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The size of the marine sulfate reservoir has grown through Earth's history, reflecting the accumulation of oxygen into the atmosphere. Sulfur isotope fractionation experiments on marine and freshwater sulfate reducers, together with the isotope record, imply that oceanic Archean sulfate concentrations were <200 microM, which is less than one-hundredth of present marine sulfate levels and one-fifth of what was previously thought. Such low sulfate concentrations were maintained by volcanic outgassing of SO2 gas, and severely suppressed sulfate reduction rates allowed for a carbon cycle dominated by methanogenesis. 相似文献
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Cowen JP Giovannoni SJ Kenig F Johnson HP Butterfield D Rappé MS Hutnak M Lam P 《Science (New York, N.Y.)》2003,299(5603):120-123
Little is known about the potential for life in the vast, low-temperature (<100 degrees C) reservoir of fluids within mid-ocean ridge flank and ocean basin crust. Recently, an overpressured 300-meter-deep borehole was fitted with an experimental seal (CORK) delivering crustal fluids to the sea floor for discrete and large-volume sampling and characterization. Results demonstrate that the 65 degrees C fluids from 3.5-million-year-old ocean crust support microbial growth. Ribosomal RNA gene sequence data indicate the presence of diverse Bacteria and Archaea, including gene clones of varying degrees of relatedness to known nitrate reducers (with ammonia production), thermophilic sulfate reducers, and thermophilic fermentative heterotrophs, all consistent with fluid chemistry. 相似文献
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Philippot et al. (Reports, 14 September 2007, p. 1534) interpreted multiple-sulfur isotopic compositions of approximately 3.5-billion-year-old marine sulfide deposits as evidence that early Archaean microorganisms were not sulfate reducers but instead metabolized elemental sulfur. However, their data can be better explained by a scenario involving poor mixing of photochemical and surface sulfide sources. 相似文献
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Extremely thermophilic archaebacteria are known to be metabolizers of elemental sulfur and the methanogens. A novel group of extremely thermophilic archaebacteria is described, which consists of sulfate-respiring organisms that contain pure factor 420 and that have been isolated from marine hydrothermal systems in Italy. They possess a third type of archaebacterial RNA polymerase structure previously unknown, indicating an exceptional phylogenetic position. Most likely, this group represents a third major branch within the archaebacteria. The existence of sulfate reducers at extremely high temperatures could explain hydrogen sulfide formation in hot sulfate-containing environments, such as submarine hydrothermal systems and deep oil wells. 相似文献
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李新 《农业图书情报学刊》2021,33(2):4-11
[目的/意义]以机器人核心关键技术RV减速机为切入点,系统、深入地剖析技术研发现状,梳理技术发展脉络,透视中国在该领域技术创新的现状和不足.[方法/过程]采用对标研究方法,围绕中日RV减速机专利技术发展历程、中日专利技术竞争者分析、专利技术研发布局、高价值专利、专利申请的法律状态等方面,对中国和日本的RV减速机技术研发... 相似文献
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减阻剂在我国输油管道上的应用试验 总被引:14,自引:1,他引:13
减阻剂是一种高分子聚合物的化学制品,能减少液体在管道内流动的摩阻。国外在7工就开始将减剂应用在原油管道上,我国于80年代中期才开始在原油管道上进行减阻剂的试验。对减阻剂的减阻机理和特性作了分析,并着重介绍了利用国外减阻剂在国内几要输油管道上做应用试验的情况,大量的试验证明了减阻剂的减效果,同时指出,在我国的输油管道上的应用减阻剂有着广阔的前景,对输油管道的增输,节能降耗,提高经济效益和社会效益都能 相似文献
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对输气管道泄漏音波的产生和传播特性进行研究,分析了泄漏音波产生的形式,获得了音波信号的时域、频域及时频特征。结果显示:泄漏音波主要由介质与管道相互作用产生的单极子、偶极子和四极子声源所引起,表现为时域上能量突变,但所占时域较窄,所占频域较宽,主要能量集中在0-100Hz。利用软件对泄漏音波在特殊管件(弯管、变径、分支)中的传播特性进行模拟研究,并利用高压输气管道泄漏装置进行试验研究,分析了泄漏音波信号的传播规律,确定了影响音波信号衰减的主要因素。结果显示:音波在管内以平面波形式传播,随着传播距离的增大,音波基本呈指数规律衰减,在较低泄漏量下,泄漏音波信号幅值基本与泄漏孔径无关:音波信号经弯管和直管的损失基本为0,经分支和变径管损失较大。根据拟合计算结果,对于现有型号的音波传感器,其理论安装距离可达100km,利于长输管道的泄漏检测。 相似文献
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SRB处理硫酸盐废水的静态试验研究 总被引:1,自引:0,他引:1
硫酸盐还原菌 SRB 处理硫酸盐废水的试验表明,厌氧环境下的硫酸盐去除率大于有氧环境下的去除率;随着反应时间的增加,溶液的 pH 值呈增加趋势;溶液的 COD/SO_4~2-比值对硫酸盐的去除率有较大影响。去除率随 COD/SO_4~2-比值的增大而增加;弱碱性(pH 值7.17左右)环境下,硫酸盐还原菌对硫酸盐的去除效果最佳;溶液中含有适当的铁离子可促进硫酸盐还原菌的生长,增加其对硫酸盐的去除率;对溶液不同时刻的碱度测试结果表明,硫酸盐还原菌还原硫酸盐的过程是一个碱度升高的过程。 相似文献
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[目的]研究硫酸阿米卡星在鳗鲡体内的药物代谢动力学及其在组织中的残留.[方法]利用高氯酸提取、固相萃取净化组织,2,4,6-三硝基苯磺酸、吡啶、4-二甲基氨基吡啶、三氟乙酸柱前衍生后,采用高效液相紫外检测法测定硫酸阿米卡星在鳗鲡体内药代动力学和残留.[结果]利用衍生法所得药物在0.05 ~50 μg/ml浓度范围内线性关系良好(R=0.9995),最低检测限为0.05 μg/ml.血液和肌肉中的平均回收率分别为75.9%和76.9%.鳗鲡在(26±1)℃以50 mg/kg单剂量肌肉注射给药物后,鳗鲡血液中的药-时曲线符合一级吸收二室模型.达峰时间为0.597.h,分布半衰期为3.52 h,表明硫酸阿米卡星在鳗鲡体内吸收分布迅速.峰浓度为22.229μg/ml,消除半衰期为46.945 h,推测该药物可能残留时间较长.鳗鲡在(26±1)℃下50 mg/kg单剂量肌肉注射硫酸阿米卡星后,5d后在肌肉组织中未检出,19 d后血液中未检出.[结论]鳗鲡肌肉注射阿米卡星后,停药期为475 ~ 513 d. 相似文献
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[目的]探讨敌百虫和硫酸铜与硫酸亚铁合剂2种防治药物对星斑川鲽(Platichthys stellatus)的安全用量范围。[方法]在水温15~17℃、盐度3.0%~3.2%的条件下,分别测定了敌百虫、硫酸铜与硫酸亚铁合剂对体长18~21 cm、平均体重194.1 g的星斑川鲽的急性毒性。[结果]敌百虫对星斑川鲽24、48 h的LC50分别为3.63和3.31 mg/L,安全浓度为0.83 mg/L;硫酸铜与硫酸亚铁合剂对星斑川鲽24、48 h的LC50分别为9.55和6.92 mg/L,安全浓度为1.09 mg/L。根据安全浓度判断,星斑川鲽对2种药物的敏感性为:敌百虫硫酸铜与硫酸亚铁合剂。[结论]在星斑川鲽疾病防治过程中应慎用或者降低浓度使用敌百虫或硫酸铜与硫酸亚铁合剂。 相似文献
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[目的]研究防治黄颡鱼斜管虫和杯体虫病安全有效的药物、剂量及用法。[方法]对患有斜管虫和杯体虫病的黄颡鱼用硫酸铜、硫酸铜和硫酸亚铁合剂(5∶2)、硫酸锌、硫酸锌和聚维酮碘制剂、福尔马林和优马林6种药物在3个浓度下使用遍洒法进行正交叉试验,以确定安全有效地防治斜管虫和杯体虫病的药物及剂量。[结果]硫酸锌和聚维酮碘制剂对黄颡鱼斜管虫和杯体虫病的防治效果最好,优马林、硫酸硫酸锌次之,硫酸铜、硫酸铜与硫酸亚铁合剂、福尔马林的防治效果较差。[结论]治疗黄颡鱼斜管虫和杯体虫病的最佳药物是硫酸锌和聚维酮碘制剂,其用药浓度为:硫酸锌0.60 mg/L、聚维酮碘2.00 mg/L;优马林0.50 mg/L也是治疗黄颡鱼斜管虫和杯体虫病的有效药物。 相似文献
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添加葡萄糖及硫酸铵对水稻土微生物生物量和功能多样性的影响 总被引:4,自引:0,他引:4
【目的】高养分浓度可能对土壤的碳氮转化和微生物特性产生显著影响。研究高养分浓度下添加葡萄糖对土壤中碳氮的转化调控及其微生物变化特征,可为正确认识特殊条件下养分转化过程特性,提出提高氮素利用效率的措施提供科学参考。【方法】采集中国亚热带地区典型的水稻土样品,设置不同硫酸铵用量和葡萄糖添加量处理,布置室内培育试验,研究了不同处理下土壤中NH4+-N、NO3--N、矿质氮、微生物生物量及微生物群落功能多样性变化。【结果】与不添加葡萄糖处理相比,高硫酸铵用量处理下,添加不同浓度葡萄糖处理NH4+-N、NO3--N和矿质氮变幅分别为-4.3%-10.2%、-8.0%-41.8%和-3.9%-10.4%,而微生物量碳显著增加了89.6%-126.7%,微生物量氮增加了11.5%-109.0%。中等硫酸铵用量处理下,添加葡萄糖处理NH4+-N、NO3--N和矿质氮浓度变幅分别为-7.5%-5.8%、6.1%-58.3%和-7.2%-49.4%;微生物量碳氮也有增大趋势。BIOLOG分析显示,高、中硫酸铵用量处理下,AWCD值、Shannon、Simpson和McIntosh指数一直处于较低水平。与常规硫酸铵用量处理相比,仅添加葡萄糖和常规硫酸铵用量下添加葡萄糖后,NH4+-N、NO3--N和矿质氮浓度显著降低了17.3%-29.0%、21.4%-92.9%和18.8%-45.9%,微生物量碳、氮没有显著增加,AWCD值和微生物功能多样性指数水平较高。葡萄糖及硫酸铵对土壤微生物量碳和AWCD值的影响存在交互作用。【结论】较高的养分浓度下添加葡萄糖,调节了土壤C/N比,土壤微生物活动增强,提高了氮素的生物固持效率,降低了土壤中无机氮的含量。在当前大量施用无机氮肥背景下,尤其要重视有机无机肥配合,调控氮素转化过程,降低氮素损失风险。 相似文献
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An experiment was carried out to investigate the relative bioavailability of tribasic zinc(Zn) sulfate relative to Zn sulfate for broilers fed a conventional corn-soybean meal diet. A total of 504 1-d-old Arbor Acres commercial male chicks were randomly assigned by body weight of birds to one of seven treatments involving a 2×3 factorial arrangement with three levels of added Zn(30, 60, or 90 mg of Zn kg–1) and two Zn sources(tribasic Zn sulfate and Zn sulfate) plus a control with no added Zn for an experimental phase of 14 d. Plasma Zn, tibia ash Zn, pancreas Zn, and pancreas metallothionein(MT) messenger RNA(m RNA) were analyzed at 6 or 14 d of age post-hatching. The results showed that plasma Zn, tibia ash Zn, pancreas Zn, and pancreas MT m RNA increased linearly(P0.002) as dietary Zn concentration increased at 6 or 14 d of age. The R2 for a linear model was greater on d 6 than on d 14 for the above 4 responsive criteria, and among these indices, the fitting of the tibia ash Zn concentration was the best(R2=0.99). Therefore, based on slope ratios from the multiple linear regressions of the above 4 indices of the birds at 6 d of age on daily intake of dietary Zn, the bioavailabilities of tribasic Zn sulfate relative to Zn sulfate(100%) were 95.6%(P=0.18), 83.5%(P=0.01), 87.9%(P=0.53), and 75.9%(P=0.38) for the tibia ash Zn, pancreas Zn, plasma Zn, and pancreas MT m RNA, respectively. The results indicated that generally, Zn from tribasic Zn sulfate was as available as Zn from Zn sulfate for broilers. 相似文献
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通过室内模拟试验,研究了硫铵、尿素对绿麦隆在土壤中吸附、解吸作用的影响。结果表明,当绿麦隆与硫铵或尿素同时施入土壤后,土壤对绿麦隆的吸附作用增加,并随氮肥浓度的增加吸附作用增强;用氮肥培养土壤6d后加入绿麦隆,吸附能力为尿素处理>对照>硫铵处理,与未经培养的处理相比降低了6.18% ̄30.99%,这与土壤中DOC的含量和种类有关。解吸试验表明,绿麦隆从未经硫铵或尿素培养土壤上的解吸能力高于对照10.53% ̄38.60%,而其从用硫铵和尿素培养6d土壤上的解吸能力与对照无明显差异。另外,其与未经培养的土壤相比,解吸能力增加了大约2倍。这些结果表明,硫铵和尿素影响绿麦隆在土壤中的吸附、解吸作用,从而影响绿麦隆在土体中的迁移。 相似文献