Effect of CaO on NOx Reduction by Selective Non-Catalytic Reduction under Variable Gas Compositions in a Simulated Cement Precalciner Atmosphere.

High-concentration CaO particles and gas compositions have a significant influence on NOx reduction by selective non-catalytic reduction (SNCR) in cement precalciners. The effect of gas composition on NOx reduction by SNCR with NH3 was studied in a cement precalciner atmosphere with and without CaO at 700-1100 °C. It was found that CaO significantly lowers NOx reduction efficiency between 750 °C and 1000 °C, which is attributed to the catalytic oxidation of NH3 to NO. Although increasing NH3 concentration was advantageous to NOx reduction, the existence of CaO led to the opposite result at 750-900 °C. Adding H2O can suppress the negative effect of CaO on NOx reduction. Decreasing O2 content from 10% to 1% shifts the temperature range in which CaO has a significant effect from 750-1000 °C to 800-1050 °C. CO has a variety of influences on the CaO effect under different experimental conditions. The influences of NH3, H2O, O2, and CO on the effect of CaO can be attributed to the impacts of the gas compositions on gas-phase NH3 conversion, gas-solid catalytic NH3 oxidation, or both processes. A proposed pathway for the effect of gas compositions on NOx reduction in CaO-containing SNCR process was developed that well predicted the CaO-containing SNCR process.

Species presence frequency and diversity in different patch types along an altitudinal gradient: Larix chinensis Beissn in Qinling Mountains (China).

Forest communities are mosaic systems composed of patches classified into four different developmental patch types: gap patch (G), building patch (B), mature patch (M) and degenerate patch (D). To study the mechanisms maintaining diversity in subalpine coniferous forests, species presence frequency and diversity in the four distinct patch types (G, B, M and D) of Larix chinensis conifer forests at three altitudinal gradients in the Qinling Mountains were analyzed. Our results were as follows: (1) Different species (or functional groups) had distinct presence frequencies in the four different patch types along the altitudinal gradient; (2) Some species or functional groups (species groups sharing similar traits and responses to the environment) only occurred in some specific patches. For seed dispersal, species using wind mainly occurred in G and D, while species using small animals mainly occurred in B and M; (3) Species composition of adjacent patch types was more similar than non-adjacent patch types, based on the lower ß diversity index of the former; (4) The maximum numbers of species and two diversity indices (D' and H') were found in the middle altitudes. Various gap-forming processes and dispersal limitation may be the two major mechanisms determining species diversity in Larix chinensis coniferous forests at the patch scale.

Ecophysiological responses to different forest patch type of two codominant tree seedlings.

According to gap-phase dynamics theory, forests can be divided into four distinct patch types: gap patch (G), building patch (B), mature patch (M), and degeneration patch (D). Varying light conditions across patch types are one of the most important factors affecting the coexistence of vegetation. Mechanisms of coexistence can be understood through detailed knowledge of ecophysiological responses of codominant tree seedlings to patch types. The following study was conducted to determine ecophysiological responses of Cyclobalanopsis glauca (an evergreen broad-leaved species) and Bothrocaryum controversum (a deciduous broad-leaved species) to four different patch types. During the gap-phase dynamics, light intensity and the magnitude of change in the four different patches followed the order of: G > B > D > M. Both species had the greatest photosynthetic capacity in the G patch. Dry leaf mass per area (LMA), Chlorophyll a + b concentration (Chl), carotenoids (Car), and nitrogen content per area (N a ) all responded to changes in light across patch type, but B. controversum showed greater sensitivity and changes than C. glauca. From G to M patch, the maximal quantum efficiency of PSII (F v /F m ) had a larger variation magnitude for B. controversum than for C. glauca. From G to M patch, B. controversum showed significant changes in gas exchange, while C. glauca showed only small changes. Ecophysiological trait partitioning of response to light in different patches provides a possible explanation of a coexistence mechanism.

The predictive performance and stability of six species distribution models.

BACKGROUND: Predicting species' potential geographical range by species distribution models (SDMs) is central to understand their ecological requirements. However, the effects of using different modeling techniques need further investigation. In order to improve the prediction effect, we need to assess the predictive performance and stability of different SDMs. METHODOLOGY: We collected the distribution data of five common tree species (Pinus massoniana, Betula platyphylla, Quercus wutaishanica, Quercus mongolica and Quercus variabilis) and simulated their potential distribution area using 13 environmental variables and six widely used SDMs: BIOCLIM, DOMAIN, MAHAL, RF, MAXENT, and SVM. Each model run was repeated 100 times (trials). We compared the predictive performance by testing the consistency between observations and simulated distributions and assessed the stability by the standard deviation, coefficient of variation, and the 99% confidence interval of Kappa and AUC values. RESULTS: The mean values of AUC and Kappa from MAHAL, RF, MAXENT, and SVM trials were similar and significantly higher than those from BIOCLIM and DOMAIN trials (p<0.05), while the associated standard deviations and coefficients of variation were larger for BIOCLIM and DOMAIN trials (p<0.05), and the 99% confidence intervals for AUC and Kappa values were narrower for MAHAL, RF, MAXENT, and SVM. Compared to BIOCLIM and DOMAIN, other SDMs (MAHAL, RF, MAXENT, and SVM) had higher prediction accuracy, smaller confidence intervals, and were more stable and less affected by the random variable (randomly selected pseudo-absence points). CONCLUSIONS: According to the prediction performance and stability of SDMs, we can divide these six SDMs into two categories: a high performance and stability group including MAHAL, RF, MAXENT, and SVM, and a low performance and stability group consisting of BIOCLIM, and DOMAIN. We highlight that choosing appropriate SDMs to address a specific problem is an important part of the modeling process.

Effects of gas compositions on NOx reduction by selective non-catalytic reduction with ammonia in a simulated cement precalciner atmosphere.

The effects of gas compositions on NOx reduction and NH3 slip by selective non-catalytic reduction (SNCR) with NH3 were investigated in a simulated cement precalciner atmosphere. The results show that the presence of H2O improves NOx reduction and widens the reduction temperature window significantly. O2 is indispensable for reducing NOx. The optimum reduction temperature decreases and the temperature window widens to a lower temperature with the increase of O2 content. In addition, the increase of O2 content also results in a decrease of the maximum NOx reduction efficiency. The effect of SO2 on NOx reduction is negligible in the simulated precalciner atmosphere. To increase CO concentration makes NO reduction take place at relatively low temperatures. However, NH3 will tend to be oxidized into NO instead of reducing NO after entering the stream containing O2 at high temperatures if it is initially blended with a high concentration of CO in an oxygen-free environment. The increase of H2O, O2, SO2 or CO concentration is helpful to reduce NH3 slip in the temperature region below 900°C. These effects are resulted from the fact that the generation and consumption of O and OH radicals which are crucial to NO reduction and formation can be influenced by the four gas compositions. In industrial operation of SNCR for cement precalciner, these effects should be taken into account to increase NOx reduction efficiency and avoid NH3 slip.

Distinguishing the importance between habitat specialization and dispersal limitation on species turnover.

Understanding what governs community assembly and the maintenance of biodiversity is a central issue in ecology, but has been a continuing debate. A key question is the relative importance of habitat specialization (niche assembly) and dispersal limitation (dispersal assembly). In the middle of the Loess Plateau, northwestern China, we examined how species turnover in Liaodong oak (Quercus wutaishanica) forests differed between observed and randomized assemblies, and how this difference was affected by habitat specialization and dispersal limitation using variation partitioning. Results showed that expected species turnover based on individual randomization was significantly lower than the observed value (P < 0.01). The turnover deviation significantly depended on the environmental and geographical distances (P < 0.05). Environmental and spatial variables significantly explained approximately 40% of the species composition variation at all the three layers (P < 0.05). However, their contributions varied among forest layers; the herb and shrub layers were dominated by environmental factors, whereas the canopy layer was dominated by spatial factors. Our results underscore the importance of synthetic models that integrate effects of both dispersal and niche assembly for understanding the community assembly. However, habitat specialization (niche assembly) may not always be the dominant process in community assembly, even under harsh environments. Community assembly may be in a trait-dependent manner (e.g., forest layers in this study). Thus, taking more species traits into account would strengthen our confidence in the inferred assembly mechanisms.

The role of p53 in the response of tumor cells to sonodynamic therapy in vitro.

p53 plays a pivotal role in apoptosis. In addition, p53 is currently extensively investigated as a promising strategy for highly specific anticancer therapy in chemotherapeutics and photodynamic therapy. However, the role of p53 in the response of tumor cells to sonodynamic therapy treatment is still unclear. In this study, we aim to investigate the activation of p53 in sonodynamic therapy. Three murine tumor models with distinct aggressiveness (S180, H-22 and EAC) were treated with 1.75MHz continuous ultrasound at an acoustic intensity (I(SATA)) of 1.4W for 3min in the presence of 20µg/ml hematoporphyrin. The DNA fragment and nuclear damage were observed by TUNEL and single cell gel electrophoresis. Western blotting and RT-PCR were used to analyze the expression of p53, PUMA, Bax and Fas. Then we checked the translocation of p53 by confocal microscopy. DNA sequencing was used to determine the status of p53 gene in three tumor cell lines. Our results indicated that the level of p53 protein and mRNA increased significantly, and p53 activated the expression of its downstream pro-apoptosis gene PUMA, Bax and Fas in the S180 and H-22 cells. Meanwhile, p53 protein translocated onto mitochondria. In the EAC cells, expression and translocation of p53 was not found; the level of PUMA, Bax and Fas remained unaltered. The S180 cells showed most serious DNA fragment and nuclear damage with 77.43% TDNA; H-22 cells in the middle with 58.85% TDNA; whereas EAC cells appeared less nuclear material lost with just 15.82% TDNA. The results of DNA sequencing showed that the sequences of exons 5-8 of the p53 gene of S180, H-22 and EAC cells were the same with the sequences of wild-type p53 provided by NCBI. These results primarily demonstrated that: (1) p53 was activated to promote SDT-induced apoptosis through extrinsic and intrinsic signaling pathways in the S180 and H-22 cells; (2) cellular responses of different cells to SDT were distinct, the aggressive S180 cells were much more sensitive than H-22, whereas EAC cells were relatively less sensitive. The discrepancy among the cell lines may be due to different activation time of p53 protein.