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121.
A. Cagan H. Schmidt J. E. Rodriguez G. A. Eiceman 《International Journal for Ion Mobility Spectrometry》2010,13(3-4):157-165
Explosives in solution were determined as mixtures containing highly volatile improvised explosives such as peroxides and conventional military grade explosives such as PETN, RDX, and Tetryl using a high speed gas chromatograph with differential mobility detector in a single measurement. Instrument parameters were evaluated and adjusted to permit detection of nanogram amounts of explosives with this broad range of vapor pressures in times under 3 min for HMTD to TNT or under 16 min for HMTD to Tetryl. As in prior studies of response to explosives with mobility spectrometers, pre-separation of sample by gas chromatography improved response in the differential mobility detector; however, unlike prior configurations, the supporting gas atmosphere did not contain modifiers to adjust selectivity in mobility and selectivity was provided only by characteristic stability of product ions in negative and positive polarities. Field dependence of product ions in purified air was determined for each explosive and patterns were sufficiently distinct to suggest the addition of selectivity through the use of several differential mobility detectors operated in parallel or series with characteristic separation voltages. 相似文献
122.
We describe a fast solver for linear systems with reconstructible Cauchy-like structure, which requires O(rn
2) floating point operations and O(rn) memory locations, where n is the size of the matrix and r its displacement rank. The solver is based on the application of the generalized Schur algorithm to a suitable augmented matrix, under some assumptions
on the knots of the Cauchy-like matrix. It includes various pivoting strategies, already discussed in the literature, and
a new algorithm, which only requires reconstructibility. We have developed a software package, written in Matlab and C-MEX,
which provides a robust implementation of the above method. Our package also includes solvers for Toeplitz(+Hankel)-like and
Vandermonde-like linear systems, as these structures can be reduced to Cauchy-like by fast and stable transforms. Numerical
experiments demonstrate the effectiveness of the software. 相似文献
123.
Arantxa Rodriguez 《Tetrahedron letters》2009,50(27):3942-357
Sydnones have been directly functionalised with alkenyl halides and an alkynyl bromide under palladium catalysis. 相似文献
124.
The present paper focuses on the renormalization effects of the band gaps in the electronic band structure of the elemental semiconductors traced to zero-point vibrations. Electron-phonon interaction and volume changes (in combination with anharmonicity) are the underlying microscopic mechanisms, both dependent on M−1/2, M being the average isotopic mass. Thus isotopically controlled crystals offer an extraordinary opportunity to test the theoretical predictions with a variety of spectroscopic techniques. The paper discusses the theoretical predictions and their experimental verifications, exploiting derivative and photoluminescence spectroscopy. Illustrative examples on Si and Ge, drawn from the investigations of the authors, are presented. 相似文献
125.
Juan M. Antelo Florencio Arce Juan Crugeiras Julia Franco Pilar Rodriguez Angel Varela 《国际化学动力学杂志》1990,22(12):1271-1282
This article reports the kinetics of the decomposition of N-bromoserine formed rapidly by bromation of serine by BrO?. The main decomposition products are glycolaldehyde, ammonia, carbon dioxide, and bromide ions at pH < 11.5, and β-hydroxypyruvic acid, ammonia, and bromide ions at pH > 11.5. The reaction is of order one with respect to N-bromoserine, and is independent of ionic strength and excess serine. The rate constant increases with increasing pH at pH > 11 and with decreasing pH at pH < 8, and over the range pH 8–11 has the constant value 1.67 × 10?3 s?1 at 298 K. 相似文献
126.
127.
L. Calvo Blazquez J. Rodriguez Flores F. Vinagre Jara A. Sanchez Misiego 《Journal of Chemical Sciences》1989,101(5):415-419
The electroanalytical behaviour of orotic acid in cathodic processes has been studied in HClO4, at several pH values in Britton-Robinson buffers, using DPP and CV techniques.
Orotic acid undergoes three cathodic waves over the entire pH range considered. Optimum conditions for determination of orotic
acid using the DPP technique are also studied. 相似文献
128.
The interaction of ultrathin films of Ni and Pd with W(110) has been examined using X-ray photoelectron spectroscopy (XPS) and the effects of annealing temperature and adsorbate coverage (film thickness) are investigated. The XPS data show that the atoms in a monolayer of Pd or Ni supported on W(110) are electronically perturbed with respect to the surface atoms of Pd(100) and Ni(100). The magnitude of the electronic perturbations is larger for Pd than for Ni adatoms. Our results indicate that the difference in Pd(3d5/2) XPS binding energies between a pseudomorphic monolayer of Pd on W(110) and the surface atoms of Pd(100) correlates with the variations observed for the desorption temperature of CO (i.e., the strength of the Pd---CO bond) on these surfaces. A similar correlation is seen for the Ni(2p3/2) XPS binding energies of Ni/W(110) and Ni(100) and the CO desorption temperatures from the surfaces. The shifts in XPS binding energies and CO desorption temperatures can be explained in terms of: (1) variations that occur in the Ni---Ni and Pd---Pd interactions when Ni and Pd adopt the lattice parameters of W(110) in a pseudomorphic adlayer; and (2) transfer of electron density from the metal overlayer to the W(110) substrate upon adsorption. Measurements of the Pd(3d5/2) XP binding energy of Pd/W(110) as a function of film thickness indicate that the Pd---W interaction affects the electronic properties of several layers of Pd atoms. 相似文献
129.
Joshua L. Brooks Phil Olsen Lijian Chen Andrew A. Rodriguez 《Tetrahedron letters》2017,58(11):1050-1052
Herein, we describe the isolation and characterization of a UnyLinker dimer which, if left uncontrolled, can become incorporated in oligonucleotide products. The dimer is formed as a result of an unusual intermolecular osmium-catalyzed etherification. We demonstrate that by simply replacing H2O2 as the co-oxidant with NMO, none of the UnyLinker dimer impurity is formed. 相似文献
130.
Regioselectivity in isoquinoline alkaloid synthesis is analyzed here. Our experiments have shown that substituents on the aromatic ring of the starting amine are determinant in isoquinoline synthesis. The use of dicyclohexylcarbodiimide in activating carboxylic acids for electrophilic aromatic substitution reactions is presented for the first time. 相似文献