Judul: Characterization of Physicochemical Properties of Nanocalcium Extracted from Tilapia (Oreochromis niloticus) Bone
Abstrak: The utilization of fish bone as minerals source such as calcium and phosphorus is an effort to increase the economic value of waste fish bones. Calcium and phosphorus are essential compounds which play an important role in metabolic processes as well as health benefits. Generally, calcium is available in micro size, which is absorbed in the metabolic system at 50% of total calcium intake then the best alternative to improve absorption is reducing the size in nano (nm) so become nanocalcium, by milling process. The research aimed to perform the extraction of nanocalcium from tilapia (Oreochromis niloticus) bones by using different types of solvents, followed by milling process and study the characterization of physicochemical changes. The research was conducted in three main phases: 1) raw material preparation, 2) the extraction of nanocalcium from fish bones and 3) characterization of physicochemical nanocalcium sample. There are some process stages to prepare raw material: washing, boiling, drying and size reduction, then performed extraction to soften and change the bone structure to be milled easily. The extractions were done as follow: water (sample A), NaOH (sample B), NaOH followed by HCl (sample C) and HCl (sample D) which is followed by milling process to become nanocalsium before characterized, using raw materials (sample BB) as a control. Physicochemical characteristics that observed are include yield, whiteness degree, particle size, proximate, calcium and phosphorus, functional groups, morphology surface and crystal structure of the sample. Physicochemical analyzed that sample C is the sample with best character because has smaller particle size (145.50 nm) and the whiteness degree (93.72%) close to commercial standards of whiteness calcium as well as low of moisture, protein and fat content while ash, calcium and phosphorus content are high with ratio of Ca/P = 1.87. Calcium obtained is close to the hydroxyapatite characteristic so aplicate it in food has good properties mainly related to its solubility and bioavailability. Absorption peaks of sample revealed by FTIR (Fourier Transform Infrared) identified that phosphate (PO4 3-) group indicated as the symmetric bending, symmetric stretching, asymmetric stretching, and asymmetric bending vibrations. Absorption band of carbonate (CO3 2-) group indicated the apatite carbonate type A and B. Morphological analysis using SEM (Scanning Electron Microscopy) showed that surface of sample is change as result of the extraction process and the type of used solvent. Extraction using acid solution made sample becomes more porous and sharper, while extraction using alkaline solution made sample surface flatter, while extraction using water did not change the surface morphology of tilapia bone powder. The result of EDS (Energy Dispersive X-ray Spectroscopy) analysis showed that sample consist of 4 main elements such as carbon (C), oxygen (O), phosphorus (P) and calcium (Ca). The type of solvent affects the mass percent of there elements. Extraction using acid solution was increased mass percent of phosphorus and decreased mass percent of carbon and calcium. XRD (X-Ray Diffraction) analysis showed crystalline phase in the sample form carbonate apatite either type A or B and hydroxyapatite [Ca5(PO4)3(OH)]. Samples performed crystalline
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Judul: Produksi Nano-Kalsium dari Tulang Ikan Tuna Yellowfin (Thunnus albacares) Melalui Perlakuan Fisikokimia
Abstrak: Pemanfaatan hasil samping dari tulang ikan sebagai sumber mineral seperti kalsium dan fosfor dapat meningkatkan nilai ekonomis dari tulang ikan. Kalsium dan fosfor merupakan senyawa yang berperan penting dalam proses metabolisme serta bermanfaat bagi kesehatan. Kalsium umumnya tersedia dalam ukuran mikro (μm) yang dalam sistem metabolisme tubuh penyerapannya hanya mencapai 50% dari total kalsium yang dikonsumsi, sehingga alternatif terbaik untuk meningkatkan penyerapannya yaitu dengan memperkecil ukuran menjadi nano partikel, beberapa cara untuk memperkecil ukuran kalsium yaitu perlakuan fisik (milling), kimia (NaOH dan HCl). Penelitian ini bertujuan untuk memproduksi dan menganalisis karakteristik fisikokimia nano-kalsium terpilih dari tulang ikan tuna yellowfin berdasarkan perlakuan fisik (milling), kimia (NaOH dan HCl). Penelitian diawali dengan pembuatan serbuk tulang ikan, kemudian dilanjutkan produksi nano-kalsium serta karakterisasi fisikokimia serbuk tulang dan nano-kalsium. Pembuatan serbuk tulang dilakukan melalui beberapa proses seperti pencucian, perebusan, pengeringan serta pengecilan ukuran. Serbuk tulang yang dihasilkan kemudian diberi perlakuan fisik (milling), kimia (NaOH dan HCl) untuk memproduksi nano-kalsium. Karakterisasi nano-kalsium meliputi rendemen, derajat putih (whiteness meter), proksimat, kalsium (AAS), fosfor (spektrofotometer UV-Vis), ukuran partikel (PSA), gugus fungsi penyusun (FTIR), analisis morfologi (SEM) dan derajat kristalinitas (XRD). Hasil analisis fisikokimia nano-kalsium terpilih dihasilkan pada perlakuan asam, hal ini dilihat dari karakteristik kimia yang meliputi kadar air 0.33%, protein 0.19%, lemak 0.22%, kadar abu 99.03%, kalsium 83.25%, fosfor 9.65%, memiliki gugus fosfat (PO43-) dalam bentuk vibrasi simetris strectching, vibrasi simetris bending, vibrasi asimetris strectching dan vibrasi asimetris bending serta memiliki pita absorpsi apatit karbonat (CO32-) dalam bentuk tipe AKB (Apatit Karbonat B), gugus hidroksil (OH-) yang menunjukkan terbentuknya gugus hidroksil kristal atau air kristal. Karakteristik fisik meliputi ukuran partikel 259 nm, derajat putih 92.61% (standar derajat putih kalsium komersial), morfologi menunjukkan permukaan fisik material terdapat serpihan yang tidak beraturan, tajam, sedikit berpori serta memiliki derajat kristalinitas 89.3% dan memiliki tingkat kemiripan dengan unsur Hydroxylapatite 100% yang disesuaikan dengan data JCPDS (Joint Comitte on Powder Diffraction Standart) pada XRD.
Keyword: fisikokimia, nano-kalsium, produksi, tulang ikan tuna

Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh.
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. ,,,
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular.