187 research outputs found
Autoimmune Glial Fibrillary Acidic Protein Astrocytopathy With Visual Field Defect: A Case Report
No full textDepartment of Neurology, The University of Hong Kong-Shenzhen Hospital, Shenzhen, PR Chin
Correction: Corrigendum: Diabetes Onset at 31–45 Years of Age is Associated with an Increased Risk of Diabetic Retinopathy in Type 2 Diabetes
No full textScientific Reports 6: Article number: 38113; published online: 29 November 2016; updated: 26 May 2017 The original version of this Article incorrectly included Haibing Chen as a corresponding author. This error has now been corrected in the PDF and HTML versions of this Article.</jats:p
BOOLEAN MATRIX DECOMPOSITION AND EXTENSION WITH APPLICATIONS
No full textBoolean matrix decomposition (BMD) refers to decomposing of an input Boolean matrix into a product of two Boolean matrices, where the first matrix represents a set of meaningful concepts, and the second describes how the observed data can be expressed as combinations of those concepts. As opposed to standard matrix factorization, BMD focuses on Boolean data and employs Boolean matrix prod-uct instead of standard matrix product. The key advantage of BMD is that BMD solutions provide much more interpretability, which enable BMD to have wide applications in multiple domains, including role mining, text mining, discrete pat-tern mining, and many others. There are three main challenges in the research of BMD. First, real applica-tions carry varying expectations and constraints on BMD solutions, which make the task of searching for a good BMD solution nontrivial. Second, BMD by itself has the issue of insufficiency in modeling some real data semantics, as only the set union operation is employed in combination. Third, BMD variants are generally i
Soil organic carbon mineralization and sequestration and its microbial influencing mechanisms under the driving of water erosion and vegetation restoration on the Loess Plateau
No full text水力侵蚀（简称侵蚀）与侵蚀劣地植被恢复（简称植被恢复）是土壤碳库的重要驱动因子，能够显著影响土壤碳库的封存与流失。在过去几十年，国内外学者针对侵蚀与植被恢复过程土壤有机碳库的动态变化进行了广泛探讨，但有关侵蚀与植被恢复环境土壤有机碳动态的微生物作用机制仍缺乏深入了解。因而，进一步研究黄土高原侵蚀与植被恢复环境微生物主导的有机碳矿化与固定潜力及其与土壤生物、非生物因子间的内在联系，对于揭示土壤侵蚀在全球碳循环中的角色定位以及探明微生物在土壤碳循环中所起的作用都具有重要意义。本研究选取黄土高原典型坝控小流域-桥子沟流域为研究对象，应用定量PCR、高通量测序与13C稳定同位素标记等分析技术，研究了侵蚀与植被恢复体系微生物主导的有机碳矿化与固定潜力及其影响机制。主要结论如下：
（1）阐明了坡面侵蚀与沉积环境土壤有机碳矿化的微生物作用机制。研究结果表明侵蚀区（坡上、坡中）细菌丰度显著高于沉积区（坡下），而细菌物种多样性与群落组成并无明显差异。此外，沉积区土壤有机碳矿化速率为19.02 mg CO2-C kg-1 d-1，分别是坡上与坡下侵蚀区的1.26和1.07倍；有机碳矿化比呈现出坡中（0.082 g CO2-C g-1 SOC）>坡上（0.070 g CO2-C g-1 SOC）>坡下（0.064 g CO2-C g-1 SOC）的变化规律。侵蚀诱导土壤团聚体的破裂虽增加了侵蚀区土壤有机碳被微生物矿化分解的风险，但表层土壤活性有机碳的大量流失导致其可供微生物分解的有机碳量减少，其CO2释放速率也相应降低。多元逐步回归分析结果表明碱解氮是土壤有机碳矿化的主要解释变量（60.2%）。相对细菌丰度与物种多样性，活性有机质是侵蚀坡面土壤有机碳矿化的主要调控因子。侵蚀坡面细菌丰度与有机碳矿化速率的空间分布异质性否定了土壤有机碳矿化微生物控制学说。研究结果表明土壤微生物对有机碳矿化表现出明显的功能冗余特征，侵蚀诱导微生物丰度与物种多样性的适度改变不会对土壤有机碳矿化产生显著影响。
（2）揭示了流域沟蚀作用下自养细菌群落与微生物固碳潜力的变化特征。 研究发现坡耕地自养细菌丰度与物种多样性指数分别是淤地坝的1.70和1.10倍，沟蚀诱导养分贫瘠土壤的沉积显著降低了淤地坝总自养细菌丰度与物种多样性，而以大气CO2为专一碳源的专性自养菌相对丰度却得到显著提升，如硫杆菌（Thiobacillus）。此外，淤地坝微生物固碳速率为5.002 Mg C km-2 yr-1，是对应坡耕地的4.67倍；微生物固碳速率与有机碳含量，多数兼性自养菌相对丰度，总自养微生物丰度与物种多样性指数存在显著负相关关系，而与多数专性自养菌相对丰度显著正相关。因而，专性自养菌可能是微生物固碳的主要贡献者。逐步回归分析结果表明，可溶性有机碳是土壤微生物固碳速率的主要解释变量（72.0%），流域侵蚀通过影响活性有机碳的空间分布可有效改变自养微生物群落结构，如兼性自养菌与专性自养菌的占比，进而影响侵蚀与沉积环境土壤微生物固碳潜力。
（3）揭示了侵蚀劣地植被恢复过程土壤微生物与有机碳矿化速率间的内在联系。研究结果表明植被恢复区土壤细菌丰度（1.47 × 107 copies g-1）显著低于坡耕地（8.39 × 108 copies g-1），而植被恢复区土壤真菌:细菌比是侵蚀区的7.68倍，侵蚀劣地植被恢复过程土壤微生物由细菌为主导的群落向以真菌为主导的群落演变。此外，植被恢复区土壤有机碳矿化速率是侵蚀区的1.29倍，土壤碳矿化比则表现出相反的变化趋势，侵蚀劣地植被恢复虽降低了土壤有机碳被微生物矿化的风险，但植被恢复区活性有机质含量的增高显著提升了土壤CO2释放速率。多元统计分析结果表明，可溶性有机碳是土壤有机碳矿化的主要解释变量（68.5%），侵蚀劣地植被恢复过程土壤活性有机质含量的高低在一定程度上调控着土壤CO2释放速率的快慢。研究指出土壤微生物是有机碳矿化的主要承担者而非关键调控者。
（4）阐明了自养细菌群落与微生物固碳潜力对侵蚀劣地植被恢复的响应特征。研究结果表明侵蚀劣地植被恢复32年，植物碎屑与根系分泌物的大量输入虽有助于土壤碳、氮库的提升，但小冠花植物巨大的蒸腾损耗显著降低了土壤水分含量。植被恢复过程土壤有效水分的降低抑制了自养微生物的快速生长与增殖，致使植被恢复区土壤自养细菌丰度与物种多样性显著低于侵蚀劣地。此外，侵蚀劣地土壤微生物固碳速率为1.114 Mg C km-2 yr-1，是植被恢复区的1.748倍。主成分分析结果表明，微生物固碳速率与土壤水分、自养细菌丰度与物种多样性呈正向耦合关系，而与土壤碳、氮养分呈负向耦合关系。干旱半干旱区植被恢复诱导土壤水分的降低是微生物固碳潜力的主要限制因素，且其主要通过改变自养细菌群落来实现。
总的来说，侵蚀与植被恢复环境土壤有机碳矿化主要受有机质自身质量所调控，微生物对土壤有机碳矿化特征表现出明显的功能冗余，微生物是土壤有机碳矿化的主要“承担者”而非关键“调控者”。此外，微生物固碳速率与专性自养微生物相对丰度显著正相关，专性自养菌可能是土壤微生物固碳的主要“贡献者”。植被恢复诱导土壤水分的降低抑制了自养菌群的快速增殖，尤其是兼性自养菌，且进一步降低了微生物固碳潜力。该研究改变了微生物丰度决定土壤有机碳矿化速率的传统观念，证实了微生物在土壤有机碳矿化中的功能冗余与固碳中的关键贡献，为侵蚀与植被恢复体系土壤有机碳动态模拟与研究提供了新的思路。</p
Over-expression of the Arabidopsis proton-pyrophosphatase AVP1 enhances transplant survival, root mass, and fruit development under limiting phosphorus conditions
No full textabstract: Phosphorus (P), an element required for plant growth, fruit set, fruit development, and fruit ripening, can be deficient or unavailable in agricultural soils. Previously, it was shown that over-expression of a proton-pyrophosphatase gene AVP1/AVP1D (AVP1DOX) in Arabidopsis, rice, and tomato resulted in the enhancement of root branching and overall mass with the result of increased mineral P acquisition. However, although AVP1 over-expression also increased shoot biomass in Arabidopsis, this effect was not observed in tomato under phosphate-sufficient conditions. AVP1DOX tomato plants exhibited increased rootward auxin transport and root acidification compared with control plants. AVP1DOX tomato plants were analysed in detail under limiting P conditions in greenhouse and field trials. AVP1DOX plants produced 25% (P=0.001) more marketable ripened fruit per plant under P-deficient conditions compared with the controls. Further, under low phosphate conditions, AVP1DOX plants displayed increased phosphate transport from leaf (source) to fruit (sink) compared to controls. AVP1DOX plants also showed an 11% increase in transplant survival (P<0.01) in both greenhouse and field trials compared with the control plants. These results suggest that selection of tomato cultivars for increased proton pyrophosphatase gene expression could be useful when selecting for cultivars to be grown on marginal soils
Changes in microbial communities and respiration following the revegetation of eroded soil
No full textIt is necessary to assess the responses of microbial communities and respiration to the revegetation of eroded soils for understanding the dynamics of soil carbon (C) pools and fluxes. In this study, three typical abandoned croplands (CL1, CL2 and CL3) and three secondary grasslands planted with Coronilla varia (GL1, GL2 and GL3)
on the Loess Plateau of China were selected for sampling, and quantitative polymerase chain reaction (qPCR) and high-throughput sequencing were applied to intuitively discern differences in the soil bacteria and fungi. Our results showed that bacterial abundance in the abandoned croplands was 57 times higher than that of the secondary grasslands (P < 0.05), but no obvious changes (P > 0.05) in fungal abundance and microbial diversity were observed after 31 years of revegetation. We observed positive responses in Actinobacteria, Firmicutes, Zygomycota and Ciliophora and negative responses in Bacteroidetes and Planctomycetes to revegetation. In addition, the maximum soil microbial respiration was observed in the GL3 site (20.86 ± 0.69 mg CO2-C kg-1 soil d-1) followed by the GL1 site (19.97 ± 0.65 mg CO2-C kg-1 soil d-1), so revegetation significantly improved (P < 0.05) soil microbial respiration. Multiple stepwise regression analysis showed that dissolved organic carbon (DOC) explained up to 68.5% of the variation in soil microbial respiration, which indicated that the effects of changes in microbial properties in response to revegetation on soil microbial respiration were likely to be smaller than the potential effects of changes in the quality of organic matter. Labile organic matter is the primary rate-limiting factor for soil microbial respiration.</p
Microbial CO2 assimilation is not limited by the decrease in autotrophic bacterial abundance and diversity in eroded watershed
No full textThe impacts of soil erosion on soil structure, nutrient, and microflora have been extensively studied but little is known about the responses of autotrophic bacterial community and associated carbon (C)-fixing potential to soil erosion. In this study, three abandoned croplands (ES1, ES2, and ES3) and three check dams (DS1, DS2, and DS3) in the Qiaozi watershed of Chinese Loess Plateau were selected as eroding sites and depositional sites, respectively, to evaluate the impacts of soil erosion on autotrophic bacterial community and associated C-fixing potential. Lower abundance and diversity of autotrophic bacteria were observed in nutrient-poor depositional sites compared with nutrient-rich eroding sites. However, the relative abundances of obligate autotrophic bacteria, such as Thiobacillus and Synechococcus, were significantly enhanced in depositional sites. Deposition of nutrient poor soil contributed to the growth of obligate autotrophic bacteria. The maximum microbial C-fixing rate was observed in DS1 site (5.568 ± 1.503 Mg C km-2 year-1), followed by DS3 site (5.306 ± 2.130 Mg C km-2 year-1), and the minimum was observed in ES2 site (0.839 ± 0.558 Mg C km-2 year-1). Soil deposition significantly enhanced microbial C-fixing rate. Assuming a total erosion area of 1.09 × 107 km2, microbial C-fixing potential in eroded landscape can range from 0.01 to 0.06 Pg C year-1. But its effect on the C pool recovery of degraded soil is limited. Dissolved organic C (DOC) was the main explanatory factor for the variation in soil microbial C-fixing rate (72.0%, P = 0.000).</p
Soil erosion-related dynamics of soil bacterial communities and microbial respiration
No full textSoil erosion can dramatically change physicochemical soil properties, but little is known about the responses of bacterial communities and microbial respiration to soil erosion. In this study, three sites (upslope, mid-slope and downslope) with different erosional and depositional characteristics were selected along three transects of abandoned land in the Qiaozi watershed of the Chinese Loess Plateau to evaluate the impacts of soil erosion on bacterial communities and microbial respiration. Samples of the topsoil (0–10 cm) and subsoil (10–20 cm), classified as Calcic Cambisols, were collected from these sites. The results showed that lower bacterial abundance was observed in the topsoil of the downslope site (7.58 × 108 copies g-1 soil) relative to the upslope (9.32 × 108 copies g-1 soil) and mid-slope (8.70 × 108 copies g-1 soil) sites. However, no obvious change (P > 0.05) in the bacterial Shannon index and community composition was observed among the sites. Runoff induced erosion and migration of sediment homogenized the bacterial communities along the eroded slopes. Soil microbial respiration in the topsoil of the downslope site (19.02 ± 0.25 mg CO2-C kg-1 soil d-1) was sig nificantly (P < 0.05) higher than that of the upslope (15.12 ± 1.07 mg CO2-C kg-1 soil d-1) and mid-slope (17.75 ± 0.73 mg CO2-C kg-1 soil d-1) sites, indicating that the deposition of sediment and associated organic matter significantly increased the soil microbial respiration. Multiple stepwise regression analyses showed that available nitrogen was the main explanatory factor for the variation in soil microbial respiration in both the topsoil (60.2%, P = 0.009) and subsoil (80.3%, P = 0.002). Compared to the bacterial properties, the labile organic matter contributed more to the variation. Our work suggested that soil microbial respiration was primarily modulated by the quality of the organic matter.</p
The mineralization and sequestration of organic carbon in relation to agricultural soil erosion
No full textThe coupling of soil erosion (especially interrill erosion by water) and the dynamics of soil organic carbon (SOC) in agricultural landscapes has been widely studied over the past two decades. To date, however, the role of soil erosion in global C cycle remains a topic of debate. Numerous questions remain to be addressed before determining the C sink/source effect of soil erosion, especially for the mineralization and sequestration of eroded SOC upon erosion, transport and deposition. In this review, we provide a comprehensive cross-disciplinary review on SOC mineralization and sequestration at sites of erosion, along the transport pathway and at depositional sites. The current state of knowledge on the impacts of erosion-induced soil aggregate breakdown and formation, removal of SOC from eroding sites and deep burial of SOC at depositional sites on the mineralization and sequestration of SOC are presented. Furthermore, we provide an overview of the conceptual relations between soil biological properties (microbial abundance, species diversity, community composition and enzyme activity) and the mineralization and sequestration of SOC in eroded agricultural landscapes, which are often overlooked by previous research and reviews. The comprehensive understanding of physical, chemical and biological mechanisms affecting the mineralization and sequestration of eroded SOC provides important insights to balance the global carbon budget and finally holds the answer on the carbon sink/source controversy.</p
The complete mitochondrial genome of Xylotrechus namanganensis (Coleoptera: Cerambycidae)
No full textThe complete mitochondrial genome of Xylotrechus namanganensis was sequenced. The genome size was 15,565 bp, which consists of 13 protein-encoding genes, 22 tRNA-encoding genes, 2 rRNA-encoding genes and 1D-loop control region. The base composition of mitogenome was biased toward A + T content, of which was 73.21%. The phylogenetic tree based on complete mitogenome sequences revealed that T. namanganensis had a closer relationship with X. grayii
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