Active planar optical devices that can dynamically manipulate light are highly sought after in modern optics and nanophotonics. The geometric phase derived from the photonic spin-orbit interaction ...provides an integrated strategy. Corresponding elements usually suffer from static functions. Here, we introduce an inhomogeneously self-organized anisotropic medium featured by photo-invertible chiral superstructure to realize geometric phase elements with continuously tunable working spectrum and light-flipped phase profile. Via preprograming the alignment of a cholesteric liquid crystal mixed with a photo-responsive chiral dopant, we demonstrate light-activated deflector, lens, Airy beam and optical vortex generators. Their polychromatic working bands are reversibly tuned in an ultra-broadband over 1000 nm covering green to telecomm region. The chirality inversion triggers facile switching of functionalities, such as beam steering, focusing/defocusing and spin-to-orbital angular momentum conversion. This work offers a platform for advanced adaptive and multifunctional flat optics with merits of high compactness, low loss and broad bandwidth.
Cholesteric liquid crystal (CLC) chiral superstructures exhibit unique features; that is, polychromatic and spin‐determined phase modulation. Here, a concept for digitalized chiral superstructures is ...proposed, which further enables the arbitrary manipulation of reflective geometric phase and may significantly upgrade existing optical apparatus. By encoding a specifically designed binary pattern, an innovative CLC optical vortex (OV) processor is demonstrated. Up to 25 different OVs are extracted with equal efficiency over a wavelength range of 116 nm. The multiplexed OVs can be detected simultaneously without mode crosstalk or distortion, permitting a polychromatic, large‐capacity, and in situ method for parallel OV processing. Such complex but easily fabricated self‐assembled chiral superstructures exhibit versatile functionalities, and provide a satisfactory platform for OV manipulation and other cutting‐edge territories. This work is a vital step towards extending the fundamental understanding and fantastic applications of ordered soft matter.
Digitalized chiral superstructures enable the generation, detection, and demultiplexing of optical vortices in a polychromatic, large‐capacity, and in situ way. Such complex but easily fabricated self‐assembled cholesteric liquid‐crystal superstructures provide a versatile platform for various cutting‐edge territories. This work brings new insights to both fundamental understanding and innovative applications of ordered soft matter.
The Van Allen Probes mission contributed to the discovery of the relativistic (∼500 keV–2 MeV) and ultra‐relativistic (∼>2 MeV) electron three‐belt structure in Earth's radiation belts. This ...structure results from the partial depletion of the preexisting outer belt and the replenishment of a new outer belt. Ultra‐low frequency and very‐low frequency waves are believed to play important roles in these processes, and substorm injections are usually not responsible for the formation of the external outer belt. In this study, based on observations from the Arase and NOAA‐18 (National Oceanic and Atmospheric Administration‐18) satellites, we report an electron three‐belt event in the energy range of ∼100–200 keV (i.e., sub‐relativistic electrons). According to the evolution of the phase space density and the dawn‐dusk asymmetric flux enhancement during this event, we conclude that the depletion of the upper part of the original outer belt was due to outward radial diffusion accompanied by magnetopause shadowing effect and convection, and the formation of the external outer belt was due to increased electron flux from convection as well as substorm injections. This discovery and its preliminary explanation may help understand the electron three‐belt structure in radiation belts more comprehensively.
Key Points
We reported a sub‐relativistic electron three‐belt event that occurred in October 2020
Electrons from injections and convection after the partial loss of the outer belt contributed to the formation of the external outer belt
The flux enhancement event during the geomagnetic storm on 24 October destroyed the sub‐relativistic electron three‐belt structure
Interplanetary (IP) shocks can trigger substorms when they interact the magnetosphere. In study of Hajra and Tsurutani (2018, https://doi.org/10.1016/0032-0633(77)90001-0), they reported a ...shock‐induced substorm event where the energy dissipation exceeded the energy input (ε $\varepsilon $ parameter). In this study, we examined 198 IP shock‐induced substorms from 1995 to 2021 and found 32 underpowered events where the energy dissipation exceeded the energy input calculated from IP shock sheath parameters. We also found underpowered events using other newly developed energy functions. To resolve this dilemma, we introduce the concept of dual compressions of the interplanetary magnetic field by both the IP shock and the bow shock, respectively. Based on in situ observations in the magnetosheath, we obtained a set of new parameters from the dual compressions. The stronger magnetic field resulting from the double compressions reconnects the geomagnetic field, leading to an increased input of energy into the magnetosphere. This new energy input is generally sufficient to balance the energy dissipation.
Plain Language Summary
The magnetosphere is the region controlled by the geomagnetic field. The ε $\varepsilon $ parameter estimates the magnetosphere energy input by considering the Poynting flux in the solar wind. In some cases, however, the energy dissipation exceeds the energy input calculated from solar wind parameters. Considering that the solar wind slows down to form a bow shock when it interacts the Earth's magnetosphere with the solar wind kinetic energy converted into magnetic energy, it is more appropriate to consider the Poynting flux in the magnetosheath. Therefore, we suggest that the ε $\varepsilon $ parameter should be calculated in the magnetosheath. By taking the values of the magnetic field and velocity in the magnetosheath after dual compressions by IP shock and Bow shock for IP shock‐induced substorm events, we obtain larger energy input compared with the ε $\varepsilon $ parameter. The new energy input is generally sufficient to balance the energy dissipation.
Key Points
The energy dissipation during some IP shock‐induced substorms exceeded the energy input by using various energy coupling functions
The dilemma can be solved by the dual compressions of interplanetary magnetic field by IP shock and bow shock, which result in more energy input
A set of new parameters based on the dual compressions are obtained, the new energy input is large enough to provide sufficient energy input
The first example of luminescent monosubstituted polyacetylenes (mono‐PAs) is presented, based on a contracted cis‐cisoid polyene backbone. It has an excellent circularly polarized luminescence (CPL) ...performance with a high dissymmetric factor (up to the order of 10−1). The luminescence stems from the helical cis‐cisoid PA backbone, which is tightly fixed by the strong intramolecular hydrogen bonds, thereby reversing the energy order of excited states and enabling an emissive energy dissipation. CPL switches are facilely achieved by the solvent and temperature through reversible conformational transition. By taking advantages of fast response and high sensitivity, the thin film of mono‐PAs could be used as a CPL‐based probe for quantitative detection of trifluoroacetic acid with a wider linear dynamic range than those of photoluminescence and circular dichroism. This work opens a new avenue to develop novel smart CPL materials through modulating conformational transition.
A strategy is described that enables the conventionally non‐luminescent monosubstituted polyacetylenes bearing no pendant fluorophore to light up and show a switchable circularly polarized luminescence (CPL) with a large dissymmetric factor (glum, 10−1), multiple reversible stimuli‐responsiveness, and quantitative detection by conformational transition of polyene backbone.
Two transition metal complexes {Co
2
(bpda)
4
(H
2
O)
2
·4H
2
O}
n
(Co-
1
) and {Ni(bpda)
2
(H
2
O)
2
·2H
2
O}(Ni-
2
) (H
2
bpda = 2,2′-bipyridine-4,4′-dicarboxylic acid) have been synthesized by a ...hydrothermal method and characterized. These two compounds can be explored as stable electrocatalysts in the hydrogen evolution reaction (HER) using two important parameters: the overpotential and Tafel slope (TS). Electrochemical studies suggest that the reaction kinetics of a Co-
1
catalyst is more favorable than that of a Ni-
2
catalyst. Co-
1
exhibits better HER performance with an overpotential of 182 mV at a current density of 10 mA cm
−2
, a small TS of 87.21 mV dec
−1
and superior long-term durability (of up to 3000 cycles). Structural analysis shows that its catalytic activity is improved due to the two mixed valence cobalt ions and the pore structure formed by hydrogen bonds in Co-
1
, which is different from that of Ni-
2
. In addition, the mechanism of the HER is also explained theoretically by DFT molecular orbital and free energy calculations in this article.
Co-
1
exhibits a three-dimensional pore structure through hydrogen bonding and π-conjugation, providing a platform for efficient charge carrier mobility and the hydrogen evolution reaction.
Startle, a basic alerting reaction common to all mammals, is described as a sudden involuntary movement of the body evoked by all kinds of sudden and unexpected stimulus. Startle syndromes are ...heterogeneous groups of disorders with abnormal and exaggerated responses to startling events, including hyperekplexia, stimulus-induced disorders, and neuropsychiatric startle syndromes. Hyperekplexia can be attributed to a genetic, idiopathic, or symptomatic cause. Excluding secondary factors, hereditary hyperekplexia, a rare neurogenetic disorder with highly genetic heterogeneity, is characterized by neonatal hypertonia, exaggerated startle response provoked by the sudden external stimuli, and followed by a short period of general stiffness. It mainly arises from defects of inhibitory glycinergic neurotransmission.
GLRA1
is the major pathogenic gene of hereditary hyperekplexia, along with many other genes involved in the function of glycinergic inhibitory synapses. While about 40% of patients remain negative genetic findings. Clonazepam, which can specifically upgrade the GABARA1 chloride channels, is the main and most effective administration for hereditary hyperekplexia patients. In this review, with the aim at enhancing the recognition and prompting potential treatment for hyperekplexia, we focused on discussing the advances in hereditary hyperekplexia genetics and the expound progress in pathogenic mechanisms of the glycinergic-synapse-related pathway and then followed by a brief overview of other common startle syndromes.
Earth-abundant nickel hydroxide (Ni(OH)2)-based cocatalysts, by virtue of its bargain price, simple synthesis and diverse structure, have attracted increasing research interest in the field of ...solar-to-fuels conversion. Herein, we intend to afford a concise review on the recent progress regarding the promising applications of nickel hydroxide-based cocatalyst for photocatalytic H2 production and CO2 reduction. In particular, the roles of nickel hydroxide-based cocatalysts for promoting photocatalytic activities are systematically discussed. Furthermore, the future prospects and current challenges on constructing high-performance Ni(OH)2-based cocatalysts are proposed, which are expected to stimulate ongoing studies to unlock the potential of Ni(OH)2-based cocatalysts in various photocatalytic application.
Display omitted
•Applications of Ni(OH)2-based cocatalysts in photocatalysis are summarized. (68 characters).•Roles of Ni(OH)2-based cocatalysts for promoting photocatalytic activities are discussed. (80 characters).•Current challenges on constructing high-performance Ni(OH)2-based cocatalyst are proposed. (82 characters).•Future feasible opportunities about the Ni(OH)2-based cocatalysts are presented. (72 characters).
Highly sensitive, wearable and durable strain sensors are vital to the development of health monitoring systems, smart robots and human machine interfaces. The recent sensor fabrication progress is ...respectable, but it is limited by complexity, low sensitivity and unideal service life. Herein a facile, cost‐effective and scalable method is presented for the development of high‐performance strain sensors and stretchable conductors based on a composite film consisting of graphene platelets (GnPs) and silicon rubber. Through calculation by the tunneling theory using experimental data, the composite film has demonstrated ideal linear and reproducible sensitivity to tensile strains, which is contributed by the superior piezoresistivity of GnPs having tunable gauge factors 27.7–164.5. The composite sensors fabricated in different days demonstrate pretty similar performance, enabling applications as a health‐monitoring device to detect various human motions from finger bending to pulse. They can be used as electronic skin, a vibration sensor and a human‐machine interface controller. Stretchable conductors are made by coating and encapsulating GnPs with polydimethyl siloxane to create another composite; this structure allows the conductor to be readily bent and stretched with sufficient mechanical robustness and cyclability.
Sensors and conductors are fabricated from developed graphene/elastomer composites. Demonstrating response time below 50 ms, high cycling durability and a gauge factor of over 100, the sensors work well as a health‐monitoring device, sound signal collector and human‐machine interface detector. The conductors can be readily bent and stretched with exceptional mechanical robustness and cyclability.
PDF
