fee Everett J.
Published: October 2008

Annual phytoplankton growth rates from 21 lakes in the Experimental Lakes Area (ELA) for the 4-yr period 1973–76 are reported. The coefficient of variation of production in most lakes over this period was about 20%. This variability was the same for both control and experimental lakes. Subthermocline populations were quantitatively unimportant in eutrophied basins but up to 50% of annual production occurred in hypolimnion chlorophyll peaks in some transparent control lakes. The exact details of chlorophyll distribution as monitored with an in vivo fluorometer are unnecessary for accurate measurements of production, even in lakes having hypolimnion chlorophyll peaks. Annual production rates were about 80% of the rates predicted with simulated cloudless weather. The common practice of not correcting production estimates for basin morphometry when reporting areal production rates resulted in overestimation of productivity by roughly 20%. The results indicate several ways for simplifying the numerical primary production model.Key words: production, morphometry, models, limnology, Experimental Lakes Area, incubator
Relationships Between Dipteran Emergence and Phytoplankton Production in the Experimental Lakes Area, Northwestern Ontario
Authors: Davies I. J.
Published: October 2008

Dipteran emergence was monitored at the Experimental Lakes Area (ELA) between 1973 and 1977 in seven lakes of different trophic status. The data were used to develop a number of equations which related the quantity and spatial distribution of average annual emergence to lake productivity. These models explained > 94% of the variation in mean emergent biomass among lakes or > 76% of the variation in numbers of emergent Diptera in terms of phytoplankton production or phosphorus loading. On average, ELA lakes produced 40.8 dipteran adults (9 mg dry weight) per gram carbon fixed by phytoplankton. A single equation for all lakes predicts the surface distribution of emergent biomass, relative to lake depth at any location, from vertical profiles of phytoplankton production. The mean size of dipteran adults was related to lake depth at the point of emergence and average phytoplankton production. An empirical model which used data on the vertical profile, and lake average, of phytoplankton production was developed to predict the number of Diptera emerging from each depth. The maximum depth of emergence was related to depth of the euphotic zone and average phytoplankton production in each lake. Initial tests suggested that the models may provide useful predictions of dipteran emergence for a wider spectrum of lakes.Key words: aquatic insects, Diptera, Chironomidae, eutrophication, primary production
Salinity and Recruitment of Atlantic Cod (Gadus morhua) in the Newfoundland Region
Authors: Myers Ransom A. , Drinkwater Kenneth F. , Barrowman Nicholas J. , Baird James W.
Published: October 2008

Recruitment predictions for Atlantic cod (Gadus morhua) in the North Atlantic, based upon a previously published regression with salinity, are found to be well correlated with recent recruitment estimates from both virtual population analysis and those derived from research surveys. The addition of spawning stock biomass in the regression significantly increased the percentage of the variance accounted for in the recruitment time series. A similar relationship between recruitment and salinity was found for two nearby stocks (southern Grand Banks and St. Pierre Bank). Oceanographic and food chain mechanisms that might be responsible for a link between salinity and recruitment are discussed.
Quantitative Impacts of Lake-Level Stabilization on Material Transfer between Water and Sediment in Newnans Lake, Florida
Authors: Gottgens J. F. , Crisman T. L.
Published: October 2008

Spillways at lake outlets reduce water-level fluctuations but may accelerate sedimentation in the lake. In eutrophic Newnans Lake, Florida, a transect of sedimentary profiles, dated with 210Pb and 137Cs by γ-ray spectroscopy, showed threefold increases in accumulation rates of organic matter, total Kjeldahl nitrogen (TKN), and total phosphorus (TP) 1200 m lakeward of a spillway since its construction in 1967. Concentrations of TKN and TP increased 3.5 and 2.4 times, respectively, in sediments deposited since 1967. These increases were progressively less at stations farther from the spillway. Postspillway accumulation of TP was focused toward the dam whereas recent TKN deposition was similar lakewide. Flocculent sediment (> 90% water) accumulated at 1.4 cm/yr. Dams designed to reduce water-level fluctuations may provide short-term benefits for lake access and navigation but in the long-term may accelerate deposition of nutrient-rich detritus, reduce lake volume, cloud the water, alter plant communities, and change lake productivity.
Heterozygosity and Morphological Variability in the Orange Roughy,Hoplostethus atlanticus(Teleostei: Trachichthyidae)
Authors: Ward Robert D. , Elliott Nicholas G.
Published: October 2008

Eleven polymorphic loci were screened in six southern Australian populations of the deepwater teleost Hoplostethus atlanticus, the orange roughy. Associations between heterozygosity and morphological variability were examined. No significant correlations between heterozygosity at individual loci and length were observed. Homozygotes at ADA* had significantly greater length variance than heterozygotes in one population whereas in another population, homozygotes for PGM-2* had significantly reduced length variance compared with heterozygotes. No other single locus/length variance comparisons were significant. One of the six populations showed a significant positive regression of individual length on multilocus heterozygosity; regressions in the other five populations were nonsignificant and variable in slope direction. No significant correlations were detected between multilocus heterozygosity category and mean length or coefficient of variance of length. Three of the populations were also examined for variation in four meristic characters and one measure of bilateral asymmetry: no consistent associations were detected between individual or multilocus heterozygosity and mean or variance of these characters. The data provide little evidence for significant relationships between individual or multilocus heterozygosity and morphological variability in orange roughy.
Relative Contributions of Dietary and Waterborne Copper to Tissue Copper Burdens and Waterborne-Copper Tolerance in Rainbow Trout (Oncorhynchus mykiss)
Authors: Miller P. A. , Lanno R. P. , McMaster M. E. , Dixon D. G.
Published: October 2008

In a 42-d study, rainbow trout (Oncorhynchus mykiss) were fed a diet containing either 13 or 684 mg Cu∙kg−1 and simultaneously exposed to waterborne-Cu concentrations of 5, 32, 55, or 106 μg∙L−1 (low-Cu diet) or 13, 38, 62, or 127 μg∙L−1 (high-Cu diet). There were no significant effects on mortality, growth, condition factor, or food conversion efficiency. Elevated dietary Cu increased Cu concentrations in liver (p < 0.001), kidney (p < 0.001), gill (p = 0.005), and digesta (p < 0.001). Increasing waterborne-Cu concentrations elevated Cu concentrations in liver (p = 0.018) and kidney (p = 0.002) but not in gill (p = 0.930) or digesta (p = 0.519). Waterborne-Cu exposure increased Zn concentrations in liver (p = 0.025) but decreased those in kidney (p = 0.045). For fish on the high-Cu diet, diet provided 99, 85, and 63% of the Cu in the liver for the 38, 62, and 127 μg∙L−1 waterborne-Cu treatments, respectively. Based on Cu tolerance (incipient lethal level for Cu), dietary and waterborne Cu partitioned into functionally different compartments. Although both waterborne-Cu (p < 0.00001) and dietary-Cu (p = 0.019) preexposure increased Cu tolerance, waterborne Cu had a much greater impact.
Forecasting Abundance from Habitat Measures Using Nonparametric Density Estimation Methods
Authors: Rice J. C.
Published: October 2008

The relationships between abundance of animals and characteristics of habitats are important for theoretical and management reasons. However, data on populations and habitats frequently are unsuitable for model-based statistical analyses. The shape of the functional relation between abundance and habitat and the form of the error distribution are rarely known accurately, and noise in the data often is large relative to the signal. Kernel estimators, a type of nonparametric probability density estimation technique, can use available data to estimate the probability density function (pdf) of abundance, given specified habitat conditions. One nonparametric estimator, related to kernel estimators and based on the Cauchy distribution, is described in detail. It is applied to data from three studies of influences of habitat on populations: stream characteristics on salmon and trout biomasses, depth of the 2 °C isotherm on codtrap catches, and bottom temperature on capelin densities. Despite the differences among the data sets, the Cauchy kernel could be applied without modification in all cases. The pdf's of abundance were interpretable readily, captured dominant features of the biology of each species, and were suitable for management applications and for tests of hypotheses.
Iron Budgets in Temperate Lakes
Authors: Nürnberg Gertrud K. , Dillon Peter J.
Published: October 2008

Iron mass balances for eight lakes (79 lake-years of data) on the Precambrian Shield were measured including catchment, atmospheric, and internal sources of iron and compared with literature data. In most cases, internal load from anoxic sediment surfaces was important. Net (Rext) and gross (Rtot) Fe retentions were correlated with internal load and with morphometry and hydrology, respectively. An average annual settling velocity of Fe computed from the relationship of Rtotwith the annual water load (qs) ranged from 12 to 26 m/yr. A simple mass balance model, similar to that used successfully for phosphorus, was used to predict annual average Fe concentration. Although model predictions of average Fe concentration of the lake outflow (Lout/qs) and observed concentrations (TFe) were significantly correlated, TFe was underestimated by the model in the Precambrian Shield lakes but overestimated in acid-stressed lakes in the Sudbury, Ontario region. Since the deviations were correlated with organic content of the water or sediment, dissolved organic carbon concentration (DOC), colour of the lake water, and loss on ignition of the surface sediments proved to be important secondary variables: the best predictive model was TFe = −43.9 + 0.81 Lout/qs + 30.0 DOC.
Seasonal and Geographic Variation in the Species Composition and Size of Prey Consumed by Grey Seals (Halichoerus grypus) on the Scotian Shelf
Authors: Bowen W. D. , Lawson J. W. , Beck B.
Published: October 2008

The grey seal (Halichoerus grypus) population on the Scotian Shelf has grown significantly over the past 20 yr, thus increasing the potential for competitive interactions between grey seals and fisheries. The relative contribution (percent wet weight) and size of prey eaten were estimated from otoliths and squid beaks recovered from 143 stomachs that contained food of the 528 collected from 1988 to 1990. Although 22 taxa were found, only four species (Atlantic herring, silver hake, Atlantic cod, and squid) accounted for 80% of the estimated weight of food eaten. The mean length of prey eaten ranged from 19 to 35 cm for six species. Only 17% of the cod and none of the pollock and squid eaten were of the length taken in commercial fisheries. However, about 80% of the silver hake and herring eaten were of commercial size. Offshore at Sable Island, northern sand lance, silver hake, and squid (in order of importance) accounted for 86.1% of the wet weight ingested by seals during summer; sand lance and cod accounted for 96.1% of prey eaten in winter. At inshore locations, herring, cod, and pollock made up 90% of the diet in summer; Atlantic mackerel, cod, squid, and herring made up 83% of the diet in winter.
Application of Near-Infrared Reflectance Spectroscopy in the Measurement of Carbon, Nitrogen, and Phosphorus in Seston from Oligotrophic Lakes
Authors: Malley D. F. , Williams P. C. , Stainton M. P. , Hauser B. W.
Published: October 2008

The application of near-infrared spectroscopy (NIRS), widely used in the agricultural, food, and pharmaceutical industries, is extended to the measurement of C, N, and P in seston from oligotrophic lakes at the Experimental Lakes Area, northwestern Ontario. Seston from 150-mL aliquots of lake water from several depths in two lakes on one mid-June sampling date was collected on Whatman GF/C filters and measured first by NIRS then analyzed by standard wet chemistry methods. Correlation between chemically measured and NIRS-predicted values gave coefficients of determination between 0.913 and 0.982. The rapid, low-cost, nonchemical, nondestructive, efficient analysis of C, N, and P in seston by NIRS is feasible.
Synthesis and characterization of novel conducting homopolymers based on amino β-styryl terthiophene
Authors: Mehenni Hakim , Dao Lê H
Published: October 2008

Novel ECPs (electronic conducting polymers) based on amino β-styryl-substituted terthiophene (AST) were synthetized by direct electropolymerization. The ECPs were characterized by cyclic voltammetry, square-wave voltammetry, Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The poly(amino β-styryl terthiophene) displayed cyclic and square-wave voltammograms with redox peaks that can be assigned to the aminophenyl moiety and the polyterthiophene backbone. The presence of free primary amine groups on the ECP film permitted further biological functionalization (i.e., covalent bonding of various bioreceptors on its surface). The electrochemical performance of Biotin grafted at the AST modified glassy carbon electrode was investigated to detect the Avidin protein in solution by cyclic voltammetry and square-wave voltammetry.Key words: electronic conducting polymer, electrode surface modification, biosensor, β-styryl-substitued terthiophene, functionalization, cyclic, square-wave voltammetry.
A Fmoc/Boc pseudoisocytosine monomer for peptide nucleic acid synthesis
Authors: Wojciechowski Filip , Hudson Robert HE
Published: October 2008

The synthesis of N-[2-(fluorenylmethoxycarbonyl)aminoethyl]-N-[(2-N-(tert-butoxycarbonyl)isocytosin-5-yl)acetyl]glycine peptide nucleic acid monomer is described. The N-tert-butoxycarbonyl protected monomer is compatible with commercially available monomers designed for the Fmoc-oligomerization strategy and is deprotected under mild acidolysis conditions.Key words: PNA, polyamide, pseudoisocytosine, J-base, triplex.
A capillary and microchip-based nanoelectrospray emitter using a mesoporous membrane
Authors: Su Shuqin , Oleschuk Richard D
Published: October 2008

A method is described for the fabrication of multipath electrospray emitters using hydrophobic porous polymer membranes. Polysulphone (PSF) and polycarbonate (PC) membranes, which possess pores with well-defined sizes, are glued onto the exit aperture of fused-silica capillaries or microfluidic chips to create multipaths to assist electrospray at moderate nano flow rates (e.g., 50–500 nL/min). A capillary-based multipath emitter fabricated with either PSF or PC membranes was prepared with a fused-silica capillary with 75 µm inner diameter and 360 µm outer diameter. Relative effects on electrospray performance at different flow rates, electrospray voltages, and solvent compositions are probed. The sensitivity and stability of electrospray signals were enhanced through spraying from multiple pores on the membrane. An embossed polycarbonate microchip was also interfaced to the mass spectrometer using the meso porous membrane approach.Key words: nanoelectrospray, membrane, emitter, multipaths, microchip.
Effect of substituents on absorption and fluorescence properties of pyrazolo[3,4-b]pyrrolo[2,3-d]pyridines
Authors: Ghotekar Bhausaheb K , Kazi Muddassar A , Jachak Madhukar N , Toche Raghunath B
Published: October 2008

A convenient route was successfully developed for the synthesis of novel heterocycles such as pyrazolo[3,4-b]pyrrolo[2,3-d]pyridines (PPP) from pyrazolo[3,4-b]pyridines in good yield. The PPP derivatives synthesized were further studied for their photophysical properties, and it was observed that absorption and emission λmax changed, owing to the substituent effect at 4 positions. These compounds were obtained from highly reactive starting materials, 5-aminopyrazoles and α-acetyl γ-butyrolactone.Key words: α-acetyl γ-butyrolactone, pyrazolo[3,4-b]pyrrolo[2,3-d] pyridine, absorption, emission, fluorescence.
Facile reductive dehalogenation of organic halides with nickel boride at ambient temperature
Authors: Khurana Jitender M , Kumar Sanjay , Nand Bhaskara
Published: October 2008

The hydrodehalogenation of a series of aryl, alkyl, allyl, and benzyl chlorides, bromides, and iodides has been carried out efficiently using nickel boride in methanol at ambient temperature, leading to the corresponding products resulting from hydrogen/halogen exchange.Key words: hydrodehalogenation, reduction, organic halides, sodium borohydride, nickel boride.
GENERALIZED IMPEDANCE BOUNDARY CONDITIONS FOR SCATTERING PROBLEMS FROM STRONGLY ABSORBING OBSTACLES: THE CASE OF MAXWELL'S EQUATIONS
Authors: HADDAR HOUSSEM , JOLY PATRICK , NGUYEN HOAI-MINH
Published: October 2008

This paper is dedicated to the construction and analysis of so-called Generalized Impedance Boundary Conditions (GIBCs) for electromagnetic scattering problems from imperfect conductors with smooth boundaries. These boundary conditions can be seen as higher order approximations of a perfect conductor condition. We consider here the 3-D case with Maxwell equations in a harmonic regime. The construction of GIBCs is based on a scaled asymptotic expansion with respect to the skin depth. The asymptotic expansion is theoretically justified at any order and we give explicit expressions till the third order. These expressions are used to derive the GIBCs. The associated boundary value problem is analyzed and error estimates are obtained in terms of the skin depth.
CONSTRUCTION AND CUSTOMIZATION OF STABLE OSCILLATION MODELS IN BIOLOGY
Authors: YIN WEIWEI , VOIT EBERHARD O.
Published: October 2008

Oscillations exist at all levels of biological systems and are often crucial for their proper functioning. Among the various types of oscillations, limit cycles have received particular attention for more than one hundred years. Specifically, theorems have been established that characterize whether a system might have the capability of exhibiting limit cycles. However, the practical application of these theorems is usually cumbersome and there are hardly any guidelines for devising de novo models that exhibit limit cycles of a desired form. In this paper, we propose a simple method for constructing and customizing stable limit cycles in two-dimensional systems according to desired features, including frequency, amplitude, and phase shift between system variables. The method is based on "inverting" a criterion proposed by Lewis for characterizing oscillations in two-dimensional S-system models. First, we execute comprehensive simulations that result in a set of over 2000 prototype limit cycles. Second, we show with examples how these prototypes can be further customized to adhere to predetermined specifications. This two-step process is fast and efficacious, especially when one considers the paucity of alternative methods. Finally, we illustrate how one may create systems with more complex dynamics by modulating the prototypes with external input signals.
SENSITIVITY ANALYSES OF POPULATION BIOMASS DYNAMICS FOR ULVA SPP. AND SARGASSUM FURCATUM AT THE CABO FRIO UPWELLING REGION OF BRAZIL
Authors: GUIMARAENS M. A. , GONÇALVES J. E. A. , LOURENÇO S. O. , COUTINHO R.
Published: October 2008

Sargassum furcatum population dynamics was studied at Cabo Frio Island, where generally the effect of upwelling waters is sporadic and occurs mainly during the summer months at Farol Beach. Model sensitivity analyses were compared for Sargassum simulations at Cabo Frio Island and for Ulva dynamics simulated with data sets collected at two other upwelling sites, Sonar and Jaconé. Field data suggests that Sargassum growth shows a delay to nutrient enrichment events, whereas Ulva growth follows nutrient peaks more closely. Algal biomass was simulated with parameter values changed plus and minus 10%, one at a time, while holding all other parameters constant. Those parameters that cause, a plus or minus change of greater than 10% in the model output, were used in the next stage of the sensitivity analyses. In the second stage, a fractional factorial design was used to evaluate the main effect of a particular parameter. The parameter literature survey and sensitivity analyses, for both Sargassum and Ulva models, suggest that parameters related to environmental factors, such as minimal cellular nutrient quota for growth- and temperature-related growth functions, should be further investigated for algae at the Cabo Frio upwelling region, since they caused a change in the biomass output greater than 10%.
TWO DYNAMIC MODELS ABOUT RABIES BETWEEN DOGS AND HUMAN
Authors: WANG XIAOWEI , LOU JIE
Published: October 2008

Our models characterize the transmission dynamics of rabies between human and dogs. Firstly, we build an ODE model to represent the natural spreading of rabies in dogs and human. We get the basic reproductive number R0 and the global stability for both the disease-free equilibrium and the endemic equilibrium. Then, we build a controlling model for rabies. We compare the efficiency of three strategies for controlling the rabies: culling, vaccination, culling and vaccination, and get controlling thresholds for different strategies. The results of analysis and simulations indicate that vaccination is the best choice and culling is the worst one to control rabies. Vaccination on dogs in cities and culling and vaccination on dogs in rural areas of China are recommended for controlling rabies. Our study provides a theoretical basis for controlling rabies in China.
REWARD FUNCTIONS AND COOPERATIVE GAMES: CHARACTERIZATION AND ECONOMIC APPLICATION
Authors: VILASECA JORDI , MESEGUER ANTONI , TORRENT JOAN , FERRERAS RAQUEL
Published: October 2008

In this paper we study network structures in which the possibilities for cooperation are restricted and the benefits of a group of players depend on how these players are internally connected. One way to represent this type of situations is the so-called reward function, which represents the profits obtainable by the total coalition if links can be used to coordinate agents' actions. For any cooperative game, a reward function is associated. Given a reward function, our aim is to analyze under which conditions it is possible to associate a cooperative game to it. We characterize the reward function by means of two conditions, component permanence and component additivity, in order to determine whether there exists or not a cooperative game associated to it. An economic application is shown to illustrate the main theoretical result. Data from Catalan firms is used to compute the reward function on the set of communication networks determined by firms, customers, distributors and suppliers.
ORDINAL GAMES
Authors: DURIEU JACQUES , HALLER HANS , QUEROU NICOLAS , SOLAL PHILIPPE
Published: October 2008

We study strategic games where players' preferences are weak orders which need not admit utility representations. First of all, we extend Voorneveld's concept of best-response potential from cardinal to ordinal games and derive the analogue of his characterization result: An ordinal game is a best-response potential game if and only if it does not have a best-response cycle. Further, Milgrom and Shannon's concept of quasi-supermodularity is extended from cardinal games to ordinal games. We find that under certain topological assumptions, the ordinal Nash equilibria of a quasi-supermodular game form a nonempty complete lattice. Finally, we extend several set-valued solution concepts from cardinal to ordinal games in our sense.
SHARE OPPORTUNITY SETS AND COOPERATIVE GAMES
Authors: CAPRARI ELISA , PATRONE FIORAVANTE , PUSILLO LUCIA , TIJS STEF , TORRE ANNA
Published: October 2008

In many share problems there is an a priori given a natural set of possible divisions to solve the sharing problem. Cooperative games related to such share sets are introduced, which may be helpful in solving share problems. Relations between properties of share sets and properties of games are investigated. The average lexicographic value for share sets and for cooperative games is studied.
ON THE LYAPUNOV SPECTRUM OF INFINITE DIMENSIONAL RANDOM PRODUCTS OF COMPACT OPERATORS
Authors: BESSA MÁRIO , CARVALHO MARIA
Published: October 2008

We consider an infinite dimensional separable Hilbert space and its family of compact integrable cocycles over a dynamical system f. Assuming that f acts in a compact Hausdorff space X and preserves a Borel regular ergodic probability which is positive on non-empty open sets, we conclude that there is a C0-residual subset of cocycles within which, for almost every x, either the Oseledets–Ruelle's decomposition along the orbit of x is dominated or all the Lyapunov exponents are equal to -∞.
SOLVING A NONLINEAR PSEUDO-DIFFERENTIAL EQUATION OF BURGERS TYPE
Authors: JACOB NIELS , POTRYKUS ALEXANDER , WU JIANG-LUN
Published: October 2008

In this paper, we study the initial value problem for a class of nonlinear equations of Burgers type in the following form: [Formula: see text] for u:(t,x) ∈ (0,∞) × ℝn↦ ℝ, where q(x,D) is a pseudo-differential operator with negative definite symbol. We solve the initial value problem for the equation on ℝnby utilising a fix point argument based upon a combination of semigroup approach and Hoh's symbolic calculus.
ONLINE LEARNING OF THE BODY SCHEMA
Authors: HERSCH MICHA , SAUSER ERIC , BILLARD AUDE
Published: October 2008

We present an algorithm enabling a humanoid robot to visually learn its body schema, knowing only the number of degrees of freedom in each limb. By "body schema" we mean the joint positions and orientations and thus the kinematic function. The learning is performed by visually observing its end-effectors when moving them. With simulations involving a body schema of more than 20 degrees of freedom, results show that the system is scalable to a high number of degrees of freedom. Real robot experiments confirm the practicality of our approach. Our results illustrate how subjective space representation can develop as a result of sensorimotor contingencies.
ROBOTSHARE: A GOOGLE FOR ROBOTS
Authors: FAN XIUYI , HENDERSON THOMAS C.
Published: October 2008

Knowledge representation is a traditional field in artificial intelligence. Researchers have developed various ways to represent and share information among intelligent agents. Agents that share resources, data, information, and knowledge perform better than agents working alone. However, previous research has also revealed that sharing knowledge among a large number of entities in an open environment is a problem yet to be solved. Intelligent robots are designed and produced by different manufacturers. They have various physical attributes and employ different knowledge representations. Therefore, any nonstandard or non-widely-adopted technology is unsuitable for providing a satisfactory solution to the knowledge sharing problem. In this research, we pose robot knowledge sharing as an activity to be developed in an open environment — the World Wide Web. Just as search engines like Google provide enormous power for information exchange and sharing for humans, we believe that a searching mechanism designed for intelligent agents can provide a robust approach to sharing knowledge among robots. We have developed: (1) a knowledge representation for robots that allows Internet access, (2) a knowledge organization and search indexing engine, and (3) a query/reply mechanism between robots and the search engine.
BIRTH OF THE OBJECT: DETECTION OF OBJECTNESS AND EXTRACTION OF OBJECT SHAPE THROUGH OBJECT–ACTION COMPLEXES
Authors: KRAFT DIRK , PUGEAULT NICOLAS , BAŞESKI EMRE , POPOVIĆ MILA , KRAGIĆ DANICA , KALKAN SINAN , WÖRGÖTTER FLORENTIN , KRÜGER NORBERT
Published: October 2008

We describe a process in which the segmentation of objects as well as the extraction of the object shape becomes realized through active exploration of a robot vision system. In the exploration process, two behavioral modules that link robot actions to the visual and haptic perception of objects interact. First, by making use of an object independent grasping mechanism, physical control over potential objects can be gained. Having evaluated the initial grasping mechanism as being successful, a second behavior extracts the object shape by making use of prediction based on the motion induced by the robot. This also leads to the concept of an "object" as a set of features that change predictably over different frames.

The system is equipped with a certain degree of generic prior knowledge about the world in terms of a sophisticated visual feature extraction process in an early cognitive vision system, knowledge about its own embodiment as well as knowledge about geometric relationships such as rigid body motion. This prior knowledge allows the extraction of representations that are semantically richer compared to many other approaches.
Contractile activity per se induces transcriptional activation of SLC2A4 gene in soleus muscle: involvement of MEF2D, HIF-1a, and TRα transcriptional factors
Authors: Lima Guilherme Alves , Anhê Gabriel Forato , Giannocco Gisele , Nunes Maria Tereza , Correa-Giannella Maria Lucia , Machado Ubiratan Fabres
Published: October 2008

Skeletal muscle is a target tissue for approaches that can improve insulin sensitivity in insulin-resistant states. In muscles, glucose uptake is performed by the GLUT-4 protein, which is encoded by the SLC2A4 gene. SLC2A4 gene expression increases in response to conditions that improve insulin sensitivity, including chronic exercise. However, since chronic exercise improves insulin sensitivity, the increased SLC2A4 gene expression could not be clearly attributed to the muscle contractile activity per se and/or to the improved insulin sensitivity. The present study was designed to investigate the role of contractile activity per se in the regulation of SLC2A4 gene expression as well as in the participation of the transcriptional factors myocyte enhancer factor 2D (MEF2D), hypoxia inducible factor 1a (HIF-1a), and thyroid hormone receptor-α (TRα). The performed in vitro protocol excluded the interference of metabolic, hormonal, and neural effects. The results showed that, in response to 10 min of electrically induced contraction of soleus muscle, an early 40% increase in GLUT-4 mRNA (30 min) occurred, with a subsequent 65% increase (120 min) in GLUT-4 protein content. EMSA and supershift assays revealed that the stimulus rapidly increased the binding activity of MEF2D, HIF-1a, and TRα into the SLC2A4 gene promoter. Furthermore, chromatin immunoprecipitation assay confirmed, in native nucleosome, that contraction induced an approximate fourfold ( P < 0.01) increase in MEF2D and HIF-1a-binding activity. In conclusion, muscle contraction per se enhances SLC2A4 gene expression and that involves MEF2D, HIF-1a, and TRα transcription factor activation. This finding reinforces the importance of physical activity to improve glycemic homeostasis independently of other additional insulin sensitizer approaches.
Hyperinsulinemia fails to augment ET-1 action in the skeletal muscle vascular bed in vivo in humans
Authors: Lteif Amale A. , Fulford Angie D. , Considine Robert V. , Gelfand Inessa , Baron Alain D. , Mather Kieren J.
Published: October 2008

Endogenous endothelin action is augmented in human obesity and type 2 diabetes and contributes to endothelial dysfunction and impairs insulin-mediated vasodilation in humans. We hypothesized that insulin resistance-associated hyperinsulinemia could preferentially drive endothelin-mediated vasoconstriction. We applied hyperinsulinemic-euglycemic clamps with higher insulin dosing in obese subjects than lean subjects (30 vs. 10 mU·m−2·min−1, respectively), with the goal of matching insulin's nitric oxide (NO)-mediated vascular effects. We predicted that, under these circumstances, insulin-stimulated endothelin-1 (ET-1) action (assessed with the type A endothelin receptor antagonist BQ-123) would be augmented in proportion to hyperinsulinemia. NO bioactivity was assessed using the nitric oxide synthase inhibitor NG-monomethyl-l-arginine. Insulin-mediated vasodilation and insulin-stimulated NO bioavailability were well matched across groups by this approach. As expected, steady-state insulin levels were approximately threefold higher in obese than lean subjects (109.2 ± 10.2 pmol/l vs. 518.4 ± 84.0, P = 0.03). Despite this, the augmentation of insulin-mediated vasodilation by BQ-123 was not different between groups. ET-1 flux across the leg was not augmented by insulin alone but was increased with the addition of BQ-123 to insulin ( P = 0.01 BQ-123 effect, P = not significant comparing groups). Endothelin antagonism augmented insulin-stimulated NO bioavailability and NOx flux, but not differently between groups and not proportional to hyperinsulinemia. These findings do not support the hypothesis that insulin resistance-associated hyperinsulinemia preferentially drives endothelin-mediated vasoconstriction.
Subunit-Specific Effects of Isoflurane on Neuronal Ih in HCN1 Knockout Mice
Authors: Chen Xiangdong , Shu Shaofang , Kennedy Dylan P. , Willcox Sarah C. , Bayliss Douglas A.
Published: October 2008

The ionic mechanisms that contribute to general anesthetic actions have not been elucidated, although increasing evidence has pointed to roles for subthreshold ion channels, such as the HCN channels underlying the neuronal hyperpolarization-activated cationic current ( Ih). Here, we used conventional HCN1 knockout mice to test directly the contributions of specific HCN subunits to effects of isoflurane, an inhalational anesthetic, on membrane and integrative properties of motor and cortical pyramidal neurons in vitro. Compared with wild-type mice, residual Ih from knockout animals was smaller in amplitude and presented with HCN2-like properties. Inhibition of Ih by isoflurane previously attributed to HCN1 subunit-containing channels (i.e., a hyperpolarizing shift in half-activation voltage [ V1/2]) was absent in neurons from HCN1 knockout animals; the remaining inhibition of current amplitude could be attributed to effects on residual HCN2 channels. We also found that isoflurane increased temporal summation of excitatory postsynaptic potentials (EPSPs) in cortical neurons from wild-type mice; this effect was predicted by simulation of anesthetic-induced dendritic Ih inhibition, which also revealed more prominent summation accompanying shifts in V1/2 (an HCN1-like effect) than decreased current amplitude (an HCN2-like effect). Accordingly, anesthetic-induced EPSP summation was not observed in cortical cells from HCN1 knockout mice. In wild-type mice, the enhanced synaptic summation observed with low concentrations of isoflurane contributed to a net increase in cortical neuron excitability. In summary, HCN channel subunits account for distinct anesthetic effects on neuronal membrane properties and synaptic integration; inhibition of HCN1 in cortical neurons may contribute to the synaptically mediated slow-wave cortical synchronization that accompanies anesthetic-induced hypnosis.
Muscarinic Modulation of Recruitment Threshold and Firing Rate in Rat Oculomotor Nucleus Motoneurons
Authors: Nieto-Gonzalez Jose Luis , Carrascal Livia , Nunez-Abades Pedro , Torres Blas
Published: October 2008

Above recruitment threshold, ocular motoneurons (Mns) show a firing rate linearly related with eye position. Current hypothesis suggests that synaptic inputs are determinant for establishing the recruitment threshold and firing rate gain in these Mns. We investigated this proposal by studying the cholinergic modulation in oculomotor nucleus Mns by intracellular recordings in rat brain slice preparation. All recorded Mns were silent at their resting membrane potential. Bath application of carbachol (10 μm) produced a depolarization and a sustained firing that was not silenced on returning membrane potential to the precarbachol value via DC injection. In response to similar membrane depolarization or equal-current steps, carbachol-exposed Mns produced a higher firing rate and a shorter spike afterhyperpolarization phase with lower amplitude. The relationship between injected current and firing rate ( I– F) was linear in control and carbachol-exposed Mns. The slope of these relationships ( I– F gain) decreased with carbachol exposure. Bath application of agonist and antagonist of nicotinic and muscarinic acetylcholine receptors in addition to immunohistochemical studies support the notion that muscarinic receptors are primarily involved in the preceding responses. We conclude that muscarinic inputs play an important role in determining the recruitment threshold and firing rate gain observed in oculomotor Mns in vivo.
Two-Photon Polymerization of Hybrid Sol-Gel Materials for Photonics Applications
Authors: Ovsianikov A. , Gaidukeviciute A. , Chichkov B. N. , Oubaha M. , MacCraith B. D. , Sakellari I. , Giakoumaki A. , Gray D. , Vamvakaki M. , Farsari M. , Fotakis C.
Published: October 2008

Two-photon polymerization of photosensitive materials has emerged as a very promising technique for the fabrication of photonic crystals and devices. We present our investigations into the structuring by two-photon polymerization of a new class of photosensitive sol-gel composites exhibiting ultra-low shrinkage. We particularly focus on two composites, the first containing a zirconium alkoxide and the second a nonlinear optical chromophore. The three-dimensional photonic crystal structures fabricated using these materials demonstrate high resolution and clear bandstops in the near IR region.
Iterative Mean Removal Superimposed Training for SISO and MIMO Channel Estimation
Authors: Longoria-Gandara O. , Parra-Michel R. , Bazdresch M. , Orozco-Lugo A. G.
Published: October 2008

This contribution describes a novel iterative radio channel estimation algorithm based on superimposed training (ST) estimation technique. The proposed algorithm draws an analogy with the data dependent ST (DDST) algorithm, that is, extracts the cycling mean of the data, but in this case at the receiver's end. We first demonstrate that this mean removal ST (MRST) applied to estimate a single-input single-output (SISO) wideband channel results in similar bit error rate (BER) performance in comparison with other iterative techniques, but with less complexity. Subsequently, we jointly use the MRST and Alamouti coding to obtain an estimate of the multiple-input multiple-output (MIMO) narrowband radio channel. The impact of imperfect channel on the BER performance is evidenced by a comparison between the MRST method and the best iterative techniques found in the literature. The proposed algorithm shows a good tradeoff performance between complexity, channel estimation error, and noise immunity.