Judul: Stimulasi Pembentukan Agregat Bakteri pada Budidaya Udang Vaname Litopenaeus vannamei dengan Teknologi Bioflok Melalui Peningkatan Kekuatan Ion
Abstrak: Biofloc technology application in aquaculture is limited by a number of limitations including the increasing of turbidity and total suspended solids (TSS). The aforementioned limitations were caused by the accumulation of metabolic wastes of feed and organic particles from the feces, as well as the low consumption level by the cultured organism, which is likely caused by the small size of bacterial aggregate. Therefore, the formation of bacterial aggregation is critical in the management system of biofloc cultivation (BFT). This study aims to evaluate the effect of ionic strength enhancement in stimulating bacterial aggregate in a BFT system. The objective of the first stage of the research was to evaluate the effect of several flocculants in stimulating bacterial aggregate represent by the decrease of turbidity. The flocculants used were kaolin, sodium sillicate, bentonite, and CaCl2. The result shows that CaCl2 is the best flocculant that reduced the water turbidity (20 NTU). The second stage was aimed to determine the most optimum ionic strength level of CaCl2. The levels tested were 5.10-5, 5.10-4, 5.10-3, 5.10-2, and 5.10-1. The result of this stage showed that I = 5.10-2 (1.7.10-2 M) resulted in the best turbidity decrease of 13.2 NTU. The third stage evaluated the effect of CaCl2 addition on shrimp survival and growth. White shrimp Litopenaeus vannamei with an average body weight of 0.3 g was stocked at a density of 20 shrimps/tank and cultured for 28 days. The result shows that CaCl2 addition has no effect on shrimp survival. CaCl2 addition at a dose of 0.46 g/L resulted in the best specific growth in this experiment.
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Judul: Efektivitas Formulasi Biostimulan Berbahan Baku Cangkang Kerang terhadap Stabilitas Bakteri Denitrifikasi dan Kualitas Air di Media Budidaya Udang Vaname Litopenaeus vannamei
Abstrak: Penambahan formulasi berbahan baku cangkang kerang dapat dijadikan sebagai sumber karbon untuk bakteri denitrifikasi dan meningkatkan kualitas air budidaya. Penelitian ini bertujuan untuk mengukur efektivitas penambahan formulasi cangkang kerang terhadap stabilitas bakteri denitrifikasi dan mengendalikan kualitas air lingkungan budidaya udang vaname Litopennaeus vannamei. Terdapat empat perlakuan dengan tiga kali pengulangan. Perlakuan yang diujikan terdiri dari kontrol (0 mg L-1), dosis 10 mg L-1, dosis 20 mg L-1, dan dosis 30 mg L-1. Udang yang digunakan stadia PL 25 dengan ukuran bobot 0,05±0,009 g dan dipelihara selama 14 hari. Hasil perlakuan menunjukkan bahwa penambahan formulasi cangkang kerang dengan dosis 30 mg L-1 merupakan perlakuan terbaik terhadap kelimpahan bakteri denitrifikasi yang mencapai 5,76 x 107 CFU mL-1 pada akhir pemeliharaan. Hasil identifikasi bakteri denitrifikasi yang didapatkan diduga termasuk pada kelompok Alcaligenes sp. dan Achromobacter sp. Penambahan formulasi cangkang kerang juga mampu menurunkan kadar nitrit di perairan hingga memiliki nilai 0,186±0,007 mg L-1.
Keyword: Clam-shell, Denitrification, Litopenaeus vannamei

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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