2,741 research outputs found
Postcard: The Way It Works
This black and white printed postcard contains an illustration of a line of men walking from a Kansas bank to an Oklahoma bank. The crowd has dollar bills and bags of cash in their hand. Printed dialogue is on the top half of the card. Printed text is at the bottom of the card. Handwriting is on the back of the card.https://scholars.fhsu.edu/tj_postcards/1621/thumbnail.jp
Nutrition of the lactating beef cow
The primary purpose of this thesis was to examine the evidence relating to the effect of nutrition on the performance of single - suckled beef cows and to determine experimentally the response of autumn - calving Hereford cross British Friesian cows to three levels of energy intake during lactation.The different methods available for measuring the milk production of beef cows were discussed on the basis of information reported in the literature and two of the methods, machine -milking twice a day and a calf -suckling technique compared experimentally. It was concluded that the calf -suckling technique described is the more reliable and precise method of measuring milk production.Two experiments were reported in each of which 36 beef cows were offered individually either 175 per cent of their estimated energy requirement for maintenance (high), 125 per cent (medium), or 90 per cent (low), during the first 150 days of lactation. The rations offered consisted of grass silage and a barley -based concentrate supplement.The estimated 150 -day cumulative milk yields of beef cows in their second lactation, measured by a calf -suckling technique, were 1385 kg, 1274 kg and 1197 kg (P <0.01) on the high, medium and low planes of nutrition respectively. The corresponding figures for live -weight loss between parturition and 150 days post partum were 31 kg, 87 kg and 139 kg (P <0.001). The results demonstrated that energy deficient beef cows will attempt to sustain milk production by mobilising body reserves. It was also demonstrated that the growth rate of a suckled calf is sensitive to a reduction in milk intake during its first 150 days of life, but the weaning weights of autumn-born calves appeared unaffected by the plane of nutrition received by their dams during the winter.The implications of the results and areas of future research were discussed
Damped Lyman alpha systems and galaxy formation models - II. High ions and Lyman limit systems
We investigate a model for the high-ionization state gas associated with
observed damped Lyman-alpha systems, based on a semi-analytic model of galaxy
formation set within the paradigm of hierarchical structure formation. In our
model, the hot gas in halos and sub-halos gives rise to CIV absorption, while
the low-ionization state gas is associated with the cold gas in galaxies. The
model matches the distribution of CIV column densities and leads naturally to
kinematic properties that are in good agreement with the data.
We examine the contribution of both hot and cold gas to sub-damped systems
and suggest that the properties of these systems can be used as an important
test of the model. We expect that sub-DLA systems will generally be composed of
a single gas disk and thus predict that they should have markedly different
kinematics than the damped systems.
Finally, we find that hot halo gas produces less than one third of Lyman
limit systems at redshift three. We model the contribution of mini-halos (halos
with virial velocities < 35 km/s) to Lyman limit systems and find that they may
contain as much gas as is observed in these systems. However, if we adopt
realistic models of the gas density distribution we find that these systems are
not a significant source of Lyman limit absorption. Instead we suggest that
uncollapsed gas outside of virialized halos is responsible for most of the
Lyman limit systems at high redshift.Comment: 12 pages, 8 figures, submitted to MNRA
Understanding the Structural Scaling Relations of Early-Type Galaxies
We use a large suite of hydrodynamical simulations of binary galaxy mergers
to construct and calibrate a physical prescription for computing the effective
radii and velocity dispersions of spheroids. We implement this prescription
within a semi-analytic model embedded in merger trees extracted from the
Bolshoi Lambda-CDM N-body simulation, accounting for spheroid growth via major
and minor mergers as well as disk instabilities. We find that without disk
instabilities, our model does not predict sufficient numbers of intermediate
mass early-type galaxies in the local universe. Spheroids also form earlier in
models with spheroid growth via disk instabilities. Our model correctly
predicts the normalization, slope, and scatter of the low-redshift size-mass
and Fundamental Plane relations for early type galaxies. It predicts a degree
of curvature in the Faber-Jackson relation that is not seen in local
observations, but this could be alleviated if higher mass spheroids have more
bottom-heavy initial mass functions. The model also correctly predicts the
observed strong evolution of the size-mass relation for spheroids out to higher
redshifts, as well as the slower evolution in the normalization of the
Faber-Jackson relation. We emphasize that these are genuine predictions of the
model since it was tuned to match hydrodynamical simulations and not these
observations.Comment: Submitted to MNRA
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