Showing papers by "University of Warwick published in 1972"

Secondary Bonding to Nonmetallic Elements

Abstract: Publisher Summary A number of recent crystal structure determinations on compounds of the nonmetals have discovered intramolecular distances that are much longer than normal bonds, and intermolecular distances that are much shorter than van der Waals distances. In this chapter, these interactions are examined and a qualitative explanation is attempted. It will become clear that in most of them an approximately linear arrangement is found, Y-A—X where Y-A is a normal bond and A—X is a short intermolecular distance. It is with these approximately linear interactions that we are particularly concerned, and it will be our contention that they are the result of directed forces and that their behavior is sufficiently regular and understandable for the name secondary bond to be appropriate. The only conclusive method of establishing the presence of secondary interactions is by crystal structure determinations. An intermolecular interaction can be recognized as being significant by being shorter than the expected intermolecular (van der Waals) distance, but if it is the result of directed forces— that is, bonds rather than electrostatic or nondirectional van der Waals forces.

Fate of seeds of some annual weeds in different depths of cultivated and undisturbed soil

Abstract: Summary. Freshly-collected seeds of twenty species of annual weeds were uniformly mixed with 2.5, 7.5 or 15 cm of soil confined in cylinders sunk in the ground outdoors. The soil was either cultivated four times a year or left undisturbed, seedling emergence was recorded, and after 5 years the numbers of viable seeds remaining were determined. Total seedling emergence from seeds incorporated to 2·5, 7·5 and 15 cm amounted to 75, 65 and 54% respectively of those added when the soil was cultivated, and 58, 36 and 21% where it was left undisturbed. The corresponding numbers of viable seeds remaining after 5 years were 2·3, 4·0 and 7·7% respectively for cultivated soil, and 6·8, 16·5 and 31·6% of the seeds initially added and then not disturbed. Individual species varied in their responses to increasing depth of incorporation and to cultivation; these differences are discussed in relation to the dormancy characteritics of the seeds. Devenir des semences de quelques mauvaises herbes annuelles a differentes profondeur dans un sol cultive et non cultive Resume. Des semences recoltees recemmeni sur vingt especes de mauvaises herbes an-nuelles furent uniformement melangees avec 2,5; 7,5 ou 15 cm de sol contenu dans des cylindres stockes dans le sol en dehors du laboratoire. Le sol fut travaille quatre fois dans l'annee, ou au contraire laisse sans facon culturale, la levee dts plantules fut enregistree, et, apres 5 ans, les semences viables restantes furent denombrees. La levee totale des semences incorporees a 2,5; 7,5 et 15 cm fut respectivement de 75, 65 et 54% pour les semences ajoutees au sol travaille et de 58, 36, et 21 % pour les semences en sol non travaille. Les nombres correspondants de semences restees viables apres 5 annees representerent respectivement 2,3; 4,0 et 7,7% du nombre initial dans le sol travaille et 6,8; 16,5 et 31,6% dans le sol non travaille, Les especes, considerees individuellement, presenterent des reactions variees a l'accroissement de la profondeur d'enfouissement et au travail du sol; ces differences sont examinees en relation avec les caracteratiques des dormances des semences. Verhalten von Samen einiger annueller Unkraauter in versckiedenen Tiefen eines bearbeiteten und nicht bearbeiteten Bodens Zusammenfassung. Frisrh gesammelte Samen von zwanzig Arten annueller Unkrauter wurden mit Boden gleichiormig gemischt und In Zylindern in 2,5; 7,5 oder 15 cm Tiefe draussen im Boden gclagert. Der Boden wurde entweder viermal im Jahr bearbeitet oder blieb unbcarbeitet. Das Auflaufen der Samen wurde ermittelt, und nach 5 Jahren wurde die Zahl der lebensfahig gebliebenen Samen bestimmt. Der gesamte Auflauf der Samen, die in 2,5; 7,5 und 15 cm Tiefe eingebracht worden waren, belief sich bei dem bearbeiteten Boden auf 75; 65 und 54% der untergemischten Samen. Im nicht bearbeiteten Boden waren cs 58; 36 und 21%. Die entsprechende Anzahl der nach 5 Jahren noch lebensfaAhig gebliebenen Samen belief sich im bearbeiteten Boden auf 2,3; 4,0 und 7,7% und im nicht bearbeiteten Boden auf 6,8; 16,5 und 31,6% der ausgcbrachten Samen. Vcrsrhiedene Arten zeigten in ihrer Reaktion aufdie zunehmende Tiefe ihrer Aussaat und aufdie Bearbeitung ein abweichendes Verhalten. Diese Unterschiede werden in Bczug zu den Dormanzcharaktc Hstika der Samen diskutiert.

Regression methods for studying genotype-environment interactions.

Abstract: WHEN the performance of a set of genotypes is compared over a number of environments it is frequently found that genotypic effects are not fixed, but that they vary between environments. In biometrical investigations the problem then arises of how to characterise genotypic effects. A number of authors (e.g. Yates and Cochran, 1938; Finlay and Wilkinson, 1963; Eberhart and Russell, 1966; Perkins and Jinks, 1968a, b) have shown that in many such cases the performance of an individual genotype can be expressed as a linear function of the environmental index (the additive environmental effect). The slope of this regression, a dimensionless quantity, is a measure of the sensitivity of the genotype to the totality of environmental factors. Where the regressions are found to account for a substantial part of the genotype environment interaction variance, this empirical approach to the problem of interactions has proved to have considerable value. An identical technique has been used by Mandel (1959) and Mandel and Lashof (1959) to compare the result of tests at several laboratories on a number of materials, and the theoretical aspects of the statistical analysis have been discussed in a series of papers by Mandel (1961, 1969, 1970, 1971) and Mandel and McCrackin (1963). There has not, to our knowledge, been any reference to this work by biologists, nor as Mather (1971) has pointed out, any discussion of the underlying reasons why the regression technique works for plant material, although various authors have either denied that any such a priori reason exists (Wright, 1971), or have attributed the success of the method to the linearising nature of the transformation (Knight, 1970). In contrast to the empirical methods mentioned above, the classical approach of plant physiologists to the problem of genotypic performance has been by multifactorial experiments and growth analysis. This approach has led to the formulation of various regression models which relate plant performance to environmental variables, and more recently to computer simulation models of the same relationship (e.g. de Wit and Brouwer, 1968). Freeman and Perkins (1971) have suggested on statistical grounds that it may be better to use this approach to analyse genotype-environment interactions, by regression on environmental variables, rather than to use regression on the environmental mean. This paper considers the two regression methods and their interrelationship from a different point of view. First we show that there is a bias in the estimates of the coefficients of regression on the environmental mean when they are derived by the usual method. After considering the relations of this approach to various other techniques, we turn to the interpretation of the values of the coefficients of regression and of the deviations from the regressions on the environmental mean. It will be shown that it is possible to account for their values in terms of the coefficients of an \"underlying\" regression model. Finally a

Biochemistry of protein synthesis in plants

Abstract: 111. Protein synthesis in chloroplasts . . . . 130 A. Introduction . . . . . . 1 3 0 B. Chloroplast autonomy . (I) DNA . (2) DNA polymerase. . (3) RNA polymerase. . (4) Protein synthesizing apparatus (a) Ribosomes . (b) Amino acid activation . (c ) Initiation . (d) Energysource . (e) Inhibitors . . I 3 1 . 132 . 136 . 1 3 6 * I37 . 140 . I41 . 142 . I43 . I43 C. Function of chloroplast ribosomes . . I 4 4 (I) Evidence from studies of inhibitors in wivo . . I 4 4 (2) Products of protein synthesis in oitro . . . . 146 IV. Protein synthesis in mitochondria . . . A. Brief description of the mitochondrion . B. DNA . . . . C. DNAreplication . D. DNA transcription . E. Protein synthesis . .

Competition, collusion, and game theory

Abstract: This original, quantitatively oriented analysis applies the theory of the core to define competition in order to describe and deduce the consequences of competitive and non-competitive behavior. Written by one of the world's leading mathematical economists, the book is mathematically rigorous. No other book is currently available giving a game theoretic analysis of competition with basic mathematical tools. Economic theorists have been working on a new and fundamental approach to the theory of competition and market structure, an approach inspired by appreciation of the earlier work of Edgeworth and Bohm-Bawerk and making use of the new tools of the theory of games as developed by von Neumann and Morgenstern. This new approach bases itself on the analysis of competitive behavior and its implications for the characteristics of market equilibrium rather than on assumptions about the characteristics of competitive and monopolistic markets. Its central concept is "the theory of the core of the market," and it is concerned, with the conditions under which markets will or will not achieve the characteristics of uniform prices and welfare optimality. Telser provides a number of insights into the symptoms of competition, when and how competition is bought into play, the mechanisms of competition and collusion, the results of competition and collusion, and the results of competition and collusion for the economy and for the general public. Many misconceptions about the nature of a competitive equilibrium are dispelled. The book is not only a mathematical analysis of core price theory but also contains extensive empirical research in private industry. These empirical findings, from research pursued over several years, enhance understanding of how competition works and of the determinants of the returns to manufacturing industries.

On the homeotopy group of a non-orientable surface

Abstract: Let X be a closed, compact connected 2-manifold (a surface ), which we will denote by O or N if we wish to stress that X is orientable or non-orientable. Let G ( X ) denote the group of all homeomorphisms X → X , D ( X ) the normal subgroup of homeomorphisms isotopic to the identity, and H ( X ) the factor group G ( X )/ D ( X ), i.e. the homeotopy group of X . The problem of determining generators for H ( O ) was considered by Lickorish in ( 7, 8 ), and the second of these papers specifies a finite set of generators of a particularly simple type. In (10) and (11) Lickorish considered the analogous problem for non-orientable surfaces, and, using Lickorish's partial results, Chilling-worth (4) determined a finite set of generators for H ( N ). While the generators obtained for H ( O ) and H ( N ) were strikingly similar, it was noteworthy that the techniques used in the two cases were different, and in particular that little use was made in the non-orientable case of the earlier results obtained on the orientable case. The purpose of this note is to show that the results of Lickorish and Chillingworth on non-orientable surfaces follow rather easily from the work in ( 7, 8 ) by an application of some ideas from the theory of covering spaces (2). Moreover, while Lickorish and Chillingworth sought only to find generators , we are able to show (Theorem 1) how in fact the entire structure of the group H ( N ) is determined by H ( O ), where O is an orientable double cover of N. Finally, we are able to determine defining relations for H ( N ) for the case where N is the connected sum of 3 projective planes (Theorem 3).

A superlattice with monoclinic symmetry based on the compound V6C5

Abstract: The ordered distribution of carbon vacancies in the compound V6C5 has been analysed by electron diffraction and dark-field electron microscopy. The dominant structure is that based on a superlattice with monoclinic symmetry having a lattice orientation relation with the disordered cubic matrix which may be summarized: The unit cell parameters, neglecting a distortion of the f.c.c. vanadium atom structure, are The vacancy distribution is related to that previously observed for this compound and found in the present investigation in minor fraction. The difference in the vacancy distribution is determined by the alternative stacking sequences of partially filled octahedral carbon atom layers. Hence one structure may be derived from the other by an ordering in the distribution of stacking faults which have been identified in the carbon sub-lattice.

Moment-Rotation Curves for Locally Buckling Beams

Abstract: Tests on composite steel-concrete beams have shown these sections to be highly susceptible to local buckling under negative bending. To further the application of plastic design to continuous composite beams an approxiamte method of predicting the moment-rotation curve of a locally buckling I-shape is developed. The method is based on the upper-bound plastic limit theorem. Solutions are given for two buckling mechanisms and their applicability is determined from test results and web slenderness criteria. Comparisons between the theoretical predictions and several test curves show consistently conservative, but reasonable agreement.

Pollen tube growth and the site of the incompatibility reaction in brassica oleracea

Abstract: Summary Unpollinated, cross-pollinated and self-pollinated stigmas of Brussels sprouts and kale were examined in a scanning electron microscope as fresh uncoated specimens. The stigmatic papillae are closely appressed in young stigmas, but are held apart in the mature stigma by the swollen bases of the papilla cells. Some self-pollen tubes show obvious signs of inhibition by being very short, or by coiling over the surface of the papilla without penetrating it. Other self-pollen tubes appear to behave like cross-pollen tubes by producing tubes which penetrate papillae directly. The implications of these observations for the identification of the site of the incompatibility reaction are discussed.

Resistance to attack by Brevicoryne brassicae among plants of Brussels sprouts

Abstract: SUMMARY Because they remained almost uncolonized by the cabbage aphid (Brevicoryne brassicae (L.)) throughout the growing season, plants of Brussels sprouts were singled out in each of 4 years, from plots heavily infested with the aphid, as possibly being resistant to attack. Clones of these plants were established from cuttings and tested in a controlled environment by inoculation with B. brassicae and later, in the field, by natural infestation. The tests confirmed that some of the plants were resistant to the aphid, and the most resistant of those from the first year of the work proved at least as resistant as any subsequently found. The resistance was expressed as antibiosis, but in the field host non-preference was also shown by incoming winged aphids. The possibility that biotypes of B. brassicae might exist, to which the resistant sprout clones were not necessarily resistant, was investigated using B. brassicae collected from sprouts from each of several areas in England. Eight sprout clones, seven of which were known to be resistant, and the other susceptible, to B. brassicae from Wellesbourne were tested with these other B. brassicae. The results showed that biotypes of the aphid, with differing abilities to colonize respective sprout clones, existed in each area, and of the seven sprout clones resistant to the Wellesbourne aphid, only one appeared never to be fully susceptible to one or more of the other biotypes of B. brassicae.

Influence of sulphate nutrition on flavour components of three cruciferous plants: Radish (Raphanus sativus), cabbage (Brassica oleracea capitata) and white mustard (Sinapis alba)

Abstract: The effect of sulphate nutrition on the flavour components of three members of the family Cruciferae (radish, cabbage and white mustard) has been investigated. The plants were grown in a glasshouse in sand culture at six concentrations of sulphate in the nutrient medium and their flavour characteristics determined by sensory and gas-chromatographic methods. The latter were based on (a) headspace samples from the raw and cooked vegetables and (b) solvent extracts chromatographed at 200°C. Sensory tests showed that the flavour strengths of the vegetables increased from low values at extreme sulphur deficiency to maxima with increase of the sulphate available to the plant. For radish and mustrad, there was no correlation between total volatile componets (determined by the headspace method) and sulphur content but a highly significant corelation was demonstrated between the latter and less volatile flavour components present in solvent extracts. In the case of mustrad seed. p-hydroxybenzyl isothiocyanate was determined colorimetrically and shown to be correlated with sulphur nutrition. With cabbage, allyl isothiocyanate and total volaile content were determined by a headspace method and each was found to be significantly correlated with sulphate nutrition. It is suggested that the flavour of these plants consists of at least two types of componnts: (a) compounds which impart a bland, generalised “vegetable” flavour to the food and (b) a specific component or components which are perceived as a burning sensation on the tongue sometimes accompanied by a characteristic odour. The former are independent of sulphur nutrition whilst the concentrations of the latter are highly correlated with sulphur nutrition. The effect of sulphate nutrition on growth response, visual deficiency symptoms and mineral composition has been reported.

The organization of ribosomal granules within mitochondrial structures of aerobic and anaerobic cells of saccharomyces cerevisae

Abstract: Difficulties in the fixation and embedding of yeast cells suitable for electron microscopy studies have been reported by many workers since the early observations on the presence of mitochondria in these cells (Agar and Douglas, 1957 ; Hagedorn, 1957; Hirano and Lindgren, 1961 ; Vitols et al ., 1961 ; Yotsuyanagi, 1962) . In particular, the reported absence of mitochondrial profiles in yeast cells grown anaerobically without lipid supplements (Polakis et al., 1964; Linnane, 1965 ; Wallace et al., 1968) has recently been shown to be due to inadequate fixation by potassium permanganate (Damsky et al ., 1969 ; Plattner and Schatz, 1969; Watson et al ., 1970, 1971) . The mitochondrial structures in the anaerobic lipid-depleted cell were observed by freeze etching (Plattner and Schatz, 1969) to be similar in morphology to those present in the aerobic and anaerobic lipid-supplemented cells . On the other hand, we have recently reported (Watson et al ., 1970, 1971) that the mitochondrial precursors in the lipid-depleted cell are quite distinct, both morphologically and biochemically, to mitochondria) structures in the aerobic and anaerobic lipid-supplemented cells. Damsky et al . (1969) have also reported the presence of primitive mitochondrial structures, similar to those isolated by Watson et al . (1970, 1971), in partially disrupted anaerobic lipid-depleted cells . A further difference was the nondetectability of mitochondrial ribosomal RNA species (Forrester et al., 1971) and an active mitochondrial protein synthesizing system (Watson et al ., 1971) in the lipid-depleted anaerobic cell, both of which are present in the case of the lipid-supplemented anaerobic cell (Watson et al ., 1971 ; Forrester et al., 1971) . The experiments on the lipid-depleted

Availability of atrazine to plants in different soils

Abstract: The concentrations of atrazine in the shoots of wheat plants growing in 12 different soils were directly proportional to the soil solution concentrations of herbicide estimated from slurry adsorption measurements. There was a marked discrepancy between the total uptake of herbicide and the amount theoretically supplied by mass-flow in response to transpiration. This discrepancy was less when plants were grown in nutrient solutions. In an experiment with one soil only, the half-life of atrazine was 22 days and when the solution concentration in this soil was corrected for this change, a much closer prediction of atrazine uptake could be obtained. The ways in which interactions between adsorption, breakdown and transpiration rates may affect herbicide toxicity under field conditions are discussed.

Class inclusion processes

Abstract: Publisher Summary This chapter discusses class inclusion processes and describes the problems of stage and transition A gap exists between the hypothetical structures and processes that form the basis of the theory and the level of performance The theoretical account is presented at a level of generality that makes it uncertain as to whether it is sufficient to account for the complex and varied behavior that it purports to explain There is no way at all of determining what can be its consequences on the level of performance A much more detailed account of the functioning of specific processes is necessary before these uncertainties can be dispelled The information processing approach provides a methodology that bridges the gap between theory and performance The most specific theory of human problem solving deals entirely with adult subjects A repeated decomposition of action chains in unfamiliar situations can ultimately lead to a series of unitary productions

The diurnal periodicity and cycle of behaviour of the adult cabbage root fly (Erioischia brassicae)

Abstract: SUMMARY Adult cabbage root fly (Erioischia brassicae (Bouche)) exhibited a diurnal periodicity in behaviour. Trapping tests indicated that the flies fed from hedgerow flowers in the morning, visited the crop in the early afternoon and returned to the hedges in the late afternoon. In the laboratory the flies also showed a cyclical pattern in behaviour. Feeding preceded oviposition by 3 days and this was reflected in the field by a relative increase in the movement of females away from the hedges and to the crop when they became gravid. The diurnal periodicity and the cycle in behaviour of males was similar to that of the females, indicating that some of the flies' movement was non-appetitive. The tendency of flies to stay for most of the day at hedges resulted in progressive declines in the numbers captured with increasing distances from hedges.

The preparation and optical properties of small silver particles in glass

Abstract: The preparation of a large number of well characterized small silver particles in a photosensitive glass and in a stained glass is described. Particles with diameters from about 10 A to greater than 100 A were produced. Using the stained glass a volume fraction of particles of at least 1% can be obtained. The width and peak position of the optical absorption due to these particles was measured for different particle sizes. A significant shift in the peak position was observed for particles less than about 25 A diameter. Both the width of the absorption and its position could be quite well described by a theory which assumes that the mean free path of the conduction electrons is proportional to the particle radius. On decrit la preparation de grands nombres de petites particules d'argent bien caracterisees dans du verre photosensitif et dans du verre teinte on a produit des particules qui avaient environ 10 A jusqu'a plus de 100 A de diametre. En se servant du verre teinte, on peut obtenir une fraction de volume des particules de 1% au moins. Pour les differentes dimensions des particules on a mesure la largeur et la valeur de pointe de l'absorption optique due a ces particules. On a observe un deplacement significant de la valeur de pointe des particules qui avaient moins d'environ 25 A de diametre. On pourrait bien expliquer et la largeur et la position de l'absorption par une theorie selon laquelle le libre parcours moyen des electrons de conduction serait proportionnelau rayon particulaire.