Hard X-Ray Emission from the Galaxy Cluster A2256.

After the positive detection by BeppoSAX of hard X-ray radiation up to approximately 80 keV in the Coma Cluster spectrum, we present evidence for nonthermal emission from A2256 in excess of thermal emission at a 4.6 sigma confidence level. In addition to this power-law component, a second nonthermal component already detected by ASCA could be present in the X-ray spectrum of the cluster, which is not surprising given the complex radio morphology of the cluster central region. The spectral index of the hard tail detected by the Phoswich Detection System on board BeppoSAX is marginally consistent with that expected for the inverse Compton model. A value of approximately 0.05 µG is derived for the intracluster magnetic field of the extended radio emission in the northern regions of the cluster, while a higher value of approximately 0.5 µG could be present in the central radio halo, which is likely related to the hard tail detected by ASCA.

Interaction in Abell 2256: The BeppoSAX View.

We present results from a spatially resolved spectral analysis of the merging cluster Abell 2256. The long integration time (135 ks) and the good spatial resolution of the Medium-Energy Concentrator/Spectrometer on board BeppoSAX allow us to derive a new and substantially improved measurement of the temperature structure. We find that, within a central region of the cluster, where the effects of the merger are visible in the ROSAT surface brightness image, the azimuthally averaged projected temperature is remarkably flat; outside this region, the projected temperature rapidly declines. The BeppoSAX data also show clear evidence of an azimuthal temperature gradient in the 4&arcmin;-8&arcmin; (0.4-0.8 Mpc) radial bin, oriented in the same direction as the merger itself. Our metal abundance profile shows, for the first time, firm evidence of an abundance gradient in a rich merging cluster. Intriguingly, the abundance map shows, in the southeast sector, i.e., the one farthest away from the merger, a sharp factor of 2 drop in abundance at a radius comparable to the core radius of the cluster. A possible interpretation is that prior to the merger event, a cooling flow had already developed in the core of the infalling subgroup, as suggested by Fabian & Daines. The interaction between the substructures would have disrupted the cooling flow, thereby reheating and remixing the gas. Since the merger in A2256 is still in a relatively early stage, the gas located on the side opposite the merger event would still retain the low abundances associated with the intracluster medium prior to the cooling flow disruption.

A BeppoSAX Observation of the Merging Cluster Abell 3266.

We present results from a BeppoSAX observation of the rich cluster Abell 3266. The broadband spectrum (2-50 keV) of the cluster, when fitted with an optically thin thermal emission model, yields a temperature of 8.1+/-0.2 keV and a metal abundance of 0.17+/-0.02 in solar units, with no evidence of a hard X-ray excess in the Phoswich Detector System spectrum. By performing a spatially resolved spectral analysis, we find that the projected temperature drops with increasing radius, going from approximately 10 keV at the cluster core to approximately 5 keV at about 1.5 Mpc. Our BeppoSAX temperature profile is in good agreement with the ASCA temperature profile of Markevitch et al. From our two-dimensional temperature map, we find that the gradient is observed in all azimuthal directions. The temperature gradient may have been caused by a recent merger event that was also responsible for a velocity-dispersion gradient measured in the optical band. The projected metal abundance profile and the two-dimensional map are both consistent with being constant.

The BeppoSAX View of the Hot Cluster Abell 2319.

We present results from a BeppoSAX observation of the rich cluster Abell 2319. The broadband spectrum (2-50 keV) of the cluster can be adequately represented by an optically thin thermal emission model with a temperature of 9.6+/-0.3 keV and a metal abundance of 0.25+/-0.03 in solar units and with no evidence of a hard X-ray excess in the PDS spectrum. From the upper limit to the hard-tail component, we derive a lower limit of approximately 0.04 µG for the volume-averaged intracluster magnetic field. By performing spatially resolved spectroscopy in the medium energy band (2-10 keV), we find that the projected radial temperature and metal abundance profiles are constant out to a radius of 16&arcmin; (1.4 Mpc). A reduction of the temperature of one-third, when going from the cluster core out to 16&arcmin;, can be excluded in the present data at the 99% confidence level. From the analysis of the temperature and abundance maps, we find evidence of a temperature enhancement and of an abundance decrement in a region localized 6&arcmin;-8&arcmin; northeast of the core, where a merger event may be taking place. Finally, the temperature map indicates that the subcluster located northwest of the main cluster may be somewhat cooler than the rest of the cluster.

Tumor microcirculation and its significance in therapy: possible role of omega-3 fatty acids as rheological modifiers.

Despite the great efforts to find new drugs or devices to suppress cancer cells, attempts to modify microcirculation and therefore the state of tumor cells and their surrounding normal tissues have not been given the attention they deserve. Solid tumors are composed of highly heterogeneous populations of malignant, stromal and inflammatory cells in a continuously adapting extracellular matrix. All of the above components interact and regulate each other to produce distinct microenvironments within the tumor mass. Abnormal microcirculation plays a particular role in the maintenance of this anomalous condition and favors the formation of metastasis, but on the other hand provides the therapist with an important site for intervention. In this brief overview we attempt to outline three aspects: (a) how the anomalous tumor blood flow provokes the nonuniform distribution of oxygen and nutrients within the tumor mass, thus determining different responses to the various cancer therapies; (b) how hemorheology is the clinical parameter most easily modified and (c) how omega-3 essential fatty acids are natural drugs that could be used in this sense beyond their antitumoral properties.