ANALYSES OF DENSELY CROSSLINKED PHENOLIC SYSTEMS USING LOW FIELD NMR

A uniform dispersion of reactants is necessary to achieve a complete reaction involving multi-components, especially for the crosslinking of rigid high-performance materials. In these reactions, miscibility is crucial for curing efficiency. This miscibility is typically enhanced by adding a third component, a plasticizer. For the reaction of the highly crystalline crosslinking agent hexamethylenetetramine (HMTA) with a strongly hydrogen-bonded phenol formaldehyde resin, furfural has been traditionally used as the plasticizer. However, the reason for its effectiveness is not clear. In this doctoral thesis work, miscibility and crosslinking efficiency of plasticizers in phenolic curing reactions are studied by thermal analysis and spectroscopic methods to elucidate the role of furfural. By combining information from NMR, infrared spectroscopy and differential scanning calorimetry, we show that the presence of furfural increases segmental mobility, disrupts the hydrogen-bonded matrix and frees the hydroxyl units, which further increases HMTA solubility. The higher solubility and segmental mobility increases the extent of crosslinking in the phenolic system. Extent of crosslinking is determined from the spin lattice relaxation time T1 measured by low field NMR (LFNMR). We demonstrate the effectiveness of this method for phenolic systems, where others methods like infrared spectroscopy and differential scanning calorimetry are inappropriate. For validation, we have also correlated extent of crosslinking with T1 using epoxy. The utilization of LFNMR in this work demonstrates its value for characterizing crosslinking of rigid thermosets. Two alternative plasticizers to furfural are substituted in these phenolic curing reactions because of their environmental friendliness: the non-reactive methyl benzoate and the reactive methyl anthranilate. Their effect on the extent of crosslinking is evaluated and compared with the traditional reactive plasticizers furfuryl alcohol and furfural

Pathomorphological changes in vital organs of buffaloes (Bubalus bubalis) naturally infected with leptospirosis

The pathological aspects of leptospirosis were studied in 7 buffaloes with a conclusive diagnosis of the disease, as confirmed by MAT. Main necropsy lesions in kindey included congestion, few shrunken/atrophied glomeruli, periglomerular infiltration of mononuclear cells, tubular degeneration and cast in tubular lumen were common findings. The hepatic lesions were characterized by distortion/disruption of hepatic cord, individualization of hepatocytes, varying degree of degenerative/necrotic changes in hepatocytes, presence of stray necrotic foci, mild congestion and mononuclear cell infiltration in portal areas. Pulmonary lesions comprised of congestion, focal area of alveolar edema, alveolar consolidation, emphysema, mononuclear cell infiltration in peri-bronchial/bronchiolar areas and foci of interalveolar thickened septae. Varying degree of congestion, lymphocytic depletion and hemosiderine pigment depositions were the histopathological features of splenic lesions

A STUDY TO EVALUATE OF TIME SINCE DEATH FROM POTASSIUM LEVEL OF VITREOUS HUMOUR

Introduction: Estimation of time since death plays a crucial roles in law enforcement agencies in most of the unnatural deaths. Estimation of post-mortem interval from changes of potassium level in vitreous humour is more diagnostic tool for forensic field. Material & methods: We prospectively studied 200 cases having known time since death for the present study at the Dept. of Forensic Medicine & Toxicology, Govt. Medical College, Surat in the year of 2015-2016. Level of potassium in vitreous humor in all subject were analysed in Bio-chemistry laboratory on the same day and various statistical tests performed. Observation: In this study age of the subjects were mostly from 26-35 years and predominantly male gender. Samples collected for this study were from 12-24 hours of post mortem interval with linear rise of potassium level in both eyes. Conclusion: Time since death was more accurately calculated with the help of potassium concentration of vitreous humour

Long-term outcomes of the global tuberculosis and COVID-19 co-infection cohort

Background: Longitudinal cohort data of patients with tuberculosis (TB) and coronavirus disease 2019 (COVID-19) are lacking. In our global study, we describe long-term outcomes of patients affected by TB and COVID-19. Methods: We collected data from 174 centres in 31 countries on all patients affected by COVID-19 and TB between 1 March 2020 and 30 September 2022. Patients were followed-up until cure, death or end of cohort time. All patients had TB and COVID-19; for analysis purposes, deaths were attributed to TB, COVID-19 or both. Survival analysis was performed using Cox proportional risk-regression models, and the log-rank test was used to compare survival and mortality attributed to TB, COVID-19 or both. Results: Overall, 788 patients with COVID-19 and TB (active or sequelae) were recruited from 31 countries, and 10.8% (n=85) died during the observation period. Survival was significantly lower among patients whose death was attributed to TB and COVID-19 versus those dying because of either TB or COVID-19 alone (p<0.001). Significant adjusted risk factors for TB mortality were higher age (hazard ratio (HR) 1.05, 95% CI 1.03-1.07), HIV infection (HR 2.29, 95% CI 1.02-5.16) and invasive ventilation (HR 4.28, 95% CI 2.34-7.83). For COVID-19 mortality, the adjusted risks were higher age (HR 1.03, 95% CI 1.02-1.04), male sex (HR 2.21, 95% CI 1.24-3.91), oxygen requirement (HR 7.93, 95% CI 3.44-18.26) and invasive ventilation (HR 2.19, 95% CI 1.36-3.53). Conclusions: In our global cohort, death was the outcome in >10% of patients with TB and COVID-19. A range of demographic and clinical predictors are associated with adverse outcomes

The role of Creative Accounting and its impact on the Credibility of Accounting Reports of Management

It was unclear whether or not investors and other stakeholders could trust the data presented in accounting reports and disclosures, which are intended to help them make educated judgements about the value of their holdings. Creative accounting is blamed for the failure of these relationships to live up to expectations. While many academics believe this technique is immoral and should be stopped, others argue that despite its role in contributing to business failures, investment losses, and economic crises, it is still a valid and important activity. This article evaluates how much this innovation has led to corporate failures, why these practises have emerged, and what obstacles they provide to accurate reporting and open disclosure from management. When compared to the findings of similar investigations, the present findings were different. According to research, underreporting of a company's financial performance is caused by accounting professionals being creative with their numbers. The inventiveness behind these methods is driven by avarice and serves to mislead the general public, potential investors, and shareholders while simultaneously increasing the rate at which firms fail. According to the research, however, the foundation for management's fake, aesthetic, and unjust reporting is a plethora of laws without proper controls, sanctions, and rewards.</jats:p

Modified wavelet-based pulse width modulation technique for cascaded H-bridge multilevel converter

Power electronics (PE) converters are crucial for providing a cost-effective, reliable, and efficient solutions for integrating renewable energy sources (RES) into the electrical grid. Over the years, many converter topologies have been developed for low, medium, and high voltage applications. However, they work more efficiently when appropriate modulation techniques are used. Many pulse width modulation (PWM) methods have been presented to decrease output harmonics, such as carrier-based (PWM methods, selective harmonic elimination (SHE), and nearest-level modulation (NLM). Regardless, these methods raise the complexity and expense of the converter, reduce the fundamental component, and increase high-frequency harmonics in the output signal. In the present work, a novel wavelet-based PWM (WPWM) method is developed for a multilevel converter. This mathematical modulation technique reduces the harmonic content at both low and high frequencies, improves the fundamental component in the output, and reduces switching losses. However, in multilevel converters, the gate pulses generated by WPWM are designed to only shape the output voltage without considering the load balancing between the DC sources or split capacitors. Hence, an additional load-balancing algorithm is necessary. This work proposes a new phase-shifting WPWM method that naturally balances load sharing between all the DC sources or split capacitors in the multi-level converter. This method operates at a low switching frequency, thereby keeping switching losses low, and reducing total harmonic distortion (THD). Moreover, since the proposed method is a mathematical closed-form PWM method, it can be evaluated within a finite number of iterations as compared to the open-ended SHE method. The proposed method is simple and runs efficiently in real-time, which enables fast system dynamics during transient conditions. Also, it does not depend on a minor computational time-step. Hence, it can be implemented on a low-cost digital controller. The validity of the proposed method is validated both by MATLAB/Simulink model, LTSpice model, and experimental tests. The results are discussed and compared against other PS-PWM methods to demonstrate the advantages of the proposed method.University of Ontario Institute of Technolog