Mechanical control of spin states in spin-1 molecules and the underscreened Kondo effect.

The ability to make electrical contact to single molecules creates opportunities to examine fundamental processes governing electron flow on the smallest possible length scales. We report experiments in which we controllably stretched individual cobalt complexes having spin S = 1, while simultaneously measuring current flow through the molecule. The molecule's spin states and magnetic anisotropy were manipulated in the absence of a magnetic field by modification of the molecular symmetry. This control enabled quantitative studies of the underscreened Kondo effect, in which conduction electrons only partially compensate the molecular spin. Our findings demonstrate a mechanism of spin control in single-molecule devices and establish that they can serve as model systems for making precision tests of correlated-electron theories.

Tuning the Kondo effect with a mechanically controllable break junction.

We study electron transport through C(60) molecules in the Kondo regime using a mechanically controllable break junction. By varying the electrode spacing, we are able to change both the width and the height of the Kondo resonance, indicating modification of the Kondo temperature and the relative strength of coupling to the two electrodes. The linear conductance as a function of T/T(K) agrees with the scaling function expected for the spin-1/2 Kondo problem. We are also able to tune finite-bias Kondo features which appear at the energy of the first C(60) intracage vibrational mode.

Underdiagnosis using SCIDR in the homeless mentally ill.

There are a growing number of studies attempting to diagnose the degree and extent of mental illness among the homeless. Increasingly, these studies are relying on structured diagnostic interviews such as the structured clinical interview for DSM III R diagnosis (SCIDR). This study examines the sensitivity of the SCID in diagnosing major mental illness among the homeless. Comparing SCID interviews with hospital chart diagnosis of twenty-three homeless individuals, the study found that whereas the positive predictive value of the SCID is high in that it accurately predicts a positive diagnosis, its negative predictive power is quite low. A negative SCID diagnosis does not accurately reflect a negative history of mental illness. The study indicates that single point interviews cannot be relied upon to accurately diagnose past history and, therefore, future need for treatment.