Abstract XRF-analysis of 18 fragments of several 14th–15th-century vessel types and an additional... more Abstract XRF-analysis of 18 fragments of several 14th–15th-century vessel types and an additional fragment of a 16th-century glass vessel, found primarily from the cesspits in the medieval town centre of Tartu, was carried out. The study reveals that these are mostly potassium-calcium silicates, containing 49–56 wt% of SiO2 and a varying high level (from 15 to 20 wt% or even more) of K2O and CaO. Four typological groups are represented: vessels with applied glass threads, high prunted beakers, lower beakers with a spiral glass thread, and beakers with a zig-zag glass thread. It is shown that all these have rather similar chemical composition. Classification by the CaO/K2O ratio hints at a possibility that besides the glass of Bohemian origin, vessels came also from the glasshouses in the present-day Germany. The blue decoration on the basic colourless glass contains Co, Cu, and Fe bearing colourants accompanied by various minor impurities like Zn, Pb, and sometimes Ni (instead of Zn). In addition, in the blue glass of the 16th century dating elements Bi and As were found. Obviously, Co from various sources was used. A fairly high level of Cu and Fe in blue decorations implies that these metals might have been added to the frit separately to get an additional shade, in the form of brass (Cu+Zn alloy) and hematite (Fe2O3, rust) respectively.
Scattered light fringe patterns are measured in thermally tempered and annealed glass plates to d... more Scattered light fringe patterns are measured in thermally tempered and annealed glass plates to determine the residual stress profile through the glass thickness. Numerically generated fringe patterns are compared with experimental ones. Stress profiles calculated from experimental fringe patterns are compared with stress profiles measured with a scattered light polariscope (SCALP).
We give an overview of results obtained in our isobaric studies of spectral holes in chlorin-dope... more We give an overview of results obtained in our isobaric studies of spectral holes in chlorin-doped glassy polystyrene, frozen n-octane and crystalline p-terphenyl under various fixed pressures up to 8.4 kbar at 4.2–18 K. Some results on low-pressure (<0.1 kbar) tuning of spectral holes at 1.5–4.2 K in benzophenone, biphenyl and frozen n-octane doped with chlorin and in frozen n-hexane
ABSTRACT Both photochemical and nonphotochemical spectral hole burning mechanisms were observed i... more ABSTRACT Both photochemical and nonphotochemical spectral hole burning mechanisms were observed in the incom-mensurate phase III ICIII of chlorin-doped biphenyl. Distributions of corresponding energetic barriers for the back reaction were acquired from temperature cycling experiments. The non-photochemical mechanism is characterized by finite unlike to glasses but low compared to the photochemical mechanism threshold of 6 –7 K and is interpreted as a photoinduced depinning-repinning of the incommensurate modulation wave. Holewidth dependence on cycling temperature up to 28 K was measured, crossing at 17 K the phase transition between two incommensurate phases in pure biphenyl. The measured irreversible hole broadening exhibits a fast close to cubic increase up to 17 K and then changes abruptly to a linear in the higher-temperature incommensurate phase II, which extrapolates back to zero at T→0 K. The results support the view that ICIII is a metastable state.
A classification of experiments on zero-phonon SHB is given and some related methodical problems ... more A classification of experiments on zero-phonon SHB is given and some related methodical problems are discussed. SHB applications in fluorescence-line-narrowing spectroscopy to improve its selectivity and the possibilities of controlling the SHB process are considered. Some technical applications of SHB in the field of transformation and recording of optical signals are discussed.
Abstract XRF-analysis of 18 fragments of several 14th–15th-century vessel types and an additional... more Abstract XRF-analysis of 18 fragments of several 14th–15th-century vessel types and an additional fragment of a 16th-century glass vessel, found primarily from the cesspits in the medieval town centre of Tartu, was carried out. The study reveals that these are mostly potassium-calcium silicates, containing 49–56 wt% of SiO2 and a varying high level (from 15 to 20 wt% or even more) of K2O and CaO. Four typological groups are represented: vessels with applied glass threads, high prunted beakers, lower beakers with a spiral glass thread, and beakers with a zig-zag glass thread. It is shown that all these have rather similar chemical composition. Classification by the CaO/K2O ratio hints at a possibility that besides the glass of Bohemian origin, vessels came also from the glasshouses in the present-day Germany. The blue decoration on the basic colourless glass contains Co, Cu, and Fe bearing colourants accompanied by various minor impurities like Zn, Pb, and sometimes Ni (instead of Zn). In addition, in the blue glass of the 16th century dating elements Bi and As were found. Obviously, Co from various sources was used. A fairly high level of Cu and Fe in blue decorations implies that these metals might have been added to the frit separately to get an additional shade, in the form of brass (Cu+Zn alloy) and hematite (Fe2O3, rust) respectively.
Scattered light fringe patterns are measured in thermally tempered and annealed glass plates to d... more Scattered light fringe patterns are measured in thermally tempered and annealed glass plates to determine the residual stress profile through the glass thickness. Numerically generated fringe patterns are compared with experimental ones. Stress profiles calculated from experimental fringe patterns are compared with stress profiles measured with a scattered light polariscope (SCALP).
We give an overview of results obtained in our isobaric studies of spectral holes in chlorin-dope... more We give an overview of results obtained in our isobaric studies of spectral holes in chlorin-doped glassy polystyrene, frozen n-octane and crystalline p-terphenyl under various fixed pressures up to 8.4 kbar at 4.2–18 K. Some results on low-pressure (<0.1 kbar) tuning of spectral holes at 1.5–4.2 K in benzophenone, biphenyl and frozen n-octane doped with chlorin and in frozen n-hexane
ABSTRACT Both photochemical and nonphotochemical spectral hole burning mechanisms were observed i... more ABSTRACT Both photochemical and nonphotochemical spectral hole burning mechanisms were observed in the incom-mensurate phase III ICIII of chlorin-doped biphenyl. Distributions of corresponding energetic barriers for the back reaction were acquired from temperature cycling experiments. The non-photochemical mechanism is characterized by finite unlike to glasses but low compared to the photochemical mechanism threshold of 6 –7 K and is interpreted as a photoinduced depinning-repinning of the incommensurate modulation wave. Holewidth dependence on cycling temperature up to 28 K was measured, crossing at 17 K the phase transition between two incommensurate phases in pure biphenyl. The measured irreversible hole broadening exhibits a fast close to cubic increase up to 17 K and then changes abruptly to a linear in the higher-temperature incommensurate phase II, which extrapolates back to zero at T→0 K. The results support the view that ICIII is a metastable state.
A classification of experiments on zero-phonon SHB is given and some related methodical problems ... more A classification of experiments on zero-phonon SHB is given and some related methodical problems are discussed. SHB applications in fluorescence-line-narrowing spectroscopy to improve its selectivity and the possibilities of controlling the SHB process are considered. Some technical applications of SHB in the field of transformation and recording of optical signals are discussed.
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Papers by Jaak Kikas