Primer registro de algunos ciliados peritricos de la laguna de San Miguel del Monte (Buenos Aires, Argentina)

Peritrichs attached to submerged macrophytes, filamentous chlorophytes and debries have been found in San Miguel del Monte pond (Buenos Aires province, Argentina) during the period March 1998- March 1999. Specimens were identified, illustrated and measured alive. Fourteen species of Subclass Peritrichia new for the country are described, illustrated and commented: Epistylis hentscheli, E. tubificis, E. vestita, Opercularia elongata, Cothurnia annulata, Cothurniopsis valvata, Pyxicola limbata, Thuricola innixa, Th. kellicotiana, Vaginicola attenuata, Vorticella picta, V. pulchella, V. rotunda, and Zoothamnium ramosissimum.Peritricos adheridos a macrófitas acuáticas, clorofitas filamentosas y partículas fueron hallados en la laguna de San Miguel del Monte (provincia de Buenos Aires, Argentina) durante el período marzo 1998 - marzo 1999. Los especímenes fueron identificados, dibujados y medidos in vivo. Se brinda una breve descripción, ilustración y algunos comentarios de catorce especies de la subclase Peritrichia, nuevas para el país: Epistylis hentscheli, E. tubificis, E. vestita, Opercularia elongata, Cothurnia annulata, Cothurniopsis valvata, Pyxicola limbata, Thuricola innixa, Th. kellicotiana, Vaginicola attenuata, Vorticella picta, V. pulchella, V. rotunda y Zoothamnium ramosissimum.Fil: Zaleski, M.. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología "dr.r.a.ringuelet"; ArgentinaFil: Claps, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología "dr.r.a.ringuelet"; Argentin

Hitts Law? A test of the relationship between information load and movement precision

Recent technological developments have made viable a man-machine interface heavily dependent on graphics and pointing devices. This has led to new interest in classical reaction and movement time work by Human Factors specialists. Two experiments were designed and run to test the dependence of target capture time on information load (Hitt's Law) and movement precision (Fitts' Law). The proposed model linearly combines Hitt's and Fitts' results into a combination law which then might be called Hitts' Law. Subjects were required to react to stimuli by manipulating a joystick so as to cause a cursor to capture a target on a CRT screen. Response entropy and the relative precision of the capture movement were crossed in a factorial design and data obtained that were found to support the model

Magnetic studies of GaN nanoceramics

The synthesis, morphology and magnetization measurements of GaN nanoceramics obtained under high pressure are reported. In particular the effect of grain size on magnetic properties of GaN nanopowders and nanoceramics was investigated. It was found that for the GaN nanoceramic characterized by the stronger deformation of nanocrystalline grains the diamagnetic signal changes with external magnetic field similarly to the Meissner effect in superconductors.Comment: 3 pages, 4 figures, accepted Appl.Phys.Let

Differential rotation of Kepler-71 via transit photometry mapping of faculae and starspots

Knowledge of dynamo evolution in solar-type stars is limited by the difficulty of using active region monitoring to measure stellar differential rotation, a key probe of stellar dynamo physics. This paper addresses the problem by presenting the first ever measurement of stellar differential rotation for a main-sequence solar-type star using starspots and faculae to provide complementary information. Our analysis uses modelling of light curves of multiple exoplanet transits for the young solar-type star Kepler-71, utilizing archival data from the Kepler mission. We estimate the physical characteristics of starspots and faculae on Kepler-71 from the characteristic amplitude variations they produce in the transit light curves and measure differential rotation from derived longitudes. Despite the higher contrast of faculae than those in the Sun, the bright features on Kepler-71 have similar properties such as increasing contrast towards the limb and larger sizes than sunspots. Adopting a solar-type differential rotation profile (faster rotation at the equator than the poles), the results from both starspot and facula analysis indicate a rotational shear less than about 0.005 rad d-1, or a relative differential rotation less than 2 per cent, and hence almost rigid rotation. This rotational shear contrasts with the strong rotational shear of zero-age main-sequence stars and the modest but significant shear of the modern-day Sun. Various explanations for the likely rigid rotation are considered

H-2 mutation affecting immune response to Thy-1.1 antigen

Mouse thymus, thymus-derived lymphocytes, and brain share an antigen determined by gene at the Thy-1 locus in chromosome 9 (1). Two alleles have been identified at this locus: Thy-1(a), coding for antigen Thy-1.1 (or θ-AKR) present in AKR and seven other strains; and Thy-1(b), coding for antigen Thy-1.2 (or{teta}-C3H) and present in C3H and all the remaining inbred strains. Injection of AKR thymocytes into inbred mice carrying the Thy-1(b) allele results in an immune response that can be measured either serologically by determining the level of antibodies in the recipients’ serum (1) or by counting plaque- forming cells (PFC) detectable in spleens of the recipients by means of an assay, with AKR thymocytes as target cells(2). The magnitude of PFC and serum antibody responses after a single thymocyte injection depends on the genetic make-up of the recipient. Three genes controlling the PFC response to the Thy- 1.1 antigen have been identified: Ir-Thy-1A and Ir-Thy-1B, which are closely linked to the major histocompatibility complex (H-2) of the mouse (3-6), and Ir-5, which is located at a distance of 17 cm to the right of the H-2 complex on chromosome 17 (6). Previous genetic mapping with H-2 recombinant strains has indicated that the two Ir-Thy-1 loci are located to the left of the IC subregion (7). Further experiments strongly suggested that either one or both Ir-Thy-1 loci map to the K rather than the I region of the H-2 complex (8). In this report, the study of an H- 2 mutant, CBA-H-2(ka) (M523) (9), and its parental strain, CBA/LacStoY (CBA) provided further evidence that one of these loci apparently resides in the K region and might even be identical with the H-2K locus in that region

Primer registro de algunos ciliados peritricos de la laguna de San Miguel del Monte (Buenos Aires, Argentina)

Peritrichs attached to submerged macrophytes, filamentous chlorophytes and debries have been found in San Miguel del Monte pond (Buenos Aires province, Argentina) during the period March 1998- March 1999. Specimens were identified, illustrated and measured alive. Fourteen species of Subclass Peritrichia new for the country are described, illustrated and commented: Epistylis hentscheli, E. tubificis, E. vestita, Opercularia elongata, Cothurnia annulata, Cothurniopsis valvata, Pyxicola limbata, Thuricola innixa, Th. kellicotiana, Vaginicola attenuata, Vorticella picta, V. pulchella, V. rotunda, and Zoothamnium ramosissimum.Peritricos adheridos a macrófitas acuáticas, clorofitas filamentosas y partículas fueron hallados en la laguna de San Miguel del Monte (provincia de Buenos Aires, Argentina) durante el período marzo 1998 - marzo 1999. Los especímenes fueron identificados, dibujados y medidos in vivo. Se brinda una breve descripción, ilustración y algunos comentarios de catorce especies de la subclase Peritrichia, nuevas para el país: Epistylis hentscheli, E. tubificis, E. vestita, Opercularia elongata, Cothurnia annulata, Cothurniopsis valvata, Pyxicola limbata, Thuricola innixa, Th. kellicotiana, Vaginicola attenuata, Vorticella picta, V. pulchella, V. rotunda y Zoothamnium ramosissimum.Contribución científica Nº 688 del Instituto de Limnología (ILPLA).Instituto de Limnología "Dr. Raúl A. Ringuelet