CFD Analysis of Hydrodynamics and Mass Transfer of a Gas-Liquid Bubble Column

Bubble columns are widely used as gas–liquid contactors and as reactors in chemical, petrochemical and biochemical industries. Effective mixing as well as high interfacial area between the phases, leading to improved heat and mass transfer characteristics, relatively cheap to install and the lack of moving parts, are the factors that render under bubble columns an attractive choice as reactors for the described processes. Gas-liquid flow in bubble column reactors is characterized by a combination of inherently unsteady complex processes with widely varying spatial and temporal scales. Understanding the complexity of the fluid dynamics and mass transfer in bubble column and is important due to its application in the chemical and bioprocess industries. The potential of Computational Fluid Dynamics (CFD) for describing the hydrodynamics and heat and mass transfer of bubble columns has been established by several publications in the past. CFD predicts what happens quantitatively, when fluids flow, often with the complications of simultaneous flow of heat, mass transfer (eg perspiration, dissolution), phase change (eg melting, freezing, boiling), chemical reaction (eg combustion, rusting), mechanical movement (eg of pistons, fans, rudders), stresses in and displacement of immersed or surrounding solids. Thus CFD can successfully be used to study the gas-liquid mass transfer in bubble column reactor. In the present work an attempt has been made to understand the hydrodynamic behavior and gas-liquid mass transfer (transfer of oxygen from air to de-aerated water) of a concurrent gas(air)-liquid(water) up-flow bubble column by CFD analysis. The system used in the study is a cylindrical column of 10 cm ID and 1.88 m height. GAMBIT 2.3.16 has been used to generate a 2D coarse grid of 0.01m by 0.01m mesh size. The eulerian-eulerian approach has been used for modeling the multiphase flow and the oxygen mass transfer from air to de-aerated water and the column hydrodynamics. The standard k-ε mixture turbulence model has been used to account the effect of turbulence. FLUENT 6.3.26 has been used to simulate the system for various hydrodynamics parameters such as phase dynamics, phase velocity profile, pressure drop and the gas-liquid mass transfer. The simulated results have been compared with the experimental results found in the literature

Intrinsic heterogeneity in the survival and proliferation capacities of naïve CD8⁺ T cells

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biological Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 125-137).This thesis describes the identification and characterization of a novel 'layer' of intrinsic non-genetic functional heterogeneity within the seemingly homogeneous naive CD8⁺ T cell population in their survival and proliferation capacities. This heterogeneity is predictably marked by the surface level of CD5. NaYve CD8⁺ T cells that are also CD5hi have a greater intrinsic capacity to proliferate both in response to IL7 alone or identical stimulation of the TCR, pathway (same dose of PMA/ionomycin) as compared to CD51' cells. In contrast, CD510 cells survive better in conditions of cytokine deprivation. The selective proliferation in response to IL7 as well as the relative CD5 level is preserved even after several rounds of activation-induced proliferation and differentiation into memory-like cells in vitro, suggesting that the relative CD5 level could be used as a lineage marker to predict the proliferation capacity of CD8⁺ T cells. Microarray analysis of two naive TCR transgenic CD8⁺ T cells, from the same genetic background, but with marked differences in CD5 levels, namely OT-1 and F5 Rag-/- T cells, revealed consistent differences in their cell survival, proliferation and metabolic pathways. Analysis of upstream regulatory networks suggests that the E2A family of transcription factors and miR-181 are likely involved in setting the proliferation and survival capacities of naive T cells, possibly during thymic development. Our estimates of spMHC-induced signals in OT-1 (CD5hi) and F5 (CD50) cells, based on cytosolic Ca2⁺ influx measurements, suggest that the differences in their lymphophenia-induced proliferation, which were previously attributed to putative corresponding differences in their strength of interaction with self-peptide MHC, may also largely be a result of intrinsic differences in their proliferation capacities in response to 1L7. Further, the potential of exogenous IL7 therapy to skew the CD8⁺ T cell repertoire towards the CD5hi phenotype was demonstrated with in vivo studies in mice. Conversely, antibody-mediated depletion of IL7 has the opposite result.by Vinay Subhash Mahajan.Ph.D

Signaling thresholds govern heterogeneity in IL-7-receptor-mediated responses of naïve CD8+ T cells

Variable sensitivity to T-cell-receptor (TCR)- and IL-7-receptor (IL-7R)-mediated homeostatic signals among naïve T cells has thus far been largely attributed to differences in TCR specificity. We show here that even when withdrawn from self-peptide-induced TCR stimulation, CD8+ T cells exhibit heterogeneous responses to interleukin-7 (IL-7) that are mechanistically associated with IL-7R expression differences that correlate with relative CD5 expression. Whereas CD5hi and CD5lo T cells survive equivalently in the presence of saturating IL-7 levels in vitro, CD5hi T cells proliferate more robustly. Conversely, CD5lo T cells exhibit prolonged survival when withdrawn from homeostatic stimuli. Through quantitative experimental analysis of signaling downstream of IL-7R, we find that the enhanced IL-7 responsiveness of CD5hi T cells is directly related to their greater surface IL-7R expression. Further, we identify a quantitative threshold in IL-7R-mediated signaling capacity required for proliferation that lies well above an analogous threshold requirement for survival. These distinct thresholds allow subtle differences in IL-7R expression between CD5lo and CD5hi T cells to give rise to significant variations in their respective IL-7-induced proliferation, without altering survival. Heterogeneous IL-7 responsiveness is observed similarly in vivo, with CD5hi naïve T cells proliferating preferentially in lymphopenic mice or lymphoreplete mice administered with exogenous IL-7. However, IL-7 in lymphoreplete mice appears to be maintained at an effective level for preserving homeostasis, such that neither CD5hi IL-7Rhi nor CD5lo IL-7Rlo T cells proliferate or survive preferentially. Our findings indicate that IL-7R-mediated signaling not only maintains the size but also impacts the diversity of the naïve T-cell repertoire

Analysis of genetic diversity among tropical and subtropical maize inbred lines using SSR markers

Genetic diversity of 24 tropical and subtropical elite maize lines was assessed at molecular level employ-ing 42 Simple Sequence Repeats. A total of 107 alleles with an average of 2.55 alleles per locus were detected. The Polymorphism Information Content (PIC) values of 42 SSR loci ranged from 0.08 (UMC1428) to 0.68 (UMC2189 and UMC2332) with the overall calculated PIC mean value of 0.44, whereas the Discrimination Rate (DR) value for SSR markers ranged from 0.09 (UMC2089) to 0.42 (UMC1311) with the average DR value of 0.26. Pair-wise genet-ic similarity (GS) values, calculated by Jaccard’s coefficients, ranged between 0.25 and 0.78 with a mean genetic similarity of 0.63, indicating the existence of adequate amount of genetic divergence among the genotypes selected for the study. The cluster dendrogram separated all the inbred lines into six main clusters with sub clusters based on genetic similarity. Factorial analysis also confirmed a nearly similar pattern for grouping these inbred lines as pre-sented by cluster dendrogram. In this study, SSR markers were found to be powerful tool for detection of genetic diversity in maize inbred lines. These findings could provide information for effective utilization of these materials for development of maize hybrids as well as for genetic improvement of inbred lines

Evaluation of maize (Zea mays) inbred lines for tolerance to low temperature stress under field conditions

In northern India, cold spell is experienced at early vegetative stage. Tolerance to cold in inbred lines is important to ensure seed production in rabi season. Sixty-six inbred lines of Indian maize program were evaluated for their tolerance to low temperature stress under field conditions. Maize (Zea mays L.) inbred lines of Bajaura Centre (BJIM 2780, BJIM 08-100, BJIM 10-1 and BJIM 10-35) and Almora Centre (V 366, V 384, V 351, V 382 and V 378) performed better with minimum leaf yellowing and good plant growth under the cold stress. Inbreds lines BJIM 10- 35, BJIM 10-43, BJIM 10-37, V 364, V 404, V 390, LM 14 and BML 6 exhibited high reduction in yellowing of leaves coupled with fast growth recovery. Expression of yellowing of leaves and plant growth showed significant negative correlation. Yellowing of leaves and recovery of plant growth due to cold spell were important parameters for cold tolerance at early vegetative stage in maize

Predictive association of gut microbiome and NLR in anemic low middle-income population of Odisha- a cross-sectional study

BackgroundIron is abundant on earth but not readily available for colonizing bacteria due to its low solubility in the human body. Hosts and microbiota compete fiercely for iron. <15% Supplemented Iron is absorbed in the small bowel, and the remaining iron is a source of dysbiosis. The gut microbiome signatures to the level of predicting anemia among low-middle-income populations are unknown. The present study was conducted to identify gut microbiome signatures that have predictive potential in association with Neutrophil to lymphocytes ratio (NLR) and Mean corpuscular volume (MCV) in anemia.MethodsOne hundred and four participants between 10 and 70 years were recruited from Odisha’s Low Middle-Income (LMI) rural population. Hematological parameters such as Hemoglobin (HGB), NLR, and MCV were measured, and NLR was categorized using percentiles. The microbiome signatures were analyzed from 61 anemic and 43 non-anemic participants using 16 s rRNA sequencing, followed by the Bioinformatics analysis performed to identify the diversity, correlations, and indicator species. The Multi-Layered Perceptron Neural Network (MLPNN) model were applied to predict anemia.ResultsSignificant microbiome diversity among anemic participants was observed between the lower, middle, and upper Quartile NLR groups. For anemic participants with NLR in the lower quartile, alpha indices indicated bacterial overgrowth, and consistently, we identified R. faecis and B. uniformis were predominating. Using ROC analysis, R. faecis had better distinction (AUC = 0.803) to predict anemia with lower NLR. In contrast, E. biforme and H. parainfluenzae were indicators of the NLR in the middle and upper quartile, respectively. While in Non-anemic participants with low MCV, the bacterial alteration was inversely related to gender. Furthermore, our Multi-Layered Perceptron Neural Network (MLPNN) models also provided 89% accuracy in predicting Anemic or Non-Anemic from the top 20 OTUs, HGB level, NLR, MCV, and indicator species.ConclusionThese findings strongly associate anemic hematological parameters and microbiome. Such predictive association between the gut microbiome and NLR could be further evaluated and utilized to design precision nutrition models and to predict Iron supplementation and dietary intervention responses in both community and clinical settings

Surfactant protein D induces immune quiescence and apoptosis of mitogen-activated peripheral blood mononuclear cells

Surfactant Protein D (SP-D) is an integral molecule of the innate immunity secreted by the epithelial cells lining the mucosal surfaces. Its C-type lectin domain offers pattern recognition functions while it binds to putative receptors on immune cells to modify cellular functions. Activated PBMCs and increased serum levels of SP-D are observed under a range of pathophysiological conditions including infections. Thus, we speculated if SP-D can modulate systemic immune response via direct interaction with activated PBMCs. Here, we have examined interaction of a recombinant fragment of human SP-D (rhSP-D) on PHA-activated PBMCs. We observed a significant downregulation of TLR2, TLR4, CD11c and CD69 upon rhSP-D treatment. rhSP-D inhibited production of Th1 (TNF-α and IFN-γ) and Th17 (IL-17) cytokines along with IL-6. Interestingly, levels of IL-2, Th2 (IL-4) and regulatory (IL-10 and TGF-β) cytokines were unaltered. Differential expression of co-stimulatory CD28 and co-inhibitory CTLA4 expression along with their ligands CD80 and CD86 revealed selective up-regulation of CTLA4 at both mRNA and protein level. In addition, rhSP-D induced apoptosis only in the activated but not in non-activated PBMCs. Blockade of CTLA4 inhibited rhSP-D mediated apoptosis, confirming an involvement of CTLA4 in induction of apoptosis. We conclude that SP-D restores immune homeostasis: it regulates expression of immunomodulatory receptors and cytokines, which is followed by apoptosis induction of immune-activated cells. These findings appear to suggest a general role for SPD in immune surveillance against activated immune cells

2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation: executive summary.

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