Uptake Rate of Ammonia-nitrogen With Sterile Ulva sp. for Water Quality Control of Intensive ShrimpCulture Ponds in Developing Countries

Ammonia-nitrogen uptake by seaweed was modeled based on the concept of ammonia-nitrogen permeation through cell membrane, and the derived model of uptake rate was experimentally verified. In this study, sterile Ulva sp. was employed as seaweed to treat model culture solution, and the distribution equilibrium of the ammonia-nitrogen between the culture solution and cell inside was measured to obtain the equilibrium. For this measurement, the seaweed was pretreated before the uptake runs to inhibit the assimilation by methionine sulfoximine for removal of the assimilation effects on the uptake rate. The parameters of the distribution equilibrium and permeation rate of ammonia-nitrogen were measured. The pretreated seaweed could uptake ammonia-nitrogen and the ammonia-nitrogen permeated through the cell membrane from the culture solution into the cell according to the concentration gradient. The seaweed saturated with ammonia-nitrogen was immersed in the culture solution without ammonia-nitrogen and it could excrete ammonia-nitrogen once taken in. In both cases of the uptake and excretion, the systems attained equilibrium after around 6 hours. The ammonia-nitrogen concentration in the cell increased with the concentration in the culture solution at equilibrium. The flux of ammonia-nitrogen was almost proportional to the concentration difference, defined as that between the ammonia-nitrogen concentration in the cell and the hypothetical concentration of ammonia-nitrogen in the cell which is in equilibrium with the culture solution. The overall permeation coefficient was measured as 9.1 · 10–3 m h–1 for both cases of uptake and excretion, and this relationship was valid when the concentration difference was large enough relative to the flux

From nonassociativity to solutions of the KP hierarchy

A recently observed relation between 'weakly nonassociative' algebras A (for which the associator (A,A^2,A) vanishes) and the KP hierarchy (with dependent variable in the middle nucleus A' of A) is recalled. For any such algebra there is a nonassociative hierarchy of ODEs, the solutions of which determine solutions of the KP hierarchy. In a special case, and with A' a matrix algebra, this becomes a matrix Riccati hierarchy which is easily solved. The matrix solution then leads to solutions of the scalar KP hierarchy. We discuss some classes of solutions obtained in this way.Comment: 7 pages, 4 figures, International Colloquium 'Integrable Systems and Quantum Symmetries', Prague, 15-17 June 200

Effects of size on the magnetic properties and crystal structures of magnetically frustrated DyMn2O5 nanoparticles

We synthesized magnetically frustrated DyMn2O5 nanoparticles in pores of mesoporous silica, with particle sizes ranging from 7 to 20 nm, and investigated their magnetostructural correlation. We found that the lattice constants of the DyMn2O5 nanoparticles deviated from those of the bulk crystal below ∼12 nm and their crystallographic structures at the unit cell level were distorted. The size dependences of the blocking temperature and coercive field drastically change at ∼12 nm. In addition, the Weiss temperature depends strongly on particle size, and its sign changes at ∼12 nm. It is considered that such features can be realized owing to the distortion caused by the ligand atoms at the surface. The orbital structures of the magnetic sites are easily modified due to the distortion of the ligand ions at the surface, so that the correlation between the crystal structure and magnetic properties can be enhanced. Moreover, magnetization of the nanoparticle results in quasi-superparamagnetic behavior. Monte Carlo calculation of the nanoparticles indicates that such a feature is realized due to the quasi-free spins induced at the surface by magnetic frustration

Magnetic properties of BiMnO3 nanoparticles in SBA-15 mesoporous silica

Nanoparticles of multiferroic material BiMnO3 were synthesized in the pores of the mesoporous silica SBA-15 and their magnetic properties were investigated. The powder X-ray diffraction pattern for the nanoparticles at room temperature was similar to that for bulk crystals with monoclinic symmetry. The particle size of the nanocrystals was estimated to be about 14 nm using Scherrer\u27s equation. The temperature dependence of the DC susceptibilities for the nanoparticles showed superparamagnetic behavior. The susceptibility and thermoremanent magnetization exhibited the ferromagnetic feature and the ferromagnetic transition temperature was almost same to that for bulk crystals, approx 100 K. However, the Weiss temperature Θ was evaluated as the negative value and the magnetization curve showed antiferromagnetic behavior. The results suggest the antiferromagnetic properties appeared prominently in the nanoparticles.Proceedings of the 25th International Conference on Low Temperature Physics (LT 25), August 6-13, 2008, Amsterdam, Netherland

The clinical utility of Lens culinaris agglutinin-reactive thyroglobulin ratio in serum for distinguishing benign from malignant conditions of the thyroid

ArticleCLINICA CHIMICA ACTA. 379(1-2): 101-104 (2007)journal articl