Raytheon

About: Raytheon is a company organization based out in Waltham, Massachusetts, United States. It is known for research contribution in the topics: Signal & Antenna (radio). The organization has 15290 authors who have published 18973 publications receiving 300052 citations.

Adiabatic Survey of Subdwarf B Star Oscillations. I. Pulsation Properties of a Representative Evolutionary Model

Abstract: We present the first results of a large, systematic adiabatic survey of the pulsation properties of models of subdwarf B (sdB) stars. This survey is aimed at providing the most basic theoretical data with which to analyze the asteroseismological properties of the recently discovered class of pulsating sdB stars (the EC 14026 stars). Such a theoretical framework has been lacking up to now. In this paper, the first of a series of three, an adiabatic pulsation code is used to compute, in the 80-1500 s period window, the radial (l = 0) and nonradial (from l = 1 up to l = 3) oscillation modes for a representative evolutionary model of subdwarf B stars. Quantities such as the periods, kinetic energies, first-order rotational splitting coefficients, eigenfunctions, and weight functions are given by the code, providing a complete set of very useful diagnostic tools with which to study the mode properties. The main goal is to determine how these quantities relate to the internal structure of B subdwarfs, a crucial and necessary step if one wants to eventually apply the tools of asteroseismology to EC 14026 stars. All modes (p, f, and g) were considered in order to build the most complete picture we can have on pulsations in these stars. In that context, we show that g-modes are essentially deep interior modes oscillating mainly in the radiative helium-rich core (but not in the convective nucleus), while p-modes are shallower envelope modes. We demonstrate that g-modes respond to a trapping/confinement phenomenon induced mainly by the He/H chemical transition between the H-rich envelope and the He-rich core of subdwarf B stars. This phenomenon is very similar in nature to the g-mode trapping and confinement mechanisms observed in pulsating white dwarf models. We emphasize that p-modes may also experience distortions of their period distribution due to this He/H transition, although these are not as pronounced as in the g-mode case. These phenomena are of great interest as they can potentially provide powerful tools for probing the internal structure of these objects, in particular, with respect to constraining the mass of their H-rich envelope. The results given in this first paper form the minimal background on pulsation mode characteristics in sdB stars. Upcoming discussions on additional mode properties in subdwarf B star models (Paper II and Paper III of this series) will strongly rely on these basic results since they provide essential guidance in understanding mode period behaviors as functions of B subdwarf stellar parameters and/or evolution.

Continued benefit from paclitaxel-eluting compared with bare-metal stent implantation in saphenous vein graft lesions during long-term follow-up of the SOS (Stenting of Saphenous Vein Grafts) trial

Abstract: Objectives This study sought to report the long-term outcomes after drug-eluting stent (DES) implantation in saphenous vein graft (SVG) lesions in the SOS (Stenting of Saphenous Vein Grafts) trial. Background The long-term outcomes after DES implantation in SVGs are poorly studied. Apart from the SOS trial, the only other randomized trial comparing DES with bare-metal stents (BMS) in SVGs reported higher mortality in the DES group at 32 months. Methods In the SOS trial, 80 patients with 112 lesions in 88 SVGs were randomized to a BMS or paclitaxel-eluting stent (PES) and demonstrated improved short-term angiographic and clinical outcomes with PES. Extended clinical follow-up was subsequently obtained. Results Mean age was 67 ± 9 years, and all patients were men. The indications for stenting included acute coronary syndrome in 60% and stable angina in 31% of patients. The mean SVG age was 12 ± 6 years. The baseline characteristics of the patients in the 2 study groups were similar. Procedural success was achieved in 77 patients (96%). During a median follow-up of 35 months, compared with patients randomized to BMS, those receiving PES had a lower incidence of myocardial infarction (hazard ratio [HR]: 0.32, p = 0.01), target lesion revascularization (HR: 0.20, p = 0.004), target vessel revascularization (HR: 0.41, p = 0.03), and target vessel failure (HR: 0.34, p = 0.001) as well as a trend toward less definite or probable stent thrombosis (HR: 0.15, p = 0.08). All-cause mortality (HR: 2.04, p = 0.19) and cardiac mortality (HR: 0.62, p = 0.51) did not differ between groups. Conclusions During long-term follow-up, use of PES was associated with significantly better clinical outcomes than BMS in SVG lesions. (Stenting of Saphenous Vein Grafts Trial [SOS]; NCT00247208 )

Environmentally isolated enclosure for electronic components

Abstract: A spray cooled enclosure and method for obtaining a substantially improved operating environment for at least one electronic component/card located within the enclosure The spray cooled enclosure includes a closed compartment that isolates the electronic components/cards from the environment A dielectric heat transfer fluid stored within the closed compartment is distributed by a spraying system such that a thin-film layer of the heat transfer fluid is continually formed over a substantial portion of the surfaces of the electronic components/cards resulting in a substantially reduced thermal gradient across the electronic components/cards Also included is closed-loop condensing system for condensing the heat transfer fluid vaporized in response to heat transferred from the electronic components/cards to the layer of heat transfer fluid

Circulators for microwave and millimeter-wave integrated circuits

Abstract: The requirements for circulators for use in combination with microwave and millimeter-wave integrated circuits are reviewed, with special emphasis on modules for phased-array antennas. Recent advances in broadbanding and in miniaturization are summarized. Novel types of circulators that are fabricated by attaching a ferrite disc and a suitable coupling structure to the surface of a dielectric of semiconductor substrate (quasimonolithic integration) are described. Methods for achieving complete monolithic integration are also discussed. >