Kinetic and mechanistic investigations of the oxidation of tramadol by ferrate and ozone

The kinetics and oxidation products (OPs) of tramadol (TRA), an opioid, were investigated for its oxidation with ferrate (Fe(VI)) and ozone (O(3)). The kinetics could be explained by the speciation of the tertiary amine moiety of TRA, with apparent second-order rate constants of 7.4 (±0.4) M(-1) s(-1) (Fe(VI)) and 4.2 (±0.3) × 10(4) M(-1) s(-1) (O(3)) at pH 8.0, respectively. In total, six OPs of TRA were identified for both oxidants using Qq-LIT-MS, LTQ-FT-MS, GC-MS, and moiety-specific chemical reactions. In excess of oxidants, these OPs can be further transformed to unidentified OPs. Kinetics and OP identification confirmed that the lone electron pair of the amine-N is the predominant site of oxidant attack. An oxygen transfer mechanism can explain the formation of N-oxide-TRA, while a one-electron transfer may result in the formation of N-centered radical cation intermediates, which could lead to the observed N-dealkylation, and to the identified formamide and aldehyde derivatives via several intermediate steps. The proposed radical intermediate mechanism is favored for Fe(VI) leading predominantly to N-desmethyl-TRA (ca. 40%), whereas the proposed oxygen transfer prevails for O(3) attack resulting in N-oxide-TRA as the main OP (ca. 90%).     

行为理论——设计活动的通用方法

 对工程设计的实证研究指出了提高解决方案质量的步骤特征:机会策略;用脑思考和用手思考(画草图)相结合;对自己的成果进行提问式反思。这些步骤特征符合工作活动的思维调控理论的预测(“行为理论”)。     

Long-term change of polycyclic aromatic hydrocarbon deposition to peatlands of eastern Canada

To date, studies about historic PAH (polycyclic aromatic hydrocarbons) deposition at a regional scale have rarely been published. To address this research gap, we sampled 17 ombrotrophic peatlands across eastern Canada. The peat cores from hollows were dated with 210Pb for the period of about 1850-2000 and analyzed fortheir PAH concentration, so PAH deposition could be reconstructed. Peat samples were extracted by accelerated solvent extraction (ASE). The extracts were purified by column chromatography with aluminum oxide and silica gel. PAH were measured by gas chromatography-tandem mass spectrometry (GC-MS/MS). Overall reconstructed deposition rates of sigma-11 PAH ranged from 4 to 1432 microg m(-2) year(-1). Three different long-term trends in PAH deposition could be distinguished: sites with two separated periods of maximum PAH deposition, sites with one period of maximum PAH deposition, and sites with no clearly separated period of maximum PAH deposition. Increasing PAH depositions were caused by rapid industrialization accompanied by extensive use of fossil fuels; decreasing PAH depositions were caused by substitution of these fuels and movements of PAH emitting industry to different regions. At all sites either phenanthrene (20-60%) or benzo[b+k]fluoranthene (10-40%) was the predominant PAH. Detailed analysis of three bogs suggested that combustion of coal and vehicle exhausts mainly contributed to the peat PAH burden. The temporal trends of PAH deposition indicated that increases in the PAH deposition rates followed the industrial development in Canada, particularly in the periods 1880-1910 and 1940-1960. Recent abatement efforts were reflected in decreased PAH deposition rates to about 15% of the maximum.     

Cultural diversity and entrepreneurship: a regional analysis for Germany

In this paper, we investigate the determinants of entrepreneurial activity in a cross section of German regions for the period 1998–2005. Departing from the knowledge spillover theory of entrepreneurship, the focus of our analysis is on the role of the regional environment and, in particular, knowledge and cultural diversity. Our main hypothesis is that both, knowledge and diversity, have a positive impact on new firm formation. As the determinants of regional firm birth rates might differ considerably with respect to the necessary technology and knowledge input, we consider start-ups at different technology levels. The regression results indicate that regions with a high level of knowledge provide more opportunities for entrepreneurship than other regions. Moreover, while sectoral diversity tends to dampen new firm foundation, cultural diversity has a positive impact on technology oriented start-ups. This suggests that the diversity of people is more conducive to entrepreneurship than the diversity of firms. Thus, regions characterized by a high level of knowledge and cultural diversity form an ideal breeding ground for technology oriented start-ups.     

Cartilage replacement by use of hybrid systems of autologous cells and polyethylene: an experimental study

This study used porous polyethylene (PE) as a scaffold in an animal model system. The surface of the scaffolds was either modified with collagen II coating or first functionalized by oxygen plasma treatment and then coated with collagen II. The specimens were inoculated with autologous chondrocytes and transplanted into the concha of guinea pigs. Bare scaffolds were used as controls. Periods of 1, 6, and 12 months after implantation, samples of cells containing specimens and control samples were evaluated microscopically. As a result, the pre-seeded specimens were better integrated into the surrounding tissue than cell-free PE-specimens. Also a weaker immune reaction and an improved cartilage generation could be detected in the pre-seeded specimen. Compared to the other surface modifications, no further improvement of cartilage development was observed in the long term in vivo animal experimental study.     

Psychosocial working conditions and well-being among immigrant and German low-wage workers.

Despite a steady increase of immigrant workers in Germany in the past decades, occupational health research has only peripherally addressed psychosocial working conditions and immigrant worker well-being. This study has two aims: (1) to investigate differences in psychosocial stressors and resources between immigrant and German low-wage workers, and (2) to examine group differences in their association with well-being using a structural equation modeling multiple group analysis approach. Eighty-nine immigrant and 146 German postmen of a German mail service company were surveyed. Results reveal more stressors in the social work environment for the immigrant workers than for their German coworkers but similar levels of task-related stressors in both groups. Stressors are more strongly associated with psychological distress among the German workers. In terms of resources, job control serves as a resource only among German workers, whereas supervisor and coworker support are more important for immigrant workers. These differences suggest that cultural factors, previous work experiences, and expectations influence the worker's experience of psychosocial working conditions and have a direct impact on worker health. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Regional unemployment structure and new firm formation

Does regional unemployment increase or rather decrease entrepreneurial activity? Although this question has been hotly debated among researchers for decades, the answers yielded so far are ambiguous and inconclusive. The paper proposes an innovative approach that takes not only interregional differences in unemployment rates, but also in unemployment duration and the human capital of the unemployed, that is, in the structure of regional unemployment into account. Both, the skill structure of the unemployed and the share of long‐term unemployment are found to have an important impact on regional start‐up activity. Moreover, the impact of unemployment structure on new firm formation is found to vary with the knowledge‐intensity of the start‐ups.