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Common Cyclic Vectors For Unitary Operators, William T. Ross, Warren R. Wogen Jan 2009

Common Cyclic Vectors For Unitary Operators, William T. Ross, Warren R. Wogen

Department of Math & Statistics Faculty Publications

In this paper, we determine whether or not certain natural classes of unitary multiplication operators on L2(dƟ) have common cyclic vectors. For some classes which have common cyclic vectors, we obtain a classification of these vectors.


Extending The Skill Test For Disease Diagnosis, Shu-Chuan Lin, Paul H. Kvam, Jye-Chyi Lu Jan 2009

Extending The Skill Test For Disease Diagnosis, Shu-Chuan Lin, Paul H. Kvam, Jye-Chyi Lu

Department of Math & Statistics Faculty Publications

For diagnostic tests, we present an extension to the skill plot introduced by Briggs and Zaretski (Biometrics 2008; 64:250–261). The method is motivated by diagnostic measures for osteopetrosis in a study summarized by Hans et al. (The Lancet 1996; 348:511–514). Diagnostic test accuracy is typically defined using the area (or partial area) under the receiver operator characteristic (ROC) curve. If partial area is used, the resulting statistic can be highly subjective because the focus region of the ROC curve corresponds to a set of low false‐positive rates that are chosen by the experimenter. This paper introduces a more …


Complementary Responses To Mean And Variance Modulations In The Perfect Integrate-And-Fire Model, Joanna R. Wares, Todd W. Troyer Jan 2009

Complementary Responses To Mean And Variance Modulations In The Perfect Integrate-And-Fire Model, Joanna R. Wares, Todd W. Troyer

Department of Math & Statistics Faculty Publications

In the perfect integrate-and-fire model (PIF), the membrane voltage is proportional to the integral of the input current since the time of the previous spike. It has been shown that the firing rate within a noise free ensemble of PIF neurons responds instantaneously to dynamic changes in the input current, whereas in the presence of white noise, model neurons preferentially pass low frequency modulations of the mean current. Here, we prove that when the input variance is perturbed while holding the mean current constant, the PIF responds preferentially to high frequency modulations. Moreover, the linear filters for mean and variance …


Biology In Mathematics At The University Of Richmond, Lester Caudill Jan 2009

Biology In Mathematics At The University Of Richmond, Lester Caudill

Department of Math & Statistics Faculty Publications

In an effort to meet the needs of science students for modeling skills, three new courses have been created at the University of Richmond: Scientific Calculus I and II, and Mathematical Models in Biology and Medicine. The courses are described, and lessons learned and future directions are discussed.


A Nonlinear Extremal Problem On The Hardy Space, William T. Ross, Stephan Ramon Garcia Jan 2009

A Nonlinear Extremal Problem On The Hardy Space, William T. Ross, Stephan Ramon Garcia

Department of Math & Statistics Faculty Publications

We relate some classical extremal problems on the Hardy space to norms of truncated Toeplitz operators and complex symmetric operators