68 resultados para Latin language, Preclassical to ca. 100 B.C.
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Silkie is a famous black-bone chicken breed with beautiful silky feather. The unique medical property of this chicken was recorded in Chinese traditional medicine dictionary about 700 years ago. In this study, we analyzed the mtDNA D-loop sequence variation of 26 Bairong Silkies from Fujian Province, China, together with 100 reported Silkie mtDNAs from China and Japan, and studied their matrilineal components and genetic relationship. A total of 21 haplotypes were detected, which could be assigned to six haplogroups (A-E, G). Among them, haplogroups D and G were exclusively presented in Japanese Silkies and Chinese Silkies, respectively. Chinese Silkies had higher frequency of lineages belonging to haplogroups A, B, and E, and lower frequency of haplogroup C than Japanese Silkies. For the four Chinese Silkie populations, most of samples of Taihe, Chengdu, and Hubei Silkies were grouped in haplogroups A, B, and C, whereas most of Bairong Silkies were grouped in haplogroup E. Five haplotypes were shared by Japanese and Chinese Silkies. The genetic diversity of each Silkie population varied, but the overall diversity of Chinese Silkies was similar to that of Japanese Silkies. Taken together, our results confirmed the genetic connection between Chinese and Japanese Silkies, but also clearly showed that the matrilineal genetic structures of Chinese and Japanese Silkies had some differences.
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Relatively little is known in relation to pathological changes of immune organs in fish when exposed to MC-LR. The ultrastructural alteration of lymphocytes was examined in the spleen and pronephros of grass carp Ctenopharyngodon idella injected experimentally with microcystin-LR. The fish were intraperitoneally injected with MC-LR at a dose of 50 mu g/kg body weight, and the spleen and pronephros were dissected out at 1, 2, 7, 14 and 21 days post intraperitoneal injection (dpi). Pathological changes were then examined by transmission electron microscopy. Apoptosis was detected only in lymphocytes in the spleen, with obvious apoptotic features observed at 2 dpi; pathological changes of lymphocytes in the pronephros were also serious with mitochondria being highly edematous. However, damaged lymphocytes were almost un-observed in the spleen and pronephros at 21 dpi. These findings suggest that MC-LR can induce toxic effect on immune organs in grass carp, and the spleen may be much more sensitive to MC-LR stimulation. (C) 2008 Elsevier B.V. All rights reserved.
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Synechocystis sp. PCC 6803 exposed to chill (5 degrees C)-light (100 mu mol photons m(-2) s(-1)) stress loses its ability to reinitiate growth. From a random insertion mutant library of Synechocystis sp. PCC 6803, a sll1242 mutant showing increased sensitivity to chill plus light was isolated. Mutant reconstruction and complementation with the wild-type gene confirmed the role of sll1242 in maintaining chill-light tolerance. At 15 degrees C, the autotrophic and mixotrophic growth of the mutant were both inhibited, paralleled by decreased photosynthetic activity. The expression of sll1242 was upregulated in Synechocystis sp. PCC 6803 after transfer from 30 to 15 degrees C at a photosynthetic photon flux density of 30 mu mol photons m(-2) S-1. sll1242, named ccr (cyanobacterial cold resistance gene)- 1, may be required for cold acclimation of cyanobacteria in light.
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The complete cytochrome b and the control region of mtDNA (about 2070 bp in total) of 10 strains belonging to three subspecies of the common carp, including three wild subspecies (the Yangtze River wild common carp - Cyprinus carpio haematopterus, Yuanjiang River wild common carp Cyprinus carpio rubrofuscus and Volga River wild common carp - Cyprinus carpio carpio) and seven domestic strains (Xingguo red carp, Russian scattered scaled mirror carp, Qingtian carp, Japanese Koi carp, purse red carp, Big-belly carp, German mirror carp) were sequenced. Phylogenetic analysis indicated that the 10 strains form three distinct clades, corresponding to C. c. haematopterus, C. c. rubrofuscus and C. c. carpio respectively. Purse red carp, an endemic domestic strain in Jiangxi province of China, showed a higher evolution rate in comparison with the other strains of C. c. haematopterus, most probably because of intensive selection and a long history of domestication. Base variation ratios among the three subspecies varied from 0.78% (between C. c. haematopterus and C. c. rubrofuscus) to 1.47%(between C. c. carpio and C. c. rubrofuscus). The topography of the phylogenetic tree and the geographic distribution of three subspecies closely resemble each other. The divergence time between C. c. carpio and the other two subspecies was estimated to be about 0.9 Myr and about 0.5 Myr between C. c. haematopterus and C. c. rubrofuscus. Based on phylogenetic analysis, C. c. rubrofuscus might have diverged from C. c. haematopterus.
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This study was undertaken to compare the sensitivity of two in vitro screening test methods and to determine the accuracy of predicted response to spiked laboratory water samples. A newly developed enzyme-linked receptor assay (ELRA) and a widely used yeast estrogen screen (YES) assay were selected to evaluate the estrogenic responses. Four natural, pharmaceutical, xenobiotic or phytobiotic chemicals: 17beta-estradiol (E2), tamoxifen, bisphenol-A and resveratrol were examined, and 17beta-E2 was used as a positive control. 17beta-E2 can strongly induce estrogenic response in both test systems, however, ELRA was found to be more sensitive to 17beta-E2 with a detection limit of 0.07 mug/l compared to 0.88 mug/l in YES assay. Similar results were obtained for bisphenol-A and resveratrol, and their estrogen potencies relative to E2 (100%) determined by ELRA were at least 5.6 times greater than produced by YES assay. ELRA was unable to distinguish the anti-estrogen tamoxifen and YES assay is also poor at distinguishing. Comparison of response to spiked laboratory water samples show that ELRA can give accurate determination to all four chemicals with recoveries among 70-120%, while YES can only give accurate determination to 17beta-E2 and bisphenol-A with recoveries among 69-112%. The comparative results provide evidence that ELRA is more suitable for rapid screening estrogenic potency of the environmental samples. Combination of ELRA and mammalian cellular assay will constitute an advantageous test to specify agonistic or antagonistic effects. (C) 2003 Elsevier Ltd. All rights reserved.
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The objective of this study was to develop type I markers for genome mapping and other genetic studies of Penaeus monodon. Primers were designed based on expressed sequence tags (ESTs) from a P monodon cephalothorax cDNA library to amplify 100-300 bp products. 34 of the primer pairs successfully amplified PCR products from genomic DNA. Single-strand conformation polymorphism analysis showed that similar to 30% of the ESTs tested exhibit polymorphism in a test panel of P monodon individuals. Mendelian inheritance of the EST-derived markers has been established in two international reference mapping families of P monodon, and mapping of these markers is in progress. Some ESTs were successfully amplified from other Penaeus species (P. chinensis, P japonicus and P vannamei), indicating that the markers are applicable in cross-species comparison. Two populations of P. japonicus could be differentiated using one of the ESTS. In conclusion, the polymorphic EST markers developed in this study are applicable in genome mapping and population genetic studies of penaeid shrimp. (C) 2002 Elsevier Science B.V. All rights reserved.
Resumo:
Theoretical calculations of the mode characteristics of an equilateral-triangle resonator (ETR) with a 10 mu m cavity side length show that the fundamental mode, with longitudinal mode index of 25, has a wavelength of 2.185 mu m and a longitudinal mode separation of 100 nm. This mode has a quality factor (similar to 2x10(5)) that is much larger than the first (similar to 5x10(4)) and second (similar to 3x10(4)) order modes, indicating that single fundamental mode lasing should be accessible over a broad wavelength tuning range. An electrically injected ETR based on this design is fabricated from an InGaAsSb/AlGaAsSb/GaSb, graded-index separate-confinement heterostructure, laser diode wafer with a 2.1 mu m emission wavelength. This device achieved single mode, continuous wave operation at 77 K with a threshold current of 0.5 mA and a single mode wavelength tuning range of 3.25 nm, which is accomplished by varying the injection current from 0.5 to 6.0 mA. (C) 2008 American Vacuum Society.
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We investigate the molecular beam epitaxy growth of GaSb films on GaAs substrates using AlSb buffer layers. Optimization of AlSb growth parameter is aimed at obtaining high GaSb crystal quality and smooth GaSb surface. The optimized growth temperature and thickness of AlSb layers are found to be 450 degrees C and 2.1 nm, respectively. A rms surface roughness of 0.67 nm over 10 x 10 mu m(2) is achieved as a 0.5 mu m GaSb film is grown under optimized conditions.
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We demonstrate 1.25-1.29 mu m metamorphic laser diodes grown on GaAs by molecular beam epitaxy (MBE) using an alloy-graded buffer layer (GBL). Use of Be in the GBL is effective to reduce surface/interface roughness and improves optical quality. The RMS surface roughness of the optimized metamorphic laser is only two atomic monolayers for 1 x 1 mu m(2). Cross-sectional transmission electron microscopy (TEM) images confirm that most dislocations are blocked in the GBL. Ridge waveguide lasers with 4 mu m wide ridge were fabricated and characterized. The average threshold current under the pulsed excitation is in 170-200 mA for a cavity length of 0.9-1.5 mm. This value can be further reduced to about 100 mA by high-reflectivity coating. Lasers can work in an ambient temperature up to at least 50 degrees C. (c) 2006 Elsevier B.V. All rights reserved.
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A new method to form nanoscale InGaN quantum dots using MOCVD is reported, This method is much different from a method. which uses surfactant or the Stranski-Krastannow growth mode. The dots were formed by increasing the energy barrier for adatoms, which are hopping by surface passivation, and by decreasing the growth temperature. Thus, the new method can be called as a passivation-low-temperature method. Regular high-temperature GaN films were grown first and were passivated. A low-temperature thin layer of GaN dot was then deposited on the surface that acted as the adjusting layer. At last the high-density InGaN dots could be fabricated on the adjusting layer. Atomic force microscopy measurement revealed that InGaN dots were small enough to expect zero-dimensional quantum effects: The islands were typically 80 nm wide and 5 nm high. Their density was about 6 x 10(10) cm(-2). Strong photoluminescence emission from the dots is observed at room temperature, which is much stronger than that of the homogeneous InGaN film with the same growth time. Furthermore, the PL emission of the GaN adjusting layer shows 21 meV blueshift compared with the band edge emission of the GaN due to quantum confine effect. (C) 2002 Elsevier Science B.V. All rights reserved.
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As reported by other authors, we have also observed that the Si growth rate decreases with increasing phosphine (PH3) flow rate in gas source-Si molecular beam epitaxy using phosphorous (P) as a n-type dopant. Why small quantity PH3 can affect Si growth rate? Up to now, the quantitative characterization of PH3 flow influence on Si growth rate is little known. In this letter, the PH, influence will be analyzed in detail and a model considering strong P surface segregation and its absorption of hydrogen will be proposed to characterize the effect. (C) 2000 Elsevier Science B.V. All rights reserved.
Resumo:
The real-time monitoring of the second-harmonic generation (SHG) was used to optimize the poling condition and to study the nonlinear optical (NLO) properties of the polyetherketone (PEK-c) guest-host polymer films. The high second-order NLO coefficient chi(33)((2)) = 11.02 pm/v measured at 1.064 mu m was achieved when the weight percent of DR1 guest in the polymer system is 20%. The NLO activity of the poled DR1/PEK-c polymer film can maintain more than 80% of its initial value when temperature is under 100 degrees C, and the normalized second-order NLO coefficient can maintain more than 85% after 2400 s at 80 degrees C. (C) 2000 Elsevier Science Ltd. All rights reserved.
Resumo:
I 理论部分:对未知结构聚合物的ESCA进行表征,一是利用已知结构小分子化合物的ESCA中结合能值进行标定,二是运用电荷电位模型经量子化学计算对谱峰进行归属。由于所处化学环境不同,用小分子化合物的ESCA峰位对象合物标定不够准确,量子化学计算又太复杂。本工作提出了电负性经验公式,可计算ESCA中C_(1S)结合能位移值,与实测值作对照即可判断聚合物结构,方法简便,准确可靠。电负性经验公式表达如下:聚合物分子链上某碳原子1S电子结合能位移ΔEc可看作该碳原子与相邻基团间电负性差值和的函数,即ΔEc = K_c ∑ from i=1 to 4 1/(n_i) (X_i - 2.5) + b。聚合物分子链上各碳原子的实际电负性为X_c = (∑ form j=1 to 4 1/(n_j) X_j/∑ form j=1 to 4 1/(n_j) + 2.5)/2运用电负性经验公式计算了九个模型化合物中C_(1S)的ΔEc,推导出F作为α、β、γ位碳上的取代基的对α位碳上1s电子结合能位移影响产生的效应值,即,对于ΔEc = aα + bβ + cγ,有α = 3.018 (±0.007),β = 0.2513 (±0.0007) γ = 0.0176 (±0.003)。此结果与ESCA实测值相符。本工作设计了十六种化合物模型,模型中具有含氟等离子体聚合物中可能存在的大部分基团,通过电负性经验公式计算求得化学环境不同的C_(1S)结合能位移值,把ESCA的实测值和计算值进行对照,可对象合物的求知结构作出大致判断。II 在辉光放电中八氟环丁烷的聚合与刻蚀反应:在碳氧化合物的辉光放电中同时存在聚合与刻蚀两种相反的过程,聚合与刻蚀竞争的结果对聚合速率,产物结构都有很大影响。本工作通过测定聚合速率、IR谱、ESCA研究了反应条件对八氟环丁烷等离子体聚合与刻蚀的影响,得到了一致的和半定量的结果。实验证实,随着功率的增大或压力的减小,刻蚀有增强的趋势,不同的等离子气体对聚合与刻蚀的竞争过程有不同的影响,刻蚀强弱的顺序为Ar>N_2>H_2>He,增加等离子气体对单体的比率,引起刻蚀增加。聚合速率不随功率的改变而变化的状态是由聚合与刻蚀间的平衡引起的。随着功率增大或压力减少,聚合产物支化程度增加,线性程度减小,F/C比相应减小。同样随等离子气体种类不同,聚合物支化程度大小的顺序是Ar>N_2>H_2>He,F/C比相应变化。总之,聚合产物支化程度的变化和聚合与刻蚀的竞争结果相一致。对等离子体聚合与刻蚀竞争过程的定量描述未见文献报导。III 八氟环丁烷等离子体聚合物的结构和表征:用IR和ESR谱测得OFCB等离子体聚合物中存在五种元素:C、F、O、N、Si,并对可能存在于结构中的基因作了分析。通过NaHSO_3的亲核双键加成反应,用IR和ESR谱证实了等离子体聚合物中存在的双键及其类型。类似工作未见文献报导。用CuSO_4·5H_2作标样,测出PPOFCB中的自由基浓度为10~(19)自旋数/克。在80、100、120、140 ℃考察PPOFCB中俘获自由基的衰减过程,证实此过程涉及两类不同的反应,一是自由基的复合反应,二是自由基的氧气的终止反应。对上述两类反应进行动力学处理,求出了自由基复合反应在不同温度时的速度常数,并得到反应治化能为374焦耳/摩尔或8.869千卡/摩尔。氧和自由基的终止反应中,氧气的扩散过程是决定反应速度的步骤,反应速度常数就是扩散速度常数,K = 5.3 * 10~(-23)自旋数~(-1)、克分~(-1)。根据VPO测出的PPOFCB的分子量和自由基浓度,算出每4.5个分子中有一个自由基。类似工作未见文献报导。PPOFCB的分子量随反应条件不同而变化,用VPO测出,在80W和40W功率,在Ar存在下制备的OFCB等离子体聚合物的分子量分别为2736和2003。用~(19)F-NMR谱对PPOFCB中的基团进行定量计算,得出在一个90W,He气中制备的聚合物分子中,CF_3-CF_2为6.1,CF_2为13.5,CF_3-CF为7.9,CF为17.5,CF_3-C为6.1,C为13.5。在用上述方法进行结构表征的基础上,提出了OFCB等离子体聚合物的结构模型。IV 八氟环丁烷等离子体聚合的反应历程:以Ar、N_2、H_2、He为等离子气体,分别对OFCB等离子体聚合的气体冷凝物进行GC-Mg、~(19)F-NMR和ESR测试,观察到在气相中,OFCB经历了等离子态反应。单体被打断的程度,和高能电子浓度有关。体系中电子浓度依赖于气体的第一电离势和气相内的化学反应类型。初级粒子二氟卡宾:CF_2和中间体六氟丙烯是气相中的主要产物。~(19)F-NMR证实气相中存在支化产物,表明聚合物在气相中发生了重排。ESR谱测得,在气相产物中存在高浓度的由二种以上组分混合而成的自由基,自由基间的复合反应是生成聚合物的主要增长过程,气相产物的分子量随放电功率的升高而增大。根据聚合物中存在的高含量CF_3基团,分析了CF_3基团对聚合过程的影响。CF_3基团产生了屏蔽效应,它既保护了聚合物不致被降解,也限制了生成高分子量产物。实验证实,CF_3基团的生长来自F的重排,同时未自支化气相产物的非均相增长。OFCB等离子体聚合物中俘获自由基主要是由高能电子轰击聚合物表面产生的,同时来自被固相吸附的带有自由基的气相产物。在碳氟化合物的等离子体聚合中,吸附是和聚合同样重要的过程,气相产物被吸附后,可继续再引发、增长、刻蚀等反应过程、直到成为固相内层分子为止。ESR谱证实,高能粒子的轰击在辉光放电中起主导作用,紫外辐射对含氟聚合物引发和脱氟作用微弱。在气相和表面反应历程讨论的基础上,提出了OFCB等离子体聚合的反应历程模型,解释了碳氢和碳氟两个等离子体象合体系遵循不同反应历程的原因。本部分工作的实验和反应历程解释基本未见文献报导。
Resumo:
1.3 mu m strained-layer multi-quantum wells complex-coupled distributed feedback lasers with a wide temperature range of 20 to 100 degrees C are reported. The low threshold current of 10mA and high single-facet slope efficiency of 0.3mW/mA were obtained for an as cleaved device. The single mode yield was as high as 80%.
Resumo:
从新几内亚核桃木的树皮中分离得到的吲哚类喹诺里西定生物碱10-Desbromoarborescidine A,因发现其具有阻滞钙离子通道的活性而倍受关注。10-Desbromoarborescidine A由A、B、C、D四个环组成,只有一个手性中心,是吲哚生物碱中结构较简单的一种,常作为此类生物碱全合成方法的模型化合物。但迄今为止,能高效而简便的实现手性10-Desbromoarborescidine A不对称全合成方法线路不多,大多数以不对称诱导的方式建立其手性中心,手性催化的方式仅有一例金属催化。从逆合成分析可知,Desbromoarborescidine A的全合成可以通过亚胺不对称催化还原进行关键的手性中心构建,而本课题组在之前的研究中通过手性有机小分子催化剂的发展,已将三氯硅烷氢转移还原亚胺发展成了一类简便实用、高效、高对映选择性并具有优良底物适应范围的不对称催化反应,我们希望以这一反应作为关键手段,发展一条Desbromoarborescidine A及其类似物不对称合成新路线。 根据我们设计的新路线,首先成功合成了其关键中间体,然后我们进行了关键的不对称催化尝试。用本实验室已有的高性能有机小分子催化剂虽得到了较好的对应选择性,但是产率很低。同时,为了验证整条线路的可行性,我们也用消旋的中间体进行拉通线路的尝试。但不幸的是,在脱除保护基时遇到了很大困难。尝试换不同的保护基,或改变脱保护基的顺序,都未能成功合成目标产物。究其原因可能是由于吲哚的特殊性造成的,吲哚类亚胺与常规的芳香亚胺有较大的差异,其NH基团无论保护还是不保护,对与其2位相联接的C=N双键均有很大的影响,导致其不对称催化还原难以进行。另外,由于所设计的还原产物含有处在吲哚苄位的胺基,稳定性较差,造成保护基脱除困难。 烯胺C-亚磺酰化反应是本课题组最近发现的一个新反应,之前未见文献报道。本研究对该反应进行了反应条件优化和底物扩展,发现带Cbz,Ac,COt-Bu,CO2Et,Bz等保护基的一系列环状和非环状烯胺在亚磺酸钠、DMAc和MeSiCl3的共同作用下能高效高产率生成β-胺基烯基亚砜类新化合物,为合成多官能团化的烯基亚砜新化合物提供了一条简便实用的途径。 The main constituent of Dracontomelum mangiferum B1, indoloquinolizidine alkaloid 10-Desbromoarborescidine A, has drawn great attention due to its calcium channel blocking activity. Its molecular structure is relatively simple compared with the other alkaloids of the same type, which has only one chiral center, albeit with four cycles A, B, C, and D. This compound is often used as a model target for exploring different strategies for the total synthesis of indole alkaloids. Nevertheless, so far there still lack practical and highly efficient methods for the asymmetric total synthesis of 10-Desbromoarborescidine A. Most of the current available methods rely on stoichiometric asymmetric synthesis for the construction of the chiral center. There is only one example reporting utilization of asymmetric catalysis, but with transition metal complex as the catalyst. Our retrosynthetic analysis shows that catalytic asymmetric reduction of imine could be used as the key step for the construction of the chiral center of Desbromoarborescidine A. Since in the previous studies our group has developed the asymmetric reduction of imines by trichlorosilane into a practical and highly efficient and enantioselective method using newly designed chiral organocatalysts, we hope to apply this method to develop a novel synthetic route for the total synthesis of Desbromoarborescidine A and its analogues in this study. According to the newly designed synthetic route, we first accomplished the synthesis of the key intermediates which was then examined for the critical asymmetric catalysis. The asymmetric reduction using the highly efficient organocatalysts, developed in our lab afforded high ee but poor yield. We tried different reaction conditions to improve the yield, but failed to get any good results. Simultaneously, to vertify the feasibility of the synthetic route we designed, we also tired to go through the route toward the racemic synthesis of Desbromoarborescidine A. But unfortunately, protection and deprotection proved to be big hurdles. All the different protection groups and different sequences of protection and deprotection we tried failed to get us through the designed synthetic sequence and furnish the final product. Most likely, the indole part is the culprit behind the failures.The NH group of the indole, no matter protected or not, may impact the catalytic asymmetric reduction of C-N double bond connected with 2-C. Additionally, the reduction product we designed contains an amino group in the β-position of the indole, which may cause problems due to its instability. C-sulfenylation of enamines is a novel reaction discovered recently by our group, which has not been seen before in the literature. In this study, optimization of the reaction conditions and exploration of the substrate scope were further undertaken for this reaction, which reveal that a series of enamines with N-Cbz, Ac, COt-Bu, CO2Et protection groups could all undergo smooth C-sulfinylations with the comined use of sodium benzene sulphinate, DAMc and MeSiCl3, efficiently furnishing the β-amino vinylsulfoxide products in high yield, affording a practical and highly efficient methods for synthesis of functional vinylsulfoxides.