Catalytic Functionalization of Organoaluminum Reagents and Olefins by Cross-Coupling with Copper and Nickel

This thesis is divided into two parts. The first part focuses on the Cu-catalyzed cross-coupling of organoaluminum reagents with organohalides. One of the most powerful tools for the construction of C-C bonds is cross-coupling. But, this reaction is predominantly catalyzed by Pd, a rare and expensive transition metal, which inevitably makes the process unsustainable in the long-term. Furthermore, Pd-catalyzed cross-coupling also shows low tolerance for alkyl and heteroaryl substrates because of β-hydride elimination and catalyst deactivation, respectively. Although these issues remain largely solved by using sterically hindered and electron-rich ligands, however making these types of ligands is synthetically challenging and often involves multi-step processes. As such, the use of these ligands in large scale productions is also cost-prohibitive. In order to alleviate these problems, we have developed the cross-coupling reaction with Cu, an earth-abundant and inexpensive transition metal. Regarding this, we have been able to discover the Cu-catalyzed coupling of alkyl-, aryl- and alkynylaluminum reagents with organohalides. This Cu-catalyzed cross-coupling does not suffer from β-hydride elimination and no rearrangement is seen when secondary alkylaluminum reagents are used. It also shows tolerance with heteroaromatic substrates. Unexpectedly, no ligand is needed when heteroaryl halides are used for cross-coupling. We have also conducted mechanistic studies through radical clock experiments, competition experiments and kinetic studies, and proposed a catalytic cycle for the Cu-catalyzed coupling of organoaluminum reagents with aryl halides. These mechanistic studies designate that the reaction proceeds through an oxidative addition-reductive elimination pathway. The second part of this thesis is about the development of Ni-catalyzed regioselective dicarbofunctionalization of olefins in styrene derivatives by intercepting Heck C(sp3)-NiX intermediates with arylzinc reagents. This method utilizes a readily removable imine as a coordinating group that plays a dual role of intercepting oxidative addition species derived from aryl halides and triflates to promote Heck carbometallation, and stabilizing the Heck C(sp3)-NiX intermediates as transient metallacycles to suppress β-hydride elimination and facilitate transmetalation/reductive elimination steps. This approach affords diversely-substituted 1,1,2-triarylethyl products that occur as structural motifs in various natural products and bioactive molecules like cassigarol B, 4-[1-(p-hydroxyphenyl)-2-phenylethyl]phenoxyacetic acid, etc

Simple method devised for rapid isolation and identification of Vibrio cholerae from water resources of Sunsari District, Nepal

Cholera is a gastrointestinal disease caused by pathogenic strain of Vibrio cholerae, the disease clinically manifested by rice-water diarrhea, nausea and vomiting. This study aimed to study the incidence of Vibrio species and employ simple method for rapid detection of Vibrio cholerae from water samples of Sunsari, Nepal. Identification of V. cholerae through biochemical tests requires extensive labor and costs. In resource limited laboratories, isolation and identification of V. cholerae often becomes difficult. Therefore, this study also aimed for selecting scope of this methodology as a scientific outcome for rapid isolation and identification of Vibrio cholerae. A total of 100 water samples were collected from Sunsari district in which 25 samples were collected from sewage, 25 from pond, 25 from tap and 25 from tube well. The samples of collected water were sent to the microbiology laboratory of Central Campus of Technology maintained in ice cold box and were enriched in Alkaline Peptone water and selectively isolated from TCBS agar and NA agar without NaCl. Pathogens were isolated and identified by conventional microbiological techniques. Out of 100 water samples collected, sucrose fermenting Vibrio species were isolated only from 16 water samples. Further the selective isolation of V. cholerae from nutrient agar without NaCl isolated 6 isolates from sewage samples and 3 isolates from pond samples. The distribution of Vibrio cholera in the water sample was found to be 9%, distribution of V. alginolyticus was found to be 4% and distribution of V. fluvialis was found to be 3%. In this study, non-sucrose fermenting Vibrio species were not isolated from the water samples. However, sucrose fermenting Vibrio species was obtained with yellow pigmentation in TCBS agar medium. The yellow pigmented colonies of Vibrio isolates recovered from TCBS and even from Nutrient Agar devoid of sodium chloride provided sufficient evidence of V. cholerae after series of other biochemical tests. This study concludes that yellow colonies (sucrose-fermenting) of Vibrio from TCBS agar medium that can grow on nutrient agar without added NaCl and which exhibit a positive oxidase reaction can be confidently identified as presumptive V. cholerae. In resource-constrained environments, this simple method can reduce the labor cost, chemicals and time-consuming procedure of performing multiple biochemical and molecular assays for identification

Epidemiological pattern of corneal foreign bodies and utilization of protective eye devices: a hospital-based cross-sectional study

Introduction: A corneal foreign body is the most common occupational ocular injury that can cause secondary infection or scars on the visual axis, decreasing vision. The study aimed to find out practices of wearing protective eye devices in the workplace and the factors influencing the utilization of such devices among patients with corneal foreign body (CFB) injury. Methods: This cross-sectional study was conducted in a tertiary eye hospital in Bhaktapur from April 2021 to August 2021. All patients with CFB attending the hospital were included in the study. CFB was removed with ocular examination under a slit lamp biomicroscope, and face-to-face interview was conducted. Results: Among 142 patients, only one was female, and 41.5% had a previous history of CFB. The most common CFB particle was metallic (n=124, 87.3%),. Three-fourths (75.1%) of patients were not using eye-protective devices at the time of injury, and 45.1% tried physically removing the CFB in a harmful way. Nearly two in five (19.7%) had used topical antibiotics eye drops before presenting for CFB removal. Sixty-six (46.5%) reported never wearing any protective eye devices, and the main reason for not-wearing was the unavailability (48.4%) of such devices in their workplace. The awareness of the need for protective eye devices (p<0.001) was significantly associated with using protective eye devices during work. Conclusion: The workers should be made aware of the consequences of harmful practices following CFB injury. The workers should wear protective eye devices to minimize the risk of ocular injury and consequent visual impairment

Temporal mapping and analysis

A compositing process for selecting spatial data collected over a period of time, creating temporal data cubes from the spatial data, and processing and/or analyzing the data using temporal mapping algebra functions. In some embodiments, the temporal data cube is creating a masked cube using the data cubes, and computing a composite from the masked cube by using temporal mapping algebra

GENETIC VARIABILITY, HERITABILITY AND GENETIC ADVANCE ESTIMATES IN MAIZE (ZEA MAYS L.) GENOTYPES IN NEPAL

Eleven early maize and ten winter maize  genotypes were evaluated in randomized complete block design (RCBD) with three replications at the research field  of Regional Agricultural Research Station (RARS), Lumle, Kaski and National Maize Research Program (NMRP), Rampur, Chitwan, Nepal respectively  to assess the magnitude of genetic variability, heritability and genetic advance for yield and yield contributing traits during summer (Kharif) and winter (rabi) seasons of 2016-2017. Analysis of variance revealed significant differences for 10 characters studied among the genotypes. The phenotypic coefficient of variation (PCV) is higher than genotypic coefficient of variation (GCV) recorded for all traits. High GCV and PCV was recorded for grain yield, thousand kernel weight and ear height. Heritability was  moderate to high  except thousand kernel weight in Kharif whereas number of kernel per ear showed lowest heritability in winter season. Genetic gain as percentage of mean (GAM) was greater for grain yield, thousand kernel weight, plant height and ear height.  As grain yield had higher genetic advance along with high heritability in both the seasons that indicated the presence of large proportion of additive gene action for deciding this trait

A retrospective study of the effect of modified multi-drug therapy in Nepali leprosy patients following the development of adverse effects due to dapsone.

INTRODUCTION: Dapsone Hypersensitivity Syndrome (DHS) occurs in approximately 2% of leprosy patients in Nepal. DHS and other adverse effects of dapsone lead to withdrawal of the drug. METHODS: We reviewed the notes of patients who had dapsone withdrawn from their multi-drug therapy (MDT) following an adverse reaction to the drug between 1990 and 2007. RESULTS: 105 patients were identified from the database and 67 had a documented completion of a modified course of MDT. The majority were treated with rifampicin and clofazimine. All 36 individuals who were slit-skin smear positive had a satisfactory fall in their mean bacterial index. There were no cases of relapse. CONCLUSIONS: Rifampicin and clofazimine appear to be satisfactory treatment for both paucibacillary and multibacillary patients who have to have dapsone stopped because of severe adverse effects

Uropathogenic Escherichia coli in urinary tract infections: A review on epidemiology, pathogenesis, clinical manifestation, diagnosis, treatments and prevention

Urinary tract infections (UTIs) are common pathological conditions observed in hospital settings and communities. Uropathogenic Escherichia coli (UPEC) is the causative agent of most of the UTIs, such as pyelonephritis and cystitis. The infectious complications may cause acute renal failure affecting both the healthy and renal transplant patient's. The untreated patients with UTI may exhibit septicemia and bacteremia. Furthermore, the multidrug resistance patterns of UPEC may result in severe septic shock. Factors that contribute to the pathogenesis of UPEC include; secreted proteins, haemolysins, capsule, lipopolysaccharides, biofilm, fimbriae adhesions and iron acquisition systems. In spite of several host protection mechanisms; however, UPEC may persist inside the urinary tract and serve as a reservoir of recurrent infections and complications. Early diagnosis and prompt treatment of UTI with broad spectrum antibiotics are essential before this infection causes other medical complications. Generally, in clinical settings, diagnosis of UTIs involves bacterial culture and antibiotic susceptibility assay, in addition to other medical examinations, which aid the physicians to prescribe the appropriate drugs and measures during UTIs treatments. This review aims to understand the epidemiology, pathogenesis, clinical manifestation, diagnosis, treatment and preventive measures of UTIs caused by the uropathogenic E. coli

Varietal evaluation of promising maize genotypes

The selection efficiency can be broadened for certain traits using estimates of genetic parameters, which are fundamental for plant breeding. The present study was carried out with ten maize genotypes grown in October, 2016 to April, 2017 using randomized complete block design with three replications at research field of National Maize Research Program, Rampur, Chitwan, Nepal. The objective of this study was to estimate the variability and correlation of agro-morphological traits in maize genotypes. Variation was observed for all the growth, phenology, yield and yield attributing traits among the genotypes. The genotypes, ZM-627 (4984 kg ha-1) and Across9942/Across9944 (4523 kg ha-1) were identified as promising genotypes. Grain yield had significant positive correlation for ear length, number of grains per row, number of ears per plot and thousand grains weight. Path analysis showed that ear height, days to 50% tasseling, anthesis-silking interval, ear length, ear diameter, number of grain rows per ear, number of grains per ear, number of ears per plot and 1000 grains weight had direct and positive effects on grain yield. Moderate to high estimates of GCV, PCV, heritability and genetic advance were found for plant height, ear height, thousand kernels weight, tasseling days, anthesis- silking interval and grain yield. Therefore, these traits can be used as selection indices for indirect selection for the improvement of maize productivity

Economics of potato (Solanum tuberosum L.) production and marketing in Darchula district of Nepal

The potato (Solanum tuberosum) is a popular root vegetable that is grown all over the world. Potato production is popular in Nepal because of its greater adaptability, high yield potential, and high demand, contributing 6.57 percent to AGDP and 2.17 percent to GDP. In Nepal, it is grown on 197,037 hectares (ha) with a yield of 13.13 metric tons per hectare and a total production of 2,586,287 metric tons. The major objective of our research was to analyze the economics and marketing state of potatoes in Api-Himal rural municipality Darchula, Nepal where a survey on potato production and marketing was conducted. A total of 60 households were randomly sampled and interviewed as the primary source of information for the research. For the residents of Api-Himal RM, there are few options for sustenance and revenue generation. The area is ideal for potato farming, and potato trading has a direct impact on rural communities' livelihoods. The B/C ratio was found to be 1.62 in the research area. The average cost of potato production was Rs. 2,67,319 while the average return was Rs. 4,32,804. The research focuses on the marketing and production of potatoes from the growers to the final customers. Low yield, insect and disease infestation, and a lack of government support are among the issues. To promote the production and marketing of potatoes, availability of improved technology, an extension of technical knowledge, efficient management of marketing channels and substantial financial support by the government as well as local bodies are recommended