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11.
Mimmi MC Gullotti M Santagostini L Battaini G Monzani E Pagliarin R Zoppellaro G Casella L 《Dalton transactions (Cambridge, England : 2003)》2004,(14):2192-2201
The dinuclear and trinuclear Cu(II) complexes of an octadentate ligand derived from (S)-1,1'-binaphthyl-2,2'-diamine have been prepared and characterized by UV/Vis, CD, EPR and NMR spectroscopy. The ligand contains two tridentate aminobis(benzimidazole) donor arms connected to a central bidentate diaminobinaphthyl linker, which hosts the chiral unit. In the dinuclear Cu complex the ligation occurs essentially within the tridentate arms of the ligand. The two Cu centers are EPR nonequivalent and noninteracting. The EPR data suggests that one of the Cu ions additionally interacts with one of the tertiary aminonaphthyl donors. In the trinuclear complex the two aminonaphthyl donors bind the third Cu ion. The EPR spectrum of this complex shows the signal for a mononuclear Cu(II) center bound to a tridentate arm, while the remaining two Cu(II) centers are coupled through hydroxo groups. The CD spectrum shows that in the free ligand a severe reduction of the dihedral angle between the naphthyl groups from the strain free range occurs. This conformation is stabilized by ring stacking interactions with the benzimidazole groups. On complex formation this interaction is removed because the benzimidazole groups are involved in metal binding. In the dinuclear Cu complex the conformation of the binaphthyl chromophore probably approaches the strain free range, while in the trinuclear Cu complex a marked flattening of the dihedral angle between the two naphthyl rings occurs. Both complexes are active catalysts in the oxidation of L-/D-Dopa derivatives to quinones. High enantioselectivity is observed in the oxidation of L-/D-Dopa methyl ester catalyzed by the dinuclear Cu complex, which exhibits strong preference for the d enantiomer. The enantioselectivity is largely lost for the trinuclear Cu complex. 相似文献
12.
R Bonfiglio RC King TV Olah K Merkle 《Rapid communications in mass spectrometry : RCM》1999,13(12):1175-1185
A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
13.
Samit Mandal J Gerl H Geissel K Hauschild M Hellström Z Janas I Kojouharov Y Kopatch RC Lemmon P Mayet Z Podolyak PH Regan H Schaffner C Schlegel J Simpson HJ Wollersheim 《Pramana》2001,57(1):161-164
Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors
(segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed. 相似文献
14.
We report measurements of non-linear charge transport in epitaxial (La1−x
Pr
x
)0.7Ca0.3MnO3 thin films fabricated on (100) oriented SrTiO3 single crystals by pulsed laser deposition. The end members of this series, namely Pr0.7Ca0.3MnO3 and La0.7Ca0.3MnO3 are canonical charge-ordered (CO) and ferromagnetic manganites, respectively. The onset of the CO state in Pr0.7Ca0.3MnO3 is manifested by a pronounced insulating behavior below ∼ 200 K. The CO state remains stable even when a large (∼ 2×105 V/cm) electric field is applied across the thin film samples. However, on substitution of Pr with La, a crossover from the
highly resistive CO state to a state of metallic character is observed at relatively low electric fields. The current-voltage
characteristics of the samples at low temperatures show hysteretic and history dependent effects. The electric field driven
charge transport in the system is modelled on the basis of an inhomogeneous medium consisting of ferromagnetic metallic clusters
dispersed in a CO background. 相似文献
15.
Bruno?Casella Gareth?O.?RobertsEmail author 《Methodology and Computing in Applied Probability》2011,13(3):449-473
We introduce a novel algorithm (JEA) to simulate exactly from a class of one-dimensional jump-diffusion processes with state-dependent
intensity. The simulation of the continuous component builds on the recent Exact Algorithm (Beskos et al., Bernoulli 12(6):1077–1098,
2006a). The simulation of the jump component instead employs a thinning algorithm with stochastic acceptance probabilities in the
spirit of Glasserman and Merener (Proc R Soc Lond Ser A Math Phys Eng Sci 460(2041):111–127, 2004). In turn JEA allows unbiased Monte Carlo simulation of a wide class of functionals of the process’ trajectory, including
discrete averages, max/min, crossing events, hitting times. Our numerical experiments show that the method outperforms Monte
Carlo methods based on the Euler discretization. 相似文献
16.
Summary A gas chromatographic method for the determination of isomeric distribution in toluenesulfonic acid samples is described.
The acids are transformed into the corresponding ethyl esters by reaction with triethyl orthoformate in toluene. The reaction
mixture can be injected, without further purification, into the gas chromatograph. The separation is best performed on columns
containing OV-210 or polyphenyl ether (6 rings) as the stationary phase. 相似文献
17.
R. C. Casella 《Il Nuovo Cimento D》1988,10(12):1439-1448
Summary A semi-phenomenological analysis is given of the effects of certain band structure features on the gap ratios 2Δ/k
B
T
c for high-T
c superconductors, including multigap systems. In addition to phonons other intermediate bosons (IB) mediating the superconducting
interaction are considered. Interesting results emerge when the IB energy exceeds the widths of possible narrow peaks in the
density of states associated with subbands presumably belonging to substructures such as stacked Cu−O planes. Comparison with
experiment is made. In particular, data obtained by Warrenet al. via nuclear-spin relaxation on Ba2YCu3O7−δ can be interpreted within the present framework in terms of a model having an IB of energy ≳1 eV, which exceeds the predicted
width (≲0.3 eV) of a peak in the density of states containing the normal-state Fermi level. This suggests that the IB is not
a phonon.
To speed up publication, the author of this paper has agreed to not receive the proofs for correction. 相似文献
18.
V. R. Casella C. T. Bishop A. A. Glosby C. A. Phillips 《Journal of Radioanalytical and Nuclear Chemistry》1981,62(1-2):257-266
A radiochemical procedure is presented for the sequential determination of uranium isotopes, thorium isotopes, and210Pb in coal and coal ash. This procedure consists of dry ashing the sample, a nitric—hydrofluoric acid dissolution, removal
of iron with ether extractions, and separation of the elements of interest by anion exchange chromatography. Uranium and thorium
isotopes are measured by alpha spectrometry, while210Pb is measured by beta counting its daugther activity,210Bi. For 10 g coal samples and 1 g ash samples, the chemical yields for the radioactivities measured were 70–80%, and the relative
standard deviations for replicate analyses were generally less than 9%. The deviations of the means from the reference values
were within the combined errors of each and were usually less than ±5%. Minimum detectable activities were about 0.02 pCi
for uranium and thorium isotopes and 0.2 pCi for210Pb. 相似文献
19.
Abstract The members of a set of conditional probability density functions are called compatible if there exists a joint probability density function that generates them. We generalize this concept by calling the conditionals functionally compatible if there exists a non-negative function that behaves like a joint density as far as generating the conditionals according to the probability calculus, but whose integral over the whole space is not necessarily finite. A necessary and sufficient condition for functional compatibility is given that provides a method of calculating this function, if it exists. A Markov transition function is then constructed using a set of functionally compatible conditional densities and it is shown, using the compatibility results, that the associated Markov chain is positive recurrent if and only if the conditionals are compatible. A Gibbs Markov chain, constructed via “Gibbs conditionals” from a hierarchical model with an improper posterior, is a special case. Therefore, the results of this article can be used to evaluate the consequences of applying the Gibbs sampler when the posterior's impropriety is unknown to the user. Our results cannot, however, be used to detect improper posteriors. Monte Carlo approximations based on Gibbs chains are shown to have undesirable limiting behavior when the posterior is improper. The results are applied to a Bayesian hierarchical one-way random effects model with an improper posterior distribution. The model is simple, but also quite similar to some models with improper posteriors that have been used in conjunction with the Gibbs sampler in the literature. 相似文献