What are the closest relatives of the hot-spring snakes (Colubridae, Thermophis), the relict species endemic to the Tibetan Plateau?

We conducted phylogenetic analyses to identify the closest related living relatives of the Xizang and Sichuan hot-spring snakes (T baileyi and T. zhaoermii) endemic to the Tibetan Plateau, using mitochondrial DNA sequences (cyt b, ND4) from eight specimen

Limnology and fisheries of the Nyumba ya Mungu, a man-made lake in Tanzania

The present paper deals with the limnology of Nyumba Ya Mungu, a man-made lake in Tanzania (Kilimanjaro Region), during the 7th and 8th years after the elosure of the Ruvu dam. The area investigated included the River, which is one of the two rivers entering the lake.

Mode-locked and single-longitudinal-mode waveguide lasers fabricated by femtosecond laser pulses in Er:Yb-doped phosphate glass

Mode-locked and single-longitudinal-mode waveguide lasers, manufactured by femtosecond laser writing in Er-Yb-doped phosphate glasses, are presented. Transform-limited 1.6-ps pulses and a cw output power exceeding 50 mW have been obtained in the two regimes. © 2007 Optical Society of America.

Influence of the matrix properties on the performances of Er-doped Si nanoclusters light emitting devices

We investigated the properties of light emitting devices whose active layer consists of Er-doped Si nanoclusters (nc) generated by thermal annealing of Er-doped SiOx layers prepared by magnetron cosputtering. Differently from a widely used technique such as plasma enhanced chemical vapor deposition, sputtering allows to synthesize Er-doped Si nc embedded in an almost stoichiometric oxide matrix, so as to deeply influence the electroluminescence properties of the devices. Relevant results include the need for an unexpected low Si excess for optimizing the device efficiency and, above all, the strong reduction of the influence of Auger de-excitation, which represents the main nonradiative path which limits the performances of such devices and their application in silicon nanophotonics. © 2010 American Institute of Physics.

Enhanced down conversion of photons emitted by photoexcited Er xY2-xSi2O7 films grown on silicon

Photon cutting with efficiencies up to 400% is demonstrated in Erx Y2-x Si2 O7 films grown on Si and its concentration dependence is analyzed. The cutting is the result of cross-energy-transfer processes occurring within a single rare earth (Er3+) acting as both sensitizer and activator. Similarities with upconversion are revealed and possible applications in solar cells are discussed. © 2010 The American Physical Society.

New approaches for enhancing light emission from Er-based materials and devices

In this work, we present some approaches recently developed for enhancing light emission from Er-based materials and devices. We have investigated the luminescence quenching processes limiting quantum efficiency in light-emitting devices based on Si nanoclusters (Si nc) or Er-doped Si nc. It is found that carrier injection, while needed to excite Si nc or Er ions through electron-hole recombination, at the same time produces an efficient non-radiative Auger de-excitation with trapped carriers. A strong light confinement and enhancement of Er emission at 1.54 μm in planar silicon-on-insulator waveguides containing a thin layer (slot) of SiO2 with Er-doped Si nc at the center of the Si core has been obtained. By measuring the guided photoluminescence from the cleaved edge of the sample, we have observed a more than fivefold enhancement of emission for the transverse magnetic mode over the transverse electric one at room temperature. Slot waveguides have also been integrated with a photonic crystal (PhC), consisting of a triangular lattice of holes. An enhancement by more than two orders of magnitude of the Er near-normal emission is observed when the transition is in resonance with an appropriate mode of the PhC slab. Finally, in order to increase the concentration of excitable Er ions, a completely different approach, based on Er disilicate thin films, has been explored. Under proper annealing conditions crystalline and chemically stable Er2Si2O7 films are obtained; these films exhibit a strong luminescence at 1.54 μm owing to the efficient reduction of the defect density. © 2008 Elsevier B.V. All rights reserved.

Thermal evolution of Er silicate thin films grown by rf magnetron sputtering

Stoichiometric Er silicate thin films, monosilicate (Er2SiO 5) and disilicate (Er2Si2O7), have been grown on c-Si substrates by rf magnetron sputtering. The influence of annealing temperature in the range 1000-1200 °C in oxidizing ambient (O 2) on the structural and optical properties has been studied. In spite of the known reactivity of rare earth silicates towards silicon, Rutherford backscattering spectrometry shows that undesired chemical reactions between the film and the substrate can be strongly limited by using rapid thermal treatments. Monosilicate and disilicate films crystallize at 1100 and 1200 °C, respectively, as shown by x-ray diffraction analysis; the crystalline structures have been identified in both cases. Moreover, photoluminescence (PL) measurements have demonstrated that the highest PL intensity is obtained for Er2Si2O7 film annealed at 1200 °C. In fact, this treatment allows us to reduce the defect density in the film, in particular by saturating oxygen vacancies, as also confirmed by the increase of the lifetime of the PL signal. © 2008 IOP Publishing Ltd.

Mode-locked and single-longitudinal-mode waveguide lasers fabricated by femtosecond laser pulses in Er: Yb-doped phosphate glass

Mode-locked and single-longitudinal-mode waveguide lasers, manufactured by femtosecond laser writing in Er-Yb-doped phosphate glasses, are presented. Transform-limited 1.6-ps pulses and a cw output power exceeding 50 mW have been obtained in the two regimes. © 2007 Optical Society of America.

Measurement of estrogen activity in two Chinese lakes

Estrogenic activities of samples from two Chinese lakes, Ya-Er Lake and Donghu Lake, were measured by in vitro recombinant yeast assay and found in both lakes polluted with industrial and domestic wastewater. In methanol extracts of lake water samples the estrogen-like activity was higher than in toluene extracts. These results have been inverted for solid samples. Furthermore, the EC50 value of the water samples was close to the original concentration in the lake.

Endocrine effects of sublethal exposure to persistent organic pollutants (POPS) on silver carp (Hypophthalmichthys molitrix)

Silver carp (Hypophthalmichthys molitrix) samples were collected from five selected sites that represent diverse levels of downgraded persistent organic pollutants (POPs) contamination in Ya-Er Lake in October 1999. Hepatic ethoxyresorufin-O-deethylase (EROD) and UDP glucuronosyltransferase (UDPGT) activities, hepatosomatic index (HSI), hepatic retinoids, serum thyroid hormones were measured. It was found that hepatic retinol and serum free 3,5,3'- tetraiodothyronine (FT3) significantly increased (P < 0.01) when both hepatic EROD and UDPGT activities significantly declined (P < 0.01) from pond 1 to 5 with decrease in the degree of pollution. This significant negative correlation (P < 0.01) suggests that the persistent organochlorinated contaminants could induce hepatic EROD and UDPGT activities, alter retinoid and thyroid hormone homeostasis, and finally lead to the reduction of retinol and FT3, the two biologically active forms of retinoids and thyroid hormone in silver carp of Ya-Er Lake. (C) 2002 Elsevier Science Ltd. All rights reserved.

Cytological and biochemical alterations in Carassius auratus hepatocytes from exposure to sediment containing dioxins and related compounds

Cytological and biochemical alterations of crucial carp (Carassius auratus) hepatocytes were characterized after exposure to sediments from a lake contaminated with dioxins and other industrial chemicals. Carp were exposed in 20 L water containing 25, 50, or 100 g of contaminated sediment for 2 and 4 weeks. Ultrastructural changes in the liver were characterized by severe enlargement of hepatocytes. Alterations in the cell. included formation of condensed and irregular cell nucleus, polynuclei, dispersed heterochromatin, enlargement of the nucleolus, and degeneration of the nucleus. Mitochondrial numbers were reduced and cristae were deformed. Myelin figures and lysosomes were increased, and sometimes cell organelles and cell matrix were totally lost after 4 weeks of exposure. The ultrastructural alterations were correlated with exposure time and sediment concentrations. Hepatosometic index was significantly increased in experimental groups at 2 and 4 weeks as compared with the control group. EROD enzyme activities were strongly induced in liver. A trend from rough endoplasmic reticulum (RER) to SER was observed. Our results suggest that the dioxin-like compounds bound by sediment were bioavailable to C. auratus and cause sublethal effects.

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.

Role of Bi3+ ions for Er3+ ions efficient 1.54 mu m light emission in Er/Bi codoped SiO2 thin film prepared by sol-gel method

Er/Bi codoped SiO2 thin films were prepared by sol-gel method and spin-on technology with subsequent annealing process. The bismuth silicate crystal phase appeared at low annealing temperature while vanished as annealing temperature exceeded 1000 degrees C, characterized by X-ray diffraction, and Rutherford backscattering measurements well explained the structure change of the films, which was due to the decrease of bismuth concentration. Fine structures of the Er3+-related 1.54 mu m light emission (line width less than 7 nm) at room temperature was observed by photoluminescence (PL) measurement. The PL intensity at 1.54 gm reached maximum at 800 degrees C and decreased dramatically at 1000 degrees C. The PL dependent annealing temperature was studied and suggested a clear link with bismuth silicate phase. Excitation spectrum measurements further reveal the role of Bi3+ ions for Er3+ ions near infrared light emission. Through sol-gel method and thermal treatment, Bi3+ ions can provide a perfect environment for Er3+ ion light emission by forming Er-Bi-Si-O complex. Furthermore, energy transfer from Bi3+ ions to Er3+ ions is evidenced and found to be a more efficient way for Er3+ ions near infrared emission. This makes the Bi3+ ions doped material a promising application for future erbium-doped waveguide amplifier and infrared LED

Strong visible and infrared photoluminescence from Er-implanted silicon nitride films

Silicon nitride films were deposited by plasma-enhanced chemical-vapour deposition. The films were then implanted with erbium ions to a concentration of 8 x 10(20) cm(-3). After high temperature annealing, strong visible and infrared photoluminescence (PL) was observed. The visible PL consists mainly of two peaks located at 660 and 750 nm, which are considered to originate from silicon nanocluster (Si-NCs) and Si-NC/SiNx interface states. Raman spectra and HRTEM measurements have been performed to confirm the existence of Si-NCs. The implanted erbium ions are possibly activated by an energy transfer process, leading to a strong 1.54 mu m PL.