Design Principles of the Non-smooth Surface of Bionic Plow Moldboard

1　IntroductionTransferringbiologyfunctiontoengineeringtech nology[1] isaprominentprogressintechnologicalfields ,whichenrichesthecontentofTRIZsystematicmethod .Thenon smoothsurfacesofthetypicalsoilan imalshavetheeffectsofreducingsoiladhesion ,whichhasbeenconvincedandgraduallyaccepted .Thebionicplowmoldboardisanappliedexampleofimitatingthecharacteristicsofsoilanimals’surfaceappearancesandpracticingtheBionicTheoryofNon SmoothSurface(TNSS) .ThebasisofTNSSisnon smoothsurfaceef fects[2 ,3] …     

Computational Model of Soil Adhesion and Resistance for a Non-smooth Bulldozing Plate

Adhesive forces exist between soil and the surfaces of soil-engaging components; they increase working resistance and energy consumption. This paper tries to find an approach to reduce the adhesion and resistance of bulldozing plate. A simplified mechanical model of adhesion and resistance between soil and a non-smooth bulldozing plate is proposed. The interaction force between moist soil and a non-smooth bulldozing plate is analyzed. The pressure and friction distribution on the bulldozing plate are computed, and the anti-adhesive effect of a corrugated bulldozing plate is simulated numerically. Numerical results show that the wavy bulldozing plate achieves an effective drag reduction in moist soil. The optimal wavy shape of the corrugated bulldozing plate with the minimal resistance is designed. The basic principle of reducing soil adhesion of the non-smooth surface is discovered.     

A Computational Model of Soil Adhesion and Resistance for a Non-smooth Bulldozing Plate

1IntroductionAdhesive forces exist between soil and the surfacesof soil-engaging components[1,2].Soil adhesion increasesthe running resistance and energy consumption,andaffects the operating quality.Soil adhesion also reducesthe working productivity of terrain machines,even worseit makes terrain machines fail to run.Reducing theadhesive force of the soil-engaging machines will have aprofound influence for cultivation.Through theinvestigation of soil animals,we have found that soilanimals poss…     

Field Studies of the Wheat Stomata Resistance Influenced by Soil Water Content

Concurrent observations of soil water potential and leaf stomata diffusion resistance were made on two, plots of wheat grown at Datun Agro-ecological Experimental Station in Beijing under two different soil water conditions. These data were further complemented by weather and physiological observation. In this paper, we mainly analysed the influence of soil water potential on the status of wheat leaf stomatal resistance. The results indicate that: (1) there is a obvious influence of soil water potential on the status of wheat leaf stomata under normal conditions and (2) there is a different upper and lower epidermis stomata of wheat leaf respond to the soil water potential. The lower epidermis stomata are more sensitive to soil water potential than upper epidermis one. (3) There is a linear relationship between the ratio of lower and upper epidermis stomata resistance and soil water potential in root layer, according to this we can diagnose the degree of wheat water deficit.     

The Impact of Resource Availability on Bacterial Resistance to Phages in Soil

Resource availability can affect the coevolutionary dynamics between host and parasites, shaping communities and hence ecosystem function. A key finding from theoretical and in vitro studies is that host resistance evolves to greater levels with increased resources, but the relevance to natural communities is less clear. We took two complementary approaches to investigate the effect of resource availability on the evolution of bacterial resistance to phages in soil. First, we measured the resistance and infectivity of natural communities of soil bacteria and phage in the presence and absence of nutrient-providing plants. Second, we followed the real-time coevolution between defined bacteria and phage populations with resource availability manipulated by the addition or not of an artificial plant root exudate. Increased resource availability resulted in increases in bacterial resistance to phages, but without a concomitant increase in phage infectivity. These results suggest that phages may have a reduced impact on the control of bacterial densities and community composition in stable, high resource environments.     

土壤微生物群落抵抗力和恢复力研究进展

人类活动的不断加剧使得土壤生态系统承受着环境干扰压力。土壤微生物受到环境干扰的响应程度（抵抗力）及恢复至原来状态的能力（恢复力）决定着土壤生态系统的可持续性。梳理和总结了土壤微生物群落对环境干扰的抵抗力和恢复力方面的研究进展。首先,在介绍土壤微生物群落抵抗力和恢复力概念的基础上,阐述了通过评估微生物群落的结构和功能的变化来系统表征抵抗力和恢复力;随后,分析了最近十年（2012-2021年）有关文献,发现土壤微生物群落的结构和（或）功能在环境干扰后的恢复力总体较弱,但耕作、有机物料添加和轮作等农田管理措施下的响应趋势表现出一定的规律性;继而,从个体水平的休眠和胁迫忍耐、种群水平的生存策略、群落水平的多样性和相互作用以及生态系统水平的历史遗留效应等方面分析了土壤微生物群落抵抗力和恢复力的维持机制;最后,从功能性状、多功能性和植物-土壤微生物整体性对未来研究做出了展望,以期为构建土壤健康评价体系及预测环境干扰对土壤功能的影响提供科学依据。     

The hummingbird's tongue: a self-assembling capillary syphon

We present the results of a combined experimental and theoretical investigation of the dynamics of drinking in ruby-throated hummingbirds. In vivo observations reveal elastocapillary deformation of the hummingbird''s tongue and capillary suction along its length. By developing a theoretical model for the hummingbird''s drinking process, we investigate how the elastocapillarity affects the energy intake rate of the bird and how its open tongue geometry reduces resistance to nectar uptake. We note that the tongue flexibility is beneficial for accessing, transporting and unloading the nectar. We demonstrate that the hummingbird can attain the fastest nectar uptake when its tongue is roughly semicircular. Finally, we assess the relative importance of capillary suction and a recently proposed fluid trapping mechanism, and conclude that the former is important in many natural settings.     

Plant Species Composition Effects on Belowground Properties and the Resistance and Resilience of the Soil Microflora to a Drying Disturbance

We hypothesised that plant species composition and richness would affect soil chemical and microbial community properties, and that these in turn would affect soil microbial resistance and resilience to an experimentally imposed drying disturbance. We performed a container experiment that manipulated the composition and species richness of common pasture plant species (Trifolium repens, Lolium perenne, and Plantago lanceolata) by growing them in monoculture, and in all the possible two and three-way combinations, along with an unplanted control soil. Experimental units were harvested at four different times over a 16-month period to determine the effect of plant community development and seasonal changes in temperature and moisture on belowground properties. Results showed that plant species composition influenced soil chemistry, soil microbial community properties and soil microbial resistance and resilience. Soil from planted treatments generally showed reduced soil microbial resistance to drying compared to unplanted control soils. Soils from under T. repens showed a higher resistance and resilience than the soils from under P. lanceolata, and a higher resistance than soils from under L. perenne. We suggest that differences across soils in either resource limitation or soil microbial community structure may be responsible for these results. Plant species richness rarely affected soil microbial community properties or soil microbial resistance and resilience, despite having some significant effects on plant community biomass and soil nitrogen contents in some harvests. The effect that treatments had for most variables differed between harvests, suggesting that results can be altered by the stage of plant community development or by extrinsic environmental factors that varied with harvest timing. These results in combination show that soil microbial resistance and resilience was affected by plant community composition, and the time of measurement, but was largely unrelated to plant species richness.     

Resistance to change in goldfish

Resistance to change has been studied in several species such as humans, rats, and pigeons. We conducted two experiments using goldfish as subjects to examine the generality of the findings on resistance to change in a phylogenetically more primitive species. In Experiment 1, five goldfish (Carassius auratus) were trained on two-component multiple schedules with different variable-interval schedules in effect. When responding was disrupted by presenting free food during intercomponent intervals or by extinction, resistance to change was greater in the component with the higher reinforcement rates. In Experiment 2, identical variable-interval schedules were presented in two multiple-schedule components, but in one of the components response-independent food was delivered concurrently according to variable-time schedules. Baseline response rates were the same for both components, which is inconsistent with previous findings with other species that the addition of response-independent food decreases response rates. However, response rates in the component with added response-independent food showed the greater resistance to change, which is similar to findings in other species. The convergence of these results across various species confirms the generality of the findings on resistance to change.     

Resistance to change as a function of concurrent reinforcer magnitude

Six pigeons responded on two keys in each of three signalled multiple-schedule components, and resistance to disruption of responding on one (target) key by extinction and by response-independent food presented during inter-component blackouts was studied. Alternative reinforcement of different magnitudes was contingent on pecking a non-target key in two components, and in the third only the target response was reinforced. Resistance to change varied with the overall quantity of reinforcement in the component, regardless of whether reinforcers were contingent on the target or non-target response, but did not differ across the two key locations. These results using different magnitudes of reinforcement confirm previous findings using rate of reinforcement as the variable, and suggest that resistance to change is dependent on stimulus-reinforcer rather than response-reinforcer contingencies.     

Compensation of Root Suction Force within a Single

A modified refractometric method (compensation in sucrose solution) was used for measuring the suction force (water potential) of active roots ofFraxinas excelsior L. in pot experiments and in the field under natural humidity conditions in two soil types. It was shown that if one part of the root system was in soil with low humidity as compared with the remaining predominant part, the suction force of roots in the “dry” soil did not rise in proportion with the rise of the suction force of the drying soil but, due to gradients of suction forces between these root parts, water was translocated into roots in the “dry” soil and thus their suction force was decreased to the relatively lowest value of suction force within the whole root system. The suction force of roots surrounded by soil of humidity below the availability limit was in these cases very low or else its value changed in parallel with changes of the suction force of the remaining part of the root system. It was completely independent of the soil water content in which it existed. The root system is thus a hydrodynamic unit, the individual parts of which do not respond to changes in soil humidity separately by changes in their suction force, but rather in mutual relationship which is brought about by gradients in suction force. These gradients are the cause of water translocation between individual branches of the root system.     

Mechanochemical switching between growth and differentiation during fibroblast growth factor-stimulated angiogenesis in vitro: role of extracellular matrix

The angiogenic factor, basic fibroblast growth factor (FGF), either stimulates endothelial cell growth or promotes capillary differentiation depending upon the microenvironment in which it acts. Analysis of various in vitro models of spontaneous angiogenesis, in combination with time-lapse cinematography, demonstrated that capillary tube formation was greatly facilitated by promoting multicellular retraction and cell elevation above the surface of the rigid culture dish or by culturing endothelial cells on malleable extracellular matrix (ECM) substrata. These observations suggested to us that mechanical (i.e., tension-dependent) interactions between endothelial cells and ECM may serve to regulate capillary development. To test this hypothesis, FGF-stimulated endothelial cells were grown in chemically defined medium on bacteriological (nonadhesive) dishes that were precoated with different densities of fibronectin. Extensive cell spreading and growth were promoted by fibronectin coating densities that were highly adhesive (greater than 500 ng/cm2), whereas cell rounding, detachment, and loss of viability were observed on dishes coated with low fibronectin concentrations (less than 100 ng/cm2). Intermediate fibronectin coating densities (100-500 ng/cm2) promoted cell extension, but they could not completely resist cell tractional forces. Partial retraction of multicellular aggregates resulted in cell shortening, cessation of growth, and formation of branching tubular networks within 24-48 h. Multicellular retraction and subsequent tube formation also could be elicited on highly adhesive dishes by overcoming the mechanical resistance of the substratum using higher cell plating numbers. Dishes coated with varying concentrations of type IV collagen or gelatin produced similar results. These results suggest that ECM components may act locally to regulate the growth and pattern-regulating actions of soluble FGF based upon their ability to resist cell-generated mechanical loads. Thus, we propose that FGF-stimulated endothelial cells may be "switched" between growth, differentiation, and involution modes during angiogenesis by altering the adhesivity or mechanical integrity of their ECM.     

Resistance of soil biota and plant growth to disturbance increases with plant diversity

Plant diversity is critical to the functioning of ecosystems, potentially mediated in part by interactions with soil biota. Here, we characterised multiple groups of soil biota across a plant diversity gradient in a long‐term experiment. We then subjected soil samples taken along this gradient to drought, freezing and a mechanical disturbance to test how plant diversity affects the responses of soil biota and growth of a focal plant to these disturbances. High plant diversity resulted in soils that were dominated by fungi and associated soil biota, including increased arbuscular mycorrhizal fungi and reduced plant‐feeding nematodes. Disturbance effects on the soil biota were reduced when plant diversity was high, resulting in higher growth of the focal plant in all but the frozen soils. These results highlight the importance of plant diversity for soil communities and their resistance to disturbance, with potential feedback effects on plant productivity.     

Underwater locomotion in a terrestrial beetle: combination of surface de-wetting and capillary forces

For the first time, we report the remarkable ability of the terrestrial leaf beetle Gastrophysa viridula to walk on solid substrates under water. These beetles have adhesive setae on their feet that produce a secretory fluid having a crucial role in adhesion on land. In air, adhesion is produced by capillary forces between the fluid-covered setae and the substrate. In general, capillary forces do not contribute to adhesion under water. However, our observations showed that these beetles may use air bubbles trapped between their adhesive setae to walk on flooded, inclined substrata or even under water. Beetle adhesion to hydrophilic surfaces under water was lower than that in air, whereas adhesion to hydrophobic surfaces under water was comparable to that in air. Oil-covered hairy pads had a pinning effect, retaining the air bubbles on their feet. Bubbles in contact with the hydrophobic substrate de-wetted the substrate and produced capillary adhesion. Additional capillary forces are generated by the pad's liquid bridges between the foot and the substrate. Inspired by this idea, we designed an artificial silicone polymer structure with underwater adhesive properties.     

Root clumping may affect the root water potential and the resistance to soil-root water transport

We have appraised for clumped root systems the widely-accepted view that the resistance to water flux from soil to roots (‘soil resistance’) is low under most field conditions, so that root water potential would closely follow the mean soil water potential. Three root spatial arrangements were studied, simulating either the regular pattern generally assumed in models, or two degrees of root clumping frequently observed in the field. We used a numerical 2-dimensional model of water transfer which assumes a control of evapotranspiration by root signalling. Calculations were carried out at two evaporative demands and for two contrasting soil hydraulic properties. The rate of soil depletion, the timing of the reduction in evapotranspiration and the difference between root water potential and mean soil water potential were all affected by the root spatial arrangement, with a greater effect at high evaporative demand and low soil hydraulic conductivity. Almost all the soil water reserve was available to plants without reduction in evapotranspiration in the regular case, while only a part of it was available in clumped cases. In the regular case, calculated ‘soil resistances’ were similar to those calculated using Newman's (1969) method. Conversely they were higher by up to two orders of magnitude in clumped root spatial arrangements. These results place doubt on the generality of the view that ‘soil resistance’ is low under common field conditions. They are consistent with the results of field experiments, especially with recent data dealing with root-to-shoot communication.     

Tetracyclines and Tetracycline Resistance in Agricultural Soils: Microcosm and Field Studies

The influence of the use of antibiotics on the prevalence of resistance genes in the environment is still poorly understood. We studied the diversity of tetracycline and sulfonamide resistance genes as influenced by fertilization with pig manure in soil microcosms and at two field locations. Manure contained a high diversity of resistance genes, regardless of whether it stemmed from a farm operation with low or regular use of antibiotics. In the microcosm soils, the influence of fertilization with manure was clearly shown by an increase in the number of resistance genes in the soil after manuring. Spiking of the tetracycline compounds to the microcosms had only little additional impact on the diversity of resistance genes. Overall, the tetracycline resistance genes tet(T), tet(W), and tet(Z) were ubiquitous in soil and pig slurries, whereas tet(Y), tet(S), tet(C), tet(Q), and tet(H) were introduced to the microcosm soil by manuring. The diversity of tetracycline and sulfonamide [sul(1), sul(2), and sul(3)] resistance genes on a Swiss pasture was very high even before slurry amendment, although manure from intensive farming had not been applied in the previous years. The additional effect of manuring was small, with the tetracycline and sulfonamide resistance diversity staying at high levels for the complete growth season. At an agricultural field site in Germany, the diversity of tetracycline and sulfonamide resistance genes was considerably lower, possibly reflecting regional differences in gene diversity. This study shows that there is a considerable pool of resistance genes in soils. Although it is not possible to conclude whether this diversity is caused by the global spread of resistance genes after 50 years of tetracycline use or is due to the natural background in soil resistance genes, it highlights a role that environmental reservoirs might play in resistance gene capture.     

Influence of Dimensions of UHMW-PE Protuberances on Sliding Resistance and Normal Adhesion of Bangkok Clay Soil to Biomimetic Plates

A number of investigations into application of polymers for macro-morphological modification of tool surface have been carried out. These researches, with extensive stress on convex or domed protuberations as one of the widely used construction units, have tried to harness benefits from using polymers in agriculture. Ultra high molecular weight polyethylene （UHMW-PE） has proved an emerging polymer in its application to reduce soil adhesion. This research was conducted to study the effect of shape （flat, semi-spherical, semi-oblate, semi short-prolate and semi long-prolate） and dimensions （base diameter and dome height） on sliding resistance and normal adhesion of biomimetic plates. To incorporate both shape and size, a dimensionless ratio of height to diameter （HDR） was introduced to characterize the effect of construction unit＇s physique. Experiments were conducted in Bangkok clay soil with dry （ 19.8% d.b.）, sticky （36.9% d.b.） and flooded （60.1% d.b.） soil conditions respectively. Soil at sticky limit exhibited the highest sliding resistance （77.8 N） and normal adhesion （3 kPa to 7 kPa）, whereas these values were 61.7 N and 〈0.2 kPa in dry, and 53.7 N and 0.5 kPa to 1.5 kPa in flooded soil conditions. Protuberances with HDR ≤ 0.5 lowered sliding resistance by 10% - 30% and the same reduced normal adhesion by 10% - 60%. The amount of reduction in both sliding resistance and normal adhesion was higher in flooded soil. Lighter normal loads obviously produced lesser resistance and adhesion.     

Wheat Resistance to Spot Blotch Potentiated by Silicon

Spot blotch, caused by the fungus Bipolaris sorokiniana, is one of the most important diseases on wheat. The effects of silicon (Si) on this wheat disease were studied. Plants of wheat cultivars BR‐18 and BRS‐208 were grown in plastic pots containing Si‐deficient soil amended with either calcium silicate (+Si) or calcium carbonate (?Si). The content of Si in leaf tissue was significantly increased by 90.5% for the +Si treatment. There was no significant difference between Si treatments for calcium content, so variations in Si accounted for differences in the level of resistance to spot blotch. The incubation period was significantly increased by 40% for the +Si treatment. The area under spot blotch progress curve, number of lesions per cm² of leaf area, and real disease severity significantly decreased by 62, 36 and 43.5% in +Si treatment. There was no significant effect of Si on lesion size. The role played by total soluble phenolics in the increased resistance to spot blotch of plants from both cultivars supplied with Si was not clear. Plants from cultivar BR‐18 supplied with Si showed the highest values for concentration of lignin‐thioglycolic acid derivatives during the most advanced stages of fungus infection. Chitinase activity was high at the most advanced stages of fungus infection on leaves from both cultivars supplied with Si and may have had an effect on fungus growth based on the reduction of the components of resistance evaluated. Peroxidase activity was found to be high only at 96 h after inoculation of both cultivars supplied with Si. Polyphenoloxidase activity had no apparent effect on resistance regardless of Si treatments. Results revealed that supplying Si to wheat plants can increase resistance against spot blotch.     

Selective Insulin Resistance in Adipocytes

Aside from glucose metabolism, insulin regulates a variety of pathways in peripheral tissues. Under insulin-resistant conditions, it is well known that insulin-stimulated glucose uptake is impaired, and many studies attribute this to a defect in Akt signaling. Here we make use of several insulin resistance models, including insulin-resistant 3T3-L1 adipocytes and fat explants prepared from high fat-fed C57BL/6J and ob/ob mice, to comprehensively distinguish defective from unaffected aspects of insulin signaling and its downstream consequences in adipocytes. Defective regulation of glucose uptake was observed in all models of insulin resistance, whereas other major actions of insulin such as protein synthesis and anti-lipolysis were normal. This defect corresponded to a reduction in the maximum response to insulin. The pattern of change observed for phosphorylation in the Akt pathway was inconsistent with a simple defect at the level of Akt. The only Akt substrate that showed consistently reduced phosphorylation was the RabGAP AS160 that regulates GLUT4 translocation. We conclude that insulin resistance in adipose tissue is highly selective for glucose metabolism and likely involves a defect in one of the components regulating GLUT4 translocation to the cell surface in response to insulin.     

Passive and active reactions of embryonic tissues to the action of dosed mechanical forces

With the help of a suction manometric device, the relation between the deformation of Xenonus laevis embryo at the gastrula and neurula stages and the value of the applied force has been studied. Stiffness modules of embryonic tissues were in the order of several dozens of Pascal and they were inversely proportional during deformation from 40 to 20%. At the gastrula stage, a uniform or an increasing rate of expansion of the embryo body in the suction capillary with the diameter of approximately half that of the embryo was observed for 30 min after the action of the suction forces. The length of the stretched portion of the embryo correlates with the value of its deformation at the first minute. As a result of the expansion, the total body surface area of the deformed embryo increases more than twice compared to intact embryos. After expelling the embryo from the capillary, its surface reduced and the deformation became smoothened within 5 min, which indicates the existence of tensional force in the expanded embryo. These data confirm that, at the embryo gastrula stage, external mechanical forces do not only passively deform the embryo but also initiate the active expansion of the embryo which takes place at zero external force and overcomes the tensional resistance of tissues. The mechanism of active expansion and its link with the processes of normal morphogenesis are discussed.