729 research outputs found
Effect of Forage Height Upon the Microtemperature of a Grass-Legume Pasture and a Comparison of Forage Composition
The use of pasture to provide low cost feed for dairy and other farm animals is an important factor in the success of livestock operations.
Some of the factors which influence the income from pasture land are: management, pasture mix, and climate. The management of a pasture can determine to a great extent the value of pasture in a farming enterprise. Irrigating the pasture at the right time, using the right fertilizer, and proper methods of harvesting are examples of some of the management problems facing the grassland farmer
Simple generalizations of Anti-de Sitter space-time
We consider new cosmological solutions which generalize the cosmological
patch of the Anti-de Sitter (AdS) space-time, allowing for fluids with
equations of state such that . We use them to derive the associated
full manifolds. We find that these solutions can all be embedded in flat
five-dimensional space-time with signature, revealing deformed
hyperboloids. The topology and causal-structure of these spaces is therefore
unchanged, and closed time-like curves are identified, before a covering space
is considered. However the structure of Killing vector fields is entirely
different and so we may expect a different structure of Killing horizons in
these solutions.Comment: 6 Pages, 5 Figures, Corrections and additions made for publication in
Journal of Classical and Quantum Gravit
The 100 most eminent psychologists of the 20th century.
A rank-ordered list was constructed that reports the first 99 of the 100 most eminent psychologists of the 20th century. Eminence was measured by scores on 3 quantitative variables and 3 qualitative variables. The quantitative variables were journal citation frequency, introductory psychology textbook citation frequency, and survey response frequency. The qualitative variables were National Academy of Sciences membership, election as American Psychological Association (APA) president or receipt of the APA Distinguished Scientific Contributions Award, and surname used as an eponym. The qualitative variables were quantified and combined with the other 3 quantitative variables to produce a composite score that was then used to construct a rank-ordered list of the most eminent psychologists of the 20th century. The discipline of psychology underwent a remarkable transformation during the 20th cen-tury, a transformation that included a shift away from the European-influenced philosophical psychology of the late 19th century to th
Non-existence of Skyrmion-Skyrmion and Skyrmion-anti-Skyrmion static equilibria
We consider classical static Skyrmion-anti-Skyrmion and Skyrmion-Skyrmion
configurations, symmetric with respect to a reflection plane, or symmetric up
to a -parity transformation respectively. We show that the stress tensor
component completely normal to the reflection plane, and hence its integral
over the plane, is negative definite or positive definite respectively.
Classical Skyrmions always repel classical Skyrmions and classical Skyrmions
always attract classical anti-Skyrmions and thus no static equilibrium, whether
stable or unstable, is possible in either case. No other symmetry assumption is
made and so our results also apply to multi-Skyrmion configurations. Our
results are consistent with existing analyses of Skyrmion forces at large
separation, and with numerical results on Skymion-anti-Skyrmion configurations
in the literature which admit a different reflection symmetry. They also hold
for the massive Skyrme model. We also point out that reflection symmetric
self-gravitating Skyrmions or black holes with Skyrmion hair cannot rest in
symmetric equilibrium with self-gravitating anti-Skyrmions.Comment: v2 Typos corrected, refs added. v3 Journal versio
Statistics of Substructures in Dark Matter Haloes
We study the amount and distribution of dark matter substructures within dark
matter haloes, using a large set of high-resolution simulations ranging from
group size to cluster size haloes, and carried our within a cosmological model
consistent with WMAP 7-year data. In particular, we study how the measured
properties of subhaloes vary as a function of the parent halo mass, the
physical properties of the parent halo, and redshift. The fraction of halo mass
in substructures increases with increasing mass. There is, however, a very
large halo-to-halo scatter that can be explained only in part by a range of
halo physical properties, e.g. concentration. At given halo mass, less
concentrated haloes contain significantly larger fractions of mass in
substructures because of the reduced strength of tidal disruption. Most of the
substructure mass is located at the outskirts of the parent haloes, in
relatively few massive subhaloes. This mass segregation appears to become
stronger at increasing redshift, and should reflect into a more significant
mass segregation of the galaxy population at different cosmic epochs. When
haloes are accreted onto larger structures, their mass is significantly reduced
by tidal stripping. Haloes that are more massive at the time of accretion
(these should host more luminous galaxies) are brought closer to the centre on
shorter time-scales by dynamical friction, and therefore suffer of a more
significant stripping. The halo merger rate depends strongly on the environment
with substructure in more massive haloes suffering more important mergers than
their counterparts residing in less massive systems. This should translate into
a different morphological mix for haloes of different mass.Comment: 13 pages, 11 figures and 1 table. MNRAS 2011 in pres
The helical phase of chiral nematic liquid crystals as the Bianchi VII(0) group manifold
We show that the optical structure of the helical phase of a chiral nematic
is naturally associated with the Bianchi VII(0) group manifold, of which we
give a full account. The Joets-Ribotta metric governing propagation of the
extraordinary rays is invariant under the simply transitive action of the
universal cover of the three dimensional Euclidean group of two dimensions.
Thus extraordinary light rays are geodesics of a left-invariant metric on this
Bianchi type VII(0) group. We are able to solve by separation of variables both
the wave equation and the Hamilton-Jacobi equation for this metric. The former
reduces to Mathieu's equation and the later to the quadrantal pendulum
equation. We discuss Maxwell's equations for uniaxial optical materials where
the configuration is invariant under a group action and develop a formalism to
take advantage of these symmetries. The material is not assumed to be impedance
matched, thus going beyond the usual scope of transformation optics. We show
that for a chiral nematic in its helical phase Maxwell's equations reduce to a
generalised Mathieu equation. Our results may also be relevant to helical
phases of some magnetic materials and to light propagation in certain
cosmological models.Comment: 15 pages, 1 figure; Version 2 updated and expanded, to appear in
Phys. Rev.
A Minimal Realization Technique for the Dynamical Structure Function of a Class of LTI Systems
The dynamical structure function of a linear time invariant (LTI) system reveals causal dependencies among manifest variables without specifying any particular relationships among the unmeasured states of the system. As such, it is a useful representation for complex networks where a coarse description of global system structure is desired without detailing the intricacies of a full state realization. In this paper, we consider the problem of finding a minimal state realization for a given dynamical structure function. Interestingly, some dynamical structure functions require uncontrollable modes in their state realizations to deliver the desired input-output behavior while respecting a specified system structure. As a result, the minimal order necessary to realize a particular dynamical structure function may be greater than that necessary to realize its associated transfer function. Although finding a minimal realization for a given dynamical structure function is difficult in general, we present a straightforward procedure here that works for a simplified class of systems
Zebrafish models in neuropsychopharmacology and CNS drug discovery
Despite the high prevalence of neuropsychiatric disorders, their aetiology and molecular mechanisms remain poorly understood. The zebrafish (Danio rerio) is increasingly utilized as a powerful animal model in neuropharmacology research and in vivo drug screening. Collectively, this makes zebrafish a useful tool for drug discovery and the identification of disordered molecular pathways. Here, we discuss zebrafish models of selected human neuropsychiatric disorders and drug-induced phenotypes. As well as covering a broad range of brain disorders (from anxiety and psychoses to neurodegeneration), we also summarize recent developments in zebrafish genetics and small molecule screening, which markedly enhance the disease modelling and the discovery of novel drug targets. © 2017 The British Pharmacological SocietyThe study was coordinated through the International Zebrafish Neuroscience Research Consortium (ZNRC), and this collaboration was funded by St. Petersburg State University, Ural Federal University and Guangdong Ocean University. A.V.K. is the Chair of ZNRC, and his research is supported by the Russian Foundation for Basic Research (RFBR) grant 16-04-00851
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