Judul: Surface Characteristics of Scots Pine (Pine sylvestris L.) Chemically Modified by Citric Acid Sorbitol and Softener
Abstrak: Penggunaan kayu sebagai bahan baku produk eksterior harus memiliki keawetan yang baik. Kayu pinus scots memiliki keawetan yang rendah, sehingga keawetannya perlu ditingkatkan melalui modifikasi kayu. Penelitian ini bertujuan untuk mengetahui pengaruh modifikasi kimia menggunakan asam sitrat-sorbitol atau CAS (dengan beberapa rasio molar dan konsentrasi larutan) dan softener terhadap karakteristik permukaan kayu pinus scots sebelum dan setelah uji kubur selama 4 bulan, 8 bulan, dan 12 bulan. Pengujian karakteristik permukaan meliputi uji kekasaran permukaan, energi bebas permukaan, keterbasahan, dan daya lekat cat. Hasil penelitian menunjukkan bahwa nilai kekasaran permukaan, energi bebas permukaan, keterbasahan, dan daya lekat cat meningkat seiring dengan semakin lamanya waktu uji kubur. Kayu dengan perlakuan CAS 1:1_20% menghasilkan nilai keterbasahan dan daya lekat cat tertinggi. Peningkatan rasio molar dan konsentrasi asam sitrat dapat menurunkan nilai kekasaran permukaan, energi bebas permukaan, keterbasahan, dan daya lekat cat pada kayu. Cat alkid menghasilkan nilai keterbasahan dan daya lekat cat lebih baik dibandingkan cat akrilik., The used of wood as a raw material for exterior products must have good durability. Scots pine (Pinus sylvestris L.) wood has low durability, hence its durability needed to be increase by a wood modification. This study aimed to determine the effect of chemical modification using citric acid-sorbitol or CAS (with several molar ratios and solution concentrations) and softener on the surface characteristics of scots pine wood before and after graveyard test for 4 months, 8 months, and 12 months. The surface characteristics studied were surface roughness, surface free energy (SFE), wettability, and bonding quality. The results show that the values of surface roughness, surface free energy, wettability, and bonding quality increased as the longer of the graveyard test. CAS 1:1_20% wood treated resulted in the highest wettability and bonding quality values. Increasing the molar ratio and concentration of citric acid could reduce the value of surface roughness, SFE, wettability, and bonding quality. Alkyd paint produced better wettability and bonding quality than acrylic paints.
Keyword: citric acid sorbitol, graveyard test, scots pine, softener, surface characteristics

Judul: Durability and Wettability of Chemically Modified Scots Pine Wood (Pinus sylvestris L.) by Softener and Citric Acid-Sorbitol
Abstrak: Pinus scots (Pinus sylvestris L.) merupakan kayu yang banyak digunakan sebagai bahan baku produksi di benua Eropa, namun kayu ini memiliki sifat ketahanan yang rendah terhadap organisme perusak kayu. Modifikasi kimia menggunakan softener dan asam sitrat (2-hydroxy-1,2,3- propanetricarboxylic acid)-sorbitol (CAS) diaplikasikan untuk meningkatkan keawetan kayu. Penelitian ini bertujuan untuk menganalisis pengaruh modifikasi kimia menggunakan softener dan CAS (dengan berbagai rasio molar dan konsentrasi larutan) terhadap keawetan dan keterbasahan kayu pinus scots. Keawetan kayu terhadap rayap diuji melalui pengujian rayap kayu kering dan uji kubur. Pengujian karakteristik permukaan dilakukan sebelum dan sesudah uji kubur. Hasil penelitian menunjukkan bahwa modifikasi kimia mengunakan softener dan CAS meningkatkan ketahanan pinus scots terhadap rayap kayu kering dan rayap tanah. Peningkatan rasio molar dan konsentrasi asam sitrat meningkatkan keawetan kayu. Energi bebas permukaan (SFE) dan keterbasahan menurun setelah perlakuan modifikasi kimia menggunakan softener dan CAS. Kekasaran permukaan, SFE, dan keterbasahan meningkat setelah uji kubur., Scots pine (Pinus sylvestris L.) is a wood that widely used as a raw material in Europe, but this wood has low resistance against wood destroying organisms. Chemical modification by softener and citric acid (2-hydroxy-1,2,3-propanetricarboxylic acid)-sorbitol (CAS) was applied to increase the wood durability. This study aimed to analyze the effect of chemical modification by softener and CAS (with various molar ratios and solution concentrations) on the durability and wettability of scotspine wood. The durability of wood against termites was tested by dry-wood termite and grave yard testing. Surface characteristics testing was carried out before and after the graveyard test. The result shows that chemical modification by softener and CAS increased the resistance of scots pine against dry-wood and subterranean termites. The increasing of molar ratio and solution concentration increased the wood durability. The surface free energy (SFE) and wettability decreased after chemical modification treatments by softener and CAS. Surface roughness, SFE, and wettability increased after graveyard test.
Keyword: citric acid and sorbitol, durability, wettability, scots pine, softener, asam sitrat dan sorbitol, keawetan, keterbasahan, pinus scots, softener

Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model