Local habitat disturbance increases bird nest predation in the Brazilian Atlantic rainforest

La perturbación del hábitat local aumenta la depredación de nidos de aves en la pluviselva atlántica del Brasil Evaluamos los efectos de la perturbación antropógena en el bosque atlántico del Brasil. Se distribuyeron nidos artificiales en fragmentos con distintos grados de perturbación antropógena. Observamos una mayor proporción de depredación de huevos en el suelo y en los fragmentos clasificados como de perturbación alta y media que en los fragmentos con un bajo grado de perturbación. La mayor depredación de huevos está probablemente relacionada con una vegetación de complejidad estructural baja y con la elevada accesibilidad de estas zonas para depredadores oportunistas. Con vistas a mantener la biodiversidad de especies de aves, proponemos que se conserven los fragmentos forestales con vegetación de complejidad estructural elevada y escasa actividad humana.We evaluated the effect of anthropogenic disturbance on nest predation in Brazilian Atlantic forest. Artificial nests were distributed in fragments with distinct degrees of anthropogenic disturbance. We found a higher proportion of egg predation on the ground and in the fragments classified as ‘high’ and ‘medium’ disturbance than in the fragments classified as ‘low’ degree of disturbance. The higher egg predation is probably linked to low structural complexity of vegetation and high accessibility of these areas to opportunistic predators. We suggest that forest fragments with high vegetation complexity and low human activity should be preserved in order to maintain the biodiversity of bird species.La perturbación del hábitat local aumenta la depredación de nidos de aves en la pluviselva atlántica del Brasil Evaluamos los efectos de la perturbación antropógena en el bosque atlántico del Brasil. Se distribuyeron nidos artificiales en fragmentos con distintos grados de perturbación antropógena. Observamos una mayor proporción de depredación de huevos en el suelo y en los fragmentos clasificados como de perturbación alta y media que en los fragmentos con un bajo grado de perturbación. La mayor depredación de huevos está probablemente relacionada con una vegetación de complejidad estructural baja y con la elevada accesibilidad de estas zonas para depredadores oportunistas. Con vistas a mantener la biodiversidad de especies de aves, proponemos que se conserven los fragmentos forestales con vegetación de complejidad estructural elevada y escasa actividad humana

Upper bounds on success probabilities in linear optics

We develop an abstract way of defining linear-optics networks designed to perform quantum information tasks such as quantum gates. We will be mainly concerned with the nonlinear sign shift gate, but it will become obvious that all other gates can be treated in a similar manner. The abstract scheme is extremely well suited for analytical as well as numerical investigations since it reduces the number of parameters for a general setting. With that we show numerically and partially analytically for a wide class of states that the success probability of generating a nonlinear sign shift gate does not exceed 1/4 which to our knowledge is the strongest bound to date.Comment: 8 pages, typeset using RevTex4, 5 EPS figure

Noise Kernel in Stochastic Gravity and Stress Energy Bi-Tensor of Quantum Fields in Curved Spacetimes

The noise kernel is the vacuum expectation value of the (operator-valued) stress-energy bi-tensor which describes the fluctuations of a quantum field in curved spacetimes. It plays the role in stochastic semiclassical gravity based on the Einstein-Langevin equation similar to the expectation value of the stress-energy tensor in semiclassical gravity based on the semiclassical Einstein equation. According to the stochastic gravity program, this two point function (and by extension the higher order correlations in a hierarchy) of the stress energy tensor possesses precious statistical mechanical information of quantum fields in curved spacetime and, by the self-consistency required of Einstein's equation, provides a probe into the coherence properties of the gravity sector (as measured by the higher order correlation functions of gravitons) and the quantum nature of spacetime. It reflects the low and medium energy (referring to Planck energy as high energy) behavior of any viable theory of quantum gravity, including string theory. It is also useful for calculating quantum fluctuations of fields in modern theories of structure formation and for backreaction problems in cosmological and black holes spacetimes. We discuss the properties of this bi-tensor with the method of point-separation, and derive a regularized expression of the noise-kernel for a scalar field in general curved spacetimes. One collorary of our finding is that for a massless conformal field the trace of the noise kernel identically vanishes. We outline how the general framework and results derived here can be used for the calculation of noise kernels for Robertson-Walker and Schwarzschild spacetimes.Comment: 22 Pages, RevTeX; version accepted for publication in PR

Vacuum Energy Density Fluctuations in Minkowski and Casimir States via Smeared Quantum Fields and Point Separation

We present calculations of the variance of fluctuations and of the mean of the energy momentum tensor of a massless scalar field for the Minkowski and Casimir vacua as a function of an intrinsic scale defined by a smeared field or by point separation. We point out that contrary to prior claims, the ratio of variance to mean-squared being of the order unity is not necessarily a good criterion for measuring the invalidity of semiclassical gravity. For the Casimir topology we obtain expressions for the variance to mean-squared ratio as a function of the intrinsic scale (defined by a smeared field) compared to the extrinsic scale (defined by the separation of the plates, or the periodicity of space). Our results make it possible to identify the spatial extent where negative energy density prevails which could be useful for studying quantum field effects in worm holes and baby universe, and for examining the design feasibility of real-life `time-machines'. For the Minkowski vacuum we find that the ratio of the variance to the mean-squared, calculated from the coincidence limit, is identical to the value of the Casimir case at the same limit for spatial point separation while identical to the value of a hot flat space result with a temporal point-separation. We analyze the origin of divergences in the fluctuations of the energy density and discuss choices in formulating a procedure for their removal, thus raising new questions into the uniqueness and even the very meaning of regularization of the energy momentum tensor for quantum fields in curved or even flat spacetimes when spacetime is viewed as having an extended structure.Comment: 41 pages, 2 figure

FTIR spectroscopic and theoretical study of matrix-isolated (E)-1-(cyclopropyldiazenyl)naphthalen-2-ol

Photochromic systems are important due to their industrial applications in variable optical transmission materials and optobioelectronic devices. For such applications, the organic photochromic compounds involved are usually incorporated in polymers, liquid crystalline materials, or other convenient host matrices [1, 2]. Herein, a photochromic compound, (E)-1-(cyclopropyldiazenyl)naphthalen-2-ol (show in Figure 1), which was synthesized by a published method [3] and characterized, was isolated in a cryogenic argon matrix and its structure as well as UV-induced phototransformations were characterized by IR spectroscopy. The structures of the starting compound and of the generated photoproducts were identified by comparison of their experimental IR spectra with the spectra theoretically calculated at the DFT (B3LYP)/6-311++G(d,p) level for several possible tautomeric and rotameric forms.Fundação para a Ciência e a Tecnologia (FCT

Development of membranes with regions with different characteristics by phase inversion technique

Separation membrane cells comprising membrane sections with different characteristics can be thebase for new separation processes. Hybrid membrane cells require new membranes with regions withdifferent characteristics. In this paper we present numerical and experimental approaches to developsuch membranes by the phase inversion technique. The two main steps of the phase inversiontechnique, the evaporation step and the immersion precipitation step, are studied by numericalmethods. The numerical approach is based on the solution of the mass transport equation to predict thefilm composition after the evaporation step and in the solution of the CahnHilliard equations topredict the structure of the membrane after the immersion precipitation step. The equations are solvedby finite difference methods. The numerical simulations are used to predict the influence of severalexperimental parameters (temperature, composition of the initial polymeric solution, evaporation time,precipitation time, immersion bath composition) in the structure of the membrane. The experimentalapproach is based on the manipulation of the experimental conditions to produce regions of differentcharacteristics in the same membrane. An experimental method to create different regions from twodifferent initial polymeric solutions is presented

Advances in the genotyping of thrombosis genetic risk factors: clinical and laboratory implications.

Since FV-Leiden polymorphism was first described in 1994, a growing number of polymorphic loci have been identified in association with increased genetic risk for thrombophilia. Often however, these risk factors have been studied in isolation of the remaining known phenotype linked polymorphisms. This fact has, at least in part, been justified by the laborious techniques traditionally used in the genotyping studies, as well as its relatively high costs. Another major problem concerning these studies has been the non-negligible incidence of dubious genotypes, resulting from the manual, labour intensive techniques applied, and their sometimes difficult to read output's. These difficulties have also hampered the widespread use of genotyping data in the clinical assessment of the genetic risk levels both in patients and their relatives, leaving some clinicians less than convinced about its clinical usefulness. Recently however, the introduction of new genetic techniques in the clinical genetics laboratory has started to change this picture. Most notably, the advent of Real-time-PCR has brought the possibility of genotyping patients and controls at a large scale, with increased specificity, automation and speed. Moreover, the use of these techniques in the clinical genetics setting has not only increased the quality of the results, but most importantly has also increased our capability of answering questions at a deeper level. Among the new questions that can now be answered without increased costs and uncertainty is the study of the association of genetic risk factors in thrombophilia. Our results show that indeed even common polymorphic loci may increase our ability to further discriminate the genetic thrombosis risk of individual patients and relatives. It must however be noted that the innovation level in the clinical genetics lab is just starting to grow. In fact we haven't even started to experience the advantages brought about by the genome program, and its massive identification of SNP's. The technology to test these is also presently being refined, and is expected to go from research to the clinical lab in the near future. Only then, can we expect to define with high certainty the combined genetic risks for such complex pathologies as the thrombophilias