Judul: N and P waste removal efficiency by freshwater clams (Pilsbryoconcha exilis) as biofilter on tilapia (Oreochromis niloticus) culture with resirculation system.
Abstrak: Nitrogen (N) and phosphorus (P) are the main end-products of fish loading, and can affect not only the rearing water, but also the environment as a whole. The study aim to determine the optimum density of freshwater clams on removing N and P waste from Tilapia culture using resirculation system. This study used a complete randomized design with four treatments and three replication (A. 0 clam, B. 30 clams, C. 60 clams, D. 90 clams). Parameters measured were waste removal efficiency, retention of N and P by Tilapia and freshwater clam, survival rate and daily growth rate of Tilapia and freshwater clam. The result showed that freshwater clam can be used as biofilter on removing N, P, TOM and TSS waste from Tilapia culture. The optimum density of freshwater clams which can support the survival rate and growth of Tilapia was 60 clams.
Keyword: 

Judul: Pertumbuhan ikan nila BEST Oreochromis sp. dalam budidaya sistem akuaponik dengan waktu tinggal aliran air yang berbeda
Abstrak: Intensive culture of BEST tilapia does not only produce fish biomass but also waste. The waste are usually managed to avoid its toxic which can hamper fish growth, and even, cause death of fish. One of the management activity is application aquaponic as a culture system. The purpose of the study was to determine water flow detention time in the hydroponic chamber to achieve optimal growth and production of the fish in the aquaponic culturing system. The water flow treatment consisted of 3 level of detention time, is 30, 60, and 120 minutes. Another treatment was culturing the tilapia in a flow through culturing system as a control. During 40 days culturing periode, the highest daily individual, biomass and length growth rate up to 0.54 g/day, 369.58 g/day and 5.58 cm respectively (P<0.05). While survival rate of the fish was at the range of 64.50-80.80%, feed conversion rate was 1.24-1.33 (P>0.05). The result showed that the detention time affected individual, biomass and length growth rate of the fish, in which the highest value reached by the detention time of 120 minutes. While survival rate and feed conversion rate were not affected by the different detention time treatments. The aquaponic system could remove total N and P up to 10.69 % and 38.10% respectively. The 120 minutes detention time treatment resulted in the highest economic benefit.
Keyword: 

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.
Keyword: