Analysis of Microstrip Patch Antennas for Dielectric Measurement

The microstrip patch antenna has been employed by Shimin [1] to measure the dielectric constant of thin slab materials. Although the applicability of the method in [1] is not restricted by the size of the material under test, the etching of the patch and the introduction of the ground plane on the material cannot be practical in many cases. A more practical approach based on the microstrip antenna is reported in [2] for the measurement of the dielectric constant of snow. The technique employs the antenna as an applicator. The antenna is brought to the close proximity or in contact with the surface of the material in order to cause interaction between the antenna’s near field and the object. The result is a change in the input impedance and the resonant frequency of the antenna. Similar to short antenna applicators [3], a patch antenna applicator can take measurements under resonant and off resonant conditions. However, at resonance, achieving accurate measurements are straight-forward. The technique can be applied to solids as well as to liquids with small or large losses. It can also be used in the thickness measurement of layered materials

Mathematical Modeling of the Interaction of Non-Uniform Field ACFM with Finite Size Cracks

The non-destructive evaluation (NDE) of metal surfaces can be accomplished using the alternating current field measurement (ACFM) technique [1]. In this technique a thin-skin eddy current is induced in the metal and the magnetic field above the metal surface is monitored for any perturbation caused by surface defects. In the non-uniform ACFM, the incident field may be produced by a coil or a wire loop carrying a high frequency current [2].</p

Slot Resonators for Characterization of Dielectrics at Microwave Frequencies

Open planar resonators like single and stacked microstrip resonators were used in the past for the measurement of dielectric constants and thicknesses of lossy and lossless dielectrics at microwave frequencies [1–3]. With a large width, the microstrip resonator effectively acts as a planar antenna in which case the fringing field is significant for the two slots at the two ends of the resonator and the resonator Q-factor is low. One of the limitations of the microstrip resonator is its spatial resolution which is determined by the size of the resonator. It is envisaged that this problem can be overcome by the use of planar slot resonators, Fig.1. Furthermore, compared to the microstrip-fed microstrip resonator, a microstrip-fed planar slot resonator would provide a better isolation between the feed and the material under test

Accurate modelling for the analysis and design of liquid-crystal-based microwave devices

Liquid crystal substrates have been shown to provide the means to develop low-cost, reconfigurable, adaptive and tuneable microwave and MM-wave devices for mobile and wireless communication systems. However, techniques for the characterisation of materials, device fabrication and design are necessary in order to take maximum advantage of the possibilities that these materials offer. This includes appropriate modelling methods to simulate accurately the switching behaviour of the liquid crystal and the characteristics of the wave propagation through the devices, taking full consideration of the point-by-point variation of the material tensor permittivity. We describe these techniques here and show their application in the design of a meander-line phase shifter

Effect of Vegetable Oil Types on Energy Expenditure, Abdominal Fat Deposition and Fatty Acid Profile of Breast and Thigh Muscles in Broilers

This experiment was conducted to determine the effect of different vegetable oil types on broiler energy expenditure, abdominal fat deposition and fatty acid profile of breast and thigh. A total number of 300 un-sexed day-old cobb 500 broiler chickens were used in a completely randomized design, consisted of five treatments (five different vegetable oil sources including soy, flaxseed, canola, corn, and sunflower oil), with five replicates and 10 chicks in each. Different vegetable oil sources had no significant effect on energy efficiency ratio and abdominal fat deposition. Flaxseed oil increased C18:3 and C20:5 in breast and C18:3, C20:3, C20:4 and C20:5 in thigh muscle (P< 0.05). The highest content of n-3 fatty acids was observed in breast of broilers fed diets treated with flaxseed oil (P< 0.05). The C18:3 content of thigh of broilers fed flaxseed was significantly higher than those chicken received other oil sources (P< 0.05). A significant increase in C20:5 was seen in the thigh of chicken received flaxseed oil, too (P< 0.05). The highest content of C18:2 was observed in the breast of the chickens fed corn oil and the lowest was seen in broilers received canola oil (P< 0.05). The results showed that dietary oil type could affect fatty acid profile of broiler breast and thigh despite lack of significant difference in broiler energy expenditure or abdominal fat deposition

Signaling from the Sympathetic Nervous System Regulates Hematopoietic Stem Cell Emergence during Embryogenesis

SummaryThe first adult-repopulating hematopoietic stem cells (HSCs) emerge in the aorta-gonads-mesonephros (AGM) region of the embryo. We have recently identified the transcription factor Gata3 as being upregulated in this tissue specifically at the time of HSC emergence. We now demonstrate that the production of functional and phenotypic HSCs in the AGM is impaired in the absence of Gata3. Furthermore, we show that this effect on HSC generation is secondary to the role of Gata3 in the production of catecholamines, the mediators of the sympathetic nervous system (SNS), thus making these molecules key components of the AGM HSC niche. These findings demonstrate that the recently described functional interplay between the hematopoietic system and the SNS extends to the earliest stages of their codevelopment and highlight the fact that HSC development needs to be viewed in the context of the development of other organs