Development of photoredox-catalysed transformation of enamides and allenamides

Enamides and allenamides are two versatile functional groups that offer a wide variety of alternatives for the inclusion of nitrogen-based moiety into an organic system. Nitrogen-containing structures are prevalent among medicinally interesting natural and unnatural products and, thus, are useful in developing new therapeutics. Their chemical utilities have been exploited by a number of research groups. They represent interesting functional groups and useful in organic synthesis. Photoredox catalytic approach was develop to synthetically transform enamides into useful products, N-acyl-N -aryl-N,N -aminals. A novel approach using iridium polypyridyl complex photoredox catalyst to initiate a three-component domino transformation of enamides to N-acyl-N -aryl-N,N -aminals via photoredox catalysed β-alkylation of enamide intermediates and their subsequent trapping with an arylamine was successfully developed. The N-acyl-N′-aryl-N,N′-aminal structural motif is prevalent within a wide range of biologically important compounds and have attracted considerable attention as building blocks for the synthesis of drug candidates. This method uses the addition of a radical precursor to an enamide, with subsequent interception of the cationic iminium intermediate with an arylamine. The reaction was found to be compatible with both electron-rich and electron-deficient arylamines, and moderate to good levels of diastereoselectivity were attained using a chiral enamide. The N-acyl-N -aryl-N,N -aminals formed were used as precursors to synthesis of valuable γ-lactams building blocks under a mild condition by cyclization. The γ-lactams were obtained by intramolecular cyclization of the N,N -aminals with the lone pair of the nitrogen atom of the arylamine as the nucleophilic centre attacking the electrophilic carbon of the carbonyl carbon of the ester in the molecule. This is a novel synthetic route to these valuable γ-lactams. The photoredox reaction procedure developed was also applied on allenamides. There are limited reports of radical reactions on allenamides, the major and seemingly single intermolecular radical cyclization involving allenamides was the one reported by Hsung. There are no reports of radical photoredox reactions on allenamides in the literature. The addition reaction was initiated by the electrophilic malonate radical generated by irradiation with blue light in the presence of iridium photoredox catalyst. The malonate radical attacked the central carbon of the allenic group which led to the formation of β-alkyl allenamide radical that was oxidized to an iminium ion intermediate. The iminium intermediate was subsequently trapped with an arylamine giving rise to α,β-addition product (N-acyl-N -aryl-N,N -aminals) with exo-methylene or β,γ-addition product leading to the formation of double bond substituted enamides. It was found that the α,β-adduct product is more favourable, however, the alternative product was formed when the α-position is sterically hindered by the substituents on the allenamide or the arylamine nucleophile

A Three-Parameter Gompertz-Lindley Distribution: Its Properties and Applications

This research proposed a three-parameter probability distribution called Gompertz-Lindley distribution using Gompertz generalized (Gompertz-G) family of distributions. The mathematical properties of the distribution such as moment, moment generating function, survival function and hazard function were derived. The parameters of the distribution were estimated using the method of maximum likelihood and the distribution was applied to model the strength of glass fibres. Gompertz-Lindley distribution performed best (AIC = 62.8537) when compared with other generalizations of the Lindley distribution. Keywords: Gompertz distribution, Lindley distribution, moment, survival function, hazard function DOI: 10.7176/MTM/9-4-04 Publication date: April 30th 2019

TRAIT ANXIETY, SEX, AGE AND DENTAL TREATMENT EXPERIENCE AS DETERMINANTS OF DENTAL ANXIETY AMONG CHRONIC DENTAL PATIENTS IN NIGERIA

Objectives - To investigate the influence of trait anxiety, sex, age andprevious dental treatment experience on dental anxiety.Design - The study utilised a cross-sectional survey design. Independentvariables are trait anxiety, sex, age and dental treatment experience.Dependent variable is dental anxiety.Setting - The dental centre of a teaching hospital in Nigeria.Participants - Data were collected from 255 (115 male and 140 female)respondents selected through purposive sampling technique. The mean agewas 28.59 years (SD=10.74 years).Results: This study revealed that respondents with high trait anxiety levelsreported significantly higher dental anxiety (t (253) =- 5.78, p <.01) thanthose with low trait anxiety. Male respondents reported significantly lowerdental anxiety (t (253) = -3.04, p < .05) than the females.Conclusion: Trait anxiety dispositions and sex are important predictors ofdental anxiety and should be taken seriously in the management of dentalanxiety at the various secondary care dental centres

TRAIT ANXIETY, SEX, AGE AND DENTAL TREATMENT EXPERIENCE AS DETERMINANTS OF DENTAL ANXIETY AMONG CHRONIC DENTAL PATIENTS IN NIGERIA

Objectives - To investigate the influence of trait anxiety, sex, age andprevious dental treatment experience on dental anxiety.Design - The study utilised a cross-sectional survey design. Independentvariables are trait anxiety, sex, age and dental treatment experience.Dependent variable is dental anxiety.Setting - The dental centre of a teaching hospital in Nigeria.Participants - Data were collected from 255 (115 male and 140 female)respondents selected through purposive sampling technique. The mean agewas 28.59 years (SD=10.74 years).Results: This study revealed that respondents with high trait anxiety levelsreported significantly higher dental anxiety (t (253) =- 5.78, p <.01) thanthose with low trait anxiety. Male respondents reported significantly lowerdental anxiety (t (253) = -3.04, p < .05) than the females.Conclusion: Trait anxiety dispositions and sex are important predictors ofdental anxiety and should be taken seriously in the management of dentalanxiety at the various secondary care dental centres

Comparison of the Nature and Strategic features of Facilities Management and Other Building Support Practices in Lagos

This study examined the features of the Lagos-Nigerian Facilities Management (FM) practice and how strategic and value adding it is. This was achieved by comparing its principles, work focus and object amongst others, with that of four other traditional Building Support Service (BSS) practices. The research design was survey, carried out through self-administered questionnaires directed to a sample of 123 BSS providers that work with office buildings in Lagos metropolis. The data were analyzed using frequency counts, means, Chi square test and Wilcoxon sign rank test. The study revealed that the FM title is largely used only as a “catch phrase” by BSS providers, to enhance patronage. It further reveals that BSS providers that are addressed as facilities managers do not adopt FM principles in their practices. Also that the principles of property management was used predominantly amongst the respondents, while the main work focus of the maintenance manager was rated “most important”. These findings imply that there is insufficient knowledge of the strategic roles of FM among BSS practitioners and that they are still largely confused about its distinctive features and value adding benefit. This highlights the need for further education on the practice of FM and greater commitment to ensuring that it plays its distinctive strategic roles. Therefore, this paper recommends that relevant professional bodies and FM training institutions must provide training and re-training opportunities nationally and internationally, in order to enhance the knowledge base of the practice, particularly its strategic content. Furthermore, the FM training curriculum should incorporate more contextual issues. This will demonstrate that the difference between FM and other BSS practices is beyond nomenclature.Keywords:Building support services practices, Facilities management, Lagos-Nigeria, Strategic features of facilities management

Investigating Rain Attenuation Models for Satellite Links in Tropical Nigeria

The analyses of rain models for satellite communication links of Ku and Ka bands in Lagos, Nigeria is the focus of this paper. The choice of these frequency bands was informed by the acknowledged fact that satellite signal fading and outages are predominant at those bands. The ITU-R P. 618-12 is the globally adopted prediction model; temperate, equatorial and tropical regions, inclusive. However, there was need to review the suitability of this model especially as it concerned equatorial and tropical stations. Rainfall data spanning a period of three years were collected from Nigerian Meteorological Agency (NIMET). The ITU-R P. 618-12 model along with some renowned prediction models were analyzed and their performances with the locally recorded measurement data were compared to establish their suitability or otherwise. The results obtained suggested ITU-R P. 618-12 exhibited the overall best performance at 12 GHz while DAH showed best performance at 26 GHz, even as both models underestimated and overestimated the measurement at Ku and Ka bands respectively. Again, at both frequencies, SST presented the worst performances

Micro/nanoscale magnetic robots for biomedical applications

Magnetic small-scale robots are devices of great potential for the biomedical field because of the several benefits of this method of actuation. Recent work on the development of these devices has seen tremendous innovation and refinement toward ​improved performance for potential clinical applications. This review briefly details recent advancements in small-scale robots used for biomedical applications, covering their design, fabrication, applications, and demonstration of ability, and identifies the gap in studies and the difficulties that have persisted in the optimization of the use of these devices. In addition, alternative biomedical applications are also suggested for some of the technologies that show potential for other functions. This study concludes that although the field of small-scale robot research is highly innovative ​there is need for more concerted efforts to improve functionality and reliability of these devices particularly in clinical applications. Finally, further suggestions are made toward ​the achievement of commercialization for these devices

Prioritising Facilities Management Services for Benchmarking in Selected Cities in Nigeria

Due to the high cost of benchmarking, it is often difficult to provide required resources for it. Therefore, to benchmark successfully, it is often necessary to identify services that are most important for the efficiency of the organisation and prioritise them. This paper examines the facilities management (FM) services that are most in need of benchmarking in Nigeria. Data were collected through self-administered questionnaires that were sent to 120 facilities management organisations in Lagos metropolis, 50 in Abuja and 15 in Port Harcourt. The survey achieved a total response rate of 76% in Lagos, 58% in Abuja and 87% in Port Harcourt respectively. The five services that need benchmarking the most were found to be: utilities, maintenance, security, cleaning and waste disposal, property management and Information Technology in that order. Also, repeated measures analysis of variance results showed that the differences indicated in the respondents' rating of how important it is to benchmark these FM services is statistically significant. Kruskal Wallis test showed that there was difference in the importance of FM services for benchmarking based on professional affiliation of the FM. The study provided information on how to prioritise these services for benchmarking in order to conserve resources of Nigerian organisations

Photoredox approach to N-Acyl-N'-aryl-N,N'-aminals using enamides and their conversion to γ-lactams

A photoredox catalytic approach to synthetically valuable N-acyl-N'-aryl-N,N'-aminals is described. This method uses the addition of a radical precursor to enamides, with subsequent interception of the cationic iminium intermediate with an arylamine. The reaction has been shown to be compatible with electron-rich and electron-deficient arylamines, and moderate to good levels of diastereoselectivity can be attained using a chiral enamide. Furthermore, the N-acyl-N'-aryl-N,N'-aminal reaction products can be readily cyclized, providing a novel synthetic route to valuable γ-lactams