Neutron irradiation effect on SiPMs up to Φneq\Phi_{neq} = 5 ×\times 1014^{14} cm−2^{-2}

Silicon Photo-Multipliers (SiPM) are becoming the photo-detector of choice for increasingly more particle detection applications, from fundamental physics to medical and societal applications. One major consideration for their use at high-luminosity colliders is the radiation damage induced by hadrons, which leads to a dramatic increase of the dark count rate. KETEK SiPMs have been exposed to various fluences of reactor neutrons up to $\Phi_{neq}$ = 5$\times$10$^{14}$ cm$^{-2}$ (1 MeV equivalent neutrons). Results from the I-V, and C-V measurements for temperatures between $-$30$^\circ$C and $+$30$^\circ$C are presented. We propose a new method to quantify the effect of radiation damage on the SiPM performance. Using the measured dark current the single pixel occupation probability as a function of temperature and excess voltage is determined. From the pixel occupation probability the operating conditions for given requirements can be optimized. The method is qualitatively verified using current measurements with the SiPM illuminated by blue LED light

An Area of Uncertainty: Practitioners’ Experiences Working with Psychopathy

Psychopathy is an area of research that has been impacted by a great deal of prejudice and stigma. Studies pertaining to therapeutic interventions for psychopathy often argue that the condition might be untreatable. However, more recent research suggests that certain approaches are helpful as they work with strengths, weaknesses, limitations and self-interests. Moreover, qualitative research into both client and practitioner experience in treatment seems to be substantially lacking. The above conflicting opinions, combined with a lack of qualitative research in the area, motivated this research, which comprises an examination of the experience of practitioners who work with psychopathy. Six semi-structured interviews were conducted and analysed using Interpretative Phenomenological Analysis (IPA), which revealed four superordinate themes: “There’s Something Powerful about that Label”, The “Continuum”, An “Area of Uncertainty, Pessimism and Nihilism” and Beyond “Hanging in There”. Each theme revealed three subordinate themes related to opinions concerning the associations and characteristics of psychopathy, while lending insight to treatment approaches. The findings showed the influence that the label could have on practitioners and clients alike, with positive and negative reactions being observed. There also seemed to be the view that psychopathy, much like other mental health diagnoses, comprised a spectrum. Treatment approaches and outcomes appeared to be met with uncertainty and pessimism, with many participants sharing the difficulty of working with psychopathy. Nonetheless, effective approaches from experience were openly shared and discussed

Constraining the true nature of an exotic binary in the core of NGC 6624

We report on the identification of the optical counterpart to Star1, the exotic object serendipitously discovered by Deutsch et al. in the core of the Galactic globular cluster NGC 6624. Star1 has been classified by Deutsch et al. as either a quiescent Cataclysmic Variable or a low-mass X-ray binary. Deutsch et al. proposed StarA as possible optical counterpart to this object. We used high-resolution images obtained with the Hubble Space Telescope to perform a variability analysis of the stars close to the nominal position of Star1. While no variability was detected for StarA, we found another star, here named COM_Star1, showing a clear sinusoidal light modulation with amplitude \Delta m_F435W~0.7 mag and orbital period of P_orb~98 min. The shape of the light curve is likely caused by strong irradiation by the primary heating one hemisphere of the companion, thus suggesting a quite hot primary.Comment: Accepted for publication by ApJ Letters; 6 pages, 5 figure

Optimization of a perishable inventory system: A simulation study in a Ho.Re.Ca. company

The main goal of this paper is to describe the optimization of the inventory management process in a real context of perishable food products. The study involves one of the largest Italian HO.RE.CA. companies, located in the north of Italy and operating as a provider of the catering, commercial and welfare services. A simulation model was set up with the purpose of adapting three traditional reordering policies (i.e. Re-Order Point, Re-Order Cycle, and (s,S)) to a set of products belonging to company's assortment and evaluating the resulting economic outcomes. To this end, each policy was modelled on Microsoft ExcelTM, so as to compute the total cost of inventory management and determine of the minimum cost strategy. A comparison with the current company's performance and that achievable with the optimized policy is also proposed

Malaria sporozoite proteome leaves a trail

Comparison of the proteomes of malaria sporozoites at different stages and mutation of selected genes reveals proteins necessary for infection of the vertebrate host

The M_BH-M_star relation of obscured AGNs at high redshift

We report the detection of broad Halpha emission in three X-ray selected obscured AGNs at z=1-2. By exploiting the Halpha width and the intrinsic X-ray luminosity, we estimate their black hole masses, which are in the range 0.1-3x10^9 Msun. By means of multi-band photometric data, we measure the stellar mass of their host galaxy and, therefore, infer their M_BH/M_star ratio. These are the first obscured AGNs at high-z, selected based on their black hole accretion (i.e. on the basis of their X-ray luminosity), that can be located on the M_BH-M_star relation at high-z. All of these obscured high-z AGNs are fully consistent with the local M_BH-M_star relation. This result conflicts with those for other samples of AGNs in the same redshift range, whose M_BH/M_star ratio departs significantly from the value observed in local galaxies. We suggest that the obscured AGNs in our sample are in an advanced evolutionary stage, have already settled onto the local M_BH-M_star relation, and whose nuclear activity has been temporarily revived by recent galaxy interactions.Comment: 4 pages, 2 figures, accepted for publication in A&A Letters, slightly revised discussion on SMG

The primordial environment of super massive black holes: large scale galaxy overdensities around z∼6z\sim6 QSOs with LBT

We investigated the presence of galaxy overdensities around four $z\sim6$ QSOs, namely SDSS J1030+0524 (z = 6.28), SDSS J1148+5251 (z = 6.41), SDSS J1048+4637 (z = 6.20) and SDSS J1411+1217 (z = 5.95), through deep $r$-, $i$- and $z$- band imaging obtained with the wide-field ($\sim23'\times25'$) Large Binocular Camera (LBC) at the Large Binocular Telescope (LBT). We adopted color-color selections within the $i-z$ vs $r-z$ plane to identify samples of $i$-band dropouts at the QSO redshift and measure their relative abundance and spatial distribution in the four LBC fields, each covering $\sim8\times8$ physical Mpc at $z\sim6$. The same selection criteria were then applied to $z$-band selected sources in the $\sim$1 deg$^2$ Subaru-XMM Newton Deep Survey to derive the expected number of dropouts over a blank LBC-sized field ($\sim$0.14 deg$^2$). The four observed QSO fields host a number of candidates larger than what is expected in a blank field. By defining as $i$-band dropouts objects with $z_{AB}1.4$ and undetected in the $r$-band, we found 16, 10, 9, 12 dropouts in SDSS J1030+0524, SDSS J1148+5251, SDSS J1048+4637, and SDSS J1411+1217, respectively, whereas only 4.3 such objects are expected over a 0.14 deg$^2$ blank field. This corresponds to overdensity significances of 3.3, 1.9, 1.7, 2.5$\sigma$, respectively. By considering the total number of dropouts in the four LBC fields and comparing it with what is expected in four blank fields of 0.14 deg$^2$ each, we find that high-z QSOs reside in overdense environments at the $3.7\sigma$ level. This is the first direct and unambiguous measurement of the large scale structures around $z\sim6$ QSOs. [shortened]Comment: 12 pages, 8 figures. Accepted for publication in A&

Probing black hole accretion in quasar pairs at high redshift

Models and observations suggest that luminous quasar activity is triggered by mergers, so it should preferentially occur in the most massive primordial dark matter haloes, where the frequency of mergers is expected to be the highest. Since the importance of galaxy mergers increases with redshift, we identify the high-redshift Universe as the ideal laboratory for studying dual AGN. Here we present the X-ray properties of two systems of dual quasars at z=3.0-3.3 selected from the SDSS-DR6 at separations of 6-8 arcsec (43-65kpc) and observed by Chandra for 65ks each. Both members of each pair are detected with good photon statistics to allow us to constrain the column density, spectral slope and intrinsic X-ray luminosity. We also include a recently discovered dual quasar at z=5 (separation of 21 arcsec, 136kpc) for which XMM-Newton archival data allow us to detect the two components separately. Using optical spectra we derived bolometric luminosities, BH masses and Eddington ratios that were compared to those of luminous SDSS quasars in the same redshift ranges. We find that the brighter component of both pairs at z=3.0-3.3 has high luminosities compared to the distribution of SDSS quasars at similar redshift, with J1622A having an order magnitude higher luminosity than the median. This source lies at the luminous end of the z~3.3 quasar luminosity function. While we cannot conclusively state that the unusually high luminosities of our sources are related to their having a close companion, for J1622A there is only a 3% probability that it is by chance.Comment: MNRAS, in pres

Does the X-ray emission of the luminous quasar RBS 1124 originate in a mildly relativistic outflowing corona?

We have observed the luminous (L2-10 keV≃ 6 × 1044 erg s−1) radio-quiet quasar RBS 1124 (z= 0.208) with Suzaku. We report the detection of a moderately broad iron (Fe) line and of a weak soft X-ray excess. The X-ray data are very well described by a simple model comprising a power-law X-ray continuum plus its reflection off the accretion disc. If the inner disc radius we measure (rin≤ 3.8 gravitational radii) is identified with the innermost stable circular orbit of the black hole space-time, we infer that the black hole powering RBS 1124 is rotating rapidly with spin a≥ 0.6. The soft excess contribution in the 0.5-2 keV band is ∼15 per cent, about half than that typically observed in unobscured Seyfert 1 galaxies and quasars, in line with the low disc reflection fraction we measure (Rdisc≃ 0.4). The low reflection fraction cannot be driven by disc truncation which is at odds not only with the small inner disc radius we infer but, most importantly, with the radiatively efficient nature of the source (LBol/LEdd≃ 1). A plausible explanation is that the X-ray corona is the base of a failed jet (RBS 1124 being radio-quiet) and actually outflowing at mildly relativistic speeds. Aberration reduces the irradiation of the disc, thus forcing a lower than standard reflection fraction, and halves the inferred source intrinsic luminosity, reducing the derived Eddington ratio from ≃1 to ≃0.5. A partial covering model provides a statistically equivalent description of the 0.3-10 keV data, but provides a worse fit above 10 keV. More importantly, its properties are not consistent with being associated to the Fe emission line, worsening the degree of self-consistency of the model. Moreover, the partial covering model implies that RBS 1124 is radiating well above its Eddington luminosity, which seems unlikely and very far off from previous estimate