A simple method was demonstrated for the fabrication of multi-scale polymer microlenses (µ-lenses) and microlens arrays (MLAs) using a drop-on-demand (DOD) droplet generator. A ultraviolet (UV) ...curable polymer used as the ink was DOD printed on the hydrophobic surfaces with different wetting conditions and cured by a UV lamp. The high quality µ-lenses and MLAs with good geometrical uniformity were fabricated. The shapes of the µ-lenses and MLAs were controlled by the different surface wetting conditions, and these shape changes affected the optical properties of the µ-lenses and MLAs, such as the numerical aperture (NA), focal distance (f) and the f-number (f#). The surface roughness of the µ-lens was measured by a white light interferometer (VSI mode) and atomic force microscope (AFM) and proved satisfactory. The influences of the surface wetting conditions on imaging and light gathering characteristics of the MLAs were evaluated by an optical microscope.
•We provide a simple drop on demand droplet generator for fabricating the microlens.•We fabricate the microlens with variety of sizes and radii on different substrates.•The numerical aperture of the microlens can be controlled ranging from 0.09 to 0.47.
Neural stem cell (NSC) differentiation and proliferation are important biological processes in the cerebral neural network. However, these two abilities of NSCs are limited. Thus, the induction of ...differentiation and/or proliferation through the administration of plant-derived small-molecule compounds could be used to repair damaged neural networks. The present study reported that gallic acid (GA), an important phenolic acid found in tea, selectively caused NSCs to differentiate into immature neurons and promoted NSC proliferation by activating the mitogen-activated protein kinase/extracellular-regulated kinase (MAPK/ERK) pathway. In addition, it was found that 3,4-dihydroxybenzoic acid was the main active structure exhibiting neurotrophic activity. The substitution of the carboxyl group on the benzene ring with the ester group may promote differentiation based on the structure of 3,4-dihydroxybenzoic acid. Furthermore, the introduction of the 5-hydroxyl group may promote proliferation. The present study identified that GA can promote the differentiation and proliferation of NSCs in vitro and exert pharmacological activity on NSCs.
Implementing the synergistic effects between the metal and the ligand has successfully streamlined the energetics for CO2 activation and gained high catalytic activities, establishing the important ...breakthroughs in photocatalytic CO2 reduction. Herein, we describe a Ni(II) N-confused porphyrin complex (NiNCP) featuring an acidic N–H group. It is readily deprotonated and exists in an anion form during catalysis. Owing to this functional site, NiNCP gave rise to an outstanding turnover number (TON) as high as 217,000 with a 98% selectivity for CO2 reduction to CO, while the parent Ni(II) porphyrin (NiTPP) was found to be nearly inactive. Our mechanistic analysis revealed a nonclassical reaction pattern where CO2 was effectively activated via the attack of the Lewis-basic ligand. The resulting ligand-bound CO2 adduct could be further reduced to produce CO. This new metal–ligand synergistic effect is anticipated to inspire the design of highly active catalysts for small molecule activations.
Implementing the synergistic effects between the metal and the ligand has successfully streamlined the energetics for CO
activation and gained high catalytic activities, establishing the important ...breakthroughs in photocatalytic CO
reduction. Herein, we describe a Ni(II) N-confused porphyrin complex (
) featuring an acidic N-H group. It is readily deprotonated and exists in an anion form during catalysis. Owing to this functional site,
gave rise to an outstanding turnover number (TON) as high as 217,000 with a 98% selectivity for CO
reduction to CO, while the parent Ni(II) porphyrin (
) was found to be nearly inactive. Our mechanistic analysis revealed a nonclassical reaction pattern where CO
was effectively activated via the attack of the Lewis-basic ligand. The resulting ligand-bound CO
adduct could be further reduced to produce CO. This new metal-ligand synergistic effect is anticipated to inspire the design of highly active catalysts for small molecule activations.
Pulse wave velocity (PWV) has been shown to influence the effects of antihypertensive drugs in the prevention of cardiovascular diseases. Data are limited on whether PWV is an independent predictor ...of stroke above and beyond hypertension control. This longitudinal analysis examined the independent and joint effect of brachial-ankle PWV (baPWV) with hypertension control on the risk of first stroke. This report included 3310 hypertensive adults, a subset of the China Stroke Primary Prevention Trial (CSPPT) with baseline measurements for baPWV. During a median follow-up of 4.5 years, 111 participants developed first stroke. The risk of stroke was higher among participants with baPWV in the highest quartile than among those in the lower quartiles (6.3% versus 2.4%; hazard ratio, 1.66; 95% confidence interval, 1.06–2.60). Similarly, the participants with inadequate hypertension control had a higher risk of stroke than those with adequate control (5.1% versus 1.8%; hazard ratio, 2.32; 95% confidence interval, 1.49–3.61). When baPWV and hypertension control were examined jointly, participants in the highest baPWV quartile and with inadequate hypertension control had the highest risk of stroke compared with their counterparts (7.5% versus 1.3%; hazard ratio, 3.57; 95% confidence interval, 1.88–6.77). There was a significant and independent effect of high baPWV on stroke as shown among participants with adequate hypertension control (4.2% versus 1.3%; hazard ratio, 2.29, 95% confidence interval, 1.09–4.81). In summary, among hypertensive patients, baPWV and hypertension control were found to independently and jointly affect the risk of first stroke. Participants with high baPWV and inadequate hypertension control had the highest risk of stroke compared with other groups.
Herein, we report a computation study based on the density functional theory calculations to understand the mechanism and ligand effect of the base-stabilized dialumenes toward dihydrogen activation. ...Among all of the examined modes of dihydrogen activation using the base-stabilized dialumene, we found that the concerted 1,2-hydrogenation of the AlAl double bond is kinetically more preferable. The concerted 1,2-hydrogenation of the AlAl double bond adopts an electron-transfer model with certain asynchrony. That is, the initial electron donation from the H–H σ bonding orbital to the empty 3p orbital of the Al1 center is followed by the backdonation from the lone pair electron of the Al2 center to the H–H σ antibonding orbital. Combined with the energy decomposition analysis on the transition states of the concerted 1,2-hydrogenation of the AlAl double bond and the topographic steric mapping analysis on the free dialumenes, we ascribe the higher reactivity of the aryl-substituted dialumene over the silyl-substituted analogue in dihydrogen activation to the stronger electron-withdrawing effect of the aryl group, which not only increases the flexibility of the AlAl double bond but also enhances the Lewis acidity of the AlAl core. Consequently, the aryl-substituted dialumene fragment suffers less geometric deformation, and the orbital interactions between the dialumene and dihydrogen moieties are more attractive during the 1,2-hydrogenation process. Moreover, our calculations also predict that the AlAl double bond has a good tolerance with the stronger electron-withdrawing group (–CF3) and the weaker σ-donating N-heterocyclic carbene (NHC) analogue (e.g., triazol carbene and NHSi). The reactivity of the dialumene in dihydrogen activation can be further improved by introducing these groups as the supporting ligand and the stabilizing base on the AlAl core, respectively.
To explore the correlation between characteristics of myocardial energy expenditure (MEE) and the degree of diastolic dysfunction in patients of heart failure with preserved ejection fraction (HFpEF) ...and its clinical significance.
125 consecutive patients diagnosed with HFpEF in the Department of Cardiology, Affiliated Zhongshan Hospital of Dalian University from January 2018 to October 2018 were enrolled. According to the degree of diastolic dysfunction, patients were divided into group A (8 ≤ E/e' ≤15) and group B (E/e'> 15), and MEE was calculated, patients finished 1-year clinical follow-up.
The level of MEE in group A was significantly lower than that in group B (
< 0.05). During 1-year follow up, MEE over 3145.69 kcal/systole was associated with increased risk of death as compared to patients with MEE less 3145.69 kcal/systole, and in patients with MEE over 101.68 kcal/min than in patients with MEE less than 101.68 kcal/min.
There is a significant correlation between MEE and diastolic dysfunction and MEE over 3145.69 kcal/systole as well as MEE over 101.68 kcal/min are linked with increased risk of 1-year mortality in HFpEF.
Understanding the precipitation variability and extreme precipitation over arid Central Asia (CA) has largely been hampered by the lack of daily precipitation observations. The gridded precipitation ...datasets over CA are large discrepancies. Here, three gauge-based gridded daily precipitation products from Asian Precipitation Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE), Global Precipitation Climatology Center (GPCC), and Climate Prediction Center Based Analysis of Global Daily Precipitation (CPC_global) were assessed and compared with 49 rain gauge daily observations precipitation (OBS) from January 1985 to December 2015 using different time-scales over CA and different climate regimes, specifically Northern CA with temperate continental climate (NCA), Southwestern CA with dry arid desert climate (SWCA), and Southeastern CA with Mediterranean continental climate (SECA). Four accuracy indices correlation coefficient (R), Bias, root mean square error (RMSE), and relative bias (RBias) were employed to evaluate the performance of the three products in depicting the spatiotemporal features of precipitation variation over CA at multiple time scales (including daily, monthly, seasonal, and yearly). The mean annual and daily precipitation of OBS and three gridded products exhibit the trend of a gradual precipitation decreased from SECA to NCA and SWCA. The best overall performance was obtained for APHRODITE and GPCC for daily and annual time-scale, whereas CPC shows noticeable underestimation precipitation in SECA. The monthly precipitation depicted distinct features with a bimodal pattern with a peak in March and another in December, include the SECA and SWCA regions. In contrast, precipitation was concentrated in summer with the peak in July over the NCA region. At monthly scale terms, APHRODITE was more accurate in the wet seasons (winter and spring months) in SWCA and SECA. Additionally, GPCC has fairly better capability in summer months in NCA. Considering the spatial distribution, the bias variability was largerly in mountainous areas than in the plains. Temporally, the bias largerly in the dry seasons than in the wet seasons. At the interannual variability scale, GPCC was capable of qualitatively increasing the CA (NCA and SECA) precipitation during the last 21 years, while APHRODITE underestimated the trends. The CPC overestimated the precipitation trends over all regions. This study can serve as a reference for selecting daily precipitation products with low densities of stations, complex topographies, and similar climatic regions.
Several octahedral Fe
3
O
4
-supported platinum catalysts were successfully synthesized via impregnation, colloid deposition and co-precipitation methods and characterized using multiple techniques. ...All Pt/Fe
3
O
4
catalysts demonstrated activity in low-temperature HCHO oxidation, with the catalyst prepared by the co-precipitation method (designated Pt/Fe
3
O
4
-CP-80) exhibiting relatively higher catalytic activity. The results of various characterization techniques revealed that the preparation method could influence the strength of metal-support interactions and the number of surface hydroxyl groups of the Pt/Fe
3
O
4
catalysts. It was observed that the metal-support interactions in Pt/Fe
3
O
4
catalysts affected their redox properties. The excellent performance of Pt/Fe
3
O
4
-CP-80 catalyst was mainly attributed to the presence of appropriate interaction between Pt and Fe species, which resulted in the formation of more active interface sites (i.e. Pt-O(OH)
x
-Fe species).
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
High temperature proton exchange membrane fuel cells (HT-PEMFCs) can operate over 100 °C without humidification, which avoids the catalyst poisoning and enhances the efficiency of the power ...conversion. However, the classic phosphoric acid (PA) doped polybenzimidazole (PBI) still remains the challenge in the trade-off between mechanical strength and proton conductivity. The γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH560), as a crosslinking agent, is widely used to improve the mechanical properties of membranes. Although it can enhance the mechanical strength of PBI membranes, it sacrifices the hydrogen of imidazole groups, resulting in a decrease in proton conductivity. In this present work, silane-crosslinked PBI proton exchange membranes (PEMs) were synthesized by the reaction between the pyridine-bridged PBI containing different hydroxyl (-OH) content with KH560. Through comprehensive structural characterization of the polymer and model compound, it has been determined that this crosslinking method does not compromise the N–H acidic sites on the imidazole ring. The crosslinking agent KH560 provides additional hydroxyl groups to PBI and participates in the construction of hydrogen bonding networks after the ring-opening reaction. It was found that the addition of pyridine and hydroxyl groups could promote the phosphoric acid uptake, and the appropriate degree of silane crosslinking could maintain the PBI membranes with reasonable mechanical properties. Proton conductivity and HT-PEMFCs performance of the obtained crosslinked films were further enhanced with the dimensional stability, thermal stability and mechanical properties. Among them, CPyOPBI–OH–20 presented the best overall performance, exhibiting the highest proton conductivity of 0.095 S cm−1 and the maximum power density of 767 mW cm−2 at 180 °C under the anhydrous condition, which was 4.2 times that of OPBI (182 mW cm−2).
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•Silane cross-linked PBI membranes were fabricated by the reaction between the epoxy group of KH560 and the hydroxyl group of PBI without consuming the N–H on the imidazole ring which was proved by model reaction.•The CPyOPBI-OH-20 membrane exhibited a peak power density of 767 mW cm−2 at 180 °C without humidification.
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