An on-chip W-band bowtie slot antenna in silicon

This paper presents a W-band fully on-chip bowtie slot antenna over a grounded low resistivity silicon substrate fabricated in 180 nm BiCMOS process. The measured results show that the proposed antenna could provide a wide input bandwidth covering the whole W-band. The simulated gain at 90 GHz is 1 dBi when considering several realistic effects. © 2012 IEEE

Metamaterial waveguide with loss compensation

This paper presents a silicon-based waveguide structure employing split ring resonators (SRRs) and distributed loss compensation mechanism suitable for fabrication. Higher phase constant is obtained by periodically loading waveguide (WG) with SRRs in sub-wavelength dimensions at the cost of extra large amount of losses. To relieve the losses problem, a circuitry is introduced in each SRR to compensate the loss while retaining the high phase constant achieved around the resonant frequency. This proposed waveguide with SRRs whose losses are compensated shows higher phase constant, lower attenuation constant and additional tunability compared to common waveguide. © 2011 IEEE

A time-marching scheme for analyzing transient scattering from nonplanar doubly periodic structures

A novel marching-on-time (MOT) based scheme for solving a time domain integral equation (TDIE) was discussed. It was observed that the scheme was pertinent to the analysis of plane wave scattering from nonplanar doubly periodic structures with unit cells comprising perfect electrically conducting (PEC) elements and inhomogeneous dielectric volumes. This scheme aimed at rendering the solver applicable to the nonplanar structures. The resulted scheme was applied without any difficulty to nonplanar doubly periodic structures comprising PEC and sculptured dielectric substrates

An efficient integral equation technique for the analysis of arbitrarily shaped capacitive waveguide circuits

In this contribution a new and efficient integral equation formulation is presented for the analysis of arbitrarily shaped capacitive waveguide devices. The technique benefits from the symmetry of the structure in order to reduce the dimensions of the problem from three to two dimensions. For the first time, this technique formulates the waveguide capacitive discontinuity problem as a 2-D scattering problem with oblique incidence, combined with an efficient calculation of the parallel plate Green's functions. The numerical method allows the efficient evaluation of the electromagnetic fields inside the analyzed structures. Results for different practical capacitive waveguide devices are successfully compared with commercial software tools for validation of the proposed theory. Finally, a novel low-pass filter implementation based on circular conducting posts has been proposed. The field contour lines in the critical gaps of the new structure are curved due to the use of rounded posts. This could result in improved power handling capabilities with respect to standard corrugated low-pass filters. Copyright 2011 by the American Geophysical Union.This work has been developed with financial support from SENECA project reference 08833/PI/08, and CICYT project reference TEC2007-67630-C03.Quesada Pereira, FD.; Vera Castejon, P.; Alvarez Melcon, A.; Gimeno Martinez, B.; Boria Esbert, VE. (2011). An efficient integral equation technique for the analysis of arbitrarily shaped capacitive waveguide circuits. Radio Science. 46:1-11. doi:10.1029/2010RS004458S1114

INFOGEST static in vitro simulation of gastrointestinal food digestion

peer-reviewedSupplementary information is available at http://dx.doi.org/10.1038/s41596-018-0119-1 or https://www.nature.com/articles/s41596-018-0119-1#Sec45.Developing a mechanistic understanding of the impact of food structure and composition on human health has increasingly involved simulating digestion in the upper gastrointestinal tract. These simulations have used a wide range of different conditions that often have very little physiological relevance, and this impedes the meaningful comparison of results. The standardized protocol presented here is based on an international consensus developed by the COST INFOGEST network. The method is designed to be used with standard laboratory equipment and requires limited experience to encourage a wide range of researchers to adopt it. It is a static digestion method that uses constant ratios of meal to digestive fluids and a constant pH for each step of digestion. This makes the method simple to use but not suitable for simulating digestion kinetics. Using this method, food samples are subjected to sequential oral, gastric and intestinal digestion while parameters such as electrolytes, enzymes, bile, dilution, pH and time of digestion are based on available physiological data. This amended and improved digestion method (INFOGEST 2.0) avoids challenges associated with the original method, such as the inclusion of the oral phase and the use of gastric lipase. The method can be used to assess the endpoints resulting from digestion of foods by analyzing the digestion products (e.g., peptides/amino acids, fatty acids, simple sugars) and evaluating the release of micronutrients from the food matrix. The whole protocol can be completed in ~7 d, including ~5 d required for the determination of enzyme activities.COST action FA1005 INFOGEST (http://www.cost-infogest.eu/ ) is acknowledged for providing funding for travel, meetings and conferences (2011-2015). The French National Institute for Agricultural Research (INRA, www.inra.fr) is acknowledged for their continuous support of the INFOGEST network by organising and co-funding the International Conference on Food Digestion and workgroup meeting

Directing Cluster Formation of Au Nanoparticles from Colloidal Solution

Discrete clusters of closely spaced Au nanoparticles can be utilized in devices from photovoltaics to molecular sensors because of the formation of strong local electromagnetic field enhancements when illuminated near their plasmon resonance. In this study, scalable, chemical self-organization methods are shown to produce Au nanoparticle clusters with uniform nanometer interparticle spacing. The performance of two different methods, namely electrophoresis and diffusion, for driving the attachment of Au nanoparticles using a chemical cross-linker on chemically patterned domains of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) thin films are evaluated. Significantly, electrophoresis is found to produce similar surface coverage as diffusion in 1/6th of the processing time with an ~2-fold increase in the number of Au nanoparticles forming clusters. Furthermore, average interparticle spacing within Au nanoparticle clusters was found to decrease from 2-7 nm for diffusion deposition to approximately 1-2 nm for electrophoresis deposition, and the latter method exhibited better uniformity with most clusters appearing to have about 1 nm spacing between nanoparticles. The advantage of such fabrication capability is supported by calculations of local electric field enhancements using electromagnetic full-wave simulations from which we can estimate surface-enhanced Raman scattering (SERS) enhancements. In particular, full-wave results show that the maximum SERS enhancement, as estimated here as the fourth power of the local electric field, increases by a factor of 100 when the gap goes from 2 to 1 nm, reaching values as large as 10(10), strengthening the usage of electrophoresis versus diffusion for the development of molecular sensors

The Truncated Floquet Wave Diffraction Theory for Planar Phased Arrays: an Overview

This paper summarizes the research activities conducted at the Uni-versity of Siena during the past six years on the truncated Floquet wave diffractiontheory under the continuous guidance of Professor Felsen. During that period, wehave analyzed and validated the diffraction phenomena in both the frequency andtime domains pertaining to large planar phased arrays of different topologies andwith quite general excitation profiles. The associated canonical dipole array Green’sfunctions (AGFs) have been expressed in terms of constituents in a generalized highfrequency asymptotic, periodicity-adapted, Floquet wave (FW)-modulated uniformgeometrical theory of diffraction (UTD), which highlights the relevant wave physics.The present paper summarizes the essentials of these AGFs for large planar rect-angular phased dipole arrays in free space, escalating sequentially from free-spacegeometries to multilayered media, with the eventual utilization of the Method ofMoments (MoM) for practical applications. Particular emphasis is given to thoseaspects which are in progress, and have not yet appeared in print