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K. Matus, M. Pawlyta, G. Matula and K. Gołombek

Abstract

The aim of this article of this paper is to present issues related to characterization of nanometric-sized carbides, nitrides and/or carbonitrides formed during tempering of carbide-steel cermets. Closer examination of those materials is important because of hardness growth of carbide-steel cermet after tempering. The results obtained during research show that the upswing of hardness is significantly higher than for high-speed steels. Another interesting fact is the displacement of secondary hardness effect observed for this material to a higher tempering temperature range. Determined influence of the atmosphere in the sintering process on precipitations formed during tempering of carbide-steel cermets. So far examination of carbidesteel cermet produced by powder injection moulding was carried out mainly in the scanning electron microscope. A proper description of nanosized particles is both important and difficult as achievements of nanoscience and nanotechnology confirm the significant influence of nanocrystalline particles on material properties even if its mass fraction is undetectable by standard methods. The following research studies have been carried out using transmission electron microscopy, mainly selected area electron diffraction and energy dispersive spectroscopy. The obtained results and computer simulations comparison were made.

Open access

M. Pawlyta, K. Labisz and K. Matus

Abstract

Aluminium recycling is cost-effective and beneficial for the environment. It is expected that this trend will continue in the future, and even will steadily increase. The consequence of the use of recycled materials is variable and difficult to predict chemical composition. This causes a significant reduction in the production process, since the properties of produced alloy are determined by the microstructure and the presence of precipitates of other phases. For this reason, the type and order of formation of precipitates were systematically investigated in recent decades. These studies involved, however, only the main systems (Al-Cu, Al-Mg-Si, Al-Cu-Mg, Al-Mg-Si-Cu), while more complex systems were not analysed. Even trace amounts of additional elements can significantly affect the alloy microstructure and composition of precipitates formed. This fact is particularly important in the case of new technologies such as laser surface treatment. As a result of extremely high temperature and temperature changes after the laser remelting large amount of precipitates are observed. Precipitates are nanometric in size and have different morphology and chemical composition. A full understanding of the processes that occur during the laser remelting requires their precise but also time effectively phase identification, which due to the diversity and nanometric size, is a major research challenge. This work presents the methodology of identification of nanometer phase precipitates in the alloy AlSi9Cu, based on the simultaneous TEM imaging and chemical composition analysis using the dispersion spectroscopy using the characteristic X-ray. Verification is performed by comparing the simulation unit cell of the identified phase with the experimental high-resolution image.

Open access

M. Dragún, G. Dóka, M. Máťuš, P. Křenek and J. Klimas

Abstract

Aim: The aim is to identify the possible changes in the expression of genes, that regulate calcium homeostasis in cardiomyocytes in diabetes mellitus.

Methods: Male Wistar rats were randomized into two experimental protocols: short-term 5-days streptozotocin-induced diabetes protocol with 20 weeks old animals at the end of the protocol (total N = 20) and long-term 4-weeks protocol with 18 weeks of age at the end of the protocol (total N = 38). 50 mg/kg of streptozotocin (STZ) was administered in both protocols by a single intraperitoneal injection in 0,1M citrate buffer (pH = 4.5). Control group (CON) received only vehiculum. Gene expressions in samples of left heart ventricle were measured by RT-qPCR method.

Results: The expression of SERCA2a in short-term protocol was decreased. In long-term protocol, decreased SERCA2a, TRPC4 and TRPC6 mRNA levels were observed (*p < 0.05). SERCA2a and TRPC4 mRNA levels exhibited statistical monotonic correlation in STZ-treated group in long-term protocol.

Conclusions: In diabetes mellitus, the calcium homeostasis in cardiomyocytes is altered and there could be a relation between alteration of internal sarcoplasmatic stores and store-operated calcium entry.

Open access

T. Jung, W. Kwaśny, Z. Rdzawski, W. Głuchowski, K. Matus, M. Pawlyta and M. Szindler

Abstract

This paper presents the study of repetitive corrugation process influence on the strengthening of annealed alloy. Based on the results of mechanical properties of deformed sample, it has been found that the microhardness, ultimate tensile strength, yield strength and apparent elastic limit are significantly increased in relation to annealed sample. Examination on transmission electron microscopy confirmed the effect of intensive plastic deformation on structure fragmentation in the nanometric scale. This work confirmed the possibility of using the repetitive corrugation process to increase mechanical properties of CuCr0.6 alloy.

Open access

Eugeniusz Mańka, Małgorzata Słomion and Maciej Matuszewski

Abstract

In this paper structural analysis of steel ropes applied in mining shaft hoists was conducted. Functions of the ropes which they fulfilled in these shaft hoists were identified. Expected operational features of ropes were indicated too. An analysis was carried out four identified groups of ropes: hoisting ropes, balance ropes, leading rope and fender ropes. Basic constructional features: geometrical and material of ropes, which they should be characterized in each of mentioned functional groups were indicated. Constructional structures of mentioned steel ropes, the most often applied in domestic mining shaft hoists were described. Observed tendencies in analyzed issues also were shown.

Open access

Luis Rafael Moscote-Salazar, Andres M. Rubiano, Hernando Raphael Alvis-Miranda, Nasly Zabaleta-Churio, Willem Guillermo Calderón-Miranda, Gabriel Alcalá-Cerra and Jorge Aquino-Matus

Abstract

Background: Intracranial hemorrhagic complications are unusual after diagnostic lumbar puncture. Case report: A diagnostic lumbar puncture was performed in a 55 year-old male for acute bacterial meningitis workup. Immediately after the procedure he developed intense headache and a head Computed Tomography (CT) was done which identified an acute subdural fluid collection. No surgical management was offered and conservative medical follow-up was indicated. Conclusion: The occurrence of a headache with red flags after a lumbar puncture may suggest the possibility of an acute subdural hematoma.