Progress of Study on Oriented Growth of Carbon Nanotubes

Owing to unique structure and characteristics of carbon nanotubes, much more are attracted attentions since they were discovered. In recent years, carbon nanotubes have been successfully synthesized by various methods. Especially, highly aligned carbon nanotubes were grown by chemical vapor deposition (CVD) and the oriented growth of carbon nanotubes became realized, resulting in many applications of carbon nanotubes and researches on them. In the work, the methods and mechanisms of orientation growth of carbon nanotubes were reviewed, and it was analyzed and discussed that different methods influenced on the process of growing carbon nanotubes. Simultaneously, it was emphatically analyzed that catalyst particles affected on orientation growth of carbon nanotubes during their growth.     

Experimental Studies on Electrolyte-gated Carbon Nanotube Field Effect Transitors

Owing to unique structure and characteristic of carbon nanotubes, much more are attractions, especially in molecular elements, including field effect transitorsmade of carbon nanotubes. Carbon nanotube field effect transitors with electrolyte-gated are investgated. Carbon nanotubes on glass substrate in this study are fabricated by hot filament vapor deposition using Fe / Ni as catalyst. Optimized multi-walled carbon nanobute transistors are made with Ag contact electrodes, and the KCl solution is used as a gate. Experimental results show that the electrolyte-gated carbon nanotube transitors exhibited a good voltage-current characteristic. The transconductance is about 0.5 mA/V at 2 V. The results obtained are discussed.     

Recent Advances in Synthesizing Single-walled Carbon Nanotubes

The main synthesis of single-walled carbon nanotubes (SWCNTS) on a large scale and in higher purity is investigated. To analyse the characteristic of different synthesis and the major parameters whose variety influence the product. The kinds and ratio of carbon source and catalyst influence the preparation of SWCNTS obviously.The factors such as current and voltage,the kind of inert gases and pressure and the cooling rate of electrodes play important roles in synthesis of SWCNTS by arc discharges. The intensity of laser bean,environmental temperature,the kind and the velocity of flow of catalyst and the frequency and interval of impulse act important parts in SWCNTS produced by laser evaporation. The flow rate of carbon resource, the grain sizes of catalyst,reaction temperature,the gases pressure and flux and matrix materials etc play key parts in SWCNTS synthesized by chemical vapor deposition.     

Catalytic Mechanism of Ni Particles in the Formation of Single-Wall Carbon Nanotubes

Usually Ni_clusters are served as catalyst in the formed processo f the single_wall carbon nanotubes by CVD. Because the different surfaces of Ni_clusters have different activity,carbon atoms adsorbed in Ni_clusters (liquid states)will be diffused from low_activity surfaces of Ni_cluster to high_activity ones and be deposited. As a result,the caves of carbon atoms surrounding the Ni_clusters are formed and the single_wall carbon nanotubes are produced. In addition,Ni_atoms served as substitutional atoms always located in the furthest outside of the network of single_wall carbon nanotubes are produced. In addition, Ni_atoms served as substitutional atoms always located in the furthest outside of the network of single_wall carbon nanotubes,and play a role of stabilization in growth of nanotubes,and promot their growth. Therefore,the catalytic mechanism of Ni_clusters as catalyst is introduced,and different morphologies of single_wall carbon nanotubes are also exlained.     

Preparation and characterization of carbon cones by reaction plasma

Carbon cones are prepared on Si substrates film in plasma-enhanced hot filament chemical vapor deposition system using CH4, H2 and NH3 as the reaction gas, and the substrates are deposited with Ti and carbon film, respectively. Morphology and structure of the carbon cones are characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX)and micro-Raman spectroscopy. The SEM results indicate that the carbon cones are formed on the Si substrate deposited with carbon film. Furthermore, the EDX and Raman spectra indicate that the formed carbon cones are carbon nitride structure, which are composed of sp 3 C-N, sp 2 C and sp 2 C=N bonds. According to the mechanisms of sputtering and diffusion, the formation of carbon cones is analyzed. Simultaneously, the photoluminescence background in the Raman spectrum of carbon cones is analyzed, and results indicate that the carbon cone evolves from nonpolar carbon material to polarity carbon material due to the doping of nitrogen.     

森林生态系统土壤碳库对氮沉降的响应研究进展

大气氮沉降的不断加剧,改变了土壤理化性质,直接影响植物的生长与发育,间接影响了陆地生态系统碳库,进而可能改变全球气候变化进程。森林是陆地生态系统的主体,因此,弄清氮沉降如何影响森林生态系统碳库,对预测全球气候变化具有重要意义。笔者旨在详细分析氮沉降对森林生态系统土壤碳库输入和输出的影响,阐述氮沉降对森林生态系统凋落物分解、细根周转和土壤呼吸的影响研究进展和作用机制。截至目前,关于氮沉降对于陆地生态系统的影响研究报道较多,且国内外诸多学者也在森林生态系统土壤碳库对氮沉降的响应领域开展了较多试验研究,但多集中于碳输入和输出的总量分析,而对输入和输出各个组分的研究相对较少。笔者综述了国内外有关森林生态系统碳库输入和输出各组分对氮沉降响应的相关研究,为进一步揭示其响应机制和途径提供参考依据。     

芝麻饼肥与化肥不同比例配施对烟叶香气质量的影响

芝麻饼肥与化肥不同比例配施对不同叶位烤烟烟叶化学成分和香气成分含量、组成的影响及其作用机理的探讨，表明以50%芝麻饼肥+50%化肥处理使上、中、下部烟叶糖碱比都较适宜，化学成分协调，新植二烯、酮类、醛类等香气物质总含量明显提高，明显改善了烟叶的综合品质，表现为烟叶香气质纯净、香气量大、柔和、杂气小、烟气净、余味舒适、劲头适中、燃烧性好，总得分提高，显著减小了叶位之间的质量差异，因此，推荐河南省植烟区烤烟生产以50%芝麻饼肥+50%化肥配施为宜。     

欠发达地区农地利用碳排放时序特征及影响因素研究

农地碳排放研究对于区域农业可持续发展具有重要意义。笔者利用1996—2013年贵州省化肥、农药、农膜、农用柴油、翻耕、灌溉六大类碳源的相关数据,对贵州省18年间农地利用碳排放进行测算,并采用kaya恒等式对农地利用碳排放的影响因素进行分析。研究表明:(1)贵州省农地利用碳排放总量和碳排放强度均呈现持续上升的态势;(2)贵州省农地利用碳排放增速呈现波动的状态,且波动幅度较大;(3)化肥是最主要的碳排放源,其次为农膜和农用柴油;(4)生产效率因素、产业结构因素对贵州省农地利用碳排放具有抑制作用,经济水平、劳动力规模对农地利用碳排放具有促进作用。最后,本文对贵州省农地利用碳排放提出对策建议。     

Magnetoresistive Effect of Diamond Films

On the basis of F S thin theory and taking the scattering of lattice vibration and impurities into account, the conductivity and the magnetoresistance of p type semiconducting diamond films (strip sample) are derived in spherical energy band and parallel connection model for light hold band,heavy hole band and split off band of diamond by solving the Boltzmann equation in the relaxation time approximation,. The relations between the magnetoresistance and thickness of diamond films,magnetic field strength and mobility are given. The magnetoresistance is influenced differently by light hole band,heavy-hole band and split off band. The deviation of the magnetoresistance is small between thick diamond films and lump. Magnetoresistive effects relate closely with temperature,magnetic filed strength and mobility.     

PE包装对西兰花贮藏品质的影响

为了明确不同厚度PE袋包装对西兰花采后品质的影响,以未装袋的西兰花作为对照(CK),采用PE微孔袋以及厚度为20、30、40、50μm的PE袋对西兰花进行包装处理,置于(15±1)℃环境下存放,通过测定贮藏期间气体体积分数、感官评价、色差、失重率、硬度、可溶性固形物含量、VC含量、叶绿素含量、挥发性物质等指标,研究不同包装处理对西兰花贮藏品质的影响。结果表明,相比于CK组,各包装组可有效降低西兰花的失重率,防止其黄化,减缓叶绿素、VC含量和硬度的下降;且相比于其他包装组,厚度为20μm的PE袋处理能显著减缓叶绿素损失,维持西兰花的感官品质和固有风味。因此,西兰花在(15±1)℃条件下采用20μm PE袋包装处理效果较好。     

壳聚糖-甲基纤维素复合膜的制作研究与性能测定

研究不同比例的壳聚糖-甲基纤维素复合膜的制作,并对复合膜进行透光性、抗张强度、透湿系数、吸湿性、延伸率和水溶性等的测试。结果表明,纯膜的透明度高于复合膜;水蒸气透过系数则是复合膜大于纯膜;随着环境中湿度的增加,膜的吸湿性增大;随着膜中甲基纤维素含量的增加,水溶性随之增大;抗张强度随着甲基纤维素含量的增加而增大。     

乙醇缓释气体处理对草莓常温保鲜效果的影响

采用不同剂量（0、1．8、3．6、7．2g）的乙醇缓释剂处理新鲜草莓,用聚乙烯保鲜袋（180mm×280mm,厚度0．03mm）包装后。分别于室温（20±2）℃下避光贮藏7d,研究乙醇缓释气体处理对草莓保鲜效果的影响。结果表明．常温条件下．乙醇缓释气体处理能够有效抑制草莓的腐烂,延缓果实硬度、水分、VC含量和可滴定酸含量的下降．乙烯产量及呼吸强度在贮藏期内均显著小于对照。与传统的使用乙醇浸泡处理或乙醇熏蒸处理方法相比．采用缓释技术能够使极低剂量的乙醇气体持续缓慢地释放到贮藏空间内．在延长果实货架期的同时．能够避免传统方法处理时果实产生的类似酒精发酵的异味。使草莓保持正常的口感与风味。该方法操作简单,成本低廉．且安全无毒副作用,具有较高的推广应用价值。     

不同品种夏橙品质的评价分析

为了提高夏橙品系品质性状的选择效率,为夏橙的品质优化提供理论依据,以湖北宜昌秭归地区9个夏橙品系为材料,分析其物理特性（单果重、果形指数、果实硬度、果皮厚、果皮颜色、果汁颜色、水分）和化学特性指标（果实纤维、可溶性固形物、可滴定酸、固酸比和维生素C）之间的关系。结果表明,物理特性中单果重、果实硬度、果皮厚的变异系数较大,果汁颜色、果性指数变异系数较小;化学特性中果实纤维、水分、可溶性固形物、可滴定酸的品系间变异系数较大。9种品种间单果重、硬度和果实纤维差异显著,其余指标变化均不显著。主成分分析表明这16项指标反映的夏橙品质可用4个主成分来表示(累计贡献率达93.37%),并且各性状的贡献率集中。不同品种夏橙品质差异为夏橙品质选择改良提供了很好的借鉴作用,并为人们日常生活中合理消费夏橙提供理论依据。     

华北平原冬小麦生态系统齐穗期水碳通量日变化的非对称响应

陆地生态系统CO_2和水热通量变化特征及其环境控制机制是理解生态系统水碳耦合循环过程和模型开发的基础.农田生态系统水碳通量特征的研究对把握作物生产力水平和水分利用效率的高低具有重要意义.本研究基于涡度相关技术对华北平原冬小麦农田生态系统齐穗期水碳通量的日变化特征进行了分析.结果表明:以C_3作物冬小麦构成的农田生态系统晴天CO_2通量、水汽通量和冠层导度均存在明显的"午休"现象,"午休"的原因是晴天强光造成的"光抑制";CO_2通量对光合有效辐射呈米氏响应,其表观量子效率为0.002 997 mg/μmol,潜在最大碳通量为3.349 4 mg/(m~2·s);水汽通量和冠层导度与光合有效辐射之间均存在极显著线性关系,但在相同光合有效辐射下,下午的冠层导度明显小于上午,其原因在于同化产物的反馈抑制;下午的水汽通量明显大于上午,则主要受控于温度和VPD的变化.由于下午的水汽通量大于上午,而CO_2通量在上午和下午无明显差异,使得农田生态系统上午的水分利用效率明显高于下午.     

不同玉米品种在不同化控剂作用下穗部性状与产量的研究

为不同玉米品种寻找出其最适的化控剂,以6 种不同的玉米杂交品种为主因素,以5 种不同的玉米化控剂处理为次因素,采用随机区组设计研究不同化控剂处理对玉米穗部性状与产量的影响。每个小区随机抽取10 穗考种,测其穗部性状,用其籽粒产量折算其群体产量。研究结果表明：在相同品种下,矮壮素较其他化控剂处理对穗部性状的影响显著,高玉金不适合对试验进行化控处理,产量与轴粗、穗粗和行粒数成正比关系;在不同化控剂处理下穗重、穗粒重与穗长与玉米群体产量密切相关,百粒重对品种的产量影响很小,‘协玉5 号’适合通过化控剂处理来提高穗部性状的表现。不同的玉米品种应采用不同的化控剂,没有一种化控剂可以同时满足各种品种。     

烟田生态系统碳收支研究

农业生态系统碳平衡对评估陆地生态系统的源和汇具有重要意义,针对烤烟生长及管理的特殊性,研究烟田生态系统碳收支,为提升烟田管理及农业碳汇估算提供依据。本研究以定位试验为平台,以单施化肥处理为研究对象,于2015—2017年观测了烤烟生长季的碳收支。研究结果表明,烤烟生物量平均为(5832.10±537.32) kg hm?2;烟株碳含量平均为(42.14±0.05)%,累积固碳量为(2459.25±233.78) kg hm?2。烤烟根系碳占烟株碳比例较高,平均为24.94%。烤烟生长季湿沉降碳达到了115.32 kg hm?2,干沉降碳量为6.54 kg hm?2,两者占根系碳的20.01%。烟生长季碳输出总量为2464.98kghm?2,其中CO2排放碳占碳支出的98.99%,径流损失碳占支出的0.76%,淋溶损失碳占支出的0.25%。烟田生态系统对大气而言是弱碳汇,碳汇量116.13kghm?2。虽然烤烟固碳总量相对较低,但其根系对土壤碳贡献却相对较高。     

冬小麦不同粒型品种茎叶组织结构与籽粒形成关系的研究

本研究观察了冬小麦不同粒型４个品种茎秆，旗叶结构以及籽粒的形成过程。结果发现：穗下节的机械组织，输和同化组织随粒型不同而有显著差异，其中以大粒型兰考８６－７９维管组织最发达，而中大粒型豫麦２５茎壁及其内同化组织最大；旗叶则随粒型增大其，叶催厚度增加，维管束数目增多及主脉结构发达。不同粒型品种灌浆强度的差异在籽粒进入灌浆盛期最为     

不同施肥处理对黑土碳素及活性有机质的影响

以东北黑土区所处的特殊自然条件为背景,以黑土为研究对象,研究了长期不同施肥处理对黑土碳素及活性有机质的影响。结果表明：各施肥处理对黑土总碳、黑土有机碳和黑土活性有机质的积累均起到积极作用;有机肥与化肥配施处理较NPK处理培肥效果更佳;有机肥与化肥配施处理中,有机肥施用量对黑土总碳、黑土有机碳和黑土活性有机质的影响不明显。     

海南省不同区域农业可持续发展评价研究

为准确把握海南省典型地区农业可持续发展状况,诊断识别各地区农业可持续发展的障碍性因子,通过基于欧氏距离的农业可持续发展评价理论对海南省农业可持续发展情况进行评价。选取海南省海口市、三亚市和琼中县的2000~2015年数据展开分析,结果表明：(1)海口市农业可持续发展指数总体变化呈下降趋势,可持续发展指数介于0.44~0.52;三亚市农业可持续发展指数呈现上升趋势,可持续发展指数处于0.31~0.59之间;琼中县农业可持续发展指数呈上升趋势,但2007年之后可持续发展指数呈波动发展,可持续发展指数处于0.27~0.31之间。三个地区均属于低可持续发展状态。(2)肥料、农药、农村灾害、农技和农村劳力等指标是海南省低可持续发展的主要原因。各地区应该因地制宜,制定符合自身情况的政策和方针。(3)评价结果较为准确地反映了海南省农业系统情况。在上述研究结果基础上,研究其时空变化特征,提出未来推动该地区农业可持续发展举措,以期为海南省农业可持续发展提供参考。     

不同生态系统凋落物分解对氮沉降的响应综述

文章旨在综合不同生态系统类型凋落物对于氮沉降的响应,完善凋落物分解与氮沉降的相互作用机理。氮是构成蛋白质的主要成分,对动物体内氮平衡起重要作用,同时对植物茎叶的生长和果实的发育也有重要影响,是与产量最密切的营养元素。但近几十年来,由于工业、农业、畜牧业等产生越来越多的含氮化合物排向大气,研究表明大气氮沉降增加将对生态系统中的动植物及微生物产生直接或间接的影响,而氮沉降将通过影响微生物的生理生化过程改变凋落物的分解速率,进而影响生态系统的物质循环和能量流动过程。20世纪70年代以来,氮沉降的研究已有诸多报道,国内外很多学者也对氮沉降对凋落物影响的研究进行过评述,但大多基于对某一个陆地生态系统类型或者凋落物降解过程、产量分布、影响因素等进行评价,而氮沉降对不同类型的生态系统凋落物分解的影响还鲜有报道。笔者归纳了氮沉降对不同类型陆地生态系统（森林、草原、荒漠、城市和农田）凋落物分解的影响,为进一步研究不同类型凋落物分解过程对氮沉降的响应提供参考。