bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolable CO2 Adducts of Polarized Alkenes: High Thermal Stability and Catalytic Activity for CO2 Chemical Transformation
Authors: Zhou Hui , Zhang Rui , Lu Xiao‐Bing 
Published: December 2018

AbstractVarious CO2 adducts of tetra‐hydropyrimidin‐2‐ylidene (THPE) derived from the commercially available 1, 5‐diazabicyclo[4.3.0]non‐5‐ene (DBN) were firstly synthesized. X‐ray single crystal analysis revealed the bent geometry of the binding CO2 having an O−C−O angle of 127.50∼129.51° for THPE−CO2 adducts. In situ FTIR experiments demonstrated that THPE−CO2 adducts had unprecedented thermal stability in DMSO, even at 100 °C without decomposition. It was found that the THPE−CO2 adducts were highly active in catalyzing the carboxylative cyclization of CO2 with propargylic alcohols under mild conditions, significantly higher than the previously reported organocatalysts. Various internal and terminal functionalized propargylic alcohols were tolerated in these processes to afford the corresponding α‐alkylidene cyclic carbonates in moderate to good yields with complete (Z)‐stereoselectivity. Isotope labeling, in combination with in‐situ FTIR and stoichiometric experiments, reveal that the catalytic reaction tends to proceed via the THPE−CO2‐mediated basic ionic pair mechanism.magnified image
Copper‐Catalyzed [3+2] Cycloaddition and Interrupted Fischer Indolization to Prepare Polycyclic Furo[2,3‐b]indolines from N‐Aryl Isatin Nitrones and Methylenecyclopropanes
Authors: Wu Si‐Yi , Chen Wei‐Li , Ma Xiao‐Pan , Liang Cui , Su Gui‐Fa , Mo Dong‐Liang 
Published: December 2018

AbstractVarious polycyclic furo[2,3‐b]indolines containing a cyclopropane ring have been prepared in moderate yields with high diastereoselectivity from N‐aryl isatin nitrones and methylenecyclopropanes using a copper‐catalyzed [3+2] cycloaddition and subsequent interrupted Fischer indolization strategy under mild reaction conditions. The obtained furo[2,3‐b]indolines were easily converted to piperidinone‐fused furo[2,3‐b]indolines by selective [1,3]‐rearrangement through N−O bond cleavage. Finally, two chiral polycyclic furo[2,3‐b]indolines were obtained by chiral auxiliary control.magnified image
Co(III)‐Catalyzed [4+1] Annulation of Amides with Allenes via C−H Activation
Authors: Boobalan Ramadoss , Santhoshkumar Rajagopal , Cheng Chien‐Hong 
Published: December 2018

AbstractA Co(III)‐catalyzed [4+1] annulation of amides with allenes to synthesize isoindolone and 1,5‐dihydro‐pyrrol‐2‐one derivatives is reported. A wide range of aromatic and vinylic amides react with allenes to give the corresponding annulation products in good to excellent yields. The mechanistic studies strongly support that the catalytic reaction proceeds through an amide‐directed C−H activation, followed by carbocobaltation of allene, β‐hydride elimination, and an intramolecular 1,2‐hydroamination.magnified image
Direct Assembly of Polysubstituted Furans via C(sp3)−H Bond Functionalization by Using Dimethyl Sulfoxide as a Dual Synthon
Authors: Liu Yufeng , Hu Yuqun , Cao Zhongzhong , Zhan Xi , Luo Weiping , Liu Qiang , Guo Cancheng 
Published: December 2018

AbstractAn unusual I2‐mediated triple C(sp3)−H functionalization reaction between aryl methyl ketones and dimethyl sulfoxide to form polysubstituted furans has been developed. In this transformation, dimethyl sulfoxide functions as a dual synthon via C(sp3)−H functionalization with formation of two C−C bonds, one C−O bond, and one C−S bond in a one‐step process. Iodine is crucial as promoter of the reaction, by which a number of ketones could be converted easily into 2,4,5‐trisubstituted furans. This provides an extremely simple and expeditious approach to high‐value‐added, biologically significant O‐heterocycles. Based on preliminary experiments, a plausible mechanism is proposed.magnified image
Enamines as Surrogates of Alkyl Carbanions for the Direct Conversion of Secondary Amides to α‐Branched Ketones
Authors: Liu Yong‐Peng , Wang Shu‐Ren , Chen Ting‐Ting , Yu Cun‐Cun , Wang Ai‐E , Huang Pei‐Qiang 
Published: December 2018

AbstractA direct transformation of secondary amides into α‐branched ketones with enamines as soft alkylation reagents was developed. In this reaction, enamines serve as surrogates of alkyl carbanions, rather than the conventional enolates equivalents in the Stork's reactions, which allowed for the easy introduction of alkyl groups with electrophilic functional groups. In the presence of 4 Å molecular sieves, the method can be extended to the one‐pot coupling of secondary amides with aldehydes to yield ketones.magnified image
Enantioselective Synthesis of CF3‐Containing 3,2’‐Pyrrolidinyl Spirooxindoles and Dispirooxindoles via Thiourea‐Catalyzed Domino Michael/Mannich [3+2] Cycloaddition Reactions
Authors: Lin Ye , Song Yong‐Xing , Du Da‐Ming 
Published: December 2018

AbstractAn efficient and practical organocatalytic asymmetric domino Michael/Mannich [3+2] cycloaddition of N‐2,2,2‐trifluoroethylisatin ketimines and arylidene azlactones by using a hydroquinine‐derived thiourea as the catalyst has been disclosed. Under mild conditions, a broad range of CF3‐containing 3,2’‐pyrrolidinyl spirooxindole/ dispirooxindole derivatives bearing four adjacent stereogenic centers including two vicinal spiro quaternary chiral centers were obtained in high yields (up to 99% yield) with excellent diastereoselectivities (>20:1 dr, in all case) and enantioselectivities (up to >99% ee).magnified image
Ion Conductivity Enhancement in Anti‐Spinel Li3OBr with Intrinsic Vacancies
Authors: Hussain Fiaz , Li Pai , Li Zhenyu , Yang Jinlong 
Published: December 2018

AbstractSolid electrolytes are expected to play an important role in modern electrochemical energy storage technologies. However, it is still very challenging to achieve a high Li‐ion conductivity in solid electrolytes. In this study, an intrinsic vacancy induced ion conductivity enhancement in a recently synthesized anti‐spinel structure of Li3OBr compared with its anti‐perovskite phase is reported. With a high stability, the intrinsic defective structure of anti‐spinel Li3OBr contains a high concentration of octahedral vacancies. Ab initio molecular dynamic simulations confirm that octahedral vacancies can lead to an extraordinarily high Li mobility (0.136 mS cm−1 at room temperature) in anti‐spinel Li3OBr. Such an ion conductivity enhancement mechanism opens a new avenue in solid electrolyte material design.
Tribo‐Induced Structural Transformation and Lubricant Dissociation at Amorphous Carbon–Alpha Olefin Interface
Authors: Li Xiaowei , Wang Aiying , Lee Kwang‐Ryeol 
Published: December 2018

AbstractAmorphous carbon (a‐C) combined with a fluid lubricant is capable of providing an ultra‐low friction state and thus achieving long lifetime and reliable operation. However, the understanding of the atomistic process occurring at the sliding friction interfaces, especially the interfacial structure transformation and lubricant dissociation at different contact states, is still not well understood. Here, using reactive molecular dynamics simulation, the friction behavior of a self‐mated a‐C system composited with different alpha olefins (AOs) as lubricants is comparatively investigated, and the results present that due to the co‐existence of tribo‐induced thermal and shearing effects, AOs exhibit different physicochemical behaviors at the a‐C–a‐C interface compared to that at the a‐C surface. Although introducing AOs into a self‐mated a‐C system reduces the friction coefficient, its efficiency strongly relies on the AO variety and contact pressure. The pressure‐driven dissociation of AOs passivates the friction interface, resulting in the evolution of the primary friction mechanism from hydrodynamic lubrication to interfacial passivation that is not accessible by experimental characterization. The corresponding scission sites of different AOs are demonstrated, which enriches the fundamental understanding on sliding friction behavior and offers a comprehensive design criterion for lubricants (viscosity, chain length, and bond saturated states) and a‐C to achieve nearly frictionless sliding interface.
Preparation and absorption properties of poly (acrylic acid‐co‐acrylamide)/graphite oxide superabsorbent composite
Authors: Zhu Linhui , Wang Fangyuan , Liu Yu , Tang Hongduo , Guan Chengdong 
Published: December 2018

AbstractPoly (acrylic acid‐co‐acrylamide)/graphite oxide (P (AA‐co‐AM)/GO) superabsorbent composite was prepared by solution intercalation polymerization of acrylic acid (AA), acrylamide (AM), and graphite oxide (GO). The composite was characterized by Fourier transform infrared spectroscopy, powder X‐ray diffraction, scanning electron microscopy, transmission electron microscope, thermogravimetric analysis , and differential scanning calorimetry. The effect of reaction conditions, including the mass ratio of monomers, dosages of cross‐linker, initiator, and GO as well as the neutralization degree of AA, on water and saline absorption was studied. Water retention properties of the composite were also discussed. It showed that interactions between GO and P (AA‐co‐AM) copolymer were the intermolecular hydrogen bonds. Thermal stabilities of the composite could be improved by the incorporation of GO. Besides, there was a remarkable improvement of absorption capacities owing to the incorporation of GO. Absorption capacities of water and 0.9% NaCl could be improved from 141.7 and 33.6 g/g, respectively, to 809.6 and 131.4 g/g, respectively, as the dosage of GO increased from 0 to 0.1 g. In addition, there was a remarkable improvement of water retention rates. Water retention rates of P(AA‐co‐AM)/GO and P(AA‐co‐AM) were 65.9% and 53.8%, respectively, after drying at 25°C for 8 hr.
3D Printing of Anisotropic Hydrogels with Bioinspired Motion
Authors: Arslan Hakan , Nojoomi Amirali , Jeon Junha , Yum Kyungsuk 
Published: December 2018

AbstractMotion in biological organisms often relies on the functional arrangement of anisotropic tissues that linearly expand and contract in response to external signals. However, a general approach that can implement such anisotropic behavior into synthetic soft materials and thereby produce complex motions seen in biological organisms remains a challenge. Here, a bioinspired approach is presented that uses temperature‐responsive linear hydrogel actuators, analogous to biological linear contractile elements, as building blocks to create three‐dimensional (3D) structures with programmed motions. This approach relies on a generalizable 3D printing method for building 3D structures of hydrogels using a fugitive carrier with shear‐thinning properties. This study demonstrates that the metric incompatibility of an orthogonally growing bilayer structure induces a saddle‐like shape change, which can be further exploited to produce various bioinspired motions from bending to twisting. The orthogonally growing bilayer structure undergoes a transition from a stretching‐dominated motion to a bending‐dominated motion during its shape transformation. The modular nature of this approach, together with the flexibility of additive manufacturing, enables the fabrication of multimodular 3D structures with complex motions through the assembly of multiple functional components, which in turn consist of simple linear contractile elements.
Matrix Rigidity‐Dependent Regulation of Ca2+ at Plasma Membrane Microdomains by FAK Visualized by Fluorescence Resonance Energy Transfer
Authors: Kim Tae‐Jin , Lei Lei , Seong Jihye , Suh Jung‐Soo , Jang Yoon‐Kwan , Jung Sang Hoon , Sun Jie , Kim Deok‐Ho , Wang Yingxiao 
Published: December 2018

AbstractThe dynamic regulation of signal transduction at plasma membrane microdomains remains poorly understood due to limitations in current experimental approaches. Genetically encoded biosensors based on fluorescent resonance energy transfer (FRET) can provide high spatiotemporal resolution for imaging cell signaling networks. Here, distinctive regulation of focal adhesion kinase (FAK) and Ca2+ signals are visualized at different membrane microdomains by FRET using membrane‐targeting biosensors. It is shown that rigidity‐dependent FAK and Ca2+ signals in human mesenchymal stem cells (hMSCs) are selectively activated at detergent‐resistant membrane (DRM or rafts) microdomains during the cell–matrix adhesion process, with minimal activities at non‐DRM domains. The rigidity‐dependent Ca2+ signal at the DRM microdomains is downregulated by either FAK inhibition or lipid raft disruption, suggesting that FAK and lipid raft integrity mediate the in situ Ca2+ activation. It is further revealed that transient receptor potential subfamily M7 (TRPM7) participates in the mobilization of Ca2+ signals within DRM regions. Thus, the findings provide insights into the underlying mechanisms that regulate Ca2+ and FAK signals in hMSCs under different mechanical microenvironments.
White‐Light‐Emitting Melamine‐Formaldehyde Microspheres through Polymer‐Mediated Aggregation and Encapsulation of Graphene Quantum Dots
Authors: Wu Youshen , Zhang Hui , Pan Aizhao , Wang Qi , Zhang Yanfeng , Zhou Guijiang , He Ling 
Published: December 2018

AbstractGraphene quantum dot (GQD) encapsulated melamine‐formaldehyde (MF) polymer microspheres with uniform particle size and tunable high‐quality white‐light emissions are prepared via a polymer‐mediated GQD assembly and encapsulation strategy. In solution, GQDs are first aggregated with MF prepolymer through electrostatic interaction and further encapsulated inside the microspheres formed by polymerization of MF prepolymer under acid catalysis and heating. During this process, the aggregated GQDs are fixed in the MF polymer matrix with their emission extended from blue to full visible range, presenting bright white luminescence under ultraviolet excitation. The prepared white‐light‐emitting GQD‐MF microspheres exhibit uniform morphology with an average particle size of 2.0 ± 0.08 µm and their luminescence properties are effectively regulated by the doping concentration of GQDs in the MF polymer matrix. A series of white‐light‐emitting GQD‐MF microspheres with quantum yields from 0.83 to 0.43, Commission Internationale de L'Eclairage coordinates from (0.28, 0.28) to (0.33, 0.32), and color rendering index from 0.75 to 0.88 are obtained with excellent photostability and thermal stability. By dispersing the GQD‐MF microspheres in cross‐linked polydimethylsiloxane matrix, flexible film with dual functions of high‐quality white‐light‐emitting and light diffusion is obtained and successfully applied for white light‐emitting diode fabrication.
Enhanced Thermoelectric Properties for PEDOT:PSS/Undoped Ge Thin‐Film Bilayered Heterostructures
Authors: Lee Dongwook , Zhou Jiawei , Chen Gang , Shao‐Horn Yang 
Published: December 2018

AbstractModulation doping is one of the strategies to improve thermoelectric power factors of nanocomposites and thin‐film bilayered heterostructures by effectively increasing electrical conductivity. Here, it is reported that thin‐film heterostructures of heavily doped p‐type organic conducting polymer, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and undoped thin‐film Ge can enhance thermoelectric power factor by modulation doping. The maximum power factor and Seebeck coefficient of the bilayered heterostructures are 154 µW m−1 K−2 and 398 µV K−1, respectively, corresponding to 47‐fold and 41‐fold increases compared to those of bulk PEDOT:PSS and 64‐fold increase compared to power factor of undoped Ge. The enhancements in power factor and Seebeck coefficient are quantitatively described by the hole transfer from PEDOT:PSS to Ge, which takes into account the band alignment at the interface detected by Kraut's method. Agreement between the simulation and experiment results also implies predictability of thermoelectric performances of nanoscale bilayered heterostructures in general, when band offset, Fermi level, and individual electronic properties are available. This work can be further extended to predict performance of other nanoscale combinations of thermoelectric and other electronic materials in general.
Silicon‐grafted Ag/AgX/rGO nanomaterials (X = Cl or Br) as dip‐photocatalysts for highly efficient p‐nitrophenol reduction and paracetamol production
Authors: Attia Yasser A. , Mohamed Yasser M.A. 
Published: December 2018

In this work, plasmonic Ag/AgX/rGO (X = Cl or Br) nano‐photocatalysts were grafted with silicon by adding trimethylsilyl chloride as silicon precursor. The synthesized Ag/AgX/rGO‐Si hybrids showed a large improvement of photocatalytic activity towards the synthesis of p‐aminophenol (PAP) as well as paracetamol (acetaminophen; APAP) through the photoreduction of p‐nitrophenol (PNP). The prepared catalysts Ag/AgX/rGO were characterized using SEM, XRD, FTIR and the reduction reaction of p‐nitrophenol was monitored by UV–Vis measurements, GC/MS and 1HNMR data. From the results, it was demonstrated that the rate order of reduction process of the PNP to PAP and to APAP under visible light irradiation of the samples was as follows; Ag/AgBr/rGO‐Si > Ag/AgCl/rGO‐Si > Ag/AgBr/rGO > Ag/AgCl/rGO. The reaction mechanism had been postulated that was supported with the spectroscopic data. In addition, the catalysts were recovered from the reaction medium and re‐used in three cycles that indicated the reusability and stability of the catalysts. This study was featured by the following; i) fast reaction, ii) the reduction of p‐nitrophenol to paracetamol was performed in a facile one‐pot reaction compared to previous approaches that tends to reduce the production cost, and iii) investigations on the catalytic properties of Ag/AgX/rGO in organic transformations open the door to find a benefice of these catalysts in other organic reactions and in the development in the synthesis of pharmaceutical products.
Environmental and strength‐enhanced nanosilica‐based composite gel for well temporary plugging in high‐temperature reservoirs
Authors: Jia Hu , Yang Xin‐Yu 
Published: December 2018

AbstractPolymer gel is widely used for well temporary plugging in petroleum engineering. This paper researched on a novel environmental and strength‐enhanced composite gel plug prepared by the nanosilica, the polymer hydrolyzed polyacrylamide and environmental friendly crosslinker polyethyleneimine, and the effect of strength enhancement and thermal stability mechanism of the nanosilica in this system was investigated. The experiments results showed that with the increase of the nanosilica concentration, the elastic modulus and viscous modulus, the stress under the same strain and the gel decompose temperature both increased. For the system containing 8% nanosilica, the elastic modulus is about 14 times than the one without it, whereas the viscous modulus is only 70.98 Pa, which is favorable for lowering the absorption damage to the formation. The strain–stress experiment results showed that to reach 45% strain, the stress of 44.6 KPa needed to be loaded (for composite gel with 8 wt% nanosilica) and during the compress process, the gel deformed with no break and after the stress was released, it got back to the original shape soon, indicating its good mechanical and elasticity performance. The differential scanning calorimetry (DSC) results revealed that the after adding nanosilica, more free water can be kept so that the system's thermal stability was effectively improved. The scanning electron microscopic images displayed that the nanosilica particles closely adhere to the polymer network; thus, the 3D structure of the composite gel became more compact and the gel's strength was improved. In the last section, some recommendations for well temporary plugging are proposed.
Core‐Shell Structured Cobalt Sulfide/Cobalt Aluminum Hydroxide Nanosheet Arrays for Pseudocapacitor Application
Authors: Cha Ji‐Hyun , Park Eun Bi , Han Sang Wook , Kim Young Dok , Jung Duk‐Young 
Published: December 2018

AbstractThe direct synthesis of nanostructured electrode materials on three‐dimensional substrates is important for their practical application in electrochemical cells without requiring the use of organic additives or binders. In this study, we present a simple two‐step process to synthesize a stable core–shell structured cobalt sulfide/cobalt aluminum hydroxide nanosheet (LDH‐S) for pseudocapacitor electrode application. The cobalt aluminum layered double hydroxide (CoAl‐LDH) nanoplates were synthesized in basic aqueous solution with a kinetically‐controlled thickness. Owing to the facile diffusion of electrolytes through the nanoplates, thin CoAl‐LDH nanoplates have higher specific capacitance values than thick nanoplates. The as‐grown CoAl‐LDH nanoplates were transformed into core–shell structured LDH‐S nanosheets by a surface modification process in Na2S aqueous solution. The chemically robust cobalt sulfide (CoS) shell increased the electrochemical stability compared to the sulfide‐free CoAl‐LDH electrodes. The LDH‐S electrodes exhibited high electrochemical performance in terms of specific capacitance and rate capability with a galvanostatic discharge of 1503 F g−1 at a current density of 2 A g−1 and a specific capacitance of 91 % at 50 A g−1.
Cost-effectiveness analysis of a multicentre randomized clinical trial comparing surgery with conservative management for recurrent and ongoing diverticulitis (DIRECT trial)
Authors: Bolkenstein H E , de Wit G A , Consten E C J , Van de Wall B J M , Broeders I A M J , Draaisma W A 
Published: December 2018

Abstract

Background
The results of the DIRECT trial, an RCT comparing conservative management with elective sigmoid resection in patients with recurrent diverticulitis or persistent complaints, showed that elective sigmoid resection leads to higher quality of life. The aim of this study is to determine the cost-effectiveness of surgical treatment at 1- and 5-year follow-up from a societal perspective.

Methods
Clinical effectiveness and resource use were derived from the DIRECT trial. The actual resource use and quality of life (EQ-5D-3L™ score) were documented prospectively per individual patient and analysed according to the intention-to-treat principle for up to 5 years after randomization. The main outcome was the incremental cost-effectiveness ratio (ICER), expressed as costs per quality-adjusted life-year (QALY).

Results
The study included 106 patients, of whom 50 were randomized to surgery and 56 to conservative treatment. At 1- and 5-year follow-up an incremental effect (QALY difference between groups) of 0·06 and 0·43 respectively was found, and an incremental cost (cost difference between groups) of €6957 and €2674 respectively, where surgery was more expensive than conservative treatment. This resulted in an ICER of €123 365 per additional QALY at 1-year follow-up, and €6275 at 5 years. At a threshold of €20 000 per QALY, operative treatment has 0 per cent probability of being cost-effective at 1-year follow-up, but a 95 per cent probability at 5 years.

Conclusion
At 5-year follow-up, elective sigmoid resection in patients with recurring diverticulitis or persistent complaints was found to be cost-effective. Registration number: NTR1478 (www.trialregistrer.nl).