Locating, characterizing and minimizing sources of error for a paper case-based structured oral examination in a multi-campus clerkship.

OBJECTIVE: To determine consistency of assessment in a new paper case-based structured oral examination in a multi-community pediatrics clerkship, and to identify correctable problems in the administration of examination and assessment process. METHOD: Nine paper case-based oral examinations were audio-taped. From audio-tapes five community coordinators scored examiner behaviors and graded student performance. Correlations among examiner behaviors scores were examined. Graphs identified grading patterns of evaluators. The effect of exam-giving on evaluators was assessed by t-test. Reliability of grades was calculated and the effect of reducing assessment problems was modeled. RESULTS: Exam-givers differed most in their "teaching-guiding" behavior, and this negatively correlated with student grades. Exam reliability was lowered mainly by evaluator differences in leniency and grading pattern; less important was absence of standardization in cases. CONCLUSIONS: While grade reliability was low in early use of the paper case-based oral examination, modeling of plausible effects of training and monitoring for greater uniformity in administration of the examination and assigning scores suggests that more adequate reliabilities can be attained.

Sensitive absorption spectroscopy by use of an asymmetric multiple-quantum-well diode laser in an external cavity.

We have developed a broadly tunable diode laser system by employing custom-designed asymmetric multiple-quantum-well (AMQW) InGaAsP lasers in an external cavity configuration. Feedback is provided by a diffractive optical element with high coupling efficiency and wavelength selectivity, allowing for single-mode tuning of the output wavelength by varying the external cavity length. This tunable laser system was used experimentally to perform absorption spectroscopy on weak CO2 lines over a broad wavelength region in the near infrared. An experimental tuning range of 80 nm has been observed for a laser cavity length of 600 micron, which is double the tuning range found with conventional, uncoated quantum-well lasers. We achieved a detection sensitivity of 5 x 10(-6) at 95% confidence over the wavelength range of 1.54-1.62 micron by employing a second-harmonic detection technique. The theoretical predictions of a broad gain profile from an ambipolar rate equation model are found to correspond to the experimentally observed increased tunability of the uncoated AMQW lasers.

Radiography of spontaneous periodontitis in dogs.

The pattern and distribution of periodontitis were investigated in 162 randomly selected dogs available for necropsy in veterinary practice. There were 82 males and 80 females of 50 different breeds (150 dogs were pure-bred and 12 were mongrels, aged between 7 months and 14 yr. Presence of periodontitis was determined by assessment of alveolar bone loss on radiographs of the skulls and jaws. Periodontitis occurred frequently with increasing age, although the prevalence varied markedly among and within different breeds. Of the breeds most represented in the sample, periodontitis was most frequently seen in poodles and dachshunds but was rarely recognized in German shepherd dogs. Regardless of age, the vast majority of the dogs displayed either one or both of two different radiographic patterns of alveolar bone loss. One pattern was characterized by slight, horizontal alveolar bone loss involving interradicular and interdental areas. The other pattern was one of predominantly crater-like, or narrow, vertical bone defects which, when advanced, often extended around a single root or tooth to surround the root apices. The two types of patterns did not seem to be breed-dependent. The posterior maxillary and mandibular premolars and molars were the most frequently affected teeth. Alveolar bone loss was most severe in the maxilla, while corresponding bone loss in the mandible was more often related to increasing age.