458 research outputs found
Micropropagation of grape rootstocks of interest for Misiones province
Con el objeto de micropropagar portainjertos
de vid de interés para la provincia
de Misiones (Paulsen 1103 y Vr 04343)
se cultivaron segmentos nodales y ápices
meristemáticos. Para el establecimiento de
segmentos nodales se evaluaron diferentes
concentraciones del medio propuesto por Murashige
y Skoog (MS) -¼, ½, 1- adicionando
diferentes concentraciones de benciladenina
(0; 1; 3 y 5 mg.L-1) y ácido naftalenacético (0 y
0,01 mg.L-1). Se evaluaron estado fisiológico y
topófisis de yemas. En fase de multiplicación
se evaluaron ápices, segmentos uni y binodales
con o sin hoja desplegada. Para el establecimiento
de ápices se evaluó el medio MS
½ suplementado con bencilaminopurina (0;
0,5; 1; 2 mg.L-1). Los mejores resultados para
el establecimiento de segmentos nodales se
obtuvieron con yema despierta en medio MS
¼ sin adición de reguladores. La multiplicación
de los mismos puede realizarse partiendo de
un explanto uni o binodal con o sin hoja. Al
utilizar ápices como explanto, se debe adicionar
al medio MS ½ bencilaminopurina en una
concentración de 0,5 mg.L-1. En la aclimatación
de las plantas, se obtuvieron valores de
supervivencia de 80 a 90%.In order to develop a micropropagation
system for different grape rootstock of interest
for Misiones Province (Paulsen 1103 and
Vr 04343), nodal segments and root tips
were culturated. Different concentrations
of the medium proposed by Murashige
and Skoog (MS) -¼, ½ , 1- adding different
concentrations of benzyladenine (0; 1; 3
and 5 mg.L-1) and naphthylacetic acid (0
and 0.01 mg.L-1) were evaluated for the
establishment of nodal segments. Topofisis
and physiological state of the buds were also
evaluated. Shoot tips and one-node and twonode
segments with or without leave were
evaluated in the multiplication stage. For the
establishment of shoot tips the medium MS ½
supplemented with benzylaminopurine (0; 0.5;
1; 2 mg.L-1) was evaluated. The best results for
establishment phase of nodal segments with
the bud were obtained with the medium MS ¼
without regulator’s addition. Multiplication
phase can start from an one or two-node
explant with or without leaf. When using shoot
tips as explant, the medium MS ½ should be
added with benzyladenine at 0.5 mg.L-1. In
acclimated plants, we obtained survival values
between 80 and 90%.Fil: Guerrero, Diego R..
Universidad Nacional del Nordeste. Facultad de Ciencias AgrariasFil: Mroginski, Luis A..
Universidad Nacional del Nordeste. Facultad de Ciencias AgrariasFil: Krivenky, Mario A..
Instituto Nacional de Tecnología Agropecuaria (Argentina). Estación Experimental Agropecuaria Cerro AzulFil: Domínguez, Martín C..
Instituto Nacional de Tecnología Agropecuaria (Argentina). Estación Experimental Agropecuaria Cerro Azu
Transverse Phase Locking for Vortex Motion in Square and Triangular Pinning Arrays
We analyze transverse phase locking for vortex motion in a superconductor
with a longitudinal DC drive and a transverse AC drive. For both square and
triangular arrays we observe a variety of fractional phase locking steps in the
velocity versus DC drive which correspond to stable vortex orbits. The locking
steps are more pronounced for the triangular arrays which is due to the fact
that the vortex motion has a periodic transverse velocity component even for
zero transverse AC drive. All the steps increase monotonically in width with AC
amplitude. We confirm that the width of some fractional steps in the square
arrays scales as the square of the AC driving amplitude. In addition we
demonstrate scaling in the velocity versus applied DC driving curves at
depinning and on the main step, similar to that seen for phase locking in
charge-density wave systems. The phase locking steps are most prominent for
commensurate vortex fillings where the interstitial vortices form symmetrical
ground states. For increasing temperature, the fractional steps are washed out
very quickly, while the main step gains a linear component and disappears at
melting. For triangular pinning arrays we again observe transverse phase
locking, with the main and several of the fractional step widths scaling
linearly with AC amplitude.Comment: 10 pages, 14 postscript figure
Orientational pinning and transverse voltage: Simulations and experiments in square Josephson junction arrays
We study the dependence of the transport properties of square Josephson
Junctions arrays with the direction of the applied dc current, both
experimentally and numerically. We present computational simulations of
current-voltage curves at finite temperatures for a single vortex in the array
(), and experimental measurements in
arrays under a low magnetic field corresponding to . We find that
the transverse voltage vanishes only in the directions of maximum symmetry of
the square lattice: the [10] and [01] direction (parallel bias) and the [11]
direction (diagonal bias). For orientations different than the symmetry
directions, we find a finite transverse voltage which depends strongly on the
angle of the current. We find that vortex motion is pinned in the [10]
direction (), meaning that the voltage response is insensitive to small
changes in the orientation of the current near . We call this
phenomenon orientational pinning. This leads to a finite transverse critical
current for a bias at and to a transverse voltage for a bias at
. On the other hand, for diagonal bias in the [11] direction the
behavior is highly unstable against small variations of , leading to a
rapid change from zero transverse voltage to a large transverse voltage within
a few degrees. This last behavior is in good agreement with our measurements in
arrays with a quasi-diagonal current drive.Comment: 9 pages, 9 figure
Angular size test on the expansion of the Universe
Assuming the standard cosmological model as correct, the average linear size
of galaxies with the same luminosity is six times smaller at z=3.2 than at z=0,
and their average angular size for a given luminosity is approximately
proportional to 1/z. Neither the hypothesis that galaxies which formed earlier
have much higher densities nor their luminosity evolution, mergers ratio, or
massive outflows due to a quasar feedback mechanism are enough to justify such
a strong size evolution. Also, at high redshift, the intrinsic ultraviolet
surface brightness would be prohibitively high with this evolution, and the
velocity dispersion much higher than observed. We explore here another
possibility to overcome this problem by considering different cosmological
scenarios that might make the observed angular sizes compatible with a weaker
evolution.
One of the models explored, a very simple phenomenological extrapolation of
the linear Hubble law in a Euclidean static universe, fits the angular size vs.
redshift dependence quite well, which is also approximately proportional to 1/z
with this cosmological model. There are no free parameters derived ad hoc,
although the error bars allow a slight size/luminosity evolution. The type Ia
supernovae Hubble diagram can also be explained in terms of this model with no
ad hoc fitted parameter.
WARNING: I do not argue here that the true Universe is static. My intention
is just to discuss which theoretical models provide a better fit to the data of
observational cosmology.Comment: 44 pages, accepted to be published in Int. J. Mod. Phys.
Potencial utilización de la termografía infrarroja para la lectura de la IDTB en cabras
En este trabajo se pretende estudiar la potencial utilización de la TI (Termografía infrarroja) en la lectura de la IDTB (intradermotuberculinización) en cabras. El análisis de las temperaturas mostró un aumento significativo a las 24h postinoculación de la tuberculina en el conjunto de los individuos, no observándose influencia significativa de la capa de los animales sobre las temperaturas. La comparación de los resultados de ambas técnicas no evidenció asociación significativa.The aim of this experiment is to study the potential use of IT (infrared termography) for measurement of PPD (Purified protein derivate) test in goats. The study of the temperatures showed a significant increase at 24hours post-inoculation of the PPD in the set of all the individuals, not being observed significant influence of the colour of the animals on the temperatures. The comparison of the results from the PPD skin test, and IT did not demonstrate significant association
The elusive nature of the r-stars
R stars are carbon stars, less luminous and hotter than the carbon stars evolving along the AGB phase. Thus, their carbon enrichment cannot be a consequence of the third dredge-up, a fact also in agreement with the lack of s-element enhancements in their envelopes. Since their discovery the absence of binaries has lead to the conclusion that a previous merger might play a fundamental role in the observed chemical composition, likely through non-standard mixing at the time of the He-flash. On the other hand numerical simulations, in which the He-flash is artificially located close to the edge of a degenerate He core, have successfully induced mixing of carbon into the envelope. In this context it has been suggested that the merger of a degenerate He core with that of a normal red giant star could lead to the formation of a rapidly rotating core undergoing o -centre He ignition in highly degenerate conditions. This scenario is also supported by statistical analysis of the potential mergers that could explain the number, and location in the Galaxy, of observed R stars. Basing on detailed stellar models we will show the evolution of these mergers, that are very common in nature, and do not seem to be the progenitors of (hot) R stars.Postprint (published version
Single nucleotide polymorphism (SNP) analysis used for the phylogeny of the Mycobacterium tuberculosis complex based on a pyrosequencing assay
Background
Different polymorphisms have been described as markers to classify the lineages of the Mycobacterium tuberculosis complex. The analysis of nine single nucleotide polymorphisms (SNPs) was used to describe seven SNPs cluster groups (SCGs). We attempted to classify those strains that could not been categorized into lineages by the genotyping methods used in the routine testing.
Results
The M. tuberculosis complex isolates collected in 2010 in our region were analysed. A new method based on multiplex-PCRs and pyrosequencing to analyse these SNPs was designed. For the pyrosequencing assay nine SNPs that defined the seven SCGs were selected from the literature: 1977, 74092, 105139, 232574, 311613, 913274, 2460626, 3352929 and gyrA95. In addition, SNPs in katG463, mgtC182, Ag85C103 and RDRio deletion were detected
Melting and transverse depinning of driven vortex lattices in the periodic pinning of Josephson junction arrays
We study the non-equilibrium dynamical regimes of a moving vortex lattice in
the periodic pinning of a Josephson junction array (JJA) for {\it finite
temperatures} in the case of a fractional or submatching field. We obtain a
phase diagram for the current driven JJA as a function of the driving current I
and temperature T. We find that when the vortex lattice is driven by a current,
the depinning transition at and the melting transition at
become separated even for a field for which they coincide in equilibrium. We
also distinguish between the depinning of the vortex lattice in the direction
of the current drive, and the {\it transverse depinning} in the direction
perpendicular to the drive. The transverse depinning corresponds to the onset
of transverse resistance in a moving vortex lattice at a given temperature
. For driving currents above the critical current we find that the
moving vortex lattice has first a transverse depinning transition at low T, and
later a melting transition at a higher temperature, .Comment: 17 pages, 19 figure
Mixed monolayers of eicosylamine and a bacterial-ferritin prepared by adsorption technique at the air-water interface
II Encuentro sobre nanociencia y nanotecnología de investigadores y tecnólogos de la Universidad de Córdoba. NANOUC
Preparación de monocapas en la interfase aire-agua: estudio de las propiedades de adsorción de una nueva bacterioferritina
II Encuentro sobre nanociencia y nanotecnología de investigadores y tecnólogos de la Universidad de Córdoba. NANOUC
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