bluuebunny/crossref_metadata_2025 huggingface dataset:
Hormone-induced Ovulation of Coho Salmon (Oncorhynchus kisutch) Held in Seawater and Fresh Water
Authors: Sower Stacia A. , Schreck Carl B. , Donaldson Edward M.
Published: June 2008

Coho salmon (Oncorhynchus kisutch) mature and spawn naturally in fresh water. We investigated the feasibility of accelerating maturation and/or ovulation of coho salmon retained in seawater during the spawning season, and compared accelerated ovulation of coho salmon in seawater and in fresh water. Effective inducers of ovulation in salmon held in fresh water were partly purified or purified salmon gonadotropin followed 3 d later by luteinizing hormone releasing hormone analogue (LH-RHa); one injection of salmon pituitary extract (SPE); chum salmon pituitary (PIT) followed at 3 d by PIT; and one injection of 17α-hydroxy-20β-dihydroprogesterone. One injection of chinook SPE; coho SPE followed at 3 d by coho SPE; or partly purified or purified salmon gonadotropin followed at 3 d by LH-RHa were effective but to a much lesser extent in those salmon held in seawater. PIT followed at 3 d by PIT, or one injection of 17α-hydroxy-20β-dihydroprogesterane were ineffective in acceleration of maturation/ovulation of coho salmon retained in seawater. Cortisone or 20β-hydroxyprogesterone, which were only tested in salmon in seawater, also failed to elicit early ovulation compared with controls. We conclude that ovarian responses to the treatments of fish retained in seawater are reduced by osmoregulatory difficulties or high adult mortalities. Thus acceleration of ovulation of coho salmon held in seawater is not feasible at this time and requires further research.Key words: coho salmon, spawning, ovulation, induced breeding, gonadotropin, luteinizing hormone releasing hormone analogue
Some Estimates of Population Density and Feeding Habits of the Rock Crab, Cancer irroratus, in a Kelp Bed in Nova Scotia
Authors: Drummond-Davis N. C. , Mann K. H. , Pottle R. A.
Published: June 2008

The population density of rock crabs (Cancer irroratus) in a kelp bed on the Atlantic coast of Nova Scotia was examined by mark–recapture techniques and found to be about one crab (> 45-mm carapace width) per 2 square metres. Prey taken by the crabs included hermit crabs (Pagurus), mussels (Mytilus), sea urchins (Strongylocentrotus), and various small crustaceans and polychaetes. It was concluded that the crab population would exert a strong predation pressure on these invertebrates.Key words: Cancer irroratus, rock crabs, predation, population density, kelp
Evaluating Forecasting Procedures for Predicting Pacific Herring (Clupea harengus pallasi) Recruitment in British Columbia
Authors: Stocker M. , Noakes D. J.
Published: June 2008

The ability of four forecasting methods to generate one-step-ahead forecasts of Pacific herring (Clupea harengus pillasi) recruitment is considered in this paper. Recruitment time series for five coastal stocks and various environmental time series are employed in the analyses. Information up to and including time t is employed to estimate the parameters of each model used to forecast recruitment in year t + 1. Parameter estimates are then updated after each time step with a total of seven one-step-ahead forecasts being generated by each model for each stock. The forecast errors are compared using the five criteria: (1) root mean squared error, (2) mean absolute deviation, (3) mean absolute percent error, (4) median absolute deviation, and (5) median absolute percent error. The results of the study indicate that time series models may provide better forecasts of recruitment for the Strait of Georgia/Johnstone Strait stocks than the other competing procedures. A Ricker stock–recruitment model that takes into account environmental data appears to produce marginally better forecasts for the Central Coast and Queen Charlotte Island stocks, while all models produced equally good/bad forecasts for the Prince Rupert district stocks.
Using the Bootstrap to Assess Statistical Significance in the Cluster Analysis of Species Abundance Data
Authors: Nemec A. F. L. , Brinkhurst R. O.
Published: June 2008

Clustering techniques are frequently used to analyze species abundance data, despite a lack of objective criteria for assessing the results of such analyses. We show that a nonparametric statistical technique known as the "bootstrap" can, in certain circumstances, be used to overcome this deficiency. The bootstrap uses the distributional properties of a "bootstrap sample", i.e. a sample obtained by an appropriate resampling of the data, to make statistical inferences about the underlying population. The method is versatile and can be readily applied to complex hypothesis testing problems, since the statistical properties of a bootstrap sample can always be determined by simulation. To illustrate the application of the bootstrap to the cluster analysis of ecological data, we derive a test for the "statistical significance" of clusters of communities and show that two dendrograms can be compared by bootstrapping the Fowlkes–Mallow statistic.
Interactions between Brook Charr, Salvelinus fontinalis, and Nonsalmonid Species: Ecological Shift, Morphological Shift, and Their Impact on Zooplankton Communities
Authors: Magnan Pierre
Published: June 2008

A quantitative survey of 26 oligotrophic Quebec lakes indicated that the presence of creek chub (Semotilus atromaculatus) or white sucker (Catostomus commersoni) had an impact on brook charr (Salvelinus fontinalis) populations. Evidence for competitive interactions among these species was provided by the observation that (1) the mean annual yield (kilograms per hectare) of charr was significantly reduced when they lived sympatrically with these species, (2) charr shifted their food habits from benthic organisms to Zooplankton in the presence of creek chub and (or) white sucker, and (3) the length of the gill rakers of charr was significantly higher in lakes containing chubs and suckers. As the length of the gill rakers is reported to be correlated with the extent of plankton feeding, this latter result was interpreted as a morphological change associated with increased exploitation of Zooplankton in sympatry. When occurring with creek chub, the niche shift of brook charr resulted in a significant change in Zooplankton community structure. The proportion of large Zooplankton organisms (>1.1 mm) declined whereas that of the smaller ones (<0.6 mm) increased. Also, the mean length of Holopedium, the larger cladocerans, was significantly reduced in sympatric creek chub–charr lakes compared with lakes where charr lived allopatrically. A similar impact on Zooplankton was not as clear when charr occurred with white sucker. When living with white sucker, brook charr populations appeared to be sufficiently reduced as to have little or no effect on Zooplankton communities.
Dynamics of Age and Size for a Stochastic Population Model
Authors: Deriso Richard B. , Parma Ana M.
Published: June 2008

We derive a fully stochastic model for the dynamics of age and size in a population. The key to our derivation is that the assumptions made about stochastic growth and survival, in conjunction with some approximations made in the analysis of size-selective fishing mortality, allow us to propagate through time the probability density function of size of individuals in the population by a recursive update of its parameters. The model permits a concise description of the size distribution at age based on mean log-length and variance. The stochastic process is characterized in the model in just a few parameters: two growth coefficients, one variance parameter associated with growth, instantaneous risk of natural mortality, instantaneous risk of fishing mortality, which is a separable function of size-specific selectivity and annual full recuitment fishing mortality, and initial conditions (year-class strength, initial size distribution). Estimation theory is developed for the model, and likelihood equations are derived which provide statistical principles for setting the trade-off between fitting data on length frequency, on total biomass of catch, and on age frequency. The tractability of the model permits a clear description of sampling probability distributions. A number of simpler models, such as catch-age models and delay-difference models, fit within the theoretical framework of our stochastic model.
Effects of Climatic and Density-Dependent Factors on Year-Class Strength of Coregonus lavaretus in Lake Constance
Authors: Eckmann Reiner , Gaedke Ursula , Wetzlar Hans Johst
Published: June 2008

The influences of density-dependent and density-independent factors on year-class strength (YCS) of Coregonus lavaretus in Lake Constance were studied by multiple linear regression analyses for the period from 1962 to 1982. Meteorological conditions that lead to early thermal stratification of the lake in April are of prime importance for YCS and account for 41% of the total YCS variance. Zooplankton concentration during spring has no significant influence on YCS. The extensive stocking program on the lake (50–200 million larvae stocked per year) significantly supports YCS, but this relationship becomes apparent only after the influence of meteorological conditions are removed from the data. Conspecifics of age-classes 1 and 2 have a negative influence on the age 0 year-class, but the nature of this intraspecific competition remains unknown. No stock–recruitment relationship could be detected in this study. The final model includes five independent variables and accounts for 84% of the total YCS variance.
Interrelationship between in vivo Fluorescence of Phytoplankton and Light Beam Transmission with Reference to Fluorescence Yield
Authors: Vandevelde Thierry , Legendre Louis , Demers Serge , Therriault Jean-Claude
Published: June 2008

In vivo fluorescence and light beam transmission were simultaneously recorded during two cruises in the St. Lawrence estuary. Marked differences in the relationship between light beam attenuation (c(660)) and in vivo fluorescence (IVF) were observed (1) along a short transect and (2) between surface (<5 m) and underlying waters (5–15 m) for a series of vertical profiles at an anchor station. In both cases, the observed differences were related to changes in fluorescence yield. At the anchor station, however, several other factors could also have affected the c(660)–IVF relationship. Below 5 m, tight linear relationships between c(660) and IVF indicate that no major change took place in either fluorescence yield or the concentration of chlorophyll per cell. In such a case, the two measurements provide consistent estimates of phytoplankton biomass.
Energetic Constraints of Juvenile Chum Salmon (Oncorhynchus keta) Migrating in Estuaries
Authors: Wissmar Robert C. , Simenstad Charles A.
Published: June 2008

Experiments on fish feeding behavior, field measures of fish sizes, migration rate, and prey resources, and an energetic growth model are used to evaluate the growth of juvenile chum salmon (Oncorhynchus keta) during outmigration in an estuary. Fish growth is defined as the difference between energy intake and metabolic costs. Energy intake is estimated from prey densities and foraging parameters, namely pursuit swimming speeds and energetic expenditures, and prey handling and encounter rates. Relationships for foraging parameters as functions of fish sizes and field prey abundance are used to evaluate energy intake by fish in the estuary. This information and calculations of metabolic costs allow predictions of fish growth during the migration. Results show that metabolic costs of maintenance and migration lie in a delicate balance with food intake and growth. Growth efficiencies exceeding 20% occur when metabolic expenditures decline and energy intake rates permit growth without depletion of the food supply. Defining such energetic balances facilitates characterization of carrying capacities of coastal ecosystems and has implications for enhancement of juvenile fish growth and, in turn, fish survival and production at sea.
Effect of Long-Term Exposure to Acid, Aluminum, and Low Calcium on Adult Brook Trout (Salvelinus fontinalis). 1. Survival, Growth, Fecundity, and Progeny Survival
Authors: Mount D. R. , Ingersoll C. G. , Gulley D. D. , Fernandez J. D. , LaPoint T. W. , Bergman H. L.
Published: June 2008

Adult brook trout (Salvelinus fontinalis) were exposed to concentrations of acid, Al, and Ca representative of acidic and acid-sensitive surface waters. At low pH (4.42–5.03), survival and growth were reduced by elevated Al concentrations (486 μg/L) and low Ca concentrations (0.5 mg/L). Fecundity (number of eggs per female) was reduced by exposure to some treatment combinations, but this effect was mediated through reduced growth; number of eggs per unit body weight was not related to treatment. Viability of eggs from ail parental exposures was high when incubated in neutral water. In spite of this high viability, eggs from parents exposed to low Ca concentrations showed greater mortality when incubated in the parental exposure conditions than did eggs from unexposed parents. Although the potential for such "carryover effects" cannot be discounted, we conclude that impairment of egg production is not a likely mechanism for loss of brook trout populations from acidic surface waters.
Effect of Long-Term Exposure to Acidf Aluminum, and Low Calcium on Adult Brook Trout (Salvelinus fontimlis). 2. Vitellogenesss and Osmoregulation
Authors: Mount D. R. , Hockett J. R. , Gern W. A.
Published: June 2008

Adult brook trout (Salvelinus fontinalis) were exposed for 193 d (previtellogenesis to spawning) to six combinations of acid, Al, and low Ca. Survival and growth were reduced by low pH combined with low Ca concentrations. After 41 d of exposure, fish in ail low pH exposures showed depressed plasma osmolality and Na concentrations, but by day 97 this apparent osmoregulatory stress was compensated for in all but the most severe treatment (pH 4.97, 47 μg inorganic Al/L, 0.5 mg Ca/L). At the observed peak of yolking (day 147), fish exposed to this treatment also had mean concentrations of plasma estradiol, vitellogenin, and Ca of only half control values. Fecundity (eggs per female) was significantly reduced as well, but this reduction was due in part to decreased growth. Despite these abnormalities in ionoregulatory and reproductive physiology, fish in all treatment conditions produced mature eggs. Among fish in stressful conditions, individual variation in growth and physiological parameters appeared to be correlated with osmoregulatory status. We hypothesize that the suite of physiological disturbances observed are linked to osmoregulatory impairment.
Influence of Exchange Flow Between the Channel and Hyporheic Zone on Nitrate Production in a Small Mountain Stream
Authors: Triska Frank J. , Duff John H. , Avanzino Ronald J.
Published: June 2008

Variation in local exchange of flows between the channel and hyporheic zone produced temporally shifting concentration gradients of dissolved oxygen, nitrate, and ammonium in subsurface waters of a small, gravel-cobble bed stream. Channel water advected laterally supplied dissolved oxygen, and groundwater supplied ammonium to support hyporheic nitrification. Nitrate production was highest in sediment slurries from aerobic hyporheic sites, was absent at nearly anoxic sites, and was stopped by nitrification inhibitors (chlorate and nitrapyrin). Ammonium amendment to sediment slurries only slightly enhanced nitrate production indicating that sorption competed with biota for available substrate. Nitrate concentration increased from 75–130 μg N/L during 9 d of ammonium amendment to a hyporheic subsurface flow. Ammonium concentration rose slowly relative to a sulfate tracer initially, and declined slowly after cutoff as ammonium desorbed. Nitrate levels remained elevated for 6 d after cutoff as desorbed ammonium became biotically available. Interactions between the channel's hydrology, lithology, and biology such as we observed in nitrate production are probably more common than reported. However, the magnitude of the resulting nutrient flux will depend on factors which determine the depth and lateral extension of suitable hyporheic habitat.
Assessment of the Piscine Micronucleus Test as an in situ Biological indicator of Chemical Contaminant Effects
Authors: Carrasco Kenneth R. , Tilbury Karen L. , Myers Mark S.
Published: June 2008

The piscine micronucleus test was assessed for sensitivity and practicality as an in situ biological indicator of chemical contaminant exposure by an application to the peripheral blood of wild white croaker (Genyonemus lineatus) collected from polluted and reference areas along the California coast. The several types of variations from the usual erythrocyte nuclear morphology observed in the blood smears collected for this study were described and the frequencies were compared with measured levels of certain classes of contaminants in white croaker bile and liver, and in sediment collected at each site, in addition, the frequencies were also compared with the prevalence of idiopathic lesions in the livers of the croaker. However, the piscine micronucleus test appeared to lack sensitivity to the presence and effects of the measured contaminants because no association was detected between the frequencies of the erythrocyte nuclear variations and levels of chemical contamination, even though most of the observed variations resembled the published descriptions of variations presumed to be nuclear lesions in earlier investigations. Even if the test had been found to be sensitive, the Sow and variable frequencies of the observed nuclear lesions would present a serious difficulty to the useful application of the test.
Effect of Wind on the Recruitment of Canadian Arctic Cisco (Coregonus autumnalis) into the Central Alaskan Beaufort Sea
Authors: Fechhelm Robert G. , Griffiths William B.
Published: June 2008

The recruitment of age 0+ Arctic cisco (Coregonus autumnalis) from Canada into the Prudhoe Bay, Alaska, area for the period 1981–88 was compared with summer wind data collected at Barter Island, Alaska. Four years of poor recruitment (1981, 1982, 1984, and 1988) were characterized by winds with net easterly components [Formula: see text] for the period 1 July—15 August. Four years in which moderate to strong recruitment occurred (1983, 1985, 1986, and 1987) were characterized by winds with net easterly components [Formula: see text]. Results suggest that the recruitment of young-of-the-year Arctic cisco from Canada to central Alaska is strongly influenced by wind-driven currents along the Beaufort Sea coast. Recruitment may be impaired by the absence of "strong" east winds without the actual presence of prevailing west winds.
Variability in Agonistic Behaviour and Salinity Tolerance between and within Two Populations of Juvenile Chinook Salmon,Oncorhynchus tshawytscha, with Contrasting Life Histories
Authors: Taylor Eric B.
Published: June 2008

Agonistic behaviour and salinity tolerance were investigated in eight families of chinook salmon, Oncorhynchus tshawytscha, from two populations in the Nanaimo River, British Columbia. From emergence to 3 mo, there were small differences in agonistic behaviour among families within populations, but "First Lake" chinook had strikingly higher levels of agonistic behaviour than salmon from the "lower Nanaimo" population. Lower Nanaimo chinook were larger, lost less weight, and had higher survival after 24 h in 20 ppt and 30 ppt seawater than First Lake salmon. Within populations, families of larger than average size tended to perform better in seawater than families of smaller size. At a common body size, salinity tolerance was similar in salmon from the two populations, but significant differences among families within populations suggest that families may differ in factors other than size that influence salinity tolerance. It was concluded that the greater agonistic behaviour of First Lake chinook has a genetic basic and is related to their longer period of territorial stream residence before seaward migration. By contrast, the two populations exhibited only small differences in salinity tolerance, but significant interfamily variation illustrates the importance of considering family effects in studies of interpopulation differentiation.
Importance of Smolt Size and Early Ocean Growth to Interannual Variability in Marine Survival of Coho Salmon (Oncorhynchus kisutch)
Authors: Holtby L. Blair , Andersen Bruce C. , Kadowaki Ronald K.
Published: June 2008

The importance of smolt size and early ocean growth to the marine survival of coho salmon was examined over a 17-yr period at Carnation Creek, British Columbia. Comparisons of overall marine survival were made both between-years, using two smolt age-groups of different mean sizes, and within-years using observed smolt size distributions and smolt size distributions back-calculated from the scales of returning adults. Large size did not confer a consistent survival advantage but large smolts did survive better in years when marine survival was relatively poor. Marine survivals were strongly correlated with early ocean growth as estimated by the spacing of the first five ocean circuli on the scales of returning adults. Marine survival and early ocean growth were positively correlated with ocean conditions indicative of strong upwelling along the northwest coast of Vancouver Island. Neither smolt survival nor early ocean growth were correlated with regional coho smolt production. Our observations suggest that interannual variability in smolt survival was being driven by ocean conditions that determined smolt growth rates which subsequently affected the susceptibility of smolts to a size-selective predator.
Variation in Pacific Hake (Merluccius productus) Summer Length-at-Age Near Southern Vancouver Island and Its Relationship to Fishing and Oceanography
Authors: Smith Barry D. , McFarlane Gordon A. , Saunders Mark W.
Published: June 2008

Male and female Pacific hake (Merluccius productus) sampled in summer off southern Vancouver Island since 1976 show a general decline, plus marked variability, in mean lengths-at-age. Multiple regression analysis related the length-at-age pattern to von Bertalanffy and density-dependent growth, length-selective fishing mortalities, and a suite of oceanographic covariates (sea level height, temperature, and salinity anomalies). Because offshore Pacific hake migrate annually between southern California and British Columbia, with larger fish migrating further north, we deduce that the summer fishery in Canadian waters selectively removes the larger hake each year causing a decline over time in mean lengths-at-age. Apart from the general decline, oceanographic factors explained most interannual variability in mean lengths-at-age. Specifically, mean lengths-at-age were generally smaller in years of above normal sea level height and temperature, and below normal salinity. Sea level anomalies in particular have been associated with the relative strength of the alongshore currents within the coastal upwelling domain; thus, we argue that stronger northward (or weaker southward) flows assist the northward migration of hake. Consequently, in years of higher than normal sea level, such as during major El Niño–Southern Oscillation (ENSO) events, more smaller hake arrive off Vancouver Island in summer resulting in lower mean lengths-at-age.
Comparison of Methods for Estimating Mixed Stock Fishery Composition
Authors: Millar R. B.
Published: June 2008

Given information on fish of known origin, and a random sample from the mixed stock fishery, the composition of that mixed fishery may be estimated in a number of ways. This study compares the performance of four classification-based estimators and a maximum likelihood estimator. Theoretical considerations show that the maximum likelihood estimator makes better use of the information contained in the mixed fishery sample. However, the classification estimators are shown to be more robust to violations in some of the model assumptions. Scale data from four regional stock groups of chinook salmon (Oncorhynchus tshawytscha) were used in an applied comparison of the five estimators. The results suggest that the maximum likelihood estimator performs best in practice.
Genetic Differences in the Early Development and Growth of Sympatric Sockeye Salmon and Kokanee (Oncorhynchus nerka), and their Hybrids
Authors: Wood Chris C. , Foote Chris J.
Published: June 2008

Anadromous (sockeye salmon) and nonanadromous (kokanee) Oncorhynchus nerka spawn sympatrically yet appear genetically distinct in a number of rivers in British Columbia. To investigate whether genetic differences are maintained by selection against -hybrid" progeny, we raised pure and reciprocal crosses of Shuswap River sockeye and kokanee under controlled hatchery conditions. Sockeye eggs were larger and survived slightly better than kokanee eggs, regardless of male type, both to the eyed egg stage and as young fry. We observed no differences in survival among cross types during the remainder of the 460 d study. Rate of yolk absorption was similar in pure sockeye and pure kokanee alevins, but significantly faster in alevins sired by sockeye than those sired by kokanee. This indicates a male genetic effect which compensates for the difference in egg size. Hybrid alevins developed differently because egg size is mismatched with the male genotype. Growth rates of fry were significantly more variable within pure kokanee families than within pure sockeye families Hybrid crosses survived as well as pure crosses under the study conditions. However, any progeny resulting from hybrid crosses in nature may sustain higher mortality than those from pure crosses.
Population decline off the Japanese sardine Sardinops melanostictus owing to recruitment failures
Authors: Watanabe Yoshiro , Zenitani Hiromu , Kimura Ryo
Published: June 2008

The Japanese sardine Sardinops melanostictus started to decline after 1989. Recruitment to age 1 population was small in four year-classes from 1988 to 1991. The population decline after 1989 resulted from recruitment failures in 4 consecutive years. Egg production was high in the years of poor recruitment. The recruitment failures were caused not by a reduction in reproductive output but by low survival between egg stage and age 1 recruitment. Abundance of post first-feeding larvae positively correlated with egg and yolksac larval abundance. Mortality at the first-feeding stage was not so variable as to destroy correlations between the abundance of early life stages. The population of age 1 recruits did not correlate with the abundance of post first-feeding larvae. Recruitment of the sardine was not fixed by the end of the first-feeding stage. Cumulative mortality through the early life stages, rather than relatively instantaneous mortality at the first-feeding stage, is thought to be responsible for the recruitment success or failure and eventual population fluctuations of the sardine.
Predatory demand and impact of striped bass, bluefish, and weakfish in the Chesapeake Bay: applications of bioenergetics models
Authors: Harfmart Kyle J. , Brandt Stephen B.
Published: June 2008

We applied bioenergetics models for dominant Chesapeake Bay piscivores, striped bass (Morone saxatilis), bluefish (Pomatomus saltatrix), and weakfish (Cynoscion regalis), along with site-specific data on diets, growth, and energy density, to examine trophic linkages and the relationship of predatory demand to prey supply. Atlantic menhaden (Brevoortia tyrannus), bay anchovy (Anchoa mitchilli), and spot (Leiostomus xanthurus) accounted for 65–99% of the annual biomass of piscivore diets (excluding age-0 striped bass that ate mostly invertebrates). The diets of young piscivores were dominated by anchovy, but menhaden and spot became increasingly important to older fish. Young (age < 2) striped bass ate mostly benthic prey. Older striped bass fed increasingly on pelagic sources, primarily menhaden, but bluefish and weakfish increased benthic resource use from 10% at age 0 to 50% by age 2. Comparison of consumption (supply) to demand (potential consumption) measured the suitability of Chesapeake Bay for predator production. Bluefish came closest to achieving their demand for prey, suggesting that they are more successful predators than either striped bass or weakfish. Results suggest that Chesapeake Bay may be a better nursery than production area for older fish, and prey supply (not temperature) may account for the movements and use of the estuary by older piscivores.
Genetic diversity and relationships among Dutch elm disease tolerantUlmus pumilaL. accessions from China
Authors: Zalapa Juan E. , Brunet Johanne , Guries Raymond P.
Published: June 2008

Elm breeding programs worldwide have relied heavily on Asian elm germplasm, particularly Ulmus pumila , for the breeding of Dutch elm disease tolerant cultivars. However, the extent and patterning of genetic variation in Asian elm species is unknown. Therefore, the objective of this research was to determine the extent of genetic diversity among 53 U. pumila accessions collected throughout the People’s Republic of China. Using 23 microsatellite loci recently developed in the genus Ulmus , a total of 94 alleles were identified in 15 polymorphic and 4 monomorphic loci. The average number of alleles per locus was 4.9, with a range of 1–11 alleles. Gene diversity estimates per locus ranged from 0.08 to 0.87, and the non-exclusion probability for the 15 polymorphic loci combined was 0.7 × 10−9. Nineteen region-specific alleles were identified, and regional gene diversity estimates were moderately high (0.48–0.57). The genetic relationships among accessions and regions were estimated by UPGMA and principal coordinate analysis. Both techniques discriminated all accessions and regions. Two microsatellite markers (UR175 + UR123 or Ulm-3) were sufficient to discriminate up to 99.7% of the accessions studied. This research provides useful information for DNA-based fingerprinting, breeding, ecological studies, and diversity assessment of elm germplasm.
Two different farnesyl diphosphate synthase genes exist in the genome of the green peach aphid,Myzus persicae
Authors: Zhang Yong-Lei , Li Zheng-Xi
Published: June 2008

Farnesyl diphosphate synthase (FPS; EC 2.5.1.1, 2.5.1.10) catalyzes biosynthesis of farnesyl diphosphate, which is important to insects as the precursor of juvenile hormone and the substrate for (E)-β-farnesene synthase. Here, two FPS cDNAs were isolated from the green peach aphid, Myzus persicae (EU334430 and EU334431). Their shared identity within the coding region is ~82%. The deduced amino acid sequences of the two M. persicae FPS cDNAs have the highly conserved motifs characteristic of most known FPSs. Phylogenetic analyses showed that they are closely related to other insect FPSs. Homology modeling of structures suggested a very good fit between the three-dimensional structures of the two putative M. persicae FPSs (designated as MpFPS1 and MpFPS2) and the avian FPS crystal structure. The corresponding genomic DNA sequences were subsequently determined (EU429295 and EU429296). Sequence comparisons revealed a different splicing pattern between the two MpFPS genes. Furthermore, the two MpFPS genes exhibited a seemingly very primitive gene-splicing pattern at 5′ ends but a gene-splicing style similar to mammalian FPS genes at 3′ ends. These data, combined with results of Southern blotting, suggest that M. persicae contains two different FPS genes. This is the first report that two different FPS genes exist in a hemipteran insect.
Microstructural investigation on bond coats in molybdenum and steel coatings for the renovation of mechanical pieces
Authors: Bradai M A , Ati A
Published: June 2008

Thermal spraying has been used in industry for many years to improve the properties of the surface of a workpiece, such as its mechanical and electrical properties and its wear resistance. Fabricating these high-quality coatings requires good cohesion of the deposited material and high adherence to the substrate. To improve adhesion of the coating to the substrate, the Company SNC ATRA (Algeria) uses molybdenum as the intermediate adhesion layer to restore the brace and bit. The purpose of this paper is to study the microstructure and morphology of the bond coat and coating using a flame-spray technique. Coatings have been characterized by scanning electron microscopy combined with traditional procedures of metallographic preparation. The results show that the substrate is thermally damaged when molybdenum is deposited as a bond coat, and that the bond coat is delaminated in its middle layer.PACS No.: 68.81
Where are the degrees of freedom responsible for black-hole entropy?
Authors: Das S , Shankaranarayanan S , Sur S
Published: June 2008

Considering the entanglement between quantum field degrees of freedom inside and outside the horizon as a plausible source of black-hole entropy, we address the question: where are the degrees of freedom that give rise to this entropy located? When the field is in ground state, the black-hole area law is obeyed and the degrees of freedom near the horizon contribute most to the entropy. However, for excited state, or a superposition of ground state and excited state, power-law corrections to the area law are obtained, and more significant contributions from the degrees of freedom far from the horizon are shown.PACS Nos.: 04.60.–m, 04.62., 04.70.–s, 03.65.Ud
A magnetization equation for nonequilibrium spin systems
Authors: Saradzhev F M
Published: June 2008

A magnetization equation for a system of spins evolving non-adiabatically and out of equilibrium is derived without specifying the internal interactions. For relaxation processes, this equation provides a general form of magnetization damping. A special case of the spin–spin exchange interaction is considered.PACS Nos.: 76.20.+q, 72.25.Ba
Designer de Sitter spacetimes
Authors: Schleich K , Witt D M
Published: June 2008

Recent observations in cosmology indicate an accelerating expansion of the Universe postulated to arise from some form of dark energy, the paradigm being positive cosmological constant. De Sitter spacetime is the well-known isotropic solution to the Einstein equations with cosmological constant. However, as discussed here, it is not the most general, locally isotropic solution. One can construct an infinite family of such solutions, designer de Sitter spacetimes, which are everywhere locally isometric to a region of de Sitter spacetime. However, the global dynamics of these designer cosmologies is very different than that of de Sitter spacetime itself. The construction and dynamics of these designer de Sitter spacetimes is detailed along with some comments about their implications for the structure of our Universe.PACS Nos.: 04.20.–q, 04.20.Ex, 04.20.Gz, 98.80.–k
The flexible atomic code
Authors: Gu M F
Published: June 2008

We describe a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionization, autoionization; and their inverse processes radiative recombination and dielectronic capture. The atomic theoretical background and numerical techniques associated with each process are discussed in detail. Sample applications and results are presented. PACS Nos.: 31.15.–p, 32.70.Cs, 34.80.Kw, 32.80.Fb, 32.80.Dz
The quantum action principle revisited
Authors: Carvalho M , Lyra A
Published: June 2008

We investigate the basic assumptions leading to Schwinger’s quantum action principle in quantum mechanics. We present this principle in a new way that clarifies some previous developments, for example, the derivation of the fundamental commutators among the canonical variables and the Heisenberg equation for operators. We define operators associated with the classical transformations of the Galilei group, i.e., translations, boosts, and rotations and show their commutators obey the Lie algebra of the Galilei group.PACS Nos.: 83.65.Ca, 11.10.Ef
Decoherence in quantum walks and quantum computers
Authors: Hines A P , Stamp P C.E.
Published: June 2008

Decoherence is the major stumbling block in the realization of a large-scale quantum computer. Ingenious methods have been devised to overcome decoherence, but their success has been proven only for over-simplified models of system-environment interaction. Whether such methods will be reliable in the face of more realistic models is a fundamental open question. In this partly pedagogical article, we study two toy models of quantum information processing, using the language of quantum walks. Decoherence is incorporated in three ways — by coupling to a noisy “projective measurement” system, and by coupling to oscillator and spin baths.PACS Nos.: 03.65.Yz, 03.67.Lx
Dual site observations of dayside Doppler-shifted hydrogen profiles: preliminary results
Authors: Holmes J M , Kozelov B V , Sigernes F , Lorentzen D A , Deehr C S
Published: June 2008

Simultaneous optical ground-based observations of auroral Balmer excited hydrogen atoms were performed during the boreal winters of 2002–2003 and 2003–2004 at Ny-Ålesund, Svalbard (NYA 76.26°N 110.98°E geomagnetic) and Longyearbyen, Svalbard (LYR 75.31°N 111.88°E geomagnetic). Balmer α (Hα) with a natural wavelength of 6563Å was detected at Ny-Ålesund, while Balmer β (Hβ) at 4861Å was measured at Longyearbyen. The emissions are well known to originate from precipitating protons whose charge exchanges with the neutral atmosphere lead to a diffuse, Doppler-shifted emission region. Measurements are made using Ebert–Fastie spectrometers that are located 118 km apart on a line of roughly constant geomagnetic longitude, thus making this configuration suitable for studying the variation of proton energy with geomagnetic latitude, the so-called “velocity filter” effect. For two different days, analysis of the spectrometer data sets was performed, yielding in both cases positive energy differences between LYR and NYA in support of the velocity filter concept. To reduce uncertainties in the determined energies obtained from the Doppler profile, distributions of energy difference were constructed using the entire time period (up to 2 h) for each case.PACS Nos.: 92.60.hw 94.20.Ac, 94.30.Aa
The 5s25p4 – (5s5p5 + 5p36s) transitions in Ce VII and 5s25p3 4S – 5s5p4 4P transitions in Ce VIII
Authors: Tauheed A , Joshi Y N
Published: June 2008

The spectrum of cerium was photographed in the 300–1230 Å wavelength region on a 3~m normal incidence spectrograph at the Antigonish laboratory and on a 3 m grazing incidence spectrograph at the Institute of Spectroscopy laboratory in Troitsk in the 250–350 Å region. The 5s25p4 – (5s5p5 + 5p36s) transitions of six-time ionized cerium (Ce~VII) were identified. All levels of these three configurations have been established. Forty spectral lines have been classified in the Ce VII spectrum. Configuration interaction Hartree–Fock calculations and least-squares-fitted parametric calculations were used to interpret the observed spectrum. In the Ce VIII spectrum, we have identified the 5s25p3S3/2 – 5s5p4P1/2, 3/2, 5/2 resonance transitions. PACS Nos.: 32.30.Jc, 32.30.–r
COMPLEX NETWORKS ANALYSIS OF MANUAL AND MACHINE TRANSLATIONS
Authors: AMANCIO DIEGO R. , ANTIQUEIRA LUCAS , PARDO THIAGO A. S. , da F. COSTA LUCIANO , OLIVEIRA OSVALDO N. , NUNES MARIA G. V.
Published: June 2008

Complex networks have been increasingly used in text analysis, including in connection with natural language processing tools, as important text features appear to be captured by the topology and dynamics of the networks. Following previous works that apply complex networks concepts to text quality measurement, summary evaluation, and author characterization, we now focus on machine translation (MT). In this paper we assess the possible representation of texts as complex networks to evaluate cross-linguistic issues inherent in manual and machine translation. We show that different quality translations generated by MT tools can be distinguished from their manual counterparts by means of metrics such as in- (ID) and out-degrees (OD), clustering coefficient (CC), and shortest paths (SP). For instance, we demonstrate that the average OD in networks of automatic translations consistently exceeds the values obtained for manual ones, and that the CC values of source texts are not preserved for manual translations, but are for good automatic translations. This probably reflects the text rearrangements humans perform during manual translation. We envisage that such findings could lead to better MT tools and automatic evaluation metrics.
EVOLVING LOCALIZATIONS IN REACTION-DIFFUSION CELLULAR AUTOMATA
Authors: ADAMATZKY ANDREW , BULL LARRY , COLLET PIERRE , SAPIN EMMANUEL
Published: June 2008

We consider hexagonal cellular automata with immediate cell neighbourhood and three cell-states. Every cell calculates its next state depending on the integral representation of states in its neighbourhood, i.e., how many neighbours are in each one state. We employ evolutionary algorithms to breed local transition functions that support mobile localizations (gliders), and characterize sets of the functions selected in terms of quasi-chemical systems. Analysis of the set of functions evolved allows to speculate that mobile localizations are likely to emerge in the quasi-chemical systems with limited diffusion of one reagent, a small number of molecules are required for amplification of travelling localizations, and reactions leading to stationary localizations involve relatively equal amount of quasi-chemical species. Techniques developed can be applied in cascading signals in nature-inspired spatially extended computing devices, and phenomenological studies and classification of non-linear discrete systems.
SELF-AFFINITY OF VEHICLE DEMAND ON THE FERRY-BOAT SYSTEM
Authors: FILHO A. N. S. , ZEBENDE G. F. , MORET M. A.
Published: June 2008

The transportation problems are in evidence due to their importance. This type of problem is usually studied by nonlinear dynamics. In this paper, we study time series of vehicle demand by using the ferry-boat system between Salvador city and Itaparica island, in Bahia, Brazil. We observe an interesting behavior since these time series allow to observe genuine self-affinity effects. The scaling exponent α and the density of crossing points ρ are variables to describe long-range correlations (self-affinity) in time series of the vehicle demand. As the result we show α and ρ variation year by year.
TEMPERATURE-DEPENDENT DIELECTRIC STRENGTH OF A MAXWELL–WAGNER TYPE RELAXATION
Authors: WANG C. C. , LU H. B. , JIN K. J. , YANG G. Z.
Published: June 2008

A relationship between the temperature and the dielectric strength of a Maxwell–Wagner (MW) type relaxation was deduced based on the conventional two-layer model for inhomogeneous systems and under the usual assumptions that the conductivity of each layer obeys the thermally activated law and the dielectric constant of each layer is relatively temperature independent. The relation shows that the relaxation peak height in the imaginary part of the complex permittivity for a MW-type relaxation increases with decreasing temperature and saturates at low enough temperature. This behavior was well-proved by both numeral and experimental results and therefore could be regarded as a fingerprint of a MW-type relaxation in most practical cases.
DIELECTRIC, ELECTROMECHANICAL AND FERROELECTRIC PROPERTIES OF (Na0.5Bi0.5)(NdxTi1-2xNbx)O3 RELAXOR CERAMICS
Authors: MAHBOOB S. , PRASAD G. , KUMAR G. S.
Published: June 2008

Polycrystalline ( Na 0.5 Bi 0.5)( Nd x Ti 1-2x Nb x) O 3 ceramics with perovskite structure were prepared through the solid state sintering route. The prepared samples were studied for their dielectric, electromechanical and ferroelectric properties. Dielectric measurements showed relaxor behavior. From electromechanical studies, a relatively high electro-mechanical coupling factor, kt (in the range 0.69–0.73) depending upon composition was observed. Among the samples studied, x = 0.0125 exhibited a higher value of remanant polarization (~ 0.50 μ C/cm 2 at coercive field (Ec = 6.30 kV/cm )).
FRACTIONAL-ORDER CHUA'S CIRCUIT: TIME-DOMAIN ANALYSIS, BIFURCATION, CHAOTIC BEHAVIOR AND TEST FOR CHAOS
Authors: CAFAGNA DONATO , GRASSI GIUSEPPE
Published: June 2008

In this tutorial the chaotic behavior of the fractional-order Chua's circuit is investigated from the time-domain point of view. The objective is achieved using the Adomian decomposition method, which enables the solution of the fractional differential equations to be found in closed form. By exploiting the capabilities offered by the decomposition method, the paper presents two remarkable findings. The first result is that a novel bifurcation parameter is identified, that is, the fractional-order q of the derivative. The second result is that chaos exists in the fractional Chua's circuit with order q = 1.05, which is the lowest order reported in literature for such circuits. Finally, a reliable and efficient binary test for chaos (called "0–1 test") is utilized to detect the presence of chaotic attractors in the system dynamics.
UNIFORM ATTRACTORS OF NONAUTONOMOUS DISCRETE REACTION–DIFFUSION SYSTEMS IN WEIGHTED SPACES
Authors: WANG BIXIANG
Published: June 2008

We study the asymptotic behavior of nonautonomous discrete Reaction–Diffusion systems defined on multidimensional infinite lattices. We show that the nonautonomous systems possess uniform attractors which attract all solutions uniformly with respect to the translations of external terms when time goes to infinity. These attractors are compact subsets of weighted spaces, and contain all bounded solutions of the system. The upper semicontinuity of the uniform attractors is established when an infinite-dimensional reaction–diffusion system is approached by a family of finite-dimensional systems. We also examine the limiting behavior of lattice systems with almost periodic, rapidly oscillating external terms in weighted spaces. In this case, it is proved that the uniform global attractors of nonautonomous systems converge to the global attractor of an averaged autonomous system.
BIFURCATION OF MULTIPLE LIMIT CYCLES FOR A ROTOR-ACTIVE MAGNETIC BEARINGS SYSTEM WITH TIME-VARYING STIFFNESS
Authors: LI J. , TIAN Y. , ZHANG W. , MIAO S. F.
Published: June 2008

The bifurcations of multiple limit cycles for a rotor-active magnetic bearings (AMB) system with the time-varying stiffness are considered in this paper. The governing nonlinear equation of motion is established for the rotor-AMB system with single-degree-of-freedom and parametric excitation. Using the method of multiple scales, the governing nonlinear equation of motion is first transformed to the averaged equation, which is in the form of a Z2-symmetric perturbed polynomial Hamiltonian system of degree 5. Then, the bifurcation theory of planar dynamical system and the method of detection function are utilized to analyze the bifurcations of multiple limit cycles of the averaged equation. Four groups of parametric controlling conditions are given to obtain the configurations of compound eyes. It is found that there exist respectively at least 17, 19, 21 and 22 limit cycles in the rotor-AMB system with the time-varying stiffness under the different controlling conditions.
CODIMENSION-TWO BIFURCATIONS IN INDIRECT FIELD ORIENTED CONTROL OF INDUCTION MOTOR DRIVES
Authors: SALAS F. , GORDILLO F. , ARACIL J. , REGINATTO R.
Published: June 2008

This paper provides further results on bifurcation analysis of indirect field oriented control of induction motors. Previous results presented on this subject [Bazanella & Reginatto, 2000, 2001; Gordillo et al., 2002] are summarized and extended by means of a codimension-two bifurcation analysis. It is shown that codimension-two bifurcation phenomena, such as a Bogdanov–Takens and zero–Hopf bifurcations, occur in IFOC as a result of parameter mismatch and certain setting of the proportional-integral speed controller. Conditions for the existence of such bifurcations are derived analytically, as long as possible, and bifurcation diagrams are presented with the help of simulation and numerical bifurcation analysis.