Formula for conferring degree to 8 pupils

Perfluoroalkyl chemicals (PFCs) are stable man-made compounds with many industrial and commercial uses. Concern has been raised that they may exert deleterious effects, especially on lipid regulation. We aimed to assess exposure to perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and seven other PFCs in occupational workers from a fluorochemical plant and nearby community residents, and to investigate the association between PFOA and serum biomarkers. Serum biomarkers included not only biochemical parameters, such as lipids and enzymes, but also circulating microRNAs (miRNAs). Samples were analyzed by high-pressure liquid chromatography/tandem mass spectrometry (HPLC-MS/MS). Circulating miRNA levels were detected by quantitative polymerase chain reaction (PCR). Analyses were conducted by correlation and linear regression. We detected PFOS, PFOA, perfluorohexane sulfonate (PFHxS), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA) in all samples. The median levels of serum PFOA and PFOS were 284.34 ng/mL and 34.16 ng/mL in residents and 1635.96 ng/mL and 33.46 ng/mL in occupational participants, respectively. To our knowledge, we found for the first time that PFOA was negatively associated with high-density lipoprotein cholesterol (HDL-C) in workers using linear regression after adjusting for potential confounders. Circulating miR-26b and miR-199a-3p were elevated with serum concentration of PFOA. Although the limitations of small sample size and the cross-sectional nature of the current study constrained causal inferences, the observed associations between PFOA and these serum biomarkers warrant further study

Efficient SO₂ Capture and Fixation to Cyclic Sulfites by Dual Ether-Functionalized Protic Ionic Liquids without Any Additives

The capture of SO₂ with ionic liquids (ILs) has attracted much attention in recent years; however, the examples involving SO₂ capture and utilization (SCU) in the same medium are scarce. Here, we demonstrated an innovative strategy for SO₂ capture and fixation to cyclic sulfites in dual ether-functionalized protic ionic liquids (PILs) for the first time. These dual ether-functionalized PILs exhibited low viscosities and remarkable SO₂ loading capacities (up to 6.12 mol of SO₂ per mol of IL and 1.34 g of SO₂ per g of IL at 1.0 bar) that is conducive to conversion of SO₂ absorbed in situ. The mechanism of absorption was proposed which includes both chemical and physical absorptions from the spectral results and theoretical calculations. Particularly, the SO₂ absorbed in the PILs was directly transformed into cyclic sulfites without any additives; meanwhile, these PILs were also used as efficient catalysts for the synthesis of a series of cyclic sulphites using equimolar SO₂ and epoxides. Good to excellent yields of cyclic sulfites were obtained for varied substrates. The dual roles of PILs as both absorbents and catalysts as well as the recyclability of the PILs are examined in detail in this paper. This innovative strategy not only eliminated the traditional intensive energy input for SO₂ desorption but also enabled the production of value-added cyclic sulfites

Sex Differences in Transcriptional Expression of FABPs in Zebrafish Liver after Chronic Perfluorononanoic Acid Exposure

Perfluorononanoic acid (PFNA), a nine carbon backbone of perfluorinated acids (PFAAs), has wide production applications and is found in environmental matrices as a contaminant. To understand the adverse effects of PFNA, adult male and female zebrafish were exposed to differing PFNA dosages (0, 0.01, 0.1, and 1.0 mg/L) for 180 days using a flow-through exposure system. Results showed body weight, body length, and hepatosomatic index (HSI) decreased in both sexes. The HPLC-MS/MS analysis found that PFNA concentrations were higher in male livers than in female livers with increasing significance in a dose-dependent manner. Total cholesterol levels increased in the livers of both sexes, whereas triglyceride (TG) levels increased in males and decreased in females. With the exception of FABP1b, the transcriptional expression levels of fatty acid binding proteins (FABPs) were up-regulated in males and down-regulated in females. A similar trend between sexes occurred for peroxisome proliferator-activated receptors (PPARs) and Ccaat-enhancer-binding proteins (C/EBPs), which may be the upstream regulatory elements of FABPs. The results indicated that PFNA exposure caused opposite adverse effects on liver TG levels between the sexes in zebrafish possibly due to the opposite expression of FABPs and its upstream genes

RhlA Exhibits Dual Thioesterase and Acyltransferase Activities during Rhamnolipid Biosynthesis

Rhamnolipids (RLs) are a desirable class of biosurfactants originating from Pseudomonas aeruginosa. Rhamnosyltransferase 1 chain A (RhlA) catalyzes the formation of β-3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) to constitute the RL lipid moiety, and the molecular structure of this moiety exerts major impacts on the physiochemical and biological properties of corresponding RLs. However, the catalytic mechanism and sequence-structure–function relationship of RhlA remain elusive. Here, we report the X-ray crystal structure of P. aeruginosa RhlA with an α/β-hydrolase fold and a canonical nucleophile/histidine/acidic catalytic triad. Unexpectedly, free 3-hydroxy fatty acids within a secondary ligand-binding pocket were observed in the crystal of RhlA, which is traditionally considered an acyltransferase that acts only on acyl carrier protein (ACP)-bound substrates. In vitro isotopic labeling, enzyme kinetics experiments, and QM/MM simulations confirmed that free β-hydroxy fatty acids are a reaction intermediate during HAA synthesis. Moreover, first-shell residue mutations that targeted different ligand-binding pockets resulted in distinct modulation patterns for the two acyl chain lengths of HAAs. In conclusion, the revealed biosynthetic mechanism may guide future engineering for the biosynthesis of designer RLs

Flexible Optical Waveguides in Heterocyclic Schiff Base Self-Assembled Hydrogen-Bonded Solvates

Flexible fluorescent crystalline materials exhibit both mechanical and optical properties and have received great attention due to their potential applications in flexible optical devices. Simultaneously adjusting the mechanical and optical properties of crystalline materials remains interesting and challenging. In the present work, a guest molecule was introduced via hydrogen-bonded solvation, which achieved excellent mechanical elasticity and higher fluorescence emission than that of the host heterocyclic Schiff base molecule crystal itself. The crystal structure–property relationship and the molecular mechanism of the elasticity were then investigated in detail. It revealed that solvent molecules play a key role in changing both the stacking of fluorescent molecules and the interaction energy framework. In addition, the flexible fluorescent solvate exhibits a good waveguide property. A bent crystal was found to have a larger optical loss coefficient than a straight crystal. Furthermore, the size effect on the optical loss coefficient of the waveguide was discussed in which the optical loss coefficient decreases as the sizes increase. Such a size effect is usually neglected in waveguide material research and should be complemented in the performance evaluation of optical waveguides

Flexible Optical Waveguides in Heterocyclic Schiff Base Self-Assembled Hydrogen-Bonded Solvates

Flexible fluorescent crystalline materials exhibit both mechanical and optical properties and have received great attention due to their potential applications in flexible optical devices. Simultaneously adjusting the mechanical and optical properties of crystalline materials remains interesting and challenging. In the present work, a guest molecule was introduced via hydrogen-bonded solvation, which achieved excellent mechanical elasticity and higher fluorescence emission than that of the host heterocyclic Schiff base molecule crystal itself. The crystal structure–property relationship and the molecular mechanism of the elasticity were then investigated in detail. It revealed that solvent molecules play a key role in changing both the stacking of fluorescent molecules and the interaction energy framework. In addition, the flexible fluorescent solvate exhibits a good waveguide property. A bent crystal was found to have a larger optical loss coefficient than a straight crystal. Furthermore, the size effect on the optical loss coefficient of the waveguide was discussed in which the optical loss coefficient decreases as the sizes increase. Such a size effect is usually neglected in waveguide material research and should be complemented in the performance evaluation of optical waveguides

Multiheterojunction Phototransistors Based on Graphene–PbSe Quantum Dot Hybrids

Graphene-semiconductor quantum dot (QD) hybrid field effect phototransistors (FEpTs) have attracted much interest due to their ultrahigh gain and responsivity in photo detection. However, most reported results are based on single-layer heterojunction, and the multiheterojunction FEpTs are often ignored. Here, we design two typical multiheterojunction FEpTs based on graphene–PbSe quantum dot (QD) hybrids, including QD at the bottom layer (QD-bottom) and graphene at the bottom layer (G-bottom) FEpTs. Through a comparative study, G-bottom FEpTs showed a multisaturation behavior due to the multigraphene layer effect, which was absent in the QD-bottom FEpTs. The mobilities for electrons and holes were μ_E = 147 cm² V^–1 s^–1 and μ_E = 137 cm² V^–1 s^–1 in the G-bottom FEpTs and μ_E = 14 cm² V^–1 s^–1 and μ_E = 59 cm² V^–1 s^–1 in the QD-bottom FEpTs. Higher responsivity (∼10⁶ A W^–1) and faster response rate were both achieved by the G-bottom FEpTs. All of the advantages in G-bottom FEpTs were attributed to the back-gate effect. Therefore, high performance is expected in those FEpTs whose heterojunctions are designed to be close to the back-gate

Additional file 2 of MRI-assessed diaphragmatic function can predict frequent acute exacerbation of COPD: a prospective observational study based on telehealth-based monitoring system

Additional file 2. Correlation between diaphragm function and clinical parameters in the COPD grou

PbS-Decorated WS₂ Phototransistors with Fast Response

Tungsten disulfide (WS₂), as a typical metal dichalcogenides (TMDs), has aroused keen research interests in photodetection. Here, field effect phototransistors (FE_pTs) based on heterojunction between monolayer WS₂ and PbS colloidal quantum dots are demonstrated to show high photoresponsivity (up to ∼14 A/W), wide electric bandwidth (∼396 Hz), and excellent stability. Meanwhile, the devices exhibit fast photoresponse times of ∼153 μs (rise time) and ∼226 μs (fall time) due to the assistance of heterojunction on the transfer of photoexcitons. Therefore, excellent device performances strongly underscore monolayer WS₂–PbS quantum dot as a promising material for future photoelectronic applications

Ambipolar Quantum-Dot-Based Low-Voltage Nonvolatile Memory with Double Floating Gates

Considerable research efforts have been devoted to promoting memory performance, especially the memory window and retention time. In this work, we develop an innovative field-effect-transistor memory with graphene oxide (GO)/gold nanoparticles (Au NPs) as double floating gates (DFG) and PbS quantum dots (QDs) as the semiconductor layer. QDs can provide both electrons and holes in the channel, which offers a chance for the floating gates to trap both of them to achieve bidirectional threshold voltage shifts after programming and erasing operations. Due to the DFG structure covering the GO sheets on the Au NP monolayer, the enhanced memory window (∼2.72 V at a programming/erasing voltage of ±10 V) can be attributed to more charge carriers being trapped in the floating gates. More importantly, because of the different energy levels between GO and Au NPs, the DFG construction brings about an energy barrier that prevents the trapped charges from leaking back to the channel, so that the retention capability is significantly improved. The outstanding memory performance will give the QD-based DFG memory great potential to have its own place in the flash memory market