10,791 research outputs found
Economic analysis of trends in beef cattle and hog prices
The long-run trend of the ratio between beef cattle prices and hog prices at Chicago has been rising since 1910 at the rate of about 1.2 percent per year.
The principal cause of this change has been an increase in the demand for beef and a decrease in the demand for pork, relative to total disposable consumer income. An additional reason has been a decline in the relative value of lard.
The reasons why these\u27 changes took place are several: (1) The percentage of urban consumers (who eat more than twice as much beef per capita as farm consumers) in the population of the United States rose. (2) Rural and urban occupations both became less muscular, decreasing our consumption of carbohydrate foods and leaving room for an increase in our demand for meat. Incomes rose, and most of the increase in the demand for meat was focused on beef. for the income-elasticity of the demand for beef is 2.5 times as high as the elasticity for pork. (3) Income in the United States became more evenly distributed. (4) Vegetable oils offered increased competition with lard
The brightest OH maser in the sky: a flare of emission in W75 N
A flare of maser radio emission in the OH-line 1665 MHz has been discovered
in the star forming region W75 N in 2003, with the flux density of about 1000
Jy. At the time it was the strongest OH maser detected during the whole history
of observations since the discovery of cosmic masers in 1965. The flare
emission is linearly polarized with a degree of polarization near 100%. A
weaker flare with a flux of 145 Jy was observed in this source in 2000 - 2001,
which was probably a precursor of the powerful flare. Intensity of two other
spectral features has decreased after beginning of the flare. Such variation of
the intensity of maser condensation emission (increasing of one and decreasing
of the other) can be explained by passing of the magneto hydrodynamic shock
across regions of enhanced gas concentration.Comment: 9 pages with 2 figures, accepted for publication in Astronomy Letter
CydDC-mediated reductant export in Escherichia coli controls the transcriptional wiring of energy metabolism and combats nitrosative stress
The glutathione/cysteine exporter CydDC maintains redox balance in Escherichia coli. A cydD mutant strain was used to probe the influence of CydDC upon reduced thiol export, gene expression, metabolic perturbations, intracellular pH homeostasis, and tolerance to nitric oxide (NO). Loss of CydDC was found to decrease extracytoplasmic thiol levels, whereas overexpression diminished the cytoplasmic thiol content. Transcriptomic analysis revealed a dramatic up-regulation of protein chaperones, protein degradation (via phenylpropionate/phenylacetate catabolism), ?-oxidation of fatty acids, and genes involved in nitrate/nitrite reduction. 1H NMR metabolomics revealed elevated methionine and betaine and diminished acetate and NAD+ in cydD cells, which was consistent with the transcriptomics-based metabolic model. The growth rate and ?pH, however, were unaffected, although the cydD strain did exhibit sensitivity to the NO-releasing compound NOC-12. These observations are consistent with the hypothesis that the loss of CydDC-mediated reductant export promotes protein misfolding, adaptations to energy metabolism, and sensitivity to NO. The addition of both glutathione and cysteine to the medium was found to complement the loss of bd -type cytochrome synthesis in a cydD strain (a key component of the pleiotropic cydDC phenotype), providing the first direct evidence that CydDC substrates are able to restore the correct assembly of this respiratory oxidase. These data provide an insight into the metabolic flexibility of E. coli , highlight the importance of bacterial redox homeostasis during nitrosative stress, and report for the first time the ability of periplasmic low molecular weight thiols to restore haem incorporation into a cytochrome complex
A model of fasciculation and sorting in mixed populations of axons
We extend a recently proposed model (Chaudhuri et al., EPL 87, 20003 (2009))
aiming to describe the formation of fascicles of axons during neural
development. The growing axons are represented as paths of interacting directed
random walkers in two spatial dimensions. To mimic turnover of axons, whole
paths are removed and new walkers are injected with specified rates. In the
simplest version of the model, we use strongly adhesive short-range inter-axon
interactions that are identical for all pairs of axons. We generalize the model
to adhesive interactions of finite strengths and to multiple types of axons
with type-specific interactions. The dynamic steady state is characterized by
the position-dependent distribution of fascicle sizes. With distance in the
direction of axon growth, the mean fascicle size and emergent time scales grow
monotonically, while the degree of sorting of fascicles by axon type has a
maximum at a finite distance. To understand the emergence of slow time scales,
we develop an analytical framework to analyze the interaction between
neighboring fascicles.Comment: 19 pages, 13 figures; version accepted for publication in Phys Rev
Non-adaptive Measurement-based Quantum Computation and Multi-party Bell Inequalities
Quantum correlations exhibit behaviour that cannot be resolved with a local
hidden variable picture of the world. In quantum information, they are also
used as resources for information processing tasks, such as Measurement-based
Quantum Computation (MQC). In MQC, universal quantum computation can be
achieved via adaptive measurements on a suitable entangled resource state. In
this paper, we look at a version of MQC in which we remove the adaptivity of
measurements and aim to understand what computational abilities still remain in
the resource. We show that there are explicit connections between this model of
computation and the question of non-classicality in quantum correlations. We
demonstrate this by focussing on deterministic computation of Boolean
functions, in which natural generalisations of the Greenberger-Horne-Zeilinger
(GHZ) paradox emerge; we then explore probabilistic computation, via which
multipartite Bell Inequalities can be defined. We use this correspondence to
define families of multi-party Bell inequalities, which we show to have a
number of interesting contrasting properties.Comment: 13 pages, 4 figures, final version accepted for publicatio
Fractional Variations for Dynamical Systems: Hamilton and Lagrange Approaches
Fractional generalization of an exterior derivative for calculus of
variations is defined. The Hamilton and Lagrange approaches are considered.
Fractional Hamilton and Euler-Lagrange equations are derived. Fractional
equations of motion are obtained by fractional variation of Lagrangian and
Hamiltonian that have only integer derivatives.Comment: 21 pages, LaTe
Chandra and HST observations of gamma-ray blazars: comparing jet emission at small and large scales
We present new Chandra and HST data for four gamma-ray blazars selected on
the basis of radio morphology with the aim of revealing X-ray and optical
emission from their jets at large scales. All the sources have been detected.
Spectral Energy Distributions of the large scale jets are obtained as well as
new X-ray spectra for the blazar cores. Modeling for each object the core
(sub-pc scale) and large-scale (>100 kpc) jet SEDs, we derive the properties of
the same jet at the two scales. The comparison of speeds and powers at
different scales supports a simple scenario for the dynamics and propagation of
high power relativistic jets.Comment: Accepted for publication in Ap
Averaging lifetimes for B hadron species
The measurement of the lifetimes of the individual B species are of great interest. Many of these measurements are well below the 10 level of precision. However, in order to reach the precision necessary to test the current theoretical predictions, the results from different experiments need to be averaged. Therefore, the relevant systematic uncertainties of each measurement need to be well defined in order to understand the correlations between the results from different experiments. \par In this paper we discuss the dominant sources of systematic errors which lead to correlations between the different measurements. We point out problems connected with the conventional approach of combining lifetime data and discuss methods which overcome these problems
Clustered Star Formation in W75 N
We present 2" to 7" resolution 3 mm continuum and CO(J=1-0) line emission and
near infrared Ks, H2, and [FeII] images toward the massive star forming region
W75 N. The CO emission uncovers a complex morphology of multiple, overlapping
outflows. A total flow mass of greater than 255 Msun extends 3 pc from
end-to-end and is being driven by at least four late to early-B protostars.
More than 10% of the molecular cloud has been accelerated to high velocities by
the molecular flows (> 5.2 km/s relative to v{LSR}) and the mechanical energy
in the outflowing gas is roughly half the gravitational binding energy of the
cloud. The W75 N cluster members represent a range of evolutionary stages, from
stars with no apparent circumstellar material to deeply embedded protostars
that are actively powering massive outflows. Nine cores of
millimeter-wavelength emission highlight the locations of embedded protostars
in W75 N. The total mass of gas & dust associated with the millimeter cores
ranges from 340 Msun to 11 Msun. The infrared reflection nebula and shocked H2
emission have multiple peaks and extensions which, again, suggests the presence
of several outflows. Diffuse H2 emission extends about 0.6 parsecs beyond the
outer boundaries of the CO emission while the [FeII] emission is only detected
close to the protostars. The infrared line emission morphology suggests that
only slow, non-dissociative J-type shocks exist throughout the pc-scale
outflows. Fast, dissociative shocks, common in jet-driven low-mass outflows,
are absent in W75 N. Thus, the energetics of the outflows from the late to
early B protostars in W75 N differ from their low-mass counterparts -- they do
not appear to be simply scaled-up versions of low-mass outflows.Comment: Astrophysical Journal, in press. 23 pages plus 10 figures (jpg
format). See http://www.aoc.nrao.edu/~dshepher/science.shtml for reprint with
full resolution figure
CLASS B1152+199 and B1359+154: Two New Gravitational Lens Systems Discovered in the Cosmic Lens All-Sky Survey
The third phase of the Cosmic Lens All-Sky Survey (CLASS) has recently been
completed, bringing the total number of sources imaged to over 15000 in the
CLASS and JVAS combined survey. In the VLA observations carried out in March
and April of 1998, two new candidate lensed systems were discovered: CLASS
B1152+199 and B1359+154. B1152+199 is a 1.6 arcsecond double, with a background
quasar at z=1.019 lensed by a foreground galaxy at z=0.439. The relatively flat
radio spectra of the lensed images, combined with a previous ROSAT detection of
the source, make B1152+199 a strong candidate for time delay studies at both
radio and X-ray wavelengths. B1359+154 is a quadruply lensed quasar at z=3.235,
with a maximum image separation of 1.7 arcseconds. As yet, the redshift of the
lensing object in this system is undetermined. The steep spectral index of the
source suggests that B1359+154 will not exhibit strong variability, and is
therefore unlikely to be useful for determining the Hubble constant from
measured time delays.Comment: accepted for publication in The Astronomical Journa
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