Preliminary modelling of sediment production and delivery in the Xihanshui River basin, Gansu, China

This paper outlines an analysis of the spatial distribution of sediment production, delivery and yield in the Xihanshui River basin, South Gansu, China, using the modelling tools of SedNet (Prosser et al., 2001). This model can assess the delivery efficiency to downstream locations, as well as identifying locations with high rates of sediment production. Preliminary model experiments assist understanding of the spatial dynamics of these sediment processes and evaluation of the effectiveness of soil conservation practices since the mid-1980s. Three scenario years (dry, average and wet) from the 1983–2005 record are identified and modelled, and land use and management are represented in the model to reflect known changes since the 1980s. Results show hillslope erosion to be a dominant source of sediment supply, causing the latter to decrease ten-fold between 1984 and 1997/2000. Estimated bank erosion and floodplain deposition rates are sensitive to parameter values, but bank erosion appears less sensitive than hillslope supply to rainfall. The model can be used to assess net changes in floodplain storage; for default parameters, floodplain deposition rates are 25–200 times the rates of bank erosion depending on the climate scenario. Comparing simulation results with measured sediment yields at the three gauging stations indicates encouraging agreement in 2000. In 1984 (the wet year), the model under-predicts, suggesting that additional unmodelled sediment production processes, especially mass movement and gully erosion, may be important in wet years. Mass movement inventory data could close the gap between the high yields measured in the wet scenario year and the estimated yield due to hillslope erosion alone. In 1997 (the dry year), the model over-predicts; this suggests that the land use change parameters required to reflect the effects of conservation may not have been sufficient, implying that conservation has been generally effective, and that evidence of declining sediment yield is not simply a reflection of drier conditions.     

Development and Variation of the Lateral Vertebral Foramen of the Atlas in Dogs

Postnatal development and variation of the bony cranial border of the lateral vertebral foramen (LVF) of the atlas was studied in 96 dogs. Developmental ossification was investigated in 8 known-aged Miniature Schnauzer pups, after each atlas was prepared either as an alizarin-red stained clearing or as a dried cleaned bone. Variation was investigated in 63 atlases from mature dogs and by study of radiographs from 25 mature dogs of various breeds. The soft tissue structures passing through the LVF and attaching to its cranial border were dissected in an additional 2 embalmed and 2 fresh cadavers. In 2-week-old pups, the LVF was represented by a notch in the cranial margin of the bony arch of the atlas, with a cartilage bar completing the foramen cranially. Between 6 and 16 weeks the bar forming the cranial bony border of the LVF ossified in its preexisting cartilage anlage. In mature dogs, the LVF was present in the craniolateral aspect of the arch of the atlas and was recognized on lateral radiographs. The vertebral artery and vein, and first cervical nerve passed through the LVF and the atlantooccipital joint capsule and dorsal membrane attached to the cranial border of the LVF. In one dog the cranial border of the LVF of the atlas was incompletely ossified bilaterally. This developmental variant was compared with variations in man and other mammals, and with proatlas neural arch derivatives.     

Endocrine changes associated with cystic ovarian degeneration in sows.

Endocrine changes in sows with ovarian cysts were determined to be comparable with those in sows in diestrus. Blood samples were collected at frequent intervals from 5 sows affected with cystic ovaries. Concentrations of serum luteinizing hormone, progesterone, estradiol-17 beta, and cortisol were determined by use of established radioimmunoassays. The development of ovarian cysts has been proposed to be associated with a deficiency of luteinizing hormone rather than an intrinsic ovarian abnormality. In contrast, the results of this study demonstrated that tonic and pulsatile luteinizing hormone release were not affected adversely in sows with cystic ovaries.