bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fiber prepared via swelling and thermal cross‐linking as reusable Fenton catalyst for methylene blue decolorization
Authors: Lv Yuanyuan , Xu Naiku , Feng Yan , Lu Yuyao 
Published: June 2018

AbstractSwelling was first adopted to transform the close‐packed structure of as‐spun poly (acrylic acid‐co‐hydroxyethyl methacrylate) fiber prepared via wet spinning into loose and porous structure. This structure enabled the fiber to carry a large number of iron ions within a certain period of time. Thermal cross‐linking was subsequently conducted to prevent methylene blue solution leaching iron ions out from the fiber. The Fenton catalyst based on the combination of the fiber and iron ions prepared via swelling and thermal cross‐linking exhibited excellent reusability in decolorizing MB. The research results showed that more than 95% of MB could be decolorized from 10 ml of MB solution with the concentration of 20 mg/L in the presence of 2 μl of H2O2 and about 5 mg of virgin catalyst, and even when the catalyst was used for the tenth time, MB decolorization efficiency still reached up to 88%. In addition, the difference of swelling processes also caused the result that the corresponding catalysts had different thermal properties.
Electrochemistry and Solid‐State Chemistry of NaMeO2 (Me = 3d Transition Metals)
Authors: Kubota Kei , Kumakura Shinichi , Yoda Yusuke , Kuroki Kazutoshi , Komaba Shinichi 
Published: June 2018

AbstractSodium 3d transition metal oxides for Na‐ion batteries have attracted attention of battery researchers because of their new chemistries and abundant material resources in the earth. Some companies have also developed Na‐ion battery prototypes mainly consisting of a layered oxide as a positive electrode material and hard carbon as the negative one for practical use. In this article, progress of Na‐containing layered transition‐metal oxides is reviewed in terms of fundamental chemistry and technology aspects for future batteries as a post Li‐ion battery. To realize practical positive electrode materials is still challenging and the practical issues are discussed. In this context the authors propose strategies for designing layered transition‐metal oxide materials toward realization of practical Na‐ion batteries.
Mucus T helper 2 biomarkers predict chronic rhinosinusitis disease severity and prior surgical intervention
Authors: Turner Justin H. , Li Ping , Chandra Rakesh K. 
Published: June 2018

BackgroundChronic rhinosinusitis (CRS) is a diverse clinical syndrome with a heterogeneous pathophysiology. Early attempts to identify CRS endotypes and biomarkers have largely relied on analysis of surgically obtained tissue, thus limiting their practical utility. This study examined the ability of mucus T helper 2 (Th2) biomarkers to predict CRS disease severity and clinical characteristics.MethodsCRS (n = 90) and healthy control subjects (n = 17) were prospectively enrolled prior to surgical intervention and mucus levels of interleukin (IL)‐4, IL‐5, and IL‐13 were determined using a multiplex cytometric bead assay. Data for relevant cytokines was then scaled, normalized, and later combined to develop standardized metrics indicative of Th2‐associated inflammation. Th2‐high and Th2‐low subgroups were consequently identified and validated against factors associated with disease severity and clinical outcomes.ResultsMucus levels of IL‐5 and IL‐13 were elevated in CRS subjects compared to controls, while no significant difference was noted for IL‐4. IL‐5 and IL‐13 high CRS were associated with worse objective measures of disease severity and greater rates of revision surgery. Similar relationships were noted for both cytokines when CRS with nasal polyps (CRSwNP) patients were analyzed separately. Th2‐high CRS and Th2‐low CRS were then categorized using a scaled IL‐5/IL‐13 metric. Th2‐high CRS was characterized by an increased number of subjects with nasal polyps and comorbid asthma, and worse symptom and computed tomography (CT) scores.ConclusionThe Th2‐associated cytokines, IL‐5 and IL‐13, are detectable in sinonasal mucus and their levels can be used to define Th2‐high and Th2‐low CRS. Identification of Th2‐high and Th2‐low endotypes using mucus‐based biomarkers could facilitate stratification of CRS subgroups and guide personalized therapies.
Complete Switch of Reaction Specificity of an Aldolase by Directed Evolution In Vitro: Synthesis of Generic Aliphatic Aldol Products
Authors: Junker Sebastian , Roldan Raquel , Joosten Henk‐Jan , Clapés Pere , Fessner Wolf‐Dieter 
Published: June 2018

AbstractA structure‐guided engineering of fructose‐6‐phosphate aldolase was performed to expand its substrate promiscuity toward aliphatic nucleophiles, that is, unsubstituted alkanones and alkanals. A “smart” combinatorial library was created targeting residues D6, T26, and N28, which form a binding pocket around the nucleophilic carbon atom. Double‐selectivity screening was executed by high‐performance TLC that allowed simultaneous determination of total activity as well as a preference for acetone versus propanal as competing nucleophiles. D6 turned out to be the key residue that enabled activity with non‐hydroxylated nucleophiles. Altogether 25 single‐ and double‐site variants (D6X and D6X/T26X) were discovered that show useful synthetic activity and a varying preference for ketone or aldehyde as the aldol nucleophiles. Remarkably, all of the novel variants had completely lost their native activity for cleavage of fructose 6‐phosphate.
An Interrupted Pummerer/Nickel‐Catalysed Cross‐Coupling Sequence
Authors: Aukland Miles H. , Talbot Fabien J. T. , Fernández‐Salas José A. , Ball Matthew , Pulis Alexander P. , Procter David J. 
Published: June 2018

AbstractAn interrupted Pummerer/nickel‐catalysed cross‐coupling strategy has been developed and used in the elaboration of styrenes. The operationally simple method can be carried out as a one‐pot process, involves the direct formation of stable alkenyl sulfonium salt intermediates, utilises a commercially available sulfoxide, catalyst, and ligand, operates at ambient temperature, accommodates sp‐, sp2‐, and sp3‐hybridised organozinc coupling partners, and delivers functionalised styrene products in high yields over two steps. An interrupted Pummerer/cyclisation approach has also been used to access carbo‐ and heterocyclic alkenyl sulfonium salts for cross‐coupling.
Ligandenaktivierte enantioselektive C‐H‐Aktivierung von Tetrahydrochinolinen und gesättigten Aza‐Heterocyclen durch RhI
Authors: Greßies Steffen , Klauck Felix J. R. , Kim Ju Hyun , Daniliuc Constantin G. , Glorius Frank 
Published: June 2018

AbstractDie erste Rhodium(I)‐katalysierte enantioselektive intermolekulare C
‐H‐Aktivierung verschiedener gesättigter Aza‐Heterocyclen einschließlich Tetrahydrochinolinen, Piperidinen, Piperazinen, Azetidinen, Pyrrolidinen, Azepanen und anderen wird beschrieben. Die Kombination eines Rhodium(I)‐Präkatalysators und eines chiralen einzähnigen Phosphonitliganden ist ein leistungsfähiges katalytisches System, um aus einfachen Ausgangsmaterialien eine Vielzahl von wichtigen enantiomeren‐angereicherten Heterocyclen herzustellen. Die C
‐H‐Aktivierung von Tetrahydrochinolinen ist aufgrund der benachbarten C
‐H‐Bindung besonders anspruchsvoll. Diese redoxneutrale Methode bietet einen neuen Syntheseweg für α‐N‐arylierte Heterocyclen mit hoher Chemoselektivität und Enantioselektivität von bis zu 97 % ee.
Sequencing 5‐Hydroxymethyluracil at Single‐Base Resolution
Authors: Kawasaki Fumiko , Martínez Cuesta Sergio , Beraldi Dario , Mahtey Areeb , Hardisty Robyn E. , Carrington Mark , Balasubramanian Shankar 
Published: June 2018

Abstract5‐hydroxymethyluracil (5hmU) is formed through oxidation of thymine both enzymatically and non‐enzymatically in various biological systems. Although 5hmU has been reported to affect biological processes such as protein–DNA interactions, the consequences of 5hmU formation in genomes have not been yet fully explored. Herein, we report a method to sequence 5hmU at single‐base resolution. We employ chemical oxidation to transform 5hmU to 5‐formyluracil (5fU), followed by the polymerase extension to induce T‐to‐C base changes owing to the inherent ability of 5fU to form 5fU:G base pairing. In combination with the Illumina next generation sequencing technology, we developed polymerase chain reaction (PCR) conditions to amplify the T‐to‐C base changes and demonstrate the method in three different synthetic oligonucleotide models as well as part of the genome of a 5hmU‐rich eukaryotic pathogen. Our method has the potential capability to map 5hmU in genomic DNA and thus will contribute to promote the understanding of this modified base.
Crystallographic Evidence for a Sterically Induced Ferryl Tilt in a Non‐Heme Oxoiron(IV) Complex that Makes it a Better Oxidant
Authors: Rasheed Waqas , Draksharapu Apparao , Banerjee Saikat , Young Victor G. , Fan Ruixi , Guo Yisong , Ozerov M. , Nehrkorn Joscha , Krzystek J. , Telser Joshua , Que Lawrence 
Published: June 2018

AbstractOxoiron(IV) units are often implicated as intermediates in the catalytic cycles of non‐heme iron oxygenases and oxidases. The most reactive synthetic analogues of these intermediates are supported by tetradentate tripodal ligands with N‐methylbenzimidazole or quinoline donors, but their instability precludes structural characterization. Herein we report crystal structures of two [FeIV(O)(L)]2+ complexes supported by pentadentate ligands incorporating these heterocycles, which show longer average Fe–N distances than the complex with only pyridine donors. These longer distances correlate linearly with log k2′ values for O‐ and H‐atom transfer rates, suggesting that weakening the ligand field increases the electrophilicity of the Fe=O center. The sterically bulkier quinoline donors are also found to tilt the Fe=O unit away from a linear N‐Fe=O arrangement by 10°.
Cinchonamine Squaramide Catalyzed Asymmetric aza‐Michael Reaction: Dihydroisoquinolines and Tetrahydropyridines
Authors: Roy Tarun Kumar , Parhi Biswajit , Ghorai Prasanta 
Published: June 2018

AbstractThe first example of a chiral cinchona‐squaramide catalyzed enantioselective intramolecular aza‐Michael addition for the synthesis of dihydroisoquinolines and tetrahydropyridines has been developed. In general, good yields and excellent enantioselctivities were observed. Broad classes of Michael acceptors, such as enones, esters, thioesters, and Weinreb amides, were successful substrates. The possibility of recycling the catalysts has also been demonstrated. An oxidation of combined enamine and keto functionalities on chiral dihydroisoquinolines leads to a single diastereomer of an architecturally unprecedented tetracyclic core without loss in enantioselectivity.
Stable Diporphyrinylaminyl Radical and Nitrenium Ion
Authors: Shimizu Daiki , Fujimoto Keisuke , Osuka Atsuhiro 
Published: June 2018

AbstractNitrenium ions, isoelectronic nitrogen counterparts of carbenes, are important intermediates in various biological and chemical processes. Herein we describe the first synthesis and characterization of a stable nitrenium ion without resonance stabilization by adjoining amino groups. Namely, a stable salt of a diporphyrinylnitrenium ion was synthesized by stepwise oxidation of the corresponding diporphyrinylamine through a stable aminyl radical. The nitrenium ion exhibits characteristic features such as a singlet ground state, enhanced double‐bond character of the central C−N bonds, no reactivity toward water and methanol, and negative solvatochromic behavior.
Continuous Visible‐Light Photoflow Approach for a Manganese‐Catalyzed (Het)Arene C−H Arylation
Authors: Liang Yu‐Feng , Steinbock Ralf , Yang Long , Ackermann Lutz 
Published: June 2018

AbstractManganese photocatalysts enabled versatile room‐temperature C−H arylation reactions by means of continuous visible‐light photoflow, thus allowing for efficient C−H arylations in 30 minutes with ample scope. The robustness of the manganese‐catalyzed photoflow strategy was shown by visible light‐induced gram‐scale synthesis, clearly outperforming the batch performance.
Ligand‐Enabled Enantioselective C–H Activation of Tetrahydroquinolines and Saturated Aza‐Heterocycles by RhI
Authors: Greßies Steffen , Klauck Felix J. R. , Kim Ju Hyun , Daniliuc Constantin G. , Glorius Frank 
Published: June 2018

AbstractThe first rhodium(I)‐catalyzed enantioselective intermolecular C
–H activation of various saturated aza‐heterocycles including tetrahydroquinolines, piperidines, piperazines, azetidines, pyrrolidines, and azepanes is presented. The combination of a rhodium(I) precatalyst and a chiral monodentate phosphonite ligand is shown to be a powerful catalytic system to access a variety of important enantio‐enriched heterocycles from simple starting materials. Notably, the C
–H activation of tetrahydroquinolines is especially challenging due to the adjacent C
−H bond. This redox‐neutral methodology provides a new synthetic route to α‐N‐arylated heterocycles with high chemoselectivity and enantioselectivity up to 97 % ee.
Palladium‐anchored multidentate SBA‐15/di‐urea nanoreactor: A highly active catalyst for Suzuki coupling reaction
Authors: Rohani Sahar , Mohammadi Ziarani Ghodsi , Badiei Alireza , Ziarati Abolfazl , Jafari Maryam , Shayesteh Alireza 
Published: June 2018

Modification of mesoporous silica was carried out by reaction of SBA‐15 with di‐urea‐based ligand. Next, with the help of this ligand, palladium ions were anchored within the multidentate SBA‐15/di‐urea pore channels with high dispersion. The SBA‐15/di‐urea/Pd catalyst was characterized using various techniques. Theoretical calculations indicated that each palladium ion was strongly interacted with one nitrogen and two oxygen atoms from the multidentate di‐urea ligand located in SBA‐15 channels and these interactions remained during the catalytic cycle. These results are in good agreement with those of hot filtration test: the palladium ions have very high stability against leaching from the SBA‐15/di‐urea support. The catalytic performance of SBA‐15/di‐urea/Pd nanostructure was examined for the Suzuki coupling reaction of phenylboronic acid and electronically diverse aryl halides under mild conditions with a minimal amount of Pd (0.26 mol%). Compared to previous reports, this protocol afforded some advantages such as short reaction times, high yields of products, catalyst stability without leaching, easy catalyst recovery and preservation of catalytic activity for at least six successive runs.
Recovery and Recycling of Isopropyl Alcohol Used in Biodiesel Production From Yellow Mustard Oil
Authors: Sinichi Sayeh , Diosady Levente L. 
Published: June 2018

AbstractThe recovery of solvents used during biodiesel synthesis is an important factor in the economic feasibility and sustainability of the entire process. In this study, we looked at the use of isopropyl alcohol (IPA) for oil extraction and biodiesel production, as well as its potential for recovery and recycling. We found that multistage extraction improved oil recovery, with up to 86% oil yield using four stages of extraction at an IPA:mustard flour (volume:weight) ratio of 1.5:1 at room temperature. Using acid–base‐catalyzed transesterification, 99% of the mustard oil was converted to biodiesel. At the end of this process, IPA was recovered from the azeotrope by salting out using potassium carbonate or sodium carbonate. The solubility behavior of the components was evaluated by means of ternary‐phase diagrams of IPA/water/sodium carbonate and IPA/water/potassium carbonate, which determined their liquid–liquid–solid equilibrium constants at ambient pressure and at room temperature. Using 20% (w:w) potassium carbonate, 95% of the IPA was recovered at 99% purity from a starting mixture of IPA containing 13% water. Azeotropic distillation of the IPA–water azeotrope with 10% potassium carbonate resulted in the recovery of 99% of the IPA at 94% purity. These results suggest that IPA is not only a suitable solvent for mustard‐oil extraction but also for salt‐enhanced azeotropic distillation resulting in near‐complete recovery from aqueous solutions.
Effect of surface chemistry and morphology of silica on the thermal and mechanical properties of silicone elastomers
Authors: Tong Yuejing , Liu Hangzhong , Chen Aicheng , Guan Huaimin , Kong Junhua , Liu Songlin , He Chaobin 
Published: June 2018

ABSTRACTIn this study, high‐temperature vulcanized silicone rubbers (HTV‐SRs) using fumed silica (FSi), precipitated silica (PSi), and modified precipitated silica (MPSi) as reinforcing fillers were prepared. The effect of morphology and surface chemistry of the silica on the thermal and mechanical properties of the resultant silicone rubbers was investigated using curing rheometer, scanning electron microscopy, mechanical test, and dynamic mechanical analysis. The thermo‐oxidative stability and solvent resistance of the vulcanized silicone rubbers were further evaluated via heat ageing test, extraction, and swelling experiments. It is shown that the mechanical properties (tensile modulus and tensile strength) of the as‐prepared HTV‐SRs are in the order of FSi > PSi > MPSi, which could be attributed to the molecular interaction between the filler and the matrix. FSi has the highest surface area, which enhances the hydrogen bonding interaction between the filler and the silicone matrix; while MPSi, in which part of SiOH groups have been consumed during modification, shows the weakest interaction among the three. The filler–matrix interaction could also explain the lowest swelling and sol fraction in FSi‐filled HTV‐SR, and the low viscosity and good processibility of PSi‐ and MPSi‐filled HTV‐SR. Furthermore, it is also shown that the MPSi‐filled HTV‐SR exhibits the highest retention of mechanical properties after thermal aging at 250 °C for 24 h, which could be attributed to the lowest acidity of the fillers. The possible mechanism for acid catalyzed hydrolytic chain scission and intramolecular chain backbiting has been proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46646.
Epoxy composites modified with microfibers of potassium polytitanates
Authors: Mostovoy Anton Stanislavovich , Kadykova Yulia Aleksandrovna , Bekeshev Amirbek Zarlykovich , Tastanova Lyazzat Knashevna 
Published: June 2018

ABSTRACTThe research we conducted shows the possibility of the directed adjustment of epoxy composite performance characteristics through the application of small additives of potassium polytitanate whiskers, the introduction of polyfunctional plasticizers with chemical and mechanical methods of activation of the whole composition and its components; this ensured the creation of a new generation of epoxy composites with high‐performance properties (breaking tension = 116 MPa and modulus of elasticity at bending = 3150 MPa, destructive tension under compression = 95 MPa, impact strength = 18 kJ/m2 that meets the requirements of most industries. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46651.
A new approach for flexible PBAT/PLA/CaCO3 films into agriculture
Authors: Rocha Daniel Belchior , Souza de Carvalho Jéssika , de Oliveira Sueli Aparecida , dos Santos Rosa Derval 
Published: June 2018

ABSTRACTThe use of flexible films in agriculture has increased intensely in the last 15 years bringing benefits to producers. However, environmental impacts increased due to their incorrect post‐use disposal which leads the degradable films to emerge as an alternative. The production films of poly(butylene adipate‐co‐terephthalate) and poly(lactic acid) reinforced with calcium carbonate (CaCO3) was studied focusing on producing lower cost materials and flexible films. Four different films (reinforcement compositions) were prepared by melt extrusion with 10 and 20 wt % of CaCO3. Mechanical and thermal properties, crystallinity, water absorption, and soil degradation, were evaluated. The addition of reinforcement leads to improved compatibility between the polymers in the matrix, which usually presented phase segregation. The films showed better mechanical properties with the addition of CaCO3. Highly orientated amorphous structures were obtained leading to low water absorption and low degradation in the simulated soil. This low degradation, suggests that the obtained films would be of interest in flexible mulch films manufacturing, particularly for Muridori plantation system, where long‐term plantations are needed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46660.
Influence of Laponite RD on the properties of poly(vinyl alcohol) hydrogels
Authors: Morariu Simona , Bercea Maria , Brunchi Cristina‐Eliza 
Published: June 2018

ABSTRACTPoly(vinyl alcohol) (PVA) hydrogels were prepared in the presence/absence of Laponite RD (LRD) by using glutaraldehyde (GL) as chemical crosslinker. The effect of GL concentration (CHO/OH ratio between 0.02 and 0.38) and of clay addition on the PVA hydrogel properties was investigated. The swollen hydrogels showed good transparency and flexibility. LRD incorporation into the PVA hydrogel, revealed by Fourier transform infrared spectroscopy, led to a significant increase of the roughness of the dried hydrogel surface (about two times), as established by atomic force microscopy. The swelling ability was affected in a small extent by the clay addition. The elastic modulus decreased from 4680 to 3340 Pa and from 2195 to 1603 Pa by addition of 0.5% LRD into PVA hydrogels obtained with CHO/OH ratio of 0.02 and 0.06, respectively. The LRD addition reduced the gelation time determined by in situ rheological monitoring of PVA crosslinking reaction. The experimental investigations showed that there is an optimum CHO/OH ratio of 0.02 for which the PVA/LRD hybrid hydrogel presents the properties required by a targeted application, as for example support material for wound dressings. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46661.
Blocked melamine–urea–formaldehyde resins and their usage in agglomerated cork panels
Authors: Antunes Ana , Gomes Ana , Paiva Nádia , Ferra João , Martins Jorge , Carvalho Luísa , Barros‐Timmons Ana , Magalhães Fernão D. 
Published: June 2018

ABSTRACTCaprolactam and o‐p‐toluenesulfonamide are tested as chain‐growth blockers for melamine–urea–formaldehyde (MUF) resins, in an attempt to reduce the crosslinking density of the cured resin and hence improve its flexibility. Agglomerated cork panels, for which flexibility is a technical demand, were produced with the modified resins and tested. The blockers were added at three different steps in the synthesis process: methylolation, condensation, and at the end of the synthesis. Besides evaluation of standard properties, resins were characterized using gel permeation chromatography and Fourier transform infrared. Blocked resins showed better storage stability and improved water tolerance, especially when caprolactam was employed. When used as binders in agglomerated cork panels, the blocked resins allowed for significantly better flexibility, evaluated in terms of mandrel bending test. The tensile resistance of the panels remained well within the desired limits for this type of material. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46663.