Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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Judul: Pengaruh vaksinasi terhadap dinamika populasi pada model SIR (Susceptible-Infected-Recovered)
Abstrak: SIR model can be used to model the spread of diseases in a closed population based on certain assumptions. In this research, the SIR model is formulated by including the factor of vaccination. As the result, the model has been shown to have two equilibrium points, i.e. disease free and endemic equilibrium. A simulation study is carried out to illustrate the model. The results show that some equilibrium points are asymptotically stable. Moreover, a minimum level of vaccination has been defined. For the vaccination level less than the minimum level, increase in the vaccination level results in decrease of the proportion of infected individuals in the corresponding equilibrium point. On the other hand, for the vaccination level greater than the minimum level, increase in the vaccination level results in decrease the proportion of susceptible individuals in the corresponding equilibrium point. Furthermore, when vaccination level is greater than the minimum level, it is found that the time needed for the disease to extinct is shorter.
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Judul: Komposisi Asam Lemak Mikroalga Jenis Skeletonema costatum, Thalassiosira sp., dan Chaetoceros gracilis.
Abstrak: Penelitian dilakukan berdasarkan pada perkembangan bioteknologi mikroalga dewasa ini yang memanfaatkan mikroalga tidak hanya untuk pakan alami, sumber pigmen alami, sel protein tunggal, bidang farmasi dan kesehatan, tetapi juga digunakan sebagai sumber energi alternatif seperti penghasil biofuel. Tujuan dari penelitian ini adalah membandingkan kandungan lipid tiga spesies diatom (Chaetoceros gracilis, Skeletonema costatum, dan Thalassiosira sp.) dan mengidentifikasi kandungan fatty acids tiga spesies diatom. Penelitian ini dilakukan pada bulan Mei sampai dengan Agustus 2011 di Laboratorium Mikroalga di Pusat Penelitian Surfaktan dan Bioenergi (SBRC) Baranangsiang, Bogor. Analisis sampel dilanjutkan pada bulan Oktober sampai dengan November di Pusat Laboratorium Terpadu Universitas Islam Negeri (UIN) Syarif Hidayatullah, Jakarta. Ekstraksi lipid mikroalga dilakukan dengan menggunakan pelarut klorofom dan heksan. Lipid yang diperoleh diesterifikasi menggunakan BF3-metanol 14% dan selanjutnya dianalisis dengan Kromatografi Gas – Spektrometri Massa (GC-MS), untuk penentuan asam lemak. Identifikasi metil esters asam lemak dilakukan dengan membandingkan mass spectra dengan data literatur. Penentuan nomor karbon pada senyawa metil esters asam lemak adalah dengan menghitung bobot molekul yang muncul pada spectra massa. Berdasarkan hasil penelitian diperoleh bahwa kandungan lipid tertinggi terdapat pada spesies Chaetoceros gracilis sedangkan kandungan lipid terendah terdapat pada spesies Skeletonema costatum. Perbedaan pelarut juga memberikan perbedaan kandungan lipid yang diperoleh dimana pelarut klorofom memberikan kandungan lipid yang lebih besar dibandingkan pelarut heksan. Kandungan Fatty Acids Methyl Esters (FAME) tertinggi pada spesies Chaetoceros gracilis adalah metil palmitic (C16:0 ) 33.29 % ekstraksi dengan pelarut klorofom dan metil palmitoleic (C16:1) 49.42 % ekstraksi dengan pelarut heksan. FAME tertinggi pada spesies Skeletonema costatum adalah metil palmitoleic (C16:1) 31.15 % ekstraksi dengan pelarut heksan dan metil myristic (C14:0) 41.46 % ekstraksi dengan pelarut klorofom. FAME tertinggi pada spesies Thalassiosira sp. adalah metil palmitic (C16:0) 34.17 % ekstraksi dengan pelarut klorofom dan metil palmitoleic (C16:1) 44.72 % ekstraksi dengan pelarut Heksan.
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