4,358 research outputs found
Free energy cascade in gyrokinetic turbulence
In gyrokinetic theory, the quadratic nonlinearity is known to play an
important role in the dynamics by redistributing (in a conservative fashion)
the free energy between the various active scales. In the present study, the
free energy transfer is analyzed for the case of ion temperature gradient
driven turbulence. It is shown that it shares many properties with the energy
transfer in fluid turbulence. In particular, one finds a forward (from large to
small scales), extremely local, and self-similar cascade of free energy in the
plane perpendicular to the background magnetic field. These findings shed light
on some fundamental properties of plasma turbulence, and encourage the
development of large eddy simulation techniques for gyrokinetics.Comment: 4 pages, 2 Postscript figure
Gyrokinetic Large Eddy Simulations
The Large Eddy Simulation (LES) approach is adapted to the study of plasma
microturbulence in a fully three-dimensional gyrokinetic system. Ion
temperature gradient driven turbulence is studied with the {\sc GENE} code for
both a standard resolution and a reduced resolution with a model for the
sub-grid scale turbulence. A simple dissipative model for representing the
effect of the sub-grid scales on the resolved scales is proposed and tested.
Once calibrated, the model appears to be able to reproduce most of the features
of the free energy spectra for various values of the ion temperature gradient
The association of statin use after cancer diagnosis with survival in pancreatic cancer patients: a SEER-medicare analysis.
BackgroundPancreatic cancer has poor prognosis and existing interventions provide a modest benefit. Statin has anti-cancer properties that might enhance survival in pancreatic cancer patients. We sought to determine whether statin treatment after cancer diagnosis is associated with longer survival in those with pancreatic ductal adenocarcinoma (PDAC).MethodsWe analyzed data on 7813 elderly patients with PDAC using the linked Surveillance, Epidemiology, and End Results (SEER) - Medicare claims files. Information on the type, intensity and duration of statin use after cancer diagnosis was extracted from Medicare Part D. We treated statin as a time-dependent variable in a Cox regression model to determine the association with overall survival adjusting for follow-up, age, sex, race, neighborhood income, stage, grade, tumor size, pancreatectomy, chemotherapy, radiation, obesity, dyslipidemia, diabetes, chronic pancreatitis and chronic obstructive pulmonary disease (COPD).ResultsOverall, statin use after cancer diagnosis was not significantly associated with survival when all PDAC patients were considered (HR = 0.94, 95%CI 0.89, 1.01). However, statin use after cancer diagnosis was associated with a 21% reduced hazard of death (Hazard ratio = 0.79, 95% confidence interval (CI) 0.67, 0.93) in those with grade I or II PDAC and to a similar extent in those who had undergone a pancreatectomy, in those with chronic pancreatitis and in those who had not been treated with statin prior to cancer diagnosis.ConclusionsWe found that statin treatment after cancer diagnosis is associated with enhanced survival in patients with low-grade, resectable PDAC
Aspects of seasonality and flood generating circulation patterns in a mountainous catchment in south-eastern Germany
International audienceAnalyses of discharge series, precipitation fields and flood producing atmospheric circulation patterns reveal that two governing flood regimes exist in the Mulde catchment in south-eastern Germany: frequent floods during the winter and less frequent but sometimes extreme floods during the summer. Differences in the statistical parameters skewness and coefficient of variation of the discharge data can be found from west to east and are discussed in the context of landscape parameters that influence the discharge. Annual maximum discharge series were assigned to the triggering GroĂźwetterlage in order to evaluate which circulation patterns are likely to produce large floods. It can be shown that the cyclone Vb-weather regime generates the most extreme flood events in the Mulde catchment, whereas westerly winds produce frequently small floods. Vb-weather regimes do not always trigger large flood events in the study area, but large floods are mostly generated by these weather patterns. Based on these findings, it is necessary to revise the traditional flood frequency analysis approach and develop new approaches which can handle different flood triggering processes within the dataset
YBaCuO/LaCaMnO bilayers: Interface coupling and electric transport properties
Heteroepitaxially grown bilayers of ferromagnetic LaCaMnO
(LCMO) on top of superconducting YBaCuO (YBCO) thin films were
investigated by focusing on electric transport properties as well as on
magnetism and orbital occupation at the interface. Transport measurements on
YBCO single layers and on YBCO/LCMO bilayers, with different YBCO thickness
and constant LCMO thickness \,nm, show a significant reduction of
the superconducting transition temperature only for \,nm,with
only a slightly stronger suppression in the bilayers, as compared to the
single layers. X-ray magnetic circular dichroism (XMCD) measurements confirm
recently published data of an induced magnetic moment on the interfacial Cu by
the ferromagnetically ordered Mn ions, with antiparallel alignment between Cu
and Mn moments. However, we observe a significantely larger Cu moment than
previously reported, indicating stronger coupling between Cu and Mn at the
interface. This in turn could result in an interface with lower transparency,
and hence smaller spin diffusion length, that would explain our electric
transport data, i.e.smaller suppression. Moreover, linear dichroism
measurements did not show any evidence for orbital reconstruction at the
interface, indicating that a large change in orbital occupancies through
hybridization is not necessary to induce a measurable ferromagnetic moment on
the Cu atoms.Comment: 8 Figure
Interleukin 7 as interleukin 9 drives phytohemagglutinin-activated T cells through several cell cycles; no synergism between interleukin 7, interleukin 9 and interleukin 4
The effects of the interlenkins IL-7 and IL-9 on cell cycle progression were investigated by conventional [3H]thymidine incorporation and by the bivariate BrdU/Hoechst technique. 8oth IL· 7 and IL-9 drive phytohemagglutinin-activated T cells through more than one cell cycle, but IL-7 wasmorepotent on cell cycle progression than IL-9. Neither synergistic nor inhibitory effects were seen between various combinations of the lymphokines IL-7, IL-9 and IL-4 compared to each lymphokine alone. When T cells are activated with phytohemagglutinin for 3 days, all or most IL-4 responsive cells respond to IL-7 as weil, whereas only a part of IL-7 responders are IL-4 responders. In contrast, when T cells are activated with phytohemagglutinin for 7 days, the quantitative data of the cell cycle distribution soggest that the population of IL-7 responders is at least an overlapping, if not a real subset of the population of the IL-4 responders
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