Spontaneous curling of freestanding Janus monolayer transition-metal dichalcogenides.

In this paper, using molecular dynamics simulations we report spontaneous curling behaviors of freestanding Janus monolayer S-Mo-Se (MoSeS) structures. Density functional theory calculations are performed to obtain the phonon dispersion and phonon spectra of the Janus monolayer MoSeS for analyzing its structural stability. The results show that the Janus monolayer MoSeS is structurally stable. Due to the lattice mismatch between MoS and MoSe domains, the Janus monolayer MoSeS at the freestanding state always spontaneously rolls up in a constant temperature and pressure system. The direction of curling is preferred along the armchair orientation. Specifically, as for the Janus monolayer MoSeS whose size is larger than ∼30 nm, it can spontaneously roll up into a nanotube structure. The underlying physical mechanisms of these phenomena are well uncovered by using classical Timoshenko plate theory and the minimum energy principle.

Effects of atomic vacancies and temperature on the tensile properties of single-walled MoS2 nanotubes.

Using molecular dynamics simulations, we study the effects of Mo and S atomic vacancies and different temperatures on the tensile properties of single-walled MoS2 nanotubes through a series of tensile tests. Both armchair and zigzag MoS2 nanotubes under uniaxial tensions show phase transitions. Two types of Mo-S bonds play different roles in this phase transition of MoS2 nanotubes. Moreover, the influences of Mo and S atomic vacancies and temperature on the Young's modulus, ultimate strength and fracture strain of single-walled MoS2 nanotubes are investigated systematically. The results show that Mo and S atomic vacancies have no influence on the Young's modulus of MoS2 nanotubes. However, Mo atomic vacancies result in a significant decrease of ultimate strength and fracture strain of MoS2 nanotubes, while S atomic vacancies have a relatively small influence on the fracture properties of MoS2 nanotubes. With an increase in temperature, the Young's modulus and ultimate strength decrease. When the temperature is higher than 300 K, the fracture is changed from brittle to ductile together with an enhanced fracture strain.

[Determination of 35 antibiotics and four ß-receptor agonists in teenagers and analysis of exposure status].

Antibiotics are mainly used for disease treatment and prevention, and ß-receptor agonists are mainly used in the clinical treatment of respiratory diseases. Both types of drugs are also widely used in animal husbandry and aquaculture to promote animal growth and prevent disease. These drugs enter the human body through many routes and cause harm to human health. Teenagers are in a critical period of growth and development, and long-term antibiotic exposure may have adverse effects on their bodies. In this study, 442 teenagers aged 11-15 years were recruited from a middle school to investigate the body burden of various antibiotics and ß-receptor agonists. The seven categories of antibiotics, including five macrolides, four tetracyclines, 10 quinolones, 11 sulfonamides, three ß-lactams, one quinoxaline, and one lincosamide, and four ß-receptor agonists were determined by isotope dilution and solid phase extraction coupled with ultra performance liquid chromatography-tandem mass spectrometry. Analyte levels were corrected using urine creatinine, and detection rates were used for data analysis. Pearson's chi-squared test was used to analyze the correlations between detection rate and gender, age, or body mass index (BMI). Logistic regression was used to evaluate the correlation between detection rate and different groups after adjusting for confounding factors. The results showed that 397 teenagers had at least one antibiotic or ß-receptor agonist in their urine, with a total detection rate of 89.8%. A total of 29 antibiotics and ß-receptor agonists were detected, and the detection rate of each compound ranged from 0.2% to 59.0%. Doxycycline, oxytetracycline, and azithromycin were the top three drugs with the highest detection rates (59.0%, 56.1%, and 34.6%, respectively). Tetracyclines and macrolides were the two antibiotic categories detected most often, with detection rates of 81.9% and 42.3%, respectively. Among the antibiotics investigated, preferred veterinary antibiotics (PVAs) had the highest detection rate (85.1%), followed by human antibiotics (HAs) (41.0%). The overall detection rate of ß-receptor agonists was 2.7%. Statistical analysis showed that the male was prone to be exposed to tetracycline antibiotics (odds ratio (OR)=2.17). The detection rates of macrolides differed among the different age groups and were higher in those aged 12-13 years than in those aged 11 years. As the BMI of the teenagers increased, the detection rate of macrolides gradually increased. After adjusting for age and gender, teenagers with obesity were found to be 2.35 times more likely to be exposed to macrolides than those with a normal weight. The findings suggest that teenagers are generally exposed to low levels of antibiotics, that food and the environment may be the main sources of antibiotic exposure in teenagers, and that macrolide exposure may be associated with adolescent obesity.

The association between per-/polyfluoroalkyl substances in serum and thyroid function parameters: A cross-sectional study on teenagers living near a Chinese fluorochemical industrial plant.

Thyroid hormones (THs) play an important role in a wide range of crucial biological functions related to growth and development, and thyroid antibodies (TAs) can influence the biosynthesis of THs. Epidemiological studies have indicated that per- and polyfluoroalkyl substances (PFAS) could induce thyroid disruption, but studies on teenagers living in areas with high PFAS exposure are limited. This cross-sectional study focused on 836 teenagers (11- 15 years) living near a Chinese fluorochemical industrial plant. Decreased levels of free thyroxine (FT4, ﹤9.6 pmol/L, abnormal rate = 19.0 %) and elevated levels of free triiodothyronine (FT3, ï¹¥6.15 pmol/L, abnormal rate = 29.8 %) were observed. Correlations of serum PFAS concentrations and TAs/THs were analyzed. Increased PFOA was identified as a risk factor of decreased FT4 by using unadjusted (OR: 11.346; 95 % CI: 6.029, 21.352, p < 0.001) and adjusted (OR: 12.566; 95 % CI: 6.549, 24.115, p < 0.001) logistic regression models. In addition, significantly negative correlations were found between log10 transformed PFOA and FT4 levels using linear (unadjusted: ß = -1.543, 95 % CI: -1.937, -1.148, p < 0.001; adjusted: ß = -1.534, 95 % CI: -1.930, -1.137, p < 0.001) and BKMR models. For abnormal FT3, a significantly positive association between PFHxS and FT3 levels was observed in a regression model (unadjusted: ß = -0.903, 95 % CI: -1.212, -0.595, p < 0.001; adjusted: ß = -0.894, 95 % CI: -1.204, -0.583, p < 0.001), and PFHxS was identified as a risk factor (unadjusted: OR: 4.387; 95 % CI: 2.619, 7.346, p < 0.001; adjusted: OR: 4.527; 95 % CI: 2.665, 7.688, p < 0.001). Sensitivity analyses confirmed the robustness of the above results. This study reported the elevated PFAS exposure and thyroid function of teenagers living near a fluorochemical industrial plant from China.

[Determination of sixteen antibiotics and four ß-agonists in human urine samples using ultra-performance liquid chromatography-tandem mass spectrometry based on high-throughput automatic solid-phase extraction].

An analytical method combining high-throughput automatic solid-phase extraction with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed to determine 16 antibiotics (macrolides, tetracyclines, quinolones, and sulfonamides) and 4 ß-agonists (terbutaline, salbutamol, ractopamine, and clenbuterol) in human urine samples. After thawing at room temperature, 1 mL of urine was sampled and the internal standard was added, followed by the addition of 200 µL ammonium acetate buffer and 20 µL ß-glucuronidase, and the mixture was incubated at 37 ℃ overnight. Automatic solid-phase extraction was used to extract the target compounds from the urine samples, and the recoveries were compared using different solid-phase extraction 96-well plates (PRiME MCX, Sep-Pak C18, PRiME HLB), types and volumes of rinse solutions and eluents. Satisfactory recoveries of the 20 target compounds were obtained using the Oasis PRiME HLB 96-well plate, with 1.5 mL 10% (v/v) methanol aqueous solution and 2.0 mL methanol as the rinse solution and eluent, respectively. The eluent was concentrated under nitrogen gas at 45 ℃, and the recoveries of the target compounds were compared under different conditions (completely or almost dry, drying to 1 mL, and adding water as a protective agent), and the recovery rate was optimal when water was added as a protective agent. In this study, two types of analytical columns (ACQUITY BEH C18 and ACQUITY HSS T3) and different gradient elution procedures and mobile phases were compared. The optimal chromatographic effect was realized using an HSS T3 column (100 mm×3.0 mm, 1.8 µm) and 0.1% (v/v) formic acid aqueous solution-0.1% (v/v) formic acid in acetonitrile as the mobile phase in gradient elution at a flow rate of 0.3 mL/min. Comparing the peaks observed using different proportions of methanol aqueous solution and the initial mobile phase as the injection solvent revealed that 30% (v/v) methanol aqueous solution was the optimal solution in terms of peak shape and signal-to-noise ratio. MS was conducted using positive electrospray ionization (ESI+) in multiple reaction monitoring (MRM) mode, and the MS parameters were optimized, including the curtain (CUR) and collision gases (CAD). The standard curve obtained using this method exhibited a good linearity (correlation coefficient>0.997), and the respective limits of detection and quantification were 0.02-0.12 ng/mL and 0.06-0.41 ng/mL. At spiked levels of 0.25, 2.5, and 12.5 ng/mL, the recoveries were in the range of 81.7%-120.0% (except that of tetracycline), the intra- and inter-day RSDs (n=6) were 1.1%-11.0% and 1.2%-13.0%, respectively. Azithromycin, trimethoprim, terbutaline, salbutamol, ractopamine, and clenbuterol displayed moderate matrix effects, but all targets exhibited weak matrix effects after correction using the isotope internal standard. To evaluate the accuracy of this method, BCR-503 (containing salbutamol and clenbuterol) and internal quality control samples were used and the concentrations of salbutamol and clenbuterol were within the reference ranges. Additionally, the mean concentrations of the 20 target compounds of two different internal quality control samples after 7 measurements were in the ranges of 0.44-0.59 ng/mL (0.5 ng/mL) and 1.72-2.16 ng/mL (2.0 ng/mL), respectively, which were satisfactory. In this study, the analytical method employed automatic sample pretreatment with a 96-well solid-phase extraction plate, and the detection efficiency was considerably improved. This method displays the advantages of simple operation, ideal recovery, a high sensitivity and weak matrix effect, which satisfies the requirements for the simultaneous determination of 16 antibiotics and 4 ß-agonists in human urine samples. This study provides a crucial method for use in monitoring antibiotics and ß-agonists in human urine and studying their exposure characteristics and health risks.

Serum concentrations of per-/polyfluoroalkyl substances and its association with renal function parameters among teenagers near a Chinese fluorochemical industrial plant: A cross-sectional study.

Currently, studies on the association between per-/polyfluoroalkyl substances (PFAS) concentrations and the renal function of residents, especially teenagers, living near fluorochemical industrial plants, are relatively rare, and not all these studies suggested associations. In this cross-sectional study, 775 local teenagers (11-15 years old) were included, and serum concentrations of 18 PFAS were measured. Perfluorooctanoic acid (PFOA) was found to be the dominant PFAS with a concentration of 22.3-3310 ng/mL (mean = 191 ng/mL), accounting for 71.5-99.1% of ΣPFAS. Statistical analyses demonstrated that internal exposure of perfluoroalkyl carboxylic acids (PFCA, C8-C10) was related to the plant. In addition, the prevalence rate of chronic kidney disease (CKD) (35.0%) in the participants was relatively high. A significantly positive association was observed between the increase in PFOA concentration and increasing risk of CKD (OR = 1.741; 95% CI: 1.004, 3.088; p = 0.048) by adjusting for gender, age, body mass index (BMI), and household income. Similar positive correlation was also observed in PFHpA with CKD (OR = 1.628, 95% CI: 1.031, 2.572; p = 0.037). However, no significant correlation was observed for concentrations of other PFAS and CKD (p > 0.05). Furthermore, linear regression analyses demonstrated that none of the PFAS concentrations were significantly correlated with estimated glomerular filtration rate (eGFR) or urine albumin/urine creatinine ratio (ACR) (p > 0.05). However, a significantly negative correlation was observed between PFOA concentration and abnormal ACR (ß = -0.141, 95% CI: -0.283, 0.001; p = 0.048) after stratifying by CKD. Sensitivity analyses further confirmed these results. This cross-sectional study is the first, to our knowledge, to investigate the association between PFAS concentrations and renal function in teenagers living near a Chinese industrial plant. Further prospective and metabonomic studies are needed to interpret the results and clarify the biological mechanisms underlying this association.

Long non-coding RNA Linc00261 as a novel potential diagnostic and prognostic biomarker for gallbladder cancer.

BACKGROUND: Linc00261 is a lncRNA that plays key roles in tumor suppression. While gallbladder carcinoma (GBC) is one of the most common cancer of the bile duct. However, the study about Linc00261's correlation with the clinicopathological characteristics and postoperative outcomes of the GBC patients is few. Therefore, we want to explore Linc00261 in GBC and assess its potential of clinical diagnosis. METHODS: Quantitative real-time PCR (qRT-PCR) was used to detect the expression of Linc00261 in specimens of GBC and adjacent tissues as well as cell lines. Chi-square test has been used to research the correlation of the Linc00261 expression in GBC with the clinicopathological features. The Cox model was used to assess the value of Linc00261 in predicting the prognosis of GBC patients. ROC curve analysis was used to test the specificity and sensitivity of diagnostic method of serum Linc00261 expression. RESULTS: The expression level of Linc00261 in GBC was significantly lower than normal tissues' and it was also up-regulated after surgery. The Linc00261 expression was significantly correlated with large tumor size (P<0.0001), late TNM stage (P=0.008), negative liver metastasis (P=0.027) and well differentiated phenotype (P=0.017). The patients with lower Linc00261 expression had significantly worse outcomes in terms of overall survival (P=0.0188) and progression-free survival (P=0.0029), and the low expression of Linc00261 was identified as an independent risk factor affecting postoperative survival rate of the patients (P<0.01). The expression of Linc00261 in serum was down-regulated of GBC patients and increased in the patients after operation. Linc00261 expressed in serum was also positively associated with its expression in GBC tissue of patients (P<0.0001). The GBC diagnosis efficacy of using the serum Linc00261 level to identify the GBC has high specificity and sensitivity (AUC 0.805). CONCLUSIONS: Linc00261 could be identified a novel gene associated with GBC development and progression. It also may serve as a new diagnostic and prognostic biomarker for patients with GBC.

Fracture behaviors of pre-cracked monolayer molybdenum disulfide: A molecular dynamics study.

The fracture strength and crack propagation of monolayer molybdenum disulfide (MoS2) sheets with various pre-existing cracks are investigated using molecular dynamics simulation (MDS). The uniaxial tensions of pre-cracked monolayer MoS2 sheets with different crack tips, different locations of crack, different crack lengths and angled cracks are simulated and studied. The results show that the configuration of crack tip can influence significantly the fracture behaviors of monolayer MoS2 sheets while the location of crack does not influence the fracture strength. With the increase of crack length, the fracture strength of monolayer MoS2 sheets reduces almost linearly, and the fracture of monolayer MoS2 sheets is transformed from almost brittle to ductile. By making comparison between the MDS results and the predictions of continuum fracture mechanics theories, including Inglis' model, Griffith's model with and without finite size effect, it is found that MDS results agree well with the predictions of Griffith's model with finite size effect, differ from the predictions of Inglis' model and Griffith's model without finite size effect. Finally, the MDS results of monolayer MoS2 sheets with different angled crack are also analyzed based on the continuum fracture mechanics model.