15,736 research outputs found
Transport and Noise Characteristics of Submicron High-Temperature Superconductor Grain-Boundary Junctions
We have investigated the transport and noise properties of submicron YBCO
bicrystal grain-boundary junctions prepared using electron beam lithography.
The junctions show an increased conductance for low voltages reminiscent of
Josephson junctions having a barrier with high transmissivity. The voltage
noise spectra are dominated by a few Lorentzian components. At low temperatures
clear two-level random telegraph switching (RTS) signals are observable in the
voltage vs time traces. We have investigated the temperature and voltage
dependence of individual fluctuators both from statistical analysis of voltage
vs time traces and from fits to noise spectra. A transition from tunneling to
thermally activated behavior of individual fluctuators was clearly observed.
The experimental results support the model of charge carrier traps in the
barrier region.Comment: 4 pages, 4 figures, to be published in Appl. Phys. Let
Plane wave/pseudopotential implementation of excited state gradients in density functional linear response theory: a new route via implicit differentiation
This work presents the formalism and implementation of excited state nuclear
forces within density functional linear response theory (TDDFT) using a plane
wave basis set. An implicit differentiation technique is developed for
computing nonadiabatic coupling between Kohn-Sham molecular orbital
wavefunctions as well as gradients of orbital energies which are then used to
calculate excited state nuclear forces. The algorithm has been implemented in a
plane wave/pseudopotential code taking into account only a reduced active
subspace of molecular orbitals. It is demonstrated for the H and N
molecules that the analytical gradients rapidly converge to the exact forces
when the active subspace of molecular orbitals approaches completeness
Singular components of spectral measures for ergodic Jacobi matrices
For ergodic 1d Jacobi operators we prove that the random singular components
of any spectral measure are almost surely mutually disjoint as long as one
restricts to the set of positive Lyapunov exponent. In the context of extended
Harper's equation this yields the first rigorous proof of the Thouless' formula
for the Lyapunov exponent in the dual regions.Comment: to appear in the Journal of Mathematical Physics, vol 52 (2011
From ab initio quantum chemistry to molecular dynamics: The delicate case of hydrogen bonding in ammonia
The ammonia dimer (NH3)2 has been investigated using high--level ab initio
quantum chemistry methods and density functional theory (DFT). The structure
and energetics of important isomers is obtained to unprecedented accuracy
without resorting to experiment. The global minimum of eclipsed C_s symmetry is
characterized by a significantly bent hydrogen bond which deviates from
linearity by about 20 degrees. In addition, the so-called cyclic C_{2h}
structure is extremely close in energy on an overall flat potential energy
surface. It is demonstrated that none of the currently available (GGA,
meta--GGA, and hybrid) density functionals satisfactorily describe the
structure and relative energies of this nonlinear hydrogen bond. We present a
novel density functional, HCTH/407+, designed to describe this sort of hydrogen
bond quantitatively on the level of the dimer, contrary to e.g. the widely used
BLYP functional. This improved functional is employed in Car-Parrinello ab
initio molecular dynamics simulations of liquid ammonia to judge its
performance in describing the associated liquid. Both the HCTH/407+ and BLYP
functionals describe the properties of the liquid well as judged by analysis of
radial distribution functions, hydrogen bonding structure and dynamics,
translational diffusion, and orientational relaxation processes. It is
demonstrated that the solvation shell of the ammonia molecule in the liquid
phase is dominated by steric packing effects and not so much by directional
hydrogen bonding interactions. In addition, the propensity of ammonia molecules
to form bifurcated and multifurcated hydrogen bonds in the liquid phase is
found to be negligibly small.Comment: Journal of Chemical Physics, in press (305335JCP
Chemotherapy-induced nausea and vomiting: A narrative review to inform dietetics practice
Chemotherapy-induced nausea and vomiting (CINV) are common nutrition-impact symptoms experienced by cancer patients. They exert a detrimental effect on dietary intake, risk of malnutrition and quality of life. While CINV are primarily managed with medication, dietitians play an important role in the management of CINV-related complications such as reduced dietary intake. This review discusses the burden of nausea and vomiting which cancer patients can experience, including its effect on quality of life, nutrition status, and treatment outcomes. Implications for dietetic practice include the need to explore the nature of reported symptoms, identify predisposing risk factors, and to consider the use of a variety of interventions that are individualised to the patient’s symptoms. There are little clinical data regarding effective dietetic interventions for nausea and vomiting. In summary, this review discusses dietetic-related issues surrounding CINV including the pathophysiology, risk factors, prevalence, and both pharmacological and dietetic treatment options
Seen But Not Heard: Advocating for Children in New York State
On November 1, 2008, the New York State Bar Association House of Delegates approved a resolution affirming their commitment towards establishing a civil right to counsel in New York State. One of the issues identified is a child\u27s right to representation not only in criminal, but also civil proceedings. Unlike other litigant groups, children have a statutorily established right to council in civil proceedings. However, as the white paper, adopted by the New State Bar Association, details, there are gaps in children \u27s advocacy throughout New York State. While significant steps towards improvement have recently taken place, there is still a long road until a collective voice for children is heard as loudly as their adult counterparts. This Comment explores the current state of the law and advocacy models in order to analyze what has been done towards improving a child\u27s right to counsel, as well as possible future steps. It is this author\u27s hope that the voices of children one day resonate as loudly as other politically powerful groups in New York. The children are New York\u27s future, and their lives need to be improved
Seen But Not Heard: Advocating for Children in New York State
On November 1, 2008, the New York State Bar Association House of Delegates approved a resolution affirming their commitment towards establishing a civil right to counsel in New York State. One of the issues identified is a child\u27s right to representation not only in criminal, but also civil proceedings. Unlike other litigant groups, children have a statutorily established right to council in civil proceedings. However, as the white paper, adopted by the New State Bar Association, details, there are gaps in children \u27s advocacy throughout New York State. While significant steps towards improvement have recently taken place, there is still a long road until a collective voice for children is heard as loudly as their adult counterparts. This Comment explores the current state of the law and advocacy models in order to analyze what has been done towards improving a child\u27s right to counsel, as well as possible future steps. It is this author\u27s hope that the voices of children one day resonate as loudly as other politically powerful groups in New York. The children are New York\u27s future, and their lives need to be improved
Winter and summer simulations with the GLAS climate model
The GLAS climate model is a general circulation model based on the primitive equations in sigma coordinates on a global domain in the presence of orography. The model incorporates parameterizations of the effects of radiation, convection, large scale latent heat release, turbulent and boundary layer fluxes, and ground hydrology. Winter and summer simulations were carried out with this model, and the resulting data are compared to observations
Quantum Fluctuations Driven Orientational Disordering: A Finite-Size Scaling Study
The orientational ordering transition is investigated in the quantum
generalization of the anisotropic-planar-rotor model in the low temperature
regime. The phase diagram of the model is first analyzed within the mean-field
approximation. This predicts at a phase transition from the ordered to
the disordered state when the strength of quantum fluctuations, characterized
by the rotational constant , exceeds a critical value . As a function of temperature, mean-field theory predicts a range of
values of where the system develops long-range order upon cooling, but
enters again into a disordered state at sufficiently low temperatures
(reentrance). The model is further studied by means of path integral Monte
Carlo simulations in combination with finite-size scaling techniques,
concentrating on the region of parameter space where reentrance is predicted to
occur. The phase diagram determined from the simulations does not seem to
exhibit reentrant behavior; at intermediate temperatures a pronounced increase
of short-range order is observed rather than a genuine long-range order.Comment: 27 pages, 8 figures, RevTe
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