DIGITAL NUDGES FOR USER ONBOARDING: TURNING VISITORS INTO USERS

Two design recommendations (digital nudges) for decreasing user churn in mobile apps are presented. We examine commitment and personalization nudges, both of which are linked to the extant literature, in the context of a randomized online experiment with 150 participants. Our experimental study reveals that commitment and personalization cues distinctly affect consumers\u27 intention to use a mobile app. Moreover, our study demonstrates that personalization amplifies the effect of commitment cues on users\u27 intention to use a mobile app

A multi-scale sub-voxel perfusion model to estimate diffusive capillary wall conductivity in multiple sclerosis lesions from perfusion MRI data.

We propose a new mathematical model to learn capillary leakage coefficients from dynamic susceptibility contrast MRI data. To this end, we derive an embedded mixed-dimension flow and transport model for brain tissue perfusion on a sub-voxel scale. This model is used to obtain the contrast agent concentration distribution in a single MRI voxel during a perfusion MRI sequence. We further present a magnetic resonance signal model for the considered sequence including a model for local susceptibility effects. This allows modeling MR signal-time curves that can be compared to clinical MRI data. The proposed model can be used as a forward model in the inverse modeling problem of inferring model parameters such as the diffusive capillary wall conductivity. Acute multiple sclerosis lesions are associated with a breach in the integrity of the blood brain barrier. Applying the model to perfusion MR data of a patient with acute multiple sclerosis lesions, we conclude that diffusive capillary wall conductivity is a good indicator for characterizing activity of lesions, even if other patient-specific model parameters are not well-known. This article is protected by copyright. All rights reserved

Function-oriented defect assessment in hybrid sheet molding compound tensile specimen using surrogate models

Glass fiber (GF) Sheet Molding Compound (SMC) composites are popular lightweight materials due to their good processability. Hybrid SMCs expand the field of operation, combining the high stiffness of unidirectional carbon fibers (CF) with the economic efficiency of GF. Combinations of manufacturing deviations (delamination, varying GF content, CF misorientation) occur during the production of hybrid SMCs and impede the mechanical performance of the part. A function-oriented quality assurance instead of strict tolerances is proposed. Finite element (FE) simulations are computationally too expensive for an assessment within the cycle time. Hence, surrogate models are trained on multiple parameterized FE simulations. The surrogate models shall allow for an individual functional assessment in real-time based on integrated measurement inputs. This work focuses on the generation of parametrized FE simulations for measurement inputs and surrogate modeling. Simulations and surrogate models show acceptable deviations from tensile tests for multiple combinations of manufacturing deviations. The measurement uncertainty of the stiffness prediction is assessed for both the FE simulation and the surrogate models in accordance with the Guide to the Expression of Uncertainty in Measurement (GUM)

Classification of trochlear dysplasia as predictor of clinical outcome after trochleoplasty

Purpose: Sulcus-deepening trochleoplasty restores the trochlear groove in patients with patellofemoral instability and underlying trochlear dysplasia. There are types of dysplasia both with (B and D) and without (A and C) a supratrochlear spur. The aim of this study was to identify influencing factors for the clinical outcome following trochleoplasty. Methods: Forty-four knees in 38 patients who underwent trochleoplasty for instability (type A in 9, B in 15, C in 9 and D in 11 knees) were assessed clinically with the Kujala score and radiologically with radiographs and MRI. The median follow-up was 4 (2-7.8) years. Results: At follow-up, the median Kujala score had improved from 68 (29-84) to 90 (42-100) points (P<0.001). Instability (P<0.001) and pain (P=0.027) decreased significantly, but in 3 knees, pain was worse postoperatively. Twenty-seven knees were ranked as excellent, 10 as good, 2 as fair and 5 as poor. Overall, dysplasia types B and D benefited more from surgery than types A and C. The postoperative MRI revealed no chondrolysis or subchondral necrosis, but deterioration of cartilage on the lateral trochlear facet was identified. Conclusion: Trochleoplasty is a useful and reliable surgical technique to improve patellofemoral instability in patients with a dysplastic trochlea. While improved stability is predictable, pain is less predictable and may even increase following surgery. The overall results were directly dependent on the type of the dysplasia, with a significantly better clinical outcome in type B and D. The clinical relevance of this study is that severe dysplasia can successfully be treated with trochleoplasty. Level of evidence: II

General scaling of maximum degree of synchronization in noisy complex networks

Peer reviewedPublisher PD

Embossing of a screw thread and TCP granules enhances the fixation strength of compressed ACL grafts with interference screws

Purpose: Fixation of soft tissue grafts with interference screws relies on the friction of the graft between the screw and the bone tunnel. The goal of this study was to precondition such grafts by mechanical compression in order to reduce anticipated and undesired viscoelastic adaptation of the graft to screw pressure. Further, the otherwise slippery graft surface was modified with impressed tricalcium phosphate granules (TCP) to improve friction and mechanical hold. Methods: Fresh flexor digitorum tendons from young bovines were used to create bundles with a diameter of 8-9mm and were divided into 10 groups to compare the pullout strength and bone damage in a variety of construct scenarios. Specifically, the effects of graft precompression to reduce preimplantation graft diameter were investigated. Further the effects of impressing TCP granules and/or a screw thread into the tendon surface during the compression process were studied. Results: In sawbone tests, radial graft compression allowed for a smaller bone tunnel (7mm), but resulted in a significantly lower pullout strength of 174N (95% CI: 97, 250), compared with controls [315N (204, 426)]. In contrast, TCP coated [402N (243, 561)], screw embossed grafts [458N (302, 614)], and the combination of TCP and embossing [409N (274, 543)] achieved higher pullout strengths when compared to the standard technique. In porcine bone, untreated grafts using an 8mm screw pulled out at 694±93N, significantly higher loads were required to pullout compressed grafts with or without TCP coating (870±74 and 878±131N), yet fixed with a 7mm screw. Conclusion: Modification of the tendon graft surface has a large influence on the biomechanical performance of interference screw fixation and results in less bone damage inflicted during insertion to a smaller tunnel diameter, while simultaneously achieving superior pullout strengt

Modeling the Formation of Urea-Water Sprays from an Air-Assisted Nozzle

Ammonia preparation from urea-water solutions is a key feature to ensure an effective reduction of nitrogen oxides in selective catalytic reduction (SCR) systems. Thereby, air-assisted nozzles provide fine sprays, which enhance ammonia homogenization. In the present study, a methodology was developed to model the spray formation by means of computational fluid dynamics (CFD) for this type of atomizer. Experimental validation data was generated in an optically accessible hot gas test bench using a shadowgraphy setup providing droplet velocities and size distributions at designated positions inside the duct. An adaption of the turbulence model was performed in order to correct the dispersion of the turbulent gas jet. The spray modeling in the near nozzle region is based on an experimentally determined droplet spectrum in combination with the WAVE breakup model. This methodology was applied due to the fact that the emerging two-phase flow will immediately disintegrate into a fine spray downstream the nozzle exit, which is also known from cavitating diesel nozzles. The suitability of this approach was validated against the radial velocity and droplet size distributions at the first measurement position downstream the nozzle. In addition, the simulation results serve as a basis for the investigation of turbulent dispersion phenomena and evaporation inside the spray

Detection of Clenbuterol in Urine of Meat Stock and Detection of Sulfamethazine in Pig Meat with the Biosensor Biacore Q

The biosensor-tool BIACORE Q was evaluated and validated to find out if it could be applicated on-site in an abattoir for the detection of veterinary drug residues. The study was focused on the following questions: - Is the biosensor-instrumentation robust enough for the on-site application in an abattoir? - Are reliable results fast enough available? - How many false-negative and false-positive results can be found? This feasibility study was carried out based on the examples clenbuterol and sulfamethazine. A total of 500 urine samples for clenbuterol residues (calf, cattle, pig, and sheep) as well as 160 meat samples for sulfamethazine residues (pig) was randomly taken at two different abattoirs in Switzerland. The samples were analysed with the Biosensor and commercially available Qflex Kits for clenbuterol and sulfamethazine. Positive samples were confirmed using LC-MS. From a technical point of view it is possible to use the biosensor directly at the slaughterhouse for screening of clenbuterol residues in urine samples and sulfamethazine residues in meat samples. Out of 500 urine samples, 3 positive samples were tested negative for clenbuterol using LC-MS. Two samples tested positive for sulfamethazine out of 160 samples were confirmed using LC-MS. The analysis method is rapid and reliable

Practical and Robust Secure Logging from Fault-Tolerant Sequential Aggregate Signatures

Keeping correct and informative log files is crucial for system maintenance, security and forensics. Cryptographic logging schemes offer integrity checks that protect a log file even in the case where an attacker has broken into the system. A relatively recent feature of these schemes is resistance against truncations, i.e. the deletion and/or replacement of the end of the log file. This is especially relevant as system intruders are typically interested in manipulating the later log entries that point towards their attack. However, there are not many schemes that are resistant against truncating the log file. Those that are have at least one of the following disadvantages: They are memory intensive (they store at least one signature per log entry), or fragile (i.e. a single error in the log renders the signature invalid and useless in determining where the error occurred). We obtain a publicly-verifiable secure logging scheme that is simultaneously robust, space-efficient and truncation secure with provable security under simple assumptions. Our generic construction uses forward-secure signatures, in a plain and a sequential aggregate variant, where the latter is additionally fault-tolerant, as recently formalized by Hartung et al. (PKC 2016). Fault-tolerant schemes can cope with a number of manipulated log entries (bounded a priori) and offer strong robustness guarantees while still retaining space efficiency. Our implementation and the accompanying performance measurements confirm the practicality of our scheme

Project Description - hermA: Automated modelling of hermeneutic processes

This article sketches the theoretical and methodological background of the interdisciplinary research project hermA. It assembles five disciplines form three academic institutions in Hamburg, that work collaboratively on medical research questions relating to the usage and application of annotation in hermeneutic text analysis in their specific fields. Their common research interest in hermA based to explore possibilities for the automation of annotations