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Charge transport through junctions consisting of insulating molecular units is a quantum phenomenon that cannot be described adequately by classical circuit laws. This paper explores tunneling current densities in self-assembled monolayer (SAM)-based junctions with the structure AgTS/O2C–R1–R2–H//Ga2O3/EGaIn, where AgTS is template-stripped silver and EGaIn is the eutectic alloy of gallium and indium; R1 and R2 refer to two classes of insulating molecular units—(CH2)n and (C6H4)m—that are connected in series and have different tunneling decay constants in the Simmons equation. These junctions can be analyzed as a form of series-tunneling junctions based on the observation that permuting the order of R1 and R2 in the junction does not alter the overall rate of charge transport. By using the Ag/O2C interface, this system decouples the highest occupied molecular orbital (HOMO, which is localized on the carboxylate group) from strong interactions with the R1 and R2 units. The differences in rates of tunneling are thus determined by the electronic structure of the groups R1 and R2; these differences are not influenced by the order of R1 and R2 in the SAM. In an electrical potential model that rationalizes this observation, R1 and R2 contribute independently to the height of the barrier. This model explicitly assumes that contributions to rates of tunneling from the AgTS/O2C and H//Ga2O3 interfaces are constant across the series examined. The current density of these series-tunneling junctions can be described by J(V) = J0(V) exp(−β1d1 – β2d2), where J(V) is the current density (A/cm2) at applied voltage V and βi and di are the parameters describing the attenuation of the tunneling current through a rectangular tunneling barrier, with width d and a height related to the attenuation factor β.
James H. Dieterich was awarded the Walter Bucher Medal at the AGU Fall Meeting Honors Ceremony which was held on December 17, 2000, in San Francisco, California. The medal honors original contributions to the basic knowledge of the Earth's crust.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReaction of .alpha.,.omega.-di-Grignard reagents with silver(I) salts forms carbocyclic ringsGeorge M. Whitesides and Francis D. GutowskiCite this: J. Org. Chem. 1976, 41, 17, 2882–2885Publication Date (Print):August 1, 1976Publication History Published online1 May 2002Published inissue 1 August 1976https://pubs.acs.org/doi/10.1021/jo00879a019https://doi.org/10.1021/jo00879a019research-articleACS PublicationsRequest reuse permissionsArticle Views773Altmetric-Citations50LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts
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This paper describes the interaction between ubiquitin (UBI) and three sodium n-alkyl sulfates (SC(n)S) that have the same charge (Z = -1) but different hydrophobicity (n = 10, 12, or 14). Increasing the hydrophobicity of the n-alkyl sulfate resulted in (i) an increase in the number of distinct intermediates (that is, complexes of UBI and surfactant) that form along the pathway of unfolding, (ii) a decrease in the minimum concentrations of surfactant at which intermediates begin to form (i.e., a more negative ΔG(binding) of surfactant for UBI), and (iii) an increase in the number of surfactant molecules bound to UBI in each intermediate or complex. These results demonstrate that small changes in the hydrophobicity of a surfactant can significantly alter the binding interactions with a folded or unfolded cytosolic protein.
Abstract : Long-chain alkanethiols, HS(CH2) (n)X, adsorb from solution onto gold and form oriented, ordered monolayers. Although alkyl chains terminated by other functional groups (e.g., trialkylphosphines, dialkyl disulfides and dialkyl sulfides) also form monolayers on gold that are stable at room temperature, thiols are adsorbed preferentially from solutions containing mixtures of a thiol and one of these other adsorbates. Surfaces containing more than one functional group can be generated by coadsorption of two or more thiols from solution. In general, the ratio of the concentrations of the two components in a mixed monolayer is not the same as in solution but reflects the relative solubilities of the components in solution and interactions between the tail groups, X, in the monolayer. Multi-component monolayers do not phase-segregate into single-component domains large enough to influence the contact angle (a few tens of angstroms across), but also do not act as ideal two-dimensional solutions. From dilute solutions in alkanes, adsorption of HS(CH2)10CH2OH is strongly preferred over HS(CH2)10CH3, probably due to the stabilization afforded by intra-monolayer hydrogen bonds between the hydroxyl tail groups. The wettability of mixed monolayers is not linear in the composition of the surface. In a surface comprising a polar and a nonpolar component, the polar component is more hydrophilic when its concentration in the monolayer is low than when the monolayer is composed largely of the polar component.
The objective of the AFaSR-MURI High-Cycle Fatigue program is to characterize and model the limiting damage states at the onset of high-cycle fatigue to facilitate mechanistic understanding and to develop a basis for life prediction. Efforts have been focused on the influence of foreign object damage (FAD) and fretting on a Ti-6A1-4V blade alloy and on a polycrystalline Ni-base disk alloy. Notable highlights during the fourth year include the characterization and quantitative modeling of fretting and FaD and the definition of the role of mixed-mode loading on HCF thresholds in Ti-6A1-4V. Accomplishments are outlined below: Worst-case fatigue threshold stress intensities have been measured in STOA Ti-6A1-4V using large (> 5 mm) cracks under representative HCF conditions (R > 0.95, 1000 Hz). Values provide a practical, frequency-independent (20 - 20,000 Hz) lower-bound for the growth of naturally-initiated, physically-small (> 40 gm) cracks.