465 research outputs found
Determination of absorption of vitamin B<SUB>12</SUB> by a double isotope tracer technique
A new simple method for the study of vitamin B12 absorption involving the use of two tracers is described. Along with 58Co labeled vitamin B12 an unabsorbable marker in the form of 51Cr labeled chromic oxide is administered to the patients. The ratio of the activities of the two isotopes in the standard is compared with the ratio of the activies of these isotopes in an aliquot of a stool sample collected after 24 or 48 hours. The absorption of labeled vitamin B12 is estimated from the alteration in the ratio of absorbable and unabsorbable isotopes in the stool sample. The method compares well with other methods of estimating vitamin B12 absorption such as Schilling's test, total faecal collection and whole body counting
Josephson Coupling through a Quantum Dot
We derive, via fourth order perturbation theory, an expression for the
Josephson current through a gated interacting quantum dot. We analyze our
expression for two different models of the superconductor-dot-superconductor
(SDS) system. When the matrix elements connecting dot and leads are featureless
constants, we compute the Josephson coupling J_c as a function of the gate
voltage and Coulomb interaction. In the diffusive dot limit, we compute the
probability distribution P(J_c) of Josephson couplings. In both cases, pi
junction behavior (J_c < 0) is possible, and is not simply dependent on the
parity of the dot occupancy.Comment: 9 pages; 3 encapsulated PostScript figure
Thyroid hormones And [<SUP>14</SUP>C] glucose metabolism in bacteria
The effects of triiodothyronine and thyroxine on metabolism and growth of bacteria were studied. It was observed that over a certain range of concentration thyroxine and triiodothyronine produced increase in 14CO2 release from [14C]-labeled glucose and also stimulated bacteria growth
Study of natural convection in inclined square enclosure with uniform heat generation.
ABSTRACT Two-dimensional laminar natural convection in an incline
Bilayers of Chiral Spin States
We study the behavior of two planes of Quantum Heisenberg Antiferromagnet in
the regime in which a Chiral Spin Liquid is stabilized in each plane. The
planes are coupled by an exchange interaction of strength . We show that
in the regime of small (for both ferromagnetic {\it and}
antiferromagnetic coupling), the system dynamically selects an
\underline{antiferromagnetic} ordering of the ground state {\it chiralities} of
the planes. For the case of an antiferromagnetic interaction between the
planes, we find that, at some critical value of the inter-layer
coupling, there is a phase transition to a valence-bond state on the interlayer
links. We derive an effective Landau-Ginzburg theory for this phase transition.
It contains two gauge fields coupled to the order parameter field. We
study the low energy spectrum of each phase. In the condensed phase an
``anti-Higgs-Anderson" mechanism occurs. It effectively restores time-reversal
invariance by rendering massless one of the gauge fields while the other field
locks the chiral degrees of freedom locally. There is no phase transition for
ferromagnetic couplings.Comment: to appear in Phys. Rev. B; shortened version; several typos correcte
Strong Phase Separation in a Model of Sedimenting Lattices
We study the steady state resulting from instabilities in crystals driven
through a dissipative medium, for instance, a colloidal crystal which is
steadily sedimenting through a viscous fluid. The problem involves two coupled
fields, the density and the tilt; the latter describes the orientation of the
mass tensor with respect to the driving field. We map the problem to a 1-d
lattice model with two coupled species of spins evolving through conserved
dynamics. In the steady state of this model each of the two species shows
macroscopic phase separation. This phase separation is robust and survives at
all temperatures or noise levels--- hence the term Strong Phase Separation.
This sort of phase separation can be understood in terms of barriers to
remixing which grow with system size and result in a logarithmically slow
approach to the steady state. In a particular symmetric limit, it is shown that
the condition of detailed balance holds with a Hamiltonian which has
infinite-ranged interactions, even though the initial model has only local
dynamics. The long-ranged character of the interactions is responsible for
phase separation, and for the fact that it persists at all temperatures.
Possible experimental tests of the phenomenon are discussed.Comment: To appear in Phys Rev E (1 January 2000), 16 pages, RevTex, uses
epsf, three ps figure
Effective Actions and Phase Fluctuations in d-wave Superconductors
We study effective actions for order parameter fluctuations at low
temperature in layered d-wave superconductors such as the cuprates. The order
parameter lives on the bonds of a square lattice and has two amplitude and two
phase modes associated with it. The low frequency spectral weights for
amplitude and relative phase fluctuations is determined and found to be
subdominant to quasiparticle contributions. The Goldstone phase mode and its
coupling to density fluctuations in charged systems is treated in a
gauge-invariant manner. The Gaussian phase action is used to study both the
-axis Josephson plasmon and the more conventional in-plane plasmon in the
cuprates. We go beyond the Gaussian theory by deriving a coarse-grained quantum
XY model, which incorporates important cutoff effects overlooked in previous
studies. A variational analysis of this effective model shows that in the
cuprates, quantum effects of phase fluctuations are important in reducing the
zero temperature superfluid stiffness, but thermal effects are small for .Comment: Some numerical estimates corrected and figures changed. to appear in
PRB, Sept.1 (2000
Phase fluctuations, dissipation and superfluid stiffness in d-wave superconductors
We study the effect of dissipation on quantum phase fluctuations in d-wave
superconductors. Dissipation, arising from a nonzero low frequency optical
conductivity which has been measured in experiments below , has two
effects: (1) a reduction of zero point phase fluctuations, and (2) a reduction
of the temperature at which one crosses over to classical thermal fluctuations.
For parameter values relevant to the cuprates, we show that the crossover
temperature is still too large for classical phase fluctuations to play a
significant role at low temperature. Quasiparticles are thus crucial in
determining the linear temperature dependence of the in-plane superfluid
stiffness. Thermal phase fluctuations become important at higher temperatures
and play a role near .Comment: Presentation improved, new references added (10 latex pages, 3 eps
figures). submitted to PR
Oral prehabilitation for patients with head and neck cancer:getting it right - the Restorative Dentistry-UK consensus on a multidisciplinary approach to oral and dental assessment and planning prior to cancer treatment
Historically, oral and dental issues for head and neck cancer patients were often not considered until after cancer treatment was complete. As a result, outcomes for oral rehabilitation were sometimes suboptimal. Inconsistencies in service delivery models and qualification, training and experience of staff delivering dental care often compounded this problem, making research and audit almost impossible. Collaborative working by consultants in restorative dentistry from all over the UK as part of a Restorative Dentistry-UK (RD UK) subgroup, renamed more recently as the RD-UK Head and Neck Cancer Clinical Excellence Network (CEN), has re-emphasised the importance of specialist restorative dentistry intervention at the outset of the head and neck cancer pathway to optimise outcomes of patient care. The CEN has driven several initiatives, reflecting Getting It Right First Time (GIRFT) principles aimed at reducing unwarranted variation. This improved consistency in approach and optimised collaborative working of the team now presents a better environment for multicentre audit and research. Ultimately, this should result in a continued improvement in patient and carer experience
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