A fly-robot interface to investigate the dynamics of closed-loop visuo-motor control in the blowfly

The blowfly Calliphora is one of the most sophisticated fliers in the animal kingdom. It displays a broad repertoire of visually guided behaviours that can readily be quantified, including gaze and flight stabilization reflexes, male chasing flights, collision avoidance and landing responses. The fly achieves such robust visuo-motor control tasks based on a comparatively simple nervous system that is highly accessible for electrophysiological recordings. The ability to investigate the fly’s performance at the behavioural and electrophysiology levels makes this animal an ideal model system to study closed-loop visual motor control. The aim of this thesis was to develop and characterize the dynamics of a fly-robot interface (FRI) while a fly performs a closed-loop visual stabilization task. A novel experimental setup involving a FRI was developed which allowed for simultaneous measurements of neural activity from the fly and the behavioural performance of the robot. In the setup, the neural activity of an identified visual interneuron, the H1 cell, was recorded and its action potentials were used to control the motion of a mobile robot that was free to rotate along its vertical axis. External visual perturbations were introduced into the closed-loop system through a rotating turn-table with the robot using the neural activity to counter-rotate and to minimize the observed visual motion. The closed-loop control delay of the FRI was 50 ms which is well within the range of visual response delays observed in fly behaviour. With the FRI, the closed-loop dynamics of a static-gain proportional controller were characterized. The results explain significant oscillations in the closed-loop responses as a possible consequence of a high controller gain which were also observed but never fully interpreted in previous behavioural studies. Varying the controller gain also offers competing control benefits to the fly, with different gains maximizing performance for different input frequency ranges and thus different behavioural tasks. Results with the proportional controller indicate the dependence of the FRI frequency response on the angular acceleration of visual motion. An adaptive controller designed to dynamically scale the feedback gain was found to increase the bandwidth of the frequency response when compared with the static-gain proportional controller. The image velocities observed under closed-loop conditions using the proportional and the adaptive controllers were correlated with the spiking activity of the H1-cell. A remarkable qualitative similarity was found between the response dynamics of the cell under closed-loop conditions with those obtained in previous open-loop experiments. Specifically, (i) the peak spike rate decreased when the mean image velocity was increased, (ii) the relationship between spike rate and image velocity was dependant on the standard deviation of the image velocities suggesting adaptive scaling of the cell’s signalling range, and (iii) the cell’s gain decreased linearly with increasing image accelerations. Despite the fact that several sensory modalities - including the motion vision pathway - process information in a non-linear fashion signal integration at stages one to two synapses away from the motor systems and the behavioural output itself have been shown to be linear. Quantifying the closed-loop dynamics of visuo-motor control at both the behavioural and neuronal level, may provide a starting point to discover the neural mechanisms underlying an appropriate combination of complementary non-linear processes which ultimately result in a linear performance of the overall system

How director remuneration impacts firm performance: an empirical analysis of executive director remuneration in Pakistan

This study empirically investigates the interrelationship between pay and performance of CEOs/board of directors in an emerging market, Pakistan. The study uses GMM approach to account for the problem of potential endogeneity and unobserved heterogeneity that arises due to the potential reverse causality (pay and performance) for a sample of non-financial firms listed in the KSE over the period of 2009e2016. This study provides evidence that pays-performance framework supports the agency theory whereby CEOs/board of directors are compensated for their prior level of market-based performance. In addition, pay performance framework weakly support the notion of the steward/tournament theory where the CEOs/board directors pay sensitivity weakly enhanced the firm performance. Thus, CEOs/board director's remuneration is highly persistent and takes time to adjust to long-run equilibrium

An Experimental Platform to Study the Closed-loop Performance of Brain-machine Interfaces

The non-stationary nature and variability of neuronal signals is a fundamental problem in brain-machine interfacing. We developed a brain-machine interface to assess the robustness of different control-laws applied to a closed-loop image stabilization task. Taking advantage of the well-characterized fly visuomotor pathway we record the electrical activity from an identified, motion-sensitive neuron, H1, to control the yaw rotation of a two-wheeled robot. The robot is equipped with 2 high-speed video cameras providing visual motion input to a fly placed in front of 2 CRT computer monitors. The activity of the H1 neuron indicates the direction and relative speed of the robot's rotation. The neural activity is filtered and fed back into the steering system of the robot by means of proportional and proportional/adaptive control. Our goal is to test and optimize the performance of various control laws under closed-loop conditions for a broader application also in other brain machine interfaces

Determinants of Dropout and Child School Enrollment: A Case Study from Rural Islamabad

Education is an important pillar for the development of any society. Generally, school enrollment in developing countries is observed very low compared to the developed countries and the situation is further worsened by the high dropout rate. The current study investigates the major factors responsible for high dropouts in Islamabad, Pakistan, particularly in rural areas. For this purpose, the primary data have been obtained through a detailed questionnaire collecting information on child socioeconomic, household, cultural, and other characteristics. For modeling purposes, Probit model is used to investigate the effects of various factors on high child dropout rate. The results revealed that besides the distance from school to home, financial constraints are the most important reason for dropping out. Moreover, the education of father, age of the child and the gender of the child are also highly significant variables that determine the probability of a child dropout

Outcome of internal fixation procedure: miniplate vs cross K wires for displaced metacarpal metaphyseal fracture

Background: Metacarpal fractures are considered a frequent orthopedic injury seen commonly in emergency units. Objectibe of thestudy was to compare the outcome of internal fixation procedure of miniplate versus cross kirschner wires (k-wires) for displaced metacarpal metaphyseal fractures.Methods: In this experimental prospective study, 100 patients with metacarpal metaphyseal fracture were considered. internal fixation was done by miniplate in one group and cross k wires in other group. Outcomes in terms of radiological union were compared between both groups. The data was analyzed by using SPSS for windows (version 26.0).Results: Mean age of the patients was 38.70±13.61 years. Male to female ratio of the patients was 1.2:1. The radiological success was noted in 76 (76.0%) patients. Statistically insignificant difference was found between the study groups in terms of radiological success of the patients (p=0.6396). K wire fixation was recorded to have significantly shorter duration of operation time in comparison to miniplate fixation (p=0.0001).Conclusions: The internal fixation procedure of both miniplate and k wire are equally effective in terms of radiological success for management displaced metacarpal metaphysis fractures. As compared to miniplate fixation, K wire fixation was found to have significantly shorter duration of operation time

SPATA: Strong Pseudonym based AuthenTicAtion in Intelligent Transport System

Intelligent Transport System (ITS) is generally deployed to improve road safety, comfort, security, and traffic efficiency. A robust mechanism of authentication and secure communication is required to protect privacy and conditional resolution of pseudonyms to revoke malicious vehicles. In a typical ITS framework, a station can be a vehicle, Road Side Unit (RSU), or a server that can participate in communication. During authentication, the real identity of an Intelligent Transport System-Station (ITSS), referred to as a vehiclečň should not be revealed in order to preserve its privacy. In this paper, we propose a Strong Pseudonym based AutenTicAtion (SPATA) framework for preserving the real identity of vehicles. The distributed architecture of SPATA allows vehicles to generate pseudonyms in a very private and secure way. In the absence of a distributed architecture, the privacy cannot be preserved by storing information regarding vehicles in a single location. Therefore, the concept of linkability of certificates based on single authority is eliminated. This is done by keeping the real identity to pseudonym mappings distributed. Furthermore, the size of the Certificate Revocation List (CRL) is kept small, as only the most recent revoked communication pseudonyms are kept in the CRL. The privacy of the vehicle is preserved during the revocation and resolution phase through the distributed mechanism. Empirical results show that SPATA is a lightweight framework with low computational overhead, average latency, overhead ratio, and stable delivery ratio, in both sparse and dense network scenarios

State-of-the-art clinical assessment of hand function

We have assembled a multi-disciplinary team of engineers, surgeons, clinicians and neuroscientists from Johns Hopkins School of Medicine and Western University to develop a new device for assessing hand function. It will be capable of sensitively measuring fingertip forces across all five fingers and along all movement directions. Then we can use this device to develop and validate a clinical hand assessment for patients with brain injuries.https://ir.lib.uwo.ca/brainscanprojectsummaries/1005/thumbnail.jp

Structure of population activity in primary motor cortex for single finger flexion and extension

Copyright © 2020 the authors How is the primary motor cortex (M1) organized to control fine finger movements? We investigated the population activity in M1 for single finger flexion and extension, using 7T functional magnetic resonance imaging (fMRI) in female and male human participants and compared these results to the neural spiking patterns recorded in two male monkeys performing the identical task. fMRI activity patterns were distinct for movements of different fingers, but were quite similar for flexion and extension of the same finger. In contrast, spiking patterns in monkeys were quite distinct for both fingers and directions, which is similar to what was found for muscular activity patterns. The discrepancy between fMRI and electrophysiological measurements can be explained by two (non-mutually exclusive) characteristics of the organization of finger flexion and extension movements. Given that fMRI reflects predominantly input and recurrent activity, the results can be explained by an architecture in which neural populations that control flexion or extension of the same finger produce distinct outputs, but interact tightly with each other and receive similar inputs. Additionally, neurons tuned to different movement directions for the same finger (or combination of fingers) may cluster closely together, while neurons that control different finger combinations may be more spatially separated. When measuring this organization with fMRI at a coarse spatial scale, the activity patterns for flexion and extension of the same finger would appear very similar. Overall, we suggest that the discrepancy between fMRI and electrophysiological measurements provides new insights into the general organization of fine finger movements in M1

BCON : Blockchain Based Access CONtrol across Multiple Conflict of Interest Domains

In today's on-demand computing and virtual coalition environment, cross-domain services are acquired and provided. These business domains may belong to either the same or different conflict of interest system. “Transitive access” can cause leakage of information between competitors through some other conflict of interest system's member. Therefore, a secure access control mechanism is required to detect and deny “transitive access” efficiently with minimal trust in externalist. Existing access control mechanisms focused on either single or multiple conflict of interest domains but with no “transitive access”. In addition, these existing mechanisms are centralized with inherited unfair access control and are a single point of failure. Blockchain (BC) is a shared digital ledger encompassing a list of connected blocks stored on a decentralized distributed network that is secured through cryptography. We propose a BC based access control for conflict of interest domains. We have integrated a BC in our architecture to make access control fair, verifiable and decentralized. Users access histories and “transitive accesses” are stored on BC ledger. We propose a novel mechanism called “Transitive Access Checking and Enforcement (TACE)” i.e., “Algorithm.1”. It makes an authorization decision based on BC endorsement that “transitive access” will not occur. “Algorithm.2” verifies and updates users access histories stored at BC before each request approval. Similarly, “Algorithm.3” detects possible future “transitive accesses” and updates Transitive Access Set (TAS) stored at BC after each request approval. The Simple Promela Interpreter (SPIN) model checker is used to verify the proposed mechanisms for “transitive access” detection and prevention. We have identified four conflicting sequences of execution that can cause “transitive access”. Results show that the proposed mechanism is safe against “transitive access” by checking all the four possible conflicting sequences of execution