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The paper discusses the complex effect of melt overheating with subsequent fast cooling down to the pouring temperature on the crystallization process, microstructure and mechanical properties of Al-Mg-Si aluminum alloy. The results obtained facilitated the establishment of rational modes of melt overheating, leading to a significant change in the dispersion and morphology of structural components. In particular, with an increase in the melt overheating temperature to 900 °C with holding and subsequent rapid cooling to the casting temperature, a decrease in the average size of dendritic cells of the aluminum solid solution from 39 μm to 13 μm was observed. We also noticed the refinement of eutectic inclusions of the Mg2Si phase with compact morphology. An increased level of mechanical properties was noted; the maximum values of tensile strength and elongation reached 228 MPa and 5.24%, respectively, which exceeded the initial values by 22.5% and 52.3%, correspondingly. The microhardness of the aluminum solid solution sequentially increased from 38.21 to 56.5 HV with an increase in the temperature during melt overheating. According to the EDS linear scanning, an increase in the superheat temperature of the melt is accompanied by an increase in the degree of saturation of the solid solution with magnesium.

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BackgroundDespite the recent advances in medicine, fever of unknown origin (FUO) remains a diagnostic and therapeutic challenge even to expert physicians. The etiological structure of FUO is determined by many factors, including the one where a person lived and where has been hospitalized. The aim of this study is to investigate the etiology and clinical characteristics of adult classical FUO with more diagnostics available and to analyze the factors for certain disease categories.MethodsThe clinical data were retrospectively analyzed from 80 patients with cFUO hospitalized at the Infectious Clinical Hospital №2 between October 2015 and October 2016 the patients who met the D.Durack criteria (1) An axillary temperature of >38.0 which corresponds oral temperature of >38.3; (2) illness duration is more than 3 weeks; (3) there is no definite diagnosis after three outpatient visits or 3 days in the hospital with intensive investigations; (4) the fever is not related to FUO of other groups: nosocomial FUO, FUO in patients with AIDS, neutropenia were included.ResultsOf the 80 FUO cases, 70 were positively diagnosed with a diagnosis rate of 87,5%. Infectious diseases were still the primary causes of FUO 63% (n = 50). Among them the most frequent diagnoses were bacterial infection of unspecified site 12.5%
(n = 10), infective endocarditis 11% (n = 9), as well as pneumonia 7.5% (n = 6) and viral infections of unspecified site 7.5% (n=6). Connective tissue diseases and other noninfectious inflammatory diseases accounted for 17.5% of the FUO cases among which SLE and autoimmune thyroiditis were the most common etiologies and made up 5% (n = 4) and 3,75% (n = 3), respectively. Neoplasms were 8% (n = 6) in our sample. Also ten patients (12,5%) could not be confirmed until they were discharged from hospital.ConclusionInfectious diseases are the major causes of FUO, and the most common cause is bacterial infection of unspecified site. To determine the etiology was difficult due to the limited conditions of the clinical hospital. Infectious endocarditis was found on the second place. The most common causative agents of infective endocarditis were MRSA (3/9) и streptococcus viridans (4/9). The frequency of undiagnosed cases was increasing, but in most FUO cases the causes can be diagnosed eventually after careful analysis of clinical data.Disclosures All authors: No reported disclosures.

Increasing the accuracy of computer simulation of the crystallization processes of aluminum alloys and the solidification of castings requires reliable data on the thermo-physical properties of the alloys used. The present paper describes a technique for calculating the heat of crystallization and heat capacity of aluminum alloys in the range from the temperature of its pouring into the mold to the average temperature of the solidified skin according to the results of thermal analysis. The proposed technique can be used to determine the values of thermo-physical properties of aluminum alloys in industrial and research laboratories and centers involved in production of high-quality castings.