Chaetoceros calcitrans can be used for natural food in aquaculture. Microalgae growth is influenced by several factors, one of which is light intensity. This study aims to determine the intensity of light that can produce the best growth in C. calcitrans microalgae. The study design used was a completely randomized design (CRD) with two replications. This study uses a treatment (light intensity) with  four levels of treatment, namely 1000 (control), 1500, 2000 and 2500 lux with a duration of lighting 12 hours light: 12 hours dark. Calculation of density and measurement of water quality parameters are carried out every day during the cultivation process. Harvesting is done in a stationary phase. The results showed that different light intensities affected the growth of C. calcitrans microalgae (p=0,000). Light intensity of 2500 lux in medium scale C. calcitrans (60 L) culture can produce the highest growth on the tenth day which is 67x10⁵ cells/ml and biomass 13,75 grams.Chaetoceros calcitrans merupakan mikroalga yang dapat digunakan sebagai pakan alami. Pertumbuhan mikroalga dipengaruhi oleh beberapa faktor, salah satunya adalah intensitas cahaya. Penelitian ini bertujuan untuk mengetahui intensitas cahaya yang dapat menghasilkan pertumbuhan terbaik pada mikroalga C. calcitrans. Rancangan penelitian yang digunakan adalah rancangan acak lengkap (RAL) dengan dua kali pengulangan. Penelitian ini menggunakan  perlakuan (intensitas cahaya) dengan empat taraf perlakuan yaitu 1000 (kontrol), 1500, 2000 dan 2500 lux dengan durasi pencahayaan 12 terang : 12 gelap. Perhitungan kepadatan dan pengukuran parameter kualitas air dilakukan setiap hari selama proses kultivasi. Pemanenan dilakukan pada fase stasioner. Hasil penelitian menunjukkan bahwa intensitas cahaya yang berbeda mempengaruhi pertumbuhan mikroalga C. calcitrans (p=0,000). Intensitas cahaya 2500 lux pada kultur C. calcitrans skala medium (60 L) dapat menghasilkan pertumbuhan tertinggi pada hari ke sepuluh yaitu 67 x 105 sel/ml dan biomasa kering 13,75 gram.

Abstract.Milling is a process of metal removal by feeding the workpiece a rotating multitoothed cutter. The objective of the study was to investigate the chip characteristics (chip length, width, and thickness) during the milling process by varying the feedrates and the types of materials used based on an experimental approach. The chosen materials were AISI 1020, AISI 1045, AISI 1090, AISI D2, and AISI 4340 with a high-speed steel (HSS) as a cutter. In this work, the feedrates were varied of 5, 10, and 15 mm/minutes with the depth of cut of 0.5 mm and a low spindle speed of 70 rpm. The results show that, in general, increasing the feedrate will lead to the growth of chip length, width, and thickness for all types of materials used. Also, related to the chip shape, AISI 1020 produces the discontinuous chip which can be related to its hardness value.

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Fucoxanthin is a pigment of the carotenoid group that can be used in the food and human health. The demand for natural carotenoid in the global market is quite high for food nutrition, food colorant, medicine, and cosmetic. Chaetoceros calcitrans included sea diatom rich in carotenoid, mainly fucoxanthin. This research aim  is to optimize C. calcitrans cultivation using different light intensity treatment to create high fucoxanthin quantity. Light intensity treatment consisted of 4 levels : 1.000, 1.500, 2.000, and 2.500 lx with 2 replications. The culture process was done in medium-scale (60 L) for 14 days, enriched with diatom’s fertilizer, vitamin B, silica at  temperature 25-27oC, salinity 32-33‰, pH 8-8,5, and DO 7-9 mg/g. Biomass and pigments were harvested in stationer phase, two days after the peak of logarithmic growth. Pigments analysis used Spektrofotometry method, absorbance values were measured in wavelengths 445, 632, 649, 663, 665, and 696 nm. The results showed that light intensity treatment was not significant in biomass weight (p=0,06), but it is very significant to cells density (p=0,01) and fucoxanthin production (p=0,01).  In conclusion, the light intensity of 2.500 lx was effective to  obtain the highest fucoxanthin  at the amount of 10,13 ±1,62 mg dw with productivity at  0,17±0,03 mg/g culture media. The increase of light intensity correlated positively with the increase of fucoxanthin production with regression equation  y = 0,006x-4,938 (r = 0,96). The increase in light intensity reaching 2500 lx in Chaetoceros calcitrans culture is proven can accelerate fucoxanthin biosynthesis, therefore the method can be applied to increase its  production. Fukosantin merupakan salah satu karotenoid yang bermanfaat dalam bidang pangan dan kesehatan manusia. Permintaan karotenoid alami di pasar global besar sekali untuk berbagai kegunaan dalam bidang nutrisi makanan, pewarna makanan, obat-obatan, dan kosmetik. Chaetoceros calcitrans  termasuk diatom laut yang kaya karotenoid, terutama fukosantin. Penelitian ini bertujuan untuk mengoptimasi kultur C. calcitrans dengan menggunakan perlakuan intensitas cahaya berbeda agar memproduksi fukosantin yang tinggi. Perlakuan intensitas cahaya terdiri dari 4 taraf : 1.000, 1.500, 2.000, dan 2.500 lx dengan 2 kali ulangan.  Kultur dilakukan dalam skala medium (60 L) selama 14 hari, diperkaya dengan pupuk diatom, vitamin B, silikat pada suhu 25-27oC, salinitas 32-33‰, pH 8-8,5, dan DO 7-9 mg/g.   Pemanenan biomassa dilakukan saat fase stasioner, yaitu 2 hari setelah puncak logaritmik.  Analisis pigmen menggunakan metode Spektrofotometri, nilai absorbansi diukur pada panjang gelombang 445, 632, 649, 663, 665, dan 696 nm.  Hasil penelitian membuktikan bahwa perlakuan intensitas cahaya tidak berpengaruh nyata (p=0,06) terhadap berat biomassa, tetapi sangat berpengaruh nyata terhadap kepadatan sel (p=0,01) dan produksi fukosantin (p=0,01). Pemberian intensitas cahaya 2.500 lx menghasilkan produksi fukosantin tertinggi, yaitu sebesar 10,13 ±1,62 mg dw dengan produktivitas sebesar 0,17±0,03 mg/g media kultur. Kenaikan intensitas cahaya berkorelasi positif dengan kenaikan produksi fukosantin dengan persamaan regresi  y = 0,006x - 4,938 (r = 0,96).  Peningkatan intensitas cahaya sampai 2500 lx  pada kultur Chaetoceros calcitrans terbukti dapat memacu biosintesis  fukosantin, sehingga metode tersebut  bisa diaplikasikan untuk menaiknya produksinya.