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Essential Nonlinearities In Hearing

The hearing organ, the cochlea, evidently poises itself at a Hopf bifurcation to maximize tuning and amplification. At a seminar sponsored by the Department of Mathematical Sciences and Center for Applied Statistics, Friday, Sept. 22, 11:30 a.m., in Cullimore Lecture Hall 2. when Marcelo Magnasco, of Rockefeller University, will present "Essential Nonlinearities in Hearing.

Magnasco will show that in this condition, several effects are expected to be generic, including compression of the dynamic angle, infinitely sharp tuning at zero input and generation of combination tones. These effects, he will say, are "essentially" nonlinear in that they become more marked the smaller the forcing because there is no audible sound soft enough not to evoke them. All the well-documented nonlinear aspects of hearing therefore appear to be consequences of the same underlying mechanism.

Classification Of A Developed Coastal Barrier

Coastal barriers will be the topic of a seminar sponsored by the Department of Mathematical Sciences and the Center for Applied Mathematics and Statistics, Wednesday, Sept. 27, 2:45 p.m., in Cullimore Lecture Hall 2.

Nancy Jackson, associate professor of geography, will address the "Classification of a Developed Coastal Barrier." According to Jackson, changes to shorelines can be attributed to both natural processes and human activity. Rising income has led to increased economic growth in coastal communities, and the result is more people at risk to coastal hazards. On developed shorelines where real estate values and tourism revenues are high, stabilization is the common hazard response and retreat is difficult for the public to accept, even with economic incentives. Successful reduction of risk in these environments is influenced by knowledge of how geomorphological and socio-economic attributes of the coastal environment interact over time. Data gathered on geomorphic and social infrastructure variables from sequential aerial photographs (1940, 1950, 1960, 1963, 1978, and 1987) of Seven Mile Island, N.J. were analyzed to classify barrier island attributes. The island is bounded by two unjettied inlets and has two residential settlements separated by a sparsely developed area. Factor analysis identified a recurring geomorphic factor of variables describing beach width, dune width and inlet distance, and a settlement factor of variables describing shore parallel walls, groins and shorefront buildings.

The geomorphic factor explained an increasing percentage of the total variance through time, despite an overall increase in buildings, due to inlet processes and hazard management policies that emphasize geomorphically compatible erosion mitigation.

Synchronization And Phase Locking In Chaotic Systems

An overview of the mathematical formulation and description of generalized synchronization and phase synchronization of chaotic systems will be the topic of a seminar sponsored by the Department of Mathematical Sciences and Center for Applied Mathematics and Statistics, Friday, Sept. 29, 11:30 a.m., in Cullimore Lecture Hall 2.

Kresimir Josic, of Boston University, will present "Synchronization and Phase Locking in Chaotic Systems," which have been studied since the 17th century and during the last decade the occurrence of the same phenomena in chaotic systems has received major attention. Although synchronization between chaotic systems is frequently defined in terms of the existence of normally hyperbolic invariant manifolds, Josic will show that recent evidence shows that this might be too restrictive. Josic will provide a number of examples of systems that are synchronized even when invariant manifolds do not exist. He also will discuss several modes in which strict synchronization gives way to more general types of synchrony and an overview of criteria for weak synchronization.

Ground Water Aquifers: Their Use And Abuse

The characteristics of ground water aquifers and how they are utilized for water supply will be the topic of a seminar for secondary school earth science teachers, co-sponsored by the Department of Civil and Environmental Engineering at NJIT and the Department of Geology at Rutgers-Newark, Thursday, Oct. 26, 9 a.m.-3 p.m., in Guttenberg Information Technologies Center 3710.

The seminar will cover the mechanisms by which aquifers become contaminated by improper waste disposal practices and innovative techniques to restore polluted aquifers.

A $25 registration fee is required. Deadline for registration is Oct. 16.
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