bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Addition of Aryl Radicals to Graphene: The Importance of Nonbonded Interactions
Authors: Denis Pablo A. 
Published: August 2013

AbstractDispersion‐corrected density functional theory is utilized to study the addition of aryl radicals to perfect and defective graphene. Although the perfect sheet shows a low reactivity against aryl diazonium salts, the agglomeration of these groups and the addition onto defect sites improves the feasibility of the reaction by increasing binding energies per aryl group up to 27 kcal mol−1. It is found that if a single phenyl radical interacts with graphene, the covalent and noncovalent additions have similar binding energies, but in the particular case of the nitrophenyl group, the adsorption is stronger than the chemisorption. The single vacancy shows the largest reactivity, increasing the binding energy per aryl group by about 80 kcal mol−1. The zigzag edge ranks second, enhancing the reactivity 5.4 times with respect to the perfect sheet. The less reactive defect site is the Stone–Wales type, but even in this case the addition of an isolated aryl radical is exergonic. The arylation process is favored if the groups are attached nearby and on different sublattices. This is particularly true for the ortho and para positions. However, the enhancement of the binding energies decreases quickly if the distance between the two aryl radicals is increased, thereby making the addition on the perfect sheet difficult. A bandgap of 1–2 eV can be opened on functionalization of the graphene sheets with aryl radicals, but for certain configurations the sheet can maintain its semimetallic character even if there is one aryl radical per eight carbon atoms. At the highest level of functionalization achieved, that is, one aryl group per five carbon atoms, the bandgap is 1.9 eV. Regarding the effect of using aryl groups with different substituents, it is found that they all induce the same bandgap and thus the presence of NO2, H, or Br is not relevant for the alteration of the electronic properties. Finally, it is observed that the presence of tetrafluoroborate can induce metallic character in graphene.
Synthesis of 9‐Oxononanoic Acid, a Precursor for Biopolymers
Authors: Otte Konrad B. , Kirtz Marko , Nestl Bettina M. , Hauer Bernhard 
Published: August 2013

AbstractPolymers based on renewable resources have become increasingly important. The natural functionalization of fats and oils enables an easy access to interesting monomeric building blocks, which in turn transform the derivative biopolymers into high‐performance materials. Unfortunately, interesting building blocks of medium‐chain length are difficult to obtain by traditional chemical means. Herein, a biotechnological pathway is established that could provide an environmentally suitable and sustainable alternative. A multiple enzyme two‐step one‐pot process efficiently catalyzed by a coupled 9S‐lipoxygenase (St‐LOX1, Solanum tuberosum) and 9/13‐hydroperoxide lyase (Cm‐9/13HPL, Cucumis melo) cascade reaction is proposed as a potential route for the conversion of linoleic acid into 9‐oxononanoic acid, which is a precursor for biopolymers. Lipoxygenase catalyzes the insertion of oxygen into linoleic acid through a radical mechanism to give 9S‐hydroperoxy‐octadecadienoic acid (9S‐HPODE) as a cascade intermediate, which is subsequently cleaved by the action of Cm‐9/13HPL. This one‐pot process afforded a yield of 73 % combined with high selectivity. The best reaction performance was achieved when lipoxygenase and hydroperoxide lyase were applied in a successive rather than a simultaneous manner. Green leaf volatiles, which are desired flavor and fragrance products, are formed as by‐products in this reaction cascade. Furthermore, we have investigated the enantioselectivity of 9/13‐HPLs, which exhibited a strong preference for 9S‐HPODE over 9R‐HPODE.
On the Reactivity of Zinc Hydroxide Acetate Dihydrate in Ethanol
Authors: Moezzi Amir , Cortie Michael B. , Shimmon Ronald , McDonagh Andrew M. 
Published: August 2013

AbstractZinc hydroxide acetate dihydrate, Zn5(OH)8(CH3CO2)2·2H2O, reacts in ethanol at room temperature to yield a mixture of zinc oxide and anhydrous zinc acetate. The process is driven by dehydration of the starting salt. Dehydration of Zn5(OH)8(CH3CO2)2·2H2O also occurs when it is heated in air, but the product obtained in that case depends on the heating rate, environment and temperature. For example, when it is kept in a sealed silica capillary at 100 °C, Zn5(OH)8(CH3CO2)2·1.5H2O is formed after 15 min, whereas treatment in the range 90–100 °C in an open environment results in the formation of anhydrous zinc hydroxide acetate. Heating of any of these products further causes their decomposition to Zn(CH3CO2)2 and ZnO. The coordination bonding mode of the acetate groups in the anhydrous layered zinc hydroxide acetate prepared by reaction with ethanol was studied by using solid‐state NMR spectroscopy. The presence of chelating, unidentate and bidentate bridging modes for the carbonyl carbon atom was revealed, but there was no evidence for the inclusion of ethanol in the resultant structure. Therefore, the reaction in ethanol offers a convenient strategy to prepare anhydrous zinc hydroxide acetate and/or zinc oxide, because it avoids the sensitivity of the thermally induced dehydroxlation process to time, temperature and environment.
Pentanuclear {Cr2Ln3} (Ln = Dy, Tb) Heterometallic Clusters Based on an Amino Acid Ligand: Slow Relaxation of Magnetization and Substitution Reactions
Authors: Wang Xiao‐Qun , Li Zhong‐Yi , Zhu Zhao‐Xiang , Zhu Jiang , Liu Shu‐Qin , Ni Jun , Zhang Jian‐Jun 
Published: August 2013

AbstractReactions between Ln3+ (Ln = Dy, Tb), Cr3+, and glycine (HGly) in aqueous solution led to two pentanuclear compounds, Na3[Dy3Cr2(HGly)6(μ3‐OH)6(H2O)9]·(ClO4)8·Cl4·14H2O (1) and Na3[Tb3Cr2(HGly)6(μ3‐OH)6(H2O)9]·(ClO4)6·Cl6·6H2O (2). Structural analyses showed that both 1 and 2 have a {Ln3Cr2} compressed trigonal‐bipyramidal skeleton in which an axial Cr3+ ion lies above and below the triangular equatorial plane defined by the three Ln3+ ions. Magnetic measurements indicated that 1 and 2 exhibit single‐molecule magnetic behavior with Ea ≈ 14.1 K and τ0 = 4.2 × 10–8 s for 1 and Ea ≈ 13.0 K and τ0 = 6.4 × 10–7 s for 2. Interestingly, the clusters are soluble in aqueous solution. The two terminal water molecules of 1 can be substituted by two monocoordinated 4,4′‐dipyridyl N,N′‐dioxide (dpyo) molecules to afford [Dy3Cr2(HGly)6(dpyo)2(μ3‐OH)6(H2O)7]·(ClO4)9·15H2O (3) with a three‐dimensional cds network formed through π–π interactions. Magnetic analysis indicated that 3 also displays slow relaxation of the magnetization with Ea ≈ 13.24 K and τ0 = 9.16 × 10–8 s.
Asymmetric Synthesis of Crispine A: Constructing Tetrahydroisoquinoline Scaffolds Using Pummerer Cyclizations
Authors: Rotte Sateesh Chandra Kumar , Chittiboyina Amar G. , Khan Ikhlas A. 
Published: August 2013

AbstractFor the first time, a concise, linear and stereoselective synthesis of both enantiomers of the natural product crispine A has been achieved in six steps with an overall yield of ≥ 20 %, starting from commercially available veratraldehyde. Asymmetric Keck allylation and trifluoroacetic anhydride‐mediated Pummerer cyclization were the key transformations used to construct the tetrahydroisoquinoline core structure.
An Unusual and Diastereoselective Rearrangement during an Intramolecular Ene Reaction Involving a Disilane
Authors: Giros Audrey , Guillot Régis , Blanco Luis , Deloisy Sandrine 
Published: August 2013

AbstractA chiral 1‐isopropenyl‐1‐(3‐oxopropyl)disilane derivative undergoes a type II ene reaction under Lewis acid catalyzed conditions to afford the silacyclic compound and an unexpected rearranged product with high diastereoselectivities. This rearrangement occurs through 1,2‐migration of a trimethylsilyl group. A common intermediate was proposed to explain the formation of both products.
Model predictions of toxaphene degradation in the atmosphere over North America
Authors: Li R. , Jin J. 
Published: August 2013

Abstract

Technical toxaphene, a broad-spectrum pesticide mixture, degrades in the environment, resulting in potential changes in toxicity. The present study uses a multimedia model that the authors developed to estimate toxaphene degradation in the atmosphere over North America. The predicted degradation has strong spatial and temporal variability determined by processes such as emission and transport of technical toxaphene, as well as the complex interactions among many species (e.g., toxaphene, hydroxyl [OH] radicals, and ozone). More toxaphene is degraded in warmer months due to higher concentrations of technical toxaphene (primarily due to higher technical toxaphene emissions in the southeastern United States and transport to other regions) and OH radicals. In the model, OH radicals are created primarily through the reactions of water vapor with the excited oxygen atom, O(1D), generated by the photolysis of ozone, which is produced primarily by reactions of volatile organic compounds and nitrogen oxides (NOx) in the presence of sunlight. The higher OH concentrations in warmer months are primarily the result of higher solar radiation and ozone concentrations. The spatial distribution of degradation depends on the distribution of technical toxaphene soil residues as well as atmospheric transport and chemistry; significant chemical degradation occurs in the southeastern United States where soils are most heavily contaminated by past applications of toxaphene. Environ Toxicol Chem 2013;32:2663–2671. © 2013 SETAC
Effect of low concentration 17β-estradiol on the emissions of CH4 and CO2 in anaerobic sediments
Authors: Ruan Aidong , Zhao Ying , Liu Chenxiao , Wang Yuan , Xie Xianchuan 
Published: August 2013

Abstract

The estrogen17β-estradiol (E2) is one of the most widely distributed natural estrogens and is the most potent estrogen in the environment. For the present study, methanogenic bacteria communities were chosen as study objects to analyze the effects of E2 on the production of methane and carbon dioxide. Microecological systems in anaerobic pore water were constructed in the laboratory. The results show that E2 played an enhancing role in methanogenic activity when the concentrations were ≤0.5 ng/L. The enhancement was the strongest at 0.3 ng/L. However, when the E2 concentration exceeded 1.0 ng/L, it inhibited the methanogenic activities of bacteria. The inhibition effect persisted for up to 264 h, beyond which the trend became unclear. On the other hand, E2 has an inhibition effect on CO2 production in anaerobic sediments, which indicates that E2 had a significant inhibition effect on microbial activities under anaerobic conditions. Based on these experiments, the authors believe that E2 in anaerobic sediments can affect sediment microbial activities and therefore influence the self-purification of water bodies and methane ebullition. Environ Toxicol Chem 2013;32:2672–2677. © 2013 SETAC
Production of ferulic acid and coniferyl alcohol by conversion of eugenol using a recombinant strain of Saccharomyces cerevisiae
Authors: Lambert Fanny , Zucca Joseph , Ness Frédérique , Aigle Michel 
Published: August 2013

ABSTRACTWe isolated an industrial strain of Saccharomyces cerevisiae 92411 able to convert coniferyl alcohol (2 g/l) into ferulic acid (1.8 g/l). To use eugenol as a substrate for the synthesis of natural ferulic acid, an optimized sequence of the Penicillium simplicissimum vaoA gene, encoding the flavoenzyme vanillyl‐alcohol oxidase (VAO), was expressed in the yeast 92411. To obtain a strong and stable expression of vaoA, an expression cassette flanked by Ty1 homologous sequences was constructed so the sequence encoding VAO could be integrated into various Ty1 loci of the host genome. The recombinant S. cerevisiae strain produced VAO. It synthesized ferulic acid directly from eugenol due to expression of the VAO activity and the natural ability of the strain to convert coniferyl alcohol into ferulic acid. In fermentation experiments, the strain produced up to 16.9 g/l of ferulic acid after 136 h. These results open new perspectives for the use of yeast biocatalysts in the biotechnological production of aromatic flavour from eugenol. Copyright © 2013 John Wiley & Sons, Ltd.
Partially Sulfonated Poly(1,4‐phenylene ether‐ether‐sulfone) and Poly(vinylidene fluoride) Blend Membranes for Fuel Cells
Authors: Unveren E. E. , Inan T. Y. , Çelebi S. S. 
Published: August 2013

AbstractBlend membranes based on high conductive sulfonated poly(1,4‐phenylene ether‐ether‐sulfone) (SPEES) and poly(vinylidene fluoride) (PVDF) having excellent chemical stability were prepared and characterized for direct methanol fuel cells. The effects of PVDF content on the proton conductivity, water uptake, and chemical stability of SPEES/PVDF blend membranes were investigated. The morphology, miscibility, thermal, and mechanical properties of blend membranes were also studied by means of scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) measurements. The blend membrane containing 90 wt.% SPEES (degree of sulfonation – DS = 72%) and 10 wt.% PVDF (Mw = 180,000) exhibits optimum properties among various SPEES72/PVDF membranes. Addition of PVDF enhanced resistance of the SPEES membrane against peroxide radicals and methanol significantly without deterioration of its proton conductivity. It's proton conductivity at 80 °C and 100% relative humidity is higher than Nafion 115 while it's methanol permeability is only half of that of Nafion 115 at 80 °C. The direct methanol fuel cell performance of the SPEES membranes was better than that of Nafion 115 membrane at 80 °C.
Designing biomarker studies for head and neck cancer
Authors: Kim Kelly Y. , McShane Lisa M. , Conley Barbara A. 
Published: August 2013

AbstractAlthough there is ample literature reporting on the identification of molecular biomarkers for head and neck squamous cell carcinoma, none is currently recommended for routine clinical use. A major reason for this lack of progress is the difficulty in designing studies in head and neck cancer to clearly establish the clinical utility of biomarkers. Consequently, biomarker studies frequently stall at the initial discovery phase. In this article, we focus on biomarkers for use in clinical management, including selection of therapy. Using several contemporary examples, we identify some of the common deficiencies in study design that hinder success in biomarker development for this disease area, and we suggest some potential solutions. The purpose of this article is to provide guidance that can assist investigators to more efficiently move promising biomarkers in head and neck cancer from discovery to clinical practice. © 2013 Wiley Periodicals, Inc. Head Neck 36: 1069–1075, 2014
Total Synthesis of a Pyrrolidin‐2‐one with the Structure Proposed for the Alkaloid Rigidiusculamide A
Authors: Radha Krishna Palakodety , Karunakar Reddy Bonepally 
Published: August 2013

AbstractThe total synthesis of the pyrrolidinone alkaloid rigidiusculamide A is reported starting from L‐tyrosine, using amidation, ring‐closing metathesis, and dihydroxylation as the key reactions.
Using response surfaces to estimate impacts of climate change on flood peaks: assessment of uncertainty
Authors: Kay A. L. , Crooks S. M. , Reynard N. S. 
Published: August 2013

AbstractThe potential impacts of climate change are an increasing focus of research, and ever‐larger climate projection ensembles are available, making standard impact assessments more onerous. An alternative way of estimating impacts involves response surfaces, which present the change in a given indicator for a large number of plausible climatic changes defined on a regular sensitivity domain. Sets of climate change projections can then be overlaid on the response surface and impacts estimated from the nearest corresponding points of the sensitivity domain, providing a powerful method for fast impact estimation for multiple projections and locations. However, the effect of assumptions necessary for initial response surface development must be assessed. This paper assesses the uncertainty introduced by use of a sensitivity framework for estimating changes in 20‐year return period flood peaks in Britain. This sensitivity domain involves mean annual and seasonal precipitation changes, and a number of simplifications were necessary for consistency and to reduce dimensionality. The effect of these is investigated for nine catchments across Britain, representing nine typical response surfaces (response types), using three sets of climate projections. The results show that catchments can have different causes of uncertainty and some catchments have an overall higher level of uncertainty than others. These differences are compatible with the underlying climatological and hydrological differences between the response types, giving confidence in generalization of the results. This enables the development of uncertainty allowances by response type, to be used alongside the response surfaces to provide more robust impact estimates. Copyright © 2013 John Wiley & Sons, Ltd.
High Expression of SGTA in Esophageal Squamous Cell Carcinoma Correlates With Proliferation and Poor Prognosis
Authors: Yang Xiaojing , Cheng Lei , Li Mei , Shi Hui , Ren Hanru , Ding Zongmei , Liu Fang , Wang Yuchan , Cheng Chun 
Published: August 2013

ABSTRACTReceptor tyrosine kinases (RTKs) expression and the growth factor such as platelet‐derived growth factor (PDGF) and their receptors have been considered relevant in the process of angiogenesis and dissemination in esophageal squamous cell carcinoma (ESCC). Small glutamine‐rich tetratricopeptide repeat‐containing protein alpha (SGTA) downstream of RTK signaling was a critical regulator of PDGF receptors (PDGFR) stability. The aim of the present study was to examine the expression of SGTA and to elucidate its clinicopathologic significance in ESCC. Immunohistochemistry and western blot analysis were performed for SGTA in ESCC samples. SGTA was up‐regulated in ESCC as compared with the adjacent normal tissue. High expression of SGTA was associated with tumor grade (P < 0.01), and SGTA was positively correlated with proliferation marker Ki‐67 (P < 0.05). Univariate analysis showed that SGTA expression did has a remarkable prediction for poor prognosis (P = 0.016). Knockdown or overexpression of SGTA affected ESCC cells proliferation and cell cycle. Additionally, after ESCC cells silenced for SGTA were treated with cisplatin (an anti‐ESCC agent), the cell growth was down‐regulated. These findings suggested that SGTA was involved in the pathogenesis of ESCC and might indicate a poor prognosis for ESCC patients. J. Cell. Biochem. 115: 141–150, 2014. © 2013 Wiley Periodicals, Inc.
Influence of Mg doping on the morphology and optical properties of ZnO films for enhanced H2sensing
Authors: Vijayalakshmi K. , Karthick K. 
Published: August 2013

ABSTRACTHighly oriented ZnO and Mg doped ZnO thin films were fabricated on Al2O3substrate by sputtering at room temperature. The effect of Mg doping on the structural, optical, and morphological properties of ZnO film was investigated. The intensity of (002) peak in X‐ray diffraction measurements revealed the influence of Mg doping on the crystallinity and orientation of ZnO film. Photoluminescence (PL) results show that the Ultraviolet (UV) emission peak was shifted to lower wavelength side for Mg:ZnO film indicating the possibility for quantum confinement. UV–vis–NIR optical absorption revealed an improvement in optical transmittance from 70 to 85%, and corresponding optical band gap from 3.25 to 3.54 eV. Atomic force microscope (AFM) images revealed the nano‐size particulate microstructure of the films. The surface topography of Mg doped ZnO film confirmed decreased grain size with large surface roughness and increased surface area, favorable for sensing. Pure ZnO and Mg doped ZnO film were used as active layer and tested for its sensing performance to hydrogen. Compared to undoped ZnO, 22 at.% Mg doped ZnO film showed much higher sensor response to H2at a concentration as low as 200 ppm and at a lower operating temperature of 180°C. A linear sensor response was observed for H2concentration in the range of 100–500 ppm.Microsc. Res. Tech. 76:1118–1124, 2013. © 2013 Wiley Periodicals, Inc.
Photoelectrons in the Enceladus plume
Authors: Coates A. J. , Wellbrock A. , Jones G. H. , Waite J. H. , Schippers P. , Thomsen M. F. , Arridge C. S. , Tokar R. L. 
Published: August 2013

AbstractThe plume of Enceladus is a remarkable plasma environment containing several charged particle species. These include cold magnetospheric electrons, negative and positive water clusters, charged nanograins, and “magnetospheric photoelectrons” produced from ionization of neutrals throughout the magnetosphere near Enceladus. Here we discuss observations of a population newly identified by the Cassini Plasma Spectrometer (CAPS) electron spectrometer instrument—photoelectrons produced in the plume ionosphere itself. These were found during the E19 encounter, in the energetic particle shadow where penetrating particles are absent. Throughout E19, CAPS was oriented away from the ram direction where the clusters and nanograins are observed during other encounters. Plume photoelectrons are also clearly observed during the E9 encounter and are also seen at all other Enceladus encounters where electron spectra are available. This new population, warmer than the ambient plasma population, is distinct from, but adds to, the magnetospheric photoelectrons. Here we discuss the observations and examine the implications, including the ionization source these electrons provide.
Volatile organic compound distributions during the NACHTT campaign at the Boulder Atmospheric Observatory: Influence of urban and natural gas sources
Authors: Swarthout Robert F. , Russo Rachel S. , Zhou Yong , Hart Andrew H. , Sive Barkley C. 
Published: August 2013

AbstractA comprehensive suite of volatile organic compounds (VOCs) was measured at the semirural Boulder Atmospheric Observatory (BAO) in northeast Colorado during the Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT) campaign during the winter of 2011. A signature of elevated nonmethane hydrocarbon (NMHC) mixing ratios was observed throughout the campaign. The C2‐C5 alkane mixing ratios were an order of magnitude greater than the regional background. Light alkane mixing ratios were similar to those at urban sites impacted by petrochemical industry emissions with ethane and propane reaching maximums of over 100 ppbv. The mean (± standard deviation) calculated total OH reactivity (7.0 ± 5.0 s−1) was also similar to urban sites. Analysis of VOC wind direction dependence, emission ratios with tracer compounds, and vertical profiles up to 250 m implicated regional natural gas production activities as the source of the elevated VOCs to the northeast of BAO and urban combustion emissions as the major VOC source to the south of BAO. Elevated acetonitrile and dimethyl sulfide mixing ratios were also associated with natural gas emissions. Fluxes of natural gas associated NMHCs were determined to estimate regional emission rates which ranged from 40 ± 14 Gg yr−1 for propane to 0.03 ± 0.01 Gg yr−1 for n‐nonane. These emissions have the potential to impact downwind air quality as natural gas associated NMHCs comprised ≈24% of the calculated OH reactivity. The measurements described here provide a baseline for determining the efficacy of future policies designed to control emissions from natural gas production activities.