OALib Journal期刊

ISSN: 2333-9721




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匹配條件: “W.S. Grant” ,找到相關結果約387875條。
Description of electrophoretic loci and tissue specific gene expression in the horseshoe bat genus Rhinolophus (Rhinolophidae)
Sarita Maree,W.S. Grant
African Zoology , 2011,
Abstract: The number of loci encoding an enzyme system, tissue specificity of gene expression and the degree of gene expression in various tissues are often not mentioned in evolutionary studies, but could indirectly provide evidence of evolutionary relationships. Protein electrophoresis was used to study the distributions and tissue specificity of gene expression of enzymes encoded by 42 loci in Rhinolophus clivosus and R. landeri, the genetically most divergent of the ten species of southern African horseshoe bats. No differences in gene expression were found between R. clivosus and R. landeri and isozyme patterns may be compared with other bat species to derive possible phylogenetic relationships.
Phylogenetic relationships and call structure in four African bufonid species
M.I. Cherry,W.S. Grant
African Zoology , 2012,
Abstract: ENGLISH ABSTRACT: Four species of toads of the genus Bufo. comprising three species endemic to southern Africa and one closely-related species, were examined electrophoretically to infer their phylogenetic relationships. The evolution of advertisement call structure in these species is discussed in relation to this phylogeny. Bufo rangeri and B. gutturalis, two species with very different call structures, are sister taxa. Two pairs of species with very similar call structures, B. pardalis and B. gutturalis, and B. rangeri and B. angusticeps, were only distantly related. Our results suggest that call parameters are poor characters to use in inferring phylogenies among congeneric species, probably because of selection for optimal audibility in different habitats, and because of the role that they play in premating isolation. The phylogeny derived from allozyme data agrees with evidence on albumin immunological distance, karyotype and morphology. *********** AFRIKAANSE OPSOMMING: Vier spesies skurwepaddas van die genus Buto, bestaande uit drie wat endemies is in Suid-Afrika en een nou-verwante spesie, is elektroforeties ondersoek om hulle filogenetiese verwantskap af te lei. Die evolusie van die struktuur van die bekendstellingsroep by hierdie spesie word met betrekking tot hierdie filogenie bespreek. Buto rangeri en B. gutturalis, twee spesies met baie verskillende roepstrukture, is suster taksa. Twee pare van spesies met baie ooreenstemmende roepstrukture, B. pardalis en B. gutturalis, en B. rangeri en B. angusticeps, was slegs ver langs verwant. Ons resultate dui daarop dat roep-parameters swak kenmerke is om te gebruik by die aflei van filogenie by verwante spesies, waarskynlik as gevolg van seleksie wat plaasvind vir optimale hoorbaarheid in verskillende habitatte, sowel as die rol wat hulle speel by die pre-paringsisolasie. Die filogenie wat van allosiemdata afgelei is, stem ooreen met getuienis oor albumien immunologiese afstand, kariotipe en morfologie .
The reliability analysis of cutting tools in the HSM processes
W.S. Lin
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: This article mainly describe the reliability of the cutting tools in the high speed turning by normaldistribution model.Design/methodology/approach: A series of experimental tests have been done to evaluate the reliabilityvariation of the cutting tools. From experimental results, the tool wear distribution and the tool life are determined,and the tool life distribution and the reliability function of cutting tools are derived. Further, the reliability ofcutting tools at anytime for high speed machining (HSM) is easily calculated from cutting parameters and toolwear limit from the derived reliability function.Findings: The higher the cutting speed, the sooner the tool flank wear, and the faster the degrade speed of thereliability curve. It means that the sooner the tool flank wear rate, the shorter the tool life, and it is the time tochange the cutting tool.Practical implications: This paper shows that the tool flank wear rate can be described by the reliabilitydegrade rate, the higher the flank wear rate, the steeper the tool reliability degrade rate.Originality/value: This article is discussing about the tool wear variation of the cutting tool from the point ofreliability. From the reliability variation of the cutting tool, we can further predict the tool life, in order to decidethe tool replacement time.
The study of high speed fine turning of austenitic stainless steel
W.S. Lin
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: The purpose of this research paper is focused on the surface roughness variation in high speed fine turning of the austenitic stainless steel.Design/methodology/approach: A series of experimental tests have been done to evaluate the possibility of high speed fine turning of the austenitic stainless steel from the surface roughness variation and machining stability.Findings: It was found that, the smaller the feed rate, the smaller the surface roughness value. But when the feed rate smaller than the critical feed rate, the chatter will occurs and the surface roughness of the work piece would be deteriorated.The higher the cutting speed is, the higher the cutting temperature of cutting tool is. The cutting tool will be soften and the surface roughness of the workpiece will be deteriorated.Research limitations/implications: The tool chattering would caused poor surface roughness in high speed fine turning for feed rate smaller than 0.02 mm/rev. The chatter suppression method must be considered when high speed fine turning of austenitic stainless steel.Originality/value: Most of the stainless steel machining proceeds at low cutting speed because the austenitic stainless steel is a hard machining material. The research result of this paper indicated that high speed fine turning of austenitic stainless steel is possible.
MgO-Au cermet films
Gold Bulletin , 1978, DOI: 10.1007/BF03216527
The development of gold drugs
Gold Bulletin , 1981, DOI: 10.1007/BF03216736
Precipitation hardening and ordering of carat gold jewellery alloys
Gold Bulletin , 1978, DOI: 10.1007/BF03216531
Abstract: The mechanical properties of gold jewellery alloys are dependant upon their thermal as well as their mechanical histories. An understanding of the mechanisms by which they harden during thermal treatment is therefore important. Two contributions to knowledge in this area are discussed in this note.
Fire regime of the Kruger National Park for the period 1980 -1992
W.S.W. Trollope
Koedoe : African Protected Area Conservation and Science , 1993, DOI: 10.4102/koedoe.v36i2.373
Abstract: Fire regime refers to the type and intensity of fire and the season and frequency of burning. In the Kruger National Park it varies according to the source of ignition of the fires. Since 1985 the different ignition sources have been controlled bums (47), refugees (23), others (20) and lightning (10). The data showed that anthropogenic fires were the most common fires and evidence on a global scale would suggest that the status quo will be maintained even if controlled burning is discontinued as is currently being considered by the National Parks Board. The most common type of fires that occur in the park are surface head fires burning with the wind but back fires and crown fires do also occur. The intensity of the fires is primarily a function of the grass fuel load which is dependent on the rainfall and consequently varies enormously from year to year. The type of fire also influences the intensity and research conducted during 1992 showed that head fires burning under similar environmental conditions were on average 36 times more intense than back fires. Anthropogenic fires generally occurred during the dry, dormant, winter period while lightning fires were more associated with the spring and summer period when dry lightning storms occur. The frequency of burning varied significantly between sourveld and sweetveld. The mean frequency of burning in sourveld areas was triennial and in the sweetveld areas octennial. Finally the general conclusion that can be drawn about the fire regime of the Kruger National Park is that it is highly variable and will continue to be so in the future. This is a very positive feature that ensures a wide diversity of habitat types.
Veld management with specific reference to game ranching in the grassland and savanna areas of South Africa
W.S.W. Trollope
Koedoe : African Protected Area Conservation and Science , 1990, DOI: 10.4102/koedoe.v33i2.443
Abstract: Veld management refers to the management of natural vegetation for specific objectives related to different forms of land use. In the wildlife context a wide spectrum of different forms of land use are practised ranging from pure nature conservation in large national parks through to smaller areas used for game farming. Consequently the products useable to society emanating from these areas vary greatly, and therefore the management of veld stocked with wildlife is extremely complex and must be adapted to the particular form of land use that is being practised. A generally accepted principle is that the smaller the area being used for wildlife the more intensively it must be managed, particularly game ranches. A prerequisite for the development of an effective veld management program is a comprehensive assessment of the condition of the veld upon which realistic veld management practices can be formulated. These practices will include stocking the veld with the appropriate species and numbers of animals, grazing and browsing management, veld burning and the provision of watering points. Finally a programme for monitoring veld condition over time is a prerequisite for sound veld management.
漢景泰,W.S. Fyfe
科學通報 , 2000,
Abstract: 以鐵的硫化物礦折黃鐵礦和磁黃鐵礦為吸附材料,在實驗室條件下研究了它們對模型水體中的砷的吸附作用。在實驗觀測基礎上討論了這些礦物材料對砷的吸附速率和效率,吸附砷的穩定性以及穩定條件,提出這些礦物去除水體中砷的有效吸附材料,對于缺乏水質處理設備條件的地區有直接的實用價值。

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