Las primeras obras públicas en el Nuevo Mundo y su financiación: Santo Domingo 1494-1572

55 pagesPeer reviewe

Analytics of partially oxidized polycyclic aromatic hydrocarbons and degradation of benzo[a]pyrene on soot aerosol particles with ozone

Eine universelle Methode zur Analyse partiell oxidierter aromatischer Kohlenwasserstoffe wurde entwickelt und auf Realproben angewandt. Die Analytik basiert auf flüssigchromatographischer Trennung durch eine phenyl-modifizierte Umkehrphase und massenspektrometrischer Detektion mit einem APCI-Quadrupol-Massenspektrometer. Damit wurde eine Datenbank erstellt (73 Referenzsubstanzen) und Realproben mit umwelttechnischer und medizinischer Relevanz untersucht. Ein weiterer Schwerpunkt der Arbeit lag in der Charakterisierung der Produkte und der Kinetik der Reaktion von Ozon mit polyzyklischen aromatischen Kohlenwasserstoffen (PAH), insbesondere mit Benzo[a]pyren (B[a]P). Dabei wurden mehrere bisher unbekannte Abbauprodukte und physikalisch-chemische Parameter bestimmt (Ratenkoeffizienten, Adsorptionsgleichgewichtskonstanten, etc.).A universal method for the efficient separation and detection of partially oxidized polycyclic aromatic hydrocarbons has been developed and was applied to real samples. These method bases on a liquid chromatographic separation with a phenyl-modified silica reversed stationary phase and mass spectrometric detection with APCI-single-quadrupole-MS. The applicability was demonstrated with 73 reference substances and with real samples of environmental, medical, and technical relevance. Another topic in this work was the characterization of products and the kinetic from the reaction of ozone with polycyclic aromatic hydrocarbons, especially with benzo[a]pyrene. Several up to now unknown degradation products and physico-chemical parameters could be determined (rate coefficients, adsorption equilibrium constants, etc)

Aluminosis – Detection of an almost forgotten disease with HRCT

The aim of this study was to investigate whether it is possible to detect high-resolution computed tomography (HRCT) findings in aluminium powder workers, which are consistent with early stages of aluminosis. 62 male workers from 8 departments of two plants producing aluminium (Al) powder were investigated using a standardized questionnaire, physical examination, lung function analysis, biological monitoring of Al in plasma and urine, chest X-ray, HRCT and immunological tests. Chronic bronchitis was observed in 15 (24.2%) of the workers, and four workers (6.5%) reported shortness of breath during exercise. HRCT findings in 15 workers (24.2%) were characterized by ill-defined centrilobular nodular opacities. Workers with ill-defined centrilobular nodular opacities had a lower vital capacity than workers who had no such HRCT-findings (90.9 % pred. vs. 101.8 % pred., p = 0.01). Biological monitoring in plasma and urine revealed higher internal exposure to Al in affected workers (33.5 μg/l plasma to 15.4 μg/l plasma, p = 0.01) and (340.5 μg/g creat. to 135.1 μg/g creat., p = 0.007). Years of exposure and concentration of aluminum in urine and plasma appear to be the best predictors for HRCT findings. Age and decreased vital capacity show borderline significance. We conclude that aluminosis is still relevant in occupational medicine. With HRCT it is possible to detect early stages of aluminosis and biological monitoring can be used to define workers at high risk

Ultra-high–strength Bainitic Steels

Novel bainitic microstructures, consisting of slender ferrite plates (tens of nm) in a matrix of retained austenite, have reported maximum yield strength of 1.4 GPa, ultimate tensile strength of 2.2 GPa, 30% ductility and respectable levels of fracture toughness (∼51 MPa m0.5). The unusual combination of properties is attributed to the fine bainitic plates and the presence of retained austenite in the microstructure.The authors acknowledge financial support from the Spanish Ministerio de Educación y Ciencia for the financial support in the form of Ramón y Cajal contracts (RyC 2002 and 2004 respectively). Some of this work was carried out under the auspices of an EPSRC/MOD sponsored project on bainitic steels at the University of Cambridge; we are extremely grateful for this support over a period of three years. The authors are extremely grateful to Prof. H. K. D.Peer reviewe

Conditional reciprocal stressor-strain effects in university students : a cross-lagged panel study in Germany

University students worldwide are facing increasing mental health challenges. Traditional stress models, like the Job/Study Demand-Resources Model, link stressors directly to strain. Yet, recent studies suggest the influence of strain on stressors may be even stronger. Our research explored these reciprocal dynamics among university students, considering social support and mindfulness as potential moderators. We conducted a two-wave panel study with 264 university students. We ran separate cross-lagged panel structural equation analyses for three key health outcomes—emotional exhaustion, depression, and well-being—each paired with perceived study stressors, specifically workload and work complexity. Findings revealed significant stressor and strain effects, with social support notably moderating the impact of emotional exhaustion on workload. These insights challenge traditional stress theories and underscore the importance of mental health support and effective stress management strategies for students, emphasizing the need for proactive mental health initiatives in academic environments

Analysis of large oxygenated and nitrated polycyclic aromatic hydrocarbons formed under simulated diesel engine exhaust conditions (by compound fingerprints with SPE/LC-API-MS)

The analysis of organic compounds in combustion exhaust particles and the chemical transformation of soot by nitrogen oxides are key aspects of assessment and mitigation of the climate and health effects of aerosol emissions from fossil fuel combustion and biomass burning. In this study we present experimental and analytical techniques for efficient investigation of oxygenated and nitrated derivatives of large polycyclic aromatic hydrocarbons (PAHs), which can be regarded as well-defined soot model substances. For coronene and hexabenzocoronene exposed to nitrogen dioxide under simulated diesel exhaust conditions, several reaction products with high molecular mass could be characterized by liquid chromatography-atmospheric pressure chemical (and photo) ionization-mass spectrometry (LC-APCI-MS and LC-APPI-MS). The main products of coronene contained odd numbers of nitrogen atoms (m/z 282, 256, 338), whereas one of the main products of hexabenzocoronene exhibited an even number of nitrogen atoms (m/z 391). Various reaction products containing carbonyl and nitro groups could be tentatively identified by combining chromatographic and mass spectrometric information, and changes of their relative abundance were observed to depend on the reaction conditions. This analytical strategy should highlight a relatively young technique for the characterization of various soot-contained, semi-volatile, and semi-polar reaction products of large PAHs

Antecedents and moderation effects of maladaptive coping behaviors among German university students

Prolonging working hours and presenteeism have been conceptualized as self-endangering coping behaviors in employees, which are related to health impairment. Drawing upon the self-regulation of behavior model, the goal achievement process, and Warr's vitamin model, we examined the antecedents and moderation effects regarding quantitative demands, autonomy, emotion regulation, and self-motivation competence of university students' self-endangering coping behaviors (showing prolonging working hours and presenteeism). Results from a cross-sectional survey of 3,546 German university students indicate that quantitative demands are positively related and autonomy has a u-shape connection with self-endangering coping. Emotion regulation was shown to be a protective factor for prolonging working hours. Moreover, self-motivation moderated the relationship between quantitative demands and prolonging of working hours, but not in the assumed direction. Self-motivation showed a systematic positive relationship with prolonging of working hours, but no relationship with presenteeism. Autonomy moderated the relationship of quantitative demands with both self-endangering behaviors. We found no moderating effects for emotion regulation of quantitative demands or autonomy and self-endangering behaviors. Besides further practical implications, the results suggest that lecturers should design their courses accordingly with less time pressure and university students should be trained in the use of autonomy