Evidence of polariton induced transparency in a single organic quantum wire

The resonant interaction between quasi-one dimensional excitons and photons is investigated. For a single isolated organic quantum wire, embedded in its single crystal monomer matrix, the strong exciton-photon coupling regime is reached. This is evidenced by the suppression of the resonant excitonic absorption arising when the system eigenstate is a polariton. These observations demonstrate that the resonant excitonic absorption in a semiconductor can be understood in terms of a balance between the exciton coherence time and the Rabi period between exciton-like and photon-like states of the polariton.Comment: 9 pages and 4 figure

Factors influencing plasma amino acids in calves

International audienc

SAT based Enforcement of Domotic Effects in Smart Environments

The emergence of economically viable and efficient sensor technology provided impetus to the development of smart devices (or appliances). Modern smart environments are equipped with a multitude of smart devices and sensors, aimed at delivering intelligent services to the users of smart environments. The presence of these diverse smart devices has raised a major problem of managing environments. A rising solution to the problem is the modeling of user goals and intentions, and then interacting with the environments using user defined goals. `Domotic Effects' is a user goal modeling framework, which provides Ambient Intelligence (AmI) designers and integrators with an abstract layer that enables the definition of generic goals in a smart environment, in a declarative way, which can be used to design and develop intelligent applications. The high-level nature of domotic effects also allows the residents to program their personal space as they see fit: they can define different achievement criteria for a particular generic goal, e.g., by defining a combination of devices having some particular states, by using domain-specific custom operators. This paper describes an approach for the automatic enforcement of domotic effects in case of the Boolean application domain, suitable for intelligent monitoring and control in domotic environments. Effect enforcement is the ability to determine device configurations that can achieve a set of generic goals (domotic effects). The paper also presents an architecture to implement the enforcement of Boolean domotic effects, and results obtained from carried out experiments prove the feasibility of the proposed approach and highlight the responsiveness of the implemented effect enforcement architectur

Component identification through program slicing

This paper reports on the development of specific slicing techniques for functional programs and their use for the identification of possible coherent components from monolithic code. An associated tool is also introduced. This piece of research is part of a broader project on program understanding and re-engineering of legacy code supported by formal methodsFundação para a Ciência e a Tecnologia (FCT) - POSI/ICHS/44304/2002, in the context of the PURe project

LDA+Gutzwiller Method for Correlated Electron Systems

Combining the density functional theory (DFT) and the Gutzwiller variational approach, a LDA+Gutzwiller method is developed to treat the correlated electron systems from {\it ab-initio}. All variational parameters are self-consistently determined from total energy minimization. The method is computationally cheaper, yet the quasi-particle spectrum is well described through kinetic energy renormalization. It can be applied equally to the systems from weakly correlated metals to strongly correlated insulators. The calculated results for SrVO$_3$, Fe, Ni and NiO, show dramatic improvement over LDA and LDA+U.Comment: 4 pages, 3 figures, 1 tabl

Interspecific differences in root foraging precision cannot be directly inferred from species' mycorrhizal status or fine root economics

Nutrient acquisition in plants can be represented by a suite of intercorrelated root traits such as root diameter, nitrogen content, root tissue density and specific root length. However, it is unclear how a plant's ability to precisely forage for nutrients in a heterogeneous soil environment (i.e. the precision of placing roots into nutrient-rich areas) relates to these traits. Mycorrhizal symbiosis also affects the relationship between the fine root traits and root foraging precision because fungal hyphae may be used for foraging instead of roots. Hypotheses matching high root foraging precision with low mycorrhizal colonization or ‘fast' acquisitive strategies of plants have been raised based either on data from tree species or a limited number of herbaceous species. To test these hypotheses, we compiled data quantifying the experimentally measured degree to which root biomass responded to patchy substrate nutrient concentrations (i.e. root foraging precision) for 123 herbaceous grassland species using a partial meta-analysis. We tested root foraging precision relationship with root traits involved in nutrient acquisition and mycorrhizal symbiosis (root diameter, specific root length, root tissue density, root tissue nitrogen content and mycorrhizal colonization). The root foraging precision data came from four different pot experiments, and the trait data were extracted from publicly available trait databases. We used a phylogenetically informed approach in order to detect the degree of conservation of the relationships. We found that root foraging precision was not significantly correlated with other fine root traits and mycorrhizal colonization. Thus, it appears unrelated to the main dimensions of the nutrient acquisition space of herbaceous species, namely acquisitive–conservative strategy and outsourcing of acquisition to the fungi. Also, we found only a very weak phylogenetic signal in root foraging precision of 123 species. Our results suggest that root foraging precision constitutes another distinct, evolutionarily independent dimension in herbaceous species' trait space.acceptedVersio

Multiple Parton Interactions, top--antitop and W+4j production at the LHC

The expected rate for Multiple Parton Interactions (MPI) at the LHC is large. This requires an estimate of their impact on all measurement foreseen at the LHC while opening unprecendented opportunities for a detailed study of these phenomena. In this paper we examine the MPI background to top-antitop production, in the semileptonic channel, in the early phase of data taking when the full power of $b$--tagging will not be available. The MPI background turns out to be small but non negligible, of the order of 20% of the background provided by W+4j production through a Single Parton Interaction. We then analyze the possibility of studying Multiple Parton Interactions in the W+4j channel, a far more complicated setting than the reactions examined at lower energies. The MPI contribution turns out to be dominated by final states with two energetic jets which balance in transverse momentum, and it appears possible, thanks to the good angular resolution of ATLAS and CMS, to separate the Multiple Parton Interactions contribution from Single Parton Interaction processes. The large cross section for two jet production suggests that also Triple Parton Interactions (TPI) could provide a non negligible contribution. Our preliminary analysis suggests that it might be indeed possible to investigate TPI at the LHC.Comment: Typos fixed. Published in JHE

Morphological Abnormalities in Vitamin B6 Deficient Tarsometatarsal Chick Cartilage

The aim of this study was to test the hypothesis that deficiency of vitamin B6 would produce morphological characteristics of osteochondral lathyrism. To accomplish this goal, morphological characteristics of chick cartilage in which lathyrism was produced by two separate dietary regimens was compared to morphological changes encountered in vitamin B6 deficiency. Vitamin B6 deficiency should reduce activity of lysyloxidase needed for producing intermolecular cross-links. The question to be addressed was: would this latter deficiency impair collagen morphological features and secondarily other structures indirectly by reducing collagen molecular assembly? Failure of cross-linking of collagen in the positive controls was related to a lack of functional aldehyde cross-link intermediates which are blocked by homocysteine and aminoacetonitrile. Day-old-male Lohmann chicks were fed adequate (6 mg/kg) or vitamin B6-deficient diets. Cross-link defects were induced by homocysteine-rich diets (0.6% w/w) or a diet containing aminoacetonitrile (0.1% w/w). Animals were sacrificed at 6 weeks of age and Ossa tarsalia articular cartilage specimens, as well as the proximal end of tarsometatarsus were dissected from the tibial metatarsal joint, a major weight-bearing site. Light microscopic observations revealed reduction of subarticular trabecular bone formation, concurrent with overexpansion of the hypertrophic cell zone. Ultrastructural electron microscopy observations of articular fibro-cartilage indicated significant thickening of collagen fibers in vitamin B6 deficient birds, as well as the positive controls in comparison to that of cage-matched control birds. It was concluded that vitamin B6 deficient cross-linking may be responsible for the observed delay in bone development and aforementioned cartilage histological alterations