236 research outputs found
Polarization-Tailored Raman Frequency Conversion in Chiral Gas-Filled Hollow Core Photonic Crystal Fibers
Broadband-tunable sources of circularly-polarized light are crucial in fields
such as laser science, biomedicine and spectroscopy. Conventional sources rely
on nonlinear wavelength conversion and polarization control using standard
optical components, and are limited by the availability of suitably transparent
crystals and glasses. Although gas-filled hollow-core photonic crystal fiber
provides pressure-tunable dispersion, long well-controlled optical
path-lengths, and high Raman conversion efficiency, it is unable to preserve
circular polarization state, typically exhibiting weak linear birefringence.
Here we report a revolutionary approach based on helically-twisted hollow-core
photonic crystal fiber, which displays circular birefringence, thus robustly
maintaining circular polarization state against external perturbations. This
makes it possible to generate pure circularly-polarized Stokes and anti-Stokes
signals by rotational Raman scattering in hydrogen. The polarization state of
the frequency-shifted Raman bands can be continuously varied by tuning the gas
pressure in the vicinity of the gain suppression point. The results pave the
way to a new generation of compact and efficient fiber-based sources of
broadband light with fully-controllable polarization state.Comment: 5 pages, 4 figure
Wightman function and Casimir densities for Robin plates in the Fulling-Rindler vacuum
Wightman function, the vacuum expectation values of the field square and the
energy-momentum tensor are investigated for a massive scalar field with an
arbitrary curvature coupling parameter in the region between two infinite
parallel plates moving by uniform proper acceleration. We assume that the field
is prepared in the Fulling-Rindler vacuum state and satisfies Robin boundary
conditions on the plates. The mode-summation method is used with a combination
of a variant of the generalized Abel-Plana formula. This allows to extract
manifestly the contributions to the expectation values due to a single boundary
and to present the second plate-induced parts in terms of exponentially
convergent integrals. Various limiting cases are investigated. The vacuum
forces acting on the boundaries are presented as a sum of the self-action and
'interaction' terms. The first one contains well known surface divergences and
needs a further renormalization. The 'interaction' forces between the plates
are investigated as functions of the proper accelerations and coefficients in
the boundary conditions. We show that there is a region in the space of these
parameters in which the 'interaction' forces are repulsive for small distances
and attractive for large distances.Comment: 20 pages, 2 figures, discussion added, accepted for publication in
Int. J. Mod. Phys.
Controlling Stray Electric Fields on an Atom Chip for Rydberg Experiments
Experiments handling Rydberg atoms near surfaces must necessarily deal with
the high sensitivity of Rydberg atoms to (stray) electric fields that typically
emanate from adsorbates on the surface. We demonstrate a method to modify and
reduce the stray electric field by changing the adsorbates distribution. We use
one of the Rydberg excitation lasers to locally affect the adsorbed dipole
distribution. By adjusting the averaged exposure time we change the strength
(with the minimal value less than at
from the chip) and even the sign of the perpendicular field component. This
technique is a useful tool for experiments handling Ryberg atoms near surfaces,
including atom chips
Dimensionalities of Weak Solutions in Hydrogenic Systems
A close inspection on the 3D hydrogen atom Hamiltonian revealed formal
eigenvectors often discarded in the literature. Although not in its domain,
such eigenvectors belong to the Hilbert space, and so their time evolution is
well defined. They are then related to the 1D and 2D hydrogen atoms and it is
numerically found that they have continuous components, so that ionization can
take place
The Coulomb-Oscillator Relation on n-Dimensional Spheres and Hyperboloids
In this paper we establish a relation between Coulomb and oscillator systems
on -dimensional spheres and hyperboloids for . We show that, as in
Euclidean space, the quasiradial equation for the dimensional Coulomb
problem coincides with the -dimensional quasiradial oscillator equation on
spheres and hyperboloids. Using the solution of the Schr\"odinger equation for
the oscillator system, we construct the energy spectrum and wave functions for
the Coulomb problem.Comment: 15 pages, LaTe
Second Hopf map and Yang-Coulomb system on 5d (pseudo)sphere
Using the second Hopf map, we perform the reduction of the eight-dimensional
(pseudo)spherical (Higgs)oscillator to a five-dimensional system interacting
with a Yang monopole. Then, using a standard trick, we obtain, from the latter
system, the pseudospherical and spherical generalizations of the Yang-Coulomb
system (the five dimensional analog of MICZ-Kepler system). We present the
whole set of its constants of motions, including the hidden symmetry generators
given by the analog of Runge-Lenz vector. In the same way, starting from the
eight-dimensional anisotropic inharmonic Higgs oscillator, we construct the
integrable (pseudo)spherical generalization of the Yang-Coulomb system with the
Stark term.Comment: 10 pages, PACS: 03.65.-w, 02.30.Ik, 14.80.H
Large aperture vibrating wire monitor with two mechanically coupled wires for beam halo measurements
Development of a new type of vibrating wire monitor (VWM), which has two mechanically coupled wires (vibrating and target), is presented. The new monitor has a much larger aperture size than the previous model of the VWM, and thus allows us to measure transverse beam halos more effectively. A prototype of such a large aperture VWM with a target wire length of 60 mm was designed, manufactured, and bench-tested. Initial beam measurements have been performed at the Fermilab High Intensity Neutrino Source facility, and key results are presented.open1
The use of integrated frequency ABC/VEN-analysis of application of medicines for the treatment of influenza and its complications in the hospital
The problem of limiting and rational use of funds in the health care system is relevant worldwide. Influenza and acute respiratory viral infections are cause of a lot of discussion about the treatment and prevention of the disease.
The aim of the work ‒ to conduct an analysis of the data of the actual practice of appointment for patients with severe forms of influenza and its complications that were hospitalized at the hospital of the Lviv Regional Infectious Diseases Clinical Hospital.
For the analysis of data of real practice of appointments were included data of 260 medical cards of patients of the Lviv Regional Infectious Clinical Hospital, which were hospitalized in 2016–2017 years with the diagnosis of influenza and SARI. We used statistical methods, real world evidence analysis, integrated frequency ABC/VEN analysis.
The results of the VEN analysis indicate that in this department pharmacotherapy performs according to the current Protocols for medical care. Integrated frequency, VEN and ABC analysis showed that the leader of applications is Reosorbilact (the rate of expenses is 19%, the frequency of applications – 14%, the percentage of patients to whom it was appointed is 85%). Very expensive antibiotic Tigacil followed them, the next medicines in this list – Xylat (a rate of of expenses 10%, a frequency of applications is 5%, a share of patients – 28%). By answering the question about use the funds for important and vitally necessary medication, we can see that the rate of expenses for medicines of category V is 88.99%, it means that there is a rational use of funds. Analyzing the frequency of using the most expensive drugs (the cost of antibiotics is 46% of the total cost of drugs), it would be advisable to study the possibility of replacing it with cheaper counterparts.
In general, pharmacological therapy is clinically and economically viable, but requires further standardization, and the analysis shows possible ways to optimize it, and reminds us how dangerous are the complications of the influenza, and which resources are needed for their treatment
Casimir energy in the Fulling--Rindler vacuum
The Casimir energy is evaluated for massless scalar fields under Dirichlet or
Neumann boundary conditions, and for the electromagnetic field with perfect
conductor boundary conditions on one and two infinite parallel plates moving by
uniform proper acceleration through the Fulling--Rindler vacuum in an arbitrary
number of spacetime dimension. For the geometry of a single plate the both
regions of the right Rindler wedge, (i) on the right (RR region) and (ii) on
the left (RL region) of the plate are considered. The zeta function technique
is used, in combination with contour integral representations. The Casimir
energies for separate RR and RL regions contain pole and finite contributions.
For an infinitely thin plate taking RR and RL regions together, in odd spatial
dimensions the pole parts cancel and the Casimir energy for the whole Rindler
wedge is finite. In spatial dimensions the total Casimir energy for a
single plate is negative for Dirichlet scalar and positive for Neumann scalar
and the electromagnetic field. The total Casimir energy for two plates geometry
is presented in the form of a sum of the Casimir energies for separate plates
plus an additional interference term. The latter is negative for all values of
the plates separation for both Dirichlet and Neumann scalars, and for the
electromagnetic field.Comment: 28 pages, 4 figures, references added, typos corrected, accepted for
publication in Phys. Rev.
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