Study of the microstructure, tensile properties and hardness of AZ61 magnesium alloy subjected to severe plastic deformation

Hot extruded (EX) AZ61 magnesium alloy was processed by the twist channel angular pressing (TCAP) method, which combines equal channel angular pressing (ECAP) and twist extrusion (TE) processes and significantly improves the efficiency of the grain refinement process. Both the initial hot extruded AZ61 alloy and the alloy after completion of TCAP processing were examined by using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) and their corresponding micro-tensile testing (M-TT) and hardness testing at room temperature. The results showed that the microstructure of hot extruded alloy was refined well by TCAP due to dynamic recrystallization (DRX) caused by TCAP. The tensile properties, investigated by micro-tensile testing (M-TT), of the AZ61 alloy were significantly improved due to refined microstructure. The highest tensile properties including YS of 240.8 MPa, UTS of 343.6 MPa and elongation of 21.4% of the fine-grained alloy with average grain size below 1.5 mu m was obtained after the third TCAP pass at 200 degrees C using the processing route B-c.Web of Science810art. no. 77

Various preconcentrator structures for determination of acetone in a wide range of concentration

In this paper, the investigation results on preconcentration of acetone at various initial concentrations are presented. The structures were made of conventional materials, such as stainless steel, quartz tube as well as fabricated in MEMS technology - micropreconcentrators. All structures have the same ‘active’ area to obtain more suitable comparison. The adsorbent materials were selected from commercial available Sigma-Aldrich Carbon Adsorbent Sampler Kit, consisting of 8 various adsorbents. The highest concentration factors were obtained by utilization of micropreconcentrator filled with Carboxen-1018, which is recommended for adsorption of C2-C3 compounds. The preconcentrators were placed into microsystem, and semiconductor gas sensor array was used as a detector unit. The microsystem was previously tested and designed for exhaled breath acetone analysis. The obtained results show that micropreconcentrator can be a useful tool for an increasing sensor sensitivity

Structure and properties of slow-resorbing nanofibers obtained by (co-axial) electrospinning as tissue scaffolds in regenerative medicine

With the rapid advancement of regenerative medicine technologies, there is an urgent need for the development of new, cell-friendly techniques for obtaining nanofibers—the raw material for an artificial extracellular matrix production. We investigated the structure and properties of PCL10 nanofibers, PCL5/PCL10 core-shell type nanofibers, as well as PCL5/PCLAg nanofibres prepared by electrospinning. For the production of the fiber variants, a 5–10% solution of polycaprolactone (PCL) (Mw = 70,000–90,000), dissolved in a mixture of formic acid and acetic acid at a ratio of 70:30 m/m was used. In order to obtain fibers containing PCLAg 1% of silver nanoparticles was added. The electrospin was conducted using the above-described solutions at the electrostatic field. The subsequent bio-analysis shows that synthesis of core-shell nanofibers PCL5/PCL10, and the silver-doped variant nanofiber core shell PCL5/PCLAg, by using organic acids as solvents, is a robust technique. Furthermore, the incorporation of silver nanoparticles into PCL5/PCLAg makes such nanofibers toxic to model microbes without compromising its biocompatibility. Nanofibers obtained such way may then be used in regenerative medicine, for the preparation of extracellular scaffolds: (i) for controlled bone regeneration due to the long decay time of the PCL, (ii) as bioscaffolds for generation of other types of artificial tissues, (iii) and as carriers of nanocapsules for local drug delivery. Furthermore, the used solvents are significantly less toxic than the solvents for polycaprolactone currently commonly used in electrospin, like for example chloroform (CHCl3), methanol (CH3OH), dimethylformamide (C3H7NO) or tetrahydrofuran (C4H8O), hence the presented here electrospin technique may allow for the production of multilayer nanofibres more suitable for the use in medical field

Nanocrystalline composites in TiO2 and SnO2 system for ammonia resistance sensors

This work describes the production of nanocrystalline TiO2 and SnO2 oxides, as well as their nanocomposites (containing 26.9, 58.7 and 79.0 wt.% of SnO2) with two-stage sol-gel method combined with high temperature treatment. The phase composition and medium size crystallites were determined using X-ray diffraction analysis (XRD) and revealed that the nanocomposites crystallize in tetragonal structures of TiO2 - anatase and SnO2 - cassiterite. Specific surface area of the nanopowders, measured using sorption method (BET), changed from 42.1 to 160.8 m2/g. The morphology of the nanopowders was observed using transmission electron microscope (TEM). As indicated by TEM images, the manufactured nanopowders were well crystallized and consisted of small, spherical grains. The obtained nanopowders were also tested for NH3 gas detection application. The presented method of nanopowders synthesis enables to obtain nanocrystalline TiO2 and SnO2 oxides, as well as composites from TiO2-SnO2 of known and controlled chemical and phase composition. It also enables to obtain composites used for gas sensors. The sensor made of composite containing 58.7 wt.% of SnO2 exhibited the best NH3 sensing features

The own method and program of isotope quantitatively assessment of perfusion in muscles of upper limbs (initial report)

BACKGROUND: The issue of blood flow in muscles has been dealt with for many years. However, most often it was assessed qualitatively with standard vascular examinations. The quantitatively perfusion assessment is indispensable in the normal and pathological conditions. Some diseases impair the perfusion mainly in the area of upper limbs. It can be observed in Raynaud’s disease, vascular occlusive diseases, neurological disturbances, and thermal injuries. Hyperhidrosis of upper limbs after sympathectomy of thoracic part of sympathetic trunk may bring closer the diagnosis statement. Nuclear medicine has the markers and methods that allow for the assessment of the volume of perfusion in muscles. The aim for creating this method and program was the development of radioisotope method allowing for quantitative assessment of perfusion in muscles of upper limbs. This should lead to calculating the perfusion index and its range of normal values in a greater group of patients and to using this method both in the healthy and pathological conditions. MATERIAL AND METHODS: 20 patients, age 30.4 ± 7.1 years, who underwent following examinations: qualification to the group, medical history, subject examinations, USG of upper limb vessels, anthropometric examinations, biochemical and hormonal blood tests, the assessment of upper limbs with USG Doppler and FMD (flow mediated dilatation), radioisotope examinations with gamma camera BrightView XCT by own program RAPUL (Radioisotope Assessment Perfusion of Upper Limb). Acquisitions were started five minutes after intravenous injection of 99mTc-MIBI (metoxyisobutylnitrite). The whole body scintigram and scintigrams of arm and forearm muscles in A-P projections were taken. RESULTS: In the examined patients, the results of anthropometric, biochemical and hormonal test were within the range of normal values. In radioisotope quantitative assessment of perfusion, perfusion indexes of left arm were 20 < PI_left < 11.90 and of the right arm 7.00 < PI_right <12.30. The dependency correlation PI_left vs. PI_right was strong r = 0.92036. The values of perfusion symmetry index (IPS) had a normal distribution and were within the following range: 0.9231 < IPS < 1.1019. CONCLUSIONS: The RAPUL method and program allow for quantitative assessment of perfusion in muscles of upper limbs. Developed program has a high repeatability of results. The results in the bigger group will allow for defining the range of normal values of perfusion index in muscles of upper limbs at rest. These will be diagnostically used both in healthy (sports medicine, military services) and pathological conditions.BACKGROUND: The issue of blood flow in muscles has been dealt with for many years. However, most often it was assessedqualitatively with standard vascular examinations. The quantitatively perfusion assessment is indispensable in the normal andpathological conditions. Some diseases impair the perfusion mainly in the area of upper limbs. It can be observed in Raynaud’sdisease, vascular occlusive diseases, neurological disturbances, and thermal injuries. Hyperhidrosis of upper limbs after sympathectomyof thoracic part of sympathetic trunk may bring closer the diagnosis statement. Nuclear medicine has the markersand methods that allow for the assessment of the volume of perfusion in muscles. The aim for creating this method andprogram was the development of radioisotope method allowing for quantitative assessment of perfusion in muscles of upperlimbs. This should lead to calculating the perfusion index and its range of normal values in a greater group of patients and tousing this method both in the healthy and pathological conditions.MATERIAL AND METHODS: 20 patients, age 30.4 ± 7.1 years, who underwent following examinations: qualification to thegroup, medical history, subject examinations, USG of upper limb vessels, anthropometric examinations, biochemical andhormonal blood tests, the assessment of upper limbs with USG Doppler and FMD (flow mediated dilatation), radioisotopeexaminations with gamma camera BrightView XCT by own program RAPUL (Radioisotope Assessment Perfusion of UpperLimb). Acquisitions were started five minutes after intravenous injection of 99mTc-MIBI (metoxyisobutylnitrite). The whole bodyscintigram and scintigrams of arm and forearm muscles in A-P projections were taken.RESULTS: In the examined patients, the results of anthropometric, biochemical and hormonal test were within the range ofnormal values. In radioisotope quantitative assessment of perfusion, perfusion indexes of left arm were 20 < PI_left < 11.90 andof the right arm 7.00 < PI_right <12.30. The dependency correlation PI_left vs. PI_right was strong r = 0.92036.The values of perfusion symmetry index (IPS) had a normal distribution and were within the following range: 0.9231 < IPS <1.1019.CONCLUSIONS: The RAPUL method and program allow for quantitative assessment of perfusion in muscles of upper limbs.Developed program has a high repeatability of results. The results in the bigger group will allow for defining the range of normalvalues of perfusion index in muscles of upper limbs at rest. These will be diagnostically used both in healthy (sports medicine,military services) and pathological conditions

Microsystem in LTCC technology for measurements of gas concentration in a sub-ppm range

Commonly used substrates for resistance-type oxide sensors are mainly alumina plates. Other types of ceramics, e.g. based on Low Temperature Cofired Ceramics (LTCC) technology could also be used for this purpose. This technology is well established and enables a creation of 3D structures with channels and cavities that can be formed inside a LTCC micromodule. The work describes manufacturing of the microsystem containing a gas preconcentration chamber and sensor substrates with improved thermal properties, all fabricated in LTCC technology

Structure and magnetic properties of thermodynamically predicted rapidly quenched Fe85-xCuxB15 alloys

In this work, based on the thermodynamic prediction, the comprehensive studies of the influence of Cu for Fe substitution on the crystal structure and magnetic properties of the rapidly quenched Fe85B15 alloy in the ribbon form are performed. Using thermodynamic calculations, the parabolic shape dependence of the DGamoprh with a minimum value at 0.6% of Cu was predicted. The DGamoprh from the Cu content dependence shape is also asymmetric, and, for Cu = 0% and Cu = 1.5%, the same DGamoprh value is observed. The heat treatment optimization process of all alloys showed that the least lossy (with a minimum value of core power losses) is the nanocomposite state of nanocrystals immersed in an amorphous matrix obtained by annealing in the temperature range of 300–330 C for 20 min. The minimum value of core power losses P10/50 (core power losses at 1T@50Hz) of optimally annealed Fe85-xCuxB15 x = 0,0.6,1.2% alloys come from completely different crystallization states of nanocomposite materials, but it strongly correlates with Cu content and, thus, a number of nucleation sites. The TEM observations showed that, for the Cu-free alloy, the least lossy crystal structure is related to 2–3 nm short-ordered clusters; for the Cu = 0.6% alloy, only the limited value of several -Fe nanograins are found, while for the Cu-rich alloy with Cu = 1.2%, the average diameter of nanograins is about 26 nm, and they are randomly distributed in the amorphous matrix. The only high number of nucleation sites in the Cu = 1.2% alloy allows for a sufficient level of grains’ coarsening of the -Fe phase that strongly enhances the ferromagnetic exchange between the -Fe nanocrystals, which is clearly seen with the increasing value of saturation induction up to 1.7T. The air-annealing process tested on studied alloys for optimal annealing conditions proves the possibility of its use for this type of material

Songbird nests on the ground as islands of diversity of ptyctimous mites (Acari: Oribatida) in the primeval Białowieża Forest (Poland)

Due to specific microclimatic conditions and accumulation of organic matter, bird nests are microhabitats that are often inhabited by various invertebrates, including mites (Acari). We tested whether nests of the ground-nesting passerine Phylloscopus sibilatrix (Bechstein) (Passeriformes: Phylloscopidae) [wood warbler] were associated with an increased local diversity of ptyctimous mites (Acari: Oribatida) on the forest floor in the Białowieża National Park, East Poland. In 2019–2020, we analysed 150 warbler nests shortly after they had been vacated by the birds, and additionally we sampled mites in leaf litter at 1 and 6 m distances from 21 of the collected nests. We found on average more mite species in nests sampled in 2020 than in nests sampled in 2019. Although the species composition largely overlapped between bird nests and the litter, bird nests contained a greater average number of mite species than litter samples, including species found only – Microtritia minima (Berlese) and Phthiracarus crenophilus Willmann – or mostly – Euphthiracarus cribrarius (Berlese) and Phthiracarus globosus (C.L. Koch) – in bird nests. The results suggest that the presence of bird nests may increase the local diversity of the invertebrate species assemblage

SARS-CoV-2 antibody response after mRNA vaccination in healthcare workers with and without previous COVID-19, a follow-up study from a university hospital in Poland during 6 months 2021

IntroductionHealthcare workers (HCWs) from the beginning of the pandemic have been at risk of exposure to SARS-CoV-2, so they were vaccinated as first.ObjectivesThe purpose of the study was to determine the level of antibodies against SARS-CoV-2 in HCWs before and after vaccination with mRNA preparations according to previous COVID- 19.Patients and methodsThe HCWs from the University Hospital in Krakow completed two surveys: the baseline survey before receiving the first dose of vaccine (in January 2021) and the follow-up survey in June 2021. In parallel, two blood samples were collected from each participant at baseline and at follow-up. Total anti-SARS-CoV-2 antibody levels were measured using the ECLIA technique.ResultsAt baseline, 41.1% of HCWs had positive antibody test results, and at follow-up, the vaccinated HCWs had almost 100 times higher antibody levels than the unvaccinated HCWs. Participants under 30 years of age had significantly higher antibody levels in June than older HCWs. Among participants with positive antibody test results in January, HCWs who had experienced asymptomatic COVID-19 had more than five times higher antibody levels in June than HCWs self-reported severe COVID-19. In total, 86.9% of HCWs received Comirnaty or Spikevax. The incidence rate of COVID-19 in the unvaccinated vs. vaccinated group was 13 times higher, 20.5% and 1.9% respectively.ConclusionsThese results confirm the effectiveness of vaccination in the prevention of COVID-19 in HCWs. It is worth getting vaccinated regardless of previous infection. Furthermore, vaccination among HCWs under 30 years of age induced more effective antibody production compared to older individuals