Eye-Tracking-Based Classification of Information Search Behavior Using Machine Learning: Evidence from Experiments in Physical Shops and Virtual Reality Shopping Environments

Classifying information search behavior helps tailor recommender systems to individual customers’ shopping motives. But how can we identify these motives without requiring users to exert too much effort? Our research goal is to demonstrate that eye tracking can be used at the point of sale to do so. We focus on two frequently investigated shopping motives: goal-directed and exploratory search. To train and test a prediction model, we conducted two eye-tracking experiments in front of supermarket shelves. The first experiment was carried out in immersive virtual reality; the second, in physical reality—in other words, as a field study in a real supermarket. We conducted a virtual reality study, because recently launched virtual shopping environments suggest that there is great interest in using this technology as a retail channel. Our empirical results show that support vector machines allow the correct classification of search motives with 80% accuracy in virtual reality and 85% accuracy in physical reality. Our findings also imply that eye movements allow shopping motives to be identified relatively early in the search process: our models achieve 70% prediction accuracy after only 15 seconds in virtual reality and 75% in physical reality. Applying an ensemble method increases the prediction accuracy substantially, to about 90%. Consequently, the approach that we propose could be used for the satisfiable classification of consumers in practice. Furthermore, both environments’ best predictor variables overlap substantially. This finding provides evidence that in virtual reality, information search behavior might be similar to the one used in physical reality. Finally, we also discuss managerial implications for retailers and companies that are planning to use our technology to personalize a consumer assistance system

A molecular state of correlated electrons in a quantum dot

Correlation among particles in finite quantum systems leads to complex behaviour and novel states of matter. One remarkable example is predicted to occur in a semiconductor quantum dot (QD) where at vanishing density the Coulomb correlation among electrons rigidly fixes their relative position as that of the nuclei in a molecule. In this limit, the neutral few-body excitations are roto-vibrations, which have either rigid-rotor or relative-motion character. In the weak-correlation regime, on the contrary, the Coriolis force mixes rotational and vibrational motions. Here we report evidence of roto-vibrational modes of an electron molecular state at densities for which electron localization is not yet fully achieved. We probe these collective modes by inelastic light scattering in QDs containing four electrons. Spectra of low-lying excitations associated to changes of the relative-motion wave function -the analogues of the vibration modes of a conventional molecule- do not depend on the rotational state represented by the total angular momentum. Theoretical simulations via the configuration-interaction (CI) method are in agreement with the observed roto-vibrational modes and indicate that such molecular excitations develop at the onset of short-range correlation.Comment: PDF file only; 24 pages, 7 figures, 2 table. Supplementary Information include

Subtoxic Concentrations of Hepatotoxic Drugs Lead to Kupffer Cell Activation in a Human In Vitro Liver Model

Drug induced liver injury (DILI) is an idiosyncratic adverse drug reaction leading to severe liver damage. Kupffer cells (KC) sense hepatic tissue stress/damage and therefore could be a tool for the estimation of consequent effects associated with DILI. Aim of the present study was to establish a human in vitro liver model for the investigation of immune-mediated signaling in the pathogenesis of DILI. Hepatocytes and KC were isolated from human liver specimens. The isolated KC yield was cells/g liver tissue with a purity of >80%. KC activation was investigated by the measurement of reactive oxygen intermediates (ROI, DCF assay) and cell activity (XTT assay). The initial KC activation levels showed broad donor variability. Additional activation of KC using supernatants of hepatocytes treated with hepatotoxic drugs increased KC activity and led to donor-dependent changes in the formation of ROI compared to KC incubated with supernatants from untreated hepatocytes. Additionally, a compound- and donor-dependent increase in proinflammatory cytokines or in anti-inflammatory cytokines was detected. In conclusion, KC related immune signaling in hepatotoxicity was successfully determined in a newly established in vitro liver model. KC were able to detect hepatocyte stress/damage and to transmit a donor- and compound-dependent immune response via cytokine production

Shape-independent scaling of excitonic confinement in realistic quantum wires

The scaling of exciton binding energy in semiconductor quantum wires is investigated theoretically through a non-variational, fully three-dimensional approach for a wide set of realistic state-of-the-art structures. We find that in the strong confinement limit the same potential-to-kinetic energy ratio holds for quite different wire cross-sections and compositions. As a consequence, a universal (shape- and composition-independent) parameter can be identified that governs the scaling of the binding energy with size. Previous indications that the shape of the wire cross-section may have important effects on exciton binding are discussed in the light of the present results.Comment: To appear in Phys. Rev. Lett. (12 pages + 2 figures in postscript

Factors affecting the acculturation strategies of unaccompanied refugee minors in Germany

BackgroundDifferent acculturation strategies might be related to different mental health outcomes and social participation of unaccompanied refugee minors (URMs), but little is known about which factors influence this acculturation process. Therefore, the aim of this investigation was to examine the impact of individual, stress-related, and contextual factors on the acculturation process of URMs in Germany.MethodsA sample of N = 132 URMs living in child and youth welfare service facilities in Germany completed questionnaires about their acculturation orientation, traumatic experiences, daily stressors, asylum stress, and perceived social support between June 2020 and October 2021. This investigation is part of the multi-center randomized control trial BETTER CARE. Data were analyzed descriptively and via multiple hierarchical regression.ResultsIntegration (43.5%) and Assimilation (37.1%) were the most common acculturation strategies used by URMs. Multiple hierarchical regression models showed that daily stressors (e.g., the lack of money) were associated with a stronger orientation toward the home country, whereas traumatic events were associated with a weaker orientation toward their home country. No significant predictors were found for the orientation toward the host country.DiscussionOverall, URMs in Germany showed favorable acculturation strategies. Nevertheless, daily stressors and traumatic experiences might influence this process. The implications for practitioners and policymakers are discussed with a view to further improving the acculturation process of URMs in Germany.Clinical Trial Registration: German Clinical Trials Register, DRKS00017453 https://drks.de/search/de/trial/DRKS00017453. Registered on December 11, 2019

Mental health problems in unaccompanied young refugees and the impact of post-flight factors on PTSS, depression and anxiety–A secondary analysis of the Better Care study

BackgroundUnaccompanied young refugees (UYRs) show elevated levels of mental distress such as post-traumatic stress symptoms (PTSS), depression, and anxiety. The individual post-arrival situation in the host country plays an important role in increasing or reducing mental health risks for these vulnerable children and youth. The study aims at examining the impact of pre- and post-migration factors on the mental health of UYRs.MethodsA cross-sectional survey of N = 131 young refugees (81.7% male, M = 16.9 years old) was conducted in 22 children and youth welfare service (CYWS) facilities in Germany. The participants provided information about pre- and post-flight experiences. Standardized measures were used to assess post-traumatic stress symptoms (CATS-2), symptoms of depression (PHQ-9), and anxiety (GAD-7). Daily stressors were assessed with the Daily Stressors Scale for Young Refugees (DSSYR), sociocultural adaptation with the Brief Sociocultural Adaptation Scale (BSAS), satisfaction with social support with the Social Support Questionnaire (SSQ6-G).ResultsOur results demonstrated clinical levels of PTSS in 42.0% of the participants, depression in 29.0%, and anxiety in 21.4%. Hierarchical regression analyses revealed that a higher number of traumatic events and social daily stressors predicted higher levels in all three domains of mental health problems. PTSS and anxiety were also predicted by the distress related to the residence status, depressive symptoms were additionally predicted by sociocultural adaptation, less family contact and length of stay. The satisfaction with social support was not a significant predictor in the regression models.ConclusionUnaccompanied young refugees in CYWS facilities are a highly vulnerable population. As traumatic events, daily stressors and level of contact to family directly impacted UYRs mental health, interventions should be trauma-focused, but also contain modules on how to cope with daily stressors. On the policy and practical level, stakeholders in host countries are called for establishing measures to reduce post-migration stressors and enhance support for UYRs on all levels

Linear and nonlinear optical properties of realistic quantum-wire structures: The dominant role of Coulomb correlation

A systematic analysis of the linear and nonlinear optical properties of realistic quantum wires is presented. The proposed theoretical approach, based on a set of generalized semiconductor Bloch equations, provides a full three-dimensional multisubband description of carrier-carrier correlation for any profile of the confinement potential, thus allowing a direct comparison with experiments on available structures. In agreement with previous investigations based on simplified one-dimensional models, our analysis shows that, also for realistic quantum-wire structures, electron-hole Coulomb correlation completely removes the one-dimensional band-edge singularities from the linear-absorption spectra. Moreover, we find that this effect is present also at high densities (corresponding to gain regimes) and contributes significantly in suppressing the ideal sharp features of the free-carrier density of states. The multisubband nature of available state-of-the-art structures is found to play a dominant role in determining the overall spectral shape in the whole density range