Computational fluid dynamics modeling of mass transfer behavior in a bioreactor for hairy root culture. I. Model development and experimental validation

A two-dimensional axisymmetric computational fluid dynamics (CFD) model based on a porous media model and a discrete population balance model was established to investigate the hydrodynamics and mass transfer behavior in an airlift bioreactor for hairy root culture.During the hairy root culture of Echinacea purpurea, liquid and gas velocity, gas holdup, mass transfer rate, as well as oxygen concentration distribution in the airlift bioreactor were simulated by this CFD model. Simulative results indicated that liquid flow and turbulence played a dominant role in oxygen mass transfer in the growth domain of the hairy root culture. The dissolved oxygen concentration in the hairy root clump increased from the bottom to the top of the bioreactor cultured with the hairy roots, which was verified by the experimental detection of dissolved oxygen concentration in the hairy root clump. This methodology provided insight understanding on the complex system of hairy root culture and will help to eventually guide the bioreactor design and process intensification of large-scale hairy root culture.     

土壤-植物系统水分运移过程的阻容电模拟

把土壤-植物系统水分运移作为一维水流运动由阻容电路进行模拟,在于将D arcy-R ichards方程从对单点的描述扩展到对一段流路的描述。由此出发,考虑到水流的非稳态性,某一流路的水阻定义为其水势差与平均流量之比,水容为其贮水量对平均水势的导数。与D arcy-R ichards方程相对应,水阻、时间常数分别为导水度、水分扩散度的倒数,相应地单位化的水阻率、比时间常数分别为导水率、水分扩散率的倒数。把SP系统沿水流通道分为若干部分,每一局部的水阻与其水容相并联,各局部间相串联。在此基础上,文章给出了土壤-植物系统水流模拟通式、总水容与分水容间的关系式、总水阻与分水阻间的关系式及特定条件下叶水势随时间变化的关系式。     

Urban development and sustainability challenges chronicled by a century of construction material flows and stocks in Tiexi,China

Construction materials are considerable forces of global environmental impacts, but their dynamics vis‐à‐vis urban development are poorly documented, in part because their long lifespans require elusive and sometimes nonexistent decade‐long high‐resolution data. This study analyzes the construction material flow and stock trends that shaped and were shaped by the development, decline, and renewal of the Tiexi district of Shenyang, a microcosm of China's urban transformations since the early 20th century. Chronicling building‐by‐building the material flows and stock accumulations involved in the buildup of this area, we shed light on the physical resource context of its socioeconomic history. We find that 42 million tonnes of construction materials were needed to develop the Tiexi district from 1910 to 2018, and 18 million tonnes of material outflows were generated by end‐of‐life building demolition. However, over 55% of inflows and 93% of outflows occurred since 2002 during a complete redevelopment of the district. Only small portions of end‐of‐life materials could have been reused or recycled because of temporal and typological mismatches of supply and demand and technical limitations. Our analysis reveals a dramatic decrease in median building lifetimes to as low as 6 years in the early 21st century. These findings contribute to the discussion of long‐term environmental efficiency and sustainability of societal development through construction and reflect on the challenges of urban renewal processes not only in China but also in other developing and developed countries that lost (or may lose) their traditional economic base and restructure their urban forms. This article met the requirements for a Silver/Silver JIE data openness badge described at http://jie.click/badges .     

The impacts of changes in vegetation cover on dry season flow in the Kikuletwa River, northern Tanzania

While the decrease in flow is obvious in the Kikuletwa River, the mechanism leading to the decrease is unclear. We assessed the influence of vegetation cover change on dry season flow in the Kikuletwa River. The combined cover of closed and open forests decreased by 68% while closed and open forests decreased by 56% and 64% respectively. Land under agroforestry decreased by 25%, while that under annual crops increased by 41%. Grasslands increased by 116% and riverine vegetation decreased by 53%. Daily dry season flow showed a slightly decreasing trend in one of the stations despite all of them receiving water from the Rundugai natural springs. On the other hand, low flow indices indicated no statistically significant changes in the long-term average flow and there was no identifiable change in the rainfall amount. The majority (93%) of the local people perceived a changing rainfall pattern and decline in dry season flow in the Kikuletwa River. Changes in the dry season flow then can be associated with the identified land cover changes. Further research to substantiate the local people perceptions is important as indigenous knowledge may be good evidence for ascertaining changes in the natural environment.     

Camponotus ants mine sand for vertebrate urine to extract nitrogen

The ability of some ant species (including Camponotus spp.) to forage on vertebrate urine to extract urea may extend their niche in competitive and strongly nitrogen‐limited environments. We examined the preference of Camponotus terebrans, a sand‐dwelling ant widespread in southern Australia, for baits including urine, and the duration of their foraging on those baits. We baited ants with liquid stains of urine (human and kangaroo), urea in water (2.5%. 3.5%, 7.0%, 10.0%) and sucrose in water (20% and 40%) poured directly on the ground, as well as hard baits in plots drawn on sandy soil (Kangaroo Island, South Australia). We counted individuals of this mostly nocturnal species to determine their attraction to different baits for one month. We checked plant growth on the plots after nine and 13 months. Ants collected insects and meat; they foraged for at least 29 days on stains. Ants were most numerous on 10% urea, followed by 7% urea, 3.5% urea, urine (which contains ~2.5% urea) and 2.5% urea, 40% sucrose and 20% sucrose; sucrose was less attractive to them than equimolar urea bait. Ants were attracted to human, kangaroo, and unidentified urines, and they collected bird guano. Baits and ant foraging did not affect plant recruitment in plots. We observed incidentally Camponotus consobrinus foraging on urine, which may be a common resource for this genus at the site. The remarkable ability of C. terebrans to extract nitrogen from dry sand over weeks explains partly its success on sandy soils. Foraging on urine may be an important strategy to address nitrogen limitation on sandy soils and exploit commensally niches in which hosts are kangaroos, wallabies and other vertebrates. The understanding of plant–vertebrate interactions must factor in the role of ants as commensal organisms. Such ants could also reduce greenhouse gas emissions from urine.     

Bumble bees (Bombus terrestris) store both food and information in honeypots

Social insect foragers often transmit information about foodsources to nest mates. In bumble bees (Bombus terrestris), forexample, successful foragers use excited motor displays anda pheromone as communication signals. In addition, bees couldmake use of an indirect pathway of information flow, via thehoney stores. We show here that, indeed, bees in the nest continuouslymonitor honeypots and sample their contents, thus obtaininginformation on supply and demand of nectar. When there is aninflux of nectar into the nest, the colony deploys more workersfor foraging. The number of new foragers depends on sugar concentration.Foragers returning with high-quality sugar solution displaymore "excited runs" on the nest structure. The recruits' response,however, does not depend on modulated behavior by foragers:more workers start to forage with high quality of incoming nectar,even when this nectar is brought by a pipette. Moreover, weshow that the readiness of bees to respond to recruitment signalsor incoming nectar also depends on colony demand. When colonynectar stores are full, the response of bees to equal amountsof nectar influx is smaller than when stores are empty. Whencolony nectar stores are depleted, foragers spend more timerunning excitedly and less time probing pots in the nest andrun with higher average speed, possibly to disperse the alertingpheromone more efficiently. However, more bees respond to nectarinflux to empty stores, whether or not this is accompanied byforager signals. Thus, honeypots serve to store informationas well as food.     

Periosteum-derived podoplanin-expressing stromal cells regulate nascent vascularization during epiphyseal marrow development

Bone marrow development and endochondral bone formation occur simultaneously. During endochondral ossification, periosteal vasculatures and stromal progenitors invade the primary avascular cartilaginous anlage, which induces primitive marrow development. We previously determined that bone marrow podoplanin (PDPN)-expressing stromal cells exist in the perivascular microenvironment and promote megakaryopoiesis and erythropoiesis. In this study, we aimed to examine the involvement of PDPN-expressing stromal cells in postnatal bone marrow generation. Using histological analysis, we observed that periosteum-derived PDPN-expressing stromal cells infiltrated the cartilaginous anlage of the postnatal epiphysis and populated on the primitive vasculature of secondary ossification center. Furthermore, immunophenotyping and cellular characteristic analyses indicated that the PDPN-expressing stromal cells constituted a subpopulation of the skeletal stem cell lineage. In vitro xenovascular model cocultured with human umbilical vein endothelial cells and PDPN-expressing skeletal stem cell progenies showed that PDPN-expressing stromal cells maintained vascular integrity via the release of angiogenic factors and vascular basement membrane-related extracellular matrices. We show that in this process, Notch signal activation committed the PDPN-expressing stromal cells into a dominant state with basement membrane-related extracellular matrices, especially type IV collagens. Our findings suggest that the PDPN-expressing stromal cells regulate the integrity of the primitive vasculatures in the epiphyseal nascent marrow. To the best of our knowledge, this is the first study to comprehensively examine how PDPN-expressing stromal cells contribute to marrow development and homeostasis.     

The geography of divergence with gene flow facilitates multitrait adaptation and the evolution of pollinator isolation in Mimulus aurantiacus

Ecological adaptation is the driving force during divergence with gene flow and generates reproductive isolation early in speciation. Although gene flow opposes divergence, local adaptation can be facilitated by factors that prevent the breakup of favorable allelic combinations. We investigated how selection, genetic architecture, and geography have contributed to the maintenance of floral trait divergence and pollinator isolation between parapatric ecotypes of Mimulus aurantiacus. Combining greenhouse, field, and genomic studies, we show that sharp clines in floral traits are maintained by spatially varying selection. Although adaptation breaks down where the ecotypes co‐occur, leading to the formation of a hybrid zone, the largely non‐overlapping distributions of the ecotypes shield them from immigrant genes, facilitating divergence across most of the range. In contrast to the sharp genetic discontinuities observed across most hybrid zones, we observed a gradual cline in genome‐wide divergence and a pattern of isolation by distance across the landscape. Thus, contrary to a long period of allopatry followed by recent re‐contact, our data suggest that floral trait divergence in M. aurantiacus may have evolved with locally restricted, but ongoing gene flow. Therefore, our study reveals how the geographic distribution of an organism can contribute to the evolution of premating isolation in the early stages of divergence with gene flow.     

树干液流径向分布格局研究进展

树干液流径向分布的不均匀性是引起热技术估算单株乃至林分蒸腾误差的主要来源。因此, 了解树干液流径向分布格局并将其定量化, 成为利用热扩散和热脉冲技术准确估算森林蒸腾的必要条件。该文详细介绍了树干液流径向分布格局的研究方法, 总结了目前4种常见的树干液流的径向分布格局, 分析了影响树干液流径向分布格局的内部结构因素和外部环境因素, 阐明了树干液流径向分布格局的时间动态特征及其影响因素, 并提出目前研究中存在的问题和可能的解决方法。