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991.
Francisco Javier González Javier Alda Jorge Simón James Ginn Glenn Boreman 《Infrared Physics & Technology》2009,52(1):48-51
In this paper the optical parameters at infrared frequencies of metallic thin films were obtained experimentally using a variable angle spectroscopic ellipsometer and used to simulate numerically the frequency response of antennas and antenna-coupled detectors at infrared frequencies (5–15 μm). The simulation results agree with previously published data and practical guidelines are presented for the design and fabrication of dipole and bowtie antennas at infrared frequencies. 相似文献
992.
993.
Karim Noui Alejandro Perez Kevin Vandersloot 《General Relativity and Gravitation》2009,41(11):2597-2618
We consider the cosmological symmetry reduction of the Plebanski action as a toy-model to explore, in this simple framework, some issues related to loop quantum gravity and spin-foam models. We make the classical analysis of the model and perform both path integral and canonical quantizations. As for the full theory, the reduced model admits two disjoint types of classical solutions: topological and gravitational ones. The quantization mixes these two solutions, which prevents the model from being equivalent to standard quantum cosmology. Furthermore, the topological solution dominates at the classical limit. We also study the effect of an Immirzi parameter in the model. 相似文献
994.
We show that the Ginzburg-Landau expansion of the grand potential for the Bogoliubov-de Gennes Hamiltonian is determined by the integrable nonlinear equations of the AKNS hierarchy, and that this provides the natural mathematical framework for a hidden nonlinear quantum mechanical supersymmetry underlying the dynamics. 相似文献
995.
Jose G. Trujillo‐Ferrara Efrn V. García‐Bez Itzia I. Padilla‐Martínez Francisco J. Martínez‐Martínez Norberto Farfan‐García 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(6):o427-o430
In exo‐2‐(3,5‐dioxo‐10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐en‐4‐yl)phenyl acetate, C16H13NO5, the plane of the acetoxy group lies almost perpendicular to that of the phenyl ring [dihedral angle = 89.8 (1)°], in contrast with the smaller deviations found in the para isomer exo‐4‐(3,5‐dioxo‐10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐en‐4‐yl)phenyl acetate, C16H13NO5, these being 63.6 (1) and 37.0 (1)° for the two crystallographically independent molecules. Irrespective of the position of the acetoxy group, both compounds pack through soft C—H⋯X (X is O or phenyl) interactions, forming interlinked centrosymmetric tetramers in the bc plane. 相似文献
996.
The reaction force is a global property of a chemical reaction that arises when applying the Hellmann–Feynmann theorem to
the potential energy surface that links reactants, products and transition states. In the present work, the reaction force
is defined rigorously from the cartesian components coming out from all forces exerted over each atom of a molecular system
during the chemical reaction; it is demonstrated that the reaction force is a scalar property.
An erratum to this article can be found at 相似文献
997.
The influence of starvation (defined as the period without substrate) and shock loads on the performance of a moving bed sequencing
batch reactor degrading 4-chlorophenol (4CP) were investigated. The biomass was acclimated to biodegrade 100 mg/L of 4CP,
and the colonization of the packing material was followed. Two starvation periods and two shock loads were studied. The degradation
capacity of the suspended and the attached biomass present on the moving bed was also evaluated. The experiments showed that,
after the starvation period, the specific degradation rate decreased from 30.5 to 28.5 and 20 mg 4CP/gVSS/h, when starvation
periods of 24 and 48 h were applied, respectively. When two concentration peaks of 500 and 1,050 mg/L were applied, a loss
of 6% and 8% on the specific degradation rate, respectively, was also observed. The moving bed thus showed great robustness
against starvation periods and shock loads. Suspended biomass presented higher specific degradation rates, but attached biomass
did not generate a metabolite that is inhibitory when it accumulates. 相似文献
998.
Mechanical recycling of poly(ethylene terephthalate) (PET) was simulated by multiple processing to assess the effects of thermo-mechanical degradation, and characterized using rheological and thermal analysis techniques. Thermo-mechanical degradation under repeated extrusion induces chain scission reactions in PET, which result in a dramatic loss in the deformation capabilities and an increase in the fluidity of the polymer under reprocessing, reducing its recycling possibilities after four extrusion cycles. Multiple reprocessing severely affects the storage modulus and the microstructure of recycled PET, both in the amorphous and crystalline regions. Multimodal melting behavior is observed for reprocessed PET, indicating heterogeneous and segregated crystalline regions. A deconvolution procedure has been applied to individually characterize each crystalline population in terms of lamellar thickness distribution and partial crystallinity. Thermal analysis techniques such as differential scanning calorimetry (DSC) and dynamic-mechanical analysis (DMA) have proved to be suitable techniques for the quality assessment of recycled PET, giving unequivocal information about its degree of degradation compared to the common technological measurements of melt-mass flow rate (MFR) or oxidative stability (TOx). 相似文献
999.
Meriem Belhachemi Rachel V.R.A. Rios Fatima Addoun Joaquín Silvestre-Albero Antonio Sepúlveda-Escribano Francisco Rodríguez-Reinoso 《Journal of Analytical and Applied Pyrolysis》2009,86(1):168-172
Two series of activated carbons have been prepared from date pits; series C, using carbon dioxide as activating agent, and series S, prepared by activation with steam under the same experimental conditions. The obtained samples were oxidized with nitric acid in order to introduce more oxygen surface groups. The surface area and porosity of the parent and oxidized activated carbons were studied by N2 adsorption at 77 K and CO2 adsorption at 273 K. The oxygen surface complexes were characterized by temperature-programmed decomposition (TPD). The results show that carbon dioxide and steam activations produce microporous carbons with an increasing amount of CO evolving groups when increasing the burn-off. On the other hand, oxidation with nitric acid increases the amount of CO and CO2 evolved by the decomposition of surface oxygen groups, this increase being related to the development of porosity in the carbon with the degree of activation and to the activating agent used (CO2 versus steam). 相似文献
1000.
Khashayar Khoshmanesh Chen Zhang Francisco J. Tovar‐Lopez Saeid Nahavandi Sara Baratchi Kourosh Kalantar‐zadeh Arnan Mitchell 《Electrophoresis》2009,30(21):3707-3717
This paper presents the development and experimental analysis of a dielectrophoresis (DEP) system, which is used for the manipulation and separation of microparticles in liquid flow. The system is composed of arrays of microelectrodes integrated to a microchannel. Novel curved microelectrodes are symmetrically placed with respect to the centre of the microchannel with a minimum gap of 40 μm. Computational fluid dynamics method is utilised to characterise the DEP field and predict the dynamics of particles. The performance of the system is assessed with microspheres of 1, 5 and 12 μm diameters. When a high‐frequency potential is applied to microelectrodes a spatially varying electric field is induced in the microchannel, which creates the DEP force. Negative‐DEP behaviour is observed with particles being repelled from the microelectrodes. The particles of different dimensions experience different DEP forces and thus settle to separate equilibrium zones across the microchannel. Experiments demonstrate the capability of the system as a field flow fraction tool for sorting microparticles according to their dimensions and dielectric properties. 相似文献