Judul: Quality improvement for several lesser-used wood species through impregnation and compregnation techniques
Abstrak: Efforts to improve the properties of the three lesser-used wood species, namely nyatoh (Palaquium spp.), sepetir (Sindora spp.), pisang putih (Mezzettia spp.) from natural rain forests in North Kalimantan Province, especially wood strength (represented by specific gravity/SG), dimensional stability and durability have been carried out in order to improve their quality and added value. The techniques used are impregnation and compregnation. Impregnation was carried out by vacuum-pressure (‒98 kPa 15 minutes and 350 kPa for 4 hours) using five types of impregnants, namely PEG (representing nonbonded-leachable), conventional phenol formaldehyde (PFK), low molecular weight PF (LmwPF) and sodium silicate (SS) (representing nonbonded-nonleachable), as well as succinic anhydride (SA) (representing bonded-nonleachable), followed by hot immersion in each impregnant solutions (80 °C) for 3 hours. Compregnation was carried out using a hot press machine (160 °C) and a specific pressure of 2,672 MPa for 15 minutes with a compression ratio (CR) of 20 and 40% from the initial thickness. All parameter measurements were carried out according to applicable standards. Apart from being compared among treatments, the results were also compared to untreated wood. The results showed that the two techniques applied could improve the properties of wood compared to untreated wood. In general, compregnation technique results in a higher improvement than impregnation. Percentage of improvement varies according to wood species and type of impregnating agents. The SG, dimensional stability and durability of impregnated and compregnated woods of nyatoh and sepetir increased significantly, but not for pisang putih wood. Compared to other impregnating agents, SA is the best. The SG and dimensional stability of SA-impregnated wood are significantly improved, while the durability is comparable to that of untreated wood. The best improvement in wood durability was obtained in the treatment using LmwPF. Result also showed that the concentration of impregnant solution also significantly contributes to that improvement. Impregnated wood with 11% LmwPF is belonged to the durable class I. Immersion in hot impregnant solution, as a pretreatment, can reduce the leachability and spring back phenomenon. In general, the characteristics of compregnated wood with SA are better than those of compregnated wood with LmwPF.
Keyword: compregnation, dimensional stability, impregnation, lesser-used species, wood durability

Judul: Sifat Fisis dan Mekanis Kayu-Polietilen Glikol dari Jenis Sengon, Manii, dan Gmelina
Abstrak: The timbers of fast growing species products of the community forests is one of the raw material supplier to the industrial timber in indonesia. The objective of this research is to obtain the physical and mechanical properties of sengon (Falcataria mollucana Miq), manii (Maesopsis eminii Engl.), and gmelina (Gmelina arborea Roxb.) that impregnated with PEG 400. Manufacture of impregnated wood in this research were using the vacuum pressure method by means of impregnation poly-ethylene glycol (PEG) 400 with 100% concentration. Sample and testing methods of physical and mechanical properties refer to the British Standard (BS) 373: 1957. Impregnation of wood with PEG 400 affect moisture content, density, shrinkage and swelling, static bending strength, shear strength, and hardness. Physical properties of PEG- wood are better than untreated wood (control), but the mechanical properties of PEG-wood are lower compared to untreated wood. Sengon woods have higher polymer loading compared to gmelina and manii, it is affected by wood anatomical structure.
Keyword: Bogor Agricultural University (IPB), impregnation, gmelina, sengon, manii, Poly Ethylene Glycol

Judul: Mathematical Analysis of a Cholera Spread Infection Model  Using Vaccination
Abstrak: Kolera merupakan penyakit diare yang disebabkan infeksi pada usus oleh bakteri Vibrio cholerae. Bakteri tersebut masuk ke dalam tubuh seseorang melalui makanan dan minuman yang telah terkontaminasi yang akan mengeluarkan enterotoksin di dalam tubuh seseorang pada bagian saluran usus, sehingga menimbulkan diare disertai muntah yang akut dan sangat hebat, dan berakibat seseorang dalam waktu hanya beberapa hari akan kehilangan banyak cairan dalam tubuhnya sehingga mengalami dehidrasi. Penelitian ini bertujuan untuk menganalisis model untuk penyebaran infeksi kolera menggunakan vaksinasi. Terdapat dua titik tetap, yaitu titik tetap bebas penyakit dan titik tetap endemik. Pada simulasi numerik jika nilai reproduksi dasar yakni ℛ0 < 1 maka jumlah individu yang terinfeksi akan berkurang sehingga penyakit hilang. dst.., Cholera is a diarrheal disease caused by infection of the intestine by the bacterium Vibrio cholerae. These bacteria enter a person's body through contaminated food and drink, which will release enterotoxins in a person's body in the intestinal tract, causing diarrhea accompanied by acute and very severe vomiting, and resulting in a person just in a few days of losing a lot of fluids in the body so it becomes dehydrated. This study aims to analyze a model for the spread of cholera infection using vaccination. dst ..
Keyword: fungsi Lyapunov, infeksi kolera, vaksinasi