Accretion and UV variability in BP Tauri

BP Tau is one of the few classical T Tauri stars for which the presence of a hot spot in the surface has been reported without ambiguity. The most likely source of heating is gravitational energy released by the accreting material as it shocks with the stellar surface. This energy is expected to be radiated mainly at UV wavelengths. In this work we report the variations of the UV spectrum of BP Tau for 1992 January 5-19, when the star was monitored with IUE during two rotation periods. Our data indicate that lines that can be excited by recombination processes, such as those from O I and He II, have periodic-like light curves, whereas lines that are only collisionally excited do not follow a periodic-like trend. These results agree with the expectations of the magnetically channeled accretion models. The kinetic energy released in the accretion shocks is expected to heat the gas to temperatures of similar to 10(6) K, which henceforth produces ionizing radiation. The UV (Balmer) continuum and the O I and He II lines are direct outputs of the recombination process. However, the C IV, Si II, and Mg II lines are collisionally excited not only in the shock region but also in inhomogeneous accretion events and in the active (and flaring) magnetosphere, and therefore their light curves are expected to be blurred by these irregular processes. We also report the detection of warm infalling gas from the presence of redshifted (81 km s(-1)) absorption components in some of the high-resolution Mg II profiles available in the IUE and Hubble Space Telescope archives

Methods and Materials for Professional Development of Lecturers

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El rol del profesor desde la perspectiva de los Espacios de Trabajo Matemático

La finalidad de este artículo es precisar algunos de los elementos que organizan un espacio de trabajo efectivo para problemas de lugares geométricos en entornos tecnológicos. Se explora como 52 futuros profesores de matemáticas progresan en su concepción de lugares geométricos a través de la apropiación de las funcionalidades específicas de cada entorno (herramienta), en relación con su propia práctica como estudiantes y su futuro ejercicio profesional. Con base en sistemas de geometría dinámica se comparan tres herramientas, las diferentes representaciones matemáticas de los lugares geométricos generadas por ellas, tanto desde la perspectiva de su dinámica matemática como de sus funcionalidades didácticas. Las funcionalidades didácticas proporcionadas desde el diseñador se han estudiado desde el modelo Espacio de Trabajo Matemático (ETM). Este modelo pone de relieve la necesidad de articular para el trabajo geométrico los niveles epistemológico y cognitivo a través de diferentes génesis de razonamiento (visual-discursiva, instrumental y discursiva)

Functional studies of p.R132C, p.R149C, p.M283V, p.E431K, and a novel c.652-2A>G mutations of the CYP21A2 gene

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is the most frequent inborn error of metabolism and accounts for 90–95% of CAH cases. In the present work, we analyzed the functional consequence of four novel previously reported point CYP21A2 mutations -p.R132C, p.R149C, p.M283V, p.E431K- found in Argentinean 21-hydroxylase deficient patients. In addition, we report an acceptor splice site novel point mutation, c.652-2A.G, found in a classical patient in compound heterozygosity with the rare p.R483Q mutation. We performed bioinformatic and functional assays to evaluate the biological implication of the novel mutation. Our analyses revealed that the residual enzymatic activity of the isolated mutants coding for CYP21A2 aminoacidic substitutions was reduced to a lesser than 50% of the wild type with both progesterone and 17-OH progesterone as substrates. Accordingly, all the variants would predict mild non-classical alleles. In one non-classical patient, the p.E431K mutation was found in cis with the p.D322G one. The highest decrease in enzyme activity was obtained when both mutations were assayed in the same construction, with a residual activity most likely related to the simple virilizing form of the disease. For the c.652-2A.G mutation, bioinformatic tools predicted the putative use of two different cryptic splicing sites. Nevertheless, functional analyses revealed the use of only one cryptic splice acceptor site located within exon 6, leading to the appearance of an mRNA with a 16 nt deletion. A severe allele is strongly suggested due to the presence of a premature stop codon in the protein only 12 nt downstream.Fil: Taboas, Melisa Ivana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud "Dr. C. G. Malbrán"; ArgentinaFil: Gómez Acuña, Luciana Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Scaia, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Bruque, Carlos David. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud "Dr. C. G. Malbrán"; ArgentinaFil: Buzzalino, Noemí Delia. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorios e Institutos de Salud "Dr. Carlos G. Malbrán". Centro Nacional de Genética Médica; ArgentinaFil: Stivel, M.. Gobierno de la Ciudad Autonoma de Buenos Aires. Hospital General de Agudos Carlos Durand.; ArgentinaFil: Ceballos, Nora Raquel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Dain, Liliana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud "Dr. C. G. Malbrán"; Argentin

The ambipolar filamentation in the warm ionized medium

We present the 2-D, two fluid ( ions + neutrals) numerical simulations that we are carrying out in order to study the ambipolar filamentation process, in which a magnetized, partially ionized plasma is stirred by turbulence in the ambipolar frequency range. The higher turbulent velocity of the neutrals in the most ionized regions gives rise to a non-linear force driving them out of these regions, and causes the ions and the magnetic flux to condense in the most ionized regions, resulting in a filamentary structure where initial ionization inhomogeneities are amplified. This mechanism might help to explain some features observed in magnetized and partially ionized astrophysical plasmas as the interstellar medium

Ultraviolet spectroscopy of the hotspot in the classical T Tauri star DI Cep: Observational indications of magnetically channelled accretion

T Tauri stars (TTS) are low-mass pre-main-sequence stars that are accreting mass from the surrounding disc. The hotspots detected in some of them are probably heated by the release of gravitational energy in the accretion of the disc material on to the star. In this work we study the UV spectrum of the hotspot detected in DI Cep to constrain the physical mechanisms heating the spot and to study the possible role of the magnetic field in channelling the accretion flow. DI Cep is a classical TTS, classified as G8 IV, with a hotspot (T similar to 8500 K) covering 1-3 per cent of the visible hemisphere. We have carried out a monitoring campaign with the Short Wavelength spectrograph (1200-2000 Angstrom) and the optical FES Camera of the International Ultraviolet Explorer (IUE) from 1992 July 12 to 26. The UV spectrum of DI Cep shows excess emission in the continuum from 1700 Angstrom towards longer wavelengths with respect to a G8 IV star. The far-UV spectrum is dominated by strong emission lines of OI, CIV, Si IV, Si II and Si III], with typical surface fluxes of similar to 10(6) erg cm(-2) s(-1). The UV fluxes (lines and continuum) vary in phase and reach the maximum when the optical flux (FES) does. The light curves are similar in all the lines: the emission from the hotspot is detected above a baseline flwe probably produced by the stellar atmosphere. There is a broad range of temperatures in the hotspot (from 10(4) to 10.5 K) that is similar to that observed in the plages of magnetically active cool stars (e.g. II Peg). However, in DI Cep the light cuwes of the UV lines and continuum are correlated with the optical continuum (T/-bnnd) light curve. DI Cep as a whole deviates only slightly from active stars in the CIV-Si II and CIV-CII flux-flux relations (there is a factor of 2 excess of Si II with respect to CIV when compared with the regression line fitted to active stars). This suggests that the chromosphere and transition region of DI Cep are heated by a mechanism similar to that of the active main-sequence stars. However, the spot is significantly shifted from these relations in the flux-flux diagrams, displaying an excess of Si II (or a defect of CIV) with respect to the surface fluxes emitted by magnetically active stars. The spot alone radiates as much energy as the rest of the atmosphere, and the spot surface fluxes are similar to 10(8) erg cm(-2) s(-1) (typically 2 orders of magnitude larger than those corresponding to the atmosphere). Our observations support the theories in which the accreting material is magnetically channelled on to the stellar surface. Variations in the temperature of the spot between observations taken 1 year apart suggest that the infalling material is more likely channelled by a transient loop structure attached to the star than by a strong stellar dipolar field. The total energy radiated in the far UV lines plus the UV continuum excess is greater than or equal to 0.07 L.. This can be accounted for by the accretion of greater than or equal to 6x10(-9) M. yr(-1) from the corotation radius (8.3 R*)

Numerical simulations of the ambipolar filamentation process

We are carying out 2-D, two-fluid (ions and neutrals) numerical simulations of the ambipolar filamentation process, in which a magnetized, weakly ionized plasma is stirred by turbulence in the ambipolar frequency range. The higher turbulent velocity of the neutrals in the mast ionized regions gives rise to a non-linear force driving them out of these regions, so that the initial ionization inhomogeneities are strongly amplified. This effect, the ambipolar filamentation, causes the ions and the magnetic flux to condense and separate from the neutrals, resulting in a filamentary structure. This mechanism might help to explain some problems arising in magnetized and partially ionized astrophysical plasmas. It might provide an explanation for the spicules emerging from the solar photosphere. We also expect it to have an important role in star Formation. Under molecular cloud conditions (supersonic turbulence), we expect the mechanism to result in an additional pressure from the most ionized to the least ionized regions that efficiently separates the ions from the neutrals, favoring the gravitational collapse of the latter

Ultraviolet emission lines of T Tauri stars

We present a study of the UV emission lines fluxes of the T Tauri stars (TTS). We have used for this purpose the final IUE sample of TTS which includes 33 TTS with good spectra in whole IUE range. We have derived the lines fluxes and compared them with the X-rays fluxes measured by the EINSTEIN satellite. Flux-flux diagrams are shown confirming that the X-rays flux of the TTSs is significantly lower than the expected if their atmospheres were similar to those of late-type main sequence stars. We have also found a weak correlation between the MgII and CIV lines fluxes suggesting that there is connection between the mechanism for line formation

Influence of Transcranial Direct Current Stimulation and Exercise on Fatigue and Quality of Life in Multiple Sclerosis

[EN] Background: Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system that leads to a great deterioration in the quality of life. Objective: We aimed to assess the effectiveness of two individual programs, one based on transcranial direct current stimulation (tDCS) and another based on the effect of physical exercise on fatigue and quality of life in patients with MS. Methods: A total of 12 patients with relapsing–remitting and progressive secondary MS participated. Fatigue and quality of life were assessed before and after intervention. The exercise program and tDCS were carried out over a 4-week period, with a washout period of 5 months. Results: The results show significant improvements in the different quality of life subscales after the application of tDCS, activities of daily living (r = 0.625; p = 0.037) (g = 0.465), psychological well-being (r = 0.856; p = 0.004) (g = 0.727) and coping (r = 0.904; p = 0.18) (g = 0.376), and in those after the application of exercise, activities of daily living (r = 0.853; p = 0.003) (g = 0.570) and psychological well-being (r = 0.693; p = 0.041) (g = 0.417). After the application of both therapies, more than 50% of the subjects did not have a positive fatigue score on the MFIS scale. Conclusion: The major findings suggest that the application of both therapies produces a beneficial effect with significant improvements in the quality of life of this sample.SIThis research was funded by a grant from the Professional Association of Physiotherapists of Castilla y Leó

Biological and reproductive parameters of Helicoverpa armigera and Helicoverpa zea reared on artificial diet in Argentina

Helicoverpa armigera and H. zea (Lepidoptera Noctuidae) are genetically and physiologically closely related species that havemating compatibility under laboratory conditions. Considering the presence of H. armigera in Argentina, the lack information aboutits biology and evolutionary relationship with H. zea, the aim of this study was to compare biological, reproductive, populationparameters and biotic potential (BP) of both species under controlled conditions. Egg and larva duration showed significant differences,being in both cases the longest duration in H. zea. Pre-oviposition, oviposition, and post-oviposition duration, and fertilitypresented significant differences. The only population parameter that did not differ between H. armigera (96.95) and H. zea (104.78)was the net reproductive rate (R0). The maximum rate of population growth occurred in the day 34 and 46 for H. armigera andH. zea respectively. Biotic potential value indicated that each female of H. armigera and H. zea can produce more than 36 quintillionand 454 trillion descendants per year respectively. These analyses determined that H. armigera and H. zea have the potential toincrease quickly their populations under controlled conditions. The results obtained provide additional information to plan andimplement strategies for the integrated management of these species with emphasis in H. armigera in Argentina.Fil: Murúa, María Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres" (p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: Fogliata, Sofia Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres" (p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; Argentina. Syngenta Company; ArgentinaFil: Herrero, María Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres" (p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: Vera, M. Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres" (p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: Casmuz, Augusto Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Tecnología Agroindustrial del Noroeste Argentino. Provincia de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial "Obispo Colombres" (p). Instituto de Tecnología Agroindustrial del Noroeste Argentino; ArgentinaFil: Sosa Gómez, Daniel. Embrapa Soja; Brasi