Judul: Aktivitas dan stabilitas urikase lactobacillus plantarum yang diimobilisasi pada zeolit alam untuk biosensor asam urat
Abstrak: Bakteri Lactobacillus plantarum telah diketahui menghasilkan enzim urikase, namun aktivitas dan stabilitasnya masih rendah. Metode pengukuran yang lebih sensitif dan selektif diperlukan untuk mengukur aktivitas dan stabilitas urikasenya. Voltametri siklik digunakan untuk menentukan perilaku katalitik pada biosensor. Penelitian ini dilakukan dengan mengimobilisasi urikase L. plantarum pada zeolit menggunakan mediator terbaik dan kondisi optimum. Penelitian bertujuan mengukur aktivitas dan stabilitas urikase yang diimobilisasi pada zeolit alam. Imobilisasi urikase L. plantarum pada zeolit dapat meningkatkan aktivitas dan stabilitasnya. Mediator terbaik untuk aktivitas urikase ini adalah Q0 (2,3- dimetoksi-5-metil-1,4-benzokuinon). Kondisi optimum imobilisasi urikase pada zeolit adalah pH 8.5, suhu 40 oC, konsentrasi asam urat 0.05 mM, dan massa zeolit 220 mg. Nilai konstanta Michaelis-Menten dan laju maksimum (KM dan Vmaks) urikase L. plantarum yang diperoleh dari persamaan Lineweaver-Burk adalah 6.0292×10-3 mM dan 6.3331 μA. Stabilitas urikase ini dapat dijaga selama 18 hari jika disimpan pada suhu 10 oC.
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Judul: Sarah Judul Pengoptimuman aktivitas dan stabilitas urikase sel Lactobacillus plantarum dengan imobilisasi pada zeolit untuk biosensor asam urat Pembimbing Iswantini, Dyah;Nurhidayat, Novik
Abstrak: Lactobacillus plantarum diketahui dapat menghasilkan urikase. Enzim tersebut dimanfaatkan sebagai komponen pengenal biologis pada biosensor asam urat. Akan tetapi, daya tahan dan stabilitas urikase dari bakteri ini masih rendah, sehingga perlu ditingkatkan melalui imobilisasi menggunakan zeolit alam. Pengukuran dilakukan pada suhu ruang (27 °C) dengan kondisi optimum massa zeolit 250 mg, volume suspensi mikrob 100 µL, konsentrasi asam urat 2.87 mM, dan pH 5. Hasilnya menunjukkan nilai konstanta Michaelis-Menten (KM) dan Vmax berturut-turut 0.92 mM dan 6.74 µA. Linearitas terdapat pada rentang konsentrasi 0.10‒0.30 mM dengan nilai r2 = 0.9667, limit deteksi dan kuantisasi berturut-turut 0.55 mM dan 1.82 mM dengan sensitivitas 1.54 µA mM-1. Stabilitas biosensor diukur menggunakan elektrode yang sama dan elektrode sekali-pakai untuk setiap kali pengukuran. Stabilitas elektrode sekali-pakai ialah 90.38%, yang lebih baik dibandingkan dengan elektrode yang sama untuk tiap kali pengukuran, yaitu 39.42% sampai hari ke 14, akan tetapi kestabilan per harinya masih fluktuatif
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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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