bluuebunny/crossref_metadata_2025 huggingface dataset:
Trace element constraints on mantle sources during mid-Proterozoic magmatism: evidence for a link between the Gardar (South Greenland) and Abitibi (Canadian Shield) mafic rocks
Authors: Halama Ralf , Joron Jean-Louis , Villemant Benoît , Markl Gregor , Treuil Michel
Published: July 2007

Trace and major element compositions of mid-Proterozoic (1.20–1.16 Ga) basaltic lava flows and dikes from the Gardar Province (South Greenland) provide evidence for two geochemically distinct magma sources. Based on distinct features of incompatible trace element ratios, such as Th/Ta, Th/Tb, or Th/Hf, they differ by the composition of their mantle source and by their partial melting trends. One mantle source is compositionally transitional between mid-ocean ridge basalt (MORB)-type and ocean-island basalt (OIB)-type sources with relatively low Ta/Hf ratios (~0.2), moderate enrichment in light rare-earth elements (LREE), and slightly positive initial εNdvalues (+2). It can be attributed to either a lithospheric mantle source or a depleted astenospheric mantle plume component that has been enriched shortly prior to eruption. The other mantle source is characterized by high Ta/Hf ratios (~0.6), a more pronounced LREE enrichment, and initial εNdvalues around 0. Elevated CeN/YbN(7.0–9.8) and TbN/YbNratios (1.6–1.8) of the rocks derived from this source indicate the presence of garnet during melting, suggesting melt generation at depths > 70 km. This mantle source has the geochemical characteristics of an OIB-type source and is interpreted as originating from a mantle plume. Samples from the slightly younger (1.14 Ga) Abitibi dike swarm (Superior Province, Canada), spatially connected to the Gardar Province, show very similar trace element characteristics and the same two distinct magma sources can be identified. The geochemical similarities between the magma sources in South Greenland and Canada support the idea of a genetic link between the two magmatic provinces. This link strengthens the idea that the system was a long-lived major intracontinental rift zone.
High-resolution organic carbon isotope record across the Cretaceous–Tertiary boundary in south-central Alberta: implications for the post-impact recovery rate of terrestrial ecosystems and use of δ13C as a boundary marker
Authors: Therrien François , Eberth David A , Braman Dennis R , Zelenitsky Darla K
Published: July 2007

A high-resolution study identified a δ13C excursion of –1.8 to –2.3 in terrestrial organic matter across the Cretaceous–Tertiary (K–T) boundary at two localities in the Scollard Formation of south-central Alberta, one of the northernmost occurrences of the K–T boundary in terrestrial settings. δ13C values are at their lowest within 6 cm above the K–T boundary claystone and return to pre-boundary levels within 10 cm above the boundary claystone. Statistical analyses reveal that the K–T isotopic shift in Alberta is related to the nature of floral changes that occurred across the K–T boundary. A radiometrically dated bentonite resting on the boundary-hosting Nevis coal at one of the localities permits us to estimate that the terrestrial carbon cycle recovered ~100 000 years after the K–T boundary event, a value that supports an existing hypothesis that terrestrial ecosystems recovered more rapidly than marine ecosystems. The organic carbon isotope record of the entire Scollard Formation demonstrates that the δ13C excursion across the K–T boundary did not reach anomalously low values by late Maastrichtian standards in Alberta. Furthermore, the occurrence of the K–T carbon isotope shift within a restricted stratigraphic interval (<10 cm) greatly limits the probability of its preservation in the context of terrestrial sedimentary environments. These observations suggest that, on their own, δ13C profiles may be unreliable for locating the K–T boundary (and possibly other geologically instantaneous events) and that they should be used in combination with other approaches (e.g., palynology) to identify the K–T boundary in sections lacking the boundary claystone and iridium anomaly.
Boreameryx, an unusual new artiodactyl (Mammalia) from the Pliocene of Arctic Canada and endemism in Arctic fossil mammals
Authors: Dawson Mary R , Harington C R
Published: July 2007

Boreameryx braskerudi, gen. et sp. nov., from Early Pliocene (about 5–4 Ma) deposits of Ellesmere Island, Nunavut, is represented by the posterior portion of a dentary with three molars, a partial calcaneum, unciform, and fragments of long bones and ribs. The incompletely known structure of Boreameryx must leave open the questions of its relationships within the pecoran ruminants. Even its possible affinities with early cervoids and the North American blastomerycines are speculative. We favour the tentative association of Boreameryx within the Cervoidea. Rather than evolving hypsodonty to deal with abrasive northern foods, Boreameryx apparently retained plesiomorphic dental structures—even augmenting those structures in a unique morphological development. We hypothesize, based on recorded relationships and ranges (both geological and geographical) of several Beaver Pond site mammals, including Boreameryx, that they indicate a significant interval of endemic development in a high northern biotic province prior to 5 Ma.
Ediacaran U–Pb zircon dates for the Lac Matapédia and Mt. St.-Anselme basalts of the Quebec Appalachians: support for a long-lived mantle plume during the rifting phase of Iapetus opening
Authors: Hodych Joseph P , Cox Richard A
Published: July 2007

It has been suggested that the rifting phase of Iapetus Ocean opening in Quebec involved a long-lived mantle plume centered near the Sutton Mountains whose dominant magmatism was first of continental flood basalt composition and later of ocean-island basalt (OIB) composition. We dated the Lac Matapédia and Mt. St.-Anselme basalts, which are thought to have originated from this plume and have dominant OIB-like composition. The U–Pb dating was done on individual zircon crystals using a laser ablation microprobe linked to an inductively coupled plasma – mass spectrometer. Zircons from two basalt flows at Lac Matapédia yielded ages of 565 ± 6 and 556 ± 5 Ma. Zircons from a basalt flow at Mt. St.-Anselme yielded an age of 550 ± 7 Ma. Although the basalts are allochthonous, these should be their ages of extrusion onto Laurentia, as shown by Grenvillian ages yielded by inherited zircons in both Lac Matapédia flows and by zircons in a granitic pebble from the Mt. St.-Anselme Formation. Our dating supports the hypothesis of a long-lived (~615 to ~550 Ma) Sutton Mountains mantle plume involved in Iapetus rifting. It does so by closing a possible gap of ~10 Ma between the end of flood basalt and the beginning of OIB magmatism, and by supporting ~540 (rather than ~570) Ma for the rift-to-drift transition in Quebec. Because plumes move slowly, this hypothesis implies that Laurentia moved slowly from ~615 to ~550 Ma. This is consistent with paleomagnetic evidence, although very rapid true polar wander at ~590 Ma may need to be invoked.
Karst-related outliers of the Cretaceous Chaswood Formation of Maritime Canada
Authors: Falcon-Lang Howard J , Fensome Robert A , Gibling Martin R , Malcolm Joanne , Fletcher Kerilyn R , Holleman Mattheus
Published: July 2007

The Lower Cretaceous Chaswood Formation is a terrestrial deposit preserved as scattered outcrops across Maritime Canada. Here we describe newly recognized outliers of the Chaswood Formation near Windsor, Nova Scotia. A Cretaceous age is confirmed only in Bailey Quarry, where sediments are provisionally assigned a Valanginian–Hauterivian (140–130 Ma) age based on palynology, making them among the oldest known deposits of the Chaswood Formation. At three nearby sites, putative Cretaceous sediments are recognized based on similar geological context, facies, and petrography; however, their age cannot be confirmed because sediments either lack palynomorphs or contain equivocal assemblages. Although the Chaswood Formation has been previously documented mainly in small tectonically generated basins, these new-found deposits are fluvial sands and gravels, and lacustrine or floodplain clays associated with a karstified gypsum surface developed on the Carboniferous Windsor Group. Deposits are preserved in karst valleys, sinkholes, and fissures, locally up to 36 m below the paleosurface. Although occupying a karstic setting, sediments were evidently deposited in a through-flowing drainage system because they are quartz-rich and show petrographic similarity to basinal deposits elsewhere. Abundant plant material, including lignite, charcoal, cuticles, and palynomorphs, implies that the surrounding landscape was covered by fire-prone forests of conifers, ginkgos, bennettites, cycads, ferns, and lycopods — typical pre-angiosperm Mesozoic vegetation. Analysis of growth patterns in fossil woods, combined with lithological indicators, suggest a humid, tropical climate, punctuated by aperiodic droughts that may have been accentuated under a karstic hydrological regime.
A new species of mosasaur (Squamata: Mosasauridae) from the Pierre Shale (lower Campanian) of Manitoba
Authors: Cuthbertson Robin S , Mallon Jordan C , Campione Nicolas E , Holmes Robert B
Published: July 2007

Plioplatecarpus nichollsae, sp. nov., from the lower Campanian (Pembina Member, Pierre Shale Formation) is diagnosed by the following: a thickened ventral rim of the external naris, a short supratemporal fenestra, a frontal shield with well-developed posterolateral lappets that overlap the parietal dorsally, proximal rib shafts with an approximately circular (but not inflated) cross section, a scapula shaped as in other Plioplatecarpus species but approximately the same size (not larger) than the coracoid, and a moderately large parietal foramen that reaches the frontoparietal suture but does not invade the frontal. The last two characters require that the diagnosis of the genus Plioplatecarpus be emended. With other Plioplatecarpus species, P. nichollsae shares a robust humerus with a distal expansion at least as great as the total length of the bone, a rectangular preorbital frontal shield, a "peg and socket" postorbitofrontal-jugal articulation, a transversely directed ectopterygoid process of the pterygoid, a large, robust quadrate with a distinct eminence on the posterior surface of its shaft, an unossified gap in the ventral wall of the basioccipital, and at least 11 pygal vertebrae. P. nichollsae also shares primitive features with Platecarpus, as well as features apparently intermediate between Platecarpus and Plioplatecarpus. Revision of the genus Platecarpus, currently hypothesized to be both paraphyletic and polyphyletic, as well as a better understanding of the early Campanian mosasaur fauna from the Morden area, are necessary before the phylogenetic significance of some of these characters, and therefore the relationships of Plioplatecarpus nichollsae, can be fully resolved.
Neomorphism of the Middle Devonian Ratner limestone related to dehydration of gypsum in south-central Saskatchewan
Authors: Fu Qilong , Qing Hairuo
Published: July 2007

The Middle Devonian Ratner Formation in south-central Saskatchewan consists of laminated carbonate and interlaminated to interbedded carbonate and anhydrite, and the Ratner carbonate is preserved as limestone in many cored intervals. Medium to very coarsely crystalline (MVC) limestone (up to 4 m in thickness) is dominantly present in the uppermost part or the upper cycle of the Ratner Formation directly overlain by the Whitkow anhydrite. Generally, both abundance and size of the MVC calcite crystals decrease downward away from contact between the Ratner carbonate and the Whitkow anhydrite. The average87Sr/86Sr ratio of the MVC calcite is 0.7078, comparable to that of Middle Devonian seawater. The Ratner MVC limestone is interpreted to result from neomorphism of the precursor microcrystalline lime mudstone in burial environments, and neomorphic fluids might have consisted of gypsum-dehydration water mixing with minor various ratios of formation waters, based on petrographic observation, O- and Sr-isotopic data, and stratigraphic evidence. This research provides a case study in which the neomorphism of limestone is related to gypsum-dehydration water.
Modelling length-at-age variability under irreversible growth
Authors: Gurney William SC , Tyldesley Graham , Wood Simon N , Bacon Philip J , Heath Michael R , Youngson Alan , Ibbotson Anton
Published: July 2007

In this paper, we describe a discrete-time formalism for describing the dynamics of the size-at-age distribution of a cohort of individuals exhibiting irreversible von Bertalanffy growth in a statistically uniform random environment. This formalism yields a highly efficient numerical implementation, which is particularly suited to automatic optimization. In the special case where mortality is sufficiently size-independent not to vary substantially across the bulk of the size distribution at any given age, we can further increase this efficiency by deriving compact update rules for the mean and coefficient of variation of size-at-age. In this case, we also demonstrate that the depensatory effect of random growth variability and the compensatory effect of deterministic von Bertalanffy growth balance to yield an attracting (initial condition independent) trajectory of mean length and length coefficient of variation against age. We demonstrate the applicability and extensibility of this formalism by two exemplary applications - juvenile salmonids and demersal cod.
Nonnative brook trout (Salvelinus fontinalis) and the demise of native brown trout (Salmo trutta) in northern boreal lakes: stealthy, long-term patterns?
Authors: Spens Johan , Alanärä Anders , Eriksson Lars-Ove
Published: July 2007

This study of 193 boreal lakes of northern Sweden suggests a long-term detrimental impact of introduced brook trout (Salvelinus fontinalis) on brown trout (Salmo trutta) populations. Thirteen of 65 (20%) brown trout populations in lakes exposed to brook trout went extinct, whereas the extinction rate in unexposed lakes was significantly lower (2%). We verified other studies that indicate that altitude strongly affects the distribution of the two species; brown trout populations in our higher altitude lakes were more sensitive to impact from brook trout. In 28 lakes above 285 m, 12 trout populations exposed to brook trout went extinct, while only one population became extinct in 37 lakes below 285 m. No effects of other environmental factors were detected (e.g., water chemistry, stocking of rainbow trout (Oncorhynchus mykiss), fish species community assembly, migration barriers, or lake morphometry on brown trout extinction). The time lag between the first record of brook trout introduction and subsequent extinction of brown trout was two decades on average (maximum 70 years). Even though further stocking of brook trout has been stopped, our analysis suggest that existing sympatric populations may continue to pose an extinction threat to brown trout.
Does male-only fishing influence reproductive success of the female spiny king crab, Paralithodes brevipes?
Authors: Sato Taku , Ashidate Masakazu , Jinbo Tadao , Goshima Seiji
Published: July 2007

Male-only fishing for spiny king crab (Paralithodes brevipes) has likely impaired the reproductive success of the stock by decreasing the availability of sperm and (or) male mates. The reproductive success of females in fished populations in 2003 and 2004 was estimated based on female reproductive potential determined in laboratory experiments. Some females had no or partial clutches and showed a low fertilization rate. As female size decreased, the fertilization rate decreased and their clutches became small. These results suggest that mating was impaired by sperm limitation, because risk of sperm limitation increases throughout the reproductive season in fished populations, and smaller females tend to mate later in the reproductive season than larger females of this species. We compared the reproductive success between these years with different fishing pressures. In 2003, the total fishing pressure was high, therefore causing decreases in availability of sperm and males. This likely resulted in the reproductive success of females being lower in 2003 than in 2004.
Oxygen as a constraining factor in egg size evolution in salmonids
Authors: Rombough Peter J
Published: July 2007

Differential survival at low oxygen levels has been proposed as a mechanism for maintaining high within-population variability in egg size in fish. Whether low oxygen levels favour large or small eggs, however, is not clear. To address this question, the effects of egg size on metabolic rates, critical dissolved oxygen levels (Pc), and P50oxygen levels of Chinook salmon (Oncorhynchus tshawytscha) embryos and alevins were determined. Embryonic metabolic rate expanded at a slower rate with increasing egg mass (allometric constant (b) = 0.30) than did capsule surface area (b = 0.67), indicating that larger eggs have larger surface areas relative to their metabolic demand for oxygen. A relatively larger area, however, did not translate into significant differences in Pcor P50values at the egg stage. After hatch, metabolic rate expanded at a rate proportional to (egg mass)0.62. Pclevels were significantly higher for alevins from larger eggs for the first but not second half of the alevin stage. Egg size had no significant effect on P50values at any time during the alevin stage. The modest impact of egg size on hypoxic tolerance of developing Chinook suggests that factors other than oxygen are involved in maintaining high within-population variability in egg size.
Multidecadal trends for three declining fish species: habitat patterns and mechanisms in the San Francisco Estuary, California, USA
Authors: Feyrer Frederick , Nobriga Matthew L , Sommer Ted R
Published: July 2007

We examined a 36-year record of concurrent midwater trawl and water quality sampling conducted during fall to evaluate habitat trends for three declining fish species in the San Francisco Estuary, California, USA: delta smelt (Hypomesus transpacificus), striped bass (Morone saxatilis), and threadfin shad (Dorosoma petenense). Generalized additive modeling revealed that Secchi depth and specific conductance were important predictors of occurrence for delta smelt and striped bass, while specific conductance and water temperature were important for threadfin shad. Habitat suitability derived from model predictions exhibited significant long-term declines for each species; the southeastern and western regions of the estuary exhibited the most dramatic changes. Declines in habitat suitability were associated with anthropogenic modifications to the ecosystem. For delta smelt, an imperiled annual species endemic to the estuary, the combined effects of fall stock abundance and water quality predicted recruit abundance during recent years of chronically low food supply. Our results are consistent with existing evidence of a long-term decline in carrying capacity for delta smelt and striped bass and demonstrate the utility of long-term data sets for evaluating relationships between fish and their habitat.
Consequences of variations in carrying capacity or migration for the perception of Atlantic bluefin tuna (Thunnus thynnus) population dynamics
Authors: Fromentin Jean-Marc , Kell Laurence T
Published: July 2007

Spectacular long-term cycles (around 110 years), independent of human exploitation, have been seen in historical catches of Atlantic bluefin tuna (Thunnus thynnus). Previous studies indicated that such variations could have been generated by contrasting but equally plausible dynamic processes, i.e., changes in carrying capacity or migration. A simulation framework was therefore used to test whether the International Commission for the Conservation of Atlantic Tuna stock assessment model, i.e., a virtual population analysis (VPA), can capture such dynamics. The main outcome is that knowledge of the underlying process is crucial, because distinct hypotheses lead to different population dynamics and contrasting performances of the stock assessment model. The VPA is indeed able to reconstruct accurately the historical stock parameters under the carrying-capacity hypothesis, but not under the migratory hypothesis, for which there is often strong bias (up to 500%) in absolute values and in trends of spawning stock biomass and F. Furthermore, it was shown that (i) different phases between exploitation and long-term cycle can induce contrasting terminal F for a same effort and (ii) that there was considerable confounding between the dynamics and increasing effort (as currently seen). We conclude that it is difficult to infer the actual dynamics on the basis of commercial catch data and that novel fishery-independent observation is needed.
Optimal growth temperature hypothesis: Why do anchovy flourish and sardine collapse or vice versa under the same ocean regime?
Authors: Takasuka Akinori , Oozeki Yoshioki , Aoki Ichiro
Published: July 2007

The out-of-phase population oscillations between anchovy and sardine have been attributed to climate changes. However, the biological processes causing these species alternations have remained unresolved. Here we propose a simple "optimal growth temperature" hypothesis, in which anchovy and sardine regime shifts are caused by differential optimal temperatures for growth rates during the early life stages. Dome-shaped relationships between growth rate and sea temperature were detected for both Japanese anchovy (Engraulis japonicus) and Japanese sardine (Sardinops melanostictus) larvae based on otolith microstructure analysis. The optimal growth rate for anchovy larvae occurred at 22.0 °C, whereas that for sardine larvae occurred at 16.2 °C. Ambient temperatures have historically fluctuated between these optima, which could lead to contrasting fluctuations in larval growth rates between the two species. This simple mechanism could potentially cause the shifts between the warm anchovy regime and the cool sardine regime in the western North Pacific. Although retrospective analysis suggested synergistic effects of other factors (e.g., trophic interactions and fishing), the optimal growth temperature concept would provide a possible biological mechanism of anchovy and sardine regime shifts.
Hierarchical analysis of relationships between brook trout (Salvelinus fontinalis) density and stream habitat features
Authors: Deschênes Julie , Rodríguez Marco A
Published: July 2007

We used hierarchical linear regression to examine relationships between brook trout (Salvelinus fontinalis) density and habitat features nested at three levels: sections within reaches, reaches within streams, and streams within a basin. Brook trout density and environmental variables were quantified at 600 stream sections distributed among 120 reaches and 22 streams in the Cascapedia River basin, Quebec, Canada. Decomposition of variance showed that variation in density among streams was small relative to that among sections or reaches and not statistically significant. Density was influenced by habitat variables at both the section (current velocity, woody debris, cover) and reach (subbasin area, height increment at flood, valley width) levels. A cross-level interaction between current velocity and subbasin area pointed to a "contextual" effect: density showed stronger decline with current velocity in larger subbasins than in smaller subbasins. This result suggests that there was no single "best scale" for examining fish–environment relationships. Accounting for contextual effects by use of hierarchical models can enhance our understanding of how habitat features influence fish densities at multiple spatial scales.
The digestive and metabolic enzyme activity profiles of a nonmetamorphic marine fish species: effects of feed type and feeding level
Authors: Lamarre Simon Gaston , François Nathalie Rose Le , Lemieux Hélène , Falk-Petersen Inger-Britt , Blier Pierre Ulrich
Published: July 2007

We investigated activity levels of metabolic and digestive enzymes in Atlantic wolffish (Anarhichas lupus) and their relationships with growth, ration level, and type of food during the first 50 days after hatch. Newly hatched wolffish were divided among three experimental groups differing in feed and ration (formulated feed in excess (FF), a maintenance ration of Artemia (LA), and Artemia in excess (EA)) that generated different growth rates. A principal component analysis revealed that activities of the glycolytic enzymes lactate dehydrogenase (LDH) and pyruvate kinase (PK) were associated with mass gain, while those of the aerobic enzymes citrate synthase and aspartate aminotransferase (AAT), and digestive enzymes (lipase and trypsin) were related to time (days) after hatch. Food restriction or food type allowed the observation of a direct relationship between the activities of trypsin and those of associated metabolic enzymes AAT and glutamate dehydrogenase in the LA group (Pearson's R of 0.71 and 0.59, respectively), as well as between the activities of amylase and those of LDH and PK (Pearson's R of 0.62 and 0.48, respectively) in the FF group. The adaptative importance of these patterns during early development of wolffish and their relationship to feeding conditions are examined.
Carry-over effects in brown trout (Salmo trutta): hypoxia on embryos impairs predator avoidance by alevins in experimental channels
Authors: Roussel Jean-Marc
Published: July 2007

Laboratory experiments on brown trout (Salmo trutta) embryos suggest that sublethal stress in the gravel nest such as hypoxia may alter the behaviour and survival of fish during the early juvenile period. Eggs and embryos were incubated at constant temperature (8.2 °C ± 0.6 standard deviation) under nonlethal dissolved oxygen (DO) concentrations (3.0 mg·L–1; 26% air saturation level) and normoxia (10.3 mg·L–1DO; 90% air saturation level). The average survival from fertilization to end of embryonic development was 70% and 85% for hypoxic and normoxic groups, respectively. Hypoxic embryos grew slowly compared with their normoxic counterparts, but similar body sizes were observed when yolk-sac absorption was completed. Fish incubated as hypoxic embryos delayed their emergence from the gravel in experimental channels. In presence of freshwater sculpin (Cottus gobio), their swimming activity was reduced by 20%, on average, and predation was enhanced by 14% compared with normoxic groups. Results support the view that subtle events early in a fish's ontogeny can have carry-over effects on later periods of its life cycle, and this phenomenon may be a significant source of variation in salmonid fitness.
Compensatory growth in threespine sticklebacks (Gasterosteus aculeatus) inhibited by experimental Schistocephalus infections
Authors: Wright Hazel A , Wootton Robert J , Barber Iain
Published: July 2007

Compensatory growth responses are made by individual fish to restore their original growth trajectory following a period of growth depression. Little is known about whether diseases impact a fish's capacity for growth compensation. In this study we investigate the effect of Schistocephalus solidus, a common cestode parasite of threespine sticklebacks (Gasterosteus aculeatus), on the ability of host fish to undertake growth compensation following short-term food deprivation. Placebo-infected controls completely compensated for a 2-week deprivation period after 3 weeks postdeprivation feeding, but experimentally infected sticklebacks showed only partial compensation and after 6 weeks of refeeding had attained only 80% of the weight of continually fed infected fish. A major factor limiting the compensatory growth response of infected fish was their reduced hyperphagic response during the period of refeeding. Feed deprivation had no effect on ultimate parasite size of infected fish. We discuss the possible mechanisms limiting hyperphagia in infected fish and consider the fitness implications — for parasites and hosts — of the reduced ability of infected fish to undertake compensatory growth responses.
The effects of hatchery domestication on competitive dominance of juvenile spring Chinook salmon (Oncorhynchus tshawytscha)
Authors: Pearsons Todd N , Fritts Anthony L , Scott Jennifer L
Published: July 2007

We tested the null hypotheses that competitive dominance among juvenile Chinook salmon (Oncorhynchus tshawytscha) in contest and scramble experiments would not be affected by domestication selection after one generation of state-of-the-art hatchery culture. Dyadic challenges of size-matched juvenile fish were conducted after a 6-day acclimation in 113.4 L aquaria. Differences in dominance and frequency of different types of agonistic interactions used were not significantly different in contest (n = 505) or scramble (n = 363) competition experiments (P > 0.05). However, wild origin fish were more aggressive than hatchery origin fish in both types of experiments (P ≤ 0.05). Furthermore, wild origin fish gained more weight than hatchery origin fish during contest experiments, and hatchery origin fish lost less weight than wild origin fish in scramble experiments (P ≤ 0.05). Dominant fish, regardless of origin, grew more than subordinate fish in both contest and scramble experiments (P ≤ 0.05). Our results indicate that aggression, and growth mediated by competition, can be affected by domestication after only one generation of state-of-the-art hatchery culture; however, impacts to competitive dominance appear to be small.
Temperature and diet effects on omnivorous fish performance: implications for the latitudinal diversity gradient in herbivorous fishes
Authors: Behrens Michael D , Lafferty Kevin D
Published: July 2007

Herbivorous fishes show a clear latitudinal diversity gradient, making up a larger proportion of the fish species in a community in tropical waters than in temperate waters. One proposed mechanism that could drive this gradient is a physiological constraint due to temperature. One prediction based on this mechanism is that if herbivorous fishes could shift their diet to animal material, they would be better able to grow, survive, and reproduce in cold waters. We tested this prediction on the omnivore Girella nigricans under different temperature and diet regimes using RNA–DNA ratios as an indicator of performance. Fish had increased performance (100%) at low temperatures (12 °C) when their diet was supplemented with animal material. In contrast, at higher temperatures (17, 22, and 27 °C) fish showed no differences between diets. This indicates that omnivorous fishes could increase their performance at low temperatures by consuming more animal matter. This study supports the hypothesis that a relative increase in the nutritional value of plant material at warmer temperatures could drive the latitudinal diversity gradient in herbivorous fishes.
High-accuracy calculations in the H+2 molecular ion: towards a measurement of mp/me
Authors: Karr J Ph. , Bielsa F , Valenzuela T , Douillet A , Hilico L , Korobov V I
Published: July 2007

We report on our recent advances in the calculation of the energy levels of the H+2 molecular ion, including relativistic and radiative corrections. These theoretical efforts are linked to the prospect of obtaining a new determination of the proton to electron mass ratio mp/me through precise vibrational spectroscopy of H+2. We describe the setup of our experiment, aiming at a measurement of the L = 2, υ = 0 → L = 2, υ = 1 two-photon transition at 9.166 μm using a phase-locked quantum cascade laser as excitation source.PACS Nos.: 31.15.Pf, 31.30.Jv, 32.10.Hq
Nonresonant corrections and limits for the accuracy of the frequency measurements in modern hydrogen experiments
Authors: Labzowsky L N , Schedrin G , Solovyev D , Plunien G
Published: July 2007

The theory of the nonresonant corrections, defining the limits of accuracy for the frequency measurements in resonance experiments, is generalized to the situation when the excitation of an atomic state is governed by one Hamiltonian Ĥin and the decay of the excited state is governed by another Hamiltonian Ĥout. The description developed here corresponds to the experimental conditions realized in most accurate modern resonance-frequency measurements of the 2s–1s transition in hydrogen. Two different variants of the theoretical description of the resonance experiments, referred to as "statistical" and "coherent" scenarios, are discussed. The criterion of how to define which scenario should be attributed to a particular resonance experiment is shown. The in and (or) out quantum electrodynamic formalism referring to different asymptotic Hamiltonians is applied. A value of 10–5 Hz, obtained for the accuracy limit in the 1s–2s experiment within the "coherent" scenario, is not so far from the accuracy already achieved experimentally (46 Hz). The accuracy limits for the Lyman-alpha frequency measurements for a "coherent" type of experiment are also obtained and shown to be comparable with recent experimental accuracy.PACS Nos.: 06.20.Jr, 31.10.+z, 32.30Bv
Energy-dependent many-body perturbation theory for few-electron systems: Pair functions with a virtual photon for helium-like systems
Authors: Hedendahl D , Salomonson S , Lindgren I
Published: July 2007

Analytical methods for atomic quantum electrodynamics (QED) calculations are mainly applicable to light elements, while available numerical methods work only for medium-heavy and heavy elements. A new numerical perturbative technique for energy-dependent interactions is being developed, based upon the recently introduced covariant evolution-operator method (Lindgren et al. Phys. Rep. 389, 181 (2004)). This could be used for combined many-body-QED calculations on light as well as heavy elements. The method is presently being implemented, and some preliminary numerical results for light helium-like ions are given.PACS Nos.: 31.30.Jv, 31.15.Md, 31.25.Jf, 33.15.Pw
Status of the muonic hydrogen Lamb-shift experiment
Authors: Nebel T , Amaro F D , Antognini A , Biraben F , Cardoso J MR , Conde C AN , Dax A , Dhawan S , Fernandes L MP , Giesen A , Hänsch T W , Indelicato P , Julien L , Knowles P E , Kottmann F , Le Bigot E , Liu Y -W , Lopes J AM , Ludhova L , Monteiro C MB , Mulhauser F , Nez F , Pohl R , Rabinowitz P , dos Santos J MF , Schaller L A , Schuhmann K , Schwob C , Taqqu D , Veloso JF CA
Published: July 2007

The Lamb-shift experiment in muonic hydrogen (μ– p) aims to measure the energy difference between the [Formula: see text] atomic levels to a precision of 30 ppm. This would allow the r.m.s. proton charge radius rp to be deduced to a precision of 10–3 and open a way to check bound-state quantum electrodynamics (QED) to a level of 10–7. The poor knowledge of the proton charge radius restricts tests of bound-state QED to the precision level of about 6 × 10–6, although the experimental data themselves (Lamb-shift in hydrogen) have reached a precision of  × 10–6. Values for rp not depending on bound-state QED results from electron scattering experiments have a surprisingly large uncertainty of 2%. In our Lamb-shift experiment, low-energy negative muons are stopped in low-density hydrogen gas, where, following the μ– atomic capture and cascade, 1% of the muonic hydrogen atoms form the metastable 2S state with a lifetime of about 1 μs. A laser pulse at λ ≈ 6 μm is used to drive the 2S → 2P transition. Following the laser excitation, we observe the 1.9 keV X-ray being emitted during the subsequent de-excitation to the 1S state using large-area avalanche photodiodes. The resonance frequency and, hence, the Lamb shift and the proton charge radius are determined by measuring the intensity of the X-ray fluorescence as a function of the laser wavelength. The results of the run in December 2003 were negative but, nevertheless, promising. One by-product of the 2003 run was the first observation of the short-lived 2S component in muonic hydrogen. Currently, improvements in the laser-system, the experimental apparatus, and the data acquisition are being implemented. PACS Nos.: 36.10.Dr, 14.20.Dh, 42.62.Fi
Two-loop effects and current status of the 4He+ Lamb shift
Authors: Jentschura U D , Haas M
Published: July 2007

We report on recent progress in the treatment of two-loop binding corrections to the Lamb shift, with a special emphasis on S and P states. We use these and other results to infer an updated theoretical value of the Lamb shift in 4He+.PACS Nos.: 12.20.Ds, 31.30.Jv, 06.20.Jr, 31.15.–p
Laser spectroscopy of hyperfine structure in highly charged ions: a test of QED at high fields
Authors: Winters D FA , Vogel M , Segal D M , Thompson R C , Nörtershäuser W
Published: July 2007

An overview is presented of laser spectroscopy experiments with cold, trapped, highly charged ions, which will be performed at the HITRAP facility at GSI in Darmstadt (Germany). These high-resolution measurements of ground-state hyperfine splittings will be three orders of magnitude more precise than previous measurements. Moreover, from a comparison of measurements of the hyperfine splittings in hydrogen-like and lithium-like ions of the same isotope, QED effects at high electromagnetic fields can be determined within a few percent. Several candidate ions suited for these laser spectroscopy studies are presented.PACS Nos.: 12.20.Fv, 21.10.Ky, 32.10.Fn, 32.30.–r
g factor of the bound electron and muon
Authors: Lee R N , Milstein A I , Terekhov I S , Karshenboim S G
Published: July 2007

Quantum electrodynamics (QED) corrections to the g factor of the bound electron and muon in the hydrogenlike atom are discussed. An approach that allows one to express the relativistic g factor of spin-1/2 particle in terms of the binding energy is applied to the calculation of the corrections to the g factor due to the finite nuclear size, including the vacuum polarization radiative correction. The contribution of the light-by-light diagram to the g factor of the bound electron and muon is calculated. For light one-electron ions, which are important for the experiment, this contribution has, so far, not been known.PACS Nos.: 31.15.Pf, 31.30.Jv, 32.10.Hq
New evaluation of proton structure corrections to hydrogen hyperfine splitting
Authors: Carlson Carl E
Published: July 2007

We consider the proton structure corrections to the hydrogen ground-state hyperfine structure, focusing on a state-of-the-art evaluation of the inelastic nucleon corrections — the polarizability corrections — using analytic fits to the most recent data. We find a value for the fractional correction Δpol of 1.3 ± 0.3 ppm. This is 1–2 ppm smaller than the value of Δpol one would deduce using hyperfine-splitting data and elastic proton structure corrections obtained from modern form factor fits. In addition, we discuss the derivations of the relevant formulas, paying attention to lepton mass effects and to questions surrounding the use of unsubtracted dispersion relations.

PACS Nos.: 31.30.Gs, 32.10.Fn, 14.20.Dh, 13.40.Gp
Nucleon form factor measurements in Mainz: past and future
Authors: Bernauer Jan C
Published: July 2007

The form factors of protons and neutrons provide a natural and direct insight into their internal structure. They were a main research goal in the nuclear physics program of the Universitat Mainz, which led to some of the most precise measurements to date. This article gives an overview, starting from the very first experiments at the now obsolete linear accelerator and ending at the exhaustive experiments currently underway at the MAMI facilities. PACS Nos.: 14.20.Dh, –13.40.Gp, –25.30.Bf
Fractality of emission of compound multiplicity in 12C–AgBr interactions at 4.5A GeV
Authors: Ghosh D , Deb A , Biswas S , Mandal P , Haldar P Kr.
Published: July 2007

This paper presents a fractality analysis of the compound multiplicity (pions + target protons) distribution in 12C–AgBr interactions at 4.5A GeV in terms of moments proposed by Takagi (Phys. Rev. Lett. 72, 32 (1994)) for both emission-angle (θ) and azimuthal-angle (ϕ) space. The generalized dimensions Dq, q = 1 to 5, have been calculated and compared to other studies. The analysis reveals the multifractal nature of particle production as a common feature of emission of different patterns in high-energy nuclear collisions.

PACS Nos.: 25.75–q, 24.60 Ky
MHD-mixed convection and mass transfer from a vertical stretching sheet with diffusion of chemically reactive species and space- or temperature-dependent heat source
Authors: El-Aziz Mohamed Abd , Salem Ahmed M
Published: July 2007

The influence of chemical reactions on the problem of coupled heat and mass transfer by natural convection from a vertical stretching surface in the presence of a space- or temperature-dependent heat source effect is investigated. The sheet is stretched linearly in the presence of a uniform transverse magnetic field. The fluid is assumed to be viscous and incompressible. The governing differential equations are transformed by introducing similarity variables into a system of nonlinear ordinary differential equations and solving them numerically on the assumption of a small magnetic Reynolds number. The effects of the various parameters on the velocity, temperature, and concentration profiles as well as the local wall shear stresses, the local Nusselt number, and the local Sherwood number are presented graphically and in tabular form. An analysis of the results obtained shows that the flow field is influenced appreciably by the chemical reaction, heat source, magnetic field, and suction or injection at the sheet.

PACS No.: 47.65.-d
Ètude des interfaces SiO2/TiO2 et TiO2/SiO2 dans la structure SiO2/TiO2/SiO2/c-Si préparée par pulvérisation cathodique radio fréquence
Authors: Hafidi K , Azizan M , Ijdiyaou Y , Ameziane E L
Published: July 2007

The atomic structure of the TiO2/SiO2 and SiO2/TiO2 interfaces has been investigated in SiO2/TiO2/SiO2 multilayers deposited by radio frequency reactive sputtering without breaking the vacuum on the crystalline substrate cooled by water. The characterizations of these interfaces have been performed using three complementary techniques sensitive to surface and interface state: X-ray photoelectron spectroscopy (XPS), grazing incidence X-ray diffraction (GIXD), and specular X-ray reflectometry (GIXR). The concentration profiles and Si2p and O1s core level chemical displacements show that TiO2/SiO2 and SiO2/TiO2 interfaces are very diffuse. The reflectometry measurements confirm this character and indicate that the silicon, titanium, and oxygen atomic concentrations vary gradually at the interfaces. The grazing incidence X-ray spectra indicates that the interfacial layers are not well crystallized and are formed by SiO2-TiO2, TiO, Ti2O3, Ti3O5, Ti5Si3, Ti5Si4, TiSi, and TiSi2 components.
Symmetry, quasisymmetry, and critical phenomena
Authors: Rowe D J
Published: July 2007

This presentation is an analysis of the role of symmetry in second-order quantum phase transitions. It seeks to explain why transitions between phases of systems, associated with different symmetries, exhibit critical phenomena. It transpires that a system in one phase, tends to hold onto the symmetry associated with that phase until a breaking point is reached at which a rapid transition occurs to a new phase associated with a different symmetry. Understanding what is happening presents the challenge of explaining how a system "holds on" to a symmetry in the face of strong symmetry-breaking interactions. The explanation is of fundamental interest in physics, for understanding why models with built in symmetries often work extremely well even when the models ignore large symmetry-breaking interactions that are known to be present. When this phenomenon occurs, we say that the system has a quasidynamical symmetry. This concept is of interest in mathematics because it turns out that quasidyndamical symmetries are the physical realizations of a new concept in group theory, which we refer to as an embedded representation.

PACS Nos.: 21.60.Fw, 21.60.Ev, 64.6–.Ht, 68.18.Jk
An improved installation for high-resolution laser spectroscopy on ion beams
Authors: Bazin M , Roy D , Larzillière M , el Idrissi M Chafik
Published: July 2007

For many years, a complex installation has been developed in our laboratory for high-resolution laser spectroscopy of fast ion and neutral beams. Various results have been obtained for different species (H2, O2+, N2+, N2O+, and CO2+). The different spectroscopic techniques applicable to an accelerated beam are presented or recalled in this work to show the performance of the apparatus. Some difficulties in understanding the b4 Σ–g O2+ predissociation process led us to modify the molecular photofragment detection system and make it more efficient, as shown by the results presented.

PACS No.: 39.30.+w
The spectrum of Yang–Mills theory in 2+1 dimensions, analytically
Authors: Leigh R G , Minic D , Yelnykov A
Published: July 2007

We review our recent work on the glueball spectrum of pure Yang–Mills theory in 2 + 1 dimensions. The calculations make use of Karabali–Nair corner variables in the Hamiltonian formalism, and involve a determination of the leading form of the ground-state wave functional.

PACS Nos.: 12.38.Lg, 11.15.Pg, 11.15.Tk
Decoherence-free subspaces and spontaneous emission cancellation
Authors: Marzlin K -P , Karasik R , Sanders B C , Whaley K B
Published: July 2007

We establish the connection between decoherence-free subspaces of quantum information and spontaneous emission cancellation in quantum optics with molecules. Both phenomena rely on the destructive interference of transition amplitudes from two initial states to a common target state. We discuss physical similarities, differences, and limitations of both phenomena.

PACS Nos.: 03.65.Yz, 42.50.–p, 03.67.Pp
Oscillatory thermoelectric effect in quasi-two-dimensional organic conductors in a magnetic field
Authors: Krstovska D , Galbova O
Published: July 2007

A theoretical analysis is presented of the dependence of the thermoelectric power, when the temperature gradient is directed along the normal to the layers, in a layered conductor, with a quasi-two-dimensional electron energy spectrum on the magnitude and orientation of a strong magnetic field relative to the layers. The angular oscillations of the thermoelectric power, when the magnetic field is noticeably tilted from the normal to the layers result from the periodic dependence of the average electron velocity on the angle between the normal to the layers and the magnetic field. It is shown that, in a quantizing magnetic field at low temperatures, giant quantum oscillations of thermoelectric power as a function of both the magnetic field magnitude and the angle between the normal to the layers and the magnetic field occur. This quantum oscillation effect can be used with a high degree of accuracy as a good spectroscopic method for the experimental study of certain characteristics of a Fermi surface of quasi-two-dimensional organic conductors, such as the quasi-two-dimensionality parameter of the electron energy spectrum, cyclotron effective electron mass, and velocity distribution of charge carriers as well as an accurate determination of the extremal cross sections.

PACS No.: 72.15.Jf
A modified Bethe Ansatz for the two-dimensional dimer problem
Authors: Schmidt J R
Published: July 2007

The two-dimensional dimer problem is studied using the tools of modern solvable models. The transfer matrix is constructed from local monodromy matrices, and is diagonalized by a modified Bethe Ansatz that does not begin with a Bethe ground state, but rather with a pair of states transformed one into the other by the transfer matrix. The resulting Bethe eigenvectors have a structure very different from those constructed in other models from a ground state, and have some properties in common with the free-fermion eigenvectors of the squared transfer matrix encountered in the literature.

PACS Nos.: 05.50+q, 02.10.Ox, 02.30.Ik, 05.20.–y