中国东部沿海地带人地关系状态分析

作为中国现代社会经济发展的主体发动机,东部沿海地区人地关系的演进状态和趋势不仅决定着地区自身而且决定着整个国家可持续发展的基本取向。有鉴于此,本文试图通过人地关系对应公式进行东部沿海地区人地关系演进状态的总体评价。评价的结果表明:第一,与中西部相比,东部沿海地区人地关系演进的实际紧张状态严峻的多,人地关系演进系数达到了2.13 (表观);第二,在地区人地关系的演进过程中,经济活动和人口集聚起着决定影响,其中尤以经济活动的作用最为关键,其贡献度达到75%;第三,未来人地关系状态的协调和改善主要取决于地区自身资源环境基础的扩展和改造能力。

人地关系时空特性分析

人地关系是一个既涉及自然过程又涉及社会过程的综合概念,它是人文地理学研究的主题。从时间角度看,人地关系的演化可分为5个阶段:混沌阶段,原始共生阶段,人类对环境的顺应阶段、大规模改造阶段和人地协调共生阶段。在人地关系演进过程中,"人"通过技术手段改变了人地关系,并且"人"与"地"是密不可分的,人类对人地关系的认识也是与特定的生产力相适应的。根据区域间人地系统要素空间流的性质和方向,区际关系可分为封闭式、掠夺式、转嫁式、互补式等4种类型,当前的人地矛盾主要表现在全球尺度、国家尺度和局部地域3个不同尺度上。为协调区际人地关系,在优化区内人地关系和公平原则条件下,应强调共同利益和跨地区补偿的理念。

企业合作在我国区域发展中的作用

改革开放以来,随着社会主义市场经济体制的逐步建立和完善,我国区域发展取得很大成就。但区域发展差异也不断加大,这在一定程度上违背了区域发展的公平性原则。为了实现区域协调发展和全国共同繁荣,我国开始实施均衡发展战略,希望通过加强东西部之间的区域合作来推动欠发达地区的经济发展,在市场经济体制下,企业成为区域经济活动的主体,区域合作主要通过企业合作来完成。本文分析了企业合作形成的动因,并总结出四种不同的企业合作模式,认为企业合作对于地区创新网络形成、区域产业结构转移、区域投资扩散和缩小区域发展差异具有重要意义。

沿海地区人地关系演化及优化分析

人地关系是人类社会同周围环境之间的相互关系 ,在不同时,随着人类社会的发展表现特征不同。本文以沿海地区“人”与“地”之间矛盾的产生、发展以及追求协调的历史过程为线索 ,将人地关系的发展变化历程划分为混沌阶段、原始和谐阶段、矛盾发展阶段、矛盾激化调整四个阶段。影响人地关系的因素较多 ,自然因素主要是地形、气候、地理位置、自然资源等 ,人为因素主要包括人口的急剧增长以及人类各种不合理的破坏性活动。从人地关系演化的历史过程 ,可知人地关系的发展是一个动态的过程 ,针对沿海地区的实际情况 ,沿海地区应突出以下几个方面以优化人地关系 :①利用中国加入世贸组织为契机 ,深化对外开放 ;②通过生态工作建设、产业结构调整、城市化等实现社会经济、资源与环境的协调发展 ;③大力发展海洋经济 ,以缓解陆上资源与环境的压力

中国区域可持续发展评价指标体系及态势分析

本文提出了一套包括基础系统、协调系统与潜力系统在内的区域可持续发展评价体系,旨在以基础—过程—潜能为主线,资源、经济、社会、生态环境为基本要素单元,并结合外部介入因素对一个地区的可持续发展进行评价,并据此对世纪之交我国的区域可持续发展态势与对策进行系统的分析与探讨。

中国电力资源结构及空间布局优化研究

电力资源是我国的重要能源 ,对于维持经济快速发展和改善人民生活具有重要的保障作用。从世界其它国家发展看 ,发电用能源占一次能源比重呈不断上升趋势 ,在新世纪 ,我国发电用能源占一次能源比重也将不断上升。我国电力生产始终保持了较高的增长速度 ,并形成了以火电为主的发电结构 ,电网互联初具规模。但是 ,与发电资源禀赋结构特点相比 ,我国电力资源在结构和空间布局上还面临一系列问题 :如电源结构不合理、水电发展滞后、水能资源空间分布和开发力度不匹配以及电网互联进展缓慢等 ,特别是水电资源丰富的优势还没有充分发挥出来 ,电力资源结构和空间布局亟待调整优化。针对上述问题 ,该文提出了电力资源结构和空间布局调整优化对策 :优化电源结构 ,加大对西南地区水电资源开发力度、积极拓宽水电建设融资渠道和促进电网互联 ,这对于促进我国电力资源优化配置和生态环境改善都具有十分重要的意义

西北地区水资源安全的生态系统途径

我国西北地区是资源型缺水地区,对水资源进行科学、有效的管理无疑是该地区可持续发展的核心问题之一。在分析了生态系统管理的概念、特点、对于自然资源管理的意义,以及影响西北地区水资源安全性的生态学原因之后,提出了西北地区确保水资源安全的生态系统途径。包括:建立以流域为单元的水资源生态系统管理模式;充分利用市场机制,完善水资源管理模式;以水资源承载力和水资源安全为基础,进行西北地区的生态环境建设;加强水生态环境管理,避免因水污染造成更加严重的水危机。

Fabrication and characterization of uniform Fe3O4 octahedral micro-crystals

Uniform Fe3O4 octahedral microcrystals with perfect appearance have been successfully synthesized by a Triton X100-assisted polyol process. During the polyols process for the preparation of Fe3O4 octahedra. the introduction of Triton X100 decreases significantly the needed concentration of NaOH. The results show that Fe3O4 octahedra are composed of eight triangular sheets, which are equilateral triangles. The edge size of Fe3O4 octahedron is about 4 mu m. The magnetic properties of Fe3O4 octahedral particles were evaluated on a SQUID magnetometer at room temperature.

Ferrimagnetic and semiconducting CaCu3Fe2Sb2O12 by first principles

CaCu3Fe2Sb2O12 is mechanically stable, thermodynamically stable at pressures above 18 GPa. Both GGA and GGA + U methods predict that it is a ferrimagnetic semiconductor with Fe3+ in high spin state (S = 5/2). The coupling of Fe-Cu is antiferromagnetic, while that of Cu-Cu is ferromagnetic. The calculated total spin moment is 6.17 mu(B).

Preparation of novel silver-gold bimetallic nanostructures by seeding with silver nanoplates and application in surface-enhanced Raman scattering

Novel silver-gold bimetallic nanostructures were prepared by seeding with silver nanoplates in the absence of any surfactants. During the synthesis process, it was found that the frameworks of silver nanoplates were normally kept though the basal plane of silver nanoplates became rugged. The real morphology of these nanostructures depended on the molar ratio of gold ions to the seed particles. When the molar ratio of gold ions to silver atoms increased from 0.5 to 4, porous or branched silver-gold bimetallic nanostructures could be made. The growth mechanism was qualitatively discussed based on template-engaged replacement reactions and seed-mediated deposition reactions. Due to the unusual structures, they exhibited interesting optical properties. Moreover, they were shown to be an active substrate for surface-enhanced Raman scattering measurements.

Synthesis and properties of novel fluorinated poly(phenylene-co-imide)s

A new class of high-performance materials, fluorinated poly(phenylene-co-imide)s, were prepared by Ni(0)-catalytic coupling of 2,5-dichlorobenzophenone with fluorinated dichlorophthalimide. The synthesized copolymers have high molecular weights ((M) over bar (W)= 5.74 x 10(4)-17.3 x 10(4) g center dot mol(-1)), and a combination of desirable properties such as high solubility in common organic solvent, film-forming ability, and excellent mechanical properties. The glass transition temperature (T(g)s) of the copolymers was readily tuned to be between 219 and 354 degrees C via systematic variation of the ratio of the two comonomers. The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 66.7-266 MPa, 2.7-13.5%, and 3.13-4.09 GPa, respectively. The oxygen permeability coefficients (P-O2) and permeability selectivity of oxygen to nitrogen (P-O2/P-N2) of these copolymer membranes were in the range of 0.78-3.01 barrer [1 barrer = 10(-10) cm(3) (STP) cm/(cm(2) center dot s center dot cmHg)] and 5.09-6.2 5, respectively. Consequently, these materials have shown promise as engineering plastics and gas-separation membrane materials.

Preparation of CeO2-ZrO2 ceramic fibers by electrospinning

Electrospinning was employed to fabricate polymer-ceramic composite fibers from solutions containing poly(vinyl pyrrolidone) (PVP), Ce(NO3)(3)(.)6H(2)O and ZrOCl2-8H(2)O. Upon firing the composite fibers at 1000 degrees C, Ce(0.67)Zr(0.33)O(2)fibers with diameters ranging from 0.4 to 2 mu m were synthesized. These fibers exhibit strong resistance to sintering. They still have specific surface area around 11.8 m(2)/g after being heated at 1000 degrees C for 6 h.

Direct electrochemistry behavior of Cytochrome c on silicon dioxide nanoparticles-modified electrode

A newfangled direct electrochemistry behavior of Cytochrome c (Cyt c) was found on glassy carbon (GC) electrode modified with the silicon dioxide (SiO2) nanoparticles by physical adsorption. A pair of stable and well-defined redox peaks of Cyt c ' quasi-reversible electrochemical reaction were obtained with a heterogeneous electron transfer rate constant of 1.66 x 10(-3) cm/s and a formal potential of 0.069 V (vs. Ag/AgCl) (0.263 V versus NHE) in 0.1 mol/L pH 6.8 PBS. Both the size and the amount of SiO2 nanoparticles could influence the electron transfer between Cyt c and the electrode. Electrostatic interaction which is between the negative nanoparticle surface and positively charged amino acid residues on the Cyt c surface is of importance for the stability and reproducibility toward the direct electron transfer of Cyt c. It is suggested that the modification of SiO2 nanoparticles proposes a novel approach to realize the direct electrochemistry of proteins.

Synthesis and characterization of beta-diketiminate terbium complex

The terbium complex supported by beta-diketiminate was synthesized and structurally characterized. Due to an efficient energy transfer from the ligand to the central Tb3+, this complex shows a strong emission corresponding to Tb3+5D4-F-7(J) (J = 6,5,4,3) transitions, with D-5(4)-F-7(5) (550 nm) green emission as the most prominent group. The decay behavior of Tb3+ luminescence depends strongly on the excitation wavelengths.

BCNU-loaded PEG-PLLA ultrafine fibers and their in vitro antitumor activity against glioma C6 cells

The purpose of the present study was to develop implantable BCNU-toaded poly(ethylene glycol)poly(L-lactic acid) (PEG-PLLA) diblock copolymer fibers for the controlled release of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). BCNU was well incorporated and dispersed uniformly in biodegradable PEG-PLLA fibers by using electrospinning method. Environmental Scanning Electron Microscope (ESEM) images indicated that the BCNU-loaded PEG-PLLA fibers looked uniform and their surfaces were reasonably smooth. Their average diameters were below 1500 nm. The release rate of BCNU from the fiber mats increased with the increase of BCNU loading amount. In vitro cytotoxicity assay showed that the PEG-PLLA fibers themselves did not affect the growth of rat Glioma C6 cells. Antitumor activity of the BCNU-loaded fibers against the cells was kept over the whole experiment process, while that of pristine BCNU disappeared within 48 h. These results strongly suggest that the BCNU/PEG-PLLA fibers have an effect of controlled release of BCNU and are suitable for postoperative chemotherapy of cancers.