15,705 research outputs found
Studies on growth rates in pigs and the effect of birth weight
End of project reportThe purpose of this study was to assess some environmental and management factors that affect growth performance on commercial pig units. In experiment 1, a survey was carried out on 22 pig units of known growth performance in south-west Ireland to compare management factors between those showing poor and good growth rates. Low growth rate appears to be due to the cumulative effect of a combination of factors. Experiment 2 was conducted to determine the effects of providing an
additional feeder on performance of weaned piglets. No benefits were
recorded. Feed consumed from the additional feeder was a replacement for
feed that otherwise would have been consumed from the control hopper
feeder.
Experiment 3 was designed to determine if pig performance and efficiency of
growth were affected by weight at birth and at weaning. Lightweight pigs
showed inferior growth performance up to the finisher period. Although they
compensated some of the inferior growth towards the time of slaughter, they
never reached the weights of the heavy birth-weight animals. Males were
either significantly heavier or tended to be heavier than females throughout.
There was no significant difference between the sexes in the number of days
to slaughter. Light and heavy pigs did not differ in the levels of IGF-1 in their
blood plasma; however lightweight pigs had significantly lower IgG preweaning.
Experiment 4 aimed to determine whether piglet birth weight influenced
growth performance, plasma IGF-1 concentrations and muscle fibre
characteristics at day 42 of life. At slaughter (Day 42) light birth weight pigs
were significantly (P < 0.001) lighter. Plasma IGF-1 concentration was lower
by 28% (P=0.06) in light pigs. Muscle fibre cross sectional area and total fibre
number were not significantly different between groups. This study should be
repeated with bigger numbers
The S2 VLBI Correlator: A Correlator for Space VLBI and Geodetic Signal Processing
We describe the design of a correlator system for ground and space-based
VLBI. The correlator contains unique signal processing functions: flexible LO
frequency switching for bandwidth synthesis; 1 ms dump intervals, multi-rate
digital signal-processing techniques to allow correlation of signals at
different sample rates; and a digital filter for very high resolution
cross-power spectra. It also includes autocorrelation, tone extraction, pulsar
gating, signal-statistics accumulation.Comment: 44 pages, 13 figure
Hydrogen-enhanced local plasticity in aluminum: an ab initio study
Dislocation core properties of Al with and without H impurities are studied
using the Peierls-Nabarro model with parameters determined by ab initio
calculations. We find that H not only facilitates dislocation emission from the
crack tip but also enhances dislocation mobility dramatically, leading to
macroscopically softening and thinning of the material ahead of the crack tip.
We observe strong binding between H and dislocation cores, with the binding
energy depending on dislocation character. This dependence can directly affect
the mechanical properties of Al by inhibiting dislocation cross-slip and
developing slip planarity.Comment: 4 pages, 3 figure
A study of protein and amino nutrition of growing pigs.
End of Project ReportProtein nutrition of the pig is concerned primarily with supplying the amino acid
requirements for fast, efficient growth and development of a lean carcass. In addition,
surplus protein contributes to a high level of nitrogen excretion in manure which is a
problem in complying with the Nitrates Directive. Metabolism of the excess protein /
nitrogen in the pig involves creation of urea and this process depresses the efficiency of
energy utilisation. As the pig grows, its requirement for individual amino acids falls but
the optimum ratio changes. Providing a diet with the correct levels and balance of the
principal amino acids is expected to improve performance.
Improvements in genetics and changes in management such as slaughter weight require
that the amino acid requirements be reassessed periodically. The objective of this study
was to examine response of pigs to variation in dietary lysine in several weight ranges
with the concentrations of the other principal amino acids held constant.
Entire males had superior FCR to females in all trials except 15 to 30kg, but differences
in dietary lysine requirements did not occur until the finishing stage. At heavier
weights, response of male and female pigs began to diverge at lysine concentrations
greater than 10.7 g/kg (ADG) and 9.7 g/kg (FCR).
There appeared to be a need to increase the threonine to lysine ratio in the diet from
0.60 to 0.70 when lysine concentration was reduced from 12.0 to 9.5 g/kg as weight of
the pig increased.
Providing the same mean lysine content (11.1 g/kg) to pigs from 38 to 97 kg in a series
of five diets declining in lysine concentration compared with a single diet did not affect
performance, or reduce N excretion. However, lowering the overall mean lysine
concentration from 11g/kg to 10.0 g/kg reduced overall N excretion by 13 %, without a
negative effect on pig performance. Pigs which were offered a low lysine diet in the
early stage of growth exhibited a compensatory response during realimentation on a
high lysine diet but it was not sufficient to equal the overall performance of pigs
previously offered a lysine-adequate diet. Nitrogen excretion was reduced by 23 % while the low lysine diet was fed in the initial period but there was no residual effect on
N excretion during realimentation.Teagasc Walsh Fellowship ProgrammeNational Development
Programme Funds (NDP
BCYCLIC: A parallel block tridiagonal matrix cyclic solver
13 pages, 6 figures.A block tridiagonal matrix is factored with minimal fill-in using a cyclic reduction algorithm that is easily parallelized. Storage of the factored blocks allows the application of the inverse to multiple right-hand sides which may not be known at factorization time. Scalability with the number of block rows is achieved with cyclic reduction, while scalability with the block size is achieved using multithreaded routines (OpenMP, GotoBLAS) for block matrix manipulation. This dual scalability is a noteworthy feature of this new solver, as well as its ability to efficiently handle arbitrary (non-powers-of-2) block row and processor numbers. Comparison with a state-of-the art parallel sparse solver is presented. It is expected that this new solver will allow many physical applications to optimally use the parallel resources on current supercomputers. Example usage of the solver in magneto-hydrodynamic (MHD), three-dimensional equilibrium solvers for high-temperature fusion plasmas is cited.This research has been sponsored by the US Department of Energy under Contract DE-AC05-00OR22725 with UT-Battelle, LLC. This research used resources of the National Center for Computational Sciences at Oak Ridge National Laboratory, which is supported by the Office of Science of the Department of Energy under Contract DE-AC05-00OR22725.Publicad
Self-stabilizing robot formations over unreliable networks
We describe how a set of mobile robots can arrange themselves on any specified curve on the plane in the presence of dynamic changes both in the underlying ad hoc network and in the set of participating robots. Our strategy is for the mobile robots to implement a self-stabilizing virtual layer consisting of mobile client nodes, stationary Virtual Nodes (VNs), and local broadcast communication. The VNs are associated with predetermined regions in the plane and coordinate among themselves to distribute the client nodes relatively uniformly among the VNs' regions. Each VN directs its local client nodes to align themselves on the local portion of the target curve. The resulting motion coordination protocol is self-stabilizing, in that each robot can begin the execution in any arbitrary state and at any arbitrary location in the plane. In addition, self-stabilization ensures that the robots can adapt to changes in the desired target formation.National Science Foundation (U.S.) (Grant No. CNS-0614993
Counter Machines and Distributed Automata: A Story about Exchanging Space and Time
We prove the equivalence of two classes of counter machines and one class of
distributed automata. Our counter machines operate on finite words, which they
read from left to right while incrementing or decrementing a fixed number of
counters. The two classes differ in the extra features they offer: one allows
to copy counter values, whereas the other allows to compute copyless sums of
counters. Our distributed automata, on the other hand, operate on directed path
graphs that represent words. All nodes of a path synchronously execute the same
finite-state machine, whose state diagram must be acyclic except for
self-loops, and each node receives as input the state of its direct
predecessor. These devices form a subclass of linear-time one-way cellular
automata.Comment: 15 pages (+ 13 pages of appendices), 5 figures; To appear in the
proceedings of AUTOMATA 2018
Energetics of hydrogen impurities in aluminum and their effect on mechanical properties
The effects of hydrogen impurities in the bulk and on the surface of aluminum
are theoretically investigated. Within the framework of density functional
theory, we have obtained the dependence on H concentration of the stacking
fault energy, the cleavage energy, the Al/H surface energy and the Al/H/Al
interface formation energy. The results indicate a strong dependence of the
slip energy barrier in the direction the cleavage energy in the
[111] direction and the Al/H/Al interface formation energy, on H concentration
and on tension. The dependence of the Al/H surface energy on H coverage is less
pronounced, while the optimal H coverage is monolayer. The
calculated activation energy for diffusion between high symmetry sites in the
bulk and on the surface is practically the same, 0.167 eV. From these results,
we draw conclusions about the possible effect of H impurities on mechanical
properties, and in particular on their role in embrittlement of Al.Comment: 9 pages, 5 figure
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