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Effect of Electron Beam Irradiation on Polymers
Get PDFElectron energy loss spectroscopy (EELS) in combination with transmission electron microscopy (TEM) is widely used for chemical state analysis of variety of chemical compounds. High beam sensitivity of substances like polymers hinders the possibility of exploring in-depth analysis provided through the high spatially resolved EELS spectroscopy. In this study, the electron beam irradiation damage on polymers were analyzed with varying dose of electron beams. The stability of the polymers under electron beam exposure depends on the chemical structure on the polymers. In this study the polymers with and without phenyl groups namely Polycarbonate, Polyethylene terephthalate, Polystyrene, Styrene Maleic Anhydride and Polymethylmethacrylate are selected for the comparative degradation study. Effect of varying the electron dose on the stability of polymers were monitored by recording the low-loss EELS spectrum in π to π* transition and (π+σ) to (π+σ)* transition region
Epitaxial Lattice Matching and the Growth Techniques of Compound Semiconductors for their Potential Photovoltaic Applications
Get PDFThis paper presents the recent advances in semiconductor alloys for photovoltaic applications. The two main growth techniques involved in these compounds are metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), that has also been discussed. With these techniques, hetero-structures can be grown with a high efficiency. A combination of more than one semiconductor like GaAs, InGaAs and CuInGaAs increases the range of their electrical and optical properties. A large range of direct band gap, high optical absorption and emission coefficients make these materials optimally suitable for converting the light to electrical energy. Their electronic structures reveal that they are highly suitable for photovoltaic applications also because they exhibit spin orbit resonance and metal/semiconductor transitions. The dissociation energy has also been discussed in reference to the increased stability of these compounds
Genetic Algorithm Parameter Effect on 3D Truss Optimization with Discrete Variable
Get PDFThe Genetic Algorithm is one of the advanced optimization techniques frequently used for solving complex problems in the research field, and there are plenty of parameters which affect the outcome of the GA. In this study, a 25-bar truss with the nonlinear constraint is chosen with the objective to minimize the mass and variables being the discrete area. For the same, GA parameter like Selection Function, Population Size, Crossover Function, and Creation Function are varied to find the best combination with minimum function evaluation. It is found that the Uniform selection gives the best result irrespective of the creation function, population size or crossover functions. But this is at the cost of a large number of function evaluations, and the other selection function fails to reach the global optimum and has a smaller number of function evaluation count. If the analysis of selection function is done one at a time, it is seen that all Cases performs better in Roulette but, Case A which is non-integer type with 200 population size being computationally cheaper than Case B and C of population size 300. In the Tournament selection, Case A, B with smaller population size and Case C with higher population size performs better. Case C performs better at Remainder selection with smaller population size, and Case A and B for Stochastic Uniform with higher population size. And, it is clear that the function evaluation count increases with the population size in every Case from this study
Science Project-based Learning Integrated with Local Potential to Promote Student’s Environmental Literacy Skills
Get PDFThe learning process of science requires teaching which gives students the opportunity to be active in direct experience learning and thinking about the problems in real-life. However, science learning method that is widely used so far only conventionally, so it has not accommodated students in providing direct experience and solutions to real life problems. In order to realize the science learning that allows students to build their own understanding of real life problems, suitable learning model is needed and one of which is project-based learning. This research was conducted to know the effectiveness of science project-based learning which is integrated with natural potential of Baruppu’ in Junior High School students’ environmental literacy skills. Sample consisted of 50 students in grade VII of SMPN 1 Baruppu’. Quasi-experimental with Non-equivalent Control-Group Design was used to know the effectiveness of learning model in student’s environmental literacy skills: cognitive skill and environmental affect components. The study design consists of two groups: 26 students of class VIIA as experimental group and 24 students of class VIIB as control group. Data collected consisted of scores that measured cognitive skill and scores from environmental affect survey. Data analysed utilizing an independent samples t-test to determine any differences in environmental literacy skills between experimental and control groups after treatment. The result showed that the science project-based learning which is integrated with natural potential of Baruppu’ was effective to promoted student’s environmental literacy skills
Integer-valued Time Series Model via Generalized Linear Models Technique of Estimation
Get PDFThe paper authenticated the need for separate positive integer time series model(s). This was done from the standpoint of a proposal for both mixtures of continuous and discrete time series models. Positive integer time series data are time series data subjected to a number of events per constant interval of time that relatedly fits into the analogy of conditional mean and variance which depends on immediate past observations. This includes dependency among observations that can be best described by Generalized Autoregressive Conditional Heteroscedasticity (GARCH) model with Poisson distributed error term due to its positive integer defined range of values. As a result, an integer GARCH model with Poisson distributed error term was formed in this paper and called Integer Generalized Autoregressive Conditional Heteroscedasticity (INGARCH). Iterative Reweighted Least Square (IRLS) parameter estimation technique type of the Generalized Linear Models (GLM) was adopted to estimate parameters of the two spilt models; Linear and Log-linear INGARCH models deduced from the identity link function and logarithmic link function, respectively. This resulted from the log-likelihood function generated from the GLM via the random component that follows a Poisson distribution. A study of monthly successful bids of auction from 2003 to 2015 was carried out. The Probabilistic Integral Transformation (PIT) and scoring rule pinpointed the uniformity of the linear INGARCH than that of the log-linear INGARCH in describing first order autocorrelation, serial dependence and positive conditional effects among covariates based on the immediate past. The linear INGARCH model outperformed the log-linear INGARCH model with (AIC = 10514.47, BIC = 10545.01, QIC = 34128.56) and (AIC = 37588.83, BIC = 37614.28, QIC = 37587.3), respectively
Phytominerals and Phytochemical Studies of Azadiracthta indica, Leea guineensis and Parkia biglobosa Leaves
Get PDFMedicinal plants have great importance in African medicine and are also used as precursors in drug discovery. The medicinal value of plants lie in their bioactive constituents which usually allow them to fight against several diseases. Plant-based natural constituents can be derived from any part of the plant like bark, leaves, flowers, roots, fruits, seeds. The mineral and phytochemical analysis of the leaves of Azadirachta indica, Parkia biglobosa and Leea guineensis were investigated. The leaves were collected from the Herbal Garden, Forestry Research Institute of Nigeria, Jericho hills, Ibadan, Nigeria and identified at Forest Herbarium Ibadan. Oyo State. The leaves were air dried and milled to powder using a medium-sized milling machine and stored in an air-tight container until needed for analysis. Phytochemical screening/analysis and mineral analysis were determined using standard analytical methods. Phytochemicals like Alkaloids, Flavonoids, Tannins, Saponins, Anthraquinone, Cardiac glycoside were determined. while Minerals, such as Potassium, Sodium determined using flame photometer; Calcium, Phosphorus, Magnesium, Iron, Zinc, Manganese, and Copper were determined using Atomic Absorption Spectrophotometer. Results indicates that the bioactive contents of the leaves varied significantly (p<0.05) among the medicinal plants. The phytochemical analysis showed that the three medicinal plants contained alkaloid, saponins, tannins, flavonoids, polyphenols, cardiac glycoside and anthraquinone in varying quantities with the trend: A indica > P. biglobosa > L. guineensis; the macro elements showed similar trend as the phytochemicals while the micro elements followed the trend: P. biglobosa > L. guineensis > A indica. These results conceivably indicate that the three medicinal plant are good source of essential minerals and phyto-nutrients which possess strong pharmacological activities and provide scientific credence for its therapeutic usage
Comparative Study of the in vitro Antioxidant Properties of Methanolic Extracts of Chromolaena odorata and Ageratum conyzoides used in Wound Healing
Get PDFThis study sought to evaluate the potential antioxidative potencies of Chromolaena odorata and Ageratum conyzoides, commonly used herbs in Nigeria for wound first aid and healing. The antioxidant potentials were evaluated by measuring their abilities to scavenge radicals, reduce oxidised iron and quench the formation of lipid peroxides. The findings showed that the extract of Ageratum conyzoides exhibited significantly higher (p<0.05) antioxidant potential than the extract of Chromolaena odorata. The study therefore suggests that Ageratum conyzoides has higher potential for therapeutic value than Chromolaena odorata in terms of antioxidant potential
Total Phenolic Contents and Antioxidant Variations in Raw and Cooked Dried Fruit of Xylopia aethiopica
Get PDFMost plant products undergo one or more different thermal processes before consumption despite the claims that cooking fruits and vegetables could have detrimental effects on the beneficial properties of the plants. This work investigated the changes in antioxidant status occurring in dried fruit of Xylopia aethiopica subjected to cooking at different temperatures. The analyses were performed on both raw and boiled samples to assess the total phenolic contents (TPCs) and the antioxidant potential through reduction of ferric chloride salt and bleaching of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The data obtained were subjected to analysis of variance and pairwise comparisons by Tukey-Kramer test at p < 0.05. There was a significant heat-trend difference between the phenolic contents of the samples at the selected temperatures with the highest TPC recorded at 70°C. Similarly, the ferric reducing potentials of the cooked samples were significantly different (p <0.05) from the raw. However, uncooked samples had significantly (p <0.05) higher percentage of DPPH radical scavenging activity compared to cooked samples. The overall effect of cooking the dried fruit of X. aethiopica was due to an elevation in total phenolics concentrations and reducing potentials of the aqueous infusions. However, boiling decreases the DPPH radical scavenging ability of the samples. Therefore, this study suggests an optimum cooking temperature of 70°C which could result in the highest retention of phenolic contents and ferric reducing potentials in the fruit of X. aethiopica and lowest appropriate temperature to conserve its intrinsic radical-scavenging activity in order to assure a higher quality food for the maintenance of human health. Moreover, losses in the phenolic contents and antioxidant potential should be considered when the procedural temperature during processing is unalterable
Communication and the Shaping of Human Personality; Deconstructing the Nature/Nurture Debate in Light of the Menace of Street Children in Nigeria
Get PDFAt the core of the knowledge inquiry about behavioural differences is the nature versus nurture debate which has been central to the development of various theories of human personality. The metaphor of a pendulum, swinging back and forth between nature and nurture, has been used to depict the opinion of scholars and practitioners in the social sciences and psychology in this debate. Nature / Nurture debate seeks to proffer answers to the following questions: why do people differ significantly in temperament, approach to challenges and level of intelligence even when they are siblings sharing from the same pool of genes? The debate also seeks to understand why people with different genetic trait behave alike within a group. How does our physical environment affect human behaviour and what role does communication play in the development of human personality? In the context of street children in Nigeria, should we attribute human personality to nature or nurture? These are issues this paper seeks to deconstruct. Methodologically, the paper examines critical theories of human personality and utilises a mix of review of relevant literature, comments and observations to discuss the role of communication in the formation of human personality. It concludes that though nature contributes towards human behaviour and personality, communication, which is the tool that drives socialisation, is central to the development of personality among the street children of Calabar. Thus, if communication can influence personality negatively, then the street children of Calabar have a chance of being rehabilitated through a different kind of communication aimed at behaviour modification
Reaching Mental Health Research Participants with Multiple Stigmas; A Description of Strategies Used in a Depression Intervention Study for YMSM of Color with HIV
Get PDFResearch indicates that stigma serves as a barrier to the recruitment of participants into mental health intervention studies. Some participants, such as those for depression intervention studies that target people with human immunodeficiency virus (HIV), may face multiple sources of stigma. The purpose of this brief report was to describe recruitment strategies used during the initial months of an ongoing preliminary pilot study designed to develop a web-based intervention for young African American and Latino gay and bisexual men living with HIV who reported symptoms of depression. We employed four primary recruitment strategies to identify potential participants in the Los Angeles metropolitan area for the study. These strategies included social media, referrals, direct contact, and recruitment flyers. Preliminary data indicated that recruitment efforts generated 57 responses from potential participants during the first four months of recruitment and study implementation. The monthly response rate from potential participants represented slightly more than 71% of the study’s minimum level targeted for participant enrollment. Findings from this preliminary study are discussed in terms of the role of stigma as a barrier to mental health participant research recruitment. Implications for both depression research and clinical interventions are considered