21,352 research outputs found
Dark energy, matter creation and curvature
The most studied way to explain the current accelerated expansion of the
universe is to assume the existence of dark energy; a new component that fill
the universe, does not clumps, currently dominates the evolution, and has a
negative pressure. In this work I study an alternative model proposed by Lima
et al. \cite{lima96}, which does not need an exotic equation of state, but
assumes instead the existence of gravitational particle creation. Because this
model fits the supernova observations as well as the CDM model, I
perform in this work a thorough study of this model considering an explicit
spatial curvature. I found that in this scenario we can alleviate the cosmic
coincidence problem, basically showing that these two components, dark matter
and dark energy, are of the same nature, but they act at different scales. I
also shown the inadequacy of some particle creation models, and also I study a
previously propose new model that overcome these difficulties.Comment: 6 pages, 4 figures. Accepted for publication in EPJC. arXiv admin
note: substantial text overlap with arXiv:0812.386
The 8.4-GHz low-noise maser pump source assembly
Improved pump source assemblies and new 8.4-GHz low noise traveling-wave masers (TWMs) were installed at the same time at Deep Space Stations 14 and 43 as part of the Mark IVA DSCC Antenna Microwave Subsystems upgrade. The pump source assemblies are part of the new 8.4-GHz TWMs, which are identified as Block IIA Low-Noise TWMs. Improved reliability of the pump source assemblies was required to meet stress analysis criteria
Cytosolic redox components regulate protein homeostasis via additional localisation in the mitochondrial intermembrane space
Oxidative protein folding is confined to the bacterial periplasm, endoplasmic reticulum and the mitochondrial intermembrane space. Maintaining a redox balance requires the presence of reductive pathways. The major thiol-reducing pathways engage the thioredoxin and the glutaredoxin systems which are involved in removal of oxidants, protein proofreading and folding. Alterations in redox balance likely affect the flux of these redox pathways and are related to ageing and diseases such as neurodegenerative disorders and cancer. Here, we first review the well-studied oxidative and reductive processes in the bacterial periplasm and the endoplasmic reticulum, and then discuss the less understood process in the mitochondrial intermembrane space, highlighting its importance for the proper function of the cell
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