Effect of feeding on plasma antibiotic concentrations in Greyhounds given ampicillin and amoxycillin by mouth

In a cross-over study, six Greyhounds were dosed by mouth with ampicillin and amoxycillin at 20 mg/kg, using three different feeding regimens (no food, canned food prior to dosing, and dry food ad lib ) with each drug. Antibiotic levels in plasma were determined by microbiological assay at intervals after dosing.
Plasma ampicillin concentrations tended to be lower in fed than in starved Greyhounds, but amoxycillin levels were relatively unaffected by feeding. In starved Greyhounds, ampicillin gave higher early levels than amoxycillin.     

The effect of the spatial distribution of plant species within the sward on the searching success of sheep when grazing

The ability of grazing sheep to exploit preferred patches of grass species according to their spatial distribution was studied. The choices made by groups of four ewes in three cocksfoot ( Dactylis glomerata ) plots (80 × 80 m), in which 136 patches (30 × 30 cm) of perennial ryegrass ( Lolium perenne ) were either randomly distributed (plot Rand ) or grouped (plots Ag.1 and Ag.2 ) to create preferred feeding sites (four rich sites of twenty-five patches and four poorer sites of nine patches) were compared. On measurement days, each group was allocated to one of the three plots, and grazed it in at least four successive 30-min tests. At the end of the experiment the ewes were allowed to graze the plots continuously for 3 months to assess the medium-term effect of grazing sheep on the depletion rate of patches. Behavioural observations showed that, once the ewes had discovered a preferred feeding site in plots Ag.1 or Ag.2 , they frequently returned to it within a test and between tests, whereas they failed to learn the precise location of many isolated patches in plot Rand . Thus in 2 h of grazing, the ewes spent 0·40 more time feeding on perennial ryegrass when the patches were grouped than when they were randomly distributed, and perennial ryegrass depletion was greater in plots Ag.1 and Ag.2 than in plot Rand (0·193 vs. 0·105 of initial height). The richer sites were also more depleted than the poorer ones (0·209 vs. 0·152 of initial height). When the plots were continuously grazed, perennial ryegrass depletion remained greater in plots Ag.1 and Ag.2 than in plot Rand for at least 3 weeks. Hence the spatial distribution of patches can affect diet selection by sheep, and so probably their impact on grasslands.     

Melting Temperature and Partial Melt Chemistry of H2O-Saturated Mantle Peridotite to 11 Gigapascals

The H2O-saturated solidus of a model mantle composition (Kilborne Hole peridotite nodule, KLB-1) was determined to be just above 1000°C from 5 to 11 gigapascals. Given reasonable H2O abundances in Earth's mantle, an H2O-rich fluid could exist only in a region defined by the wet solidus and thermal stability limits of hydrous minerals, at depths between 90 and 330 kilometers. The experimental partial melts monotonously became more mafic with increasing pressure from andesitic composition at 1 gigapascal to more mafic than the starting peridotite at 10 gigapascals. Because the chemistry of the experimental partial melts is similar to that of kimberlites, it is suggested that kimberlites may be derived by low-temperature melting of an H2O-rich mantle at depths of 150 to 300 kilometers.     

Universality Classes of Optimal Channel Networks

Energy minimization of both homogeneous and heterogeneous river networks shows that, over a range of parameter values, there are only three distinct universality classes. The exponents for all three classes of behavior are calculated.     

The extreme Kuiper Belt binary 2001 QW322

The study of binary Kuiper Belt objects helps to probe the dynamic conditions present during planet formation in the solar system. We report on the mutual-orbit determination of 2001 QW322, a Kuiper Belt binary with a very large separation whose properties challenge binary-formation and -evolution theories. Six years of tracking indicate that the binary's mutual-orbit period is approximately 25 to 30 years, that the orbit pole is retrograde and inclined 50 degrees to 62 degrees from the ecliptic plane, and, most surprisingly, that the mutual orbital eccentricity is <0.4. The semimajor axis of 105,000 to 135,000 kilometers is 10 times that of other near-equal-mass binaries. Because this weakly bound binary is prone to orbital disruption by interlopers, its lifetime in its present state is probably less than 1 billion years.