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P ′ P ′ precursors have been used to detect discontinuities in the lower mantle of the Earth, but some seismic phases propagating along asymmetric ray paths or scattered waves could be misinterpreted as reflections from mantle discontinuities. By forward modeling in standard 1D Earth models, we demonstrate that the frequency content, slowness, and decay with distance of precursors about 180 s before P′P′ arrival are consistent with those of the PKPPdiff phase (or PdiffPKP) at epicentral distances around 78° rather than a reflection from a lower mantle interface. Furthermore, a beamforming technique applied to waveform data recorded at the USArray demonstrates that PKPPdiff can be commonly observed from numerous earthquakes. Hence, a reference 1D Earth model without lower mantle discontinuities can explain many of the observed P′P′ precursors signals if they are interpreted as PKPPdiff, instead of P′785P′. However, this study does not exclude the possibility of 785 km interface beneath the Africa. If this interface indeed exists, P′P′ precursors at distances around 78° would better not be used for its detection to avoid interference from PKPPdiff. Indeed, it could be detected with P′P′ precursors at epicentral distances less than 76° or with other seismic phases such as backscattered PKP·PKP waves.

THE TEACHER AND THE SCHOOL SYSTEM SERVE AS THE KEY MEDIATORS IN THE ACCULTURATION OF STUDENTS FROM DEVIANT SUBCULTURES. HOWEVER, THE TEACHER'S COMMITMENT TO THE ETHICS OF WORK AND COMPETITION, HER FUTURE-ORIENTED VALUE SYSTEM, AND HER CONCEPT OF A FATHER-DOMINATED NUCLEAR FAMILY STRUCTURE TEND TO ALIENATE HER FROM HER STUDENTS. AS A RESULT, MANY INDIAN AND EAST HARLEM CHILDREN, WHOSE CULTURE IS DIFFERENT FROM HERS, MAY NEVER ACQUIRE THE TOOLS FOR FULL ACCULTURATION. ALIENATION BETWEEN STUDENT AND TEACHER IS FURTHER REINFORCED BY THE CHILD'S CONCEPT OF THE TEACHER AS A SUCCESS IN A HOSTILE CULTURE AND BY THE TEACHER'S MATERIALISTIC MOTIVATION FOR CHOOSING HER PROFESSION. MOREOVER, THE EDUCATOR'S OPPORTUNITY FOR PERSONAL, INDIVIDUAL EVALUATION OF STUDENTS IS OFTEN LIMITED BY ADMINISTRATIVE PROSCRIPTIONS. SEVERAL IMPORTANT STEPS IN TEACHER EDUCATION CAN ASSURE A MORE SUCCESSFUL CULTURAL BRIDGE BETWEEN STUDENT AND SCHOOL PERSONNEL. THE STAFF SHOULD UNDERSTAND AND ACCEPT THE PRESENCE OF ALIEN SUBCULTURES IN THEIR SCHOOL AND INITIATE MEASURES FOR PARENT COOPERATION AND STUDENT PARTICIPATION IN PROGRAMS FOR DEVELOPING SKILLS AND RAISING THE ASPIRATION LEVEL. TEACHERS SHOULD ALSO EXHIBIT FLEXIBILITY IN RECOGNIZING AND REWARDING EVIDENCES OF NONVERBAL ACHIEVEMENT. (NC)

The social-psychological bases of programs to prepare teachers for disadvantaged youth are as important to the eventual success of the program as any technique or lesson plan which seems to be momentarily fruitful. In view of the predicted oversupply of teachers, the school system must try to select teachers who will function best in the classroom, be able to see his role as a teacher instead of as a functionary, and give a longer period of service to teaching. The involvement of all relevant parties in the program is essential for success. A commitment to the human-centered aspect of teaching is crucial if the teacher is to reach the child. The focus of teaching must be directed to goals which are clearly related to the function of teaching. Feedback to teachers concerning the results of programs, the new procedures, the community concerns, and other matters relating to the school in a disadvantaged area is critical if programs are to receive the support of the teaching staff. [This paper was prepared for a book entitled "Urban Education in the 1970's," edited by A. Harry Passow, to be published by Teachers College Press, Fall 1970.] (JM)