Broadband electromagnetic analysis of dispersive, periodic structures for radiometer calibration

This thesis primarily focusses on the full wave electromagnetic analysis of radiometer calibration targets using doubly dispersive 3D Finite Difference Time Domain (FDTD) formulation. The boundary conditions are set up to solve for doubly periodic structures. The thesis contains very detailed derivation and equations regarding this formulation. One of the novelty in this formulation is the handling of magnetically and electrically dispersive media (usually it is just the electrical dispersion which is incorporated). Using a custom developed code which can be run on a distributed computing system, the reflectivity spectrum of calibration targets of different geometries, coating thicknesses and aspect ratios are analyzed. The results are well validated using commercial simulation software and custom Geometric Optics (GO) code. The geometries analyzed include square pyramids, conical pyramids, truncated square pyramids and truncated conical pyramids with spherical top. The coating thicknesses used are 1 mm, 2 mm and 3 mm. The aspect ratios (ratio of base to height) used include 1 : 1, 1 : 2 and 1 : 4. The nominal target structure has 1 : 4 aspect ratio and 2 mm coating thickness. The material used for simulation is ECCOSORB MF112. The material properties of other materials such as MF110 and MF114 are listed. It should be remarked that measured material properties are available only in the frequency range [8, 26] GHz and a Debye series extrapolation was used for simulation at frequencies outside this range. Throughout this work 0.5′′ base was used. Some significant conclusions include the following: 1) 1:4 aspect ratio or better is required to achieve a -50 dB reflectivity or lower 2) Low frequency reflectivity is independent of the target geometry. 3) At high frequencies, the conical target results in better performance when compared to square pyramids (by about 10 dB). 4) The reflectivity spectrum exhibits a general trend of high reflectivity at low frequencies followed by decreasing reflectivity as frequency is increased. There is a reflectivity jump at frequencies where non-specular Floquet modes start propagating. This is followed by nearly sinusoidal oscillations at high frequencies. 5) Asymptotic techniques can be used at high frequencies instead of full wave analysis. The plane wave reflectivity estimated using full wave analysis is an approximate method to calculate brightness temperature as measured by antenna during radiometer calibration. It assumes two conditions: 1) The calibration targets have a uniform temperature profile. 2) Antenna is in the far field. These two conditions are never met in practice. In order to estimate the near field thermal emission, Fluctuation Dissipation Theorem (FDT) must be used. Dyadic Green Function (DGF) along with FDT can be used to calculate the thermal emission from simple geometries. Analytical formulations to this end is given in this thesis. The rest of the thesis (∼ 50%) contains work related to numerical methods applied to radiative transfer and computational electromagnetics. In the first part, a novel method to calculate the absorption coefficient, scattering coefficient, backscattering coefficient and phase asymmetry parameter of a polydispersed distribution of liquid water and ice hydrometeors is presented. The conventional method of calculating these coefficients can be time consuming, because of the Mie series summation to calculate Mie coefficients and the numerical quadrature over a distribution of spheres to calculate the requried coefficients. By using spline interpolation on a precomputed look up table, the calculation procedure can be accelerated. The second part deals with time domain analysis of dispersive, periodic structures for oblique plane wave incidence. This is a difficult problem with only one work available in literature till now. The proposed method uses Laguerre Marching-In-On-Degree (MoD) where time dependant quantities are expressed as an expansion of Laguerre basis functions. Using several properties of Laguerre basis functions, the time dependant problem is converted to a time independent problem in Laguerre basis coefficients. This in turn is solved using the familiar finite difference format. The novel method was validated with analytical results for incident angles as large as 75o

Nicotinic Acetylcholine Receptor Signaling in Tumor Growth and Metastasis

Cigarette smoking is highly correlated with the onset of a variety of human cancers, and continued smoking is known to abrogate the beneficial effects of cancer therapy. While tobacco smoke contains hundreds of molecules that are known carcinogens, nicotine, the main addictive component of tobacco smoke, is not carcinogenic. At the same time, nicotine has been shown to promote cell proliferation, angiogenesis, and epithelial-mesenchymal transition, leading to enhanced tumor growth and metastasis. These effects of nicotine are mediated through the nicotinic acetylcholine receptors that are expressed on a variety of neuronal and nonneuronal cells. Specific signal transduction cascades that emanate from different nAChR subunits or subunit combinations facilitate the proliferative and prosurvival functions of nicotine. Nicotinic acetylcholine receptors appear to stimulate many downstream signaling cascades induced by growth factors and mitogens. It has been suggested that antagonists of nAChR signaling might have antitumor effects and might open new avenues for combating tobacco-related cancer. This paper examines the historical data connecting nicotine tumor progression and the recent efforts to target the nicotinic acetylcholine receptors to combat cancer

Assessment of Radio Frequency Electromagnetic Field Exposure Induced by Base Stations in Several Micro-Environments in France

Recently, the monitoring of the radiofrequency electromagnetic field (RF-EMF) exposure induced by cellular networks has received a great deal of attention. In this work, a set of 70 microenvironments (MEs) located in urban and rural areas are selected in France under, on the one hand, the French Beyond5G project, and on the other hand, the 5G expOsure, causaL effects and rIsk perception through citizen engagement (GOLIAT) EU project. The purpose of this study is to assess the RF-EMF DL exposure in residential areas, downtowns, business areas, train stations, and public transport rides. For that, we employ the personal ExpoM-RF4 dosimeter placed inside a backpack to perform the measurements in different MEs. To take into consideration the effect of the presence of the human body near the dosimeter, we propose a correction approach that is mainly based on comparing the measurements given by ExpoM-RF4 to the ones provided by a reference system using the Tektronix real-time spectrum analyzer (RTSA) far from the body. Then, we use metrics, such as the quadratic mean, standard deviation, and median of the electric (E) field to carry out a comparative study between different MEs with different RF bands. It was found that the RF-EMF exposure levels for all MEs are well below the maximum allowable exposure limit prescribed by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). In addition, we perform clustering analyses using the K-Means technique to group the MEs with comparable exposure levels. The results show that the exposure level is low, but generally higher in MEs located in Paris than in the other considered areas (i.e., Massy and three villages, namely Igny, Bures-sur-Yvette and Gif-Sur-Yvette). For example, we observe that outdoor MEs can be grouped into three clusters, where the average total E fields (ATEFs) are 0.77 V/m, 0.35 V/m, and 0.08 V/m for the MEs belonging to the first, second and third clusters, respectively. Note that the first cluster here mainly contains the MEs located in Paris. This can be explained by the important number of antennas deployed in that area to serve the huge amount of users. We also observe few locations with exceptions confirming the presence of heterogeneous environments in the vicinity of some areas.</p

Decentralized Cohesive Motion Control of Multi-Agent Formations

This paper presents a set of decentralized control laws for the cohesive motion of 2-dimensional multi-agent formations. We consider rigid and constraint-consistent formations that can be modeled by directed graphs. We analyze both of the two main hierarchical structures for such 2-dimensional formations: The leader-follower and the three-coleader structures. For each structure, we derive a control scheme that moves a given rigid and constraint-consistent formation whose initial position and orientation are specified to a new desired position and orientation cohesively, i.e., without deforming the shape of the formation during the motion. We elaborate our designs considering the path smoothness, chattering, and agent kinematics issues and demonstrate their effectiveness via a set of simulation results

Modeling of Power Distribution Networks for Path Finding

In this paper an algorithm is described for obtaining the response of Power Distribution Networks (PDN) arising in chip, package or pcb during an early design phase. Results are provided for power grids arising in silicon interposers to validate the approach

βArrestin-1 and Mcl-1 modulate self-renewal growth of cancer stem-like side-population cells in non-small cell lung cancer.

Side population (SP) cells have been reported to have properties of cancer stem-like cells (CSCs) in non-small cell lung carcinoma (NSCLC), yet their molecular features have not been fully elucidated. Here we show that, NSCLC-SP cells were enriched in G(0)/G-(1) phase of cell cycle, had higher aldehyde dehydrogenase activity as well as higher clonogenic and self-renewing ability compared to main population (MP) cells. Interestingly, SP cells were also able to trans-differentiate into angiogenic tubules in vitro and were highly tumorigenic as compared to MP cells. SP-derived tumors demonstrated the intratumoral heterogeneity comprising of both SP and MP cells, suggesting the self-renewal and differentiation ability of SP cells are manifested in vivo as well. βArrestin-1 (βArr1) is involved in the progression of various cancers including NSCLCs and we find that depletion of βArr1 significantly blocked the SP phenotype; whereas depletion of βArr2 had relatively minor effects. Ectopic expression of βArr1 resulted in increased SP frequency and ABCG2 expression while abrogation of βArr1 expression suppressed the self-renewal growth and expansion of A549 cells. Anti-apoptotic protein Mcl-1 is known to be one of the key regulators of self-renewal of tissue stem cells and is thought to contribute to survival of NSCLC cells. Our experiments show that higher levels of Mcl-1 were expressed in SP cells compared to MP cells at both transcriptional and translational levels. In addition, Obatoclax, a pharmacological inhibitor of Mcl-1, could effectively prevent the self-renewal of both EGFR-inhibitor sensitive and resistant NSCLC cells. In conclusion, our findings suggest that βArr1 and Mcl-1 are involved in the self-renewal and expansion of NSCLC-CSCs and are potential targets for anti-cancer therapy