A discrete variable representation study of the dynamics of the double proton transfer in bicyclic oxalamidines

DFT electronic calculations are performed for the double proton transfer in bicyclic oxalamidines 2,2^′-bis-(3,4,5,6-tetrahydro-1,3-diazine) (OA6) and 2,2^′-bis-(4,5,6,7-tetrahydro-1,3-diazepine) (OA7). Bidimensional potential energy surfaces retaining the characteristics of the stationary points located in the whole potential are built to calculate the vibrational levels through the discrete variable representation (DVR) method. Zero-point tunneling splittings are similar for both systems but for a given energy there are much less tunneling doublets available in OA6, this being the key factor responsible for the different temperature dependence of the rate for the two systems.     

Thomas–Fermi approximation for the quasi‐two‐dimensional electron gas

To take into account static correlation effects in the quasi‐two‐dimensional electron gas a screened Coulombic interaction between particles is studied. The Thomas–Fermi approximation is used and the potential screening appears as a function of the Wigner–Seitz density parameter r_s and the effective width t of the system. With the self‐consistent field theory applied to the modified deformable jellium, the ground‐state energy per particle and the conditions for electron localization are obtained in terms of the interparticle distance and the screening parameter μ. A critical minimum characteristic width t_c is obtained; below t_c no long‐range order is obtained. For larger widths a stable localized state is predicted at finite densities. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 269–276, 2001     

In situ characterization of undulator magnetic fields

A new in situ method is proposed to characterize the peak magnetic fields of undulator sources. The X‐ray beam emitted by the HU52 Apple‐2 undulator of the DEIMOS beamline of the SOLEIL synchrotron is analyzed using the Bragg diffraction of a Si(111) crystal. Measurements over the undulator gap range in linear horizontal polarization are compared with simulations in order to rebuild the Halbach function linking the undulator gaps to their peak magnetic fields. The method presented also allows information about the electron beam to be obtained.     

In vitro evaluation of the amoebicidal activity of rosemary (Rosmarinus officinalis L.) and cloves (Syzygium aromaticum L. Merr. & Perry) essential oils against Acanthamoeba polyphaga trophozoites

Several species of the genus Acanthamoeba cause human diseases. Treatment of infections involves various problems, emphasising the need to develop alternative antiprotozoal agents. We studied the anti-amoebic activity of Essential Oils (EOs), derived from rosemary (Rosmarinus officinalis L.) and cloves (Syzygium aromaticum L. Merr. & Perry), against Acanthamoeba polyphaga strain. The amoebicidal activity of cloves and rosemary EOs was preliminary demonstrated by the morphology change (modifications in the cell shape, the presence of precipitates in the cytoplasm, autophagic vesicles, membrane blends) of the treated trophozoites. The cell-counts, carried out after staining trophozoites with a Trypan blue solution, revealed that both EOs were active in a dose-dependent manner and in relation to the exposure time. This activity was evident after few hours, with encouraging results obtained in particular with cloves EO, able to act at the lower concentrations and after 1 h, probably for its high eugenol content (65.30%).     

Conformational landscape and hydrogen bonding in (S)-(−)-perillyc acid: experimental VCD,IR, Raman,and theoretical DFT studies

(S)-(?)-Perillyc acid (4-isopropenylcyclohexene-1-carboxylic acid) is an intermediate in the limonene and pinene pathway degradation and its measurement in urine is used to monitor cancer patients receiving oral limonene. For the first time, a theoretical study of the conformational preference in the monomer and H-bonded dimers complemented with a theoretical and experimental analysis of the infrared, raman, and vibrational vircular dichroism spectra of (S)-(?)-perillyc acid in solution and solid phases is presented. With regard to the monomer, theoretical calculations revealed the existence of two conformers depending on the position of the isopropenyl group (axial and equatorial) and 24 rotamers (12 equatorials and 12 axials). The study of the H-bonded dimers revealed great complexity in the conformational landscape with a total of 36 structures studied. Herein, from a reliable assignment of the IR and Raman spectra and with help from the study of the VCD spectrum of the title compound, the most stable rotamers of the H-bonded complexes have been detected experimentally in the liquid and solid phases. Additionally, natural bond orbitals (NBO) analysis indicates an electronic delocalization between the two subunits in the dimer. The IR, Raman, and VCD are helpful and complementary techniques to characterize flexible systems, such as terpenes, which present several conformers and H-bonded aggregates.     

Determination of mycophenolic acid in human plasma by ultra‐performance liquid chromatography–tandem mass spectrometry and its pharmacokinetic application in kidney transplant patients

To implement and validate an analytical method by ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC MS/MS) to quantify mycophenolic acid (MPA) in kidney transplant patients. Quantification of MPA was performed in an ACQUITY UPLC H Class system coupled to a Xevo TQD detector and it was extracted from plasma samples by protein precipitation. The chromatographic separation was achieved through an ACQUITY HSS C₁₈ SB column with 0.1% formic acid and acetonitrile (60:40 vol/vol) as mobile phase. The pharmacokinetic parameters were calculated by non‐compartmental analysis of MPA plasma concentrations from 10 kidney transplant patients. The linear range for MPA quantification was 0.2–30 mg/L with a limit of detection of 0.07 mg/L; the mean extraction recovery was 99.99%. The mean intra‐ and inter‐day variability were 2.98% and 3.4% with a percentage of deviation of 8.4% and 6.6%, respectively. Mean maximal concentration of 10 mg/L at 1.5 h, area under the concentration–time curve of 36.8 mg·h/L, elimination half‐life of 3.9 h, clearance of 0.32 L/h/kg and volume of distribution of 1.65 L/kg were obtained from MPA pharmacokinetics profiles. A simple, fast and reliable UPLC–MS/MS method to quantify MPA in plasma was validated and has been applied for pharmacokinetic analysis in kidney transplant patients.     

Electric and magnetic optical response of dielectric nanospheres: Optical forces and scattering anisotropy

Nanospheres made of non-magnetic materials are shown to present non-conventional scattering properties similar to those previously reported for somewhat hypothetical magnetodielectric particles. We find a wide window in the near-infrared, where light scattering by lossless submicrometer semiconductor nanospheres is fully described by their induced electric and magnetic dipoles. The interference between electric and magnetic dipolar fields is shown to lead to anisotropic angular distributions of scattered intensity, including zero backward and almost zero forward scattered intensities at specific wavelengths. Interesting new consequences for the corresponding optical forces are derived from the interplay, both in and out of resonance, between the electric- and magnetic-induced dipoles.     

Statistical properties and economic implications of jump-diffusion processes with shot-noise effects

The shot-noise jump-diffusion (SNJD) model aims to reflect how economic variables respond to the arrival of sudden information. This paper analyzes the SNJD model, providing its statistical distribution and closed-form expressions for the characteristic function and moments. We also analyze the dynamics of the model, concluding that the degree of serial autocorrelation is related to the occurrence and magnitude of abnormal information. In addition, we provide some useful approximations in a particular case that considers exponential-type decay. Empirically, we propose a GMM approach to estimate the parameters of the model and present an empirical application for the stocks included in the Dow Jones Averaged Index. Our findings seem to confirm the presence of shot-noise effects in 73% of the stocks and a strong relationship between the shot-noise process and the autocorrelation pattern embedded in data.