Papers by Luis Carlos Udaeta Rodriguez
Physical Review B, 1998
We investigated with ac susceptibility the mixed state of twinned, deoxygenated single crystals a... more We investigated with ac susceptibility the mixed state of twinned, deoxygenated single crystals and highly c-axis-oriented melt-textured samples of YBa2Cu3O6+x with oxygen stoichometry corresponding to that of the orthorhombic II phase. In the single crystal we found, below H*~700 Oe and over almost four orders of magnitude in frequency, a frequency-independent ``irreversibility line'' (IL). Complementry dc magnetization measurements seem to disregard an IL arising from geometric effects when H||c, and they suggest a possible meltinglike transition of the flux-line lattice below H*. The reduced value of H* is associated with the increased anisotropy induced by the oxygen depletion, and an upper limit of the anisotropy parameter is estimated as gammamax~147. However, in the twinned melt-textured sample having a major grade of disorder due to the presence of micrometric nonsuperconducting precipitates of Y2BaCuO5, the IL is frequency dependent for all applied magnetic fields, suggesting a cancellation of H* in the sufficiently disordered specimen.
Biosystems Engineering, 2016
Manual De Prevencion Y Rehabilitacion De Lesiones Deportivas 2002 Isbn 84 9756 003 5 Pags 331 344, 2002
Acceso de usuarios registrados. Acceso de usuarios registrados Usuario Contraseña. ...
Arch Microbiol, 1986
Saccharomyces cerevisiae alpha factor pheromone arrest growth of cells of the a mating type (MAT ... more Saccharomyces cerevisiae alpha factor pheromone arrest growth of cells of the a mating type (MAT a) at the G1 phase of the cell cycle. When treatment of MAT a cells with alpha factor was carried out in the presence of anticalmodulin drugs, trifluoperazine or chlorpromazine, the extent of cell growth arrest induced by alpha factor was reduced or even became undetectable. These results lend support to the hypothesis that calmodulin plays a role as mediator in the action of alpha factor on MAT a cells.
... DL MICKEY, Inst. for Astron., Univ. ... LF RODRIGUEZ and EJ CHAISSON, c.~a - Using the Haysta... more ... DL MICKEY, Inst. for Astron., Univ. ... LF RODRIGUEZ and EJ CHAISSON, c.~a - Using the Haystack Observatory 120-foot radio telescope, we have mapped nine galactic H II regions with an angular resolution of l!4 and a pointing accuracy of 15' . ...
Psicothema, 2006
... M., Grande Pérez, I., Valero i Ventura, S. y Punti i Vi-dal, J. (2001). Personalidad y conduc... more ... M., Grande Pérez, I., Valero i Ventura, S. y Punti i Vi-dal, J. (2001). Personalidad y conducta delictiva autoinformada en adultos jóvenes. Psicothema, 13(2), 252-257. Page 6. MARGARITA ORTIZ-TALLO, ALFREDO FIERRO, MARÍA JOSÉ BLANCA, VIOLETA CARDENAL Y LUIS ...
Astrophys J, 1998
The extragalactic radio source NGC 6334B is the most strongly scattered object known, with an ang... more The extragalactic radio source NGC 6334B is the most strongly scattered object known, with an angular size of 3" at 20 cm wavelength. Its angular size scales as the square of the observing wavelength, and its phase structure function has a power-law dependence on projected baseline length. These properties suggest that NGC 6334B is a point source, probably a quasar, scatter broadened by an intervening region of turbulent plasma. The line of sight to the source intercepts the northern lobe of the bipolar H II region NGC 6334A, which is probably the source of the scattering. We discuss observations of NGC 6334B with the VLA at 1.4, 2, 6, 20, and 90 cm, and with the VLBA at 1.4, 3.6, and 6 cm. The VLA observations indicate that the scattering disk of NGC 6334B is anisotropic, with an axial ratio of ~1.2 at 20 and 6 cm, and ~1.5 at 2 cm. This anisotropy is probably due to the effects of a magnetic field in the scattering medium. The position angle of the scattering disk implies that the mean projected magnetic field direction is parallel to the outflow from NGC 6334A. The position angle of the scattering disk rotates slightly between 6 and 2 cm; we use this rotation to place an upper limit on the outer scale of turbulence, rout <~ 1016 cm. We present a new algorithm to detect the presence of weak (<3 σ) fringes in interferometric data. Detections of low-level excess visibility on long VLBA baselines at 3.6 cm place an upper limit on the inner dissipative scale of turbulence rin of 1011-12 cm, while the baseline scaling of fringe visibility amplitude and the wavelength scaling of scattering-disk size place a lower limit on rin of 5 × 106 cm. Nearby high-velocity (-80 km s-1) H2O maser features show little sign of broadening, implying that they are in front of, or less than 100 pc behind, the scattering region.
Ieee Transactions on Antennas and Propagation, Dec 1, 2008
Simple equivalent surface currents perturbed from the physical optics (PO) are proposed, which pr... more Simple equivalent surface currents perturbed from the physical optics (PO) are proposed, which predict accurate scattering fields without using a special knowledge about the high frequency asymptotic theories such as the geometrical theory of diffraction (GTD). A novel and empirical concept named ldquomodified surface-normal vectorsrdquo is introduced in the classical definition of the PO current, which is defined in a
Proceedings of Spie the International Society For Optical Engineering, Jul 1, 2008
A Deformable Mirror Controller (DMC) has been devised to overcome the open-loop nature of Multi O... more A Deformable Mirror Controller (DMC) has been devised to overcome the open-loop nature of Multi Object Adaptive Optics (MOAO), in particular for AO systems with update rates of 1 ms or less. The system is based on a figure sensor, which uses a monochromatic illumination source and a Shack-Hartmann (SH) wavefront sensor (WFS) to obtain a fine sampling of DM's 3D surface. The sensor's beam is optically separated from the science path in order to not interfere with science observations. The DMC incorporates a real-time controller in charge of driving the DM. This controller runs in a dedicated Field-Programmable-Gate-Array (FPGA) based processor to keep up with stringent speed requirements. The DMC is being tested in the laboratory and is part of CANARY, an MOAO on-sky demonstrator to be installed at the William Hershel Telescope.
Astrophys J, 1998
We have observed simultaneously the 1.3 cm continuum and H2O maser emission toward the core of th... more We have observed simultaneously the 1.3 cm continuum and H2O maser emission toward the core of the star-forming region NGC 2071 using the Very Large Array in its A configuration. Two 1.3 cm continuum sources have been detected in the region, coinciding with the infrared sources IRS 1 and IRS 3, respectively. The radio emission in IRS 3 is consistent with an ionized thermal bipolar radio jet. Two clusters of H2O maser spots are detected, one associated with IRS 1 (22 spots) and the other one associated with IRS 3 (13 spots). The H2O maser distribution in IRS 1 seems to be tracing at scales of 300 AU the larger scale H2 outflow observed at a few thousands of AU from the exciting source. On the other hand, the H2O masers in IRS 3 are distributed as an apparent disk of ~=0.05" (~=20 AU) radius, oriented almost perpendicular to the major axis of the radio jet. There is a clear velocity gradient (~=0.35 km s-1 AU-1) along the major axis of the H2O maser distribution, which can be gravitationally bound by a central mass of ~=1 M&sun;. These results, together with the low-mass and early evolutionary stage of IRS 3, suggest that masers around this source are tracing a rotating proto-planetary disk within a proto-solar-like system. This represents direct kinematic evidence of the smallest rotating circumstellar disk ever observed around a young stellar object (YSO). We discuss the dichotomy of H2O masers tracing either outflows or disks around YSOs, based on the evolutionary scheme proposed in our earlier work. We suggested that systems in which H2O masers trace disks are less evolved than those in which masers trace outflows. In this scheme, IRS 3 would then represent a relatively less evolved object than IRS 1. This prediction is consistent with independent infrared observations showing that IRS 3 is at an earlier phase of evolution.
Astrophys J, 1993
We present NH3(1, 1) and (2, 2) observations of the young stellar sources HL Tau and L1551-IRS 5 ... more We present NH3(1, 1) and (2, 2) observations of the young stellar sources HL Tau and L1551-IRS 5 using the VLA in its B-configuration, which provides an angular resolution of about 0.4 arcsec (about 50 AU at 140 pc) at 1.3 cm wavelength. Our goal was to detect and resolve circumstellar molecular disks with radius of the order of 100 AU around these two sources. No ammonia emission was detected toward either of them. The 3-sigma levels were 2.7 mJy/beam and 3.9 mJy/beam for HL Tau and L1551-IRS 5, respectively, with a velocity resolution of about 5 km/s. With this nondetection, we estimate upper limits to the mass of the proposed protoplanetary molecular disks (within a radius of 10 AU from the central stars) on the order of 0.02/(X(NH3)/10 exp -8) solar mass for HL Tau and 0.1/(X(NH3)/10 exp -8) solar mass for L1551-IRS 5.
Fungal Genetics and Biology, Oct 31, 2004
The protein secretory pathway has not been studied in depth in Candida albicans despite its essen... more The protein secretory pathway has not been studied in depth in Candida albicans despite its essential role in the secretion of enzymes and cell surface components related to the ability of the fungus to colonize the human host. To gain further insight into the elements that participate in the first stages of the secretory process in this fungal pathogen we have isolated and characterized the C. albicans ortholog of SEC61. In other species SEC61 has been shown to encode the core element of the protein translocation apparatus within the ER membrane. The cloned gene appears to be essential for cell viability and encodes a highly conserved protein, very similar to the Sec61p from other yeast species both in sequence and hydropathy profile. However, CaSec61p is not able to complement the thermosensitive-growth phenotype of a Saccharomyces cerevisiae sec61 mutant, even though it is expressed and correctly incorporated into the ER membrane of the transformant cells. We report results indicating that the lack of functional complementation could be related to differences in the primary structure of the cytosolic domain located between the fourth and fifth transmembrane domains of the accepted topological model of Sec61p.
Psiquiatria Com, Jul 30, 2014
Proceedings of the International Astronomical Union, 2001
Several extraordinary clusters of massive stars near the Galactic center have recently been revea... more Several extraordinary clusters of massive stars near the Galactic center have recently been revealed at near-infrared wavelengths. The Arches and Quintuplet clusters each harbor at least 100 OB supergiants and other highly evolved, mass-losing stellar types such as Wolf-Rayet stars. The expanding, ionized winds of these stars should be detectable at radio wavelengths. Here, we present multi-frequency (ranging from 6 cm to 7 mm), high resolution (0''.3 to 3'') VLA observations of a number of sources that show rising spectra (Sν ∝ να), characteristic of radio detections of ionized stellar winds. In addition, the majority of these detections are coincident in position with near-infrared counterparts located in the Arches and Quintuplet clusters, confirming that these detections are likely to be the ionized winds associated with massive stars in these clusters. The large integrated ionizing flux of the clusters can explain the ionization of the two sets unusually-shaped H II regions found in the central 50 pc of the Galaxy. The interaction of individual stellar winds can also produce a powerful stellar wind that might impact on and alter the surrounding interstellar medium. We are also undertaking a VLA study to detect the winds arising from the massive stars which surround the supermassive black hole, SgrA*, and to determine the effects of tidal shearing on the ionized winds in such an extreme environment.
Agronomia Colombiana, Apr 1, 2008
Abstract The study was realized in the provinces of Center, Marquez, Sugamuxi and Tundama of the ... more Abstract The study was realized in the provinces of Center, Marquez, Sugamuxi and Tundama of the Department of Boyacá with the purpose to analyze the group of agricultural enterprises that produce deciduous fruits in the region. Taking into account the design of ...
Anuario De Estudios Filologicos, 2005
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Papers by Luis Carlos Udaeta Rodriguez