A selective conductive polymer-based sensor for volatile halogenated organic compounds (VHOC)

A novel poly(p-xylylene), PPX, derivative bearing alkoxyphenyl side groups was electrochemically synthesized in 87% yield. The polymer, poly(4`-hexyloxy-2,5-biphenyleneethylene) (PHBPE), presented a fraction (92%) soluble in common organic solvents. It showed to be thermally resistant up to 185 degrees C. UV-vis analysis revealed an E-gap of 3.5 eV Gas sensors made from thin films of 10-camphorsulfonic acid-doped PHBPE deposited on interdigitated electrodes exhibited significant changes in electrical conductance upon exposure to five VHOCs: 1,2-dichloroethane, bromochloromethane, trichloromethane, dichloromethane and tetrachloromethane. The conductance decreased after exposure to tetrachloromethane and increased after exposure to all the other VHOCs. Three-dimensional plots of relative response versus time of half response versus time of half recovery showed good discrimination between the five VHOCs tested. (c) 2008 Elsevier B.V. All rights reserved.

Absolute Configuration and Selective Trypanocidal Activity of Gaudichaudianic Acid Enantiomers

Gaudichaudianic acid, a prenylated chromene isolated from Piper gaudichaudianum, has been described as a potent trypanocidal compound against the Y-strain of Trypanosoma cruzi. We herein describe its isolation as a racemic mixture followed by enantiomeric resolution using chiral HPLC and determination of the absolute configuration of the enantiomers as (+)-S and (-)-R by means of a combination of electronic and vibrational circular dichroism using density functional theory calculations. Investigation of the EtOAc extract of the roots, stems, and leaves from both adult specimens and seedlings of P. gaudichaudianum revealed that gaudichaudianic acid is biosynthesized as a racemic mixture from the seedling stage onward. Moreover, gaudichaudianic acid was found exclusively in the roots of seedlings, while it is present in all organs of the adult plant. Trypanocidal assays indicated that the (+)-enantiomer was more active than its antipode. Interestingly, mixtures of enantiomers stowed a synergistic effect, with the racemic mixture being the most active.

Selective Allylic oxidation of Cyclohexene by a Magnetically Recoverable Cobalt Oxide Catalyst

In this work, we prepared a new magnetically recoverable CoO catalyst through the deposition of the catalytic active metal nanoparticles of 2-3 nm on silica-coated magnetite nanoparticles to facilitate the solid separation from liquid media. The catalyst was fully characterized and presented interesting properties in the oxidation of cyclohexene, as for example, selectivity to the allylic oxidation product. It was also observed that CoO is the most active species when compared to Co(2+), Co(3)O(4) and Fe(3)O(4) in the catalytic conditions studied.

Methylmercury localization in Danio rerio retina after trophic and subchronic exposure: A basis for neurotoxicology

Methylmercury is a known neurotoxic organometal which affects visual functions and few studies concerns to wild fish are available. The autometallography mercury distribution in the retina of Danio rerio was mapped using light and electron microscopy. Abundant mercury deposits were found in the photoreceptor layer (outer and inner segments of the photoreceptors) and in the inner and outer nuclear layers. Occasionally, the presence of mercury deposits in plexiform layers was observed and very rarely in the ganglion cell layer. Also the occurrence of mercury deposits in cells from the disc region was observed, but not in the nerve fiber layer. An interesting difference was found between mercury accumulation in the central and peripheral regions of the retina. These results demonstrate that mercury after trophic exposure to Danio rerio is able to cross the blood-retina barrier and accumulate in the cells of the retina even under subchronic exposure. (C) 2010 Elsevier Inc. All rights reserved.

Electrocatalytic behavior of glassy carbon electrodes modified with multiwalled carbon nanotubes and cobalt phthalocyanine for selective analysis of dopamine in presence of ascorbic acid

This work describes the development, electrochemical characterization and utilization of a cobalt phthalocyanine modified carbon nanotube electrode for the quantitative determination of dopamine in 0.2 mol L-1 phosphate buffer contaminated with high concentration of ascorbic acid. The electrode surface was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy which showed a modified surface presenting a charge transfer resistance of 500 Omega, against the 16.46 k Omega value found for the bare glassy carbon surface. A pseudo rate constant value of 5.4 x 10(-4) cm s(-1) for dopamine oxidation was calculated. Voltammetric experiments showed a shift of the peak potential of DA oxidation to less positive value at 390 mV as compared with that of a bare GC electrode at 570 mV. The electrochemical determination of dopamine, in presence of ascorbic acid in concentrations up to 0.1 mol L-1 by differential pulse voltarnmetry, yielded a detection limit as low as 2.56 x 10(-7) mol L-1.

Selective photoinactivation of C. albicans and C. dubliniensis with hypericin

The genus Candida includes different species that have the potential to invade and colonize the human body and C. albicans is the most common cause of skin, nail and mucous infections. The increasing resistance against antifungal drugs has renewed the search for new treatment procedures and antimicrobial photodynamic inactivation (PDI) is a propitious candidate. Hypericin (HY) has several wanted properties to be used as a photosensitizer in this technique including a high quantum yield of singlet oxygen generation, a high extinction coefficient near 600 nm, and a relatively low dark toxicity. Although the phototoxicity of HY on several tumor cells has been reported, the data concerning its photoactivity on microorganisms are scarce. The aim of this study was to obtain the experimental parameters to achieve an acceptable selective hypericinphotoinactivation of two species of Candida comparing with fibroblasts and epithelial cells which are the constituents of some potential host tissues, such mucosas, skin and cavities. Microorganisms and cells were incubated with the same HY concentrations and short incubation time followed by irradiation with equal dose of light. The best conditions to kill just Candida were very low HY concentration (0.1-0.4 mu g ml(-1)) incubated by 10 min and irradiated with LED 590 nm with 6 J cm(-2).

Development and Application of a Highly Selective Biomimetic Sensor for Detection of Captopril, an Important Ally in Hypertension Control

A biomimetic sensor is proposed as a promising new analytical method for determination of captopril in different classes of samples. The sensor was prepared by modifying a carbon paste electrode with iron (II) phthalocyanine bis(pyridine) [FePe(dipy)] complex. Amperometric measurements in a batch analytical mode were first carried out in order to optimize the sensor response. An applied potential lower than 0.2 V vs Ag vertical bar AgCl in 0.1 mol L(-1) of TRIS buffer at pH 8.0 provided the best response, with a linear range of 2.5 x 10(-5) to 1.7 x 10(-4) mol L(-1). A detailed investigation of the selectivity of the sensor, employing seventeen other drugs, was also performed. Recovery studies were carried out using biological and environment samples in order to evaluate the sensor`s potential for use with these sample classes. Finally, the performance of the biomimetic sensor was optimized in a flow injection (FIA) system using a wall jet electrochemical cell. Under optimized flow conditions, a broad linear response range, from 5.0 x 10(-4) to 2.5 x 10(-2) mol L(-1), was obtained for captopril, with a sensitivity of 210 +/- 1 mu A L mol(-1).

Fast separation of selective serotonin reuptake inhibitors antidepressants in plasma sample by nonaqueous capillary electrophoresis

A simple, fast, and sensitive liquid-liquid extraction method followed by nonaqueous capillary electrophoresis (LLE/NACE) was developed and validated for Simultaneous determination of four antidepressants (fluoxetine, sertraline, citalopram and paroxetine) in human plasma. Several experimental separation conditions using aqueous and nonaqueous media separation were tested by varying the electrolyte pH value (for aqueous medium) and the ionic strength concentration considering the similar mobility of the compounds. High-resolution separation was achieved with a mixture of 1.25 mol L(-1) of phosphoric acid in acetonitrile. The quantification limits of the LLE/CE method varied between 15 and 30 ng mL(-1), with a relative standard deviation (RSD) lower than 10.3%. The method was successfully applied in therapeutic drug monitoring and should be employed in the evaluation of plasma levels in urgent toxicological analysis. (C) 2009 Elsevier B.V. All rights reserved.

Immobilized analogues of sunflower trypsin inhibitor-1 constitute a versatile group of affinity sorbents for selective isolation of serine proteases

Sunflower trypsin inhibitor-1 (SFI-1), a natural 14-residue cyclic peptide, and some of its synthetic acyclic variants are potent protease inhibitors displaying peculiar inhibitory profiles. Here we describe the synthesis and use of affinity sorbents prepared by coupling SFTI-1 analogues to agarose resin. Chymotrypsinand trypsin-like proteases could then be selectively isolated from pancreatin; similarly, other proteases were obtained from distinct biological sources. The binding capacity of [Lys5]-SFTI-1-agarose for trypsin was estimated at over 10 mg/mL of packed gel. SFTI-1-based resins could find application either to improve the performance of current purification protocols or as novel protease-discovery tools in different areas of biological investigation. (C) 2009 Elsevier B.V. All rights reserved.

Face Detection and Facial Feature Localization for multi-pose faces and complex backgroundimages

The objective of this thesis work, is to propose an algorithm to detect the faces in a digital image with complex background. A lot of work has already been done in the area of face detection, but drawback of some face detection algorithms is the lack of ability to detect faces with closed eyes and open mouth. Thus facial features form an important basis for detection. The current thesis work focuses on detection of faces based on facial objects. The procedure is composed of three different phases: segmentation phase, filtering phase and localization phase. In segmentation phase, the algorithm utilizes color segmentation to isolate human skin color based on its chrominance properties. In filtering phase, Minkowski addition based object removal (Morphological operations) has been used to remove the non-skin regions. In the last phase, Image Processing and Computer Vision methods have been used to find the existence of facial components in the skin regions.This method is effective on detecting a face region with closed eyes, open mouth and a half profile face. The experiment’s results demonstrated that the detection accuracy is around 85.4% and the detection speed is faster when compared to neural network method and other techniques.

Localization in splitting of matter waves

In this paper we present an analysis of how matter waves, guided as propagating modes in potential structures, are split under adiabatic conditions. The description is formulated in terms of localized states obtained through a unitary transformation acting on the mode functions. The mathematical framework results in coupled propagation equations that are decoupled in the asymptotic regions as well before as after the split. The resulting states have the advantage of describing propagation in situations, for instance matter-wave interferometers, where local perturbations make the transverse modes of the guiding potential unsuitable as a basis. The different regimes of validity of adiabatic propagation schemes based on localized versus delocalized basis states are also outlined. Nontrivial dynamics for superposition states propagating through split potential structures is investigated through numerical simulations. For superposition states the influence of longitudinal wave-packet extension on the localization is investigated and shown to be accurately described in quantitative terms using the adiabatic formulations presented here.

From the road network database to a graph for localization purposes

The problems of finding best facility locations require complete and accurate road network with the corresponding population data in a specific area. However the data obtained in road network databases usually do not fit in this usage. In this paper we propose our procedure of converting the road network database to a road graph which could be used in localization problems. The road network data come from the National road data base in Sweden. The graph derived is cleaned, and reduced to a suitable level for localization problems. The population points are also processed in ordered to match with that graph. The reduction of the graph is done maintaining most of the accuracy for distance measures in the network.

Gravitational self-localization for spherical masses

In this work, I consider the center-of-mass wave function for a homogenous sphere under the influence of the self-interaction due to Newtonian gravity. I solve for the ground state numerically and calculate the average radius as a measure of its size. For small masses, M≲10−17 kg, the radial size is independent of density, and the ground state extends beyond the extent of the sphere. For masses larger than this, the ground state is contained within the sphere and to a good approximation given by the solution for an effective radial harmonic-oscillator potential. This work thus determines the limits of applicability of the point-mass Newton Schrödinger equations for spherical masses. In addition, I calculate the fringe visibility for matter-wave interferometry and find that in the low-mass case, interferometry can in principle be performed, whereas for the latter case, it becomes impossible. Based on this, I discuss this transition as a possible boundary for the quantum-classical crossover, independent of the usually evoked environmental decoherence. The two regimes meet at sphere sizes R≈10−7 m, and the density of the material causes only minor variations in this value.

Selective Synthesis of Oxacalix[6]arenes and Mixed Oxacalix[4]arenes

Calixarenesare macrocycles composed of benzene rings meta linked to each other by one carbon atom. These exotic compounds can be used for a variety of purposes including metalleaching for environmental cleanup, surface technology, luminescent probes, nuclear waste treatment, among others. A variety of calixarenesexist, including azacalix[n]arenesthiocalix[n]arenes(where n = the number of benzene rings) and oxacalix[n]arenes; these macrocycles use nitrogen, sulfur and oxygen, respectively, as the atom whichlinks the benzene rings together. My research has focused on synthesizing oxacalix[6]arenes (“hexamer”) in high yield, which is a synthetic challenge because it is generally accepted that oxacalix[n>4]arenes will thermodynamically decompose to the oxacalix[4]arene (“tetramer”); i.e. heating the reaction mixture will yield the tetramer, not the hexamer. To generate the hexamer, “trimer”precursors have been synthesized, in the hopes of facilitating hexamer ring closure.