Judul: Nanofibrilation of Cellulose from Ulva  lactuca treated by Deep Eutectic Solvents at Times and Temperatures Dependence
Abstrak: Nanofibrilasi selulosa merupakan proses pembentukan serabut/fibril selulosa menjadi nanofibril dengan diameter 1-100 nm dan panjang 500-2000 nm yang pemanfaatannya sangat luas. Rumput laut Ulva lactuca merupakan salah satu sumber potensial nanofibril selulosa karena mengandung selulosa tinggi dan rendah lignin. Produksi nanofibril selulosa menggunakan Deep Eutetic Solvents (DES) berbasis choline chloride dan urea menarik dilakukan karena ramah lingkungan. Penelitian ini bertujuan untuk karakterisasi nanofibril selulosa dari rumput laut hijau U. lactuca menggunakan DES choline chloride urea dengan waktu dan suhu berbeda. Tahapan penelitian meliputi preparasi U. lactuca, ekstraksi selulosa, sintesis DES, dan nanofibrilasi selulosa. Nanofibrilasi dengan DES dilakukan pada durasi 1, 2, dan 3 jam pada suhu 80 ⁰C serta perlakuan suhu 50, 65, dan 80 ⁰C selama 3 jam. Rendemen nanofibril selulosa yang dihasilkan semakin rendah seiring dengan peningkatan waktu dan suhu nanofibrilasi selulosa (0,08±0,02-1,36±0,25%). Nanofibril selulosa yang dihasilkan dari perlakuan DES memiliki diameter fiber antara 8-489 nm. Nanofibrilasi selulosa dengan DES pada waktu dan suhu yang tinggi menyebabkan degradasi selulosa dan menghasilkan tipe selulosa yang amorphous., Cellulose nanofibrillation is process of forming cellulose fibers/fibrils into nano-sized with diameter 1-100 nm and length 500-2000 nm which has very wide utilization. Ulva lactuca seaweed is potential sources of nanofibril cellulose because of high cellulose and low lignin contents. The production of cellulose nanofibril with Deep Eutetic Solvents (DES) based choline chloride urea is environmentally friendly. This study aimed to characterize cellulose nanofibril from U. lactuca treated by DES at times and temperatures dependence. The steps of research included preparation of U. lactuca, cellulose extraction, DES synthesis, and cellulose nanofibrillation. DES nanofibrilation was performed at times 1, 2, and 3 hours at 80 ⁰C and temperatures at 50, 65, and 80 ⁰C for 3 hours. The yield of cellulose nanofibril produced decreased with increasing treatment times and temperature of cellulose nanofibrillation (0.08±0.02-1.36±0.25%). Cellulose nanofibril produced from DES had diameter fibers between 8-489 nm. Cellulose nanofibrillation with DES at times and temperatures dependence caused degradation of cellulose from U. lactuca and produced amorphous cellulose.
Keyword: green solvents, cellulose nanofibre, seaweed

Judul: Extraction of Ulvan from Seaweed Ulva lactuca Using Different Types and Concentration Deep Eutectic Solvents (DES)
Abstrak: Ulva lactuca atau biasa disebut selada laut adalah rumput laut hijau yang memiliki pertumbuhan tiga kali lebih cepat dibanding dengan jenis rumput lain dan kandungan polisakarida bersulfat tinggi yang dapat dimanfaatkan untuk aktivitas biologisnya. Deep Eutectic Solvents (DES) muncul sebagai alternatif untuk mengekstrak ulvan karena sifatnya yang biodegradable, ramah lingkungan, dan tidak berbahaya. Penelitian ini bertujuan menentukan jenis dan konsentrasi DES yang dapat menghasilkan karakteristik ekstrak ulvan terbaik berdasarkan analisis rendemen, FTIR, dan viskositas serta uji kadar air dan kadar sulfat. Tahapan penelitian yang dilakukan meliputi preparasi dan karakteristik bahan baku, sintesis DES, ekstraksi, serta analisis dan uji lanjutan. Perbedaan jenis dan konsentrasi DES berpengaruh terhadap hasil analisis. Hasil uji menunjukkan rendemen ulvan tertinggi terdapat pada perlakuan jenis DES kolin klorida-urea 30% (KKU30), sedangkan nilai kadar sulfat, dan viskositas tertinggi terdapat pada perlakuan kolin klorida-gliserol 30% (KKG30). Gugus fungsi ulvan pada perlakuan kolin klorida-gliserol 30% (KKG30) menunjukkan hasil pita serapan yang serupa dengan perlakuan HCl., Ulva lactuca commonly called sea lettuce is a green seaweed that grows three times faster than other types of grass and contains high sulfated polysaccharides which can be utilized its biological activity. Deep Eutectic Solvents (DES) have emerged as an alternative to extract ulvan because of their biodegradable, environmentally friendly, and harmless properties. This study aims to determine the type and concentration of DES which can produce the best characteristics of ulvan extract based on yield, FTIR, viscosity also tests for water content and sulphate content. DES synthesis, extraction, further analysis and testing. Different types and concentrations of DES affect the result of the analysis. The test results showed that the highest yield of ulvan was found in the type treatment choline chloride-urea 30% (KKU30), whereas the highest sulfate content, and viscosity were found in the DES treatment choline chloride-gliserol 30% (KKG30). The ulvan functional group in the treatment choline chloride-gliserol 30% (KKG30) showed similiar absorption band to the HCl treatment.
Keyword: DES, extraction, polysaccharide, Ulva lactuca, ulvan

Judul: Approximation of the Median of Poisson Distribution Using the Relation of Poisson-Gamma Distribution
Abstrak: A major drawback of median is that median cannot usually be defined in closed form, even in the cases where their distribution functions are known. This study gives an approximation of the closed form for the median of the Poisson distribution by using the relation of Poisson-Gamma distribution. The approximation uses elementary techniques based on the monotonicity of certain sequences involving tail probabilities of the Poisson distribution and the Central Limit Theorem. Furthermore, a closed form expression for the mean absolute deviation 􀜧|􀜰􀰒 􀵆 􀜯􀝁􀝀􁈺􀜰􀰒􁈻| is also studied. The median is relevant because of the fact that it minimizes the mean absolute deviation of a Poisson random variable (􀜰􀰒􁈻 by considering median as central tendency.
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