Judul: Antioxidant Activity of Waterleaf (Talinum triangulare (Jacq.) Willd) Cultivated with Organic Fertilizers during the Rainy Season
Abstrak: Talinum triangulare (Jacq.) Willd, known as ginseng Jawa or kolesom Jawa in Indonesia, is one of tropical plants that has been widely used as traditional herbal medicine and consumed as vegetable in Indonesia. The leaf from the plant contains bioactive compound identified as flavonoid which can function as antioxidant. The objective of this research was to measure the antioxidant activity and total phenolic compound of waterleaf in five different treatments of organic fertilization. Extraction of the leaf was carried out with the method of ultrasound assisted extraction/UAE (sample:MeOH=1:10 b/v, t=20 minutes, cold extraction room temperature). The present research resulted that the different organic fertilizer treatments significantly influenced the secondary metabolites content e.g. phenolic content of Talinum triangulare (Jacq.) Willd (p<0.05). High total phenolic content did not always exhibit high antioxidant activity as the highest total phenolic content group (PK+RP: 10.76 mg GAE/g dry sample) had weaker antioxidant activity (DPPH: 1.73 ± 0.01 mg AEAC/g GAE) than thus lower in phenolic content. Organic fertilizer RP+AS (rock phosphate and husk ash) treatment (7.36 ± 0.00 g GAE/g dry sample) exhibited the highest antioxidant activity in scavenging DPPH free radicals and strongest reducing power among all groups (2.06 ± 0.01 mg AEAC/g GAE; 0.022 ± 0.000 mg AEAC/g GAE respectively). Organic fertilizer influenced the secondary metabolite produced by the waterleaf
Keyword: Bogor Agricultural University (IPB), total phenolic content, Talinum triangulare (Jacq.) Willd, organic fertilization, DPPH, antioxidant activity

Judul: Growth, shoot production, and metabolite content of waterleaf (talinum triangulare (jacq.) willd) with repeated organic fertilization.
Abstrak: Waterleaf (Talinum triangulare (Jacq.) Willd) can be consumed as vegetable by consuming its shoot. Waterleaf is known as functional vegetable because the shoot contains some bioactive compounds to maintain human health. The purpose of this research was to investigate the effect of organic fertilizer combination to growth, production and metabolite content of waterleaf i.e. vitamin C, flavonoid, and peroxidase (POD) activity in the first and second planting season and organic fertilizer residue with repeated harvesting. This research was conducted at Leuwikopo Darmaga Bogor and Plant Analysis and Chromatography Laboratory, Department of Agronomy and Horticulture, IPB in November 2012-May 2013. The organic fertilizers were cow manure (CM), rock phosphate (RP) and rice-hull ash (HA). The fertilizer was combined into four combinations, CM + RP, CM + HA, RP +HA, and CM +RP +HA; with one control (without fertilizer). Treatment was arranged with randomized completely block design with three replications. Two experiments were set in the second season, i.e. the effect of organic fertilizing in the second season and the effect of organic fertilizer residue. The result showed that organic fertilizer gave same effect on growth, shoot production and metabolite content of waterleaf. Vitamin C was positively correlated to flavonoid content while flavonoid and vitamin C content was negatively correlated to K. Low rain intensity in the second harvest increased POD activity while flavonoid content decreased that was caused by precursor competition in flavonoid and lignin biosynthesis. Lignin biosynthesis is catalyzed by POD enzyme. Application of organic fertilizer in the second season increased growth, production, and metabolite content of waterleaf shoot. Cow manure + rock phosphate + rice-hull ash treatment gave the highest increase of shoot production compared to control treatment. Organic fertilizer residue from first season gave the same effect on growth and shoot production compared to control treatment. There was no significant difference effect between residual effect and organic fertilizer added in the second season. Growth and shoot production in the second season was lower than first season that was caused by low of rain intensity that inhibited the growth of waterleaf. The same condition also occurred in waterleaf metabolite content. Vitamin C content decreased in the second season while flavonoid content increased.
Keyword: flavonoid, POD, repeated harvesting, Talinum triangulare, vitamin C

Judul: Estimating Parameter and the Convergence of Parameter Estimator of Poisson Hidden Markov Model
Abstrak: Model hidden Markov terdiri dari sepasang proses stokastik yaitu proses observasi dan proses yang memengaruhi observasi. Proses stokastik yang memengaruhi observasi ini diasumsikan membentuk rantai Markov dan tidak diamati. Model Poisson hidden Markov (MPHM) adalah salah satu model hidden Markov diskret dan proses observasinya jika diketahui proses yang memengaruhinya diasumsikan menyebar Poisson., A hidden Markov model (HMM) consists of a pair of stochastic processes, that is the observation process and process that affected observation. The stochastic process which causes this observation is assumed to form a Markov chain and is not observed. Poisson hidden Markov models (PHMM) is one of the discrete HMM and the observation process given the cause is assumed having a Poisson distribution.
Keyword: Poisson hidden Markov model, Forward-Backward algorithm, Expectation Maximization algorithm