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"Meyer, Marcel"
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The Evolution and Challenges of the Concept of Organizational Virtuousness in Positive Organizational Scholarship
2018
This paper critically reviews and discusses the concept of organizational virtuousness as presented in positive organizational scholarship (POS). It identifies Kim S. Cameron, David S. Bright, and Airan Caza as the most influential researchers within this field and portrays commonalities, differences, and inconsistencies among the various notions of organizational virtuousness offered in positive organizational literature throughout the last 15 years. While the commonalities refer to attributes, levels of analyses, outcomes, and methodology, the variances concern the locus of residence, the priority of outcomes, indicators, supporting features and the virtues included in positive organizational virtuousness. The analysis further discusses the strengths and weaknesses of these differences and stresses the challenges which the POS movement needs to face in order to clarify its definition of organizational virtuousness and, maybe, converge on one unified meaning. Finally, these challenges are summarized and linked to future research proposals which offer potential ideas on how to further develop the concept of positive organizational virtuousness.
Journal Article
Agricultural intensification reduces microbial network complexity and the abundance of keystone taxa in roots
by
van der Heijden, Marcel G. A.
,
Walder, Florian
,
Keller, Thomas
in
631/326/2565/855
,
704/158
,
Abundance
2019
Root-associated microbes play a key role in plant performance and productivity, making them important players in agroecosystems. So far, very few studies have assessed the impact of different farming systems on the root microbiota and it is still unclear whether agricultural intensification influences the structure and complexity of microbial communities. We investigated the impact of conventional, no-till, and organic farming on wheat root fungal communities using
PacBio SMRT sequencing
on samples collected from 60 farmlands in Switzerland. Organic farming harbored a much more complex fungal network with significantly higher connectivity than conventional and no-till farming systems. The abundance of keystone taxa was the highest under organic farming where agricultural intensification was the lowest. We also found a strong negative association (
R
2
= 0.366;
P
< 0.0001) between agricultural intensification and root fungal network connectivity. The occurrence of keystone taxa was best explained by soil phosphorus levels, bulk density, pH, and mycorrhizal colonization. The majority of keystone taxa are known to form arbuscular mycorrhizal associations with plants and belong to the orders
Glomerales
,
Paraglomerales
, and
Diversisporales
. Supporting this, the abundance of mycorrhizal fungi in roots and soils was also significantly higher under organic farming. To our knowledge, this is the first study to report mycorrhizal keystone taxa for agroecosystems, and we demonstrate that agricultural intensification reduces network complexity and the abundance of keystone taxa in the root microbiome.
Journal Article
Shared control of a 16 semiconductor quantum dot crossbar array
by
Motz, Sayr
,
Scappucci, Giordano
,
Borsoi, Francesco
in
639/766/483/2802
,
639/925/927/1007
,
Arrays
2024
The efficient control of a large number of qubits is one of the most challenging aspects for practical quantum computing. Current approaches in solid-state quantum technology are based on brute-force methods, where each and every qubit requires at least one unique control line—an approach that will become unsustainable when scaling to the required millions of qubits. Here, inspired by random-access architectures in classical electronics, we introduce the shared control of semiconductor quantum dots to efficiently operate a two-dimensional crossbar array in planar germanium. We tune the entire array, comprising 16 quantum dots, to the few-hole regime. We then confine an odd number of holes in each site to isolate an unpaired spin per dot. Moving forward, we demonstrate on a vertical and a horizontal double quantum dot a method for the selective control of the interdot coupling and achieve a tunnel coupling tunability over more than 10 GHz. The operation of a quantum electronic device with fewer control terminals than tunable experimental parameters represents a compelling step forward in the construction of scalable quantum technology.
An efficient control strategy is designed for quantum dot arrays, drawing inspiration from classical semiconductor technology. A two-dimensional array of 16 semiconductor quantum dots is operated using only a few shared control lines.
Journal Article
Demonstration of measurement-free universal logical quantum computation
by
Pogorelov, Ivan
,
Monz, Thomas
,
Müller, Markus
in
639/766/483/2802
,
639/766/483/481
,
Algorithms
2026
The ability to perform quantum error correction (QEC) and robust gate operations on encoded qubits opens the door to demonstrations of quantum algorithms. Contemporary QEC schemes typically require mid-circuit measurements with feed-forward control, which are challenging for qubit control, often slow, and susceptible to relatively high error rates. In this work, we propose and experimentally demonstrate a universal toolbox of fault-tolerant logical operations on error-detecting codes without mid-circuit measurements on a trapped-ion quantum processor. We present modular logical state teleportation between two four-qubit error-detecting codes without measurements during algorithm execution. Moreover, we realize a fault-tolerant universal gate set on an eight-qubit error-detecting code hosting three logical qubits, based on state injection, which can be executed by coherent gate operations only. We apply this toolbox to experimentally realize Grover’s quantum search algorithm fault-tolerantly on three logical qubits encoded in eight physical qubits, with the implementation displaying clear identification of the desired solution states. Our work demonstrates the practical feasibility and provides first steps into the largely unexplored direction of measurement-free quantum computation.
Measurement-free quantum error correction allows to avoid costly mid-circuit measurements and feed-forward controls. Here, the authors present a toolbox of logical operations needed for measurement-free fault-tolerant universal quantum computing and demonstrate a measurement-free logical fault-tolerant logical algorithm using an error-detecting code on an ion-trap quantum processor.
Journal Article
7 tesla multiscale entropy analysis reveals increased resting-state complexity in key regions for fear and anxiety in spider-fearful individuals
2025
•Multiscale entropy is a measure of neural information production and complexity.•First study to asses 7T MRI complexity.•Spider phobia shows increased multiscale entropy in fear and anxiety networks.•The bed nucleus of the stria terminalis shows most entropy changes in spider phobia.•Multiscale entropy correlates with phobia severity but not trait anxiety.
Resting-state functional connectivity is limited in assessing the temporal dynamics of brain networks and, due to an insufficient signal-to-noise ratio, in detecting subtle changes at 3T MRI. Nonetheless, measures of complexity, which capitalize on temporal dynamics, have revealed alterations for some affective disorders at this field strength. Anxiety disorders have received only scant attention in this regard, despite indications of altered functional brain architecture in spider-fearful participants (SP). To address this gap, we probed resting-state complexity using 7T MRI, comparing 28 adults with SP with 45 healthy controls (HC). We computed multiscale entropy (MSE) on ten scales (1 – 0.1 Hz) for brain regions of the fear and anxiety networks in HC and SP. The MSE scales interacted with group (HC, SP) and brain area, revealing MSE increments in limbic regions in SP (versus HC). Whilst most MSE changes related to SP ranged between 1 and 0.33 Hz, the MSE of the bed nucleus of the stria terminalis (BNST), a nucleus involved in anxiety and the hormonal system, exhibited increases on all scales bar two for SP (i.e., for 0.5 – 0.125, and 0.1 Hz). MSE was also positively associated with SP severity (but not trait anxiety) in the BNST. Altogether, 7T fMRI detected elevated MSE in SP, indicating excessive intra-regional processing in brain regions key to fear and anxiety. The most pronounced effects were found in the BNST, corroborating its central role in the anxiety circuit.
[Display omitted]
Journal Article
Baseband control of single-electron silicon spin qubits in two dimensions
by
Ivlev, Alexander S.
,
Veldhorst, Menno
,
Raymenants, Eline
in
639/301/119/1000/1017
,
639/925/357/997
,
639/925/927/1062
2025
Micromagnet-enabled electric-dipole spin resonance (EDSR) is an established method for high-fidelity single-spin control in silicon, although so far experiments have been restricted to one-dimensional arrays. In contrast, qubit control based on hopping spins has recently emerged as a compelling alternative, with high-fidelity baseband control realized in sparse two-dimensional hole arrays in germanium. In this work, we commission a
28
Si/SiGe 2 × 2 quantum dot array both as a four-qubit device using EDSR and as a two-qubit device using baseband hopping control. We establish a lower bound on the fidelity of the hopping gate of 99.50(6)%, which is similar to the average fidelity of the resonant gate. The hopping gate also circumvents the transient pulse-induced resonance shift from heating observed during EDSR operation. To motivate hopping spins as an attractive means of scaling silicon spin-qubit arrays, we propose an extensible nanomagnet design that enables engineered baseband control of large spin arrays.
Quantum dot spin qubits in Si can be controlled using micromagnet-based electric-dipole spin resonance, but experiments have been limited to small 1D arrays. Here the authors address qubit control in 2D Si arrays, demonstrating low-frequency control of qubits in a 2 x 2 array using hopping gates.
Journal Article
Low disorder and high valley splitting in silicon
by
Degli Esposti, Davide
,
Arbiol, Jordi
,
Veldhorst, Menno
in
639/301
,
639/766
,
Classical and Quantum Gravitation
2024
The electrical characterisation of classical and quantum devices is a critical step in the development cycle of heterogeneous material stacks for semiconductor spin qubits. In the case of silicon, properties such as disorder and energy separation of conduction band valleys are commonly investigated individually upon modifications in selected parameters of the material stack. However, this reductionist approach fails to consider the interdependence between different structural and electronic properties at the danger of optimising one metric at the expense of the others. Here, we achieve a significant improvement in both disorder and valley splitting by taking a co-design approach to the material stack. We demonstrate isotopically purified, strained quantum wells with high mobility of 3.14(8) × 10
5
cm
2
V
−1
s
−1
and low percolation density of 6.9(1) × 10
10
cm
−2
. These low disorder quantum wells support quantum dots with low charge noise of 0.9(3) μeV Hz
−1/2
and large mean valley splitting energy of 0.24(7) meV, measured in qubit devices. By striking the delicate balance between disorder, charge noise, and valley splitting, these findings provide a benchmark for silicon as a host semiconductor for quantum dot qubits. We foresee the application of these heterostructures in larger, high-performance quantum processors.
Journal Article
An early warning system to predict and mitigate wheat rust diseases in Ethiopia
by
Hodson, David P
,
Hort, Matthew C
,
Millington, Sarah C
in
agricultural science
,
Agronomy
,
atmospheric transport
2019
Wheat rust diseases pose one of the greatest threats to global food security, including subsistence farmers in Ethiopia. The fungal spores transmitting wheat rust are dispersed by wind and can remain infectious after dispersal over long distances. The emergence of new strains of wheat rust has exacerbated the risks of severe crop loss. We describe the construction and deployment of a near real-time early warning system (EWS) for two major wind-dispersed diseases of wheat crops in Ethiopia that combines existing environmental research infrastructures, newly developed tools and scientific expertise across multiple organisations in Ethiopia and the UK. The EWS encompasses a sophisticated framework that integrates field and mobile phone surveillance data, spore dispersal and disease environmental suitability forecasting, as well as communication to policy-makers, advisors and smallholder farmers. The system involves daily automated data flow between two continents during the wheat season in Ethiopia. The framework utilises expertise and environmental research infrastructures from within the cross-disciplinary spectrum of biology, agronomy, meteorology, computer science and telecommunications. The EWS successfully provided timely information to assist policy makers formulate decisions about allocation of limited stock of fungicide during the 2017 and 2018 wheat seasons. Wheat rust alerts and advisories were sent by short message service and reports to 10 000 development agents and approximately 275 000 smallholder farmers in Ethiopia who rely on wheat for subsistence and livelihood security. The framework represents one of the first advanced crop disease EWSs implemented in a developing country. It provides policy-makers, extension agents and farmers with timely, actionable information on priority diseases affecting a staple food crop. The framework together with the underpinning technologies are transferable to forecast wheat rusts in other regions and can be readily adapted for other wind-dispersed pests and disease of major agricultural crops.
Journal Article
Key Role for Similarity in Vicarious Reward
by
Calder, Andrew J
,
Passamonti, Luca
,
Schweizer, Susanne
in
Adult
,
Basal Ganglia - physiology
,
Biological and medical sciences
2009
Humans appear to have an inherent prosocial tendency toward one another in that we often take pleasure in seeing others succeed. This fact is almost certainly exploited by game shows, yet why watching others win elicits a pleasurable vicarious rewarding feeling in the absence of personal economic gain is unclear. One explanation is that game shows use contestants who have similarities to the viewing population, thereby kindling kin-motivated responses (for example, prosocial behavior). Using a game show-inspired paradigm, we show that the interactions between the ventral striatum and anterior cingulate cortex subserve the modulation of vicarious reward by similarity, respectively. Our results support studies showing that similarity acts as a proximate neurobiological mechanism where prosocial behavior extends to unrelated strangers.
Journal Article
Evoked Potentials Differentiate Developmental Coordination Disorder From Attention-Deficit/Hyperactivity Disorder in a Stop-Signal Task: A Pilot Study
by
Meachon, Emily J.
,
Meyer, Marcel
,
Wilmut, Kate
in
Adults
,
Attention deficit hyperactivity disorder
,
Auditory evoked potentials
2021
Developmental Coordination Disorder and Attention-Deficit/Hyperactivity Disorder are unique neurodevelopmental disorders with overlaps in executive functions and motor control. The conditions co-occur in up to 50% of cases, raising questions of the pathological mechanisms of DCD versus ADHD. Few studies have examined these overlaps in adults with DCD and/or ADHD. Therefore, to provide insights about executive functions and motor control between adults with DCD, ADHD, both conditions (DCD + ADHD), or typically developed controls, this study used a stop-signal task and parallel EEG measurement. We assessed executive performance via go accuracy and go reaction time, as well as motor response inhibition via stop-signal reaction time. This was complemented with analysis of event-related potentials (ERPs). Based on existing investigations of adults with DCD or ADHD, we expected (1) groups would not differ in behavioral performance on stop and go trials, but (2) differences in ERPs, particularly in components N200 (index of cognitive control) and P300 (index of attention and inhibition) would be evident. The sample included N = 50 adults with DCD ( n = 12), ADHD ( n = 9), DCD + ADHD ( n = 7), and control participants ( n = 22). We replicated that there were no between-group differences for behavioral-level executive performance and motor response inhibition. However, on a physiological level, ERP components N200 and P300 differed between groups, particularly during successful response inhibition. These ERPs reflect potential endophenotypic differences not evident in overt behavior of participants with ADHD and/or DCD. This suggests a disorder specific employment of inhibition or general executive functions in groups of adults with DCD, DCD + ADHD, ADHD, or control participants.
Journal Article