345 research outputs found

    Modelling the response of phytoplankton in a shallow lake (Loch Leven, UK) to changes in lake retention time and water temperature.

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    The phytoplankton community of Loch Leven in 2005 was modelled and subjected to a combination of different flushing rates and water temperatures in order to assess the lake’s sensitivity to these two climatic drivers. Whilst the simulated annual mean total chlorophyll a proved relatively insensitive to these changes, at the species level marked changes were recorded. Some species responded positively to increased temperature (e.g. Aulacoseira), some negatively (e.g. Asterionella), whilst others were negatively affected by increased flow (e.g. Aphanocapsa) and others enhanced (e.g. Stephanodiscus). However, this relationship with flow was season dependent with, for example, a simulated increase in summer inflows actually benefiting some species through increased nutrient supply, whereas an equivalent increase in flow in wetter seasons would have negatively affected those species (i.e. through flushing loss). Overall, the simulations showed that the range of species types simulated in the community was sufficient for one species to always benefit from the changing niches created by the multiple climatic drivers applied in this study. The level of exploitation by such a species was only constrained by the nutrient carrying capacity of the system, which led to the overall dampened response in the total chlorophyll a measure, both at the annual and season scale. Thus, whilst overall biomass showed relatively little reaction to the two climatic drivers tested, the phytoplankton community composition responded markedly

    Semi- and Non-relativistic Limit of the Dirac Dynamics with External Fields

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    We show how to approximate Dirac dynamics for electronic initial states by semi- and non-relativistic dynamics. To leading order, these are generated by the semi- and non-relativistic Pauli hamiltonian where the kinetic energy is related to m2+ξ2\sqrt{m^2 + \xi^2} and ξ2/2m\xi^2 / 2m, respectively. Higher-order corrections can in principle be computed to any order in the small parameter v/c which is the ratio of typical speeds to the speed of light. Our results imply the dynamics for electronic and positronic states decouple to any order in v/c << 1. To decide whether to get semi- or non-relativistic effective dynamics, one needs to choose a scaling for the kinetic momentum operator. Then the effective dynamics are derived using space-adiabatic perturbation theory by Panati et. al with the novel input of a magnetic pseudodifferential calculus adapted to either the semi- or non-relativistic scaling.Comment: 42 page

    Microcirculatory perfusion is preserved during off-pump but not on-pump cardiac surgery

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    OBJECTIVE: This study investigated the perioperative course of microcirculatory perfusion in off-pump compared with on-pump surgery. Additionally, the impact of changes in systemic hemodynamics, hematocrit, and body temperature was studied. DESIGN: Prospective, nonrandomized, observational study. SETTING: Tertiary university hospital. PARTICIPANTS: Patients undergoing coronary artery bypass grafting with (n = 13) or without (n = 13) use of cardiopulmonary bypass. INTERVENTIONS: Microcirculatory measurements were obtained at 5 time points ranging from induction of anesthesia to ICU admission. MEASUREMENTS AND MAIN RESULTS: Microcirculatory recordings were performed with sublingual sidestream dark field imaging. Despite a comparable reduction in intraoperative blood pressure between groups, the perfused vessel density decreased more than 20% after onset of extracorporeal circulation but remained stable in the off-pump group. The reduction in microvascular perfusion in the on-pump group was further paralleled by decreased hematocrit and temperature. Although postbypass hematocrit levels and body temperature were restored to similar levels as in the off-pump group, the median microvascular flow index remained reduced after bypass (2.4 [2.3-2.7]) compared with baseline (2.8 [2.7-2.9]; p = 0.021). CONCLUSIONS: Microcirculatory perfusion remained unaltered throughout off-pump surgery. In contrast, microvascular perfusion declined after initiation of cardiopulmonary bypass and did not recover in the early postoperative phase

    Prospects for comparing European hospitals in terms of quality and safety

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    Purpose. Being able to compare hospitals in terms of quality and safety between countries is important for a number of reasons. For example, the 2011 European Union directive on patients’ rights to cross-border health care places a requirement on all member states to provide patients with comparable information on health-care quality, so that they can make an informed choice. Here, we report on the feasibility of using common process and outcome indicators to compare hospitals for quality and safety in five countries (England, Portugal, The Netherlands, Sweden and Norway). Main Challenges Identified. The cross-country comparison identified the following seven challenges with respect to comparing the quality of hospitals across Europe: different indicators are collected in each country; different definitions of the same indicators are used; different mandatory versus voluntary data collection requirements are in place; different types of organizations oversee data collection; different levels of aggregation of data exist (country, region and hospital); different levels of public access to data exist; and finally, hospital accreditation and licensing systems differ in each country. Conclusion. Our findings indicate that if patients and policymakers are to compare the quality and safety of hospitals across Europe, then further work is urgently needed to agree the way forward. Until then, patients will not be able to make informed choices about where they receive their health care in different countries, and some governments will remain in the dark about the quality and safety of care available to their citizens as compared to that available in neighbouring countries

    A Novel Combined Term Suggestion Service for Domain-Specific Digital Libraries

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    Interactive query expansion can assist users during their query formulation process. We conducted a user study with over 4,000 unique visitors and four different design approaches for a search term suggestion service. As a basis for our evaluation we have implemented services which use three different vocabularies: (1) user search terms, (2) terms from a terminology service and (3) thesaurus terms. Additionally, we have created a new combined service which utilizes thesaurus term and terms from a domain-specific search term re-commender. Our results show that the thesaurus-based method clearly is used more often compared to the other single-method implementations. We interpret this as a strong indicator that term suggestion mechanisms should be domain-specific to be close to the user terminology. Our novel combined approach which interconnects a thesaurus service with additional statistical relations out-performed all other implementations. All our observations show that domain-specific vocabulary can support the user in finding alternative concepts and formulating queries.Comment: To be published in Proceedings of Theories and Practice in Digital Libraries (TPDL), 201

    Moving towards adaptive search in digital libraries

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    Search applications have become very popular over the last two decades, one of the main drivers being the advent of the Web. Nevertheless, searching on the Web is very different to searching on smaller, often more structured collections such as digital libraries, local Web sites, and intranets. One way of helping the searcher locating the right information for a specific information need in such a collection is by providing well-structured domain knowledge to assist query modification and navigation. There are two main challenges which we will both address in this chapter: acquiring the domain knowledge and adapting it automatically to the specific interests of the user community. We will outline how in digital libraries a domain model can automatically be acquired using search engine query logs and how it can be continuously updated using methods resembling ant colony behaviour. © 2011 Springer-Verlag

    Daily interruption of sedation in critically ill children: Study protocol for a randomized controlled trial

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    Background: In adult patients who are critically ill and mechanically ventilated, daily interruption of sedation (DSI) is an effective method of improving sedation management, resulting in a decrease of the duration of mechanical ventilation, the length of stay in the intensive care unit (ICU) and the length of stay in the hospital. It is a safe and effective approach and is common practice in adult ICUs. For critically ill children it is unknown if DSI is effective and feasible. The aim of this multicenter randomized controlled trial is to evaluate the safety and
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