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Thermoelectric materials, capable of converting heat directly into electricity without moving parts, provide a promising solid-state solution for waste heat harvesting. However, currently available commercial thermoelectric materials PbTe and Bi2Te3 are based on tellurium, an extremely scarce and expensive element, which prohibits large scale applications. Herein, we present a systematic study on a new low-cost Te-free material, n-type Se-doped Mg3Sb1.5Bi0.5, by combining the structure and property characterization with electronic structure and electrical transport modeling. Compared with pure Mg3Sb2, Se-doped Mg3Sb1.5Bi0.5 shows the considerably enhanced power factor as well as much lower thermal conductivity. The excellent electrical transport originates from a nontrivial near-edge conduction band with six conducting carrier pockets and a light conductivity effective mass as well as the weak contribution from a secondary conduction band with a valley degeneracy of 2. The accurate location of the conduction band minimum is revealed from the Fermi surface, which appears to be crucial for the understanding of the electronic transport properties. In addition, the total thermal conductivity is found to be reasonably low (~0.62 W m-1 K-1 at 725 K). As a result, an optimal zT of 1.23 at 725 K is obtained in Mg3.07Sb1.5Bi0.48Se0.02. The high zT, as well as the earth-abundant constituent elements, makes the low-cost Se-doped Mg3Sb1.5Bi0.5 a promising candidate for the intermediate-temperature thermoelectric application. Moreover, the systematic electronic structure and transport modeling provide an insightful guidance for the further optimization of this material and other related Zintl compounds. [ABSTRACT FROM AUTHOR]

La/Mn codoped Ba0.63Sr0.37TiO3 (BST) films were grown on LaNiO3-coated Si substrates via RF magnetron sputtering. We also fabricated pure BST and La-doped BST films for comparison. Results show that moderate La/Mn codoping improves dielectric tunability (59.6%) as compared to pure BST (28.2%) at 700 kV/cm, and yields lower dielectric loss (tanδ=0.0170) and higher figure of merit (FOM=35.06) comparing with La-doped BST (tanδ=0.0242, FOM=26.32). This work demonstrated that La/Mn codoping could be an effective method to obtain high tunability and low loss tangent. [ABSTRACT FROM AUTHOR]

[Objective] The research aimed to establish SWAT distributed hydrologic model and analyze influence of the climatic change on runoff in Beijiang River basin. [Method] Beijiang River basin as research object, SWAT model was used to simulate runoff in basin. Monthly water flow in Shijiao station from 1961 to 1980 was used to determine model parameter, while monthly water flow from 1981 to 1990 was used to verify. Setting 15 kinds of climate change scenarios, SWAT model was used to simulate influence of the future climatic change on runoff in Beijiang River basin.[Result]Simulated accuracy of the SWAT model was high, and it could be used to simulate runoff in Beijiang River basin. Under the situation of invariable rainfall, temperature rise made that evaporation capacity increased, and runoff depth decreased. When temperature unchanged, rainfall increase made that evaporation capacity and runoff depth increased somewhat. [Conclusion] The research could provide reference basis for water resource management in Beijiang River basin. [ABSTRACT FROM AUTHOR]

We investigated the capability of Microcystis aeruginosa to cause apoptosis by pursuing morphological, molecular and physiological characteristics after exposure to H202. Microcystis proliferation was only weakly affected after exposure to 150 &mgr;M H202 but cell numbers decreased dramatically after exposures of 250 and 325 &mgr;M H202. Cells exposed to 250 and 325 jiM H202 were examined using transmission electron microscopy, and they exhibited membrane deformation and partial disintegration of thylakoids. Correspondingly, fluorescence imaging of DNA by Hoechst 33342 staining revealed the condensation of nucleoid chromatin. Moreover, cellular injury was concomitant with dramatic decreases in photosynthetic efficiency (ratio of variable fluorescence to maximum fluorescence [Fv/Fm], maximum electron transport rate [ETRmax]) and elevated caspase-3-like activity after exposure of 250 and 325 &mgr;M H202. Terminal deoxynucleotidyl transferase Deoxyuridine 5-triphosphate nick end labelling (TUNEL) positive staining appeared in cells exposed to 250 &mgr; and 325 &mgr;M H202, and the percentage staining increased with increasing H202 concentration. These data suggested that M. aeruginosa exposed to H202 underwent an apoptotic event. Additionally, cells exposed to H202 had increased cytoplasmic vacuolation and nontypical DNA laddering. Increased caspase-3-like activity was not inhibited in the presence of the synthetic caspase inhibitor carbobenzoxy-valyl-alanyl-aspartyl-[0-methyl]-fluoromethylketone. Therefore, H202 induced apoptotic-like cell death in a dose-dependent manner. Taken together, our results provided a novel mechanism for explaining cyanobacterial bloom dynamics in response to environmental stress. The results also contributed to the understanding of the origin and evolution of programmed cell death. [ABSTRACT FROM AUTHOR]

Microcystis has become increasingly dominant during periods of algae bloom in freshwater environments where phosphorus (P) is usually the primary element limiting its propagation. In order to understand the mechanism of Microcystis dominance, the present study investigates the physiological, biochemical and ultrastructural responses of Microcystis aeruginosa (FACHB 469) to eight different in-organic phosphorus (Pi) concentrations under batch culture condition. The results showed that growth of M. aeruginosa was significantly restrained when Pi concentration was below 0.20 mg/L. Its alkaline phosphatase activity (APA) was induced under P deficiency stress and there was also a negative correlation between APA and external Pi concentration. Nevertheless, polyphosphate bodies (PP) were observed after M. aeruginosa, pre-cultured under Pi starvation, was exposed to higher Pi concentration. These results suggest that APA induction uptake and storage strategies of P might have ensured the dominance of M. aeruginosa in the freshwater environment with varying Pi concentrations. [ABSTRACT FROM AUTHOR]

The invasive cyanobacterium, Cylindrosperinopsis raciborskii, was cultured semicontinuously for 18 days at different carbon and phosphorus levels. Growth and photosynthesis were measured to study the combined effects of CO2 and phosphorus availabilities. The results showed that enrichment of CO2 or inorganic phosphorus (Pi) levels in the culture medium significantly increased specific growth rate (μ), light-saturated photosynthesis (Ek) and photosynthetic efficiency (μ), but tended to decrease dark respiratory rate (Rd), saturating irradiance for photosynthesis (Ek) and the light compensation point (Ec). However, photosynthetic responses to inorganic carbon concentration in C. raciborskii were affected by interactions between CO2 and Pi. At high Pi concentration, elevated CO2 significantly increased the inorganic carbon-saturated photosynthesis rate ~ and substrate concentration giving half-maximal photosynthetic rate [K0.5 (DIC)], whereas at low Pi levels, elevated CO2 slightly decreased the values of Vmax and K0.5 (DIC). Additionally, enrichment with Pi significantly increased K0.5 (DIC) and Vmax regardless of the CO2 level, suggesting that Pi plays a role in photosynthetic carbon fixation in C. raciborskii. Furthermore, when C. raciborskii was batch cultured in different carbon and phosphorus concentrations for 72 h, the uptake rate of nitrogen increased with enrichment of both CO2 and Pi, while the uptake rate of phosphorus was enhanced only by increases in Pi concentration. The results suggest that the availability of CO2 and phosphorus have combined and independent effects on photosynthesis and nutrient uptake in C. raciborskii, reflecting that changes in environmental factors could influence the dominance of this invasive cyanobacterium. These combined effects need to be considered when generalizing this species response to changing CO2 levels. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of a low-cost hybrid adsorbent from activation of fly ash and bentonite to remove 2-methylisoborneol (MIB) and geosmin from water. These substances produce objectionable taste and odor problems at levels as low as 4-10 ng/L and an effective, low-cost method of removal would be useful. The effect of the initial pH, contact time and adsorbent dosage on the adsorption process was investigated. In the range of 42-234 ng/L of MIB and geosmin, the maximal adsorption efficiency was obtained at the conditions of a dose level of 15 mg/L adsorbent, pH 8 and 60 min contact time, reaching 59.9 and 63.7%, respectively. Comparing to the natural fly ash and bentonite, the adsorbent showed higher surface area and micropores. The interlayer distance of the hybrid adsorbent was 0.59 nm, in accord with the molecular dimension of MIB and geosmin. The effect of humic acid, representative of natural organic matter (NOM), on MIB and geosmin adsorption was investigated for absorbent systems and indicated the presence of NOM would decrease adsorption slightly. The leaching experiments showed that the leaching of heavy metals from the adsorbent was negligible. [ABSTRACT FROM AUTHOR]

A 90-day growth trial was conducted on hybrid sturgeon ( Acipenser baeri ♀ × A. gueldenstaedtii ♂) to investigate the effect of dietary inclusion of cyanobacteria on growth, feed utilization, and fish tissue microcystins (MCs) accumulation and the recovery of fish when they were free of cyanobacteria. Four diets were formualted isonitrogenous and isocaloric to contain different MCs concentrations: the control diet (free of cyanobacteria), low cyanobacteria diet (LCD, 26.60 μg MCs/g diet), medium cyanobacteria diet (MCD, 78.82 μg MCs/g diet), and high cyanobacteria diet (HCD, 201.03 μg MCs/g diet). During the first 47 days, each diet was fed to fish in five replicates and then all fish were fed the control diet during the next 43 days. The results showed that a dose-dependent decrease in feeding rate (FR) and specific growth rate (SGR) were observed in the fish fed with MCD and HCD. MCs contents in fish liver, intestine, and dorsal white muscle increased with dietary MCs and were time dependent ( P < 0.05). After the 43-day recovery, there were no significant differences in FR or SGR between the fish previously fed LCD or MCD and the fish fed with the control diet ( P > 0.05), while the fish previously fed HCD showed higher FR and SGR than those fed the control diet ( P < 0.05). MCs clearance in fish liver and intestine showed time-dependence during the 43-day recovery. © 2009 Wiley Periodicals, Inc. Environ Toxicol 2009. [ABSTRACT FROM AUTHOR]

Microcystin-LR (MCLR) and linear alkylbenzene sulfonate (LAS) are present widely in aquatic and terrestrial ecosystems, but their combined ecotoxicological risk is unknown. This study investigated the toxic effects of MCLR, LAS and their mixture on lettuce ( Lactuca sativa L .) and evaluated MCLR accumulation level in lettuce with or without LAS. The changes in seed germination and shoot/root growth, responses of the antioxidative defense system, and the accumulation of MCLR in lettuce were tested to evaluate the single and combined toxic effect of MCLR and LAS in well-controlled conditions. The results showed that seedling growth (except for root elongation and leaf weight) was more sensitive to toxicant exposure than seed germination. For seedling leaves, lipid peroxidation was not observed when the antioxidative defense system (including superoxide dismutase, catalase and glutathione) was activated to relieve the adverse effects of oxidative stress via different pathways. Our results also confirmed that the interaction between MCLR and LAS was synergistic. Both toxicants in combination not only significantly inhibited seedling growth, but also increased the activities of superoxide dismutase and catalase, as well as the contents of glutathione. Furthermore, LAS dramatically enhanced the accumulation of MCLR in the plant, thus leading to a reduction in quality and yield and posing greater potential risk to humans via consumption of these edible plants. [ABSTRACT FROM AUTHOR]

For the purpose of elucidating the environmental characteristics of anion surfactants [linear alkylbenzene sulfonates (LAS)] in the water of Lake Dianchi, a sampling investigation in the field from October 2006 to July 2007 and a batch of biodegradation experiments in the laboratory were carried out. The results showed that concentrations of LAS ranged from 18.6 to 260.1 μg L, and the average concentration was 52.6 μg L in Lake Dianchi. The highest concentrations of LAS were found in the Northwest region, and the distribution of LAS varied through seasons, with much lower concentrations in fall than in any other seasons. LAS can be primarily biodegraded by microorganisms in the lake water, and the percentage of degradation was >97% after 28 days. Biodegradation of LAS was well-fitted with the kinetic model presented in this paper, and the half-lives ranged from 3.2 to 16.3 days. Temperature, pH, and initial concentrations could affect the biodegradation of LAS, among which temperature was the major factor influencing on biodegradation of LAS in water of Lake Dianchi. [ABSTRACT FROM AUTHOR]

This study aimed to determine whether actinomycetes could contribute to the odours occurring in Lake Lotus, China. In total, 55 actinomycete strains were isolated from sediments in Lake Lotus and their odorous metabolites, geosmin and 2-methylisoborneol (2-MIB), were identified using HSPME-GC-MS. Results showed that 24, 23 and 34 strains produced geosmin and/or 2-MIB in Gause, TSB and M liquid media, respectively. Of odour-producing actinomycetes, most could produce geosmin and some produced both metabolites, while few of them produced only 2-MIB. Six isolates with high-level odour were selected for further investigation. Their biomass and odour-producing abilities were monitored in both the slants and liquid media. The results suggest that TSB was the most suitable medium for the growth of mycelium; Gause and M slant supported good production of spores, while M liquid medium was the most favourable for the production of both geosmin and 2-MIB. Those strains that produced geosmin only were less influenced than those that produced both geosmin and 2-MIB under shaking conditions. The results indicate that actinomycetes from sediments should be taken into consideration when off-flavours occur in water columns. According to the 16S rRNA sequences, six actinomycetes were classified in the Streptomyces. [ABSTRACT FROM AUTHOR]

Abstract  The effects of temperature and light on the growth and geosmin production of Lyngbya kuetzingii were determined. Of the three temperatures tested, 10, 25 and 35°C, the maximal geosmin concentration and geosmin productivity were yielded at 10°C, while the highest chl a production was observed at 25°C. In the studies on light intensity, the maximal geosmin concentration and geosmin productivity were observed at 10 μmol m−2 s−1, while the highest chl a production was at 20 μmol m−2 s−1. It was suggested that more geosmin was synthesized with lower chl a demand. Meanwhile, the relative amounts of extra- and intracellular geosmin were investigated. Under optimum growth conditions (20 μmol m−2 s−1, 25°C; BG-11 medium), the amounts of extracellular geosmin increased as the growth progressed and reached the maximum in the stationary phase, while the intracellular geosmin reached its maximum value in the late exponential phase, and then began to decline. However, under the low temperature (10°C) or light (10 μmol m−2 s−1) conditions, more intracellular geosmin was synthesized and mainly accumulated in the cells. The proportions of extracellular geosmin were high, to 33.33 and 32.27%, respectively, during the stationary phase at 35°C and 20 μmol m−2 s−1. It was indicated that low temperature or light could stimulate geosmin production and favor the accumulation of geosmin in cells, while more intracellular geosmin may be released into the medium at higher temperatures or optimum light intensity. [ABSTRACT FROM AUTHOR]

Abstract  Arsenic pollution and eutrophication are both prominent issues in the aquaculture ponds of Taiwan. It is important to study the effects of arsenic on algal growth and toxin production in order to assess the ecological risk of arsenic pollution, or at least to understand naturally occurring ponds. The sensitivity of algae to arsenate has often been linked to the structural similarities between arsenate and phosphate. Thus, in this study we examined the effects of arsenate (10−8 to 10−4 M) on Microcystis aeruginosa TY-1 isolated from Taiwan, under two phosphate regimes. The present study showed that M. aeruginosa TY-1 was arsenate tolerant up to 10−4 M, and that this tolerance was not affected by extracellular phosphate. However, it seems that extracellular phosphate contributed to microcystin production and leakage by M. aeruginosa in response to arsenate. Under normal phosphate conditions, total toxin yields after arsenate treatment followed a typical inverted U-shape hormesis, with a peak value of 2.25 ± 0.06 mg L−1 in the presence of 10−7 M arsenate, whereas 10−8 to 10−6 M arsenate increased leakage of ∼75% microcystin. Under phosphate starvation, total toxin yields were not affected by arsenate, while 10−6 and 10−5 M arsenate stimulated microcystin leakage. It is suggested that arsenate may play a role in the process of microcystin biosynthesis and excretion. Given the arsenic concentrations in aquaculture ponds in Taiwan, arsenate favors survival of toxic M. aeruginosa in such ponds, and arsenate-stimulated microcystin production and leakage may have an impact on the food chain. [ABSTRACT FROM AUTHOR]

This article discusses research on the effects of arsenic species on cyanobacterial growth and toxin yields to assess the ecological risk of blooms that threaten to pollute global water supplies. The correlation between cyanobacteria and arsenate has been linked to the structural similarities of arsenate and phosphate. The arsenate tolerance of a specific microcystin strain was examined. The researchers provided evidence that microcystins may in fact be impacted by by arsenate if it is present in algal blooms.

Several assay methods were screened for viability assessment in cyanobacteria using Microcysris aeruginosa FACHB 905. Compared with fluorescent diacetate (FDA), Evan's Blue and autofluorescence, the 3-[4,5-dimethylthiazol-2-yl]- 2,5-diphenyl tetrazolium bromide (MTT) assay, which was based on the ability of viable cells to reduce MTT to formazan, was found to be reliable and was selected for further study. MTT concentration, incubation time and temperature were optimized for M. aeruginosa. Improvements to the sensitivity and reproducibility of the MTT assay included performing it in the dark to reduce the effects of formazan light sensitivity when extracted in DMSO. Another improvement involved collecting viability data by cell by counting rather than colourimetrically, which was concluded from the fact that oxidoreductase activity, responsible for MTT reduction, would elevate or decrease under stress conditions. Half-life of oxidoreductase in dead cell was calculated to be 3 h. The MTT assay was also found to be applicable to other cyanobacteria and diatoms, including field samples, but not for algae belonging to Chlorophyta, Euglenophyta, Pyrrophyta or Chrysophyta. Based on the above results, we proposed an optimized procedure for the MTT method on Microcystis strains. The use of this assay may be of importance to better understand the dynamics of bloom and the fate of Microcystis under natural or disturbed conditions. [ABSTRACT FROM AUTHOR]

Lake Dianchi is one of the most extensively impacted freshwater lakes by algal blooms. To investigate the response of dominant algal genera, neural networks were applied to model the relationship between water quality parameters and the biomass of four dominant genera (Microcystic spp., Anabaena sp., Quadricauda (Turp.) Breb, Pediastrum Mey) in Dianchi. Results showed that the timing and magnitude of algal blooms of Microcystic spp., Anabaena sp., Quadricauda (Turp.) Breb, and Pediastrum Mey in Dianchi could be successfully predicted. The evaluation of environmental factors showed that pH had more significant impact on concentrations of all the four dominant algal genera than the nutrient factors, such as total phosphorus and total nitrogen. [ABSTRACT FROM AUTHOR]

The paper demonstrates the nonstationarity of algal population behaviors by analyzing the historical populations of Nostocales spp. in the River Darling, Australia. Freshwater ecosystems are more likely to be nonstationary, instead of stationary. Nonstationarity implies that only the near past behaviors could forecast the near future for the system. However, nonstionarity was not considered seriously in previous research efforts for modeling and predicting algal population behaviors. Therefore the moving window technique was incorporated with radial basis function neural network (RBFNN) approach to deal with nonstationarity when modeling and forecasting the population behaviors of Nostocales spp. in the River Darling. The results showed that the RBFNN model could predict the timing and magnitude of algal blooms of Nostocales spp. with high accuracy. Moreover, a combined model based on individual RBFNN models was implemented, which showed superiority over the individual RBFNN models. Hence, the combined model was recommended for the modeling and forecasting of the phytoplankton populations, especially for the forecasting. [ABSTRACT FROM AUTHOR]

A radial basis function neural network was employed to model the abundance of cyanobacteria. The trained network could predict the populations of two bloom forming algal taxa with high accuracy, Nostocales spp. and Anabaena spp., in the River Darling, Australia. To elucidate the population dynamics for both Nostocales spp. and Anabaena spp., sensitivity analysis was performed with the following results. Total Kjeldahl nitrogen had a very strong influence on the abundance of the two algal taxa, electrical conductivity had a very strong negative relationship with the population of the two algal species, and flow was identified as one dominant factor influencing algal blooms after a scatter plot revealed that high flow could significantly reduce the algal biomass for both Nostocales spp. and Anabaena spp. Other variables such as turbidity, color, and pH were less important in determining the abundance and succession of the algal blooms. [ABSTRACT FROM AUTHOR]

Lake Dianchi is in Yunnan Province in southwestern China. In recent years, significant cyanobacterial blooms have occurred in this lake nearly every year because of eutrophication. Monitoring data for the past 5 years acquired by our research group showed that phytoplankton composition alternated between species of Microcystis sp. during warm seasons and those of Aphanizomenon sp. during cool seasons. In March 2003, when phytoplankton composition was highly dominated by Aphanizomenon sp., samples were taken from the lake for toxin detection and immediate strain isolation. A mouse bioassay with extracts from the lyophilized field material showed obvious intoxication from paralytic shellfish poisons (PSPs), and all mice died within 30 min. Further analysis of both field and isolated algal strain Aphanizomenon DC-1 by the postcolumn HPLC-FLD method confirmed its PSP-producing ability. The analogues found in the extracts from the field material were neoSTX, dcSTX, and dcGTX3, with contents of 2.279, 1.135, and 0.547 ng/mg DW, respectively. Under laboratory culture condition, toxin content in the Aphanizomenon strain DC-1 varied greatly during different growth phases, with two peaks: in the early-exponential and late-stationary growth phases. When the culture grew at a relatively high rate during the mid- to late-exponential growth phase, toxin content declined gradually. Moreover, the types of toxin in the DC-1 strain varied greatly during a single culture cycle. The HPLC results showed that dcSTX was the only toxin isomer detected throughout the culture period, and its level remained stable. On the other hand, dcGTX2 and GTX4 were the major toxins during the early-exponential and stationary phases, respectively. This article presents the first data on the identification and detection of paralytic shellfish toxins from cyanobacteria in Lake Dianchi. As far as we know, this is also the first report of this type of toxin in inland water bodies in China. Our study indicates the threat associated with PSP toxins in Lake Dianchi and suggests that necessary measures and programs for control are urgently needed to prevent the spread of toxic cyanobacterial blooms. [ABSTRACT FROM AUTHOR]

A Chrysophyceae species, Poterioochromonas sp., was isolated from Microcystis cultures. This species can efficiently prey on Microcystis and can grow faster phagotrophically than autotrophically. The growth of Poterioochromonas sp. was stimulated in the presence of microcystin-LR and microcystin-RR (in concentrations ranging from 0.1 to 4 mg/L). The growth rate of Poterioochromonas was 45 times higher than the control, indicating the toxins serve as growth stimuli for this organism. A subculture of toxin-treated cells, however, showed low cellular viability, suggesting that growth enhancement by microcystins was not a normal process. The antioxidant enzymatic activity of Poterioochromonas sp. was screened for toxicology analysis. Glutathione, malondialdehyde, and superoxide dismutase (SOD) content was up-regulated within 8 h of exposure to microcystin-LR (500 g/L). A high level of SOD activity during exposure to the toxin indicated that SOD was involved in decreasing oxidative stress caused by microcystin-LR. Simultaneously with growth, Poterioochromonas was able to degrade microcystin-LR even, at a toxin concentration of 4 mg/L. This putative degradation mechanism in Poterioochromonas is explored further and discussed in this article. Our findings may shed light on understanding the role of Poterioochromonas in the aquatic ecosystem, in particular, as a grazer of toxic cyanobacteria and a biodegrader for microcystins. 2005 Wiley Periodicals, Inc. Environ Toxicol 20: 373380, 2005. [ABSTRACT FROM AUTHOR]

In the current study, the toxicological mechanisms of microcystin-LR and its disadvantageous effects on Daphnia magna were examined. Survival rate, number of newborn, activity of several important enzymes [glutathione S-transferase (GST), lactate dehydrogenase (LDH), phosphatases, and glutathione], accumulated microcystins, and ultrastructural changes in different organs of Daphnia were monitored over the course of 21-day chronic tests. The results indicated that low concentrations of dissolved microcystin had no harmful effect on Daphnia. On the contrary, stimulatory effects were detected. In the presence of toxin at high dosage and for long-term exposure, GST and glutathione levels decreased significantly. The decreased enzyme activity in the antioxidant system probably was caused by detoxification reactions with toxins. And these processes of detoxification at the beginning of chronic tests may enable phosphatases in Daphnia magna to withstand inhibition by the toxins. At the same time, we also found that the LDH activity in test animals increased with exposure to microcystin-LR, indicating that adverse effects occurred in Daphnia. With microcystin given at a higher dosage or for a longer exposure, the effect on Daphnia magna was fatal. In the meantime, microcystin began to accumulate in Daphnia magna, and phosphatase activity started to be inhibited. From the ultrastructure results of cells in D. magna, we obtained new information: the alimentary canal may be the target organ affected by exposure of microcystins to D. magna. The results of the current study also suggested that the oxidative damage and PPI (protein phosphatase inhibition) mechanisms of vertebrates also are adapted to Daphnia. 2005 Wiley Periodicals, Inc. Environ Toxicol 20: 323330, 2005. [ABSTRACT FROM AUTHOR]

Compared with other approaches for modeling and predicting, artificial neural networks are more effective in describing complex and non-linear systems. The occurrence of cyanobacterial blooms has been a continuous and serious problem over the past decades in hypereutrophic Lake Dianchi. Yet, the main factor(s) initiating these blooms remain(s) unclear. During 2001-2002 at 40 sampling sites in Lake Dianchi, physicochemical parameters possibly relating to the blooms were measured. Parameters directly or indirectly relating to the cyanobacterial blooms were used as driving factors in a back-propagation network to model the concentration of chlorophyll a. According to sensitivity analysis, chemical oxygen demand was identified as a very significant environmental factor for algal growth in Lake Dianchi. [ABSTRACT FROM AUTHOR]

Microcystins are small hepatotoxic peptides produced by a number of cyanobacteria. They are synthesized non-ribosomally by multifunctional enzyme complex synthetases encoded by the mcy genes. Primers deduced from mcy genes were designed to discriminate between toxic microcystin-producing strains and non-toxic strains. Thus, PCR-mediated detection of mcy genes could be a simple and efficient means to identify potentially harmful genotypes among cyanobacterial populations in bodies of water. We surveyed the distribution of the mcyB gene in different Microcystis strains isolated from Chinese bodies of water and confirmed that PCR can be reliably used to identify toxic strains. By omitting any DNA purification steps, the modified PCR protocol can greatly simplify the process. Cyanobacterial cells enriched from cultures, field samples, or even sediment samples could be used in the PCR assay. This method proved sensitive enough to detect mcyB genes in samples with less than 2,000 Microcystis cells per ml. Its accuracy, specificity and applicability were confirmed by sequencing selected DNA amplicons, as well as by HPLC, ELISA and mouse bioassay as controls for toxin production of every strain used. [ABSTRACT FROM AUTHOR]

Determines toxicity of microcystin-leucine arginine (MC-LR) on isolated carp hepatocytes and observation of ultrastructural alterations of cells induced by MC-LR. Cytological alterations on cell membrane, nuclei and cytoskeleton; Implications of disrupted cytoskeletal structure on blabbing of cell membrane and apoptosis induced by MC-LR.

Presents a study which described the cyanobacterium Anabaena species' photosynthetic utilization of carbon dioxide and bicarbonate. Cyanobacteria culture; Methodology used; Results and discussion.