in situ interlaboratory comparisons for dissolved oxygen concentration and pH

Organization, benefits, and possible drawbacks of in situ interlaboratory comparison are discussed using the example of dissolved oxygen concentration and pH measurements organized at the University of Tartu. In situ interlaboratory comparisons are intercomparison measurements, where all the participants (with their technical equipment and using their own competence) are measuring the same sample continuously at the same time, at the same site. In the field of proficiency testing–especially in chemical measurements–the in situ schemes are not yet widespread. Their main advantage emerges in the fields where, due to non-stability of samples, traditional comparison schemes can fail. Direct exchange of experience between the participants and presentations during measurements may add the value to in situ interlaboratory comparison. Dissolved oxygen concentration and pH measurements are among the most widespread chemical measurements. Both measurements are complex and less robust than often considered. In this paper, we describe in situ interlaboratory comparisons of dissolved oxygen concentration and pH organized at University of Tartu Testing Centre. Electronic Supplementary Material  Supplementary material is available for this article if you access the article at . The Final Report of the DO Concentration and pH Intercomparison is available in the electronic supplementary material.

Atomic layer deposition of tungsten(III) oxide thin films from W2(NMe2)6 and water: precursor-based control of oxidation state in the thin film material

The atomic layer deposition of W2O3 films was demonstrated employing W2(NMe2)6 and water as precursors with substrate temperatures between 140 and 240 degrees C. At 180 degrees C, surface saturative growth was achieved with W2(NMe2)6 vapor pulse lengths of >/=2 s. The growth rate was about 1.4 A/cycle at substrate temperatures between 140 and 200 degrees C. Growth rates of 1.60 and 2.10 A/cycle were observed at 220 and 240 degrees C, respectively. In a series of films deposited at 180 degrees C, the film thicknesses varied linearly with the number of deposition cycles. Time-of-flight elastic recoil analyses demonstrated stoichiometric W2O3 films, with carbon, hydrogen, and nitrogen levels between 6.3 and 8.6, 11.9 and 14.2, and 4.6 and 5.0 at. %, respectively, at substrate temperatures of 160, 180, and 200 degrees C. The as-deposited films were amorphous. Atomic force microscopy showed root-mean-square surface roughnesses of 0.7 and 0.9 nm for films deposited at 180 and 200 degrees C, respectively. The resistivity of a film grown at 180 degrees C was 8500 microhm cm.     

Effects of prolonged oral reading on F0, SPL, subglottal pressure and amplitude characteristics of glottal flow waveforms

The effects of prolonged (5x45 minute) reading (vocal loading) on fundamental frequency (F0), sound pressure level (SPL), subglottal (intraroral) pressure (p), and two glottal flow waveform parameters (AC amplitude of glottal flow, f, and negative peak amplitude of differentiated flow (d) of normal female and male subjects (N = 80) were studied. Two rest (morning and noon) and three loading (two in the morning and one in the afternoon) samples were recorded and analyzed. The glottal waveforms were obtained by inverse filtering of the acoustic pressure waveforms of speaking voice samples. The analyses were based on measurement and inverse filtering of the first stressed syllable of "paappa" words repeated 3x5 times for normal, as soft as possible, and as loud as possible phonation. In normal phonation the parameter values changed statistically significantly due to loading. In many cases the values obtained in the morning samples changed after the first loading session. This is interpreted as a vocal "warming-up effect." Especially in soft phonation p, d, and f were sensitive indicators of vocal loading. In both normal and soft phonation, the SPL, p, d, and f values tended to rise due to prolonged reading in the morning and afternoon samples, indicating increased effort (normal phonation) and a rise in the phonatory threshold (soft phonation). The lunch break vocal rest ("rest effect") considerably affected the parameter values in many cases.     

Reactivity of oil shale ashes in the binding of SO<Subscript>2</Subscript>

The extensive use of fossil fuels in energy production causes serious pollution of atmosphere with SO₂, CO₂, NO_x, etc. In Estonia the electricity production is based mainly on the pulverized firing (PF) of low-grade local fuel – Estonian oil shale (EOS) which is characterized by a low calorific value (~9 MJ kg^–1) and a high content of mineral matter (65–70%) from which approximately 50% are carbonates. Since 2004, also two boilers based on circulating fluidized bed combustion (CFBC) of EOS are in exploitation. The present study is focused on the comparative investigation of the efficiency of different ashes collected from different technological points of CFB and PF boilers as sorbents for SO₂. The influence of experimental temperature on the SO₂-binding characteristics of ashes as well as the possibilities of activation of ashes (grinding, hydration) were investigated. It was shown that the SO₂-binding capacity of initial ashes at 700°C and p(SO₂)=190 mm Hg was for CFBC ashes 24–30 mg and for PF ashes 10–23 mg SO₂ per 100 mg sample, the best binding capacities belonging to economizer ash (ECOA) and electrostatic precipitator ash from the 1st field (PESPA1f), respectively. However, during initial stage of binding the best results were obtained with air pre-heater ash (PHAA) and ESPA1f (both CFBC ashes). Grinding improved the SO₂-binding ability, being the most effective in the case of bottom ash (BA) from CFBC and cyclone ash (PCA) from PF – increase in binding capacity 2 and 2.3 times, respectively. As compared to initial CFBC ashes, the binding characteristics of PF ashes remained lower even after grinding. Hydration and previous calcination improved the binding characteristics only of PF ashes. Hereby, the SO₂-binding ability of CFBC ashes is better than of PF ashes and they are more promising sorbents for acidic gases, for example, for sulphur dioxide.     

ISO 17025 quality system in a university environment

The experience of working under an ISO 17025 compliant quality system in a university environment is described in the example of the Testing Centre of University of Tartu. University-specific features of the quality system include that the Testing Centre acts as the “quality system server” for other units of the university and graduate students participate in the work carried out under the quality system. The benefits for the university and the graduate students are discussed. It is concluded that implementation of an ISO 17025 compatible quality system in a university is fully accomplishable and gives significant added value to the university by helping to destroy the ivory tower perception about universities and by introducing real-world flavour into the studies and broaden the minds (quality awareness) of the students.     

Optimal correlation function for Fermi HNC equations

We show how to find variational equations for the Jastrow pair-correlation function which minimizes the energy of a normal Fermi liquid in the hypernetted chain approximation. By a straightforward extension of the method of Lagrange multipliers, a set of coupled, non-linear integrodifferential equations is obtained. The solutions give both the trial function and the corresponding radial distribution function. For bosons, our equations coincide with the results of paired-phonon analysis.     

Towards the Discrimination of Carboxylates by Hydrogen‐Bond Donor Anion Receptors

The binding constants (log K_ass) of small synthetic receptor molecules based on indolocarbazole, carbazole, indole, urea and some others, as well as their combinations were measured for small carboxylate anions of different basicity, hydrophilicity and steric demands, that is, trimethylacetate, acetate, benzoate and lactate, in 0.5 % H₂O/[D₆]DMSO by using the relative NMR‐based measurement method. As a result, four separate binding affinity scales (ladders) including thirty‐eight receptors were obtained with the scales anchored to indolocarbazole. The results indicate that the binding strength is largely, but not fully, determined by the strength of the primary hydrogen‐bonding interaction. The latter in turn is largely determined by the basicity of the anion. The higher is the basicity of the anion the stronger in general is the binding, leading to the approximate order of increasing binding strength, lactate<benzoate<acetate≤trimethylacetate, which holds with all investigated receptors. Nevertheless, there are a number of occasions when the binding order changes with changing of the carboxylate anion, sometimes quite substantially. Principal component analysis (PCA) reveals that this is primarily connected to preferential binding of trimethylacetate, supposedly caused by an additional hydrophobic/solvophobic interaction. These findings enable making better predictions, which receptor framework or cavity is best suited for carboxylate anions in receptor design.