Rational Ehrhart quasi-polynomials

Ehrhart's famous theorem states that the number of integral points in a rational polytope is a quasi-polynomial in the integral dilation factor. We study the case of rational dilation factors and it turns out that the number of integral points can still be written as a rational quasi-polynomial. Furthermore the coefficients of this rational quasi-polynomial are piecewise polynomial functions and related to each other by derivation.Comment: 15 pages, several changes in the expositio

3. Wochenbericht CE0913

Vom 26. Juli bis zum 14. August sind Wissenschaftler vom IFM-GEOMAR auf dem irischen Forschungsschiff Celtic Explorer in der Nordsee unterwegs. Die Expedition CE 0913 unter Fahrtleitung von Dr. Peter Linke findet im Rahmen des Projekts „Fluid- und Gasaustritte in der südlichen deutschen Nordsee“ in Zusammenarbeit mit der Christian-Albrechts-Universität zu Kiel, dem Bundesamt für Seeschifffahrt und Hydrographie und Wintershall statt und dient der Auffindung von Fluid- und Gasaustritten. Die Art und Weise des Austritts und die chemische und isotopische Zusammensetzung der austretenden Gase sollen genauer analysiert werden. Dabei kommen der Tiefseeroboter ROV KIEL 6000, Vibrocorers und Landersysteme zum Einsatz. CELTIC EXPLORER CE 0913: 2. Wochenbericht (10.‐14.08.2009

Cone-volume measures of polytopes

The cone-volume measure of a polytope with centroid at the origin is proved to satisfy the subspace concentration condition. As a consequence a conjectured (a dozen years ago) fundamental sharp affine isoperimetric inequality for the U-functional is completely established -- along with its equality conditions.Comment: Slightly revised version thanks to the suggestions of the referees and other readers; two figures adde

Comparative advantage, multi-product firms and trade liberalisation : An empirical test

This paper investigates how economies of scope in multi-product firms interact with comparative advantage in determining the effect of trade liberalisation on resource reallocation, using Belgian manufacturing firm- and firm-product-level data over the period 1997-2007. We first provide evidence on industry integration induced by multi-product firms producing simultaneously in multiple industries and on the extent to which industry integration occurs between industries that have different degrees of comparative advantage. We then examine the impact of opening up trade with low-wage countries on both inter- and intra-industry resource reallocation, taking into account heterogeneity in the integration rate across sectors and industries. Our results indicate that, within more closely integrated sectors, trade liberalisation with low-wage countries leads to less reallocation from low-skill-intensity (comparative-disadvantage) industries to high-skill-intensity (comparative-advantage) industries, both in terms of employment and output. We also find that more integrated industries experience less skill upgrading after trade liberalisation with low-wage countries. Furthermore, we find that within sectors with a low integration rate, trade liberalisation with low-wage countries induces relatively more aggregate TFP and average firm output growth in comparative-advantage industries than in comparative-disadvantage industries, in line with the prediction of Bernard, Redding and Schott (2007), while the opposite is true in highly integrated sectors. Decomposition of the industry-level aggregate TFP changes reveals that the result is mainly driven by reallocation between incumbent firms within industries. Overall, the results are highly consistent with the predictions of the Song and Zhu (2010) model.trade liberalisation, industry integration, comparative advantage, firm heterogeneity, microeconomic panel data, Total Factor Productivity

'Managing scarcity'- a qualitative study on volunteer-based healthcare for chronically ill, uninsured migrants in Berlin, Germany

OBJECTIVES: In Germany, healthcare for people lacking legal residency status and European Union citizens without health insurance is often provided by non-governmental organisations. Scientific studies assessing the situation of the patients with chronic diseases in this context are scarce. We aimed to characterise medical care for chronically ill migrants without health insurance and outline its possibilities and limitations from the treating physicians' perspective. DESIGN: Qualitative semi-structured interviews; qualitative content analysis. SETTING: Organisations and facilities providing healthcare for uninsured migrants: free clinics, medical practices and public health services. PARTICIPANTS: 14 physicians working regularly in healthcare for uninsured migrants. RESULTS: Delayed contact to the healthcare system was frequently addressed in the interviews. Care was described as constrained by a scarcity of resources that often impedes adequate treatment for many conditions, most pronounced in the case of oncological diseases or chronic viral infections (HIV, hepatitis). For other chronic conditions such as cardiovascular diseases or diabetes, some diagnostics and basic medications were described as partially available, while management of complications or rehabilitative measures are frequently unfeasible. For the patients with mental health problems, attainability of psychotherapeutic treatment is reported as severely limited. Care is predominantly described as fragmented with limitations to information flow and continuity. Which level of care a patient receives appears to depend markedly on the respective non-governmental organisation and the individual commitment, subjective decisions and personal connections of the treating physician. CONCLUSIONS: Restrictions in medical care for uninsured migrants have even more impact on chronically ill patients. Volunteer-based care often constitutes an inadequate compensation for regular access to the healthcare system, as it is strongly influenced by the limitation of its resources and its arbitrariness

Reversible electron-hole separation in a hot carrier solar cell

Hot-carrier solar cells are envisioned to utilize energy filtering to extract power from photogenerated electron-hole pairs before they thermalize with the lattice, and thus potentially offer higher power conversion efficiency compared to conventional, single absorber solar cells. The efficiency of hot-carrier solar cells can be expected to strongly depend on the details of the energy filtering process, a relationship which to date has not been satisfactorily explored. Here, we establish the conditions under which electron-hole separation in hot-carrier solar cells can occur reversibly, that is, at maximum energy conversion efficiency. We thus focus our analysis on the internal operation of the hot-carrier solar cell itself, and in this work do not consider the photon-mediated coupling to the sun. After deriving an expression for the voltage of a hot-carrier solar cell valid under conditions of both reversible and irreversible electrical operation, we identify separate contributions to the voltage from the thermoelectric effect and the photovoltaic effect. We find that, under specific conditions, the energy conversion efficiency of a hot-carrier solar cell can exceed the Carnot limit set by the intra-device temperature gradient alone, due to the additional contribution of the quasi-Fermi level splitting in the absorber. We also establish that the open-circuit voltage of a hot-carrier solar cell is not limited by the band gap of the absorber, due to the additional thermoelectric contribution to the voltage. Additionally, we find that a hot-carrier solar cell can be operated in reverse as a thermally driven solid-state light emitter. Our results help explore the fundamental limitations of hot-carrier solar cells, and provide a first step towards providing experimentalists with a guide to the optimal configuration of devices.Comment: 31 pages, 5 figure

Import Competition from and Outsourcing to China: A Curse or Blessing for Firms?

We use Belgian manufacturing firm-level data over the period 1996- 2007 to analyze the impact of imports from different origins on firm growth, exit, and skill upgrading. For this purpose we use both industry-level and firm-level imports by country of origin and distinguish between firm-level outsourcing of final versus intermediate goods. Results indicate that China is different from both other low-wage and OECD countries. Industry-level import competition and firm-level outsourcing to China reduce firm employment growth and induce skill upgrading. In contrast, industry-level imports have no effect on Belgian firm survival, while firm-level outsourcing of finished goods to China even increased firm's probability of survival. In terms of skill upgrading, the effect of Chinese imports is large. Import competition from China accounts for 42% (20%) of the within firm increase in the share of skilled workers (non-production workers) in Belgian manufacturing over the peri od of our analysis, but these effects, as well as the employment reducing effect, remain mainly in low-tech industries. Firm-level outsourcing to China further accounts for a small but significant increase in the share of non-production workers. This change in employment structure is in line with predictions of recent model of trade-induced technological change and offshoring.import competition, outsourcing, China, skill upgrading, technological change

Dissolved methane pluming mapping using Membrane Inlet Mass-Spectrometry (MIMS) at a blowout site in the North Sea

A blow out site in the North Sea (well 22/4-b, UK EEZ) in a water depth of 83 m, served as a test area to demonstrate MIMS as a powerful tool for the continuous measurement of dissolved methane simultaneously to the partial pressure of carbon dioxide, nitrogen and oxygen as well as other gases. A pump-CTD arrangement was used to generate a continuous water stream through a 2.5 cm thick tube to the ship laboratory and was analyzed using a membrane inlet quadrupole mass spectrometer (GAM 200, InProcessInstruments). The pump-CTD was further equipped with calibrated HydroC CH4/CO2 sensors. The MIMS measurements were conducted under fully controlled temperature conditions and were calibrated for CH4, N2, O2, and pCO2. The pump-CTD arrangement was towed along transects across the blow out and dissolved gas concentrations as well as physical water column data were synchronized and geo-referenced. The transects were repeated in three different depth layers, including a bottom layer of � 2 m above the sea floor, 60 m above the sea floor just below the thermocline and a third plane in 10 m water depth. During the tows water samples were taken for later onboard methane analysis and cross-calibration with the MIMS and HydroC data. After data selection under consideration of the tidal regime lateral and vertical plume dimensions of dissolved methane were constructed. Dissolved methane concentrations ranged between background and up to about 18�M. Below the thermocline, which represents an effective barrier for the vertical distribution of dissolved methane, methane distinctively spreads laterally. Only at locations were the gas bubble stream and concurrently advected water from below the thermocline reaches the sea surface enhanced methane emission into the atmosphere took place