bluuebunny/crossref_metadata_2025 huggingface dataset:
Using phylogeny and ultrastructure to study cystidia of twoPsathyrellaspecies: reciprocal illumination
Authors: Padamsee Mahajabeen , Celio Gail J. , McLaughlin David J.
Published: October 2008

Ultrastructure of the cystidia of Psathyrella aff. nolitangere (Fr.) A. Pearson & Dennis and Psathyrella rhodospora Weaver & Smith (Agaricales) was examined primarily using freeze substitution, with the goal of evaluating whether these cells could provide phylogenetically informative characters with which to study morphological evolution. Within the Agaricales, the diversity of cystidial form coupled with the limited number of studies makes accurate character coding for use in phylogenetic analyses problematic. This study revealed many common cystidial characteristics between the two closely related species examined, including well-formed apical crystals, abundant free ribosomes, and scattered smooth endoplasmic reticulum. Transmission electron microscopy was used for the first time to examine calcium oxalate crystals in cystidia, and demonstrated the formation of a pre-crystalline matrix at the apex of each cell that possibly disrupts the wall as the crystals form. The shared subcellular traits suggest that ultrastructural details of cystidia may provide additional characters for and signal in phylogenetic analyses.
Growth and reproduction of invasiveVincetoxicum rossicumandV. nigrumunder artificial defoliation and different light environments
Authors: Milbrath Lindsey R.
Published: October 2008

The exotic vines Vincetoxicum rossicum (Kleopow) Barbar. and Vincetoxicum nigrum (L.) Moench have become increasingly invasive in low- and high-light habitats in North America, and a biological control program is being developed. These plants experience little damage in North America, so it is unclear how they might respond to introduced herbivores. I conducted an artificial defoliation study on seedlings and mature plants of V. rossicum and V. nigrum grown under different light environments. Under high light, V. nigrum produced more seed and allocated more resources to aboveground tissue (root:shoot ratios < 1), whereas V. rossicum allocated more resources to roots with root:shoot ratios of 1.9 for mature plants and > 3 for seedlings. These differences disappeared with shading. Increasing frequencies of 100% defoliation caused greater reductions in biomass and seed production for both species and plant stages. Shading further reduced biomass and no seed was produced. Defoliation of shaded, but not unshaded, plants caused high mortality. Additional cutting of stem tips increased branching only. Defoliation may be effective against Vincetoxicum plants growing in low-light environments such as forest understories, but appears to be of more limited value in high-light environments unless repeated defoliation occurs.
Effects of a Windstorm and Forest Fire on Chemical Losses from Forested Watersheds and on the Quality of Receiving Streams
Authors: Schindler D. W. , Newbury R. W. , Beaty K. G. , Prokopowich J. , Ruszczynski T. , Dalton J. A.
Published: October 2008

A severe natural windstorm followed by a high intensity forest fire caused significant increases in runoff and in losses of nitrogen, phosphorus, and potassium from two small Precambrian watersheds. Both the windstorm and the fire had significant effects on water and chemical yields. Water yields in the two basins were 1.6 and 1.8 times the pre-impact means, respectively, in the year after the burn. Maximum chemical losses were observed for nitrate, with values of 3.4 and 9 times the pre-impact means for the two basins in the year after the burn. Increases in annual yields of most chemical parameters were 1.1 to 2.9 times the background. Both increased concentrations and increased flow volumes appear to be responsible for the increased nutrient losses.Key words: forest fire, windstorm, stream water quality, phosphorus, nitrogen, potassium losses, water yield
Experimental Acidification of Lake 223, Experimental Lakes Area: Background Data and the First Three Years of Acidification
Authors: Schindler D. W. , Wagemann R. , Cook R. B. , Ruszczynski T. , Prokopowich J.
Published: October 2008

Sulfuric acid was used to add 1.60 eq∙m−2 of hydrogen ion ([H+]) to Lake 223 over a 3-yr period from 1976 to 1978, to simulate the effects of acid precipitation on chemical and biological characteristics of the lake. The pH of epilimnion water was lowered from 6.7 to 7.0 in 1976, to 6.0–6.2 in 1977, and to 5.7–5.9 in 1978. The effectiveness of acid addition at depleting alkalinity from the water column in the first 2 yr was 31–38%. As a result, the pH of the lake did not decrease as much as predicted from theoretical calculations. The low efficiency of acidification appeared to be due to generation of dissolved inorganic carbon (DIC) by sulfate reduction in anoxic regions of the hypolimnion. Sulfate reduction increased as addition of sulfuric acid caused the concentration of sulfate in the lake to increase. Mobilization of iron from hypolimnion sediments during anoxic periods caused DIC respired by decomposers to be accumulated as HCO3− to balance the Fe+2 charge, buffering against acidification of the lake. Most of the reduced sulfur was precipitated from the lake as FeS. As a result, H2S in the hypolimnion was usually undetectable. Concentrations of ammonia, iron, manganese, zinc, and aluminum were higher in 1977 than in 1976. The transparency of the lake increased, although there was no apparent change in chlorophyll, dissolved color, dissolved organic carbon, or primary production.Key words: lake acidification, acid rain, mass balance, water chemistry, sulfur cycling
Effects of Artificial Acidification on the Growth of Periphyton
Authors: Müller Peter
Published: October 2008

Acidification caused an increase in periphyton growth in large enclosures in the littoral zone of Lake 223. Diatomeae decreased in relative abundance above [H+] = 10−6 mol/L, and were replaced by filamentous Chlorophyta. The genus Mougeotia, dominant in many acidified Scandinavian lakes, was the most tolerant of high acidity. Fewer species and lower species diversity were observed at higher [H+]. Although increases in standing crop were observed, there were no corresponding increases in production. The abundance of invertebrates and microbiota were also unaffected by hydrogen ion concentration.Key words: lake acidification, periphyton, microcosms, acid rain
Effects of Acidification on Mobilization of Heavy Metals and Radionuclides from the Sediments of a Freshwater Lake
Authors: Schindler D. W. , Hesslein R. H. , Wagemann R. , Broecker W. S.
Published: October 2008

Large (10 m) diameter enclosures were sealed to the sediments in 2–2.5 m of water in Lake 223. Two tubes were held at control pH (6.7–6.8), one was lowered to pH 5.7 and one to pH 5.1, using H2SO4. Aluminum, manganese, zinc, and iron were released from lake sediments at pH 5 and 6. Concentrations of zinc in the overlying water column exceeded 300 μg∙L−1. Radioisotopes of several heavy metals added to the water of the enclosure showed the following: all metals were removed from the water at log-linear rates, with half-times of 5–25 d. Acidification caused several metals to become more soluble, including Fe-59, Co-60, Mn-54, and Zn-65. Solubility of V-48 and Hg-203 decreased with increasing acidity. Acidification also slowed the loss to sediments of Mn-54 and Zn-65. Losses of Ba-133, Se-75, Cs-134, and V-48 were more rapid under acid conditions. The fractions of any isotope retained by a 0.45-μm filter, activated charcoal and mixed-bed ion exchange resin remained constant throughout the experiment at any given pH.Key words: sediment–water interactions, heavy metals, radionuclides, lake acidification
Experimental Study of Trace Metal Chemistry in Soft-Water Lakes at Different pH Levels
Authors: Jackson Togwell A. , Kipphut George , Hesslein Raymond H. , Schindler David W.
Published: October 2008

The biogeochemistry of Hg, Zn, Co, Fe, Mn, Cr, V, Th, Ba, Cs, As, and Se in two soft-water lakes of the Canadian Shield was investigated by means of carrier-free γ-emitting isotopes introduced into limnocorrals in which the pH of the water was varied from 6.8 to 5.1. The residence times of the radionuclides in the water were determined, and the partitioning of the nuclides among different metal-binding agents in the water and sediments was studied with the aid of membrane filtration, dialysis, solvent extractions, and fractionation on Sephadex columns.Metal behaviour varied systematically with metal properties. Metals of high crystal field stabilization energy, high electronegativity, or small ionic radius were most readily scavenged by> 0.45 μm suspended particles and dispersed colloids in the water, disappeared most rapidly from the water column, and were preferentially accumulated by sedimentary binding agents, including organic substances. Which property of a metal had the dominant effect on metal behavior depended on environmental factors, such as the ambient pH and the nature of the binding agents. Thus, Hg was removed fairly rapidly from the water at pH 6.7–6.8 owing to its high electronegativity but was removed more slowly than any other metal at pH 5.1 owing to its large ionic radius.Most metals were strongly chemisorbed or complexed by mud and organic ooze, and only Ba could be redissolved by cation exchange. Therefore, 0.1 N NaOH and 0.1 N or 1 N HCl were more efficient extractants than H2O, 1 N CaCl2, or benzene/methanol, and the metals were largely nonextractable by any of these solvents. The major NaOH-extractable metal-binding agents were the higher molecular weight fractions of a group of organic (probably humic) substances characterized by a UV absorption band at [Formula: see text]. The affinity of metals for the highest molecular weight "humic" (NaOH-extractable) substances increased with electronegativity, being greatest for Hg. Hg and Se were nonextractable by HCl but were the elements most readily extracted by NaOH, implying exceptionally strong covalent bonding by humic matter. The more electropositive metals were more readily extracted by HCl than by NaOH, suggesting weaker, less highly covalent bonding or preferential sorption by acid-soluble hydrated oxides.Acidification of lake water to pH 5.1 interfered with accumulation of Hg and other metals by organic ooze, probably owing in part to interference with the deposition or formation of the complexing agents with the 265 nm absorption band. Acidification also lowered the concentration of NaOH-extractable colloidal phosphate in the ooze but had no effect on NaOH-extractable orthophosphate content.Key words: metals, lakes, chemistry, pH, humic matter, organic matter, phosphorus, radioactive tracers, acidification
Dynamics of Cadmium-Stressed Plankton Communities
Authors: Marshall J. S. , Mellinger D. L.
Published: October 2008

Structural and functional responses of plankton communities to cadmium stress were studied during 1977 in Lake Michigan using small-volume (8 L) completely sealed enclosures, and in Canada's Experimental Lakes Area (ELA) Lake 223 using large-volume (1.5 × 105 L) open-surface enclosures. In Lake Michigan, reductions of the average abundance of micro-crustaceans by cadmium were significantly greater in "light" or shallow epilimnetic incubations than they were in "dark" or deep epilimnetic incubations. Measurements of dissolved oxygen indicated that this interaction with light (depth) was an indirect effect due to a reduction of photosynthesis and primary production. Zooplankton density and species diversity were not significantly affected within 21 d by cadmium concentrations [Formula: see text] and [Formula: see text] Cd/L, respectively, whereas final dissolved oxygen concentration and percentage similarity (PS) of the crustacean zooplankton community were significantly reduced by [Formula: see text] Cd/L. In the ELA Lake 223 experiment, the reducing effect of cadmium on zooplankton density increased up to 31 d after Cd enrichment and then decreased, probably due to decreasing Cd concentrations in the water. Values of PS on day 24 for the ELA enclosures enriched with 1 and 3 μg Cd/L were within the 95% confidence limits for individual values predicted from a regression of PS on cadmium for the 21-d Lake Michigan experiments.Key words: plankton communities, zooplankton, phytoplankton, cadmium stress, Lake Michigan, Canadian Shield lakes
Gas Exchange, Photosynthetic Uptake, and Carbon Budget for a Radiocarbon Addition to a Small Enclosure in a Stratified Lake
Authors: Bower Peter , McCorkle Daniel
Published: October 2008

9250 kBq (250 μCi) of 14C as NaHCO3 were added to the mixed-layer waters inside a long, cylindrical plastic enclosure anchored in an oligotrophic lake of the Canadian Shield. Loss of 14C from the epilimnion was predominantly in the form of irreversible gas-exchange across the liquid–air interface. This loss was measured by 14C inventory of the epilimnion and thermocline waters. Using the Lewis and Whitman boundary layer model, values for the mass transfer coefficient of 126, 58, and 100 cm/d were determined for three distinct phases in the deepening of the epilimnion during autumn cooling. The relationship between these mass transfer coefficients and the average wind speeds over the same three time periods were consistent with the results of previous wind-tunnel, gas-exchange experiments.Two significant features of the carbon budget during the course of the experiment were the large net outflux of CO2 from the corral (with [Formula: see text] in the epilimnion 3–7 times atmospheric levels) and the doubling of the total dissolved inorganic carbon (DIC) content of the epilimnion. The major source of carbon for these two processes was the entrainment of dissolved inorganic carbon as the epilimnion deepened during the cool days of late summer. Particulate organic carbon was also entrained and its oxidation contributed to the net DIC increase and CO2 loss. Simultaneous determinations of daily integral primary productivity by an incubator technique and by direct measurement of 14C uptake inside the enclosure were consistent. Dark respiration was 45–53% of daily integral primary productivity, but total respiration was nearly two times that for dark plus light respiration. Net primary productivity was thus substantially negative.Key words: Gas exchange, photosynthetic uptake, carbon budget
Comparison of Fin-Ray and Scale Age Determinations for Lake Whitefish (Coregonus clupeaformis) and Their Implications for Estimates of Growth and Annual Survival
Authors: Mills K. H. , Beamish R. J.
Published: October 2008

Fifteen populations of lake whitefish (Coregonus clupeaformis) were sampled to compare the fin-ray and scale aging techniques. There was good agreement between aging methods in fast growing populations, but usually fin-ray ages were larger than scale ages in slow-growing populations. The validity of each aging method was tested by comparing fin-ray and scale ages taken from three populations of whitefish when marked and when recaptured at least 1 yr later. When growth was rapid, recaptured fish formed annular marks on both fin-rays and scales. When growth was slower, annular marks were distinguished on fin-ray sections more often than on scales of recaptured fish. When growth was extremely poor, annular marks on scales of recaptured fish were rarely distinguishable, but still recognizable on the majority of fin-ray sections. When fin-ray ages were consistently larger than scale ages for a given population, fin-ray based estimates of annual survival were higher and growth slower than corresponding scale age based estimates. In general, the fin-ray method was more reliable than the scale method of aging lake whitefish.Key words: lake whitefish, age determination, scales, fin-rays, annual survival, growth
In Situ Measurements of Pore Water Diffusion Coefficients Using Tritiated Water
Authors: Hesslein R. H.
Published: October 2008

In situ diffusion coefficients in the pore waters of Lake 227 were measured by monitoring the movement of tritiated water into the pore waters. The diffusion coefficients were determined by analytical and numerical modeling of the tritium profiles. During the summer, tritiated water diffuses into the sediment by molecular diffusion and this process is well approximated by a constant diffusivity model. The summer coefficients for diffusion were 1–2 × 10−5 cm2∙s−1 at a water depth of 1.5 m (20 °C) and 0.3–0.8 × 10−6 cm2∙s−1 at 8.75 m (4 °C). During fall overturn, clear evidence was found for enhanced mixing of pore waters to a sediment depth of 10 cm at water depths of 0.75 and 3.85 m. This enhanced mixing was not accompanied by mixing of the solid phase of the sediments.Key words: sediments, pore water, diffusion coefficients, tritium, lake sediments
Relationships among Smolt Size, Marine Growth, and Sea Age at Maturity of Atlantic Salmon (Salmo salar) in Northern Spain
Authors: Nicieza A. G. , Braña F.
Published: October 2008

Scale analysis indicated that two-sea-winter (2SW) Atlantic salmon (Salmo salar) had a greater growth increment during the first year at sea than 1SW of the same smolt year in the Rivers Narcea and Esva, but no differences were found between sea age-classes in the River Cares. Interannual variation in marine growth was synchronized among rivers. Variation among years was greater than variation between sea age-classes, suggesting that marine growth per se does not determine age at maturity. In the River Narcea, 2SW salmon were larger than 1SW at the end of the first marine period, but differences between sea age-groups were not significant in the other two rivers. Some of this variability could be attributed to differences in size at smolting; for two rivers (Esva and Cares), 1SW salmon had been larger as smolts than 2SW salmon. Length increment during the first marine growth period was inversely correlated with smolt size (age-1 smolts); in spite of that compensatory effect, large smolts tended to maintain their size advantage at the time of formation of the first marine annulus, as indicated by positive correlations between smolt size and length at the first sea winter.
Spectral Characteristics of Salmonid Migratory Routes from Southern Vancouver Island (British Columbia)
Authors: Flamarique Iñigo Novales , Hawryshyn Craig W.
Published: October 2008

Spectral irradiance was measured from 300 to 850 nm under clear and overcast skies in Saanich Inlet and Trevor Channel (Vancouver Island) using an underwater spectroradiometer. The values obtained were corrected for ocular media transmission and pigment absorption of the four visual pigments in small rainbow trout, Oncorhynchus mykiss (UV, short, middle, and long wavelength sensitive), to estimate the light available to stimulate each of these photoreceptors. Light levels were compared with particle counts, Chl a, and dissolved organic matter (DOM) concentrations at various sites and with similar parameters previously measured for freshwater systems. There was sufficient light to stimulate all the photoreceptors down to 15 m, which was the limiting depth in Saanich Inlet for UV cone simulation and for stimulation of the β absorption band of middle wavelength cones. UV light levels diminished with increasing DOM and Chl a concentrations; however, no statistically discernable relationship was found between UV levels and Chl a concentrations with distance from the spawning rivers. Under completely overcast conditions, directionality of the sun's rays is maintained under some types of cloud cover. This indicates that navigation using polarized light may occur under variable atmospheric conditions provided enough polarized light is present in the water column.
Elevated Levels of Arginine Vasotocin in the Brain of Brook Trout (Salvelinus fontinalis) from Acid Lakes: A Field Test of a Potential Biomarker for Acid Stress
Authors: Hontela A. , Rasmussen J. B. , Lederis K. , Tra H. V. , Chevalier G.
Published: October 2008

The levels of arginine vasotocin (AVT), an osmoregulatory peptide, were determined by radioimmunoassay in brain tissue of brook trout (Salvelinus fontinalis) of a wide size range (50–380 mm) from softwater Laurentian lakes ranging in pH from 5.0 to 6.9 at different seasons. Multivariate models (ANCOVA) were developed to quantify the relationship between AVT, pH, body size, and season. Brain AVT levels increased with body size, and the allometric slope was highest in the low-pH lakes (pH 5.0-5.5). Although brook trout > 150 mm had higher brain AVT levels at low pH, no significant differences were detected for brook trout < 150 mm. We hypothesize that the sensitivity of brook trout at the parr stage to acid stress may be linked to their inability to mobilize a hormonal response involving AVT. The seasonal variation in brain AVT levels was similar in all the lakes studied, summer levels being the highest. Although this field study revealed that AVT levels depend also on factors other than acid stress (body size and season), our ANCOVA models allow adjustment for the effects of these covariables. Analyses of this type can be used to field test and calibrate biomarkers for use in ecotoxicology.
Harvesting Strategies and Fishing Mortality Reference Point Comparisons for the Northwest Atlantic Stock of Atlantic Mackerel (Scomber scombrus)
Authors: Overholtz William J.
Published: October 2008

Previous research indicated that density dependence in population-level responses such as growth and predation mortality rate may play a major role in regulating the dynamics of the Northwest Atlantic stock of Atlantic mackerel (Scomber scombrus). Simulation studies, utilizing this compensatory model of the mackerel stock, suggest that expected yields and spawning stock sizes under conditions of constant harvest rate or constant catch would be quite disparate. Yields and spawning stock size would be less variable and slightly larger under a constant catch strategy for catches of mackerel up to approximately 200 000 t. However, a constant harvest rate strategy would provide higher long-term yields and a more stable spawning stock at catches greater than 200 000 t. A comparison of a constant catch policy with F0.1, F20, and Fmax fishing strategies (constant F) suggests that the Fmax and F20 strategies would cause a long-term decline in the spawning stock below the current minimum spawning stock target and provide highly variable yields. A constant catch strategy could produce nearly the same level of yield with considerably less variability and maintain a larger mean spawning stock biomass than the F0.1 strategy.
Comparison of Dynamic Models for Edible Phytoplankton
Authors: Carpenter Stephen R. , Lathrop Richard C. , Muñoz-del-Rio Alejandro
Published: October 2008

Alternative models for the dynamics of edible phytoplankton were compared using long-term data from mesotrophic Paul Lake and eutrophic Lake Mendota. Alternative models fit to the data contrasted linear versus logistic algal growth, type I versus type II functional response, and prey-dependent versus ratio-dependent predation. In both lakes, the model with lowest prediction error had logistic algal growth and a type I, prey-dependent functional response. Under these models, the spring bloom and clear-water phase of productive lakes can be explained as an incomplete predator–prey cycle: the spring pulse of edible algae is followed by a peak of Zooplankton; then, edible algae are overgrazed leading to the clear-water phase and collapse of the grazer biomass. This study demonstrates the use of time series data at the ecosystem scale to identify process-based models, contrast alternative models on a probabilistic basis, and estimate parameters. This approach avoids the assumptions involved in extrapolating ecosystem models from smaller scale studies.
THREE-DIMENSIONAL EXTERIOR PROBLEM OF DARWIN MODEL AND ITS NUMERICAL COMPUTATION
Authors: FANG NENGSHENG , YING LUNG-AN
Published: October 2008

Darwin model is a good approximation to Maxwell's equations, and this paper is concerned with the boundary value problem of the Darwin model in three-dimensional exterior domains. Firstly we establish the variational formulations of Darwin model in exterior domains and prove the existence and uniqueness. Then we prove a useful decomposition theorem that any function in unbounded exterior domains belonging to L2(Ω) can be decomposed into the sum of a function's gradient and another function's rotation, such decomposition is crucial in inducing the Darwin model. At last we spend some energy in using the infinite element method to solve the Darwin model in axis-symmetric exterior domains cases. Error estimates are obtained in weighted spaces, and numerical examples verify the convergence once again.
NUMERICAL EVIDENCE FOR THE NON-EXISTENCE OF STATIONARY SOLUTIONS OF THE EQUATIONS DESCRIBING ROTATIONAL FIBER SPINNING
Authors: GÖTZ THOMAS , KLAR AXEL , UNTERREITER ANDREAS , WEGENER RAIMUND
Published: October 2008

The stationary, isothermal rotational spinning process of fibers is considered. The investigations are concerned with the case of large Reynolds (δ = 3/ Re ≪ 1) and small Rossby numbers (ε ≪ 1). Modelling the fibers as a Newtonian fluid and applying slender body approximations, the process is described by a two-point boundary value problem of ODEs. The involved quantities are the coordinates of the fiber's centerline, the fluid velocity and viscous stress. The inviscid case δ = 0 is discussed as a reference case. For the viscous case δ > 0 numerical simulations are carried out. Transfering some properties of the inviscid limit to the viscous case, analytical bounds for the initial viscous stress of the fiber are obtained. A good agreement with the numerical results is found. These bounds give strong evidence, that for δ > 3ε2 no physical relevant stationary solution can exist.
CLASSIFICATION OF CLOSED VIRTUAL 2-BRAIDS
Authors: KADOKAMI TERUHISA
Published: October 2008

We classify closed virtual 2-braids completely as virtual links. For the proof, we use surface bracket polynomial due to Dye and Kauffman, Kuperberg's theorem which states existence and uniqueness of a minimal realization for a virtual link, and a subgroup of the 3-braid group.
THISTLETHWAITE'S THEOREM FOR VIRTUAL LINKS
Authors: CHMUTOV SERGEI , VOLTZ JEREMY
Published: October 2008

The celebrated Thistlethwaite theorem relates the Jones polynomial of a link with the Tutte polynomial of the corresponding planar graph. We give a generalization of this theorem to virtual links. In this case, the graph will be embedded into a (higher genus) surface. For such graphs we use the generalization of the Tutte polynomial discovered by Bollobás and Riordan.
ALEXANDER POLYNOMIAL FOR EVEN GRAPHS WITH REFLECTIVE SYMMETRY
Authors: JIN XIAN'AN , ZHANG FUJI
Published: October 2008

Based on the connection with Alexander polynomial of special alternating links, Murasugi and Stoimenow introduced the Alexander polynomial of even graphs. In this paper, we study the Alexander polynomial of spatial even graphs with reflective symmetry. Roughly speaking, we prove that the Alexander polynomial of one half of a spatial even graph with reflective symmetry is a divisor of that of the whole spatial even graph. Then, we apply the result to a family of special alternating links, expressing the Alexander polynomial of such a link as the product of Alexander polynomials of two smaller special alternating links derived from the two isotopic "halves" of the original link.
FACTORING FAMILIES OF POSITIVE KNOTS ON LORENZ-LIKE TEMPLATES
Authors: SULLIVAN MICHAEL C.
Published: October 2008

We show that for m and n positive, composite closed orbits realized on the Lorenz-like template L(m, n) have two prime factors, each a torus knot; and that composite closed orbits on L(-1, -1) have either two for three prime factors, two of which are torus knots.
BACKWARD BIFURCATION IN A DISCRETE SIS MODEL WITH VACCINATION
Authors: JANG SOPHIA R.-J.
Published: October 2008

A simple discrete SIS model with vaccination is proposed. Its dynamics depend on a lumped parameter R vac . The model exhibits the classical threshold behavior when vaccination is totally ineffective. When vaccination is partially effective, a backward transcritical bifurcation may occur at R vac = 1. In this case, the model also undergoes a saddle–node bifurcation at certain parameter values when R vac < 1. The disease can persist for R vac > 1 and can be eradicated for R vac < 1 if a forward transcritical bifurcation occurs at R vac = 1. However, the disease may persist even when R vac < 1 if a backward bifurcation occurs at R vac = 1.
DYNAMICS OF A MODEL FOR VIRULENT PHAGE T4
Authors: QIU ZHIPENG
Published: October 2008

In this paper, the asymptotical behavior of a chemostat model for E. coli and the virulent phage T4 is analyzed. The basic reproduction number R0 is proved to be a threshold which determines the outcome of the virulent phage T4. If R0 < 1, the virus dies out; if R0 > 1, the virus persists. Sufficient conditions for the Hopf bifurcation are also established. The theoretical results show that increasing the input of nutrient will result in an increase in the equilibrium population density of the virulent bacteriophage T4, but will have no effect on the equilibrium population density of E. coli. The results also show that increasing the input of nutrient or increasing the average lytic time for the infected E. coli can destabilize the interaction between E. coli and T4.
SELECTIVITY IMPROVEMENT IN A MODEL OF OLFACTORY RECEPTOR NEURON WITH ADSORPTION-DESORPTION NOISE
Authors: VIDYBIDA A. K. , USENKO A. S. , ROSPARS J.-P.
Published: October 2008

In biological olfactory systems, interaction of odorant molecules with olfactory receptor proteins is driven by Brownian motion. As a result, at chemical equilibrium, the total number of bound receptors changes randomly in time. Here we investigate the role of this effect, known in physics as adsorption-desorption noise, in the discriminating ability of olfactory receptor neurons. For this purpose we developed a computer program, which generates the adsorption-desorption process in a model neuron. We compared the processes resulting from two different odorants with different affinities for the receptor proteins. We took into account the threshold at which spikes are triggered and we calculated the neuronal selectivity due to the differences in the threshold-crossing statistics for the processes resulting from both odorants. We conclude that selectivity of the spiking response of the whole neuron is much greater than that of its receptor proteins in the near-threshold range of odorant concentrations.
STOCHASTIC CAHN–HILLIARD EQUATION WITH FRACTIONAL NOISE
Authors: BO LIJUN , JIANG YIMING , WANG YONGJIN
Published: October 2008

We study the existence and uniqueness of global mild solutions to a class of stochastic Cahn–Hilliard equations driven by fractional noises (fractional in time and white in space), through a weak convergence argument.
Involvement of the p66Shcprotein in glucose transport regulation in skeletal muscle myoblasts
Authors: Natalicchio Annalisa , De Stefano Francesca , Perrini Sebastio , Laviola Luigi , Cignarelli Angelo , Caccioppoli Cristina , Quagliara Anna , Melchiorre Mariangela , Leonardini Anna , Conserva Antonella , Giorgino Francesco
Published: October 2008

The p66Shcprotein isoform regulates MAP kinase activity and the actin cytoskeleton turnover, which are both required for normal glucose transport responses. To investigate the role of p66Shcin glucose transport regulation in skeletal muscle cells, L6 myoblasts with antisense-mediated reduction (L6/p66Shcas) or adenovirus-mediated overexpression (L6/p66Shcadv) of the p66Shcprotein were examined. L6/Shcas myoblasts showed constitutive activation of ERK-1/2 and disruption of the actin network, associated with an 11-fold increase in basal glucose transport. GLUT1 and GLUT3 transporter proteins were sevenfold and fourfold more abundant, respectively, and were localized throughout the cytoplasm. Conversely, in L6 myoblasts overexpressing p66Shc, basal glucose uptake rates were reduced by 30% in parallel with a ∼50% reduction in total GLUT1 and GLUT3 transporter levels. Inhibition of the increased ERK-1/2 activity with PD98059 in L6/Shcas cells had a minimal effect on increased GLUT1 and GLUT3 protein levels, but restored the actin cytoskeleton, and reduced the abnormally high basal glucose uptake by 70%. In conclusion, p66Shcappears to regulate the glucose transport system in skeletal muscle myoblasts by controlling, via MAP kinase, the integrity of the actin cytoskeleton and by modulating cellular expression of GLUT1 and GLUT3 transporter proteins via ERK-independent pathways.
Role of Primate Cerebellar Hemisphere in Voluntary Eye Movement Control Revealed by Lesion Effects
Authors: Ohki Masafumi , Kitazawa Hiromasa , Hiramatsu Takahito , Kaga Kimitake , Kitamura Taiko , Yamada Jinzo , Nagao Soichi
Published: October 2008

The anatomical connection between the frontal eye field and the cerebellar hemispheric lobule VII (H-VII) suggests a potential role of the hemisphere in voluntary eye movement control. To reveal the involvement of the hemisphere in smooth pursuit and saccade control, we made a unilateral lesion around H-VII and examined its effects in three Macaca fuscata that were trained to pursue visually a small target. To the step (3°)-ramp (5–20°/s) target motion, the monkeys usually showed an initial pursuit eye movement at a latency of 80–140 ms and a small catch-up saccade at 140–220 ms that was followed by a postsaccadic pursuit eye movement that roughly matched the ramp target velocity. After unilateral cerebellar hemispheric lesioning, the initial pursuit eye movements were impaired, and the velocities of the postsaccadic pursuit eye movements decreased. The onsets of 5° visually guided saccades to the stationary target were delayed, and their amplitudes showed a tendency of increased trial-to-trial variability but never became hypo- or hypermetric. Similar tendencies were observed in the onsets and amplitudes of catch-up saccades. The adaptation of open-loop smooth pursuit velocity, tested by a step increase in target velocity for a brief period, was impaired. These lesion effects were recognized in all directions, particularly in the ipsiversive direction. A recovery was observed at 4 wk postlesion for some of these lesion effects. These results suggest that the cerebellar hemispheric region around lobule VII is involved in the control of smooth pursuit and saccadic eye movements.
Treatment of Low-Grade Bulbar Transitional Cell Carcinoma with Urethral Instillation of Mitomycin C
Authors: Melonakos Emmanuel J. , Santucci Richard A.
Published: October 2008

A 63-year old man was referred to us after three rapid recurrences of low-grade urethral papillary transitional cell carcinoma of the bulbar urethra, after repeated primary excision. Cystoscopy confirmed 3-4 low-grade urethral transitional cell carcinomas, which were subsequently fulgurated. After urethral healing, a solution of Mitomycin C (40 mg/80 cc) was instilled into the urethra for fifteen minutes and held in place with a penile clamp. Urethral instillations were repeated weekly for six weeks. The patient is currently disease-free more than one year and three months posttreatment. This case highlights the successful treatment of urethral carcinoma with topical chemotherapy, which is usually reserved for the bladder, using a slight modification of standard technique.
Is Port State Control an Effective Means to Combat Vessel-Source Pollution? An Empirical Survey of the Practical Exercise by Port States of Their Powers of Control
Authors: Bang Ho-Sam
Published: October 2008

It has become conventional wisdom that because flag states have been unwilling or unable to exercise effective jurisdiction or control over their vessels, port states have a major role to play in combating sub-standard ships and reducing vessel-source pollution. This article seeks to test conventional wisdom by examining in practice how far port states have exercised their powers of control against sub-standard ships and contributed to reducing vessel-source operational pollution.
Inner Dynamics of the Chinese House Church Movement: The Case of the Word of Life Community
Authors: Xin Yalin
Published: October 2008

The Word of Life house church movement is considered to be one of the most influential Christian movements in China for the past three decades, with its network touching all 23 provinces and autonomous zones in China. It is also one of the largest house church networks that emerged in central China in the past three decades. This paper gears at investigating the inner dynamics that has underscored the growth and vitality of the movement by incorporating some insights from studies on historical Christian renewal movements. A variety of categories or models are employed, such as paradigm shifts, the role of key leaders, its basic structure, system of training, community, gospel for the poor, dynamic and vitality, through which the WOL movement is closely examined. Hopefully, this paper opens a window of understanding of the Word of Life movement and yields some insights that may be referenced in the larger hermeneutical community.
The Integration of Mission Theology and Practice: Zinzendorf and the Early Moravians
Authors: Gallagher Robert
Published: October 2008

This paper explores the key characteristics of Count Nikolaus Ludwig von Zinzendorf's mission theology that influenced the early Moravian missional practice. After discussing the early eighteenth century European historical context and the Spirit-renewal of the Herrnhut community, the paper considers Zinzendorf's theology on the death of Christ, the prominent role of the Holy Spirit, and harvesting the "first fruits." These theological distinctives contributed in determining the motivation and message of these pioneer Protestant missionaries. It then takes into account some of the subsequent methods such as working with the marginalized, practicing the love of Christ in cultural humility, and preaching the gospel in the vernacular. The main contributions of the early Moravians to mission were that they brought an understanding that spiritual renewal preceded mission renewal, the atoning death of Christ is central to mission theology, and a Protestant recognition that it had an obligation to do mission. On the other hand, the foremost negative aspects of Moravian mission were their obsession with the physical death of Christ and an ignorance of the broader social issues that at times resulted in a lack of contextualization, religious syncretism, indifference to social justice, and extreme subjectivism.
Bishop Vincent McCauley, CSC: Ecumenical Pioneer
Authors: Gribble Richard
Published: October 2008

Vincent McCauley, bishop and missionary, was a great champion of the Second Vatican Council (1962–1965). As Bishop of Fort Portal, Uganda, a new diocese in the Western portion of the country (1961–1971), McCauley was instrumental in the full implementation of the 16 documents of Vatican II, but his principal legacy will be his work in the area of ecumenism. Overcoming significant and long standing hostility between Roman Catholics and Anglicans, McCauley was able to forge ecumenical dialogue and programs on various levels. Beginning simply through prayer services and a vernacular translation of the New Testament, he graduated to be a founder and initial chairman of the Uganda Joint Christian Council (UJCC), an organization which made great strides in removing government opposition to religion and forging dialogue between Christians in areas of sacraments and social justice. Both simultaneously and after his tenure in Fort Portal, McCauley served as chairman and secretary general of the Association of Member Episcopal Conferences of Eastern Africa (AMECEA). These positions allowed him to continue his ecumenical work on a broader scope.He was instrumental in setting up numerous conferences to foster ecumenical dialogue, various pastoral programs and certain educational initiatives, including the Interdisciplinary Urban Seminar, for which McCauley served as a member of the Academic Board. He was also integrally involved as a member of the advisory board of the Christian Organization Research and Advisory Trust (CORAT), an organization that sought to train church members in organization and management.Vincent McCauley stands as a significant example of one who implemented the ecumenical teachings of Vatican II on local and regional levels. His contribution continues to serve the church in Eastern Africa today.
To Have and to Have Not
Authors: Bancroft Kim
Published: October 2008

This year-long ethnographic study analyzed three California charter middle schools: one served mostly low-income, urban African American students; the second served students from working class Latino families; and the third served a middle class, predominantly White suburb. The study illustrates how socioeconomic context of a charter school's community, combined with charter reforms, affect school operations. Significantly, charters serving poor students lacked resources to fulfill their needs, and teachers lacked necessary professional development. As a result of financial and pedagogical difficulties, some charters took a more selective approach to finding students who would help the school, and its teachers, succeed.
Surface characterisation of electroless copper plated polyester fibres
Authors: Guo R. H. , Jiang S. Q. , Yuen C. W. M . , Ng M. C. F.
Published: October 2008

Electroless copper plating on polyester fibres was investigated in this work to develop functional textiles. The surface modification of copper plated polyester fibres was characterised by the scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscope. A possible mechanism of electroless copper plating on polyester was proposed. The results showed that copper particles with high purity were uniformly deposited of polyester fibres and the copper film had a rather perfect crystal structure, demonstrating that electroless deposition was a suitable technique for the uniform deposition of copper.
CXCR4 expression and biologic activity in acute myeloid leukemia are dependent on oxygen partial pressure
Authors: Fiegl Michael , Samudio Ismael , Clise-Dwyer Karen , Burks Jared K. , Mnjoyan Zakar , Andreeff Michael
Published: October 2008

The CXCR4/SDF-1 axis has been studied extensively because of its role in development and hematopoiesis. In acute myeloid leukemia (AML), elevated expression of CXCR4 has been shown to correlate with shortened survival. Hy-poxia increases CXCR4 in several tumor models, but the impact of reduced O2 partial pressure (pO2) on expression and biologic function of CXCR4 in AML is unknown. We determined pO2 in bone marrows of AML patients as 6.1% (±1.7%). At this pO2, CXCR4 surface and total expression were up-regulated within 10 hours in leukemic cell lines and patient samples as shown by Western blotting, fluorescence-activated cell sorting, and microscopy. Interestingly, hypoxic cells failed to internalize CXCR4 in response to SDF-1, and upon reoxygenation at 21% O2, surface and total expression of CXCR4 rapidly decreased independent of adenosine triphosphate or proteasome activity. Instead, increased pO2 led to alteration of lipid rafts by cholesterol depletion and structural changes and was associated with increased shedding of CXCR4-positive microparticles, suggesting a novel mechanism of CXCR4 regulation. Given the importance of CXCR4 in cell signaling, survival, and adhesion in leukemia, the results suggest that pO2 be considered a critical variable in conducting and interpreting studies of CXCR4 expression and regulation in leukemias.
The role of positive selection in determining the molecular cause of species differences in disease
Authors: Vamathevan Jessica J , Hasan Samiul , Emes Richard D , Amrine-Madsen Heather , Rajagopalan Dilip , Topp Simon D , Kumar Vinod , Word Michael , Simmons Mark D , Foord Steven M , Sanseau Philippe , Yang Ziheng , Holbrook Joanna D
Published: October 2008

Background

Related species, such as humans and chimpanzees, often experience the same disease with varying degrees of pathology, as seen in the cases of Alzheimer's disease, or differing symptomatology as in AIDS. Furthermore, certain diseases such as schizophrenia, epithelial cancers and autoimmune disorders are far more frequent in humans than in other species for reasons not associated with lifestyle. Genes that have undergone positive selection during species evolution are indicative of functional adaptations that drive species differences. Thus we investigate whether biomedical disease differences between species can be attributed to positively selected genes.

Results

We identified genes that putatively underwent positive selection during the evolution of humans and four mammals which are often used to model human diseases (mouse, rat, chimpanzee and dog). We show that genes predicted to have been subject to positive selection pressure during human evolution are implicated in diseases such as epithelial cancers, schizophrenia, autoimmune diseases and Alzheimer's disease, all of which differ in prevalence and symptomatology between humans and their mammalian relatives.

In agreement with previous studies, the chimpanzee lineage was found to have more genes under positive selection than any of the other lineages. In addition, we found new evidence to support the hypothesis that genes that have undergone positive selection tend to interact with each other. This is the first such evidence to be detected widely among mammalian genes and may be important in identifying molecular pathways causative of species differences.

Conclusion

Our dataset of genes predicted to have been subject to positive selection in five species serves as an informative resource that can be consulted prior to selecting appropriate animal models during drug target validation. We conclude that studying the evolution of functional and biomedical disease differences between species is an important way to gain insight into their molecular causes and may provide a method to predict when animal models do not mirror human biology.
A homogenous nature of native Chinese duck matrilineal pool
Authors: He Da-Qian , Zhu Qing , Chen Shi-Yi , Wang Hui-Ying , Liu Yi-Ping , Yao Yong-Gang
Published: October 2008

Background

China, with around 30 unique breeds, has a diverse duck genetic pool. Currently, there is no systematic report which investigates the genetic diversity, phylogenetic relationship, and matrilineal genetic structure of these domestic breeds and wild mallards (Anas platyrhynchos).

Results

In this study, we sequenced the mitochondrial DNA (mtDNA) control region segments in 278 domestic ducks (Anas platyrhynchos domestica) from 19 indigenous breeds/populations and 70 wild mallard samples and analyzed them together with the 101 control region sequences from published sources. Fifty-two samples were then sequenced for a cytochrome b (Cyt b) gene fragment to solidify the pattern emerged from the control region sequences. All domestic duck and wild mallard haplotypes were essentially indistinguishable and were clustered together in the phylogenetic tree. There was no geographic differentiation and breed/population-specific distribution of duck lineages.

Conclusion

Our results showed that unlike other domesticated farm animals in China such as chicken, cattle, goat, and yak with multiple matrilineal components, the matrilineal pool of Chinese ducks was homogenous.