733 research outputs found
Remarks on the representation theory of the Moyal plane
We present an explicit construction of a unitary representation of the
commutator algebra satisfied by position and momentum operators on the Moyal
plane.Comment: 10 pages, minor changes, refs. adde
Neutrino mixing and masses in a left-right model with mirror fermions
In the framework of a left-right model containing mirror fermions with gauge
group SU(3),
we estimate the neutrino masses, which are found to be consistent with their
experimental bounds and hierarchy. We evaluate the decay rates of the Lepton
Flavor Violation (LFV) processes , and . We obtain upper limits for the
flavor-changing branching ratios in agreement with their present experimental
bounds. We also estimate the decay rates of heavy Majorana neutrinos in the
channels , and , which are roughly equal for large values of the heavy
neutrino mass. Starting from the most general Majorana neutrino mass matrix,
the smallness of active neutrino masses turns out from the interplay of the
hierarchy of the involved scales and the double application of seesaw
mechanism. An appropriate parameterization on the structure of the neutrino
mass matrix imposing a symmetric mixing of electron neutrino with muon and tau
neutrinos leads to Tri-bimaximal mixing matrix for light neutrinos.Comment: Accepted by European Physical Journal
On the noncommutative eikonal
We study the eikonal approximation to quantum mechanics on the Moyal plane.
Instead of using a star product, the analysis is carried out in terms of
operator-valued wavefunctions depending on noncommuting, operator-valued
coordinates.Comment: 18 page
Arginine-rich peptides destabilize the plasma membrane, consistent with a pore formation translocation mechanism of cell penetrating peptides
Recent molecular dynamics simulations (Herce and Garcia, PNAS, 104: 20805
(2007)) have suggested that the arginine-rich HIV Tat peptides might be able to
translocate by destabilizing and inducing transient pores in phospholipid
bilayers. In this pathway for peptide translocation, arginine residues play a
fundamental role not only in the binding of the peptide to the surface of the
membrane but also in the destabilization and nucleation of transient pores
across the bilayer, despite being charged and highly hydrophilic. Here we
present a molecular dynamics simulation of a peptide composed of nine arginines
(Arg-9) that shows that this peptide follows the same translocation pathway
previously found for the Tat peptide. We test this hypothesis experimentally by
measuring ionic currents across phospholipid bilayers and cell membranes
through the pores induced by Arg-9 peptides. We find that Arg-9 peptides, in
the presence of an electrostatic potential gradient, induce ionic currents
across planar phospholipid bilayers, as well as in cultured osteosarcoma cells
and human smooth muscle cells freshly isolated from the umbilical artery. Our
results suggest that the mechanism of action of Arg-9 peptide involves the
creation of transient pores in lipid bilayers and cell membranes.Comment: This is an extended version of the published manuscript, which had to
be shortened before publication to fit within the number of pages required by
the journa
On the noncommutative eikonal
We study the eikonal approximation to quantum mechanics on the Moyal plane. Instead of using a star product, the analysis is carried out in terms of operator-valued wavefunctions depending on noncommuting, operator-valued coordinates
The Carina Nebula and Gum 31 molecular complex: II. The distribution of the atomic gas revealed in unprecedented detail
We report high spatial resolution observations of the HI 21cm line in the
Carina Nebula and the Gum 31 region obtained with the Australia Telescope
Compact Array. The observations covered 12 deg centred on , achieving an angular resolution of 35
arcseconds. The HI map revealed complex filamentary structures across a wide
range of velocities. Several "bubbles" are clearly identified in the Carina
Nebula Complex, produced by the impact of the massive star clusters located in
this region. An HI absorption profile obtained towards the strong extragalactic
radio source PMN J1032--5917 showed the distribution of the cold component of
the atomic gas along the Galactic disk, with the Sagittarius-Carina and Perseus
spiral arms clearly distinguishable. Preliminary calculations of the optical
depth and spin temperatures of the cold atomic gas show that the HI line is
opaque ( 2) at several velocities in the Sagittarius-Carina
spiral arm. The spin temperature is K in the regions with the highest
optical depth, although this value might be lower for the saturated components.
The atomic mass budget of Gum 31 is of the total gas mass. HI self
absorption features have molecular counterparts and good spatial correlation
with the regions of cold dust as traced by the infrared maps. We suggest that
in Gum 31 regions of cold temperature and high density are where the atomic to
molecular gas phase transition is likely to be occurring.Comment: 20 pages, 1 table, 16 Figures, Accepted for Publication in the
Monthly Notices of the Royal Astronomical Society Journa
Early alterations in vascular contractility associated to changes in fatty acid composition and oxidative stress markers in perivascular adipose tissue
<p>Abstract</p> <p>Aim</p> <p>To test the early effect of fructose-induced changes in fatty acid composition and oxidative stress markers in perivascular adipose tissue (PVAT) upon vascular contractility.</p> <p>Methods</p> <p>Adult male Wistar rats were fed a commercial diet without (CD) or with 10% fructose (FRD) in the drinking water for 3 weeks. We measured plasma metabolic parameters, lipid composition and oxidative stress markers in aortic PVAT. Vascular contractility was measured in aortic rings sequentially, stimulated with serotonin (5-HT) and high K<sup>+</sup>-induced depolarization using intact and thereafter PVAT-deprived rings.</p> <p>Results</p> <p>Comparable body weights were recorded in both groups. FRD rats had increased plasma triglyceride and fructosamine levels. Their PVAT had an increased saturated to mono- or poly-unsaturated fatty acid ratio, a significant decrease in total superoxide dismutase and glutathione peroxidase activities and in the total content of glutathione. Conversely, lipid peroxidation (TBARS), nitric oxide content, and gluthathione reductase activity were significantly higher, indicating an increase in oxidative stress. In aortic rings, removal of PVAT increased serotonin-induced contractions, but the effect was significantly lower in rings from FRD rats. This effect was no longer observed when the two contractions were performed in PVAT-deprived rings. PVAT did not affect the contractions triggered by high K<sup>+</sup>-induced depolarization either in CD or FRD rats.</p> <p>Conclusions</p> <p>FRD induces multiple metabolic and endocrine systemic alterations which also alter PVAT and the vascular relaxant properties of this tissue. The changes in PVAT would affect its paracrine modulation of vascular function.</p
Neutrino masses and mixing parameters in a left-right model with mirror fermions
In this work we consider a left-right model containing mirror fermions with
gauge group SU(3). The model has several free parameters which here we have
calculated by using the recent values for the squared-neutrino mass
differences. Lower bound for the mirror vacuum expectation value helped us to
obtain crude estimations for some of these parameters. Also we estimate the
order of magnitude of the masses of the standard and mirror neutrinos.Comment: 13 pages, version submitted to European Physical Journal
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