Effects of particle diameter and inlet flow rate on gas-solid flow patterns of fluidized bed

The complex multiscale characteristics of particle flow are notoriously difficult to predict. In this study, the evolution process of bubbles and the variation of bed height were investigated by conducting high-speed photographic experiments to verify the reliability of numerical simulations. The gas-solid flow characteristics of bubbling fluidized beds with different particle diameters and inlet flow rates were systematically investigated by coupling computational fluid dynamics (CFD) and discrete element method (DEM). The results show that the fluidization in the fluidized bed will change from bubbling fluidization to turbulent fluidization and finally to slugging fluidization, and the conversion process is related to the particle diameter and inlet flow rate. The characteristic peak is positively correlated with the inlet flow rate, but the frequency corresponding to the characteristic peak is constant. The time required for the Lacey mixing index (LMI) to reach 0.75 decreases with increasing inlet flow rate; at the same diameter, the inlet flow rate is positively correlated with the peak of the average transient velocity; and as the diameter increases, the distribution of the average transient velocity curve changes from M to linear. The results of the study can provide theoretical guidance for particle flow characteristics in biomass fluidized beds

Activation of both TLR and NOD signaling confers host innate immunity-mediated protection against microbial infection

The detection of microbial pathogens relies on the recognition of highly conserved microbial structures by the membrane sensor Toll-like receptors (TLRs) and cytosolic sensor NOD-like receptors (NLRs). Upon detection, these sensors trigger innate immune responses to eradicate the invaded microbial pathogens. However, it is unclear whether TLR and NOD signaling are both critical for innate immunity to initiate inflammatory and antimicrobial responses against microbial infection. Here we report that activation of both TLR and NOD signaling resulted in an augmented inflammatory response and the crosstalk between TLR and NOD led to an amplified downstream NF-kB activation with increased nuclear transactivation of p65 at TNF-a and IL-6 promoters. Furthermore, co-stimulation of macrophages with TLR and NOD agonists maximized antimicrobial activity with accelerated phagosome maturation. Importantly, administration of both TLR and NOD agonists protected mice against polymicrobial sepsis-associated lethality with increased serum levels of inflammatory cytokines and accelerated bacterial clearance from the circulation and visceral organs. These results demonstrate that activation of both TLR and NOD signaling synergizes to induce efficient inflammatory and antimicrobial responses, thus conferring protection against microbial infection

School environmental contamination of methicillin-sensitive Staphylococcus aureus as an independent risk factor for nasal colonization in schoolchildren: An observational, cross-sectional study.

ObjectiveWe aim to assess the similarities of proportional, phenotypic, and molecular characteristics between the school environment and schoolchildren on methicillin-sensitive S. aureus (MSSA) isolates.MethodsA cross-sectional study was conducted between March 2016 and August 2016 in eight elementary schools in Guangzhou, China. Nasal swabs from students and environmental swabs from school environments were collected. Univariate and multivariate logistic regression analyses under a multistage stratified cluster cross-sectional survey design were performed to access the prevalence relationship and influencing factors, respectively. Phenotypic and molecular characterizations of MSSA isolates were conducted using the Kirby-Bauer disk diffusion method and polymerase chain reaction assays, respectively.ResultsIn total, 1705 schoolchildren and 1240 environmental samples from 40 classes in eight elementary schools obtained between March and August 2016 were include in this study. The rates of MSSA prevalence among schoolchildren and the environment were 11.44% (195/1705) and 4.60% (57/1240), respectively. The odds ratios and 95% confidence intervals (CIs) on the prevalence of MSSA isolates were 1.11 (95% CI, 1.05-1.29; P = 0.010) and 1.04 (95% CI, 1.01-1.07; P = 0.003) for the school or class environment and students, respectively. Similar phenotypic and molecular characteristics were identified between schoolchildren and the environment. A cause and effect relationship could not be established because the study design was cross-sectional.ConclusionsBecause of the cross-sectional design, we can reveal the association between school environment and schoolchildren on MSSA, but it is not a cause and effect relationship

Cours de dessin professé à l'École La Martinière (2e édition) / par Louis Dupasquier,...

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Physical plugging of lost circulation fractures at microscopic level

Drilling fluid loss into formation fractures is one of the most common and costly problems encountered during the exploration and development of oil and gas resources. At present, the most extensive solution is to use physical lost circulation materials (LCMs) to form high-strength plugging zone in fractures. However, it is still unclear how the plugging is initiated and formed in the fracture. In this paper, a microscopic visualization experimental device for the formation of plugging zone is used to observe the dynamic plugging performance of spherical materials, flaky materials and fibers in fracture. Experimental results show that the formation of fracture plugging zone can be divided into retention stage and plugging stage. Spherical materials have three main retention modes: single-particle straining, dual-particle bridging and multi-particle bridging. Flaky materials assist the retention and plugging of spherical materials through three modes: embedded, intercepted and supported. Fibers take part in the retention of spherical materials through three ways: forming a net at the entrance of the fracture, forming a net after bridging the particle materials, and transverse filling in the fracture. The results achieved in this work provide a basis for the selection and design of LCMs for lost circulation control in deep fractured tight reservoir