Photophysical studies of copolymers of N‐vinylcarbazole

The absorption, fluorescence excitation and emission spectroscopy, and time‐dependent spectrofluorimetry have been used to study the photophysics of copolymers of N‐vinylcarbazole with different monomers like vinyl acetate, methyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate in dichloromethane. In all the copolymers and at different N‐vinylcarbazole content, the absorption spectra reflect only the monomer carbazole units. The two kinds of excited monomer species of N‐vinylcarbazole are present in S₁ state. Short‐lived (～3 ns) excited monomer decays forming low energy excimer obtained by the complete overlap of the excited carbazole monomer. The long‐lived excited monomer (～8 ns) decays to ground state without formation of any excimer. The high energy excimer is relatively short‐lived and is formed by the partial overlap of the carbazole units. The presence of bulky group in the copolymer chain hinders the formation of excimers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 372–380, 2006     

鸡爪芋化学成分研究

鸡爪芋在广东民间用于治疗胃病、肝炎,有特效。为研究其有效成分,对鸡爪芋干燥根茎95％乙醇提物进行了分离。通过反复柱层析分离、离心薄层色谱分离,重结晶等方法分离得到8个晶体,它们是分别是豆甾醇、β-谷甾醇、棕榈酸、棕榈酸乙酯、十六酸单甘油酯、9,12,15-三烯十八酸乙酯、二十二酸乙酯、葫萝卜甙。     

含氮天然气液化脱氮精馏塔液位控制模型和仿真

提出了用精馏塔对含氮天然气脱除N2生产液化天然气（LNG）,精馏塔塔釜液位的一种控制方法。该方法以脱氮分离效率和稳定的产品（LNG）出料温度为控制目标,建立了塔釜液位控制模型并仿真。整个闭环控制模型包括被控对象传递函数,调节阀传递函数,PID控制传递函数和检测传递函数。其中调节阀传递函数的建立,采用先计算阀位-Cv值（流量系数）曲线;然后通过系统辨识法[1]求得数学模型;最后利用泰勒级数把非线性化转化为线性化并求得传递函数。通过Matlab软件[2]的仿真,在阶跃干扰下,得到了合适的液位变化曲线和合适的阀位变化[3]。     

Gas Hold‐Up in Stirred Tank Reactors in the Presence of Inorganic Electrolytes

Gas hold‐up (?_G) in air‐aqueous electrolyte solutions in stirred tank reactors (STR) is correlated using a relative gas dispersion parameter, N/N_cd and a surface tension factor (STF), (c/z)(dδ/dc)². For electrolyte concentration below transition concentration (c_t) a single correlation in the form of ?_G = f(N/N_cd, vvm, STF) shows good agreement with gas hold‐up data over a wide range of system and operating conditions. Above ct no effect of STF on gas hold‐up is observed and the correlation obtained is of the form ?_G = f(N/N_cd, vvm). Data available in the literature on large STR show good fit with the proposed correlation.     

Nitrogen incorporated diamond-like carbon films by microwave surface wave plasma CVD

Nitrogen incorporated diamond like carbon films have been deposited by microwave surface wave plasma chemical vapor deposition (MW-SWP-CVD), using methane (CH₄) as the source of carbon and with different nitrogen flow rates (N₂ / CH₄ flow ratios between 0 and 3). The influence of the nitrogen incorporation on the optical, structural properties and surface morphology of the carbon films were investigated using different spectroscopic techniques. The nitrogen has been incorporated into DLC:N films which was confirmed by the X-ray photoelectron spectroscopy (XPS) measurement. Moreover, the nitrogen incorporation was accompanied by a variation in the optical gap, which was attributed to the removal or creation of band tail states.     

Biocidal hydantoinylsiloxane polymers. IV. N‐halamine siloxane‐functionalized silica gel

The monomer 5,5‐dimethyl‐3‐(3′‐triethoxysilylpropyl)hydantoin and its hydrolysis product polymer poly[3‐(5,5‐dimethylhydantoinylpropyl)hydroxysiloxane] were employed to functionalize the surfaces of silica gel particles in order to produce an adhered film that becomes biocidal upon chlorination with dilute sodium hypochlorite bleach. The biocidal efficacy of the functionalized silica gel was demonstrated in a cartridge filter experiment against the bacterial pathogens Staphylococcus aureus and Escherichia coli O157:H7. Complete 6 log inactivations of the two bacterial species were observed within 30 s of contact. Moreover, upon loss of biocidal activity due to depletion of bound chlorine, the coated silica gel particles could be recharged by further exposure to dilute bleach. Potential uses of the biocidal silica gel include disinfection and odor control in water treatment facilities and recirculating baths. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3448–3454, 2006     

CDs/ZnO/g-C3N4三元组份协同作用促进光催化降解染料

采用浸渍-热聚合法制备CDs/ZnO/g-C3N4复合材料，考察其对罗丹明B的光降解效率。利用 XRD、TEM、XPS、UV-Vis DRS、FI-IR等手段对催化剂进行表征和评价。结果表明：CDs/ZnO/g-C3N4仍保持石墨相g-C3N4的晶型结构，三元组份相互协同作用使CDs/ZnO/g-C3N4表现出优异的光催化性能，其降解罗丹明B的效果优于单体g-C3N4、ZnO及ZnO/g-C3N4，脱色率可达到70%左右。     

二维石墨相氮化碳纳米片的制备及其光催化性能

利用水热反应法将三聚氰胺悬浊液在200℃下反应生成中间产物,中间产物经煅烧直接制成了二维石墨相氮化碳(g-C3N4)纳米片(WCN),并与本体g-C3N4(CN)、传统热氧剥离法得到的g-C3N4纳米片(OCN)进行了比较.采用SEM、XRD、FTIR、Raman、AFM、PL对样品进行了表征,探讨了其光电化学性能和光催化性能.结果表明,两种方法均实现了对CN的剥离,WCN和OCN与CN的晶体结构和组成相同,WCN和OCN比表面积分别是CN的3.6倍和3.1倍.光电化学分析显示,WCN具有更好的载流子迁移与分离效率,具有较好的光催化活性.可见光照射下,WCN对亚甲基蓝(MB)的光催化降解率达到82.0％,分别是OCN和CN的2.4倍和6.7倍,光催化降解过程符合一级动力学方程.WCN具有优良的稳定性和可重复利用性能.     

Effect of granule size and the placement geometry on the efficiency of urea supergranules for wetland rice grown on a permeable soil

In a laboratory experiment 5 cm depth of water was allowed to percolate daily down through a 15 cm thick soil (Typic Ustipsamment) layer. It was observed that leaching losses of urea supergranules (USG)-N could be decreased by about 20% by the placement of four 0.25 g granules at four points instead of one 1 g granule at one point. In field microplots, the placement of approximately 30 granules of 0.30 g size instead of 9 granules of 1.00 g size resulted in reduced leaching of USG-N and, in turn, increased rice yield. In a follow-up field study, the advantage of more frequently placed USG was confirmed. As compared with 1 g USG placed in the usual manner in the center of four rice hills, increasing the density of placement in soil produced 15% more rice grain. Further increase in rice yield could be obtained by increasing the number of USG placed in the soil and decreasing the size of the granule from 1.00 g to 0.70 or 0.35 g. With USG of 0.35 and 0.70 g yields were equal or sometimes even slightly higher than with split application of prilled urea on a heavily percolating, low-CEC, light-textured soil.     

Relations between damage symptoms and nutritional status of Norway spruce stands (Picea abies Karst.) in southwestern Germany

Since the mid-1970s new types of forest damage are observed in the Federal Republic of Germany. Typical damage symptoms in coniferous tree species are needle yellowing, reddening and premature loss of older foliage. Needle analysis carried out in damaged Norway spruce stands indicated that these phenomena, most of all needle yellowing, are influenced by the nutritional status of the trees. For the investigated sites Mg but also other elements, particularly P, S, K, Ca and Zn may play a causal role. As N is the most abundant element in the plant its form of uptake is important for a balanced nutrition. On the contrary to NO₃-N high NH₄-N uptake reduces the uptake of cations, particularly Mg and Ca, eventually inducing foliar discoloration symptoms on specific sites. Fertilizer experiments indicated that Mg fertilization is an appropriate tool to mitigate forest damages associated with Mg deficiency for a sustained time period. The application of N in the form of NH₄-N may impede Mg uptake. This mechanism may cause severe damage in forest areas receiving continuously high NH₄-N deposition.