To Reduce Bias, You Must Identify It First! Towards Automated Gender Bias Detection

Stereotypical gender representation in textbooks influences the personal and professional development of children. For example, if women do not pursue a STEM career because of gender stereotypes, this is not only an individual problem but also negative for society in general. It is hence crucial that textbooks do not convey gender stereotypes but are gender-balanced. Currently, textbook analysis is predominantly conducted manually, if at all. However, this is time-consuming and consequently cost-intensive. Therefore, as part of a design science research project, we developed a gender language analyzer. Our initial prototype is already capable of automatically analyzing textbooks and recommending suggestions regarding gender-balancing. We will further improve our prototype in the next design science research cycle (e.g., by integrating self-learning techniques). With this tool, publishers will be able to automatically analyze textbooks to reduce gender bias. Moreover, we provide the scientific community with design knowledge regarding automated identification of gender bias

Beyond the Rating Matrix: Debiasing Implicit Feedback Loops in Collaborative Filtering

Implicit feedback collaborative filtering recommender systems suffer from exposure bias that corrupts performance and creates filter bubbles and echo chambers. Our study aims to provide a practical method that does not inherit any exposure bias from the data given the information about the user, the choice, and the choice set associated with each observation. We validated the model’s functionality and capability to reduce bias and compared it to baseline mitigation strategies by simulation. Our model inherited little to no bias, while the other approaches failed to mitigate all bias. To the best of our knowledge, we are first to identify a feasible approach to tackle exposure bias in recommender systems that does not require arbitrary parameter choices or large model extensions. With our findings, we encourage the recommender systems community to move away from rating-matrix-based towards discrete-choice-based models

RENEB intercomparisons applying the conventional Dicentric Chromosome Assay (DCA)

Purpose: Two quality controlled inter-laboratory exercises were organized within the EU project ‘Realizing the European Network of Biodosimetry (RENEB)’ to further optimize the dicentric chromosome assay (DCA) and to identify needs for training and harmonization activities within the RENEB network. Materials and methods: The general study design included blood shipment, sample processing, ana lysis of chromosome aberrations and radiation dose assessment. After manual scoring of dicentric chro mosomes in different cell numbers dose estimations and corresponding 95% confidence intervals were submitted by the participants. Results: The shipment of blood samples to the partners in the European Community (EU) were per formed successfully. Outside the EU unacceptable delays occurred. The results of the dose estimation demonstrate a very successful classification of the blood samples in medically relevant groups. In com parison to the 1st exercise the 2nd intercomparison showed an improvement in the accuracy of dose estimations especially for the high dose point. Conclusions: In case of a large-scale radiological incident, the pooling of ressources by networks can enhance the rapid classification of individuals in medically relevant treatment groups based on the DCA. The performance of the RENEB network as a whole has clearly benefited from harmonization processes and specific training activities for the network partners.European Commission (FP7, GA 295513

RENEB intercomparisons applying the conventional Dicentric Chromosome Assay (DCA)

Purpose: Two quality controlled inter-laboratory exercises were organized within the EU project ‘Realizing the European Network of Biodosimetry (RENEB)’ to further optimize the dicentric chromosome assay (DCA) and to identify needs for training and harmonization activities within the RENEB network. Materials and methods: The general study design included blood shipment, sample processing, analysis of chromosome aberrations and radiation dose assessment. After manual scoring of dicentric chromosomes in different cell numbers dose estimations and corresponding 95% confidence intervals were submitted by the participants. Results: The shipment of blood samples to the partners in the European Community (EU) were performed successfully. Outside the EU unacceptable delays occurred. The results of the dose estimation demonstrate a very successful classification of the blood samples in medically relevant groups. In comparison to the 1st exercise the 2nd intercomparison showed an improvement in the accuracy of dose estimations especially for the high dose point. Conclusions: In case of a large-scale radiological incident, the pooling of ressources by networks can enhance the rapid classification of individuals in medically relevant treatment groups based on the DCA. The performance of the RENEB network as a whole has clearly benefited from harmonization processes and specific training activities for the network partners

Fructooligosacharides Reduce Pseudomonas aeruginosa PAO1 Pathogenicity through Distinct Mechanisms

Pseudomonas aeruginosa is ubiquitously present in the environment and acts as an opportunistic pathogen on humans, animals and plants. We report here the effects of the prebiotic polysaccharide inulin and its hydrolysed form FOS on this bacterium. FOS was found to inhibit bacterial growth of strain PAO1, while inulin did not affect growth rate or yield in a significant manner. Inulin stimulated biofilm formation, whereas a dramatic reduction of the biofilm formation was observed in the presence of FOS. Similar opposing effects were observed for bacterial motility, where FOS inhibited the swarming and twitching behaviour whereas inulin caused its stimulation. In co-cultures with eukaryotic cells (macrophages) FOS and, to a lesser extent, inulin reduced the secretion of the inflammatory cytokines IL-6, IL-10 and TNF- a . Western blot experiments indicated that the effects mediated by FOS in macrophages are associated with a decreased activation of the NF- k B pathway. Since FOS and inulin stimulate pathway activation in the absence of bacteria, the FOS mediated effect is likely to be of indirect nature, such as via a reduction of bacterial virulence. Further, this modulatory effect is observed also with the highly virulent ptxS mutated strain. Co-culture experiments of P. aeruginosa with IEC18 eukaryotic cells showed that FOS reduces the concentration of the major virulence factor, exotoxin A, suggesting that this is a possible mechanism for the reduction of pathogenicity. The potential of these compounds as components of antibacterial and anti-inflammatory cocktails is discussed.The authors acknowledge financial support from FEDER funds and Fondo Social Europeo through grants from the Spanish Ministry of Economy and Competitiveness (grants SAF2011-22922, SAF2011-22812) the Andalusian regional government Junta de Andalucía (grant CVI-7335) and the Centre of Networked Biomedical Research on Hepatic and Digestive Diseases (CIBERehd) which is funded by the Carlos III Health Institute and the Ramón Areces Foundation, Spain

Atom probe reconstruction with a locally varying tip shape

In this thesis, a new approach for the reconstruction of data taken from an atom probe tomography experiment is presented. The goal of the study is to develop an algorithm, which is able to overcome well-known drawbacks of the conventional reconstruction technique, mainly caused by local magnification effects. At the same time, the algorithm should be easy to use and also fast enough, so that it might be routinely used as an improved alternative to the established reconstruction technique. The idea is based on the already existing possibility to simulate an entire atom probe experiment on a realistic length. Since the successive calculation of ion trajectories starting at the emitter surface and hitting the detector after a flight of a few centimeters can be realized, the concept is designed to invert the field evaporation process by making use of this trajectory calculation. To this end, the detected emitter volume needs to be rebuilt from the bottom to the top, which is an important difference compared to the conventional technique. In a first test, this inversion of the simulated experiment is demonstrated for a few prominent example cases. The decisive criterion for the positioning of an atom at a specific lattice site on the current emitter surface is the accordance of the impact position of the corresponding calculated trajectory with the measured coordinates on the detector. For every possible surface position, first an ion trajectory is calculated and its detector impact position is compared to the measured impact position. Finally, the best-matching trajectory defines the reconstruction coordinates. The approach is performed for some prominent example emitter structures with strongly varying evaporation fields of the involved material, which is known for causing tremendous artifacts in the reconstruction derived by the standard technique. In this first attempt, the algorithm is restricted to a rigid lattice, which means that detected atoms can only be positioned at sites belonging to the former lattice of the emitter. In a second step, the restriction to a rigid lattice is dropped. In this way, the reconstruction algorithm describes a more realistic scenario, since the exact lattice structure and its orientation might be unknown in the majority of experiments. The possibilities and limitations of the approach are discussed. It is found that an additional criterion for the determination of the reconstruction coordinates is needed in this case, since the algorithm is very sensitive to the misplacement of atoms. The stability can be significantly improved by the consideration of an inter-atomic potential, which acts as a filter that exclusively allows surface sites with a sufficiently high amount of neighbor atoms. For a perfect detector efficiency the algorithm yields promising results, but a decrease of the efficiency towards realistic values gives rise to artifacts. As a consequence of these numerical experiments, a new concept has been developed, which neglects the consideration of exact ion trajectories in order to make the algorithm more stable and fast. This third approach assumes rotational symmetry for the investigated emitter volume. An absolutely new characteristic of the technique is the capability to extract the shape of a field emitter directly from the observed pattern of ion impacts on the detector. This feature is a very important difference to the conventional technique, which assumes a constant spherical emitter shape. To the best of the authors knowledge, such a technique with this capability did not exist before. The promising features are demonstrated for several simulated but nevertheless realistic emitter structures. The improved quality of the reconstruction that can be achieved by the application of the here developed technique is shown by direct comparison to the result of the established reconstruction approach. The impressive benefits are illustrated for relevant emitter structures containing either precipitates or layers of different materials with strongly varying evaporation fields (44% or 56% relative variation). In addition, a simple modification of the technique is described, which yields homogenized atomic densities in the reconstructed volumes. Without this modification, the emitter surface is treated like a rigid curved plane, which is shifted upwards with every reconstructed atom during reconstruction. Once the surface is no longer considered to be rigid, individual parts can be lifted separately, yielding a significantly homogenized atomic density. Finally, the new concept of shape extraction is extended for the application to arbitrary emitter structures. The main idea of extracting the information about the emitter shape from the local density of measured events on the detector is maintained. In order to extend the approach to the application to structures without rotational symmetry, a relation between the local density of events on the detector and the Gaussian curvature on the emitter surface is derived. With the help of an iterative finite difference method, the Gaussian curvature at several positions on the tip surface is set. Consequently, a reasonable description of the emitter surface can be obtained and the reconstruction of an arbitrary data set can be performed. The concept is tested and discussed for a simulated example emitter structure

Modelling an Acoustically Perturbed Rocket Engine Combustion Chamber with Cryogenic Propellant Injection

An experimental combustor, dubbed BKH, has been developed at DLR Lampoldshausen to investigate combustion instability phenomena. The combustor operates with cryogenic liquid oxygen and hydrogen propellants at supercritical pressure conditions analogous to real rocket engines. The BKH combustor has been modelled using a specially developed version of the DLR TAU code with real gas capabilities for supercritical injection. The TAU code CFD results are compared with optical data recorded during BKH experiments. The numerical flame and liquid oxygen distributions match experimental observations. The acoustic field inside the BKH combustor has also been calculated separately with an acoustic solver that uses a realistic acoustic property distribution from the CFD calculations. The resonant modes are successfully predicted using the acoustic solver

Experimental and numerical study of transcritical oxygen-hydrogen rocket flame response to transverse acoustic excitation

The response of a transcritical oxygen-hydrogen flame to transverse acoustic velocity was investigated using a combination of experimental analyses and numerical modelling. The experiment was conducted on a rectangular rocket combustor with shear coaxial injectors and continuously forced transverse acoustic field. Simultaneous high-speed shadowgraph and filtered OH* radiation images were collected and reduced using dynamic mode decomposition in order to characterise the flame response to the acoustic disturbance. CFD modelling of a representative single injector under forcing conditions was carried out to gain insights into the three-dimensional features of the reacting flow field. Invisible in the 2D projection, the model reveals that the excited LOX jet develops into a flattened and widened structure normal to the imposed acoustic velocity. The comparison of co-located structures allowed features in the imaging to be attributed to the deformation and transverse displacement of lower density oxygen surrounding the denser liquid oxygen core by the transverse acoustic velocity