Measuring X-ray anisotropy in solar flares. Prospective stereoscopic capabilities of STIX and MiSolFA

During the next solar maximum, two upcoming space-borne X-ray missions, STIX on board Solar Orbiter and MiSolFA, will perform stereoscopic X-ray observations of solar flares at two different locations: STIX at 0.28 AU (at perihelion) and up to inclinations of $\sim25^{\circ}$, and MiSolFA in a low-Earth orbit. The combined observations from these cross-calibrated detectors will allow us to infer the electron anisotropy of individual flares confidently for the first time. We simulated both instrumental and physical effects for STIX and MiSolFA including thermal shielding, background and X-ray Compton backscattering (albedo effect) in the solar photosphere. We predict the expected number of observable flares available for stereoscopic measurements during the next solar maximum. We also discuss the range of useful spacecraft observation angles for the challenging case of close-to-isotropic flare anisotropy. The simulated results show that STIX and MiSolFA will be capable of detecting low levels of flare anisotropy, for M1-class or stronger flares, even with a relatively small spacecraft angular separation of 20-30{\deg}. Both instruments will directly measure the flare X-ray anisotropy of about 40 M- and X-class solar flares during the next solar maximum. Near-future stereoscopic observations with Solar Orbiter/STIX and MiSolFA will help distinguishing between competing flare-acceleration mechanisms, and provide essential constraints regarding collisional and non-collisional transport processes occurring in the flaring atmosphere for individual solar flares

Late postpancreatectomy hemorrhage after pancreaticoduodenectomy: is it possible to recognize risk factors?

CONTEXT: Post-pancreatectomy hemorrhage is one of the most common complications after pancreaticoduodenectomy. OBJECTIVE: To evaluate the late post-pancreatectomy hemorrhage rate according to the International Study Group of Pancreatic Surgery criteria and to recognize factors related to its onset. METHODS: A prospective study of 113 patients who underwent pancreaticoduodenectomy was conducted. Late post-pancreatectomy hemorrhage was defined according to the criteria of the International Study Group of Pancreatic Surgery. Demographic, clinical, surgical and pathological data were considered and related to late post-pancreatectomy hemorrhage. RESULTS: Thirty-one (27.4%) patients had a post-pancreatectomy hemorrhage. Twenty-five (22.1%) patients developed late post-pancreatectomy hemorrhage: 19 (16.8%) grade B, 6 (5.3%) grade C. Surgical re-operation was performed in 2 out of the 25 cases with late post-pancreatectomy hemorrhage (8.0%) grade C associated with postoperative pancreatic fistula. At univariate analysis, the only factor significantly related to late post-pancreatectomy hemorrhage was postoperative pancreatic fistula (P<0.001). Multivariate analysis underlined that the severity of postoperative pancreatic fistula (P<0.001) and pancreatic anastomosis (P=0.049) independently increased the risk of late hemorrhage. CONCLUSION: In patients undergoing pancreaticoduodenectomy, the criteria introduced by International Study Group of Pancreatic Surgery to define late postpancreatectomy hemorrhage are related to a higher incidence of hemorrhage than previously detected because they considered also mild hemorrhage

Space-Fluid Adaptive Sampling: A Field-Based, Self-organising Approach

A recurrent task in coordinated systems is managing (estimating, predicting, or controlling) signals that vary in space, such as distributed sensed data or computation outcomes. Especially in large-scale settings, the problem can be addressed through decentralised and situated computing systems: nodes can locally sense, process, and act upon signals, and coordinate with neighbours to implement collective strategies. Accordingly, in this work we devise distributed coordination strategies for the estimation of a spatial phenomenon through collaborative adaptive sampling. Our design is based on the idea of dynamically partitioning space into regions that compete and grow/shrink to provide accurate aggregate sampling. Such regions hence define a sort of virtualised space that is “fluid”, since its structure adapts in response to pressure forces exerted by the underlying phenomenon. We provide an adaptive sampling algorithm in the field-based coordination framework. Finally, we verify by simulation that the proposed algorithm effectively carries out a spatially adaptive sampling

Hydrological Uncertainty and Hydropower: New Methods to Optimize the Performance of the Plant☆

Abstract Hydrological uncertainty due to daily flow variability and to the effect of climate change on water resources is a critical topic in the feasibility evaluations of hydro-power projects, especially for run-of-river power plant. The effect produced by these factors on the annual energy output of such type of plant was investigated. Empirical methods to improve the performance of the plant are proposed, which enable the choice of the most suitable design flow (Q d ) according to the hydrological features of the river, to the frequency of dry and wet years in the basin and to the target energy production

Experimental study of masonry wall exposed to blast loading

The challenge of protecting the nation against the attack of terrorism has raised the importance to explore the understanding of building materials against the explosion. Unlike most of the building materials, brick masonry materials offer relatively small resistance against blast loading. In this research, a brick masonry wall was exposed to varying blast load at different scaled distances. Six tests with different amounts of explosives at various distances were carried out. Pressure time history, acceleration time history and strain at specific location were measured. The parameters measured from experimental pressure time history and acceleration time history is compared with those determined by ConWep to establish the correlations between experimental determined records and ConWep values. The experimental results were also compared with some researchers. These correlations may assist in understanding the behaviour of masonry structures subjected to explosive loading

Polyvinylamine membranes containing graphene-based nanofillers for carbon capture applications

In the present study, the separation performance of new self-standing polyvinylamine (PVAm) membranes loaded with few-layer graphene (G) and graphene oxide (GO) was evaluated, in view of their use in carbon capture applications. PVAm, provided by BASF as commercial product named Lupamin\u2122, was purified obtaining PVAm films with two degrees of purification: Low Grade (PVAm-LG) and High Grade (PVAm-HG). These two-grade purified PVAm were loaded with 3 wt% of graphene and graphene oxide to improve mechanical stability: indeed, pristine tested materials proved to be brittle when dry, while highly susceptible to swelling in humid conditions. Purification performances were assessed through FTIR-ATR spectroscopy, DSC and TGA analysis, which were carried out to characterize the pristine polymer and its nanocomposites. In addition, the membranes\u2032 fracture surfaces were observed through SEM analysis to evaluate the degree of dispersion. Water sorption and gas permeation tests were performed at 35 \ub0C at different relative humidity (RH), ranging from 50% to 95%. Overall, composite membranes showed improved mechanical stability at high humidity, and higher glass transition temperature (Tg) with respect to neat PVAm. Ideal CO2/N2 selectivity up to 80 was measured, paired with a CO2 permeability of 70 Barrer. The membranes\u2019 increased mechanical stability against swelling, even at high RH, without the need of any crosslinking, represents an interesting result in view of possible further development of new types of facilitated transport composite membranes