Electrochemical oxidation of several chlorophenols on diamond electrodes Part I. Reaction mechanism

The electrochemical oxidation of 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol aqueous wastes using boron-doped diamond electrodes was studied. This treatment led to complete mineralization of the wastes regardless of the operating conditions. A simple mechanistic model is consistent with the voltammetric and electrolysis results. According to this model, the electrochemical treatment of chlorophenol aqueous wastes involves the anodic and cathodic release of chlorine followed by the formation of non-chlorinated aromatic intermediates. Subsequent cleavage of the aromatic ring gives rise to non-chlorinated carboxylic acids. Chlorine atoms arising from the hydrodehalogenation of the chlorophenols are converted into more oxidized molecules at the anode. These molecules react with unsaturated C₄ carboxylic acid to finally yield trichloroacetic acid through a haloform reaction. The non-chlorinated organic acids are ultimately oxidized to carbon dioxide and the trichloroacetic acid into carbon dioxide and volatile organo-chlorinated molecules. Both direct and mediated electrochemical oxidation processes are involved in the electrochemical treatment of chlorophenols.     

Thermodynamics of gas-solid flow

New thermodynamic fundamentals for vertical pneumatic conueying are proposed with derivation based strictly on mass conservation and continuum concept. For a 1-D, vertical, steady gas-solid flow, these new mass and energy balances allowed the derivation of a new nondimensional energy factor containing the pressure drop. This energy factor correlated quite well with the difference between the inlet gas velocity and solids terminal velocity, when tested against high-pressure, 15-m-high, vertical pneumatic transport data from Institute of Gas Technology. The energy factor was also checked against atmospheric-pressure data of the 5-m lift line of the Pennsylvania State Uniuersity. The new energy factor covers quite well both the atmospheric- and high-pressure sets of data (923 tests) including two heights, lean- and dense-phase transports, several pipe diameters, broad and narrow particle-size distributions, and different materials. The dissipation terms in gas-solid flow were also clearly identified.     

Experimental results of a low-power roadheader driving a gallery with different types of rock at the face

In this paper, the experimental results of a 45-kW and 15-t roadheader excavating a gallery with two different types of rock at the face using two different cutting heads are shown. It is proved that the roadheader works properly with both cutting heads. In comparison with other results in the literature, the principal parameters, i.e. specific energy, cutting rate and tool wear, are at a level that can be considered satisfactory taking into account the low power of the roadheader. On the other hand, the influence of the number of picks, which is the main difference between the two cutting heads, on the operational parameters is shown.     

Copper phthalocyanine as corrosion inhibitor for ASTM A606-4 steel in 16% hydrochloric acid

A study based on the corrosion inhibition properties of copper phthalocyanine is described. Coverage degrees of copper phthalocyanine (Cu-phcy) on ASTM-A606-4 steel, obtained by weight loss measurements, were fitted to Langmuir, Frumkin, Temkin and Flory–Huggins adsorption isotherms. A better fit to the Langmuir isotherm was obtained. The polarization curves showed that polarization of both the anodic and cathodic reactions were verified for concentrations higher than 10^–4 M, indicating a mixed type action. Only the anodic reactions were polarized for lower concentrations. At high frequencies the Nyquist diagrams showed one capacitive loop attributable to double layer charging and a small one at intermediary frequencies attributable to the faradaic process of hydrogen evolution. The formation of an adsorbed film was characterized by increasing charge transfer resistance values in the low frequency range for increasing inhibitor concentrations. According to the techniques used in this study, copper phthalocyanines showed a high corrosion inhibiting efficiency for all concentrations.     

Extrusion-rotomolding of plasticized PVC formulations

In this work, we present a novel process to produce plasticized PVC articles. Plasticized PVC dispersion resin (dry blend) was extruded and poured into a hot mold. The mold was transferred to a rotomolding machine, where the final geometry was obtained. Formulations using commercial PVC suspension resin and three different types of plasticizers were prepared under different processing conditions. The physical appearance of the articles and the tensile properties of the materials were evaluated.     

In-situ-Messung der Stickoxidkonzentration in turbulenten Diffusionsflammen

Zusammenfassung Die laserspektroskopischen Me?methoden laserinduzierte Fluoreszenz und spontane Ramanspektroskopie werden eingesetzt zur Messung der Konzentrationen von Stickoxid, Hydroxyl sowie der chemischen Hauptkomponenten und der Temperatur. Betrachtet wird die thermische Umsetzung von Wasserstoff mit Luftsauerstoff. Es wird die experimentelle Vorgehensweise und Problematik dargestellt. Ebenso wird der Weg der Modellierung und Berechnung turbulenter Verbrennungsvorg?nge am konkreten Beispiel skizziert. Die Annahme chemischen Gleichgewichts stellt sich als ungenügend in der Berechnung der Stickoxid- und Hydroxylkonzentrationen heraus. Eine deutlich bessere Vorhersage wird durch Einführen einer Reaktionsfortschrittsvariablen für das chemische Modell erreicht.     

Helicobacter pylori at Hospital Santo Tomás

We studied the incidence of infection with Helicobacter pylori in Panamanians with chronic dyspepsia, gastric or duodenal ulcer, gastritis or gastric cancer. The histopathology was positive in 54 (81%) of 66 patients; the urea test was positive in 52 (82.5%) of 63 cases; the impromptu was positive in 51 (79.6) of 64 patients; the endoscopic examination was positive in 64 (82.9%) of 77 examinations.     

Acute endocarditis of the native aortic valve caused by Propionibacterium acnes

Propionibacterium acnes is often considered to be a contaminant but it has also been found to be the principal pathogen in serious infections. P. acnes is a rare cause of infective endocarditis. It has been suggested that aortic root abscesses are caused by bacteria that are particularly virulent. The strongest risk factor for serious infections by this bacteria is the presence of foreign bodies. A case is presented in which endocarditis of a native aortic valve caused by P. acnes was associated with an aortic root abscess. Transesophageal echocardiography is particularly helpful in the diagnosis of this severe complication of infective endocarditis. The literature for P. acnes endocarditis is reviewed.     

From the individual element test to finite element templates: Evolution of the patch test

This paper starts a sequence of three articles that follow an unconventional approach in finite element research. The ultimate objective is to construct high-performance elements and element-level error estimators for those elements. The approach takes off from our previous work in high-performance elements and culminates with the development of finite element templates. The present paper concentrates on the patch test and evolved versions of the test that have played a key role in this research. Following a brief review of the historical roots, we present the Individual Element Test (IET) of Bergan and Hanssen in an expanded context that encompasses several important classes of new elements. The relationship of the IET to the multielement forms A, B and C of the patch test and to the single-element test are investigated. An important consequence of the IET application is that the element stiffness equations decompose naturally into basic and higher-order parts. The application of this decomposition to the “sanitization” of the non-convergent BCIZ element is described and verified with numerical experiments. Two sequel papers in preparation are subtitled ‘the algebraic approach’ and ‘element-level error estimation’. These apply the fundamental decomposition to the derivation of templates for specific mechanical elements and to the construction of element-level error estimators, respectively.     

RF antenna analysis with the ICANT code

The ICANT code computes self-consistently the surface current distribution on a 3D antenna model radiating in a plasma or vacuum and has been used to analyze the coupling properties of various antenna models. In this work it is used to assess near-fields generated by different versions of the TCABR (Tokamak Chauffage Alfvén wave heating experiment in Brazil) antenna as well as coupling properties of the TEXTOR tokamak in Forshungszentrum Jülich. Two different strap models planned for the TCABR antenna are shown to be practically equivalent in terms of maximum electric field. Textor coupling calculations are close to experimental values.