bluuebunny/crossref_metadata_2025_split huggingface dataset:
Probing the Influence of Alloyed Sn on Pt(100) Surface Chemistry by CO Chemisorption
Authors: Panja Chameli , Koel Bruce E. 
Published: November 2013

AbstractThe chemisorption properties of the c(2×2) and (3√2×√2)R45° Sn/Pt(100) alloy surfaces, along with the clean Pt(100) surface, were investigated using CO as a probe molecule. Temperature‐programmed desorption (TPD) studies revealed a reduction in CO desorption peak temperature, and thus the chemisorption bond energy, by alloying Sn into the Pt(100) surface. A large decrease was observed in the saturation coverage of CO on these alloyed surfaces at 150 K compared to the Pt(100) surface. The initial sticking coefficient of CO was found, however, to be nearly independent of the surface Sn concentration. High‐resolution electron energy loss spectroscopy (HREELS) studies showed that CO was only chemisorbed on atop sites on both alloys. Sn incorporation results in isolated Pt atoms at the surface of these two Sn/Pt(100) alloys and eliminates the possibility of CO bonding to multiple Pt centers, i.e., to pure‐Pt 2‐ and 3‐fold bridging sites.
Selective Oxidation of Propene at Cesium and Cesium‐modified Ag(100) Surfaces
Authors: Carley Albert F. , Chambers Alan , Roberts M. Wyn , Santra Ashok K. 
Published: November 2013

AbstractThe oxidation of propene at Ag(100), Ag(100)–Cs, and Cs surfaces has been investigated by X‐ray photoelectron spectroscopy in the temperature range 80–298 K. The atomically clean Ag(100) surface is unreactive, while cesium surfaces effect mainly dehydrogenation or selective oxidation with some metal–carbon bond formation, but with complete oxidation a minor pathway. Partially cesiated Ag(100) surfaces, on the other hand, result in complete oxidation to give surface carbonate at 160 K. Two key intermediates responsible for the alternative reaction pathways have been delineated through their very different, but characteristic, C(1s) spectra at 80 K.
Dynamic Monte Carlo Simulations of Oscillatory Reactions
Authors: Gelten Ronald J. , Jansen Tonek P.J. , van Santen Rutger A. , Lukkien Johan J. , Segers John P.L. , Hilbers Peter A.J. 
Published: November 2013

AbstractThe dynamic Monte Carlo method has been used to simulate the 2 A + B2 → 2 AB reaction catalyzed by a reconstructing substrate. Oscillatory behavior and spatio‐temporal is studied as a function of grid size. Spatio‐temporal pattern formation has been simulated in various forms: cellular patterns, target patterns, rotating spirals, and turbulent patterns. Cellular patterns are a manifestation of a local synchronization mechanism in which all reaction fronts periodically extinguish each other. This illustrates that dynamic Monte Carlo simulations form a promising technique and can be used to predict macroscopic kinetic phenomena on a molecular basis.
Laser and Probe Diagnostics in Fundamental Combustion Research
Authors: Kohse‐Höinghaus Katharina 
Published: November 2013

AbstractCombustion diagnostics using lasers has matured considerably during the last decade. By now, lasers are routinely relied upon in many practical applications where direct inspection of the combustion process is necessary. Quantitative information, however, may still be a major challenge. In this article, some essential features of laser techniques for fundamental combustion research are discussed in view of their potential and limitations. Laser methods are complemented by molecular beam mass spectrometry. Applications include diagnostics in laminar and turbulent diffusion flames, in fuel‐rich and sooting flames, and in combustion chemical vapor deposition (CVD) of thin diamond films. Avenues for further research will be discussed.
CH, NH, and NH2 Concentration Profiles in Methane/Air Flames Doped with N2O
Authors: Derzy Igor , Lozovsky Vladimir A. , Cheskis Sergey 
Published: November 2013

AbstractIntracavity Laser Absorption Spectroscopy (ICLAS) and Cavity Ring‐Down Spectroscopy (CRDS) were used to measure concentration profiles of the CH, NH, and NH2 radicals in a low‐pressure (30 Torr) stoichiometric methane/oxygen/nitrogen flat flame doped with a small amount of nitrous oxide (1.7%). Concentration profiles of the CH and NH radicals were measured by CRDS, whereas the NH2 radical profile was measured by ICLAS. Temperature profiles were obtained using measured CRDS spectra of the OH radical. The radical absorption spectra were recorded with good signal‐to‐noise ratio. For the first time, absolute concentrations of NH and NH2 were measured in flames of this kind. The obtained experimental profiles and peak amounts agree well with model predictions based on GRI‐Mech 2.11 (Gas Research Institute Mechanism). The mechanism also describes well the observed decreasing CH concentration with addition of N2O.
Synthesis and Structure of New Dimeric Cyclopentadienyl Titanium Fluorine–Oxygen Systems: [Cp*TiF(μ‐F)(μ‐OPOPh2)]2, [Cp*TiF(μ‐F)(μ‐OSO2‐p‐C6H4Me)]2 and [Cp*TiF2(μ‐OMe)]2
Authors: Gindl Judith , Said Musa A. , Yu Peihua , Roesky Herbert W. , Noltemeyer Mathias , Schmidt Hans‐Georg 
Published: November 2013

AbstractThe reactions of Cp*TiF3 with Me3SiOPOPh2, Me3SiOSO2‐p‐C6H4Me, and Al(OMe)3 resulted in the formation of the dimers [Cp*TiF(μ‐F)(μ‐OPOPh2)]2 1, [Cp*TiF(μ‐F)(μ‐OSO2‐p‐C6H4Me)]2 2, and [Cp*TiF2(μ‐OMe)]2 3, respectively, in good yields. In contrast to the formation of 3, Cp*TiF3 reacts with Al(OH)3 to afford the known tetramer [Cp*TiF(μ‐O)]4 4. The structures of 1–3 have been determined by X‐ray crystallography; compounds 1 and 3 crystallize in the monoclinic space group P21/c and compound 2 in the monoclinic space group P2/n. Compound 1 is the first example of a dimeric Cp*‐titanium phosphinate containing a fluorine ligand. The core of the dimeric structure of both 1 and 2 consists of two Ti atoms bridged by two fluorine atoms and two bidentate groups. In contrast, the dimeric structure of 3 consists of two Ti atoms bridged only by two methoxy groups. An equilibrium of isomers of 1 and 2 has been observed in solution by 1H and 19F NMR. The 19F NMR spectra of 1–3 are discussed in detail.
Electrochemical Direct Fluorination of Lactams
Authors: Sawaguchi Masanori , Hara Shoji , Fukuhara Tsuyoshi , Yoneda Norihiko 
Published: November 2013

AbstractThe electrochemical fluorination of a variety of N‐protected lactams was carried out and Et3N–5HF was found to be superior to Et3N–3HF as the electrolyte. When 5‐ and 6‐membered N‐acetyl or ethoxycarbonyl lactams were used as substrates, the fluorination reaction selectively took place at the α‐position of the lactam nitrogen and the corresponding monofluoro products could be obtained in good yields.
Electrophilic Fluorination of Aromatics with Selectfluor™ and Trifluoromethanesulfonic Acid1
Authors: Shamma Tatyana , Buchholz Herwig , Prakash G.K. Surya , Olah George A. 
Published: November 2013

Abstract1‐(chloromethyl)‐4‐fluoro‐1,4‐diazabicyclo[2.2.2]octane bis (tetrafluoroborate) [Selectfluor™ F‐TEDA‐BF4 (TEDA = triethylenediamine)] in the presence of trifluoromethanesulfonic acid has been found to be a very effective reagent system for the direct electrophilic fluorination of a wide variety of aromatic compounds under mild reaction conditions to the corresponding fluoroaromatics in good to excellent yields.
Consequences of Protonation of Diamines in the Gas Phase and the Solid State
Authors: Woźniak Krzysztof , Raczyñska Ewa D. , Korybut‐Daszkiewicz Bogdan 
Published: November 2013

AbstractAn interesting model class of compounds are proton sponges—aromatic diamines characterized by exceptional basicity, such as 1,8‐bis(dimethylamino)naphthalene (DMAN). For these compounds, protonation causes substantial redistribution of electron density which may be traced by observing the changes of structural parameters as well as of the properties of electron density at bond critical points. On protonation, electron density in DMAN goes from the terminal atoms towards the center of the molecule. This redistribution can also be confirmed by good quality neutron structural data.An ionic complex of DMAN with triformylmethane (TFM) acid has been studied by X‐ray diffraction. We propose a multicenter model of hydrogen bonding {[Me2N–H0.5….0.5H–NMe2]+… X−} in this complex. The influence of weak intermolecular interactions of the DMANH+cation with the nearest electronegative atom from the counterion on the strong intramolecular [N–H···N]+hydrogen bonding has been demonstrated. Such interactions affect the localization of the proton in the intramolecular [N–H···N]+hydrogen bridge.
Acid Ionization of HBr in a Small Water Cluster
Authors: Gertner Bradley J. , Peslherbe Gilles H. , Hynes James T. 
Published: November 2013

AbstractThe acid ionization by which HBr transfers a proton to a water molecule is studied for HBr in small water clusters as a first stage in a study of the corresponding Arctic atmospheric process. Electronic structure calculations, involving relatively large basis sets and including electron correlation effects, indicate that HBr is acid‐ionized in a cluster of four water molecules. The most stable structure in the general HBr(H2O)4 system is a diamond‐like (trigonal bipyramidal) structure in which the bromide and hydronium ion species are bridged by three water molecules, and infrared spectral and ionization potential characteristics potentially useful for experimental study are provided. This structure is calculated to remain the thermodynamically most stable one up to about 180 K, where HBr + (H2O)4 becomes more stable. Aspects of the formation of the acid‐ionized cluster from both HBr + (H2O)4 and H2O + HBr(H2O)3 are discussed. Possible implications for HBr acid ionization at the surface of ice, believed to be important for Arctic atmosphere ozone depletion mechanisms, are briefly discussed.
Hydrogen‐Bond Dynamics and Solvation of Electronically Excited States as Determined by Femtosecond Vibrational Spectroscopy
Authors: Nibbering Erik T.J. , Chudoba Christian , Elsaesser Thomas 
Published: November 2013

AbstractThe ultrafast dynamics of site‐specific hydrogen bonds between an organic chromophore serving as hydrogen acceptor and a hydrogen‐donating species in solution is studied by femtosecond vibrational spectroscopy. This new method gives specific insight into microscopic structural changes of hydrogen bonds initiated by electronic excitation of the chromophore. We study H‐bonded complexes of coumarin 102 with the solvent CHCl3, and with phenol. Upon electronic excitation, the intermolecular hydrogen bond between proton donor and acceptor is cleaved within 200 fs, followed by a slower reorientation dynamics of the donor molecules extending into the picosecond regime. For CHCl3, this slower rearrangement is interpreted in terms of polar solvation. In complexes consisting of a coumarin molecule and two phenol moieties, the slower dynamics is related to geometry changes of the phenol–phenol hydrogen bond. The consequences of those results for a microscopic picture of polar solvation are discussed.
An Extended Empirical Valence Bond Model for Describing Proton Mobility in Water
Authors: Vuilleumier Rodolphe , Borgis Daniel 
Published: November 2013

AbstractIn order to study the microscopic nature of the hydrated proton and its transport mechanism, we have introduced a multistate empirical valence bond model, fitted to ab initio results. This model was applied to the study, at low computational cost, of the structure and dynamics of an excess proton in liquid water. The quantum character of the proton is included by means of an effective parametrization of the model using preliminary path‐integral calculations. The mechanism of proton transfer is interpreted as the translocation of a special O–H+–O bond along the hydrogen network, i.e., a series of reactions of the form H5O2+ + H2O ⇌ H2O + H5O2+, rather than H3O+ + H2O → H2O + H3O+ as usually described. The translocation of the special bond can be described as a diffusion process with a jump time of 1 ps. A time‐dependent correlation function analysis of the special pair relaxation yields two timescales, 0.3 and 3.5 ps. The first time is attributed to the interconversion between a delocalized (H5O2+‐like) and a localized (H9O4+‐like) form of the hydrated proton within a given special pair. The second one is the relaxation time of the special pair, including return trajectories. The computed diffusion constant, as well as the isotopic substitution effect, are in good agreement with experiment. The hydration structure around the excess proton is discussed in terms of various radial distribution functions around the water molecules involved in the special pair and those in the first solvation shell. The hydrogen‐bond‐dynamics which accompanies the translocation process is studied statistically. The “Moses mechanism” proposed by Noam Agmon for proton mobility in water is partially verified by our simulations.
Quantum Properties of the Excess Proton in Liquid Water
Authors: Schmitt Udo W. , Voth Gregory A. 
Published: November 2013

AbstractThe classical and quantum equilibrium properties of an excess proton in bulk phase water are examined computationally with a special emphasis on the influence of an explicit quantum dynamical treatment of the nuclei on the calculated observables. The potential model used, our recently developed multistate empirical valence bond (MS‐EVB) approach is described. The MS‐EVB model takes into account the interaction of an exchange charge distribution of the charge‐transfer complex with the polar solvent, which qualitatively changes the nature of the solvated complex. The impact and importance of the exchange term on the stability of the solvated H5O2+ (Zundel) cation relative to the H9O4+ (Eigen) cation in the liquid phase is demonstrated. Classical and quantum path‐integral molecular dynamics (PIMD) simulations of an excess proton in bulk phase water reveal that quantization of the nuclear degrees of freedom results in an increased stabilization of the solvated Zundel cation relative to the Eigen cation, and that species intermediate between the two are also probable. Quantum effects lead to a significant broadening of the probability distributions used to characterize the two species, and a definite differentiation and sharp characterization of the species connected to the excess proton in liquid water is found to be difficult.
Comparative analysis of in vitro oxidative degradation of poly(carbonate urethanes) for biostability screening
Authors: Dempsey David K. , Carranza Christopher , Chawla Chander P. , Gray Patrick , Eoh Joon H. , Cereceres Stacy , Cosgriff‐Hernandez Elizabeth M. 
Published: November 2013

AbstractThe resistance to oxidation and environmental stress cracking of poly(carbonate urethanes) (PCUs) has generated significant interest as potential replacements of poly(ether urethanes) in medical devices. Several in vitro models have been developed to screen segmented polyurethanes for oxidative stability. High concentrations of reactive oxygen intermediates produced by combining hydrogen peroxide and dissolved cobalt ions has frequently been used to predict long‐term oxidative degradation with short‐term testing. Alternatively, a 3% H2O2 concentration without metal ions is suggested within the ISO 10993‐13 standard to simulate physiological degradation rates. A comparative analysis which evaluates the predictive capabilities of each test method has yet to be completed. To this end, we have utilized both systems to test three commercially available PCUs with low and high soft segment content: Bionate® PCU and Bionate® II PCUs, two materials with different soft segment chemistries, and CarboSil® TSPCU, a thermoplastic silicone PCU. Bulk properties of all PCUs were retained with minor changes in molecular weight and tensile properties indicating surface oxidative degradation in the accelerated system after 36 days. Soft segment loss and surface damage were comparable to previous in vivo data. The 3% H2O2 method exhibited virtually no changes on the surface or in bulk properties after 12 months of treatment despite previous in vivo results. These results indicate the accelerated test method more effectively characterized the oxidative degradation profiles than the 3% H2O2 treatment system. The lack of bulk degradation in the 12‐month study also supports the hydrolytic stability of these PCUs. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3649–3665, 2014.
Modeling of porous scaffold deformation induced by medium perfusion
Authors: Podichetty Jagdeep T. , Madihally Sundararajan V. 
Published: November 2013

AbstractIn this study, we tested the possibility of calculating permeability of porous scaffolds utilized in soft tissue engineering using pore size and shape. We validated the results using experimental measured pressure drop and simulations with the inclusion of structural deformation. We prepared Polycaprolactone (PCL) and Chitosan–Gelatin (CG) scaffolds by salt leaching and freeze drying technique, respectively. Micrographs were assessed for pore characteristics and mechanical properties. Porosity for both scaffolds was nearly same but the permeability varied 10‐fold. Elastic moduli were 600 and 9 kPa for PCL and CG scaffolds, respectively, while Poisson's ratio was 0.3 for PCL scaffolds and ∼1.0 for CG scaffolds. A flow‐through bioreactor accommodating a 10 cm diameter and 0.2 cm thick scaffold was used to determine the pressure‐drop at various flow rates. Additionally, computational fluid dynamic (CFD) simulations were performed by coupling fluid flow, described by Brinkman equation, with structural mechanics using a dynamic mesh. The experimentally obtained pressure drop matched the simulation results of PCL scaffolds. Simulations were extended to a broad range of permeabilities (10−10 m2 to 10−14 m2), elastic moduli (10–100,000 kPa) and Poisson's ratio (0.1–0.49). The results showed significant deviation in pressure drop due to scaffold deformation compared to rigid scaffold at permeabilities near healthy tissues. Also, considering the scaffold as a nonrigid structure altered the shear stress profile. In summary, scaffold permeability can be calculated using scaffold pore characteristics and deformation could be predicted using CFD simulation. These relationships could potentially be used in monitoring tissue regeneration noninvasively via pressure drop. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 737–748, 2014.
Complete subchondral bone defect regeneration with a tricalcium phosphate collagen implant and osteoinductive growth factors: A randomized controlled study in Göttingen minipigs
Authors: Gotterbarm Tobias , Breusch Steffen J. , Jung Martin , Streich Nikolaus , Wiltfang Jörg , Berardi Vilei Simona , Richter Wiltrud , Nitsche Tobias 
Published: November 2013

AbstractThe restoration and reconstruction of osseous defects close to the joint, constitutes a challenging field for reconstructive surgery. A dual‐layer implant of β‐tricalcium phosphate (TCP) and a collagens I/III scaffold was evaluated in a prospective, randomized comparison in a larger animal model. For this purpose, a standardized osteochondral defect was created in the medial facet of the patellar groove in both stifle joints of Göttingen minipigs. Critical‐size osseous defects were either left empty (spontaneous healing; group 1; n = 12) or treated with the two‐layer TCP collagen implant (group 2; n = 12). In group 3 (n = 12), additional growth factor mixture (GFM) was supplemented (bone morphogenetic proteins 2, 3, 4, 6, 7, and TGF‐β1, 2, 3). Osseous defect regeneration was assessed at 6, 12, and 52 weeks postoperatively (n = 4). Qualitative and quantitative histomorphometric assessment of defect regeneration and bone substitute resorption was conducted by means of light microscopy, fluorescence microscopy, and microradiography. Critical‐size defects did not heal spontaneously throughout follow‐up (group 1: max. 21.84 ± 2.81% defect area at 52 weeks). The TCP layer of the implant significantly increased the amount of new bone formation with 29.8 ± 9.68% at 6 weeks and 40.09 ± 4.76% at 12 weeks when compared with controls. After 52 weeks, the TCP was almost fully degraded (4.35 ± 3.70%) and the defect was restored with lamellar trabecular bone (31.28 ± 5.02%). Growth factor supplementation resulted in earlier resorption of the TCP implant and faster defect regeneration. The dual‐layer TCP collagen implant is suitable to restore subchondral osseous defects. Additional use of GFM increased the resorption of the TCP layer, but did not foster new bone formation. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 933–942, 2014.
A Genetic Algorithm‐Based Method for the Automatic Reduction of Reaction Mechanisms
Authors: Sikalo N. , Hasemann O. , Schulz C. , Kempf A. , Wlokas I. 
Published: November 2013

ABSTRACTAn automatic method for the reduction of chemical kinetic mechanisms under specific physical or thermodynamic conditions is presented. The method relies on the genetic algorithm search logic to gradually reduce the number of reactions from the detailed mechanism while still preserving its ability to describe the overall chemistry at an acceptable error. Accuracy of the reduced mechanism is determined by comparing its solution to the solution obtained with the full mechanism under the same initial and/or physical conditions. However, not only the chemical accuracy and the size of the mechanism are considered but also the time for its solution which helps to avoid stiff and slow converging mechanisms, thus preferring the fast solutions. The reduction method is demonstrated for a detailed mechanism for methane combustion, GRI‐Mech 3.0, which was reduced from 325 reactions and 53 species to 58 reactions and 26 species, and for an iron oxide formation mechanism from iron pentacarbonyl doped flames by Wlokas et al. (Int J Chem Kinet 2013, 45(8), 487–498), originally consisting of 144 reactions and 34 species, which was reduced to 37 reactions and 24 species. The performance of the reduced mechanisms is shown for homogeneous constant pressure reactors and for burner‐stabilized flames. The results show a good agreement between reduced and full mechanisms for both the reactor and flame cases. The presented method is flexible and can be easily adjusted to either yield more accurate (but bigger) or smaller (but less accurate) reduced mechanisms, depending on the user's preference.
Cluster TOF‐SIMS imaging as a tool for micrometric histology of lipids in tissue
Authors: Bich Claudia , Touboul David , Brunelle Alain 
Published: November 2013

AbstractRecent developments in instrumentation, ion beams or analyzers, for cluster time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) imaging are described here. The methods which are employed to increase the sensitivity or to perform three‐dimensional analyses in the organic materials are also illustrated. This review shows the improvements made for lipid imaging by cluster TOF‐SIMS in various types of material and applications, and gives reasons for the expansion of its utilization. © 2013 Wiley Periodicals, Inc. Mass Spec Rev 33: 442–451, 2014.