Judul: The Use of Vector Autoregressive to See the Impact of COVID-19 on Sectoral Indices
Abstrak: Pasar modal menjadi salah satu bidang yang terkena dampak COVID-19. Hal ini terlihat dari menurunnya indeks saham di berbagai sektor di Indonesia. Penelitian ini bertujuan menguraikan pengaruh COVID-19 terhadap indeks saham sektoral. Data yang digunakan merupakan data harian periode 15 Maret 2020 hingga 16 Maret 2021 yang terdiri atas data indeks saham sektoral dan data kasus harian COVID-19. Interpolasi linier digunakan pada data indeks saham sektoral untuk menduga data hilang. Uji kausalitas Granger digunakan untuk mengetahui hubungan sebab-akibat antara COVID-19 dan indeks saham sektoral. Selanjutnya vector autoregressive digunakan untuk memodelkan pengaruh COVID-19 terhadap indeks saham sektoral. Hasil penelitian menunjukkan bahwa pengaruh guncangan sebesar satu simpangan baku perubahan kasus harian COVID-19 akan direspon perubahan relatif indeks saham sektoral selama 3 sampai dengan 4 hari ke depan. Besarnya kontribusi perubahan kasus harian COVID-19 dalam memengaruhi perubahan relatif indeks saham sektoral relatif kecil dengan persentase kurang dari 5%. Selain itu, perubahan kasus harian COVID-19 memengaruhi perubahan relatif indeks saham sektor infrastruktur, utilitas, dan transportasi pada taraf nyata 5%., The capital market is one of the sectors affected by COVID-19. This can be seen from the decline of stock index in various sectors in Indonesia. This study aims to describe the effect of COVID-19 on sectoral indices. The data used is daily data for the period March 15, 2020 until March 16, 2021, which consists of sectoral indices data and daily COVID-19 case data. Linear imputation is used to estimate missing observations on the sectoral indices data. Granger causality test is used to determine the causal relationship between COVID-19 and sectoral indices. The effect of COVID-19 on sectoral indices is then modelled using the vector autoregressive model. The results show that one standard deviation shock in changes in daily COVID-19 cases will be responded by relative changes in sectoral indices over the next 3 to 4 days. Changes in daily COVID-19 cases contribute to a relatively small influence in the relative changes of sectoral indices, with percentage of less than 5%. Furthermore, changes in the daily COVID-19 cases affect the relative changes in the stock index of the infrastructure, utilities, and transportation sectors at a significant level of 5%.
Keyword: COVID-19, sectoral indices, vector autoregressive (VAR)

Judul: The Relationship between stock price index and  interest rates in ASEAN-5 countries before and during the Covid-19 pandemic
Abstrak: Pandemi Covid-19 adalah fenomena yang terjadi pada akhir tahun 2019, Covid-19 memiliki dampak tidak hanya bagi kesehatan juga berdampak pada keadaan ekonomi suatu negara. Hal tersebut juga berpengaruh terhadap tingkat suku bunga dan indeks harga saham pada negara ASEAN-5. Tujuan dari penelitian ini adalah untuk menganalisis hubungan tingkat suku bunga dan ineks harga saham di negara ASEAN-5 pada masa sebelum dan saat pandemi Covid-19. Penelitian ini menggunakan metode deskriptif dan kuantitatif dengan menggunakan analisis VARX (Vector Autoregressive with Exogenous). Hasil dari penelitian ini yaitu pada masa sebelum pandemi Covid-19 indeks harga saham negara ASEAN-5 cenderung stabil dikarenakan kebijakan moneter yang eketif melalui suku bunga, namun pada masa pandemi Covid-19 suku bunga tidak berpengaruh secara signifika terhadap indeks harga saham, hal tersebut dikarenakan tingginya sentimen negatif investor terhadap indeks harga saham saat pandemi Covid-19. Berdasarkan interpretasi IRF exogenous, indeks harga saham dan suku bunga negara ASEAN-5 masih berfluktuatif dengan adanya guncangan penambahan kasus Covid-19. Hal tersebut menunjukkan bahwa ekonomi negara ASEAN-5 masih rentan terhadap guncangan pandemi Covid-19., The Covid-19 pandemic is a phenomenon that occurred at the end of 2019. Covid-19 has an impact not only on health but also on the economic state of a country. This also affects interest rates and stock price indexes in ASEAN-5 countries. The purpose of this study was to analyze the relationship between interest rates and stock price indexes in ASEAN-5 countries before and during the Covid-19 pandemic. This study used descriptive and quantitative methods using VARX (Vector Autoregressive with Exogenous) analysis. The results of this study in the period before the Covid-19 pandemic the stock price index of ASEAN-5 countries tended to be stable due to effective monetary policy through interest rates, but during the Covid-19 pandemic interest rates did not significantly affect the stock price index, it was due to high negative investor sentiment towards the stock price index during the Covid-19 pandemic. Based on the IRF exogenous interpretation, the stock price index and interst rate of ASEAN-5 are still fluctuating whit their shock of Covid-19 cases. This shows that the ASEAN-5 economies are still vulnerable to the shocks of the Covid-19 pandemic.
Keyword: ASEAN-5, Covid-19, interest rate, stock price index, VARX, ASEAN-5, Covid-19, interest rate, stock price index, VARX

Judul: Synthesis of Apatite - Chitosan Composite Using Duck Eggshell and Chitosan with Temperature and pH Control
Abstrak: Composite of apatite-chitosan was prepared by using chitosan as polymer matrix. Calcium phosphate was prepared from CaO and (NH4)2HPO4, which the ratio Ca : P had to be 1.67. Chitosan is produced by deacetilase from biopolymer chitin. Duck eggshell (95% CaCO3) as starting material was converted to be calcium oxide (CaO) through calcinations with temperature 1000oC for 5 hours. In-situ and ex-situ methods were prepared from apatite and chitosan (dissolved with acetate acid 2%). Calcium phosphate prepared for bone implantation, but it is too fragile and brittle to be implant into the body. So addition of chitosan can decrease crystalinity and increase mechanic characteristic (tougher). Composite apatite-chitosan was resulted by fast precipitation. Fast precipitation was held in a breaker glass with nitrogen atmosphere, under controlled temperature at 37oC and pH 7, in order to increase amount of hydroxyapatite. Precipitation with CaO which was dropped by (NH4)2HPO4. Hydroxyapatite and chitosan were appearing at samples with in-situ and ex-situ methods which indicating by peak matching of XRD (closed lattice parameter, crystal size), overlapping at FTIR spectra and supporting by SEM picture (homogenous and agglomerated particle). However, it still needs further research to examine biocompatibility osteoconductive degree of sample by in-vivo and in-vitro test.
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