Quantification of the depletion of ozone in the plume of Mount Etna

Volcanoes are an important source of inorganic halogen species into the atmosphere. Chemical processing of these species generates oxidised, highly reactive, halogen species which catalyse considerable O₃ destruction within volcanic plumes. A campaign of ground-based in situ O₃, SO₂ and meteorology measurements was undertaken at the summit of Mount Etna volcano in July/August 2012. At the same time, spectroscopic measurements were made of BrO and SO₂ columns in the plume downwind. <br><br> Depletions of ozone were seen at all in-plume measurement locations, with average O₃ depletions ranging from 11–35 nmol mol⁻¹ (15–45%). Atmospheric processing times of the plume were estimated to be between 1 and 4 min. A 1-D numerical model of early plume evolution was also used. It was found that in the early plume O₃ was destroyed at an approximately constant rate relative to an inert plume tracer. This is ascribed to reactive halogen chemistry, and the data suggests the majority of the reactive halogen that destroys O₃ in the early plume is generated within the crater, including a substantial proportion generated in a high-temperature "effective source region" immediately after emission. The model could approximately reproduce the main measured features of the ozone chemistry. Model results show a strong dependence of the near-vent bromine chemistry on the presence or absence of volcanic NO_x emissions and suggest that near-vent ozone measurements can be used as a qualitative indicator of NO_x emission

Euler Integration of Gaussian Random Fields and Persistent Homology

In this paper we extend the notion of the Euler characteristic to persistent homology and give the relationship between the Euler integral of a function and the Euler characteristic of the function's persistent homology. We then proceed to compute the expected Euler integral of a Gaussian random field using the Gaussian kinematic formula and obtain a simple closed form expression. This results in the first explicitly computable mean of a quantitative descriptor for the persistent homology of a Gaussian random field.Comment: 21 pages, 1 figur

Montmorilonit – usporedba metoda za njegovo određivanje u ljevaoničkim bentonitima

A comparison and estimation of usefulness of a quantitative analysis of montmorillonite in foundry bentonites, was the aim of this research. The investigations were made by means of three different techniques: methylene blue (MB) adsorption method, Cu(II)-triethylenetetramine complex (Cu(II)-TET) adsorption method, and infrared spectroscopy (FTIR) method. Tests were performed for 9 kinds of bentonites originated from various producers. The achieved results indicated that, the results obtained by the FTIR method were, in general, even 10% lower than the ones obtained by other methods. The best correlation with the data given by the producers were obtained for the Cu(II)-TET method. In addition, this method was characterised by the smallest value of standard deviations. A very essential advantage of the Cu(II)-TET method is a much shorter time needed for the analysis and its easier execution, which is important under production conditions.Cilj ovog istraživanja je bila procjena upotrebljivosti kvantitativne analize montmorilonita u ljevaoničkim bentonitima. Istraživanja su provedena pomoću tri različite tehnike: adsorpcija metilenskog modrila (MB), adsorpcija Cu(II)-trietilentetramin kompleksa (CU(II)-TET), i infracrvena spektroskopija (FTIR). Ispitivanja su provedena na 9 vrsta bentonita koji potječu od različitih proizvođača. Rezultati dobiveni FTIR metodom u prosjeku su za čak 10,0% niži od rezultata dobivenih ostalim metodama. Najbolja korelacija s podatcima od proizvođača dobivena je primjenom Cu(II)-TET metode. Osim toga, kod te metode najmanje su vrijednosti standardnih devijacija. Vrlo važna prednost Cu(II)-TET metode je znatno kraće vrijeme potrebno za anaalizu i lakše provođenje, što je značajno u proizvodnim uvjetima

Cosine families and semigroups really differ

We reveal three surprising properties of cosine families, distinguishing them from semigroups of operators: (1) A single trajectory of a cosine family is either strongly continuous or not measurable. (2) Pointwise convergence of a sequence of equibounded cosine families implies that the convergence is almost uniform for time in the entire real line; in particular, cosine families cannot be perturbed in a singular way. (3) A non-constant trajectory of a bounded cosine family does not have a limit at infinity; in particular, the rich theory of asymptotic behaviour of semigroups does not have a counterpart for cosine families. In addition, we show that equibounded cosine families that converge strongly and almost uniformly in time may fail to converge uniformly.Adam Bobrowski and Wojciech Chojnack

Investigations of Protective Coatings for Castings of High-manganese Cast Steels

When cast steel castings are made in moulding sands on matrices of high-silica sand, which has a low fire resistance the problem of theso-called chemical penetration is distinctly visible. Whereas this effect appears to a small degree only when moulding sand matrices are of chromite, zircon or olivine sands. Therefore in case of making castings of high-manganese cast steel (e.g. Hadfield steel) sands not containing free silica should be applied (e.g. olivine sand) or in case of a high-silica matrix protective coatings for moulds and cores should be used. Two protective coatings, magnesite alcoholic (marked as coating 1 and coating 2) originated from different producers and intended for moulds for castings of the Hadfield steel, were selected for investigations. Examinations of the basic properties were performed for these coatings: viscosity, thermal analysis, sedimentation properties, wear resistance. In order to estimate the effectiveness of protective coatings the experimental castings were prepared. When applying coating 1, the surface quality of the casting was worse and traces of interaction between the casting material (cast steel) and the coating were seen. When protective coating 2 was used none interactions were seen and the surface quality was better

Kinetics of gas emission from aluminosilicates used as a relaxing additive for moulding and core sands

The article presents the results of gas emissions generated during heating of mineral additives – aluminosilicates (perlite ore and vermiculite). The test on a laboratory stand for a 1 g sample at 1 000 °C was carried out. It has been shown, that there is a correlation between the degree of fragmentation and the amount of gas generated. The finest fraction of perlite ore caused a similar quantitative gas emission as ground vermiculite. The presence of additives in molding sands, regardless of the size of fraction, should not affect the formation of casting defects. The addition of perlite ore and vermiculite does not effect the ecological properties of moulding sand