Search

We developed a boundary integral formulation to simulate a red blood cell (RBC) squeezing through a submicron slit under prescribed inlet and outlet pressures. The main application of this computational study is to investigate splenic filtrations of RBCs and the corresponding in vitro mimicking microfluidic devices, during which RBCs regularly pass through inter-endothelial slits with a width less than 1.0 µm. The diseased and old RBCs are damaged or destroyed in this mechanical filtration process. We first derived the boundary integral equations of a RBC immersed in a confined domain with prescribed inlet and outlet pressures. We applied a unified self-adaptive quadrature to accurately evaluate singular and nearly singular integrals, which are especially important in this fluid-structure interaction problem with strong lubrication. A multiscale model is applied to calculate forces from the RBC membrane, and it is coupled to boundary integral equations to simulate the fluid-structure interaction. After multi-step verifications and validations against analytical and experimental results, we systematically investigated the effects of pressure drop, volume-to-surface-area ratio, internal viscosity, and membrane stiffness on RBC deformation and internal stress. We found that spectrins of RBCs could be stretched by more than 2.5 times under high hydrodynamic pressure and that the bilayer tension could be more than 500 pN/μm, which might be large enough to open mechanosensitive channels but too small to rupture the bilayer. On the other hand, we found that the bilayer-cytoskeletal dissociation stress is too low to induce bilayer vesiculation. [ABSTRACT FROM AUTHOR]

The shortage of protein feed resources and environmental pollution restrict the healthy and sustainable development of breeding industry, so it is imperative to promote low protein diet. Based on the current industry trends and national policies, this paper analyzes the background conditions, significance and specific measures of popularizing low-protein diets, in order to provide policy, theoretical and technical support for the implementation of low-protein diets throughout the year. [ABSTRACT FROM AUTHOR]

Low water temperature is a prevailing abiotic stress which adversely impacts global shrimp growth and production. In this study, a high-density genetic linkage map of L. vannamei was constructed using double-digest restriction site-associated DNA sequencing (ddRAD-seq) with an F1 full-sib family mapping panel comprising 148 progenies and 2 parents. A total of 2528 single-nucleotide polymorphisms (SNPs) were assigned to 48 linkage groups (LGs), with a total genetic map length of 3227.383 centimorgans (cM) and an inter-locus density of 0.783 cM/locus. The number of markers per LG ranged from 12 to 190, with a mean of 56. The length of LGs varied from 15.07 to 158.314 cM, with a mean length of 67.237 cM. Five quantitative trait loci (QTLs) for low-temperature tolerance with a logarithm of odds (LOD) threshold≥2.5 were detected, of which only one was identified based on a linkage group-wide significant LOD threshold. Notably, two growth-trait (body weight) related QTLs were located on LG36 with a genome-wide significant LOD threshold. According to the genome and relevant annotations of L. vannamei , a major growth-related candidate gene, tRNA methyltransferase 10 homolog A (TRMT10A), was identified from genomic scaffolds. Further analysis demonstrated that four linked missense mutation SNPs within TRMT10A were closely related to the body weight. Taken together, the constructed genetic linkage map under low-temperature stress provides a valuable reference for QTL mapping and future genomic studies. Its application can facilitate comparative mapping with other populations, as well as marker-assisted selection (MAS) breeding of L. vannamei. • A high-quality genetic linkage map was constructed by using an F1 full-sib family. • A linkage group-wide significant low temperature tolerance-related QTL was identified. • Two genome-wide significant growth-related QTLs were identified. • A major growth-related candidate gene TRMT10A was identified. • The polymorphisms of TRMT10A was closely related with shrimp body weight. [ABSTRACT FROM AUTHOR]

The thermal degradation of decabromodiphenyl ether (BDE-209) featuring fully substituted bromines was investigated over an as-prepared FeO micro/nano-material at 300 °C. Degradation followed pseudo-first-order kinetics with k = 0.15 min higher than that for decachlorobiphenyl (CB-209). Twenty-six newly produced polybrominated diphenyl ether (PBDE) congeners were identified using the available PBDE standards, while four PBDE congener products were predicted using third-order polynomial regression equation. Analysis of the products indicated that BDE-209 underwent stepwise hydrodebromination over as-prepared FeO. Similar to the case for CB-209, two initial hydrodebromination steps are favored at the BDE-209 meta-positions, giving the major products BDE-207 and BDE-197. However, the variance about the preferred products began to emerge from the start of heptabromodiphenyl ethers (hepta-BDEs). The majorly produced hepta-BDE isomer with BDE-183 is unbrominated at one ortho-position. However, this is different from the reported degradation of CB-209, which always produced the products chlorinated at all four ortho-positions until the ortho-position had to be removed for the formation of trichlorobiphenyls and dichlorobiphenyl still majorly chlorinated at three or two ortho-positions. The early BDE-209 hydrodebromination steps appear to be strongly influenced by steric effects, whereas subsequent hydrodebromination steps, as more bromine atoms are removed, will be gradually governed more by thermodynamics. [ABSTRACT FROM AUTHOR]

Membrane biofouling is a complex process that involves bacterial adhesion, extracellular polymeric substances (EPS) excretion and utilization, and species interactions. To obtain a better understanding of the microbial ecology of biofouling process, this study conducted rigorous, time-course analyses on the structure, EPS and microbial composition of the fouling layer developed on ultrafiltration membranes in a nitrification bioreactor. During a 14-day fouling event, three phases were determined according to the flux decline and microbial succession patterns. In Phase I (0–2 days), small sludge flocs in the bulk liquid were selectively attached on membrane surfaces, leading to the formation of similar EPS and microbial community composition as the early biofilms. Dominant populations in small flocs, e.g., Nitrosomonas , Nitrobacter , and Acinetobacter spp., were also the major initial colonizers on membranes. In Phase II (2–4 d), fouling layer structure, EPS composition, and bacterial community went through significant changes. Initial colonizers were replaced by fast-growing and metabolically versatile heterotrophs (e.g., unclassified Sphingobacteria ). The declining EPS polysaccharide to protein (PS:PN) ratios could be correlated well with the increase in microbial community diversity. In Phase III (5–14 d), heterotrophs comprised over 90% of the community, whereas biofilm structure and EPS composition remained relatively stable. In all phases, AOB and NOB were constantly found within the top 40% of the fouling layer, with the maximum concentrations around 15% from the top. The overall microbial succession pattern from autotrophic colonization to heterotrophic domination implied that MBR biofouling could be alleviated by forming larger bacterial flocs in bioreactor suspension (reducing autotrophic colonization), and by designing more specific cleaning procedures targeting dominant heterotrophs during typical filtration cycles. [ABSTRACT FROM AUTHOR]