bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hochkooperatives Photoschalten in Dihydropyren‐Dimeren
Authors: Liesfeld Pauline , Garmshausen Yves , Budzak Simon , Becker Jonas , Dallmann André , Jacquemin Denis , Hecht Stefan 
Published: July 2020

AbstractWir präsentieren eine Strategie für hochkooperatives Photoschalten, bei dem das anfängliche Schaltereignis den nachfolgenden Schaltprozess der benachbarten Einheit erheblich erleichtert. Durch die Verknüpfung von Donor/Akzeptor‐substituierten Dihydropyrenen über geeignete π‐konjugierte Brücken wird die Quantenausbeute für den zweiten photochemischen Ringöffnungsprozess im Vergleich zur ersten Ringöffnung um mehr als zwei Größenordnungen erhöht. Infolgedessen kann der intermediäre Zustand während der Photoisomerisierung nicht erfasst werden, obwohl er während der thermischen Rückreaktion beobachtet wird. Der Vergleich experimenteller und theoretischer Ergebnisse verschiedener Dimere trug dazu bei, die Rolle der Brückeneinheit, die die beiden photochromen Einheiten verbindet, zu entschlüsseln. Das vorgestellte Dihydropyren‐Dimer dient als Modellsystem für längere kooperative Schaltketten, die prinzipiell eine effiziente und direktionale Informationsübertragung entlang eines molekular definierten Weges eröffnen. Darüber hinaus ermöglicht unser Konzept die Erhöhung der Lichtempfindlichkeit in oligomeren und polymeren Systemen und deren Materialien.
A Truxenone‐based Covalent Organic Framework as an All‐Solid‐State Lithium‐Ion Battery Cathode with High Capacity
Authors: Yang Xiye , Hu Yiming , Dunlap Nathan , Wang Xubo , Huang Shaofeng , Su Zhiping , Sharma Sandeep , Jin Yinghua , Huang Fei , Wang Xiaohui , Lee Se‐hee , Zhang Wei 
Published: July 2020

AbstractAll‐solid‐state lithium ion batteries (LIBs) are ideal for energy storage given their safety and long‐term stability. However, there is a limited availability of viable electrode active materials. Herein, we report a truxenone‐based covalent organic framework (COF‐TRO) as cathode materials for all‐solid‐state LIBs. The high‐density carbonyl groups combined with the ordered crystalline COF structure greatly facilitate lithium ion storage via reversible redox reactions. As a result, a high specific capacity of 268 mAh g−1, almost 97.5 % of the calculated theoretical capacity was achieved. To the best of our knowledge, this is the highest capacity among all COF‐based cathode materials for all‐solid‐state LIBs reported so far. Moreover, the excellent cycling stability (99.9 % capacity retention after 100 cycles at 0.1 C rate) shown by COF‐TRO suggests such truxenone‐based COFs have great potential in energy storage applications.
Maßgeschneiderte Synthese von Graphennanostrukturen mit Zickzack‐Rändern
Authors: Liu Junzhi , Feng Xinliang 
Published: July 2020

AbstractExperimentelle und theoretische Studien haben die starke Abhängigkeit der physikalischen und chemischen Eigenschaften des Graphens von seiner Topologie nachgewiesen. Daher ist die atomgenaue Synthese von Graphennanostrukturen essenziell. Ein besonderes Beispiel sind Nanographene mit Zickzack‐Muster in ihrer Randstruktur. Durch ihre spinpolarisierten Zustände an den Ecken zeigen sie einzigartige (opto)elektronische und magnetische Eigenschaften. Die Entwicklung neuer Syntheserouten, Strategien und Analysemethoden gibt Zugang zu dieser beispiellosen Klasse von Graphennanostrukturen, die bis dato nur rechnerisch zugänglich waren. Dies ermöglicht tiefe Einblicke in die Struktur‐Eigenschafts‐Beziehungen sowie die Erschließung neuer Anwendungen in der organischen, kohlenstoffbasierten Elektronik und Spintronik. In diesem Kurzaufsatz werden die neuesten Entwicklungen bei der kontrollierten Synthese von Zickzack‐Graphennanostrukturen verschiedener Topologien durch Bottom‐up‐Synthese diskutiert.
Idiosyncratic Ag7Pt2O7: An Electron Imprecise yet Diamagnetic Small Band Gap Oxide
Authors: Thakur Gohil S. , Dinnebier Robert , Hansen Thomas C. , Assenmacher Wilfried , Felser Claudia , Jansen Martin 
Published: July 2020

AbstractThe seminal qualitative concepts of chemical bonding, as presented by Walter Kossel and Gilbert Newton Lewis back in 1916, have lasting general validity. These basic rules of chemical valence still serve as a touchstone for validating the plausibility of composition and constitution of a given chemical compound. We report on Ag7Pt2O7, with a composition that violates the basic rules of chemical valence and an exotic crystal structure. The first coordination sphere of platinum is characteristic of tetravalent platinum. Thus, the electron count corresponds to Ag7Pt2O7*e−, where excess electrons are associated with the silver substructure. Such conditions given, it is commonly assumed that the excess electrons are either itinerant or localized in Ag−Ag bonds. However, the material does not show metallic conductivity, nor does the structure feature Ag‐Ag pairs. Instead, the excess electrons organize themselves in 2e−4c bonds within the silver substructure. This subvalent silver oxide reveals a new general facet pertinent to silver chemistry.
Tuning the Reactivity of a Heterogeneous Catalyst using N‐Heterocyclic Carbene Ligands for C−H Activation Reactions
Authors: Palazzolo Alberto , Naret Timothée , Daniel‐Bertrand Marion , Buisson David‐Alexandre , Tricard Simon , Lesot Philippe , Coppel Yannick , Chaudret Bruno , Feuillastre Sophie , Pieters Grégory 
Published: July 2020

AbstractWe report the dramatic impact of the addition of N‐heterocyclic carbenes (NHCs) on the reactivity and selectivity of heterogeneous Ru catalysts in the context of C−H activation reactions. Using a simple and robust method, we prepared a series of new air‐stable catalysts starting from commercially available Ru on carbon (Ru/C) and differently substituted NHCs. Associated with C−H deuteration processes, depending on Ru/C‐NHC ratios, the chemical outcome can be controlled to a large extent. Indeed, tuning the reactivity of the Ru catalyst with NHC enabled: 1) increased chemoselectivity and the regioselectivity for the deuteration of alcohols in organic media; 2) the synthesis of fragile pharmaceutically relevant deuterated heterocycles (azine, purine) that are otherwise completely reduced using unmodified commercial catalysts; 3) the discovery of a novel reactivity for such heterogeneous Ru catalysts, namely the selective C‐1 deuteration of aldehydes.
Controlling the Oxidation State of Pt Single Atoms for Maximizing Catalytic Activity
Authors: Jeong Hojin , Shin Dongjae , Kim Beom‐Sik , Bae Junemin , Shin Sangyong , Choe Chanyeong , Han Jeong Woo , Lee Hyunjoo 
Published: July 2020

AbstractSingle‐atom catalysts (SACs) have emerged as promising materials in heterogeneous catalysis. Previous studies reported controversial results about the relative level in activity for SACs and nanoparticles (NPs). These works have focused on the effect of metal atom arrangement, without considering the oxidation state of the SACs. Here, we immobilized Pt single atoms on defective ceria and controlled the oxidation state of Pt SACs, from highly oxidized (Pt0: 16.6 at %) to highly metallic states (Pt0: 83.8 at %). The Pt SACs with controlled oxidation states were then employed for oxidation of CO, CH4, or NO, and their activities compared with those of Pt NPs. The highly oxidized Pt SACs presented poorer activities than Pt NPs, whereas metallic Pt SACs showed higher activities. The Pt SAC reduced at 300 °C showed the highest activity for all the oxidations. The Pt SACs with controlled oxidation states revealed a crucial missing link between activity and SACs.
Mass‐Spectrometric Imaging of Electrode Surfaces—a View on Electrochemical Side Reactions
Authors: Fangmeyer Jens , Behrens Arne , Gleede Barbara , Waldvogel Siegfried R. , Karst Uwe 
Published: July 2020

AbstractElectrochemical side reactions, often referred to as “electrode fouling”, are known to be a major challenge in electro‐organic synthesis and the functionality of modern batteries. Often, polymerization of one or more components is observed. When reaching their limit of solubility, those polymers tend to adsorb on the surface of the electrode, resulting in a passivation of the respective electrode area, which may impact electrochemical performance. Here, matrix‐assisted laser‐desorption/ionization mass spectrometry (MALDI‐MS) is presented as valuable imaging technique to visualize polymer deposition on electrode surfaces. Oligomer size distribution and its dependency on the contact time were imaged on a boron‐doped diamond (BDD) anode of an electrochemical flow‐through cell. The approach allows to detect weak spots, where electrode fouling may take place and provides insight into the identity of side‐product pathways.
Atroposelective Ring Opening of Cyclic Diaryliodonium Salts with Bulky Anilines Controlled by a Chiral Cobalt(III) Anion
Authors: Zhang Xue , Zhao Kun , Li Na , Yu Jie , Gong Liu‐Zhu , Gu Zhenhua 
Published: July 2020

AbstractThe present work demonstrates a CuCl and anionic chiral cobalt(III)‐catalyzed enantioselective ring‐opening reaction. The small‐size, ligand‐free copper species enabled the cross‐coupling of iodonium salts with a series of bulky aromatic amines in high ee values. The chiral cobalt(III) anion causes appreciable chemical shift changes of cyclic diaryliodoniums in 1H NMR spectra.
Single‐Atom Electrocatalysts from Multivariate Metal–Organic Frameworks for Highly Selective Reduction of CO2 at Low Pressures
Authors: Jiao Long , Yang Weijie , Wan Gang , Zhang Rui , Zheng Xusheng , Zhou Hua , Yu Shu‐Hong , Jiang Hai‐Long 
Published: July 2020

AbstractSingle‐atom catalysts (SACs) are of great interest because of their ultrahigh activity and selectivity. However, it is difficult to construct model SACs according to a general synthetic method, and therefore, discerning differences in activity of diverse single‐atom catalysts is not straightforward. Herein, a general strategy for synthesis of single‐atom metals implanted in N‐doped carbon (M1‐N‐C; M=Fe, Co, Ni and Cu) has been developed starting from multivariate metal–organic frameworks (MOFs). The M1‐N‐C catalysts, featuring identical chemical environments and supports, provided an ideal platform for differentiating the activity of single‐atom metal species. When employed in electrocatalytic CO2 reduction, Ni1‐N‐C exhibited a very high CO Faradaic efficiency (FE) up to 96.8 % that far surpassed Fe1‐, Co1‐ and Cu1‐N‐C. Remarkably, the best‐performer, Ni1‐N‐C, even demonstrated excellent CO FE at low CO2 pressures, thereby representing a promising opportunity for the direct use of dilute CO2 feedstock.
Microsatellite development and detection of admixture among three sympatric Haploblepharus species (Carcharhiniformes: Scyliorhinidae)
Authors: van Staden Michaela , Gledhill Katie Samantha , Gennari Enrico , McCord Meaghen Erica , Parkinson Matthew , Watson Ralph Gareth Andrew , Rhode Clint , Bester‐van der Merwe Aletta Elizabeth 
Published: July 2020

Abstract

Haploblepharus is an understudied genus comprising four recognized scyliorhinid species that are endemic to southern Africa. Species identification within this group has historically been problematic due to a high degree of morphological conservatism among congeners, further complicated by the possibility of interspecific hybridization.
This study describes the development of two microsatellite panels comprising 10 polymorphic markers for the puffadder shyshark, Haploblepharus edwardsii. The markers were characterized in 35 H. edwardsii specimens and tested for cross‐species utility in Haploblepharus fuscus, Haploblepharus pictus, and the more distantly related scyliorhinid Halaelurus natalensis.
Genetic diversity statistics were estimated for each species, and the presence of population differentiation was tested for in H. edwardsii and H. pictus. Furthermore, interspecific genetic differentiation was examined to infer the potential use of these markers for species identification as well as for detecting signatures of admixture among Haploblepharus species.
All microsatellite markers were polymorphic in each species, with polymorphism information contents ranging from 0.43 to 0.62. Population differentiation was only evident for H. pictus, where genetic discontinuity was detected among geographically distant sampling sites.
Statistically significant differentiation (fixation index between populations FST = 0.091 to 0.382) was found between all species; however, the level of differentiation between H. fuscus and H. pictus was low in comparison and seemingly at a population level rather than at a species level. Species assignment using Bayesian clustering analysis resulted in approximately 57% of 88 genotyped specimens being unambiguously assigned to a distinct genetic cluster that confirmed accurate taxonomic assignment.
Overall, the low levels of differentiation together with the presence of distinct and admixed genetic clusters suggests a recent divergence and possible contemporary hybridization within the genus Haploblepharus. As such, conservation strategies should be focused on the generic level until such a time that Haploblepharus species can be readily identified.
Topological data analysis in digital marketing
Authors: Lakshminarayan Choudur , Yin Mingzhang 
Published: July 2020

AbstractThe ubiquitous internet is a multipurpose platform for finding information, an avenue for social interaction, and a primary customer touch‐point as a marketplace to conduct e‐commerce. The digital footprints of browsers are a rich source of data to drive sales. We use clickstreams (clicks) to track the evolution of session‐level customer browsing for modeling. We apply Markov chains (MC) to calculate probabilities of page‐level transitions from which relevant topological features (persistence diagrams) are extracted to determine optimal points (URL pages) for marketing intervention. We use topological summaries (silhouettes, landscapes) to distinguish the buyers and nonbuyers to determine the likelihood of conversion of active user sessions. Separately, we model browsing patterns via Markov chain theory to predict users' propensity to buy within a session. Extensive analysis of data applied to a large commercial website demonstrates that the proposed approaches are useful predictors of user behavior and intent. Utilizing computational topology in digital marketing holds tremendous promise. We demonstrate the utility of topological data analysis combined with MC and present its merits and disadvantages.
Doing more and doing better are two different entities: Different patterns of family control and environmental performance
Authors: Yu Byungjun , Zeng Saixing , Chen Hongquan , Meng Xiaohua , Tam Chiming 
Published: July 2020

AbstractFamily firms bear two types of agency costs, including type I and type II agency problems, in corporate environmental practices: (1) Outside executives at family firms hesitate to engage in environmental strategies, which can lead to drops in profits; (2) Controlling families employ opportunistically environmental management to achieve their interests. We argue that a primary cause for the agency problems lies on ineffective internal corporate governance at family firms, which can cause loss of managerial (or power) balance between outside executives and family executives. Our findings show that family firms with ownership and strategic control (FSC), which family executives and outside executives monitor and constrain each other, can achieve the highest environmental performance. Moreover, external controls, including product market competition and provincial environmental regulations, substitute effective internal control of FSC. The environmental performance premium of FSC is more prevalent when the production market competition is lower. Family firms with ownership, operational, and strategic control (FOSC) can achieve higher environmental performance within a province with more stringent environmental regulations.
miR‐495 and miR‐5688 are down‐regulated in non‐small cell lung cancer under hypoxia to maintain interleukin‐11 expression
Authors: Zhao Meng , Chang Jiao , Liu Ran , Liu Yahui , Qi Jin , Wang Yanhui , Zhang Xinwei , Qiao Lu , Jin Yu , An Haohua , Ren Li 
Published: July 2020

AbstractBackgroundHypoxia is a hallmark of cancer and is associated with poor prognosis. However, the molecular mechanism by which hypoxia promotes tumor progression remains unclear. MicroRNAs dysregulation has been shown to play a critical role in the tumor and tumor microenvironment. Here, we investigated the roles of miR‐495 and miR‐5688 in human non‐small cell lung cancer (NSCLC) and their underlying mechanism.MethodsThe expression levels of miR‐495 and miR‐5688 in human NSCLC tissue specimens were measured by quantitative real‐time polymerase chain reaction (qRT‐PCR). Deferoxamine (DFO) was used to determine whether the regulation of miR‐495 and miR‐5688 under hypoxia was dependent on hypoxia‐inducible factor 1‐alpha (HIF‐1α). Furthermore, the functions of miR‐495 and miR‐5688 in tumor progression were evaluated using colony formation, 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium (MTS), wound healing, transwell assays, and xenograft model. Two algorithms, PicTAR and Targetscan, were used to predict the target gene of these two miRNAs, and dual‐luciferase reporter assay was conducted to confirm the target. The unpaired two‐tailed t test, Pearson correlation analysis, and Fisher's exact probability test were performed for statistical analyses.ResultsTwo miRNAs, miR‐495 and miR‐5688, were found to participate in NSCLC progression under hypoxia. They were down‐regulated in NSCLC tissues compared with normal tissues. We determined that hypoxia led to the down‐regulation of miR‐495 and miR‐5688 in NSCLC cells, which was independent of HIF‐1α and cellular metabolic energy. In addition, miR‐495 and miR‐5688 suppressed cell proliferation, migration, and invasion in vitro. The NSCLC xenograft model showed that miR‐495 and miR‐5688 inhibited tumor formation in vivo. Interestingly, we found that miR‐495 and miR‐5688 had the same target, interleukin‐11 (IL‐11). Recombinant human IL‐11 counteracted the effects of miR‐495 and miR‐5688 on NSCLC cells, suggesting that miR‐495 and miR‐5688 executed their tumor suppressive role by repressing IL‐11 expression.ConclusionWe found that hypoxia down‐regulated the expression levels of miR‐495 and miR‐5688 in NSCLC to enhance IL‐11 expression and tumor progression, indicating that the miR‐495/miR‐5688/IL‐11 axis may serve as a therapeutic target and potential biomarker for NSCLC.
Extending the Library of Light‐Dependent Protochlorophyllide Oxidoreductases and their Solvent Tolerance, Stability in Light and Cofactor Flexibility
Authors: Schmermund Luca , Bierbaumer Sarah , Schein Viktor K. , Winkler Christoph K. , Kara Selin , Kroutil Wolfgang 
Published: July 2020

AbstractBiocatalysis is increasingly used in combination with light to develop new and more sustainable synthetic methods. Thereby, mostly a chemical photocatalyst harvesting the light energy is combined with an established enzymatic reaction, thus the biocatalyst itself does not require the light for its specific reaction. Here we expand the library of an enzyme which requires light for its natural reaction, namely the light‐dependent protochlorophyllide oxidoreductase (LPOR). This enzyme catalyzes the NADPH‐dependent reduction of a C=C in a N‐heterocycle. Out of five LPORs identified by sequence search, four were found to be well expressible in E. coli and active. Investigating the light intensity, which is an important parameter describing energy input and subsequently may enable fast reaction, it turned out that the four LPORs can stand the maximum light intensity reachable with the equipment used (1450 μmol photons m−2 s−1). However, the natural substrate and product were degraded at these conditions, allowing only 15 % of the maximum input (211 μmol photons m−2 s−1). Furthermore, the LPORs accepted seven different water miscible solvents with a solvent content of up to 20 % v/v and were active at a pH from 6 to 10. While all LPORs known to date are exclusively NADPH dependent, two LPORs identified here were active also with NADH. The cofactor selectivity could be pinned to three amino acid residues, which interestingly do not directly bind to the cofactor.
Immobilization of Ethynyl‐π‐Extended Electron Acceptors with Amino‐Terminated SAMs by Catalyst‐Free Click Reaction
Authors: Nakano Kyohei , Sanematsu Haruki , Kaji Yumiko , Takai Atsuro , Tajima Keisuke 
Published: July 2020

AbstractSurface modification of SiO2 using a catalyst‐free quantitative reaction between an amine and an ethynyl‐π‐extended naphthalenediimide was investigated. A post‐reaction method, in which the catalyst‐free reaction was performed at the surface after the formation of amino‐terminated self‐assembled monolayers (SAMs), resulted in dense, uniform modification of the SiO2 surface with the naphthalenediimide molecules. Both X‐ray reflectivity and angle‐resolved X‐ray photoemission spectroscopy showed consistent results for the layer thickness and density. In contrast, a pre‐reaction method, in which an amino‐silane and the ethynyl‐π‐extended naphthalenediimide reacted first and then formed a SAM, afforded a sparse SAM on the SiO2 surface, probably due to the steric hindrance of the naphthalenediimide moieties. The in situ decoration of the SiO2 surface by a catalyst‐free quantitative reaction offers a facile route for modifying surface properties with various π‐conjugated molecules suitable for many applications.
Unveiling the Occurrence of Co(III) in NiCo Layered Electroactive Hydroxides: The Role of Distorted Environments
Authors: Hunt Diego , Oestreicher Víctor , Mizrahi Martín , Requejo Félix G. , Jobbágy Matías 
Published: July 2020

AbstractCo‐ and Ni‐based layered hydroxides constitute a unique class of two‐dimensional inorganic materials with exceptional chemical diversity, physicochemical properties and outstanding performance as supercapacitors and overall water splitting catalysts. Recently, the occurrence of Co(III) in these phases has been proposed as a key factor that enhance their electrochemical performance. However, the origin of this centers and control over its contents remains as an open question. We employed the Epoxide Route to synthesize a whole set of α‐NiCo layered hydroxides. The PXRD and XAS characterization alert about the occurrence of Co(III) as a consequence of the increment in the Ni content. DFT+U simulation suggest that the shortening of the Co−O distance promotes a structural distortion in the Co environments, resulting in a double degeneration in the octahedral Co 3d orbitals. Hence, a strong modification of the electronic properties leaves the system prone to oxidation, by the appearance of Co localized electronic states on the Fermi level. This work combines a microscopic interpretation supported by a multiscale crystallochemical analysis, regarding the so‐called synergistic redox behavior of Co and Ni, offering fundamental tools for the controllable design of highly efficient electroactive materials. To the best of our knowledge, this is the first computational–experimental investigation of the electronic and structural details of α‐NiCo hydroxides, laying the foundation for the fine tuning of electronic properties in layered hydroxides.