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

NGC 3312: A victim of ram pressure sweeping

Researchers are undertaking a volume limited survey of the Hydra I cluster in neutral hydrogen using the National Radio Astronomy Observatory's Very Large Array (VLA). The main purpose is to study the effects of a dense environment on the gaseous component of the galaxies. Observational evidence has been accumulating recently that ram pressure sweeping does occur in the centers of clusters, but it is possible that tidal interactions play a role as well. Results of high resolution HI imaging of NGC 3312, the large peculiar spiral near the cluster center are presented. Hydra I (= A1060) is the nearest rich cluster beyond Virgo and, as such, presents a unique opportunity to do a complete survey of a cluster. It is similar to the Virgo cluster in many of its general physical characteristics, such as size, x ray luminosity, velocity dispersion, and galaxy content (high spiral fraction). However, Hydra I appears to be more regular and relaxed. This is evident in the x ray distribution in its central region, which is radially symmetric and centered on the dominant galaxy, NGC 3311, a cD-like elliptical. The observed x ray luminosity implies a central gas density of 4.5 x 10 to the 3rd power cm(-3). Gallagher (1978) argued from optical images of NGC 3312 that this galaxy might be an ideal candidate to directly study effects of the ram pressure process; it might currently be undergoing stripping of its interstellar medium. The researchers' data are consistent with this suggestion, but other origins of the peculiar appearance cannot yet be ruled out

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

PMN J0525-3343: soft X-ray spectral flattening in a blazar at z=4.4

We report optical, radio and X-ray observations of a new distant blazar, PMN J0525-3343, at a redshift of 4.4. The X-ray spectrum measured from ASCA and BeppoSAX flattens below a few keV, in a manner similar to the spectra of two other z>4 blazars, GB 1428+4217 (z=4.72) reported by Boller et al and RXJ 1028.6-0844 (z=4.28) by Yuan et al. The spectrum is well fitted by a power-law continuum which is either absorbed or breaks at a few keV. An intrinsic column density corresponding to 2 x 10^23 H-atoms cm-2 at solar abundance is required by the absorption model. This is however a million times greater than the neutral hydrogen, or dust, column density implied by the optical spectrum, which covers the rest-frame UV emission of the blazar nucleus. We discuss the problems raised and suggest that, unless there is intrinsic flattening in the spectral distribution of the particles/seed photons producing X-rays via inverse Compton scattering, the most plausible solution is a warm absorber close to the active nucleus.Comment: 7 pages, 7 figures; MNRAS, in pres

Calculating Nonlocal Optical Properties of Structures with Arbitrary Shape

In a recent Letter [Phys. Rev. Lett. 103, 097403 (2009)], we outlined a computational method to calculate the optical properties of structures with a spatially nonlocal dielectric function. In this Article, we detail the full method, and verify it against analytical results for cylindrical nanowires. Then, as examples of our method, we calculate the optical properties of Au nanostructures in one, two, and three dimensions. We first calculate the transmission, reflection, and absorption spectra of thin films. Because of their simplicity, these systems demonstrate clearly the longitudinal (or volume) plasmons characteristic of nonlocal effects, which result in anomalous absorption and plasmon blueshifting. We then study the optical properties of spherical nanoparticles, which also exhibit such nonlocal effects. Finally, we compare the maximum and average electric field enhancements around nanowires of various shapes to local theory predictions. We demonstrate that when nonlocal effects are included, significant decreases in such properties can occur.Comment: 30 pages, 12 figures, 1 tabl

Bilateral Isokinetic Torque Differences in Trained Swimmers

Please view abstract in the attached PDF file