Hydrogen oxidation on gold electrode in sulphuric acid solution

The aim of this work is to study the electrochemical oxidation of Hydrogen on gold electrodes in sulphuric acid solution and to compare the results with those obtained in a similar study in perchloric acid solution. In both electrolytes, the reaction is irreversible because the atomic H, which appears as reaction intermediate, diffuses inside of the metal. The reactive is introduced in two ways: by electrolysis at a cathodic potential during different times and by saturating the solution with the gaseous reactive. During the cathodic electrolysis the different crystalline planes of the surface reconstruct and this feature has an influence on the reaction kinetics. The catalytic influence of the incipient hydrous gold oxide on the H electrooxidation is also shown. The presence of sulphate and perchlorate ions leads to unlike voltamperometric profiles in the double layer charging potential region. A gold compound is formed during the metal treatment and an attempt has been done to identify it with FTIR.     

Urban anglers' perception of risk from contaminated fish.

The Newark Bay Complex includes the Newark Bay, tidal portions of the Hackensack River, Passaic River, Arthur Kill, and Kill van Kull. It is a highly industrialized urban area including five counties and more than 20 local governments with a large racially-mixed population of more than 3 million people. In 1982, research conducted by the New Jersey Department of Environmental Protection (NJDEP) showed elevated levels of chemical contaminants in five species of fish and one type of crab in the Newark Bay Complex. Subsequently, the State of New Jersey adopted advisories to guide citizens on safe consumption practices for fish and crabs. Since then, fish consumption advisories have been issued primarily through the Fish and Game Digest, a publication distributed by the state to licensed anglers. However, anglers in the Complex are not required to have a fishing license because the waters are marine. Therefore, most anglers in this area do not receive advisory information. To gain greater insight into the information sources and risk perceptions of urban anglers, a survey was conducted of 300 anglers at 26 fishing and crabbing locations in the Newark Bay Complex during the summer and early fall of 1995. The objectives of the study were to learn anglers': (1) knowledge of fish consumption advisories; (2) belief in the advisories; (3) perception of how safe fish are to eat; (4) sources for information about fish and fishing; and (5) sources for information on fish consumption advisories. The study concluded that while 60% had heard about advisories, they either did not believe or were unconcerned about health effects from eating contaminated species. In addition, the most used source for information about fish and fishing was other fishermen, while newspapers were selected as a source for information about community news, health, and food safety.     

The depolarization near-field scanning optical microscope: comparison of experiment and theory

The depolarization near-field scanning optical microscope allows for sub-wavelength optical resolution with uncoated optical fibre tips. We show by a simple thought experiment, by numerical solution of the Maxwell equations for a realistic geometry, and by direct experiments, that this novel apparatus images gradients of the dielectric function of a sample in the direction of the incident electric field vector. The near-field images obtained from experiment and theory agree well.     

Gasdurchlässigkeit von mit Hexamethylen-bis-methyloldihydroxyäthylenharnstoff vernetztem Zellglas. II. Vernetzung von Zellglas mit Hexamethylen-bis-methyloldihydroxyäthylenharnstoff und Messung der Gasdurchlässigkeit der vernetzten Folie

The oxygen permeation coefficients of cellophane, crosslinked with hexamethylene-bis-methyloldihydroxyethyleneurea [(CH₂)₆ bis-MDHÄH], were determined. It could be shown, that above all in the very important range of low concentrations, the ?molar barring efficiency”? of this compound is higher than that of all the other crosslinking agents investigated so far. With that the following order for the efficiency, concerning comparable molar concentrations, is valid now: (CH₂)₆--bis-MDHÄH > DMDHÄH ? FA > DMÄH > DMH. Cellophane at 64% relative humidity of gas, which contains 21 percent by weight of (CH₂)₆ bis-MDHÄH, is 12-43 times more impermeable against oxygen than different types of Saran. The course of the curve, showing the dependance of the oxygen permeability on the rel. humidity of gas for this film is very similar to the course of earlier investigated films, crosslinked with other derivatives of methylolureas. Hence it follows, that the crosslinkage with (CH₂)₆ bis-MDHÄH takes place in rather the same morphological areas of the cellulose as the linkage with the other derivatives of urea. Treating cellophane with aqueous solutions of (CH₂)₆ bis-MDHÄH there was found that the crosslinking agent (applied in the range of low concentrations) was taken up by the film in a quantity being proportional to the bath concentration. This is no longer the case when applying comparably high concentrations, in contrast to the earlier investigated other derivatives of urea; now the taking up is less than proportional. This is attributed to the comparably more difficult accessibility of certain morphological areas of the cellophane to the larger and less polar molecules of the (CH₂)₆ bis-MDHÄH. Further there was found after crosslinking the resulting molar barring efficiency being more than a third lower, when cellophane is treated with the same bath concentration of (CH₂)₆ bis-MDHÄH but at pH 8 instead of pH 6,5. This ist attributed to the diminished catalytic activity of the applied MgCl₂. 6H₂O as a crosslinking catalyst, caused by the weak alkaline medium.     

Über den Einfluß der Grenzflächenspannung auf die Haftfestigkeit

The values of adhesion between four diffrent adhesive,and (i) steel substrates whose surface energy had been altered by adsorption, and (ii) several polymer having different surface energies, had been measured. The results show that the adhesion has a maximum value when the surface energy of the hardened adhesive is equals to that of the substrate, i.e. when the interfacial energy adhesive/substrate is a minimum. The adhesion of the adhesives to the polymer was much smaller than to the steel sprcimens and the dependence of the adhesion onm the interfacial energy was sharper in the case of the polymers. The decrease of the adhesion with increasing interfacial energy was fiund to be greater if the liquid adhesive wets the substrate badly than the steel speciman.     

Zum Verhalten von Polyamidcarbonsäuren aus Pyromellithsäuredianhydrid und Benziding in Lösung. I. Streulicht- und Viskositätsmessungen in Dimethylacetamid

Poly(amic acids) of M _w = 48000 to 434000 were prepared by Polycondensation of pyromellitic dianhydride (PMDA) and benzidine using different stoichiometric ratios of the monomers. The poly(amic acids) were investigated through light scattering and viscosity measurements in dimethylacetamide solutions. In solutions containing LiBr, the polyelectrolyte effects are completely supressed; it is therefore possible to determine the molecular weights, the end-to-end distances and the second virial coefficients. The viscosity equation for poly(amic acid) from PMDA and benzidine in LiBr-dimethylacetamide is as follows: [η] = 3,40 × 10^?2 × M _w^0,78 ml/g. The relatively high [η]-values or correspondingly the low coil densities indicate a loose coiling of the poly(amic acid) molecules. As it is shown by the comparison of the unperturbed dimensions of these poly(amic acids) with the corresponding Avalues of other polymers, the loose coiling of the poly(amic acid) molecules is caused not only through the strong solvation of the polymer molecules by the solvent, but also through the long and stiff benzidine-units in the chain. In LiBr-free dimethylacetamide the beginning dissoziation of the COOH-groups has been noticed through decrease in the intensity of the scattered rays with decreasing angles of observation in the region of small angles and low concentrations. This effect is interpreted by external interferences of the scattered rays, caused by a more regular distribution of the macromolecules in the solutions. The intramolecular interaction of the negative charges produced by the dissoziation of the COOH-groups causes in LiBr-free systems a certain widening of the coil, which is noticed on the higher [η]-values as compared to the systems containing LiBr. As shown by the increase in the optical anisotropy in solutions without LiBr, a change in the coil configuration on the dilution takes place in such a way that it leads to an increase in the ratio of the ellipsoid axis, eventually joined with a geometical widening of the coil.     

Bestimmung des molekulargewichts von „mikrogelhaltigem”︁ polystyrol mit der ultrazentrifuge (methode archibald)

The weight average molecular weight M_w of a mixture of two polystyrenes with very high and relatively low molecular weights (M_w = 16.1 · 10⁶ and 98 · 10³ g/mole), as a model for polymers containing microgel, was determined by ultracentrifugation with the ARCHIBALD-methode. M_w decreases with increasing number of rotation N. The exact molecular weight can only be determined by extrapolation to N = 0. This value depends nearly completely on the molecular weight and weight percentage of the “microgel”. It is not suitable for the characterization of the whole sample.     

Über alkalisch vernetzbare polymerisate mit reaktiven chlormethylcarbonyl-gruppen

Copolymers containing reactive compounds are cross-linkable under the influence of heat and shifting of the pH. In practice reactive groups, e. g. methylol-compounds, are mostly used, which react under the influence of acids. However cross-linking agents for alkaline media are often demanded. In the group of examined monomers with chloroacetic-groups olefinically unsaturated N-(chloroacetamidomethyl)-carboxylic amides show good cross-linking agent properties in their copolymers. Emulsions of these polymers have proved to be particularly suitable for use as binders for textile, leather, and paper.     

Exposure to environmental and mainstream tobacco smoke and risk of spontaneous abortion

The present nationwide, multicenter clinical study was carried out in 26 departments of surgery to define the incidence and attendant mortality of intestinal infarction following abdominal aortic surgery, and to identify patients at risk of it. The data consist of 1752 patients who underwent abdominal aortic reconstruction during 1991-1993 as recorded in the Finnish national vascular registry (FINNVASC). Among the 1752 operations, 27 patients treated at 14 different hospitals had intestinal ischemia, and the complete patient records of all 27 cases were reanalyzed. The incidence of bowel infarction was 1.2%. Among patients operated on for a ruptured aneurysm it was 3.1%, whereas 1.0% of patients with nonruptured aneurysm and 0.6% of those operated on for aortoiliac occlusive disease developed intestinal infarction. In 14 patients (67%) the lesion affected the left colon. The overall 30-day mortality rate was 13% but reached 67% among those with intestinal infarction. We conclude that acute intestinal ischemia with bowel infarction is an infrequent but serious complication of abdominal aortic surgery. It is mainly related to surgery due to aneurysmal disease, and patients with occlusive aortoiliac disease present ischemic complications in the intestines less often. Hypotensive patients being treated for ruptured aneurysm are at greatest risk of intestinal ischemia.