Judul: Penggunaan Ice Gel sebagai Media Pendingin Selada Air (Nasturtium officinale L.) dalam Kemasan Pembawa dari Packing House ke Buyer
Abstrak: Selada air merupakan sayuran daun yang rentan terhadap dehidrasi sehingga mudah layu. Upaya untuk mempertahankan kesegaran selada air dengan perlakuan dingin. Pendinginan yang dilakukan biasanya menggunakan pecahan es dan kertas doorslag sebagai media pembatas antara sayuran dengan pecahan es. Pencairan dari es menyebabkan adanya genangan air menjadikan sayuran mudah cepat membusuk serta kertas mengotori selada air. Berdasarkan hal tersebut, dilakukan penelitian penggunaan ice gel sebagai media pendingin pengganti dari pecahan es dalam kemasan selada air. Tujuan dari penelitian ini adalah untuk mengetahui pengaruh penggunaan ice gel terhadap perubahan mutu (kesegaran) dan mengukur tingkat kontaminasi mikroba pada selada air. Penelitian dilakukan dengan merancang posisi media pendingin dalam kotak dengan dimensi 50x40x32 cm yang diisi 30 ikat selada air. Hasil terbaik dari penelitian ini adalah selada air dengan media pendingin ice gel dalam kotak. Hal ini dikarenakan penurunan mutu selada air lebih lambat serta kontaminasi mikroba rendah (2.25x10⁷ CFU/g).
Keyword: selada air, pecahan es, ice gel, kemasan

Judul: Kajian Penggunaan Ice Gel sebagai Media Pendingin pada Kemasan untuk Distribusi Sawi Hijau (Brassica juncea L.)
Abstrak: The green cabbage is one of vegetable which is susceptible by heat, so it can wilted easily. The way to keep the freshness of green cabbage is by cooling the comodity using cold storage. Ice gel is kind of liquid cold storage which is used to store the crops at low temperature. Based on the idea, if need some study about the using of ice gel as cold storage in packaging to ditribute green cabbage. The used method was designing pattern of placement of ice gel inside packaging. Four pieces of ice gels with dimension 30x20x3 cm with 1 kg of weight were placed in the packaging with two position. Parameters which are measured were temperature distribution and changes of green cabbages quality. The characteristic of ice gel with dimension 30x20x3 cm and 1 kg of weight had frozen temperature -7 ⁰C, melting temperature 0.5⁰C, and long liquidation 850 minutes. Temperature distribution of green cabbage with hydrocooling or without hydrocooling inside ice gel cold storage in first position had stability of temperature between 22 ⁰C-24 ⁰C during 1400-1500 minutes, meanwhile for second position can stand under 20 ⁰C relatively during 1600-1800 minutes. Ice gel has good effect to all measured parameters of green cabbages.
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Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model