ALBERT

Description: A realistic theoretical model of steady Langmuir circulations is constructed. Vorticity in the wind direction is generated by the Stokes drift of the gravity-wave field acting upon spanwise vorticity deriving from the wind-driven current. We believe that the steady Langmuir circulations represent a balance between this generating mechanism and turbulent dissipation. Nonlinear equations governing the motion are derived under fairly general conditions. Analytical and numerical solutions are sought for the case of a directional wave spectrum consisting of a single pair of gravity waves propagating at equal and opposite angles to the wind direction. Also, a statistical analysis, based on linearized equations, is developed for more general directional wave spectra. This yields an estimate of the average spacing of windrows associated with Langmuir circulations. The latter analysis is applied to a particular example with simple properties, and produces an expected windrow spacing of rather more than twice the length of the dominant gravity waves. The relevance of our model is assessed with reference to known observational features, and the evidence supporting its applicability is promising. © 1976, Cambridge University Press. All rights reserved.

Description: Using the Orr-Sommerfeld equation with the wavenumber as the eigenvalue, a search for higher eigenstates in the stability theory of the Blasius boundary layer has revealed the existence of a number of viscous states in addition to the long established fundamental state. The viscous states are discrete, belong to two series, and are all heavily damped in space. Within the limits of the investigation the number of viscous states existing in the layer increases as the Reynolds number and the angular frequency of the perturbation increase. It is suggested that the viscous eigenstates may be responsible for the excitation of some boundary-layer disturbances by disturbances in the free stream. © 1976, Cambridge University Press. All rights reserved.

Description: SummaryThree spring barley varieties, Proctor, Vada and Mosanne, were inoculated with Rhynchosporium secalis(Oudem.) J. J. Davies at Growth Stages 3, 7, 10·1 and 10·5 (Large, 1954). The treatments included single inoculation at each growth stage and multiple inoculations at two, three and four of the above growth stages. There was no effect of inoculation oil the number of fertile tillers. Thousand-grain weight was reduced in all seven inoculation treatments in Mosanne but only the quadruple inoculation adversely affected the other two varieties. Numbers of grains of both Mosanne and Vada were reduced by treatments which included an inoculation at ear emergence but Proctor was affected only by the quadruple inoculation. In terms of disease assessment Mosanne was very susceptible and Proctor moderately resistant but Vada, with symptom scores only slightly better than Mosanne, exhibited a degree of tolerance which was reflected by the grain weight results in which small increases were recorded. This tolerance mechanism, possibly acting through compensation in this variety, is compared with compensation reported in wheat.

Description: SummaryS. 24 perennial ryegrass, containing 2·9 g nitrogen/100 g D.M.〉, was conserved by freezing (to represent the fresh material) or by drying. Three dehydration treatments were imposed, comprising low temperature (inlet temperature 145 °C) high temperature (inlet temperature 900 °C) or oven drying (100 °C for 18 h) and in addition part of the high temperature dried grass was treated with formalin (1 g/100 g crude protein) prior to feeding.The digestion of the energy and nitrogen components of all diets was investigated using sheep fitted with re-entrant cannulae at the proximal duodenum and terminal ileum.Dehydration and formalin of the grass reduced nitrogen solubility and apparent energy and nitrogen (P 〈 0·001) digestibilities but led to increased quantities of nitrogen entering the small intestine (P 〈 0·01) compared with the frozen diet. A significant relationship describing nitrogen transformations was established: Y = 165–1·13X (r = –0·98, P 〈 0·001), where Y is g nitrogen entering the small intestine per 100 g N consumed and X is dietary nitrogen solubility. All dried diets showed increased losses of nitrogen within the small intestine compared with the frozen diet, the largest values being observed on the oven-dried and formalin-treated diets.Neither total VFA production within the rumen nor overall cellulose digestibility was influenced by dehydration, but on the formalin-treated diet there was a marked shift of cellulose digestion from the rumen to the caecum and colon compared with the other diets, associated presumably with the large reduction in protein solubility on this diet.Dehydration improved the efficiency of conversion of ruminally digested energy to VFA energy within the rumen, and in relation to the nature of the total absorbed nutrients a significant relationship was established:Y = 30·97–0·22X (r = –0·98; P 〈 0·001),where Y is g digestible crude protein lost in the total intestines per 100 g digestible organic matter intake and X is dietary nitrogen solubility.

Description: SUMMARYThe effect of six intervals between harvests and three levels of N application on the proportion and yield of green leaf, dead leaf, ‘stem’ and inflorescence was studied in four ryegrass (Lolium) varieties during a 30-week period in the first harvest year in a field experiment. In one variety, S.23, the ‘stem’ was divided into true stem, leaf sheath, unemerged leaf and unemerged inflorescence.There was a bigger yield of ‘stem’ and a bigger total herbage yield response to doubling the interval between harvests in S.321 and S.22 than in S.23 and S.24.In the absence, but not generally in the presence, of applied N, S.321 outyielded the other varieties. S.24 was particularly responsive to applied N, especially in terms of green leaf yield.There was a large positive effect on yield of doubling the interval (from 3, 4 or 5 weeks to 6, 8 or 10 weeks respectively) during the main period of stem development. During the subsequent period, however, doubling the interval produced very little extra yield of total herbage and reduced green leaf yield substantially.The percentage increase in yield due to the application of N progressively decreased as the interval was increased.Maximum net production of green leaf was obtained by harvesting every 4 or 5 weeks for most of the season, extending to 6 weeks at the end. Harvesting every 3 weeks, by comparison, resulted in a slightly lower annual green leaf yield, but with a distinctly higher proportion of green leaf in the crop.Applied N generally had little effect on the proportion of crop fractions, but reduced the proportion of green leaf and increased that of' stem' in S.23 and S.24 at the August and September harvests.

Description: SummaryTwo spring wheat varieties, Cardinal and Kolibri, were inoculated with Septoria nodorum Berk and S. tritici Rob. & Desm. at Growth Stages 3, 7, 10.1 and 10.5 of the Feekes' scale. The treatments included single inoculations at each growth stage and multiple inoculations at 2, 3 and 4 of the above growth stages.Thousand-grain weights of both varieties were reduced by inoculation with either pathogen, S. nodorum causing the largest reduction. Numbers of grain per head in Cardinal were severely reduced by S. nodorum, particularly after the multiple inoculations. In Kolibri, there was evidence of increases in numbers of grain with S. tritici inoculation which nullified the grain size reductions. The results are discussed in relation to compensatory mechanisms and disease tolerance.

Description: SummaryThe effect of six intervals between harvests and three levels of N application on the number of tillers was studied in four ryegrass (Lolium) varieties in the first harvest year and in two varieties in the second and part of the third harvest years in a field experiment. Weight/tiller was recorded in the first 2 years and weight/green leaf and number of green leaves harvested were recorded in the first year.There was a large negative interaction between level of N and interval between harvests in respect of number of tillers, the number being increased by N with short intervals and tending to be reduced by N with long intervals. The interaction was larger in the second and third years than in the first. The negative interaction in respect of number of tillers and number of green leaves harvested was associated with a reduction in the percentage increase in yields of dry matter, digestible organic matter and N due to the application of N as the interval was increased. It is suggested that one should in general avoid a combination of high N and long intervals between harvests with present varieties of perennial ryegrass.The effects of interval between harvests, N application, variety and time of year on number of tillers and weight/tiller are discussed in relation to their effects on yield to show how tiller information can contribute to a better understanding of the ways in which yields are achieved. Rather low yields in the late summer and early autumn of the second harvest year were in many instances attributable to a rather low number of tillers rather than to low weight/tiller.There was a considerable increase in number of tillers between the end of one growing season and the early part of the next, suggesting that the period in which this increase is achieved may be an important one in relation to the continued vigour of the sown species.A reduction in annual yield of green leaf with extension of interval from 6 to 10 weeks with N applied resulted from a reduction in the number of green leaves harvested/harvest and in the number of harvests, which outweighed an increase in number of green leaves harvested/tiller and in weight/green leaf. Increasing the level of N with intervals of 3–6 weeks increased the number of tillers, the number of green leaves harvested per tiller and per unit area of ground and weight/green leaf and hence consistently increased green leaf yield.

Description: SummaryOne side of each of 51 carcasses of Hereford, Angus, Friesian and Charolais cross-bred steers was dissected and the weights of individual muscles and total carcass muscle were obtained. The percentage distribution of total carcass muscle weight in muscles and in. standard groups of muscles was determined. In addition, the percentage distribution of total carcass muscle weight in wholesale cuts was determined from the weights of whole and part muscles specified as comprising the respective cuts.Minor breed differences only were found in muscle weight distribution among muscles, groups of muscles and wholesale cuts. Similarity of muscle weight distribution in the different types of carcasses studied shows that carcass shape is not associated with differences in the distribution of muscle weight in wholesale cuts.

Description: SummaryThe effect of six intervals between harvests and three levels of N application on digestibility, digestible yield and nitrogen content and yield was studied in four ryegrass(Lolium) varieties during a 30-week period in the first harvest year in a field experiment.Digestibility was higher with a 3-week than with a longer interval between harvests. Yield of digestible organic matter was increased by extending the interval from 3 to 6 weeks, but was slightly reduced by extending from 6 to 10 weeks.Increase in the level of applied N increased the degree of curvature downwards in the response to extending the interval in both yield of digestible organic matter and yield of N, supporting the view that N use should be accompanied by shortened intervals between harvests.Digestibility varied by up to 15 units D-value from one time of the year to another with a constant interval between harvests. The highest values were in the spring. Autumn values were low in spite of a relatively high proportion of green leaf.During the period immediately following the main period of stem development, doubling the interval from 4 to 8 or from 5 to 10 weeks reduced digestibility by 10 units and reduced digestible yield by 22%.In the absence of applied N, the N yield of S. 321 was 31% greater than the average of S. 22, S. 23 and S. 24. However, the apparent recovery of applied N in S. 321 was much lower than in the other varieties.

Description: SummaryFat cell diameters were measured at 2-mm intervals throughout the depth of cores of subcutaneous shoulder and mid-back fat from ten Large White pigs. Five of the pigs were examined at 39 kg live weight and five at 70 kg live weight.In the shoulder fat of both groups there was a gradual change in fat cell size from the skin to the musculature. Cells were relatively small beneath the skin and adjacent to the underlying muscle and increased in size towards the junction of the inner and outer fat layers. The major difference between the two groups of pigs was that the cells closest to the skin and in the bulk of the inner layer were larger in the heavier animals whereas the cells at the junction of the two layers and closest to the muscle were similar in size. Such a uniform picture was not observed in the mid-back region where cells from the inner layer were larger than those from the outer layer.Cell size was Normally distributed at each site throughout the tissue. When the cell measurements for all the sites in each layer were combined there was no consistency in the type of distributions obtained although there was a tendency for them to be bimodal.In both layers of the shoulder fat there was a significant increase in the number of cells present in the 70 kg pigs compared with the 39 kg pigs and the new cells contributed considerably to the growth of the tissue between these weights. The observed cell size distributions and the cell size gradients within the tissue suggest that in the inner shoulder layer the new cells arise adjacent to the muscle. In the mid-back there was no significant difference in the number of fat cells present in the two groups of pigs and the growth of the mid-back fat was due to an increase in the size of fat cells already present.