Treatment of Linear and Nonlinear Dielectric Property of Molecular Monolayer and Submonolayer with Microscopic Dipole Lattice Model: I. Second Harmonic Generation and Sum-Frequency Generation

In the currently accepted models of the nonlinear optics, the nonlinear radiation was treated as the result of an infinitesimally thin polarization sheet layer, and a three layer model was generally employed. The direct consequence of this approach is that an apriori dielectric constant, which still does not have a clear definition, has to be assigned to this polarization layer. Because the Second Harmonic Generation (SHG) and the Sum-Frequency Generation vibrational Spectroscopy (SFG-VS) have been proven as the sensitive probes for interfaces with the submonolayer coverage, the treatment based on the more realistic discrete induced dipole model needs to be developed. Here we show that following the molecular optics theory approach the SHG, as well as the SFG-VS, radiation from the monolayer or submonolayer at an interface can be rigorously treated as the radiation from an induced dipole lattice at the interface. In this approach, the introduction of the polarization sheet is no longer necessary. Therefore, the ambiguity of the unaccounted dielectric constant of the polarization layer is no longer an issue. Moreover, the anisotropic two dimensional microscopic local field factors can be explicitly expressed with the linear polarizability tensors of the interfacial molecules. Based on the planewise dipole sum rule in the molecular monolayer, crucial experimental tests of this microscopic treatment with SHG and SFG-VS are discussed. Many puzzles in the literature of surface SHG and SFG spectroscopy studies can also be understood or resolved in this framework. This new treatment may provide a solid basis for the quantitative analysis in the surface SHG and SFG studies.Comment: 23 pages, 3 figure

Investigation on stall characteristics of marine centrifugal pump considering transition effect

Marine centrifugal pumps are used as boiler feed pumps and condensate pumps in ocean engineering. Centrifugal pump stall is a transient flow structure, which may disrupt the uniformity of the flow field and have destructive effects on the pump. Centrifugal pump simulations are usually limited to the application of turbulence, ignoring the transition characteristics of the blade boundary layer. Aiming at the transient characteristics of centrifugal pump stall vortex, the calculation strategy considering the transition effect is established. This strategy determines the near-wall mesh based on the transition flow parameters and is applied to calculate the centrifugal pump stall for the first time. It is found that at deep stall conditions, the number of stall cells calculated by the transition model increases, while the stall frequency decreases. The microscopic flow structure calculated by the transition model and its relationship with the hump of the centrifugal pump head is obtained. The laminar separation bubbles near the blade leading edge will increase as the flow rate decreases, causing an increase in the friction loss on the blade surface, which lead to a hump in the pump head characteristics. The dynamic mode decomposition (DMD) method is used to extract the characteristic frequencies and corresponding modes of the 0.2Qd condition. In the high-order mode of the stall flow field with transition, a low-pressure zone formed at the head of the blade has a tendency to fall off from the wall, which shows the high-order motion characteristics of the stall vortex. The results could guide centrifugal pump design and operation.</p

Peripheral anti-inflammatory effects explain the ginsenosides paradox between poor brain distribution and anti-depression efficacy

<p>Abstract</p> <p>Background</p> <p>The effectiveness of ginseng in preventing and treating various central nervous system (CNS) diseases has been widely confirmed. However, ginsenosides, the principal components of ginseng, are characterized by poor accessibility to the brain, and this pharmacokinetic-pharmacological paradox remains poorly explained. Anti-inflammatory approaches are becoming promising therapeutic strategies for depression and other CNS diseases; however, previous studies have focused largely on anti-inflammatory therapies directed at the central nervous system. It is thus of interest to determine whether ginsenosides, characterized by poor brain distribution, are also effective in treating lipopolysaccharide- (LPS) induced depression-like behavior and neuroinflammation.</p> <p>Methods</p> <p>In an LPS-induced depression-like behavior model, the antidepressant effects of ginseng total saponins (GTS) were assessed using a forced swimming test, a tail suspension test, and a sucrose preference test. The anti-inflammatory efficacies of GTS in brain, plasma, and LPS-challenged RAW264.7 cells were validated using ELISA and quantitative real-time PCR. Moreover, indoleamine 2,3-dioxygenase (IDO) activity in the periphery and brain were also determined by measuring levels of kynurenine/tryptophan.</p> <p>Results</p> <p>GTS significantly attenuated LPS-induced depression-like behavior. Moreover, LPS-induced increases in 5-HT and tryptophane turnover in the brain were significantly reduced by GTS. IDO activities in brain and periphery were also suppressed after pretreatment with GTS. Furthermore, GTS-associated recovery from LPS-induced depression-like behavior was paralleled with reduced mRNA levels for IL-1β, IL-6, TNF-α, and IDO in hippocampus. Poor brain distribution of ginsenosides was confirmed in LPS-challenged mice. GTS treatment significantly decreased production of various proinflammatory cytokines in both LPS-challenged mice and RAW264.7 cells.</p> <p>Conclusion</p> <p>This study suggests that the anti-depression efficacy of GTS may be largely attributable to its peripheral anti-inflammatory activity. Our study also strengthens an important notion that peripheral anti-inflammation strategies may be useful in the therapy of inflammation-related depression and possibly other CNS diseases.</p

Novel PAX9 compound heterozygous variants in a Chinese family with non-syndromic oligodontia and genotype-phenotype analysis of PAX9 variants

Studies have reported that &gt;91.9% of non-syndromic tooth agenesis cases are caused by seven pathogenic genes. Objective: To report novel heterozygous PAX9 variants in a Chinese family with non-syndromic oligodontia and summarize the reported genotype-phenotype relationship of PAX9 variants. Methodology: We recruited 28 patients with non-syndromic oligodontia who were admitted to the Hospital of Stomatology Hebei Medical University (China) from 2018 to 2021. Peripheral blood was collected from the probands and their core family members for whole-exome sequencing (WES) and variants were verified by Sanger sequencing. Bioinformatics tools were used to predict the pathogenicity of the variants. SWISS-MODEL homology modeling was used to analyze the three-dimensional structural changes of variant proteins. We also analyzed the genotype-phenotype relationships of PAX9 variants. Results: We identified novel compound heterozygous PAX9 variants (reference sequence NM_001372076.1) in a Chinese family with non-syndromic oligodontia: a new missense variant c.1010C&gt;A (p.T337K) in exon 4 and a new frameshift variant c.330_331insGT (p.D113Afs*9) in exon 2, which was identified as the pathogenic variant in this family. This discovery expands the known variant spectrum of PAX9; then, we summarized the phenotypes of non-syndromic oligodontia with PAX9 variants. Conclusion: We found that PAX9 variants commonly lead to loss of the second molars

Detection of QTL for phosphorus efficiency and biomass traits at the seedling stage in wheat

Phosphorus (P) is one of the most vital nutrient elements in crop output and quality formation. In this study, four biomass, four P uptake efciency (PupE), and three P-utilization efciency (PutE) traits were investigated using a set of recombinant inbred lines (RILs) derived from a cross of “SN0431×LM21”, under hydroponic culture trials at low P (LP) and normal P (NP) levels in two diferent seasons, respectively. A total of 85 QTL were identifed on 18 chromosomes except for 1D, 2A, and 3D. Among them, 36 and 42 QTL were detected under LP and NP, respectively, and seven QTL were simultaneously detected under LP and NP. Seventeen relatively high-frequency QTL (RHF-QTL) were detected. The average contributions of 13 major RHF-QTL were over 10.00%. Five important QTL clusters were detected on chromosomes 4D, 5A, and 5B. Among them, positive linkages were observed between PutE and biomass traits at four QTL clusters, C1, C2, C3, and C6, showing these loci may be hot spots for genetic control of both phosphorus utilization and biomass accumulation in wheat seedlings. In addition, correlation analysis indicated that three biomass traits (SDW, RDW, and TDW) should be used as primary selection indexes for PE at the seedling stage