空气催化氧化亚硫酸铵制备硫酸铵

采用单因素实验研究了亚硫酸铵初始浓度、反应温度、空气流量、催化剂硫酸钴浓度等因素对催化氧化亚硫酸铵的效率的影响.结果表明,低浓度亚硫酸铵较易氧化,亚硫酸铵浓度越高,氧化越困难;反应的最佳温度为50℃,氧化速率随着空气流量和催化剂硫酸钴浓度的增加而加快.通过正交实验确定最佳氧化反应条件为:亚硫酸铵初始浓度1.1 mol·L-1,催化剂硫酸钴浓度0.015 mol·L-1,反应温度50℃.     

LaNi5储氢合金中氢扩散动力学的单颗粒电化学研究

基于对单颗粒准球形储氢合金的电势阶跃计时电流曲线的全程拟合,采用"扩散和表面转化混合控制"模型取代流行的纯扩散模型,并根据该模型,估算出储氢合金氢的扩散系数D约为6×10-10 cm3·s-1、氢的初始浓度c约为0.008 mol·cm-1、表面转化步骤的表观反应速率常数K约为8×10-6 cm·s-1.     

聚甲基丙烯酸甲酯预聚物作为助稳定剂的细乳液聚合速率研究

以聚甲基丙烯酸甲酯(PMMA)预聚物为助稳定剂、十二烷基硫酸钠为乳化剂、十六醇为助乳化剂和过硫酸钾为引发剂,研究甲基丙烯酸甲酯(MMA)的细乳液聚合反应速率.考察乳化剂浓度、助乳化剂浓度、引发剂浓度、预聚物浓度、预聚物分子量以及反应温度对聚合速率的影响.结果表明:聚合速率RP随着乳化剂浓度或反应温度的提高而增加,随着助乳化剂浓度的提高而减小,引发剂浓度对RP影响不明显.在相同条件下,加入预聚物的细乳液体系聚合速率RP在聚合反应前期比常规细乳液有明显提高:PMMA(MH=520000)浓度为2×10-3mmol·L-1时,RP的最大峰值为1.84×10-2mol·L-1·min-1.预聚物PMMA在MMA细乳液聚合体系中,可以提高聚合速率和增加体系稳定性.     

用全氟磺酸离子交换膜传递水溶液中的甘氨酸

用全氟磺酸Na~ ,Ag~ ,和Cs~ 型离子交换膜对传递甘氨酸进行了研究。传递的特性和传递初始通量取决于膜的离子类型。Na~ 型膜的初始通量不随甘氨酸浓度的增加而增加。Cs~ 型膜传递的初始通量随甘氨酸浓度的增加而缓慢增加,但整个的初始通量很低。Ag~ 型膜则不同,当甘氨酸浓度低时,其初始传递通量迅速增加,随着甘氨酸浓度的增加,初始传递通量增加的趋势逐渐减缓。当甘氨酸的浓度为2.0mol/L,pH6,温度26℃时,测得Na~ 、Ag~ 和Cs~ 型膜的初始传递通量分别为4.5×10~(-8)mol/s·cm~2、8.0×10~(-8)mol/s·cm~2和1.6×10~(-8)mol/s·cm~2。测得甘氨酸通过Na~ 型膜的表观活化能为5.5 k cal/mol。pH 值对甘氨酸初始传递通量也有影响,当pH 在8—10之间时可获得高的初始传递通量。     

基于阳离子表面活性剂缔合微粒共振瑞利散射光谱法测定痕量O_3

以pH=4.0 HAC-NAAC缓冲溶液为介质,用硼酸碘化钾溶液(BKI)作为O3吸收剂。O3将I-氧化生成为I2,溶液中过量的I-与I2又可形成I-3,有阳离子表面活性剂(CS)如氯代十六烷基吡啶(CPCI),溴代十四烷基吡啶(TPB),十六烷基三甲基溴化铵(CTMAB),十四烷基苄基二甲基氯化铵(TDMAC)存在时,CS与I-3形成稳定的(CS-I3)n缔合微粒,在470 nm处有一个较强的共振瑞利散射峰(RRS),随着O3浓度的增大,体系中的I-3增多,I-3与CS形成的(CS-I3)n缔合微粒越多,470 nm处的RRS强度I增强,O3浓度与其增强值ΔI成线性关系,各体系的线性范围分别为15~50,50~100,5~25,1~50μmol·L-1,回归方程分别为ΔI=8.81c-4.01,ΔI=5.44c-3.11,ΔI=15.39c-1.55,ΔI=16.88c+0.51,检出限分别为4.9,12,2.85,0.56μmol·L-1O3。实验考察了共存物质的影响,当O3浓度为2.5×10-6mol·L-1,相对误差在±10%内时,4.0×10-5mol·L-1Hg2+,8.7×10-5mol·L-1Fe3+,5.0×10-5mol·L-1Ca2+,2.5×10-5mol·L-1Zn2+和Cu2+,2.8×10-6mol·L-1Pb2+和Cr3+,4.2×10-5mol·L-1Mg2+,Mn2+和Ba2+对体系的测定无干扰。说明该方法具有良好的选择性。选用TDMAC体系检测空气中的O3,结果令人满意。采用激光散射技术研究了(TDMAC-I3)n缔合微粒体系的粒径分布。当通入O3后,过量KI与O3反应形成I-3,I-3与TDMAC反应生成(TDMAC-I3)n缔合微粒,其粒径集中分布在1 106~3 091 nm之间。     

维生素C对碘猝灭荧光素荧光抑制作用的研究

碘能够与荧光素发生取代反应,由于重原子效应使荧光素的荧光被显著猝灭。而维生素C能够抑制这一反应,它可与碘发生氧化还原反应,使体系荧光恢复。通过实验,我们发现当维生素C浓度在0.8×10-6 mol·L-1~3.0×10-6 mol·L-1范围内时,荧光的恢复和维生素C浓度具有良好的线性关系,线性回归方程:F=990.17C+1221.96(C单位为10-6 mol·L-1),相关系数r=0.99138。并检测了稀释后达能牌饮料中维生素C的浓度,取得满意结果。     

黄芪甲苷联用维生素D_3对二维回转培养大鼠原代成骨细胞增殖的影响

探讨了黄芪提取物黄芪甲苷与维生素D3联用对二维回转培养大鼠原代成骨细胞增殖的影响。离体培养大鼠原代成骨细胞后,用碱性磷酸酶染色、茜素红染色等方法对细胞进行鉴定;通过细胞回转器模拟微重力效应,采用MTT、细胞计数等方法研究不同浓度配比的黄芪甲苷与维生素D3混合液对大鼠原代成骨细胞增殖的影响。结果表明,单用黄芪甲苷或维生素D3均对正常培养成骨细胞增殖具有促进作用,最佳促增殖浓度分别为1×10-7 mol·L-1和1×10-8 mol·L-1,当1×10-7 mol·L-1黄芪甲苷分别配以1×10-9 mol·L-1或1×10-8 mol·L-1维生素D3时,其相对增殖率可达200%和196%;不同浓度配比的黄芪甲苷与维生素D3混合液对模拟微重力下二维回转培养成骨细胞的增殖有显著促进作用,其最佳促增殖浓度为1×10-7 mol·L-1黄芪甲苷配以1×10-9 mol·L-1维生素D3。     

膨润土负载磷钼酸催化碘离子氧化反应的研究

采用恒温浸渍蒸发法制备负载型磷钼酸/膨润土(PMo/BEN)催化材料。通过FT-IR、XRD、BET、SEM等对其结构加以表征。以过氧化氢为氧化剂,运用PMo/BEN催化碘离子氧化,同时考察催化剂的负载量、反应温度、溶液pH、过氧化氢用量等因素对反应速率的影响。结果表明:PMo高度分散在BEN表面上,PMo/BEN具有良好的催化活性。在温度为55℃、pH为1.7、过氧化氢浓度为3.6×10-3 mol/L、负载量为8%的条件下,其反应速率达到1.65×10-5mol/(L·s),反应速率提高了12倍。反应前10 min碘离子转化成碘单质的转化率高达99%,连续循环使用8次后,前10 min碘离子的转化率仍为95%。     

臭氧法降解水中氟苯的动力学研究

采用臭氧法降解含氟苯模拟废水.研究了氟苯降解的影响因素和动力学,考察了反应液初始pH值、反应物初始浓度、臭氧投量、反应温度对臭氧氧化降解氟苯反应速率的影响.结果表明,氟苯初始浓度0.52 mmol·L-1,pH 9,臭氧投量1.25×10-6 mol·s-1,常温下反应60 min后氟苯降解率达95%以上.氟苯在臭氧氧化下的降解符合表观一级动力学,采用幂指数方程描述反应动力学,得到方程C = C0exp(-0.324exp(-7437/RT) QO30.41C0-0.372[OH-]0.0942t).通过GC-MS测定氟苯降解主要中间产物为苯酚、苯醌、呋喃二酮、亚联苯等.     

罗丹明6G共振散射光谱法测定痕量铜(Ⅱ)

在盐酸溶液中,铜离子催化过硫酸钾氧化过量碘化钾生成I3-,I3-与带正电荷的罗丹明6G形成缔合物微粒而产生共振散射效应,据此建立了检测痕量铜的共振散射光谱法.用单变量变换法优化测定条件,选择盐酸的浓度为3.33 mmol·L-1、碘化钾浓度为1.5 mmol·L-1、罗丹明6G浓度为6.33 μmol·L-1、过硫酸钾...     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.