Filtern
Dokumenttyp
Volltext vorhanden
- ja (8)
Gehört zur Bibliographie
- nein (8)
Schlagworte
- Physics (8) (entfernen)
Institut
- Physik (3)
- Geowissenschaften / Geographie (1)
- Gesellschaftswissenschaften (1)
- Medizin (1)
This paper contributes to the clarification of the concept of “typicality” discussed in contemporary philosophy of physics by conceiving the nomological status of a typical behaviour such as that expressed in the Second Law of Thermodynamics as a “minutis rectis law”. A brief sketch of the discovery of “typicality” shows that there were ideas of typical behaviour not only in physics but also in sociology. On this basis and in analogy to the Second Law of Thermodynamics, it is shown that the nomological status of sociological laws such as Gresham’s Law can also be conceived as “minutis rectis laws”.
Der folgende Beitrag präsentiert die Problematik der Eponyme in der Fachsprache und beschäftigt sich mit deren Vorkommen in ausgewählten naturwissenschaftlichen Bereichen. Naturwissenschaften stellen eine reiche Quelle eponymischer Bezeichnungen dar. Für die Analyse wurden drei Disziplinen ausgewählt: Medizin, Chemie und Physik. Alle drei naturwissenschaftlichen Disziplinen wurden in deutscher Sprache analysiert und konfrontiert. Die Analyse konzentriert sich auf die Besonderheiten der Eponyme, d.h. Struktur, Gebrauch, Vorkommen, Kategorisierung und Evaluierung im Rahmen der ausgewählten Disziplinen. Mit der Problematik der Eponyme haben sich mehrere Autoren beschäftigt, z.B. Morton S. Freeman und Dorothy Auchter. In der Slowakei haben sich den Eponymen Mária Bujalková, Božena Džuganová, Gabriela Poláčková und Ivan Masár gewidmet. I. Masár benutzt den Terminus dedikačné termíny (Dedikationstermini, aus dem Griechischen dedicare = widmen). In der deutschen Sprachforschung sind Hans-R. Fluck und Ingrid Wiese zu nennen...
In order to understand the origin of the elements in the universe, one must understand the nuclear reactions by which atomic nuclei are transformed. There are many different astrophysical environments that fulfill the conditions of different nucleosynthesis processes. Even though great progress has been made in recent decades in understanding the origin of the elements in the universe, some questions remain unanswered. In order to understand the processes, it is necessary to measure cross sections of the involved reactions and constrain theoretical model predictions. A variety of methods have been developed to measure nuclear reaction cross sections relevant for nuclear astrophysics. In this thesis, two different experiments and their results, both using the well-established activation method, are presented.
A measurement of the proton capture cross section on the p-nuclide 96Ru was performed at the Institute of Structure and Nuclear Astrophysics ISNAP - Notre Dame, USA. The main goal of this experiment was to compare the results with those obtained by Mei et al. in a pioneering experiment using the method of inverse kinematics at the GSI Helmholtzzentrum für Schwerionenforschung GmbH - Darmstadt, Germany. Therefore, the activations were taken out at the same center of mass energies of 9 MeV, 10 MeV and 11 MeV. Another activation was taken out at an energy of 3.2 MeV to compare the result to a measurement of Bork et al. who also used the activation method. While the results at 3.2 MeV agree quite well with those of Bork et al., the results at higher energies show significantly smaller cross sections than those measured by Mei et al.. Experimental details, the data analysis and sources of uncertainties are discussed.
The second part of this thesis describes a neutron capture cross section experiment. At the Institut für Kernphysik - Goethe Universtität Frankfurt an experimental setup allows to produce quasi maxwell-distributed neutron fields to measure maxwell-averaged cross sections (MACS) relevant for s-process nucleosynthesis. The setup was upgraded by a fast electric linear guide to transport samples from the activation to the detection site. The cyclic activation of the sample allows to increase the signal-to-noise ratio and to measure neutron captures that lead to nuclei with
half-lives on the order of seconds. In a first campaign, MACS of the reactions 51V(n,γ), 107,109Ag(n,γ) and 103Rh(n,γ) were measured. The new components of the setup aswell as the data analysis framework are described and the results of the measurements are discussed.
Previous investigation of seismic anisotropy indicates the presence of a simple mantle flow regime beneath the Turkish-Anatolian Plateau and Arabian Plate. Numerical modeling suggests that this simple flow is a component of a large-scale global mantle flow associated with the African superplume, which plays a key role in the geodynamic framework of the Arabia-Eurasia continental collision zone. However, the extent and impact of the flow pattern farther east beneath the Iranian Plateau and Zagros remains unclear. While the relatively smoothly varying lithospheric thickness beneath the Anatolian Plateau and Arabian Plate allows progress of the simple mantle flow, the variable lithospheric thickness across the Iranian Plateau is expected to impose additional boundary conditions on the mantle flow field. In this study, for the first time, we use an unprecedented data set of seismic waveforms from a network of 245 seismic stations to examine the mantle flow pattern and lithospheric deformation over the entire region of the Iranian Plateau and Zagros by investigation of seismic anisotropy. We also examine the correlation between the pattern of seismic anisotropy, plate motion using GPS velocities and surface strain fields. Our study reveals a complex pattern of seismic anisotropy that implies a similarly complex mantle flow field. The pattern of seismic anisotropy suggests that the regional simple mantle flow beneath the Arabian Platform and eastern Turkey deflects as a circular flow around the thick Zagros lithosphere. This circular flow merges into a toroidal component beneath the NW Zagros that is likely an indicator of a lateral discontinuity in the lithosphere. Our examination also suggests that the main lithospheric deformation in the Zagros occurs as an axial shortening across the belt, whereas in the eastern Alborz and Kopeh-Dagh a belt-parallel horizontal lithospheric deformation plays a major role.
The article sketches a critical paradigm for interdisciplinary work that is centred on tension as a highly ambiguous and ultimately deeply paradoxical notion. It highlights that a unifying account of what tension is or a systematic classification of its diverse meanings would risk resolving tensions between different approaches and privileging a particular mode of doing so. Successively focussing on aesthetic, socio-political, and physical tensions, the essay articulates tension rather as a broad umbrella term that is stretched by multi-perspectival articulations, unified through its intensive surface tension, and at the same time full of transformative and generative potentials. In particular, it proposes that tensions between different cultural or disciplinary fields can be made productive by inducing tensions within each field so that different fields can be related to each other on the basis of tension rather than some substantial commonality.
The aim of this study was to detect a response difference in primary (PLC) and secondary liver tumors (SLC) with magnetic resonance elastography (MRE) after TACE therapy. Thirty-one patients (25/31 male; mean age 69.6 years [range: 39–85 years]) with repeated TACE therapy of HCC were compared with twenty-seven patients (27/27 female; mean age 61.2 years [range 39–81 years]) with repeated TACE therapy of metastatic liver disease due to breast cancer. Both groups underwent either one (n = 31) or two (n = 27) repetitive magnetic resonance imaging (MRI) and MRE exams in 4- to 6-week intervals using a 1.5-T-scanner. MRE-based liver stiffness and size measurements were evaluated in tumorous lesions and in healthy liver lobe controls. PLC showed a significantly larger tumor size compared to SLC (26.4 cm2 vs. 11 cm2, p = 0.007) and a higher degree of stiffness (5.8 kPa vs. 5.1 kPa, p = 0.04). Both tumors decreased in size during the cycles (PLC: p = 0.8 and SLC: p < 0.0001) and lesions showed an increase in stiffness (PLC: p = 0.002 and SLC: p = 0.006). MRE demonstrates that PLC and SLC have similar responses to TACE therapy. PLC had a greater increase in stiffness and SLC got smaller. An increasing stiffness and decrease in size could show a good response.
The rapid spread of the Coronavirus (COVID-19) confronts policy makers with the problem of measuring the effectiveness of containment strategies, balancing public health considerations with the economic costs of social distancing measures. We introduce a modified epidemic model that we name the controlled-SIR model, in which the disease reproduction rate evolves dynamically in response to political and societal reactions. An analytic solution is presented. The model reproduces official COVID-19 cases counts of a large number of regions and countries that surpassed the first peak of the outbreak. A single unbiased feedback parameter is extracted from field data and used to formulate an index that measures the efficiency of containment strategies (the CEI index). CEI values for a range of countries are given. For two variants of the controlled-SIR model, detailed estimates of the total medical and socio-economic costs are evaluated over the entire course of the epidemic. Costs comprise medical care cost, the economic cost of social distancing, as well as the economic value of lives saved. Under plausible parameters, strict measures fare better than a hands-off policy. Strategies based on current case numbers lead to substantially higher total costs than strategies based on the overall history of the epidemic.
Most of the elements heavier than iron are produced through neutron capture reactions in the s- and r -process. The overall path of the s-process is well understood and can be accurately reproduced in network simulations. However, there are still some neutron capture reactions of unstable nuclei involved in the s-process, which were not yet measured due to the difficulty in producing suitable targets. In those cases, theoretical models have to be used to estimate the missing cross section.
One example is the branching point nucleus 86Rb, whose neutron capture cross section cannot be directly measured due to its short half life of 18.86 days. It is, however, also possible to measure its inverse, the 87Rb(g,n) reaction in order to obtain the 86Rb(n,g) cross section through the principle of detailed balance.
Natural rubidium was irradiated with a quasi-monoenergetic photon beam in the energy range between 10.7 MeV and 16 MeV in order to investigate the photo-dissociation cross section of 87Rb. The results are presented in this thesis. Not only the total cross section of 87Rb(g,n), but also the partial production cross section of the ground and isomeric state of 84Rb through the 85Rb(g,n) reaction was measured.
Not all isotopes can be reached via neutron capture reaction, and are therefore bypassed by the s- and r -process. These 35 proton-rich isotopes are called p-nuclei and are produced in the γ-process by a chain of photo-disintegration reactions in Type II supernovae. Network calculations of Type II supernova show that the γ-process can explain the production of most p-nuclei, but some – especially 92/94Mo and 96/98Ru – are heavily underproduced. While this could be the result of deficiencies in the corresponding stellar models or insufficient knowledge of the involved reaction rates, it is also possible that the missing p-nuclei are synthesized in other production scenarios.
An alternative scenario for 92Mo is the production via a chain of proton capture reactions in Type Ia supernovae. One important reaction in this chain is the 90Zr(p,g) reaction. The reaction cross section was already measured several times, but the results were inconclusive. In the present work, the 90 Zr(p,g) reaction was measured using the in-beam gamma-ray spectroscopy technique and the discrepancies between the data sets could be largely explained.