Four Years of Extreme Ultraviolet Observations of Markarian 421: II. Temporal Analysis

The Extreme Ultraviolet Explorer (EUVE) satellite accumulated ~one million seconds of public data between 1994 and 1997 for the BL Lacertae object Markarian 421. This is the second of two papers in which we present the results of spectral and temporal analysis of this EUVE data set. We analyze in the present paper the imaging data by means of power spectrum and structure function techniques, while the spectral analysis is presented in a companion paper. We find for MRK 421 a power spectrum with slope -2.14 +- 0.28 with a break at ~3 days. This is the first time that a break in the power spectrum of a BL Lacertae object has been found. We also find evidence of non-stationarity for MRK 421 EUV emissionComment: Accepted for publication in the Astrophysical Journal. 16 pages, 14 Postscript figures, 3 Table

An Application Of Artificial Immune System In A Wastewater Treatment Plant

Guaranteeing the continuity and the quality of services in network plants is a key issue in the research area of asset management. Especially when the plants are located in a wide area where machines are not continuously monitored by the operators. In particular, the pervasive adoption of smart sensors could be able to develop intelligent maintenance system through an elaboration of data coming from the machines: this data could be processed by diagnostics algorithms to warn preventively the fault status of the components or machines monitored. The algorithms’ structure is contained in a multiple system of agents that have different tasks to manage both the single machine and the information exchanged within the whole system. This paper aims to present an application of Artificial Immune System defining, for each plant section, the kind of agents employed and the related sensors that must be adopted to collect the useful data. In order to provide a practical example, the structure of an Artificial Immune System has been implemented in a wastewater treatment plant where the agents are tested with noteworthy results. © 20164928556

Prediction of hearing recovery in sudden deafness treated with intratympanic steroids

The present study aims to obtain a probability model allowing the prediction of the auditory recovery in patients affected by sudden sensorineural hearing loss treated exclusively with intratympanic steroids. A monocentric retrospective chart review of three-hundred eighty-one patients has been performed. A Probit model was used to investigate the correlation between the success of the treatment (marked or total recovery according to Furuashi's criteria), and the delay between the onset of disease and the beginning of therapy. The age of the patients and the audiometric curve shapes were included in the analysis. Results show that delay is negatively correlated with the variable success. Considering the entire sample, each day of delay decreases by 3% the probability of success. The prediction model shows that for every day that passes from the onset of the disease the probability of success declines in absence of the medical treatment, hence we conclude that early treatment is strongly recommended

Four Years of Extreme Ultraviolet Observations of Markarian 421. II. Temporal Analysis

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A Medium Survey of the Hard X-Ray Sky with ASCA. II.: The Source's Broad Band X-Ray Spectral Properties

A complete sample of 60 serendipitous hard X-ray sources with flux in the range $\sim 1 \times 10^{-13}$ \ecs to $\sim 4 \times 10^{-12}$ \ecs (2 - 10 keV), detected in 87 ASCA GIS2 images, was recently presented in literature. Using this sample it was possible to extend the description of the 2-10 keV LogN(>S)-LogS down to a flux limit of $\sim 6\times 10^{-14}$ \ecs (the faintest detectable flux), resolving about a quarter of the Cosmic X-ray Background. In this paper we have combined the ASCA GIS2 and GIS3 data of these sources to investigate their X-ray spectral properties using the "hardness" ratios and the "stacked" spectra method. Because of the sample statistical representativeness, the results presented here, that refer to the faintest hard X-ray sources that can be studied with the current instrumentation, are relevant to the understanding of the CXB and of the AGN unification scheme.Comment: 28 pages plus 6 figures, LaTex manuscript, Accepted for publication in the Astrophysical Journal, Figure 5 can retrieved via anonymous ftp at ftp://ftp.brera.mi.astro.it/pub/ASCA/paper2/fig5.ps.g

Persistent and Transient Blank Field Sources

Blank field sources (BFS) are good candidates for hosting dim isolated neutron stars (DINS). The results of a search of BFS in the ROSAT HRI images are revised. We then focus on transient BFS, arguing that they belong to a rather large population. The perspectives of future research on DINS are then discussed.Comment: 3 pages, 0 figures. Paper presented at the Conference "Isolated Neutron Stars: from the interior to the surface", London, April 2006. Astrophysics and Space Science, in pres

Constraining the black hole mass and accretion rate in the narrow-line Seyfert 1 RE J1034+396

We present a comprehensive study of the spectrum of the narrow-line Seyfert 1 galaxy RE J1034+396, summarizing the information obtained from the optical to X-rays with observations from the William Herschel 4.2m Telescope (WHT), the Hubble Space Telescope, the Extreme UltraViolet Explorer, ROSAT, ASCA and BeppoSAX. The BeppoSAX spectra reveal a soft component which is well-represented by two blackbodies with kT of about 60 eV and 160 eV, mimicking that expected from a hot, optically-thick accretion disc around a low-mass black hole. This is borne out by our modeling of the optical to X-ray nuclear continuum, which constrains the physical parameters of a NLS1 for the first time. The models demonstrate that RE J1034+396 is likely to be a system with a nearly edge-on accretion disk (60 to 75 degrees from the disk axis), accreting at nearly Eddington rates (0.3 to 0.7 L_edd) onto a low mass (about 2 million solar masses) black hole (abridged).Comment: ApJ accepte