不同预处理方法对漂白针叶木硫酸盐浆制备溶解浆性能的影响

以漂白针叶木硫酸盐化学浆为原料,分别采用9%NaOH,6%NaOH+3%H2O2,1%H2SO4,9%H2O2等化学法和木聚糖酶、漆酶及混合酶等生物法进行处理,探讨不同处理方式对漂白针叶木纸浆改性制备黏胶纤维用溶解浆的影响。试验结果表明:采用9%NaOH,1%H2SO4能有效提高α-纤维素含量和纤维素反应性能,而木聚糖酶或漆酶的处理效果不明显。     

Identification of hemocyanin as a novel non-cross-reactive allergen from the giant freshwater shrimp Macrobrachium rosenbergii

Scope : Sensitization to giant freshwater shrimp Macrobrachium rosenbergii (Mr) was recently reported. However, the allergens have yet to be identified. This study aimed to identify and characterize a novel allergen of Mr shrimp. Methods and results: Extracted proteins were separated and purified by anion and in some experiments, size‐exclusion chromatography. Serum IgE from shrimp allergic donors identified a candidate protein, which was characterized by LC‐MS/MS. The specificity of IgE binding was tested using immunoblotting and inhibition ELISA. The IgE‐binding profiles from 12 of 13 Mr allergic subjects that were pre‐incubated with an extract of Penaeus monodon showed residual binding to ～60–80 kDa proteins. The 60–80 kDa IgE‐bound proteins were fractionated in the flow‐through of anion chromatography showing a high IgE reactivity. Peptides identified by LC‐MS/MS showed the proteins closely match subunits of hemocyanin (Hcs). Purified Hcs from hemolymph markedly inhibited binding of IgE from sera of Mr allergic subjects to solid‐phased Mr proteins in inhibition ELISA. Conclusion: Hcs were identified as heat‐stable, non‐cross‐reactive, high‐molecular‐weight (MW) allergens from Mr shrimp. Since circulatory organs are not always removed during food preparation, high concentrations of Hcs may be present along with shrimp meat, which contains the known cross‐reactive tropomyosin protein.     

Anxiety sensitivity and panic reactivity to bodily sensations: Relation to quit-day (acute) nicotine withdrawal symptom severity among daily smokers making a self-guided quit attempt.

The current investigation explored the main and interactive effects of panic attacks in response to laboratory-induced bodily sensations and anxiety sensitivity in predicting acute nicotine withdrawal symptoms among daily smokers making a self-guided quit attempt. Participants were 99 daily smokers (58% women; Mage = 28.4 years, SD = 11.7) who completed a battery of questionnaires, a voluntary hyperventilation challenge, and a measure of nicotine withdrawal symptoms 12 hr after making a self-guided quit attempt. Results indicated that the interaction of anxiety sensitivity and panic responsivity to the challenge predicted quit-day nicotine withdrawal symptom severity above and beyond the main effects (p     

偏氯乙烯-氯乙烯悬浮共聚合动力学模型

研究单体配比、引发剂浓度、聚合温度等主要因素对偏氯乙烯-氯乙烯共聚物组成和分子量、悬浮共聚速率的影响.在30、45、70℃下测定了两单体的竞聚率,讨论了共聚物组成的偏移情况,提出了速率模型,在35～65℃范围内求出了模型参数,建立了分子量模型,提供了粘均分子量与二氯乙烷杂质浓度、引发剂浓度、温度间的定量关系.     

石灰石活性对SO2吸收的影响

为考察石灰石的脱硫活性对SO2吸收的影响,基于气体吸收的双膜理论,建立了通过石灰石种类和粒径分布来预测喷淋塔脱硫性能的数学模型,并进行了相应的试验研究.该模型中,石灰石种类的不同对SO2吸收的影响通过石灰石的表面反应速率常数来解释;对于同种石灰石,粒径越小,比表面积越大,溶解越快,越有利于SO2的吸收.     

Free radical copolymerization of N,N‐dimethylaminoethyl methacrylate with styrene and methyl methacrylate: monomer reactivity ratios and glass transition temperatures

BACKGROUND: The properties of copolymers depend strongly on their composition; therefore in order to tailor some for specific applications, it is necessary to control their synthesis, and, in particular, to know the reactivity ratios of their constituent monomers. Free radical copolymerizations of N,N‐dimethylaminoethyl methacrylate (DMAEM) with styrene (ST) and methyl methacrylate (MMA) in toluene solution using 1‐di(tert‐butylperoxy)‐3,3,5‐trimethylcyclohexane as initiator at 70 °C were investigated. Monomer reactivity ratios were determined for low conversions using both linear and nonlinear methods. RESULTS: For the DMAEM/ST system the average values are r₁ = 0.43 and r₂ = 1.74; for the DMAEM/MMA system the average values are r₁ = 0.85 and r₂ = 0.86. The initial copolymerization rate, R_p, for DMAEM/ST sharply decreases as the content of ST in the monomer mixture increases up to 30 mol% and then attains a steady value. For the DMAEM/MMA copolymerization system the composition of the feed does not have a significant influence on R_p. The glass transition temperatures (T_g) of the copolymers were determined calorimetrically and calculated using Johnston's sequence length method. A linear dependence of T_g on copolymer composition for both systems is observed: T_g increases with increasing ST or MMA content. CONCLUSION: Copolymerization reactivity ratios enable the design of high‐conversion processes for the production of copolymers of well‐defined properties for particular applications, such as the improvement of rheological properties of lubricating mineral oils. Copyright © 2009 Society of Chemical Industry     

Directions of theoretical and experimental investigations into the mechanisms of heterogeneous catalysis

The roles of the atomic structure and the electronic structure of the active surface sites in bonding of reactants and causing bond breaking or bond formation have been the focus of theoretical studies. In addition to calculations on static systems, usually clusters, modelling of the transition states and the dynamics of elementary reaction steps (adsorption, dissociation, surface diffusion, desorption) have been performed. Variations of electronic structure of elements across the periodic table have been shown to be responsible for the unique importance of transition metals in catalysis.Experimental studies utilize catalysts with well-characterized structure (zeolites, crystal surfaces) and information about surface structure, composition and chemical bonding of adsorbates becomes available on the molecular level. Deliberate alteration of catalyst structure, surface composition by alloying and electronic structure by addition of electron donor and electron acceptor promoters have been utilized to modify reaction rates and selectivity. This way many of the molecular ingredients of heterogeneous catalytic reactions have been identified.In recent years evidence has been accumulating that indicates periodic and long term restructuring of the catalyst surface as necessary for chemical change and reaction turnover. These findings point to the need of time resolved studies and in-situ investigations of both the substrate and the adsorbate sides of the surface chemical bonds simultaneously on a time scale shorter than the reaction turnover frequency.Close collaboration between theorists and experimentalists is essential if we are to succeed in designing heterogeneous catalysts.     

一元线性回归处理逆动态法实验数据

阐述了一元线性回归处理逆动态法实验数据的原理。采用该方法除能获得反应性外还,可得到外中子有效源强。根据逆动态法实验原理和一元线性回归方法编写了计算程序,对俄罗斯动力研究院零功率装置BFS-1的实验数据进行处理,并与俄罗斯的计算结果进行了比较。计算结果表明：利用一元线性回归方法处理逆动态法实验数据可准确获得反应性和有效源强,提高了测量结果的精度,利用计算出的反应性可方便获得中心元件的效率;在反应堆功率较低、外源较强的情况下,应考虑外源对反应性测量的影响。