Polyculture of freshwater prawn, Macrobrachium rosenbergii, de Man with carps: effects of prawn stocking density

Effects of three stocking densities, viz., 35, 50 and 65/decimal (1 decimal = 40.48 m2) of juvenile freshwater prawn (Macrobrachium rosenbergii) on prawn and fish production were tested in a polycuture system with silver carp (Hypophthalmichthys molitrix), catla (Catla catla), Grass carp (Ctenophmyngodon idella) and silver barb (Barbodes gonionotus). The fish stocking density was 19/decimal with the species combination of silver carp-10, catlac-6, grass carp-1 and silver barb-2. In a 8-month culture period, the prawn yield 423 ± 144 kg/ha was significantly lower (P< 0.5) with the prawn stocking density of 35/decimal than that of 548 ± 178 kg/ha and 662 ± 243 kg/ha with 50 and 65/decimal respectively. The fish production (1844-1891 kg/ha) did not differ significantly (p <0.05) among the three treatments indicating that prawn stocking densities had no influence on fish yield. The lower mean harvest weight (62 g) and survival rate (67 g) and higher yield (2.67 kg/decimal) with the highest stocking rate of prawn reveals that as density was increased, prawn survival and individual weight at harvest decreased but total yield increased.

Effects of socking [sic] density on ammonia excretion and the growth of Nile tilapia (Oreochromis niloticus L.)

The effects of stocking density (10, 15, 50 & 75 fish in 65L tank) and ammonia excretion on the growth of Nile tilapia, Oreochromis niloticus (12.19 ± 1.21 g) were investigated. Increasing stocking density of Nile tilapia from 15 fish/tank (2.81 g fish/L) to 75 fish/tank (14.07 g fish/L) resulted in associated increase in ammonia level (1.48 ± 0.87 mg/L to 26.44 ± 11.4 mg/L) and significantly lower growth rates. Significantly better feed conversion ratios were found for fish reared at lower (15 fish/tank) stocking densities compared to higher (75 fish/tank) stocking densities. Individual growth rates were significantly better for fish reared at a lower stocking density 15 fish/tank compared to higher stocking density 75 fish/tank and size variation (coefficient of variation in weight) were positively correlated with stocking density. Although water exchange did not have a significant effect on the growth of Nile tilapia for fish stocked at 10 fish/tank (1.88 g fish/L) and 50 fish/tank (9.38 g fish/L), however, the fish in the higher stocking density (9.38 g fish/L) groups and without water exchange, significantly changed the coloration of their bodies (silver to black) which may be due to the lower oxygen levels combined with higher ammonia levels. Ammonia level increased with increasing stocking density and without water exchange. In this study, it may be suggested that when fish reared at higher stocking densities then water exchange must be taken in to consideration so as to help avoid environmental and physiological stress to the fish.

Effects of stocking density on growth and survival of Mystus gulio in nursery ponds

A study on the effect of stocking density on growth and survival of nona tengra (Mystus gulio) was carried out in brackishwater earthen nursery ponds (2 decimal each) for a period of 42 days. Five-day old captive bred tengra post-larvae (ABL: 4.53±0.83 mm and ABW:3.33 mg) were stocked at four different densities of 200/m² (Treatment-1), 250/m² (Treatment-2), 350/m² (Treatment-3) and 450/m² (Treatment-4). Fries were fed twice a day with a mixture of fine rice bran, mustard oil cake and fishmeal at the ratio of 2:1:1. The specific growth rate (SGR) of larvae did not vary significantly (p>0.05) between T1 (5.096% mg/day) and T2 (5.08% mg/day), but it was found significantly (p<0.05) higher from T3 (4.98% mg/day) and T4 (4.91% mg/day), respectively. The final survival rates of 89.25±5.41% in T1 and 88.72±6.09% in T2 were found similar (p>0.05), but significantly higher (p<0.05) than those of, 76.20±4.77% in T3 and 70.34±5.71% in T4. The results indicate that 5-day old hatchery bred nona tengra post-larvae can be nursed in earthen pond at a stocking density of 200-250/m².

Growth of ultrahigh density single-walled carbon nanotube forests by improved catalyst design.

We have grown vertically aligned single-walled carbon nanotube forests with an area density of 1.5 × 10(13) cm(-2), the highest yet achieved, by reducing the average diameter of the nanotubes. We use a nanolaminate Fe-Al(2)O(3) catalyst design consisting of three layers of Al(2)O(3), Fe, and Al(2)O(3), in which the lower Al(2)O(3) layer is densified by an oxygen plasma treatment to increase its diffusion barrier properties, to allow a thinner catalyst layer to be used. This high nanotube density is desirable for using carbon nanotubes as interconnects in integrated circuits.

Low temperature growth of ultra-high mass density carbon nanotube forests on conductive supports

We grow ultra-high mass density carbon nanotube forests at 450°C on Ti-coated Cu supports using Co-Mo co-catalyst. X-ray photoelectron spectroscopy shows Mo strongly interacts with Ti and Co, suppressing both aggregation and lifting off of Co particles and, thus, promoting the root growth mechanism. The forests average a height of 0.38 μm and a mass density of 1.6 g cm -3. This mass density is the highest reported so far, even at higher temperatures or on insulators. The forests and Cu supports show ohmic conductivity (lowest resistance ∼22 kΩ), suggesting Co-Mo is useful for applications requiring forest growth on conductors. © 2013 AIP Publishing LLC.

Fourier spectrum based extraction of an equivalent trap state density in indium gallium zinc oxide transistors

Segregating the dynamics of gate bias induced threshold voltage shift, and in particular, charge trapping in thin film transistors (TFTs) based on time constants provides insight into the different mechanisms underlying TFTs instability. In this Letter we develop a representation of the time constants and model the magnitude of charge trapped in the form of an equivalent density of created trap states. This representation is extracted from the Fourier spectrum of the dynamics of charge trapping. Using amorphous In-Ga-Zn-O TFTs as an example, the charge trapping was modeled within an energy range of ΔEt 0.3 eV and with a density of state distribution as Dt(Et-j)=Dt0exp(-ΔEt/ kT)with Dt0 = 5.02 × 1011 cm-2 eV-1. Such a model is useful for developing simulation tools for circuit design. © 2014 AIP Publishing LLC.

Effects of silver carp density on zooplankton and water quality: Implications for eutrophic lakes in China

We examined the responses of zooplankton community, water transparency, chlorophyll a and nutrients to manipulation of density of silver carp (Hypophthyalmichthys molitrix) in an one-way factorial experiment using enclosures placed in Donghu (East Lake, 30 degrees 33' N, 114 degrees 23' E), located in Wuhan, P. R. China. Enclosures (18.75 m(3)) were treated with four silver carp densities, 0, 81, 225, 485 g/m(2). Total zooplankton abundance (excluding nauplii and rotifers except for Asplanchna sp.) and the mean size of dominant cladoceran species were significantly greater in enclosures with 0 and 81 fish densities than those in enclosures with 225 and 485 fish densities. Water transparency also improved significantly when silver carp densities were 0 or 81 g/m(2). We did not find significant effects of silver carp density on chlorophyll a, total phosphorus, or total nitrogen concentrations. We conclude that by reducing planktivorous fish to below the current density (190 g/m(2)), the zooplankton community can be shifted from the dominance of small-bodied Moina sp. to dominance of large-bodied Daphnia sp. Further, the water clarity can be increased.

Low threshold current density operation of strain-compensated quantum cascade laser

We report the low threshold current density operation of strain-compensated In0.64Ga0.36As/In0.38Al0.62As quantum cascade lasers emitting near 4.94 mu m. By employing an enlarged strain-compensated structure and optimizing the injector doping density, a rather low threshold current density of 0.57 kA/cm(2) at 80K is achieved for an uncoated 20-mu m-wide and 2.5-mm-long laser.

Silicon doping induced increment of quantum dot density

Low-indium-content self-assembled InGaAs/GaAs quantum dots (SAQD) were grown using solid-source molecular beam epitaxy (MBE) and investigated by atomic force microscopy and photoluminescence (PL) spectroscopy. Silicon, which was doped at different quantum dot (QD) growth stages, markedly increased the density of QD. We obtained high density In0.35Ga0.65As/GaAs(001) quantum dots of 10(11)/cm(2) at a growth temperature of 520degreesC. PL spectra and distribution statistics show the high quality and uniformity of our silicon-doped samples. The density increment can be explained using the lattice-hardening mechanism due to silicon doping.

Temperature dependent photoluminescence of an In(Ga)As/GaAs quantum dot system with different areal density

We have systematically studied the temperature dependent photoluminescence of a self-assembled In(Ga)As/GaAs quantum dot (QD) system with different areal densities from similar to 10(9) to similar to 10(11) cm(-2). Different carrier channels are revealed experimentally and confirmed theoretically via a modified carrier equation model considering a new carrier transfer channel, i.e. continuum states ( CS). The wetting layer is demonstrated to be the carrier quenching channel for the low-density QDs but the carrier transfer channel for the high-density QDs. In particular, for the InGaAs/GaAs QDs with a medium density of similar to 10(10) cm(-2), the CS is verified to be an additional carrier transfer channel in the low temperature regime of 10-60 K, which is studied in detail via our models. The possible carrier channels that act on different temperature regimes are further discussed, and it is demonstrated that density is not a crucial factor in determining the carrier lateral coupling strength.

Study of a high power density sodium polysulfide/bromine energy storage cell

Nickel catalyst supported on carbon was made by reduction of nickelous nitrate with hydrogen at high temperature. Ni/ C catalyst characterization was carried out by XRD. It was found that the crystal phase of NiS and NiS2 appeared in the impregnated catalyst. Ni/ C and Pt/ C catalysts gave high performance as the positive and negative electrodes of a sodium polysulfide/ bromine energy storage cell, respectively. The overpotentials of the positive and negative electrodes were investigated. The effect of the electrocatalyst loading and operating temperature on the charge and discharge performance of the cell was investigated. A power density of up to 0.64 W cm(-2) ( V = 1.07 V) was obtained in this energy storage cell. A cell potential efficiency of up to 88.2% was obtained when both charge and discharge current densities were 0.1 A cm(-2).

Change of the dominant luminescent mechanism with increasing current density in molecularly doped organic light-emitting devices

We have fabricated and measured a series of electroluminescent devices with the structure of ITO/TPD/Eu(TTA)(3)phen (x):CBP/BCP/ ALQ/LiF/Al, where x is the weight percentage of Eu(TTA)3phen (from 0% to 6%). At very low current density, carrier trapping is the dominant luminescent mechanism and the 4% doped device shows the highest electroluminescence (EL) efficiency among all these devices. With increasing current density, Forster energy transfer participates in EL process. At the current density of 10.0 and 80.0mA/ cm(2), 2% and 3% doped devices show the highest EL efficiency, respectively. From analysis of the EL spectra and the EL efficiency-current density characteristics, we found that the EL efficiency is manipulated by Forster energy transfer efficiency at high current density. So we suggest that the dominant luminescent mechanism changes gradually from carrier trapping to Forster energy transfer with increasing current density. Moreover, the conversion of dominant EL mechanism was suspected to be partly responsible for the EL efficiency roll-off because of the lower EL quantum efficiency of Forster energy transfer compared with carrier trapping.

Electrochemical study of PW12O403- in poly(ethylene glycol) electrolyte

The electrochemical properties Of PW12O403- (abbreviated as PW12) anion in poly(ethylene glycol) (PEG) have been studied by cyclic voltammetry, complex impedance and FT-IR spectroscopy. The PW12 anion in PEG-LiClO4 electrolyte shows reasonable facile electrochemistry, and the diffusion coefficients Of PW12 were measured with microelectrode. It is shown that ionic conductivity of polymer electrolytes based on low molecular weight PEG can be improved by the addition of PW12. The increase of conductivity is coupled with decrease of transient cross-links density of polymer chains which is evidenced by the downshift of C-O-C stretching mode. The phenomena are explained in view of ion-ion and ion-polymer interactions.

Effect of stocking density on growth, settlement and survival of clam larvae, Meretrix meretrix

To determine the optimal larval density for hatchery culture of the clam Meretrix meretrix, experiments with stocking densities of 5, 10, 20, 40 and 60 larvae ml(-1) were designed, which included the developmental stages from D-veliger to 8 days postsettlement. Shell length, settlement time and survival rate of the larvae were recorded. Results showed that, at each sampling time, larvae reared at the highest density had the smallest mean size, whereas larvae reared at the lowest density had the largest mean size. Statistical differences in mean shell length at different stocking densities appeared from day 2, and greater differences occurred with increased culture time. Specific growth rate (SGR) in the rapid growing stage (day 0-3) was negatively correlated with density; however, no correlation was found between SGR and density in the slow growing stage (days 3-7). Settlement time was prolonged and shell length of settled larvae decreased as density increased. However, larval survival rate (74.8-79.1%) was independent of stocking density. Results showed that a high stocking density, in the designated range, is feasible for larval culture of the clam M. meretrix. However, for large-scale culture, in the interest of costs and safety, a stocking density of 10-20 larvae ml(-1) is recommended. (c) 2006 Elsevier B.V. All rights reserved.

Effects of diet, stocking density, and environmental factors on growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum larvae

A series of experiments was conducted to evaluate the effects of diet, stocking density, and environmental factors on growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum larvae. These experiments examined the following factors: diet (Isochrysts spp., Chlorella spp., and a mixture of Isochrysis spp. and Chlorella spp. [ 1: 1 w/w]), stocking density (5, 10, 15, and 20 larvae ml(-1)), light intensity (un-shaded, partially shaded, and fully shaded), water filtration (unfiltered and sand-filtered), water exchange (50% and 100% once every other day, 25%, 50%, and 100% once daily; 50% and 100% twice daily), and the use of substrate (with and without sand as the substrate). Results indicated that Chlorella spp. could replace 50% of Isochrysis spp. as a food source for the Manila clam larvae without affecting growth, survival, and metamorphosis. Larval growth decreased significantly with increasing stocking density. A density of 5-10 larvae ml(-1) appeared to be optimal for normal growth of Manila clam larvae. Neither diet nor stocking density used in the study had a significant effect on larval survival. Under partially shaded (light intensity = 1000-5000 lx) and fully shaded (light intensity <500 lx) conditions, larval growth was significantly faster than under direct sunlight (un-shaded). A water exchange rate of 50% twice daily provided optimum larval growth. Larvae grew significantly faster in the unfiltered water than in the sand-filtered water. Using sand as the substrate in the culture system significantly depressed the metamorphosis rate. The type and particle size of sand used as the substrate did not significantly affect growth and metamorphosis rates of the larvae. (C) 2005 Published by Elsevier B.V.