Showing papers by "University of Liverpool published in 1977"

The historical supernovae

Abstract: Only a few civilisations throughout the world have contributed significantly to the written records of astronomical phenomena from the historical past. Pre-eminent among these must be Europe, China (together with Korea and Japan), Babylon and the Arab World. A wealth of pre-telescopic data from these sources is readily accessible, and it is in this that searches for historical supernova sightings have been concentrated.

Life-history variation in poa annua.

Abstract: 1 Present address: Department of Botany, University of Sheffield, Sheffield 510 2TN, UK. Patterns of life-history evolution in populations experiencing different kinds of regulation raise some interesting problems. One problem which has been the subject of some discussion, concerns the evolutionary consequences of density-independent and density-dependent regulation. MacArthur and Wilson (1967) argued that under density-independent regulation, genotypes with the greatest intrinsic rates of natural increase would be selected (r selection) , whereas under density-dependent regulation, those with the greatest carrying capacities would be favoured (K selection). Thus if genetic variability for life histories exists in natural populations, life histories maximising r should be found in populations with histories of density-independent selection and life histories maximising K in those with histories of density-dependent selection. There is of course only one life history which ultimately maximises fitness, irrespective of the environment. This is the life history of an immortal organism which begins to reproduce immediately after birth and produces prodigous numbers of progeny at the shortest possible intervals thereafter. But in the real world resources are

Graphs, surfaces, and homology

Abstract: Homology theory is a powerful algebraic tool that is at the centre of current research in topology and its applications. This accessible textbook will appeal to mathematics students interested in the application of algebra to geometrical problems, specifically the study of surfaces (sphere, torus, Mobius band, Klein bottle). In this introduction to simplicial homology - the most easily digested version of homology theory - the author studies interesting geometrical problems, such as the structure of two-dimensional surfaces and the embedding of graphs in surfaces, using the minimum of algebraic machinery and including a version of Lefschetz duality. Assuming very little mathematical knowledge, the book provides a complete account of the algebra needed (abelian groups and presentations), and the development of the material is always carefully explained with proofs given in full detail. Numerous examples and exercises are also included, making this an ideal text for undergraduate courses or for self-study.

Some properties of the order of an autoregressive model selected by a generalization of Akaike∘s EPF criterion

Abstract: SUMMARY The asymptotic distribution of the order of an autoregression selected by a generalization of Akaike's FPE criterion is given. Some of the properties of the distribution are investigated. The use of this criterion is illustrated by a simulation study.

Space-Group Determination of the Low-Temperature W { 001 } ( 2 × 2 ) R 45 ° Surface Structure by Low-Energy-Electron Diffraction

Abstract: Low-energy-electron diffraction $I\ensuremath{-}V$ spectra obtained from the clean, cooled $\mathrm{W}{001}(\sqrt{2}\ifmmode\times\else\texttimes\fi{}\sqrt{2})R45\ifmmode^\circ\else\textdegree\fi{}$ surface structure at 190 K display $2mm$ point-group symmetry, revealing a preferential orienting of equivalent domains. A further novel effect, that the half-order beam spectra ($\ifmmode\pm\else\textpm\fi{}\frac{h}{2}, \ifmmode\pm\else\textpm\fi{}\frac{h}{2}$) are identical in relative intensity to the ($\ifmmode\pm\else\textpm\fi{}\frac{h}{2}, \ensuremath{\mp}\frac{h}{2}$) spectra but different in absolute intensity by a constant factor, uniquely establishes the space-group symmetry of the domains as $p2\mathrm{mg}$. A structure for a single-layer surface rearrangement is proposed.

Persistent truncus arteriosus. A study of 66 autopsy cases with special reference to definition and morphogenesis.

Abstract: Sixty-six hearts were examined in which a single arterial trunk, leaving the base of the heart through a single semilunar valve, supplied the aorta, pulmonary artery and coronary arteries. Careful attention was paid to the infundibular morphologic features in these hearts, and these were compared with findings in 24 hearts with single aortic trunk, pulmonary atresia and ventricular septal defect. It was concluded that the two anomalies represented morphologically discrete conditions. This was particularly true with regard to the disposition of the infundibular septum, the ventriculo-infundibular fold and the relation of the coronary arteries to the semilunar sinuses. Although it is theoretically possible for a heart with true persistent truncus arteriosus to have absence of the pulmonary trunk and right and left pulmonary arteries, it is argued that such hearts (“truncus type IV”) are best classified as pulmonary atresia with ventricular septal defect. It is also argued that hearts with a common arterial trunk supplied through discrete ventricular outflow tracts and two semilunar valves are best considered examples of aorticopulmonary window. It is suggested that persistent truncus arteriosus is best defined as that condition in which a single arterial trunk leaves the heart through a single semilunar valve and supplies the aorta, one or both pulmonary arteries and the coronary arteries.

Biogenic lipids in particulates from the lower atmosphere over the eastern Atlantic

Abstract: The occurrence, isolation, and characterization of terrigenous lipids in aeolian dusts from the eastern Atlantic are discussed. It is pointed out that such lipids have also been found in aeolian dust from other oceanic areas. A description is presented of the collection and extraction of samples. The dust samples were extracted with two aliquots of toluene and methanol (3:1) for lipid analysis. The extracts were concentrated on a rotary evaporator. General aeolian dust collection data and sample descriptions are presented in a table. The origin of the samples is discussed.

Disease and Mobility: A Neglected Factor in Epidemiology

Abstract: There is much historical evidence of the spread of disease through human mobility. Today in spite of medical advances and international health measures there is still much cause for concern. There is now more mobility, facilitated by modern transport and sometimes precipitated by major natural and man-made disasters. Redistribution of population is occuring in the developing world, particularly massive rural-urban movements. Population mobility has contributed to the transmission of malaria and prejudiced programmes for control and eradication; but mobility and other human factors have not been adequately studied. Parasites and vectors receive more attention than do people. Epidemiological studies need to pay greater attention to the nature and variety of population movements and to their differing impacts upon disease and health. It is essential to distinguish between migration (involving change of residence) and circulation (movement away from residence with sebsequent return). In tropical Africa various spatial and temporal dimensions can be applied to differentiate within these two major categories of mobility. In turn there are various associated physical and psychological health hazards.

Seasonal Occurrence of Helminths in Freshwater Fishes Part I. Monogenea

Abstract: Publisher Summary This chapter discusses the seasonal occurrence of monogeneans of freshwater fishes. The chapter considers monogeneans as one of five classes within the Phylum Platyhelminthes. The members of the class monogenoidea are ectoparasites of the gills, skin, and orifices of fishes, and, less frequently, of the oesophageal tracts and bladders of amphibians and turtles. The chapter discusses the subclass polyonchoinea of seasonal studies, including order dactylogyridea, order gyrodactylidea, and order tetraonchidea. The subclass oligonchoinea of seasonal studies includes order diclybothriidea and order mazocraeidea. The chapter also discusses the seasonal studies in world climatic zones. The distributions of plants and animals are influenced by climate. Climate is determined by and varies with latitude, longitude, and altitude. It is the end product of infinite and changing combinations of temperature, wind, rain, water currents, land and water masses, mountain ranges, and vegetational cover. The climate zones are divided into tropical, subtropical, mid-latitude or temperate, polar, and mountain climates.

Immunoreactive component resembling cholecystokinin octapeptide in intestine.

Abstract: MANY hormones exist in several molecular forms. The intestinal hormone cholecystokinin has been isolated from hog duodenum in the form of peptides of 33 and 39 amino acid residues (CCK33 and CCK39)1–4. Extracts of hog cerebral cortex have been shown to contain components with CCK-like immunoreactivity5, but on gel filtration the main component in brain had the properties of the COOH-terminal octapeptide (CCK8) of CCK33 and CCK395. Several other hormonal and related peptides probably occur in identical forms in brain and gut6, so it seemed possible that a CCK8-like factor would also be found in intestine. Synthetic CCK8 is known to be about twice as potent on a molar basis as CCK33 on the main target organs of the hormone (gall bladder and exocrine pancreas)7 so that the possible existence of CCK8 in the intestine is of physiological significance. We have studied immunoreactive CCK-like factors in extracts of hog duodenum and jejunum and we report here the presence of relatively high concentrations of a CCK8-like component. This factor was poorly extracted by the method used to purify CCK33 and CCK39 which may explain why it was previously overlooked.

The social conditions, consequences and limitations of careers guidance

Abstract: The recent influence of developmental theories of occupational choice upon guidance practice in Britain is criticised. It is suggested that people do not typically ‘choose’ occupations in any meaningful sense: they simply take what is available. Moreover, the career of the typical industrial worker cannot be meaningfully understood in terms of self-actualisation and implementing a self-concept: guidance work based upon these concepts is accordingly unrealistic. An adequate theory for understanding school-leavers' transition to employment in Britain needs to be based around the concept not of ‘occupational choice’, but of ‘opportunity structure’. Guidance should concentrate not on raising unrealistic expectations, but on helping people to adjust successfully within the opportunity structures open to them.

Long-range coherence in biological systems

Abstract: The great success of molecular biology arises from tile discovery of the detailed structure of biomoleeules such ~s DNA ~md enzymes. :No systematic spaeial order was found, and it wa, s concluded tha t these molecules do not possess a physical order. Physical order, however, does not express itself in special order only. Thus superfluid helium, or the electrons in ~ superconductor exhibit an order tha t might be termed . This type of order is connected with the existence of macroscopic w~ve functions, which implies the existence of cert~fin quantum phase correlations over macroscopic distances or the existence of coherent states. Other correlations connected with the phase of oscillating systems rather than with those of m~eroscopic w:~ve functions ~re ~lso well known when those systems are lifted from their thermal equilibrium. A well-known example are laser systems which need not exhibit :~ spa~ebfl order as, e.g., in the c~se of gas lasers. Many other types of physical order m'~y be imposed on certain systems

Variation in the Spire Index of Some Coiled Gastropod Shells, and Its Evolutionary Significance

Abstract: The spire index (height/maximum diameter of shell) is a fairly adequate measure of the shape of the coiled shell of most terrestrial and freshwater gastropod shells but less so in complex marine shells with thorns, flanges and spouts. In this study, only adult free-crawling forms with several whorls, able to retract completely into the shell, are considered. In the Stylommatophora of the Western European terrestrial fauna the distribution of the spire index is markedly bimodal, the modes, with values of about 3 and about 0.5, corresponding respectively to shells with a high to very high spire (and small spire angle) and those varying from more or less globular or trochoid to very flattened and disk-like (spire angle from 60 $^\circ$ to 180 $^\circ$ ). The same two modes are found in the taxonomically different terrestrial stylommatophorans of the U.S.A., and in the faunas of Puerto Rico (Caribbean) and New Caledonia (southwest Pacific). Basommatophorans also show two, rather different, modes. North American marine archaeogastropods are mainly equidimensional but with a few disk-like forms and a very few high-spired ones, marine mesogastropods are mainly high-spired but with disk-like forms, neogastropods high-spired, and relevant euthyneurans sharply bimodal, like the stylommatophorans. Fossil archaeogastropods of the Palaeozoic were much more various at first than modern forms. There is some indication that they became restricted in variety as caenogastropods became abundant, but also that the proportion of marine disk-like shells has decreased markedly since the Palaeozoic. Modes of h/d are characteristic of large taxonomic groups but not taxonomically restricted since given values may appear as specific, generic or subfamilial variants from a mode, and appear sporadically in unrelated forms. There is also no broad association between modal value and broad ecological characters. Since nearly all values do occur in some group or other, no mechanical requirement can be invoked to explain such variation. In the land Stylommatophora enough is known of the broad ecology to suggest that in extreme habitats species with very different size or shell-shape may occur together, and that generalized feeders with similar shells may show separation, ecological or geographical (but in that case, also ecological). Since different shapes of shell will have different mechanical characteristics when considered as burdens to be carried, it is suggested tentatively that they may be related to the positions in which different species normally walk and hence to their preferred feeding places. This would explain an apparent tendency for different taxonomic groups to occupy the same part of the scatter of h/d in different regions of the world, for many groups in the same region to occupy different portions of the scatter, and perhaps the apparent exclusion by caenogastropods of archaeogastropods from part of the scatter since the Palaeozoic. It is argued that the distributions discovered are explicable only by natural selection.

A method for decreasing patients' medication errors.

Abstract: Eighty anxious and eighty depressed patients were assigned randomly to receiving one of three versions of an information leaflet about their medication, or to receiving no leaflet at all. Mean medication errors were reduced from 15 to 4% by provision of suitably constructed leaflets. The results show the practical importance of informing patients about their medication and of paying attention to the difficulty level of any leaflets issued.

The n.m.r. spectra of porphyrins. 13—A ring current model for the porphyrin and chlorin (7,8‐dihydroporphyrin) rings

Abstract: The equivalent dipole model of the ring current shift in benzene is shown to be equivalent to that of the well-known two current loop calculation. A network model of the ring current effect in the porphyrin system is described, using the double–dipole approximation, to give a calculation of the ring current shifts in the porphyrin system; this agrees with the observed shifts of protons both in the ring-plane and above it. A simple modification of the model enables treatment of ring current shifts in the chlorin ring. These models may be used to provide, very simply, good estimates of the ring current shifts of the porphyrin and chlorin rings at points above and outside the current loops; the agreement is sufficiently good to allow assignments of peripheral substituents to be made, and to provide information on their orientation. The model is consistent with a peripheral ring current loop in both the free-base porphyrins and their metal complexes. The relationship of these results to calculations in polycyclic aromatics and to protonation shifts in porphyrins is discussed.

The decomposition of vegetation growing on metal mine waste

Abstract: Aspects of the decomposition of metal tolerant vegetation growing on mine waste containing high concentrations of lead and zinc were studied and compared with those on an adjacent uncontaminated site. High concentrations of Pb and, to a lesser extent, Zn, accumulated in metal-tolerant grass. Retarded decomposition of this vegetation as compared with that on the uncontaminated site was indicated by a greater accumulation of litter, less humus formation, reduced soil urease activity and smaller microbial and microfaunal populations. Some evidence for increased metal tolerance in microbes from the mine waste was obtained. Concentrations of lead tolerated under laboratory conditions were much lower than those extracted from the mine waste and its vegetation, probably due to the lack of an accurate method for assessing the availability of lead in soil and vegetation.