Humboldt-Universität zu Berlin
Recent publications
Using a map in an unfamiliar environment requires identifying correspondences between elements of the map's allocentric representation and elements in egocentric views. Aligning the map with the environment can be challenging. Virtual reality (VR) allows learning about unfamiliar environments in a sequence of egocentric views that correspond closely to the perspectives and views that are experienced in the actual environment. We compared three methods to prepare for localization and navigation tasks performed by teleoperating a robot in an office building: studying a floor plan of the building and two forms of VR exploration. One group of participants studied a building plan, a second group explored a faithful VR reconstruction of the building from a normal-sized avatar's perspective, and a third group explored the VR from a giant-sized avatar's perspective. All methods contained marked checkpoints. The subsequent tasks were identical for all groups. The self-localization task required indication of the approximate location of the robot in the environment. The navigation task required navigation between checkpoints. Participants took less time to learn with the giant VR perspective and with the floorplan than with the normal VR perspective. Both VR learning methods significantly outperformed the floorplan in the orientation task. Navigation was performed quicker after learning in the giant perspective compared to the normal perspective and the building plan. We conclude that the normal perspective and especially the giant perspective in VR are viable options for preparing for teleoperation in unfamiliar environments when a virtual model of the environment is available.
Subsidies for temporary laying-up (TLU) are often introduced to support commercial fishers in crises. We studied the effect of a German TLU in response to quota cuts and the COVID-19 pandemic on fishers’ revenue frontiers and efficiency by stochastic frontier analysis, and on species composition by fixed-effects models using monthly landings declarations from 2008 to 2020. Own laying-up days increased inefficiency and decreased revenue frontiers. Subsidies were related to outward shifts in the revenue frontier, and were linked to small increases in landings of unregulated marine species. Laying-up periods by other fishers were not related to changes in the revenue frontier or efficiency, but to changes in species composition of unregulated species, away from freshwater species and flatfish, and towards eel and other marine species. Technical efficiency mostly decreased over time, offsetting temporal outward shifts in the revenue frontier.
Global farmland biodiversity has declined rapidly in recent decades due to the homogenization of agricultural landscapes, including an increase in field sizes and decrease in woody features, such as hedgerows. Restructuring landscapes by (re)introducing woody features and decreasing field sizes can support biodiversity but at the cost of lower returns in farming. Striking a balance between biodiversity and agricultural net returns is increasingly pertinent. Here, we use spatial multi-objective optimization to allocate woody features and adapt average field sizes at the landscape scale to assess the trade-off between biodiversity, measured as the occurrence of farmland birds, and potential net returns from crop production. Our results suggest that, compared to the current landscape configuration, both agricultural net returns and biodiversity can be simultaneously increased. Restructuring only 5% of the landscape can improve bird abundance by 2% and generate about €2 million in agricultural net returns. We show that increases in farmland bird diversity are highly dependent on the location and on farmers’ willingness to accept negative impacts on agricultural net returns. Our spatially explicit approach supports spatially targeted land use planning that can strike a better balance between the economic objectives of farmers and the societal desire to conserve biodiversity.
The northern pike (Esox lucius) is an iconic predatory fish species of significant recreational value and ecological role in the Baltic Sea. Some earlier studies indicate local declines of pike in the region, but a thorough spatial evaluation of regional population trends of pike in the Baltic Sea is lacking. In this study, we collate data from 59 unique time-series from fisheries landings and fishery-independent monitoring programs to address temporal trends in pike populations since the mid-2000′s in eight countries surrounding the Baltic Sea. In a common analysis considering all time-series in concert, we found indications of an overall regional temporal decline of pike in the Baltic Sea, but trends differed among countries. Individual negative trends in time-series were moreover found in several regions of the Baltic Sea, but predominantly so in the central and southern parts, while positive trends were only found in Estonia and northern Finland. The mix of data used in this study is inherently noisy and to some extent of uncertain quality, but as a result of the overall negative trends, together with the socioeconomic and ecological importance of pike in coastal areas of the Baltic Sea, we suggest that actions should be taken to protect and restore pike populations. Management measures should be performed in combination with improved fishery-independent monitoring programs to provide data of better quality and development of citizen-science approaches as a data source for population estimates. Possible measures that could strengthen pike populations include harvest regulations (including size limits, no-take areas and spawning closures), habitat protection and restoration, and an ecosystem-based approach to management considering also the impact of natural predators.
The FeIVO complexes of bispidines (3,7-diazabicyclo[3.3.1]nonane derivatives) are known to be highly reactive oxidants - with the tetradentate bispidine, the so far most reactive ferryl complex has been reported and two isomeric pentadentate ligands also lead to very reactive high-valent oxidants. With a series of 4 new bispidine derivatives we now try to address the question why the bispidine scaffold in general leads to very reactive oxidants and how this can be tuned by ligand modifications. The study is based on a full structural, spectroscopic and electrochemical analysis of the iron(II) precursors, spectroscopic data of the iron(IV)-oxido complexes, a kinetic analysis of the stoichiometric oxidation of thioanisole by five different bispidine‑iron(IV)-oxido complexes and on product analyses of reactions by the five ferryl oxidants with thioanisole, β-methylstyrene and cis-stilbene as substrates.
Purpose of Review The incidence of sport-related concussion (SRC) has been increasing in different sports and its impact on long-term cognitive function is increasingly recognized. In this study, we review the epidemiology, neuropathophysiology, clinical symptoms, and long-term consequences of SRC with a specific focus on cognition. Recent Findings Repeated concussions are associated with an increased risk of several neurologic diseases and long-term cognitive deficits. To improve cognitive outcomes in athletes with SRC, standardized guidelines for the assessment and management of SRC are vital. However, current concussion management guidelines lack procedures for rehabilitating acute and long-term cognitive symptoms. Summary Increased awareness for the management and rehabilitation of cognitive symptoms in SRC is needed in all clinical neurologists treating professional and amateur athletes. We propose cognitive training as a prehabilitation tool to alleviate the severity of cognitive symptoms and as a rehabilitative tool to improve cognitive recovery postinjury.
  • Trevor M Nolan
    Trevor M Nolan
  • Nemanja Vukašinović
    Nemanja Vukašinović
  • Che-Wei Hsu
    Che-Wei Hsu
  • [...]
  • Philip N Benfey
    Philip N Benfey
Brassinosteroids are plant steroid hormones that regulate diverse processes, such as cell division and cell elongation, through gene regulatory networks that vary in space and time. By using time series single-cell RNA sequencing to profile brassinosteroid-responsive gene expression specific to different cell types and developmental stages of the Arabidopsis root, we identified the elongating cortex as a site where brassinosteroids trigger a shift from proliferation to elongation associated with increased expression of cell wall-related genes. Our analysis revealed HOMEOBOX FROM ARABIDOPSIS THALIANA 7 (HAT7) and GT-2-LIKE 1 (GTL1) as brassinosteroid-responsive transcription factors that regulate cortex cell elongation. These results establish the cortex as a site of brassinosteroid-mediated growth and unveil a brassinosteroid signaling network regulating the transition from proliferation to elongation, which illuminates aspects of spatiotemporal hormone responses.
  • Ivelina Ivanova
    Ivelina Ivanova
  • Kaspar Bienefeld
    Kaspar Bienefeld
Varroa-sensitive hygiene (VSH) is highly influenced by the worker bee’s olfactory ability. Workers bred for VSH and non-selected control line workers were tested for differences in their speed and perception ability when presented with highly diluted stimuli. Four different substances (citral – dilution 1:1300, linalool dilution 1:1300, Varroa-parasitized brood extract, isopropanol) were used as tactile stimuli for differential conditioning with the proboscis extension response (PER). Discrimination ability and generalization were assessed. In a second set of conditioning experiments differences in sensitivity to the highly diluted citral and the Varroa-parasitized brood extract as reinforced stimuli (Cs +) were explored between workers from both lines. The worker bees were classified into three groups (Time points) depending on how long before they started correctly extending their proboscis to the Cs + , and results were examined separately for each of the two stimuli and group. While the VSH-selected line exhibited a significantly higher perception ability for the parasitized brood extract than the non-selected line, the two lines showed no differences when conditioned with the floral stimulus citral as Cs + . Furthermore, the VSH-selected line displayed a significantly higher number of worker bees that perceived the complex bouquet of the Varroa-parasitized brood extract at the earliest time grouping (Time point 1). The odds of perception at the earliest possible time point were 2.6-times higher for the VSH-selected line. Although no comparison was made between healthy and parasitized brood, the results indicate an enhanced specific sensitivity in VSH-selected workers towards chemical cues emitted by the brood, which might play a role in the detection of Varroa destructor.
  • Meng Su
    Meng Su
  • Benjamin Lindner
    Benjamin Lindner
We study transport properties of an active Brownian particle with an Rayleigh-Helmholtz friction function in a biased periodic potential. In the absence of noise and depending on the parameters of the friction function and on the bias force, the motion of the particle can be in a locked state or in different running states. According to the type of solutions, the parameter plane of friction and bias force can be divided into four regions. In these different regimes, there is either only a locked state, only a running state, a bistability between locked and running states, or a bistability of two different running states (corresponding to a systematic motion to the left or right, respectively). In the presence of noise, the mean velocity depends in different ways on the noise intensity for the various parameter regimes. These dependences are explored by means of numerical simulations and simple analytical estimates for limiting cases.
  • David Burmeister
    David Burmeister
  • Michael Janus Bojdys
    Michael Janus Bojdys
  • Alberto Eljarrat
    Alberto Eljarrat
  • [...]
  • Emil List-Kratochvil
    Emil List-Kratochvil
Graphitic carbon nitrides are covalently-bonded, layered, and crystalline semiconductors with high thermal and oxidative stability. These properties make graphitic carbon nitrides potentially useful in overcoming the limitations of 0D molecular and 1D polymer semiconductors. In this contribution, we study structural, vibrational, electronic and transport properties of nano-crystals of poly(triazine-imide) (PTI) derivatives with intercalated Li- and Br-ions and without intercalates. Intercalation-free poly(triazine-imide) (PTI-IF) is corrugated or AB stacked and partially exfoliated. We find that the lowest energy electronic transition in PTI is forbidden due to a non-bonding uppermost valence band and that its electroluminescence from the π-π* transition is quenched which severely limits their use as emission layer in electroluminescent devices. THz conductivity in nano-crystalline PTI is up to eight orders of magnitude higher than the macroscopic conductivity of PTI films. We find that the charge carrier density of PTI nano-crystals is among the highest of all known intrinsic semiconductors, however, macroscopic charge transport in films of PTI is limited by disorder at crystal-crystal interfaces. Future device applications of PTI will benefit most from single crystal devices that make use of electron transport in the lowest, π-like conduction band.
  • Aravind Battaje
    Aravind Battaje
  • Oliver Brock
    Oliver Brock
  • Martin Rolfs
    Martin Rolfs
We implement Adelson and Bergen's spatiotemporal energy model with extension to three-dimensional (x–y–t) in an interactive tool. It helps gain an easy understanding of early (first-order) visual motion perception. We demonstrate its usefulness in explaining an assortment of phenomena, including some that are typically not associated with the spatiotemporal energy model.
  • Francis Liu
    Francis Liu
  • Natalie Packham
    Natalie Packham
  • Meng-Jou Lu
    Meng-Jou Lu
  • Wolfgang Karl Härdle
    Wolfgang Karl Härdle
The introduction of derivatives on Bitcoin enables investors to hedge risk exposures in cryptocurrencies. Because of volatility swings and jumps in cryptocurrency prices, the traditional variance-based approach to obtain hedge ratios may not be suitable for hedgers. In this work, we consider two extensions of the traditional approach: first, different dependence structures are modelled by different copulae, such as the Gaussian, Student-t, Normal Inverse Gaussian and Archimedean copulae; second, different risk measures, such as value-at-risk, expected shortfall and spectral risk measures are employed to find the optimal hedge ratio. Extensive out-of-sample tests using the data from the time period December 2017 until May 2021 give insights in the practice of hedging various cryptos and crypto indices, including Bitcoin, Ethereum, Cardano, the CRIX index and a number of crypto-portfolios. Evidence shows that BTC futures can effectively hedge BTC and BTC-involved indices. This promising result is consistent across different risk measures and copulae except for the Frank copula. On the other hand, we observe complex and diverse dependence structures between non-BTC-related cryptocurrencies and the BTC futures. As a consequence, the hedge performance of non-BTC-related cryptocurrencies is mixed and even suitable for some assets.
This special issue of the Journal of Integrative Bioinformatics contains updated specifications of COMBINE standards in systems and synthetic biology. The 2022 special issue presents three updates to the standards: CellML 2.0.1, SBML Level 3 Package: Spatial Processes, Version 1, Release 1, and Synthetic Biology Open Language (SBOL) Version 3.1.0. This document can also be used to identify the latest specifications for all COMBINE standards. In addition, this editorial provides a brief overview of the COMBINE 2022 meeting in Berlin.
UV radiation is an underrated radiation currently missing in many horticultural production systems of vegetables in protected cultivation. It can be added e.g., in LED light sources. Using lettuce as a model plant, this study determined whether the use of UVB LEDs is suitable (1) for use in consistent systems (indoor farming) or (2) inconsistent systems (greenhouse). Blue and red LEDs were selected as additional artificial lighting to UVB LEDs. Both approaches led to a reproducible increase of desired flavonol glycosides, such as quercetin-3-O-(6''-O-malonyl)-glucoside or quercetin-3-O-glucuronide and the anthocyanin cyanidin-3-O-(6''-O-malonyl)-glucoside in lettuce. The impact of the consistent UVB treatment is higher with up to tenfold changes than that of the inconsistent UVB treatment in the greenhouse. Varying natural light and temperature conditions in greenhouses might affect the efficiency of the artificial UVB treatment. Here, UVB LEDs have been tested and can be recommended for further development of lighting systems in indoor farming and greenhouse approaches.
The present work comprises a practical tutorial on the topic of correlative microscopy and its application to optoelectronic semiconductor materials and devices. For the assessment of microscopic structure–property relationships, correlative electron microscopy, combined also with scanning-probe and light microscopy, exhibits a collection of indispensable tools to analyze various material and device properties. This Tutorial describes not only the various microscopy methods but also the specimen preparation in detail. Moreover, it is shown that electron microscopy can serve to monitor phase segregation processes on various length scales in semiconductor nanoparticles and thin films. Algorithms used to extract phase information from high-resolution transmission electron micrographs are explained.
This paper studies the old Greek children’s radio show Edo Lilipoupoli transmitted from December 1977 to May 1980 by the Third Program of the Greek State Radio. The considerations of this paper result from the examination of the content of the radio show regarding its cultural and social parameters and correlations as a collective media project. The insight gained from this endeavour is significant, particularly due to the common claim among the broadcast listeners and contributors that the children’s radio program Edo Lilipoupoli functioned as a “mirror” of Greek society. The broadcast can be therefore understood as a kind of social snapshot depicting the ideological and identity conflict between the conservative and the progressive voices prevailing in society during that time. The analytical interest focuses on one specific song, very popular in the context of the radio show, with the title “We are not Zulu”. This approach will include an analysis of the lyrics in connection to their setting, i.e. morphology, harmony, instrumentation as well as the singer’s performance. Within the framework of this music-aesthetic and linguistic analytical point of view, I will try to identify the role and function of humour in the song and pursue an interpretive approach in the context of its sociocultural implications. The conclusions will form an attempt to bring out the point of view of the show’s contributors.
Arbuscular mycorrhizal fungi (AMF) alter plant water relations and contribute to soil structure. Although soil hydraulic properties depend on soil structure and may limit plant water uptake, little is known about how AMF influence soil water retention (the relation between the soil water content and soil water potential) and hydraulic conductivity in different soils. Instead, these soil hydraulic properties often are considered to be independent of AMF presence in experiments. We asked if this assumption holds true for both sand and loam. We grew maize plants either inoculated with Rhizophagus irregularis or with autoclaved inoculum in pots filled with quartz sand or loam soil until extraradical spread of the fungus throughout the pots was achieved. Each pot contained a hyphal compartment made of a soil sampling core (250 cm³) covered with a 20-µm nylon mesh to encourage fungus ingrowth but to exclude root ingrowth. We measured soil water retention and unsaturated hydraulic conductivity in these undisturbed root-free soil volumes. We observed that in loam harboring the mycorrhizal fungus, the soil water retention decreased, while in sand, it increased without detectable changes in the soil bulk density. The effects of the fungus on the soil water potential were strongest at low soil water contents in both soils. As a consequence of the altered water potentials in soils with the mycorrhizal fungus, soil hydraulic conductivity increased in loam but decreased in sand after fungus ingrowth. We conclude that in our study, the mycorrhizal fungus acted as a soil conditioner even distant from roots, which encouraged drainage in loams prone to sogginess but enhanced water storage in sands prone to quick desiccation. We recommend considering soil hydraulic properties as being dynamic in future studies on water relations of mycorrhizal plants.
Industrial contaminants accumulated in Arctic permafrost regions have been largely neglected in existing climate impact analyses. Here we identify about 4500 industrial sites where potentially hazardous substances are actively handled or stored in the permafrost-dominated regions of the Arctic. Furthermore, we estimate that between 13,000 and 20,000 contaminated sites are related to these industrial sites. Ongoing climate warming will increase the risk of contamination and mobilization of toxic substances since about 1100 industrial sites and 3500 to 5200 contaminated sites located in regions of stable permafrost will start to thaw before the end of this century. This poses a serious environmental threat, which is exacerbated by climate change in the near future. To avoid future environmental hazards, reliable long-term planning strategies for industrial and contaminated sites are needed that take into account the impacts of cimate change.
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Dan Benesh
  • Department of Biology
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