The importance of individual behaviour for successful settlement of juvenile plaice (Pleuronectes platessa L.): a modelling and field study in the eastern Irish Sea

To study the transport of plaice (Pleuronectes platessa L.) eggs and larvae in the eastern Irish Sea, we constructed a 3D‐baroclinic physical model and coupled it to a particle‐tracking scheme that allowed aspects of larval behaviour to be simulated. Starting positions for eggs were based upon data from a series of ichthyoplankton surveys and final positions were compared with results of settled plaice distributions from two beam trawl surveys conducted on beaches around the eastern Irish Sea. If simulated larval behaviour was limited to passive drift or horizontal swimming, the particles diffused away from the spawning areas but failed to reach nursery grounds in significant numbers (85–90% remaining offshore). In contrast, switching on circatidal vertical swimming significantly increased the numbers of larvae reaching the coast (only 23–30% remained offshore). Particles tended to accumulate in bays and estuaries and this pattern compared well with the distribution of settled plaice from the field surveys. Studies in the southern North Sea (where spawning and nursery grounds are widely separated) have also demonstrated the importance of selective tidal stream transport for successful recruitment of settling plaice to nursery grounds. Although our understanding of the ontogeny of this behaviour is still poor, the model results presented suggest that this aspect of behaviour is a key factor influencing plaice settlement success.     

Factors affecting the strength of undisturbed cores from soils with low structural stability

Undisturbed core samples of two similar sandy clay loam soils (Big Ground and Plum Orchard) were equilibrated at matric potentials of ?0.01, ?0.1 and ?1 MPa and tested for indirect tensile strength (ITS) and unconfined compressive strength (UCS). Rate of deformation was found to have significant and large effects on the measured ITS and UCS. In general, both ITS and UCS increased with increasing deformation rates although, particularly for UCS tests, the effect was variable. For ITS, the effect of rate of deformation was attributed to water having insufficient time to move towards any incipient failure plane. For UCS, the effect of rate of deformation was partly attributed to loss of moisture during loading, since samples strained at lower deformation rates generally had lower moisture contents; and partly to the different modes of failure seen. ITS and UCS of Big Ground were invariably higher than those of Plum Orchard at all matric potentials. This was attributed to Big Ground having been under an intensive management system for approximately 10 years longer than Plum Orchard. Simple pretreatment effects are also considered. In a comparison of measured and theoretically predicted ITS and UCS, theory provided good estimates of measured strengths of samples equilibrated at ?0.1 MPa, although samples were considerably weaker than theoretically predicted at ?1 MPa.     

江苏南部几种水稻土的有机-矿貭复合体性貭的初步研究

近几年来的研究表明,丰产水稻土不但具有供給水稻生长的良好的土壤环境,而且还具有便于調节肥力因素的土壤特性^[2,3]。同时,在羣众經驗总結中,也发现我国农民对土壤的評价不仅有“肥瘦”之分,而且还有“好坏”之別。而判別“好坏”的标准看来也就是土壤是否易于調节其肥力因素以滿足不同作物或同一作物在不同生育时期生活的需要。     

The potentiometric measurement of stability constants of soil polycar boxy late-Cu2+ chelates

Stability constants describing Cu²⁺ combination with three natural and one synthetic polycarboxylates were calculated from pH measurements alone, and using a Cu²⁺ ion selective electrode. Good agreement between the two methods justified the theory for polymer-cation association. The results were consistent with the formation of a single complex CuL₂ over a fairly wide range of metal-ligand (L) ratios. The stability constant (β^H_Cu) that was independent of polymer charge allowed the prediction of copper speciation in soil solution as a function of pH and soluble organic matter.     

The 18O/16O and 17O/16O ratios in atmospheric nitrous oxide: A mass-independent anomaly

Measurements of the oxygen isotope ratios (18O/16O and 17O/16O) in atmospheric nitrous oxide (N2O) from La Jolla, Pasadena, and the White Mountain Research Station (elevation, 3801 meters) in California and the White Sands Missile Range in New Mexico show that N2O has a mass-independent composition. These data suggest the presence of a previously undefined atmospheric process. The La Jolla samples can be explained by a mixing between an atmospherically derived source of mass-independent N2O and biologically derived mass-dependent N2O. Possible origins of the mass-independent anomaly in N2O are discussed.     

Demethylation of chlorpromazine-(N-methyl)-C14

Chlorpromazine methyl-C(14) was administered to three groups of rats-orally to one group following chronic oral administration of the unlabeled drug; orally to an unprimed group; and intravenously to another unprimed group. Appearance of C(14)O(2) in the air expired by all animals indicated that the rat metabolized the side chain of the labeled drug.