22,804 research outputs found

    Detonation interaction with an interface

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    Detonation interaction with an interface was investigated, where the interface separated a combustible from an oxidizing or inert mixture. The ethylene-oxygen combustible mixture had a fuel-rich composition to promote secondary combustion with the oxidizer in the turbulent mixing zone (TMZ) that resulted from the interaction. Sharp interfaces were created by using a nitro-cellulose membrane to separate the two mixtures. The membrane was mounted on a wood frame and inserted in the experimental test section at a 45° angle to the bulk flow direction. The membrane was destroyed by the detonation wave. The interaction resulted in a transmitted and reflected wave at a node point similar to regular shock refraction. A detonation refraction analysis was carried out to compare with the measured shock angles. It was observed that the measured angle is consistently lower than the predicted value. An uncertainty analysis revealed possible explanations for this systematic variation pointing to factors such as the incident wave curvature and the role of the nitro-cellulose diaphragm. Analysis of the TMZ and Mach stem formed from the reflection of the transmitted shock wave off the solid boundary were carried out and found to justify the size and strength of these features as a function of the test gas composition. The role of secondary combustion in the TMZ was also investigated and found to have a small influence on the wave structure

    Selective gas phase hydrogenation of nitroarenes over Mo2C-supported Au–Pd

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    Open Access via RSC Gold 4 Gold Financial support to Dr. X. Wang through the Overseas Research Students Award Scheme (ORSAS) is acknowledged. Dr. N. Perret also acknowledges financial support from COST Action MP0903 Nanoalloys.Peer reviewedPublisher PD

    Nitrosyl-heme and anion-arene complexes: structure, reactivity and spectroscopy

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    Two topics are selected and illustrated to exemplify (i) a biological and (ii) an organic ionic intermediate. The reactivity behavior of NO adducts with ferric and ferrous hemes has shown remarkable similarities when examined in the gas phase, demonstrating that the largely different NO affinity displayed in solution and in biological media is due to the different coordination environment. In fact, ferrous hemes present a vacant or highly labile axial coordination site, prone to readily bind NO. The vibrational signatures of the NO ligand have also been probed in vacuo for the first time in the nitrosyl complexes deriving from ferrous and ferric hemes under strictly comparable five-coordination at the metal center. Negatively charged sigma-adducts, from the association of anions with 1,3,5-trinitrobenzene, an exemplary pi-electron-deficient arene, have been probed by IRMPD spectroscopy and found to display variable binding motifs from a strongly covalent sigma-adduct (Meisenheimer complex) to a weakly covalent sigma-complex, depending on the anion basicity

    Uncoupled Hartree-Fock calculations of the polarizability and hyperpolarizabilities of nitrophenols

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    The polarizability and hyperpolarizabilities of nitrophenols as model compounds for studying nonlinear optics have been investigated at the Hartree-Fock level of approximation by means of the Dalgarno Uncoupled Hartree-Fock (DUHF) or Sum Over Orbitals (SOO) method. The additive character and the charge transfer effects in α,β,γ and have been analyzed in terms of the δ and π molecular orbital contributions, the contribution of the individual π molecular orbitals, and the contribution of the highest occupied and the lowest unoccupied\ud molecular orbitals. Within the SOO approach, the reliability of the Two-Level Model has been tested and the influence of the rotation of the nitro group and of the presence of the intramolecular hydrogen bonding in ortho-nitrophenol have been studied. The results show that the present method is a reliable and efficient tool for the prediction of trends in the molecular polarizability and hyperpolarizabilities of large molecule

    Boston University Wind Ensemble, April 21, 2009

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    This is the concert program of the Boston University Wind Ensemble performance on Tuesday, April 21, 2009 at 7:30 p.m., at the Tsai Performance Center, 685 Commonwealth Avenue, Boston, Massachusetts. Works performed were Nitro by Frank Ticheli, Celebration, A Praeludium for Wind, Brass, Percussion, Harp, and Piano by Edward Gregson, For Purple Mountain Magesties by Roger Cichy, First Suite in Eb, op. 28, no. 1 by Gustav Holst, and Symphony No. 2 by John Barnes Chance. Digitization for Boston University Concert Programs was supported by the Boston University Center for the Humanities Library Endowed Fund

    The Cowl - v.83 - n.4 - Sep 27, 2018

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    The Cowl - student newspaper of Providence College. Vol 83 - No. 4 - September 27, 2018. 24 pages

    Electron Capture Dissociation Mass Spectrometry of Tyrosine Nitrated Peptides

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    In vivo protein nitration is associated with many disease conditions that involve oxidative stress and inflammatory response. The modification involves addition of a nitro group at the position ortho to the phenol group of tyrosine to give 3-nitrotyrosine. To understand the mechanisms and consequences of protein nitration, it is necessary to develop methods for identification of nitrotyrosine-containing proteins and localization of the sites of modification.Here, we have investigated the electron capture dissociation (ECD) and collision-induced association (CID) behavior of 3-nitrotyrosine-containing peptides. The presence of nitration did not affect the CID behavior of the peptides. For the doubly-charged peptides, addition of nitration severely inhibited the production of ECD sequence fragments. However, ECD of the triply-charged nitrated peptides resulted in some singly-charged sequence fragments. ECD of the nitrated peptides is characterized by multiple losses of small neutral species including hydroxyl radicals, water and ammonia. The origin of the neutral losses has been investigated by use of activated ion (AI) ECD. Loss of ammonia appears to be the result of non-covalent interactions between the nitro group and protonated lysine side-chains

    The Effects of Arsenical Compounds on Growth and Enzymes of Klebsiella Pneumoniae

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    For many years people have equated arsenic or compounds containing arsenic with poison. Inorganic arsenic compounds are used as chemotherapeutic agents as well as poisons. Organic arsenicals were introduced at the start of this century launching modern chemotherapy. The introduction of antibiotics in the 1940’s virtually replaced organic arsenicals in chemotherapy. Solutions of inorganic arsenic compounds are used as tonics for animals and to finish animals for show. Because arsenicals are excreted by animals in much the same structure as they are consumed and arsenite prevents both putrefaction and growth, it is possible the decomposition of animal excreta will be inhibited. The decomposition of animal wastes is of interest to the laboratory and to the nation. Thus, this study was undertaken to determine if growth could be inhibited by either the feed additive 3-nitro-40hydroxyphenylarsonic acid or 3-nitro-4 hydroxyphenlarsine oxide. Enzyme investigations were made to determine whether these two arsenicals inhibited enzymes of the tricarboxylic acid cycle

    5-deazaflavin derivatives as inhibitors of p53 ubiquitination by HDM2

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    Based on previous reports of certain 5-deazaflavin derivatives being capable of activating the tumour suppressor p53 in cancer cells through inhibition of the p53-specific ubiquitin E3 ligase HDM2, we have conducted an structure–activity relationship (SAR) analysis through systematic modification of the 5-deazaflavin template. This analysis shows that HDM2-inhibitory activity depends on a combination of factors. The most active compounds (e.g., 15) contain a trifluoromethyl or chloro substituent at the deazaflavin C9 position and this activity depends to a large extent on the presence of at least one additional halogen or methyl substituent of the phenyl group at N10. Our SAR results, in combination with the HDM2 RING domain receptor recognition model we present, form the basis for the design of drug-like and potent activators of p53 for potential cancer therapy

    Spatially resolved electronic structure of an isovalent nitrogen center in GaAs

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    Small numbers of nitrogen dopants dramatically modify the electronic properties of GaAs, generating very large shifts in the conduction-band energies with nonlinear concentration dependence, and impurity-associated spatially-localized resonant states within the conduction band. Cross-sectional scanning tunneling microscopy provides the local electronic structure of single nitrogen dopants at the (110) GaAs surface, yielding highly anisotropic spatial shapes when the empty states are imaged. Measurements of the resonant states relative to the GaAs surface states and their spatial extent allow an unambiguous assignment of specific features to nitrogen atoms at different depths below the cleaved (110) surface. Multiband tight binding calculations around the resonance energy of nitrogen in the conduction band match the imaged features. The spatial anisotropy is attributed to the tetrahedral symmetry of the bulk lattice. Additionally, the voltage dependence of the electronic contrast for two features in the filled state imaging suggest these features could be related to a locally modified surface state
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