ALBERT

Description: A method has been developed at the Arizona AMS facility for production of graphite directly from CO2 by catalytic reduction of CO/H2 mixtures. The method is a modification of procedures discussed by Vogel et al (1984). Currents of 12C− from these targets vary considerably, but have a median value which is 70% of that achieved from spectroscopic graphite. Precisions of ±60 to 100 yr are routinely achieved for 14C ages of 5000-yr-old samples containing one milligram of carbon. The yield of 14C from “blank” targets is 0.6 ± 0.1% of that from modern material.

Description: The relative viscosities of suspensions of randomly oriented rods in a Newtonian fluid were measured using falling-ball rheometry. The rods were monodisperse and sufficiently large to render colloidal and Brownian forces negligible. Steel and brass ball bearings were dropped along the centreline of cylindrical columns containing the suspensions. The terminal velocities of the falling balls were measured and used to determine the average viscosities of the suspensions. The suspensions behaved as Newtonian fluids in that they were characterized by a constant viscosity. They exhibited a linear relative viscosity-volume fraction relationship for volume fractions less than 0.125, and, for volume fractions between 0.125 and 0.2315, the specific viscosity increased with the cube of the volume fraction. The relative viscosity was found to be independent of falling-ball size for a ratio of falling ball to fibre length greater than 0.3. It was found to be independent of the diameter of the containing cylindrical column for a ratio of column diameter to fibre length greater than 3.2. The value determined for the intrinsic viscosity is in good agreement with theoretical predictions for suspensions of randomly oriented rods. © 1989, Cambridge University Press. All rights reserved.

Description: The topology of the organized motion has been obtained in the slightly heated self-preserving far wake of a circular cylinder at a Reynolds number, based on the cylinder diameter, of about 1200. In a frame of reference moving with the organized motion, the toplogy in the plane of main shear reduces to a succession of centres and saddles, located at about the wake half-width. Centres are identifiable by large values of spanwise vorticity associated with the coherent large-scale motion. Saddles occur at the intersection of converging and diverging separatrices, the latter being identifiable with the high strain rate due to the large-scale motion. Large values of the longitudinal turbulence intensity associated with the smaller-scale motion occur at the centres. High values of the normal and shear stresses, the temperature variance and heat fluxes associated with the large-scale motion occur on either side of each saddle point along the direction of the diverging separatrix. Contours for the production of energy and temperature variance associated with the small-scale motion are aligned along the diverging separatrices, and have maxima near the saddle point. Contours for one component of the dissipation of small-scale temperature variance also have a high concentration along the diverging separatrix. Flow visualizations in the far wake suggest the existence of groups of three-dimensional bulges which are made up of clusters of vortex loops. © 1987, Cambridge University Press. All rights reserved.

Description: It is shown that a consideration of the magnetic field in a highly conducting turbulent medium, using Lagrange variables, involves deriving kinetic equations of fluid-particle transition probability densities. A derivation of such equations is performed for joint probability densities of n particles up to n = 4. By assuming normality of one particle distribution function it was found that these kinetic equations are the generalized Kolmogorov-Fokker-Planck (KFP) equations. The dynamics of mean and fluctuating magnetic fields is described by means of these equations. The eddy diffusivity of a mean field for processes described by generalized KFP equations coincides with that of a scalar field (depending in general on helicity in implicit form). It is shown that at sufficiently large magnetic Reynolds number, a turbulence with any spectrum generates fluctuating magnetic fields. © 1986, Cambridge University Press. All rights reserved.

Description: The effect of wall suction on the organized motion of a tubulent boundary layer is examined experimentally both in a wind tunnel and in a water tunnel. In the wind-tunnel boundary layer, which developed over a slighly heated surface, temperature fluctuations were simultaneously obtained at several points, aligned in either the x (streamwise) or y (normal to the wall) direction. The temperature traces reveal the existence of two spatially coherent events, characterized either by a sudden decrease (cooling) or by a sudden increase (heating) of temperature. Estimates are presented for the average convection velocity, and average frequency of these events. The average convection velocity of ‘ coolings ’ is about 15 % larger than that of£ heatings ’, the velocity of both events exhibiting an important local maximum in the buffer region. Near the wall, the convection velocity of both events is increased slightly by suction while their average frequency is reduced by suction. Away from the wall, the average inclination of‘ coolings ’ and 4 heatings ’ is about 40° without suction suction does not alter the inclination of ‘ coolings ’ but increases that of ‘ beatings ’ to about 50°. Visualizations in the water tunnel indicate that suction increases the stability and the longitudinal coherence of low-speed streaks. They also show that suction reduces the average frequency of dye ejections into the outer layer. © 1988, Cambridge University Press. All rights reserved.

Description: A modification is made to the traditional Lagrangian approach to the derivation of the mean EMF of turbulent fluids which allows for finite conductivities. Consideration is confined to the case of homogeneous, isotropic but generally mirror-non-invariant and compressible turbulence. The eddy magnetic diffusivity and the coefficient a of the alpha-effect are expressed in terms of statistical moments of displacements of adjacent particles which undergo convective transport and microscopic diffusion in a turbulent flow. These expressions, being valid for arbitrary conductivities, reproduce known results in the cases of both very large and very small magnetic Reynolds numbers. Difficulties and advantages of the use of the results obtained for evaluations of the mean EMF are discussed. © 1989, Cambridge University Press. All rights reserved.

Description: SummaryTo quantify changes in rates of metabolism and nutrient uptake of gravid uteiine, foetal and utero-placental tissues throughout gestation, mature Hereford cows received surgery at 132 ± 0·6 (n = 12), 176 ± 0·5 (n = 8), 220 ±0·4 (n = 11) and 245 ±1·5 (n = 7) days after mating. Indwelling catheters were implanted into a uterine artery and vein of all cows. Foetal catheters also were implanted into an umbilical vein and foetal femoral artery and vein (days 176 and 220) or into a placental artery and two placental veins (days 132 and 245). Approximately 5 days after surgery, deuterium oxide was infused into a foetal femoral venous or placental venous catheter during a 3 h period to quantify uterine and umbilical blood flows by steady-state diffusion methods. Oxygen, glucose, lactate and α-amino acid nitrogen concentrations were determined for uterine and foetal blood samples collected during this procedure.Uterine blood flow increased 4·5-fold (2·92–13·181/min) and umbilical blood flow increased 21-fold (0·28–5·861–min) during the interval of gestation studied. The relative rate of increase of umbilical blood flow was about twice as great as that of uterine blood flow. Uterine arterial and umbilical venous concentrations as well as uterine arterial-venous and umbilical venous-arterial concentration differences in metabolites changed little with stage of gestation. However, because rates of blood flow increased, uptakes of O2, glucose and α-amino N by the gravid uterus and foetus increased as gestation advanced. The proportion of gravid uterine uptakes utilized by the foetus increased from day 137 to 226 for O2 (24–58%) and from day 137 to 180 for glucose (4–19%), then remained relatively constant. The proportion of gravid uterine α-amino N uptake utilized by the foetus remained relatively constant and averaged 60%. A net secretion of lactate from the utero-placenta to the uterine and foetal circulations was observed and increased as gestation advanced. These data indicate that increased rates of uptake or secretion of metabolites by tissues of the gravid uterus can be explained primarily by increased rates of uterine and umbilical blood flows.

Description: SummaryPre-emergence herbicides applied at field recommended doses, 3 days after transplanting (DAT) rice plants, inhibited growth and N2-fixation of Azolla pinnata (Bangkok) and BGA (blue-green algae) inoculated 10 DAT. This inhibition was up to 15 DAT in Azolla and up to 20 DAT in BGA. Butachlor and Oxadiazon resulted in higher toxicity to Azolla and BGA than Benthiocarb and Pendimethalin. The application of 0·5 kg/ha active ingredient of 2,4-DNa did not inhibit growth of Azolla but inhibited BGA growth. However, 2,4-DEE, a post-emergence herbicide, applied 30 DAT showed inhibitory effects on the growth and N2-fixation of both Azolla and BGA. Inoculation of 2·0 t/ha of fresh Azolla 10 DAT produced maximum biomass within 20–25 days of herbicide treatments, depending upon the season. The inoculation of 10 kg/ha of a dry mixture of BGA 10 DAT could produce the maximum biomass 60 and 80 DAT in control and herbicide treated plots, respectively. The biomass and nitrogen produced by Azolla recorded at maximum mat formation were similar in both herbicide treated and untreated plots, but in BGA these were higher in controls than those of herbicide treated plots.The use of Azolla and BGA biofertilizers along with herbicides increased the grain and straw yields, and panicle number and nitrogen uptake, by rice over no Azolla or BGA treatments. The Azolla and BGA treatments even without weeding increased rice yield up to that of herbicide and biofertilizer treatments.

Description: SummaryTwenty fine-wool, ruminally cannulated lambs (average weight 45–9 kg) were used in a completely random design to evaluate the ability of three internal markers to predict dry matter digestibility and two external markers to estimate faecal output. Lambs were allotted randomly to one of four diets: 100% prairie hay (PH), 100% lucerne hay (LH), 50% prairie hay:50% sorghum grain (PS) and 50% lucerne hay: 50% sorghum grain (LS). The trial consisted of a 14-day adaptation period followed by a 7-day total faecal collection period. Feed and faecal samples were subjected to 96 h ruminal fluid and 48 h acid-pepsin digestions, followed by extraction with acid detergent (IVADF) or neutral detergent (IVNDF) solution. Dry matter digestibility (DMD) calculated from feed:faeces ratios of IVADF, IVNDF and acid detergent lignin (ADL) was compared with in vivoapparent digestibility. Ytterbium-labelled forage (YLF) and dysprosium-labelled faeces (DLF) were pulse-dosed via ruminal cannulae, and faecal Yb and Dy excretion curves were fitted to a one-compartment, agedependent model for estimation of faecal output, paniculate passage rate (PPR) and mean gastrointestinal retention time. In vivoDMD in lambs fed PH was greater (P 005) from marker estimates. In vivoDMD for lambs fed PS did not differ from IVNDF or IVADF estimates but was greater than (P 005) were observed in recovery among the three internal markers for any of the diets. Faecal output for lambs fed PH did not differ {P 〉005) from marker estimates but was overestimated by 15 to 20% by YLF and DLF. Faecal output for lambs fed LH was similar to the estimate from YLF, but less than (P

Description: SUMMARYThe rumen anaerobic fungus Neocallimastix sp. LM1 was specifically labelled in batch culture with either [14C]lysine, [14C]lysine + [3H] tyrosine, [14C] methionine, or [35S] sulphide. Fractionation of acid hydrolysates of fungal biomass on an amino acid analyser showed that the labelled amino acids were directly incorporated into fungal protein with little or no degradation. [35S] Sulphide was incorporated into cysteine and methionine.Absorption of amino acids from the small intestine was measured in sheep with permanent fistulae in the abomasum and terminal ileum, by introducing radiolabelled fungal biomass into the abomasum together with Cr-EDTA as the marker for digesta flow. The proportions of [14C] lysine (Expt 1), [14C] lysine + [3H] tyrosine (Expt 2), [14C] methionine (Expt 3) and the sulphur amino acids from [35S] sulphide (Expt 4) which appeared unabsorbed at the terminal ileum averaged 0·13, 0·07 + 0·08, 0·13 and 0·02, respectively. These proportions reflect the high digestibility of certain essential amino acids and the sulphur amino acids of fungal proteins. The results indicate that the true fractional digestibility of fungal proteins is c. 0·9. Consequently, a large biomass of anaerobic fungi in rumen digesta would be expected to provide a valuable source of digestible amino acids to ruminants.