Solid particle erosion resistance of Al alloy and Al alloy-fly ash composite subjected to equal-channel angular pressing

This paper describes the influence of deformation by equal-channel angular pressing (ECAP) on the solid particle erosion resistance of the AlSi7Mg0.3 alloy and AlSi7Mg0.3 based composite material reinforced with the addition of 4 % of fly ash (FA) particles. Both, alloy and composite samples were produced using the compo-casting method. The samples have been subjected to ECAP in multiple passes with the rotation of samples around the vertical axis for the angle of 90° after each pass. Particles of silicon carbide (SiC) have been used as erodent while their impact angle was varied (30° and 90°). Observed samples of AlSi7Mg0.3 alloy generally showed higher wear resistance at 90° angle where material fatigue predominates, than at a 30° angle where abrasion-related phenomena predominate. On the other hand, AlSi7Mg0.3 based composite material exhibited erosion wear at 30° angle less than at 90° angle after one ECAP pass. Evaluation of the erosion resistance has been made based on mass and volume loss. After two passes of ECAP, the matrix structure of the AlSi7Mg0.3 based composite material, as well as that of the AlSi7Mg0.3 alloy was improved from the aspect of erosion resistance

Failure analysis of jet engine turbine blade

Jet engine turbine blade cast by investment precision casting of Ni-base superalloy, which failed during exploatation, was the subject of investigation. Failure analysis was executed applying optical microscopy (OM), transmission electron microscopy (TEM) using replica technique, scaning electron microscopy (SEM) and stress rupture life tests. On the ground of obtained results it was concluded that the failure occurred as a result of structural changes caused by turbine blade overheating above the exploitation temperature

Fractographic analysis of the aluminum matrix composite prepared by accumulative roll bonding

Recent research in the material science field is focused on the easy-to-apply and cost-effective production of the structural components with enhanced mechanical properties. As an answer to these new trends in the present study, the inexpensive household aluminum foils are used to produce the multilayer aluminum matrix composite. The aluminum matrix composites are manufactured by hot-rolling of the sandwiched foils and afterward subjected to microstructural characterization and mechanical testing. Analysis of the produced composite microstructure and fracture surface obtained after tensile testing was performed using the scanning electron microscopy (SEM). The qualitative fractographic analysis revealed that the ductile fracture features prevail in the overall fracture mode of the investigated multilayer composite, while the quantitative fractographic investigation allowed more detailed insight into the composite failure process and depicted critical parameters that led to the composite failure

Proteinases from buckwheat (Fagopyrum esculentum moench) seeds: Purification and properties of the 47 kDa enzyme

Analizirane su aspartične proteinaze semena heljde. Upotrebom pepstatin A afinitetne hromatografije, iz zrelog semena izdvojene su tri forme aspartičnih proteinaza, od 47 kDa, 40 kDa i 28 kDa, dok je u ekstraktu nezrelog semena odsustvovala forma od 40 kDa. Protein od 47 kDa naknadno je razdvojen od ostalih formi kada je hromatografiji prethodila amonijum-sulfatna precipitacija. Pokazano je da tip proteolitičkog delovanja prečišćene forme enzima odgovara delovanju himozina, aspartične proteinaze animalnog porekla, čime bi se mogla objasniti njegova sposobnost da koaguliše mleko. Enzim je lokalizovan u membranskoj ćelijskoj frakciji.Aspartic proteinases from buckwheat seeds are analyzed. Three forms of 47 kDa, 40 kDa and 28 kDa, were purified from mature buckwheat seeds, while two forms of 47 kDa and 28 kDa were detected in developing buckwheat seeds using pepstatin A affinity chromatography. A form of 47 kDa was selectively precipitated from other forms by ammonium sulfate precipitation. This enzyme resembles the chymosin-like pattern of proteolytic activity, as it was shown using BSA and k-casein as substrates, clarifying its ability for milk-clotting. The 47 kDa aspartic proteinase form is localized in the membrane fraction

Proteinases from buckwheat (Fagopyrum esculentum moench) seeds: Purification and properties of the 47 kDa enzyme

Aspartic proteinases from buckwheat seeds are analyzed. Three forms of 47 kDa, 40 kDa and 28 kDa, were purified from mature buckwheat seeds, while two forms of 47 kDa and 28 kDa were detected in developing buckwheat seeds using pepstatin A affinity chromatography. A form of 47 kDa was selectively precipitated from other forms by ammonium sulfate precipitation. This enzyme resembles the chymosin-like pattern of proteolytic activity, as it was shown using BSA and k-casein as substrates, clarifying its ability for milk-clotting. The 47 kDa aspartic proteinase form is localized in the membrane fraction.

Correlation Between Morphology and Structure of Galvanostatically Electrodeposited Tin Dendrites

Tin dendrites found wide application in various industries.1 They can be obtained by both non-electrochemical and electrochemical methods of synthesis. In this study, they were produced by a galvanostatic regime of electrolysis from alkaline hydroxide solution at a current density of –3 mA cm–2 , 1.5 times larger than the limiting diffusion current density, with an amount of the electricity of 200 and 400 mC. In the dependence of an amount of the passed electricity, Sn dendrites of various morphology and crystal orientation were obtained: the fern-like dendrites predominantly oriented in (220), (440) crystal planes are obtained with 200 mC and the spear-like and the dendrites with prismatic branches showing the strong (200),(400) preferred orientationwere obtained with 400 mC. The strong correlation between morphology and structure of Sn dendrites is established and it can be explained by analysis of chronopotentiometry response obtained at the given current density and by morphological and structural analyses of Sn dendrites obtained by a potentiostatic regime at cathodic potentials corresponding to values attained after the passed amount of the electricity of 200 and 400 mC. The chronopotentiometry response after spent 200 mC was dominantly in the (–1600 – 1740) mV vs. Ag/AgCl range, and the fern-like dendrites with the strong (220), (440) preferred orientation were obtained in this potential range. After spent 400 mC, the chronopotentiometry response was about –1200 mV vs. Ag/AgCl, and the spear-like and the dendrites with prismatic branches with the strong (200),(400) preferred orientationwere obtained at this cathodic potential

Optical microscopy as a simple method for analysis of boiler tube failure

A severely damaged low carbon steel boiler tube was the object of this investigation. Detailed microstructural characterization was performed by optical microscopy, whereas scanning electron microscopy (SEM) was applied only in a few cases. Results show that a variety of microstructures was formed in the material of the damaged boiler tube during its exploitation. The failure of the tube is the result of very inhomogeneous overheating. The side of the boiler tube toward fire (F) was exposed to high overheating temperature, which in some locations was well above the A3 transformation temperature. The side toward boiler (BL) was subjected to lower temperatures, i.e. in the region mostly between A1 and A3 temperatures. Variations in temperatures and cooling rates, which resulted in microstructural inhomogeneity, are the main cause for the formation and multiplication of stresses leading to the rupture of the tube

Successful production of recombinant buckwheat cysteine-rich aspartic protease in Escherichia coli

U ovom radu predstavljena je ekspresija rekombinantne atipične aspartatne proteinaze heljde (Fagopyrum esculentum) bogate cisteinom, gde su testirana različita ekspresiona svojstva pet sojeva E. coli. Takođe je analiziran i uticaj fuzionih partnera (His6 i MBP) na efikasnost ekspresije. U slučaju His6-FeAPL1, dobijena je velika količina nerastvornog proteina, smeštenog u inkluzionim telima. S druge strane, MBP-FeAPL1 je bio lokalizovan i u citoplazmi i u inkluzionim telima u oba upotrebljena soja E. coli (BL21 i Rosetta-gami). Međutim, samo za rekombinantni protein proizveden u soju Rosetta-gami, dokazana je proteolitička aktivnost na supstratu BSA, pri pH 3,0. Rezultati su takođe ukazali da FeAPL1 sadrži PRO segment, čije je odstranjivanje neophodno za njegovu proteolitičku aktivnost. Aktivnost FeAPL1, pokazana samo u soju Rosetta-gami, gde je moguće formiranje disulfidnih veza, ukazuje na značaj 12 cisteina u uspostavljanju pravilne strukture koja omogućava funkcionalnost enzima.Herein, the expression of recombinant cysteine-rich atypical buckwheat (Fagopyrum esculentum) aspartic protease (FeAPL1) in five Escherichia coli strains differing in their expression capabilities is presented. It was shown that the expression success depended highly on the choice of FeAPL1 fusion partner. His6-FeAPL1 was produced in large quantities as an insoluble protein localized in inclusion bodies. On the other hand, MBP-FeAPL1 was localized in both the cytoplasm and inclusion bodies in BL21 and Rosetta-gami strains. Only purified soluble MBP-FeAPL1 from Rosetta-gami cells showed proteolytic activity at pH 3.0 with BSA as the substrate. The results also indicated that FeAPL1 contained a PRO segment that had to be removed for the enzyme activity to appear. The activity of FeAPL1 produced in the Rosetta-gami strain, which enables disulfide bond formation, indicated the importance of the twelve cysteine residues for correct folding and functionality

Tensile properties and fracture mechanism of IN-100 superalloy in high temperature range

Tensile properties and fracture mechanism of a polycrystalline IN-100 superalloy have been investigated in the range from room temperature to 900 °C. Optical microscopy (OM) and transmission electron microscopy (TEM) applying replica technique were used for microstructural investigation, whereas scanning electron microscopy (SEM) was utilized for fracture study. High temperature tensile tests were carried out in vacuumed chamber. Results show that strength increases up to 700 °C, and then sharply decreases with further increase in temperature. Elongation increases very slowly (6-7.5%) till 500 °C, then decreases to 4.5% at 900 °C. Change in elongation may be ascribed to a change of fracture mechanism. Appearance of a great number of microvoids prevails up to 500 °C resulting in a slow increase of elongation, whereas above this temperature elongation decrease is correlated with intergranular crystallographic fracture and fracture of carbides

A search of Brassica SI-involved orthologs in buckwheat leads to novel buckwheat sequence identification: MLPK possibly involved in SI response

Kod biljaka cvetnica postoje genetički određeni sistemi self-inkompatibilnosti (SI), koji sprečavaju samooprašivanje i ukrštanje u srodstvu održavajući genetičku raznovrsnost vrsta. SI se javlja u dva oblika, kao gametofitna i sporofitna SI, koje se razlikuju u načinu određivanja SI fenotipa polena - kod GSI je SI fenotip polena određen polenovim sopstvenim haploidnim genomom, dok je kod SSI određen dipolidnim genotipom majke biljke. SSI se javlja kao homomorfna (jedan tip cveta u biljaka jedne vrste) i heteromorfna (dva ili tri tipa cveta u biljaka jedne vrste). Heteromorfna SSI je u poređenju sa homomorfnom SSI i GSI izuzetno malo proučena i za sada je upoznavanje na molekularnom nivou tek započelo. Kod heljde je prisutna distilna heteromorfna SSI, o kojoj je sakupljeno dosta podataka na fiziološkom nivou, ali o kojoj za sada nema molekularnih podataka. Na osnovu fiziološke sličnosti SI odgovora biljaka rodova Brassica i Prunus sa tram i pin morfom heljde, respektivno, zatim na osnovu toga što postoje dokazi da slični biohemijski mehanizmi leže u osnovi različitih SI odgovora i na osnovu toga što i evolutivno udaljene SI vrste mogu posedovati iste ili slične predačke SI gene, mi smo odlučili da ispitamo prisustvo ortologih gena uključenih u SI odgovore Brassica i Prunus u genomu heljde. Upotrebom izrođenih prajmera dizajniranih na osnovu evolutivno očuvanih regiona SRK, SLG, SP11 i MLPK sekvenci Brassica rapa, kao i S-RNaza i SFB gena roda Prunus, dostupnih u NCBI bazi podataka, ispitano je prisustvo ortologa ovih gena u genomu heljde. Takođe je prisustvo S-RNaza ispitano u proteinskim izolatima neoprašenih i kompatibilno i inkompatibilno oprašenih tučkova heljde oba morfa. Rezultati su pokazali da nema ortologa SRK, SLG, SP11, kao ni S-RNaza i SFB u genomu heljde, ali da postoji MLPK ortolog kod heljde. Izvedena aminokiselinska sekvenca pokazala je 80 % sličnosti sa MLPKf2 sekvencom Brassica rapa i APK1A Arabidopsis thaliana, potvrđujući da su u pitanju ortolozi koji bi mogli da imaju i sličnu ulogu. Naš sledeći korak je dobijanje cele nukleotidne sekvence MLPK heljde uz is- pitivanje postojanja alternativnih mesta iskrajanja i određivanje nivoa ekspresije po tkivima, kao i ispitivanje moguće uloge u SI odgovoru heljde. Ovi odgovori omogućiće bolje upoznavanje heteromorfnih SSI sistema koji su još uvek u svojoj najranijoj fazi istraživanja i obezbediće podatke nužne za uvid u evoluciju SI sistema biljaka cvetnica. Najzad, rasvetljavanjem SSI sistema heljde, koja se koristi u ishrani, biće moguće genetički kontrolisati ukrštanje heljde i dobijanje linija sa željenim hranljivim i/ili fiziološkim osobinama.Self-incompatibility (SI) systems, gamethophytic (GSI) and sporophytic (SSI), prevent self-pollination in angiosperms. Buckwheat displays heteromorphic SSI, with pollination allowed only between different flower morphs - thrum and pin. The physiology of thrum and pin morph SI responses are entirely different, resembling homomorphic Brassica SSI and Prunus GSI responses, respectively. Considering angiosperm species may share ancestral SI genes, we examined the presence of Brassica and Prunus SI-involved gene orthologs in the buckwheat genome. We did not find evidence of SRK, SLG and SP11 Brassica or S-RNase and SFB Prunus orthologs in the buckwheat genome, but we found a Brassica MLPK ortholog. We report the partial nucleotide sequence of the buckwheat MLPK and discuss the possible implications of this finding