嵌段聚醚酯化物的结构分析

本文对合成的嵌段聚醚酯化物的分子结构做了红外、高压液相色谱和~(13)C核磁共振分析,得出其构象和各种原子连接的方式,这些特征图谱为研究和生产此类型表面活性剂提供了可靠的检测依据。     

Forecasting using high‐frequency data: a comparison of asymmetric financial duration models

The first purpose of this paper is to assess the short‐run forecasting capabilities of two competing financial duration models. The forecast performance of the Autoregressive Conditional Multinomial–Autoregressive Conditional Duration (ACM‐ACD) model is better than the Asymmetric Autoregressive Conditional Duration (AACD) model. However, the ACM‐ACD model is more complex in terms of the computational setting and is more sensitive to starting values. The second purpose is to examine the effects of market microstructure on the forecasting performance of the two models. The results indicate that the forecast performance of the models generally decreases as the liquidity of the stock increases, with the exception of the most liquid stocks. Furthermore, a simple filter of the raw data improves the performance of both models. Finally, the results suggest that both models capture the characteristics of the micro data very well with a minimum sample length of 20 days. Copyright © 2008 John Wiley & Sons, Ltd.     

Mutations in IHH, encoding Indian hedgehog, cause brachydactyly type A-1.

Brachydactyly type A-1 (BDA-1; MIM 112500) is characterized by shortening or missing of the middle phalanges (Fig. 1a). It was first identified by Farabee in 1903 (ref. 2), is the first recorded example of a human anomaly with Mendelian autosomal-dominant inheritance and, as such, is cited in most genetic and biological textbooks. Here we show that mutations in IHH, which encodes Indian hedgehog, cause BDA-1. We have identified three heterozygous missense mutations in the region encoding the amino-terminal signaling domain in all affected members of three large, unrelated families. The three mutant amino acids, which are conserved across all vertebrates and invertebrates studied so far, are predicted to be adjacent on the surface of IHH.     

人体血浆晶体和分子生物胶体非新代谢组织及基因破坏

介绍了血浆在薄层状态中的结构化表征和物理化学性质：焓和导电性对温度的依赖性、谱性质、结合类型、冠状动脉梗塞病人血液的结合键从针状晶体向球状的结构改变以及此情况下脂蛋白的结构相变、“三明治”类型血液细胞中血浆薄状组织的表面能关系(表面能有如下关系：γs^d:γs^ρ≌0．1)以及包括红外和傅立叶光谱分析在内的用于观察血浆的复杂的、系统的方法．     

Hyperthermia-induced apoptosis and the inhibition of DNA laddering by zinc supplementation and withdrawal of calcium and magnesium in suspension culture of tobacco cells

In the present paper we report examination of stereotypic hallmarks of apoptosis in heat-treated tobacco cells. Hyperthermia (44 °C, 4 h) caused apoptosis in 53.6% of cells when assayed 24 h after heat treatment. The induction of apoptosis by heat treatment was confirmed by flow cytometric assay. Cytological observations revealed condensation of the cytoplasm and nucleus, as well as nuclear collapse. DNA ladders were observed in DNA extracted from heat-treated cells, whereas DNA from control cells remained undegraded. The terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay revealed that 51.8% of the heat-treated cells (44 °C, 4 h) show positive reaction after a 24-h recovery. When cells were cultured in a medium supplemented with 0.4–5.0 mM ZnSO₄, internucleosomal DNA fragmentation induced by heat shock was completely negated. Strikingly, when cells were cultured in Ca²⁺ and/or Mg²⁺ free medium for 44 h followed by heat treatment, DNA laddering was not observed. The results suggest hyperthermia-induced apoptosis and a correlation between the regula tion of endonucleases and heat shock signal in apoptotic tobacco cells. Received 17 September 1998; received after revision 4 January 1999; accepted 4 January 1999     

The prolyl isomerase Pin1 restores the function of Alzheimer-associated phosphorylated tau protein.

One of the neuropathological hallmarks of Alzheimer's disease is the neurofibrillary tangle, which contains paired helical filaments (PHFs) composed of the microtubule-associated protein tau. Tau is hyperphosphorylated in PHFs, and phosphorylation of tau abolishes its ability to bind microtubules and promote microtubule assembly. Restoring the function of phosphorylated tau might prevent or reverse PHF formation in Alzheimer's disease. Phosphorylation on a serine or threonine that precedes proline (pS/T-P) alters the rate of prolyl isomerization and creates a binding site for the WW domain of the prolyl isomerase Pin1. Pin1 specifically isomerizes pS/T-P bonds and regulates the function of mitotic phosphoproteins. Here we show that Pin1 binds to only one pT-P motif in tau and copurifies with PHFs, resulting in depletion of soluble Pin1 in the brains of Alzheimer's disease patients. Pin1 can restore the ability of phosphorylated tau to bind microtubules and promote microtubule assembly in vitro. As depletion of Pin1 induces mitotic arrest and apoptotic cell death, sequestration of Pin1 into PHFs may contribute to neuronal death. These findings provide a new insight into the pathogenesis of Alzheimer's disease.     

Frequency of the various stages of the seminiferous epithelium in different strains of male mice.

The duration of the various development stages of the seminiferous epithelium in different strains of male mice was determined by scoring the frequency distribution in randomly selected tubule cross-sections. The results obtained show a difference in the duration of the various stages between the different strains.     

The rapid formation of a large rotating disk galaxy three billion years after the Big Bang

Observations and theoretical simulations have established a framework for galaxy formation and evolution in the young Universe. Galaxies formed as baryonic gas cooled at the centres of collapsing dark-matter haloes; mergers of haloes and galaxies then led to the hierarchical build-up of galaxy mass. It remains unclear, however, over what timescales galaxies were assembled and when and how bulges and disks--the primary components of present-day galaxies--were formed. It is also puzzling that the most massive galaxies were more abundant and were forming stars more rapidly at early epochs than expected from models. Here we report high-angular-resolution observations of a representative luminous star-forming galaxy when the Universe was only 20% of its current age. A large and massive rotating protodisk is channelling gas towards a growing central stellar bulge hosting an accreting massive black hole. The high surface densities of gas, the high rate of star formation and the moderately young stellar ages suggest rapid assembly, fragmentation and conversion to stars of an initially very gas-rich protodisk, with no obvious evidence for a major merger.