225 research outputs found
Fluctuations in Energy Intake and Fertility in Cattle.
End of Project ReportsReproductive failure in dairy cows results in fewer calves born, lower
milk sales, slower genetic progress and consequently, significant financial
loss to the industry. Dairy cattle breed improvement programmes have,
at least until very recently, focused primarily on increasing the yields of
milk or milk solids. The resulting genetic improvement has led to
significant increases in milk yield per cow but this increase is now
associated with a significant decline in cow reproductive wastage. An
important part of the Teagasc research programme in this area is to
determine the time at which embryo loss occurs and also to determine
whether the extent of the embryo loss is affected by the energy nutrition
of the cow and to devise strategies to reduce its extent. This project has
focused on the relationship between changes in dietary energy intake
near the time of insemination and the extent and pattern of embryo
survival. The main results are summarised in this report and detailed
results of the several experiments involved have been published in the
papers listed at the end of this report.
•
•
4
The objectives of this project were to determine the effect of
changes in energy intake near the time of insemination on
embryo loss rate, on the timing of embryo loss and on the
possible biological mechanisms involved.
Cross bred heifers were provided with either high or low energy
intakes that were based on pasture allowances calculated to
provide either 0.8 or 2.0 times their maintenance requirements.
These energy intakes were allocated for two weeks before and
about five weeks after insemination. The effect of the changes
in energy intake on embryo loss and on the time at which
embryo loss occurred, relative to the time of insemination, was
established. Possible associations between embryo loss and
blood concentrations of progesterone, NEFAs, insulin and
glucose were examined. A sudden reduction from a high to a low energy intake imposed
for two weeks from the day of insemination reduced the
subsequent embryo survival rate by 30 percentage points to a
survival rate of 38%. When energy intake over this same period
was either maintained or increased, embryo survival rate
remained high (overall mean, 69%), within a range of 65-71%.
The time at which embryo loss occurred was established.
Embryo survival or pregnancy rates measured on days 14 and
30 after insemination and at full term were 68%, 76% and
72%, respectively. These results provide new information
indicating that most embryo loss, at least in heifers, had
occurred on or before day 14 after insemination.
There was no evidence of any association between the shortterm
changes in energy intake either before or after AI and
blood progesterone concentration. Neither was there any
evidence that the detrimental effect of the sudden reduction in
energy intake on embryo survival was mediated through
changes in the systemic concentrations of non-esterified fatty
acids (NEFAs) or insulin. There was a suggestion, however, that
the detrimental effect of the reduced energy intake may operate
through a reduction in systemic glucose concentrations.Dairy Levy Farmer Fun
Gravitational non-commutativity and G\"odel-like spacetimes
We derive general conditions under which geodesics of stationary spacetimes
resemble trajectories of charged particles in an electromagnetic field. For
large curvatures (analogous to strong magnetic fields), the quantum
mechanicical states of these particles are confined to gravitational analogs of
{\it lowest Landau levels}. Furthermore, there is an effective
non-commutativity between their spatial coordinates. We point out that the
Som-Raychaudhuri and G\"odel spacetime and its generalisations are precisely of
the above type and compute the effective non-commutativities that they induce.
We show that the non-commutativity for G\"odel spacetime is identical to that
on the fuzzy sphere. Finally, we show how the star product naturally emerges in
Som-Raychaudhuri spacetimes.Comment: Two sections added (Relation to the fuzzy sphere, Emergence of the
star product). 10 pages, Revtex. To appear in General Relativity and
Gravitatio
Critical Temperature of the Deconfining Phase Transition in (2+1)d Georgi-Glashow Model
We find the temperature of the phase transition in the (2+1)d Georgi-Glashow
model. The critical temperature is shown to depend on the gauge coupling and on
the ratio of Higgs and gauge boson masses. In the BPS limit of light Higgs the
previous result by Dunne, Kogan, Kovner, and Tekin is reproduced.Comment: 17 pages, 3 figures, REVTeX
Poincare covariant mechanics on noncommutative space
The Dirac approach to constrained systems can be adapted to construct
relativistic invariant theories on a noncommutative (NC) space. As an example,
we propose and discuss relativistic invariant NC particle coupled to
electromagnetic field by means of the standard term . Poincare
invariance implies deformation of the free particle NC algebra in the
interaction theory. The corresponding corrections survive in the
nonrelativistic limit.Comment: 7 pages, JHEP style, final versio
The polyanalytic Ginibre ensembles
We consider a polyanalytic generalization of the Ginibre ensemble. This
models allowing higher Landau levels (the Ginibre ensemble corresponds to the
lowest Landau level). We study the local behavior of this point process under
blow-ups.Comment: 31 page
Landau Analog Levels for Dipoles in the Noncommutative Space and Phase Space
In the present contribution we investigate the Landau analog energy
quantization for neutral particles, that possesses a nonzero permanent magnetic
and electric dipole moments, in the presence of an homogeneous electric and
magnetic external fields in the context of the noncommutative quantum
mechanics. Also, we analyze the Landau--Aharonov--Casher and
Landau--He--McKellar--Wilkens quantization due to noncommutative quantum
dynamics of magnetic and electric dipoles in the presence of an external
electric and magnetic fields and the energy spectrum and the eigenfunctions are
obtained. Furthermore, we have analyzed Landau quantization analogs in the
noncommutative phase space, and we obtain also the energy spectrum and the
eigenfunctions in this context.Comment: 20 pages, references adde
New Strong-Field QED Effects at ELI: Nonperturbative Vacuum Pair Production
Since the work of Sauter, and Heisenberg, Euler and K\"ockel, it has been
understood that vacuum polarization effects in quantum electrodynamics (QED)
predict remarkable new phenomena such as light-light scattering and pair
production from vacuum. However, these fundamental effects are difficult to
probe experimentally because they are very weak, and they are difficult to
analyze theoretically because they are highly nonlinear and/or nonperturbative.
The Extreme Light Infrastructure (ELI) project offers the possibility of a new
window into this largely unexplored world. I review these ideas, along with
some new results, explaining why quantum field theorists are so interested in
this rapidly developing field of laser science. I concentrate on the
theoretical tools that have been developed to analyze nonperturbative vacuum
pair production.Comment: 20 pages, 9 figures; Key Lecture at the ELI Workshop and School on
"Fundamental Physics with Ultra-High Fields", 29 Sept - 2 Oct. 2008,
Frauenworth Monastery, Germany; v2: refs updated, English translations of
reviews of Nikishov and Ritu
Thorium speciation in seawater
Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 100 (2006): 250-268, doi:10.1016/j.marchem.2005.10.024.Since the 1960’s, thorium isotopes occupy a special place in the oceanographer’s toolbox as
tracers for determining rates and mechanisms of oceanic scavenging, particle dynamics, and
carbon fluxes. Due to their unique and constant production rates from soluble parent nuclides of
uranium and radium, their disequilibrium can be used to calculate rates and time scales of
sinking particles. In addition, by ratio-ing particulate 234Th (as well, in principle, other Thnuclides)
to carbon (and other elements), and linking this ratio to the parent-daughter
disequilibrium in the water column, it is possible to calculate fluxes of carbon and other
elements. Most of these applications are possible with little knowledge of the dissolved chemical
properties of thorium, other than its oxidation state (IV) and tendency to strongly sorb to
surfaces, i.e., its “particle- or surface-activity”. However, the use of any tracer is hindered by a
lack of knowledge of its chemical properties. Recent observations in the variability of carbon to
234Th ratios in different particle types, as well as of associations of Th(IV) with various marine
organic biomolecules has led to the need for a review of current knowledge and what future
endeavors should be taken to understand the marine chemistry of thorium.The writing of this paper was supported, in parts by NSF (OCE-0351559; OCE-0350758, and
OCE 0354757)
On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection
A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)
Protocol for a partially nested randomised controlled trial to evaluate the effectiveness of the scleroderma patient-centered intervention network COVID-19 home-isolation activities together (SPIN-CHAT) program to reduce anxiety among at-risk scleroderma patients
Objective: Contagious disease outbreaks and related restrictions can lead to negative psychological outcomes, particularly in vulnerable populations at risk due to pre-existing medical conditions. No randomised controlled trials (RCTs) have tested interventions to reduce mental health consequences of contagious disease outbreaks. The primary objective of the Scleroderma Patient-centered Intervention Network COVID-19 Home-isolation Activities Together (SPIN-CHAT) Trial is to evaluate the effect of a videoconference-based program on symptoms of anxiety. Secondary objectives include evaluating effects on symptoms of depression, stress, loneliness, boredom, physical activity, and social interaction.Methods: The SPIN-CHAT Trial is a pragmatic RCT that will be conducted using the SPIN-COVID-19 Cohort, a sub-cohort of the SPIN Cohort. Eligible participants will be SPIN-COVID-19 Cohort participants without a positive COVID-19 test, with at least mild anxiety (PROMIS Anxiety 4a v1.0 T-score >= 55), not working from home, and not receiving current counselling or psychotherapy. We will randomly assign 162 participants to intervention groups of 7 to 10 participants each or waitlist control. We will use a partially nested RCT design to reflect dependence between individuals in training groups but not in the waitlist control. The SPIN-CHAT Program includes activity engagement, education on strategies to support mental health, and mutual participant support. Intervention participants will receive the 4-week (3 sessions per week) SPIN-CHAT Program via video-conference. The primary outcome is PROMIS Anxiety 4a score immediately post-intervention.Ethics and dissemination: The SPIN-CHAT Trial will test whether a brief videoconference-based intervention will improve mental health outcomes among at-risk individuals during contagious disease outbreak
- …