bluuebunny/crossref_metadata_2025 huggingface dataset:
Mixing Enhancement by Microrotor in Step Channel
Authors: Dinh Thien X. , Ogami Yoshifumi
Published: February 2011

In this paper, the mixing enhancement of a micromixer consisting of a step channel and a shuttlecock rotor suspended in the step is numerically analyzed. Asymptotic mixing performance is investigated as a function of Strouhal and Peclet numbers by particle tracking simulation and the Eulerian approach. The simulation results show that the rotor creates downward and inward flows in behind the rotor paddles, whereas the upward and outward flows are produced in front of the rotor paddles. At a small Strouhal number, convective mixing is very poor. However, the mixing direction is rotated by 90 deg, which can reduce the mixing time by the square of the aspect ratio of the cross section of the channel. In contrast, at a relatively large Strouhal number, good convective mixing occurs. Quantitative analysis of mixing performance of the mixer demonstrates that the mixing structures are similar for the same Strouhal number and mixing is improved with increasing Strouhal number. The mixing efficiency of the mixer decreases linearly with increasing log of the Peclet number at a relatively large Strouhal number.
A Combined Numerical and Experimental Study of Hydrodynamics for an Air-Water External Loop Airlift Reactor
Authors: Law Deify , Jones Samuel T. , Heindel Theodore J. , Battaglia Francine
Published: February 2011

The external loop airlift reactor (ELALR) is a modified bubble column reactor that is composed of two vertical columns that are interconnected with two horizontal tubes and is often preferred over traditional bubble column reactors because they can operate over a wider range of conditions. In the present work, the gas-liquid flow dynamics in an ELALR was simulated using an Eulerian–Eulerian ensemble-averaging method in two-dimensional (2D) and three-dimensional (3D) coordinate systems. The computational fluid dynamics (CFD) simulations were compared to experimental measurements from a 10.2 cm diameter ELALR for superficial gas velocities ranging from 1 cm/s to 20 cm/s. The effect of specifying a mean bubble diameter to represent the gas phase in the CFD modeling was investigated, and 2D and 3D simulations were found to be in good agreement with the experimental data. The ELALR flow regimes were compared for the reactor operating in bubble column, closed vent, and open vent modes, and the 2D simulations qualitatively predicted the behavior of bubble growth in the downcomer. However, it was found that 3D simulations were necessary to capture the physics of the ELALR for gas holdup, bulk density differences, and riser superficial liquid velocity.
Spectroscopic ellipsometry on thin titanium oxide layers grown on titanium by plasma oxidation
Authors: Droulers G. , Beaumont A. , Beauvais J. , Drouin D.
Published: February 2011

Electronic devices based on tunnel junctions require tools able to accurately control the thickness of thin metal and oxide layers on the order of the nanometer. This article shows that multisample ellipsometry is an accurate method to reach this goal on plain uniform layers, in particular for titanium. From these measurements, the authors carefully studied the oxidation rate of titanium thin films in an oxygen plasma. The authors found that the oxide thickness saturates at 5.4±0.4 nm after 10 min in the plasma with an ion acceleration power of 30 W. Increasing this power to 240 W increases the saturation value to 7.6±0.4 nm. An x-ray photoelectron spectroscopy study of the oxide has shown that the oxide created by O2 plasma is stoichiometric (TiO2). The developed model was also used to measure the thicknesses of titanium and titanium oxide layers that have been polished using a chemical mechanical planarization process and a material removal rate of 5.9 nm/min is found with our planarization parameters.
Suppression of Collisional Shifts in a Strongly Interacting Lattice Clock
Authors: Swallows Matthew D. , Bishof Michael , Lin Yige , Blatt Sebastian , Martin Michael J. , Rey Ana Maria , Ye Jun
Published: February 2011

Keeping Time

Optical lattice clocks are comprised of atoms placed in an optical lattice formed by opposing laser beams and can be more precise than traditional microwave atomic clocks because of the higher frequency at which they operate, and the number of atoms available for interrogation. However, interactions between the atoms may lead to shifts in the frequency of the clock transition, usually proportional to the atomic density.

Swallows
et al.

(p.
1043
, published online 3 February) demonstrate an opposite and unexpected effect of interactions: For sufficiently strongly interacting systems, the frequency shift is suppressed. Indeed, in a strontium-based fermionic lattice clock, the shift and its associated spread were reduced by an order of magnitude.
A Sorting Platform Determines the Order of Protein Secretion in Bacterial Type III Systems
Authors: Lara-Tejero María , Kato Junya , Wagner Samuel , Liu Xiaoyun , Galán Jorge E.
Published: February 2011

The bacterial enteropathogen
Salmonella
sorts its effector protein substrates prior to secretion.
Oiling the wheels of change
Authors: Girotti Ray
Published: February 2011

Change is having a greater impact on our lives than ever before. It has always been there, whether as evolution or as revolution, but the speed and impact of change has altered, and understanding the concept of change and how to deal with it is an essential capability for the leaders and managers of every practice. In this article, Ray Girotti outlines how to deal with change in today's veterinary practice.
Diagnosis and management of equine rhabdomyolysis
Authors: Keen John
Published: February 2011

Our knowledge of rhabdomyolysis has increased greatly in the past 10 years. Detailed clinical and molecular investigations are starting to uncover and identify more diverse disorders that lead to a clinical end‐point that represents signs of muscle disease. In equine practice, despite the fact that cases of acute sporadic rhabdomyolysis (ie, ‘tying up’) are quite common, the pathophysiology of this disease is still poorly understood. The astute clinician can, however, recognise chronic cases that may have an underlying metabolic defect that predisposes to muscle disease even when management practices are optimal. This article describes the most commonly seen types of rhabdomyolysis in horses, discusses the approach to diagnosis and highlights the options for treatment in affected cases.
Expression and mutation analysis of EGFR, c-KIT, and β-catenin in pulmonary blastoma
Authors: Macher-Goeppinger Stephan , Penzel Roland , Roth Wilfried , Dienemann Hendrik , Thomas Michael , Schnabel Philipp Albert , Schirmacher Peter , Bläker Hendrik
Published: February 2011

Introduction

Pulmonary blastoma (PB) is a rare malignant lung tumour with an immature mesenchymal and epithelial component resembling fetal lung. In order to define potential therapeutic targets in PB, the authors analysed the status and possible role of EGFR, HER2 and c-KIT in the pathogenesis of this tumour type, and the diagnostic value of β-catenin mutation analysis in PB.

Methods

5 PBs were analysed for EGFR, HER2, c-KIT, and β-catenin expression, as well as for mutations inEGFR,c-KIT,k-rasand the β-catenin gene (CTNNB1).

Results

EGFR expression was observed in all PBs. An EGFR mutation was found in one of the tumours. No overexpression of c-KIT or HER2 was seen. No mutations were found ink-rasorc-KIT. 3 of 5 PBs displayedCTNNB1mutations. Nuclear translocation of β-catenin was seen in 2 of these tumours.

Conclusions

Detection of EGFR expression and mutation in PB suggest EGFR inhibition as a potential therapeutic option in the treatment of advanced PB. Moreover, the data confirm a crucial role ofCTNNB1mutations in the pathogenesis of PB, and indicate thatCTNNB1gene sequencing may be a useful in distinguishing PB from other types of lung cancer.
Could some people be wronged by contracting swine flu? A case discussion on the links between the farm animal sector and human disease
Authors: Deckers Jan
Published: February 2011

This paper uses the imaginary case of Gemma, presented initially at the International Swine Flu Conference (London, March 2010), to discuss whether a nurse who disagrees with most ways in which animals are farmed would be wronged if she contracted swine flu. It is argued that the farm animal sector has contributed to the emergence of H1N1 flu, and that the sector in general contributes significantly to the burden of human disease. The aim of this paper is to promote debate on the question as to whether a range of systems used by the farm animal sector survive moral scrutiny in light of these concerns.
Brain death revisited: it is not ‘complete death’ according to Islamic sources
Authors: Bedir Ahmet , Aksoy Şahin
Published: February 2011

Concepts, such as death, life and spirit cannot be known in their quintessential nature, but can be defined in accordance with their effects. In fact, those who think within the mode of pragmatism and Cartesian logic have ignored the metaphysical aspects of these terms. According to Islam, the entity that moves the body is named the soul. And the aliment of the soul is air. Cessation of breathing means leaving of the soul from the body. Those who agree on the diagnosis of brain death may not able to agree unanimously on the rules that lay down such diagnosis. That is to say, there are a heap of suspicions regarding the diagnosis of brain death, and these suspicions are on the increase. In fact, Islamic jurisprudence does not put provisions, decisions on suspicious grounds. By virtue of these facts, it can be asserted that brain death is not absolute death according to Islamic sources; for in the patients diagnosed with brain death the soul still has not abandoned the body. Therefore, these patients suffer in every operation performed on them.
The economic impact of Mexico City's smoke-free law
Authors: Guerrero López Carlos Manuel , Jiménez Ruiz Jorge Alberto , Reynales Shigematsu Luz Myriam , Waters Hugh R
Published: February 2011

Objective

To evaluate the economic impact of Mexico City's 2008 smoke-free law—The Non-Smokers' Health Protection Law on restaurants, bars and nightclubs.

Material and methods

We used the Monthly Services Survey of businesses from January 2005 to April 2009—with revenues, employment and payments to employees as the principal outcomes. The results are estimated using a differences-in-differences regression model with fixed effects. The states of Jalisco, Nuevo León and México, where the law was not in effect, serve as a counterfactual comparison group.

Results

In restaurants, after accounting for observable factors and the fixed effects, there was a 24.8% increase in restaurants' revenue associated with the smoke-free law. This difference is not statistically significant but shows that, on average, restaurants did not suffer economically as a result of the law. Total wages increased by 28.2% and employment increased by 16.2%. In nightclubs, bars and taverns there was a decrease of 1.5% in revenues and an increase of 0.1% and 3.0%, respectively, in wages and employment. None of these effects are statistically significant in multivariate analysis.

Conclusions

There is no statistically significant evidence that the Mexico City smoke-free law had a negative impact on restaurants' income, employees' wages and levels of employment. On the contrary, the results show a positive, though statistically non-significant, impact of the law on most of these outcomes. Mexico City's experience suggests that smoke-free laws in Mexico and elsewhere will not hurt economic productivity in the restaurant and bar industries.
Blood cigarettes: cigarette smuggling and war economies in central and eastern Africa
Authors: Titeca Kristof , Joossens Luk , Raw Martin
Published: February 2011

Objective

To analyse cigarette smuggling practices in central and eastern Africa.

Methods

Primary data were gathered during long-term qualitative field research in which about 400 interviews were conducted. Analysis of secondary sources included academic literature and reports from non-government organisations, multilateral organisations and the press.

Results

Our research suggests that the following factors play an important role in cigarette smuggling in eastern and central Africa: (1) government officials encounter difficulties monitoring the long and porous borders; (2) there is a general problem of corrupt government officials and particularly those who allow large-scale smugglers to operate; (3) criminal elements also play an important role in smuggling—cigarette smuggling has helped rebel groups to finance their activities, something illustrated through examples from the war economy in the eastern part of the Democratic Republic of Congo.

Conclusions

Our research suggests that cigarette smuggling in this region is not primarily the result of different taxation levels in neighbouring states, but rather the outcome of weak state capacity, high levels of corruption and the activities of rebel groups. Under these conditions smuggling cigarettes becomes an attractive option as taxation is so easily avoided. This explains why in the low-income countries in this study there are high levels of smuggling in spite of low cigarette prices. Comprehensive supply control and enforcement legislation, and cooperation at national, regional and global level are needed to tackle fraudulent practices facilitated by corruption at state level, and to effectively punish interaction between cigarette traders and rebel groups.
Electronic tags and genetics explore variation in migrating steelhead kelts (Oncorhynchus mykiss), Ninilchik River, Alaska
Authors: Nielsen Jennifer L. , Turner Sara M. , Zimmerman Christian E.
Published: February 2011

Acoustic and archival tags examined freshwater and marine migrations of postspawn steelhead kelts ( Oncorhynchus mykiss ) in the Ninilchik River, Alaska, USA. Postspawn steelhead were captured at a weir in 2002–2005. Scale analysis indicated multiple migratory life histories and spawning behaviors. Acoustic tags were implanted in 99 kelts (2002–2003), and an array of acoustic receivers calculated the average speed of outmigration, timing of saltwater entry, and duration of residency in the vicinity of the river mouth. Ocean migration data were recovered from two archival tags implanted in kelts in 2004 (one male and one female). Archival tags documented seasonal differences in maximum depth and behavior with both fish spending 97% of time at sea <6 m depth (day and night). All study fish were double tagged with passive integrated transponder (PIT) tags implanted in the body cavity. Less than 4% of PIT tags were retained in postspawn steelhead. Molecular genetics demonstrated no significant differences in genetic population structure across years or among spawning life history types, suggesting a genetically panmictic population with highly diverse life history characteristics in the Ninilchik River.
Estimating larval production of a broadcast spawner: the influence of density, aggregation, and the fertilization Allee effect
Authors: Lundquist Carolyn J. , Botsford Louis W.
Published: February 2011

The effect of fishing on reproduction is typically quantified by computing the effects of changes in the species abundance and age structure on egg production. For broadcast spawners, reproduction also depends on the local spatial distribution of individuals. Broadcast spawners exhibit an Allee effect at low density: a decline in the fertilization of eggs, owing to increased distance between spawners. We present a method for assessing the likely impact of a fishery on broadcast spawners, based on gamete dispersion dynamics and individual spatial distributions. We use an individual-based model to simulate larval production over a range of uncertainties in dispersion characteristics. We illustrate our method for the red sea urchin, Strongylocentrotus franciscanus , fishery in northern California, USA. The density of red sea urchins varied over space (0.1–1.6·m–2), and indices of aggregation were highest at low densities. As gamete dispersion distances increased, larval production exhibited a more linear relationship with density. Average larval production in 1996–1998 was 33.8% of production near the inception of the fishery. After accounting for decreases in mean density, the fertilization Allee effect accounted for 21.7 ± 4.1% of the decrease in larval production, and 45.2 ± 21.7% if sea urchins were not aggregated.
Urban stressors alter the trophic basis of secondary production in an agricultural stream
Authors: Gücker Björn , Brauns Mario , Solimini Angelo G. , Voss Maren , Walz Norbert , Pusch Martin T.
Published: February 2011

We compared the invertebrate production and stable isotope signatures of key ecosystem compartments of urban sites subjected to the input of tertiary-treated wastewater with those of upstream sites in an agricultural lowland stream. We detected a significant shift in the trophic basis of invertebrate production from upstream, natural and agricultural resources, to urban resources, i.e., wastewater-derived organic matter as well as autochthonous primary production based on wastewater-derived nutrients. Invertebrate production was higher at urban sites than at agricultural sites. However, the median contribution of the most important secondary producer, the shredder Gammarus roeseli , to total invertebrate production was lower at urban sites (9%) than at agricultural sites (61%). The low production of G. roeseli at urban sites was associated with the absence of allochthonous coarse particulate organic matter (CPOM) habitats, rather than the loss of CPOM as a food resource. Our results suggest that contemporary urban stressors in developed countries affect secondary producers less severely than historically recorded, but still profoundly change the matter fluxes and ecosystem functioning of running waters. Restoration of the native riparian vegetation, channel naturalization, and adequate dilution of tertiary-treated wastewater may partially mitigate adverse effects on invertebrate communities and their secondary production.
Minimum viable population size for lake sturgeon (Acipenser fulvescens) using an individual-based model of demographics and genetics
Authors: Schueller Amy M. , Hayes Daniel B.
Published: February 2011

Population viability analysis is a useful tool to explore the relationship between extinction risk and population size, but often does not include genetic factors. Our objectives were to determine minimum viable population size (MVP) for lake sturgeon ( Acipenser fulvescens ) and examine how inbreeding depression may affect MVP. Our individual-based model incorporated inbreeding depression in two ways: individuals with inbreeding coefficients above a threshold experienced inbreeding depression (threshold), and individuals experienced inbreeding depression at a rate related to their inbreeding coefficient (gradual). Three mechanisms relating inbreeding to fitness were explored (young-of-the-year (YOY) viability, post-YOY viability, number of progeny). The criterion we used to determine MVP was a 5% chance of extinction over 250 years. The estimated MVP without inbreeding effects was 80 individuals. For some scenarios incorporating inbreeding, MVP did not change, but for others, MVP was substantially higher, reaching values up to 1800. Results demonstrate that extinction risk and MVP can be influenced by both demographic stochasticity and inbreeding depression. This research should inform management by determining MVP and how inbreeding, which is expected to accrue in remnant populations because of generations of low abundance, may affect MVP.
Isolation or metapopulation: whence and whither the Smith Sound cod?
Authors: Rose George A. , Nelson R. John , Mello Luiz G.S.
Published: February 2011

In April 1995, a spawning aggregation of “northern” Atlantic cod ( Gadus morhua ) (10 000 t) appeared in Smith Sound, Newfoundland, growing to 26 000 t by year 2000. The origin of the founder year classes (primarily the 1990 and 1992 year classes) and potential for expansion remains controversial, with genetic isolation used to justify reopenings of coastal fisheries. We investigated the origin using historical, demographic, and genetic data. History provided no evidence of large aggregations before 1995. Demographics in the early 1990s suggested few spawners in Smith Sound, but many in the adjacent Bonavista Corridor. The strong 1990 year class was not evident until 1995 and the strong 1992 year class until 1997 (both age 5 and first maturity). Genetic study of six microsatellite loci from 791 cod from overwintering aggregations in Smith Sound and offshore regions indicated little to no differentiation (FST) among southern groups (Smith Sound, Bonavista Corridor, Halibut Channel). These results provide a perspective that these groups comprise a metapopulation and that the Smith Sound aggregation arose not from self-recruitment but immigration. By 2009, the aggregation had dispersed, with large concurrent increases in the Bonavista Corridor.
Sea lice (Lepeophtheirus salmonis) infestations and the productivity of pink salmon (Oncorhynchus gorbuscha) in the Broughton Archipelago, British Columbia, Canada
Authors: Krkošek Martin , Hilborn Ray
Published: February 2011

The spread of salmon lice ( Lepeophtheirus salmonis ) from salmon farms may threaten some wild salmon populations. Infestations of wild juvenile pink salmon ( Oncorhynchus gorbuscha ) have been associated with high mortality and population decline. Using stock–recruit data for pink salmon from the central coast of British Columbia, we analyzed how fishing mortality and spatial covariation combine with louse infestation to affect pink salmon population dynamics. The results indicate substantial coherence in survival at nested spatial scales — large-scale regional covariation and smaller scale covariation within management areas. Populations exposed to salmon farms (those from the Broughton Archipelago) show a sharp decline in productivity during sea lice infestations relative to pre-infestation years. Unexposed populations (comprising four management areas) did not experience a change in productivity during infestation years and had similar productivity to exposed populations before infestations. Our results suggest that sea lice infestations may result in declines of pink salmon populations and that management and policy of salmon farms should consider protecting wild juvenile salmon from exposure to sea lice.
Effects of thermocline deepening on lake plankton communities
Authors: Cantin Ariane , Beisner Beatrix E. , Gunn John M. , Prairie Yves T. , Winter Jennifer G.
Published: February 2011

Theory predicts, and some evidence demonstrates that in lakes, the depth of the thermocline can have a large structural influence on the spatial distribution, and strongly influences the composition of plankton communities. However, experimental assessments of responses of the planktonic food web to thermocline depth have not yet been done at the whole-basin scale. We conducted an experiment wherein we artificially lowered the thermocline in an isolated basin of a three-basin lake, maintaining another isolated basin as a control. The vertical distribution and taxonomic composition of both phytoplankton and zooplankton were monitored throughout the summer months. Greater phytoplankton production, especially in the epilimnion, attributable mainly to increases in the chlorophytes was observed with thermocline deepening, but at the deepest thermoclines, production was limited. Total zooplankton biomass was unaffected by thermocline depth, suggesting top-down control by predators. Zooplankton biomass peaks were less pronounced in the manipulated basin, but tended to follow the thermocline whether at its normal position or as it was deepened. Zooplankton composition was significantly altered by large increases in densities of predatory cyclopoid copepods and rotifers; taxa commonly found in turbulent environments. Overall, both phytoplankton and zooplankton communities demonstrated important shifts in structure and composition in response to thermocline deepening.
Historic divergence with contemporary connectivity in a catadromous fish, the estuary perch (Macquaria colonorum)
Authors: Shaddick Kim , Gilligan Dean M. , Burridge Christopher P. , Jerry Dean R. , Truong Kiet , Beheregaray Luciano B.
Published: February 2011

The estuary perch ( Macquaria colonorum ) represents an important model for assessing how historical changes in coastal geomorphology and current oceanographic and estuarine conditions may have impacted connectivity in a catadromous fish. A fragment of the mitochondrial control region and six microsatellite DNA markers were used to clarify connectivity in 17 populations (n = 354) of estuary perch from the southeast and southern coasts of Australia. The mtDNA data showed a latitudinal disjunction in haplotype frequencies that divided populations into two groups (ΦST= 0.419), in a pattern suggestive of isolation by geographic distance. However, no marked structure or correlation with distance was apparent within each group, a result consistent with microsatellite data that showed high contemporary population connectivity across large distances. This was contrary to expectations that the species would exhibit moderate to strong genetic structure consistent with a one-dimensional stepping stone pattern. Coalescent phylogeographic and population genetic analyses provided support for a historical divergence probably due to the emergence of the Bassian Isthmus in southern Australia. Current connectivity appears to be maintained by both large- and fine-scale oceanographic currents and processes, highlighting the important role of the marine environment for an estuarine resident species.
Variable population responses by large decapod crustaceans to the establishment of a temperate marine no-take zone
Authors: Hoskin M. G. , Coleman R. A. , von Carlshausen E. , Davis C. M.
Published: February 2011

In 2003, an area adjacent to Lundy Island was designated as the United Kingdom’s first no-take zone (NTZ) for nature conservation. The only significant fishery at Lundy was for lobster ( Homarus gammarus L.) and various crabs. The Lundy NTZ provided an opportunity to test hypotheses about the recovery of crustacean populations from fishing. Using an experimental potting program, we simultaneously compared changes in the crustacean populations within the NTZ with those in proximal control (Near Control) locations and two distant control (Far Control) locations. Comparisons were replicated over 4 years, and the results analysed using asymmetrical analysis of variance. There was evidence of a rapid, large increase in the abundance and sizes of legal-sized lobsters within the NTZ, and evidence of spillover of sublegal lobsters from the NTZ to adjacent areas. The NTZ also appeared to cause a small, but significant increase in the size of brown crab ( Cancer pagurus L.) and a decrease in the abundance of velvet crabs ( Necora puber L.) (the latter potentially owing to predation and (or) competition from lobsters). Unlike many previous studies, these results are unambiguous, owing to a robust asymmetrical experimental design. We suggest that regulatory and conservation agencies use this approach, which we have demonstrated to be relatively straightforward, whenever the NTZ requiring evaluation cannot be replicated.
Rapid growth in the early marine period improves the marine survival of Chinook salmon (Oncorhynchus tshawytscha) in Puget Sound, Washington
Authors: Duffy Elisabeth J , Beauchamp David A
Published: February 2011

We examined the effect of early marine entry timing and body size on the marine (smolt-to-adult) survival of Puget Sound Chinook salmon ( Oncorhynchus tshawytscha ). We used data from coded wire tag release groups of hatchery Chinook salmon to test whether hatchery release date, release size, and size in offshore waters in July and September influenced marine survival. Marine survival was most strongly related to the average body size in July, with larger sizes associated with higher survivals. This relationship was consistent over multiple years (1997–2002), suggesting that mortality after July is strongly size-dependent. Release size and date only slightly improved this relationship, whereas size in September showed little relationship to marine survival. Specifically, fish that experienced the highest marine survivals were released before 25 May and were larger than 17 g (or 120 mm fork length) by July. Our findings highlight the importance of local conditions in Puget Sound (Washington, USA) during the spring and summer, and suggest that declines in marine survival since the 1980s may have been caused by reductions in the quality of feeding and growing conditions during early marine life.
Salmon subsidies alleviate nutrient limitation of benthic biofilms in southeast Alaska streams
Authors: Rüegg Janine , Tiegs Scott D. , Chaloner Dominic T. , Levi Peter S. , Tank Jennifer L. , Lamberti Gary A.
Published: February 2011

Using nutrient-diffusing substrata (NDS) in seven streams in southeast Alaska, USA, we tested whether (i) nutrient limitation of autotrophic and heterotrophic biofilms was alleviated by salmon resource subsidies, and (ii) whether the degree of alleviation could be predicted by environmental variables. Before salmon spawners arrived, autotrophic biofilms were nitrogen (N)-limited, or co-limited by N and phosphorus (P), whereas heterotrophic biofilms were either P-limited, or co-limited by N and P. Combined N and P amendments resulted in a 2.6-fold increase in biofilm chlorophyll a, and a 3.2-fold increase in community respiration. After salmon arrived, autotroph nutrient limitation was alleviated in six of the seven streams. Heterotrophs still exhibited nutrient limitation in six streams, but most streams shifted from co-limitation to P-limitation. Nutrient-diffusing substrata amended with salmon tissue indicated that salmon could also be an important source of organic carbon for biofilms. Autotrophs responded less to N and P amendments as streamwater ammonium concentration increased with the arrival of salmon. For heterotrophs, ammonium concentration and N:P ratio best predicted changes in response following the arrival of salmon. We provide the first direct evidence that biofilm nutrient limitation can be alleviated by salmon spawners in nutrient-poor streams.
How useful is the ratio of fish density outside versus inside no-take marine reserves as a metric for fishery management control rules?
Authors: Babcock Elizabeth A. , MacCall Alec D.
Published: February 2011

A management strategy evaluation (based on five species in the California, USA, nearshore fishery) of control rules that reduce relative fishing effort as a function of the ratio of fish density outside versus inside no-take marine reserves (as a measure of depletion) showed that although the control rules allowed effort to increase at first, in the long term, they were effective at maintaining spawning stock biomass and yield for all simulated species, including depleted ones. Scenarios with fish movement, illegal fishing in the reserve, or post-dispersal density dependence in recruitment required higher density ratio targets, such as 60% of mature fish or 80% of all fish, to avoid stock depletion. The effort allowed by multispecies density-ratio control rules depended on the relative weight given to more or less depleted species. High variability in recruitment or in monitoring data caused the allowable effort to fluctuate. Density-ratio control rules have the advantages that they require no historical data, they can be used at local spatial scales, and they adjust to changing environmental conditions.
Population differences in otolith chemistry have a genetic basis in Menidia menidia
Authors: Clarke Lora M. , Thorrold Simon R. , Conover David O.
Published: February 2011

The number of studies using otolith chemistry as a tool to reconstruct the environmental history of fishes and to detect population structure continues to rise, despite the fact that factors influencing otolith deposition are not fully understood. Many studies have examined the influence of environmental parameters on otolith composition, but none to date have tested the possible influence of intrinsic factors. Using lab broodstock populations, we examined the influence of genetics and temperature on Mg:Ca, Mn:Ca, Sr:Ca, and Ba:Ca concentrations and partition coefficients in the otoliths of juvenile Atlantic silversides, Menidia menidia . Fish from two populations, South Carolina, USA, and Nova Scotia, Canada, were reared in 15, 21, and 27 °C. We found significant (p < 0.05) differences in otolith Mg:Ca, Mn:Ca, and Ba:Ca ratios as well as in Mg, Mn, and Ba partition coefficients among populations. Such genetic influences on otolith elemental concentrations have important implications for understanding the physiological mechanisms underlying otolith deposition and enhance the utility of otolith chemistry as a marker of fish population structure in the wild.
Incorporating climate changes into population dynamic modelling: an individual-based modelling approach for lobster
Authors: Chang Yi-Jay , Sun Chi-Lu , Chen Yong , Zhang Yuying , Yeh Su-Zan
Published: February 2011

One of the most challenging issues in fisheries management is the evaluation of the effects of fishing in the context of a changing environment. Using the pronghorn spiny lobster ( Panulirus penicillatus ) fishery off the eastern coast of Taiwan as an example, we developed an individual-based model (IBM) that is capable of describing the temperature-dependent life history processes and fishery practices for the spiny lobster. We then used the model to evaluate potential impacts of increased ocean temperature on the estimation of mortality-based biological reference points for fisheries management. We demonstrate that a warming temperature would increase the yield-per-recruit and eggs-per-recruit values and consequently reduce the risk of overexploitation under the current exploitation level. However, there is likely a high risk of overexploitation in the long term if higher temperatures induce extra-high natural mortality. The evaluation of effectiveness of size regulations suggests that increasing minimum legal size is proposed as a good candidate measure to reduce the risk of overexploitation for pessimistically unfavorable environmental conditions. This study suggests that an explicit incorporation of the relationships between environmental variables and biological processes can greatly improve fisheries assessment and management.
Greenland halibut (Reinhardtius hippoglossoides) spawn annually but successive cohorts of oocytes develop over 2 years, complicating correct assessment of maturity
Authors: Kennedy James , Gundersen Agnes C. , Høines Åge S. , Kjesbu Olav S.
Published: February 2011

Ovary development in Greenland halibut ( Reinhardtius hippoglossoides ) is complex, with several cohorts of developing oocytes present during vitellogenesis; this is unusual for a determinate spawner. There are also speculations that Greenland halibut are not capable of spawning every year. To investigate this possibility, ovaries from Greenland halibut caught throughout the year were examined histologically, and successive cohorts of oocytes were tracked through development. Results showed that the initial maturation of the ovaries from immature to spawning takes more than 1 year. The ovary initially develops as far as early vitellogenesis; however, the time scale for this is unclear. During the final year of development, the cohort of vitellogenic oocytes splits to form two cohorts; the larger cohort increases in size and is spawned in the coming spawning season. The smaller cohort also continues to develop, but at a much lower rate, in preparation for development for spawning in the following year. Within each month, there is a large range of oocyte sizes between fish; this leads to the extended spawning season that is known in many populations of this species. This complicates the assessment of maturity, and a more accurate microscopic maturity scale is proposed.
Evaluating otolith Sr/Ca as a tool for reconstructing estuarine habitat use
Authors: Phillis Corey C. , Ostrach David J. , Ingram B. Lynn , Weber Peter K.
Published: February 2011

There is no standard method to determine the applicability of otolith Sr/Ca ratio to reconstructing estuary use. We have developed a novel method to determine the response of otolith Sr/Ca to changes in water Sr/Ca and salinity in San Francisco Estuary (California, USA). We perform correlated, spatially resolved Sr/Ca and Sr isotope measurements using otoliths from adult striped bass ( Morone saxatilis ) in the San Francisco Estuary to estimate the otolith–water Sr/Ca partition coefficient (DSr = 0.305 ± 0.009). DSr did not vary significantly with salinity, and therefore the salinity–otolith Sr/Ca model was constructed by substituting the partition coefficient into the nonlinear salinity–water Sr/Ca mixing model for the system. The model demonstrates that the primary factor controlling the response of Sr/Ca to salinity is the Ca concentration in the freshwater source flowing into the estuary. A concentration of 60 ppm Ca is an approximate threshold below which estuary Sr/Ca increases rapidly to near the marine Sr/Ca at low salinities (5‰–15‰), thereby providing sharp delineation of estuary entrance, but little to no discrimination among higher salinity habitats. Our approach provides a general framework for assessing the potential utility of Sr/Ca in estuarine systems and specifically for the San Francisco Estuary.
Analysis of anchor foundation with root caissons loaded in nonhomogeneous soils
Authors: Huang Maosong , Zhang Chenrong , Mu Linlong , Gong Weiming
Published: February 2011

This paper presents a novel type of deep foundation — an anchor foundation with root caissons, which improve the soil–caisson interaction using penetrating roots. A simplified analytical procedure is proposed for calculating responses of the new anchor foundation subjected to combined vertical, horizontal, and moment loadings. Caisson–soil interaction is simulated by a Winkler subgrade reaction model, with an improved Winkler spring constant to consider the reinforcement effect of roots. The method incorporates limiting soil stress to investigate soil nonlinear behavior and a transfer matrix to represent nonhomogeneous soils, with a passive caisson model accounting for group effects. The effectiveness of the present approach is evaluated by comparison with full-scale field load tests and a finite element analysis on a small-scale anchor foundation to give a preliminary design guideline for the Ma’anshan Yangtze River Bridge in China.
Consequence factors in the ultimate limit state design of shallow foundations
Authors: Fenton Gordon A. , Griffiths D. V. , Ojomo Olaide O.
Published: February 2011

The reliability-based design of shallow foundations is generally implemented via a load and resistance factor design methodology embedded in a limit state design framework. For any particular limit state, the design proceeds by ensuring that the factored resistance equals or exceeds the factored load effects. Load and resistance factors are determined to ensure that the resulting design is sufficiently safe. Load factors are typically prescribed in structural codes and take into account load uncertainty. Factors applied to resistance depend on both uncertainty in the resistance (accounted for by a resistance factor) and desired target reliability (accounted for by a newly introduced consequence factor). This paper concentrates on how the consequence factor can be defined and specified to adjust the target reliability of a shallow foundation designed to resist bearing capacity failure.
Development of a new calibration chamber for conducting cone penetration tests in unsaturated soils
Authors: Pournaghiazar Mohammad , Russell Adrian R. , Khalili Nasser
Published: February 2011

A calibration chamber has been developed to conduct laboratory-controlled cone penetration tests in unsaturated soils. The chamber allows independent application of lateral and vertical pressures to an unsaturated soil specimen. Horizontal pressure is applied by cell water pressure pushing on a rubber membrane enclosing the specimen, while vertical pressure is maintained by a hydraulic loading ram at the base of the specimen. Suction is controlled using the axis-translation technique. Air pressure is applied to the top of the chamber where it spreads uniformly across the top of the specimen. Pore-water pressure is applied through eight high air-entry value porous disks embedded in the bottom plate. A particularly original aspect of the chamber design is the specimen formation system comprising four moveable cylinder quarters, which enables the creation of specimens of repeatable properties from a variety of soil types. The results of typical cone penetration tests conducted on dry, saturated, and unsaturated sand specimens are presented and highlight the contribution of suction to cone penetration resistance.
Experimental study on the performance of light and dense backfills
Authors: Siddiqua Sumi , Blatz James , Siemens Greg
Published: February 2011

Numerical modeling is a cost-effective and important approach to examine the long-term performance of engineered materials. However, to identify the appropriate constitutive model for a particular material it is necessary to measure physical properties in a laboratory. Laboratory experiments provide the data from which the input parameters for the selected model can be interpreted. This paper studies the mechanical behaviour of two clay-based sealing materials — light backfill and dense backfill — recommended for use in disposal of nuclear waste in a proposed Canadian repository. Test specimens of light and dense backfills were saturated in a triaxial cell and then subjected to specified isotropic and shearing stress paths to measure consolidation and shear characteristics. The triaxial results are interpreted in a critical state context. The light backfill results suggest that it has similar stress–strain behaviour to a bentonite–sand buffer, which has a similar composition, but different preparation procedures and design requirements. Results from testing of dense backfill indicate that it is a much stiffer and stronger material than light backfill. Dense backfill is expected to provide mechanical support to the used-fuel container and other sealing components of the Canadian repository, and the mechanical behaviour of dense backfill satisfies these requirements.
Earth pressures on twin positive projecting and induced trench box culverts under high embankments
Authors: McGuigan Benjamin L. , Valsangkar Arun J.
Published: February 2011

Although twin culverts are often preferred for watercourse crossing, little is known about the earth pressures they experience under high embankments. Centrifuge test results have been used in this research to verify a numerical model used to evaluate culvert spacing and compressible zone geometry for twin positive projecting and induced trench box culverts. Lower pressures were calculated for twin positive projecting culverts than for a single culvert. For the induced trench case, one compressible zone spanning both culverts was the preferred geometry for culverts spaced at 0.5Bcand 1.0Bc(where Bcis the culvert width), while two zones 1.2Bcwide were found to be optimal for 1.5Bcspacing. The twin configurations generally resulted in slightly higher vertical and lower lateral earth pressures than a single culvert configuration. The base contact pressures were 25%–76% greater than the top pressure plus dead load because of shear stresses mobilized along the sidewalls; however, they were 41%–47% lower than the pressures for positive projecting configurations. The maximum bending moments calculated for the induced trench culverts were 54%–59% lower than for the positive projecting ones. Induced trench construction therefore appears to be viable for twin box culverts, provided that frictional forces along the sidewalls are taken into account.
Volume–mass unsaturated soil constitutive model for drying–wetting under isotropic loading–unloading conditions
Authors: Pham Hung Q. , Fredlund Delwyn G.
Published: February 2011

A rigorous volume–mass constitutive model is proposed for the representation of drying–wetting under isotropic loading–unloading conditions for unsaturated soils. The proposed model utilizes concepts arising from soil physics and geotechnical engineering research and requires readily obtainable soils data for soil properties. The model can be used to predict void ratio and water content constitutive relationships (and therefore degree of saturation) for a wide range of unsaturated soils. Various stress paths (i.e., loading–unloading and drying–wetting) can be simulated, and hysteresis associated with the soil-water characteristic curve is taken into account. Two closed-form equations for the volume–mass constitutive relationships are presented for soils starting from slurry conditions. A number of test results (i.e., from experimental programs reported in the research literature) were used during the verification of the proposed volume–mass constitutive model. The volume–mass constitutive model captures key unsaturated soil conditions such as air-entry value, water-entry value, and residual conditions. The proposed model appears to satisfactorily predict unsaturated soil behavior for soils ranging from low compressible sands to high compressible clays.
A new procedure for the determination of soil-water retention curves by continuous drying using high-suction tensiometers
Authors: Lourenço S. D.N. , Gallipoli D. , Toll D. G. , Augarde C. E. , Evans F. D.
Published: February 2011

Soil-water retention curves (SWRCs) can be determined using high-suction tensiometers (HSTs) following two different procedures that involve either continuous or discrete measurement of suction. In the former case, suction measurements are taken while the sample is permanently exposed to the atmosphere and the soil is continuously drying. In the latter case, the drying or wetting process is halted at different stages to ensure equalization within the sample before measuring suction. Continuous drying has the advantage of being faster; however, it has the disadvantage that the accuracy of mass measurements (necessary for the determination of water content) is affected by the weight and stiffness of the cable connecting the HST to the logger. To overcome this problem, an alternative continuous drying procedure is presented in this paper in which two separate but nominally identical samples are used to obtain a single SWRC; one sample is used for the mass measurements, while a second sample is used for suction measurements. It is demonstrated that the new continuous drying procedure gives SWRCs that are similar to those obtained by discrete drying.