Lensless acousto-optical convolver

A lensless acousto-optical convolver has been realised with surface acoustic waves, which relies on a technique of polarisation discrimination detection of the diffracted light. A polariser may, then, filter the light signal directly in the Fresnel field, thus allowing realisation of a strictly compact device that retains properties of easy adjustment and simplicity.     

Optimized spinning design for low PMD fibers: an analyticalapproach

It is known that the differential group delay (DGD) due to polarization mode dispersion (PMD) can be effectively reduced by spinning the fiber during drawing. In this paper, we propose an analytical approach that allows optimization of the spinning design. The fundamental idea is that, in the absence of polarization coupling, an optimized spinning profile can balance the effects of the intrinsic linear birefringence so that the differential group delay can be forced to be periodic and, consequently, have a limited amplitude as a function of distance. Our approach Is independent of the spin profile. In other words, with a fixed set of parameters that characterize a particular spin function, we are able to find analytically the values corresponding to a periodic DGD in a deterministic regime. Numerical results based on waveplate model confirm the analytical prediction and show that PMD can be reduced by about two orders of magnitude with respect to the same fiber without spinning, even after the introduction of random polarization coupling     

Molecular features of sulfonic acids used for synthesis of overbased detergent additives

Overbased calcium sulfonates are used in many modern oil formulations to provide cleaning action and to neutralize the organic acids formed during combustion, preventing corrosion. The performance of detergents is related to their molecular structure, which is generally known only as a chemical category. In the present work, nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization mass spectrometry are used to analyze the molecular structure of three alkyl‐benzene sulfonic acids in detail. Some important molecular features were obtained by elaborating the NMR signal intensities, such as the number and positions of alkyl substituents on the benzene ring, the distribution of alkyl chain lengths and the mole fraction of 1‐phenyl isomers (synthesized by alkylation of benzene with α‐olefin). Ion‐trap mass spectrometry is used to obtain the mass spectrometry/mass spectrometry (MS²) spectra of the principal molecular ions. By choosing suitable molecular ions, MS² spectra can ascertain the presence of different substituted benzene isomers within a mixture because the MS² spectra show specific fragments due to the number of alkyl substituents on the aromatic ring. Copyright © 2006 John Wiley & Sons, Ltd.     

Lichens and moss as bioindicators and bioaccumulators in air pollution monitoring

In this study, we review research conducted in the La Spezia district during 1989, 1992, and 1994, using lichens and moss as indicators of air pollution. SO2 pollution was examined by means of an Index of Atmospheric Purity (IAP) based on the frequency of epiphytic lichen within a sampling grid. Metal deposits were estimated using the lichen Parmelia caperata and the moss Hypnum cupressiforme as bioaccumulators. IAP maps show progressive air quality improvement from 1989 to 1994. This trend correlates to a decrease in SO2 emissions during recent years that is attributed to the use of methane for residential heating and the closing of a coal-fired power plant. Metal contamination maps show that the most polluted area is now in the southeastern part of the gulf. The pattern of pollution coincides with the location of the chief pollution sources in the area. From 1989 to 1994, the metal concentrations in lichens decreased, but metal deposits in the southeastern area were cause for concern. High concentrations of lead in the area are related to emissions from a waste incinerator and a plant that produces lead oxide. Epidemiological investigations reveal that the area population has the highest levels of lead in their blood. The use of bioindicators and bioaccumulators permits long-term and large-scale monitoring of environmental pollutant levels in full agreement with traditional methods.     

Comments on “Theoretical analysis of evolutionary algorithmswith an infinite population size in continuous space. I. Basicproperties of selection and mutation” [and reply]

In this paper, Gao points out two crucial errors in the proof of the theorem on the convergence of genetic algorithms (GAs) in the above paper by Qi-Palmieri (ibid., vol.5 (1994)). He presents two counter examples and comments that the errors may cause misleading on the convergence nature of GAs. He demonstrates that the sequence of mutation probabilities that increases the probability mass of the average set does not necessarily increase the mean fitness. In reply, Qi-Palmieri points out that the Theorem 3 simply states that it is possible to find a sequence of mutation densities that still guarantees convergence. The proof of Theorem 3 may be incomplete, but the result is unquestionably solid. They conclude that Gao's counterexamples may not add much insight into the nature of the problem, and they would rather encourage constructive contributions to the difficult, still open problems of the evolutionary paradigm.     

Nitric Oxide Modulates Metabolic Processes in the Tumor Immune Microenvironment

The metabolic requirements and functions of cancer and normal tissues are vastly different. Due to the rapid growth of cancer cells in the tumor microenvironment, distorted vasculature is commonly observed, which creates harsh environments that require rigorous and constantly evolving cellular adaption. A common hallmark of aggressive and therapeutically resistant tumors is hypoxia and hypoxia-induced stress markers. However, recent studies have identified alterations in a wide spectrum of metabolic pathways that dictate tumor behavior and response to therapy. Accordingly, it is becoming clear that metabolic processes are not uniform throughout the tumor microenvironment. Metabolic processes differ and are cell type specific where various factors promote metabolic heterogeneity within the tumor microenvironment. Furthermore, within the tumor, these metabolically distinct cell types can organize to form cellular neighborhoods that serve to establish a pro-tumor milieu in which distant and spatially distinct cellular neighborhoods can communicate via signaling metabolites from stroma, immune and tumor cells. In this review, we will discuss how biochemical interactions of various metabolic pathways influence cancer and immune microenvironments, as well as associated mechanisms that lead to good or poor clinical outcomes.     

Solvent‐Free Non‐Covalent Organocatalysis: Enantioselective Addition of Nitroalkanes to Alkylideneindolenines as a Flexible Gateway to Optically Active Tryptamine Derivatives

A catalytic asymmetric addition of nitroalkanes to alkylideneindolenines, generated in situ from arylsulfonylindoles, is presented. Despite the weakness of the non‐covalent H‐bond interactions between catalyst and substrates, the performance of the bifunctional organocatalyst used was found to be essentially unaffected by the polarity of the reaction medium. Nitroalkanes, mostly used in nearly stoichiometric amounts, could thus function both as solvents and reagents, resulting in a truly solvent‐free reaction. The broad substrate scope shown by the present transformation allowed the preparation of some optically active tryptamine precursors that are not accessible through the previous catalytic asymmetric methods.