Identification of parameters of cohesive elements for modeling of adhesively bonded joints of epoxy composites

Adhesively bonded joints can be numerically simulated using the cohesive crack model. The critical strain energy release rate and the critical opening displacement are the parameters which must be known when cohesive elements in MSC.Marc software are used. In this work, the parameters of two industrial adhesives Hunstman Araldite 2021 and Gurit Spabond 345 for bonding of epoxy composites are identified. Double Cantilever Beam (DCB) and End Notched Flexure (ENF) test data were used for the identification. The critical opening displacements were identified using an optimization algorithm where the tests and their numerical simulations were compared

Dielectric breakdown analysis of composites consisting of epoxy resin and polyimide film

The breakdown phenomena and determination of dielectric strength is one of the essential topics in the field of insulating materials for high-voltage applications. In the case of basic thermosetting plastics, including epoxy resins, dielectric breakdown analysis has been performed many times, and the mechanism of conducting channel formation is already well known. However, the situation becomes more complicated if other material components are combined with the base polymer. The application of composites in electrical insulation systems is currently becoming more common. Of all available electrical insulating types of composites, the attention is paid to sandwich composite in this contribution. Specifically, a sandwich structure, which is an interconnection of a heat-resistant thermoplastic (polyimide film) and a conventional thermoset for high-voltage applications (epoxy resin layer), is analyzed. Tested structures were prepared as the composition of each one of the three different types of polyimide films and always the same conventional epoxy resin which is cured at elevated temperature after the amine curing agent addition. In the case of performed testing of sandwich composites, the conductive channel is formed rapidly through the two polymer layers, which are very different in chemical structure. In addition, an interface is formed between the material layers when these layers are interconnected during the epoxy resin curing process, and the effect of this interface must also be considered in the analysis of dielectric breakdown. This contribution is focused primarily on visual description of differences in a breakdown that occurs when different polyimide films without or even with a certain surface treatment are tested. The values of dielectric strength determined by the dynamic method for tested structures are also mentioned. It appears that the choice of a suitable polyimide film can be quite ignificant in the sandwich structure of the electrical insulation system in terms of dielectric strength

Innovated relays for railway signalling and interlocking

This paper deals with accelerated life tests and a verification of technical parameters of an innovated electromechanical relay intended for applications in railway signalling and interlocking

The Use of Biomarkers in Early Diagnostics of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal solid malignancies with increasing incidence. The poor prognosis is due to the aggressive nature of the tumor, late detection, and the resistance to chemotherapy and radiotherapy. A radical surgery procedure is the only treatment that has been shown to improve the 5-year survival rate to 20-25%. However, the majority of patients (80-85%) are diagnosed with locally advanced or metastatic disease and just 15-20% patients are diagnosed in an early stage allowing them to undergo the potentially curative surgical resection. The early detection of PDAC without the use of invasive methods is challenging and discovery of a cost-effective biomarker with high specificity and sensitivity could significantly improve the treatment and survival in these patients. In this review, we summarize current and newly examined biomarkers in early PDAC detection

16S rRNA gene primer choice impacts off-target amplification in human gastrointestinal tract biopsies and microbiome profiling

Abstract 16S rRNA amplicon sequencing or, more recently, metatranscriptomic analysis are currently the only preferred methods for microbial profiling of samples containing a predominant ratio of human to bacterial DNA. However, due to the off-target amplification of human DNA, current protocols are inadequate for bioptic samples. Here we present an efficient, reliable, and affordable method for the bacteriome analysis of clinical samples human DNA content predominates. We determined the microbiota profile in a total of 40 human biopsies of the esophagus, stomach, and duodenum using 16S rRNA amplicon sequencing with the widely used 515F-806R (V4) primers targeting the V4 region, 68F-338R primers and a modified set of 68F-338R (V1-V2M) primers targeting the V1–V2 region. With the V4 primers, on average 70% of amplicon sequence variants (ASV) mapped to the human genome. On the other hand, this off-target amplification was absent when using the V1–V2M primers. Moreover, the V1–V2M primers provided significantly higher taxonomic richness and reproducibility of analysis compared to the V4 primers. We conclude that the V1–V2M 16S rRNA sequencing method is reliable, cost-effective, and applicable for low-bacterial abundant human samples in medical research

Different Clinical Utility of Oropharyngeal Bacterial Screening prior to Percutaneous Endoscopic Gastrostomy in Oncological and Neurological Patients

Background. The aim of this study was to monitor oropharyngeal bacterial colonization in patients indicated for percutaneous endoscopic gastronomy (PEG). Methods. Oropharyngeal swabs were obtained from patients prior to PEG placement. A development of peristomal infection was evaluated. The analysis of oropharyngeal and peristomal site pathogens was done. Results. Consecutive 274 patients referred for PEG due to neurological disorder or cancer completed the study. Oropharyngeal colonization with pathogens was observed in 69% (190/274), dominantly in the neurologic subgroup of patients (P < 0.001). Peristomal infection occurred in 30 (10.9%) of patients and in 57% of them the correlation between oropharyngeal and peristomal agents was present. The presence of oropharyngeal pathogens was assessed as an important risk factor for the development of peristomal infection only in oncological patients (OR = 8.33, 95% CI: 1.66–41.76). Despite a high prevalence of pathogens in neurological patients, it did not influence the risk of peristomal infection with the exception for methicillin resistant Staphylococcus aureus (MRSA) carriers (OR 4.5, 95% CI: 1.08–18.76). Conclusion. During oropharyngeal microbial screening prior to the PEG insertion, the detection of pathogens may be a marker of the increased risk of peristomal infection in cancer patients only. In neurological patients the benefit of the screening is limited to the detection of MRSA carriers

Different Clinical Utility of Oropharyngeal Bacterial Screening prior to Percutaneous Endoscopic Gastrostomy in Oncological and Neurological Patients

Background. The aim of this study was to monitor oropharyngeal bacterial colonization in patients indicated for percutaneous endoscopic gastronomy (PEG). Methods. Oropharyngeal swabs were obtained from patients prior to PEG placement. A development of peristomal infection was evaluated. The analysis of oropharyngeal and peristomal site pathogens was done. Results. Consecutive 274 patients referred for PEG due to neurological disorder or cancer completed the study. Oropharyngeal colonization with pathogens was observed in 69% (190/274), dominantly in the neurologic subgroup of patients (P < 0.001). Peristomal infection occurred in 30 (10.9%) of patients and in 57% of them the correlation between oropharyngeal and peristomal agents was present. The presence of oropharyngeal pathogens was assessed as an important risk factor for the development of peristomal infection only in oncological patients (OR = 8.33, 95% CI: 1.66–41.76). Despite a high prevalence of pathogens in neurological patients, it did not influence the risk of peristomal infection with the exception for methicillin resistant Staphylococcus aureus (MRSA) carriers (OR 4.5, 95% CI: 1.08–18.76). Conclusion. During oropharyngeal microbial screening prior to the PEG insertion, the detection of pathogens may be a marker of the increased risk of peristomal infection in cancer patients only. In neurological patients the benefit of the screening is limited to the detection of MRSA carriers

Hybrid steel–composite cross-arm for distribution power lines

This paper describes the development of electrically insulating hybrid steel–composite cross-arm for mediumvoltage overhead distribution power lines with three conductors. The main goal was to achieve substantial weight savings ompared to a common steel cross-arm with three ceramic insulators widely used in the Czech Republic. The structure has been designed as a combination of two main composite components – a pultruded horizontal profile and a braided vertical conical tube. These components are connected by a steel locking component which also serves for attaching the whole cross-arm to common concrete utility poles. The hybrid cross-arm is conceived to insulate electrical current in the default configuration thanks to the properties of the glass fiber reinforced composite materials, yet additional insulating elements can be used to further increase the electrical insulation distance. The materials and components used for the construction are chosen by combining finite element simulations of mechanical and electrical behavior with experimental testing and verification of important characteristics on selected substructures. The final design of the cross-arm is then manufactured and subjected to long-term testing in real-life environmental conditions. The achieved reduction of weight exceeds 50% while maintaining the mechanical rigidity and strength of the steel solution as well as the required insulation properties. The future trend of the cross-arm development is aiming at the weight reduction and increase of manipulation capabilities resulting in lowering many additional costs. In this work the designed cross-arm has half the weight of the original one