4,940 research outputs found
Correlated measurements of UHF radar signatures, RF radiation and electric field changes from lightning
During Storm Hazards - 82, simultaneous measurements are made of radar echoes, fast and slow field changes and RF radiation from lightning. Radio frequency radiation and radar echoes are also obtained during periods when the research aircraft is struck by lightning. These data are presently used to better understand the electrical processes which occur during strikes to the aircraft. Preliminary conclusions verify that the events recorded aboard the aircraft occurred during lightning but also indicate that they occur with surprising frequency very early in the flash
NN Interaction JISP16: Current Status and Prospect
We discuss realistic nonlocal NN interactions of a new type - J-matrix
Inverse Scattering Potential (JISP). In an ab exitu approach, these
interactions are fitted to not only two-nucleon data (NN scattering data and
deuteron properties) but also to the properties of light nuclei without
referring to three-nucleon forces. We discuss recent progress with the ab
initio No-core Shell Model (NCSM) approach and respective progress in
developing ab exitu JISP-type NN-interactions together with plans of their
forthcoming improvements.Comment: 9 pages, 3 figures, to be published in Proceedings of Few-body 19
conferenc
String theory extensions of Einstein-Maxwell fields: the static case
We present a new approach for generation of solutions in the four-dimensional
heterotic string theory with one vector field and in the five-dimensional
bosonic string theory starting from the static Einstein-Maxwell fields. Our
approach allows one to construct the solution classes invariant with respect to
the total subgroup of the three-dimensional charging symmetries of these string
theories. The new generation procedure leads to the extremal
Israel-Wilson-Perjes subclass of string theory solutions in a special case and
provides its natural continuous extension to the realm of non-extremal
solutions. We explicitly calculate all string theory solutions related to
three-dimensional gravity coupled to an effective dilaton field which arises
after an appropriate charging symmetry invariant reduction of the static
Einstein-Maxwell system.Comment: 19 pages in late
Defining rural areas of Visegrad countries
The article is focused on the introduction and categorization of various approaches to rurality, and
the identification and delimitation of rural areas in Visegrad countries. Three substantively different groups of
conceptualizations and definitions of rural and rurality are described as follows: functional definitions, rural as
locality (political-economic approaches), and social representation. Latter, basic sorts of methods and appro
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aches to the delimitation of rural areas in V4 countries are introduced emphasizing its historical development,
differences in spatial level and criteria of delimitation in current research. Due to different nature of rural areas
and even local administrative units (the basic units usually used for delimitation of rural areas), it is not possible
to reach sufficient and reliable identification of rural areas for whole V4 area using any of criteria or definitions
applied in the research at national levels. Therefore, the average population density of entire V4 area was used
as a main criterion for distinguishing between urban and rural LAU 2 at the whole Visegrad area level. Such
approach is also affected by generalization but it captures various conditions in each country relatively well and
moreover, it is comparable with the OECD and European Union methods to some extent
Population of isomers in decay of the giant dipole resonance
The value of an isomeric ratio (IR) in N=81 isotones (Ba, Ce,
Nd and Sm) is studied by means of the ( reaction.
This quantity measures a probability to populate the isomeric state in respect
to the ground state population. In ( reactions, the giant dipole
resonance (GDR) is excited and after its decay by a neutron emission, the
nucleus has an excitation energy of a few MeV. The forthcoming decay
by direct or cascade transitions deexcites the nucleus into an isomeric or
ground state. It has been observed experimentally that the IR for Ba
and Ce equals about 0.13 while in two heavier isotones it is even less
than half the size. To explain this effect, the structure of the excited states
in the energy region up to 6.5 MeV has been calculated within the Quasiparticle
Phonon Model. Many states are found connected to the ground and isomeric states
by , and transitions. The single-particle component of the wave
function is responsible for the large values of the transitions. The calculated
value of the isomeric ratio is in very good agreement with the experimental
data for all isotones. A slightly different value of maximum energy with which
the nuclei rest after neutron decay of the GDR is responsible for the reported
effect of the A-dependence of the IR.Comment: 16 pages, 4 Fig
A Quantum Mechanical Model of the Reissner-Nordstrom Black Hole
We consider a Hamiltonian quantum theory of spherically symmetric,
asymptotically flat electrovacuum spacetimes. The physical phase space of such
spacetimes is spanned by the mass and the charge parameters and of the
Reissner-Nordstr\"{o}m black hole, together with the corresponding canonical
momenta. In this four-dimensional phase space, we perform a canonical
transformation such that the resulting configuration variables describe the
dynamical properties of Reissner-Nordstr\"{o}m black holes in a natural manner.
The classical Hamiltonian written in terms of these variables and their
conjugate momenta is replaced by the corresponding self-adjoint Hamiltonian
operator, and an eigenvalue equation for the ADM mass of the hole, from the
point of view of a distant observer at rest, is obtained. Our eigenvalue
equation implies that the ADM mass and the electric charge spectra of the hole
are discrete, and the mass spectrum is bounded below. Moreover, the spectrum of
the quantity is strictly positive when an appropriate self-adjoint
extension is chosen. The WKB analysis yields the result that the large
eigenvalues of the quantity are of the form , where
is an integer. It turns out that this result is closely related to
Bekenstein's proposal on the discrete horizon area spectrum of black holes.Comment: 37 pages, Plain TeX, no figure
Intrinsic regulation of FIC-domain AMP-transferases by oligomerization and automodification
Filamentation induced by cyclic AMP (FIC)-domain enzymes catalyze adenylylation or other posttranslational modifications of target proteins to control their function. Recently, we have shown that Fic enzymes are autoinhibited by an α-helix (αinh) that partly obstructs the active site. For the single-domain class III Fic proteins, the αinh is located at the C terminus and its deletion relieves autoinhibition. However, it has remained unclear how activation occurs naturally. Here, we show by structural, biophysical, and enzymatic analyses combined with in vivo data that the class III Fic protein NmFic from Neisseria meningitidis gets autoadenylylated in cis, thereby autonomously relieving autoinhibition and thus allowing subsequent adenylylation of its target, the DNA gyrase subunit GyrB. Furthermore, we show that NmFic activation is antagonized by tetramerization. The combination of autoadenylylation and tetramerization results in nonmonotonic concentration dependence of NmFic activity and a pronounced lag phase in the progress of target adenylylation. Bioinformatic analyses indicate that this elaborate dual-control mechanism is conserved throughout class III Fic proteins
Aharonov-Bohm interference in quantum ring exciton: effects of built-in electric fields
We report a comprehensive discussion of quantum interference effects due to
the finite structure of excitons in quantum rings and their first experimental
corroboration observed in the optical recombinations. Anomalous features that
appear in the experiments are analyzed according to theoretical models that
describe the modulation of the interference pattern by temperature and built-in
electric fields.Comment: 6 pages, 7 figure
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