东海区海岸带景观格局变化对生态系统服务价值的影响

对大尺度、长时序的海岸带景观格局和生态系统服务价值(ecosystem services value,ESV)的研究,有利于更好地促进区域生态系统保护工作的开展。以1990,1995,2000,2005,2010,2015年6期遥感影像解译结果为基础,对东海区海岸带景观格局变化特征和ESV时空演变进行了分析,并探讨了ESV与景观格局变化二者间的关系。结果表明,1990—2015年的25 a间,受人类活动的影响,东海区海岸带农田和海域面积大量减少,建设用地面积大幅增加;在所研究的5类地貌类型中,除中起伏山地外,其余地貌类型景观面积转移都较为剧烈。25 a间东海区海岸带斑块数量、斑块密度、边界密度、shannon多样性指数等不断增加,景观破碎化、复杂化、多样化增强。农田景观的最大斑块指数、形态指数、边界密度等变化均较大。东海区海岸带ESV呈先增加后减小的趋势,其中森林景观对ESV总量贡献最大;水文调节、生物多样性维持、气候调节、土壤保持、废物处理和气体调节是东海区海岸带主要的生态系统服务功能;在空间上表现出以单位面积中、低ESV为主导的空间分布,高、极高和极低ESV分布较少。研究区ESV总量与农田和海域以及水域和建设用地面积显著相关;与斑块密度、边界密度和形态指数呈显著负相关。同时,食物生产、气体调节、气候调节、土壤保持和生物多样性维持的服务价值与景观指数间均显著相关。     

Study of<Emphasis Type="Italic"> β</Emphasis>–<Emphasis Type="Italic">α</Emphasis> recrystallization of the polypropylene

The crystalline modifications and of polypropylene (PP) were studied by using polarized light microscopy (PLM), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). Typically crystals surrounded by spherulites were observed at low temperature. With increasing temperature the crystals melted and a new crystal appeared. More interestingly, the melting temperature of the new crystal was about 5 ° higher than that of spherulites originally present in the sample formed isothermally. It was assumed that this new crystal was the recrystalline crystal. This assumption was supported by the DSC results. Furthermore, the crystallization kinetics of the PP used was studied on the basis of the traditional Avrami analysis. As a result, the Avrami exponents of crystallization temperature from 120 to 130 °C ranged between 4.21 and 3.60, indicating that the crystallization mechanism of PP order melt was spherulitic growth and random nucleation.     

化学修饰法表征Bacillus smithii T7产耐热菊粉酶催化活性中心的必需氨基酸残基

采用化学修饰法研究了史氏芽胞杆菌Bacillus smithiiT7产耐热菊粉酶活性中心氨基酸残基,发现该酶活性中心存在一个组氨酸残基和一个谷氨酸(或天冬氨酸)残基.修饰前后的酶动力学参数变化表明组氨酸残基参与了底物的结合和催化过程,而谷氨酸(或天冬氨酸)的羧基亲核攻击促使底物分解.邹氏作图法证明酶活性中心存在两个必需的色氨酸残基,荧光和圆二色光谱研究表明色氨酸残基在酶的催化和酶的耐热性方面起重要作用.     

垂直上升管内气液两相流流型鉴别研究

本文以低压空气一水作介质,进行了垂直上升管内气液两相流流型鉴别的实验研究;采用沿垂直管局部轴向压差信号及压差信号的统计分析并借助高速闪光观测仪进行可视化观察鉴别流型。实验结果发现,利用压差的时域信号和信号的功率谱密度函数（ＰＳＤ）,可以客观地判别垂直上升管内泡状、弹状和环状三种主要流型。     

Intensity image denoising for laser active imaging system using nonsubsampled contourlet transform and SURE approach

This paper presents an algorithm based on nonsubsampled contourlet transform (NSCT) and Stein's unbiased risk estimate with a linear expansion of thresholds (SURE-LET) approach for intensity image denoising. First, we analyzed the multiplicative noise model of intensity image and make the non-logarithmic transform on the noisy signal. Then, as a multiscale geometric representation tool with multi-directivity and shift-invariance, NSCT was performed to capture the geometric information of images. Finally, SURE-LET strategy was modified to minimize the estimation of the mean square error between the clean image and the denoised one in the NSCT domain. Experiments on real intensity images show that the algorithm has excellent denoising performance in terms of the peak signal-to-noise ratio (PSNR), the computation time and the visual quality.     

Monte Carlo simulation of miscibility of polymer blends with repulsive interactions: effect of chain structure

The effects of the chain structure and the intramolecular interaction energy of an A/B copolymer on the miscibility of the binary blends of the copolymer and homopolymer C have been studied by means of a Monte Carlo simulation. In the system, the interactions between segments A, B and C are more repulsive than those between themselves. In order to study the effect of the chain structure of the A/B copolymer on the miscibility, the alternating, random and block copolymers were introduced in the simulations, respectively. The simulation results show that the miscibility of the binary blends strongly depends on the intramolecular interaction energy () between segments A and B within the A/B copolymers. The higher the repulsive interaction energy, the more miscible the A/B copolymer and homopolymer C are. For the diblock copolymer/homopolymer blends, they tend to form micro phase domains. However, the phase domains become so small that the blend can be considered as a homogeneous phase for the alternating copolymer/homopolymer blends. Furthermore, the investigation of the average end-to-end distance () in different systems indicates that the copolymer chains tend to coil with the decrease of whereas the of the homopolymer chains depends on the chain structure of the copolymers. As for the system containing the alternating or the random copolymers, the homopolymer chains also tend to coil with the decrease of . However, for the systems including the block copolymers, there is a slight difference in the of the homopolymer chains with the variation of .     

The scaling behavior of the second virial coefficient of linear and ring polymer

The scaling behavior of the second virial coefficient of ring polymers at the theta temperature of the corresponding linear polymer(θ_L) is investigated by off-lattice Monte Carlo simulations. The effects of the solvents are modeled by pairwise interaction between polymer monomers in this approach. Using the umbrella sampling, we calculate the effective potential U(r) between two ring polymers as well as the second virial coefficient A_2 of ring polymers at θ_L, which results from a combination of 3-body interactions and topological constraints. The trend in the strength of the effective potential with respect to chain length shows a non-monotonic behavior, differently from that caused only by topological constraints. Our simulation suggests that there are three regimes about the scaling behavior of A_2 of ring polymers at θ_L: 3-body interactions dominating regime, the crossover regime, and the topological constraints dominating regime.     

Conformational Study on Thin Films of Symmetric AnB2nAn Triblock Copolymer

Summary: The behavior of symmetric A_nB_2nA_n triblock copolymer films confined between two hard neutral walls was explored by Monte Carlo simulation. The thicknesses of the films were between ≈1R_g0 and ≈7R_g0, where R_g0 is the unperturbed radius of gyration in the bulk. The confinement leads to a lamellar structure normal to the wall and the order‐disorder transition (ODT) temperature was found to be a function of film thickness. When the film thickness (D) was less than a critical value, D_C, which is between 3R_g0 and 4R_g0, the ODT temperature (T*_ODT) reduced by chain length N (T*_ODT/N) decreased with decreasing film thickness. However, T*_ODT/N was nearly independent of the film thickness when it was greater than D_C. In the case of strong confinement (D < D_C), the B block shrinks along the direction perpendicular to the wall and stretches along the direction parallel to the wall with decreasing film thickness, and the volume occupied by the B block shrinks. Under weak confinement conditions (D > D_C), the volume of the B block is nearly independent of film thickness. The conformations of the B block in the disordered state are quite different from those in the lamellae. If the film is thick enough, the volume of the B block approaches its value in the unperturbed state, regardless of the morphology. When temperature decreases, the B block stretches in the direction perpendicular to the A/B interface and shrinks in the other two directions. In addition, decreasing the temperature leads to the chains adopting two main extreme conformations, coiling or stretching as much as they can. The scaling behavior of the fraction of bridge chains vs. the temperature obtained in the weak segregation limit was different from that predicted in the strong segregation limit.

Schematic diagram of the X, Y and Z axis definition.     

The Critical Lowest Molecular Weight for PEG to Crystallize in Cross‐Linked Networks

Summary: Poly(ethylene glycol) (PEG) networks were synthesized by γ‐irradiation. The crystalline behavior of PEG was investigated by differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD). It was shown that the crystallinity of PEG is dramatically lower in the cross‐linked networks than in pure PEG. When the molecular weight of PEG in the networks decreased to 1 000, it could not crystallize at all. Moreover, we also found that the melting temperature of PEG is greatly affected by the presence of a cross‐linked network.

The DSC curves of PEG ( = 1 500) and the corresponding cross‐linked PEG.     

重组质粒在花生根瘤菌中的稳定性

以花生根瘤菌高效工程菌株ＨＮ１１，ＨＮ１２和ＨＮ１３各自的增效重组质粒为材料，在共生条件下和非共生人工液体培养基中，研究其在各自宿主快生型花生根瘤菌８５－７和慢生型花生根瘤菌ＣＯ２－５中的稳定性．结果表明：在根瘤内，８５－７宿主中重组质粒与空载体Ｐ（ＬＡＰＲ１）丢失程度相似，与外源片段存在无关；而在ＣＯ２－５宿主中ＨＮ１３的增效重组质粒比无效重组质粒及空载体Ｐ（ＬＡＰＲ１）丢失程度较轻，在人工液体培养基中，Ｐ（ＬＡＰＲ１）及其重组质粒在同一宿主中丢失程度相似．并讨论了以Ｐ（ＬＡＰＲ１）为载体的重组质粒丢失较严重的原因，提出了保持工程菌中重组质粒稳定性的相应措施．