Abstract
Tuning metal–support interaction has been considered as an effective approach to modulate the electronic structure and catalytic activity of supported metal catalysts. At the atomic level, ...the understanding of the structure–activity relationship still remains obscure in heterogeneous catalysis, such as the conversion of water (alkaline) or hydronium ions (acid) to hydrogen (hydrogen evolution reaction, HER). Here, we reveal that the fine control over the oxidation states of single-atom Pt catalysts through electronic metal–support interaction significantly modulates the catalytic activities in either acidic or alkaline HER. Combined with detailed spectroscopic and electrochemical characterizations, the structure–activity relationship is established by correlating the acidic/alkaline HER activity with the average oxidation state of single-atom Pt and the Pt–H/Pt–OH interaction. This study sheds light on the atomic-level mechanistic understanding of acidic and alkaline HER, and further provides guidelines for the rational design of high-performance single-atom catalysts.
Chiral perovskites have emerged as a significant class of materials showing promising optoelectronic and spintronic applications. Reports of chiral perovskite ferroelectrics, however, have been ...scarce. In this work, we have successfully synthesized homochiral lead–iodide perovskite ferroelectrics (R)‐N‐(1‐phenylethyl)ethane‐1,2‐diaminiumPbI4 and (S)‐N‐(1‐phenylethyl)ethane‐1,2‐diaminiumPbI4 by introducing a methyl group into the organic cation of the parent (N‐benzylethane‐1,2‐diaminium)PbI4. Vibrational circular dichroism spectra identify the chiral mirroring relationship. They both undergo 222F2‐type paraelectric–ferroelectric behavior at around 378 K coupled with clear ferroelastic domain “ON/OFF” switching. Besides, they exhibit an evident thermochromism with color change from orange–yellow to orange–red. To our knowledge, the discovery of integrated ferroelectricity, ferroelasticity, and reversible thermochromism in chiral perovskites is unprecedented.
2D homochiral lead‐iodide perovskites were constructed by the introduction of a chiral center. The perovskites exhibit coexisting ferroelectricity, ferroelasticity, and reversible thermochromism, offering great application prospects for next‐generation smart devices.
Purpose
Prior studies on brand relationships tend to overlook the mediator(s) between the relationships between brand experience and brand loyalty. Hence, the main purpose of this paper is to examine ...these mediating roles of brand love and brand trust on the brand experience and brand loyalty relationships. While the literature does not examine the distinct dimensions of brand experience and brand loyalty, this study fills up this gap and examines their detailed dimensions and effects on brand loyalty.
Design/methodology/approach
A total of 237 valid questionnaires on mobile phone brands were collected from respondents aged between 18 and 30, and analyzed using the partial least squares method.
Findings
Sensory experience is the major driver of brand love. Sensory experience mainly drives customers’ brand trust, while intellectual experience has no effects on brand trust. Brand love is the main mechanism in developing customers’ behavioral loyalty, so does brand trust in shaping their attitudinal loyalty. Brand love and brand trust have the mediating effects on the relationships between brand experience and brand loyalty.
Originality/value
It demonstrates two mediating roles of brand love and brand trust in the brand experience and brand loyalty relationships, and thus deepens the understanding of the processes in shaping customers’ brand loyalty. It departs from the prior works and examines the distinct dimensions of brand experience and brand loyalty, and thus presents a more detailed examination on these two constructs and their effects, than prior studies. It demonstrates the validities of the brand resonance model, the C-A-B and A-C-B models, key mediating variable model, particularly in mobile phone industry.
A very challenging task in ionospheric studies is to determine the separate contributions of penetration and disturbance dynamo processes in the generation of equatorial plasma drift during magnetic ...storms. In this study, we analyze the ion drift measured by the Communications/Navigation Outage Forecasting System satellite during the magnetic storm on 15–16 July 2012. A unique feature of this storm is the exceptionally long period of continuous southward interplanetary magnetic field (IMF) for 32 hr. The storm‐induced net change of the meridional/vertical ion drift, the difference drift between the storm time and the quiet time, is derived during the storm main phase and the first 20 hr of the recovery phase with southward IMF. The difference drift during the recovery phase cannot be explained by the disturbance dynamo effect alone. A new method is used to separate the drifts caused by the penetration and disturbance dynamo processes. The penetration drift is represented by an empirical pattern of penetration electric field and depends on the IMF magnitude, and the disturbance dynamo drift is obtained by subtracting the penetration drift from the measured difference drift. The derived disturbance dynamo drift is in good agreement with previous statistical pattern. This is the first effort to identify the separate contributions of the penetration and disturbance dynamo processes to the total drift from observed data. The results have important implications in identifying storm‐time penetration and disturbance dynamo electric fields and their effects on the generation and evolution of plasma bubbles.
Key Points
A new method is proposed to separate the storm‐time penetration and disturbance dynamo electric fields from ion drift measurements
The derived disturbance dynamo drifts in this storm are in reasonable agreement with previous statistical pattern
The combined penetration and dynamo effects provide a good explanation of post‐midnight plasma bubbles during the storm recovery phase
We present the first systematic analysis of global ionospheric disturbance current systems caused by multiple processes of solar and magnetospheric origin, including reorientations of the ...interplanetary magnetic field (IMF), sudden changes in the solar wind dynamic pressure, magnetospheric sawtooth substorms, and ultralow frequency (ULF) waves. Measurements from global magnetometer networks are used to derive the equivalent disturbance currents from the polar cap to the equator. A surprising result is that the equivalent disturbance current systems are very similar, although the driving processes are completely different. The equivalent disturbance current system in response to IMF reorientation or substorm onset is characterized by a large vortex on the dayside and evening sector and a smaller vortex near dawn, and the polarity of the current vortices depends on the IMF direction. The equivalent disturbance current system caused by a sudden change in the solar wind pressure or by ULF waves consists of a single vortex at middle and low latitudes and a very small vortex above ~60° magnetic latitude near dawn. The similar disturbance current systems caused by different solar wind and magnetospheric processes suggest that the global distribution of the ionospheric currents is determined by the intrinsic property of the ionosphere. The global current system takes only ~1 min to completely reconstruct, indicating that the current system can reach a new steady state within 1 min. A scenario is proposed to explain the global distribution and fast reconstruction of the current systems.
Key Points
Global ionospheric equivalent disturbance current systems caused by multiple processes are derived and systematically analyzed for the first time
A time scale of 1 min for global ionospheric disturbance current system to reconstruct is identified
A scenario is proposed to explain the global distribution and fast reconstruction of the ionospheric current systems
To cope with manganese (Mn) deficiency, plants have evolved an efficient transport system to uptake and redistribute Mn. However, the underlying molecular mechanisms remain to be demonstrated.
We ...carried out a forward genetic screen in a root high-affinity Mn transporter nramp1 mutant background in Arabidopsis thaliana and identified an uncharacterized Mn transport NRAMP2. We investigated the effect of nramp2 mutation on root growth and reactive oxygen species (ROS) accumulation and we also examined the NRAMP2 expression pattern, and the subcellular localization and transport activity of NRAMP2.
Mutation of NRAMP2 impaired plant growth, while overexpression of NRAMP2 improved plant growth under low Mn conditions. In the nramp2-1nramp1 double mutant, Mn deficiency inhibited root cell elongation and root hair development, which was associated with increased hydrogen peroxide (H2O2) accumulation. NRAMP2 is preferentially localized to the trans-Golgi network. NRAMP2 has Mn influx transport activity in yeast, and mutation of NRAMP2 led to greater Mn retention in roots.
Our results suggest that under Mn-deficient conditions, increased accumulation of H2O2 is partially responsible for the root growth inhibition and NRAMP2 is involved in remobilization of Mn in Golgi for root growth.
Penetration electric fields and disturbance dynamo electric fields are the two major disturbance electric fields in the equatorial ionosphere during geomagnetic storms. In this study, we analyze ...equatorial ion drifts measured by radar and satellites during the geomagnetic storm on November 7–11, 2004. The magnetic storm had two main phases, with minimum Dst values of −373 and −289 nT, respectively. The equatorial vertical ion drifts in the dusk‐evening sector were continuously enhanced in the upward direction for 13 h on November 7–8, including 7 h of the first main phase and 6 h of the early stage of the recovery phase. On November 10, the equatorial vertical ion drifts were continuously enhanced in the upward direction for ∼10 h, including ∼9 h of the second main phase and ∼1.5 h of the early stage of the recovery phase. Enhanced thermospheric nitric oxide 5.3 μm emission and westward disturbance winds were measured in the equatorial region during the two main phases of the magnetic storm, indicating occurrence of disturbance dynamo electric fields. The observations show that penetration electric fields are the dominant electric fields in the equatorial ionosphere for 13 and 10 h with continuous southward IMF even if disturbance winds already occur. Very large westward ion drifts are generated in the dusk‐evening equatorial region during the magnetic storm. It is suggested that the westward drifts are caused by penetration of electric fields associated with subauroral polarization streams.
Key Points
Equatorial ion drifts, neutral winds, and thermospheric nitric oxide emission are measured simultaneously with multiple satellites
Relative importance of penetration and disturbance dynamo electric fields is identified from ion drift and neutral wind data
Dominance of penetration electric fields over dynamo electric fields in the equatorial ionosphere for 10–13 h is verified
Penetration electric fields during geomagnetic storms have important effects on the equatorial ionospheric electrodynamics. Previous studies focus on the vertical ion drifts, corresponding to ...electric fields in the zonal direction, in the equatorial ionosphere. In this study, we analyze the characteristics of the zonal ion drifts in the equatorial region measured by the Defense Meteorological Satellite Program (DMSP) satellites during 10 severe magnetic storms with a minimum Dst < −200 nT in the solar maximum years of 2000–2003. It is found that the net change of the equatorial zonal ion drifts caused by magnetic storms is westward and can reach 200–300 m s−1 in the evening sector and that the westward ion drifts remain in the same direction during both the storm main and recovery phases. The storm‐induced zonal ion drifts are highly correlated with the Dst index, and the correlation coefficient between the average zonal drift and the average Dst value during the 10 storms is 0.89. The magnitude of the storm‐induced westward ion drifts is approximately linearly proportional to the Dst index in the evening sector, and on average, a change of −100 nT in Dst causes a change of −52 m s−1 in the zonal drift. The westward ion drifts caused by magnetic storms become small when Dst recovers to the range of −55 to −123 nT. A new mechanism is proposed to explain the generation of the westward plasma drifts in the nighttime equatorial ionosphere. This new mechanism is that the poleward electric fields associated with the subauroral polarization stream (SAPS) penetrate or extend to low latitudes, producing the westward plasma drifts in the equatorial region. The results of this study provide new insight into equatorial ionospheric electrodynamics during geomagnetic storms.
Key Points
Zonal plasma drifts in the nighttime equatorial ionosphere during 10 severe magnetic storms are analyzed systematically
High correlation between the Dst index and the storm time zonal plasma drift in the nighttime equatorial ionosphere is identified
A new mechanism is proposed to explain the generation of equatorial westward plasma drifts during magnetic storms
Recent application of immunotherapy in clinical oncology revolutionized our management of advanced human cancers. Check point inhibitors targeting CTLA4 and PD-1/PD-L1 axis are immunotherapeutic ...agents currently available to treat a variety of cancers. However, a novel therapeutic approach is needed to further improve patient outcome with these agents. Indoleamine 2,3-dioxygenase 1 (IDO1) is a rate-limiting enzyme in the metabolism of essential amino acid tryptophan in the peripheral tissue. IDO1 is overexpressed in human cancer cells and suppresses effector T cell function and promotes regulatory T cells (Tregs). Overexpression of IDO1 is associated with poor patient survival in several types of human cancer. These findings indicate that IDO1 is a promising target that can improve the treatment outcome in the field of Immuno-oncology. Several orally available IDO1 inhibitors including Epacadostat have entered human clinical trials over the last few years without a major safety concern. Although there is no objective response in single-agent trials, combination regimens with PD-1 inhibitors appear to exceed the activity of PD-1 inhibitors alone. Recent phase III ECHO 301 trial testing the combination of Epacadostat with Pembrolizumab in melanoma did not show superior outcome compared to Pembrolizumab alone. This lead to halting of other phase III trials using IDO1 inhibitors. In this minireview, we will discuss the recent clinical development of Epacadostat and other IDO1 inhibitors.
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