Judul: Analisis kestabilan model permintaan tryptophan operonpada sel escherichia coli
Abstrak: Dari sudut pandang bioteknologi tujuan terpenting dari fermentasi biologis adalah untuk menghasilkan metabolit seballyak mungkin dalam kondisi yang stabil. Tetapi biasanya mikro organisme cenderung membatasi produksi yang dilepaskan sel, sehingga perlu dikembangkan strategi yang akan mengatasi mekanisme natural yang menjadi penghambat ini.
Keyword: 

Judul: Analisis dinamik pertumbuhan mikroba dengan dua substrat
Abstrak: Mikroba sebagai unsur utama produksi antibiotik membutuhkan makanan berupa substrat untuk pertumbuhan dan perkembangannya. Agar proses konsumsi (penyederhanaan) substrat dapat berlangsung diperlukan suatu katalisator berupa enzim inducible (e) yaitu enzim yang keberadaannya ditentukan oleh keberadaan substrat yang digunakan. Umumnya mikroba hanya mengkonsumsi satu jenis substrat tertentu. Namun karena kurang ekonomis dan memerlukan banyak waktu di laboratorium, maka dilakukan peningkatan jumlah substrat menjadi dua (5) dan 52) dengan jenis yang berlainan. Pola pertumbuhan mikroba dengan mengkonsumsi dua subsuar berbeda dapat diklasifikasikan menjadi: CL Pola pertumbuhan sequensial (bergantian); ii. Pola pertumbulian simultan (bersama-sama) Penggunaan dua substrát ini menjadi dasir pembentukkan model matematika. Model yang didapat kemudian dianalisis kedinamikannya. Pola pertumbuhan mikroba dengan konst nsi dua substrat dapat ditentukan dengan analisis dinamik model reduksi (enzim inducible) dan model reduksi yang telah disederhanakan (tanpa katabolit repressi). Analisis model reduksi dilakukan dengan menggunakan metode mull chines dan analisis model reduksi tanpa katabolit repressi dilakukan dengan analisis kestabilan di sekitar tititk tetap model Hasil analisis menunjukkan bahwa penjadaan parameter katabolit repressi (K) mengakibatkan terjadinya perubahan pola pertumbuhan mikroba dari sequensial menjadi simultan. Pola pertumbuhan sequensial menggambarkan terjadinya kompetisi antara kedua substrat agar dapat digunakan mikroba terlebih dahulu (diausik). Pola pertumbuhan simultan menggambarkan tidak terjadinya kompetisi diantara kedua substrat, sehingga kedua substrat digunakan secara bersama-sama
Keyword: 

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: