IMMOBILE TRACE ELEMENTS DISCRIMINATION DIAGRAMMS WITH ZEOLITIZED VOLCANICLASTICS FROM THE EVROS - THRACE - RHODOPE VOLCANIC TERRAIN

The Rhodope and Evros areas of the Thrace Region in north-eastern Greece and the adjusted areas in Bulgaria are characterized by wide spread volcanic formations of Upper Eocene to Miocene in age. The volcaniclastic materials associated with such formations have, in some cases, undergone inter alia a notable zeolitization process. The mineralogy of the altered volcaniclastics is often dominated by clinoptilolite -heulandite type of minerals. The Winchester and Floyd (1977) plots indicating rhyodacite/dacite to trachyandesite parent materials, while the similar diagram, as modified by Pearce (1986), indicate andesite to trachyandesite precursors. The alkalinity index (Nb/Y ratio) seems to coincide between the two types of diagrams, but, there is a notable difference of the differentiation index, i.e. the Zr/TiO2 ratio. The Th-Co diagram (Hastie et al., 2007) unfolds a clearer picture for the nature of the precursors and reveals a clear progression of a calc-alkaline to a high-K calc alkaline affinity of the parental volcanic materials

MAGMA GENERATION AND MIXING IN THE EARLIEST VOLCANIC CENTRE OF SANTORINI (AKROTIRI PENINSULA). MINERAL CHEMISTRY EVIDENCE FROM THE AKROTIRI PYROCLASTICS

Santorini is a dominant expression of magma generation and subsequent volcanism in the Meditereanean area, where a calk-alkaline, high-alumina, basalt-andesite-dacite type of volcanism was expressed from eight centres. The volcanics of the Akrotiri peninsula are considered to be the products of the earliest (Pliocene Pleistocene) volcanic centre. The present study has investigated the mineral chemistry of some major pyrogenic phenocrysts, such as plagioclase and Fe-Ti oxides, of the Akrotiri pyroclatics unit, which have undergone a notable zeolitization procedure. The results are compatible with magma mixing mechanism of a primitive mantle derived, saturated, of mafic composition component with silicic magma in shallow crustal depths

2017-2018 Festival of the Arts Boca

Program Symphony No. 1 in C Minor, op. 68 / Johannes Brahms Summertime / George Gershwin By Strauss / George Gershwin Embraceable You / George Gershwin Vilija from the Merry Widow / Franz Lehár A Real Slow Drag from Treemonisha / Scott Joplin Please contact the Archives ([email protected]) if you would like to see the entire program booklet.https://spiral.lynn.edu/conservatory_philharmonia/1099/thumbnail.jp

Velocity‐resolved laser‐induced desorption for kinetics on surface adsorbates

Most experimental methods for studying the kinetics of surface reactions – for example, temperature programmed desorption (TPD), molecular beam relaxation spectrometry (MBRS) and velocity-resolved kinetics (VRK) – employ detection schemes that require thermal desorption. However, many adsorbates – for example reaction intermediates – never leave the surface under reaction conditions. In this paper, we present a new method to measure adsorbate concentrations on catalytic surfaces and demonstrate its utility for studying thermal desorption kinetics. After a short-pulsed molecular beam deposits CO or NH3 on Pt (111), the surface is irradiated with an ultrashort laser pulse that induces desorption. Another tightly focused ultrashort laser pulse ionizes the gas-phase molecules by a non-resonant multiphoton process and the ions are detected. This two-laser signal is then recorded as a function of time after the dosing molecular beam pulse and decays exponentially. First-order thermal desorption rate constants are obtained over a range of temperatures and found to be in good agreement with past reports. Ion detection is done mass selectively with ion-imaging, dispersing the gas phase molecules by their velocities. Since laser-induced desorption (LID) produces hyperthermal gas phase molecules, they can be detected with little or no background. This approach is highly surface-specific and exhibits sensitivity below 10−4 ML coverage. Because the signals are linearly proportional to adsorbate concentration, the method can be employed at lower temperatures than VRK, whose signal is proportional to reaction rate

Stark shift and parity non-conservation for near-degenerate states of xenon

We identify a pair of near-degenerate states of opposite parity in atomic Xe, the 5p^5 10s \,\, ^2[3/2]_2^o at $\rm{E}=94759.927$ cm$^{-1}$ and 5p^5 6f \,\, ^2[5/2]_2 at $\rm{E}= 94759.935$ cm$^{-1}$, for which parity- and time-odd effects are expected to be enhanced by the small energy separation. We present theoretical calculations which indicate narrow widths for both states and we report a calculated value for the weak matrix element, arising from configuration mixing, of $|W|=2.1$ Hz for $^{132}$Xe. In addition, we measured the Stark effect of the $5p^5\,6f$ $^2[5/2]_{2}$ and $5p^5 \,6f \ ^2[3/2]_2$ ($\rm{E} =94737.121\,\rm{cm}^{-1}$) states. The Stark-shift of the $6f$ states is observed to be negative, revealing the presence of nearby $6g$ states at higher energies, which have not been observed before. The Stark-shift measurements imply an upper limit on the weak matrix element of $|W|\!<\!5$ Hz for the near-degenerate states (10s \,\, ^2[3/2]_2^o and 6f \,\, ^2[5/2]_2), which is in agreement with the presented calculations.Comment: 11 pages, 6 figure

Adsorption and absorption energies of hydrogen with palladium

Thermal recombinative desorption rates of HD on Pd(111) and Pd(332) are reported from transient kinetic experiments performed between 523 and 1023 K. A detailed kinetic model accurately describes the competition between recombination of surface-adsorbed hydrogen and deuterium atoms and their diffusion into the bulk. By fitting the model to observed rates, we derive the dissociative adsorption energies (E0, adsH2 = 0.98 eV; E0, adsD2 = 1.00 eV; E0, adsHD = 0.99 eV) as well as the classical dissociative binding energy ϵads = 1.02 ± 0.03 eV, which provides a benchmark for electronic structure theory. In a similar way, we obtain the classical energy required to move an H or D atom from the surface to the bulk (ϵsb = 0.46 ± 0.01 eV) and the isotope specific energies, E0, sbH = 0.41 eV and E0, sbD = 0.43 eV. Detailed insights into the process of transient bulk diffusion are obtained from kinetic Monte Carlo simulations