Radio Halo and Relic Candidates from the NRAO VLA Sky Survey

We present the first results of the search of new halo and relic candidates in the NRAO VLA Sky Survey. We have inspected a sample of 205 clusters from the X-ray-brightest Abell-type clusters presented by Ebeling et al (1996), and found 29 candidates. Out of them, 11 clusters are already known from the literature to contain a diffuse cluster-wide source, while in 18 clusters this is the first indication of the existence of this type of sources. We classify these sources as halos or relics according to their location in the cluster center or periphery, respectively. We find that the occurrence of cluster halos and relics is higher in clusters with high X-ray luminosity and high temperature. We also confirm the correlation between the absence of a cooling flow and the presence of a radio halo at the cluster center.Comment: 25 Pages, 4 Figures included in the text, Figures 3a to 3g in separated files. New Astronomy in pres

The reaction of Pseudomonas nitrite reductase and nitrite. A stopped-flow and EPR study.

The reaction between reduced Pseudomonas nitrite reductase and nitrite has been studied by stopped-flow and rapid-freezing EPR spectroscopy. The interpretation of the kinetics at pH 8.0 is consistent with the following reaction mechanism (where k1 and k3 much greater than k2). [formula: see text] The bimolecular step (Step 1) is very fast, being lost in the dead time of a rapid mixing apparatus; the stoichiometry of the complex has been estimated to correspond to one NO2- molecule/heme d1. The final species is the fully reduced enzyme with NO bound to heme d1; and at all concentrations of nitrite, there is no evidence for dissociation of NO or for further reduction of NO to N2O. Step 2 is assigned to an internal electron transfer from heme c to reduced NO-bound heme d1 occurring with a rate constant of 1 s-1; this rate is comparable to the rate of internal electron transfer previously determined when reducing the oxidized enzyme with azurin or cytochrome c551. When heme d1 is NO-bound, the rate at which heme c can accept electrons from ascorbate is remarkably increased as compared to the oxidized enzyme, suggesting an increase in the redox potential of the latter heme

EVN Observations of GRS1915+105

We obtained EVN observations of the X-ray transient source GRS1915+105 in its radio-loud state. In 2 images obtained before a major flare, the source is resolved, showing two opposite asymmetric jets. This indicates that steady jets exist also before a major flare, with an estimated velocity of 0.2-0.6c.Comment: Proceedings of the 5th EVN Symposium, Eds. J. Conway, A. Polatidis, R. Booth, Onsala Observatory, Sweden (June 2000

‘Priming’ exercise and O2 uptake kinetics during treadmill running

We tested the hypothesis that priming exercise would speed kinetics during treadmill running. Eight subjects completed a square-wave protocol, involving two bouts of treadmill running at 70% of the difference between the running speeds at lactate threshold (LT) and max, separated by 6-min of walking at 4 km h−1, on two occasions. Oxygen uptake was measured breath-by-breath and subsequently modelled using non-linear regression techniques. Heart rate and blood lactate concentration were significantly elevated prior to the second exercise bout compared to the first. However, kinetics was not significantly different between the first and second exercise bouts (mean ± S.D., phase II time constant, Bout 1: 16 ± 3 s vs. Bout 2: 16 ± 4 s; slow component amplitude, Bout 1: 0.24 ± 0.10 L min−1vs. Bout 2: 0.20 ± 0.12 L min−1; mean response time, Bout 1: 34 ± 4 s vs. Bout 2: 34 ± 6 s; P > 0.05 for all comparisons). These results indicate that, contrary to previous findings with other exercise modalities, priming exercise does not alter kinetics during high-intensity treadmill running, at least in physically active young subjects. We speculate that the relatively fast kinetics and the relatively small slow component in the control (‘un-primed’) condition negated any enhancement of kinetics by priming exercise in this exercise modality

A vertical facility based on raster scan configuration for the x-ray scientific calibrations of the ATHENA optics

The ATHENA X-ray observatory is a large-class ESA approved mission, with launch scheduled in 2028. The technology of Silicon Pore Optics (SPO) was selected since 2004 as the baseline for making the X-ray Mirror Assembly. Up to 700 mirror modules to obtain a nested Wolter like optics. The maximum diameter of the shells will be 2.5 m while the focal length is 12 m. The requirements for on-axis angular resolution and effective area at 1 keV are 5 arcsec HEW and 1.4 m2, while the field of view will be 40 arcmin in diameter (50 % vignetting). While in this moment there an on-going effort aiming at demonstrating the feasibility of a so large optics with so stringent scientific requirements, an important aspect to be considered regards the scientific calibrations of the X-ray optics. In this respect, the Point Spread Function and effective area have to be correctly measured and calibrated on-ground at different energies across the entire field of view, with a low vignetting. The approach considered so far foresees the use of a long (several hundreds of meters) facility to allow a full illumination with low divergence of the entire optics module (or at least of large sections of it). The implementation of similar configurations in a completely new facility to be realized in Europe (friendly called "super Panter") or the retrofitting existing facilities like the XRCF at NASA/MSFC are being considered. In both cases the costs and the programmatic risks related to the implementation of these huge facilities, with their special jigs for the alignment of the ATHENA optics, represent important aspects to be considered. Moreover, the horizontal position of the optics to be used in full illumination facilities would determine gravitational deformations, not easy to be removed with actuators or by modeling. In this talk we will discuss a completely different concept, based on the mount of the optics in vertical position and the use of a raster scan of the ATHENA optics with a small (a few cm2 wide) highly collimated (1 arcsec or so) white beam X-ray. This system will allow us to operate a much compact system. The use of a vertical configuration will imply smaller gravitational deformations, that can be controlled with actuators able to compensate them. A proper camera system with a sufficient energy resolution will be able to grant a correct measurement of both PSF and effective area of the Mirror Assembly within the calibration requirements and in a reasonable integration time. Moreover, it may allow us also to perform end-to-end tests using the two flight focal plane instruments of ATHENA. The cost and risks for the implementation would be much lower than for the full illumination systems. The conceptual configuration and preliminary expected performance of the facility will be discussed

Glycine propionyl-L-carnitine increases plasma nitrate/nitrite in resistance trained men

We have recently demonstrated that oral intake of glycine propionyl-L-carnitine (GPLC) increases plasma nitrate/nitrite (NOx), a surrogate measure of nitric oxide production. However, these findings were observed at rest, and in previously sedentary subjects