1,570 research outputs found
Microscopic approach to pion-nucleus dynamics
Elastic scattering of pions from finite nuclei is investigated utilizing a
contemporary, momentum--space first--order optical potential combined with
microscopic estimates of second--order corrections. The calculation of the
first--order potential includes:\ \ (1)~full Fermi--averaging integration
including both the delta propagation and the intrinsic nonlocalities in the
- amplitude, (2)~fully covariant kinematics, (3)~use of invariant
amplitudes which do not contain kinematic singularities, and (4)~a
finite--range off--shell pion--nucleon model which contains the nucleon pole
term. The effect of the delta--nucleus interaction is included via the mean
spectral--energy approximation. It is demonstrated that this produces a
convergent perturbation theory in which the Pauli corrections (here treated as
a second--order term) cancel remarkably against the pion true absorption terms.
Parameter--free results, including the delta--nucleus shell--model potential,
Pauli corrections, pion true absorption, and short--range correlations are
presented. (2 figures available from authors)Comment: 13 page
Synthesis and gas-sensing properties of pd-doped SnO2 nanocrystals. A case study of a general methodology for doping metal oxide nanocrystals
Pd-modified SnO2 nanocrystals, with a Pd/Sn nominal atomic ratio of 0.025, were prepared by injecting SnO2 sols and a Pd precursor solution into tetradecene and dodecylamine at 160 degrees C. Two different doping procedures were investigated: in co-injection, a Pd acetylacetonate solution in chloroform was mixed with the SnO2 sol before the injection; in sequential injection, the Pd solution was injected separately after the SnO2 sol. The obtained suspensions were heated at the resulting 80 degrees C temperature, then the product was collected by centrifugation and dried at 80 degrees C. When using co-injection, in the dried products PdO and Pd nanoparticles were observed by high-resolution transmission electron microscopy. Only SnO2 nanocrystals were observed in dried products prepared by sequential injection. After heat-treatment at 500 degrees C, no Pd species were observed for both doping procedures. Moreover, X-ray photoelectron spectroscopy showed that, in both the doping procedures, after heat-treatment Pd is distributed only into the SnO2 nanocrystal structure. This conclusion was reinforced by the measurement of the electrical properties of Pd-doped nanocrystals, showing a remarkable increase of the electrical resistance if compared with pure SnO2 nanocrystals. This result was interpreted as Pd insertion as a dopant inside the cassiterite lattice of tin dioxide. The addition of Pd resulted in a remarkable improvement of the gas-sensing properties, allowing the detection of carbon monoxide concentrations below 50 ppm and of very low concentrations (below 25 ppm) of other reducing gases such as ethanol and acetone
Teor de carotenóides totais e beta-caroteno em bolo biofortificado com batata doce de polpa alaranjada.
ConXsense - Automated Context Classification for Context-Aware Access Control
We present ConXsense, the first framework for context-aware access control on
mobile devices based on context classification. Previous context-aware access
control systems often require users to laboriously specify detailed policies or
they rely on pre-defined policies not adequately reflecting the true
preferences of users. We present the design and implementation of a
context-aware framework that uses a probabilistic approach to overcome these
deficiencies. The framework utilizes context sensing and machine learning to
automatically classify contexts according to their security and privacy-related
properties. We apply the framework to two important smartphone-related use
cases: protection against device misuse using a dynamic device lock and
protection against sensory malware. We ground our analysis on a sociological
survey examining the perceptions and concerns of users related to contextual
smartphone security and analyze the effectiveness of our approach with
real-world context data. We also demonstrate the integration of our framework
with the FlaskDroid architecture for fine-grained access control enforcement on
the Android platform.Comment: Recipient of the Best Paper Awar
Robots that can adapt like animals
As robots leave the controlled environments of factories to autonomously
function in more complex, natural environments, they will have to respond to
the inevitable fact that they will become damaged. However, while animals can
quickly adapt to a wide variety of injuries, current robots cannot "think
outside the box" to find a compensatory behavior when damaged: they are limited
to their pre-specified self-sensing abilities, can diagnose only anticipated
failure modes, and require a pre-programmed contingency plan for every type of
potential damage, an impracticality for complex robots. Here we introduce an
intelligent trial and error algorithm that allows robots to adapt to damage in
less than two minutes, without requiring self-diagnosis or pre-specified
contingency plans. Before deployment, a robot exploits a novel algorithm to
create a detailed map of the space of high-performing behaviors: This map
represents the robot's intuitions about what behaviors it can perform and their
value. If the robot is damaged, it uses these intuitions to guide a
trial-and-error learning algorithm that conducts intelligent experiments to
rapidly discover a compensatory behavior that works in spite of the damage.
Experiments reveal successful adaptations for a legged robot injured in five
different ways, including damaged, broken, and missing legs, and for a robotic
arm with joints broken in 14 different ways. This new technique will enable
more robust, effective, autonomous robots, and suggests principles that animals
may use to adapt to injury
Avaliação de minerais em feijão (Phaseolus vulgaris, L.) submetido a diferentes tratamentos de hidratação - secagem.
O objetivo do presente trabalho é avaliar os teores dos minerais, ferro, zinco, cálcio e manganês em grãos de feijão biofortificados descascados após diferentes tratamentos de hidratação-secagem
Limits on GNSS Performance at High Latitudes
As climate change will likely lead to more of a human presence in the higher latitudes, it is important to consider how well our safety-critical positioning systems work near the poles. The orbits of the GPS (and other GNSS) preclude satellites with high elevation in these regions; hence, it is clear that at least vertical accuracy is impacted. This paper characterizes this positioning performance loss by developing lower bounds on GDOP as a function of receiver latitude. Examples with actual ephemeris data are included for comparison to the bounds
Preferência de massa alimentícia formulada com farinha de batata-doce de polpa alaranjada e arroz.
Identification of pheromone components and their binding affinity to the odorant binding protein CcapOBP83a-2 of the Mediterranean fruit fly, Ceratitis capitata
The Mediterranean fruit fly (or medfly), Ceratitis capitata (Wiedemann; Diptera: Tephritidae), is a serious pest of agriculture worldwide, displaying a very wide larval host range with more than 250 different species of fruit and vegetables. Olfaction plays a key role in the invasive potential of this species. Unfortunately, the pheromone communication system of the medfly is complex and still not well established. In this study, we report the isolation of chemicals emitted by sexually mature individuals during the “calling” period and the electrophysiological responses that these compounds elicit on the antennae of male and female flies. Fifteen compounds with electrophysiological activity were isolated and identified in male emissions by gas chromatography coupled to electroantennography (GC–EAG). Within the group of 15 identified compounds, 11 elicited a response in antennae of both sexes, whilst 4 elicited a response only in female antennae. The binding affinity of these compounds, plus 4 additional compounds known to be behaviourally active from other studies, was measured using C. capitata OBP, CcapOBP83a-2. This OBP has a high homology to Drosophila melanogaster OBPs OS-E and OS-F, which are associated with trichoid sensilla and co-expressed with the well-studied Drosophila pheromone binding protein LUSH. The results provide evidence of involvement of CcapOBP83a-2 in the medfly's odorant perception and its wider specificity for (E,E)-α-farnesene, one of the five major compounds in medfly male pheromone emission. This represents the first step in the clarification of the C. capitata and pheromone reception pathway, and a starting point for further studies aimed towards the creation of new powerful attractants or repellents applicable in the actual control strategies
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