25,818 research outputs found
Cyclic cosmology from Lagrange-multiplier modified gravity
We investigate cyclic and singularity-free evolutions in a universe governed
by Lagrange-multiplier modified gravity, either in scalar-field cosmology, as
well as in one. In the scalar case, cyclicity can be induced by a
suitably reconstructed simple potential, and the matter content of the universe
can be successfully incorporated. In the case of -gravity, cyclicity can
be induced by a suitable reconstructed second function of a very
simple form, however the matter evolution cannot be analytically handled.
Furthermore, we study the evolution of cosmological perturbations for the two
scenarios. For the scalar case the system possesses no wavelike modes due to a
dust-like sound speed, while for the case there exist an oscillation
mode of perturbations which indicates a dynamical degree of freedom. Both
scenarios allow for stable parameter spaces of cosmological perturbations
through the bouncing point.Comment: 8 pages, 3 figures, references added, accepted for publicatio
Bounce and cyclic cosmology in extended nonlinear massive gravity
We investigate non-singular bounce and cyclic cosmological evolutions in a
universe governed by the extended nonlinear massive gravity, in which the
graviton mass is promoted to a scalar-field potential. The extra freedom of the
theory can lead to certain energy conditions violations and drive cyclicity
with two different mechanisms: either with a suitably chosen scalar-field
potential under a given Stuckelberg-scalar function, or with a suitably chosen
Stuckelberg-scalar function under a given scalar-field potential. Our analysis
shows that extended nonlinear massive gravity can alter significantly the
evolution of the universe at both early and late times.Comment: 20 pages, 5 figures, version published at JCA
Analysis of Ensiling Suitability of Moringa, a Woody Plant
To effectively use the woody plant resources as animal feed, the ensiling suitability of Moringa including the dynamics of microbial community, chemical composition, and silage fermentation were studied. Tender stems and leaves of Moringa at the full-bloom stage of second cutting was used for silage preparation in Guizhou, China. After 3, 7, 15, 30, and 60 days of ensiling, five silos for each treatment were opened to analyze the fermentation characteristics. Moringa before ensiling contained 104 lactic acid bacteria (LAB), 106 aerobic bacteria, 104 coliform bacteria, 102 yeast, and 104 mold based on colony-forming unit/g of fresh matter (FM). The aerobic bacteria were dominant microbial population in the fresh Moringa. After 3 days of ensiling, the LAB increased as the highest numbers to dominate the silage fermentation. After 7 days of ensiling, the coliform bacteria and mold counts in Moringa silage dropped below the detection levels. The dry matter (DM) of fresh Moringa was 26.57%, their neutral detergent fiber (NDF) and crude protein (CP) contents were 27.40% and 20.90% on a DM basis, respectively. During ensiling, all silages did not emerge great difference in chemical composition. After 7 days of ensiling, all silages displayed a good fermentation patterns, with a low pH value. The result suggested that Moringa can be prepare as silage to be potential woody feed resources for livestock
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