Revisiting Robustness in Graph Machine Learning

Many works show that node-level predictions of Graph Neural Networks (GNNs) are unrobust to small, often termed adversarial, changes to the graph structure. However, because manual inspection of a graph is difficult, it is unclear if the studied perturbations always preserve a core assumption of adversarial examples: that of unchanged semantic content. To address this problem, we introduce a more principled notion of an adversarial graph, which is aware of semantic content change. Using Contextual Stochastic Block Models (CSBMs) and real-world graphs, our results uncover: $i)$ for a majority of nodes the prevalent perturbation models include a large fraction of perturbed graphs violating the unchanged semantics assumption; $ii)$ surprisingly, all assessed GNNs show over-robustness - that is robustness beyond the point of semantic change. We find this to be a complementary phenomenon to adversarial examples and show that including the label-structure of the training graph into the inference process of GNNs significantly reduces over-robustness, while having a positive effect on test accuracy and adversarial robustness. Theoretically, leveraging our new semantics-aware notion of robustness, we prove that there is no robustness-accuracy tradeoff for inductively classifying a newly added node.Comment: Published as a conference paper at ICLR 2023. Preliminary version accepted as an oral at the NeurIPS 2022 TSRML workshop and at the NeurIPS 2022 ML safety worksho

Arbeitskreis: Problemlösen

Bericht von der (Online-)Herbsttagung 2020 und Ausblick auf den GDM-Monat 2021 sowie die Herbsttagung 2021

Over-the-scope-grasper: A new tool for pancreatic necrosectomy and beyond - first multicenter experience

BACKGROUND Endoscopic treatment of pancreatic necrosis can be challenging and time-consuming because sticky necrotic debris is sometimes difficult to remove. The over-the-scope-grasper, a new tool that has recently become available for this purpose, might also be useful for other indications. However, clinical data on the efficacy and safety of this new device are lacking. AIM To evaluate the technical success and safety of the device in a multicenter setting. METHODS The over-the-scope-grasper was used in nine selected endoscopic centers between November 2020 and October 2021 for appropriate indications. Overall, 56 procedures were included in the study. We retrospectively evaluated procedural parameters of all endoscopic interventions using a predefined questionnaire, with special respect to technical success, indications, duration of intervention, type of sedation, and complications. In the case of pancreatic necrosectomy, the access route, stent type, number of necrosis pieces removed, and clinical handling were also recorded. RESULTS A total of 56 procedures were performed, with an overall technical success rate of 98%. Most of the procedures were endoscopic pancreatic necrosectomies (33 transgastric, 4 transduodenal). In 70% of the procedures, access to the necrotic cavity was established with a lumen apposing metal stent. The technical success of pancreatic necrosectomy was 97%, with a mean of 8 pieces (range, 2-25 pieces) of necrosis removed in a mean procedure time of 59 min (range, 15-120 min). In addition, the device has been used to remove blood clots (n = 6), to clear insufficiency cavities before endoluminal vacuum therapy (n = 5), and to remove foreign bodies from the upper gastrointestinal tract (n = 8). In these cases, the technical success rate was 100%. No moderate or severe/fatal complications were reported in any of the 56 procedures. CONCLUSION These first multicenter data demonstrate that the over-the-scope-grasper is a promising device for endoscopic pancreatic necrosectomy, which is also appropriate for removing foreign bodies and blood clots, or cleaning insufficiency cavities prior to endoluminal vacuum therapy

Bariatric surgery prevents carotid wall thickness progression.

BACKGROUND Bariatric surgery is a treatment option for patients with severe obesity and improves parameters of cardiovascular and/or metabolic disease. Carotid intima media thickness (C-IMT) is a surrogate measure of subclinical atherosclerosis. Previous studies showed short to mid-term arrest and even regression of C‑IMT progression following bariatric surgery. We aimed to investigate the long-term effect of weight loss on C‑IMT progression 10 years after bariatric surgery in comparison to a population-based control cohort. METHODS In total, 21 eligible patients were examined preoperatively, at 5 and 10 years after bariatric surgery. Anthropometric parameters, plasma triglycerides, total cholesterol, high-density lipoprotein cholesterol (HDL-C), insulin, and glucose were assessed at all three study visits. C‑IMT was measured via B‑mode scans of the common carotid artery. C‑IMT progression was measured in an age-matched and BMI-matched cohort selected from the population-based Bruneck study to compare with changes in C‑IMT progression after bariatric surgery. RESULTS C‑IMT remained stable over the 10-year observation period after bariatric surgery. The control cohort showed a significant C‑IMT progression over 10 years. The difference in C‑IMT progression over 10 years was significant (p < 0.01) between both cohorts. CONCLUSION Weight loss induced by bariatric surgery halts the natural progression of C‑IMT over a 10-year observation period

Microelectrode Array Electrophysiological Recording of Neuronal Network Activity during a Short-Term Microgravity Phase

During spaceflight, humans are subjected to a variety of environmental factors which deviate from Earth conditions. Especially the lack of gravity poses a big challenge to the human body and has been identified as a major trigger of many detrimental effects observed in returning astronauts but also in participants of spaceflight-analog studies. Structural alterations within the brain as well as declines in cognitive performance have been reported, which has brought the topic of brain health under microgravity into the focus of space research. However, the physiological mechanisms underlying these observations remain elusive. Every aspect of human cognition, behavior and psychomotor function is processed by the brain based on electro-chemical signals of billions of neurons, which relay information via neuronal networks throughout the body. Alterations in neuronal activity are the main cause of a variety of mental disorders and changed neuronal transmission may also lead to diminished human performance in space. Thus, understanding the functioning of these fundamental processes under the influence of altered gravity conditions on a cellular level is of high importance for any manned space mission. Previous electrophysiological experiments using patch clamp have shown that propagation velocity of action potentials (APs) is dependent on gravity. With this project, we aim to advance the electrophysiological approach from a single-cell level to a complex network level by employing Microelectrode array (MEA) technology. MEAs feature the advantage of real-time electrophysiological recording of a complex and mature neuronal network in vitro, without the need for invasive patch clamp insertion into cells. Using a custom-built pressure chamber, we were able to integrate and conduct our experiment on the ZARM Drop Tower platform, exposing the entire system to 4.7 s of high-quality microgravity (10-6 to 10-5 x g0). With this setup we were able to evaluate the functional activity patterns of iPSC-derived neuronal networks subjected to microgravity, while keeping them under controlled and stable temperature and pressure conditions. Activity data was acquired constantly - immediately before the drop, during the free-fall (microgravity) phase and during a subsequent post-drop recording phase. For neuronal activity analysis the action potential frequency in each experiment phase was calculated for the single electrodes. We found that during the 4.7 s lasting microgravity phase the mean action potential frequency across the neuronal networks was significantly elevated. Additionally, electrical activity readapted back to baseline level within 10 minutes of post-drop recordings. Our preliminary data shows that real-time, electrophysiological recording of neuronal network activity based on MEA technology is possible under altered gravity conditions and that differences in activity can be detected already in very short time frames in the second range. Furthermore, the observation that microgravity has an effect on the electrophysiological activity of neuronal networks is in line with previously published findings in single neurons and poses further questions with regards to astronaut brain health on manned space missions. The MEA payload system was approved for autonomous recording of redundant cellular electrophysiological data in the Drop Tower. It will be applied on other microgravity platforms such as sounding rockets and parabolic flights and thus increased experimental time. Apart from neurons, various other electrically active cellular systems such as myocytes or myotubes could be examined using this hardware

Impact of COVID-19 on 1-Year Survival Outcomes in Hepatocellular Carcinoma:A Multicenter Cohort Study

IntroductionThe COVID-19 pandemic has caused severe disruption of healthcare services worldwide and interrupted patients' access to essential services. During the first lockdown, many healthcare services were shut to all but emergencies. In this study, we aimed to determine the immediate and long-term indirect impact of COVID-19 health services utilisation on hepatocellular cancer (HCC) outcomes.MethodsA prospective cohort study was conducted from 1 March 2020 until 30 June 2020, correlating to the first wave of the COVID-19 pandemic. Patients were enrolled from tertiary hospitals in the UK and Germany with dedicated HCC management services. All patients with current or past HCC who were discussed at a multidisciplinary meeting (MDM) were identified. Any delay to treatment (DTT) and the effect on survival at one year were reported.ResultsThe median time to receipt of therapy following MDM discussion was 49 days. Patients with Barcelona Clinic Liver Cancer (BCLC) stages-A/B disease were more likely to experience DTT. Significant delays across all treatments for HCC were observed, but delay was most marked for those undergoing curative therapies. Even though severe delays were observed in curative HCC treatments, this did not translate into reduced survival in patients.ConclusionInterruption of routine healthcare services because of the COVID-19 pandemic caused severe delays in HCC treatment. However, DTT did not translate to reduced survival. Longer follow is important given the delay in therapy in those receiving curative therapy

DNA methylation-based classification of central nervous system tumours.

Accurate pathological diagnosis is crucial for optimal management of patients with cancer. For the approximately 100 known tumour types of the central nervous system, standardization of the diagnostic process has been shown to be particularly challenging-with substantial inter-observer variability in the histopathological diagnosis of many tumour types. Here we present a comprehensive approach for the DNA methylation-based classification of central nervous system tumours across all entities and age groups, and demonstrate its application in a routine diagnostic setting. We show that the availability of this method may have a substantial impact on diagnostic precision compared to standard methods, resulting in a change of diagnosis in up to 12% of prospective cases. For broader accessibility, we have designed a free online classifier tool, the use of which does not require any additional onsite data processing. Our results provide a blueprint for the generation of machine-learning-based tumour classifiers across other cancer entities, with the potential to fundamentally transform tumour pathology

Congenital Diarrhea and Cholestatic Liver Disease: Phenotypic Spectrum Associated with MYO5B Mutations

Myosin Vb (MYO5B) is a motor protein that facilitates protein trafficking and recycling in polarized cells by RAB11- and RAB8-dependent mechanisms. Biallelic MYO5B mutations are identified in the majority of patients with microvillus inclusion disease (MVID). MVID is an intractable diarrhea of infantile onset with characteristic histopathologic findings that requires life-long parenteral nutrition or intestinal transplantation. A large number of such patients eventually develop cholestatic liver disease. Bi-allelic MYO5B mutations are also identified in a subset of patients with predominant early-onset cholestatic liver disease. We present here the compilation of 114 patients with disease-causing MYO5B genotypes, including 44 novel patients as well as 35 novel MYO5B mutations, and an analysis of MYO5B mutations with regard to functional consequences. Our data support the concept that (1) a complete lack of MYO5B protein or early MYO5B truncation causes predominant intestinal disease (MYO5B-MVID), (2) the expression of full-length mutant MYO5B proteins with residual function causes predominant cholestatic liver disease (MYO5B-PFIC), and (3) the expression of mutant MYO5B proteins without residual function causes both intestinal and hepatic disease (MYO5B-MIXED). Genotype-phenotype data are deposited in the existing open MYO5B database in order to improve disease diagnosis, prognosis, and genetic counseling.This research was funded by Jubiläumsfonds der Österreichischen Nationalbank, grant no.16678 (to A.R.J.), grant no. 18019 (to G.-F.V.) and Tiroler Wissenschaftsfonds, grant No. 0404/2386 (toG.-F.V.).info:eu-repo/semantics/publishedVersio