Voltage ‐ Current Study of an Atmospheric Dielectric Barrier Discharge

The discharge behaviour of an atmospheric dielectric barrier parallel plate discharge, used for surface treatment, is studied. Since an uniform plasma is preferable for surface treatment, filaments must be avoided in the discharge. The occurrence of filaments can be detected by measuring the current flowing through the discharge. Current and voltage measurements give an indication of the power consumption by the plasma. The power consumption of the plasma as function of the applied frequency is examined. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solvolysis-decomposition of 2-adamantyl chloroformate: evidence for two reaction pathways

Reaction of 2-adamantyl chloroformate under a variety of solvolytic conditions leads to 2-adamantyl chloride accompanied by solvolysis products, some with and some without retention of the CO(2) unit. For example, in 100% ethanol, only 4.8% 2-adamantyl chloride is formed with the mixed carbonate (88%) being the dominant product, and in 100% 2,2,2-trifluoroethanol, the products are both formed with loss of CO(2), 59% of the chloride and 41% of the ether. With exclusion of the specific rates in 100% and 90% ethanol and methanol, a good Grunwald-Winstein plot against Y(Cl) values (solvent ionizing power) is obtained, with a slope of 0.47 +/- 0.03. The results are compared with those reported earlier for 1-adamantyl chloroformate and isopropyl chloroformate and mechanistic conclusions are drawn.     

Investigation of Tin and Chromium Metal Plasmas by Langmuir Probe Measurements

Double Langmuir probe measurements are performed during the deposition of tin and chromium coatings in order to examine the degree of ionisation and the deviation from thermal equilibrium of these metal plasmas.     

Examination of the Degreasing of Metal Surfaces by the Use of a Plasma Torch

Metal surfaces can be degreased via a combustion reaction upon the metal surface by the use of a plasma torch jet. The required energy and the reaction rate of the combustion reaction are examined here. It turns out that the reaction rate can limit the cleaning performance. In such case, the cleaning performance is not improved at higher powers. It is suggested to increase the temperature at which combustion takes place such that the cleaning performance can improve again at higher powers. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A combinatorial approach toward the generation of ambiphilic peptide-based inhibitors of protein:geranylgeranyl transferase-1

A combinatorial synthesis of oligopeptide analogues and their evaluation as protein:geranylgeranyl transferase inhibitors is presented. The combinatorial strategy is based on the random mutation, in each new generation, of one of any of the four amino acid building blocks of which the most effective compounds of the previous generation are assembled. In this way, a progressive improvement of the average inhibitory activity was observed until the fifth generation. The most active inhibitors were found to inhibit PGGT-1 in the low micromolar range (IC(50): 3.8-8.1 microM).     

Calculation of the Townsend Discharge Coefficients and the Paschen Curve Coefficients

The determination of Paschen curve coefficients A and B and the first and second Townsend coefficient are discussed for the creation of gas discharges from extraordinary gasses. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Rate and product studies in the solvolyses of N,N-dimethylsulfamoyl and 2-propanesulfonyl chlorides

Contrary to earlier suggestions of an S(N)1 pathway for solvolyses of N,N-dimethylsulfamoyl chloride (1), an extended Grunwald-Winstein equation treatment of the specific rates of solvolysis in 32 solvents shows an appreciable sensitivity towards changes in both solvent nucleophilicity and solvent ionizing power. The actual values are very similar to those obtained in earlier studies of the solvolyses of sulfonyl and phosphoryl chlorides, solvolyses which are believed to proceed by an S(N)2 pathway. The observation of similar selectivities in aqueous-alcohol solvents further supports this assignment. In a recent report, an addition-elimination (association-dissociation) pathway was proposed for solvolyses of 2-propanesulfonyl chloride (2). A severe multicollinearity problem has been removed by the addition of several specific rates of solvolysis in fluoroalcohol-containing solvents. The new analyses using the extended Grunwald-Winstein equation lead to sensitivities similar to those for and the previously studied related compounds, and these solvolyses are also best described as following an S(N)2 pathway.     

Spatial distribution multimedia fate model: Numerical aspects and ability for spatial analysis

A spatial distribution multimedia fate model is proposed for the rigorous simulation of the environmental multimedia fate of hazardous chemicals emitted from a variety of sources. To solve the relevant equation, we introduce an explicit finite difference method applied to uniform grids. We assessed the numerical properties of the model, including stability and accuracy. A new dimensionless number (multimedia transport number) is proposed for determining the numerical stability of the unsteady-state method. The model was verified by comparison with analytical solutions for the transport of non-conservative substances in two-phase open-channel flow. The spatial resolution of the spatial distribution model was tested via a comparison with a general multimedia fate model in a practical application related to toluene emissions in Seoul, South Korea.     

Breakdown magnetic field in an inductively coupled plasma

The Paschen curve shows that the breakdown voltage over a gap is a non-linear function of the product of the gas pressure and the gap distance for plasmas which are generated inside an electric field driven source. The Paschen breakdown relationship does not depend on the applied frequency and covers secondary emission at the electrodes of the discharge. Adapting the Paschen curve, a breakdown curve for a time-dependent magnetic field, typical for inductively coupled plasmas which sources are without electrodes, is examined here. It is shown that in this case the magnetic field breakdown curve does depend on the applied frequency.     

Fast and sensitive trace analysis of malachite green using a surface-enhanced Raman microfluidic sensor

A rapid and highly sensitive trace analysis technique for determining malachite green (MG) in a polydimethylsiloxane (PDMS) microfluidic sensor was investigated using surface-enhanced Raman spectroscopy (SERS). A zigzag-shaped PDMS microfluidic channel was fabricated for efficient mixing between MG analytes and aggregated silver colloids. Under the optimal condition of flow velocity, MG molecules were effectively adsorbed onto silver nanoparticles while flowing along the upper and lower zigzag-shaped PDMS channel. A quantitative analysis of MG was performed based on the measured peak height at 1615 cm⁻¹ in its SERS spectrum. The limit of detection, using the SERS microfluidic sensor, was found to be below the 1–2 ppb level and this low detection limit is comparable to the result of the LC-Mass detection method. In the present study, we introduce a new conceptual detection technology, using a SERS microfluidic sensor, for the highly sensitive trace analysis of MG in water.