Appearance of perichromatin granules in decondensing sperm nuclei in fertilized mouse eggs

A number of granular structures measuring about 35-45 nm in diameter appeared in the dispersing chromatin materials of the decondensing sperm nuclei in fertilized mouse eggs. These granules were contrasted by the bismuth staining en bloc following either formaldehyde or glutaraldehyde fixation, and were encircled by an electron-lucent "halo." The facts indicate that these are perichromatin granules.     

Galvanomagnetic properties of bismuth films with a thin antimony coating or sublayer

The effect of modification of the surfaces of bismuth thin films with an antimony layer of 10 nm thick was studied. Three types of structures deposited onto mica substrates are compared: a bismuth film, an antimony layer as a sublayer for the bismuth film, and an antimony layer as the coating of the bismuth film. A substantial difference in the galvanomagnetic properties of the obtained structures is revealed in the dependence on the position of the antimony layer in the structure and on the bismuth-film thickness.     

Comparative structural biology of the genome: nano-scale imaging of single nucleus from different kingdoms reveals the common physicochemical property of chromatin with a 40 nm structural unit

Genome function is closely linked to the higher-order chromatin structures. To reveal a structural basis for the interphase chromatin organization, the 'on-substrate' lysis procedure was applied to nuclei isolated from human HeLa cells, chicken erythrocyte cells and yeast Schizosaccharomyces pombe, which possessed different intrinsic properties of the genomes such as histone composition and inter-nucleosomal distance. The isolated nuclei on a coverslip were successively treated with a detergent and a high-salt solution to extract the nuclear membrane and the nucleoplasm, and therefore, atomic force microscopy (AFM) visualized the structural changes in response to the lysis procedure. After the nucleoplasm was extracted, AFM clarified that chromatin fibers, approximately 40 nm in width, were partially released out of the nuclei and that the other chromatin still remaining in the nuclei was composed of granular structures with diameter of 80-100 nm. Thus, these results suggest that the approximately 40 nm fiber would be a stable structural unit and fold the 80-100 nm granules into a one-step higher unit. A common mechanism could be implied regardless of the intrinsic properties of the eukaryotic genomes.     

Bismuth–Ceramic Nanocomposites with Unusual Thermal Stability via High‐Energy Ball Milling

Electrically conducting nanocomposites of bismuth metal and insulating ceramic phases of SiO₂ and MgO were generated via high‐energy ball milling for 24 h using zirconia milling media. The resulting nanocomposites contain Bi nanoparticles with sizes down to 5 nm in diameter. The morphology is a strong function of the oxide phase: specifically, the Bi appears to wet MgO while it forms spherical nanoparticles on the SiO₂. X‐ray diffraction measurements indicate a nominal bismuth grain size of 50 nm, and peak fitting to a simple bidisperse model yields a mixture of approximately 57 % bulk bismuth and 43 % 27 nm diameter crystallites. Nanoparticles as small as 5 nm are observed in transmission electron microscopy (TEM), but may not constitute a significant volume fraction of the sample. Differential scanning calorimetry reveals dramatic broadening in the temperatures over which melting and freezing occur and a surprising persistence of nanostructure after thermal cycling above the melting point of the Bi phase.     

水热合成钛酸铋纳米粉体的研究

采用Bi(NO3)3.5H2O和TiCl4的混合物为前驱物,以KOH为矿化剂,在高压釜内经不同温度和时间的水热处理,获得了晶粒完整的Bi4Ti3O12粉体。借助XRD、SEM及TEM对Bi4Ti3O12的晶相组成、粒度、形貌进行了分析。研究结果表明:随水热温度的提高及时间的延长,晶体发育越完整,粒度越大;当温度为240℃,反应时间为4 h时,Bi4Ti3O12为短轴在30 nm左右,长轴大于100 nm的矩形片状晶体。     

Temperature Coefficient of Electrical Resistivity in Individual Single-Crystal Bismuth Nanowires

The temperature dependence of electrical resistivity and the crystal orientation of single-crystal bismuth nanowires each encapsulated in a quartz template were studied. The electrical resistivities of four bismuth nanowires with diameter of 356 nm, 376 nm, 622 nm, and 633 nm were measured in the temperature range from 4.2 K to 300 K. The temperature coefficient of resistivity of 376-nm- and 633-nm-diameter nanowires was negative in the low-temperature region. On the other hand, a positive temperature coefficient appeared in 356-nm- and 622-nm-diameter nanowires. The positive temperature coefficient was not explained by carrier mean free path limitation. Thus, the crystal orientation of the bismuth nanowires was observed by x-ray diffraction measurements to study the relationship between electrical resistivity and crystal orientation. It was confirmed that the temperature dependence of electrical resistivity strongly depended on the crystal orientation of the bismuth nanowire.     

Influence of bismuth on the optical properties of Ge2Sb2Te5 thin films

Chalcogenide alloys in the Ge-Sb-Te system are promising for application in phase-change memory devices. We investigated the influence of bismuth on the optical properties of Ge₂Sb₂Te₅ thin films and established that the bismuth doping in them allows the optical contrast of the thin films to be increased by about 30% at a wavelength of 400 nm. The experimental results are explained in an assumption on the impurity substitution of bismuth for antimony.     

WO3对掺铒碲酸盐玻璃的光谱性质的影响

为了满足光通信技术发展对光放大器材料的带宽要求,采用固相法制备了掺铒碲钨酸盐玻璃,研究了其光谱性质和热稳定性。用Judd-Ofelt理论计算了光谱的强度参量,根据McCumber理论计算了受激发射截面,其最大受激发射截面为1.85×10-20cm2,荧光半峰全宽最大值为104nm;用差热法分析了玻璃的热稳定性,析晶温度和转变温度之差最大值为131℃。结果表明,掺铒碲钨酸盐玻璃是一种良好的宽带放大器材料。     

Microchips for the Investigation of Thermal and Electrical Properties of Individual Nanowires

This paper focuses on the determination of thermal and electrical properties of individual thermoelectric nanowires, primarily bismuth and bismuth compound nanowires, as functions of their crystallinity, diameter, and composition. For measurements of the Seebeck coefficient and the electrical and thermal conductivity, specially designed microchips have been developed and employed. Finite-element simulations demonstrate that the temperature profiles of the microchips provide suitable temperature gradients for Seebeck-effect measurements and heat-sink conditions for thermal conductivity investigations. First measurements of thermal conductivity of metallic nanowires and of Seebeck coefficients of granular nanowires prepared by focused electron-beam-induced deposition are presented. Some of these results are discussed in the framework of finite-size-effect theory.     

Four-Wire Resistance Measurements of a Bismuth Nanowire Encased in a Quartz Template Utilizing Focused Ion Beam Processing

Four-wire resistance measurements were performed using a bismuth nanowire, 750?nm in diameter, 1.96?mm in length, and encapsulated in a quartz template. One side of the quartz template was polished to allow focused ion beam (FIB) processing, and metal film layers were deposited on the polished side to form electrodes. Nanofabrication was employed to remove a selected portion of the quartz, and FIB processing was used to expose the surface of the bismuth nanowire. A local area of the bismuth wire was successfully exposed, and a carbon electrode was deposited on the bismuth wire in?situ by a chemical reaction between the ion beam and phenanthrene gas. Additional carbon deposition on the initial carbon electrode was used to connect to a metal film on the quartz template. In total, four nanofabrications were performed on the bismuth wire to create the desired electrical contacts. The resistivity of the nanowire was measured by a four-wire method to be 1.29??????m at 300?K, corresponding to that of bulk bismuth. The temperature dependence of the resistivity was also measured, and was qualitatively and quantitatively in good agreement with previous calculated and experimental results using other bismuth nanowires. The present results demonstrate the successful development of a technique to fabricate an electrode on a local area of a nanowire using FIB processing to form suitable electrical contacts.     

A new MOD method to prepare Sr0.7Bi2.2Ta2O9 ferroelectric films for non-volatile RAM memories

Strontium bismuth tantalate, Sr_0.7Bi_2.2Ta₂O₉ (SBT), thin films were prepared by a new metalorganic decomposition (MOD) method using strontium (2,2,6,6-tetramethyl-3,5-heptanedionate), bismuth (2,2,6,6-tetramethyl-3,5-heptanedionate), and tantalum ethoxide as the metalorganic precursors. Films with a thickness of 300 nm were prepared on Si(1 0 0) with a layered bottom electrode (Pt/TiO₂/SiO₂). After crystallization in oxygen for 60 min at 750°C, single orthorhombic-phased films were obtained as determined by XRD, but no preferred crystalline orientation was revealed using this technique. Characterization by AFM showed that the polycrystalline films were densely packed and crack-free, and had an average surface roughness (rms) of 8 nm and a mean grain size of 150 nm. The remnant polarization and coercive field were 6 μC cm⁻² and 74 kV cm⁻¹, respectively. The SBT films showed a very low polarization fatigue after 10¹¹ switching cycles and good retention properties.     

Ag纳米颗粒对Er3+/Tm3+/Yb3+共掺铋锗酸盐玻璃上转换发光特性的影响

采用传统熔融淬冷法制备了系列Er³⁺/Tm 3+/Yb³⁺共掺复合Ag纳米颗粒的铋锗酸盐玻璃样品。从吸收光谱中 确定了Ag纳米颗粒表面等离子体共振(SPR)峰位于545nm附近;透射 电镜(TEM)图像中观察到均匀分布的Ag纳米颗粒,尺寸 约为6～18nm。研究了纳米Ag含量对Er3＋/Tm3＋ 共掺复合Ag纳米颗粒铋锗酸盐玻璃上转换发光特性的影响,结果表 明,Tm³⁺离子472nm处的上转换蓝光、Er³⁺离子525nm处的上转换绿光、543nm处的上转换 绿光和661nm处的上转换红光发光强度在AgCl含量的质量百分数为 1%时达到最大值,与未掺杂AgCl的基质玻璃相比,分别提高了约3.2、3.8、5.4倍。     

反射z扫描方法测量碲化铋晶体的非线性折射率

为了研究3维拓扑绝缘体碲化铋(Bi2Te3)的非线性光学特性,采用反射z扫描方法,实验测量了800nm飞秒脉冲激光的非线性折射系数。通过理论计算与实验数据拟合获得碲化铋晶体的非线性折射率达到10-14 m2/W数量级,为石英的105倍;随着入射功率的增大,其非线性折射率逐渐减小,在峰值光强达到85GW/cm2后趋于常数不变。结果表明,碲化铋是一种高非线性光学材料,有望应用于全光信号处理、光开关等方面。     

铒镱共掺铋磷酸盐玻璃光谱性能的研究

基于光通信技术发展对光放大器材料的带宽要求,研究了掺铒铋磷酸盐玻璃的结构、熔制性能,以及其光谱性能,并且用Judd-Ofelt理论进行了光谱计算分析。得到了一种以铋磷酸盐为基质的光放大器玻璃材料,其折射率为1.778,荧光半峰全宽为54nm,发射截面为0.61×10-20cm2,其荧光寿命达到了8ms。结果表明,铒镱共掺铋磷酸盐玻璃是一种良好的宽带放大器材料。     

On-substrate lysis treatment combined with scanning probe microscopy revealed chromosome structures in eukaryotes and prokaryotes

The proper function of the genome largely depends on the higher-order architecture of the chromosome. To understand the detailed chromosome structure in a native state, we developed an on-substrate procedure of subcellular fractionation suitable for the observation by atomic force microscopy (AFM). HeLa cells on a coverslip were successively treated with a detergent and a high-salt solution to remove the cytoplasmic and nucleoplasmic materials. A closer observation of the nucleus by AFM revealed that the interphase chromosome is composed of a granular unit of approximately 80 nm in diameter. Subsequent mild treatment with deoxyribonuclease I (10 U ml(-1)) exposed these units more clearly, which enabled us to uncover the 80-nm granules forming a fibre of approximately 80 nm width. In the cytoplasmic regions, cytoskeletal fibres with varying widths (10-70 nm) were observed. These observations suggest that the 80 nm granular fibre is a fundamental structural unit of the interphase chromosome. This on-substrate procedure was also applied to Escherichia coli. Cells attached on a coverslip were successively treated with lysozyme and detergent to partially release the nucleoid onto the substrate. The AFM observation revealed that the approximately 80 nm fundamental structural unit forms a granular fibre similar to that of HeLa cells. These results suggest that the fundamental mechanism of chromosome packing is common in both prokaryotes and eukaryotes.     

掺铋光纤铋活性中心发光机理的研究进展

掺铋光纤具有独特的发光特性,在光纤放大器和激光器中有着广阔的应用前景。为了掌握掺铋光纤的发光机理,研制出高效率、高性能的掺铋材料,整理了掺铋光纤发光机理的研究成果,从铋活化中心的结构和发光特性出发,总结了掺铋光纤中不同结构与发光波长之间的关系。掺铋材料由于具有荧光寿命长、光谱范围宽等优点,有望在超宽带光源、超宽带放大器、可调谐激光器等领域得到更为广泛的应用。     

Fabrication of Thermoelectric Devices by Applying Microsystems Technology

Microsystems technologies were applied in the fabrication of thermoelectric (TE) microconverters. Common techniques used in microelectromechanical systems (MEMS) fabrication, namely wet etching, lift-off (with SU-8 photoresist), reactive ion etching (RIE), and lithography-electroplating-molding, were compared in the fabrication process of TE microsystems based on Bi, Sb, and Te thin-film compounds. Thin films of bismuth and antimony tellurides were deposited by co-evaporation, with figures of merit comparable to those of bulk materials. Test structures were fabricated using lithography and wet etching. The etching recipe was optimized by varying the etchant dilution and composition until higher etch rates and desired material selectivity were attained. Since the etching process is applied after deposition, this process allows prior deposition of TE materials by any deposition method; thus, films with high figure of merit can be fabricated. Moreover, wet etching does not require the use of expensive equipment.     

小麦根端分生组织细胞核仁的超微结构与rDNA复制位置

应用常规电镜和电镜放射自显影技术，观察到小麦根端分生细胞核仁的超微结构是由纤维中心（FC），密集纤维成分（DFC）和颗粒成分（G）等构成的，小麦根尖用3H－胸腺嘧啶脱氧核苷标记，电镜放射自显影研究的结果显示，银粒大多分布在核仁边缘的颗粒区，密集纤维成分次之，纤维中心和密集纤维成分的交界区出现的银粒最少，我们推测，rDNA的复制主要发生在颗粒区，但有时在纤维中心与密集纤维成分交界处就开始复制，然后向颗粒区转移。     

Crystal Orientation and Transport Properties of a 633-nm-Diameter Bismuth Nanowire

The crystal orientation and resistivity of a bismuth nanowire (diameter 633 nm, length 1.91 mm) encased in quartz were measured. The nanowire surface was irradiated with a high-intensity, collimated x-ray beam through the quartz template, and several Laue spots were observed with no streak patterns. Therefore, we concluded that the nanowire was a single crystal. The crystal orientation could be determined by measuring the relationship between the Laue spot distribution and the location of the nanowire fixed by a goniometer. The direction along the wire length was strongly directed toward the bisectrix axis of bismuth. The temperature dependence of the nanowire resistivity was measured; the resistivity at 300 K was 1.40 μΩ m, which is somewhat greater than that of the bulk sample due to the lower mobility of the nanowire. The temperature coefficient of resistivity was positive in the temperature range from 300 K to 165 K, and it became negative below 165 K. The temperature dependence can be modeled by accounting for the limited electron mean free path in the bismuth nanowire based on the crystal orientation determined by the Laue measurements.     

用动态激光散射技术对冠心病危重病人血红蛋白结构的研究

目的:研究冠心病危重病人血红蛋白结构大小,为临床的诊断和治疗提供新信息。方法利用动态激光散射技术,分别对分散于pH=7.4、8.0缓冲液中的6例冠心病危重病人血红蛋白的粒径分布进行检测。结果:(1)在pH=7.4时冠心病危重病人的血红蛋白粒径保持为四聚体结构(5.62nm左右),与健康人相同。(2)pH=8.0时以粒径3.16nm左右为主,为单聚体结构,粒径4.22nm左右其次,为二聚体结构,粒径5.62nm左右非常少,为四聚体结构,与健康人在碱性环境下的粒径一致。结论:冠心病人危重病人血红蛋白的结构大小与健康人在相同条件下一致,没有发生病变。