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

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

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

Polarimetric variations of binary stars. III Periodic polarimetric variations of the Herbig Ae/Be star MWC 1080

We present polarimetric observations of a massive pre-main sequence short-period binary star of the Herbig Ae/Be type, MWC 1080. The mean polarization at 7660 A is 1.60% at 81.6 deg, or 0.6% at 139 deg if an estimate of the interstellar polarization is subtracted. The intrinsic polarization points to an asymmetric geometry of the circumstellar or circumbinary environment while the 139 deg intrinsic position angle traces the axis of symmetry of the system and is perpendicular to the position angle of the outflow cavity. The polarization and its position angle are clearly variable, at all wavelengths, and on time scales of hours, days, months, and years. Stochastic variability is accompanied by periodic variations caused by the orbital motion of the stars in their dusty environment. These periodic polarimetric variations are the first phased-locked ones detected for a pre-main sequence binary. The variations are not simply double-periodic (seen twice per orbit) but include single-periodic (seen once per orbit) and higher-order variations. The presence of single-periodic variations could be due to non equal mass stars, the presence of dust grains, an asymmetric configuration of the circumstellar or circumbinary material, or the eccentricity of the orbit. MWC 1080 is an eclipsing binary with primary and secondary eclipses occurring at phases 0.0 and 0.55. The signatures of the eclipses are seen in the polarimetric observations.Comment: 30 pages, 8 figures, to be published in the Astronomical Journa

Suicide as a Compensable Claim under Workers\u27 Compensation Statutes: A Guide for the Lawyer and the Psychiatrist

We live in a highly complex, industrialized environment. Specific work-related events occurring within this context frequently impact negatively on those who are essential to the operation of our industrial system. Often the impact of events produces human misery, suffering and death. Men and women are injured, maimed and killed. Workers\u27 compensation statutes exist to ameliorate the plight of workers and their families through the utilization of compensation in the form of cash-wage benefits and medical care. The economic burden of compensation is ultimately borne by consumers, because the cost of insurance taken out by employers is passed on in the price of the goods and services produced. Both workers\u27 compensation statutes and the systems produced by those statutes are appropriate responses to the perceived needs of all who have an interest in a productive economy and a just social order. As in any decision-making system designed to deal with complex cases, however, there exist opportunities for disagreement concerning the legal disposition of certain cases. This article deals with one of those matters which is subject to such serious debate: When should suicide, following a trauma experienced within the job context, give rise to a compensable claim under workers\u27 compensation statutes? Although there has been prior general commentary on the problem, this article will offer some additional and perhaps useful information to both the attorney representing the claimant and the psychiatrist called to testify as an expert witness. A working comprehension of the psychiatric aspects of suicide is necessary in order to prepare and prosecute a successful claim or to organize a defense in this area of the law. Additionally, the expert, even if carefully selected, must understand the legal framework in which his or her testimony will be interpreted. Unquestionably, a working relationship between the attorney and the psychiatrist is a necessity in terms of preparation. Many practitioners, however, may initially fail to realize that the early decisions recognizing suicide as a compensable workers\u27 compensation claim erroneously focus upon knowledge, cognition and uncontrollable impulses. Since the articulated models utilized by these courts in the earlier cases have become entrenched in some jurisdictions and in the minds of many judicial decision-makers, the psychiatric expert will often be forced to apply modern theories of psychiatry to illegitimately unscientific modes of legal analysis. These factors become increasingly important since many courts, when confronted with the generally liberal application of workers\u27 compensation statutes and the advent of modern scientific insights into the causes of suicide, have been forced to consider the issue of whether an employee\u27s suicide which follows a compensable on-the-job injury should constitute a separate ground for workers\u27 compensation benefits. The theory behind successful claims of this nature has been that an employee who has suffered a compensable injury, which in turn triggers a psychiatric disorder resulting in suicide, is entitled to both an inter vivos compensation award and a death benefit. It is clear, however, that since suicide is generally defined as an intentional act (without regard to whether or not suicide is psychiatrically considered volitional or nonvolitional), many jurisdictions would deny workers\u27 compensation death benefits to employees who take their own lives. Classic concepts indicate that recovery should be granted, if at all, only when there has been a work related harmful change in the human organism, arising out of and in the course of employment ... Nevertheless, when a direct causal relationship can be established among a work-related injury, a psychiatric disorder, and subsequent suicide, traditional notions should be updated and expanded to permit death benefit awards. Courts, when confronted with this dilemma, have utilized four different types of analyses. These modes of analysis can properly be identified as the Sponatski test, the New York rule, the English rule and the chain of causation test. This article examines the evolution of judicial understanding of suicide as related to the workers\u27 compensation system, endorses the liberal chain of causation test, and demonstrates that the chain of causation approach most closely corresponds with modern psychiatric theory

Probabilistic Graphical Model Representation in Phylogenetics

Recent years have seen a rapid expansion of the model space explored in statistical phylogenetics, emphasizing the need for new approaches to statistical model representation and software development. Clear communication and representation of the chosen model is crucial for: (1) reproducibility of an analysis, (2) model development and (3) software design. Moreover, a unified, clear and understandable framework for model representation lowers the barrier for beginners and non-specialists to grasp complex phylogenetic models, including their assumptions and parameter/variable dependencies. Graphical modeling is a unifying framework that has gained in popularity in the statistical literature in recent years. The core idea is to break complex models into conditionally independent distributions. The strength lies in the comprehensibility, flexibility, and adaptability of this formalism, and the large body of computational work based on it. Graphical models are well-suited to teach statistical models, to facilitate communication among phylogeneticists and in the development of generic software for simulation and statistical inference. Here, we provide an introduction to graphical models for phylogeneticists and extend the standard graphical model representation to the realm of phylogenetics. We introduce a new graphical model component, tree plates, to capture the changing structure of the subgraph corresponding to a phylogenetic tree. We describe a range of phylogenetic models using the graphical model framework and introduce modules to simplify the representation of standard components in large and complex models. Phylogenetic model graphs can be readily used in simulation, maximum likelihood inference, and Bayesian inference using, for example, Metropolis-Hastings or Gibbs sampling of the posterior distribution

Multi-Scale Analysis of Magnetic Fields in Filamentary Molecular Clouds in Orion A

New visible and K-band polarization measurements on stars surrounding molecular clouds in Orion A and stars in the BN vicinity are presented. Our results confirm that magnetic fields located inside the Orion A molecular clouds and in their close neighborhood are spatially connected. On and around the BN object, we measured the angular offsets between the K-band polarization data and available submm data. We find high values of the polarization degree, P_{K}, and of the optical depth, \tau_{K}, close to an angular offset position of 90^{\circ} whereas lower values of P_{K} and \tau_{K} are observed for smaller angular offsets. We interpret these results as evidence for the presence of various magnetic field components toward lines of sight in the vicinity of BN. On a larger scale, we measured the distribution of angular offsets between available H-band polarization data and the same submm data set. Here we find an increase of with angular offset which we interpret as a rotation of the magnetic field by \lesssim 60^{\circ}. This trend generalizes previous results on small scale toward and around lines of sight to BN and is consistent with a twist of the magnetic field on a larger scale towards OMC-1. A comparison of our results with several other studies suggests that a two-component magnetic field, maybe helical, could be wrapping the OMC-1 filament.Comment: 53 pages, 21 figures, 7 tables, Accepted in the Astrophysical Journa