Evaluation of modern hydrogen masers

The masers were tested for environmental sensitivities (magnetic field, temperature, barometric pressure) and long-term aging. Allan variance runs of 72 days were made in order to attain averaging times from several seconds to 1 million seconds. Auto- and cross-correlation techniques were used to determine the effects of uncontrolled parameters such as humidity. Three-cornered-hat and other data reduction techniques were used to determine the characteristics of the individual masers

Aerodynamics of lift fan V/STOL aircraft

Aerodynamic characteristics of lift fan installation for direct lift V/STOL aircraf

Growth rates of the Weibel and tearing mode instabilities in a relativistic pair plasma

We present an algorithm for solving the linear dispersion relation in an inhomogeneous, magnetised, relativistic plasma. The method is a generalisation of a previously reported algorithm that was limited to the homogeneous case. The extension involves projecting the spatial dependence of the perturbations onto a set of basis functions that satisfy the boundary conditions (spectral Galerkin method). To test this algorithm in the homogeneous case, we derive an analytical expression for the growth rate of the Weibel instability for a relativistic Maxwellian distribution and compare it with the numerical results. In the inhomogeneous case, we present solutions of the dispersion relation for the relativistic tearing mode, making no assumption about the thickness of the current sheet, and check the numerical method against the analytical expression.Comment: Accepted by PPC

Detection and Mapping of Decoupled Stellar and Ionized Gas Structures in the Ultraluminous Infrared Galaxy IRAS 12112+0305

Integral field optical spectroscopy with the INTEGRAL fiber-fed system and HST optical imaging are used to map the complex stellar and warm ionized gas structure in the ultraluminous infrared galaxy IRAS 12112+0305. Images reconstructed from wavelength-delimited extractions of the integral field spectra reveal that the observed ionized gas distribution is decoupled from the stellar main body of the galaxy, with the dominant continuum and emission-line regions separated by projected distances of up to 7.5 kpc. The two optical nuclei are detected as apparently faint emission-line regions, and their optical properties are consistent with being dust-enshrouded weak-[OI] LINERs. The brightest emission-line region is associated with a faint (m_{I}= 20.4), giant HII region of 600 pc diameter, where a young (about 5 Myr) massive cluster of about 2 $\times$ 10$^7$ $M_{\odot}$ dominates the ionization. Internal reddening towards the line-emitting regions and the optical nuclei ranges from 1 to 8 magnitudes, in the visual. Taken the reddening into aacount, the overall star formation in IRAS 12112+0305 is dominated by starbursts associated with the two nuclei and corresponding to a star formation rate of 80 $M_{\odot}$ yr$^{-1}$.Comment: 2 figures, accepted to Ap.J. Letter

A Structural Analysis of Star-Forming Region AFGL 490

We present Spitzer IRAC and MIPS observations of the star-forming region containing intermediate-mass young stellar object (YSO) AFGL 490. We supplement these data with near-IR 2MASS photometry and with deep SQIID observations off the central high extinction region. We have more than doubled the known membership of this region to 57 Class I and 303 Class II YSOs via the combined 1-24 um photometric catalog derived from these data. We construct and analyze the minimum spanning tree of their projected positions, isolating one locally over-dense cluster core containing 219 YSOs (60.8% of the region's members). We find this cluster core to be larger yet less dense than similarly analyzed clusters. Although the structure of this cluster core appears irregular, we demonstrate that the parsec-scale surface densities of both YSOs and gas are correlated with a power law slope of 2.8, as found for other similarly analyzed nearby molecular clouds. We also explore the mass segregation implications of AFGL 490's offset from the center of its core, finding that it has no apparent preferential central position relative to the low-mass members.Comment: 44 pages, 13 figures, accepted to Ap