Judul: Nanohidrogel Berbasis Selulosa Tongkol Jagung dengan Metode Ikat Silang Kimia dan Iradiasi Sinar Gamma
Abstrak: Hidrogel dari polimer alam memiliki sifat biokompatibel dan biodegradabel sehingga lebih ramah lingkungan. Penelitian ini, selulosa limbah tongkol jagung diolah menjadi nanohidrogel dengan metode ikat silang kimia, yaitu epiklorohidrin (Ech) dan iradiasi sinar gamma. Pengecilan ukuran selulosa dilakukan dengan proses wet milling. Selulosa dilarutkan dalam pelarut NaOH/PEG pada suhu 55 ºC. Jumlah pelarut dan konsentrasi Ech divariasikan dengan perbandingan selulosa:pelarut sebesar 1:2 dan 1:4 serta konsentrasi Ech sebesar 4%, 16% dan 28%. Parameter yang diamati meliputi rasio swelling, fraksi gel, tekstur dan morfologi. Hasil yang optimum diperoleh dari nanohidrogel dengan perbandingan selulosa:pelarut sebesar 1:4 dan konsentrasi Ech sebesar 28% yang memiliki parameter rasio swelling 366%, fraksi gel 52% dan hardness 0.37 mJ. Nanohidrogel dengan metode iradiasi sinar gamma, dimana selulosa setelah proses wet milling diiradiasi dengan dosis 20 kGy dan laju dosis 5.4 kGy/jammemiliki rasio swelling 204%, fraksi gel 99% dan hardness 0.33 mJ. Rendahnya rasio swelling nanohidrogel dengan metode iradiasi sinar gamma dikarenakan dosis yang digunakan terlalu tinggi untuk polimer alam. Hidrogel mempunyai potensi yang luas sebagai bahan penyerap air di daerah pertanian sebagai agen pembawa pupuk.
Keyword: epiklorohidirin, hidrogel, selulosa, sinar gamma

Judul: Sintesis Nanohidrogel Tapioka Menggunakan Metode Crosslinking Kimia dan Iradiasi Sinar Gamma
Abstrak: Penelitian ini mensintesis nanohidrogel berbahan dasar tapioka yang dimodifikasi menjadi partikel berukuran nano menggunakan metode hidrolisis asam dan presipitasi etanol. Nanohidrogel disintesis menggunakan metode crosslinking kimia dengan penambahan epiklorohidrin yang konsentrasinya divariasikan, yaitu 5%, 10%, dan 20% juga menggunakan iradiasi sinar gamma dengan dosis 20 kGy. Parameter yang diamati meliputi : kemampuan mengembang (swelling), fraksi gel, tekstur, dan morfologi. Analisis swelling menunjukkan penambahan epiklorohidrin menurunkan swelling, namun meningkatkan kekerasan nanohidrogel yang dihasilkan. Berdasarkan hasil yang diperoleh, nanohidrogel yang paling optimum adalah nanohidrogel dari pati terhidrolisis 2 jam dengan konsentrasi epiklorohidrin 5%, dengan nilai swelling 353.55%, fraksi gel 77.71%, dan kekerasan 5.72 mJ. Hasil perhitungan swelling nanohidrogel dengan crosslinking iradiasi sinar gamma adalah 256.81% untuk nanohidrogel dari pati terhidrolisis 2 jam dan 233.86% untuk nanohidrogel dari pati terhidrolisis 24 jam.
Keyword: crosslinking, epiklorohidrin, nanohidrogel, sinar gamma, tapioka

Judul: Exchange Market Pressure and Central Bank Intervention for Three ASEAN Countries
Abstrak: Two of the exchange rate systems which are adopted by many countries are the floating and the fixed exchange rate system. Both the exchange rate systems have different characteristics. Countries that implement fixed exchange rates system tend to set their domestic currency exchange rate at a certain point. On the contrary, countries which implement floating exchange rate system tend to let their domestic currency exchange rate to move flexibly and thus their value will always change according to the demand and supply of the currency in the foreign exchange market. Countries which implement floating exchange rate system are facing the risk of fluctuation in the exchange rate of their domestic currency against foreign currencies. The currency exchange rate fluctuation may be caused by economic problems such as a financial crisis. A country can also be potentially affected by other countries’ earlier financial crisis. This effect could potentially happen if these countries are in the same region, such as ASEAN. The 1997 ASEAN economic crisis was an example of a country’s financial crisis could affect other countries. At that time, some countries such as Indonesia, Malaysia and Thailand had to change their currency exchange rate system from the fixed exchange rate system to the floating exchange rate system due to the high costs which has to be incurred if they were to enforce the fixed exchange rate system. During 2002 until 2012, the domestic exchange rate of Indonesia, Malaysia and Thailand against the U.S. dollar had tended to fluctuate. If the domestic currency exchange rate fluctuated excessively then the central bank would intervene to stabilize the exchange rate in the foreign exchange market. The pressure on domestic currency exchange rate pressures has forced the central bank to intervene. The amount of those pressures can be analyzed by calculating the Exchange Market Pressure (EMP) index. Apart from that, the time when interventions are done by the central bank can be known based on EMP by calculating the Exchange Market Intervention (EMI) index. The purposes of this study were to determine the level of international pressure on the currency exchange market and monetary authorities intervene in three ASEAN countries, as well as to determine the effect of the monetary authorities intervene on the exchange rate of the domestic currency against the U.S. dollar in those three ASEAN countries. Based on the EMP index calculation results which are obtained during 2002 to 2012 period, the exchange rate of Indonesia, Malaysia and Thailand’s domestic currency had always fluctuated and the results of the EMP index indicated that each country were under diverse level of currency exchange rate appreciation and depreciation pressures. Thailand was the country with the highest currency exchange rate pressure compared to Indonesia and Malaysia. The results on the intervention index calculation showed that Indonesia, Malaysia and Thailand have intervention index between zero and one and more than one. We can also see from the intervention index that Indonesia and Thailand implement the controlled floating currency exchange rate instead of the freely floating one. Based on the calculation of the currency exchange rate by comparing
Keyword: exchange rate, exchange market pressure, intervention