Effects of damming on population sustainability of Chinese sturgeon, Acipenser sinensis: evaluation of optimal conservation measures

The numbers of spawning sites for Chinese sturgeon have been drastically reduced since the construction of the Gezhouba Dam across the Yangtze River. This dam has blocked migration of Chinese sturgeon to their historic spawning ground causing a significant decline of the Chinese sturgeon population. We conducted a VORTEX population viability analysis to estimate the sustainability of the population and to quantify the efficiency of current and alternative conservation procedures. The model predicted the observed decline of Chinese sturgeon, resulting from the effect of the Gezhouba Dam. These simulations demonstrated the potential interest of two conservation measures: increasing spawning area and reducing predation on sturgeon eggs. The simulations also demonstrated that the actual restocking program is not sufficient to sustain sturgeon population as the artificial reproduction program induce the loss of more wild mature adults that the recruitment expected by the artificial reproduction.

Effects of dietary cyanobacteria of two different sources on growth and recovery of hybrid tilapia (Oreochromis niloticus x O. aureus)

A 115 days feeding trial was conducted to evaluate the effect of dietary cyanobacteria on growth, microcystins (MCs) accumulation in hybrid tilapia (Oreochromis niloticus x O. aureus) and the recovery when the fish were free of cyanobacteria. Three experimental diets were formulated: the control (cyanobacteria free diet); one test diet with cyanobacteria from Lake Taihu (AMt 80.0 mu g MCs g(-1) diet) and one with cyanobacteria from Lake Dianchi (AMd, 410.0 rho g MCs g(-1) diet). Each diet was fed to fish for 60 days and then all fish were free of cyanobacteria for another 55 days. A significant increase in feeding rate (FR) was observed in fish fed AMd diet after a first 30-day exposure (1(st) EP), and in fish fed both AMt diet and AMd diet after a second 30-day exposure (2(nd) EP). Specific growth rates (SGR) of fish fed AMt diet and AMd diet were both obviously affected after the first 30-day exposure, but SGR was only significantly affected in fish fed AMt diet after the second 30-day exposure. After a 55-day recovery, there were no significant differences among diets in the indices mentioned above. Much higher concentrations of MCs were accumulated in tissues of all fish exposed to cyanobacteria. After the 55-day recovery, MC concentrations in fish tissues were significantly lower than those on day 60. (C) 2009 Elsevier Ltd. All rights reserved.

Photosynthetic recovery of desiccated intertidal seaweeds after rehydration

Intertidal seaweeds experience periodical desiccation and rehydration to different extents due to the tidal cycles and their vertical distributions. Their photosynthetic recovery process during the rehydration may show different patterns among the seaweeds from different zonations or depths at intertidal zone. In this study 12 species of seaweeds collected from the upper, middle, lower and sublittoral zones were examined. The relationship of the photosynthetic recovery to vertical distribution was assessed by comparing their patterns of photosynthetic and respiratory performances after rehydration following desiccation. Both the photosynthesis and dark respiration declined during emersion, showing certain degrees of recovery after re-immersion into seawater for most species, but the extents were markedly different from one species to the other. The species from upper intertidal zone after being rehydrated for 1 hour, following 2 hours of desiccation, achieved 100 % recovery of their initial physiological activity, while most of the lower or sublittoral species did not achieve full recovery. It is the ability to withstand desiccation stress (fast recovery during rehydration), but not that to avoid desiccation (water retaining ability) that determines the distribution of intertidal seaweeds. Such physiological behavior during rehydration after desiccation reflects the adaptive strategy of intertidal seaweeds against desiccation and their capability of primary production in the process of rehydration.

Dried field populations of Nostoc flagelliforme (Cyanophyceae) require exogenous nutrients for their photosynthetic recovery

The effects of nutrients on the photosynthetic recovery of Nostoc flagelliforme during re-hydration were investigated in order to see if their addition was necessary. Net photosynthesis was negligible in distilled water without nutrient-enrichment. Addition of K+ resulted in significant enhancement of net photosynthesis, whereas other nutrients (Fe3+, Mg2+, Na+, NO3-, PO43-, Cl-) and trace-metals (A(5)) showed little effect. The recovered net photosynthetic activity increased with the increased K+, and reached the maximum at concentrations above 230 mu M. Desiccation and re-hydration did not affect the dependence of photosynthetic recovery on K+. It was concluded that dried field populations of N. flagelliforme require exogenous addition of potassium for photosynthetic recovery and that growth may be potassium-limited in nature.

Light dependency of the photosynthetic recovery of Nostoc flagelliforme

PS II photochemical efficiency (F-v/F-m) of Nostoc flagelliforme was examined after rewetting in order to investigate the light-dependency of its photosynthetic recovery. F-v/F-m was not detected in the dark, but was immediately recognized in the light. Different levels of light irradiation (4, 40 and 400 mu mol photon m(2) s(-1)) displayed different effects on the recovery process of photosynthesis. The intermediate level led to the best recovery of photochemical efficiency; the low light required longer and the high light inhibited the extent of the recovered efficiency. It was concluded that the photosynthetic recovery of N. flagelliforme is both light-dependent and influenced by photon flux density.

Investigation of gain recovery for InAs/GaAs quantum dot semiconductor optical amplifiers by rate equation simulation

The gain recoveries in quantum dot semiconductor optical amplifiers (QD SOAs) are numerically studied by rate equation simulation. Similar to the optical pump-probe experiment, the injection of double 150 fs optical pulses is used to simulate the gain recovery of a weak continuous signal under different injection levels, inhomogeneous broadenings, detuning wavelengths, and pulse signal energies for the QD SOAs. The obtained gain recoveries are then fitted by a response function with multiple exponential terms to determine the response times. The gain recovery can be described by three exponential terms with the time constants, which can be explained as carrier relaxation from the excited state to the ground state, carrier captured by the excited state from the wetting layer, and the supply of the wetting layer carriers. The fitted lifetimes decrease with the increase of the injection currents under gain unsaturation, slightly decrease with the decrease of inhomogeneous broadening of QDs, and increase with the increase of detuning wavelength between continuous signal and pulse signal and the increase of the pulse energy.

Coherence loss and recovery of an electron spin coupled inhomogeneously to a one-dimensional interacting spin bath: An adaptive time-dependent density-matrix renormalization group study

Coherence evolution and echo effect of an electron spin, which is coupled inhomogeneously to an interacting one-dimensional finite spin bath via hyperfine-type interaction, are studied using the adaptive time-dependent density-matrix renormalization group method. It is found that the interplay of the coupling inhomogeneity and the transverse intrabath interactions results in two qualitatively different coherence evolutions, namely, a coherence-preserving evolution characterized by periodic oscillation and a complete decoherence evolution. Correspondingly, the echo effects induced by an electron-spin flip at time tau exhibit stable recoherence pulse sequence for the periodic evolution and a single peak at root 2 tau for the decoherence evolution, respectively. With the diagonal intrabath interaction included, the specific feature of the periodic regime is kept, while the root 2 tau-type echo effect in the decoherence regime is significantly affected. To render the experimental verifications possible, the Hahn echo envelope as a function of tau is calculated, which eliminates the inhomogeneous broadening effect and serves for the identification of the different status of the dynamic coherence evolution, periodic versus decoherence.

Optimal teleportation via thermal entangled states of a two-qubit Heisenberg chain

We study the optimal teleportation based on Bell measurements via the thermal states of a two-qubit Heisenberg XXX chain in the presence of the Dzyaloshinsky-Moriya (DM) anisotropic antisymmetric interaction and obtain an optimal unitary transformation. The explicit expressions of the output state and the teleportation fidelity are presented and compared with those of the standard protocol. It is shown that in this protocol the teleportation fidelity is always larger and the unit fidelity is achieved at zero temperature. The DM interaction can enhance the teleportation fidelity at finite temperatures, as opposed to the effect of the interaction in the standard protocol. Cases with other types of anisotropies are also discussed. Copyright (C) EPLA, 2009

Simulation on Gain Recovery of Quantum Dot Semiconductor Optical Amplifiers by Rate Equation

The gain recoveries in quantum dot semiconductor optical amplifiers are numerically studied by rate equation models. Similar to the optical pump-probe experiment, the injection of double optical pulses is used to simulate the gain recovery of a weak continuous signal for the QD SOAs. The gain recoveries are fitted by a response function with multiple exponential terms. For the pulses duration of 10 ps, the gain recovery can be described by three exponential terms with the time constants, and for the pulse with the width of 150 fs, the gain recovery can be described by two exponential terms, the reason is that the short pulse does not consume lot of carriers.

All-optical clock recovery using a ridge width varied two-section partly gain-coupled DFB self-pulsation laser

A 1.55 mu m InGaAsP-InP partly gain-coupled two-section DFB self-pulsation laser (SPL) with a varied ridge width has been fabricated. The laser produces self-pulsations with a frequency tuning range of more than 135 GHz. All-optical clock recovery from 40 Gb/s degraded data streams has been demonstrated. Successful lockings of the device at frequencies of 30 GHz, 40 GHz, 50 GHz, and 60 GHz to a 10 GHz sidemode injection are also conducted, which demonstrates the capability of the device for all-optical clock recovery at different frequencies. This flexibility of the device is highly desired for practical uses. Crown Copyright