Fabrication of MgB2 superconducting films by different methods

MgB₂ superconducting films have been successfully fabricated on single crystal MgO(111) and c-AL₂O₃ substrates by different methods. The film deposited by pulsed laser deposition is c-axis oriented with zero resistance transition temperature of 38.4 K, while the other two films fabricated by chemical vapor deposition and electrophoresis are c-axis textured with the zero resistance transition temperature of 38 K and 39 K, respectively. Magnetization hysteresis measurements yield critical current density J_c of 10⁷ A/cm² at 15 K in zero field for the thin film and of 10⁵ A/cm² for the thick film. For the thin film deposited by chemical vapor deposition, the microwave surface resistance at 10 K is found to be as low as 100 μΩ, which is comparable with that of a high-quality high-temperature superconducting thin film of YBCO.     

Distribution of growth hormone-like immunoreactive cells and somatostatin receptors in the nervous system and Hatschek's pit of amphioxus, Branchiostoma belcheri

Using immunohistochemical method and double staining technique, the localization of growth hormone (GH) and somatostatin receptors in the nervous system and Hatschek's pit of amphioxus has been investigated. The results showed that the growth hormone-like nerve cells and endocrine cells as well as three subtypes of somatostatin receptors exist in the nervous system and Hatschek's pit, and GH-like nerve cells and endocrine cells co-exist with three subtypes of somatostatin receptors in the brain vesicle and Hatschek's pit. It is suggested that a primitive control system of inhibitory growth hormone secretion in Hatschek's pit could have been developed in amphioxus, as in vertebrates. The present study provides new evidence for the endocrinology and the evolution of Hatschek's pit.     

Lp(［0,1］)-characterizations of multi-knot piecewise linear spectral sequences

There exists a class of new orthonormal basis for L²(［0,1］), whose exponential parts are multi-knot piecewise linear functions called spectral sequences. In this paper, we show that these bases constitute bases, but not unconditional bases, for L^p(［0,1］) with 1＜p＜∞, p≠2. In addition, we give the corresponding convergence theorem in L^p, Carleson-Hunt theorem on almost everywhere convergence, Littlewood-Paley theorem and Poisson summation formula related to these bases.     

C-banding pattern and nucleolar organizer regions of Cynoglossus semilaevis Günther, 1873

The C-banding pattern and nucleolar organizer regions of the metaphase chromosomes of Cynoglossus semilaevis are reported. The interstitial regions in all chromosomes including the pair of sex chromosomes had positive C-bands, and the 6th and 12th pairs of chromosomes were entirely stained in most cases. Some chromosomes such as the 1st, 2nd, 7th, 8th, 9th and 10th pairs showed C-bands at centromeric or distal ends. The C-banding heretochromatin occupies 30.03% of the total chromosome surface in C. semilaevis, which is similar to that of amphibians such as Mixophyes fasciolatus (30.2%) and M. schevilli (20.7%), but is rather lower than that of cephalochordate Branchiostoma belcheri (54.3%). Silver staining revealed a single pair of nucleolar organizer regions (NORs) located in the telomeric regions of Chromosome 2. The association of NORs with heterochromatin observed in vertebrates also occurs in C. semilaevis as the telomeric regions of Chromosome 2 are always stained positively with C-banding.     

Density functional theory study of the reaction paths of reactions of CH3C(O)O2 radicals with HO2 in the gas phase

A DFT study on the reactions between CH₃C(O)O₂ and HO₂ radicals has been carried out. It is suggested that both the triplet and singlet potential surfaces involve a complex mechanism with the formation of loosely bound intermediate complexes of reactants and products. The reaction prefers to occur on the triplet surface to produce peracetic acid (CH₃C(O)O₂H) and triplet O₂ molecule. The CH₃C(O)O₂H can further convert into CH₃C(O)O and HO radicals.     

Phase-selection and metastable phase formation in highly undercooled eutectic Ni78.6Si21.4 alloys

A large undercooling (250 K) was achieved in eutectic Ni_78.6Si_21.4 melt by the combination of molten-glass denucleation and cyclic superheating. The metastable phase formation process in the bulk undercooled eutectic Ni_78.6Si_21.4 melts was investigated. With the increase of undercooling, different metastable phases form in eutectic Ni_78.6Si_21.4 melts and part of these metastable phases can be kept at room temperature through slow post-solidification. Under large undercooling, the metastable phases β₂-Ni₃Si, Ni₃₁Si₁₂ and Ni₃Si₂ were identified. Especially, the Ni₃Si₂ phase was obtained in eutectic Ni_78.6Si_21.4 alloy for the first time. Based on the principle of free energy minimum and transient nucleation theory, the solidification behavior of melts was analyzed with regard to the metastable phase formation when the melts were in highly undercooled state.     

Shenzhousia qilianshanensis gen. et sp. nov. (Protodonata, Meganeuridae), a giant dragonfly from the Upper Carboniferous of China

A new dragonfly of family Meganeuridae Shenzhousia qilianshanensis gen. et sp. nov., discovered from Ningxia Hui Autonomous Region in North China, is described in the present paper. It has an estimated wingspan of about 450?500 mm and may be the largest fossil insect in Late Carboniferous Namurian Stage discovered by far. The new species is referred to Meganeuridae because of the presence of the characteristic oblique vein between anterior branch of radius (RA) and posterior branch of radius (RP) near the base of RP2. It differs from other genera within the family in the following characteristics: Precostal area short and not extending to the midwing; posterior branch of subcostal vein short, merging into costal vein near the level of originating point of IR₂; RP forking earlier than anterior branch of media basally; RP_1＋2 and RP_3＋4 parallel and close to each other for a long distance, and then diverge gradually surpass midwing.     

企业级IP电话系统的设计与实现

描述基于H.323协议的企业级IP电话系统的设计与实现。包括H.323协议的介绍,IP电话系统的设计和结构,网关的设计和模块实现,网守的设计与实现,系统初始化过程和呼叫的处理过程。     

关于证券组合在安全区域内的最优投资策略问题

本文讨论了一类安全区域内的最优证券组合问题,给出了投资者为了使自己的财富在尽可能短的时间内达到预定的目标财富所应采取的最优控制策略,并且针对具体的目标财富值及金融市场参数进行了数据分析,得出了为获得既定目标财富所需平均时间的最小值.     

保鲜香菇中甲醛含量的分析研究

采用乙酰丙酮法测定不同产地不同品种的香菇在其保鲜过程中甲醛的含量,同时还对沸水处理后的香菇中甲醛含量进行测试,结果说明我国北方香菇甲醛含量未超标,能达到保鲜香菇出口质量要求.