Intermediate Phases, structural variance and network demixing in chalcogenides: the unusual case of group V sulfides

We review Intermediate Phases (IPs) in chalcogenide glasses and provide a structural interpretation of these phases. In binary group IV selenides, IPs reside in the 2.40 < r < 2.54 range, and in binary group V selenides they shift to a lower r, in the 2.29< r < 2.40 range. Here r represents the mean coordination number of glasses. In ternary alloys containing equal proportions of group IV and V selenides, IPs are wider and encompass ranges of respective binary glasses. These data suggest that the local structural variance contributing to IP widths largely derives from four isostatic local structures of varying connectivity r; two include group V based quasi-tetrahedral (r = 2.29) and pyramidal (r = 2.40) units, and the other two are group IV based corner-sharing (r = 2.40) and edge-sharing (r = 2.67) tetrahedral units. Remarkably, binary group V (P, As) sulfides exhibit IPs that are shifted to even a lower r than their selenide counterparts; a result that we trace to excess Sn chains either partially (As-S) or completely (P-S) demixing from network backbone, in contrast to excess Sen chains forming part of the backbone in corresponding selenide glasses. In ternary chalcogenides of Ge with the group V elements (As, P), IPs of the sulfides are similar to their selenide counterparts, suggesting that presence of Ge serves to reign in the excess Sn chain fragments back in the backbone as in their selenide counterparts

Rapid spectral and timing variability of Be/X-ray binaries during type II outbursts

We have investigated the spectral and timing variability of four accreting X-ray pulsars with Be-type companions during major X-ray outbursts. Different spectral states were defined according to the value of the X-ray colours and flux. Transient Be/X-ray binaries exhibit two branches in their colour-colour and colour-intensity diagrams: the horizontal branch corresponds to a low-intensity state and shows the larger fractional rms, similar to the the island state in atolls and horizontal branch in Z sources; the diagonal branch corresponds to a high-intensity state, in which the source spends about 75% of the total duration of the outburst. Despite the complexity of the power spectra due to the peaks of the pulse period and its harmonics, the aperiodic variability of Be/X-ray binaries can be described with a relatively low number of Lorentzian components. Some of these components can be associated with the same type of noise as that seen in low-mass X-ray binaries, although the characteristic frequencies are about one order of magnitude lower. The pattern traced by V 0332+53 results in a Z shaped track, similar to the low-mass Z sources, without the flaring branch. In contrast, the horizontal branch in 4U 0115+63, KS 1947+300 and EXO 2030+375 corresponds to a low/soft state, not seen in other types of X-ray binaries. The noise at very low frequencies follows a power law in V 0332+53 (like in LMXB Z) and it is flat-topped in 4U 0115+63, KS 1947+300 and EXO 2030+375 (like in LMXB atoll). V 0332+53 shows a noise component coupled with the periodic variability that it is not seen in any of the other three sources

The LOFT mission concept: a status update

The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, >8m2 effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission

Double Hydrophilic Block Copolymer Self-Assembly in Aqueous Solution

Self‐assembly of double hydrophilic block copolymers (DHBCs) in water is an emerging area of research. The self‐assembly process can be derived from aqueous two‐phase systems that are composed of hydrophilic homopolymers at elevated concentration. Consecutively, DHBCs form self‐assembled structures like micelles, vesicles, or particles at high concentrations in water and without the use of external triggers that would change solubility of individual blocks. Careful choice of the two hydrophilic blocks and design of the polymer structure allows formation of self‐assembled structures with high efficiency. The present contribution highlights recent research in the area of DHBC self‐assembly, including the polymer types employed and strategies for crosslinking of the self‐assembled structures. Moreover, an overview of aqueous multiphase systems and theoretical considerations of DHBC self‐assembly are presented, as well as an outlook regarding potential future applications in areas such as the biomedical field

Brain–gut–microbiome interactions in obesity and food addiction

Normal eating behavior is coordinated by the tightly regulated balance between intestinal and extra-intestinal homeostatic and hedonic mechanisms. By contrast, food addiction represents a complex, maladaptive eating behavior that reflects alterations in brain–gut–microbiome (BGM) interactions and a shift of this balance towards hedonic mechanisms. Each component of the BGM axis has been implicated in the development of food addiction, with both brain to gut and gut to brain signaling playing a role. Early life influences can prime the infant gut microbiome and brain for food addiction, which might be further reinforced by increased antibiotic usage and dietary patterns throughout adulthood. The ubiquitous availability and marketing of inexpensive, highly palatable and calorie dense food can further shift this balance towards hedonic eating through both central (disruptions in dopaminergic signaling) and intestinal (vagal afferent function, metabolic toxaemia, systemic immune activation, changes to gut microbiome and metabolome) mechanisms. In this Review, we propose a systems biological model of BGM interactions, which incorporates published reports on food addiction, and provides novel insights into treatment targets aimed at each level of the BGM axis