Judul: Chemical Characteristics of Gemor Bark (Alseodaphne spp.)
Abstrak: Sifat kimia merupakan salah satu sifat dasar yang berpengaruh pada pemanfaatan biomasa berdasarkan komponennya seperti untup pulp, energi, farmasi, dan bahan kimia lainnya. Untuk meningkatkan nilai manfaat kulit gemor dapat dilakukan melalui pengembangan produk berdasarkan komponen kimianya, sehingga diperlukan informasi tentang kadar komponen kimia dan sifat kimianya. Penelitian ini bertujuan untuk menguji kadar komponen kimia, proksimat, dan fitokimia kulit kayu gemor. Sampel kulit gemor berasal dari Kabupaten Katingan, Kalimantan Tengah. Penentuan kadar komponen kimia mengacu pada TAPPI dan metode Browning, analisis proksimat mengacu pada standar ASTM, dan analisis fitokimia mengacu pada metode Harbone. Kadar komponen kimia kulit gemor terdiri atas holoselulosa 63,59%, α-selulosa 46,19%, hemiselulosa 17,39%, lignin 43,56%, kadar abu 1,32%, kelarutan dalam air panas 19,49%, kelarutan dalam air dingin 18,21%, kelarutan dalam NaOH 1% 47,65%, dan ethanol-benzena 27,66%. Kulit gemor memiliki zat terbang 78,04% dan karbon terikat 20,64%. Analisis fitokimia mengkonfirmasi adanya senyawa flavanoid, phenolic, alkaloid, tannin, saponin, triterpenoid, steroid dalam kulit kayu gemor. Kulit gemor berpotensi sebagai bahan baku bioenergi karena mengandung kadar lignin dan zat ekstraktif yang tinggi., Chemical properties is one of the basic properties that affect the utilization of biomass based on its components such as for pulp, energy, pharmaceuticals, and other chemicals. To increase the value of the benefits of gemor bark , it can be done through product development based on its chemical components, so information about the content of chemical components is needed. This study aims to examine the content of chemical components, proximate, and phytochemical gemor bark. Gemor bark samples were taken from Katinga, Central Kalimantan. Determination of chemical component content refers to TAPPI standard and Browning method, proximate analysis refers to ASTM standard, and phytochemical analysis refers to the Harbone method. The chemical component content of gemor bark consists of holocellulose 63.59%, α-cellulose 46.19%, hemicellulose 17.39%, lignin 43.56%, ash content 1.32%, solubility in hot water 19.49%, solubility in cold water 18.21%, solubility in 1% NaOH 47.65%, and ethanol-benzene 27.66%. Gemor bark has 78.04% volatile matter and 20.64% fixed carbon. Phytochemical analysis confirmed the presence of flavonoid, phenolic, alkaloid, tannin, saponin, triterpenoid, steroid compounds in gemor bark. Gemor bark has the potential as a bioenergy raw material because it contains high content of lignin and extractive substances.
Keyword: gemor bark, chemical components, phytochemicals, biomass, pulp

Judul: Identification of Tannins from Sawmill as a Potenstial Vegetable Tanning Agent
Abstrak: Tanin merupakan senyawa polifenol hasil metabolit sekunder dari kulit kayu tanaman dan berfungsi sebagai bahan penyamak nabati. Penelitian ini bertujuan mengidentifikasi kandungan tanin dan jenis tanin, mengetahui kadar tanin total dan kadar flavonoid pada limbah kulit kayu, serta memilih kulit kayu potensial sebagai bahan penyamak. Senyawa tanin diuji secara kualitatif dan kuantitatif. Identifikasi kualitatif menggunakan uji FeCl3, larutan gelatin, kalium ferisianida + ammonia, asam asetat + Pb asetat, dan uji pereaksi Stiasny. Identifikasi kuantitatif menggunakan metode permanganometri dan pengeringan. Uji kualitatif menunjukkan delapan dari dua belas jenis kulit kayu teridentifikasi positif mengandung tanin. Delapan jenis kulit kayu tersebut adalah, kayu mangium, mahoni, sengon, afrika, mindi, kweni, kecapi, dan puspa. Empat jenis kulit kayu lainnya yang negatif adalah kayu lame, kisampang, nangka dan karet. Hasil uji kuantitatif tanin total secara berurut untuk kayu mangiun, mahoni, sengon, afrika, mindi, kweni, kecapi, dan puspa adalah 56,03%; 27,58%; 21,70%; 7,15%; 14,11%; 17,72%; 16,76%; dan 16,52% dan nilai flavonoidnya berturut-turut adalah 21,90%; 13,81%; 8,92%; 6,11%; 5,55%; 5,94%; 11,76%; dan 4,46%. Hasil uji statistik two way anova menghasilkan nilai sig. 0,00 <0,05, menunjukkan terdapat perbedaan hasil kualitas kayu berdasarkan jenis kayu, jenis uji flavonoid/tanin, dan terdapat interaksi antara jenis kayu dengan uji flovonoid/tanin dalam menentukan kayu., Tanins are polyphenol compounds produced by secondary metabolism from plant bark and function as vegetable taning materials. This study aimed to identify the tanin content and type of tanin, to determine the total tanin content and flavonoid levels in the bark waste, and to select potential bark as a taning material. Tanins were tested qualitatively and quantitatively. Qualitative identification used the FeCl3 test, gelatin solution, potassium + ammonia, acetic acid + Pb acetate, and the Stiasny reagent test. Quantitative identification used permanganometric and drying methods. The qualitative test showed that eight of the twelve types of bark were identified as positive for tanin. The eight types of bark were mangium, mahogany, sengon, africa, mindi, kweni, kecapi, and puspa. The other four barks were negative for tanin tests, i.e. lame, kisampang, jackfruit and karet. Total tanin quantitative test results in sequence for mangium, mahogany, sengon, africa, mindi, kweni, kecapi, and puspa wood barks were 56.03%, 27.58%, 21.70%, 7.15%, 14.11%, 17.72%, 16.76%, and 16.52%, respectively. The flavonoid values of the barks were 21.90%, 13.81%, 8.92%, 6.11%, 5.55%, 5.94%, 11.76%, and 4.46%, respectively. The two way ANOVA statistical test resulted in a sig. 0.00 < 0.05, indicating that there were differences in the results of wood quality based on wood type, type of flavonoid / tanin test, and there was an interaction between wood species and the flovonoid / tanin test in determining wood.
Keyword: Flavonoid, Kualitatif, Kuantitatif, Kulit Kayu, Tanin

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