Judul: Sintesis Oksida Grafena dari Gambir (Uncaria gambir Roxb.) sebagai Antibakteri dan Antioksidan
Abstrak: Oksida grafena merupakan produk nanoteknologi yang memiliki banyak keunggulan dan saat ini masih terus dikembangkan dalam berbagai penelitian. Penelitian ini bertujuan menghasilkan senyawa oksida grafena berbahan dasar gambir sebagai antibakteri dan antioksidan. Oksida grafena dari arang tersebut berhasil disintesis menggunakan modifikasi metode Hummers. Hasil spektrum ultraviolet terdapat puncak serapan pada 224,8 nm. Gugus fungsi beroksigen yang muncul pada spektrum inframerah menandakan oksida grafena berhasil terbentuk. Hasil analisis difraksi sinar X menggunakan puncak 2θ pada sudut 25,04°. Hasil uji Raman menunjukkan adanya tiga puncak yaitu puncak D, puncak G, dan puncak 2D pada bilangan ~1373 cm-1, ~1592 cm-1, dan ~2866 cm-1. Diameter zona hambat pertumbuhan bakteri Escherichia coli sebesar 8,82 mm lebih kecil dari bakteri Staphylococcus aureus sebesar 9,21 mm. Nilai IC50 oksida grafena metode DPPH (2,2-difenil-1-pikrilhidrazil) adalah 220,77 μg/mL, termasuk tingkat antioksidan sedang dan IC50 oksida grafena metode FRAP (Ferric Reducing Antioxidant Power) adalah 64,24 μg/mL, termasuk tingkat antioksidan kuat., Graphene oxide is a nanotechnology product with many advantages and is currently still being developed in various studies. This study aims to produce graphene oxide compounds based on gambier as antibacterial and antioxidant. Graphene oxide from charcoal was successfully synthesized using a modification of the Hummers method. The ultraviolet spectrum result showed an absorption peak of 224,8 nm. Oxygen functional groups that appear in the infrared spectrum indicate that graphene oxide has been successfully formed. The results of X-ray diffraction analysis used a 2θ peak at an angle of 25,04°. Raman test results showed three peaks, namely D peak, G peak, and 2D peak at ~1373 cm-1, ~1592 cm-1, and ~2866 cm-1. The diameter of the inhibition zone for Escherichia coli bacteria was 8,82 mm. It was 9,21 mm smaller than that of Staphylococcus aureus. The IC50 value of graphene oxide by the DPPH (2,2-diphenyl-1-picrylhydrazyl) method was 220,77 μg/mL, including moderate antioxidant levels and the IC50 value of graphene oxide by the FRAP (Ferric Reducing Antioxidant Power) method was 64,24 μg/mL, including intense antioxidant levels.
Keyword: antibacterial, antioxidant, gambier, graphene oxide, Hummers method

Judul: Sintesis Oksida Grafena dari Tempurung Kelapa untuk Aplikasi Antibakteri.
Abstrak: Penelitian material baru terus berkembang hingga saat ini, salah satunya ialah oksida grafena. Oksida grafena merupakan senyawa dengan lapisan tipis yang terdiri atas karbon berbentuk planar. Gugus-gugus fungsi yang terdapat pada oksida grafena antara lain gugus hidroksil, epoksida, karbonil, dan karboksil. Penelitian ini bertujuan menyintesis oksida grafena menggunakan metode Hummers yang dimodifikasi untuk diaplikasikan sebagai material antibakteri. Bahan baku yang digunakan adalah tempurung kelapa. Penelitian ini menggunakan Staphylococcus aureus yang mewakili bakteri Gram positif dan Escherichia coli yang mewakili bakteri Gram negatif. Hasil analisis spektrum ultraviolet menunjukkan puncak serapan pada 232 nm. Spektrum inframerah memperlihatkan gugus fungsi C-H, C-O, O-H, dan C=C. Hasil analisis difraksi sinar X menggambarkan puncak 2θ pada sudut 22,52º dengan nilai kristalinitas 6,85%. Berdasarkan analisis particle size analyzer, oksida grafena memiliki ukuran rata-rata 33,79 nm. Hasil pengujian antibakteri ditandai dengan terbentuknya zona bening sehingga oksida grafena memiliki aktivitas antibakteri.
Keyword: antibakteri, metode Hummers, oksida grafena, tempurung kelapa

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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