Energy Supply Rate Research Articles

Nonlinear effects in the interaction of periodic pulsed energy supply and shock-wave structure during transonic streamlining of wing profiles

We have evaluated the possibility of controlling the aerodynamic characteristics of wing profiles by means of a local periodic pulsed energy supply in transonic flight regimes. The influence of the energy supply rate and the position and area of the zone of energy supply on the flow structure near a symmetric wing profile and on the wave drag has been studied using a numerical solution of two-dimensional nonstationary equations of gasdynamics. The energy supply in front of the breakdown shock wave within extended zones in the immediate vicinity of the streamlined contour leads to a significant decrease in the wave drag of a given wing profile. The nature of this phenomenon is elucidated and it is established that there exists a limiting rate of energy supply.

Biochemical universality of living matter and its metabolic implications

Summary Recent discussions of metabolic scaling laws focus on the model of West, Brown & Enquist (WBE). The core assumptions of the WBE model are the size‐invariance of terminal units at which energy is consumed by living matter and the size‐invariance of the rate of energy supply to these units. Both assumptions are direct consequences of the biochemical universality of living matter. However, the second assumption contradicts the central prediction of the WBE model that mass‐specific metabolic rate q should decrease with body mass with a scaling exponent µ = −1/4, thus making the model logically inconsistent. Examination of evidence interpreted by WBE and colleagues in favour of a universal µ = −1/4 across 15 and more orders of magnitude range in body mass reveals that this value resulted from methodological errors in data assortment and analysis. Instead, the available evidence is shown to be consistent with the existence of a size‐independent mean value of mass‐specific metabolic rate common to most taxa. Plotted together, q‐values of non‐growing unicells, insects and mammals in the basal state yield µ ≈ 0. Estimated field metabolic rates of bacteria and vertebrates are also size‐independent. Standard mass‐specific metabolic rates of most unicells, insects and mammals studied are confined between 1 and 10 W kg−1. Plant leaves respire at similar rates. This suggests the existence of a metabolic optimum for living matter. With growing body size and diminishing surface‐to‐volume ratio organisms have to change their physiology and perfect their distribution networks to keep their q in the vicinity of the optimum.

A simple turbulent energy-based model of fine suspended sediments in the Irish Sea

Energy is required to maintain a particle heavier than water in suspension in the sea. In equilibrium, energy must be supplied at a rate equal to the product of the weight of the particle and its sinking velocity. If the energy supply rate is known, it becomes possible to predict the total weight, and hence the concentration of suspended particles in the sea. This principle has been applied to a model of fine suspended sediments in the Irish Sea. The model is used to test the hypothesis that the supply of turbulent kinetic energy (TKE) alone controls both the spatial pattern and seasonal changes in concentration. TKE is supplied by the tide and wind, and a fixed fraction of this energy is used to keep sediment in suspension. There is assumed to be a readily available supply of fine sediments at the sea bed, which rises into suspension as soon as TKE becomes available, and sinks down again when it is not. The model incorporates 2-layer thermal stratification and vertical mixing between layers but there is no horizontal advection or diffusion. The model is driven by smoothly varying wind speeds and heating over the year and spatially varying tidal stirring. The particles have a constant settling velocity of 10 m day −1, and a density twice that of water. A fraction 0.00006 of the total (tide+wind) TKE energy input is used to stir the sediment. The results of the model are in agreement with both the observed spatial pattern and the seasonal variation of fine suspended sediments in the surface waters of the Irish Sea to within the limits of measurement accuracy and natural variability. This energy model performs at least as well as conventional stress-driven models in this regard. We therefore conclude that the general behaviour of fine suspended sediments in the Irish Sea can be explained by TKE supply alone. Other factors, such as changes in particle size and density over the year, can be used for fine tuning but are not necessary to give a broadly correct picture. The result is that we have a simple, physically coherent, method of predicting the turbidity (and hence the light regime) of a shelf sea from physical inputs alone.

Excitation and Damping of Low‐Degree Solarp‐Modes during Activity Cycle 23: Analysis of GOLF and VIRGO Sun Photometer Data

We have used observations made by the Global Oscillations at Low Frequency (GOLF) and the Variability of Irradiance and Gravity Oscillations Sun Photometer (VIRGO/SPM) instruments on board the ESA/NASA Solar and Heliospheric Observatory satellite to study variations in the excitation and damping of low angular degree (low-l) solar p-modes on the rising phase of activity cycle 23. Our analysis includes a correction procedure that for the first time allows GOLF data to be treated as a single homogeneous set, thereby compensating for the change of operational configuration partway through the mission. Over the range 2.5 ≤ ν ≤ 3.5 mHz, we uncover an increase in damping and decrease in mode power that is consistent with previous findings. Furthermore, an excellent level of agreement is found between the variations extracted from the GOLF and VIRGO/SPM data. We find no net long-term changes to the modal energy supply rate. However, an analysis of the residuals uncovers the presence of a quasi-periodic signature of period ≈1.5 yr (most pronounced for SPM). While it is true that several workers claim to have uncovered similar periodicities in other phenomena related to the near-surface layers of the Sun here, we are at present more inclined to attribute our finding to an artifact of the mode-fitting procedure. We also uncover a significant change in the asymmetry of mode peaks in the GOLF data, as found in previous studies of much longer data sets. These assumed that the dominant contribution to this arose from the switch in operating configuration partway through the mission (which altered the depth in the solar atmosphere sampled by the instrument). However, our preliminary analysis of data collected over the 100 day period beginning 2002 November 19—when the instrument switched back to its original configuration—suggests that this change may have a solar cycle component.

Study ofp-mode excitation and damping rate variations from IRIS++observations

11 years of low degree helioseismic data collected by the IRIS ++ network ( International Research of the Interior of the Sun ) have been analyzed. The epoch covered (mid-1989 to end-1999) spans the maximum and the falling phase of solar cycle 22 and the rising phase of the current solar cycle 23. Annual timeseries with an overlap of 6 months are used to study the variations with solar activity of the p -mode frequencies $\nu_{n,\ell}$, heights $H_{n,\ell}$, and linewidths $\Gamma_{n,\ell}$, taking into account the effects of the window function. These are used to infer variations in the velocity power $ $ and the energy supply rate $\dot{E}_{n,\ell}$ which relate to changes in the excitation and the damping of the modes. We find global changes over the range 2600 $\leq \nu \leq 3600~\mu$Hz of about -26%, 11%, -11% for the heights, the linewidths, and the velocity power respectively, and a constant energy supply to the modes.

Numerical 3D constraints on convective eddy time-correlations: Consequences for stochastic excitation of solarp modes

A 3D simulation of the upper part of the solar convective zone is used to obtain information on the frequency component,k, of the correlation product of the turbulent velocity field. This component plays an important role in the stochastic excitation of acoustic oscillations. A time analysis of the solar simulation shows that a Gaussian function does not correctly reproduce the-dependency ofk inferred from the 3D simuation in the frequency range where the acoustic energy injected into the solar p modes is important (' 2 4m Hz). The-dependency ofk is fitted with dierent analytical functions which can then conveniently be used to compute the acoustic energy supply rate P injected into the solar radial oscillations. With constraints from a 3D simulation, adjustment of free parameters to solar data is no longer necessary and is not performed here. The result is compared with solar seismic data. Computed values of P obtained with the analytical function which fits best k are found2.7 times larger than those obtained with the Gaussian model and reproduce better the solar seismic observations. This non-Gaussian description also leads to a Reynolds stress contribution of the same order as the one arising from the advection of the turbulent fluctuations of entropy by the turbulent motions. Some discrepancy between observed and computed P values still exist at high frequency and possible causes for this discrepancy are discussed.

Does the Energy Supplied to Low-[CLC][ITAL]l[/ITAL][/CLC] Solar [CLC][ITAL]p[/ITAL][/CLC]-Modes Vary over the Activity Cycle?

We report on the average behavior of the excitation and damping of low angular degree (low l) solar p-mode oscillations over the decade from 1991 to 2000 using both long and short time duration Fourier transforms. The data in question were collected by the ground-based Birmingham Solar Oscillations Network. Throughout most of the period under study, the energy supply rate to the modes remains roughly constant—implying a near-constant level of forcing—while the damping and velocity power show a fairly smooth increase and decrease, respectively, in response to increasing levels of solar activity (in line with previous findings). However, here we uncover evidence of there being a sharp increase in the mode velocity power over a brief period of approximately 100 days centered on 1998 late March. The magnitude and sign of this are contrary to the expectation based on the long-timescale, solar-cycle trend; such unusual behavior is absent in the damping. This implies that the forcing of, or rate of energy supplied to, the modes increased in magnitude over this period.

Does solar flare activity lag behind sunspot activity

Recently, Wheatland and Litvinenko (2001) have suggested that over the solar cycle both the flaring rate and the magnetic free energy in the corona lag behind the energy supply to the system. To test this model result, we analyzed the evolution of solar flare occurrence with regard to sunspot numbers (as well as sunspot areas), using Hα flare data available for the period 1955–2002, and soft X-ray flare data (GOES 1–8 A) for the period 1976–2002. For solar cycles 19, 21, and 23, we find a characteristic time lag between flare activity and sunspot activity in the range 10≲τ≲15 months, consistent with the model predictions by Wheatland and Litvinenko (2001). The phenomenon turns out to be more prominent for highly energetic flares. The investigation of solar activity separately for the northern and southern hemisphere allows us to exclude any bias due to overlapping effects from the activity of both hemispheres and confirms the dynamic relevance of the delay phenomenon. Yet, no characteristic time lag τ>0 is found for solar cycles 20 and 22. The finding that in odd-numbered cycles flare activity is statistically delayed with respect to sunspot activity, while in even-numbered cycles it is not, suggests a connection to the 22-year magnetic cycle of the Sun. Further insight into the connection to the 22-year magnetic cycle could possibly be gained when a 22-year variation in the energy supply rate is taken into account in the Wheatland and Litvinenko (2001) model. The existence of a 22-year modulation in the energy supply rate is suggested by the empirical Gnevyshev – Ohl rule, and might be caused by a relic solar field.

Allometric scaling of maximum population density: a common rule for marine phytoplankton and terrestrial plants

A primary goal of macroecology is to identify principles that apply across varied ecosystems and taxonomic groups. Here we show that the allometric relationship observed between maximum abundance and body size for terrestrial plants can be extended to predict maximum population densities of marine phytoplankton. These results imply that the abundance of primary producers is similarly constrained in terrestrial and marine systems by rates of energy supply as dictated by a common allometric scaling law. They also highlight the existence of general mechanisms linking rates of individual metabolism to emergent properties of ecosystems.

Localizing Width and Energy of Solar Globalp‐Modes

We present the first attempt at localizing in latitude the temporal variation of mode energy, energy supply rate, and lifetime of global acoustic modes. We use Global Oscillation Network Group (GONG) and Michelson Doppler Imager data analyzed with the GONG peak-fitting algorithm to measure mode width and amplitude of individual (l, n, m) modes. While measured amplitude and width values are inherently noisier than frequency measurements, it is possible to use the (m/l) dependence of these mode parameters to extract their variation in latitude. With the currently analyzed data sets, we construct maps in time and latitude of acoustic mode energy, lifetime (inverse of mode width), and energy supply rate covering the rising phase of the current solar cycle from the previous minimum to the current maximum. We find that the energy and width of global modes vary in latitude as well as in time and that the variation is clearly related to the distribution of magnetic flux. After removing the average quantity, the residual mode width shows a linear correlation with magnetic activity with a correlation coefficient of 0.88, while the corresponding residual mode energy is anticorrelated with magnetic activity with a correlation coefficient of -0.90. These mode parameters derived from global p-modes respond to the local distribution of surface magnetic activity. The energy supply rate shows no correlation with the latitudinal distribution of magnetic activity within the limits of the current measurements. We estimate the variation of global mode energy in response to an individual magnetic feature, such as a plage, and find that the global mode energy and the mode lifetime are reduced by about 40% by an active region compared to the quiet Sun.

EFECTO DEL HOJUELADO AL VAPOR SOBRE LA DEGRADABILIDAD RUMINAL DEL GRANO DE MAIZ

With the objective of estimating the effect of steam flaking of corn grain on its rumen degradability and degradation kinetics, samples of grain either ground (control) or steam rolled whole (HVE) or steam rolled ground (HVM), were subjected to seriated (0 to 48 h) rumen fermentations by the in situ technique with polyester bags. When fitting dry matter disappearance values to the function from Orskov and McDonald (1979) to estimate the terms representing the soluble fraction (a), insoluble degradable fraction (b) and the fractional degradation rate (c), the control treatment showed lower a fraction (26.18%) than HVE (28%) and HVM (33.16%). Control treatment also presented higher b fraction (72.02%) than HVE (53.94%) and HVM (54.82%), lower c degradation rate (0.0419) than HVE (0.0863) and HVM (0.0768), and higher potential degradation a+b (98.2%) than HVE (81.94%) and HVM (87.98%). Effective degradabilities computed for different ruminal fractional outflow rates (from 0.04 to 0.1) were higher with steam rolled treatments and moreover, increasing of the outflow rate resulted in less severe reductions in effective degradability for these treatments in relation to control. It is concluded that treating corn grain with temperature and high pressure steam, followed by rolling, results in an increased rate of energy supply at rumen level.

Contrasting Brood Sizes in Common and Arctic Terns: The Roles of Food Provisioning Rates and Parental Brooding

AbstractArctic Terns (Sterna paradisaea) and Common Terns (S. hirundo) are similar in many aspects of their breeding ecology, but Common Terns generally lay three eggs per clutch whereas Arctic Terns lay two. In our study, Common Terns had a higher rate of food delivery and energy supply to the nest and higher nest attendance, indicating that they made trips of shorter average duration. This suggests that the number of chicks raised by these two species was primarily limited by the rate at which parents could supply food. However, estimated daily metabolizable energy intake of chicks was about 30% higher in Common Terns than in Arctic Terns. Common Tern chicks apparently spent a higher proportion of daily energy intake on maintenance of body temperature. It remains unknown whether this difference was because Common Tern parents could not brood three chicks as effectively as Arctic Terns brooded two or because the energy requirements for heat production in the third-hatched Common Tern chick were particularly high. If brooding did play a less important role in the energy budgets of Common Terns, the number of chicks that Arctic Terns could raise may have been limited not only by the rate at which parents could supply food to the nest but also by the requirements of chicks for brooding. We suggest that more detailed studies on the role of brooding constraints in limiting brood size in these species are required to clarify this matter.

CONTRASTING BROOD SIZES IN COMMON AND ARCTIC TERNS: THE ROLES OF FOOD PROVISIONING RATES AND PARENTAL BROODING1

Abstract Arctic Terns (Sterna paradisaea) and Common Terns (S. hirundo) are similar in many aspects of their breeding ecology, but Common Terns generally lay three eggs per clutch whereas Arctic Terns lay two. In our study, Common Terns had a higher rate of food delivery and energy supply to the nest and higher nest attendance, indicating that they made trips of shorter average duration. This suggests that the number of chicks raised by these two species was primarily limited by the rate at which parents could supply food. However, estimated daily metabolizable energy intake of chicks was about 30% higher in Common Terns than in Arctic Terns. Common Tern chicks apparently spent a higher proportion of daily energy intake on maintenance of body temperature. It remains unknown whether this difference was because Common Tern parents could not brood three chicks as effectively as Arctic Terns brooded two or because the energy requirements for heat production in the third-hatched Common Tern chick were particul...

Width and Energy of Solarp‐Modes Observed by Global Oscillation Network Group

We present measurements of mode width, Γ, and mean square velocity power, , derived from all currently processed 108 day Global Oscillation Network Group (GONG) time series and discuss their implications for p-mode excitation and damping. Assuming stochastic excitation, we estimate the energy per mode, E, and the energy supply rate, dE/dt. For modes with l = 9-150, the mean square velocity power and the mode energy peak at about 3.15 mHz reaching values of ≈ 1.4 × 103 cm2 s-2 and E ≈ 2.2 × 1028 ergs. The energy supply rate reaches a maximum value of dE/dt ≈ 2.5 × 1023 ergs s-1 near 3.6 mHz. The mode width shows the familiar plateau between 2.5 and 3.1 mHz with a near 2.9 mHz, which is strongest for l ≈ 40. This dip is most prominent during solar cycle minimum and disappears with increasing magnetic activity. The energy supply rate decreases on average by about 2.7% from the previous activity minimum to the currently highest level of activity. The solar cycle variation of dE/dt shows no frequency dependence, which is in marked contrast to the other mode parameters. The mode parameters are adequately represented by power laws in several frequency ranges, for example, dE/dt ~ ν6.89±0.07 for 2.4 mHz ≤ ν < 3.0 mHz and dE/dt ~ ν-5.62±0.27 for 3.75 mHz ≤ ν < 4.5 mHz. The solar cycle variation of these parameters can then be expressed as changes of a few percent in the power-law exponents and multipliers. Our results agree reasonably well with previous studies of Birmingham Solar-Oscillations Network and Big Bear Solar Observatory data.

The effects of synchronizing the rate of dietary energy and nitrogen supply to the rumen on milk production and metabolism of ewes offered grass silage based diets

AbstractTwenty-four multiparous ewes were used to test the hypothesis that synchronizing the hourly rate of release of energy and nitrogen in the rumen would optimize milk production. Three diets were formulated using the in situ degradability of the food ingredients, to differ in their rate of organic matter (OM) and nitrogen (N) release in the rumen. All diets contained 400 g grass silage per kg dry matter (DM) and were predicted to have a similar content of metabolizable energy (11·8 MJ/kg DM), metabolizable protein (102 g/kg DM), neutral-detergent fibre (365 g/kg DM) and daily ratio of N: OM supply to the rumen but differ in their hourly pattern of nutrient release to be either synchronous (S), asynchronous (A) or intermediate (I). The diets were offered ad libitum as a complete feed in a 3×3 Latin-square design consisting of three periods each of 28 days duration. Synchronizing the hourly supply of energy and N to the rumen did not significantly alter milk or milk fat yield (g/d), milk protein content (g/kg), DM intake (kg/day), total time spent eating or the number of meals per day. However, compared with ewes offered diets I or A, those offered diet S had a lower milk fat content (g/kg;P&lt; 0·05) whilst protein yield (g/day) tended to be increased (P= 0·05). Animals offered the synchronous diet (S) had lower plasma urea concentrations throughout the day and significantly higher beta-hydroxybutyrate concentrations at 14:00 and 18:00 h than those offered diets I or A. In conclusion, synchronizing dietary energy and N supply to the rumen did not have a major effect on milk production in ewes.

Inverse optimal adaptive control for non-linear uncertain systems with exogenous disturbances

A Lyapunov-based inverse optimal adaptive control-system design problem for non-linear uncertain systems with exogenous ℒ2 disturbances is considered. Specifically, an inverse optimal adaptive non-linear control framework is developed to explicitly characterize globally stabilizing disturbance rejection adaptive controllers that minimize a nonlinear-nonquadratic performance functional for non-linear cascade and block cascade systems with parametric uncertainty. It is shown that the adaptive Lyapunov function guaranteeing closed-loop stability is a solution to the Hamilton–Jacobi–Isaacs equation for the controlled system and thus guarantees both optimality and robust stability. Additionally, the adaptive Lyapunov function is dissipative with respect to a weighted input–output energy supply rate guaranteeing closed-loop disturbance rejection. For special integrand structures of the performance functionals considered, the proposed adaptive controllers additionally guarantee robustness to multiplicative input uncertainty. In the case of linear-quadratic control it is shown that the operations of parameter estimation and controller design are coupled illustrating the breakdown of the certainty equivalence principle for the optimal adaptive control problem. Finally, the proposed framework is used to design adaptive controllers for jet engine compression systems with uncertain system dynamics. Copyright © 2000 John Wiley & Sons, Ltd.

Long-term perspective on the development of solar energy

We use dynamic optimization methods to analyze the development of solar technologies in light of the increasing scarcity and environmental pollution associated with fossil fuel combustion. Learning from solar R&D efforts accumulates in the form of knowledge to gradually reduce the cost of solar energy, while the scarcity and pollution externalities associated with fossil fuel combustion come into effect through shadow prices that must be included in the effective cost of fossil energy. Accounting for these processes, we characterize the optimal time profiles of fossil and solar energy supply rates and the optimal investment in solar R&D. We find that the optimal rate of fossil energy supply should decrease over time and vanish continuously upon depletion of the fossil fuel reserves, while the optimal supply of solar energy should gradually increase and eventually take over the entire energy demand. The optimal solar R&D investment should initially be set at the highest feasible rate, calling for early engagement in solar R&D programs, long before large scale solar energy production becomes competitive.

The effects of synchronizing the rate of dietary energy and nitrogen supply to the rumen on the metabolism and growth of ram lambs given food at a restricted level

AbstractThe effects of diets formulated to have two rates of organic matter (OM) release and to be either synchronous or asynchronous with respect to their hourly release of OM and nitrogen (N) in the rumen on N retention, microbial N production, growth and metabolism of ram lambs offered food at a restricted level was studied in two experiments. Four diets were formulated to differ in their rate and extent of OM and N release in the rumen based on the sum of in situ degradability data of the ingredients. All diets were formulated to have a similar metabolizable energy (10·4 MJ/kg dry matter (DM)), crude protein (140 g/kg DM) and daily ratio of N : OM released (34 g N per kg OM) and were either synchronous or asynchronous with respect to their hourly N : OM release. The four diets were slow energy, synchronous (SS), slow energy asynchronous (SA), fast energy, synchronous (FS) and fast energy asynchronous (FA). In both experiments the diets were offered at a rate of 1·75 maintenance energy requirements as two equal meals at 09:00 and 17:00 h. In experiment 1 there was no significant effect of diet on OM apparent digestibility or N retention. Lambs given diet FS had the highest daily production of allantoin (7·82 mmol per day; P &lt; 0·05) and microbial N (7·80 g/day; P &lt; 0Ό5). Hourly plasma urea and ß-hydroxy butyrate (3-OHB) concentrations exhibited a cyclical trend between meals with maximum concentrations occurring within 3 h of feeding and were higher in lambs given diet FA.In experiment 2 the four diets were offered to 32 growing ram lambs. Animals given synchronous diets (SS and FS) had a significantly higher live-weight gain than those given asynchronous diets (SA and FA; (132 g/day v. 107 g/day respectively; P &lt; 0·001). Food conversion efficiency (FCE; kg gain per kg DM intake) was improved proportionately by 0·23 in animals offered synchronous diets compared with asynchronous diets (P &lt; 0·001). There was little effect of diet on carcass composition except kidney fat, which was greater in lambs offered the synchronous diets (P &lt; 0·01). Plasma 3-OHB concentrations were higher throughout the growth period in lambs given diet FA whilst plasma urea concentrations were greater in lambs given the diet SS. In conclusion, greater attention to the formulation of diets to be synchronous for their hourly release of N : OM in the rumen can improve the growth rate and FCE of lambs. This effect may be due to an improvement in energy rather than N metabolism.

The effects of synchronizing the rate of dietary energy and nitrogen supply to the rumen on the production and metabolism of sheep: food characterization and growth and metabolism of ewe lambs given food ad libitum

Abstract The effects of diets formulated to have two rates of organic matter (OM) release and to be either synchronous or asynchronous with respect to their hourly release of nitrogen (N) and OM in the rumen on the growth, intake and metabolism of ewe lambs was studied. In experiment 1, the in situ degradation characteristics of N and OM for 16 food ingredients was determined. The foods varied considerably in their chemical composition and degradability coefficients of N and OM. Based on this information, four diets were formulated to differ in their rate of N and OM release in the rumen but to have a similar content of metabolizable energy (10·4 MJ/kg dry matter (DM)), crude protein (140 g/kg DM), daily ratio of N: OM released (34 g N per kg OM) and digestible undegradable protein (32 g/kg DM) but to be synchronous or asynchronous with respect to hourly N: OM ratio. The four diets were slow energy, synchronous (SS), slow energy asynchronous (SA), fast energy, synchronous (FS) and fast energy asynchronous (FA). In experiment 2 the four diets were offered ad libitum to 24 ewe lambs of an initial live weight of 25 kg in a 2 × 2 factorial design. Lambs were slaughtered at 40 kg live weight. Animals offered diets FS and FA had a higher growth rate than those offered diets SA and SS (266 v. 225 g/day respectively; P &lt; 0·05). There was a significant interaction between rate ofOM and N release on DM intake (DMI) with lambs offered diet FS consuming less than those offered FA (1·47 v. 1·67 kg DM per day; P &lt; 0·05). Rate of energy release and synchrony had an effect on food conversion efficiency (FCE; kg gain per kg DMI) with lambs offered diets FS and FA having a greater FCE than those offered SS and SA (0·170 v. 0·146 respectively; P &lt; 0·001) and those offered diets SS and FS had a greater FCE than those offered diets SA and FA (0·164 v. 0·152 respectively; P &lt; 0·05). Diet had little effect on carcass composition. The proportion of propionate in rumen fluid was greater in lambs offered diets FS and FA than in those offered diets SS and SA (222 v. 168 mmol/mol respectively; P &lt; 0·01). Plasma urea concentrations exhibited a cyclical trend throughout the day with highest concentrations occurring 2 h after fresh food was offered. Lambs offered diet FS had lower plasma urea concentrations at 6, 10 and 14 h after feeding. Plasma concentrations of ß-hydroxybutyrate were lower throughout the day in lambs offered diet FS. The current findings are consistent with the view that a rapid release of OM and synchronizing hourly N: OM release in the rumen can improve the efficiency of growth through improvements in protein and/or energy metabolism.

Solar p-mode excitation: further insight from recent low- BiSON helioseismological data

We present measurements of low-degree solar p-mode velocity powers, energies and energy supply rates between similar to 1600 mu Hz and similar to 4700 mu Hz, as derived from the analysis of several years of high-quality helioseismological data collected by the Birmingham Solar-Oscillations Network (BiSON). For the radial (l = 0) modes, we find that the total energy E per mode (kinetic plus potential) peaks at similar to 3200 mu Hz, reaching approximate to 10(28) erg. The rate at which energy is supplied to the modes (E) over dot = 2 pi Delta nu . E, where Delta nu is the FWHM modal line width, is observed to plateau between similar to 3000 and similar to 4000 mu Hz, reaching a maximum of approximate to 10(23) erg s(-1). At frequencies below the plateau, the supply rate follows a simple power law with a dependence of (E) over dot proportional to nu(7.0+/-0.4); and at very-high frequencies the data follow (E) over dot proportional to nu(-4.5+/-1.1). These assume modal inertias normalized at T = T-eff; with the mode-mass calculation normalized at the optical depth of the BiSON observations, the fitted power laws in (E) over dot are approximately similar to nu(6.5+/-1.1) and similar to nu(-6.2+/-1.1) respectively.