Axially chiral styrenes bearing a chiral axis between a sterically non-congested acyclic alkene and an aryl ring are difficult to prepare due to low rotational barrier of the axis. Disclosed here is ...an N-heterocyclic carbene (NHC) catalytic asymmetric solution to this problem. Our reaction involves ynals, sulfinic acids, and phenols as the substrates with an NHC as the catalyst. Key steps involve selective 1,4-addition of sulfinic anion to acetylenic acylazolium intermediate and sequential E-selective protonation to set up the chiral axis. Our reaction affords axially chiral styrenes bearing a chiral axis as the product with up to > 99:1 e.r., > 20:1 E/Z selectivity, and excellent yields. The sulfone and carboxylic ester moieties in our styrene products are common moieties in bioactive molecules and asymmetric catalysis.
Disclosed herein is the first carbene‐organocatalyzed asymmetric addition of phosphine nucleophiles to the in situ generated α,β‐unsaturated acyl azolium intermediates. Our reaction ...enantioselectively constructs carbon–phosphine bonds and prepares chiral phosphines with high optical purities. The phosphine products are suitable for transforming to chiral ligands or catalysts with applications in asymmetric catalysis. The diarylalkyl or trialkyl phosphine products from our catalytic reactions, air‐sensitive and reactive in nature, can be trapped (and stored) in their sulfur‐oxidized form for operational simplicities.
Carbene‐catalyzed asymmetric addition of phosphorus atoms to α,β‐unsaturated acyl azolium intermediates affords chiral phosphines with potential applications as ligands and catalysts.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Objective:
The COVID-19 epidemic has generated great stress throughout healthcare workers (HCWs). The situation of HCWs should be fully and timely understood. The aim of this meta-analysis is to ...determine the psychological impact of COVID-19 pandemic on health care workers.
Method:
We searched the original literatures published from 1 Nov 2019 to 20 Sep 2020 in electronic databases of PUBMED, EMBASE and WEB OF SCIENCE. Forty-seven studies were included in the meta-analysis with a combined total of 81,277 participants.
Results:
The pooled prevalence of anxiety is 37% (95% CI 0.31–0.42, I
2
= 99.9%) from 44 studies. Depression is estimated in 39 studies, and the pooled prevalence of depression is 36% (95% CI 0.31–0.41, I
2
= 99.6%). There are 10 studies reported the prevalence of insomnia, and the overall prevalence of insomnia is 32% (95% CI 0.23–0.42, I
2
= 99.5%). The subgroup analysis showed a higher incidence of anxiety and depression among women and the frontline HCWs compared to men and non-frontline HCWs respectively.
Conclusions:
The COVID-19 pandemic has caused heavy psychological impact among healthcare professionals especially women and frontline workers. Timely psychological counseling and intervention ought to be implemented for HCWs in order to alleviate their anxiety and improve their general mental health.
Stimulated Brillouin scattering is a fundamental interaction between light and travelling acoustic waves and arises primarily from electrostriction and photoelastic effects, with an interaction ...strength several orders of magnitude greater than that of other relevant non-linear optical processes. Here we report an experimental demonstration of Brillouin-scattering-induced transparency in a high-quality whispering-gallery-mode optical microresonantor. The triply resonant Stimulated Brillouin scattering process underlying the Brillouin-scattering-induced transparency greatly enhances the light-acoustic interaction, enabling the storage of light as a coherent, circulating acoustic wave with a lifetime up to 10 μs. Furthermore, because of the phase-matching requirement, a circulating acoustic wave can only couple to light with a given propagation direction, leading to non-reciprocal light storage and retrieval. These unique features establish a new avenue towards integrated all-optical switching with low-power consumption, optical isolators and circulators.
In this paper, we demonstrate for the first time the use of gliadin colloid particles (GCPs) as an effective particulate stabilizer of oil-in-water emulsions of natural oils and water. For this ...purpose, we fabricated GCPs through a facile anti-solvent precipitation procedure and demonstrated their uses in the formation of Pickering emulsions as well as Pickering high internal phase emulsions (HIPEs). We found that unmodified GCPs can produce stable, surfactant-free o/w emulsions with microscale droplet sizes under experimental mixing conditions at pH 4 and above. In contrast, the emulsions were not stable against coalescence at ∼pH 3.0. The microstructures, e.g., interfacial framework, GCPs partition between the continuous phase and interfacial region, and state of the droplets, of Pickering emulsions as a function of pH were visualized by optical microscopy and confocal laser scanning microscopy (CLSM), confirming that in addition to Pickering stabilization, the GCPs-based network and/or dispersed droplets-based network also contributed to the stabilization of the emulsions, in a pH-dependent manner. Clear correlations exist between colloid properties of the GCPs dispersions and the emulsion characteristics. Interestingly, stable surfactant-free Pickering HIPEs were fabricated by a facile shearing emulsification. This study opens a promising route based on Pickering HIPEs to transform liquid oils into viscoelastic emulsion gels with zero trans-fat and less saturated fat. The Pickering HIPEs possess promising potentials to replace solid fat in food formulations, which outline new directions for future fundamental research.
Display omitted
•Food-grade Pickering HIPEs were made for the first time by protein-based colloid particles.•This study opens a promising route via Pickering HIPEs to structure liquid oils into solid-like fats.•Stable GCPEs were formed by the particles with ζ –potential of a few mV.•Clear correlations exist between the colloid properties of the GCPs and the emulsion characteristics.•A possible formation route of GCPEs is proposed to establish the structure-function relationship.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The fractional Fourier transform (FRFT) is a potent tool to analyze the chirp signal. However, it fails in locating the fractional Fourier domain (FRFD)-frequency contents which is required in some ...applications. The short-time fractional Fourier transform (STFRFT) is proposed to solve this problem. It displays the time and FRFD-frequency information jointly in the short-time fractional Fourier domain (STFRFD). Two aspects of its performance are considered: the 2-D resolution and the STFRFD support. The time-FRFD-bandwidth product (TFBP) is defined to measure the resolvable area and the STFRFD support. The optimal STFRFT is obtained with the criteria that maximize the 2-D resolution and minimize the STFRFD support. Its inverse transform, properties and computational complexity are presented. Two applications are discussed: the estimations of the time-of-arrival (TOA) and pulsewidth (PW) of chirp signals, and the STFRFD filtering. Simulations verify the validity of the proposed algorithms.
Aluminum (Al) toxicity is the main limiting factor of crop growth in acid soil. Plants can resist Al toxicity by regulating a series of mechanisms. Many physiological functions have been developed to ...improve the Al tolerance in plants which can be briefly outlined as two mechanisms. One such well-documented mechanism is external exclusion, which mainly reduces Al entry into cells, and the other one is the internal detoxification, consisting of the antioxidant defense system, the redistribution of Al
3+
such as vacuolar compartmentalization, and the response of auxin. In external exclusion mechanism, with special emphasis on the mechanism of Al-induced organic acid secretion from roots, the current understanding of genes regulating organic acid secretion has been reviewed. In terms of the internal detoxification mechanism, we generalized the deposition and redistribution of Al in the cytoplasm, particularly, summarized the genes encoding Al
3+
absorption and transport, and also discussed other possible mechanisms for improving plant tolerance to Al. Therefore, this review describes the recent research progress of Al tolerance mechanisms in plants, and provide future perspectives regarding more practical approaches for Al toxicity alleviation, which can create important social benefits and huge economic value for screening Al-tolerant plants and developing crop breeding.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Melamine foam (MF) is a widely used commercial product and exhibits wide applications in many fields ranging from building, transportation to daily chemical product. Recent researches confirm that ...the special three-dimensional (3D) framework structure of MF can be an ideal substrate to prepare functional materials. In this work, the water-soluble polyethylenimine (PEI) was grafted onto the framework of MF to develop the water purification material toward heavy metal ions removal. The grafting of PEI on MF was achieved with the aids of polydopamine (PDA) coating and epoxy chloropropane (ECH) cross-linking successively. The 3D framework of MF could be well reserved and PEI was homogeneously grafted onto the framework surface. The adsorption capacity of the adsorbent was dependent upon the molecular wight of PEI. Lower PEI molecular weight endowed the adsorbent with better adsorption ability. The maximum adsorption capacity reached 328.95 mg/g, and the adsorbent exhibited extremely high adsorption stability with increasing cycling measurement numbers. Further results showed that the adsorbent also exhibited high reduction ability and induced about 62.5% toxic Cr(VI) to be reduced. This work confirms that the PEI-modified MF sample is a promising adsorbent in the removal of heavy metal ions and it can be used in wastewater treatment.
Display omitted
•Melamine foam (MF) was successfully modified by grafting polyethylenimine (PEI).•The three-dimensional framework of MF was well reserved.•The dependence of adsorption capacity on PEI molecular weight was investigated.•The adsorbent exhibited excellent adsorption capacity toward Cr(VI).•Extremely high adsorption stability was achieved for the new adsorbent.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Information thermodynamics has developed rapidly over past years, and the trapped ions, as a controllable quantum system, have demonstrated feasibility to experimentally verify the theoretical ...predictions in the information thermodynamics. Here, we address some representative theories of information thermodynamics, such as the quantum Landauer principle, information equality based on the two-point measurement, information-theoretical bound of irreversibility, and speed limit restrained by the entropy production of system, and review their experimental demonstration in the trapped ion system. In these schemes, the typical physical processes, such as the entropy flow, energy transfer, and information flow, build the connection between thermodynamic processes and information variation. We then elucidate the concrete quantum control strategies to simulate these processes by using quantum operators and the decay paths in the trapped-ion system. Based on them, some significantly dynamical processes in the trapped ion system to realize the newly proposed information-thermodynamic models is reviewed. Although only some latest experimental results of information thermodynamics with a single trapped-ion quantum system are reviewed here, we expect to find more exploration in the future with more ions involved in the experimental systems.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Plasmon induced water splitting is a promising research area with the potential for efficient conversion of solar to chemical energy, yet its atomic mechanism is not well understood. Here, ultrafast ...electron–nuclear dynamics of water splitting on gold nanoparticles upon exposure to femtosecond laser pulses was directly simulated using real time time-dependent density functional theory (TDDFT). Strong correlation between laser intensity, hot electron transfer, and reaction rates has been identified. The rate of water splitting is dependent not only on respective optical absorption strength, but also on the quantum oscillation mode of plasmonic excitation. Odd modes are more efficient than even modes, owing to faster decaying into hot electrons whose energy matches well the antibonding orbital of water. This finding suggests photocatalytic activity can be manipulated by adjusting the energy level of plasmon-induced hot carriers, through altering the cluster size and laser parameter, to better overlap adsorbate unoccupied level in plasmon-assisted photochemistry.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
PDF
