1,350 research outputs found
Sustainable organic dyes from winemaking lees for photoelectrochemical dye-sensitized solar cells
During the last two decades, Dye Sensitized Solar Cells (DSSCs) have received a great deal of attention as a promising, low-cost alternative to conventional silicon photovoltaic devices. Natural dye molecules can be used as a sensitizer for their low cost, good light absorbance, easy preparation process, and biodegradability. In this study, dyes were obtained from wine lees, the last by-product of winemaking process, supplied by a venetian winery (Italy). Polyphenols, like tannins and anthocyanins, which were extracted from winemaking lees, were adsorbed on a nanostructured ordered mesoporous titanium dioxide, previously treated at different temperatures (400-600 ffiC). Both dyes and titania semiconductor samples were studied with different techniques. The tests were carried out on prototypes to evaluate the cell power and the photocurrent generated under simulated solar light irradiation. The obtained solar energy conversion efficiencies are comparable to those that were reported in literature by using organic dyes extracted from vegetables, fruits, and plants. It is significant that these dyes are largely available and cost effective, since recovered from a waste otherwise to be disposed of, opening up a perspective of feasibility for inexpensive and environmentally friendly dye solar cells to generate green electricity and transforming agri-food waste into a resource
The influence of personality traits and facets on visuo-spatial task performance and self-assessed visuo-spatial inclinations in young and older adults.
Aims Personality traits are suggested to influence adults\u2019 cognitive performance, but little is known about their association with visuo-spatial competence, in terms of those visuo-spatial abilities and inclinations crucial to remaining autonomous, especially with aging. This study newly investigated whether, and to what extent, major traits and narrower facets of personality influence young and older adults\u2019 performance in the so-called objective visuo-spatial abilities (mental rotation and visuo-spatial working memory [VSWM]), and self-assessed visuo-spatial inclinations (pleasure and anxiety in exploring places). Method Seventy young adults (18\u201335 years old) and 70 older adults (65\u201375 years old) completed the Big-Five questionnaire, objective rotation and VSWM tasks, and spatial self-assessments on pleasure and anxiety in exploring places. Results Hierarchical regression models confirmed that age negatively predicted the variance in objective visuo-spatial tasks, but not in self-assessed visuo-spatial inclinations, while only the latter were slightly influenced by gender (in favor of men). Further, both objective visuospatial abilities (albeit modestly) and self-assessed visuo-spatial inclinations were predicted by higher Conscientiousness. The latter were also predicted by higher Emotional Stability. Finally, a better objective visuo-spatial performance was explained (again modestly) by lower Dynamism and Politeness, and higher Emotion Control, while higher Perseverance, Emotion Control and Cooperativeness explained a moderate part of the variance in the positive self-assessed visuo-spatial inclinations. Conclusions Our findings indicate that, beyond age and gender, some personality traits and facets predict self-assessed visuo-spatial inclinations to a larger extent than objective visuo-spatial performance. These results are discussed within the spatial cognition and aging framework
Weighing simulated galaxy clusters using lensing and X-ray
We aim at investigating potential biases in lensing and X-ray methods to
measure the cluster mass profiles. We do so by performing realistic simulations
of lensing and X-ray observations that are subsequently analyzed using
observational techniques. The resulting mass estimates are compared among them
and with the input models. Three clusters obtained from state-of-the-art
hydrodynamical simulations, each of which has been projected along three
independent lines-of-sight, are used for this analysis. We find that strong
lensing models can be trusted over a limited region around the cluster core.
Extrapolating the strong lensing mass models to outside the Einstein ring can
lead to significant biases in the mass estimates, if the BCG is not modeled
properly for example. Weak lensing mass measurements can be largely affected by
substructures, depending on the method implemented to convert the shear into a
mass estimate. Using non-parametric methods which combine weak and strong
lensing data, the projected masses within R200 can be constrained with a
precision of ~10%. De-projection of lensing masses increases the scatter around
the true masses by more than a factor of two due to cluster triaxiality. X-ray
mass measurements have much smaller scatter (about a factor of two smaller than
the lensing masses) but they are generally biased low by 5-20%. This bias is
ascribable to bulk motions in the gas of our simulated clusters. Using the
lensing and the X-ray masses as proxies for the true and the hydrostatic
equilibrium masses of the simulated clusters and averaging over the cluster
sample we are able to measure the lack of hydrostatic equilibrium in the
systems we have investigated.Comment: 27 pages, 21 figures, accepted for publication on A&A. Version with
full resolution images can be found at
http://pico.bo.astro.it/~massimo/Public/Papers/massComp.pd
A comunicação da Embrapa Trigo em um dia de campo de inverno 2013.
Editores tĂ©cnicos: Joseani Mesquita Antunes, Ana LĂdia Variani Bonato, Márcia Barrocas Moreira Pimentel
Path Learning in Individuals With Down Syndrome: The Floor Matrix Task and the Role of Individual Visuo-Spatial Measures
Environment learning is essential in everyday life. In individuals with Down syndrome (DS), this skill has begun to be examined using virtual exploration. Previous studies showed that individuals with DS can learn and remember paths in terms of sequences of turns and straight stretches, albeit with some difficulty, and this learning is supported by their cognitive abilities. This study further investigates environment learning in the DS population, newly examining their ability to learn a path from actual movements, and to learn increasingly long paths, and how their performance relates to their visuo-spatial abilities and everyday spatial activities. A group of 30 individuals with DS and 30 typically-developing (TD) children matched for receptive vocabulary performed a 4
7 4 Floor Matrix task in a grid comprising 16 squares (total area 2.3
7 2.3 meters). The task involved repeating increasingly long sequences of steps by actually moving in the grid. The sequences were presented in two learning conditions, called Observation (when participants watched the experimenter\u2019s moves), or Map (when they were shown a map reproducing the path). Several visuo-spatial measures were also administered. The results showed a clear difference between the two groups\u2019 performance in the individual visuo-spatial measures. In the Floor Matrix task, after controlling for visuo-spatial reasoning ability, both groups benefited to the same degree from the Observation condition vis-\ue0-vis the Map condition, and no group differences emerged. In the group with DS, visuo-spatial abilities were more predictive of performance in the Floor Matrix task in the Observation condition than in the Map condition. The same was true of the TD group, but this difference was much less clear-cut. The visuo-spatial working memory and visualization tasks were the strongest predictors of Floor Matrix task performance. Finally, the group with DS showed a significant relation between Floor Matrix task performance in the Observation condition and everyday spatial activity. These results enlarge on what we know about path learning in individuals with DS and its relation to their visuo-spatial abilities. These findings are discussed within the frame of spatial cognition and the atypical development domain
The impact of gas physics on strong cluster lensing
Previous studies of strong gravitational lensing by galaxy clusters neglected
the potential impact of the intracluster gas. Here, we compare simulations of
strong cluster lensing including gas physics at increasing levels of
complexity, i.e. with adiabatic, cooling, star-forming, feedback-receiving, and
thermally conducting gas, and with different implementations of the artificial
viscosity in the SPH simulations. Each cluster was simulated starting from the
same initial conditions such as to allow directly comparing the simulated
clusters. We compare the clusters' shapes, dynamics and density profiles and
study their strong-lensing cross sections computed by means of ray-tracing
simulations. We find that the impact of adiabatic gas depends on the amount of
turbulence that builds up, which means that the artificial viscosity plays an
important role. With the common viscosity implementation, adiabatic gas has
little effect on strong cluster lensing, while lower viscosity allows stronger
turbulence, thus higher non-thermal pressure and a generally broader gas
distribution which tends to lower lensing cross sections. Conversely, cooling
and star formation steepen the core density profiles and can thus increase the
strong-lensing efficiency considerably.Comment: 8 pages, 10 figures, revised version published in A&A, added
discussion of artificial viscosit
Reconstruction of the two-dimensional gravitational potential of galaxy clusters from X-ray and Sunyaev-Zel'dovich measurements
The mass of galaxy clusters is not a direct observable, nonetheless it is
commonly used to probe cosmological models. Based on the combination of all
main cluster observables, that is, the X-ray emission, the thermal
Sunyaev-Zel'dovich (SZ) signal, the velocity dispersion of the cluster
galaxies, and gravitational lensing, the gravitational potential of galaxy
clusters can be jointly reconstructed. We derive the two main ingredients
required for this joint reconstruction: the potentials individually
reconstructed from the observables and their covariance matrices, which act as
a weight in the joint reconstruction. We show here the method to derive these
quantities. The result of the joint reconstruction applied to a real cluster
will be discussed in a forthcoming paper. We apply the Richardson-Lucy
deprojection algorithm to data on a two-dimensional (2D) grid. We first test
the 2D deprojection algorithm on a -profile. Assuming hydrostatic
equilibrium, we further reconstruct the gravitational potential of a simulated
galaxy cluster based on synthetic SZ and X-ray data. We then reconstruct the
projected gravitational potential of the massive and dynamically active cluster
Abell 2142, based on the X-ray observations collected with XMM-Newton and the
SZ observations from the Planck satellite. Finally, we compute the covariance
matrix of the projected reconstructed potential of the cluster Abell 2142 based
on the X-ray measurements collected with XMM-Newton. The gravitational
potentials of the simulated cluster recovered from synthetic X-ray and SZ data
are consistent, even though the potential reconstructed from X-rays shows
larger deviations from the true potential. Regarding Abell 2142, the projected
gravitational cluster potentials recovered from SZ and X-ray data reproduce
well the projected potential inferred from gravitational-lensing observations.
(abridged)Comment: accepted for publication in the journal A&
Fatigue strength of austempered ductile iron-to-steel dissimilar arc-welded joints
Nowadays, the use of different classes of materials in the same structure is increased to keep pace with innovation and high structural performances. In this context, structural components made of different materials need to be joined together and a possible solution is given by arc welding. Dissimilar welded joints must often be able to withstand fatigue loads; however, Design Standards provide fatigue strength categories only for homogeneous welded joints. The aim of the present paper is to compare the fatigue behaviour of EN-GJS-1050 austempered ductile iron-to-S355J2 steel dissimilar joints to the categories of the corresponding homogeneous steel welded joints, as suggested in International Standards and Recommendations. For this purpose, experimental fatigue tests were performed on a selection of dissimilar welded details. First, the microstructure was identified by metallographic analysis; micro-hardness measurements were collected and residual stress profiles were obtained by using the X-ray diffraction technique on a selection of joints. Misalignments were quantified for all specimens. Then, experimental fatigue tests have been performed on a number of joint geometries subject to axial or bending fatigue loadings and tested in the as-welded conditions. The fracture surfaces of the joints have been analysed to locate fatigue crack nucleation sites
The Renaissance of fullerenes with perovskite solar cells
Fullerenes have been extensively used for more than two decades for the development of organic photovoltaics (OPV). While OPV seems to be a technology almost ready for the market, in the last few years fullerenes are attracting a big interest for the improvement they afford on the already well-performing perovskite solar cells (PSCs). Thanks to PSC integration, interest in fullerenes is rising again, opening up new exciting perspectives for photovoltaics. This review article aims at analyzing the landmark contributions that gave birth to the novel application of fullerenes in PSCs and to the technological solutions that are emerging with them
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