"Coulomb Staircase" at Room Temperature in a Self-Assembled Molecular Nanostructure

Double-ended aryl dithiols [alpha,alpha'-xylyldithiol (XYL) and 4,4'-biphenyldithiol] formed self-assembled monolayers (SAMs) on gold(111) substrates and were used to tether nanometer-sized gold clusters deposited from a cluster beam. An ultrahigh-vacuum scanning tunneling microscope was used to image these nanostructures and to measure their current-voltage characteristics as a function of the separation between the probe tip and the metal cluster. At room temperature, when the tip was positioned over a cluster bonded to the XYL SAM, the current-voltage data showed "Coulomb staircase" behavior. These data are in good agreement with semiclassical predictions for correlated single-electron tunneling and permit estimation of the electrical resistance of a single XYL molecule (approximately18 ± 12 megohms).     

A new form of raabeia-type actinosporean (Myxozoa) from the oligochaete Uncinais uncinata

In a study of the oligochaete fauna and their actinosporean parasites in three lakes in Algonquin Park, Canada, a novel form of raabeia-type actinosporean was observed in a single specimen of Uncinais uncinata (?ersted) (Naididae). This form differs from those previously described in its small size, and by having caudal processes that gradually widen and terminate with a single prominent branch.     

Probing the Local Effects of Magnetic Impurities on Superconductivity

The local effects of isolated magnetic adatoms on the electronic properties of the surface of a superconductor were studied with a low-temperature scanning tunneling microscope. Tunneling spectra obtained near magnetic adsorbates reveal the presence of excitations within the superconductor's energy gap that can be detected over a few atomic diameters around the impurity at the surface. These excitations are locally asymmetric with respect to tunneling of electrons and holes. A model calculation based on the Bogoliubov-de Gennes equations can be used to understand the details of the local tunneling spectra.     

Project hindsight. A Defense Department study of the utility of research

Recently developed weapon systems were compared with systems of similar function in use 10 to 20 years earlier. The most significant finding was that the improvement in performance or reduction in cost is largely the synergistic effect of a large number of scientific and technological innovations, of which only about 10 percent had been made at the time the earlier system was designed. The common scientific and technological base of the systems was not analyzed. Of the innovations, or Events, 9 percent were classified as science and 91 percent as technology. Ninety-five percent of all Events were funded by the defense sector. Nearly 95 percent were motivated by a recognized defense need. Only 0.3 percent came from undirected science. The results of the study do not call in question the value of undirected science on the 50-year-or-more time scale. In light of our finding that 5 to 10 years are often required before even a piece of highly applied research is "fitted in" as an effective contributing member of a large assembly of other Events, it is not surprising that "fragments" of undirected science are infrequently utilized on even a 20-year time scale. The most obvious way in which undirected science appears to enter into technology and utilization on a substantial scale seems to be in the compressed, highly organized form of a well-established, clearly expressed general theory, or in the evaluated, ordered knowledge of handbooks, textbooks, and university courses.