Judul: Penyakit Busuk Buah Kopi (Colletotrichum sp.) terhadap Mutu dan Cita Rasa pada Kopi Arabika (Coffea arabica L.)
Abstrak: Kopi merupakan salah satu komoditas perkebunan yang memegang peranan penting di Indonesia, terutama dalam hal perekonomian. Penyakit busuk buah pada tanaman kopi telah menyebabkan kerugian yang besar bagi para petani kopi. Penyakit busuk buah menyebabkan kerugian serius telah dilaporkan pertama kali dari Kenya, sebesar 75% di beberapa perkebunan. Penyakit ini menyebabkan matinya tanaman kopi di beberapa daerah di Kenya dan Ethiopia. Di daerah lain, kerugian dapat mencapai 80%. Perkiraan konservatif lebih dari kerugian yang terjadi di Kenya adalah 20%. Gejala serangan penyakit busuk buah kopi dapat dilihat dari bercak hitam yang ada pada buah kopi. Hal ini menyebabkan buah kopi akan berubah warna menjadi hitam yang sebelumnya berwarna hijau. Jika buah kopi dibelah, maka seluruh dagingnya juga akan terlihat berwarna hitam. Kopi melalui berbagai rangkaian proses yang panjang mulai dari lahan hingga produk disajikan di dalam cangkir (from farm to cup). Setiap tahapan proses tersebut turut andil dalam cita rasa dan mutu produk yang dihasilkan. Produksi yang tinggi harus diikuti dengan kalitas dan citarasa yang baik, sehingga harga jual yang diperoleh petani atau perusahaan menjadi lebih tinggi. Penelitian ini bertujuan mengetahui penyakit busuk buah kopi (Colletotrichum sp.) terhadap mutu dan cita rasa pada kopi arabika (Coffea arabica L.). Pengamatan dilakukan pada empat petak perkebunan kopi. Tanaman contoh diamati sebanyak 20 tanaman di setiap petak, dengan metode pengambilan tanaman contoh secara diagonal. Pengamatan kejadian dan keparahan penyakit sebanyak empat kali dengan interval waktu satu minggu. Pengamatan busuk buah kopi diamati buah kopi yang terinfeksi. Wawancara dilakukan terhadap konsumen kopi. Wawancara berisi pertanyaan mengenai kesukaan terhadap rasa kopi. Data primer yang diperoleh dari pengamatan langsung di lapangan disajikan dalam Microsoft Excel 2013. Penyakit busuk buah kopi memberikan pengaruh terhadap mutu dan cita rasa kopi. Buah kopi yang terinfeksi Colletotrichum sp. menjadi cacat. Buah kopi yang terinfeksi dapat menghasilkan rasa pahit., Coffee is one of the plantation commodities that plays an important role in Indonesia, especially in terms of the economy. Coffee berry disease has caused great losses for coffee farmers. Coffee berry disease causing serious losses was first reported from Kenya, amounting to 75% on some plantations. This disease causes the death of coffee plants in some areas of Kenya and Ethiopia. In other areas, losses can be as high as 80%. A more conservative estimate of the losses incurred in Kenya is 20%. Symptoms of coffee berry disease can be seen from the black spots on the coffee cherries. This causes the coffee cherries to change color to black which was previously green. If the coffee cherries are split, the entire flesh will also look black. Coffee goes through a long series of processes starting from the farm to the product served in a cup (from farm to cup). Each stage of the process contributes to the taste and quality of the resulting product. High production must be followed by good quality and taste, so that the selling price obtained by farmers or companies becomes higher. The objective of this study is to observe the effect of coffee berry disease (Colletotrichum sp.) on the quality and taste in Arabica coffee (Coffea arabica L.).
Keyword: disease severity, pathogen, quality

Judul: Disease Incidence and Severity of Coffee Leaf  Rust (Hemileia vastatrix) in Seponti District, Kayong Utara Regency, West Kalimantan
Abstrak: Kopi merupakan salah satu komoditas penting dalam sektor perkebunan di Indonesia. Namun, penyakit karat daun kopi (Hemileia vastatrix) menjadi faktor pembatas penting terhadap produksi kopi. Penelitian ini bertujuan untuk mengkaji insidensi dan keparahan penyakit karat daun kopi di sentra produksi kopi di Kecamatan Seponti, Kabupaten Kayong Utara, Kalimantan Barat. Selain itu, dikaji pula hubungan antara teknik budi daya, kondisi lingkungan, dengan perkembangan penyakit karat daun kopi. Pengamatan dilakukan di 8 lahan pertanaman kopi. Sebanyak 30 sampel tanaman kopi dari setiap lahan percobaan diamati selama penelitian. Periode pengukuran insidensi dan keparahan penyakit yaitu 5 minggu dengan interval 1 minggu. Hasil pengamatan menunjukkan bahwa insidensi dan keparahan penyakit karat daun kopi meningkat seiring waktu. Insidensi penyakit tertinggi terjadi di lahan A sebesar 96% (tanaman berumur 26 tahun) dan insidensi penyakit yang paling rendah terjadi di lahan H sebesar 82,7% (tanaman berumur 18 tahun). Sementara itu, keparahan penyakit karat daun kopi yang paling tinggi terjadi di lahan G sebesar 52,67% (ada tanaman penaung) dan keparahan penyakit karat daun kopi terendah yaitu di lahan D sebesar 38,83% (tanpa tanaman penaung). Faktor lingkungan seperti suhu yaitu berkisar dari 27 – 28,3°C dan kelembapan 80,2 – 84,5%, dan lama penyinaran matahari selama 30,9 – 53,2 jam/minggu dapat menyebabkan peningkatan terhadap perkembangan penyakit karat daun kopi. Selain itu, curah hujan juga dapat meningkatkan perkembangan penyakit karat daun kopi, karena hujan dapat membantu proses penyebaran penyakit karat daun kopi. Curah hujan pada saat pengamatan berkisar dari 19,5 - 77 mm/minggu. Kata kunci: budi daya, curah hujan, penaung, sektor perkebunan, suhu., Coffee is one of the important commodities in the plantation sector of Indonesia. However, coffee leaf rust disease (Hemileia vastatrix) become an important limiting factor to coffee production. This study was aimed to assess the incidence and severity of coffee leaf rust disease in coffee production centers in Seponti District, Kayong Utara Regency, West Kalimantan. Moreover, the relationship among cultivation technique, environmental condition, and development of coffee leaf rust disease were also studied. Observations were undertaken in 8 plots of coffee plantations. A total of 30 samples of coffee plants from each experimental plots observed during the study. Measurement period of disease incidence and severity was 5 weeks with 1 week interval. The results showed that the incidence and severity of coffee leaf rust disease increased over time. The highest incidence of disease was occurred in A plot of 96% (plants aged 26 years) and the lowest incidence of disease was occurred in H plot of 82.7% (plants aged 18 years). Meanwhile, the high severity of coffee leaf rust was occurred in G plot at 52.67% (there are shade plants) and the lowest severity of coffee leaf rust in D plot at 38.83% (without shade plants). Environmental factors such as temperature which range from 27 – 28,3°C, humidity 80,2 – 84,5%, and long irradiation which from 30,9 - 49,1 hours/week can cause an increase in disease progress of coffe leaf rust disease. Moreover, rainfall can also increase in disease progress of coffe leaf rust disease, because rain can can help the spread of coffee leaf rust disease. Rainfall at the
Keyword: cultivation, plantation sector, rainfall, shade, temperature

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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