Intrinsic Self-Trapped Excitons in Graphitic Carbon Nitride.

Graphitic carbon nitrides (g-C3N4) as low-cost, chemically stable, and ecofriendly layered semiconductors have attracted rapidly growing interest in optoelectronics and photocatalysis. However, the nature of photoexcited carriers in g-C3N4 is still controversial, and an independent charge-carrier picture based on the band theory is commonly adopted. Here, by performing transient spectroscopy studies, we show characteristics of self-trapped excitons (STEs) in g-C3N4 nanosheets including broad trapped exciton-induced absorption, picosecond exciton trapping without saturation at high photoexcitation density, and transient STE-induced stimulated emissions. These features, together with the ultrafast exciton trapping polarization memory, strongly suggest that STEs intrinsically define the nature of the photoexcited states in g-C3N4. These observations provide new insights into the fundamental photophysics of carbon nitrides, which may enlighten novel designs to boost energy conversion efficiency.

Efficient, Color-Stable, Pure-Blue Light-Emitting Diodes Based on Aromatic Ligand-Engineered Perovskite Nanoplatelets.

Perovskite nanoplatelets (NPLs) show great potential for high-color-purity light-emitting diodes (LEDs) due to their narrow line width and high exciton binding energy. However, the performance of perovskite NPL LEDs lags far behind perovskite quantum dot-/film-based LEDs, owing to their material instability and poor carrier transport. Here, we achieved efficient and stable pure blue-emitting CsPbBr3 NPLs with outstanding optical and electrical properties by using an aromatic ligand, 4-bromothiophene-2-carboxaldehyde (BTC). The BTC ligands with thiophene groups can guide two-dimensional growth and inhibit out-of-plane ripening of CsPbBr3 NPLs, which, meanwhile, increases their structural stability via strongly interacting with PbBr64- octahedra. Moreover, aromatic structures with delocalized π-bonds facilitate charge transport, diminish band tail states, and suppress Auger processes in CsPbBr3 NPLs. Consequently, the LEDs demonstrate efficient and color-stable blue emissions at 465 nm with a narrow emission line width of 17 nm and a maximum external quantum efficiency (EQE) of 5.4%, representing the state-of-the-art CsPbBr3 NPL LEDs.

Electrocatalytic Cascade Selenylation/Cyclization/Deamination of 2-Hydroxyaryl Enaminones: Synthesis of 3-Selenylated Chromones under Mild Conditions.

Herein, we disclosed a highly efficient pathway toward 3-selenylated chromone derivatives via electrocatalytic cascade selenylation/cyclization/deamination of 2-hydroxyaryl enaminones with diselenides. This method showed mild conditions, easy operation, wide substrate scope, and good functional group tolerance. Furthermore, this electrosynthesis strategy was amendable to scale-up the reaction. Additionally, the preliminary experiments revealed that this reaction probably proceeded via a cation pathway instead of a radical pathway.

The effect of L-cysteine on starch and protein degradation during barley germination.

OBJECTIVES: In order to investigate the impact of L-cysteine (L-Cys) on starch and protein degradation during barley germination. The amylase activities, degradation of macromolecules during germination were determined in this study. METHODS: Barley was germinated in petri dish for 0 to 5 days with different levels of L-Cys (0 mM, 2.5 mM, 5 mM, 10 mM). RESULTS: L-Cys addition increased the total limit dextrinase (LD) activities and decreased the LD inhibitor activities during whole germination stage. The activities of α-amylase, ß-amylase and free LD were increased with the addition of 2.5, 5 mM L-Cys at germination days 1 to 4. Due to higher amylase in malt with the addition of L-Cys, the non-fermentable sugars were reduced and the glucose, maltotriose were improved. Furthermore, the protein degradation analysis showed that low molecular weight protein increased and middle molecular weight protein decreased obviously in wort from the malt germinated with L-Cys, demonstrating that the L-Cys promote the protein degradation. Lastly, the filtration performance of malt with the addition of L-Cys during malting was better than the control. CONCLUSION: In conclusion, L-Cys can promote the degradation of storage material (starch, protein) during barley germination, leading to a better green malt quality.

Synthesis of fused 3-trifluoromethyl-1,2,4-triazoles via base-promoted [3 + 2] cycloaddition of nitrile imines and 1H-benzo[d]imidazole-2-thiols.

Here we report a strategy for the facile assembly of fused 3-trifluoromethyl-1,2,4-triazoles, which are difficult to synthesize using traditional strategies, in 50-96% yields through a triethylamine-promoted intermolecular [3 + 2] cycloaddition pathway. This protocol features high efficiency, good functional group tolerance, mild conditions, and easy operation. Furthermore, a gram-scale reaction and product derivatizations were carried out smoothly to illustrate the practicability of this method.

Recent advances in the efficient degradation of lignocellulosic metabolic networks by lytic polysaccharide monooxygenase.

Along with long-term evolution, the plant cell wall generates lignocellulose and other anti-degradation barriers to confront hydrolysis by fungi. Lytic polysaccharide monooxygenase (LPMO) is a newly defined oxidase in lignocellulosic degradation systems that significantly fuels hydrolysis. LPMO accepts electrons from wide sources, such as cellobiose dehydrogenase (CDH), glucose-methanol-choline (GMC) oxidoreductases, and small phenols. In addition, the extracellular cometabolic network formed by cosubstrates improves the degradation efficiency, forming a stable and efficient lignocellulose degradation system. In recent years, using structural proteomics to explore the internal structure and the complex redox system of LPMOs has become a research hotspot. In this review, the diversity of LPMOs, catalytic domains, carbohydrate binding modules, direct electron transfer with CDH, cosubstrates, and degradation networks of LPMOs are explored, which can provide a systematic reference for the application of lignocellulosic degradation systems in industrial approaches.

Observation of Phonon Cascades in Cu-Doped Colloidal Quantum Wells.

Electronic doping has endowed colloidal quantum wells (CQWs) with unique optical and electronic properties, holding great potential for future optoelectronic device concepts. Unfortunately, how photogenerated hot carriers interact with phonons in these doped CQWs still remains an open question. Here, through investigating the emission properties, we have observed an efficient phonon cascade process (i.e., up to 27 longitudinal optical phonon replicas are revealed in the broad Cu emission band at room temperature) and identified a giant Huang-Rhys factor (S ≈ 12.4, more than 1 order of magnitude larger than reported values of other inorganic semiconductor nanomaterials) in Cu-doped CQWs. We argue that such an ultrastrong electron-phonon coupling in Cu-doped CQWs is due to the dopant-induced lattice distortion and the dopant-enhanced density of states. These findings break the widely accepted consensus that electron-phonon coupling is typically weak in quantum-confined systems, which are crucial for optoelectronic applications of doped electronic nanomaterials.

Discovery of Bacteroides uniformis F18-22 as a Safe and Novel Probiotic Bacterium for the Treatment of Ulcerative Colitis from the Healthy Human Colon.

Previous studies have demonstrated that the intestinal abundance of Bacteroides uniformis is significantly higher in healthy controls than that in patients with ulcerative colitis (UC). However, what effect B. uniformis has on the development of UC has not been characterized. Here, we show for the first time that B. uniformis F18-22, an alginate-fermenting bacterium isolated from the healthy human colon, protects against dextran-sulfate-sodium (DSS)-induced UC in mice. Specifically, oral intake of B. uniformis F18-22 alleviated colon contraction, improved intestinal bleeding and attenuated mucosal damage in diseased mice. Additionally, B. uniformis F18-22 improved gut dysbiosis in UC mice by increasing the abundance of anti-inflammatory acetate-producing bacterium Eubacterium siraeum and decreasing the amount of pro-inflammatory pathogenetic bacteria Escherichia-Shigella spp. Moreover, B. uniformis F18-22 was well-tolerated in mice and showed no oral toxicity after repeated daily administration for 28 consecutive days. Taken together, our study illustrates that B. uniformis F18-22 is a safe and novel probiotic bacterium for the treatment of UC from the healthy human colon.

Age-specificity and generalization of behavior-associated structural and functional networks and their relevance to behavioral domains.

Behavior-associated structural connectivity (SC) and resting-state functional connectivity (rsFC) networks undergo various changes in aging. To study these changes, we proposed a continuous dimension where at one end networks generalize well across age groups in terms of behavioral predictions (age-general) and at the other end, they predict behaviors well in a specific age group but fare poorly in another age group (age-specific). We examined how age generalizability/specificity of multimodal behavioral associated brain networks varies across behavioral domains and imaging modalities. Prediction models consisting of SC and/or rsFC networks were trained to predict a diverse range of 75 behavioral outcomes in a young adult sample (N = 92). These models were then used to predict behavioral outcomes in unseen young (N = 60) and old (N = 60) subjects. As expected, behavioral prediction models derived from the young age group, produced more accurate predictions in the unseen young than old subjects. These behavioral predictions also differed significantly across behavioral domains, but not imaging modalities. Networks associated with cognitive functions, except for a few mostly relating to semantic knowledge, fell toward the age-specific end of the spectrum (i.e., poor young-to-old generalizability). These findings suggest behavior-associated brain networks are malleable to different degrees in aging; such malleability is partly determined by the nature of the behavior.

Asymmetric generalizability of multimodal brain-behavior associations across age-groups.

Machine learning methods have increasingly been used to map out brain-behavior associations (BBA), and to predict out-of-scanner behavior of unseen subjects. Given the brain changes that occur in the context of aging, the accuracy of these predictions is likely to depend on how similar the training and testing data sets are in terms of age. To this end, we examined how well BBAs derived from an age-group generalize to other age-groups. We partitioned the CAM-CAN data set (N = 550) into the young, middle, and old age-groups, then used the young and old age-groups to construct prediction models for 11 behavioral outcomes using multimodal neuroimaging features (i.e., structural and resting-state functional connectivity, and gray matter volume/cortical thickness). These models were then applied to all three age-groups to predict their behavioral scores. When the young-derived models were used, a graded pattern of age-generalization was generally observed across most behavioral outcomes-predictions are the most accurate in the young subjects in the testing data set, followed by the middle and then old-aged subjects. Conversely, when the old-derived models were used, the disparity in the predictive accuracy across age-groups was mostly negligible. These findings hold across different imaging modalities. These results suggest the asymmetric age-generalization of BBAs-old-derived BBAs generalized well to all age-groups, however young-derived BBAs generalized poorly beyond their own age-group.

Ultrafast modulation of a high harmonic generation in a bulk ZnO single crystal.

Optical modulation of high harmonic generation (HHG) is of fundamental interest in science and technology, which can facilitate understanding of HHG generation mechanisms and expand the potential optoelectronic applications. However, the current established works have neither shown the advanced modulation performance nor provided a deep understanding of modulation mechanisms. In this work, taking wurtzite zinc oxide (ZnO) single crystal as a prototype, we have demonstrated an all-optical intensity modulation of high-order HHG with a response time of less than 0.2 ps and a depth of more than 95%, based on the pump-probe configuration with two different pumping wavelengths. Besides the achieved excellent modulation performance, we have also revealed that the modulation dynamics in ZnO single crystal highly depend on the excitation conditions. Specifically, the modulation dynamics with the near-bandgap or above-bandgap excitation are attributed to the non-equilibrium interband carrier relaxations, while for mid-gap excitation, the modulation dynamics are dominated by the nonlinear frequency mixing process. This work may enhance the current understanding of the HHG modulation mechanism and enlighten novel device designs.

Differential associations between simple physical performance tests with global and specific cognitive functions in cognitively normal and mild cognitive impairment: a cross-sectional cohort study of Asian community-dwelling older adults.

BACKGROUND: Physical performance declines and executive dysfunctions are predictors of dementia. However, their associations are not well understood in Asian older adults without dementia (cognitively normal [CN] and mild cognitive impairment [MCI]), especially in a single study. OBJECTIVE: Examine the associations between physical performance measures with executive function (EF)-based and non-EF-based neurocognitive tests and whether preclinical dementia cognitive status i.e., CN and MCI, moderated these associations. METHODS: We examined cross-sectional cohort of 716 community-dwelling older adults without dementia (CN = 562 and MCI = 154) using multivariable linear regression models. We associated three simple physical performance measures, namely timed-up-and-go (TUG), fast gait speed (FGS), and 30-s chair stand test (30 s-CST), with a comprehensive neurocognitive test battery measuring EF and non-EF cognitive functions. Moderating effects of cognitive status on the associations were examined. In all models, we controlled for pertinent covariates, including age, education, medical and psychiatric status. RESULTS: Upon controlling for covariates, TUG was most strongly and positively associated with multiple EF-based neurocognitive tests, followed by FGS, with 30 s-CST having the weakest associations. For all physical performance measures, no significant associations with non-EF-based neurocognitive tests were detected. Cognitive status significantly moderated the associations between all physical measures and several neurocognitive tests, with stronger associations in the MCI than CN. CONCLUSION: Compared to FGS and 30 s-CST, TUG had the most robust associations with multiple EF-based cognitive functions. Given their differential associations with global and detailed neurocognitive tests and significant moderating effects of cognitive status, findings highlight a need to carefully consider the choices of simple physical performance tests when using these tests with a heterogenous group of community-dwelling older adults without dementia.

Reduced sensitivity of lager brewing yeast to premature yeast flocculation via adaptive evolution.

Malt-induced premature yeast flocculation (PYF) is a sporadic problem within the brewing industry. The use of PYF malts is concomitant with a number of negative impacts on beer quality, including incomplete fermentation and/or flavor defects. Although malt-induced PYF is widely acknowledged, actions taken so far have proved insufficient to solve the PYF-related issues. To limit the detrimental effects of PYF malts on beer production, an adaptive laboratory evolution (ALE) process was applied in this study to an industrial lager brewing yeast strain (TT02), in an attempt to generate variant strains with improved fermentation performance in PYF wort. Through a batch fermentation-based adaptation process, evolved variants were isolated and screened for their phenotypic and metabolic traits. The investigation focused mainly on the tendency to remain in suspension, fermentation capacity and final acetaldehyde concentration. We successfully obtained a variant (TT02-30 T) with improved fermentation properties. The improvement was seen in worts prepared from different types of PYF malt as well as normal malt. Furthermore, ALE of lager brewing yeast in PYF wort yielded a wide array of mutations. Several changes in the genomes (copy number variation in flocculin encoding gene FLO1 and a missense SNP in a putative mitochondrial membrane protein coding gene FMP10) of the variant strains relative to the original strain were observed. These could potentially contribute to the improved yeast suspension during fermentation. Importantly, mutational enrichment in genes related to ion binding in PYF-evolved strains suggests the involvement of the yeast ion transportation process in dealing with the PYF stress. Our study demonstrates the possibility of attenuating yeast sensitivity to PYF malts over time through adaptive laboratory evolution via spontaneous mutation.

Assembled Exciton Dynamics in Porphyrin Metal-Organic Framework Nanofilms.

Metal-organic frameworks (MOFs) provide a novel strategy to precisely control the alignment of molecules to enhance exciton diffusion for high-performance organic semiconductors. In this paper, we characterize exciton dynamics in highly ordered and crystalline porphyrin MOF nanofilms by time-resolved photoluminescence and femtosecond-resolved transient absorption spectroscopy. Results suggest that porphyrin MOF nanofilms could be a promising candidate for high-performance organic photovoltaic semiconductors in which the diffusion coefficient and diffusion length of excitons are 9.0 × 10-2 cm2 s-1 and 16.6 nm, respectively, comparable with or even beyond that of other excellent organic semiconductors. Moreover, by monitoring real-time exciton dynamics it is revealed that excitons in MOF nanofilms undergo high-efficient intermolecular hopping and multiexciton annihilation due to the short intermolecular distance and aligned molecular orientation in MOF structure, thus providing new insights into the underlying physics of exciton dynamics and many-body interaction in molecular assembled systems.

Directional Effects of Social Isolation and Quality of Life on Anxiety Levels Among Community-Dwelling Older Adults During a COVID-19 Lockdown.

OBJECTIVE: The COVID-19 lockdown could see older adults facing increased anxiety levels due to social isolation. Additionally, the lockdown could be more difficult for those with lower Quality of Life (QoL). We aim to understand predictive factors of older adult's anxiety symptoms during the lockdown as it is a main psychological concern of COVID-19. METHODS: Four hundred eleven participants (Mage = 68.95, S.D. = 5.60) completed questionnaires at two time points - before the pandemic and during the lockdown period. Cross-lagged analysis was carried out on two structural equation models - social isolation and anxiety symptoms, and QoL and anxiety symptoms. RESULTS: Baseline social isolation was associated with more anxiety symptoms at follow-up. However, baseline anxiety symptoms were not associated with social isolation subsequently. For QoL and anxiety symptoms, the relationship was bidirectional. CONCLUSION: Older adults who were previously socially isolated and had a lower QoL are particularly vulnerable to the negative psychological impacts of the COVID-19 lockdown.

The Art of Remediating Age-Related Cognitive Decline: Art Therapy Enhances Cognition and Increases Cortical Thickness in Mild Cognitive Impairment.

OBJECTIVE: Previous research on art therapy (AT) in cognitive aging has been lacking. AT can potentially engender significant cognitive gains, due to its rigorous cognitive involvement, making it useful to tackle age-related cognitive decline. Along with these cognitive gains, associated neuroplastic changes are hypothesized to arise from AT as well. The current intervention examined the effects of an AT intervention on cognitive outcomes and cortical thickness (CT) among participants with mild cognitive impairment. METHOD: Participants were assigned to AT (n = 22) and an active control group (n = 27). In both, weekly 45-min sessions were carried out across 3 months. Cognitive assessments and structural magnetic resonance imaging scans were carried out at baseline and 3-month follow-up. Whole brain analyses on CT were carried out. Cognitive outcomes were analyzed using hierarchical linear models. RESULTS: Significant gains in immediate memory and working memory span were observed in the AT group, relative to the control group. Significantly increased CT in the AT group, relative to controls, was observed in a right middle frontal gyrus (MFG) cluster. Furthermore, CT changes in this cluster were significantly and positively correlated with changes in immediate memory. CONCLUSION: These findings highlighted the role of MFG neuroplasticity in enhancing certain cognitive functions in AT. AT is a neuroplastic intervention capable of engendering significant cognitive gains and associated cortical changes in the context of age-related cognitive decline, even when executed as a low-intensity intervention across 3 months. Given the preliminary nature of these findings, future larger sampled studies are needed.

The individualized prediction of cognitive test scores in mild cognitive impairment using structural and functional connectivity features.

Neuropsychological assessments are essential in diagnosing age-related neurocognitive disorders. However, they are lengthy in duration and can be unreliable at times. To this end, we explored a modified connectome-based predictive modeling approach to estimating individualized scores from multiple cognitive domains using structural connectivity (SC) and functional connectivity (FC) features. Multi-shell HARDI and resting-state functional magnetic resonance imaging scans, and scores from 10 cognitive measures were acquired from 91 older adults with mild cognitive impairment. SC and FC matrices were derived from these scans and, in various combinations, entered into models along with demographic covariates to predict cognitive scores. Leave-one-out cross-validation was performed. Predictive accuracy was assessed via the correlation between predicted and observed scores (rpredicted-observed). Across all cognitive measures, significant rpredicted-observed (0.402 to 0.654) were observed from the best-predicting models. Six of these models consisted of multimodal features. For three cognitive measures, their best-predicting models' rpredicted-observed were similar to that of a model that included only demographic covariates- suggesting that SC and/or FC features did not contribute significantly on top of demographics. Cross-prediction models revealed that the best-predicting models were similarly accurate in predicting scores of related cognitive measures- suggesting their limited specificity in predicting cognitive scores. Generally, multimodal connectomes together with demographics, can be exploited as sensitive markers, though with limited specificity, to predict cognitive performance across a spectrum in multiple cognitive domains. In certain situations, it may not be worthwhile to acquire neuroimaging data, considering that demographics alone can be similarly accurate in predicting cognitive scores.

Multi-Session Anodal Prefrontal Transcranial Direct Current Stimulation does not Improve Executive Functions among Older Adults.

OBJECTIVE: Findings from single-session online studies highlighted the potential of using anodal prefrontal transcranial direct current stimulation (tDCS) to enhance executive functions (EF) in the context of aging. However, tDCS must be executed as a multi-session offline intervention to ascertain its viability in this context. Relatedly, findings from multi-session studies remained inconclusive. To this end, we examined the effects of multi-session anodal prefrontal tDCS on EF in an intervention. METHOD: The intervention consisted of 15 sessions; in each, healthy older participants (Agemean = 66.7) received either 15 min of 1.5 mA tDCS (Ncompleted = 35) or sham stimulation (Ncompleted = 33) while performing EF training tasks. EF measures were assessed at baseline, post-intervention, and 1-month follow-up. Hierarchical linear models were used to examine the effect of tDCS on EF outcomes. RESULTS: Both groups of participants did not differ significantly in side effect ratings and attendance. There were no significant tDCS-associated gains in any EF outcomes in the intervention. CONCLUSIONS: Multi-session prefrontal tDCS did not lead to any significant gains in EF in the current intervention. More research is needed to optimize the use of tDCS before it can be effectively used to enhance EF among older adults.

Protective effects of enzyme degradation extract from Porphyra yezoensis against oxidative stress and brain injury in D-galactose-induced ageing mice.

The present study investigated the effects of Porphyra yezoensis enzyme degradation extract (PYEDE) on the brain injuries and neurodegenerative diseases due to oxidative stress. We used in vitro antioxidant systems to verify the antioxidant potential of PYEDE. The results indicated that the PYEDE alleviated weight loss and organ atrophy, reduced the levels of lipid peroxidation and protein carbonylation and elevated reduced glutathione (GSH) content in the serum and brains of the d-galactose-induced ageing model mice. The PYEDE also renewed the glutathione peroxidase (GSH-Px), superoxide dismutase and total antioxidant capability activities, down-regulated the inducible nitric oxide synthase activity and nitric oxide levels, normalised the hippocampal neurons and modulated multiple neurotransmitter systems by inhibiting the activities of acetylcholinesterase and monoamine oxidase in the up-regulation of acetylcholine, dopamine and noradrenaline levels. Overall, the PYEDE is a promising supplement for the alleviation of oxidative stress and age-associated brain diseases.

Flexible, ultra-stable and color tunable fluorescent films based on all inorganic perovskite quantum dots embedded in polymer.

Colloidal perovskite CsPbX3 (X = Cl, Br, I) nanocrystals (CPNCs)/polymers composites have attracted extensive attention due to their potential to be developed as flexible phosphor films for lighting applications. However, to maintain high quantum efficiency and photo stability of CPNCs in such composites remains a daunting challenge. Here, we have demonstrated a layered composite structure consisting of CPNCs and polydimethylsiloxane (PDMS) with multi-color emission and long-term stability. By tuning the molar ratio between CsPbCl1.58Br1.42 and CsPbBr1.35I1.65, flexible fluorescent films as down-converter layers with a high luminescent efficiency and a controllable color temperature spanning from 3194 K to 5901 K have been demonstrated. Furthermore, due to embedding inside such composites, the quantum efficiency of CPNCs exhibited negligible changes during seven months in ambient conditions. The carrier dynamics based on time-resolved photoluminescence (PL) and transient absorption spectroscopy reveal that the hot electron tunneling and trapping process are significant in the composite film. This work provides a good understanding of CPNC materials in complex composite for the development of flexible, robust, color controllable fluorescent films for lighting applications.