543 research outputs found
An implantable monophasic/biphasic atrial defibrillation system using transcutaneo RF power delivery
Quantum Mechanics and Black Holes in Four-Dimensional String Theory
In previous papers we have shown how strings in a two-dimensional target
space reconcile quantum mechanics with general relativity, thanks to an
infinite set of conserved quantum numbers, ``W-hair'', associated with
topological soliton-like states. In this paper we extend these arguments to
four dimensions, by considering explicitly the case of string black holes with
radial symmetry. The key infinite-dimensional W-symmetry is associated with the
coset structure of the dilaton-graviton sector that is a
model-independent feature of spherically symmetric four-dimensional strings.
Arguments are also given that the enormous number of string {\it discrete
(topological)} states account for the maintenance of quantum coherence during
the (non-thermal) stringy evaporation process, as well as quenching the large
Hawking-Bekenstein entropy associated with the black hole. Defining the latter
as the measure of the loss of information for an observer at infinity, who -
ignoring the higher string quantum numbers - keeps track only of the classical
mass,angular momentum and charge of the black hole, one recovers the familiar a
quadratic dependence on the black-hole mass by simple counting arguments on the
asymptotic density of string states in a linear-dilaton background.Comment: 18 page
On the connection between Quantum Mechanics and the geometry of two-dimensional strings
On the basis of an area-preserving symmetry in the phase space of a
one-dimensional matrix model - believed to describe two-dimensional string
theory in a black-hole background which also allows for space-time foam - we
give a geometric interpretation of the fact that two-dimensional stringy black
holes are consistent with conventional quantum mechanics due to the infinite
gauged `W-hair' property that characterises them.Comment: 19 page
The Origin of Space-Time as Symmetry Breaking in String Theory
Physics in the neighbourhood of a space-time metric singularity is described
by a world-sheet topological gauge field theory which can be represented as a
twisted superconformal Wess-Zumino model with a bosonic symmetry. The measurable -hair associated with the
singularity is associated with Wilson loop integrals around gauge defects. The
breaking of
is associated with expectation values for open Wilson lines that
make the metric non-singular away from the singularity. This symmetry breaking
is accompanied by massless discrete `tachyon' states that appear as leg poles
in -matrix elements. The triviality of the -matrix in the high-energy
limit of the string model, after renormalisation by the leg pole factors,
is due to the restoration of double -symmetry at the singularity.Comment: 13 page
Phase diagrams of classical spin fluids: the influence of an external magnetic field on the liquid-gas transition
The influence of an external magnetic field on the liquid-gas phase
transition in Ising, XY, and Heisenberg spin fluid models is studied using a
modified mean field theory and Gibbs ensemble Monte Carlo simulations. It is
demonstrated that the theory is able to reproduce quantitatively all
characteristic features of the field dependence of the critical temperature
T_c(H) for all the three models. These features include a monotonic decrease of
T_c with rising H in the case of the Ising fluid as well as a more complicated
nonmonotonic behavior for the XY and Heisenberg models. The nonmonotonicity
consists in a decrease of T_c with increasing H at weak external fields, an
increase of T_c with rising H in the strong field regime, and the existence of
a minimum in T_c(H) at intermediate values of H. Analytical expressions for
T_c(H) in the large field limit are presented as well. The magnetic para-ferro
phase transition is also considered in simulations and described within the
mean field theory.Comment: 14 pages, 12 figures (to be submitted to Phys. Rev. E
Spin effects in intramolecular electron transfer in naproxen-N-methylpyrrolidine dyad
[EN] The intramolecular electron transfer in the naproxen-N-methylpyrrolidine dyad has been investigated by spin chemistry methods. The existence of CIDNP in a high magnetic field points to electron transfer as a possible mechanism of the quenching of the excited state of a dyad. However, the failure to detect magnetic field effects on triplet yield makes us conclude that this quenching mechanism is not the only one. The observation of CIDNP effects in the dyad in the media of low polarity and the short risetime of triplet state formation indicate a potential role of exciplex in the quenching of the excited state of the dyad.This work was supported by the Grants 08-03-00372 and 11-03-01104 of Russian Foundation of Basic Research, and the grant of Priority Programs of RAS, No. 5.1.5.Magin, I.; Polyakov, N.; Khramtsova, E.; Kruppa, A.; Tsentalovich, Y.; Leshina, T.; Miranda Alonso, MÁ.... (2011). Spin effects in intramolecular electron transfer in naproxen-N-methylpyrrolidine dyad. Chemical Physics Letters. 516(1-3):51-55. https://doi.org/10.1016/j.cplett.2011.09.057S51555161-
Tomato: a crop species amenable to improvement by cellular and molecular methods
Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures.
In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.
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