Self-organization of Ce adatoms on Ag(111): a kinetic Monte Carlo study

One of the most fascinating experimental results in fabrication of artificial nanostructures is the creation of the macroscopically ordered superlattice of Ce adatoms on Ag111 F. Silly et al., Phys. Rev. Lett. 92, 016101 2004. Here, performing kinetic Monte Carlo simulations, we study the formation of Ce superlattice at the atomic scale. It is demonstrated that the surface-state mediated long-range interaction between Ce adatoms can lead to their self-assembly into a well ordered structure. The temperature of the substrate and the concentration of Ce adatoms are shown to play a key role in this process

Effect of the long-range adsorbate interactions on the atomic self-assembly on metal surfaces

Recent experimental studies have demonstrated that short linear chains are often formed in the early stage of heteroepitaxy on the (111) noble metal surfaces at low temperatures. Here, we show that the surface-state mediated long-range interaction between adsorbates is the driving force for the self-organization of adsorbates at very low temperatures. Our kinetic Monte Carlo simulations for Co adatoms on Cu(111) and for Ce adatoms on Ag(111) reveal that these interactions can lead to the formation of linear chains

Bilayer growth of nanoscale Co islands on Cu(111)

Combining kinetic Monte Carlo and molecular static simulations, we follow at the atomic scale the growth of Co nanoislands on Cu(111) surface over a wide range of surface temperatures (130-300K). Atomistic processes responsible for the interlayer mass transport of Co atoms and the formation of 2 ML high nanoislands at temperatures &gt; 200 K are revealed. Transition from the two- to the three-dimensional growth mode with decreasing the temperature is demonstrated. Strain relaxations induced in the Cu substrate and in the Co nanoislands are found to have a strong impact on the formation of triangle Co islands at room temperatures. Results of our theoretical studies are supported by the scanning tunneling microscope measurements.</p

Regulation of Sodium Channel Activity by Capping of Actin Filaments

Ion transport in various tissues can be regulated by the cortical actin cytoskeleton. Specifically, involvement of actin dynamics in the regulation of nonvoltage-gated sodium channels has been shown. Herein, inside-out patch clamp experiments were performed to study the effect of the heterodimeric actin capping protein CapZ on sodium channel regulation in leukemia K562 cells. The channels were activated by cytochalasin-induced disruption of actin filaments and inactivated by G-actin under ionic conditions promoting rapid actin polymerization. CapZ had no direct effect on channel activity. However, being added together with G-actin, CapZ prevented actin-induced channel inactivation, and this effect occurred at CapZ/actin molar ratios from 1:5 to 1:100. When actin was allowed to polymerize at the plasma membrane to induce partial channel inactivation, subsequent addition of CapZ restored the channel activity. These results can be explained by CapZ-induced inhibition of further assembly of actin filaments at the plasma membrane due to the modification of actin dynamics by CapZ. No effect on the channel activity was observed in response to F-actin, confirming that the mechanism of channel inactivation does not involve interaction of the channel with preformed filaments. Our data show that actin-capping protein can participate in the cytoskeleton-associated regulation of sodium transport in nonexcitable cells

A spin-selective approach for surface states at Co nanoislands

During recent years the surface electronic states of cobalt nanoislands grown on Cu(111) and Au(111) have been extensively studied and still yield fascinating results. Among magnetic surfaces, cobalt islands are particularly appealing because of their spin-polarized electronic states near the Fermi energy, involving localized d states of minority character, as well as free-like s–p states of majority character. We show here that these states are a sensitive probe to minute changes of structural details such as strain and stacking, and therefore constitute an ideal playground to study the interplay between structural and spin-related properties. Due to their size, cobalt islands on Cu(111) offer the additional opportunity to host single-magnetic adsorbates suitable for spin-polarized scanning tunneling microscopy and spectroscopy (SP-STM and SP-STS). We establish here that, in an energy interval just below the Fermi level, the spin-polarization of a transition-metal atom is governed by surface-induced states opposite in sign compared to the island, while the spin-polarization of Co-Phthalocyanine molecules is governed by molecular states. This opens up interesting perspectives for controlling and engineering spin-polarized phenomena at the nanoscale