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: Ulva lactuca Cellulose Microfibrillation using Deep Eutectic Solvent (DES) with Concentration Variation
Abstrak: Mikrofibril selulosa merupakan biomaterial yang dapat diaplikasikan pada berbagai bidang. Rumput laut Ulva lactuca merupakan salah satu sumber potensial untuk mikrofibrilasi selulosa. Deep Eutectic Solvent (DES) merupakan pelarut baru yang ramah lingkungan dan dapat dijadikan sebagai pelarut dalam mikrofibrilasi selulosa. Penelitian ini bertujuan menentukan konsentrasi DES untuk menghasilkan mikrofibril selulosa dan mengkarakterisasi fisiko-kimia mikrofibril selulosa dari rumput laut Ulva lactuca. Penelitian ini meliputi preparasi bahan baku, penghilangan ulvan, delignifikasi, bleaching, dan mikrofibrilasi selulosa dengan perlakuan HCl dan DES (ChCl/urea 1:2) dengan konsentrasi 10%, 20%, dan 30%. Mikrofibrilasi dengan DES dengan konsentrasi 10-30% berhasil menghasilkan mikrofibril selulosa yang berbentuk seperti jaring laba-laba. Diameter mikrofibril selulosa terkecil diperoleh perlakuan DES 10%. Mikrofibril selulosa dengan perlakuan DES termasuk ke dalam selulosa amorphous. Selulosa amorphous dapat dimanfaatkan untuk bidang biomedis dan bioenergi. DES memiliki potensi sebagai pelarut untuk mikrofibrilasi., Cellulose microfibril is biomaterials that can be applied to various fields. Green macroalgae Ulva lactuca is one of the potential sources for the cellulose microfibrillation. Deep Eutectic Solvent (DES) is a new green solvent that can be used to cellulose microfibrillation. This reseacrh aimed to determine the concentration of DES to produce cellulose microfibril and to characterize the physico-chemical properties of cellulose microfibrils from Ulva lactuca. This research method includes preparing raw materials, separation ulvan, delignification, bleaching, and cellulose microfibrillation with HCl and DES (ChCl/urea 1:2) with concentration of 10%, 20%, dan 30%. Microfibrillation using DES with a concentration of 10-30% produced cellulose microfibrils shaped like spider webs. The smallest diameter of cellulose microfibrils was obtained by 10% DES treatment. Cellulose microfibrils treated with DES are classified as amorphous cellulose. Amorphous cellulose can be used in biomedical and bioenergy fields. DES has the potential as a solvent for microfibrillation.
Keyword: cellulose microfibril, choline chloride (ChCl), seaweed, urea

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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