Judul: Bifurkasi pada Model Interaksi Tumbuhan dan Herbivora
Abstrak: Saha dan Bandyopadhyay (2005) memodelkan sistem mangsa-pemangsa yang merepresentasikan interaksi tumbuhan dan herbivora. Pada karya ilmiah ini, dicari bifurkasi yang terjadi dengan terlebih dulu menganalisis kestabilan titik tetap. Ada tiga titik tetap yang diperoleh dengan jenis kestabilan titik tetap ditentukan oleh nilai eigen yang diperoleh dari ketiga titik tetap tersebut. Titik tetap pertama dan kedua bersifat sadel dan terdapat empat kasus pada titik tetap ketiga agar mencapai kestabilan. Dengan pemilihan parameter tertentu, diperoleh bifurkasi Hopf yakni terjadinya perubahan kestabilan dari spiral stabil menjadi spiral tak stabil dan terdapat limit cycle pada titik tetap ketiga.
Keyword: bifurkasi Hopf, limit cycle, model interaksi tumbuhan dan herbivora

Judul: Bifurkasi Hopf pada Model Mangsa-Pemangsa Holling-Tanner Tipe II
Abstrak: In this paper a mathematical prey-predator model of Holling-Tanner type II and the existence of Hopf bifurcation were studied. In this model, three fixed points are obtained, in which one of them is a saddle point. The prey-predator population dynamics was simulated based on four cases, by increasing the interaction value of prey and predator. In the third case, the stable spiral changed into an unstable spiral and also observed the presence of limit cycles. This is known as Hopf bifurcation. Furthermore, for the fourth case both populations were almost extincted due to the increase of the interaction rate. Generally, it can be concluded that increasing the value of prey and predator interaction rate would change the stability of population. The prey-predator population will be stable when the prey and predator interaction rate is low, whereas the higher interaction rate would cause the extinction of both prey and predator populations
Keyword: prey-predator., limit cycle, Holling-Tanner type II, Hopf bifurcation

Judul: Penetapan Umur Simpan Telur Asin Rendah Kolesterol pada Penyimpanan Suhu Ruang
Abstrak: Pemanfaatan telur bebek sebagai bahan pangan salah satunya yaitu telur asin. Namun, muncul kesadaran masyarakat akan tingginya kandungan kolesterol pada telur asin sehingga dikembangkan inovasi telur asin rendah kolesterol. Produk telur asin di pasaran memiliki umur simpan pendek tetapi belum diidentifikasi parameter penentu kerusakan produk. Penelitian ini bertujuan untuk mengetahui perubahan mutu dan menetapkan umur simpan telur asin selama penyimpanan suhu ruang. Penelitian ini dilakukan dengan membuat telur asin kemudian dilakukan pengemasan vakum, lalu disimpan hingga terjadi kerusakan pada suhu ruang. Penentuan umur simpan dilakukan dengan metode extended storage studies berdasarkan parameter kadar air, pH, kadar kolesterol, kecerahan, organoleptik, serta uji total plate count. Hasil karakteristik penyimpanan hari ke-10 telur asin diperoleh nilai tingkat kecerahan putih telur sebesar 25,96, kecerahan kuning telur 25,98, pH 7,19, kadar air putih telur 84,64%, kadar air kuning telur 38,72%, dan total mikroba 4,1 × 105 cfu/mL. Kadar kolesterol sebesar 233,39 mg/100 g pada hari pertama dan mengalami penurunan menjadi 131,61 mg/100 g pada hari kesepuluh. Mutu telur asin mengalami perubahan yang mengarah pada kerusakan selama penyimpanan suhu ruang. Telur asin tanpa kemasan memiliki umur simpan hingga 9 hari dengan total mikroba sebesar 1,0 x 105 cfu/mL., The utilization of duck eggs as a food ingredient includes salted eggs. However, public awareness of the high cholesterol content in salted eggs has led to the development of low-cholesterol salted egg innovations. Salted egg products in the market have a short shelf life, but the determining parameters for product spoilage have not been identified. This research aims to understand the quality changes and establish the shelf life of salted eggs during room temperature storage. The study involves producing salted eggs, vacuum packaging them, and then storing them at room temperature until spoilage occurs. The determination of the shelf life is based on extended storage studies, considering parameters such as moisture content, pH, cholesterol content, brightness, organoleptic, as well as a total plate count test. The characteristic results after 10 days of storage show that the brightness of the egg whites is 25.96, the brightness of the egg yolks is 25.98, pH is 7.19, the moisture content of egg whites is 84.64%, the moisture content of egg yolks is 38.72%, and the total microbial count is 4.1 × 105 cfu/mL. The cholesterol content decreases from 233.39 mg/100 g on the first day to 131.61 mg/100 g on the tenth day. The quality of salted eggs undergoes changes that lead to spoilage during room temperature storage. Unpackaged salted eggs have a shelf life of up to 9 days with a total microbial count of 1.0 x 105 cfu/mL.
Keyword: Duck eggs, Low cholesterol, Salted eggs, Shelf life