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991.
Adrián Carretero‐Genevrier Jaume Gázquez Teresa Puig Narcís Mestres Felip Sandiumenge Xavier Obradors Etienne Ferain 《Advanced functional materials》2010,20(6):892-897
A novel and general methodology for preparing vertical, complex‐oxide nanostructures from a sol–gel‐based polymer‐precursor solutions is developed using track‐etched polymers directly buffering substrates. This method is able to develop a nanostructure over the entire substrate, the dimensions and localization of the vertical nanostructures being preset by the polymeric nanotemplate. Thereby, nanostructures with lateral sizes in the range of 100 to 300 nm and up to 500 nm in height have been grown. Two examples are presented herein, the latter being the evolution of the initial, metastable nanostructure. Specifically, La0.7Sr0.3MnO3 polycrystalline rods are grown at mild temperatures (800 °C); upon strong thermal activation (1000 °C) they suffer a profound transformation into vertical, single‐crystalline (La,Sr)xOy nanopyramids sitting on a La0.7Sr0.3MnO3 epitaxial wetting layer. The driving force for this outstanding nanostructural evolution is the minimization of the total energy of the system, which is reached by reducing the grain‐boundary, total‐surface, and strain‐relaxation energies. Finally, advanced electron‐microscopy techniques are used to highlight the complex phase separation and structural transformations occurring when the metastable state is overcome. 相似文献
992.
Subchronic treatment with grape‐seed phenolics inhibits ghrelin production despite a short‐term stimulation of ghrelin secretion produced by bitter‐sensing flavanols 下载免费PDF全文
993.
Bojana Balanč Ana Kalušević Ivana Drvenica Maria Teresa Coelho Verica Djordjević Vitor D Alves Isabel Sousa Margarida Moldão‐Martins Vesna Rakić Viktor Nedović Branko Bugarski 《Journal of food science》2016,81(1):E65-E75
Carqueja (Pterospartum tridentatum) is an endemic species and various bioactive compounds have been identified in its aqueous extract. The aim of this study was to protect the natural antioxidants from the aqueous extract of carqueja by encapsulation in Ca–alginate microbeads and Ca–alginate microbeads containing 10% and 20% (w/v) of inulin. The microbeads produced by electrostatic extrusion technique had an average diameter from 625 μm to 830 μm depending on the portion of inulin. The sphericity factor of the hydrogel microbeads had values between 0.014 and 0.026, while freeze dried microbeads had irregular shape, especially those with no excipient. The reduction in microbeads size after freeze drying process (expressed as shrinkage factor) ranged from 0.338 (alginate microbeads with 20% (w/v) of inulin) to 0.523 (plain alginate microbeads). The expressed radical scavenging activity against ABTS and DPPH radicals was found to be between 30% and 40% for encapsulated extract, while the fresh extract showed around 47% and 57% of radical scavenging activity for ABTS and DPPH radicals, respectively. The correlation between antioxidant activity and the total phenolic content were found to be positive (in both assay methods, DPPH and ABTS), which indicate that the addition of inulin didn't have influence on antioxidant activity. The presence of inulin reduced stiffness of the hydrogel, and protected bead structure from collapse upon freeze‐drying. Alginate–inulin beads are envisaged to be used for delivery of aqueous P. tridentatum extract in functional food products. 相似文献
994.
Nicolás Mujica Marı´a Teresa Cerda Rodrigo Espinoza Judit Lisoni Fernando Lund 《Acta Materialia》2012,60(16):5828-5837
Dislocations are at the heart of the plastic behavior of crystalline materials yet it is notoriously difficult to perform quantitative, non-intrusive measurements of their single or collective properties. Dislocation density is a critical variable that determines dislocation mobility, strength and ductility. On the one hand, individual dislocations can be probed in detail with transmission electron microscopy. On the other hand, their collective properties must be simulated numerically. Here we show that ultrasound technology can be used to measure dislocation density. This development rests on theory—a generalization of the Granato–Lücke theory for the interaction of elastic waves with dislocations—and resonant ultrasound spectroscopy (RUS) measurements. The chosen material is aluminum, to which different dislocation contents were induced through annealing and cold-rolling processes. The dislocation densities obtained with RUS compare favorably with those inferred from X-ray diffraction, using the modified Williamson–Hall method. 相似文献
995.
CuMn2O4 nanocatalysts synthesised by silica aquagel confined co-precipitation were analysed for the preferential oxidation of CO at different temperatures and concentration conditions. The catalysts show a higher activity than copper–ceria catalysts synthesised by the same method but, like these, they suffer from slow deactivation during the reaction. Surface analysis (FTIR and XPS) was used to unravel the deactivation mechanisms. Gradual reduction of the catalysts by the carbon monoxide present in the PROX stream was concluded to be the main cause of deactivation. 相似文献
996.
997.
Sónia Simões Filomena Viana Volker Ventzke Mustafa Koçak A. Sofia Ramos M. Teresa Vieira Manuel F. Vieira 《Journal of Materials Science》2010,45(16):4351-4357
With the stimulus of temperature and pressure Ni and Al can quickly react and produce the intermetallic compound NiAl. This
reaction is highly exothermic and high temperatures can be attained in the surroundings. These characteristics make Ni/Al
multilayers very attractive to technological applications as localised heat sources. In this study, Ni/Al multilayer thin
films are used to promote bonding between TiAl intermetallic alloys. Ni and Al alternated nanolayers were deposited by d.c.
magnetron sputtering onto TiAl samples, with periods of 5, 14 and 30 nm. Joining experiments were performed at 900 °C for
60 or 30 min, in a vertical furnace with a vacuum level better than 10−2 Pa. Applied pressures of 5 MPa were tested. The microstructure of the cross-sections of the bond interface was analysed by
energy dispersive X-ray spectroscopy and characterised by scanning electron microscopy. The observation of the microstructure
for 14 and 30 nm period multilayers revealed sound bonding, while for 5 nm period porosity and cracks within the interlayer
thin film were observed. The interface is divided into three distinct zones: one with columnar grains, another with very small
equiaxed grains and the third with larger equiaxed grains. The joining process appears to depend on the diffusion of Ni and
Ti across the interface and is assisted by the nucleation of nanometric grains at the interface. The mechanical strength of
the joints was evaluated by shear tests. The bonds produced at 900 °C/5 MPa/60 min/14 nm exhibited the highest shear strength
of 314 MPa. 相似文献
998.
Daryl J. McGoldrick Janice L. Metcalfe-Smith Michael T. Arts Donald W. Schloesser Teresa J. Newton Gerald L. Mackie Emy M. Monroe Johann Biberhofer Kennon Johnson 《Journal of Great Lakes research》2009
The Lake St. Clair delta (∼ 100 km2) provides an important refuge for native freshwater mussels (Unionidae) wherein 22 of the ∼ 35 historical species co-occur with invasive dreissenids. A total of 1875 live unionids representing 22 species were found during snorkeling surveys of 32 shallow (∼ 1 m) sites throughout the delta. Richness and density of unionids and zebra mussel infestation rates varied among sites from 3 to 13 unionid species, 0.02 to 0.12 unionids/m2, and < 1 to 35 zebra mussels/unionid, respectively. Zebra mussel infestation of unionids in the delta appears to be mitigated by dominant offshore currents, which limit densities of zebra mussel veligers in nearshore compared to offshore waters (13,600 vs. 28,000/m3, respectively). Glycogen concentrations in the tissues of a common and widespread species in the delta (Lampsilis siliquoidea) suggest that zebra mussels may be adversely affecting physiological condition of unionids in a portion of the Lake St. Clair delta. Physiological condition and community structure of unionids within the delta may also be influenced by differences in food quantity and quality resulting from the uneven distribution of water flowing from the St. Clair River. The delta likely supports the largest living unionid community in the lower Great Lakes and includes several species that have been listed as Endangered or Threatened in Canada and/or the state of Michigan, making it an important refuge for the conservation of native unionids. 相似文献
999.
Antn L. Martínez Jos Brea Sara Rico María Teresa de los Frailes María Isabel Loza 《International journal of molecular sciences》2021,22(18)
Schizophrenia is a major mental illness characterized by positive and negative symptoms, and by cognitive deficit. Although cognitive impairment is disabling for patients, it has been largely neglected in the treatment of schizophrenia. There are several reasons for this lack of treatments for cognitive deficit, but the complexity of its etiology—in which neuroanatomic, biochemical and genetic factors concur—has contributed to the lack of effective treatments. In the last few years, there have been several attempts to develop novel drugs for the treatment of cognitive impairment in schizophrenia. Despite these efforts, little progress has been made. The latest findings point to the importance of developing personalized treatments for schizophrenia which enhance neuroplasticity, and of combining pharmacological treatments with non-pharmacological measures. 相似文献
1000.
The oxidation of NH3 during oxy-fuel combustion of methane, i.e., at high [CO2], has been studied in a flow reactor. The experiments covered stoichiometries ranging from fuel rich to very fuel lean and temperatures from 973 to 1773 K. The results have been interpreted in terms of an updated detailed chemical kinetic model. A high CO2 level enhanced formation of NO under reducing conditions while it inhibited NO under stoichiometric and lean conditions. The detailed chemical kinetic model captured fairly well all the experimental trends. According to the present study, the enhanced CO concentrations and alteration in the amount and partitioning of O/H radicals, rather than direct reactions between N-radicals and CO2, are responsible for the effect of a high CO2 concentration on ammonia conversion. When CO2 is present as a bulk gas, formation of NO is facilitated by the increased OH/H ratio. Besides, the high CO levels enhance HNCO formation through NH2+CO. However, reactions NH2+O to form HNO and NH2+H to form NH are inhibited due to the reduced concentration of O and H radicals. Instead reactions of NH2 with species from the hydrocarbon/methylamine pool preserve reactive nitrogen as reduced species. These reactions reduce the NH2 availability to form NO by other pathways like via HNO or NH and increase the probability of forming N2 instead of NO. 相似文献