Effect of monomer concentration on characteristics of methacrylic acid-grafted polyethylene film prepared by photografting

The effect of monomer concentration on photografting of methacrylic acid (MAA) onto linear low-density polyethylene (PE) film (thickness=30 μm) was investigated at 60 °C in water solvent together with the location of MAA-grafted chains. Xanthone was used as a photoinitiator which was coated on the film sample earlier. The higher percentage of grafting and graft efficiency were afforded for the system with the higher monomer concentration. The resultant MAA-grafted films were subjected to measurements of pH-responsive character and ability to adsorb cupric ion in order to understand the characteristics of function introduced. The grafted samples exhibited the pH-responsive character, where they shrank and swelled in acidic and alkaline media, respectively. The pH-responsive character of the grafted films was higher for the samples prepared in the system with a higher monomer concentration. Moreover, the grafted samples exhibited the ability to adsorb cupric ion, and the ability was reduced when the sample was prepared in the system with a higher monomer concentration. The different extents of the pH-responsive character and ability to adsorb cupric ion of the resulting grafted PE films were discussed in terms of location of grafted chains in the film substrate, which was determined by a scanning electron microscope and an attenuated total reflection infrared spectroscopy.     

Operator Splitting Multiscale Finite Volume Element Method for Two-Phase Flow with Capillary Pressure

A numerical method used for solving a two-phase flow problem as found in typical oil recovery is investigated in the setting of physics-based two-level operator splitting. The governing equations involve an elliptic differential equation coupled with a parabolic convection-dominated equation which poses a severe restriction for obtaining fully implicit numerical solutions. Furthermore, strong heterogeneity of the porous medium over many length scales adds to the complications for effectively solving the system. One viable approach is to split the system into three sub-systems: the elliptic, the hyperbolic, and the parabolic equation, respectively. In doing so, we allow for the use of appropriate numerical discretization for each type of equation and the careful exchange of information between them. We propose to use the multiscale finite volume element method (MsFVEM) for the elliptic and parabolic equations, and a nonoscillatory difference scheme for the hyperbolic equation. Performance of this procedure is confirmed through several numerical experiments.     

A residual-type a posteriori error estimate of finite volume element method for a quasi-linear elliptic problem

In this paper, we analyze a residual-type a posteriori error estimator of the finite volume element method for a quasi-linear elliptic problem of nonmonotone type and derive computable upper and lower bounds on the error in the H ¹-norm. Numerical experiments are provided to illustrate the performance of the proposed estimator.     

In-Vitro Screenings for Biological and Antioxidant Activities of Water Extract from Theobroma cacao L. Pod Husk: Potential Utilization in Foods

Increasing production of cocoa (Theobroma cacao L.) leads to a higher environmental burden due to its solid waste generation. Cocoa pod husk, one of the major solid wastes of cocoa production, contains rich bioactive compounds unveiling its valorization potential. With that in mind, our research aimed to explore the biological and antioxidant activities of aqueous extracts from cocoa pod husks. In this present work, cocoa pod husk was extracted using water and subsequentially partitioned using n-hexane, ethyl acetate, and methanol. The antimicrobial investigation revealed that the ethyl acetate solubles were active against the Staphylococcus aureus, Escherichia coli, and Candida albicans, where at a 20% w/v concentration, the inhibition diameters were 6.62 ± 0.10, 6.52 ± 0.02, and 11.72 ± 0.36 mm, respectively. The extracts were found non-toxic proven by brine shrimp lethality tests against Artemia salina with LC₅₀ scores ranging from 74.1 to 19,054.6 μg/mL. The total phenolic content and total flavonoid content were obtained in the range of 47.44 to 570.44 mg/g GAE and 1.96 to 4.34 mg/g QE, respectively. Antioxidant activities of the obtained extracts were revealed by 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) assay with EC₅₀ reached as low as 9.61 μg/mL by the ethyl acetate soluble. Phytochemical screening based on gas chromatography—mass spectroscopy analysis on the sample with the highest antioxidant activities revealed the dominant presence of three phytosterols, namely gamma-sitosterol, stigmasterol, and campesterol.     

Characteristics of acrylic acid-grafted polyethylene prepared by photografting using mixed solvents consisting of water and organic solvent

Photografting of acrylic acid (AA) on linear-low density polyethylene film (thickness=30 μm) was investigated at 60 °C using mixed solvent consisting of water and organic solvents such as acetone and methanol. Xanthone was used as photoinitiator, which was coated on the film earlier. With longer photoirradiation time, such as 40 and 60 min, the percentage of grafting decreased with increasing the concentration of organic solvent in the mixed solvent, where formation of homopolymer occurred preferentially over the grafting reaction. In the system with photoirradiation of 20 min, on the other hand, a maximum percentage of grafting was observed at a certain concentration of organic solvent, in which formation of grafted polymer rather than homopolymer was emphasized. Photografting using the mixed solvent resulted in AA-grafted film with homogeneous distribution of grafted chains, exhibiting larger pH-responsive character, where the grafted film shrinks in an acidic medium, while it swells in an alkaline region. Polymer catalysts for hydrolysis of p-nitrophenylacetate, which was performed at 40 °C in water/ethanol (1/4, v/v)-mixed solvent at pH=9.0, could be prepared by reacting the AA-grafted film with L-histidine and its catalytic activity was slightly influenced by location of grafted chains.     

The preparation and activities of ASV’98 in Bedugul-Bali, Indonesia

The preparation and activities of the Asian Symposium for Visualization ’98 that was held from March 8^th-11^th, 1999 in Bedugul-Bali, Indonesia will be presented in this article. In this article some story of the postponed ASV’98 in Serpong, and the process of moving the symposium to the new site in Bali, are also included.     

Visualization activities in Indonesia

Though it is still in its initial state, visualization techniques as one of the supportive components in the industrial transformation as well as a research tool have, however, gained some supports in universities and research institutes. This paper presents a review of activities related to the visualization research and application in universities and research institutes in Indonesia, namely at the Center for Applied Physics — Indonesia Institute for Sciences (P3FT-LIPI), University of Indonesia (UI), Institute of Technology Surabaya (ITS), Institute of Technology Bandung (ITB), and Aero-Gas Dynamics and Vibration Laboratory (LAGG-BPP-Teknologi).     

Construction of locally conservative fluxes for the SUPG method

We consider the construction of locally conservative fluxes by means of a simple postprocessing technique obtained from the finite element solutions of advection diffusion equations. It is known that a naive calculation of fluxes from these solutions yields nonconservative fluxes. We consider two finite element methods: the usual continuous Galerkin finite element method for solving nondominating advection diffusion equations and the streamline upwind/Petrov‐Galerkin method for solving advection dominated problems. We then describe the postprocessing technique for constructing conservative fluxes from the numerical solutions of the general variational formulation. The postprocessing technique requires solving an auxiliary Neumann boundary value problem on each element independently and it produces a locally conservative flux on a vertex centered dual mesh relative to the finite element mesh. We provide a convergence analysis for the postprocessing technique. Performance of the technique and the convergence behavior are demonstrated through numerical examples including a set of test problems for advection diffusion equations, advection dominated equations, and drift‐diffusion equations. © 2015 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 1971–1994, 2015