Light scattering spectroscopy of the liquid-glass transition : comparison with idealized and extended mode coupling theory
Light scattering experiments were performed on several fragile glass-forming materials at temperatures ranging from above the melting temperature T, to below the calorimetric glass transition temperature T, in the frequency range 0.2 GHz to 4000 GHz. The experimental susceptibility spectra x”(o) exhibit both the form and the scaling properties predicted by the idealized mode coupling theory. In particular, the scaling frequency o, was found to obey the power law w, a 1 T T,_jzO for three different materials, confirming the predicted “critical slowing down” as T+ Tc from either above or below. At low frequencies and temperatures the spectra deviate from the predictions due to the neglect of ergodicity-restoring activated transport (hopping) processes. We have therefore reanalyzed the data using the extended version of the theory, including activated transport.
Light scattering spectroscopy of the liquid-glass transition
Supercooled liquids approaching the liquid-glass transition exhibit unusual properties associated with structural relaxation. The mode-coupling theory (MCT) of supercooled liquid dynamics shows that non-linear interactions among density fluctuation modes can produce effects resembling these observations. MCT produces detailed predictions for the dynamics of density fluctuations in supercooled liquids, including a crossover from liquid to glassy dynamics at a critical temperature Tc. Recent light scattering studies of supercooled CaKNO3 are described that have provided detailed tests of MCT both above and below Tc, including a cusp in the scaling time at Tc=105+or-5 degrees C. These experiments are reviewed, and comparisons with both the idealized and extended versions of MCT are described.
Therapist-case managers: more than brokers of services.
For satisfactory adjustment into the community, the long-term patient often needs assistance in dealing with a bureaucracy of agencies and departments. Some professionals have suggested establishing the role of case manager, but the case manager system is susceptible to becoming an impersonal bureaucracy itself. The author suggests that case management functions are part of the normal duties of a conscientious therapist, and that only through significant therapeutic involvement does a case manager acquire the in-depth knowledge of the patient to adequately assess his needs and facilitate the processes for meeting them. Thus the case manager should be not simply an intermediate broker of services but the patient's primary therapist. With the "therapist-case manager," the functions of therapy and case management would be combined. If therapists fail to do case management or to treat long-term patients altogether, this problem should be dealt with directly rather than simply by adding another member to the team.