Circulating Metabolic Hormones During the Peripubertal Period and Their Association with Testicular Development in Bulls

The objective of the present study was to characterize changes in serum metabolic hormones concentrations from 20 weeks before to 20 weeks post-puberty in bulls and to investigate the associations of metabolic hormones concentrations with testicular development. Leptin concentrations increased from 16 weeks before puberty to 8 weeks post-puberty and insulin concentrations increased from puberty to 8 weeks post-puberty. Growth hormone concentrations decreased after 4 weeks post-puberty, whereas IGF-I concentrations increased from 8 weeks before puberty to 8 weeks post-puberty. During this period, testicular growth was accelerated and testosterone secretion increased substantially, without any significant changes in gonadotropin secretion. Monthly circulating concentrations of leptin, IGF-I and insulin accounted for 63% of the variation in scrotal circumference and 59% of the variation in paired testes volume. In conclusion, the secretion of metabolic hormones was not associated with changes in gonadotropins concentrations. Furthermore, the associations of leptin, IGF-I and insulin concentrations with testes size indicated that these hormones might be involved in a gonadotropin-independent mechanism regulating the testicular development in peripubertal bulls.     

High-power directional emission from microlasers with chaotic resonators

High-power and highly directional semiconductor microcylinder lasers based on an optical resonator with deformed cross section are reported. In the favorable directions of the far-field, a power increase of up to three orders of magnitude over the conventional circularly symmetric lasers was obtained. A "bow-tie"-shaped resonance is responsible for the improved performance of the lasers in the higher range of deformations, in contrast to "whispering-gallery"-type modes of circular and weakly deformed lasers. This resonator design, although demonstrated here in midinfrared quantum-cascade lasers, should be applicable to any laser based on semiconductors or other high-refractive index materials.     

A comparison of two methodologies for assessment of irrigation performance under the Warabandi system

A water management study of Warabandi in northwest India in 1983 developed a methodology for assessing the performance of large scale smallholder irrigation schemes by observing irrigated areas and carrying out random crop cutting. A study of Warabandi in 1988 took a shorter amount of time and concentrated on direct measurements of flow and seepage in order to assess the performance of the physical conveyance system. This paper contrasts these two approaches and gives practical guidance on how to go about carrying out a rapid assessment of the performance of the physical conveyance system of an irrigation scheme.     

Selection of drainage and its phased implementation for salinity control

Soil salinity has often become a long-term problem associated with irrigated agriculture in the arid and semi-arid regions. But the problem can be controlled by good management of surface and groundwater resources. Management of groundwater is achieved through drainage, although drainage may not be necessary for some time after the initial construction of a scheme. This paper introduces a regional model for predicting expected soil salinity conditions and groundwater depths over an irrigation scheme. The model considers all the main hydrological systems which influence soil salinity and makes optimal use of sparse point field data from grid surveys. The model can be used to identify priority areas for reclamation measures, ie areas where conditions combine to produce high salinity levels. Thus drainage development can be phased over a period of time and targeted where it will be most effective.     

Ongoing performance assessment — a case study of Kraseio Project,Thailand

The introduction of computer assisted irrigation scheduling to a 20,000 ha smallholder rice and sugarcane irrigation project in Thailand has provided an opportunity for continuous performance assessment. The provision of weekly information on performance is exerting an influence on the management of the system thus enabling timely response to operational problems.Kraseio Project has been operating with an improved water management system for two seasons, incorporating simple performance indicators, namely: actual versus targetted supply, along with equity, reliability and adequacy measures. Over these seasons the value of regular feedback of performance information has been demonstrated, in terms of increased awareness by project staff of operating constraints and their ability to quantify project performance.