194 research outputs found
Modelo de rehabilitación ambiental para edificios terciarios: el caso del palacio de congresos Europa de Vitoria-Gasteiz
Este artículo presenta el desarrollo y resultados de la primera fase del asesoramiento ambiental que forma parte del proceso de rehabilitación y ampliación del Palacio de Congresos Europa (PEV-G) del Ayuntamiento de Vitoria-Gasteiz, en el marco de las actuaciones que esta ciudad ha decidido emprender como European Green Capital, a partir de haber obtenido este reconocimiento en 2012.
Es un desarrollo de Green Building Council España (GBCe) en colaboración con Societat Orgànica (SO) que propone una metodología y unas acciones para abordar un proceso continuo de mejora ambiental para que el edificio, sus actividades y los actores directamente relacionados puedan alcanzar los máximos niveles posibles de sostenibilidad ambiental, atendiendo también a las dimensiones económica y social.
A través de diferentes modelos se ha estudiado el edificio existente, así como las hipótesis de ampliación y rehabilitación determinadas por el ayuntamiento en su anteproyecto, empleando la metodología del análisis de ciclo de vida simplificado centrada en los vectores ambientales de energía, agua, materiales y residuos. Se han determinado diferentes opciones de mejora basadas en aspectos pasivos, activos y de gestión del edificio que han permitido establecer los objetivos ambientales a los cuales debe responder el proyecto, rehabilitación, ampliación y uso del PEV-G. Por último, se han redactado los requerimientos que forman parte de los pliegos de licitación del proceso que va del proyecto al edificio acabado, así como el protocolo ambiental a aplicar en las fases aun no ejecutadas.
Los trabajos realizados incluyen el desarrollo inicial de una nueva herramienta de certificación de la calidad ambiental de los edificios Verde RH EQ Rehabilitación de Equipamientos, que se suma a las existentes.
De la visión, objetivos, metodología y acciones de reducción de impactos ambientales aplicables al PEV-G se ha obtenido un protocolo de actuación válido para ser aplicado en otros equipamientos de Vitoria-Gasteiz, el País Vasco y el resto de España, a ser rehabilitados en el futuro próximo
High performance free-standing films by layer-by-layer assembly of graphene flakes and ribbons with natural polymers
In this work, novel free-standing (FS) films based on chitosan, alginate and graphene oxide (GO) were developed through layer-by-layer assembly. First, GO was synthesized from graphite and multi-walled carbon nanotubes using a modified Hummer's method, yielding oxidized graphene flakes (o-GFs) and oxidized graphene nanoribbons (o-GNRs), respectively, which were then characterized. Then FS films were produced and their morphological, thermal and mechanical properties, as well as the o-GF and o-GNR dispersion along the films were assessed. Their degradation and swelling profiles as well as their biological behavior were evaluated. Graphite and nanotubes were successfully oxidized and exfoliated forming stable suspensions that could be combined with chitosan (CHI) and alginate (ALG) solutions by layer-by-layer processing. The addition of o-GFs and o-GNRs resulted in rougher, hydrophilic FS films with significantly improved mechanical properties relative to CHI/ALG films. The presence of o-GFs or o-GNRs did not affect the thermal stability and the addition of o-GFs resulted in films with enhanced cytocompatibility. The results demonstrate the high potential of the GO reinforced films for biomedical applications, in particular o-GF films, for wound healing, and cardiac and bone engineering applications.The authors acknowledge the Portuguese Foundation for Science
and Technology (FCT) and the European program FEDER/
COMPETE for the financial support through project BioSeaGlue:
EXPL/CTM-BIO/0646/2013 (FCOMP-01-0124-FEDER-041105) and
for project PEst-C/CTM/LA0025/2013 (Strategic Project – LA 25 –
2013-2014). This work was also financially supported by FCT
through the scholarships SFRH/BPD/96797/2013 granted to
Sofia G. Caridade, SFRH/BD/97606/2013 granted to Maria Sousa,
and SFRH/BD/87214/2012 granted to Eunice Cunha
Evaluation of cardiovascular protective effect of different apple varieties - Correlation of response with composition
NOTICE: this is the author’s version of a work that was accepted for publication in Food Chemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Food Chemistry, Vol. 135, Issue 4, 2012. DOI http://dx.doi.org/10.1016/j.foodchem.2012.07.067"Epidemiological evidence supports the concept that diets rich in fruits and vegetables
promote health and attenuate or delay the onset of cardiovascular disease (CVD). In
particular, a reduced risk of CVD has been associated with apple consumption, probably
due to the cholesterol-lowering effect of the main bioactive compounds, namely fiber
and polyphenols.
In this work, the effect of diet supplementation with 20% of three Portuguese apple
cultivars (Bravo de Esmolfe, Malápio Serra and Golden), containing distinct phenolic
and fiber concentrations, on serum lipid profile and oxLDL of male Wistar rats fed a
cholesterol-enriched diet (2%) was evaluated. After 30 days, only Bravo de Esmolfe
apple was able to decrease significantly serum levels of triglycerides, total and LDL
cholesterol concentrations (reductions of 27.2%, 21.0% and 20.4%, respectively, in
relation to the cholesterol-enriched diet group, p<0.05) . The levels of oxLDL were also
significantly improved with the consumption of this apple variety (reductions of 20.0%
and 11.9%, in relation to the cholesterol-enriched diet group and control group,
respectively, p>0.05) as well as with Malapio da Serra apple (reductions of 9.8% in
relation to the cholesterol-enriched diet group, p<0.05). Correlation of the bioactive
response with chemical composition showed that catechin, epicatechin, procyanidin B1
and -carotene are the major phytocompounds responsible for the cholesterol lowering
ability of apples. The antioxidant potential may have also contributed to this beneficial
effect.
Revisiting the explodability of single massive star progenitors of stripped-envelope supernovae
Stripped-envelope supernovae (Types IIb, Ib, and Ic) that show little or no
hydrogen comprise roughly one-third of the observed explosions of massive
stars. Their origin and the evolution of their progenitors are not yet fully
understood. Very massive single stars stripped by their own winds ( at solar metallicity) are considered viable progenitors of
these events. However, recent 1D core-collapse simulations show that some
massive stars may collapse directly into black holes after a failed explosion,
with a weak or no visible transient. In this letter, we estimate the effect of
direct collapse into a black hole on the rates of stripped-envelope supernovae
that arise from single stars. For this, we compute single-star MESA models at
solar metallicity and map their final state to their core-collapse outcome
following prescriptions commonly used in population synthesis. According to our
models, no single stars that have lost their entire hydrogen-rich envelope are
able to explode, and only a fraction of progenitors left with a thin hydrogen
envelope do (IIb progenitor candidates), unless we use a prescription that
takes the effect of turbulence into account or invoke increased wind mass-loss
rates. This result increases the existing tension between the single-star
paradigm to explain most stripped-envelope supernovae and their observed rates
and properties. At face value, our results point toward an even higher
contribution of binary progenitors to stripped-envelope supernovae.
Alternatively, they may suggest inconsistencies in the common practice of
mapping different stellar models to core-collapse outcomes and/or higher
overall mass loss in massive stars.Comment: Published in Astronomy & Astrophysics Letters; One main enhancement:
added Couch et al. (2020) in the list of supernova engine
The impact of mass-transfer physics on the observable properties of field binary black hole populations
We study the impact of mass-transfer physics on the observable properties of
binary black hole populations formed through isolated binary evolution. We
investigate the impact of mass-accretion efficiency onto compact objects and
common-envelope efficiency on the observed distributions of ,
and . We find that low common envelope efficiency translates to
tighter orbits post common envelope and therefore more tidally spun up
second-born black holes. However, these systems have short merger timescales
and are only marginally detectable by current gravitational-waves detectors as
they form and merge at high redshifts (), outside current detector
horizons. Assuming Eddington-limited accretion efficiency and that the
first-born black hole is formed with a negligible spin, we find that all
non-zero systems in the detectable population can come only from
the common envelope channel as the stable mass-transfer channel cannot shrink
the orbits enough for efficient tidal spin-up to take place. We find the local
rate density () for the common envelope channel is in the range
considering a range of while for the stable mass transfer channel the rate density is . The latter drops by two orders of magnitude if the mass
accretion onto the black hole is not Eddington limited because conservative
mass transfer does not shrink the orbit as efficiently as non-conservative mass
transfer does. Finally, using GWTC-2 events, we constrain the lower bound of
branching fraction from other formation channels in the detected population to
be . Assuming all remaining events to be formed through either stable
mass transfer or common envelope channels, we find moderate to strong evidence
in favour of models with inefficient common envelopes.Comment: 26 pages, 13 figures, accepted for publication in A&
POSYDON: A General-Purpose Population Synthesis Code with Detailed Binary-Evolution Simulations
Most massive stars are members of a binary or a higher-order stellar systems,
where the presence of a binary companion can decisively alter their evolution
via binary interactions. Interacting binaries are also important astrophysical
laboratories for the study of compact objects. Binary population synthesis
studies have been used extensively over the last two decades to interpret
observations of compact-object binaries and to decipher the physical processes
that lead to their formation. Here, we present POSYDON, a novel, binary
population synthesis code that incorporates full stellar-structure and
binary-evolution modeling, using the MESA code, throughout the whole evolution
of the binaries. The use of POSYDON enables the self-consistent treatment of
physical processes in stellar and binary evolution, including: realistic
mass-transfer calculations and assessment of stability, internal
angular-momentum transport and tides, stellar core sizes, mass-transfer rates
and orbital periods. This paper describes the detailed methodology and
implementation of POSYDON, including the assumed physics of stellar- and
binary-evolution, the extensive grids of detailed single- and binary-star
models, the post-processing, classification and interpolation methods we
developed for use with the grids, and the treatment of evolutionary phases that
are not based on pre-calculated grids. The first version of POSYDON targets
binaries with massive primary stars (potential progenitors of neutron stars or
black holes) at solar metallicity.Comment: 60 pages, 33 figures, 8 tables, referee's comments addressed. The
code and the accompanying documentations and data products are available at
https:\\posydon.or
Nucleon-Nucleon Interaction: A Typical/Concise Review
Nearly a recent century of work is divided to Nucleon-Nucleon (NN)
interaction issue. We review some overall perspectives of NN interaction with a
brief discussion about deuteron, general structure and symmetries of NN
Lagrangian as well as equations of motion and solutions. Meanwhile, the main NN
interaction models, as frameworks to build NN potentials, are reviewed
concisely. We try to include and study almost all well-known potentials in a
similar way, discuss more on various commonly used plain forms for two-nucleon
interaction with an emphasis on the phenomenological and meson-exchange
potentials as well as the constituent-quark potentials and new ones based on
chiral effective field theory and working in coordinate-space mostly. The
potentials are constructed in a way that fit NN scattering data, phase shifts,
and are also compared in this way usually. An extra goal of this study is to
start comparing various potentials forms in a unified manner. So, we also
comment on the advantages and disadvantages of the models and potentials partly
with reference to some relevant works and probable future studies.Comment: 85 pages, 5 figures, than the previous v3 edition, minor changes, and
typos fixe
Gas Accretion and Star Formation Rates
Cosmological numerical simulations of galaxy evolution show that accretion of
metal-poor gas from the cosmic web drives the star formation in galaxy disks.
Unfortunately, the observational support for this theoretical prediction is
still indirect, and modeling and analysis are required to identify hints as
actual signs of star-formation feeding from metal-poor gas accretion. Thus, a
meticulous interpretation of the observations is crucial, and this
observational review begins with a simple theoretical description of the
physical process and the key ingredients it involves, including the properties
of the accreted gas and of the star-formation that it induces. A number of
observations pointing out the connection between metal-poor gas accretion and
star-formation are analyzed, specifically, the short gas consumption time-scale
compared to the age of the stellar populations, the fundamental metallicity
relationship, the relationship between disk morphology and gas metallicity, the
existence of metallicity drops in starbursts of star-forming galaxies, the
so-called G dwarf problem, the existence of a minimum metallicity for the
star-forming gas in the local universe, the origin of the alpha-enhanced gas
forming stars in the local universe, the metallicity of the quiescent BCDs, and
the direct measurements of gas accretion onto galaxies. A final section
discusses intrinsic difficulties to obtain direct observational evidence, and
points out alternative observational pathways to further consolidate the
current ideas.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dav\'e, to be published by
Springe
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