174 research outputs found
Efectividad de las técnicas de relajación en oncología antes de realizar pruebas diagnósticas en neuroimagen
Psychophysiological arousal was observed in cancer patients during the application of relaxation techniques prior to a diagnostic scan (PET-CT). The aim of the study is twofold: firstly, it is sought to establish whether such techniques can minimize patient arousal before diagnostic screening begins, and secondly to measure which of them are most effective. The dependent variable is electrodermal activity, recording the attentional level and emotional response, and the independent variable comprises the relaxation techniques used, namely Jacobson, breathing and visualization. The 39 patients were split into experimental groups to whom the relaxation techniques (Jacobson, breathing exercises, and visualization) were applied before they went for the PET-CT. An activity-module procedure was applied to track electrodermal activity during the relaxation sessions, consisting of instructions, timeout; wait, task; relaxation and end of the recording session. The control group received no relaxation techniques before the PET-CT. Session-end results show that patients who perform relaxation techniques achieve greater attentional focus using Jacobson''s technique (M = .212) and enhanced emotional containment using visualization (M = .206). It is concluded that relaxation techniques minimize the state of activation during the waiting period before a diagnostic scan
The detection of single electrons by means of a Micromegas-covered MediPix2 pixel CMOS readout circuit
A small drift chamber was read out by means of a MediPix2 readout chip as
direct anode. A Micromegas foil was placed 50 m above the chip, and
electron multiplication occurred in the gap. With a He/Isobutane 80/20 mixture,
gas multiplication factors up to tens of thousands were achieved, resulting in
an efficiency for detecting single electrons of better than 90% . We recorded
many frames containing 2D images with tracks from cosmic muons. Along these
tracks, electron clusters were observed, as well as delta-rays.Comment: 15 pages, 9 included postscript figures, 5 separate jpeg figures,
submitted to Nucl. Instr. and Meth. A. A complete postscript version with
high resolution figures 1, 3, 11, 12 and 14 can be found at
http://www.nikhef.nl/~i06/RandD/final/letter4.p
Readout of GEM Detectors Using the Medipix2 CMOS Pixel Chip
We have operated a Medipix2 CMOS readout chip, with amplifying, shaping and
charge discriminating front-end electronics integrated on the pixel-level, as a
highly segmented direct charge collecting anode in a three-stage gas electron
multiplier (Triple-GEM) to detect the ionization from Fe X-rays and
electrons from Ru. The device allows to perform moderate energy
spectroscopy measurements (20 % FWHM at 5.9 keV -rays) using only digital
readout and two discriminator thresholds. Being a truly 2D-detector, it allows
to observe individual clusters of minimum ionizing charged particles in
(70:30) and (70:30) mixtures and to achieve excellent
spatial resolution for position reconstruction of primary clusters down to
, based on the binary centroid determination method.Comment: 18 pages, 14 pictures. submitted to Nuclear Instruments and Methods
in Physics Research
Timing performance of the Timepix4 front-end
A characterisation of the Timepix4 pixel front-end with a strong focus on
timing performance is presented. Externally generated test pulses were used to
probe the per-pixel time-to-digital converter (TDC) and measure the time-bin
sizes by precisely controlling the test-pulse arrival time in steps of 10 ps.
The results indicate that the TDC can achieve a time resolution of 60 ps,
provided that a calibration is performed to compensate for frequency variation
in the voltage controlled oscillators of the pixel TDCs. The internal clock
distribution system of Timepix4 was used to control the arrival time of
internally generated analog test pulses in steps of about 20 ps. The analog
test pulse mechanism injects a controlled amount of charge directly into the
analog front-end (AFE) of the pixel, and was used to measure the time
resolution as a function of signal charge, independently of the TDC. It was
shown that for the default configuration, the AFE time resolution in the
hole-collecting mode is limited to 105 ps. However, this can be improved up to
about 60 ps by increasing the preamplifier bias-current at the cost of
increased power dissipation. For the electron-collecting mode, an AFE time
resolution of 47 ps was measured for a bare Timepix4 device at a signal charge
of 21 ke. It was observed that additional input capacitance from a bonded
sensor reduces this figure to 62 ps
Timing performance of the LHCb VELO Timepix3 Telescope
We performed a detailed study of the timing performance of the LHCb VELO
Timepix3 Telescope with a 180 GeV/c mixed hadron beam at the CERN SPS. A
twofold method was developed to improve the resolution of single-plane time
measurements, resulting in a more precise overall track time measurement. The
first step uses spatial information of reconstructed tracks in combination with
the measured signal charge in the sensor to correct for a mixture of different
effects: variations in charge carrier drift time; variations in signal
induction, which are the result of a non-uniform weighting field in the pixels;
and lastly, timewalk in the analog front-end. The second step corrects for
systematic timing offsets in Timepix3 that vary from -2 ns to 2 ns. By applying
this method, we improved the track time resolution from 43816 ps to
2764 ps
Identification of particles with Lorentz factor up to with Transition Radiation Detectors based on micro-strip silicon detectors
This work is dedicated to the study of a technique for hadron identification
in the TeV momentum range, based on the simultaneous measurement of the
energies and of the emission angles of the Transition Radiation (TR) X-rays
with respect to the radiating particles. A detector setup has been built and
tested with particles in a wide range of Lorentz factors (from about to
about crossing different types of radiators. The measured
double-differential (in energy and angle) spectra of the TR photons are in a
reasonably good agreement with TR simulation predictions.Comment: 31 pages, 12 figures, paper published on Nuclear Instruments &
Methods
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