Seasonal dynamics of the hepatotoxic microcystins in various organs of four freshwater bivalves from the large eutrophic Lake Taihu of subtropical China and the risk to human consumption

So far, little is known on the distribution of hepatotoxic microcystin (MC) in various organs of bivalves, and there is no study on MC accumulation in bivalves from Chinese waters. Distribution pattern and seasonal dynamics of MC-LR, -YR and -RR in various organs (hepatopancreas, intestine, visceral mass, gill, foot, and rest) of four edible freshwater mussels (Anodonta woodiana, Hyriopsis cumingii, Cristaria plicata, and Lamprotula leai) were studied monthly during Oct. 2003-Sep. 2004 in Lake Taihu with toxic cyanobacterial blooms in the summer. Qualitative and quantitative determinations of MCs in the organs were done by LC-MS and HPLC. The major toxins were present in the hepatopancreas (45.5-55.4%), followed by visceral mass with substantial amount of gonad (27.6-35.5%), whereas gill and foot were the least (1.8-5.1%). The maximum MC contents in the hepatopancreas, intestine, visceral mass, gill, foot, and rest were 38.48, 20.65, 1.70, 0.64, 0.58, and 0.61 mu g/g DW, respectively. There were rather good positive correlation in MC contents between intestines and hepatopancreas of the four bivalves (r = 0.75-0.97, p < 0.05). There appeared to be positive correlations between the maximum MC content in the hepatopancreas and the delta(13)C (r = 0.919) or delta(15)N (r = 0.878) of the foot, indicating that the different MC content in the hepatopancreas might be due to different food ingestion. A glutathione (GSH) conjugate of MC-LR was also detected in the foot sample of C. plicata. Among the foot samples analyzed, 54% were above the provisional WHO tolerable daily intake (TDI) level, and the mean daily intakes from the four bivalves were 8-23.5 times the TDI value when the bivalves are eaten as a whole, suggesting the high risk of consuming bivalves in Lake Taihu. (C) 2005 Wiley Periodicals, Inc.

Selective control of toxic Microcystis water blooms using lysine and malonic acid: An enclosure experiment

Three enclosures (10 x 10 x 1.5-1.3 m in depth) were set beside Dianch Lake, Kunming, People's Republic of China, for the period from July 28 to August 26, 2002. The enclosures were filled with cyanobacterial (Microcystis aeruginosa) water bloom-containing lake water. Lake sediment that contained macrophytes and water chestnut seeds was spread over the entire bottom of each enclosure. Initially, 10 g/m(2) of lysine was sprayed in Enclosure B, and 10 g/m(2) each of lysine and malonic acid were sprayed together in Enclosure C. Enclosure A remained untreated and was used as a control. The concentrations of lysine, malonic acid, chlorophyll a, and microcystin as well as the cell numbers of phytoplankton such as cyanobacteria, diatom, and euglena were monitored. On day 1 of the treatment, formation of cyanobacterial blooms almost ceased in Enclosures B and C, although Microcystis cells in the control still formed blooms. On day 7 Microcystis cells in Enclosure B that had been treated with lysine started growing again, whereas growth was not observed in Microcystis cells in Enclosure C, which had been treated with lysine and malonic acid. On day 28 the surface of Enclosure B was covered with water chestnut (Trapa spp.) and the Microcystis blooms again increased. In contrast, growth of macrophytes (Myriophllum spicatum and Potamogeton crispus) was observed in Enclosure C; however, no cyanobacterial blooms were observed. Lysine and malonic acid had completely decomposed. The microcystin concentration on day 28 decreased to 25% of the initial value, and the pH shifted from the initial value of 9.2 to 7.8. We concluded that combined treatment with lysine and malonic acid selectively controlled toxic Microcystis water blooms and induced the growth of macrophytes. (c) 2005 Wiley Periodicals, Inc.

Physiological and biochemical microcystin-RR toxicity to the Synechococcus elongatus

Freshwater Microcystis may form dense blooms in eutrophic lakes. It is known to produce a family of related cyclic hepatopeptides (microcystins, MC) that constitute a threat to aquatic ecosystems. Most toxicological studies of microcystins have focused on aquatic animals and plants, with few examining the possible effects of microcystins on phytoplankton. In this study we chose the unicellular Synechococcus elongatus (one of the most studied and geographically most widely distributed cyanobacteria in the picoplankton) as the test material and investigated the biological parameters: growth, pigment (chlorophyll-a, phycocyanin), photosynthetic activity, nitrate reductase activity, and protein and carbohydrate content. The results revealed that microcystin-RR concentrations above 100 mug (.) L-1 significantly inhibited the growth of Synechococcus elongatus. In addition, a change in color of the toxin-treated algae (chlorosis) was observed in the experiments. Furthermore, MC-RR markedly inhibited the synthesis of the pigments chlorophyll-a and phycocyanin. A drastic reduction in photochemical efficiency of PSII (F-v/F-m) was found after a 96-h incubation. Changes in protein and carbohydrate concentrations and in nitrate reductase activity also were observed during the exposure period. This study aimed to evaluate the mechanisms of microcystin toxicity on a cyanobacterium, according to the physiological and biochemical responses of Synechococcus elongatus to different doses of microcystin-RR. The ecological role of microcystins as an allelopathic substance also is discussed in the article. (C) 2004 Wiley Periodicals, Inc.

ON PARADICRANOPHORUS-ACULEATUS (NEISTWESTNOVA-SHADINA, 1935) WITH REMARKS ON ALL OTHER SPECIES OF THE GENUS (ROTIFERA, DICRANOPHORIDAE)

In 1934, the rotifer Paradicranophorus aculeatus was discovered by NEISTWESTNOVA-SHADINA in the River Oka near Murom (Russia). She described it as a Dicranophorus species. In 1958, the rheophilic rotifer was rediscovered in the Polish River Grabia by PAWLOWSKI. This paper reports a third occurence in three samples from the Yun Nan Luoxiao River in China, allowing additional studies of this rare species.

FREQUENCY AND TEMPORAL COHERENCE PROPERTIES OF DISTRIBUTED BRAGG REFLECTOR LASER

This article presents the investigation of frequency and temporal coherence properties of distributed Bragg reflector laser. In this scheme, a square-wavefrom voltage is applied to the phase section of the laser to little optical wavelength, and delayed optical heterodyne technique is used for the analysis of spectral characteristics. Experiments show that lightwaves emitted from the same active region asynchronously are partially frequency and temporal coherent. When the two wavelengths are closer, the two waves are strong v coherent, and the coherence properties get weak as the delay v time increases. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Left 52: 822-825, 2010 Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25031

Single mode operation of a Fabry-Perot laser locked by a tunable laser

In this article, the single mode operation of a Fabry-Perot laser (FP-LD) subject to the optical injection from a tunable laser is investigated. The maximum side mode suppression ratio (SMSR) is 53 dB, and the locked wavelength range is about 46 nm, which can cover 58 International Telecommunication Union (ITU) wavelengths with 100 GHz spacing or 115 ITU wavelengths with 50 GHz spacing for wavelength division multiplexing (WDM) system. In the wavelength range front 1535 to 1569 nm, the SMSR is over 46 dB, and the frequency response of the injection-locked FP-LD can be improved with the proper wavelength detuning. (c) 2008 Wiley Periodicals, Inc.

High-frequency characterization of packaging network in to-can photodiode modules

A simple method for analyzing the effects of TO packaging network on the high-frequency response of photodiode modules is presented. This method is established based on the relations of the scattering parameters of the packaging network, photodiode chip, and module. It is shown that the results obtained by this method agree well with those obtained by the conventional comparison method. The proposed method is much more convenient since only the electrical domain measurements are required. (C) 2008 Wiley Periodicals, Inc.

Subtraction of scattering parameters for adiabatic intrinsic responses of semiconductor lasers

Thermal effects will make chip temperature change with bias current of semiconductor lasers, which results in inaccurate intrinsic response by the conventional subtraction method. In this article, an extended subtraction method of scattering parameters for characterizing adiabatic responses of laser diode is proposed. The pulsed injection operation is used to determine the chip temperature of packaged semiconductor laser, and an optimal injection condition is obtained by investigating the dependence of the lasing wavelength on the width and period of the injection pulse in a relatively wide temperature range. In this case, the scattering parameters of laser diode are measured on adiabatic condition and the adiabatic intrinsic responses of packaged laser diode are first extracted. It is found that the adiabatic intrinsic responses are evidently superior to those without thermal consideration. The analysis results indicate that inclusion of thermal. effects is necessary to acquire accurate intrinsic responses of semiconductor lasers. (C) 2008 Wiley Periodicals, Inc.

Dispersion-compensating photonic crystal fibers with special characteristics

Based on the modified dual core structure, three kinds of special photonic crystal fibers are presented, which are extremely large negative dispersion, super-broad bond, and large area made field dispersion-compensating photonic crystal fibers (DCPCF). For extremely large negative dispersion DCPCF, the peak of negative dispersion reaches -5.9 x 10(4) ps/(mn km). Super-broad bond DCPCF has broadband large negative dispersion and the dispersion value varies linearly from -380 ps/(nm km) to -420 ps/(nm km) in the C band. The designed large area made field DCPCF has a peak dispersion of -1203 ps/(nm km) with the inner core mode area of 47 mu m(2) and outer core mode area of 835 mu m(2). Furthermore, for the large area mode field DCPCF, the experimental result is also obtained. (C) 2008 Wiley Periodicals, Inc.

Characterization of parasitics from scattering parameters of laser diode

A novel method for characterizing the parasitics of parasitic network is proposed based on the relations between the scattering parameters of a semiconductor laser chip and laser diode. Experiments are designed and performed using our method. The analysis results are in good agreement with the measurements. Furthermore, how the parasitics change with the parasitic element values are investigated. The method only needs reflection coefficient of laser diode to be measured, which is simple because of the developed electrical-domain measurement techniques. 2007 Wiley Periodicals, Inc.

DISCRETELY TUNABLE FIBER RING LASER USING FBG TUNABLE FILTER AND MACH-ZEHNDER INTERFEROMETER

A discretely tunable Er-doped fiber-ring laser using a fiber Mach-Zehnder interferometer (MZI) and a tunable fiber Bragg grating (FBG) is proposed. In this scheme, the combination of MZI and FBG acts as a discrete wavelength selector. Analysis of its transmission function shows that discrete wavelength tuning can be realized, and experiments demonstrate 64 single-mode outputs with a mode spacing of 181.7 pm, and the output power is quite stable in the whole tuning range. (C) 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51 2595-2598, 2009; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.24690

FREQUENCY RESPONSE OF FIBER RING RESONATOR AND ITS APPLICATION IN DFB LASER WAVELENGTH VARIATION MEASUREMENT

Frequency response of a fiber ring resonator (FRR) composed of an ordinary optical coupler and a segment of optical fiber is theoretically and experimentally investigated. The frequency response equation based oil small-signal modulation is derived and studied in detail. It is shown that the shape of the frequency response curve is very sensitive to the wavelength; as a result, the FRR can be applied to measure the wavelength of a lightwave source with high resolution. With this method, we demonstrate the measurement of tiny changes of wavelength of a DFB laser. (C) 2009 Wiley Periodicals. Inc. Microwave Opt Technol Lett 51 2444-2448, 2009 Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24608

MEMBRANE-BASED FIBER BRAGG GRATING PRESSURE SENSOR WITH HIGH SENSITIVITY

A fiber Bragg grating (FBG) pressure sensor packaged by using a hard core in the membrane is presented. By utilizing the unique membrane-based FBG packagine method, its pressure sensitivity has been effectively enhanced. The pressure sensitivity of the FBG reaches 5.75 X 10(-3)/MPa within the pressure range of 0.0.16 Mpa. (C) 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51 1279-1281, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24335

Effect of metal contact's reflection on the effective coupling coefficient of second-order DFB laser diodes

For a second-order DFB-LD, the presence of a metal contact layer can reduce I-st-order radiation. Part of the reflected power is redistributed into guided modes and results in a variation of the effective coupling coefficient kappa(eff). In this paper, we study the effect of the Au top contact's reflection on the kappa(eff) of 2(nd)-order DFB lasers. (C) 2004 Wiley Periodicals, Inc.

Methods for characterization of packaging parasitics of semiconductor lasers

Two novel methods for analyzing the parasitics of packaging networks are proposed based on the relations between the scattering parameters of a semiconductor laser before and after packaging, and the experiments are designed and performed using our methods. It is found that the analysis results of the two methods are in good agreement with the measurements. Either of the two methods can provide an alternative approach for characterizing the packaging parasitics for semiconductor lasers, and both are convenient due to the developed measurement techniques. (c) 2005 Wiley Periodicals, Inc.