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Background: Breast cancer (BCA) is the second most common cancer among women in India and accounts for 7% of global burden of BCA. The axillary lymph node status is an independent prognostic factor. The combined estrogen receptor (ER), progesterone receptor (PR), and HER2/neu biomarker expression is a predictor of BCA status for therapeutic guidance. Studies have demonstrated that these biomarkers are unstable throughout their tumor progression. Varying concordance and discordance rates in the biomarker expression between primary breast carcinoma (PBC) and metastatic axillary lymph node (MALN) status are reported.Aim: This study was conducted for studying and comparing the expression of immunohistochemistry (IHC) markers, i.e., ER, PR, HER2/neu, p53, and Ki67 between PBC and their corresponding MALN for prognostication and therapeutic purpose.Methods: Sixty cases of PBC with metastasis to axillary lymph nodes diagnosed between years 2008 and 2014 were included in the study. A technique of manual tissue array was employed for cases subjected to IHC. Analyses of the expression of IHC markers were attempted between the PBC and their corresponding synchronous MALN and classified as concordant or discordant. Results were subjected to statistical analysis.Results: Substantial agreement was observed for biomarker ER, PR, HER2/neu, p53, and Ki67 expression between PBC and MALN with k-value 0.79, 0.75, 0.89, 0.7, and 0.6, respectively.Conclusion: There was high concordance for the IHC markers: ER, PR, HER2/neu, p53, and Ki67 expression in matched pairs of PBC and corresponding synchronous MALN. However, the discordance noted in small subgroups cannot be overlooked. Thus, there is a need to perform ER, PR, HER2/neu, p53, and Ki67 IHC studies routinely in both PBC and MALN to help design therapies that are tailored to target the specific tumor clones and render maximum benefit to patients. [ABSTRACT FROM AUTHOR]

Fine-needle aspiration cytology (FNAC) is a simple, non-invasive diagnostic modality which can be performed with ease on any superficially palpable lesion. Surgical scar endometriosis is a rare entity which presents as an abdominal lump in women of reproductive age. It is often a diagnostic pitfall for clinicians due to its nonspecific symptoms. It displays characteristic morphology, which needs to be identified and recognized by a cytopathologist for accurate diagnosis. FNAC can be used as a key diagnostic tool in cases of abdominal wall mass for appropriate patient management, thereby avoiding unnecessary diagnostic procedures. Here, we report the case of a 35-year-old woman who presented with an abdominal lump where FNAC played a vital role in the patient's management. [ABSTRACT FROM AUTHOR]

Melanocytic schwannoma (MS) is an extremely rare soft tissue tumor accounting for less than 1% of all primitive nerve sheath tumors, with a predilection for spinal nerve involvement. To date, only 20 cases of cutaneous/subcutaneous MS have been described in literature. Here, we describe a case of MS presenting as a subcutaneous nodule in a 22-year-old male in right thigh. On examination, the nodule measured 2.5 x 2.0 x 1.5 cm with overlying skin showing a bluish hue and an ulcer. With a preoperative diagnosis of hemangioma, the patient was taken up for wide local excision and was diagnosed as a case of non psammomatous melanocytic schwannoma based on clinical, histological, and immunohistochemical studies. Immunohistochemistry revealed positivity with S-100, HMB-45, and Melan A with pericellular Laminin positivity. Carney's syndrome was ruled out. MS needs to be differentiated from other pigmented lesions like pigmented neurofibroma, Bednar tumor, cellular blue neavus, and especially malignant melanoma, which has an obvious ominous prognosis. Since MS can show unpredictable behavior especially in absence of overt malignant features, a long term follow up with or without radiotherapy is recommended. [ABSTRACT FROM AUTHOR]

Merkel cell carcinoma also known as neuroendocrine carcinoma of the skin is a very rare skin tumor. It commonly presents in the old age and the common sites are head, neck and extremities. The diagnosis requires histopathological examination with immunohistochemical correlation. We report a case of Merkel cell carcinoma stage IIIB with bilateral inguinal lymphadenopathy that on FNAB showed metastatic deposits of the tumor. [ABSTRACT FROM AUTHOR]

Background. Xanthogranulomatous inflammation is an uncommon affection of the female genital tract. The youngest case reported of xanthogranulomatous salpingooophoritis in literature was by Shilpa et al. in 2013 in an eighteen-year-old female. Case Report. We report a case of 2-year-old female child with right-sided xanthogranulomatous salpingooophoritis presented as mass in abdomen. This is a case report of the youngest documented case of xanthogranulomatous salpingooophoritis in literature. As per abdominal examination, there was generalized distention of abdomen and a mass was palpable which was arising out of pelvis more on the right side. The ultrasonography (USG) abdomen and pelvis revealed a thick-walled mass measuring 9.2 cm × 6.0 cm × 7.6 cm in pelvis. We did right salpingooophorectomy of the patient. On histopathology, the diagnosis of xanthogranulomatous salpingooophoritis was confirmed. Conclusion. Clinical presentation, radiological appearance, and gross features of xanthogranulomatous lesions of ovary can mimic neoplastic lesions and lead to misdiagnosis. Though, it is very rare in pediatric age group, xanthogranulomatous salpingooophoritis as one of the differential diagnoses should be kept in mind while dealing with tuboovarian masses in this age group. [ABSTRACT FROM AUTHOR]

Giant soft tissue chondromas (STCs) of the wrist are seldom encountered in clinical practice. Precise diagnosis of benign STC may pose diagnostic difficulties on clinical and radiological findings alone. We encountered a slowly growing soft tissue neoplasm in the radial aspect of the wrist joint of the right hand in a 52-year-old male, masquerading as a calcified hematoma, as suggested by magnetic resonance imaging. On cytohistopathological examination, it turned out to be a rare giant STC. The variable cellularity, in conjunction with cellular immaturity and atypia, could mislead one to a malignant pathological interpretation. Diagnosis is based on both radiological and cytohistological evaluation, which is indispensable for determining the tumor type. The detailed clinical, radiological, cytomorphological, and immune-histopathological study was carried out, which has prompted us to report this case along with a review of the literature. [ABSTRACT FROM AUTHOR]

Primary giant cell tumors of soft tissues (GCT-ST) are extremely rare soft tissue tumors, located in both superficial and deep soft tissues. They resemble osseous giant cell tumors morphologically and immunohistochemically. The tumor exhibits strong positive immunoreactivity for cluster of differentiation 68 (CD68) within multinucleated osteoclast-like giant cells and focal staining of mononuclear cells. Case reports describing the cytohistological features of this entity are very few. We report a case of GCT-ST of low malignant potential diagnosed on fine needle aspiration (FNA) and confirmed on histological and immunohistochemical studies. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Giant Pilomatricoma of the arm: A diagnostic challenge for cytopathologist" by Siddhi Gaurish in the 2015 issue.

The paper discusses the concept of a mini custom power park in which the voltage inside the park is tightly regulated by a distribution static compensator (DSTATCOM). It will be shown on the basis of simulations with ideal components that solid state protection devices, along with the DSTATCOM will eliminate many transients in all the loads of the park during disturbances. Moreover, the DSTATCOM, backed by a diesel generator, will supply the most sensitive loads during the total line outages, thereby nearly making them both transient and interruption free. In this paper, a configuration of the park is proposed and then various issues involved with the operation of the park are discussed. The proposed operation of the custom power park is verified through extensive digital computer simulation studies. [ABSTRACT FROM AUTHOR]

Voltage imbalance in capacitors is a well-known problem in compensator topologies which use two or more capacitors. This imbalance may exist even if the load does not contain any dc component, due to practical factors. However, when the load contains a dc part, the voltage imbalance problem becomes critical. In this paper, a two-quadrant chopper has been used to regulate the capacitor voltages in a two-capacitor compensator structure. Two different control strategies for the two-quadrant chopper to equalize the voltage of the capacitors have been proposed. The strategies are validated through detailed simulation studies. Experiments have also been carried out to validate the hysteresis control of chopper. [ABSTRACT FROM AUTHOR]

Presents an approach for generating reference currents for an active filter and/or a static compensator in a power distribution system. Compensating star connected loads; Compensating delta connected loads; Compensator structure.

This article proposes a systematic synthesis method to identify the optimum converter topology for a specified voltage conversion ratio. This gain-oriented converter synthesis is formulated as an inverse problem around the inductor flux balance equations. The proposed synthesis method consists of two processes. A set of distinct converter topologies is first synthesized from the specified voltage conversion ratio by obtaining the solutions for a set of six inverse equations in twelve unknowns. The optimal topology for any intended application can be identified based on the desired performance metrics. The complete synthesis method is illustrated with quadratic buck–boost gain as an example. In total, 25 distinct topologies are synthesized using the first process, and their feasibility is validated by PLECS simulation. In total, three case studies are reported to explain the second process. Ground-referenced output and the minimum number of switches are used as the first two selection criteria in all the case studies. Minimum peak inductor current, minimum component stress factor, and minimum voltage and current stress are the third selection criterion in Case Studies-1, 2, and 3, respectively. The steady-state operations of two optimal converters selected in Case Study-1 were verified experimentally. [ABSTRACT FROM AUTHOR]

This article presents an analytical method to derive an optimum converter topology for a specified voltage conversion ratio (G). An optimum topology for any given G can be identified after obtaining the comprehensive pool of converter topologies. This gain-oriented converter synthesis is formulated as an inverse problem around the principle of inductor flux balance. A step-by-step method is proposed to solve the inverse problem and obtain a comprehensive set of non-redundant converter topologies for any given voltage conversion ratio. Consequently, the number of possible converter topologies for a specified voltage conversion ratio is also identified. The optimum converter topology is chosen from the comprehensive set based on three selection criteria, viz., ground-referenced output, a minimum number of switches, and minimum peak inductor current. The proposed solution methodology is illustrated with quadratic boost and quadratic buck gains as case studies. A comprehensive set of non-redundant topologies is identified in both cases. The steady-state operations of all the topologies are studied with PLECS simulation. Based on the selection criteria, an optimum topology is selected in each case, and their steady-state operation is verified experimentally using lab-developed prototypes. [ABSTRACT FROM AUTHOR]

Nonisolated dc–dc converters are fundamental building blocks in the power supply for a wide range of applications. To cater to this heterogeneity in applications, development of dc–dc converters with suitable voltage conversion ratio (G) is imperative. Given a converter topology, G can be found out uniquely by using the principle of inductor volt-second balance, and the process of obtaining the voltage conversion ratio from the topology is simple. In contrast, the inverse problem, i.e., the process of obtaining the converter topology for a given voltage conversion ratio (G) is a challenging task, and the obtained topology is also not unique. This article presents a simple method to obtain a family of converter topologies from a required voltage conversion ratio. This method utilizes the principle of inductor flux balance as a synthesis tool. The step-by-step procedure to synthesize the converter topologies is outlined. To illustrate the efficacy of the proposed method, it is applied to synthesize various quadratic buck–boost topologies, and a family of converters is identified. Operation and feasibility of two novel topologies, identified by the proposed theory, are verified experimentally. [ABSTRACT FROM AUTHOR]

The inverse problem for the dc–dc converters refers to synthesizing converter topologies from a specified voltage gain expression. Though the flux balance principle is widely used in the analysis of dc–dc converters, its application as a synthesis tool has not been explored. This letter describes a mathematical approach to synthesize converter topologies from a required voltage gain expression by utilizing the principle of inductor flux balance. At first, the general form of gain expression for second-order converters is derived. From the general form of gain expression, the inverse problem is formulated by identifying the governing equations. The mathematical formulation of the inverse problem and highlighting challenges involved in solving it are the primary subjects of this article. To outline these challenges, a probable solution strategy of this inverse problem is presented. In order to derive a converter topology, at first, the appropriate flux balance equations are determined, and then the circuit topology is derived to establish the required flux balance. In contrast to the forward problem, the solution to the inverse problem is neither direct nor unique. Hence, getting the optimum closed-form solution to this inverse problem is an open-ended challenge with many possible approaches. [ABSTRACT FROM AUTHOR]

Due to the pulsating power at the inverter output terminals, the passive storage elements of the boost stage of the current-fed switched inverter (CFSI) contain a power frequency harmonic component (100 Hz), apart from dc and switching frequency components. In prior designs, the second harmonic component is suppressed by increasing the size of the input filter inductor and capacitor or by using additional circuits. This paper presents a complete characterization of a control-based approach to suppress the power frequency harmonic component in the input inductor current of a CFSI. It also presents a comprehensive characterization of the harmonic power redistribution. Using the proposed approach, it is demonstrated that the inductor value of a CFSI is reduced by 61% for the same peak-to-peak ripple. This leads to an improvement in the conversion ratio, efficiency, and power density of the overall converter. A SiC MOSFET-based CFSI with 75-kHz switching frequency is used to verify the proposed design philosophy. [ABSTRACT FROM AUTHOR]

Impedance source inverters (ISIs) are gaining attention due to features such as single-stage conversion, buck-boost capability, and inherent shoot-through protection. To maintain the required ac output voltage, typically ISIs are operated at a higher dc-link voltage due to constrained modulation index. This also increases voltage stress across capacitors and switches of the converter. This voltage stress is approximately double compared to that of voltage source inverter with preboost stage (Boost-VSI). To mitigate this problem, a new pulsewidth modulation (PWM) scheme for the active-front-end based ISIs (AFE-ISIs) is proposed. The proposed scheme enables the ISIs to produce high ac gain with lower voltage stress across the capacitor and switches. In other words, the proposed scheme blends the advantages of Boost-VSI into ISIs. With the new PWM scheme, there are also reductions in output voltage total harmonic distortion, switching frequency ripple in the inductor current, and power loss in the converter. A prototype of the current-fed switched inverter, an AFE-ISI, is designed, and the proposed PWM scheme is implemented. Experimental results obtained are in accordance with the proposed theory and show that the voltage stress has reduced from 325 V to 203 V for an ac output of 110 V. [ABSTRACT FROM AUTHOR]

Introduction: Breast carcinoma (BCa) is one of the most common cancers among women globally. Increased vimentin expression has been reported in various epithelial cancers. Aim: This study examines the expression of vimentin in BCa and its correlation with various prognostic factors such as tumor size, histological grade, lymph node status, estrogen receptor (ER), progesterone receptor (PR), HER2/neu, and Ki67 status. Materials and Methods: Seventy cases of BCa diagnosed between 2014 and 2015 were included in the study. A technique of manual tissue microarray was employed for the analysis of expression of immunohistochemical (IHC) markers such as vimentin, ER, PR, HER2/neu, and Ki67. Results were subjected to statistical analysis. Results: Vimentin was found positive in 53 (75.7%) cases of BCa, of which 18 cases (25.7%) were triple-negative BCa (TNBC). Positivity for ER, PR, Her2, and Ki67 was 32.8%, 31.4%, 60%, and 99%, respectively. Vimentin expression was significantly associated with ER negativity. All 53 cases expressing vimentin showed positive Ki67 labeling index; however, this was not statistically significant. Maximum vimentin expression was observed in the age group >50 years, postmenopausal women, BCa cases showing lymphovascular invasion (LVI), axillary lymph node metastasis, higher stage and higher grade of tumor, negative PR expression, and positive HER2/neu expression. However, this was not statistically significant. In TNBC, vimentin expression was significantly associated with histological grade and LVI. Conclusion: Vimentin expression was associated with well-established poor prognostic factors of BCa. Vimentin expression if routinely included in histopathology report would aid in better understanding of tumor behavior. [ABSTRACT FROM AUTHOR]

Responds to comments on an article appearing in the January 2000 issue of 'IEEE Transactions on Power Delivery,' which dealt with an approach to load balancing in power distribution system. Configuration of the load; Aim of the compensator; Plot of the voltage vector in the complex plane.

Introduction: Endometrial carcinoma is the second most common gynecologic malignancy in the developing countries. Endometrial Hyperplasia (EH) is a precursor to Endometrioid Adenocarcinoma (EMAC). A 23% of Atypical Hyperplasias (AEH) progress to EMAC. Aim: This study was undertaken to analyse ER, PR, p53 and Ki67 in EH and endometrial carcinomas and attempt correlation with clinical and histopathological findings. Materials and Methods: The present study was conducted over a period of seven years. A manual tissue array technique was employed for cases subjected to IHC. Analysis of the expression of IHC markers (ER, PR, p53, Ki67) in EH and endometrial carcinoma was attempted. Results were subjected to statistical analysis. The results were considered to be significant when the p-value <0.05. Results: An 85 cases of EH and 28 cases of endometrial carcinoma were included in the study. EH (75.22%) was more common than endometrial carcinoma (24.78%). Among 28 cases of endometrial carcinomas, EMAC was most common (78.57%) followed by Clear Cell Carcinoma (CCC) (14.28%), and Uterine Serous Carcinoma (USC) (7.14%). ER and PR expression decreased as lesion progressed from EH to EMAC. ER and PR expression was negative in USC and CCC. The p53 expression and mean Ki67 labelling index increased as the severity of lesion increased from EH to endometrial carcinoma. Conclusion: The ER, PR, p53, Ki67 IHC markers may be included in every case of endometrial carcinoma to understand the tumour biological behavior which in turn could help individual treatment strategies. [ABSTRACT FROM AUTHOR]

Introduction: The ampulla of Vater consists of papilla, common channel, distal common bile duct and the distal main pancreatic duct. Ampullary carcinomas arise from two different types of mucosa, reflecting their broad histomorphological spectrum. Adenocarcinomas originating in the ampulla of Vater are classified as having either 'Intestinal' or 'Pancreatobiliary' type of differentiation. Pancreatobiliary type has consistently shown a worse prognosis. Various types of mucins are distributed in normal tissues and gastrointestinal tumours. MUC1, MUC2 and MUC5AC are known to be the most important amongst all. Aim: To study clinicopathological features of different types of carcinoma of ampulla with MUC1, MUC2 and MUC5AC expression. Materials and Methods: We included 20 cases of ampullary adenocarcinoma in this study, diagnosed after radical surgery. The histopathological slides were reviewed and the tumours were classified into intestinal type, pancreatobilliary and other types. Representative block of tumours was subjected to immunohistochemical (IHC) study with MUC1, MUC2 and MUC5AC antibodies. Results were subsequently analysed. Results: Pancreaticobiliary type of ampullary carcinoma cases predominated (50%) over intestinal type (25%). Carcinomas of "other types" included one case each of mucinous carcinoma, adenosquamous carcinoma and undifferentiated carcinoma and well differentiated neuroendocrine tumours. Pancreatobiliary type of carcinomas was associated with higher tumour stage and grade and lymph node metastasis. All the pancreatobiliary type expressed MUC1 and all intestinal type carcinomas expressed MUC2. MUC 5AC expression was seen predominantly in pancreatobiliary type of ampullary carcinomas. Conclusion: Mucin markers are associated with two different subtypes of ampullary carcinomas which have different prognosis. Immunohistochemical study of mucin expression can define the different types of carcinomas of ampulla of Vater with better objective criteria. [ABSTRACT FROM AUTHOR]

Introduction: Breast Cancer (BC) is the second most common cancer among women in India and accounts for 7% of global burden of BC and one-fifth of all Cancers (CA) among women in India. Aim: This study was conducted for studying the expression of MUC1, MUC2 and MUC5AC in breast carcinoma. Materials and Methods: Fifty cases of primary breast carcinoma diagnosed between years 2013 to 2015 were included in the study. Manual tissue array technique was applied for cases subjected to Immunohistochemistry (IHC). An analysis of the expression of IHC markers (MUC1, MUC2, MUC5AC, ER, PR and HER2/neu) was attempted. Results were subjected to statistical analysis. They were considered to be significant when the p-value was less than 0.05. Results: The positivity for MUC1, MUC2 and MUC5AC in BC was 58%, 8% and 6% and for ER, PR and HER2 was 48%, 36% and 64% respectively. There was a significant correlation between MUC1 expression and ER and PR positivity. There was a significant correlation between MUC2 expression and ER positivity. No significant association was observed between MUC2 and PR expression, MUC5AC expression and ER and PR positivity. There was statistically significant correlation between negative MUC2 and MUC5AC expression and histopathological grade. It was noted that MUC2 and MUC5AC negative tumours were associated with higher tumour stage though not statistically significant. It was noted that MUC5AC negative tumours showed higher frequency of lymphovascular invasion though not statistically significant. Conclusion: Our experience with the present study highlights the role of mucins in the development and progression of BC. [ABSTRACT FROM AUTHOR]

Introduction: Solitary Thyroid Nodule (STN) has provoked increased concern owing to higher incidence of malignancy. The inter and intra observer variation in the histomorphological diagnosis of Papillary Thyroid Carcinomas (PTC) may sometimes pose a diagnostic difficulty. Aim: This study was undertaken to analyse immunohistochemical (IHC) markers (CK-19, CD-56, p53, Ki-67) to differentiate between benign and malignant surgically resected STN along with their utility in the identification of PTC. Materials and Methods: The present cross sectional study was conducted over a period of 4 years. A technique of manual tissue array was employed for cases subjected to IHC. The primary antibodies used were CK-19, CD-56, p53 and Ki- 67. Analysis of the expression of IHC markers (p53, Ki-67) to distinguish between benign and malignant STN was done. Evaluation and correlation of expression of IHC markers (CK-19, CD-56) to determine its utility in reaching definitive diagnosis and assessing prognosis of PTC was tried. Results were subjected to statistical analysis. The results were considered to be significant when the p-value <0.05. Results: Out of the 160 cases of surgically resected STN specimens, 68 cases were non-neoplastic, 24 cases were benign and 68 cases were of malignant tumours (7 cases of follicular carcinoma (FCa), 61 cases of PTC). CK-19 was found to be a sensitive (83.61%) and a highly specific positive marker (100%) for the diagnosis of PTC. The difference in CD- 56 expression between PTC and non-PTC group was found to be highly statistically significant. CD-56 was found to be a sensitive (85.86%) and specific (82.25%) negative marker in differentiating PTC from follicular lesions/neoplasms. The difference in p53 expression between the malignant and nonmalignant STN cases was found to be highly statistically significant with a sensitivity and specificity 85.29% and 70.65% respectively. The statistical difference in mean Ki-67 Labeling Index (LI) was found to be significant between PTC versus FA, PTC versus non-neoplastic lesions, FA versus FCa and FVPTC versus FA. Conclusion: The panel of four IHC markers (CK-19, CD-56, p53, Ki-67) may be used for differentiating doubtful benign STN cases from malignant ones and also for definitive diagnosis of PTC along with histopathological examination. [ABSTRACT FROM AUTHOR]

Cancers of the urinary bladder account for about 3.2% of all cancers worldwide. Clear cell adenocarcinomas (CCAs) of urinary bladder are rare. CCA must be differentiated from benign condition such as nephrogenic adenoma (NA) as well as malignant conditions such as urothelial carcinoma with clear cells, metastasis from ovary and kidney, and urinary bladder myomelanocytic tumor. The diagnosis is based on characteristic histopathological and immunohistochemical features. We present a rare case of CCA of urinary bladder with aggressive clinical behavior in a 72-year-old female. [ABSTRACT FROM AUTHOR]

Power-hardware-in-the-loop (PHIL) simulations are used to test power hardware with the help of computer-based real-time simulations. Generally, buck-based power amplifiers that have good dynamic performance are used to construct a PHIL simulator because of their linear large signal control-to-output characteristics. However, their output voltage peak is limited to the applied dc input in the linear region of modulation. In this paper, a differential boost converter (DBC)-based power amplifier is proposed for PHIL simulations, which does not suffer from the aforementioned limitations of a buck-based amplifier. A conventional DBC exhibits highly nonlinear control-to-output behavior. A feedback linearization technique is used to linearize the DBC in a large signal and dynamic sense, which makes it suitable for PHIL applications. Using this power amplifier and a MATLAB/Simulink toolbox for real-time simulations, the PHIL simulator is constructed. Experimental results under various operating conditions of source voltages, such as unipolar, bipolar, transients in frequency, and the dc step, and various load conditions, such as reactive, nonlinear, and transient faults, are provided to confirm the efficacy of the proposed PHIL simulator. [ABSTRACT FROM PUBLISHER]

Buck-converter-based topologies are used to generate high-frequency sinusoidal outputs. Buck-based inversion circuits such as voltage source inverters or class-D amplifiers have inherent control-to-output linearity in large-signal sense. However, in these topologies, the instantaneous output is always smaller than the dc-input during linear modulation. A differential boost inverter (DBI) is a boost-based topology that is used to generate a sinusoidal output. In DBI, the instantaneous output can be higher or lower than the dc-input voltage. DBI exhibits nonlinear control-to-output behavior in large-signal dynamic sense. Therefore, generating a high-frequency sinusoidal output using this topology is a challenge. The issues associated with a DBI for high-frequency sine wave generation are characterized in this paper. Conventional linear and nonlinear control techniques fail to produce a high-quality sine wave output at higher operating frequency. A nonlinear feedback linearization technique is proposed, which forces the output to be linear with respect to the reference even at higher operating frequency. This leads to a high-frequency high-quality sine wave generation using a DBI. The proposed modulator is verified using a laboratory prototype to generate a sine wave up to 2 kHz. A triangular wave of 100-Hz frequency is also generated by the proposed technique. Superior dynamic responses of a dynamic linearizing modulator controlled DBI for a step change in frequency, load current, input voltage, and reference are also experimentally verified. [ABSTRACT FROM AUTHOR]

Introduction: Fibroepithelial tumours are a heterogeneous group of biphasic neoplasms consisting of a proliferation of both epithelial and stromal components. Fibroadenoma (FA) and Phyllodes Tumour (PT) constitute the major entities. It is crucial to distinguish benign from borderline PT (low grade malignant PT), because the former do not metastasize, have a lesser risk of local recurrence and initial local recurrences are histologically benign in almost all instances. Multiple Immunohistochemical (IHC) markers are being studied to find their utility in grading the PT accurately for planning proper treatment. Aim: To study, the IHC expression of CD10 in the stromal cells of a series of PTs and FA, with the aim of determining whether the degree of CD10 expression in the stromal cells is related to the grade of the tumour. Materials and Methods: Records of 28 cases of PT and 35 cases of FA received in the Department of Pathology in a tertiary care hospital were obtained. Histopathology reports and slides of all the cases were reviewed and clinical data such as age and histomorphological features such as tumour cellularity, stromal overgrowth, mitotic count and nuclear atypia were noted. Representative block of the tumour with maximum cellularity was subjected to CD10 staining. For FA and benign PT a technique of tissue microarray was used. For borderline and malignant PT, representative section was used. Stromal cell staining was assessed, using cytoplasmic staining of the breast myoepithelium as internal control. Results: Present study included 35 cases of FA, 20 cases of benign PT, five cases of borderline PT and three cases of malignant PT. The mean age of the patients increased with the increasing tumour grade of PT and this was also observed for FA and benign PT. The mean age increased with increase in tumour grade of PT and was statistically significant (p<0.05). The mean size did not increase with the increasing tumour grade of PT and was statistically insignificant (p=0.0429). Mean tumour size was more in benign PT as compared to FA and was highly statistically significant (p<0.01). CD10 staining was diffuse (Grade-3) and strong in malignant PT. The staining intensity was strong but patchy (Grade-2) in borderline PT. Weak and patchy (Grade-1) CD10 staining was seen in four benign PT and six FA. Other cases of benign PT and FA were negative for CD10 immunoreactivity. Conclusion: Our study showed that CD10 expression strongly correlates with the PT grade, which can help in the differentiation between benign and malignant variants of PT. [ABSTRACT FROM AUTHOR]

The Z-source inverter (ZSI) employs an LC impedance network between the main inverter bridge and the power source. The unique feature of the ZSI is that it can operate either in buck or boost mode with a wide range of obtainable output voltages from a given input voltage. This topology also exhibits better electromagnetic-interference noise immunity when compared to a traditional voltage-source inverter (VSI). However, the LC impedance network of ZSI significantly increases the size and cost of the power converter and can make it unsuitable for low-power applications. This paper proposes a novel topology called switched boost inverter (SBI) which exhibits similar advantages of ZSI with lower number of passive components and more active components compared to ZSI. The steady-state and small-signal analyses of SBI, along with its pulsewidth modulation (PWM) control strategies, have been discussed in this paper. This paper also presents a comparison of SBI and ZSI with the same input and output parameters. The theoretical analysis given in this paper has been validated using a laboratory prototype of SBI, and the experimental results are presented for verification. The experimental harmonic spectrum of the inverter's output voltage with the proposed PWM technique is also plotted and compared with that of a traditional VSI. All the experimental results show good correlation between theory and experiments. [ABSTRACT FROM PUBLISHER]

Electronic load (E-load) is commonly used to test power supplies. In order to test computer power supplies, the E-load must possess an ideal controlled current source property which draws a desired load current even in the case of a very low terminal voltage of the source under test (SUT). It also needs to have superior dynamic performance to simulate high-slew-rate load transients. This paper proposes the design of a switching-converter-based E-load with very large operational bandwidth. The overall architecture of the E-load consists of a low-bandwidth converter, which functions under steady state, and a high-bandwidth auxiliary circuit that is only active during transient state. The converter circuit is realized using a novel switched-boost topology, and the auxiliary circuit is realized using a MOSFET operating at the edge of saturation and linear region. The proposed topology is capable of sinking a specific amount of load current even with a very low SUT terminal voltage. Simulation and experimental validations are provided to verify the proposed concepts. A prototype has been built to test the proposed architecture. The operational input voltage (SUT voltage) ranges of the prototype are between 0.5 and 6 V. The load current range is between 0.75 and 7 A. The results validate the excellent dynamic characteristics of the proposed architecture. [ABSTRACT FROM PUBLISHER]

The flying capacitor multicell inverter (FCMI) possesses natural balancing property. With the phase-shifted carrier-based scheme, natural balancing can be achieved in a straightforward manner. However, to achieve natural balancing with the harmonically optimal phase-disposition (PD) carrier-based scheme, the conventional approaches require (n − 1) × (n − 1) trapezoidal carrier signals for an n-level inverter, which is ( n − 1) × (n − 2) times more than that in the standard PD scheme. This paper proposes two improved natural balancing strategies for FCMI under PD scheme, which use the same (n − 1) carrier signals as used in the standard PD scheme. In the first scheme, the on-line detections are performed of (i) the band in which the modulation signal is located, (ii) corresponding period number of the carrier, and (iii) rising or falling half cycle of the carrier waveform to generate the switching signals based on certain rules. In the second strategy, the output voltage level selection is first processed and the switching signals are then generated according to a rule based on preferential cell selection algorithm. These methods are easy to use and can be simply implemented as compared to the other available methods. Simulation and experimental results are presented for a five-level inverter to verify these proposed schemes. [ABSTRACT FROM AUTHOR]

The hysteresis modulation for power electronic converters is attractive in many different applications because of its unmatched dynamic response and wide command-tracking bandwidth. Its application and benefits for two-level converters are well understood, but the extension of this strategy to multilevel converters is still under development. This paper summarizes and reviews the various hysteresis modulation approaches available in the literature for multilevel converters. The pros and cons of various techniques are described and compared for tracking the reference signal in order to attain an adequate switching optimization, excellent dynamic responses and high accuracy in steady-state operation. By using the recently developed multilevel hysteresis modulation approaches, the advantages of using several accessible dc potentials in a multilevel inverter have been fully exploited. All of these hysteresis modulation approaches are tested for tracking a current reference when applied to a five-level inverter. The relevant simulation and experimental results are also presented. This study will provide a useful framework and point of reference for the future development of hysteresis modulation for multilevel converters. [ABSTRACT FROM AUTHOR]

In this paper, the performance of voltage-source converter-based shunt and series compensators used for load voltage control in electrical power distribution systems has been analyzed and compared, when a nonlinear load is connected across the load bus. The comparison has been made based on the closed-loop frequency response characteristics of the compensated distribution system. A distribution static compensator (DSTATCOM) as a shunt device and a dynamic voltage restorer (DVR) as a series device are considered in the voltage-control mode for the comparison. The power-quality problems which these compensator address include voltage sags/swells, load voltage harmonic distortions, and unbalancing. The effect of various system parameters on the control performance of the compensator can be studied using the proposed analysis. In particular, the performance of the two compensators are compared with the strong ac supply (stiff source) and weak ac-supply (non-stiff source) distribution system. The experimental verification of the analytical results derived has been obtained using a laboratory model of the single-phase DSTATCOM and DVR. A generalized converter topology using a cascaded multilevel inverter has been proposed for the medium-voltage distribution system. Simulation studies have been performed in the PSCAD/EMTDC software to verify the results in the three-phase system. [ABSTRACT FROM AUTHOR]

This paper proposes a flying-capacitor-based chopper circuit for dc capacitor voltage equalization in diode-clamped multilevel inverters. Its important features are reduced voltage stress across the chopper switches, possible reduction in the chopper switching frequency, improved reliability, and ride-through capability enhancement. This topology is analyzed using three-and four-level flying-capacitor-based chopper circuit configurations. These configurations are different in capacitor and semiconductor device count and correspondingly reduce the device voltage stresses by half and one-third, respectively. The detailed working principles and control schemes for these circuits are presented. It is shown that, by preferentially selecting the available chopper switch states, the dc-link capacitor voltages can be efficiently equalized in addition to having tightly regulated flying-capacitor voltages around their references. The various operating modes of the chopper are described along with their preferential selection logic to achieve the desired performances. The performance of the proposed chopper and corresponding control schemes are confirmed through both simulation and experimental investigations. [ABSTRACT FROM AUTHOR]

In this paper, a generalized multiband hysteresis modulation and its characterization have been proposed for the sliding-mode control of cascaded H-bridge multilevel-inverter (CHBMLI)-controlled systems. A frequency-domain method is proposed for the determination of net hysteresis bandwidth for a given desired maximum switching frequency of the inverter. The switching transition concept of Tsypkin's method and the describing function of nonlinear relay have been used for the derivation of results. A hierarchical switching algorithm has been suggested for the modular cells of the cascaded multilevel inverter. The hierarchy of each cell is swapped sequentially to provide the self-balancing capability in case the dc-link voltage is supported by the capacitors. The simulation and experimental verification of the derived results are provided through a single-phase distribution static compensator (DSTATCOM) model. The application in the three-phase system has been shown through simulation studies on a 3.3-kV distribution-system compensation using DSTATCOM. Verification on both single- and three-phase systems is obtained using a five-level cascaded-multilevel-inverter topology. [ABSTRACT FROM AUTHOR]

Cervical cancer is the most frequent type of cancer in women in many developing countries. Squamous cell carcinoma of the cervix spreads principally by lymphatics and less commonly through blood vessels. The most frequent sites for those who develop distant metastasis include lungs (21%), lumbar and thoracic spine (16%), and para-aortic lymph nodes (7%). Metastasis to the kidney is extremely rare with <10 previously reported cases. We report a case of renal metastasis from squamous cell carcinoma of the cervix detected in end-stage kidney due to hydronephrosis. [ABSTRACT FROM AUTHOR]

In this paper, a fixed-switching-frequency closed-loop modulation of a voltage-source inverter (VSI), upon the digital implementation of the modulation process, is analyzed and characterized. The sampling frequency of the digital processor is considered as an integer multiple of the modulation switching frequency. An expression for the determination of the modulation design parameter is developed for smooth modulation at a fixed switching frequency. The variation of the sampling frequency, switching frequency, and modulation index has been analyzed for the determination of the switching condition under closed loop. It is shown that the switching condition determined based on the continuous-time analysis of the closed-loop modulation will ensure smooth modulation upon the digital implementation of the modulation process. However, the stability properties need to be tested prior to digital implementation as they get deteriorated at smaller sampling frequencies. The closed-loop modulation index needs to be considered maximum while determining the design parameters for smooth modulation. In particular, a detailed analysis has been carried out by varying the control gain in the sliding-mode control of a two-level YSI. The proposed analysis of the closed-loop modulation of the VSI has been verified for the operation of a distribution static compensator. The theoretical results are validated experimentally on both single- and three-phase systems. [ABSTRACT FROM AUTHOR]

Perifolliculitis capitis abscedens et suffodiens is the least common of the three conditions included in the follicular occlusion triad. It is one of the causes of scarring alopecia in adult males. Clinically it has to be differentiated from other causes of folliculitis affecting the scalp. The histopathology is diagnostic. The treatment is prolonged and the clinical course is characterized by remissions and relapses. [ABSTRACT FROM AUTHOR]

This paper examines the application of a diodeclamped multilevel inverter (DCMLI).based distribution static compensator (DSTATCOM) connected to a three-phase, four-wire (3p4w) distribution system. The DCMLI has an inherent unbalancing problem among its dc capacitor voltages. Additionally, when the load contains a dc part, the neutral point of the compensator also becomes unbalanced. In this paper, the effects of different loading conditions on the dc capacitor voltages of the inverter are studied. Two new control circuits are proposed for equalizing the capacitor voltages. Different control techniques are presented for the equalizing circuits. Equations of the proposed equalizing controllers are developed corresponding to the control of the switching devices. Comparative studies of different control techniques and the performances of the two controllers are performed. Simulation studies are performed using PSCADIEMTDC to validate the efficacy of the proposed equalizing controller circuits. [ABSTRACT FROM AUTHOR]

In this paper, the method of triangular carrier switching control of two-level inverters is extended to cascaded multilevel inverters using phase-shifted multicarrier unipolar pulsewidth modulation (PWM). The condition for smooth modulation is obtained using the Bessel's function representation of the PWM output and the switching condition of the multilevel- inverter-controlled system. A method is proposed for the determination of the minimum amplitude of the triangular carrier for smooth modulation at fixed switching frequency. It is shown that the multilevel modulation based on the phase-shifted carriers significantly reduces the ripple magnitude in the switching function and allows the use of a smaller carrier amplitude under closed loop. This increases the forward gain and, hence, improves the tracking characteristics. The proposed cascaded multilevel inverter control is implemented for the operation of a distribution static compensator (DSTATCOM) in the voltage control mode. The experimental verification of the theoretical and simulation results is provided through a field-programmable gate array (FPGA) based control of a laboratory model of a single-phase DSTATCOM. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of multilevel hysteresis current regulation strategies. Two such strategies have been discussed and some modifications in their control tasks have been proposed to achieve more reliable and improved performance. In general, the multiband concept has been used while making the proposals. The hysteresis band size considerations have also been presented by taking into account the desired and existing system conditions. The proposed modulation schemes have been applied to a five-level flying-capacitor inverter, whose operation under hysteresis current control mode is much less established. A new method of flying-capacitor voltage balancing is proposed which ensures balanced flying-capacitor voltages and, at the same time, maintains the desired current profile. It uses a time-based approach for controlling the capacitor voltages and achieves appreciable voltage spectrum under wide range of load power factor conditions. The performance of the proposed strategies is confirmed through both simulation and experimental investigations. [ABSTRACT FROM AUTHOR]

In this paper, load compensation using multilevel inverter-based distribution static compensator (DSTATCOM) is presented. The DSTATCOM is connected to a three-phase four-wire (3p4w) distribution system. Two different multilevel inverter topologies are used to realize the DSTATCOM. They are diode-clamped multilevel inverter (DCMLI) and flying capacitor multilevel inverter (FCMLI). A compensating technique has been derived, which uses the state feedback control to the multilevel inverters-based DSTATCOMs. A switching strategy for the multi-level inverters that ensures utilization of all output voltage states of the inverter for efficient tracking of references has been proposed. The schemes of dc-link capacitor volthge control for DCMLI and flying capacitor voltage control for FCMLI have been discussed. Comparative studies of performances of the two DSTATCOM topologies are performed. The simulation studies are performed using PSCAD/EMTDC to validate the efficacy of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Flying capacitor multilevel inverter (FCMLI) is a multiple voltage level inverter topology intended for high voltage and power operations with low distortion. It uses capacitors, called flying capacitors for clamping the voltage across the power semiconductor devices. In this paper, the implementation of a distribution static compensator (DSTATCOM) using an FCMLI is presented. A hysteresis current control technique for controlling the injected current by the FCMLI-based DSTATCOM is discussed. A new method for controlling the flying capacitor voltages is proposed which ensures that their voltages remain constant and at the same time maintain the desired current profile under the hysteresis current control operation. Simulation studies are performed using PSCAD/EMTDC to validate the efficacy of the control scheme and the FCMLI-based DSTATCOM. [ABSTRACT FROM AUTHOR]

This paper proposes a new connection for a unified power quality conditioner (UPQC) to improve the power quality of two feeders in a distribution system. A UPQC consists of a series voltage-source converter (VSC) and a shunt VSC both joined together by a common dc bus. It is demonstrated how this device is connected between two independent feeders to regulate the bus voltage of one of the feeders while regulating the voltage across a sensitive load in the other feeder. Since the UPQC is connected between two different feeders (lines), this connection of the UPQC will be called an interline UPQC (IUPQC). The structure, control and capability of the IUPQC are discussed in this paper. The efficacy of the proposed configuration has been verified through simulation studies using PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

The flying capacitor multilevel inverter (FCMLI) is a multiple voltage level inverter topology intended for high-power and high-voltage operations at low distortion. It uses capacitors, called flying capacitors, to clamp the voltage across the power semiconductor devices. A method for controlling the FCMLI is proposed which ensures that the flying capacitor voltages remain nearly constant using the preferential charging and discharging of these capacitors. A static synchronous compensator (STATCOM) and a static synchronous series compensator (SSSC) based on five-level flying capacitor inverters are proposed. Control schemes for both the FACTS controllers are developed and verified in terms of voltage control, power flow control, and power oscillation damping when installed in a single-machine infinite bus (SMIB) system. Simulation studies are performed using PSCAD/EMTDC to validate the efficacy of the control scheme and the FCMLI-based flexible alternating current transmission system (FACTS) controllers. [ABSTRACT FROM AUTHOR]

The paper discusses the operating principles and control characteristics of a dynamic voltage restorer (DVR) that protects sensitive but unbalanced and/or distorted loads. The main aim of the DVR is to regulate the voltage at the load terminal irrespective of sag/swell, distortion, or unbalance in the supply voltage. In this paper, the DVR is operated in such a fashion that it does not supply or absorb any active power during the steady-state operation. Hence, a dc capacitor rather than a dc source can supply the voltage source inverter realizing the DVR. The proposed DVR operation is verified through extensive digital computer simulation studies. [ABSTRACT FROM AUTHOR]

In this paper, a static synchronous series compensator (SSSC), along with a fixed capacitor, is used to avoid torsional mode instability in a series compensated transmission system. A 48-step harmonic neutralized inverter is used for the realization of the SSSC. The system under consideration is the IEEE first benchmark model on SSR analysis. The system stability is studied both through eigenvalue analysis and EMTDC/PSCAD simulation studies. It is shown that the combination of the SSSC and the fixed capacitor improves the synchronizing power coefficient. The presence of the fixed capacitor ensures increased damping of small signal oscillations. At higher levels of fixed capacitor compensation, a damping controller is required to stabilize the torsional modes of SSR. [ABSTRACT FROM AUTHOR]