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: Physical, Mechanical Properties and Durability of Impregnated Sengon Wood by Nano Silica orignated from Betung Bamboo Leaves
Abstrak: Sengon (Falcataria moluccana Miq.) merupakan jenis kayu cepat tumbuh yang memiliki beberapa kelemahan, yaitu berat jenis, kekuatan, keawetan, kerapatan dan stabilitas dimensi yang rendah. Penelitian ini bertujuan untuk menganalisis pengaruh perlakuan impregnasi menggunakan monoethylene glycol (MEG) dan nano silika daun bambu betung terhadap sifat fisis, mekanis dan keawetan kayu sengon. Salah satu metode modifikasi kayu adalah impregnasi. Proses impregnasi memiliki keunggulan yaitu dapat meningkatan kerapatan dan kekerasan kayu dengan memasukkan polimer ke dalam struktur kayu. Larutan impregnasi yang digunakan yaitu kontrol (tanpa perlakuan), MEG, MEGSilika 0.5% dan MEGSilika 1%. Proses impregnasi dimulai dengan pemberian vakum 0.5 bar selama 60 menit dan dilanjutkan dengan pemberian tekanan 2.5 bar selama 120 menit. Hasil penelitian menunjukkan perlakuan impregnasi MEG dan nano silika berpengaruh nyata dan meningkatkan nilai weight percent gain (WPG), kerapatan, perubahan warna (ΔΕ), MOE, MOR, kekerasan dan persentase mortalitas rayap tanah Coptotermes curvignathus serta menurunkan persentase kehilangan berat pada kayu sengon. Secara keseluruhan perlakuan MEGSilika 1% merupakan perlakuan yang paling optimum untuk kayu sengon yang berumur 5 tahun, Sengon (Falcataria moluccana Miq.) is fast growing wood species which has inferior characteristics i.e. low specific gravity, strength, durability, density and dimensional stability. The objective of this study was to analysis the effect of monoethylene glycol (MEG) and nano silica originated from betung bamboo leaves impregnation treatment on physical, mechanical properties and durability of sengon wood. One of wood modification methods is impregnation. Impregnation process could increase the wood density and hardness by introducing polymer into wood structure. The impregnation solution were consisted of water treated (untreated), MEG, MEGSilika 0.5% and MEGSilika 1%. The impregnation process was initiated by applying 0.5 bar of vacuum for 60 min and followed by 2.5 bar of pressure for 120 min. The results showed that MEG and nano silica impregnation treatment had significant effect on and increased weight percent gain (WPG), density, color changes (ΔΕ), MOE, MOR, hardness and mortality percentage of termite Coptotermes curvignathus and decreased weight loss percentage. MEGSilika 1% was the optimum treatment for of 5-year-old sengon wood.
Keyword: daun bambu betung, impregnasi, keawetan, nano silika, sengon, betung bamboo leaves, durability, impregnation, nano silica

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