An evaluation of the performance of six smallholder irrigation schemes in Zimbabwe     

Enos M. Shumba  Roy Maposa 《Irrigation and Drainage Systems》1996,10(4):355-366

Informal and formal survey procedures were used to assess the performance of six smallholder irrigation schemes. The predominant crops grown at the schemes were maize (Zea mays) in summer and beans (Phaseolus vulgaris) in winter. Average crop yields range from 2.7 to 7.4 t/ha for maize and 0.4 to 2.4 t/ha for beans at the lowest and highest yielding schemes respectively. There was also a large gap between the lower and higher producing farmers at each scheme. Only one out of the six schemes realized a profit margin of more than ZWD 223 per month per plotholder (the minimum wage rate for agriculture workers) after operating and maintenance costs (currently met by government) were deducted. Major constraints on the schemes included limited cash for input purchases, unreliable water supplies for winter cropping, limited market outlets and poor roads. Ways of alleviating some of these constraints to improve overall scheme performance are proposed.  相似文献   

Assembly of feline calicivirus-like particle and its immunogenicity     

Di Martino B  Marsilio F  Roy P 《Veterinary microbiology》2007,120(1-2):173-178

Virus-like particles (VLPs) were produced in insect cells infected with a recombinant baculovirus containing the capsid gene of feline calicivirus strain F9 (FCV-F9). The FCV VLPs were morphologically and antigenically similar to the native virus and contained a single capsid protein with a molecular weight of approximately 60 kDa that reacted with FCV antiserum. Moreover, following immunization of rabbits, VLPs were able to elicit neutralizing antibodies against several FCV strains isolated from clinical samples. Our preliminary results showed that FCV-VLP could be considered a candidate vaccine against FCV infections.  相似文献   

Quantifying the effects of bycatch reduction devices in Queensland''s (Australia) shallow water eastern king prawn (Penaeus plebejus) trawl fishery     

A.J. Courtney  M.L. Tonks  M.J. Campbell  D.P. Roy  S.W. Gaddes  P.M. Kyne  M.F. O&#x;Neill 《Fisheries Research》2006,80(2-3):136-147

This study presents results from an experimental 10-day research charter that was designed to quantify the effects of (a) a turtle excluder device (TED), (b) a radial escape section bycatch reduction device (BRD) and (c) both devices together, on bycatch and prawn catch rates in the Queensland shallow water eastern king prawn (Penaeus plebejus) trawl fishery. The bycatch was comprised of 250 taxa, mainly gurnards, whiting, lizard fish, flathead, dragonets, portunid crabs, turretfish and flounders. The observed mean catch rates of bycatch and marketable eastern king prawns from the standard trawl net (i.e., net with no TED or BRD) used during the charter were 11.06 kg/hectare (ha⁻¹) (S.E. 0.90) swept by the trawl gear and 0.94 kg ha⁻¹, respectively. For the range of depths sampled (20.1–90.7 m), bycatch rates declined significantly at a rate of 0.14 kg ha⁻¹ for every 1 m increase in depth, while prawn catch rates were unaffected. When both the TED and radial escape section BRD were used together, the bycatch rate declined by 24% compared to a standard net, but at a 20% reduction in marketable prawn catch rate. The largest reductions were achieved for stout whiting Sillago robusta (57% reduction) and yellowtail scad Trachurus novaezelandiae (32% reduction). Multidimensional scaling and analysis of similarities revealed that bycatch assemblages differed significantly between depths and latitude, but not between the different combinations of bycatch reduction devices. Despite the lowered prawn catch rates, the reduced bycatch rates are promising, particularly for S. robusta, which is targeted in another fishery. Prawn trawl operators are not permitted to retain S. robusta and the devices examined herein offer the potential to significantly reduce the incidental fishing mortality that this species experiences.  相似文献   

Genes required for mitotic spindle assembly in Drosophila S2 cells     

Goshima G  Wollman R  Goodwin SS  Zhang N  Scholey JM  Vale RD  Stuurman N 《Science (New York, N.Y.)》2007,316(5823):417-421

The formation of a metaphase spindle, a bipolar microtubule array with centrally aligned chromosomes, is a prerequisite for the faithful segregation of a cell's genetic material. Using a full-genome RNA interference screen of Drosophila S2 cells, we identified about 200 genes that contribute to spindle assembly, more than half of which were unexpected. The screen, in combination with a variety of secondary assays, led to new insights into how spindle microtubules are generated; how centrosomes are positioned; and how centrioles, centrosomes, and kinetochores are assembled.  相似文献   

Murine MHC polymorphism and T cell specificities   总被引：10，自引：0，他引：10  

S Roy  M T Scherer  T J Briner  J A Smith  M L Gefter 《Science (New York, N.Y.)》1989,244(4904):572-575

The major histocompatibility complex (MHC) genes are polymorphic in mouse and man. The products of these genes are receptors for peptides, which while bound, are displayed to T lymphocytes. When bound peptides from antigens are recognized by T lymphocytes, an immune response is initiated against the antigens. This study assessed the relation of the polymorphic MHC molecules to their peptide specificity. The results indicate that although an individual of the species has a limited ability to recognize antigens, the species as a whole has broad reactivity. This rationalizes the extreme polymorphism observed.  相似文献   

Egg quality determinants in cod (Gadus morhua L.): egg performance and lipids in eggs from farmed and wild broodstock   总被引：1，自引：0，他引：1  

Guillaume Salze  Douglas R Tocher  William J Roy  & Derek A Robertson 《Aquaculture Research》2005,36(15):1488-1499

Lipids and essential fatty acids, particularly the highly unsaturated fatty acids, 20:5n‐3 (eicosapentaenoic acid; EPA), 22:6n‐3 (docosahexaenoic acid; DHA) and 20:4n‐6 (arachidonic acid, AA) have been shown to be crucial determinants of marine fish reproduction directly affecting fecundity, egg quality, hatching success, larval malformation and pigmentation. In Atlantic cod (Gadus morhua L.) culture, eggs from farmed broodstock can have much lower fertilization and hatching rates than eggs from wild broodstock. The present study aimed to test the hypothesis that potential quality and performance differences between eggs from different cod broodstock would be reflected in differences in lipid and fatty acid composition. Thus eggs were obtained from three broodstock, farmed, wild/fed and wild/unfed, and lipid content, lipid class composition, fatty acid composition and pigment content were determined and related to performance parameters including fertilization rate, symmetry of cell division and survival to hatching. Eggs from farmed broodstock showed significantly lower fertilization rates, cell symmetry and survival to hatching rates than eggs from wild broodstock. There were no differences in total lipid content or the proportions of the major lipid classes between eggs from the different broodstock. However, eggs from farmed broodstock were characterized by having significantly lower levels of some quantitatively minor phospholipid classes, particularly phosphatidylinositol. There were no differences between eggs from farmed and wild broodstock in the proportions of saturated, monounsaturated and total polyunsaturated fatty acids. The DHA content was also similar. However, eggs from farmed broodstock had significantly lower levels of AA, and consequently significantly higher EPA/AA ratios than eggs from wild broodstock. Total pigment and astaxanthin levels were significantly higher in eggs from wild broodstock. Therefore, the levels of AA and phosphatidylinositol, the predominant AA‐containing lipid class, and egg pigment content were positively related to egg quality or performance parameters such as fertilization and hatching success rates, and cell symmetry.  相似文献   

A Mathematical Model in Locating an Unknown Emission Source     

Islam  M. A.  Roy  G. D. 《Water, air, and soil pollution》2002,136(1-4):331-345

A method is developed to locate an unknown emission source. Theproposed method is based on the assumption that the GaussianPlume model (GPM) completely describes the dispersion ofpollutants in atmospheric air. A concept called `Equipotentialpollution source' is applied to locate the source. The samplingsites are chosen in such a manner that the straight linejoining them is perpendicular to the wind direction. The methodprovides an opportunity to sample from one side of a probablepollution source. The uncertainty in the method is alsodiscussed. A program in Fortran is developed to identify thezone containing the unknown source. The technique is developedin such a way that the zone can be identified without knowingall the parameters of the GPM.  相似文献   

Air pollution in Montreal: A statistical analysis of sulphur dioxide data     

R. Cléroux  R. Roy  N. Fortin 《Water, air, and soil pollution》1980,13(2):143-156

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An improved simulation of void structure, water retention and hydraulic conductivity in soil with the Pore-Cor three-dimensional network     

A. Johnson  I. M. Roy  G. P. Matthews  & D. Patel 《European Journal of Soil Science》2003,54(3):477-490

We present a new method of characterizing the void structures of soils from water retention curves as the primary source of data. The method avoids the problems of other current approaches, which use smoothing curves and can miss the subtleties of soil structure, and usually ignore the shielding of large pores by the small connecting throats surrounding them. In the new method, software we have named ‘Pore‐Cor’ is used to generate simple three‐dimensional networks of voids that have the same water retention characteristics and porosities as the soils. To find the geometry of the required networks, we have introduced a Boltzmann‐annealed simplex which works in four parametric and three Boolean dimensions of parameter space. Also, a more robust measure of the difference between the experimental and simulated water retention curves has been developed. The method is applied to water retention curves for a wide range of English and Welsh soils, both experimental and generated from a pedotransfer function. The resulting simulated void structures have void sizes that change as expected across the soil texture diagram, have different structures as highlighted by the locations of retained water, but have connectivities (number of connecting throats per pore) that vary little. A wide range of other calculations of wetting and non‐wetting fluid transport properties, and calculations of the behaviour of fluid‐borne pollutants, are now possible. The main bar to further progress is a lack of sufficiently accurate and comprehensive data for water retention, and for saturated and unsaturated hydraulic conductivity.  相似文献   

Toxicokinetics,recovery, and metabolism of triclopyr butotyl (ACTP) ester in goats     

Sar TK  Bagchi B  Das SK  Mandal TK  Chakraborty AK  Bhattacharyya A  Choudhury A 《Journal of agricultural and food chemistry》2002,50(15):4202-4209

Toxicokinetic behavior, recovery, and metabolism studies of ACTP ester and its effect on cytochrome P(450) content of liver microsomal pellet were carried out in black Bengal goat after a single intravenous administration of 11.88 mg kg(-1) and consecutive oral administration of 79.22 mg kg(-1) for 7 days. ACTP ester achieved a maximum blood concentration of 42.64 +/- 4.26 microg mL(-1) at 0.08 h after intravenous administration followed by a sharp decline until 0.5 h, and the minimum blood concentration was recorded at 36 h (1.93 +/- 0.14 microg mL(-1)) postdosing. The kinetic behavior of ACTP ester followed a "two-compartment open model". Comparatively shorter alpha (0.81 +/- 0.02 h(-1)) and greater t1/2 (alpha) (0.86 +/- 0.03 h) indicated a slower rate of distribution of ACTP ester in goat. The t1/2(beta)()) (14.83 +/- 1.49 h) and V(d(area)) (0.91 +/- 0.19 L kg(-1)) suggested a longer elimination phase with general distribution in all compartments of the body. The higher T/B and K12/K21 values associated with a lower f(c) value suggested longer persistence in the tissue compartment at higher concentration. The higher Cl(R) compared to Cl(H) indicated the major amount was eliminated by the kidney. Maximum concentration of ACTP ester including its metabolites, triclopyr acid and trichloropyridinol, was excreted through urine at 48 h. The recovery of ACTP ester including metabolites after repeated nontoxic oral dose administration was 70.09%, of which recovery from feces was 4.45%, suggesting the major portion of administered ACTP ester was absorbed through the gastrointestinal tract of the goat. All of the tissues contained ACTP ester and its metabolites. ACTP ester did not alter the cytochrome P(450) content of the liver tissue following repeated nontoxic oral dose administration for 7 days.  相似文献