有机-无机复合质子交换膜的制备与界面特性

有机-无机复合质子交换膜的开发是燃料电池用质子交换膜的一个重要研究方向,本文综述了有机-无机复合质子交换膜的制备方法,分析了两相之间的界面特性,并对这种复合膜的研究前景进行了展望.     

Cytoskeletal involvement in cotton fiber growth and development

The organization of cellulose microfibrils in plant cell walls influences physical properties of the wall and thus cell expansion characteristics. Developing cotton fiber represents an excellent model system for the analysis of the biological regulation of cell wall patterns. Current research indicates that the cytoskeleton has a major role in directing the deposition and organization of cellulose microfibrils in the cell walls of many plant systems, including developing cotton fibers. Both microtubules and microfilaments appear to be involved in regulating changes observed in microfibril patterns during fiber development. The polylamellate architecture of the fiber wall can be attributed to changes in the orientation of cytoplasmic microtubules which appear to direct the orientation of microfibril deposition in each successive layer of the fiber wall. In the drug-induced absence of microtubules, cellulose is deposited in the fiber wall in a swirled pattern of bundled microfibrils. Interaction between adjacent microfibrils may influence cell wall organization on a localized level. In contrast to the direct involvement of microtubules on wall organization, microfilaments appear to be indirectly involved in the deposition of cellulose microfibrils. Current evidence indicates that microfilaments influence wall organization by controlling changes in microtubules patterns. Although a greater understanding of the relationship between the cytoskeleton and the fiber wall is needed, there is sufficient evidence to indicate that genetic manipulation of cytoskeletal components is one path toward future direct manipulation of cell expansion characteristic in many plant systems and may lead to improvements in the textile qualities of cotton fibers.     

一种精确检测细胞真实边缘的算法

分析了传统边缘检测算法在细胞边缘检测和形态分析中存在的缺陷。提出了最佳阈值分割和轮廓提取相结合的细胞边缘检测新方法。通过理论分析和实验,证明该方法能有效抑制噪声干扰的影响,实现细胞真实边缘的精确检测。     

Supporting hydrogen based transportation: case studies with Global MARKAL Model

Steadily growing prices of oil and emissions coming from conventional vehicles, might force a switch to an alternative and less polluting fuel in the coming future. In this article we analyze the potential influence of selected factors for successful market penetration of hydrogen fuel cell vehicles in hydrogen based private transportation economy. Using a world scale, full energy system, bottom-up, optimization model (Global MARKAL Model—GMM) we address the possibility of supporting the fuel cell vehicle technology to become competitive in the markets. In a series of optimizations we evaluate the potential influence of governmental supports and the internalization of externalities related to CO₂ and local pollution emissions originating from the transportation sector, as well as preferential crediting options and demonstration projects promoting fuel cell vehicles. The results suggest that the crucial element is the price of fuel cells and their further potential to reduce costs. This reduction of costs may be triggered by governmental support such as direct subsidies to fuel cells, preferential crediting options for the buildup of hydrogen infrastructure as well as penalization of emitters of CO₂ and/or local pollutants.     

DNA damage induced by laser-hematoporphyrin derivative

Irradiation caused DNA single-strand breaks in S180 cells in the presence oflaser-hematoporphyrin derivative(HPD).The number of single strand breaks was 3.69 ×10~(10)break dolton~(-1).The analysis of base composition of DNA showed that the effect of laser-HPDirradiation on guanine was the highest,being 5-12 times as high as those of the three others(adenine,cytosine and thymine).It was different from the nature of DNA damage caused by γ-ray irradiation.     

Numerical analysis of the developing fluid flow in a circular duct rotating steadily about a parallel axis

A numerical analysis of the flow pattern in the inlet region of a circular pipe rotating steadily about an axis parallel to its own is presented. Both finite cell and finite element methods are used to analyse the problem and they give qualitatively similar results which show that a swirling fluid motion is induced in the pipe inlet region. The analyses show that the direction of swirl is opposite to that of the pipe rotation when viewed along the flow axis and that its magnitude depends on the speed of pipe rotation and throughflow Reynolds number. Neither numerical analysis predicts the marked upturn in friction factor (or pressure drop) which has been observed experimentally. However, a dependence on the pipe inlet boundary conditions is demonstrated.     

Femoral head avascular necrosis in sickle cell anemia: MR characteristics

Since considerable expansion of hematopoietic marrow occurs in patients with sickle cell anemia (SCA), magnetic resonance images of 20 hips in 10 patients with known homozygous SCA were reviewed to determine a) if low signal hematopoietic marrow extended into the femoral capital epiphysis and b) if the MR characteristics of avascular necrosis (AVN) differed depending on the type of epiphyseal marrow. Our results revealed variable epiphyseal marrow type; mixed (fatty and hematopoietic) marrow (42%), fatty marrow (32%), hematopoietic marrow (16%) and hemosiderotic marrow (10%). AVN occurred irrespective of the underlying marrow. Segmental areas of low signal intensity in variable shapes (ring, band, crescent or large homogeneous area) was the most consistent MR manifestation of AVN in SCA. A low signal intensity peripheral rim surrounding a central zone, isointense with epiphyseal marrow on T₁ and T₂ weighted images, was most frequently observed similar to that described in patients without hemoglobinopathy. The notable difference, however, was of segmental areas within the same femoral head that demonstrated variable central zone signal on T₂ weighted images. Further, while an increase in hip joint fluid is commonly seen with both early and advanced AVN in patients without hemoglobinopathy; it was increased in only one hip in patients with SCA. The observed differences in MR characteristics may be due to different pathophysiology of AVN in patients with SCA.     

The L2-optimal cell width for the histogram

We give the value of the cell width which minimizes the integrated mean squared error of the histogram estimate of a multivariate density.     

β-BaB2O4晶体高压相变的X光衍射研究

 我们用金刚石压砧装置（DAC）高压X射线粉末衍射照相方法，研究了β-BaB₂O₄晶体的相变。压力从0.1 MPa逐步加至17.6 GPa，发现BBO由室温下的六方相经历了若干次相变后，当压力加至11.5 GPa时，转变为无定形相。在11.5 GPa压力前的相变是可逆的，一旦进入无定形相，则相变是不可逆的。     

固体聚合物电解质燃料电池的研究

报道了固体聚合物电解质燃料电池的电极制备方法和温度，压力以及阴极气量对电池性能的影响。