940 research outputs found

    Mitochondrial ATP synthase genes may be implicated in cytoplasmic male sterility in Sorghum bicolor

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    Incompatible 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

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    Stimulation of macromolecular synthesis by ascorbat

    Isolated elliptical galaxies in the local Universe

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    We 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

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    The 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

    Disarmament: What kind? how much?

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    https://stars.library.ucf.edu/prism/1567/thumbnail.jp

    Toward a sane nuclear policy

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    A Nuclear test ban treaty now

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    https://stars.library.ucf.edu/prism/1023/thumbnail.jp

    Scalable Approach to Uncertainty Quantification and Robust Design of Interconnected Dynamical Systems

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    Development 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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