1,178 research outputs found
Success Factors for New Generation Cooperatives
The goal of this research was to determine success factors for New Generation Cooperatives (NGCs). A self-explicated approach was used to assess the importance of various factors grouped in broad categories using data collected from a mailout survey of NGC managers. Results suggest that factors in the "Planning and Development" and "Financing and Costs" categories are considered to be critically important by NGC managers, though differences in factor rankings exist between managers of enterprises involved in the processing of different commodities.New Generation Cooperative, self-explication, Agribusiness,
SUCCESS FACTORS FOR VALUE ADDED NEW GENERATION COOPERATIVES
Two surveys of New Generation Cooperative (NGC) managers were carried out to ascertain the factors most important to their success. Factors in the Planning and Development as well as the Financing and Cost categories were most important, and NGCs with more employees and more members' equity are most successful.Agribusiness,
First Assessment of Mountains on Northwestern Ellesmere Island, Nunavut, as Potential Astronomical Observing Sites
Ellesmere Island, at the most northerly tip of Canada, possesses the highest
mountain peaks within 10 degrees of the pole. The highest is 2616 m, with many
summits over 1000 m, high enough to place them above a stable low-elevation
thermal inversion that persists through winter darkness. Our group has studied
four mountains along the northwestern coast which have the additional benefit
of smooth onshore airflow from the ice-locked Arctic Ocean. We deployed small
robotic site testing stations at three sites, the highest of which is over 1600
m and within 8 degrees of the pole. Basic weather and sky clarity data for over
three years beginning in 2006 are presented here, and compared with available
nearby sea-level data and one manned mid-elevation site. Our results point to
coastal mountain sites experiencing good weather: low median wind speed, high
clear-sky fraction and the expectation of excellent seeing. Some practical
aspects of access to these remote locations and operation and maintenance of
equipment there are also discussed.Comment: 21 pages, 2 tables, 15 figures; accepted for publication in PAS
Formation of Primordial Protostars
The evolution of collapsing metal free protostellar clouds is investigated
for various masses and initial conditions.
We perform hydrodynamical calculations for spherically symmetric clouds
taking account of radiative transfer of the molecular hydrogen lines and the
continuum, as well as of chemistry of the molecular hydrogen.
The collapse is found to proceed almost self-similarly like Larson-Penston
similarity solution.
In the course of the collapse, efficient three-body processes transform
atomic hydrogen in an inner region of \sim 1 M_{\sun} entirely into molecular
form.
However, hydrogen in the outer part remains totally atomic although there is
an intervening transitional layer of several solar masses, where hydrogen is in
partially molecular form.
No opaque transient core is formed although clouds become optically thick to
H collision-induced absorption continuum, since H dissociation
follows successively.
When the central part of the cloud reaches stellar densities (), a very small hydrostatic core (\sim
5 \times 10^{-3} M_{\sun}) is formed and subsequently grows in mass as the
ambient gas accretes onto it.
The mass accretion rate is estimated to be 3.7 \times 10^{-2} M_{\sun}
{\rm yr^{-1}} (M_{\ast}/M_{\sun})^{-0.37}, where is instantaneous
mass of the central core, by using a similarity solution which reproduces the
evolution of the cloud before the core formation.Comment: 20 pages, 5 Postscript figures, uses AAS LaTe
Protostellar Collapse with Various Metallicities
The thermal and chemical evolution of gravitationally collapsing protostellar
clouds is investigated, focusing attention on their dependence on metallicity.
Calculations are carried out for a range of metallicities spanning the local
interstellar value to zero. During the time when clouds are transparent to
continuous radiation, the temperatures are higher for those with lower
metallicity, reflecting lower radiative ability. However, once the clouds
become opaque, in the course of the adiabatic contraction of the transient
cores, their evolutionary trajectories in the density-temperature plane
converge to a unique curve that is determined by only physical constants. The
trajectories coincide with each other thereafter. Consequently, the size of the
stellar core at the formation is the same regardless of the gas composition of
the parent cloud.Comment: 30 pages. The Astrophysical Journal, 533, in pres
Forming the First Stars in the Universe: The Fragmentation of Primordial Gas
In order to constrain the initial mass function (IMF) of the first generation
of stars (Population III), we investigate the fragmentation properties of
metal-free gas in the context of a hierarchical model of structure formation.
We investigate the evolution of an isolated 3-sigma peak of mass 2x10^6 M_solar
which collapses at z_coll=30 using Smoothed Particle Hydrodynamics. We find
that the gas dissipatively settles into a rotationally supported disk which has
a very filamentary morphology. The gas in these filaments is Jeans unstable
with M_J~10^3 M_solar. Fragmentation leads to the formation of high density
(n>10^8 cm^-3) clumps which subsequently grow in mass by accreting surrounding
gas and by merging with other clumps up to masses of ~10^4 M_solar. This
suggests that the very first stars were rather massive. We explore the complex
dynamics of the merging and tidal disruption of these clumps by following their
evolution over a few dynamical times.Comment: 7 pages, 3 figures, uses emulateapj.sty. Accepted for publication in
the Astrophysical Journal Letter
Primordial Star Formation under Far-ultraviolet radiation
Thermal and chemical evolution of primordial gas clouds irradiated with
far-ultraviolet (FUV; < 13.6 eV) radiation is investigated. In clouds
irradiated by intense FUV radiation, sufficient hydrogen molecules to be
important for cooling are never formed. However, even without molecular
hydrogen, if the clouds are massive enough, they start collapsing via atomic
hydrogen line cooling. Such clouds continue to collapse almost isothermally
owing to successive cooling by H^{-} free-bound emission up to the number
density of 10^{16} cm^{-3}. Inside the clouds, the Jeans mass eventually falls
well below a solar mass. This indicates that hydrogen molecules are dispensable
for low-mass primordial star formation, provided fragmentation of the clouds
occurs at sufficiently high density.Comment: 32 pages and 9 figures. ApJ, in pres
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