Synchronous Counting and Computational Algorithm Design

Consider a complete communication network on $n$ nodes, each of which is a state machine. In synchronous 2-counting, the nodes receive a common clock pulse and they have to agree on which pulses are "odd" and which are "even". We require that the solution is self-stabilising (reaching the correct operation from any initial state) and it tolerates $f$ Byzantine failures (nodes that send arbitrary misinformation). Prior algorithms are expensive to implement in hardware: they require a source of random bits or a large number of states. This work consists of two parts. In the first part, we use computational techniques (often known as synthesis) to construct very compact deterministic algorithms for the first non-trivial case of $f = 1$. While no algorithm exists for $n < 4$, we show that as few as 3 states per node are sufficient for all values $n \ge 4$. Moreover, the problem cannot be solved with only 2 states per node for $n = 4$, but there is a 2-state solution for all values $n \ge 6$. In the second part, we develop and compare two different approaches for synthesising synchronous counting algorithms. Both approaches are based on casting the synthesis problem as a propositional satisfiability (SAT) problem and employing modern SAT-solvers. The difference lies in how to solve the SAT problem: either in a direct fashion, or incrementally within a counter-example guided abstraction refinement loop. Empirical results suggest that the former technique is more efficient if we want to synthesise time-optimal algorithms, while the latter technique discovers non-optimal algorithms more quickly.Comment: 35 pages, extended and revised versio

Blockchain Research in Information Systems: Current Trends and an Inclusive Future Research Agenda

The potential of blockchain has been extensively discussed in practitioner literature, yet rigorous empirical and theory-driven information systems (IS) research on blockchain remains scarce. This special issue addresses the need for innovative research that offers a fresh look at the opportunities and challenges of blockchain. This editorial integrates and goes beyond the papers included in this special issue by providing a framework for blockchain research in IS that emphasizes two important issues. First, we direct the attention of IS research toward the blockchain protocol level, which is characterized by recursive interactions between human agents and the blockchain protocol. Second, we highlight the need for IS research to consider how the protocol level constrains and affords blockchain applications, and how these constraints and other concerns at the application level lead to changes at the protocol level. Rooted in a socio-material view of IS, we offer a multi-paradigmatic IS research agenda that underscores the need for behavioral (individual, group, and organizational), design science, and IS economics research on blockchain. Our research agenda emphasizes issues of blockchain governance, human and material agency, blockchain affordances and constraints, as well as the consequences of its use

MaxSAT-Based Bi-Objective Boolean Optimization

Peer reviewe

The Design of Pseudo-Participation

Participation is key to building an equitable, realistic and democratic future. Yet a lack of agency in decision making and agenda-setting is a growing phenomenon in the design of digital public services. We call this pseudo-participation by and in design. The configuration of digital artifacts and/or processes can provide an illusion of participation but lack supportive processes and affordances to allow meaningful participation to happen. This exploratory paper examines the realm of pseudo-participation in the design of public digital services through two concepts: 1) pseudo-participation by design, digital interfaces, and tools that provide the illusion of participation to the people, 2) pseudo-participation in design, processes in which those affected by the design decisions are marginalized and not given any agency. We contribute to the re-imagination of participatory design in modern societies where the role of politics has become ubiquitous and is yet to be critically scrutinized by designers.Peer reviewe

Radiographic and safety details of vertebral body stenting : results from a multicenter chart review

Background: Up to one third of BKP treated cases shows no appreciable height restoration due to loss of both restored height and kyphotic realignment after balloon deflation. This shortcoming has called for an improved method that maintains the height and realignment reached by the fully inflated balloon until stabilization of the vertebral body by PMMA-based cementation. Restoration of the physiological vertebral body height for pain relief and for preventing further fractures of adjacent and distant vertebral bodies must be the main aim for such a method. A new vertebral body stenting system (VBS) stabilizes the vertebral body after balloon deflation until cementation. The radiographic and safety results of the first 100 cases where VBS was applied are presented. Methods: During the planning phase of an ongoing international multicenter RCT, radiographic, procedural and followup details were retrospectively transcribed from charts and xrays for developing and testing the case report forms. Radiographs were centrally assessed at the institution of the first/senior author. Results: 100 patients (62 with osteoporosis) with a total of 103 fractured vertebral bodies were treated with the VBS system. 49 were females with a mean age of 73.2 years; males were 66.7 years old. The mean preoperative anterior-middle-posterior heights were 20.3-17.6-28.0 mm, respectively. The mean local kyphotic angle was 13.1°. The mean preoperative Beck Index (anterior edge height/posterior edge height) was 0.73, the mean alternative Beck Index (middle height/posterior edge height) was 0.63. The mean postoperative heights were restored to 24.5-24.6-30.4 mm, respectively. The mean local kyphotic angle was reduced to 8.9°. The mean postoperative Beck Index was 0.81, the mean alternative one was 0.82. The overall extrusion rate was 29.1%, the symptomatic one was 1%. In the osteoporosis subgroup there were 23.8% extrusions. Within the three months followup interval there were 9% of adjacent and 4% of remote new fractures, all in the osteoporotic group. Conclusions: VBS showed its strengths especially in realignment of crush and biconcave fractures. Given that fracture mobility is present, the realignment potential is sound and increases with the severity of preoperative vertebral body deformation

Real-Time MEG Source Localization Using Regional Clustering

With its millisecond temporal resolution, Magnetoencephalography (MEG) is well suited for real-time monitoring of brain activity. Real-time feedback allows the adaption of the experiment to the subject’s reaction and increases time efficiency by shortening acquisition and off-line analysis. Two formidable challenges exist in real-time analysis: the low signal-to-noise ratio (SNR) and the limited time available for computations. Since the low SNR reduces the number of distinguishable sources, we propose an approach which downsizes the source space based on a cortical atlas and allows to discern the sources in the presence of noise. Each cortical region is represented by a small set of dipoles, which is obtained by a clustering algorithm. Using this approach, we adapted dynamic statistical parametric mapping for real-time source localization. In terms of point spread and crosstalk between regions the proposed clustering technique performs better than selecting spatially evenly distributed dipoles. We conducted real-time source localization on MEG data from an auditory experiment. The results demonstrate that the proposed real-time method localizes sources reliably in the superior temporal gyrus. We conclude that real-time source estimation based on MEG is a feasible, useful addition to the standard on-line processing methods, and enables feedback based on neural activity during the measurements.Deutsche Forschungsgemeinschaft (grant Ba 4858/1-1)National Institutes of Health (U.S.) (grants 5R01EB009048 and 2P41EB015896)Universitätsschule Jena (J21)German Academic Exchange Servic

Mne-X: MEG/EEG real-time acquisition, real-time processing, and real-time source localization framework

Providing millisecond-temporal resolution for non-invasive mapping of human brain functions, Magneto-/Electroencephalography (MEG/EEG) is predestined to monitor brain activity in real-time. While data analysis to date is mostly done subsequent to the acquistion process we introduce here an acquisition and real-time analysis application. Online feedback allows the adaption of the experiment to the subject’s reaction creating a whole set of new options and increasing time efficiency by shortening acquisition and offline analysis. To build a standalone application, we first designed MNE-CPP a cross-platform open source Qt5 C++ library, which implements the validated parts of our scripting toolboxes MNE-Python/MATLAB. Based on MNE-CPP we built MNE-X, which allows realtime acquisition, processing, and source localization

Arginine-rich cell-penetrating peptides induce membrane multilamellarity and subsequently enter via formation of a fusion pore

Arginine-rich cell-penetrating peptides do not enter cells by directly passing through a lipid membrane; they instead passively enter vesicles and live cells by inducing membrane multilamellarity and fusion. The molecular picture of this penetration mode, which differs qualitatively from the previously proposed direct mechanism, is provided by molecular dynamics simulations. The kinetics of vesicle agglomeration and fusion by an iconic cell-penetrating peptide-nonaarginine-are documented via real-time fluorescence techniques, while the induction of multilamellar phases in vesicles and live cells is demonstrated by a combination of electron and fluorescence microscopies. This concert of experiments and simulations reveals that the identified passive cell penetration mechanism bears analogy to vesicle fusion induced by calcium ions, indicating that the two processes may share a common mechanistic origin.Peer reviewe