Judul: Diversity of Tilapia Oreochromis niloticus fry with Twice Sorting
Abstrak: Tilapia Oreochromis niloticus is one of the important, especially freshwater, aquaculture commodity in Indonesia. The main obstacle in developing tilapia culture in Indonesia is the insufficient amount of tilapia fry. The problem lies on the quality of the produced fry. Fry quality includes genetic factor, precise harvest time, and precise size (equality of size). Generally speaking, the more fry having equal size the better their qualities are. This research aimed to observe the diversity of standard length (body length) and weight of tilapia fry with twice sorting. This research is divided into three cases, 1 control, and cumulative of all cases. Observed parameters are survival rate, standard length, weight, and the diversity of standard length and weight of tilapia fry. Sorting was carried out at the first and second month and cumulative can increase the average standard length and decrease the variance. Average standard length and diversity increased again on the next month. After three months rearing, standard deviation and CV of weight on control is relatively higher than fry population on all cases and cumulative.
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Judul: Keragaman Benih Ikan Nila Oreochromis niloticus dengan Satu Kali Penyortiran
Abstrak: Tilapias are among the most important aquaculture species in the world, the adaptability and tolerance to a wide range of environments has resulted in a rapid expansion of tilapia farming. However, the expansion of tilapia farming had a few obstacles such as lack of availability in good quality of seed. Therefore sorting was needed to incrased the quality of seed. Sorting was put in the right order activity of certain size from largest into smallest then eliminated a little part of the smallest size however grading was only devided certain size into groups without elimination. The experiment was aimed to knew and saw the role of once sorting to the size variety of tilapia seed. The experiment was done toward of seed tilapia that get from cross breeding on various strain of tilapia that are : (A) case-1 : the black tilapia male broodstock of GESIT breed with the red tilapia female broodstock, (B) case-2 : the white tilapia male broodstock with the black tilapia female broodstock of Nirwana, (C) case-3 : the white tilapia male broodstock with the red tilapia female broodstock, (D) control : the black tilapia male broodstock of GESIT breed with the red tilapia female broodstock. The data that have got was analysed with MS. Excel 2007. Parameter that watched were average, standard deviation, variance of standard length and weight, survival rate and ratio of male and female. After done sorting in first month, the average of standard length increased as big as 1.28 % (case-1), 4.73 % (case-2), 1.93 % (case-3) and 3.42 % (cumulative). Meanwhile, the variation decreased as big as 15.19% and 28.08% on case-1, 21.52% and 38.41% on case-2, 7.75% and 14.41% on case-3, 13.88% and 25.84% on cumulative with this sorting. After rereared, in the second and third month the average and variation value increased on entire cases and cumulative. However on control the value of length standard average was not increased and the variation was not decreased on the first month.
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Judul: Perkiraan paparan radiasi eksternal dari pemakaian beton ringan aerasi hebel untuk bahan bangunan
Abstrak: Telah dilakukan perhitungan paparan radiasi gamma dari salah satu bahan bangunan yaitu beton ringan aerasi Hebel buatan P.T. Hebel Indonesia, Karawang Timur. Perhitungan yang dilakukan meliputi pengukuran konsentrasi radionuklida alam Ra-226, Th-228 dan K-40, pengukuran koefisien absorbsi dan perkiraan dosis radiasi gamma dari beton ringan aerasi Hebel. Konsentrasi radionuklida alam Ra-226, Th-228 dan K-40 diukur dengan menggunakan Spektrometer Gamma. Kandungan konsentrasi radionuklida alam Ra -226 pada Hebel sebesar (25,11 ± 0,32) Bq/kg. Konsentrasi Th-228 sebesar (31,82 ± 0,41) Bq/kg. Konsentrasi K-40 sebesar (28,28 ± 0,29) Bq/kg. Konsentrasi radionuklida alam Ra-226, Th-228 dan K-40 dari hasil penelitian ini bila dibandingkan dengan data dari hasil penelitian konsentrasi radionuklida alam di dalam bahan bangunan lainnya yang digunakan di Surabaya, Jakarta dan sekitarnya jauh lebih kecil. Pada pengukuran koefisien absorbsi, pada saat sumber radiasi dari luar dipancarkan langsung pada detektor (tanpa Hebel) menghasilkan laju cacah yang lebih besar dibandingkan setelah dipasang Hebel diantara sumber dan detektor. Hal ini dikarenakan sebagian radiasi yang dipancarkan sumber diserap oleh Hebel. Paparan radiasi gamma dari perhitungan didapatkan nilainya sebesar 0,25 mSv/tahun. Nilai ini jauh lebih kecil dibandingkan paparan radiasi gamma dari bahan bangunan yang dilaporkan oleh UNSCEAR tahun 2000 yaitu sebesar 0,41 mSv/tahun. Jadi, Hebel aman digunakan untuk bahan dinding bangunan baik rumah maupun gedung-gedung perkantoran karena paparan radiasi gammanya kurang dari harga standar yang direkomendasikan oleh Komisi Internasional Perlindungan Bahaya Radiasi (International Commision on Radiological Protection/ICRP) yaitu 1 mSv/Th.
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