809 research outputs found
Disaster and emergency communications prior to computers/Internet: a review
When communications are needed the most desperately and most urgently, the difficulty of effecting the desired communications increases exponentially. Recent natural disasters in different parts of the world have provided eloquent testament to this. The history of disaster or emergency communications can provide us with a foundation for understanding the problems encountered today, and can offer us insight into how we might improve the systems and processes for communications. The first applications of communication technology that allowed messages to be sent more rapidly than the fastest form of transportation were mainly military in origin. This review takes us from the days of optical or visual telegraphy, through the early development of mobile and radio communications, and up to the current sophisticated technologies. We pay particular attention to the use of amateur radio operators in times of emergency, and relate their activities to those of the most effective military communications. The germane assumption made in this discussion is that any emergency or disaster communications would necessarily be involved in response and resolution of medical aspects of those emergencies
A Quarter-Century of Observations of Comet 10P/Tempel 2 at Lowell Observatory: Continued Spin-Down, Coma Morphology, Production Rates, and Numerical Modeling
We report on photometry and imaging of Comet 10P/Tempel 2 obtained at Lowell
Observatory from 1983 through 2011. We measured a nucleus rotation period of
8.950 +/- 0.002 hr from 2010 September to 2011 January. This rotation period is
longer than the period we previously measured in 1999, which was itself longer
than the period measured in 1988. A nearly linear jet was observed which varied
little during a rotation cycle in both R and CN images acquired during the 1999
and 2010 apparitions. We measured the projected direction of this jet
throughout the two apparitions and, under the assumption that the source region
of the jet was near the comet's pole, determined a rotational pole direction of
RA/Dec = 151deg/+59deg from CN measurements and RA/Dec = 173deg/+57deg from
dust measurements (we estimate a circular uncertainty of 3deg for CN and 4deg
for dust). Different combinations of effects likely bias both gas and dust
solutions and we elected to average these solutions for a final pole of RA/Dec
= 162 +/- 11deg/+58 +/- 1deg. Photoelectric photometry was acquired in 1983,
1988, 1999/2000, and 2010/2011. The activity exhibited a steep turn-on ~3
months prior to perihelion (the exact timing of which varies) and a relatively
smooth decline after perihelion. The activity during the 1999 and 2010
apparitions was similar; limited data in 1983 and 1988 were systematically
higher and the difference cannot be explained entirely by the smaller
perihelion distance. We measured a "typical" composition, in agreement with
previous investigators. Monte Carlo numerical modeling with our pole solution
best replicated the observed coma morphology for a source region located near a
comet latitude of +80deg and having a radius of ~10deg. Our model reproduced
the seasonal changes in activity, suggesting that the majority of Tempel 2's
activity originates from a small active region located near the pole.Comment: Accepted by AJ; 29 pages of text (preprint style), 8 tables, 7
figure
The Increasing Rotation Period of Comet 10P/Tempel 2
We imaged comet 10P/Tempel 2 on 32 nights from 1999 April through 2000 March.
R-band lightcurves were obtained on 11 of these nights from 1999 April through
1999 June, prior to both the onset of significant coma activity and perihelion.
Phasing of the data yields a double-peaked lightcurve and indicates a nucleus
rotational period of 8.941 +/- 0.002 hr with a peak-to-peak amplitude of ~0.75
mag. Our data are sufficient to rule out all other possible double-peaked
solutions as well as the single- and triple- peaked solutions. This rotation
period agrees with one of five possible solutions found in post-perihelion data
from 1994 by Mueller and Ferrin (1996, Icarus, 123, 463-477), and unambiguously
eliminates their remaining four solutions. We applied our same techniques to
published lightcurves from 1988 which were obtained at an equivalent orbital
position and viewing geometry as in 1999. We found a rotation period of 8.932
+/- 0.001 hr in 1988, consistent with the findings of previous authors and
incompatible with our 1999 solution. This reveals that Tempel 2 spun-down by
~32 s between 1988 and 1999 (two intervening perihelion passages). If the
spin-down is due to a systematic torque, then the rotation period prior to
perihelion during the 2010 apparition is expected to be an additional 32 s
longer than in 1999.Comment: Accepted by The Astronomical Journal; 22 pages of text, 3 tables, 6
figure
Spitzer Space Telescope Observations of the Nucleus of Comet 103P/Hartley 2
We have used the Spitzer Space Telescope InfraRed Spectrograph (IRS) 22-μm peakup array to observe thermal emission from the nucleus and trail of comet 103P/Hartley 2, the target of NASA’s Deep Impact Extended Investigation (DIXI). The comet was observed on UT 2008 August 12 and 13, while 5.5 AU from the Sun. We obtained two 200 frame sets of photometric imaging over a 2.7 hr period. To within the errors of the measurement, we find no detection of any temporal variation between the two images. The comet showed extended emission beyond a point source in the form of a faint trail directed along the comet’s antivelocity vector. After modeling and removing the trail emission, a NEATM model for the nuclear emission with beaming parameter of 0.95 ± 0.20 indicates a small effective radius for the nucleus of 0.57 ± 0.08 km and low geometric albedo 0.028 ± 0.009 (1σ). With this nucleus size and a water production rate of 3 × 10^(28) molecules s^(-1) at perihelion, we estimate that ~100% of the surface area is actively emitting volatile material at perihelion. Reports of emission activity out to ~5 AU support our finding of a highly active nuclear surface. Compared to Deep Impact’s first target, comet 9P/Tempel 1, Hartley 2’s nucleus is one-fifth as wide (and about one-hundredth the mass) while producing a similar amount of outgassing at perihelion with about 13 times the active surface fraction. Unlike Tempel 1, comet Hartley 2 should be highly susceptible to jet driven spin-up torques, and so could be rotating at a much higher frequency. Since the amplitude of nongravitational forces are surprisingly similar for both comets, close to the ensemble average for ecliptic comets, we conclude that comet Hartley 2 must have a much more isotropic pattern of time-averaged outgassing from its nuclear surface. Barring a catastrophic breakup or major fragmentation event, the comet should be able to survive up to another 100 apparitions (~700 yr) at its current rate of mass loss
Associations between natural resource extraction and incidence of acute and chronic health conditions: evidence from Tanzania
Natural resource extraction projects are often accompanied by complex environmental and social-ecological changes. In this paper, we evaluated the association between commodity extraction and the incidence of diseases. We retrieved council (district)-level outpatient data from all public and private health facilities from the District Health Information System (DHIS2). We combined this information with population data from the 2012 national population census and a geocoded list of resource extraction projects from the Geological Survey of Tanzania (GST). We used Poisson regression with random effects and cluster-robust standard errors to estimate the district-level associations between the presence of three types of commodity extraction (metals, gemstone, and construction materials) and the total number of patients in each disease category in each year. Metal extraction was associated with reduced incidence of several diseases, including chronic diseases (IRR = 0.61, CI: 0.47-0.80), mental health disorders (IRR = 0.66, CI: 0.47-0.92), and undernutrition (IRR = 0.69, CI: 0.55-0.88). Extraction of construction materials was associated with an increased incidence of chronic diseases (IRR = 1.47, CI: 1.15-1.87). This study found that the presence of natural resources commodity extraction is significantly associated with changes in disease-specific patient volumes reported in Tanzania's DHIS2. These associations differed substantially between commodities, with the most protective effects shown from metal extraction
The Claims Culture: A Taxonomy of Industry Attitudes
This paper presents an analysis of a familiar aspect of construction industry culture that we have dubbed 'the claims culture'. This is a culture of contract administration that lays a strong emphasis on the planning and management of claims. The principal elements of the analysis are two sets of distinctions. The first comprises economic and occupational orders, referring to two kinds of control that are exercised over the construction process; predicated respectively on economic ownership and occupational competence. The second refers to contrasting attitudes towards relationships and problem solving within these orders: respectively 'distributive' and 'integrative'. The concepts of economic and occupational order entail further sub-categories. The various attitudes associated with these categories and sub-categories are described. They are assessed as to their consequences for change initiatives in the industry
Rotation-stimulated structures in the CN and C3 comae of comet 103P/Hartley 2 around the EPOXI encounter
In late 2010 a Jupiter Family comet 103P/Hartley 2 was a subject of an
intensive world-wide investigation. On UT October 20.7 the comet approached the
Earth within only 0.12 AU, and on UT November 4.6 it was visited by NASA's
EPOXI spacecraft. We joined this international effort and organized an
observing campaign. The images of the comet were obtained through narrowband
filters using the 2-m telescope of the Rozhen National Astronomical
Observatory. They were taken during 4 nights around the moment of the EPOXI
encounter. Image processing methods and periodicity analysis techniques were
used to reveal transient coma structures and investigate their repeatability
and kinematics. We observe shells, arc-, jet- and spiral-like patterns, very
similar for the CN and C3 comae. The CN features expanded outwards with the
sky-plane projected velocities between 0.1 to 0.3 km/s. A corkscrew structure,
observed on November 6, evolved with a much higher velocity of 0.66 km/s.
Photometry of the inner coma of CN shows variability with a period of
18.32+/-0.30 h (valid for the middle moment of our run, UT 2010 Nov. 5.0835),
which we attribute to the nucleus rotation. This result is fully consistent
with independent determinations around the same time by other teams. The
pattern of repeatability is, however, not perfect, which is understendable
given the suggested excitation of the rotation state, and the variability
detected in CN correlates well with the cyclic changes in HCN, but only in the
active phases. The revealed coma structures, along with the snapshot of the
nucleus orientation obtained by EPOXI, let us estimate the spin axis
orientation. We obtained RA=122 deg, Dec=+16 deg (epoch J2000.0), neglecting at
this point the rotational excitation.Comment: 9 pages, 10 figures, submitted to Astron. Astrophy
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