608 research outputs found
Synthesis of Benzylidene and Azo Containing Polymers for Photophisical Application
In the present work, the polymers built with the use of the free radical polymerization of methacrylic monomers incorporating an azobenzene side-group and monomers with benzylidene fragments have been synthesized. The polymerization was carried out in DMF with AIBN as initiator. The products of polymerization were characterized by HNMR. The results of investigations of photochemical and optical activities of the corresponding polymers are presented
Non-Gaussian signatures of Tachyacoustic Cosmology
I investigate non-Gaussian signatures in the context of tachyacoustic
cosmology, that is, a noninflationary model with superluminal speed of sound. I
calculate the full non-Gaussian amplitude , its size ,
and corresponding shapes for a red-tilted spectrum of primordial scalar
perturbations. Specifically, for cuscuton-like models I show that , and the shape of its non-Gaussian amplitude peaks for
both equilateral and local configurations, the latter being dominant. These
results, albeit similar, are quantitatively distinct from the corresponding
ones obtained by Magueijo {\it{et. al}} in the context of superluminal bimetric
models.Comment: Some comments and references added. Matches the version published in
JCA
Quaternionic factorization of the Schroedinger operator and its applications to some first order systems of mathematical physics
We consider the following first order systems of mathematical physics.
1.The Dirac equation with scalar potential. 2.The Dirac equation with
electric potential. 3.The Dirac equation with pseudoscalar potential. 4.The
system describing non-linear force free magnetic fields or Beltrami fields with
nonconstant proportionality factor. 5.The Maxwell equations for slowly changing
media. 6.The static Maxwell system.
We show that all this variety of first order systems reduces to a single
quaternionic equation the analysis of which in its turn reduces to the solution
of a Schroedinger equation with biquaternionic potential. In some important
situations the biquaternionic potential can be diagonalized and converted into
scalar potentials
Effects of Nonlinear Dispersion Relations on Non-Gaussianities
We investigate the effect of non-linear dispersion relations on the
bispectrum. In particular, we study the case were the modified relations do not
violate the WKB condition at early times, focusing on a particular example
which is exactly solvable: the Jacobson-Corley dispersion relation with quartic
correction with positive coefficient to the squared linear relation. We find
that the corrections to the standard result for the bispectrum are suppressed
by a factor where is the scale where the modification
to the dispersion relation becomes relevant. The modification is {\it mildly}
configuration-dependent and equilateral configurations are more suppressed with
respect to the local ones, by a factor of one percent. There is no
configuration leading to enhancements. We then analyze the results in the
framework of particle creation using the approximate gluing method of
Brandenberger and Martin, which relates more directly to the modeling of the
trans-Planckian physics via modifications of the vacuum at a certain cutoff
scale. We show that the gluing method overestimates the leading order
correction to the spectrum and bispectrum by one and two orders, respectively,
in . We discuss the various approximation and conclude that for
dispersion relations not violating WKB at early times the particle creation is
small and does not lead to enhanced contributions to the bispectrum. We also
show that in many cases enhancements do not occur when modeling the
trans-Planckian physics via modifications of the vacuum at a certain cutoff
scale. Most notably they are only of order O(1) when the Bogolyubov
coefficients accounting for particle creation are determined by the Wronskian
condition and the minimization of the uncertainty between the field and its
conjugate momentum.Comment: v1: 11 pages, 2 figures; v2: references update
Внутрішньовенна інфузія лідокаїну для знеболення під час лапароскопічних холецистектомій
Лапароскопічна холецистектомія є методом вибору для хірургічного лікування гострого холециститу, який дозволяє скоротити перебування пацієнтів у стаціонарі, зменшити витрати коштів та прискорити відновлення працездатності. Але поряд із перевагами постає перешкода – через малий термін госпіталізації після втручання стає неможливим використання інвазивних методів знеболення. Саме тому біль є головною причиною відтермінування виписки пацієнта, що спонукає до пошуків способу підвищення ефективності періопераційного знеболення. Системне введення лідокаїну інтраопераційно може покращити знеболення пацієнтів під час лапароскопічних холецистектомій (ЛХЕ) та зменшити опіат-асоційовані побічні ефекти. Метою дослідження було визначити ефективність та безпечність внутрішньовенної інфузії лідокаїну для знеболення під час ЛХЕ. Проспективне контрольоване дослідження проводилось на клінічній базі кафедри хірургії, анестезіології та інтенсивної терапії Інституту післядипломної освіти НМУ імені О. О. Богомольця. У дослідження було включено 60 дорослих пацієнтів з гострим та хронічним холециститом, яким планувалась ЛХЕ, та рандомізовано до груп дослідження – група Л (лідокаїну) та група К (контрольна). Інтраопераційна внутрішньовенна інфузія лідокаїну під час ЛХЕ зменшувала середню інтенсивність болю у спокої та при рухах, кількість пацієнтів з помірним та сильним болем, кількість знеболень “за вимогою”. Застосування інтраопераційної інфузії лідокаїну дозволяло достовірно зменшити споживання анестетиків та анальгетиків інтраопераційно та у ранньому післяопераційному періоді, та відповідно зменшити частоту опіат-асоційованих побічних ефектів, прискорити відновлення функцій кишечника після ЛХЕ та зменшити інтраопераційну інцидентність артеріальної гіпертензії
Phonon-Coupled Electron Tunneling in Two and Three-Dimensional Tunneling Configurations
We treat a tunneling electron coupled to acoustical phonons through a
realistic electron phonon interaction: deformation potential and piezoelectric,
in two or three-dimensional tunneling configurations. Making use of slowness of
the phonon system compared to electron tunneling, and using a Green function
method for imaginary time, we are able to calculate the change in the
transition probability due to the coupling to phonons. It is shown using
standard renormalization procedure that, contrary to the one-dimensional case,
second order perturbation theory is sufficient in order to treat the
deformation potential coupling, which leads to a small correction to the
transmission coefficient prefactor. In the case of piezoelectric coupling,
which is found to be closely related to the piezoelectric polaron problem,
vertex corrections need to be considered. Summing leading logarithmic terms, we
show that the piezoelectric coupling leads to a significant change of the
transmission coefficient.Comment: 17 pages, 4 figure
Role of beam polarization in the determination of and couplings from
We evaluate the constraints on anomalous trilinear gauge-boson couplings that
can be obtained from the study of electron-positron annihilation into pairs
at a facility with either the electron beam longitudinally polarized or both
electron and positron beams transversely polarized. The energy ranges
considered in the analysis are the ones relevant to the next-linear collider
and to LEP~200. We discuss the possibilities of a model independent analysis of
the general conserving anomalous effective Lagrangian, as well as its
restriction to some specific models with reduced number of independent
couplings. The combination of observables with initial and final state
polarizations allows to separately constrain the different couplings and to
improve the corresponding numerical bounds.Comment: 24 pages, LaTeX, 9 figures (available on request from the authors
Discrete breathers in classical spin lattices
Discrete breathers (nonlinear localised modes) have been shown to exist in
various nonlinear Hamiltonian lattice systems. In the present paper we study
the dynamics of classical spins interacting via Heisenberg exchange on spatial
-dimensional lattices (with and without the presence of single-ion
anisotropy). We show that discrete breathers exist for cases when the continuum
theory does not allow for their presence (easy-axis ferromagnets with
anisotropic exchange and easy-plane ferromagnets). We prove the existence of
localised excitations using the implicit function theorem and obtain necessary
conditions for their existence. The most interesting case is the easy-plane one
which yields excitations with locally tilted magnetisation. There is no
continuum analogue for such a solution and there exists an energy threshold for
it, which we have estimated analytically. We support our analytical results
with numerical high-precision computations, including also a stability analysis
for the excitations.Comment: 15 pages, 12 figure
Can residuals of the Solar system foreground explain low multipole anomalies of the CMB ?
The low multipole anomalies of the Cosmic Microwave Background has received
much attention during the last few years. It is still not ascertained whether
these anomalies are indeed primordial or the result of systematics or
foregrounds. An example of a foreground, which could generate some non-Gaussian
and statistically anisotropic features at low multipole range, is the very
symmetric Kuiper Belt in the outer solar system. In this paper, expanding upon
the methods presented by Maris et al. (2011), we investigate the contributions
from the Kuiper Belt objects (KBO) to the WMAP ILC 7 map, whereby we can
minimize the contrast in power between even and odd multipoles in the CMB,
discussed discussed by Kim & Naselsky (2010). We submit our KBO de-correlated
CMB signal to several tests, to analyze its validity, and find that
incorporation of the KBO emission can decrease the quadrupole-octupole
alignment and parity asymmetry problems, provided that the KBO signals has a
non-cosmological dipole modulation, associated with the statistical anisotropy
of the ILC 7 map. Additionally, we show that the amplitude of the dipole
modulation, within a 2 sigma interval, is in agreement with the corresponding
amplitudes, discussed by Lew (2008).Comment: 24 pages, 9 figures, 5 tables. Matches version in JCA
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