Judul: Pembentukan Biofilm Lactobacillus plantarum Serta Penentuan Aktivitas dan Stabilitas Urikase Biofilm Untuk Biosensor Asam Urat
Abstrak: Penelitian mengenai biosensor asam urat dengan menggunakan bakteri Lactobacillus plantarum telah dilakukan. Bakteri ini diketahui memiliki urikase yang dapat mengukur asam urat. Daya tahan hidup bakteri yang cukup singkat membuat aktivitas urikase tidak cukup lama untuk mendeteksi asam urat. Biofilm adalah suatu komunitas sel bakteri yang terstruktur, saling menempel dan dapat membuat bakteri mampu bertahan dalam lingkungan yang ekstrem. Tujuan penelitian ini adalah menentukan dan membandingkan aktivitas urikase dari biofilm L. plantarum dan bakteri planktonik pada elektrode pasta karbon serta menentukan stabilitas elektrode biofilm. Optimisasi dengan parameter suhu, pH dan konsentrasi substrat menunjukkan bahwa aktivitas urikase pada biofilm mampu meningkatkan arus oksidasi. Biosensor dengan menggunakan urikase biofilm menghasilkan arus sebesar 47 μA pada kondisi pH 10, suhu 40 ℃ dan konsentrasi asam urat sebesar 5 mM sedangkan pada kondisi yang sama arus oksidasi yang dihasilkan oleh urikase bakteri planktonik sebesar 23 μA. Stabilitas elektrode yang mengandung urikase biofilm L. plantarum menurun pada jam ke-10 sebesar 86%. Kestabilan yang cukup rendah mungkin disebabkan karena tapak aktif enzim tidak terlindungi sehingga enzim lebih cepat terdenaturasi.
Keyword: biofilm, biosensor, Lactobacillus plantarum, uricase

Judul: Validasi dan Stabilitas Biosensor Asam Urat Berbasis Biofilm Lactobacillus plantarum pada Screen-Printed Carbon Electrode.
Abstrak: Lactobacillus plantarum dapat mengekskresikan urikase sebagai pengenal hayati pada biosensor asam urat. Namun, daya tahan hidup bakteri yang singkat mengakibatkan rendahnya aktivitas urikase. Kelemahan ini dapat ditingkatkan dengan membentuk biofilm L. plantarum. Screen-printed carbon electrode (SPCE) digunakan sebagai tempat pelekatan biofilm menggantikan elektrode kerja pasta karbon (EPK). Respons pengukuran terbaik diperoleh dari SPCE biofilm yang disimpan pada suhu ruang 1 hari sebelum digunakan dengan volume suspensi bakteri yang diteteskan 70 μL, konsentrasi asam urat 4 mM, serta pH 7. Nilai KM dan Vmaks urikase masing-masing 0.7500 mM dan 147.06 μA. Nilai limit deteksi dan limit kuantitasi pengukuran masing-masing 0.0148 mM dan 0.0449 mM, dengan sensitivitas 44.591 μA mM-1. Linearitas pengukuran memiliki koefisien determinasi (R2) 0.9951 dan nilai simpangan baku relatif (%SBR) 0.25%. Biosensor asam urat stabil hingga 35 hari pemakaian dengan interval pengukuran selama 7 hari, dengan sisa aktivitas 93.29% dan keterulangan yang cukup baik.
Keyword: biofilm, biosensor asam urat, Lactobacillus plantarum, screen-printed carbon electrode, urikase

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.
Keyword: