ALBERT

Description: This is the first detailed analysis of cephalopod beaks from the stomach of a northern bottlenosed whale, Hyperoodon ampullatus (Forster, 1770). The digestive action of many predators barely affects the chitinous beaks of cephalopods and some cetaceans accumulate the beaks in considerable numbers in their stomachs. The present beaks are clean and unbroken. Identification of cephalopod beaks from stomachs of predators such as sperm whales (see Clarke, 1977), seals (Clarke & Trillmich, 1980) and albatrosses (Clarke, Croxall & Prince, 1980) throws considerable light on the biology and relative ecological importance of the species of cephalopods concerned as well as providing useful information on the diet of the predators.

Description: Cephalopod statoliths are paired calcareous stones which lie in cavities, the statocysts, within the skull. They have a form which, though variable, shows promise as a source of criteria for taxonomic and evolutionary studies. As a preliminary to more detailed studies, Clarke (1978) published a description of the form of a generalized teuthoid statolith, coined nomenclature for the various parts and gave a very brief survey of variation of statoliths within the living Cephalopoda. This nomenclature was used in a detailed description of fossilized teuthoid statoliths by Clarke & Fitch (1979). Here, descriptions of the statoliths of the living species Berryteuthis magister (Berry, 1913), Gonatopsis borealis Sasaki, 1923, Gonatopsis (Boreoteuthis) makko Okutani & Nemoto, 1964 and Gonatus fabricii (Lichtenstein, 1818) are given and the fossil Berryteuthis species described in outline by Clarke & Fitch (1979) is compared with B. magister. A statistical analysis of measurements of the statoliths of these five species has been made and the results are presented. This forms the first part of a general description of teuthoid statoliths and similar studies on the Ommastrephidae and the Loliginidae are in preparation.

Description: This note provides some explanation of the fact that, contrary to the requirements of local isotropy, the skewness S of the streamwise temperature derivative ∂θ/∂x1 has been observed to be a non-zero constant of magnitude of about unity in high-Reynolds-number and high-Péclet-number turbulent shear flows. Measurements in slightly heated homogeneous shear flows and in unsheared grid turbulence suggest that S is non-zero only when the mean shear dU1/dx2 and the mean temperature gradient dT/dx2 are both non-zero. The sign of S is given by –sgn (dU1/dx2).sgn (dT/dx2). For fixed dU1/dx2, S is of the form tanh (αdT/dx2), α being a constant, while for fixed dT/dx2, it is of the form S/S* = 1 − β1 exp (− β2τ), where S* is a characteristic value of S, β1 and β2 are positive constants, and τ can be interpreted as a ‘total strain’. The derivative skewness data in other (inhomogeneous) shear flows are also compatible with the latter relation. Predictions from a simplified transport equation for [formula omitted], derived in the light of the present experimental observations, are in reasonable agreement with the measured values of S. A possible physical mechanism maintaining S is discussed. © 1980, Cambridge University Press. All rights reserved.

Description: When pure solvent is separated from a solution of non-zero concentration Cb by a semi-permeable membrane, permeable to solvent (water) but not to solute, water flows osmotically across the membrane towards the solution. Its velocity J is given by J = PΔC, where P is a constant and ΔC is the concentration difference across the membrane. Because the osmotic flow advects solute away from the membrane, ΔC is usually less than Cb, by a factor γ which depends on the thickness of and flow in a concentration boundary layer. In this paper the layer is analysed on the assumption that the stirring motions in the bulk solution, which counter the osmotic advection, can be represented as two-dimensional stagnation-point flow. The steady-state results are compared with those of the standard physiological model in which the layer has a given thickness δ and the osmotic advection is countered only by diffusion. It turns out that the standard theory, although mechanistically inadequate, accurately predicts the value of γ over a wide range of values of the governing parameter β = PCbδ/D (where D is the solute diffusivity) if δ is given by where ν is the kinematic viscosity of the fluid and α is the stirring parameter. The final approach to the steady state is also analysed, and it is shown to be achieved in a time scale (D/ν)1/3/αk′ where k′ is a dimensionless number whose dependence on β is computed. Moreover, if β exceeds a certain critical value (≈ 10), the approach to the steady state is not monotonic but takes the form of a damped oscillation (in practice, however, β is unlikely to rise significantly above 1). The theory is extended to the case where the solute concentration is non-zero on both sides of the membrane and in that case it is shown that J is bounded as β → ∞. © 1980, Cambridge University Press. All rights reserved.

Description: Steady potential flow around a two-dimensional bubble with surface tension, either free or attached to a wall, is considered. The results also apply to a liquid drop. The flow and the bubble shape are determined as functions of the contact angle β and the dimensionless pressure ratio γ = (pb − ps)/½ρU2. Here pb is the pressure in the bubble, ps = p∞ + ½ρU2 is the stagnation pressure, p∞ is the pressure at infinity, ρ is the fluid density and U is the velocity at infinity. The surface tension σ determines the dimensions of the bubble, which are proportional to 2σ/ρU2. As γ tends to ∞, the bubble surface tends to a circle or circular arc, and as γ decreases the bubble elongates in the direction normal to the flow. When γ reaches a certain value γ0(β), opposite sides of the bubble touch each other. The problem is formulated as an integrodifferential equation for the bubble surface. This equation is discretized and solved numerically by Newton's method. Bubble profiles, the bubble area, the surface energy and the kinetic energy are presented for various values of β and γ. In addition a perturbation solution is given for γ large when the bubble is nearly a circular arc, and a slender-body approximation is presented for β ∼ ½π and γ ∼ γ0(β), when the bubble is slender. © 1980, Cambridge University Press. All rights reserved.

Description: Based on the parabolic approximation, a refraction—diffraction model for linear water waves is developed. With the assumption that the water depth (refraction index) is slowly varying, the model equation describes the forward-scattered wavefield. Two examples are considered in particular: (i) wave diffraction by a long thin barrier on a uniform slope, and (ii) wave convergence over a semicircular step shoal. For the former problem, a similarity solution in terms of Fresnel integrals is obtained for the wavefield in the neighbourhood of the shadow boundary. For the latter problem, the resulting Schrödinger equation is solved numerically. The wavefield near the caustics as well as in the shadow region is obtained and compared with experimental data. © 1980, Cambridge University Press. All rights reserved.

Description: A generalized eddy-viscosity function νT, is introduced in order to express the Reynolds stress in an incompressible dusty gas as a linear combination of the Kronecker and rate-of-strain tensors. On the basis of Saffman's dusty-gas model a transport equation for the eddy viscosity is derived from the general turbulence energy equations, thereby introducing two additional functions, the specific turbulence kinetic energy E1, and a scale variable s. In order to determine the three variables modified Prandtl–Wieghardt relation among them is accepted and a transport equation for s is postulated in the same manner as in the clean-gas turbulence transport model (firstly proposed by Harlow & Nakayama 1967) but with the inclusion of an additional term accounting for the dust particles stabilizing action. We are considering values of loading (mass ratio of particles) of order of unity, with particle/gas density ratios of order of 103 and volume concentrations of the order of 10−3, so that particle–particle interactions are neglected. Supposing that the particles nearly follow the gas motion, following well at large scales and poorly at small, an application of the theory to problem of numerical calculations of the dusty-gas parameters such as mean velocity profile of turbulent pipe flow is given. © 1980, Cambridge University Press. All rights reserved.

Description: Measurements of the thermal and velocity structure of the near-surface mixing layer of a freshwater lake in moderate wind conditions from fixed or mobile arrays of sensors reveal large-scale coherent structures consisting of narrow fronts across which both the temperature and the horizontal component of the current increase. These fronts are generally transverse to the wind direction and are inclined to the vertical, and appear to be similar to fronts, reported as temperature ‘ramps’, in the near-surface atmospheric boundary layer. The time derivatives of the temperature are skewed in a sense consistent with observations in laboratory and atmospheric boundary layers, and of a magnitude consistent with measurements in the latter. Evidence is presented to show that bubbles generated by breaking waves are carried down in the large-scale pattern of flow associated with the fronts in the mixing layer. The presence of a Langmuir circulation associated with wind rows has not been established in these experiments. The relevance of the observations to the ocean mixing layer is discussed. © 1980, Cambridge University Press. All rights reserved.

Description: The convective instability of a layer of fluid heated from below is studied on the assumption that the flux of heat through the boundaries is unaffected by the motion in the layer. It is shown that when the heat flux is above the critical value for the onset of convection, motion takes place on a horizontal scale much greater than the layer depth. Following Childress & Spiegel (1980) the disparity of scales is exploited in an expansion scheme that results in a nonlinear evolution equation for the leading-order temperature perturbation. This equation which does not depend on the vertical co-ordinate, is solved analytically where possible and numerically where necessary; most attention is concentrated on solutions representing two-dimensional rolls. It is found that for any given heat flux a continuum of steady solutions is possible for all wave numbers smaller than a given cut off. Stability analysis reveals, however, that each mode is unstable to one of longer wavelength than itself, so that any long box will eventually contain a single roll, even though the most rapidly growing mode on linear theory has much shorter wavelength. © 1980, Cambridge University Press. All rights reserved.

Description: A new class of three-dimensional, deep-water gravity waves of permanent form has been found using an equation valid for weakly nonlinear waves due to Zakharov (1968). These solutions appear as bifurcations from the uniform two-dimensional wave train. The critical wave heights are given as functions of the modulation wave vector. The three-dimensional patterns may be skewed or symmetrical. An example of the skewed wave pattern is given and shown to be stable. The results become exact in the limit of very oblique modulations. © 1980, Cambridge University Press. All rights reserved.

Description: A laser-Doppler velocimeter (LDV) study of velocity profiles in the laminar boundary layer adjacent to a heated flat plate revealed that the seed particles used for the LDV measurements were driven away from the plate surface by thermophoretic forces, causing a particle-free region within the boundary layer of approximately one half the boundary-layer thickness. Measurements of the thickness of this region were compared with particle trajectories calculated according to several theories for the thermophoretic force. It was found that the theory of Brock, with an improved value for the thermal slip coefficient, gave the best agreement with experiment for low Knudsen numbers, λ/R = O(10−1), where λ is the mean free path and R the particle radius. Data obtained by other experimenters over a wider range of Knudsen numbers are compared, and a fitting formula for the thermophoretic force useful over the entire range 0 ≤ λ/R ≤ ∞ is proposed which agrees within 20% or less with the majority of the available data. © 1980, Cambridge University Press. All rights reserved.

Description: The usual way of posing the problem for the reflexion of wave trains from beaches seems inevitably to imply perfect reflexion. Energy considerations show that wave absorption must be associated with the degradation of mechanical energy either through wave breaking or viscous effects. Some experiments reported here showed substantial wave absorption in the absence of any breaking. We describe some theoretical and experimental work aimed at assessing the role played by friction at the bottom in determining the reflexion coefficient of a beach. The results suggest that, if the parameter (νω3)½½gα2 is not too small, bottom friction can be a significant factor in the absorption process for waves on beaches. Here ν represents the kinematic viscosity (or perhaps an ‘eddy’ viscosity) of the fluid, ω is the frequency of the motions, α is the slope of the beach and g is the acceleration due to gravity. © 1980, Cambridge University Press. All rights reserved.

Description: The frequency of vortex shedding from a circular cylinder in a uniform shear flow and the flow patterns around it were experimentally investigated. The Reynolds number Re, which was defined in terms of the cylinder diameter and the approaching velocity at its centre, ranged from 35 to 1500. The shear parameter, which is the transverse velocity gradient of the shear flow non-dimensionalized by the above two quantities, was varied from 0 to 0·25. The critical Reynolds number beyond which vortex shedding from the cylinder occurred was found to be higher than that for a uniform stream and increased approximately linearly with increasing shear parameter when it was larger than about 0·06. In the Reynolds-number range 43 〈 Re 〈 220, the vortex shedding disappeared for sufficiently large shear parameters. Moreover, in the Reynolds-number range 100 〈 Re 〈 1000, the Strouhal number increased as the shear parameter increased beyond about 0·1. © 1980, Cambridge University Press. All rights reserved.

Description: A rational asymptotic theory describing the perturbed flow in a turbulent boundary layer encountering a small two-dimensional hump is presented. The theory is valid in the limit of very high Reynolds number in the case of an aerodynamically smooth surface, or in the limit of small drag coefficient in the case of a rough surface. The method of matched asymptotic expansions is used to obtain a multiple-structured flow, along the general lines of earlier laminar studies. The leading-order velocity perturbations are shown to be precisely the inviscid, irrotational, potential flow solutions over most of the domain. The Reynolds stresses are found to vary across a thin layer adjacent to the surface, and display a singular behaviour near the surface which needs to be resolved by an even thinner wall layer. The Reynolds stress perturbations are calculated by means of a second-order closure model, which is shown to be the minimum level of sophistication capable of describing these variations. The perturbation force on the hump is also calculated, and its order of magnitude is shown to depend on the level of turbulence closure; a cruder turbulence model gives rise to spuriously large forces. © 1980, Cambridge University Press. All rights reserved.

Description: The evolution of the shape of a slender inviscid drop in an axisymmetric straining motion is studied at low Reynolds numbers. It is found that the shape equation can be solved by polynommals with time-dependent coefficients. A global stability result can be used to show simply that only one possible equilibrium is stable. It is further shown that if the slender drop starts with a long-wavelength waist then it cannot go to this stable equilibrium and must either extend indefinitely or burst. In the class of trinomial shapes, it is shown that the drop either bursts or goes to the stable equilibrium, depending on whether or not the initial shape has a waist. © 1980, Cambridge University Press. All rights reserved.

Description: Conditions are found for the appearance of non-uniform progressive waves of permanent form from a long-wave modulation of a finite-amplitude Stokes wave on deep water. The waveheight at which the modulated waves can occur is a very slowly decreasing function of the modulation wavelength for values up to 150 times the original wavelength. Some qualitative remarks are made about the problem of determining the stability of the new waves. © 1980, Cambridge University Press. All rights reserved.

Description: The coherent structure dynamics in the near field of a circular jet has been experimentally explored by inducing ‘stable’ vortex pairing through controlled excitation (see Zaman & Hussain 1980) and applying phase-averaging techniques. Hot-wire measurements were made in a 7·62 cm air jet with laminar exit boundary layer at the Reynolds number ReD = 3·2 × 104, excited at the Strouhal number StD = 0·85. At a particular phase during the pairing process, spatial distributions of the phase-average longitudinal and lateral velocity perturbations (〈u)〉, 〈v〉), vorticity, streamlines, the coherent and background Reynolds stresses and turbulence intensities have been educed. These data have been obtained for four different locations occupied by the vortices at the same phase (preceding, during, and following the pairing event), in the region 0 〈 x/D 〈 5. Spatial distributions of these measures at four successive phases during the pairing process are also educed in an attempt to further understand the vortex-pairing dynamics. The flow physics is discussed on the basis of measurements over the physical extent of the vortical structures, phase-locked to specific phases of the pairing event and thus do not involve use of the Taylor hypothesis. The computed pseudostream functions at particular phases are compared with the corresponding streamlines drawn by the method of isoclines. Transition of the vortices is examined on the basis of vorticity diffusion, the superimposed random fluctuation field intensities and Reynolds stress and phase-locked circumferential correlation measurements. The peak vorticity drops rapidly owing to transition and interaction of the vortices during pairing but, farther downstream, the decay can be attributed to destruction of the coherent vorticity by the background turbulence Reynolds stress, especially at the locations of the latter's ‘saddle points’. Controlled excitation enhances the initial circumferential coherence of the vortical structures, but is ineffective in delaying turbulent breakdown near the end of the potential core; the breakdown appears to occur through evolution of the circumferential lobe structures. The coherent structure Reynolds stress is found to be much larger than the background turbulence Reynolds stress for 0 〈 x/D ≲ 3, but these two are comparable near the end of the jet potential core. The zone average of the coherent structure Reynolds stress over the cross-section of the merging vortex pair is much larger than that over a single vortical structure either before or after the completion of pairing. During the pairing process, such average correlations are found to be the largest at an early phase of the process while entrainment, turbulent breakdown as well as rapid diffusion of vorticity occur at a later phase. The regions of alternate positive and negative coherent Reynolds stresses associated with the structures and their interactions help explain ‘negative production’. © 1980, Cambridge University Press. All rights reserved.

Description: The authors consider an homogeneous non-isotropic turbulence which develops without mean velocity gradient so that it should return to isotropy. This turbulence has been obtained by application of two successive plane strains to a grid-generated turbulence, and this configuration has already been described in a preceding paper. It is shown in particular that the nonlinear effects make no significant contribution to the rotation of the principal axes of the Reynolds stress tensor. In the case of the return to isotropy, an important parameter connected with the turbulent energy distribution between three directions comes into play. In the present experiment it has a positive sign whereas in previous experiments this sign was negative. In particular, the authors conclude that, when this parameter is positive, the return to isotropy is slower than in the opposite case. © 1980, Cambridge University Press. All rights reserved.

Description: The steady movement of a fluid meniscus in a circular capillary tube is analysed by means of finite-element numerical simulation for a range of values of contact angles and contact-line velocities with minute slippage of the fluid on the tube wall, thus relaxing the conventional no-slip boundary condition. The resulting flow field does not produce unbounded forces at contact line, contrary to that with the no-slip condition. The unknown meniscus shape is determined by an iterative scheme in which the imbalance in the normal-stress boundary condition is the basis for improving the shape. Comparison of the numerical results found here and the experimental results of a number of investigators suggests the possibility that the contact angle does not vary with contact-line velocity. © 1980, Cambridge University Press. All rights reserved.

Description: The time development of the symmetrical standing zone of recirculation, which is formed in the early stage of the flow due to a circular cylinder impulsively set in motion perpendicular to its generators, has been studied using a flow visualization technique. The Reynolds numbers (based upon the diameter) range from 40 to 104. Some new phenomena indicated in the flow patterns are revealed, and several different regimes are differentiated by a detailed analysis of the evolution of the main flow characteristics. A correlation with some theoretical results is established. © 1980, Cambridge University Press. All rights reserved.

Description: Previous studies of the distortion of the electric double layer around a charged sphere have assumed that the electric stresses are small compared with the viscous stresses. The flow around the particle is therefore changed only slightly by the presence of the charge cloud. This change is measured by the Hartmann number, and in § 6 we remove the restriction that it should be small. It is found that the previous linearized theory is sufficiently accurate for typical experimental values of the Hartmann number. Previous studies have also assumed that the potential at the surface of the particle is small. This assumption is removed in § 7 of this paper. For values of the non-dimensional surface potential smaller than 2 the predictions are altered by less than 10 %. For higher values the differences between linear and nonlinear theory are not negligible, especially when the charge cloud is thin compared with the radius of the charged sphere. © 1980, Cambridge University Press. All rights reserved.

Description: Hot-wire and flow-visualization studies have been carried out in three air jets subjected to pure-tone acoustic excitation, and the instability, vortex roll-up and transition as well as jet response to the controlled excitation have been investigated. The centreline fluctuation intensity can be enhanced by inducing stable vortex pairing to a level much higher than even that at the ‘preferred mode’, but can also be suppressed below the unexcited level under certain conditions of excitation. The conditions most favourable to vortex pairing were determined as a function of the excitation Strouhal number, the Reynolds number (ReD), and the initial shear-layer state, i.e. laminar or turbulent. It is shown that the rolled-up vortex rings undergo pairing under two distinct conditions of excitation: ‘the shear layer mode’ when the Strouhal number based on the initial shear-layer momentum thickness (Stθ) is about 0·012, and ‘the jet column mode’ when the Strouhal number based on the jet diameter (StD) is about 0·85. The former involves pairing of the near-exit thin vortex rings when the initial boundary layer is laminar, irrespective of the value of StD. The latter involves pairing of the thick vortex rings at x/D ≅ 1·75, irrespective of Stθ or whether the initial boundary layer is laminar or turbulent. For laminar exit boundary layer, pairing is found to be stable, i.e., occurring regularly in space and time, for ReD 〈 5 × 104, but becomes intermittent with increasing ReD or fluctuation intensity in the initial boundary layer. The trajectories of the vortex centres and their convection velocities during a pairing event have been recorded through phase-locked measurements. In the presence of stable vortex pairing, the time average profiles of fluctuation intensities and Reynolds stress show noticeable deviations from those in the unexcited jet. The vortex pairing phenomenon produce considerably larger excursions of the [formula omitted] signal than the time-average Reynolds stress reveals, suggesting that only certain phases of the pairing process may be important in entrainment, and production of Reynolds stress and jet noise. © 1980, Cambridge University Press. All rights reserved.

Description: SUMMARYTwo experiments were conducted to study the influence of heat treatment of Vicia faba beans on the productive performance of laying hens fed diets containing large proportions of the beans. In the first experiment, the effects of extruding and pelleting the beans were studied while in the second experiment the effects of autoclaving at 121 °C for 30 min the cotyledons and hulls of the beans were evaluated. Hyline-W36 layers were used in the first experiment while two strains (Shaver-288 and Dekalb) of birds were used in the second experiment. Each experiment lasted 5 months during which data on egg production, egg weight, feed intake, mortality and body-weight gain of birds were collected. The results obtained indicated that heat treatment (extruding, pelleting and autoclaving) of the beans, cotyledons and hulls had no beneficial effect on the productive performance of laying hens fed on diets containing large proportions of the heated beans, cotyledons and hulls. Egg-size reducing factors appeared to be concentrated in the cotyledons rather than the hulls of the beans.

Description: SUMMARYExperiments were made over a 3-year period in order to evolve a production package for yam that would eliminate the laborious operations of hand weeding and staking. First, nine herbicides were applied to yam plots before or after yam emergence. On the basis of weed control effectiveness and low phytotoxicity to yam plants, ametryne (2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-S-triazine) was chosen for subsequent experimentation. Next, ametryne at 2, 4 or 6 kg/ha was applied to yam plots either immediately after planting, or with 1 kg/ha paraqviat (l, 1'-dimethyl-4,4'- bipyridinium ion) 3 weeks after planting. The delayed applications gave more effective weed control and higher yields than the early applications. For the delayed application, 4 and 6 kg ametryne/ha did not give significantly different yields, but yielded significantly more than 2 kg/ha. When a combination of ametryne at 4 kg/ha and paraquat at 1 kg/ha was applied 3, 6 or 9 weeks after planting, the weed control effectiveness was greatest at 6 weeks after planting while the 3- and 6-week applications did not give significantly different yields. Herbicide applied 9 weeks after planting gave the poorest weed control and the lowest yields.Finally comparisons were made between the conventional staked, hand-weeded yam production, and a new production package in which the yams were not staked and weeds were controlled with ametryne (4 kg/ha) + paraquat (1kg/ha) applied at or just before emergence. When small (150g) setts were used, yields from the new package were not significantly lower than those from the conventional system, even though the new package was considerably less laborious. Cultivation with large setts, however, resulted in a decrease in yield when the plants were not staked. Strategies that could further enhance the attractiveness of the new production

Description: SUMMARYThe effects of N, P and K fertilizers on the yield and N, P and K contents of grass cut for conservation, measured during 1958–63, were again measured during 1964–7. Grass given 38 kg N/ha per cut needed 31 kg K/ha per cut for full yield, grass given 75 or 113 kg N/ha per cut needed twice as much K. With sufficient K, at least 75 kg N/ha per cut was justified. The grass responded little to P.Percentage N in the grass, though greatly increased by N fertilizer, was little altered by K fertilizer. Percentage K, whilst greatly increased by K fertilizer, was decreased by N unless 62 kg K/ha per cut also was given. Percentage P in the grass was little increased by P fertilizer.Exchangeable K in the surface soil (0–20 cm) was maintained with time where the grass was given either 38 kg N plus 31 kg K or 75 kg N plus 62 kg K/ha per cut, corresponding to an N:K ratio of 1:0·82. Percentage K in the grass decreased with time throughout. Whereas a N:K ratio of 1:1·66 best maintained % K in grass during 1958–63 it was no better than an N:K ratio of 1:0·82 during 1964–7.Although exchangeable Mg in the surface soil decreased markedly between 1958 and 1967 (Mg fertilizer was not applied), % Mg in the grass did not. Mg in the grass was increased by N, but decreased by K fertilizer, and exceeded 0·2% (in dry matter) only in 1967 and then only where 75 or 113 kg N/ha per cut was applied.

Description: Sesame (Sesamum indicum L.) is a crop of great antiquity which is widely grown in tropical and subtropical regions of Asia, Africa, South and North America and to some extent in Russia for edible oil and for animal feed purposes. The average yield in India is only about 235 kg/ha. Even under good management practices the seed yields usually remain poor and, therefore, commercial prospects of sesame production are not good.

Description: Agri-silviculture is the simultaneous husbandry of forest tree crops and food crops. In the first 1–3 years of forest crops such as teak, pine and Gmelina arborea, they are interplanted with food crops such as yam, maize and cassava in plantation. In humid countries such as Nigeria and Burma agrisilviculture evolved out of the needs to boost food production and satisfy labourers who work on afforestation programmes.

Description: SUMMARYFishmeal, soya-bean meal and urea were compared as nitrogen sources in diets rich in fibre for yearling cattle, using feeding trials and digestibility and nitrogen retention studies. All animals were individually fed. Diets supplemented with fishmeal supported the highest rates of daily live-weight gain and nitrogen retention. There was no response in dry-matter intake and digestibility from extra nitrogen, either from fishmeal or urea, when the crude protein of the diet was 8·5% or over, and a small response in digestibility when soya-bean meal was used.Molar proportions of VFA, rumen NH3-N concentrations and blood urea nitrogen concentrations were all affected by both amount and source of nitrogen supplementation. Multiple regression analysis showed the undegradable protein supply to be more critical with high than with low fibre diets.

Description: SUMMARYIn a field experiment in the north-west region of Tasmania, poppies (Papaver somniferum L.) were harvested at weekly intervals beginning 10 days after full bloom and continuing until 4 weeks after the dry commercial harvest stage. At each harvest the plants were cut off at ground level and partitioned into terminal capsules, lateral capsules, seed and the combined stem plus leaf component.The dry-matter yield of total plant and of all the components except seed achieved maximum values 2–3 weeks after full bloom and then progressively declined. For the total plant this decrease between maximum dry weight and that at the time of commercial harvest (8 weeks after full bloom) amounted to 26% while for terminal capsules it was 37% for lateral capsules 15% and for stem plus leaves 39%. In contrast, the dry-matter yield of total seed rose to a maximum by 4 weeks after full bloom and then remained constant for the duration of the experiment.The morphine concentration of both terminal and lateral capsules reached a maximum value of 1·1% 6 weeks after full bloom and then decreased by about 10% at the dry harvest stage. The morphine concentration of stem and leaves also reached a maximum of 0·1% about the same time as capsules but decreased rapidly and had halved by dry commercial harvest. The mutually compensating factors of decreasing dry-matter yield and increasing morphine concentration gave similar total plant morphine yields at any time of harvest from 2 to 7 weeks after full bloom. The morphine extracted from the whole plant at these times of harvest was about 50% greater than that derived from capsules alone at the time of dry commercial harvest.

Description: SUMMARYDNA and protein concentrations were measured in selected muscles from foetal and neonatal pigs; the protein: DNA ratios of hind-limb muscles were similar to those of the forelimb from 83 days gestation to 27 days after birth. The ratios increased during the perinatal period, providing evidence that maturation of muscle began in the last few days of pregnancy. RNA concentration, cathepsin D activity and tritiated thymidine incorporation were measured in muscles from the neonatal animals and the results indicated a surge of biosynthetic activity in the first days of life. Values obtained from the hind- and forelimb muscles were similar throughout the period of study with RNA: DNA ratio, cathepsin D activity and thymidine incorporation reaching maximum values at 4 days of age. A considerable proportion of thymidine incorporation was attributed to the mitotic activity of satellite cells.

Description: SUMMARYAqueous glutaraldehyde, in the presence of wetting agents Tween-20 or Haemosol, reacted with fresh cut lucerne (Medicago sativa L.), complete reaction being obtained with about 7·2 g (72 mmol)/kg herbage, or 18g/100g crude protein. Reaction with 25% w/v aqueous glutaraldehyde sprayed on to fresh lucerne was rapid, and at the rate of 66 mmol/kg lucerne, all aldehyde had reacted in 3 h and about 60% of the soluble leaf protein became insoluble. Formaldehyde at twice the molar concentration of glutaraldehyde was absorbed rapidly, but a longer time, up to 24 h, was required for the protein to become insoluble. Treatments with 22, 44 and 66 mmol glutaraldehyde/kg lucerne, and 44, 88 and 132 mmol formaldehyde/kg showed that reaction with leaf protein was approximately proportional to the amount of aldehyde. A major effect on the leaf cells was the fixation of chloroplasts, and intact fixed chloroplasts were isolated from treated lucerne with high protein: chlorophyll ratios of 5·8:1 to 9·5:1.Two varieties of lucerne, Kabul and Europe, pot-grown in a controlled environment cabinet, reacted rapidly when sprayed with glutaraldehyde and in 3 h soluble leaf protein was reduced from 30 to 16–17% of the total N. The plants rapidly lost water and the dry matter of the leaves rose to 42% for Kabul and 45% for Europe in 24 h. Stems showed little effect. Field spraying of lucerne with glutaraldehyde similarly fixed soluble leaf protein and caused desiccation of the leaves, rising to 47–50% D. M. in 3 days. The stems were little affected and subsequent regrowth of the plants was not inhibited.Feeding glutaraldehyde- and formaldehyde-sprayed lucerne to rumen-fistulated cattle showed that release of soluble leaf protein into the rumen fluid was greatly reduced, mean values being 40 and 43% respectively of the values obtained when control lucerne was fed. Mean ammonia concentrations were similarly reduced to 49 and 33% of the control values. Formaldehyde-treated lucerne, even after reaction for several days, frequently showed toxic effects on rumen micro-organisms, particularly protozoa. Glutaraldehyde reacted more rapidly with herbage and no toxic effects were observed. Both glutaraldehyde- and formaldehyde-treated lucerne were highly palatable to cattle.

Description: SUMMARYThirty-six mature Finnish Landrace × Dorset Horn ewes, each suckling two lambs, were used in a comparative slaughter experiment to measure changes in body tissues during early lactation. Two levels of body fatness at lambing were established by giving ewes a complete diet containing 10 MJ metabolizable energy (ME) and 139 g crude protein (CP)/kg d.m. either close to requirements or ad libitum during the second half of pregnancy. In lactation half the ewes in each group were given a complete diet containing either 90 (diet A) or 60 (diet B) % milled hay ad libitum. These diets contained 7·9 and 9·2 MJ ME and 121 and 132 g CP/kg d.m. respectively.Ewes fed at the two levels in pregnancy contained 8·4 and 19·6 kg chemically determined fat 5 days after lambing but had similar amounts of body protein, ash and water. Over 6 weeks of lactation ewes given diet A lost 60 and 69% of these weights of fat respectively, while ewes given diet B gained 5% and lost 30% respectively. Up to 26 g of body protein was lost daily from ewes given diet A but none from ewes on diet B. During early lactation the weight of the empty digestive tract increased while the weights of most other body components, particularly the carcass, decreased. The ratio of body energy change to live-weight change varied from 24 to 90 MJ/kg. Thus live-weight change did not accurately reflect relative or absolute changes in body energy.Voluntary food intake was greater for ewes given the high-energy diet (B) than for those given diet A and was depressed in the fatter ewes. Differences in intake could be explained by the effects of body fatness and diet on the weight of gut contents. Milk yield was not significantly affected by body fat reserves but was higher on diet B than A. Fat content of milk was higher and protein content lower for ewes with the higher fat reserves at lambing.As the contribution of fat loss to energy available for milk synthesis increased there appeared to be a reduction in the energetic efficiency of milk synthesis. A number of possible reasons for this are discussed.

Description: SUMMARYEwes in body condition scores of 2·4 (thin) or 3·2 (fat) on a 5-point scale and suckling twin lambs were grazed at two stocking rates for the first 16 weeks of lactation. Paddocks were grazed for periods of 2 weeks at densities of 80 and 160 ewes/ha in weeks 1–8 and then 70 and 140 ewes/ha in weeks 9/16 of lactation.Intakes of herbage by ewes were not significantly affected by body condition. Estimation of milk yield by weekly measurement of secretion rates over 4 h failed to demonstrate significant differences due to body condition except in weeks 9, 11 and 12, although there was a tendency throughout for fat ewes to produce more milk. However, the daily growth rates of the lambs during the first 8 weeks and the overall live-weight gains were significantly higher for lambs suckled by fat ewes than for those suckled by thin ewes. Intake of herbage by lambs was not affected by the body condition of the ewes.Herbage intakes, milk yields and lamb growth rates were all significantly higher at the low stocking density than at the high stocking density.

Description: SUMMARYRadiological examinations were carried out on ten sheep to see what changes in intestinal motility and flow of digesta were caused by intestinal cannulation. Barium sulphate was injected or infused into the abomasum via an implanted catheter; its passage through the intestine and associated muscular contractions were observed using X-ray image intensification. Once the normal pattern had been established for each individual, single or re-entrant cannulae were inserted into one of four positions in the small intestine.All the cannulations caused some disruption of the normal flow of digesta, causing retention of digesta and distension of the intestine around and proximal to the intraluminal flanges of the cannulae. The duodenum was affected the most, particularly by one type of re-entrant cannula which reduced the degree of jejunal filling; peristaltic contractions often failed to propagate beyond these cannulae and also caused some retrograde movement of digesta between the cannulation site and the duodenal bulb during the irregular contraction phase (ICP) of the migrating myoelectric complex (MMC). These re-entrant cannulae also impaired the clearing effect of regular contraction phase (RCP).

Description: SUMMARYThe efficacy of estimates of gut contents and total body water in increasing the precision with which the chemical composition of the body could be estimated in early lactation was evaluated in 36 Finnish Landrace × Dorset Horn ewes. The ewes were fed at two levels in pregnancy, and, in lactation, given diets of two metabolizable energy concentrations.The allometric relationships relating weight of chemical fat and protein to emptybody weight were not affected by treatment or stage of lactation. Inclusion of an index of gut contents, based on dry-matter intake, indigestibility and retention time of food residues, together with live weight in a regression equation predicting weight of body fat, only slightly increased the precision of estimate compared with equations using live weight alone.There was a close negative relationship between the proportions of water and fat in live weight. Inclusion of weight of body water with live weight in a regression equation predicting weight of body fat markedly increased the precision of estimate and the residual error (0·81 kg) was similar at different stages of lactation. However, when deuterium oxide space was used instead of body water there was only a small increase in precision of estimate and the residual error varied from 5·3 kg in early lactation to 2·1 kg in mid-lactation. The relationship between deuterium oxide space and body water was shown to be variable and altered by stage of lactation, and these differences were associated with differences in rate of water turnover in the animal's body.It is concluded that estimates of body water are unsuitable for estimating weight of body fat in early lactation.

Description: SUMMARYCabbage accessions were screened for resistance to turnip mosaic (TuMV) and cauliflower mosaic (CaMV) viruses in glasshouse and field tests. None was immune to infection by either virus, but some were highly resistant to one or both viruses. TuMV induced severe necrotic lesions on the outer leaves of susceptible plants at harvest, and this was associated with severe internal necrosis in heads stored for 8 months at 0–1 °C. This correlation was not observed in CaMV infected plants. Pepper-spot necrosis was low in stored heads of some accessions but high in others.

Description: SUMMARYA high level of resistance to the bean common mosaic virus strains NL3 and NL4 when inoculated separately or together was confirmed in the cultivars Turkish Brown, Valja and 1750–73. Following crosses between the susceptible cv. The Prince and all three resistant cultivars, inoculation of F2 and F3 populations revealed that the cvs Turkish Brown and Valja each differed from The Prince in being homozygous for a major recessive gene conferring resistance to both NL3 and NL4. Homology tests indicated that the same gene was present in both Turkish Brown and Valja. Polygenes in Turkish Brown and Valja also appeared to confer some resistance to NL3, or environmental variation led to continuous distribution patterns in the F2's of resistant parents crossed with The Prince. Although a major recessive gene controlled resistance to NL3 in cv. 1750–73, it differed from that in the two other resistant cultivars. In addition, cv. 1750–73 carried a dominant gene determining reaction to the virus; probably the I gene originally found in Corbett Refugee. An attempt is made to relate these results to Drijfhout's (1978) gene-for-gene model. Using Drijfhout's gene nomenclature all the cultivars tested appear to carry the strain nonspecific gene bc-u. Further genetical tests will be necessary to determine with certainty which, if any, of Drijfhout's strain-specific resistant bc-genes are present in the three resistant cultivars studied here.

Description: SUMMARYIn St Vincent, West Indies, the yellow passionfruit (known as Passiflora edulisf. flavicarpa Degener, but probably specifically distinct from P. edulis Sims) is grown commercially and is pollinated by the indigenous bee Xylocopa mordax Smith. The diel patterns of anthesis and nectar availability are described and related to the timing of bee visits and pollination. Flower-bagging experiments confirmed that the setting of fruit depended on cross-pollination, was prevented by exclusion of flower visitors, and was sometimes limited in the field by inadequate pollination.Bees collected Passiflora nectar, and evaporated it on their tongues from 45–50 % to 62–63 % sugar before storing it. But the Passiflora pollen deposited on the bee's dorsum was groomed off and rejected; only Gliriddia pollen was used for bee bread. Thus the bees treated ‘acceptable’ (Gliriddia) pollen and ‘unacceptable’ (Passiflora) pollen differently, and since pollen unacceptability improves the pollen's chance of reaching a stigma, it may be a widespread adaptation.The yellow passionfruit flower shows many features characteristic of tropical Xylocopa flowers. Here, as elsewhere, this introduced crop depends for its pollination on indigenous bees which, though suitable morphologically and behaviourally, are not abundant enough to cause a high proportion of flowers to set fruit. The setting of fruit might be improved by increasing bee populations through provision of more timber for nestsites, and suitable flowers to supply pollen and nectar throughout the year.

Description: SUMMARYThe joint action of several insecticide formulations with a constant concentration of the antifeedant Du-ter that gives 50% starvation with the fourth instar of Spodoptera littoralis (Boisd.) was assessed. The results provided evidence that the toxicity of all the tested insecticides to the cotton leafworm can be markedly increased by using Du-ter in combination with each of the candidate insecticides. Since Du-ter proved to be highly synergistic, its mixtures with insecticides can result in a decrease in the rate of insecticide application.

Description: SUMMARYAn analysis is suggested for an experiment investigating plant competition between different genotypes grown in pure culture and in binary mixtures with unequal proportions of genotypes. Worked examples are presented.

Description: SUMMARYDuring a period without rainfall the upper layers of the soil may become dry whilst the lower layers provide sufficient moisture for the plant to continue growing. In experimental conditions simulating such a soil environment, new main root axes ceased to be produced by plants of perennial ryegrass. Shoot growth and leaf elongation rate were little affected during the first 2 weeks of the treatment. The subsequent introduction of moisture round the base of the plant resulted in the rapid production of new root axes and increase in the leaf elongation rate. Although there was considerable intra-varietal genetic variation in the rate of development of new root axes and leaf elongation after wetting it is concluded that this would be of doubtful value as a selection criterion.

Description: SUMMARYIn Expt 1, lactating dairy cows grazing kikuyu grass (Pennisetum clandestinum) were given no supplement (C), supplements of rolled barley grain at 4 (4R) and 6 (6R) kg/day and supplements of NaOH-treated whole barley grain at 4 (4A) and 6 (6A) kg/day. Daily production of milk (kg/day), fat and protein (g/day) and live-weight changes (g/day) respectively were C 7·82, 303, 276, 450; 4R 9·26, 338, 315, 865; 4A 10·23, 366, 349, 529; 6R 10·09, 352, 343, 672; 6A 10·61, 363, 348, 361.Milk production was significantly higher (P 〈 0·05) and live-weight gain significantly lower (P 〈 0·05) on NaOH-treated grain than on rolled grain.In Expt 2, yearling steers in pens were fed pasture hay ad libitum with no supplement (C) and 3 kg/day of barley grain which was either rolled (3R) or NaOH-treated whole grain (3A). Mean intakes of hay (g/day) and DOMD in vivo (%) respectively were C 7684, 60; 3R 5224, 65; 3A 6209, 60.Hay intake was significantly higher (P 〈 0·05) on NaOH-treated grain than on rolled grain.Fractional disappearance rates of rolled and NaOH-treated grain from nylon bags suspended in the rumen were, respectively, 0·15 and 0–07/h for the period 0–4 h, and 0·07 and 0·02/h for the period 4–12 h incubation. In Expt 2, rumen pH was higher and the digestion rate of hay in nylon bags in vivo was higher on C than on 3R and 3A. Volatile fatty acid (VFA) concentrations in the rumen did not differ significantly between diets.It was concluded that greater milk production and hay intakes when cattle were fed NaOH-treated whole barley than when they were fed rolled barley were attributable to the slower rate of digestion of the former. The NaOH treatment (30 g NaOH/kg grain) was probably too low and further study is necessary to determine optimum levels of treatment, which are likely to vary with the ratio of grain: forage in the diet.

Description: SUMMARYEating behaviour and the diet selected by cattle progressively defoliating a crop of Lablab purpureus cv. Rongai were measured in three periods each of 12 days. Crop composition during defoliation was recorded.At the beginning of grazing the crop contained 2230 kg green leaf/ha but after 12 days' grazing the crop contained only 300 kg/ha. In the first 6 days cattle selected a diet which contained 85% green leaf but after 12 days' grazing the selected diet contained only 17% green leaf. As available leaf declined, grazing time increased from 465 min on day 1 to 685 on day 6 before declining to 490 min on day 12. Maximum grazing time occurred with a green leaf yield of 1185 kg/ha. The number of eating bites increased from 26000 to 44500 between days 1 and 6 and then declined to 30000 after 12 days' grazing. Grazing time and the number of eating bites were significantly correlated (r = 0·99).Bite size declined from 410 mg organic matter (OM)/bite on day 1 to 90 mg OM/bite on day 12. This decrease in bite size caused a linear decline (927 g/day) in estimated organic-matter intake. The rapid decline in bite size and intake was caused by the reduction in the quantity of leaf per unit area and the lack of desire of cattle to eat stem.It was concluded that the desire of cattle to select leaf is so strong that stem yield should be largely disregarded when considering Rongai as a grazing crop.

Description: SUMMARYAn experiment at Rothamsted during 1958–67 measured effects on yield, on K uptake and on soil K of applying all combinations of 38, 75 and 113 kg N and 0, 31 and 62 kg K/ha per cut to grass leys, which were cut and removed. Soil K was depleted most where most N and least K were given. Annual applications of 0, 33 and 66 kg P/ha were also tested; soil P was not depleted. The grass was then ploughed.In 1968, residual effects were measured by spring wheat. In 1969 and in 1970 104 kg/ha of fresh K was applied on half of each plot; potatoes (1969) and spring wheat (1970) valued residual and fresh effects of K.In 1971 potatoes tested 0, 104 and 208 kg/ha of fresh K, cumulatively with the three amounts given to the grass and also extra K (104 kg/ha) on half-plots, cumulatively with that given in 1969 and 1970. In 1972 winter wheat, and in 1974 and 1975 spring barley, measured residues of all treatments previously applied (the site was fallowed in 1973).Finally, in 1976, potatoes tested 0, 156 and 312 kg/ha of fresh K on whole plots, cumulatively with the previous dressings of K, and also 156 kg/ha of extra K on half-plots, again cumulatively. All these test crops were given basal N.Yields and K contents of wheat at ear emergence and yields of wheat grain were largest after grass given 38 kg N and 62 kg K/ha per cut, because here soil K depletion was least. Wheat grain yields benefited consistently from fresh K. K content of the wheat at ear emergence was a good indicator of the need for K, but K content of grain was not, because it was unaltered by K fertilizer. Barley was a poor test crop for K, because yields of grain were little affected by previous treatments.Percentage K in potato leaves (in July in 1969 and 1971, in August in 1976) and yield of tubers were well correlated. Largest yields in 1969, 1971 and 1976 came where the leaves contained 3·43, 3·76 and 2·82% K, respectively, i.e. from soil containing most exchangeable K, plus most fresh K. There was no indication that maximum yields had been obtained, so the largest amounts (kg/ha) of fresh K tested (104 in 1969, 312 in 1971 and 468 in 1976) were insufficient to counteract depletion of soil K by the grass. Because the grass did not deplete soil P, the test crops benefited only little from either residual or fresh P.

Description: SUMMARYIn 1974 three cultivars of barley of different straw lengths, Mazurka, Julia and Midas, were grown alone and with each of four cultivars of red and two of white clover in a split-plot randomized-block experiment of four replications. Although the barley cultivars differed significantly in yield the barley x clover interaction was not significant and yield of grain was not affected by the presence of the clovers.In the following year the entire experimental area was sown with Mazurka barley. Significantly higher grain yields were obtained on those plots sown with clover in 1974 than in plots where no clover had been sown. In no case was the combined yield of barley from the 2 years on any treatment involving clover lower than that of the mean of the no-clover control plots, although the highest increase in yield, 11% from the S.123 red clover treatment, over the no-clover control was not shown to be significant.

Description: SUMMARYThree experiments, each consisting of a feeding trial plus a digestibility and nitrogen retention study, compared long barley straw with rolled barley as basal diets and oat hulls with maize starch as energy supplements for yearling dairy cattle. The protein ontent of the diets was varied by the addition of flshmeal.Growth rates were reduced by the dietary combination of high fibre and low protein, so that diets rich in straw, or containing a supplement of oat hulls, gave a large response to a supplement of fishmeal compared with low straw or maize starch supplemented diets. The data suggest a crude protein concentration of 115 g/kg dry matter as a requirement for high fibre diets supplemented with fishmeal, when fed to yearling cattle. Retention of nitrogen reflected the pattern of live-weight gain. Molar proportions of VFA were affected by changes in the roughage: concentrates ratio, except where energy and protein intakes were both low.Barley straw was of a higher nutritive value than oat hulls.