Judul: Isolasi nanoserat selulosa dari ampas tapioka dan aplikasinya sebagai bahan pengisi film tapioka
Abstrak: Starch-based films limit their application due to poor mechanical properties. An effort to overcome these poor characteristics was using fibers or nanofibers as reinforcement filler. Cassava bagasse, a solid by-product of cassava starch industry, is a source of natural fibers. Cellulose nanofibers from the renewable sources have gained more attention in recent years because of their exceptional mechanical properties and environmental friendly. This research aims: (1) to know of cellulose nanofibers character produced from cassava bagasse; (2) to know physical and mechanical properties of film produced by application of cellulose nanofibers; and (3) to know of mechanical properties stability of film during storage at different environmental humidity conditions. Cellulose nanofibres from cassava bagasse were obtained by three methods, namely method I (alkali treatment + bleaching + mechanical treatment), method II (alkali treatment + bleaching + acid hydrolysis + mechanical treatment), and method III (acid hydrolysis + mechanical treatment). Cellulose nanofibers produced from method I have diameter of 20-30 nm, while cellulose nanofibers produced from method II and III have diameter of 5-8 nm with several micrometer of length. Cellulose nanofibers suspension have good stability, indicated by zeta potential value of method I, II, and III are 46.47 mV, 52.45 mV, and 33.75 mV, respectively. All method improved crystallinity of fibers from 14.52% in cassava bagasse to 33.25% (method I), 39.73% (method II), and 31.23% (method III). It was observed that the addition of cellulose nanofibers was improved tensile strength of films as much as 2.44-2.71 N/mm2, but tends to decrease of elongation at break as much as 16.51-31.14%. Water vapour transmission rate of film in range 143.21-166.56 g/m2.day and water vapoor permeability of film is 28.52-31.98 g.mm/m2.day.kPa. The addition of cellulose nanofibers also decreased the transparency of film. Storage condition with RH 75% for seven days cause tensile strength generally increased but elongation at break is decreased. Modulus of elasticity of film has increased during storage, indicating that the film stiffness also increased. Storage condition with RH 97% for seven days caused tensile strength and elongation at break decreased. Modulus of elasticity of film tends to decrease, indicating film structure getting soft during storage. Stability of cellulose nanofibers suspension not only reflects its ability to be well distributed in the matrix of the film, but also related to the crystallinity of cellulose nanofibers, further affect the mechanical properties of the film, improving the effectiveness cellulose nanofibers as a water vapour transmission barrier, and to support the transparency properties of the film. Cellulose nanofibers with higher crystallinity not only support the increased the strength of the film, but it can increase the effectiveness of the film as a water vapour transmission barrier, as well as inhibit the reduction of film transparency due to the use of fillers.
Keyword: cellulose nanofibers, cassava bagasse, filler, tapioca-film

Judul: Pengembangan Bionanokomposit Film Berbasis Tapioka/Nanopartikel Perak dan Tapioka/Nanopartikel Seng Oksida dengan Plasticizer Gliserol.
Abstrak: Cassava starch can be formed into bioplastic film which is transparance as synthetic plastic films. However, pure cassava starch film has some drawbacks such as brittle, poor barrier to water vapour, sensitive to humidity and not stable during the application. The addition of nanoparticles in film was intended to increase the elongation and tensile strength, moisture stability and to provide antimicrobial activity. Meanwhile, the addition of glycerol was intended to increase the plasticity of films so they will not be easily cracked. The main purpose of this research is to elaborate the functional packaging characteristics of bionanocomposites films made from cassava starch with or without silver nanoparticles (Ag-Np) of zinc oxide nanoparticles (ZnO-Np) with glycerol as plasticizer. The addition of nanoparticles was conducted at the amount of 0%, 0,5%, and 1% by weight of the starch, whereas glycerol was used at the amount of 0% and 20% by weight of the solids (starch only or starch+nanoparticles). The value of water vapor transmission decreased significantly with the addition of Ag-Np and ZnO-Np at the concentration of 1% (from 18,0569 g/hm2 to 12,0574 g/hm2) so it enhance the water barrier of the films as packaging materials. The addition of Ag-Np and ZnO-Np at the amount of 1% with 20% of glycerol was also able to inreased the value of elongation (from 1,2% to 88,8%), but decreased the value of tensile strength (from 22,93 MPa to 4,03 MPa). The addition of glycerol gave contrary effect to the tensile strength because it produces low tensile strength values. Moreover, the results show that films made with ZnO-Np had a stronger antimicrobial activity than those made with Ag-Np for both gram positive and gram negative bacteria. In overall, it seems that the formulation of 1% ZnO-Np is the best formulation for developing bionanocomposite film based on cassava starch.
Keyword: Bionanocomposite Films, Silver Nanoparticle (Ag-Np), Zinc Oxide Nanoparticle (ZnO-Np), Cassava Starch, Antibacterial Films

Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh.
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. ,,,
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular.