Transient Simulation on Dynamic Response of Liquid Annular Seals

Transient change of the operating parameters has a serious influence on the stability of liquid annular seals. Take the liquid annular seals as a research object, a numerical method based on six-degree-of-freedom (6DOF) to analyze the dynamic response of liquid annular seals under gravity impact load. The variations of the force of liquid seal and pressure as well as the axis trajectory in time history are investigated. The influence of different sealing clearance, different liquid viscosity and different rotor speed is also studied. The results show that the maximum sealing pressure and sealing force of gravity direction will increase greatly in a very short time and then reduce rapidly. When sealing clearance increases, the displacement response amplitudes of axis trajectory, the maximum sealing force of gravity direction and maximum sealing pressure also increase. When liquid viscosity increases, the displacement response am plitudes of axis trajectory, the maximum sealing force of gravity direction and maximum sealing pressure decrease. We also found that different rotor speed has almost no influence on the maximum sealing force of gravity direction and maximum sealing pressure

High Frequency of CD4+CXCR5+ TFH Cells in Patients with Immune-Active Chronic Hepatitis B

BACKGROUND: T follicular helper (TFH) cells are a special subpopulation of T helper cells and can regulate humoral immune responses. This study examined whether the frequency of CD4(+)CXCR5(+) TFH cells could be associated with active immunity in chronic hepatitis B (CHB) patients. METHODOLOGY AND FINDINGS: The frequencies of peripheral blood CD4(+)CXCR5(+) TFH cells, inducible T cell costimulator (ICOS), and/or programmed death 1 (PD-1) positive CD4(+)CXCR5(+) TFH cells in immune-active (IA), immune-tolerant (IT) CHB, and healthy controls (HC) were characterized by flow cytometry analysis. The effect of adevofir dipivoxil treatment on the frequency of CD4(+)CXCR5(+) TFH cells, the concentrations of serum IL-2, IFN-γ, TNF-α, IL-4, IL-6, IL-10, IL-21, ALT, AST, HBsAg, HBsAb, HBeAg, HBeAb and HBV loads in IA patients were determined. The potential association of the frequency of CD4(+)CXCR5(+) TFH cells with clinical measures was analyzed. In addition, the frequency of splenic and liver CD4(+)CXCR5(+) TFH cells in HBV-transgenic mice was examined. We found that the frequency of CD4(+)CXCR5(+) TFH cells in IA patients was significantly higher than that of IT patients and HC, and the percentages of CD4(+)CXCR5(+) TFH in IA patients were positively correlated with AST. Furthermore, the percentages of ICOS(+), PD-1(+), and ICOS(+)PD-1(+) in CD4(+)CXCR5(+) TFH cells in CHB patients were significantly higher than that of HC. Treatment with adefovir dipivoxil reduced the frequency of CD4(+)CXCR5(+) TFH, PD-1(+)CD4(+)CXCR5(+) TFH cells and the concentrations of HBsAg and HBeAg, but increased the concentrations of HBsAb, HBeAb, IL-2 and IFN-γ in IA patients. Moreover, the frequency of splenic and liver CD4(+)CXCR5(+) TFH cells in HBV-transgenic mice was higher than that of wild-type controls. CONCLUSIONS: These data indicate that CD4(+)CXCR5(+) TFH cells may participate in the HBV-related immune responses and that high frequency of CD4(+)CXCR5(+) TFH cells may be a biomarker for the evaluation of active immune stage of CHB patients

CFD-predicted rotordynamic characteristics of a high temperature sodium liquid seal

Rotordynamic characteristics of a high temperature sodium liquid (HTSL) seal were studied in this paper by using CFD software. Compared with the water liquid seal, the HTSL seal has a larger leakage flow rate and a lower drag power loss. The HTSL seal has a larger direct stiffness coefficient and the effective stiffness coefficient Keff is also larger than the water liquid seal, which means the HTSL seal has a better stiffness capacity. The HTSL seal possesses a positive effective damping coefficient Ceff in the whole whirling frequency range, which means better stability for the rotor system especially in high rotor speeds

CFD-Predicted Rotordynamic Characteristics for High-Temperature Water Liquid Seal Considering Tooth Deformation

With the development of high-temperature centrifugal pump, the temperature of the medium in the pump must be higher than the normal water temperature. It is particularly important to study the rotordynamic characteristics of the seal at high temperature due to it being the core component of the rotor system. This paper takes the high temperature water liquid seal as a research object to study its rotordynamic characteristics based on the fluid-solid-thermal coupling, the deformation of seal teeth under thermal and dynamic loads was calculated. Based on the test rig, the leakage flow rate and drag power loss of water liquid seal at 20 °C, 50 °C, and 86 °C temperatures were tested and compared with the CFD (Computational Fluid Dynamics) calculation. Meanwhile, the DEFINE-CG-MOTION and DEFINE-PROFILE control macro were used to establish the rotor whirling equation, the frequency-independent rotordynamic coefficients (K, k, C, c) and frequency-dependent rotordynamic coefficients (Keff,Ceff) were evaluated by transient CFD method. This analysis was done at three different pressure drops (2.08, 4.12, and 8.25 bar) and three rotational speeds (2000, 4000, and 6000 r/min). The results show that with the increase of water temperature, both the leakage flow rate and drag power loss decrease, indicating the 86 °C water seal has a better sealing capacity. From the rotordynamic perspective, with the increase of water temperature, the direct stiffness coefficient decreases, and the effective stiffness coefficient Keff for 20 °C water seal possesses a better stiffness capability than the other two temperature seals. The effective damping coefficient Ceff for 20 °C water seal is larger than the other two temperature seals, which means it is more stable for the rotor system

Hollow black TiAlOx nanocomposites for solar thermal desalination

Although a solar–thermal conversion technique shows great potential for seawater desalination, there remains a grand challenge in exploring low-cost and high-efficiency photothermal materials. We report here a molten salt assisted galvanic replacement method for preparing a hollow black TiAlOx composite, which features a high solar absorptivity with up to 90.2% and has a high efficiency of 71.1% in a high salinity solution containing 15.3 wt% NaCl (∼5 times more concentrated than seawater). We exemplify the practical application of such hollow black TiAlOx composites as photothermal composites by setting up the automatic and manual tracking of solar desalination devices with a photic area of ∼1.0 m2, which can produce purified water with a rate of above 4.0 L m−2 day−1 in high-salinity water under natural light irradiation, and maintains good stability upon 5 days of continuous running. The advantages of the as-developed hollow black TiAlOx composites, including scalability, low cost, and high photothermal conversion efficiency, may open up a promising avenue practical application in seawater desalination.We would like to thank the support of the NSFC (51702284, 21875253), the Fundamental Research Funds for the Central Universities (112109*172210171) and the Startup Foundation for Hundred-Talent Program of Zhejiang University (112100- 193820101/001/022)

Structural dynamics of receptor recognition and pH-induced dissociation of full-length Clostridioides difficile Toxin B.

Clostridioides difficile secretes Toxin B (TcdB) as one of its major virulence factors, which binds to intestinal epithelial and subepithelial receptors, including frizzled proteins and chondroitin sulfate proteoglycan 4 (CSPG4). Here, we present cryo-EM structures of full-length TcdB in complex with the CSPG4 domain 1 fragment (D1401-560) at cytosolic pH and the cysteine-rich domain of frizzled-2 (CRD2) at both cytosolic and acidic pHs. CSPG4 specifically binds to the autoprocessing and delivery domains of TcdB via networks of salt bridges, hydrophobic and aromatic/proline interactions, which are disrupted upon acidification eventually leading to CSPG4 drastically dissociating from TcdB. In contrast, FZD2 moderately dissociates from TcdB under acidic pH, most likely due to its partial unfolding. These results reveal structural dynamics of TcdB during its preentry step upon endosomal acidification, which provide a basis for developing therapeutics against C. difficile infections