Modelling genetic networks with noisy and varied experimental data: the circadian clock in Arabidopsis thaliana.

Circadian clocks in all organisms include feedback loops that generate rhythmic expression of key genes. We model the first such loop proposed for the clock of Arabidopsis thaliana, the experimental model species for circadian timing in higher plants. As for many biological systems, there are no experimental values for the parameters in our model, and the data available for parameter fitting is noisy and varied. To tackle this we constructed a cost function, which quantifies the agreement between our model and various key experimental features. We then undertook an efficient global search of parameter space, to test whether the proposed circuit can fit the experimental data. Using this approach we show that circadian clock models can function well with low cooperativity in transcriptional regulation, whereas high cooperativity has been a feature of previous (hand-fitted) clock models in other species. Our optimized solution for the Arabidopsis clock model fits several, but not all, of the key experimental features. We test the predicted effects of well-characterized mutations in the clock circuit and show the phases of the circadian cycle where additional components that are yet to be identified experimentally must be present to complete the circadian feedback loop.

Board certification in optometry.

BACKGROUND: In keeping with current expectations in the health care community, the purpose of the American Board of Optometric Practice (ABOP) is to enhance the quality of optometric care available to the public by fostering continued competence for practitioners through administering education and examinations for certification and re-certification. The formation of ABOP makes possible for the first time a board certification process for optometrists. METHODS: The optometry model for board certification and recertification emphasizes the breadth of the profession. ABOP certification will be accomplished through a combination of examinations and high-quality, tested Board Certified Continuing Education (BCCE). Specific requirements for practitioners at various stages of their careers are presented. RESULTS: Board certification provides one important mechanism for an optometrist to demonstrate commitment to quality, professionalism, and ongoing clinical competence. The optometrist benefits from high-quality continuing education designed for timeliness, importance, and breadth. The public benefits by the enhancement of continued competence within the optometric profession. Health care agencies benefit by being able to recognize providers who have elected to demonstrate their qualifications through certification. CONCLUSIONS: Through board certification, optometrists will be able to demonstrate their commitment to maintaining clinical competence through a nationally uniform program, and they will be able to comply with standards that are generally recognized and required throughout the health care community.