Influence of Alumina Grade on Sintering Properties and Possible Application in Binder Jetting Additive Technology.

Alumina is one of the most popular ceramic materials widely used in both tooling and construction applications due to its low production cost, and high properties. However, the final properties of the product depend not only on the purity of the powder, but also, e.g., on its particle size, specific surface area, and the production technology used. These parameters are particularly important in the case of choosing additive techniques for the production of details. Therefore, the article presents the results of comparing five grades of Al2O3 ceramic powder. Their specific surface area (via Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods), particle size distribution, and phase composition by X-ray diffraction (XRD) were determined. Moreover, the surface morphology was characterized by the scanning electron microscopy (SEM) technique. The discrepancy between generally available data and the results obtained from measurements has been indicated. Moreover, the method of spark plasma sintering (SPS), equipped with the registration system of the position of the pressing punch during the process, was used to determine the sinterability curves of each of the tested grades of Al2O3 powder. Based on the obtained results, a significant influence of the specific surface area, particle size, and the width of their distribution at the beginning of the Al2O3 powder sintering process was confirmed. Furthermore, the possibility of using the analyzed variants of powders for binder jetting technology was assessed. The dependence of the particle size of the powder used on the quality of the printed parts was demonstrated. The procedure presented in this paper, which involves analyzing the properties of alumina varieties, was used to optimize the Al2O3 powder material for binder jetting printing. The selection of the best powder in terms of technological properties and good sinterability makes it possible to reduce the number of 3D printing processes, which makes it more economical and less time-consuming.

Evaluation of Selected Properties of Dielectric Barrier Discharge Plasma Jet.

In the technological processes requiring mild treatment, such as soft materials processing or medical applications, an important role is played by non-equilibrium plasma reactors with dielectric barrier discharge (DBD), that when generated in noble gases allows for the effective treatment of biological material at a low temperature. The aim of this study is to determine the operating parameters of an atmospheric pressure, radio-frequency DBD plasma jet reactor for the precise treatment of biological materials. The tested parameters were the shape of the discharge (its length and volume), current and voltage signals, as well as the power consumed by the reactor for various composition and flow rates of the working gas. To determine the applicability in medicine, the temperature, pH, concentrations of H2O2, NO2- and NO3- and Escherichia coli log reduction in the plasma treated liquids were determined. The obtained results show that for certain operating parameters, a narrow shape of plasma stream can generate significant amounts of H2O2, allowing for the mild decontamination of bacteria at a relatively low power of the system, safe for the treatment of biological materials.

Pilot study on the use of cold atmospheric plasma for preservation of bread.

Cold atmospheric plasma (CAP) is used as an emerging technology for food preservation. In this study, CAP treatment has been applied to bakery products for the first time. The aim of the work was to investigate the effect of the use of CAP on the amount of microorganisms during bread storage. Basic physicochemical properties and bread texture were determined during storage for 0, 3, and 6 days. The study material included gluten-free and mixed wheat-rye bread treated with CAP for 2 and 10 min. The results showed that no mesophilic bacteria or fungi were found after ten minutes of the bread exposure to CAP. In addition, only 2-min non-thermal sterilization resulted in complete inhibition of yeast and mould growth in the gluten-free and wheat-rye bread. A decrease in the microbial growth in the bread was noted; however, a simultaneous decrease in the moisture content of the bread was observed. After the application of plasma for 2 or 10 min, both the gluten-free and mixed wheat-rye bread was characterized by reduced humidity, which also resulted in a significant increase in the hardness and a slight increase in the springiness of the bread. The use of CAP in storage of bread is promising; nevertheless, it is necessary to further study the effect of this treatment in bread with improvers, especially with hydrocolloids and fibers.

Migration of Subtalar Implants in Paediatric Flatfoot Correction: A Pilot Study in Synthetic Bone Models.

BACKGROUND: Subtalar implant migration as a complication following subtalar arthroeresis has been described in the scientific literature. However, clinical studies do not allow for unequivocally determining the underlying causes. The aim of the study is to determine the risk of migration of two geometric types of subtalar implants. Biomechanical tests were carried out on a synthetic bone model with a soft tissue substitute, which allowed for reduction of variability of results caused by biological differences. MATERIAL AND METHODS: A foot model mirroring natural anatomy was made from synthetic bone and a silicone soft tissue substitute with the same hardness as that of the soft tissues of the foot. Two types of 11 mm Ti6Al4V titanium alloy implants were studied, namely, a rectangular subtalar screw and a cylindrical subtalar screw, a type commonly used in flatfoot reconstruction surgery in children. The screws were placed in the sinus tarsi and subjected to cyclic loading (up to 1,000,000 cycles at a frequency of 5 Hz, with a maximum load of 500 N). Comparative pull-out force tests were performed immediately following implantation and after the dynamic loading test. Wyniki. Following the dynamic loading test, all 12 samples were qualified for the pull-out force test. Cylindrical screws demonstrated higher pull-out force values both for the samples tested immediately following implantation and for those that underwent dynamic loading. Implants of the same shape did not show statistically significant differences in the Mann-Whitney U test (p >0.05). Wniosek. The synthetic research model produces reproducible results in the assessment of risk of implant migration. Long-term loading does not significantly affect the risk of implant migration.

Influence of ultrasound on selected microorganisms, chemical and structural changes in fresh tomato juice.

The paper presents the possibility of applying ultrasonic technology for inactivation of mesophilic aerobic microorganisms, lactic acid bacteria, coliform bacteria, and yeast with the maintenance of the chemical and structural properties of tomato juice. The research was conducted on fresh tomato juice obtained from the Apis F1 variety. Pressed juice was exposed to high power ultrasound and frequency 20 kHz with three operational parameters: ultrasound intensity (28 and 40 W cm-2), treatment time (2, 5, and 10 min), and product storage time (1, 4, 7 and 10 days). The temperature of the juice during the sonication ranged from 37 to 52 °C depending on the intensity of ultrasound and time of treatment. Effectiveness of the tested microorganisms eradication in the juice depended on the amplitude and duration of the ultrasound treatment. It was shown that the juice exposed to an ultrasonic field with an intensity of 40 W cm-2 for 10 min was microbiologically pure and free from spoilage microorganism even after 10 storage days. No statistically significant differences in pH were found between the untreated juice and the sonicated samples. The ultrasonic treatment was found to change the content of lycopene in small degree (both an increase and a decrease, depending on the processing time) and to induce a small decrease in the vitamin C content. The study suggests that the ultrasonic treatment can be successfully implemented on an industrial scale for the production of not-from-concentrate (NFC) tomato juice.

Possibility to extend the shelf life of NFC tomato juice using cold atmospheric pressure plasma.

Cold Atmospheric pressure Plasma (CAP) is a non-thermal method used in food processing. CAP generated with the use of nitrogen in a Glide-arc device for 300 to 600 s exhibited high potential for microbial decontamination and did not induce substantial changes in the physicochemical properties of NFC tomato juice. Samples exposed to cold atmospheric plasma had mostly an intact structure, as revealed by digital microscopy. The investigations indicate that CAP can be applied for biological and chemical waste-free decontamination of food and extension of its shelf life.

Morphological and physiological changes in Lentilactobacillus hilgardii cells after cold plasma treatment.

Atmospheric cold plasma (ACP) inactivation of Lentilactobacillus hilgardii was investigated. Bacteria were exposed to ACP dielectric barrier discharge with helium and oxygen as working gases for 5, 10, and 15 min. The innovative approach in our work for evaluation of bacterial survival was the use in addition to the classical plate culture method also flow cytometry which allowed the cells to be sorted and revealed different physiological states after the plasma treatment. Results showed total inhibition of bacterial growth after 10-min of ACP exposure. However, the analysis of flow cytometry demonstrated the presence of 14.4% of active cells 77.5% of cells in the mid-active state and 8.1% of dead cells after 10 min. In addition, some of the cells in the mid-active state showed the ability to grow again on culture medium, thus confirming the hypothesis of induction of VBNC state in L .hilgardii cells by cold plasma. In turn, atomic force microscopy (AFM) which was used to study morphological changes in L. hilgardii after plasma treatment at particular physiological states (active, mid-active, dead), showed that the surface roughness of the mid-active cell (2.70 ± 0.75 nm) was similar to that of the control sample (2.04 ± 0.55 nm). The lack of considerable changes on the cell surface additionally explains the effective cell resuscitation. To the best of our knowledge, AFM was used for the first time in this work to analyze cells which have been sorted into subpopulations after cold plasma treatment and this is the first work indicating the induction of VBNC state in L. hilgardii cells after exposure to cold plasma.

Positive Effect of Cold Atmospheric Nitrogen Plasma on the Behavior of Mesenchymal Stem Cells Cultured on a Bone Scaffold Containing Iron Oxide-Loaded Silica Nanoparticles Catalyst.

Low-temperature atmospheric pressure plasma was demonstrated to have an ability to generate different reactive oxygen and nitrogen species (RONS), showing wide biological actions. Within this study, mesoporous silica nanoparticles (NPs) and FexOy/NPs catalysts were produced and embedded in the polysaccharide matrix of chitosan/curdlan/hydroxyapatite biomaterial. Then, basic physicochemical and structural characterization of the NPs and biomaterials was performed. The primary aim of this work was to evaluate the impact of the combined action of cold nitrogen plasma and the materials produced on proliferation and osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells (ADSCs), which were seeded onto the bone scaffolds containing NPs or FexOy/NPs catalysts. Incorporation of catalysts into the structure of the biomaterial was expected to enhance the formation of plasma-induced RONS, thereby improving stem cell behavior. The results obtained clearly demonstrated that short-time (16s) exposure of ADSCs to nitrogen plasma accelerated proliferation of cells grown on the biomaterial containing FexOy/NPs catalysts and increased osteocalcin production by the cells cultured on the scaffold containing pure NPs. Plasma activation of FexOy/NPs-loaded biomaterial resulted in the formation of appropriate amounts of oxygen-based reactive species that had positive impact on stem cell proliferation and at the same time did not negatively affect their osteogenic differentiation. Therefore, plasma-activated FexOy/NPs-loaded biomaterial is characterized by improved biocompatibility and has great clinical potential to be used in regenerative medicine applications to improve bone healing process.

Biomechanical evaluation of single- and multi-level anterior cervical discectomy and fusion with polyetheretherketone cages: radiological and clinical outcomes.

OBJECTIVE: The aim of this study was to analyse the outcomes of single- and multi-level anterior cervical discectomy and fusion (ACDF) with standalone polyetheretherketone (PEEK) cages, with particular emphasis on the risk of secondary adjacent segment disease. MATERIALS AND METHODS: This retrospective study included 30 patients with single- or multi-level cervical disc herniation. Before the ACDF, and one year thereafter, the patients underwent clinical and radiological evaluation including determination of cervical pain severity with a numerical rating scale (NRS), and a survey with a Polish adaptation of the neck disability index questionnaire (NDI-PL). Biomechanical parameters of the cervical spine were determined using the Cobb method. RESULTS: One year after ACDF, all patients had achieved complete fusions, and 97% showed a significant reduction of pain severity. Also, a significant decrease in all NDI-PL indices was observed. A significant decrease in overall cervical spine mobility coexisted with a significant increase in the mobility of the segment above the one operated upon and a non-significant decrease in the mobility of the segment below. No statistically significant change was found in the intervertebral disc space height (IVH) above and below the operated segment, and no evidence of degeneration within the segments adjacent to the operated one was documented. CONCLUSION: One- and two-level ACDF with standalone PEEK cages provided high fusion rates. Surgical spondylosis contributed to a reduction of spinal mobility despite the hypermobility in adjacent spinal segments. No degeneration in adjacent spinal segments was documented within a year of ACDF, and the treatment seemed to improve patients' quality of life.

Evaluation of selected microbial and physicochemical parameters of fresh tomato juice after cold atmospheric pressure plasma treatment during refrigerated storage.

The Cold Atmospheric pressure Plasma (CAP) technology is an emerging technology used for conditioning and microbiological decontamination of biomaterials including food. A novel tool for inactivation of juice background spoilage microorganisms, as well as high count of inoculated yeast while maintaining physicochemical properties in tomato juice - CAP technology was utilized in this study. Dry matter content and pH were not significantly influenced by CAP generated in GlidArc reactor. Small increase of lycopene, and slight loss of vitamin C content were observed.

Effects of atmospheric pressure plasma jet operating with DBD on Lavatera thuringiaca L. seeds' germination.

The paper presents the results of an experiment on the effect of pre-sowing stimulation of seeds with atmospheric pressure plasma jet operating with dielectric barrier discharge (DBD plasma jet) on the process of germination of Thuringian Mallow (Lavatera thuringiaca L.). Five groups of seeds characterized by a different exposure times (1, 2, 5, 10 and 15 minutes) as well as untreated seeds-control were used. Pre-sowing plasma stimulation of seeds improved germination parameters such as: germination capacity and germination energy for all tested groups relative to control. The highest germination parameters were obtained for seeds stimulated with plasma for the exposure times of 2 and 5 min. The analysis of the contact surface angle indicated the decrease of its' mean values upon seed stimulation while no statistical effects were observed. Analysis of the SEM scans revealed the increase in seed pattern intensity which could be attributed to removing of the surface parts of cuticle possibly covered with wax upon short time-2 and 5 min plasma treatment. Such a phenomenon can act similarly to mechanical scarification of seeds. Longer exposure of seeds to plasma resulted in affecting the deeper zone of cuticle and damage or fracture of some parts of the cuticle. Lower germination parameters of seeds upon longer exposure times to plasma may indicate mechanical damage of the seeds.

Assessment of Idiopathic Scoliosis Patients' Satisfaction with Thoracolumbar Brace Treatment.

BACKGROUND: Bracing is the most efficient non-surgical method of treatment for idiopathic scoliosis patients with 25-45° curvature according to Cobb. The aim of the present study was to assess compliance of idiopathic scoliosis patients with medical instructions concerning the time patients should spend wearing orthopedic braces, patients' self-perceived health status and problems occurring in patients with idiopathic scoliosis. MATERIAL AND METHODS: A total of 51 patients aged between 9 to 18 years (84% females) treated for adolescent idiopathic scoliosis with a thoracolumbar brace were asked to complete a survey titled ''The profile of quality of life with spine deformity". Survey data were subjected to statistical analysis. RESULTS: Mean brace-wearing compliance among the patients was about 70% of the required time of 23 h/day. The vast majority of patients - 48 (94%) -were satisfied with the treatment method and the results. Pain of about 4 pts (VAS scale) was reported by 18 patients. Excoriations occurred in 70% of the patients. We did not find a significant correlation between the time of brace-wearing per day vs. pain (p=0.18) and excoriations (p=0.36). CONCLUSIONS: 1. Increasing the number of brace-wearing hours per day does not interfere with the socioeconomic relations and does not affect the child's sleep quality. 2. High awareness of the faulty posture is an important factor improving patients' assessment of the progress and methods of treatment. 3. The number of brace-wearing hours per day does not correlate with pain and epidermal injury; appropriate fitting of the brace to a given patient is of key importance here.