329 research outputs found
Phosphorus nutrition and management â overcoming constraints to wider adoption
The importance of phosphorus nutrition for cattle grazing northern Australian rangelands has been well documented and demonstrated. Phosphorus is clearly one of the most important nutritional deficiencies, within the limitations of potential metabolizable energy intakes, of grazing cattle in the seasonally dry tropics. Nevertheless it appears that only a small proportion of cattle grazing phosphorus deficient pastures are supplemented or otherwise managed to alleviate phosphorus deficiency. Estimated requirements for dietary phosphorus by various classes of cattle grazing tropical pastures have recently been revised (CSIRO 2007). The development of faecal near infrared spectroscopy (F.NIRS) allows the routine estimation of metabolizable energy and nitrogen concentrations in the diet, and thus the potential productivity, of cattle grazing northern rangelands.
The concentration of phosphorus in the diet of grazing cattle can be estimated from the concentration of phosphorus in the faeces, at least in cattle not fed phosphorus supplements.
Combining estimates of diet metabolizable energy, nitrogen and phosphorus allows estimation whether current needs of the animal are supplied by the diet. Phosphorus-replete cattle have substantial body reserves of phosphorus which can be mobilized, especially in late pregnancy and lactation, to alleviate a dietary deficiency. However, these body reserves need to be replenished in late lactation or post-lactation if mobilization occurs each year. Diagnosis of subclinical phosphorus deficiency in grazing cattle, and prediction of animal responses to phosphorus supplements is difficult. In growing cattle the concentration of inorganic phosphorus in blood (Pi), in the late wet or early dry season, combined with information on diet metabolizable energy and nitrogen concentrations obtained by F.NIRS, provides the most reliable test. In pregnant or lactating cows measurements of faecal phosphorus concentration and F.NIRS provide the best estimate of whether phosphorus intake meets the current needs of the animal. However, estimates of adequacy of phosphorus supply need to also consider possible mobilization of body phosphorus reserves.
Indicative responses to provision of phosphorus supplements by cattle grazing pastures ranging from marginal to acute deficiency are summarized. Economic evaluation of benchmark enterprises where cattle are expected to be phosphorus deficient indicate that phosphorus supplementation is highly cost-effective. Major obstacles to more widespread adoption of phosphorus supplementation appear to be lack of knowledge and appreciation by managers of the phosphorus status of their cattle, lack of appreciation of the cost-effectiveness of a phosphorus supplementation particularly for some classes of cattle, and the practical difficulties in implementing phosphorus supplementation during the wet season
Observation of two relaxation mechanisms in transport between spin split edge states at high imbalance
Using a quasi-Corbino geometry to directly study electron transport between
spin-split edge states, we find a pronounced hysteresis in the I-V curves,
originating from slow relaxation processes. We attribute this long-time
relaxation to the formation of a dynamic nuclear polarization near the sample
edge. The determined characteristic relaxation times are 25 s and 200 s which
points to the presence of two different relaxation mechanisms. The two time
constants are ascribed to the formation of a local nuclear polarization due to
flip-flop processes and the diffusion of nuclear spins.Comment: Submitted to PR
An algebraic/numerical formalism for one-loop multi-leg amplitudes
We present a formalism for the calculation of multi-particle one-loop
amplitudes, valid for an arbitrary number N of external legs, and for massive
as well as massless particles. A new method for the tensor reduction is
suggested which naturally isolates infrared divergences by construction. We
prove that for N>4, higher dimensional integrals can be avoided. We derive many
useful relations which allow for algebraic simplifications of one-loop
amplitudes. We introduce a form factor representation of tensor integrals which
contains no inverse Gram determinants by choosing a convenient set of basis
integrals. For the evaluation of these basis integrals we propose two methods:
An evaluation based on the analytical representation, which is fast and
accurate away from exceptional kinematical configurations, and a robust
numerical one, based on multi-dimensional contour deformation. The formalism
can be implemented straightforwardly into a computer program to calculate
next-to-leading order corrections to multi-particle processes in a largely
automated way.Comment: 71 pages, 7 figures, formulas for rank 6 pentagons added in Appendix
Meaningful time for professional growth or a waste of time? A study in five countries on teachersâ experiences within masterâs dissertation/thesis work
The relationship between masterâs thesis work and teachersâ professional development has rarely been explored empirically, yet. Drawing upon a larger study, this paper investigates how teachers who were studying for or who have recently graduated from Master of Education programmes offered in five countries â Poland, Portugal, England, Latvia, Romania â perceive the usefulness of dissertation/thesis work for their professional development and how they attempt to use their MA research results in their (future) teaching practice. Results suggest that although most respondents recognized their MA dissertation/thesis work as having a positive impact on their professional development by enhancing their professionalism, personal development and growth, and understanding the relationship between research and practice, they were less confident about the use of MA research findings in their (future) workplaces. These results are discussed in the context of current challenges regarding masterâs level education for teachers, national governmentsâ educational policies, and the relationship between research, teachersâ practices and professional development
Counting BPS states on the Enriques Calabi-Yau
We study topological string amplitudes for the FHSV model using various
techniques. This model has a type II realization involving a Calabi-Yau
threefold with Enriques fibres, which we call the Enriques Calabi-Yau. By
applying heterotic/type IIA duality, we compute the topological amplitudes in
the fibre to all genera. It turns out that there are two different ways to do
the computation that lead to topological couplings with different BPS content.
One of them leads to the standard D0-D2 counting amplitudes, and from the other
one we obtain information about bound states of D0-D4-D2 branes on the Enriques
fibre. We also study the model using mirror symmetry and the holomorphic
anomaly equations. We verify in this way the heterotic results for the D0-D2
generating functional for low genera and find closed expressions for the
topological amplitudes on the total space in terms of modular forms, and up to
genus four. This model turns out to be much simpler than the generic B-model
and might be exactly solvable.Comment: 62 pages, v3: some results at genus 3 corrected, more typos correcte
Model Building with Gauge-Yukawa Unification
In supersymmetric theories with extra dimensions, the Higgs and matter fields
can be part of the gauge multiplet, so that the Yukawa interactions can arise
from the gauge interactions. This leads to the possibility of gauge-Yukawa
coupling unification, g_i=y_f, in the effective four dimensional theory after
the initial gauge symmetry and the supersymmetry are broken upon orbifold
compactification. We consider gauge-Yukawa unified models based on a variety of
four dimensional symmetries, including SO(10), SU(5), Pati-Salam symmetry,
trinification, and the Standard Model. Only in the case of Pati-Salam and the
Standard Model symmetry, we do obtain gauge-Yukawa unification. Partial
gauge-Yukawa unification is also briefly discussed.Comment: 23 page
STECF Fisheries Dependent Information â FDI (STECF-19-11)
Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4â10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines. The STECF reviewed the report of the EWG on Fisheries-dependent Information during its winter 2019 plenary meeting
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
- âŠ