# Research

## Complex Systems: Mathematics, Computation & Science

### Wednesday, November 26, 2003

Information for this presentation is not available.

### Wednesday, November 19, 2003

Title: Deoxyribozyme-based decision-making networks: Logic gates, circuits and automata
Speaker: Milan Stojanovic, Department of Chemistry
Columbia University
Time: 1:00pm–2:00pm
Place: SCA 202

#### Abstract

Deoxyribozymes are nucleic acid enzymes. Using modular design, deoxyribozymes may be turned into sensors for oligonucleo-tides. Extending this principle, a complete set of logic gates can be constructed, with oligonucleotides with inputs and catalytic chemical reaction as an output. These logic gates could be arranged into solution-phase circuits and automata, capable of more complex Boolean calculations.

### Wednesday, November 12, 2003

Information for this presentation is not available.

### Wednesday, October 29, 2003

Title: When will it happen? “Stopping Time” and “Concentration”
Speaker: MGreg McColm
Time: 1:00pm–2:00pm
Place: SCA 202

#### Abstract

Many phenomena involve a scientist waiting to see WHEN something will happen. The time WHEN it happens is called the "stopping time," as that is when the scientist can stop waiting.

Some phenomena are actually complexes of many simpler phenomena, and what we are waiting for is some global event that is a consequence of many local events. The question is: how predictable is the time the global event occurs?

We will look at some of the examples, issues and outstanding problems in this area.

NOTE: This presentation will be designed to be accessible to non-mathematicians.

### Wednesday, October 15, 2003

Title: Dispersal Ecology: Why it's Important Biologically, and Why and Where Current Models Fail
Speaker: Gordon Fox, Biology Department, USF
Time: 1:00pm–2:00pm
Place: SCA 202

TBA

### Wednesday, October 1, 2003

Title: Bifurcation of Kidney Hemodynamics in Hypertension
Speaker: Daniel Yip, Physiology and Biophysics Department, USF
Time: 1:00pm–2:00pm
Place: SCA 202

#### Abstract

Each rat kidney is composed of 250,000-500,000 functional subunits called nephron. Each nephron is a limited cycle oscillator coupled to adjacent nephrons that supplied by the same cortical radial artery. The oscillations are due to the time delays and intrinsic nonlinearity in the intra-nephron feedback loop, tubuloglomerular feedback. Oscillations of $$30$$ mHz are found in hydraulic pressure, flow and chloride concentrations within each nephron. The oscillations become aperiodic in animal with genetic hypertension, or experimentally induced hypertension. The time series of these apparent random fluctuations bear some characteristic of deterministic chaos. Using non-invasive laser doppler velocimetry to monitor the spontaneous variations of blood flow in a single nephron. We detected a fast oscillation ($$100$$-$$150$$ mHz) superimposes on top of the tubuloglomerular feedback mediated oscillations ($$30$$ mHz). We suggested that these two oscillatory mechanisms interact in a nonlinear manner, and that development of hypertension alters this interaction and leads to the bifurcation of kidney hemodynamics.

### Wednesday, September 17, 2003

Title: Mathematical Models for Recombinant DNA Processes
Speaker: Nataša Jonoska and Masahico Saito
Time: 1:00pm–2:00pm
Place: SCA 202

#### Abstract

We will present a mathematical observation about how knot theory could give a possible explanation for actions of topoisomerases. We also present another mathematical observation about possible use of formal language theory in explaining the gene assembly in ciliates. We hope to start a discussion about these and other genetic processes that could be explained by some of these techniques.