366 research outputs found
Dynamic cyclic performance of phenol-formaldehyde resin derived carbons for pre-combustion CO2 capture : An experimental study
Acknowledgments This work was carried out with financial support from the Spanish MINECO (Project ENE2011-23467), co-financed by the European Regional Development Fund (ERDF).Peer reviewedPublisher PD
Recycling of residues as precursors of carbons for supercapacitors
En: 1st Spanish National Conference on Advances in Materials Recycling and Eco – Energy Madrid, 12-13 November 2009.-- Editors: F. A. López, F. Puertas, F. J. Alguacil and A. Guerrero.-- 4 pages, 3 figures, 1 table.It is shown that industrial wastes such as apple pulp
(generated in the cider production), cherry stones
(from the industrial manufacture of Kirsh and jam)
and PET (plastic vessels) can be recycled as
activated carbons for electrode material in
supercapacitors.
These precursors allow obtaining carbons with large
specific surface areas (up to 1200 m2g-1) and
average pore sizes around 0.9-1.3 nm, which makes
them accessible to electrolyte ions. These features
lead to electrical capacitances at low current density
as high as 230 F g-1 in 2M H2SO4 aqueous electrolyte
and 120 F g-1 in the aprotic medium 1M (C2H5)4NBF4
/ acetonitrile. Furthermore, high performance is also
achieved at high current densities, which means that
the activated carbons derived from residues compete
well with commercial carbons used at present in
supercapacitors.Peer reviewe
Where the city lights shine? Measuring the effect of sprawl on electricity consumption in Spain
Urban sprawl is a phenomenon that is generally growing across all continents. As a result, modern city structures need larger areas for similar populations. Few studies have evaluated the effects of sprawl on an important aspect in terms of sustainable development: energy consumption. The aim of this paper is to analyse whether urban sprawl has a significant effect on electricity consumption in Spanish municipalities. The increase in sprawl in Spanish cities is heterogeneous, and the growth of household income during recent decades has allowed households to move to scattered residential areas. This situation makes this country especially interesting as a case study to evaluate the impacts of urban sprawl. In this paper, by disaggregating the electricity consumption of households at the local level using entropy, we measure the effect of sprawl to evaluate whether there is an effect on household energy consumption. The joint consideration of disaggregated data and spatial heterogeneity allows us to assess the effect that sprawl has for certain urban configurations on electricity consumption, which points to the need for policies that involve national, regional and local land use policies
Imaging compact boson stars with hot-spots and thin accretion disks
In this work we consider the observational properties of compact boson stars
with self-interactions orbited by isotropically emitting (hot-spot) sources and
optically thin accretion disks. We consider two families of boson stars
supported by quartic and sixth-order self-interaction potentials, and choose
three samples of each of them in growing compactness; only those with large
enough compactness are capable to hold light-rings, namely, null bound orbits.
For the hot-spots, using inclination angles we find a secondary track plunge-through image of photons crossing
the interior of the boson star, which can be further decomposed into additional
images if the star is compact enough. For accretion disks we find that the
latter class of stars actually shows a sequence of additional secondary images
in agreement with the hot-spot analysis, a feature absent in typical black hole
space-times. Furthermore, we also find a shadow-like central brightness
depression for some of these stars in both axial observations and at the
inclination angles above. We discuss our findings in relation to the capability
of boson stars to effectively act as black hole mimickers in their optical
appearances as well as potential observational discriminators.Comment: 17 pages, 16 figure
Photon rings as tests for alternative spherically symmetric geometries with thin accretion disks
The imaging by the Event Horizon Telescope (EHT) of the supermassive central
objects at the heart of the M87 and Milky Way (Sgr A) galaxies, has
marked the first step into peering at the shadow and photon rings that
characterize the optical appearance of black holes surrounded by an accretion
disk. Recently, Vagnozzi et. al. [S.~Vagnozzi, \textit{et al.} arXiv:2205.07787
[gr-qc]] used the claim by the EHT that the size of the shadow of Sgr A
can be inferred by calibrated measurements of the bright ring enclosing it, to
constrain a large number of spherically symmetric space-time geometries. In
this work we use this result to study some features of the first and second
photon rings of a restricted pool of such geometries in thin accretion disk
settings. The emission profile of the latter is described by calling upon three
analytic samples belonging to the family introduced by Gralla, Lupsasca and
Marrone, in order to characterize such photon rings using the Lyapunov exponent
of nearly bound orbits and discuss its correlation with the luminosity
extinction rate between the first and second photon rings. We finally elaborate
on the chances of using such photon rings as observational discriminators of
alternative black hole geometries using very long baseline interferometry.Comment: 17 pages, 58 figures/image
Intracranial atherosclerotic plaque enhancement and long-term risk of future strokes: A prospective, longitudinal study
Background and Purpose
The prognostic significance of postcontrast enhancement of intracranial atheromatous plaque is uncertain. Prospective, long-term follow-up studies in Caucasians, using a multicenter design, are lacking. We aimed to evaluate whether this radiological sign predicts long-term new stroke in symptomatic and asymptomatic intracranial atherosclerotic disease (ICAD) patients.
Methods
This was a prospective, observational, longitudinal, multicenter study. We included a symptomatic and an asymptomatic cohort of ICAD patients that underwent 3T MRI including high-resolution sequences focused on the atheromatous plaque. We evaluated grade of stenosis, plaque characteristics, and gadolinium enhancement ratio (postcontrast plaque signal/postcontrast corpus callosum signal). The occurrence of new events was evaluated at 3, 6, 9, and 12 months and annually thereafter. The association between plaque characteristics and new stroke was studied using Cox multiple regression survival analysis and Kaplan-Meier curves.
Results
Forty-eight symptomatic and 13 asymptomatic patients were included. During 56.3 ± 16.9 months, 11 patients (18%) suffered a new event (seven ischemic, two hemorrhagic, and two transient ischemic attacks). A receiver operating characteristic curve identified an enhancement ratio of >1.77 to predict a new event. In a multivariable Cox regression, postcontrast enhancement ratio >1.77 (hazard ratio [HR]= 3.632; 95% confidence interval [CI], 1.082-12.101) and cerebral microbleeds (HR = 5.244; 95% CI, 1.476-18.629) were independent predictors of future strokes. Patients with a plaque enhancement ratio >1.77 had a lower survival free of events (p < .05).
Conclusions
High intracranial postcontrast enhancement is a long-term predictor of new stroke in ICAD patients. Further studies are needed to elucidate whether postcontrast enhancement reflects inflammatory activity of intracranial atheromatous plaque.This study has been funded by the Spanish Ministry of Science, via FIS project PI13/02544, PI16/01396, and PI19/01398 and through the INVICTUS PLUS research network RD16/0019. Beatriz Gómez-Vicente received a research contract from the Junta de Castilla y León and European Social Fund, Spain. María Hernandez-Perez was funded by The Instituto de Salud Carlos III, Spain (JR17/00006)
Hubs and clusters approach to unlock the development of carbon capture and storage - Case study in Spain
Many countries have assigned an indispensable role for carbon capture and storage (CCS) in their national climate change mitigation pathways. However, CCS deployment has stalled in most countries with only limited commercial projects realised mainly in hydrocarbon-rich countries for enhanced oil recovery. If the Paris Agreement is to be met, then this progress must be replicated widely, including hydrocarbon-limited countries. In this study, we present a novel source-to-sink assessment methodology based on a hubs and clusters approach to identify favourable regions for CCS deployment and attract renewed public and political interest in viable deployment pathways. Here, we apply this methodology to Spain, where fifteen emission hubs from both the power and the hard-to-abate industrial sectors are identified as potential CO2 sources. A priority storage structure and two reserves for each hub are selected based on screening and ranking processes using a multi-criteria decision-making method. The priority source-to-sink clusters are identified indicating four potential development regions, with the North-Western and North-Eastern Spain recognised as priority regions due to resilience provided by different types of CO2 sources and geological structures. Up to 68.7 Mt CO2 per year, comprising around 21% of Spanish emissions can be connected to clusters linked to feasible storage. CCS, especially in the hard-to-abate sector, and in combination with other low-carbon energies (e.g., blue hydrogen and bioenergy), remains a significant and unavoidable contributor to the Paris Agreement's mid-century net-zero target. This study shows that the hubs and clusters approach can facilitate CCS deployment in Spain and other hydrocarbon-limited countries
Observation of the Charmed Baryon at CLEO
The CLEO experiment at the CESR collider has used 13.7 fb of data to
search for the production of the (css-ground state) in
collisions at {\rm GeV}. The modes used to
study the are ,
, , , and
. We observe a signal of 40.49.0(stat) events
at a mass of 2694.62.6(stat)1.9(syst) {\rm MeV/}, for all modes
combined.Comment: 10 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Measurement of the Relative Branching Fraction of to Charged and Neutral B-Meson Pairs
We analyze 9.7 x 10^6 B\bar{B}$ pairs recorded with the CLEO detector to
determine the production ratio of charged to neutral B-meson pairs produced at
the Y(4S) resonance. We measure the rates for B^0 -> J/psi K^{(*)0} and B^+ ->
J/psi K^{(*)+} decays and use the world-average B-meson lifetime ratio to
extract the relative widths f+-/f00 = Gamma(Y(4S) -> B+B-)/Gamma(Y(4S) ->
B0\bar{B0}) = = 1.04 +/- 0.07(stat) +/- 0.04(syst). With the assumption that
f+- + f00 = 1, we obtain f00 = 0.49 +/- 0.02(stat) +/- 0.01(syst) and f+- =
0.51 +/- 0.02(stat) +/- 0.01(syst). This production ratio and its uncertainty
apply to all exclusive B-meson branching fractions measured at the Y(4S)
resonance.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Hadronic Mass Moments in Inclusive Semileptonic B Meson Decays
We have measured the first and second moments of the hadronic mass-squared
distribution in B -> X_c l nu, for P(lepton) > 1.5 GeV/c. We find <M_X^2 -
M_D[Bar]^2> = 0.251 +- 0.066 GeV^2, )^2 > = 0.576 +- 0.170
GeV^4, where M_D[Bar] is the spin-averaged D meson mass.
From that first moment and the first moment of the photon energy spectrum in
b -> s gamma, we find the HQET parameter lambda_1 (MS[Bar], to order 1/M^3 and
beta_0 alpha_s^2) to be -0.24 +- 0.11 GeV^2. Using these first moments and the
B semileptonic width, and assuming parton-hadron duality, we obtain |V_cb| =
0.0404 +- 0.0013.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to PR
- …