Judul: Pengaruh penggunaan bahan pengokdidasi terhadap mutu kulit samoa pada penyamakan  kulit menggunakan minyak biji karet
Abstrak: Leather tanning using oil as the tanning agent has disadvantages, such as the time of oxidation which is takes a long time in about 9 days. Using sodium percarbonate as oxidizing agent in the tanning process, known to shorten the time into two days, eventhough, the high cost of sodium percarbonate was being obstacle in its use. Other oxidizing agents such as hydrogen peroxide and sodium hypochlorite may have the same function with sodium percarbonate, i.e. acceleration of the oxidation process. The objectives of this research were to investigate the influence of the oxidizing agents and their concentrations on the quality of chamois leather and to determine the best combination of type and concentration of oxidizing agents in the production process of chamois leather. The main research consisted of leather tanning using rubber seed oil, oxidation in drum with three types and concentrations of the oxidizing agents, measurements of physical, chemical and organoleptic properties of chamois leather. The results showed that the three types of the oxidizing agent could be used to accelerate the oxidation process in the manufacture of chamois leather. The type of oxidizing agent gave significant effect on shrinkage temperature, ash content, colour and odour of leather, while the oxidizing agent concentration significantly affected the colour and odour of chamois leather. The treatment of experiment selected based on the quality of leather was sodium hypochlorite with the concentration of 2%. Tanning by using this treatment produced chamois leather with the properties as follows: shrinkage temperature of 75.2oC, tensile strength of 30.5 N/mm2, elongation at break of 134.3%, tear strength of 86.2 N/mm, water absorption of 265% (2 hours) and 286% (24 hours), pH 6.56, oil content of 8.71%, ash content of 1.12%, softness of 8-9, colour of 7-8 and odour
Keyword: Hydraulic pressing, Oxidizing agent, Sanitizer

Judul: Pengaruh waktu oksidasi terhadap mutu kulit Samoa pada proses penyamakan minyak yang dipercepat dengan Hidrogen Peroksida
Abstrak: Leather tanning is a process of modifying the structure of collagen fibres, so as to transform animal skin that decay easily, into leather which is durable and stable to the environmental influences. One of the leather products is oil tanned leather, known as chamois leather. It has unique uses for cleaning, drying, and filtration. It can be produced by using rubber seed oil and oxidizing agent of hydrogen peroxide. The best condition for the tanning needs to be applied in order to improve process efficiency and to obtain good quality leather. In this research, optimizations of oxidation times inside and outside the rotary drum in chamois tanning were investigated. The objectives of the research were to determine the best condition of oxidation time inside and outside the rotary drum for tanning process. The experiment was conducted by tanning of goat pickle pelts for 4, 6, and 8 hours of oxidation times inside the rotary drum and 1, 2, and 3 days of oxidation times outside the rotary drum. The chemical, physical, and organoleptic properties of the leather were measured. This study shows that the chemical, physical, and organoleptic properties met the quality requirements for the chamois leather. The best conditions for the tanning were an oxidation time of 8 hours inside the rotary drum and 1 day outside the rotary drum. The chemical properties of the leathers were oil content of 2.75%, ash content of 1.92%, and pH of 6.88. Their physical properties were thickness of 0.6 mm, shrinkage temperature of 71.63oC, water absorption of 291.36% (2 hours) and 323.89% (24 hours), tear strength of 59.45 N/mm, tensile strength of 26.18 N/mm2, and elongation at break of 163.33%. The organoleptic properties of the leathers, i.e. softness, colour, and odour were considered good.
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Judul: Analisis Model Pandemik dan Prepandemik Avian Influenza pada Populasi Manusia
Abstrak: Avian influenza is a viral disease caused by a virus within the subtype of H5N1 in which its transmission caused by birds or human. In human population, transmission process of avian influenza is discussed in the model called: bird model, prepandemic model and pandemic model. The bird model has two equlibrium points. These are saddle disease free equilibrium and stable endemic equilibrium. The endemic equlibrium occurred when the reproduction number of avian influenza is greater than one. In the endemic equilibrium, avian influenza may infect both bird and human. The prepandemic model has two equilibrium points. These are avian influenza dominant equilibrium and human influenza dominant equilibrium. The human influenza dominant equilibrium occurred when the reproduction number of human influenza is greater than one. The pandemic model has one pandemic equlibrium. The human influenza pandemic occurred when the ratio of human influenza invasion, pandemic invasion and the reproduction number of human influenza is greater than one, respectively. The avian influenza pandemic occurred when the ratio of human influenza invasion, pandemic invasion is less than one and the reproduction number of avian influenza greater than one, respectively.
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