A boundary integral equation approach to three dimensional electromagnetic wave scattering problems

Electromagnetic scattering models are finding increasing interest in many applications ranging from nondestructive evaluation (NDE) to design of optical systems. The availability of a computational scattering model characterizing the underlying system serves several purposes. First, it serves as an inexpensive test bed to simulate a variety of test situations. For instance, the forward model can be used to evaluate various polarizations and incidence angles of the incident source fields and the corresponding spatial distribution of the scattered fields which in turn provides information useful for optimizing the measurement of scattered fields. By preserving some of the realism that is usually possible in purely analytical methods, it provides valuable insight into the physics of actual problems. Second, forward scattering models are important in solving the inverse problem where the scattered fields are used for characterizing the size, the shape and the constitution of the scatterer;The development of theoretical models largely relies on the use of numerical techniques such as boundary element method (BEM), finite element method (FEM), or finite difference method (FDM). However, no single numerical method has emerged as the optimal method for solving all electromagnetic scattering problems. One numerical method might be preferred over others, depending on the nature of the problem. For instance, problems which involve homogeneous scatterers and propagation of waves in an infinite medium are typically solved using the BEM whereas problems which involve a naturally truncated region are modeled using FEM and FDM;This dissertation presents a boundary integral equation (BIE) formulation for the problem of electromagnetic scattering due to homogeneous dielectric scatterers. The governing BIEs are then evaluated numerically using the BEM. Several fundamental electromagnetic scattering geometries are considered. The first problem involves solving for the scattered fields in the presence of a single, three dimensional, arbitrarily shaped, dielectric scatterer suspended in an infinite medium. The formulation is then extended to modeling the scattered fields in the presence of multiple dielectric scatterers as well as a dielectric scatterer in the proximity of an infinite perfect conducting plane. Lastly, the problem of a dielectric scatterer situated close to a dielectric half-space is discussed. The geometries are chosen so that the work presented in this dissertation will serve as a basic model and solutions to a large range of problems can be obtained by modifying one or more of the configurations presented

Low energy scattering with a nontrivial pion

An earlier calculation in a generalized linear sigma model showed that the well-known current algebra formula for low energy pion pion scattering held even though the massless Nambu Goldstone pion contained a small admixture of a two-quark two-antiquark field. Here we turn on the pion mass and note that the current algebra formula no longer holds exactly. We discuss this small deviation and also study the effects of an SU(3) symmetric quark mass type term on the masses and mixings of the eight SU(3) multiplets in the model. We calculate the s wave scattering lengths, including the beyond current algebra theorem corrections due to the scalar mesons, and observe that the model can fit the data well. In the process, we uncover the way in which linear sigma models give controlled corrections (due to the presence of scalar mesons) to the current algebra scattering formula. Such a feature is commonly thought to exist only in the non-linear sigma model approach.Comment: 15 pages, 8 figure

Macroglobulinémie de Waldenström et atteinte oculaire : rapport de cas et examen

La macroglobulinémie de Waldenström (MW) est un lymphome malin prolifératif à lymphocytes B rare qui provoque une accumulation excessive de protéines monoclonales. La MW est associé à une accumulation excessive d’immunoglobulines M (IgM) qui engendre une hyperviscosité du sang et peut endommager de nombreux organes et appareils. Ce rapport décrit le cas d’un patient qui a été suivi chaque année mais qui a rapidement manifesté des hémorragies à la mi-périphérie et au pôle postérieur importantes en raison d’une hyperviscosité dans la rétine. Cet article examine les manifestations oculaires associées à la MW et propose des suggestions de prise en charge. La prise en charge de cette affection dépend de l’atteinte maculaire et a lieu conjointement avec un oncologue

Waldenstrom Macroglobulinemia and the Eye: A case report and review

Waldenstrom macroglobulinemia (WM) is a rare, malignant lymphoproliferative B-cell disorder causing an excessive buildup of monoclonal protein. WM is associated with excessive buildup of IgM, which can cause blood hyperviscosity and damage many organ systems. This case report describes a patient who was followed annually but rapidly developed posterior pole and significant midperipheral hemorrhages secondary to a hyperviscosity condition of the retina. Management of this condition is dependent on macular involvement and must be co-managed with an oncologist

Characterization of the Modal Characteristics of Structures Operating in Dense Liquid Oxygen Turbopumps

A number of valuable conclusions can be drawn from this study. First, knockdown factors for a specific fluid are not constant but instead are dependent on the mode shape, although the largest this variability gets is about 10% for LOX, the densest fluid. The factors decrease the most for lower frequency shapes and less for higher ones. It follows, therefore, that mode number mismatch between air and fluid operation becomes not only possible, but common, as a knockdown factor for a particular mode shape may be higher than for another mode shape. Since this is a function of added mass, the mismatch is more prevalent for higher density fluids, but it initiates even for very low density ones. Another important conclusion reached is that it appears that the basic mode shapes of a structure do not change if it is fully symmetric, which includes its geometry and boundary conditions. There is some indication of small changes in the relative magnitudes within the mode shape. This conclusion is evident in the results from the cantilever rectangular plate and the inducer, which are not symmetric, and the fixed-fixed plate and the annular disk, which are. For non-symmetric structures, though, the mode shapes almost universally change for dense fluids, as shown by the very low MAC calculations. For the inducer in particular, the changes follow a trend of reduced parabolic and sine wavelengths with increasing density. It is critical to recognize the change in mode shape for several reasons. First, model updating with modal test becomes problematic if the shapes change. Second, design to avoid resonance is highly critical on the mode shape for modes other than the primary ones, as resonance is only a factor when the excitation shape matches the mode shape. Finally, application of the modal superposition method of forced response analysis is dependent on the use of accurate mode shapes. A more-refined assessment of the "knockdown" factor values and ranges than any previously reported in the literature for a realistic engineering structure is also presented in this paper. This data is of tremendous benefit for preliminary analysis and design, where a quick estimate is necessary. These results are important not just for rocket engine turbomachinery, but for water pumps and turbines, propellers, and any other structure operating in a heavy fluid with dynamic excitation. The clear avenue for future work for this endeavor is to expand the analytical techniques discussed in the literature to develop analytical expressions and justification for the mode shape changes and associated frequency knockdowns. These expressions must be able to accurately predict the functional relationship to the shapes, which will enable accurate tracing of the mode number from vacuum analysis (or testing in air) to analysis and operation in the intended fluid environment

An investigation into the use of the ocular pulse as a diagnostic tool

If the IOP is measured continuously a cyclic fluctuation called the ocular pulse is noted. The diagnostic value of this pulse was studied by screening 80 subjects for their pulse amplitude values which when analyzed on the basis of the subjects\u27 ages, were correlated with the presence or absence of diabetes and hypertension. Once the mean values for each age and condition group were calculated, it was found that, with age held constant, there was no significant difference between the mean values for the normal, diabetic, or hypertensive groups. While the inter-eye variation in ocular pulse amplitude values of one hypertensive population was significantly lower than that of the normal population, this difference approximated the measurement reliability. Still, the norms established by this study were able to isolate one subject with systemic vascular conditions which had not been previously determined by other objective methods

Stops and MET: the shape of things to come

LHC experiments have placed strong bounds on the production of supersymmetric colored particles (squarks and gluinos), under the assumption that all flavors of squarks are nearly degenerate. However, the current experimental constraints on stop squarks are much weaker, due to the smaller production cross section and difficult backgrounds. While light stops are motivated by naturalness arguments, it has been suggested that such particles become nearly impossible to detect near the limit where their mass is degenerate with the sum of the masses of their decay products. We show that this is not the case, and that searches based on missing transverse energy (MET) have significant reach for stop masses above 175 GeV, even in the degenerate limit. We consider direct pair production of stops, decaying to invisible LSPs and tops with either hadronic or semi-leptonic final states. Modest intrinsic differences in MET are magnified by boosted kinematics and by shape analyses of MET or suitably-chosen observables related to MET. For these observables we show that the distributions of the relevant backgrounds and signals are well-described by simple analytic functions, in the kinematic regime where signal is enhanced. Shape analyses of MET-related distributions will allow the LHC experiments to place significantly improved bounds on stop squarks, even in scenarios where the stop-LSP mass difference is degenerate with the top mass. Assuming 20/fb of luminosity at 8 TeV, we conservatively estimate that experiments can exclude or discover degenerate stops with mass as large as ~ 360 GeV and 560 GeV for massless LSPs.Comment: Version submitted to journal with improved analysis and small fixes, 27 pages, 11 figures, 2 table

Randomized control trial of computer-based rehabilitation of spatial neglect syndrome: the RESPONSE trial protocol

Background: Spatial neglect is a frequent and debilitating consequence of acquired brain injury and currently has no widely accepted standard of care. While previous interventions for spatial neglect have targeted patients’ overt spatial deficits (e.g., reduced contralesional visual scanning), far fewer have directly targeted patients’ non-spatial deficits (e.g., sustained attention deficits). Considering that non-spatial deficits have shown to be highly predictive of long-term disability, we developed a novel computer based training program that targets both sustained (tonic) and moment-to-moment (phasic) aspects of non-spatial attention (Tonic and Phasic Alertness Training, TAPAT). Preliminary studies demonstrate that TAPAT is safe and effective in improving both spatial and non-spatial attention deficits in the post-acute recovery phase in neglect patients. The purpose of the current trial (referred to as the REmediation of SPatial Neglect or RESPONSE trial) is to compare TAPAT to an active control training condition, include a larger sample of patients, and assess both cognitive and functional outcomes. Methods/Design We will employ a multi-site, longitudinal, blinded randomized controlled trial (RCT) design with a target sample of 114 patients with spatial neglect. Patients will either perform, at their home, the experimental TAPAT training program or an active control computer games condition for thirty minutes/day, five days a week, over three months. Patients will be assessed on a battery of cognitive and functional outcomes on three occasions: a) immediately before training, b) within forty-eight hours post completion of total training, and c) after a three-month no-contact period post completion of total training, to assess the longevity of potential training effects. Discussion The strengths of this protocol are that it tests an innovative, in-home administered treatment that targets a fundamental deficit in neglect, employs highly sensitive computer-based assessments of cognition as well as functional outcomes, and incorporates a large sample size (relative to other neglect treatment studies) in an RCT design. Trial registration ClinicalTrials.gov identifier, NCT0196595

Cosmological Constraints from Galaxy Clusters and Groups in the eROSITA Final Equatorial Depth Survey

We present the first cosmological study of a sample of $eROSITA$ clusters, which were identified in the $eROSITA$ Final Equatorial Depth Survey (eFEDS). In a joint selection on X-ray and optical observables, the sample contains $455$ clusters within a redshift range of $0.1<z<1.2$, of which $177$ systems are covered by the public data from the Hyper Suprime-Cam (HSC) survey that enables uniform weak-lensing cluster mass constraints. With minimal assumptions, at each cluster redshift $z$ we empirically model (1) the scaling relations between the cluster halo mass and the observables, which include the X-ray count rate, the optical richness, and the weak-lensing mass, and (2) the X-ray selection in terms of the completeness function $\mathtt{C}$. Using the richness distribution of the clusters, we directly measure the X-ray completeness and adopt those measurements as informative priors for the parameters of $\mathtt{C}$. In a blinded analysis, we obtain the cosmological constraints $\Omega_{\mathrm{m}} = 0.245^{+0.048}_{-0.058}$, $\sigma_{8} = 0.833^{+0.075}_{-0.063}$ and $S_{8} \equiv \sigma_{8}\left(\Omega_{\mathrm{m}}/0.3\right)^{0.3}= 0.791^{+0.028}_{-0.031}$ in a flat $\Lambda$CDM cosmology. Extending to a flat $w$CDM cosmology leads to the constraint on the equation of state parameter of the dark energy of $w = -1.25\pm 0.47$. The eFEDS constraints are in good agreement with the results from the $Planck$ mission, the galaxy-galaxy lensing and clustering analysis of the Dark Energy Survey, and the cluster abundance analysis of the SPT-SZ survey at a level of $\lesssim1\sigma$. With the empirical modelling, this work presents the first fully self-consistent cosmological constraints based on a synergy between wide-field X-ray and weak lensing surveys.Comment: Accepted for publication in MNRAS. Figures 18 and 19 contain the main results. Chains and cluster masses are at https://github.com/inonchiu/eFEDSproduct