Super-luminous supernovae (SLSNe) are tremendously luminous explosions whose power sources and progenitors are highly debated. Broad-lined SNe Ic (SNe Ic-bl) are the only type of SNe that are ...connected with long-duration gamma-ray bursts (GRBs). Studying the spectral similarity and difference between the populations of hydrogen-poor SLSNe (SLSNe Ic) and of hydrogen-poor stripped-envelope core-collapse SNe, in particular SNe Ic and SNe Ic-bl, can provide crucial observations to test predictions of theories based on various power source models and progenitor models. In this paper, we collected all of the published optical spectra of 32 SLSNe Ic, 21 SNe Ic-bl, as well as 17 SNe Ic, quantified their spectral features, constructed average spectra, and compared them in a systematic way using new tools we have developed. We find that SLSNe Ic and SNe Ic-bl, including those connected with GRBs, have comparable widths for their spectral features and average absorption velocities at all phases. Thus, our findings strengthen the connection between SLSNe Ic and GRBs. In particular, SLSNe Ic have average Fe ii λ5169 absorption velocities of −15,000 2600 km s−1 at 10 days after peak, which are higher than those of SNe Ic by ∼7000 km s−1 on average. SLSNe Ic also have significantly broader Fe ii λ5169 lines than SNe Ic. Moreover, we find that such high absorption and width velocities of SLSNe Ic may be hard to explain with the interaction model, and none of the 13 SLSNe Ic with measured absorption velocities spanning over 10 days has a convincing flat velocity evolution, which is inconsistent with the magnetar model in one dimension. Lastly, we compare SN 2011kl, the first SN connected with an ultra-long GRB, with the mean spectrum of SLSNe Ic and of SNe Ic-bl.
In this paper, based on the advantages of q-rung orthopair fuzzy sets (q-ROFSs), complex fuzzy sets (CFSs) and cubic sets (CSs), the concept of complex cubic q-rung orthopair fuzzy sets (CCuq-ROFSs) ...is introduced and their operation rules and properties are discussed. The objective of this paper was to develop some novel Maclaurin symmetric mean (MSM) operators for any complex cubic q-rung orthopair fuzzy numbers (CCuq-ROFNs) using Hamacher t-norm and t-conorm inspired arithmetic operations. The advantage of employing Hamacher t-norm and t-conorm based arithmetic operations with the MSM operator lies in their ability to take into account not only the interrelationships among multiple attributes but also to provide flexibility in the aggregation process due to the involvement of additional parameters. Also, the prominent characteristic of the MSM is that it can capture the interrelationship among the multi-input arguments and can provide more flexible and robust information fusion. Thus, based on the CCuq-ROF environment, we develop some new Hamacher operations for CCuq-ROFSs, such as the complex cubic q-rung orthopair fuzzy Hamacher average (CCuq-ROFHA) operator, the weighted complex cubic q-rung orthopair fuzzy Hamacher average (WCCuq-ROFHA) operator, the complex cubic q-rung orthopair fuzzy Hamacher Maclaurin symmetric mean (CCuq-ROFHMSM) operator and the weighted complex cubic q-rung orthopair fuzzy Hamacher Maclaurin symmetric mean (WCCuq-ROFHMSM) operator. Further, we develop a novel multi-attribute group decision-making (MAGDM) approach based on the proposed operators in a complex cubic q-rung orthopair fuzzy environment. Finally, a numerical example is provided to demonstrate the effectiveness and superiority of the proposed method through a detailed comparison with existing methods.
By performing in situ transmission electron microscope (TEM) experiments and three dimensional dislocation tomography, we report the effect of low angle grain boundary (LAGB) on deformation of a ...titanium material and its size effect. It is found that at large scale the LAGB can either act as dislocation nucleation site or as “tunable” barrier that allows selective transmission of dislocations. As the physical dimension of the sample decreases to submicron scale, LAGB was found to strongly hinder dislocation motion but dissipate energy through migration under high stress, similar to the behavior of high angle grain boundaries at large scale.
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Lithium‐rich layered oxides with the capability to realize extraordinary capacity through anodic redox as well as classical cationic redox have spurred extensive attention. However, the ...oxygen‐involving process inevitably leads to instability of the oxygen framework and ultimately lattice oxygen release from the surface, which incurs capacity decline, voltage fading, and poor kinetics. Herein, it is identified that this predicament can be diminished by constructing a spinel Li4Mn5O12 coating, which is inherently stable in the lattice framework to prevent oxygen release of the lithium‐rich layered oxides at the deep delithiated state. The controlled KMnO4 oxidation strategy ensures uniform and integrated encapsulation of Li4Mn5O12 with structural compatibility to the layered core. With this layer suppressing oxygen release, the related phase transformation and catalytic side reaction that preferentially start from the surface are consequently hindered, as evidenced by detailed structural evolution during Li+ extraction/insertion. The heterostructure cathode exhibits highly competitive energy‐storage properties including capacity retention of 83.1% after 300 cycles at 0.2 C, good voltage stability, and favorable kinetics. These results highlight the essentiality of oxygen framework stability and effectiveness of this spinel Li4Mn5O12 coating strategy in stabilizing the surface of lithium‐rich layered oxides against lattice oxygen escaping for designing high‐performance cathode materials for high‐energy‐density lithium‐ion batteries.
A heterostructured spinel Li4Mn5O12 encapulated lithium‐rich layered oxide cathode is designed by the controlled KMnO4 oxidiation strategy. Spinel Li4Mn5O12 is chosen due to its lattice stability against oxygen release as well as a 3D lithium diffusion framework with minimal Jahn–Teller distortion. Such uniform coating can suppress lattice oxygen release, associated phase transformation, and catalytic side reactions, consequently ensuring improved electrochemical performance.
A new kind of nitrogen‐doped graphene/carbon nanotube nanocomposite can be synthesized by a facile hydrothermal process under mild conditions, which exhibits synergistically enhanced electrochemical ...activity for the oxygen reduction reaction. This research provides a new route to access a metal‐free electrocatalyst with high activity under mild conditions.
Photo‐Induced C−H Methylation Reactions Li, Qian‐Yu; He, Yuhang; Lin, Yu‐Mei ...
Chemistry : a European journal,
December 22, 2023, Volume:
29, Issue:
72
Journal Article
Peer reviewed
Direct C−H methylation is a highly valuable approach for introducing methyl groups into organic molecules, particularly in pharmaceutical chemistry. Among the various methodologies available, ...photo‐induced methylation stands out as an exceptional choice due to its mild reaction conditions, energy efficiency, and compatibility with functional groups. This article offers a comprehensive review of photochemical strategies employed for the direct and selective methylation of C(sp3)−H, C(sp2)−H, and C(sp)−H bonds in various organic molecules. The discussed methodologies encompass transition‐metal‐based photocatalysis, organophotocatalysis, as well as other metal‐free approaches, including electron donor‐acceptor (EDA)‐enabled transformations. Importantly, a wide range of easily accessible agents such as tert‐butyl peroxide, methanol, DMSO, methyl tert‐butyl ether, TsOMe, N‐(acetoxy)phthalimide, acetic acid, methyl halides, and even methane can serve as effective methylating reagents for modifying diverse targets. These advancements in photochemical C−H methylation are anticipated to drive further progress in the fields of organic synthesis, photocatalysis, and pharmaceutical development, opening up exciting avenues for creating novel organic molecules and discovering new drug compounds.
In this review, we present a concise overview of recent breakthroughs in photochemical C−H methylation. These advancements encompass a variety of methodologies, including transition metal‐based photocatalysis, organophotocatalysis, and various metal‐free approaches, such as electron donor‐acceptor ‐enabled processes.
Oxygen‐redox of layer‐structured metal‐oxide cathodes has drawn great attention as an effective approach to break through the bottleneck of their capacity limit. However, reversible oxygen‐redox can ...only be obtained in the high‐voltage region (usually over 3.5 V) in current metal‐oxide cathodes. Here, we realize reversible oxygen‐redox in a wide voltage range of 1.5–4.5 V in a P2‐layered Na0.7Mg0.2Fe0.2Mn0.6□0.2O2 cathode material, where intrinsic vacancies are located in transition‐metal (TM) sites and Mg‐ions are located in Na sites. Mg‐ions in the Na layer serve as “pillars” to stabilize the layered structure during electrochemical cycling, especially in the high‐voltage region. Intrinsic vacancies in the TM layer create the local configurations of “□–O–□”, “Na–O–□” and “Mg–O–□” to trigger oxygen‐redox in the whole voltage range of charge–discharge. Time‐resolved techniques demonstrate that the P2 phase is well maintained in a wide potential window range of 1.5–4.5 V even at 10 C. It is revealed that charge compensation from Mn‐ and O‐ions contributes to the whole voltage range of 1.5–4.5 V, while the redox of Fe‐ions only contributes to the high‐voltage region of 3.0–4.5 V. The orphaned electrons in the nonbonding 2p orbitals of O that point toward TM‐vacancy sites are responsible for reversible oxygen‐redox, and Mg‐ions in Na sites suppress oxygen release effectively.
Na0.7Mg0.2Fe0.2Mn0.6□0.2O2 with native transitional metal (TM) vacancies is designed as a novel cathode material for sodium‐ion batteries. The TM vacancies lead to nonbonding O 2p orbitals in this material, pointing toward these vacancies triggering reversible whole‐voltage‐range oxygen redox during charge and discharge processes. This work provides new ideals for design of cathode materials in anionic redox chemistry.
This work presents a full reliability-based analysis framework for fiber-reinforced polymer (FRP)-to-concrete bonded joints considering model uncertainty. Eight frequently used bond strength models ...for FRP-to-concrete bonded joints were calibrated by defining a model factor. A total of 641 well-documented tests were considered. Four of the eight models had model factors that correlated with input design parameters and the systematic part of the model factor was removed by a regression equation f. By doing this type of characterization, all eight model factors could be comparatively uniform and described by lognormally distributed random variables. The merit of the uniform model uncertainties after calibration for the eight models was established by the reliability analysis. This study improves the predictability of concrete strengthened with fiber composites and provides useful suggestions on their model uncertainties in engineering practice.
Besides generating vision, light modulates various physiological functions, including mood. While light therapy applied in the daytime is known to have anti-depressive properties, excessive light ...exposure at night has been reportedly associated with depressive symptoms. The neural mechanisms underlying this day-night difference in the effects of light are unknown. Using a light-at-night (LAN) paradigm in mice, we showed that LAN induced depressive-like behaviors without disturbing the circadian rhythm. This effect was mediated by a neural pathway from retinal melanopsin-expressing ganglion cells to the dorsal perihabenular nucleus (dpHb) to the nucleus accumbens (NAc). Importantly, the dpHb was gated by the circadian rhythm, being more excitable at night than during the day. This indicates that the ipRGC→dpHb→NAc pathway preferentially conducts light signals at night, thereby mediating LAN-induced depressive-like behaviors. These findings may be relevant when considering the mental health effects of the prevalent nighttime illumination in the industrial world.
Creativity of employees is a major focus of research in the organization sciences. In this study we examine the relationships between both micro (intrinsic and extrinsic motivation) and molar (team ...climate) variables with manager-rated creativity of R&D employees. Specifically, we hypothesize that (a) extrinsic motivation has a direct relationship with creativity, (b) intrinsic motivation is more strongly related to creativity when extrinsic motivation is low compared to when it is high, (c) team collaborative and competitive climates have direct effects on creativity as well as indirect effects through individual motivation, and (d) intrinsic motivation mediates relationships of the climate variables with creativity, which in turn is moderated by extrinsic motivation. Data were collected from R&D engineers and their managers at a large high-tech company headquartered in Taiwan. Results indicate that a collaborative team climate has a direct positive relationship with creativity as well as one that operates through intrinsic motivation, which in turn was moderated by employee’s extrinsic motivation level. A competitive team climate positively related to extrinsic motivation, but extrinsic motivation did not directly relate to creativity. However, extrinsic motivation did have strong relationships with creativity when intrinsic motivation was low. Results suggest that perhaps the different types of motivation relate to different types of creativity (incremental versus radical). Managerial and theoretical implications of results are discussed as are the study’s limitations.
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