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A novel method for the forensic analysis of commercial petroleum products is presented. In this approach, the petroleum sample is extracted with nitromethane and then separated by capillary liquid chromatography with laser-induced fluorescence detection. The addition of selective fluorescence quenching agents allows the sample to be profiled by the distribution of alternant and nonalternant polycyclic aromatic hydrocarbons (PAHs). In preliminary studies, the quenching behavior of nitromethane and diisopropylamine was established by using a standard mixture of sixteen PAHs ranging in size from two to six aromatic rings. Subsequent examination of new and used motor oil demonstrated that characteristic differences arise in the PAH content, which may allow for the unique identification of oil from a particular engine or vehicle. In addition, three brands of petrolatum jelly were successfully distinguished. Although a number of alternant alkylated and heterocyclic PAHs were found in all petrolatum samples, there were significant differences in the relative concentrations of alternant as well as nonalternant PAHs. This allowed for clear differentiation of the samples through qualitative inspection of their chromatograms as well as quantitative statistical correlation techniques. 相似文献
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Opinion Backlash and Public Attitudes: Are Political Advances in Gay Rights Counterproductive?
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Benjamin G. Bishin Thomas J. Hayes Matthew B. Incantalupo Charles Anthony Smith 《American journal of political science》2016,60(3):625-648
One long‐recognized consequence of the tension between popular sovereignty and democratic values like liberty and equality is public opinion backlash, which occurs when individuals recoil in response to some salient event. For decades, scholars have suggested that opinion backlash impedes policy gains by marginalized groups. Public opinion research, however, suggests that widespread attitude change that backlash proponents theorize is likely to be rare. Examining backlash against gays and lesbians using a series of online and natural experiments about marriage equality, and large‐sample survey data, we find no evidence of opinion backlash among the general public, by members of groups predisposed to dislike gays and lesbians, or from those with psychological traits that may predispose them to lash back. The important implication is that groups pursuing rights should not be dissuaded by threats of backlash that will set their movement back in the court of public opinion. 相似文献