Advanced Electro-active Dry Adhesive Actuated by an Artificial Muscle Constructed from an Ionic Polymer Metal Composite Reinforced with Nitrogen-doped Carbon Nanocages

An advanced electro-active dry adhesive,which was composed of a mushroom-shaped fibrillar dry adhesive array actuated by an Ionic Polymer Metal Composite (IPMC) artificial muscle reinforced with nitrogen-doped carbon nanocages (NCNCs),was developed to imitate the actuation of a gecko's toe.The properties of the NCNC-reinforced Nafion membrane,the electromechanical properties of the NCNC-reinforced IPMC,and the related electro-active adhesion ability were investigated.The NCNCs were uniformly dispersed in the 0.1 wt％ NCNC/Nafion membrane,and there was a seamless connection with no clear interface between the dry adhesive and the IPMC.Our 0.1 wt％ NCNC/Nafion-IPMC actuator shows a displacement and force that are 1.6-2 times higher than those of the recast Nafion-IPMC.This is due to the increased water uptake (25.39％) and tensile strength (24.5 MPa) of the specific 3D hollow NCNC-reinforced Nafion membrane,as well as interactions between the NCNCs and the sulfonated groups of the Nafion.The NCNC/Nafion-IPMC was used to effectively actuate the mushroom-shaped dry adhesive.The normal adhesion forces were 7.85 mN,12.1 mN,and 51.7 mN at sinusoidal voltages of 1.5 V,2.5 V,and 3.5 V,respectively,at 0.1 Hz.Under the bionic leg trail,the normal and shear forces were approximately 713.5 mN (159 mN·cm-2) and 1256.6 mN (279 mN·cm-2),respectively,which satisfy the required adhesion.This new electro-active dry adhesive can be applied for active,distributed actuation and flexible grip in robots.     

In Situ,Fast, High‐Temperature Synthesis of Nickel Nanoparticles in Reduced Graphene Oxide Matrix

For the first time, a fast heating–cooling process is reported for the synthesis of carbon‐coated nickel (Ni) nanoparticles on a reduced graphene oxide (RGO) matrix (nano‐Ni@C/RGO) as a high‐performance H₂O₂ fuel catalyst. The Joule heating temperature can reach up to ≈2400 K and the heating time can be less than 0.1 s. Ni microparticles with an average diameter of 2 µm can be directly converted into nanoparticles with an average diameter of 75 nm. The Ni nanoparticles embedded in RGO are evaluated for electro‐oxidation performance as a H₂O₂ fuel in a direct peroxide–peroxide fuel cell, which exhibits an electro‐oxidation current density of 602 mA cm^?2 at 0.2 V (vs Ag/AgCl), ≈150 times higher than the original Ni microparticles embedded in the RGO matrix (micro‐Ni/RGO). The high‐temperature, fast Joule heating process also leads to a 4–5 nm conformal carbon coating on the surface of the Ni nanoparticles, which anchors them to the RGO nanosheets and leads to an excellent catalytic stability. The newly developed nano‐Ni@C/RGO composites by Joule heating hold great promise for a range of emerging energy applications, including the advanced anode materials of fuel cells.     

桃江县毛竹林生态系统碳储量及其空间分布

采用标准地调查和生物量实测方法,研究了湖南省桃江县毛竹林生态系统生物量、碳含量、碳储量及空间分布格局。结果表明,不同年龄毛竹林生态系统总生物量分别为:28.147、30.889 t/hm~2和57.763 t/hm~2,其中竹林层生物量为20.254、25.036、55.685 t/hm~2,各器官生物量均以竹竿最高,占器官生物量的63.0%以上。不同年龄毛竹各器官碳平均含量为0.466—0.483 g C/g;灌木层碳含量为0.474—0.489 g C/g;草本层为0.472—0.490 g C/g;死地被物层为0.213—0.276 g C/g;土壤层有机碳含量为14.790—34.503 g C/g。各年龄毛竹林生态系统总碳储量分别为131.273、139.089 t/hm~2和167.817 t/hm~2,其中植被层碳储量为13.627—28.419 t/hm~2,占系统总碳储量的9.935%—16.935%;死地被物为0.307—0.420 t/hm~2,占0.234%—0.265%;土壤层为117.339—138.978 t/hm~2,占82.815%—89.799%。毛竹林生态系统碳储量分布格局为:土壤层植被层死地被物层。研究结果可为深入研究毛竹林的碳平衡提供基础数据。     

植物挥发性气体(VOCs)研究进展

植物挥发性气体(VOCs)在植物一植食性昆虫-天敌三级营养关系、植物间信息传递及适应性改变上都发挥着重要作用.植物释放VOCs具特异性、系统性、时序性与节律性等特点,VOCs主要在寄主选择行为、产卵行为、求偶行为、引来昆虫夭敌干涉等方面影响植食性昆虫.VOCs-介导的植物间信息传递作用包括4个过程:"释放者"植物合成及释放气体、气体在空气中的运输、气体在植物表面的吸附及"接收者"植株对气体信号的感知.收集VOCs的方法主要有吸附-溶剂洗脱法和吸附-热脱附法.     

Responses of growth and litterfall production to nitrogen addition treatments from common shrublands in Mt. Dongling,Beijing, China

Aims The shrublands of northern China have poor soil and nitrogen (N) deposition has greatly increased the local soil available N for decades. Shrub growth is one of important components of C sequestration in shrublands and litterfall acts as a vital link between plants and soil. Both are key factors in nutrient and energy cycling of terrestrial ecosystems, which greatly affected by nitrogen (N) addition (adding N fertilizer to the surface soil directly). However, the effects and significance of N addition on C sequestration and litterfall in shrublands remain unclear. Thus, a study was designed to investigate how N deposition and related treatments affected shrublands growth related to C sequestration and litterfall production of Vitex negundo var. heterophylla and Spiraea salicifolia in Mt. Dongling region of China.
Methods A N enrichment experiment has been conducted for V. negundo var. heterophylla and S. salicifolia shrublands in Mt. Dongling, Beijing, including four N addition treatment levels (control (N₀, 0 kg N·hm^-2·a^-1), low N (N₁, 20 kg N·hm^-2·a^-1), medium N (N₂, 50 kg N·hm^-2·a^-1) and high N (N₃, 100 kg N·hm^-2·a^-1)). Basal diameter and plant height of shrub were measured from 2012-2013 within all treatments, and allometric models for different species of shrub’s live branch, leaf and root biomass were developed based on independent variables of basal diameter and plant height, which will be used to calculate biomass increment of shrub layer. Litterfall (litterfall sometimes is named litter, referring to the collective name for all organic matter produced by the aboveground part of plants and returned to the surface, and mainly includes leaves, bark, dead twigs, flowers and fruits.) also was investigated from 2012-2013 within all treatments.
Important findings The results showed 1) mean basal diameter of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were increased by 1.69%, 2.78%, 2.51%, 1.80% and 1.38%, 1.37%, 1.59%, 2.05% every year; 2) The height growth rate (the shrub height relative growth rate is defined with the percentage increase of plant height) of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were 8.36%, 8.48%, 9.49%, 9.83% and 2.12%, 2.86%, 2.36%, 2.52% every year, respectively. Thee results indicated that N deposition stimulated growth of shrub layer both in V. negundo var. heterophylla and S. salicifolia shrublands, but did not reach statistical significance among all nitrogen treatments. The above-ground biomass increment of shrub layer in the V. negundo var. heterophylla and S. salicifolia shrublands were 0.19, 0.23, 0.14, 0.15 and 0.027, 0.025, 0.032, 0.041 t C·hm^-2·a^-1 respectively, which demonstrated that short-term N addition had no significant effects on the accumulation of C storage of the two shrublands. The litter production of the V. negundo var. heterophylla and S. salicifolia communities in 2013 were 135.7 and 129.6 g·m^-2 under natural conditions, respectively. Nitrogen addition promoted annual production of total litterfall and different components of litterfall to a certain extent, but did not reach statistical significance among all nitrogen treatments. Above results indicated that short-term fertilization, together with extremely low soil moisture content and other related factors, lead to inefficient use of soil available nitrogen and slow response of shrublands to N addition treatments.     

红壤退化地森林恢复后土壤有机碳对土壤水库库容的影响

亚热带红壤侵蚀退化地实施生态恢复后生物生产力恢复迅速,但土壤尤其是土壤水库的功能并未获得同步恢复,导致土壤水库对于降水和地表径流的调节能力低下,区域性洪涝灾害和季节性干旱依然突出。采用野外调查和室内分析相结合的方式,研究了南方红壤侵蚀退化地典型植被恢复类型(马尾松与阔叶树复层林、木荷与马尾松混交林、阔叶混交林)0—60cm土层土壤水库各种库容差异,以及土壤总有机碳和活性有机碳密度分布特征,采用典型相关分析方法对土壤水库库容与土壤有机碳密度两组指标进行相关分析。结果表明:随着土层深度的增加,各森林恢复类型死库容呈上升趋势,兴利库容和最大有效库容呈下降趋势,防洪库容变化趋势不明显,木荷与马尾松混交林兴利库容略高。不同森林恢复类型同一土层土壤总有机碳密度均表现为马尾松与阔叶树复层林木荷与马尾松混交林阔叶混交林,而活性有机碳密度则以阔叶混交林最大。典型相关分析表明,土壤有机碳水平对土壤水库库容的增加具有显著的因果影响关系(P=0.01),其中对有机碳水平起到主导性贡献作用的是水溶性有机碳。因此,对于退化红壤地森林恢复初期,可通过适当密植和立体种植,提高林地生物量和土壤碳密度,并在马尾松等先锋树种针叶林分中补植阔叶乔灌木,以增加土壤活性有机碳含量,增大土壤水库容量,从而有利于土壤水库结构和功能以及退化生态系统的快速恢复。     

Metal‐Organic Frameworks for Carbon Dioxide Capture and Methane Storage

In the global transition to a sustainable low‐carbon economy, CO₂ capture and storage technology still plays a critical role for deep emission reduction, particularly for the stationary sources in power generation and industry. However, for small and mobile emission sources in transportation, CO₂ capture is not suitable and it is more practical to use relatively clean energy, such as natural gas. In these two low‐carbon energy technologies, designing highly selective sorbents is one of the key and most challenging steps. Toward this end, metal‐organic frameworks (MOFs) have received continuously intensive attention in the past decades for their highly porous and diversified structures. In this review, the recent progress in developing MOFs for selective CO₂ capture from post‐combustion flue gas and CH₄ storage for vehicle applications are summarized. For CO₂ capture, several promising strategies being used to improve CO₂ adsorption uptake at low pressures are highlighted and compared. In addition, the conventional and novel regeneration techniques for MOFs are also discussed. In the case of CH₄ storage, the flexible and rigid MOFs, whose CH₄ storage capacity is close to the target set by U.S. Department of Energy are particularly emphasized. Finally, the challenge of using MOFs for CH₄ storage is discussed.     

Dry conditions disrupt terrestrial–aquatic linkages in northern catchments

Aquatic ecosystems depend on terrestrial organic matter (tOM) to regulate many functions, such as food web production and water quality, but an increasing frequency and intensity of drought across northern ecosystems is threatening to disrupt this important connection. Dry conditions reduce tOM export and can also oxidize wetland soils and release stored contaminants into stream flow after rainfall. Here, we test whether these disruptions to terrestrial–aquatic linkages occur during mild summer drought and whether this affects biota across 43 littoral zone sites in 11 lakes. We use copper (Cu) and nickel (Ni) as representative contaminants, and measure abundances of Hyalella azteca, a widespread indicator of ecosystem condition and food web production. We found that tOM concentrations were reduced but correlations with organic soils (wetlands and riparian forests) persisted during mild drought and were sufficient to suppress labile Cu concentrations. Wetlands, however, also became a source of labile Ni to littoral zones, which was linked to reduced abundances of the amphipod H. azteca, on average by up to 70 times across the range of observed Ni concentrations. This reveals a duality in the functional linkage of organic soils to aquatic ecosystems whereby they can help buffer the effects of hydrologic disconnection between catchments and lakes but at the cost of biogeochemical changes that release stored contaminants. As evidence of the toxicity of trace contaminant concentrations and their global dispersion grows, sustaining links among forests, organic soils and aquatic ecosystems in a changing climate will become increasingly important.     

Anthropogenic N deposition increases soil organic matter accumulation without altering its biochemical composition

Accumulating evidence indicates that future rates of atmospheric N deposition have the potential to increase soil C storage by reducing the decay of plant litter and soil organic matter (SOM). Although the microbial mechanism underlying this response is not well understood, a decline in decay could alter the amount, as well as biochemical composition of SOM. Here, we used size‐density fractionation and solid‐state ¹³C‐NMR spectroscopy to explore the extent to which declines in microbial decay in a long‐term (ca. 20 yrs.) N deposition experiment have altered the biochemical composition of forest floor, bulk mineral soil, as well as free and occluded particulate organic matter. Significant amounts of organic matter have accumulated in occluded particulate organic matter (~20%; oPOM); however, experimental N deposition had not altered the abundance of carboxyl, aryl, alkyl, or O/N‐alkyl C in forest floor, bulk mineral soil, or any soil fraction. These observations suggest that biochemically equivalent organic matter has accumulated in oPOM at a greater rate under experimental N deposition, relative to the ambient treatment. Although we do not understand the process by which experimental N deposition has fostered the occlusion of organic matter by mineral soil particles, our results highlight the importance of interactions among the products of microbial decay and the chemical and physical properties of silt and clay particles that occlude organic matter from microbial attack. Because oPOM can reside in soils for decades to centuries, organic matter accumulating under future rates of anthropogenic N deposition could remain in soil for long periods of time. If temperate forest soils in the Northern Hemisphere respond like those in our experiment, then unabated deposition of anthropogenic N from the atmosphere has the potential to foster greater soil C storage, especially in fine‐texture forest soils.