No abstract

In this paper, it will be studied local stability of equilibrium points of  a SEIR epidemic model with infectious force in latent, infected and immune period. From the model it will be found investigated the existence and its stability of points its equilibrium by Hurwitz matrices. The local stability of equilibrium points is depending on the value of the basic reproduction number  If   the disease free equilibrium is local asymptotically stable.

Identification of active compounds in cacao pod rind has been done. Cacao pod rind contained active compound alkaloid, theobromine (3,7-dimethylxanthine). Cacao pod rind extract contained some other active compounds mixed flavonoid or condensed tannin such as anthocyanin, anthocyanidin, catechin, epicatechin, epigallocatechin, and leucoanthocyanidin. Cacao pod rind was extracted by maceration using methanol 70% and fractionated with hexane and ethyl acetate to obtain polar extracts. This study used an experimental method that was analyzed descriptively using Gas Chromatography-Mass Spectrometry (GC-MS) and Liquid Chromatography-Mass Spectrometry (LC-MS). Phytochemical screening test showed cocoa pod rind extracts contained alkaloids, flavonoids, tannins, terpenoids, and saponins. GC-MS analysis showed that cacao pod rind extracts contained 24 compounds. Polar extracts analysis with LC-MS obtained 10 compounds contained hydroxy groups, which can be used as corrosion inhibitors on metal. The result of this study showed that cocoa pod rind has potential as corrosion inhibitor. It also has potential as an anti-bacterial and antioxidant.

Soil stabilizer polymer hasil campuran lateks polyester tak jenuh Yukalac 157 BQTN-EX dengan lateks pekat karet alam (LPKA),  disebut soil stabilizer termoset (SSTS). Campuran ini homogen pada perbandingan 90/10 dan stabil hingga hari ke 28 penyimpanan, dapat digunakan sebagai perekat tanah pasir untuk meningkatkan sifat kekuatannya. Melalui berinteraksi gugus polar pada polester dengan partikel tanah pasir diprediksi dapat membentuk komposit yang memiliki sifat mekanis yang tangguh sebagai material jalan. Hasil uji mekanis komposit tanah yang distabilkan dengan SSTS  meningkat hingga penambahan SSTS 35%. Kuat tekan meningkat hingga penambahan  SSTS 25% dan menurun pada penambahan  lebih tinggi . Daya serap air menurun dengan peningkatan jumlah SSTS. Hasil uji termal terdapat pergeseran puncak dari  polyester, SSTS dan komposit campuran SSTS dengan tanah pasir.

No abstract