Towards an Accurate Prediction of Nitrogen Chemical Shifts by Density Functional Theory and Gauge-Including Atomic Orbital

An effcient, yet accurate, computational protocol for predicting nitrogen NMR chemical shifts based on density functional theory and the gauge-including atomic orbital approach has been proposed. A database of small and relatively rigid compounds containing nitrogen atoms was compiled. Scaling factors for the linear correlation between experimental 15N chemical shifts and calculated isotropic shielding constants have been systematically investigated with seven different levels of theory in both chloroform and dimethyl sulfoxide, two commonly used solvents for NMR experiments. The best method yields a root-mean-square deviation of about 5.30 ppm and 7.00 ppm in CHCl3 and DMSO, respectively. Moreover, another set of scaling factors for -NH2 chemical shifts was also proposed based on a separate database with three levels of theory. Furthermore, it is encouraging that a reasonable transferability for the linear correlation has been found between these two solvents. This finding will enable broader applications of the developed empirical scaling factors to other commonly used solvents in NMR experiments. The consistency between theoretical predictions and experimental results for structural elucidations was illustrated for selected examples including regioisomers, tautomers, oxidation states, and protonated structures

11B NMR Chemical Shift Predictions via Density Functional Theory and Gauge-Including Atomic Orbital Approach: Applications to Structural Elucidations of Boron-Containing Molecules

11B nuclear magnetic resonance (NMR) spectroscopy is a useful tool for studies of boron-containing compounds in terms of structural analysis and reaction kinetics monitoring. A computational protocol, which is aimed at an accurate prediction of 11B NMR chemical shifts via linear regression, was proposed based on the density functional theory and the gauge-including atomic orbital approach. Similar to the procedure used for carbon, hydrogen, and nitrogen chemical shift predictions, a database of boron-containing molecules was first compiled. Scaling factors for the linear regression between calculated isotropic shielding constants and experimental chemical shifts were then fitted using eight different levels of theory with both the solvation model based on density and conductor-like polarizable continuum model solvent models. The best method with the two solvent models yields a root-mean-square deviation of about 3.40 and 3.37 ppm, respectively. To explore the capabilities and potential limitations of the developed protocols, classical boron-hydrogen compounds and molecules with representative boron bonding environments were chosen as test cases, and the consistency between experimental values and theoretical predictions was demonstrated

Damage mechanism of CFRP laminates with different curvatures impacted by ice projectile at high velocity

The spherical ice projectile impacting vertically on Carbon Fiber Reinforced Plastic laminates (CFRP laminates) with different curvatures was developed by using the one-stage light gas gun loading system. The numerical simulation results of the vertical impact of the arched CFRP laminates with different curvatures by SHI were compared with the experimental test results, Scanning Electron Microscopy micro failure mode and the image acquisition of the high speed camera by using ABAQUS/Explicit finite element software. The deformation process and failure mode of arched CFRP laminates with different curvatures and simulated hail ice (SHI)were analyzed, and the reliability of the numerical simulation was verified. By establishing a two-hinged simply supported mechanical physical model of arched laminates, the principal stresses of each layer along the direction of 0° and 90° of fibers in arched laminates were obtained. It would provide technical support for the prediction of fiber failure and delamination damage in the process of impacting on laminates at high velocity

The analysis on the inversion of the seawater intrusion based on RS - A case study of Longkou City

Hydrosphere movement in coastal zone performs as salty and fresh water mutual function. The Longkou city coastal zone which moves in the humanity under the intervention, has initiated the large-scale sea water intrusion, and therefore was especially under severe circumstances since 1980s. Until the end of 1980s and the beginning of the 90's, the sea water intrusion zone has formed the belt which spread fast from several hundred meters to several thousand meters along the coastal zone of Longkou city. Taking the landsat TM images in 2000 as data sources, first we applied the principal components transformation and analysis to analyze the six TM wave bands, and then use the histogram equalizing to deal with them. We use the two-value approach to be possible to remove the villages and small towns, the path, the pond (fishpond), the vegetables greenhouses, the rivers, the sand very conveniently. We take wave band as the research band, TM3, TM4 and TM5, which passed through correlation coefficient confirmation. Using the principal components analysis method to determine vegetation degree of coverage, the bare land index and the green index, the humidity analyzed in turn as four factors of the sea water intrusion. Inversion model of sea water intrusion is build up with the four factors. Finally a case study on the Longkou city, the analysis is obtained that the results have a very good correlation with the field measurements, and in accordance with the extent of the intrusion is divided into four categories. © 2009 Copyright SPIE - The International Society for Optical Engineering

Coupled controls of the infiltration of rivers, urban activities and carbonate on trace elements in a karst groundwater system from Guiyang, Southwest China

Hydrogeochemical processes of trace elements (TEs) are of considerable significance to river water and groundwater resource assessment and utilization in the karst region. Therefore, seven TEs were analyzed to investigate their contents, spatial variations, sources, and controlling factors in Guiyang, a typical karst urban area in southwest China. The results showed that the average content of TEs in river water (e.g., As = 1.44 ± 0.47 μg/L andCo = 0.15 ± 0.06 μg/L) was higher than that of groundwater (e.g., As = 0.51 ± 0.42 μg/L andCo = 0.09 ± 0.05 μg/L). The types of groundwater samples were dominated by Ca/Mg-HCO3 and Ca/Mg-Cl types, while those of the river water samples were Ca-Cl and Ca/Mg-Cl types. Principal component analysis (PCA) and correlation analysis (CA) analyses indicated that As and Mn in the groundwater of the study area were related to river infiltration. The end-member analysis further revealed that river infiltration (As = 0.86–1.81 μg/L, Cl/SO42- = 0.62–0.89) and urban activities (As = 0.21–0.32 μg/L, Cl/SO42- = 0.51–0.89) were two main controlling factors of TEs (e.g., As, Co, and Mn) in the study area. In addition, the ion ratios in river and groundwater samples indicated that the weathering of carbonates was also an important control on the hydrogeochemistry of TEs (e.g., Fe and Mn) in Guiyang waters. This study showed that the trace element (TE) contents of groundwater in the Guiyang area were greatly associated with urban input and river recharge, and provided a new perspective for understanding the geochemical behavior of TEs in urban surface and groundwater bodies, which will help the protection of groundwater in the karst areas of southwest China

Temporal Variations of Spring Water in Karst Areas: A Case Study of Jinan Spring Area, Northern China

Jinan is known as “Spring City,” because of its famous 72 artesian springs. Spring water plays an important role in the social and economic development of Jinan. However, the accelerating process of urbanization and more intensive human activities have significantly affected the Jinan springs. Based on the data from four spring groups (2015–2018), the hydrochemical characteristics of spring water were analyzed and 14 parameters were selected to evaluate the quality of spring water. In addition, the main ions variation characteristics of spring water in Jinan from 1958 to 2018 were analyzed, based on the previous studies. Subsequently, the spring flow dynamics of the Jinan spring area from 1958 to 2012 were also discussed. Overall, the water quality of the four spring groups is good. The chemical composition of the spring water is mainly controlled by the dissolution of calcite, followed by dolomite, and de-dolomitization. However, spring water is affected by human activities, and the hydrochemical type tends to evolve from HCO3-Ca to HCO3·SO4-Ca or HCO3-Ca·Mg. From 1958 to 2013, the main ions in spring water increased, while a relatively steady and certain fluctuation trend was observed from 2015 to 2018. Since 1958, the spring water flow in Jinan has experienced four stages, from decline to recovery. The exploitation of karst groundwater, change of land use type, and decrease of atmospheric precipitation are the three most important factors, affecting spring discharge dynamics. The slowdown of the increase of the main ion concentration in Jinan spring water and the resumption of spring water flowing indicate that remarkable achievements have been made to protect spring water, but there is still a long way to go to fully protect Jinan spring water

A Novel in Duck Myoblasts: The Transcription Factor Retinoid X Receptor Alpha (RXRA) Inhibits Lipid Accumulation by Promoting CD36 Expression

Retinoid X receptor alpha (RXRA) is a well-characterized factor that regulates lipid metabolism; however, the regulatory mechanism in muscle cells of poultry is still unknown. The overexpression and the knockdown of RXRA in myoblasts (CS2 cells), RT-PCR, and western blotting were used to detect the expression levels of genes and proteins related to PPAR-signaling pathways. Intracellular triglycerides (TGs), cholesterol (CHOL), and nonesterified free fatty acids (NEFAs) were detected by the Elisa kit. Fat droplets were stained with Oil Red O. The double-fluorescein reporter gene and chromatin immunoprecipitation (CHIP) were used to verify the relationship between RXRA and candidate target genes. The RXRA gene was highly expressed in duck breast muscle, and its mRNA and its protein were reduced during the differentiation of CS2 cells. The CS2 cells, with the overexpression of RXRA, showed reduced content in TGs, CHOL, NEFAs, and lipid droplets and upregulated the mRNA expression of CD36, ACSL1, and PPARG genes and the protein expression of CD36 and PPARG. The knockdown of RXRA expression in CS2 cells enhanced the content of TGs, CHOL, NEFAs, and lipid droplets and downregulated the mRNA and protein expression of CD36, ACLS1, ELOVL6, and PPARG. The overexpression of the RXRA gene, the activity of the double-luciferase reporter gene of the wild-type CD36 promoter was higher than that of the mutant type. RXRA bound to −860/−852 nt, −688/−680 nt, and −165/−157 nt at the promoter region of CD36. Moreover, the overexpression of CD36 in CS2 cells could suppress the content of TGs, CHOL, NEFAs, and lipid droplets, while the knockdown expression of CD36 increased the content of TGs, CHOL, NEFAs, and lipid droplets. In this study, the transcription factor, RXRA, inhibited the accumulation of TGs, CHOL, NEFAs, and fat droplets in CS2 cells by promoting CD36 expression

Prophylactic and therapeutic protection of human IgG purified from sera containing anti-exotoxin A titers against pneumonia caused by Pseudomonas aeruginosa

Antibodies are effective alternative tools to combat infections caused by Pseudomonas aeruginosa (PA), especially multi-drug-resistant PA. Thus, to solve the urgent need for an anti-PA antibody drug, we hypothesized that anti-PA intravenous immunoglobulins could be a practical attempt. Exotoxin A (ETA) is one of the most important factors for PA infection and is also a critical target for the development of immune interventions. In this study, a total of 320 sera were collected from healthy volunteers. The concentration of ETA-specific antibodies was determined by a Luminex-based assay and then purified by affinity chromatography. The purified IgGs were able to neutralize the cytotoxicity of ETA in vitro. We showed they had a prophylactic and therapeutic protective effect in PA pneumonia and ETA toxemia models. In addition, administration of nonspecific IgGs also provided partial protection. Collectively, our results provide additional evidence for IVIG-based treatment of infections caused by multi-drug-resistant PA and suggest that patients at high risk of PA pneumonia could be prophylactically treated with anti-ETA IgGs or even with nonspecific IgGs