Enhancing the carbonation of MgO cement porous blocks through improved curing conditions

The use of reactive magnesia (MgO) as the binder in porous blocks demonstrated significant advantages due to its low production temperatures and ability to carbonate, leading to significant strengths. This paper investigates the enhancement of the carbonation process through different curing conditions: water to cement ratio (0.6-0.9), CO2 concentration (5-20%), curing duration (1-7 days), relative humidity (55-98%), and wet/dry cycling frequency (every 0-3 days), improving the carbonation potential through increased amounts of CO2 absorbed and enhanced mechanical performance. UCS results were supported with SEM, XRD, and HCl acid digestion analyses. The results show that CO2 concentrations as low as 5% can produce the required strengths after only 1 day. Drier mixes perform better in shorter curing durations, whereas larger w/c ratios are needed for continuous carbonation. Mixes subjected to 78% RH outperformed all the others, also highlighting the benefits of incorporating wet/dry cycling to induce carbonation. © 2014 Elsevier Ltd.

Meat and bone meal replacement in diets for juvenile gibel carp (Carassius auratus gibelio): effects on growth performance, phosphorus and nitrogen loading

A 11-week growth trial was conducted in a flow-through system with juvenile gibel carp Carassius auratus gibelio to evaluate the effects of gradual replacement of fish meal (FM) by meat and bone meal (MBM) on growth performance, phosphorus (P) and nitrogen (N) loading. Six isonitrogenous (crude protein: 410 g kg(-1)) and isoenergetic (gross energy: 18 kJ g(-1)) diets were formulated. FM was used as the control protein. In the other five diets, 20, 40, 60, 80 and 100% FM protein was substituted with MBM20, MBM40, MBM60, MBM80, MBM100, respectively. Total P content in the diets ranged from 16.0 to 28.3 g kg(-1) and the available P was 5.0-6.6 g kg(-1). The results showed that the best growth was achieved with fish fed on the control diet and MBM20. Final body weight, weight gain, feed efficiency, protein retention efficiency and energy retention efficiency decreased with increased dietary MBM. No significant differences were found in the feeding rate and hepatosomatic index between the groups. Apparent digestibility coefficient (ADC) of dry matter, protein and P decreased with increase in dietary MBM, while there were no significant differences in the ADC of energy. P and N retention decreased linearly while P and N loading increased linearly with the increased dietary MBM levels. No significant differences were observed in the activity of alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase, as well as pyruvate kinase in liver or in serum. Total superoxide dismutase activity in MBM20 was significantly higher than that of MBM100.

Effect of dietary carbohydrate sources on growth performance and utilization for gibel carp (Carassius auratus gibelio) and Chinese longsnout catfish (Leiocassis longirostris Gunther)

The nutritional function of monosaccharides, disaccharides and polysaccharides for omnivorous gibel carp and carnivorous Chinese longsnout catfish were investigated and the ability of these two species to utilize carbohydrates was compared. For each species, triplicate groups of fish were assigned to each of five groups of isoenergetic and isonitrogenous experimental diets with different carbohydrate sources: glucose, sucrose, dextrin, soluble starch (acid-modified starch) and alpha-cellulose. The carbohydrates were included at 60 g kg(-1) in Chinese longsnout catfish diets and at 200 g kg(-1) in gibel carp diets. A growth trial was carried out in a recirculation system at 27.8 +/- 1.9 degrees C for 8 weeks. The results showed that fish with different food habits showed difference in the utilization of carbohydrate sources. For gibel carp, better specific growth rate (SGR) and feed efficiency (FE) were observed in fish fed diets containing soluble starch and cellulose, but for Chinese longsnout catfish, better SGR and FE were observed in fish fed diets containing dextrin and sucrose. Apparent digestibility coefficient of dry matter (ADC(d)) and apparent digestibility coefficient of energy (ADC(e)) were significantly affected by dietary carbohydrate sources in gibel carp. ADC(d) and ADC(e) significantly decreased as dietary carbohydrate complexity increased in Chinese longsnout catfish except that glucose diet had medium ADC(d) and ADC(e). In both species, no significant difference of apparent digestibility coefficient of protein was observed between different carbohydrate sources. Dietary carbohydrate sources significantly affected body composition, and liver phosphoenolpyruvate carboxykinase (PEPCK), pyruvate kinase (PK), glucose 6-phosphate dehydrogenase (G6PD) and malic enzyme (ME) activities also varied according to dietary carbohydrate complexity. Fish with different food habits showed different abilities to synthesize liver glycogen, and the liver glycogen content in gibel carp was significantly higher than in Chinese longsnout catfish. The influence of carbohydrate source on gluconeogenesis and lipogenesis was also different in the two fish species.

Nutritional homeostasis in carnivorous southern catfish (Silurus meridionalis): is there a mechanism for increased energy expenditure during carbohydrate overfeeding?

In previous growth experiments with carnivorous southern catfish (Silurus meridionalis), the non-fecal energy lose was positively related to dietary. carbohydrate level. To test whether metabolic energy expenditure accounts for such energy loss, an experiment was performed with southern catfish juveniles (33.2-71.9 g) to study the effect of dietary carbohydrate level on fasting metabolic rate and specific dynamic action (SDA) at 27.5 degreesC. The fasting metabolic rate in this catfish was increased with dietary carbohydrate level, and the specific dynamic action (SDA) coefficient (energy expended on SDA as percent of assimilated energy) was not affected by dietary carbohydrate level. The results suggest that in southern catfish, carbohydrate overfeeding increases metabolic rate to oxidize unwanted assimilated carbohydrate. A discussion on the poor capacity of intermediate metabolism for adapting dietary carbohydrate in carnivorous fish and its possible relationship with facultative component of SDA was also documented in this paper. (C) 2004 Elsevier Inc. All rights reserved.

Temporal and spatial variations in kinetics of alkaline phosphatase in sediments of a shallow Chinese eutrophic lake (Lake Donghu)

Monthly sediment and interstitial water samples were collected in a shallow Chinese freshwater lake (Lake Donghu) from three areas to determine if alkaline phosphatase activity (APA) plays an important role in phosphorus cycling in sediment. The seasonal variability in the kinetics of APA and other relevant parameters were investigated from 1995-1996. The phosphatase hydrolyzable phosphorus (PHP) fluctuated seasonally in interstitial water, peaking in the spring. A synchronous pattern was observed in chlorophyll a contents in surface water in general. The orthophosphate (o-P) concentrations in the interstitial water increased during the spring. An expected negative relationship between PHP and V-max of APA is not evident in interstitial water. The most striking feature of the two variables is their co-occurring, which can be explained in terms of an induction mechanism. It is argued that phosphatase activity mainly contributes to the driving force of o-P regeneration from PHP in interstitial water, supporting the development of phytoplankton biomass in spring. The V-max values in sediment increased during the summer, in Conjunction with lower K-m values in interstitial water that suggest a higher affinity for the substrate. The accumulation of organic matter in the sediment could be traced back to the breakdown of the algal spring bloom, which may stimulate APA with higher kinetic efficiency, by a combination of the higher V-max in sediments plus lower K-m values in interstitial water, in Summer. In summary, a focus On phosphatase and its substrate in annual scale may provide a useful framework for the development of novel P cycling, possible explanations for the absence of a clear relationship between PHP and APA were PHP released from the sediment which induced APA, and the presence of kinetically higher APA both in sediment and interstitial water which permitted summer mineralization of organic matter derived from the spring bloom to occur. The study highlighted the need for distinguishing functionally distinct extracellular enzymes between the sediment and interstitial water of lakes. (C) 2002 Elsevier Science Ltd. All rights reserved.

Nutrient dynamics and the eutrophication of shallow lakes Kasumigaura (Japan), Donghu (PR China), and Okeechobee (USA)

We compared the nutrient dynamics of three lakes that have been heavily influenced by point and non-point source pollution and other human activities. The lakes, located in Japan (Lake Kasumigaura), People's Republic of China (Lake Donghu), and the USA (Lake Okeechobee), all are relatively large(>30 km(2)), very shallow (<4 m mean depth), and eutrophic. In all three lakes we found strong interactions among the sediments, water column, and human activities. Important processes affecting nutrient dynamics included nitrogen fixation, light limitation due to resuspended sediments, and intense grazing on algae by cultured fish. As a result of these complex interactions, simple empirical models developed to predict in-lake responses of total phosphorus and algal biomass to external nutrient loads must be used with caution. While published models may provide 'good' results, in terms of model output matching actual data, this may not be due to accurate representation of lake processes in the models. The variable nutrient dynamics that we observed among the three study lakes appears to be typical for shallow lake systems. This indicates that a greater reliance on lake-specific research may be required for effective management, and a lesser role of inter-lake generalization than is possible for deeper, dimictic lake systems. Furthermore, accurate predictions of management impacts in shallow eutrophic lakes may require the use of relatively complex deterministic modeling tools. (C) 2000 Elsevier Science Ltd. All rights reserved.

Effects of submerged macrophytes on kinetics of alkaline phosphatase in Lake Donghu - I. Unfiltered water and sediments

The impacts of submerged macrophytes on kinetics of alkaline phosphatase were studied in two 680 m(2) enclosures in a shallow Chinese freshwater lake (Donghu Lake) from April to October 1996, and two experimental pools (120 m(2)) built inland in 1998. The submerged macrophytes were Vallisneria sp, Potamogeton crispus. In the presence of macrophytes, the concentration of orthophosphate was significantly lower, coupled with the decreasing function of organic P hydrolysis, in terms of lower V-max and higher K-m values of aIkaline phosphatase in water, filtered and unfiltered (0.45 mu m); in the interstitial water, the V-max values of the enzyme in sediments were significantly lower, exhibited by a spatial and vertical profile. The results implied the key role of submerged macrophytes was the retention of P nutrients. (C) 2000 Elsevier Science Ltd. All rights reserved.

Improvement of the stability of hydrogenated amorphous silicon films by intermittent illumination treatment at elevated temperature

The intermittent illumination treatment by white light at elevated temperature is proved to be a convenient and efficient method for the improvement of the stability of hydrogenated amorphous silicon (a-Si:H) films. The effect of the treatment on electrical properties, light-induced degradation, and gap states of undoped a-Si:H films has been investigated in detail. With the increase of cycling number, the dark- as well as photo-conductivities in annealed state and light-soaked state approach each other, presenting an unique irreversible effect. The stabilization and ordering processes by the present treatment can not be achieved merely by annealing under the same conditions. It is shown that the treatment proposed here results in a shift to higher values of the energy barriers between defects and their precursors, and hence an improved stability of a-Si:H films. (C) 1996 American Institute of Physics.

808-nm fiber coupled module with a CW output power up to 130 W

A fiber coupled module is fabricated with integrating the emitting light from four laser diode bars into multimode fiber bundle. The continuous wave (CW) output power of the module is about 130 W with a coupling efficiency of around 80%. The output power is very stable after the temperature cycling and vibration test. No apparent power decrease has been observed as the device working continuously for 500 h.

落叶松人工林养分循环与养分利用效率研究

通过对抚顺市温道林场20、53和69年生长白落叶松（Larix olgensis）人工林生物量和营养元素的积累与分配、养分利用效率和养分再吸收效率、养分生物循环的研究，探讨了长白落叶松生长发育不同阶段的养分生态学特征；对东北林业大学帽儿山实验林场17年生兴安落叶松（Larix gmelinii）人工林进行5年的施肥（NH4NO3，15 g•m-2•a-1），研究了施肥对人工林养分生物循环的影响。结果表明： （1）20、53和69年生单株落叶松生物量分别为33.14 kg•tree-1、311.42 kg•tree-1和408.46 kg•tree-1，随林龄的增长而增加。各器官生物量的分配格局为：树干>根>树枝>树皮>针叶。树干生物量的分配比例为50.16%~69.20%，随林龄的增长比例增大，而其他器官生物量的分配比例则逐渐减小。20、53和69年生单株落叶松净生产力分别为3.04 kg•tree-1•a-1、9.68 kg•tree-1•a-1和10.21 kg•tree-1•a-1，随林龄的增长而增大。针叶和树干的净生产力最大，分别占整株林木净生产力的40.07%~47.93%和27.32%~40.97%，并且随林龄的增长而增大。树枝、树皮和根的净生产力则表现出随林龄的增长呈抛物线状。 （2）20、53和69年生单株落叶松N、P、K、Ca、Mg等5种营养元素的总贮量分别为308.14 g•tree-1、2021.01 g•tree-1和2485.24 g•tree-1，随林龄的增长而增加。5种营养元素的贮量大小为：Ca>N>K>Mg>P。树干养分贮量的分配比例为19.74%~34.23%，随林龄的增长呈抛物线状。针叶、树枝和树皮的养分贮量占整株林木养分贮量的比例为35.16%~45.59%，建议在采伐木材时实施去皮、打枝等措施，留下针叶、树枝和树皮在林地中，让其自然分解以使营养元素重新归还利用，对于维持林地的养分平衡和长期生产力具有积极作用。 （3）20、53和69年生单株落叶松年吸收养分量分别为35.31 g•tree-1•a-1、97.83 g•tree-1•a-1和100.08 g•tree-1•a-1，随林龄的增长而增加。5种营养元素的年吸收量大小为：Ca>N>K>Mg>P。落叶松的养分利用效率随林龄的增长而增大，但生长到一定年龄阶段后，其养分利用效率逐渐趋于稳定。落叶松的最佳采伐年龄应为养分利用效率保持稳定时的年龄，此时采伐单位干材所带走的林地养分量较少。不同营养元素的利用效率不同，P的利用效率最高，Mg、K次之，N、Ca最低。不同器官的养分利用效率不同，树干的养分利用效率最高，其次是根、树枝、树皮，针叶最低。随着林龄的增长，树干和根的养分利用效率增大，而树枝和树皮的养分利用效率减小。 （4）落叶松叶片的N再吸收效率为50.76%~55.11%，随林龄的增长表现出增大的趋势；P和K再吸收效率分别为64.38%~68.85%和87.85%~90.62%，随林龄的增长表现出减小的趋势。从养分利用效率和养分再吸收效率综合判断，本研究区落叶松生长可能受土壤N、P、K供应的限制，3种营养元素的限制作用大小为：K>P>N。 （5）落叶松人工林养分的年吸收量、年存留量和年归还量分别为51.94~78.35 kg•hm-2•a-1、17.77~29.43 kg•hm-2•a-1和34.18~48.92 kg•hm-2•a-1，均随林龄的增长而减少，这与林分密度逐渐减小有关。5种营养元素的年吸收量和年存留量大小均为：Ca>N>K>Mg>P，年归还量大小为：Ca>N>Mg>K>P。落叶松人工林的养分循环速率为0.624~0.658，随林龄的增长而增大。5种营养元素的循环速率以Mg、N最快，Ca、P次之，K最慢。K的循环速率较低，可能与研究区土壤K含量较低而表现出的K再吸收效率较高有关。 （6）施肥导致落叶松叶片N再吸收效率显著降低，而凋落叶片的N浓度显著增加，从而使凋落叶片的C/N比由80.29降低到60.29。施肥林地凋落叶片C/N比的降低使其分解速率加快，有利于其养分归还土壤，从而加快了系统的养分循环速率，提高了系统的养分利用率。因此，在人工林经营中，施肥不仅能提高林地生产力，而且对于维持林地养分循环具有积极作用。

全球变化背景下科尔沁沙地生态系统C、N循环过程

工业革命以来，由于人口的快速增加和人类活动的强烈干扰（主要包括煤炭、石油等石化燃料的燃烧、化肥生产和使用）导致土地利用/覆被变化、大气CO2浓度升高、N沉降等一系列全球环境变化问题。有关陆地生态系统生物地球化学循环，尤其是陆地生态系统C、N循环及其耦合过程方面的研究成为全球变化科学研究领域的重要内容。 干旱/半干旱地区占地球陆地总面积的1/3。与湿润地区相比较，干旱/半干旱地区生态系统稳定性比较差，往往属于生态脆弱区。因此，全球变化对干旱/半干旱地区生态系统影响更加敏感。科尔沁沙地位于我国北方干旱/半干旱地区，是我国典型的农牧交错区和生态脆弱区。科尔沁沙地是世界上人口密度最高的干旱/半干旱地区之一，人类活动对其影响剧烈。然而，有关科尔沁沙地生态系统C、N元素生物地球化学循环过程对土地利用/覆被变化、N沉降等全球变化响应及其反馈机制的研究非常缺乏。因此，本文以科尔沁沙地退化沙质草地、农田、不同年龄樟子松和杨树人工林等生态系统为对象，开展了造林、模拟N沉降和凋落物管理对生态系统C、N元素循环过程影响的研究。 在科尔沁沙地东南缘，以退化沙质草地、樟子松（Pinus sylvestris var. mongolica）人工林（15、24和30年生）、杨树（Poplus xiaozhuanica）人工林（7、11和15年生）为对象，研究草地转变为林地对生态系统C、N储量影响；以退化草地、榆树疏林草地和32年生樟子松人工林为对象，比较草地造林对土壤C、N循环过程及其土壤微生物性状的影响；以农田和5、10、15年生杨树人工林为对象，研究退耕还林对生态系统C、N储量和循环过程影响；以35年生樟子松人工林为对象，模拟研究N沉降和凋落物管理对生态系统C、N循环过程影响。通过上述研究，得到以下主要结果： （1）草地生态系统总C储量为34.38 Mg ha-1，15、24和30年生樟子松人工林生态系统总C储量分别为43.56、60.45和66.59 Mg ha-1，7、11和15年生杨树人工林生态系统总C储量分别为34.54、48.26和78.77 Mg ha-1；与农田相比，退耕5年的杨树人工林生态系统总C库储量下降13%，而10年和15年杨树人工林分别增加了176%和5倍；随着人工林年龄的增加，地上植被生物量C库储量占生态系统总C库储量的比例逐渐增加，并主要分配在树干。草地生态系统总N库储量为2.54 Mg ha-1，15、24和30年生樟子松人工林生态系统总N库储量分别为1.96、2.10和2.19 Mg ha-1，7、11和15年生杨树人工林生态系统总N库储量分别为2.27、1.84和2.60 Mg ha-1；与农田相比，退耕5年的杨树人工林生态系统总N库储量下降32%，而10年和15年杨树人工林分别增加了47%和76%；农田和草地造林后生态系统N储量依然主要分配在土壤中。 （2）草地和农田造林后土壤C、N库储量的变化受多因子的影响，例如林龄、树种种类以及立地条件等。农田和草地造林初期，土壤C、N库储量表现出下降趋势，随着林龄的增加，土壤C、N储量逐渐恢复。草地营造樟子松人工林30年后，0–60 cm深度土壤C、N储量依然显著低于草地；与草地相比，15年生杨树人工林土壤C、N储量差异不显著。在立地条件较好的情况下，10年杨树人工林土壤C、N储量已显著高于农田；然而，在立地条件相对较差的情况下，15年杨树人工林土壤C、N储量仍然与农田相比差异不显著。 （3）土地利用变化能够强烈地改变土壤C、N循环过程。与草地或疏林草地相比，32年生樟子松人工林土壤C、N、P含量显著降低；土壤C、N矿化过程发生显著变化，并且受季节变化的影响；在不同季节，土壤微生物量碳含量、代谢熵（qCO2）、微生物熵（MBC/TOC）以及土壤酶活性等在不同土地利用条件下表现出规律不一致。同样，农田退耕杨树人工林能够显著影响土壤C、N矿化过程，土壤无机氮（铵态氮+硝态氮）含量，土壤微生物量碳含量以及土壤微生物活性。草地造林在一定程度上导致土壤质量下降。而农田造林有利于土壤质量改善，尤其在在立地条件较好情况下。 （4）N添加增加对沙地樟子松人工林地上和地下C、N元素含量影响不大；N添加1年后，仅林下植被C、N含量显著增加，高氮处理（N15）凋落物N含量显著增加。N添加抑制了沙地樟子松人工林凋落物的早期分解和N、P元素释放。5、6、8和9月份土壤无机N含量均随着N输入增加表现出一定程度的增加，然而，7月份N添加导致土壤无机N含量降低。N添加对土壤潜在N矿化速率影响不显著。7和8月份N添加影响土壤C矿化速率，而其它月份影响不显著。低氮处理（N5）有利于增加土壤微生物量碳含量，而高氮处理（N15）在一定程度上降低土壤微生物量碳含量。 （5）凋落物输入变化（凋落物添加和凋落物移出）在一定程度上改变了35年生沙地樟子松人工林生态系统C、N循环过程。凋落物移出（C0）增加了林下植被C含量，降低了树木叶片N含量。凋落物移出抑制了凋落物分解和P元素的释放，而增加了C元素的早期释放速率，对N元素释放过程影响不显著。凋落物输入变化对不同月份土壤无机N含量和土壤N矿化过程影响均不显著。仅在6月份凋落物移出显著抑制了土壤C矿化速率，其它月份差异均不显著。凋落物管理对土壤微生物量碳含量影响不显著。 以上研究结果表明，土地利用变化、N沉降和凋落物输入改变等能够影响半干旱地区沙地生态系统C、N储量和循环过程。尤其是土地利用变化强烈改变沙地生态系统C、N储量、分配格局和循环过程，并且受到多因子的影响。科尔沁沙地樟子松人工林生态系统C、N元素生物地球化学循环存在密切的耦合关系。今后有必要进一步结合3S技术、同位素技术、模型模拟以及分子生物学技术等，从微观-宏观不同尺度上，研究半干旱地区沙地生态系统C、N循环过程对全球变化的响应及其反馈机制。

长白山阔叶红松林碳循环对CO2升高响应过程的模型模拟研究

以长白山原始阔叶红松林和连续多个生长季500ppmCO2处理的红松幼苗为研究对象，采用TECO模型及参数的优化，结合长白山阔叶红松林生态系统的碳通量多年连续监测数据、开顶箱系统(Open-Top-Chambers，高浓度CO2处理)的实地连续监测数据以及相关研究结论的比较，定量模拟生态系统群落水平和个体水平的碳收支(碳通量和碳密度)、碳分配格局和蒸发散等年际变化。模拟结果显示： 1)生态系统群落水平的碳通量和碳密度模拟结果与通量塔监测数据对比发现：长白山阔叶红松林生态系统目前仍是个大气的碳 “汇”。碳汇强度的季节变化波动较大。土壤碳密度占整个阔叶红松林生态系统总密度的67.9%。 2) 开顶箱的个体水平的模型模拟与实地观测显示：CO2升高显著提高红松幼苗的总初级生产力和净初级生产力；地上生物量受到抑制，地下生物量显著增加。 3) CO2对红松幼苗蒸发量和蒸腾量的影响要高于生态系统，CO2提高红松幼苗蒸发量，但对幼苗的蒸腾量影响不大。