Effects of Sterile Ulva sp. Growth Rate on Water Quality Control of Intensive Shrimp Culture Pond in Developing Countries

To control the water quality in the intensive shrimp mariculture pond by uptaking the total ammonia-nitrogen with sterile Ulva sp., the growth rate of sterile Ulva sp. was experimentally measured and the influence of the rate on the water quality control evaluated. The specific growth rate constant of the seaweed increased with the total ammonia-nitrogen concentration, photosynthetic photon flux density and operating temperature. Then the dynamics of ammonia-nitrogen in the modeled culture pond for the intensive shrimp farming in the tropical region were numerically simulated, in which the seaweed was used to uptake ammonia-nitrogen. The seaweed could uptake ammonia-nitrogen effectively during daytime mainly due to the high intensity of sun light, and the total ammonia-nitrogen concentration in the shrimp pond could be kept very low. The required seaweed density to control the total ammonia-nitrogen concentration less than the recommended maximum concentration of 1.0 ⋅ 10–3 kg N m–3 was estimated to be reasonable

Phase transitions of an intrinsic curvature model on dynamically triangulated spherical surfaces with point boundaries

An intrinsic curvature model is investigated using the canonical Monte Carlo simulations on dynamically triangulated spherical surfaces of size upto N=4842 with two fixed-vertices separated by the distance 2L. We found a first-order transition at finite curvature coefficient \alpha, and moreover that the order of the transition remains unchanged even when L is enlarged such that the surfaces become sufficiently oblong. This is in sharp contrast to the known results of the same model on tethered surfaces, where the transition weakens to a second-order one as L is increased. The phase transition of the model in this paper separates the smooth phase from the crumpled phase. The surfaces become string-like between two point-boundaries in the crumpled phase. On the contrary, we can see a spherical lump on the oblong surfaces in the smooth phase. The string tension was calculated and was found to have a jump at the transition point. The value of \sigma is independent of L in the smooth phase, while it increases with increasing L in the crumpled phase. This behavior of \sigma is consistent with the observed scaling relation \sigma \sim (2L/N)^\nu, where \nu\simeq 0 in the smooth phase, and \nu=0.93\pm 0.14 in the crumpled phase. We should note that a possibility of a continuous transition is not completely eliminated.Comment: 15 pages with 10 figure

Effects of Inhibitory Factor on Uptake Rate of Ammonia-Nitrogen with Sterile Ulva sp. for Water Quality Control of Intensive Shrimp Culture Ponds

Ammonia-nitrogen uptake by sterile Ulva sp. was studied for the control of culture pond water of intensive shrimp farming. The uptake rates were measured by batch and semi-continuous operations, and analyzed with the Michaelis-Menten model of uncompetitive inhibition. For the batch uptake operations, the Michaelis-Menten parameters were estimated, and the maximum rate and Michaelis constants were estimated as 3.4 × 10–2 kg kg–1 h–1 and 5.5 × 10–3 kg m–3, respectively. The inhibitory factor increased with the uptake time and with the decrease of the seaweed density. In the cases of semi-continuous operations, the seaweed could continuously treat with the model farming culture solution. Although the ratio of the seaweed density relative to the rate of ammonia-nitrogen generation should be appropriately adjusted to keep lower inhibitory factor in the seaweed, the ammonia-nitrogen concentration could be maintained at a relatively low level during operation. Then the ammonia-nitrogen uptake by the alga water was roughly simulated and operation with moderate density of the algae in the pond could maintain the ammonia-nitrogen concentration at a sufficiently low level in the shrimp farming pond. The suggested treatment process might be attractive to control pond water quality for intensive shrimp farming

Isotropic photonic band gap and anisotropic structures in transmission spectra of two-dimensional 5-fold and 8-fold symmetric quasiperiodic photonic crystals

We measured and calculated transmission spectra of two-dimensional quasiperiodic photonic crystals (PCs) based on a 5-fold (Penrose) or 8-fold (octagonal) symmetric quasiperiodic pattern. The photonic crystal consisted of dielectric cylindrical rods in air placed normal to the basal plane on vertices of tiles composing the quasiperiodic pattern. An isotropic photonic band gap (PBG) appeared in the TM mode, where electric fields were parallel to the rods, even when the real part of a dielectric constant of the rod was as small as 2.4. An isotropic PBG-like dip was seen in tiny Penrose and octagonal PCs with only 6 and 9 rods, respectively. These results indicate that local multiple light scattering within the tiny PC plays an important role in the PBG formation. Besides the isotropic PBG, we found dips depending on the incident angle of the light. This is the first report of anisotropic structures clearly observed in transmission spectra of quasiperiodic PCs. Based on rod-number and rod-arrangement dependence, it is thought that the shapes and positions of the anisotropic dips are determined by global multiple light scattering covering the whole system. In contrast to the isotropic PBG due to local light scattering, we could not find any PBGs due to global light scattering even though we studied transmission spectra of a huge Penrose PC with 466 rods.Comment: One tex file for manuscript and 12 PNG files for figures consisting of Fig.1a-d, 2,3, ...