Current measurement in power electronic and motor drive applications - a comprehensive study

Current measurement has many applications in power electronics and motor drives. Current measurement is used for control, protection, monitoring, and power management purposes. Parameters such as low cost, accuracy, high current measurement, isolation needs, broad frequency bandwidth, linearity and stability with temperature variations, high immunity to dv/dt, low realization effort, fast response time, and compatibility with integration process are required to ensure high performance of current sensors. Various current sensing techniques based on different physical effects such as Faraday\u27s induction law, Ohm\u27s law, Lorentz force law, magneto-resistance effect, and magnetic saturation are studied in this thesis. Review and examination of these current measurement methods are presented. The most common current sensing method is to insert a sensing resistor in the path of an unknown current. This method incurs significant power loss in a sense resistor at high output currents. Alternatives for accurate and lossless current measurement are presented in this thesis. Various current sensing techniques with self-tuning and self-calibration for accurate and continuous current measurement are also discussed. Isolation and large bandwidth from dc to several kilo-hertz or mega-hertz are the most difficult, but also most crucial characteristics of current measurement. Electromagnetic-based current sensing techniques, which are used to achieve these characteristics, are analyzed. Many applications require average current information for control purposes. Different average current sensing methods of measuring average current are also reviewed. --Abstract, page iii

Synthesis, characterization and biological evaluation of sulfonamide based transition metal complexes

In the present study a noval 4-oxo-4-(4-sulfamoylphenylamino)but-2-enoic acid (OSPAB) was prepared by reaction of maleic anhydride with sulphanilamide. The prepared ligand was characterized by elemental analysis and spectral studies. The transition metal complexes viz. Cu2+, Ni2+ , Co2+ , Mn2+ and  Zn2+  of OSPAB were prepared and characterized by metal-ligand (M:L) ratio, IR, reflectance spectroscopies and magnetic properties. All the prepared metal complexes and ligand were studies as antimicrobial agent. Among all the metal complexes, Zn2+ and Cu2+ metal complexes have shown significant activity. Â

Current Sensing for Automotive Electronics -- A Survey

Current sensing is widely used in power electronic applications such as dc-dc power converters and adjustable-speed motor drives. Such power converters are the basic building blocks of drivetrains in electric, hybrid, and plug-in hybrid electric vehicles. The performance and control of such vehicles depend on the accuracy, bandwidth, and efficiency of its sensors. Various current-sensing techniques based on different physical effects such as Faraday\u27s induction law, Ohm\u27s law, Lorentz force law, the magnetoresistance effect, and the magnetic saturation effect are described in this paper. Each technique is reviewed and examined. The current measurement methods are compared and analyzed based on their losslessness, simplicity, and ease of implementation

OPTIMIZATION OF BACOSIDE A LOADED SNEDDS USING D-OPTIMAL MIXTURE DESIGN FOR ENHANCEMENT INSOLUBILITY AND BIOAVAILABILITY

Objective: The objective of present study is to enhance solubility and bioavailability of poorly soluble bacoside A present in Bacopa monnieri extract using self nano emulsifying drug delivery system (SNEDDS) for the treatment of Alzheimer's disease.Methods: Solubility of the drug was assessed in various oils (edible as well as synthetic oil), surfactant and co-surfactant by saturation solubility study. Pseudo-ternary phase diagram was used to obtain appropriate concentration ranges of components include oil, surfactant and co-surfactant.Results: From the result of saturated solubility study and phase diagram, oleic acid, tween 20 and ethanol was selected as oil, surfactant and co-surfactant. The D-Optimal mixture design was used to optimize the formulation on the basis of solubility of drug and dilution potential. In vitro dissolution, study showed 89% of drug release from optimized SNEDDS formulation compared to untreated drug extract with 24% of drug release in 60 min. Ex vivo diffusion study showed more than 90% of drug diffused from optimized SNEDDS formulation compared to pure extract.Conclusion: In a nutshell, the developed SNEDDS formulation using the design of experimentation approach held great potential as a possible alternative to traditional oral formulations of poorly soluble Bacoside A to improve solubility and bioavailability

Profile of patients with intellectual disability visiting a tertiary care center in western India

Background:Intellectual disability is commonly associated with variety of etio-pathological and co-morbid conditions influencing outcome of rehabilitative measures. Understanding of these factors helps in better management of disabled condition.Methods:A qualitative retrospective case record review, of patients with intellectual disability, visiting psychiatry department of a tertiary care hospital, within a period of one year, was conducted to assess their epidemiological and clinical profile.Results: Patients with Intellectual disability are brought to the hospital at all ages and commonly by their parents. Etiologically related various peri-natal factors (delayed birth cry and seizures being most common) as well as childhood medical conditions (epilepsy and recurrent respiratory/GI infections being most common) were commonly found in these patients. Milestones are delayed in almost 60-70% of cases whereas various physical and psychiatric conditions commonly co-existed with disability.Conclusion:Clinical profile of these patients demands a comprehensive evaluation and management apart from routine IQ assessment

Working psychologically in inpatient services

Background: Literature has suggested that therapeutic engagement is considered as an important construct to assess as premature termination of therapy can influence clinical outcome and increase the chances of services becoming cost ineffective (McMurrana, Huband & Overton, 2010). This study aimed to explore how Psychologists' make sense of and understand their engagement with service users in a Medium Secure Unit (MSU). Method: Semi-structured interviews were conducted with six participants (psychologists working in a MSU) and the transcripts were subjected to lnterpretative Phenomenological Analysis (IPA). Results: Three super-ordinate themes emerged from the data with sub-ordinate themes: 'being human together', 'the matryoshka doll of containment' and 'the psychologist as an empowerer in a disempowering system'. The research identified that the participants in the study described experiences of relating to service users at a humanistic level, their experiences of feeling contained, and being a facilitator of containment. The narratives also captured the experiential claims of service users being in a disempowered system but also the psychologists being a facilitator of empowerment. Conclusions: The recommendations that arose were placed within literature and the methodological limitations of the study. They were centered on how services and psychologists can aid service users' engagement in psychological therapies, within MSU

Chemically diverse polyacrylate and polyacrylamide surfaces for human cardiomyocyte culture and their effect on phenotype

Human pluripotent stem cell (hPSC) derived cardiomyocytes can provide robust in vitro models for pharmaceutical drug screening and modelling cardiac disease. To fully realise these potentials, hPSC-cardiomyocytes must be reproducibly cultured to a more mature state than has thus far been achieved. Defined and well controlled culture conditions underpin the ability to derive hPSC-cardiomyocytes of consistent quality. These include cell source, culture medium and substrate. This thesis is concerned with the latter; culture substrates are currently biological in nature creating inherent variability in culture conditions. There is limited knowledge on the interaction between cardiomyocytes and synthetic, non-biological substrates making rational design of materials impractical. To aid discovery of novel culture substrates, 115 polyacrylate and polyacrylamide substrates were microarrayed and investigated using a parallel screening approach. The use of polyacrylates and polyacrylamides as biomaterials has been demonstrated previously, including contact lenses, bone cements and hydrogels to support cells. The diverse chemistry exhibited across the range of polymers enables modelling of structure-activity relationships between substrate chemistry and cardiomyocyte behaviour. Cardiomyocytes derived from human embryonic stem cells (hESC) were cultured on the microarrays in the presence and absence of serum. Attachment density (nuclei count via DAPI staining) and cardiomyocyte spread (surface area using sarcomeric α-actinin immunostaining) on each substrate was acquired by automated fluorescence microscopy and image analysis software. From this primary screen, 70 % of polymers were found to support cardiomyocytes adhesion in serum conditioned arrays, BM34 (fufuryl methacrylate) supported the highest relative cell density (0.59 ±0.28) and also the largest cell size (1364 ±937 µm2), which was comparable to gelatin control. In serum free conditions, only 10 % of polymers supported cardiomyocyte attachment. The highest relative cell density was on AM38 (Dimethylamino-propyl acrylate) and largest cell size on BM49 (Tert-butylamino-ethyl methacrylate), 274 ±75 µm2, which was significantly lower than cell density and cell area (2019 ±596 µm2) on gelatin control. To investigate if synergy exists between polymers that enable adhesion in serum free conditions and those that support larger cell areas in serum conditioned arrays, 24 polymers were mixed pair-wise to form second generation microarrays comprising of 576 co-polymers. This diverse library enabled unique combinations of chemical moieties to be explored and co-polymers were found to have a greater proportion (74 %) that supported cardiomyocyte attachment in serum free conditions, largest average cell size was now 1089 ±260 µm2 on BM80/AM64 (Methacryloyloxy)ethyl acetoacetate/ Hexadecafluoro-9-(trifluoromethyl)decyl acrylate). Five co-polymers were chosen to perform more detailed characterisation of cardiomyocytes cultured on them for 5 and 25 days. Electrophysiological profiling and quantification of myofibril organisation identified co-polymers AD17/BM54 (Hexanediol ethoxylate diacrylate/ Ethoxyethyl methacrylate) and BM80/AD17 to be comparable to control gelatin. Partial least squares multivariate regression analysis correlated chemical species from the polymeric substrate, identified using time of flight secondary ion mass spectrometry, with cardiomyocyte response and identified moieties beneficial or detrimental for cardiomyocyte adhesion and cell area. This may aid rational design of tailor-made non-biological substrates for cell culture. In summary, the parallel screening of co-polymers of acrylates and acrylamides has been the first step in a discovery process of lead materials capable of progressing the culture of cardiomyocytes in more reproducible, economical and defined conditions. Only five substrates were analysed in detail, leaving a large library of co-polymers worthy of further investigation, including the physical properties of the polymers that need to be considered for practical use of the polymers in culture

Study of pulmonary functions in male current smokers and never smokers

Background: Cigarettes smoking is the principal cause of preventable disease, disability, and premature death in the world. Tobacco smoking affects multiple organ systems resulting in numerous tobacco-related diseases. The study aimed to investigate interrelationship of pulmonary functions between current smokers and never smokers. Methods: Asymptomatic, 50 males current tobacco smokers and 50 healthy never smokers aged between 25 to 50 years were selected as cases and controls. Detailed description of the subject’s selection, data collection and methods used for performing the test. Results: Maximum incidence was seen in >31 yrs of age with mean of 38.681±4.5. The study found that never smokers had significantly higher pulmonary functions as compared to current smokers:- FVC in liters (3.43±0.55 Vs 2.44±0.58; p<0.05); FEV1 in liters (2.86±0.57 Vs 1.76±0.32; p<0.05); FEV1/FVC in percentage (82.72±8.67 Vs 73.72±11.40; p<0.05); FEF 25-75 ratio in percentage (3.18±0.91 Vs 1.60±0.45; p<0.05); PEFR in liters per second (6.63±2.00 Vs 3.16±1.26; p<0.05); breath holding time in seconds (25.54±2.14 Vs 21.36±2.10; p<0.05); 40mm endurance test in seconds (22.36±1.58 Vs 17.70±2.01; p<0.05); MEP in mmHg (83.48±5.28 Vs 64.38±5.31; p<0.05) were found significant. Conclusions: The strong relationship between cigarette smoking and respiratory disease has been seen independent of the other risk factors in a number of well-designated epidemiologic studies. Spirometry is an excellent screening test to detect chronic airflow obstruction, but may be useful in detecting restrictive disorders as well to study the effect of tobacco smoking on pulmonary functions