Judul: Morphological Characterization and Ability of Actinobacteria as Nitrogen Fixer In Vitro
Abstrak: Aktinobakteri ditemukan hidup sebagai endofit dan rizosfer berpotensi sebagai pemacu tumbuh tanaman. Nitrogen merupakan unsur utama yang diperlukan tanaman untuk pertumbuhannya. Informasi tentang aktinobakteri penambat N2 masih jarang dilaporkan, sedangkan keberadaan aktinobakteri di lingkungan sangat banyak. Penelitian ini bertujuan mengkarakterisasi morfologi aktinobakteri endofit dan rizosfer serta mengkaji kemampuannya dalam menambat N2 secara in-vitro. Tahapan penelitian meliputi peremajaan isolat aktinobakteri, karakterisasi morfologi, pertumbuhan pada media bebas nitrogen, uji produksi amonia, serta pola produksi amonia. Delapan isolat aktinobakteri asal endofit dan rizosfer dikarakterisasi secara makroskopis dan mikroskopis berdasarkan morfologi koloni, penataan rantai spora, warna miselium aerial dan substrat pada empat media berbeda. Hasil karakterisasi morfologi menunjukkan delapan isolat yang diamati memiliki kedekatan dengan Streptomyces spp.. Delapan isolat aktinobakteri mampu menambat N2 berdasarkan pertumbuhan pada media bebas nitrogen dan menghasilkan amonia berkisar antara 4,851 ± 0,100 - 9,474 ± 0,136 ppm. Tiga isolat diantaranya menghasilkan amonia paling baik berasal dari endofit tanaman padi, yaitu IPBCC.b.14.1531, IPBCC.b.14.1534, dan IPBCC.b.14.1535 dengan amonia sebesar 9,474 ppm; 8,587 ppm; dan 6,083 ppm. Pola produksi amonia ketiga isolat terus meningkat seiring makin lamanya masa inkubasi dengan amonia paling tinggi dihasilkan pada hari ke-15. Tiga isolat aktinobakteri tersebut berpotensi menjadi PGPB yang dapat dikembangkan sebagai bakteri pemacu tumbuh tanaman. Kata kunci: aktinobakteri, amonia, morfologi koloni, Streptomyces., Endophytic and rhizosphere actinobacteria have the potential to promote plant growth. Nitrogen is the main element needed by plants for growth. Information about N2-fixing actinobacteria still rarely reported, while the presence of actinobacteria in environment is abundant. This study aimed to characterize the morphology of endophytic and rhizosphere actinobacteria and to study their ability to fix N2 in vitro. The research stages included rejuvenation of isolates, morphological characterization, growth on nitrogen-free media, ammonia-production test and patterns. Eight actinobacteria isolates origin were characterized macroscopically and microscopically based on colony morphology, spore chain arrangement, aerial and substrate mycelium color on four different media. The results of morphological characterization showed that eight isolates observed were close to Streptomyces spp.. Eight isolates were able to fix N2 based on growth on nitrogen-free media and produced ammonia in range of 4.851±0.100 - 9.474±0.136 ppm. The three best ammonia-producing isolates from rice plant endophytes, namely IPBCC.b.14.1531, IPBCC.b.14.1534, and IPBCC.b.14.1535 with ammonia level i.e. 9.474; 8,587; 6.083 ppm respectively. The ammonia production pattern of three isolates continued to increase along with the longer incubation period and the highest ammonia produced on the 15th day. Three isolates have potential to become PGPB which can be developed further as plant growth-promoting bacteria. Keywords: actinobacteria, ammonia, colony morphology, Streptomyces.
Keyword: actinobacteria, ammonia, colony morphology, Streptomyces

Judul: Kemampuan Aktinomiset Endofit sebagai Penambat Nitrogen dan Perannya dalam Meningkatkan Pertumbuhan Tanaman Padi, Pemanfaatan Filterisasi untuk Meningkatkan Daya Tampung Pesan pada Steganografi Pixel Value Differences (PVD)
Abstrak: Nitrogen is the nutrient that most frequently limits on paddy productivity. Excessive chemical nitrogen fertilizer applied on conventional farming may have negative impact to the degradation of environment. An alternative solution for this problem is by using biological nitrogen fixation (BNF) to enhance crop growth which can be done by applying nitrogen fixing endophytic actinomycetes. The objective of this research was to obtain endophytic actinomycetes isolates which have the capability in fixing N2 based on in-vitro and in-planta assay. Based on in-vitro assay, SSW-02 was considered as the most promising N2 fixing bacteria based on its ability to reduce 2.1750 nmol acetylene/hour and produced ammonia 2.144 ppm for 15 days in free nitrogen medium. In-planta assessment was conducted in a greenhouse using IR-64 rice variety on sterile and non sterile soil with two-factors completely randomized factorial design. The factors were endophytic actinomycetes treatments which consisted of SSW-02, AB131-2, control and urea dosage which consisted of 0%, 50%, 100% dosage from 200 Kg/Ha. Each treatment had been done in three replications. Based on in-planta assay, SSW-02 application with 100% urea dosage increased total plant dry weight and leaf color. Although not significantly different, SSW-02 application with 50% urea dosage also had the highest number of tillering and ability to increase plant height and root length. Nitrogen content also increased by SSW-02 application with 100% urea dosage in sterile soil. Microscopic observation of SSW-02 and AB131-2 of rice treatment using reducing tetrazolium method showed that both of isolates were able to penetrate and colonize the root of rice, confirming them as endophytes. The results indicated that SSW-02 had promising role as a N2 fixing bacteria on rice plant.
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Judul: Perbandingan Metode Monte Carlo dan Kuasi Monte Carlo dalam Penentuan Harga Opsi Eropa
Abstrak: Opsi adalah suatu kontrak antara dua pihak di mana pemegang opsi mempunyai hak untuk membeli atau menjual suatu aset tertentu dengan harga yang telah ditentukan, pada atau sebelum waktu jatuh tempo. Opsi sebagai produk derivatif dapat mengurangi dampak risiko dalam berinvestasi dengan melakukan hedging (lindung nilai). Opsi Eropa merupakan opsi yang hanya dapat dieksekusi pada saat jatuh tempo. Karya ilmiah ini membahas penentuan harga opsi Eropa dengan menggunakan metode Monte Carlo dan Kuasi Monte Carlo dan hasilnya dibandingkan dengan harga opsi standar yang telah dihitung dengan menggunakan model Black Scholes. Berdasarkan hasil penghitungan, metode Kuasi Monte Carlo lebih cepat konvergen dengan galat relatif yang lebih kecil dibandingkan dengan metode Monte Carlo dalam penentuan harga opsi Eropa. Dengan demikian, dapat disimpulkan bahwa metode Kuasi Monte Carlo merupakan metode yang lebih baik dibandingkan metode Monte Carlo dalam penentuan harga opsi Eropa.
Keyword: opsi Eropa, Black Scholes, Monte Carlo, Kuasi Monte Carlo