bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tris(4,4′‐dimethyl‐2,2′‐bipyridine)iron(II)‐Exchanged Nafion for Arsenite Determination in Water Samples
Authors: Azad Uday Pratap , Ganesan Vellaichamy 
Published: December 2013

AbstractA low cost and easy‐to‐construct electrochemical sensor is fabricated for the determination of arsenite in water by using an Fe(dmbpy)32+‐exchanged (dmbpy=4,4′‐dimethyl‐2,2′‐bipyridine) Nafion (Nf) film. Arsenite at a glassy carbon electrode (GCE) coated with the Fe(dmbpy)32+‐exchanged Nf film is shown to be electrocatalytically oxidized at lower overpotentials than at a bare GCE, and a tentative mechanism is proposed for the electrocatalytic oxidation. This new electrochemical sensing platform (ESP) exhibits a wide linear calibration range (from 10 μM to 100 mM) with a correlation coefficient above 0.99 for the precise determination of arsenite; the ESP exhibits a detection limit of 10.0 μM for arsenite determination. Utility of the developed sensor is further assured by determining the concentration of arsenite present in standard aqueous samples and in samples from different water sources. Among the several interferences studied, high concentrations of Zn2+ (50 times higher than arsenite) can affect arsenite determination. Kinetic parameters, such as the diffusion coefficient, catalytic rate constant, and so forth, are determined by using chronocoulometry and chronoamperometry techniques.
Base‐Catalyzed Hydrosilylation of Ketones and Esters and Insight into the Mechanism
Authors: Revunova Kseniya , Nikonov Georgii I. 
Published: December 2013

AbstractSimple bases (KOtBu, KOH) catalyze the silane‐promoted reduction of ketones and esters to alcohols and of aldimines to amines. The inexpensive silane PMHS (polymethylhydrosiloxane) can be used as the reducing reagent. Double and triple bonds, as well as nitro‐ and cyano‐groups are tolerated. Careful dosing of the silane allows for chemoselective reduction of a more reactive group in the presence of a less reactive group (for example, aldehyde reduction in the presence of ketone/ketone reduction in the presence of ester group). Mechanistic studies showed that addition of base to silanes leads to silicate species, which are the acting reducing agents. Under basic conditions, hydrosiloxanes (tetramethyldisiloxane, TMDS; PMHS) convert into simple silanes (H2SiMe2, H3SiMe), making this a practical method to generate these challenging silanes.
Quantum Mechanics/Molecular Mechanics Study on the Oxygen Binding and Substrate Hydroxylation Step in AlkB Repair Enzymes
Authors: Quesne Matthew G. , Latifi Reza , Gonzalez‐Ovalle Luis E. , Kumar Devesh , de Visser Sam P. 
Published: December 2013

AbstractAlkB repair enzymes are important nonheme iron enzymes that catalyse the demethylation of alkylated DNA bases in humans, which is a vital reaction in the body that heals externally damaged DNA bases. Its mechanism is currently controversial and in order to resolve the catalytic mechanism of these enzymes, a quantum mechanics/molecular mechanics (QM/MM) study was performed on the demethylation of the N1‐methyladenine fragment by AlkB repair enzymes. Firstly, the initial modelling identified the oxygen binding site of the enzyme. Secondly, the oxygen activation mechanism was investigated and a novel pathway was found, whereby the catalytically active iron(IV)–oxo intermediate in the catalytic cycle undergoes an initial isomerisation assisted by an Arg residue in the substrate binding pocket, which then brings the oxo group in close contact with the methyl group of the alkylated DNA base. This enables a subsequent rate‐determining hydrogen‐atom abstraction on competitive σ‐ and π‐pathways on a quintet spin‐state surface. These findings give evidence of different locations of the oxygen and substrate binding channels in the enzyme and the origin of the separation of the oxygen‐bound intermediates in the catalytic cycle from substrate. Our studies are compared with small model complexes and the effect of protein and environment on the kinetics and mechanism is explained.
Self‐Assembly of Carboxylic Acid Appended Naphthalene Diimide Derivatives with Tunable Luminescent Color and Electrical Conductivity
Authors: Molla Mijanur Rahaman , Gehrig Dominik , Roy Lisa , Kamm Valentin , Paul Ankan , Laquai Frédéric , Ghosh Suhrit 
Published: December 2013

AbstractSelf‐assembly of a series of carboxylic acid‐functionalized naphthalene diimide (NDI) chromophores with a varying number (n=1–4) of methylene spacers between the NDI ring and the carboxylic acid group has been studied. The derivatives show pronounced aggregation due to the synergistic effects of H‐bonding between the carboxylic acid groups in a syn–syn catemer motif and π stacking between the NDI chromophores. Solvent‐dependent UV/Vis studies reveal the existence of monomeric dye molecules in a “good” solvent such as chloroform and self‐assembly in “bad” solvents such as methylcyclohexane. The propensity of self‐assembly is comparable for all samples. Temperature‐dependent spectroscopic studies show high thermal stability of the H‐bonding‐mediated self‐assembled structures. In the presence of a protic solvent such as MeOH, self‐assembly can be suppressed, suggesting a decisive role of H‐bonding, whereas π stacking is more a consequence of than a cause for self‐assembly. Syn–syn catemer‐type H‐bonding is supported by powder XRD studies and the results corroborate well with DFT calculations. The morphology as determined by AFM is found to be dependent on the value of n; with increasing n, the morphology gradually shifts from 2D nanosheets to 1D nanofibers. Emission spectra show sharp emission bands with relatively small Stokes shifts. In addition, a rather broad emission band is observed at longer wavelengths because of the in situ formation of excimer‐type species. Due to such a heterogeneous nature, the emission spectrum spans almost the entire red–green–blue region. Depending on the value of n, the ratio of intensities of the two emission bands is changed, which results in a tunable luminescent color. Furthermore, in the case of n=1 and 3, almost pure white light emission is observed. Time‐resolved photoluminescence spectra show a very short lifetime (a few picoseconds) of monomeric dye molecules and biexponential decays with longer lifetimes (on the order of nanoseconds) for aggregated species. Current–voltage measurements show electrical conductivity in the range of 10−4 S cm−1 for the aggregated chromophores, which is four orders of magnitude higher than the value for a structurally similar NDI control molecule lacking the H‐bonding functionality.
Fast and Efficient 18F‐Labeling by [18F]Fluorophenylazocarboxylic Esters
Authors: Fehler Stefanie K. , Maschauer Simone , Höfling Sarah B. , Bartuschat Amelie L. , Tschammer Nuska , Hübner Harald , Gmeiner Peter , Prante Olaf , Heinrich Markus R. 
Published: December 2013

AbstractIntroduction of [18F]fluoride ion into the aromatic core of phenylazocarboxylic esters was achieved in only 30 seconds, with radiochemical yields of up to 95 % (85(±10) %). For labeling purposes, the resulting 18F‐substituted azoester can be further converted in radical‐arylation reactions to give biaryls, or in substitutions at its carbonyl unit to produce azocarboxamides.
Enhancing the Water Splitting Efficiency of Sn‐Doped Hematite Nanoflakes by Flame Annealing
Authors: Wang Lei , Lee Chong‐Yong , Mazare Anca , Lee Kiyoung , Müller Julian , Spiecker Erdmann , Schmuki Patrik 
Published: December 2013

AbstractThe effect of flame annealing on the water‐splitting properties of Sn decorated hematite (α‐Fe2O3) nanoflakes has been investigated. It is shown that flame annealing can yield a considerable enhancement in the maximum photocurrent under AM 1.5 (100 mW cm−2) conditions compared to classic furnace annealing treatments. Optimizing the annealing time (10 s at 1000 °C) leads to a photocurrent of 1.1 mA cm−2 at 1.23 V (vs. RHE) with a maximum value 1.6 mA cm−2 at 1.6 V (vs. RHE) in 1 M KOH. The improvement in photocurrent can be attributed to the fast direct heating that maintains the nanoscale morphology, leads to optimized Sn decoration, and minimizes detrimental substrate effects.
Directing the Structural Features of N2‐Phobic Nanoporous Covalent Organic Polymers for CO2 Capture and Separation
Authors: Patel Hasmukh A. , Je Sang Hyun , Park Joonho , Jung Yousung , Coskun Ali , Yavuz Cafer T. 
Published: December 2013

AbstractA family of azo‐bridged covalent organic polymers (azo‐COPs) was synthesized through a catalyst‐free direct coupling of aromatic nitro and amine compounds under basic conditions. The azo‐COPs formed 3D nanoporous networks and exhibited surface areas up to 729.6 m2 g−1, with a CO2‐uptake capacity as high as 2.55 mmol g−1 at 273 K and 1 bar. Azo‐COPs showed remarkable CO2/N2 selectivities (95.6–165.2) at 298 K and 1 bar. Unlike any other porous material, CO2/N2 selectivities of azo‐COPs increase with rising temperature. It was found that azo‐COPs show less than expected affinity towards N2 gas, thus making the framework “N2‐phobic”, in relative terms. Our theoretical simulations indicate that the origin of this unusual behavior is associated with the larger entropic loss of N2 gas molecules upon their interaction with azo‐groups. The effect of fused aromatic rings on the CO2/N2 selectivity in azo‐COPs is also demonstrated. Increasing the π‐surface area resulted in an increase in the CO2‐philic nature of the framework, thus allowing us to reach a CO2/N2 selectivity value of 307.7 at 323 K and 1 bar, which is the highest value reported to date. Hence, it is possible to combine the concepts of “CO2‐philicity” and “N2‐phobicity” for efficient CO2 capture and separation. Isosteric heats of CO2 adsorption for azo‐COPs range from 24.8–32.1 kJ mol−1 at ambient pressure. Azo‐COPs are stable up to 350 °C in air and boiling water for a week. A promising cis/trans isomerization of azo‐COPs for switchable porosity is also demonstrated, making way for a gated CO2 uptake.
Ferromagnetic Ordering in the Layer‐Structured Pd(HS2O7)2
Authors: Bruns Jörn , Niehaus Oliver , Pöttgen Rainer , Wickleder Mathias S. 
Published: December 2013

AbstractThe reaction of (NO2)(CF3SO3) and elemental palladium in oleum (65 % SO3) leads to violet single crystals of Pd(HS2O7)2 (monoclinic, P21/c, Z=2, a=927.80(9), b=682.58(7), c=920.84(9) pm, β=117.756(2)°, wR2=0.0439). In the crystal structure, the Pd2+ ions show an uncommon octahedral coordination of six oxygen atoms belonging to six HS2O7− ions. The linkage of [PdO6] octahedra and the hydrogendisulfate anions leads to a layer structure, and the layers are held together by hydrogen bonds. The unusual coordination of the Pd2+ ions results in an electronic d8 high‐spin configuration, which leads to the paramagnetic behavior of the compound. Moreover, at low temperature, a ferromagnetic ordering was observed with a Curie temperature of 8 K.
Catalytic Effect of Cesium Cation Adduct Formation on the Decarboxylation of Carboxylate Ions in the Gas Phase
Authors: Mayeux Charly , Massi Lionel , Gal Jean‐François , Charles Laurence , Burk Peeter 
Published: December 2013

AbstractThe effect of Cs+ ligation on the decarboxylation of malonic acids (unsubstituted and methyl‐, dimethyl‐, ethyl‐, and phenyl‐substituted) in their carboxylate form was studied in the gas phase using tandem mass spectrometry. The study is based on the comparison of the decarboxylation of the bare monoanion (hydrogen malonates) and of the cesium adduct of the cesium salt (Cs+[cesium hydrogen malonates]) under collisional activation. Energy‐resolved dissociation curves of the negative and positive ions exhibit major differences. Decarboxylation of the cationic adducts of substituted malonic acid salts occurs at significantly lower collisional activation than for the corresponding bare hydrogen malonate anions. The conclusions from these experiments are supported by DFT calculations. The calculated activation parameters (enthalpy and Gibbs energy) confirm that the cesium cation coordination assists the decarboxylation of the carboxylate form.
Investigation of a Lithium–Halogen Exchange Flow Process for the Preparation of Boronates by Using a Cryo‐Flow Reactor
Authors: Newby James A. , Huck Lena , Blaylock D. Wayne , Witt Paul M. , Ley Steven V. , Browne Duncan L. 
Published: December 2013

AbstractConducting low‐temperature organometallic reactions under continuous flow conditions offers the potential to more accurately control exotherms and thus provide more reproducible and scalable processes. Herein, progress towards this goal with regards to the lithium–halogen exchange/borylation reaction is reported. In addition to improving the scope of substrates available on a research scale, methods to improve reaction profiles and expedite purification of the products are also described. On moving to a continuous system, thermocouple measurements have been used to track exotherms and provide a level of safety for continuous processing of organometallic reagents. The use of an in‐line continuous liquid–liquid separation device to circumvent labour intensive downstream off‐line processing is also reported.
Synthesis of 7‐Triazole‐substituted Camptothecin via Click Chemistry and Evaluation of in vitro Antitumor Activity
Authors: Wang Lei , Yuan Wei , Zhang Jie , Tong Linjiang , Luo Yu , Chen Yi , Lu Wei , Huang Qingqing 
Published: December 2013

AbstractCamptothecin (CPT) is a natural topoisomerase I inhibitor with powerful antineoplastic activity against colorectal, breast, lung and ovarian cancers. To discover more potent antitumor agents, a series of new CPT derivatives were synthesized utilizing click chemistry. All compounds were assessed for cytotoxicity against A549, HCT‐116, HT‐29, LoVo, MDA‐MB‐231 cell lines, and some compounds exhibited good in vitro potency. Furthermore, all compounds kept or enhanced Topo I inhibition.
Design, Synthesis and Structure–Activity Relationships Studies on the D Ring of the Natural Product Triptolide
Authors: Xu Hongtao , Tang Huanyu , Feng Huijin , Li Yuanchao 
Published: December 2013

AbstractTriptolide is a diterpene triepoxide natural product isolated from Tripterygium wilfordii Hook F, a traditional Chinese medicinal herb. Triptolide has previously been shown to possess antitumor, anti‐inflammatory, immunosuppressive, and antifertility activities. Earlier reports suggested that the five‐membered unsaturated lactone ring (D ring) is essential for potent cytotoxicity, however, to the best of our knowledge, systematic structure–activity relationship studies have not yet been reported. Here, four types of D ring‐modified triptolide analogues were designed, synthesized and evaluated against human ovarian (SKOV‐3) and prostate (PC‐3) carcinoma cell lines. The results suggest that the D ring is essential to potency, however it can be modified, for example to C18 hydrogen bond acceptor and/or donor furan ring analogues, without complete loss of cytotoxic activity. Interestingly, evaluation of the key series of C19 analogues showed that this site is exquisitely sensitive to polarity. Together, these results will guide further optimization of this natural product lead compound for the development of potent and potentially clinically useful triptolide analogues.
Risk factors for clinician‐reported symptom clusters in patients with advanced head and neck cancer in a phase 3 randomized clinical trial: RTOG 0129
Authors: Xiao Canhua , Hanlon Alexandra , Zhang Qiang , Movsas Benjamin , Ang Kian , Rosenthal David I. , Nguyen‐Tan P. Félix , Kim Harold , Le Quynh , Bruner Deborah Watkins 
Published: December 2013

BACKGROUNDChemoradiotherapy has become the standard of care for head and neck squamous cell carcinoma; however, those patients often experience multiple treatment‐related symptoms or symptom clusters. Two symptom clusters have been identified for this population. Little is known about the risk factors of these symptom clusters.METHODSSubjects comprised 684 patients who were treated with concurrent chemoradiotherapy in a phase 3 randomized clinical trial. This trial compared standard fractionation radiotherapy to accelerated fractionation radiotherapy. Symptom clusters were evaluated at the end of the first and the second cycle of chemotherapy, and 3 months after the start of radiotherapy. Mixed‐effect modeling was used to observe risk factors for symptom clusters.RESULTSRace and education were independent predictors for the head and neck cluster, whereas sex and history of tobacco use were independent predictors for the gastrointestinal cluster. Primary cancer site was only significant for the head and neck cluster when other factors were not controlled: patients with oropharyngeal cancer had more severe symptoms in the head and neck clusters than did patients with laryngeal cancer. In addition, patients receiving accelerated fractionation radiotherapy experienced more symptoms of radiomucositis, pain, and nausea at 3 months after the start of radiotherapy than those receiving standard fractionation radiotherapy.CONCLUSIONSDemographic characteristics were more predictive to symptom clusters, whereas clinical characteristics, such as cancer site and treatment arms, were more significant for individual symptoms. Knowing the risk factors will enhance the capability of clinicians to evaluate patients' risk of severe symptom clusters and to personalize management strategies. Cancer 2014;120:848–854. © 2013 American Cancer Society.
Mood lighting system reflecting music mood
Authors: Moon Chang Bae , Kim HyunSoo , Lee Dong Won , Kim Byeong Man 
Published: December 2013

AbstractThe emotional impact of music or color can be maximized if they are used together. This article presents a mood‐lighting system that automatically detects the mood of a piece of music and expresses the mood via synchronized lighting. To do this, the relationship between mood words and colors was analyzed via a web questionnaire (n = 202) on moods associated with music and colors. Data analysis generated lighting scenarios reflecting changes in the mood of music. Each piece of music was divided into several segments using structural analysis, with the mood of each segment detected by the mood classification module using the neural network. A matching color was then assigned. The best performance of our mood classification module was <70%, which is not sufficient for commercial use; however, this figure is high enough to show the potential of this approach. © 2013 Wiley Periodicals, Inc. Col Res Appl, 40, 201–212, 2015
Synthesis of Well‐Defined Dawson‐Type Poly(N,N‐diethylacrylamide) Organopolyoxometalates
Authors: Lesage de la Haye Jennifer , Beaunier Patricia , Ruhlmann Laurent , Hasenknopf Bernold , Lacôte Emmanuel , Rieger Jutta 
Published: December 2013

AbstractAn organotin‐substituted Dawson‐type phosphotungstate was covalently linked to a trithiocarbonate group by postfunctionalization methods. This organopolyoxometalate led to a series of polyoxometalate (POM)–poly(N,N‐diethylacrylamide) hybrids in a controlled way through reversible addition–fragmentation chain transfer (RAFT) polymerization. Detailed comparison with and without the presence of POMs revealed that they do not profoundly disturb the RAFT mechanism, despite their oxidative power. The molar masses of the polymers were in the range of 10 to 100 kg mol−1 and molar mass dispersities of the composites were low (Mw/Mn<1.5). The POM building block in the hybrids retained the photocatalytic reactivity of the parent Dawson polyanion [P2W18O62]6−. Smaller, more homogeneous, and colloidally more stable silver nanoparticles were formed with the covalently linked POM–polymer compound than with its single unbound components.
Spray‐Painted Binder‐Free SnSe Electrodes for High‐Performance Energy‐Storage Devices
Authors: Wang Xianfu , Liu Bin , Xiang Qingyi , Wang. Qiufan , Hou Xiaojuan , Chen Di , Shen Guozhen 
Published: December 2013

AbstractSnSe nanocrystal electrodes on three‐dimensional (3D) carbon fabric and Au‐coated polyethylene terephthalate (PET) wafer have been prepared by a simple spray‐painting process and were further investigated as binder‐free active‐electrodes for Lithium‐ion batteries (LIBs) and flexible stacked all‐solid‐state supercapacitors. The as‐painted SnSe nanocrystals/carbon fabric electrodes exhibit an outstanding capacity of 676 mAh g−1 after 80 cycles at a current density of 200 mA g−1 and a considerable high‐rate capability in lithium storage because of the excellent ion transport from the electrolyte to the active materials and the efficient charge transport between current collector and electrode materials. The binder‐free electrodes also provide a larger electrochemical active surface compared with electrodes containing binders, which leads to the enhanced capacities of energy‐storage devices. A flexible stacked all‐solid‐state supercapacitor based on the SnSe nanocrystals on Au‐coated PET wafers shows high capacitance reversibility with little performance degradation at different current densities after 2200 charge–discharge cycles and even when bent. This allows for many potential applications in facile, cost‐effective, spray‐paintable, and flexible energy‐storage devices. The results indicate that the fabrication of binder‐free electrodes by a spray painting process is an interesting direction for the preparation of high‐performance energy‐storage devices.
Fischer–Tropsch Catalysts for the Production of Hydrocarbon Fuels with High Selectivity
Authors: Zhang Qinghong , Cheng Kang , Kang Jincan , Deng Weiping , Wang Ye 
Published: December 2013

AbstractFischer–Tropsch synthesis is a key reaction in the utilization of non‐petroleum carbon resources, such as methane (natural gas, shale gas, and biogas), coal, and biomass, for the sustainable production of clean liquid fuels from synthesis gas. Selectivity control is one of the biggest challenges in Fischer–Tropsch synthesis. This Minireview focuses on the development of new catalysts with controllable product selectivities. Recent attempts to increase the selectivity to C5+ hydrocarbons by preparing catalysts with well‐defined active phases or with new supports or by optimizing the interaction between the promoter and the active phase are briefly highlighted. Advances in developing bifunctional catalysts capable of catalyzing both CO hydrogenation to heavier hydrocarbons and hydrocracking/isomerization of heavier hydrocarbons are critically reviewed. It is demonstrated that the control of the secondary hydrocracking reactions by using core–shell nanostructures or solid‐acid materials, such as mesoporous zeolites and carbon nanotubes with acid functional groups, is an effective strategy to tune the product selectivity of Fischer–Tropsch synthesis. Very promising selectivities to gasoline‐ and diesel‐range hydrocarbons have been attained over some bifunctional catalysts.