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

Phase separation and pairing regimes in the one-dimensional asymmetric Hubbard model

We address some open questions regarding the phase diagram of the one-dimensional Hubbard model with asymmetric hopping coefficients and balanced species. In the attractive regime we present a numerical study of the passage from on-site pairing dominant correlations at small asymmetries to charge-density waves in the region with markedly different hopping coefficients. In the repulsive regime we exploit two analytical treatments in the strong- and weak-coupling regimes in order to locate the onset of phase separation at small and large asymmetries respectively.Comment: 13 pages, RevTeX 4, 12 eps figures, some additional refs. with respect to v1 and citation errors fixe

Robust output synchronization of a network of heterogeneous nonlinear agents via nonlinear regulation theory

In this paper, we consider the output synchronization problem for a network of heterogeneous diffusively-coupled nonlinear agents. Specifically, we show how the (non-identical) agents can be controlled in such a way that their outputs asymptotically track the output of a prescribed nonlinear exosystem. The problem is solved in two steps. In the first step, the problem of achieving consensus among (identical) nonlinear reference generators is addressed. In this respect, it is shown how the techniques recently developed to solve the consensus problem among linear agents can be extended to agents modeled by nonlinear d-dimensional differential equations, under the assumption that the communication graph is connected. In the second step, the theory of nonlinear output regulation is applied in a decentralized control mode, to force the output of each agent of the network to robustly track the (synchronized) output of a local reference model.Comment: Submitted to 52nd IEEE Conference on Decision and Contro

BIOMECHANICAL OPTIMIZATION OF CO2ANGIOGRAPHY

Carbon dioxide (CO2) angiography represents an important technique to overcome most clinical problems related to the use of iodine contrast medium. The recent technologic advancements in the fields of gas injection and image reconstructions made CO2 angiography a very efficient method for clinical evaluation of peripheral cardiovascular system. Despite that, some challenges are still open and a better knowledge of the biomechanical behavior of CO2 and its interactions with blood flowing into the vessels is necessary to optimize this technology and to expand its field of application. This paper presents a quick overview about biomechanical behavior of carbon dioxide during injection, suggesting possible optimization tricks to make CO2 angiography procedures more effective to improve imaging and reduce the patients' radiological dose. Particular attention has been also paid to 3D imaging techniques, which can certainly be opened to the use of carbon dioxide

The Local Interstellar Spectrum of Cosmic Ray Electrons

The direct measurements of electrons and positrons over the last 30 years, corrected for the solar effect in the force-field approximation, are considered. The resulting overall electron spectrum may be fitted with a single power law above few GeV with spectral index ($\gamma_{-} = 3.41 \pm 0.02$), consistent with the spectral index of the positron spectrum ($\gamma_{+} = 3.40 \pm 0.06$), therefore suggesting a common acceleration process for both species. We propose that the engine was a shock wave originating from the last supernova explosion among those that formed the local bubble. In addition, at low energy, the electron spectrum measured during the last $A+$ solar phase is damped, whereas the positron spectrum is well represented by a single power law down to the lowest inferred local interstellar energy (0.8 GeV). We suggest that this difference arises from a time- and charge-dependent effect of the solar modulation that is not taken into account by the force-field approximation.Comment: 10 pages, 9 figures, 1 table. OBSOLETE: please refer to ApJ 612 (2004) 262-267, that is the final version of this wor

The Time of Flight System of the AMS-02 Space Experiment

The Time-of-Flight (TOF) system of the AMS detector gives the fast trigger to the read out electronics and measures velocity, direction and charge of the crossing particles. The new version of the detector (called AMS-02) will be installed on the International Space Station on March 2004. The fringing field of the AMS-02 superconducting magnet is $1.0\div2.5$ kG where the photomultiplers (PM) are installed. In order to be able to operate with this residual field, a new type of PM was chosen and the mechanical design was constrained by requiring to minimize the angle between the magnetic field vector and the PM axis. Due to strong field and to the curved light guides, the time resolution will be $150\div180$ ps, while the new electronics will allow for a better charge measurement.Comment: 5 pages, 4 figures. Proc. of 7th Int. Conf. on Adv. Tech. and Part. Phys., 15-19 October 2001,Como (Italy

Treatment of squamous cell carcinoma of the anal canal: A new strategies with anti-EGFR therapy and immunotherapy

The incidence of squamous cell carcinoma of the anal canal (SCAC) is increasing in both sexes but the standard treatment remains that of 20 years ago. However, interesting data have recently emerged on the use of anti-epidermal growth factor receptor (EGFR) agents and immunotherapy in advanced disease. Thus, new avenues of research are opening up that will hopefully lead to more effective therapeutic strategies. We provide an overview of the latest studies published on this tumor and discuss the possible future therapeutic options for combination therapy, anti-EGFR treatment and radiotherapy