Authors:Oluwaseun Adeyeye, Zurni Omar Abstract: This article presents a new generalized algorithm for developing k-step (m+1)th derivative block methods for solving mth order ordinary differential equations. This new algorithm utilizes the concept from the conventional Taylor series approach of developing linear multistep methods. Certain examples are shown to show the simplicity involved in the usage of this new generalized algorithm. PubDate: 2018-03-30 Issue No:Vol. 50 (2018)

Authors:Anggraini Barlian, Yemima Dani Riani Abstract: Recent studies have shown hypoxia-induced gene expression correlated with cellular senescence. HIF-1α (hypoxia-inducible factor 1-alpha), p53, and pRB were induced under hypoxia and correlated with cellular senescence. The localization and expression of HIF-1α, p53, and pRB in Chelonia mydas lung epithelial and dermal fibroblast cell cultures were analyzed under normoxic and hypoxic conditions (at 4 and 24 hours). Human dermal fibroblast was used for comparison purposes. Protein localization was analyzed with immunocytochemistry, while protein expression was analyzed with the Western blot and enhanced chemiluminescence (ECL) method. HIF-1α, p53, and pRB were localized in the nuclei of the C. mydas cell cultures treated with hypoxia. The C. mydas lung epithelial cell cultures had a higher increase of HIF-1α expression than the human dermal fibroblast cell culture. The hypoxic conditions did not affect p53 expression significantly in C. mydas lung epithelial and dermal fibroblast cell cultures. Meanwhile, pRB expression changed significantly under hypoxia in the C. mydas dermal fibroblast cells. Expression of p53 and pRB in the human cell cultures was higher than in the C. mydas cell cultures. This research suggests that C. mydas and human cell cultures have different pro-senescence protein expression responses under hypoxic conditions. PubDate: 2018-03-30 Issue No:Vol. 50 (2018)

Authors:Cemil Tunc, Timur Ayhan Abstract: In this paper, we consider a nonlinear integro-vector differential equation of the second order. We establish sufficient conditions that guarantee the global existence and boundedness of solutions of the equation considered. The method of proof involves constructing a suitable Lyapunov functional that gives meaningful results for the problem to be investigated. The result obtained is new and complements that found in the literature. We give an example to verify the result obtained and for illustration purposes. Using MATLAB-Simulink, the behaviors of the orbits of the equation considered are clearly shown. PubDate: 2018-03-24 Issue No:Vol. 50 (2018)

Authors:Bunbun Bundjali, Muhammad Masykuri, Fitri Widya Hartanti, I Made Arcana Abstract: Poly(urethane) (PU) as a prepolymer was prepared by polymerization of the diol compound (9-ethoxy-1,10-octadecanediol) and 4,4-methylen-bis phenyl isocyanate (MDI) under nitrogen atmosphere at 85 °C. The 9-ethoxy-1,10-octadecanediol was obtained by several reaction steps, i.e. epoxydation of oleic acid obtained from palm oil, ring-opening of oleic acid epoxide, and reduction of oleic acid ester. All compounds obtained in this work were characterized by chemical structure analysis (FTIR and 1H NMR), supported by analysis of iodine value, acid value, and hydroxyl value determined by titration methods and thermal analysis, especially for poly(urethane). The 9-ethoxy-1,10-octadecanediol as the diol compound for preparation of poly(urethane) was analyzed by FTIR, supported by hydroxyl numbers determined by titration. Poly(urethane-urea) (PUU) was obtained by addition of ethylene diamine as chain extender to poly(urethane). The thermal stability of poly(urethane-urea) is higher than that of poly(urethane). The addition of ethylene diamine as chain extender in poly(urethane) can improve the intrinsic viscosity of polymer to form poly(urethane-urea). These results are supported by chemical structure analysis. PubDate: 2018-03-24 Issue No:Vol. 50 (2018)

Authors:Sunday O. Edeki, Grace O. Akinlabi Abstract: In this study, approximate solutions of a system of time-fractional coupled Burger equations were obtained by means of a local fractional operator (LFO) in the sense of the Caputo derivative. The LFO technique was built on the basis of the standard differential transform method (DTM). Illustrative examples used in demonstrating the effectiveness and robustness of the proposed method show that the solution method is very efficient and reliable as – unlike the variational iteration method – it does not depend on any process of identifying Lagrange multipliers, even while still maintaining accuracy. PubDate: 2018-03-24 Issue No:Vol. 50 (2018)

Authors:Amer Ibrahim Al-Omari Abstract: An acceptance sampling plan problem based on truncated life tests when the lifetime following a Sushila distribution is considered in this paper. For various acceptance numbers, confidence levels and values of the ratio between fixed experiment time and particular mean lifetime, the minimum sample sizes required to ascertain a specified mean life were found. The operating characteristic function values of the suggested sampling plans and the producer’s risk are presented. Some tables are provided and the results are illustrated by an example of a real data set. PubDate: 2018-03-24 Issue No:Vol. 50 (2018)

Authors:Marco Vianello Abstract: A polynomial mesh on a multivariate compact set or manifold is a sequence of finite norming sets for polynomials whose norming constant is independent of degree. We apply the recently developed theory of polynomial meshes to an elementary discrete approach for polynomial optimization on nonstandard domains, providing a rigorous (over)estimate of the convergence rate. Examples include surface/solid subregions of sphere or torus, such as caps, lenses, lunes, and slices. PubDate: 2018-03-24 Issue No:Vol. 50 (2018)

Authors:Mamat Rokhmat, Edi Wibowo, Sutisna Sutisna, Khairurrijal Khairurrijal, Mikrajuddin Abdullah Abstract: A simple method is proposed to develop a low-cost TiO2/CuO/Cu based solar cell. The cell is made by employing a lower grade (technical grade) of TiO2 as the active material. CuO powder is synthesized using a wet chemical method and mixed with TiO2 powder to give impurity to the TiO2. A layer of TiO2/CuO is then deposited onto fluorin-doped tin oxide (FTO) by spraying. Copper particles are grown on the spaces between the TiO2 and/or CuO particles by electroplating for more feasible electron migration. The TiO2/CuO/Cu solar cell is finalized by sandwiching a polymer electrolyte between the film and the counter electrode. Current-voltage measurement was performed for various parameters, such as the molarity of NaOH for producing CuO particles, the weight ratio of CuO over TiO2, and the current in the electroplating process. A highest efficiency of 1.40% and a fill factor of 0.37 were achieved by using this combined spray and electroplating method. PubDate: 2018-03-24 Issue No:Vol. 50 (2018)