bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copper(II) Pyridyl Aminophenolates: Hypoxia‐Selective, Nucleus‐Targeting Cytotoxins, and Magnetic Resonance Probes
Authors: Prosser Kathleen E. , Xie Da , Chu Annica , MacNeil Gregory A. , Varju Bryton R. , Kadakia Rahul T. , Que Emily L. , Walsby Charles J. 
Published: April 2021

AbstractTargeting the low‐oxygen (hypoxic) environments found in many tumours by using redox‐active metal complexes is a strategy that can enhance efficacy and reduce the side effects of chemotherapies. We have developed a series of CuII complexes with tridentate pyridine aminophenolate‐based ligands for preferential activation in the reduction window provided by hypoxic tissues. Furthermore, ligand functionalization with a pendant CF3 group provides a 19F spectroscopic handle for magnetic‐resonance studies of redox processes at the metal centre and behaviour in cellular environments. The phenol group in the ligand backbone was substituted at the para position with H, Cl, and NO2 to modulate the reduction potential of the CuII centre, giving a range of values below the window expected for hypoxic tissues. The NO2‐substituted complex, which has the highest reduction potential, showed enhanced cytotoxic selectivity towards HeLa cells grown under hypoxic conditions. Cell death occurs by apoptosis, as determined by analysis of the cell morphology. A combination of 19F NMR and ICP‐OES indicates localization of the NO2 complex in HeLa cell nuclei and increased cellular accumulation under hypoxia. This correlates with DNA nuclease activity being the likely origin of cytotoxic activity, as demonstrated by cleavage of DNA plasmids in the presence of the CuII nitro complex and a reducing agent. Selective detection of the paramagnetic CuII complexes and their diamagnetic ligands by 19F MRI suggests hypoxia‐targeting theranostic applications by redox activation.
In‐Situ Synthesis of N, O, P‐Doped Hierarchical Porous Carbon from Poly‐bis(phenoxy)phosphazene for Polysulfide‐Trapping Interlayer in Lithium‐Sulfur Batteries
Authors: Qiu Munan , Fu Xuewei , Yang Fan , Qi Shengli , Wu Zhanpeng , Zhong Wei‐Hong 
Published: April 2021

AbstractThe shuttling of polysulfides is the most detrimental contribution to degrading the capacity and cycle stability of lithium‐sulfur (Li−S) batteries. Adding a carbon interlayer to prevent the polysulfides from migrating is feasible, and a rational design of the structures and surface properties of the carbon layer is essential to increasing its effectiveness. Herein, we report a hierarchical porous carbon (HPC) created by carbonization of bis(phenoxy)phosphazene and in‐situ doping of triple heteroatoms into the carbon lattice to fabricate an effective polysulfide‐trapping interlayer. The generated carbon integrates the advantages of a hierarchical porous structure, a high specific area and rich dopants (N, O and P), to yield chemisorption and physical confinement for polysulfides and fast ion‐transport synergistically. The HPC interlayer significantly improves the electrochemical performance of Li−S batteries, including an exceptional discharge capacity of 1509 mA h/g at 0.06 C and a high capacity retention of 83.7 % after 250 cycles at 0.3 C. This work thus proposes a facile in‐situ synthesis of heteroatom‐doped carbon with rational porous structures for suppressing the shuttle effect.
Axial Ligand Coordination Tuning of the Electrocatalytic Activity of Iron Porphyrin Electrografted onto Carbon Nanotubes for the Oxygen Reduction Reaction
Authors: Zhou Xin‐You , Xu Chao , Guo Peng‐Peng , Sun Wei‐Li , Wei Ping‐Jie , Liu Jin‐Gang 
Published: April 2021

AbstractThe oxygen reduction reaction (ORR) is essential in many life processes and energy conversion systems. It is desirable to design transition metal molecular catalysts inspired by enzymatic oxygen activation/reduction processes as an alternative to noble‐metal‐Pt‐based ORR electrocatalysts, especially in view point of fuel cell commercialization. We have fabricated bio‐inspired molecular catalysts electrografted onto multiwalled carbon nanotubes (MWCNTs) in which 5,10,15,20‐tetra(pentafluorophenyl) iron porphyrin (iron porphyrin FeF20TPP) is coordinated with covalently electrografted axial ligands varying from thiophene to imidazole on the MWCNTs’ surface. The catalysts’ electrocatalytic activity varied with the axial coordination environment (i. e., S‐thiophene, N‐imidazole, and O‐carboxylate); the imidazole‐coordinated catalyst MWCNTs‐Im‐FeF20TPP exhibited the highest ORR activity among the prepared catalysts. When MWCNT‐Im‐FeF20TPP was loaded onto the cathode of a zinc−air battery, an open‐cell voltage (OCV) of 1.35 V and a maximum power density (Pmax) of 110 mW cm−2 were achieved; this was higher than those of MWCNTs‐Thi‐FeF20TPP (OCV=1.30 V, Pmax=100 mW cm−2) and MWCNTs‐Ox‐FeF20TPP (OCV=1.28 V, Pmax=86 mW cm−2) and comparable with a commercial Pt/C catalyst (OCV=1.45 V, Pmax=120 mW cm−2) under similar experimental conditions. This study provides a time‐saving method to prepare covalently immobilized molecular electrocatalysts on carbon‐based materials with structure–performance correlation that is also applicable to the design of other electrografted catalysts for energy conversion.
Photoluminescent Carbon Quantum Dots: Synthetic Approaches and Photophysical Properties
Authors: Hagiwara Kenta , Horikoshi Satoshi , Serpone Nick 
Published: April 2021

AbstractA number of synthetic methodologies and applications of carbon quantum dots (CQDs) have been reported since they were first discovered nearly two decades ago. Unlike metal‐based or semiconductor‐based (e. g., metal chalcogenides) quantum dots (MSQDs), CQDs have the unique feature of being prepared through a variety of synthetic protocols, which are typically understood from considerations of reaction models and photoluminescence mechanisms. Consequently, this brief review article describes quantum dots, in general, and CQDs, in particular, from various viewpoints: (i) their definition, (ii) their photophysical properties, and (iii) the superiority of CQDs over MSQDs. Where possible, comparisons are made between CQDs and MSQDs. First, however, the review begins with a general brief description of quantum dots (QDs) as nanomaterials (sizes≤10 nm), followed by a short description of MSQDs and CQDs. Described subsequently are the various top‐down and bottom‐up approaches to synthesize CQDs followed by their distinctive photophysical properties (emission spectra; quantum yields, Φs).
Probing Multiconfigurational States by Spectroscopy: The Cerium XAS L3‐edge Puzzle
Authors: Sergentu Dumitru‐Claudiu , Booth Corwin H. , Autschbach Jochen 
Published: April 2021

AbstractInvited for the cover of this issue are Prof. Jochen Autschbach and Dr. Dumitru‐Claudiu Sergentu of State University of New York at Buffalo, and Dr. Corwin H. Booth of Lawrence Berkeley National Laboratory. The image depicts high‐energy X‐ray beams as lightnings probing Ce at the L3 edge in the iconic covalent‐bonded Ce(C8H8)2 and in CeO2. The mountain peaks in the background represent the double‐peaked L3 edges. The peaks turn out to be intuitively interpreted in terms of localized orbitals and hence metal oxidation states. Read the full text of the article at 10.1002/chem.202100145.
Development of Non‐Hydrolysable Oligosaccharide Activity‐Based Inactivators for Endoglycanases: A Case Study on α‐1,6 Mannanases
Authors: Schröder Sybrin P. , Offen Wendy A. , Males Alexandra , Jin Yi , de Boer Casper , Enotarpi Jacopo , Marino Laura , van der Marel Gijsbert A. , Florea Bogdan I. , Codée Jeroen D. C. , Overkleeft Herman S. , Davies Gideon J. 
Published: April 2021

AbstractThere is a vast genomic resource for enzymes active on carbohydrates. Lagging far behind, however, are functional chemical tools for the rapid characterization of carbohydrate‐active enzymes. Activity‐based probes (ABPs) offer one chemical solution to these issues with ABPs based upon cyclophellitol epoxide and aziridine covalent and irreversible inhibitors representing a potent and widespread approach. Such inhibitors for enzymes active on polysaccharides are potentially limited by the requirement for several glycosidic bonds, themselves substrates for the enzyme targets. Here, it is shown that non‐hydrolysable trisaccharide can be synthesized and applied even to enzymes with challenging subsite requirements. It was found that incorporation of carbasugar moieties, which was accomplished by cuprate‐assisted regioselective trans‐diaxial epoxide opening of carba‐mannal synthesised for this purpose, yields inactivators that act as powerful activity‐based inhibitors for α‐1,6 endo‐mannanases. 3‐D structures at 1.35–1.47 Å resolutions confirm the design rationale and binding to the enzymatic nucleophile. Carbasugar oligosaccharide cyclophellitols offer a powerful new approach for the design of robust endoglycosidase inhibitors, while the synthesis procedures presented here should allow adaptation towards activity‐based endoglycosidase probes as well as configurational isosteres targeting other endoglycosidase families.
Longitudinal intravital imaging nerve degeneration and sprouting in the toes of spared nerve injured mice
Authors: Yeh Han‐Yuan , Lee Jye‐Chang , Chi Han‐Hsiung , Chen Chih‐Cheng , Liu Qin , Yen Chen‐Tung 
Published: April 2021

AbstractNeuropathic pain is pain caused by damage to the somatosensory nervous system. Both degenerating injured nerves and neighboring sprouting nerves can contribute to neuropathic pain. However, the mesoscale changes in cutaneous nerve fibers over time after the loss of the parent nerve has not been investigated in detail. In this study, we followed the changes in nerve fibers longitudinally in the toe tips of mice that had undergone spared nerve injury (SNI). Nav1.8‐tdTomato, Thy1‐GFP and MrgD‐GFP mice were used to observe the small and large cutaneous nerve fibers. We found that peripheral nerve plexuses degenerated within 3 days of nerve injury, and free nerve endings in the epidermis degenerated within 2 days. The timing of degeneration paralleled the initiation of mechanical hypersensitivity. We also found that some of the Nav1.8‐positive nerve plexuses and free nerve endings in the fifth toe survived, and sprouting occurred mostly from 7 to 28 days. The timing of the sprouting of nerve fibers in the fifth toe paralleled the maintenance phase of mechanical hypersensitivity. Our results support the hypotheses that both injured and intact nerve fibers participate in neuropathic pain, and that, specifically, nerve degeneration is related to the initiation of evoked pain and nerve sprouting is related to the maintenance of evoked pain.
Dual Vacancies Confined in Nickel Phosphosulfide Nanosheets Enabling Robust Overall Water Splitting
Authors: Tong Yun , Chen Pengzuo , Chen Lu , Cui Xinjiang 
Published: April 2021

AbstractExploring highly efficient electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for addressing energy and environmental crises. Vacancy engineering has been regarded as a promising way to optimize the catalytic activity of electrocatalysts. Herein, we put forward a conceptually new dual Ni,S vacancy engineering on 2D NiPS3 nanosheet (denoted as V−NiPS3) by a simple ball‐milling treatment with ultrasonication. This material presents an ideal model for exploring the role of dual vacancies in improving the catalytic activity for overall water splitting. Structural analyses make clear that the formation of dual Ni,S vacancies regulates the electronic structure and catalytic active sites of NiPS3 nanosheet, leading to the superior HER/OER performance. Smaller overpotentials of 124 mV and 290 mV can be achieved at a current density of 10 mA cm−2 for HER and OER, respectively. The OER performance of V−NiPS3 is the best value among all state‐of‐the‐art NiPS3 catalysts. In addition, the assembled two‐electrode cell incorporating V−NiPS3 exhibits enhanced catalytic performance with a low cell voltage of 1.60 V at 10 mA cm−2. This work offers a promising avenue to improve the electrocatalytic performance of the catalysts by engineering dual vacancies for large‐scale water splitting.
Capitulation of mitigation techniques of packet drop attacks in MANET to foreground nuances and ascertain trends
Authors: Singh Sandeep , Bhasin Anshu , Kalia Anshul 
Published: April 2021

SummaryMANET is a kind of wireless ad hoc networks, in which mobile nodes operate in dynamic, distributed, and cooperative environment. Open nature of MANET makes it vulnerable to various kinds of attacks. Of these, the most severe are the packet drop attacks such as Blackhole attack, Cooperative Blackhole, and Grayhole attacks. The malicious nodes drop the packets as these packets are routed through them in accordance with the malefic strategy of the particular packet drop attack, which adversely affects the network performance. A substantial amount of research papers focus on dealing with packet drop attacks in the last few years, but security is still an impending issue. In this paper, we have presented the systematic review of the literature of last 6 years on all variants of packet drop attacks. We have classified these techniques into four categories, namely, mathematical based, monitoring based, network dependent, and amalgamation based which are further sub divided into 12 categories. These papers are categorized in a well‐defined structure to bring out their contribution, to underline the left‐out things, and to foreground the emerging issues for future research. Detailed observations are recorded following a panoptic study in order to identify and divulge more eligible and effective mitigation techniques in a particular environment.
Reusable Catalysts for Hydroformylation‐Based Reactions
Authors: Rodrigues Fábio M. S. , Carrilho Rui M. B. , Pereira Mariette M. 
Published: April 2021

AbstractCatalytic hydroformylation is an important reaction, widely studied by academics and applied in the chemical industry, and it is a paradigmatic example of a chemical reaction that is aligned with most of the Green Chemistry principles. In the last years, the global requirement for more sustainable chemical processes has boosted the development of more active, selective, and reusable hydroformylation catalysts. In this review, we highlight the most recent advances regarding the creation and expansion of reusable catalysts for hydroformylation and sequential processes that use hydroformylation as central reaction. The most relevant strategies for immobilization of hydroformylation catalysts are discussed, along with a critical analysis of their application in synthesis, based on catalytic activity, selectivity, and reusability.
Stepwise Introduction of Flexibility into Aromatic Dicarboxylates Forming Uranyl Ion Coordination Polymers: a Comparison of 2‐Carboxyphenylacetate and 1,2‐Phenylenediacetate
Authors: Thuéry Pierre , Harrowfield Jack 
Published: April 2021

Abstract2‐Carboxyphenylacetate (cpa2−) and 1,2‐phenylenediacetate (1,2‐pda2−) have been reacted with uranyl cations under solvo‐hydrothermal conditions to generate six homo‐ or heterometallic complexes. Both [UO2(cpa)] (1) and [UO2(cpa)(phen)] (2), where phen is 1,10‐phenanthroline, crystallize as monoperiodic coordination polymers. [Ni(bipy)3][(UO2)2(cpa)3]⋅2.5H2O (3), is a diperiodic network with the hcb topology, in which the hexagonal cells distort to accommodate the counterions. [UO2(cpa)2Ni(R,S‐Me6cyclam)] (4) crystallizes as a heterometallic diperiodic network in which uranyl dicarboxylate chains are assembled by bridging NiII cations. While [dmaepH2][(UO2)2(1,2‐pda)3]⋅3H2O (5), where dmaep is 1,4‐bis(2′‐dimethylaminoethyl)piperazine, is a diperiodic hcb network, [QH]2[(UO2)2(1,2‐pda)3]⋅3CH3CN (6), where Q is quinuclidine, is the first example of a triperiodic framework in the uranyl–phenylenediacetate family, its topological type being bto. The complex involving the related ligand 1,4‐phenylenediacetate (1,4‐pda2–), [QH]2[(UO2)2(1,4‐pda)3]⋅2CH3CN (7), is a daisy‐chain‐like monoperiodic polymer. These and previously reported results are discussed in terms of ligand flexibility and ability to form large chelate rings.
Amino−Organolithium Compounds and their Aggregation for the Synthesis of Amino−Organoaluminium Compounds
Authors: Bodach Alexander , Ortmeyer Jochen , Herrmann Bastian , Felderhoff Michael 
Published: April 2021

AbstractHere, we present a thorough structural study of small, easily accessible amino−organolithium compounds with bridging phenyl and naphthyl moieties. Their crystal structures most likely represent their aggregation as tetramers and dimers in both hydrocarbon and ethereal solvents. These amino−organolithium compounds were further used to generate their corresponding aluminium compounds as a model system. Their crystal structures are reported too. All structures are discussed with a focus on the different steric demands and bridging moieties. Additionally, the crystal structures of neophyllithium and decomposition products of some of the compounds mentioned above are reported. This study provides additional data for the future design and synthesis of amine stabilised organolithium and ‐aluminium compounds.
[Ag]2[B12Cl12] as a Catalyst in PhICl2 Mediated Chlorination**
Authors: Poynder Tiffany B. , Houston Sevan D. , Dutton Jason L. 
Published: April 2021

AbstractThe weakly coordinating dianion [B12Cl12]2− originates from a family of carboranes typically reserved for application in coordination chemistry. Herein, we show that its readily accessible Ag(I) salt, [Ag]2[B12Cl12], can be used as a catalyst in the PhICl2 mediated chlorination of arenes, alkenes, and alkynes. The promising activity displayed by [Ag]2[B12Cl12] over a variety of commercially available Ag(I) sources merits its incorporation to the toolkit of commonly screened silver catalysts in synthesis.
Comparison of streamflow recession between plantations and native forests in small catchments in Central‐Southern Chile
Authors: Balocchi Francisco , Flores Neftali , Arumí José Luis , Iroumé Andrés , White Don A. , Silberstein Richard P. , Ramírez de Arellano Pablo 
Published: April 2021

AbstractIn central Chile, many communities rely on water obtained from small catchments in the coastal mountains. Water security for these communities is most vulnerable during the summer dry season and, from 2010 to 2017, rainfall during the dry season was between 20% and 40% below the long‐term average. The rate of decrease in stream flow after a rainfall event is a good measure of the risk of flow decreasing below a critical threshold. This risk of low flow can be quantified using a recession coefficient (α) that is the slope of an exponential decay function relating flow to time since rainfall. A mathematical model was used to estimate the recession coefficient (α) for 142 rainstorm events (64 in summer; 78 in winter) in eight monitored catchments between 2008 and 2017. These catchments all have a similar geology and extend from 35 to 39 degrees of latitude south in the coastal range of south‐central Chile. A hierarchical cluster analysis was used to test for differences between the mean value of α for different regions and forest types in winter and summer. The value of α did not differ (p < 0.05) between catchments in winter. Some differences were observed during summer and these were attributed to morphological differences between catchments and, in the northernmost catchments, the effect of land cover (native forest and plantation). Moreover, α for catchments with native forest was similar to those with pine plantations, although there was no difference (p < 0.05) between these and Eucalyptus plantations. The recession constant is a well‐established method for understanding the effect of climate and disturbance on low flows and baseflows and can enhance local and regional analyses of hydrological processes. Understanding the recession of flow after rainfall in small headwater catchments, especially during summer, is vital for water resources management in areas where the establishment of plantations has occurred in a drying climate.
An efficient and eco‐friendly route to prepare graphene nanosheet and its effect on the flammability of polypropylene composites
Authors: Tang Wufei , Wang Hao , Yang Qian , Liu Fang , Dessie Wubliker , Luo Xiaofang , Peng Cun , Zhang Sheng , Shi Keren , Sun Wenxiang , Qin Zuodong , Gu Xiaoyu 
Published: April 2021

AbstractA rapid, green, and cost‐effective route for the preparation of graphene nanosheets (GRNs) from their layered bulks by the ultrasonic together with mechanical grinding was reported. The whole exfoliation process of synthesizing GRNs lasted just 2 hours without involvement of any acid solvent or other organic solvents; only one kind of waste biomass as adhesive could be used. The structure and morphology of GRNs were characterized and then was then introduced into polypropylene by melt blending, and the cone calorimetry test results indicated that the presence of GRNs could enhance the flame retardancy of PP composite.
Progressive mean control chart is not a special case of an exponentially weighted moving average control chart
Authors: Zafar Raja Fawad , Khoo Michael B. C. , Saha Sajal , Chong Zhi Lin 
Published: April 2021

AbstractThe progressive mean (PM) statistic is based on a simple idea of accumulating information of each subgroup by calculating the average progressively. Its weighting structure is based on a subgroup number that changes arithmetically, which makes the PM chart unique and efficient compared with the existing classical memory control charts. In a recent article (see reference 1), it was claimed that the PM chart is a special case of the exponentially weighted moving average (EMWA) chart. In this article, it is shown that even though the PM statistic can be written in the form of an EWMA statistic, the variance of the PM statistic is different from that of the EWMA statistic. Consequently, the limits of the PM chart are different from that of the EWMA chart. Therefore, it is found that the PM chart is not a special case of the EWMA chart; hence, the claim in reference 1 is incorrect. Furthermore, it is pointed out in this paper that no adaptive property in the weighting parameter of the PM statistic exists, further contradicting the claim in reference 1.
Indefinite multiple Lyapunov functions ofpth moment input‐to‐state stability andpth moment integral input‐to‐state stability for the nonlinear time‐varying stochastic systems with Markovian switching
Authors: Liu Qian , He Yong , Ning Chongyang 
Published: April 2021

AbstractThepth moment input‐to‐state stability and thepth moment integral input‐to‐state stability of stochastic systems with Markovian switching are investigated in this article. Sufficient conditions are provided by indefinite multiple Lyapunov functions (iMLFs) with a time‐varying sojourn time condition. These criteria quantify the stability of each individual subsystem with time‐varying infinitesimal generator of Lyapunov function, which allows infinitesimal generators to be positive in some intervals. An integral form of the sojourn time is introduced to replace the switch count process, which proposes a relaxed switching constraint. Uniformly asymptotic stability and uniformly exponential stability conditions with iMLFs are also presented. Some comparisons are given through theoretical derivations to show the advantages of the proposed results. Finally, two numerical examples verify the effectiveness and the advantages of the presented results.