10,798 research outputs found
Einstein-Cartan formulation of Chern-Simons Lorentz-violating Gravity
We consider a modification of the standard Einstein theory in four
dimensions, alternative to R. Jackiw and S.-Y. Pi, Phys. Rev. D 68, 104012
(2003), since it is based on the first-order (Einstein-Cartan) approach to
General Relativity, whose gauge structure is manifest. This is done by
introducing an additional topological term in the action which becomes a
Lorentz-violating term by virtue of the dependence of the coupling on the
space-time point. We obtain a condition on the solutions of the Einstein
equations, such that they persist in the deformed theory, and show that the
solutions remarkably correspond to the classical solutions of a collection of
independent 2+1-d (topological) Chern-Simons gravities. Finally, we study the
relation with the standard second-order approach and argue that they both
coincide to leading order in the modulus of the Lorentz-violating vector field.Comment: Final versio
TFD Extension of Open String Field Theory
We study the application of the rules of Thermo Field Dynamics (TFD) to the
covariant formulation of Open String Field Theory (OSFT). We extend the states
space and fields according to the duplication rules of TFD and construct the
corresponding classical action. The result is interpreted as a theory whose
fields would encode the statistical information of open strings.
The physical spectrum of the free theory is studied through the cohomology of
the extended BRST charge, and, as a result, we get new fields in the spectrum
emerging by virtue of the quantum entanglement and, noticeably, it presents
degrees of freedom that could be identified as those of closed strings. We also
show, however, that their appearing in the action is directly related to the
choice of the inner product in the extended algebra, so that different sectors
of fields could be eliminated from the theory by choosing that product
conveniently.
Finally, we study the extension of the three-vertex interaction and provide a
simple prescription for it whose results at tree-level agree with those of the
conventional theory.Comment: 25 pages, no figures. File format, typos, Abstract and references
modified. New subsection and concluding comments were added. To appear in
Phys. Rev.
Relationship between chromatin bridges in anaphase and chromosomal aberrations induced by TMP+UVA (365 nm) in CHO cells
In a recent paper, the hypothesis of 'conservative pairing' between complementary DNA strands belonging to both sister chromatids has been proposed as a phenomenon that could account for, at least in part, sister chromatid pairing in late G(2)/mitosis. The hypothesis was verified through a cytogenetic approach, studying the so-called 'sister chromatid chromatin bridges' (SCCBs), induced in the previous G(2)/mitosis by a crosslinking (TMP + UVA 365 nm) treatment in CHO cells (Rizzoni, M., E. Cundari, P. Perticone and B. Gustavino (1993) Chromatin bridges between sister chromatids induced in late G(2) mitosis in CHO cells by trimethylpsoralen + UVA, Experimental Cell Res., 209, 149-155; [1]). The purpose of the present paper is the study of the relationship between chromatin bridges without fragments in ana-telophase, which were demonstrated to be SCCBs, and chromosomal aberrations, in order to investigate their mechanism of induction. The evolution along the time of the two classes of mitotic anomalies was studied and a comparison was carried out to verify whether the bridges rise as a direct and immediate effect of the treatment or represent the misrepair-mediated effect of it. The present data show that single bridges without fragments come from a direct effect of photoinduced crosslinks in late G(2)/mitosis. Moreover TMP + 365 nm UVA treatment shows an S-dependent clastogenic effect. The proposed hypothesis of 'conservative pairing' between DNA strands of sister chromatids is further supported
SCINTILLA A European project for the development of scintillation detectors and new technologies for nuclear security
Europe monitors transits using radiation detectors to prevent illicit
trafficking of nuclear materials. The SCINTILLA project aims to develop a
toolbox of innovative technologies designed to address different usage cases.
This article will review the scope, approach, results of the first benchmark
campaign and future plans of the SCINTILLA project.Comment: To appear on the Proceedings of the 13th ICATPP Conference on
Astroparticle, Particle, Space Physics and Detectors for Physics
Applications, Villa Olmo (Como, Italy), 23--27 October, 2013, to be published
by World Scientific (Singapore
Investigations on anomalies of ovule development and on pollination in mutated grapevines, cv. Barbera
In order to point out the reasons for reduced fertility in tetraploid and 2n-4n periclinal chimera grapevines, ovule development and pollination shown by these plants were investigated.Anomalies in embryo sac formation and non-fertilization, mainly due to difficulties in pollination, were observed and related to fertility
Molecular characterization of twenty seeded and seedless table grape cultivars (Vitis vinifera L.)
DNA and isoenzyme analyses were used to characterize 20 table grape cultivars including Moscato d'Amburgo, Italia, Sultanina, Bicane and some recently released new varieties. GPI and PGM isoenzyme systems were able to separate the cultivars into 9 groups whereas the 8 microsatellite loci that were analysed revealed a higher discriminating power. In fact, all the cultivars could be distinguished by DNA profiles except Sugraone from its sport Sugrafive. Parentage analysis confirmed that the cultivar Italia was obtained from the crossing Bicane x Moscato d'Amburgo. A difference was observed at one microsatellite locus between Sultanina and the published data for Thompson Seedless, considered to be its synonym. The different microsatellite loci were evaluated for their informativeness
Towards a Conditional and Multi-preferential Approach to Explainability of Neural Network Models in Computational Logic (Extended Abstract)
Autonomous detection and ascent of a step for an electric wheelchair
With the number of individuals using a wheelchair on the rise, the issue of removing architectural barriers, or at least overcoming them, has to be faced to improve independence, inclusiveness, and participation of wheelchair users. Some electric wheelchairs can climb and descend stairs and obstacles, however, the actual operations required to do so safely may be complex and may require an experienced or trained user. To overcome this issue, a method to first detect and classify a step and then autonomously climb it safely is proposed here. The same method is then applied and tested on an actual stair-climbing wheelchair prototype to prove its reliability in different conditions
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