Growth of thin chemically bonded diamondlike films by ion beam deposition

Carbon films with a diamondlike structure that are chemically bonded to surfaces have been deposited by means of low-energy C(+) ion beams. When mass-selected C(+) beams at energies in the range from 20 to 200 electron volts impinge on atomically clean surfaces, the first carbon monolayer grows as a carbide structure that is chemically bonded to the surface. As deposition continues, the structure evolves over the next several atomic layers into a diamondlike structure. These pure carbon films are strongly adhered to the surface through the carbide bonds, which also provide for an intimate interface. There are significant applications for such films, particularly as insulators and doped semiconductors.     

Synthesis of ultra-incompressible superhard rhenium diboride at ambient pressure

The quest to create superhard materials rarely strays from the use of high-pressure synthetic methods, which typically require gigapascals of applied pressure. We report that rhenium diboride (ReB2), synthesized in bulk quantities via arc-melting under ambient pressure, rivals materials produced with high-pressure methods. Microindentation measurements on ReB2 indicated an average hardness of 48 gigapascals under an applied load of 0.49 newton, and scratch marks left on a diamond surface confirmed its superhard nature. Its incompressibility along the c axis was equal in magnitude to the linear incompressibility of diamond. In situ high-pressure x-ray diffraction measurements yielded a bulk modulus of 360 gigapascals, and radial diffraction indicated that ReB2 is able to support a remarkably high differential stress. This combination of properties suggests that this material may find applications in cutting when the formation of carbides prevents the use of traditional materials such as diamond.     

"数字地球"与"数字农业"

“数字地球”就是信息化的地球，它包括全部地球资料的数字化、网络化、智能化和可视化的过程在内。数字地球的核心思想是用数字化手段整体性地解决地球问题并最大限度地利用信息资源。“数字农业”是实施“数字地球”战略的重要组成部分。本文分别论述了“数字地球”、“数字农业”的源起、概念、内涵、特点及中国的发展战略。     

Carbon structures with three-dimensional periodicity at optical wavelengths

Porous carbons that are three-dimensionally periodic on the scale of optical wavelengths were made by a synthesis route resembling the geological formation of natural opal. Porous silica opal crystals were sintered to form an intersphere interface through which the silica was removed after infiltration with carbon or a carbon precursor. The resulting porous carbons had different structures depending on synthesis conditions. Both diamond and glassy carbon inverse opals resulted from volume filling. Graphite inverse opals, comprising 40-angstrom-thick layers of graphite sheets tiled on spherical surfaces, were produced by surface templating. The carbon inverse opals provide examples of both dielectric and metallic optical photonic crystals. They strongly diffract light and may provide a route toward photonic band-gap materials.     

Artificially structured thin-film materials and interfaces

The ability to artificially structure new materials on an atomic scale by using advanced crystal growth methods such as molecular beam epitaxy and metal-organic chemical vapor deposition has recently led to the observation of unexpected new physical phenomena and to the creation of entirely new classes of devices. In particular, the growth of materials of variable band gap in technologically important semiconductors such as GaAs, InP, and silicon will be reviewed. Recent results of studies of multilayered structures and interfaces based on the use of advanced characterization techniques such as high-resolution transmission electron microscopy and scanning tunneling microscopy will be presented.     

Current issues and problems in the chemical vapor deposition of diamond

Current issues and problems in the chemical vapor deposition (CVD) of diamond are those which relate to its characterization, its nucleation on foreign surfaces, the question of its formation in preference to the other phases of solid carbon (for example, graphite, chaoite, or lonsdaleite), why different morphologies and crystallographic orientations (textures) are seen in different experiments or with different parameters in the same experiment, and finally whether well-crystallized metastable phases can be obtained by CVD in other material systems or are only a peculiarity of carbon chemistry. Whether a given carbon coating is justly described as diamond has been such an issue, and coatings should clearly show evidence for diamond by x-ray diffraction and Raman spectroscopy before the claim of diamond is made. Experimental results have not been consistent in many cases, and much work remains to be done before an accurate assessment can be made of the technological impact of the development.     

极早熟李品种"红美丽"的组织培养与快速繁殖

[目的]建立极早熟李优良品种"红美丽"的组织培养快繁技术体系。[方法]以半木质化的嫩枝茎段为外植体,研究基本培养基对腋芽萌发的影响。以试管苗为试材,研究基本培养基及不同浓度的植物生长调节物质对试管苗增殖及生根的影响。[结果]以半木质化的嫩枝茎段为外植体进行腋芽的启动培养,QL比MS明显提高腋芽萌发率;试管苗增殖培养以WPM最佳,其次为MS和QL;不同生长素浓度上的生根率无显著差异,但较高浓度(2 mg/L)IBA上的平均单株生根数显著高于较低浓度(1 mg/L)IBA上的。最佳生根培养基为MS+2 mg/L IBA+0.5 mg/L NAA,生根率为83.5%。[结论]该研究为"红美丽"李无病毒苗木的生产及利用生物技术育种方法进行品种改良奠定了研究和技术基础。     

中国古典园林对"日本庭园"的影响

日本庭园以再现自然风景为基调,与中国园林有共通之处,但是其细部表现技法有所不同。本研究从land-scape architecture的3个展开阶段,即从(1)concept making(构思力)(2)landscape planning(规划力)(3)landscape design(造景力)3个水准方面,将中国园林的思想和方法对日本造园和庭园产生的影响进行了论述。其结论是,作为人类理想目标建造Garden具有意义,从美好安全舒适有水有绿适于生存的景观和空间角度来看,可说是“造园思想”水准上日中是共通的,日本全面接受了中国原理。但是,当地各自不同的自然条件、政治、社会经济文化条件的日中之间,技术水平即意匠、材料、施工等“造园方法”迥然不同,可认为是“中国园林”和“日本庭园”典型的庭园样式发展,对世界造园形式的多样化作出了贡献。     

如何认定原因自由行为的着手

原因自由行为是为给那些由于行为人故意或过失地使自己陷入无责任能力,然后在无责任能力状态下,实施犯罪行为提供处罚依据的一种理论。然而,这一理论从一引进来就引起了学者们的激烈争论。对于这一理论,如何认定其着手,学者们意见分歧,本文认为在解决着手的认定之前,首先应当明确原因自由行为的处罚对象。原因自由行为中原因行为的可罚性。能否可以通过立法的方式赋予原因行为具有实行行为性,这是解决原因自由行为着手认定的关键所在。     

羊肚菌驯化栽培试验初报

研究了两个羊肚菌种在6种栽培料上菌丝的生长情况和菌核的培养特征。结果表明,普通羊肚菌在菌丝生长和菌核形成方面都优于黑脉羊肚菌;以北芪渣为辅料的栽培料效果最佳,菌丝生长快,菌核形成多,其次是杨树根土和草木灰栽培料。     

Prediction of new low compressibility solids

An empirical model and an ab initio calculation of the bulk moduli for covalent solids are used to suggest possible new hard materials. The empirical model indicates that hypothetical covalent solids formed between carbon and nitrogen are good candidates for extreme hardness. A prototype system is chosen and a first principles pseudopotential total energy calculation on the system is performed. The results are consistent with the empirical model and show that materials like the prototype can have bulk moduli comparable to or greater than diamond. It may be possible to synthesize such materials in the laboratory.     

扁桃品种“Nonpareil Mission”离体繁殖技术研究

以新疆喀什、和田地区栽培的引种自美国的扁桃品种“NonpareilMission”成株树上的幼嫩枝条为试材,成功地进行了离体繁殖。经试验研究筛选出“NonpareilMission”两品种最适增殖培养基分别为:MS BA0.8mg/L IBA0.1mg/L GA30.5mg/L;MS BA1.0mg/L IBA0.2mg/L GA30.8mg/L。利用100mg/LIBA对增殖后的嫩茎基部浸泡处理,然后在不含任何生长素的1/2MS培养基上进行生根和生长。最适浸泡时间及初期黑暗培养时间分别为60min和14d,获得了较理想的生根效果,受试品种试管苗的移栽驯化应在各阶段中逐渐降低湿度,适应外界条件可保证较高的成活率。     

文学现代化的误区与“拿来主义”

中国文学现代化的努力已一个世纪有余,然而文坛经典之作却屈指可数;尤其是近十年来,伴随着话语转型而来的却是“失语”的焦虑;“颠覆”“消解”之后却不见有效的重构。具体表现在:一,我们的文艺理论一直在西方的文艺理论里徜徉;二,我们的创作在一味地模仿西方的现代形式。显然,我们的现代化己走入误区。鲁迅先生的拿来主义是照亮我们走出误区的圣火。     

The mechanism of diamond nucleation from energetic species

A model for diamond nucleation by energetic species (for example, bias-enhanced nucleation) is proposed. It involves spontaneous bulk nucleation of a diamond embryo cluster in a dense, amorphous carbon hydrogenated matrix; stabilization of the cluster by favorable boundary conditions of nucleation sites and hydrogen termination; and ion bombardment-induced growth through a preferential displacement mechanism. The model is substantiated by density functional tight-binding molecular dynamics simulations and an experimental study of the structure of bias-enhanced and ion beam-nucleated films. The model is also applicable to the nucleation of other materials by energetic species, such as cubic boron nitride.     

“循环经济”在啤酒企业中的应用研究

"循环经济"是一种以资源的高效利用和循环利用为原则,以低消耗、高效率、低排放为基本特征的经济增长方式。通过介绍"循环经济"的内容,指出在啤酒企业实施"循环经济"的必要性,探讨啤酒企业实施"循环经济"的具体做法。     

Polycrystalline CVD Diamond Films with High Electrical Mobility

Advances in the deposition process have led to dramatic improvements in the electronic properties of polycrystalline diamond films produced by chemical vapor deposition (CVD). It is now possible to produce CVD diamond with properties approaching those of IIa natural diamonds. The combined electron-hole mobility, as measured by transient photoconductivity at low carrier density, is 4000 square centimeters per volt per second at an electric field of 200 volts per centimeter and is comparable to that of the best single-crystal IIa natural diamonds. Carrier lifetimes measured under the same conditions are 150 picoseconds for the CVD diamond and 300 picoseconds for single-crystal diamond. The collection distance at a field of 10 kilovolts per centimeter is 15 micrometers for the CVD diamond as compared to 30 micrometers for natural diamonds. The electrical qualities appear to correlate with the width of the diamond Raman peak. Also, although the collection distance at the highest fields in the films nearly equals the average grain size, there is no evidence of deleterious grain boundary effects.     

"Big" growth hormone components from human plasma: decreased reactivity demonstrated by radioreceptor assay

Plasma as well as pituitary immunoreactive human growth hormone (HGH) comprises at least two discrete components which have been designated as "big" HGH and "little" HGH. Using a newly developed radioreceptor assay, which depends on the ability of a substance to compete with labeled HGH for binding sites on cultured human lymphocytes, we find that the big HGH component from both normal and acromegalic subjects has much less activity in the radioreceptor assay than in the radioimmunoassay, whereas the little HGH component has simnilar activity in both assays.     

新时期我国农村“增长性贫困”的预防对策

在界定＂增长性贫困＂概念的基础上,通过分析新时期我国农村的经济现状,找出我国农村居民经济弱势的成因。分析了市场消费经济对＂增长性贫困＂的影响,指出我国农村较快经济增长下可能导致的＂增长性贫困＂现象,一是城乡居民收入差距不断拉大,物价持续上扬,农村居民市场消费能力不足;二是财富集中程度较高,农村居民大多数收入偏低。提出了预防农村＂增长性贫困＂的对策建议：改革户籍制度,让农村居民获取自由迁移权利,增加地位收益;统筹城乡发展,加强农业和农村基础设施建设,实现公共资源公平配置;科学有效进行收入再分配,健全农村社会保障体系,缩小城乡收入差距,把比较优势转化为竞争优势,以规避＂增长性贫困＂。     

Cometary particles: thin sectioning and electron beam analysis

Thin sections (500 to 1000 angstroms thick) of individual micrometeorites (5 to 15 micrometers) have been prepared with an ultramicrotome equipped with a diamond knife. Electron microscopic examination of these sections has revealed the internal structures of chondritic micrometeorites, and a subset of highly porous, fragile particles has been identified. Delicate meteoritic materials such as these are characteristic of debris from cometary meteors.     

栅极偏压对纳米金刚石薄膜沉积过程的影响

在HFCVD系统中施加栅极偏压和衬底偏压,采用双偏压成核和栅极偏压生长的方法成功制备了高质量的纳米金刚石薄膜.采用显微Raman高分辨率SEM和AFM等现代理化分析手段分析纳米金刚石膜的微结构,结果表明双偏压显著促进了金刚石的成核密度,平均晶粒尺寸在20 nm以内.试验观察和理论分析表明栅极偏压促进了热丝附近的等离子体浓度,提高了衬底附近的碳氢基团和氢原子浓度,提高了金刚石的成核密度、在保持晶粒的纳米尺寸的同时保持了较高的成膜质量和较低的生长缺陷.