Judul: Sintesis ester glukosa laurat dari metil laurat dan glukosa pentaasetat
Abstrak: Ester karbohidrat asam lemak telah menjadi subjek penelitian intensif pada beberapa dasawarsa. Senyawa ini memiliki sifat biodegradabel dan tidak menimbulkan iritasi. Ester karbohidrat asam lemak dapat disintesis dari senyawa alami yang dapat diperbaharui, contohnya gula dan lemak. Penelitian ini dilakukan melalui beberapa tahapan, yaitu sintesis ester metil laurat dan sintesis glukosa pentaasetat (GPA), sintesis ester glukosa laurat dengan nisbah mol GPA:metil laurat 1:1, 1:2, dan 1:3, dan analisis produk menggunakan spektrofotometer fourier transform infrared (FTIR). Rendemen rerata sintesis metil laurat sebesar 78.98% dengan densitas 0.0871027 g ml-1 dan rendemen rerata GPA sebesar 47.55% dengan kisaran titik leleh 105–112 oC. Rendemen rerata ester glukosa laurat untuk nisbah mol GPA:metil laurat 1:1, 1:2, dan 1:3 masing-masing sebesar 56.98, 78.68, dan 54.44% dengan kisaran titik leleh yang sama, yaitu 100–110 oC. Spektrum FTIR ester glukosa laurat menunjukkan serapan khas C=O yang merupakan pita kuat dan tajam pada bilangan gelombang 1744 cm-1 dan munculnya pita yang kuat di daerah sidik jari 1110–1300 cm-1 akibat serapan uluran C─O. Terjadinya subtitusi gugus asetil oleh lauril ditunjukkan pada bilangan gelombang 2800–3000 cm-1, pita yang muncul akibat uluran C─H alifatik dari gugus lauril.
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Judul: Sintesis ester glukosa stearat melalui reaksi interesterifikasi dengan metode bebas pelarut
Abstrak: Ester karbohidrat-asam lemak merupakan jenis surfaktan nonionik yang banyak digunakan pada industri kosmetik, farmasi, detergen, dan makanan. Umumnya ester karbohidrat-asam lemak disintesis menggunakan pelarut beracun, seperti dimetilasetamida, dimetilformamida, dan dimetilsulfoksida sehingga produk yang dihasilkan memiliki keterbatasan sebagai bahan tambahan pada industri makanan. Penelitian ini dilakukan melalui 4 tahapan, yaitu (1) sintesis glukosa pentaasetat (GPA) melalui reaksi antara glukosa dan anhidrida asetat, (2) sintesis metil stearat melalui reaksi antara asam stearat dan metanol, (3) sintesis ester glukosa stearat melalui reaksi antara GPA dan metil stearat (nisbah mol 1:1, 1:2, dan 1:3) dengan katalis zeolit, dan (4) pemisahan hasil sintesis ester glukosa stearat dari metil stearat dan GPA yang tidak bereaksi. Persentase hasil GPA dan metil stearat yang diperoleh masing-masing sebesar 45.52 dan 84.60%. Persentase hasil ester glukosa stearat tiap nisbah mol GPA dan metil stearat 1:1, 1:2, dan 1:3 secara berturut-turut 76.24, 38.30, dan 9.98%. Spektrum fourier transform infrared ester glukosa stearat menghasilkan ciri pita serapan pada bilangan gelombang 2800–3000 cm-1 yang menunjukkan vibrasi ulur C–H dari CH3, –CH2– rantai alifatik jenuh.
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Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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