Air- and Water-Stable Gold-Coated Gadolinium Metal Nanocrystals

Gold-coated gadolinium nanocrystals, with an average diameter of 3.20 ± 0.35 nm, have been synthesized at ambient temperature by alkalide reduction. Whereas uncoated gadolinium nanoparticles react violently with air and water, the gold-coated gadolinium nanocrystals reported here show no reaction even upon long-term exposure. This is the first example of air- and water-stable lanthanide metal nanocrystals, which may allow for the development of magnetic and biomedical applications of gadolinium and other lanthanide metal and alloy nanocrystals

Production of Hydroxylated Polybrominated Diphenyl Ethers (OH-PBDEs) from Bromophenols by Manganese Dioxide

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are of significant concern because of their enhanced toxicological effects compared to PBDEs. Research to date has attributed the origin of OH-PBDEs to biological metabolism of PBDEs and natural production in the environment. However, it is unclear how OH-PBDEs are formed naturally. In this study, we explored the formation of OH-PBDEs via the oxidative transformation of simple bromophenols (BPs, e.g., 4-BP, 2,4-DBP, and 2,4,6-TBP) by birnessite (δ-MnO₂). Results showed that OH-PBDEs were readily produced by δ-MnO₂ with BPs as precursors. For example, oxidation of 2,4-DBP by δ-MnO₂ yielded 2′-OH-BDE-68 and 2′,5′-OH-BDE-25. Other OH-PBDEs, such as 6-OH-BDE-13, 2′,5′-OH-BDE-3, 4′-OH-BDE-121, and 2′,5′-OH-BDE-69, were detected from the reaction with 4-BP and 2,4,6-TBP. The formation of OH-PBDEs likely resulted from the oxidative coupling of bromophenoxy radicals. Mild acidic conditions enhanced while coexisting cations (e.g., Na⁺, Mg²⁺, and Ca²⁺) suppressed the transformation. Given the ubiquity of BPs and δ-MnO₂, oxidation of BPs by δ-MnO₂ and other metal oxides is likely an abiotic route for the formation of OH-PBDEs in the environment

Kinetics of the Reaction of CH₃O₂ Radicals with OH Studied over the 292–526 K Temperature Range

Reaction of methyl peroxy radicals with hydroxyl radicals, CH₃O₂ + OH → CH₃O + HO₂ (1a) and CH₃O₂ + OH → CH₂OO + H₂O (1b) was studied using pulsed laser photolysis coupled to transient UV–vis absorption spectroscopy over the 292–526 K temperature range and pressure 1 bar (bath gas He). Hydroxyl radicals were generated in the reaction of electronically excited oxygen atoms O­(¹D), produced in the photolysis of N₂O at 193.3 nm, with H₂O. Methyl peroxy radicals were generated in the reaction of methyl radicals, CH₃, produced in the photolysis of acetone at 193.3 nm, and subsequent reaction of CH₃ with O₂. Temporal profiles of OH were monitored via transient absorption of light from a DC discharge H₂O/Ar low-pressure resonance lamp at ca. 308 nm. The absolute intensity of the photolysis light was determined by accurate in situ actinometry based on the ozone formation in the presence of molecular oxygen. The overall rate constant of the reaction is <i>k</i>_1a+1b = (8.4 ± 1.7) × 10^–11(<i>T</i>/298 K)^−0.81 cm³ molecule^–1 s^–1 (292–526 K). The branching ratio of channel 1b at 298 K is less than 5%

From Stereochemically Tunable Homopolymers to Stereomultiblock Copolymers: Lewis Base Regulates Stereochemistry in the Coordination Polymerization of 2‑Vinylpyridine

Excellent isoselectivity (<i>mmmm</i> > 99%) and high activity (TOF > 4000 h^–1) were achieved for the first time in the polymerization of the polar 2-vinylpyridine by using the simple lutetium-based catalysts, Lu­(CH₂SiMe₃)₃(THF)_<i>x</i>(Py)_2–<i>x</i> (<i>x</i> = 0, 1, 2). The isoselectivity (<i>mm</i>) of the polymer could be varied between 37% and 99% through simply altering the quantity of Lewis base (tetrahydrofuran, 1,4-diazabicyclo[2.2.2]­octane, 3-bromopyridine, and pyridine) added. Moreover, a novel method for preparing isotactic–atactic stereomultiblock poly­(2-vinylpyridine)­s was developed by the addition and removal of THF during polymerization. The polymerization process including stereoselective control mechanism was deduced by DFT calculations

Development of Evaporative Light Scattering Detector for Capillary Electrochromatography and Capillary Liquid Chromatography

The paper describes a microfluidic evaporative light scattering detector (μELSD) for capillary electrochromatography and capillary liquid chromatography. The detector, consisting of a microfluidic nebulizer, a miniaturized evaporative module, a sheath gas module, and a light scattering chamber, was developed and optimized. Carrier gas exits from an extremely narrow circular gap (about 5 μm) between the spraying capillary o.d. and the nozzle i.d., impacting on the mobile phase liquid with supersonic velocity, to nebulize the effluent of a few hundred nL/min from the capillary outlet. The evaporation process was found to be accomplished at ambient temperature. A sheath gas module featuring a structural necking subsequent to drift tube endings was found to enhance the reproducibility and increase the S/N. Excellent linearity of the optimal μELSD was 3 orders of magnitude (0.2–40 ng; <i>R</i>² = 0.9998). The limit of detection (LOD) for glucose with a capillary column was 100 pg. Finally, the μELSD coupled to pressurized capillary eletrochromatography (pCEC) was applied to the analysis of six active components in traditional Chinese medicine extract, demonstrating the feasibility of the detector for capillary liquid separation system

Reaction CH₃ + CH₃ → C₂H₆ Studied over the 292–714 K Temperature and 1–100 bar Pressure Ranges

Reaction of recombination of methyl radicals, CH₃ + CH₃ → C₂H₆ (1) was studied using pulsed laser photolysis coupled to transient UV–vis absorption spectroscopy over the 292–714 K temperature and 1–100 bar pressure ranges (bath gas He), very close to the high-pressure limit. Methyl radicals were produced by photolysis of acetone at 193.3 nm or in the reaction of electronically excited oxygen atoms O­(¹D), produced in the photolysis of N₂O at 193.3 nm, with CH₄, and subsequent reaction of OH with CH₄. Temporal profiles of CH₃ were recorded via absorption at 216.36 and 216.56 nm using a xenon arc lamp and a spectrograph. The absolute intensity of the photolysis light inside the reactor was determined by an accurate <i>in situ</i> actinometry based on the ozone formation in photolysis of N₂O/O₂/N₂ mixtures. The rate constant of reaction 1 in the high-pressure limit has a negative temperature dependence: <i>k</i>_1,inf = (5.66 ± 0.43) × 10^–11(<i>T</i>/298 K)^−0.37 cm³ molecule^–1 s^–1 (292–714 K)

Scalable Preparation of Fully Coated Ag@BaTiO₃ Core@Shell Particles via Poly(vinylpyrrolidone) Assistance for High‑<i>k</i> Applications

This paper reports a poly­(vinylpyrrolidone) (PVP)-assisted synthesis of Ag@BaTiO₃ (BT) core@shell particles, consisting of smooth and fully coated BT shells on Ag cores. PVP adheres to Ag by coordination attraction, and it is present as a framework on the Ag surface. Driven by the adhesion forces from PVP, fully coated BT shells form on the template of the PVP framework. The shell phase is formed through a modified low-temperature direct synthesis method. Scanning electron microscopy examination of morphological evolution reveals smooth surfaces of the oxide coatings on Ag cores. X-ray diffraction pattern, energy-dispersive X-ray spectra, line scan, and mapping confirm the phase, chemical composition, and configuration of the shells. The synthesis method in this paper can achieve controllability of the growth rate and shell thickness. Because of the fully coated shells of BT, the poly­(dimethylsiloxane) composites filled with synthesized core@shell fillers have very small leakage currents of ∼10^–8–10^–7 A/cm². A high permittivity of 202 (ε_r/ε_m = 84) and a low dielectric loss of 0.003 are achieved at 1 MHz in composites filled with 40 vol % Ag@BT fillers. Lichtenecker’s theory containing the equivalent permittivity of core@shell Ag@BT originating from interfacial polarization is used to account for the dielectric constant of the composite. The smooth and fully coated Ag@BT core@shell particles can be used in composite materials for high-dielectric-constant and low-loss applications

Table_1_The association between physical activity and mental health in medical postgraduates in China during COVID-19 pandemic.docx

BackgroundChinese medical postgraduates (CMPs) are a special subpopulation that has a great risk of mental health due to high workload, and heavy academic and clinical pressure during the COVID-19 pandemic. Physical activity has been demonstrated to be positive for the mental health of human being. However, little is known about the risks to mental health among CMPs as well as the potential effects of physical activity on mental health in CMPs during the COVID-19 pandemic.AimsIn the present study, the aims are to (1) investigate the levels of PA and mental health that CMPs had; (2) to identify the potential factors that contribute to mental health among CMPs; (3) to explore the potential effects of PA on the mental health in CMPs.MethodsThe survey was conducted online across 25 provinces of mainland China in 28 medical colleges or universities with structured questionnaires. Physical Activity Rating Scale-3 (PARS-3), Depression, Anxiety, Stress Scales (DASS-21), and General Self-Efficacy Scale (GSES) were employed to assess the levels of PA, Negative emotional states, and self-efficacy of the participants, respectively. Resilience was evaluated using Connor-Davidson Resilience Scale (CD-RISC). The chi-square and Wilcoxon rank-sum tests were used to compare inter-group differences in demographic data and mental health conditions. Spearman's rank correlation test and partial correlation analysis were used to assess associations between exercise scores and mental health.ResultsWe found some socio-demographic variables such as the location, education levels of parents and the levels of degrees they are training had potential effects on outcomes of mental health among 2,217 CMPs (P ConclusionWe concluded that for Chinese postgraduate medical students, taking part in physical activity would depress negative emotions such as depression, anxiety, and stress, but improve their self-efficacy and resilience, which will benefit them in completing their studies and training.</p

Diagnosis and Anti-Reflux Therapy for GERD with Respiratory Symptoms: A Study Using Multichannel Intraluminal Impedance-pH Monitoring

<div><p>Background/Aims</p><p>Respiratory symptoms are often associated with gastroesophageal reflux disease (GERD). Although the role of multichannel intraluminal impedance–pH (MII-pH) monitoring in GERD is clear, little is known regarding the characteristics of patients with respiratory symptoms based on MII-pH monitoring and anti-reflux therapy. We evaluated a cohort of GERD patients to identify the MII-pH parameters of GERD-related respiratory symptoms and to assess the anti-reflux therapy outcomes.</p><p>Methods</p><p>We undertook a prospective study of patients who were referred for GERD evaluation from January 2011 to January 2012. One hundred ninety-five patients underwent MII-pH monitoring and esophageal manometry, and one hundred sixty-five patients underwent invasive anti-reflux therapy that included laparoscopic Toupet fundoplication (LTF) and the Stretta procedure. The patient characteristics and MII-pH parameters were analyzed, and the symptom scores were assessed at baseline and at 1- and 3-year follow-up evaluations.</p><p>Results</p><p>Of the 195 patients, 96 (49.2%) exhibited respiratory symptoms and significantly more reflux episodes (70.7±29.3) than patients without respiratory symptoms (64.7±24.4, <i>p</i> = 0.044) based on the MII-pH monitoring results. Moreover, the group of patients with respiratory symptoms exhibited more proximal reflux episodes (35.2±21.3) than the non-respiratory symptomatic group (28.3±17.9, <i>p</i> = 0.013). One hundred twenty-five patients following the Stretta procedure (n = 60, 31 with respiratory symptoms) or LTF (n = 65, 35 with respiratory symptoms) completed the designated 3-year follow-up period and were included in the final analysis. The symptom scores after anti-reflux therapy all decreased relative to the corresponding baseline values (<i>p</i><0.05), and there were no significant differences in the control of respiration between the Stretta procedure and LTF (<i>p</i>>0.05). However, LTF significantly reduced the recurrence (re-operation) rate compared with the Stretta procedure (0 vs. 19.4%, <i>p</i> = 0.006).</p><p>Conclusions</p><p>MII-pH monitoring effectively detected respiratory-related predictive parameters, including total/proximal reflux episodes and symptom correlations. We found that GERD patients with respiratory symptoms exhibited more proximal and total reflux episodes but not more acid-related episodes, as determined by MII-pH monitoring. Thus, such monitoring could be useful for diagnosing atypical GERD patients with respiratory symptoms. Furthermore, LTF exhibited a more significant effect on controlling typical symptoms in all GERD patients and reducing the recurrence rate than the Stretta procedure in patients with respiratory symptoms.</p></div

Relationship between MLVA type, P1 type, and macrolide resistance between 2003 and 2015.

<p>Relationship between MLVA type, P1 type, and macrolide resistance between 2003 and 2015.</p