The bipolar outflow and disk of the brown dwarf ISO217

We show that the very young brown dwarf candidate ISO217 (M6.25) is driving an intrinsically asymmetric bipolar outflow with a stronger and slightly faster red-shifted component based on spectro-astrometry of forbidden [SII] emission lines observed in UVES/VLT spectra taken in 2009. ISO217 is only one of a handful of brown dwarfs and VLMS (M5-M8) for which an outflow has been detected and that show that the T Tauri phase continues at the substellar limit. We measure a spatial extension of the outflow of +/-190mas (+/-30AU) and velocities of +/-40-50kms/s. We show that the velocity asymmetry between both lobes is variable on timescales of a few years and that the strong asymmetry of a factor of 2 found in 2007 might be smaller than originally anticipated when using a more realistic stellar rest-velocity. We also detect forbidden [FeII]7155 emission, for which we propose as potential origin the hot inner regions of the outflow. To understand the ISO217 system, we determine the disk properties based on radiative transfer modeling of the SED. This disk model agrees very well with Herschel/PACS data at 70mu. We find that the disk is flared and intermediately inclined (~45deg). The total disk mass (4e-6 Msun) is small compared to the accretion and outflow rate of ISO217 (~1e-10 Msun/yr). We propose that this discrepancy can be explained by either a higher disk mass than inferred from the model (strong undetected grain growth) and/or by an on average lower accretion and outflow rate than the determined values. We show that a disk inclination significantly exceeding 45deg, as suggested from Halpha modeling and from both lobes of the outflow being visible, is inconsistent with the SED data. Thus, despite its intermediate inclination angle, the disk of this brown dwarf does not appear to obscure the red outflow component, which is very rarely seen for T Tauri objects (only one other case).Comment: Accepted for publication at A&A; minor changes (language editing

Vortex pinning by natural defects in thin films of YBa2Cu3O7−δ

Although vortex pinning in laser-ablated YBa2Cu3O7−δ films on (100) SrTiO3 is dominated by threading dislocations, many other natural pinning sites are present. To identify the contribution from twin planes, surface corrugations and point defects, we manipulate the relative densities of all defects by post-annealing films with various as-grown dislocation densities, ndisl. While a universal magnetic field B dependence of the transport current density js(B, T) is observed (independently of ndisl, temperature T and the annealing treatment), the defect structure changes considerably. Correlating the microstructure to js(B, T), it becomes clear that surface roughness, twins and point defects are not important at low magnetic fields compared to linear defect pinning. Transmission electron microscopy indicates that threading dislocations are not part of grain boundaries nor are they related to the twin domain structure. We conclude that js(B, T) is essentially determined by pinning along threading dislocations, naturally induced during the growth process. Even in high magnetic fields, where the vortex density outnumbers ndisl, it appears that linear defects stabilize the vortex lattice by means of the vortex–vortex interaction.

Influence of vortex-vortex interaction on critical currents across low-angle grain boundaries in YBa2Cu3O7-delta thin films

Low-angle grain boundaries with misorientation angles theta < 5 degrees in optimally doped thin films of YBCO are investigated by magnetooptical imaging. By using a numerical inversion scheme of Biot-Savart's law the critical current density across the grain boundary can be determined with a spatial resolution of about 5 micrometers. Detailed investigation of the spatially resolved flux density and current density data shows that the current density across the boundary varies with varying local flux density. Combining the corresponding flux and current pattern it is found that there exists a universal dependency of the grain boundary current on the local flux density. A change in the local flux density means a variation in the flux line-flux line distance. With this knowledge a model is developped that explains the flux-current relation by means of magnetic vortex-vortex interaction.Comment: 7 pages, 14 figure

Dynamics of Flux Creep in Underdoped Single Crystals of Y_1-xPr_xBa_2Cu_3O_7-d

Transport as well as magnetic relaxation properties of the mixed state were studied on strongly underdoped Y_1-xPr_xBa_2Cu_3O_7-d crystals. We observed two correlated phenomena - a coupling transition and a transition to quantum creep. The distribution of transport current below the coupling transition is highly nonuniform, which facilitates quantum creep. We speculate that in the mixed state below the coupling transition, where dissipation is nonohmic, the current distribution may be unstable with respect to self-channeling resulting in the formation of very thin current-carrying layers.Comment: 11 pages, 9 figures, Submitted to Phys. Rev.

A VLT/NACO Survey for Triple and Quadruple Systems among Visual Pre-Main Sequence Binaries

This paper describes a systematic search for high-order multiplicity among wide visual Pre-Main Sequence (PMS) binaries. We conducted an Adaptive Optics survey of a sample of 58 PMS wide binaries from various star-forming regions, which include 52 T Tauri systems with mostly K- and M-type primaries, with the NIR instrument NACO at the VLT. Of these 52 systems, 7 are found to be triple (2 new) and 7 quadruple (1 new). The new close companions are most likely physically bound based on their probability of chance projection and, for some of them, on their position on a color-color diagram. The corresponding degree of multiplicity among wide binaries (number of triples and quadruples divided by the number of systems) is 26.9 +/- 7.2% in the projected separation range 0.07-12 arcsec, with the largest contribution from the Taurus-Auriga cloud. We also found that this degree of multiplicity is twice in Taurus compared to Ophiuchus and Chamaeleon for which the same number of sources are present in our sample. Considering a restricted sample composed of systems at distance 140-190pc, the degree of multiplicity is 26.8 +/- 8.1%, in the separation range 10/14 AU - 1700/2300 AU (30 binaries, 5 triples, 6 quadruples). The observed frequency agrees with results from previous multiplicity surveys within the uncertainties, although a significant overabundance of quadruple systems compared to triple systems is apparent. Tentatively including the spectroscopic pairs in our restricted sample and comparing the multiplicity fractions to those measured for solar-type main-sequence stars in the solar neighborhood leads to the conclusion that both the ratio of triples to binaries and the ratio of quadruples to triples seems to be in excess among young stars. [...]Comment: 24 pages, accepted for publication in Astronomy & Astrophysic

Variation in styles of rifting in the Gulf of California

Author Posting. © Nature Publishing Group, 2007. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 448 (2007): 466-469, doi:10.1038/nature06035.The rifting of continental lithosphere is a fundamental solid-earth process that leads to the formation of rifted continental margins and ocean basins. Understanding of this process comes from observations of the geometry of rifted margins and the magmatism resulting from rifting, which inform us about the strength of the lithosphere, the state of the underlying mantle, and the transition from rifting to seafloor spreading. Here we describe results from the PESCADOR seismic experiment in the southern Gulf of California and present the first crustal-scale images across conjugate margins of multiple segments within a single rift that has reached the stage of oceanic spreading. A surprisingly large variation in rifting style and magmatism is observed between these segments, from wide rifting with minor syn-rift magmatism to narrow rifting in magmatically robust segments. These differences encompass much of the variation observed across nearly all other non-end-member continental margins. The characteristics of magmatic endmember margins are typically explained in terms of mantle temperature. Our explanations for the variation in the Gulf of California, in contrast, invoke mantle depletion to account for wide, magma-poor rifting and mantle fertility and possibly the influence of sediments to account for robust rift and post-rift magmatism in the Gulf of California. These factors may vary laterally over small distances in regions that have transitioned from convergence to extension, as is the case for the Gulf of California and many other rifts.This work was funded by a grant from the U.S. NSF-MARGINS program

Reimbursement and economic factors influencing dialysis modality choice around the world

The worldwide incidence of kidney failure is on the rise and treatment is costly; thus, the global burden of illness is growing. Kidney failure patients require either a kidney transplant or dialysis to maintain life. This review focuses on the economics of dialysis. Alternative dialysis modalities are haemodialysis (HD) and peritoneal dialysis (PD). Important economic factors influencing dialysis modality selection include financing, reimbursement and resource availability. In general, where there is little or no facility or physician reimbursement or payment for PD, the share of PD is very low. Regarding resource availability, when centre HD capacity is high, there is an incentive to use that capacity rather than place patients on home dialysis. In certain countries, there is interest in revising the reimbursement structure to favour home-based therapies, including PD and home HD. Modality selection is influenced by employment status, with an association between being employed and PD as the modality choice. Cost drivers differ for PD and HD. PD is driven mainly by variable costs such as solutions and tubing, while HD is driven mainly by fixed costs of facility space and staff. Many cost comparisons of dialysis modalities have been conducted. A key factor to consider in reviewing cost comparisons is the perspective of the analysis because different costs are relevant for different perspectives. In developed countries, HD is generally more expensive than PD to the payer. Additional research is needed in the developing world before conclusive statements may be made regarding the relative costs of HD and PD

Contrasting Patterns of Sequence Evolution at the Functionally Redundant bric à brac Paralogs in Drosophila melanogaster

Genes with overlapping expression and function may gradually diverge despite retaining some common functions. To test whether such genes show distinct patterns of molecular evolution within species, we examined sequence variation at the bric à brac (bab) locus of Drosophila melanogaster. This locus is composed of two anciently duplicated paralogs, bab1 and bab2, which are involved in patterning the adult abdomen, legs, and ovaries. We have sequenced the 148 kb genomic region spanning the bab1 and bab2 genes from 94 inbred lines of D. melanogaster sampled from a single location. Two non-coding regions, one in each paralog, appear to be under selection. The strongest evidence of directional selection is found in a region of bab2 that has no known functional role. The other region is located in the bab1 paralog and is known to contain a cis-regulatory element that controls sex-specific abdominal pigmentation. The coding region of bab1 appears to be under stronger functional constraint than the bab2 coding sequences. Thus, the two paralogs are evolving under different selective regimes in the same natural population, illuminating the different evolutionary trajectories of partially redundant duplicate genes

Cost-effectiveness of In-home Automated External Defibrillators for Individuals at Increased Risk of Sudden Cardiac Death

In-home automated external defibrillators (AEDs) are increasingly recommended as a means for improving survival of cardiac arrests that occur at home. The current study was conducted to explore the relationship between individuals' risk of cardiac arrest and cost-effectiveness of in-home AED deployment. Design : Markov decision model employing a societal perspective. Patients : Four hypothetical cohorts of American adults 60 years of age at progressively greater risk for sudden cardiac death (SCD): 1) all adults (annual probability of SCD 0.4%); 2) adults with multiple SCD risk factors (probability 2%); 3) adults with previous myocardial infarction (probability 4%); and 4) adults with ischemic cardiomyopathy unable to receive an implantable defibrillator (probability 6%). Intervention : Strategy 1: individuals suffering an in-home cardiac arrest were treated with emergency medical services equipped with AEDs (EMS-D). Strategy 2: individuals suffering an in-home cardiac arrest received initial treatment with an in-home AED, followed by EMS. Results : Assuming cardiac arrest survival rates of 15% with EMS-D and 30% with AEDs, the cost per quality-adjusted life-year gained (QALY) of providing in-home AEDs to all adults 60 years of age is $216,000. Costs of providing in-home AEDs to adults with multiple risk factors (2$132,000, $104,000, and$88,000, respectively. Conclusions : The cost-effectiveness of in-home AEDs is intimately linked to individuals' risk of SCD. However, providing in-home AEDs to all adults over age 60 appears relatively expensive.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72168/1/j.1525-1497.2005.40247.x.pd