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151.
Medana C Calza P Dal Bello F Raso E Minero C Baiocchi C 《Journal of mass spectrometry : JMS》2011,46(1):24-40
This paper deals with the photocatalytic transformation of N,N-diethyl-m-toluamide (DEET), one of the most widespread and efficient mosquito repellents, under simulated solar irradiation using titanium dioxide as the photocatalytic source of oxidizing species. The investigation involved monitoring of the DEET decomposition, the identification of intermediate compounds and the assessment of mineralization. High-resolution mass spectrometry was employed to assess the evolution of the photocatalyzed process over time. Fifty-one main species were identified after DEET transformation. Several isomeric species were formed and were characterized by analyzing MS and MS(n) spectra in full, and by comparison with parent molecule fragmentation pathways. In the DEET molecule, the initial transformation involved mono- and polyhydroxylation followed by oxidation of the alcohol groups, cleavage of the alkyl chains or ring opening. All these intermediates are easily degraded and DEET is completely mineralized after 4 h of irradiation. Microtox bioassay (Vibrio fischeri) was employed to evaluate the ecotoxicity of solutions treated by photocatalysis. 相似文献
152.
A new phenolic digycoside 1 was produced as stress metabolite in the fresh leaves of Viburnum ichangense (Hemsl.) Rehd ., in response to abiotic stress elicitation by CuCl2. The stress metabolite was characterized as 1‐O‐[α‐L ‐arabinofuranosyl(1→6)‐β‐D ‐glucopyranosyl]‐erythro‐1,2‐bis(4‐hydroxy‐3‐methoxyphenyl)propane‐1,3‐diol ( 1 ). A new flavan dimer, 2,3‐epoxyflavan‐3′,4′,5,7‐tetraol‐(4→8″)‐flavan‐3″,3′′′,4′′′,5′′′,6″‐pentaol ( 2 ), and two known compounds, hovetrichoside A ( 3 ) and asperglaucide ( 4 ), were also isolated. Their structures were established by spectroscopic means. 相似文献
153.
Polyacetylenes are main toxic ingredients in Bupleurum longiradiatum, a poisonous plant that has ever been misused as substitutes for Chaihu (Bupleuri Radix). For the first time, a high-performance liquid chromatography method coupled with diode array detector and mass spectrometry (HPLC-DAD-MS) was developed for qualitative and quantitative analysis of nine polyacetylenes in Bupleurum species. All references, including two new polyacetylenes, were isolated from B. longiradiatum and purified using a semi-preparation HPLC chromatography. The analysis was performed on a TSKgel ODS-100V C18 column (3 μm, 150 mm x 4.6 mm i.d.) using a gradient system of acetonitrile and water, with diode array detection (254 nm). The method was validated for linearity, precision, accuracy, limit of detection and quantification. A total of 27 Bupleurum samples were examined with this method, which showed a great variety in the distribution and contents of the polyacetylenes. It was found that polyacetylenes (1-8) were the main ingredients in B. longiradiatum, while a few kinds of polyacetylenes (5-8) were also identified in B. smithii, B. smithii var. parvifolium, B. bicaule and B. angustissimum. However, no polyacetylenes (1-9) were detected in the authentic Chaihu samples and the other Bupleurum species. The results indicated that the toxic B. longiradiatum could readily be distinguished from other medicinal Bupleurum species based on the polyacetylene profiles, and the guidelines and quality control of polyacetylenes for Chaihu are useful. The acute toxicity of the ethanol extract of B. longiradiatum and its fractions was also investigated. 相似文献
154.
155.
Shen M Zhang L Lee KM Vermeulen R Hosgood HD Li G Yin S Rothman N Chanock S Smith MT Lan Q 《Experimental & molecular medicine》2011,43(6):374-378
Benzene, a recognized hematotoxicant and carcinogen, can damage the human immune system. We studied the association between single nucleotide polymorphisms (SNPs) in genes involved in innate immunity and benzene hematotoxicity in a cross-sectional study of workers exposed to benzene (250 workers and 140 controls). A total of 1,236 tag SNPs in 149 gene regions of six pathways were included in the analysis. Six gene regions were significant for their association with white blood cell (WBC) counts (MBP, VCAM1, ALOX5, MPO, RAC2, and CRP) based on gene-region (P<0.05) and SNP analyses (FDR<0.05). VCAM1 rs3176867, ALOX5 rs7099684, and MPO rs2071409 were the three most significant SNPs. They showed similar effects on WBC subtypes, especially granulocytes, lymphocytes, and monocytes. A 3-SNP block in ALOXE3 (rs7215658, rs9892383, and rs3027208) showed a global association (omnibus P = 0.0008) with WBCs even though the three SNPs were not significant individually. Our study suggests that polymorphisms in innate immunity genes may play a role in benzene-induced hematotoxicity; however, independent replication is necessary. 相似文献
156.
157.
基于2016~2018年月度数据,通过独立估计的单曲线样条模型和SV 模型、联合估计的多曲线样条模型和SV模型拟合公司债信用利差期限结构,进而对模型拟合效果进行比较,讨论模型在宏观经济预测中的应用,得到以下结论:(1)拟合模型的函数形式是导致理论信用利差期限结构曲线翻折的原因。样条模型和SV模型拟合的信用利差曲线形状完全不同,且模型函数变动引起的误差变动大于曲线变动引起的误差变动。(2)联合估计模型可以修正独立估计模型的人为扭曲形式。多曲线模型的结果更接近实际信用利差,误差波动性明显减小,曲线更为平滑,且联合估计的多曲线样条模型优于独立估计的单曲线样条模型、独立估计的SV 模型和联合估计的SV模型。(3)公司债信用利差期限结构在一定程度上蕴含了市场对未来宏观经济的预期信息,且在短期内预测结果随先行期限延长而改善。因此,宏观经济政策制定者需关注信用利差和期限结构模型拟合研究,重视对信用利差期限结构的深度信息挖掘,从而提高中国宏观政策制定者调控手段的前瞻性和有效性。 相似文献
158.
159.
本文在碳交易机制下,考虑制造商之间存在竞争且减排成本系数为低碳制造商私有信息的情况,分别构建信息完全对称和信息非对称情形下的供应链模型,对低碳制造商减排率和产品销售价格进行决策。通过引入由批发价和成本共担组成的联合契约,促使低碳制造商传递真实的减排成本信息,并通过算例对碳交易价格和减排成本系数等进行灵敏度分析。研究发现:引入联合契约能够使得信息非对称下的供应链利润基本达到集中决策水平;碳交易价格的增加会激励制造商积极减排、降低碳排放总量、提高供应链利润;低碳制造商减排成本系数的降低有助于减少碳排放量、增加产品市场需求、实现供应链利润增长。 相似文献
160.
This paper concentrates on considering the down/up crossing property of weighted Markov collision processes. The joint probability generating function of down crossing and up crossing numbers of weighted Markov collision processes until its extinction are obtained by constructing and studying a related multi-dimensional Markov chain. Hence, the joint probability distribution of down crossing and up crossing numbers and the mean numbers are obtained. 相似文献