Gut contents of silver carp, Hypophthalmichthys molitrix, and the disruption of a centric diatom, Cyclotella, on passage through the esophagus and intestine

The digestibility of algae by stomachless filter-feeding fish has been debated for decades. Results from gut contents and digestive enzyme analysis suggest poor utilization, while the measurement of food assimilation using radiolabeled isotope techniques indicate reasonable assimilation efficiency. Phytoplankton in the gut contents of the planktivorous filter-feeding silver carp were studied during March-May. The fish were cultured in a large net cage in a shallow, hypertrophic subtropical Chinese lake, Lake Donghu. In terms of biomass, the dominant phytoplankton in the fore-gut contents were Cyclotella (average 77.8%, range 69.7-93.5%) and Cryptomonas (average 9.57%, range 0-20.4%). The Ivlev's electivity index E of silver carp was much higher for Cyclotella (1.54) than for Cryptomonas (0.56). The majority of the phytoplankton found in the intestines of silver carp were 8-20 mu m, but they were also able to collect particles as small as 4.5-10 mu m, smaller than their filtering net meshes, suggesting that the secretion of mucus may play an important role in collecting such small particles. We conclude that disruption of cell walls is principally by the pharyngeal teeth, explaining previous contradictory conclusions. (C) 1999 Elsevier Science B.V. All rights reserved.

Influence of dioxin and metal-contaminated sediment on phase I and II biotransformation enzymes in silver crucian carp

Several biochemical responses were measured in silver crucian carp (Carassius auratus gibelio) after exposure to sediments obtained from contaminated Ya-Er Lake, No, 1 pond, and an unpolluted reference site, Honglian Lake. After 1 week of exposure, a significant induction of the phase I biotransformation enzyme (ethoxylresorufin-o-deethylase, EROD) was found (83-fold of control), whereas the phase II biotransformation enzyme (glutathione S-transferase, GST) exhibited a slight, but significant induction (1,4-fold of control) after 4 weeks of exposure. The level of cellular glutathione in the liver was also slightly elevated after 4 weeks of exposure. The delayed response of GST to the contaminants indicates that the phase I and phase II biotransformation enzymes are regulated differently in fish. The results suggest that EROD is a sensitive bioindicator to assess the toxicity of dioxin-contamined sediment in the laboratory, (C) 1998 Academic Press.

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.

Organic light emitting diodes using magnesium doped organic acceptor as electron injection layer and silver as cathode

Organic light emitting diodes employing magnesium doped electron acceptor 3, 4, 9, 10 perylenetetracarboxylic dianhydride (Mg: PTCDA) as electron injection layer and silver as cathode were demonstrated. As compared to Mg: Ag cathode, the combination of the Mg: PTCDA layer and silver provided enhanced electron injection into tris (8-quinolinolato) aluminium. The device with 1: 2 Mg: PTCDA and Ag showed an increase of about 12% in the maximum current efficiency, mainly due to the improved hole-electron balance, and an increase of about 28% in the maximum power efficiency, as compared to the control device using Mg: Ag cathode. The properties of Mg: PTCDA composites were studied as well.

Effect of silver growth temperature on the contacts between Ag and ZnO thin films

Highly c-axis oriented ZnO thin films were deposited on Si substrates by the pulsed laser deposition (PLD) method. At different growth temperatures, 200 nm silver films as the contact metal were deposited on the ZnO thin films. The growth temperatures have great influence on the crystal quality of Ag films. Current-voltage characteristics were measured at room temperature. The Schottky contacts between Ag and ZnO thin films were successfully obtained when silver electrodes were deposited at 150A degrees C and 200A degrees C. Ohmic contacts were formed while the growth temperatures were lower than 150A degrees C or higher than 200A degrees C. After analysis, the forming of Ag/ZnO Schottky contacts was shown to be dependent on the appearance of the p-type inversion layer at the interface between Ag and ZnO layers.

Raman scattering of non-planar graphite: arched edges, polyhedral crystals, whiskers and cones

Planar graphite has been extensively studied by Raman scattering for years. A comparative Raman study of several different and less common non-planar graphitic materials is given here. New kinds of graphite whiskers and tubular graphite cones (synthetic and natural) have been introduced. Raman spectroscopy has been applied to the characterization of natural graphite crystal edge planes, an individual graphite whisker graphite polyhedral crystals and tubular graphite cones. Almost all of the observed Raman modes were assigned according to the selection rules and the double-resonance Raman mechanism. The polarization properties related to the structural features, the line shape of the first-order dispersive mode and its combination modes, the frequency variation of some modes in different carbon materials and other unique Raman spectral features are discussed here in detail.

Raman scattering from an individual tubular graphite cone

　

Enhanced near-infrared photoluminescence from isoelectronic luminescent centers in sulfur-implanted silicon with copper or silver coimplantation

Enhanced near-infrared photoluminescence (PL) from sulfur-related isoelectronic luminescent centers in silicon was observed from thermally quenched sulfur-implanted silicon in which additional copper or silver ions had been coimplanted. The PL from the sulfur and copper coimplanted silicon peaked between 70 and 100 K and persisted to 260 K. This result strongly supports the original conjecture from the optical detection of magnetic resonance studies that the strong PL from sulfur-doped silicon comes from S-Cu isoelectronic complexes [Frens , Phys. Rev. B 46, 12316 (1992); Mason , ibid. 58, 7007 (1998).]. (c) 2007 American Institute of Physics.

The plasmon resonance absorption of Ag/SiO2 nanocomposite films

The plasmon resonance absorption of the Ag/SiO2 nanocomposite film is investigated. The measured absorption spectra are compared with those calculated by the Mie theory. The results indicate that the Mie theory on the basis of classical electrodynamics can only partially explain the optical absorption spectra of the Ag/SiO2 nanocomposite film. We believe that the plasmon resonance absorption is mainly an intrinsic quality of the metal particle, and can be explained only with the electronic structure of the metal particle. In the latter, surface resonance state is introduced to systematically discuss the optical absorption spectra of the Ag/SiO2 nanocomposite film. (C) 2003 Elsevier Science B.V. All rights reserved.

Influence of ambient atmosphere on the plasmon resonance absorption of Ag/SiOx(0 <= x <= 2) nanocomposite film

Nanocomposite films consisting of nanosized Ag particles embedded in partially oxidized amorphous Si-containing matrices were prepared by radio frequency magnetron co-sputtering deposition. We studied the influence of ambient atmosphere during the preparation and heat-treatment of Ag/SiOx (0 less than or equal to x less than or equal to 2) nanocompositefilm on its optical absorption properties. We found that the plasmon resonance absorption peak shifts to shorter wavelengths with the increasing oxygen content in the SiOx matrix. The analysis indicates that the potential barrier between Ag nanoparticles and SiOx matrix increases with the increasing x value, which will induce the surface resonance state to shift to higher energy. The electrons in the vicinity of the Fermi level of Ag nanoparticles must absorb more energy to be transferred to the surface resonance state with the increasing x value. It was also found that the plasmon resonance absorption peaks of the samples annealed in different ambient atmospheres are located at about the same position. This is because the oxidation surface layer is dense enough to prevent the oxygen from penetrating into the sample to oxidize the silicon in the inner layer.