The techniques employed on samples from the Hercies Road Experiment (Part I) were used to determine if chemical changes occurring during thc weathering of road tar could be detected and to obtain information on the nature of these changes.The main changes were attributable to evaporation and condensation, and chemical changes due to the action of air and light play a relatively minor part.
A process for the production of edible protein by the microbiological oxidation of petroleum hydrocarbons has recently been developed to pilot-plant scale. By fermentation with yeasts, n-alkanes are selectively oxidized in the presence of other types of saturated hydrocarbons in lubricating-oil fractions, and are converted almost quantitatively to high-protein cellular material.1The use of other forms of fossil organic matter as sources of carbon for the production of protein, amino acids, and other supplementary edible materials is of interest, and it has been found in this laboratory that certain types of coal derivatives and humic materials will support the growth of microorganisms. The microbiological treatment of some by-products of coal processing has lately been investigated2 and it has been shown that Cll-C15 paraffins and olefins present in low-temperature coal tar fractions will support the growth of the yeast Candida, giving cell yields similar to those obtained from petroleum fractions boiling in the same range. Also, the biochemical degradation of hydrocarbons and other compounds present in oils, tars, effluents, and industrial wastes is a research topic of growing importance because of the increasing pollution of rivers, lakes, and beaches and the vital necessity, in many industrial areas, of more efficient conservation and purification of water supplies.I n a preliminary investigation of the microbiological oxidation of materials of this type, a continuous-vertical-retort coal tar was extracted with aqueous acid and alkali to remove bases and phenols. A fraction of the neutral tar (20.2 g, b.p. 220-250°/20 mm) was stirred in a nutrient salt medium (1500 ml) containing ammonium sulphate (0.1 %), magnesium sulphate (0.02%), dipotassium phosphate (0.2%), sodium dihydrogen phosphate (0.3%), sodium carbonate (0.01%), calcium chloride (0.001%), and ammonium nitrate (0.1%) a t 25-35". The mixture was inoculated with enriched cultures of paraffin-consuming and 2-methylnaphthaleneconsuming soil microorganisms, consisting mainly of rod-shaped bacteria.Aliquot samples were removed at intervals during a total incubation period of 40 days. Unconverted neutral material was removed from each fraction by extracting with ether a t pH 8 -0 and the cell material was collected by centrifuging and washed with ether. Acidic and phenolic oxidation products were recovered by adjusting the pH to 3.0 and re-extracting with ether. The aqueous liquors were evaporated to dryness in a rotary evaporator under vacuum at 100'. The solid residue was extracted with acetone to recover other water-soluble products.
In the development of unimolecular reaction rate theory it has been possible to achieve much in terms of the concept of averaged rate constants together with classical or semi-classical approximations for the sums and densities of the molecular states involved. Even the widely successful RRKM theory in its normal mode of application relies partly on a quantum-mechanical treatment of vibrational states and partly on a classical motion of the system over the potential barrier associated with an empirically assigned transition state.It has long been recognised that certain problems such as the incorporation of the concept of weak intermolecular collisions and more recently the adequate interpretation of laser-induced unimolecular processes require a state-to-state treatment and formulation of the unimolecular process as a master equation involving all the individual molecular energy states of interest.The vast number of vibrational-rotational states for most molecules near to the threshold energy for unimolecular reaction has made this formulation a formidable problem. Although with the advent of computer methods the ability to handle large numbers of simultaneous equations has increased, problems still remain in estimating associated transition probabilities and individual rate constants and in reducing such formulations to a tractable size. As explained in the Preface to the book, the work of Professor Pritchard and his coworkers in recent years has been parallel to the development of mainstream unimolecular theory. It is, therefore, very appropriate and timely that this book should appear to summarise his individual contribution to the subject and trace its progress in a logical sequence.The first chapter presents a very useful and concise summary of the main observed features of thermal unimolecular reactions, particularly in relation to factors affecting their fall-off behaviour. This is followed by the treatment of a unimolecular reaction as a perturbation of internal molecular relaxation processes. The mathematics of the master equation is recast into matrix form and is not particularly easy. The reader is, however, given help by ample references to the original papers and to mathematical texts and recourse to these will be essential to anyone wishing to pursue the theory in detail. The unimolecular rate constant is derived as the lowest eigenvalue of the perturbed matrix and the problem of its evaluation is aided by 'graining' the many energy levels into groups and treating all dissociations from a given group as having the same rate constant. These rate constants are evaluated as in the Forst procedure from the observed A and E values.Detailed comparisons with some known experimental data are made and computer programs appended to enable this method to be applied more generally. Further chapters in the book deal with attempts to apply a dynamic state-to-state process more rigorously in the case of some triatomic molecules and approximate methods for larger molecules are discussed. Related topics dealt with ...
This volume contains the published proceedings of the Conference on "Liquid Crystals of One-and Two-dimensional Order and Their Applications" held at Garmisch-Partenkirchen in January 1980. The conference was a great success, although the published proceedings do not properly represent this success. Indeed, they are often infuriatingly inadequate and not particularly as a result of the brevity of most of the papers, although one is often left wishing for a fuller exposition, because after all brevity with clarity is a rare and precious virtue. No, they are inadequate and infuriatingly so because too many of the conference contributions are described here only by an abstract. There are 83 titles of papers of which no less than 41 are merely abstracts. There is a marvellous richness of interesting material referred to or hinted at but it is repeatedly galling not to have enough information to do more than whet the appetite.Despite these criticisms, however, the richness and the presence of a number of outstanding papers adequately compensate and the book is a stimulating hors d'oeuore for anyone interested in the very wide range of subject matter covered. This range and breadth is worth emphasizing because the field of liquid crystals is no longer (if it ever was) a narrow esoteric plantation of rare species but has lost its fences and merges into or overlaps a wide range of other subjects. The subject headings in the book will illustrate this: I, Ordered Smectic Phases and Structures (12 titles); 11, A and C Smectic Phases and Structures (1 1 titles); 111, Defects, Elasticity and Rheology of Smectics (5 titles); IV, Special Phase Transitions: Smectic A1-A2, Re-entrant Nematic, and Nematic-Isotropic Liquid Crystals (9 titles); V, Cholesterics and Electro-optical Applications of Non-nematics (10 titles); VI, Liquid-crystalline Polymers (8 ,titles); VII, Lyotropic Liquid Crystals (1 1 titles); VIII, Interfaces, Bi-and Mono-layers and Biological Applications (12 titles); IX, Mesophases of Disc-like Molecules (5 titles). Under each heading the first article and one or two others are of high quality and give a good representative picture of modern work. There are many other informative and interesting short contributions (and even abstracts) so that the whole adds up to a valuable addition to my library, and, I suggest, to many others.
The material covers the generation of radiation in the wavelength range 10-2000 pn (frequency 1000-5 cm-'), thus embracing traditional incoherent far-infrared radiation sources as well1 as microwave generators and low frequency optical lasers, optical and microwave transmission systems, detectors, cyclotron resonance, plasma theory and finally a long section on the theory of rotational, vibrational and electronic absorption and scattering spectra.The experimental chapters constitute about three-quarters of the book and represent a state of the art description of the field up to 1972. Microwaves are understandably treated in less detail but then little useful could probably have been added to the classic text of Townes and Schawlow. As the main subject matter of the text is one of intense research activity the text is rapidly dating, but will still represent a useful source of information for some years to come. In one section an untried interesting electron cyclotron resonance method of radiation detection is proposed and analysed in detail.The section on spectral interpretation is too brief to be other than a useful summary of basics suitable for teaching purposes. For instance, only 40 pages are devoted to rotational and vibrational spectra, which are covered far more adequately in numerous other texts, such as Townes and Schawlow, or Allen and Cross, and seem rather inappropriate here. The theory of magnetic resonances is less frequently discussed in standard text books and a summary of this theory is more appropriate to the main theme.It is slightly confusing at times to have frequencies quoted in Hz, then in cm-', in the same page in which wavelengths (pm) are used. Few errors were noted. The text is not written in a fashion conducive to undergraduate study and must be considered largely a reference text for graduate students and other research workers.
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