A Compartmental Model to Investigate Local and Global Ca2+ Dynamics in Astrocytes

Intracellular Ca2+ dynamics in astrocytes can be triggered by neuronal activity and in turn regulate a variety of downstream processes that modulate neuronal function. In this fashion, astrocytic Ca2+ signaling is regarded as a processor of neural network activity by means of complex spatial and temporal Ca2+ dynamics. Accordingly, a key step is to understand how different patterns of neural activity translate into spatiotemporal dynamics of intracellular Ca2+ in astrocytes. Here, we introduce a minimal compartmental model for astrocytes that can qualitatively reproduce essential hierarchical features of spatiotemporal Ca2+ dynamics in astrocytes. We find that the rate of neuronal firing determines the rate of Ca2+ spikes in single individual processes as well as in the soma of the cell, while correlations of incoming neuronal activity are important in determining the rate of “global” Ca2+ spikes that can engulf soma and the majority of processes. Significantly, our model predicts that whether the endoplasmic reticulum is shared between soma and processes or not determines the relationship between the firing rate of somatic Ca2+ events and the rate of neural network activity. Together these results provide intuition about how neural activity in combination with inherent cellular properties shapes spatiotemporal astrocytic Ca2+ dynamics, and provide experimentally testable predictions

Polychrony as Chinampas

We study the flow of signals through paths with the following condition: a node emits a signal if two incoming signals from other nodes arrive coincidentally or if it receives an external stimuli. We apply our study to count and describe families of polychrony groups on a line, and we introduce triangular sequences.Comment: 32 pages. We refocus our study on nonlinear signal-flow graphs. We add possible generalizations of our wor

Investigating Intumescent Expanding Coatings for Process Safety

This document outlines the methodology for testing an intumescent material paint as a means of filling container punctures within hydrogen fuel cells. Working from existing literature on similar materials, as well as design specifications provided by the sponsors, a scale model of a hydrogen fuel cell was constructed in order to model the system. A commercial, low-temperature intumescent paint was used as a preliminary test material. This material failed to properly seal the artificial puncture in the fuel cell model. Additional research is recommended to develop intumescent materials that react at lower temperatures

Traffic Mobility Patterns on the Ocean Drive Corridor

In recent years vehicle congestion has become a problem in Acadia National Park. The Ocean Drive Corridor is one area of the park where congestion is a major problem. Our project collects data through the use of Streetlight, in-person monitoring, camera monitoring and questionnaires. We found that visitors do not stay in the Sand Beach Area very long, the majority of people do not visit Sand Beach, visitors are willing to use a reservation system and the Island Explorer is an option for transportation in the Ocean Drive Corridor. Our recommendations for Acadia are the implementation of a new pilot reservation system specifically at the Sand Beach Parking Lot and increasing advertisement of the Island Explorer

Fournier?s gangrene - delayed pedicle flap based upon the anterior abdominal wall

Introduction Fournier’s gangrene is a poly-microbial necrotizing fasciitis that involves the perineum and/or external genitalia. Urgent surgical debridement is well recognized as essential acute treatment yet unique challenges arise for plastic surgical reconstruction to obtain a complete functional recovery. This case describes a successful delayed pedicle flap repair based upon the anterior abdominal wall. Case description A 24 year old man was admitted to ICU ten days after elective circumcision with Fournier’s gangrene. He underwent a number of surgical debridements, and was referred for plastic surgical management. He had penile reconstruction using a random pattern abdominal flap, which was performed as a three stage procedure including flap vascular delay technique. Discussion Perineal and penile skin loss can be significant and is difficult to repair. Various techniques have been used to reconstruct lost tissue: skin grafts, transposition of the testes and spermatic cords to the thigh, flaps, and other types of pediculated myocutaneous flaps. Muscle flap reconstruction provides an environment that allows for complete regeneration of the urethral epithelium but is bulky and unsightly. Skin grafts contract and may produce painful and dysfunctional reconstructions. This novel technique produces a functional, and aesthetic reconstruction. Conclusion Penile skin recovery following Fournier’s gangrene recovery is problematic. This case demonstrates the functionality of a delayed flap repair using the anterior abdominal wall

Polychrony as Chinampas

In this paper, we study the flow of signals through linear paths with the nonlinear condition that a node emits a signal when it receives external stimuli or when two incoming signals from other nodes arrive coincidentally with a combined amplitude above a fixed threshold. Sets of such nodes form a polychrony group and can sometimes lead to cascades. In the context of this work, cascades are polychrony groups in which the number of nodes activated as a consequence of other nodes is greater than the number of externally activated nodes. The difference between these two numbers is the so-called profit. Given the initial conditions, we predict the conditions for a vertex to activate at a prescribed time and provide an algorithm to efficiently reconstruct a cascade. We develop a dictionary between polychrony groups and graph theory. We call the graph corresponding to a cascade a chinampa. This link leads to a topological classification of chinampas. We enumerate the chinampas of profits zero and one and the description of a family of chinampas isomorphic to a family of partially ordered sets, which implies that the enumeration problem of this family is equivalent to computing the Stanley-order polynomials of those partially ordered sets