7,148 research outputs found
Rocket experiments for spectral estimation of electron density fine structure in the auroral and equatorial ionosphere and preliminary results
Sounding rockets equipped to monitor electron density and its fine structure were launched into the auroral and equatorial ionosphere in 1980 and 1983, respectively. The measurement electronics are based on the Langmuir probe and are described in detail. An approach to the spectral analysis of the density irregularities is addressed and a software algorithm implementing the approach is given. Preliminary results of the analysis are presented
An X-ray Survey in SA 57 with XMM-Newton
The maximum number density of Active Galactic Nuclei (AGNs), as deduced from
X-ray studies, occurs at z<~1, with lower luminosity objects peaking at smaller
redshifts. Optical studies lead to a different evolutionary behaviour, with a
number density peaking at z~2 independently of the intrinsic luminosity, but
this result is limited to active nuclei brighter than the host galaxy. A
selection based on optical variability can detect low luminosity AGNs (LLAGNs),
where the host galaxy light prevents the identification by non-stellar colours.
We want to collect X-ray data in a field where it exists an optically-selected
sample of "variable galaxies'', i.e. variable objects with diffuse appearance,
to investigate the X-ray and optical properties of the population of AGNs,
particularly of low luminosity ones, where the host galaxy is visible. We
observed a field of 0.2 deg^2 in the Selected Area 57, for 67ks with
XMM-Newton. We detected X-ray sources, and we correlated the list with a
photographic survey of SA 57, complete to B_J~23 and with available
spectroscopic data. We obtained a catalogue of 140 X-ray sources to limiting
fluxes 5x10^-16, 2x10^-15 erg/cm^2/s in the 0.5-2 keV and 2-10 keV
respectively, 98 of which are identified in the optical bands. The X-ray
detection of part of the variability-selected candidates confirms their AGN
nature. Diffuse variable objects populate the low luminosity side of the
sample. Only 25/44 optically-selected QSOs are detected in X-rays. 15% of all
QSOs in the field have X/O<0.1.Comment: 13 pages, 6 figures, 4 tables, A&A in pres
United Kingdom: An example of the impact of high stakes accountability regimes on STEM education
In this chapter we focus on science, technology, engineering and mathematics (STEM) education in the United Kingdom. We examine government policy and describe various strategies and programmes that have been designed and implemented with a view to improving the system. The UK, and particularly England, provides a case study of high stakes accountability regimes. Root and branch reforms have seen major changes in curriculum and assessment at a number of levels as well as an attempt to impose a national pedagogic strategy
Mathematical transitions: a report on the mathematical and statistical needs of students undertaking undergraduate studies in various disciplines
First Results from the HDMS experiment in the Final Setup
The Heidelberg Dark Matter Search (HDMS) is an experiment designed for the
search for WIMP dark matter. It is using a special configuration of Ge
detectors, to efficiently reduce the background in the low-energy region below
100 keV. After one year of running the HDMS detector prototype in the Gran
Sasso Underground Laboratory, the inner crystal of the detector has been
replaced with a HPGe crystal of enriched Ge. The final setup started
data taking in Gran Sasso in August 2000. The performance and the first results
of the measurement with the final setup are discussed.Comment: 8 pages, revtex, 7 figures, Home Page of Heidelberg Non-Accelerator
Particle Physics Group: http://www.mpi-hd.mpg.de/non_acc
High sensitivity phonon-mediated kinetic inductance detector with combined amplitude and phase read-out
The development of wide-area cryogenic light detectors with good energy
resolution is one of the priorities of next generation bolometric experiments
searching for rare interactions, as the simultaneous read-out of the light and
heat signals enables background suppression through particle identification.
Among the proposed technological approaches for the phonon sensor, the
naturally-multiplexed Kinetic Inductance Detectors (KIDs) stand out for their
excellent intrinsic energy resolution and reproducibility. To satisfy the large
surface requirement (several cm) KIDs are deposited on an insulating
substrate that converts the impinging photons into phonons. A fraction of
phonons is absorbed by the KID, producing a signal proportional to the energy
of the original photons. The potential of this technique was proved by the
CALDER project, that reached a baseline resolution of 1547 eV RMS by
sampling a 22 cm Silicon substrate with 4 Aluminum KIDs. In this
paper we present a prototype of Aluminum KID with improved geometry and quality
factor. The design improvement, as well as the combined analysis of amplitude
and phase signals, allowed to reach a baseline resolution of 824 eV by
sampling the same substrate with a single Aluminum KID
New application of superconductors: high sensitivity cryogenic light detectors
In this paper we describe the current status of the CALDER project, which is
developing ultra-sensitive light detectors based on superconductors for
cryogenic applications. When we apply an AC current to a superconductor, the
Cooper pairs oscillate and acquire kinetic inductance, that can be measured by
inserting the superconductor in a LC circuit with high merit factor.
Interactions in the superconductor can break the Cooper pairs, causing sizable
variations in the kinetic inductance and, thus, in the response of the LC
circuit. The continuous monitoring of the amplitude and frequency modulation
allows to reconstruct the incident energy with excellent sensitivity. This
concept is at the basis of Kinetic Inductance Detectors (KIDs), that are
characterized by natural aptitude to multiplexed read-out (several sensors can
be tuned to different resonant frequencies and coupled to the same line),
resolution of few eV, stable behavior over a wide temperature range, and ease
in fabrication. We present the results obtained by the CALDER collaboration
with 2x2 cm2 substrates sampled by 1 or 4 Aluminum KIDs. We show that the
performances of the first prototypes are already competitive with those of
other commonly used light detectors, and we discuss the strategies for a
further improvement
Characterization of the KID-Based Light Detectors of CALDER
The aim of the Cryogenic wide-Area Light Detectors with Excellent Resolution
(CALDER) project is the development of light detectors with active area of
cm and noise energy resolution smaller than 20 eV RMS,
implementing phonon-mediated kinetic inductance detectors. The detectors are
developed to improve the background suppression in large-mass bolometric
experiments such as CUORE, via the double read-out of the light and the heat
released by particles interacting in the bolometers. In this work, we present
the characterization of the first light detectors developed by CALDER. We
describe the analysis tools to evaluate the resonator parameters (resonant
frequency and quality factors) taking into account simultaneously all the
resonance distortions introduced by the read-out chain (as the feed-line
impedance and its mismatch) and by the power stored in the resonator itself. We
detail the method for the selection of the optimal point for the detector
operation (maximizing the signal-to-noise ratio). Finally, we present the
response of the detector to optical pulses in the energy range of 0-30 keV
A case of post–traumatic cervicogenic headache treated by cervical cord stimulation
The case of a 26–year–old woman suffering from cervical trauma with disc herniation presenting with arm and neck pain is presented. She underwent cervical discectomy with fusion because the pain did not improve with medical therapies; as the neck pain resumed after surgery, a cervical cord neurostimulator was implanted, with improvement for cervicogenic headache. This report underlines the presence of two pathologies and the relationship between C2 and trigeminal pathways
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