Radio- and thermoluminescence of single-doped and codoped lithium-sodium sulfate

Radioluminescence at room temperature and thermoluminescence (TL) measurements of single-doped and codoped LiNaSO₄ above room temperature are reported here. The codoped samples were studied to investigate the possibility of enhancing the TL sensitivity of LiNaSO₄:Eu. This objective was not satisfied and the codopants (Ce, Sm, Ho and Er) decrease the TL sensitivity and slightly shift the dosimetric peak to lower temperatures. Samples doped with Mg, K, Bi and Tl were used with the hope that they may alter the trapping centers stability and introduce new peaks in the temperature range 430–500 K to observe any TL discontinuity or wavelength shift in their spectra as observed in CL measurements. This objective was fulfilled with Tl and Bi, where there is a discontinuity and/or wavelength shift at about 460 K. Such intensity and/or wavelength variations are ascribed to microstructural phase changes within the LiNaSO₄ crystals that may result from twin boundaries behaving like Na₂SO₄.     

THE HADAMARD INEQUALITY FOR CONVEX FUNCTION VIA FRACTIONAL INTEGRALS

In this paper, we establish several inequalities for some differantiable mappings that are connected with the Riemann-Liouville fractional integrals. The analysis used in the proofs is fairly elementar...     

On the role of the definition of potential models in Gibbs ensemble phase equilibria simulations of the H2S-pentane mixture

The effect of treating explicitly the coulombic and polarization interactions is investigated through the calculation of the coexistence curve of the pentane-H₂S binary mixture. In this work, potential models have been developed for hydrogen sulphide and pentane, which include electrostatic sites—estimated from ab initio calculations—and polarizable sites—estimated from experimental data—in addition to Lennard-Jones sites. Compared to existing models, these new models have the same number of fitting parameters to experimental thermodynamic data. They are shown to correctly describe the coexistence curve of the pure compounds. When applied to the case of mixtures, together with Lorentz-Berthelot combining rules, they allow one to obtain a more accurate prediction of the coexisting compositions of the mixture. Furthermore, it is shown that the interaction energy in this kind of mixture cannot be properly described by using effective potential models usually considered for pure compounds.     

Modulating the Ground‐ and Excited‐State Oxidation Potentials of Diaminonaphthalene by Sequential N‐Methylation

A series of 1,5‐diaminonaphthalene derivatives were synthesized and characterized to provide ground‐ and excited‐state electron donors of similar structure but varying potential. Electrochemical and spectroscopic properties of the series are reported and together illustrate two opposing consequences of alkyl substitution on the aryl amines. Inductive effects of methylation are evident from the decrease in ground‐state oxidation potential for derivatives containing monomethylamino substituents. In contrast, steric effects seem to dominate the increase in the ground‐state oxidation potential of derivatives containing dimethylamino substituents since the conformational constraints created by dimethylation suppress delocalization of the nonbonding electrons. Absorption and emission properties also respond to increasing levels of N‐methylation, and the excited‐state oxidation potentials of the parent 1,5‐diaminonaphthalene and its monomethylamine derivatives (ca. ?3.2 V) are approximately 200 mV lower than the corresponding dimethylamino derivatives (?3.0 V).     

Meeting to discuss laser cavity design for photon linear collider — Daresbury,UK, 10 January 2006

The outcome of the meeting to discuss the proposed design for a laser cavity for the photon linear collider is presented.      

Development of an online two-dimensional nano-scale liquid chromatography/mass spectrometry method for improved chromatographic performance and hydrophobic peptide recovery

An online two-dimensional (2D) strong cation-exchange (SCX)/reversed-phase (RP) nano-scale liquid chromatography/mass spectrometry (nanoLC/MS) method was developed for improved separation and hydrophobic peptide recovery. Sharper and more symmetric RP peaks were observed with the use of a "band re-focusing method", in which an analytical RP column with more hydrophobicity than the RP trap column was used in the system. To recover hydrophobic peptides still unreleased from the SCX column after a conventional salt step gradient due to hydrophobic interaction, a RP step gradient from 10% to 30% acetonitrile (ACN) was applied to the SCX column in the presence of a high salt concentration following the salt gradient. There were 301 unique hydrophobic E. coli peptides identified from the RP fractions. These peptides, which were 19% of all E. coli peptides identified from a 2D run, would not have been identified without the application of the RP gradient to the SCX column.     

On the spectra luminescence properties of charoite silicate

Charoite is a hydrous alkali calcium silicate mineral [K₄NaCa₇Ba_0.75Mn_0.2Fe_0.05(Si₆O₁₅)₂(Si₂O₇)Si₄O₉(OH)·3(H₂O)] exhibiting an intense lilac colour related to Mn²⁺ and Fe³⁺ colour centres. These ions also contribute to a strong luminescence at ∼585 and 705 nm. This work studies the thermal dependence of these luminescent centres by (i) thermoluminescence (TL) of pre-heated and pre-irradiated charoite aliquots, (ii) by time-resolved cathodoluminescence (TRS-CL) at room and cryogenic temperatures (RT and CT), (iii) by spatially resolved spectra CL under scanning electron microscopy (SRS-CL-SEM) and (iv) by ion beam spectra luminescence (IBL) with H⁺, H₂⁺ and ⁴He⁺ ions at RT and LT. The main peak, ∼585 nm, is linked to a transition ⁴T_1,2 (G)→⁶A₇(S) in Mn²⁺ ions in distorted six-fold coordination and the emission at ∼705 nm with Fe²⁺→Fe³⁺ oxidation in Si⁴⁺ lattice sites. Less intense UV-blue emissions at 340 and 390 nm show multi-order kinetic TL glow curves involving continuous processes of electron trapping and de-trapping along with an irreversible phase transition of charoite by de-hydroxylation and lattice shortening of Δa=0.219 Å, Δb=0.182 Å; Δc=0.739 Å. The Si-O stressed lattice of charoite has non-bridging oxygen or silicon vacancy-hole centres, and Si-O bonding defects which seem to be responsible for the 340 nm emission. Extrinsic defects such as the alkali (or hydrogen)—compensated [AlO₄/M⁺] centres could be linked with the 390 nm emission. Large variations in 585 and 705 nm intensities are strongly temperature dependent, modifying local Fe-O and Mn-O bond distances, short-range-order luminescence centres being very resistant under the action of the heavy ion beam of ⁴He⁺. The SRS-CL demonstrates strong spatial heterogeneity in the luminescence of the charoite.