Aurones: A Golden Resource for Active Compounds

Deemed as poorly represented in nature, aurones have been often overlooked by researchers compared to other members of the flavonoid superfamily. However, over the past two decades, they have been reassessed by the scientific community, who are increasingly appreciating their ability to modulate several biological pathways. This review summarizes the recent literature on this class of compounds, which has been analyzed from both a chemical and a functional point of view. Original articles, reviews and editorials featured in Pubmed and Scifinder over the last twenty years have been taken into account to provide the readers with a view of the chemical strategies to obtain them, their functional properties, and their potential of technological use. The resulting comprehensive picture aims at raising the awareness of these natural derivatives as effective drug candidates, fostering the development of novel synthetic analogues.     

Characteristic ratio of the mean-square end-to-end distance of poly(vinylidene fluoride) with microstructural defects

The segment length distribution of isoregic head-to-head and tail-to-tail sequences in poly-(vinylidene fluoride) (PVF₂)

1 System. name: poly(1,1-difluoroethylene).

chains is calculated from ¹⁹F NMR literature data. It is found that the average length of inverse segments is very close to one unit; therefore almost all head-to-head defects are immediately repaired by an adjacent tail-to-tail addition. The role of microstructure on the characteristic ratio of the end-to-end distance is then investigated. Results obtained by two different methods indicate that, in agreement with previous Monte Carlo calculations, defects play a minor role for the conformational characteristics of PVF₂. However, a slight contraction of about 4% is expected for very defective chains.     

Time-dependent observables and diabatic curve crossing: a model study

We study the diabatic crossing of two electronic surfaces from the time-dependent point of view, looking at the time and frequency-resolved spontaneous emission spectra and to the total population of the excited state, which for a pump and-probe experiment with two δ-like pulses, is proportional to the total emission. The results of some computations on a model case are presented and discussed.     

Measuring the 13C/12C isotope ratio in atmospheric CO2 by means of laser absorption spectrometry: a new perspective based on a 2.05-microm diode laser

The potential use of high sensitivity laser absorption spectroscopy for measuring the 13C/12C isotope ratio in atmospheric CO2 has been demonstrated, using a GaSb-based diode laser at 2.05 microm. In this spectral region, the overlapping between relatively strong 12CO2 and 13CO2 absorption features gives rise to several line pairs which are well suitable for a spectroscopic determination of the isotope ratio. Preliminary results have demonstrated that a short-term precision better than 1 per thousand can be easily obtained, for a CO2 concentration of 1000 ppm. We extensively discuss the influence of a possible non-linearity in the detectors' response on the delta-value and suggest an instrumental development that would allow to eliminate this effect.     

Dimensional Reduction Over the Quantum Sphere and Non-Abelian q-Vortices

We extend equivariant dimensional reduction techniques to the case of quantum spaces which are the product of a K?hler manifold M with the quantum two-sphere. We work out the reduction of bundles which are equivariant under the natural action of the quantum group SU _q (2), and also of invariant gauge connections on these bundles. The reduction of Yang–Mills gauge theory on the product space leads to a q-deformation of the usual quiver gauge theories on M. We formulate generalized instanton equations on the quantum space and show that they correspond to q-deformations of the usual holomorphic quiver chain vortex equations on M. We study some topological stability conditions for the existence of solutions to these equations, and demonstrate that the corresponding vacuum moduli spaces are generally better behaved than their undeformed counterparts, but much more constrained by the q-deformation. We work out several explicit examples, including new examples of non-abelian vortices on Riemann surfaces, and q-deformations of instantons whose moduli spaces admit the standard hyper-K?hler quotient construction.     

Phase shifting photoelasticity in white light

The availability of image acquisition systems has led to the development of digital photoelasticity both in monochromatic and white light. In particular white light has been used mainly with the following methods: Spectral Content Analysis, RGB photoelasticity and phase shifting photoelasticity. Phase shifting photoelasticity in the colour domain has been used effectively for the determination of the isoclinic parameter in order to reduce the influence of the isochromatic fringes. The method has been also proposed for the determination of the isochromatic fringe order. This paper concerns the general characteristics of phase shifting photoelasticity in the colour domain. Special attention is drawn towards the influence of spectral content of the light source, the spectral response of the colour camera filters, the dispersion of the birefringence and the error of quarter wave plates.     

Higher-order Poincaré sphere, stokes parameters, and the angular momentum of light

A higher-order Poincaré sphere and Stokes parameter representation of the higher-order states of polarization of vector vortex beams that includes radial and azimuthal polarized cylindrical vector beams is presented. The higher-order Poincaré sphere is constructed by naturally extending the Jones vector basis of plane wave polarization in terms of optical spin angular momentum to the total optical angular momentum that includes higher dimensional orbital angular momentum. The salient properties of this representation are illustrated by its ability to describe the higher-order modes of optical fiber waveguides, more exotic vector beams, and a higher-order Pancharatnam-Berry geometric phase.     

Point approximation of a space-homogeneous transport equation

Summary We present an approximation method of a space-homogeneous transport equation which we prove is convergent. The method is very promising for numerical computation. Comparison of a numerical computation with an exact solution is given for the Master equation.