bluuebunny/crossref_metadata_2025 huggingface dataset:
Geology and geochemistry of the Dengjiashan Zn–Pb SEDEX deposit, Qinling Belt, China
Authors: Ma Guoliang , Beaudoin Georges , Zhong Shaojun , Li Ying , Zeng Zhangren
Published: July 2007

Dengjiashan, with 25 Mt at 4.77% Zn, 1.27% Pb, and 14 g/t Ag, is one of the largest SEDEX (sedimentary-exhalative) Zn–Pb sulfide deposits in the western Qinling orogenic belt, China. The ore is hosted in chert stratigraphically conformable with underlying bioclastic micrite and overlying phyllite of an intensely folded and faulted Middle Devonian sedimentary sequence. The fact that the major orebodies are located between platformal limestone and overlying phyllite indicates that mineralization took place when the Dengjiashan sedimentary sub-basin subsided from an open platform to a shallow-marine basin within an extensional tectonic setting. The deposit comprises 16 sulfide orebodies, of which the #1 and #9 orebodies are the two largest and account for 95% of ore reserves. The massive sulfide lenses are mainly composed of sphalerite, pyrite, and galena, with minor chalcopyrite, tetrahedrite, cinnabar, pyrargyrite, freibergite, boulangerite, polybasite, and trace amounts of owyheeite and native gold. The gangue is dominated by quartz, calcite, barite, and ankerite, with minor amounts of sericite, chlorite, celsian, cymrite, and albite. The rare-earth element patterns of sulfide beds and host chert suggest that the mineralizing fluids were dominated by oxidized seawater that leached Eu from feldspar in basement rocks. Strontium isotopes also suggest that the hydrothermal fluids were composed of Devonian seawater that leached radiogenic Sr along the flow path. Lead isotope ratios form an array between the upper crust and orogene curves in the 207Pb/204Pb–206Pb/204Pb diagram, indicating that lead was leached from crustal rocks below the deposits. Sulfur isotopes indicate that bacterial sulfate reduction (BSR) sulfide formed in a sub-basin restricted to sulfate where it mixed with heavy hydrothermal sulfur from thermochemical sulfate reduction (TSR) of Devonian seawater sulfate.
Laurentide and montane glaciation along the Rocky Mountain Foothills of northeastern British Columbia
Authors: Bednarski Jan M , Smith I Rod
Published: July 2007

Mapping the surficial geology of the Trutch map area (NTS 94G) provides new data on the timing of continental and montane glaciations along the Foothills of northeastern British Columbia. Striated surfaces on mountain crests were dated to the Late Wisconsinan substage by cosmogenic dating. The striations were produced by eastward-flowing ice emanating from the region of the Continental Divide. This ice was thick enough to cross the main ranges and overtop the Rocky Mountain Foothill summits at 2000 m above sea level (asl). It is argued here that such a flow, unhindered by topography, could only have been produced by the Cordilleran Ice Sheet and not by local cirque glaciation. During this time, the Cordilleran Ice Sheet dispersed limestone and schist erratics of western provenance onto the plains beyond the mountain front. Conversely, the Laurentide Ice Sheet did not reach its western limit in the Foothills until after Cordilleran ice retreated from the area. During its maximum, the Laurentide ice penetrated the mountain valleys up to 17 km west of the mountain front, and deposited crystalline erratics from the Canadian Shield as high as 1588 m asl along the Foothills. In some valleys a smaller montane advance followed the retreat of the Laurentide Ice Sheet.
Modèles d'astroblèmes d'après le déplacement des masses rocheuses : Charlevoix et le Ries
Authors: Rondot Jehan
Published: July 2007

One can determine the movement of rock masses in the formation of an astrobleme by ascertaining the displacements of stratigraphic reference levels before and during the impact. A discontinuity in the zone of shock metamorphism in the Charlevoix (Quebec, Canada) structure corresponds with a major fault separating an irregularly uplifted crown area from a depressed inner zone. The displacement along this circular fault is inverse to the normal displacement of the layers of this structure, that is to say, a broad collapsed area of terraces and grabens on the outside, and a gradual central build-up in the inner zone. This phenomenon can be explained as a consequence of the formation of a crater of excavation through impact, where a force of expansion tends to raise the edges of the crater, as insertion continues to the bottom of the crater. An essentially similar model for small and large craters is inferred in the first phase of formation. The readjustment that follows depends on the size of the crater and the material impacted. Started by decompression, the readjustment tends to continue until balance occurs along the fracture slip surfaces that initially formed on impact. The fractures are filled by impact fault breccias, particularly by mylolisthenites. This readjustment also depends on the speed of the meteorite at impact, as suggested by the central prominences found in the Charlevoix and the bassin form for the Ries (Germany).
Paleomagnetism, U–Pb geochronology, and geochemistry of Lac Esprit and other dyke swarms, James Bay area, Quebec, and implications for Paleoproterozoic deformation of the Superior Province
Authors: Buchan Kenneth L , Goutier Jean , Hamilton Michael A , Ernst Richard E , Matthews William A
Published: July 2007

An extensive set of north- to northwest-trending diabase dykes, termed the Lac Esprit swarm, is identified in the Superior Province east of James Bay based on geological mapping and a distinctive paleomagnetic pole (61.7°N, 169.1°E, dm = 7.7°, dp = 5.5°). The Lac Esprit swarm yields a U–Pb baddeleyite age of 2069 ± 1 Ma similar to that of the 2076+5–4 Ma Fort Frances swarm of the western Superior Province. Their paleomagnetic declinations differ by 23° ± 12° after correction to a common reference locality. The difference is likely due mainly to counterclockwise rotation about a vertical axis of the Fort Frances area relative to the Lac Esprit area. Differential rotation of 10°–20° has been proposed more locally across the Kapuskasing Structural Zone separating the eastern and western Superior Province in earlier paleomagnetic studies of ca. 2450 Ma Matachewan and 2170 Ma Biscotasing dyke swarms. Thus, relative rotation may have involved the entire eastern and western Superior Province, perhaps in response to collisional events associated with the Trans-Hudson Orogen to the north or the Penokean orogen to the south, or in response to rifting beneath Hudson Bay. Other dykes in the study area are interpreted from a combination of paleomagnetism, trend, and geochemistry to belong to the Senneterre, Matachewan, and Mistassini swarms. The 2216 Ma Senneterre dykes form part of a giant swarm that fans across the eastern Superior Province. Paleomagnetic directions and geometry of this swarm rule out substantial block rotations within the eastern Superior Province since dyke emplacement.
The Lower Cretaceous Chaswood Formation in southern New Brunswick: provenance and tectonics
Authors: Piper David JW , Pe-Piper Georgia , Hundert Thian , Venugopal D V
Published: July 2007

The most northwesterly outcrop of Lower Cretaceous Chaswood Formation is in a pit at Vinegar Hill, south of Sussex, New Brunswick. New mapping and boreholes show thick, fluvial, loosely lithified conglomerates and lesser sandstones unconformably overlying 12 m of mudstone in a 1 km2 basin bounded to the northwest by the Clover Hill fault. Sparse paleocurrent indicators to the southwest parallel this fault. The tectonic setting is similar to that of the Chaswood Formation in the fault-bounded Elmsvale basin in Nova Scotia. In both cases, a basal unit is paraconformable on underlying upper Mississippian rocks, was folded into a syncline within which a middle unit accumulated and was further deformed, and is capped by thin flat-lying sandstone and conglomerate. The tectonic style of the Chaswood Formation at Vinegar Hill demonstrates that early Cretaceous deformation was widespread in the southern Maritimes. Gravel clasts consist overwhelmingly of vein quartz, but sparse lithic clasts match source rocks in south-central New Brunswick. Heavy minerals are mostly ilmenite (40%–70%) and staurolite (20%–40%), with monazite, zircon, and andalusite more abundant than at other Chaswood Formation localities. Heavy mineral chemistry and monazite geochronology suggest a provenance from Silurian metasedimentary rocks and tourmaline granites in central New Brunswick. Different mineral assemblages from the Chaswood Formation in Nova Scotia suggest that an ancestral St. John River drained western New Brunswick and supplied sediment to the Shelburne delta of the Scotian basin.
Late Holocene vegetation and climate change at Moraine Bog, Tiedemann Glacier, southern Coast Mountains, British Columbia
Authors: Arsenault T A , Clague John J , Mathewes R W
Published: July 2007

Moraine Bog lies just outside the outermost lateral moraine of Tiedemann Glacier in the southern Coast Mountains of British Columbia. A sediment core taken from the wetland was analyzed for pollen, magnetic susceptibility, and loss on ignition to reconstruct changes in vegetation and climate during the late Holocene. Vegetation changed little between about 3500 and 2400 14C years BP. A period of local disturbance marked by deposition of a silty clay bed and increases in Alnus pollen, likely reflecting cooler moister conditions, coincides with an extensive Holocene advance of Tiedemann Glacier about 2400 14C years BP. Warm dry conditions between about 1900 and 1500 14C years BP are suggested by peak values of Pseudotsuga pollen and increasing Nuphar sclereids; the latter suggests lowered water levels. This period coincides with a time of drought and increased fire frequency in the southernmost Coast Mountains. About 1300 14C years BP, the forest became more coastal in composition with abundant Tsuga heterophylla and Abies. An increase in Tsuga mertensiana pollen suggests the onset of cool and wet conditions by ca. 500 14C years BP, coincident with the Little Ice Age. The record of inferred climate change at Moraine Bog is broadly synchronous with other paleoclimate records from the Coast Mountains and, at the centennial scale, with records elsewhere in the world.
Hydraulic geometry as a physical template for the River Continuum: application to optimal flows and longitudinal trends in salmonid habitat
Authors: Rosenfeld Jordan S , Post John , Robins Geneva , Hatfield Todd
Published: July 2007

The River Continuum Concept lacks a quantitative physical model to represent downstream trends in habitat. We evaluate whether hydraulic geometry relationships can be used as a physical template to predict longitudinal trends in habitat availability and optimal flows for different life-history stages of rainbow trout (Oncorhynchus mykiss). Optimal flows based on hydraulic geometry indicate that (i) optimal flows are higher for larger fish, (ii) optimal flows proportionally increase as streams became smaller and decrease downstream, and (iii) maximum predicted habitat suitabilities for fry and juveniles are in small streams, and maximum suitabilities are displaced progressively downstream for later life-history stages. These patterns are an emergent property of downstream increases in channel depth and velocity and changes in habitat suitability curves associated with increased swimming performance of larger fish. Nonlinear downstream trends in habitat imply that fixed flow percentages recommended by the Tenant method may substantially underestimate optimal flows in small streams. Despite oversimplifying complex channel structure, hydraulic geometry relationships should serve as a useful physical model for testing downstream trends in habitat-related processes along the river continuum.
Consequences of assuming an incorrect error structure in von Bertalanffy growth models: a simulation study
Authors: Eveson J Paige , Polacheck Tom , Laslett Geoff M
Published: July 2007

The underlying sources of growth variability in a population cannot generally be known, so when modelling growth it is important to understand the consequences of assuming an incorrect error structure. In this study, four error models for a von Bertalanffy growth curve with asymptotic length parameter L∞ and growth rate parameter k are considered. Simulations are carried out in which data are generated according to one of the models and fitted assuming each of the models to be true. This is done for two types of data: direct age–length and tag–recapture. For direct age–length data, the consequences of not accounting for individual growth variability, or assuming the wrong source of variability, are minor, even when individual variability is high or data coverage is poor. For tag–recapture data, some substantial biases in growth estimates can arise when individual variability exists but is not accounted for. Importantly, however, incorporating variability in just one parameter (be it L∞ or k), even if the variability truly stems from the other or both parameters, generally leads to much smaller biases than assuming no individual variability. Often the alternative models cannot be distinguished using standard model selection procedures, so caution is warranted in using model selection to draw inferences about underlying sources of growth variability.
Using the particle filter to geolocate Atlantic cod (Gadus morhua) in the Baltic Sea, with special emphasis on determining uncertainty
Authors: Andersen K H , Nielsen A , Thygesen U H , Hinrichsen H -H , Neuenfeldt S
Published: July 2007

The use of archival tags on fish gives information of individual behaviour with an unprecedented high resolution in time. A central problem in the analysis of data from retrieved tags is the geolocation, namely the infererence of movements of the fish by comparing the data from the tags with environmental observations like temperature, tide, day length, etc. The result is usually represented as a track; however, the spatial and temporal variability in the precision is often substantial. In this article, the particle filter is applied to geolocate Atlantic cod (Gadus morhua) in the Baltic Sea, leading to a representation of the results as probability distributions for each time step, thus giving an explicit representation of uncertainty. Furthermore, the method is used to estimate the magnitude of the error in the measurements by the tags and the swimming velocity of the fish. The average swimming velocity during a day was estimated to be around 0.20 m·s–1 for fish of ~60 cm length. The method is general and the presentation is formulated to facilitate implementation for different systems where other quantities are observed.
Is growth a reliable indicator of habitat quality and essential fish habitat for a juvenile estuarine fish?
Authors: Searcy Steven P , Eggleston David B , Hare Jonathan A
Published: July 2007

A common assumption throughout the marine ecological and fisheries literature is that growth is a valid indicator of habitat quality and can be used as a criterion for designation of essential fish habitat (EFH). In this study, the validity of growth as an index of habitat quality was tested by examining how variability in otolith growth was related to abiotic and biotic environmental conditions and could be biased by previous growth history, density dependence, and selective mortality. The study was conducted with juvenile Atlantic croaker (Micropogonias undulatus) collected in two North Carolina, USA, estuaries during two seasons of two recruitment years. Water temperature, a component of habitat quality, explained nearly 40% of the variability in juvenile otolith growth. There was also evidence that estimates of growth could be biased by density dependence (slower growth at higher conspecific abundance) and by selective mortality (higher mortality of individuals with relatively slower larval and juvenile otolith growth). Studies using growth-based assessment of habitat quality that fail to identify factors underlying growth rate differences among habitats may reach incorrect decisions regarding quality of different habitats and assignment of EFH.
Is boldness towards predators related to growth rate in naïve captive-reared Arctic char (Salvelinus alpinus)?
Authors: Laakkonen Mika VM , Hirvonen Heikki
Published: July 2007

Previous studies have shown that the antipredator responsiveness of fish degenerates through generations in captive breeding. However, detailed knowledge of the underlying mechanism is still largely lacking. We tested the hypothesis that hatchery fish supposedly selected for faster growth in the hatchery environment are bolder towards predators than their slower-growing conspecifics. This was examined by comparing the antipredator behavior of predator- naïve fast- and slow-growing individuals of a captive-bred Arctic char (Salvelinus alpinus) population to chemical cues from natural predators burbot (Lota lota) and pikeperch (Sander lucioperca). As behavioral responses depended on char body size, we compared boldness towards predators of size-matched fast- and slow-growing char. We found no differences in four behavioral antipredator traits between size-matched groups of fast- and slow-growing char. According to these results, boldness to predator cues is not related to individual growth rate in captive-bred Arctic char.
The effect of sea lice infestation on the salinity preference and energetic expenditure of juvenile pink salmon (Oncorhynchus gorbuscha)
Authors: Webster Sandra J , Dill Lawrence M , Butterworth Kevin
Published: July 2007

Ocean-going juvenile salmonids heavily infected with salmon louse, Lepeophtheirus salmonis, have been observed prematurely returning to freshwater. This change in salinity preference may be an attempt either to regain osmotic balance or to remove the lice. For either hypothesis to be true, freshwater habitats must provide infected fish with a higher net fitness than saltwater habitats. The objectives of this study were to use behavioural titration to quantify the energetic cost of different salinities to infected and uninfected pink salmon (Oncorhynchus gorbuscha) and to determine if infection alters salinity preference. Results demonstrate that infection changes the salinity preference of fish from saltwater to freshwater. The cost paid by these freshwater-preferring infected fish foraging in saltwater increased with lice density during trials conducted between 13–33 days after infection. Other infection-induced behavioural changes include a 14-fold increase in the jumping frequency of infected versus control fish and a decrease in foraging between 13 and 33 days after infection.
Large-scale frequency dynamics of alternative male phenotypes in natural populations of coho salmon (Oncorhynchus kisutch): patterns, processes, and implications
Authors: Koseki Yusuke , Fleming Ian A
Published: July 2007

Using over 20 years of annual spawner survey data collected from 46 natural populations of coastal Oregon coho salmon (Oncorhynchus kisutch), we examined large-scale spatial and temporal dynamics of alternative male pheno types (age-3 hooknoses and age-2 jacks). Fluctuations in jack and hooknose abundance were synchronous among populations (i.e., region-wide synchrony), similar to patterns seen previously in Oregon hatchery populations and indicative of oceanic processes operating at large spatial and temporal scales. By contrast, regional-scale synchrony in the ratio of jack to hooknose males was likely attributable to the influences of the freshwater environment. Moreover, within-population variation in phenotype ratio was lower by brood year than by return year (i.e., weak cohort relationship), contrary to previous patterns in hatchery populations. The spatial and temporal patterns of phenotype ratio observed in natural populations but not in hatchery populations, where freshwater effects were statistically controlled, indicate that the frequency dynamics of coho male alternative phenotypes are influenced more strongly by freshwater than by marine processes. The environmentally induced variability in phenotype ratio suggests that there may be constant perturbations of fitness functions for alternative phenotypes, such that the system should be less stable than predicted from the status-dependent selection model with fixed fitness functions.
Phenological and geographical patterns of walleye pollock (Theragra chalcogramma) spawning in the western Gulf of Alaska
Authors: Ciannelli Lorenzo , Bailey Kevin M , Chan Kung-Sik , Stenseth Nils Chr.
Published: July 2007

Over 20 years of egg sampling data were used to reconstruct the geographical and phenological patterns of walleye pollock (Theragra chalcogramma) spawning aggregations in the Gulf of Alaska (GOA). The analyzed time series (1972, 1978–1979, 1981–2000) included a documented event of climate change (i.e., 1988–1989) and the rise and fall of the GOA pollock population abundance and harvests. We compared results from two generalized additive model (GAM) formulations: one assuming no change of egg distribution and phenology over the examined time series (stationary) and the other admitting such changes (nonstationary) across an epoch determined from the data. Results from both model formulations corroborate the existence of a high egg concentration in Shelikof Strait, historically the primary spawning area of pollock in the GOA. However, model results also highlight the presence of other secondary, and possibly transitory, centers of egg distribution at various locations along the shelf and slope regions of the GOA. In addition, results from the nonstationary (and statistically superior) formulation indicate that the abundance of the non-Shelikof aggregations has increased over time, along with a tendency for earlier occurrence and displacement toward shallower areas of the high egg density regions.
Evaluation of the robustness of maximum sustainable yield based management strategies to variations in carrying capacity or migration pattern of Atlantic bluefin tuna (Thunnus thynnus)
Authors: Kell Laurence T , Fromentin Jean-Marc
Published: July 2007

In this study, we examine the performances of current stock assessment methods with respect to their ability to (i) provide estimates of maximum sustainable yield (MSY), FMSY, and BMSY and (ii) assess stock status and exploitation level relative to MSY targets. The robustness of the current International Commission for the Conservation of Atlantic Tunas (ICCAT) management strategy is then evaluated with respect to uncertainty about the true population dynamics and contrasted with a simpler management strategy based solely on a size limit. Reference points are more robust to dynamic uncertainty than the estimates of absolute values and trends in F and spawning stock biomass. However, their performances depend on the underlying dynamics (they perform better when fluctuations come from changes in the carrying capacity than migration) and on when they are implemented relative to the intrinsic cycle of the population. Reference points based on F were less biased and more precise than those based on biomass and (or) yield. Although F0.1 appeared to be the best proxy for FMSY, it cannot indicate past and current levels of exploitation relative to FMSY when there is uncertainty about the dynamics. Finally, the F0.1 management strategy of ICCAT performed only slightly better than a simpler strategy based on size limit and led to lower catch levels.
The effects of domestication on the relative vulnerability of hatchery and wild origin spring Chinook salmon (Oncorhynchus tshawytscha) to predation
Authors: Fritts Anthony L , Scott Jennifer L , Pearsons Todd N
Published: July 2007

We tested whether one generation of state-of-the-art hatchery culture influenced the vulnerability of Chinook salmon (Oncorhynchus tshawytscha) fry to predators. Size-matched hatchery and wild origin spring Chinook salmon fry were exposed to rainbow trout (Oncorhynchus mykiss) and torrent sculpin (Cottus rhotheus) predators in 10.8 m3net pens. The hatchery origin fry were the offspring of first generation hatchery-reared broodstock, and the wild origin fry had no history of hatchery culture; both originated from the same stock. Wild origin fry were found to have a 2.2% (p = 0.016) survival advantage over hatchery origin fry during 2 years of predation challenges. The most important findings of this study are (i) domestication can affect the susceptibility to predators after only one generation of state-of-the-art hatchery culture practices, and (ii) the domestication effect was very small.
Overwintering of sea trout (Salmo trutta) in freshwater: escaping salt and low temperature or an alternate life strategy?
Authors: Thomsen Dennis S , Koed Anders , Nielsen Christian , Madsen Steffen S
Published: July 2007

Brown trout (Salmo trutta) show large phenotypic plasticity. Juveniles may reside in their native freshwater habitat until maturation or migrate into the ocean as 1- to 3-year-old smolts. Sea-going fish (sea trout) reside at sea for 2–3 years until migrating back to their native stream for reproduction. However, immature fish may leave the ocean during their first or second winter at sea and overwinter in freshwater. The question is why does this occur? We tested the hypothesis that hypo-osmoregulatory capacity is compromised by low temperature in two coastal sea trout populations, one representing high salinity and the other, low salinity. Immature sea-run trout were caught in lower parts of two rivers during winter and acclimated to laboratory conditions. Subgroups were challenged with high salinity or low water temperature or both, and their osmoregulatory performance was investigated. Low temperature compromised the hypo-osmoregulatory ability, as indicated by insufficient compensatory adjustments of ion-transport mechanisms. Tagging experiments revealed that descent of overwintering fish into the ocean occurred over a narrow time period coincident with increasing water temperature. We conclude that overwintering in freshwater is partly driven by compromised osmoregulatory physiology, but because not all fish in a population do so, the phenomenon may also reflect diverging life strategies.
A state–space mixture approach for estimating catastrophic events in time series data
Authors: Ward Eric J , Hilborn Ray , Towell Rod G , Gerber Leah
Published: July 2007

Catastrophic events are considered a major contributor to extinction threats, yet are rarely explicitly estimated in population models. We extend the basic state–space population dynamics model to include a mixture distribution for the process error. The mixture distribution consists of a "normal" component, representing regular process error variability, and a "catastrophic" component, representing rare events that negatively affect the population. Direct estimation of parameters is rarely possible using a single time series; however, estimation is possible when time series are combined in hierarchical models. We apply the catastrophic state–space model to simulated time series of abundance from simple, nonlinear population dynamics models. Applications of the model to these simulated time series indicate that population parameters (such as the carrying capacity or growth rate) and observation and process errors are estimated robustly when appropriate time series are available. Our simulations indicate that the power to detect a catastrophe is also a function of the strength of catastrophes and the magnitude of observation and process errors. To illustrate one potential application of this model, we apply the state–space catastrophic model to four west coast populations of northern fur seals (Callorhinus ursinus).
Ecosystem-based fisheries management: some practical suggestions
Authors: Marasco Richard J , Goodman Daniel , Grimes Churchill B , Lawson Peter W , Punt Andre E , Quinn II Terrance J
Published: July 2007

Globally, there is increased scientific and public interest in the concept of ecosystem-based fisheries management (EBFM). This trend is fueled by a widespread perception that large-scale fishing operations are powerful forces altering the structure and function of marine ecosystems. It is acknowledged that management needs to better account for variations in ocean productivity, stock structure, and changing social values. Many countries are contemplating how to improve ocean fishery management. In the United States, fishery management bodies are experiencing pressure to undertake the daunting task of moving from their current single-species management plans to EBFM. Impediments include lack of a clear definition of EBFM, what it entails, or how to proceed. In this paper, characteristics of fishery management that are unique to EBFM are identified. The transition to EBFM needs to be evolutionary rather than revolutionary. A course of action is outlined that can be used to guide this transition. Modeling approaches and metrics useful for planning, implementing, and evaluating EBFM are discussed, with particular emphasis on management strategy evaluation.
Recruitment and survival of Northeast Pacific Ocean fish stocks: temporal trends, covariation, and regime shifts
Authors: Mueter Franz J , Boldt Jennifer L , Megrey Bernard A , Peterman Randall M
Published: July 2007

Two measures of productivity for fish stocks (recruitment and stock–recruit residuals) within two large marine ecosystems (Gulf of Alaska and eastern Bering Sea – Aleutian Islands) showed significant positive covariation within several groups of species and significant negative covariation between certain others. For example, stock–recruit residuals of gadids (Gadidae) in the Bering Sea were inversely related to those of shelf flatfishes (Pleuronectidae), suggesting that environmental forcing affects these groups in opposite ways. Salmon (Oncorhynchus spp.), Pacific herring (Clupea pallasii), and groundfish stocks each showed strong patterns of covariation within these taxonomic groups and within ecosystems, and both salmon and groundfish stocks showed positive covariation between the two ecosystems. However, we found little evidence of covariation between salmon and herring stocks or between these stocks and demersal stocks. Recruitment and stock–recruit residuals in individual stocks did not show a consistent response to known climatic regime shifts. However, combined indices of productivity across stocks showed decadal-scale variability (regime-like patterns), suggesting that both pelagic productivity (mostly salmon) and demersal productivity increased in response to the well-documented 1976–1977 climatic regime shift, whereas the 1988–1989 regime shift produced inconsistent or short-lived responses.
Population genetic structure in the North Atlantic Greenland halibut (Reinhardtius hippoglossoides): influenced by oceanic current systems?
Authors: Knutsen Halvor , Jorde Per Erik , Albert Ole Thomas , Hoelzel A Rus , Stenseth Nils Chr.
Published: July 2007

We report statistically significant genetic structure among samples of Greenland halibut (Reinhardtius hippoglossoides), rejecting the null hypothesis of panmixia in the North Atlantic. The species appears instead to be subdivided into partially isolated populations, with some evidence for isolation by distance. However, there is a dichotomy between transatlantic sample comparisons and those within a regional current system, even when geographic distance is similar. Calculating geographic distance along the flow of ocean currents gave a more linear correlation with genetic differentiation than straight-line geographic distances, suggesting that gene flow follows ocean currents. We hypothesize that gene flow is mediated by drift of eggs and larvae with ocean currents, a hypothesis that is consistent with the extended pelagic phase of Greenland halibut larvae. This implies an important role for ocean currents in shaping the genetic structure of this and potentially other deep-sea species.
Three-loop radiative corrections to Lamb shift and hyperfine splitting
Authors: Eides Michael I , Shelyuto Valery A
Published: July 2007

We consider three-loop radiative corrections to the Lamb shift and hyperfine splitting. Corrections of order α3(Zα)5m are the largest still unknown contributions to the Lamb shift in hydrogen. We calculate radiative corrections to the Lamb shift and hyperfine splitting generated by the diagrams with insertions of one radiative photon and electron polarization loops in the graphs with two external photons. We also obtain corrections generated by the gauge-invariant sets of diagrams with two reducible radiative photon insertions in the electron line and a polarization operator insertion in one of the radiative photons, and diagrams with two reducible radiative photon insertions in the electron line and a polarization operator insertion in one of the external photons. Corrections to the Lamb shift and hyperfine splitting generated by the diagrams with insertions of the three-loop one-particle reducible diagrams with radiative photons in the electron line are calculated in the Yennie gauge.PACS Nos.: 12.20.Ds, 31.30.Jv, 32.10.Fn, 36.10.Dr
Weighing the antiproton by parts-per-billion-scale laser spectroscopy of antiprotonic helium
Authors: Hayano R S
Published: July 2007

A femtosecond optical frequency comb and continuous-wave pulse-amplified laser were used to measure 12 transition frequencies of antiprotonic helium (metastable three-body system consisting of an antiproton, an electron, and a helium nucleus) to fractional precisions of (9–16) × 10–9. One of these is between two states having microsecond-scale lifetimes hitherto unaccessible to our precision laser spectroscopy method. Comparisons with three-body QED calculations yielded an antiproton-to-electron mass ratio of [Formula: see text] = 1836.152 674(5).PACS Nos.: 36.10.–k, 14.20.Dh, 32.70.Jz
First protonium production in a nested Penning trap and related topics
Authors: Rizzini E Lodi
Published: July 2007

After the synthesis of antihydrogen, the ATHENA collaboration has succeeded in the synthesis of protonium (a [Formula: see text] atom). The synthesis occurs at the "chemical" energy scale and we observe free protonium atoms with kinetic energies in the range 1–700 meV. We show that in the ATHENA apparatus protonium atoms with lifetime of the order of 1 µs have been produced after collisions with [Formula: see text] inside the e+ cloud in the nested Penning trap. This result could open a new scenario about measurements in fundamental physics.PACS Nos.: 36.10-k, 34.80.Lx, and 52.20.Hq
Two-loop QED corrections in few-electron ions
Authors: Yerokhin V A , Indelicato P , Shabaev V M
Published: July 2007

Results of a calculation valid to all orders in the nuclear-strength parameter Zα are presented for the two-loop Lamb shift, notably for the two-loop self-energy correction, for the ground and first excited states of ions with the nuclear charge numbers Z = 60–100. A detailed comparison of the all-order calculation with earlier investigations based on an expansion in the parameter Zα is given. The calculation removes the largest theoretical uncertainty for the 2pj–2s transition energies in heavy Li-like ions and is important for interpretation of experimental data.PACS Nos.: 31.30.Jv, 31.30.–i, 31.10.+z
The negative ion of positronium: measurement of the decay rate and prospects for further experiments
Authors: Fleischer F , Gwinner G , Hugenschmidt C , Schreckenbach K , Thirolf P , Wolf A , Schwalm D
Published: July 2007

The negative positronium (Ps–) ion consisting of two electrons and a positron (e+e–e–), represents the simplest three-body system with a bound state. Its constituents are stable, point-like particles, and it is essentially free from perturbations by strong interaction effects. Together with the rather unique mass ratio, these properties make the positronium ion an interesting object for studying the quantum-mechanical three-body problem. We present a new determination of the decay rate of Ps–, using a beam-foil method and a stripping-based detection technique. The measured value of Γ = 2.089(15) ns–1 is a factor of six times more precise than the previous experimental result, and there is excellent agreement both with the latter and with the theoretical value. With the new high-intensity positron source NEPOMUC at the FRM-II research reactor in Munich being available, a further improvement in precision seems possible. Moreover, the high flux of low-energy positrons at this facility brings other properties of this exotic system within reach of experiments. The prospects for such investigations are discussed.PACS No.: 36.10Dr
High-accuracy crystal spectroscopy of the n = 2 energy level of helium-like uranium
Authors: Trassinelli M , Banaś D , Beyer H F , Jagodziński P , Kumar A , Pajek M , Stöhlker Th.
Published: July 2007

We present a new experiment for the accurate study of the intrashell transition 1s2p 3P2 → 1s2s 3S1 in helium-like uranium near 4.5 keV using a Johann-type Bragg spectrometer with a spherically bent crystal. The focusing property of the bent crystal enhances the spectrometer's efficiency compared to flat crystal spectrometers and it will enable us, for the first time, to evaluate, accurately, the Lamb shift for n = 2 states in highly charged helium-like ions. The data will be acquired at the storage ring ESR of GSI using a fast H-like uranium beam colliding with a gas target. This measurement will provide the most sensitive test for the relativistic electron–electron interaction in a strong Coulomb field.PACS Nos.: 07.85.Nc, 12.20.Fv, 29.30.Kv and 32.30.Rj
Correlations in many electron systems: theory and applications
Authors: Tomaselli M , Ursescu D , Fritzsche S , Kühl T
Published: July 2007

In this contribution, we present calculations performed for interacting electron systems within a nonperturbative formulation of the cluster theory. Extrapolation of the model to describe the time dependence of the interacting systems is feasible and planned. The theory is based on the unitary operator eiS (S is the correlation operator) formalism which, in this paper, is treated non perturbatively within many-particle correlations. The application of the derived equations to few-body systems is realized in terms of generalized linearization approximations and via the cluster factorization theory. To check the reliability of the model, we present two different applications. In the first, we evaluate the transitions energies in helium-, lithium-, beryllium-, and boron-like oxygen. The calculation aims for a precise determination of the satellite transitions that play an important role in plasma diagnostics. In the second application we investigate a nonperturbative method to evaluate the charge radii of the helium and lithium isotopes by using the isotopic shift theory. We found that our model leads naturally to components of e––e+ pair in the two-electron wave functions of the helium isotopes and three-electron wave functions of the lithium isotopes. The possible connection of these terms to the quantum electrodynamics leading diagrams is postulated.PACS Nos.: 31.10.+z, 31.30.Gs, 32.30.–r
Kaonic hydrogen X-rays — experiments at DAFNE
Authors: Cargnelli M , Ishiwatari T , Kienle P , Marton J , Widmann E , Zmeskal J , Beer G , Bragadireanu A M , Ponta T , Bazzi M , Catitti M , Curceanu (Petrascu) C , Guaraldo C , Iliescu M , Sandri P Levi , Lucherini V , Pietreanu D , Sirghi D L , Sirghi F , Lechner P , Soltau H , Bombelli L , Fiorini C , Frizzi T , Longoni A , Ghio F , Girolami B , Struder L
Published: July 2007

At the DAΦNE electron–positron collider of Laboratori Nazionali di Frascati we study kaonic atoms, taking advantage of the low-energy kaons produced in the Φ-meson decay. The low-energy kaon–nucleon interaction in kaonic hydrogen and kaonic deuterium can be investigated under favorable conditions. The DEAR (DAΦNE Exotic Atom Research) experiment at LNF delivered the most precise data on kaonic hydrogen up to now. DEAR and its follow-up experiment SIDDHARTA (Silicon Drift Detector for Hadronic Atom Research by Timing Application) are using X-ray spectroscopy of kaonic hydrogen and kaonic deuterium atoms to measure the strong interaction-induced shift and width of the ground state. From these quantities the isospin-dependent antikaon–nucleon scattering lengths can be determined, quantities useful for testing the understanding of chiral symmetry breaking in the strangeness sector. Within the SIDDHARTA project new X-ray detectors are being developed. We will use an array of large area silicon drift detectors (SDDs) having excellent energy resolution but also providing a timing capability that will result in a huge suppression of background and so overcome the precision limits of the former experiments.PACS Nos.: 36.10.k, 13.75.Jz, 32.30.Rj and 29.40.Wk
Fractal fits to Riemann zeros
Authors: Slater P B
Published: July 2007

Wu and Sprung (Phys. Rev. E, 48, 2595 (1993)) reproduced the first 500 nontrivial Riemann zeros, using a one-dimensional local potential model. They concluded — as did van Zyl and Hutchinson (Phys. Rev. E, 67, 066211 (2003)) — that the potential possesses a fractal structure of dimension d = 3/2. We model the nonsmooth fluctuating part of the potential by the alternating-sign sine series fractal of Berry and Lewis A(x,γ). Setting d = 3/2, we estimate the frequency parameter (γ), plus an overall scaling parameter (σ) that we introduce. We search for that pair of parameters (γ,σ) that minimizes the least-squares fit Sn(γ,σ) of the lowest n eigenvalues — obtained by solving the one-dimensional stationary (nonfractal) Schrodinger equation with the trial potential (smooth plus nonsmooth parts) — to the lowest n Riemann zeros for n = 25. For the additional cases, we study, n = 50 and 75, we simply set σ = 1. The fits obtained are compared to those found by using just the smooth part of the Wu–Sprung potential without any fractal supplementation. Some limited improvement — 5.7261 versus 6.392 07 (n = 25), 11.2672 versus 11.7002 (n = 50), and 16.3119 versus 16.6809 (n = 75) — is found in our (nonoptimized, computationally bound) search procedures. The improvements are relatively strong in the vicinities of γ = 3 and (its square) 9. Further, we extend the Wu-Sprung semiclassical framework to include higher order corrections from the Riemann–von Mangoldt formula (beyond the leading, dominant term) into the smooth potential.

PACS Nos.: 02.10.De, 03.65.Sq, 05.45.Df, 05.45.Mt
Gauging Newton's law
Authors: Wheeler James T
Published: July 2007

We derive both Lagrangian and Hamiltonian mechanics as gauge theories of Newtonian mechanics. Systematic development of the distinct symmetries of dynamics and measurement suggest that gauge theory may be motivated as a reconciliation of dynamics with measurement. Applying this principle to Newton's law with the simplest measurement theory leads to Lagrangian mechanics, while use of conformal measurement theory leads to Hamiltonian mechanics.

PACS Nos.: 45.20.Jj, 11.25.Hf, 45.10.–b
D-branes behind the horizon
Authors: Rozali M
Published: July 2007

We review the study of D-particles in the two-dimensional black-hole background, concentrating on aspects of the dynamics that are sensitive to the region behind the horizon. Surprisingly, the portion of the trajectory behind the horizon appears to an asymptotic observer as ghost D-particle. This suggests a way of constructing a matrix model for the Lorentzian black-hole background.

PACS No.: 11.25.Uv
Formation of antihydrogen in the ground state
Authors: Kulhar V S
Published: July 2007

Cross sections for antihydrogen formation in the ground state for the process [Formula: see text] + Ps(nlm) → [Formula: see text](1s) + e– have been calculated using charge conjugation and time reversal invariance. Calculations are based on a two-state approximation method, used by the author earlier for positron–hydrogen charge -exchange process (e+ – H → Ps(nlm) + p). Cross-section results are reported in the intermediate- and high-energy region (20 keV – 500 keV).

PACS No.: 36.10.Dr
Maxwell–Chern–Simons Q-balls
Authors: Deshaies-Jacques M , MacKenzie R
Published: July 2007

We examine the energetics of Q-balls in Maxwell–Chern–Simons theory in two space dimensions. Whereas gauged Q-balls are unallowed in this dimension in the absence of a Chern–Simons term due to a divergent electromagnetic energy, the addition of a Chern–Simons term introduces a gauge-field mass and renders finite the otherwise-divergent electromagnetic energy of the Q-ball. Similar to the case of gauged Q-balls , Maxwell–Chern–Simons Q-balls have a maximal charge. The properties of these solitons are studied as a function of the parameters of the model considered, using a numerical technique known as relaxation. The results are compared to expectations based on qualitative arguments.

PACS Nos.: 11.10.Lm, 11.10.–z, 11.15.Kc
Is there new physics in B decays?
Authors: Datta A
Published: July 2007

Rare decays of the B meson are sensitive to new physics effects. Several experimental results on these decays have been difficult to understand within the Standard Model (SM) though more precise measurements and a better understanding of SM theory predictions are needed before any firm conclusions can be drawn. In this note we try to understand the present data assuming the presence of new physics. We find that the data points to new physics of an extended Higgs sector and we present a two-Higgs-doublet model with a 2–3 flavor symmetry in the down-type quark sector that can explain the deviations from the Standard Model reported in several rare B decays.

PACS Nos.: 11.30.Er, 11.30.Hv, and 13.20.He
Convergence issues in baryon chiral perturbation theory for the reaction π + N → 2π + N
Authors: Mobed N , Zhang J , Singh D
Published: July 2007

We study the reaction π + N → 2π + N within the framework of heavy-baryon chiral perturbation theory of chiral order three. We find that contributions from amplitudes of chiral order three are large and play an essential role in reproducing the experimental data. In addition, we evaluate a polarization observable (target asymmetry) for the transverse polarization of the proton target and find that the asymmetry is generally small for the reaction under consideration.

PACS Nos.: 25.80.Hp, 13.75.Gx, 11.30.Rd, 11.10.Ef
Nonseparability of continuously measured quantum systems in the classical limit
Authors: Ghose S , Sanders B C , Alsing P M , Deutsch I H
Published: July 2007

We analyze the question of separability in a continuously measured quantum system as it approaches the classical limit. We show that the record of position measurements can approach the classical limit even when the system is described by highly nonseparable states. In particular, in systems with a chaotic classical limit, chaos can work to enhance the entanglement in the system in the classical regime. This coexistence of nonclassical states and classical dynamics can be understood by analyzing the conditioned evolution of the measured system and the conditions for the quantum-to-classical transition.

PACS Nos.: 03.65.Ta, 03.65.Ud, 03.67.Mn, 05.45.Mt, 03.67.–a
Reflection and refraction of thermo-viscoelastic waves at the interface between two micropolar viscoelastic media without energy dissipation
Authors: Othman M I , Song Y Q
Published: July 2007

Reflection and refraction of a plane harmonic wave at the interface between two viscoelastic media are studied under generalized thermo-viscoelastic theory. Using potential function, the governing equations reduce to two fourth-order ifferential equations. Coefficient ratios of reflection and refraction of different waves with the angle of incidence are obtained using continuous boundary conditions. By numerical calculations, the variation of coefficient ratios of reflection and refraction with the angle of incidence are illustrated graphically for aluminium–epoxy and magnesium crystal micropolar viscoelastic materials. Also, the effects of viscous and micropolar elastic are illustrated by numerical results in the theory of thermo-viscoelasticity without energy dissipation.

PACS No.: 62.20.Dc