Permeability and Load Capacity of Iron Porous Bearings with the Addition of Hexagonal Boron Nitride

Due to their properties, porous sliding bearings are considered to be maintenance-free, which means that no lubrication is required during operation. Their design enables operation at low rotational speeds with high load. Another effect of this bearing design is the lubrication continuity in the tribological pair. In this study, the selected tribological properties (such as load capacity and permeability) of new-generation iron porous bearings with boron nitride powder were experimentally investigated. Tests were carried out under various conditions, using unique test apparatus. The addition of 3% (weight) of hexagonal boron nitride (hBN) significantly increased the load capacity of tested porous bearings in comparison to the same standard bearings containing 2.5% copper. The obtained p_gr·v rating reached almost 7 MPa, which is a value almost three times higher than the requirements for this type of bearing. It is worth emphasizing that such a result was obtained despite a noticeable deterioration in the air and oil permeability of the bearing.     

The Effect of Antimony (III) Oxide on the Necessary Amount of Precursors Used in Laser-Activated Coatings Intended for Electroless Metallization

The article presents research on the potential use of organometallic compounds with the addition of antimony (III) oxide Sb₂O₃ as a coating additive that will make coatings susceptible to electroless metallization after prior surface irradiation with 193 nm wavelength laser radiation and a different number of laser pulses. The surface modification and activation effects were assessed by optical-imagining as well as by scanning electron microscopy (SEM) with energy dispersive analysis (EDX). It was found that the presence of Sb₂O₃ in the coating made it possible to reduce the content of the copper complex, causing an intensive surface ablation, resulting in the formation of a conical structure with a higher content of metallic copper nuclei.     

Prevalence of Orthorexia in Groups of Students with Varied Diets and Physical Activity (Silesia,Poland)

(1) Background: The literature emphasizes the role of many factors influencing the onset of eating disorders (EDs) and their mutual influence on each other. Therefore, this study aimed to evaluate and compare the prevalence of orthorexic behaviors in groups of health-related and non-health-related students in terms of their differential health behaviors—diet and physical activity levels. (2) The study included 300 individuals representing two equal groups of fields of study, which for the study were called the health-related field (HRF) and the non-health-related field (NRF). (3) Results: Based on the results of the dietary assessment, it was found that the best dietary model was characterized by the HRF group; in this group, 97.2% of students were characterized by a very good and good dietary mode. The NRF group, on the other hand, was dominated by a sufficient dietary mode for 64.4% of all cases in this group (94 people), while the dietary model marked as “good” was less popular, at 24.6% of this group (36 people). (4) Conclusions: Based on the cited self-research and information from the literature, it can be concluded that the problem of orthorexia is still a new issue at the level of social sciences, medical sciences, and health sciences. The psychometric tools used in this study allowed us to demonstrate the prevalence of the aforementioned eating disorders in the sample groups of students.     

Radial head prosthesis with a mobile head

Radial head replacement is a useful method in the treatment of comminuted radial head fractures. Because such injuries are a common clinical problem and many complications have been reported after radial head replacements, a new radial head prosthesis is proposed. This new design, based on the shape-dimensional identification of the radial head, consists of two parts. The head, made of ultra-high molecular weight polyethylene, is articulated with a Vitallium stem. A series of functional quality and strength tests were conducted on this new prosthetic design. The implant was also examined via the finite element method. General preclinical investigations of clinical cases show that this prosthesis is a very promising design.     

Post-stenting intravascular brachytherapy trials on hypercholesterolemic rabbits using 32P liquid sources: implications for prevention of in-stent restenosis

PURPOSE: Liquid sources of radiation delivered in angioplasty balloons may be a convenient self-centering device used for prevention of in-stent restenosis. To test the effectiveness of this method an intravascular brachytherapy study was performed using 32P liquid sources in an animal model. METHODS: The radial dose distribution around angioplasty balloons filled with solutions of Na 2H 32PO 4 was calibrated by thermoluminescence dosimetry. The animal experiments were performed in rabbits with induced hypercholesterolemia. The balloons containing 32P were introduced into iliac arteries immediately after stent implantation. Estimated 7-49 Gy doses required 30-100 min irradiations. Radiation effects were evaluated by comparing the thickness of various components of the artery wall. RESULTS: Doses of 7, 12, 16 or 49 Gy on the internal artery surface required 30-100 min of irradiation. The dose of 49 Gy at "zero" distance corresponding to 16 Gy at 1.0 mm from the balloon surface reduced hypertrophy in every layer of the arterial wall: in the intima the cross-sectional areas were 0.13 versus 0.91 mm 2, in the media were 0.5 versus 0.46 mm 2 and in the adventitia were 0.04 versus 0.3 mm 2 (p <0.05). A dose of 7 Gy at the balloon surface produced adverse irradiation effects: the intimal area of the artery was 2.087 versus 0.857 mm 2, the medial area was 0.59 versus 0.282 mm 2 and the adventitial area was 0.033 versus 0.209 mm 2 in treated and control arteries, respectively. CONCLUSION: Application of a 49 Gy irradiation dose to the internal arterial surface effectively prevented in-stent restenosis.     

Femoral and iliac vein stenoses after prolonged femoral vein catheter insertion.

BACKGROUND/AIMS: Catheterization of the femoral vein is a safe and recommended method of temporary access for haemodialysis. In some patients, however, because of the lack of other possibilities, it is necessary to maintain long-term femoral cannulation. The aim of the study was to evaluate the frequency of stenosis after prolonged femoral cannulation. METHODS: The 24 patients incorporated in the study were divided into two groups. Group 1 consisted of 10 end-stage kidney failure patients (four females and six males, aged 32-75 years, average 55.6+/-13.6 years) in whom femoral catheters were maintained for less than 2 weeks (5-14 days, average 9.3+/-3.6 days). Group 2 included 14 chronic haemodialysis patients (six females and eight males aged 23-65 years, average 49.5+/-13.27 years). The time of catheter maintenance ranged from 2 to 16 weeks (average 6.4+/-4.2 weeks). Femoral and iliac vein status was evaluated using magnetic resonance imaging. RESULTS: A feature of venous stenosis of both the femoral and iliac veins was disclosed in four patients in whom femoral cannulation lasted more than 4 weeks. There were no stenoses in group 1. CONCLUSION: Long-term femoral cannulation for more than 4 weeks may be associated with a significant risk of stenosis in the femoral and/or external iliac veins.     

Stapled aortic anastomoses: a minimally invasive, feasible alternative to videoscopic aortic suturing?

Widespread applications of totally laparoscopic aortic reconstructions have been limited by the long cross-clamp time required to suture the aortic anastomosis despite improvement in instrumentation. The authors' hypothesis was that a "one-step anastomosis concept" using an intraluminal stapler would allow shorter cross-clamp time but similar patency and imperviousness as videoscopic suturing techniques. An intraluminal stapler (Endopath-ILS, Ethicon) with a modified anvil was used to perform videoscopic-assisted thoracic aorta-to-iliac artery bypass with a 21 mm by 8 mm polytetrafluoroethylene (PTFE) graft in 22 sheep through a minimally invasive approach using a 5 cm thoracotomy. The graft-to-iliac artery anastomoses were hand sutured through a flank incision. Twelve sheep were used to establish the technique and 10 subsequent animals constituted the study group. Aortic cross-clamp time, imperviousness, and need for additional sutures were recorded and compared to previously reported data using videoscopic suturing in pigs. Patency was assessed by comparing lower limb arterial pressures. Macroscopic and microscopic examinations of the anastomoses were performed at different time-points within the first 3 months. Videoscopic-assisted stapled anastomoses were also performed on atherosclerotic aortas of 3 human cadavers. Stapled anastomoses between the thoracic aorta and PTFE graft were completed in 8 of 10 animals. Two animals were euthanized after stapler failure and anastomotic bleeding. Sutures to strengthen the anastomosis had to be used in 4 cases. Mean aortic cross-clamp time in 8 successful cases was 4.3 +/-2.9 minutes (range 2-11 minutes) and was significantly shorter than clamp time of videoscopic suturing technique (48.7 +/-9.4 minutes, p < 0.0001). Imperviousness was good or excellent in 4 animals and fair in 4 animals. All anastomoses were patent at the end of the procedure. Examination of the anastomosis of the 2 failed interventions showed medial aortic tear surrounding the anastomosis in 1 case and misfired staples in the other. No graft occlusion was noted during follow-up ranging from 0 to 12 weeks. At the time of harvest, no bleeding was noted after epinephrine and volume infusion to increase mean arterial pressure to 200 mm Hg for 15 minutes. Macroscopic examination of the anastomoses revealed adequate healing with circumferential stapling of the prosthesis to the aortic wall and no stenosis or thrombus except in 1 false aneurysm (1/7, 14%). Surface electron microscopy showed cells coverage of the anastomosis surface. When applied on human cadaver thoracic and abdominal aorta with atherosclerotic changes, clamping times of less than 5 minutes were achieved. However, imperviousness tested with saline was poor. An automatic stapling device allows performance of a graft-to-aorta anastomosis through a minimally invasive approach with shorter clamping time than a videoscopic suturing technique. However, the current technique of aortic stapling is unreliable and further improvements are needed.     

Anterior approach for complex cervical spondylotic myelopathy

Cervical spondylotic myelopathy (CSM) is a slowly progressive disease resulting from age-related degenerative changes in the spine that can lead to spinal cord dysfunction and significant functional disability. The degenerative changes and abnormal motion lead to vertebral body subluxation, osteophyte formation, ligamentum flavum hypertrophy, and spinal canal narrowing. Repetitive movement during normal cervical motion may result in microtrauma to the spinal cord. Disease extent and location dictate the choice of surgical approach. Anterior spinal decompression and instrumented fusion is successful in preventing CSM progression and has been shown to result in functional improvement in most patients.     

Low-level laser irradiation effect on endothelial cells under conditions of hyperglycemia

Diabetes mellitus is considered to be a very serious lifestyle disease leading to cardiovascular complications and impaired wound healing observed in the diabetic foot syndrome. Chronic hyperglycemia is the source of the endothelial activation. The inflammatory process in diabetes is associated with the secretion of inflammatory cytokines by endothelial cells, e.g., tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6). The method of phototherapy using laser beam of low power (LLLT—low-level laser therapy) effectively supports the conventional treatment of diabetic vascular complications such as diabetic foot syndrome. The aim of our study was to evaluate the effect of low-power laser irradiation at two wavelengths (635 and 830 nm) on the secretion of inflammatory factors (TNF-α and IL-6) by the endothelial cell culture—HUVEC line (human umbilical vein endothelial cell)—under conditions of hyperglycemia. It is considered that adverse effects of hyperglycemia on vascular endothelial cells may be corrected by the action of LLLT, especially with the wavelength of 830 nm. It leads to the reduction of TNF-α concentration in the supernatant and enhancement of cell proliferation. Endothelial cells play an important role in the pathogenesis of diabetes; however, a small number of studies evaluate an impact of LLLT on these cells under conditions of hyperglycemia. Further work on this subject is warranted.