Active MoS_(2)-based electrode for green ammonia synthesis

Nitrogen electro-reduction under mild conditions is one promising alternative approach of the energyconsuming Haber-Bosch process for the artificial ammonia synthesis.One critical aspect to unlocking this technology is to discover the catalysts with high selectivity and efficiency.In this work,the N_(2)-to-NH_(3)conversion on the functional MoS_(2)is fully investigated by density functional theory calculations since the layered MoS_(2)provides the ideal platform for the elaborating copies of the nitrogenase found in nature,wherein the functionalization is achieved via basal-adsorption,basal-substitution or edge-substitution of transition metal elements.Our results reveal that the edge-functionalization is a feasible strategy for the activity promotion;however,the basal-adsorption and basal-substitution separately suffer from the electrochemical instability and the NRR inefficiency.Specifically,MoS_(2)functionalized via edge W-substitution exhibits an exceptional activity.The energetically favored reaction pathway is through the distal pathway and a limiting potential is less than 0.20 V.Overall,this work escalates the rational design of the high-effective catalysts for nitrogen fixation and provides the explanation why the predicated catalyst have a good performance,paving the guidance for the experiments.

Fluctuating Asymmetry of Elopes lacerta (Valenciennes, 1847) Otoliths in the Western African Waters

The importance of this study lies in the in-depth exploration of the ecological diversity of otoliths in Elopes lacerta, based on the analysis of data from 260 individuals collected from various sites, including the Porto Novo lagoon, the Cotonou lagoon, Lake Nokou, and the Atlantic coast in southern Benin. The results highlight significant variations in otolith morphology, establishing relevant links with the biological parameters of the fish at each site. Exploration of the asymmetry between the right and left sides reveals notable distinctions between these two aspects. Analysis of otolith shape thus emerges as a valuable tool for discriminating between stocks and providing a better understanding of ecological variations. The local diversity observed highlights the crucial importance of implementing adaptive management strategies to ensure effective conservation of the species and its habitat.

氮气吸附法表征杨木应拉木的孔隙结构

在常规解剖特征分析的基础上,采用氮气吸附法对杨木应拉木的比表面积及孔径分布等孔结构参数进行研究,并通过解析氮气吸附等温线判断孔隙的形状。结果表明:杨木应拉木BET比表面积为21.9m2.g-1,是对应木的13倍;杨木应拉木试样具有完好的介孔特征(孔径2～50nm),并具有一定量的微孔和大孔;内部存在"墨水瓶"状和狭缝状孔隙,孔径为5nm的孔体积分布密度最大,孔径在4～7nm的孔体积占总孔体积的74.4%,孔径超过15nm的孔体积占总体积的10.8%。杨木应拉木中大量存在的中孔孔隙可归因于应拉木木纤维中的厚壁胶质层。

聚苯胺衍生物膜修饰电极的电化学和催化性质

采用聚-2,5-二甲氧基苯胺(PDMAn)、聚邻甲苯胺(POT)膜修饰电极,以异丙醇(i-P)氧化为模型反应,研究功能性膜电极的电催化性能.两种聚合物的伏安行为都表现为两对氧化还原峰;与镀铂的Pt电极比较,Pt金属化的PDMAn和POT修饰电极,大大提高了i-P氧化电流密度,而且随着循环次数增加,氧化电流不断增大,表明功能性膜修饰电极具有较高的催化活性.POT修饰电极在较低的铂含量下就表现出对i-P的强烈催化活性,而且对低浓度i-P的氧化,具有较高的响应灵敏度;此外POT还具有良好的环境稳定性,可望成为一种具有实际应用前景的电化学传感器.

基于生物气候因子聚类的植物群组划分及其中国生物群区模拟

本研究基于10′×10′空间分辨率运用GIS软件对中国植被分布地理配准数字化,提取获得196个优势植物的地理分布数据以及内插相关的气候因子,运用分位数函数计算获得各个植物地理分布的气候阈值;在此基础上采用生物气候群组(BAGs)的分类方法,对196个优势植物气候因子数据进行聚类分析,同时结合中国植被的地理分布特征,最后划分出29个BAG组,包括13个乔木组(6个常绿阔叶和2个落叶阔叶群组,4个常绿针叶和1个落叶针叶群组)、10个灌木组(5个常绿灌木和5个落叶灌木群组)和6个草本组。本研究的BAGs划分是建立在较高空间分辨率和定量气候因子阈值的基础上,因此,通过计算获得BAGs气候阈值(包括每日温度变化幅度、地表霜冻频率、月均温度、月降雨量、相对湿度、日照时数和>5℃年积温等),运用生物圈碳循环CARAIB模型,模拟出中国19个生物群区的现代潜在分布。模拟结果较好地表达了中国植被类型的地理分布,尤其较详细地展示了热带、亚热带、温带和高原地区的不同植被类型地理分布格局,但由于东北地区、西部草原以及热带原生植被受人类活动严重干扰,使得模拟结果比该地区的原生植被地理分布的实际面积偏大。总体而言,本研究获得的29个生物气候群组对模拟现代生物群区分布提供了理想的分类依据,其气候阈值也是进行过去和未来生物群区模拟的重要参照数据。

取代聚苯胺的聚集态结构

环取代基及掺杂对聚苯胺分子链结构产生影响的同时也对大分子聚集态结构产生影响.通过对聚合物膜的XRD、SEM研究,表明在所合成的环取代聚苯胺衍生物中,聚合物的结晶性依POT(聚邻甲苯胺)、PDMAn(聚-2,5-二甲氧基苯胺)、PmClAn(聚间氯苯胺)顺序增加;与本征态的比较,质子酸掺杂后聚合物的结晶性有所提高.POT基本上表现出了非晶聚合物的性质;PDMAn具有同质多晶的结构特征,但结晶度较低;PmClAn表现出了典型高分子晶体性质,符合单斜晶系的特征(晶胞参数为a=0.679nm,b=2.304nm,c=0.5734nm,α=90°,β=100.9°,γ=90°).采用HyperChem程序包中的MM+分子力学方法对1H-NMR和XRD实验结果进行结构优化,确定了苯式结构/醌式结构为3/2的PmClAn大分子链的构象.

闽江下游全新世孢粉记录的植被与环境变化

为了揭示闽江下游闽侯盆地第四纪沉积环境演变与人类活动历史,对闽江下游闽侯盆地庄边山遗址附近的FZ5钻孔进行了孢粉、硅藻分析。结果表明:闽侯盆地全新世海侵初始发生时间约为9 000 cal.a B.P.,至7 500cal.a B.P.达到最大海侵范围,晚全新世海退的发生时间在闽侯盆地大约为1 900 cal.a B.P.。孢粉分析证实了当地早中全新世温暖的亚热带气候以及浓密的常绿阔叶林植被。在7 500―1 900 cal.a B.P.之间无论植被覆盖还是气候环境均比较稳定,高海平面时期的适宜气候以及海湾环境也有利于当地以渔猎经济方式为主的新石器文化(昙石山文化)的兴起和发展。自1 900 cal.a B.P.以后,孢粉组合突变为以先锋植物芒萁属(Dicranopteris)、禾本科(Poaceae)、松属(Pinus)等类型为主,揭示了当地植被受到人类农业刀耕火种的影响而发生显著变化。高含量的禾本科花粉(含一定数量的水稻)仅在剖面上部明显增加这一事实,证实了闽侯和福州一带水稻种植的大面积发展始于距今1 900 a前后。

环取代基对金属化聚苯胺衍生物膜修饰电极性能的影响

通过比较聚 2 ,5 -二甲氧基苯胺 (PDMAn)、聚邻甲基苯胺 (POT)和聚间氯苯胺 (Pm Cl An)膜修饰电极的氧化还原电位、沉积在这 3种聚合物上的铂微粒的表面形态与晶面取向以及异丙醇在分散 Pt微粒的聚苯胺膜修饰电极上的氧化行为 ,从电子效应和立体效应探讨了聚合物电化学性质与环取代基的关系以及不同聚合物基质对 Pt沉积机理和电极催化性能的影响 .结果表明 ,在硫酸溶液中 PDMAn膜修饰电极的氧化还原电位最负、 POT次之、 Pm Cl An最正 .Pt在 PDMAn和 POT膜上的电沉积机理与在 Pm Cl An膜上的不同 ,聚合物膜上沉积的 Pt微粒呈现 (2 0 0 )晶面择优取向 ,其中 POT膜上择优取向度最大 ,PDMAn次之 ,Pm Cl An最小 .异丙醇在金属化聚合物膜电极上的氧化电位取决于聚苯胺的本质 ,在 POT膜修饰电极上异丙醇的电氧化主要发生在 POT的活性电位区 ,而在 PDMAn与 Pm Cl An膜上的电氧化则主要发生在 Pt上的氧化电位区 ,说明聚合物膜不仅作为 Pt微粒的分散介质 ,而且本身可能产生催化作用 .

CARAIB陆地碳循环模型研究进展及其应用

陆地生态系统碳循环是全球变化研究中的重要组成部分,多种模型已用于陆地生态系统碳循环的模拟。文中着重论述了陆地生物圈碳循环模型CARAIB的原理、方法及其应用和最新进展。CARAIB模型主要是基于叶面光合作用子模型、冠层子模型和木质呼吸作用3个子模型的耦合,应用大气环流模式气候数据模拟出生态系统碳存储量和生物群区分布。介绍了欧洲利用植物数字化地理配准数据库重新划分植物群组(BAGs)的方法,比较BAGs与传统的植物功能型(PFTs)划分在方法上的差异,根据植物群组应用CARAIB模型进行生物群区分布模拟,并提出利用CARAIB模型模拟我国陆地碳循环和生物群区分布的可行性,为研究中国植被对气候变化的响应模型和预测提供区域尺度的新方法。

ATHYS模型及其在巢湖流域丰乐河水文过程模拟中的应用

以巢湖典型支流丰乐河流域为例,利用分布式水文模型ATHYS对流域降雨—径流过程进行模拟,以期为丰乐河流域水土保持、防洪、水资源利用和非点源污染防治等提供科学依据。ATHYS模型将流域分为大小相同的空间小单元,以库模型进行产流计算,以滞后演算法(lag and route)方法进行汇流计算,并以Nash and Sutcliffe指数作为检验模拟结果的标准,模拟流域出口断面日径流量,初步分析流域径流实测值与模拟值的年际变化。模型模拟结果表明,在率定期和验证期模拟与实测径流量的总Nash and Sutcliffe值(Nash值)都可以达到0.80以上,相关系数均可达0.89以上。除了部分峰值和基流,模型能较好地模拟丰乐河的径流过程。模型模拟径流总量的相对误差在率定期为23.1%,验证期为34.6%。流域降雨量、径流量的年内、年际变化均比较明显,径流实测值和模拟值的年际变化也都比较大。综合来看,模型比较适用于所研究流域的日径流模拟。

^13CH4分子ν3振动带空气和氮气加宽系数温度依赖性研究

采用中红外波段连续可调谐二极管激光器和自行研制的低温吸收池,测量了温度为296 K,252 K,213K,173 K时,3.38μm附近13CH4分子的四条跃迁谱线的氮气和空气加宽光谱;首次通过实验获得空气和氮气对13CH4分子的碰撞加宽系数,以及谱线加宽系数的温度依赖系数.实验过程中,利用Voigt线型对所测量的光谱进行拟合.实验结果表明,氮气和空气对13CH4分子的碰撞诱导加宽系数随温度的降低而增大;相同温度下,氮气对13CH4分子的碰撞加宽系数普遍大于空气加宽系数.实验数据为地球和外星体大气遥感探测提供了依据.

Probing CENP-E function in chromosome dynamics using small molecule inhibitor syntelin

Dear Editor, Chromosome movements during mitosis are orches- trated primarily by the interaction of spindle microtu- bules with the kinetochore [1], the site for attachment of spindle microtubules to the centromere. The kinetochore has an active function in chromosomal segregation through microtubule-based motors located at or near it [1-2]. CENP-E is a microtubule-based kinesin motor [3],

Polyorogenic evolution of the Paleoproterozoic Trans-North China Belt--New insights from the Luliangshan-Hengshan-Wutaishan and Fuping massifs

The Trans-North China Belt （TNCB） is a Paleoproterozoic collisional orogen （ca. 1.9-1.8 Ga） responsible for the amalgamation of the North China Craton. Detailed field works in Liiliangshan, Hengshan, Wutaishan and Fuping massifs where the belt is well exposed, allow us to draw a new tectonic map and crustal-scale cross sections. The available petrologic, radiometric, geochronologic data are integrated in a geodynamic evolution scheme for this orogen. The Low Grade Mafic Unit （LGMU） is interpreted as an ophiolitic nappe rooted in a suture zone located in the western part of the Lüliangshan. This ophiolitic nappe overthrusts to the SE upon the Orthogneiss-Volcanites Unit （OVU） that consists of a bimodal volcanic-sedimentary series metamorphosed under amphibolite facies conditions intruded by calcalkaline orthogneiss. The OVU is a composite Neoarchean-Paleoproterozoic magmatic arc developed during two stages （ca. 2500 and 2100 Ma） upon a continental basement corresponding to the western extension of the Neoarchean Fuping massif The OVU overthrusts to the SE the Fuping massif along the Longquanguan shear zone. This stack of nappes, coeval with an amphibolite facies metamorphism, is dated at ca. 1880 Ma. Subsequently, the metamorphic series experienced a widespread migmatization at 1850 Ma and was intruded by post-orogenic plutons dated at 1800 Ma. The weakly to unmetamorphosed Hutuo Supergroup unconformably overlies the metamorphosed and ductilely deformed units （OVU and LGMU）, but it is also involved in a second tectonic phase developed in subsurface conditions. These structural features lead us to question the ca. 2090 Ma age attributed to the Hutuo supergroup. Moreover, in the Fuping massif several structural and magmatic lines of evidence argue for an earlier orogenic event at ca. 2100 Ma that we relate to an older west-directed subduction below the Fuping Block. The Taihangshan Fault might be the location of a possible suture zone between the Fuping Block and an eastern one. A geodynamic model at variance with previous ones, is proposed to account for the formation of the TNCB. In this scheme, three Archean continents, namely from west to east, the Ordos, Fuping and Eastern Blocks are separated by the Lüliang and Taihang Oceans. The closure of the Taihang Ocean at ca. 2100 Ma by westward subduction below the Fuping Block accounts for the arc magmatism and the 2100 Ma orogeny. The second collision at 1900-1880 Ma between the Fuping and Ordos blocks is responsible for the main structural metamorphic and magmatic features of the Trans-North China Belt.

Cyclin A2:At the crossroads of cell cycle and cell invasion

Cyclin A2 is an essential regulator of the cell division cycle through the activation of kinases that participate to the regulation of S phase as well as the mitotic entry. However,whereas its degradation by the proteasome in mid mitosis was thought to be essential for mitosis to proceed,recent observations show that a small fraction of cyclin A2 persists beyond metaphase and is degraded by autophagy. Its implication in the control of cytoskeletal dynamics and cell movement has unveiled its role in the modulation of Rho A activity. Since this GTPase is involved in both cell rounding early in mitosis and later,in the formation of the cleavage furrow,this suggests that cyclin A2 is a novel actor in cytokinesis. Taken together,these data point to this cyclin as a potential mediator of cell-niche interactions whose dysregulation could be taken as a hallmark of metastasis.

通向地幔之旅

在人类首次尝试地幔钻探50周年之际,Damon Teagle和Benoit Ildefonse表示,曾经的科幻现在有可能变成现实。

Role of Aedes aegypti and Aedes albopictus during the 2011 dengue fever epidemics in Hanoi, Vietnam

Objective: To record the human cases of dengue fever(DF) and investigate the Aedes mosquito species circulating during the Hanoi 2011 DF epidemics. Methods: 24 different outbreak points were recorded in 8 districts between August and December 2011. Results: 140 patients were hospitalized following dengue diagnostic with a predominance of males(59.3%) and the 15-34 age class. Only DENV-1(11.27%) and DENV-2(88.73%) serotypes were detected in human samples. Mosquito sampling performed in and around patients households revealed the predominance of Aedes aegypti(95.15%) versus Aedes albopictus(4.85%). There is a positive correlation between the population density of Aedes aegypti and the number of human cases and duration of outbreaks. Conclusions: This was not observed for Aedes albopictus. 3 pools of Aedes aegypti were positive with dengue virus, two with DENV-1 and one with DENV-2.

Maternal environment and seed size are important for successful germination and seedling establishment of Pterocarpus erinaceus (Fabaceae)

Seed size and the growth environment are important variables that influence seed germination, growth and biomass of seedlings and future tree harvest and should thus be taken into account in agroforestry and reforestation programmes for endangered species like Pterocarpus erinaceus. In the present study, to assess seedling germination and vigour in P. erinaceus as a function of seed size in two environments, 1080 seeds and 360 seedlings were evaluated at two separate sites in Côte d'Ivoire. The results show that large seeds had very high germination rates (up to 100%) and produced more vigorous plants better able to adapt to climate change. The maternal environment and seed size had a significant influence on seed germination (P < 0.05) and seedling development (P < 0.05) and biomass (P < 0.05). Seedlings were most successful at the site with a humid tropical climate (Daloa). Seedling leaves had the same resistance regardless of seed size and study site, but leaf moisture content was more stable in seedlings grown from medium and small seeds. These results will help guide conservation strategies for the species and are key factors for rural populations, loggers, and forest management structures for the silviculture of this species.

Interactive roles of geometrical distribution and geomechanical deformation of fracture networks in fluid flow through fractured geological media

In this study,the combined effects of geometrical distribution and geomechanical deformation of fracture networks on fluid flow through fractured geological media are investigated numerically.We consider a finite-sized model domain in which the geometry of fracture systems follows a power-law length scaling.The geomechanical response of the fractured rock is simulated using a hybrid finitediscrete element model,which can capture the deformation of intact rocks,the interaction of matrix blocks,the displacement of discrete fractures and the propagation of new cracks.Under far-field stress loading,the locally variable stress distribution in the fractured rock leads to a stress-dependent variable aperture field controlled by compression-induced closure and shear-induced dilatancy of rough fractures.The equivalent permeability of the deformed fractured rock is calculated by solving for the fracture-matrix flow considering the cubic relationship between fracture aperture and flow rate at each local fracture segment.We report that the geometrical connectivity of fracture networks plays a critical role in the hydromechanical processes in fractured rocks.A well-connected fracture system under a high stress ratio condition exhibits intense frictional sliding and large fracture dilation/opening,leading to greater rock mass permeability.However,a disconnected fracture network accommodates much less fracture shearing and opening,and has much lower bulk permeability.We further propose an analytical solution for the relationship between the equivalent permeability of fractured rocks and the connectivity metric(i.e.percolation parameter)of fracture networks,which yields an excellent match to the numerical results.We infer that fluid flow through a well-connected system is governed by traversing channels(forming an“in parallel”architecture)and thus equivalent permeability is sensitive to stress loading(due to stress-dependent fracture permeability),whilst fluid flow through a disconnected system is more ruled by matrix(linking isolated clusters“in series”)and has much less stress dependency.

Steinernema tbilisiensis sp. n. （Nematoda： Steinernematidae）--A New Species of Entomopathogenic Nematode from Georgia

A new species of entomopathogenic nematode （EPN）, Steinernema tbilisiensis sp. n. is described. The species was isolated from soil samples of the deciduous forest located in the Tbilisi area. Morphological and morphometric data as well as phylogenetic analysis show that S. tbilisiensis sp. n. belongs to the group S. affine/intermedium. S. tbilisiensis sp. n. has been attributed to the group S. affine/intermedium on the basis of spicule and gubernaculum structure. The new species differs from other species of S. affine/intermedium group in the following diagnostic characters： the spicule of S. tbilisiensis sp. n. is the smallest and the gubernaculum of S. tbilisiensis sp. n. is shorter than other species of the S. affine/intermedium group. Infective juveniles （IJs） of S. tbilisiensis sp. n. are distinguished by a relatively long body （L = 866 pm）, the position of excretory pore （EP = 72 ram）, the length of the esophagus （ES = 140 ~tm） and the length of the anal body width （ABW = 25μm）. IJs ofS. tbilisiensis sp. n. have four lateral lines like S. beddingi, but the number of lines is six in S. affine, S. sichuanense and S. intermedium. Also the analysis of rDNA （28S and ITS） gene sequences depicts this Steinernema species as a distinct and unique entity. The symbiotic bacteria of S. tbilisiensis sp. n. was isolated and found to be Xenorhabdus bovienii using a multigene approach.

The Effect of Four Abiotic Factors on Macro-Anatomical Markers Development in <i>Parkia biglobosa</i>, Jack, R. Br., 1830 (Fabaceae) Crown

Interpretation of primary growth markers (modules) is neglected in sustainable resource management processes, yet it opens up prospects for long time series on tree crown development, necessary for their characterization in the current context of climate change. This study aimed to assess the morphological variation of crown shoots in Parkia biglobosa in the face of a changing environment. Axis growth modules of 420 individuals of different ages were retrospectively analyzed in the presence or absence of shading during the wet and dry seasons in seven localities in Cote d’Ivoire. The results showed that the developmental environment of individuals did not influence the growth modules dimensions (P > 0.05). However, module size remained significantly different between locations (P < 0.05). The southern part of the gradient is still favourable and has priority for the establishment of permanent plots. The modules morphology differs from the youngest to the oldest individuals (P < 0.05). The rainy season remains the ideal period for the implementation of agroforestry reforestation programmes based on this species (P < 0.05). Parkia biglobosa is a monochasial sympod (Pseudo-monopod) with a relay axis that follows the Paul Champagnat architectural model in the young stage, and transits to the Wilhelm Troll model later in the adult and old stage. This information contributes to the understanding of the functioning of crown and the adaptation of this species to a varying environment. It could guide choice of suitable environment and ideal genotype for the implementation of a reforestation or agroforestry programme based on Parkia biglobosa.