Effect of disorder on the conductance of a Cu atomic point contact

We present a systematic study of the effect of the disorder in copper point contacts. We show that peaks in the conductance histogram of copper point contacts shift upon addition of nickel impurities. The shift increases initially linerarly with the nickel concentration, thus confirming that it is due to disorder in the nanowire, in accordance with predictions. In general, this shift is modelled as a resistance R_s which is placed in series with the contact resistance R_c. However, we obtain different R_s values for the two peaks in the histogram, R_s being larger for the peak at higher conductance.Comment: 6 pages, 4 figure

Nambu monopoles in lattice Electroweak theory

We considered the lattice electroweak theory at realistic values of $\alpha$ and $\theta_W$ and for large values of the Higgs mass. We investigated numerically the properties of topological objects that are identified with quantum Nambu monopoles. We have found that the action density near the Nambu monopole worldlines exceeds the density averaged over the lattice in the physical region of the phase diagram. Moreover, their percolation probability is found to be an order parameter for the transition between the symmetric and the broken phases. Therefore, these monopoles indeed appear as real physical objects. However, we have found that their density on the lattice increases with increasing ultraviolet cutoff. Thus we conclude, that the conventional lattice electroweak theory is not able to predict the density of Nambu monopoles. This means that the description of Nambu monopole physics based on the lattice Weinberg - Salam model with finite ultraviolet cutoff is incomplete. We expect that the correct description may be obtained only within the lattice theory that involves the description of TeV - scale physics.Comment: LATE

Magnetic properties of Co doped Nb clusters

From magnetic deflection experiments on isolated Co doped Nb clusters we made the interesting observation of some clusters being magnetic, while others appear to be non-magnetic. There are in principle two explanations for this behavior. Either the local moment at the Co site is completely quenched or it is screened by the delocalized electrons of the cluster, i.e. the Kondo effect. In order to reveal the physical origin, we conducted a combined theoretical and experimental investigation. First, we established the ground state geometry of the clusters by comparing the experimental vibrational spectra with those obtained from a density functional theory study. Then, we performed an analyses based on the Anderson impurity model. It appears that the non-magnetic clusters are due to a complete quenching of the local Co moment and not due to the Kondo effect. In addition, the magnetic behavior of the clusters can be understood from an inspection of their electronic structure. Here magnetism is favored when the effective hybridization around the chemical potential is small, while the absence of magnetism is signalled by a large effective hybridization around the chemical potential.Comment: 14 pages, 8 figure

Interaction between episodic and semantic memory networks in the acquisition and consolidation of novel spoken words

When a novel word is learned, its memory representation is thought to undergo a process of consolidation and integration. In this study, we tested whether the neural representations of novel words change as a function of consolidation by observing brain activation patterns just after learning and again after a delay of one week. Words learned with meanings were remembered better than those learned without meanings. Both episodic (hippocampus-dependent) and semantic (dependent on distributed neocortical areas) memory systems were utilised during recognition of the novel words. The extent to which the two systems were involved changed as a function of time and the amount of associated information, with more involvement of both systems for the meaningful words than for the form-only words after the one-week delay. These results suggest that the reason the meaningful words were remembered better is that their retrieval can benefit more from these two complementary memory system

Social Innovation: Integrating Micro, Meso, and Macro Level Insights From Institutional Theory

© The Author(s) 2018. Social innovations are urgently needed as we confront complex social problems. As these social problems feature substantial interdependencies among multiple systems and actors, developing and implementing innovative solutions involve the re-negotiating of settled institutions or the building of new ones. In this introductory article, we introduce a stylized three-cycle model highlighting the institutional nature of social innovation efforts. The model conceptualizes social innovation processes as the product of agentic, relational, and situated dynamics in three interrelated cycles that operate at the micro, meso, and macro levels of analysis. The five papers included in this special issue address one or more of these cycles. We draw on these papers and the model to stimulate and offer guidance to future conversations on social innovations from an institutional theory perspective