Mechanical properties and damage constitutive model of mud shale under different drilling fluids immersion

In the process of shale oil and gas drilling, the long-term erosion and weakening of drilling fluids promotes the extension and expansion of micro-fractures on mud shale, which leads to the reduction of rock mass strength and seriously threatens the stability of borehole wall. In order to explore the mechanical properties and damage evolution rules of mud shale under different drilling fluids immersion, Firstly, the mineral composition and structure of shale were analyzed by X-ray diffraction and environmental scanning electron microscopy. Then, uniaxial compression tests were carried out under different immersion systems and different immersion times, and the variation mechanism of mechanical parameters such as peak strength, elastic modulus and Poisson's ratio of shale under the weakening of drilling fluids were studied. Finally, based on the strain equivalence principle and Weibull statistical distribution theory, the damage constitutive model of rock under drilling fluids immersion and uniaxial loading was established. The results showed that the main body of mud shale has high content of clay minerals, abundant brittle minerals and dense distribution of micro-fractures. the elastic modulus of shale varied with the immersion environment and the increase of immersion time. Compared with the rock samples immersed in oil-based drilling fluid, the weakening effect of water-based drilling fluid soaking on its strength and elastic modulus is more obvious; by fitting the change trend of the mechanical parameters of shale under the weakening effect of different drilling fluids, the prediction model of elastic modulus of rock samples soaked in water-based drilling fluid and oil-based drilling fluid with respect to soaking time was proposed; For the mud shale under the weakening of drilling fluid, a uniaxial loading rock damage constitutive model considering the effect of pore compression stage is introduced. The evolution rules revealed the weakening damage mechanism of shale under different drilling fluids immersion

Verification of model simulated mass balance, flow fields and tabular calving events of the Antarctic ice sheet against remotely sensed observations

The Antarctic ice sheet (AIS) has the greatestpotential for global sea level rise. This study simulates AISice creeping, sliding, tabular calving, and estimates the totalmass balances, using a recently developed, advanced icedynamics model, known as SEGMENT-Ice. SEGMENTIceis written in a spherical Earth coordinate system.Because the AIS contains the South Pole, a projectiontransfer is performed to displace the pole outside of thesimulation domain. The AIS also has complex ice-watergranularmaterial-bedrock configurations, requiringsophisticated lateral and basal boundary conditions.Because of the prevalence of ice shelves, a ‘girder yield’type calving scheme is activated. The simulations of presentsurface ice flow velocities compare favorably with InSARmeasurements, for various ice-water-bedrock configurations.The estimated ice mass loss rate during 2003–2009agrees with GRACE measurements and provides morespatial details not represented by the latter. The modelestimated calving frequencies of the peripheral ice shelvesfrom 1996 (roughly when the 5-km digital elevation andthickness data for the shelves were collected) to 2009compare well with archived scatterometer images. SEGMENT-Ice’s unique, non-local systematic calving schemeis found to be relevant for tabular calving. However, theexact timing of calving and of iceberg sizes cannot besimulated accurately at present. A projection of the futuremass change of the AIS is made, with SEGMENT-Iceforced by atmospheric conditions from three differentcoupled general circulation models. The entire AIS is estimatedto be losing mass steadily at a rate of*120 km3/a atpresent and this rate possibly may double by year 2100

Plant Genotype Shapes the Soil Nematode Community in the Rhizosphere of Tomatoes with Different Resistance to <i>Meloidognye incognita</i>

Soil nematodes are considered indicators of soil quality due to their immediate responses to changes in the soil environment and plants. However, little is known about the effects of plant genotypes on the soil nematode community. To elucidate this, high-throughput sequencing and gas chromatography/mass spectrometry analysis was conducted to analyze the soil nematode community and the structure of root exudates in the rhizosphere of tomatoes with different resistance to Meloidognye incognita. The dominant soil nematode group in the soil of resistant tomatoes was Acrobeloides, while the soil nematode group in the rhizosphere of the susceptible and tolerant tomatoes was Meloidognye. Hierarchical clustering analysis and non-metric multidimensional scaling showed that the three soil nematode communities were clustered into three groups according to the resistance level of the tomato cultivars. The soil nematode community of the resistant tomatoes had a higher maturity index and a low plant-parasite index, Wasilewska index and disease index compared to the values of the susceptible and tolerant tomatoes. Redundancy analysis revealed that the disease index and root exudates were strongly related to the soil nematode community of three tomato cultivars. Taken together, the resistance of the tomato cultivars and root exudates jointly shapes the soil nematode community. This study provided a valuable contribution to understanding the mechanism of plant genotypes shaping the soil nematode community

Genome-wide identification and expression analysis of jasmonate ZIM domain gene family in tuber mustard (Brassica juncea var. tumida).

Tuber mustard, which is the raw material of Fuling pickle, is a crop with great economic value. However, during growth and development, tuber mustard is frequently attacked by the pathogen Plasmodiophora brassicae and frequently experiences salinity stress. Jasmonic acid (JA) is a hormone related to plant resistance to biotic and abiotic stress. Jasmonate ZIM domain proteins (JAZs) are crucial components of the JA signaling pathway and play important roles in plant responses to biotic and abiotic stress. To date, no information is available about the characteristics of the JAZ family genes in tuber mustard. Here, 38 BjJAZ genes were identified in the whole genome of tuber mustard. The BjJAZ genes are located on 17 of 18 chromosomes in the tuber mustard genome. The gene structures and protein motifs of the BjJAZ genes are conserved between tuber mustard and Arabidopsis. The results of qRT-PCR analysis showed that BjuA030800 was specifically expressed in root, and BjuA007483 was specifically expressed in leaf. In addition, 13 BjJAZ genes were transiently induced by P. brassicae at 12 h, and 7 BjJAZ genes were induced by salt stress from 12 to 24 h. These results provide valuable information for further studies on the role of BjJAZ genes in the regulation of plant growth and development and in the response to biotic and abiotic stress

The Soybean GmNARK Affects ABA and Salt Responses in Transgenic Arabidopsis thaliana

GmNARK (Glycine max nodule autoregulation receptor kinase) is the homolog of Arabidopsis thaliana CLAVATA1 (CLV1) and one of the most important regulators in the process of AON (Autoregulation of Nodulation), a process that restricts excessive nodule numbers in soybean. However, except for the function in AON, little is known about this gene. Here, we report that GmNARK plays important roles in process of plant response to abiotic stresses. Bioinformatic analysis and subcellular localization experiment results showed that GmNARK was a putative receptor like kinase and located at membrane. The promoter of GmNARK contains manifold cis regulatory elements that are responsive to hormone and stresses. Gene transcript expression pattern analysis in soybean revealed GmNARK was induced by ABA and NaCl treatment in both shoot and root. Overexpression of GmNARK in Arabidopsis resulted in higher sensitivity to ABA and salt treatment during seed germination and greening stages. We also checked the expression levels of some ABA response genes in the transgenic lines; the results showed that the transcript level of all the ABA response genes were much higher than that of wild type under ABA treatment. Our results revealed a novel role of GmNARK in response to abiotic stresses during plant growth and development

Genome-wide identification and gene expression analysis of SOS family genes in tuber mustard (Brassica juncea var. tumida).

The Salt Overly Sensitive (SOS) pathway in Arabidopsis thaliana plays important roles in maintaining appropriate ion homeostasis in the cytoplasm and regulating plant tolerance to salinity. However, little is known about the details regarding SOS family genes in the tuber mustard crop (Brassica juncea var. tumida). Here, 12 BjSOS family genes were identified in the B. juncea var. tumida genome including two homologous genes of SOS1, one and three homologs of SOS2 and SOS3, two homologs of SOS4, two homologs of SOS5 and two homologs of SOS6, respectively. The results of conserved motif analysis showed that these SOS homologs contained similar protein structures. By analyzing the cis-elements in the promoters of those BjSOS genes, several hormone- and stress-related cis-elements were found. The results of gene expression analysis showed that the homologous genes were induced by abiotic stress and pathogen. These findings indicate that BjSOS genes play crucial roles in the plant response to biotic and abiotic stresses. This study provides valuable information for further investigations of BjSOS genes in tuber mustard

Infection of Plasmodiophora brassicae changes the fungal endophyte community of tumourous stem mustard roots as revealed by high-throughput sequencing and culture-dependent methods.

Diverse fungal endophytes live in plants and are shaped by some abiotic and biotic stresses. Plant disease as particular biotic stress possibly gives an impact on the communities of fungal endophytes. In this study, clubroot disease caused by an obligate biotroph protist, Plasmodiophora brassicae, was considered to analyze its influence on the fungal endophyte community using an internal transcribed spacer (ITS) through high-throughput sequencing and culture-dependent methods. The results showed that the diversity of the endophyte community in the healthy roots was much higher than the clubroots. Ascomycota was the dominant group of endophytes (Phoma, Mortierella, Penicillium, etc.) in the healthy roots while P. brassicae was the dominant taxon in the clubroots. Hierarchical clustering, principal component analysis (PCA), principal coordinates analysis (PCoA) and analysis of similarities (ANOSIM) indicated significant differences between the endophyte communities in the healthy roots and clubroots. Linear discriminant analysis effect size (LefSe) analysis showed that the dominant genera could be regarded as potential biomarkers. The endophyte community in the healthy roots had a more complex network compared with the clubroots. Also, many plant pathogenic Fusarium were isolated from the clubroots by the culture-dependent method. The outcome of this study illustrates that P. brassicae infection may change the fungal endophyte community associated with the roots of tumourous stem mustard and facilitates the entry of soil pathogen into the roots

Table_1_The Soybean GmNARK Affects ABA and Salt Responses in Transgenic Arabidopsis thaliana.DOCX

<p>GmNARK (Glycine max nodule autoregulation receptor kinase) is the homolog of Arabidopsis thaliana CLAVATA1 (CLV1) and one of the most important regulators in the process of AON (Autoregulation of Nodulation), a process that restricts excessive nodule numbers in soybean. However, except for the function in AON, little is known about this gene. Here, we report that GmNARK plays important roles in process of plant response to abiotic stresses. Bioinformatic analysis and subcellular localization experiment results showed that GmNARK was a putative receptor like kinase and located at membrane. The promoter of GmNARK contains manifold cis regulatory elements that are responsive to hormone and stresses. Gene transcript expression pattern analysis in soybean revealed GmNARK was induced by ABA and NaCl treatment in both shoot and root. Overexpression of GmNARK in Arabidopsis resulted in higher sensitivity to ABA and salt treatment during seed germination and greening stages. We also checked the expression levels of some ABA response genes in the transgenic lines; the results showed that the transcript level of all the ABA response genes were much higher than that of wild type under ABA treatment. Our results revealed a novel role of GmNARK in response to abiotic stresses during plant growth and development.</p