阿莫西林的热分解行为研究

利用热重分析（TG）采用不同升温速率（5,10,15,20,30℃/min）在氮气气氛下对阿莫西林热分解动力学进行了研究。采用Coats-Redfern和Ozawa热分析处理动力学数据的方法,计算阿莫西林热分解反应活化能E及指前因子A。结果表明,阿莫西林的热分解反应为一级反应,在15%～35%的失重率时热分解表观活化能为51.43～56.34 kJ/mol,指前因子lgA值为8.76～9.38。     

F-12纤维热分解特性研究

采用热重方法研究杂环芳纶F-12纤维的热分解行为,非等温方法研究热分解反应动力学,利用分解反应动力学参数估算纤维在高温下的使用时间,并进一步分析热分解反应机理。结果表明:F-12纤维耐热性好,在空气和氮气气氛下开始分解温度分别为450℃和480℃;纤维可以在250℃以下长期使用;F-12纤维热分解反应的平均活化能是E=261.49±10 kJ/mol,指前因子A=(1.43×1017)±104min-1。     

四元聚合物吸水树脂的热分解动力学及保水性研究

采用静置热聚合法,在交联剂N,N′–亚甲基双丙烯酰胺的存在下,制备了丙烯酸/2–丙烯酰胺基–2–甲基丙磺酸/顺丁烯二酸酐/淀粉(AA/AMPS/MA/St)四元聚合物吸水树脂,对树脂分别进行保水性测试和热稳定性分析,并通过Kissinger法、Ozawa法和Crane法对该树脂的热分解动力学分别进行了研究。结果表明:该四元聚合物吸水树脂热分解的活化能为117.81 k J/mol;指前因子为7.56 s–1;反应级数为0.93,反应为一级反应。     

非等温热重法研究聚苯醚热分解动力学

采用非等温热重法对聚苯醚的热分解动力学进行研究,计算了反应活化能,采用积分法结合36种动力学函数来判断聚苯醚热分解的机理函数,得到了聚苯醚热动力学参数即反应的动力学函数,平均活化能（E_a）为211.64kJ/mol,指前因子（A）的平均值为6.24×10⁷s^-1,也获得了对应的热分解动力学方程。     

2-巯基吡啶镉(Ⅱ)、汞(Ⅱ)配合物的热分解动力学研究

采用TG-DTG技术研究了2-巯基吡啶镉(Ⅱ)、汞(Ⅱ)配合物在氮气气氛中的热分解机理及非等温动力学。采用积分法(Coats-Refern方程,HM方程,MKN方程)和微分法(Achar方程)对非等温动力学数据进行了分析,得到了配合物第一步热分解反应的机理函数、动力学参数和热分解动力学方程。结果表明:其热分解过程属F2(化学反应)机理控制,非等温热分解的动力学方程为dα/dT=A/β.e-E/RT(1-α)2,其中镉(Ⅱ)配合物的表观活化能E=86.35 kJ/mol,指前因子A=4.72×107s-1;汞(Ⅱ)配合物的表观活化能E=189.67 kJ/mol,指前因子A=3.79×1018s-1。     

非等温热重法研究聚苯硫醚热分解动力学

采用非等温热重法对聚苯硫醚的热分解动力学进行研究,通过比较计算结果选定拟合结果更好的迭代法计算反应活化能,采用积分法结合36种动力学函数来判断聚苯硫醚热分解的机理函数。得到了聚苯硫醚热分解动力学参数平均活化能E、指前因子A和对应的热分解动力学方程。     

二氯丙烯胺的热分解动力学

用热分析的方法研究了二氯丙烯胺的热分解动力学,起始分解温度在120℃左右,并用无模式函数法计算出反应活化能、指前因子。     

高岭土热分解动力学

采用综合热分析仪在动态空气气氛条件下研究了高岭土的热分解过程,利用热重分析数据对高岭土的热分解过程进行了动力学分析.用迭代的等转化率方法获取了准确的活化能,将得到的活化能应用到Malek方法中推测其反应机理,并进一步求得了指前因子A.结果发现:高岭土在400～700℃脱去羟基过程遵循化学反应的模型,其微分和积分表达式分别为:f(α):(1-α)n,G(α)=1-(1-α)1-n/1-n(其中:α为转化率,反应级数n=2.1,表观活化能为182.428kJ/mol),指前因子A的范围为:(4.566～4.635)×1011s-1.     

新型阻燃剂1,3,5-三(5,5-二溴甲基-1,3-二氧杂己内磷酰氧基)苯的热分解动力学研究

以TG-DTG为手段,研究了1,3,5-三(5,5-二溴甲基-1,3-二氧杂己内磷酰氧基)苯(TDDB)在氮气气氛中的热分解动力学,利用Kissinger法、Flynn-Wall-Ozawa(FWO)法对TDDB进行热分解动力学分析,求出该物质的热分解动力学参数,利用Coast-Redfen法研究该物质的热分解机理.结果表明:Kissinger法所求得的活化能为344.48 kJ/mol,指前因子lnA为66.02;Flynn-Wall-Ozawa法所求得的活化能为337.61 kJ/mol.TDDB的热分解的动力学方程为g(α)=α2.反应级数n=2.     

聚对苯二甲酸丁二醇酯的热分解动力学研究

通过热重分析(TGA)法研究了聚对苯二甲酸丁二醇酯(PBT)在氮气气氛中不同升温速率下的热分解过程,采用不同的动力学数据处理方法研究了PBT的热分解机理。结果表明:采用Kissinger法、FlynnWall-Ozawa法和Friedman法计算PBT的热分解反应活化能分别为179.93,175.83,161.07 kJ/mol,平均值为172.28 kJ/mol,与Coast-Redfern法计算的活化能180.41 kJ/mol接近,取PBT热分解反应活化能为180.41kJ/mol,计算得指前因子为2.68×10~(10)s~(-1);采用Coast-Redfern法和Criado法研究了PBT的固相热分解反应机理,认为PBT的热分解机理属于相边界控制的收缩圆柱体反应机理,反应级数为0.5。     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

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.     

ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究

建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。