Showing papers by "University of Reading published in 1987"

Improving water use efficiency of annual crops in the rainfed farming systems of West Asia and North Africa

Abstract: Farming systems in west Asia and north Africa have evolved to cope with the problems of highly variable and, frequently, chronically deficient rainfall. Cereals (mainly wheat and barley) are the dominant arable crops with food legumes (chickpea, lentil and faba bean) occupying only 5 to 10% of the area planted to cereals. Livestock is closely integrated into the farming system and crop production practices often reflect the importance of animals as a major source of income, particularly on the smaller farms. Soils of the region are predominantly calcareous, frequently phosphate deficient, and their depth and texture are important in determining the maximum amount of water that can be stored which, in turn, may determine the effective length of the growing season.Rain falls mainly during the winter months so that crops must often rely on stored soil moisture when they are growing most rapidly. Analysis of equations relating crop growth and water use shows that there are three ways in which the ‘water use efficiency’ of dry matter production can be increased. First, the amount of dry matter produced per unit of water transpired might be increased; second, if the water supply is limited, the amount of water transpired might be increased relative to evaporation from the soil surface; and third, the total amount of water used might be increased to produce extra growth provided that this results in increased transpiration rather than simply increasing evaporation from the soil surface.These three possible routes to increased crop growth are reviewed in relation to possible improvements in water management and crop genotypes in the Mediterranean environment. Scope for improving transpiration efficiency is limited although genotypic differences exist and may be useful in the future. More immediately, changes in crop management, such as applications of fertilizer, improved tillage and better weed control, will all increase the amount of water transpired. Application of mulches will also reduce evaporation from the soil surface but crop residues are usually eaten by livestock and are, therefore, often unavailable.The barley/livestock farming system of west Asia is used as a case study to illustrate how the Fanning Systems Programme of ICARDA has developed on-farm research programmes of direct relevance to current farming systems. Research on experimental sites directed at improving water use efficiency has been developed into on-farm trials and into collaborative trials with the Syrian Soils Directorate.

Baroclinic Instability in an Environment of Small Stability to Slantwise Moist Convection. Part I: Two-Dimensional Models

Abstract: In the semigeostrophic system, the growth rate of baroclinic waves varies with the inverse square root of the potential vorticity, which acts as the effective static stability. Recent observations in the ascent regions of middle latitude cyclones show that the effective potential vorticity for saturated air is very near zero. In this paper we examine the structure and rate of growth of baroclinic cyclones when the effective potential vorticity is small for upward (saturated) displacements but large in regions of descent. Analytic solutions for two-dimensional disturbances in a two-layer semigeostrophic model and numerical simulations using a multilevel semigeostrophic model show that when the effective potential vorticity is small in regions of upward motion, growth rates are modestly increased and the region of ascent intensifies and collapses onto a thin ascending sheet. In the limit of zero moist potential vorticity the fastest growing wave has a finite growth rate which is about 2.5 times the...

Suppression of Baroclinic Instability in Horizontally Sheared Flows

Abstract: Baroclinic instability in the presence of a meridionally sheared barotropic component to the basic flow is studied using a two-level model. The inclusion of a linear shear results in merldionally confined normal modes with growth rates much reduced compared to the unsheared case. Similar results hold for more complicated situations, such as a baroclinic jet with barotropic shear. The results are applied to life cycle calculations in which it is shown that the nonlinear decay phase of a baroclinic disturbance sets up barotropic shears whichtend to suppress further baroclinic developments. An example of the Southern Hemisphere winter mean flow is found to be strongly stabilized by virtue of a strong sheared barotropic part of the zonal flow.

Femtosecond dynamics of multielectron dissociative ionization by use of a picosecond laser.

Abstract: The multiple ionization of molecular nitrogen has been studied by use of an intense picosecond laser (0.6 ps: 3\ifmmode\times\else\texttimes\fi{}${10}^{15}$ W/${\mathrm{cm}}^{2}$: wavelength 600 nm). By measurement of the energies of the various fragment atomic ions (${\mathrm{N}}^{+}$, ${\mathrm{N}}^{2+}$, and ${\mathrm{N}}^{3+}$) with a time-of-flight mass spectrometer it has proved possible to investigate the dynamics of the multielectron dissociative ionization process on a time scale of about 30 fs.

The interactive effect of spatial resolution and degree of internal variability within land-cover types on classification accuracies

Abstract: A study is made to assess the effect of spatial resolution on the degree of internal variability within land-cover classes and then to examine how this within-class variance affects classification accuracy. Airborne Multispectral Scanner data flown at 5 m resolution are degraded to simulate 10 and 20 m data. Classification accuracies within internally homogeneous classes are found to be high at all spatial resolutions. In contrast, classification accuracies of land-cover types characterized by a high degree of internal variability or scene noise improve by up to 20 per cent as spatial resolution is coarsened because the proportion of scene noise is reduced. A further improvement in classification can be achieved by smoothing the imagery prior to classification using various spatial filters. The extent of this improvement was found to be as much as 25 per cent depending on the type of spatial filter used, the window size of the filter, the spatial resolution of the data and the land-cover type bei...

Geochemistry of High-silica Peralkaline Rhyolites, Naivasha, Kenya Rift Valley

Abstract: The Recent ( 5 per cent phenocrysts. Phenocryst minerals are quartz-sanidine-ferrohedenbergite-fayalite-titanomagnetite-ilmenite-riebeckite-arfvedsonite-aenigmatite-biotite-zircon. Ferrohedenbergite and zircon are restricted to less peralkaline, and amphibole, aenigmatite, and biotite to more peralkaline, rocks.The comendites show unusually strong enrichment in Cs, F, Hf, Nb, Rb, REE, Ta, Th, U, Y, Zn, and Zr, and extreme depletion in Mg, Ca, Ba, Co, and Sr. REE patterns are moderately LREE-enriched, with large, negative Eu anomalies. Values of LIL/HFS element ratios, such as Th/Ta and Rb/Zr, are unusually high for peralkaline rhyolites, and are consistent with a substantial crustal component in the comendites. Parameters such as LREE/HREE and Zr/Nb ratios indicate that the Naivasha rhyolites represent several pulses of closely related, but subtly different, magmas. Sanidine/glass partition coefficients for Ba, Pb, Rb, Sr, U, and the REE are presented for one specimen.Major and trace element modelling, and feldspar-rock relationships, show that closed system crystal fractionation cannot alone account for the overall compositional variations in the comendites. A model involving partial melting of variable crustal source rocks and migration of dissolved volatile-metal complexes may be appropriate at Naivasha.

Maturation of the respiratory response to acute hypoxia in the newborn rat.

Abstract: 1. We used a non-invasive method to measure the breathing of conscious newborn rat pups continuously and studied the maturation of the respiratory response to reductions in inspired O2 fraction (FI,O2) from 0.21 to 0.15, 0.12 or 0.08 for 6 min. Newborn rats, like many other species, showed a "biphasic" respiratory response, ventilation (VE) increasing during the first 1-2 min of hypoxia (phase 1) and then falling towards control, or below it, over the next 4 min (phase 2). 2. The secondary fall in VE decreased with age up to 14 days. The presence of a significant fall in VE in phase 2 depended on the FI,O2 to which the pups were exposed acutely; the lower the FI,O2 the greater the age at which a biphasic VE response was observed. 3. Our results are discussed in terms of two opposing components which determine VE during acute hypoxia in the neonate: (a) a fast arterial chemoreceptor-mediated stimulation of VE and (b) a slower central nervous component which inhibits VE, possibly a persistence of a suprapontine mechanism which inhibits fetal breathing movements during hypoxia in utero. Both of these components undergo maturation after birth.

The Elements of the Concept of Ideology

Abstract: This article, based upon an extensive examination of the literature on the concept of ideology, identifies some 27 definitional components or ‘elements' which are discussed in turn to ascertain their utility and coherence as definitional criteria. On the basis of this examination a number of these elements are found to be essential to the concept, and are built into a definition which allows consideration of, among other things, the expressive and justificatory dimension of beliefs often ignored in other definitions.

The Location Choice of Offices of International Companies

Abstract: There has been a structural shift of employment in developed countries towards the tertiary sector, and an increase in the proportion of economic activity being conducted by international firms. This paper is an examination of the factors that influence location choice of international offices, by means of survey data that facilitate a sectoral analysis of location choice. Analysis of the motives that lead to direct foreign operations is based on the ownership–location–internalisation paradigm, which suggests that international firms tend to be most active in those sectors in which their ownership advantages are most pronounced, and in which these advantages are best exploited internally to the firm. A branch–regional classification is used to distinguish cases in which office-location choice is dominated by external market forces (branch offices) and those in which location is determined by internal organisational forces.The primary influences on location choice are market size and the need for personal ...

The solar chimney—overall efficiency, design and performance

Abstract: SYNOPSIS An analysis is developed for the soiar chimney, aimed particularly at deriving overall efficiency and significant performance data. Numerical values are consistent with available information on the 200 m solar chimney at Manzanares, Spain, and projected designs. Overall efficiency is directly related to the height of the chimney and is shown to be about 1% for a height of 1000 m. It is concluded that the solar chimney is essentially a power generator of large scale.

Effects of chronic hypoxia from birth on the ventilatory response to acute hypoxia in the newborn rat.

Abstract: 1. Newborn rats and their mothers were exposed from birth in a normobaric environmental chamber to an inspired O2 fraction (FI,O2) of 0.13-0.15 for 5-10 weeks. 2. The respiratory response to reducing FI,O2 to 0.12 or 0.08 for 6 min was measured in the conscious chronically hypoxic rat pups on post-natal days 5 and 14 and again at 5-10 weeks of age. On days 5 and 14 the responses were compared to those of normoxic control pups also exposed acutely to an FI,O2 of 0.12 or 0.08. 3. No significant respiratory response to the acute reduction in FI,O2 was found in the chronically hypoxic pups on post-natal days 5 and 14, whereas the normoxic pups showed a "biphasic" respiratory response on day 5 and a sustained ('adult') response on day 14. A "biphasic" respiratory response to an FI,O2 of 0.08, but not to an FI,O2 of 0.12, was seen in the chronically hypoxic pups at 5-10 weeks of age. 4. At 5-10 weeks recordings from the carotid sinus nerve were made in anaesthetized, paralysed and artificially ventilated rats. The isocapnic hypoxic response curves of chronically hypoxic rats were not significantly different from those of age-matched normoxic rats. 5. Our results suggest that limiting the rise in arterial O2 pressure which usually occurs at birth alters the ventilatory response to acute hypoxia by post-natal day 5 and this alteration is still evident at 5-10 weeks of age.(ABSTRACT TRUNCATED AT 250 WORDS)

The occurrence of copper—norstictic acid in lichens from cupriferous substrata

Abstract: The localization of norstictic acid and copper in green, copper-rich specimens of Acarospora smaragdula and Lecidea lactea from cupriferous substrata was studied by optical microscopy, scanning electron microscopy, and electron probe microanalysis. Infrared absorption spectroscopy of lichen material and a synthetic Cu-norstictic acid complex, and the other studies, provide evidence that complexing of copper by norstictic acid occurs within the cortex of these lichens and leads to their unusual surface coloration. Preliminary observations suggest that copper may also form a complex with psoromic acid and colour lichen thalli green. There is a strong possibility that other metal-lichen acid complexes may occur.

Effects of protein concentration on responses to dietary lysine by chicks.

Abstract: 1. Chicks were fed on diets varying in crude protein (CP) content (140 to 280 g/kg diet) in either 8 steps, experiment 1, or 6 steps, experiment 2. Protein composition was held constant in each experiment. At each protein concentration, 5 (experiment 1) or 6 (experiment 2) concentrations of lysine were tested, ranging from 40 to 60 g/kg CP. 2. Growth rate and efficiency of food utilisation to 21 d of age responded to increasing dietary protein contents up to about 230 g CP/kg. An estimate of lysine requirement at each protein concentration was obtained by fitting a quadratic curve to the response data and calculating the dose of lysine (g/kg CP) needed to maximise either growth rate or gain/food ratio. 3. Although no growth response to dietary protein was obtained between 240 and 280 g CP/kg, the amount of lysine needed to maximise growth and gain/food ratio over this range increased systematically when expressed as g/kg diet, but remained constant if expressed as g/kg CP. 4. The regression of ly...

Growth, water use and yield of barley in Mediterranean-type environments

Abstract: Relations between yield, water use and pre-anthesis growth were analysed for cropsof barley grown for three seasons at several sites in northern Syria. The relations obtained were compared with those for other cereal crops grown in similar regions of Mediterranean climates.Phosphorus fertilizer application increased the rate of crop development from emergence to floral initiation and advanced anthesis by up to 11 days. Grain and total shoot dry-matter yields were increased by fertilizer (nitrogen + phosphorus) applications at all sites in all years, in most cases without increasing total evapotranspiration. The increased dry matter at anthesis was produced without having used a larger proportion of the total evapotranspiration in the whole season. Consequently, the ratio of grain yield to total above-ground dry-matter yield (harvest index) and kernel weight were also relatively stable between sites and years, despite some very low amounts of post-anthesis water use. Grain yield appeared to be largely determined by anthesis and there were strong linear relationships between grain yield or total dry-matter yield and number of kernels. Differences in water use efficiency of crops given fertilizer between sites and years were closely related to the differences in amounts of winter growth.Some responses differed from those predicted from models of growth, water use and yield developed in other regions with similar climates. It is concluded that agronomists and breeders should increase amounts of early growth thereby increasing grain and dry-matter yields. Future research emphasis should also be on the development of dynamic simulation models of pre-anthesis growth and water use.

Natural resource management and the use of multiple criteria decision-making techniques: A review

Abstract: This paper attempts to improve the awareness in the agricultural economics profession of the potential role that multiple criteria decision-making (MCDM) techniques can play in analyzing problems involving several objectives. Important applications of the MCDM techniques to planning and management problems in fisheries, forestry, water, and land resources are reviewed, and some 150 applications are brought together to provide a unified source of reference. Copyright 1987 by Oxford University Press.

The Theory of Empty Categories and the Pro-drop Parameter in Modern Greek.

Abstract: One of the most promising new developments of recent research into theoretical syntax within the model of Government and Binding (GB) as presented in Chomsky (1981) and (1982) has been the new importance given to the study of languages other than English. This has stimulated a great deal of work into a variety of languages (see, for example, Rizzi, 1982; Borer, 1983; Bouchard, 1984; Huang, 1984 and others). It has also been welcomed by linguists outside the TG tradition. Thus, Comrie, (1984:155) expresses his delight that ‘Chomsky (1981) makes clear that generative grammarians have come to realize that an adequate study of syntax within universal grammar requires the study of languages of different types. Chomsky's main concern has always been to formulate a theory that would achieve ‘explanatory adequacy’ by providing a restrictive set of principles which could characterize universally the notion ‘natural language’. However, detailed and in-depth analyses of various languages have revealed that in order to achieve ‘descriptive adequacy’ the theory has to allow for cross-linguistic differences, or ‘parametric variation’. The concept of parametric variation weakens some-what the restrictiveness of the universal grammar (UG) hypothesis and even more so its purported innateness, since the values for the parameters must be arrived at by the child through induction from empirical evidence. Nevertheless, explanatory adequacy may still be attained if the number of parameters is very small and each parameter has few values.

Nutritional aspects of fermented milk products

Abstract: Fermented milk products are a palatable and economical source of a wide range of nutrients. The nutrient composition is similar to that in milk, but concentrations of vitamins are in general a little lower, with the possible exception of folic acid. Concentrations of lactic acid, galactose, free amino acids and fatty acids are increased as a result of the fermentation. Lactose-intolerant individuals tolerate lactose when it is consumed in yoghurt better than when it is taken in the equivalent quantity of milk. The mechanism of this effect has not been clearly established. By far the greatest proportion of published material freely available in the West concerns yoghurt; reference is made to other cultured products where results are available to indicate interesting differences.

A study of the heat stabilities of a number of indigenous milk enzymes

Abstract: Heat stability profiles of a number of indigenous bovine milk enzymes were examined with the object of being able to monitor heat treatments slightly more severe than typical pasteurization conditions by measurements of residual enzyme activity after heating. Assay procedures were limited to simple fluorimetric, or preferably colorimetric, methods that would be most likely to form the basis of a quick, simple and inexpensive test. Both lipoprotein lipase and α-fucosidase were relatively sensitive to heat and were totally inactivated at temperature/time combinations below those of pasteurization, but the latter may be satisfactory for studying temperatures in the range 55–65°C. Rather more heat stable were N-acetyl-β-glucosaminidase and γ-glutamyl transpeptidase, which may be most appropriate for 65–75°C and 70–80°C respectively. Higher temperature treatments between 80 and 90°C could best be investigated by following α-mannosidase or xanthine oxidase activity.