258 resultados para La_(2-x)Sr_xCuO_4


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We report on the effect of various alkaline-earth metal oxides on the broadband infrared luminescence covering 1000-1600 nm wavelength region from bismuth-doped silicate glasses. The full width at half maximum (FWHM) of the infrared luminescence and the fluorescent lifetime is more than 200 nm and 400 mu s, respectively. The fluorescent intensity decreases with increasing basicity of host glasses. Besides the broadband infrared luminescence, luminescence centered at 640 nm was also observed, which should be ascribed to Bi2+ rather than to the familiar Bi3+. We suggest that the infrared luminescence should be assigned to the X-2 (2)Pi (3/2) -> X-1 (2)Pi(1/2) transition of BiO molecules dispersed in the host glasses. (c) 2006 Elsevier Ltd. All rights reserved.

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This is about the first reported laser glass with very low no, high Er3+ concentration and no quenching. In this work, a series of high Er3+ concentration (10.6-12.2 x 10(20) ions/cm(3)), low refractive index (n(1550) < 1.47) and relatively high fluorescence lifetime (6.8-12.6 ms) fluorophosphate glasses were made. A cw-pumping evanescent wave optical amplifier experiment was performed with it, and a relative gain of around 2dB at 1550 nm wavelength was achieved while the noise level was almost unchanged. To our knowledge, this is the first successful relative gain in evanescent wave optical amplifiers (EWOA) demonstrated with cw pumping. It is a valuable study of specially designed fluorophosphate glass suitable for EWOA communication experiment. (C) 2008 Elsevier B.V. All rights reserved.

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利用射频磁控溅射法室温下在Si(100)衬底上制备了N掺杂的TiO2薄膜,并且采用x射线衍射(XRD)、X射线光电子能谱(XPS)和透射光谱对薄膜进行了表征。XRD结果表明在纯Ar和N2(33.3%)/Ar气氛下制备的TiO2-xNx薄膜均为单一的金红石相,薄膜结晶性良好,呈高度(211)择优取向,而在N2(50.0%)/Ar下制备的薄膜结晶性明显变差;对于N掺杂的TiO2薄膜,XPS表明部分N原子进入TiO2晶格,并且以N—Ti—O、N—O键以及间隙式N原子形式存在;透射光谱表明掺N后的TiO2薄膜吸收边发生了红移。

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Based on Maxwell's equations, standard boundary conditions are imposed on resultant electric- and magnetic-field vectors at interfaces, and the propagating characteristics of extraordinary waves, such as the forward- and backward-propagating directions of wave vectors, rays and their corresponding refractive indices are determined in a uniaxially birefringent thin film. Furthermore, 2 x 2 characteristic matrices of a birefringent thin film are derived including multiple reflections for the extraordinary wave.

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In this paper, 2 X 2 characteristic matrices of uniaxially anisotropic thin film for extraordinary and ordinary wave are deduced at oblique incidence. Furthermore, the reflectance and transmittance of thin films are calculated separately for two polarizations, which provide a new concept for designing non-polarizing thin films at oblique incidence. Besides, using the multilayer birefringent thin films, non-polarizing designs, such as beam splitter thin film at single wavelength, edge filter and antireflection thin film over visible spectral region are obtained at oblique incidence.

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As the principal section consistent with the principal plane, electromagnetic propagation in a uniaxially birefingent thin film can be described with a concise 2 x 2 characteristic matrix, in which the refractive indices of the forward and backward propagating extraordinary rays are different and dependent. In this letter, based on Huygen's construction, the refractive indices and effective optical admittances of the forward and backward propagating extraordinary rays are discussed further, and the 2 x 2 characteristic matrix is simplified. Furthermore, the input optical admittance, reflectance and transmittance of assembly is presented, just as an isotropic thin film. The result can be extended to the general case of multilayer uniaxially birefringent thin films with their optic axes in the incident plane. Copyright (c) EPLA, 2007.

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本研究选取毛茛目99属,利用四个叶绿体和核基因或DNA片段,并结合形态性状,在属的水平上构建毛茛目的系统发育关系。分子数据用简约法和似然法分析,分子和形态性状联合数据用简约法分析。具体结果如下: 1) 毛茛目的单系性 毛茛目的单系性在所有的分析中都得到强支持。这也被形态性状所支持,包括大的S-型筛管分子、表皮层具蜡质的管、离生并折合状发生的心皮、两层珠被形成的珠孔、无托叶、轮状花被(花被在领春木科可能是次生性丢失)和2-3层细胞组成的内珠被等。 2) 科间系统发育关系 毛茛目由三个主要分支构成:领春木科、罂粟科和核心毛茛目。罂粟科是核心毛茛目的姊妹群,二者通常具复叶、单叶分裂或单叶掌状脉,雄蕊轮状排列以及胚珠无丹宁酸组织。核心毛茛目的单系性得到强支持,花3基数、雄蕊和花被片对生以及外部花被片具三或更多的微管束迹等是其共有衍征。木通科和星叶草科形成一支,细胞型胚乳是它们的共有衍征。防己科、小檗科和毛茛科形成一支,核型胚乳和具小檗碱支持该支的单系性。小檗科和毛茛科的姊妹群关系得到草本习性、具根状茎、V-型木质部和外珠被至少四层细胞等性状的支持。 3) 科下系统发育关系 a. 罂粟科 罂粟科分为两个单系支:狭义罂粟科形成一支,Pteridophyllm、角茴香属和狭义荷包牡丹科形成另一支。是否具乳汁、小苞片状的萼片是否包着其他花部器官、雄蕊数目和花粉外壁纹饰等性状支持这种划分。这两支分别被给予亚科的分类等级。Pteridophyllm是角茴香属的姊妹群也得到分辨,叶和雄蕊的性状支持这两属近缘。 b. 星叶草科 独叶草属和星叶草属形成一支得到强支持,二者组成星叶草科。二叉状分支的叶脉、条纹状的花粉纹饰、单珠被、薄珠心和无外种皮等性状是该科的共有衍征。 c. 木通科 木通科的单系性得到强支持。大血藤属是其他木通科的姊妹群,因其在心皮数目、心皮排列、胚珠数目、胚珠方向、染色体数目和植物化学等方面不同于其他类群,建议给予亚科的分类等级。此外,猫儿屎属和串果藤属均具有一些独特的性状,分别给予族的等级。 d. 防己科 古山龙属和Anamirta形成一支,意味着族Anamirteae sensu Diels应该被承认;广义的青牛胆族应包括天仙藤族;无胚乳的粉绿藤族嵌合在蝙蝠葛族之内。子叶和花柱残基对科内的划分是非常重要的。虽然传统上认为胚乳是科下划分最重要的性状,但它在防己科内应该是次生性丢失。 e. 小檗科 六个间断分布的属或属对被证实。单心皮瓶状发生是小檗科的共有衍征。小檗科分为三个主要分支:南天竹属(x = 10)和染色体基数为8的类群形成强支持的一支,这也得到胚珠数目(2-4)和圆锥花序等性状的支持;x = 7的类群形成一支,花瓣基部内侧具2枚腺体,花粉具平滑的外壁和未分化的外表层等是其共有衍征;x = 6的类群形成一支,被条纹状的花粉外壁和不连续的花粉外壁内层所支持。这三支分别被给予亚科的分类等级。 f. 毛茛科的单系性得到强支持。雄蕊多数和胚珠多数是毛茛科的共有衍征。毛茛科由五个分支组成:Glaucidium、Hydrastis、染色体基数为9的类群形成一支、染色体基数为7的类群形成一支、染色体基数为8的类群形成一支,分别给予亚科的分类等级。Glaucidium是所有其他毛茛科的姊妹群。染色体基数为8的类群的单系性得到极弱的支持,不含有或者含微量的苄基异喹啉生物碱及具R-型染色体似乎也支持该支为单系。星果草属应隶属于毛茛亚科而与黄连属和(/或)人字果属关系遥远。在唐松草亚科,具瘦果的唐松草属嵌合在具蓇葖果的类群之内,意味着依据果实类型划分该亚科是不合适的。美花草属和毛茛族及银莲花族形成一支,而与侧金盏花属关系遥远。美花草属在胚珠着生位置、珠被数目和植物化学等方面不同与毛茛族和银莲花族,因此我们建议给予美花草属族的分类等级。 根据分析结果,我们提出了毛茛目一个新的分类系统

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以流式细胞仪分离小麂(Muntiacus reevesi)Y染色体和黑麂(M. crinifrons)Y_(1),Y_(2),X+4和1号染色体,利用DOP-PCR技术富集了分离的各单条染色体。然后,将小麂的Y染色体的DOP-PCR产物经Cy_(3)标记后直接作为涂染探针,应用染色体涂染技术与雌雄黑麂的核型标本进行杂交,确认了黑麂真正的Y染色体为Y_(2)染色体。再以黑麂的Y_(1),Y_(2),X+4和1号染色体的DOP-PCR产物为模板,用人的特异性的SRY基因引物对其进行扩增,结果表明黑麂只有Y_(2)染色体出现了SRY扩增片段。

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By Sephadex G-50 gel filtration, Resource Q anionic exchange and C4 reversed phase liquid high performance liquid chromatography, a proteinase inhibitor protein (Ranaserpin) was identified and purified from the eggs of the odour frog, Rana grahami. The protein displayed a single band adjacent to the molecular weight marker of 14.4 kDa analyzed by SDS-PAGE. The inhibitor protein homogeneity and its molecular weight were confirmed again by MALDI-TOF mass spectrometry analysis. The MALDI-TOF mass spectrum analysis gave this inhibitor protein an m/z of 14422.26 that was matched well with the result from SDS-PAGE. This protein is a serine proteinase inhibitor targeting multiple proteinases including trypsin, elastase, and subtilisin. Ranaserpin inhibited the proteolytic activities of trypsin, elastase, and subtilisin. It has an inhibitory constant (K-i) of 6.2 x 10(-8) M, 2.7 x 10(-7) M and 2.2 x 10(-8) M for trypsin, elastase, and subtilisin, respectively. This serine proteinase inhibitor exhibited bacteriostatic effect on Gram-positive bacteria Bacillus subtilis (ATCC 6633). It was suggested that ranaserpin might act as a defensive role in resistance to invasion of pests or pathogens. This is the first report of serine proteinase inhibitor and its direct defensive role from amphibian eggs. (C) 2007 Elsevier Inc. All rights reserved.

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用染色体分带技术分析表明云南兔2n=48, 常染色体中有6对中着丝点染色体、5对亚中着丝 点染色体、10对亚端着丝粒染色体和2对端着丝粒染色体。x染色体为一较大的亚中着丝粒染色体。c-带核型中, Nos.9,14,16,20染色体着丝粒c-带呈阴性, 而13,15,18呈很弱的阳性 。图版1表2参22(邓琳珠)

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A novel bradykinin-potentiating peptide (BPP), designated as TmF, has been purified to homogeneity from the venom of Trimeresurus mucrosquamatus by 70% cold methanol extraction, Sephadex G-15 gel filtration and reverse-phase high performance liquid chromatography (RP-HPLC). The amino acid sequence of TmF was determined to be pGlu-Gly-Arg-Pro-Leu-Gly-Pro-Pro-Ile-Pro-Pro (pGlu denotes pyroglutamic acid), which shared high homology with other BPPs. The molecular mass of TmF was 1.1107 kD as determinated by electrospray ionization-mass spectrometry (ESI-MS), which was in accordance with the calculated value of 1.1106 kD. The potentiating "unit" of TmF to bradykinin-induced (BK-induced) contraction on the guinea-pig ileum in vitro was (1.13 +/- 0.3) unit (mg/L), and TmF (5.0 x 10(-4) mg/kg) increased the pressure-lowering-effect of bradykinin (5.0 x 10(-5) mg/kg) with approximate descent value of (14 +/- 2) mmHg. In addition, TmF inhibited the conversion of angiotensin I to angiotensin 11, 2 x 10(-3) mg of TmF caused 50% inhibition (IC50) of angiotensin-converting enzyme (ACE) hydrolyzing activity to bradykinin.

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A new amino silica monolithic column was developed for DNA extraction in a miniaturized format. The monolithic column was prepared in situ by polymerization of tetraethoxysilane (TEOS) and N-(beta-aminoethyl)-gamma-aminopropylmethyldimethoxysilane (AEAPMDMS). DNA was loaded in 50 mM tris(hydroxylmethyl)aminomethane-EDTA buffer at pH 7.0 and eluted with 300 mM potassium phosphate solution at pH 10.0. Under optimal condition, a 6.0-cm monolithic column provided a capacity of 56 ng DNA with an extraction efficiency of 71 +/- 5.2% (X +/- RSD). When the amino silica monolithic column was applied to extract genomic DNA from the whole blood of crucian carp, an extraction efficiency of 52 +/- 5.6% (X +/- SD) was obtained by three extractions. Since the chaotropic-based sample loading and organic solvent wash steps were avoided in this procedure, the purified DNA was suitable for downstream processes such as PCR. This amino silica monolithic column was demonstrated to allow rapid and efficient DNA purification in microscale.

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Background: Short and long interspersed elements (SINEs and LINEs, respectively), two types of retroposons, are active in shaping the architecture of genomes and powerful tools for studies of phylogeny and population biology. Here we developed special protocol to apply biotin-streptavidin bead system into isolation of interspersed repeated sequences rapidly and efficiently, in which SINEs and LINEs were captured directly from digested genomic DNA by hybridization to bead-probe complex in solution instead of traditional strategy including genomic library construction and screening. Results: A new couple of SINEs and LINEs that shared an almost identical 3'tail was isolated and characterized in silver carp and bighead carp of two closely related species. These SINEs (34 members), designated HAmo SINE family, were little divergent in sequence and flanked by obvious TSD indicated that HAmo SINE was very young family. The copy numbers of this family was estimated to 2 x 10(5) and 1.7 x 10(5) per haploid genome by Real-Time qPCR, respectively. The LINEs, identified as the homologs of LINE2 in other fishes, had a conserved primary sequence and secondary structures of the 3'tail region that was almost identical to that of HAmo SINE. These evidences suggest that HAmo SINEs are active and amplified recently utilizing the enzymatic machinery for retroposition of HAmoL2 through the recognition of higher-order structures of the conserved 42-tail region. We analyzed the possible structures of HAmo SINE that lead to successful amplification in genome and then deduced that HAmo SINE, SmaI SINE and FokI SINE that were similar in sequence each other, were probably generated independently and created by LINE family within the same lineage of a LINE phylogeny in the genomes of different hosts. Conclusion: The presented results show the advantage of the novel method for retroposons isolation and a pair of young SINE family and its partner LINE family in two carp fishes, which strengthened the hypotheses containing the slippage model for initiation of reverse transcription, retropositional parasitism of SINEs on LINEs, the formation of the stem loop structure in 3'tail region of some SINEs and LINEs and the mechanism of template switching in generating new SINE family.

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We experimentally demonstrate a small-size and high-speed silicon optical switch based on the free carrier plasma dispersion in silicon. Using an embedded racetrack resonator with a quality factor of 7400, the optical switch shows an extinction ratio exceeding 13 dB with a footprint of only 2.2 x 10(-3) mm(2). Moreover, a novel pre-emphasis technique is introduced to improve the optical response performance and the rise and the fall times are reduced down to 0.24 ns and 0.42 ns respectively, which are 25% and 44% lower than those without the pre-emphasis.

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The crystalline, surface, and optical properties of the (10 (1) over bar(3) over bar) semipolar GaN directly grown on m-plane sapphire substrates by hydride vapor phase epitaxy (HVPE) were investigated. It was found that the increase of V/III ratio led to high quality (10 (1) over bar(3) over bar) oriented GaN epilayers with a morphology that may have been produced by step-flow growth and with minor evidence of anisotropic crystalline structure. After etching in the mixed acids, the inclined pyramids dominated the GaN surface with a density of 2 X 10(5) cm(-2), revealing the N-polarity characteristic. In the low-temperature PL spectra, weak BSF-related emission at 3.44eV could be observed as a shoulder of donor-bound exciton lines for the epilayer at high V/III ratio, which was indicative of obvious reduction of BSFs density. In comparison with other defect related emissions, a different quenching behavior was found for the 3.29 eV emission, characterized by the temperature-dependent PL measurement. (C) 2009 Elsevier B.V. All rights reserved.