1,405 research outputs found
Community Organization Practice: An Elaboration of Rothman\u27s Typology
Four change approaches encompass much purposive social change at the community level: locality development, traditional planning, advocacy planning and social action. Locality development and traditional planning are similar on at least six dimensions, as are advocacy planning and social action. On two other dimensions similarities exist between locality development and social action and between traditional planning and advocacy planning. If social change practitioners are to select the most effective strategies for the situations in which they will act, it is essential that they understand the characteristics and assumptions of these approaches
Radio Emission from SN 2001gd in NGC 5033
We present the results of monitoring the radio emission from the Type IIb
supernova SN 2001gd between 2002 February 8 and 2002 October 28. Most of the
data were obtained using the Very Large Array at the five wavelengths of
1.3 cm (22.4 GHz), 2.0 cm (14.9 GHz), 3.6 cm (8.44 GHz), 6.2
cm (4.86 GHz), and 21 cm (1.4 GHz). Observations were also made with Giant
Meterwave Radio Telescope at 21 cm (1.4 GHz). The object was
discovered optically well after maximum light, making any determination of the
early radio evolution difficult. However, subsequent observations indicate that
the radio emission has evolved regularly in both time and frequency and is well
described by the SN shock/circumstellar medium interaction model.Comment: 16 pages 2 figures to appear in Astrophysical Journa
Neutrino Phenomenology in a 3+1+1 Framework
Evidence continues to grow in the MiniBooNE (MB) antineutrino mode supporting
a low-energy excess compatible with the MB neutrino mode and possibly also
confirming the results of the LSND experiment. At least one sterile neutrino is
required to explain the anomalies consistent with the observations of other
experiments. At the same time, there is a strong tension between the positive
signals of LSND and MB and the null results of nu_e and nu_mu disappearance
experiments. We explore a scenario, first proposed in \cite{Nelson:2010hz},
where the presence of an additional heavy sterile neutrino (with mass well
above an eV) can alleviate tension between LSND, MB and the null results of
disappearance experiments. We compare and contrast this 3+1+1 scenario with the
more standard 3+1 scenario and carry out global fits to all oscillation data
including new 2011 MB anti-nu data. We find that the tension can be somewhat
alleviated and that a phenomenologically viable window for the heavy neutrino,
consistent with rare decays and BBN constraints, can be found if the fifth
neutrino has a mass of order 0.3 - 10 GeV. We also find, however, that the 2011
MB anti-nu data exacerbates the tension with null experiments in both the 3+1
and 3+1+1 models when the lowest energy bins are included, resulting in little
improvement in the global fit. We also discuss the implications of an
additional neutrino for the reactor and gallium anomalies, and show that an
oscillation explanation of the anomalies is disfavored by cosmological
considerations, direct searches, and precision electroweak tests.Comment: 22 pages, 5 figures; replaced to reflect journal versio
The Insect Situation in 1968
What happened last year will have some influence on insect conditions in 1968. The authors provice some suggestions on what to look for, and how to handle both crop and livestock insect problems
Insect Control in 1967
Advances in chemical control and farming procedures will let you win the battle agaisnt the bugs, but many questions concerning these measures need to be answered for you
Recovery of the Historical SN1957D in X-rays with Chandra
SN1957D, located in one of the spiral arms of M83, is one of the small number
of extragalactic supernovae that has remained detectable at radio and optical
wavelengths during the decades after its explosion. Here we report the first
detection of SN1957D in X-rays, as part of a 729 ks observation of M83 with
\chandra. The X-ray luminosity (0.3 - 8 keV) is 1.7 (+2.4,-0.3) 10**37 ergs/s.
The spectrum is hard and highly self-absorbed compared to most sources in M83
and to other young supernova remnants, suggesting that the system is dominated
at X-ray wavelengths by an energetic pulsar and its pulsar wind nebula. The
high column density may be due to absorption within the SN ejecta. HST WFC3
images resolve the supernova remnant from the surrounding emission and the
local star field. Photometry of stars around SN1957D, using WFC3 images,
indicates an age of less than 10**7 years and a main sequence turnoff mass more
than 17 solar masses. New spectra obtained with Gemini-South show that the
optical spectrum continues to be dominated by broad [O III] emission lines, the
signature of fast-moving SN ejecta. The width of the broad lines has remained
about 2700 km/s (FWHM). The [O III] flux dropped precipitously between 1989 and
1991, but continued monitoring shows the flux has been almost constant since.
In contrast, radio observations over the period 1990-2011 show a decline rate
inf the flux proportional to t**-4, far steeper than the rate observed earlier,
suggesting that the primary shock has overrun the edge of a pre-SN wind.Comment: 28 pages, including 3 tables and 7 figures, accepted for publication
in Ap
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