On the compression of search trees

Let X=_x1,_x2,…,_xn$X=x_1\text{,}{x}_2\text{,}\dots \text{,}{x}_n$ be a sequence of non-decreasing integer values. Storing a compressed representation of X that supports access and search is a problem that occurs in many domains. The most common solution to this problem uses a linear list and encodes the differences between consecutive values with encodings that favor small numbers. This solution includes additional information (i.e. samples) to support efficient searching on the encoded values. We introduce a completely different alternative that achieves compression by encoding the differences in a search tree. Our proposal has many applications, such as the representation of posting lists, geographic data, sparse bitmaps, and compressed suffix arrays, to name just a few. The structure is practical and we provide an experimental evaluation to show that it is competitive with the existing techniques.     

Predicting intraindividual changes in teacher burnout: The role of perceived school environment and motivational factors

Based on self-determination theory, this study proposes and tests a motivational model of intraindividual changes in teacher burnout (emotional exhaustion, depersonalization, and reduced personal accomplishment). Participants were 806 French-Canadian teachers in public elementary and high schools. Results show that changes in teachers’ perceptions of classroom overload and students’ disruptive behavior are negatively related to changes in autonomous motivation, which in turn negatively predict changes in emotional exhaustion. Results also indicate that changes in teachers’ perceptions of students’ disruptive behaviors and school principal’s leadership behaviors are related to changes in self-efficacy, which in turn negatively predict changes in three burnout components.     

Practices and opinions reported by coordinators of graduate programs

Information is presented about the organization of graduate studies, based on questionnaire responses of 582 coordinators of Canadian graduate programs. These coordinators, who were representative of disciplines and geographic regions, provided information about a wide range of matters, including enrolments, staff, admissions, supervision, research, publications, financial support, teaching experience, and completion rates and times. Many substantial differences were noted among the percentage frequencies of responses for departments classified by discipline and size. For example, students were perceived to choose their doctoral theses topics themselves much more frequently in education, social sciences, and humanities than in engineering, medical sciences, physical sciences, and biological sciences. Also, departments with smaller numbers of full-time graduate students tended to provide all doctoral students, with some teaching experience to a greater extent than did larger departments.     

Personality profiles and dogmatism in undergraduate teacher education students

A sample of 435 junior education majors in a large Southwestern university were given the 16 Personality Factor Questionnaire and the Opinion Scale. Correlations were computed between these two scales, and a profile of personality factors was developed which defined the nature of authoritarianism or dogmatism. A step-wise multiple regression analysis revealed that an accurate prediction formula for dogmatism could not be developed from the personality factor scores. Implications for teacher education programs include research to determine if treatment programs can be developed to change a student's degree of dogmatism, and the importance of screening procedures which include an assessment of open-mindedness.