Judul: Antioxidant Activities of Some Medicine Plant Use Natural Zeolite as Supporting Material
Abstrak: Traditional medicine has a key role in health care worldwide. Obtaining scientific information about the efficacy and safety of the plants from our region is one of the goals of our research. In this report, five plants were selected and collected from Bogor areas. The dried plants were separated into leaves: kedawung (Parkia roxburghii G. Don), salam (Syzygium polyanthum Wight), sirih merah (Piper crocatum Ruiz & Pav), jambu biji (Psidium guajava), and rhizome: bangle (Zingiber cassumunar, syn. Z. purpureum Roxb.). Each plant was extracted with ethanol 30% and 96%. The extracts were tested for their antioxidant activity using a DPPH free radical assay. Identification of crude extract of the compound used phytochemical test and thin layer chromatography tehnique. The results of the best antioxidant activity formula showed by the formulation of kedawung and guava. Formula with ratio of 4:1 selected formula was mixed with supporting material, which were natural zeolit from Bayah and Cikalong. The antioxidant activity of composite extract formulation with zeolite were optimum at 0.1 mg/mL extract formulation, 100 mg Bayah zeolite and 500 mg Cikalong zeolite. Zeolite as supporting material also showed lower antioxidant activity tan extract formulation.
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Judul: Potensi Zeolit Alam Sebagai Antioksidan
Abstrak: Zeolite is an aluminosilicate mineral which are three dimensional frameworks in its structure, has cavities and channels connected to each other creating wide surface so that effective as an adsorbent. Besides, zeolite has negative charge, which can interact with charged compounds or molecules such as 1,1-diphenyl-2-picrylhydrazyl (DPPH). The aim of this research is to measure the activity of Indonesian natural zeolites from Banten, Lampung, Sukabumi, and Tasikmalaya to scavenge DPPH free-radical. Antioxidant activity test against DPPH performed on the untreated zeolite, temperature-activated zeolite, and acid-activated zeolite. The highest antioxidant activity was shown by Sukabumi zeolite, which was 85.56% when activated at 100 °C and 65.56% when activated with 1 M HCl. The results of scanning electrone microscopy and X-ray diffraction analysis showed that zeolites from Banten, Lampung, Sukabumi, and Tasikmalaya are clinoptilolite typ
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Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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