DEVELOPMENT OF A LOCALIZED ELECTROCHEMICAL PROPERTIES TEST METHOD： A STUDY OF CoCrMo AND Ti ALLOY LOCALIZED ELECTROCHEMICAL BEHAVIOR

Abstract: Corrosion of metallic biomaterials in biomedically-relevant environments depends on the local physical and chemical structure of the metal surface at the metal-solution interface, and the geometry of the electrode system. Local surface structure, including defects, inclusions, and grain boundaries may locally alter the electrode behavior, while local geometries, including crevice-like geometries or small electrode areas will give rise to specific changes in electrochemical behavior. Methods to detect local defects or surface flaws electrochemically may be possible with the appropriate combination of microelectrodes and pipette geometries. In order to have a better understanding of the localized electrochemical behavior under given conditions, a localized electrochemical impedance spectroscopy (LEIS) technique was developed and evaluated along with standard polarization testing. CoCrMo and Ti samples were tested using this technique and under varying conditions to simulate small areas, and the presence of crevice-like geometries. The reference and counter electrodes were positioned within a small-diameter pipette tube with varying cross sectional diameters and varying heights from the working electrode surface. In addition, two conditions were examined with solution both inside and outside of the pipette or with solution only on the inside. These conditions were selected to approximate different electrode conditions, surfaces and geometries relevant to medical device surfaces. Significant differences in both impedance and polarization behavior were seen with this local electrode system depending on the absence or presence of external solution, the diameter of the pipette, the distance of the pipette from the working electrode surface and the materials tested. The polarization resistance of the working electrode for both Ti and CoCrMo decreased, and the corrosion current increased with increasing pipette cross sectional area (i.e., electrode area) when no external solution was present. In the external solution condition, E¬corr of CoCrMo samples became more negative and R¬p,(the polarization resistance from the Tafel fitting result) also decreased with increasing exposed area, while the Icorr was not affected; for Titanium, the value of Ecorr, Icorr, and Rp changed relatively little compared to the behavior in the no-electrolyte-covered condition. The impedance behavior of this electrode system was affected by the presence of external solution or not. In the no-external-electrolyte condition, the response behaved according to a constant phase element Randles circuit with increasing area increasing the capacitance (CPE-T) for both CoCrMo and Titanium, while the polarization resistance Rp value for both CoCrMo and Titanium sample decreased. With external solution present, the impedance behavior followed a crevice corrosion model proposed by Swaminathan and Gilbert. Increasing the internal area, caused decreases in both internal pipette resistance (Ro) and crevice resistance (Rcr) for both Titanium and CoCrMo samples, while the internal capacitance (CPEo) increased, and external capacitance (CPEoc) as well as external surface resistance (Roc) changed relatively little compared to other parameters. In the external solution case, the distance between the microelectrode and the sample surface caused the crevice resistance, Rcr, to decrease exponentially as distance increased. There is a critical distance which leads to a sudden Rcr value drop. Keywords: Corrosion, Electrochemical Impedance Spectroscopy, Localized Electrochemical Impedance Spectroscopy, crevice corrosion, CoCrMo, Titanium allo

Tree-ring stable carbon isotope-based April-June relative humidity reconstruction since AD 1648 in Mt. Tianmu, China

Based on accurate dating, we have determined the stable carbon isotope ratios (delta C-13) of five Cryptomeria fortunei specimens from Mt. Tianmu, a subtropical area in southern China. The five delta C-13 time series records are combined into a single representative delta C-13 time series using a "numerical mix method." These are normalized to remove temporal variations of delta(13) C in atmospheric CO2 to obtain a carbon isotopic discrimination (Delta C-13) time series, in which we observe a distinct correlation between Delta C-13 and local April to June mean relative humidity (RH (AMJ) ) (n = 64, r = 0.858, p < 0.0001). We use this relationship to reconstruct RH (AMJ) variations from ad 1648 to 2014 at Mt. Tianmu. The reconstructed sequence show that over the past 367 years, Mt. Tianmu area was relatively wet, but in the latter part of the twentieth century, under the influence of increasing global warming, it has experienced a sharp reduction in relative humidity. Spatial correlation analysis reveals a significant negative correlation between RH (AMJ) at Mt. Tianmu and Sea Surface Temperature (SSTs) in the western equatorial Pacific and Indian Ocean. In other words, there is a positive correlation between tree-ring delta C-13 in Mt. Tianmu and SSTs. Both observed and reconstructed RH (AMJ) show significant positive correlations with East Asian and South Asian monsoons from 1951 to 2014, which indicate that RH (AMJ) from Mt. Tianmu reflects the variability of the Asian summer monsoon intensity to a great extent. The summer monsoon has weakened since 1960. However, an increase in relative humidity since 2003 implies a recent enhancement in the summer monsoon

Giant magnetic quantum oscillations in the thermal conductivity of TaAs: Indications of chiral zero sound

Charge transport of topological semimetals has been in the focus of intensive investigations because of their non-trivial band topology. Heat transport of these materials, on the other hand, is largely unexplored and remains elusive. Here we report on an observation of unprecedented, giant magnetic quantum oscillations of thermal conductivity in the prototypical Weyl semimetal TaAs. The oscillations are antiphase with the quantum oscillating electronic density of states of a Weyl pocket, and their amplitudes amount to two orders of magnitude of the estimation based on the Wiedemann-Franz law. Our analyses show that all the conventional heat-transport mechanisms through diffusions of propagating electrons, phonons and electron-hole bipolar excitations, are far inadequate to account for these phenomena. Taking further experimental facts that the parallel field configuration favors much higher magneto-thermal conductivity, we propose that the newly proposed chiral zero sound provides a reasonable explanation to these exotic phenomena. More work focusing on other topological semimetals along the same line is badly called for.Comment: 15 pages, 5 figure

Clinical and transcriptomic features of persistent exacerbation-prone severe asthma in U-BIOPRED cohort

Background: Exacerbation-prone asthma is a feature of severe disease. Yet, the basis for its persistency remains unclear. Objectives: To determine the clinical and transcriptomic features of the frequent-exacerbator (FE) and of persistent FEs (PFE) in U-BIOPRED cohort. Methods: We compared features of FE (≥2 exacerbations in past year) to infrequent exacerbators (IE, <2 exacerbations) and of PFE with repeat ≥2 exacerbations during the following year to persistent IE (PIE). Transcriptomic data in blood, bronchial and nasal epithelial brushings, bronchial biopsies and sputum cells were analysed by gene set variation analysis for 103 gene signatures. Results: Of 317 patients, 62.4 % were FE of whom 63.6% were PFE, while 37.6% were IE of whom 61.3% were PIE. Using multivariate analysis, FE was associated with short-acting beta-agonist use, sinusitis and daily oral corticosteroid use, while PFE with eczema, short-acting beta-agonist use and asthma control index. CEA Cell Adhesion Molecule 5 (CEACAM5) was the only differentially-expressed transcript in bronchial biopsies between PE and IE. There were no differentially-expressed genes in the other 4 compartments. There were higher expression scores for Type 2 , T-helper type-17 and Type 1 pathway signatures together with those associated with viral infections in bronchial biopsies from FE compared to IE, while higher expression scores of Type 2, Type 1 and steroid insensitivity pathway signatures in bronchial biopsies of PFE compared to PIE. Conclusion: FE group and its PFE subgroup are associated with poor asthma control while expressing higher Type 1 and Type 2 activation pathways compared to IE and PIE, respectively

Determinants of SARS-CoV-2 receptor gene expression in upper and lower airways

The recent outbreak of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has led to a worldwide pandemic. One week after initial symptoms develop, a subset of patients progresses to severe disease, with high mortality and limited treatment options. To design novel interventions aimed at preventing spread of the virus and reducing progression to severe disease, detailed knowledge of the cell types and regulating factors driving cellular entry is urgently needed. Here we assess the expression patterns in genes required for COVID-19 entry into cells and replication, and their regulation by genetic, epigenetic and environmental factors, throughout the respiratory tract using samples collected from the upper (nasal) and lower airways (bronchi). Matched samples from the upper and lower airways show a clear increased expression of these genes in the nose compared to the bronchi and parenchyma. Cellular deconvolution indicates a clear association of these genes with the proportion of secretory epithelial cells. Smoking status was found to increase the majority of COVID-19 related genes including ACE2 and TMPRSS2 but only in the lower airways, which was associated with a significant increase in the predicted proportion of goblet cells in bronchial samples of current smokers. Both acute and second hand smoke were found to increase ACE2 expression in the bronchus. Inhaled corticosteroids decrease ACE2 expression in the lower airways. No significant effect of genetics on ACE2 expression was observed, but a strong association of DNA- methylation with ACE2 and TMPRSS2- mRNA expression was identified in the bronchus.</p

Determinants of expression of SARS-CoV-2 entry-related genes in upper and lower airways.

Funder: Dutch Research Council (NWO)Funder: Cancer Research UK Cambridge CentreFunder: ATS Foundation/Boehringer Ingelheim Pharmaceuticals Inc. Research FellowshipFunder: The Netherlands Ministry of Spatial Planning, Housing, and the EnvironmentFunder: Chan Zuckerberg InitiativeFunder: The Netherlands Ministry of Health, Welfare, and SportFunder: Longfonds Junior FellowshipFunder: Cambridge BioresourceFunder: The Netherlands Organization for Health Research and DevelopmentFunder: Cambridge NIHR Biomedical Research CentreFunder: Parker B. Francis FellowshipFunder: China Scholarship Counci

Speech Signal Processing and Analysis Based on Mongolian long-tune Folk Songs

This paper mainly analyzes the speech signal of Mongolian long-tune folk songs through the method of speech acoustic analysis. From the perspective of duration, it studies the changes in the length of the passages, sentences and vocabulary of Mongolian long-tune folk songs, discusses the phonetic and acoustic characteristics of Mongolian long-tune folk songs, provides basic data for the protection and digital inheritance of oral culture, and explores the establishment of oral culture database

Frequency of variants in the UK Biobank for 82 fine-scale populations

Data generated from the paper "Leveraging fine-scale population structure reveals conservation in genetic effect sizes between human populations across a range of human phenotypes" by Sile Hu et al. 2023 (in press). It contains the allele frequency of every variant (25,485,749 in total) in the UK Biobank Imputed dataset in each of 82 populations containing enough ancestry from the 127 ancestries modelled in Hu et al

Molecular Evolution and Protein Structure Variation of <i>Dkk</i> Family

Dkks have inhibitory effects on the Wnt signaling pathway, which is involved in the development of skin and its appendages and the regulation of hair growth. The nucleotide sequences were compared and analyzed to further investigate the relationship between the structure and function of the Dkk gene family and vertebrate epidermal hair. The analysis of the molecular evolution of the Dkk family revealed that the evolution rate of the genes changed significantly after speciation, with the Aves and Reptilia branches showing accelerated evolution. Additionally, positive selection was observed at specific sites. The tertiary structure of the protein was also predicted. The analysis of the functional divergence of the Dkk family revealed that the functional divergence coefficient of each gene was greater than 0, with most of the functional divergence sites were located in the Cys-2 domain and a few in the Cys-1 domain. This suggests that the amino acid and functional divergence sites may play a role in regulating the binding of the Dkk family to LRP5/6, and thus affect the inhibition of Wnt signaling, leading to different functions of Dkk1, Dkk2, and Dkk4 in the development of skin hair follicles. In addition, the Dkk families of Aves and Reptilia may have undergone adaptive evolution and functional divergence