Dynamic analysis of charge transport in fluidized bed electrodes: Impedance techniques for electroactive beds

Impedance techniques are used to investigate the average dynamic behaviour of a fluidized bed of gold-coated beads in potassium ferri-ferrocyanide/NaOH solution. A transmission line is used as a model. The main features of the fluidized bed are correctly interpreted, especially the capacitive high frequency impedance related to the intermittent contacts between the particles. The use of a nonuniform transmission line is attempted in order to study the influence of a distance dependent charge transfer mechanism in the bulk of the fluidized bed.     

Ohmic drops in the ion-exchange bed of cationic electrodeionisation cells

The work was aimed at investigating the ohmic drop in ion-exchanging resin beds in EDI cells, by using two techniques. The case of CuSO₄–H₂SO₄ solutions was treated here, using Dowex resins of various degrees of cross-linking. Impedance measurements in a dedicated cell filled with resin packed beds were interpreted by using a model for the conductivity of two-phase media. Secondly, the voltage recorded in a small EDI cell for continuous treatment of copper solutions, led to the bed conductivity, using a model for potential distribution in the cell. The consistency of the two techniques was discussed, and side electrical phenomena in the EDI cell were shown to be the source of an unexpectedly significant increase in the cell voltage.     

Detection of CO<Subscript>2</Subscript> and O<Subscript>2</Subscript> by iron loaded LTL zeolite films

Detection of oxygen and carbon dioxide is important in the field of chemical and biosensors for atmosphere and biosystem monitoring and fermentation processes. The present study reports on the preparation of zeolite films doped with iron nanoparticles for detection of CO₂ and O₂ in gas phase. Pure nanosized LTL type zeolite with monomodal particle size distribution loaded with iron (Fe-LTL) was prepared under hydrothermal condition from colloidal precursor suspensions. The zeolite was loaded with iron to different levels by ion exchange. The Fe-LTL suspensions were used for preparation of thin films on silicon wafers via spin coating method. The reduction of the iron in the zeolite films was carried out under H₂ flow (50% H₂ in Ar) at 300 °C. The presence of iron nanoparticles is proved by in situ ultra-violet-visible spectroscopy. The properties of the films including surface roughness, thickness, porosity, and mechanical stability were studied. In addition, the loading and distribution of iron in the zeolite films were investigated. The Fe-LTL zeolite films were used to detect O₂ and CO₂ in a concentration dependent mode, followed by IR spectroscopy. The changes in the IR bands at 855 and 642 cm^–1 (Fe?O?H and Fe?O bending vibrations) and at 2363 and 2333 cm^–1 (CO₂ asymmetric stretching) corresponding to the presence of O₂ and CO₂, respectively, were evaluated. The response to O₂ and CO₂ was instant, which was attributed to great accessibility of the iron in the nanosized zeolite crystals. The saturation of the Fe-LTL films with CO₂ and O₂ at each concentration was reached within less than a minute. The Fe-LTL films detected both oxygen and carbon dioxide in contrast, to the pure LTL zeolite film.

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Use of chitosan complex with aminophosphonic groups and cobalt for the removal of Sr2+ ions

We briefly describe the adsorbent performance of the chitosan complex with aminophosphonic groups and cobalt in the removal process of Sr²⁺ ions from aqueous solutions. The strontium adsorption was studied as a function of pH, contact time, and initial strontium concentration. Adsorption isotherms such as Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin were used to analyze the equilibrium data at different concentrations. The kinetics of the Sr²⁺ sorption was analyzed using the pseudo-first-order and pseudo-second-order kinetic models. The results clearly indicate that the chitosan complex with aminophosphonic groups and cobalt is an efficient adsorbent with respect to its capacity to absorb Sr²⁺ ions from aqueous solutions.     

Multi-layer models of friction between solids

Recent simulations of processes in surface layers of rubbing solids have shown the formation of a boundary layer, called quasi-fluid layer. To better understand the physical nature of the quasi-fluid layer, we investigate the processes occurring in the surface layer of rubbing solids in the frame of a simple multi-layer model, which also leads to the formation of a quasi-fluid layer. The multi-layer model can further be used to investigate how the friction force is determined by the material and loading parameters. It has been shown that the friction force and the thickness of the quasi-fluid layer depend on sliding velocity, the viscosity of the material and on a microscopic parameter (layer thickness). Subsequently, two different ways of extending the discussed model are proposed aiming at a model that can also predict the influence of normal pressure and surface topography on the friction force and on the formation of the quasi-fluid layer.     

Pseudomonas Phage MD8: Genetic Mosaicism and Challenges of Taxonomic Classification of Lambdoid Bacteriophages

Pseudomonas phage MD8 is a temperate phage isolated from the freshwater lake Baikal. The organisation of the MD8 genome resembles the genomes of lambdoid bacteriophages. However, MD8 gene and protein sequences have little in common with classified representatives of lambda-like phages. Analysis of phage genomes revealed a group of other Pseudomonas phages related to phage MD8 and the genomic layout of MD8-like phages indicated extensive gene exchange involving even the most conservative proteins and leading to a high degree of genomic mosaicism. Multiple horizontal transfers and mosaicism of the genome of MD8, related phages and other λ-like phages raise questions about the principles of taxonomic classification of the representatives of this voluminous phage group. Comparison and analysis of various bioinformatic approaches applied to λ-like phage genomes demonstrated different efficiency and contradictory results in the estimation of genomic similarity and relatedness. However, we were able to make suggestions for the possible origin of the MD8 genome and the basic principles for the taxonomic classification of lambdoid phages. The group comprising 26 MD8-related phages was proposed to classify as two close genera belonging to a big family of λ-like phages.     

Composition and antimalarial activity in vitro of volatile components of Lippia multiflora

The essential oil of Lippia multiflora was prepared by hydrodistillation of leaves and stalks and characterized by GC and mass spectroscopy. The oil was tested for antimalarial activity on in vitro cultures of Plasmodium falciparum (FcB1-Columbia chloroquine-resistant strain and F32-Tanzania chloroquine-sensitive strain). The dilutions inhibiting the in vitro growth of the parasite by 50% 24 and 72 hr after administration of the essential oil to the parasite culture were 1/12,000 and 1/21,000, respectively. When tested on a highly synchronized culture, the essential oil inhibited growth mostly at the trophozoite-schizont step, indicating a potential effect on the first nuclear division of the parasite.     

Detection of the eroding surface in the EDM process based on the current signal in the gap

To achieve high removal rate and low electrode wear in sinking electrical discharge machining process (EDM), rough machining parameters have to be selected according to the size of the eroding surface. In general, the size of the eroding surface varies according to the depth of the machining. Thus, it has to be determined on-line. This paper shows that the electric current signal in the gap depends on the size of the eroding surface. The significance of the process attributes of the electric current signal is established by inductive machine learning and the general decision rules are derived. The size of the eroding surface can be detected on-line by monitoring and evaluating the electric current signal in the gap.     

Influence of Ultrasonic Oscillation on Static and Sliding Friction

Vibrations of varying frequency and amplitude are used in many technological areas to control and reduce friction. In this study we report the results of systematic high-precision measurements of the static and sliding friction under the influence of ultrasonic oscillations. We investigate the effect of ultrasonic oscillations for in-plane and out-of-plane oscillations in the completely relevant interval of oscillation amplitudes and sliding velocities and for various material pairings. The experimental results are interpreted on the basis of both macroscopic and microscopic models. There are two main effects which are of interest for tribological applications. Firstly, the frictional force typically decreases with increasing oscillation amplitude, with an oscillation amplitude of about 0.1???m typically being sufficient for a significant decrease of frictional force. Secondly, the decrease of force is larger at smaller sliding velocities; therefore, at sufficiently large oscillation amplitudes, the frictional force always increases with sliding velocity. This effect can be used to suppress frictionally induced vibrations.     

Experimental study of a mechanically ventilated double-skin façade with venetian sun-shading device: A full-scale investigation in controlled environment

The aim of this article is to present results of an experimental campaign performed on a full-scale facility provided with a double-skin façade. The behaviour of this architectural concept is tested under controlled climatic conditions. A summer case is scrutinised under different configurations: variation of the airflow through the double-skin façade and different angle of the solar shading device. This paper describes the experimental conditions, as well the test facility and the tested façade element. The results show the temperatures of the test cell and the façade and how they depend on the climatic conditions and the sun-shading device blade angles. One objective of this research was to measure and provide extensive data set detailing air and surface temperatures on the double-skin façade, together with airflow rates and air velocities. The experiments are fully described so that the results can be used for the validation of numerical models dealing with ventilated double-skin façades with venetian sun-shading device.