High efficiency optical beamsplitter designed for operation in the infrared region

Beamsplitter system uses potassium bromide as substrate for operating in the spectral region between 5 and 30 microns and calcium fluoride for narrowband applications. It uses a 13-layer film which yields nearly equal broadband infrared reflectance and transmittance

Multilayer infrared beamsplitter film system

Multilayer infrared beamsplitter film system on a potassium bromide crystal substrate is operational over a wavelength range of 2.5 to 25 microns with nearly equal broadband reflectance and transmittance. It is useful in optical coating, vacuum deposition, radiometry, interferometry, and spectrometry

Unsupported thin film beam splitter

Multilayer beam splitter system yielding nearly equal broadband infrared reflectance and transmittance in the 5 to 50 micron spectral region has been developed which will significantly reduce size and cost of light path compensating devices in infrared spectral instruments

Polarimetric variations of binary stars. VI. Orbit-induced variations in the pre-main-sequence binary AK Sco

We present simultaneous UBV polarimetric and photometric observations of the pre-main-sequence binary AK Sco, obtained over 12 nights, slightly less than the orbital period of 13.6 days. The polarization is a sum of interstellar and intrinsic polarization, with a significant intrinsic polarization of 1% at 5250A, indicating the presence of circumstellar matter distributed in an asymmetric geometry. The polarization and its position angle are clearly variable on time scales of hours and nights, in all 3 wavelengths, with a behavior related to the orbital motion. The variations have the highest amplitudes seen so far for pre-main-sequence binaries (~1%, ~30deg) and are sinusoidal with periods similar to the orbital period and half of it. The polarization variations are generally correlated with the photometric ones: when the star gets fainter, it also gets redder and its polarization increases. The color-magnitude diagram B-V, V exhibits a ratio of total to selective absorption R=4.3 higher than in normal interstellar clouds (R=3.1). The interpretation of the simultaneous photometric and polarimetric observations is that a cloud of circumstellar matter passes in front of the star, decreasing the amount of direct, unpolarized light, and hence increasing the contribution of scattered (blue) light. We show that the large amplitude of the polarization variations can not be reproduced with a single scattering model and axially symmetric circumbinary or circumstellar disks.Comment: 24 pages, 10 figures, accepted for publication in the Astronomical Journa

Encapsulated formulation of the Selective Frequency Damping method

We present an alternative "encapsulated" formulation of the Selective Frequency Damping method for finding unstable equilibria of dynamical systems, which is particularly useful when analysing the stability of fluid flows. The formulation makes use of splitting methods, which means that it can be wrapped around an existing time-stepping code as a "black box". The method is first applied to a scalar problem in order to analyse its stability and highlight the roles of the control coefficient $\chi$ and the filter width $\Delta$ in the convergence (or not) towards the steady-state. Then the steady-state of the incompressible flow past a two-dimensional cylinder at $Re=100$, obtained with a code which implements the spectral/hp element method, is presented

La mention de la méthodologie des sondages électoraux dans les quotidiens québécois de 1979 à 1997

Faute de réglementation gouvernementale, la capacité autorégulatrice des médias et un marché concurrentiel permettent-ils d’améliorer la présentation de la méthodologie des sondages électoraux? L’analyse de 390 comptes rendus de sondages électoraux publiés de 1979 à 1997 révèle que le nombre d’informations méthodologiques transmises est demeuré stable après une légère hausse entre 1979 et 1984. L’identité du commanditaire, la nationalité du sondeur, l’intervention d’experts dans le travail journalistique et l’unité territoriale sur laquelle porte le sondage influencent la présentation de la méthodologie. En conclusion, l’autorégulation et la concurrence n’améliorent pas la qualité de la présentation de la méthodologie en raison des intérêts et des contraintes des entreprises de presse, des journalistes et des firmes de sondage.Can the media self-regulation ability and a competitive market improve the publication quality of methodological data about electoral polls, without a governmental regulation? An analysis of 390 reports on electoral polls published from 1979 to 1997 shows the stability of the number of methodological data included, after a small increase between 1979 and 1984. The sponsor's identity, the pollster's nationality, the interacting between journalists and experts, in addition to the territorial unit on which the results are applicable influence the presentation of methodology. In conclusion, the author states that the self-regulation and the competition do not improve the publication quality of methodological data owing to the interests and constraints of press companies, journalists and pollsters

An Examination of Volunteer Motivations and Characteristics Between Required Volunteer Service and Non-Required Volunteer Service in College Students: An Exploratory Study

Volunteerism in the undergraduate years can enhance students’ academic development, civic responsibility, and life skills (Astin & Sax, 1998). Whether a student volunteers in high school can be a predictor of continued volunteerism in college and later in life (Planty & Regnier, 2003; Astin & Sax, 1998). Participants of this study were 283 college students enrolled in first year seminar courses at a large university in the Southeastern United States. Participants completed a questionnaire developed by Gage and Thapa (2012) which included the Volunteer Function Inventory (Clary et al. 1998) that served to investigate the volunteering characteristics and volunteering motivations of college students, as well as the relationship between volunteerism in high school, required volunteerism in high school, and volunteerism in college. Data analysis was conducted using descriptive statistics and Pearson Correlation. Results showed that there was no significant correlation between required volunteerism in high school or required volunteerism in high school and volunteerism in college. Results also indicated that students are more interested in volunteering time and skills contributions for organizations, particularly those involved in human services. On average, students scored higher on values and career motivational functions than other motivational functions

Polarimetric variations of binary stars. II. Numerical simulations for circular and eccentric binaries in Mie scattering envelopes

We present numerical simulations of the periodic polarimetric variations produced by a binary star placed at the center of an empty spherical cavity inside a circumbinary ellipsoidal and optically thin envelope made of dust grains. Mie single-scattering is considered along with pre- and post-scattering extinction factors which produce a time-varying optical depth and affect the morphology of the periodic variations. We are interested in the effects that various parameters will have on the average polarization, the amplitude of the polarimetric variations, and the morphology of the variability. We show that the absolute amplitudes of the variations are smaller for Mie scattering than for Thomson scattering. Among the four grain types that we have studied, the highest polarizations are produced by grains with sizes in the range 0.1-0.2 micron. In general, the variations are seen twice per orbit. In some cases, because spherical dust grains have an asymmetric scattering function, the polarimetric curves produced also show variations seen once per orbit. Circumstellar disks produce polarimetric variations of greater amplitude than circumbinary envelopes. Another goal of these simulations is to see if the 1978 BME (Brown, McLean, & Emslie, ApJ, 68, 415) formalism, which uses a Fourier analysis of the polarimetric variations to find the orbital inclination for Thomson-scattering envelopes, can still be used for Mie scattering. We find that this is the case, if the amplitude of the variations is sufficient and the true inclinations is i_true > 45 deg. For eccentric orbits, the first-order coefficients of the Fourier fit, instead of second-order ones, can be used to find almost all inclinations.Comment: 23 pages, 5 figures, to be published in Astronomical Journa