含异亚丙基聚亚胺醚酮空心微球的制备

以1,4-双-（4’-溴苯酰基）苯和2,2-双-[4-（4-氨基苯氧基）苯基]丙烷为单体,以三（二亚苄基丙酮）二钯为催化剂,1,1’-联萘-2,2’-二苯膦（BINAP）为配体,由钯催化的胺基化反应缩聚合成了含异亚丙基的聚亚胺醚酮（pr—PIEK）,并通过微封装法制备了pr—PIEK空心微球．     

层状复合氢氧化物的药物控释动力学机制

以层状复合氢氧化物(LDH)为载体组装乙酰苯甲酸(ASP)的插层复合物LDH-ASP,以pH2.48~6.89的磷酸盐溶液为介质进行药物释放动力学实验,通过对不同时间药物释放度的测定及释放药物后载体结构变化分析研究了LDH对层间药物的控制释放机制。结果表明粉末状LDH-ASP能在较宽的pH范围表现明显缓控释作用,药物释放度积分方程与Higchi方程、Ritger-Peppas方程、Bhaskar方程及一级动力学方程等经验模型吻合。复合物与溶出介质的反应机制研究表明,药物释放速率及释放度大小取决于交换配比n(ASP)/n[HnPO4(3-n)-]所决定的LDH层间通道畅阻情况。     

苯甲酸(苯并三唑基)苯酯类紫外光稳定剂的合成及表征

以邻硝基苯胺和间苯二酚为原料,经重氮化-偶合、环化、酯化合成了6个新型苯甲酸(苯并三唑基)苯酯类化合物:3-羟基-4-苯并三唑基-4′-硝基苯甲酸苯酯(58.6%)、3-羟基-4-苯并三唑基-2′-硝基苯甲酸苯酯(60.7%)、3-羟基-4-苯并三唑基-3′-硝基苯甲酸苯酯(55.7%)、3-羟基-4-苯并三唑基-3′,5′-二硝基苯甲酸苯酯(62.1%)、3-羟基-4-苯并三唑基-2′-羟基苯甲酸苯酯(48.6%)和3-羟基-4-苯并三唑基-2′-羟基-3′,5′-二硝基苯甲酸苯酯(52.2%)。通过1H-NMR、FT-IR和MS确定了这些化合物的分子结构,紫外光谱测试表明它们均具有较好的紫外吸收性能。     

Selective etching of graphene edges by hydrogen plasma

We devised a controlled hydrogen plasma reaction at 300 °C to etch graphene and graphene nanoribbons (GNRs) selectively at the edges over the basal plane. Atomic force microscope imaging showed that the etching rates for single-layer and few-layer (≥2 layers) graphene are 0.27 ± 0.05 nm/min and 0.10 ± 0.03 nm/min, respectively. Meanwhile, Raman spectroscopic mapping revealed no D band in the planes of single-layer or few-layer graphene after the plasma reaction, suggesting selective etching at the graphene edges without introducing defects in the basal plane. We found that hydrogen plasma at lower temperature (room temperature) or a higher temperature (500 °C) could hydrogenate the basal plane or introduce defects in the basal plane. Using the hydrogen plasma reaction at the intermediate temperature (300 °C), we obtained narrow, presumably hydrogen terminated GNRs (sub-5 nm) by etching of wide GNRs derived from unzipping of multiwalled carbon nanotubes. Such GNRs exhibited semiconducting characteristics with high on/off ratios (～1000) in GNR field effect transistor devices at room temperature.     

三江平原湿地非使用价值支付意愿的影响因素

为了更好地保护三江平原湿地生态系统,应用条件价值评估法(CVM)这一当前国际上流行的生态系统经济价值评价方法,对三江平原湿地的非使用价值进行评价.研究中采用实地调研的方式,进行支付意愿问卷调查,共发放支付卡式CVM问卷552份,回收有效问卷513份.得出三江平原湿地2007年人均支付意愿为71.66元/年.通过对问卷数据的描述性统计,得到支付意愿的分布情况和在各单一因素影响下的变化规律.用主成分分析简化影响因素,运用有序多分类Logit模型,得到在所有影响因素中,个人平均年收入、个人受教育程度以及个人环保态度是影响受访者对三江平原湿地非使用价值支付意愿的主要因素.研究结论使得三江平原湿地开发和保护价值比较成为可能,为政府制定相关政策提供理论基础与科学依据.     

关于分布重尾程度的一类刻画

针对应用概率研究的需要,提出了较重尾分布的概念,以失效函数为工具,着重探讨并得到了一些利用相互比较重尾程度来确定分布族的方法.     

Reversibly controlled morphology transformation of an amphiphilic DNA-dendron hybrid

Spherical micelles and nanofibers assembled from an amphiphilic DNA-dendron hybrid can be reversibly achieved under optimum assembly conditions. The possible morphology transformation mechanism is proposed and further confirmed by X-ray diffraction, TEM and DLS experiments.     

pH-induced morphology-shifting of DNA-b-poly(propylene oxide) assemblies

The designed DNA sequences can make DNA-b-PPO undergo in situ transition between diblock and triblock upon pH changes, consequently, induce a morphology-shifting from spherical micelles to nanofibers. This process is reversible and the assembled structures have been characterized by CD, TEM and fluorescent experiments.     

电沉积法制备ZnO纳米柱及其机制研究

采用阴极还原方法,以Zn(NO₃)₂水溶液为电解液制备ZnO纳米柱。分析了不同沉积电位和不同沉积时间的缓冲层对ZnO纳米柱的密度、形貌及取向的影响。通过分析缓冲层在不同沉积时间下的电流密度变化,研究了缓冲层对ZnO纳米柱密度影响的机理。利用扫描电子显微镜(SEM)和X射线衍射(XRD)分析了样品的表面形貌及结构。研究结果表明,缓冲层能够增加ZnO纳米柱的密度及c轴的取向性,当缓冲层的沉积时间为60 s时,可以得到密度最大、取向最好的ZnO纳米柱。     

Performance of concatenated codes over an APD-based optical system with estimated channel-state information

In this paper, we investigate the efficiency of serially concatenated codes using a BCH (32400, 32208) inner code and an LDPC (64800, 32400) outer code over a free-space optical communication (FSOC) system with APD detectors. Based on the experimental optical signals recorded from a FSO (free-space optical) link with the distance z = 11.8 km, the bit error rate (BER) performance of the concatenated codes is evaluated from the aspect of simulation under weak turbulence conditions (for which the scintillation index σ _I ² = 0.18) and strong turbulence conditions (for which σ _I ² = 1.49). The results indicate that the fade level P _T can be set much lower for the FSOC system using the concatenated codes, leading to shorter fade length and interleavers in smaller size. The concatenated codes are shown to even outperform the (4, 1, 7) convolutional code in both cases. In addition, we analyze the BER performance of these concatenated codes on the basis of pilot-aided channel estimation with different numbers of pilot symbols.