A Moving Bump in a Continuous Manifold: A Comprehensive Study of the Tracking Dynamics of Continuous Attractor Neural Networks

Understanding how the dynamics of a neural network is shaped by the network structure, and consequently how the network structure facilitates the functions implemented by the neural system, is at the core of using mathematical models to elucidate brain functions. This study investigates the tracking dynamics of continuous attractor neural networks (CANNs). Due to the translational invariance of neuronal recurrent interactions, CANNs can hold a continuous family of stationary states. They form a continuous manifold in which the neural system is neutrally stable. We systematically explore how this property facilitates the tracking performance of a CANN, which is believed to have clear correspondence with brain functions. By using the wave functions of the quantum harmonic oscillator as the basis, we demonstrate how the dynamics of a CANN is decomposed into different motion modes, corresponding to distortions in the amplitude, position, width or skewness of the network state. We then develop a perturbative approach that utilizes the dominating movement of the network's stationary states in the state space. This method allows us to approximate the network dynamics up to an arbitrary accuracy depending on the order of perturbation used. We quantify the distortions of a Gaussian bump during tracking, and study their effects on the tracking performance. Results are obtained on the maximum speed for a moving stimulus to be trackable and the reaction time for the network to catch up with an abrupt change in the stimulus.Comment: 43 pages, 10 figure

Campus Apartment Architecture Style and Likelihood to Graduate: An Exploratory Study at a Southern Public Liberal Arts University

Because of increased opportunities for social interaction, undergraduate students living on campus are more likely to persist and graduate than their counterparts.  Residence hall design also contributes to student interaction.  This study explores the relationship between campus apartment design and graduation rates of a sophomore cohort attending a southern public liberal arts university.  Initial findings indicate students living in a communal apartment complex were more likely to graduate than those living in traditional complexes; a multivariate logistic regression finds the strongest predictors of graduation are race/ethnicity and semester credit hours earned.  Implications and suggestions for future research are discussed

Campus Apartment Architecture Style and Likelihood to Graduate

Because of increased opportunities for social interaction, undergraduate students living on campus are more likely to persist and graduate than their counterparts. Residence hall design also contributes to student interaction. This study explores the relationship between campus apartment design and graduation rates of a sophomore cohort attending a southern public liberal arts university. Initial findings indicate students living in a communal apartment complex were more likely to graduate than those living in traditional complexes; a multivariate logistic regression finds the strongest predictors of graduation are race/ethnicity and semester credit hours earned. Implications and suggestions for future research are discussed

Development of a vaccine based on recombinant subunit proteins to protect humans and animals against filovirus disease

Ebola Virus Disease (EVD) is the most prominent example of filovirus disease and as a zoonotic virus fits the characteristics of a neglected tropical disease. Despite being characterized as a Category A Priority Pathogen by NIH/NIAID over a decade ago, EVD lacked public and private research resources due to the absence of a commercial market. Previously, outbreaks of limited scale linked to transmission from livestock or wild animals into the human population occurred in the endemic areas located in the forested regions of Central Africa and the Philippines (for Reston ebolavirus), therefore other public health threats garnered more attention. This changed recently in 2013-2015 when an Ebola virus (EBOV) outbreak of increasing size in several West African countries started to reveal the true epidemic potential that filovirus infections can have when entering an urban setting in a highly mobile society. As typical in an epidemic with a significant number of infectious patients traveling within and from the endemic area, the disease was also exported outside the outbreak region as has been shown with introductions into Nigeria, Mali, and the United States (amongst other countries averting in-country transmission from imported cases). This demonstrated the threat posed to the global public health systems if spread of Ebola or a related filovirus cannot be contained at its source. We have produced three soluble recombinant filovirus glycoproteins (GP) and the matrix proteins of EBOV (VP24 and VP40) using the Drosophila S2 cell expression system. For each antigen, a specific immunoaffinity chromatography method was developed to allow purification to purity levels \u3e90%. The immunogenicity of recombinant subunits and admixtures formulated with or without clinically relevant adjuvants was subsequently evaluated in mice, guinea pigs and macaques. Strong antigen-specific IgG titers as well as virus neutralizing titers were observed after administering two or three doses of adjuvanted formulations. In mice and non-human primates subunit proteins were also shown to elicit cell mediated immune responses. Analysis of secreted cytokines in batch-cultured, antigen-stimulated splenocytes or PBMC’s demonstrated antigen-induced Th1 and Th2 type responses. Recombinant vaccine candidates were tested in mice for protection against challenge with mouse-adapted EBOV. All vaccine formulations containing EBOV GP generated protective responses and serum transfer from such animals into naïve mice demonstrated that humoral immunity alone can be fully protective. Furthermore, the transfer of immune splenocytes into naïve mice showed that recombinant GP and VP24 subunits elicit functional T cell responses that lead to protection against live virus challenge. Immunogenicity and efficacy studies in guinea pigs were focused on optimized antigen dosing, antigenic balance and adjuvantation. Multiple formulations consistently produced strong antibody responses and demonstrated 100% protective efficacy in the EBOV guinea pig model. Results from studies in two species of non-human primates suggest that vaccination with GP+VP40+VP24 and an emulsion-based adjuvant consistently produces high anti-EBOV IgG and virus neutralizing titers. This prevents viremia subsequent to live virus challenge and protects animals from terminal EBOV disease. These studies suggest that we have defined a viable Ebola virus vaccine candidate based on non-replicating viral subunits. Current efforts in our laboratory are focused on defining correlates of protection to allow clinical development of a monovalent vaccine candidate for protection against EVD and further formulation optimization towards a trivalent, recombinant subunit vaccine with protective efficacy against EBOV, Sudan ebolavirus (SUDV) and Marburgvirus (MARV) infection

Minimizing Unsatisfaction in Colourful Neighbourhoods

Colouring sparse graphs under various restrictions is a theoretical problem of significant practical relevance. Here we consider the problem of maximizing the number of different colours available at the nodes and their neighbourhoods, given a predetermined number of colours. In the analytical framework of a tree approximation, carried out at both zero and finite temperatures, solutions obtained by population dynamics give rise to estimates of the threshold connectivity for the incomplete to complete transition, which are consistent with those of existing algorithms. The nature of the transition as well as the validity of the tree approximation are investigated.Comment: 28 pages, 12 figures, substantially revised with additional explanatio

Surgical Approaches to Create Murine Models of Human Wound Healing

Wound repair is a complex biologic process which becomes abnormal in numerous disease states. Although in vitro models have been important in identifying critical repair pathways in specific cell populations, in vivo models are necessary to obtain a more comprehensive and pertinent understanding of human wound healing. The laboratory mouse has long been the most common animal research tool and numerous transgenic strains and models have been developed to help researchers study the molecular pathways involved in wound repair and regeneration. This paper aims to highlight common surgical mouse models of cutaneous disease and to provide investigators with a better understanding of the benefits and limitations of these models for translational applications

Dynamical and Stationary Properties of On-line Learning from Finite Training Sets

The dynamical and stationary properties of on-line learning from finite training sets are analysed using the cavity method. For large input dimensions, we derive equations for the macroscopic parameters, namely, the student-teacher correlation, the student-student autocorrelation and the learning force uctuation. This enables us to provide analytical solutions to Adaline learning as a benchmark. Theoretical predictions of training errors in transient and stationary states are obtained by a Monte Carlo sampling procedure. Generalization and training errors are found to agree with simulations. The physical origin of the critical learning rate is presented. Comparison with batch learning is discussed throughout the paper.Comment: 30 pages, 4 figure