550 research outputs found
Factors affecting the growth and survival of Matebele goat kids in a semi-arid environment under smallholder management
A research article on factors affecting effective goat rearing in Zimbabwe's rural areas.Performance of 631 kids belonging to seven smallholder farmers in southern Zimbabwe was monitored over a two-year period. Least square mean live weights at 14,150 and 360 days (d) of growth were 4.3 + 0.04,11.5 + 0.11 and 19.9 + 0.19 kg, respectively. Exit rate between birth and 150 days was 35 percent. Live weight at all the three stages of growth and pre-weaning exit rates varied significantly (p<0.001) between birth months and between flocks (p<0.001). Pre-weaning growth rates tended to be relatively faster for kids born between September and January (dry to early wet seasons) but were depressed post-weaning as a result of dry season feed shortages. Consequently, kids born in September-January tended to weigh less at 360 days compared to kids born in February-July. Male kids and singles were significantly heavier (p<0.001) at all ages than female kids and twins, respectively. Age of the doe significantly affected kid weight at 150 d, with kids born to does of 1 to 2 years of age being 13-25 percent lighter (p<0.01) than kids born to older does. Exit rates were highest (33 percent) in July, the month where maximum births occur. Exit rates were significantly higher (p<0.001) in year 1 (52 + 0.22 percent) than in year 2 (48 + 0.31 percent). Kid survival was not influenced by age of the doe, sex or birth type of the kids. It is concluded that growth and survival of Matebele kids could be improved through strategic management of seasonal effects and better understanding of local management
Toric self-dual Einstein metrics as quotients
We use the quaternion Kahler reduction technique to study old and new
self-dual Einstein metrics of negative scalar curvature with at least a
two-dimensional isometry group, and relate the quotient construction to the
hyperbolic eigenfunction Ansatz. We focus in particular on the
(semi-)quaternion Kahler quotients of (semi-)quaternion Kahler hyperboloids,
analysing the completeness and topology, and relating them to the self-dual
Einstein Hermitian metrics of Apostolov-Gauduchon and Bryant.Comment: 30 page
Supersymmetric Field-Theoretic Models on a Supermanifold
We propose the extension of some structural aspects that have successfully
been applied in the development of the theory of quantum fields propagating on
a general spacetime manifold so as to include superfield models on a
supermanifold. We only deal with the limited class of supermanifolds which
admit the existence of a smooth body manifold structure. Our considerations are
based on the Catenacci-Reina-Teofillatto-Bryant approach to supermanifolds. In
particular, we show that the class of supermanifolds constructed by
Bonora-Pasti-Tonin satisfies the criterions which guarantee that a
supermanifold admits a Hausdorff body manifold. This construction is the
closest to the physicist's intuitive view of superspace as a manifold with some
anticommuting coordinates, where the odd sector is topologically trivial. The
paper also contains a new construction of superdistributions and useful results
on the wavefront set of such objects. Moreover, a generalization of the
spectral condition is formulated using the notion of the wavefront set of
superdistributions, which is equivalent to the requirement that all of the
component fields satisfy, on the body manifold, a microlocal spectral condition
proposed by Brunetti-Fredenhagen-K\"ohler.Comment: Final version to appear in J.Math.Phy
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Digestion, rumen fermentation and circulating concentrations of insulin, growth hormone and IGF-1 in steers fed diets based on different proportions of maize silage and grass silage
Replacing grass silage with maize silage results in a fundamental change in the ratio of structural to non-structural carbohydrates with commensurate changes in rumen fermentation patterns and nutrient utilisation. This study investigated the effects of feeding four forage mixtures, namely grass silage (G); 67 g/100 g grass silage133 g/100 g maize silage (GGM); 67 g/100 g maize silage133/100 g grass silage (MMG); maize silage (M) to four ruminally and duodenally canulated Holstein Friesian steers. All diets were formulated to be isonitrogenous (22.4 g N/kg DM) using a concentrate mixture. Dietary dry matter (DM) and organic matter (OM) digestibility increased with ascending maize silage inclusion (P,0.1) whereas starch and neutral detergent fibre digestibility declined (P,0.05). Ratio of non-glucogenic to glucogenic precursors in the rumen fluid increased with maize silage inclusion (P,0.01) with a commensurate reduction in rumen pH (P,0.05). Mean circulating concentrations of insulin were greatest and similar in diets MMG and GGM, lower in diet M and lowest in diet G (P,0.01). There were no effects of diet on the mean circulating concentration of growth hormone (GH), or the frequency, amplitude and duration of GH pulses, or the
mean circulating concentrations of IGF-1. Increasing levels of DM, OM and starch intakes with the substitution of grass silage with maize silage affected overall digestion, nutrient partitioning and subsequent circulating concentrations of insulin
Pore-scale Modeling of Viscous Flow and Induced Forces in Dense Sphere Packings
We propose a method for effectively upscaling incompressible viscous flow in
large random polydispersed sphere packings: the emphasis of this method is on
the determination of the forces applied on the solid particles by the fluid.
Pore bodies and their connections are defined locally through a regular
Delaunay triangulation of the packings. Viscous flow equations are upscaled at
the pore level, and approximated with a finite volume numerical scheme. We
compare numerical simulations of the proposed method to detailed finite element
(FEM) simulations of the Stokes equations for assemblies of 8 to 200 spheres. A
good agreement is found both in terms of forces exerted on the solid particles
and effective permeability coefficients
A Map-Reduce Parallel Approach to Automatic Synthesis of Control Software
Many Control Systems are indeed Software Based Control Systems, i.e. control
systems whose controller consists of control software running on a
microcontroller device. This motivates investigation on Formal Model Based
Design approaches for automatic synthesis of control software.
Available algorithms and tools (e.g., QKS) may require weeks or even months
of computation to synthesize control software for large-size systems. This
motivates search for parallel algorithms for control software synthesis.
In this paper, we present a Map-Reduce style parallel algorithm for control
software synthesis when the controlled system (plant) is modeled as discrete
time linear hybrid system. Furthermore we present an MPI-based implementation
PQKS of our algorithm. To the best of our knowledge, this is the first parallel
approach for control software synthesis.
We experimentally show effectiveness of PQKS on two classical control
synthesis problems: the inverted pendulum and the multi-input buck DC/DC
converter. Experiments show that PQKS efficiency is above 65%. As an example,
PQKS requires about 16 hours to complete the synthesis of control software for
the pendulum on a cluster with 60 processors, instead of the 25 days needed by
the sequential algorithm in QKS.Comment: To be submitted to TACAS 2013. arXiv admin note: substantial text
overlap with arXiv:1207.4474, arXiv:1207.409
Hidden Spacetime Symmetries and Generalized Holonomy in M-theory
In M-theory vacua with vanishing 4-form F, one can invoke the ordinary
Riemannian holonomy H \subset SO(1,10) to account for unbroken supersymmetries
n=1, 2, 3, 4, 6, 8, 16, 32. However, the generalized holonomy conjecture, valid
for non-zero F, can account for more exotic fractions of supersymmetry, in
particular 16<n<32. The conjectured holonomies are given by H \subset G where G
are the generalized structure groups G=SO(d-1,1) x G(spacelike), G=ISO(d-1) x
G(null) and G=SO(d) x G(timelike) with 1<=d<11. For example,
G(spacelike)=SO(16), G(null)=[SU(8) x U(1)] \ltimes R^{56} and
G(timelike)=SO*(16) when d=3. Although extending spacetime symmetries, there is
no conflict with the Coleman-Mandula theorem. The holonomy conjecture rules out
certain vacua which are otherwise permitted by the supersymmetry algebra.Comment: Notes added addressing Hull's results in hep-th/0305039. We agree
with the necessity of SL(32,R) for classifying generalized holonomy.
References added. 18 pages, late
N=31, D=11
We show that eleven-dimensional supergravity backgrounds with thirty one
supersymmetries, N=31, admit an additional Killing spinor and so they are
locally isometric to maximally supersymmetric ones. This rules out the
existence of simply connected eleven-dimensional supergravity preons. We also
show that N=15 solutions of type I supergravities are locally isometric to
Minkowski spacetime.Comment: 17 page
Generalized holonomy of M-theory vacua
The number of M-theory vacuum supersymmetries, 0 <= n <= 32, is given by the
number of singlets appearing in the decomposition of the 32 of SL(32,R) under H
\subset SL(32,R) where H is the holonomy group of the generalized connection
which incorporates non-vanishing 4-form. Here we compute this generalized
holonomy for the n=16 examples of the M2-brane, M5-brane, M-wave, M-monopole,
for a variety of their n=8 intersections and also for the n>16 pp waves.Comment: 24 pages, LaTe
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