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Search Results: 1 - 10 of 1848 matches for " Ronny Lutz "
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The EXOTIME targets HS0702+6043 and HS0444+0458
Ronny Lutz,Sonja Schuh,Roberto Silvotti
Physics , 2010, DOI: 10.1063/1.3570968
Abstract: Pulsations in subdwarf B (sdB) stars are an important tool to constrain the evolutionary status of these evolved objects. Interestingly, the same data used for this asteroseismological approach can also be used to search for substellar companions around these objects by analyzing the timing of the pulsations by means of a so-called O-C diagram. Substellar objects around sdB stars are important for two different reasons: they are suspected to be able to influence the evolution of their host-star and they are an ideal test case to examine the properties of exoplanets which have survived the red giant expansion of their host stars.
EXOTIME: searching for planets and measuring Pdot in sdB pulsators
Ronny Lutz,Sonja Schuh,Roberto Silvotti
Physics , 2013, DOI: 10.1002/asna.201211793
Abstract: We review the status of the EXOTIME project (EXOplanet search with the TIming MEthod). The two main goals of EXOTIME are to search for sub-stellar companions to sdB stars in wide orbits, and to measure the secular variation of the pulsation periods, which are related to the evolutionary change of the stellar structure. Now, after four years of dense monitoring, we start to see some results and present the brown dwarf and exoplanet candidates V1636 Ori b and DW Lyn b.
Water Status in the Syrian Water Basins  [PDF]
Khaldoon A. Mourad, Ronny Berndtsson
Open Journal of Modern Hydrology (OJMH) , 2012, DOI: 10.4236/ojmh.2012.21003
Abstract: Syrian water resources face economic and physical water scarcity. This together with a large population and development increase and the climate change may lead to increasing risks for international controversies and disputes in the coming decades. According to FAO, the available water resource per capita AWPC is going to be half by 2025. Depending on its seven water basins, this paper analyses water demand and supply in the Syria with their projections till 2050. The paper shows that two of the seven Syrian basins need a specific concern as they face water scarcity problem. However, two basins have extra water. Therefore, the paper focuses on the need for a sustainable water management, which takes all nonconventional water resources into account to contribute in the Syrian water balance such as rainwater harvesting and wastewater reuse.
Prophylactic antibiotic treatment is superior to therapy on-demand in experimental necrotising pancreatitis
Stefan Fritz, Werner Hartwig, Ronny Lehmann, Katja Will-Schweiger, Mechthild Kommerell, Thilo Hackert, Lutz Schneider, Markus W Büchler, Jens Werner
Critical Care , 2008, DOI: 10.1186/cc7118
Abstract: Treatment groups received meropenem either therapeutically 24 hours after induction of necrotising pancreatitis or prophylactically before development of pancreatic superinfection. At 24 and 72 hours, pancreatic injury was investigated by histology and translocation by bacterial cultures of pancreatic tissue and mesenteric lymph nodes. Septic complications were evaluated by blood cultures and survival.Without antibiotic treatment, pancreatic superinfection was observed in almost all cases after induction of necrotising pancreatitis. The 72-hour-mortality rate was 42.9% and bacterial infection of mesenteric lymph nodes and bacteraemia was found in 87.5% of the surviving animals. Therapeutic administration of meropenem on-demand reduced bacteraemia to 50% and mortality to 27.3%. However, prophylactic antibiotic treatment significantly reduced bacteraemia to 25.0% (p = 0.04) and pancreatic superinfection as well as mortality to 0% (p < 0.001 and p = 0.05, respectively) compared with controls.In the present study both prophylactic and delayed antibiotic treatment on-demand reduced septic complications in a standardised setting of experimental necrotising pancreatitis. However, pancreatic superinfection, bacteraemia and mortality rates were reduced significantly by early treatment. Thus, in the absence of statistically relevant and well-designed clinical trials, the study demonstrates that prophylactic antibiotic treatment is superior to antibiotic treatment on-demand.Although, the clinical course of acute pancreatitis is often mild and self-limiting, in 15% to 20% of patients severe necrotising pancreatitis develops, associated with local or systemic complications and high mortality rates [1]. One of the main reasons for fatal aggravation of the disease is bacterial superinfection of necrotic pancreatic tissue and the subsequent development of septic complications [2-4]. The risk of pancreatic superinfection is dependent on the amount of necrosis. The risk is about 20%
The EXOTIME project: a status report on PG 1325+101 (QQ Vir)
Serena Benatti,Roberto Silvotti,Riccardo U. Claudi,Sonja Schuh,Ronny Lutz,Seung-Lee Kim,Rimvydas Janulis,Margit Paparò,Andrzej Baran,Roy ?stensen
Physics , 2010,
Abstract: After the discovery of V391 Peg b, the first planet detected around a post Red Giant phase star (Silvotti et al. 2007), the EXOTIME (EXOplanet search with the TIming MEthod) project is focused on the search for new planets with similar characteristics. The aim of the project is to organize a global observing network to collect as much data as possible for a sample of five subdwarf B (sdB) stars and share them in order to obtain a more precise analysis. These evolved pulsators may have extremely regular oscillation periods. This feature makes these stars suitable to search for planetary companions with the timing method as in the case of pulsars. In this contribution we present the project and some preliminary results for the star PG 1325+101 (QQ Vir) after the first two years of activity.
Accidentes de trabajo en Costa Rica
Ronny Arias
Medicina Legal de Costa Rica , 1997,
Constat de beauté (poèmes)
Ronny Someck
Yod : Revue des études Hébra?ques et Juives , 2011, DOI: 10.4000/yod.351
Abstract: La vengeance de l’enfant bègue . . , " - " . ...
Reciprocal Regulation as a Source of Ultrasensitivity in Two-Component Systems with a Bifunctional Sensor Kinase
Ronny Straube
PLOS Computational Biology , 2014, DOI: doi/10.1371/journal.pcbi.1003614
Abstract: Two-component signal transduction systems, where the phosphorylation state of a regulator protein is modulated by a sensor kinase, are common in bacteria and other microbes. In many of these systems, the sensor kinase is bifunctional catalyzing both, the phosphorylation and the dephosphorylation of the regulator protein in response to input signals. Previous studies have shown that systems with a bifunctional enzyme can adjust the phosphorylation level of the regulator protein independently of the total protein concentrations – a property known as concentration robustness. Here, I argue that two-component systems with a bifunctional enzyme may also exhibit ultrasensitivity if the input signal reciprocally affects multiple activities of the sensor kinase. To this end, I consider the case where an allosteric effector inhibits autophosphorylation and, concomitantly, activates the enzyme's phosphatase activity, as observed experimentally in the PhoQ/PhoP and NRII/NRI systems. A theoretical analysis reveals two operating regimes under steady state conditions depending on the effector affinity: If the affinity is low the system produces a graded response with respect to input signals and exhibits stimulus-dependent concentration robustness – consistent with previous experiments. In contrast, a high-affinity effector may generate ultrasensitivity by a similar mechanism as phosphorylation-dephosphorylation cycles with distinct converter enzymes. The occurrence of ultrasensitivity requires saturation of the sensor kinase's phosphatase activity, but is restricted to low effector concentrations, which suggests that this mode of operation might be employed for the detection and amplification of low abundant input signals. Interestingly, the same mechanism also applies to covalent modification cycles with a bifunctional converter enzyme, which suggests that reciprocal regulation, as a mechanism to generate ultrasensitivity, is not restricted to two-component systems, but may apply more generally to bifunctional enzyme systems.
Strongly hyperbolic Hamiltonian systems in numerical relativity: Formulation and symplectic integration
Ronny Richter
Physics , 2009, DOI: 10.1088/0264-9381/26/14/145017
Abstract: We consider two strongly hyperbolic Hamiltonian formulations of general relativity and their numerical integration with a free and a partially constrained symplectic integrator. In those formulations we use hyperbolic drivers for the shift and in one case also for the densitized lapse. A system where the densitized lapse is an external field allows to enforce the momentum constraints in a holonomically constrained Hamiltonian system and to turn the Hamilton constraint function from a weak to a strong invariant. These schemes are tested in a perturbed Minkowski and the Schwarzschild space-time. In those examples we find advantages of the strongly hyperbolic formulations over the ADM system presented in [arXiv:0807.0734]. Furthermore we observe stabilizing effects of the partially constrained evolution in Schwarzschild space-time as long as the momentum constraints are enforced.
Generalized uncertainty principles
Ronny Machluf
Physics , 2008,
Abstract: The phenomenon in the essence of classical uncertainty principles is well known since the thirties of the last century. We introduce a new phenomenon which is in the essence of a new notion that we introduce: "Generalized Uncertainty Principles". We show the relation between classical uncertainty principles and generalized uncertainty principles. We generalized "Landau-Pollak-Slepian" uncertainty principle. Our generalization relates the following two quantities and two scaling parameters: 1) The weighted time spreading $\int_{-\infty}^\infty |f(x)|^2w_1(x)dx$, ($w_1(x)$ is a non-negative function). 2) The weighted frequency spreading $\int_{-\infty}^\infty |\hat{f}(\omega)|^2w_2(\omega)d\omega$. 3) The time weight scale $a$, ${w_1}_a(x)=w_1(xa^{-1})$ and 4) The frequency weight scale $b$, ${w_2}_b(\omega)=w_2(\omega b^{-1})$. "Generalized Uncertainty Principle" is an inequality that summarizes the constraints on the relations between the two spreading quantities and two scaling parameters. For any two reasonable weights $w_1(x)$ and $w_2(\omega)$, we introduced a three dimensional set in $R^3$ that is in the essence of many uncertainty principles. The set is called "possibility body". We showed that classical uncertainty principles (such as the Heiseneberg-Pauli-Weyl uncertainty principle) stem from lower bounds for different functions defined on the possibility body. We investigated qualitative properties of general uncertainty principles and possibility bodies. Using this approach we derived new (quantitative) uncertainty principles for Landau-Pollak-Slepian weights. We found the general uncertainty principles related to homogeneous weights, $w_1(x)=w_2(x)=x^k$, $k\in N$, up to a constant.
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