Van Hove singularities (VHS) in the density of states of multiwalled carbon nanotubes (MWNTs) have been observed by optical spectroscopy for the first time to the authors' knowledge. Additionally, unexpected visible luminescence has been observed on photoexcitation at 1064 nm. This luminescence is believed to arise from radiative transitions between energy states in the VHS. A mechanism describing the underlying processes, which involve multiphoton absorption followed by upconverted luminescence from VHS energy states, is presented. Our results show that the presence of VHS readily facilitates efficient optical transitions in
Studies documenting the usage patterns of electronic journals have compared print and e-journal characteristics, surveyed faculty for their perceptions and expectations, and analyzed the impact on library practices. This study, a qualitative exploration of a wide array of issues related to the research and teaching habits of early adopters of e-journals in a research setting, was conducted in the spring of 2001 with faculty in the basic and health sciences at the University of Illinois at Chicago. Open-ended questionnaires provided a framework to wide-ranging discussions of perceptions, expectations, and changing practices pertaining to e-journals and other electronic resources. The results were analyzed with a specific focus on shared behaviors and values, discipline-dependent variations, and changing research and teaching habits. Several challenges for library resources and services are identified and discussed.
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