Asymmetric orientational writing dependence on polarization and direction in Li2O–Nb2O5–SiO2 glass with femtosecond laser irradiation

Strong birefringence photo-induced by the femtosecond laser irradiation and a sensitivity to the orientation of the laser movement versus the laboratory reference (i.e., difference between rightward and leftward or between upward and downward) have been demonstrated in 32.5Li₂O–27.5Nb₂O₅–40SiO₂ glass. An asymmetry with the orientation of the laser scanning was firstly observed by one of the authors in 2003 in pure silica (Poumellec et al. in Opt Express 11:1070, 2003). Here, we show in addition that this asymmetric orientational sensitivity is dependent on the direction of laser polarization and the laser scanning (i.e., when the direction is horizontal or vertical). In particular, no asymmetric writing is detected when both laser scanning and polarization directions are vertical. These observations are not explained by the available model.     

Properties ofΛ-hypernuclei from p+A reactions

We study the production ofΛ hyperons inp+A reactions on the basis of a BUU transport approach for³² S,⁶⁵ Cu,¹²⁰ Sn,¹⁹⁷ Au,²⁰⁸ Pb and²³⁸ U from 1.1 to 1.7 GeV beam energy and evaluate the properties of the hypernuclei produced with respect to excitation energy, transverse and longitudinal momentum, angular momentum and mass. Furthermore, the decay of the hypernuclei by particle emission in competition with fission channels is followed by a statistical model calculation. We find the systemp+¹⁹⁷ Au at about 1.5 GeV to be optimally suited for the production of heavy hypernuclei, where theΛ-decay is expected to be dominated by nonmesonic decay channels.     

"Acid extractable" metal concentrations in solid matrices: a comparison and evaluation of operationally defined extraction procedures and leaching tests

Different frequently used methods to determine the influence of acid conditions on heavy metal release from soils, sediments and waste materials, namely pH_stat leaching tests and acid extractions with acetic acid (HOAc) (0.11 M and 0.43 M) and sodium acetate (NaOAc) (1 M) were compared for 30 samples (soils, sediments and waste materials) with different physico-chemical properties and a different degree of contamination. However, no distinct relationship was found between physico-chemical sample characteristics, total element concentrations and acid-extractable metal concentrations in the presented dataset.

pH played an important role in explaining the release of metals from the contaminated soils, sediments and waste materials. The pH-shift after extraction with the different acetic acid solutions (0.11 M and 0.43 M) was both explained by the initial pH of the sample and its acid neutralizing capacity. The pH of the NaOAc extract was well buffered and the release of elements from solid matrices by NaOAc was both the result of the complexation with acetate and pH (pH 5). Generally, a linear correlation was found between the amount of Zn and Cd extracted by 0.11 M HOAc, 0.43 M HOAc and 1 M NaOAc. The amounts of Zn and Cd extracted with HOAc (0.11 M and 0.43 M) were comparable with amounts of respectively Zn and Cd released during pH_stat leaching at pH 4. However, for Cu, Pb and As, it was often not possible to relate the results of a pH_stat leaching test to the results of single extractions with acetic acid solutions.     

Rational Synthesis of Molybdenum(V) Tetramers Consisting of [Mo2O4]2+ Dimers Held Together by Bridging Phosphinate Ligands and the Tungsten(VI) Dimer [(CH3O)2(O)W(μ-O)(μ-O2PPh2)2W(O)(CH3O)2]: Structural and Theoretical Considerations

Reacting MoO₂(acac)₂ with Ph₂POOH or Me₂POOH in EtOH results in the formation of the tetranuclear molybdenum (V) clusters Mo₄(μ ₃-O)₄(μ-O₂PR₂)₄O₄, PR₂ = PPh₂, 1, or PMe₂, 2, in functional yields (>90% and 55% respectively). The reaction of WO₂(acac)₂ with Ph₂POOH in MeOH affords the tungsten dimer [(CH₃O)₂(O)W(μ-O)(μ-O₂PPh₂)₂W(O)(CH₃O)₂], 3. The single crystal X-ray determined structures of complexes 1–3 are reported. In 1 and 2, the four Mo=O units are interconnected by four triply bridging oxygen atoms, resulting in a distorted cubic-like structure for the Mo₄(μ ₃-O)₄O₄ units. Each molybdenum atom forms two additional Mo–O bonds with two oxygen atoms from different adjacent phosphinato ligands. Complex 3, a tungsten dimer, contains packing disorder and consists of bridging oxo and diphenylphosphinato ligands. The bonding of 1 and 2 assessed by density-functional methods showed that bonding between the Mo(V) centers occurs through σ overlap of the d _xy orbitals. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Dedicated to the memory of Professor F. A. Cotton. Veritas numquam perit.     

Biomarkers of alcohol abuse in racehorses by liquid chromatography/tandem mass spectrometry

A rapid and sensitive method was developed for the screening, quantification and confirmation of ethyl glucuronide (EG) and ethyl sulfate (ES) as biomarkers for alcohol administration to racehorses using liquid chromatography coupled on-line with triple quadrupole tandem mass spectrometry. Urine sample aliquots (0.1 mL) were pre-treated by protein precipitation. Separation of EG and ES was achieved on an Ultra PFP column. Isocratic elution with a flush step was performed using 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B). Analysis was performed by negative electrospray ionization in multiple reaction monitoring mode. The retention times for EG and ES were 1.7 +/- 0.30 and 3.4 +/- 0.30 min, respectively. The internal standard used was d(5)-ethyl glucuronide with a retention time of 1.7 +/- 0.30 min. The entire separation was completed in <5 min. The limit of detection (LOD) and of quantification (LOQ) for both analytes were 100 ng/mL (S/N > or =3) and 500 ng/mL, respectively. The limit of confirmations (LOC) for EG and ES were 500 ng/mL and 1.0 microg/mL, respectively. The assay was linear over a concentration range of 0.5-100 microg/mL (r(2) > 0.995). Intra- and inter-day accuracy and precision were less than 15%. The analytes were stable in urine for 24 h at room temperature, 10 days at 4 degrees C and 21 days at -20 degrees C and -70 degrees C. Ion suppression or enhancement due to matrix effect was negligible. The measurement uncertainty was <14% for EG and <25% for ES. This method was successfully used for the quantification of EG and ES in urine samples following alcohol administration to research horses and for screening and confirmation of EG and ES in urine samples obtained from racehorses post-competition. The method is simple, rapid, inexpensive, and reliably reproducible.     

Energy-gaining formation and catalytic behavior of active structures in a SiO(2)-supported unsaturated Ru complex catalyst for alkene epoxidation by DFT calculations

The formation and catalytic behavior of active structures in a SiO(2)-supported unsaturated Ru complex catalyst for alkene epoxidation were studied by means of hybrid density functional theory (DFT) calculations. An energy-gaining route for the catalyst activation was found to allow the formation of active unsaturated Ru complexes and the remarkable alkene epoxidation via an exothermic reaction path between isobutyraldehyde and oxygen. In the proposed Bartlett mechanism, Ru promotes the formation of peracid intermediate and facilitates the intermolecular hydrogen transfer in the peracid intermediate, while alkene molecules do not directly coordinate to the Ru site. It was found that stilbene epoxidation is easier to achieve than ethene epoxidation thanks to the electron donating phenyl groups.     

Agonistic and antagonistic estrogens in licorice root (Glycyrrhiza glabra)

The roots of licorice (Glycyrrhiza glabra) are a rich source of flavonoids, in particular, prenylated flavonoids, such as the isoflavan glabridin and the isoflavene glabrene. Fractionation of an ethyl acetate extract from licorice root by centrifugal partitioning chromatography yielded 51 fractions, which were characterized by liquid chromatography–mass spectrometry and screened for activity in yeast estrogen bioassays. One third of the fractions displayed estrogenic activity towards either one or both estrogen receptors (ERs; ERα and ERβ). Glabrene-rich fractions displayed an estrogenic response, predominantly to the ERα. Surprisingly, glabridin did not exert agonistic activity to both ER subtypes. Several fractions displayed higher responses than the maximum response obtained with the reference compound, the natural hormone 17β-estradiol (E₂). The estrogenic activities of all fractions, including this so-called superinduction, were clearly ER-mediated, as the estrogenic response was inhibited by 20–60% by known ER antagonists, and no activity was found in yeast cells that did not express the ERα or ERβ subtype. Prolonged exposure of the yeast to the estrogenic fractions that showed superinduction did, contrary to E₂, not result in a decrease of the fluorescent response. Therefore, the superinduction was most likely the result of stabilization of the ER, yeast-enhanced green fluorescent protein, or a combination of both. Most fractions displaying superinduction were rich in flavonoids with single prenylation. Glabridin displayed ERα-selective antagonism, similar to the ERα-selective antagonist RU 58668. Whereas glabridin was able to reduce the estrogenic response of E₂ by approximately 80% at 6 × 10⁻⁶ M, glabrene-rich fractions only exhibited agonistic responses, preferentially on ERα.