Electronics and Chemistry: Varying Single Molecule Junction Conductance Using Chemical Substituents

We measure the low bias conductance of a series of substituted benzene diamine molecules while breaking a gold point contact in a solution of the molecules. Transport through these substituted benzenes is by means of nonresonant tunneling or superexchange, with the molecular junction conductance depending on the alignment of the metal Fermi level to the closest molecular level. Electron-donating substituents, which drive the occupied molecular orbitals up, increase the junction conductance, while electron-withdrawing substituents have the opposite effect. Thus for the measured series, conductance varies inversely with the calculated ionization potential of the molecules. These results reveal that the occupied states are closest to the gold Fermi energy, indicating that the tunneling transport through these molecules is analogous to hole tunneling through an insulating film.Comment: 14 pages, 4 figure

Joseph E. Johnson Author Of Frontier News, Promotion, And Progress

News editors in the nineteenth century have been viewed as paramount figures in establishing the community life of small towns. While opinions differ over exactly how much influence to ascribe to these newspersons, most historians agree that they held a prominent place. Political parties, as a primary source of funding for newspapers at the time, ensured that reporting provided a favorable spin on things. News editors of the frontier usually mixed together short items on travel, neighboring settlements, politics, editorial commentary, and advertisements, driven by patron political interests and the desire for community growth. In this process, editors functioned as open promoters, not expected to restrain their views with the lens of impartiality—nor expecting in return that readers would question the bright future that they saw as destiny. This brought newspapers into a kind of alliance with railroad companies as both sides campaigned to increase the population in support of their own economic and social interests, with news editors doing the promoting and railroads bringing people and trade prospects. But all of this depended on the cultural backdrop of “manifest destiny” at the time, a composite of American dreams for progress generally equated with the advancement of white settlement westward. Joseph Ellis (J. E.) Johnson fit this profile of editor-promoter, but he also expanded it, often placing greater stock in advertisements and community observations than in political issues. When he took the reins as editor of the Council Bluffs Bugle in 1853, he shifted the paper’s emphasis significantly toward local business, greatly increasing the advertising space. While the Bugle maintained a definite orientation toward the Democratic Party and its politics in the region, Johnson’s championing of party interests does not distinguish him from his contemporaries. Many other papers relied heavily on anonymous descriptions in praise of their town’s surrounding land, but Johnson more often filled this role himself, traveling regularly and crafting various romantic portrayals of the area

Joseph E. Johnson Author Of Frontier News, Promotion, And Progress

News editors in the nineteenth century have been viewed as paramount figures in establishing the community life of small towns. While opinions differ over exactly how much influence to ascribe to these newspersons, most historians agree that they held a prominent place. Political parties, as a primary source of funding for newspapers at the time, ensured that reporting provided a favorable spin on things. News editors of the frontier usually mixed together short items on travel, neighboring settlements, politics, editorial commentary, and advertisements, driven by patron political interests and the desire for community growth. In this process, editors functioned as open promoters, not expected to restrain their views with the lens of impartiality—nor expecting in return that readers would question the bright future that they saw as destiny. This brought newspapers into a kind of alliance with railroad companies as both sides campaigned to increase the population in support of their own economic and social interests, with news editors doing the promoting and railroads bringing people and trade prospects. But all of this depended on the cultural backdrop of “manifest destiny” at the time, a composite of American dreams for progress generally equated with the advancement of white settlement westward. Joseph Ellis (J. E.) Johnson fit this profile of editor-promoter, but he also expanded it, often placing greater stock in advertisements and community observations than in political issues. When he took the reins as editor of the Council Bluffs Bugle in 1853, he shifted the paper’s emphasis significantly toward local business, greatly increasing the advertising space. While the Bugle maintained a definite orientation toward the Democratic Party and its politics in the region, Johnson’s championing of party interests does not distinguish him from his contemporaries. Many other papers relied heavily on anonymous descriptions in praise of their town’s surrounding land, but Johnson more often filled this role himself, traveling regularly and crafting various romantic portrayals of the area

The Principal Axis of the Virgo Cluster

Using accurate distances to individual Virgo cluster galaxies obtained by the method of Surface Brightness Fluctuations, we show that Virgo's brightest ellipticals have a remarkably collinear arrangement in three dimensions. This axis, which is inclined by 10 to 15 degrees from the line of sight, can be traced to even larger scales where it appears to join a filamentary bridge of galaxies connecting Virgo to the rich cluster Abell 1367. The orientations of individual Virgo ellipticals also show some tendency to be aligned with the cluster axis, as does the jet of the supergiant elliptical M87. These results suggest that the formation of the Virgo cluster, and its brightest member galaxies, have been driven by infall of material along the Virgo-A1367 filament.Comment: 8 pages, 4 figures, accepted for publication in ApJ Letter

Towards Understanding Photodegradation Pathways in Lignins:The Role of Intramolecular Hydrogen Bonding in Excited States

The photoinduced dynamics of the lignin building blocks syringol, guaiacol, and phenol were studied using time-resolved ion yield spectroscopy and velocity map ion imaging. Following irradiation of syringol and guaiacol with a broad-band femtosecond ultraviolet laser pulse, a coherent superposition of out-of-plane OH torsion and/or OMe torsion/flapping motions is created in the first excited 1ππ* (S1) state, resulting in a vibrational wavepacket, which is probed by virtue of a dramatic nonplanar → planar geometry change upon photoionization from S1 to the ground state of the cation (D0). Any similar quantum beat pattern is absent in phenol. In syringol, the nonplanar geometry in S1 is pronounced enough to reduce the degree of intramolecular H bonding (between OH and OMe groups), enabling H atom elimination from the OH group. For guaiacol, H bonding is preserved after excitation, despite the nonplanar geometry in S1, and prevents O–H bond fission. This behavior affects the propensities for forming undesired phenoxyl radical sites in these three lignin chromophores and provides important insight into their relative “photostabilities” within the larger biopolymer