105,536 research outputs found
Incidence of SARs-CoV-2 in Gütersloh county, Germany, after the outbreak in the slaughterhouse and meat packing plant Tönnies
No full textFigure
Seven day incidence of SARS-CoV-2 per 100,000 people from March 15 to September 3, 2020 in Gütersloh, North Rhine-Westphalia, Germany
Table
Pandemic control measures in Gütersloh countyThis is a supplement to a rapid response published in BMJ:
Stang A, Keil U. Incidence of SARs-CoV-2 in Gütersloh county, Germany, after the outbreak in the slaughterhouse and meat packing plant Tönnies. BMJ 2020
Our letter is related to:
Middleton J, Reintes R, Lopes H. Meat plants – a new front line in the COVID-19 pandemic. BMJ 2020;370:m2716; http://dx.doi.org/10.1136/bmj.m271
Characterisation of fibre content, distribution and orientation to predict Fibre Reinforced Concrete behaviour
No full textThis paper calculates the flexural behaviour (load-displacement and stress-crack opening distributions) of “real” beams where the contribution of every single fibre is considered. It therefore, allows clarifying to what extent a link between single fibre pull-out models and post-cracking behaviour can be established when the uncertainty about the actual fibre content, distribution and orientation is eliminated by using a computed tomography (CT) - imagery algorithm. The results were compared to three point bending tests of the same beams. The CT algorithm also presents a solution to the difficult problem of separating clusters that occur when fibres pack together within the concrete matrix
Setting staffing requirements for time-dependent queueing networks: the case of accident and emergency departments
No full textAn incentive scheme aimed at reducing patients’ waiting times in accident and emergency departments was introduced by the UK government in 2000. It requires 98% of patients to be discharged, transferred, or admitted to inpatient care within 4 hours of arrival. Setting the minimal hour by hour medical staffing levels for achieving the government target, in the presence of complexities like time-varying demand, multiple types of patients, and resource sharing, is the subject of this paper. Building on extensive body of research on time dependent queues, we propose an iterative scheme which uses infinite server networks, the square root staffing law, and simulation to come up with a good solution. The implementation of this algorithm in a typical A&E department suggests that significant improvement on the target can be gained, even without increase in total staff hour
Schulnahe Curriculumentwicklung und Handlungsforschung.
No full textKlafki W, Scheffer U, Koch-Priewe B, Stöcker H, Huschke P, Stang H. Schulnahe Curriculumentwicklung und Handlungsforschung. Weinheim, Basel; 1982.Forschungsbericht des Marburger Grundschulprojekte
Micromechanical damage of FRC: Modeling and parametric analyses
No full textIn the present paper the nonlinear response of fiber reinforced concrete
(FRC) material is investigated in the framework of the micromechanics
of heterogeneous materials. In fact, FRC is regarded as
a composite with fibers embedded into a concrete matrix. A 2D
unit cell, with a single fiber, subjected to tensile strain in the fiber
direction is considered. To model the progressive FRC damage, i.e.
the fiber debonding and pull-out and the concrete cracking, fibermatrix
elastoplastic and matrix-matrix damaging interfaces are
introduced. Then, numerical analyses are performed to investigate
the interaction between the fiber debonding and the crack propagation,
and to derive the overall macroscopic response of the FRC
composite material. The numerical results obtained allow to verify
the accurancy of the model adopted for the computation and its
limits. Furthermore, several different analyses are performed in
order to investigate on the role played by the fundamental material
and geometric parameters
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
C—H oxidation reactions in complex molecule synthesis: application and development
No full textAmong the frontier challenges in chemistry in the 21st century are the interconnected goals of increasing synthetic efficiency and diversity in the construction of complex molecules. Oxidation reactions of C–H bonds, particularly when applied at late-stages of complex molecule syntheses, hold special promise for achieving both these goals by minimizing the use of functional group manipulations typically required to synthesize these molecules. Traditionally, C–H oxidation reactions install oxidized functionality onto a preformed molecular skeleton, resulting in a local molecular change. However, the use of C–H activation chemistry to construct complex molecular scaffolds is a new area with tremendous potential in synthesis. This work showcases a late-stage C–H oxidation strategy in the total synthesis of 6-deoxyerythronolide B (6-dEB), the aglycone precursor to the erythromycin antibiotics. An advanced intermediate is cyclized to the 14-membered macrocyclic core of 6-dEB using a late-stage (step 19 of 22) C–H oxidative macrolactonization reaction that proceeds with high regio-, chemo-, and diastereoselectivity (>40:1). A chelate-controlled model for macrolactonization predicted the stereochemical outcome of C–O bond formation and guided the discovery of conditions for synthesizing the first diastereomeric 13-epi-6-dEB precursor. Overall, this C–H oxidation strategy affords a highly efficient and stereochemically versatile synthesis of the erythromycin core.
Throughout the erythromycin’s rich synthetic history, no concept has been entrenched as deeply as the perceived need for biasing elements in order to effect 14-membered macrocyclization. This work showcases the cyclizations of completely unbiased 6-deoxyerythronolide B precursors, using either C–H oxidative or Yamaguchi macrolactonization reactions. Late-stage and stereodivergent C–H oxidation reactions enabled seco acid formation with both configurations at C13. Consequently, it is shown that both the natural and unnatural C13 configurations can be formed in the macrocyclization of the 6-dEB core in the absence of preorganizational elements. Overall these findings require revision of the 30-year-old dogma that preorganization is mandatory for achieving macrocyclization of the erythromycins.
Sequential transformations in a single reaction have the potential to dramatically increase synthetic efficiency by rapidly building molecular complexity while lowering step count and intermediate isolations. Catalytic dehydrogenation reactions of hydrocarbons represent a powerful reaction class capable of activating an otherwise non-reactive substrate through sequential C–H bond activations. As a result, coupling a dehydrogenation transformation to a complexity generating reaction would lead to complex molecular architectures from topologically simple starting materials in a rapid fashion. We report a Pd(II)/bis-sulfoxide catalyzed dehydrogenative Diels-Alder reaction that converts simple terminal olefins into complex cyclohexenyl adducts in good yields and selectivities. Based on the high functional group tolerance, this method enables expedient access to a wide variety of biologically and medicinally relevant heterocycles, such as hydroisoindolines, cis-decalins, hydroisoquinolines, and isoindoloquinolines. Mechanistic studies indicate the reaction proceeds through a sequential allylic C–H cleavage and homoallylic β-hydride elimination to produce a mixture of E and Z terminal 1,3-dienes, which isomerize to the Diels-Alder capable (E)-isomer via Pd(II)-catalysis, followed by a thermal Diels-Alder cycloaddition.Item withdrawn by Mark Zulauf ([email protected]) on 2011-09-08T20:44:03Z
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University of Illinois Theses & Dissertations (ID: 1)
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Approximating multiple class queueing models with loss models
No full textMultiple class queueing models arise in situations where some flexibility is sought through pooling of demands for different services. Earlier research has shown that most of the benefits of flexibility can be obtained with only a small proportion of cross-trained operators. Predicting the performance of a system with different types of demands and operator pools with different skills is very difficult. We present an approximation method that is based on equivalent loss systems. We successively develop approximations for the waiting probability, The average waiting time and the service level. Our approximations are validated using a series of simulations. Along the way we present some interesting insights into some similarities between queueing systems and equivalent loss systems that have to our knowledge never been reported in the literature.
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