bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neutral‐Eosin‐Y‐Photocatalyzed Silane Chlorination Using Dichloromethane
Authors: Fan Xuanzi , Xiao Pin , Jiao Zeqing , Yang Tingting , Dai Xiaojuan , Xu Wengang , Tan Jin Da , Cui Ganglong , Su Hongmei , Fang Weihai , Wu Jie 
Published: July 2019

AbstractChlorosilanes are versatile reagents in organic synthesis and material science. A mild pathway is now reported for the quantitative conversion of hydrosilanes to silyl chlorides under visible‐light irradiation using neutral eosin Y as a hydrogen‐atom‐transfer photocatalyst and dichloromethane as a chlorinating agent. Stepwise chlorination of di‐ and trihydrosilanes was achieved in a highly selective fashion assisted by continuous‐flow micro‐tubing reactors. The ability to access silyl radicals using photocatalytic Si−H activation promoted by eosin Y offers new perspectives for the synthesis of valuable silicon reagents in a convenient and green manner.
Polymer Networks: From Plastics and Gels to Porous Frameworks
Authors: Gu Yuwei , Zhao Julia , Johnson Jeremiah A. 
Published: July 2019

AbstractPolymer networks, which are materials composed of many smaller components—referred to as “junctions” and “strands”—connected together via covalent or non‐covalent/supramolecular interactions, are arguably the most versatile, widely studied, broadly used, and important materials known. From the first commercial polymers through the plastics revolution of the 20thcentury to today, there are almost no aspects of modern life that are not impacted by polymer networks. Nevertheless, there are still many challenges that must be addressed to enable a complete understanding of these materials and facilitate their development for emerging applications ranging from sustainability and energy harvesting/storage to tissue engineering and additive manufacturing. Here, we provide a unifying overview of the fundamentals of polymer network synthesis, structure, and properties, tying together recent trends in the field that are not always associated with classical polymer networks, such as the advent of crystalline “framework” materials. We also highlight recent advances in using molecular design and control of topology to showcase how a deep understanding of structure–property relationships can lead to advanced networks with exceptional properties.
Molecular Semiconductor Surfactants with Fullerenol Heads and Colored Tails for Carbon Dioxide Photoconversion
Authors: Kunkel Marius , Sutter Sebastian , Polarz Sebastian 
Published: July 2019

AbstractThe leaf is a prime example of a material converting waste (CO2) into value with maximum sustainability. As the most important constituent, it contains the coupled photosystems II and I, which are imbedded in the cellular membrane of the chloroplasts. Can key functions of the leaf be packed into soap? We present next‐generation surfactants that self‐assemble into bilayer vesicles (similar to the cellular membrane), are able to absorb photons of two different visible wavelengths, and exchange excited charge carriers (similar to the photosystems), followed by conversion of CO2 (in analogy to the leaf). The amphiphiles contain five dye molecules as the hydrophobic entity attached exclusively to one hemisphere of a polyhydroxylated fullerene (Janus‐type). We herein report on their surfactant, optical, electronic, and catalytic properties. Photons absorbed by the dyes are transferred to the fullerenol head, where they can react with different species such as CO2 to give formic acid.
Perquinolines A–C: Unprecedented Bacterial Tetrahydroisoquinolines Involving an Intriguing Biosynthesis
Authors: Rebets Yuriy , Nadmid Suvd , Paulus Constanze , Dahlem Charlotte , Herrmann Jennifer , Hübner Harald , Rückert Christian , Kiemer Alexandra K. , Gmeiner Peter , Kalinowski Jörn , Müller Rolf , Luzhetskyy Andriy 
Published: July 2019

AbstractMetabolic profiling of Streptomyces sp. IB2014/016‐6 led to the identification of three new tetrahydroisoquinoline natural products, perquinolines A–C (1–3). Labelled precursor feeding studies and the cloning of the pqr biosynthetic gene cluster revealed that 1–3 are assembled by the action of several unusual enzymes. The biosynthesis starts with the condensation of succinyl‐CoA and l‐phenylalanine catalyzed by the amino‐7‐oxononanoate synthase‐like enzyme PqrA, representing rare chemistry in natural product assembly. The second condensation and cyclization events are conducted by PqrG, an enzyme resembling an acyl‐CoA ligase. Last, ATP‐grasp RimK‐type ligase PqrI completes the biosynthesis by transferring a γ‐aminobutyric acid or β‐alanine moiety. The discovered pathway represents a new route for assembling the tetrahydroisoquinoline cores of natural products.
Coupling of Solar Energy and Thermal Energy for Carbon Dioxide Reduction: Status and Prospects
Authors: Wang Zhou‐jun , Song Hui , Liu Huimin , Ye Jinhua 
Published: July 2019

AbstractEnormous efforts have been devoted to the reduction of carbon dioxide (CO2) by utilizing various driving forces, such as heat, electricity, and radiation. However, the efficient reduction of CO2 is still challenging because of sluggish kinetics. Recent pioneering studies from several groups, including us, have demonstrated that the coupling of solar energy and thermal energy offers a novel and promising strategy to promote the activity and/or manipulate selectivity in CO2 reduction. Herein, we clarify the definition and principles of coupling solar energy and thermal energy, and comprehensively review the status and prospects of CO2 reduction by coupling solar energy and thermal energy. Catalyst design, reactor configuration, photo‐mediated activity/selectivity, and mechanism studies in photo‐thermo CO2 reduction will be emphasized. The aim of this Review is to promote understanding towards CO2 activation and provide guidelines for the design of new catalysts for the efficient reduction of CO2.
Nucleophilic Iron Complexes in Proton‐Transfer Catalysis: An Iron‐Catalyzed Dimroth Cyclocondensation
Authors: Baykal Aslihan , Zhang Dihan , Knelles Jakob , Alt Isabel T. , Plietker Bernd 
Published: July 2019

AbstractThe nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) is an active catalyst in C−H‐amination but also in proton‐transfer catalysis. Herein, we describe the successful use of this complex as a proton‐transfer catalyst in the cyclocondensation reaction between azides and ketones to the corresponding 1,2,3‐triazoles. Cross‐experiments indicate that the proton‐transfer catalysis is significantly faster than the nitrene‐transfer catalysis, which would lead to the C−H amination product. An example of a successful sequential Dimroth triazole–indoline synthesis to the corresponding triazole‐substituted indolines is presented.
On the validity of time‐dependent AUC estimation in the presence of cure fraction
Authors: Beyene Kassu M. , El Ghouch Anouar , Oulhaj Abderrahim 
Published: July 2019

AbstractDuring the last decades, several approaches have been proposed to estimate the time‐dependent area under the receiver operating characteristic curve (AUC) of risk tools derived from survival data. The validity of these estimators relies on some regularity assumptions among which a survival function being proper. In practice, this assumption is not always satisfied because a fraction of the population may not be susceptible to experience the event of interest even for long follow‐up. Studying the sensitivity of the proposed estimators to the violation of this assumption is of substantial interest. In this paper, we investigate the performance of a nonparametric simple estimator, developed for classical survival data, in the case when the population exhibits a cure fraction. Motivated from the current practice of deriving risk tools in oncology and cardiovascular disease prevention, we also assess the loss, in terms of predictive performance, when deriving risk tools from survival models that do not acknowledge the presence of cure. The simulation results show that the investigated method is valid even under the presence of cure. They also show that risk tools derived from survival models that ignore the presence of cure have smaller AUC compared to those derived from survival models that acknowledge the presence of cure. This was also attested with a real data analysis from a breast cancer study.
External validation of a prognostic model to predict survival of patients with sentinel node-negative melanoma
Authors: Ipenburg N A , Nieweg O E , Ahmed T , van Doorn R , Scolyer R A , Long G V , Thompson J F , Lo S 
Published: July 2019

Abstract

Background
Identifying patients with sentinel node-negative melanoma at high risk of recurrence or death is important. The European Organisation for Research and Treatment of Cancer (EORTC) recently developed a prognostic model including Breslow thickness, ulceration and site of the primary tumour. The aims of the present study were to validate this prognostic model externally and to assess whether it could be improved by adding other prognostic factors.

Methods
Patients with sentinel node-negative cutaneous melanoma were included in this retrospective single-institution study. The β values of the EORTC prognostic model were used to predict recurrence-free survival and melanoma-specific survival. The predictive performance was assessed by discrimination (c-index) and calibration. Seeking to improve the performance of the model, additional variables were added to a Cox proportional hazards model.

Results
Some 4235 patients with sentinel node-negative cutaneous melanoma were included. The median follow-up time was 50 (i.q.r. 18·5–81·5) months. Recurrences and deaths from melanoma numbered 793 (18·7 per cent) and 456 (10·8 per cent) respectively. Validation of the EORTC model showed good calibration for both outcomes, and a c-index of 0·69. The c-index was only marginally improved to 0·71 when other significant prognostic factors (sex, age, tumour type, mitotic rate) were added.

Conclusion
This study validated the EORTC prognostic model for recurrence-free and melanoma-specific survival of patients with negative sentinel nodes. The addition of other prognostic factors only improved the model marginally. The validated EORTC model could be used for personalizing follow-up and selecting high-risk patients for trials of adjuvant systemic therapy.
Effect of Solvent, Role of Formic Acid and Rh/C Catalyst for the Efficient Liquefaction of Lignin
Authors: Matsagar Babasaheb M. , Wang Zheng‐Yen , Sakdaronnarong Chularat , Chen Season S. , Tsang Daniel C. W. , Wu Kevin C.‐W. 
Published: July 2019

AbstractWe demonstrate highly efficient liquefaction of alkali lignin with a very high yield of THF‐soluble bio‐oil (91.5 wt %) using formic acid (FA) and Rh/C catalyst under relatively mild reaction conditions (250 °C, 6 h) in EtOH−H2O co‐solvent system. The monomeric products are identified in which alkyl guaiacols accounts for the main proportion. The role of FA was not only used as a liquid‐phase in‐situ hydrogen source but also acts as organic acid which can catalyze the hydrolysis reaction of −C−O−C ether bonds of lignin. Moreover, in the present study, the role of Rh/C and FA is demonstrated for the liquefaction of lignin. The replacement of pure H2 gas by the liquid‐phase FA (hydrogen source) can effectively prevent the char formation. The utilization of Rh/C catalyst helps for the conversion of alkenyl guaiacols to alkyl guaiacols suggesting the hydrogenation of phenolic monomers and further cleavage by hydrogenation results in the formation of bio‐oil with lower molecular weight (Mn=466 g mol−1) as well as lower O/C ratio (0.26).
HFIP‐Functionalized Co3O4 Micro‐Nano‐Octahedra/rGO as a Double‐Layer Sensing Material for Chemical Warfare Agents
Authors: Alali Khaled Tawfik , Liu Jingyuan , Chen Rongrong , Liu Qi , Zhang Hongsen , Li Jundong , Hou Jindi , Li Rumin , Wang Jun 
Published: July 2019

AbstractSemiconductor metal oxides (SMO)‐based gas‐sensing materials suffer from insufficient detection of a specific target gas. Reliable selectivity, high sensitivity, and rapid response–recovery times under various working conditions are the main requirements for optimal gas sensors. Chemical warfare agents (CWA) such as sarin are fatal inhibitors of acetylcholinesterase in the nerve system. So, sensing materials with high sensitivity and selectivity toward CWA are urgently needed. Herein, micro‐nano octahedral Co3O4 functionalized with hexafluoroisopropanol (HFIP) were deposited on a layer of reduced graphene oxide (rGO) as a double‐layer sensing materials. The Co3O4 micro‐nano octahedra were synthesized by direct growth from electrospun fiber templates calcined in ambient air. The double‐layer rGO/Co3O4‐HFIP sensing materials presented high selectivity toward DMMP (sarin agent simulant, dimethyl methyl phosphonate) versus rGO/Co3O4 and Co3O4 sensors after the exposure to various gases owing to hydrogen bonding between the DMMP molecules and Co3O4‐HFIP. The rGO/Co3O4‐HFIP sensors showed high stability with a response signal around 11.8 toward 0.5 ppm DMMP at 125 °C, and more than 75 % of the initial response was maintained under a saturated humid environment (85 % relative humidity). These results prove that these double‐layer inorganic–organic composite sensing materials are excellent candidates to serve as optimal gas‐sensing materials.
ZnO Quantum Dots Coupled with Graphene toward Electrocatalytic N2 Reduction: Experimental and DFT Investigations
Authors: Liu Ya‐ping , Li Yu‐biao , Huang Da‐jian , Zhang Hu , Chu Ke 
Published: July 2019

AbstractElectrochemical reduction of N2 to NH3 is a promising method for artificial N2 fixation, but it requires efficient and robust electrocatalysts to boost the N2 reduction reaction (NRR). Herein, a combination of experimental measurements and theoretical calculations revealed that a hybrid material in which ZnO quantum dots (QDs) are supported on reduced graphene oxide (ZnO/RGO) is a highly active and stable catalyst for NRR under ambient conditions. Experimentally, ZnO/RGO was confirmed to favor N2 adsorption due to the largely exposed active sites of ultrafine ZnO QDs. DFT calculations disclosed that the electronic coupling of ZnO with RGO resulted in a considerably reduced activation‐energy barrier for stabilization of *N2H, which is the rate‐limiting step of the NRR. Consequently, ZnO/RGO delivered an NH3 yield of 17.7 μg h−1 mg−1 and a Faradaic efficiency of 6.4 % in 0.1 m Na2SO4 at −0.65 V (vs. RHE), which compare favorably to those of most of the reported NRR catalysts and thus demonstrate the feasibility of ZnO/RGO for electrocatalytic N2 fixation.
Gold(I) Complexes Stabilized by Nine‐ and Ten‐Membered N‐Heterocyclic Carbene Ligands
Authors: Cervantes‐Reyes Alejandro , Rominger Frank , Rudolph Matthias , Hashmi A. Stephen K. 
Published: July 2019

AbstractNine‐ and ten‐membered N‐heterocyclic carbene (NHC) ligands have been developed and for the first time their gold(I) complexes were synthesized. The protonated NHC pro‐ligands 2 a–h were prepared by the reaction of readily available N,N′‐diarylformamidines with bis‐electrophilic building blocks, followed by anion exchange. In situ deprotonation of the tetrafluoroborates 2 a–h with tBuOK in the presence of AuCl(SMe2) provided fast access to NHC‐gold(I) complexes 3–10. These new NHC‐gold(I) complexes show very good catalytic activity in a cycloisomerization reaction (0.1 mol % catalyst loading, up to 100 % conversion) and their solid‐state structures reveal high steric hindrance around the metal atom (%Vbur up to 53.0) which is caused by their expanded‐ring architecture.
Tuning Redox Active Polyoxometalates for Efficient Electron‐Coupled Proton‐Buffer‐Mediated Water Splitting
Authors: Lei Jie , Yang Jun‐Jie , Liu Ting , Yuan Ru‐Ming , Deng Ding‐Rong , Zheng Ming‐Sen , Chen Jia‐Jia , Cronin Leroy , Dong Quan‐Feng 
Published: July 2019

AbstractWe present strategies to tune the redox properties of polyoxometalate clusters to enhance the electron‐coupled proton‐buffer‐mediated water splitting process, in which the evolution of hydrogen and oxygen can occur in different forms and is separated in time and space. By substituting the heteroatom template in the Keggin‐type polyoxometalate cluster, H6ZnW12O40, it is possible to double the number of electrons and protonation in the redox reactions (from two to four). This increase can be achieved with better matching of the energy levels as indicated by the redox potentials, compared to the ones of well‐studied H3PW12O40 and H4SiW12O40. This means that H6ZnW12O40 can act as a high‐performance redox mediator in an electrolytic cell for the on‐demand generation of hydrogen with a high decoupling efficiency of 95.5 % and an electrochemical energy efficiency of 83.3 %. Furthermore, the H6ZnW12O40 cluster also exhibits an excellent cycling behaviour and redox reversibility with almost 100 % H2‐mediated capacity retention during 200 cycles and a high coulombic efficiency >92 % each cycle at 30 mA cm−2.
Cover Picture: Catalytic Enantioselective Protonation of Monofluorinated Silyl Enol Ethers towards Chiral α‐Fluoroketones (Chin. J. Chem. 8/2019)
Authors: Liao Kui , Hu Xiao‐Si , Zhu Ren‐Yi , Rao Ruo‐Han , Yu Jin‐Sheng , Zhou Feng , Zhou Jian 
Published: July 2019

The cover picture shows a highly enantioselective organocatalytic protonation of monofluorinated silyl enol ethers to α‐secondary α‐fluoroketones using water as proton source. Notably, in the presence of D2O and MeOD, the facile access of chiral α‐deuterated α‐fluoroketones in excellent enantioselectivity is achieved. More details are discussed by Zhou et al. on page 799–806.
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On the Oxidation State of Cu2O upon Electrochemical CO2 Reduction: An XPS Study
Authors: Permyakova Anastasia A. , Herranz Juan , El Kazzi Mario , Diercks Justus S. , Povia Mauro , Mangani Léa Rose , Horisberger Michael , Pătru Alexandra , Schmidt Thomas J. 
Published: July 2019

AbstractThe encouraging selectivity of copper oxides for the electroreduction of CO2 into ethylene and alcohols has led to a vivid debate on the possible relation between their operando (sub‐)surface oxidation state (i. e. fully reduced or partially oxidized) and this distinct reactivity. The high roughness of the Cu oxides used in previous studies on this matter adds complexity to this controversy and motivated us to prepare quasi‐planar Cu2O thin films that displayed a CO2 reduction selectivity similar to that of oxide‐derived copper catalysts reported in previous studies. Most importantly, when the post‐mortem thin films were transferred for characterization in an air‐free environment, X‐ray photoelectron spectroscopy measurements confirmed their complete reduction in the course of the CO2 reduction reaction. Thus, our results indicate that the selectivity of the Cu oxides featured in previous studies stems from their enhanced roughness, highlighting the importance of controlled sample transfer upon post‐mortem characterization with ex situ techniques.
Influences of potential oil and gas development and future climate on Sage‐grouse declines and redistribution
Authors: Heinrichs Julie A. , O'Donnell Michael S. , Aldridge Cameron L. , Garman Steven L. , Homer Collin G. 
Published: July 2019

AbstractMultiple environmental stressors impact wildlife populations, but we often know little about their cumulative and combined influences on population outcomes. We generally know more about past effects than potential future impacts, and direct influences such as changes of habitat footprints than indirect, long‐term responses in behavior, distribution, or abundance. Yet, an understanding of all these components is needed to plan for future landscapes that include human activities and wildlife. We developed a case study to assess how spatially explicit individual‐based modeling could be used to evaluate future population outcomes of gradual landscape change from multiple stressors. For Greater Sage‐grouse in southwest Wyoming, USA, we projected oil and gas development footprints and climate‐induced vegetation changes 50 years into the future. Using a time‐series of planned oil and gas development and predicted climate‐induced changes in vegetation, we recalculated habitat selection maps to dynamically modify future habitat quantity, quality, and configuration. We simulated long‐term Sage‐grouse responses to habitat change by allowing individuals to adjust to shifts in habitat availability and quality. The use of spatially explicit individual‐based modeling offered a useful means of evaluating delayed indirect impacts of landscape change on wildlife population outcomes. The inclusion of movement and demographic responses to oil and gas infrastructure resulted in substantive changes in distribution and abundance when cumulated over several decades and throughout the regional population. When combined, additive development and climate‐induced vegetation changes reduced abundance by up to half of the original size. In our example, the consideration of only a single population stressor the final possible population size by as much as 50%. Multiple stressors and their cumulative impacts need to be broadly considered through space and time to avoid underestimating the impacts of multiple gradual changes and overestimating the ability of populations to withstand change.
Northern forest winters have lost cold, snowy conditions that are important for ecosystems and human communities
Authors: Contosta Alexandra R. , Casson Nora J. , Garlick Sarah , Nelson Sarah J. , Ayres Matthew P. , Burakowski Elizabeth A. , Campbell John , Creed Irena , Eimers Catherine , Evans Celia , Fernandez Ivan , Fuss Colin , Huntington Thomas , Patel Kaizad , Sanders‐DeMott Rebecca , Son Kyongho , Templer Pamela , Thornbrugh Casey 
Published: July 2019

AbstractWinter is an understudied but key period for the socioecological systems of northeastern North American forests. A growing awareness of the importance of the winter season to forest ecosystems and surrounding communities has inspired several decades of research, both across the northern forest and at other mid‐ and high‐latitude ecosystems around the globe. Despite these efforts, we lack a synthetic understanding of how winter climate change may impact hydrological and biogeochemical processes and the social and economic activities they support. Here, we take advantage of 100 years of meteorological observations across the northern forest region of the northeastern United States and eastern Canada to develop a suite of indicators that enable a cross‐cutting understanding of (1) how winter temperatures and snow cover have been changing and (2) how these shifts may impact both ecosystems and surrounding human communities. We show that cold and snow covered conditions have generally decreased over the past 100 years. These trends suggest positive outcomes for tree health as related to reduced fine root mortality and nutrient loss associated with winter frost but negative outcomes as related to the northward advancement and proliferation of forest insect pests. In addition to effects on vegetation, reductions in cold temperatures and snow cover are likely to have negative impacts on the ecology of the northern forest through impacts on water, soils, and wildlife. The overall loss of coldness and snow cover may also have negative consequences for logging and forest products, vector‐borne diseases, and human health, recreation, and tourism, and cultural practices, which together represent important social and economic dimensions for the northern forest region. These findings advance our understanding of how our changing winters may transform the socioecological system of a region that has been defined by the contrasting rhythm of the seasons. Our research also identifies a trajectory of change that informs our expectations for the future as the climate continues to warm.