Search results for "electromagnetism"

Factors affecting the moisture permeability of lipid-based edible films: a review.

2002

Moisture transfers inside food products could be controlled or limited by the use of edible films. These are usually based on hydrophobic substances such as lipids to improve barrier efficiency. Water permeability of films is affected by many factors, depending on both the nature of barrier components, the film structure (homogeneous, emulsion, multilayer, etc.), crystal type, shape, size and distribution of lipids, and thermodynamics such as temperature, vapor pressure, or the physical state of water in contact to the films. After a brief presentation of lipids and hydrophobic substances used as moisture barrier, cited in the scientific literature, this article reviews all of the parameter…

Influence of sodium lauryl sulphate on the in vitro percutaneous absorption of compounds with different lipophilicity

1997

Abstract The effects of sodium lauryl sulphate (SLS) at different concentrations on the “in vitro” percutaneous absorption of a number of compounds (5-fluorouracil, antipyrine, pentoxifylline, salicylamide, 4-ethylaniline, 4-n-butylaniline and indomethacin) with a wide range of lipophilicity values (log POCT from −0.95 to 4.42) through rat skin were analysed. After pretreatment of the skin with SLS (1% and 5%, w/w) the permeability coefficients increased only for compounds having a log POCT

Rigidity transition in two-dimensional random fiber networks

2000

Rigidity percolation is analyzed in two-dimensional random fibrous networks. The model consists of central forces between the adjacent crossing points of the fibers. Two strategies are used to incorporate rigidity: adding extra constraints between second-nearest crossing points with a probability p(sn), and "welding" individual crossing points by adding there four additional constraints with a probability p(weld), and thus fixing the angles between the fibers. These additional constraints will make the model rigid at a critical probability p(sn)=p(sn)(c) and p(weld)=p(weld)(c), respectively. Accurate estimates are given for the transition thresholds and for some of the associated critical e…

Rigidity of random networks of stiff fibers in the low-density limit.

2001

Rigidity percolation is analyzed in two-dimensional random networks of stiff fibers. As fibers are randomly added to the system there exists a density threshold ${q=q}_{\mathrm{min}}$ above which a rigid stress-bearing percolation cluster appears. This threshold is found to be above the connectivity percolation threshold ${q=q}_{c}$ such that ${q}_{\mathrm{min}}=(1.1698\ifmmode\pm\else\textpm\fi{}{0.0004)q}_{c}.$ The transition is found to be continuous, and in the universality class of the two-dimensional central-force rigidity percolation on lattices. At percolation threshold the rigid backbone of the percolating cluster was found to break into rigid clusters, whose number diverges in the…

Rigorous Multimode Equivalent Network Representation of Multilayer Planar Circuits

2018

The objective of this paper is to extend the use of the Multimode Equivalent Network formulation, originally developed to analyze waveguide junctions, to the analysis of planar circuits that include arbitrary rectangular printed, zero thickness metallizations together with internal and external ports in the transverse plane. The theoretical derivations lead to an accurate and computationally efficient tool for the analysis of boxed, multilayer microwave printed circuits. In addition to theory, the tool developed is used here to analyze two practical examples: a dual-bandpass and a 4-pole bandpass boxed microstrip filters. Good agreement with respect to commercial software tools and measurem…

The study of correlation between microstructure of ferrites and their complex permeability spectra

2013

Theoretical model for complex permeability of polycrystalline ferrite (based on effects arising from realities of typical microstructure of sample) is correlated with experimental data. In the case of NiZn-ferrites there is observed a close agreement with the model and the data; for samples of MnZn-ferrites this agreement is only for small-sized cores; for bigger ones the dimensional effects (dimensional resonance) appear and the model cease to be valid.

Computer-aided design of substrate integrated waveguide filters for microwave and millimeter-wave applications

2009

In this paper, a Computer-Aided Design (CAD) tool of Substrate Integrated Waveguide (SIW) filters for high frequency applications is described. Some synthesis techniques are successfully combined with a fast and accurate full-wave analysis method, thus designing several practical examples of in-line and cross-coupled SIW filters. Prototypes have been manufactured and measured showing good results for different filter topologies. A novel zigzag coupling scheme is proposed for SIW compact filters in order to achieve very restrictive specifications of ultra-wideband (UWB) systems.

Purcell-enhancement of the radiative PL decay in perylenediimides by coupling with silver nanoparticles into waveguide modes

2017

In this work, an interesting approach to enhance the coupling between excitons and plasmons is proposed by integrating highly luminescent perylenediimides (PDIs) and Ag metal nanoparticles (MNPs) in the core of a multilayer dielectric waveguide. The combination of the weak plasmonic coupling and the high scattering of MNPs gives rise to a significant improvement of the PDI photoluminescence and Purcell factor (PF) in forward-scattering geometry. Furthermore, when the PDI-MNP system is used as the core of a multilayer waveguide, a Purcell factor enhancement larger than 10 is observed, which is explained by an increase in the exciton-plasmon coupling under the light confinement in the wavegui…

Front Cover: The Important Role of the Nuclearity, Rigidity, and Solubility of Phosphane Ligands in the Biological Activity of Gold(I) Complexes (Che…

2018

Ondas de D'yakonov en metamateriales

2013

En este trabajo Fin de Máster se analiza en profundidad la propagación de ondas de superficie localizadas en la interfase entre una nano-estructura semi-infinita laminada metal-dieléctrico y un dieléctrico. Se demuestra que las ondas de superficie propuestas por M. I. D'yakonov (llamadas dyakonones) con polarización híbrida se propagarán en un amplio rango angular. Como consecuencia, los paquetes de ondas basados en dyakonones (DWPs) pueden formar haces con anchuras menores que las longitudes de onda de trabajo. La dispersión cuadrática aparente del haz, sin embargo, es debida a los efectos de disipación en el metal. I analyze propagation of ultralocalized surface waves that takes place at …