Judul: Analisis hubungan curah hujan - limpasan langsung sub sub daerah aliran sungai ciliwung hulu
Abstrak: Suatu daerah aliran sungai (DAS) dapat dipandang sebagai sistem yang menentukan kontribusi curah hujan terhadap limpasan. Selama sifat-sifat fisik DAS tidak berubah, variasi-variasi dalam hubungan curah hujan dengan limpasan merupakan akibat adanya variasi hujan serta faktor kebasahan awal DAS.
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Judul: Analisis hidrograf dan faktor-faktor yang mempengaruhi besar limpasan sub das Ciesek (Daerah Aliran Sungai Ciliwung)
Abstrak: Penelitian ini bertujuan untuk mengetahui parameter- parameter karakteristik DAS, melihat pengaruh tipe hujan dan fisiografik DAS terhadap pola hidrograf satuan, menyusun hidrograf satuan untuk lama waktu hujan efektif tertentu, dan mendapatkan model hubungan antara beberapa parameter hidrograf satuan. Hidrograf merupakan gambaran dari sifat aliran limpas- an terhadap waktu. Bentuk dan ukurannya dipengaruhi oleh faktor fisiografik dan curah hujan. Hidrograf satuan dengan tipe hujan efektif dipercepat (advanced), waktu untuk mencapai puncak limpasan lebih cepat, sedangkan hidrograf satuan dengan tipe hujan efektif diperlambat (delayed), waktu untuk mencapai puncak limpasan juga lebih lama. Waktu untuk mencapai puncak limpasan juga dipengaruhi oleh kondisi kelembaban tanah pada permulaan turunnya hujan. Parameter yang diperoleh dari hasil analisis hidrograf satuan untuk masing-masing kejadian hujan, 7-9-1986; 7-11-1986; 9-11-1986; 4-1-1987; 6-6-1987 dan 6-11-1987...
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Judul: Heterologous Expression Of Endo-Β-Xylanase From Bacillus Pumilus Strain Bcrs-01 In Escherichia Coli.
Abstrak: Xylanases are glycoside hydrolase family 11 which depolymerise xylan in the plant cell wall, the most excessive form of hemicellulose. Endo-β-xylanases (EC 3.2.1.8) are most important to breakdown β-1,4-glicoside bond of xylan to produce disaccaride xyloolygosaccaride (XOs) and xylose (monomer). Bovine rumen fluids have potential to obtain endo-β-xylanase produced of bacteria. The objectives of this study were to obtain xylanase producing bacteria and to express xynA gene encoding endo-β-xylanase from bacterium in Escherichia coli. Twenty nine isolate bacteria have been succesfully isolated from bovine rumen fluid in agar medium containing birchwood xylan. Isolate BCRS-01 bacterium was previously screened for the high production of xylanase. Based on 16S rRNA gene sequence analysis, BCRS-01 showed high similarity (99%) to Bacillus pumilus (accession number NR043241). The crude xylanase had optimal activity at 55oC, pH 7.0. Furthermore, the crude xylanase exhibited broad pH stability from 4.0 to 10.0 and remained more than 60% and 40% of its activity after incubation at pH 4.0 until 10.0, respectively for 60 min. It also showed a stability at temperature 25-50oC since it retained 80% and 50% of its activity when incubated at 50oC or 30 and 60 min, respectively. The xylanase activity was strongly inhibited by Ca2+ and Cu2+ at concentration 10 mM, and as little as 1 mM for Mn2+. Therefore, this xylanase has potentially used as additive feeds in animal feed industry. The DNA sequence xynA gene encoded endo-β-xylanase was amplified and cloned into the expression vector pET-15by under the control of T7 promoter. The recombinant protein had succesfully expressed in Escherichia coli BL21 (DE3) pLysS. A protein recombinant of approximately, 26.7 kDa was observed on the SDS-PAGE analysis. Crude extract of recombinant endo-β-xylanase demonstrated activity of enzyme at 56 U mL-1 using birchwood xylan as a substrate at 55oC for 10 min.
Keyword: Bacillus pumilus, bovine rumen fluid, endo-β-xylanase, heterologous expression.