29,255 research outputs found
Effect of fumaric acid, calcium formate and mineral levels in diets on the intake and growth performance of newly weaned pigs
peer-reviewedThe weaned pig has limited ability to acidify its stomach contents. The objective of this study (comprising three experiments) was to examine the effect of feeding diets
containing fumaric acid (FA), calcium formate (CF) or diets of low acid binding capacity (ABC) on post-weaning pig performance. In all three experiments, pigs (10 per treatment) were weaned at 19 to 24 days, blocked on sex and weight and assigned at random to one of six treatments. In Experiment 1, treatments were: (1) control diet, (2) control 20 g/kg FA, (3) control 15 g/kg CF, (4) low Ca (2.8 g/kg) and P (5.1 g/kg) (LCaP) diet for seven days followed by the control diet, (5) LCaP diet for seven days followed by control 20 g/kg FA, and (6) LCaP diet for seven days followed by control 15 g/kg CF. In Experiment 2, treatments were: (1) control diet, (2) control 20 g/kg FA, (3) control 15 g/kg CF, (4) LCaP diet for 14 days followed by the control diet, (5) LCaP diet for 14 days followed by control 20 g/kg FA, and (6) LCaP diet for seven days followed by control diet. In Experiment 3, treatments were: (1) high Ca (HC) diet (12 g/kg), (2) medium Ca (MC) diet (9 g/kg), (3) low Ca (LC) diet (6 g/kg), (4) HC 20 g/kg FA, (5) MC 20 g/kg FA, and (6) LC 20 g/kg FA. Pigs were individually fed for 26 days. In Experiment 1, CF tended to depress daily feed intake (DFI) in the final two weeks (691 v. 759 and 749, (s.e. 19) g/day, P = 0.07) and overall average daily gain (322 v. 343 and 361 (s.e. 11) g/day, P = 0.09) compared with the control and FA supplemented diets, respectively. Feeding diets with LCaP for seven days post
weaning increased DFI (208 v. 178, (s.e. 8) g/day, P < 0.01) in week 1 and tended to
improve feed conversion rate in the first two weeks (1.65 v. 1.85, s.e. 0.10, P = 0.09). In Experiment 2, treatment had no significant effect on pig performance but feed conversion rate in weeks three and four was improved for Treatment 5 compared with
Treatment 4 (1.30 v. 1.39 (s.e. 0.06) g/g, P < 0.01). In experiment 3, FA increased (P <
0.05) pig weight at day 14 (8.4 v. 7.7 (s.e. 0.2) kg) and feed intake in weeks one and two
(223 v. 251, (s.e. 9) g/day). It is concluded that CF did not improve performance but reducing diet ABC or including FA in the diet did improve performance
Semi-automatic selection of summary statistics for ABC model choice
A central statistical goal is to choose between alternative explanatory
models of data. In many modern applications, such as population genetics, it is
not possible to apply standard methods based on evaluating the likelihood
functions of the models, as these are numerically intractable. Approximate
Bayesian computation (ABC) is a commonly used alternative for such situations.
ABC simulates data x for many parameter values under each model, which is
compared to the observed data xobs. More weight is placed on models under which
S(x) is close to S(xobs), where S maps data to a vector of summary statistics.
Previous work has shown the choice of S is crucial to the efficiency and
accuracy of ABC. This paper provides a method to select good summary statistics
for model choice. It uses a preliminary step, simulating many x values from all
models and fitting regressions to this with the model as response. The
resulting model weight estimators are used as S in an ABC analysis. Theoretical
results are given to justify this as approximating low dimensional sufficient
statistics. A substantive application is presented: choosing between competing
coalescent models of demographic growth for Campylobacter jejuni in New Zealand
using multi-locus sequence typing data
Knudsen Diffusion in Silicon Nanochannels
Measurements on helium and argon gas flow through an array of parallel,
linear channels of 12 nm diameter and 200 micrometer length in a single
crystalline silicon membrane reveal a Knudsen diffusion type transport from
10^2 to 10^7 in Knudsen number Kn. The classic scaling prediction for the
transport diffusion coefficient on temperature and mass of diffusing
species,D_He ~ sqrt(T), is confirmed over a T range from 40 K to 300 K for He
and for the ratio of D_He/D_Ar ~ sqrt(m_Ar/m_He). Deviations of the channels
from a cylindrical form, resolved with transmission electron microscopy down to
subnanometer scales, quantitatively account for a reduced diffusivity as
compared to Knudsen diffusion in ideal tubular channels. The membrane
permeation experiments are described over 10 orders of magnitude in Kn,
encompassing the transition flow regime, by the unified flow model of Beskok
and Karniadakis.Comment: 4 pages, 3 figure
The Spin--Symmetry of the Quark Model
Corrections to the exact heavy--quark symmetry results are expected to follow
the mass effect of the heavy--quark. We show, by an explicit
calculation, that there is something other than the mass effect that suppresses
the breaking of the spin symmetry
Interpreting Dark Matter Direct Detection Independently of the Local Velocity and Density Distribution
We demonstrate precisely what particle physics information can be extracted
from a single direct detection observation of dark matter while making
absolutely no assumptions about the local velocity distribution and local
density of dark matter. Our central conclusions follow from a very simple
observation: the velocity distribution of dark matter is positive definite,
f(v) >= 0. We demonstrate the utility of this result in several ways. First, we
show a falling deconvoluted recoil spectrum (deconvoluted of the nuclear form
factor), such as from ordinary elastic scattering, can be "mocked up" by any
mass of dark matter above a kinematic minimum. As an example, we show that dark
matter much heavier than previously considered can explain the CoGeNT excess.
Specifically, m_chi < m_Ge} can be in just as good agreement as light dark
matter, while m_\chi > m_Ge depends on understanding the sensitivity of Xenon
to dark matter at very low recoil energies, E_R ~ 6 keVnr. Second, we show that
any rise in the deconvoluted recoil spectrum represents distinct particle
physics information that cannot be faked by an arbitrary f(v). As examples of
resulting non-trivial particle physics, we show that inelastic dark matter and
dark matter with a form factor can both yield such a rise
Femtosecond resolution timing jitter correction on a TW scale Ti:sapphire laser system for FEL pump-probe experiments
Intense ultrashort pulse lasers are used for fs resolution pumpprobe
experiments more and more at large scale facilities, such as free electron
lasers (FEL). Measurement of the arrival time of the laser pulses and
stabilization to the machine or other sub-systems on the target, is crucial for
high time-resolution measurements. In this work we report on a single shot,
spectrally resolved, non-collinear cross-correlator with sub-fs resolution.
With a feedback applied we keep the output of the TW class Ti:sapphire
amplifier chain in time with the seed oscillator to ~3 fs RMS level for several
hours. This is well below the typical pulse duration used at FELs and supports
fs resolution pump-probe experiments. Short term jitter and long term timing
drift measurements are presented. Applicability to other wavelengths and
integration into the timing infrastructure of the FEL are also covered to show
the full potential of the device
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