Maser action in methanol transitions

We report the detection with the ATCA of 6.7 GHz methanol emission towards OMC-1. The source has a size between 40'' and 90'', is located to the south-east of Ori-KL and may coincide in position with the 25 GHz masers. The source may be an example of an interesting case recently predicted in theory where the transitions of traditionally different methanol maser classes show maser activity simultaneously. In addition, results of recent search for methanol masers from the 25 and 104.3 GHz transitions are reported.Comment: To appear in the Proceedings of the 2004 European Workshop: "Dense Molecular Gas around Protostars and in Galactic Nuclei", Eds. Y.Hagiwara, W.A.Baan, H.J. van Langevelde, 2004, a special issue of ApSS, Kluwer; author list has been corrected, text is unchange

Inability to sustain intraphagolysosomal killing of Staphylococcus aureus predisposes to bacterial persistence in macrophages

Macrophages are critical effectors of the early innate response to bacteria in tissues. Phagocytosis and killing of bacteria are interrelated functions essential for bacterial clearance but the rate-limiting step when macrophages are challenged with large numbers of the major medical pathogen Staphylococcus aureus is unknown. We show that macrophages have a finite capacity for intracellular killing and fail to match sustained phagocytosis with sustained microbial killing when exposed to large inocula of S. aureus (Newman, SH1000 and USA300 strains). S. aureus ingestion by macrophages is associated with a rapid decline in bacterial viability immediately after phagocytosis. However, not all bacteria are killed in the phagolysosome, and we demonstrate reduced acidification of the phagolysosome, associated with failure of phagolysosomal maturation and reduced activation of cathepsin D. This results in accumulation of viable intracellular bacteria in macrophages. We show macrophages fail to engage apoptosis-associated bacterial killing. Ultittop mately macrophages with viable bacteria undergo cell lysis, and viable bacteria are released and can be internalized by other macrophages. We show that cycles of lysis and reuptake maintain a pool of viable intracellular bacteria over time when killing is overwhelmed and demonstrate intracellular persistence in alveolar macrophages in the lungs in a murine model

Wave packet revivals and the energy eigenvalue spectrum of the quantum pendulum

The rigid pendulum, both as a classical and as a quantum problem, is an interesting system as it has the exactly soluble harmonic oscillator and the rigid rotor systems as limiting cases in the low- and high-energy limits respectively. The energy variation of the classical periodicity ($\tau$) is also dramatic, having the special limiting case of $\tau \to \infty$ at the 'top' of the classical motion (i.e. the separatrix.) We study the time-dependence of the quantum pendulum problem, focusing on the behavior of both the (approximate) classical periodicity and especially the quantum revival and superrevival times, as encoded in the energy eigenvalue spectrum of the system. We provide approximate expressions for the energy eigenvalues in both the small and large quantum number limits, up to 4th order in perturbation theory, comparing these to existing handbook expansions for the characteristic values of the related Mathieu equation, obtained by other methods. We then use these approximations to probe the classical periodicity, as well as to extract information on the quantum revival and superrevival times. We find that while both the classical and quantum periodicities increase monotonically as one approaches the 'top' in energy, from either above or below, the revival times decrease from their low- and high-energy values until very near the separatrix where they increase to a large, but finite value.Comment: 27 pages, 8 embedded .eps figures; to appear, Annals of Physic

Spectroscopic and photometric analysis of HS 1136+6646: A hot young DAO+K7V post-common- envelope, pre-cataclysmic variable binary

Copyright © 2004 IOP Publishing / American Astronomical SocietyExtensive photometric and spectroscopic observations have been obtained for HS 1136+6646. The observations reveal a newly formed post–common-envelope binary system containing a hot ~DAO.5 primary and a highly irradiated secondary. HS 1136+6646 is the most extreme example yet of a class of short-period hot H-rich white dwarfs with K–M companion systems such as V471 Tau and Feige 24. HS 1136+6646 is a double-line spectroscopic binary showing emission lines of H I, He II, C II, Ca II, and Mg II, due in part to irradiation of the K7 V secondary by the hot white dwarf. Echelle spectra reveal the hydrogen emission lines to be double-peaked with widths of ~200 km s-1, raising the possibility that emission from an optically thin disk may also contribute. The emission lines are observed to disappear near the inferior conjunction. An orbital period of 0.83607 ± 0.00003 days has been determined through the phasing of radial velocities, emission-line equivalent widths, and photometric measurements spanning a range of 24 months. Radial velocity measurements yield an amplitude of KWD = 69 ± 2 km s-1 for the white dwarf and KK7V = 115 ± 1 km s-1 for the secondary star. In addition to orbital variations, photometric measurements have also revealed a low-amplitude modulation with a period of 113.13 minutes and a semiamplitude of 0.0093 mag. These short-period modulations are possibly associated with the rotation of the white dwarf. From fits of the Balmer line profiles, the white dwarf is estimated to have an effective temperature and gravity of ~70,000 K and log g ~ 7.75, respectively. However, this optically derived temperature is difficult to reconcile with the far-UV spectrum of the Lyman line region. Far Ultraviolet Spectroscopic Explorer spectra show the presence of O VI absorption lines and a spectral energy distribution whose slope persists nearly to the Lyman limit. The extremely high temperature of the white dwarf, from both optical and UV measurements, indicates that the binary system is one of the earliest post–common-envelope objects known, having an age around 7.7 × 105 yr. Although the spectrum of the secondary star is best represented by a K7 V star, indications are that the star may be overly luminous for its mass.NASAParticle and Astronomy Research Council, UKNS

Genetic Homogeneity of the Invasive Lionfish Across the Northwestern Atlantic and the Gulf of Mexico Based On Single Nucleotide Polymorphisms

Despite the devastating impact of the lionfish (Pterois volitans) invasion on NW Atlantic ecosystems, little genetic information about the invasion process is available. We applied Genotyping by Sequencing techniques to identify 1,220 single nucleotide polymorphic sites (SNPs) from 162 lionfish samples collected between 2013 and 2015 from two areas chronologically identified as the first and last invaded areas in US waters: the east coast of Florida and the Gulf of Mexico. We used population genomic analyses, including phylogenetic reconstruction, Bayesian clustering, genetic distances, Discriminant Analyses of Principal Components, and coalescence simulations for detection of outlier SNPs, to understand genetic trends relevant to the lionfish’s long-term persistence. We found no significant differences in genetic structure or diversity between the two areas (FST p-values \u3e 0.01, and t-test p-values \u3e 0.05). In fact, our genomic analyses showed genetic homogeneity, with enough gene flow between the east coast of Florida and Gulf of Mexico to erase previous signals of genetic divergence detected between these areas, secondary spreading, and bottlenecks in the Gulf of Mexico. These findings suggest rapid genetic changes over space and time during the invasion, resulting in one panmictic population with no signs of divergence between areas due to local adaptation

Optical and transport properties in doped two-leg ladder antiferromagnet

Within the t-J model, the optical and transport properties of the doped two-leg ladder antiferromagnet are studied based on the fermion-spin theory. It is shown that the optical and transport properties of the doped two-leg ladder antiferromagnet are mainly governed by the holon scattering. The low energy peak in the optical conductivity is located at a finite energy, while the resistivity exhibits a crossover from the high temperature metallic-like behavior to the low temperature insulating-like behavior, which are consistent with the experiments.Comment: 13 pages, 5 figures, accepted for publication in Phys. Rev. B65 (2002) (April 15 issue