Efficient absolute aspect determination of a balloon borne far infrared telescope using a solid state optical photometer

The observational and operational efficiency of the TIFR 1 meter balloon borne far infrared telescope has been improved by incorporating a multielement solid state optical photometer (SSOP) at the Cassegrain focus of the telescope. The SSOP is based on a 1-D linear photo diode array (PDA). The online and offline processing schemes of the PDA signals which have been developed, lead to improvement in the determination of absolute telescope aspect ($\sim$ 0\farcm8), which is very crucial for carrying out the observations as well as offline analysis. The SSOP and its performance during a recent balloon flight are presented here.Comment: To appear in the February 2000 issue of the PAS

Cohesion, Elastic Constants and Vibrational Mechanics of Fcc Platinum

A model in real space has been developed by extending the generalized form of the exponential potential known as extended generalized exponential potential (EGEP) to account for (a) the correct nature of repulsive and attractive components of forces for all the separations in general and that of small separations in particular, (b) the three-body forces such as volume forces in an indirect way in the framework of EGEP through the parameter n, (c) the dielectric screening functions in an alternative and simpler form through the parameter m. The model is employed to compute the cohesive energy, second-order elastic constants and phenon spectra for fcc platinum. The predictions show promising agreement with experimental findings.Author Affiliation: Divesh Verma A. F. School of Engineering and Technology, Dhauj-121 004, Haryana, India M L Verma* and A Verma Department of Physics, GGDSD College, Palwal-121 102, Haryana, India and R P S Rathore Department of Physics, B.M.A.S. Engineering College, Agra-282 002, Uttar Pradesh, India1.A. F. School of Engineering and Technology, Dhauj-121 004, Haryana, India 2.Department of Physics, GGDSD College, Palwal-121 102, Haryana, India 3.Department of Physics, B.M.A.S. Engineering College, Agra-282 002, Uttar Pradesh, Indi

Star formation activity in the southern Galactic HII region G351.63-1.25

The southern Galactic high mass star-forming region, G351.6-1.3, is a HII region-molecular cloud complex with a luminosity of 2.0 x 10^5 L_sun, located at a distance of 2.4 kpc. In this paper, we focus on the investigation of the associated HII region, embedded cluster and the interstellar medium in the vicinity of G351.6-1.3. We address the identification of exciting source(s) as well as the census of stellar populations. The ionised gas distribution has been mapped using the Giant Metrewave Radio Telescope (GMRT), India at three continuum frequencies: 1280, 610 and 325 MHz. The HII region shows an elongated morphology and the 1280 MHz map comprises six resolved high density regions encompassed by diffuse emission spanning 1.4 pc x 1.0 pc. The zero age main-sequence (ZAMS) spectral type of the brightest radio core is O7.5. We have carried out near-infrared observations in the JHKs bands using the SIRIUS instrument on the 1.4 m Infrared Survey Facility (IRSF) telescope. The near-infrared images reveal the presence of a cluster embedded in nebulous fan-shaped emission. The log-normal slope of the K-band luminosity function of the embedded cluster is found to be 0.27 +- 0.03 and the fraction of the near-infrared excess stars is estimated to be 43%. These indicate that the age of the cluster is consistent with 1 Myr. The champagne flow model from a flat, thin molecular cloud is used to explain the morphology of radio emission with respect to the millimetre cloud and infrared brightness.Comment: 18 pages, 8 figures, To be published in MNRA

Método alterno para valores críticos de t de Student precisos y exactos con aplicación en las geociencias

We applied an alternative Monte Carlo simulation approach to obtain precise and accurate critical values (with 3 to 8 decimal places) for the Student´s t test for normal samples of degrees of freedom up to 6000 and for two-sided confidence levels of 50% to 99.9% and correspondingly for one-sided confidence levels of 75% to 99.95%. As an innovation, unlike the existing literature precision estimates of critical values are also individually reported. Prior to our work, critical values (with 2 or 3 decimal places) were available in tables in the published literature. Twenty-eight regression models were evaluated to obtain the best regression fitting of the tabulated data. All conventional polynomial (from quadratic up to 8th order) regressions failed for this purpose. New equations based on double or triple natural logarithm-transformations are proposed for all not-tabulated degrees of freedom, including fractional values if required as well as for probability computations. More importantly, we suggest that these kinds of log-transformations are likely to be useful for all cases where conventional polynomial regressions fail to perform satisfactorily. To demonstrate the utility of these new critical values and best-fit equations, we provide specific examples of applications in geochemistry, chemistry and medicine. The probability estimates, obtained from the present explicit approach, are consistent with commercial and freely available software. Additionally, a more extensive application of our t values is given for processing inter-laboratory data for geochemical reference materials granites G-1 and G-2 from U.S.A. as well as for evaluating geochemical data for basic rocks from the Canary and Azores IslandsAplicamos un método de simulación alterno tipo Monte Carlo para obtener valores críticos precisos y exactos de t de Student (de 3 a 8 puntos decimales) para muestras normales con grados de libertad hasta 6000 y para niveles de confianza de dos colas de 50% a 99.9% y por consecuencia, para niveles de confianza de una cola de 75% a 99.95%. Como una innovación, se reporta en forma individual la precisión de los valores críticos, lo cual no sucede en la literatura publicada. Previo a nuestro trabajo, en las tablas de la literatura publicada se disponía de los valores críticos con solamente 2 ó 3 puntos decimales. Veintiocho modelos de regresión fueron evaluados con el propósito de obtener el mejor ajuste de los datos tabulados. Todos los modelos convencionales con polinomio de cuadrático hasta la potencia 8 fracasaron para este propósito. Ecuaciones nuevas basadas en transformaciones logarítmicas de tipo doble o triple han sido propuestas para estimar los valores críticos correspondientes a grados de libertad no-tabulados, incluyendo grados no-enteros si esto fuese necesario, así como también para las computaciones de probabilidad. Aún más importante sería el hecho de que estos tipos de transformaciones logarítmicas podrían ser útiles en todos aquellos casos donde las regresiones polinomiales convencionales fracasan. Con el fin de demostrar la utilidad de los nuevos valores críticos y las ecuaciones mejor ajustadas, se proporcionan ejemplos específicos de aplicación en geoquímica, química y medicina. Las estimaciones de probabilidad obtenidas del presente método explícito son consistentes con software comercial y de acceso libre. Además, una aplicación más extensa de nuestros valores de t se presenta para procesar datos entre-laboratorios de los materiales de referencia geoquímica granitos G-1 y G-2 de los Estados Unidos de Norte-América, así como para evaluar los datos geoquímicos de rocas básicas provenientes de las Islas Canarias y de Azores