SUMMARY
Understanding the fluid dependence of the poroelastic stiffness constants of a layered porous package is of great importance in subsurface exploration and development. While the effects of ...the pore-fluid distribution caused by coarse-scale heterogeneities within an isotropic medium have been studied for several decades, the role of these heterogeneities on the poroelastic constants of a finely layered package is still largely unexplored. In this study, we apply the poroelastic upscaling methods to estimate the fluid-dependent poroelastic stiffness constants of a layered package at the coarse scale. The numerical results show that the refined Gassmann's fluid substitution formulae presented in this paper is applicable if a single fluid phase is uniformly saturated within a layered package. The stiffness constants (${c_{11}}$ and ${c_{33}}$) of the layered package with patchy saturations are always higher than or equal to those obtained for the medium with homogeneous saturations, the stiffness constants predicted by the refined fluid substitution formulae for the package simultaneously saturated with different fluids fall between them. Experimental results confirm the relationship between the undrained vertical stiffness constant and the effective pore-fluid bulk modulus for the patch saturated package, indicating that a reasonable result can be achieved by properly choosing an effective poroelastic model that accounts both for the fluid hydraulic communication and the anisotropy of the medium. The results improve the understanding of the coarse-scale fluid dependence of the poroelastic stiffness constants of a layered package, and therefore, it can be used to interpret the seismically inverted elastic parameter for the petrophysical properties in heterogeneous reservoirs.
SUMMARY
Understanding the fluid dependence of poroelastic constants of a layered porous package is important for various aspects of applied and fundamental geosciences. To decouple the effects of ...fluid substitutions and anisotropy in a layered package on vertical stiffness constants, a set of approximations to anisotropic fluid substitution theory is introduced in conjunction with Thomsen's anisotropy parameters. Validation of the approximations is performed by physical modelling and theoretical examples. In physical modelling, synthetic porous layers are used and interbedded by Plexiglas sheets to build a layered transversely isotropic symmetry with a vertical symmetry axis package. Seismic acquisitions over the physical model saturated with air, oil and water are carefully conducted, respectively. The reflection amplitudes are properly corrected and inverted by a specific seismic inversion scheme to recover P- and S-wave impedances. Poroelastic constants of the thin package then are deduced from the inverted results. Applying the approximations to the physical modelling results, a good match between the estimated vertical stiffness constant values of the physical model and the theoretical predictions is observed. Results of both physical modelling and theoretical analysis demonstrate that fluid substitutions when going from drained to undrained behaviour will enhance or reduce the degree of anisotropy of the medium, depending on the sign and magnitude of Thomsen's anisotropy parameter δ. Results show that the shear modulus of the individual layer plays a key role in controlling the degree of the initial anisotropy of the thin package, which directly dominates the effect of pore fluids on poroelastic constants of the upscaled medium.
Partitioning between nitrate reduction pathways, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) determines the fate of nitrate removal and thus it is of great ecological ...importance. Sulfide (S2−) is a potentially important factor that influences the role of denitrification and DNRA. However, information on the impact of microbial mechanisms for S2− on the partitioning of nitrate reduction pathways in freshwater environments is still lacking. This study investigated the effects of long-term (108 d) S2− addition on nitrate reduction pathways and microbial communities in the sediments of two different freshwater lakes. The results show that the increasing S2− addition enhanced the coupling of S2− oxidation with denitrification instead of DNRA. The sulfide-oxidizing denitrifier, Thiobacillus, was significantly enriched in the incubations of both lake samples with S2− addition, which indicates that it may be the key genus driving sulfide-oxidizing denitrification in the lake sediments. During S2− incubation of the Hongze Lake sample, which had lower inherent organic carbon (C) and sulfate (SO42−), Thiobacillus was more enriched and played a dominant role in the microbial community; while during that of the Nansi Lake sample, which had higher inherent organic C and SO42−, Thiobacillus was less enriched, but increasing abundances of sulfate reducing bacteria (Desulfomicrobium, Desulfatitalea and Geothermobacter) were observed. Moreover, sulfide-oxidizing denitrifiers and sulfate reducers were enriched in the Nansi Lake control treatment without external S2− input, which suggests that internal sulfate release may promote the cooperation between sulfide-oxidizing denitrifiers and sulfate reducers. This study highlights the importance of sulfide-driven denitrification and the close coupling between the N and S cycles in freshwater environments, which are factors that have often been overlooked.
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•Long-term sulfide input favors chemoautotrophic denitrification instead of DNRA.•Thiobacillus was the key genus driving sulfide-oxidizing denitrification.•Inherent C and S in the samples influenced microbial interactions under S2− input.•Internal SO42− release increased cooperation between N and S cycling microorganisms.
Long-term sulfide input favors chemoautotrophic denitrifiers instead of DNRA bacteria in freshwater sediments.
The bacterial diversity and volatile flavor compounds (VFCs) during suancai fermentation in different temperatures were investigated by Illumina Hiseq sequencing and GC-MS. Firmicutes and ...Proteobacteria were observed to be the dominant phyla during the fermentation. Lactobacillus, Serratia, Leuconostoc, Pseudomonas, Pseudomonas, Pediococcus, etc., were observed as the main genus. Serratia and Pseudomonas predominated the early stage of suancai fermentation, while Lactobacillus predominated the later stage. Leuconostoc predominated the fermentation at 10 °C and 15 °C, while Weissella and Lactococcus predominated at 20 °C and 25 °C. A total of 86 VFCs were detected in all suancai samples. With the increase of the fermentation temperature, the kinds of VFCs were also increased. Lactobacillus, Pediococcus, Lactococcus, Brochothrix, Psychrobacter, Pseudoalteromonas, Acinetobacter and Enterobacter were the important bacteria related to VFCs during the fermentation. The bacteria were highly correlated with the VFCs in suancai fermentation. As the most dominant genus, Lactobacillus was significantly positive correlated with 13 VFCs. The correlation between the bacteria and VFCs in suancai could be used to search for microbial markers. In conclusion, 20 °C could accelerate the maturation and improve the sensory quality of suancai. This study could provide useful guidelines for screening of strains that contribute to the flavor formation in suancai fermentation.
•Firmicutes and Proteobacteria were observed as dominant phylum in suancai.•Lactobacillus predominated the later stage of the suancai fermentation.•The biomarkers in suancai fermented under different temperature were different.•Eight important genera were significant correlated with the VFCs in suancai.•Lactobacillus was significant positive correlated with 13 VFCs in suancai.
Alzheimer's disease (AD) is the leading cause of dementia in aged population. Oxidative stress and neuroinflammation play important roles in the pathogenesis of AD. Investigation of hub genes for the ...development of potential therapeutic targets and candidate biomarkers is warranted. The differentially expressed genes (DEGs) in AD were screened in GSE48350 dataset. The differentially expressed oxidative stress genes (DEOSGs) were analyzed by intersection of DEGs and oxidative stress-related genes. The immune-related DEOSGs and hub genes were identified by weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) analysis, respectively. Enrichment analysis was performed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. The diagnostic value of hub genes was assessed by receiver operating characteristic analysis and validated in GSE1297. The mRNA expression of diagnostic genes was determined by qRT-PCR analysis. Finally, we constructed the drug, transcription factors (TFs), and microRNA network of the diagnostic genes. A total of 1160 DEGs (259 up-regulated and 901 down-regulated) were screened in GSE48350. Among them 111 DEOSGs were identified in AD. Thereafter, we identified significant difference of infiltrated immune cells (effector memory CD8 T cell, activated B cell, memory B cell, natural killer cell, CD56 bright natural killer cell, natural killer T cell, plasmacytoid dendritic cell, and neutrophil) between AD and control samples. 27 gene modules were obtained through WGCNA and turquoise module was the most relevant module. We obtained 66 immune-related DEOSGs by intersecting turquoise module with the DEOSGs and identified 15 hub genes through PPI analysis. Among them, 9 hub genes (CCK, CNR1, GAD1, GAP43, NEFL, NPY, PENK, SST, and TAC1) were identified with good diagnostic values and verified in GSE1297. qRT-PCR analysis revealed the downregulation of SST, NPY, GAP43, CCK, and PENK and upregulation of NEFL in AD. Finally, we identified 76 therapeutic agents, 152 miRNAs targets, and 91 TFs regulatory networks. Our study identified 9 key genes associated with oxidative stress and immune reaction in AD pathogenesis. The findings may help to provide promising candidate biomarkers and therapeutic targets for AD.
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•Iron-based denitrification improved nitrogen removal at low C/N ratio in freshwaters.•Microbially mediated denitrification dominated rather than chemodenitrification.•Five ...fast-growing microbes accounted for over 99% of the community.•Amino acids and vitamins needed by an organism could be satisfied by another member.•The two-partner relationships increased community stability without limiting activity.
Iron-dependent denitrification is a safe and promising technology for nitrogen removal in freshwaters. However, the understanding of microbial physiology and interactions during the process was limited. Denitrifying systems inoculated with freshwater samples were operated with and without iron(II) at a low C/N ratio for 54 days. Iron addition improved nitrogen removal. Batch experiments confirmed that microbially mediated reaction rather than abiotic reaction dominated during the process. Metagenomics recovered genomes of the five most abundant microorganisms, which accounted for over 99% of the community in every triplicate of the iron-based system. Based on codon usage bias, all of them were fast-growing organisms. The total abundance of fast-growing organisms was 38% higher in the system with iron than in the system without iron. Notably, the most abundant organism Diaphorobacter did not have enzymes for asparagine and aspartate biosynthesis, whereas Rhodanobacter could not produce serine and cobalamin. Algoriphagus and Areminomonas lost synthesis enzymes for more amino acids and vitamins. However, they could always obtain these growth-required substances from another microorganism in the community. The two-partner relationship minimized the limitation on microbial reproduction and increased community stability. Our results indicated that iron addition improved nitrogen removal by supplying electron donors, promoting microbial growth, and building up syntrophic interactions among microorganisms with timely communications. The findings provided new insights into the process, with implications for freshwater remediation.
Wind energy harvesting using piezoelectric transduction is becoming a promising alternative for battery-free wireless electronics. To offer a promising solution for low structure reliability of ...Piezoelectric Wind-induced Vibration Energy Harvesters (PWVEHs) under fairly high wind speed, a Downwind-Vibrating Piezoelectric Energy Harvester under the disturbance of a downstream baffle (DVPEH) is proposed in this paper. Unlike the most existing PWVEHs of which the bluff body swung against the wind, the structure reliability of energy harvester was improved with the downstream structure of the DVPEH. A downstream baffle was introduced to adjust the working characteristics of DVPEH to avoid the disadvantage of small amplitude of downwind structure. Meanwhile, the dynamic and electrical characteristics of the DVPEH under the disturbance of a downstream baffle was explored to enhance the power generation capacity. To prove the structural feasibility and ascertain the influence of the downstream baffle, theoretical investigation, simulation, fabrication and experimental testing were conducted. The results showed that the interaction of vortex-induced vibration and galloping was induced by the downstream baffle to accelerate the oscillation of the bluff body. Besides, the distance-diameter ratio, width-diameter ratio and length ratio brought significant effects on the performance in terms of electric output and cut-in wind speed. A maximum power of 0.42 mW was achieved at the optimal load resistance of 100 kΩ with the wind speed of 16 m/s and 20 blue LEDs in series was successfully driven by the DVPEH. It was expected that this study could provide a reference for improving the structure reliability and electric output of traditional PWVEHs.
•Piezoelectric wind energy harvester uses a downwind bluff body and downstream baffle.•The working mode of bluff body downwind vibration is used to improve the reliability.•Dual-purpose downstream baffle can accelerate and attenuate vibration of bluff body.•Critical wind speed, wind bandwidth and output voltage can be adjusted by the baffle.
The two-stage stochastic variational inequality (TSVI) is a popular modeling paradigm recently with a wide range of applications in stochastic programming, game problems, equilibrium, etc. To ...numerically solve a TSVI, samples drawn from the true probability distribution are employed to discretely approximate the original problem with continuous probability distribution. However, this key assumption can hardly be fulfilled in practice because the perceived data may usually contain noise. This leads to the so-called statistically robust analysis. This paper considers the statistical robustness of TSVIs. We first give some preliminaries on both TSVIs and statistical robustness, which lay the foundation for the subsequent discussion. Then both qualitative and quantitative statistical robustness of TSVIs are studied.
Suancai is a popular fermented product of Brassica vegetable in China. As important additive, salt concentration has crucial effects on the quality of suancai. To investigate the effects of salt ...concentration on suancai fermentation, the microbial diversity and volatile compounds (VCs) during fermentation were investigated by using Illumina HiSeq sequencing and GC-MS. Firmicutes, Proteobacteria and Ascomycota were detected as the main phylum during the fermentation with different salt concentrations. Lactobacillus, Lactococcus, Klebsiella, Weissella, Pediococcus, Candida, Cladosporium, Gibberella, Aspergillus, etc., were detected were observed during the fermentation with different concentrations. After fermentation, Lactobacillus predominated the fermentation of suancai and was not affected by salt concentration. Pediococcus, Leuconostoc, Weissella, Sporobolomyces, Azospirillum, Klebsiella, Acinetobacter and Cladosporium were significant affected by salt concentration. Salt addition could affect the VCs profiles and reduce the isothiocyanates after fermentation. Seventy-nine VCs were detected and strongly correlated with the dominant genus Lactobacillus during suancai fermentation. The inoculated fermentation of Lactobacillus could improve the VCs during fermentation. In conclusion, 6% salt addition could acquire a higher Lactobacillus abundance and a better taste quality. These results may facilitate the understanding of the effect of salt concentration on the fermentation ecology to improve suancai characteristics.
•The 6% (w/w) salt addition was the best for suancai fermentation and quality.•Lactobacillus and unclassified fungus were dominant genera in suancai.•Seventy-nine VCs were detected during suancai fermentation with different salinity.•VCs were strongly correlated with Lactobacillus during suancai fermentation.•The inoculation of L. plantarum increased the VCs during suancai fermentation.
The objective of this study was to investigate the antioxidant and antibacterial activities of exopolysaccharide (EPS) from Bifidobacterium bifidum WBIN03 (B-EPS) and Lactobacillus plantarum R315 ...(L-EPS). The 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging, hydroxyl radical-scavenging, and superoxide radical-scavenging abilities were measured to evaluate antioxidant activity. Inhibition of erythrocyte hemolysis and lipid peroxidation was also measured. Both B-EPS and L-EPS had strong scavenging ability against DPPH and superoxide radicals at high concentration. The inhibitory effect of B-EPS on erythrocyte hemolysis was stronger than that of L-EPS in a concentration range from 0.30 to 1.00mg/mL, whereas the hydroxyl scavenging ability of L-EPS (39.15±0.58%) was significantly higher than that of 0.15mg/mL ascorbic acid (24.33±1.17%) and B-EPS (17.89±3.30%) at 0.10mg/mL. The inhibition of lipid peroxidation of 0.50mg/mL B-EPS and L-EPS was 13.48±1.74% and 12.43±0.51%, respectively, values lower than that of ascorbic acid at the same concentration (23.20±1.41%). Furthermore, all these abilities were enhanced in a concentration-dependent manner. Agar diffusion assay showed that both EPS exhibited antibacterial activities against tested pathogens such as Cronobacter sakazakii, Escherichia coli, Listeria monocytogenes, Staphyloccocus aureus, Candida albicans, Bacillus cereus, Salmonella typhimurium, and Shigella sonnei at 300μg/mL. In conclusion, both EPS have antimicrobial and antioxidant activities and could have applications in the food industry.
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