4,923 research outputs found
Coordinated egg production and marketing in the north central states V. Least-cost egg marketing organization under alternative production patterns
Important changes are taking place in the mid-western egg industry. Changes in Iowa are broadly representative of the transformations taking place in this industry throughout the region. One of the most significant changes has been the decline in the number of farms producing eggs. In 1940, 198,000 Iowa farms -or 93 percent of all farms-reported chickens on hand. In 1950, the number was 174,000, or 86 percent. By 1959, there had been a further decline to 68 percent.
Along with the changing number of farms producing eggs, there has been a change in the sizes of flocks on farms. In Iowa, the proportion of very small flocks has remained nearly constant. In 1940 and 1950, roughly 13 percent of all Iowa flocks had fewer than 50 hens. This rose to about 15 percent in 1959. A sharp decline in medium-sized flocks of 50 to 400 hens occurred in the same period, from 86 percent in 1940 to 71 percent in 1959. Numbers of flocks larger than 400 hens have shown substantial increases, as shown in table 1 (1, 8, 14).
Small flocks (less than 50 hens) are of little commercial importance. They are maintained mainly to supply the farm household with eggs for consumption. Farm flocks of 50 to 400 hens are most numerous; they have served as a means of acquiring a steady flow of cash for the household and an outlet for family labor on the family farm. For our study, flocks of this size take on great importance; they are the main component of the existing production pattern. Flocks larger than 400 hens are increasing rapidly and will probably continue to increase because of economies of scale in egg production and possible economies in marketing operations. This study emphasizes these larger flocks to ascertain their relationship to assembly and processing costs
HERUS: the far-IR/submm spectral energy distributions of local ULIRGs and photometric atlas
We present the Herschel-SPIRE photometric atlas for a complete flux limited sample of 43 local ultraluminous infrared galaxies (ULIRGs), selected at 60 μm by IRAS, as part of the HERschel ULIRG Survey (HERUS). Photometry observations were obtained using the SPIRE instrument at 250, 350, and 500 μm. We describe these observations, present the results, and combine the new observations with data from IRAS to examine the far-infrared spectral energy distributions (SEDs) of these sources. We fit the observed SEDs of HERUS objects with a simple parametrized modified blackbody model, where temperature and emissivity β are free parameters. We compare the fitted values to those of non-ULIRG local galaxies, and find, in agreement with earlier results, that HERUS ULIRGs have warmer dust (median temperature T = 37.9 ± 4.7 K compared to 21.3 ± 3.4 K) but a similar β distribution (median β = 1.7 compared to 1.8) to the Herschel reference sample (HRS, Cortese et al. 2014) galaxies. Dust masses are found to be in the range of 107.5–109 M⊙, significantly higher than that of HRS sources. We compare our results for local ULIRGs with higher redshift samples selected at 250 and 850 μm. These latter sources generally have cooler dust and/or redder 100-to-250 μm colours than our 60 μm-selected ULIRGs. We show that this difference may in part be the result of the sources being selected at different wavelengths rather than being a simple indication of rapid evolution in the properties of the population
The Energetics of Molecular Gas in NGC 891 from H2 and FIR Spectroscopy
We have studied the molecular hydrogen energetics of the edge-on spiral
galaxy NGC\,891, using a 34-position map in the lowest three pure rotational
H lines observed with the Spitzer Infrared Spectrograph. The S(0), S(1),
and S(2) lines are bright with an extinction corrected total luminosity of
L, or 0.09\% of the total-infrared luminosity
of NGC\,891. The H line ratios are nearly constant along the plane of the
galaxy -- we do not observe the previously reported strong drop-off in the
S(1)/S(0) line intensity ratio in the outer regions of the galaxy, so we find
no evidence for the very massive cold CO-free molecular clouds invoked to
explain the past observations. The H level excitation temperatures increase
monotonically indicating more than one component to the emitting gas. More than
99\% of the mass is in the lowest excitation (T 125 K) ``warm''
component. In the inner galaxy, the warm H emitting gas is 15\% of
the CO(1-0)-traced cool molecular gas, while in the outer regions the fraction
is twice as high. This large mass of warm gas is heated by a combination of the
far-UV photons from stars in photo-dissociation regions (PDRs) and the
dissipation of turbulent kinetic energy. Including the observed far-infrared
[OI] and [CII] fine-structure line emission and far-infrared continuum emission
in a self-consistent manner to constrain the PDR models, we find essentially
all of the S(0) and most (70\%) of the S(1) line arises from low excitation
PDRs, while most (80\%) of the S(2) and the remainder of the S(1) line emission
arises from low velocity microturbulent dissipation.Comment: Accepted for publication in The Astrophysical Journal. Figure 10
available at http://www.physics.uoc.gr/~vassilis/papers/ngc891.pd
Experiencing stigma as sex work researchers in professional and personal lives
Researchers have demonstrated the challenges associated with sex work research; negotiating the stigma attached to its subject matter, the perceived dangerousness of participants, and the barriers faced in reaching hidden populations. By reflecting upon our separate research experiences and drawing upon a body of reflexive sex work research, this article explores how, as sex work researchers, we experienced stigma not only in our professional roles as researchers, but also in our personal lives. We apply Goffman's (1968) notion of stigma by association; and consider how stigma often associated with prostitution became transposed onto us. In particular, we compare and contrast our separate experiences of conducting sex work research to demonstrate our similar experiences of stigma by association
Spitzer/IRS 5-35 um Low-Resolution Spectroscopy of the 12 um Seyfert Sample
We present low-resolution 5.5-35 um spectra for 103 galaxies from the 12 um
Seyfert sample, a complete unbiased 12 um flux limited sample of local Seyfert
galaxies selected from the IRAS Faint Source Catalog, obtained with the
Infrared Spectrograph (IRS) on-board Spitzer Space Telescope. For 70 of the
sources observed in the IRS mapping mode, uniformly extracted nuclear spectra
are presented for the first time. We performed an analysis of the continuum
emission, the strength of the Polycyclic Aromatic Hydrocarbon (PAH) and
astronomical silicate features of the sources. We find that on average, the
15-30 um slope of the continuum is alpha_{15-30}=-0.85+-0.61 for Seyfert 1s and
-1.53+-0.84 for Seyfert 2s, and there is substantial scatter in each type.
Moreover, nearly 32% of Seyfert 1s, and 9% of Seyfert 2s, display a peak in the
mid-infrared spectrum at 20 um, which is attributed to an additional hot dust
component. The PAH equivalent width decreases with increasing dust temperature,
asindicated by the global infrared color of the host galaxies. However, no
statistical difference in PAH equivalent width is detected between the two
Seyfert types, 1 and 2, of the same bolometric luminosity. The silicate
features at 9.7 and 18um in Seyfert 1 galaxies are rather weak, while Seyfert
2s are more likely to display strong silicate absorption. Those Seyfert 2s with
the highest silicate absorption also have high infrared luminosity and high
absorption (hydrogen column density N_H>10^23 cm^-2 as measured from the
X-rays. Finally, we propose a new method to estimate the AGN contribution to
the integrated 12 um galaxy emission, by subtracting the "star formation"
component in the Seyfert galaxies, making use of the tight correlation between
PAH 11.2 um luminosity and 12 um luminosity for star forming galaxies.Comment: accepted for publication in Ap
Mid-Infrared Spectroscopy of Two Lensed Star-forming Galaxies
We present low-resolution, rest-frame ~ 5 - 12 micron Spitzer/IRS spectra of
two lensed z ~ 2 UV-bright star-forming galaxies, SDSS J120602.09+514229.5 and
SDSS J090122.37+181432.3. Using the magnification boost from lensing, we are
able to study the physical properties of these objects in greater detail than
is possible for unlensed systems. In both targets, we detect strong PAH
emission at 6.2, 7.7, and 11.3 microns, indicating the presence of vigorous
star formation. For J1206, we find a steeply rising continuum and significant
[S IV] emission, suggesting that a moderately hard radiation field is powering
continuum emission from small dust grains. The strength of the [S IV] emission
also implies a sub-solar metallicity of ~ 0.5 Z_{Sun}, confirming published
rest-frame optical measurements. In J0901, the PAH lines have large rest-frame
equivalent widths (> 1 micron) and the continuum rises slowly with wavelength,
suggesting that any AGN contribution to L_{IR} is insignificant, in contrast to
the implications of optical emission-line diagnostics. Using [O III] line flux
as a proxy for AGN strength, we estimate that the AGN in J0901 provides only a
small fraction of its mid-infrared continuum flux. By combining the detection
of [Ar II] with an upper limit on [Ar III] emission, we infer a metallicity of
> 1.3 Z_{Sun}. This work highlights the importance of combining rest-frame
optical and mid-IR spectroscopy in order to understand the detailed properties
of star-forming galaxies at high redshift.Comment: 20 pages, 3 figures, 2 tables. ApJ accepte
The Mid-Infrared High-Ionization Lines from Active Galactic Nuclei and Star-Forming Galaxies
We used Spitzer/IRS spectroscopic data on 426 galaxies including quasars,
Seyferts, LINER and HII galaxies to investigate the relationship among the
mid-IR emission lines. There is a tight linear correlation between the [Ne
V]14.3 um and 24.3 um (97.1 eV) and the [O IV]25.9 um (54.9 eV) high-ionization
emission lines. The correlation also holds for these high-ionization emission
lines and the [Ne III]15.56 um (41 eV) emission line, although only for active
galaxies. We used these correlations to calculate the [Ne III] excess due to
star formation in Seyfert galaxies. We also estimated the [O IV] luminosity due
to star formation in active galaxies and determined that it dominates the [O
IV] emission only if the contribution of the active nucleus to the total
luminosity is below 5%. We find that the AGN dominates the [O IV] emission in
most Seyfert galaxies, whereas star-formation adequately explains the observed
[O IV] emission in optically classified HII galaxies. Finally we computed
photoionization models to determine the physical conditions of the narrow line
region where these high-ionization lines originate. The estimated ionization
parameter range is -2.8 < log U < -2.5 and the total hydrogen column density
range is 20 < log nH (cm-2) < 21.Comment: Accepted for Publication in ApJ, 19 pages, 13 figure
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