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Introduction: Some patients with coronary heart disease are diagnosed with severe aortic stenosis. For further treatment, coronary angiography is performed in these patients. For intermediate lesions, obtaining coronary artery physiological data can facilitate clinical decision-making regarding revascularization. Aim: The study compared the physiological significance of coronary artery stenosis using the fractional flow reserve (FFR) method with instantaneous wave-free pressure ratio (iFR) and quantitative flow ratio (QFR) in patients qualified for aortic valve replacement. Material and methods: Data were collected on patients hospitalized in the years 2019-2020 at the 2nd Department of Cardiology, University Hospital in Krakow. Results: Twelve patients with severe aortic stenosis and borderline lesions in the coronary artery were qualified for physiological assessment. There were 6 women, whose mean age was 73.8 ±7.5 years. The mean left ventricular ejection fraction was 52 ±15%. The mean aortic valve area was 0.80 ±0.16 cm2. The left anterior descending artery was assessed in 12 from 13 cases (92%). In comparison to FFR, all iFR measurements were concordant with FFR. The total agreement between QFR and FFR/iFR assessment was 69%. Conclusions: Despite the controversy and uncertainty of some operators regarding the interpretation of the FFR test in patients with severe aortic stenosis, we obtained complete agreement of FFR with iFR assessment. This fact suggests that in patients with severe aortic stenosis the choice of an invasive method to assess the physiological significance of the stenosis in the coronary artery is not crucial - both iFR and FFR allow comparable results. [ABSTRACT FROM AUTHOR]

Polyurethanes (PURs) are a group of polymers with the most versatile properties and the broadest spectrum of application. Their name comes from the urethane group. PURs were introduced to the market on a large-scale basis by Bayer in 1942, in the form of Perlon U and Igamid U fibers produced by gradual polyaddition of diisocyanates and polyols. The development of PURs-production technology and the multitude of applications resulted in their widespread use. This group is so extensive that polyurethanes alone accounted for about 6% of the global production of polymers (2019)—most of them in the form of foam. Therefore, polyurethane can be found in a huge number of products—some of them stored in the vicinity of ammonium nitrate (AN). In the previous two articles, we showed that polymers and AN—stored within the same building—in fire conditions may, under certain circumstances, spontaneously transform into a material of explosive properties. The aim of this article is to check whether PUR, when in contact with AN, creates additional hazards, similarly to the previously tested polymers. [ABSTRACT FROM AUTHOR]

This article is a continuation of a case study in which we presented the results of research on processes generated under fire conditions by mixing molten ammonium nitrate (AN) with selected polymers. Here, we present an analysis of how certain materials, which may frequently appear in farm buildings and are commonly used in the immediate vicinity of humans, can potentially form explosives. The chosen materials include polyamides (PA) from which the wear-resistant machine elements are made (e.g., high-performance gears, wheels of transport trolleys); polyvinyl chloride (PVC) used, i.e., in construction carpentry, electrical insulation, and hydraulic pipes; polystyrene (PS) used, i.e., in insulation and containers; and poly(methyl methacrylate) (PMMA), i.e., so-called organic glass and plexiglass. The research results showed that these seemingly harmless and safe materials, mixed with AN and heated under fire conditions, may turn into explosives and stimulate stored AN. This creates significant risks of an uncontrolled fire progress. [ABSTRACT FROM AUTHOR]

On 2 October 2003 in Saint-Romain-en-Jarez (France) a fire in a farm building triggered an explosion in which 26 people were injured. Police investigation, based solely on an analysis of the effects and on general engineering knowledge, showed that the explosion was caused by an uncontrollably generated mixture of ammonium nitrate (AN) and molten plastic crates which formed an explosive mixture similar to ammonium nitrate fuel oil (ANFO). This is the only commonly known example of an ammonium nitrate blast taking place at its end user destination. Is such an explanation of the incident plausible and could a similar blast possibly happen anywhere else? The experimental results support this thesis of French investigators but raise further doubts. Laboratory reconstruction of the self-acting process of generating the explosive material confirmed the investigators' report. However, other materials at the incident site could have influenced the final outcome too. The lab-recreated explosion of a mixture of AN and molten plastic partially confirmed the report's thesis. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of methods to increase the efficiency of heat transfer in heat exchangers. The scope of the research included analysis of efficiency optimization using the example of two tubular heat exchanger structures most often used in industry. The obtained efficiency of heat recovery from the ground of the examined exchangers was over 90%, enabling the reduction of emissions of the heating systems of buildings. The paper presents the results of tests of two types of heat pipes using R134A, R404A, and R407C working agents. The paper also presents the results of experimental tests using the R410A working medium. The results included in the study will also enable the effective use of land as a heat store. [ABSTRACT FROM AUTHOR]