380 research outputs found
Added dietary cobalt or vitamin B12, or injecting vitamin B12 does not improve performance or indicators of ketosis in pre- and post-partum Holstein-Friesian dairy cows
Vitamin B12 is synthesised in the rumen from cobalt and has a major role in metabolism in the peripaturient period, although few studies have evaluated the effect of the dietary inclusion of cobalt (Co), vitamin B12 or injecting vitamin B12 on the metabolism, health and performance of high yielding dairy cows. Fifty-six Holstein-Friesian dairy cows received one of four treatments from 8 weeks prior to calving to 8 weeks post calving: C, no added Co; DC, additional 0.2 mg Co/kg DM; DB, additional 0.68 mg vitamin B12/kg DM; IB, intra-muscular injection of vitamin B12 to supply 0.71 mg/cow/day pre-partum and 1.42 mg/cow/day post-partum. The basal and lactation rations both contained 0.21 mg Co/kg DM. Cows were weighed and condition scored at drying off, 4 weeks prior to calving, within 24 h of calving and at 2, 4 and 8 weeks post-calving, with blood samples collected at drying off, 2 weeks pre-calving, calving and 2, 4 and 8 weeks post-calving. Liver biopsy samples were collected from all animals at drying off and 4 weeks post-calving. Live weight changed with time, but there was no effect of treatment (P>0.05), whereas cows receiving IB had the lowest mean body condition score and DB the highest (P0.05) with mean values of 21.6 kg/day, 39.6 kg/day and 40.4 g/kg respectively. Cows receiving IB had a higher plasma vitamin B12 concentration than those receiving any of the other treatments (P0.05) of treatment on homocysteine or succinate concentrations, although mean plasma methylmalonic acid concentrations were lower (P=0.019) for cows receiving IB than for Control cows. Plasma β-hydroxybutyrate concentrations increased sharply at calving followed by a decline, but there was no effect of treatment. Similarly, there was no effect (P>0.05) of treatment on plasma non-esterified fatty acids or glucose. Whole tract digestibility of DM and fibre measured at week 7 of lactation were similar between treatments, and there was little effect of treatment on the milk fatty acid profile except for C15:0, which was lower in cows receiving DC than IB (P<0.05). It is concluded that a basal dietary concentration of 0.21 mg Co/kg DM is sufficient to meet the requirements of high yielding dairy cows during the transition period, and there is little benefit from additional Co or vitamin B12
The Fermi Liquid as a Renormalization Group Fixed Point: the Role of Interference in the Landau Channel
We apply the finite-temperature renormalization-group (RG) to a model based
on an effective action with a short-range repulsive interaction and a rotation
invariant Fermi surface. The basic quantities of Fermi liquid theory, the
Landau function and the scattering vertex, are calculated as fixed points of
the RG flow in terms of the effective action's interaction function. The
classic derivations of Fermi liquid theory, which apply the Bethe-Salpeter
equation and amount to summing direct particle-hole ladder diagrams, neglect
the zero-angle singularity in the exchange particle-hole loop. As a
consequence, the antisymmetry of the forward scattering vertex is not
guaranteed and the amplitude sum rule must be imposed by hand on the components
of the Landau function. We show that the strong interference of the direct and
exchange processes of particle-hole scattering near zero angle invalidates the
ladder approximation in this region, resulting in temperature-dependent
narrow-angle anomalies in the Landau function and scattering vertex. In this RG
approach the Pauli principle is automatically satisfied. The consequences of
the RG corrections on Fermi liquid theory are discussed. In particular, we show
that the amplitude sum rule is not valid.Comment: 25 pages, RevTeX 3.
Ensemble density functional theory of the fractional quantum Hall effect
We develop an ensemble density functional theory for the fractional quantum
Hall effect using a local density approximation. Model calculations for edge
reconstructions of a spin-polarized quantum dot give results in good agreement
with semiclassical and Hartree-Fock calculations, and with small system
numerical diagonalizations. This establishes the usefulness of density
functional theory to study the fractional quantum Hall effect, which opens up
the possibility of studying inhomegeneous systems with many more electrons than
has heretofore been possible.Comment: Improved discussion of ensemble density functional theory. 4 pages
plus 3 postscript figures, uses latex with revtex. Contact
[email protected]
Condensed matter and AdS/CFT
I review two classes of strong coupling problems in condensed matter physics,
and describe insights gained by application of the AdS/CFT correspondence. The
first class concerns non-zero temperature dynamics and transport in the
vicinity of quantum critical points described by relativistic field theories. I
describe how relativistic structures arise in models of physical interest,
present results for their quantum critical crossover functions and
magneto-thermoelectric hydrodynamics. The second class concerns symmetry
breaking transitions of two-dimensional systems in the presence of gapless
electronic excitations at isolated points or along lines (i.e. Fermi surfaces)
in the Brillouin zone. I describe the scaling structure of a recent theory of
the Ising-nematic transition in metals, and discuss its possible connection to
theories of Fermi surfaces obtained from simple AdS duals.Comment: 39 pages, 12 figures; Lectures at the 5th Aegean summer school, "From
gravity to thermal gauge theories: the AdS/CFT correspondence", and the De
Sitter Lecture Series in Theoretical Physics 2009, University of Groninge
A new synthesis route for sustainable gold copper utilization in direct formic acid fuel cells
In the efforts to develop a more sustainable energy mix there is an urgent need to develop new materials for environmentally friendly processes. Developing low metal loading anode catalyst with high electrocatalytic activity for liquid fuel cells remains a great challenge. Polyvinylpyrrolodoneprotected AuCu-C core-shell was fabricated by a facile one-pot modified chemical reduction method. The nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM) analyses. XRD analysis indicates the preferential orientation of catalytically active (111) planes in AuCu-C core-shell nanoparticles. The inclusion of Cu in the AuCuC catalysts increased catalytic activities, which can be attributed to the increases lattice parameters. Comparative results show that AuCu-C catalyst exhibited much better electrocatalytic activity and stabilization compared to commercial Au nanoparticle on carbon support catalyst. The high performance of AuCu-C catalyst may be attributed to the electronic coupling or synergistic interaction between Cu core structure, and the Au shell makes it a promising for DFAFCs application
Channel Mobility and Contact Resistance in Scaled ZnO Thin-Film Transistors
ZnO thin-film transistors (TFTs) with scaled channel lengths of 10 m, 5 m, 4 m, and 2 m exhibit increasing intrinsic channel electron mobility at a gate bias of 10 V (15 V) from 0.782 cm/Vs (0.83 cm/Vs) in the 10 m channel length TFT to 8.9 cm/Vs (19.04 cm/Vs) for the channel length scaled down to 2 m. Current-voltage measurements indicate an n-type channel enhancement mode transistor operation, with threshold voltages in the range of V to V, maximum drain currents of 41 A/m, 96 A/m, 193 A/m, and 214 A/m at a gate bias of 10 V, and breakdown voltages of 80 V, 70 V, 62 V, and 59 V with respect to channel lengths of 10 m, 5 m, 4 m, and 2 m. The channel electron mobility (excluding contact resistance) is extracted by the transmission line method (TLM) from the effective electron mobility (including contact resistance). The contact sheet resistance of /sq extracted from the measurements, which is larger than the contact sheet resistance of /sq obtained from the DFT calculation and the 1D self-consistent Poisson-Shrödinger simulation, largely limits the drive current in the scaled ZnO TFTs
Measurement of the branching fraction for
We have studied the leptonic decay of the resonance into tau
pairs using the CLEO II detector. A clean sample of tau pair events is
identified via events containing two charged particles where exactly one of the
particles is an identified electron. We find . The result is consistent with
expectations from lepton universality.Comment: 9 pages, RevTeX, two Postscript figures available upon request, CLNS
94/1297, CLEO 94-20 (submitted to Physics Letters B
Study of the B^0 Semileptonic Decay Spectrum at the Upsilon(4S) Resonance
We have made a first measurement of the lepton momentum spectrum in a sample
of events enriched in neutral B's through a partial reconstruction of B0 -->
D*- l+ nu. This spectrum, measured with 2.38 fb**-1 of data collected at the
Upsilon(4S) resonance by the CLEO II detector, is compared directly to the
inclusive lepton spectrum from all Upsilon(4S) events in the same data set.
These two spectra are consistent with having the same shape above 1.5 GeV/c.
From the two spectra and two other CLEO measurements, we obtain the B0 and B+
semileptonic branching fractions, b0 and b+, their ratio, and the production
ratio f+-/f00 of B+ and B0 pairs at the Upsilon(4S). We report b+/b0=0.950
(+0.117-0.080) +- 0.091, b0 = (10.78 +- 0.60 +- 0.69)%, and b+ = (10.25 +- 0.57
+- 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes,
tau+/tau0.Comment: 14 page, postscript file also available at
http://w4.lns.cornell.edu/public/CLN
Measurement of the Decay Asymmetry Parameters in and
We have measured the weak decay asymmetry parameters (\aLC ) for two \LC\
decay modes. Our measurements are \aLC = -0.94^{+0.21+0.12}_{-0.06-0.06} for
the decay mode and \aLC = -0.45\pm 0.31 \pm
0.06 for the decay mode . By combining these
measurements with the previously measured decay rates, we have extracted the
parity-violating and parity-conserving amplitudes. These amplitudes are used to
test models of nonleptonic charmed baryon decay.Comment: 11 pages including the figures. Uses REVTEX and psfig macros. Figures
as uuencoded postscript. Also available as
http://w4.lns.cornell.edu/public/CLNS/1995/CLNS95-1319.p
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