Rotating frame spin—lattice relaxation in solid hydrated methaemoglobin

Proton T_1? relaxation times in two samples of methaemoglobin with different water contents showed that a process occurs with a correlation time of the order 10^?s s at 240 K. This is probably an exchange of molecules between bound and free water.     

An improved prototype apparatus and process for separating cellulosic materials from municipal solid waste

Applied Biochemistry and Biotechnology - A new prototype steam classification process apparatus has been designed, fabricated, and tested. The optimum operating conditions for the unit have been...     

A solid-state NMR study of cellulose degradation

A series of laboratory-aged transformer insulating papers were investigated using solid-state NMR spectroscopy. Carbon-13 CPMAS, and proton MAS experiments were carried out along with static proton relaxation (T₁, and T₁) and free induction decay (FID) measurements. Some proton CRAMPS and proton-carbon-13 correlation (WISE) experiments were also undertaken. A change in the proton T₁ and FID with ageing was detected. No detectable change was found in the proton T₁. Some amorphous cellulose was detected in the carbon-13 spectrum. There was, however, no evidence for a substantial change in the nature of the cellulose with ageing. The carbon-13 spectra from some aged samples showed signals not present in the spectrum from an unaged sample. This was taken to be evidence of chemical degradation. Proton MAS and the WISE exeriment gave some information about the nature of the water in the sample.     

Surface chemistry studies in relation to adhesion

Summary The paper reviews recent surface chemistry studies, concerning aluminium adhesive joints. The work of adhesion corresponds to breaking stresses ten times those observed. This result may point to the effect of stress concentrations. Actually work of adhesion is still relevant to joint stress in so far as it effects spreading of the adhesive, and thereby a) contact area, b) contact angle at the free meniscus, c) radii of trapped air bubbles. The enthalpy of adhesion may be evaluated for cases where the work of adhesion is inaccessible (i. e. contact angle equal zero). It has been determined for a range of liquids and epoxypolymers with aluminium powder. When compared with results on the failure load of aluminium epoxy-polymer joints, it is inferred that the latter was not determined byinterfacial crack propagation in this instance, but more probably by cohesive failure. The results point to the importance of oxide film structure in determining heats of wetting.

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Zusammenfassung Es wird ein Überblick über die Grenzflächenstudien gegeben, der Aluminiumklebverbindungen betrifft. Die Adhäsionsarbeit entspricht Bruchspannungen, zehnmal größer als beobachtet. Dieses mag auf dem Effekt von Spannungskonzentrationen beruhen. Die tatsächliche Adhäsionsarbeit bleibt noch insofern bedeutsam für Festigkeit von Klebung, als sie das Spreiten des Klebstoffes beeinflußt, a) die Kontaktfläche, b) den Kontaktwinkel am freien Meniskus, c) den Radius von eingeschlossenen Luftblasen. Die Adhäsionsenthalpie kann für Fälle, in denen die Adhäsionsarbeit unzulänglich ist, ausgewertet werden (z. B. für den Kontaktwinkel 0). Sie wurde für eine Reihe von Flüssigkeiten und Epoxyharzen und Aluminiumpulver bestimmt. Verglichen mit den Ergebnissen der Bruchlast von Aluminium-Epoxyharz-Klebstellen läßt sich schließen, daß letztere nicht durch Ausbreitung des Oberflächenbruches, sondern wahrscheinlicher durch Klebfehlstellen bestimmt wird. Die Ergebnisse weisen auf die Wichtigkeit der Oxidfilmstruktur beim Bestimmen von Benetzungswärmen hin.

     

On the requirement and mode of action of long-chain aldehydes during bacterial bioluminescence

Abstract— We have reinvestigated the role of aldehyde in bacterial bioluminescence relative to its absolute requirement for light emission. We have found that aldehyde is an absolute requirement for light emission at 25°C as well as in the frozen state (—3° to — 9°C). As found by earlier workers, certain luciferase preparations isolated from Ph. Jischeri do not appear to require aldehyde for bioluminescence from the frozen state. We can now attribute this behavior to contaminating levels of aldehyde in those preparations. The results suggest that reactant puddling exist in the frozen state in which micro regions of liquid form within the ice crystals resulting in enormous increases in reactant concentration.     

Preliminary studies on the processing sequence for southern red oak and municipal solid waste using a hybrid dilute acid/ enzymatic hydrolysis process for ethanol production

Based on this preliminary study, a metric ton of dry southern red oak chips subjected to a first-stage dilute sulfuric acid hydrolysis would yield 132 kg of xylose and 40 kg of glucose and mannose. A second-stage dilute sulfuric acid hydrolysis on the first-stage residue would yield only 128 kg of additional glucose, but a second-stage cellulytic enzyme hydrolysis on the first-stage residue would yield an additional 265 kg of glucose. Fermentation of these hydrolyzates would show that the hybrid process would yield over 50% more ethanol. Results on other biomass are also included.     

Nanojunction‐Mediated Photocatalytic Enhancement in Heterostructured CdS/ZnO,CdSe/ZnO,and CdTe/ZnO Nanocrystals

A series of highly efficient semiconductor nanocrystal (NC) photocatalysts have been synthesized by growing wurtzite‐ZnO tetrahedrons around pre‐formed CdS, CdSe, and CdTe quantum dots (QDs). The resulting contact between two small but high‐quality crystals creates novel CdX/ZnO heterostructured semiconductor nanocrystals (HSNCs) with extensive type‐II nanojunctions that exhibit more efficient photocatalytic decomposition of aqueous organic molecules under UV irradiation. Catalytic testing and characterization indicate that catalytic activity increases as a result of a combination of both the intrinsic chemistry of the chalcogenide anions and the heterojunction structure. Atomic probe tomography (APT) is employed for the first time to probe the spatial characteristics of the nanojunction between cadmium chalcogenide and ZnO crystalline phases, which reveals various degrees of ion exchange between the two crystals to relax large lattice mismatches. In the most extreme case, total encapsulation of CdTe by ZnO as a result of interfacial alloying is observed, with the expected advantage of facilitating hole transport for enhanced exciton separation during catalysis.     

The adsorption and reaction of CO and O2 on PdAu alloy wires

Temperature programmed desorption (TPD) of CO and O₂ on PdAu alloy wires has been studied. The heat of adsorption, sticking coefficient and maximum coverage of CO were recorded for Pd, 83 Pd 17 Au, 60 Pd 40 Au. For Pd and Pd-rich alloys the heat of adsorption remained fairly constant but the maximum coverage fell markedly from 0.42 for Pd to less than 0.05 for bulk palladium atom fraction X_B^pd ? 0.83. The heat of adsorption, sticking coefficient and maximum coverage of O₂ were investigated for pure Pd. A very limited adsorption was recorded on 83 Pd 17 Au and none on the more Au-rich alloys. The adsorption data are used to discuss the CO + O₂ reaction. Activation energy and frequency factor are estimated on Pd, for the TPD conditions used here. Earlier rate constants (0.2 Torr, 150°C) for CO + O₂ on PdAu as a function of Au content correlates with the maximum coverage of chemisorbed CO, which in turn is correlated with the probability of finding a Pd_9±1 ensemble in the surface. Modern results on the d-band structure of the PdAu alloys suggest that the Pd₉ ensemble, i.e. a surface Pd atom without an Au atom in its coordination shell, would tend to optimise both the donor and acceptor actions of the Pd atoms involved in chemisorbing CO.