Judul: Potential of White Rot Fungi for Expanded Polystyrene Biodegradation
Abstrak: Studies on Expanded polystyrene (EPS) degradation using white rot fungi (WRF) is still limited. This research aimed to evaluate the ability of six strains WRF (BRB 11, BRB 73, BRB 81, EDN 082, EDN 134 and D7) to degrade EPS. The WRF were first studied on their ability to produce laccase in Malt Extract Broth (MEB) containing EPS in four weeks incubation. Degradation was measured on the weight reduction, and morphological damage of EPS that was supported by characterization of the intermediate polymers (functional grups, molecule transformations to volatile subtances, thermal stability and crystallinity) after degradation. Medium containing EPS without WRF was used as control. The result showed that all six strains of WRF produced laccase and were capable of colonizing the EPS surface. BRB 11 was the best EPS colonizer as it grew faster 1.86 cm/d than other WRF at 10.000 ppm EPS. After 30 days of incubation BRB 11 and BRB 73 caused EPS mass loss about 16% and 1% respectively. Meanwhile EPS treated BRB 11 showed the highest decreasing of aromatic (-47%) and vinyl compound (-76%). It also produced more new intermediate-compounds compared to the control. BRB 73 caused the highest decrease in thermal stability with mass loss 10% at 300°C and 15,4 % at 380°C. Which is in accordance with its crystallinity. BRB 11 and BRB 73 were recommended to be studied further on their capacity for EPS biodegradation.
Keyword: Biodegradation, Expanded Polystyrene (EPS), White Rot Fungi (WRF)

Judul: Characterization and Biodegradation of Polyblend (Styrofoam-Starch) with Polylactid acid (PLA) as Biocompatizer.
Abstrak: Styrofoam is a kind of polystyrene which can not be naturally decomposed. The increasing amount of using styrofoam causes environment pollution. In facing this problem, modification of recyclable styrofoam is needed to produce degradable plastic. Starch can be a solution because it is a polymer that can be biologically decomposed. The mixture of starch to the styrofoam composite creates biodegradable plastic. Unfortunately, various polarity of styrofoam and starch is difficult to mixed homogenously, so we need polylactic acid (PLA) as the biocompatizer. Styrofoam and starch of four different concentrations of PLA, 5, 10, 15, and 20%. Film with the highest homogeneity was given by 80:20 concentration of styrofoam and starch combination with 20 % of PLA addition. The more PLA, the more homogenous of film we got. Film with the highest homogeneity produced substantial weight reduction which about 10%. The film that has been produced was amorphous since it had wide melting point, 155 °C to 185 °C. Infrared spectrum film showed the existence of C-O ester on 1184 cm-1 region. Ester functional group indicated that the film could be biodegraded. The infrared spectrum of the film did not show new functional groups, so we concluded that the film was a product of physical mixture between styrofoam and starch.
Keyword: 

Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf