361 research outputs found
‘Kangaroo mother care’ to prevent neonatal deaths due to preterm birth complications
Background ‘Kangaroo mother care’ (KMC) includes thermal care through continuous skin-to-skin contact, support for exclusive breastfeeding or other appropriate feeding, and early recognition/response to illness. Whilst increasingly accepted in both high- and low-income countries, a Cochrane review (2003) did not find evidence of KMC’s mortality benefit, and did not report neonatal-specific data
Determining the azimuthal properties of coronal mass ejections from multi-spacecraft remote-sensing observations with stereo secchi
We discuss how simultaneous observations by multiple heliospheric imagers can
provide some important information about the azimuthal properties of Coronal
Mass Ejections (CMEs) in the heliosphere. We propose two simple models of CME
geometry that can be used to derive information about the azimuthal deflection
and the azimuthal expansion of CMEs from SECCHI/HI observations. We apply these
two models to four CMEs well-observed by both STEREO spacecraft during the year
2008. We find that in three cases, the joint STEREO-A and B observations are
consistent with CMEs moving radially outward. In some cases, we are able to
derive the azimuthal cross-section of the CME fronts, and we are able to
measure the deviation from self-similar evolution. The results from this
analysis show the importance of having multiple satellites dedicated to space
weather forecasting, for example in orbits at the Lagrangian L4 and L5 points.Comment: 7 pages, 4 figures, 1 table, accepted to Ap
Position Reconstruction in Drift Chambers operated with Xe, CO2 (15%)
We present measurements of position and angular resolution of drift chambers
operated with a Xe,CO(15%) mixture. The results are compared to Monte Carlo
simulations and important systematic effects, in particular the dispersive
nature of the absorption of transition radiation and non-linearities, are
discussed. The measurements were carried out with prototype drift chambers of
the ALICE Transition Radiation Detector, but our findings can be generalized to
other drift chambers with similar geometry, where the electron drift is
perpendicular to the wire planes.Comment: 30 pages, 18 figure
A new regime of nanoscale thermal transport: collective diffusion counteracts dissipation inefficiency
Understanding thermal transport from nanoscale heat sources is important for
a fundamental description of energy flow in materials, as well as for many
technological applications including thermal management in nanoelectronics,
thermoelectric devices, nano-enhanced photovoltaics and nanoparticle-mediated
thermal therapies. Thermal transport at the nanoscale is fundamentally
different from that at the macroscale and is determined by the distribution of
carrier mean free paths in a material, the length scales of the heat sources,
and the distance over which heat is transported. Past work has shown that
Fourier's law for heat conduction dramatically over-predicts the rate of heat
dissipation from heat sources with dimensions smaller than the mean free path
of the dominant heat-carrying phonons. In this work, we uncover a new regime of
nanoscale thermal transport that dominates when the separation between
nanoscale heat sources is small compared with the dominant phonon mean free
paths. Surprisingly, the interplay between neighboring heat sources can
facilitate efficient, diffusive-like heat dissipation, even from the smallest
nanoscale heat sources. This finding suggests that thermal management in
nanoscale systems including integrated circuits might not be as challenging as
projected. Finally, we demonstrate a unique and new capability to extract mean
free path distributions of phonons in materials, allowing the first
experimental validation of differential conductivity predictions from
first-principles calculations.Comment: Main text: 18 pages, 4 figures. Supplementary Information: 13 pages,
9 figure
Particle tracking in kaon electroproduction with cathode-charge sampling in multi-wire proportional chambers
Wire chambers are routinely operated as tracking detectors in magnetic
spectrometers at high-intensity continuous electron beams. Especially in
experiments studying reactions with small cross-sections the reaction yield is
limited by the background rate in the chambers. One way to determine the track
of a charged particle through a multi-wire proportional chamber (MWPC) is the
measurement of the charge distribution induced on its cathodes. In practical
applications of this read-out method, the algorithm to relate the measured
charge distribution to the avalanche position is an important factor for the
achievable position resolution and for the track reconstruction efficiency. An
algorithm was developed for operating two large-sized MWPCs in a strong
background environment with multiple-particle tracks. Resulting efficiencies
were determined as a function of the electron beam current and on the signal
amplitudes. Because of the different energy-losses of pions, kaons, and protons
in the momentum range of the spectrometer the efficiencies depend also on the
particle species
Beyond the RICH: Innovative Photosensitive Gaseous Detectors for new Fields of Applications
We have developed and successfully used several innovative designs of
detectors with solid photocathodes. The main advantage of these detectors is
that rather high gains (>10E4) can be achieved in a single multiplication step.
This is possible by, for instance, exploiting the secondary electron
multiplication and limiting the energy of the steamers by distributed
resistivity. The single step approach also allows a very good position
resolution to be achieved in some devices: 50 micron on line without applying
any treatment method (like center of gravity). The main focus of our report is
new fields of applications for these detectors and the optimization of their
designs for such purposes.Comment: 14 pages, 7 figures, 3 table
Photosensitive Gaseous Detectors for Cryogenic Temperature Applications
There are several proposals and projects today for building LXe Time
Projection Chambers (TPCs) for dark matter search. An important element of
these TPCs are the photomultipliers operating either inside LXe or in vapors
above the liquid.
We have recently demonstrated that photosensitive gaseous detectors (wire
type and hole-type) can operate perfectly well until temperatures of LN2. In
this paper results of systematic studies of operation of the photosensitive
version of these detectors (combined with reflective or semi-transparent CsI
photocathodes) in the temperature interval of 300-150 K are presented. In
particular, it was demonstrated that both sealed and flushed by a gas detectors
could operate at a quite stable fashion in a year/time scale. Obtained results,
in particular the long-term stability of photosensitive gaseous detectors,
strongly indicate that they can be cheap and simple alternatives to
photomultipliers or avalanche solid-state detectors in LXe TPC applications.Comment: Submitted to the Proceedings of the PSD-7 Conf. in Liverpool, U
The Drift Chambers Of The Nomad Experiment
We present a detailed description of the drift chambers used as an active
target and a tracking device in the NOMAD experiment at CERN. The main
characteristics of these chambers are a large area, a self supporting structure
made of light composite materials and a low cost. A spatial resolution of 150
microns has been achieved with a single hit efficiency of 97%.Comment: 42 pages, 26 figure
Experimental search for the LSND anomaly with the ICARUS detector in the CNGS neutrino beam
We report an early result from the ICARUS experiment on the search for nu_mu
to nu_e signal due to the LSND anomaly. The search was performed with the
ICARUS T600 detector located at the Gran Sasso Laboratory, receiving CNGS
neutrinos from CERN at an average energy of about 20 GeV, after a flight path
of about 730 km. The LSND anomaly would manifest as an excess of nu_e events,
characterized by a fast energy oscillation averaging approximately to
sin^2(1.27 Dm^2_new L/ E_nu) = 1/2. The present analysis is based on 1091
neutrino events, which are about 50% of the ICARUS data collected in 2010-2011.
Two clear nu_e events have been found, compared with the expectation of 3.7 +/-
0.6 events from conventional sources. Within the range of our observations,
this result is compatible with the absence of a LSND anomaly. At 90% and 99%
confidence levels the limits of 3.4 and 7.3 events corresponding to oscillation
probabilities of 5.4 10^-3 and 1.1 10^-2 are set respectively. The result
strongly limits the window of open options for the LSND anomaly to a narrow
region around (Dm^2, sin^2(2 theta))_new = (0.5 eV^2, 0.005), where there is an
overall agreement (90% CL) between the present ICARUS limit, the published
limits of KARMEN and the published positive signals of LSND and MiniBooNE
Collaborations.Comment: 10 pages, 7 figure
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