The importance of singlet oxygen (
O
) in the environmental and biomedical fields has motivated research for effective
O
production. Electrocatalytic processes hold great potential for ...highly-automated and scalable
O
synthesis, but they are energy- and chemical-intensive. Herein, we present a Janus electrocatalytic membrane realizing ultra-efficient
O
production (6.9 mmol per m
of permeate) and very low energy consumption (13.3 Wh per m
of permeate) via a fast, flow-through electro-filtration process without the addition of chemical precursors. We confirm that a superoxide-mediated chain reaction, initiated by electrocatalytic oxygen reduction on the cathodic membrane side and subsequently terminated by H
O
oxidation on the anodic membrane side, is crucial for
O
generation. We further demonstrate that the high
O
production efficiency is mainly attributable to the enhanced mass and charge transfer imparted by nano- and micro-confinement effects within the porous membrane structure. Our findings highlight a new electro-filtration strategy and an innovative reactive membrane design for synthesizing
O
for a broad range of potential applications including environmental remediation.
Members of the diverse superfamily of AAA+ proteins are molecular machines responsible for a wide range of essential cellular processes. In this review we summarise structural and functional data ...surrounding the nucleotide binding pocket of these versatile complexes. Protein Data Bank (PDB) structures of closely related AAA+ ATPase are overlaid and biologically relevant motifs are displayed. Interactions between protomers are illustrated on the basis of oligomeric structures of each AAA+ subgroup. The possible role of conserved motifs in the nucleotide binding pocket is assessed with regard to ATP binding and hydrolysis, oligomerisation and inter-subunit communication. Our comparison indicates that in particular the roles of the arginine finger and sensor 2 residues differ subtly between AAA+ subgroups, potentially providing a means for functional diversification. This article is part of a Special Issue entitled: AAA ATPases: structure and function.
► We provide an overview of the current classification of AAA+ proteins. ► The characteristic features of the AAA+ nucleotide binding pocket are presented. ► We assemble biochemical data summarising the effects of site directed mutations in the nucleotide binding pocket. ► We assess the structural conservation of AAA+ domains and their nucleotide binding pockets. ► PDB structures of oligomeric AAA+ proteins are examined regarding protomer interactions at the nucleotide binding pocket.
Abstract
The viscosity and its temperature dependence, the fragility, are key properties of a liquid. A low fragility is believed to promote the formation of metallic glasses. Yet, the fragility ...remains poorly understood, since experimental data of its compositional dependence are scarce. Here, we introduce the film inflation method (FIM), which measures the fragility of metallic glass forming liquids across wide ranges of composition and glass-forming ability. We determine the fragility for 170 alloys ranging over 25 at.% in Mg–Cu–Y. Within this alloy system, large fragility variations are observed. Contrary to the general understanding, a low fragility does not correlate with high glass-forming ability here. We introduce crystallization complexity as an additional contribution, which can potentially become significant when modeling glass forming ability over many orders of magnitude.
High Entropy Alloys are inherently complex and span a vast composition space, making their research and discovery challenging. Developing quantitative predictions of their phase selection requires a ...large quantity of consistently determined experimental data. Here, we use combinatorial methods to fabricate and characterize 2478 quinary alloys based on Al and transition metals. All data are publicly available at http://materialsatlasproject.org/. Phase selection can be predicted for considered alloys when combining the content of FCC/BCC elements and the constituents’ atomic size difference. Mining our data reveals that High Entropy Alloys with increasing atomic size difference prefer BCC structure over FCC. This preference is typically overshadowed by other selection motifs, which dominate during close-to-equilibrium processing. Not suggested by the Hume-Rothery rules, this preference originates from the ability of the BCC structure to accommodate a large atomic size difference with lower strain energy penalty which can be practically only realized in High Entropy Alloys.
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Employment contracts are often incomplete, leaving many responsibilities subject to workers' discretion. High work morale is therefore essential for sustaining voluntary cooperation and high ...productivity in firms. We conducted a field experiment to test whether workers reciprocate wage cuts and raises with low or high work productivity. Wage cuts had a detrimental and persistent impact on productivity, reducing average output by more than 20%. An equivalent wage increase, however, did not result in any productivity gains. The results from an additional control experiment with high monetary performance incentives demonstrate that workers could still produce substantially more output, leaving enough room for positive reactions. Altogether, these results provide evidence consistent with a model of reciprocity, as opposed to inequality aversion.
Abstract
The underlying atomistic mechanism of deformation is a central problem in mechanics and materials science. Whereas deformation of crystalline metals is fundamentally understood, the ...understanding of deformation of amorphous metals lacks behind, particularly identifying the involved temporal and spatial scales. Here, we reveal that at small scales the size-dependent deformation behavior of amorphous metals significantly deviates from homogeneous flow, exhibiting increasing deformation rate with reducing size and gradually shifted composition. This transition suggests the deformation mechanism changes from collective atomic transport by viscous flow to individual atomic transport through interface diffusion. The critical length scale of the transition is temperature dependent, exhibiting a maximum at the glass transition. While viscous flow does not discriminate among alloy constituents, diffusion does and the constituent element with higher diffusivity deforms faster. Our findings yield insights into nano-mechanics and glass physics and may suggest alternative processing methods to epitaxially grow metallic glasses.
In disordered mesopore networks, the size distribution and connection between adjacent pores control desorption. How network characteristics can be extracted from corresponding physisorption ...isotherms is still a matter of research. To elucidate this, we study krypton physisorption (117.8 K) in the mesopore networks of “Nakanishi”-type monolithic silica. Combining physisorption in scanning acquisition mode with synchrotron-based in-situ SAXS provides complementary information on pore-filling states. These data reveal a mean pore size gradient in which pores grow smaller towards the material’s network center. This structural motif cannot be derived through conventional isotherm analysis, but it is clearly exposed through scanning desorption curves which do not quite converge but merge individually with the main desorption isotherm before the lower hysteresis closing point. Hence, our findings provide the basis to build advanced models for analyzing scanning isotherms and extracting network characteristics through new descriptors, such as pore size and connectivity distributions as a function of the distance from the network center.
The glass forming ability (GFA) of metallic glasses (MGs) is quantified by the critical cooling rate (R
). Despite its key role in MG research, experimental challenges have limited measured R
to a ...minute fraction of known glass formers. We present a combinatorial approach to directly measure R
for large compositional ranges. This is realized through the use of compositionally-graded alloy libraries, which were photo-thermally heated by scanning laser spike annealing of an absorbing layer, then melted and cooled at various rates. Coupled with X-ray diffraction mapping, GFA is determined from direct R
measurements. We exemplify this technique for the Au-Cu-Si system, where we identify Au
Cu
Si
as the alloy with the highest GFA. In general, this method enables measurements of R
over large compositional areas, which is powerful for materials discovery and, when correlating with chemistry and other properties, for a deeper understanding of MG formation.
Traditionally, the virtue of democratic elections has been seen in their role as means of screening and sanctioning shirking public officials. This article proposes a novel rationale for elections ...and political campaigns considering that candidates incur psychological costs of lying, in particular from breaking campaign promises. These nonpecuniary costs imply that campaigns influence subsequent behavior, even in the absence of reputational or image concerns. Our lab experiments reveal that promises are more than cheap talk. They influence the behavior of both voters and their representatives. We observe that the electorate is better off when their leaders are elected democratically rather than being appointed exogenously—but only in the presence of electoral campaigns. In addition, we find that representatives are more likely to serve the public interest when their approval rates are high. Altogether, our results suggest that elections and campaigns confer important benefits beyond their screening and sanctioning functions.
The microstructure and temperature dependence of linear thermal expansion and elastic properties of a two-phase, A2 + B2, Al
10
Nb
20
Ta
15
Ti
30
V
5
Zr
20
refractory superalloy (RSA) and its ...constituent phases are reported. After slow cooling from 1400 °C, this alloy has a nanometer-sized, two-phase microstructure consisting of Nb-rich BCC (A2 crystal structure) cuboidal precipitates at the volume fraction of 0.63 and continuous channels of a Zr-rich ordered B2 matrix phase. This two-phase microstructure forms by spinodal decomposition of a high-temperature BCC phase. Differential scanning calorimetry shows that the order–disorder transformation in the Zr-rich phase occurs in the temperature range of 550 °C to 850 °C. The coefficient of thermal expansion (CTE) of the Nb-rich BCC phase increases slightly from 8.9 × 10
−6
to 9.1 × 10
−6
K
−1
with increasing temperature from 20 °C to 1200 °C. The Zr-rich phase has CTE of 9.1 × 10
−6
K
−1
in the ordered (B2) state, at 20 °C to 550 °C, and 12.2 × 10
−6
K
−1
in the disordered (A2) state, at 900 °C to 1200 °C. The Nb-rich phase has higher Young’s and shear moduli, but lower bulk modulus and Poisson’s ratio, as compared to the Zr-rich phase, at 20 °C to 600 °C. The CTE and elastic properties of the two-phase RSA approximately follow the rule of mixtures of the constituent phases in the studied temperature ranges. Correlations between the morphology of the spinodally decomposed microstructure in the two-phase RSA and the thermal and elastic properties of the constituent A2 and B2 phases are established.
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