In vitro simulation of intraoperative vertebroplasty applied for pedicle screw augmentation. A biomechanical evaluation

Background and purpose The purpose of this study was to evaluate the effect of an in vitro simulation of intraoperative vertebroplasty on embedded pedicle screws resistance to pullout. This method involved an application of acrylic cement into the vertebral bodies only after pedicle screws implementation. Materials and methods For the purpose of conducting this research, the authors used the spines of fully-grown pigs. The procedure was as follows: firstly, the pedicle screws were bilaterally implemented in 10 vertebrae; secondly, cancellous bone was removed from vertebral bodies selected for screws augmentation and lastly it was replaced by polymethylmethacrylate (PMMA). Six vertebrae with implemented pedicle screws served as a control group. The pullout strength of thirty-two screws (20 augmented and 12 control) was tested. All screws were pulled out at a crosshead speed of 5mm/min. Results The PMMA-augmented screws showed a 1.3 times higher average pullout force than the control group: respectively 1539.68N and 1156.59N. In essence, no significant discrepancy was determined between average pullout forces of screws which were pulled as first when compared with consecutive contralateral ones. Conclusions An in vitro simulation of intraoperative injection of PMMA in the vertebral body instrumented with screws (intraoperative vertebroplasty) resulted in enhancing its pullout strength by 33%. Pulling of one of the pedicular screws from the augmented vertebral body did not affect the pullout resistance of the contralateral one

Formalization model of expert knowledge about a technical index level of engineering products

The authors set a timely problem that concerns development of decision making models, which allow formalizing expert subjective ideas about technical index level of engineering products. The authors proposed a formalization model of expert knowledge about technical index level of engineering products on the basis of fuzzy sets. The model has a method of membership-function construction for linguistic variable terms on the basis of exponential functions

Ca–Cu looping process for CO2 capture from a power plant and its comparison with Ca-looping, oxy-combustion and amine-based CO2 capture processes

Carbon capture for fossil fuel power generation draws an increasing attention because of significant challenges of global climate change. This study aims to explore the integration of a 453 MWe natural gas combined cycle (NGCC) power plant with an MEA-based post-combustion carbon capture (PCC) process and CO₂ compression train. The steady state models of the NGCC power plant, the PCC process and compression train were developed using Aspen Plus® and were validated with the published data and experimental data. The interfaces between NGCC and PCC were discussed. Exhaust gas recirculation (EGR) was also investigated. With EGR, a great size reduction of the absorber and the stripper was achieved. An advanced supersonic shock wave compressor was adopted for the CO₂ compression and its heat integration was studied. The case study shows net efficiency based on low heating value (LHV) decreases from 58.74% to 49.76% when the NGCC power plant is integrated with the PCC process and compression. Addition of EGR improves the net efficiency to 49.93% and two compression heat integration options help to improve the net efficiency to 50.25% and 50.47% respectively. This study indicates NGCC including EGR integrated with PCC and supersonic shock wave compression with new heat integration opportunity would be the future direction of carbon capture deployment for NGCC power plant

Wpływ gięcia na charakterystykę in vitro anodowej warstwy wierzchniej implantowego stopu tytanu Ti6Al4V ELI

promotor: dr hab. inż. Elżbieta Krasicka-Cydzik, prof. UZ

Development of Fe2O3-based, Al2O3-stabilized Oxygen Carriers using Sol-gel Technique for H2 Production via Chemical Looping

A modification of the chemical looping combustion (CLC) process allows the production of high purity hydrogen from biomass (with simultaneous CO2 capture) on the distributed scale. Here, we report the development of Fe2O3- based, Al2O3-supported oxygen carriers using a sol-gel technique. We assess the influence of the iron precursor on the morphological properties, chemical composition and cyclic redox stability of the oxygen carrier. Three iron precursors, i.e. iron nitrate, iron chloride and iron acetylacetonate, were used to synthesize oxygen carriers containing 80 wt. % of Fe2O3. Using iron nitrate and iron acetylacetonate as the iron precursor resulted in materials with a high H2 yield. However, both materials showed some decay in the hydrogen yield with cycle number. Al2O3-stabilized Fe2O3 synthesized using iron chloride as the iron precursor showed no appreciable decay over the 15 cycles tested, albeit the amount of hydrogen produced was significantly lower when compared to the other two iron precursors. This observation can be attributed to the large fraction of hercynite (FeAl2O4) in this material. Hercynite stabilizes iron and prevents sintering, but does not participate in the redox reactions.ISSN:1876-610

Chemical Looping Partial Oxidation of Methane: Reducing Carbon Deposition through Alloying

In chemical looping, Fe-containing oxygen carriers can catalyze as a side reaction the decomposition of methane, which results in the deposition of carbon on their surface with multiple adverse effects. In this work, we propose a strategy to reduce the extent of carbon deposition by using Co as a second redox-active metal that forms a bimetallic phase with Fe during reduction. We show for a perovskite-based oxygen carrier that the formation of the bimetallic Fe-Co phase improves the dispersion and decreases the size of iron within the material, which may influence its catalytic effect on the decomposition of methane (in addition to potential changes in its electronic structure).ISSN:0887-0624ISSN:1520-502

Inverse Opal-Like, Ca3Al2O6-Stabilized, CaO-Based CO2 Sorbent: Stabilization of a Highly Porous Structure To Improve Its Cyclic CO2 Uptake

ISSN:2574-096

Sol-gel Synthesis of MgAl2O4-stabilized CaO for CO2 Capture

Ca-based, MgAl2O4-stabilized sorbents for CO2 capture were prepared using a sol-gel approach. The chemical composition and morphology of the sorbents were characterized using scanning electron microscopy, X-ray diffraction and N2 adsorption analysis. The cyclic CO2 uptake of the materials was studied in a thermogravimetric analyzer and fluidized bed reactor. It was found that the calcium precursor and condensation catalyst strongly influenced the chemical composition and morphology of the sorbents and, in turn, their cyclic CO2 uptake capabilities. The material that was synthesized using Ca(CH3COO)2 as the calcium precursor and acetic acid as a condensation catalyst possessed the highest cyclic CO2 uptake, viz. 0.39 g CO2/g sorbent after 10 cycles of calcination and carbonation, a value that compares favorably to the CO2 uptake of the reference limestone of 0.18 g CO2/g sorbent.ISSN:1876-610

Development of High-performance CaO-based CO2 Sorbents Stabilized with Al2O3 or MgO

Two organic templating methods, viz., a Pechini and a resorcinol/formaldehyde (RF) carbon-gel approach were employed to prepare CaO-based, Al2O3- and MgO-stabilized CO2 sorbents. Scanning electron microscopy confirmed the formation of micro- and nanostructured morphologies in the synthetic sorbents. The cyclic CO2 uptake performance of the sorbents was assessed in a thermo-gravimetric analyzer and compared to the reference limestone. It was found that as little as 10 mol% Al3+ was required to obtain cyclically stable CO2 sorbents independent of the synthesis method used. However, a sintering-induced capacity decay of MgO-supported CaO could only be overcome via RF carbon-gel templating approach using at least 20 mol% of Mg2+ for stabilization. X-ray diffraction revealed the formation of mayenite, whereas MgO did not form a solid solution with CaO. The CO2 uptake of the best synthetic sorbent exceeded limestone by more than 300% (after 10 carbonation/calcination cycles).ISSN:1876-610

Bactericidal Activity of Ready-To-Use Alcohol-Based Commercial Wipes According to EN 16615 Carrier Standard

Background: The effectiveness of ready-to-use disinfectant wipes was previously assessed in standardized suspension tests, which were inadequate because they ignored that the wipes are rubbed against a surface. Thus, we assessed the effectiveness of commercially available disinfectant wipes impregnated with an alcoholic solution according to the 16615 standard, which includes a test with mechanical action. Methods: According to the EN 16615 standard, under clean conditions, four squares (5 cm × 5 cm), placed next to one another, were marked on a test surface. Enterococcus hirae, Pseudomonas aeruginosa, and Staphylococcus aureus were inoculated on the leftmost square, and a wipe impregnated with an alcoholic solution was placed to the left of that square. Then, the wipe was pressed with a 2.5 kg weight and moved to the right and back to the left. After contact times of 1, 5, 10, or 15 min, we measured the reduction in bacterial load. Results: Alcohol-based ready-to-use commercial wipes did not show sufficient bactericidal activity at the contact times of 1, 5, 10 and 15 min. Wipes containing propan-1-ol and a mixture of propan-1-ol and propan-2-ol were active against Pseudomonas aeruginosa at the contact times of 1 min and 15 min. None of the examined wipes were active against Enterococcus hirae or Staphylococcus aureus. Conclusion: Bactericidal parameters of ready-to-use disinfectant wipes should be determined in surface tests, in addition to suspension tests, because suspension tests do not simulate the conditions under which disinfectant wipes are used in practice