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71.
Berwyck L. J. Poad Huong T. Pham Michael C. Thomas Jessica R. Nealon J. Larry Campbell Todd W. Mitchell Stephen J. Blanksby 《Journal of the American Society for Mass Spectrometry》2010,21(12):1989-1999
Ozone-induced dissociation (OzID) exploits the gas-phase reaction between mass-selected lipid ions and ozone vapor to determine
the position(s) of unsaturation. In this contribution, we describe the modification of a tandem linear ion-trap mass spectrometer
specifically for OzID analyses wherein ozone vapor is supplied to the collision cell. This instrumental configuration provides
spatial separation between mass-selection, the ozonolysis reaction, and mass-analysis steps in the OzID process and thus delivers
significant enhancements in speed and sensitivity (ca. 30-fold). These improvements allow spectra revealing the double-bond
position(s) within unsaturated lipids to be acquired within 1 s: significantly enhancing the utility of OzID in high-throughput
lipidomic protocols. The stable ozone concentration afforded by this modified instrument also allows direct comparison of
relative reactivity of isomeric lipids and reveals reactivity trends related to (1) double-bond position, (2) substitution
position on the glycerol backbone, and (3) stereochemistry. For cis- and trans-isomers, differences were also observed in the branching ratio of product ions arising from the gas-phase ozonolysis reaction,
suggesting that relative ion abundances could be exploited as markers for double-bond geometry. Additional activation energy
applied to mass-selected lipid ions during injection into the collision cell (with ozone present) was found to yield spectra
containing both OzID and classical-CID fragment ions. This combination CID-OzID acquisition on an ostensibly simple monounsaturated
phosphatidylcholine within a cow brain lipid extract provided evidence for up to four structurally distinct phospholipids
differing in both double-bond position and sn-substitution. 相似文献
72.
Zucchi G Thuéry P Rivière E Ephritikhine M 《Chemical communications (Cambridge, England)》2010,46(48):9143-9145
Reaction between EuCl(2) and 2,2'-bipyrimidine (bpm) in de-oxygenated water afforded a cationic molecular complex [EuCl(bpm)(2)(H(2)O)(4)][Cl]·H(2)O (1). When performed in an organic solvent such as THF or methanol, the same reaction yielded a 3-dimensional coordination polymer of formula [EuCl(2)(bpm)(MeOH)(0.5)](∞) (2) in which both bpm and the chloride ions act as linkers between the Eu(II) ions. Upon replacing Cl(-) by I(-), two coordination polymers of formula {[Eu(bpm)(2)(H(2)O)(3)][I](2)·0.5bpm}(∞) (3) and {[Eu(I)(bpm)(MeOH)][I]}(∞) (4) were obtained from reaction in water and methanol, respectively. All these compounds were characterized by X-ray crystallography. Investigations of the magnetic properties revealed a weak antiferromagnetic coupling in 2, while 3 and 4 showed a weak ferromagnetic coupling at low temperature. 相似文献
73.
Thang M. Ngo Nam M. Hoang Tram T. M. Tran 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):287-293
The effects of absorbed doses, initial pH and 1-naphthol concentration onto its radiolysis in aqueous sulphuric and hydrochloric
acids by gamma rays from 60Co were investigated. Under the experimental conditions, 1-naphthol degradation yields increased with increasing the absorbed
doses (0.3–3.0 kGy) and with decreasing the initial 1-naphthol concentration (20–1 ppm). It was found out that the hydrated
electrons did not play any significant roles in 1-naphthol radiolysis, as the degradation yields were higher at pH0 ~ 0.46 compared to those at pH0 ~ 2.0–5.0. The corresponding radiolytic yields G(−1-naphthol) were (6.13 ± 1.00)) × 10−2 and (5.11 ± 0.22) × 10−2 μmol/J in sulphuric acids, (15.61 ± 3.85) × 10−2 and (4.76 ± 0.48) × 10−2 μmol/J in hydrochloric acids. 1-Naphthol degradation rates could be described by the kinetic equations of pseudo-first-order
reactions. An empirical relation between the observed reaction constants k
D and the initial 1-naphthol concentrations was established, enabling to predict the absorbed doses required for a given treatment
efficiency. Three products of 1-naphthol degradation were revealed using an HPLC/UV procedure. 相似文献
74.
Luu Viet Hung O. D. Maslov M. V. Gustova Trinh Thi Thu My Phung Khac Nam Ho 《Physics of Particles and Nuclei Letters》2011,8(4):412-416
The leaves, stem, and roots of two types of shrubs (tea (Camellia sinensis) and sweet leaf (Sauropus androgynus)) and two types of herbs (vetiver grass (Vetiveria zizanioides L. Nash) and maize (Zea mays L)) and the Thucuc soil where the plants were growing were collected to be studied. The contents of 22 elements in the samples
were determined by three methods: X-Ray fluorescence analysis (XRFA), gamma activation analysis (GAA), and the tracking method
to study the distribution of these elements in plants and the soil-plant relationship. This study was carried out at the Flerov
Laboratory of Nuclear Reactions (FLNR), Joint Institute for Nuclear Research (JINR), Dubna, Russia. The distribution of the
elements in the soil-plant system was studied. 相似文献
75.
76.
Helen L. Ngo 《Tetrahedron letters》2005,46(4):595-597
Polar bisphosphonic acid-derived Ru(BINAP)(DPEN)Cl2 precatalysts were synthesized and immobilized in room temperature ionic liquids (RTILs) for asymmetric hydrogenation of aromatic ketones with ee values of up to 98.7%. The performance of the Ru catalysts is highly dependent on the nature of imidazolium ILs. For the imidazolium ILs without acidic protons, both ILs and Ru catalysts were recycled by simple extraction and reused. Such a simple immobilization approach also prevented the leaching of Ru (and Ru catalysts) into the chiral secondary alcohol products, and should prove desirable for the production of pharmaceutical intermediates that are free from metal contaminants. 相似文献
77.
The value of the central density is of key importance for annihilation processes. For the ground state we discuss its determination from the moments of the ground state density. We first review the way of reaching the moments from the spectrum. In particular we show how to get the lowest moments in D = 3, namely 〈r−2〉 and 〈r−1〉 from the series expansion of the Laplace transform of the density. We then recall a method to obtain the central density based on the Stieltjes moment problem. If the number of known moments is finite, this technique yields a lower bound. We investigate the possibilities to estimate the accuracy of the bound and the corresponding asymptotic value. An application to the muonic 208Pb atom is presented. 相似文献
78.
Tran Dan Thu 《Journal of Combinatorial Theory, Series A》2007,114(8):1504-1514
The powerful AZ identity is a sharpening of the famous LYM-inequality. More generally, Ahlswede and Zhang discovered a generalization in which the Bollobás inequality for two set families can be lifted to an identity.In this paper, we show another generalization of the AZ identity. The new identity implies an identity which characterizes the deficiency of the Bollobás inequality for an intersecting Sperner family. We also give some consequences relating to Helly families and LYM-style inequalities. 相似文献
79.
Dr. George N. Khairallah Dr. Alan T. Maccarone Dr. Huong T. Pham Timothy M. Benton Dr. Tony Ly Dr. Gabriel da Silva Prof. Stephen J. Blanksby Prof. Richard A. J. O'Hair 《Angewandte Chemie (International ed. in English)》2015,54(44):12947-12951
Although the deleterious effects of ozone on the human respiratory system are well‐known, many of the precise chemical mechanisms that both cause damage and afford protection in the pulmonary epithelial lining fluid are poorly understood. As a key first step to elucidating the intrinsic reactivity of ozone with proteins, its reactions with deprotonated cysteine [Cys?H]? are examined in the gas phase. Reaction proceeds at near the collision limit to give a rich set of products including 1) sequential oxygen atom abstraction reactions to yield cysteine sulfenate, sulfinate and sulfonate anions, and significantly 2) sulfenate radical anions formed by ejection of a hydroperoxy radical. The free‐radical pathway occurs only when both thiol and carboxylate moieties are available, implicating electron‐transfer as a key step in this reaction. This novel and facile reaction is also observed in small cys‐containing peptides indicating a possible role for this chemistry in protein ozonolysis. 相似文献
80.
Vu Thi Huong Jen-Chih Yao Nguyen Dong Yen 《Journal of Optimization Theory and Applications》2017,174(2):567-612
We present a continuous-time generalization of the seminal research and development model of d’Aspremont and Jacquemin (Am Econ Rev 78(5):1133–1137, 1988) to examine the trade-off between the benefits of allowing firms to cooperate in research and the corresponding increased potential for product market collusion. We show the existence of a solution to the optimal investment problem using a combination of results from viscosity theory and the theory of planar dynamical systems. In particular, we show that there is a critical level of marginal cost at which firms are indifferent between doing nothing and starting to develop the technology. We find that colluding firms develop further a wider range of initial technologies, pursue innovations more quickly, and are less likely to abandon a technology. Product market collusion could thus yield higher total surplus. 相似文献