2,579 research outputs found
Direct Measurements of Interplanetary Dust Particles in the Vicinity of Earth
The direct measurements made by the Explorer VIII satellite provide the first sound basis for analyzing all available direct measurements of the distribution of interplanetary dust particles. The model average distribution curve established by such an analysis departs significantly from that predicted by the (uncertain) extrapolation of results from meteor observations. A consequence of this difference is that the daily accretion of interplanetary particulate matter by the earth is now considered to be mainly dust particles of the direct measurements range of particle size. Almost all the available direct measurements obtained with microphone systems on rockets, satellites, and spacecraft fit directly on the distribution curve defined by Explorer VIII data. The lack of reliable datum points departing significantly from the model average distribution curve means that available direct measurements show no discernible evidence of an appreciable geocentric concentration of interplanetary dust particles
Relativistic Proton Production During the 14 July 2000 Solar Event: The Case for Multiple Source Mechanisms
Protons accelerated to relativistic energies by transient solar and
interplanetary phenomena caused a ground-level cosmic ray enhancement on 14
July 2000, Bastille Day. Near-Earth spacecraft measured the proton flux
directly and ground-based observatories measured the secondary responses to
higher energy protons. We have modelled the arrival of these relativistic
protons at Earth using a technique which deduces the spectrum, arrival
direction and anisotropy of the high-energy protons that produce increased
responses in neutron monitors. To investigate the acceleration processes
involved we have employed theoretical shock and stochastic acceleration
spectral forms in our fits to spacecraft and neutron monitor data. During the
rising phase of the event (10:45 UT and 10:50 UT) we find that the spectrum
between 140 MeV and 4 GeV is best fitted by a shock acceleration spectrum. In
contrast, the spectrum at the peak (10:55 UT and 11:00 UT) and in the declining
phase (11:40 UT) is best fitted with a stochastic acceleration spectrum. We
propose that at least two acceleration processes were responsible for the
production of relativistic protons during the Bastille Day solar event: (1)
protons were accelerated to relativistic energies by a shock, presumably a
coronal mass ejection (CME). (2) protons were also accelerated to relativistic
energies by stochastic processes initiated by magnetohydrodynamic (MHD)
turbulence.Comment: 38 pages, 9 figures, accepted for publication in the Astrophysical
Journal, January, 200
XMM-Newton Surveys of the Canada-France Redshift Survey Fields - III: The Environments of X-ray Selected AGN at 0.4<z<0.6
The environmental properties of a sample of 31 hard X-ray selected AGN are
investigated, from scales of 500 kpc down to 30 kpc, and are compared to a
control sample of inactive galaxies. The AGN all lie in the redshift range
0.4<z<0.6. The accretion luminosity-density of the Universe peaks close to this
redshift range, and the AGN in the sample have X-ray luminosities close to the
knee in the hard X-ray luminosity function, making them representative of the
population which dominated this important phase of energy conversion.
Using both the spatial clustering amplitude and near neighbour counts it is
found that the AGN have environments that are indistinguishable from normal,
inactive galaxies over the same redshift range and with similar optical
properties. Typically, the environments are of sub-cluster richness, in
contrast to similar studies of high-z quasars, which are often found in
clusters with comparable richness to the Abell R>=0 clusters.
It is suggested that minor mergers with low mass companions is a likely
candidate for the mechanism by which these modest luminosity AGN are fuelled.Comment: 12 pages, 6 figures, accepted by MNRA
XMM—Newton surveys of the Canada—France Redshift Survey Fields — III. The environments of X-ray selected active galactic nuclei at 0.4 < z < 0.6
The environmental properties of a sample of 31 hard X-ray selected active galactic nuclei (AGN) are investigated, from scales of 500 kpc down to 30 kpc, and are compared to a control sample of inactive galaxies. All the AGN lie in the redshift range 0.4 < z < 0.6. The accretion luminosity density of the Universe peaks close to this redshift range, and the AGN in the sample have X-ray luminosities close to the knee in the hard X-ray luminosity function, making them representative of the population that dominated this important phase of energy conversion. Using both the spatial clustering amplitude and near-neighbour counts, it is found that the AGN have environments that are indistinguishable from normal, inactive galaxies over the same redshift range and with similar optical properties. Typically, the environments are of subcluster richness, in contrast to similar studies of high-z quasars, which are often found in clusters with comparable richness to the Abell R≥ 0 clusters. It is suggested that minor mergers with low-mass companions are a likely candidate for the mechanism by which these modest luminosity AGN are fuelle
MAPIR: An Airborne Polarmetric Imaging Radiometer in Support of Hydrologic Satellite Observations
In this age of dwindling water resources and increasing demands, accurate estimation of water balance components at every scale is more critical to end users than ever before. Several near-term Earth science satellite missions are aimed at global hydrologic observations. The Marshall Airborne Polarimetric Imaging Radiometer (MAPIR) is a dual beam, dual angle polarimetric, scanning L band passive microwave radiometer system developed by the Observing Microwave Emissions for Geophysical Applications (OMEGA) team at MSFC to support algorithm development and validation efforts in support of these missions. MAPIR observes naturally-emitted radiation from the ground primarily for remote sensing of land surface brightness temperature from which we can retrieve soil moisture and possibly surface or water temperature and ocean salinity. MAPIR has achieved Technical Readiness Level 6 with flight heritage on two very different aircraft, the NASA P-3B, and a Piper Navajo
Measuring ‘self’: preliminary validation of a short form of the self experiences questionnaire in people with chronic pain
Background: People with chronic pain often struggle with their sense of self and this can adversely impact their functioning and wellbeing. Acceptance and Commitment Therapy particularly includes a process related to this struggle with self. A measure for this process, the Self Experiences Questionnaire, was previously developed in people with chronic pain.
Purpose: The aim of the current study was to validate a shorter version of the Self Experiences Questionnaire in people with chronic pain to reduce respondent burden and facilitate further research.
Methods: Data from 477 participants attending an interdisciplinary pain management programme were included. Participants completed measures of treatment processes (self-as-context, pain acceptance, cognitive fusion, and committed action) and outcomes (pain, pain interference, work and social adjustment, and depression) at baseline and post-treatment. Confirmatory factor analysis was used for item reduction. Correlations between scores from the shorter Self Experiences Questionnaire and other process and outcome variables were calculated to examine validity. Change scores of the shorter Self Experiences Questionnaire and their correlations with changes in outcome variables were examined for responsiveness.
Results: An eight-item SEQ (SEQ-8) scale including two factors, namely Self-as-Distinction and Self-as-Observer, emerged, demonstrating good reliability (Cronbach’s α=.87-.90) and validity (|r|=.14-.52). Scores from SEQ-8 significantly improved after the treatment (d=.15-21), and these improvements correlated with improvements in most outcomes.
Conclusions: The SEQ-8 appears to be a reliable and valid measure of self. This shorter format may facilitate intensive longitudinal investigation into sense of self and functioning and wellbeing
Can Graduating Students Design Software Systems?
This paper examines software designs produced by students nearing completion of their Computer Science degrees. The results of this multi-national, multi-institutional experiment present some interesting implications for educators
Nurses\u27 Alumnae Association Bulletin, June 1969
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Officers and Chairmen
Financial Report
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