13,787 research outputs found
SiO and H2O Maser Observations of Red Supergiants in Star Clusters Embedded in the Galactic Disk
We present the result of radio observations of red supergiants in the star
cluster, Stephenson's #2, and candidates for red supergiants in the star
clusters, Mercer et al. (2005)'s #4, #8, and #13, in the SiO and HO maser
lines.The Stephenson's #2 cluster and nearby aggregation at the South-West
contain more than 15 red supergiants. We detected one at the center of
Stephenson's #2 and three in the south-west aggregation in the SiO maser line,
and three of these 4 were also detected in the H2O maser line. The average
radial velocity of the 4 detected objects is 96 km s^{-1}, giving a kinematic
distance of 5.5 kpc, which locates this cluster near the base of the
Scutum-Crux spiral arm. We also detected 6 SiO emitting objects associated with
the other star clusters. In addition, mapping observations in the CO J=1--0
line toward these clusters revealed that an appreciable amount of molecular gas
still remains around Stephenson's #2 cluster in contrast to the prototypical
red-supergiant cluster, Bica et al.'s #122. It indicates that a time scale of
gas expulsion differs considerably in individual clusters.Comment: high res. figures available at
http://www.nro.nao.ac.jp/~lib_pub/report/data/no674.pdf. PASJ 62, No.2 (2010,
April 25 issue) in pres
Similar Microbial Communities Found on Two Distant Seafloor Basalts.
The oceanic crust forms two thirds of the Earth's surface and hosts a large phylogenetic and functional diversity of microorganisms. While advances have been made in the sedimentary realm, our understanding of the igneous rock portion as a microbial habitat has remained limited. We present the first comparative metagenomic microbial community analysis from ocean floor basalt environments at the Lō'ihi Seamount, Hawai'i, and the East Pacific Rise (EPR; 9°N). Phylogenetic analysis indicates the presence of a total of 43 bacterial and archaeal mono-phyletic groups, dominated by Alpha- and Gammaproteobacteria, as well as Thaumarchaeota. Functional gene analysis suggests that these Thaumarchaeota play an important role in ammonium oxidation on seafloor basalts. In addition to ammonium oxidation, the seafloor basalt habitat reveals a wide spectrum of other metabolic potentials, including CO2 fixation, denitrification, dissimilatory sulfate reduction, and sulfur oxidation. Basalt communities from Lō'ihi and the EPR show considerable metabolic and phylogenetic overlap down to the genus level despite geographic distance and slightly different seafloor basalt mineralogy
Structural relaxation in a system of dumbbell molecules
The interaction-site-density-fluctuation correlators, the dipole-relaxation
functions, and the mean-squared displacements of a system of symmetric
dumbbells of fused hard spheres are calculated for two representative
elongations of the molecules within the mode-coupling theory for the evolution
of glassy dynamics. For large elongations, universal relaxation laws for states
near the glass transition are valid for parameters and time intervals similar
to the ones found for the hard-sphere system. Rotation-translation coupling
leads to an enlarged crossover interval for the mean-squared displacement of
the constituent atoms between the end of the von Schweidler regime and the
beginning of the diffusion process. For small elongations, the superposition
principle for the reorientational -process is violated for parameters
and time intervals of interest for data analysis, and there is a strong
breaking of the coupling of the -relaxation scale for the diffusion
process with that for representative density fluctuations and for dipole
reorientations.Comment: 15 pages, 14 figures, Phys. Rev. E in pres
Engineering multiple levels of specificity in an RNA viral vector
Synthetic molecular circuits could provide powerful therapeutic capabilities, but delivering them to specific cell types and controlling them remains challenging. An ideal "smart" viral delivery system would enable controlled release of viral vectors from "sender" cells, conditional entry into target cells based on cell-surface proteins, conditional replication specifically in target cells based on their intracellular protein content, and an evolutionarily robust system that allows viral elimination with drugs. Here, combining diverse technologies and components, including pseudotyping, engineered bridge proteins, degrons, and proteases, we demonstrate each of these control modes in a model system based on the rabies virus. This work shows how viral and protein engineering can enable delivery systems with multiple levels of control to maximize therapeutic specificity
QCD Effects in High Energy Processes
In this talk, some important QCD effects in Higgs physics, supersymmetry and
top physics, as well as the factorization and resummation techniques in QCD are
reviewed.Comment: LaTeX, 13 pages, uses ws-ijmpa.cls. Based on an invited talk at the
International Conference on QCD and Hadronic Physics, Beijing, China, June
16--20, 2005. Minor change
Novelty Search in Competitive Coevolution
One of the main motivations for the use of competitive coevolution systems is
their ability to capitalise on arms races between competing species to evolve
increasingly sophisticated solutions. Such arms races can, however, be hard to
sustain, and it has been shown that the competing species often converge
prematurely to certain classes of behaviours. In this paper, we investigate if
and how novelty search, an evolutionary technique driven by behavioural
novelty, can overcome convergence in coevolution. We propose three methods for
applying novelty search to coevolutionary systems with two species: (i) score
both populations according to behavioural novelty; (ii) score one population
according to novelty, and the other according to fitness; and (iii) score both
populations with a combination of novelty and fitness. We evaluate the methods
in a predator-prey pursuit task. Our results show that novelty-based approaches
can evolve a significantly more diverse set of solutions, when compared to
traditional fitness-based coevolution.Comment: To appear in 13th International Conference on Parallel Problem
Solving from Nature (PPSN 2014
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