On Dark Matter Annihilation in the Local Group

Under the hypothesis of a Dark Matter composed by supersymmetric particles like neutralinos, we investigate the possibility that their annihilation in the haloes of nearby galaxies could produce detectable fluxes of $\gamma$-photons. Expected fluxes depend on several, poorly known quantities such as the density profiles of Dark Matter haloes, the existence and prominence of central density cusps and the presence of a population of sub-haloes. We find that, for all reasonable choices of Dark Matter halo models, the intensity of the $\gamma$-ray flux from some of the nearest extragalactic objects, like M31, is comparable or higher than the diffuse Galactic foreground. We show that next generation ground-based experiments could have the sensitivity to reveal such fluxes which could help us unveiling the nature of Dark Matter particles.Comment: 11 pages, 10 figures. Accepted for publication in Phys. Rev. D.; added a new paragraph on the detectability of Galactic sub-halos in our Galaxy; added a discussion on their model dependence. The relation of our results with the "CDM crisis" issue has also been adde

Regularity of a kind of marginal functions in Hilbert spaces

We study well-posedness of some mathematical programming problem depending on a parameter that generalizes in a certain sense the metric projection onto a closed nonconvex set. We are interested in regularity of the set of minimizers as well as of the value function, which can be seen, on one hand, as the viscosity solution to a Hamilton-Jacobi equation, while, on the other, as the minimal time in some related optimal time control problem. The regularity includes both the Fréchet differentiability of the value function and the Hölder continuity of its (Fréchet) gradient

Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory

Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius $A$. Also the events detected simultaneously by the surface and fluorescence detectors (the `hybrid' data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction.Comment: Matches published versio

Functional and genetic analysis of regulatory regions of coliphage H-19B: location of shiga-like toxin and lysis genes suggest a role for phage functions in toxin release

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74784/1/j.1365-2958.1998.00890.x.pd

Clusters of galaxies: setting the stage

Clusters of galaxies are self-gravitating systems of mass ~10^14-10^15 Msun. They consist of dark matter (~80 %), hot diffuse intracluster plasma (< 20 %) and a small fraction of stars, dust, and cold gas, mostly locked in galaxies. In most clusters, scaling relations between their properties testify that the cluster components are in approximate dynamical equilibrium within the cluster gravitational potential well. However, spatially inhomogeneous thermal and non-thermal emission of the intracluster medium (ICM), observed in some clusters in the X-ray and radio bands, and the kinematic and morphological segregation of galaxies are a signature of non-gravitational processes, ongoing cluster merging and interactions. In the current bottom-up scenario for the formation of cosmic structure, clusters are the most massive nodes of the filamentary large-scale structure of the cosmic web and form by anisotropic and episodic accretion of mass. In this model of the universe dominated by cold dark matter, at the present time most baryons are expected to be in a diffuse component rather than in stars and galaxies; moreover, ~50 % of this diffuse component has temperature ~0.01-1 keV and permeates the filamentary distribution of the dark matter. The temperature of this Warm-Hot Intergalactic Medium (WHIM) increases with the local density and its search in the outer regions of clusters and lower density regions has been the quest of much recent observational effort. Over the last thirty years, an impressive coherent picture of the formation and evolution of cosmic structures has emerged from the intense interplay between observations, theory and numerical experiments. Future efforts will continue to test whether this picture keeps being valid, needs corrections or suffers dramatic failures in its predictive power.Comment: 20 pages, 8 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 2; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke

Pulsar Wind Nebulae with Bow Shocks: Non-thermal Radiation and Cosmic Ray Leptons

Pulsars with high spin-down power produce relativistic winds radiating a non-negligible fraction of this power over the whole electromagnetic range from radio to gamma-rays in the pulsar wind nebulae (PWNe). The rest of the power is dissipated in the interactions of the PWNe with the ambient interstellar medium (ISM). Some of the PWNe are moving relative to the ambient ISM with supersonic speeds producing bow shocks. In this case, the ultrarelativistic particles accelerated at the termination surface of the pulsar wind may undergo reacceleration in the converging flow system formed by the plasma outflowing from the wind termination shock and the plasma inflowing from the bow shock. The presence of magnetic perturbations in the flow, produced by instabilities induced by the accelerated particles themselves, is essential for the process to work. A generic outcome of this type of reacceleration is the creation of particle distributions with very hard spectra, such as are indeed required to explain the observed spectra of synchrotron radiation with photon indices Γ≲ 1.5. The presence of this hard spectral component is specific to PWNe with bow shocks (BSPWNe). The accelerated particles, mainly electrons and positrons, may end up containing a substantial fraction of the shock ram pressure. In addition, for typical ISM and pulsar parameters, the e+ released by these systems in the Galaxy are numerous enough to contribute a substantial fraction of the positrons detected as cosmic ray (CR) particles above few tens of GeV and up to several hundred GeV. The escape of ultrarelativistic particles from a BSPWN—and hence, its appearance in the far-UV and X-ray bands—is determined by the relative directions of the interstellar magnetic field, the velocity of the astrosphere and the pulsar rotation axis. In this respect we review the observed appearance and multiwavelength spectra of three different types of BSPWNe: PSR J0437-4715, the Guitar and Lighthouse nebulae, and Vela-like objects. We argue that high resolution imaging of such objects provides unique information both on pulsar winds and on the ISM. We discuss the interpretation of imaging observations in the context of the model outlined above and estimate the BSPWN contribution to the positron flux observed at the Earth

Microvascular bed volume evaluated by near infrared spectroscopy in healthy and critically ill subjects

Cattedra di Anestesiologia e Rianimazione, I Università, II Facoltà di Medicina e Chirurgia, Roma, Italy Introduction: The microvascular tone regulation can be very useful to be assessed to titrate therapy in critical conditions. In the present study, we use near infrared (NIR) spectroscopy in the frequency domain on critically ill patients and healthy subjects, to obtain the measurement of microcirculatory compliance and the regulation of vascular tone. Methods: Two groups of subjects have been studied: the first group was composed by 17 healthy subjects (H) at rest, in the second group five critically ill patients were treated with noradrenalin infusion (N). In the N group the measurements have been performed at different noradrenalin doses: the first dose (d1) was established by the head physician, then the dose was doubled (d2) and finally reduced at the half of the first dose (d3). The probe of the spectrometer used in this study (ISS incorporated, Urbana, IL, USA), have been applied on the forearm skin, in a zone corresponding to brachioradial muscle. A serial of a pneumatic cuff compressions have been performed at the arm. Measurements of the total hemoglobin [Hbt] in tissue and blood volume, derived from [Hbt] have been obtained. The linear coefficient correlating blood volume to cuff compressions was considered as a measurement of venous and capillary compliance. Results: The [Hbt] and Hb in the blood of the two groups are shown in Table 1, the Hb content in the blood was lower in N than in H group. There was no difference about [Hbt] between the groups. In the H group in no subject [Hbt] change, at cuff pressure of 10 mmHg, was evidenced while only five subjects out of 17 showed a [Hbt] increase at 20 mmHg. In the N group, three subjects out of five (60%) showed a [Hbt] increase at 20 mmHg pressure. The capillary and venular bed compliance is shown in Table 1. Conclusions: From our results is shown clearly that in critically ill subjects the microvascular bed volume rose, in fact even if the Hb in blood was low the [Hbt] in tissue did not change. References: 1. De Blasi RA, Ferrari M, Natali A, et al.: A non invasive measurament of forearm blood flow and oxygen consumption by near–infrared spectroscopy. J Appl Physiolol 1994, 76(3):1388-1393. 2. Fantini S, Franceschini MA, Maier JS, et al.: Frequency domain multichannel optical detector for non-invasive tissue spectroscopy and oxymetry. Opt Eng 1995, 34:32-42. 3. Shrier I, Magder S: Pressure–flow relationship in a vitro model of compartment syndrome. J Appl Physiolol 1995, 79:214-221

Propofol sedation reduces diaphragm activity in spontaneously breathing patients: Ultrasound assessment

BACKGROUND: The diaphragm is the most important respiratory muscle in humans, and the close relationship between inspired volume and diaphragmatic movement in normal subjects has led to investigations into diaphragmatic activity using ultrasound, during spontaneous breathing and sedative drug infusion. METHODS: A total of 36 consecutive patients undergoing diagnostic procedures under deep propofol sedation were studied. Ultrasound measurements included the following: diaphragmatic thickening end-inspiration (TEI) and endexpiration (TEE). Diaphragmatic thickening fraction (DTF) was calculated from [(TEI TEE) / TEE] at various time points (at T0 basal; at T1 during propofol infusion; at T2 awakening). Oxygen was administered at 4 L/min, and oxygen saturation (SpO2), end tidal CO2 (EtCO2) and respiratory rate (RR) were recorded. RESULTS : TEI, and TEE decreased by 26.7% and 17.4%, respectively, during propofol infusion (T0 versus T1) (P&lt;0.001), and rapidly recovered at T2 (22.7% and 15.8%). At procedure end (T0 versus T2), TEI maintained a significant reduction (10%, P&lt;0.001), whereas TEE recovered completely. DTF decreased by 56.7% at T1 (P&lt;0.001) but increased by 76.9% (P=0.001) at T2. Recovery after awakening (T0 versus T2) did not reach the baseline value, with a 23.4% difference (P&lt;0.001). SpO2 remained above 96% and EtCO2 below 43 mmHg with no desaturation episodes observed. CONCLUSIONS: Our study showed that deep propofol sedation affects muscle activity in healthy patients. While diaphragmatic strength decreased during sedation, there was no clinically relevant effect on SpO2. The study also confirmed that ultrasound is suitable for measuring diaphragm activity during a normal clinical procedure