The Treder and Barbour-Bertotti models of relativistic Lagrangians using only relative coordinates and velocities are compared in light of Leibnitz-Mach ideas. The plausible relationship between cosmological and vacuum asymmetries is noted, and the possibility of a modernized hierarchical model is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 86–90, July, 1978. 相似文献
Citrate precursor method has been used to obtain nanosized particles of barium hexaferrite at low temperatures. Samples were annealed at 450 °C for 3 and 5 h. Quenching of the third sample was done by taking the crucible out from the muffle furnace after annealing it for 5 h and putting it abruptly into an ice bath. The saturation magnetization has been found to be 4.36 and 0.04 emu g?1 for the samples obtained upon annealing at 450 °C for 3 and 5 h, respectively, while that of the quenched sample has been found to be 4.61 emu g?1. In case of the sample obtained after 5-h annealing, the squareness value was found to be maximum indicating significance in memory and switching applications. For the quenched and the 3-h annealing products, the magnetic data values are similar. Creation of spin disorders on the surface upon prolonged annealing, due to disappearance of oxygen ions and subsequent breakage of superexchange interactions between cations, has been undone upon quenching. The XRD and TEM data indicate that the particle size (9–17 nm) gets lower in case of the quenched samples. Photoluminescence study of the quenched sample furnished prominent peaks in UV, visible and near-IR regions under 200-nm excitation. The TG–DSC data were analysed for the kinetic parameters, activation energy (E), pre-exponential factor (A) using the Kissinger isoconversion and the Ozawa–Flynn–Wall methods for the first-step decomposition of the quenched sample. 相似文献
Eco-friendly sustainable materials provide an appealing template to replace contemporary synthetic-nonrenewable resource-based materials while maintaining the acceptable material properties to meet the performance requirements. Here, a layer-by-layer (LBL) self-assembly technique was used for fabricating multilayer composite films using all bio-based polymers/polysaccharides, i.e. cationic guar gum (CGg), carboxylated cellulose nanocrystals (cCNCs) and hydroxypropyl methylcellulose (HPMC). A five layered composite film was fabricated by depositing polymeric layers as follows: CGg→cCNCs→HPMC→cCNCs→CGg. The structural analysis of (CGg/cCNCs/HPMC)5 L multilayered composite films indicated the existence of electrostatic interaction as well as H-bonding between polymeric layers that resulted in homogenous, dense and compact film surface with improved smoothness and strength properties. As compared to pure CGg film, the (CGg/cCNCs/HPMC)5 L multilayered composite films showed improved tensile strength (84.8?% increment) and modulus (29.19?% improvement). Importantly, the deposition of HPMC layer contributed in achieving multilayer composite films with more flexible behavior (46.55?% improvement in elongation at break). Furthermore, owing to the high transparency (89.5?% transmittance), appreciable gas and oil barrier performance and resistance to various solvents (e.g. acetone, THF and DMAc), these multilayer films are promising candidates for various applications including renewable/sustainable packaging materials.
Chirped probe pulse femtosecond coherent anti‐Stokes Raman scattering (CPP fs‐CARS) thermometry was performed at 5 kHz in a hydrogen jet diffusion flame with an air co‐flow. Measurements were performed at different heights and radial locations within the jet diffusion flame, up to 16 nozzle exit diameters downstream (x/d = 16). The near‐nozzle measurements were characterized by large, organized, buoyancy‐driven instabilities that become more chaotic at the downstream locations x/d ≥ 4. The diffusion flame results highlight temperature fluctuations characteristic of the buoyancy‐driven Kelvin–Helmholtz‐type instability and provide new insights into the transient structure of these flames. At some measurement locations, the time‐varying temperatures ranged from 300 K to nearly 2400 K. The CPP fs‐CARS signal intensity is a factor of approximately 1000 times lower at 2400 K compared with 300 K. A dual‐channel detection system was used to increase the dynamic range of the CARS measurements. The determination of temperature from the single shot spectra is discussed in detail. Laser and detection system parameters were determined from CPP fs‐CARS spectra obtained from a near‐adiabatic laminar calibration flame apparatus. The temperature precision of the system was determined from these calibration measurements and was found to be better than 2.0% at 2200 K. The influence of an instrument response function on spectral fitting parameters is systematically assessed. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
Uniform sized silica and zirconia mixed titania samples were prepared in presence of a surfactant (CETAB) using controlled hydrolysis of corresponding metal alkoxides. Photocatalytic activity towards reduction of lead and cadmium metal in aqueous solution was evaluated both in UV and visible light in a 100 ml capacity reactor. In particular mixing of 10 wt% silica with titania not only increases the surface area of the material but also increases the photocatalytic activity in UV light. Whereas mixing of zirconia with titania proved to be beneficial for visible light reaction. However, addition of hole scavenger increases the activity many folds and complete removal of Pb(2+) and Cd(2+) was possible in 60 min of reaction using synthesized catalysts. Among all the organic hole scavengers used, sodium formate is found to be the most active one. Interestingly quite high metal removal (89%) is also observed in presence of visible light within 60 min of reaction. Thus the above study indicates that the presence of certain oxides in low quantity (10 wt%) with titania can facilitates the photocatalytic process selectively in UV as well as visible light. 相似文献
A novel synthetic pathway to approach 3-(imino)isoindolin-1-ones by the Co-catalyzed cyclization reaction of 2-bromobenzamides with carbodiimides has been developed. This catalytic reaction can tolerate a variety of substituents and provide corresponding products in moderate yields for most cases. According to the literature, the reaction mechanism is proposed through the formation of a five-membered aza-cobalacycle complex, which carries out the following reaction subsequence, including nucleophilic addition and substitution, to furnish the desired structures. 相似文献
Kinetics and Catalysis - The current study focuses on the photocatalytic oxidation of benzyl alcohol in acetonitrile under air bubbling conditions comparing titania-based materials, Cu–MOF,... 相似文献