933 research outputs found
Mitochondrial ATP synthase genes may be implicated in cytoplasmic male sterility in Sorghum bicolor
Get PDFIncompatible nuclear-cytoplasmic interactions are responsible for the phenomenon of cytoplasmic male sterility in plants. We have analysed male sterile (2077A, 296A), maintainer fertile (2077B, 296B) and fertility restored (2077R, 296R) lines of sorghum for the restriction fragment locations of various mitochondrial genes and their transcripts. We report here a polymorphism in genes related to the ATP synthase complex between two different cytoplasms from the A and B set of lines of 2077 and 296. There is also a difference in the transcript size of theatpA gene between the A and B cytoplasms. We propose that incompatibility in nuclear cytoplasmic interactions may be explained in terms of incompatible subunits being synthesized by the mitochondria and nucleus for a multisubunit complex of the mitochondrial membrane such as ATPase
Stimulation of macromolecular synthesis by ascorbate in Neurospora
Get PDFStimulation of macromolecular synthesis by ascorbat
Isolated elliptical galaxies in the local Universe
Get PDFWe have studied a sample of 89 very isolated, elliptical galaxies at z < 0.08
and compared their properties with elliptical galaxies located in a
high-density environment such as the Coma supercluster. Our aim is to probe the
role of environment on the morphological transformation and quenching of
elliptical galaxies as a function of mass. In addition, we elucidate the nature
of a particular set of blue and star-forming isolated ellipticals identified
here. We study physical properties of ellipticals such as color, specific star
formation rate, galaxy size, and stellar age, as a function of stellar mass and
environment based on SDSS data. We analyze the blue star-forming isolated
ellipticals in more detail, through photometric characterization using GALFIT,
and infer their star formation history using STARLIGHT. Among the isolated
ellipticals ~ 20% are blue, 8% are star forming, and ~ 10% are recently
quenched, while among the Coma ellipticals ~ 8% are blue and just <= 1% are
star forming or recently quenched. There are four isolated galaxies (~ 4.5%)
that are blue and star forming at the same time. These galaxies, with masses
between 7 x 10^9 and 2 x 10^10 h-2 M_sun, are also the youngest galaxies with
light-weighted stellar ages <= 1 Gyr and exhibit bluer colors toward the galaxy
center. Around 30-60% of their present-day luminosity, but only < 5% of their
present-day mass, is due to star formation in the last 1 Gyr. The processes of
morphological transformation and quenching seem to be in general independent of
environment since most of elliptical galaxies are 'red and dead', although the
transition to the red sequence should be faster for isolated ellipticals. In
some cases, the isolated environment seems to propitiate the rejuvenation of
ellipticals by recent (< 1 Gyr) cold gas accretion.Comment: 23 pages, 15 figures (16 pages and 9 figures without appendices).
A&A, in pres
Matter-positronium interaction: An exact diagonalization study of the He atom - positronium system
Full text linkThe many-body system comprising a He nucleus, three electrons, and a positron
has been studied using the exact diagonalization technique. The purpose has
been to clarify to which extent the system can be considered as a
distinguishable positronium (Ps) atom interacting with a He atom and, thereby,
to pave the way to a practical atomistic modeling of Ps states and annihilation
in matter. The maximum value of the distance between the positron and the
nucleus is constrained and the Ps atom at different distances from the nucleus
is identified from the electron and positron densities, as well as from the
electron-positron distance and center-of-mass distributions. The polarization
of the Ps atom increases as its distance from the nucleus decreases. A
depletion of the He electron density, particularly large at low density values,
has been observed. The ortho-Ps pick-off annihilation rate calculated as the
overlap of the positron and the free He electron densities has to be corrected
for the observed depletion, specially at large pores/voids.Comment: 18 pages, 8 figure
Scalable Approach to Uncertainty Quantification and Robust Design of Interconnected Dynamical Systems
Full text linkDevelopment of robust dynamical systems and networks such as autonomous
aircraft systems capable of accomplishing complex missions faces challenges due
to the dynamically evolving uncertainties coming from model uncertainties,
necessity to operate in a hostile cluttered urban environment, and the
distributed and dynamic nature of the communication and computation resources.
Model-based robust design is difficult because of the complexity of the hybrid
dynamic models including continuous vehicle dynamics, the discrete models of
computations and communications, and the size of the problem. We will overview
recent advances in methodology and tools to model, analyze, and design robust
autonomous aerospace systems operating in uncertain environment, with stress on
efficient uncertainty quantification and robust design using the case studies
of the mission including model-based target tracking and search, and trajectory
planning in uncertain urban environment. To show that the methodology is
generally applicable to uncertain dynamical systems, we will also show examples
of application of the new methods to efficient uncertainty quantification of
energy usage in buildings, and stability assessment of interconnected power
networks
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