Judul: Distribution and Bioaccumulation of Heavy Metals Related to Methionine, Cystine in Gonggong Conch (Laevistrombus canarium) in Coastal Waters of Bangka Island
Abstrak: Industry and the community have carried out tin mineral exploration on Bangka Island for a long time. Industrial mining has been going on for 200 years, while community mining has been carried out illegally (Unconventional Mining/UM). UM has increased since the period of regional autonomy in 2008. UM is carried out using the land opening method. It has a significant impact on the damage to the tailing’s expanse. The land becomes nutrient-poor, and many basins are formed (kolong). Tailings (fine grain) are suspected of containing heavy metals because, naturally, heavy metals are contained in soil minerals. Several studies have indicated the contamination of heavy metals in marine waters and their accumulation in aquatic resources. One of the commercial resources is the gonggong conch (Laevistrombus canarium). This study reveals the level of heavy metal contamination and the biological aspects of the gonggong conch resource related to the presence of tin mining exploration. The study was conducted by purposive sampling: areas affected by mining and far from mining activities. The samples used were sediment, seagrass and L. canarium. Sediment samples were taken at twelve points around Bangka Island. This sample describes the distribution of heavy metals on Bangka Island. L. canarium and seagrass data were collected using a quadratic transect (1 x 1m) in six L. canarium habitats. The research variables included measurements of heavy metal concentrations (Zn, Cu, Pb, Cd, Sn) in sediments and L. canarium (gills and meat), methionine and cystine in L. canarium (gills, meat) and hepatopancreas histology of L. canarium. The total heavy metals were measured according to APHA (2012) by Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-EOS). Amino acid preparation and measurement with modified AOAC (2005) method using Liquid chromatography-mass spectrometry (LC-MS). Statistical approach (Kruskal – Wallis and Pairwise Comparison test) was used to explain the effect of heavy metals due to mining activities on the habitat of L. canarium, the relationship between environmental conditions and the growth/health of L. canarium (population and structure/age group, amino acid content of methionine, cystine, and histology). The analysis reveals that almost all sediment samples are contaminated with heavy metals (Zn, Cu, Pb, Cd, and Sn). Concentrations of Zn, Cu, and Pb consistently show relatively high values in the environs of Teluk Kelabat and Tanah Merah Beach, as locations around mining activities. Based on the Enrichment Factor (EF) category, Zn and Cu contamination in the research area was still relatively small (EF < 2), except for Pb, which had undergone high enrichment (EF 5-20). The high Pb still requires further research to find the cause. Is it related to the soil geology of the Bangka area as an indication of tailings waste or anthropogenic impact?. The presence of heavy metals in these sediments can still be classified as relatively safe when referring to quality standards such as CCME or ANZECC/ARMCANZ. L. canarium is relatively low, with a density range of 6-8 ind/m2. The organism's condition also showed poor growth as indicated by the negative allometric growth form (b<3), and the body condition was classified as thin. A negative allometric is a growth
Keyword: Gonggong conch (Laevistrombus canarium), hepatopancreas, negative allometric, tin mining

Judul: Heavy Metal Content (Hg, Cd, Pb, and Cu) in Mud Crab (Scylla serrata) in Banten Bay
Abstrak: Perkembangan industri dan pemukiman penduduk di sekitar perairan Teluk Banten dapat meningkatkan masukan limbah logam berat dan menyebabkan akumulasi pada biota perairan, khususnya pada kepiting bakau (Scylla serrata). Penelitian ini bertujuan menentukan tingkat akumulasi kandungan logam berat (Hg, Cd, Pb, dan Cu) yang terdapat pada daging kepiting bakau di perairan Bojonegara, Teluk Banten. Pengambilan sampel kepiting bakau dilakukan selama tiga bulan yaitu bulan Agustus hingga Oktober 2020 di perairan tersebut. Pengukuran kandungan logam berat dilakukan dengan menggunakan AAS (Atomic Absorption Spectrophotometer). Kandungan logam berat Hg, Cd, dan Pb pada daging kepiting bakau berada di bawah nilai sensitivitas AAS yang digunakan yaitu sebesar <0,001 mg kg-1, <0,005 mg kg-1, <0,030 mg kg-1, sedangkan untuk logam berat Cu berkisar antara 4,44 sampai 13,52 mg kg-1. Nilai tersebut masih berada di bawah baku mutu yang ditetapkan. Tingkat akumulasi kandungan logam berat kepiting bakau dalam air tergolong akumulasi tinggi. Ukuran sampel tidak berpengaruh secara signifikan terhadap logam berat yang terkandung pada daging kepiting bakau. Batas aman konsumsi daging kepiting bakau yang didapatkan dari perairan tersebut adalah 12,9348 kg daging/minggu (dewasa) dan 3,8831 kg daging/minggu (anak-anak)., The development of industry and residential areas around the waters of Banten Bay can increase the input of heavy metal waste and cause accumulation in aquatic biota, especially in mud crab (Scylla serrata). This study aims to determine the level of accumulation of heavy metals (Hg, Cd, Pb, and Cu) contained in mud crab meat in Bojonegara Coastal Waters, Banten Bay. Sampling of the mud crabs was carried out monthly for three months, from August to October 2020 in the waters. Analysis of heavy metal content was carried out using AAS (Atomic Absorption Spectrophotometer). According to the analysis, content of heavy metals Hg, Cd, and Pb in mud crab was under the AAS sensitivity value used, which was <0.001 mg kg-1, <0.005 mg kg-1, <0.030 mg kg- 1, respectively, while for heavy metal Cu ranged from 4.44 to 13.52 mg kg-1. Based on the results, this value was still below the quality standards. The accumulation level of heavy metal content of mud crab in water is classified as high accumulation. The sample size did not significantly affect the heavy metals contained in the mud crab meat. The safe limit for consumption of the mud crab meat taken in the waters was 12.9348 kg meat/week (adults) and 3.8831 kg meat/week (children).
Keyword: accumulation, Banten Bay, heavy metals, mud crab

Judul: Kajian frieze groups untuk klasifikasi dan konstruksi desain berdasarkan simetri pada pola
Abstrak: Frieze groups adalah konsep matematika untuk mengklasifikasikan desain pada dua dimensi permukaan yang berulang-ulang dalam satu arah berdasarkan simetri pada pola. Frieze groups merupakan grup yang mempertahankan bentuk pola. Pergerakan bentuk pola terdiri dari translasi, refleksi dan rotasi 180o. Tujuan dari karya ilmiah ini adalah mengkaji sifat Frieze group, mengkaji penggunaan Frieze group dalam mengklasifikasikan simetri pada pola dan mengkonstruksi pola dengan menggunakan software tesselmania. Hasil yang telah diperoleh, bahwa jenis Frieze groups merupakan subgroup dari grup pergerakan pola. Selain itu dapat dilihat dari sifat isomorfik berbagai jenis Frieze groups. Untuk mengkonstruksi sebuah bentuk pola dapat menggunakan salah satu software untuk membentuk sebuah pola bidang datar (dua dimensi) yaitu tesselmania.
Keyword: Frieze groups, Simetri, Pola