NUR HAZWANI DAHON  

2011 

Determination of total phenol, cendensed tannin and flavanoid contents and antioxidant activity of Uncaria gambir extracts M. Jain Kassim, M. Hazwan Hussin*, A. Achmad, N. Hazwani Dahon, T. Kim Suan and H. Safley Hamdan Material Chemistry and Corrosion Laboratory, School of Chemical Sciences, Universiti Sains Malaysia Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it. or This email address is being protected from spambots. You need JavaScript enabled to view it. Uncaria gambir, a well known Southeast Asia plant have been previously used as an alternative medicine for treatment such as diarrheal, sore throat and spongy gums. Due to its useful properties, in this study we have analysed the total phenol, condensed tannin, flavonoid content and antioxidant activity of Uncaria gambir in three different solvent extracts. Characterization and quantification analysis using Fourier Transform Infrared (FTIR) spectroscopy and reverse phasehigh performance liquid chromatography (RPHPLC) has confirmed that the major chemical constituents of Uncaria gambir are mainly catechins. It was revealed that the ethyl acetate gambir extract gives the highest catechin content and antioxidant activity compared with other solvent extracts. Keywords: Uncaria gambir, antioxidant activity, condensed tannin, flavonoid 

The effect of Tinospora crispa extracts as a natural mild steel corrosion inhibitor in 1 M HCl solution M. Hazwan Hussin *, M. Jain Kassim, N.N. Razali, N.H. Dahon, D. Nasshorudin Material and Corrosion Chemistry Laboratory, School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia *Corresponding author: Tel.: +60 4 653 4023; fax: +60 4 657 4854. Email address: This email address is being protected from spambots. You need JavaScript enabled to view it.. The potential of Tinospora crispa extracts as a corrosion inhibitor of mild steel in 1 M HCl was determined using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy methods (EIS). Maximum inhibition was attained at the concentration of 800 and 1000 ppm for TCDW (T. crispa water extract) and TCAW (T. crispa acetone–water extract). The inhibition efficiencies of T. crispa extracts obtained from the impedance and polarization measurements were in good agreement where the maximum inhibition is around 70–80%. Potentiodynamic polarization measurement studies revealed that T. crispa extracts behave predominantly as an anodic inhibitor. The adsorption of T. crispa extracts was found to follow Langmuir’s adsorption model. Keywords: Tinospora crispa; Mild steel; Polarization; EIS; Acid inhibition 


CHE HAZIQAH CHE HUSSIN  

2011 

On the Solution of Fractional Order Nonlinear Boundary Value Problems By Using Differential Transformation Method Che Haziqah Che Hussin^{1} Adem Kılıçman^{2,*} ^{1} Department of Mathematics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia ^{2} Department of Mathematics and Institute for Mathematical Research, Faculty of Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia *Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it. In this research, we study about fractional order for nonlinear of fifthorder boundary value problems and produce a theorem for higher order of fractional of nthorder boundary value problems. The aim of this study was to evaluate and validate the theorem and provide several numerical examples to test the performance of our theorem. We also make comparison between exact solutions and differential transformation method(DTM) by calculating the error between them. It is shown that DTM has very small error and suitable in several numerical solutions since it is effective and provide high accuracy. 2000 Mathematics Subject Classifications: 35C10,74S30, 65L10, 34B05, 34B15 Keywords: Differential transformation method, Taylor series, fractional order of nonlinear boundary value problems 

On the Solutions of Nonlinear HigherOrder Boundary Value Problems by Using Differential Transformation Method and Adomian Decomposition Method Che Haziqah Che Hussin and Adem Kilicman* Department of Mathematics, University Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia *Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it. We study higherorder boundary value problems HOBVP for higherorder nonlinear differential equation. We make comparison among differential transformation method DTM , Adomian decomposition method ADM , and exact solutions. We provide several examples in order to compare our results. We extend and prove a theorem for nonlinear differential equations by using the DTM. The numerical examples show that the DTM is a good method compared to the ADM since it is effective, uses less time in computation, easy to implement and achieve high accuracy. In addition, DTM has many advantages compared to ADM since the calculation of Adomian polynomial is tedious. Fromthe numerical results,DTM is suitable to apply for nonlinear problems. 