853 research outputs found

    Hyperstars: phase transition to (meta)-stable hyperonic matter in neutron stars

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    Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars is investigated. We find that the equation of state exhibits a second stable minimum at large hyperon contents which is in accord with existing hypernuclear data. This second solution gives rise to new effects for neutron star properties which are similar to the ones proposed for the deconfinement transition to strange quark matter and absolutely stable strange stars. We find that the corresponding hyperstars can have rather small radii of R=6-8 km independent of the mass. PACS: 26.60+c, 21.65+f, 97.60.Gb, 97.60.J

    Phase transition to hyperon matter in neutron stars

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    Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars are investigated. We find that a hadronic equation of state with hyperons allows for a first order phase transition to hyperonic matter. The corresponding hyperon stars can have rather small radii of R ~ 8 km. PACS: 26.60+c, 21.65+f, 97.60.Gb, 97.60.J

    Neutron star properties in the quark-meson coupling model

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    The effects of internal quark structure of baryons on the composition and structure of neutron star matter with hyperons are investigated in the quark- meson coupling (QMC) model. The QMC model is based on mean-field description of nonoverlapping spherical bags bound by self-consistent exchange of scalar and vector mesons. The predictions of this model are compared with quantum hadrodynamic (QHD) model calibrated to reproduce identical nuclear matter saturation properties. By employing a density dependent bag constant through direct coupling to the scalar field, the QMC model is found to exhibit identical properties as QHD near saturation density. Furthermore, this modified QMC model provides well-behaved and continuous solutions at high densities relevant to the core of neutron stars. Two additional strange mesons are introduced which couple only to the strange quark in the QMC model and to the hyperons in the QHD model. The constitution and structure of stars with hyperons in the QMC and QHD models reveal interesting di erences. This suggests the importance of quark structure e ects in the baryons at high densities. PACS number(s): 26.60.+c, 21.65.+f, 12.39.Ba, 24.85.+

    Strange quark stars within the Nambu-Jona-Lasinio model

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    We investigate the properties of charge neutral equilibrium cold quark matter within the Nambu Jona-Lasinio model. The calculations are carried out for di erent ratios of coupling constants characterizing the vector and scalar 4 fermion interaction, xi = GV /GS. It is shown that for xi < 0.4 the stars near to the maximum mass have a large admixture of strange quarks in their interiors. PACS number: 14.65.-q, 26.60.+c, 97.10.-

    Neutron star properties in a chiral SU(3) model

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    We investigate various properties of neutron star matter within an e ective chiral SU(3)L × SU(3)R model. The predictions of this model are compared with a Walecka-type model. It is demonstrated that the importance of hy- peron degrees are strongly depending on the interaction used, even if the equation of state near saturation density is nearly the same in both models. While the Walecka-type model predicts a strange star core with strangeness fraction fS 4/3, the chiral model allows only for fS 1/3 and predicts that 0, + and 0 will not exist in star, in contrast to the Walecka-type model. PACS: 26.60+c, 21.65+f, 24.10J

    Epidemiology and direct medical costs of osteoporotic fractures in men and women in Switzerland

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    The aim of this study was to estimate the hospitalization incidence and the total number of hospital days related to all fractures and osteoporotic fractures in the year 2000 in Switzerland and to compare these with data from other frequent disorders in men and women. The official administrative and medical statistics database of the Swiss Federal Office of Statistics (SFOS) from the year 2000 was used. It covered 81.2% of all registered patient admissions and was considered to be representative of the entire population. We included the ICD-10 codes of 84 diagnoses that were compatible with an underlying osteoporosis and applied the best matching age-specific osteoporosis attribution rates published for the ICD-9 diagnosis codes to the individual ICD-10 codes. To preserve comparability with previously published data from 1992, we grouped the data related to the ICD-10 fracture codes into seven diagnosis pools (fractures of the axial skeleton, fractures of the proximal upper limbs, fractures of the distal upper limbs, fractures of the proximal lower limbs, fractures of the distal lower limbs, multiple fractures, and osteoporosis) and analyzed them separately for women and men by age group. Incidences of hospitalization due to fractures were calculated, and the direct medical costs related to hospitalization were estimated. In addition, we compared the results with those from chronic pulmonary obstructive disease (COPD), stroke, acute myocardial infarction, heart failure, diabetes and breast carcinoma from the same database. In Switzerland during 2000, 62,535 hospitalizations for fractures (35,586 women and 26,949 men) were registered. Fifty-one percent of all fractures in women and 24% in men were considered as osteoporotic. The overall incidences of hospitalization due to fractures were 969 and 768 per 100,000 in women and men, respectively. The hospitalization incidences for fractures of the proximal lower limbs and the axial skeleton increased exponentially after the age of 65 years. The direct medical cost of hospitalization of patients with osteoporosis and/or related fractures was 357million CHF. Hip fractures accounted for approximately half of these costs in women and men. Among other common diseases in women and men, osteoporosis ranked number1 in women and number2 (behind COPD) in men. When compared with data from 1992, the average length of stay had shortened by 8.4 days for women and 4.7 days for men, leading to a decrease of almost 40% in direct medical costs related to acute hospitalizations. This apparent decrease in cost might result from a shift into the ambulatory cost segment, for which the assessment and management tools need to be developed. We conclude that, in 2000, osteoporosis continued to be a heavy burden on the Swiss healthcare system. Lack of awareness of the disease and its consequences prevents widespread use of drugs with anti-fracture efficacy. This limits their potential to reduce cost

    Catastrophic rearrangement of a compact star due to the quark core formation

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    We study properties of compact stars with the deconfinement phase transition in their interiors. The equation of state of cold baryon-rich matter is constructed by combining a relativistic mean-field model for the hadronic phase and the MIT Bag model for the deconfined phase. In a narrow parameter range two sequences of compact stars (twin stars), which differ by the size of the quark core, have been found. We demonstrate the possibility of a rapid transition between the twin stars with the energy release of about 10 ^52 ergs. This transition should be accompanied by the prompt neutrino burst and the delayed gamma-ray burst

    Platform to Assist Medical Experts in Training, Application, and Control of Machine Learning Models Using Patient Data from a Clinical Information System

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    In recent years, clinical data scientists achieved major breakthroughs advancing machine learning models for the medical domain, which have great potential assisting medical experts. Machine learning models can be leveraged to assist medical experts in tasks such as analyzing and diagnosing patient data, for example, from computed tomography scans. However, it is a challenge to translate the latest advancements in academic research fields such as computer sciences and physics into clinical practice. For this purpose, clinical data scientists and medical experts need to closely collaborate. This thesis tackles challenges of accessibility and usability of state-of-the-art machine learning models as well as designing a scalable computing architecture. Hence, conceptual ideas of possible strategies, as well as a prototype of such a machine learning platform, are presented. A systematic literature review was conducted on the current approaches to create medical machine learning platforms, the management of machine learning models, and the version management of large data sets. Afterward, the functional and nonfunctional requirements of the new machine learning platform were elicited as part of the requirements analysis. Two streamlined workflows for clinical data scientists and medical experts were derived from the requirement analysis. The workflow for the clinical data scientists includes steps to define, train, and share machine learning methods, including pre- and postprocessing modules, and management of data sets. Medical experts are able to analyze patient data using pre-defined machine learning methods. Building on the result of these analyses, the architecture of the platform was derived. The architecture consists of a scalable infrastructure stack, a lightweight and easy-to-use web interface, as well as a backend component to provide the required functionalities. The final design decisions solve the issue of efficiently standardizing, parallelizing, and applying machine learning workflows within a scalable computing infrastructure. The proposed platform was evaluated with 22 participants, consisting of clinical data scientists (N=12) and medical experts (N=10). Both groups were asked to rate specific workflows of the platform, as well as the platform as a whole, and to provide additional ideas and feedback. 92% of the medical experts and 90% of the clinical data scientists rated their overall impression of the platform as very good. Furthermore, medical experts and clinical data scientists strongly agreed that the platform facilitates method development and collaborations with 92% and 90%, respectively. The conducted expert survey suggests that the here proposed platform could be used to develop, optimize, and apply machine learning methods in the medical domain and beyond, thereby easing the collaboration between medical experts and clinical data scientists

    Verfahren zur Prädiktion des Rollwiderstands bei variablen Betriebsparametern auf Basis standardisierter Rollwiderstandsmessungen

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    Als Beitrag zum Umweltschutz wurde das EU-Reifenlabel eingeführt. Doch kann vom besten Labelwert nicht auf den Reifen mit dem niedrigsten Rollwiderstand im realen Betrieb geschlossen werden. Ziel dieser Arbeit ist es, ein Rollwiderstandsmodell für PKW-Reifen zu entwickeln, das mittels einfacher Rollwiderstandsmessungen bedatet werden kann. Hierzu wird der Reifen durch ein einfaches physikalisches Modell beschrieben, das den Zusammenhang zwischen Reifentemperatur und Rollwiderstand modelliert

    Use of meat juice and blood serum with a miniaturised protein microarray assay to develop a multi-parameter IgG screening test with high sample throughput potential for slaughtering pigs

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    Background Serological screening of pig herds at the abattoir is considered a potential tool to improve meat inspection procedures and herd health management. Therefore, we previously reported the feasibility of a miniaturised protein microarray as a new serological IgG screening test for zoonotic agents and production diseases in pigs. The present study investigates whether the protein microarray-based assay is applicable for high sample throughput using either blood serum or meat juice. Material and methods Microarrays with 12 different antigens were produced by Abbott (formerly Alere Technologies GmbH) Jena, Germany in a previously offered ‘ArrayTube’ platform and in an ‘ArrayStrip’ platform for large-scale use. A test protocol for the use of meat juice on both microarray platforms was developed. Agreement between serum and meat juice was analysed with 88 paired samples from three German abattoirs. Serum was diluted 1:50 and meat juice 1:2. ELISA results for all tested antigens from a preceding study were used as reference test to perform Receiver Operating Characteristic analysis for both test specimens on both microarray platforms. Results High area under curve values (AUC > 0.7) were calculated for the analysis of T. gondii (0.87), Y. enterocolitica (0.97), Mycoplasma hyopneumoniae (0.84) and Actinobacillus pleuropneumoniae (0.71) with serum as the test specimen and for T. gondii (0.99), Y. enterocolitica (0.94), PRRSV (0.88), A. pleuropneumoniae (0.78) and Salmonella spp. (0.72) with meat juice as the test specimen on the ArrayStrip platform. Cohens kappa values of 0.92 for T. gondii and 0.82 for Y. enterocolitica were obtained for the comparison between serum and meat juice. When applying the new method in two further laboratories, kappa values between 0.63 and 0.94 were achieved between the laboratories for these two pathogens. Conclusion Further development of a miniaturised pig-specific IgG protein microarray assay showed that meat juice can be used on microarray platforms. Two out of twelve tested antigens (T. gondii, Y. enterocolitica) showed high test accuracy on the ArrayTube and the ArrayStrip platform with both sample materials
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