Judul: Pemodelan nilai tukar rupiah terhadap US dollar menggunakan hidden markov
Abstrak: Suatu masalah proses stokastik dengan serangkaian data yang diberikan namun penyebabnya tidak diamati secara langsung, dapat dimodelkan dengan model Hidden Markov (Hidden Markov model, HMM). Model Hidden Markov adalah model rantai Markov yang merupakan pasangan penyebab suatu kejadian yang penyebabnya tidak diamati secara langsung, serta kejadian itu sendiri. Tulisan ini mengkaji metode pendugaan parameter model Hidden Markov dari serangkaian data pengamatan serta menentukan peluang kejadiannya dengan menggunakan pemrograman Mathematica 5.1
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Judul: Pemodelan Nilai Tukar Rupiah Terhadap US Dollar Menggunakan Deret Waktu Hidden Markov Model Hamilton
Abstrak: Nilai tukar Rupiah terhadap US Dollar mengalami perubahan setiap waktunya. Perubahan nilai tukar Rupiah dapat diakibatkan karena perang, krisis keuangan dan ekonomi, atau perubahan yang cukup signifikan pada kebijakan pemerintah, sehingga menimbulkan mosi tidak percaya bagi investor asing yang akan menginvestasikan dananya di Indonesia. Hal ini berakibat pada tingginya nilai tukar Rupiah terhadap US Dollar. Namun kejadian ini, tidak diamati secara langsung (hidden). Untuk menggambarkan perilaku nilai tukar Rupiah tersebut, dalam karya ilmiah digunakan model deret waktu hidden Markov model Hamilton (1994). Model ini mengasumsikan bahwa nilai tukar Rupiah terhadap US Dollar bergantung pada rantai Markov yang merupakan penyebab kejadian yang tidak diamati dan nilai tukar Rupiah suatu waktu sebelumnya.
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Judul: Responses on Performance and Minerals Digestibility by Novel Consensus Bacterial 6-Phytase  Variant (PHY-G) Supplementation in Broiler Diet
Abstrak: Plant feedstuffs normally contain phytic acid which poorly hydrolized by monogastric especially broiler. Further, 80% of phosphorus (P) in plant feedstuff is complexed with phytic acid. In that case, high amount of inorganic P sources is needed to fulfill P requirement. Since it has capability to bind with some nutrients such as bi- or trivalent minerals and amino acids then phytase is widely utilized in poultry feed to improve the nutrient digestibility. Today, the use of 500-1000 FTU phytases in poultry feed is widely applied by feed industry and its capability releasing phytate-bound phosphorus is very well documented. Novel consensus bacterial 6-phytase variant (PHY-G) is newest 6-phytase derived from bacterial phytase gene Buttiauxella sp. expressed in Trichoderma reesei with enhanced functionality for better phytic acids degradation. The present research was conducted to evaluate the efficacy of PHY-G in different doses (1000, 1500 and 2000 FTU/kg) on high phytic acids content diets which at least contained 0.30% Phytate-P. A total 3,675 male broilers Indian River/IR (105 pens, 35 birds/pen) were provided mixed grain diets in seven treatments with fifteen replications, they were divided into two phases of rearing which were starter (1 – 21 d) and finisher (22 – 35 d). Treatments were positive control (PC) using standard diet following IR’s nutrient requirement, negative control 1 (NC1) with nutrient reduction at 0.21 percent unit calcium (Ca), 0.21 percent units available phosphorus (AvP), 0.34 percent unit crude protein (CP) and 66 kcal/kg AME, NC2 with nutrient reduction at 0.23 percent unit Ca & AvP, 0.45 percent unit CP and 75 kcal/kg AME, followed by NC3 with nutrient reduction at 0.24 percent unit Ca & AvP, 0.52 percent unit CP and 79 kcal/kg AME. PHY-G supplementation with dose 1000, 1500 and 2000 FTU/kg on top of NC1, NC2 and NC3 respectively. PHY-G supplementation at any level significantly improved body weight gain/BWG and corrected FCR/McFCR (P<0.05) on starter (1,083 – 1,093 g/bird) and overall phase (2,482 – 2,532 g/bird) compared to any NCs (1,063-1,084 g/bird on starter and 2,387 – 2,398 g/bird on finisher). No significant different were observed on mortality of all treatments but PHY-G supplementation significantly improved (P<0.05) broiler index/BI (444 - 463) versus NCs (427 - 430) and able to maintain it equivalent to PC (455). Toe ash was significantly improved (P<0.05) by all doses of PHY-G (13.28 – 13.56%) compared to NC (12.3 – 12.7%). Apparent ileal digestibility (AID) of Ca was not affected by PHY-G but 1000, 1500 and 2000 FTU/kg PHY-G supplementation significantly improvemed on AID of P (P<0.05) which were 64.97%, 75.60% and 78.29% compared to NCs (42.64%, 48.88% and 46.17% for NC1, NC2 and NC3 respectively). This These data indicated that PHYG supplementation effectively improved broiler growth performance, bone mineralization and P digestibility at any level of dose on high content of phytic acid in the diets.
Keyword: broiler, growth performance, phytase, phytic acid, toe ash