考虑输出刚度不确定性的柔顺机构拓扑优化设计

为了降低机构性能对输出刚度不确定因素的敏感程度,提出一种考虑输出刚度不确定性的柔顺机构拓扑优化设计方法。采用区间模型描述输出刚度的不确定性,利用多项式混沌展开式(Polynomial chaos expansion, PCE)和Smolyak稀疏网格积分法计算随机响应统计矩,以机构输出位移的期望值最大化和标准差最小化为目标函数,以机构结构体积为约束,建立考虑输出刚度不确定性的柔顺机构稳健性拓扑优化模型,采用移动渐近线优化算法更新设计变量。夹持器和咬合机构数值算例验证提出设计方法的有效性,与确定性拓扑优化结果比较,稳健性拓扑优化设计获得的柔顺机构构型有所不同,机构的输出位移标准差减小,有效地降低机构对输出刚度不确定性的敏感程度。随着加权系数增大,获得的柔顺机构输出位移标准差和期望值减小。随着不确定输出刚度幅值增大,获得的柔顺机构输出位移标准差增大,并且输出位移期望值有所减小。     

动物脂肪组织的分化起源

动物脂肪组织是机体重要的器官,主要负责能量的储存和代谢,同时分泌多种脂肪细胞因子(adipokines)参与机体生理功能的调控。脂肪组织的功能紊乱与人类的肥胖病、糖尿病以及代谢综合症密切相关,多年以来动物脂肪组织的细胞分化起源一直是研究的热点。白色脂肪、棕色脂肪和肌肉组织都来源于机体的间充质干细胞(mesenchymal stem cells,MSCs),长期以来,人们一直以为白色脂肪和棕色脂肪的分化起源更加亲近,但随着对棕色脂肪分化机制的深入研究,发现白色脂肪和棕色脂肪在早期发育阶段有着不同的前体细胞,而棕色脂肪组织与肌肉组织的分化支系更加亲近。以往的脂肪分化研究往往利用基质血管组分(stromal vascular fractions,SVF)或肌卫星细胞等混合细胞群作为实验材料,随着流式细胞仪、转基因动物模型和干细胞表面标志抗原识别等技术的发展,使我们可以从这样的混合细胞群中分离得到纯的前体脂肪细胞系,从而提示我们之前的研究可能过高的估计了这样的混合细胞群体的活体分化潜能。进一步深入研究动物脂肪组织的分化起源,有助于我们理解机体脂肪沉积的具体机制,从而为治疗脂肪代谢相关疾病以及提高动物肉品品质提供理论依据。     

A study of spring-and autumn-spawned herring (Clupea harengus L.) larvae in the Norwegian Coastal Current during spring 1990

An intensive sampling program for yolk-sac herring larvae and microzooplankton was carried out in the main spawning area of Norwegian spring-spawning herring during March to April 1990 (between 62^o and 63^o30'N) to estimate their hatching period and the abundance of copepod eggs and nauplii. Additional investigations were carried out in the Skagerrak area during January-March and on the Norwegian Shelf in May to study the otolith microstructure of the herring larvae. In May both autumn- and spring-spawned herring larvae were found in the samples from the Norwegian Shelf. They were easily distinguished by differences in otolith microstructure. The pattern in increment widths in the otoliths of the autumn-spawned larvae indicated that these larvae had not been transported through the Skagerrak area, but more likely were carried directly from the northern North Sea across the Norwegian Trench and into the Norwegian Coastal Current system. The calculated hatching of the spring-spawned larvae sampled in May occurred significantly later than the observed hatching over the spawning grounds. The results suggest a mismatch between the abundance of first-feeding herring larvae and their prey organisms, resulting in a higher survival of those herring larvae hatching during the latest part of the spawning period. This coincides with a general increase towards the middle of April in the abundance of prey organisms, from 1 to 4 1^_1. There were no differences in otolith microstructure among spring-spawned herring larvae sampled on the shelf in May, indicating that these larvae originated from the same cohort and were well mixed throughout the whole shelf area.     

Marine Low Molecular Weight Natural Products as Potential Cancer Preventive Compounds

Due to taxonomic positions and special living environments, marine organisms produce secondary metabolites that possess unique structures and biological activities. This review is devoted to recently isolated and/or earlier described marine compounds with potential or established cancer preventive activities, their biological sources, molecular mechanisms of their action, and their associations with human health and nutrition. The review covers literature published in 2003–2013 years and focuses on findings of the last 2 years.     

丙基双氢茉莉酮酸酯诱导棉花耐黄萎病的效应

温室内以10mg·L 1的丙基双氢茉莉酮酸酯(PDJ)灌根预处理后,再用黄萎病菌(Verticilliumdahliae)孢子悬浮液接种棉苗,处理棉苗与对照相比发病率和病情指数有所降低,表现出对棉花黄萎病的耐病性。对一些生化指标进行测定发现,PDJ灌根和接种都可引起棉苗叶片中苯丙氨酸解氨酶(PAL)活性升高和木质素含量的增加,与此同时棉花叶片中的过氧化物酶(POD)活性及丙二醛(MDA)含量也都有所上升,在此基础上对PDJ诱导棉花耐黄萎病的可能生化机制作了归纳。     

Relevance of sexual polyploidization for crop improvement – A review

Colchicine induced polyploids have not directly contributed for crop improvement in the past. On the other hand, the so-called natural polyploids, derived from the functioning of numerically unreduced(2n) gametes have been shown to be more relevant for crop improvement in many cases. Different types of cytological abnormalities during meiosis can give rise to 2n gametes and the genetic composition of these gametes is variable. Depending on the type meiotic abnormalities, various types of 2ngametes, such as first division restitution(FDR), second division restitution (SDR),indeterminate meiotic restitution (IMR) and post meiotic restitution (PMR) gametes,among others, have been described in recent years. For the improvement of autopolyploids such as potato, alfalfa,Vaccinium spp., and some of the fodder grasses, FDR gametes have been proved to be highly useful. However, the use of 2n gametes for the improvement of allopolyploid crops has received much less attention so far. Some of the investigations on allopolyploids, derived from Festuca-Lolium, Alstroemeria and Lilium species hybrids, have revealed that 2ngametes can be most useful for the introgression of alien genes and chromosomes into cultivars. An important feature of using sexual polyploidization in the case of allopolyploids is that introgression can be achieved through recombination due to genetic crossing-over between alien chromosomes as well as addition of alien chromosomes, which is extremely difficult or impossible to achieve in the case of colchicine induced allopolyploids. Because of the recent developments in the field of plant molecular biology, methods have become available for the analysis of 2ngametes and sexual polyploid progenies more accurately and to develop systematic breeding approaches. The methods include DNA in situ hybridization (GISH and FISH)and molecular mapping (AFLP, RFLP, RAPDs).In addition to providing basic information on the genetic and genome composition of the polyploid progenies, these methods can be potentially useful for a more efficient creation of desirable breeding material and cultivars. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of cytoplasmic male-sterility in sorghum on host plant interaction with sorghum midge,Contarinia sorghicola

Summary Sorghum midge, Contarinia sorghicola Coq. (Diptera: Cecidomyiidae) is one of the most important pests of grain sorghum worldwide. We studied the reaction of midge-resistant and midge-susceptible genic-cytoplasmic male-sterile (A-lines) and their maintainers (B-lines), and the effect of resistant and susceptible restorers on sorghum midge. Midge damage and adult emergence were significantly lower on the B-lines of midge-resistant genotypes (PM 7061 and PM 7068) than their corresponding A-lines, while the reverse was true for the midge-susceptible genotypes (296A and ICSA 42). Differences in midge damage and the number of midges emerged were not significant between the midge-resistant and midge-susceptible A-lines when infested without pollination (except midge emergence on PM 7061A). Pollination with a midge-resistant restorer (DJ6541) reduced midge emergence significantly in one of two seasons. Source of pollen did not influence midge emergence on the highly-resistant A-line, PM 7061A. The implications of these observations in the development of midge-resistant hybrids were discussed.     

Molecular functions of genes related to grain shape in rice

Because grain shape is an important component of rice grain yield, the discovery of genes related to rice grain shape has attracted much attention of rice breeding programs. In recent years, some of these genes have been cloned and studied. They have been found not only regulate grain shape by changing the shape of the spikelet hull, but also regulate endosperm development through control of cell division using different molecular mechanisms. In this paper, we review the recent research on genes related to rice grain shape and their possible regulatory mechanisms.     

Mechanisms of resistance to shoot fly, <Emphasis Type="Italic">Atherigona soccata</Emphasis> in sorghum

Summary Sorghum shoot fly, Atherigona soccata (Rondani) is an important pest of sorghum in Asia, Africa, and Mediterranean Europe, and host plant resistance is an important component for the management of this pest. The levels of resistance in the cultivated germplasm are low to moderate, and therefore, it is important to identify genotypes with different mechanisms of resistance to pyramid the resistance genes. We studied the antixenosis for oviposition, antibiosis, and tolerance components of resistance in a diverse array of shoot fly-resistant and -susceptible genotypes. The main plants and tillers of SFCR 151, ICSV 705, SFCR 125, and, IS 18551 experienced lower shoot fly deadhearts at 28 days after seedling emergence, produced more number of productive tillers. The insects fed on these genotypes also exhibited longer larval period (10.1–11.0 days compared to 9.3 days on Swarna), lower larval survival and adult emergence (54.7–67.8 and 46.7–52.2% compared to 73.3 and 60.6% on Swarna, respectively), and lower growth and adult emergence indices as compared to the susceptible check, Swarna. Physico-chemical traits such as leaf glossiness, trichome density, and plumule and leaf sheath pigmentation were found to be associated with resistance, and chlorophyll content, leaf surface wetness, seedling vigor, and waxy bloom with susceptibility to shoot fly and explained 88.5% of the total variation in deadhearts. Step-wise regression indicated that 90.4% of the total variation in deadhearts was due to leaf glossiness and trichome density. The direct and indirect effects, correlation coefficients, multiple and step-wise regression analysis suggested that deadhearts, plants with eggs, leaf glossiness, trichomes on the abaxial surface of the leaf, and leaf sheath pigmentation can be used as marker traits to select for resistance to shoot fly, A. soccata in sorghum.     

Relative susceptibility of different male-sterile cytoplasms in sorghum to shoot fly, <Emphasis Type="Italic">Atherigona soccata</Emphasis>

Summary The shoot fly, Atherigona soccata is an important pest of sorghum, and host plant resistance is one of the most effective components for managing this pest. Most of the hybrids grown in India based on milo cytoplasm (A₁ cytoplasm) are highly susceptible to shoot fly. Therefore, the present studies were undertaken to evaluate different male-sterile cytoplasms (CMS) for their relative susceptibility to sorghum shoot fly. Oviposition and deadheart formation were significantly lower on the maintainer lines as compared to the corresponding male-sterile lines. Among the cytoplasms tested, A₄M cytoplasm showed antixenosis for oviposition and suffered lower deadheart formation than the other cytoplasms tested. The A₄G₁ and A₄M cytoplasms suffered lower deadhearts in tillers than the other cytoplasms. Recovery following shoot fly damage in A₄M, A₃, and A₂ cytoplasms was better than in the other cytoplasms tested. The larval and pupal periods were longer and male and female pupal weights lower in A₄M and A₄VzM CMS backgrounds compared to the other CMS systems. Fecundity and antibiosis indices on CMS lines were lower than on the B-lines. The A₄M cytoplasm was found to be relatively resistant to sorghum shoot fly, and can be exploited for developing shoot fly-resistant hybrids for sustainable crop production in future.