640 research outputs found
O que estão fazendo os homens maduros que não trabalham, não procuram trabalho e não são aposentados?
Biopolymer Extracted from Anadenanthera colubrina (Red Angico Gum) Exerts Therapeutic Potential in Mice: Antidiarrheal Activity and Safety Assessment
Decaying Dark Matter in the Supersymmetric Standard Model with Freeze-in and Seesaw mechanims
Inspired by the decaying dark matter (DM) which can explain cosmic ray
anomalies naturally, we consider the supersymmetric Standard Model with three
right-handed neutrinos (RHNs) and R-parity, and introduce a TeV-scale DM sector
with two fields \phi_{1,2} and a discrete symmetry. The DM sector only
interacts with the RHNs via a very heavy field exchange and then we can explain
the cosmic ray anomalies. With the second right-handed neutrino N_2 dominant
seesaw mechanism at the low scale around 10^4 GeV, we show that \phi_{1,2} can
obtain the vacuum expectation values around the TeV scale, and then the
lightest state from \phi_{1,2} is the decay DM with lifetime around \sim
10^{26}s. In particular, the DM very long lifetime is related to the tiny
neutrino masses, and the dominant DM decay channels to \mu and \tau are related
to the approximate \mu-\tau symmetry. Furthermore, the correct DM relic density
can be obtained via the freeze-in mechanism, the small-scale problem for power
spectrum can be solved due to the decays of the R-parity odd meta-stable states
in the DM sector, and the baryon asymmetry can be generated via the soft
leptogensis.Comment: 24 pages,3 figure
3D point cloud in the evaluation of processes that generate instability of the lumbar spine
Ultra-steep side facets in multi-faceted SiGe/Si(001) Stranski-Krastanow islands
For the prototypical Ge/Si(001) system, we show that at high growth temperature a new type of Stranski-Krastanow islands is formed with side facets steeper than {111} and high aspect ratio. Nano-goniometric analysis of the island shapes reveals the presence of six new facet groups in addition to those previously found for dome or barn-shaped islands. Due to the highly multi-faceted island shape and high aspect ratio, the new island types are named "cupola" islands and their steepest {12 5 3} side facet is inclined by 68°to the substrate surface. Assessing the relative stability of the new facets from surface area analysis, we find that their stability is similar to that of {113} and {15 3 23} facets of dome islands. The comparison of the different island shapes shows that they form a hierarchical class of geometrical structures, in which the lower aspect ratio islands of barns, domes and pyramids are directly derived from the cupola islands by successive truncation of the pedestal bases without facet rearrangements. The results underline the key role of surface faceting in the process of island formation, which is as crucial for understanding the island's growth evolution as it is important for device applications
The porin and the permeating antibiotic: A selective diffusion barrier in gram-negative bacteria
Gram-negative bacteria are responsible for a large proportion of antibiotic resistant bacterial diseases. These bacteria have a complex cell envelope that comprises an outer membrane and an inner membrane that delimit the periplasm. The outer membrane contains various protein channels, called porins, which are involved in the influx of various compounds, including several classes of antibiotics. Bacterial adaptation to reduce influx through porins is an increasing problem worldwide that contributes, together with efflux systems, to the emergence and dissemination of antibiotic resistance. An exciting challenge is to decipher the genetic and molecular basis of membrane impermeability as a bacterial resistance mechanism. This Review outlines the bacterial response towards antibiotic stress on altered membrane permeability and discusses recent advances in molecular approaches that are improving our knowledge of the physico-chemical parameters that govern the translocation of antibiotics through porin channel
A política social brasileira em tempos de crise: na rota de um modelo social liberal privado?
Surface Morphology Transformation Under High-Temperature Annealing of Ge Layers Deposited on Si(100)
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