Preparation of MEMO silane-coated SiO2 nanoparticles under high pressure of carbon dioxide and ethanol

The objective of this study is to investigate and compare methods of nanosilica coating with γ-methacryloxypropyltrimethoxy (MEMO) silane using supercritical carbon dioxide and carbon dioxide-ethanol mixture. Characterization of grafted silane coupling agent on the nanosilica surface was performed by the infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The d₅₀ value and particle size distribution were determined by laser particle size analyzer (PSA). The operating parameters of silanization process at 40 °C, such as the silica/silane weight ratio, the presence of ethanol, and the pressure, were found to be important for the successful coating of silica particles with minimum agglomeration. The results indicate that presence of ethanol in high-pressure carbon dioxide plays an important role in achieving successful deagglomeration of coated nanoparticles. Dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) revealed that dispersion of the silica particles in the PMMA matrix and interfacial adhesion between silica particles and polymer matrix were enhanced, when silica nanoparticles treated with silane under high pressure of carbon dioxide and ethanol were used for the nanocomposite preparation.     

Some Experiments and Directions in Molecular Computing and Robotics

In this review I present a chemist’s perspective on molecular computing and molecular robotics. I start with nucleic acid catalysts and then show how the application of some concepts from computer sciences and macroscopic robotics enable engineering of interesting behaviors in molecular systems.     

Mechanical and electrical bonding between silicon wafer and glass wafer with etched channels containing metal tracks

In this paper a novel process to bond and, at the same time, to electrically connect a silicon wafer to a glass wafer is presented. It consists of a low temperature anodic bonding process between silicon and glass by using a glass wafer with etched channels in order to contain metal tracks. The glass-to-silicon anodic bonding process at low temperatures (not exceeding 300°C) assures a strong mechanical link (Berthold et al. in Transducers 1999, June:7–10, 1999). The electrical contacts between the metal pads on the backside of a silicon wafer and the metal pads on the glass wafer are achieved by sintering and diffusion of metals due to a kind of thermo compression bonding. This bonding method permits a high vertical control due to a well-controlled etching of the cavity depth and to the thickness precision of both metallization (pads on silicon wafers and metal tracks on glass wafer). This IC-processing compatible approach opens up the way to a new electrical connection concept keeping, at the same time, a strong mechanical bond between glass and silicon wafers for an easier fabrication of a more complex micro-system.     

Potential Barrier of (Zn,Nb)SnO2‐Films Induced by Microwave Thermal Diffusion of Cr3+ for Low‐Voltage Varistor

The effect of Cr³⁺ on the electrical properties of SnO₂‐based films deposited by electrophoresis on Si/Pt substrate was considered. The films were sintered in a microwave oven at 1000°C/40 min and then the surface was modified with deposition of Cr³⁺ ions by electrophoresis. The diffusion of Cr³⁺ contributes to the modification of the potential barrier formed on the grain boundary improving the electrical properties due to electron acceptor species adsorption on the grain boundary. The influence on the properties of grain boundary was verified by I versus V characterization in as a function of temperature. The films showed nonlinear coefficient over 9, potential barrier height over 0.5 eV and resistivity greater than 10⁷ Ω·cm. 4 samples were prepared at same conditions and presented similar electrical behavior, showing the efficiency of technique on reproducibility to varistor properties control. Thereby the nonlinear coefficient increases while decreasing the conductivity of the system is noticed.     

Evaluation of optimal bandwidth in optical FSK system influenced bylaser phase noise

In this paper, an optical frequency shift keying (FSK) system with TFS (two-filter structure), also known as dual-filter FSK, is observed in the presence of laser phase noise. Sensitivity of the receiver is shown as a function of intermediate frequency (IF) bandwidth and a bandwidth of the low-pass postdetection filter. It is shown that there is an optimal pair of bandwidths which minimizes required sensitivity; a few figures for different amounts of phase noise are given. The results in this paper are based on truncated Taylor expansion method and a method based on complex analysis is used to evaluate the integrals involved     

Investigation of the aluminium electrodeposition process in cryolite-based melts using a rotating ring-disc electrode: evidence for the existence of a subvalent intermediate species

The rotating ring-disc electrode technique has been used to investigate the reaction mechanism of the aluminium electrodeposition process in cryolite-based electrolytes. Laboratory studies using high temperature gold-molybdenum and platinum-molybdenum rotating ring-disc electrodes have provided evidence for the existence of a subvalent intermediate species (Al (I)). In a cryolite-alumina electrolyte (bath ratio: 1.5), two well separated convective-diffusion controlled oxidation processes were observed at both a gold and a platinum ring during aluminium electrodeposition at the disc. On the basis of the data presented, a reaction scheme involving reduction of A1(III) to A1(0) via A1(I), followed by chemical dissolution of A1(0) into the bulk electrolyte was proposed. The loss of current efficiency in aluminium smelting was primarily attributed to the chemical dissolution of A1(0), rather than to the formation of a subvalent intermediate species.     

Robust identification of pneumatic servo actuators in the real situations

Intensive research in the field of mathematical modelling of the pneumatic cylinder has shown that its mathematical model is nonlinear and that a lot of important details cannot be included in the model. Selection of the model and the identification method have been conditioned by the following facts:

1. The nonlinear model of the system can be approximated by a linear model with time-variant parameters.
2. There is the influence of the combination of heat coefficient, unknown discharge coefficient and change of temperature on the pneumatic cylinder model. Therefore it is assumed that the parameters of the pneumatic cylinder are random (stochastic parameters).
3. In practical conditions, observations have a non-Gaussian distribution.

Due to the abovementioned reasons, it is assumed that the pneumatic cylinder model is a linear stochastic model with variable parameters. The Masreliez-Martin filter (robust Kalman filter) was used for identification of parameters of the model. For the purpose of increasing the practical value of the filter, the following two heuristic modifications were performed:

1. It was adopted that T(k)=1 holds for the scalar transformation of residuals.
2. Fisher information was approximated by a derivative of the Huber??s function.

The proposed modifications were confirmed through intensive simulations. In order to provide persistent excitation, the autocovariance function ??1/f?? of the signal was used. The behaviour of the new approach to identification of the pneumatic cylinder is illustrated by simulations.     

Ionic liquids for extraction of metals and metal containing compounds from communal and industrial waste water

In a fundamental study the potential of ionic liquids based on quaternary ammonium- and phosphonium cations and thiol-, thioether-, hydroxyl-, carboxylate- and thiocyanate-functionalized anions has been assessed for future application in advanced sewage treatment. The elimination of the metal(oid)s Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Pt, Sn, Zn and the cancerostatic platinum compounds cisplatin and carboplatin was screened using a liquid phase micro-extraction set-up. The analytical tool-set consisted of ICP-SFMS and LC-ICP-MS for quantification of metal(oid)s and cancerostatic platinum compounds, respectively. The purity of the ILs was assessed for the investigated metal(oid)s on the base of present EU environmental quality standards and was found to be sufficient for the intended use. In model solutions at environmental relevant concentrations extraction efficiencies ≥95% could be obtained for Ag, Cu, Hg and Pt with both phosphonium- and ammonium-based ILs bearing sulphur functionality in the form of thiosalicylate and 2-(methylthiobenzoate) anions, as well as with tricaprylmethylammonium thiocyanate within an extraction time of 120 min. All other metals were extracted to a lower extent (7-79%). In the case of cancerostatic platinum compounds a phosphonium-based IL bearing thiosalicylate functionality showed high extraction efficiency for monoaquacisplatin.For the first time, liquid phase micro extraction with ionic liquids was applied to industrial and communal waste water samples. The concentration of all investigated metal(oid)s could be significantly reduced. The degree of elimination varied with the initial concentration of metals, pH and the amount of suspended particulate matter.     

Tail Extrapolation in MLSE Receivers Using Nonparametric Channel Model Estimation

This paper presents a method for determining the probability of rare events, in particular for probability density function (pdf) and bit error rate (BER) estimation. The derivation of the method is based on the presumption that the pdf is a member of a family of distributions very often named as the generalized exponential (GE) class of distributions. Based on high reliability estimations obtained in short simulation/measurement times, the low probably events are estimated accurately by extrapolation. The suggested method can be applied to some distributions that are different from GE distributions, such as noncentral chi-square distributions, to extrapolate to low probability events, with some extrapolation error. It can also be applied to BER estimation. The method is in particular helpful for estimating channels suffering from both severe signal distortion causing undesired intersymbol interference (ISI) of several symbols, and from severe noise. Such conditions prevail, for example, in metro and long haul high-speed optical fiber communication systems. So the method may be implemented in particular in maximum-likelihood sequence estimation (MLSE) optical receivers using nonparametric channel model estimation. A special use of the extrapolation method is explained for practical systems using trellis branch metrics derived from the estimated pdf to decode the transmitted sequence of symbols.     

The in vivo effect of liposomes on hematopoiesis

The influence of liposome structure on hematopoiesis in vivo was assessed in relation to the different contents and origins of phospholipids that make up their membrane structures. Changes within different hematopoietic cells and serum tumor necrosis factor alpha (TNF-alpha) levels were estimated up to 14 days following intravenous administration of liposomes made of either pure egg yolk phosphatidylcholine (LEY) or a soybean phospholipid preparation (LSB) into normal CBA mice. In peripheral blood, only transient changes within white blood cells were observed. In bone marrow, a persistent decline in the number of mature granulocytes, monocytes, and lymphocytes was found. The changes within femoral granulocytic proliferative compartments in various stages of differentiation and a maturation compartment pointed out that, parallel with the depletion of the granulocyte-storage pool, stimulation of de novo production of granulocytic cells occurred. Although both types of tested liposomes induced similar cellular changes, only liposomes made of pure egg yolk phosphatidylcholine induced a transient increase in serum TNF-alpha levels.