Surface pressure measurements at two tips of a model helicopter rotor in hover

Surface pressures were measured near the tip of a hovering single-bladed model helicopter rotor with two tip shapes. The rotor had a constant-chord, untwisted blade with a square, flat tip which could be modified to a body-of-revolution tip. Pressure measurements were made on the blade surface along the chordwise direction at six radial stations outboard of the 94 percent blade radius. Data for each blade tip configuration were taken at blade collective pitch angles of 0, 6.18 and 11.4 degrees at a Reynolds number of 736,000 and a Mach number of 0.25 both based on tip speed. Chordwise pressure distributions and constant surface pressure contours are presented and discussed

Cycloadditions of cyclohexynes and cyclopentyne.

We report the strategic use of cyclohexyne and the more elusive intermediate, cyclopentyne, as a tool for the synthesis of new heterocyclic compounds. Experimental and computational studies of a 3-substituted cyclohexyne are also described. The observed regioselectivities are explained by the distortion/interaction model

The ASCA spectrum of the z=4.72 blazar, GB 1428+4217

The X-ray luminous quasar GB 1428+4217 at redshift 4.72 has been observed with ASCA. The observed 0.5-10 keV flux is 3.2E-12 erg/s/cm2. We report here on the intrinsic 4-57 keV X-ray spectrum, which is very flat (photon index of 1.29). We find no evidence for flux variability within the ASCA dataset or between it and ROSAT data. We show that the overall spectral energy distribution of GB 1428+4217 is similar to that of lower redshift MeV blazars and present models which fit the available data. The Doppler beaming factor is likely to be at least 8. We speculate on the number density of such high redshift blazars, which must contain rapidly-formed massive black holes.Comment: 5 pages, 3 Postscript figures, to appear in MNRA

Flank instability at Mount Etna: testing the sensitivity of forward models to the internal structure

The deformation recorded at Mount Etna during the last 15 years clearly shows that there is an interplay between activity of magmatic sources and instability of the SE sector. In particular, the anomalous sliding of the SE flank can be triggered by summit or flank eruptions (e.g., 2002), but it is also observed during quiescent loading phases (e.g., 1993-1997). This deformation is usually modeled by sub-horizontal dislocation surfaces (embedded in an elastic half space) whose parameters are determined fitting the observed surface deformation. The purpose of this paper is to investigate whether models forced by a simple isotropic expansion source but taking into account the internal structure of Mount Etna are capable to focus a significant amount of horizontal deformation in the eastern flank. We perform computations based on the finite element method along a 2D cross section. The deformation models include both topography and a synthetic reconstruction of the internal layering constrained by geology, seismic tomography and experimental measurements of Etnean rocks. We study the sensitivity of the predicted surface displacement to variations of internal layers rheology and/or mechanical parameters. Our first results suggest that significant contributions to increase the deformation in the SE sector are due to plastic rheology of the clay layers and to asymmetrical distribution of elastic parameters related to the high velocity body underneath Mount Etna imaged by seismic tomography

Bilateral Isokinetic Torque Differences in Trained Swimmers

Please view abstract in the attached PDF file

Revealing Cosmic Rotation

Cosmological Birefringence (CB), a rotation of the polarization plane of radiation coming to us from distant astrophysical sources, may reveal parity violation in either the electromagnetic or gravitational sectors of the fundamental interactions in nature. Until only recently this phenomenon could be probed with only radio observations or observations at UV wavelengths. Recently, there is a substantial effort to constrain such non-standard models using observations of the rotation of the polarization plane of cosmic microwave background (CMB) radiation. This can be done via measurements of the $B$-modes of the CMB or by measuring its TB and EB correlations which vanish in the standard model. In this paper we show that $EB$ correlations-based estimator is the best for upcoming polarization experiments. The $EB$ based estimator surpasses other estimators because it has the smallest noise and of all the estimators is least affected by systematics. Current polarimeters are optimized for the detection of $B$-mode polarization from either primordial gravitational waves or by large scale structure via gravitational lensing. In the paper we also study optimization of CMB experiments for the detection of cosmological birefringence, in the presence of instrumental systematics, which by themselves are capable of producing $EB$ correlations; potentially mimicking CB.Comment: 10 pages, 3 figures, 2 table

VLBI imaging of extremely high redshift quasars at 5 GHz

We present very long baseline interferometry (VLBI) images of ten very high redshift (z>3) quasars at 5 GHz. The sources 0004+139, 0830+101, 0906+041, 0938+119 and 1500+045 were observed in September 1992 using a global VLBI array, while 0046+063, 0243+181, 1338+381, 1428+423 and 1557+032 were observed in October 1996 with the European VLBI Network and Hartebeesthoek, South Africa. Most of the sources are resolved and show asymmetric structure. The sample includes 1428+423, the most distant radio loud quasar known to date (z=4.72). It is barely resolved with an angular resolution of about 2.0*1.4 mas.Comment: Astronomy and Astrophysics, in press, Latex2e, 10 pages, 3 figures (and lots of sub-figures

Detection of a Lyman-alpha Emission-Line Companion to the z=4.69 QSO BR1202-0725

We report the detection of a nearby emission-line companion to the z=4.695 quasar BR1202-0725. Deep narrow-band exposures on this field from the UH 2.2 m show a Ly alpha flux of 1.5\times\ten{-16} ergs cm^{-2} s^{-1}. High-resolution HST WFC2 imaging in the F814W filter band shows continuum structure near the emission position, at 2.6" NW of the quasar, corresponding to a projected separation of ~7.5 h^{-1} kpc for \qnought=0.5, where h=\hnought/100\kms Mpc^{-1}. We discuss possible explanations for the combined line and color properties. The ionization is most likely produced by the quasar, but if due to underlying star formation would require a star formation rate of ~7 h^2 solar masses per yr.Comment: 12 pages LaTeX (aastex4.0 macros: aasms4.sty, flushrt.sty) plus 3 figures. To appear in the Astrophysical Journal Letters. Typo in original submission ("2" should have been "7" in luminosity: 7e42 h^{-2} ergs and in the star formation rate: 7 h^{-2} \msun per yr). Resubmitted with figure