2,839 research outputs found
Zeeman response of d-wave superconductors: Born approximation for impurity and spin-orbit scattering potentials
The effects of impurity and spin-orbit scattering potentials can strongly
affect the Zeeman response of a d-wave superconductor. Here, both the phase
diagram and the quasiparticle density of states are calculated within the Born
approximation and it is found that the spin-orbit interaction influences in a
qualitatively different way the Zeeman response of d-wave and s-wave
superconductors.Comment: 19 pages, 6 eps figures, submitted to Physica
Anisotropic random resistor networks: a model for piezoresistive response of thick-film resistors
A number of evidences suggests that thick-film resistors are close to a
metal-insulator transition and that tunneling processes between metallic grains
are the main source of resistance. We consider as a minimal model for
description of transport properties in thick-film resistors a percolative
resistor network, with conducting elements governed by tunneling. For both
oriented and randomly oriented networks, we show that the piezoresistive
response to an applied strain is model dependent when the system is far away
from the percolation thresold, while in the critical region it acquires
universal properties. In particular close to the metal-insulator transition,
the piezoresistive anisotropy show a power law behavior. Within this region,
there exists a simple and universal relation between the conductance and the
piezoresistive anisotropy, which could be experimentally tested by common
cantilever bar measurements of thick-film resistors.Comment: 7 pages, 2 eps figure
Ion implantation and low-temperature epitaxial regrowth of GaAs
Channeling and transmission electron microscopy have been used to investigate the parameters that govern the extent of damage in ionâimplanted GaAs and the crystal quality following capless furnace annealing at low temperature (âŒ400â°C). The implantationâinduced disorder showed a strong dependence on the implanted ion mass and on the substrate temperature during implantation. When the implantation produced a fully amorphous surface layer the main parameter governing the regrowth was the amorphous thickness. Formation of microtwins after annealing was observed when the initial amorphous layer was thicker than 400 Ă
. Also, the number of extended residual defects after annealing increased linearly with the initial amorphous thickness and extrapolation of that curve predicts good regrowth of very thin (<400 Ă
) GaAs amorphous layers produced by ion implantation. A model is presented to explain the observed features of the lowâtemperature annealing of GaAs
Epitaxial regrowth of thin amorphous GaAs layers
Channeling and transmission electron microscopy have been used to investigate the parameters that govern the crystal quality following capless funace annealing at low temperature (~ 400 °C) in ion-implanted GaAs. From the results obtained, we concluded that the crystal quality after annealing depends strongly on the thickness of the amorphous layer generated by ion implantation and the number of residual defects increases linearly with the thickness of the implanted layer. Single-crystal regrowth free of defects detectable by megaelectron volt He + channeling was achieved for a very thin amorphous layer (<~ 400 Ă
)
Cyclin dependent kinase 1-dependent activation of APC/C ubiquitin ligase
Error-free genome duplication and segregation are ensured through the timely activation of ubiquitylation enzymes. The anaphase-promoting complex/cyclosome (APC/C), a multisubunit E3 ubiquitin ligase, is regulated by phosphorylation. However the mechanism remains elusive. Using systematic reconstitution and analysis of vertebrate APC/Cs under physiological conditions, we show how cyclin-dependent kinase 1 (CDK1) activates the APC/C through coordinated phosphorylation between Apc3 and Apc1. Phosphorylation of the loop domains by p9/Cks2 (CDK regulatory subunit)-CDK1 controlled loading of coactivator Cdc20 onto APC/C. A phosphomimetic mutation introduced into Apc1 allowed Cdc20 to increase APC/C activity in interphase. These results define a previously
unrecognised subunit-subunit communication over a distance and the functional consequences of CDK phosphorylation. Cdc20 is a potential therapeutic target and our findings may facilitate the development of specific inhibitors
Design for subjective wellbeing: towards a design framework for constructing narrative
We explore the role that interaction with products and services can play in the narratives that we develop about ourselves. We propose a four-level model, which seeks to explain this and use it as the basis for analyzing eight immersion studies. In each, we investigate the role that products and services play in shaping narratives, which in turn reflect our self-identity. We also look at archetypes â the various ideals that we can have about ourselves â and at how the alignment of narratives with these enhances our wellbeing. The model offers the potential to link narrative to design features and to identify new market opportunities. However, we recognize there may be challenges in enabling people to articulate narrative and identify their ideal archetype
Zeeman effects on the impurity-induced resonances in d-wave superconductors
It is shown how the resonant states induced by a single spinless impurity in
a d-wave superconductor evolve under the effect of an applied Zeeman magnetic
field. Moreover, it is demonstrated that the spin-orbit coupling to the
impurity potential can have important and characteristic effects on the
resonant states and their response to the Zeeman field, especially when the
impurity is close to the unitary limit. For zero or very small spin-orbit
interaction, the resonant states becomes Zeeman splitted by the magnetic field
while when the spin-orbit coupling is important, new low-lying resonances arise
which do not show any Zeeman splitting.Comment: 5 pages with 5 eps figures embedded. To appear on Phys. Rev.
Nonadiabatic Superconductivity and Vertex Corrections in Uncorrelated Systems
We investigate the issue of the nonadiabatic superconductivity in
uncorrelated systems. A local approximation is employed coherently with the
weak dependence on the involved momenta. Our results show that nonadiabatic
vertex corrections are never negligible, but lead to a strong suppression of
with respect to the conventional theory. This feature is understood in
terms of the momentum-frequency dependence of the vertex function. In contrast
to strongly correlated systems, where the small -selection probes the
positive part of vertex function, vertex corrections in uncorrelated systems
are essentially negative resulting in an effective reduction of the
superconducting pairing. Our analysis shows that vertex corrections in
nonadiabatic regime can be never disregarded independently of the degree of
electronic correlation in the system.Comment: 4 pages, 3 eps fig
Nonadiabatic Pauli susceptibility in fullerene compounds
Pauli paramagnetic susceptibility is unaffected by the electron-phonon
interaction in the Migdal-Eliashberg context. Fullerene compounds however do
not fulfill the adiabatic assumption of Migdal's theorem and nonadiabatic
effects are expected to be relevant in these materials. In this paper we
investigate the Pauli spin susceptibility in nonadiabatic regime by following a
conserving approach based on Ward's identity. We find that a sizable
renormalization of due to electron-phonon coupling appears when
nonadiabatic effects are taken into account. The intrinsic dependence of
on the electron-phonon interaction gives rise to a finite and negative isotope
effect which could be experimentally detected in fullerides. In addition, we
find an enhancement of the spin susceptibility with temperature increasing, in
agreement with the temperature dependence of observed in fullerene
compounds. The role of electronic correlation is also discussed.Comment: Revtex, 10 pages, 8 figures include
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