56 research outputs found
Application of direct bioautography and SPME-GC-MS for the study of antibacterial chamomile ingredients
The isolation and characterization of antibacterial chamomile components were performed by the use of direct bioautography and solid phase microextraction (SPME)-GC-MS. Four ingredients, active against Vibrio fischeri, were identified as the polyacetylene geometric isomers cis- and trans-spiroethers, the coumarin related herniarin, and the sesquiterpene alcohol (-)-alpha-bisabolol
Coherent states on spheres
We describe a family of coherent states and an associated resolution of the
identity for a quantum particle whose classical configuration space is the
d-dimensional sphere S^d. The coherent states are labeled by points in the
associated phase space T*(S^d). These coherent states are NOT of Perelomov type
but rather are constructed as the eigenvectors of suitably defined annihilation
operators. We describe as well the Segal-Bargmann representation for the
system, the associated unitary Segal-Bargmann transform, and a natural
inversion formula. Although many of these results are in principle special
cases of the results of B. Hall and M. Stenzel, we give here a substantially
different description based on ideas of T. Thiemann and of K. Kowalski and J.
Rembielinski. All of these results can be generalized to a system whose
configuration space is an arbitrary compact symmetric space. We focus on the
sphere case in order to be able to carry out the calculations in a
self-contained and explicit way.Comment: Revised version. Submitted to J. Mathematical Physic
Isometry theorem for the Segal-Bargmann transform on noncompact symmetric spaces of the complex type
We consider the Segal-Bargmann transform for a noncompact symmetric space of
the complex type. We establish isometry and surjectivity theorems for the
transform, in a form as parallel as possible to the results in the compact
case. The isometry theorem involves integration over a tube of radius R in the
complexification, followed by analytic continuation with respect to R. A
cancellation of singularities allows the relevant integral to have a
nonsingular extension to large R, even though the function being integrated has
singularities.Comment: Final version. To appear in Journal of Functional Analysis. Minor
revision
Studies on the maize cold tolerance tests in the Martonvásár phytotron
The climatic conditions in Hungary and in the countries to which seed is exported
makes the study of maize cold tolerance and constant improvements in the cold tolerance
of Martonvásár hybrids especially important. An improvement in the early spring cold
tolerance of maize would allow it to be grown in more northern areas with a cooler
climate, while on traditional maize-growing areas the profitability of maize production
could be improved by earlier sowing, leading to a reduction in transportation and drying
costs and in diseases caused by Fusarium sp. The recognition of this fact led Martonvásár
researchers to start investigating this subject nearly four decades ago. The phytotron has
proved an excellent tool for studying and improving the cold tolerance of maize. The
review will give a brief summary of the results achieved in the field of maize cold
tolerance in the Martonvásár institute in recent decades
Coherent states for compact Lie groups and their large-N limits
The first two parts of this article surveys results related to the
heat-kernel coherent states for a compact Lie group K. I begin by reviewing the
definition of the coherent states, their resolution of the identity, and the
associated Segal-Bargmann transform. I then describe related results including
connections to geometric quantization and (1+1)-dimensional Yang--Mills theory,
the associated coherent states on spheres, and applications to quantum gravity.
The third part of this article summarizes recent work of mine with Driver and
Kemp on the large-N limit of the Segal--Bargmann transform for the unitary
group U(N). A key result is the identification of the leading-order large-N
behavior of the Laplacian on "trace polynomials."Comment: Submitted to the proceeding of the CIRM conference, "Coherent states
and their applications: A contemporary panorama.
General relativistic radiation hydrodynamics of accretion flows. I: Bondi-Hoyle accretion
We present a new code for performing general-relativistic
radiation-hydrodynamics simulations of accretion flows onto black holes. The
radiation field is treated in the optically-thick approximation, with the
opacity contributed by Thomson scattering and thermal bremsstrahlung. Our
analysis is concentrated on a detailed numerical investigation of hot
two-dimensional, Bondi-Hoyle accretion flows with various Mach numbers. We find
significant differences with respect to purely hydrodynamical evolutions. In
particular, once the system relaxes to a radiation-pressure dominated regime,
the accretion rates become about two orders of magnitude smaller than in the
purely hydrodynamical case, remaining however super-Eddington as are the
luminosities. Furthermore, when increasing the Mach number of the inflowing
gas, the accretion rates become smaller because of the smaller cross section of
the black hole, but the luminosities increase as a result a stronger emission
in the shocked regions. Overall, our approach provides the first
self-consistent calculation of the Bondi-Hoyle luminosity, most of which is
emitted within r~100 M from the black hole, with typical values L/L_Edd ~ 1-7,
and corresponding energy efficiencies eta_BH ~ 0.09-0.5. The possibility of
computing luminosities self-consistently has also allowed us to compare with
the bremsstrahlung luminosity often used in modelling the electromagnetic
counterparts to supermassive black-hole binaries, to find that in the
optically-thick regime these more crude estimates are about 20 times larger
than our radiation-hydrodynamics results.Comment: With updated bibliographyc informatio
Berezin-Toeplitz quantization on Lie groups
Let K be a connected compact semisimple Lie group and Kc its
complexification. The generalized Segal-Bargmann space for Kc, is a space of
square-integrable holomorphic functions on Kc, with respect to a K-invariant
heat kernel measure. This space is connected to the "Schrodinger" Hilbert space
L^2(K) by a unitary map, the generalized Segal-Bargmann transform. This paper
considers certain natural operators on L^2(K), namely multiplication operators
and differential operators, conjugated by the generalized Segal-Bargmann
transform. The main results show that the resulting operators on the
generalized Segal-Bargmann space can be represented as Toeplitz operators. The
symbols of these Toeplitz operators are expressed in terms of a certain
subelliptic heat kernel on Kc. I also examine some of the results from an
infinite-dimensional point of view based on the work of L. Gross and P.
Malliavin.Comment: To appear in Journal of Functional Analysi
Screening of bat faeces for arthropod-borne apicomplexan protozoa: Babesia canis and Besnoitia besnoiti-like sequences from Chiroptera
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