191 research outputs found
Argentina spectral-agronomic multitemporal data set
A multitemporal LANDSAT spectral data set was created. The data set is over five 5 nm-by-6 nm areas over Argentina and contains by field, the spectral data, vegetation type and cloud cover information
The ALTCRISS project on board the International Space Station
The Altcriss project aims to perform a long term survey of the radiation
environment on board the International Space Station. Measurements are being
performed with active and passive devices in different locations and
orientations of the Russian segment of the station. The goal is to perform a
detailed evaluation of the differences in particle fluence and nuclear
composition due to different shielding material and attitude of the station.
The Sileye-3/Alteino detector is used to identify nuclei up to Iron in the
energy range above 60 MeV/n. Several passive dosimeters (TLDs, CR39) are also
placed in the same location of Sileye-3 detector. Polyethylene shielding is
periodically interposed in front of the detectors to evaluate the effectiveness
of shielding on the nuclear component of the cosmic radiation. The project was
submitted to ESA in reply to the AO in the Life and Physical Science of 2004
and data taking began in December 2005. Dosimeters and data cards are rotated
every six months: up to now three launches of dosimeters and data cards have
been performed and have been returned with the end of expedition 12 and 13.Comment: Accepted for publication on Advances in Space Research
http://dx.doi.org/10.1016/j.asr.2007.04.03
Randomized trial of conventional transseptal needle versus radiofrequency energy needle puncture for left atrial access (the TRAVERSE-LA study).
BackgroundTransseptal puncture is a critical step in achieving left atrial (LA) access for a variety of cardiac procedures. Although the mechanical Brockenbrough needle has historically been used for this procedure, a needle employing radiofrequency (RF) energy has more recently been approved for clinical use. We sought to investigate the comparative effectiveness of an RF versus conventional needle for transseptal LA access.Methods and resultsIn this prospective, single-blinded, controlled trial, 72 patients were randomized in a 1:1 fashion to an RF versus conventional (BRK-1) transseptal needle. In an intention-to-treat analysis, the primary outcome was time required for transseptal LA access. Secondary outcomes included failure of the assigned needle, visible plastic dilator shavings from needle introduction, and any procedural complication. The median transseptal puncture time was 68% shorter using the RF needle compared with the conventional needle (2.3 minutes [interquartile range {IQR}, 1.7 to 3.8 minutes] versus 7.3 minutes [IQR, 2.7 to 14.1 minutes], P = 0.005). Failure to achieve transseptal LA access with the assigned needle was less common using the RF versus conventional needle (0/36 [0%] versus 10/36 [27.8%], P < 0.001). Plastic shavings were grossly visible after needle advancement through the dilator and sheath in 0 (0%) RF needle cases and 12 (33.3%) conventional needle cases (P < 0.001). There were no differences in procedural complications (1/36 [2.8%] versus 1/36 [2.8%]).ConclusionsUse of an RF needle resulted in shorter time to transseptal LA access, less failure in achieving transseptal LA access, and fewer visible plastic shavings
Spaceflight Radiation Health program at the Lyndon B. Johnson Space Center
The Johnson Space Center leads the research and development activities that address the health effects of space radiation exposure to astronaut crews. Increased knowledge of the composition of the environment and of the biological effects of space radiation is required to assess health risks to astronaut crews. The activities at the Johnson Space Center range from quantification of astronaut exposures to fundamental research into the biological effects resulting from exposure to high energy particle radiation. The Spaceflight Radiation Health Program seeks to balance the requirements for operational flexibility with the requirement to minimize crew radiation exposures. The components of the space radiation environment are characterized. Current and future radiation monitoring instrumentation is described. Radiation health risk activities are described for current Shuttle operations and for research development program activities to shape future analysis of health risk
Parametrizations of Inclusive Cross Sections for Pion Production in Proton-Proton Collisions
Accurate knowledge of cross sections for pion production in proton-proton
collisions finds wide application in particle physics, astrophysics, cosmic ray
physics and space radiation problems, especially in situations where an
incident proton is transported through some medium, and one requires knowledge
of the output particle spectrum given the input spectrum. In such cases
accurate parametrizations of the cross sections are desired. In this paper we
review much of the experimental data and compare to a wide variety of different
cross section parametrizations. In so doing, we provide parametrizations of
neutral and charged pion cross sections which provide a very accurate
description of the experimental data. Lorentz invariant differential cross
sections, spectral distributions and total cross section parametrizations are
presented.Comment: 32 pages with 15 figures. Published in Physical Review D62, 094030.
File includes 6 tex files. The main file is paper.tex which has include
statements refering to the rest. figures are in graphs.di
The relationship of myocardial contraction and electrical excitationâthe correlation between scintigraphic phase image analysis and electrophysiologic mapping
Phase imaging derived from equilibrium radionuclide angiography presents the ventricular contraction sequence. It has been widely but only indirectly correlated with the sequence of electrical myocardial activation.
We sought to determine the specific relationship between the sequence of phase progression and the sequence of myocardial activation, contraction and conduction, in order to document a noninvasive method that could monitor both.
In 7 normal and 9 infarcted dogs, the sequence of phase angle was correlated with the epicardial activation map in 126 episodes of sinus rhythm and pacing from three ventricular sites.
In each episode, the site of earliest phase angle was identical to the focus of initial epicardial activation. Similarly, the serial contraction pattern by phase image analysis matched the electrical epicardial activation sequence completely or demonstrated good agreement in approximately 85% of pacing episodes, without differences between normal or infarct groups.
A noninvasive method to accurately determine the sequence of contraction may serve as a surrogate for the associated electrical activation sequence or be applied to identify their differences
Constraining the population of cosmic ray protons in cooling flow clusters with gamma-ray and radio observations: Are radio mini-halos of hadronic origin?
We wish to constrain the cosmic-ray proton (CRp) population in galaxy
clusters. By hadronic interactions with the thermal gas of the intra-cluster
medium (ICM), the CRp produce gamma-rays for which we develop an analytic
formalism to deduce their spectral distribution. Assuming the CRp-to-thermal
energy density ratio X_CRp and the CRp spectral index to be spatially constant,
we derive an analytic relation between the gamma-ray and bolometric X-ray
fluxes, F_gamma and F_X. Based on our relation, we compile a sample of suitable
clusters which are promising candidates for future detection of gamma-rays
resulting from hadronic CRp interactions. Comparing to EGRET upper limits, we
constrain the CRp population in the cooling flow clusters Perseus and Virgo to
X_CRp < 20%. Assuming a plausible value for the CRp diffusion coefficient
kappa, we find the central CRp injection luminosity of M 87 to be limited to
10^43 erg s^-1 kappa/(10^29 cm^2 s^-1). The synchrotron emission from secondary
electrons generated in CRp hadronic interactions allows even tighter limits to
be placed on the CRp population using radio observations. We obtain excellent
agreement between the observed and theoretical radio brightness profiles for
Perseus, but not for Coma without a radially increasing CRp-to-thermal energy
density profile. Since the CRp and magnetic energy densities necessary to
reproduce the observed radio flux are very plausible, we propose synchrotron
emission from secondary electrons as an attractive explanation of the radio
mini-halos found in cooling flow clusters. This model can be tested with future
sensitive gamma-ray observations of the accompanying pi0-decays. We identify
Perseus (A 426), Virgo, Ophiuchus, and Coma (A 1656) as the most promising
candidate clusters for such observations.Comment: 20 pages, 8 figures. Corrected Figure 3 to match the erratum accepted
by A&
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Galactic cosmic radiation in the interplanetary space through a modern secular minimum
Recent solar conditions indicate a persistent decline in solar activityâpossibly similar to thepast solar grand minima. During such periods of low solar activity, the fluxes of galactic cosmic rays(GCRs) increase remarkably, presenting a hazard for long-term crewed space missions. We used data fromthe Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter(LRO) to examine the correlation between the heliospheric magnetic field, solar wind speed, and solarmodulation potential of the GCRs through Cycle 24. We used this correlation to project observations frompast secular solar minima, including the Dalton minimum (1790â1830) and the Gleissberg minimum(1890â1920), into the next cycle. For the case of conditions similar to the Dalton (or Gleissberg) minimum,the heliospheric magnetic field could drop to 3.61 (or 4.06) nT, leading to a dose rate increase of75% (or34%). We showed that accounting for a floor in the modulation potential, invoked by the Badhwar-O'Neill2014 model, moderates the projected radiation levels in Cycle 25. We used these results to determine themost conservative permissible mission duration (PMD,290.4+37.7â35.9and 204.3+26.6â25.2days for 45-year-old maleand female astronauts, respectively) based on a 3% risk of exposure-induced death (REID) at the upper95% confidence interval in interplanetary space
Balloon Measurements of Cosmic Ray Muon Spectra in the Atmosphere along with those of Primary Protons and Helium Nuclei over Mid-Latitude
We report here the measurements of the energy spectra of atmospheric muons
and of the cosmic ray primary proton and helium nuclei in a single experiment.
These were carried out using the MASS superconducting spectrometer in a balloon
flight experiment in 1991. The relevance of these results to the atmospheric
neutrino anomaly is emphasized. In particular, this approach allows
uncertainties caused by the level of solar modulation, the geomagnetic cut-off
of the primaries and possible experimental systematics to be decoupled in the
comparison of calculated fluxes of muons to measured muon fluxes. The muon
observations cover the momentum and depth ranges of 0.3-40 GeV/c and 5-886
g/cmsquared, respectively. The proton and helium primary measurements cover the
rigidity range from 3 to 100 GV, in which both the solar modulation and the
geomagnetic cut-off affect the energy spectra at low energies.Comment: 31 pages, including 17 figures, simplified apparatus figure, to
appear in Phys. Rev.
Artificial intelligence for dementia research methods optimization
Artificial intelligence (AI) and machine learning (ML) approaches are increasingly being used in dementia research. However, several methodological challenges exist that may limit the insights we can obtain from high-dimensional data and our ability to translate these findings into improved patient outcomes. To improve reproducibility and replicability, researchers should make their well-documented code and modeling pipelines openly available. Data should also be shared where appropriate. To enhance the acceptability of models and AI-enabled systems to users, researchers should prioritize interpretable methods that provide insights into how decisions are generated. Models should be developed using multiple, diverse datasets to improve robustness, generalizability, and reduce potentially harmful bias. To improve clarity and reproducibility, researchers should adhere to reporting guidelines that are co-produced with multiple stakeholders. If these methodological challenges are overcome, AI and ML hold enormous promise for changing the landscape of dementia research and care
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