The anode oxygen evolution reaction (OER) is known to largely limit the efficiency of electrolyzers owing to its sluggish kinetics. While crystalline metal oxides are promising as OER catalysts, ...their amorphous phases also show high activities. Efforts to produce amorphous metal oxides have progressed slowly, and how an amorphous structure benefits the catalytic performances remains elusive. Now the first scalable synthesis of amorphous NiFeMo oxide (up to 515 g in one batch) is presented with homogeneous elemental distribution via a facile supersaturated co‐precipitation method. In contrast to its crystalline counterpart, amorphous NiFeMo oxide undergoes a faster surface self‐reconstruction process during OER, forming a metal oxy(hydroxide) active layer with rich oxygen vacancies, leading to superior OER activity (280 mV overpotential at 10 mA cm−2 in 0.1 m KOH). This opens up the potential of fast, facile, and scale‐up production of amorphous metal oxides for high‐performance OER catalysts.
Amorphous NiFeMo oxide (up to 515 g one batch) with homogeneous elemental distribution was synthesized through a facile supersaturated co‐precipitation method. The amorphous NiFeMo oxide undergoes rapid surface self‐reconstruction during OER that forms a metal oxy(hydroxide) active layer with oxygen vacancies, enabling efficient OER catalysis.
The efficacy and synthetic versatility of asymmetric organocatalysis have contributed enormously to the field of organic synthesis since the early 2000s. As asymmetric organocatalytic methods mature, ...they have extended beyond the academia and undergone scale-up for the production of chiral drugs, natural products, and enantiomerically enriched bioactive molecules. This review provides a comprehensive overview of the applications of asymmetric organocatalysis in medicinal chemistry. A general picture of asymmetric organocatalytic strategies in medicinal chemistry is firstly presented, and the specific applications of these strategies in pharmaceutical synthesis are systematically described, with a focus on the preparation of antiviral, anticancer, neuroprotective, cardiovascular, antibacterial, and antiparasitic agents, as well as several miscellaneous bioactive agents. The review concludes with a discussion of the challenges, limitations and future prospects for organocatalytic asymmetric synthesis of medicinally valuable compounds.
This review provides a comprehensive overview of the recent applications of organocatalytic strategies in pharmaceutical synthesis, with a focus on the preparation of antiviral, anticancer, neuroprotective, cardiovascular, antibacterial and antiparasitic agents.
Optical characteristics of luminescent materials, including emission color (wavelength), lifetime, and excitation mode, play crucial roles in data communication and information security. Conventional ...luminescent materials generally display unicolor, unitemporal, and unimodal (occasionally bimodal) emission, resulting in low‐level readout and decoding. The development of multicolor, multitemporal, and multimodal luminescence in a single material has long been considered to be a significant challenge. In this study, for the first time, the superior integration of colorful (red–orange–yellow–green), bitemporal (fluorescent and delayed), and four‐modal (thermo‐/mechano‐motivated and upconverted/downshifted) emissions in a particular piezoelectric particle via optical multiplexing of dual‐lanthanide dopants is demonstrated. The as‐prepared versatile NaNbO3:Pr3+,Er3+ luminescent microparticles shown are particularly suitable for embedding into polymer films to achieve waterproof, flexible/wearable and highly stretchable features, and synchronously to provide multidimensional codes that can be visually read‐out using simple and commonly available tools (including the LED of a smartphone, pen writing, cooling–heating stimuli, and ultraviolet/near‐infrared lamps). These findings offer unique insight for designing highly integrated stimuli‐responsive luminophors and smart devices toward a wide variety of applications, particularly advanced anticounterfeiting technology.
Thermo‐mechano‐opto‐responsive bitemporal (fluorescent and delayed) colorful (red–orange–yellow–green) luminescence is designed and achieved through optical multiplexing of dual‐lanthanides of Pr3+ and Er3+ in NaNbO3 piezoelectric microparticles. The smart materials are well‐embedded into polymer elastomers to show waterproof, flexible/wearable and highly‐stretchable features, and provide multidimensional codes that enable visual readout using commonly available tools (e.g., smartphone flashlight, pen writing, and cooling‐heating stimuli).
The combination of photoredox and enzymatic catalysis for the direct asymmetric one‐pot synthesis of 2,2‐disubstituted indol‐3‐ones from 2‐arylindoles through concurrent oxidization and alkylation ...reactions is described. 2‐Arylindoles can be photocatalytically oxidized to 2‐arylindol‐3‐one with subsequent enantioselective alkylation with ketones catalyzed by wheat germ lipase (WGL). The chiral quaternary carbon center at C2 of the indoles was directly constructed. This mode of concurrent photobiocatalysis provides a mild and powerful strategy for one‐pot enantioselective synthesis of complex compounds. The experiments proved that other lipases containing structurally analogous catalytic triad in the active site also can catalyze the reaction in the same way. This reaction is the first example of combining the non‐natural catalytic activity of hydrolases with visible‐light catalysis for enantioselective organic synthesis and it does not require any cofactors.
Look, no cofactors! The combination of photoredox and enzymatic catalysis enables the direct asymmetric one‐pot synthesis of C2‐quaternary indolin‐3‐ones from 2‐arylindoles. This reaction is the first example of combining the non‐natural catalytic activity of hydrolases with visible‐light catalysis for enantioselective organic synthesis, and it does not require any cofactors.
Hydroxide exchange membrane fuel cells offer possibility of adopting platinum-group-metal-free catalysts to negotiate sluggish oxygen reduction reaction. Unfortunately, the ultrafast hydrogen ...oxidation reaction (HOR) on platinum decreases at least two orders of magnitude by switching the electrolytes from acid to base, causing high platinum-group-metal loadings. Here we show that a nickel-molybdenum nanoalloy with tetragonal MoNi
phase can catalyze the HOR efficiently in alkaline electrolytes. The catalyst exhibits a high apparent exchange current density of 3.41 milliamperes per square centimeter and operates very stable, which is 1.4 times higher than that of state-of-the-art Pt/C catalyst. With this catalyst, we further demonstrate the capability to tolerate carbon monoxide poisoning. Marked HOR activity was also observed on similarly designed WNi
catalyst. We attribute this remarkable HOR reactivity to an alloy effect that enables optimum adsorption of hydrogen on nickel and hydroxyl on molybdenum (tungsten), which synergistically promotes the Volmer reaction.
This paper seeks to enhance understanding of the cross-correlation patterns between meteorological factors and pollutants. The observed databases of daily meteorological elements (temperature, ...humidity and wind speed), as well as pollutants (CO, NOx, PM10 and SO2) levels during 2005–2014, is collected. Based on the database, the cross-correlation test is carried out firstly and the results indicate that cross-correlation behaviors exist statistically between them. Then the detrended cross-correlation analysis is performed for further analysis. With a detailed comparison, long-term cross-correlation behaviors are found to be more obvious in rural area. Beside, the influences of meteorological factors on multifractal property for pollutants are investigated. In contrast to humidity and wind speed, the long-term cross-correlation behaviors between temperature with pollutants are found to be more evident in both urban and rural areas. Furthermore, the difference of multifractal property for varied pollutants is explored. The strengths of multifractal spectra between meteorological factors with PM10 are strongest while the corresponding values between meteorological factors with SO2 are weakest. These findings successfully illustrate that the multifractal analysis is a useful tool for uncovering the interactive pattern in environmental issues.
Display omitted
•Verify the existence of multifractal property between meteorological factors and pollutants.•Reveal the difference of multifractal property between urban and rural areas.•Clarify the influence of meteorological factors on cross-correlation behavior.•Compare the difference of multifractal property for varied pollutants.
We construct a minimal viable extension of the standard model (SM) with classical scale symmetry. Its scalar sector contains a complex singlet in addition to the SM Higgs doublet. The scale-invariant ...and CP-symmetric Higgs potential generates radiative electroweak symmetry breaking à la Coleman–Weinberg, and gives a natural solution to the hierarchy problem, free from fine-tuning. Besides the 125 GeV SM-like Higgs particle, it predicts a new CP-even Higgs (serving as the pseudo-Nambu–Goldstone boson of scale symmetry breaking) and a CP-odd scalar singlet (providing the dark matter candidate) at weak scale. We systematically analyze experimental constraints from direct LHC Higgs searches and electroweak precision tests, as well as theoretical bounds from unitarity, triviality and vacuum stability. We demonstrate the viable parameter space, and discuss implications for new Higgs searches at the upcoming LHC runs and the on-going direct detections of dark matter.
A
bstract
We study the mechanism of topological mass-generation for 3d Chern-Simons (CS) gauge theories, where the CS term can retain the gauge symmetry and make gauge boson topologically massive. ...Without CS term the 3d massless gauge boson has a single physical transverse polarization state, while adding the CS term converts it into a massive physical polarization state and conserves the total physical degrees of freedom. We formulate the mechanism of topological mass-generation at
S
-matrix level. For this, we propose and prove a Topological Equivalence Theorem (TET) which connects the
N
-point scattering amplitude of the gauge boson’s physical polarization states (
A
P
a
) to that of the transverse polarization states (
A
T
a
) under high energy expansion. We present a general 3d power counting method on the leading energy dependence of the scattering amplitudes in both topologically massive Yang-Mills (TMYM) and topologically massive gravity (TMG) theories. With these, we uncover
a general energy cancellation mechanism for N -gauge boson scattering amplitudes
which predicts the cancellation
E
4
→ E
4
−N
at tree level. Then, we compute the 4-gauge boson amplitudes of
A
P
a
-states and
A
T
a
-states, with which we explicitly demonstrate the TET and establish such energy cancellations for
N
= 4. We further extend the double-copy approach to reconstruct the massive 4-graviton amplitude of TMG from the massive 4-gauge boson amplitude of TMYM. With these, we uncover
striking large energy cancellations in the 4-graviton amplitude: E
12
→ E
1
, and establish
its correspondence to the leading energy cancellation E
4
→ E
0
in the 4-gauge boson amplitude of TMYM
.
PDF
