Tuning heat transport via coherent structure manipulation: recent advances in thermal turbulence.

Tuning transport properties through the manipulation of elementary structures has achieved great success in many areas, such as condensed matter physics. However, the ability to manipulate coherent structures in turbulent flows is much less explored. This article reviews a recently discovered mechanism of tuning turbulent heat transport via coherent structure manipulation. We first show how this mechanism can be realized by applying simple geometrical confinement to a classical thermally driven turbulence, which leads to the condensation of elementary coherent structures and significant heat-transport enhancement, despite the resultant slower flow. Some potential applications of this new paradigm in passive heat management are also discussed. We then explain how the heat transport behaviors in seemingly different turbulence systems can be understood by this unified framework of coherent structure manipulation. Several future directions in this research area are also outlined.

A member of the immunoglobulin superfamily lrig-1 might be involved in the immune priming of Scylla paramamosain in response to the infection and re-infection by Vibrio parahaemolyticus.

A member of the immunoglobulin superfamily designated leucine-rich repeats and immunoglobulin-like domains protein-1 (lrig-1) encoding a protein with 1109 amino acids with a characteristic IGc2 domain was identified from the transcriptome data of mud crab Scylla paramamosain. Lrig-1 contained: one signaling peptide; one LRR_NT domain; nine LRR domains; three LRR_TYP domains; one LRR_CT domain; three IGc2 regions; one transmembrane region; C-terminal cytoplasmic tail. lrig-1 was widely expressed in all tissues of mud crab and was responsive in hemocytes to first and second Vibrio parahaemolyticus infections. lrig-1 knockdown mediated by RNAi repressed expression of several antimicrobial peptides significantly. Its orthologs in 19 crustacean species were identified and showed high conservation. These results suggest that lrig-1 have a vital role in mud crabs against V. parahaemolyticus infection through expression of multiple antimicrobial peptides. The results obtained in the present study imply the potential roles the lrig-1 played in immune priming in crabs.

Centrifugal-Force-Induced Flow Bifurcations in Turbulent Thermal Convection.

An important and unresolved issue in rotating thermal turbulence is when the flow starts to feel the centrifugal effect. This onset problem is studied here by a novel experiment in which the centrifugal force can be varied over a wide range at fixed Rossby numbers by offsetting the apparatus from the rotation axis. Our experiment clearly shows that the centrifugal force starts to separate the hot and cold fluids at the onset Froude number 0.04. Additionally, this flow bifurcation leads to an unexpected heat transport enhancement and the existence of an optimal state. Based on the dynamical balance and characteristics of local flow structures, both the onset and optimal states are quantitatively explained.

Characterization of the foxl2 gene involved in the vtg expression in mud crab (Scylla paramamosain).

Forkhead box protein L2 (Foxl2) is involved in multiple physiological processes, such as ovarian development, granulosa cell differentiation, ovarian follicle development, and oocyte growth. In this study, a Spfoxl2 gene encoded 530 amino acid protein with characteristic forkhead (FH) domain was identified from transcriptome data of mud crab Scylla paramamosain and validated the accuracy by PCR technology. Meanwhile, the orthologues of the Spfoxl2 gene in other 14 crustacean species were identified with the same method. Further multiple sequence alignment analysis revealed the Foxl2 was highly conserved, especially in the FH domain, even completely identical in several species. Besides, the semi-quantitative PCR (Sq-PCR) result showed Spfoxl2 gene was mainly expressed in the gonad (testis and ovary). Further quantitative real-time PCR (qRT-PCR) result demonstrated its expression level in the testis was significantly higher than that in the ovary (p < 0.01). In addition, the qRT-PCR result showed that in zoea V, megalopa, and larval I, the expression level of Spfoxl2 in megalopa is the highest. In addition, a putative Foxl2 binding site was identified on the promoter region of Spvtg, and knockdown of Spfoxl2 mediated by RNAi technology increased the expression of Spvtg in the ovary, suggesting Spfoxl2 might be the upstream negative regulator of Spvtg. Overall, this study provided new insights into the role of Spfoxl2 in ovary development through regulating Spvtg expression in S. paramamosain.

Characterization and antimicrobial evaluation of a new Spgly-AMP, glycine-rich antimicrobial peptide from the mud crab Scylla paramamosain.

Antimicrobial peptide (AMP) is a crucial component of the innate immune system in crustaceans. In mud crab, Scylla paramamosain, a commercially important species, a glycine-rich antimicrobial peptide (Spgly-AMP) gene was newly identified and putatively encoded a 26aa signal peptide and 37aa mature peptide. To understand the function of Spgly-AMP, the expression profile of Spgly-amp gene was characterized, which showed Spgly-amp was expressed widely in most tissues of adult crabs with the highest expression level in hemocytes. After Vibrio parahaemolyticus, PGN, or Poly I:C stimulations, the expression level of Spgly-amp was significantly up-regulated in the hemocytes. In antimicrobial assays, chemically synthesized Spgly-AMP peptides exhibited strong antibacterial activities against both Gram-positive and Gram-negative bacteria and high thermal stability after high-temperature heating. These findings in the present study verified the importance of the Spgly-AMP in defense of pathogenic bacteria infection in the mud crab and provided a promising candidate of antimicrobial agents in the crab aquaculture.

N, P-co-doped carbon dots as a dual-mode colorimetric/ratiometric fluorescent sensor for formaldehyde and cell imaging via an aminal reaction-induced aggregation process.

Novel colorimetric and ratiometric fluorometric dual-mode N, P-co-doped carbon nanodots, BPEI-CDs, for highly sensitive and selective detection of formaldehyde (FA) were successfully prepared from N-(phosphonomethyl)iminodiacetic acid (PMIDA) and branched polyethyleneimine (BPEI). The treatment of FA caused a remarkable linear enhancement of ratiometric fluorescence (F501 nm/F408 nm) in a wide range of 0-40 µM with a detection limit (LOD) of 0.47 µM (3σ/k), along with distinct color changes from colorless to light yellow. Mechanistic study shows that this electron-rich system, formed by the cooperative roles of N and P, promoted the FA-induced Schiff bases formation reaction, which contributed to the CD aggregation-induced emission (AIE) "turn-on" response and enhancement of π-conjugation-induced bathochromic behaviors. Furthermore, N, P-co-doped BPEI-CDs were successfully applied to the determination of FA in bean sprout samples. Using the standard addition method, the recoveries ranged from 96.9 to 101.8%, and the relative standard deviation (RSD) was in the range 2.23 to 3.21%. The application for intracellular FA sensing further verified that this novel nanoprobe may offer a new venue for the design of simple, low-cost, and sensitive biosensors. Graphical abstract.

Flow Topology Transition via Global Bifurcation in Thermally Driven Turbulence.

We report an experimental observation of a flow topology transition via global bifurcation in a turbulent Rayleigh-Bénard convection. This transition corresponds to a spontaneous symmetry breaking with the flow becomes more turbulent. Simultaneous measurements of the large-scale flow (LSF) structure and the heat transport show that the LSF bifurcates from a high heat transport efficiency quadrupole state to a less symmetric dipole state with a lower heat transport efficiency. In the transition zone, the system switches spontaneously and stochastically between the two long-lived metastable states.