60 research outputs found
Gene flow in admixed populations and implications for the conservation of the Western honeybee, Apis mellifera
Anthropogenic activity, especially modern apiculture, has considerable impact on the natural distribution of the Western honeybee, Apismellifera, leading to the spread, replacement and fragmentation of many subspecies. This creates demand for the conservation of some subspecies, in particular, Apismelliferamellifera, which once was widely distributed in Western Europe and nowadays is endangered through habitat loss and fragmentation. Moreover, A.m.mellifera may be further endangered by hybridisation in populations that now occur in artificial sympatry with other subspecies. Here, we quantify and compare individual hybridisation between sympatric and allopatric honeybee populations of A.m.mellifera and A.m.carnica using microsatellite markers and a Bayesian model-based approach. We had a special focus on pure breeding populations, which are a major tool in honeybee conservation. Our results demonstrate that subspecies are still highly differentiated, but gene flow is not prevented by the current management strategies, creating urgent demand for an improved conservation management of A.m.mellifera. However, the occurrence of a high number of pure individuals might suggest that some sort of hybrid barrier acts against the complete admixture of the two subspecie
Stenosis Length and Degree Interact With the Risk of Cerebrovascular Events Related to Internal Carotid Artery Stenosis
Background and Purpose: Internal carotid artery stenosis (ICAS)â„70% is a leading cause of ischemic cerebrovascular events (ICVEs). However, a considerable percentage of stroke survivors with symptomatic ICAS (sICAS) have <70% stenosis with a vulnerable plaque. Whether the length of ICAS is associated with high risk of ICVEs is poorly investigated. Our main aim was to investigate the relation between the length of ICAS and the development of ICVEs.Methods: In a retrospective cross-sectional study, we identified 95 arteries with sICAS and another 64 with asymptomatic internal carotid artery stenosis (aICAS) among 121 patients with ICVEs. The degree and length of ICAS as well as plaque echolucency were assessed on ultrasound scans.Results: A statistically significant inverse correlation between the ultrasound-measured length and degree of ICAS was detected for sICASâ„70% (Spearman correlation coefficient Ï = â0.57, p < 0.001, n = 51) but neither for sICAS<70% (Ï = 0.15, p = 0.45, n = 27) nor for aICAS (Ï = 0.07, p = 0.64, n = 54). The median (IQR) length for sICAS<70% and â„70% was 17 (15â20) and 15 (12â19) mm (p = 0.06), respectively, while that for sICAS<90% and sICAS 90% was 18 (15â21) and 13 (10â16) mm, respectively (p < 0.001). Among patients with ICAS <70%, a cut-off length of â„16 mm was found for sICAS rather than aICAS with a sensitivity and specificity of 74.1% and 51.1%, respectively. Irrespective of the stenotic degree, plaques of the sICAS compared to aICAS were significantly more often echolucent (43.2 vs. 24.6%, p = 0.02).Conclusion: We found a statistically insignificant tendency for the ultrasound-measured length of sICAS<70% to be longer than that of sICASâ„70%. Moreover, the ultrasound-measured length of sICAS<90% was significantly longer than that of sICAS 90%. Among patients with sICASâ„70%, the degree and length of stenosis were inversely correlated. Larger studies are needed before a clinical implication can be drawn from these results
Seroprevalence of SARS-CoV-2 in healthcare workers from outpatient facilities and retirement or nursing homes in a Swiss canton.
BACKGROUND
Healthcare workers are more frequently exposed to SARS-CoV-2 than the general population. Little is known about healthcare settings outside of hospitals. We studied the seroprevalence of SARS-CoV-2 among healthcare workers in outpatient facilities and retirement or nursing homes in the Canton of Solothurn, Switzerland in the first wave of the COVID-19 pandemic.
METHODS
Longitudinal seroprevalence study among healthcare workers with examinations at baseline and 2 months between June and September 2020. The Abbott SARS-CoV-2 IgG and Liaison/Diasorin SARS-CoV-2 S1/S2 IgG assay were used to detect antibodies against SARS-CoV-2. All participants provided demographic information. We report descriptive statistics and calculated the seroprevalence with 95% confidence intervals.
RESULTS
We included 357 healthcare workers; their median age was 43 years (interquartile range 29-54), and 315 (88.2%) were female. Forty-nine (13.7%) were physicians, 87 (24.4%) practice assistants and 221 (61.9%) nurses. Overall seroprevalence among healthcare workers in outpatient facilities and retirement or nursing homes was 3.4% (12/357). The 12 seropositive healthcare workers were all nurses (12/221, 5.5%); 11 worked at retirement or nursing homes and one at the hospital's outpatient clinic. Symptoms such as loss of smell or taste, shortness of breath, and fever were more prevalent among seropositive healthcare workers than seronegative healthcare workers. No close contact had detectable antibodies against SARS-CoV-2.
CONCLUSIONS
Seroprevalence among healthcare workers was low, but higher among nursing staff of retirement or nursing homes. Healthcare workers at private practices were able to protect themselves well during the first wave of the COVID-19 pandemic
Why are Switzerland's Foreign Assets so Low? The Growing Financial Exposure of a Small Open Economy
Impact of Cerebral Microbleeds in Stroke Patients with Atrial Fibrillation
OBJECTIVES: Cerebral microbleeds are associated with the risks of ischemic stroke and intracranial hemorrhage, causing clinical dilemmas for antithrombotic treatment decisions. We aimed to evaluate the risks of intracranial hemorrhage and ischemic stroke associated with microbleeds in patients with atrial fibrillation treated with Vitamin K antagonists, direct oral anticoagulants, antiplatelets, and combination therapy (i.e. concurrent oral anticoagulant and antiplatelet) METHODS: We included patients with documented atrial fibrillation from the pooled individual patient data analysis by the Microbleeds International Collaborative Network. Risks of subsequent intracranial hemorrhage and ischemic stroke were compared between patients with and without microbleeds, stratified by antithrombotic use. RESULTS: A total of 7,839 patients were included. The presence of microbleeds was associated with an increased relative risk of intracranial hemorrhage (aHR 2.74, 95% confidence interval 1.76 - 4.26) and ischemic stroke (aHR 1.29, 95% confidence interval 1.04 - 1.59). For the entire cohort, the absolute incidence of ischemic stroke was higher than intracranial hemorrhage regardless of microbleeds burden. However, for the subgroup of patients taking combination of anticoagulant and antiplatelet therapy, the absolute risk of intracranial hemorrhage exceeded that of ischemic stroke in those with 2-4 microbleeds (25 vs 12 per 1,000 patient-years) and â„11 microbleeds (94 vs 48 per 1,000 patient-years). INTERPRETATION: Patients with atrial fibrillation and high burden of microbleeds receiving combination therapy have a tendency of higher rate of intracranial hemorrhage than ischemic stroke, with potential for net harm. Further studies are needed to help optimize stroke preventive strategies in this high-risk group. This article is protected by copyright. All rights reserved
Turbine layout for and optimization of solar chimney power conversion units
Thesis (PhD (Mechanical and Mechatronic Engineering))--Stellenbosch University, 2008.ENGLISH ABSTRACT: The power conversion unit of a large solar chimney power plant converts the fluid power, first into mechanical power, and then into electrical power. In this
dissertation a tool is developed to determine the layout and the number of turbines
of the solar chimney power conversion unit providing the lowest cost of
electricity.
First, the history of the solar chimney concept and the related fields of research
are presented. Potential features and configurations of the power conversion
unit are introduced, and it is shown how the solar chimney power conversion
unit compares to those of other applications. An outline of the dissertation
is given, and its potential impact is discussed.
An analytical turbine model is developed. Several modelling approaches and
the performance of single rotor and counter rotating turbine layouts are compared.
Preliminary turbine designs are investigated, experimentally and numerically.
The main aim of the experimental investigation is to verify the applicability
of the loss model used in the analytical turbine model. The aim of the numerical
investigation is to evaluate a commercial software package as a tool in context
with solar chimney turbines.
For each component of the power conversion unit an analytical performance
model is introduced. Using these models, the single vertical axis, multiple vertical
axis and multiple horizontal axis turbine configurations are compared from
an efficiency and energy yield point of view, and the impact of the various losses
on the overall performance is highlighted. A detailed cost model for the power
conversion unit is also presented. To optimize for cost of electricity this cost
model is then linked to the performance models, and the resulting optimization
scheme is applied to several plant configurations.
It is shown that for a large solar chimney power plant the power conversion
unit providing minimal cost of electricity consists of multiple horizontal axis turbines
using a single rotor layout including inlet guide vanes.AFRIKAANSE OPSOMMING: Die drywingsomsettingseenheid van ân groot sonskoorsteenaanleg sit die vloeidrywing om, eers in meganiese drywing en dan in elektriese drywing. In hierdie
proefskrif word ân gereedskapstuk ontwikkel om die uitleg en aantal turbines van
die sonskoorsteen-drywingsomsettingseenheid te bepaal wat die laagste koste
van elektrisiteit lewer. Eerstens word die geskiedenis van die sonskoorsteen en verwante navorsingsvelde
behandel. Moontlike eienskappe en konfigurasies vir die drywingsomsettingseenheid word
voorgestel, en daar word aangetoon hoe die sonskoorsteendrywingsomsettings-
eenheid vergelyk met ander toepassings. ân Raamwerk van
die proefskrif word gegee, en die potensiële trefkrag daarvan word bespreek.
ân Analitiese turbine-model word ontwikkel. Verskeie nabootsingsbenaderings
en die vertoning van ân enkelrotor en teenroterende turbine-uitlegte word
vergelyk. Voorlopige turbine-ontwerpe word ondersoek, eksperimenteel en numeries.
Die hoofdoel van die eksperimentele ondersoek is om die toepaslikheid
van die verliesmodel in die analitiese turbine-model te bevestig. Die doel van die
numeriese ondersoek is om kommersiĂ«le sagteware op te weeg as ân gereedskapstuk
in die konteks van sonskoorsteenturbines.
Vir elke onderdeel van die drywingsomsettingseenheid word ân analitiese model
voorgestel. Met gebruik van hierdie modelle word die enkele vertikale-as, die
veelvoudige vertikale-as an die veelvoudige horisontale-as turbinekonfigurasies
vergelyk vanuit ân benuttingsgraad- en energie-opbrengsoogpunt,en die uitwerking
van die verskillende verliese op die algehele gedrag word uitgewys. ân Kostemodel
in besonderhede word vir die drywingsomsettingseenheid aangebied. Om
vir die koste van elektrisiteit te optimeer word hierdie kostemodel dan gekoppel
aan die vertoningsmodelle, en die gevolglike optimeringskema word toegepas op
verskeie aanlegkonfigurasies.
Daar word aangetoon dat vir ân groot sonskoorsteenaanleg die drywingsomsettingseenheid wat
die minimumkoste van elektrisiteit gee, bestaan uit veelvoudige
horisontale-as turbines met enkelrotoruitleg en inlaatleilemme.Centre for Renewable and Sustainable Energy Studie
Gene flow in admixed populations and implications for the conservation of the Western honeybee, Apis mellifera
Pollen consumption in honey bee larvae: a step forward in the risk assessment of transgenic plants
In order to assess the potential impacts of transgenic plants on larvae of the honey bee, Apis mellifera, information on pollen consumption is needed. We here report on experiments that were conducted with small bee colonies kept in field cages (8Â ĂÂ 14 m) containing only flowering maize plants as protein source. Fully grown worker bee larvae were found to contain between 1720 and 2310 maize pollen grains in their gut before defecation, corresponding to 1.52â2.04 mg of pollen consumed per larva. On average, 74.5% of pollen grains were completely digested while 23.3% were partially digested and 2.2% remained undigested. Our data indicate that the contribution of the protein by directly feeding larvae with pollen is less than 5% in relation to the total amount of protein necessary for complete larval development. We suggest that our measurement for pollen consumption should be taken into account when establishing dose regimes to assess the risk that transgenic plants pose for honey bee larvae
Techno-economic assessment of new material developments in central receiver solar power plants
For the evaluation of functional material developments in the EU-project RAISELIFE, a tool chain of ray tracing, thermal FEM simulation and dynamic system simulation has been created. Multi-year simulations allow considering degradation of optical parameters. With this tool chain, the thermal energy output of a reference plant with one non-selective and one generic selective coating was simulated. The LCOE (Levelized Cost of Electricity) was calculated based on these results. The LCOE of the selective coating is 2.6 % lower, if the same costs are assumed. Furthermore, the ideal recoating interval for the reference system was identified. Finally, it was demonstrated that dynamic system simulation shows benefits to evaluate in-service performance of functional materials as dynamic behavior of solar thermal power plants can change quite significantly, if another coating is used
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