The thesis begins with an account of the behaviour of molecules on electron impact and explains how bond dissociation energies may be deduced from a study of ionization processes. The experimental work was carried out with a mass spectrometer designed and built for the purpose, and a full description of this instrument is provided, together with an account of the problems which arose during its construction and development, and the performance of which it was ultimately capable. After the reliability of the instrument had been tested by investigating some simple ionization processes, it was used to study the formation of benzyl ions from a number of related aromatic compounds. When the appearance potentials obtained in this way are combined with the ionization potential of the benzyl radical (which is the subject of a separate and direct determination) it is possible to make provisional estimates of the benzyl-x bond energy in dibenzyl, benzyl chloride, and benzyl iodide. The derived value of D (PhCH2 -CH2Ph) is used to verify Swarc's value of 77.5 kcal for D (PhCH2 -H). From this quantity, the following bond energies may be deduced thermochemically: D (PhCH2 -CH2Ph) - 45±3 kcal;/ D (PhCH2 -CH3) - 63±3 kcal; D(PhCH2-Ph) - 74.4±3 kcal, D (PhCH2 -I) - 36.6±4 kcal; D (PhCH2 -C1) - 62±4 kcal. The last two values are confirmed by the direct electron impact data. Lastly, an indirect estimate of I(Ph) - 9.7 eV is based on a measurement of the appearance potential of this radical from benzene, and a thermochemical value for D (Ph-H). The thesis ends with a description of how the instrument was modified by the inclusion of a reactor furnace in order to study the mechanisms of thermal decomposition reactions. Results are included of a brief experiment involving the pyrolysis of benzyl iodide out by this means.

In this work we will discuss fragmentation and molecular growth processes in collisions of Polycyclic Aromatic Hydrocarbon (PAH) molecules, fullerenes, or their clusters with atoms or atomic ions. Simple collision models as well as molecular structure calculations are used to aid the interpretations of the present and other experimental results. Fragmentation features at center-of-mass collision energies around 10 keV are dominated by interactions between the fast ion/atom and the electron cloud in the molecules/clusters (electronic stopping processes). This electronic excitation energy is rapidly distributed on the vibrational degrees of freedom of the molecule or of the molecules in a cluster and may result in fragmentation. Here, the fragmentation is statistical and favors the lowest-energy dissociation channels which are losses of intact molecules from clusters, H- and C2H2-losses from isolated PAHs, and C2-loss from fullerene monomers. We will also discuss the possibility of formation of molecular H2 direct from native PAHs which reach high enough energies when interacting with ions, electrons, or photons. For the experiments at lower center of mass collision energies (~100 eV) a single atom may be knocked out in close atom-atom interaction. Such non-statistical fragmentation are due to nuclear stopping processes and gives highly reactive fragments which may form covalent bonds with other molecules in a cluster on very short time scales (picoseconds). This process may be important when considering the formation of new species. For collision between 12 keV Ar2+ and clusters of pyrene (C16H10) molecules, new molecules, e.g. C17H10+, C30H18+, C31H19+, etc are detected. We also observe molecular fusion processes for He and Ar ions colliding with clusters of C60 molecules. These and related molecular fusion processes may play a key role for understanding molecular growth processes under certain astrophysical conditions.

This study is concerned with the problems of regional development. In modern times, the different institutions within the nation-state have multiplied in number and increased in size and complexity so that it is becoming more and more difficult for these institutions, functioning centrally, to achieve economic and social progress and to create efficient political and administrative systems. Local diversities and interests as well as national goals need to be observed and coordinated in order to achieve the required progress. Accordingly many countries are now tending to develop regional systems to suit their particular conditions, the aim being to lessen the risk of the central institutions' monopolizing political, economic and social powers, and at the same time to keep individual regions integrated into a single coherent unit for the good of the nation as a whole and for the good of the regions themselves. The present work comprises two parts. Part One deals with definitions and some general problems of regional development. For the purpose of exemplifying these generalisations, as well as glancing at the background of Aswan Region, we shall refer at this stage to some cases from Egypt. Part Two deals with regional development in the Aswan Region of Egypt. This Region may provide a useful example of economic and social development related to planned growth. The Aswan High Dam and the intensive development programmes in the Region play an important role in the changes that are taking place both in that Region and in the rest of Egypt. Part Two will also examine the background of Aswan Region, describing the High Dam and evaluating its consequences, then evaluating the regional development of Aswan Region and considering how far the concept of regional planning is applicable to the activities taking place there. The study, it is emphasized, is intended to be primarily a descriptive and analytical one, and no attempt is made to construct mathematical regional and interregional models.

No description available.

1. The spectral, spatial and temporal properties of receptive fields of dark-adapted, on-off retinal ganglion cells in the intact eye of the plaice, have been analysed by recording responses from their axon terminals in the superficial layers of the contra-lateral optic tectum with indium micro-electrodes. 2 Two cell-types have been identified on criteria of discharge patterns. The first type gives spectrally opponent "on-off" responses to coloured stimuli, with no subdivision of receptive fields into centre and periphery. On and "off" response-components are mutually inhibitory. The second type gives slow-adapting, "on-off" or "off" responses for different stimulus positions within the receptive field, with centre-surround or adjacent field patterns. Only "on-off" centre, off"-surround cells, or "off"-centre, "on-off" surround cells have been found, "On-off" centre cells exhibit mutual antagonism between field centre and surround. "Off"-centre cells possess inhibitory centres. This cell-type gives only weak opponent, or possibly non-opponent responses. 3. Moot cells of each type receive rod input in addition to input from cones. At stimulus intensities suprathreshold for cones, response-components give spectral maxima or more of four wavelength ranges; blue, 440-460 mum; blue-green, 470-490 mμ; green, 510-540 mμ; and orange, 560-590 mμ. No cello give red sensitivity maxima. At low stimulus intensities all cells with rod input give a single spectral peak between 520 and 530 mμ.

The objective of this thesis is to show that a study of medical images produced by British artists in the eighteenth century can contribute to the knowledge of the social history of medicine of the period, and to show that, by careful analysis of the medical images portrayed, some insight may be obtained into the meaning of works of art in which such images might otherwise be dismissed as merely irrelevant or gratuitous details. The thesis is cast In two main sections preceded by an introductory chapter which provides some background information with regard to the development of medical services in England and sets the scene from which literary and graphic artists drew their images, Works of the artist William Hogarth form the basis of the first section, The artist made extensive and knowing reference to medical imagery in many of his works, some of which are described and interpreted with due regard to the conventions employed, to the world around him, to literary works of his contemporaries and, where appropriate, to contemporary medical literature, Independent control with regard to the validity of the medical images and practices portrayed is provided where descriptions of such practices and Images correspond with each other. It is contended that such integration of written and visual sources of medical Imagery, in an empirical approach, enhances the information to be gained from either source viewed separately. Although mainly satirical in nature, it is argued that the images must have a foundation of truth and therefore deserve to be examined closely so that the truth of the situation portrayed may be revealed. The second section discusses the use of medical images from the late eighteenth century and early nineteenth century, mainly through the works of Thomas Rowlandson, although works of other artists such as James Gillray and George Cruikshank are included. Through their works information may be gleaned about a range of contemporary medical issues including lay perceptions of disease, pain and death, fashions in disease and treatment and the impact that advancing scientific knowledge had upon medical treatment and upon the practitioners involved. In addition, certain contemporary philosophical ideas are highlighted which have some bearing upon contemporary popular and medical opinion. The nature and function of medical images are discussed throughout the thesis. They are read, not as straightforward documents, but within a framework of recognisable practices. Medical and artistic changes took place throughout the century and the effects of some of these changes are commented upon during the course of the thesis, which concludes by assessing the arguments put forward in both sections and indicates how the two disciplines of the History of Art and the social History of Medicine can be bridged or annexed with benefit to both.

The field of quadrupole mass spectrometry has grown enormously since the early 1980's. The invention of the triple quadrupole mass spectrometer led to the development of tandem quadrupole mass spectrometers of many different configurations. A large number of tandem quadrupole mass spectrometers have also been developed by linking one or more quadrupole mass filters to a traditional magnetic or electric filter. The versatility of multiple quadrupole mass spectrometers along with their potential to rapidly produce a huge amount of data on a particular ion makes them ideal instruments for routine analytical analysis as well as for fundamental research The quinquaquadrupole mass spectrometer has been developed as an extension to the available multiple quadrupole systems. It offers the possibility to obtain even more data on the fragmentation of ions as well as enabling the study of novel ions to be carried out. The development of the quinquaquadrupole mass spectrometer forms the main part of this thesis. Also discussed are the reactions studied to evaluate the instrumental performance. The the ion molecule reactions of some halogen containing cations with saturated and unsaturated hydrocarbons performed on the triple quadrupole mass spectrometer are also discussed.

Observations have been carried out on the lampbrush chromosomes of Notophthalmus (Triturus) viridescens, the American newt; especially of chromosome II and XI. Chromosome II regularly bears two and occasionally three pairs of giant loops situated close to the centromere, The giant loops are distinguished from the majority of the normal loops by the greater bulk of their matrix and their length, which may vary from 60 mum to 300 mum. The giant loops are usually observed aa single loop pairs arising from a single chromomere but occasionally they occur as multiple loop pairs from a single chromomere. The giant loops also show variation in the distribution of their RNP matrix and more than one polarized matrix unit may be present on a single loop. The size of the loops and the matrix distribution pattern around any one loop pair is constant in oocytes ranging in size in any particular animal. The effect of increasing and decreasing the metabolic rate of the newt, by using hormone injections and cold treatment respectively, on the length and matrix distribution patterns of the giant loops was investigated. Hormone injections may cause changes in loop length, usually an increase but in one case a decrease, or have no effect. This may be due to the initial loop length or the level of gonadotrophin already present in the animal. After hormone injections the matrix distribution pattern, in multipolarized loops, alters with an increase in the proportion of the loop occupied by the first matrix unit. The constancy of loop characteristics over a range of oocyte sizes and the effect of hormone treatment are discussed in terms of matrix roving round a stationary loop axis. Cold treatment causes a dramatic shortening of the majority of lateral loops but leaves the giant loops virtually unaltered. Autoradiographic experiments have shown that the rate of RNA synthesis in the giant loops is half the rate of synthesis on the ordinary loops and that the RNA transcribed by the giant loops contains very little guanine. These results are discussed in terms of differing rates of RNA polymerase movement or attachment, different types of RNA polymerase molecules and the organization of highly repetitive sequences in the genome. The effect of inversion heterozygosity on chiasma distribution in bivalent XI was also studied, 15 out of 94 females studied were heterozygous for an inversion involving almost the whole of the longer arm of bivalent XI and including' the sequentially labelling loops situated close to the end which are transferred, by the inversion, to a position close to the centromere. The chiasma distribution in normal bivalents XI was compared with that of normal bivalents II and inversion heterozygote bivalents XI. Normal bivalents XI have chiasmata restricted to the chromosome ends while normal bivalents II have unrestricted distribution of chiasmata. In inversion heterozygote bivalents XI no chiasmata at all are formed in the longer inverted arm pair and chiasmata become distributed throughout the length of the shorter non-inverted am pair. Chiasma distribution was found to be similar in both sexes. These results are discussed in terms of the availability of recombination nodules and the time of their association with the synaptonemal complex.

Estuarine and montane plants of Armeria maritima (Mill.) Willd., differ slightly in anatomy. In their natural environment estuarine plants are frequently subjected to substantial variation in the total salinity of the root medium, while montane plants are not. Salt regulation in the two races was studied comparatively, using an electrochemical approach. The plants were grown in the laboratory in dilute culture, and subsequently exposed to increasing salinity up to the concentration of artificial sea water, the relative cationic composition of which was varied. The electrical potentials between the leaf water free space (W.F.S.) and the bathing media were measured, as were concentrations of the major ions in the W.F.S. and the bathing media, and the data applied to the Nernst Ussing-Tcorell equations. Comparison of predicted with actual fluxes obtained using radio-tracers showed active expert of Na+ and uptake of Cl- . K+ appeared to be actively imported at low external concentrations and passively distributed, with the possibility of active export at high and very high ambient concentrations. On the basis of purely electrical studies, a hypothesis in proposed for the role of the root in controlling the internal ionic environment of these plants with changes in the concentration of the bathing medium. The mode of action and efficiency as de-salinators of the salt glands present in the leaf are considered.

In Experiments 1 to 8 an attempt was made to examine the nature of the displacements found in the traditional line bisection test when applied to normal (right-handed), as well as brain lesioned subjects. The problem with this test is that it invariably confounds perceptual and motor components which might both contribute to the observed errors. However, use of the 'landmark task' enables an examination of perceptual effects in isolation. It was found that five out of six neglect patients judged the left half-line of a centrally bisected line as shorter than the right half-line. Moreover, it was consistently shown that cueing strongly influenced judgements in normal and left and right hemisphere lesioned subjects (without neglect) in that it caused them to overestimate the cued part of the line. It was argued that the perception of relative size is subject to systematic distortion as a function of this selective attention within the visual field. Neglect patients may present an abnormal example of this attentionally- induced illusion in that their attentional resources may be abnormally biased towards the ipsilesional space. The result of this imbalance may be to cause, quite directly, a gross abnormality of size perception. Nonetheless one of the neglect patients did not show spatial misperception but spatially misdirected actions, in line with what has been described as directional hypokinesia. Experiments 9 to 12 were designed to demonstrate any possible contribution the right hemisphere might make to visuomotor control, but the data on normal subjects gave little indication of a specific right hemisphere involvement in such tasks. Neither use of a spatial bisection task, nor absence of visual feedback of the moving hand or arm seemed to produce left hand advantages on the dependent measures. On the other hand, RCVA patients proved to be impaired in their reaching behaviour in that they erred systematically to the right of the true target over all three spatial positions, in the absence of visual feedback. The bias was interpreted as a pure example of directional hypokinesia.