The First Year of College: A Follow-up Normative Report

The major purpose of this ongoing research program is to determine how students are affected by the colleges they attend (Astin, Panos, and Creager, 1966). Consequently, subsamples of the original groups of participating students have been periodically followed up. These follow-up surveys consist in part of post-tests on selected items administered previously in the Freshman Information Form and in part of items that cover the student\u27s experiences and achievements at his institution, his aspirations and plans for the future, his perceptions and evaluations of the college environment, and his educational outcomes and academic standing

National Norms for Entering College Freshmen—Fall 1969

This report presents national normative data on the characteristics of students entering colleges as first-time, full-time freshmen in 1969. It is the fourth such annual report developed as part of the Cooperative Institutional Research Program being conducted by the Office of Research of the American Council on Education. The major purpose of this ongoing research program is to determine how students are affected by the colleges they attend (Astin, Panos, and Creager, 1966). As evidenced by the wide response to the earlier normative reports (Astin, Panos, and Creager, 1967a, 1967b; Panos, Astin and Creager, 1967; and Creager, Astin,Boruch, and Bayer, 1968), the information provided has been valuable to those engaged in guidance, counseling, administration, educational research, and manpower studies

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Time-resolved and continuous-wave optical spin pumping of semiconductor quantum wells

Experimental and theoretical studies of all-optical spin pump and probe of resident electrons in CdTe/(Cd,Mg)Te semiconductor quantum wells are reported. A two-color Hanle-MOKE technique (based on continuous-wave excitation) and time-resolved Kerr rotation in the regime of resonant spin amplification (based on pulsed excitation) provide a complementary measure of electron spin relaxation time. Influence of electron localization on long-lived spin coherence is examined by means of spectral and temperature dependencies. Various scenarios of spin polarization generation (via the trion and exciton states) are analyzed and difference between continuous-wave and pulsed excitations is considered. Effects related to inhomogeneous distribution of $g$-factor and anisotropic spin relaxation time on measured quantities are discussed.Comment: 26 pages, 19 figures, submitted to special issue on Optical Orientation of Semiconductor Science and Technolog

Dynamic Glass Transition in Two Dimensions

The question about the existence of a structural glass transition in two dimensions is studied using mode coupling theory (MCT). We determine the explicit d-dependence of the memory functional of mode coupling for one-component systems. Applied to two dimensions we solve the MCT equations numerically for monodisperse hard discs. A dynamic glass transition is found at a critical packing fraction phi_c^{d=2} = 0.697 which is above phi_c^{d=3} = 0.516 by about 35%. phi^d_c scales approximately with phi^d_{\rm rcp} the value for random close packing, at least for d=2, 3. Quantities characterizing the local, cooperative 'cage motion' do not differ much for d=2 and d=3, and we e.g. find the Lindemann criterion for the localization length at the glass transition. The final relaxation obeys the superposition principle, collapsing remarkably well onto a Kohlrausch law. The d=2 MCT results are in qualitative agreement with existing results from MC and MD simulations. The mean squared displacements measured experimentally for a quasi-two-dimensional binary system of dipolar hard spheres can be described satisfactorily by MCT for monodisperse hard discs over four decades in time provided the experimental control parameter Gamma (which measures the strength of dipolar interactions) and the packing fraction phi are properly related to each other.Comment: 14 pages, 15 figure