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In an era of increasing environmental awareness, stricter federal and state regulation of pollutant emissions are emerging. A major source of pollution arises from automobiles which inadvertently form gaseous products such as nitric oxide (NO x ), carbon monoxide (CO), and hydrocarbons (HC). Since the early 1980's, these effluents have been converted to safer forms using a three-way catalytic converter that employs a high dispersion of rhodium and platinum particles supported on a large surface area of transitional γ-phase alumina. Unfortunately such a converter is susceptible to decreased performance over time, and this degradation has been attributed to changes in the catalyst microstructure. The nanoscaled nature of the transition metal catalysts and the submicron-scaled size of the transitional alumina necessitates the use of the high spatial resolution analyses made possible by transmission electron microscopy.
The\nfirst unsubstituted olefin-linked covalent organic framework,\ntermed COF-701, was made by linking 2,4,6-trimethyl-1,3,5-triazine\n(TMT) and 4,4′-biphenyldicarbaldehyde (BPDA) through Aldol\ncondensation. Formation of the unsubstituted olefin (-CHCH-)\nlinkage upon reticulation is confirmed by Fourier transform infrared\n(FT-IR) spectroscopy and solid-state <sup>13</sup>C cross-polarization\nmagic angle spinning (CP-MAS) NMR spectroscopy of the framework and\nof its <sup>13</sup>C-isotope-labeled analogue. COF-701 is found to\nbe porous (1715 m<sup>2</sup> g<sup>–1</sup>) and to retain\nits composition and crystallinity under both strongly acidic and basic\nconditions. The high chemical robustness is attributed to the unsubstituted\nolefin linkages. Immobilization of the strong Lewis acid BF<sub>3</sub>·OEt<sub>2</sub> in the pores of the structure yields BF<sub>3</sub>⊂COF-701. In the material, the catalytic activity of\nthe guest is retained, as evidenced in a benchmark Diels–Alder\nreaction.
The \nwork at the University of California, Berkeley, was supported \nby the Miller Institute for Basic Research in Science, by NSF grant AST 94-17213, and by grant GO-7505 from \nthe Space Telescope Science Institute, which is operated by \nthe Association of Universities for Research in Astronomy, \nInc., under NASA contract NAS 5-26555.
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As technologies continue to evolve at exponential rates, online platforms are becoming an increasingly salient social context for adolescents. Adolescents are often early adopters, savvy users, and innovators of technology use. This not only creates new vulnerabilities but also presents new opportunities for positive impact-particularly, the use of technology to promote healthy learning and adaptation during developmental windows of opportunity. For example, early adolescence appears to represent a developmental inflection point in health trajectories and in technology use in ways that may be strategically targeted for prevention and intervention. The field of adolescent health can capitalize on technology use during developmental windows of opportunity to promote well-being and behavior change in the following ways: (1) through a deeper understanding of the specific ways that developmental changes create new opportunities for motivation and engagement with technologies; (2) by leveraging these insights for more effective use of technology in intervention and prevention efforts; and (3) by combining developmental science-informed targeting with broader-reach technologic approaches to health behavior change at the population level (e.g., leveraging and changing social norms). Collaboration across disciplines-including developmental science, medicine, psychology, public health, and computer science-can create compelling innovations to use digital technology to promote health in adolescents.
A strategy based on reticulating metal ions and organic carboxylate links into extended networks has been advanced to a point that allowed the design of porous structures in which pore size and functionality could be varied systematically.The pore size can be varied from 3.5 to 28.8 Å and crystal density from 1 to 0.2 g/cm 3 .
The long-standing dream of scientists to be able to link molecules together into crystalline, extended (infinite) 2D and 3D structures is now realized by the establishment of reticular chemistry through the discovery and development of metal-organic frameworks and covalent organic frameworks. The architectural, thermal, and chemical stability of such frameworks allowed study of their ultra-high porosity, reactivity and many applications including carbon capture and conversion to fuels, and water harvesting from desert air.
Some of the geometric problems of interest to molecular biologists have macroscopic analogues in the field of robotics. Two examples of such analogies are those between protein docking and model-based perception, and between ring closure and inverse kinematics. Molecular dynamics simulation, too, has much in common with the study of robot dynamics. In this paper we give a brief survey of recent work on these and related problems.
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