Light energy conversion into H-2 by Anabaena variabilis mutant PK84 dense cultures exposed to nitrogen limitations

Concentrated cultures (25-86 mg Chl a l(-1)) of Anabaena variabilis PK84 were incubated under 99% Ar+1% CO2 atmosphere in the photobioreactor made of coaxial cylinders. Under illumination equal to 353 mu E m(-2) s(-1) they produced hydrogen with the rate more than 20 ml l(-1) h(-1) for several days. The efficiency of light energy conversion into H-2 was approx. 1% and did not depend significantly on initial Chl a concentration. H-2/O-2 ratio reached 41.5% of theoretical value for water photolysis. Data indicate that dense cultures might be used for outdoor systems under direct sun light. Supra-optimal temperatures 36 degrees C were not harmful for cultures even for 2 days period. Short-term incubation of cultures under 36 degrees C even increased H2 production rate and efficiency of light energy bioconversion by 1.25 times. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Effects of temperature on CO2 exchange between the atmosphere and an alpine meadow

The alpine meadow ecosystem on the Qinghai-Tibetan Plateau is characterized by low temperatures because of its high elevation. The low-temperature environment may limit both ecosystem photosynthetic CO2 uptake and ecosystem respiration, and thus affect the net ecosystem CO2 exchange (NEE). We clarified the low-temperature constraint on photosynthesis and respiration in an alpine meadow ecosystem on the northern edge of the plateau using flux measurements obtained by the eddy covariance technique in two growing seasons. When we compared NEE during the two periods, during which the leaf area index and other environmental parameters were similar but the mean temperature differed, we found that NEE from 9 August to 10 September 2001, when the average temperature was low, was greater than that during the same period in 2002, when the average temperature was high, but the ecosystem gross primary production was similar during the two periods. Further analysis showed that ecosystem respiration was significantly higher in 2002 than in 2001 during the study period, as estimated from the relationship between temperature and nighttime ecosystem respiration. The results suggest that low temperature controlled the NEE mainly through its influence on ecosystem respiration. The annual NEE, estimated from 15 January 2002 to 14 January 2003, was about 290 g CO2 m(-2) year(-1). The optimum temperature for ecosystem NEE under light-saturated conditions was estimated to be around 15 degrees C.

Effect of ambient pressure and radiation reabsorption of atmosphere on the flame spreading over thermally thin combustibles in microgravity

For the flame spread over thermally thin combustibles in an atmosphere, if the atmosphere cannot emit and absorb the thermal radiation (e.g. for atmosphere Of O-2-N-2), the conductive heat transfer from the flame to the fuel surface dominates the flame spread at lower ambient atmosphere. As the ambient pressure increases, the flame spread rate increases, and the radiant heat transfer from the flame to the fuel surface gradually becomes the dominant driving force for the flame spread. In contrast, if the atmosphere is able to emit and absorb the thermal radiation (e.g. for atmosphere Of O-2-CO2), at lower pressure, the heat transfer from flame to the fuel surface is enhanced by the radiation reabsorption of the atmosphere at the leading edge of the flame, and both conduction and thermal radiation play important roles in the mechanism of flame spread. With the increase in ambient pressure, the oxygen diffuses more quickly from ambient atmosphere into the flame, the chemical reaction in the flame is enhanced, and the flame spread rate increases. When the ambient pressure is greater than a critical value, the thermal radiation from the flame to the solid surface is hampered by the radiation reabsorption of ambient atmosphere with the further increase in ambient pressure. As a result, with the increase in ambient pressure, the flame spread rate decreases and the heat conduction gradually dominates the flame spread over the fuel surface.

土壤微生物和酶对大气CO2浓度与温度升高的响应

土壤微生物(Soil microbes)是生态系统的重要组成部分，它参与土壤中复杂有机物质的分解和再合成，也参与C、N、S、P等的循环。土壤酶(Soil enzyme)是土壤中具有生物活性的蛋白质，它与微生物一起推动着土壤的生物化学过程，并在树木营养物质的转化中起着重要的作用。鉴于土壤微生物和土壤酶对环境变化的敏感性，它们在CO2浓度和温度升高时的反应将在很大程度上影响森林生态系统的结构和功能。因此，要全面评价大气CO2浓度和温度升高对整个生态系统的影响，有必要对CO2浓度和温度升高条件下的土壤微生物的反应进行深入的研究与探讨。本文应用自控、封闭、独立的生长室系统，研究了川西亚高山岷江冷杉（Abies faxoniana）根际、非根际土壤微生物数量，红桦（Betula albosinensis）根际微生物数量以及根际、非根际土壤酶活性对大气CO2浓度(环境CO2浓度+350±25μmol·mol-1，EC)和温度(环境温度+2.0±0.5℃，ET)升高及两者同时升高(ECT)的响应。结果表明： 1) EC和ET显著增加岷江冷杉根际微生物数量，但不同微生物种类对EC和ET的反应有所差异。6、8和10月，岷江冷杉根际微生物数量与对照(CK)相比，EC处理的根际细菌数量分别增加了35%、164%和312%，ET处理增加了30%、115%和209%；EC和ET处理对根际放线菌和根际真菌数量影响不显著。ECT处理的根际放线菌数量分别增加了49%、50%和96%，根际真菌数量增加了151%、57%和48%；而ECT对根际细菌数量影响不显著。EC、ET和ECT处理对岷江冷杉土壤微生物总数的根际效应明显，其R/S值分别为1.93、1.37和1.46(CK的R/S值为0.81)。 2) 红桦根际微生物数量对EC、ET和ECT的响应不同。生长季节(5~10月)，高密度的红桦根际细菌数量与CK 相比，EC的根际细菌数量分别增加28%、33%、423%、65%、43%和79%，而低密度的红桦根际细菌数量增加不显著。ET能显著增加根际细菌数量(7~10月)，其中高密度的根际细菌数量分别增加了377%、107%、35%、22%，而低密度的根际细菌数量分别增加了27%、27%、64%、48%；ECT对两个密度水平下根际细菌数量均未产生有显著的影响。高、低密度的红桦根际放线菌和根际真菌数量与 CK 相比，EC显著增加了低密度的红桦根际放线菌数量，而对高密度的根际放线菌数量无显著影响；ET和ECT对高低密度的红桦根际放线菌数量均未产生显著影响。EC和ET对高低密度的根际真菌数量也无显著影响，而ECT却显著增加了高低密度的根际真菌数量。 3) EC、ET和ECT处理的低密度红桦根际微生物(细菌、放线菌和真菌)数量没有显著高于或低于高密度根际微生物数量，表明短期内密度对红桦根际微生物数量不产生影响。 4) 不同种类的氧化还原酶对EC、ET和ECT的响应不同。5~10月，EC的红桦根际过氧化氢酶活性是CK 的1.44、1.06、1.11、1.10、1.12和1.24倍，差异显著(6月除外)；ET和ECT处理根际过氧化氢酶活性无显著增加。EC的红桦根际多酚氧化酶活性比CK显著增加；ET的根际多酚氧化酶活性显著高于CK(8月除外)。ECT的根际多酚氧化酶活性高于CK，差异不显著。EC的根际脱氢酶活性分别增加了46%、40%、133%、48%、17%和26%，差异显著。5~7月，ET和ECT的根际脱氢酶活性高于CK的脱氢酶活性，而8~9月则相反，差异性均不显著。 5) EC、ET和ECT对不同种类的水解酶的影响不同。EC能显著增加红桦根际脲酶活性，5~10月分别增加了29%、42%，、70%、67%、59%和57%。ET和ECT 对根际脲酶活性未产生显著影响。EC显著提高根际转化酶活性，5、6和9月EC的根际转化酶活性分别比CK高51%、42%和40%。5和10月，ET的根际转化酶活性低于CK，而其余月份却高于CK，但均具有显著性差异。ECT的根际转化酶活性与CK的根际转化酶活性有显著性差异(9月除外)，5、6和7月的根际转化酶活性分别提高了94%、198%和67%。 6) 与CK相比，EC、ET和ECT的非根际土壤微生物数量以及非根际土壤酶活性均无显著提高。EC、ET和ECT的过氧化氢酶、脲酶的根际效应明显，而多酚氧化酶和脱氢酶根际效应不明显。EC和ECT的转化酶根际效应明显，而ET的转化酶根际效应不明显。 It is well known that atmospheric CO2 concentration and temperature are increasing as a consequence of human activities. In past decades, considerable efforts had been put into investigating the effects of climate change on processes of forest ecological system. In general, studies had been mainly focused on the effects of elevated atmospheric CO2 on plant physiology and development, litter quality, and soil microorganisms. Studies showed that there was variation in the responses of root development and below-ground processes to climate between different plant communities. Since the concentration of CO2 in soil was much higher (10~50 times) than in the atmosphere, increasing levels of atmospheric CO2 may not directly in fluence below ground processes. Betula albosinensis and Abies faxoniana, as the dominated tree species of subalpine dark coniferous forest in the western Sichuan province, which play an important role in the structure and function of this kind of forest ecosystem. In our study, effects of elevated atmospheric CO2 concentration (350±25μmol·mol-1), increased temperature (2.0±0.5℃) and both of the two on the number of rhizospheric microbe and rhizospheric enzyme activity were studied by the independent and enclosed-top chamber’ system under high-frigid conditions. Responses of rhizospheric bacteria, actinomycetes and fungi number of Betula albosinensis and Abies faxoniana under different densities(high density with 84 stems·m-2, low density with 28 stems·m-2 ), and rhizospheric enzyme activity of Betula albo-sinensis to elevated CO2 concentration and increased temperature were analyzed and discussed. The results are as the following, 1) In comparion with the control, the numbers of rhizospheric bacteria of Abies faxoniana were increased by 35%, 164% and 312% significantly in June, August and October respectively of EC, and were increased by 30%, 115% and 209% respectively of ET.However the effect of EC and ET on rhizospheric actinomycetes and fungi was not significant. The number of rhizospheric actinomycetes of ECT were increased significantly by 49%, 50% and 96% respectively, and the increment of rhizospheric fungi were 151%, 57% and 48% respectively .The effect of ECT on rhizospheric bacteria was not significant. Rhizospheric effect of soil microbe for all treatments was significant, with the R/S of 1.93, 1.27 and 1.46 for EC, ET and ECT, respectively. 2) Treatment EC improved the number of rhizospheric bacteria of Betula albosinensis under high density significantly in comparison with the control, over the growing season, the greatest increment of rhizospheric bacteria was from July. However, EC had no effect on the number of rhizospheric bacteria under low density. Except May and June, treatment ET improved the number of rhizospheric signifcantly. The effect of treatment ECT on the number of rhizospheric bacteria under different densities was not significant. Of treatment EC, the number of rhizospheric actinomycetes of Betula albosinensis under low density were increased significantly, however, treatment EC did not stimulate the number of rhizospheric actinomycetes under high density. Simultaneously, treatment ET and ECT did not stimulate the number of rhizospheric actinomycetes. Finally, in treatment ECT, the number of rhizospheric fungi under high density were increased significantly, however treatment EC and ET did not stimulate the number of rhizospheric fungi under different densities. 3) Of treatment EC, ET and ECT, the number of rhizospheric microbe of Betula albosinensis under low density were not more or fewer than that of microbe under hign density along the growing season, which showed that plant density had no effect on the nmber of microbe. 4) From May to October, 2004，rhizospheric catalase activity of Betula albosinensis of treatment EC was 1.44, 1.06, 1.11, 1.10, 1.12 and 1.24 times as treatment CK respectively, and the difference was statistically significant(except June). Treatment ET and ECT did not increase rhizospheric catalase activity significantly. In treatment EC, the rhizospheric pohyphenol oxidase activity was higher than treatment CK significantly. The rhizospheric pohyphenol oxidase activity of treatment ET was higher than CK significantly (except August). The rhizospheric pohyphenol oxidase activity of treatment ECT was higher than CK, but the difference was not statistically significant. Over the growing period, the rhizospheric dehydrogenase activity were increased 46%, 40%, 133%, 48%, 17% and 26% respectively by treatment EC, and the difference was statistically significant. From May to July, the rhizospheric dehydrogenase activity in treatment ET and ECT was higher than CK, but from August to October, the rhizospheric dehydrogenase activity was lower than CK, the difference was not significant. 5) Treatment EC increased rhizospheric urease activity significantly, from May to October, rhizospheric urease activity were increased 29%, 42%, 70%, 67%, 59% and 57% respectively by EC. Treatment ET and ECT had no effect on rhizospheric urease activity. Treatment EC improved rhizospheric invertase activity significantly, in May, June and September, the rhizospheric invertase activity of treatment EC were increased 51%, 42% and 40% in comparison with the control. Except May and October, the rhizospheric invertase activity of treatment ET was markly higher than CK. The rhizospheric invertase activity of treatment ECT was significantly different from CK (except September), in May, June and July treatment ECT increased rhizospheric invertase activity by 94%, 198% and 67% respectively. 6) In comparison with the control, treatment EC, ET, and ECT had no effect on the number of non-rhizospheric microbe and non-rhizospheric enzyme activity. Rhizospheric effect of catalase and urease for all treatments was significant, but rhizospheric effect of pohyphenol oxidase and dehydrogenase was not significant. Rhizospheric effect of invertase of EC and ECT was significant, but rhizospheric effect of invertase of ET was not significant.

Analysis of the sea-level variability along the Chinese coast and estimation of the impact of a CO2-perturbed atmospheric circulation

The relationship between monthly sea-level data measured at stations located along the Chinese coast and concurrent large-scale atmospheric forcing in the period 1960-1990 is examined. It is found that sea-level varies quite coherently along the whole coast, despite the geographical extension of the station set. A canonical correlation analysis between sea-level and sea-level pressure (SLP) indicates that a great part of the sea-level variability can be explained by the action of the wind stress on the ocean surface. The relationship between sea-level and sea-level pressure is analyzed separately for the summer and winter half-years. In winter, one factor affecting sea-level variability at all stations is the SLP contrast between the continent and the Pacific Ocean, hence the intensity of the winter Monsoon circulation. Another factor that affects coherently all stations is the intensity of the zonal circulation at mid-latitudes. In the summer half year, on the other hand, the influence of SLP on sea-level is spatially less coherent: the stations in the Yellow Sea are affected by a more localized circulation anomaly pattern, whereas the rest of the stations is more directly connected to the intensity of the zonal circulation. Based on this analysis, statistical models (different for summer and winter) to hindcast coastal sealevel anomalies from the large-scale SLP field are formulated. These models have been tested by fitting their internal parameters in a test period and reproducing reasonably the sea-level evolution in an independent period. These statistical models are also used to estimate the contribution of the changes of the atmospheric circulation on sea-level along the Chinese coast in an altered climate. For this purpose the ouput of 150 year-long experiment with the coupled ocean-atmosphere model ECHAM1-LSG has been analyzed, in which the atmospheric concentration of greenhouse gases was continuously increased from 1940 until 2090, according to the Scenario A projection of the Intergovermental Panel on Climate Change. In this experiment the meridional (zonal) circulation relevant for sea-level tends to become weaker (stronger) in the winter half year and stronger (weaker) in summer. The estimated contribution of this atmospheric circulation changes to coastal sea-level is of the order of a few centimeters at the end of the integration, being in winter negative in the Yellow Sea and positive in the China Sea with opposite signs in the summer half-year.

Dissolved inorganic carbon and CO2 fluxes across Jiaozhou Bay air-water interface

On the basis of data collected in the Jiaozhou Bay in June and July 2003, the DIC distribution in seawater is studied, and an average air-sea flux of CO2 is estimated. The results show that the content of DIC inside the bay is markedly higher than outside the bay in June, but the content of DIC outside the bay is markedly higher than inside the bay in July. The trend of DIC distribution inside the bay is similar, viz. the content is the maximum in the northeast, then decreases gradually toward the west, and the content is the minimum in the west. The total trend of vertical distribution is to increase gradually from surface to bottom. This characteristic of DIC distribution is determined by Jiaozhou Bay hydrology and there is a close relation between DIC and particulate N,P. Average CO2 flux across the air-sea interface is 0.55 mol/(m(2.)a) in June and 0.72 mol/(m(2.)a) in July. Jiaozhou Bay is considered as a net annual source for atmospheric CO2 in June and July, and the total CO2 flux from seawater into atmosphere is about 740 t in June and 969 t in July.

Role of the Jiaozhon Bay as a source/sink of CO2 over a seasonal cycle

The seasonal evolution of dissolved inorganic carbon (DIC) and CO2 air-sea fluxes in the Jiaozhou Bay was investigated by means of a data set from four cruises covering a seasonal cycle during 2003 and 2004. The results revealed that DIC had no obvious seasonal variation, with an average concentration of 2035 mu mol kg(-1) C in surface water. However, the sea surface partial pressure of CO2 changed with the season. pCO(2) was 695 mu atm in July and 317 mu atm in February. Using the gas exchange coefficient calculated with Wanninkhof's model, it was concluded that the Jiaozhou Bay was a source of atmospheric CO, in spring, summer, and autumn, whereas it was a sink in winter. The Jiaozhou Bay released 2.60 x 10(11) mmol C to the atmosphere in spring, 6.18 x 10(11) mmol C in summer, and 3.01 x 10(11) mmol C in autumn, whereas it absorbed 5.32 x 10(10) mmol C from the atmosphere in winter. A total of 1.13 x 10(11) mmol C was released to the atmosphere over one year. The behaviour as a carbon source/sink obviously varied in the different regions of the Jiaozhou Bay. In February, the inner bay was a carbon sink, while the bay mouth and the Outer bay were carbon sources. In June and July, the inner and Outer bay were carbon sources, but the strength was different, increasing from the inner to the outer bay. In November, the inner bay was a carbon source, but the bay Mouth was a carbon sink. The outer bay was a weaker CO2 Source. These changes are controlled by many factors, the most important being temperature and phytoplankton. Water temperature in particular was the main factor controlling the carbon dioxide system and the behaviour of the Jiaozhou Bay as a carbon source/sink. The Jiaozhou Bay is a carbon dioxide source when the water temperature is higher than 6.6 degrees C. Otherwise, it is a carbon sink. Phytoplankton is another controlling factor that may play an important role in behaviour as a carbon source or sink in regions where the source or sink nature is weaker.

Carbon Dioxide Exchange Between the Atmosphere and an Alpine Shrubland Meadow During the Growing Season on the Qinghai-Tibetan Plateau

In the present study, we used the eddy covariance method to measure CO2 exchange between the atmosphere and an alpine shrubland meadow ecosystem (37°36'N, 101°18'E; 3 250 m a.s.l.) on the Qinghai-Tibetan Plateau, China, during the growing season in 2003, from 20 April to 30 September. This meadow is dominated by formations of Potentilla fruticosa L. The soil is Mol-Cryic Cambisols. During the study period, the meadow was not grazed. The maximum rates of CO2 uptake and release derived from the diurnal course of CO2 flux were -9.38 and 5.02 μmol•m-2•s-1, respectively. The largest daily CO2 uptake was 1.7 g C•m-2•d-1 on 14 July, which is less than half that of an alpine Kobresia meadow ecosystem at similar latitudes. Daily CO2 uptake during the measurement period indicated that the alpine shrubland meadow ecosystem may behave as a sink of atmospheric CO2 during the growing season. The daytime CO2 uptake was correlated exponentially or linearly with the daily photo synthetic photon flux density each month. The daytime average water use efficiency of the ecosystem was 6.47 mg CO2/g H2O. The efficiency of the ecosystem increased with a decrease in vapor pressure deficit.

Carbon dioxide exchange between the atmosphere and an alpine meadow ecosystem on the Qinghai-Tibetan Plateau, China

We used the eddy covariance method to measure the M exchange between the atmosphere and an alpine meadow ecosystem (37degrees29-45'N, 101degrees12-23'E, 3250m a.s.l.) on the Qinghai-Tibetan Plateau, China in the 2001 and 2002 growing seasons. The maximum rates Of CO2 uptake and release derived from the diurnal course Of CO2 flux (FCO2) were -10.8 and 4.4 mumol m(-2) s(-1), respectively, indicating a relatively high net carbon sequestration potential as compared to subalpine coniferous forest at similar elevation and latitude. The largest daily CO2 uptake was 3.9 g cm(-2) per day on 7 July 2002, which is less than half of those reported for lowland grassland and forest at similar latitudes. The daily CO2 uptake during the measurement period indicated that the alpine ecosystem might behave as a sink of atmospheric M during the growing season if the carbon lost due to grazing is not significant. The daytime CO2 uptake was linearly correlated with the daily photosynthetic photon flux density each month. The nighttime averaged F-CO2 showed a positive exponential correlation with the soil temperature, but apparently negative correlation with the soil water content. (C) 2004 Elsevier B.V. All rights reserved.

Numerical simulation of an adaptive optics system with laser propagation in the atmosphere

A comprehensive model of laser propagation in the atmosphere with a complete adaptive optics (AO) system for phase compensation is presented, and a corresponding computer program is compiled. A direct wave-front gradient control method is used to reconstruct the wave-front phase. With the long-exposure Strehl ratio as the evaluation parameter, a numerical simulation of an AO system in a stationary state with the atmospheric propagation of a laser beam was conducted. It was found that for certain conditions the phase screen that describes turbulence in the atmosphere might not be isotropic. Numerical experiments show that the computational results in imaging of lenses by means of the fast Fourier transform (FFT) method agree well with those computed by means of an integration method. However, the computer time required for the FFT method is 1 order of magnitude less than that of the integration method. Phase tailoring of the calculated phase is presented as a means to solve the problem that variance of the calculated residual phase does not correspond to the correction effectiveness of an AO system. It is found for the first time to our knowledge that for a constant delay time of an AO system, when the lateral wind speed exceeds a threshold, the compensation effectiveness of an AO system is better than that of complete phase conjugation. This finding indicates that the better compensation capability of an AO system does not mean better correction effectiveness. (C) 2000 Optical Society of America.

Flow Characteristics and Its Friction Coefficient of Laminar Near-Wall Boundary Layer in Dusty Atmosphere

采用双向耦合的双流体模型,研究了大气悬浮沙尘的存在对大气边界层中层流底层流动特性及摩阻系数的影响,计算并讨论了不同沙尘含量下含尘大气相对于无尘大气摩阻系数的变化。结果表明：摩阻系数的变化取决于悬浮沙尘的初始运动状态和质量载荷率。

Laminar Plasma Spraying of Metal Wire in Atmosphere

利用层流等离子体射流，以普通工程铁丝为喷涂材料，在Q235基体表面制备金属涂层，并利用喷涂系统的参数可调性研究工艺参数对涂层质量的影响。结果表明，利用层流等离子体射流喷涂可以得到具有典型层状结构、氧化较少的致密涂层。

Gust-Induced Movement of Dusts Suspended in Atmosphere

在气固两相流的单向耦合模型框架下,研究大气悬浮沙尘在阵风作用下的运动轨迹及其随大气风速、沙尘粒径的变化,揭示了在Stokes阻力、Saffman力和重力共同作用下,沙尘悬移可能转换为跃移的现象。

Numerical Study Of Heat Transfer Mechanism In Turbulent Supercritical Co2 Channel Flow

Direct numerical simulation (DNS) of supercritical CO2 turbulent channel flow has been performed to investigate the heat transfer mechanism of supercritical fluid. In the present DNS, full compressible Navier-Stokes equations and Peng-Robison state equation are solved. Due to effects of the mean density variation in the wall normal direction, mean velocity in the cooling region becomes high compared with that in the heating region. The mean width between high-and low-speed streaks near the wall decreases in the cooling region, which means that turbulence in the cooling region is enhanced and lots of fine scale eddies are created due to the local high Reynolds number effects. From the turbulent kinetic energy budget, it is found that compressibility effects related with pressure fluctuation and dilatation of velocity fluctuation can be ignored even for supercritical condition. However, the effect of density fluctuation on turbulent kinetic energy cannot be ignored. In the cooling region, low kinematic viscosity and high thermal conductivity in the low speed streaks modify fine scale structure and turbulent transport of temperature, which results in high Nusselt number in the cooling condition of the supercritical CO2.

A model of an isolated magnetic-flux tube in a stratified atmosphere

A two-dimensional model of a magnetic flux tube confined in a gravitational stratified atmosphere is discussed. The magnetic field in the flux tube is assumed to be force-free. By using the approximation of large scale height, the problem of a free boundary with nonlinear conditions may be reduced to one involving a fixed boundary. The two-dimensional features are obtained by applying the perturbation method and adopting the Luest-Schlueter model as the basic state. The results show that the configuration of a flux tube confined in a gravitational stratified atmosphere is divergent, and the more twisted the magnetic field, the more divergent is the flux tube.