3,223 research outputs found

    Potential Vorticity Evolution of a Protoplanetary Disk with An Embedded Protoplanet

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    We present two-dimensional inviscid hydrodynamic simulations of a protoplanetary disk with an embedded planet, emphasizing the evolution of potential vorticity (the ratio of vorticity to density) and its dependence on numerical resolutions. By analyzing the structure of spiral shocks made by the planet, we show that progressive changes of the potential vorticity caused by spiral shocks ultimately lead to the excitation of a secondary instability. We also demonstrate that very high numerical resolution is required to both follow the potential vorticity changes and identify the location where the secondary instability is first excited. Low-resolution results are shown to give the wrong location. We establish the robustness of a secondary instability and its impact on the torque onto the planet. After the saturation of the instability, the disk shows large-scale non-axisymmetry, causing the torque on the planet to oscillate with large amplitude. The impact of the oscillating torque on the protoplanet's migration remains to be investigated.Comment: 17 pages total with 9 figures (Fig.4,5,9 are in .jpg), accepted to Ap

    Book Reviews

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    THE FUTURE OF GERMANY It is significant that the most brilliant and penetrating analysis of the West German democracy comes from the pen of the leading German philosopher, Karl Jaspers. This fact demonstrates that German philosophy which used to be exclusively an ivory tower affair has finally come to grips with contemporary social problems. The English edition contains not only the translation of Jaspers\u27 German bestseller, but also of the philosopher\u27s just published Answer to My Critics. reviewer: Josef Rysan ============================= THE ENGLISH by David Frost and Antony Jay 255 pages Stein and Day, New York, 1968. reviewer: L.G. ============================= REPORT FROM IRON MOUNTAIN ON THE POSSIBILITY AND DESIRABILITY OF PEACE By John Doe DIAL PRESS,1967, NEW YORK reviewer: G.C. ============================== OLD MYTHS AND NEW REALITIES By J.W. Fulbright 147 pp, New York: Random House. reviewer: R.P.B. ============================== GREECE: THE STRUGGLE FOR FREEDOM Stephanos Zotos 186 pages. by Tomas Y. Crowell reviewer: W.E.W

    D1-brane with Overcritical Electric Field in AdS3 and S-brane

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    We study aspects of Dirichlet S-branes, which are defined as Dirichlet boundary condition on a time like embedding of open strings, in general backgrounds. By applying T-duality along an isometry of the unphysical dS2-branes in NS-NS supported AdS3-background, we find S0-brane. We also study the time dependent tachyon condensation on the unstable Dp-brane and interpret the singular solutions as lower dimensional S(p-1)-brane that couples to real Ramond-Ramond fields while to imaginary NS-NS modes.Comment: 23 pages, JHEP style, V2: minor changes, typos fixe

    An Intense Wave/Particle Event in the Auroral Ionosphere

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    An intense burst of VLF waves, at frequencies just above the local proton gyrofrequency, was observed shortly after each of two intense bursts of field‐aligned suprathermal electrons (E \u3c 250eV) by instruments carried on a sounding rocket flown in diffuse aurora. If the two phenomena are associated with each other, the implication is that the electron acceleration occurred nearby, in a relatively small volume

    Sudden unexpected death in Parkinson’s disease (SUDPAR): a review of publications since the decade of the brain

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    FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior)FAPESP/CNPq/MCT (Instituto Nacional de Neurociencia Translacional)Univ Fed Sao Paulo EPM UNIFESP, Escola Paulista Med, Disciplina Neurociencia, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Biblioteca Campus Sao Paulo, Sao Paulo, SP, BrazilPUC SP, Programa Estudos Posgrad Fonoaudiol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo EPM UNIFESP, Escola Paulista Med, Dept Fonoaudiol, Sao Paulo, SP, BrazilKrankenanstalt Rudolfstiftung Wien, Dept Neurol, Vienna, AustriaUniv Fed Sao Paulo EPM UNIFESP, Escola Paulista Med, Dept Neurol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo EPM UNIFESP, Escola Paulista Med, Disciplina Neurociencia, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Biblioteca Campus Sao Paulo, Sao Paulo, SP, BrazilUniv Fed Sao Paulo EPM UNIFESP, Escola Paulista Med, Dept Fonoaudiol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo EPM UNIFESP, Escola Paulista Med, Dept Neurol, Sao Paulo, SP, BrazilWeb of Scienc

    Note About Hamiltonian Formalism of Healthy Extended Horava-Lifshitz Gravity

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    In this paper we continue the study of the Hamiltonian formalism of the healthy extended Horava-Lifshitz gravity. We find the constraint structure of given theory and argue that this is the theory with the second class constraints. Then we discuss physical consequence of this result. We also apply the Batalin-Tyutin formalism of the conversion of the system with the second class constraints to the system with the first class constraints to the case of the healthy extended Horava-Lifshitz theory. As a result we find new theory of gravity with structure that is different from the standard formulation of Horava-Lifshitz gravity or General Relativity.Comment: 17 pages, v.2. references added, v.3. typos corrected, references adde

    Long-term changes in the acid and salt concentrations of the Greenland Ice Core Project ice core from electrical stratigraphy

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    Continuous electrical records covering a climatic cycle are presented for the Greenland Ice Core Project deep ice core from Greenland. Electrical conductivity measurement (ECM) measures the acid content of the ice, and the dielectric profile (DEP) responds to acid, ammonium, and chloride. All features seen can be explained by chemical changes in the ice, and there is no evidence so far for any major change in electrical response with depth or age of the ice. Both records are dominated by the acidity of the ice which varies strongly from acidic in warm periods to alkaline in cold periods, controlled by neutralization by alkaline dust (calcareous and other mineral dust). When Ca is low, the acidity (mainly nitric acid) has a fairly constant background level throughout the cycle, with slightly lower values in ice believed to be from the last interglacial. Ca has to rise only slightly to neutralize the available acidity, so that acidity is a highly nonlinear reflection of climate changes. If neutralization occurred in the aerosol (rather than in the ice), then the number of cloud condensation nuclei over parts of the northern hemisphere could have been reduced, leading to reduced cloud albedo. This nonlinear feedback may have some importance for modeling of climate change. When both acid and ammonium levels are low, the DEP signal can be used to give a rapid indication of chloride trends

    A Study of Thymidylate Synthase Expression as a Biomarker for Resectable Colon Cancer: Alliance (Cancer and Leukemia Group B) 9581 and 89803.

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    PurposeTumor levels of thymidylate synthase (TS), a target of 5-fluorouracil (5-FU)-based chemotherapy for colorectal cancer, have been studied as a predictive or prognostic biomarker with mixed results.Patients and methodsTumor TS levels were prospectively evaluated in two adjuvant therapy trials for patients with resected stage II or III colon cancer. TS expression was determined by standard immunohistochemistry and by automated quantitative analysis. Tumor mismatch repair deficiency (MMR-D) and BRAF c.1799T > A (p.V600E) mutation status were also examined. Relationships between tumor TS, MMR-D, and BRAF mutation status, overall survival (OS), and disease-free survival (DFS) were investigated in the subset of stage III patients.ResultsPatients whose tumors demonstrated high TS expression experienced better treatment outcomes, with DFS hazard ratio (HR) = 0.67, 95% confidence interval (CI) = 0.53, 0.84; and OS HR = 0.68, 95% CI = 0.53, 0.88, for high versus low TS expression, respectively. No significant interaction between TS expression and stage was observed (DFS: interaction HR = 0.94; OS: interaction HR = 0.94). Tumors with high TS expression were more likely to demonstrate MMR-D (22.2% vs. 12.8%; p =  .0003). Patients whose tumors demonstrated both high TS and MMR-D had a 7-year DFS of 77%, compared with 58% for those whose tumors had low TS and were non-MMR-D (log-rank p =  .0006). Tumor TS expression did not predict benefit of a particular therapeutic regimen.ConclusionThis large prospective analysis showed that high tumor TS levels were associated with improved DFS and OS following adjuvant therapy for colon cancer, although tumor TS expression did not predict benefit of 5-FU-based chemotherapy. The Oncologist 2017;22:107-114Implications for Practice: This study finds that measurement of tumor levels of thymidylate synthase is not helpful in assigning specific adjuvant treatment for colorectal cancer. It also highlights the importance of using prospective analyses within treatment clinical trials as the optimal method of determining biomarker utility

    Responses of Ileal and Fecal Microbiota to Withdrawal of Pancreatic Enzyme Replacement Therapy in a Porcine Model of Exocrine Pancreatic Insufficiency

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    Little is known regarding the interplay between microbiota and pancreas functions in humans as investigations are usually limited to distal sites, namely the analyses of fecal samples. The aim of this study was to investigate both ileal and fecal microbiota in response to pancreatic enzyme replacement therapy (PERT) in a porcine model of exocrine pancreatic insufficiency (EPI). PERT was stopped for ten days in ileo-cecal fistulated minipigs with experimentally induced EPI (n = 8) and ileal digesta as well as fecal samples were obtained before withdrawal, during withdrawal and after the reintroduction of PERT. Profound community changes occurred three days after enzyme omission and were maintained throughout the withdrawal phase. A reduction in α-diversity together with relative abundance changes in several taxa, in particular increases in Bifidobacteria (at both sites) and Lactobacilli (only feces) were observed. Overall, dysbiosis events from the ileum had accumulating effects in distal parts of the gastrointestinal tract with additional alterations occurring only in the colon. Changes were reversible after continuing PERT, and one week later, bacterial communities resembled those at baseline. Our study demonstrates the rapid and profound impacts of enzyme withdrawal in bacterial communities, contributing to our understanding of the interplay between pancreas function and microbiot

    Risk Assessment and Comparative Effectiveness of Left Ventricular Assist Device and Medical Management in Ambulatory Heart Failure Patients The ROADMAP Study 2-Year Results

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    OBJECTIVES The authors sought to provide the pre-specified primary endpoint of the ROADMAP (Risk Assessment and Comparative Effectiveness of Left Ventricular Assist Device and Medical Management in Ambulatory Heart Failure Patients) trial at 2 years. BACKGROUND The ROADMAP trial was a prospective nonrandomized observational study of 200 patients (97 with a left ventricular assist device [LVAD], 103 on optimal medical management [OMM]) that showed that survival with improved functional status at 1 year was better with LVADs compared with OMM in a patient population of ambulatory New York Heart Association functional class IIIb/IV patients. METHODS The primary composite endpoint was survival on original therapy with improvement in 6-min walk distance \u3e= 75 m. RESULTS Patients receiving LVAD versus OMM had lower baseline health-related quality of life, reduced Seattle Heart Failure Model 1-year survival (78% vs. 84%; p = 0.012), and were predominantly INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) profile 4 (65% vs. 34%; p \u3c 0.001) versus profiles 5 to 7. More LVAD patients met the primary endpoint at 2 years: 30% LVAD versus 12% OMM (odds ratio: 3.2 [95% confidence interval: 1.3 to 7.7]; p = 0.012). Survival as treated on original therapy at 2 years was greater for LVAD versus OMM (70 +/- 5% vs. 41 +/- 5%; p \u3c 0.001), but there was no difference in intent-to-treat survival (70 +/- 5% vs. 63 +/- 5%; p = 0.307). In the OMM arm, 23 of 103 (22%) received delayed LVADs (18 within 12 months; 5 from 12 to 24 months). LVAD adverse events declined after year 1 for bleeding (primarily gastrointestinal) and arrhythmias. CONCLUSIONS Survival on original therapy with improvement in 6-min walk distance was superior with LVAD compared with OMM at 2 years. Reduction in key adverse events beyond 1 year was observed in the LVAD group. The ROADMAP trial provides risk-benefit information to guide patient- and physician-shared decision making for elective LVAD therapy as a treatment for heart failure. (Risk Assessment and Comparative Effectiveness of Left Ventricular Assist Device and Medical Management in Ambulatory Heart Failure Patients [ROADMAP]; NCT01452802
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