共查询到20条相似文献，搜索用时 31 毫秒
1.
The thiophene oligomer alpha-hexathienylene (alpha-6T) has been successfully used as the active semiconducting material in thin-film transistors. Field-induced conductivity in thin-film transistors with alpha-6T active layers occurs only near the interfacial plane, whereas the residual conductivity caused by unintentional doping scales with the thickness of the layer. The two-dimensional nature of the field-induced conductivity is due not to any anisotropy in transport with respect to any molecular axis but to interface effects. Optimized methods of device fabrication have resulted in high field-effect mobilities and on/off current ratios of > 10(6). The current densities and switching speeds are good enough to allow consideration of these devices in practical large-area electronic circuits. 相似文献
2.
Tunneling spectroscopy has been used to characterize the magnitude and temperature dependence of the superconducting energy gap (triangle up) for K(3)C(60) and Rb(3)C(60). At low temperature the reduced energy gap, 2triangle upkappaT(c) (where T(c) is the transition temperature) has a value of 5.3 +/- 0.2 and 5.2 +/- 0.3 for K(3)C(60) and Rb(3)C(60), respectively. The magnitude of the reduced gap for these materials is significantly larger than the value of 3.53 predicted by Bardeen-Cooper-Schrieffer theory. Hence, these results show that the pair-coupling interaction is strong in the M(3)C(60) superconductors. In addition, measurements of triangle up(T) for both K(3)C(60) and Rb(3)C(60) exhibit a similar mean-field temperature dependence. The characterization of triangle up and triangle up(T) for K(3)C(60) and Rb(3)C(60) provides essential constraints for theories evolving to describe superconductivity in the M(3)C(60) materials. 相似文献
3.
By means of an approach that employs alkali-metal alloys, bulk single-phase (RbxK1-x)(3)C(6O) superconductors have been prepared for all x between 0 and 1. For x = 1 it is shown that the maximum superconducting fraction, which approaches 100% in sintered pellets, occurs at a Rb to C(60) ratio of 3:1. More importantly, single-phase superconductors are formed at all intermediate values of x, and it is shown that the transition temperature (T(c)) increases linearly with x in this series of materials. The formation of a continuous range of solid solutions demonstrates that the rubidium- and potassium-doped C(60) superconducting phases must be isostructural, and furthermore, suggests that the linear increase in T(c) with x results from a chemical pressure effect. 相似文献
4.
目的观察加味寿胎颗粒联合α-2b干扰素治疗慢性乙型肝炎的临床疗效。方法 60例e抗原阳性的慢性乙肝患者随机分为治疗组和对照组各30例,对照组单用α-2b干扰素(安福隆)500万u,皮下注射,隔日1次;治疗组采用干扰素注射联合加味寿胎颗粒冲服,10 g/次,3次/d,疗程6个月。结果治疗组e抗原阴转率60%,HBV-DNA转阴率为76.7%;对照组e抗原阴转率33.3%,HBV-DNA转阴率为43.3%,两组比较,差异有统计学意义(P<0.05)。结论α-2b干扰素联合加味寿胎颗粒可以显著提高e抗原阳性的慢性乙型肝炎的治疗效果。 相似文献
5.
Krusic PJ Wasserman E Keizer PN Morton JR Preston KF 《Science (New York, N.Y.)》1991,254(5035):1183-1185
Photochemically generated benzyl radicals react with C(60) producing radical and nonradical adducts Rn C(60) (R = C(6)H(5)CH(2)) with n = 1 to at least 15. The radical adducts with n = 3 and 5 are stable above 50 degrees C and have been identified by electron spin resonance (ESR) spectroscopy as the allylic R(3)C(60)(.) (3) and cyclopentadienyl R(5)C(60)(.) (5) radicals. The unpaired electrons are highly localized on the C(60) surface. The extraordinary stability of these radicals can be attributed to the steric protection of the surface radical sites by the surrounding benzyl substituents. Photochemically generated methyl radicals also add readily to C(60). Mass spectrometric analyses show the formation of (CH(3))nC(60) with n = 1 to at least 34. 相似文献
6.
The electrical properties of organic molecular crystals, such as polyacenes or C60, can be tuned from insulating to superconducting by application of an electric field. By structuring the gate electrode of such a field-effect switch, the charge carrier density, and therefore also the superfluid density, can be modulated. Hence, weak links that behave like Josephson junctions can be fabricated between two superconducting regions. The coupling between the superconducting regions can be tuned and controlled over a wide range by the applied gate bias. Such devices might be used in superconducting circuits, and they are a useful scientific tool to study superconducting material parameters, such as the superconducting gap, as a function of carrier concentration or transition temperature. 相似文献
7.
JIANG Hui GAO Qing-rong LI Luo-jiang KONG Ling-rang ZHANG Wei-dong WU Shi-wen YANGYa-li 《中国农业科学(英文版)》2010,9(5):615-625
The male-sterile lines with Ms2 gene were highly evaluated in recurrent selection in wheat （Triticum aestivum L.）. Three populations C6 （population after six cycles of selection）, C7 （population after seven cycles of selection）, and C8 （population after eight cycles of selection） were constructed through recurrent selection with 12 parental materials （P）. Acid polyacrymide gel electrophoresis （A-PAGE） analysis was used to identify gliadin patterns and evaluate the genetic diversity in 12 parents and three populations. A total of 63 bands were identified, of which 17 polymorphic bands and 7 unique bands were present in populations and seven polymorphic bands and four unique bands were present in parents. The number of polymorphic and unique bands decreased gradually from C6 to C8, especially for to- and y-gliadins. The genetic distances in C6, C7, and C8 were calculated. The distributions of genetic distance were different in three recurrent selection populations. From C6 to C8, the genetic distance was 0.2687, 0.2652 and 0.1987, respectively. Statistically significant differences were detected between C7 and C8 with the T value of 37.9718. The result of cluster analysis based on genetic similarity matrix of three populations fitted well to those of principle coordinates analysis （PCoA）. Compared with 12 parents, almost all individuals of three populations are new genotypes. Most of the individuals from C6 and C7 could be divided into two groups, while most individuals of C8 were in one cluster. In conclusion, the results indicated that the genetic diversity was decreased severely according to the information revealed by A-PAGE, although some variations could be created in the recurrent selection. It was necessary to introduce diverse germplasm based on the genetic database of recurrent population to maintain and improve the breeding efficiency in the further program. 相似文献
8.
A new superacid, H(CB11H6X6) (where X = chlorine or bromine), whose conjugate base is the exceptionally inert CB11H6X6- carborane anion, separates Bronsted acidity from oxidizing capacity and anion nucleophilicity in a manner not previously achieved. Reaction of this superacid with C60 gives HC60+ as a stable ion in solution and in the solid state. In a separate experiment, an oxidant was developed such that the long-sought C60.+ ion can be synthesized in solution. The preparation of these two fullerene carbocations is a notable departure from the prevalent chemistry of C60, which is dominated by the formation of anions or the addition of nucleophiles. The H(CB11H6X6) superacid overcomes the major limitations of presently known superacids and has potentially wide application. 相似文献
9.
前后做了２个试验．试验Ⅰ选用８０只６０周龄海兰褐商品蛋鸡,随机分为１个对照组（ＣＫ）和４个处理组（Ｔ１、Ｔ２、Ｔ３、Ｔ４）．处理组Ｔ１、Ｔ２分别在日粮中添加质量分数为０．４×１０－ ６和０．８×１０－ ６（以Ｃｒ计）的无机氯化铬（ＣｒＣ１３·６Ｈ２Ｏ）;处理组Ｔ３、Ｔ４分别在日粮中添加质量分数为０．４×１０－ ６和０．８×１０－ ６（以Ｃｒ计）的铬酵母（Ｃｒｙｅａｓｔ, Ｃｒ－Ｙ）．试验Ⅱ选用９０只５５周龄父母代种用蛋鸡,同样分成１个ＣＫ 组和４个处理组（ｔ１、ｔ２、ｔ３、ｔ４）．处理组ｔ１,ｔ２分别在日粮中添加质量分数为０．４×１０－ ６和０．８×１０－ ６（以Ｃｒ计）的Ｃｒ－Ｙ;ｔ３,ｔ４分别在日粮中添加质量分数为０．４×１０－ ６和０．８×１０－ ６（以Ｃｒ计）的烟酸铬（Ｃｒ ｎｉｃｏｔｉｎａｔｅ, Ｃｒ－Ｎｉｃ）．２个试验均为期１个月．结果表明,日粮补充无机Ｃｒ或有机Ｃｒ对产蛋鸡各项生产性能未见明显影响,但于试验未,添加有机Ｃｒ组的蛋黄胆固醇质量分数和血清总胆固醇水平均比ＣＫ组和无机Ｃｒ组显著降低,而血清高密度脂蛋白胆固醇水平则有所提高;有机Ｃｒ组中质量分数为０．８×１０－ ６的与０．４×１０－ ６的相比,前者作? 相似文献
10.
短芒大麦耐盐碱新品系的生理生化和分子生物学分析 总被引：4，自引：0，他引：4
以经60 Co物理诱变种子、EMS诱变和耐盐反复筛选后已稳定 6代的短芒大麦耐盐碱突变体N1、T3 、T4、T5及其亲本野生短芒大麦为材料 ,进行耐盐碱生理生化指标 (脯氨酸、质膜透性 )测定及RAPD分析。发现突变体与野生型相比 ,不仅在生理生化指标上有明显的差异 ,而且在DNA水平上发生了突变。研究结果为耐盐碱突变体的真实性提供了有力的证据 ,表明突变体N1、T3 、T4、T5是耐盐碱短芒大麦新品系。 相似文献
11.
The room temperature Raman spectra of the intramolecular modes between 100 cm(-1) and 2000 cm(-1) are reported for alkali-metal doped AxC(60) films. For A = K, Rb, and Cs, phase separation is observed with the spectra of C(60), K(3)C(60), K(6)C(60), Rb(3)C(60), Rb(6)C(60), and Cs(6)C(60) phases reported. The x = 3 phases show only three Raman active modes: two of Ag symmetry and only the lowest frequency Hg mode. The other Hg modes regain intensity in the x = 6 films, with several mode splittings observed. For A = Na, such phase separation is not clearly observed, and reduced mode shifts are interpreted as due to incomplete charge transfer in these films. 相似文献
12.
Van der Waals forces that bind C(60) molecular solids are found to be sufficiently strong to allow the reproducible fabrication of free-standing C(60) membranes on (100) silicon wafers. Membranes, 2000 to 6000 angstroms thick, were fabricated by a modified silicon micro-machining process and were found to be smooth, flat, and mechanically robust. An important aspect of the silicon-compatible fabrication procedure is the demonstration that C(60) films can be uniformly and nondestructively thinned in a CF(4) plasma. Young's modulus and fracture strength measurements were made on membranes with areas larger than 6 millimeters by 6 millimeters. It may be possible to use C(60), membranes for physical property measurements and applications. 相似文献
13.
Iwasa Y Arima T Fleming RM Siegrist T Zhou O Haddon RC Rothberg LJ Lyons KB Carter HL Hebard AF Tycko R Dabbagh G Krajewski JJ Thomas GA Yagi T 《Science (New York, N.Y.)》1994,264(5165):1570-1572
The fullerene C(60) can be converted into two different structures by high pressure and temperature. They are metastable and revert to pristine C(60) on reheating to 300 degrees C at ambient pressure. For synthesis temperatures between 300 degrees and 400 degrees C and pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with a lattice parameter a(o) = 13.6 angstroms. When treated at 500 degrees to 800 degrees C at the same pressure, C(60) transforms into a rhombohedral structure with hexagonal lattice parameters of a(o) = 9.22 angstroms and c(o) = 24.6 angstroms. The intermolecular distance is small enough that a chemical bond can form, in accord with the reduced solubility of the pressure-induced phases. Infrared, Raman, and nuclear magnetic resonance studies show a drastic reduction of icosahedral symmetry, as might occur if the C(60) molecules are linked. 相似文献
14.
Chung DY Hogan T Brazis P Rocci-Lane M Kannewurf C Bastea M Uher C Kanatzidis MG 《Science (New York, N.Y.)》2000,287(5455):1024-1027
Thermoelectric (Peltier) heat pumps are capable of refrigerating solid or fluid objects, and unlike conventional vapor compressor systems, they can be miniaturized without loss of efficiency. More efficient thermoelectric materials need to be identified, especially for low-temperature applications in electronics and devices. The material CsBi(4)Te(6) has been synthesized and its properties have been studied. When doped appropriately, it exhibits a high thermoelectric figure of merit below room temperature (ZT(max) approximately 0.8 at 225 kelvin). At cryogenic temperatures, the thermoelectric properties of CsBi(4)Te(6) appear to match or exceed those of Bi(2-x)Sb(x)Te(3-y)Se(y) alloys. 相似文献
15.
为分析VIPR-1基因是否能作为鹌鹑早期生长性状的相关分子标记或者候选基因,以中国黄羽鹌鹑、中国白羽鹌鹑、朝鲜鹌鹑3个蛋用鹌鹑品种作为实验对象,采用PCR-RFLP技术和测序技术检测VIPR-1基因的外显子6-7的多态性,并分析该基因多态性与蛋用鹌鹑早期生长性状的关联程度。结果表明,在3个蛋用鹌鹑品种中的VIPR-1基因外显子6-7区域共检测出15个SNP位点,分别为A94G、G97T、C201T、A204G、A233G、C260G、A299T、C354T、A355G、C378T、C407G、A425C、A543G、G585T、A586G。对HpyCH4IV位点(A355G)进行酶切分析,可以检测到3种基因型即AA(285 bp/811 bp)、AG(285 bp/811 bp/1 096 bp)和GG(1 096 bp)。中国黄羽鹌鹑和中国白羽鹌鹑的AA、AG、GG基因型频率分别为0.227、0.636、0.136和0.087、0.609、0.304。朝鲜鹌鹑AG和GG基因型频率分别为0.235和0.765。1~4周龄时,VIPR-1基因的HpyCH4IV位点与中国黄羽鹌鹑的日增重、体重、胫长、胸宽、胸深、胸骨长、胫围有显著关联性(P<0.05)。HpyCH4IV位点与中国白羽鹌鹑的胫围有显著关联性(P<0.05)。HpyCH4IV位点与朝鲜鹌鹑的体重、胸宽、胸深有显著关联性(P<0.05)。5~7周龄时,VIPR-1基因的HpyCH4IV位点与中国黄羽鹌鹑的体重、胸骨长、胫长、体长、胸宽、胸深、胫围、日增重和相对生长率均有显著的关联性(P<0.05)。HpyCH4IV位点与中国白羽鹌鹑的日增重和相对生长均有显著的关联性(P<0.05)。HpyCH4IV位点与朝鲜鹌鹑的体重有显著的关联性(P<0.05)。综上研究表明,VIPR-1基因外显子6-7的HpyCH4IV位点(A355G)对蛋用鹌鹑的早期生长性状具有一定影响。 相似文献
16.
Johnson RD Yannoni CS Dorn HC Salem JR Bethune DS 《Science (New York, N.Y.)》1992,255(5049):1235-1238
The rotational dynamics of C(60) in the solid state have been investigated with carbon-13 nuclear magnetic resonance ((13)C NMR). The relaxation rate due to chemical shift anisotropy (1/9T1(CSA)(1)) was precisely measured from the magnetic field dependence of T(1), allowing the molecular reorientational correlation time, tau, to be determined. At 283 kelvin, tau = 9.1 picoseconds; with the assumption of diffusional reorientation this implies a rotational diffusion constant D = 1.8 x 10(10) per second. This reorientation time is only three times as long as the calculated tau for free rotation and is shorter than the value measured for C(60) in solution (15.5 picoseconds). Below 260 kelvin a second phase with a much longer reorientation time was observed, consistent with recent reports of an orientational phase transition in solid C(60). In both phases tau showed Arrhenius behavior, with apparent activation energies of 1.4 and 4.2 kilocalories per mole for the high-temperature (rotator) and low-temperature (ratchet) phases, respectively. The results parallel those found for adamantane. 相似文献
17.
Synthesis of functional human hemoglobin in transgenic mice 总被引：18，自引：0，他引：18
R R Behringer T M Ryan M P Reilly T Asakura R D Palmiter R L Brinster T M Townes 《Science (New York, N.Y.)》1989,245(4921):971-973
Human alpha- and beta-globin genes were separately fused downstream of two erythroid-specific deoxyribonuclease (DNase) I super-hypersensitive sites that are normally located 50 kilobases upstream of the human beta-globin gene. These two constructs were coinjected into fertilized mouse eggs, and expression was analyzed in transgenic animals that developed. Mice that had intact copies of the transgenes expressed high levels of correctly initiated human alpha- and beta-globin messenger RNA specifically in erythroid tissue. An authentic human hemoglobin was formed in adult erythrocytes that when purified had an oxygen equilibrium curve identical to the curve of native human hemoglobin A (Hb A). Thus, functional human hemoglobin can be synthesized in transgenic mice. This provides a foundation for production of mouse models of human hemoglobinopathies such as sickle cell disease. 相似文献
18.
Sparn G Thompson JD Huang SM Kaner RB Diederich F Whetten RL Grüner G Holczer K 《Science (New York, N.Y.)》1991,252(5014):1829-1831
The superconducting compound K(3)C(60) (with transition temperature T(c) = 19.3 kelvin at ambient pressure), formed as a single phase by reaction of alkali vapor with solids of the icosahedral C(60) molecule (buckminsterfullerene), shows a very large decrease of T(c) with increasing pressure. Susceptibility measurements on sintered pellets showing bulk superconductivity are reported up to 21 kilobars of pressure, where T(c) is already less than 8 kelvin. The results are consistent with a piling up of the density of states at the Fermi level. 相似文献
19.
智能化家具对居住者影响因素的分析与评价 总被引：1，自引：0，他引：1
根据智能化家具系统的影响因素,将对身心健康有影响的因素分为2类,即:绿色材料、保健装置;对突发情况归纳出3类因素:应急设备、防护装置、卫警系统.应有层次分析法、虚拟现实技术,研究了智能化的实现过程中对居住者造成的影响,对可能出现的困难做出了必要的估计. 相似文献
20.
Photoemission spectra of compounds prepared by the reaction of C(60) films with calcium show two distinct metallic phases, whereas alkali-doped C(60) films have only one. In the first phase the bulk t(1u) band, derived from the lowest unoccupied molecular orbital of C(60), is partially occupied. This is followed by an insulating phase that has the composition Ca(3)C(60) in which the t(1u) band is filled and has properties analogous to those of K(6)C(60). Continued exposure to calcium produces a second metallic phase in which electrons are donated into the t(1g) band. The superconductivity of Ca(5)C(60) is associated with the t(1g) band. 相似文献