Judul: Dynamics Model for Rural and Urban Economic Growth
Abstrak: Lewis theory of structural change has focused on mechanisms that allow countries to transform their domestic economic structure to a more modern economy. The proposed model deals with the mechanism of interaction between rural and urban Economic. This model is concerned with the process of labor transfer from rural to urban areas. This study aims to model the dynamics of economic growth in rural and urban areas, including determining the equilibrium solution and to carry out simulation of the model. The simulation results show that the transfer of labor from rural to urban areas will increase the rate of change of capital so that structural changes can be realized. In addition, increased propensity to save in rural areas will also accelerate structural change
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Judul: Dinamika sistem Inter-urban hirarkis
Abstrak: Sistem urban bersifat dinamis, sehingga dapat mengalami pertumbuhan, penyusutan maupun pembaharuan. Dinamika sistem urban dapat berakibat timbulnya beragam struktur spasial dan berubahnya bentuk penggunaan lahan. Kelemahan utama dalam pengembangan teori dinamik penggunaan lahan dan ukuran kota urban adalah penggunaan model kota monosentrik sebagai dasar pengembangan. Model ini memiliki kekuatan yang terbatas untuk menjelaskan fenomena spasial urban, yang terkait dengan teori urban dinamik. Zheng (1996), mengembangkan suatu model dinamik inter-urban hirarkis yang menghasilkan tiga macam pola spasial pola monosentrik, pola multisentrik, dan pola terpisah. Perubahan kesejahteraan dan ukuran kota urban, yang dicirikan oleh pendapatan dan populasi urban, akan mengakibatkan transformasi spasial dari pola spasial yang satu menjadi pola spasial yang lain. Transformasi spasial ini terjadi karena konfigurasi yang terpusat dapat menghasilkan kesejahteraan yang lebih tinggi untuk masyarakat dibanding dengan konfigurasi yang menyebar (desentral), sehingga perubahan ukuran kota dan kesejahteraan mengakibatkan struktur penggunaan lahan urban berubah. Model didinamiskan dengan membentuk suatu persamaan diferensial biasa orde satu dan melakukan pencarian solusi. Pada proses dinamika urban, optimalitas yang dilibatkan berdasarkan standar sosial. Masalah yang dihadapi adalah pemaksimuman pendapatan wilayah dengan menggunakan metode Lagrange. Ada kemungkinan terjadi konsistensi maupun inkonsistensi garis pertumbuhan dinamik pada saat kesetimbangan dan garis pertumbuhan dinamik yang optimal, bergantung pada jenis struktur spasial sistem urban itu sendiri.
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Judul: Durability of Specific Immunoglobulin (Ig) Y Againts Influenza and Covid-19 in Sunscreen
Abstrak: The benefit of specific immunoglobulin Y (Ig Y) as an active ingredient in personal care products such as sunscreen has not been properly studied. Our study aims to evaluate the reliability of specific IgY against influenza and the COVID-19 virus in a sample sunscreen product. Specific IgY influenza and COVID-19 viruses were inserted in the sample sunscreen at two concentrations of 0.1% and 0.25%. Three treatments were observed: control (C) sunscreen without IgY, treatment 1 (T1) sunscreen with 0.1% IgY, and treatment 2 (T2) sunscreen with 0.25% IgY. Organoleptic observations were carried out to monitor changes in aroma, color, and texture, and sunscreen sampling was done every week for 6 weeks. The durability of IgY was evaluated using an enzyme-linked immunosorbent assay (ELISA) and a neutralization assay. Organoleptic observation from weeks 1 to 6 showed consistency in its aroma, color, and texture. Enzyme-linked immunosorbent assay and neutralization assay (NA) results of the T1 and T2 groups showed negative results except for sample T1 at week 5, which showed a positive result in the Influenza A ELISA. Based on the results, it seems that IgY concentrations of 0.1% or 0.25% were not optimal. However, this negative result might be due to low concentration of the IgY and the presence of beeswax, which inhibits IgY and causes it to dissolve in distilled water, thus preventing it from being detected in the assay.
Keyword: Immunoglobulin Y, Sunscreen, Influenza, COVID-19, Biological Activity