Judul: Synthesis of Ulvan-based Hydrogel from Ulva lactuca Seaweed as Probiotic Immobilization Scaffold
Abstrak: Hidrogel berbasis polisakarida bersulfat ulvan terbuat dengan tambahan polimer pendukung yaitu matriks alginat. Sintesis hidrogel berbasis ulvan-alginat sebagai scaffold untuk imobilisasi probiotik belum pernah dilaporkan. Ulvan merupakan polisakarida bersulfat yang berasal dari rumput laut hijau Ulva. Ulvan diperoleh dari ekstraksi rumput laut Ulva lactuca yang umumnya dilakukan dengan suhu tinggi dan waktu yang lama sehingga diperlukan metode alternatif dalam proses ekstraksinya untuk menghasilkan ulvan dengan kualitas baik namun efisien dalam prosesnya. Alternatif proses ekstraksi yang bisa dilakukan yaitu penggunaan ultrasonikasi yang dapat mengurangi penggunaan pelarut organik dan energi yang tinggi. Penelitian bertujuan mengkarakterisasi Ulva lactuca, menentukan pengaruh Ultrasound-assisted Extraction (UAE) terhadap mutu ulvan, dan menentukan formulasi hidrogel terbaik berbasis ulvan untuk imobilisasi probiotik. Tahapan penelitian meliputi preparasi sampel, optimasi ekstraksi ulvan, dan sintesis hidrogel dengan variasi ulvan (0, 1, 2, 3, dan 4 %)) dan konsentrasi tetap alginat 4%. Ulvan terpilih berdasarkan kandungan sulfat terbesar yaitu 57,20 ± 0,11 % hasil ekstraksi dengan NaOH berbantu ultrasonikasi. Hidrogel ulvan-alginat menghasilkan fraksi gel dan rasio swelling terbaik sebesar 31,88 ± 3,80 % dan 57,18 ± 19,88 % dengan total bakteri probiotik sebesar 8,5 ± 4,9 × 106 log CFU/g. Ulvan dapat berperan sebagai bahan makanan pada hidrogel scaffold sehingga mampu mempertahankan keberadaan bakteri probiotik.
Keyword: imobilisasi probiotik, hidrogel, Ulva lactuca, ulvan

Judul: Extraction and Synthesis of Biohydrogel Film Based on Sulfated  Polysaccharide-Ulvan from Ulva lactuca
Abstrak: Salah satu permasalahan yang muncul pada proses ekstraksi ulvan dalam pengembangannya sebagai polimer alami penyusun biohidrogel film ialah penggunaan suhu tinggi yang berpotensi menyebabkan ulvan terdegradasi. Metode ekstraksi berbantu ultrasonikasi (UAE) pada suhu rendah dipilih sebagai metode alternatif dalam ekstraksi ulvan untuk mendapatkan hasil yang optimal. Penelitian ini bertujuan menentukan pengaruh UAE terhadap mutu ulvan dan menentukan karakteristik ulvan terpilih sebagai bahan penyusun biohidrogel film. Ulvan diekstraksi dari rumput laut Ulva lactuca menggunakan pelarut akuades dan HCl, pada suhu 50, 60, dan 70°C, selama 45 dan 90 menit. Ulvan terpilih diaplikasikan dalam pembuatan biohidrogel film dengan perlakuan konsentrasi ulvan sebesar 2%, 4%, dan 8%. UAE secara signifikan meningkatkan nilai rendemen dan kadar sulfat, serta menurunkan kadar air ulvan. UAE tidak berpengaruh secara signifikan terhadap penurunan viskositas dan bobot molekul ulvan. Ulvan terpilih (UAE, pelarut HCl, suhu 60°C, 90 menit) memiliki nilai rendemen, viskositas, bobot molekul, kadar air, dan kadar sulfat berturut-turut sebesar 17,35%, 58,4 cP, 287,09 kDa, 9,84%, dan 58,57%. Nilai sifat tarik film dari yang paling rendah ke yang paling tinggi berturut-turut ditunjukkan oleh biohidrogel film dengan konsentrasi ulvan 2%, 4%, dan 8%.
Keyword: biohidrogel film, ultrasonikasi, ulvan

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