非晶态合金Fe-B-P催化活性和磁性的理论研究

采用原子簇方法,对倍受关注的Fe基非晶态合金Fe-B-P的催化活性和磁性进行研究.通过合理设计可调Fe含量的系列原子簇FenBP（n=1～4）可能构型三十余种,利用密度泛函理论（DFT）分别在单、三重态下进行优化计算.在不同多重度下,对所确定的原子簇FenBP（n=1～4）最稳定构型的几何结构、能量、能隙差、费米能级和d轨道布局数进行分析,结果表明：多重度对原子簇FenBP（n=1～4）几何构型影响较大;三重态比单重态稳定且催化加氢活性较好,其中三重态的Fe3BP活性最好;单重态的磁矩明显低于三重态,其中单重态的Fe4BP磁矩最小,表现出软磁性.     

非晶态合金Co-Mn-B的电荷转移及其催化性质的DFT研究

为深入了解非晶态合金Co-Mn-B的电子及其催化性能,利用密度泛函理论(DFT)方法,在B3LYP/Lan12dz水平下,将原子簇Co2MnB2的十余种可能构型分别在二、四重态下进行全参数优化计算和频率验证,最后获得两种类型的稳定构型(三角双锥型和变形四方锥型),其中三角双锥构型均是以金属原子为两锥、一金属原子和双B原子位于三角平面。对这些稳定构型的电荷转移及其催化活性进行研究分析,结果表明:原子簇Co2MnB2稳定构型中电子主要由Mn原子向B原子转移,Mn原子的引入起到调变B原子的电子流向作用。金属Co、Mn原子在二、四重态下对HOMO、LUMO轨道的贡献大小不一样;Mn原子的饱和轨道比Co原子更富电子。原子簇Co2MnB2因空轨道易于接受反应物的电子而具有良好的催化性能;构型4(2)具有较好的催化加氢、固氮活性。     

CoFe_2BP团簇的组成、电子及磁学性质的研究

根据各优化构型之间的能量差,首次从能量学视角提出一种定量计算团簇CoFe2BP各优化稳定构型组成比例的方法,同时对团簇的电子和磁学性质进行研究,得出:各优化构型中,四重态构型所占的组成比例最大且立体结构趋于多样化;B原子接受电子,P原子提供电子,B原子所带负电荷量与B原子和周围成键金属原子数呈负相关,各原子中所有价轨道均参与成键;Co原子的磁矩小于Fe原子的平均磁矩;受各构型稳定性的影响,Fe原子磁矩在二、四重态中分别呈"凹"、"凸"形变化,Co原子的磁矩变化相对比较平缓;多重度的改变会对Co、Fe原子的磁矩变化产生不同的影响,同时Co、Fe原子的磁矩与构型的立体结构息息相关。     

Fe-B非晶态合金中电子转移问题的DFT研究

利用一系列原子簇模型 Fen B2 (n=1～ 4)对 Fe- B非晶态合金的电子结构 ,用 DFT方法进行高水平的量子化学计算 ,结果表明 ,模型体系 Fen B2 (n=1～ 4)中 ,B原子供给 Fe原子电子 ,这与非晶态合金的实验结果一致 ;模型体系不存在类似于 Ni- B非晶态合金中 B- B近距离接触 ,为了比较 ,也选择了单硼原子簇 Fen B(n=1～ 4)模型 ,计算结果与实验不符 ,说明双硼原子簇模型 Fen B2 能在一定程度上反映 Fe- B非晶态合金的局域结构特征。     

Ni-Co-B非晶态合金电子性质的理论研究

根据 Ni- Co- B非晶态合金结构的短程有序、Ni、Co、B之间是较强的化学作用以及化学键理论 ,利用一系列原子簇模型 Ni4-n Con B2 ( n=0～ 4)对 Ni- Co- B非晶态合金用 DFT方法进行较高水平的量子化学计量 ,结果表明 ,模型体系 Ni4-n Con B2 中 ,B原子供给 Ni原子、Co原子电子 ,这与非晶态合金的实验结果一致 ,同时计算结果也表明了在三元非晶态合金 Ni- Co- B中 ,很可能存在与二元 Ni- B非晶态合金类似的 B- B近距离直接接触 ;Co原子得电子能力强于 Ni原子 ,钴的引入对镍的电子结构有调变作用     

Fe-P非晶态合金局域结构和电子性质的理论研究

根据Fe-P非晶态合金结构的短程有序、Fe和P之间具较强化学作用和结构中可能存在P-P相互作用的实验事实,选择了单磷原子簇模型FenP(n=1～6,8)和双磷原子簇模型FenP2(n=1～4),用密度泛函理论方法对其进行计算。结果表明,在单磷模型体系中,Fe原子供给P原子电子;而在双磷模型体系中,电子转移方向发生变化,P原子供给Fe原子电子,这与Fe-P非晶态合金的实验结果一致,说明单磷和双磷原子簇模型能较全面反映Fe-P非晶态合金的结构特点。     

团簇Ni3B2多重态热力学稳定性和磁学性质

为了探究团簇Ni_3B_2的热力学稳定性和磁学性质,基于密度泛函理论对多重态构型进行了优化运算,结果得到7种稳定存在的构型,其中三重态四种,五重态三种;通过对比优化构型的热力学参数及电子自旋情况得知:稳定性顺序依次为1~((5))1~((3))2~((5))2~((3))3~((3))4~((3))3~((5));并且向上自旋电子自旋轨道密度的分立降低了构型的稳定性;通过对电子自旋情况的进一步研究讨论得知:团簇Ni_3B_2的磁性主要由3d轨道贡献;此外,三重态的构型中存在Ni—B间分子轨道的解离,解离出的向上自旋电子分布在Ni原子周围,向下自旋电子分布在B原子周围。     

团簇Co_xFe_yB_2的结构特点与磁学性质的密度泛函数理论研究

为了深入了解非晶态合金Co-Fe-B的结构特点以及磁学性质,利用密度泛函数理论(DFT)方法,在B3LYP/Lan12dz水平下,对团簇Co_2FeB_2和CoFe_2B_2的十余种可能存在的构型在不同重态下进行全参数优化计算和频率验证,共得到17种不同构型,分别是三角双锥型、戴"帽"三角锥型、四方锥型以及平面型。对这些稳定构型的结构特点以及磁学性质进行研究分析,结果表明:团簇CoFe_2B_2比团簇Co_2FeB_2更具有结构多样性,而且各化学键的配置更加均匀、合理;在两团簇各构型中,二、三、四重态下的Co原子的磁矩非常接近,Fe原子的磁矩也是如此,且Co和Fe原子对磁性的贡献均较高;单重态下的Co和Fe原子对磁性的贡献较低;Fe原子对磁性的贡献大于Co原子的。     

非晶态合金Co80P20体系局域结构及稳定性的DFT研究

利用含相关校正能的DFT方法在B3LYP/Lan12dz水平下,对原子簇模型Co<,4>P<,30>余种可能存在构型在二、四、六重态下进行全参数优化和频率计算,确定了8种稳定构型.从其能量、结合能、几何参数、过渡态及成键等方面对其稳定构型分析,结果显示,8种稳定构型主要是三角双锥和类螺旋桨两种结构,在二重态和四重态中最...     

非晶态合金Co-P-B体系的组成和催化性质研究

利用团簇Co3PB模型来研究非晶态合金Co-P-B体系,从能量学视角对团簇Co3PB中五种稳定构型所占比例进行定量分析后,可知共有四种主要存在构型,按构型稳定性排序后,二、四重态构型随能量的升高呈交替排列样式。Co原子是催化反应的活性质点,此结论与实验结果相同。结合态密度图分析,在催化反应中,团簇Co3PB易接受反应物的电子,使反应物活化。     

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.     

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.     

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.