Judul: Kajian Model Hidden Markov Diskret dan Aplikasinya pada Harga Gabah Kering Panen
Abstrak: A discrete hidden Markov model is a model which consists of the cause of event and observations process. This model assumes that the cause of event is Markov chain which is not observed directly. The observations process has discrete-range. Parameters of this model are transition probabilities and expectation of observations process. They are estimated by using the maximum likelihood method and expectation maximization algorithm. The estimation procedure involves change of measure. The estimation of parameters uses Mathematica 6.0, a functional programming based algebraic computer systems. The model is then applied to the price of harvest dry rice from January 2000 until March 2007. The estimated parameters are used to calculate expectation of harvest dry rice price. The result of this study shows that the discrete hidden Markov model can be applied to model the harvest dry rice price.
Keyword: Markov chain, Discrete hidden markov model, Expectation maximization algorithm

Judul: Kajian Model Hidden Markov Kontinu dan Aplikasinya pada Harga Beras
Abstrak: Continuous hidden Markov model with discrete time (Elliot et al. 1995) is a model consists of the cause of event and observation process. This model assumes that the cause of event is a Markov chain in discrete time, observed indirectly. The observation process has continuous range and future observation is influenced by the cause of present event. Parameters of this model are transition probability matrices of the cause of event, vector and vector of observation process; they are estimated by using the maximum likelihood method and expectation maximization algorithm that involves the change of measure. Model parameters were estimated by using Mathematica 7.0 functional programming computer algebra systems. The model is then applied to the price change of rice from February 2004 until May 2009. The estimated parameters are used to calculate the expectation value of rice price. As a result, this research convinces that the hidden Markov model can be applied to the price of rice.
Keyword: 

Judul: Durability of Specific Immunoglobulin (Ig) Y Againts Influenza and Covid-19 in Sunscreen
Abstrak: The benefit of specific immunoglobulin Y (Ig Y) as an active ingredient in personal care products such as sunscreen has not been properly studied. Our study aims to evaluate the reliability of specific IgY against influenza and the COVID-19 virus in a sample sunscreen product. Specific IgY influenza and COVID-19 viruses were inserted in the sample sunscreen at two concentrations of 0.1% and 0.25%. Three treatments were observed: control (C) sunscreen without IgY, treatment 1 (T1) sunscreen with 0.1% IgY, and treatment 2 (T2) sunscreen with 0.25% IgY. Organoleptic observations were carried out to monitor changes in aroma, color, and texture, and sunscreen sampling was done every week for 6 weeks. The durability of IgY was evaluated using an enzyme-linked immunosorbent assay (ELISA) and a neutralization assay. Organoleptic observation from weeks 1 to 6 showed consistency in its aroma, color, and texture. Enzyme-linked immunosorbent assay and neutralization assay (NA) results of the T1 and T2 groups showed negative results except for sample T1 at week 5, which showed a positive result in the Influenza A ELISA. Based on the results, it seems that IgY concentrations of 0.1% or 0.25% were not optimal. However, this negative result might be due to low concentration of the IgY and the presence of beeswax, which inhibits IgY and causes it to dissolve in distilled water, thus preventing it from being detected in the assay.
Keyword: Immunoglobulin Y, Sunscreen, Influenza, COVID-19, Biological Activity