6,952 research outputs found
Voltammetric determination of melatonin in tablet dosage forms and human serum
The electrochemical oxidation of melatonin is studied in Britton-Robinson buffer in the pH range 2.2-11.8 by cyclic voltammetry at glassy carbon electrode. Three irreversible, diffusion-controlled oxidation peaks were obtained. The utility of using differential pulse and square wave techniques for determination of melatonin was examined. Different parameters affecting the peak current were analylzed and at optimum conditions, linear calibration plots from 0.02-0.5 mM and 0.04 to 0.5 mM of melatonin were obtained applying the two techniques, respectively. The differential pulse mode was successfully applied to the determination of melatonin in commercial tablets containing about three-folds of vitamin B6 without previous separation. The same technique was also used for melatonin determination in human serum with acceptable accuracy.Colegio de Farmacéuticos de la Provincia de Buenos Aire
Voltammetric determination of melatonin in tablet dosage forms and human serum
The electrochemical oxidation of melatonin is studied in Britton-Robinson buffer in the pH range 2.2-11.8 by cyclic voltammetry at glassy carbon electrode. Three irreversible, diffusion-controlled oxidation peaks were obtained. The utility of using differential pulse and square wave techniques for determination of melatonin was examined. Different parameters affecting the peak current were analylzed and at optimum conditions, linear calibration plots from 0.02-0.5 mM and 0.04 to 0.5 mM of melatonin were obtained applying the two techniques, respectively. The differential pulse mode was successfully applied to the determination of melatonin in commercial tablets containing about three-folds of vitamin B6 without previous separation. The same technique was also used for melatonin determination in human serum with acceptable accuracy.Colegio de Farmacéuticos de la Provincia de Buenos Aire
Effects of dissipation in an adiabatic quantum search algorithm
We consider the effect of two different environments on the performance of
the quantum adiabatic search algorithm, a thermal bath at finite temperature,
and a structured environment similar to the one encountered in systems coupled
to the electromagnetic field that exists within a photonic crystal. While for
all the parameter regimes explored here, the algorithm performance is worsened
by the contact with a thermal environment, the picture appears to be different
when considering a structured environment. In this case we show that, by tuning
the environment parameters to certain regimes, the algorithm performance can
actually be improved with respect to the closed system case. Additionally, the
relevance of considering the dissipation rates as complex quantities is
discussed in both cases. More particularly, we find that the imaginary part of
the rates can not be neglected with the usual argument that it simply amounts
to an energy shift, and in fact influences crucially the system dynamics.Comment: 18 pages, 9 figure
Stationary Josephson effect in a weak-link between nonunitary triplet superconductors
A stationary Josephson effect in a weak-link between misorientated nonunitary
triplet superconductors is investigated theoretically. The non-self-consistent
quasiclassical Eilenberger equation for this system has been solved
analytically. As an application of this analytical calculation, the
current-phase diagrams are plotted for the junction between two nonunitary
bipolar wave superconducting banks. A spontaneous current parallel to the
interface between superconductors has been observed. Also, the effect of
misorientation between crystals on the Josephson and spontaneous currents is
studied. Such experimental investigations of the current-phase diagrams can be
used to test the pairing symmetry in the above-mentioned superconductors.Comment: 6 pages and 6 figure
A Deep Cascade of Convolutional Neural Networks for MR Image Reconstruction
The acquisition of Magnetic Resonance Imaging (MRI) is inherently slow.
Inspired by recent advances in deep learning, we propose a framework for
reconstructing MR images from undersampled data using a deep cascade of
convolutional neural networks to accelerate the data acquisition process. We
show that for Cartesian undersampling of 2D cardiac MR images, the proposed
method outperforms the state-of-the-art compressed sensing approaches, such as
dictionary learning-based MRI (DLMRI) reconstruction, in terms of
reconstruction error, perceptual quality and reconstruction speed for both
3-fold and 6-fold undersampling. Compared to DLMRI, the error produced by the
method proposed is approximately twice as small, allowing to preserve
anatomical structures more faithfully. Using our method, each image can be
reconstructed in 23 ms, which is fast enough to enable real-time applications
Coverage maximization for a poisson field of drone cells
The use of drone base stations to provide wireless connectivity for ground terminals is becoming a promising part of future technologies. The design of such aerial networks is however different compared to cellular 2D networks, as antennas from the drones are looking down, and the channel model becomes height-dependent. In this paper, we study the effect of antenna patterns and height-dependent shadowing. We consider a random network topology to capture the effect of dynamic changes of the flying base stations. First we characterize the aggregate interference imposed by the co-channel neighboring drones. Then we derive the link coverage probability between a ground user and its associated drone base station. The result is used to obtain the optimum system parameters in terms of drones antenna beamwidth, density and altitude. We also derive the average LoS probability of the associated drone and show that it is a good approximation and simplification of the coverage probability in low altitudes up to 500 m according to the required signal-to-interference-plus-noise ratio (SINR)
Voltammetric determination of melatonin in tablet dosage forms and human serum
The electrochemical oxidation of melatonin is studied in Britton-Robinson buffer in the pH range 2.2-11.8 by cyclic voltammetry at glassy carbon electrode. Three irreversible, diffusion-controlled oxidation peaks were obtained. The utility of using differential pulse and square wave techniques for determination of melatonin was examined. Different parameters affecting the peak current were analylzed and at optimum conditions, linear calibration plots from 0.02-0.5 mM and 0.04 to 0.5 mM of melatonin were obtained applying the two techniques, respectively. The differential pulse mode was successfully applied to the determination of melatonin in commercial tablets containing about three-folds of vitamin B6 without previous separation. The same technique was also used for melatonin determination in human serum with acceptable accuracy.Colegio de Farmacéuticos de la Provincia de Buenos Aire
Wigner distribution function formalism for superconductors and collisionless dynamics of the superconducting order parameter
A technique to study collisionless dynamics of a homogeneous superconducting
system is developed, which is based on Riccati parametrization of Wigner
distribution function. The quantum evolution of the superconductiung order
parameter, initially deviated from the equilibrium value, is calculated using
this technique. The effect of a time-dependent BCS paring interaction on the
dynamics of the order parameter is also studied.Comment: 14 pages, 5 figure
Josephson effect in point contacts between ''f-wave'' superconductors
A stationary Josephson effect in point contacts between triplet
superconductors is analyzed theoretically for most probable models of the order
parameter in UPt_{3} and Sr_{2}RuO_{4}. The consequence of misorientation of
crystals in superconducting banks on this effect is considered. We show that
different models for the order parameter lead to quite different current-phase
dependences. For certain angles of misorientation a boundary between
superconductors can generate the parallel to surface spontaneous current. In a
number of cases the state with a zero Josephson current and minimum of the free
energy corresponds to a spontaneous phase difference. This phase difference
depends on the misorientation angle and may possess any value. We conclude that
experimental investigations of the current-phase dependences of small junctions
can be used for determination of the order parameter symmetry in the mentioned
above superconductors.Comment: 11 pages, 8 figure
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