Birefringent fibre ring resonators: Analysis and stabilization techniques

The polarization stability of single-mode fibre resonators has been recognized as a potential problem in their operation. One method to overcome the polarization drift is to use a polarization-maintaining optical fibre, in the resonator system. Even this kind of resonators, still suffer from environmentally-induced polarization instabilities. Depending on the type of resonator, these instabilities are manifest as a split resonant dip, reduced finesse, reduced fringe modulation, fringe asymmetry, and unequal spacing between successive fringes. If we assume that a non zero amount of polarization crosstalk at the coupler is inevitable, then there is only one ideal type of resonator which is free from instabilities: a resonator made from polarizing fibre (or one that incorporates a perfectly aligned polarizer in the loop). The fringe shape variation can be reduced if the resonator is made with a deliberate 90 deg. axis twist at the splice or coupler, or if it is made with a polarization-selective coupler. No practical technique has been demonstrated so far, for producing consistently stable resonators with high finesse, using birefringent fibre. This is because the tolerable amount of coupler polarization crosstalk is very small, and the above ideal form is not easily made. It is therefore important to compare the output stability of the different resonator types as well as to investigate possible techniques for passive or active stabilization of the output. In this thesis work we have developed a experimentally verifiable resonator model that can be applied to different resonator types with minor modifications. We have derived tolerances for the coupler polarization crosstalk, splice alignment, and input polarization mode purity necessary for optimum operation of each type. A fringe shape stabilization system has been constructed, for use with fibre ring resonators with power exchange between the birefringent axes. The system works by keeping the depth of successive resonant dips equal, through a feedback electronic servo system, that controls the fibre birefringence. Two schemes for controlling the fibre birefringence are investigated

Verifying Model Transformations by Structural Correspondence

Model transformations play a significant role in model based software development, and the correctness of the transformation is crucial to the success of the development effort. We have previously shown how we can use bisimulation to verify the preservation of certain behavioral properties across a transformation. However, transformations are often used to construct structurally different models, and we might wish to ensure that there is some structural correspondence to the original model. It may be possible to verify such transformations without having to explicitly specify the dynamic semantics of the source and target languages. In this paper, we present a technique to verify such transformations, by first specifying certain structural correspondence rules between the source and target languages, and extending the transformation so that these rules can be easily evaluated on the instance models. This will allow us to conclude if the output model has the expected structure. The verification is performed at the instance level, meaning that each execution of the transformation is verified. We will also look at some examples using this technique

The Graph Rewriting and Transformation Language: GReAT

In this paper, we describe the language and features of our graph transformation tool, GReAT.We begin with a brief introduction and motivation, followed by an overview of the actual language, the modeling framework, and the tools that were written to support transformations. Finally, we compare GReAT to other similar tools, discuss additional functionality we are currently implementing, and describe some of our experiences with the tool thus far

Role of High-sensitivity Cardiac Troponin in Acute Coronary Syndrome

Chest pain is one of the most common reasons for an emergency room (ER) visit in the US, with almost 6 million ER visits annually. High-sensitivity cardiac troponin (hscTn) assays have the ability to rapidly rule in or rule out acute coronary syndrome with improved sensitivity, and they are increasingly being used. Though hscTn assays have been approved for use in European, Australian, and Canadian guidelines since 2010, the FDA only approved their use in 2017. There is no consensus on how to compare the results from various hscTn assays. A literature review was performed to analyze the advantages and limitations of using hscTn as a standard biomarker to evaluate patients with suspected ACS in the emergency setting

Muscle cell membrane damage by very low serum sodium

A 63-year-old male was admitted with complaints of upper gastrointestinal symptoms with fatigue and myalgia. Investigations revealed severe hyponatremia with elevated creatine phosphokinase levels. Following further workup, it was diagnosed as a case of hyponatremia induced rhabdomyolysis. Because of prompt correction of hyponatremia, his renal function was preserved and myoglobinuria induced renal failure was avoided. The importance of early recognition of this potentially dangerous condition is emphasized

A Subgraph Operator for Graph Transformation Languages

In practical applications of graph transformation techniques to model transformations one often has the need for copying, deleting, or moving entire subgraphs that match a certain graph pattern. While this can be done using elementary node and edge operations, the transformation is rather cumbersome to write. To simplify the transformation, we have recently developed a novel approach that allows selecting subgraphs from the matched portion of the host graph, applying a filter condition to the selection, and performing a delete, move, or copy operation on the filtered result in the context of a transformation rule. The approach has been implemented in the GReAT language and tested on examples that show the practical efficacy of the technique. The paper describes the technique in detail and illustrates its use on a real-life example

Coexisting aegirine and magnesioriebeckite from Bababudan Hills, Mysore State

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