The impact of electron anisotropy on the polarization of the X-ray emission from black hole accretion disks and implications for the black hole X-ray binary 4U 1630-47

The Imaging X-ray Polarimetry Explorer (IXPE) observations of the X-ray binary 4U 1630-47 in the high soft state revealed linear polarization degrees (PDs) rising from 6% at 2 keV to 10% at 8 keV. Explaining the results in the framework of the standard optically thick, geometrically thin accretion disk scenario requires careful fine-tuning of the relevant model parameters. We argue here that the emission of polarized Bremsstrahlung by anisotropic electrons in the accretion disk atmosphere can account for the overall high PDs and the increase of the PDs with energy. We discuss plasma and accretion effects that can generate electron anisotropies at a level required by the 4U 1630-47 results. We conclude by emphasizing that X-ray polarimetry affords us the opportunity to obtain information about the magnetization of the accretion disk atmosphere.Comment: 8 pages and 6 figures, submitted to the Astrophysical Journal Letter

Geometry dominated fluid adsorption on sculptured substrates

Experimental methods allow the shape and chemical composition of solid surfaces to be controlled at a mesoscopic level. Exposing such structured substrates to a gas close to coexistence with its liquid can produce quite distinct adsorption characteristics compared to that occuring for planar systems, which may well play an important role in developing technologies such as super-repellent surfaces or micro-fluidics. Recent studies have concentrated on adsorption of liquids at rough and heterogeneous substrates and the characterisation of nanoscopic liquid films. However, the fundamental effect of geometry has hardly been addressed. Here we show that varying the shape of the substrate can exert a profound influence on the adsorption isotherms allowing us to smoothly connect wetting and capillary condensation through a number of novel and distinct examples of fluid interfacial phenomena. This opens the possibility of tailoring the adsorption properties of solid substrates by sculpturing their surface shape.Comment: 6 pages, 4 figure

Phase diagram for morphological transitions of wetting films on chemically structured substrates

Using an interface displacement model we calculate the shapes of thin liquidlike films adsorbed on flat substrates containing a chemical stripe. We determine the entire phase diagram of morphological phase transitions in these films as function of temperature, undersaturation, and stripe widthComment: 15 pages, RevTeX, 7 Figure

Macroscopic transport by synthetic molecular machines

Nature uses molecular motors and machines in virtually every significant biological process, but demonstrating that simpler artificial structures operating through the same gross mechanisms can be interfaced with—and perform physical tasks in—the macroscopic world represents a significant hurdle for molecular nanotechnology. Here we describe a wholly synthetic molecular system that converts an external energy source (light) into biased brownian motion to transport a macroscopic cargo and do measurable work. The millimetre-scale directional transport of a liquid on a surface is achieved by using the biased brownian motion of stimuli-responsive rotaxanes (‘molecular shuttles’) to expose or conceal fluoroalkane residues and thereby modify surface tension. The collective operation of a monolayer of the molecular shuttles is sufficient to power the movement of a microlitre droplet of diiodomethane up a twelve-degree incline.

Anomalous k-dependent spin splitting in wurtzite AlxGa1-xN/GaN heterostructures

We have confirmed the k-dependent spin splitting in wurtzite AlxGa1-xN/GaN heterostructures. Anomalous beating pattern in Shubnikov-de Haas measurements arises from the interference of Rashba and Dresselhaus spin-orbit interactions. The dominant mechanism for the k-dependent spin splitting at high values of k is attributed to Dresselhaus term which is enhanced by the Delta C1-Delta C3 coupling of wurtzite band folding effect

Is there a link between bacteriuria and a reversible encephalopathy in dogs and cats?

Bacteriuria has been associated with abnormal neurological status in humans, particularly the geriatric population. In this report, we review 11 cases (7 dogs and 4 cats) that support an association between bacteriuria and abnormal neurological status in veterinary medicine. The included cases presented with neurological deficits consistent with a diffuse forebrain ± brainstem localisation, in which structural brain disease was excluded with magnetic resonance imaging of the head and cerebrospinal fluid analysis, but in which urine bacteriological culture was positive, and neurological deficits improved or resolved with initiation of antibiosis ± fluid therapy and levetiracetam. While further studies are needed to definitively confirm or refute the link between bacteriuria and a reversible encephalopathy, urine bacteriological culture should be considered in veterinary patients presented with an acute onset forebrain (± brainstem) neuro-anatomical localisation, even in the absence of clinical signs of lower urinary tract inflammation

Sibling relationships and family functioning in siblings of early adolescents, adolescents and young adults with autism spectrum disorder

The purpose of the study was to investigate how family functioning (defined as the ability that family members hold to manage stressful events, and intimate and social relationships), the degree to which family members feel happy and fulfilled with each other (called family satisfaction), and the demographical characteristics of siblings (age and gender) impacted on sibling relationships. The Circumplex Model of Marital and Family Systems and Behavioral Systems constituted the theoretical frameworks that guided our study. Eighty-six typically developing adolescents and young adults having a sister or a brother with autism spectrum disorder were enrolled. Results indicated that the youngest age group (early adolescents) reported to engage more frequently in negative behaviors with their siblings with ASD than the two older age groups (middle adolescents and young adults). No significant differences were found among the three age groups regarding behaviors derived from attachment, caregiving and affiliative systems. Family satisfaction and age significantly predicted behaviors during sibling interactions. Suggestions on prevention and intervention programs were discussed in order to prevent parentification among typically developing siblings and decrease episodes of quarrels and overt conflicts between brothers and sisters with and without AS