Flowing liquid crystal simulating the Schwarzschild metric

We show how to simulate the equatorial section of the Schwarzschild metric through a flowing liquid crystal in its nematic phase. Inside a liquid crystal in the nematic phase, a traveling light ray feels an effective metric, whose properties are linked to perpendicular and parallel refractive indexes, n _o and n _e respectively, of the rod-like molecule of the liquid crystal. As these indexes depend on the scalar order parameter of the liquid crystal, the Beris-Edwards hydrodynamic theory is used to connect the order parameter with the velocity of a liquid crystal flow at each point. This way we calculate a radial velocity profile that simulates the equatorial section of the Schwarzschild metric, in the region outside of Schwarzschild’s radius, in the nematic phase of the liquid crystal. In our model, the higher flow velocity can be on the order of some meters per second.     

Bioreduction of β-carboline imines to amines employing Saccharomyces bayanus

β-Carboline imine reductions mediated by Saccharomyces bayanus have been described achieving moderate to good enantiomeric excesses of the amine products. The enantiomeric excesses of the bioreduction showed a dependence on the imine substituents. Compounds presenting C₁–C₁₁ aliphatic substituent groups afforded amines with an (S)-configuration, whereas C₁₅ and higher aliphatic- and aromatic-substituted β-carboline imines achieved inversion of the configuration in the final (R)-2 amine products. Based on this data, a model for the Saccharomyces reduction is proposed.     

Cadmium determination in biological samples by direct solid sampling flame atomic absorption spectrometry

A direct solid sampling flame atomic absorption spectrometric procedure for trace determination of cadmium in biological samples has been developed. Test samples (0.05–2.00 mg) were ground and weighed into small polyethylene vials, which were connected to the device for solid sample introduction into a conventional air/acetylene flame. Test samples were carried as a dry aerosol to a quartz cell, placed between the burner and the optical path, which had a perpendicular entrance and a slit in the upper part. The atomic vapor generated in the flame produced a transient signal that was totally integrated within 1 s. The effect of operating conditions and the extent of grinding on the analytical signal were evaluated. Background signals were always low and a characteristic mass of 0.29 ng Cd was obtained. Calibration was performed using different masses of solid certified reference materials. Results obtained for certified and in-house reference materials were typically within the 95% confidence interval of the certified and/or reference value, and the precision, expressed as relative standard deviation, was between 3.8 and 6.7%. The proposed system is simple and it might be adapted to conventional atomic absorption spectrometers allowing the determination of Cd in more than 80 test samples per hour, excluding weighing.     

Nonvisual Opsins and the Regulation of Peripheral Clocks by Light and Hormones

The molecular clock machinery is conserved throughout evolution. However, how environmental cues are perceived has evolved in such a way that peripheral clocks in mammals require a variety of signals, including hormones. On the other hand, in nonmammalian cells able to directly detect light, light seems to play a major role in the synchronization of the clock. The interaction between perception of circadian light by nonvisual opsins and hormones will be discussed under the perspective of clock synchronization at the molecular level.     

Capillary electrophoresis and hollow fiber liquid-phase microextraction for the enantioselective determination of albendazole sulfoxide after biotransformation of albendazole by an endophytic fungus

Hollow fiber liquid-phase microextraction and CE were applied for the determination of albendazole sulfoxide (ASOX) enantiomers in liquid culture medium after a fungal biotransformation study. The analytes were extracted from 1 mL of liquid culture medium spiked with the internal standard (rac-hydroxychloroquine) and buffered with 0.50 mol/L phosphate buffer, pH 10. The analytes were extracted into 1-octanol impregnated in the pores of the hollow fiber, and into an acid acceptor solution inside the polypropylene hollow fiber. The electrophoretic separations were carried out in 0.05 mol/L tris(hydroxymethyl)aminomethane buffer, pH 9.3, containing 3.0% w/v sulfated-β-CD (S-β-CD) with a constant voltage of +15 kV and detection at 220 nm. The method was linear over the concentration range of 250-5000 ng/mL for each ASOX enantiomer. Within-day and between-day assay precision and accuracy for the analytes were studied at three concentration levels and the values of RSD% and relative error % were lower than 15%. The developed method was applied for the determination of ASOX after a biotransformation study employing the endophytic fungus Penicillium crustosum (VR4). This study showed that the endophytic fungus was able to metabolize the albendazole to ASOX enantioselectively. In addition, it was demonstrated that hollow fiber liquid-phase microextraction coupled to CE can be an excellent and environmentally friendly technique for the analysis of samples obtained in biotransformation studies.     

Information visualization techniques for sensing and biosensing

The development of new methods and concepts to visualize massive amounts of data holds the promise to revolutionize the way scientific results are analyzed, especially when tasks such as classification and clustering are involved, as in the case of sensing and biosensing. In this paper we employ a suite of software tools, referred to as PEx-Sensors, through which projection techniques are used to analyze electrical impedance spectroscopy data in electronic tongues and related sensors. The possibility of treating high dimension datasets with PEx-Sensors is advantageous because the whole impedance vs. frequency curves obtained with various sensing units and for a variety of samples can be analyzed at once. It will be shown that non-linear projection techniques such as Sammon's Mapping or IDMAP provide higher distinction ability than linear methods for sensor arrays containing units capable of molecular recognition, apparently because these techniques are able to capture the cooperative response owing to specific interactions between the sensing unit material and the analyte. In addition to allowing for a higher sensitivity and selectivity, the use of PEx-Sensors permits the identification of the major contributors for the distinguishing ability of sensing units and of the optimized frequency range. The latter will be illustrated with sensing units made with layer-by-layer (LbL) films to detect phytic acid, whose capacitance data were visualized with Parallel Coordinates. Significantly, the implementation of PEx-Sensors was conceived so as to handle any type of sensor based on any type of principle of detection, representing therefore a generic platform for treating large amounts of data for sensors and biosensors.     

Algebras of holomorphic mappings in (DF)-spaces

Let U be an absolutely convex open subset of a complex barrelled (DF)-space E and let F be a commutative Banach algebra with identity. Let H_b(U, F) be the space of holomorphic mappings from U into F that are bounded on the U-bounded sets and let H_b (U, F) be the space of the holomorphic mappings from U into F that are uniformly weakly continuous on the U-bounded sets, both endowed with the topology τ_b of uniform convergence on the U-bounded sets. The spectra of (H_wu (U, F), τ_b) and (H_b(U, F), τ_b) are studied.     

Self-interaction in the von Kármán cosmic string street configuration

We study the problem of electromagnetic self-interaction of line sources in the presence of an array of parallel cosmic strings akin to the von Kármán vortex street configuration. Keeping in mind possible applications in condensed matter physics we consider also a mixed array where both deficit angle and excess angle cosmic strings appear. We obtain explicit expressions for both the electric and magnetic self-energies for the cases studied and demonstrate that these results reproduce the known self-energies in the single-string limit.