Development of a tool to measure applicability of the general systems theory to generic social work

The goal of this project was to test the applicability of the General Systems Theory to the traditionally held concept of generic social work If an applicability existed, a direct survey of the field would be feasible. This could lead to the development of a general or a core conceptualization of social work practice. General Systems Theory was extended to include the properties of the open organismic human group system. There were twenty-one categories at this level of abstraction. Internal consistency of the General Systems Theory model was tested and related to social work treatment concepts. To do this, 427 concepts which describe social work actions were isolated from traditional social work literature and its three methods of practice. The reliability of classifying these action concepts into the twenty-one General Systems Theory categories was tested. All of the action concepts could be classified into the General Systems Theory categories. None of the action concepts was classified into the twenty-second, residual category. Non-parametric statistical tests were used to measure reliability. Reliability was found to be low. The low reliability was inversely related to training and was not related to other factors tested. Grouping the action concepts in a number of different ways did not significantly change the low reliability. The social work action concepts were found to be vague, not discrete, and of uncertain levels of abstraction. Specific, concrete definition of any given action concept was found to be difficult. Within the limits of this study, it was suggested that actual social work practice would have to be reconceptualized in more accurate terms before General Systems Theory and social work practice could be reconciled

Observation of the Kapitza-Dirac Effect

In their famous 1927 experiment, Davisson and Germer observed the diffraction of electrons by a periodic material structure, so showing that electrons can behave like waves. Shortly afterwards, Kapitza and Dirac predicted that electrons should also be diffracted by a standing light wave. This Kapitza-Dirac effect is analogous to the diffraction of light by a grating, but with the roles of the wave and matter reversed. The electron and the light grating interact extremely weakly, via the ‘ponderomotive potential,’ so attempts to measure the Kapitza-Dirac effect had to wait for the development of the laser. The idea that the underlying interaction with light is resonantly enhanced for electrons in an atom led to the observation that atoms could be diffracted by a standing wave of light. Deflection of electrons by high-intensity laser light, which is also a consequence of the Kapitza-Dirac effect, has also been demonstrated. But the coherent interference that characterizes wave diffraction has not hitherto been observed. Here we report the diffraction of free electrons from a standing light wave—a realization of the Kapitza-Dirac effect as originally proposed

Temporal lenses for attosecond and femtosecond electron pulses

Here, we describe the “temporal lens” concept that can be used for the focus and magnification of ultrashort electron packets in the time domain. The temporal lenses are created by appropriately synthesizing optical pulses that interact with electrons through the ponderomotive force. With such an arrangement, a temporal lens equation with a form identical to that of conventional light optics is derived. The analog of ray diagrams, but for electrons, are constructed to help the visualization of the process of compressing electron packets. It is shown that such temporal lenses not only compensate for electron pulse broadening due to velocity dispersion but also allow compression of the packets to durations much shorter than their initial widths. With these capabilities, ultrafast electron diffraction and microscopy can be extended to new domains,and, just as importantly, electron pulses can be delivered directly on an ultrafast techniques target specimen