Technische Universität Berlin
Recent publications
Modulation of commensal gut microbiota is increasingly recognized as a promising strategy to reduce mortality in patients with malignant diseases, but monitoring for dysbiosis is generally not routine clinical practice due to equipment, expertise and funding required for sequencing analysis. A low-threshold alternative is microbial diversity profiling by single-cell flow cytometry (FCM), which we compared to 16S rRNA sequencing in human fecal samples and employed to characterize longitudinal changes in the microbiome composition of patients with aggressive B-cell non-Hodgkin lymphoma undergoing chemoimmunotherapy. Diversity measures obtained from both methods were correlated and captured identical trends in microbial community structures, finding no difference in patients' pretreatment alpha or beta diversity compared to healthy controls and a significant and progressive loss of alpha diversity during chemoimmunotherapy. Our results highlight the potential of FCM-based microbiome profiling as a reliable and accessible diagnostic tool that can provide novel insights into cancer therapy-associated dysbiosis dynamics.
COVID-19 has caused unprecedented disruption to previously settled everyday routines, prompting a period of forced experimentation as people have adjusted to rapid changes in their private and working lives. For discussions regarding consumption, this period of experimentation has been interesting, as the apparent instability has disturbed the ongoing trajectory of consumption practices, and with it has created possibilities for transition toward sustainability. In this article, we examine food practices (e.g., food shopping, preparation, and eating) in seven countries (France, Germany, Italy, Netherlands, Norway, UK, and Vietnam) to assess what we can learn to accelerate transitions toward sustainable consumption. Grounded in a practice theoretical approach, our empirical analysis shows how disruption of everyday routines has generated socio-materially bounded experimentation. We demonstrate commonalities across contexts in how lockdown measures have restricted the performance of previously taken-for-granted practices. We also show diversity in experimentation as food consumption is entangled in other everyday practices. Our study, on one hand, portrays how adaptation of food practices allows disruption to be managed, demonstrating creativity in working within and around restrictions to continue to provide services for everyday life. On the other hand, we reveal that the capacity of experimentation is not evenly distributed among people and this variation helps in identifying the wider socio-material conditions that constrain and enable opportunities for readjustment. Understanding disparities that affect experimentation (e.g., integration of food practices with work and caring practices) is informative when thinking about how to stimulate sustainability transformations in food practices and provides critical reflections on strategies to enable sustainable consumption.
Standfirst Among the existing machine learning frameworks, reservoir computing demonstrates fast and low-cost training, and its suitability for implementation in various physical systems. This Comment reports on how aspects of reservoir computing can be applied to classical forecasting methods to accelerate the learning process, and highlights a new approach that makes the hardware implementation of traditional machine learning algorithms practicable in electronic and photonic systems.
Electronic properties of selected quantum dot (QD) systems are surveyed based on the multi-band k·p method, which we benchmark by direct comparison to the empirical tight-binding algorithm, and we also discuss the newly developed “linear combination of quantum dot orbitals” method. Furthermore, we focus on two major complexes: First, the role of antimony incorporation in InGaAs/GaAs submonolayer QDs and In 1− x Ga x As y Sb 1− y /GaP QDs, and second, the theory of QD-based quantum cascade lasers and the related prospect of room temperature lasing.
Background In 2013–2014, Israel accelerated adoption of activity-based payments to hospitals. While the effects of such payments on patient length of stay (LoS) have been examined in several countries, there have been few analyses of incentive effects in the Israeli context of capped reimbursements and stretched resources. Methods We examined administrative data from the Israel Ministry of Health for 14 procedures from 2005 to 2016 in all not-for-profit hospitals (97% of the acute care beds). Survival analyses using a Weibull distribution allowed us to examine the non-negative and right-skewed data. We opted for a Bayesian approach to estimate relative change in LoS. Results LoS declined in 7 of 14 procedures analyzed, notably, in 6 out of 7 urological procedures. In these procedures, reduction in LoS ranged between 11% and 20%. The estimation results for the control variables are mixed and do not indicate a clear pattern of association with LoS. Conclusions The decrease in LoS freed resources to treat other patients, which may have resulted in reduced waiting times. It may have been more feasible to reduce LoS for urological procedures since these had relatively long LoS. Policymakers should pay attention to the effects of decreases in LoS on quality of care. Stretched hospital resources, capped reimbursements, retrospective subsidies and underpriced procedures may have limited hospitals' ability to reduce LoS for other procedures where no decrease occurred (e.g., general surgery).
The Special Issue “Connecting materials science with fungal biology” celebrates recent breakthroughs in the fabrication of fungal-based materials, all of which have been made possible by the interdisciplinary and transdisciplinary collaboration of fungal biologists and biotechnologists with artists, designers, materials scientists, and architects. It features conceptual considerations and latest developments of these joint research efforts and the paradigm shift that is involved. The aim of this collection of twelve papers is to highlight the infinite possibilities for the development of innovative fungal-based materials which can be realized through integrating the knowledge and methods from different disciplines.
In this paper, we report on polarization combining two-dimensional grating couplers (2D GCs) on amorphous Si:H, fabricated in the backend of line of a photonic BiCMOS platform. The 2D GCs can be used as an interface of a hybrid silicon photonic coherent transmitter, which can be implemented on bulk Si wafers. The fabricated 2D GCs operate in the telecom C-band and show an experimental coupling efficiency of − 5 dB with a wafer variation of ± 1.2 dB. Possibilities for efficiency enhancement and improved performance stability in future design generations are outlined and extension toward O-band devices is also investigated. Online available at: https://rdcu.be/cLRfN
Physical unclonable functions (PUFs) have been proposed as a way to identify and authenticate electronic devices. Recently, several ideas have been presented to that aim to achieve the same for quantum devices. Some of these constructions apply single-qubit gates in order to provide a secure fingerprint of the quantum device. In this work, we formalize the class of classical readout quantum PUFs (CR-QPUFs) using the statistical query (SQ) model and explicitly show insufficient security for CR-QPUFs based on single-qubit rotation gates, when the adversary has SQ access to the CR-QPUF. We demonstrate how a malicious party can learn the CR-QPUF characteristics and forge the signature of a quantum device through a modelling attack using a simple regression of low-degree polynomials. The proposed modelling attack was successfully implemented in a real-world scenario on real IBM Q quantum machines. We thoroughly discuss the prospects and problems of CR-QPUFs where quantum device imperfections are used as a secure fingerprint.
Surgical face masks reduce the spread of airborne pathogens but also disturb the flow of information between individuals. The risk of getting seriously ill after infection with SARS-COV-2 during the present COVID-19 pandemic amplifies with age, suggesting that face masks should be worn especially during face-to-face contact with and between older people. However, the ability to accurately perceive and understand communication signals decreases with age, and it is currently unknown whether face masks impair facial communication more severely in older people. We compared the impact of surgical face masks on dynamic facial emotion recognition in younger (18–30 years) and older (65–85 years) adults (N = 96) in an online study. Participants watched short video clips of young women who facially expressed anger, fear, contempt or sadness. Faces of half of the women were covered by a digitally added surgical face mask. As expected, emotion recognition accuracy declined with age, and face masks reduced emotion recognition accuracy in both younger and older participants. Unexpectedly, the effect of face masks did not differ between age groups. Further analyses showed that masks also reduced the participants’ overall confidence in their emotion judgements, but not their performance awareness (the difference between their confidence ratings for correct and incorrect responses). Again, there were no mask-by-age interactions. Finally, data obtained with a newly developed questionnaire ( attitudes towards face masks, atom ) suggest that younger and older people do not differ in how much they feel impaired in their understanding of other people’s emotions by face masks or how useful they find face masks in confining the COVID-19 pandemic. In sum, these findings do not provide evidence that the impact of face masks on the decoding of facial signals is disproportionally larger in older people.
Sustainability in tourism is a topic of global relevance, finding multiple mentions in the United Nations Sustainable Development Goals. The complex task of balancing tourism's economic, environmental, and social effects requires detailed and up-to-date data. This paper investigates whether online platform data can be employed as an alternative data source in sustainable tourism statistics. Using a web-scraped dataset from a large online tourism platform, a sustainability label for accommodations can be predicted reasonably well with machine learning techniques. The algorithmic prediction of accommodations' sustainability using online data can provide a cost-effective and accurate measure that allows to track developments of tourism sustainability across the globe with high spatial and temporal granularity. Supplementary information: The online version contains supplementary material available at 10.1140/epjds/s13688-022-00354-6.
Ferroelectric tunnel junction (FTJ) is a promising emerging memristor for the artificial synapse in neuro-inspired computing, which has parallel data processing and low power consumption. The achievement of high-performance electronic synapses requires in-depth exploration of the correlation between the material properties and the device performances as well as the related physical mechanism, which are, however, still quite lacking. We demonstrate here a robust electronic synapse realized by epitaxial ferroelectric Hf0.5Zr0.5O2 (HZO) films with a high Curie temperature of 930 °C and a pristine highly uniform polarization. Based on the optimized ferroelectric HZO film and in-depth understanding of the FTJ mechanism, a robust and high-performance electronic synapse has been successfully realized with high ON/OFF ratio of >500, large continuous conductance regulation range of 1–250 nS and high reliability with the retention of >10⁴ s. Such electronic synapses show good multilevel conductance modulations and synaptic behaviors, such as long-term potentiation (LTP), long-term depression (LTD) and spike-timing dependent plasticity (STDP). A simulated neural network with the synaptic characteristics indicates high recognition accuracy (93.7%) for MNIST database. These results pave a pathway to apply HZO based electronic synapses as the active block in future neuromorphic computing.
In recent years, there has been a substantial increase in the induced seismicity associated with geothermal systems. However, understanding and modeling of injection-induced seismicity have still remained as a challenge. This paper presents a two-dimensional fully thermo-hydro-mechanical (THM) coupled boundary element approach to characterize the fault response to forced fluid injection and assess the effect of different injection protocols on seismic risk mitigation as well as permeability enhancement. The laboratory-derived rate-and-state friction law was used to capture the frictional paradigm observed in mature faults produced in granite rocks. All phases of stick-slip cycles, including aseismic slip, propagation of dynamic rupture, and interseismic periods, were simulated. The modeling results showed that the residual values of effective normal stress and static shear stress after a particular event completely dominate the constitutive behavior of fault friction during the next seismic event. The seismic energy analyses indicated that there is a negative correlation between the seismic magnitude and the total injected volume, such that a prolonged monotonic injection eventually results in the steady slip, rather than the seismic slip. Several fluid injection protocols were designed based on a volume-controlled (VC) approach and traffic light systems (TLS) to explore their effectiveness on the seismic risk mitigation and permeability enhancement. The results showed that cyclic injection based on TLS is the most effective approach for irreversible permeability enhancement of faults through promoting slow and steady slips. Our numerical simulations also revealed that fluid extraction (backflow-fixing bottom hole pressure at atmospheric pressure), regardless of the injection style, can considerably reduce the seismicity-related risks by preventing the fast-accelerated fracture slip during the post-injection stage. This study presents novel insights into modeling the rate-and-state governed faults exposed to forced fluid injection, and provides useful approaches for shear stimulation of faults with reduced seismic risks.
This paper examines the reciprocal relationship between artists and cities by analyzing how cities influence artists' critical engagement. We hypothesize that a set of specific urban conditions suggests distinct forms of artistic engagement, which we call the artistic spirit of the city. Based on qualitative fieldwork in four cities in Germany and Israel, we explore how cities influence the self-perception, motivation, and practice of the artists who work and live in them. We found that artists are indeed highly influenced by the particular spirit or the intrinsic logic of the city in which they live and work, and they are embedded within the city's particular socio-political and spatial structures, which in turn influence their outlooks and visions as artistic city-zens.
Pulsating heat pipes (PHPs) are increasingly used for the thermal management of hot spots. A major goal in the design process of PHPs is the handling of high heat fluxes and, thus, improved thermal resistance. The thermal resistance can be reduced by increasing the latent or convective heat transfer. Two design approaches with that goal are presented in this study: a flower-shaped PHP design to increase the latent heat transfer and a star-shaped PHP design to increase the convective heat transfer. We compare the proposed designs to a state-of-the-art, meander-shaped PHP design. Thereby, we quantify the thermal performance and the flow pattern of the different PHP designs. The copper PHPs were filled with acetone and tested horizontally and vertically. The filling ratios varied from 0 % to 90 % and the heat inputs increased from 50 W to 200 W. Our results illustrate that the flower-shaped PHP design reduces the thermal resistance by 7 % in horizontal and 12 % in vertical position. We found a strong interrelation between flow pattern and heat transfer in PHPs. Our study shows that phase change plays a key role for the thermal resistance. Based on that, we provide design criteria to optimize the thermal capabilities of PHPs with a special focus on hot spots.
For a fixed simple digraph F and a given simple digraph D, an F-free k-coloring of D is a vertex-coloring in which no induced copy of F in D is monochromatic. We study the complexity of deciding for fixed F and k whether a given simple digraph admits an F-free k-coloring. Our main focus is on the restriction of the problem to planar input digraphs, where it is only interesting to study the cases k∈{2,3}. From known results it follows that for every fixed digraph F whose underlying graph is not a forest, every planar digraph D admits an F-free 2-coloring, and that for every fixed digraph F with Δ(F)≥3, every oriented planar graph D admits an F-free 3-coloring. We show in contrast, that • if F is an orientation of a path of length at least 2, then it is NP-hard to decide whether an acyclic and planar input digraph D admits an F-free 2-coloring. • if F is an orientation of a path of length at least 1, then it is NP-hard to decide whether an acyclic and planar input digraph D admits an F-free 3-coloring.
In this paper we study anisotropic weighted (p, q)-equations with a parametric right-hand side depending on the gradient of the solution. Under very general assumptions on the data and by using a topological approach, we prove existence and uniqueness results and study the asymptotic behavior of the solutions when both the q(·)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$q(\cdot )$$\end{document}-Laplacian on the left-hand side and the reaction term are modulated by a parameter. Moreover, we present some properties of the solution sets with respect to the parameters.
A distributed optimal control problem for a semilinear parabolic partial differential equation is investigated. The stability of locally optimal solutions with respect to perturbations of the initial data is studied. Based on different types of sufficient optimality conditions for a local solution of the unperturbed problem, Lipschitz or Hölder stability with respect to perturbations are proved. Moreover, a particular example with semilinear equation, constant initial data, and standard quadratic tracking type objective functional is constructed that has at least two different locally optimal solutions. By the perturbation analysis, the existence of a problem with non-constant initial data is shown that also has at least two different locally optimal solutions.
Enzymes continue to gain recognition as valuable tools in synthetic chemistry as they enable transformations, which elude conventional organochemical approaches. As such, the progressing expansion of the biocatalytic arsenal has introduced unprecedented opportunities for new synthetic strategies and retrosynthetic disconnections. As a result, enzymes have found a solid foothold in modern natural product synthesis for applications ranging from the generation of early chiral synthons to endgame transformations, convergent synthesis, and cascade reactions for the rapid construction of molecular complexity. As a primer to the state-of-the-art concerning strategic uses of enzymes in natural product synthesis and the underlying concepts, this review highlights selected recent literature examples, which make a strong case for the admission of enzymatic methodologies into the standard repertoire for complex small-molecule synthesis.
In precision agriculture, methods for analysing 3D point clouds of plants have been introduced, particularly pointing to the high accuracy of light detection and ranging (LiDAR) laser scanning under field conditions. In the present work, LiDAR-based 3D point clouds of cherry trees (n = 255) were analysed for estimating the leaf area as the main factor for water interception. Canopies were scanned for segmenting leaf area pointing to a high variability of canopy surface. The derived tree-specific data of leaf area index (LAI) were implemented into the Community Land Model (CLM), which takes into account canopy interception processes during rainfall events. During canopy development of perennial trees the LAI increased resulting in increased water interception. Events with low rain fall the interception reached 38-100 % capturing LAI of 0.76-2.11 m 2 /m 2 , respectively. In high rainfall events, interception varied 10-14 % capturing the same LAI range. An equation for describing the varying effects of rainfall intensity and LAI is proposed. The evapotranspiration and water interception data point to a substantial decrease of effective water supply that varies tree-individually during the season. In commercial fruit production, the proposed method can support precise irrigation management.
A two-step model for generating random polytopes is considered. For parameters d, m, and p, the first step is to generate a simple polytope P whose facets are given by m uniform random hyperplanes tangent to the unit sphere in , and the second step is to sample each vertex of P independently with probability p and let Q be the convex hull of the sampled vertices. We establish results on how well Q approximates the unit sphere in terms of m and p as well as asymptotics on the combinatorial complexity of Q for certain regimes of p.
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15,244 members
Axel Küpper
  • Department of Telecommunication Systems
Stefan Frielingsdorf
  • Department of Chemistry
Patrick Ehrenbrink
  • Department of Software Engineering and Theoretical Computer Science
Anatolij Zubow
  • Department of Telecommunication Systems
Hendrik Kalb
  • Department of Information Systems and Knowledge-Based Methods
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