Zsolt Bendő

Effectiveness of a high purity chlorine dioxide solution in eliminating intracanal Enterococcus faecalis biofilm

We investigated the effectiveness of chlorine dioxide (ClO2) solution in comparison to sodium hypochlorite (NaOCl) and chlorhexidine gluconate (CHX) in the elimination of intracanal Enterococcus faecalis biofilm. Extracted human teeth were inoculated with E. faecalis. After preparation the canals were irrigated with ClO2, NaOCl, CHX or physiologic saline for control. Two and five days later bacterial samples were collected and streaked onto Columbia agar. CFU/mL were counted. The canal walls were investigated by scanning electron microscopy (SEM). The gas phase was investigated in an upside down Petri dish where E. faecalis was inoculated onto blood agar. The irrigants were placed on absorbent paper into the cover. Bacteria were detectable in the control group, but not in any of the irrigants groups. There was a massive reinfection 2 or 5 days after irrigation in the control group. The lowest reinfection was found after the ClO2 treatment. These findings were confirmed by SEM images. We observed an antibacterial effect of ClO2 and NaOCl gas phases on E. faecalis growth, but not of CHX. ClO2 eliminates intracanal biofilm and keeps canal nearly free from bacteria. We suggest the use of high purity ClO2 as a root canal irrigant in clinical practice.

The relevance of dawsonite precipitation in CO2 sequestration in the Mihályi-Répcelak area, NW Hungary

Abstract A natural CO2 reservoir system with a sandstone lithology in NW Hungary has been studied due to its similarities to a large saline reservoir formation that is widespread in the the Pannonian Basin (Central Europe) and is suggested to be one of the best candidates for industrial CO2 storage. A range of analytical techniques has been used on core samples from CO2-containing sandstone layers that represent a wide range of pressures (90–155 bar), temperatures (79–95°C) and pore fluid compositions (total dissolved solids between 18 000 and 50 700 mg l−1) to identify the mineralogy and textural characteristics of the natural reservoir. The only clear CO2-related feature in the studied lithology was the occurrence of dawsonite (NaAlCO3(OH)2) in a close textural relationship with albite. This is in clear agreement with our geochemical modelling results, which also underline the presence of albite as a precondition for the crystallization of dawsonite at the given P–T–X conditions. Our results suggest that, at least in the Pannonian Basin, dawsonite may be an important mineral for the safe sequestration of industrial CO2 in the subsurface.

Medieval Gilding Technology of Historical Metal Threads Revealed by Electron Optical and Micro-Raman Spectroscopic Study of Focused Ion Beam-Milled Cross Sections

Although gilt silver threads were widely used for decorating historical textiles, their manufacturing techniques have been elusive for centuries. Contemporary written sources give only limited, sometimes ambiguous information, and detailed cross-sectional study of the microscale soft noble metal objects has been hindered by sample preparation. In this work, to give a thorough characterization of historical gilt silver threads, nano- and microscale textural, chemical, and structural data on cross sections, prepared by focused ion beam milling, were collected, using various electron-optical methods (high-resolution scanning electron microscopy (SEM), wavelength-dispersive electron probe microanalysis (EPMA), electron backscattered diffraction (EBSD) combined with energy-dispersive electron probe microanalysis (EDX), transmission electron microscopy (TEM) combined with EDX, and micro-Raman spectroscopy. The thickness of the gold coating varied between 70-400 nm. Data reveal nano- and microscale metallurgy-related, gilding-related and corrosion-related inhomogeneities in the silver base. These inhomogeneities account for the limitations of surface analysis when tracking gilding methods of historical metal threads, and explain why chemical information has to be connected to 3D texture on submicrometre scale. The geometry and chemical composition (lack of mercury, copper) of the gold/silver interface prove that the ancient gilding technology was diffusion bonding. The observed differences in the copper content of the silver base of the different thread types suggest intentional technological choice. Among the examined textiles of different ages (13th-17th centuries) and provenances narrow technological variation has been found.

High pressure metaophiolite polished stone implements found in Hungary

Good quality high pressure (HP) metaophiolite rock types (e.g. Na-pyroxenite/jade, eclogite) suitable for making prehistoric polished stone implements were unknown among Hungarian findings for a long time. Nowadays they are still among the rarest types of polished stone implements found in Hungary in the respect of raw material. After the first discovery of Neolithic stone tools made of HP metaophiolites in the records of Hungarian archaeological assemblages, detailed petrological investigations of large stone implement collections revealed their presence in a relatively large number. According to our current knowledge, 25 HP metaophiolite stone implements are known as found in Hungary. Unfortunately, most of them are stray finds, but 11 pieces from four localities have a known archaeological context. They were mainly located in Transdanubia (except for one piece from Tiszántúl) and are mostly attributable to the Late Neolithic Lengyel Culture and secondarily to the Late Neolithic Tisza Culture. In this study, we used only non-destructive analytical methods (macroscopic observation, magnetic susceptibility measurements, non-destructive SEM-EDX, and Prompt Gamma Activation Analysis). As a result of this study, the prehistoric stone implements were classified into raw material types. Based on our data, the high pressure-low temperature (HP-LT) metaophiolite stone implements found in Hungary probably originated from the same raw material sources as the Italian HP-LT metaophiolite stone tools (sourcing from North-western Italy). According to the literature on the topic, both primary (Western Alps in the vicinity of the Monviso in Piedmont or the Voltri Massif in Liguria) and secondary occurrences (in Quaternary deposits of the rivers Po, Staffora and Curone) are potential sources. These analyses confirmed the existence of long-distance trade routes connecting the Po Valley and its vicinity with the Carpathian Basin during the Vth Millennium BC.

Characterization and 10Be content of iron carbonate concretions for genetic aspects – Weathering, desert varnish or burning: Rim effects in iron carbonate concretions

The research investigated three iron carbonate (siderite) sedimentary concretions from Nagykovácsi, Úri and Délegyháza, Hungary. To identify possible source rocks and effects of the glaze-like exposed surface of the concretions, we carried on comparative petrological, mineralogical, geochemical and isotopic studies. The samples were microbially mediated siderite concretions with embedded metamorphous and igneous mineral clasts, and had specific rim belts characterized by semi-concentric outer Fe-oxide layers, fluffy pyrite-rich outer belts and siderite inner parts. We investigated the cross section of the Fe-carbonate concretions by independent methodologies in order to identify their rim effects. Their surficial oxide layers showed evidence of degassing of the exposed surface caused most probably by elevated temperatures. The inner rim pyrite belt in the concretions excluded the possibility of a prolonged wet surface environment. Microtextural and mineralogical features did not support desert varnish formation. 10Be nuclide values of the Nagykovácsi and Uri concretions were far above the level of terrestrial in-situ cosmogenic nuclides, but they were consistent with the lowest levels for meteorites. Though the data were not conclusive to confirm any kind of known origin, they are contradictary, and open possibilities for a scenario of terrestrial meteorite origin.