Direct observation of ordered trimers on Si(111) sqrt 3 x sqrt 3 R30 degrees-Au by scanned-energy glancing-angle Kikuchi electron wave-front reconstruction

Comprehensive Mechanism of Gene Silencing and Its Role in Plant Growth and Development

Gene silencing is a negative feedback mechanism that regulates gene expression to define cell fate and also regulates metabolism and gene expression throughout the life of an organism. In plants, gene silencing occurs via transcriptional gene silencing (TGS) and post-transcriptional gene silencing (PTGS). TGS obscures transcription via the methylation of 5' untranslated region (5'UTR), whereas PTGS causes the methylation of a coding region to result in transcript degradation. In this review, we summarized the history and molecular mechanisms of gene silencing and underlined its specific role in plant growth and crop production.

(Tl, Au)/Si(1 1 1)[Formula: see text] 2D compound: an ordered array of identical Au clusters embedded in Tl matrix

Formation of the highly-ordered [Formula: see text]-periodicity 2D compound has been detected in the (Tl, Au)/Si(1 1 1) system as a result of Au deposition onto the Tl/Si(1 1 1) surface, its composition, structure and electronic properties have been characterized using scanning tunneling microscopy, angle-resolved photoelectron spectroscopy and density-functional-theory calculations. On the basis of these data, the structural model of the Tl-Au compound has been proposed, which adopts 12 Tl atoms and 10 Au atoms (in total, 22 atoms) per [Formula: see text] unit cell, i.e.  ∼1.71 ML of Tl and  ∼1.43 ML of Au (in total, ∼3.14 ML). Qualitatively, the model can be visualized as consisting of truncated-pyramid-like Au clusters with a Tl atom on top, while the other Tl atoms form a double layer around the Au clusters. The (Tl, Au)/Si(1 1 1)[Formula: see text] compound has been found to exhibit pronounced metallic properties at least down to temperatures as low as  ∼25 K, which makes it a promising object for studying electrical transport phenomena in the 2D metallic systems.

A strategy to create spin-split metallic bands on silicon using a dense alloy layer

To exploit Rashba effect in a 2D electron gas on silicon surface for spin transport, it is necessary to have surface reconstruction with spin-split metallic surface-state bands. However, metals with strong spin-orbit coupling (e.g., Bi, Tl, Sb, Pt) induce reconstructions on silicon with almost exclusively spin-split insulating bands. We propose a strategy to create spin-split metallic bands using a dense 2D alloy layer containing a metal with strong spin-orbit coupling and another metal to modify the surface reconstruction. Here we report two examples, i.e., alloying reconstruction with Na and Tl/Si(111)1 × 1 reconstruction with Pb. The strategy provides a new paradigm for creating metallic surface state bands with various spin textures on silicon and therefore enhances the possibility to integrate fascinating and promising capabilities of spintronics with current semiconductor technology.

Stepwise self-assembly of C₆₀ mediated by atomic scale moiré magnifiers

Self-assembly of atoms or molecules on a crystal surface is considered one of the most promising methods to create molecular devices. Here we report a stepwise self-assembly of C₆₀ molecules into islands with unusual shapes and preferred sizes on a gold-indium-covered Si(111) surface. Specifically, 19-mer islands prefer a non-compact boomerang shape, whereas hexagonal 37-mer islands exhibit extraordinarily enhanced stability and abundance. The stepwise self-assembly is mediated by the moiré interference between an island with its underlying lattice, which essentially maps out the adsorption-energy landscape of a C₆₀ on different positions of the surface with a lateral magnification factor and dictates the probability for the subsequent attachment of C₆₀ to an island's periphery. Our discovery suggests a new method for exploiting the moiré interference to dynamically assist the self-assembly of particles and provides an unexplored tactic of engineering atomic scale moiré magnifiers to facilitate the growth of monodispersed mesoscopic structures.