15,888 research outputs found
Braneworld with Induced Axial Symmetry
We take arbitrary gravitational perturbations of a 5d spacetime and reduce it
to the form an axially symmetric warped braneworld. Then, we write the filed
equations for the linearized gravity perturbations. We obtain the equations
that describes the graviton, gravivector and the graviscalar fluctuations and
analyse the effects of the Schr\"odinger potentials that appear in these
equations.Comment: 3 pages, one figure, typos corrected, to apear in the special issue
of Brazilian Journal of Physics dedicated to the conference 100 years of
relativity, Sao Paulo, Brazil, 200
Wave polarizations for a beam-like gravitational wave in quadratic curvature gravity
We compute analytically the tidal field and polarizations of an exact
gravitational wave generated by a cylindrical beam of null matter of finite
width and length in quadratic curvature gravity. We propose that this wave can
represent the gravitational wave that keep up with the high energy photons
produced in a gamma ray burst (GRB) source.Comment: 5 pages, 3 figures, minor corrections, to appear in CQ
Regeneration of plants from apical meristem tips and nodal segments of Arachis pintoi
The in vitro regeneration potential of shoot apical tips (2 to 3 mm in length), meristems (0.3 to 0.5 mm in length), and nodal segments (4 to 7 mm long with an axillary bud) of diploid (2n = 2x = 20) and triploid (2n = 3x = 30) cytotypes of Arachis pintoi was evaluated. Explants were cultured on MS medium supplemented with different concentrations and combinations of naphthaleneacetic acid (NAA) and benzyladenine (BA). In one experiment the effect of gibberellic acid was tested. The cultures were done in liquid and solid media. Plant regeneration can be readily achieved from all explants in one step of 30 d culture on MS + 0.01 mg/L each of NAA and BA or two steps consisting of 1) shoots regeneration through culture of explants on MS + 0.01 mg/L each of NAA and BA, and 2) induction of rooting in regenerated shoots by reculture on MS + 0.01 mg/L NAA. The plantlets were successfully transferred to pots in a greenhouse.Fil: Rey de Badaró, Hebe Yolanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Mroginski, Luis Amado. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentin
Cryopreservation of plant germplasm in Argentina
This review describes the current status of development of methods for cryopreservation (at -196ºC) of plants germplasm in Argentina. Arachis pintoi, a forage legume, has been maintained as seeds using vitrification method. Additionally, apical meristems, shoot tips, and somatic embryos have been cryopreserved using encapsulation-dehydration. Zygotic embryos, encapsulated and dehydrated, have permitted the cryopreservation of seven species of the genus Ilex. Various explants (apical meristems, uninodal segments, buds and somatic embryos) of Melia azedarach have been cryopreserved using the encapsulation-dehydration method. Protocols based in encapsulation-dehydration have also been developed for shoot tips of Citrus sinensis, seeds and protocorms of Oncidum bifolium and anthers of Oryza sativa. Vitrification protocols have been developed forcryopreservation of shoot tips of Solanum tuberosum and seeds of Toona ciliata.Fil: Mroginski, Luis Amado. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Rey de Badaró, Hebe Yolanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentin
Nonholomorphic N=2 terms in N=4 SYM: 1-Loop Calculation in N=2 superspace
The effective action of N=2 gauge multiplets in general includes
higher-dimension UV finite nonholomorphic corrections integrated with the full
N=2 superspace measure. By adding a hypermultiplet in the adjoint
representation we study the effective action of N=4 SYM. The nonanomalous SU(4)
R-symmetry of the classical N=4 theory must be also present in the on-shell
effective action, and therefore we expect to find similar nonholomorphic terms
for each of the scalars in the hypermultiplet. The N=2 path integral
quantization formalism developed in projective superspace allows us to compute
these hypermultiplet nonholomorphic terms directly in N=2 superspace. The
corresponding gauge multiplet expression can be successfully compared with the
result inferred from a N=1 calculation in the abelian subsector.Comment: 12 pages, LaTex, includes 4 .eps figures, sign convention in path
integral definition changed, sign of nonholomorphic potential change
Organogenesis and plant regeneration of Arachis villosa Benth. (Leguminosae) through leaf culture
With the aim of developing an efficient plant regeneration protocol, leaflet explants of three accessions of Arachis villosa Benth. (S2866, S2867 and L97) were cultured on basic Murashige and Skoog medium supplemented with different combinations of plant growth regulators: α-naphthalenacetic acid, indole-3-butyric acid, 6-benzylaminopurine, kinetin and thidiazuron. The accession L97 was the only one able to differentiate buds through indirect organogenesis. The most suitable combination for bud regeneration was the basic medium added with 13.62 μM thidiazuron and 4.44 μM 6-benzylaminopurine. These results show the important role of the genotype in morphogenetic responses and the organogenetic effect of thidiazuron in Arachis villosa accession L97. A thidiazuron lacking media (only 0.54 μM α-naphthalenacetic acid, 13.95 μM kinetin and 13.32 μM 6-benzylaminopurine were added) promoted the elongation of the regenerated buds. Adventitious rooting was achieved 90 days after the isolated shoots were transferred to a rooting medium containing 0.54 μM α-naphthalenacetic acid.Fil: Fontana, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Mroginski, Luis Amado. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Rey de Badaró, Hebe Yolanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentin
Diffusion of Hydrogen in Pd Assisted by Inelastic Ballistic Hot Electrons
Sykes {\it et al.} [Proc. Natl. Acad. Sci. {\bf 102}, 17907 (2005)] have
reported how electrons injected from a scanning tunneling microscope modify the
diffusion rates of H buried beneath Pd(111). A key point in that experiment is
the symmetry between positive and negative voltages for H extraction, which is
difficult to explain in view of the large asymmetry in Pd between the electron
and hole densities of states. Combining concepts from the theory of ballistic
electron microscopy and electron-phonon scattering we show that H diffusion is
driven by the -band electrons only, which explains the observed symmetry.Comment: 5 pages and 4 figure
The Matrix Formulation of Type IIB Five-Branes
We present a matrix model which interpolates between type IIA and type IIB NS
five-branes. The matrix description involves a three-dimensional bulk quantum
field theory interacting with impurities localized in one spatial direction. We
obtain a dual matrix formulation for the exotic six-dimensional theory on
coincident type IIB NS five-branes by studying the T-dual description in terms
of Kaluza-Klein monopoles in type IIA string theory. After decoupling the bulk
physics, the matrix description reduces to the conformal field theory of the
Coulomb branch for the type IIA matrix string propagating on certain singular
spaces. In many ways, this dual realization of superconformal theories is the
two-dimensional analogue of three-dimensional mirror symmetry.Comment: 15 pages, harvmac; minor changes to the tex
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