Judul: Pengaruh beberapa senyawa nitrogen organik tanah pada aktifitas fiksasi nitrogen oleh Azoidbacter vinelandii pada media cair modifikasi burk
Abstrak: Penelitian ini bertujuan melihat pengaruh beberapa senyawa nitrogen organik tanah dilihat dari aspek biokimia /biologi terhadap aktifitas fiksasi nitrogen (fn) oleh A­ zotobacter vinelandii pada skala laboratorium. Penclitian dasar ini akan mengungkapkan beberapa aspek biokimia/bio­ logi fn oleh A. vinelandii secara nonsimbiose (mandiri) pada media cair modifikasi Burk sebagai media baku. Aspek biokimia yang akan dipelajari meliputi : gambaran laju per tumbuhan dengan mencoba selang waktu pengamatan setiap 3, 6, 12 dan 24 jam, ketergantungan aktifitas fn terhadap asam n trilotriasetat dan garam Mo. pengaruh 8 senyawa nit­ rogen organik tanah, urea serta nitrat pada media. Obyek pengamatan ialah tingkat aktifitas fn dengan menggunakan 4 parameter yaitu : gambar kurva laju pertumbuhan selama pengamatan, kekeruhan, bohot kering biomassa sel, populasi sel dan N-terfiksasi atau N-total biomassa sel pada saat akhir fase pertumbuhan eksponensial.
Keyword: Modifikasi Burk;, Azotobacter Vinelandi;, Soil Microbiology;

Judul: Pengaruh Inokulasi Azotobacter sp. terhadap ..Perakaran Jagung pada Beberapa Tingkat Pemberian KNO3 di Media Padat Watanabe
Abstrak: Pemupukan N merupakan salah satu upaya yang dilakukan untuk meningkatkan ketersediaan hara N yang diperlukan tanaman untuk pertumbuhan. Sumber nitrogen yang terdapat dalam tanah, tidak selalu mencukupi kebutuhan tanaman, sehingga perlu diberikan pupuk sintetik yang merupakan sumber nitrogen untuk mempertinggi produksi pertanian. Akan tetapi penggunaan pupuk sintetik yang berlebihan menimbulkan residu yang membahayakan lingkungan. Oleh karena itu diperlukan alternatif lain untuk mengatasinya, salah satunya adalah penggunaan pupuk hayati yang mengandung mikroba tanah. Salah satu mikroba tersebut adalah Azotobacter sp. Azotobacter sp. dikenal sebagai bakteri penambat N2 non simbiotik dan penghasil zat pengatur tumbuh. Inokulasi Azotobacter sp. mampu meningkatkan produksi dan memperbaiki pertumbuhan tanaman pangan. Penelitian ini dilakukan untuk mengetahui kemampuan beberapa isolat Azotobacter sp. dalam memperbaiki perakaran jagung pada beberapa tingkat pemberian hara N dalam bentuk KNO3 pada media padat Watanabe.
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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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