36,674 research outputs found
Computational Study of the Structure and Thermodynamic Properties of Ammonium Chloride Clusters Using a Parallel J-Walking Approach
The thermodynamic and structural properties of (NHCl) clusters,
n=3-10 are studied. Using the method of simulated annealing, the geometries of
several isomers for each cluster size are examined. Jump-walking Monte Carlo
simulations are then used to compute the constant-volume heat capacity for each
cluster size over a wide temperature range. To carry out these simulations a
new parallel algorithm is developed using the Parallel Virtual Machine (PVM)
software package. Features of the cluster potential energy surfaces, such as
energy differences among isomers and rotational barriers of the ammonium ions,
are found to play important roles in determining the shape of the heat capacity
curves.Comment: Journal of Chemical Physics, accepted for publicatio
Thin Films of 3He -- Implications on the Identification of 3 He -A
Recently the identification of 3He-A with the axial state has been
questioned. It is suggested that the A-phase can actually be in the axiplanar
state. We point out in the present paper that experiments in a film geometry
may be useful to distinguish the above two possibilities. In particular a
second order phase transition between an axial and an axiplanar state would
occur as a function of thickness or temperature.Comment: 3 pages, no figures latex- revtex aps accepted by J. of Low
Temperature Physic
Robust CNOT gates from almost any interaction
There are many cases where the interaction between two qubits is not
precisely known, but single qubit operations are available. In this paper we
show how, regardless of an incomplete knowledge of the strength or form of the
interaction between two qubits, it is often possible to construct a CNOT gate
which has arbitrarily high fidelity. In particular, we show that oscillations
in the strength of the exchange interaction in solid state Si and Ge structures
are correctable.Comment: 5 pages, 2 figure
Development of the Magnetic Excitations of Charge-Stripe Ordered La(2-x)Sr(x)NiO(4) on Doping Towards Checkerboard Charge Order
The magnetic excitation spectrums of charge stripe ordered La(2-x)Sr(x)NiO(4)
x = 0.45 and x = 0.4 were studied by inelastic neutron scattering. We found the
magnetic excitation spectrum of x = 0.45 from the ordered Ni^2+ S = 1 spins to
match that of checkerboard charge ordered La(1.5)Sr(0.5)NiO(4). The distinctive
asymmetry in the magnetic excitations above 40 meV was observed for both doping
levels, but an additional ferromagnetic mode was observed in x = 0.45 and not
in the x = 0.4. We discuss the origin of crossover in the excitation spectrum
between x = 0.45 and x = 0.4 with respect to discommensurations in the charge
stripe structure.Comment: 4 Figures. To be appear in the J. Kor. Phys. Soc. as a proceedings
paper from the ICM 2012 conferenc
Enhancing Bremsstrahlung Production From Ultraintense Laser-Solid Interactions With Front Surface Structures
We report the results of a combined study of particle-in-cell and Monte Carlo
modeling that investigates the production of Bremsstrahlung radiation produced
when an ultraintense laser interacts with a tower-structured target. These
targets are found to significantly narrow the electron angular distribution as
well as produce significantly higher energies. These features combine to create
a significant enhancement in directionality and energy of the Bremstrahlung
radiation produced by a high-Z converter target. These studies employ
short-pulse, high intensity laser pulses, and indicate that novel target design
has potential to greatly enhance the yield and narrow the directionality of
high energy electrons and -rays. We find that the peak -ray
brightness for this source is 6.010 at 10MeV and 1.410 at 100MeV (0.1 bandwidth).Comment: arXiv admin note: text overlap with arXiv:1310.328
The Schrodinger-like Equation for a Nonrelativistic Electron in a Photon Field of Arbitrary Intensity
The ordinary Schrodinger equation with minimal coupling for a nonrelativistic
electron interacting with a single-mode photon field is not satisfied by the
nonrelativistic limit of the exact solutions to the corresponding Dirac
equation. A Schrodinger-like equation valid for arbitrary photon intensity is
derived from the Dirac equation without the weak-field assumption. The
"eigenvalue" in the new equation is an operator in a Cartan subalgebra. An
approximation consistent with the nonrelativistic energy level derived from its
relativistic value replaces the "eigenvalue" operator by an ordinary number,
recovering the ordinary Schrodinger eigenvalue equation used in the formal
scattering formalism. The Schrodinger-like equation for the multimode case is
also presented.Comment: Tex file, 13 pages, no figur
A Normal Stellar Disk in the Galaxy Malin 1
Since its discovery, Malin 1 has been considered the prototype and most
extreme example of the class of giant low surface brightness disk galaxies.
Examination of an archival Hubble Space Telescope I-band image reveals that
Malin 1 contains a normal stellar disk that was not previously recognized,
having a central I-band surface brightness of mu_0 = 20.1 mag arcsec^-2 and a
scale length of 4.8 kpc. Out to a radius of ~10 kpc, the structure of Malin 1
is that of a typical SB0/a galaxy. The remarkably extended, faint outer
structure detected out to r~100 kpc appears to be a photometrically distinct
component and not a simple extension of the inner disk. In terms of its disk
scale length and central surface brightness, Malin 1 was originally found to be
a very remote outlier relative to all other known disk galaxies. The presence
of a disk of normal size and surface brightness in Malin 1 suggests that such
extreme outliers in disk properties probably do not exist, but underscores the
importance of the extended outer disk regions for a full understanding of the
structure and formation of spiral galaxies.Comment: 13 pages, 7 figures. To appear in AJ. Typographical error correcte
The impact of a school-based water supply and treatment, hygiene, and sanitation programme on pupil diarrhoea: a cluster-randomized trial.
The impact of improved water, sanitation, and hygiene (WASH) access on mitigating illness is well documented, although impact of school-based WASH on school-aged children has not been rigorously explored. We conducted a cluster-randomized trial in Nyanza Province, Kenya to assess the impact of a school-based WASH intervention on diarrhoeal disease in primary-school pupils. Two study populations were used: schools with a nearby dry season water source and those without. Pupils attending 'water-available' schools that received hygiene promotion and water treatment (HP&WT) and sanitation improvements showed no difference in period prevalence or duration of illness compared to pupils attending control schools. Those pupils in schools that received only the HP&WT showed similar results. Pupils in 'water-scarce' schools that received a water-supply improvement, HP&WT and sanitation showed a reduction in diarrhoea incidence and days of illness. Our study revealed mixed results on the impact of improvements to school WASH improvements on pupil diarrhoea
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