On the transition to efficiency in Minority Games

The existence of a phase transition with diverging susceptibility in batch Minority Games (MGs) is the mark of informationally efficient regimes and is linked to the specifics of the agents' learning rules. Here we study how the standard scenario is affected in a mixed population game in which agents with the `optimal' learning rule (i.e. the one leading to efficiency) coexist with ones whose adaptive dynamics is sub-optimal. Our generic finding is that any non-vanishing intensive fraction of optimal agents guarantees the existence of an efficient phase. Specifically, we calculate the dependence of the critical point on the fraction $q$ of `optimal' agents focusing our analysis on three cases: MGs with market impact correction, grand-canonical MGs and MGs with heterogeneous comfort levels.Comment: 12 pages, 3 figures; contribution to the special issue "Viewing the World through Spin Glasses" in honour of David Sherrington on the occasion of his 65th birthda

Von Neumann's expanding model on random graphs

Within the framework of Von Neumann's expanding model, we study the maximum growth rate r achievable by an autocatalytic reaction network in which reactions involve a finite (fixed or fluctuating) number D of reagents. r is calculated numerically using a variant of the Minover algorithm, and analytically via the cavity method for disordered systems. As the ratio between the number of reactions and that of reagents increases the system passes from a contracting (r1). These results extend the scenario derived in the fully connected model (D\to\infinity), with the important difference that, generically, larger growth rates are achievable in the expanding phase for finite D and in more diluted networks. Moreover, the range of attainable values of r shrinks as the connectivity increases.Comment: 20 page

A label-free biosensor based on graphene and reduced graphene oxide dual-layer for electrochemical determination of beta-amyloid biomarkers

A label-free biosensor is developed for the determination of plasma-based Aβ1–42 biomarker in Alzheimer’s disease (AD). The platform is based on highly conductive dual-layer of graphene and electrochemically reduced graphene oxide (rGO). The modification of dual-layer with 1-pyrenebutyric acid N-hydroxysuccinimide ester (Pyr-NHS) is achieved to facilitate immobilization of H31L21 antibody. The effect of these modifications were studied with morphological, spectral and electrochemical techniques. The response of the biosensor was evaluated using differential pulse voltammetry (DPV). The data was acquired at a working potential of ~ 180 mV and a scan rate of 50 mV s−1. A low limit of detection (LOD) of 2.398 pM is achieved over a wide linear range from 11 pM to 55 nM. The biosensor exhibits excellent specificity over Aβ1–40 and ApoE ε4 interfering species. Thus, it provides a viable tool for electrochemical determination of Aβ1–42. Spiked human and mice plasmas were used for the successful validation of the sensing platform in bio-fluidic samples. The results obtained from mice plasma analysis concurred with the immunohistochemistry (IHC) and magnetic resonance imaging (MRI) data obtained from brain analysis.This work was financially supported by H2020 MSCA-ITN-ETN BBDiag project under grant no. 721281.Peer reviewe

Dynamic Control of a Novel Planar Cable-Driven Parallel Robot with a Large Wrench Feasible Workspace

Cable-Driven Parallel Robots (CDPRs) are special manipulators where rigid links are replaced with cables. The use of cables offers several advantages over the conventional rigid manipulators, one of the most interesting being their ability to cover large workspaces since cables are easily winded. However, this workspace coverage has its limitations due to the maximum permissible cable tensions, i.e., tension limitations cause a decrease in the Wrench Feasible Workspace (WFW) of these robots. To solve this issue, a novel design based in the addition of passive carriages to the robot frame of three degrees-of-freedom (3DOF) fully-constrained CDPRs is used. The novelty of the design allows reducing the variation in the cable directions and forces increasing the robot WFW; nevertheless, it presents a low stiffness along the x direction. This paper presents the dynamic model of the novel proposal together with a new dynamic control technique, which rejects the vibrations caused by the stiffness loss while ensuring an accurate trajectory tracking. The simulation results show that the controlled system presents a larger WFW than the conventional scheme of the CDPR, maintaining a good performance in the trajectory tracking of the end-effector. The novel proposal presented here can be applied in multiple planar applications

Staying Connected – Interactive Student Learning during the COVID Transition to Remote Learning

Background. How can we transition courses in one week, while maintaining a similar experience for students? This was probably the initial response by faculty across universities as they transitioned to remote learning, mid-semester, in response to the SARS-CoV-2 pandemic. Our approach is supported by the ICAP framework which posits that “as activities move from passive to active to constructive to interactive, students undergo different knowledge-change processes and, as a result, learning will increase.” (Chi and Wylie, 2014) Purpose/Hypothesis. How we could foster students’ interactions with course material, instructors, and their peers using collaborative technology and course activities? It was hypothesized that a collaborative environment, coupled with appropriately designed activities, would promote the interactive learning described by the ICAP framework. Design/Method. Faculty members used Microsoft Teams (Teams) and Marquette University’s Learning Management System Desire2Learn (D2L) for their courses. Each instructor developed student groups to promote peer and instructor engagement via the Teams channel function. Results. Initial results from Likert 5-point scale responses support three positive findings to this approach: Finding 1 (Instructor Engagement and Student Confidence): Students had a positive reaction to the instructor engagement (4.67 ± 0.6) and student confidence (4.07 ± 1.1). Finding 2 (Consistent Coursework): Students reported the amount of work in courses with the interactive tools was consistent (3.90 ± 1.2) with the in-class experience. Finding 3 (Collaborative Technology): Using collaborative technology (3.84 ± 1.2) enabled the students to successfully interact with their peers. The survey also provided data on opportunities for improvement for future on-line courses: Opportunity 1 (Communication): Student communication (2.57 ± 1.5) is still a barrier with collaborative technology. Opportunity 2 (On-line Format): Students also reported an overall dislike (2.44 ± 1.4) of the on-line learning format. Conclusions. The use of Teams shows that instructor engagement contributes the most to the positive experiences for confidence, consistency, and use of collaborative technology. We believe there are opportunities to develop more advantages than traditional approaches and will provide students an easier transition to industry, which already use these remote communication tools

Criticality in diluted ferromagnet

We perform a detailed study of the critical behavior of the mean field diluted Ising ferromagnet by analytical and numerical tools. We obtain self-averaging for the magnetization and write down an expansion for the free energy close to the critical line. The scaling of the magnetization is also rigorously obtained and compared with extensive Monte Carlo simulations. We explain the transition from an ergodic region to a non trivial phase by commutativity breaking of the infinite volume limit and a suitable vanishing field. We find full agreement among theory, simulations and previous results.Comment: 23 pages, 3 figure