Infrared and UV–vis studies of metallocene immobilization on silica are reported here. The results have indicated changes in the Zr coordination sphere of metallocene depending on the immobilization route used. The reaction of [(Cp)2ZrCl2] with silica formed [(Cp)2ZrCl]+[SiO]− species. The same metallocene, reacting with TMA modified silica, formed monomethylated and dimethylated species by the substitution of chloro for methyl ligands, stabilized on the surface by interaction with “MAO-like” species (methylaluminoxane, MAO). These monomethylated and dimethylated cationic zirconium species are the active centers for the polymerization reaction. Different order of TMA addition in the silica modification step generated surface species of a similar nature, differing in their relative quantities. The highest amount of these active species was obtained when the support was added to the TMA solution rather than adding the TMA solution to the silica support. This was the most significant parameter affecting catalytic activity in ethylene polymerization. 相似文献
The effect of CeO2 loading (1–20 wt.%) on the properties and catalytic behaviors of CeO2–Al2O3-supported Pt catalysts on the partial oxidation of methane was studied. The catalysts were characterized by SBET, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and oxygen storage capacity (OSC). XRD and TPR results showed that the pretreatment temperature of the support influences on the amount of CeO2 with fluorite structure. The pretreatment temperature of the support and CeO2 loading influenced the morphology of Pt. OSC analysis showed a significant increase in the oxygen storage capacity per weight of CeO2 for samples with high CeO2 loading (12 and 20 wt.%). TPR analyses showed that the addition of Pt promotes the reduction of CeO2. This effect was more significant for the catalysts with high CeO2 loading (≥12 wt.%). The dispersion of Pt, measured by the rate of cyclohexane dehydrogenation, increases with increasing of the pretreatment temperature of the support. It was shown that the kind of the support is very important for obtaining of catalysts resistant to carbon formation. The catalysts with high CeO2 loading (≥12 wt.%) showed the highest catalytic activity and stability in the reaction of partial oxidation of methane due to a higher Pt–CeO2 interface. 相似文献
Mercury is a severe environmental pollutant with neurotoxic effects, especially when exposed for long periods. Although there are several evidences regarding mercury toxicity, little is known about inorganic mercury (IHg) species and cerebellum, one of the main targets of mercury associated with the neurological symptomatology of mercurial poisoning. Besides that, the global proteomic profile assessment is a valuable tool to screen possible biomarkers and elucidate molecular targets of mercury neurotoxicity; however, the literature is still scarce. Thus, this study aimed to investigate the effects of long-term exposure to IHg in adult rats’ cerebellum and explore the modulation of the cerebellar proteome associated with biochemical and functional outcomes, providing evidence, in a translational perspective, of new mercury toxicity targets and possible biomarkers. Fifty-four adult rats were exposed to 0.375 mg/kg of HgCl2 or distilled water for 45 days using intragastric gavage. Then, the motor functions were evaluated by rotarod and inclined plane. The cerebellum was collected to quantify mercury levels, to assess the antioxidant activity against peroxyl radicals (ACAPs), the lipid peroxidation (LPO), the proteomic profile, the cell death nature by cytotoxicity and apoptosis, and the Purkinje cells density. The IHg exposure increased mercury levels in the cerebellum, reducing ACAP and increasing LPO. The proteomic approach revealed a total 419 proteins with different statuses of regulation, associated with different biological processes, such as synaptic signaling, energy metabolism and nervous system development, e.g., all these molecular changes are associated with increased cytotoxicity and apoptosis, with a neurodegenerative pattern on Purkinje cells layer and poor motor coordination and balance. In conclusion, all these findings feature a neurodegenerative process triggered by IHg in the cerebellum that culminated into motor functions deficits, which are associated with several molecular features and may be related to the clinical outcomes of people exposed to the toxicant. 相似文献
The compaction of fresh concrete by an internal poker vibrator has been analysed using closed-form solutions for the propagation of the shear and compressive waveforms, assuming that concrete conforms to the Bingham model. In the inner liquefied zone around the vibrator the flow is due to shear whereas in the outer unsheared zone propagation is due to compressive waves. The analysis gives a method of predicting the radial position at which the flow changes, which coincides with the radius of action of the vibrator. Theory and experiment agree well and confirm that the peak velocity of the vibration governs its efficacy, with radius of action increasing with increasing velocity. The radius of action increases with decreasing yield stress and with increasing plastic viscosity. The work offers the potential to optimise the design and use of vibrators. 相似文献
An alternative for reducing emissions from marine fuel is to blend bio-oil from lignocellulose non-edible feedstocks to diesel fossil fuels. Phase diagrams of the ternary systems were built to represent the transition from heterogeneous regions to homogeneous regions. Four homogeneous blends of bio-oil of eucalyptus-bioethanol-marine gasoil were experimentally characterized with respect to the most important fuel parameters for marine engines: water content, flash point, low heating value, viscosity, and acidity. Blends with closer properties to marine gasoil replacement, lower costs, and environmental impacts should be tested for large engines. 相似文献
Dampness is an important degradation issue especially in old buildings and monumental heritage, particularly a rising one as the result of capillary movement of water in the lower sections of walls and other ground-supported structures by capillary action. There are several methods to treat this kind of dampness among which is the wall base hygro-regulated ventilation system an interesting solution for high thick walls with considerable heterogeneity.
A significant number of studies have been undertaken around this method which have been implemented and validated in several heritage buildings. Such achievement has led to the adoption of the HUMIVENT patent system which aims to increase evaporation through peripheral channels on the base of the ventilated walls. A pre-sizing design program was also created and was called HUMIVENT PREDIM.
This study aims to develop a set of auxiliary abacus for pre-sizing wall base ventilation systems. This approach aims to provide fast and expeditious systems sizing in the design and rehabilitation project offices. It allows an easy awareness in the several parameters that influence the wet front and the preliminary ventilation system design. It is a very useful tool for designers allowing them to obtain pre-sizing without extensive knowledge of the program and the associated parameters and with quick understanding of the drying process optimization. For better awareness of the abacus’ potentiality and use, an application example is provided thereof. It is concluded that the abacus can straightforwardly be used for sensitivity studies and for the selection of the best solution in each case. 相似文献
One of the earliest synthetic antimalarial drugs, quinacrine, was recently reported as interesting for the treatment of acute myeloid leukemia. Inspired by this and similar findings, we evaluated a set of quinacrine analogues against gastric (MKN‐28), colon (Caco‐2), and breast (MFC‐7) cancer cell lines and one normal human fibroblast cell line (HFF‐1). All the compounds, previously developed by us as dual‐stage antimalarial leads, displayed antiproliferative activity, and one of the set stood out as selective toward the gastric cancer cell line, MKN‐28. Interestingly, this compound was transported across an in vitro MKN‐28 model cell line in low amounts, and approximately 80 % was trapped inside those cells. Nuclear targeting of the same compound and its interactions with calf thymus DNA were assessed through combined fluorescence microscopy, spectroscopy, and calorimetry studies, which provided evidence for the compound's ability to reach the nucleus and to interact with DNA. 相似文献