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In this article, the fourth in a series reviewing the role of food workers in foodborne outbreaks, background information on the presence of enteric pathogens in the community, the numbers of organisms required to initiate an infe...
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In this article, the fourth in a series reviewing the role of food workers in foodborne outbreaks, background information on the presence of enteric pathogens in the community, the numbers of organisms required to initiate an infection, and the length of carriage are presented. Although workers have been implicated in outbreaks, they were not always aware of their infections, either because they were in the prodromic phase before symptoms began or because they were asymptomatic carriers. Pathogens of fecal, nose or throat, and skin origin are most likely to be transmitted by the hands, highlighting the need for effective hand hygiene and other barriers to pathogen contamination, such as no bare hand contact with ready-to-eat food. The pathogens most likely to be transmitted by food workers are norovirus, hepatitis A virus, Salmonella, Shigella, and Staphylococcus aureus. However, other pathogens have been implicated in worker-associated outbreaks or have the potential to be implicated. In this study, the likelihood of pathogen involvement in foodborne outbreaks where infected workers have been implicated was examined, based on infectious dose, carriage rate in the community, duration of illness, and length of pathogen excretion. Infectious dose estimates are based on volunteer studies (mostly early experiments) or data from outbreaks. Although there is considerable uncertainty associated with these data, some pathogens appear to be able to infect at doses as low as 1 to 100 units, including viruses, parasites, and some bacteria. Lengthy postsymptomatic shedding periods and excretion by asymptomatic individuals of many enteric pathogens is an important issue for the hygienic management of food workers.
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We explored correlation in diet trends for five piscivorous predators that reproduce on the Pribilof Islands as illustrative of the shifting structure of the Bering Sea ecosystem. We evaluated the size and species of prey consumed...
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We explored correlation in diet trends for five piscivorous predators that reproduce on the Pribilof Islands as illustrative of the shifting structure of the Bering Sea ecosystem. We evaluated the size and species of prey consumed by adult female and juvenile northern fur seals (Callorhinus ursinus) and adults and chicks of black-legged kittiwakes (Rissa tridactyla), red-legged kittiwakes (Rissa brevirostris), thick-billed murres (Uria lomvia), and common murres (Una aalge) from data collected between July and October 1960-2000. Sample sources included stomachs from seals and seabirds collected on pelagic foraging grounds in the eastern Bering Sea, seal scats from rookeries and seabird regurgitations and whole prey from nest sites on St. Paul and St. George Islands of the Pribilof Island archipelago. Typical prey included small fish and invertebrates (≤ 20 cm for seals and ≤ 12 cm for seabirds) that concentrate along frontal boundaries of the continental shelf/slope and in the epi-pelagic zone. Squids and fishes including walleye pollock (Theragra chalcogramma), capelin (Mallotus villosus), and sand lance (Ammodytes hexapterus) were variably important in the diet of all five predators. Some prey, such as capelin, were principal in predator diets during the 1960s (seals) and into the early 1980s (seabirds), but declined or disappeared from all predator diets thereafter while others, such as walleye pollock, occurred with increasing frequency from the 1970s forward. As the number of individuals consuming walleye pollock increased, the overall volume of pollock in seabird diets declined. This decline was coincident with a decrease in the age and body size of pollock consumed by both seabirds and fur seals. Squid and pollock were negatively correlated in the diets of their primary consumers, northern fur seals (Pearson's coefficient -0.71, p = 0.016) and thick-billed murres (Pearson's coefficient = -0.74, p = 0.015) from the 1970s forward. Inter-island variation in diet was evident to varying degrees for all predators, with a prevalence offish on St. Paul Island and invertebrates on St. George Island. Bayesian time-series analysis of synthesized data described significant temporal cross-correlation in diet among northern fur seals, red- and black-legged kittiwakes, and thick-billed murres. For all correlated predators except common murres, beta-binomial modeling indicated that trends in the occurrence of four of the five primary prey (sand lance, capelin, squid, and pollock) evaluated, were significantly associated with eastern Bering Sea time-series trends in sea surface temperature, ice retreat or a combination of both. Data synthesis highlighted potential competition and a scenario for the effects of an altered prey field on the population stability of predators. The association between correlated diet changes among predators and indices of oceanographic shifts in the 1970s and the 1990s allow scrutiny of hypotheses concerning causal mechanisms in population declines.
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The paper presents an iterative method for obtaining footprint, pressure distribution, local deformation and sub-surface stress field for the contact between a rigid cylindrical indenter and an elastic flat substrate. The methodol...
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The paper presents an iterative method for obtaining footprint, pressure distribution, local deformation and sub-surface stress field for the contact between a rigid cylindrical indenter and an elastic flat substrate. The methodology is applicable for semi-infinite, as well as for thin or thick bonded elastic layered solids with high or low elastic moduli. All findings are in accord with the observed behaviour of hard wear resistant and soft solid lubricating coatings. It is shown that the decomposed contact pressure distribution into a series of harmonic waves induces sub-surface stress fields that decay into the depth of the solid according to their wavelengths. Consequently, conditions vis-a-vis fatigue spalling and adhesion performance may be predicted for given thickness of layered bonded elastic solids.
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During three replicate studies, cream, compressed and dry yeast samples were stored for 21 days at 4, 10, 25 and 37C. At 3-day intervals, bacteria were quantified using standard plate counting procedures, and 1,044 predominant col...
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During three replicate studies, cream, compressed and dry yeast samples were stored for 21 days at 4, 10, 25 and 37C. At 3-day intervals, bacteria were quantified using standard plate counting procedures, and 1,044 predominant colonies isolated and characterized. The highest counts of aerobic bacteria and Enterococcus spp., up to 7 and 8 log colony-forming units (cfu) per mL or g, were found when cream and compressed yeast samples were exposed to elevated temperatures (25 and 37C), while lower counts (4 and 6 log cfu/mL or g) were obtained from refrigerated samples (4C). At 10C, counts of aerobic bacteria and Enterococcus spp. increased from 4 to 7 log cfu/mL or g, highlighting the importance of temperature control during the storage and distribution of perishable cream and compressed yeast. Vacuum-packaging of dry yeast reduced the growth of aerobic populations. Throughout storage, Lacto-bacilli dominated the bacterial populations in both cream and compressed yeast (45 to 78%), while Enterococcaceae predominated in vacuum-packaged dry yeast (54 to 68%), suggesting they were primarily responsible for the spoilage of commercial yeast products.
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Time-resolved optical spectroscopy has been used to measure the shock pressure steadiness, emissivity, and temperature of liquid deuterium shocked to 22-90 GPa. The shock was produced using magnetically accelerated flyer plate imp...
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Time-resolved optical spectroscopy has been used to measure the shock pressure steadiness, emissivity, and temperature of liquid deuterium shocked to 22-90 GPa. The shock was produced using magnetically accelerated flyer plate impact, and spectra were acquired with a suite of four fiber-optic-coupled spectrometers with streak camera detectors. The shock pressure changes by an average of -1.2% over the 10-30 ns cell transit time, determined from the relative changes in the shock front self-emission with time. The shock front reflectivity was measured from 5140 A and 5320 A laser light reflected from the D_2 shock. The emissivity inferred from the reflectivity measurements was in reasonably good agreement with quantum molecular dynamics simulation predictions. The spectral radiance wavelength dependence was found to agree well (average normalized χ~2=1.6) with a Planckian multiplied by the emissivity. The shock front temperature was determined from the emissivity and the wavelength-dependent shock self-emission. Thirty-seven temperature measurements spanning the 22-90 GPa range were accumulated. The large number of temperature measurements enables a comparison of the scatter in the data with expectations for a Gaussian distribution. This facilitates determination of uncertainties that incorporate both apparatus contributions and otherwise unquantified systematic effects that cause self-emission variations from one experiment to another. Agreement between temperatures determined from the absolute spectral radiance and from the relative shape of the spectrum further substantiates the absence of systematic biases. The weighted mean temperature uncertainties were as low as ±3-4%, enabling the discrimination between competing models for the D_2 equation of state (EOS). The temperature results agree well with models that predict a maximum compression of ～4.4. Softer models that predict approximately sixfold compression are inconsistent with the data to a very high statistical confidence level. Previous analysis [D. Saumon and T. Guillot, Astrophys. J. 609, 1170 (2004)] of Jupiter's internal structure has shown that the core mass is restricted to be less than approximately three times the mass of the Earth, if EOS models consistent with these temperature measurements are employed.
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It is known that elementary bosons condense in a unique state, not so much because this state has the lowest free-particle energy but because it costs a macroscopic amount of energy to put the particles into different states which...
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It is known that elementary bosons condense in a unique state, not so much because this state has the lowest free-particle energy but because it costs a macroscopic amount of energy to put the particles into different states which can then interact through quantum particle exchanges. Since individual exchanges between the two fermions of a composite boson are ignored when composite particles are replaced by elementary bosons, it is of importance to reconsider the exchange-energy argument for the stability of the Bose-Einstein condensate in the case of composite bosons. We do this here in the light of the new many-body theory which allows us to take exactly into account all possible exchanges between the fermionic components of the composite bosons. We confirm that the condensate of composite bosons occupies a single state, this state being moreover pure: a coherent superposition of states close in energy is shown to be less favorable for both elementary and composite bosons.
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This study evaluated the performance of two water quality models in accordance to specific tasks designated in the USDA Agricultural Research Service Conservation Effects Assessment Project. The Soil and Water Assessment Tool (SWA...
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This study evaluated the performance of two water quality models in accordance to specific tasks designated in the USDA Agricultural Research Service Conservation Effects Assessment Project. The Soil and Water Assessment Tool (SWAT) and the Annualized Agricultural Non-Point Source (AnnAGNPS) models were applied uncalibrated to the Cedar Creek watershed within the St. Joseph River watershed in northeastern Indiana to predict streamflow and atrazine losses. In order to ultimately assess the benefits of conservation practices in agricultural watersheds (which is one of the major goals of the Conservation Effects Assessment Project), proper application of the SWAT and AnnAGNPS models is essential including baseline comparisons made in an uncalibrated mode aimed at eliminating bias due to parameter optimization. Streamflow prediction results show that SWAT model performance was superior to AnnAGNPS, with SWAT model efficiency values ranging from 0.66 to 0.25 and AnnAGNPS model efficiency values ranging from 0.13 to -2.06 for monthly and annual streamflow, respectively. For uncalibrated conditions, neither model was able to adequately simulate atrazine loss concentrations. Overall results suggest that for Conservation Effects Assessment Project modeling applications at the Cedar Creek watershed scale in this study, the use of the SWAT model would be preferable to AnnAGNPS in terms of overall model performance and model support technology (e.g., model interface and documentation).
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The paper analyzes the importance of credible institutions in the process of trade liberalization. It combines aspects of credible policy announcements with adjustment costs. We show that if industries' profits are subject to adju...
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The paper analyzes the importance of credible institutions in the process of trade liberalization. It combines aspects of credible policy announcements with adjustment costs. We show that if industries' profits are subject to adjustment costs, a dynamic link between periods arises that creates constituencies for a non-discretionary trade policy regime. The conditions for a government to select such an institutional solution are derived.
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The objective of this research was to develop a community carbon footprint model that could be used to assess the size and major components of a community's carbon dioxide (CO_2) emissions. The town of Biggar aims to become Scotla...
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The objective of this research was to develop a community carbon footprint model that could be used to assess the size and major components of a community's carbon dioxide (CO_2) emissions. The town of Biggar aims to become Scotland's first carbon neutral town. As expected for this rural community, car transport accounted for nearly half of the CO_2 emissions, with natural gas and electricity consumption resulting in a further 24% and 12% of total emissions, respectively, and air travel being the last major component at 10% of emissions. An assessment was also made of the wind and solar resources of the town. One large wind turbine would provide the town's electricity, while three to four turbines would be needed to offset all CO_2 emissions. In contrast, offsetting by tree planting would require in the region of 2,000 ha of trees.
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We analyzed 151 organohalogen chemicals (OHCs) in whole blood and subcutaneous fat of 57 polar bears sampled along the Alaskan Beaufort Sea coast in spring, 2003. All major organochlorine pesticides, PCBs, PBDEs and their congener...
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We analyzed 151 organohalogen chemicals (OHCs) in whole blood and subcutaneous fat of 57 polar bears sampled along the Alaskan Beaufort Sea coast in spring, 2003. All major organochlorine pesticides, PCBs, PBDEs and their congeners were assessed. Concentrations of most OHCs continue to be lower among Southern Beaufort Sea polar bears than reported for other populations. Additionally, toxaphenes and related compounds were assessed in adipose tissue, and 8 perflourinated compounds (PFCs) were examined in blood. Perfluorooctane sulfonate (PFOS) concentrations exceeded those of any other contaminant measured in blood. SChlordane concentrations were higher in females, and both EPCBs and EChlordane concentrations in adipose tissue decreased significantly with age. The rank order of OHC mean concentrations; ΣPCB ＞ Σ10PCB ＞ PCB153 ＞ ΣChlordane> Oxychlordane ＞ PCB180 ＞ ΣHCH ＞ β-HCH＞ ΣDDT ＞ p,p-DDE ＞ ΣPBDE ＞ HCB ＞ Toxaphene was similar for compounds above detection limits in both fat and blood. Although correlation between OHC concentrations in blood and adipose tissue was examined, the predictability of concentrations in one matrix for the other was limited.
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