Reactive Atom Plasma (RAP) figuring machine for meter class optical surfaces

A new surface figuring machine called Helios 1200 is presented in this paper. It is designed for the figuring of meter sized optical surfaces with form accuracy correction capability better than 20 nm rms within a reduced number of iterations. Unlike other large figuring facilities using energy beams, Helios 1200 operates a plasma torch at atmospheric pressure, offers a high material removal rate, and a relatively low running cost. This facility is ideal to process large optical components, lightweight optics, silicon based and difficult to machine materials, aspheric, and free form surfaces. Also, the surfaces processed by the reactive atom plasma (RAP) are easy to fine polish through hand conventional sub-aperture polishing techniques. These unique combined features lead to a new capability for the fabrication of optical components opening up novel design possibilities for optical engineers. The key technical features of this large RAP machine are fast figuring capabilities, non-contact material removal tool, the use of a near Gaussian footprint energy beam, and a proven tool path strategy for the management of the heat transfer. Helios 1200 complies with the European machine safety standard and can be used with different types of reactive gases using either fluorine or chlorine compounds. In this paper, first the need for large optical component is discussed. Then, the RAP facility is described: radio frequency R.F generator, plasma torch, and 3 axis computer numerically controlled motion system. Both the machine design and the performance of the RAP tool is assessed under specific production conditions and in the context of meter class mirror and lens fabrication

Thermomechanical deformation behavior of a dynamic strain aging alloy, Hastelloy X

An experimental study was performed to identify the effects of dynamic strain aging (solute drag) and metallurgical instabilities under thermomechanical loading conditions. The study involved a series of closely controlled thermomechanical deformation tests on the solid-solution-strenghened nickel-base superalloy, Hastelloy X. This alloy exhibits a strong isothermal strain aging peak at approximately 600 C, promoted by the effects of solute drag and precipitation hardening. Macroscopic thermomechanical hardening trends are correlated with microstructural characteristics through the use of transmission electron microscopy. These observations are compared and contrasted with isothermal conditions. Thermomechanical behavior unique to the isothermal database is identified and discussed. The microstructural characteristics were shown to be dominated by effects associated with the highest temperature of the thermomechanical cycle. Results indicate that the deformation behavior of Hastelloy X is thermomechanically path dependent. In addition, guidance is given pertaining to deformation modeling in the context of macroscopic unified theory. An internal state variable is formulated to qualitatively reflect the isotropic hardening trends identified in the TMD experiments

Platelets in Non-alcoholic Fatty Liver Disease

Non alcoholic steatohepatitis (NASH) is the inflammatory reaction of the liver to excessive accumulation of lipids in the hepatocytes. NASH can progress to cirrhosis and hepatocellular carcinoma (HCC). Fatty liver is the hepatic manifestation of metabolic syndrome. A subclinical inflammatory state is present in patients with metabolic alterations like insulin resistance, type-2 diabetes, obesity, hyperlipidemia, and hypertension. Platelets participate in immune cells recruitment and cytokines-induced liver damage. It is hypothesized that lipid toxicity cause accumulation of platelets in the liver, platelet adhesion and activation, which primes the immunoinflammatory reaction and activation of stellate cells. Recent data suggest that antiplatelet drugs may interrupt this cascade and prevent/improve NASH. They may also improve some metabolic alterations. The pathophysiology of inflammatory liver disease and the implication of platelets are discussed in details

HST/STIS Optical Transit Transmission Spectra of the hot-Jupiter HD209458b

We present the transmission spectra of the hot-Jupiter HD209458b taken with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. Our analysis combines data at two resolutions and applies a complete pixel-by-pixel limb-darkening correction to fully reveal the spectral line shapes of atmospheric absorption features. Terrestrial-based Na I and H I contamination are identified which mask the strong exoplanetary absorption signature in the Na core, which we find reaches total absorption levels of ~0.11% in a 4.4 Ang band. The Na spectral line profile is characterized by a wide absorption profile at the lowest absorption depths, and a sharp transition to a narrow absorption profile at higher absorption values. The transmission spectra also shows the presence of an additional absorber at ~6,250 Ang, observed at both medium and low resolutions. We performed various limb-darkening tests, including using high precision limb-darkening measurements of the sun to characterize a general trend of Atlas models to slightly overestimate the amount of limb-darkening at all wavelengths, likely due to the limitations of the model's one-dimensional nature. We conclude that, despite these limitations, Atlas models can still successfully model limb-darkening in high signal-to-noise transits of solar-type stars, like HD209458, to a high level of precision over the entire optical regime (3,000-10,000 Ang) at transit phases between 2nd and 3rd contact.Comment: 18 pages, 11 figures, Accepted to Ap

Multidimensional indexing structure for use with linear optimization queries

Linear optimization queries, which usually arise in various decision support and resource planning applications, are queries that retrieve top N data records (where N is an integer greater than zero) which satisfy a specific optimization criterion. The optimization criterion is to either maximize or minimize a linear equation. The coefficients of the linear equation are given at query time. Methods and apparatus are disclosed for constructing, maintaining and utilizing a multidimensional indexing structure of database records to improve the execution speed of linear optimization queries. Database records with numerical attributes are organized into a number of layers and each layer represents a geometric structure called convex hull. Such linear optimization queries are processed by searching from the outer-most layer of this multi-layer indexing structure inwards. At least one record per layer will satisfy the query criterion and the number of layers needed to be searched depends on the spatial distribution of records, the query-issued linear coefficients, and N, the number of records to be returned. When N is small compared to the total size of the database, answering the query typically requires searching only a small fraction of all relevant records, resulting in a tremendous speedup as compared to linearly scanning the entire dataset

A Spectroscopic and Photometric Study of the Metal-Poor, Pulsating, Post-AGB Binary HD 46703

The metal-poor post-AGB star HD 46703 is shown to be a single-line spectroscopic binary with a period of 600 days, a high velocity of -94 km/s, and an orbital eccentricity of 0.3. Light curve studies show that it also pulsates with a period of 29 days. High-resolution, high signal-to-noise spectra were used for a new abundance study. The atmospheric model determined is T(eff) = 6250 K, log(g) = 1.0, V(t) = 3.0 km/s, and a metal abundance of [M/H] = -1.5. A low carbon abundance and lack of s-process element enhancement indicate that the star has not experienced third dredge-up on the AGB. The sulfur and zinc abundances are high compared with iron, and the chemical abundances show a clear anti-correlation with condensation temperature. The abundance depletion pattern is similar to that seen in other post-AGB binaries, and, like them, is attributed to the chemical fractionation of refractory elements onto dust stored in a circumbinary disk and the re-accretion of volatiles in the stellar atmosphere. The infrared excess is small but the excess energy distribution is very similar to what can expected from a disk. HD 46703 joins the growing list of depleted, post-AGB stars which are likely surrounded by a dusty and stable circumbinary disk.Comment: Machine readable files not include

Methods and apparatus for extraction and tracking of objects from multi-dimensional sequence data

An object tracking technique is provided which, given: (i) a potentially large data set; (ii) a set of dimensions along which the data has been ordered; and (iii) a set of functions for measuring the similarity between data elements, a set of objects are produced. Each of these objects is defined by a list of data elements. Each of the data elements on this list contains the probability that the data element is part of the object. The method produces these lists via an adaptive, knowledge-based search function which directs the search for high-probability data elements. This serves to reduce the number of data element combinations evaluated while preserving the most flexibility in defining the associations of data elements which comprise an object

Kepler Input Catalog: Photometric Calibration and Stellar Classification

We describe the photometric calibration and stellar classification methods used to produce the Kepler Input Catalog (KIC). The KIC is a catalog containing photometric and physical data for sources in the Kepler Mission field of view; it is used by the mission to select optimal targets. We derived atmospheric extinction corrections from hourly observations of secondary standard fields within the Kepler field of view. Repeatability of absolute photometry for stars brighter than magnitude 15 is typically 2%. We estimated stellar parameters Teff, log(g), log (Z), E_{B-V} using Bayesian posterior probability maximization to match observed colors to Castelli stellar atmosphere models. We applied Bayesian priors describing the distribution of solar-neighborhood stars in the color-magnitude diagram (CMD), in log (Z)$, and in height above the galactic plane. Comparisons with samples of stars classified by other means indicate that in most regions of the CMD, our classifications are reliable within about +/- 200 K and +/- 0.4 dex in log (g). It is difficult to assess the reliability of our log(Z) estimates, but there is reason to suspect that it is poor, particularly at extreme Teff. Of great importance for the Kepler Mission, for Teff <= 5400 K, the distinction between main-sequence stars and giants has proved to be reliable with better than 98% confidence. The KIC is available through the MAST data archive.Comment: 77 pages, 12 figures, 1 Table. Accepted by Astronomical Journal 24 July 201