1,180 research outputs found
Transmission fiber chromatic dispersion dependence on temperature: implications on 40 Gb/s performance
In this letter we will evaluate the performance degradation of a 40 km high-speed (40 Gb/s) optical System, induced by optical fiber variations of the chromatic dispersion induced by temperature changes. The chromatic dispersion temperature sensitivity will be estimated based on the signal quality parameters
Análises fitoquímicas em extrato das folhas de Anthurium affine Schott (milho de urubu)
Apesar da ampla disposição de medicamentos no mercado, muitas dificuldades ainda existem quanto ao tratamento de determinados tipos de doenças, como é o caso das dermatites nos animais domésticos, mais especificamente nos cães. Apoiando-se na hipótese de que plantas da família das Araceae podem oferecer insumos importantes no tratamento deste tipo de doença, idealizou-se este trabalho tendo-se como principal objetivo estudar mais precisamente a composição fitoquímica do Anthurium affine Schott (A. affine), conhecido popularmente como “milho de urubu”. A partir de amostras da planta colhidas na Região Metropolitana do Grande Recife, foi confeccionado o extrato hidroalcóolico (etanol a 70%), das folhas da planta, sendo colocado para maceração por sete dias. A partir desta etapa o material foi submetido a procedimentos de filtragem e caracterização do extrato final obtido. Posteriormente, alíquotas deste material foram colhidas e trabalhadas para a realização dos ensaios de identificação fitoquímica, conforme protocolo padrão disponível na literatura. Como resultados, obteve-se um extrato hidroalcóolico da planta na concentração de 85 mg/mL; as análises fitoquímicas apresentaram resposta positiva para taninos, flavonóides, alcalóides e saponinas. Verificou-se que o A. affine apresentou um potencial fitoterápico mais rico do que normalmente se apresenta, embora estudos mais precisos sejam necessários para se avaliar os reais riscos de toxicidade no uso terapêutico da planta, como também para melhor definir os mecanismos de ação por traz dos efeitos farmacológicos atribuídos aos seus extratos
Structural phase transition in IrTe: A combined study of optical spectroscopy and band structure calculations
IrPtTe is an interesting system showing competing phenomenon
between structural instability and superconductivity. Due to the large atomic
numbers of Ir and Te, the spin-orbital coupling is expected to be strong in the
system which may lead to nonconventional superconductivity. We grew single
crystal samples of this system and investigated their electronic properties. In
particular, we performed optical spectroscopic measurements, in combination
with density function calculations, on the undoped compound IrTe in an
effort to elucidate the origin of the structural phase transition at 280 K. The
measurement revealed a dramatic reconstruction of band structure and a
significant reduction of conducting carriers below the phase transition. We
elaborate that the transition is not driven by the density wave type
instability but caused by the crystal field effect which further
splits/separates the energy levels of Te (p, p) and Te p bands.Comment: 16 pages, 5 figure
Improving the Creation of Hot Spot Policing Patrol Routes: Comparing Cognitive Heuristic Performance to an Automated Spatial Computation Approach
Hot spot policing involves the deployment of police patrols to places where high levels of crime have previously concentrated. The creation of patrol routes in these hot spots is mainly a manual process that involves using the results from an analysis of spatial patterns of crime to identify the areas and draw the routes that police officers are required to patrol. In this article we introduce a computational approach for automating the creation of hot spot policing patrol routes. The computational techniques we introduce created patrol routes that covered areas of higher levels of crime than an equivalent manual approach for creating hot spot policing patrol routes, and were more efficient in how they covered crime hot spots. Although the evidence on hot spot policing interventions shows they are effective in decreasing crime, the findings from the current research suggest that the impact of these interventions can potentially be greater when using the computational approaches that we introduce for creating hot spot policing patrol routes
Thermoelectric spin voltage in graphene
In recent years, new spin-dependent thermal effects have been discovered in
ferromagnets, stimulating a growing interest in spin caloritronics, a field
that exploits the interaction between spin and heat currents. Amongst the most
intriguing phenomena is the spin Seebeck effect, in which a thermal gradient
gives rise to spin currents that are detected through the inverse spin Hall
effect. Non-magnetic materials such as graphene are also relevant for spin
caloritronics, thanks to efficient spin transport, energy-dependent carrier
mobility and unique density of states. Here, we propose and demonstrate that a
carrier thermal gradient in a graphene lateral spin valve can lead to a large
increase of the spin voltage near to the graphene charge neutrality point. Such
an increase results from a thermoelectric spin voltage, which is analogous to
the voltage in a thermocouple and that can be enhanced by the presence of hot
carriers generated by an applied current. These results could prove crucial to
drive graphene spintronic devices and, in particular, to sustain pure spin
signals with thermal gradients and to tune the remote spin accumulation by
varying the spin-injection bias
Satisfaction with Life Scale among adolescents and young adults in Portugal: extending evidence of construct validity
The paper presents three empirical studies designed to extend the test of the
construct validity of the Satisfaction With Life Scale (SWLS) among Portuguese students.
In the first study, the responses of 461 elementary and secondary education students were
submitted to a principal component analysis. A solution of one single factor was chosen, accounting for 55.7 % of the total variance, with Cronbach alpha coefficient and inter-item correlation above .70 and .20, respectively. The second study used a sample of 317
undergraduate students and registered a similar factor solution for SWLS (/pq = 0.99), which accounted for 65.6 % of the total variance (Cronbach alpha .89 and inter-item correlation above .20). A test–retest analysis registered coefficients of .70 (T2) and .77 (T3) and no significant statistically differences between T2, T3 and T1. The third study used a sample of 107 foster care youths from elementary and secondary education. Confirmatory factor analysis results indicate adequate fit indexes for the one-factor solution (v2/df = 2.70, GFI = .96, CFI = .96), which showed convergent validity, reliability and homogeneity. In conclusion, there is psychometric evidence for the one-factor structure of the SWLS in Portugal.FCTCOMPET
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Pressure-induced Anderson-Mott transition in elemental tellurium
AbstractElemental tellurium is a small band-gap semiconductor, which is always p-doped due to the natural occurrence of vacancies. Its chiral non-centrosymmetric structure, characterized by helical chains arranged in a triangular lattice, and the presence of a spin-polarized Fermi surface, render tellurium a promising candidate for future applications. Here, we use a theoretical framework, appropriate for describing the corrections to conductivity from quantum interference effects, to show that a high-quality tellurium single crystal undergoes a quantum phase transition at low temperatures from an Anderson insulator to a correlated disordered metal at around 17 kbar. Such insulator-to-metal transition manifests itself in all measured physical quantities and their critical exponents are consistent with a scenario in which a pressure-induced Lifshitz transition shifts the Fermi level below the mobility edge, paving the way for a genuine Anderson-Mott transition. We conclude that previously puzzling quantum oscillation and transport measurements might be explained by a possible Anderson-Mott ground state and the observed phase transition.</jats:p
A molecular method for the detection of sally lightfoot crab larvae (Grapsus grapsus, Brachyura, Grapsidae) in plankton samples
The decapod Grapsus grapsus is commonly found on oceanic islands of the Pacific and Atlantic coasts of the Americas. In this study, a simple, quick and reliable method for detecting its larvae in plankton samples is described, which makes it ideal for large-scale studies of larval dispersal patterns in the species
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Results from on-the-ground efforts to promote sustainable cattle ranching in the Brazilian Amazon
Agriculture in Brazil is booming. Brazil has the world’s second largest cattle herd and is the second largest producer of soybeans, with the production of beef, soybeans, and bioethanol forecast to increase further. Questions remain, however, about how Brazil can reconcile increases in agricultural production with protection of its remaining natural vegetation. While high hopes have been placed on the potential for intensification of low-productivity cattle ranching to spare land for other agricultural uses, cattle productivity in the Amazon biome (29% of the Brazilian cattle herd) remains stubbornly low, and it is not clear how to realize theoretical productivity gains in practice. We provide results from six initiatives in the Brazilian Amazon, which are successfully improving cattle productivity in beef and dairy production on more than 500,000 hectares of pastureland, while supporting compliance with the Brazilian Forest Code. Spread across diverse geographies, and using a wide range of technologies, participating farms have improved productivity by 30-490%. High-productivity cattle ranching requires some initial investment (R410-2180/ha), with average pay-back times of 2.5-8.5 years. We conclude by reflecting on the challenges that must be overcome to scale up these young initiatives, avoid rebound increases in deforestation, and mainstream sustainable cattle ranching in the Amazon.E.K.H.J.zE was funded by BBSRC grant BB/J014540/1 and the Tim Whitmore 215 Trust Fund
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