1,720,988 research outputs found
A 8-channels low-noise CMOS readout circuit for silicon detectors with on-chip front-end JFET
No full textWe propose a CMOS circuit designed to be used with silicon drift detectors (SDDs) coupled to scintillators for /spl gamma/-ray imaging applications. The circuit is composed by 8 analog channels, each including a low-noise preamplifier, a 6th order semiGaussian shaping amplifier with four selectable peaking times from 1.8 /spl mu/s up to 6 /spl mu/s, a peak stretcher and a baseline holder. The integrated time constant used for the shaping are implemented by means of a recently proposed 'RC' cell. This cell is based on the de-magnification of the current flowing in a resistor R by means of the use of current mirrors. The 8 analog channels of the chip are multiplexed to a single analog output. A suitable digital section provides self-resetting of the channels, trigger output and the programming of independent threshold on the analog channels by means of a programmable serial register and 3-bit DACs. In this work, the main features of the circuit are first presented. The experimental results obtained in the characterization of the prototype are then reported and discussed. The energy resolution measured using a single channel of the chip with a silicon drift detector droplet (SDD/sup 3/) is of 128 eV at 6 keV with the detector cooled at -20/spl deg/C
An 8-channel DRAGO readout circuit for silicon detectors with integrated front-end JFET
No full textWe have developed a CMOS circuit to be used with Silicon Drift Detectors (SDDs) for X-ray spectroscopy and γ-ray imaging applications. The circuit operates with the input transistor integrated directly on the detector wafer. The circuit is composed of 8 analog channels, each including a low-noise voltage preamplifier, a 6th order semi-Gaussian shaping amplifier, with four selectable peaking times from 1.8 μs up to 6 μs, and a peak stretcher. The integrated time constant used for the shaping are implemented by means of a recently proposed 'RC' cell. This cell is based on the de-magnification of the current flowing in a resistor R thanks to the use of current mirrors. The 8 analog channels of the chip are multiplexed to a single analog output. A digital section provides self-resetting of the channels, trigger output and the external programming of independent threshold on the analog channels by means of a 3 bit DAC and a programmable serial register. In this work, the main features of the circuit are described. The measurement results obtained in the characterization of the prototype are then reported and discussed. The energy resolution measured using a single channel of the chip with a Silicon Drift Detector Droplet (SDD 3) is of 128 eV at 6 keV with the detector cooled at -20°C. Spectroscopy measurements using a multi-element SDD are also shown. © 2006 IEEE
Detection and study of a palimpsest: macro-X-ray fluorescence scanning in the Loggia Room of Galatea
No full textWithin the frame of a collaboration among the Accademia Nazionale dei Lincei, XGLab-Bruker and ENEA, some of the Renaissance wall paintings decorating Villa Farnesina interiors have been investigated by macro-X-ray fluorescence (MAXRF). In this paper is presented and discussed a case study concerning some sketches discovered about 50 years ago during the detachment of painted curtains. Results have brought to light a palimpsest whose discussion calls into question the attribution proposed when it has been discovered
A CMOS circuit for high-stability X-ray Spectroscopy with Silicon Drift Detectors with on-chip JFET
No full textWe propose a CMOS circuit designed to be used with silicon drift detectors (SDDs) for high-resolution and high peak stability X-ray spectroscopy. The circuit is developed in the framework of a project for researches on 'exotic atoms' (e.g. kaonic hydrogen) at e/sup -//e/sup +/ colliders. The circuit is composed by a low-noise charge preamplifier and by a 6th order semiGaussian shaping amplifier with four selectable peaking times from 0.7 /spl mu/s up to 3 /spl mu/s. The preamplifier operates with the input JFET directly integrated on the detector itself. A low-frequency current-mode feedback loop allows to stabilize the operating point of the input JFET with respect to background and leakage current variations. The feedback capacitor is integrated on the detector and its value is not known precisely in advance. The preamplifier is designed with the possibility to adjust externally its decay time to match the fixed time constant of the pole/zero network. A baseline holder senses the baseline voltage shifts at the output of the circuits due to the DC changes of the drain voltage of the input JFET in correspondence of background variations and provides a feedback loop back to the preamplifier to stabilize the output baseline. A bipolar shaping provides a timing signal required by the experiment. A first prototype has been realized in the 0.35 /spl mu/m AMS technology. The energy resolution measured using the chip with a SDD of 5 mm/sup 2/ is of 137 eV at 6 keV (ENC = 8e/sup -/ rms)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
From noise to information. Analysing macro-XRF mapping of strontium impurities in Raphael's Baglioni Entombment in the Galleria Borghese, Rome
No full textIn the paintings of the Old Masters, strontium is present only as an impurity of the materials, that is the gypsum used for the preparation of the panels, and for this reason its presence is generally considered – at best – accidental information. However, an in-depth study of the distribution of strontium beneath the surface of Raphael's Entombment in the Borghese Gallery in Rome by means of MA-XRF provided detailed information regarding a reapplication of the preparatory gypsum ground layers on an area probably damaged before the painter began the execution of the painting. Furthermore, the comparison of MA-XRF distribution maps for lead and strontium with radiographic images, aimed to establish at what point the painter decided to eliminate a female figure in the centre of the painting, and the state of completion of the figure when this occurred
- …
