2,132 research outputs found
First results of a cryogenic optical photon counting imaging spectrometer using a DROID array
Context. In this paper we present the first system test in which we
demonstrate the concept of using an array of Distributed Read Out Imaging
Devices (DROIDs) for optical photon detection. Aims. After the successful S-Cam
3 detector the next step in the development of a cryogenic optical photon
counting imaging spectrometer under the S-Cam project is to increase the field
of view using DROIDs. With this modification the field of view of the camera
has been increased by a factor of 5 in area, while keeping the number of
readout channels the same. Methods. The test has been performed using the
flexible S-Cam 3 system and exchanging the 10x12 Superconducting Tunnel
Junction array for a 3x20 DROID array. The extra data reduction needed with
DROIDs is performed offline. Results. We show that, although the responsivity
(number of tunnelled quasiparticles per unit of absorbed photon energy, e- /eV)
of the current array is too low for direct astronomical applications, the
imaging quality is already good enough for pattern detection, and will improve
further with increasing responsivity. Conclusions. The obtained knowledge can
be used to optimise the system for the use of DROIDs.Comment: 7 pages, 9 figures, accepted for publicaiton in A&
The Public Administration Performance Appraisal Integrated System (SIADAP) and the Portuguese civil servants perceptions
As part of managerial reform process, in 2004 the Public Administration Performance Appraisal Integrated System (SIADAP) was set up in Portugal. This study aimed to analyze the perceptions of Portuguese civil servants on this appraisal system. A second drive was to understand how those perceptions change depending on what extent the model is perceived as fair or not. A survey was carried out and data were collected from 2066 civil servants, including managers. The results show very negative perceptions, in particular regarding SIADAP’s objectivity, transparency and fairness. Also, Kruskal-Wallis tests and post-hoc paired comparisons reveal that civil servants who see the system as “unfair” tend to have more negative perceptions on it than those who see it as “fair” or those who are not sure about the fairness of the system.info:eu-repo/semantics/acceptedVersio
Main Fuel Cells mathematical models: Comparison and analysis in terms of free parameters
This paper resumes the main mathematical models of Fuel Cells (PEM models). In particular, a comparison study of the various models introduced in the technical literature is presented and the dependency of the various model parameters is analyzed in different operating conditions. As the manifold of the model parameter is very wide and their determination is difficult, it is mandatory to introduce approximations and simplifications on which each model is based. The novelty of this work is the organization of the existing models in three categories with regard to the number of free parameters and to the dependency of such parameters on the different running conditions and the usage of a reference model in order to compare the difference between the latter once both in terms of fast execution of the simulation and care of the simulation results
Reducing variability in conditions for cell handling improves MSC yields
Efficient cell expansion in vitro is essential to commercialization of human MSC as a cellular therapy. The cost of goods sold (COGS) is dramatically affected by how long it takes to expand the cells in vitro and the cell yield determines the number of doses generated for profit. Therefore, maximizing MSC growth in culture is critical for the success of MSC-based cellular therapies. Studies by others have shown that temperature differences in cell production can adversely affect cell yields. Here we study the effects of variability in temperature and CO2, like changes seen during routine cell handling in a room air BSC, on human MSC yield. We cultured human bone marrow mesenchymal stromal/stem cells for 8 biweekly subpassages (P4-P12) with conventional room air CO2 incubator conditions (37 degrees C/ 5% CO2). The culture was divided into separate cultures for routine cell handling in two different conditions (1) room air BSC conditions (RT/ 0.1% CO2) (variable) or (2) the same conditions as incubation (constant). At each passage, cells were plated in 96-well plates which were assayed over time for cell growth kinetics. Consistently, MSC incubated and handled in constant conditions recovered more quickly after subpassage and were more likely to continue to divide, improving final cell yields. We conclude that constant conditions for cell handling are critical for maximum MSC cell yield
Gamma-ray burst observations with new generation imaging atmospheric Cerenkov Telescopes in the FERMI era
After the launch and successful beginning of operations of the FERMI
satellite, the topics related to high-energy observations of gamma-ray bursts
have obtained a considerable attention by the scientific community.
Undoubtedly, the diagnostic power of high-energy observations in constraining
the emission processes and the physical conditions of gamma-ray burst is
relevant. We briefly discuss how gamma-ray burst observations with ground-based
imaging array Cerenkov telescopes, in the GeV-TeV range, can compete and
cooperate with FERMI observations, in the MeV-GeV range, to allow researchers
to obtain a more detailed and complete picture of the prompt and afterglow
phases of gamma-ray bursts.Comment: 9 pages, two figures. Proceeding for the 6th "Science with the New
Generation of High Energy Gamma-Ray Experiments" worksho
Novel technique for monitoring the performance of the LAT instrument on board the GLAST satellite
The Gamma-ray Large Area Space Telescope (GLAST) is an observatory designed
to perform gamma-ray astronomy in the energy range 20 MeV to 300 GeV, with
supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. GLAST will
be launched at the end of 2007, opening a new and important window on a wide
variety of high energy astrophysical phenomena . The main instrument of GLAST
is the Large Area Telescope (LAT), which provides break-through high-energy
measurements using techniques typically used in particle detectors for collider
experiments. The LAT consists of 16 identical towers in a four-by-four grid,
each one containing a pair conversion tracker and a hodoscopic crystal
calorimeter, all covered by a segmented plastic scintillator anti-coincidence
shield. The scientific return of the instrument depends very much on how
accurately we know its performance, and how well we can monitor it and correct
potential problems promptly. We report on a novel technique that we are
developing to help in the characterization and monitoring of LAT by using the
power of classification trees to pinpoint in a short time potential problems in
the recorded data. The same technique could also be used to evaluate the effect
on the overall LAT performance produced by potential instrumental problems.Comment: 2 pages, 1 figure, manuscript submitted on behalf of the GLAST/LAT
collaboration to First GLAST symposium proceeding
A Concept for an STJ-based Spectrograph
We describe a multi-order spectrograph concept suitable for 8m-class
telescopes, using the intrinsic spectral resolution of Superconducting
Tunneling Junction detectors to sort the spectral orders. The spectrograph
works at low orders, 1-5 or 1-6, and provides spectral coverage with a
resolving power of R~8000 from the atmospheric cutoff at 320 nm to the long
wavelength end of the infrared H or K band at 1800 nm or 2400 nm. We calculate
that the spectrograph would provide substantial throughput and wavelength
coverage, together with high time resolution and sufficient dynamic range. The
concept uses currently available technology, or technologies with short
development horizons, restricting the spatial sampling to two linear arrays;
however an upgrade path to provide more spatial sampling is identified. All of
the other challenging aspects of the concept - the cryogenics, thermal baffling
and magnetic field biasing - are identified as being feasible.Comment: Accepted in Monthly Notices of the Royal Astronomical Society, 12
pages with 10 figure
Pengaruh Senam Lansia Terhadap Kadar Kolesterol Total Pada Lansia Di BPLU Senja Cerah Manado
: Many changes occur in the elderly include changes in body composition, muscle, bones and joints, cardiovascular system, respiratory and cognition. One of the efforts to maintain, improve health and physical fitness for the elderly is to exercise. The aim of this research is to know the effect of the elderly gymnastics on the levels of total cholesterol in elderly at BPLU Senja Cerah Manado. This research is experimental study with one group pre-post test design. The research respondents are 18 elderly people in BPLU Senja Cerah Manado. Cholesterol levels are measured before the first gymnastics session and after final gymnastics session. Respondents do gymnastics three times a week for eight weeks. The research results is analyzed by Wilcoxon test using a computer program. The result of the research shows that the mean level of cholesterol before first elderly gymnastics 222,17 mg/dL and after final elderly gymnastics 231,50 mg/dL. There is no significant effect on respondents total cholesterol after doing elderly gymnastics for three times a week for eight weeks
Galactic center at very high-energies
Employing data collected during the first 25 months' observations by the
Fermi-LAT, we describe and subsequently seek to model the very high energy
(>300 MeV) emission from the central few parsecs of our Galaxy. We analyze the
morphological, spectral and temporal characteristics of the central source,
1FGL J1745.6-2900. Remarkably, the data show a clear, statistically significant
signal at energies above 10 GeV, where the Fermi-LAT has an excellent angular
resolution comparable to the angular resolution of HESS at TeV energies, which
makes meaningful the joint analysis of the Fermi and HESS data. Our analysis
does not show statistically significant variability of 1FGL J1745.6-2900. Using
the combination of Fermi data on 1FGL J1745.6-2900 and HESS data on the
coincident, TeV source HESS J1745-290, we show that the spectrum of the central
gamma-ray source is inflected with a relatively steep spectral region matching
between the flatter spectrum found at both low and high energies. We seek to
model the gamma-ray production in the inner 10 pc of the Galaxy and examine, in
particular, cosmic ray (CR) proton propagation scenarios that reproduce the
observed spectrum of the central source. We show that a model that instantiates
a transition from diffusive propagation of the CR protons at low energy to
almost rectilinear propagation at high energies (given a reasonable
energy-dependence of the assumed diffusion coefficient) can well explain the
spectral phenomenology. In general, however, we find considerable degeneracy
between different parameter choices which will only be broken with the addition
of morphological information that gamma-ray telescopes cannot deliver given
current angular resolution limits.We argue that a future analysis done in
combination with higher-resolution radio continuum data holds out the promise
of breaking this degeneracy.Comment: submitted to Ap
- …