bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photolysis of Ketene‐Oxygen Mixtures between 253 K and 323 K in Relation to the Formation of Criegee Intermediates
Authors: Horie O. , Moortgat G. K. 
Published: May 2011

AbstractKetene was photolyzed in a flow reactor in Ar/O2 = 80/20 carrier gas between 253 and 323 K. Products observed by matrix‐isolation FTIR spectroscopy were CO, CO2, O3, HCHO, HCOOH, and CH3C(O)OC(O)H, formic‐acetic anhydride. Addition of HCHO did not produce hydroxymethyl formate, CH2(OH)OCHO, a product expected from the reaction of the stabilized Criegee intermediate H2COO with HCHO. Photolysis in the presence of a large excess of water vapour did not change the product pattern. It was concluded that no stabilized Criegee intermediates were formed under the experimental conditions.
FTIR Studies on the Photooxidation Mechanisms of CH3Cl, CH3Br, CHBr3 and CF3Br
Authors: Weller R. , Lorenzen‐Schmidt H. , Schrems O. 
Published: May 2011

AbstractThe Photooxidations of CH3Cl, CH3Br, CF3Br, and CHBr3 in dry‐air have been investigated at 298 K in a static reaction vessel by means of FTIR spectroscopy. Irradiation of the reaction mixtures has been performed by Hg‐resonance lamps (184.9 nm and 253.7 nm lines) and broad band UV‐fluorescence lamps (300–400 nm). The photooxidation mechanism of CH3Cl and CH3Br is governed by two different pathways: 1) photolytical release of halogen atoms and subsequent oxidation of the CH3 radical, 2) abstraction of an H‐atom and oxidation of the respective CH2Cl and CH2Br‐fragment. The second path leads to the formation of the formyl‐halides HClCO and HBrCO which are transferred to CO and HCl or CO and HBr, respectively. Addition of trace amounts of NO to the gas mixture decreases the HClCO yield strongly. We suggest that NO reacts with the transient H2ClCO‐radical to ClNO + H2CO. HBrCO, Br2CO and the final products CO, CO2, and HBr could be identified after Hg‐resonance lamps induced photooxidation of CHBr3. The Cl2/fluorescence lamps induced photooxidation, however, yielded solely Br2CO, CO2, and HBr. In contrast to the labile species HClCO, HBrCO, and Br2CO, the photooxidation product of CF3Br, carbonyl fluoride (F2CO) is relatively inert under our reaction conditions.
A Novel Laser‐Based Technique for the Time‐Resolved Study of Integrated Hydrocarbon Oxidation Mechanisms
Authors: Hoffmann A. , Mörs V. , Zellner R. 
Published: May 2011

AbstractAn experimental method has been developed to study the formation of OH radicals and of NO2 in the integrated oxidation chain of hydrocarbons under NOx‐rich tropospheric conditions. In this technique the oxidation of hydrocarbons is initiated by laser pulse photolysis of Cl2 and the temporal behaviour of OH and NO2 is monitored by direct time‐resolved cw‐laser absorption and LIF, respectively. Combined with computer modelling of the complete oxidation mechanisms the results allow the determination of (i) the extent of NO/NO2 conversion and hence the ozone formation potential of individual hydrocarbons and (ii) the branching ratio of HO2 formation relative to other reaction channels of alkoxy radicals. First applications of this technique to the oxidation of C2H6 and C3H8 are presented.
Electron Attachment Processes in Molecular Aggregates
Authors: Hashemi Reza , Meinke Martina , Jaffke Thomas , Illenberger Eugen 
Published: May 2011

AbstractReactions in negatively charged clusters following resonant electron attachment have been studied in a supersonic beam experiment. The results are discussed with respect to the correspondent processes from single molecules in the gas phase and from condensed molecules. It is shown that electron capture by oxygen clusters allows the population of electronic states in O2− not accessible in the single‐electron‐molecule frame of reference (violation of the σ− selection rule). Clusters composed of O2/CF2Cl2 yield ionic products composed of both constituents. They are generated along a complex scattering process within the ionized aggregate. The resonance profiles of their ion yields contain information on their genesis, i.e. the initial step of electron capture by the electrophore in the cluster. Since these reactions occur predominantly at low energies, sometimes at zero eV, we consider them as highly relevant in any environment (gaseous or condensed) where low energy electrons are present.
Metal Ion Catalyzed Autoxidation of Sulfur(IV)‐Oxides: Redox Cycling of Metal Ions Induced by Sulfite
Authors: van Eldik R. , Coichev N. , Bal Reddy K. , Gerhard A. 
Published: May 2011

AbstractThe important role of metal ion catalyzed autoxidation reactions of sulfur(IV)‐oxides in aqueous solution has been confirmed by numerous investigations. In general, transition metals such as Co, Fe and Mn in the 3+ oxidation state can rapidly oxidize HSO3−/SO32‐ to produce the reduced metal ions in the 2 + oxidation state and the SO3− radical, which can subsequently initiate a series of free radical propagation reactions. Experimental results are reported to demonstrate how low concentration levels of sulfite can effectively induce the autoxidation of the reduced metal ions in order to complete the catalytic cycle. In this way the mentioned metal ions exhibit redox cycling in which the nature of the redox process is determined by the sulfite and oxygen concentration levels in solution. A general mechanism to account for these observations, as well as for the synergistic effect usually observed for such reactions, is presented.
Kinetics and Mechanism of Sulfur(IV) Oxidation by Hydrogen Peroxide in Aqueous Phase: The Non‐Linear Parts of the pH‐Profile
Authors: Drexler C. , Elias H. , Fecher B. , Wannowius K. J. 
Published: May 2011

AbstractStopped‐flow spectrophotometry was used to study the oxidation of S(IV) by H2O2 at 285 K and 298 K, respectively, in the pH range −0.3 to 13 in buffered aqueous solution under pseudo‐first‐order conditions (I = 0.5, 1.0 and 2.0 M NaClO4, respectively). The reaction of HSO3− with H2O2 is subject to general‐acid catalysis whereas that of the SO32‐ ion is not. The dependence of the experimental first‐order rate constant on the concentration of the excess partner [H2O2] was studied in detail. — In the pH range −0.3 to 6 the rate is given by Eq. (1) (KR1 and KS1: acid dissociation constants of H3O2+ and SO2, respectively; [H] = proton activity).magnified imageKexp is the experimental overall equilibrium constant for the various protonation steps involved in the formation of the intermediate peroxosulfurous acid (= PSA), whereas K is the equilibrium constant for the formation of PSA. Its decay (k = 740 s−1 at 285 K) controls the rate of S(V1) formation. The pKa of the species H3O2+ as derived from the kinetic data, is found to be pKR1 = 1.5–2.0. —In the pH range 6–8, the rate is given by pKa(HSO3−)).magnified imageAt pH > 8, the rate is governed by Eq. (3) pKa(HSO3−magnified imageThe data for k, K, kH, kHOH, k and k are presented and the mechanistic implications of rate laws (1)–(3) are discussed.
Vertical Transport of Trace Species by Thunderstorms — A Transilient Transport Model
Authors: Alheit R. R. , Hauf T. 
Published: May 2011

AbstractA 2D‐cloud model with spectral microphysics including ice physics and aerosol particle scavenging effects is used to simulate the 19 July 1981 CCOPE thunderstorm case. The net vertical transport of a chemically inert tracer between 30 respective levels by a single thunderstorm was determined in terms of a transilient matrix. Additionally, the redistribution of sulfur which was assumed to be initially present in aerosol particles was investigated. Beside transport with the mean wind, nucleation scavenging, particle scavenging, and wet deposition contribute to the observed redistribution. — The simulations show that even a moderate thunderstorm may reduce the pollution in the boundary layer by 50%. Trace species may be transported in less than half an hour from the ground to the upper troposphere and, in contrast, trace species originating from the upper troposphere may not have the change to be transported down to the ground. Net mixing strongly depends on the detailed dynamical and microphysical structure of the investigated thunderstorm. The hypothesis that thunderstorms play an important role in redistribution and wet deposition of airborne aerosol particle mass is confirmed.
Meta-analysis of two randomized controlled trials to identify long-term symptoms after division of the short gastric vessels during Nissen fundoplication
Authors: Engström C , Jamieson G G , Devitt P G , Watson D I 
Published: May 2011

Abstract

Background
Randomized trials suggest that division of the short gastric vessels during Nissen fundoplication is unnecessary. Some trials report an increased risk of gas bloat symptoms following division of the short gastric vessels. In this study long-term follow-up data from the two largest randomized clinical trials of division versus no division of the short gastric vessels during laparoscopic Nissen fundoplication were combined to determine whether there were differences in late outcome.

Methods
Patients with gastro-oesophageal reflux disease who underwent primary laparoscopic antireflux surgery and were included in two previously reported randomized trials were studied. Of 99 patients enrolled in the Swedish study and 102 in the Australian study, the short gastric vessels were divided in 104 and left intact in 97. Data sets were combined and late clinical outcomes analysed.

Results
At 10–12 years' follow-up (mean 11·5 years) clinical data were obtained from 170 patients (86 with vessels divided, 84 undivided). Statistical analysis of the combined data set showed no significant differences in symptoms of heartburn or dysphagia, ability to belch or vomit, and use of antisecretory medications. Division of the short gastric vessels was associated with a higher rate of bloating symptoms (72 versus 48 per cent; P = 0·002).

Conclusion
Division of the short gastric vessels is followed by a slightly poorer clinical outcome at late follow-up after Nissen fundoplication. Surgeons should avoid dividing these vessels when undertaking a laparoscopic Nissen fundoplication.
Analysis of aggregate size as a process variable affecting paclitaxel accumulation in Taxus suspension cultures
Authors: Kolewe Martin E. , Henson Michael A. , Roberts Susan C. 
Published: May 2011

AbstractPlant cell aggregates have long been implicated in affecting cellular metabolism in suspension culture, yet the rigorous characterization of aggregate size as a process variable and its effect on bioprocess performance has not been demonstrated. Aggregate fractionation and analysis of biomass‐associated product is commonly used to assess the effect of aggregation, but we establish that this method is flawed under certain conditions and does not necessarily agree with comprehensive studies of total culture performance. Leveraging recent advances to routinely measure aggregate size distributions, we developed a simple method to manipulate aggregate size and evaluate its effect on the culture as a whole, and found that Taxus suspension cultures with smaller aggregates produced significantly more paclitaxel than cultures with larger aggregates in two cell lines over a range of aggregate sizes, and where biomass accumulation was equivalent before elicitation with methyl jasmonate. Taxus cuspidata (T. cuspidata) P93AF cultures with mean aggregate sizes of 690 and 1,100 μm produced 22 and 11 mg/L paclitaxel, respectively, a twofold increase for smaller aggregates, and T. cuspidata P991 cultures with mean aggregate sizes of 400 and 840 μm produced 6 and 0.3 mg/L paclitaxel, respectively, an increase of 20‐fold for smaller aggregates. These results demonstrate the importance of validating experiments aimed at a specific phenomenon with total process studies, and provide a basis for treating aggregate size as a targeted process variable for rational control strategies. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011
Quantitative Contrast Evaluation of an Industry‐Style Rhodium Nanocatalyst with Single Atom Sensitivity
Authors: Specht Petra , Gulotty Robert J. , Barton David , Cieslinski Robert , Rozeveld Steve , Kang Joo H. , Dubon Oscar. D. , Kisielowski Christian 
Published: May 2011

AbstractAberration‐corrected electron microscopy opens new ways for material characterization. In catalyst research it will enable the observation of single atom arrangements, such as the location of promoter atoms on catalyst particles. However, quantitative procedures must be developed to account for dynamic contrast changes resulting from beam‐sample interactions and incoherent instrument aberrations. We demonstrate that at low acceleration voltage (80 kV), for which knock‐on damage is suppressed, the residual intensity fluctuations can be attributed to the presence of phonons resulting in 3D low frequency atom displacements. For rhodium [110] oriented particles it was found that the catalysts are platelets with an aspect ratio of about 0.2 and a surface roughness of ±1 atom. Observation of single surface atoms requires minimization of phonon‐induced motion.
Dealloying Ag–Al Alloy to Prepare Nanoporous Silver as a Substrate for Surface‐Enhanced Raman Scattering: Effects of Structural Evolution and Surface Modification
Authors: Qiu Huajun , Zhang Zhonghua , Huang Xirong , Qu Yinbo 
Published: May 2011

AbstractSensitive detection of molecules by using the surface‐enhanced Raman scattering (SERS) technique depends on the nanostructured metallic substrate and many efforts have been devoted to the preparation of SERS substrates with high sensitivity, stability, and reproducibility. Herein, we report on the fabrication of stable monolithic nanoporous silver (NPS) by chemical dealloying of Ag–Al precursor alloys with an emphasis on the effect of structural evolution on SERS signals. It was found that the dealloying conditions had great influence on the morphology (the ligament/pore size) and the crystallization status, which determined the SERS signal of rhodamine 6G on the NPS. NPS with small pores, low residual Al, and perfect crystallization gave high SERS signals. A high enhancement factor of 7.5×105 was observed on bare NPS obtained by dealloying Ag30Al70 in 2.5 wt % HCl at room temperature followed by 15 min aging at around 85 °C. After coating Ag nanoparticles on the NPS surface, the enhancement factor increased to 1.6×108 owing to strong near‐field coupling between the ligaments and nanoparticles.
Remarkable Differences in the Coordination Chemistry of Structurally Related 1,2,4‐Triphosphaferrocenes with Copper(I) Halides and Silver(I) Salts
Authors: Deng Shining , Schwarzmaier Christoph , Zabel Manfred , Nixon John F. , Bodensteiner Michael , Peresypkina Eugenia V. , Balázs Gábor , Scheer Manfred 
Published: May 2011

AbstractThe coordination behavior of 1,2,4‐triphosphaferrocenes [FeCpR(η5‐P3C2tBu2)] [CpR = Cp (1), Cp″′ = η5‐C5H2tBu3 (3)] towards CuI halides is significantly influenced by the substitution pattern of the cyclopentadienyl ring attached to the iron atom. The reaction of the Cp derivative 1 with CuBr in a 1:1 stoichiometry leads to the dimeric complex [{FeCp(η5:η1:η1‐P3C2tBu2)}{μ‐CuBr(MeCN)}]2 (5b), in which two 1,2,4‐triphosphaferrocenes are linked by two CuBr units. By using a 1:2 stoichiometry, the 1D polymeric compound [{FeCp(η5:η1:η1:η1‐P3C2tBu2)}μ‐{(CuBr)3(MeCN)2}]n (6) is formed in which the triphosphaferrocenes are bridged by (CuBr)2{CuBr(MeCN)2} units. Starting from CuI, independent of the stoichiometry, the cage compound [{FeCp(η5:η1:η1‐P3C2tBu2)}3{Cu(μ‐I)}3{Cu(μ3‐I)}3{Cu(NCMe)}(μ6‐I)](7) is formed. However, if the bulky Cp″′ derivative 3 is used already in a 1:1 stoichiometry with CuBr, a transformation of the initially five‐membered 1,2,4‐triphospholyl ring into a four‐membered 1,2‐diphosphete ligand is observed, which is linked by CuBr moieties forming the dimeric paramagnetic complex [{FeCp″′(η4:η1:η1‐P2C2tBu2)}(μ‐CuBr)]2 (9). Furthermore, applying a 1:2 stoichiometry between 3 and CuX (X = Br, I) the complete fragmentation of the 1,2,4‐triphospholyl ring under mild conditions into a tetraphosphabutadiene ligand is observed. In the formed 1D polymeric complexes [{(FeCp″′)2(μ,η4:η1:η1‐P4)}{(μ‐CuX)2(MeCN)}]n [X = Br (10a), I (10b)] this ligand represents now the middle deck of the triple‐decker sandwich complexes linked by four‐membered [(CuX)2(CH3CN)] moieties. Moreover, the reaction of the Cp derivative 1 with the Ag salt of the weakly coordinating anion [Al{OC(CF3)3}]4– leads to the dimeric Ag(CH3CN)‐bridged dicationic product [{FeCp(η5‐P3C2tBu2)}Ag(MeCN)]2[Al{OC(CF3)3}4]2 (11).
Preparation of Nitrogen‐Substituted Ferrocene Derivatives by Aza‐Wittig Methodologies
Authors: Molina Pedro , Tárraga Alberto , Alfonso María 
Published: May 2011

AbstractSeveral methodologies based on the aza‐Wittig reaction, mainly developed by our research group, have been used for the preparation of a wide variety of ferrocenes containing nitrogen functionalities. Syntheses of mononuclear and nitrogen‐rich multinuclear ferrocenophanes, ferrocenyl‐pyrazine, quinoline, imidazole and oxazole derivatives have been performed through aza‐Wittig reactions and by aza‐Wittig/heterocumulene‐mediated annulation, aza‐Wittig/electrocyclic ring‐closure and aza‐Wittig/intramolecular halide displacement methodologies.
Efficacy of C–N Coupling Reactions with a New Multinuclear Copper Complex Catalyst and Its Dissociation into Mononuclear Species
Authors: Zou Yan , Lin Haisheng , Maggard Paul A. , Deiters Alexander 
Published: May 2011

AbstractA new tetranuclear copper(I)–pyridazine (pda)/rhenate hybrid has been synthesized under hydrothermal conditions and structurally characterized by X‐ray crystallography. The activity of this catalyst, as well as its dissociation into mononuclear species, was investigated in homogeneous C–N arylation reactions. A variety of N‐arylamides and ‐azoles were synthesized in good to excellent yields, revealing the effect of polynuclear versus mononuclear Cu complexation in this type of coupling reaction.
Association of grip strength with dementia in a Korean older population
Authors: Shin Hee‐Young , Kim Sung‐Wan , Kim Jae‐Min , Shin Il‐Seon , Yoon Jin‐Sang 
Published: May 2011

BackgroundSeveral studies have found that low grip strength is associated with dementia in Western populations. However, there have been few studies in Asian populations. This cross‐sectional study aimed to examine whether grip strength is independently associated with dementia after controlling for other related factors in a Korean older population.MethodsOne thousand thirty‐eight community‐dwelling older people aged 65 or over within a defined geographic area were screened for dementia. Data on grip strength, sit‐to‐stand score, body mass index (BMI), socio‐demographic factors (age, gender, marital status, education), and medical conditions (diabetes, hypertension, heart disease, stroke) were collected. Dementia was diagnosed with the 10/66 dementia diagnostic algorithm.ResultsEleven percent of the participants were found to have dementia. After adjustment for other factors, grip strength (per 8‐kg decrease) was independently associated with dementia (odds ratio, 1.59; 95% confidence interval, 1.19–2.14). Adjusted grip strength by BMI interaction terms showed marginal significance (p = 0.098); that is, older people with both reduced grip strength and low BMI were likely to be at higher risk for dementia.ConclusionsReduced grip strength was independently associated with dementia in a Korean older population. This association was partially influenced by BMI. Copyright © 2011 John Wiley & Sons, Ltd.
A simple and efficient synthesis and dynamic NMR studies of some new podands of dithiocarbamates formed from bis(naphthyl) derivatives
Authors: Shockravi Abbas , Kamali Mahmood , Sorkhei Farhad , Jafari Reza 
Published: May 2011

AbstractThe reaction of dithiocarbamate salts (IVa − c) with bis(naphthalene chloroacetates) (IIa,b) and bis(naphthalene ethoxybromide) (IIc) in dimethylformamide (DMF) furnished corresponding podands as Va − i in high to excellent yields. Three reacting ligands, (IIa,b) and (IIc), were obtained in the reaction of bis(naphthalene) (Ia,b) with chloroacetylchloride and 1,2‐dibromoethane. Dynamic NMR spectroscopic data of three series of podands (Va − c, Vd−f, and Vg − i) are discussed, and their free energy of activation (Δ GC≠) at coalescence temperatures are figured out. The Δ GC≠ s of these podands were attributed to conformational isomerization in the range of 14.5–18.3 kcal mol−1 due to rotation and resonance effects about thioamide CN bond. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:659–668, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20730
Synthesis of phosphorus‐containing dipeptide mimetics via the Kabachnik–Fields reaction
Authors: Todorov Petar T. , Aneva Ogniana , Naydenova Emilia D. 
Published: May 2011

AbstractThe synthesis of three novel dimethyl (2‐(4,4‐dimethyl‐2,5‐dioxoimidazolidin‐1‐ylamino)‐ 2‐oxoethylamino)methylphosphonate, dimethyl (1‐ (4,4‐dimethyl‐2,5‐dioxoimidazolidin‐1‐ylamino)‐4‐ methyl‐1‐oxopentan‐2‐ylamino)methylphosphonate, and dimethyl (1‐(4,4‐dimethyl‐2,5‐dioxoimidazolidin‐ 1‐ylamino)‐1‐oxo‐3‐phenylpropan‐2‐ylamino)methylphosphonate, respectively, is reported. The newly synthesized compounds were prepared via the Kabachnik–Fields reaction. Their structures have been characterized by elemental analysis, IR, and NMR (1H, 13C, and 31P) spectra. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:669–672, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20731
Fibrillar films obtained from sodium soap fibers and polyelectrolyte multilayers
Authors: Zawko Scott A. , Schmidt Christine E. 
Published: May 2011

AbstractAn objective of tissue engineering is to create synthetic polymer scaffolds with a fibrillar microstructure similar to the extracellular matrix. Here, we present a novel method for creating polymer fibers using the layer‐by‐layer method and sacrificial templates composed of sodium soap fibers. Soap fibers were prepared from neutralized fatty acids using a sodium chloride crystal dissolution method. Polyelectrolyte multilayers (PEMs) of polystyrene sulfonate and polyallylamine hydrochloride were deposited onto the soap fibers, crosslinked with glutaraldehyde, and then the soap fibers were leached with warm water and ethanol. The morphology of the resulting PEM structures was a dense network of fibers surrounded by a nonfibrillar matrix. Microscopy revealed that the PEM fibers were solid structures, presumably composed of polyelectrolytes complexed with residual fatty acids. These fibrillar PEM films were found to support the attachment of human dermal fibroblasts. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 2011.
Arginine conjugation affects the endocytic pathways of chitosan/DNA nanoparticles
Authors: Zhang Hailing , Zhu Dunwan , Song Liping , Liu Lanxia , Dong Xia , Liu Zhenbao , Leng Xigang 
Published: May 2011

AbstractPrevious reports showed that arginine‐rich peptides and oligoarginines facilitated the cellular internalization of DNA and proteins. A number of studies demonstrated that arginine‐conjugated chitosan (CS)/DNA nanoparticles (ACGN) mediated significantly higher expression of the transgenes when compared with CS/DNA nanoparticles (CGN). However, the underlying mechanisms remain poorly understood. In the current study, the endocytic pathways through which cells internalize ACGN and CGN were explored by incubating the fluorescent CGN or ACGN with A10 cells in the presence of a variety of inhibitors of different endocytic pathways. The data accumulated in the current study revealed that conjugation of arginine moieties onto CS molecules enhanced the cellular uptake of the polymer/DNA nanoparticles and their transgenic efficacy, probably due to changes in the endocytic pathways, which led to the preference of internalization of ACGN by the caveolin‐mediated endocytosis in comparison with that of CGN. These findings provide further support to the previous observations that ACGN mediated much higher expression of the transgenes when compared with CGN. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 2011.