Judul: Pembuatan dan Pencirian Polipaduan Poliasamlaktat-Lilin Lebah
Abstrak: Nondegradable plastic waste could cause an environment problem due to its difficulty in degradation. The development of biodegradable polylacticacid (PLA)-beeswax polyblend is necessary to give alternatives of nondegradable plastic. PLA-beeswax polyblend were produced by mixing PLA and beeswax solution with various compositions namely 40:60, 50:50, 60:40, 70:30, and 80:20 by weight. The polyblends were tested for their tensile strength, density, fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). PLA-beeswax polyblends were white in color. Tensile strength, elongation, and density increases as increasing of PLA constituents. FTIR spectrum of polyblend PLA-beeswax 80:20 did not show any new functional groups, meaning that the film was merely a physical mixture. Structure of the polyblend film revealed a homogenous film.
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Judul: Pembuatan dan Karakterisasi Film Biodegradabel dari Kitosan/PLA (Poly Lactic Acid) dengan Pemlastis Polietilen Glikol (PEG)
Abstrak: Plastic has many advantages such as good mechanical and barrier characteristics, cheap, easy to form, and flexible in application, so it becomes the most used material as food packaging. Unfortunately, plastic waste is difficult to be degraded in nature, therefore polluting the environment. Moreover, global warming issue has driven to create an eco-friendly packaging such as biodegradable plastics made from renewable resources. The objective of this research was to develop biodegradable plastic made from chitosan and poly(lactic acid) (PLA) with the addition of poly (ethylene glycol) (PEG) as plasticizer. The main goal of these blends is to improve the water vapor barrier of chitosan by blending with PLA and to improve the elasticity of chitosan/PLA blended films. The obtained films were characterized in terms of physicochemical and mechanical properties including water activity (aw), thickness, tensile strength, elongation at break, and water vapour permeability (WVP). Moreover, Scanning Electronic Microscopy (SEM) and Differential Scanning Calorimetry (DSC) were used to confirm the miscibility of PLA and chitosan. Films of chitosan/PLA blends had aw values range from 0.71 until 0.76. Generally, the blend films prepared with lactic acid as chitosan solvent were thicker than those prepared with acetic acid as chitosan solvent. The same phenomenon was observed in addition of PEG, where films containing PEG as plasticizer were thicker than those without PEG. The tensile strength and elongation at break of the obtained films decreased with the addition of PLA and PEG. It appeared that the obtained films produced with lactic acid as solvent and with the addition of PEG were more elastic than those produced with acetic acid as chitosan solvent and without the addition of PEG. In term of barrier properties, the WVP value of film chitosan/PLA ranged from 111.8 to 208.9 gr/m2/day for films prepared with lactic acid as chitosan solvent and from 233.3 to 358.15 gr/m2/day for films prepared with acetic acid as solvent. Furthermore, the observation on microstructure of the chitosan/PLA composite films, conducted with SEM, has revealed that PLA particles have been well distributed in chitosan matrix. However, the average diametre of PLA particles was in the range of 2 – 3 m, therefore this blending was categorized as microcomposites.
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Judul: SEIRS Stochastic Model with Quarantine on the Spread of Covid-19 Disease
Abstrak: Penyakit Covid-19 merupakan penyakit yang disebabkan oleh virus yang bernama Severe Acute Respiratory Syndrome Coronavirus-2 (SARSCoV-2). Virus ini menyebar dari manusia ke manusia melalui droplet akibat batuk dan bersin. Virus juga dapat ditularkan dari orang tanpa gejala sehingga sulit mendeteksi penyebarannya. Upaya yang dapat dilakukan untuk menekan penyebarannya yaitu mematuhi protokol kesehatan dan melakukan karantina jika dinyatakan terinfeksi, baik isolasi mandiri ataupun dirawat di rumah sakit. Untuk memodelkan penyebaran penyakit Covid-19, dapat menggunakan model epidemik stokastik. Penelitian ini bertujuan untuk (1) membangun model SEIRS dengan karantina pada penyebaran penyakit Covid-19, (2) menentukan peluang transisi dan peluang wabah dengan menggunakan pendekatan CTMC, (3) melakukan simulasi untuk mengetahui pengaruh peningkatan laju transmisi tanpa karantina dan laju karantina pada sistem. Data yang digunakan untuk menentukan parameter model yaitu data harian Covid-19 DKI Jakarta mulai dari 25 Maret 2020 sampai 24 Maret 2021. Data tersebut terdiri dari data kasus Covid-19 masing-masing kelurahan di DKI Jakarta. Peluang transisi ditentukan dengan mengasumsikan terdapat enam peubah acak dan satu peubah yang nilainya dapat ditentukan secara pasti. Peubah acak tersebut meliputi banyaknya individu pada subpopulasi rentan, rentan yang dikarantina, terinfeksi tanpa gejala, terinfeksi tanpa gejala yang dikarantina (isolasi mandiri), terinfeksi dengan gejala, serta terinfeksi dengan gejala yang dikarantina (dirawat), sedangkan banyaknya individu sembuh dapat ditentukan secara pasti. Peluang wabah diperoleh melalui proses bercabang berganda. Pada proses bercabang berganda, peluang wabah bernilai 0 ketika nilai harapan banyaknya individu terinfeksi (m)≤ 1, dan lebih dari 0 ketika nilai harapan banyaknya individu terinfeksi (m) > 1. Simulasi pengaruh peningkatan laju karantina untuk individu terinfeksi dilakukan dengan 100 kali pengulangan untuk memperoleh sebaran peluang waktu bebas penyakitnya, selanjutnya dapat ditentukan rata-rata waktu bebas penyakitnya. Berdasarkan hasil simulasi, untuk nilai harapan banyaknya individu terinfeksi (m)≤1, didapatkan bilangan reproduksi dasar (R_0)<1. Ketika nilai m>1, peningkatan nilai m membuat peluang wabah semakin besar. Adapun nilai R_0,m, dan peluang wabah diperoleh secara analitik. Terdapat tiga skenario dalam simulasi numerik, yaitu pengaruh peningkatan laju transmisi dari individu rentan yang dipengaruhi individu tanpa gejala (β_1) dan dengan gejala (β_2), peningkatan laju karantina untuk individu dengan gejala (θ_3 ), dan peningkatan laju karantina untuk individu tanpa gejala (θ_2 ). Hasil simulasi pada skenario pertama menyatakan bahwa peningkatan β_1 dan β_2 dapat menaikkan R_0,m, dan waktu bebas penyakit. Sebaliknya, hasil simulasi pada skenario kedua menunjukkan bahwa peningkatan θ_3 dapat menurunkan nilai R_0, m, dan rata-rata waktu bebas penyakit. Sama halnya dengan hasil simulasi pada skenario ketiga menyatakan bahwa peningkatan θ_2 dapat menurunkan nilai R_0,m, serta rata-rata waktu bebas penyakit. Hasil simulasi skenario ketiga juga menunjukkan bahwa peningkatan θ_2 dengan ditetapkannya nilai θ_3, menyebabkan nilai R_0,m, dan rata-rata waktu bebas penyakit lebih kecil dibandingkan tanpa θ_3., Covid-19 disease is a disease caused by virus called Severe Acute Respiratory Syndrome Coronavirus-2 (SARSCoV-2). This virus spreads from person to person through droplets caused by coughing and sneezing. The virus can also be transmitted from asymptomatic individuals, making it difficult to detect its spread. Efforts that can be made to suppress the spread are complying with health protocols and quarantine if declared infected, either self-isolation or hospitalized. To model the spread of Covid-19 disease, we can
Keyword: continuous time Markov chain, Covid-19 disease, outbreak probability, quarantine