Advanced materials for FDM/FFF 3D print

Předložená práce pojednává o problematice FDM/FFF 3D tisku se zaměřením na matriály s přidanými uhlíkovými vlákny. Cílem práce je experimentálně analyzovat vliv karbonového aditiva na tištěné dílce pomocí mechanických a termomechanických zkoušek. Testování vybraných materiálů prokázalo, že vliv karbonové příměsi se liší podle použitého základního materiálu. Například karbon v materiálu PET–G snížil rázovou houževnatost až o 64 %. Avšak uhlíkem naplněné CPE projevilo schopnost absorbovat rázovou energii až o 28,5 % vyšší. Rozdílný vliv uhlíku byl měřen u materiálu CPE při zkoušce tahem, kde při zatěžování vzorků za pokojové teploty došlo ke snížení meze pevnosti, avšak ke zvýšení modulu pružnosti. Absolutně pozitivní vliv karbonu byl měřen u všech pozorovaných materiálů při termomechanické zkoušce 3-bodovým ohybem, kdy uhlíkové verze filamentů dosahovaly lepších výsledků. Naměřená data přináší v oblasti výzkumu rozšíření možnosti porovnání výsledků s dalšími typy materiálů vhodných k 3D tisku. Z praktického hlediska lze výsledky testů použít také k samotné volbě materiálu při tisku modelů se specifickými podmínkami využití. Dalším praktickým využitím analyzovaných dat je využití výsledků tisknutelnosti pokročilých materiálů k tvorbě tiskových profilů pro další stolní 3D tiskárny typu FDM/FFF.The presented work deals with the issue of FDM / FFF 3D printing with a focus on materials with added carbon fiber. The aim of this work is to experimentally analyze the effect of carbon additive on printed parts using mechanical and thermomechanical tests. Testing of selected materials has shown that the effect of carbon additive varies according to the used base material. For example, carbon in PET-G has reduced impact strength by up to 64%. However, carbon filled CPE has demonstrated the ability to absorb impact energy up to by 28.5%. The different effect of carbon fiber was measured on the CPE material in a tensile test, where the yield strength was reduced during the stretching of the samples at room temperature, but the modulus of elasticity was increased. The absolutely positive effect of carbon was measured on all observed polymer filaments in the thermomechanical 3-point bending test, when the carbon versions of the materials achieved better results. The measured data brings an extension of the possibility of comparing the results with other types of materials suitable for 3D printing in the field of research. From a practical point of view the test results can be used for the actual choice of material when printing models has specific conditions of use. Another practical use of the analyzed data is the use of printable results of advanced materials for the creation of print profiles for other desktop 3D printers of the FDM/FFF type.

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Surface treatment methods applied to 3D printed samples and their analysis

The presented paper deals with the issue of smoothing parts produced using FFF 3D printing technology. The aim of the paper was to compare technical surface treatment methods and economic side. Emphasis was placed especially on the degree of reduction of surface roughness while maintaining an acceptable level of process costs. Chemical smoothing, local CO2 laser melting, tumbling and surface treatment based on filler spraying were used to smooth the plastic prints. Prints made of ABS, PLA, PolySmooth and PolyCast were subjected to the smoothing process. Printing parameters were first determined for individual materials and test samples were produced on their basis. After determining the process parameters for individual surface treatment methods, the finished surfaces were measured with a profilometer. Based on the results, the chemical etching method was evaluated as the most effective surface smoothing method. Due to the etching of the surface layer of the sample made of PolySmooth material, the surface roughness parameter Sa was reduced in diameter compared to the reference sample. by 99,56 %. The least effective method was tumbling technology, which showed an average roughness reduction of 30,07 % in the case of ABS. However, the technology based on grinding parts with grinding stones had the lowest process costs for finishing the samples. Technical The economically best choice of all tested combinations was the technology of chemical etching of ABS polymer prints. The results and conclusions of the work will serve not only to select the finishing operation and material for specific applications of prints in practice, but also to expand the possibilities of using additively produced components

Advanced materials for FDM/FFF 3D print

The presented work deals with the issue of FDM / FFF 3D printing with a focus on materials with added carbon fiber. The aim of this work is to experimentally analyze the effect of carbon additive on printed parts using mechanical and thermomechanical tests. Testing of selected materials has shown that the effect of carbon additive varies according to the used base material. For example, carbon in PET-G has reduced impact strength by up to 64%. However, carbon filled CPE has demonstrated the ability to absorb impact energy up to by 28.5%. The different effect of carbon fiber was measured on the CPE material in a tensile test, where the yield strength was reduced during the stretching of the samples at room temperature, but the modulus of elasticity was increased. The absolutely positive effect of carbon was measured on all observed polymer filaments in the thermomechanical 3-point bending test, when the carbon versions of the materials achieved better results. The measured data brings an extension of the possibility of comparing the results with other types of materials suitable for 3D printing in the field of research. From a practical point of view the test results can be used for the actual choice of material when printing models has specific conditions of use. Another practical use of the analyzed data is the use of printable results of advanced materials for the creation of print profiles for other desktop 3D printers of the FDM/FFF type

Approximation of intestinal anastomosis in newborns with low birth weight - an experimental model

Klinika dětské chirurgieDepartment of Paediatric Surgery2. lékařská fakultaSecond Faculty of Medicin

Polystyrene Microstructured Foams Formed by Thermally Induced Phase Separation from Cyclohexanol Solution

Tepelně indukovanou fázovou separaci lze využít k přípravě materiálů s různě mikrostrukturovanými morfologiemi, které definují jejich využití. V této práci popisujeme výrobu, charakterizujeme a modelujeme pěny vytvořené z roztoku polystyren-cyklohexanolu. Abychom získali relevantní termodynamický popis, body zákalu jsou měřeny pomocí námi vyrobeného termo-optického zařízení. Porovnáváme experimentální výsledky s předpovědí dříve publikovaného matematického modelu. Předkládaná práce rozšiřuje znalosti o mechanismu a kinetice vývoje morfologie pěn používaných pro tepelnou a zvukovou izloaci.The thermally induced phase separation can be used to prepare materials of various microstructured morphologies that define their applications. In this work, foams formed from a polystyrene-cyclohexanol solution are prepared, characterized, and modeled. To obtain a reliable thermodynamic description, cloud points are determined by an in-house fabricated thermooptical device. The Flory–Huggins lattice model combined with Hansen solubility theory is employed as input to the Cahn–Hilliard model of phase separation dynamics. The previously reported model is extended by incorporating polar interactions. The resulting experimental and predicted morphologies are compared and good prediction capabilities of the model regarding the resulting morphology and its characteristics are obtained. The experimental and modeling work extends the knowledge of the mechanism and the kinetics of foam morphology evolution for thermal and sound insulation applications

Urinary Intestinal Fatty Acid-Binding Protein Can Distinguish Necrotizing Enterocolitis from Sepsis in Early Stage of the Disease

Necrotizing enterocolitis (NEC) is severe disease of gastrointestinal tract, yet its early symptoms are nonspecific, easily interchangeable with sepsis. Therefore, reliable biomarkers for early diagnostics are needed in clinical practice. Here, we analyzed if markers of gut mucosa damage, caspase cleaved cytokeratin 18 (ccCK18) and intestinal fatty acid-binding protein (I-FABP), could be used for differential diagnostics of NEC at early stage of disease. We collected paired serum (at enrollment and week later) and urine (collected for two days in 6 h intervals) samples from 42 patients with suspected NEC. These patients were later divided into NEC (n=24), including 13 after gastrointestinal surgery, and sepsis (n=18) groups using standard criteria. Healthy infants (n=12), without any previous gut surgery, served as controls. Both biomarkers were measured by a commercial ELISA assay. There were no statistically significant differences in serum ccCK18 between NEC and sepsis but NEC patients had significantly higher levels of serum and urinary I-FABP than either sepsis patients or healthy infants. Urinary I-FABP has high sensitivity (81%) and specificity (100%) and can even distinguish NEC from sepsis in patients after surgery. Urinary I-FABP can be used to distinguish NEC from neonatal sepsis, including postoperative one, better than abdominal X-ray