5,331 research outputs found
Updated constraints on spatial variations of the fine-structure constant
Recent work by Webb {\it et al.} has provided indications of spatial
variations of the fine-structure constant, , at a level of a few parts
per million. Using a dataset of 293 archival measurements, they further show
that a dipole provides a statistically good fit to the data, a result
subsequently confirmed by other authors. Here we show that a more recent
dataset of dedicated measurements further constrains these variations: although
there are only 10 such measurements, their uncertainties are considerably
smaller. We find that a dipolar variation is still a good fit to the combined
dataset, but the amplitude of such a dipole must be somewhat smaller:
ppm for the full dataset, versus ppm for the Webb {\it
et al.} data alone, both at the confidence level. Constraints on the
direction on the sky of such a dipole are also significantly improved. On the
other hand the data can't yet discriminate between a pure spatial dipole and
one with an additional redshift dependence.Comment: 10 pages, 4 figure
Constraining spatial variations of the fine-structure constant in symmetron models
We introduce a methodology to test models with spatial variations of the
fine-structure constant , based on the calculation of the angular power
spectrum of these measurements. This methodology enables comparisons of
observations and theoretical models through their predictions on the statistics
of the variation. Here we apply it to the case of symmetron models. We
find no indications of deviations from the standard behavior, with current data
providing an upper limit to the strength of the symmetron coupling to gravity
() when this is the only free parameter, and not able to
constrain the model when also the symmetry breaking scale factor is
free to vary.Comment: Phys. Lett. B (in press
Membrane processing of grape must for control of the alcohol content in fermented beverages
The great demand of beverages, both alcohol-free and with low alcohol content, is a great challenge for the production of beverages with controlled alcohol content through the use
of sustainable enological practices. The present work addresses this challenge with the processing of grape must by reverse osmosis (RO) for must reconstitution with different sugar
contents prior to the alcoholic fermentation. The original must came from grapes grown in Quinta do Quinto, in Santarém, collected after destemming and mechanic crushing, and
preserved in a refrigerated chamber at -1.6 °C until processing by RO. The RO processing was carried out in Escola Superior Agråria de Santarém, with a pilot plant equipped with RO
spiral wound modules, M38RO, from Alfa Laval, Denmark. The total membrane permeation area is 15 m2. The work pressure was 55 bar. The original must had 23.7 oBrix, a density
of 1108 g.L-1, 15.2% (v/v) of probable alcohol, and a conductivity of 2.01 mS.cm-1. The must reconstitution was carried out, by mixing the concentrated grape must with the vegetal
water produced by RO (permeate) to obtain beverages with a nominal alcohol content of 5%, 7%, 10% and 13% (v/v). The fermentation average temperature was between 18.2 and
19.7 °C, and the final density rounded about 993 g.cm-3. The beverages were analysed by different parameters, including total polyphenols, total anthocyanins, colour intensity and
hue, the coordinates CIELab, alcohol content, total acidity, volatile acidity, pH, free SO2 and total SO2. The attributes of the beverage, corresponding to the visual appearance, aroma
and taste senses, as well as the overall judgment were evaluated by the tasters. The proposed method can produce beverages with controlled low alcohol content. The decrease of the
alcohol content led to lower content of polyphenols compounds which influenced the sensory evaluation.info:eu-repo/semantics/publishedVersio
Who and how should participate in health care priority setting? Evidence from a Portuguese survey
This article provides highlights of the evolution of the health care rationing debate towards a more transparent and open approach involving public participation. Discretionary models that have dominated health sector decision-making are being questioned by different sectors of society. Using data from 442 college students, we explore publicâs views on its involvement in health care rationing decisions. Findings suggest that although citizens wish to be consulted, they believe doctors should play the most important role on the rationing decisions. Nonetheless, the confidence in doctors is not independent of the criteria used to support their decisions.Priorities setting, Public involvement; Explicit rationing; Health-care.
Some remarks on the attractor behaviour in ELKO cosmology
Recent results on the dynamical stability of a system involving the
interaction of the ELKO spinor field with standard matter in the universe have
been reanalysed, and the conclusion is that such system does not exhibit
isolated stable points that could alleviate the cosmic coincidence problem.
When a constant parameter related to the potential of the ELKO field
is introduced in the system however, stable fixed points are found for some
specific types of interaction between the ELKO field and matter. Although the
parameter is related to an unknown potential, in order to satisfy the
stability conditions and also that the fixed points are real, the range of the
constant parameter can be constrained for the present time and the
coincidence problem can be alleviated for some specific interactions. Such
restriction on the ELKO potential opens possibility to apply the ELKO field as
a candidate to dark energy in the universe, and so explain the present phase of
acceleration of the universe through the decay of the ELKO field into matter.Comment: 17 pages, section III with minor changes and section IV rewritten
with a new analysi
Tensile properties of geosynthetics after installation damage
In this paper, data from field installation trials of geosynthetics and laboratory tests are presented and analysed. The influence of several factors was assessed, namely nominal strength and type of geosynthetic, soil, compaction energy and method used to induce installation damage. Visual observations using a scanning electron microscope were performed. From the data collected, reduction factors for installation damage were derived using tensile strength values (traditional approach) and stiffness modulus (for 2% strain). Relative to the stiffness approach, the results obtained indicate that the traditional approach can be conservative. The reduction factors, determined using the traditional approach, were also compared with interval estimates from the literature. To contribute to supporting a shift from a factor of safety approach to a limit state design, bias statistics to correct the deterministic predictions were determined from the results. Different correlations were also established to enable using these results to interpolate reduction factors for similar installation conditions and/or geosynthetics from the same family of products. Installation damage reduction factors should be used in limit state design (ultimate and serviceability). Nevertheless, the stiffness approach can only be used for limit states where tensile failure of the geosynthetics will not occur
Reinforcement with geosynthetics of walls of the saltpans of the Aveiro lagoon
The aim of this article is to investigate the solution for the reinforcement of the walls of the saltpans of the Aveiro lagoon by using geosynthetics. For that purpose literature research has been done to collect both the properties and the geometry of the walls and of the soils. Simultaneously, methods for the design of reinforced soils using geosynthetics were collected, particularly to allow the consideration of two types of backfill soil: granular and fine. So, two solutions for such walls were studied using granular and fine soils, respectively. The design methods used were the ones proposed by: Jewell (1996) and Rogbeck et al. (2002) for granular soils and Naughton et al. (2001) for fine soils. Finally, the verification of the external stability of the profiles of a selected wall has been made using the methodology described in Eurocode 7: EN1997-1: 2004
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