Electrochemical characteristics of the Mn(iii)/Mn(ii) and Co(iii)/Co(ii) systems at platinum in anhydrous acetic acid solutions

The electrochemical oxidation of Mn(ii) and Co(ii) and reduction of Mn(iii) and Co(iii) at Pt in glacial acetic acid has been investigated by the rotating disc electrode technique. The diffusion coefficients of Mn(iii), Mn(ii), Co(iii) and Co(ii) ions, formal potentials and kinetic parameters of the Mn(iii)/Mn(ii) and Co(iii)/Co(ii) electrode reactions were evaluated. It was shown that the anodic oxidation of Mn(ii) and Co(ii) occurs at the surface blocked by a layer of adsorbed acetate ions. In addition, some experiments with an electrochemical quartz crystal microbalance (EQCM) were performed to explain the acetate adsorption on the surface of the polycrystalline platinum electrode.     

Electrochemical characteristics of the Mn(iii)/Mn(ii) and Co(iii)/Co(ii) systems at platinum in anhydrous acetic acid solutions

The electrochemical oxidation of Mn(ii) and Co(ii) and reduction of Mn(iii) and Co(iii) at Pt in glacial acetic acid has been investigated by the rotating disc electrode technique. The diffusion coefficients of Mn(iii), Mn(ii), Co(iii) and Co(ii) ions, formal potentials and kinetic parameters of the Mn(iii)/Mn(ii) and Co(iii)/Co(ii) electrode reactions were evaluated. It was shown that the anodic oxidation of Mn(ii) and Co(ii) occurs at the surface blocked by a layer of adsorbed acetate ions. In addition, some experiments with an electrochemical quartz crystal microbalance (EQCM) were performed to explain the acetate adsorption on the surface of the polycrystalline platinum electrode.     

Fabrication and Characterization of Nonwoven Auxetic Polymer Stent

Synthetic biomaterials have better controlled physical and mechanical properties and can be used to tailor both soft and hard tissues. A tiny, expandable mesh tubes called stents keep blood vessels open and allow blood flow and treat blockage to improve quality of patient’s life. The main focus of this work is to (i) fabricate a polymeric sheet of melt electrospun polycaprolactone microfibers; (ii) tailor auxetic geometry by micromachining on polycaprolactone microfiber and polycaprolactone sheet; (iii) fabricate a cylindrical tube to make auxetic stents. Final results for mechanical characterization and performance analysis of auxetic polymer stents are discussed.     

Development of RYUGA for three-dimensional dynamic visualization of molecular dynamics results

We have developed a new computer graphics (CG) code RYUGA for three-dimensional dynamic visualization of molecular dynamics (MD) results. The applicability of RYUGA for visualizing and analyzing the dynamics of atomic motions in various materials was demonstrated. RYUGA supports various functions, such as solid-modeling CG pictures (called the CPK model), CG animation of the MD results, Miller plane cutting of crystal structures, building graphs, etc., similar to other CG codes for MD simulation. In addition, RYUGA has a number of advantages as follows: (i) a perspective is employed for drawing CG pictures, (ii) three-dimensional trajectories of atoms can be constructed, (iii) an operator can travel inside the materials, (iv) graphic speed and animation speed are enhanced because of the specific algorithms, and (v) it works on any workstations, moreover even personal computers with a UNIX operating system and an X window system are available.     

Synthesis and studies of two proton–receptor fluorescent probes based on 1,8-naphthalimide

Two isomeric proton–receptor fluorescent probes 1 and 2 were designed and synthesised by employing the photoinduced electron transfer (PET) principle of a ‘fluorophore–spacer–receptor’ module. Their photophysical characteristics were investigated in organic solvents and Britton–Robinson buffer/EtOH (1:1, v/v) solution. Probe 1 was sensitive in the stronger acidic region of 2.21–4.56, while probe 2 displayed a good response towards protons within the pH scope of 4.10–6.09. The specificity of the probes toward protons in commonly used buffer solutions and in the presence of metal cations, Na(i ), K(i ), Ca(ii ), Mg(ii ), Al(iii ), Pb(ii ), Fe(iii ), Ni(ii ), Zn(ii ), Cu(ii ), Hg(ii ), Ag(i ), Co(ii ), Cr(iii ), Mn(ii ), and Cd(ii ) ions, was studied by monitoring the changes in their fluorescence intensity. The tested metal ions exerted no noticeable influence. The results obtained show that the synthesised proton–receptor fluorescent probes have the capability to act as pH-sensitive probes for monitoring pH variations in the range 2.21–6.09.     

Structure–property relation in varieties of silk fibers

Crystallite shape ellipsoid in different varieties of silk fibers namely (i) Chinese (ii) Indian, and (iii) Japanese, has been computed using wide‐angle X‐ray data and Hosemann's one‐dimensional paracrystalline model. The estimated microcrystalline parameters are correlated with the observed physical property of the silk fibers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1979–1985, 2001     

The flow of suspensions

Most rheological and rheo-optical properties of suspensions such as viscosity and light-scattering intensities can be expressed in terms of the average orientation and/or the average concentration distribution of the suspended particles. In general one can distinguish several distinct regimes: (i) infinitely dilute, (ii) dilute, (iii) semi-dilute or moderately concentrated, and (iv) concentrated suspensions. Cases (i) and (ii) are regimes in which particle interactions are either absent or only two-body interactions are important. These cases can, in general, be well described theoretically. Regime (iii) is characterized by n-body (n ≥ 2) interactions and is the least understood. Regime (iv) can often be described in terms of a cell model in which the motion of a reference particle, or the fluid motion around it, is described.     

Decomposition of N2O on Perovskite-Related Oxides

Mixed metal oxides crystalizing in a perovskite-related structure have long been of interest to solid state chemists and physicists because of their technologically important physical properties. The ready availability of a family of isomorphic solids with controllable physical properties makes these oxides suitable for basic research in catalysis. These mixed metal oxides are more advantageous and are better catalytic materials than simple oxides because: (i) the crystal structure can accomodate various metal ions and can stabilize unusual and mixed valence states of active metal ion; (ii) appropriate formulation of these oxides leads to easy tailoring of many desirable properties such as valence state of transition metal ion, distance between active sites, binding energy, diffusion of oxygen in the lattice, magnetic and conducting properties of the solid; (iii) the catalytic activity can be correlated to solid state properties since many of their solid state properties are thoroughly understood; (iv) the surface of these oxides can be regenerated by suitable activation procedure.     

BUBBLE FREQUENCY AND DISTRIBUTION IN FLUIDIZED BEDS

The distribution of bubbles and the rate of coalescence of bubbles are important factors in the overall behaviour of fluidized beds. A simple model capable of predicting bubble distribution and bubble-size distribution is most desirable. Stages in the development of such a simple model are presented. Early studies examined coalescence and related bubble properties in two-dimensional beds and led to the formulation of a simple computer model for two-dimensional beds. The work was then extended to three-dimensional beds covering the following cases: (i) a single orifice; (ii) a row of orifices in a line and (iii) orifices arranged in a plane. Reasonable agreement with experimental data was obtained for cases (i) and (iii), there being no data available for (ii). The present program is probably adequate for engineering purposes, so far as the prediction of bubble sizes and bubble distribution is concerned, in fluidized beds without internals, although some qualifications are still necessary.     

BUBBLE FREQUENCY AND DISTRIBUTION IN FLUIDIZED BEDS

The distribution of bubbles and the rate of coalescence of bubbles are important factors in the overall behaviour of fluidized beds. A simple model capable of predicting bubble distribution and bubble-size distribution is most desirable. Stages in the development of such a simple model are presented. Early studies examined coalescence and related bubble properties in two-dimensional beds and led to the formulation of a simple computer model for two-dimensional beds. The work was then extended to three-dimensional beds covering the following cases: (i) a single orifice; (ii) a row of orifices in a line and (iii) orifices arranged in a plane. Reasonable agreement with experimental data was obtained for cases (i) and (iii), there being no data available for (ii). The present program is probably adequate for engineering purposes, so far as the prediction of bubble sizes and bubble distribution is concerned, in fluidized beds without internals, although some qualifications are still necessary.     

Decomposition of N2O on Perovskite-Related Oxides

Mixed metal oxides crystalizing in a perovskite-related structure have long been of interest to solid state chemists and physicists because of their technologically important physical properties. The ready availability of a family of isomorphic solids with controllable physical properties makes these oxides suitable for basic research in catalysis. These mixed metal oxides are more advantageous and are better catalytic materials than simple oxides because: (i) the crystal structure can accomodate various metal ions and can stabilize unusual and mixed valence states of active metal ion; (ii) appropriate formulation of these oxides leads to easy tailoring of many desirable properties such as valence state of transition metal ion, distance between active sites, binding energy, diffusion of oxygen in the lattice, magnetic and conducting properties of the solid; (iii) the catalytic activity can be correlated to solid state properties since many of their solid state properties are thoroughly understood; (iv) the surface of these oxides can be regenerated by suitable activation procedure.     

Convolutional neural nets in chemical engineering: Foundations,computations, and applications

In this article, we review the mathematical foundations of convolutional neural nets (CNNs) with the goals of: (i) highlighting connections with techniques from statistics, signal processing, linear algebra, differential equations, and optimization, (ii) demystifying underlying computations, and (iii) identifying new types of applications. CNNs are powerful machine learning models that highlight features from grid data to make predictions (regression and classification). The grid data object can be represented as vectors (in 1D), matrices (in 2D), or tensors (in 3D or higher dimensions) and can incorporate multiple channels (thus providing high flexibility in the input data representation). CNNs highlight features from the grid data by performing convolution operations with different types of operators. The operators highlight different types of features (e.g., patterns, gradients, geometrical features) and are learned by using optimization techniques. In other words, CNNs seek to identify optimal operators that best map the input data to the output data. A common misconception is that CNNs are only capable of processing image or video data but their application scope is much wider; specifically, datasets encountered in diverse applications can be expressed as grid data. Here, we show how to apply CNNs to new types of applications such as optimal control, flow cytometry, multivariate process monitoring, and molecular simulations.     

Heterogeneous photocatalysis: state of the art and present applications In honor of Pr. R.L. Burwell Jr. (1912–2003), Former Head of Ipatieff Laboratories, Northwestern University, Evanston (Ill).

In the present paper, the basic fundamentals of photocatalysis are explained with the influence of the five main parameters which govern the kinetics: (i) mass of catalyst, (ii) wavelength, (iii) partial pression and/or concentrations of reactants, (iv) temperature (at a second degree) and (v) the radiant flux. The main types of photocatalytic reactions presently described (all performed at room temperature) concern (i) the selective mild oxidation of hydrocarbons, (ii) the hydrogen production and (iii) the total oxidation reactions of organics in presence of water. The last point constitutes the ensemble of the last recent developments in photocatalysis. Most of organic contaminants, including dangerous pesticides, can be easily totally degraded and mineralized.Dyes are also not only decolorized, but mineralized in colored aqueous effluents. The most abundant ones (the azo-dyes) have their azo-group(s) –N=N– decomposed into N2(g), which represents an ideal decontamination case.Photocatalytic engineering is under development, now using deposited titania in a fixed bed. Some (solar) photocatalytic pilot reactors and prototypes are described. The use of solar energy as a source of activating UV–A irradiation is described as a sub-discipline called helio-photocatalysis.     

Bounded risk estimation of a finite population mean optimal strategies

Bounded risk estimation of the mean of a finite population is considered under three simple random sampling strategies: (i) with replacement, mean per unit estimation, (ii) with replacement, mean per distinct unit estimation, and (iii) without replacement, mean per unit estimation. It is well known that in the fixed sample size scheme, (iii) fares better than (ii) and (ii) better than (i). However, in the current context, the sample sizes are dictated by (possibly, degenerate) stopping times, and visualizing the cost (due to measurements/recording, etc.) as a function of the number of distinct units in the sample, it is shown that the second strategy still fares better than the first, although the third strategy may not perform better than the second one. Actually, in the case of known population variance, it is shown that in the light of the number of distinct units, the difference of ASN for the second and third strategies can never be greater than two or less than minus one. A similar relationship also holds in the case of unknown population variance when we define the stopping rules in a coherent manner. The theoretical results are backed up by numerical examples too. Also, dominance of strategy (ii) over (i) in a general sequential setup constitutes an important task of the current study. Finally, to reconcile strategies (ii) and (iii) in a general sequential setup, the coherence of the associated stopping times has also been discussed thoroughly.     

A rapid and simple approach to identify different sunflower oil types by means of near-infrared reflectance spectroscopy

The potential of near-infrared reflectance spectroscopy (NIRS) to perform an easy and rapid classification of different sunflower oil types was investigated. A total of 118 oil samples showing large variation in their fatty acid compositions were analyzed by both NIRS and gas-liquid chromatography (GLC). They were classified into five classes, characterized by (i) high palmitic acid content (>29%), (ii) high palmitic acid in high oleic acid background (>27 and >51%, respectively), (iii) high stearic acid content (>22%), (iv) high oleic acid content (>83%), and (v) standard oil type. Second-derivative transformation and scatter corrections were applied to the original log (1/R) spectra, and the correlation coefficients between NIRS spectral information and GLC fatty acid values were studied to identify the wavelengths with the best discriminating ability. The use of the spectral data at 2134 nm permitted all the samles with high levels of total saturated fatty acids (>29%, classes i, ii, and iii) to be discriminated from the samples with standard levels (<22%, classes iv and v). The use of a second wavelength, 2192 nm, led to a further separation of the samples with high C_18:1 content within each group (classes ii and iv, respectively). Therefore, an accurate discrimination of four of the five sunflower oil types was achieved by using the spectral information at two wavelengths exclusively. The oil samples belonging to classes i and iii could not be separated with this approach, which was explained on the basis of the small spectral differences observed between the two classes.     

Selective Hydrogenation of Ethyne in Ethene‐Rich Streams on Palladium Catalysts,Part 2: Steady‐State Kinetics and Effects of Palladium Particle Size,Carbon Monoxide,and Promoters

Developments in the last three decades of kinetics of selective hydrogenation of ethyne in ethene‐rich streams on palladium catalysts are reviewed. Most of the studies can be described comprehensively by a model that assumes carbonaceous deposits (i) create irreversibly on the palladium surface small A types of active site (selective to ethene) and large E types of active site (selective to ethane), and (ii) are involved in hydrogenation of ethene on E _s sites on the support. The relative importance of these sites, with varying (i) reaction conditions, (ii) palladium dispersion, (iii) process modifiers, and (iv) promoters, is discussed.     

Pore structure characterization of cement pastes blended with high-volume fly-ash

The pore structure of cement pastes incorporating fly-ash was evaluated during their hydration process through gravimetry method, mercury intrusion porosimetry (MIP) and nitrogen adsorption/desorption (NAD) methods. The pore structure of samples is characterized by the total porosity, pore size distribution (PSD), pore internal surface area as well as characteristic pore sizes. The correlation between the hydration process and the formed pore structure is investigated. The results indicate that: (i) w/b ratios have determinant impact on all characteristics of pore structure; (ii) fly-ash replacement ratio can influence the pore structure significantly at early age but this influence becomes less important with sample age by fly-ash hydration process; (iii) the total porosity and specific surface area are well correlated with the chemical kinetics of hydration through hydration degree or the formed gel/space ratio but the critical pore size is rather independent on the chemical kinetics.     

Catalase and superoxide dismutase mimics for the treatment of inflammatory diseases

Conjugation of a metal ion chelator to aromatic amino acids generates a series of novel metal-binding anti-oxidant enzyme mimics. Our catalytic peptoids are designed to suppress oxidative damage via a number of routes. These include: (i) binding redox-active metal ions that further generate/activate RONS, (ii) removal of hydrogen peroxide by catalase activity, (iii) removal of superoxide by superoxide dismutase activity, and (iv) preventing the formation of hydroxyl radicals and peroxynitrite by removal of their precursors [as in (ii) and (iii)]. Thus, the redox-active metal ions are changed from detrimental RONS producers to beneficial RONS scavengers. In conclusion, we present a series of biomimetic peptoids that (i) bind redox-active metal ions, (ii) detoxify RONS and (iii) have potential therapeutic applications in inflammatory diseases.     

Polymers for audio and video equipment

Polymers find widespread use in present-day audio and video equipment. Their applications can be divided into: (i) polymers used for the outside of the equipment, (ii) polymers used for mounting, encapsulation or passivation of electronic devices, (iii) polymers for other stationary or moving parts, (iv) polymers used for audio and video data storage, and (v) photosensitive polymers that play a temporary role in the structuring of fine details. In this paper, attention is focussed on transparent polymers (“optical plastics”) that are employed in projection television (PTV) and optical disc systems. First, the principles of these systems and the polymer properties they require are summarized, after which the polymers and technologies used in these applications are described. These polymers can be divided into two categories: (i) UV-curable coatings on a substrate of a different nature, and (ii) transparent thermoplastics and thermosets. Finally, some shortcomings of the currently available materials are mentioned.