Sulphate reduction in oxic and sub-oxic North-East Atlantic sediments

Abstract Oxic and sub-oxic N.-E. Atlantic sediments were examined for sulphate-reducing activity. Oxygen and/or nitrate reduction are probably the dominant mineralisation processes in the abyssal plain sediment studied. A low rate of sulphate reduction (0.1 nmol SO²⁻₄/ml/day) was recorded in the surface 5 cm of the continental slope sediment, together with the presence of a range of sulphate-reducing bacteria (SRB). A higher activity of sulphate reduction (2.2 nmol SO²⁻₄/ml/day) occurred in the continental shelf sediment which led to a small decrease in pore water sulphate and an increase in titration alkalinity. This sediment contained approx. 10²–10³ acetate, lactate and propionate oxidising SRB/ml. No low- M _r organic acids were detected in these sediments. However, amendment with 75 μM acetate stimulated sulphate-reducing activity in the shelf sediment.     

A phytosociological study of weed communities on the southwestern Coastal Plain of North Carolina

Summary The vegetation of cultivated, fallow and ‘old’ fields of Scotland County, N.C. was both randomly and subjectively sampled throughout the growing season of 1973. Relevés were placed in each of the above management units, and the data collected in this relevé analysis were sorted into phytosociological charts, with the aid of the digital computer. Weed associations delimited in the charts reflected the importance of edaphic factors, time (aspect), and man's agricultural activities as causal factors in the determination of characteristic assemblages of weeds. Several character and differential species were denoted, in a tentative classification of the weed associations. The cultivated and fallow stands in the spring aspect were noted to be dominated by a group of spring annuals. Summer annuals were more prevalent in homologous situations in the summer. It was determined that perennials, appearing mainly as seedlings in cultivated and fallow fields, attained dominance in ‘old’ fields, one to five years in age. Within each of the major spheres of management, and in each season, associations of weeds mainly reflected differences in edaphic factors. Many character species were noted to maintain affinities to an assortment of soil types that ranged from moist loams to xeric, sterile sands. A study of roadsides, hedgerows, field margins and other ecotonal areas inhabited by weeds was carried throughout the growing season of 1973, also. Species presence was documented in each of these habitat types and reported in Sharp (1974). The weed flora of Scotland County was found to be rich in species. A total of 506 species representing 248 genera and 80 families were encountered throughout the study. Of the total number of species listed, approximately 25 percent were of foreign origin, and 28 percent represented additions to the flora of Scotland County. This paper is the short version of a masters thesis for the Department of Botany, University of North Carolina at Chapel Hill. The author would like to extend his appreciation and gratitude to Professors H. Lieth, A. E. Radford and J. Hardin for their generous advice and encouragement extended through the duration of the study.     

Les cabanes de type « Anosovka-Mézine » du site de Yudinovo : éléments de construction,architecture, classification

The study is focused on comparative analysis of the five dwellings of the Anosov-Mezin type from the East-Epigravettian site of Yudinovo (Bryansk region, Russia). The analysis is based on data on previously unknown structural elements and methods of installation of mammoth skulls in the basement of dwelling N^o 5, which were revealed during excavations in 2015–2018. Apart of this the non-utilitarian actions that accompanied the process of dwellings construction was considered. Based on the revealed differences in structural elements and features, it was suggested that the currently used concept Anosovka-Mezin type of dwellings includes two types of the circular structures made of skulls and large mammoth bones.     

三江平原湿地开垦对土壤氨基糖积累特征的影响

微生物残体在土壤有机质的形成和稳定过程中发挥着重要作用,但湿地开垦对土壤微生物残体积累特征的影响尚不清楚。本研究以三江平原小叶章湿地为对象,采集原始自然湿地和开垦改种豆科作物后不同耕作年限(5年、10年和25年)的土壤,以氨基糖为微生物残体的标识物,探讨湿地开垦对土壤微生物残体积累特征的影响。结果表明: 自然湿地开垦为农田后显著降低了土壤中氨基糖的含量,且随着开垦年限的增加,氨基糖的损失比例也增加。与自然湿地相比,开垦25年后土壤中的氨基葡萄糖、氨基半乳糖和胞壁酸含量分别下降38.0%、38.1%和35.9%,且在开垦最初5年中细菌来源的胞壁酸下降速率(25.8%)远高于真菌来源的氨基葡萄糖(14.9%),说明短期内湿地开垦对细菌的影响较真菌更加迅速。湿地开垦为农田5、15和25年后,土壤氨基糖总量分别下降21.1%、34.0%和38.0%;同时,氨基糖总量占土壤有机质的比例也受到湿地开垦的显著影响,由自然湿地中的4.8%降至开垦25年后的4.4%。这说明长期湿地开垦加速了土壤有机质中微生物来源有机组分的分解转化,进而改变土壤有机质的组成。这些变化将影响湿地生态系统中土壤有机质的长期稳定和功能演变。     

Potential roles and targeted therapy of the CXCLs/CXCR2 axis in cancer and inflammatory diseases

The chemokine receptor CXCR2 and its ligands are implicated in the progression of tumours and various inflammatory diseases. Activation of the CXCLs/CXCR2 axis activates multiple signalling pathways, including the PI3K, p38/ERK, and JAK pathways, and regulates cell survival and migration. The CXCLs/CXCR2 axis plays a vital role in the tumour microenvironment and in recruiting neutrophils to inflammatory sites. Extensive infiltration of neutrophils during chronic inflammation is one of the most important pathogenic factors in various inflammatory diseases. Chronic inflammation is considered to be closely correlated with initiation of cancer. In addition, immunosuppressive effects of myeloid-derived suppressor cells (MDSCs) against T cells attenuate the anti-tumour effects of T cells and promote tumour invasion and metastasis. Over the last several decades, many therapeutic strategies targeting CXCR2 have shown promising results and entered clinical trials. In this review, we focus on the features and functions of the CXCLs/CXCR2 axis and highlight its role in cancer and inflammatory diseases. We also discuss its potential use in targeted therapies.     

华北驼绒藜种群数量动态与生殖特性的相关性

采用立木级法研究华北驼绒藜种群的大小级结构,利用各龄级的存活数编制种群静态生命表和存活曲线,构建时间序列预测图对种群数量动态过程进行预测,利用生活史特征观察结果分析其生殖对策,探讨了生殖特性与种群动态的关系。结果表明:华北驼绒藜种群幼龄和老龄级个体数较少,中龄级个体数量较多,呈稳定或衰退趋势;种群生命表和存活曲线的分析表明,尽管生境条件不同,但存活曲线基本接近DeeveyⅢ型;种群数量的时间序列预测表明,华北驼绒藜种群会随时间推移,呈现老龄级株数先增加后减少的趋势,种群稳定性长期维持困难;生活史特征表明,华北驼绒藜在长期进化过程中形成了兼具r-对策和k-对策的双重特性来维持种群的相对稳定。良好的生殖适应性是物种发展的关键,华北驼绒藜种群年龄结构、生命表、存活曲线以及时间序列预测图反映出其种群数量动态与生殖特性具有密切的相关性,传粉系统效率低、胚胎发育过程营养失调、种子向幼苗的转化率低以及种群更新对母株的依赖性强等生殖生物学特性与种群动态相吻合;生境恶劣和人为干扰也成为其种群发展的制约因素。     

Early-stage litter decomposition and its influencing factors in the wetland of the Sanjiang Plain, China

Using the litter bag technique, the decomposition rates and their influencing factors were studied by investigating three wetland macrophytes, Calamagrostics angustifolia, Carex meyeriana and Carex lasiocapa, in Sanjiang Plain, Northeast China. It was revealed that C. lasiocapa lost 28.91% of its weight, C. angustifolia lost 31.98% and C. meyeriana lost 32.99% after 164 days. Another finding was that the amount of organic carbon in the litter of C. angustifolia and C. lasiocapa fluctuated, but continuously decreased in that of C. meyeriana. However, all the three types of litter released organic carbon. Nitrogen was released substantially from the litter of both C. angustifolia and C. meyeriana, but accumulated in the litter of C. lasiocapa. Phosphorus concentrations in all the three types of litter apparently decreased first and then slightly increased. Overall, P release was observed in all the three types of litter. The C/N and C/P ratios varied significantly in the decomposition process. The decomposition rates and nutrient content variations were simultaneously influenced by the quality of the litter as well as the environmental factors in the Sanjian Plain, but they were more strongly affected by the quality of the litter.     

Migration and retention of dissolved iron in three mesocosm wetlands

Three mesocosm wetlands (250 cm × 100 cm × 100 cm) with different wetland plants (Calamgrostis angustifolia, CA, Carex lasiocarpa, CL, and C. angustifolia/C. lasiocarpa mixture, AL, respectively) and hydrologic regimes were set to test migration and retention of exogenous dissolved iron ((NH₄)₂Fe(SO₄)₂of 40 mg Fe(II) L⁻¹) in the Sanjiang Plain Wetland in northeast China. The experiment was designed as two stages: open migration period (OMP) for 1.5 d and close retention period (CRP) for 28.5 d. Based on the outflow Fe(II) concentration during the OMP, retention efficiencies (RE) and iron retention fluxes adjusted by area (RF_ad) in the three mesocosm wetlands were calculated, and the migration of iron were modeled using the first-order kinetic model. Outflow pH decreased gradually from a weak alkaline condition to a weak acid condition during the OMP, and then increased during the CRP, while outflow Eh and DO decreased during the experiment. The three mesocosm wetlands had considerable RE ranging from 75% to 98%, with the averaged RF_ad of 4.31 ± 0.17, 4.20 ± 0.16, and 4.37 ± 0.13 g m⁻² h⁻¹ for CA, CL, and AL, respectively. The reduction conditions in the mesocosm wetlands developed after 4 d or 12 d and the former retained iron during the OMP became mobile and discharged primarily in the form of Fe(III). The first-order kinetic model could simulate the outflow concentration of dissolved iron during the OMP (R² = 0.91, 0.69, and 0.68 for CA, CL, and AL, respectively), while the outflow dissolved iron during the CMP was difficult to model because the changed pH and Eh conditions in the mesocosm wetlands cause the former precipitated iron to be mobile after several days.     

Spatial and temporal variation of atmospheric nitrogen deposition in the North China Plain

A monitoring network of nine sites was established to determine the spatial and temporal variation of atmospheric nitrogen (N) deposition in the North China Plain (NCP) over a two-year period. The annual bulk deposition of inorganic N in the North China Plain ranged from 18.4 to 38.5 kg/hm² and averaged 28.0 kg/hm². The concentration of NH₄ -N and NO₃^--N in rainwater averaged 3.76 and 1.85 mg/L, respectively, which were significantly higher than the values at background sites in China (normally less than 0.5 mg/L). Annual bulk deposition of inorganic N in the Beijing area (32.5 kg/hm²) was higher than that in Shandong and Hebei provinces (21.2 kg/hm² on an average). Also bulk N deposition was much greater in Dongbeiwang and Fangshan than in Yanqing and Shunyi counties. Significant spatial variation of bulk deposition was observed in the Beijing area because of variation of precipitation, and 60% of bulk deposition occurred from June to September. Bulk deposition of NH₄ -N was 2.0 times that of NO₃^--N deposition at the rural monitoring sites. However, the situation was reversed at the Beijing Academy of Agricultural-Forestry Sciences (BAAFS), the unique urban monitoring site. The results suggest that reduced N in precipitation is dominant in rural regions, but oxidized N is the major form in urban regions. The positive relationship between inorganic N deposition and precipitation can be fitted by a power equation (r²= 0.67), showing an increase of NH₄ -N and NO₃^--N inputs with increased precipitation. Wet deposition of N accounted for 73% of the bulk deposition, implying that dry deposition of N, particularly NH₄ -N from dust, is important in the North China Plain.     

高羊茅草对盐碱地原油污染土壤微生物的影响

采用常规土壤理化分析和Biolog-Eco微孔板鉴定系统,研究了松嫩平原盐碱土地区高羊茅草的生长对原油污染土壤pH、总盐含量和微生物群落的影响.结果表明: 石油污染导致表征土壤微生物代谢活性的平均颜色变化率(AWCD)、物种多样性指数和碳源利用数增加, 微生物碳源利用模式发生改变.高羊茅草对石油污染土壤有较好的修复作用,降低了土壤pH和石油烃(TPH)含量,提高了土壤含水率.高羊茅草根际土壤的AWCD和碳源利用丰富度指数明显高于裸地土壤,为其根际微生物的生长发育提供了适宜的环境.