14 research outputs found
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 SO<sub>2</sub> Capture and Fixation to Cyclic Sulfites by Dual Ether-Functionalized Protic Ionic Liquids without Any Additives
The capture of SO<sub>2</sub> with
ionic liquids (ILs) has attracted
much attention in recent years; however, the examples involving SO<sub>2</sub> capture and utilization (SCU) in the same medium are scarce.
Here, we demonstrated an innovative strategy for SO<sub>2</sub> 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 SO<sub>2</sub> loading
capacities (up to 6.12 mol of SO<sub>2</sub> per mol of IL and 1.34
g of SO<sub>2</sub> per g of IL at 1.0 bar) that is conducive
to conversion of SO<sub>2</sub> 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 SO<sub>2</sub> 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 SO<sub>2</sub> 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 SO<sub>2</sub> 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<sub>E</sub> =
147 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> and
μ<sub>E</sub> = 137 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> in the G-bottom FEpTs and μ<sub>E</sub> = 14
cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> and μ<sub>E</sub> = 59 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> in the QD-bottom FEpTs. Higher responsivity (∼10<sup>6</sup> A W<sup>–1</sup>) 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 WS<sub>2</sub> Phototransistors with Fast Response
Tungsten disulfide (WS<sub>2</sub>), as a typical metal dichalcogenides
(TMDs), has aroused keen research interests in photodetection. Here,
field effect phototransistors (FE<sub>p</sub>Ts) based on heterojunction
between monolayer WS<sub>2</sub> 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 WS<sub>2</sub>–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