1,679 research outputs found
La igualdad de oportunidades en el acceso a la educación superior
This work analyzes equality of access to the university in Galicia (Spain) as it was influenced by the political decision to finance higher education at between 80% and 85% of its real cost. The composition of the student body with respect to the level of their parents' education is examined. The analysis confirms that in spite of the significant effort at public financing, the objective of equal access will not be reached.Este trabajo analiza la igualdad de oportunidades de acceso a los estudios universitarios en Galicia (España). El examen se realiza teniendo en cuenta la decisión adoptada políticamente de financiar la educación superior entre un 80% y un 85% del costo real. Al tenor del enorme esfuerzo de financiación pública se examina la composición del alumnado en función del nivel de estudios de los padres. El análisis confirma que con la política de financiación pública aplicada no se podrá alcanzar el objetivo de igualdad de acceso a la universidad
Analysis of the resolution of split-ring metamaterial lenses with application in parallel magnetic resonance imaging
In this work, we experimentally determine the resolution of split-ring metamaterials lenses with emphasis in magnetic resonance imaging applications. Two small sources are used to determine the minimal resolution of the lens, which is compared with previous theoretical predictions. Taking into account this minimal resolution, a second experiment is designed in order to study the ability of a split-ring lens to improve the localization of the field produced by two closely spaced coils. This ability could find application in parallel magnetic resonance imaging, which take advantage of the distinct coil sensitivities in order to reduce the image acquisition time. © 2011 American Institute of Physics
Heavy top quark from Fritzsch mass matrices
It is shown, contrary to common belief, that the Fritzsch ansatz for the
quark mass matrices admits a heavy top quark. With the ansatz prescribed at the
supersymmetric grand unified (GUT) scale, one finds that the top quark may be
as heavy as 145 GeV, provided that tan (the ratio of the vacuum
expectation values of the two higgs doublets) . Within a
non-supersymmetric GUT framework with two (one) light higgs doublets, the
corresponding approximate upper bound on the top mass is GeV. Our
results are based on a general one--loop renormalization group analysis of the
quark masses and mixing angles and are readily applied to alternative mass
matrix ans\"{a}tze.Comment: LaTeX, 14 figures (not included, available on request
Electrospun nanosized cellulose fibers using ionic liquids at room temperature
Aiming at replacing the noxious solvents commonly employed, ionic-liquid-based solvents have been recently explored as novel non-volatile and non-flammable media for the electrospinning of polymers. In this work, nanosized and biodegradable cellulose fibers were obtained by electrospinning at room temperature using a pure ionic liquid or a binary mixture of two selected ionic liquids. The electrospinning of 8 wt% cellulose in 1-ethyl-3-methylimidazolium acetate medium (a low viscosity and room temperature ionic liquid capable of efficiently dissolving cellulose) showed to produce electrospun fibers with average diameters within (470 ± 110) nm. With the goal of tailoring the surface tension of the spinning dope, a surface active ionic liquid was further added in a 0.10 : 0.90 mole fraction ratio. Electrospun cellulose fibers from the binary mixture composed of 1-ethyl-3-methylimidazolium acetate and 1-decyl-3-methylimidazolium chloride ionic liquids presented average diameters within (120 ± 55) nm. Scanning electron microscopy, X-ray diffraction analysis, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric assays were used as core methods to evaluate the structural integrity, morphology and crystallinity of the raw, electrospun, and regenerated samples of cellulose. Moreover, the photoluminescence spectra of both raw and electrospun fibers were acquired, and compared, indicating that the cellulose emitting centers are not affected by the dissolution of cellulose in ionic liquids. Finally, the use of non-volatile solvents in electrospinning coupled to a water coagulation bath allows the recovery of the ionic fluid, and represents a step forward into the search of environmentally friendly alternatives to the conventional approaches
A DNA Vaccine against Yellow Fever Virus: Development and Evaluation
Attenuated yellow fever (YF) virus 17D/17DD vaccines are the only available protection from YF infection, which remains a significant source of morbidity and mortality in the tropical areas of the world. The attenuated YF virus vaccine, which is used worldwide, generates both long-lasting neutralizing antibodies and strong T-cell responses. However, on rare occasions, this vaccine has toxic side effects that can be fatal. This study presents the design of two non-viral DNA-based antigen formulations and the characterization of their expression and immunological properties. The two antigen formulations consist of DNA encoding the full-length envelope protein (p/YFE) or the full-length envelope protein fused to the lysosomal-associated membrane protein signal, LAMP-1 (pL/YFE), aimed at diverting antigen processing/presentation through the major histocompatibility complex II precursor compartments. The immune responses triggered by these formulations were evaluated in H2b and H2d backgrounds, corresponding to the C57Bl/6 and BALB/c mice strains, respectively. Both DNA constructs were able to induce very strong T-cell responses of similar magnitude against almost all epitopes that are also generated by the YF 17DD vaccine. The pL/YFE formulation performed best overall. In addition to the T-cell response, it was also able to stimulate high titers of anti-YF neutralizing antibodies comparable to the levels elicited by the 17DD vaccine. More importantly, the pL/YFE vaccine conferred 100% protection against the YF virus in intracerebrally challenged mice. These results indicate that pL/YFE DNA is an excellent vaccine candidate and should be considered for further developmental studies
Predictive fermion mass matrix ansatzes in non-supersymmetric SO(10) grand unification
We investigate the status of predictive fermion mass ansatzes which make use
of the grand unification scale conditions , , and in non-supersymmetric SO(10) grand unification.
The gauge symmetry below an intermediate symmetry breaking scale is
assumed to be that of the standard model with either one Higgs doublet or two
Higgs doublets . We find in both cases that a maximum of 5 standard model
parameters may be predicted within experimental ranges. We find that
the standard model scenario predicts the low energy to be in
a range which includes its experimental mid-value 0.044 and which for a large
top mass can extend to lower values than the range resulting in the
supersymmetric case. In the two Higgs standard model case, we identify the
regions of parameter space for which unification of the bottom quark and tau
lepton Yukawa couplings is possible at grand unification scale. In fact, we
find that unification of the top, bottom and tau Yukawa couplings is possible
with the running b-quark mass within the preferred range provided is near the low end of its allowed
range. In this case, one may make 6 predictions which include
within its confidence limits. However unless the running mass , third generation Yukawa coupling unification requires the top mass to be
greater thanComment: 30 pages, 8 figures available on request from
[email protected], Late
Combined System of Activated Sludge and Ozonation for the Treatment of Kraft E1 Effluent
The treatment of paper mill effluent for COD, TOC, total phenols and color removal was investigated using combined activated sludge-ozonation processes and single processes. The combined activated sludge-O3/pH 10 treatment was able to remove around 80% of COD, TOC and color from Kraft E1 effluent. For the total phenols, the efficiency removal was around 70%. The ozonation post treatment carried out at pH 8.3 also showed better results than the single process. The COD, TOC, color and total phenols removal efficiency obtained were 75.5, 59.1, 77 and 52.3%, respectively. The difference in the concentrations of free radical produced by activated sludge-O3/pH 10 and activated sludge-O3/pH 8.3 affected mainly the TOC and total phenol removal values
Detection of IMBHs from microlensing in globular clusters
Globular clusters have been alternatively predicted to host intermediate-mass
black holes (IMBHs) or nearly impossible to form and retain them in their
centres. Over the last decade enough theoretical and observational evidence
have accumulated to believe that many galactic globular clusters may host IMBHs
in their centres, just like galaxies do. The well-established correlations
between the supermassive black holes and their host galaxies do suggest that,
in extrapolation, globular clusters (GCs) follow the same relations. Most of
the attempts in search of the central black holes (BHs) are not direct and
present enormous observational difficulties due to the crowding of stars in the
GC cores. Here we propose a new method of detection of the central BH -- the
microlensing of the cluster stars by the central BH. If the core of the cluster
is resolved, the direct determination of the lensing curve and lensing system
parameters are possible; if unresolved, the differential imaging technique can
be applied. We calculate the optical depth to central BH microlensing for a
selected list of Galactic GCs and estimate the average time duration of the
events. We present the observational strategy and discuss the detectability of
microlensing events using a 2-m class telescope.Comment: 10 pages, 11 figures, accepted in New Astronom
The bifurcation periods in low-mass X-ray binaries: the effect of magnetic braking and mass loss
The bifurcation period in low-mass X-ray binaries is the initial orbital pe-
riod which separates the formation of converging systems (which evolve with
decreasing orbital periods until the donor becomes degenerate) from the
diverging systems (which evolve with increasing orbital periods until the donor
star loses its envelope and a wide detached binary is formed). We calculate
systematically the bifurcation periods of binary systems with a 1.4M_\sun
neutron star and a 0.5-2M_\sun donor star, taking into account different kinds
of magnetic braking and mass loss mechanisms. Our results show that the
saturated magnetic braking can considerably decrease the values of bifurcation
period compared to the traditional magnetic braking, while the influence of
mass loss mechanisms on bifurcation periods is quite weak. We also develop a
semi-analytical method to compute the bifurcation period, the result of which
agrees well with the numerical method in the leading order.Comment: 18 pages, 4 figures, 1 table. Accepted to be published in Ap
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