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101.
The results of a 15 months' intensive study on seven flocks of indigenous goats in the Southern Darfur region of the Sudan are discussed in this paper. Birth rates in the region approached 2-1 kids per doe per year. A high total offtake of 28 per cent and a weighted average death rate of about 16-5 per cent were insufficient to offset this high birth rate and flock numbers are increased. Mortality in kids was unrelated to number of births. Weighted average rate of gain for all surviving kids was 87 g per day to 3 months and 67 g per day to 6 months of age. The growth rates of twin and single were similar, but triplet kids grew at a slower rate. For each kilogramme liveweight of breeding females, goats produced 1-5 and 8 times the weight of meat produced by sheep and cattle respectively under the same management and environmental conditions. 相似文献
102.
Similar depressions in growth were observed when rats consumed a 10% casein basal diet containing equal quantities of either methionine or S-methyl-L-cysteine. Supplemental glycine or serine partially alleviated the growth depression caused by the high levels of methionine but were ineffective in alleviating the growth depression caused by high levels of S-methylcysteine. Histological examination of five organs of rats fed the basal, high methionine or high S-methylcysteine diet for 6, 13 or 20 days revealed that only the spleens were affected in that there was erythrocyte engorgement and an accumulation of hemosiderin. The intensity of iron staining in spleens decreased from the second to the third week. The similarity in the depression of growth and splenic damage observed in rats consuming high levels of methionine or S-methylcysteine is consistent with an earlier suggestion that metabolism of the methionine or S-methylcysteine is consistent with an earlier suggestion that metabolism of the methyl group is in some way involved in the toxicity of methionine. 相似文献
103.
Aerosol particle deposition due to gravitational settling in a horizontal circular duct is examined for steady laminar flow, which develops from a uniform velocity profile at the entrance to a parabolic velocity profile downstream. Numerical calculation methods, based on the analysis of the limiting trajectories of the particles, are used to determine the deposition efficiency as a function of the duct entrance length. The results show that the deposition for the limiting cases of very large or small settling approach the solutions for deposition in a slug or a Poiseuille flow, respectively. In addition, particle inertial effects were included and for relatively large inertia, the deposition rate was significantly affected. 相似文献
104.
A system for the quantitative assessment of uterine activity during an oxytocin-induced labour has been developed. This has been achieved using relatively simple analogue techniques and can easily be used in the labour ward alongside existing monitoring equipment. Initial results indicate that a plateau of uterine activity can be easily recognised from the display and maintained at oxytocin dosage levels below those that might normally be used. 相似文献
105.
In earlier work, we have explored the relevance of hydrodynamic stability theory to fully developed turbulent wall flows.
Using an extended Orr-Sommerfeld Equation, based on an anisotropic eddy-viscosity model, it was shown that there exists a
wide range of unstable wave numbers (wall modes), which mimic some of the key features of turbulent wall flows. Here we present
experimental confirmation for the same. There is good qualitative and quantitative agreement between theory and experiment.
Once the dominant coherent structure is obtained from stability theory, control of turbulence would be the next logical step.
As shown, the use of a compliant wall shows considerable promise.
We also present some theoretical work for bypass transition (Klebanoff/K-modes), wherein the receptivity of a laminar boundary layer to a vortex sheet in the freestream has been studied. Further,
it is shown that triadic interaction between K-modes, 2D TS waves and 3D TS waves can lead to rapid algebraic growth. A similar mechanism seems to carry over to inner wall
structures in wall turbulence and perhaps this is the “root cause” for sustenance of turbulence. 相似文献
106.
The global stability of the von Kármán boundary layer on the rotating disk is reviewed. For the genuine, radially inhomogeneous
base flow, linearized numerical simulations indicate that convectively propagating forms of disturbance are predominant at
all radii. The presence of absolute instability does not lead to the formation of any unstable linear global mode, even though
the temporal growth rate of the absolute instability increases along the radial direction. Analogous behaviour can be found
in the impulse solutions of a model amplitude equation, namely the linearized complex Ginzburg–Landau equation. These solutions
show that, depending on the precise balance between spatial variations in the temporal growth rate and the corresponding shifts
in the temporal frequency, globally stable behaviour can be obtained even in the presence of a strengthening absolute instability.
The radial dependency of the absolute temporal frequency is sufficient to detune the disturbance oscillations at different
radial positions, thus overcoming the radially increasing absolute growth, thereby giving rise to a stable global response.
The origin of this form of behaviour can be traced to the fact that the cylindrical geometry of the rotating-disk flow dictates
a choice of a globally valid time non-dimensionalization that, when properly employed, leads to a significant radial variation
in the frequency for the absolute instability. 相似文献
107.
108.
109.
Membrane trafficking intermediates involved in the transport of proteins between the TGN and the lysosome-like vacuole in the yeast Saccharomyces cerevisiae can be accumulated in various vps mutants. Loss of function of Vps45p, an Sec1p-like protein required for the fusion of Golgi-derived transport vesicles with the prevacuolar/endosomal compartment (PVC), results in an accumulation of post-Golgi transport vesicles. Similarly, loss of VPS27 function results in an accumulation of the PVC since this gene is required for traffic out of this compartment. The vacuolar ATPase subunit Vph1p transits to the vacuole in the Golgi-derived transport vesicles, as defined by mutations in VPS45, and through the PVC, as defined by mutations in VPS27. In this study we demonstrate that, whereas VPS45 and VPS27 are required for the vacuolar delivery of several membrane proteins, the vacuolar membrane protein alkaline phosphatase (ALP) reaches its final destination without the function of these two genes. Using a series of ALP derivatives, we find that the information to specify the entry of ALP into this alternative pathway to the vacuole is contained within its cytosolic tail, in the 13 residues adjacent to the transmembrane domain, and loss of this sorting determinant results in a protein that follows the VPS-dependent pathway to the vacuole. Using a combination of immunofluorescence localization and pulse/chase immunoprecipitation analysis, we demonstrate that, in addition to ALP, the vacuolar syntaxin Vam3p also follows this VPS45/27-independent pathway to the vacuole. In addition, the function of Vam3p is required for membrane traffic along the VPS-independent pathway. 相似文献
110.
Nina Orlovskaya Mykola Lugovy Cassandra Carpenter Siddhartha Pathak David Steinmetz Edgar Lara-Curzio Christine Klemenz Miladin Radovic 《Acta Materialia》2009,57(10):2984-2992
The thermal expansion and vibrational properties of [1 0 0] and [0 0 1] LaGaO3 single crystals have been studied by thermal mechanical analysis and micro-Raman spectroscopy. A first-order orthorhombic to rhombohedral phase transition has been confirmed by both techniques, as well as by in situ heating using optical microscopy. The appearance of a metastable intermediate phase, tentatively assigned as monoclinic, has been detected both by optical microscopy and Raman spectroscopy upon heating of the [1 0 0] and [0 0 1] LaGaO3 single crystals. Not only temperature, but the stress-induced orthorhombic to rhombohedral phase transition has also been detected by Raman mapping of the residual impression made by Vickers indentation. The position map of bands belonging to the lower-temperature/pressure orthorhombic and the higher-temperature/pressure rhombohedral phase show that the rhombohedral phase is located inside the impression, where the applied indentation stresses are the highest, whereas no rhombohedral phase is detected outside the impression, where the surface has not been altered by contact stresses. 相似文献