球形约束变分不等式的光滑化牛顿方法

研究球形约束变分不等式求解的算法 ,提出一种光滑化牛顿方法 ,证明了该方法具有全局收敛性和超线性收敛     

Magnetic resonance imaging appearance of hypertensive encephalopathy in a dog

A 16-year-old female spayed English Staffordshire terrier was presented for evaluation of a 10-month history of intermittent myoclonic episodes, and a one weeks history of short episodes of altered mentation, ataxia and collapse. Magnetic resonance imaging identified subcortical oedema, predominately in the parietal and temporal lobes and multiple cerebral microbleeds.Serum biochemistry, indirect blood pressure measurements and magnetic resonance imaging abnormalities were consistent with hypertensive encephalopathy secondary to chronic kidney disease.     

温度对越夏代日本松干蚧发育和扩散的影响

日本松干蚧是为害松树的外来入侵害虫,一年发生两代即越冬代和越夏代,目前在东北地区逐渐向北扩散蔓延.随着地理纬度升高,夏季热量条件能否满足越夏代日本松干蚧的生长发育并产下健康的卵是其进一步为害和扩散的基础.本文通过温度控制进行了10、15、20和25℃共4个温度梯度的模拟试验,同时,对日本松干蚧的高温耐受能力进行测试.结果表明：25℃条件下日本松干蚧发育最快,20℃时生长发育进度与当地野外条件下相当,15℃时发育较缓慢,10℃条件下日本松干蚧卵孵化迟缓,无法完成正常发育并繁殖下一代,故10℃可以作为阻止日本松干蚧北扩的下限温度,根据这一指标,越夏代日本松干蚧可以继续向北扩散至黑龙江所有区域.耐高温测试结果表明,持续生活在东北地区的日本松干蚧耐高温能力仍很强,若传到南方高温区域仍可继续生存扩散.研究结果可为探究东北地区越夏代日本松干蚧适宜生存范围提供依据.     

高粱的起源、驯化与传播

关于高粱的起源、驯化和传播,中外学者提出了多种猜想。最早有印度起源说,再有非洲起源说,中国高粱中国起源说,以及多元起源说等。本文从高粱历史遗存的考古发现、古籍记载、分子生物学研究结果等方面论述了栽培高粱的起源、驯化和传播。认为高粱起源于苏丹热带草原,距今8 000～6 000 a前开始驯化栽培,并向非洲大陆、印度、中东、西亚等周边传播,距今5 000年前传播到印度,4 000～3 000 a前传播到中国西南的云、贵地区。由于远古时期就开始传播,受不同地域气候条件、栽培条件等的影响,原始高粱的形态学性状和生理特性在不同的区域产生了不同的变异,形成了现今五大高粱栽培种之间的差异。中国高粱非中国起源,但中国无疑是高粱的重要驯化中心之一。     

H1[0,1]空间中多尺度分析在数值逼近问题中的应用

应用H1[0,1]空间多尺度分析方法解决数值逼近问题,仿真及误差分析结果表明了这一方法对函数逼近的可行性,从而为再生核空间数值逼近提供了一种新的思路。     

陕西土壤磷素扩散的某些影响因素的研究

采用32~P标记扩散池法研究了土壤水分、容重、CaCO₃含量和温度等因素对陕西主要农业土壤磷自扩散系数(D_α)的影响.结果表明,D_α值随土壤水吸力(S)减小(即土壤含水量增加)而增大,并符合幂函数D_α=αS^-b.在容重1.2～1.6g/cm³范围内,随容重增加D_α值近线性增大,且相同含水量下增幅为黄绵土>黑垆土>土>黄褐土,呈现出随质地变粘增幅减小、同一土壤含水量高时增幅较大的趋势.去除CaCO₃后,D_α值增大,D_α值与土壤CaCO₃含量呈线性或指数负相关.温度升高,D_α值增大;5～45℃下升温10℃,D_α值增加量平均约30%左右.     

一类次对称矩阵反问题的最小二乘解

讨论了一类次对称矩阵反问题的最小二乘解，得到了解的具体表达式；并就这类矩阵的左右逆特征对问题进行了讨论，得到了有解的充分条件及解的通式。     

Long-term dynamics and population viability in one of the last populations of the endangered Spiranthes spiralis (Orchidaceae) in the Netherlands

During the last decades, most orchid species in much of Western Europe have suffered significant declines and the long-term survival of the remaining populations remains to a large extent uncertain. In particular, populations at range margins may be more prone to extinction than more central populations, as the former tend to be small and isolated, occur in ecologically marginal habitats and have a lower per-capita reproductive rate. In this study, we investigated the long-term dynamics and population viability of a population at the margin of its range of Spiranthes spiralis in the Netherlands. At present, only 2 out of 40 previously known populations persist. Individual plants were monitored for 24 years and their life span, flowering frequency and vegetative growth were determined. Individual plants showed large temporal variation in sexual and vegetative growth among years. The proportion of flowering plants varied from 0 (no plants were flowering) to 100 (all plants were flowering). Vegetative growth, on the other hand, increased when the number of individuals decreased. Dormancy was present, but occurred only in a few individuals. Using a non-structured population viability model, future prospects of this species were assessed. Calculation of extinction probabilities and estimated times to extinction using the diffusion approximation model showed that the species had a relatively high probability (79%) of surviving the next 20 years, whereas the median time to extinction was forty years. However, because 95% confidence intervals of the population growth included 1, we suggest that continued monitoring and additional genetic research are needed to assess the long-term viability of this species.     

Mild drying of sandy soil can physically limit the uptake of phosphorus by rainfed lowland rice in northeast Thailand

ABSTRACT

Poor response of rice to phosphorus (P) fertilization and low phytoavailability of soil P have been reported in sandy rainfed fields in northeast Thailand. In order to evaluate the effects of mild soil drying on the uptake of P by rainfed lowland rice, we carried out nutrient omission trials for nitrogen (N) and P at Ubon Ratchathani Rice Research Center under rainfed and flooded conditions. The surface soil was classified as sandy loam. To avoid severe soil drying and drought stress in the rainfed field, soil water potential at a depth of 20 cm was maintained at the field capacity (> ?20 kPa) by flush irrigation. The effects of flooding and drying on the soil properties were also evaluated in the laboratory using soils with diverse textures in and around the center. In the field experiments, the above-ground biomass of rice plants (RD6) did not respond significantly to P fertilization in the rainfed field, although it responded positively to N fertilization. Root length in the surface 10 cm under the rainfed condition was significantly smaller than that under the flooded condition due partly to the increased soil hardness upon drying, but this could not quantitatively explain the large discrepancy of P uptake observed between the rainfed and flooded conditions. Under the rainfed condition, the P uptake did not increase significantly, even when the concentration of soil Bray P was tripled by transferring the surface soil from the flooded to the rainfed field. From the laboratory experiments, it was further suggested that soil P was supplied mainly by diffusion and that the effective diffusion coefficient for P can become less than one-tenth of the value in the flooded field when the sandy soil with clay at around 10% dried to ?100 kPa. Our results suggest that the uptake of P by the rainfed lowland rice grown in sandy soil can be limited physically by mild soil drying that reduces the supply of P to roots by diffusion rather than the chemical extractability of soil P.