bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Surface Chemistry of 1‐Iodopropane Adsorbed on Pt(111)
Authors: Scoggins Troy B. , Ihm Hyeran , White John M. 
Published: November 2013

AbstractOn Pt(111) at 110 K, 1‐iodopropane, C3H7I, adsorbs molecularly, but for doses below 1.7 × 1014 molecules cm−2, only H2 and I appear in thermal desorption. C–I bond cleavage occurs between 160 and 220 K, forming adsorbed n‐propyl, C(a)H2CH2CH3, and atomic iodine, based on temperature‐programmed desorption (TPD), high‐resolution electron energy loss spectroscopy (HREELS), and X‐ray photoelectron spectroscopy (XPS). n‐Propyl undergoes β‐hydride elimination forming propylene, with desorption peaks at 185 and 240 K. At 240 K, hydrogenation to propane also occurs. Some di‐σ bonded propylene, C(a)H2C(a)HCH3, remains at 240 K and it rearranges to propylidyne near 300 K. Atomic H, bound to Pt, recombines and desorbs at ca. 260 K. Further desorption of H2 is limited by C–H bond breaking and occurs over a broad temperature range with local maxima at ca. 280, 320, and 420 K, typical of propylidyne fragments on Pt. Atomic iodine desorbs in a broad feature at 825 K.
A Compact UHV Tandem Quadrupole Mass Spectrometer for Surface‐Induced Dissociation Studies Using Well‐Characterized Surfaces
Authors: Bernasek Steven L. , Park Frederick D.S. , Phelan Lynn M. , Hayward Mark J. 
Published: November 2013

AbstractCollision of low‐energy polyatomic ions with surfaces can be an effective method for ion activation and fragmentation for ion structural analysis. In order for this method to be more widely used, a better understanding of low‐energy ion‐surface reactions must be obtained. The design and construction of a compact tandem quadrupole mass spectrometer which can be used to investigate low‐energy ion‐surface reactions on well‐characterized surfaces is described. This UHV‐compatible instrument is designed to fit entirely on a standard eight‐inch UHV flange, and so can be easily mounted on a typical UHV electron spectroscopy system for preparing and characterizing the scattering surface. The operation of this instrument is illustrated by the discussion of two examples: the first, the associative reaction between benzene ions and a hydrocarbon surface to form C7H7+ via a sputtered‐ion mechanism; the second, an examination of the effect of organic monolayer structure on the reactivity of the monolayer for protonation of incident benzene ions.
Adsorption and Reactivity of CO2 on Potassium‐Covered Re(001)
Authors: Zhao Wei , Chacham Ilan , Vackart Yahel , Asscher Micha 
Published: November 2013

AbstractThe interaction of CO2 with potassium‐covered Re(001) has been investigated. This system has been studied by means of work function (Δϕ), optical second harmonic generation (SHG), and temperature‐programmed desorption (TPD) measurements. Strong electronic interaction between carbon dioxide and potassium is observed upon adsorption at 90 K. This is indicated by a rapid quenching of the SHG signal of K following postadsorption of CO2, with a quenching cross section of 70 Å2. Work function change measurements are consistent with such interaction, evidenced by an undepolarization effect, namely, further decrease of the work function upon CO2 adsorption, below the minimum obtained by pure potassium. In the presence of potassium, the dissociation probability of 0.5 ML adsorbed carbon dioxide increases from 0.5 on the clean metal surface to 0.85 on 1 ML potassium‐covered Re(001), information obtained from TPD measurements following heating to 1250 K. It is concluded that a K–CO2 surface compound is formed upon adsorption at 95 K on the potassium‐covered surface.
Absolute Concentration Measurements of Chemically‐Important Flame Radicals
Authors: Crosley David R. , Jeffries Jay B. , Smith Gregory P. 
Published: November 2013

AbstractA fundamental understanding of flame chemistry is a necessary part of designing and optimizing combustors to meet environmental regulations while maintaining system efficiency. We have performed quantitative, absolute concentration measurements for several free radicals to test various aspects of the predictive capabilities of the natural gas combustion chemistry mechanism, GRI‐Mech 2.11, the chemical mechanism for methane combustion. The CH, NO, OH, and HCO radicals were studied in a series of low‐pressure methane/O2/N2 flames using the technique of laser‐induced fluorescence. The results show that GRI‐Mech 2.11 predicts well the hydrocarbon oxidation chemistry in lean and near stoichiometric flames, but appears to possess some inadequacies for rich flames. Of special importance is the finding that the rate coefficient for the important CH + N2 reaction in the current version of GRI‐Mech appears to be too low. Also, reburn of NO is correctly predicted in a lean flame but not a rich one.
Oxidation of Dimethyl Ether and its Interaction with Nitrogen Oxides
Authors: Alzueta Maria U. , Muro Julio , Bilbao Rafael , Glarborg Peter 
Published: November 2013

AbstractThe oxidation of dimethyl ether (DME) under flow reactor conditions has been studied experimentally and in terms of a detailed chemical kinetic model. The experiments were performed at atmospheric pressure in the temperature range 600–1500 K and at different air/fuel ratios. Of particular interest was the interaction of DME with nitrogen oxides. The results show that the oxidation of DME occurs readily at temperatures above 1000 K, largely independent of the stoichiometry. Addition of NO under stoichiometric and fuel‐rich conditions does not affect the oxidation chemistry for DME, but above 1100 K a minor amount of the NO is reduced to HCN and N2 in reburn‐type reactions. Addition of NO or NO2 under oxidizing conditions significantly enhances the oxidation rate of DME and shifts the temperature for onset of oxidation to lower values, a phenomenon similar to that of NOx‐sensitized oxidation of hydrocarbons.The proposed chemical kinetic model provides a good description of DME oxidation in the absence of nitrogen oxides. Under the conditions of the present study, the conversion of DME proceeds mainly through the high‐temperature mechanism, with little importance of the intermediate peroxy species. In the presence of NO or NO2, the reaction CH3 + NO2 ⇌ CH3O + NO, followed by dissociation of CH3O, readily provides H atoms and thereby promotes the oxidation. At lower temperatures the mechanism involves CH3OCH2O2 and CH3O2 radicals. While the effect of NOx generally is described satisfactorily by the model, deviations at lower temperatures may indicate inadequacies in the reaction subset for these peroxy species.
Kinetics of Hexafluoropropylene Oxide Pyrolysis Studied by Gas‐Phase NMR. Kinetic Measurements Made Easy
Authors: Krusic Paul J. , Roe D. Christopher , Smart Bruce E. 
Published: November 2013

AbstractGas‐phase NMR complemented with a high‐temperature probe makes possible quantitative kinetic studies of homogeneous vapor‐phase reactions with unprecedented ease, as demonstrated with a study of the thermal fragmentation of hexafluoropropylene oxide. The reaction follows strictly first‐order kinetics, is unaffected by surface chemistry, and the resulting Arrhenius activation parameters compare well with those obtained by more laborious classical methods of gas‐phase reaction kinetics. The fragmentation kinetics is also unaffected by the presence of oxygen. The profiles for the evolution of the final products in this case show very graphically that singlet difluorocarbene, one of the initial products of the fragmentation of hexafluoropropylene oxide, does not react with oxygen, a ground‐state triplet, at chemically significant rates.
Free Radical Chemistry. Part 9.1 Approaches to Fluorinated Polyethers—Model Compound Studies
Authors: Chambers Richard D. , Hutchinson John , Kelly Noel M. , Joel Andrew K. , Rees Anthony J. , Telford Peter T. 
Published: November 2013

AbstractUsing peroxide, γ‐, and UV‐irradiation, free radical addition reactions of hexafluoropropene to diethers and to 18‐crown‐6 have been investigated and mono‐, di‐, and poly‐adducts have been obtained. Factors influencing these additions, especially polar characteristics of intermediate radicals, have been elucidated. Adducts of 18‐crown‐6 retain a capacity to complex to alkali‐metal ions.
1,8H‐Perfluorocyclooctatetraene and its Congeners. Dynamic Equilibrium among Four Valence Isomers
Authors: Takenaka Natalie E. , Hamlin Robert , Spector Tami , Junk Christopher P. , Lemal David M. 
Published: November 2013

AbstractSynthesized from hexafluorobenzene, the title compound was found to interconvert readily via bond–shift isomerization and electrocyclization with significant amounts of three other valence isomers. The mobile equilibria were revealed by 19F NMR spectroscopy, and spin–saturation transfer experiments played a key role in identifying the isomers, tracing their interconversions, and assigning their spectra. The influence of fluorine substitution on the stability of carbon–carbon double bonds and of 4‐membered rings is discussed in the light of these results.
Fluorinated Isopentenyladenines: Synthesis and Cytokinin Activity
Authors: Marival‐Hodebar Laurence , Tordeux Marc , Wakselman Claude , Dias Marylène , Mornet René , Laloue Michel 
Published: November 2013

AbstractAnalogs of N6‐isopentenyladenine bearing one or two fluorine atoms at the allylic position were synthesized from simple fluorinated ketones. The monofluoro analog was found to be more active than N6‐isopentenyladenine and equivalent to the more potent zeatin, another natural plant growth hormone. The difluoro analog was even more powerful than zeatin.
Lewis Acid Mediated Peterson Fluoroolefination
Authors: Welch John T. , Gregor Tamas , Kornilov Andrei 
Published: November 2013

AbstractPeterson olefination of the alkyl and aryl aldehydes with C,O‐bis(triethylsilyl)fluoroketene acetal 1 promoted by titanium tetrachloride and dimethylaluminum chloride was investigated. Desired fluoroolefins were formed with high stereoselectivity and moderate to high yields.
Photoinduced Double Proton Transfer: Inter‐ and Intramolecular Cases
Authors: Kyrychenko Alexander , Herbich Jerzy , Izydorzak Marcin , Gil Michał , Dobkowski Jacek , Wu Feiyue , Thummel Randolph P. , Waluk Jacek 
Published: November 2013

AbstractPhotoinduced two‐proton tautomerization has been studied in two types of chromophores: (i) alcohol complexes of azaaromatic molecules possessing both proton donor and acceptor groups; (ii) constitutional isomers of porphyrin. The reaction path for the intermolecular process may involve solvent reorientation around the excited chromophore. In this case, rapid internal conversion is activated, efficiently competing with proton transfer. Another possibility arises if cyclic, doubly‐hydrogen‐bonded complexes exist already in the ground state. Excitation of such species leads to a fast tautomerization, which is not stopped even at low temperatures. Excited‐state double proton transfer also has been observed in cyclic dimers in the crystal phase. In porphyrin isomers, the rate of the process is a function of the strength of the intramolecular hydrogen bond. Dependence of the phototautomerization rate on temperature and on the nature of the surrounding matrix has also been studied.
Evidence for 1La, 1Lb Dual State Emission in 1‐naphthol and 1‐methoxynaphthalene Fluorescence in Liquid Solutions
Authors: Magnes Ben‐Zion , Strashnikova Natalya V. , Pines Ehud 
Published: November 2013

AbstractThe steady‐state fluorescence spectra of 1‐methoxynaphthalene and 1‐naphthol were measured in pure organic solvents and in binary mixtures of water and several organic solvents. The 1‐isomers exhibited a much larger fluorescence Stokes‐shift than the corresponding 2‐isomers. The emission spectra of 1‐methoxynaphthalene and 1‐naphthol in pure nonpolar organic solvents exhibited roughly the same structured spectral features, while the fluorescence spectra in water and formamide exhibited much broader red‐shifted and less structured spectral features. In accord with previous observations, we attribute these spectral changes to two emitting states, 1Lb and 1La, whose relative fluorescence intensities are sensitive to solvent polarity. Our analysis of the fluorescence spectra of 1‐naphthol and 1‐methoxynaphthalene by Pekarian functions have demonstrated that the 1La state becomes the dominant emitting state in polar solvents. In addition, the 1La state was found to be further stabilized in hydrogen‐bond‐donating solvents. In contrast to previous suggestions, the onset of the excited‐state proton transfer reaction from 1‐naphthol occurred at higher solvent polarities than those required for the establishment of a dominantly 1La emitting state.
Gauging of Cytochrome c Structural Fluctuation by Time‐Resolved Proton Pulse
Authors: Marantz Yael , Nachliel Esther 
Published: November 2013

AbstractA brief proton pulse technique, based on photo‐excitation of pyranine, was employed for measuring the protonation dynamics of cytochrome c in aqueous solutions. Time‐resolved monitoring of the protonation state of the pyranine anion yielded detailed information from which the temporal state protonation of the surface carboxylates and histidine residues were deduced.The surface groups were found to be coupled by electrostatic interaction where the state of protonation of one affects the pK of the others. In the same sense, altering the charge distribution of a protein by a redox reaction affects the reactivity of the surface groups with protons in the bulk.The surface groups can exchange protons among themselves at a very high rate. The velocities of these reactions are functions of the connectivity between the proton binding sites. A single proton exchange reaction between the surface groups could be identified as the proton exchange between H26 and E44. The reaction is fast and affected by the redox state of the protein. It is proposed that the enhanced rate of this reaction is coupled with transient conformational changes that are not noticeable in time‐averaging measurements such as X‐ray diffraction or NMR.
Evaluation of the potential anti‐adhesion effect of the PVA/Gelatin membrane
Authors: Bae Sang‐Ho , Son So‐Ra , Kumar Sakar Swapan , Nguyen Thi‐Hiep , Kim Shin‐Woo , Min Young‐Ki , Lee Byong‐Taek 
Published: November 2013

ABSTRACTA common and prevailing complication for patients with abdominal surgery is the peritoneal adhesion that follows during the post‐operative recovery period. Biodegradable polymers have been suggested as a barrier to prevent the peritoneal adhesion. In this work, as a preventive method, PVA/Gelatin hydrogel‐based membrane was investigated with various combinations of PVA and gelatin (50/50, 30/70/, and 10/90). Membranes were made by casting method using hot PVA–gelatin solution and the gelatin was cross‐linked by exposing UV irradiation for 5 days to render stability of the produced sheathed form in the physiological environment. Physical crosslinking was chosen to avoid the problems of potential cytotoxic effect of chemical crosslinking. Their materials characterization and mechanical properties were evaluated by SEM surface characterization, hydrophilicity, biodegradation rate, and so forth. Cytocompatibility was observed by in vitro experiments with cell proliferation using confocal laser scanning microscopy and the MTT assay by L‐929 mouse fibroblast cells. The fabricated PVA/Gel membranes were implanted between artificially defected cecum and peritoneal wall in rats and were sacrificed after 1 and 2 weeks post‐operative to compare their tissue adhesion extents with that of control group where the defected surface was not separated by PVA/Gel membrane. The PVA/Gel membrane (10/90) significantly reduced the adhesion extent and showed to be a potential candidate for the anti‐adhesion application. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 840–849, 2014.
Segmental mandibular bone reconstruction with a carbonate‐substituted hydroxyapatite‐coated modular endoprosthetic poly(ɛ‐caprolactone) scaffold in Macaca fascicularis
Authors: Chanchareonsook Nattharee , Tideman Henk , Feinberg Stephen E. , Jongpaiboonkit Leenaporn , Lee Shermin , Flanagan Colleen , Krishnaswamy Gita , Jansen John 
Published: November 2013

AbstractA bio‐degradable scaffold incorporating osteoinductive factors is one of the alternative methods for achieving the regeneration of a mandibular bone defect. The current pilot study addressed such a bone reconstruction in a non‐human primate model, Macaca fascicularis monkeys, with an engineered poly(ɛ‐caprolactone) (PCL) scaffold, provided with a carbonate‐substituted hydroxyapatite coating. The scaffolds were implanted into unilaterally created mandibular segmental defects in 24 monkeys. Three experimental groups were formed: (1) scaffolds with rhBMP‐2 (n = 8), (2) scaffolds with autologous mixed bone marrow cells (n = 8), and (3) empty scaffolds as a control group (n = 8). Evaluation was based on clinical observation as well as micro‐CT, mechanical, and histological analyses. Despite a high infection rate, the overall results showed that the currently designed PCL scaffolds had insufficient load‐bearing capability, and complete bone union was not achieved after 6 months of implantation. Nevertheless, the group of PCL scaffolds loaded with rhBMP‐2 showed evidence of bone‐regenerative potential, in contrast to PCL with autologous mixed bone marrow cells and the control group. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 962–976, 2014.
Morphology, drug release, antibacterial, cell proliferation, and histology studies of chamomile‐loaded wound dressing mats based on electrospun nanofibrous poly(ɛ‐caprolactone)/polystyrene blends
Authors: Motealleh Behrooz , Zahedi Payam , Rezaeian Iraj , Moghimi Morvarid , Abdolghaffari Amir Hossein , Zarandi Mohammad Amin 
Published: November 2013

AbstractFor the first time, it has been tried to achieve optimum conditions for electrospun poly(ε‐caprolactone)/polystyrene (PCL/PS) nanofibrous samples as active wound dressings containing chamomile via D‐optimal design approach. In this work, systematic in vitro and in vivo studies were carried out by drug release rate, antibacterial and antifungal evaluations, cell culture, and rat wound model along with histology observation. The optimized samples were prepared under the following electrospinning conditions: PCL/PS ratio (65/35), PCL concentration 9%(w/v), PS concentration 14%(w/v), distance between the syringe needle tip and the collector 15.5 cm, applied voltage 18 kV, and solution flow rate 0.46 mL h−1. The FE‐SEM micrographs showed electrospun PCL/PS (65/35) nanofibrous sample containing 15% chamomile had a minimum average diameter (∼175 nm) compared to the neat samples (∼268 nm). The drug released resulted in a gradual and high amount of chamomile from the optimized PCL/PS nanofibrous sample (∼70%) in respect to PCL and PS nanofibers after 48 h. This claim was also confirmed by antibacterial and antifungal evaluations in which an inhibitory zone with a diameter of about 7.6 mm was formed. The rat wound model results also indicated that the samples loaded with 15% chamomile extract were remarkably capable to heal the wounds up to 99 ± 0.5% after 14 days post‐treatment periods. The adhesion of mesenchymal stem cells and their viability on the optimized samples were confirmed by MTT analysis. Also, the electrospun nanofibrous mats based on PCL/PS (65/35) showed a high efficiency in the wound closure and healing process compared to the reference sample, PCL/PS nanofibers without chamomile. Finally, the histology analysis revealed that the formation of epithelial tissues, the lack of necrosis and collagen fibers accumulation in the dermis tissues for the above optimized samples. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 977–987, 2014.
Applications of Stable Isotope Analysis in Zooarchaeology: An Introduction
Authors: Zangrando A. F. , Tessone A. , Ugan A. , Gutiérrez M. A. 
Published: November 2013

ABSTRACTThis special volume brings together works that present cases of studies that combine analysis of stable isotopes and zooarchaeology in different areas of Chile and Argentina, with special emphasis on the latter. These analyses were conducted in order to examine paleoecological conditions and interactions between humans and animal resources in different spatial and temporal contexts. In this introduction, we examine three ways in which stable isotopes have been applied in zooarcheology: (i) past animal‐human relations, (ii) stable isotopes and zooarchaeology in conservation biology, and (iii) species biogeography, climate, and environment. The implications of the results of each of the papers in this volume stress that this type of study is a fruitful and promising line of research as it expands the thematic spectrum investigated, tests archaeological hypothesis, explores new lines of analysis, and enriches the interpretations about the past. Copyright © 2014 John Wiley & Sons, Ltd.
Obesity consults—comprehensive obesity management in 2013: Understanding the shifting paradigm
Authors: Kushner Robert F. , Apovian Caroline M. , Fujioka Ken 
Published: November 2013

Although serious health concerns are associated with obesity, losing even 5% of body weight can produce clinically relevant effects. The initial goal of obesity management is usually a 5% to 10% weight reduction. Some people will sustain weight loss with changes in diet and exercise alone; however, these patients represent the minority, and a large percentage are unable to maintain weight loss over time.Patients and providers often wish to intensify obesity treatment, and therefore interest in new medications has been considerable. Until recently, only two antiobesity medications have received Food and Drug Administration approval for long‐term use. In June and July of 2012, respectively, lorcaserin and combination phentermine/topiramate extended‐release were approved for obesity therapy. The first section of this article reviews mechanisms, clinical trials, benefits and risks of available medications for treating obesity.Bariatric surgery is the next step for patients with a body mass index of ≥40 kg/m2 or ≥35 kg/m2 with comorbidities, based on National Institutes of Health Clinical Guidelines. These procedures and their risks and benefits are reviewed in the second section. The final section presents common clinical scenarios with guidance for choosing among evidence‐based recommendations for developing optimal, individualized, long‐term strategies for patients with obesity.
Characterization of ADN/GAP‐Based and ADN/Desmophen®‐Based Propellant Formulations and Comparison with AP Analogues
Authors: Cerri Sara , Bohn Manfred A. , Menke Klaus , Galfetti Luciano 
Published: November 2013

AbstractSeveral ADN‐based rocket propellant formulations containing different pre‐polymers (GAP diol/triol, Desmophen® 2200), curing agents (BPS, Desmodur® N100, Desmodur® N3400), plasticizers (BDNPA‐F, TMETN), and filler types (Al, HMX) have been manufactured. Propellant formulations were characterized by tensile tests, SEM analyses and DMA measurements. The study has focused on characterizations of the propellants in terms of evaluation of the strength and strain capability, investigation of the presence/absence of dewetting phenomena, compatibility issues and evaluation of the glass transition temperature. Ammonium perchlorate‐based propellant formulations have also been manufactured and analyzed in order to make comparisons. Aging was investigated using mass loss measurements.