The Sub-Index of Critical Points of Distance Functions

We define a new notion---the sub-index of a critical point of a distance function. We show how sub-index affects the homotopy type of sublevel sets of distance functions.Comment: We corrected a mistake in the proof of Theorem 3.

Giant planet migration during the disc dispersal phase

Transition discs are expected to be a natural outcome of the interplay between photoevaporation (PE) and giant planet formation. Massive planets reduce the inflow of material from the outer to the inner disc, therefore triggering an earlier onset of disc dispersal due to PE through a process known as Planet-Induced PhotoEvaporation (PIPE). In this case, a cavity is formed as material inside the planetary orbit is removed by PE, leaving only the outer disc to drive the migration of the giant planet. We investigate the impact of PE on giant planet migration and focus specifically on the case of transition discs with an evacuated cavity inside the planet location. This is important for determining under what circumstances PE is efficient at halting the migration of giant planets, thus affecting the final orbital distribution of a population of planets. For this purpose, we use 2D FARGO simulations to model the migration of giant planets in a range of primordial and transition discs subject to PE. The results are then compared to the standard prescriptions used to calculate the migration tracks of planets in 1D planet population synthesis models. The FARGO simulations show that once the disc inside the planet location is depleted of gas, planet migration ceases. This contradicts the results obtained by the impulse approximation, which predicts the accelerated inward migration of planets in discs that have been cleared inside the planetary orbit. These results suggest that the impulse approximation may not be suitable for planets embedded in transition discs. A better approximation that could be used in 1D models would involve halting planet migration once the material inside the planetary orbit is depleted of gas and the surface density at the 3:2 mean motion resonance location in the outer disc reaches a threshold value of $0.01\,\mathrm{g\,cm^{-2}}$.Comment: 16 pages, 11 figures; accepted for publication in A&

Solid accretion onto planetary cores in radiative disks

The solid accretion rate, necessary to grow gas giant planetary cores within the disk lifetime, has been a major constraint for theories of planet formation. We tested the solid accretion rate efficiency on planetary cores of different masses embedded in their birth disk, by means of 3D radiation-hydrodynamics, where we followed the evolution of a swarm of embedded solids of different sizes. We found that using a realistic equation of state and radiative cooling, the disk at 5 au is able to cool efficiently and reduce its aspect ratio. As a result, the pebble isolation mass is reached before the core grows to 10 Earth masses, stopping efficiently the pebble flux and creating a transition disk. Moreover, the reduced isolation mass halts the solid accretion before the core reaches the critical mass, leading to a barrier to giant planet formation, and it explains the large abundance of super-Earth planets in the observed population.Comment: Published in A&A, 8 pages, 9 figure

Kontrolle der Gewalt – Ein Blick auf das Konzept der Kontrolle

Haupt H-G, Heitmeyer W, Kaletta B, Kirschner A. Control of violence - a view on the concept of control. ZiF-Mitteilungen. 2008;2008(3):4-13

Recovery of donor hearts after circulatory death with normothermic extracorporeal machine perfusion

OBJECTIVES A severe donor organ shortage leads to the death of a substantial number of patients who are listed for transplantation. The use of hearts from donors after circulatory death could significantly expand the donor organ pool, but due to concerns about their viability, these are currently not used for transplantation. We propose short-term ex vivo normothermic machine perfusion (MP) to improve the viability of these ischaemic donor hearts. METHODS Hearts from male Lewis rats were subjected to 25 min of global in situ warm ischaemia (WI) (37°C), explanted, reconditioned for 60 min with normothermic (37°C) MP with diluted autologous blood and then stored for 4 h at 0-4°C in Custodiol cold preservation solution. Fresh and ischaemic hearts stored for 4 h in Custodiol were used as controls. Graft function was assessed in a blood-perfused Langendorff circuit. RESULTS During reconditioning, both the electrical activity and contractility of the ischaemic hearts recovered rapidly. Throughout the Langendorff reperfusion, the reconditioned ischaemic hearts had a higher average heart rate and better contractility compared with untreated ischaemic controls. Moreover, the reconditioned ischaemic hearts had higher tissue adenosine triphosphate levels and a trend towards improved tissue redox state. Perfusate levels of troponin T, creatine kinase and lactate dehydrogenase were not significantly lower than those of untreated ischaemic controls. The micro- and macroscopic appearance of the reconditioned ischaemic hearts were improved compared with ischaemic controls, but in both groups myocardial damage and oedema were evident. CONCLUSIONS Our results indicate that functional recovery from global WI is possible during short-term ex vivo reperfusion, allowing subsequent cold storage without compromising organ viability. We expect that once refined and validated, this approach may enable safe transplantation of hearts obtained from donation after circulatory deat

The screening power of methylenetetrahydrofolate reductase C677T polymorphism versus plasma homocysteine concentration in patients with stenosis of the internal carotid artery

BACKGROUND: Hyperhomocysteinemia is an important and independent risk factor for vascular disease. About 35% of patients with stroke and 47% of patients with peripheral arterial disease have elevated plasma homocysteine (HCY) concentrations. The relationship between plasma HCY and the methylentetrahydrofolate reductase (MTHFR) C677T polymorphism is still unclear, especially in regard to screening/diagnostic power. METHODS: This case-control study was performed on 96 patients, who underwent surgery due to asymptomatic or symptomatic high grade stenosis of the internal carotid artery (ICA), and 96 healthy age and sex-matched, controls. Plasma HCY concentration was determined using a commercial kit for fully automated analysis (AxSYM, Abbott). The C677T polymorphism of the MTHFR-gene was assessed by PCR. RESULTS: The mean plasma HCY concentration was significantly higher in the group with stenosis of ICA compared to the controls, 12.43 ± 6.96 μM and 10.16 ± 3.16 μM, respectively, (p < 0.05). An HCY plasma concentration of 1.5 SD above the mean value of the control group, was defined as cut-off for a pathological versus physiological plasma concentration. The sensitivity and specificity of HCY was 0.27 and 0.94, respectively. The positive predictive value was 0.82. There was no significant difference in the frequency of the MTHFR 677 CT and TT genotype between patients and controls (47% vs. 47% and 8.3% vs. 11.4%, respectively). Carriers of the T-allele (CT and TT genotypes) have significantly higher plasma HCY concentrations than CC patients, 14.1 ± 7.6 μM and 10.29 ± 5.2 μM, respectively, p < 0.05. Sensitivity and specificity of the MTHFR C677T polymorphism (T-allele) were 0.56 and 0.40, respectively. The positive predictive value was 0.48. There was no significant difference in plasma HCY or genotype frequency of the MTHFR C677T polymorphism between asymptomatic and symptomatic patients. CONCLUSION: Our study shows that in a population with a given pretest disease probability of 50%, the determination of plasma HCY concentration, with a positive predictive value of 0.82, is more suitable for screening of patients at risk than analysis of the MTHFR C677T polymorphism

Abstieg vom Konjunkturgipfel: Thesen zum 40. Kieler Konjunkturgespräch

Die konjunkturelle Expansion in den Industrieländern setzte sich im ersten Halbjahr 1989 zügig fort; die Zuwachsrate des Bruttosozialprodukts betrug etwa 3,5 vH. Allerdings gab es deutliche regionale Unterschiede. Während es in den Vereinigten Staaten, Kanada und dem Vereinigten Königreich zu einer merklichen Abkühlung kam, nahmen Nachfrage und Produktion in den meisten Ländern Westeuropas lebhaft zu. In Japan und in den asiatischen Schwellenländern (Newly Industrializing Economies - NIEs) blieb die Aufwärtsentwicklung trotz leichter Abschwächung gegenüber dem Vorjahr sehr kräftig. Haupttriebfeder der Konjunktur in den Industrieländern war die starke Investitionstätigkeit der Unternehmen. Neben verbesserten Gewinnerwartungen spielte vor allem die hohe Auslastung der Kapazitäten eine Rolle, die inzwischen in den meisten Ländern über der des vorhergehenden konjunkturellen Höhepunktes liegt. Die lebhafte Expansion von Nachfrage und Produktion führte zu einer weiterhin raschen Ausweitung des Welthandels. Mit der deutlich aufwärtsgerichteten Konjunktur stieg die Beschäftigung im ersten Halbjahr 1989 spürbar an. In den meisten Ländern kam es zu einem leichten Rückgang der Arbeitslosenquoten, wobei in Westeuropa die Arbeitslosigkeit nach wie vor vergleichsweise hoch ist. Trotzdem machten sich auch hier vermehrt Engpässe auf dem Arbeitsmarkt bemerkbar. In vielen Ländern hat sich der Lohnkostendruck infolge beschleunigt steigender Löhne und abnehmender Produktivitätszuwachse verstärkt. Das Preisniveau erhöhte sich deutlich rascher als zuvor. Dies ist zwar zum Teil darauf zurückzuführen, daß sich Erdöl nach Produktionsausfällen Anfang 1989 spürbar verteuert hat. Hauptgrund für die ansteigenden Inflationsraten ist aber, daß die Geldpolitik der letzten Jahre sehr expansiv war und einen starken Nachfragesog induziert hat. Dies erleichtert es den Unternehmen, ihre gestiegenen Kosten zu überwälzen. Um der Inflationsgefahr zu begegnen, haben die Notenbanken in den USA und im Vereinigten Königreich schon vor geraumer Zeit einen geldpolitisch restriktiven Kurs eingeschlagen. In Japan und in den meisten Ländern Westeuropas hat sich die Geldmengenausweitung erst in den letzten Monaten deutlich verringert. --