Dissipative and nonaxisymmetric standard-MRI in Kepler disks

Deviations from axial symmetry are necessary to maintain self-sustained MRI-turbulence. We define the parameters region where nonaxisymmetric MRI is excited and study dependence of the unstable modes structure and growth rates on the relevant parameters. We solve numerically the linear eigenvalue problem for global axisymmetric and nonaxisymmetric modes of standard-MRI in Keplerian disks with finite diffusion. For small magnetic Prandtl number the microscopic viscosity completely drops out from the analysis so that the stability maps and the growth rates expressed in terms of the magnetic Reynolds number Rm and the Lundquist number S do not depend on the magnetic Prandtl number Pm. The minimum magnetic field for onset of nonaxisymmetric MRI grows with Rm. For given S all nonaxisymmetric modes disappear for sufficiently high Rm. This behavior is a consequence of the radial fine-structure of the nonaxisymmetric modes resulting from the winding effect of differential rotation. It is this fine-structure which presents severe resolution problems for the numerical simulation of MRI at large Rm. For weak supercritical magnetic fields only axisymmetric modes are unstable. Nonaxisymmetric modes need stronger fields and not too fast rotation. If Pm is small its real value does not play any role in MRI.Comment: 4 pages, 6 figures, A&A Lette

Experimental demonstration of higher-order Laguerre-Gauss mode interferometry

The compatibility of higher-order Laguerre-Gauss (LG) modes with interferometric technologies commonly used in gravitational wave detectors is investigated. In this paper we present the first experimental results concerning the performance of the LG33 mode in optical resonators. We show that the Pound-Drever-Hall error signal for a LG33 mode in a linear optical resonator is identical to that of the more commonly used LG00 mode, and demonstrate the feedback control of the resonator with a LG33 mode. We succeeded to increase the mode purity of a LG33 mode generated using a spatial-light modulator from 51% to 99% upon transmission through a linear optical resonator. We further report the experimental verification that a triangular optical resonator does not transmit helical LG modes

An illustration of and programs estimating attributable fractions in large scale surveys considering multiple risk factors

Background: Attributable fractions (AF) assess the proportion of cases in a population attributable to certain risk factors but are infrequently reported and mostly calculated without considering potential confounders. While logistic regression for adjusted individual estimates of odds ratios (OR) is widely used, similar approaches for AFs are rarely applied. Methods: Different methods for calculating adjusted AFs to risk factors of cardiovascular disease (CVD) were applied using data from the National Health and Nutrition Examination Survey (NHANES). We compared AFs from the unadjusted approach using Levin's formula, from Levin's formula using adjusted OR estimates, from logistic regression according to Bruzzi's approach, from logistic regression with sequential removal of risk factors ('sequential AF') and from logistic regression with all possible removal sequences and subsequent averaging ('average AF'). Results: AFs following the unadjusted and adjusted (using adjusted ORs) Levin's approach yielded clearly higher estimates with a total sum of more than 100% compared to adjusted approaches with sums < 100%. Since AFs from logistic regression were related to the removal sequence of risk factors, all possible sequences were considered and estimates were averaged. These average AFs yielded plausible estimates of the population impact of considered risk factors on CVD with a total sum of 90%. The average AFs for total and HDL cholesterol levels were 17%, for hypertension 16%, for smoking 11%, and for diabetes 5%. Conclusion: Average AFs provide plausible estimates of population attributable risks and should therefore be reported at least to supplement unadjusted estimates. We provide functions/macros for commonly used statistical programs to encourage other researchers to calculate and report average AFs

American College of Cardiology/ European Society of Cardiology international study of angiographic data compression phase III Measurement of image quality differences at varying levels of data compression

AbstractOBJECTIVESWe sought to investigate up to which level of Joint Photographic Experts Group (JPEG) data compression the perceived image quality and the detection of diagnostic features remain equivalent to the quality and detectability found in uncompressed coronary angiograms.BACKGROUNDDigital coronary angiograms represent an enormous amount of data and therefore require costly computerized communication and archiving systems. Earlier studies on the viability of medical image compression were not fully conclusive.METHODSTwenty-one raters evaluated sets of 91 cine runs. Uncompressed and compressed versions of the images were presented side by side on one monitor, and image quality differences were assessed on a scale featuring six scores. In addition, the raters had to detect pre-defined clinical features. Compression ratios (CR) were 6:1, 10:1 and 16:1. Statistical evaluation was based on descriptive statistics and on the equivalence t-test.RESULTSAt the lowest CR (CR 6:1), there was already a small (15%) increase in assigning the aesthetic quality score indicating “quality difference is barely discernible—the images are equivalent.” At CR 10:1 and CR 16:1, close to 10% and 55%, respectively, of the compressed images were rated to be “clearly degraded, but still adequate for clinical use” or worse. Concerning diagnostic features, at CR 10:1 and CR 16:1 the error rate was 9.6% and 13.1%, respectively, compared with 9% for the baseline error rate in uncompressed images.CONCLUSIONSCompression at CR 6:1 provides equivalence with the original cine runs. If CR 16:1 were used, one would have to tolerate a significant increase in the diagnostic error rate over the baseline error rate. At CR 10:1, intermediate results were obtained

The CONSTANS gene of arabidopsis promotes flowering and encodes a protein showing similarities to zinc finger transcription factors

AbstractThe vegetative and reproductive (flowering) phases of Arabidopsis development are clearly separated. The onset of flowering is promoted by long photoperiods, but the constans (co) mutant flowers later than wild type under these conditions. The CO gene was isolated, and two zinc fingers that show a similar spacing of cysteines, but little direct homology, to members of the GATA1 family were identified in the amino acid sequence. co mutations were shown to affect amino acids that are conserved in both fingers. Some transgenic plants containing extra copies of CO flowered earlier than wild type, suggesting that CO activity is limiting on flowering time. Double mutants were constructed containing co and mutations affecting gibberellic acid responses, meristem identity, or phytochrome function, and their phenotypes suggested a model for the role of CO in promoting flowering

A standardized and modular power electronics platform for academic research on advanced grid-connected converter control and microgrids

This paper introduces a multifunctional converter platform rated at 30kW. Individual units allow research on advanced grid-connected converter control, while their interconnection enables isolated microgrid investigations. The standardized and modular design allows simple reconfiguration of the system for different setups, for which multiple measurements are presented

An NMR Study of Biomimetic Fluorapatite - Gelatine Mesocrystals

The mesocrystal system fluoroapatite—gelatine grown by double-diffusion is characterized by hierarchical composite structure on a mesoscale. In the present work we apply solid state NMR to characterize its structure on the molecular level and provide a link between the structural organisation on the mesoscale and atomistic computer simulations. Thus, we find that the individual nanocrystals are composed of crystalline fluorapatite domains covered by a thin boundary apatite-like layer. The latter is in contact with an amorphous layer, which fills the interparticle space. The amorphous layer is comprised of the organic matrix impregnated by isolated phosphate groups, Ca3F motifs and water molecules. Our NMR data provide clear evidence for the existence of precursor complexes in the gelatine phase, which were not involved in the formation of apatite crystals, proving hence theoretical predictions on the structural pre-treatment of gelatine by ion impregnation. The interfacial interactions, which may be described as the glue holding the composite materials together, comprise hydrogen bond interactions with the apatite PO43− groups. The reported results are in a good agreement with molecular dynamics simulations, which address the mechanisms of a growth control by collagen fibers and with experimental observations of an amorphous cover layer in biominerals