Judul: Metil Ester Gondorukem sebagai Kandidat Bahan Bakar Nabati
Abstrak: The objective of this research is to produce ester of rosin distillate using methanol and H2SO4 (pa) as a catalyst. The result showed an optimum yield of methyl ester was 88.5% at an operating condition of 1.2 mL catalyst in 1.5 hours. The infrared spectra showed that carboxyl groups was replaced by C=O ester group, proofing that the rosin distillate was esterified. Furthermore, the gas chromatography-mass spectrometer spectra showed that the resin acids consists of ester derivates of abietic acid, sandaracopimaric acid, dehidroabietic acid, isopimaric acid, palustric acid. Based on SNI 04 -7182-2006, the kinematic viscosity at 40ºC (4.2 mm2/s), cloud point (-18ºC), total sulfur (67 ppm), acid number (0.1 mg-KOH/g), iodine number (12.8%), and total alkyl ester (99.8%), the methyl ester of pine rosin would be feasible to be used as a biodiesel material. The flash point was considered too low for biodiesel, but would be suitable f or biogasoline.
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Judul: Rasio Molar dan Konsentrasi Katalis Methyl Ester Sulfonic Acid pada Proses Sintesis Gliseril Ester
Abstrak: Glycerol is a by-product of biodiesel industry production which still can be further processed into more value-added products. The example is the utilization of glycerol by means of esterification between glycerol and oleic acid with methyl ester sulfonic acid (MESA) catalyst, producing glyceril ester. The purpose of this study was to obtain the conditions of esterification with variable factors were molar ratio between oleic acid and glycerol and the concentrations of added MESA catalyst. Before esterification, crude glycerol was purified by adding 5% (v/v) phosphoric acid 85%, producing glycerol with ±80% glycerol content. Furthermore, glycerol was then esterified with supply of nitrogen, at temperature of 180 °C, and the stirring speed of 400 rpm for 90 minutes. The best combination of molar ratio and concentration of catalyst MESA is on ratio molar 0,8:1 (glycerol : oleic acid) with 0,5% added of catalyst MESA. Esterification on that condition produced glyceryl ester with the yield of 79,55%, density 0,940 g/cm3, acid value 44 mg KOH/g sample, viscosity 90 cP (30 oC), kinematic viscosity 49,04 cSt (40 oC), flash point 206 oC, pour point -1,5 oC, and boiling point 105 oC.
Keyword: Bogor Agricultural University (IPB), glyceryl ester, esterification, MESA, glycerol

Judul: Model’s Dynamics for Lymphocytes Recovery on the HIV presence with Protease Inhibitor Therapy.
Abstrak: HIV is a member of retrovirus that especially attacks lymphocytes or white blood cells, known as CD4+ T cells. New T cells created from sources within the body such as the thymus and by proliferation of existing T cells. In this paper, influence of protease inhibitor therapy in HIV dynamics will be analyzed. The influence can be categoried in three models, which are model HIV without drug therapy, model HIV with protease inhibitor and model T cell recovery. In the models, three parameters which are uninfected cells population, infected cells population and virus population are studied. From HIV without drug therapy model it is obtained two types fixed point which are uninfected fixed point and infected fixed point. The stability of fixed point depends on basic reproduction number which is influenceed by the total number of virus produced by a cell during its lifetime. From HIV with protease inhibitor therapy model it is obtained two type fixed points. The stability of fixed point depends on basic reproduction number. Other than influenceed by the total number of virus produced by a cell during its lifetime, basic reproduction number of this model also affected by the effectiveness of a protease inhibitor. Basic reproduction number of this model is smaller than that of model HIV without drug therapy. In the model T cell recovery, new T cells created only from sources within the body, and T cells can be invulnerable to HIV infection after the therapy. From the model it is obtained only one fixed point that is uninfected fixed point. The stability of fixed point depends on basic reproduction number. The total number of virus produced by a cell during its lifetime and the effectiveness of a protease inhibitor determine the basic reproduction number. Basic reproduction number of this model is smallest than that of other models.
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