Selective voltammetric determination of electroactive neuromodulating species in biological samples using iron(II) phthalocyanine modified multi-wall carbon nanotubes paste electrode

Iron(II) phthalocyanine (FePc) modified multi-wall carbon nanotubes paste electrodes (MWCNTPEs) were used as voltammetric sensors to selectively detect dopamine (DA) in the presence of serotonin (5-HT). The electrochemical behavior of DA at the new modified electrode was investigated using CV. The enhanced current response of DA indicates that FePc modification of the MWCNTPE surface results in a high catalytic activity for the redox reaction of DA. Differential pulse voltammetry was applied in detection of DA and 5-HT at FePc-MWCNTPE. The method parameters were optimized. Detection limit of 2.05 × 10⁻⁷ M was obtained for DA by using the electrocatalytic oxidation signal corresponding to the Fe^II/Fe^III redox process. The separation between the peak potentials of DA and 5-HT is 170 mV which is large enough for the simultaneously, selective determination of the two chemical species in their mixtures. There was no electrochemical response for ascorbic acid (AA) added in the sample. The monoamine neurotransmitter measuring method has been tested in analyzing deproteinized serum samples.     

Pole placement with sensitivity function shaping using 2nd order digital notch filters

This technical note deals with the design of robust digital controllers using pole placement with sensitivity shaping by means of the use of digital notch (band-stop) filters. The use of this type of filters drastically simplifies the effective shaping of the sensitivity functions and the resulting procedure competes with the procedure based on the use of Q-parameterization combined with convex optimization (Automatica 35 (1999) 1111). The feasibility of the technique is illustrated by its application to the control of a very flexible arm.     

Dynamic modeling of the secondary drying stage of freeze drying reveals distinct desorption kinetics for bound water

In freeze drying, the desorption step for reaching a low target moisture content may take a significant fraction of the total process duration. Because the long-term stability of freeze-dried biological products strongly depends on the current moisture content, modeling the desorption process may help safely optimize the secondary drying step. Most published models assume a first-order desorption kinetic, but experimental evidence shows that strongly bound water in the monolayer takes a much longer time to be desorbed than less bound water in multilayer. The proposed model for desorption of freeze-dried lactic acid bacteria preparation accounts for monolayer and multilayer water state in the solid matrix, with very different desorption kinetics. Results showed that the ratio of characteristic desorption times (monolayer/multilayer) was almost 30. Temperature dependence was adequately described by an Arrhenius law in the range of 15 to 40°C. Model parameter identification used simultaneously gravimetric measurements with high time resolution and direct Karl-Fisher titration, from several experiments at different, time-varying temperatures.     

Interactions Between Calix[8]arenes and Fullerenes. Molecular Dynamics and Molecular Mechanics Simulation of the 1:1 and 1:2 complexes

Abstract

The interaction of tBu-calix[8]arene with C60 and C70 in the 1:1 and 1:2 models have been investigated by means of molecular dynamics and molecular mechanics (CVFF91 force field) calculations. The results reveal that one C60 molecule can be encapsulated in the cavity of the calixarene which adopts a conformation with six phenyl groups oriented upward and the other two (1 and 5) outward. The relatively weak bonded 1:1 C60-calixarene system is a result of attractive π…H(C-tBu. C-methylene) and repulsive π…π interactions. C70, more voluminous than C60 can not be accommodated in the cavity of the calixarcnc and forces it to a relatively opened conformation where the number of atractive interactions is less than in the C60-calixarene system. This conformation allows however the interaction with a second molecule and thus 1:2 adducts are formed. Thus, if proper substituents are on the calixarene and the fullerene size permite the encapsulation, 1:1 complexes are obtainable while if the fullerene size is larger than the cavity of the calixarene can cope with, only the 1:2 adducts can be separated.

     

Resistance to High-Temperature Oxidation and Wear of Various Ferrous Alloys Used in Rolling Mills

Various materials are commonly used to manufacture work rolls for hot rolling mills, such as ICDP (Indefinite Chill Double Pour) cast irons, high-chromium white cast irons, and high speed steels (HSS). Various chemical compositions and microstructures are studied in order to optimize the in-use behavior of those grades of rolls. In this paper, six grades of ferrous alloys (an ICDP cast iron; an ICDP cast iron enriched in vanadium, niobium, and molybdenum; a HSS; a graphitic HSS; a high-chromium white cast iron (Hi-Cr); and a niobium-molybdenum-doped high-chromium white cast iron) were investigated. High-temperature oxidation tests with gravimetric means at 575 °C in water vapor atmosphere and sliding wear tests were carried out. The oxidation kinetics was followed during oxidation test. The microstructure was observed by optical and scanning electron microscopies. The oxides formed on the surface of the samples were analyzed by XRD and EDS. The thickness of the oxide scales and the mass gain were measured after oxidation test. The results showed that the behavior of all the grades differed. The oxide scale of HSS and HSS-G grades was fine and their friction coefficient was low. The weight gain after oxidation test of HSS was high. Hi-Cr and M-Hi-Cr grades presented highly porous oxide layer and an important increase of the friction coefficient during wear test. ICDP and M-ICDP had intermediate behavior.     

Physical–chemical characterization of titanium dioxide layers sensitized with the natural dyes carmine and morin

The titanium dioxide (TiO₂)-based layers sensitized with carmine and morin dyes were prepared using commercial P25 TiO₂ powder as starting material. The influence of natural colorants as natural photosensitizers on TiO₂ photoactivity was discussed from the point of view of UV–VIS and Fourier transform infra-red (FTIR) spectroscopy, fluorescence analysis, microscopy, X-ray diffraction and nitrogen adsorption-desorption isotherms determination. A shift to visible region of the sensitized TiO₂ layers is observed. The decrease of sensitized TiO₂ band gap improves its photoactivity in the visible domain. The fluorescence quenching of TiO₂ sensitized with carmine is correlated with better adsorption of the dye molecules to the TiO₂ surface and with electron injection process, also. The FTIR absorption spectra of samples proved the presence of dye molecules on TiO₂ nanoparticles surface. Thus, the investigated sensitized TiO₂-based layers could have potential in photoelectrochemical applications.     

Altering the emission properties of conjugated polymers

Many technological applications that have had tremendous impact on our society and lifestyle are exploiting the emission properties of organic species such as conjugated polymers and organic small‐molecule semiconductors. The most prominent case‐in‐point here are possibly organic light‐emitting diodes, which have found use in information displays, touch screens and beyond. To further advance the rapid development of these powerful and versatile technologies, it will be of paramount importance to gain fundamental insights about which strategies and processes we can employ to alter, control and eventually enhance the emission properties of this interesting class of material. In this work, we focus on macromolecular systems and review the most important categories of tools that can be employed to efficiently alter their emission properties by manipulating their molecular architecture and electronic structure; by influencing their molecular ordering, packing motifs and overall microstructure; as well as by utilizing the ability of some of these materials to respond to external stimuli and other physical parameters (pressure, light exposure etc.) and/or to interact with other compounds, including systems of different functionalities. © 2015 Society of Chemical Industry     

Neural network modeling of the preparation process of a siloxane‐organic polyazomethine

Although apparently simple, the polycondensation reaction leading to polyazomethine is difficult to control because of its equilibrium character, the conversion degree being influenced by a series of parameters. The reaction between a siloxanediamine, 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane, and terephthalaldehyde was performed here in solution (in tetrahydrofuran) without by‐products removal and in absence of any catalyst or pH modifier. Different conditions (co‐monomers ratio, dilution, and temperature), considered as input parameters for the process modeling, were varied according to a pre‐established experimental program. The viscosity of the reaction mixture was chosen as output parameter, being monitored with a Haake Viscotester 7 Plus‐L. The process modeling was performed using a hybrid combination of artificial neural networks and differential evolution algorithm, the last one having the role of developing the neural model in an optimal form. The simulation results showed that the methodology provides accurate results, the model predictions being in close correlation with the experimental data. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42552.     

Pullulan: A versatile coating agent for superparamagnetic iron oxide nanoparticles

Ultrasmall superparamagnetic iron oxide (Fe₃O₄) nanoparticles coated by biocompatible pullulan (Pu‐USPIO) with sizes below 10 nm and having a magnetite core and a hydrophilic outer shell of pullulan were prepared. The formed Pu‐USPIOs were thoroughly characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy, and small‐angle X‐ray scattering experiments. The content of magnetic nanoparticles embedded into the pullulan matrix was determined by thermogravimetric analysis. Vibrating sample magnetometry analysis was used to evaluate the magnetic properties of the Pu‐USPIO samples. Because of the presence of pullulan, these nanoparticles could be conditioned in many versatile forms, from a clear solution to magnetic films, for potential applications, including magnetic hyperthermia mediators. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42926.     

The Optimization of the Production of Methyl Esters from Corn Oil Using Barium Hydroxide as a Heterogeneous Catalyst

In recent years, vegetable oils, as renewable raw materials, became a promising feedstock for chemicals and biodiesel production. The main products derived from oils are esters of fatty acids, especially methyl esters, obtained by their transesterification with methanol, in presence of acid or alkaline catalysts. The use of such catalysts implies the need for washing operations, which leads to environmental pollution. In the present paper, the response surface methodology based on a central composite design, has been developed to optimize the process of transesterification of corn oil. Ba(OH)₂ in presence of diethyl ether was used as catalyst. A quadratic polynomial equation was obtained. It correlates the reaction parameters [methanol/oil molar ratio (x _r), reaction time (x _t) and catalyst concentration (x _c)] with methyl esters yield. Analysis of variance analysis showed that only methanol/oil molar ratio and catalyst concentration have had the most significant influences on the conversion. The maximum methyl esters yield was obtained using the following optimum parameters: methanol/corn oil ratio of 11.32, reaction time of 118 min and catalyst concentration of 3.6 wt%.