The manufacturability and compression properties of the Schwarz Diamond type Ti6Al4V cellular lattice fabricated by selective laser melting

Selective laser melting technology makes it possible to produce 3D cellular lattice structures with controlled porosity. The paper reflects to machining and examination of structures with predefined distribution, shape and size of the pores. In the study, the porous structures of Ti6Al4V were investigated. The tests were carried out using structures of spatial architecture of Schwarz D TPMS geometry with a total porosity of 60% and 80% and various pore sizes. Dimensional accuracy of additively manufactured structures was measured in relation to the 3D model. Geometry of the final structure differed from the CAD model in the range ± 0.3 mm. The surfacemorphology and porosity of the solid struts were also checked. Themechanical properties of the structures were determined in a static compression test

Modelling, manufacturability and compression properties of the CpTi grade 2 cellular lattice with radial gradient TPMS architecture

In the present study, a titanium cellular lattice structure with a mathematical designed porosity gradient was successfully fabricated using the selective laser melting method. The samples with smooth gradient transition of porosity of between 60% and 80% were received for different elementary cell geometries. Elementary cells belong to the triply periodic minimal surfaces family (G, D, I2Y, IWP). Each sample was subjected to a comprehensive analysis including: dimensional metrology and assessment of material defects (X-ray micro-tomography), surface morphology tests (scanning electron microscopy) and mechanical properties (universal testing machine). It has been shown that a cellular lattice with high dimensional accuracy (+0.16/–0.08 mm) and full dense struts can be obtained. According to the assumption, the gradient increases the strength of the cellular lattice samples. The highest increase in plateau stress between the samples with and without gradient was found for the I2Y series (about 185%). Furthermore, it was found that the stress-strain response of the samples depends not only on total porosity, but also on the 3D geometry of the cellular lattice. The stress-strain curves for G, IWP and I2Y samples are smooth and exhibit three characteristic regions: linear elasticity, plateau region and densification region. The size of regions depends on the geometric features of the cellular lattice. For series D, in the plateau region, the fluctuations in stress value are clearly visible. The smoothest stress-strain curve can be noted for the G series, which combined with good mechanical properties (the plateau stress and energy absorbed, at respectively 25.5 and 43.2 MPa, and 46.3J and 59.5J for Gyr_80 and Gyr_6080, which corresponds to a strain of almost 65% and 50%) positively affects the applicability of cellular structures with such geometry

Krzywa uczenia się laparoskopowego wyłączenia żołądkowo-jelitowego na podstawie doświadczenia nowo powstałego ośrodka bariatrycznego

Wstęp: Laparoskopowe wyłączenie żołądkowo-jelitowe (LRYGB) jest jednym z najczęstszych sposobów leczenia chorobliwej otyłości. Krzywa uczenia się tej procedury dla pojedynczego chirurga wynosi około 50–75 przypadków i jest uważana za najważniejszy czynnik zarówno w zmniejszaniu liczby powikłań, jak i śmiertelności. Prezentujemy nasze doświadczenie i krzywą uczenia się LRYGB dla nowo powstałego ośrodka bariatrycznego w Polsce. Materiały i metody: Badanie prowadzono w II Katedrze Chirurgii Ogólnej UJCM w oparciu o prospektywnie gromadzone dane chorych, u których w okresie od 06.2010 do 03.2019 wykonano LRYGB z powodu otyłości olbrzymiej. Pacjentów podzielono na grupy po 30 osób (G1-G10) w kolejności wykonanych zabiegów. W badaniu: (1) analizowano przebieg operacji i hospitalizacji pacjentów oraz (2) ustalono krzywą uczenia dla nowo utworzonego ośrodka bariatrycznego. Wyniki: Czas operacyjny w G1-G3 różnił się istotnie od tego w G4-G10. Punktem stabilizacji była 90. procedura. Powikłania okołooperacyjne zaobserwowano u 36 (12,63%) pacjentów. Zarówno trudności śródoperacyjne i zdarzenia niepożądane, jak i powikłania okołooperacyjne, nie różniły się istotnie pomiędzy grupami. Liberalne wykorzystanie „konwersji operatora” od chirurga do bardziej doświadczonego chirurga zapewnia bezpieczeństwo i zapobiega komplikacjom. Wnioski: Instytucjonalny punkt stabilizacji procesu uczenia się LRYGB w nowo powstałym ośrodku bariatrycznym to około 90 operacji. LRYGB jest bezpiecznym zabiegiem w takcie osiągania krzywej uczenia się. Specjalistyczny trening bariatryczny pod nadzorem doświadczonego chirurga bariatry w bariatrycznym centrum doskonałości może poprawić wyniki i bezpieczeństwo w czasie krzywej uczenia się LRYGB.Introduction: Laparoscopic Roux-en-Y gastric bypass (LRYGB) is one of the most common treatments for morbid obesity. The learning curve for this procedure is 50–75 cases for an independent surgeon, and it is considered the most important factor in decreasing complications and mortality. We present our experience and learning curve with LRYGB for a newly established bariatric center in Poland. Material and methods: A prospectively collected database containing 285 LRYGB procedures performed in the II Department of General Surgery of the Jagiellonian University MC in Krakow between 06.2010 and 03.2019 was retrospectively reviewed. Patients were divided into groups of 30 (G1–G10) in the order of the procedures performed by each surgeon. The study analyzed the course of the operation and patient hospitalization, comparing those groups. Learning curve for the newly created bariatric center was established. Results: Operative time in G1–G3 differed significantly from G4–G10 (P < 0.0001). The stabilization point was the 90th procedure. Perioperative complications were observed in 36 (12.63%) patients. Perioperative complications, intraoperative difficulties and adverse events did not differ importantly among groups. Liberal use of “conversions of the operator” from a surgeon to a senior surgeon provides reasonable safety and prevents complications. Conclusions: The institutional learning process stabilization point for LRYGB in a newly established bariatric center is around the 90th operation. LRYGB can be a safe procedure from the very beginning in newly established bariatric centers. Specific bariatric training with active proctoring by an experienced surgeon in a bariatric centre can improve the laparoscopic gastric bypass outcome during the learning curve

Synthesis and characterisation of PEG-peptide surfaces for proteolytic enzyme detection

Peptide surfaces were obtained by the covalent immobilisation of fluorescently labelled pentapeptides carboxyfluorescein–glycine–arginine–methionine–leucine–glycine, either directly or through a poly(ethylene glycol) (PEG) linker on modified silicon wafers. Each step during the preparation of the peptide surfaces was confirmed by several surface characterisation techniques. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy were used to determine the surface composition, the wafers philicity was measured by contact angle and atomic force microscopy was used to investigate the surface morphology. Exposure of the peptide surfaces to trypsin resulted in the release of a fluorescently labelled peptide product, which allowed the kinetics of the enzymatic reaction to be followed with the aid of fluorescence spectroscopy. The electrospray ionisation mass spectrometry analysis of the post-digestion solution confirmed that the pentapeptides attached to the solid support undergo specific trypsin hydrolysis at the C-terminus of the arginine residues. Detailed surface analyses before and after the enzyme action was performed using ToF-SIMS. Because of the limited accessibility of the short peptide directly attached to the surface, a quantitative yield of enzymatic hydrolysis was observed only in case when the peptide was bound through the PEG linker. The insertion of the PEG linker increased the number of immobilised peptides and the rate of enzymatic digestion which consequently improved the quality of the enzyme assays. The described approach may be used for different peptide sequences designed for other proteases. Figure Monitoring of trypsin hydrolysis on PEG-peptide surfac

Laparoscopic adrenalectomy for pheochromocytoma is more difficult compared to other adrenal tumors

INTRODUCTION: Laparoscopic adrenalectomy is the gold standard for the treatment of benign adrenal tumors. However, some authors raise the problem of differences in surgery for pheochromocytoma in comparison to other lesions. AIM: To compare laparoscopic adrenalectomy for pheochromocytoma and for other tumors. MATERIAL AND METHODS: Four hundred and thirty-seven patients with adrenal tumors were included in the retrospective analysis. Patients were divided into two groups: 1 (124 patients treated for pheochromocytoma) and 2 (313 patients with other types of tumor). The two groups were compared with respect to mean operative time, intraoperative blood loss, conversion rate, complication rate and the relationship of tumor size with operative time. RESULTS: The mean operative time in group 1 was 91 min, and in group 2 it was 82 min (p = 0.016). In both groups 1 and 2, tumor size correlated with operative time (p < 0.0001 and p = 0.0003, respectively). The mean blood loss in groups 1 and 2 was 117 ml and 54 ml, respectively (p = 0.0011). The complication rate in groups 1 and 2 was 4% and 4.2%, respectively (p = 0.9542). In groups 1 and 2, conversion was necessary in 2 (1.6%) and 5 (1.6%) cases, respectively (p = 0.9925). CONCLUSIONS: Longer operative time and higher blood loss after laparoscopic adrenalectomy for pheochromocytoma indicate its greater difficulty. However, despite these drawbacks, minimally invasive surgery still seems to be an effective and safe method

Przekształcenia struktur regionalnych

Praca recenzowana / peer-reviewed pape