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192 results on '"Yahaya, N. A."'

5. Cyclometallation at Pd, Mn and Co : functionalisation of C-H and C≡C bonds involving cyclisation, rearrangement and isomerisation processes

Author

Yahaya, N. P., Fairlam, Ian, and Duckett, Simon

Subjects
541
Abstract

This thesis describes cyclometallation at Pd, Mn and Co: functionalisation of C H and C≡C bonds involving cyclisation, rearrangement and isomerisation processes. The use of NaNO2/NaNO3 as an oxidant in oxidative Pd-catalyzed processes has recently been reported as a complementary co-catalyst to other common oxidants (e.g. CuII/AgI salts). In view of this (Chapter two) the synthesis of a series of palladacyclic complexes containing a C^N ligand backbone, and the geometry and linkage isomerism at NO2 Pd, has been studied. The geometry about the Pd(II) centre shows the crucial role played by bulky ligands in creating hindrance and affecting phosphine dissociation. Mn-catalysed C-H bond activation is a powerful strategy for the functionalisation of organic compounds containing metal-directing groups. Chapter three of this thesis reports the characterisation of a highly reactive 7-membered MnI species which acts as anvil point between protonation and reductive elimination to deliver alkenylated and/or pyridinium products respectively. Both processes are exemplified through the reactions of a substrate containing a 2-pyridyl directing group and electron-deficient 2-pyrone motif at MnI, where C-H bond activation occurs regioselectively at C3 within the 2-pyrone. An unprecedented regioselective Diels-Alder reaction also occurs on both the pyridine and 2-pyrone ring systems. These findings provide a unique insight into MnI-mediated C-H bond activation processes, especially how relatively minor changes in substrate structure influence the product distribution. The study shows that MnI-based metallocycles warrant further study more generally in organic and organometallic chemistry The intermolecular Pauson-Khand (PK) reactions of sterically comparable (2-pyridylethynyl)-heteroaromatic compounds with norbornene, mediated by Co2(CO)8 to give cyclopentenone products, were examined in Chapter four of this thesis. The π-deficient heteroaromatic substrate, 2-pyrone, favoured the -position while the π-rich heteroaromatics such as 2-thiophene favour the β-position. The position of the nitrogen in pyridyl-containing alkyne substrates also affects the regiochemical outcome of the PK reaction. A 2-pyridyl alkyne, possessing a proximal nitrogen atom, influences the regioselectivity relative to a 4-pyridyl variant, quite dramatically, favouring the β-position in the newly formed cyclopentenone ring. Overall, the type of heteroaromatic group greatly influences PK regioselectivity. The PK cycloadducts undergo a 6π-electrocyclisation–oxidative aromatisation reaction in the presence of light, which is promoted by a LED UV-light controlled system, affording benzo[h]indeno[1,2-f]isochromene type products.

Published
2016

7. Enhancing Students' HOTS in Laboratory Educational Activity by Using Concept Map as an Alternative Assessment Tool

Author

Ghani, I. B. A., Ibrahim, N. H., Yahaya, N. A., and Surif, J.

Abstract

Educational transformation in the 21st century demands in-depth knowledge and understanding in order to promote the development of higher-order thinking skills (HOTS). However, the most commonly reported problem with respect to developing a knowledge of chemistry is poor mastery of basic concepts. Chemistry laboratory educational activities are shown to be less effective in developing an optimum conceptual understanding and HOTS among students. One factor is a lack of effective assessment and evaluation tools. Therefore, the primary focus of this study is to explore concept maps as an assessment tool in order to move students' thinking skills to a higher level during laboratory learning activities. An embedded mixed method design is used in this study, which has also employed a pre-experimental research design. This design triangulates quantitative and qualitative data, which are combined to strengthen the findings. A low-directed concept mapping technique, convergence scoring method, and pre-post laboratory concept map were used in this study. An electrolysis HOTS test was used as the research instrument in order to measure the level of student achievement with respect to high-level questions. In addition, the thought process that is involved when students construct concept maps has been explored and studied in detail by utilising a think-aloud protocol. Results showed a positive development towards understanding and higher level thinking skills in students with respect to electrolysis concepts learned through chemistry laboratory activities. An investigation of the students' thinking processes showed that high-achieving students were more capable of giving a content-based explanation of electrolysis and engaged in monitoring activities more often while building a concept map. Nonetheless, all categories of students managed to show a positive increase in the activities of explanation and monitoring during the construction of concept maps after they were exposed to the assessment tool in the laboratory learning activities. In conclusion, the assessment activity using concept maps in laboratory learning activities has a positive impact on students' understanding and stimulates students to increase their HOTS.

Published
2017
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14. A Simple Insulated Monopole Sensor Technique for Determination of Moisture Content in Hevea Rubber Latex

Author

Ansarudin F., Abbas Z., Hassan J., Yahaya N. Z., and Ismail M. A.

Subjects
reflection coefficient, phase shift, relative error, Mathematics, QA1-939
Abstract

This paper describes the application of a SMA stub contact panel as an insulated monopole sensor for determination of moisture content in hevea rubber latex. Comparison results between measured and calculated reflection coefficient using King’s model are presented. Calibration equations relating moisture content to phase shift have been established in the frequency range from 100 MHz to 5 GHz. The accuracy of the technique was 1.3% when compared to actual moisture content obtained using the gravimetric method.

Published
2012
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24. Online reciprocal peer tutoring approach in Facebook: Measuring students' critical thinking

Author

Zulkifli, N.N.B., Abd Halim, N.D., Yahaya, N., Meijden, H.A.T. van der, Mohd Zaid, N., A Rashid, A.H., Hashim, S., Zulkifli, N.N.B., Abd Halim, N.D., Yahaya, N., Meijden, H.A.T. van der, Mohd Zaid, N., A Rashid, A.H., and Hashim, S.

Abstract

Contains fulltext : 246434.pdf (Publisher’s version ) (Open Access), Critical thinking skills are one of essential employability skills for graduates when entering the workforce. The lack of critical thinking skills among Malaysian graduates is a concern as these skills are important for success in the 21st century. Therefore, this paper aims to study the effects of online reciprocal peer tutoring (RPT) through Facebook discussion on students’ critical thinking. In this study, the online RPT approach in Facebook was used to nurture students to think critically. In RPT, the tutor role is switched between participants in each task, giving equal opportunities to all learners to benefit from the tutor and tutee role. This approach was integrated into their learning for 4 weeks to increase students' critical thinking. During the learning process, they need to involve in 4 critical thinking tasks based on Bloom's taxonomy. 29 undergraduate students from the school of education, Faculty of Social Sciences and Humanities at Universiti Teknologi Malaysia completed the validated instrument, Watson-Glaser Critical Thinking Appraisal test (inference, assumption, deduction, interpretation, evaluation arguments) before and after the treatment. The findings show that it is significantly different in making inference (Z=-3.85, p=.000<*.05) and deduction (Z=-3.627, p=.000<*.05) criterion in post-test. These revealed that students who engaged in the online RPT environment showed positive improvements in those criteria in critical thinking after the treatment. In conclusion, students’ critical thinking can be taught to students using Facebook with active learning strategies such as online RPT.

Published
2021

31. Patterns of critical thinking processing in online reciprocal peer tutoring through Facebook discussion

Author

Zulkifli, N.N.B., Halim, N.D.A., Yahaya, N., Meijden, H.A.T. van der, Zulkifli, N.N.B., Halim, N.D.A., Yahaya, N., and Meijden, H.A.T. van der

Abstract

Contains fulltext : 216278.pdf (publisher's version ) (Open Access), Reciprocal Peer tutoring (RPT) can support students in enhancing their critical thinking during learning process. The evolution of internet technology has shifted face-to-face peer tutoring to an online environment such as use of a social networking site, Facebook. In addition, Facebook Group provides a space for students and instructor to discuss academic related matters. However, depending solely on the Facebook medium without proper design learning activities do not guarantee active learning among students. In addition, educators might face multiple challenges by using social networking site such as Facebook for teaching and learning purpose. Thus, this study integrated online reciprocal peer tutoring arrangements in Facebook to stimulate students' critical thinking. A total of 29 students involved in the online discussions through Facebook with 14 Facebook Group pages were created. During discussion, tutor will used guided peer questioning strategy initiate tutee to think to the higher levels. This study employed lag sequential analysis to empirically explore patterns of critical thinking processing in Facebook discussions among High and Low critical thinking groups. The results showed that, apparently, High critical thinking group emerged thinking pattern which progressing from lower to higher order thinking processes which are very crucial in shaping their thinking to the higher levels. Additionally, by asking students' prior knowledge and understanding frequently can help students to gain greater understanding of the topic and further initiate their higher level of critical thinking.

Published
2020

32. Corrosion study of pipeline material for seabed sediment in tropical climate

Author

Budiea, A M A, Yahaya, N, Noor, N M, Abdullah, A H, W Ibrahim, M H, Suratkon, A, Muthusamy, K, Budiea, A M A, Yahaya, N, Noor, N M, Abdullah, A H, W Ibrahim, M H, Suratkon, A, and Muthusamy, K

Abstract

Corrosive environments such as marine sediments can cause corrosion to steel pipelines at any time when certain conditions are met. Seabed sediment could cause severe corrosion damage due to its corrosiveness to the pipelines buried under it. Many consequences could take place in case if there is incident in oil/gas pipelines. Successfully identifying elements of corrosion in marine sediment would enhance the future of steel structure protection and monitoring systems. This article focuses on the behaviour of corrosion rate of steel located near shore environment and the aim is to determine the effect of sediment on corrosion of steel. To investigate that, simulated near shore sediment conditions have been used where the steel coupons buried in sediments which have different characteristics. Weight loss technique has been implemented to determine the weight loss rate of the steel specimens. Based on the results of this study, metal weight loss increases as the duration of exposure to seabed sediment environment become longer. The sea sediment simulated condition has given significant levels of corrosion. Conclusively, the corrosion rate of steel in seabed sediment located in tropical region is complicated and further studies are suggested.

Published
2020

34. My_Atmos: Novel Method to Analyse Ultrafine Particles Using an Artificial Intelligence Approach

Author

Yahaya, N. Z., Tight, Miles R., Tate, James E., and Ibrahim, Zul Fadhli

Subjects
Algorithm, Earth sciences, atmospheric environment data, ddc:550, Stochastic Boosted Regression Trees (BRT), variable interactions
Abstract

This presentation will discuss the used of an artificial intelligent method namely the ‘stochastic boosted regression trees’ (BRT) approach that uses an algorithm that applied to an air pollution data namely particle number count concentrations ([PNC]), an ultrafine particles data and particulate matter data case study in United Kingdom and Malaysia. The development of the BRT model involves determining the model algorithm settings of the main model input parameters (learning rate, number of trees and interaction depth) that were tested using the R software (version 3.02) by choosing a10-fold cross-validation approach with combination of lr 0.05 and tc 5 of training set for BRT models. It was found, that the coefficient of determination (R2) value for the BRT best iteration models were above 0.60 for [PNC] in urban environment. The fine and course particle number (FPNC and CPNC) were found to be 0.75 and 0.72 respectively for one of coastal dataset while R2 value of 0.78 and 0.85 were obtained for Malaysia data. Further investigated were performed to rank factor influenced. It was found, that Carbon monoxide (30.28 %) gas and followed by temperature (16.81%) and wind direction (16.4%) were found the high factor influenced PM10 in urban environment. The interaction index (H-index) between parameters to concentration of pollutants were also examined graphically and in numerical form (H-Index). It was found that the H-Index between parameters 0.3 to 0.4 indicated that the BRT technique able to explain the science of air pollution. The consistent results to produce the best model from the best iteration, able to rank the best parameters that influence most to the concentration of predictor and able to predict interaction between variables premise BRT as one of the method or tools to analyse air pollution data.

Published
2019
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35. Zoochemical Screening and Antimicrobial Potential of Ground Beetle (Carabidae)

Author

Sakina Aa, Yahaya N, Haassan A, and Muhammad S

Subjects
chemistry.chemical_classification, Traditional medicine, Glycoside, medicine.disease_cause, Antimicrobial, medicine.disease, Typhoid fever, Terpene, chemistry, Staphylococcus aureus, medicine, Agar diffusion test, Antibacterial activity, Escherichia coli
Abstract

Insects and their substances have been used as medicinal resources by different cultures since ancient time because of chemical compounds such as pheromones, defensive sprays, venoms and toxins, which were sequestered from plants or prey and later concentrated or transformed for their own use. This study is aimed at determining zoochemical and antibacterial potential of ground beetle (Carabidae). The Clinical bacterial isolates used are Methicillin-Resistance Staphylococcus aureus (MRSA), Salmanylla typhi, Yersinia pestis and Escherichia coli. The results of zoochemical screening of methanol extract revealed the presence of carbohydrates, steroids/triterpenes, alkaloids, saponins, tannins and flavonoids, while antraquinones and cardiac glycosides were not detected. The results of antibacterial activity revealed that methanol extract showed higher antibacterial activity than n-hexane extract. The methanol extract showed following zone of inhibition on E. coli (23.33 ± 1.52), Y. pestis (13.66 ± 0.57), S. typhii (16.00 ± 1.00) and MRSA (9.67 ± 0.57) at 10 mg/mL, while that of n-hexane showed the following zones of inhibition against E. coli (11.33 ± 0.57), Y. pestis (11.66 ± 0.57), S. typhii (29.00 ± 5.29) and MRSA (12.67 ± 0.57) at 10 mg/L. The MIC result ranged between 0.63-1.25 mg/mL for n-hexane extract and 0.63 - 2.50 mg/mL for methanol extract. The MBC of n-hexane extract ranged between 1.25 - 2.50 mg/mL while that of methanol extract ranges between 0.63 -2.50 mg/ Ml. The results suggested the potential use of the extract in the treatment of bacterial infections such as diarrhea, dysentery, typhoid fever, and enuresis.

Published
2019
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