The deepest X-ray look at the Universe

The origin of the X-ray background, in particular at hard (2-10 keV) energies, has been a debated issue for more than 30 years. The Chandra deep fields provide the deepest look at the X-ray sky and are the best dataset to study the X-ray background. We searched the Chandra Deep Field South for X-ray sources with the aid of a dedicated wavelet-based algorithm. We are able to reconstruct the Log N-Log S source distribution in the soft (0.5-2 keV) and hard (2-10 keV) bands down to limiting fluxes of 2x10^{-17} erg s^{-1} cm^{-2} and 2x10^{-16} erg s^{-1} cm^{-2}, respectively. These are a factor ~5 deeper than previous investigations. We find that the soft relation continues along the extrapolation from higher fluxes, almost completely accounting for the soft X-ray background. On the contrary, the hard distribution shows a flattening below ~2x10^{-14} erg s^{-1} cm^{-2}. Nevertheless, we can account for >68% of the hard X-ray background, with the main uncertainty being the sky flux itself.Comment: Accepted for publication on ApJL. Two figures, requires emulateapj5 (included

Testing the gamma-ray burst variability/peak luminosity correlation on a Swift homogeneous sample

We test the gamma-ray burst correlation between temporal variability and peak luminosity of the $\gamma$-ray profile on a homogeneous sample of 36 Swift/BAT GRBs with firm redshift determination. This is the first time that this correlation can be tested on a homogeneous data sample. The correlation is confirmed, as long as the 6 GRBs with low luminosity (<5x10^{50} erg s^{-1} in the rest-frame 100-1000 keV energy band) are ignored. We confirm that the considerable scatter of the correlation already known is not due to the combination of data from different instruments with different energy bands, but it is intrinsic to the correlation itself. Thanks to the unprecedented sensitivity of Swift/BAT, the variability/peak luminosity correlation is tested on low-luminosity GRBs. Our results show that these GRBs are definite outliers.Comment: Accepted for Publication in MNRAS. 10 pages, 5 figures, 3 table

Three years field trials to assess the effect of kaolin made particles and copper on olive-fruit fly (B.oleae Gmelin) infestations in Sicily

In most countries of Mediterranean Basin, Bactrocera oleae (Gmel), the olive fruit fly, is the key pest insect on olives. In Sicily this pest causes losses of fruits and a poor quality olive oil. Many researchers have recently carried out some field studies which were based on the use of kaolin and copper against the olive-fruit fly. In the last years these products have been effective several times in reducing olive fly infestation. Kaolin had, also, some important effect in reducing heat-stress in fruit crops and olive-trees. The aim of the present study was to assess the effect of kaolin and copper treatment on olive infestations in Sicily and to evaluate chemical and sensory parameters of oils extracted. For this reason, within 2003-2005, the IX Servizio of Assessorato Regionale Agricoltura e Foreste, selected some olive groves where to carry out trials with kaolin and copper and to realize information and divulgation activities

Hybrid UWB-Inertial TDoA-based Target Tracking with Concentrated Anchors

In this paper, hybrid radio/inertial mobile target tracking for accurate and smooth path estimation is considered. The proposed tracking approach builds upon an Ultra WideBand (UWB)-based positioning algorithm, based on the Linear Hyperbolic Positioning System (LinHPS), with Time Difference of Arrival (TDoA) processing and anchors concentrated on a single hotspot at the center of the environment where the target moves. First, we design an Adaptive Radio-based Extended Kalman Filter (AREKF), which does not require a priori statistical knowledge of the noise in the target movement model and estimates the measurement noise covariance, at each sampling time, according to a proper LookUp Table (LUT). In order to improve the performance of AREKF, we incorporate inertial data collected from the target and propose three “hybrid” radio/inertial algorithms, denoted as Hybrid Inertial Measurement Unit (IMU)-aided Radio-based EKF (HIREKF), Hybrid Noisy Control EKF (HNCEKF), and Hybrid Control EKF (HCEKF). Our results on experimentally acquired paths show that the proposed algorithms achieve an average instantaneous position estimation error on the order of a few centimeters. Moreover, the minimum target path length estimation error, obtained with HCEKF, is on the order of 6% and 1% for two paths with lengths equal to approximately 17 m and 46 m, respectively

Monitoring and modelling of soil–plant interactions: the joint use of ERT, sap flow and eddy covariance data to characterize the volume of an orange tree root zone

Abstract. Mass and energy exchanges between soil, plants and atmosphere control a number of key environmental processes involving hydrology, biota and climate. The understanding of these exchanges also play a critical role for practical purposes e.g. in precision agriculture. In this paper we present a methodology based on coupling innovative data collection and models in order to obtain quantitative estimates of the key parameters of such complex flow system. In particular we propose the use of hydro-geophysical monitoring via "time-lapse" electrical resistivity tomography (ERT) in conjunction with measurements of plant transpiration via sap flow and evapotranspiration (ET) from eddy covariance (EC). This abundance of data is fed to spatially distributed soil models in order to characterize the distribution of active roots. We conducted experiments in an orange orchard in eastern Sicily (Italy), characterized by the typical Mediterranean semi-arid climate. The subsoil dynamics, particularly influenced by irrigation and root uptake, were characterized mainly by the ERT set-up, consisting of 48 buried electrodes on 4 instrumented micro-boreholes (about 1.2 m deep) placed at the corners of a square (with about 1.3 m long sides) surrounding the orange tree, plus 24 mini-electrodes on the surface spaced 0.1 m on a square grid. During the monitoring, we collected repeated ERT and time domain reflectometry (TDR) soil moisture measurements, soil water sampling, sap flow measurements from the orange tree and EC data. We conducted a laboratory calibration of the soil electrical properties as a function of moisture content and porewater electrical conductivity. Irrigation, precipitation, sap flow and ET data are available allowing for knowledge of the system's long-term forcing conditions on the system. This information was used to calibrate a 1-D Richards' equation model representing the dynamics of the volume monitored via 3-D ERT. Information on the soil hydraulic properties was collected from laboratory and field experiments. The successful results of the calibrated modelling exercise allow for the quantification of the soil volume interested by root water uptake (RWU). This volume is much smaller (with a surface area less than 2 m2, and about 40 cm thick) than expected and assumed in the design of classical drip irrigation schemes that prove to be losing at least half of the irrigated water which is not taken up by the plants

Timing accuracy of the Swift X-Ray Telescope in WT mode

The X-Ray Telescope (XRT) on board Swift was mainly designed to provide detailed position, timing and spectroscopic information on Gamma-Ray Burst (GRB) afterglows. During the mission lifetime the fraction of observing time allocated to other types of source has been steadily increased. In this paper, we report on the results of the in-flight calibration of the timing capabilities of the XRT in Windowed Timing read-out mode. We use observations of the Crab pulsar to evaluate the accuracy of the pulse period determination by comparing the values obtained by the XRT timing analysis with the values derived from radio monitoring. We also check the absolute time reconstruction measuring the phase position of the main peak in the Crab profile and comparing it both with the value reported in literature and with the result that we obtain from a simultaneous Rossi X-Ray Timing Explorer (RXTE) observation. We find that the accuracy in period determination for the Crab pulsar is of the order of a few picoseconds for the observation with the largest data time span. The absolute time reconstruction, measured using the position of the Crab main peak, shows that the main peak anticipates the phase of the position reported in literature for RXTE by ~270 microseconds on average (~150 microseconds when data are reduced with the attitude file corrected with the UVOT data). The analysis of the simultaneous Swift-XRT and RXTE Proportional Counter Array (PCA) observations confirms that the XRT Crab profile leads the PCA profile by ~200 microseconds. The analysis of XRT Photodiode mode data and BAT event data shows a main peak position in good agreement with the RXTE, suggesting the discrepancy observed in XRT data in Windowed Timing mode is likely due to a systematic offset in the time assignment for this XRT read out mode.Comment: 6 pages, 4 figures. Accepted for publication on Astronomy&Astrophysic

P02.123. The anti-diabetic and cholesterol-lowering effects of common and cassia cinnamon (Cinnamomum verum and C. aromaticum): a randomized controlled trial

This paper accompanies a poster presentation on the anti-diabetic and cholesterol-lowering effects of common and cassia cinnamon (Cinnamomum verum and C. aromaticum)

GRB051210: Swift detection of a short gamma ray burst

The short/hard GRB051210 was detected and located by the Swift-BAT instrument and rapidly pointed towards by the narrow field instrumens. The XRT was able to observe a bright X-ray afterglow, one of the few ever observed for this class of bursts. We present the analysis of the prompt and afterglow emission of this event The BAT spectrum is a power-law with photon index 1.1 +/-0.3. The X-ray light curve decays with slope 2.58+/-0.11 and shows a small flare in the early phases. The spectrum can be described with a power law with photon index 1.54+/-0.16 and absorption (7.5 (-3.2, +4.3)*10^20 cm-2 We find that the X-ray emission is consistent with the hypothesis that we are observing the curvature effect of a GRB occurred in a low density medium, with no detectable afterglow. We estimate the density of the circumburst medium to be lower than 4*10^-3 cm^-3. We also discuss different hypothesis on the possible origin of the flare.Comment: 5 pages, 3 figures, submitted to A&A Letter