Characterization of the electrical behavior of a discontinuous hybrid yarn textile made of recycled carbon and PA6 fibers during Joule heating

The Joule heating of carbon fiber-based textiles enables an energy- and cost-efficient processing of carbon fiber reinforced thermoplastic parts. This article introduces a new method to pass direct current into a dry, not pre-consolidated hybrid yarn textile based on recycled carbon fibers and polyamide 6 fibers. The aim is to melt polyamide fibers, subsequently impregnate carbon fibers, and finally consolidate the material to form a composite part in a single process step. To increase the reliability of this technology, the electrical properties and the behavior of the material during the heating process must be thoroughly investigated. It will be addressed how the material is characterized during the process and how the changing resistivity of the textile affects the current flow between the electrodes to generate intrinsic heat. Moreover, a method to determine the effective material resistivity by finite element simulation on the fiber scale based on a CT scan is presented. Thus, a validated material model with respect to the temperature development in the textile based on ρ = ρ (T) was established

T lymphocytes from patients with primary biliary cirrhosis produce reduced amounts of lymphotoxin, tumor necrosis factor and interferon-gamma upon mitogen stimulation

Primary biliary cirrhosis (PBC) is considered an autoimmune disease characterized by destruction of small intrahepatic bile ducts by lymphocytes. Altered functions of these lymphocytes might reflect an abnormal immune response leading to tissue damage. We investigated lymphokine secretion by mitogen-stimulated T lymphocytes from the liver biopsies of patients with PBC and for comparison also peripheral blood. In PBC, diminished synthesis of lymphotoxin (TNFP), tumor necrosis factor (TNFa) and interferon-y (IFIVy) was found both in T-cell lines from liver tissue and in peripheral blood. The reduction was most prominent for TNFP in early histological stages of PBC, and appeared to be a stable phenomenon when T cells were tested after long-term tissue culture. Analysis of mRNA levels indicates a possible link between reduced TNFP production and a defect in interleukin-2 transcription. The data suggest that diminished lymphokine production in patients with PBC may play ;In important role in the immanopathogenesis of this disease

Quantification and Classification of Cortical Perfusion during Ischemic Strokes by Intraoperative Thermal Imaging

Thermal imaging is a non-invasive and marker-free approach for intraoperative measurements of small temperature variations. In this work, we demonstrate the abilities of active dynamic thermal imaging for analysis of tissue perfusion state in case of cerebral ischemia. For this purpose, a NaCl irrigation is applied to the exposed cortex during hemicraniectomy. The cortical temperature changes are measured by a thermal imaging system and the thermal signal is recognized by a novel machine learning framework. Subsequent tissue heating is then approximated by a double exponential function to estimate tissue temperature decay constants. These constants allow us to characterize tissue with respect to its dynamic thermal properties. Using a Gaussian mixture model we show the correlation of these estimated parameters with infarct demarcations of post-operative CT. This novel scheme yields a standardized representation of cortical thermodynamic properties and might guide further research regarding specific intraoperative diagnostics

Speaking up about patient safety concerns: view of nursing students.

BACKGROUND "Speaking up" is considered an important patient safety behaviour. The main idea is to voice patient safety concerns; however, several studies revealed that the organisational culture can be obstructive. In previous studies, we already identified barriers for doctors, nurses and medical students. In the current study, we explore how nursing students use "speaking up" during their internship in an academic teaching hospital. METHODS Between 2019 and 2020, 212 nursing students were invited to take part in the survey. The validated Speaking Up about Patient Safety Questionnaire (SUPS-Q) was used to assess speaking up behaviours in nursing students. The SUPS-Q consisted of three behaviour related scales (11 items), three culture related scales (11 items), a question regarding barriers to speak up as well as a clinical vignette assessing a hypothetical speaking up situation. RESULTS In total, 118 nursing students took part in the survey (response rate: 56%). Most of them noticed specific safety concerns, observed errors or rule violations. The vignette was seen as very realistic and harmful to the patient. However, the majority responded that they did not speak up and remained silent. They reported a rather discouraging environment and high levels of resignation towards speaking up. However, more advanced students were less likely to speak up than less advanced students (p = 0.027). Most relevant barriers were fear of negative reaction (64%), reaction not predictable (62%) and ineffectiveness (42%). CONCLUSIONS Survey results of nursing students imply that speaking-up behaviours and remaining silent are common behaviours and coexist in the same individual. The clinical vignette and barriers to speaking up revealed that a hierarchical system does not support speaking-up behaviours. Organizational development is needed to foster professional teamwork, support attentive listening, encourage critical thinking, and problem-solving skills

Suppression of the quantum-confined Stark effect in polar nitride heterostructures

Recently, we suggested an unconventional approach (the so-called Internal-Field-Guarded-Active-Region Design “IFGARD”) for the elimination of the quantum-confined Stark effect in polar semiconductor heterostructures. The IFGARD-based suppression of the Stark redshift on the order of electronvolt and spatial charge carrier separation is independent of the specific polar semiconductor material or the related growth procedures. In this work, we demonstrate by means of micro-photoluminescence techniques the successful tuning as well as the elimination of the quantum-confined Stark effect in strongly polar [000-1] wurtzite GaN/AlN nanodiscs as evidenced by a reduction of the exciton lifetimes by up to four orders of magnitude. Furthermore, the tapered geometry of the utilized nanowires (which embed the investigated IFGARD nanodiscs) facilitates the experimental differentiation between quantum confinement and Stark emission energy shifts. Due to the IFGARD, both effects become independently adaptable.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

Factors affecting the mechanical and geometrical properties of electrostatically flocked pure chitosan fiber scaffolds

The field of articular cartilage tissue engineering has developed rapidly, and chitosan has become a promising material for scaffold fabrication. For this paper, wet-spun biocompatible chitosan filament yarns were converted into short flock fibers and subsequently electrostatically flocked onto a chitosan substrate, resulting in a pure, highly open, porous, and biodegradable chitosan scaffold. Analyzing the wet-spinning of chitosan revealed its advantages and disadvantages with respect to the fabrication of the fiber-based chitosan scaffolds. The scaffolds were prepared using varying processing parameters and were analyzed in regards to their geometrical and mechanical properties. It was found that the pore sizes were adjustable between 65 and 310 µm, and the compressive strength was in the range 13–57 kPa