An actuated dissipative spring-mass walking model: Predicting human-like ground reaction forces and the effects of model parameters

Simple models are widely used to understand the mechanics of human walking. The optimization-based minimal biped model and spring-loaded-inverted-pendulum (SLIP) model are two popular models that can achieve human-like walking patterns. However, ground reaction forces (GRF) from these two models still deviate from experimental data. In this paper, we proposed an actuated dissipative spring-mass model by integrating these two models to realize more human-like GRF patterns. We first explored the function of stiffness, damping, and weights of both energy cost and force cost in the objective function and found that these parameters have distinctly different influences on the optimized gait and GRF profiles. The stiffness and objective weight affect the number and size of peaks in the vertical GRF and stance time. The damping changes the relative size of the peaks but has little influence on stance time. Based on these observations, these parameters were manually tuned at three different speeds to approach experimentally measured vertical GRF and the highest correlation coefficient can reach 0.983. These results indicate that the stiffness, damping, and proper objective functions are all important factors in achieving human-like motion for this simple walking model. These findings can facilitate the understanding of human walking dynamics and may be applied in future biped models.     

Characterization of Bradyrhizobium strains indigenous to Western Australia and South Africa indicates remarkable genetic diversity and reveals putative new species

Bradyrhizobium are N₂-fixing microsymbionts of legumes with relevant applications in agricultural sustainability, and we investigated the phylogenetic relationships of conserved and symbiotic genes of 21 bradyrhizobial strains. The study included strains from Western Australia (WA), isolated from nodules of Glycine spp. the country is one genetic center for the genus and from nodules of other indigenous legumes grown in WA, and strains isolated from forage Glycine sp. grown in South Africa. The 16S rRNA phylogeny divided the strains in two superclades, of B. japonicum and B. elkanii, but with low discrimination among the species. The multilocus sequence analysis (MLSA) with four protein-coding housekeeping genes (dnaK, glnII, gyrB and recA) pointed out seven groups as putative new species, two within the B. japonicum, and five within the B. elkanii superclades. The remaining eleven strains showed higher similarity with six species, B. lupini, B. liaoningense, B. yuanmingense, B. subterraneum, B. brasilense and B. retamae. Phylogenetic analysis of the nodC symbiotic gene clustered 13 strains in three different symbiovars (sv. vignae, sv. genistearum and sv. retamae), while seven others might compose new symbiovars. The genetic profiles of the strains evaluated by BOX-PCR revealed high intra- and interspecific diversity. The results point out the high level of diversity still to be explored within the Bradyrhizobium genus, and further studies might confirm new species and symbiovars.     

Capitalizing on multi-element interactions through balanced nutrition — A pathway to improve nitrogen use efficiency in China,India and North America

A viable option for increasing nitrogen (N) use efficiency and mitigation of negative impacts of N on the environment is to capitalize on multi-element interactions through implementation of nutrient management programs that provide balanced nutrition. Numerous studies have demonstrated the immediate efficacy of this approach in the developing regions like China and India as well as developed countries in North America. Based on 241 site-years of experiments in these countries, the first-year N recovery efficiency (RE) for the conventional or check treatments averaged 21% while the balanced treatments averaged 54% RE, for an average increase of 33% in RE due to balanced nutrition. Effective policies to promote adoption are most likely those that enable site-specific approaches to nutrient management decisions rather than sweeping, nation-wide incentives supporting one nutrient over another. Local farmers, advisers and officials need to be empowered with tools and information to help them define necessary changes in practices to create more balanced nutrient management.

     

Carbohydrate formation in rewetted terrestrial cyanobacteria

Summary In the terrestrial cyanobacterium Nostoc commune Vauch. formation of carbohydrate polymers was measured upon rewetting the mats in a light-dark regime. To discriminate between carbohydrates of different physiological function, total carbohydrate was determined as anthrone-reactive material (ARM) and storage carbohydrate (glycogen) assayed by an enzymic test. In the dry thalli glycogen was found to represent less than one tenth of the ARM. After rewetting an increase of total carbohydrate was observed in illuminated samples. Only glycogen, however, showed a regular pattern of synthesis and degradation during a 12:12 h light-dark cycle. This indicates that most carbohydrates detected by anthrone belong to the metabolically inert sheath material.When illuminated colonies were kept submerged after rewetting glycogen was hydrolyzed indicative of being used in the rapid recovery of cellular functions as observed in rewetted colonies. Apparently, photosynthesis allowed for net glycogen synthesis only, provided the mats were sufficiently aerated. These findings give evidence that the (carbohydrate) sheath plays an important role in water retention in an organism bound to a terrestrial habitat.     

抗阿特拉津转基因大豆植株后代的遗传分析

本试验用阿特拉津溶液涂抹、荧光诱导动力学检测、分子杂交等方法对抗阿特拉津转基因大豆植株的后代进行了鉴定,在第二代及第三代中检测到了抗性基因的存在,表明从龙葵中得到的此抗阿特拉津 psbA 基因不仅能导人大豆叶绿体基因组中获得表达,而且可以遗传到后代。     

湖南邵东中泥盆统棋梓桥组层孔虫生物群及其生态环境

湖南中部泥盆纪地层和生物礁相当发育。湖南邵东中泥盆世棋梓桥期的泥质石灰岩中层孔虫广泛分布,本文共描述邵东廉桥马鞍山棋梓桥期层孔虫12属18种,其中Stromatopora wenshanensis为一新名,代替1982年根据一个云南标本定名为Stromatopora irregularis的种名。 马鞍山礁是—发育在海底平台上的厚度稍有变化的层状礁,马鞍山礁的沉积相变化过程,是由近岸浅海到展状礁普遍发育的开阔台地,再到封闭或半封闭的泻湖或潮坪环境。生物组合和沉积物也随沉积环境的变化而发生相应的变化。     

Recovery of adenine-nucleotide pools in terrestrial blue-green algae after prolonged drought periods

Summary The response of Nostoc commune and Nostoc flagelliforme (terrestrial blue-green algae), grown in their natural habitat, towards rewetting after prolonged drought periods (2 weeds up to five years) has been investigated. In Nostoc flagelliforme, the energy charge (EC) about 0.18 in dry condition increases rapidly (EC=0.7 after 1 h) and more slowly in a second phase (EC=0.8 after 6 h). The total content of AXP (=ATP+ADP+AMP) apparently increases due to de novo synthesis of adenine nucleotides. ATP-build-up after a drought period is probably provided by oxidative phosphorylation. It has been found to be about the same, regardless of whether the foregoing drought period had been extended over 6 months or 5 years.Dry samples of colony mats of N. commune exhibit very low ATP-, but high ADP-contents. Within 6 h after rewetting, the final level of extractable ATP (60–100 nmol/mg chlorophyll) is recovered.     

RFLP-based maps of the homoeologous group-6 chromosomes of wheat and their application in the tagging of Pm12, a powdery mildew resistance gene transferred from Aegilops speltoides to wheat

Genetic maps of the homoeologous group-6 chromosomes of bread wheat, Triticum aestivum, have been constructed spanning 103 cM on 6A, 90 cM on 6B and 124 cM on 6D. These maps were transferred to a Chinese Spring (CS) x line #31 cross to locate a dominant powdery mildew resistance gene, Pm12, introgressed into line #31 from Aegilops speltoides. Pm12 was shown to lie on the short arm of translocation chromosome 6BS-6SS.6SL in line #31, but could not be mapped more precisely due to the lack of recombination between the 6S Ae. speltoides segment and chromosome 6B. Possible strategies to reduce the size of the alien segment, which probably encompasses the complete long arm and more than 82% of the short arm of chromosome 6B, are discussed.     

朱顶红花粉萌发过程中营养细胞质的超微结构变化

本文应用透射电镜对朱顶红成熟花粉水合、活化和萌发的动态过程中营养细胞质的结构和组成变化进行了观察。成熟花粉具质体、线粒体、内质网、高尔基体。微丝束以聚集体的形式存在。花粉活化后,细胞器的数目和结构发生显著变化：质体和线粒体的片层明显增加,内质网片层狭窄,高尔基体活跃产生小泡,脂体降解及微丝聚集体散开。花粉萌发后,细胞质中出现周质微管和被刺小泡,此期细胞器的变化不明显。微丝以纤丝状遍布整个花粉管中。