123 research outputs found
Microalgae culture media and glass ware
Microalgae culture with desired species of flagellates or diatoms is the basis of
any finfish or shell fish larval rearing and culture system. Natural sea water is a complex
culture medium containing more elements and organic compounds, and which supports
mixture of all phytoplankton and zooplankton. But in the laboratory culture, monospecies
culture of micro algae is being maintained to support different culture requirements.
Natural sea water with added nutrients is recommended, because direct sea water may not
provide the optimum nutritional requirement of specific algae. So enrichment of natural
sea water is necessary with the addition of macro nutrients, micro nutrients, trace
elements and vitamins. Each micro alga needs the specific culture media, with basic
nutrients like nitrogen, phosphorous, vitamins and trace metals for better growth and
multiplication
Stock culture maintenance and mass culture of micro algae
Marine micro algae are found in marine systems living both in water as well as in
sediment have an important role in ecological pyramid of the marine ecosystem. These
are the base of the trophic web and provide energy for all successive trophic level in the
marine eco system. These are single celled, chlorophyll bearing organisms uses solar
energy and nutrients from water to convert it into organic matter. Out of 8 Lakhs
species of different genera of algae available from marine ecosystem very few have
been tapped for their use as availability of biomedical compounds and also as feed in
different finfish, shellfish and molluscan hatchery. Their role is also very much vital
and critical in a successful mariculture hatchery management. An alga serves as a feed
for other zooplanktons and also added to the larval rearing tanks to improve quality of
water as green water technology. Among microalgae, flagellate and diatom species are
cultured in hatcheries in suitably treated seawater enriched with nutrients such as
nitrates, phosphates, essential trace elements and vitamins. To support growth of high
densities of larvae and juveniles reared in the hatchery high density of micro algal
culture is essential. Considering the importance of marine algal culture, different indoor
laboratories and outdoor mass culture systems being carried out in various hatcheries in
world like Japan, Taiwan, China, Philippines, Indonesia as well as India
Selection of candidate species for cage culture in India
In recent years, cage culture has emerged as one of the most viable method
of sea farming. This aquaculture farming system offers the farmer a chance to
utilize existing water resources, which is not used for other purposes. At present,
situations like increase in consumption of fish, decline in wild stock and poor
return from other culture systems paved strong interest for the fish production
through cage culture among the fish farmers. Selection of fish species is playing
major role in cage culture operation. Therefore, while selecting the species the
biological as well as economical criteria should be taken into consideration, which
includes available source of fish seed either from wild or hatcheries, seasonal
abundance of the fish seeds in wild, acceptance to artificial feeds, consumer
acceptance to the fish, economic value of the fish in local and international
market, regional preference, compatibility of the species to culture in various
system, resistance to disease and stress, ability to breed and produce the seed in
confined environments. By considering the above criteria, a variety of
commercially important marine fish species are highly found suitable for cage
farming. The important candidate species from different parts of the world
includes cobia (Rachycentron canadum), seabass (Lates calcarifer), snappers
(Lutjanus sp.), pompanos (Trachinotus sp.) and groupers (Epinephelus sp.), etc.
Commercial level seed production technology for majority of these fishes has
been developed in many of the South East Asian countries. In India, the seed
production of cobia, silver pompano, seabass and orange spotted grouper has been
achieved successfully by different fisheries research institutions
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High Thermal Conductivity Coatings via LENSтДв for Thermal Management Applications
Surface modification has been used to improve wear resistance, corrosion resistance and thermal
barrier properties of metals. However, no significant attempts have been made to improve
thermal conductivity by surface modification. In this work, we have examined the feasibility of
enhancing thermal conductivity (TC) of stainless steel by depositing brass using Laser
Engineered Net Shaping (LENS). The coating increased the TC of the substrate by 65% at 100
C┬░. Significantly low thermal contact resistance was observed between the coating and the
substrate due to minimal dilution and defect free sound interface. Our results indicate that laser
processing can be used on low coefficient of thermal expansion metal matrix composites to
create feature based coatings to enhance their heat transfer capability.Mechanical Engineerin
Engineering aspects of cage design, mooring and net design for open sea cage farming in India
Cage is an aquaculture production structure comprising of a rigid floating
frame, flexible net materials and mooring system (synthetic mooring rope, buoy
and anchor) with a round or square shape floating net pen to hold and culture
large number of fishes and other aquatic resources which can be installed in
reservoir, river, lake or sea. The design and operating variables in engineering
aspects of an open sea cage is of great concern in mariculture operations as they
are installed in exposed sites in the off shore areas. The design of the cage and its
accessories is specially made in agreement to the individual farmerтАЩs
requirements. A well engineered cage design will provide the opportunity to
reduce the cost of the cages. HDPE material is found to be suitable to make cage
frame for open sea cages. The HDPE float frames installed in open unprotected
water can withstand wave conditions. Round cage (volume depends on diameter)
with floatation system made of butt-welded HDPE pipes, designed for the culture
of fishes such as milkfish, mullet, cobia or pompano, sea bass and lobsters, and
this very well used in many countries
Capture based aquaculture - Alternate method for sustainable fish production
Global aquaculture has grown considerably and contributing significant
quantities to the worldтАЩs supply of fish for human consumption and it has shown
to be an attractive option for enhancing the fish production in the world. It is the
fastest growing, animal based food production sector with 73.8 million tonnes of
production in 2014. Food and Agriculture Organization of the United Nations
(FAO) define aquaculture as it is the farming of aquatic organisms including fish,
molluscs, crustaceans and aquatic plants. Farming implies some sort of
intervention in the rearing process to enhance production, such as regular
stocking, feeding, protection from predators, etc. It is a diverse sector, which
employs different strategies for fish production. There are two major strategies are
followed in the sector including hatchery based aquaculture (HBA) and capture
based aquaculture (CBA). The HBA allows the commercial and viable production
for number of organisms through the management of their entire life cycles
Marine microalgae culture techniques for finfish and shellfish larval rearing
Aquaculture system is based on microalgae and their animal consumers. The
uptake of microalgae biomass by filter-feeders is very promising from the energetic
standpoint. Microalgae are the biological starting point for energy flow through
most aquatic ecosystems, and are the basis of the food chain in all most all
aquaculture operations. Microalgae are used for rearing larvae and juveniles of
many species of commercially important molluscs, crustaceans and fish (marine
and freshwater) either directly as a source of feed or indirectly through zooplankton
(rotifers, copepod or Artemia). In addition, the microalgae are directly introduced
in the larval tanks (green water techniques) during marine finfish larval rearing,
where they are believed to play a role in stabilizing the water quality, provide
nutrition to the larvae and enable microbial control. Thus the management of
microalgae population and their culture is considered to be an integral part of
hatchery operations
Effects of Hot Isostatic Pressing on the Properties of Laser-Powder Bed Fusion Fabricated Water Atomized 25Cr7Ni Stainless Steel
25Cr7Ni stainless steel (super duplex stainless steels) exhibits a duplex microstructure of ferrite and austenite, resulting in an excellent combination of high strength and corrosion resistance. However, Laser-Powder Bed Fusion fabrication of a water-atomized 25Cr7Ni stainless steel of novel chemical composition resulted in a purely ferritic microstructure and over 5% porosity. The current study investigated the effects of two hot isostatic pressing parameters on the physical, mechanical, and corrosion properties as well as microstructures of water-atomized 25Cr7Ni stainless steel of novel composition fabricated by L-PBF for the first time in the literature. The corrosion behaviour was studied using linear sweep voltammetry in a 3.5% NaCl solution. The Hot Isostatic Pressing-treated sample achieved over 98% densification with a corresponding reduction in porosity to less than 0.1% and about 3 similar to 4% in annihilation of dislocation density. A duplex microstructure of ferrite 60% and austenite 40%was observed in the X-Ray Diffraction and etched metallography of the HIP-treated samples from a purely ferritic microstructure prior to the HIP treatment. With the evolution of austenite phase, the HIP-treated samples recorded a decrease in Ultimate Tensile Strength, yield strength, and hardness in comparison with as-printed samples. The variation in the morphology of the evolved austenite grains in the HIP-treated samples was observed to have a significant effect on the elongation. With a reduction in porosity and the evolution of the austenite phase, the HIP-treated samples showed a higher corrosion resistance in comparison with the as-printed samples
Characteristics of CVD Grown Diamond Films on Langasite Substrates
Surface acoustic wave (SAW) devices consist of a piezoelectric substrate with interdigitated (IDT) electrodes. These devices can be used to fabricate wireless and passive sensors that can be mounted in remote and/or inaccessible places. If encapsulated with CVD diamond, the SAW devices can be made to operate under extremely hostile conditions. The piezoelectric layer (AlN, ZnO etc.) deposited on the diamond or an inverse system can increase the frequency of the SAW device. Most piezoelectric materials (such as quartz) show phase transition temperatures below diamond deposition temperature (650┬║-1100┬║C), preventing their use as a substrate for diamond growth. Langasite La3Ga5SiO14 (LGS) is recently fabricated piezoelectric material that can withstand high temperatures without being deteriorated. LGS does not have phase transitions up to its melting point of 1470┬░C.Here we report the deposition of diamond films by microwave plasma CVD in methane-hydrogen gas mixtures on polished and rough surfaces of the LGS substrates seeded with nanodiamonds. No buffer layer between the substrate and the coating had been used. The effect of substrate pretreatment (PT) was also investigated on the growth behaviour of diamond films on LGS. The resulting films are characterised by Raman spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS). The effect of substrate roughness on the growth behaviour was found to favour bigger grain sizes on the unpolished substrates. Whereas, the effect of substrate pretreatment (PT) was found to produce unique microstructural features with better polycrystalline diamond (PCD) quality than on the substrates without PT. Raman signals confirm the deposition of PCD in all the cases but the X-ray results interestingly show new phase formation of hcp and rhombohedral diamond lattice structures under CVD growth environment
Photo bioreactor-based microalgae culture for mariculture applications
Microalgae are considered as a valuable organic resource with a potential
application in finfish, shellfish and molluscan culture. Being, rich source of essential
fatty acids (EPA and DHA), the microalgae have very important role even in human
nutrition. Microalgae culture forms an inevitable component in aquaculture venture
especially seed production of either finfishes or shell fishes. Cultivated microalgae
have long been integral to the hatchery production of many farmed finfish, shellfish
and other commercially important aquaculture species. Molluscs like oysters,
mussels and clams filter them from the sea water in all stages of life. Rotifers and
brine shrimps also ingest algae, and are then themselves used as food for larval
fish and prawns. The shrimp hatcheries use micro algae as food for the early larvae
and later for the water quality maintenance. In many hatchery systems algae are
added to the water containing larvae to improve the тАШqualityтАЩ of water as green
water systems. The production of live algae is very critical in the successful hatchery
management. In the natural environment, the larvae feed on any minute plant
components which are readily available to them. But in a hatchery, the feed which
are acceptable to the larvae for their growth and further development have to be
identified and isolated. In the early critical stages of the rearing larvae of fin fishes
and shellfishes, the phyto-flagellates (species of Isochrysis, Pavlova, Dicrateria,
Chromulina and Tetraselmis) and other nanoplankters (species of Chlorella and
Synechocystis) form the basic food. But in the post larval stages of crustaceans
and spat or juvenile stages of bivalves, the diatoms (species of Chaetoceros,
Skeletonema and Thalassiosira) form the primary food. Hence the culture of micro
algae is an essential prerequisite for the rearing operations of economically
important cultivable organisms in a hatchery system
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