10,905 research outputs found
The Changing Debt Maturity Structure of U.S. Farms
The objectives of this paper are to examine the debt maturity structure of farm businesses and to investigate the determinants of the farm businesses’ choice of the maturity structure. Based on 2008 ARMS data, our findings indicate that size, asset maturity, financial risk, region, and type of farm operation influenced the debt maturity structure in 2008.Debt maturity structure, farm debt, tobit, Agricultural Finance, G10,
Arable land allocations as a winter forage reserve for cattle in communal areas of central eastern Cape Province, South Africa
Parameters affecting ion intensities in transmission-mode Direct Analysis in Real-Time mass spectrometry
A survey of the effect of temperature, transmission module material and analysis time on ion intensities in transmission mode direct analysis in real time mass spectrometry is presented. Ion intensity profiles obtained for two related compounds are similar when analysed separately but are very different when analysed as a mixture
BioNetGen 2.2: Advances in Rule-Based Modeling
BioNetGen is an open-source software package for rule-based modeling of
complex biochemical systems. Version 2.2 of the software introduces numerous
new features for both model specification and simulation. Here, we report on
these additions, discussing how they facilitate the construction, simulation,
and analysis of larger and more complex models than previously possible.Comment: 3 pages, 1 figure, 1 supplementary text file. Supplementary text
includes a brief discussion of the RK-PLA along with a performance analysis,
two tables listing all new actions/arguments added in BioNetGen 2.2, and the
"BioNetGen Quick Reference Guide". Accepted for publication in Bioinformatic
Spatial variation of the physical conditions of molecular gas in galaxies
Multi-line studies of CO-12, CO-13, C-18O, HCN, and HCO(+) at 3 mm, 1.3 mm, and 0.8 mm using the Institute for Radio Astronomy in the Millimeter range (IRAM) 30 m telescope, with the IRAM superconductor insulator superconductor (SIS) receivers and the Max Planck Institute for External Physics (MPE) 350 GHz SIS receiver, show that the densities and temperatures of molecular gas in external galaxies change significantly with position. CO-12 measures the densities and temperature of diffuse interclump molecular gas, but not the bulk of the molecular gas. Simple one-component models, with or without external heating, cannot account for the weakness of the CO-12 J = 3 to 2 line relative to J = 2 to 1 and J = 1 to 0. CO-12 does not trace the bulk of the molecular gas, and optical depth effects obviate a straightforward interpretation of CO-12 data. Instead, researchers turned to the optically thin CO isotopes and other molecular species. Isotopic CO lines measure the bulk of the molecular gas, and HCN and HCO(+) pick out denser regions. Researchers find a warm ridge of gas in IC 342 (Eckart et al. 1989), denser gas in the starburst nucleus of IC 342, and a possible hot-spot in NGC 2903. In IC 342, NGC 2146, and NGC 6764, the CO-13 J = 2 to 1 line is subthermally populated, implying gas densities less than or equal to 10(exp 4) cm(-3)
Rating the Financial Health of U.S. Production Agriculture using Synthetic Credit Rating
Agribusiness, Agricultural and Food Policy, Production Economics,
Communities and bottlenecks: Trees and treelike networks have high modularity
Much effort has gone into understanding the modular nature of complex
networks. Communities, also known as clusters or modules, are typically
considered to be densely interconnected groups of nodes that are only sparsely
connected to other groups in the network. Discovering high quality communities
is a difficult and important problem in a number of areas. The most popular
approach is the objective function known as modularity, used both to discover
communities and to measure their strength. To understand the modular structure
of networks it is then crucial to know how such functions evaluate different
topologies, what features they account for, and what implicit assumptions they
may make. We show that trees and treelike networks can have unexpectedly and
often arbitrarily high values of modularity. This is surprising since trees are
maximally sparse connected graphs and are not typically considered to possess
modular structure, yet the nonlocal null model used by modularity assigns low
probabilities, and thus high significance, to the densities of these sparse
tree communities. We further study the practical performance of popular methods
on model trees and on a genealogical data set and find that the discovered
communities also have very high modularity, often approaching its maximum
value. Statistical tests reveal the communities in trees to be significant, in
contrast with known results for partitions of sparse, random graphs.Comment: 9 pages, 5 figure
Report on the 2013 Rapid Assessment Survey of Marine Species at New England Bays and Harbors
Introduced species (i.e., non-native species that have become established in a new location) have increasingly been recognized as a concern as they have become more prevalent in marine and terrestrial environments (Mooney and Cleland 2001; Simberloff et al. 2005). The ability of introduced species to alter population, community, and ecosystem structure and function, as well as cause significant economic damage is well documented (Carlton 1989, 1996b, 2000; Cohen and Carlton 1995; Cohen et al. 1995; Elton 1958; Meinesz et al. 1993; Occhipinti-Ambrogi and Sheppard 2007; Pimentel et al. 2005; Thresher 2000). The annual economic costs incurred from managing the approximately 50,000 introduced species in the United States alone are estimated to be over $120 billion (Pimentel et al. 2005). Having a monitoring network in place to track new introductions and distributional changes of introduced species is critical for effective management, as these efforts may be more successful when species are detected before they have the chance to become established. A rapid assessment survey is one such method for early detection of introduced species. With rapid assessment surveys, a team of taxonomic experts record and monitor marine species–providing a baseline inventory of native, introduced, and cryptogenic (i.e., unknown origin) species (as defined by Carlton 1996a)–and document range expansions of previously identified species. Since 2000, five rapid assessment surveys have been conducted in New England. These surveys focus on recording species at marinas, which often are in close proximity to transportation vectors (i.e., recreational boats). Species are collected from floating docks and piers because these structures are accessible regardless of the tidal cycle. Another reason for sampling floating docks and other floating structures is that marine introduced species are often found to be more prevalent on artificial surfaces than natural surfaces (Glasby and Connell 2001; Paulay et al. 2002). The primary objectives of these surveys are to: (1) identify native, introduced, and cryptogenic marine species, (2) expand on data collected in past surveys, (3) assess the introduction status and range extensions of documented introduced species, and (4) detect new introductions. This report presents the introduced, cryptogenic, and native species recorded during the 2013 survey
Interstellar Carbon in Translucent Sightlines
We report interstellar C II column densities or upper limits determined from
weak absorption of the 2325.4029 A intersystem transition observed in six
translucent sightlines with STIS. The sightlines sample a wide range of
interstellar characteristics including total-to-selective extinction, R_{V} =
2.6 - 5.1; average hydrogen density along the sightline, = 3 - 14
cm^{-3}; and fraction of H in molecular form, 0 - 40%. Four of the sightlines,
those toward HD 37021, HD 37061, HD 147888 and HD 207198, have interstellar
gas-phase abundances that are consistent with the diffuse sightline ratio of
161 +/- 17 carbon atoms in the gas per million hydrogen nuclei. We note that
while it has a gas-phase carbon abundance that is consistent with the other
sightlines, a large fraction of the C II toward HD 37061 is in an excited
state. The sightline toward HD 152590 has a measured interstellar gas-phase
carbon abundance that is well above the diffuse sightline average; the column
density of C in this sightline may be overestimated due to noise structure in
the data. Toward HD 27778 we find a 3 sigma abundance upper limit of <108 C
atoms in the gas per million H, a substantially enhanced depletion of C as
compared to the diffuse sightline value. The interstellar characteristics
toward HD 27778 are otherwise not extreme among the sample except for an
unusually large abundance of CO molecules in the gas.Comment: Accepted for publication in the Astrophysical Journa
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