10,476 research outputs found
An Investigation of the Adsorption Characteristics of 5'ATP and 5'AMP onto the Surface of Caso4 x 2H2O
A model has been proposed in which solid surfaces can act as a site for cataletic activity of condensation reactions for certain biomolecules. From this model, the adsorption characteristics of 5'ATP and 5'AMP onto the surface of CaSO4.2H2O was chosen for study. It has been proven that 5'ATP and 5'AMP do adsorb onto the surface of CaSO4. Studies were then made to determine the dependence of absorption versus time, concentration, ionic strength and pH. It was found that the adsorption of the nucleotides is highly pH dependent, primarily determined by the phosphate acid groups of the nucleic acid molecule. From this investigation, the data obtained is discussed in relation to the model for the prebiotic earth
An investigation of the adsorption characteristics of 5 prime ATP and 5 prime AMP onto the surface of CaSO sub 4 x 2H sub 2 O
A model has been proposed (Lahev and Chans, 1982) in which solid surfaces can act as a site for catalytic activity of condensation reactions for certain biomolecules. From this model, the adsorption characteristics of 5'ATP and 5'AMP onto the surface of CaSO4 2H2O was chosen for study. It has been proven that 5'ATP and 5'AMP do adsorb onto the surface of CaSO4. Studies were then made to determine the dependence of adsorption versus time, concentration, ionic strength and pH. It was found that the adsorption of the nucleotides is highly pH dependent, primarily determined by the phosphate acid groups of the nucleic acid molecule. From this investigation, the data obtained are discussed in relation to the model for the prebiotic earth
Tight binding model for iron pnictides
We propose a five-band tight-binding model for the Fe-As layers of iron
pnictides with the hopping amplitudes calculated within the Slater-Koster
framework. The band structure found in DFT, including the orbital content of
the bands, is well reproduced using only four fitting parameters to determine
all the hopping amplitudes. The model allows to study the changes in the
electronic structure caused by a modification of the angle formed by
the Fe-As bonds and the Fe-plane and recovers the phenomenology previously
discussed in the literature. We also find that changes in modify the
shape and orbital content of the Fermi surface sheets.Comment: 12 pages, 6 eps figures. Figs 1 and 2 modified, minor changes in the
text. A few references adde
Valley interference effects on a donor electron close to a Si/SiO2 interface
We analyze the effects of valley interference on the quantum control and
manipulation of an electron bound to a donor close to a Si/SiO2 interface as a
function of the valley-orbit coupling at the interface. We find that, for
finite valley-orbit coupling, the tunneling times involved in shuttling the
electron between the donor and the interface oscillate with the interface/donor
distance in much the same way as the exchange coupling oscillates with the
interdonor distance. These oscillations disappear when the ground state at the
interface is degenerate (corresponding to zero valley-orbit coupling).Comment: 7 pages, 5 figure
Survival and Nonescape Probabilities for Resonant and Nonresonant Decay
In this paper we study the time evolution of the decay process for a particle
confined initially in a finite region of space, extending our analysis given
recently (Phys. Rev. Lett. 74, 337 (1995)). For this purpose, we solve exactly
the time-dependent Schroedinger equation for a finite-range potential. We
calculate and compare two quantities: (i) the survival probability S(t), i.e.,
the probability that the particle is in the initial state after a time t; and
(ii) the nonescape probability P(t), i.e., the probability that the particle
remains confined inside the potential region after a time t. We analyze in
detail the resonant and nonresonant decay. In the former case, after a very
short time, S(t) and P(t) decay exponentially, but for very long times they
decay as a power law, albeit with different exponents. For the nonresonant case
we obtain that both quantities differ initially. However, independently of the
resonant and nonresonant character of the initial state we always find a
transition to the ground state of the system which indicates a process of
``loss of memory'' in the decay.Comment: 26 pages, RevTex file, figures available upon request from
[email protected] (To be published in Annals of Physics
Optical conductivity and Raman scattering of iron superconductors
We discuss how to analyze the optical conductivity and Raman spectra of
multi-orbital systems using the velocity and the Raman vertices in a similar
way Raman vertices were used to disentangle nodal and antinodal regions in
cuprates. We apply this method to iron superconductors in the magnetic and
non-magnetic states, studied at the mean field level. We find that the
anisotropy in the optical conductivity at low frequencies reflects the
difference between the magnetic gaps at the X and Y electron pockets. Both gaps
are sampled by Raman spectroscopy. We also show that the Drude weight
anisotropy in the magnetic state is sensitive to small changes in the lattice
structure.Comment: 14 pages, 10 figures, as accepted in Phys. Rev. B,
explanations/discussion added in Secs. II, III and V
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