Relationships between microcystins and environmental parameters in 30 subtropical shallow lakes along the Yangtze River, China

1. A survey of 30 subtropical shallow lakes in the middle and lower reaches of the Yangtze River area in China was conducted during July-September in 2003-2004 to study how environmental and biological variables were associated with the concentration of the cyanobacterial toxin microcystin (MC). 2. Mean MC concentration in seasonally river-connected lakes (SL) was nearly 33 times that in permanently river-connected lakes (RL), and more than six times that in city lakes (NC) and non-urban lakes (NE) which were not connected to the Yangtze River. The highest MC (8.574 mu g L-1) was detected in Dianshan Lake. 3. MC-RR and MC-LR were the primary toxin variants in our data. MC-RR, MC-YR and MC-LR were significantly correlated with Ch1 a, biomass of cyanobacteria, Microcystis and Anabaena, indicating that microcystins were mainly produced by Microcystis and Anabaena sp. in these lakes. 4. Nonlinear interval maxima regression indicated that the relationships of Secchi depth, total nitrogen (TN) : total phosphorus UP) and NH4+ with MC were characterised by negative exponential curves. The relationships between MC and TN, TP, NO3- + NO2- were fitted well with a unimodal curve. 5. Multivariate analyses by principal component and classifying analysis indicated that MC was mainly affected by Microcystis among the biological factors, and was closely related with temperature among physicochernical factors.

Restudy on the wave functions of Gamma(nS) states in the light-front quark model and the radiative decays of Gamma(nS) -> eta(b) + gamma

The light-front quark model has been applied to calculate the transition matrix elements of heavy hadron decays. However, it is noted that using the traditional wave functions of the light-front quark model given in the literature, the theoretically determined decay constants of the Gamma(nS) obviously contradict the data. This implies that the wave functions must be modified. Keeping the orthogonality among the nS states and fitting their decay constants, we obtain a series of the wave functions for Gamma(nS). Based on these wave functions and by analogy with the hydrogen atom, we suggest a modified analytical form for the Gamma(nS) wave functions. Using the modified wave functions, the obtained decay constants are close to the experimental data. Then we calculate the rates of radiative decays of Gamma(nS) -> eta(b) + gamma. Our predictions are consistent with the experimental data on decays Gamma(3S) -> eta(b) + gamma within the theoretical and experimental errors.

Spin and spin-isospin instabilities and Landau parameters of Skyrme interactions with tensor correlations

The Landau parameters of Skyrme interactions in the spin and spin-isospin channels are studied using various Skyrme effective interactions with and without tensor correlations. We focus on the role of the tensor terms on the spin and spin-isospin instabilities that can occur in nuclear matter above saturation density. We point out that these instabilities are realized in nuclear matter at the critical density of about two times the saturation density for all the adopted parameter sets. The critical density is shown to be very much dependent not only on the choice of the Skyrme parameter set, but also on the inclusion of the tensor terms.

Two-quasiparticle K-isomeric states in strongly deformed neutron-rich Nd and Sm isotopes: a projected shell-model analysis

Motivated by recent spectroscopy data from fission experiments, we apply the projected shell model to study systematically the structure of strongly deformed, neutron-rich, even-even Nd and Sm isotopes with neutron number from 94 to 100. We perform calculations for rotational bands up to spin I = 20 and analyze the band structure of low-lying states with quasiparticle excitations, with emphasis given to rotational bands based on various negative-parity two-quasiparticle (2-qp) isomers. Experimentally known isomers in these isotopes are described well. The calculations further predict proton 2-qp bands based on a 5(-) and a 7(-) isomer and neutron 2-qp bands based on a 4(-) and an 8(-) isomer. The properties for the yrast line are discussed, and quantities to test the predictions are suggested for future experiment.

Analytical potential energy function and spectroscopic parameters for the ground and excited states of NaH

set of energies at different internuclear distances for the ground electronic state and two excited electronic states of NaH molecule have been calculated using valence internally contracted multireference configuration interaction(MRCI) including Davidson correction and three basis sets. Then, a potential energy curve (PEC) for each state was determined by extrapolating MRCI energies to the complete basis sets limit. Based on the PECs, accurate vibrational energy levels and rotational constants were determined. The computational PECs are were fitted to analytical potential energy functions using the Murrell-Sorbie potential function. Then, accurate spectroscopic parameters were calculated. Compared with experimental results, values obtained with the basis set extrapolation yield a potential energy curve that gives accurate vibrational energy levels, rotational constants and spectroscopic parameters for the NaH molecule. (C) 2004 Elsevier B.V. All rights reserved.

Theoretical study on analytical potential function and spectroscopic parameters for CaF molecule

The equilibrium properties and potential energy curves of the ground electronic state of CaF have been calculated using the Brueckner Doubles calculation with a triples contribution added [BD(T)] and the gradient-corrected density functional theory with three-parameter exact exchange mixing (B3LY-P) method, with 6-311 + G*,6-311 + G(2df,2pd) and 6-311 + G(3df,3pd) basis sets. All the computational PECs are fitted to analytical potential energy functions using Murrell-Sorbie, Huxley and Tang-Toennies potentials. Based on this, the spectroscopic parameters are calculated, and then compared with some other theoretical and experimental data. (C) 2004 Elsevier B.V. All rights reserved.

Uniform YVO4:Ln(3+) (Ln = Eu, Dy, and Sm) nanocrystals: Solvothermal synthesis and luminescence properties

Well-dispersed YVO4:Ln(3+) (Ln = Eu, Dy, and Sm) nanocrystals with uniform morphology and size have been synthesized via a facile solvothermal route. XRD results demonstrate that all of the three samples can be well indexed to the pure tetragonal phase Of YVO4, indicating that the Eu3+, Dy3+, and Sm3+ have been effectively doped into the host lattices of YVO4. TEM images show that the YVO4 nanocrystals exhibit ellipsoid shape and a mean size of about 20 nm, which is in good agreement with the estimation of XRD results.

Novel Near-Infrared Luminescent Hybrid Materials Covalently Linking with Lanthanide [Nd(III), Er(III), Yb(III), and Sm(III)] Complexes via a Primary beta-Diketone Ligand: Synthesis and Photophysical Studies

A series of novel, colorless, and transparent sot-gel derived hybrid materials Ln-DBM-Si covalently grafted with Ln(DBM-OH)(3)center dot 2H(2)O (where DBM-OH = o-hydroxydibenzoylmethane, Ln = Nd, Er, Yb, and Sin) were prepared through the primary beta-diketone ligand DBM-OH. The structures and optical properties of Ln-DBM-Si were studied in detail. The investigation results revealed that the lanthanide complexes were successfully in situ grafted into the corresponding hybrids Ln-DBM-Si. Upon excitation at the maximum absorption of ligands, the resultant materials displayed excellent near-infrared luminescence.

Facile Synthesis and Luminescence Properties of Highly Uniform MF/YVO4:Ln(3+) (Ln = Eu, Dy, and Sm) Composite Microspheres

Uniform MF/YVO4:Ln(3+) (Ln = Eu, Dy, and Sm) composite microspheres have been prepared via a simple and economical wet-chemical route at ambient pressure and low temperature. Monodisperse micrometer-sized melamine formaldehyde (MF) colloidal particles were first fabricated by a condensation process of melamine with formaldehyde. Subsequently, well-dispersed YVO4 nanoparticles were successfully grown onto the MF microspheres to form core-shell structured composite particles in aqueous Solution. The as-obtained composite microspheres with perfect spherical shape are uniform in size and distribution, and the thickness and roughness of the YVO4 shells on MF cores could be tuned by varying the reaction temperature. The MF/YVO4:Ln(3+) composite phosphors show strong light emissions with different colors coming from different activator ions under ultraviolet excitation, which might find potential applications in fields such as light phosphor powders and advanced flat panel displays.

PREPARATION STRUCTURE AND PHYSICAL-PROPERTIES OF NEW SILVER LANTHANIDE MOLYBDENUM OXIDES [AGLNMO(2)O(8)(LN=LA-ND AND SM)]

We present the synthesis of AgLnMo(2)O(8) compounds with Ln = La-Nd and Sm. These compounds represent a scheelite-type structure characterized by MoO4- tetrahedrons. IR spectra show five absorption peaks in the region of 1000-400cm(-1), around 800cm(-1) and 400cm(-1), which correspond to the modes of the tetrahedral MoO42- groups. All of AgLnMo(2)O(8) (Ln = La-Nd and Sm) oxides are dielectric materials at room temperature. The temperature dependence of the magnetic susceptibility ofAgLnMo(2)O(8) (Ln = Ce-Nd and Sm) shows Curie-Weiss law behavior from 100K to 300K. This indicates that both Ce and Pr exist in +3 oxidation state in AgLnMo(2)O(8). For AgLaMo2O8, diamagnetic properties are found as expected.

CRYSTAL-STRUCTURE AND THERMODYNAMIC PARAMETERS OF NYLON-1010

WAXD, SAXS, FTIR, DSC and density techniques have been used to investigate the crystal structure, crystal density rho(c), amorphous density rho(a), equilibrium heat of fusion DELTAH(m)degrees and equilibrium melting temperature T(m)degrees. By extrapolating the straight lines in the FTIR absorbance against density plot to zero intensity, rho(c) and rho(a) were estimated to be 1.098 and 1.003 g/cm3 respectively. The rho(c) obtained was too low in value. From X-ray diffraction patterns of uniaxially oriented fibres, the crystal structure of Nylon-1010 was determined. The Nylon-1010 crystallized in the triclinic system, with lattice dimensions: a = 4.9 angstrom, b = 5.4 angstrom, c = 27.8 angstrom, alpha = 49-degrees, beta = 77-degrees, gamma = 63.5-degrees. The unit cell contained one monomeric unit, the space group was P1BAR, and the correct value of rho(c) was 1.135 g/cm3. The degree of crystallinity of the polymer was determined as about 60% (at RT) using Ruland's method. SAXS has been used to investigate the crystalline lamellar thickness, long period, transition zone, the specific inner surface and the electron density difference between the crystalline and amorphous regions for Nylon-1010. The analysis of data was based upon a one-dimensional electron-density correlation function. DELTAH(m)degrees was estimated to be 244.0 J/g by extrapolation of DELTAH(m)degrees in the plot of heat of fusion against specific volume of semicrystalline specimens to the completely crystalline condition (V(sp)c = 1/rho(c)). Owing to the ease of recrystallization of melt-crystallized Nylon-1010 specimens, the well-known Hoffman's T(m)-T(c) method failed in determining T(m)degrees and a Kamide double extrapolation method was adopted. The T(m)degrees value so obtained was 487 K.

GLASS-TRANSITION TEMPERATURE AND MOLECULAR-PARAMETERS OF POLYMER

A new relationship, which correlates the glass transition temperature (T(g)) with other molecular parameters, is developed by using Flory's lattice statistics of polymer chain and taking the dynamic segment as the basic statistical unit. The dependences of T(g) on the chain stiffness factor (sigma-2), dynamic stiffness factor (beta = -d ln-sigma-2/dT) and molecular weight of polymer are discussed in detail based on the theory. The theory is compared with experimental data for many linear polymers and good agreement is obtained. It is shown that T(g) is essentially governed by the chain stiffness factor at T(g). Moreover, a simple correlation between the parameter K(g) of the Fox-Flory equation (T(g) = T(g)infinity - K(g)/M(n)) and other molecular parameters is deduced. The agreement between theoretical predictions and experimental measurements of K(g) has been found to be satisfactory for many polymers.