Diet overlap between the endemic fish Anablariflus grahami(Cyprinidae) and the exotic noodlefish Neosalanx taihuensis (Salangidae) in lake Fuxian, China

We studied diet composition and overlap of the exotic noodlefish (Neosalanx taihuensis) and the endemic fish Anaborilius grahami in a deep, oligotrophic lake in the Yunnan Plateau. A. grahami dominated the fish community in Lake Fuxian before the invasion of N. taihuensis in 1982, but it is now in the process of extinction, corresponding with an explosive increase in N. taihuensis population. Schoener's index (alpha=0.773) indicate that N. taihuensis and A. grahami have significant diet overlap, with both fish feeding mainly on zooplankton. An increased proportion of littoral prey, such as Procladius spp., Coleoptera, and epiphytes, in the diet of A. grahami indicated that this endemic fish shifted its main habitat from the off-shore zone in the late 1980s to the littoral zone at the present. A difference in reproduction between the two fishes, along with the overfishing, may have exacerbated the occupation of A. grahami's pelagic niche by N. taihuensis. The endemic species has shown large competitive disadvantage for food and space in the presence of N. taihuensis.

Food composition and dietary overlap of macroinvertebrates in a shallow eutrophic lake in China: spatial and temporal variations

The present study was conducted in Lake Donghu, a suburban eutrophic lake arising from the middle reaches of the Yangtze River, China. Food composition of 32 taxa of zoobenthos was analyzed from 1251 gut samples. Macroinvertebrate primary consumers ingested mainly detritus, sand grains and diatoms. The predators primarily preyed on rotifers, crustaceans, oligochaetes and chironomid larvae. The dietary overlap was relatively high among collector taxa but low among other macroinvertebrates. Food composition and dietary overlap of macroinvertebrates changed considerably, both spatially and temporally. Food web structure differed between inshore and offshore regions of Lake Donghu. The inshore web was relatively complex and dynamic whereas the offshore web was simple and stable. Taxon-specific changes of diet seem to have little effect on the benthic food web structure in offshore waters of a eutrophic lake.

On detection wavelength and electron-hole wave function overlap of type II InAs/In-x Ga1-x Sb superlattice infrared photodetector

In this paper, the detection wavelength and the electron-hole wave function overlap of InAs/IrxGa1-xSb type II superlattice photodetectors are numerically calculated by using the envelope function and the transfer matrix methods. The band offset is dealt with by employing the model solid theory, which already takes into account the lattice mismatch between InAs and InxGa1-xSb layers. Firstly, the detection wavelength and the wave function overlap are investigated in dependence on the InAs and InxGa1-xSb layer thicknesses, the In mole fraction, and the periodic number. The results indicate that the detection wavelength increases with increasing In mole fraction, InAs and InxGa1-xSb layer thicknesses, respectively. When increasing the periodic number, the detection wavelength first increases distinctly for small periodic numbers then increases very slightly for large period numbers. Secondly, the wave function overlap diminishes with increasing InAs and InxGa1-xSb layer thicknesses, while it enhances with increasing In mole fraction. The dependence of the wave function overlap on the periodic number shows the same trend as that of the detection wavelength on the periodic number. Moreover, for a constant detection wavelength, the wave function overlap becomes greater when the thickness ratio of the InAs over InxGa1-xSb is larger.

ANALYSIS OF ANGULAR OVERLAP PARAMETERS FOR THE LAOXEU3+ (X = CL, BR, I) SERIES

The Angular Overlap Model (AOM) is applied to the LaOX:Eu3+(X = Cl, Br, I) series involving sigma, pi, delta and phi effects based on the experimental energy levels. The calculations are made in two cases. (1) Consider oxygen and halogen having the same bond-length. (2) Consider the real structure. In both cases, the results show that for sigma-bonding parameters, the values of e(sigma) decrease with increasing charge number of halogen, i.e. Cl- > Br- > I-, this indicates that the bonding ability also decreases with this order. The absolute values of each parameter are much larger than zero-therefore they all must be included in a practical analysis. In the second case, the values of the e(pi) parameter are negative, which means a ''back-bonding'' is formed, and this is profitable for the formation of sigma-bonding, usually referred to as ''synergic effect''.

APPLICATION OF FACTOR-ANALYSIS TO CORRECTION OF SPECTRAL OVERLAP INTERFERENCE IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

Correction of spectral overlap interference in inductively coupled plasma atomic emission spectrometry by factor analysis is attempted. For the spectral overlap of two known lines, a data matrix can be composed from one or two pure spectra and a spectrum of the mixture. The data matrix is decomposed into a spectra matrix and a concentration matrix by target transformation factor analysis. The component concentration of interest in a binary mixture is obtained from the concentration matrix and interference from the other component is eliminated. This method is applied to correcting spectral interference of yttrium on the determination of copper and aluminium: satisfactory results are obtained. This method may also be applied to correcting spectral overlap interference for more than two lines. Like other methods of correcting spectral interferences, factor analysis can only be used for additive spectral overlap. Results obtained from measurements on copper/yttrium mixtures with different white noise added show that random errors in measurement data do not significantly affect the results of the correction method.

ANALYSIS OF ANGULAR OVERLAP PARAMETERS FOR EU3+ - LN2O2S (LN = LU, Y, GD, LA) CRYSTAL SERIES

The angular overlap model (AOM) is applied to 4f6 electron systems. The crystal field parameters are interpreted and covalency between 4f electrons and ligands is investigated based on the experimental energy levels. For Eu3+:Ln2O2S (Ln = Lu, Y, Gd, La) crystal series, we adopt two computational schemes. First of all, we assume that the distances to all ligands are equal, and then the distances to all ligands are divided into two groups, namely, oxygens as one group, sulfurs as the other. Of course, much information about covalency will be obtained from the latter case. Obviously, our results show that the covalency of Ln-O bonding is stronger than that of Ln-S bonding in line with much shorter bondlength for the former than that for the latter. The two schemes yield the same results, that is, for sigma and pi bonding, ligands are strong donors as well as sigma, pi effects are dominant over delta, phi effects.