Study of the complexation of Cu(II) by fulvic acids extracted from a sewage sludge and its compost

 The complexation of Cu(II) by two samples of fulvic acids (FA) extracted from the raw sewage sludge (RsFA) of a waste water processing plant and from the composted sludge (CsFA) obtained upon aerobical digestion was studied at pH 6.0. Synchronous molecular fluorescence spectroscopy was used to monitor the association of FA with Cu(II) and a self-modelling mixture analysis method (SIMPLISMA) was used to preprocess the spectral data to calculate the number of components with different quenching profiles as function of the Cu(II) concentration and their spectra. The stability constants and a rough estimation of the binding site concentrations were obtained by a Stern-Volmer analysis, by a non-linear least-square method and by a linear procedure. The analysis of the SyF spectra allowed the identification of two binding sites for both samples. The logarithm of the conditional stability constant corresponding to the 1:1 complex formed between the stronger binding site and Cu(II) is about 4 for both samples. Received: 22 April 1996 / Revised: 5 August 1996 / Accepted: 7 August 1996     

Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO2‐Supported Ziegler–Natta Catalyst

The very early stages of gas‐phase ethylene polymerization on an SiO₂‐supported Ziegler–Natta catalyst were studied with the help of a short‐stop reactor. The short‐stop‐reactor‐based technique was useful in studying nascent polymerization, providing insights at very short, controlled times into important phenomena regarding catalyst fragmentation and the activation and deactivation of catalyst sites that take place during the very early stages of the reaction. Experimental results indicate that the growth of the polymer chains occurs at unsteady conditions during the initial stages of the polymerization. Hydrogen has a strong influence on the initial kinetics, leading to a significant decrease of polymerization activity. Polymer crystallinity increases with the reaction time, probably due to the formation of long chains with a high degree of crystallinity.

     

Positron annihilation study of pore size in ordered SBA-15

Ordered mesoporous materials such as SBA-15 possess a network of channels and pores with a well-defined size in the nanoscale range (2–50 nm). This particular pore architecture makes them suitable candidates for a variety of applications. Different techniques have been used to measure pore diameters. PALS (positron annihilation lifetime spectroscopy) nanoprobe has been used to investigate free volume in several materials, including mesoporous silica. PALS can be used to find out if the micropore and mesopore structures of samples prepared under different experimental conditions are different. Indeed, considering that the pores present a cylindrical shape, an equation was developed that uses specific pore volumes, theoretical density, and specific surface measurements to evaluate structural connectivity. Our goal is to determine the influence of aging temperature on the porous structure of SBA-15 samples. The structural evolution was studied by PALS, small-angle X-ray (SAXS), N₂ adsorption desorption isotherms and computational modeling to evaluate connectivity. The variation of aging temperature changes the pore structure, indicating the presence of micropores and connections between mesopores. Materials aged at high temperatures present the lowest microporosity.     

Preparation of calcium alginate nanoparticles using water-in-oil (W/O) nanoemulsions

A procedure for the preparation of calcium alginate nanoparticles in the aqueous phase of water-in-oil (W/O) nanoemulsions was developed. The emulsions were produced from mixtures of the nonionic surfactant tetraethylene glycol monododecyl ether (C(12)E(4)), decane, and aqueous solutions of up to 2 wt % sodium alginate by means of the phase inversion temperature (PIT) emulsification method. This method allows the preparation of finely dispersed emulsions without a large input of mechanical energy. With alginate concentrations of 1-2 wt % in the aqueous phase, emulsions showed good stability against Ostwald ripening and narrow, monomodal distributions of droplets with radii <100 nm. Gelation of the alginate was induced by the addition of aqueous CaCl(2) to the emulsions under stirring, and particles formed were collected using a simple procedure based on extraction of the surfactant on addition of excess oil. The final particles were characterized using cryo-transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS). They were found to be essentially spherical with a homogeneous interior, and their size was similar to that of the initial emulsion droplets. The herein presented "low-energy" method for preparation of biocompatible nanoparticles has the potential to be used in various applications, e.g., for the encapsulation of sensitive biomacromolecules.     

Low voltage organic field effect transistors with a poly(hexylthiophene)–ZnO nanoparticles composite as channel material

We report on solution processable organic field effect transistors prepared using a poly(3‐hexylthiophene)–ZnO nanoparticles composite as channel semiconductor material and cross‐linked polyvinyl alcohol as gate insulator. Our transistors show a field effect mobility of 0.35 ± 0.06 cm²/V s, threshold voltage of –1.30 ± 0.11 V, and I_on/I_off ratio of (1.0 ± 0.1) × 10³. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Two-dimensional electrophoresis of Cereus peruvianus (Cactaceae) callus tissue proteins

Two-dimensional electrophoresis of Cereus peruvianus callus tissues grown in culture media containing two different 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin combinations was used to identify minor differences in polypeptide composition of these cell clones. Altered expression during growth in the two 2,4-D and kinetin combinations was apparent for 13 polypeptides when calluses in the two media were compared. The number of proteins with differential expression (presence or absence of specific spots) was higher in callus tissues cultured in the 4.0 mg/L 2,4-D and 8.0 mg/L kinetin combination than in callus tissues cultured in the 4.0 mg/L 2,4-D and 4.0 mg/L kinetin combination. The present results show that the callus tissues maintained at 4.0 mg/L 2,4-D and 8.0 mg/L kinetin can be used as a matrix for in vitro selection programs.     

Graphene Nanosheets and Quantum Dots: A Smart Material for Electrochemical Applications

A novel material for the electrochemical determination of endocrine disruptors using a composite based on graphene oxide modified with cadmium telluride quantum dots has been evaluated. The morphology, structure and electrochemical performance of the composite electrodes were characterised by transmission electron microscopy, dynamic light scattering, UV‐visible absorption spectra, fluorescence spectra, Raman spectra and cyclic voltammetry. The dynamic light scattering, transmission electronic microscopy and spectrophotometric measurements all showed good distribution of the quantum dots with a small particle size. The electrochemical measurements demonstrated the high performance of the composite response in the presence of a light source. Differential pulse voltammetry allowed the development of a method to determine 17β‐estradiol levels in the range from 0.2 to 4.0 μmol L ^?1 with a detection limit of 2.8 nmol L ^?1 (0.76 μg L ^?1).     

Biosensor Based on Electrocodeposition of Carbon Nanotubes/Polypyrrole/Laccase for Neurotransmitter Detection

A new biosensor has been developed by a simple electrocodeposition of multiwalled carbon nanotubes (MWCNT), polypyrrole (PPy) and laccase (Lac) on the platinum (Pt) electrode surface. The neurotransmitter biosensor was applied to the detection of dopamine in urine samples using differential pulse voltammetry (DPV). The Pt/MWCNT/PPy/Lac biosensor exhibited a detection limit of 0.14 µM, which is an adequate level for monitoring dopamine in urine. Reproducibility and repeatability values of 2.9 % and 1.7 %, respectively, were obtained compared to the conventional procedure. The proposed biosensor was successfully applied in the determination of dopamine in urine, and the obtained results were in full agreement with those from the HPLC procedure.     

Entropy analysis of human death uncertainty

Nonlinear Dynamics - Uncertainty about the time of death is part of one’s life, and plays an important role in demographic and actuarial sciences. Entropy is a measure useful for...     

A Genetic Programming-Based Low-Level Instructions Robot for Realtimebattle

RealTimeBattle is an environment in which robots controlled by programs fight each other. Programs control the simulated robots using low-level messages (e.g., turn radar, accelerate). Unlike other tools like Robocode, each of these robots can be developed using different programming languages. Our purpose is to generate, without human programming or other intervention, a robot that is highly competitive in RealTimeBattle. To that end, we implemented an Evolutionary Computation technique: Genetic Programming. The robot controllers created in the course of the experiments exhibit several different and effective combat strategies such as avoidance, sniping, encircling and shooting. To further improve their performance, we propose a function-set that includes short-term memory mechanisms, which allowed us to evolve a robot that is superior to all of the rivals used for its training. The robot was also tested in a bout with the winner of the previous “RealTimeBattle Championship”, which it won. Finally, our robot was tested in a multi-robot battle arena, with five simultaneous opponents, and obtained the best results among the contenders.