新型期权模型研究

分别介绍了篮子期权和亚式期权这两种新型期权定价模型.使用Mellin变换法在Black-Scholes模型框架下研究了常值波动率及无风险利率情况下,求解和分析了一篮子期权的定价模型;以算术平均价格的平均价格型亚式看涨期权为例来建立亚式期权定价模型.这两种新型定价模型较之标准期权定价模型有较大优势,因而对它们的研究具有现实意义.     

The potential impact of projected change in farming by 2015 on the importance of the agricultural sector as a sediment source in England and Wales

In association with a major initiative aimed at identifying policy packages for inclusion in the Programmes of Measures (POM's) comprising EU Water Framework Directive (WFD) River Basin Management Plans (RBMP's), recent work has evaluated the gap between current and compliant suspended sediment losses due to farming across England and Wales. The work required national scale sediment source apportionment to assess the current contributions of diffuse agricultural and urban sector losses, channel bank erosion and point source discharges to the total suspended sediment loads delivered to all rivers. Results suggested that the agricultural sector dominates present day (year 2000) sediment inputs to rivers (1929 kt = 76%) compared to eroding channel banks (394 kt = 15%), diffuse urban sources (147 kt = 6%) and point source discharges (76 kt = 3%). Projected change in farming by 2015, represented by the Business as Usual forecast of structural developments and predicted uptake of sediment mitigation methods, suggested an overall 9% reduction in sediment loss from the agricultural sector across England and Wales. The projected reduction is unlikely to deliver sediment compliance in all catchments. Key limitations of the integrated modelling approach are discussed.     

四川省低碳经济影响因素及减排对策分析

[目的]研究四川省低碳经济的影响因素及减排对策。[方法]通过对STIRPAT模型的扩展,应用主成分回归方法,计量分析人口、经济和技术因素对2000～2009年四川省碳排放量的影响,并提出减少二氧化碳排放的对策。[结果]现阶段四川省人口规模对碳排放影响最大,其次是单位工业增加值能耗及工业增加值占GDP比重;人口规模对碳排放的影响力仍然大于人口结构,技术因素对碳排放也具有一定的解释力。可通过控制人口过快增长,鼓励低碳的生活方式和消费模式,注重产业结构的战略性调整,逐步降低高碳产业比重,鼓励支持节能减排和新能源技术领域的科技创新等途径减少二氧化碳的排放,以适应四川省低碳经济的发展。[结论]该研究为碳减排政策的制定提供了理论依据。     

Reducing interactions between seabirds and trawl fisheries: Responses to foraging patches provided by fish waste batches

Seabird bycatch in trawl fisheries is driven by the attraction of birds to foraging opportunities, i.e., the discharge of catch processing waste and the contents of trawl nets. The risk of seabird captures increases with seabird abundance and exposure to fishing gear. We investigated (1) how quickly seabirds responded to discharges of trawl catch processing waste and (2) whether decreasing numbers of seabirds attended trawlers during processing waste discharge events as the time interval between these events increased. Waste was retained onboard the vessel for four different holding periods (30 min, 2 h, 4 h, 8 h), one of which was applied each day using a randomised block design. We determined seabird responses to batch discharge events after the prescribed holding periods using the abundance of large (albatrossses and giant petrels Macronectes spp.) and small (all other petrels except cape petrels Daption capense, shearwaters and prions) seabirds in a semi-circle of 40 m radius, centred on the stern of the experimental trawler. Seabird responses reflected the type of discharge released: birds moved from the air to the water, as the amount of food available increased from no discharge, through sump discharge to batch discharge. When discharge occurred, seabird abundance increased faster than could be resolved with the 5 min sampling period. However, abundance decreased more slowly over a 10-15 min period after the discharge event. The number of large seabirds attending the vessel during discharge events decreased significantly when waste was held for 4 h. For small birds, significant decrease occurred after 8 h. Such holding periods emphasise the tenacity of foraging seabirds, although we have not evaluated any long-term habituation to a particular discharge regime. While holding waste for less than 4 h may not reduce seabird attendance during discharge events, holding for shorter intervals can still reduce bycatch risk, e.g., prior to and during net shooting and hauling.     

Quality Protein Maize: Overcoming the Hurdles

SUMMARY

Quality Protein Maize (QPM), a nutritionally enhanced maize, was developed by researchers from CIMMYT using too genetic systems–opaque-2 and genetic modifiers. The use of these two genetic systems overcame the highly complex problems that were inherent in the original soft endosperm opaques. This review describes the ever-evolving breeding options and strategies for the development of QPM with examples from the CIMMYT maize program, where much of the research and practical breeding work has been done. The soft endosperm opaque-2 materials developed earlier had poor agronomic performances and lacked producer and consumer acceptance. To overcome these constraints, subsequent research explored various options, with and without high lysine mutants. Like other institutions, CIMMYT researchers tried and critically examined the merits and demerits of different strategies. Of all the strategies available, the selection for modified kernels in which CIMMYT scientists had gained information, experience, and confidence seemed viable. To implement this strategy, modified opaque-2 donor stocks were built and were subsequently used for expanding the QPM developmental efforts. A large volume of QPM germplasm was developed using different breeding options, which were later merged and reorganized into a fixed number of pools and populations to permit working in homozygous opaque-2 genetic backgrounds. The development of QPM hybrids was the next turning point in the mid-80s. During the QPM developmental process, serious problems inherent in the opaques were circumvented and since then, rapid progress has been made. There is a renewed interest in QPM and several countries have recently released QPM varieties and hybrids. To further accelerate the QPM developmental process, to enhance its popularity amongst nations and its farmers, and to meet future challenges, innovative ideas and the tools of biotechnology will be needed.     

Increased hippuric acid content of urine can reduce soil N2O fluxes

Urine patches in grazed pastures are a major source of nitrous oxide (N₂O) emission. It is well-documented that the relative concentration of the various nitrogenous urine constituents varies significantly with diet. The effect of these variations on N₂O emissions from urine patches, however, has never been reported. The aim of this study was to test whether variations in urine composition, consistent with different diets, lead to significant differences in N₂O emission. Four varieties of artificial urine, all with similar total N concentrations, but varying in the relative contribution of the nitrogenous constituents, were applied to undisturbed cores from a sandy pasture soil. N₂O fluxes were monitored for 65 days at two moisture treatments; 92% WFPS for the entire incubation, and 70% WFPS up to day 41 and 92% afterwards. Extra replicates were included for destructive analysis on mineral N concentrations and pH. Urine composition was a significant (P<0.001) factor determining N₂O emissions. An increase in the relative hippuric acid concentration from 3 to 9% of total N resulted in a significant decline in average N₂O fluxes, from 16.4 to 8.7 μg N₂O-N h⁻¹ kg⁻¹ soil (averaged over all treatments). Cumulative emission decreased from 8.4 to 4.4% of the applied urine-N (P<0.01). Soil mineral N showed a modest but significant decrease with an increase of hippuric acid content. pH did not show any significant relationship with urine composition. Increasing the urea concentration with 12% of applied urinary N did not significantly affect N₂O emissions. Moisture content significantly affected N₂O emissions (P<0.001), but no interaction between moisture and urine composition was found. As the inhibitory effect of hippuric acid could not be linked directly to mineral N concentrations in the soil, we hypothesize that the breakdown product benzoic acid either inhibits denitrification or decreases the N₂O/N₂ ratio. We conclude that hippuric acid concentration in urine is an important factor influencing N₂O emission, with a potential for reducing emissions with 50%. We suggest alternative rationing leading to higher hippuric acid concentrations in urine as a possible strategy to mitigate N₂O emission from grazed pastures.     

实物期权评价中波动率全阶段估算研究

针对现行投资评价方法的局限,建立投资项目实物期权评价模型和评判标准。分析实物期权模型中波动率参数估算方法的局限性,以净现值法为基础,提出基于蒙特卡洛模拟的全阶段波动率估算方法,解决实物期权评价投资决策难题。     

Assessing ecological equivalence in biodiversity offset schemes: Key issues and solutions

Habitat loss through development is one of the major causes of biodiversity loss. The increasingly common legal requirement to first avoid, then reduce and, if necessary, offset impacts of plans and projects on biodiversity has however not always been appropriately enforced. The blame lies mainly in bad governance such as patchy monitoring or poorly defined liabilities. Biodiversity offsets also suffer from the lack of formal methods for designing and sizing offset requirements. We address this gap by reviewing different tools, methods and guidelines that have been developed in different regulatory contexts. We then formulate a typology of approaches that variously combine these methods and guidelines. We discuss how these relate to the objectives of offset policies and the components of biodiversity and ecosystems to which they apply. Together, these perspectives should contribute to improving existing methods (e.g. by incorporating time-related issues) and our typology should support the development of offset policies.     

Carbon recovery rates following different wildfire risk mitigation treatments

Sequestered forest carbon can provide a climate change mitigation benefit, but in dry temperate forests, wildfire poses a reversal risk to carbon offset projects. Reducing wildfire risk requires a reduction in and redistribution of carbon stocks, the benefit of which is only realized when wildfire occurs. To estimate the time needed to recover carbon removed and emitted during treatment, we compared the 7-year post-treatment carbon stocks for mechanical thinning and prescribed fire fuels reduction treatments in Sierra Nevada mixed-conifer forest and modeled annual carbon accumulation rates. Within our 7-year re-sample period, the burn only and understory thin treatments sequestered more carbon than had been removed or emitted during treatment. The understory thin and burn, overstory thin, and overstory thin and burn continued to have net negative carbon stocks when emissions associated with treatment were subtracted from 7-year carbon stock gains. However, the size of the carbon deficit in the understory thin and burn 7 years post-treatment and the live tree growth rates suggest that the remaining trees may sequester treatment emissions within several more years of growth. Overstory tree thinning treatments resulted in a large carbon deficit and removed many of the largest trees that accumulate the most carbon annually, thereby increasing carbon stock recovery time. Our results indicate that while there is an initial carbon stock reduction associated with fuels treatments, treated forests can quickly recover carbon stocks if treatments do not remove large, fire-resistant overstory trees.