Increasing the Interactivity in Software Engineering MOOCs - A Case Study

MOOCs differ from traditional university courses: instructors do not know the learners who have a diverse background and cannot talk to them in person due to the worldwide distribution. This has a decisive influence on the interactivity of teaching and the learning success in online courses. While typical online exercises such as multiple choice quizzes are interactive, they only stimulate basic cognitive skills and do not reflect software engineering working practices such as programming or testing. However, the application of knowledge in practical and realistic exercises is especially important in software engineering education. In this paper, we present an approach to increase the interactivity in software engineering MOOCs. Our interactive learning approach focuses on a variety of practical and realistic exercises, such as analyzing, designing, modeling, programming, testing, and delivering software stimulating all cognitive skills. Semi-automatic feedback provides guidance and allows reflection on the learned theory. We applied this approach in the MOOC software engineering essentials SEECx on the edX platform. Since the beginning of the course, more than 15,000 learners from more than 160 countries have enrolled. We describe the design of the course and explain how its interactivity affects the learning success

PYRO-NN: Python Reconstruction Operators in Neural Networks

Purpose: Recently, several attempts were conducted to transfer deep learning to medical image reconstruction. An increasingly number of publications follow the concept of embedding the CT reconstruction as a known operator into a neural network. However, most of the approaches presented lack an efficient CT reconstruction framework fully integrated into deep learning environments. As a result, many approaches are forced to use workarounds for mathematically unambiguously solvable problems. Methods: PYRO-NN is a generalized framework to embed known operators into the prevalent deep learning framework Tensorflow. The current status includes state-of-the-art parallel-, fan- and cone-beam projectors and back-projectors accelerated with CUDA provided as Tensorflow layers. On top, the framework provides a high level Python API to conduct FBP and iterative reconstruction experiments with data from real CT systems. Results: The framework provides all necessary algorithms and tools to design end-to-end neural network pipelines with integrated CT reconstruction algorithms. The high level Python API allows a simple use of the layers as known from Tensorflow. To demonstrate the capabilities of the layers, the framework comes with three baseline experiments showing a cone-beam short scan FDK reconstruction, a CT reconstruction filter learning setup, and a TV regularized iterative reconstruction. All algorithms and tools are referenced to a scientific publication and are compared to existing non deep learning reconstruction frameworks. The framework is available as open-source software at \url{https://github.com/csyben/PYRO-NN}. Conclusions: PYRO-NN comes with the prevalent deep learning framework Tensorflow and allows to setup end-to-end trainable neural networks in the medical image reconstruction context. We believe that the framework will be a step towards reproducible researchComment: V1: Submitted to Medical Physics, 11 pages, 7 figure

Generalizable Classification of UHF Partial Discharge Signals in Gas-Insulated HVDC Systems Using Neural Networks

Undetected partial discharges (PDs) are a safety critical issue in high voltage (HV) gas insulated systems (GIS). While the diagnosis of PDs under AC voltage is well-established, the analysis of PDs under DC voltage remains an active research field. A key focus of these investigations is the classification of different PD sources to enable subsequent sophisticated analysis. In this paper, we propose and analyze a neural network-based approach for classifying PD signals caused by metallic protrusions and conductive particles on the insulator of HVDC GIS, without relying on pulse sequence analysis features. In contrast to previous approaches, our proposed model can discriminate the studied PD signals obtained at negative and positive potentials, while also generalizing to unseen operating voltage multiples. Additionally, we compare the performance of time- and frequency-domain input signals and explore the impact of different normalization schemes to mitigate the influence of free-space path loss between the sensor and defect location.Comment: 8 pages, submitted to IEEE Transactions on Power Deliver

Gas-induced segregation in Pt-Rh alloy nanoparticles observed by in-situ Bragg coherent diffraction imaging

Bimetallic catalysts can undergo segregation or redistribution of the metals driven by oxidizing and reducing environments. Bragg coherent diffraction imaging (BCDI) was used to relate displacement fields to compositional distributions in crystalline Pt-Rh alloy nanoparticles. 3D images of internal composition showed that the radial distribution of compositions reverses partially between the surface shell and the core when gas flow changes between O2 and H2. Our observation suggests that the elemental segregation of nanoparticle catalysts should be highly active during heterogeneous catalysis and can be a controlling factor in synthesis of electrocatalysts. In addition, our study exemplifies applications of BCDI for in situ 3D imaging of internal equilibrium compositions in other bimetallic alloy nanoparticles

Heat accumulation during femtosecond laser treatment at high repetition rate – A morphological, chemical and crystallographic characterization of self-organized structures on Ti6Al4V

This study presents a detailed characterization of self-organized nano- and microstructures on Ti6Al4V evoked by different scanning strategies and fluences with a 300 fs laser operating at a laser wavelength of 1030 nm. The resulting surface morphology was visualized via field emission scanning electron microscopy (FEG-SEM) images of the surface and cross-sections. X-ray diffraction (XRD)-analysis was performed to analyse changes in crystal structures. The chemical surface composition of the near-surface layer was determined by X-ray photoelectron spectroscopy (XPS). Results show a significant influence of heat accumulation while processing with high laser repetition rates on the formation, crystallinity and chemical composition of self-organized structures depending on the scanning strategy. The ablation with different laser scanning strategies led to varying dynamics of growth-mechanisms of self-organized structures, formation of intermetallic phases (Ti3Al), sub-oxides and oxides (Ti6O, TiO) as well as ions (Ti3+, Ti4+) in surface layer reliant on applied fluence. Furthermore, investigations revealed a heat-affected zone up to several micrometers in non-ablated material. © 2021 The Author

Magnesium corrosion particles do not interfere with the immune function of primary human and murine macrophages

Magnesium is currently under investigation as a prospective biodegradable implant material. Biodegradation of magnesium causes a release of magnesium, hydroxide ions and hydrogen gas but it can also lead to the formation of particulate debris. Implant-derived particles may have immunotoxic effects. To investigate the influence of magnesium-derived particles on the immune functions of primary macrophages, up to 500 mu g/ml magnesium or magnesium corrosion particles were added to the cell culture medium. No major effects were observed on cell viability and on the release of the proinflammatory cytokine tumor necrosis factor (TNF)alpha. In addition, the ability of macrophages to stimulate proliferation of allogenic lymphocytes in a mixed leukocyte reaction remained unaffected. When macrophages were incubated with magnesium particles and then infected with the apathogenic Mycobacterium smegmatis, infection-induced TNF alpha secretion from murine macrophages was inhibited but not from human macrophages. However, the bactericidal activity of either cell type was not influenced. In conclusion, magnesium-related particles did not restrict the immune function of macrophages, suggesting that magnesium implants and corrosion particles derived thereof are highly biocompatible and have a low inflammatory potential

Implant-based immediate reconstruction in prophylactic mastectomy: is the caudal dermis flap a reliable alternative to synthetic mesh or acellular dermal matrix?

Introduction The demand for prophylactic mastectomy has increased significantly over the last 10 years. This can be explained by a substantial gain of knowledge about the clinical risk and outcome of patients with high risk mutations such as BRCA1 and 2, the improved diagnostic possibilities for detecting the genetic predisposition for the development of breast cancer and the awareness for those mutations by health care professionals as well as patients. In addition to expander-to-implant reconstruction and microsurgical flap surgery, definitive immediate reconstruction with subpectoral insertion of breast implants is often preferred. The prosthesis is covered at its inferior pole by a synthetic mesh or acellular dermal matrix. In these cases, in addition to the silicone prosthesis, a further foreign body must be implanted. This can be exposed in the event of wound healing disorder or necrosis of the usually thin soft tissue covering after subcutaneous mastectomy, thus calling into question the reconstructive result. In this study, the coverage of the lower pole by a caudal deepithelialized dermis flap, which allows the implant to be completely covered with well vascularized tissue, is compared to coverage by a synthetic mesh or acellular dermal matrix. Patients and methods From January 2014 to June 2020, 74 patients (106 breasts) underwent breast reconstruction following uni or bilateral prophylactic mastectomy. Reconstruction was performed with autologous tissue (15 breasts), with tissue expander or implant without implant support (15 breasts), with implant and use of an acellular dermal matrix or synthetic mesh (39 breasts) and with implant and caudal dermis flap (37 breasts). In this study, we compared the patients with implant and dermal matrix/mesh to the group reconstructed with implant and dermal flap. Results In the group with the caudal dermis flap, 4 patients developed skin necrosis, which all healed conservatively due to the sufficient blood supply through the dermis flap. In the group with the use of a synthetic mesh or acellular dermal matrix, skin necrosis was found in three cases. In one of these patients the implant was exposed and had to be removed. Discussion For patients with excess skin or macromastia, the caudal dermis flap is a reliable and less expensive option for complete coverage of an implant after prophylactic mastectomy. In particular, the vascularized dermis flap can protect the implant from the consequences of skin necrosis after prophylactic mastectomy

Implants Versus Lipograft: Analysis of Long-Term Results Following Congenital Breast Asymmetry Correction

Aims Congenital breast asymmetry represents a particular challenge to the classic techniques of plastic surgery given the young age of patients at presentation. This study reviews and compares the long-term results of traditional breast augmentation using silicone implants and the more innovative technique of lipografting. Methods To achieve this, we not only captured subjective parameters such as satisfaction with outcome and symmetry, but also objective parameters including breast volume and anthropometric measurements. The objective examination was performed manually and by using the Vectra® H2 photogrammetry scanning system. Results Differences between patients undergoing either implant augmentation or lipograft were revealed not to be significant with respect to patient satisfaction with surgical outcome (p = 0.55) and symmetry (p = 0.69). Furthermore, a breast symmetry of 93 % was reported in both groups. Likewise, no statistically significant volume difference between the left and right breasts was observed in both groups (p < 0.41). However, lipograft patients needed on average 2.9 procedures to achieve the desired result, compared with 1.3 for implant augmentation. In contrast, patients treated with implant augmentation may require a number of implant changes during their lifetime. Conclusion Both methods may be considered for patients presenting with congenital breast asymmetry. Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266

Surgery of congenital breast asymmetry-which objective parameter influences the subjective satisfaction with long-term results

PURPOSE: Congenital breast asymmetry is a serious gynecological malformation for affected patients. The condition hits young women in puberty and is associated with socio-esthetic handicap, depression, and psychosexual problems. Surgical treatment is usually early in the patient's lifetime, so a long-term sustainable solution is important. Although postoperative outcome has been evaluated in several studies before, this study is the first to analyze which objective parameters have the greatest influence on subjective satisfaction with long-term results. METHODS: Thirty-four patients diagnosed with congenital breast asymmetry that underwent either lipofilling or implant therapy between the years of 2008 to 2019 were examined. On average, our collective comprised patients seven years after surgery. Data were mainly gathered through manual measurements, patient-reported outcome measures (Breast Q(™)), and breast volumetry based on 3D scans (Vectra(®) H2, Canfield Scientific). RESULTS: Among all analyzed parameters, only areolar diameter correlated significantly negatively with the subjective outcome satisfaction of the patient. Regarding the subjective assessment of postoperative satisfaction with similarity of the breasts, again the mean areolar diameter, but also the difference in areolar diameter and breast volume between the right and left breasts correlated significantly negatively. CONCLUSION: Areolar diameter was revealed as being a significant factor influencing subjective long-term satisfaction in breast asymmetry patients. Moreover, 3D volumetry proves to be an effective tool to substantiate subjective patient assessments. Our findings may lead to further improvements to surgical planning and will be expanded in further studies