1,397 research outputs found
NIEL Dose Dependence for Solar Cells Irradiated with Electrons and Protons
The investigation of solar cells degradation and the prediction of its
end-of-life performance is of primary importance in the preparation of a space
mission. In the present work, we investigate the reduction of solar-cells'
maximum power resulting from irradiations with electrons and protons. Both GaAs
single junction and GaInP/GaAs/Ge triple junction solar cells were studied. The
results obtained indicate how i) the dominant radiation damaging mechanism is
due to atomic displacements, ii) the relative maximum power degradation is
almost independent of the type of incoming particle, i.e., iii) to a first
approximation, the fitted semi-empirical function expressing the decrease of
maximum power depends only on the absorbed NIEL dose, and iv) the actual
displacement threshold energy value (Ed=21 eV) accounts for annealing
treatments, mostly due to self-annealing induced effects. Thus, for a given
type of solar cell, a unique maximum power degradation curve can be determined
as a function of the absorbed NIEL dose. The latter expression allows one to
predict the performance of those solar cells in space radiation environment.Comment: To appear on the Proceedings of the 13th ICATPP Conference on
Astroparticle, Particle, Space Physics and Detectors for Physics
Applications, Villa Olmo (Como, Italy), 23--27 October, 2013, to be published
by World Scientific (Singapore
A multi-wavelength study of the peculiar galaxy NGC 2976
Researchers are currently studying NGC 2976 at many wavelengths to investigate the extent to which an interaction with M81 may have affected the star formation history of this galaxy. Here, researchers present observations of NGC 2976 made at 50 microns with the high resolution (CPC) instrument onboard Infrared Astronomy Satellite (IRAS) at 21-cm (both HI line and radio continuum) with the Westerbork Synthesis Radio Telescope (WSRT) and in the H alpha line with the Kitt Peak National Observatory (KPNO) 36 inch telescope. The far infrared emission is not centrally peaked as in other spirals (e.g., Wainscoat et al. 1987), but has obvious intensity peaks near the ends of the disk. The ionized gas as inferred from the H alpha observations, is largely confined to two large, symmetrically placed emission regions near the ends of the disk. Finally, the HI and 21-cm radio continuum emission also exhibit this strongly double-peaked structure. At all of the above wavelengths the emission peaks are roughly coincident and lie approx. 1.2 minutes to the NW and approx. 1.1 minutes to the SE of the optical center of this galaxy
Dense Molecular Gas and the Role of Star Formation in the Host Galaxies of Quasi-Stellar Objects
New millimeter-wave CO and HCN observations of the host galaxies of
infrared-excess Palomar Green quasi-stellar objects (PG QSOs) previously
detected in CO are presented. These observations are designed to assess the
validity of using the infrared luminosity to estimate star formation rates of
luminous AGN by determining the relative significance of dust-heating by young,
massive stars and active galactic nuclei (AGN) in QSO hosts and IRAS galaxies
with warm, AGN-like infrared colors. The HCN data show the PG QSO host IZw1 and
most of the warm IRAS galaxies to have high L_IR / L'_HCN (>1600) relative to
the cool IRAS galaxy population for which the median L_IR / L'_HCN ~
890(+440,-470). If the assumption is made that the infrared emission from cool
IRAS galaxies is reprocessed light from embedded star-forming regions, then
high values of L_IR / L'_HCN are likely the result of dust heating by the AGN.
Further, if the median ratio of L'_HCN / L'_CO ~ 0.06 observed for Seyfert
galaxies and IZw1 is applied to the PG QSOs not detected in HCN, then the
derived L_IR / L'_HCN correspond to a stellar contribution to the production of
L_IR of ~ 7-39%, and star formation rates ~ 2-37 M_sun/yr are derived for the
QSO hosts. Alternatively, if the far-infrared is adopted as the star formation
component of the total infrared in cool galaxies, the stellar contributions in
QSO hosts to their L_FIR are up to 35% higher than the percentages derived for
L_IR. This raises the possibility that the L_FIR in several of the PG QSO
hosts, including IZw1, could be due entirely to dust heated by young, massive
stars. Finally, there is no evidence that the global HCN emission is enhanced
relative to CO in galaxies hosting luminous AGN.Comment: LaTex, 31 pages, including 9 postscript figures, AJ, in press
(December 2006
Talc pleurodesis for malignant pleural effusion: efficacy and factors predicting recurrence
Objectives: To identify potential factors predicting recurrence after talc pleurodesis for malignant pleural effusion.
Methods: Retrospective study of two cohorts of consecutive patients undergoing surgery for malignant pleural effusion (T VATS/talc pleurodesis number of procedures n = 41, IPC VATS/indwelling pleural catheter n = 41). Data analysed: ASA, performance status, underlying histology, amount of effusion drained at initial procedure, morbidity, recurrence of effusion (RecEff), redo surgery due to recurrence. The definition of RecEff was based on imaging (at least CxR) and related report issued by a senior radiologist. Median radiological follow-up of both groups was identical (8 months). Statistical analysis was done through SPSS ver 21.
Results: The RecEff rate was 20% in the IPC group and 32% in the T group. Fifty percent (4/8) of patients with failed pleurodesis in the IPC group required redo surgery compared to 92% (12/13) in the T group, which was significant. Median time to recurrence in the IPC group was 9 months, in the T group 4 months. In the T group the only relevant factor associated with recurrence was lung cancer histology (P = 0.055). The statistical significance of ASA score >2 (P = 0.042) and performance status 2 (P = 0.019) in this context is difficult to interpret. There were no significant differences between cohorts in age (69.5 years [60-78.2]), gender (41 males and 41 females), ASA (3 [2-3]), performance status (1 [1-2]), millilitres of effusion drained (1600 [1000-2550]), site of primary (mesothelioma 32% of patients, lung Ca 21%) and morbidity (7%).
Conclusions: The recurrence rate after talc pleurodesis was notably higher compared to the IPC group in our study and a significant number of patients affected required redo surgery. Lung cancer histology was the only clinically relevant predictor of recurrence in the talc group, potentially favouring the choice of a primary IPC insertion for these patients rather than chemical pleurodesis
Using Hypervideo to support undergraduate students' reflection on work practices: a qualitative study
Abstract According to several exploratory studies, the HyperVideo seems to be particularly useful in highlighting the existing connections between the school-based and the work-based contexts, between authentic work situations and theoretical underpinnings. This tool and its features, in particular, the video annotation, seems to constitute an instrument which facilitates the students' reflection on work-practices. Even though several researchers have already studied the efficacy of HyperVideo, studies concerning the qualitative differences between a reflection process activated with or without its use are still missing. Therefore, the present contribution is focused on the reflective processes activated by two groups of students engaged in a higher education course while they carry out a reflective activity on work practices using the HyperVideo or not. The aim is to investigate wether the HyperVideo can be useful for students to foster the connection between theoretical concepts and work practices. Through multi-step qualitative analysis which combined Thematic Qualitative Text Analysis and Grounded Theory, a sample of reflective reports drafted by a group of students who employed HiperVideo to make a video-interview on a work-practice and to reflect on it (Group A) was compared with a sample of reflective reports drafted by a group who did not use it to complete the same task (Group B). The results emerging from the comparison of the coding frequencies between the two groups show that HyperVideo can support the reflective processes of students, better connecting theory and professional practice
The use ultrasound guided for refilling intrathecal baclofene pump in complicated clinical cases: A practical approach
Muscular spasticity due to neurological disorders is a heavy cause of severe pain and disability for many patients, compromising the independence and quality life. Baclofene is a good tool to guarantee patients independence and pain control. Anyway in chronic therapy oral treatment become unsatisfactory. In all these cases, intrathecal baclofen therapy (ITB), after sub fascial implantation of intrathecal pumps is used as an important long term treatment to reduce spasticity. After pump implantation the drug reservoir must be refilled periodically in order to maintain the reduction of spasticity and avoid the symptoms and signs of withdrawal. ITB refilling, which involves the insertion of a needle through the skin until the access port of the pump, is often hard, mainly due to the layer of abdominal fat, spasticity, suboptimal pump positioning, pump rotation or inversion, and scar formation over the implantation site. To avoid the difficulties of ITB refilling radiography or other invasive supportive examinations are sometimes needed. We reported here our experience and we suggest a simple method to use the ultrasound in refilling with particular attention to some cases with complications after implantation with a difficult approach in refilling. We used the ultrasound examination to identify the access port of her pump so as to avoid multiple needle punctures and infections and radiation exposition. Ultrasound-guided technique may facilitate ITB refill in technically challenging cases. With ultrasound ITB was easily detectable and was quite simple to identify the exact point of needle injection. In the last years different new applications for ultrasounds are emerging. In our opinion the use of Doppler ultrasounds in the study of muscles and nerves represent an emerging tool for the physician's neurological rehabilitation
Nuclear and Non-Ionizing Energy-Loss for Coulomb Scattered Particles from Low Energy up to Relativistic Regime in Space Radiation Environment
In the space environment, instruments onboard of spacecrafts can be affected
by displacement damage due to radiation. The differential scattering cross
section for screened nucleus--nucleus interactions - i.e., including the
effects due to screened Coulomb nuclear fields -, nuclear stopping powers and
non-ionization energy losses are treated from about 50 keV/nucleon up to
relativistic energies.Comment: Accepted for publication in the Proceedings of the ICATPP Conference
on Cosmic Rays for Particle and Astroparticle Physics, Villa Olmo (Como,
Italy), 7--8 October, 2010, to be published by World Scientifi
Electrical Characterization of SiPM as a Function of Test Frequency and Temperature
Silicon Photomultipliers (SiPM) represent a promising alternative to
classical photomultipliers, for instance, for the detection of photons in high
energy physics and medical physics. In the present work, electrical
characterizations of test devices - manufactured by ST Microelectronics - are
presented. SiPMs with an area of 3.5x3.5 micron^2 and a cell pitch of 54 micron
were manufactured as arrays of 64x64 cells and exhibiting a fill factor of 31%.
The capacitance of SiPMs was measured as a function of reverse bias voltage at
frequencies ranging from from 20 Hz up to 1 MHz and temperatures from 300 K
down to 85 K. While leakage currents were measured at temperatures from 400 K
down to 85 K. Thus, the threshold voltage - i.e., voltage corresponding to that
at which the multiplication regime for the leakage current begins - could be
determined as a function of temperature. Finally, an electrical model suited to
reproduce the dependence of the frequency dependence of capacitance is
presented.Comment: To appear on the Proceedings of the 13th ICATPP Conference on
Astroparticle, Particle, Space Physics and Detectors for Physics
Applications, Villa Olmo (Como, Italy), 3-7 October, 2011, to be published by
World Scientific (Singapore
Enhanced [CII] emission in a z=4.76 submillimetre galaxy
We present the detection of bright [CII] emission in the z=4.76 submillimetre
galaxy LESS J033229.4-275619 using the Atacama Pathfinder EXperiment. This
represents the highest redshift [CII] detection in a submm selected,
star-formation dominated system. The AGN contributions to the [CII] and
far-infrared (FIR) luminosities are small. We find an atomic mass derived from
[CII] comparable to the molecular mass derived from CO. The ratio of the [CII],
CO and FIR luminosities imply a radiation field strength G_0~10^3 and a density
~10^4 cm^-3 in a kpc-scale starburst, as seen in local and high redshift
starbursts. The high L_[CII]/L_FIR=2.4x10^-3 and the very high
L_[CII]/L_CO(1-0) ~ 10^4 are reminiscent of low metallicity dwarf galaxies,
suggesting that the highest redshift star-forming galaxies may also be
characterised by lower metallicities. We discuss the implications of a reduced
metallicity on studies of the gas reservoirs, and conclude that especially at
very high redshift, [CII] may be a more powerful and reliable tracer of the
interstellar matter than CO.Comment: 5 pages, 2 figures; accepted for publication in Astronomy &
Astrophysics Letter
Proton Modulation in the Heliosphere for Different Solar Conditions and Prediction for AMS-02
Spectra of Galactic Cosmic Rays (GCRs) measured at the Earth are the
combination of several processes: sources production and acceleration,
propagation in the interstellar medium and propagation in the heliosphere.
Inside the solar cavity the flux of GCRs is reduced due to the solar
modulation, the interaction which they have with the interplanetary medium. We
realized a 2D stochastic simulation of solar modulation to reproduce CR spectra
at the Earth, and evaluated the importance in our results of the Local
Interstellar Spectrum (LIS) model and its agreement with data at high energy.
We show a good agreement between our model and the data taken by AMS-01 and
BESS experiments during periods with different solar activity conditions.
Furthermore we made a prediction for the flux which will be measured by AMS-02
experiment.Comment: Accepted for publication in the Proceedings of the ICATPP Conference
on Cosmic Rays for Particle and Astroparticle Physics, Villa Olmo (Como,
Italy), 7-8 October, 2010, to be published by World Scientific (Singapore
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