bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of Ultrathin, Continuous Metal–Organic Framework Membranes on Flexible Polymer Substrates
Authors: Hou Jingwei , Sutrisna Putu D. , Zhang Yatao , Chen Vicki 
Published: February 2016

AbstractMetal–organic framework (MOF) materials have an enormous potential in separation applications, but to realize their potential as semipermeable membranes they need to be assembled into thin continuous macroscopic films for fabrication into devices. By using a facile immersion technique, we prepared ultrathin, continuous zeolitic imidazolate framework (ZIF‐8) membranes on titania‐functionalized porous polymeric supports. The coherent ZIF‐8 layer was surprisingly flexible and adhered well to the support, and the composite membrane could sustain bending and elongation. The membranes exhibited molecular sieving behavior, close to the theoretical permeability of ZIF‐8, with hydrogen permeance up to 201×10−7 mol m−2 s−1 Pa−1 and an ideal H2/CO2 selectivity of 7:1. This approach offers significant opportunities to exploit the unique properties of MOFs in the fabrication of separation and sensing devices.
Organocatalysis by Networks of Cooperative Hydrogen Bonds: Enantioselective Direct Mannich Addition to Preformed Arylideneureas
Authors: Lillo Victor J. , Mansilla Javier , Saá José M. 
Published: February 2016

AbstractThe concept of noncovalent organocatalysis by means of networks of cooperative hydrogen bonds (NCHB organocatalysis) has been explored. Arylideneureas were chosen as ideal substrates because of their powerful donor–acceptor properties. We have examined their uncatalyzed, direct Mannich reaction with acetoacetates in comparison with that catalyzed by a number of salan derivatives capable of providing a network of cooperative hydrogen bonds. Catalyst D [(R,R)‐N,N′‐bis(salicyl)cyclohexane‐1,2‐diamine] was found to drive the above direct Mannich reaction in an enantioselective manner, thereby allowing the synthesis of several Biginelli dihydropyrimidinones with high enantioselectivity. DFT calculations (B3LYP‐D‐PCM/6‐31+G*//B3LYP/6‐31+G*) revealed that the NCHB organocatalyst lowers the energy barrier of the reaction. The NCHB organocatalysts appear to function as biomimetic catalysts.
The Origin of Ultralow Thermal Conductivity in InTe: Lone‐Pair‐Induced Anharmonic Rattling
Authors: Jana Manoj K. , Pal Koushik , Waghmare Umesh V. , Biswas Kanishka 
Published: February 2016

AbstractUnderstanding the origin of intrinsically low thermal conductivity is fundamentally important to the development of high‐performance thermoelectric materials, which can convert waste‐heat into electricity. Herein, we report an ultralow lattice thermal conductivity (ca. 0.4 W m−1 K−1) in mixed valent InTe (that is, In+In3+Te2), which exhibits an intrinsic bonding asymmetry with coexistent covalent and ionic substructures. The phonon dispersion of InTe exhibits, along with low‐energy flat branches, weak instabilities associated with the rattling vibrations of In+ atoms along the columnar ionic substructure. These weakly unstable phonons originate from the 5s2 lone pair of the In+ atom and are strongly anharmonic, which scatter the heat‐carrying acoustic phonons through strong anharmonic phonon–phonon interactions, as evident in anomalously high mode Grüneisen parameters. A maximum thermoelectric figure of merit (z T) of about 0.9 is achieved at 600 K for the 0.3 mol % In‐deficient sample, making InTe a promising material for mid‐temperature thermoelectric applications.
Duale genetische Kodierung von Acetyllysin und nicht‐hydrolysierbarem Thioacetyllysin mittels Flexizym
Authors: Xiong Hai , Reynolds Noah M. , Fan Chenguang , Englert Markus , Hoyer Denton , Miller Scott J. , Söll Dieter 
Published: February 2016

AbstractDie Acetylierung von Lysin‐Bausteinen ist eine wichtige posttranslationale Proteinmodifikation. Die Lysin‐Acetylierung in Histonproteinen und deren Interaktion mit anderen posttranslationalen Modifikationen in Histon‐ und nicht‐Histon‐Proteinen ist essentiell bei der DNA‐Replikation, DNA‐Reparatur und Transkriptionsregulation. Wir verwendeten die Flexizym‐Technologie, um die Aminosäuren Acetyllysin (AcK) und nicht‐hydrolysierbares Thioacetyllysin (ThioAcK) in vitro in intakte Proteine einzubauen. ThioAcK und AcK wurden in humanes Histon H3 positionsspezifisch inkorporiert. Dies erfolgte entweder individuell oder paarweise bei verschiedenen Lysin‐Positionen innerhalb des humanen Histon H3. Die Thioacetylgruppe im Histon H3 konnte nicht durch die Histon‐Deacetylase Sirtuin (Typ 1) abgespalten werden, wie durch diese Studie gezeigt wurde. Diese Methode des AcK‐ und ThioAcK‐Einbaus stellt ein wichtiges Werkzeug für die Untersuchung der Protein‐Acetylierung sowie deren Rolle in der Interaktion mit weiteren posttranlationalen Modifizierungen dar.
Functional Organosulfide Electrolyte Promotes an Alternate Reaction Pathway to Achieve High Performance in Lithium–Sulfur Batteries
Authors: Chen Shuru , Dai Fang , Gordin Mikhail L. , Yu Zhaoxin , Gao Yue , Song Jiangxuan , Wang Donghai 
Published: February 2016

AbstractLithium–sulfur (Li‐S) batteries have recently received great attention because they promise to provide energy density far beyond current lithium ion batteries. Typically, Li‐S batteries operate by conversion of sulfur to reversibly form different soluble lithium polysulfide intermediates and insoluble lithium sulfides through multistep redox reactions. Herein, we report a functional electrolyte system incorporating dimethyl disulfide as a co‐solvent that enables a new electrochemical reduction pathway for sulfur cathodes. This pathway uses soluble dimethyl polysulfides and lithium organosulfides as intermediates and products, which can boost cell capacity and lead to improved discharge–charge reversibility and cycling performance of sulfur cathodes. This electrolyte system can potentially enable Li‐S batteries to achieve high energy density.
Turn‐On Luminescent Probes for the Real‐Time Monitoring of Endogenous Hydroxyl Radicals in Living Cells
Authors: Zhou Wenjuan , Cao Yuqing , Sui Dandan , Lu Chao 
Published: February 2016

AbstractThe utilization of semiconductor quantum dots (QDs) as optical labels for biosensing and biorecognition has made substantial progress. However, the development of a suitable QD‐based luminescent probe that is capable of detecting individual reactive oxygen species (ROS) represents a great challenge, mainly because the fluorescence of QDs is quenched by a wide variety of ROS. To overcome this limitation, a novel QD‐based turn‐on luminescent probe for the specific detection of .OH has been designed, and its application in monitoring the endogenous release of .OH species in living cells is demonstrated. Metal citrate complexes on the surfaces of the QDs can act as electron donors, injecting electrons into the LUMO of the QDs, while .OH can inject holes into the HOMO of the QDs. Accordingly, electron–hole pairs are produced, which could emit strong luminescence by electron–hole recombination. Importantly, this luminescent probe does not respond to other ROS.
Bio‐Inspired Renewable Surface‐Initiated Polymerization from Permanently Embedded Initiators
Authors: Du Tao , Li Bin , Wang Xiaolong , Yu Bo , Pei Xiaowei , Huck Wilhelm T. S. , Zhou Feng 
Published: February 2016

AbstractHerein, we describe a simple and robust approach to repeatedly modify surfaces with polymer brushes through surface‐initiated atomic transfer radical polymerization (SI‐ATRP), based on an initiator‐embedded polystyrene sheet that does not rely on specific surface chemistries for initiator immobilization. The surface‐grafted polymer brushes can be wiped away to expose fresh underlying initiator that re‐initiates polymerization. This strategy provides a facile route for modification of molded or embossed surfaces, with possible applications in the preparation of fluidic devices and polymer‐embedded circuits.
Structural Revisions of a Class of Natural Products: Scaffolds of Aglycon Analogues of Fusicoccins and Cotylenins Isolated from Fungi
Authors: Tang Ying , Xue Yongbo , Du Guang , Wang Jianping , Liu Junjun , Sun Bin , Li Xiao‐Nian , Yao Guangmin , Luo Zengwei , Zhang Yonghui 
Published: February 2016

AbstractThe reisolation and structural revision of brassicicene D is described, and inspired us to reassign the core skeletons of brassicicenes C–H, J and K, ranging from dicyclopenta[a,d]cyclooctane to tricyclo[9.2.1.03,7]tetradecane using quantum‐chemical predictions and experimental validation strategies. Three novel, highly modified fusicoccanes, brassicicenes L–N, were also isolated from the fungus Alternaria brassicicola, and their structures were unequivocally established by spectroscopic data, ECD calculations, and crystallography. The reassigned structures represent the first class of bridgehead double‐bond‐containing natural products with a bicyclo[6.2.1]undecane carbon skeleton. Furthermore, their stabilities were first predicted with olefin strain energy calculations. Collectively, these findings extend our view of the application of computational predictions and biosynthetic logic‐based structure elucidation to address problems related to the structure and stability of natural products.
Anion–π Catalysis of Enolate Chemistry: Rigidified Leonard Turns as a General Motif to Run Reactions on Aromatic Surfaces
Authors: Cotelle Yoann , Benz Sebastian , Avestro Alyssa‐Jennifer , Ward Thomas R. , Sakai Naomi , Matile Stefan 
Published: February 2016

AbstractTo integrate anion–π, cation–π, and ion pair–π interactions in catalysis, the fundamental challenge is to run reactions reliably on aromatic surfaces. Addressing a specific question concerning enolate addition to nitroolefins, this study elaborates on Leonard turns to tackle this problem in a general manner. Increasingly refined turns are constructed to position malonate half thioesters as close as possible on π‐acidic surfaces. The resulting preorganization of reactive intermediates is shown to support the disfavored addition to enolate acceptors to an absolutely unexpected extent. This decisive impact on anion–π catalysis increases with the rigidity of the turns. The new, rigidified Leonard turns are most effective with weak anion–π interactions, whereas stronger interactions do not require such ideal substrate positioning to operate well. The stunning simplicity of the motif and its surprisingly strong relevance for function should render the introduced approach generally useful.
Selective Alkane Oxidation by Manganese Oxide: Site Isolation of MnOx Chains at the Surface of MnWO4 Nanorods
Authors: Li Xuan , Lunkenbein Thomas , Pfeifer Verena , Jastak Mateusz , Nielsen Pia Kjaer , Girgsdies Frank , Knop‐Gericke Axel , Rosowski Frank , Schlögl Robert , Trunschke Annette 
Published: February 2016

AbstractThe electronic and structural properties of vanadium‐containing phases govern the formation of isolated active sites at the surface of these catalysts for selective alkane oxidation. This concept is not restricted to vanadium oxide. The deliberate use of hydrothermal techniques can turn the typical combustion catalyst manganese oxide into a selective catalyst for oxidative propane dehydrogenation. Nanostructured, crystalline MnWO4 serves as the support that stabilizes a defect‐rich MnOx surface phase. Oxygen defects can be reversibly replenished and depleted at the reaction temperature. Terminating MnOx zigzag chains on the (010) crystal planes are suspected to bear structurally site‐isolated oxygen defects that account for the unexpectedly good performance of the catalyst in propane activation.
Werner Complexes with ω‐Dimethylaminoalkyl Substituted Ethylenediamine Ligands: Bifunctional Hydrogen‐Bond‐Donor Catalysts for Highly Enantioselective Michael Additions
Authors: Ghosh Subrata K. , Ganzmann Carola , Bhuvanesh Nattamai , Gladysz John A. 
Published: February 2016

AbstractThe racemic carbonate complex [Co(en)2O2CO]+ Cl− (en=1,2‐ethylenediamine) and (S)‐[H3NCH((CH2)nNHMe2)CH2NH3]3+ 3 Cl− (n=1–4) react (water, charcoal, 100 °C) to give [Co(en)2((S)‐H2NCH((CH2)nNHMe2)CH2NH2)]4+ 4 Cl− (3 a–d H4+ 4 Cl−) as a mixture of Λ/Δ diastereomers that separate on chiral‐phase Sephadex columns. These are treated with NaOH/Na+ BArf− (BArf=B(3,5‐C6H3(CF3)2)4) to give lipophilic Λ‐ and Δ‐3 a–d3+ 3 BArf−, which are screened as catalysts (10 mol %) for additions of dialkyl malonates to nitroalkenes. Optimal results are obtained with Λ‐3 c3+ 3 BArf− (CH2Cl2, −35 °C; 98–82 % yields and 99–93 % ee for six β‐arylnitroethenes). The monofunctional catalysts Λ‐ and Δ‐[Co(en)3]3+ 3 BArf− give enantioselectivities of <10 % ee with equal loadings of Et3N. The crystal structure of Δ‐3 a H4+ 4 Cl− provides a starting point for speculation regarding transition‐state assemblies.
Ligand‐Enabled Arylation of γ‐C−H Bonds
Authors: Li Suhua , Zhu Ru‐Yi , Xiao Kai‐Jiong , Yu Jin‐Quan 
Published: February 2016

AbstractPdII‐catalyzed arylation of γ‐C(sp3)−H bonds of aliphatic acid‐derived amides was developed by using quinoline‐based ligands. Various γ‐aryl‐α‐amino acids were prepared from natural amino acids using this method. The influence of ligand structure on reactivity was also systematically investigated.
Nucleophilic Reactivity of a Nitride‐Bridged Diuranium(IV) Complex: CO2 and CS2 Functionalization
Authors: Falcone Marta , Chatelain Lucile , Mazzanti Marinella 
Published: February 2016

AbstractThermolysis of the nitride‐bridged diuranium(IV) complex Cs{(μ‐N)[U(OSi(OtBu)3)3]2} (1) showed that the bridging nitride behaves as a strong nucleophile, promoting N−C bond formation by siloxide ligand fragmentation to yield an imido‐bridged siloxide/silanediolate diuranium(IV) complex, Cs{(μ‐NtBu)(μ‐O2Si(OtBu)2)U2(OSi(OtBu)3)5}. Complex 1 displayed reactivity towards CS2 and CO2 at room temperature that is unprecedented in f‐element chemistry, affording diverse N‐functionalized products depending on the reaction stoichiometry. The reaction of 1 with two equivalents of CS2 yielded the thiocyanate/thiocarbonate complex Cs{(μ‐NCS)(μ‐CS3)[U(OSi(OtBu)3)3]2} via a putative NCS−/S2− intermediate. The reaction of 1 with one equivalent of CO2 resulted in deoxygenation and N−C bond formation, yielding the cyanate/oxo complex Cs{(μ‐NCO)(μ‐O)[U(OSi(OtBu)3)3]2}. Addition of excess CO2 to 1 led to the unprecedented dicarbamate product Cs{(μ‐NC2O4)[U(OSi(OtBu)3)3]2}.
Crystal‐Structure‐Guided Design of Self‐Assembling RNA Nanotriangles
Authors: Boerneke Mark A. , Dibrov Sergey M. , Hermann Thomas 
Published: February 2016

AbstractRNA nanotechnology uses RNA structural motifs to build nanosized architectures that assemble through selective base‐pair interactions. Herein, we report the crystal‐structure‐guided design of highly stable RNA nanotriangles that self‐assemble cooperatively from short oligonucleotides. The crystal structure of an 81 nucleotide nanotriangle determined at 2.6 Å resolution reveals the so‐far smallest circularly closed nanoobject made entirely of double‐stranded RNA. The assembly of the nanotriangle architecture involved RNA corner motifs that were derived from ligand‐responsive RNA switches, which offer the opportunity to control self‐assembly and dissociation.
Gel structure phase behavior in micro nanofibrillated cellulose containing in situ precipitated calcium carbonate
Authors: Dimic‐Misic Katarina , Rantanen Juuso , Maloney Thad C. , Gane Patrick A. C. 
Published: February 2016

ABSTRACTSpeciality high‐strength board, packaging grades, and novel cellulose‐based nanocomposites may incorporate microcellulosic nanofibrillated materials (MNFC), although the rheological properties of such strongly water sorbing structures are challenging for processing technologies. This study introduces rheological methods for the evaluation of dewatering and flow behavior of such high consistency furnishes to exemplify the effect of energy input on microfibrillar material (MFC), as produced by a combination of enzymatic pretreatment and increased levels of fluidization. The large number of fibril contact points act to entrap water, held both on the fibril surface as immobilized water and in the interfibril spacing forming the gel structure. Tuning of the rheological and dewatering properties has been enabled by in situ precipitation of calcium carbonate filler (in situ PCC) on the MFC, which results in the production of a more uniform furnish. Such in situ PCC coated MFC fibrils incorporated into furnish were seen to increase dewatering rate over that of the furnish mix without the in situ precipitated filler primarily because of the reduction in total surface area of the fibers and fibrils when the pigment is present on the fibrillary surface. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43486.
Proton exchange membrane based on crosslinked sulfonated polyphosphazene containing pendent perfluorosulfonic acid groups with sulfonated poly(ether ether ketone)
Authors: Dong Yan , Zhang Yan‐Xia , Xu Hu‐Lin , Luo Tian‐Wei , Fu Feng‐Yan , Zhu Chang‐Jin 
Published: February 2016

ABSTRACTA series of crosslinked membranes based on new sulfonated polyphosphazene bearing pendent perfluorosulfonic acid groups (PMFP‐g‐PS) and sulfonated poly (ether ether ketone) were prepared and evaluated as proton exchange membranes for direct methanol fuel cells (DMFCs). The structure of PMFP‐g‐PS was characterized by Fourier transform infrared spectroscopy,1H and19F NMR spectra. In comparison with the pristine PMFP‐g‐PS membrane, the crosslinked membranes showed improved water uptakes and proton conductivities. The methanol permeability values of the membranes were in the range of 1.32 × 10−7to 3.85 × 10−7cm2/s, which were lower than Nafion 117 (12.1 × 10−7cm2/s). The selectivity of all the membranes was much higher compared with Nafion 117. Furthermore, transmission electron microscopy observation revealed that clear phase‐separated structures were well dispersed and connected to each other in the membranes. These membranes displayed high water uptakes and low swelling ratios, high proton conductivities, low methanol permeability values, good thermal, and oxidative stabilities. The results indicate that these membranes are potential candidate proton exchange membrane materials for DMFCs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 43492.
Preparation of highly concentrated inverse emulsions of acrylamide‐based anionic copolymers as efficient water rheological modifiers
Authors: González Rivera José , Hernández Barajas José , Gutiérrez Carrillo Atilano , Aguilera Alvarado Alberto F. 
Published: February 2016

ABSTRACTHighly concentrated inverse anionic polymeric emulsions (with a solid content of up to 63 wt %) were prepared using a two‐step methodology: (i) First, acrylamide, acrylic acid, and its ammonium salts crosslinked copolymers were obtained by inverse emulsion polymerization, (ii) The water/volatile oil mixture was then separated from the heterogeneous system by vacuum distillation. To maintain sufficient stability during the reaction and distillation processes, a ternary surfactant mixture was used. A surface response methodology was employed to obtain the optimal values of the factors involved in both process and product specifications, and to maximize the high performance of these inverse anionic polymer emulsions. This yielded a product containing up to 63.2 wt % solids capable of achieving Brookfield viscosities as high as 40.3 Pa·s, using an aliquote of these concentrated inverse polymer emulsions (1.8 wt % in deionized water). Rheological characterization (oscillatory and rotational measurements) was carried out to evaluate the behavior of the diluted inverse anionic polymer emulsion in water thickening. The methodology developed can be used to formulate a wide range of viscoelastic (G″/G′) water‐based products from anionic water soluble polymers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43502.
Solvent‐free synthesis of polyols from 1‐butene metathesized palm oil for use in polyurethane foams
Authors: Pillai Prasanth K. S. , Li Shaojun , Bouzidi Laziz , Narine Suresh S. 
Published: February 2016

ABSTRACTGreen Polyols were synthesized from a 1‐butene cross metathesized palm oil (PMTAG) using a green, solvent free epoxidation and hydroxylation pathway. The synthetic strategy was adapted to control the degree of double bond epoxidation and ultimately the hydroxyl value of the polyols. The polyols comprised diol and tetrol monomers with terminal hydroxyl groups content as high as ∼18 mol %, and achieved hydroxyl values between 83 and 119 mg KOH g−1. Functional Rigid and highly flexible foams were prepared from two designer Green Polyols. The foams presented a high thermal stability (Ton of degradation of ∼270 °C), suitable glass transition temperatures (∼−12 °C and ∼50 °C) and compressive strength (0.21 MPa at 10% strain and ∼1 MPa at 10% strain for the flexible and rigid foams, respectively) which are superior to existing lipid‐based counterparts. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43509.
Ionic conductivity and dielectric behavior of novel poly(vinyl formal)‐based single‐ion‐conductor polymer electrolytes
Authors: Guan Hong‐Yan , Guo Zhong‐Bao , Ding Jian‐Jun , Lian Fang 
Published: February 2016

ABSTRACTNovel single‐ion‐conductor polymer (SCP) electrolytes based on oxalate‐chelated‐borate‐structure‐grafted poly(vinyl formal) (PVFM) were synthesized via a solution casting technique. The influence of the molar ratio of OH and boron atoms in PVFM on the ionic conductivity (σ) of the SCP electrolytes at different temperatures was investigated with alternating‐current impedance spectroscopy in the frequency range of 0.01 Hz to 1 MHz. The results show that σ of the SCP electrolytes at 15–60 °C was about 10−6–10−5 S/cm, and temperature dependence of the conductivity of the electrolytes followed the Vogel–Tamman–Fulcher relationship. The dielectric behaviors of the SCP electrolytes were analyzed in view of the dielectric permittivity and dielectric modulus of the electrolytes. Dielectric analysis revealed that the transport of Li+ ions in the PVFM‐based SCP electrolytes mainly followed a hopping mechanism coupled with the segmental motion of the polymer chain. Additionally, a dielectric relaxation was found in the high‐frequency region; this was a thermally activated result and also implied the appearance of carrier hopping. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43510.
Changes in tropical cyclone activity offset the ocean surface warming in northwest Pacific: 1981–2014
Authors: June Chang Chiung‐Wen , Simon Wang S.‐Y. , Hsu Huang‐Hsiung 
Published: February 2016

AbstractTropical cyclones (TCs) leave a cold wake in the sea surface temperature (SST). In the northwest Pacific, TC activity and SST have both increased since the 1980s, but the extent to which ocean surface warming is affected by the changing TC activity is unknown. Analysis of the 1981–2014 period indicates that the intensified effect of TC cold wakes has offset the SST warming trend by 37% during the typhoon season, implying that the observed SST warming might be underestimated. This factor could affect long‐term climate simulations that are forced with prescribed SST.