678 research outputs found
Some modern extensions of liability for negligence : inaugural lecture delivered at Rhodes University
Inaugural lecture delivered at Rhodes UniversityRhodes University Libraries (Digitisation
Determining the Gluon Distributions in the Proton and Photon from Two-Jet Production at HERA
Two-jet production from the direct photon contribution at HERA is a sensitive
measure of the small- gluon in the proton. We propose measurements of ratios
of the jet cross-sections which will clearly distinguish between gluons with or
without singular behaviour at small . Furthermore, we show that analogous
ratio measurements for the resolved photon contribution provide a sensitive way
of determining the gluon distribution in the photon.Comment: Rutherford Appleton Laboratory report RAL-93-071 7 pages 3 figs Fig2
and Fig3 included as psfile
Pinning down the Glue in the Proton
The latest measurements of at HERA allow for a {\it combination} of
gluon and sea quark distributions at small that is significantly different
from those of existing parton sets. We perform a new global fit to
deep-inelastic and related data. We find a gluon distribution which is larger
for x \lapproxeq 0.01, and smaller for , and a flatter input sea
quark distribution than those obtained in our most recent global analysis. The
new fit also gives . We study other experimental
information available for the gluon including, in particular, the constraints
coming from fixed-target and collider prompt production data.Comment: 8 pages, LATEX, 6 figs available as .uu fil
How to grow brand post engagement on Facebook and Twitter for airlines? An empirical investigation of design and content factors
acceptedVersio
Self-consistent model of ultracold atomic collisions and Feshbach resonances in tight harmonic traps
We consider the problem of cold atomic collisions in tight traps, where the
absolute scattering length may be larger than the trap size. As long as the
size of the trap ground state is larger than a characteristic length of the van
der Waals potential, the energy eigenvalues can be computed self-consistently
from the scattering amplitude for untrapped atoms. By comparing with the exact
numerical eigenvalues of the trapping plus interatomic potentials, we verify
that our model gives accurate eigenvalues up to milliKelvin energies for single
channel s-wave scattering of Na atoms in an isotropic harmonic trap,
even when outside the Wigner threshold regime. Our model works also for
multi-channel scattering, where the scattering length can be made large due to
a magnetically tunable Feshbach resonance.Comment: 7 pages, 4 figures (PostScript), submitted to Physical Review
Structure and Functional Evaluation of TendonâSkeletal Muscle Constructs Engineered in Vitro
During muscle contraction, the integrity of the myotendinous junction (MTJ) is important for the transmission of force from muscle to tendon. We evaluated the contractile and structural characteristics of 3-dimensional (3-D) skeletal muscle constructs co-cultured with engineered self-organized tendon constructs (n = 4), or segments of adult (n = 4) or fetal (n = 5) rat-tail tendon. We hypothesized that the co-culture of tendon and muscle would produce constructs with viable muscleâtendon interfaces that remain intact during generation of force. Construct diameter (lm) and maximum isometric force (”N) were measured, and specific force (kPa) was determined. After measure of force, constructs were loaded at a constant strain rate until failure and surface strains were recorded optically across the tendon, the muscle and the interface and used to determine the tangent modulus (passive stiffness) of the construct. Frozen samples were used for Trichrome Masson staining and immunofluorescent analysis of the MTJ-specific protein paxillin. No differences were observed between the groups with respect to diameter, maximum force, or specific force. The MTJ was robust and withstood tensile loading beyond the physiological strain range. The majority of the constructs failed in the muscle region. At the MTJ, there is an increase in the expression and localization of paxillin. In conclusion, using 3 sources of tendon tissue, we successfully engineered 3-D muscleâtendon constructs with functionally viable MTJ, characterized by structural features and protein expression patterns resembling neonatal MTJs in vivo.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63387/1/ten.2006.12.3149.pd
Recommended from our members
New Molecular Collisional Interaction Effect in Low-Energy Sputtering
Y. Yao, Z. Hargitai, M. Albert, R. G. Albridge, A. V. Barnes, J. M. Gilligan, B. Pratt Ferguson,
G. LĂŒpke, V. D. Gordon (currently with UT Austin), and N. H. Tolk are with the
Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 -- J. C. Tully is with the
Department of Physics and Department of Chemistry, Yale University, New Haven, Connecticut 06520 -- G. Betz and W. Husinsky are with the
Institut fĂŒr Allgemeine Physik, Technische UniversitĂ€t Wien, A-1040 Vienna, AustriaAn unexpected pronounced enhancement is observed in sputtering yields per atom for N2+
compared
to N+ from a polycrystalline gold target. This effect is seen when the kinetic energy per projectile
atom is below 500 eV and increases as projectile energy decreases to near-threshold energies.
Enhancements for O2+
over O+ begin at even lower kinetic energies below 100 eV per atom. This
new molecular interaction effect may be explained qualitatively by invoking a simple energy transfer
model which involves the vibrational frequency of the molecule and the collisional interaction time.
[S0031-9007(98)06668-X]Chemistr
The Use of IQ and Descriptions of People with Intellectual Disabilities in the Scientific Literature
Methane Emissions from Grazing Holstein-Friesian Heifers at Different Ages Estimated Using the Sulfur Hexafluoride Tracer Technique
Publication history: Accepted - 9 May 2017; Published online - 17 May 2017Although the effect of animal and diet factors on enteric methane (CH4) emissions from confined cattle has
been extensively examined, less data is available regarding CH4 emissions from grazing young cattle. A study
was undertaken to evaluate the effect of the physiological state of Holstein-Friesian heifers on their enteric
CH4 emissions while grazing a perennial ryegrass sward. Two experiments were conducted: Experiment 1
ran from May 2011 for 11 weeks and Experiment 2 ran from August 2011 for 10 weeks. In each experiment,
Holstein-Friesian heifers were divided into three treatment groups (12 animals/group) consisting of calves,
yearling heifers, and in-calf heifers (average ages: 8.5, 14.5, and 20.5 months, respectively). Methane emissions were estimated for each animal in the final week of each experiment using the sulfur hexafluoride
tracer technique. Dry matter (DM) intake was estimated using the calculated metabolizable energy (ME)
requirement divided by the ME concentration in the grazed grass. As expected, live weight increased with
increasing animal age (P < 0.001); however, there was no difference in live weight gain among the three
groups in Experiment 1, although in Experiment 2, this variable decreased with increasing animal age
(P < 0.001). In Experiment 1, yearling heifers had the highest CH4 emissions (g·dâ1) and in-calf heifers produced more than calves (P < 0.001). When expressed as CH4 emissions per unit of live weight, DM intake,
and gross energy (GE) intake, yearling heifers had higher emission rates than calves and in-calf heifers
(P < 0.001). However, the effects on CH4 emissions were different in Experiment 2, in which CH4 emissions
(g·dâ1) increased linearly with increasing animal age (P < 0.001), although the difference between yearling
and in-calf heifers was not significant. The CH4/live weight ratio was lower in in-calf heifers than in the other two groups (P < 0.001), while CH4 energy output as a proportion of GE intake was lower in calves than in
yearling and in-calf heifers (P < 0.05). All data were then pooled and used to develop prediction equations for
CH4 emissions. All relationships are significant (P < 0.001), with R2
values ranging from 0.630 to 0.682. These
models indicate that CH4 emissions could be increased by 0.252 g·dâ1 with an increase of 1 kg live weight
or by 14.9 g·dâ1 with an increase of 1 kg·dâ1 of DM intake; or, the CH4 energy output could be increased by
0.046 MJ·dâ1 with an increase of 1 MJ·dâ1 of GE intake. These results provide an alternative approach for estimating CH4 emissions from grazing dairy heifers when actual CH4 emission data are not availableThe study was funded by the Department for Environment Food
& Rural Affairs, the Scottish Government, the Department of Agriculture and Rural Development for Northern Ireland, and the Welsh
Government, as part of the UKâs Agricultural GHG Research Platform
initiativ
Electron spin coherence in semiconductors: Considerations for a spin-based solid state quantum computer architecture
We theoretically consider coherence times for spins in two quantum computer
architectures, where the qubit is the spin of an electron bound to a P donor
impurity in Si or within a GaAs quantum dot. We show that low temperature
decoherence is dominated by spin-spin interactions, through spectral diffusion
and dipolar flip-flop mechanisms. These contributions lead to 1-100 s
calculated spin coherence times for a wide range of parameters, much higher
than former estimates based on measurements.Comment: Role of the dipolar interaction clarified; Included discussion on the
approximations employed in the spectral diffusion calculation. Final version
to appear in Phys. Rev.
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