技术进步与就业增长

现代失业理论主要包括:由经济周期引起的周 期性失业,与谋求满意度更高的岗位相联系的摩擦 性失业,以及由于分工的发展,代表着先进技术的大 规模机器的运用,使得劳动力被解雇的结构性失 业。对技术进步的就业效应分析,相关的研究大体 反映出两种思路:一方面,是秉承古典经济学的思 想,直接分析技术进步的就业效应,着眼于技术

用马赛克形貌装饰法研究碗形分子柱状向列相的向错和分子指向矢分布

选用香兰素为原料, 采用传统的三聚成环法, 合成了两种碗形CTV 系衍生物—— CTV-1 和CTV-2, 前者的外围基团是—OCH3 和—OCH2CH3, 后者的外围基团是—OCH3 和—OCH2COOCH3. 两种碗形CTV 分子均是热致液晶, 呈现向列相典型的粒状织构和单微区的均匀织构, 还观察到规则美观的马赛克形貌, 每块矩形马赛克的尺寸为数十微米数量级, 多次升降温循环能重复出现和消失. 发现马赛克形貌实质上是在冻结的向列相织构上结晶化并收缩龟裂而装饰出来的光学图案. 通过扫描电镜的研究, 观察到马赛克形貌是由片晶组装而成的, 每块马赛克就是一块矩形 的多层片晶, 多层片晶由单层片晶堆积而成. 直接观察到片晶的组成单元是直径约1 微米的微纤, 而微纤应当是束状的碗形分子柱. 马赛克形貌装饰在碗形分子柱状向列相上, 通过这种新方法观察到s = +1(δ = 0 和δ = 90°)和s = ±1/2 多种点向错和Nèel 微区壁等周围的分子指向矢分布情况. 说明碗形分子柱状向列相与一般向列相 有类似的液晶行为, 但取向的基本结构单元是碗形分子柱, 或者由碗形分子柱组成的束(即微纤), 而不是碗形分子本身. 碗形分子柱起了一般向列相中棒状分子的作用, 所以本文以一个新名称“碗形分子柱状向列相”BCN (Bowlic Columnar Nematic)来表示这种不同常规的向列相.国家自然科学基金基金(批准号:20774077); 福建省自然科学基金(E0510003); 厦门市科技计划项目（3502Z20055013)

Studies on Synthesis of Two Novel Bowl-like Molecules and Their Fibrous Crystals

[中文文摘]以香兰素为原料,采用三聚法合成了2种外围脂肪族基团碳数分别为3和5的环三亚藜芦基(cyclotriveratrylene,CTV)系衍生物碗形分子——CTV-3和CTV-5,其中,用先关环后衍生化的合成路线克服了因CTV-5的外围基团太长、分子对称性不好而无法用传统方法合成的难题。产物的化学结构经1H NMR、13CNMR、质谱以及元素分析确认。在偏光显微镜下观察到纤维状晶叠加在碗形分子的向列液晶织构上。纤维状晶是从液晶态冷却时形成并装饰在原液晶织构上的一种结晶形态。通过SEM测定,观察到纤维状晶实际上是由厚度约为100～200nm、宽度为2～5μm的无限长的单层片晶组成的多层片晶,而片晶则是由直径约为100nm的微纤组成的。微纤可以推断是碗形分子柱的束状聚集体。[英文文摘]　Two novel bowl-like cyclotriveratrylene (CTV) ,i. e. CTV23 and CTV25 termed according to the different peripheral groups with carbon number 3 and 5 espectively,were synthesized. CTV23 was prepared by a the typical trimerization via a multistep sequence from vanillin ,however it remains restricted to the preparation of the CTV25 with larger peripheral group and less molecular symmetry via this conventional method. In this paper ,an alternative synthesis route with first closing ring and then derivatization was designed to prepare CTV25. The chemical structures of the products were characterized by means of 1H NMR ,13C NMR ,mass spectrometry and element analysis. For the final products CTV23 and CTV25 ,many fibrous crystals were observed under polarized optical microscopy ,which crystallized during the cooling from nematic phase ,and decorated the so-called liquid crystal grainy texture. By means of scanning electron microscope ,it can be observed the fibrous crystals were actually very long multi-layer lamellae ,which consist of single layer lamellae with the thickness of about 100 to 200nm ,width of 2 to 5μm and infinite length. The single layer lamellae were further composed of fibrils which diameter was about 100nm. It could be deduced that these fibrils were the aggregates of bowlic molecular columns国家自然科学基金项目(20774077); 福建省自然科学基金项目(E0510003); 厦门市科技计划项目(3502Z20055013)资助

含碗形CTV侧基的甲基丙烯酸酯类单体和聚合物

采用三聚法合成外围基团中含羟十一碳氧基的CTV衍生物(CTV-H),然后结合柱层析分离技术合成和分离出外围基团中含单甲基丙烯酸酯基团的CTV衍生物(CTV-M).以CTV-M为单体,本体聚合得到含碗形CTV侧基的甲基丙烯酸酯类聚合物(BPM).CTV-H和CTV-M都具有热致液晶性,是新的碗状液晶.SAXS和WAXD测定表明,液晶结构为六方柱相(Φh),柱直径为4.4 nm和4.8 nm,与理论计算结果相符.而BPM没有液晶性,呈非晶态

新型环三藜芦烃衍生物的合成及其热致液晶行为的研究

设计了先关环再衍生的方法,合成了系列外围含不同反应性官能团的新的环三藜芦烃(CTV)衍生物.利用1 H-NMR、13C-NMR、元素分析、质谱等对合成的CTV衍生物进行了结构表征.研究表明,分子间作用力增大会导致CTV衍生物的热致液晶性减弱,结晶性增强.合成的CTV-A具有热致液晶性;CTV-D和CTV-E由于氨基的存在产生了较强的分子间氢键作用,既形成了热致液晶态,又发生冷结晶;而CTV-B和CTV-C由于含有羧基、羰基、羟基或氨基等,分子间作用力强,只出现冷结晶,不能形成热致液晶.研究发现,通过外围基团的分子设计,调节氢键能力或柔性间隔基,可调节分子间作用力和熵的大小,从而控制CTV衍生物的热致液晶性

壳寡糖和聚丙烯酸的自组装行为

研究了壳寡糖和聚丙烯酸在共同溶剂水中的自组装行为.两种聚电解质之间不仅存在库仑力,而且存在相当强的氢键相互作用.在超声波作用下,能形成亚微米尺寸的球形自组装聚集体,并利用动态光散射的方法和透射电镜研究了这种自组装微球的尺寸和形态

Synthesis and Liquid Crystal Behavior of Dodob Acid Grafted Chitosan

[中文文摘]甲壳素/壳聚糖是拥有多个反应性官能团的天然多糖,而树状分子则是一类可以在分子水平上控制和设计大小、形状、结构和功能基团的化合物,将其作为侧链通过接枝反应引入到壳聚糖主链上有望获得新型的天然高分子液晶材料.我们利用经典的收敛法合成了DOBOB酸(3,4,5-三[对-(十二烷氧基)苄氧基]苯甲酸)树枝状分子,并且以对甲苯磺酰氯为催化剂,在吡啶/无水氯化锂的溶剂体系中将其接枝到壳聚糖分子链上,产物的化学结构经红外1、H-NMR1、3C-NMR以及元素分析表征验证.通过DSC和热台偏光显微镜研究表明,这种树枝状分子接枝壳聚糖化合物同时具有热致和溶致液晶性,是一种全新的壳聚糖衍生物液晶.[英文文摘]Chitin/chitosan are natural polysaccharide which have multiple functional groups,whereas dendrimers are a new category of dendritic molecules which have highly structure order.The molecule size,shape,structure and functional groups of the latter can be controlled and designed on the molecular scale.By the way of grafting reaction,dendrimers can be attached to chitosan mainchain as the side chain bearing unique qualities and functions.The resulting compound may became a new type of natural polymer liquid-crystal material. 1-Bromododecane , p-hydroxybenzaldehyde and methyl-3 ,4 ,5-trihydroxybenzoate were used as raw materials to synthesize a dendrimer (DOBOB acid) by the way of constringency, then grafted onto a chitosan (CS) mainchain in reaction system of pyridine/ LiCl ,using p-TsCl as the catalyst . Their chemical structures were charasterized by FTIR ,？H-NMR ,？C-NMR and element analysis. The final product DOBOB2g2CS was observed to possess both the behaviors of thermot ropic liquid crystal and lyotropic liquid crystal under POM. We achieved a new species liquid crystal of chitosan derivative ultimately.国家自然科学基金(20774077); 福建省自然科学基金(E0510003); 厦门市科技计划项目(3502Z20055013）

用断裂力学和声发射法预计疲劳寿命

符 号a——穿透裂纹的裂纹长度,硬币形裂纹 的裂纹半径;a_0——初始裂纹长度;A——在N-K关系(方程1)中的比例 常数;B——试件厚度;C——在裂纹扩展关系(方程2)中的比 例常数;D——塑性体积和声发射计数中的比例常 数(方程14);F——在楔形张开加载(WOL)断裂韧 性试件上的拉伸载荷

Preparation and Electrochemical Performance of Hollow Carbon Spheres/Sulfur Composite

采用PMMA为模板制备碳空心球材料，并以碳空心球材料为导电骨架与硫材料复合制得碳空心球/硫复合材料. SEM和TEM照片显示，硫材料能均匀地填充在碳空心球的孔道和腔体内部. 采用恒电流充放电测试碳空心球/硫复合电极的电化学性能. 结果表明，在100 mA·g-1、500 mA·g-1、1 A·g-1、2 A·g-1 和5 A·g-1电流密度下，碳空心球/硫复合电极可逆放电容量分别为1145 mAh·g-1、824 mAh·g-1、702 mAh·g-1、586 mAh·g-1和395 mAh·g-1，呈现出较优异的倍率循环寿命.Hollow carbon spheres were prepared by the PMMA template. Hollow carbon spheres/sulfur composite was made from sulfur and hollow carbon spheres as a conducting framework. The results of SEM and TEM showed that sulfur was uniformly filled in both of the shell and hollow core of hollow carbon spheres. The electrochemical performance of hollow carbon spheres/sulfur composite was characterized by the charge/discharge method. The results showed the excellent rate and cycle performance of hollow carbon spheres/sulfur composite. The reversible capacities of hollow carbon spheres/sulfur composite are 1145 mAh·g-1, 824 mAh·g-1, 702 mAh·g-1, 586 mAh·g-1 and 395 mAh·g-1 at the current densities of 100 mA·g-1, 500 mA·g-1, 1 A·g-1, 2 A·g-1 and 5 A·g-1, respectively.国家自然科学基金项目（No. 200933005，No. 21021002）、973项目（No. 2009CB220102）和厦门市纯电动汽车重大专项（No. 3502Z20121002）资助作者联系地址：1. 厦门大学 固体表面物理化学国家重点实验室，化学化工学院化学系，福建 厦门 361005； 2. 厦门产业技术研究院，福建 厦门，361001Author's Address: 1. State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China; 2. Amoy Institute of Technovation, Xiamen 361001, Fujian, Chin