Presumed tuberculous keratopathy: a rare presentation of “serpiginious-like” keratic precipitates in a unilateral anterior uveitis case

A 43-year-old lady with no underlying medical illness was referred for chronic recurrent unilateral anterior uveitis. She had no previous ocular trauma or surgical intervention to the eye. Upon presentation, she was found to have unilateral anterior uveitis with a very unusual “serpiginious-like” pattern of keratic precipitate. Initial investigations revealed no infective cause and patient was commenced on topical and oral steroids. Unfortunately, her ocular symptoms worsened and developed steroid induced glaucoma. A repeat infective screening revealed positive results for tuberculosis. Patient has since responded very well to treatment with antitubercular agents with complete resolution of the inflammation and good visual recovery. In this case report, we wish to emphasize that ocular tuberculosis presentation is highly variable and in such cases its best to employ a high index of suspicion to initiate the right treatment timely. An infective etiology should promptly be suspected in patients who are not showing response to topical or systemic steroids. Even in an immunosuppressed state, ocular tuberculosis may remain unilateral throughout the course of the disease, as seen in the patient. Injudicious use of steroid can make a simple anterior granulomatous uveitis progress to florid granulomatous uveitis with confluent keratic precipitates

Parameter Estimation of Asymmetrical Six-phase Induction Machines using Modified Standard Tests

In multiphase machine drives, accuracy of the estimated machine parameters is crucial for effective performance prediction and/or control. While a great amount of work has been done on parameter estimation for three-phase machines, corresponding discussions for six-phase machine remain scarce. It has been proven in the literature that the effect of mutual leakage inductance between different winding layers has a significant impact on the equivalent machine reactance, which challenges the standard separation method of stator and rotor leakage inductances from the measured locked-rotor impedance. In this paper, parameter identification of an asymmetrical six-phase induction machine using six-phase no-load and locked-rotor tests is discussed. A zero-sequence test using an improved equivalent circuit is proposed to improve the accuracy of the estimated parameters. The concept is verified using experimental results obtained from a low-power prototype asymmetrical six-phase machine

Fault-tolerant efficient control of six-phase induction generators in wind energy conversion systems with series-parallel machine-side converters

This work discusses the implementation of an efficient fault-tolerant control m a multiphase wind energy conversion system. The conversion system consists of an asymmetrical six-phase induction generator supplied by four voltage source converters (VSCs) m a hybrid series/parallel configuration. Post-fault operation must preserve the current ratings of the system and should also maximize the generated power by means of a proper flux adjustment. Both requirements are achieved m this work using a non-linear optimization analysis and some modifications m the control scheme. Simulation results confirm the optimal and safe performance of the wind energy system under study

Current Control Methods for an Asymmetrical Six-Phase Induction Motor Drive

Using the vector space decomposition approach, the currents in a multiphase machine with distributed winding can be decoupled into the flux and torque producing α-β components, and the loss-producing x-y and zero-sequence components. While the control of α-β currents is crucial for flux and torque regulation, control of x-y currents is important for machine/converter asymmetry and dead-time effect compensation. In this paper, an attempt is made to provide a physically meaningful insight into current control of a six-phase machine, by showing that the fictitious x-y currents can be physically interpreted as the circulating currents between the two three-phase windings. Using this interpretation, the characteristics of x-y currents due to the machine/converter asymmetry can be analyzed. The use of different types of x-y current controllers for asymmetry compensation and suppression of dead-time-induced harmonics is then discussed. Experimental results are provided throughout the paper, to underpin the theoretical considerations, using tests on a prototype asymmetrical six-phase induction machine. © 1986-2012 IEEE

Fault-Tolerant Operation of Six-Phase Energy Conversion Systems With Parallel Machine-Side Converters

The fault tolerance provided by multiphase machines is one of the most attractive features for industry applications where a high degree of reliability is required. Aiming to take advantage of such postfault operating capability, some newly designed full-power energy conversion systems are selecting machines with more than three phases. Although the use of parallel converters is usual in high-power three-phase electrical drives, the fault tolerance of multiphase machines has been mainly considered with single supply from a multiphase converter. This study addresses the fault-tolerant capability of six-phase energy conversion systems supplied with parallel converters, deriving the current references and control strategy that need to be utilized to maximize torque/power production. Experimental results show that it is possible to increase the postfault rating of the system if some degree of imbalance in the current sharing between the two sets of threephase windings is permitted

Postfault operation of an asymmetrical six-phase induction machine with single and two isolated neutral points

The paper presents a study of postfault control for an asymmetrical six-phase induction machine with single and two isolated neutral points, during single open-phase fault. Postfault control is based on the normal decoupling (Clarke) transformation, so that reconfiguration of the controller is minimized. Effect of the single open-phase fault on the machine equations under this control structure is discussed. Different modes of postfault operation are analyzed and are further compared in terms of the achievable torque and stator winding losses. Validity of the analysis is verified using experimental results obtained from a six-phase induction motor drive prototype. © 1986-2012 IEEE

Postfault Operation of an Asymmetrical Six-Phase Induction Machine With Single and Two Isolated Neutral Points

The paper presents a study of postfault control for an asymmetrical six-phase induction machine with single and two isolated neutral points, during single open-phase fault. Postfault control is based on the normal decoupling (Clarke) transformation, so that reconfiguration of the controller is minimized. Effect of the single open-phase fault on the machine equations under this control structure is discussed. Different modes of postfault operation are analyzed and are further compared in terms of the achievable torque and stator winding losses. Validity of the analysis is verified using experimental results obtained from a six-phase induction motor drive prototype

Operation of a Six-Phase Induction Machine Using Series-Connected Machine-Side Converters

This paper discusses the operation of a multiphase system, which is aimed at both variable-speed drive and generating (e.g., wind energy) applications, using back-to-back converter structure with dual three-phase machine-side converters. In the studied topology, an asymmetrical six-phase induction machine is controlled using two three-phase two-level voltage source converters connected in series to form a cascaded dc link. The suggested configuration is analyzed, and a method for dc-link midpoint voltage balancing is developed. Voltage balancing is based on the use of additional degrees of freedom that exist in multiphase machines and represents entirely new utilization of these degrees. The validity of the topology and its control is verified by simulation and experimental results on a laboratory-scale prototype, thus proving that it is possible to achieve satisfactory dc-link voltage control under various operating scenarios. © 1982-2012 IEEE

Quality assurance for Chinese herbal formulae: standardization of IBS-20, a 20-herb preparation

<p>Abstract</p> <p>Background</p> <p>The employment of well characterized test samples prepared from authenticated, high quality medicinal plant materials is key to reproducible herbal research. The present study aims to demonstrate a quality assurance program covering the acquisition, botanical validation, chemical standardization and good manufacturing practices (GMP) production of IBS-20, a 20-herb Chinese herbal formula under study as a potential agent for the treatment of irritable bowel syndrome.</p> <p>Methods</p> <p>Purity and contaminant tests for the presence of toxic metals, pesticide residues, mycotoxins and microorganisms were performed. Qualitative chemical fingerprint analysis and quantitation of marker compounds of the herbs, as well as that of the IBS-20 formula was carried out with high-performance liquid chromatography (HPLC). Extraction and manufacture of the 20-herb formula were carried out under GMP. Chemical standardization was performed with liquid chromatography-mass spectrometry (LC-MS) analysis. Stability of the formula was monitored with HPLC in real time.</p> <p>Results</p> <p>Quality component herbs, purchased from a GMP supplier were botanically and chemically authenticated and quantitative HPLC profiles (fingerprints) of each component herb and of the composite formula were established. An aqueous extract of the mixture of the 20 herbs was prepared and formulated into IBS-20, which was chemically standardized by LC-MS, with 20 chemical compounds serving as reference markers. The stability of the formula was monitored and shown to be stable at room temperature.</p> <p>Conclusion</p> <p>A quality assurance program has been developed for the preparation of a standardized 20-herb formulation for use in the clinical studies for the treatment of irritable bowel syndrome (IBS). The procedures developed in the present study will serve as a protocol for other poly-herbal Chinese medicine studies.</p

Indium Tin Oxide@Carbon Core–Shell Nanowire and Jagged Indium Tin Oxide Nanowire

This paper reports two new indium tin oxide (ITO)-based nanostructures, namely ITO@carbon core–shell nanowire and jagged ITO nanowire. The ITO@carbon core–shell nanowires (~50 nm in diameter, 1–5 μm in length,) were prepared by a chemical vapor deposition process from commercial ITO nanoparticles. A carbon overlayer (~5–10 in thickness) was observed around ITO nanowire core, which was in situ formed by the catalytic decomposition of acetylene gas. This carbon overlayer could be easily removed after calcination in air at an elevated temperature of 700°C, thus forming jagged ITO nanowires (~40–45 nm in diameter). The growth mechanisms of ITO@carbon core–shell nanowire and jagged ITO nanowire were also suggested