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231.
Domestication of desirable forest resources in agroforestry is expected to contribute to community based forest conservation efforts, but there may be an optimum level of domestication in this respect. Aren or sugar palm (Arenga pinnata (Wurmb) Merr.) is a multipurpose tree that provides livelihoods for local people and food for other biota in the landscape. However, its domestication is still limited in many places, such as in Batang Toru Forest Block, an area of high conservation value, including habitat for the Sumatran orangutan (Pongo abelii). Options for aren management were prioritized as part of a landscape-scale conservation study by comparing domestication levels in the area. Data on economic indicators and ecological knowledge were gathered through interviews with key farmers, focus groups and transect walks. Four representative villages were selected for the study, that is, (i) two villages with no domestication of aren; and (ii) two villages with aren cultivation in rubber-based land-use systems. Costbenefit analyses suggested that in a rich biodiversity area, such as Batang Toru, although aren was one of the sources of local livelihoods, additional investment for domestication beyond cultivation was not an option considered by farmers. Farmers still perceived wildlife as an efficient mode of aren regeneration, supported by the coexistence of people and other biota in the area. It appears the value of aren for local people’s livelihoods and conservation can be enhanced by increasing its stocking density. There is also scope for improving market access and share of end-user value received by farmers.  相似文献   
232.
Dey S  Joshi A 《Science (New York, N.Y.)》2006,312(5772):434-436
Very few experimental studies have examined how migration rate affects metapopulation dynamics and stability. We studied the dynamics of replicate laboratory metapopulations of Drosophila under different migration rates. Low migration stabilized metapopulation dynamics, while promoting unstable subpopulation dynamics, by inducing asynchrony among neighboring subpopulations. High migration synchronized subpopulation dynamics, thereby destabilizing the metapopulations. Contrary to some theoretical predictions, increased migration did not affect average population size. Simulations based on a simple non-species-specific population growth model captured most features of the data, which suggests that our results are generalizable.  相似文献   
233.
Summary Genetics of rust resistance against stem rust race 122 in Chhoti Lerma was studied both by conventional and aneuploid analysis. Observations on F1, F2 and F2 backcross progenies revealed the operation of two recessive genes, controlling resistance in Chhoti Lerma. Monosomic analysis confirmed the operation of two recessive genes conferring resistance to race 122 located on chromosomes 1D and 7D. A minor gene or modifier was also located on chromosome 1B. This was concluded from the fact that F2 of mono's x Chhoti Lerma exhibited skewness in favour of resistant plants.  相似文献   
234.
Joshi AK 《Science (New York, N.Y.)》1991,253(5025):1242-1249
Natural language processing (NLP) is the study of mathematical and computational modeling of various aspects of language and the development of a wide range of systems. These include spoken language systems that integrate speech and natural language; cooperative interfaces to databases and knowledge bases that model aspects of human-human interaction; multilingual interfaces; machine translation; and message-understanding systems, among others. Research in NLP is highly interdisciplinary, involving concepts in computer science, linguistics, logic, and psychology. NLP has a special role in computer science because many aspects of the field deal with linguistic features of computation and NLP seeks to model language computationally.  相似文献   
235.
The availability of timber in the United States depends largely on forest management and investment decisions of nonindustrial private forest landowners since they hold the largest share of forest land in the nation. Since NIPF landowners are so diverse, there is a need to better understand the determinants of their decisions so that policies could be in place to motivate them. A survey was carried out in 2005 to the nonindustrial private forest landowners of West Virginia to examine the factors affecting their forest management decisions. The study looked at four categories of decisions related to forest management: timber harvest, silvicultural activities (i.e., tree planting, herbicide application, fertilization, thinning, grapevine control, and timber stand improvement), property management activities (i.e., road construction, road maintenance, surveying/boundary maintenance, and access control), and wildlife habitat management and recreation improvement activities. Four models were developed to examine factors affecting each category of forest management activity. The results showed that landowner, ownership, and management characteristics of NIPF landowners are associated with their forest management decisions. Specifically, age, education, profession, income, ownership size, period of forestland acquisition, distance of the forestland to the place of residence, whether the forestland was purchased or acquired through inheritance or as a gift, primary objective of forestland ownership, and presence of a written forest management plan were found to be significant determinants for at least one of the categories of forest management activities. The models explained 25%, 27%, 31%, and 24% of the variation in timber harvesting, silvicultural activities, property management activities, and wildlife habitat management and recreation improvement activities, respectively. Understanding the underlying factors influencing forest management decisions of this diverse group of forest landowners could form the basis for developing, modifying and targeting policy instruments to motivate NIPF landowners in forest management.  相似文献   
236.
Octamethyl-POSS and Octaphenyl-POSS reinforced polypropylene nanocomposite monofilaments were prepared by melt blending route. It was observed that incorporation of Octamethyl-POSS and Octaphenyl-POSS in polypropylene show improvement in mechanical as well as thermal properties. Octaphenyl POSS/PP nanocomposites show significant increase in thermal stability even at very low concentration as compared to neat polymer matrix. An increase of 100 and 140 °C was observed in thermal degradation temperature at 5 wt% loss and maximum degradation over neat PP filaments respectively at low OP-POSS loadings (<5 wt%). Both Octamethyl-POSS and Octaphenyl-POSS act as lubricating agents facilitating drawing which results in improvement in orientation as well as mechanical properties.  相似文献   
237.

Background  

We recently reported that the altitude of origin altered the photic and thermal sensitivity of the circadian pacemaker controlling eclosion and oviposition rhythms of high altitude Himalayan strains of Drosophila ananassae. The present study was aimed at investigating the effects of altitude of origin on the pacemaker controlling the adult locomotor activity rhythm of D. helvetica.  相似文献   
238.
The neutron activation analysis was used to determine 129I in water and air samples collected in the neighbourhood of a reprocessing plant. The method involved preconcentration of 129I on AgI from water samples, separation of Ag+, followed by distillation, loading on Dowex-1, irradiation and post irradiation purification steps. Filter air samples were wet oxidised follwed by distillation and other chemical procedure steps as described for water samples. The concentration of 129I in rain water and air samples ranged from 0.155×10?3 to 0.327×10?3 Bq L?1 and 0.054×10?6 to 0.295×10?6 Bq m?3 respectively. The average concentration of 129I in seawater samples was 0.157×10?3 Bq L?1. The concentration of 129I obtained in these samples have been translated to dose rates to an individual and have been found to be insignificant.  相似文献   
239.
Recently deposited fine-grained sediments in Lake Ontario off the mouth of Niagara River contain highly toxic238Pu,239,240pu, and241Pu (241Am) from global fallout as well as from low level releases of these radionuclides from the West Valley radioactive waste management site. This is demonstrated through sediment core radionuclide inventories, radionuclide activity ratios, and assignment of independently-derived210Pb dates to sediment core segments. Reasonable agreement between measured and calculated inventories, derived using various assumptions and available discharge and environmental monitoring data, suggests that nearly all of the West Valley-delivered239,240Pu and 24241Am resides in the bottom sediments of Lake Ontario, comprising about 36 and 80%, respectively, of the measured (1982) inventories of these radionuclides. The West Valley241Am is largely derived from the decay of241Pu and, assuming negligible further deliveries of241pu (241Am), its growth is expected to continue until about 2040.  相似文献   
240.
We report the genetic structure and evolutionary relationship of the endangered Toda buffalo of Nilgiris in South India with Kanarese and two other riverine buffalo breeds. The upgma phylogeny drawn using Nei’s distance grouped South Kanara and Toda buffaloes at a single node while Marathwada and Murrah together formed a separate node. Principal component analysis was performed with pairwise interindividual chord distances which revealed clustering of Murrah and Marathwada buffaloes distinctly, while individuals of Toda and South Kanara breeds completely intermingled with each other. Furthermore, there were highly significant group variances (p < 0.01) when the breeds were grouped based on phylogeny, thus revealing the existence of cryptic genetic structure within these buffalo breeds. To know the evolutionary relationship among these breeds, 537‐bp D‐loop region of mitochondrial DNA was analysed. The phylogenetic analysis of mtDNA haplotypes following NJ algorithm with Chinese swamp buffalo as outgroup revealed a major cluster that included haplotypes from all the four investigated breeds and two minor clusters formed by South Kanara and Toda haplotypes. Reduced median network analysis revealed haplotypes of South Kanara and Toda to be quite distinct from the commonly found haplotypes indicating that these might have been ancestral to all the present‐day haplotypes. Few mutations in two of the haplotypes of South Kanara buffalo were found to have contributed to ancestral haplotypes of Toda buffalo suggesting the possible migration of buffaloes from Kanarese region towards Nilgiris along the Western Ghats. Considering the close social, economic and cultural association of Todas with their buffaloes, the present study supports the theory of migration of Toda tribe from Kanarese/Mysore region along with their buffaloes.  相似文献   
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