Quantitative Analysis of Electrotonic Structure and Membrane Properties of NMDA-Activated Lamprey Spinal Neurons

Parameter optimization methods were used to quantitatively analyze frequency-domain-voltage-clamp data of NMDA-activated lamprey spinal neurons simultaneously over a wide range of membrane potentials. A neuronal cable model was used to explicitly take into account receptors located on the dendritic trees. The driving point membrane admittance was measured from the cell soma in response to a Fourier synthesized point voltage clamp stimulus. The data were fitted to an equivalent cable model consisting of a single lumped soma compartment coupled resistively to a series of equal dendritic compartments. The model contains voltage-dependent NMDA sensitive (INMDA), slow potassium (IK), and leakage (IL) currents. Both the passive cable properties and the voltage dependence of ion channel kinetics were estimated, including the electrotonic structure of the cell, the steady-state gating characteristics, and the time constants for particular voltage- and time-dependent ionic conductances. An alternate kinetic formulation was developed that consisted of steady-state values for the gating parameters and their time constants at half-activation values as well as slopes of these parameters at half-activation. This procedure allowed independent restrictions on the magnitude and slope of both the steady-state gating variable and its associated time constant. Quantitative estimates of the voltage-dependent membrane ion conductances and their kinetic parameters were used to solve the nonlinear equations describing dynamic responses. The model accurately predicts current clamp responses and is consistent with experimentally measured TTX-resistant NMDA-induced patterned activity. In summary, an analysis method is developed that provides a pragmatic approach to quantitatively describe a nonlinear neuronal system

American Muslims: How the “American Creed” Fosters Assimilation and Pluralism

This article examines the status of American Muslims in the United States in relationship to other cultural groups and some of the widespread stereotypes that plague Muslims in contemporary society. Much has been written about the discrimination faced by Muslims, particularly after the September 11, 2001 attacks, spawned by religious, racial, and ethnic bigotry. Some polls show many Americans harbor some prejudices against Muslims, but these prejudices have not resulted in widespread violence or discrimination; although there has been some violence and discrimination experienced by some Muslims, the empirical data show that the majority of American Muslims are very successful economically, educationally, socially content, and politically active. This can be explained by America’s commitment to the “American Creed: The core values of the United States—liberty, democracy, equality of opportunity, the rule of law, individualism, separation of church and state, and social justice—have allowed Muslims, like other cultural groups, to assimilate into America’s political and economic culture and maintain their distinct religious identity. This demonstrates that America’s historical and painful struggle to evolve—defined as the attempt to narrow the gap between our ideals and actual behavior—has produced a more just and democratic, albeit imperfect, society

Doctor of Philosophy

dissertationA fundamental challenge for the immune system is the distinction between self and nonself, or infected and uninfected. Autoimmune disease arises when the immune response mounts an immune response against the hosts tissues. Via a mathematical model, we show that the immune system can distinguish self from nonself via the interaction of T-cells and and dendritic cells (DCs) and explain how autoimmunity is avoided in most people most of the time. The NOD mouse develops Type 1 diabetes, an autoimmune disease, spontaneously with an incidence of about 80% in females. The progression of Type 1 diabetes may be either accelerated or delayed by viral infection. We first create a mathematical model to understand the factors that affect progression in uninfected mice and how it may be interrupted via certain treatments. We categorize which types of viral infection should accelerate Type 1 diabetes or delay. We find that the timing of infection is important, as well as the cell type infected

Fatigue testing a plurality of test specimens and method

Described is a fatigue testing apparatus for simultaneously subjecting a plurality of material test specimens to cyclical tension loading to determine the fatigue strength of the material. The fatigue testing apparatus includes a pulling head having cylinders defined therein which carry reciprocating pistons. The reciprocation of the pistons is determined by cyclical supplies of pressurized fluid to the cylinders. Piston rods extend from the pistons through the pulling head and are attachable to one end of the test specimens, the other end of the test specimens being attachable to a fixed base, causing test specimens attached between the piston rods and the base to be subjected to cyclical tension loading. Because all the cylinders share a common pressurized fluid supply, the breaking of a test specimen does not substantially affect the pressure of the fluid supplied to the other cylinders nor the tension applied to the other test specimens

Time, action and psychosis: using subjective time to investigate the effects of ketamine on sense of agency

Sense of agency refers to the experience of initiating and controlling actions in order to influence events in the outside world. A disturbed sense of agency is found in certain psychiatric and neurological disorders, most notably schizophrenia. Sense of agency is associated with a subjective compression of time: actions and their outcomes are perceived as bound together in time. This is known as ‘intentional binding’ and, in healthy adults, depends partly on advance prediction of action outcomes. Notably, this predictive contribution is disrupted in patients with schizophrenia. In the present study we aimed to characterise the psychotomimetic effect of ketamine, a drug model for psychosis, on the predictive contribution to intentional binding. It was shown that ketamine produced a disruption that closely resembled previous data from patients in the early, prodromal, stage of schizophrenic illness. These results are discussed in terms of established models of delusion formation in schizophrenia. The link between time and agency, more generally, is also considered

Supersonic through-flow fan design

The NASA Lewis Research Center has embarked on a program to experimentally prove the concept of a supersonic through-flow fan which is to maintain supersonic velocities throughout the compression system with only weak shock-wave flow losses. The detailed design of a supersonic through-flow fan and estimated off-design performance with the use of advanced computational codes are described. A multistage compressor facility is being modified for the newly designed supersonic through-flow fan and the major aspects of this modification are briefly described