Moiré superlattices in twisted two-dimensional halide perovskites.

Moiré superlattices have emerged as a new platform for studying strongly correlated quantum phenomena, but these systems have been largely limited to van der Waals layer two-dimensional materials. Here we introduce moiré superlattices leveraging ultrathin, ligand-free halide perovskites, facilitated by ionic interactions. Square moiré superlattices with varying periodic lengths are clearly visualized through high-resolution transmission electron microscopy. Twist-angle-dependent transient photoluminescence microscopy and electrical characterizations indicate the emergence of localized bright excitons and trapped charge carriers near a twist angle of ~10°. The localized excitons are accompanied by enhanced exciton emission, attributed to an increased oscillator strength by a theoretically predicted flat band. This research showcases the promise of two-dimensional perovskites as unique room-temperature moiré materials.

Mobile Colistin Resistance and Plasmid-Mediated Quinolone Resistance Genes in Escherichia coli from China, 1993-2019.

Plasmid-mediated quinolone resistance (PMQR) genes and mobile colistin resistance (MCR) genes in Escherichia coli (E. coli) have been widely identified, which is considered a global threat to public health. In the present study, we conducted an analysis of MCR genes (mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5) and PMQR genes [qnrA, qnrB, qnrC, qnrD, qnrE1, qnrVC, qnrS, aac(6')-Ib-cr, qepA, and oqxAB] in E. coli from China, 1993-2019. From the 3,663 E. coli isolates examined, 1,613 (44.0%) tested positive for PMQR genes, either individually or in combination. Meanwhile, 262 isolates (7.0%) carried the MCR genes. Minimum inhibitory concentration (MIC) analyses of 17 antibiotics for the MCR gene-carrying strains revealed universal multidrug resistance. Resistance to polymyxin varied between 4 µg/mL and 64 µg/mL, with MIC50 and MIC90 at 8 µg/mL and 16 µg/mL, respectively. In addition, fluctuations in the detection rates of these resistant genes correlated with the introduction of antibiotic policies, host origin, temporal trends, and geographical distribution. Continuous surveillance of PMQR and MCR variants in bacteria is required to implement control and prevention strategies.

Unraveling the Effect of Stacking Configurations on Charge Transfer in WS2 and Organic Semiconductor Heterojunctions.

Photoinduced interfacial charge transfer plays a critical role in energy conversion involving van der Waals (vdW) heterostructures constructed of inorganic nanostructures and organic materials. However, the effect of molecular stacking configurations on charge transfer dynamics is less understood. In this study, we demonstrated the tunability of interfacial charge separation in a type-II heterojunction between monolayer (ML) WS2 and an organic semiconducting molecule [2-(3″',4'-dimethyl-[2,2':5',2':5″,2″'-quaterthiophen]-5-yl)ethan-1-ammonium halide (4Tm)] by rational design of relative stacking configurations. The assembly between ML-WS2 and the 4Tm molecule forms a face-to-face stacking when 4Tm molecules are in a self-aggregation state. In contrast, a face-to-edge stacking is observed when 4Tm molecule is incorporated into a 2D organic-inorganic hybrid perovskite lattice. The face-to-face stacking was proved to be more favorable for hole transfer from WS2 to 4Tm and led to interlayer excitons (IEs) emission. Transient absorption measurements show that the hole transfer occurs on a time scale of 150 fs. On the other hand, the face-to-edge stacking resulted in much slower hole transfer without formation of IEs. This inefficient hole transfer occurs on a similar time scale as A exciton recombination in WS2, leading to the formation of negative trions. These investigations offer important fundamental insights into the charge transfer processes at organic-inorganic interfaces.

One-Step Solution Patterning for Two-Dimensional Perovskite Nanoplate Arrays.

Two-dimensional perovskite crystals have attracted significant attention for their diverse optoelectronic characteristics, owing to their superior semiconducting properties. However, the majority of studies to date have focused on single crystals, which pose challenges for integration into device arrays due to their incompatibility with selective growth or conventional lithography techniques. Here, a facile one-step solution process for synthesizing 2D perovskite crystal arrays is proposed through meniscus-guided coating on patterned substrates. We further utilized this method for the synthesis of lateral heterostructure nanoplate arrays. Six different 2D perovskite nanoplate arrays, including epitaxial heterostructures, are successfully realized. Optical and crystallographic characterizations show the high optical performance and crystallinity of the nanoplates. Moreover, this method is further employed to prepare high-performance 2D perovskite nanoplate photosensor arrays. This strategy can be utilized as a guideline for the fundamental investigation of optical properties and the development of high-performance optoelectronics of perovskite materials including photosensors and displays.

Holistic energy landscape management in 2D/3D heterojunction via molecular engineering for efficient perovskite solar cells.

Constructing two-dimensional (2D) perovskite atop of 3D with energy landscape management is still a challenge in perovskite photovoltaics. Here, we report a strategy through designing a series of π-conjugated organic cations to construct stable 2D perovskites and to realize delicate energy level tunability at 2D/3D heterojunctions. As a result, the hole transfer energy barriers can be reduced both at heterojunctions and within 2D structures, and the preferable work function shift reduces charge accumulation at interface. Leveraging these insights and also benefitted from the superior interface contact between conjugated cations and poly(triarylamine) (PTAA) hole transporting layer, a solar cell with power conversion efficiency of 24.6% has been achieved, which is the highest among PTAA-based n-i-p devices to the best of our knowledge. The devices exhibit greatly enhanced stability and reproducibility. This approach is generic to several hole transporting materials, offering opportunities to realize high efficiency without using the unstable Spiro-OMeTAD.

Gray and white matter structural examination for diagnosis of major depressive disorder and subthreshold depression in adolescents and young adults: a preliminary radiomics analysis.

BACKGROUND: Radiomics is an emerging image analysis framework that provides more details than conventional methods. In present study, we aimed to identify structural radiomics features of gray matter (GM) and white matter (WM), and to develop and validate the classification model for major depressive disorder (MDD) and subthreshold depression (StD) diagnosis using radiomics analysis. METHODS: A consecutive cohort of 142 adolescents and young adults, including 43 cases with MDD, 49 cases with StD and 50 healthy controls (HC), were recruited and underwent the three-dimensional T1 weighted imaging (3D-T1WI) and diffusion tensor imaging (DTI). We extracted radiomics features representing the shape and diffusion properties of GM and WM from all participants. Then, an all-relevant feature selection process embedded in a 10-fold cross-validation framework was used to identify features with significant power for discrimination. Random forest classifiers (RFC) were established and evaluated successively using identified features. RESULTS: The results showed that a total of 3030 features were extracted after preprocessing, including 2262 shape-related features from each T1-weighted image representing GM morphometry and 768 features from each DTI representing the diffusion properties of WM. 25 features were selected ultimately, including ten features for MDD versus HC, eight features for StD versus HC, and seven features for MDD versus StD. The accuracies and area under curve (AUC) the RFC achieved were 86.75%, 0.93 for distinguishing MDD from HC with significant radiomics features located in the left medial orbitofrontal cortex, right superior and middle temporal regions, right anterior cingulate, left cuneus and hippocampus, 70.51%, 0.69 for discriminating StD from HC within left cuneus, medial orbitofrontal cortex, cerebellar vermis, hippocampus, anterior cingulate and amygdala, right superior and middle temporal regions, and 59.15%, 0.66 for differentiating MDD from StD within left medial orbitofrontal cortex, middle temporal and cuneus, right superior frontal, superior temporal regions and hippocampus, anterior cingulate, respectively. CONCLUSION: These findings provide preliminary evidence that radiomics features of brain structure are valid for discriminating MDD and StD subjects from healthy controls. The MRI-based radiomics approach, with further improvement and validation, might be a potential facilitating method to clinical diagnosis of MDD or StD.

Multidrug resistance and prevalence of quinolone resistance genes of Salmonella enterica serotypes 4,[5],12:i:- in China.

Salmonella 4,[5],12:i:- is a monophasic variant of Salmonella Typhimurium, which is responsible for global foodborne disease outbreaks. Here, 255 S. 4,[5],12:i:- strains isolated from humans (11.0%) or food-borne animals (89.0%) between 2010 and 2018 were examined. Tests of susceptibility to 19 antimicrobial agents using the broth micro dilution method showed that 99.2% (n = 253) of the isolates were resistant to at least one compound. Antibiotic susceptibility analysis demonstrated that 91.8% of the isolates were multidrug-resistant (MDR) strains with predominant resistance to tetracycline (90.6%), followed by resistance to ampicillin (86.3%), streptomycin (63.5%), chloramphenicol (62.7%), and trimethoprim-sulfamethoxazole (55.3%). The 5 major distinct patterns of multi-resistance were identified as R-type AST, R-type ACTSxt, R-type ACSTSxt, R-type ACGSTSxt and R-type ASTSxt. Among the PMQR genes examined in this study, oqxAB and aac (6')-Ib-cr were the most prevalent resistance genes in the multi-resistant isolates. Our findings highlight the prevalence of the resistance of S. 4,[5],12:i:- in some regions of China, and several common types of multidrug resistance phenotypes, to provide valuable information for epidemiological studies, risk management, and public health strategies.

Multidrug-Resistant Escherichia coli Strain Isolated from Swine in China Harbors mcr-3.1 on a Plasmid of the IncX1 Type That Cotransfers with mcr-1.1.

An Escherichia coli strain isolated from the feces of swine at a pork slaughterhouse in Henan province China was found to possess two colistin-resistance genes, mcr-1 and mcr-3, plus 16 additional resistance genes. Genes mcr-1.1 and mcr-3.1 were identified on IncHI2 and IncX1 type plasmids, respectively. Transconjugants (containing mcr-3, mcr-1&mcr-3) were obtained that were 64- and 512-fold higher than the minimum inhibitory concentration of colistin on the recipient bacteria (E. coli C600), respectively. The IncX1 plasmid containing mcr-3.1 displayed a very specific structure compared with previous mcr-3. Variable and stable regions were similar across different plasmids, multiple insertion sequences and transposases.

Vibronic spectroscopy of methyl anthranilate and its water complex: hydrogen atom dislocation in the excited state.

Laser-induced fluorescence (LIF) excitation, dispersed fluorescence (DFL), UV-UV-hole burning, and UV-depletion spectra have been collected on methyl anthranilate (MA, methyl 2-aminobenzoate) and its water-containing complex (MA-H2O), under jet-cooled conditions in the gas phase. As a close structural analog of a sunscreen agent, MA has a strong absorption due to the S0-S1 transition that begins in the UV-A region, with the electronic origin at 28 852 cm-1 (346.6 nm). Unlike most sunscreens that have fast non-radiative pathways back to the ground state, MA fluoresces efficiently, with an excited state lifetime of 27 ns. Relative to methyl benzoate, inter-system crossing to the triplet manifold is shut off in MA by the strong intramolecular NHO[double bond, length as m-dash]C H-bond, which shifts the 3nπ* state well above the 1ππ* S1 state. Single vibronic level DFL spectra are used to obtain a near-complete assignment of the vibronic structure in the excited state. Much of the vibrational structure in the excitation spectrum is Franck-Condon activity due to three in-plane vibrations that modulate the distance between the NH2 and CO2Me groups, ν33 (421 cm-1), ν34 (366 cm-1), and ν36 (179 cm-1). Based on the close correspondence between experiment and theory at the TD-DFT B3LYP-D3BJ/def2TZVP level of theory, the major structural changes associated with electronic excitation are evaluated, leading to the conclusion that the major motion is a reorientation and constriction of the 6-membered H-bonded ring closed by the intramolecular NHO[double bond, length as m-dash]C H-bond. This leads to a shortening of the NHO[double bond, length as m-dash]C H-bond distance from 1.926 Å to 1.723 Å, equivalent to about a 25% reduction in the HO distance compared to full H-atom transfer. As a result, the excited state process near the S1 origin is a hydrogen atom dislocation that is brought about primarily by heavy atom motion, since the shortened H-bond distance results from extensive heavy-atom motion, with only a 0.03 Å increase in the NH bond length relative to its ground state value.

Conformer-Specific and Diastereomer-Specific Spectroscopy of αßα Synthetic Foldamers: Ac-Ala-ßACHC-Ala-NHBn.

The folding propensities of a capped, cyclically constrained, mixed α/ß diastereomer pair, ( SRSS) Ac-Ala-ßACHC-Ala-NHBn (hereafter RS) and ( SSRS) Ac-Ala-ßACHC-Ala-NHBn ( SR), have been studied in a molecular beam using single-conformation spectroscopic techniques. These α/ß-tripeptides contain a cyclohexane ring across each Cα -Cß bond, at which positions their stereochemistries differ. This cyclic constraint requires any stable species to adopt one of two ACHC configurations: equatorial C═O/axial NH or equatorial NH/axial C═O. Resonant two-photon ionization (R2PI) and infrared-ultraviolet hole-burning (IR-UV HB) spectroscopy were used in the S0-S1 region of the UV chromophore, revealing the presence of three unique conformational isomers of RS and two of SR. Resonant ion-dip infrared spectra were recorded in both the NH stretch (3200-3500 cm-1) and the amide I (1600-1800 cm-1) regions. These experimental vibrational frequencies were compared with the scaled calculated normal-mode frequencies from density functional theory at the M05-2X/6-31+G(d) level of theory, leading to structural assignments of the observed conformations. The RS diastereomer is known in crystalline form to preferentially form a C11/C9 mixed helix, in which alternating hydrogen bonds are arranged in near antiparallel orientation. This structure is preserved in one of the main conformers observed in the gas phase but is in competition with both a tightly folded C7eq/C12/C8/C7eq structure, in which all four amide NH groups and four C═O groups are engaged in hydrogen bonding, as well as a cap influenced C7eq/NH···π/C11 structure. The SR diastereomer is destabilized by inducing backbone dihedral angles that lie outside the typical Ramachandran angles. This diastereomer also forms a C11/C9 mixed helix as well as a cap influenced bifurcated C7ax-C11/NH···π/C7eq structure as the global energy minimum. Assigned structures are compared with the reported crystal structure of analogous α/ß-tripeptides, and disconnectivity graphs are presented to give an overview of the complicated potential energy surface of this tripeptide diastereomer pair.

Effects of Antarctic krill oil on lipid and glucose metabolism in C57BL/6J mice fed with high fat diet.

BACKGROUND: Obesity and other metabolic diseases have become epidemic which greatly affect human health. Diets with healthy nutrition are efficient means to prevent this epidemic occurrence. Novel food resources and process technology were needed for these purpose. In this study, Antarctic krill oil (KO) extracted from a dry krill by a procedure of hot pump dehydration in combined with freezing-drying was used to investigate health effect in animals including the growth, lipid and glucose metabolism. METHODS: C57BL/6J mice were fed with a lard based high fat (HF) diet and substituted with KO for a period of 12 weeks in comparison with low fat normal control (NC) diet. Mice body weight and food consumption were recorded. Serum lipid metabolism - of C57BL/6J mice serum was measured. A glucose tolerance tests (GTTs) and pathology analysis of mice were performed at the end of the experiment. RESULTS: The KO fed mice had less body weight gain, less fat accumulation in tissue such as adipose and liver. Dyslipidemia induced by high fat diet was partially improved by KO feeding with significant reduction of serum low density lipoprotein-cholesterol (LDL-C) content. Furthermore, KO feeding also improved glucose metabolism in C57BL/6J mice including a glucose tolerance of about 22% vs. 32% of AUC (area under the curve) for KO vs HF diet and the fast blood glucose level of 8.5 mmol/L, 9.8 mmol/L and 9.3 mmol/L for NC, HF and KO diet groups, respectively. In addition, KO feeding also reduced oxidative damage in liver with a decrease of malondialdehyde (MDA) content and increase of superoxide dismutase (SOD) content. CONCLUSION: This study provided evidence of the beneficial effects of KO on animal health from the processed technology, particularly on lipid and glucose metabolism. This study confirmed that as the Antarctic krill was extracted with a procedure of efficient energy, it might make it possible for Krill oil to be available for food industry.

Effect of water content on thermal oxidation of oleic acid investigated by combination of EPR spectroscopy and SPME-GC-MS/MS.

Promotion of water to the thermal oxidation of oleic acid was detected by the combination of EPR, SPME-GC-MS/MS and GC. Spin-trapping technique was used to identify and quantify the radical species formed during thermal oxidation of oleic acid by using DMPO as electron spin trap. The most abundant radical species were identified as DMPO-alkyl radical adducts. EPR intensity plateau of the samples with 5% water content was 140% higher than the samples without water. It implies oleic acid samples with high water content had high level of oxidation rates. The proportion of aldehydes of the samples with 2% water content was the maximum about 59.97%. Among the formed products, (E,E)-2,4-decadienal has genotoxic and cytotoxic effects, whose percentage was nearly twice comparing with that of 5-0% water content. This study demonstrated that higher water content in frying systems would contribute to seriously oxidation and degradation of oleic acids.

Effects of Polar Compounds Generated from the Deep-Frying Process of Palm Oil on Lipid Metabolism and Glucose Tolerance in Kunming Mice.

In the present study, effects of deep-fried palm oil, specifically polar compounds generated during the frying process, on animal health including lipid and glucose metabolism and liver functions were investigated. Kunming mice were fed a high-fat diet containing deep-fried palm oil or purified polar compounds for 12 weeks. Their effects on animal health including hepatic lipid profile, antioxidant enzyme activity, serum biochemistry, and glucose tolerance were analyzed. Our results revealed that the consumption of polar compounds was related to the change of lipid deposition in liver and adipose tissue, as well as glucose tolerance alteration in Kunming mice. Correspondingly, the transcription study of genes involved in lipid metabolism including PPARα, Acox1, and Cpt1α indicated that polar compounds probably facilitated the fatty acid oxidation on peroxisomes, whereas lipid oxidation in mitochondria was suppressed. Furthermore, glucose tolerance test (GTT) revealed that a high amount of polar compound intake impaired glucose tolerance, indicating its effect on glucose metabolism in vivo. Our results provide critical information on the effects of polar compounds generated from the deep-frying process of palm oil on animal health, particularly liver functions and lipid and glucose metabolism, which is important for the evaluation of the biosafety of frying oil.

Inactivation of Lipase and Lipoxygenase of Wheat Germ with Temperature-Controlled Short Wave Infrared Radiation and Its Effect on Storage Stability and Quality of Wheat Germ Oil.

Wheat germ (WG) is quite susceptible to deterioration due to the presence of lipase (LA) and lipoxygenase (LOX). Therefore it is indispensable to adopt a stabilization step to decrease the activity of LA and LOX while retaining a maximum level of nutrients. But over-drying can make foodstuffs more susceptible to autoxidation. So a stabilization protocol for inactivating LA and LOX of WG with a temperature- controlled short wave infrared (SIR) radiation system was adopted to retard its rancidity and retain a maximum level of fat-soluble nutrients. Meanwhile, the critical storage water activity (Aw) of WG for inhibiting both hydrolytic and oxidative rancidity was appraised. Results indicate that WG irradiated at 90°C for 20 min acquired the optimal stabilization effect, and its residual LA and LOX activity were 18.02% and 19.21%, respectively. At this condition, the free fatty acids (FFA) content and peroxide value (PV) increment of WG oil at 40°C remained below 5% and 2.24 meq O2/kg for 60 days, respectively. The residual Aw of this WG sample was 0.13, and it is near the Aw corresponding to its monolayer. No significant decrease of fatty acids was observed during SIR processing, while about 96.42% of its original tocopherols still retained in WG treated at 90°C for 20 min.

Subcritical Butane Extraction of Wheat Germ Oil and Its Deacidification by Molecular Distillation.

Extraction and deacidification are important stages for wheat germ oil (WGO) production. Crude WGO was extracted using subcritical butane extraction (SBE) and compared with traditional solvent extraction (SE) and supercritical carbon dioxide extraction (SCE) based on the yield, chemical index and fatty acid profile. Furthermore, the effects of the molecular distillation temperature on the quality of WGO were also investigated in this study. Results indicated that WGO extracted by SBE has a higher yield of 9.10% and better quality; at the same time, its fatty acid composition has no significant difference compared with that of SE and SCE. The molecular distillation experiment showed that the acid value, peroxide value and p-anisidine value of WGO were reduced with the increase of the evaporation temperatures, and the contents of the active constituents of tocopherol, polyphenols and phytosterols are simultaneously decreased. Generally, the distillation temperature of 150 °C is an appropriate condition for WGO deacidification with the higher deacidification efficiency of 77.78% and the higher retention rate of active constituents.