The catalytic activity of Pd catalysts supported on Ce0.73Tb0.27Ox/SiO2, Ce0.6Zr0.4Ox/SiO2, Ce0.73Tb0.27Ox/La2O3-Al2O3 and Ce0.6Zr0.4Ox/La2O3-Al2O3 was studied using the reduction of NO by CO. The catalysts were characterized by X-ray fluorescence, surface area, X-ray diffraction, temperature-programmed reduction, CO chemisorption and oxygen storage capacity. Temperature-programmed reduction results indicated that Tb or Zr incorporation improves the reducibility and oxygen storage capacity. CO chemisorption data suggested the presence of large PdO particles due to the low CO/Pd ratio. No significant differences were obtained in light off temperatures (TLight off) for all Pd catalysts and the most active was 1.5%Pd/Ce0.6Zr0.4Ox/SiO2. 相似文献
Wildlife data often show spatial organization, demonstrating positive correlations either as a result of processes occurring
over the landscape or due to the influence of spatially structured environmental variables. It is, thus, essential to consider
non-random spatial structure when evaluating the underlying causes of biological variation. In this study, we analyzed the
population structure of Chilina dombeyana shell morphology of 14 populations that are close geographically and belong to the same hydrographic basin. We utilized a
variation partitioning approach to evaluate the importance of spatial processes, such as migration, acting over the landscape,
and environmental characteristics, including habitat and hydrologic characteristics, and the occurrence of aquatic predators
in promoting between population variation. Our results demonstrate spatially structured variation in C. dombeyana shell morphology, with populations living near each other having more similar shell sizes than populations living farther
apart. The shell size variation partition indicated that both spatially structured environmental factors and genetic relationships
resulting from migration or shared common ancestry may explain this pattern. Shell shape variation, in contrast, was found
to be essentially under the influence of non-spatially structured environmental factors, with habitat and water characteristics
accounting for about half of the total variation among populations. The large proportion of the variation in shell size that
is spatially structured demonstrates that spatial structure on morphological traits might be strong and highlights the need
to consider such phenomenon in intraspecific studies of phenotypic evolution. 相似文献
ABSTRACT This study explores the experience of the sub-urban slum residents in Okpoko (Anambra State), Ngwa-road Aba (Abia State), Ajegunle (Lagos State) and Gwagwalada (Abuja), to underscore the elitist and western contexts of Covid-19 lockdown and physical distancing policies. The study apprehends these policies as being counter-productive due to Nigeria’s peculiar socio-economic circumstances, and brainstorms on the need and prospects for adaption and institutionalisation of an indigenous Afro-centred approach towards the containment of the Covid-19 pandemic. The use of herbal mixtures or local concoctions such as parboiled garlic cloves, lemon and ginger juice in the treatment and/or prevention of Covid-19 pandemic is a popular home-grown indigenous approach/practice which is generally believed to have inhibitory effects against Covid-19 by majority of the local people. These herbal remedies should be formally investigated, validated and encouraged in Nigeria as an alternative indigenous approach for the prevention and treatment of Covid-19 pandemic. 相似文献
A modified sequential mass-suspension polymerization was employed to ensure adequate dispersion of lignin into the monomeric phase. Due to its complex macromolecular structure and low compatibility with styrene, eucalyptus wood-extracted lignin, via a modified Kraft method, was esterified with methacrylic anhydride to ensure organic phase homogeneity into the reaction medium. Infrared spectroscopy showed a decrease in the hydroxyl band, a characteristic of natural lignin (3200–3400 cm?1) and an increase in the characteristic ester band (1720–1740 cm?1) whereas nuclear magnetic resonance measurements exhibited intense peaks in the range from 1.7 to 2.05 ppm (–CH3) and 5.4 to 6.2 ppm (=CH2), related to methacrylic anhydride. Comparatively, the esterified lignin also displayed an increase of its glass transition temperature for 98?°C, related to natural lignin, whose Tg was determined to be equal to 91?°C. Styrene/lignin-based polymers exhibited higher average molar masses in comparison to the values observed for polystyrene synthesized with similar amounts of benzoyl peroxide, due to the ability of lignin to act as a free-radical scavenger. Composites obtained with styrene and natural or esterified lignin were successfully synthesized, presenting regular morphology and proper lignin dispersion. Based on a very simple polymerization system, it is possible to enhance the final properties of polystyrene through the incorporation of lignin, which represents an important platform for developing attractive polymeric materials from renewable resources. 相似文献
A growing body of literature argues that subjective factors can more accurately explain individual adaptation to climate change than objective measurers of adaptive capacity. Recent studies have shown that personal belief in climate change and affect are much better in explaining climate awareness and action than income, education or gender. This study focuses on the process of individual adaptation to climate change. It assesses and compares the influence of cognitive, experiential and structural factors on individuals’ views and intentions regarding climate change adaptation. Data from this study comes from a survey with 836 forest owners in Sweden. Ordinal and binary logistic regression was used to test hypotheses about the different factors. Results show that cognitive factors—namely personal level of trust in climate science, belief in the salience of climate change and risk assessment—are the only statistically significant factors that can directly explain individuals’ intention to adapt to climate change and their sense of urgency. Findings also suggest that structural or socio-demographic factors do not have a statistically significant influence on adaptation decision-making among Swedish forest owners. The study also offers valuable insights for communication interventions to promote adaptation. Findings strongly suggest that communication interventions should focus more strongly on building trust and addressing stakeholders’ individual needs and experiences.
This paper describes an experimental evaluation of anaerobic digestion technology as an option for the management of organic solid waste in developing countries. As raw material, a real and heterogeneous organic waste from urban solid wastes was used. In the first experimental phase, seed selection was achieved through an evaluation of three different anaerobic sludges coming from wastewater treatment plants. The methanization potential of these sludges was assessed in three different batch digesters of 500 mL, at two temperature levels. The results showed that by increasing the temperature to 15 degrees C above room temperature, the methane production increases to three times. So, the best results were obtained in the digester fed with a mixed sludge, working at mesophilic conditions (38-40 degrees C). Then, this selected seed was used at the next experimental phase, testing at different digestion times (DT) of 25, 20 and 18 days in a bigger batch digester of 20 L with a reaction volume of 13 L. The conversion rates were registered at the lowest DT (18 days), reaching 44.9 L/kg(-1) of wet wasteday(-1). Moreover, DT also has a strong influence over COD removal, because there is a direct relationship between solids removal inside the reactor and DT. 相似文献
The increasing number of nanomaterial based consumer products raises concerns about their possible impact on the environment. This study provides an assessment of the effluent from a commercially available silver nanowashing machine. The washing machine released silver in its effluent at an average concentration of 11μgL(-1), as determined by inductive coupled mass spectrometry (ICP-MS). The presence of silver nanoparticles (AgNPs) was confirmed by single particle ICP-MS as well as ion selective electrode measurements and filtration techniques. Size measurements showed particles to be in the defined nanosize range, with an average size of 10nm measured with transmission electron microscopy (TEM) and 60-100nm determined with nanoparticle tracking analysis (NTA). The effluent was shown to have negative effects on a natural bacterial community as its abundance was clearly reduced when exposed to the nanowash water. If washing machines capable of producing AgNPs become a common feature of households in the future, wastewater will contain significant loadings of AgNPs which might be released into the environment. 相似文献
The ability of fungal strains to attack a composite material obtained from poly(vinyl alcohol) (PVA) and bacterial cellulose
(BC) is investigated. The fungal strain tested was Aspergillus niger. This fungal strain was able to change not only the polymer surface from smoother to rougher, but also to disrupt the polymer.
The degradation results were confirmed by visual observations, scanning electron microscopy (SEM) analyses, X-ray diffraction
analyses and FTIR spectra of the film samples. SEM micrographs confirmed the growth of fungi on the composite film surface.
The degree of microbial degradation depends on culture medium and on composition of polymeric materials, especially on PVA
content. The biodegradation process is accelerated by the presence of glucose in the culture medium as an easily available
carbon source. 相似文献
Calorimetry has been used in order to identify the runaway behavior of 2-methylpyridine-N-oxidation (2-picoline-N-oxidation). Experiments were performed in an Automatic Pressure Tracking Adiabatic Calorimeter (APTAC), employing 2-methylpyridine-N-oxide (2-picoline-N-oxide) with or without catalyst, 2-methylpyridine-N-oxide, hydrogen peroxide, 2-methylpyridine (2-picoline) and catalyst, and 2-methylpyridine, hydrogen peroxide and catalyst. Approximately 16.5 g of aqueous solutions were used in 100 ml closed glass cells in all but one measurement. Measurements were performed isothermally or employing the Heat-Wait-Search (HWS) technique. During reaction runaway, any excess of hydrogen peroxide and the produced 2-methylpyridine-N-oxide decompose releasing non-condensable gases and raising the pressure. It was found that the reaction runaway is condition-sensitive. Catalyst, the presence of 2-picoline and/or its N-oxide, affect hydrogen peroxide and/or 2-picoline-N-oxide decomposition rates. Further research accompanied by analytical measurements of the gas and liquid phase would provide indications in regard to the decomposition mechanisms followed in those cases. 相似文献