We present an experimental determination of the conduction channel distribution in lead nanoscale contacts with total conductances ranging from 1 to 15 G 0 , where G 0 = 2e 2 /h. It is found that even for contacts having a cross section much smaller than the mean free path the distribution tends to be remarkably close to the universal diffusive limit. With the help of theoretical calculations we show that this behavior can be associated with the specific band structure of lead which produces a significant contribution of partially open channels even in the absence of atomic disorder. Published in Europhysics Letters, Electron transport properties in a quantum coherent conductor are fully characterized by the set of transmission coefficients {τ n } corresponding to the conductance eigenchannels of the system [1,2]. Clearly, the whole set {τ n } cannot be extracted from the total conductance which only yields information on ∑ n τ n . The possibility of an accurate determination of the individual {τ n } was demonstrated by Scheer et al. [3] for the case of one-atom contacts, by analyzing electron transport in the superconducting state [4]. This technique allowed to prove that the number of channels for one-atom contacts is basically determined by the valence orbital structure while the particular values in the set {τ n } depend also on the contact geometry at the atomic scale [5].A natural question that arises is how the set {τ n } evolves as the size of the contact is increased. One would expect that for sufficiently large contacts (where the size is larger than the mean free path) the transmission coefficients would be distributed according to P(T ) = ∑ n δ (T − τ n ) = G / 2G 0 T √ 1 − T , i.e. the universal distribution function predicted for a quantum conductor in the diffusive regime [6,7]. Although indirect evidence of this distribution has been obtained through shot-noise measurements [8] a direct determination of P(T ) in this regime is still an open experimental challenge.In the present work we combine experimental and theoretical efforts in order to analyze the evolution of the channel distribution in nanocontacts as the size of the contact is increased from the atomic-size limit. We obtain the set {τ n } from transport measurements in lead nanocontacts with conductances ranging from 1 to 15 G 0 . These results are compared with model calculations in which the effects of geometry, atomic disorder, and band structure can be included. We find that even for small contacts (G ∼3-4 G 0 ) the channels distribution for Pb is unexpectedly close to the diffusive limit. We show that this behavior can be attributed to the particular band structure of Pb.Highly stable atomic scale contacts are formed using a mechanically controlled break-junction (MCBJ) [9]. A notched lead wire 99.99% pure is glued on top of a flexible substrate.

In this article, we describe and test a novel way to extend a low temperature scanning tunneling microscope with the capability to measure forces. The tuning fork that we use for this is optimized to have a high quality factor and frequency resolution. Moreover, as this technique is fully compatible with the use of bulk tips, it is possible to combine the force measurements with the use of superconductive or magnetic tips, advantageous for electronic spectroscopy. It also allows us to calibrate both the amplitude and the spring constant of the tuning fork easily, in situ and with high precision.

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Rorschach content analysis has been and continues to be a very controversial subject. Weiner (1977) has pointed out that Rorschach content interpretations are subjected to error at each step in the inferential process. Lerner (1991) has commented that there is no area of Rorschach analysis more misused and more underused than content. Aronow and Reznikoff (1976) have argued that it will be content interpretation that fulfills the promise of the Rorschach test as a significant and valid assessment instrument. Whatever the importance or limits assigned to content analysis, the different authors agree that Rorschach clinicians rely very much on content in interpreting the test.Among the nontraditional uses of content indicators (Haley, Draguns, & Phillips, 1967), scales to evaluate psychological variables are again becoming veiy popular. The type of contents studied, which traditionally have been associated with such variables as anxiety, hostility, or dependency, has recently been extended to include applications of the Rorschach test in studying object relations theories.Normative and psychosocial considerations combine to warrant the type of research with Rorschach thematic content scales that we report in this paper. On the one hand, progress in research with these variables requires the collection of normative data; there is a notable dearth of normative data bearing content scales (Aronow & Reznikoff, 1976), in contrast to the extensive normative data that are available on Rorschach structural variables (Exner, 1986). On the other hand, we are interested in learning the consequences for Rorschach interpretation, if any, of the postulate that personality is not only resident in the person. It has been claimed diat the assumption that persons are self-contained individuals 68 This document is copyrighted by the American Psychological Association or one of its allied publishers.This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.

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