International Interlaboratory Comparison of Thermogravimetric Analysis of Graphene-Related Two-Dimensional Materials.

Research on graphene-related two-dimensional (2D) materials (GR2Ms) in recent years is strongly moving from academia to industrial sectors with many new developed products and devices on the market. Characterization and quality control of the GR2Ms and their properties are critical for growing industrial translation, which requires the development of appropriate and reliable analytical methods. These challenges are recognized by International Organization for Standardization (ISO 229) and International Electrotechnical Commission (IEC 113) committees to facilitate the development of these methods and standards which are currently in progress. Toward these efforts, the aim of this study was to perform an international interlaboratory comparison (ILC), conducted under Versailles Project on Advanced Materials and Standards (VAMAS) Technical Working Area (TWA) 41 "Graphene and Related 2D Materials" to evaluate the performance (reproducibility and confidence) of the thermogravimetric analysis (TGA) method as a potential new method for chemical characterization of GR2Ms. Three different types of representative and industrially manufactured GR2Ms samples, namely, pristine few-layer graphene (FLG), graphene oxide (GO), and reduced graphene oxide (rGO), were used and supplied to ILC participants to complete the study. The TGA method performance was evaluated by a series of measurements of selected parameters of the chemical and physical properties of these GR2Ms including the number of mass loss steps, thermal stability, temperature of maximum mass change rate (Tp) for each decomposition step, and the mass contents (%) of moisture, oxygen groups, carbon, and impurities (organic and non-combustible residue). TGA measurements determining these parameters were performed using the provided optimized TGA protocol on the same GR2Ms by 12 participants across academia, industry stakeholders, and national metrology institutes. This paper presents these results with corresponding statistical analysis showing low standard deviation and statistical conformity across all participants that confirm that the TGA method can be satisfactorily used for characterization of these parameters and the chemical characterization and quality control of GR2Ms. The common measurement uncertainty for each parameter, key contribution factors were identified with explanations and recommendations for their elimination and improvements toward their implementation for the development of the ISO/IEC standard for chemical characterization of GR2Ms.

Thickness measurements of graphene oxide flakes using atomic force microscopy: results of an international interlaboratory comparison.

Flake thickness is one of the defining properties of graphene-related 2D materials (GR2Ms), and therefore requires reliable, accurate, and reproducible measurements with well-understood uncertainties. This is needed regardless of the production method or manufacturer because it is important for all GR2M products to be globally comparable. An international interlaboratory comparison on thickness measurements of graphene oxide flakes using atomic force microscopy has been completed in technical working area 41 of versailles project on advanced materials and standards. Twelve laboratories participated in the comparison project, led by NIM, China, to improve the equivalence of thickness measurement for two-dimensional flakes. The measurement methods, uncertainty evaluation and a comparison of the results and analysis are reported in this manuscript. The data and results of this project will be directly used to support the development of an ISO standard.

Particle Size Distributions for Cellulose Nanocrystals Measured by Transmission Electron Microscopy: An Interlaboratory Comparison.

Particle size is a key parameter that must be measured to ensure reproducible production of cellulose nanocrystals (CNCs) and to achieve reliable performance metrics for specific CNC applications. Nevertheless, size measurements for CNCs are challenging due to their broad size distribution, irregular rod-shaped particles, and propensity to aggregate and agglomerate. We report an interlaboratory comparison (ILC) that tests transmission electron microscopy (TEM) protocols for image acquisition and analysis. Samples of CNCs were prepared on TEM grids in a single laboratory, and detailed data acquisition and analysis protocols were provided to participants. CNCs were imaged and the size of individual particles was analyzed in 10 participating laboratories that represent a cross section of academic, industrial, and government laboratories with varying levels of experience with imaging CNCs. The data for each laboratory were fit to a skew normal distribution that accommodates the variability in central location and distribution width and asymmetries for the various datasets. Consensus values were obtained by modeling the variation between laboratories using a skew normal distribution. This approach gave consensus distributions with values for mean, standard deviation, and shape factor of 95.8, 38.2, and 6.3 nm for length and 7.7, 2.2, and 2.9 nm for width, respectively. Comparison of the degree of overlap between distributions for individual laboratories indicates that differences in imaging resolution contribute to the variation in measured widths. We conclude that the selection of individual CNCs for analysis and the variability in CNC agglomeration and staining are the main factors that lead to variations in measured length and width between laboratories.

Electro- and photon-induced cooling in BNT-BT-SBET relaxors with in situ optical temperature sensing.

A novel lead-free luminescent ferroelectric (FE) ceramic, ${{\rm Bi}_{0.5}}{{\rm Na}_{0.5}}{{\rm TiO}_3} {-} {0.{06\; \rm BaTiO}_3} {-} {0.{055\;\rm Sr}_{0.7}}{{\rm Bi}_{0.18}}{{\rm Er}_{0.02 \,\square\, 0.1}}$Bi0.5Na0.5TiO3-0.06BaTiO3-0.055Sr0.7Bi0.18Er0.02◻0.1${{\rm TiO}_3}$TiO3 (BNT-BT-SBET), is developed with an adiabatic temperature change ($\Delta T$ΔT) of 0.7 K under an electric field ($E$E) of 60 kV/cm at room temperature, an anti-Stokes fluorescence cooling, and a maximum optical $T$T sensitivity of ${0.0055}\;{{\rm K}^{ - 1}}$0.0055K-1 at 522 K. Interestingly, the electrocaloric response reaches a saturation at permittivity shoulder $T$T of 100°C; meanwhile, the maximized emission intensity of $^2{{\rm H}_{11/2}}{ \to ^4}{{\rm I}_{15/2}}$2H11/2→4I15/2 occurs. $T$T- and $E$E-tunable enhancement of $^2{{\rm H}_{11/2}}{ \to ^4}{{\rm I}_{15/2}}$2H11/2→4I15/2 emission intensity is due to the population inversion from the $^4{{\rm S}_{3/2}}$4S3/2 to $^2{{\rm H}_{11/2}}$2H11/2 states caused by an incoherent regime consisting of FE phase and polar nanoregions in a relaxor matrix.

Thyroid autoantibodies in pregnancy are associated with hypertensive disorders of pregnancy: Ma'anshan Birth Cohort Study.

OBJECTIVE: Hypertensive disorders of pregnancy (HDP) have been associated with adverse health outcomes for both mothers and children. Previous studies examining associations of maternal thyroid autoantibodies with HDP indicate conflicting results. The objective of this study was to examine associations of maternal thyroid autoantibody positivity in the first and the second trimesters with the risk of HDP. DESIGN, PARTICIPANTS AND MEASUREMENTS: In the Ma'anshan Birth Cohort study, a population-based prospective study in China, a total of 3474 pregnant women were enrolled between May 2013 and September 2014. Thyroid autoantibodies, including antithyroperoxidase autoantibody (TPOAb) and antithyroglobulin autoantibody (TgAb), as well as thyroid function tests, were measured in both the first and the second trimesters in 2893 pregnant women. Multivariate logistic regression analyses were conducted to calculate the odds ratio (OR) and 95% confidence interval (CI) for the associations between thyroid autoantibodies and HDP. RESULTS: Multivariate logistic regression analyses showed that TPOAb positivity in the first trimester was associated with a 1.80 (95% CI = 1.17-2.78) increased odds of HDP after adjustment for confounders, which was mainly due to an increased risk of gestational hypertension (OR = 1.93, 95% CI = 1.17-3.18). In addition, TgAb positivity in the first trimester was associated with a higher risk of HDP (OR = 1.78, 95% CI = 1.16-2.73) after adjustment for confounders, which was mainly due to an increased risk of gestational hypertension (OR = 1.89, 95% CI = 1.15-3.11). These associations were also seen among euthyroid women. Women with positive TPOAb in the second trimester seemed to have a higher risk of gestational hypertension (OR = 1.87, 95% CI = 1.02-3.43) after adjustment for confounders. However, among euthyroid women, TPOAb positivity in the second trimester was not associated with HDP. The TgAb status in the second trimester was not associated with HDP. CONCLUSIONS: Our results show that TPOAb positivity and TgAb positivity in the first trimester are associated with an increased risk of HDP. These data demonstrate that these associations are even seen among euthyroid women.

Body image as risk factor for emotional and behavioral problems among Chinese adolescents.

BACKGROUND: Being overweight and obesity during adolescence are worldwide public health problems. This study examined the relationship between actual weight, body image, and emotional and behavioral problems among Chinese adolescents. METHODS: A total of 3841 adolescents (age range, 11-16 years) from 5 Chinese cities were included in this cross-sectional study. All of the study participants were asked to complete questionnaires (including demographic features, strengths and difficulties questionnaires, pubertal development scale), and their height and weight were measured at the same time. Body image was measured in two ways: self-perceived weight and body satisfaction. The relationship between weight status and mental health was estimated by multivariate logistic regression for boys and girls. RESULTS: Our study showed a difference by sex for prevalence of being overweight/obesity and body dissatisfaction among Chinese adolescents. Boys were more likely to be overweight or obese than girls (30.4% vs. 21.5%, p < 0.05), but girls were more likely to be dissatisfied with their bodies than boys (41.2% vs. 27.9%, p < 0.05). In the logistic regression, body image, not actually being overweight, was significantly associated with a higher risk of emotional and behavioral problems. Compared to perceived normal weight boys, boys who perceived themselves as underweight had an increased likelihood of emotional problems (adjusted odds ratio [OR] = 1.73; 95% confidence interval (CI), 1.16-2.57), conduct problems (OR = 1.73; 95% CI, 1.20-2.50), and total difficulties (OR = 1.50; 95% CI, 1.09-2.05). Compared to body satisfaction, body dissatisfaction was a risk factor for emotional problems (boys: OR = 2.80; 95% CI, 1.84-4.25; girls: OR = 2.18; 95% CI, 1.42-3.36), conduct problems (boys: OR = 1.87, 95% CI, 1.26-2.76; girls: OR = 2.79; 95% CI, 1.46-5.30), hyperactivity problems (boys: OR = 1.67; 95% CI, 1.09-2.55; girls: OR = 2.04; 95% CI, 1.13-3.69), and total difficulties (boys: OR = 2.03; 95% CI, 1.45-2.84; girls: OR = 2.30; 95% CI, 1.46-3.56). CONCLUSIONS: Being overweight and obese during adolescence are very serious public health problems in China. Body image was a more substantial predictor for adolescent emotional and behavioral problems than actually being overweight/obesity.

Emotion regulation, emotional eating and the energy-rich dietary pattern. A population-based study in Chinese adolescents.

Research investigating the influence of emotion regulation (ER) strategies on emotional eating and diet among Chinese adolescents is scarce. The aim of this study was to test associations between two ER strategies (suppression/cognitive reappraisal), emotional eating, and an energy-rich dietary pattern. A total of 4316 adolescents from 10 high schools were surveyed. Dietary patterns were derived using factor analysis. Bivariate correlations were analyzed to examine associations between ER strategies, emotional eating behavior and an energy-rich dietary pattern, by gender. The mediating effect of emotional eating in the relationship between ER and energy-rich food consumption by gender was estimated using structural equation modeling. A higher level of suppression, but no lack of cognitive reappraisal, was associated with emotional eating in boys and girls. A higher level of suppression and lack of cognitive reappraisal were associated with a greater intake of energy-rich foods in girls only. Emotional eating mediated the relationship between a higher level of suppression and a greater intake of energy-rich food in girls. This study revealed significant associations between two ER strategies and an energy-rich dietary pattern in girls, and provided evidence that higher levels of suppression may put girls at risk for emotional eating, potentially affecting the energy-rich dietary pattern.

[Calibration Procedure of Laser Confocal Micro-Raman Spectrometer].

As a common spectral characterization technique, Raman spectroscopy is widely used and has a specified calibration procedure. Based on laser confocal micro-Raman spectrometer, in this paper, we briefly introduced the principle, configuration and main components of Raman spectrometer. In addition, the calibration procedures were also presented, with an emphasis on the calibration of spectrometer (spectrograph) and that of excitation laser wavelength. On the basis of conventional calibration method, a novel and more accurate method was proposed to obtain the actual excitation wavelength, that is, calibration at the point of Raman shift Δν=0. Using this novel calibration method of excitation wavelength, Raman frequency shift values of sulfur were measured, and compared with the standard values from American Society Testing and Materials (ASTM). As a result, the measured values after calibration were consistent with those ASTM values, which indicated that the calibration method is accurate. Thus, a more reasonable calibration procedure of the laser confocal micro-Raman spectrometer was provided.

Chemiluminescence accompanied by the reaction of acridinium ester and manganese (II).

An acridinium ester (AE) alkaline solution can react with Mn(II) to generate a strong chemiluminescence (CL) centered at 435 nm. The effects of reaction conditions such as pH and Mn(II) concentration on CL intensity were examined. In order to explore the CL mechanism, the effect of oxygen on the CL reaction was examined and an X-ray photoelectron spectroscopy study of the reaction precipitate was carried out. The results indicated that oxygen participated in the CL reaction and Mn(IV) was the primary product in the system. A possible mechanism was proposed that involved two pathways: (1) dissolved oxygen was reduced to reactive oxygen radicals by Mn(II), these reactive intermediates then reacted with AE to produce excited state acridone; (2) Mn(II) could reduce AE to partly reduced AE, which then reacted with oxygen to form excited state acridone. The reactions of other metal ions with AE were also tested, and only Mn(II) was shown to trigger strong CL emission of AE, which indicated that the system had good selectivity for Mn(II).

Revolutionizing targeting precision: microfluidics-enabled smart microcapsules for tailored delivery and controlled release.

As promising delivery systems, smart microcapsules have garnered significant attention owing to their targeted delivery loaded with diverse active materials. By precisely manipulating fluids on the micrometer scale, microfluidic has emerged as a powerful tool for tailoring delivery systems based on potential applications. The desirable characteristics of smart microcapsules are associated with encapsulation capacity, targeted delivery capability, and controlled release of encapsulants. In this review, we briefly describe the principles of droplet-based microfluidics for smart microcapsules. Subsequently, we summarize smart microcapsules as delivery systems for efficient encapsulation and focus on target delivery patterns, including passive targets, active targets, and microfluidics-assisted targets. Additionally, based on release mechanisms, we review controlled release modes adjusted by smart membranes and on/off gates. Finally, we discuss existing challenges and potential implications associated with smart microcapsules.

Mechanistic study of the retro-aza-Michael reaction in saccharothriolide L: identification of 2-amino-4-methylphenol as an effective protecting tool for the Michael acceptor.

Saccharothriolide L (1), a derivative of saccharothriolides (STLs) produced by the rare actinomycete Saccharotrix sp. A1506, was synthesized through the precursor-directed in situ synthesis (PDSS) method. The structure of 1 was determined by 1D and 2D NMR and HR-ESI-MS data analyses. A comparison of the rate of the retro-aza-Michael reaction between saccharothriolide L (1) and saccharothriolide B (2) indicated that the 2-amino-4-methylphenol group in 1 might be an effective masking tool for highly reactive, bioactive α, ß-unsaturated carbonyl compounds.

Study on the Effect of Sn, In, and Se Co-Doping on the Thermoelectric Properties of GeTe.

GeTe and Ge0.99-xIn0.01SnxTe0.94Se0.06 (x = 0, 0.01, 0.03, and 0.06) samples were prepared by vacuum synthesis combined with spark plasma sintering (SPS). The thermoelectric properties of GeTe were coordinated by multiple doping of Sn, In, and Se. In this work, a maximum zT(zT = S2σT/κ) of 0.9 and a power factor (PF = S2σ) of 3.87 µWmm-1 K-2 were obtained in a sample of Ge0.99In0.01Te0.94Se0.06 at 723K. The XRD results at room temperature show that all samples are rhombohedral phase structures. There is a peak (~27°) of the Ge element in GeTe and the sample (x = 0), but it disappears after Sn doping, indicating that Sn doping can promote the dissolution of Ge. The scattering mechanism of the doped samples was calculated by the conductivity ratio method. The results show that phonon scattering Is dominant in all samples, and alloy scattering is enhanced with the increase in the Sn doping amount. In doping can introduce resonance energy levels and increase the Seebeck coefficient, and Se doping can introduce point defects to suppress phonon transmission and reduce lattice thermal conductivity. Therefore, the thermoelectric properties of samples with x = 0 improved. Although Sn doping will promote the dissolution of Ge precipitation, the phase transition of the samples near 580 K deteriorates the thermoelectric properties. The thermoelectric properties of Sn-doped samples improved only at room temperature to ~580 K compared with pure GeTe. The synergistic effect of multi-element doping is a comprehensive reflection of the interaction between elements rather than the sum of all the effects of single-element doping.

Associations between urinary level of bisphenol A, phthalates, 8-iso-prostaglandin-F2α, and emotional and behavioral problems among Chinese adolescents.

BACKGROUND: Emotional and behavioral problems (EBPs) of adolescents is a worldwide public health problem. Bisphenol A (BPA) and phthalate (PAEs) are prevalent and potentially toxic to human health. Therefore, this study aimed to investigate the associations between urinary level of BPA, PAEs, 8-iso-prostaglandin-F2α (8-iso-PGF2α), and EBPs. METHODS: A total of 865 Chinese adolescents were included in this study and EBPs was assessed using the Strengths and Difficulties Questionnaire (SDQ). Urinary concentrations of BPA and seven PAEs metabolites in adolescents were determined by high performance liquid chromatography-tandem mass spectrometry. Urinary 8-iso-PGF2α concentration was detected by enzyme-linked immunosorbent assay (ELISA). Spearman rank correlation analysis, multivariate logistic regression analysis, restricted cubic spline functions were used to explore the relationship between the levels of BPA, PAEs, 8-iso-PGF2α and EBPs. RESULTS: BPA and PAEs metabolites were positively associated with EBPs in Chinese adolescents. And the 8-iso-PGF2α was significantly non-linearly correlated with emotional symptoms, conduct problems, peer problems and total difficulties. Furthermore, 8-iso-PGF2α may partially mediate the association between BPA and PAEs exposure and EBPs. LIMITATIONS: This study was a cross-sectional study, the cause-effect relationship between BPA, PAEs exposure and EBPs could not be determined. A single spot urine sample for BPA and PAEs exposure characterization maybe could not represent their long-term exposure level. CONCLUSIONS: High exposure of BPA and PAEs are associated with EBPs, which may be partly mediated by oxidative stress among adolescents. The results of this study could provide certain ideas for subsequent related research.

A ROS-responsive and scavenging hydrogel for postoperative abdominal adhesion prevention.

Postoperative abdominal adhesion (PAA) widely occurs after abdominal surgery, which often produces severe complications. However, there were still no satisfactory anti-adhesive products including barriers and anti-adhesive agents. Herein, we developed a ROS-responsive and scavenging hydrogel barrier, termed AHBC/PSC, wherein the monomer AHBC was synthesized by phenylboronic acid (PBA)-modified hyaluronic acid (HA-PBA) further grafted with adipic dihydrazide (ADH) and PBA-based chlorogenic acid (CGA) via ROS-sensitive borate ester bond, and the other monomer PSC was constructed by polyvinyl alcohol (PVA) grafted with sulfated betaine (SB) and p-hydroxybenzaldehyde (CHO). Further, the double crosslinked AHBC/PSC hydrogel was successfully fabricated between AHBC and PSC via forming dynamic covalent acylhydrazone bonds and borate ester bonds. Results showed that AHBC/PSC hydrogel had in situ gelation behavior, satisfactory mechanical properties (storage modulus of about 1 kPa and loss factor Tan δ of about 0.5), suitable wet tissue adhesion strength of about 2.3 kPa on rat abdominal wall, and good biocompatibility, achieving an ideal physical barrier. Particularly, CGA could be responsively released from the hydrogel by breakage of borate ester bonds between CGA and PBA based on high reactive oxygen species (ROS) levels of damaged tissue and exhibited great ROS scavenging capability to regulate inflammation and promote the polarization of macrophages from pro-inflammatory M1 phenotype to anti-inflammatory M2 phenotype. Moreover, the grafted SB as a zwitterionic group could reduce protein adsorption and fibroblast adhesion. Finally, the in vivo experiments revealed that AHBC/PSC hydrogel with good safety and in vivo retention behavior of about 2 weeks, effectively prevented PAA by regulating the inflammatory microenvironment and alleviating the fibrosis process. In brief, the versatile AHBC/PSC hydrogel would provide a more convenient and efficient approach for PAA prevention. STATEMENT OF SIGNIFICANCE: Postoperative abdominal adhesion (PAA) widely occurs after surgery and is often accompanied by severe complications. Excessive inflammation and oxidative stress are very crucial for PAA formation. This study provides a ROS-responsive and scavenging hydrogel with suitable mechanical properties, good biocompatibility and biodegradability, and resistance to protein and fibroblast. The antioxidant and anti-inflammatory active ingredient could be responsively released from the hydrogel via triggering by the high ROS levels in the postoperative microenvironment thereby regulating the inflammatory balance. Finally, the hydrogel would effectively regulate the development process of PAA thereby achieving non-adhesion wound healing.

ROS-responsive sprayable hydrogel as ROS scavenger and GATA6+ macrophages trap for the prevention of postoperative abdominal adhesions.

Postoperative abdominal adhesions are a common clinical problem after surgery and can cause many serious complications. Current most commonly used antiadhesion products are less effective due to their short residence time and focus primary on barrier function. Herein, we developed a sprayable hydrogel barrier (sHA-ADH/OHA-E) with self-regulated drug release based on ROS levels at the trauma site, to serve as a smart inflammatory microenvironment modulator and GATA6+ macrophages trap for non-adherent recovery from abdominal surgery. Sulfonated hyaluronic acid (HA) conjugates modified with adipic dihydrazide (sHA-ADH), and oxidized HA conjugates grafted with epigallocatechin-3-gallate (EGCG) via ROS-cleavable boronate bonds (OHA-E) were synthesized. sHA-ADH/OHA-E hydrogel was facilely fabricated within 5 s after simply mixing sHA-ADH and OHA-E through forming dynamic covalent acylhydrazones. With good biocompatibility, appropriate mechanical strength, tunable shear-thinning, self-healing, asymmetric adhesion, and reasonable in vivo retention time, sHA-ADH/OHA-E hydrogel meets the requirements of a perfect physical barrier. Intriguingly, sulfonic acid groups endowed the hydrogel with satisfactory anti-fibroblast and macrophage attachment capability, and were demonstrated for the first time to act as polyanion traps to prevent GATA6+ macrophages aggregation. Importantly, EGCG could be intelligently released by ROS triggering to alleviate oxidative stress and promote proinflammatory M1 macrophage polarize to antiinflammatory M2 phenotype. Further, the fibrinolytic system balance was restored to reduce fibrosis. Thanks to the above advantages, the sHA-ADH/OHA-E hydrogel exhibited excellent anti-adhesion effects in a rat sidewall defect-cecum abrasion model and is expected to be a promising and clinically translatable antiadhesion barrier.

The characterization of the concentration of the single-walled carbon nanotubes in aqueous dispersion by UV-Vis-NIR absorption spectroscopy.

Current and future applications of single-wall carbon nanotubes (SWCNTs) depend on the dispersion of the SWCNTs in aqueous solution and their quantitation. The concentration of SWCNTs is an important indicator to evaluate the dispersibility of the surfactant-dispersed SWCNTs suspension. Due to the complexity of the SWCNTs suspension, it is necessary to determine both the total concentration of the dispersed SWCNTs and the concentration of individually dispersed SWCNTs in aqueous suspensions, and these were evaluated through the absorbance and the resonance ratios of UV-Vis-NIR absorption spectra, respectively. However, there is no specific and reliable position assigned for either calculation of the absorbance or the resonance ratio of the UV-Vis-NIR absorption spectrum. In this paper, different ranges of wavelengths for these two parameters were studied. From this, we concluded that the wavelength range between 300 nm and 600 nm should be the most suitable for evaluation of the total concentration of dispersed SWCNTs in the suspension; also, wavelengths below 800 nm should be most suitable for evaluation of the concentration of individually dispersed SWCNTs in the suspension. Moreover, these wavelength ranges are verified by accurate dilution experiments.

Characterization of protoberberine alkaloids in Coptidis Rhizoma (Huanglian) by HPLC with ESI-MS/MS.

This study aims to qualitatively analyze protoberberine alkaloids in crude extract of Coptidis Rhizoma using HPLC with ESI-MS/MS. Possible specific molecular weights of protoberberine alkaloids were firstly deduced according to literatures and were adopted to screen the alkaloids in the HPLC with ESI-MS of crude extract of Coptidis Rhizoma. As a result, 21 protoberberine alkaloids were found, including compounds of very low concentration and compounds coeluted in one peak. Among these, two compounds were positively identified and verified by comparison with standards. Ten of these compounds were first reported in this study for Coptidis Rhizoma. In addition, chromatographic retention parameters a and c of all compounds were obtained using their retention times under five gradient conditions and were applied to confirm the deduction about the structures of protoberberine alkaloids by tandem mass data.

Effects of growth conditions on the GaAs/AlAs superlattices by grazing incidence X-ray reflectivity.

The effects of growth conditions on the structural properties of the GaAs/AlAs superlattices were investigated by grazing incidence X-ray reflectivity (GIXRR), transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The GaAs/AlAs superlattices were prepared by molecular beam epitaxy (MBE) at different growth temperatures (500 degrees C, 600 degrees C and 660 degrees C) and growth rates (1.0 microm/h and 0.7 microm/h for GaAs). And the thicknesses, surface/interface roughnesses and densities of the GaAs/AlAs superlattices were obtained by GIXRR by fitting the whole spectral reflectance curves based on the Parratt recurrence formula. The homogeneity of samples was also studied at different growth conditions. The results indicate that the superlattices grown at a high temperature and large growth rate ratio (rate of AlAs to that of GaAs) possess better structure and more homogeneity.

The Effect of Cu Content on the Microstructure and Properties of the Wire Arc Additive Manufacturing Al-Cu Alloy.

Al-Cu alloy has broad application prospects in the field of aerospace due to its excellent performance. In this paper, deposits with different Cu contents were prepared by the wire arc additive manufacturing (WAAM) process, and the effects of Cu content on the microstructure and mechanical properties were investigated. The microstructure of Al-Cu alloy was investigated by metallography, scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), and transmission electron microscope (TEM). The results show that both the number and size of the precipitated θ phases (Al2Cu) in the as-deposited material increase with the increase of Cu content. After the T4 treatment, the solid solution amount of Cu in the matrix showed a trend of first increasing and then remaining stable. When the content of Cu was greater than 5.65%, as the Cu content increased, the number and size of the remaining θ phases both increased. In the peak ageing state, the amount of precipitated θ' phase showed a trend of increasing and then remaining stable. After the T6 treatment, the mechanical properties showed a trend of first increasing and then decreasing with the increase of the content of Cu. When the Cu content was 5.65%, the deposit achieved the best mechanical properties, and the anisotropy of the mechanical properties disappeared. The tensile strength, yield strength, and elongation reached 538 MPa, 478 MPa, and 10.5%, respectively. When the content of Cu was greater than 5.65%, the anisotropy of mechanical properties was obvious, and the fracture mode of the vertical specimen changed from ductile fracture to brittle fracture.

The Abnormal Accumulation of Lipopolysaccharide Secreted by Enriched Gram-Negative Bacteria Increases the Risk of Rotavirus Colonization in Young Adults.

Human rotavirus (HRV) is an enteric virus that causes infantile diarrhea. However, the risk factors contributing to HRV colonization in young adults have not been thoroughly investigated. Here, we compared the differences in dietary habits and composition of gut microbiota between asymptomatic HRV-infected young adults and their healthy counterparts and investigated potential risk factors contributing to HRV colonization. Our results indicated that asymptomatic HRV-infected adults had an excessive intake of milk and dairy and high levels of veterinary antibiotics (VAs) and preferred veterinary antibiotic (PVAs) residues in urine samples. Their gut microbiota is characterized by abundant Gram-negative (G-) bacteria and high concentrations of lipopolysaccharide (LPS). Several opportunistic pathogens provide discriminatory power to asymptomatic, HRV-infected adults. Finally, we observed an association between HRV colonization and disrupted gut microbiota caused by the exposure to VAs and PVAs. Our study reveals the traits of disrupted gut microbiota in asymptomatic HRV-infected adults and provides a potential avenue for gut microbiota-based prevention strategies for HRV colonization.