Determination of Surface Functional Groups in Lignocellulosic Materials by Chemical Derivatization and ESCA Analysis

Simple and convenient methods for determining surface chemical composition of lignocellulosic materials are described. The methods are based on vapor phase fluorine surface derivatization with either trifluoro acetic anhydride (TFAA), tri-fluoro ethanol (TFE) or pentafluorophenyl hydrazine (PFPH) and subsequent Electron Spectroscopy for Chemical Analysis (ESCA). Model cellulosic surfaces with well defined functionalities were used to optimize the derivatization reaction conditions. Detection and accessibility of surface hydroxyl functional groups were investigated in cotton and regenerated cellulose as models. Carboxymethyl cellulose (CMC) was used as a model surface for detection and quantification of carboxylic acid groups. Theoretical conversion curves for derivatization reactions were calculated and used to evaluate the extent of the reactions on the model surfaces. It was found that the conversion was higher for the regenerated cellulose and CMC than for cotton. The protocols developed using the model surfaces were applied to a case study on wood fibers with different degrees of complexity, namely dissolving and chemithermomechanical (CTMP) pulp. Untreated and oxygen-plasma modified pulps were compared with respect to the surface composition of functional groups. According to the derivatization reactions, functionalities containing oxygen were significantly increased on the plasma-treated samples. The effect of the treatment was found to be dependent on the type of pulp. Fluorine derivatization is shown to be an unambiguous method for clear assessment of the chemical functionalities of cellulosic surfaces.     

Mixing mechanisms of vortex ring formed by gravity slumping motion

 This paper is concerned with an experimental investigation of the mixing inside the vortex ring formed by the gravity slumping motion of a dense cloud in a less dense atmosphere. The dynamics of the spreading and instantaneous structures of the turbulent flow were examined by visualization, single and multi-point measurements of velocity and concentration for two heavy gases, carbondioxide (CO₂) and dichlorodifluoromethane (CCl₂F₂), in a configuration in that heavy gas, initially trapped in a reservoir, was released with the rise of a shutter into calm air of a sector-shaped dispersion channel. Visualization of the cloud as a whole showed a spreading motion in which an advancing frontal structure was followed by a stratified flow with a layer of dense fluid of higher velocities near the wall and, on top of it, a layer of dilute fluid whose concentration is controlled by the mixing mechanisms within the head. During the course of spreading, there was always a phase in which the head attained to a constant speed of advance, which occurred as 0.13 m/s for CO₂ and 0.48 m/s for CCl₂F₂. It was interesting to observe for CO₂ that the phase of constant speed took place in between two acceleration phases; the former was due to the initial slumping of the cloud at the exit of the reservoir, and the latter was attributed to the collapse of the head on the transition to the passive dispersion phase. Instantaneous two-dimensional velocity field, measured with particle image velocimeter (PIV), showed that the cloud overran the ambient air which caused the approaching dense fluid deflected away from the wall with significant vertical velocities and downstream-moving separation, and the air trapped under the head resulted in the density inversion which introduced further intricacy to the turbulent structure of the head. Instabilities at the upper free shear layer due to density and velocity discontinuity rolled into periodic array of vortices which engulfed a considerable amount of air as they were convected backwards over the head, but the incorporation of heavy and light fluids was completed with the appearance of microscales after the collapse on the stratified layer. Analyses of the cloud head at different downstream locations also revealed that its size remained unchanged when the speed of advance was constant, allowing the rate of change of the cloud volume being modeled with the rate of spreading. Contours of concentration obtained from digitized PIV pictures confirmed the kinematic features of the mixing revealed by the velocity field and that the concentration values within the large structures were higher than those at the upper part of the stratified layer. Motivated by the experimental observations, a semi-empirical analysis was presented to describe the results and based on local values of the Richardson and Reynolds numbers. Received: 4 October 1995 / Accepted: 4 July 1996     

Solubility of carbon dioxide in aqueous solutions of sodium chloride: Experimental results and correlation

The solubility of carbon dioxide in aqueous solutions of sodium chloride was measured in the temperature range from 40 to 160°C, up to 6 mol-kg salt solutions and total pressures up to 10 MPa. Pitzer's⁽¹⁾ equations as well as the Chen and Evans⁽²⁾ model were used to correlate the new data. Results are reported and compared to literature data and correlations.     

Fracture strength of class II slot cavities restored with polymerizable restorative materials

This study compared the fracture strength of Class II slot cavities restored with polymerizable restorative materials. Sixty, caries-free, posterior teeth were divided into five groups of 12 teeth. The Class II slot cavities were prepared. The teeth were restored with two packable composites (Filtek P60, Surefil), a microhybrid composite (Filtek Z250)and two ormocer (Definite, Admira). The restorations were then subjected to fracture resistance tests. The marginal ridges of the restorations were loaded at an angle of 13.5° to the long axis of the tooth in an Universal Testing Machine until failure. Analysis of mean forces indicated that, Filtek P60, Surefil and Filtek Z250 exhibited better performance than Definite and Admira. The tested resin composites differed in their mechanical properties. This study suggested that fracture behavior were highly influenced by the filler system. Overall, Filtek P60, Surefil, Filtek Z250, demonstrated good fracture resistance. Copyright © 2003 John Wiley & Sons, Ltd.     

Preliminary analyses of natural radionuclides in selected Turkish power plant lignites

This preliminary study presents the experimental results concerning the concentrations of selected radionuclides (²³⁸U, ²³²K, ²²⁶Ra, ²³²Th) in Af?in-Elbistan, Çan, Çay?rhan, Erzurum, Göynük, Kangal, Orhaneli, Saray, Seyitömer, Soma, Tunçbilek, Yata?an and Yeniköy lignites, which are primarily utilized as fuel for thermal power plants in Turkey. Gamma-spectrometry of 39 representative lignite samples gave results with the following concentration ranges: 8 to 296 Bq/kg for ²³⁸U, 3 to 79 Bq/kg for ²³²Th, 17 to 360 Bq/kg for 40K, and 5 to 130 Bq/kg for ²²⁶Ra. The ²³⁸U results reported here are higher than other literature values for various world coals, earth's crust and world average.     

Synthese und Geruch von (Z)-Dehydro-homo-β-santalol

Summary Guided by molecular modeling studies, the synthesis of the title compound is described. The organoleptic evaluation proved the predicted real sandal like odour of (Z)-dehydro-homo--santalol.

Aus den Diplomarbeiten von C.P. (1991), I.P. und B.Ö. (1992), Universität Wien     

Progress in multi-ion counting spark-source mass spectrometry (MIC-SSMS) for the analysis of geological samples

Spark source mass spectrometry (SSMS) has experienced important and significant improvements in nearly all analytical features by the use of a multiple ion counting (MIC) system. Two procedures have recently been developed to further increase the analytical capabilities of MIC-SSMS in geochemistry. These are a mathematical correction of interferences, which is often necessary for the ultra trace element analysis of Nb, Ta, Zr, Hf and Y, and the development of an autospark system to hold the total ion beam constant. New analytical data for geological samples, especially international reference materials, are presented using the improved MIC-SSMS technique. The data set consists of high precision and low abundance data for Zr, Nb and Y in depleted reference materials. The MIC-SSMS results are compared with those of conventional SSMS using photoplates for ion detection. The precision of the MIC-SSMS isotope ratio measurements (about 1%) is more than a factor of 3 better than that of conventional SSMS, as demonstrated by analyses of Hawaiian samples. Total uncertainties of MIC-SSMS concentration data including all sources of error are generally between 2 and 5% for concentrations higher than about 0.3 microg/g and about 10% for trace element abundances in the ng/g range.     

Vacuum-ultraviolet induced oxidation of the polymers polyethylene and polypropylene

The emission from low-pressure microwave plasmas in the vacuum-ultraviolet (VUV) region (λ < 200 nm) was investigated in order to use these plasmas as light sources for the study of the VUV photochemistry of polyethylene (PE) and polypropylene (PP) as part of the study of plasma-polymer interaction. These polymers, immersed in low-presure oxygen, were exposed to radiation with wavelengths down to 112 nm, the cut off of magnesium fluoride used as a window to separate the polymer specimen from the plasma light source. Total oxygen incorporation in the surface [O], and the formation of hydroxyl, carbonyl, and carboxyl groups were measured using XPS in combination with chemical derivatizations, particularly their dependence upon the radiation spectrum and the oxygen pressure around the sample. In most experiments the surface oxygen concentration [O] attained a constant value that appears to be related to the initial oxidation rate; this suggests a competition between oxygen incorporation and chain scission reactions, followed by the removal of volatile oxidation products. PE is usually oxidized to a higher level than PP, the latter appearing to be more susceptible to reaction with atomic oxygen than PE. A general initiation mechanism for the VUV experiments is proposed that allows us to explain the observed differences in behavior between PE and PP, and the results obtained under different irradiation conditions. The nature of oxidation products is in both cases very similar to what is observed after direct plasma treatment of the polymers. We conclude that short wavelength radiation contributes very appreciably to the observed surface modification effects during plasma treatment of PE and PP. © 1995 John Wiley & Sons, Inc.     

New glyoxime derivatives and their transition metal complexes

Two new vic-dioxime ligands and their complexes with Co⁺², Ni⁺², Cu⁺², Cd⁺², and Zn⁺² ions were synthesized. Primer amines (3,4-methylenedioxaaniline and 4-methylbenzylamine) reacted with antichloroglyoxime to give 3,4-methylenedioxaphenylaminoglyoxime (H₂L¹) and N-(4-methylbenzyl)aminoglyoxime (H₂L²) ligands. Structures of the ligands and their complexes are proposed based on elemental analyses, IR, UV-Vis, and ¹H NMR spectra, magnetic susceptibility measurements, and thermogravimetric analyses (TGA). The article was submitted by the authors in English.