Directional charge separation in isolated organic semiconductor crystalline nanowires.

One of the fundamental design paradigms in organic photovoltaic device engineering is based on the idea that charge separation is an extrinsically driven process requiring an interface for exciton fission. This idea has driven an enormous materials science engineering effort focused on construction of domain sizes commensurate with a nominal exciton diffusion length of order 10 nm. Here, we show that polarized optical excitation of isolated pristine crystalline nanowires of a small molecule n-type organic semiconductor, 7,8,15,16-tetraazaterrylene, generates a significant population of charge-separated polaron pairs along the π-stacking direction. Charge separation was signalled by pronounced power-law photoluminescence decay polarized along the same axis. In the transverse direction, we observed exponential decay associated with excitons localized on individual monomers. We propose that this effect derives from an intrinsic directional charge-transfer interaction that can ultimately be programmed by molecular packing geometry.

Manual-Driven group cognitive-behavioral therapy for adolescents with obsessive-compulsive disorder: a pilot study.

OBJECTIVE: Concerns about isolation, compromised development, partial pharmacotherapy response, therapist scarcity, and inadequate cognitive-behavioral therapy (CBT) adherence led the authors to adapt a CBT protocol to a group format for adolescents with obsessive-compulsive disorder (OCD). A naturalistic, open trial of group CBT for adolescent OCD is described. The authors predicted symptom improvement and format acceptability. METHOD: Over a 1 -year period, 18 adolescents aged 13 to 17 years with OCD received 14-week group CBT based on March and Mulle's OCD in Children and Adolescents: A Cognitive-Behavioral Treatment Manual in four consecutive sessions of five to nine patients. Eighty-three percent had undergone at least one medication trial, and 78% had previous CBT experience. RESULTS: OCD symptoms measured by the Children's Yale-Brown Obsessive Compulsive Scale improved significantly, both statistically and clinically. Adolescents consistently shared information and designed exposure interventions for themselves and others during sessions. Repeated self-report measures confirmed adolescents' satisfaction with therapy. CONCLUSIONS: This pilot study demonstrates that a manual-based treatment protocol may be exported for clinical use, adaptable for the end-user's needs, and palatable to adolescent patients. Clinical improvement and patient satisfaction justify further investigation in a controlled study.

Computer automation of data acquisition from a Knudsen, torsion-effusion pendulum.

A computer-automated data acquistion system has been developed for a dynamic torsion pendulum applied to measurement of vapor pressures at high temperatures by the torsion-effusion method. Laser beams reflected from mirrors on the pendulum are detected by a bank of photodetectors which, in turn, transmit signals representing pendulum positions through an encoder and interface to a laboratory computer with an internal clock. The computer uses pendulum position and time data with stored information to solve the equation of motion of the pendulum and to calculate vapor pressures. The physical parts, electronic circuits, and software are described and discussed. The rest point of a dynamic torsion pendulum has been reproduced within 1 min of arc.

A spectral study of the charge forms of Coomassie blue G.

The Coomassie brilliant blue protein assay is commonly used because of its superior sensitivity, but it is not well understood on the molecular level. This paper attempts to gain better understanding of the assay by studying the three charge forms of the free dye present at the usual pH of the assay. A linear least squares method is outlined which allows calculation of the spectra of the red, green, and blue charge forms of the dye and also calculates the two related pKa's with values of 1.15 and 1.82. The pure component dye spectra were found to differ substantially from the spectrum of the dye-protein complex. The presence of a fourth, pink, ionic state of the free dye at high pH (pKa = 12.4) is also shown. The signs and magnitudes of the ionic charges for the free dye forms are deduced and discussed. The results of this investigation are also discussed in terms of the potential for improvement of the CBB protein assay, and the conclusion is drawn that the assay conditions have been well optimized by earlier workers.