A low temperature surface preparation method for STM nano-lithography on Si(1 0 0)

Registration markers are crucial in connecting scanning tunneling microscope (STM) lithographed nano- and atomic-scale devices to the outside world. In this paper we revisit an ultra high vacuum annealing method with a low thermal budget that is fully compatible with etched registration markers and results in clean 2 × 1 reconstructed Si(1 0 0) surfaces required for STM lithography. Surface contamination is prevented by chemically stripping and reforming a protective silicon oxide layer before transferring the sample to the vacuum system. This allows for annealing temperatures of only 900 °C, where normally carbon contaminants result in the formation of SiC clusters on the surface at annealing temperatures below 950 °C. Reactive ion etched marker structures with an etch depth of 60 nm and a typical lateral dimension of only 150 nm survive a 900 °C flash anneal.     

Weak ergodicity of stationary pairwise independent processes

It is proven that a stationary process of pairwise independent random variables with values in a separable metric space is weakly ergodic, i.e. each random variable is independent of the system of invariant sets of the process. An example shows that a process of identically distributed pairwise independent random variables is in general, however, not weakly ergodic.

     

Ruthenium(II)-Catalyzed Double Annulation of Quinones: Step-Economical Access to Valuable Bioactive Compounds

Double ruthenium(II)-catalyzed alkyne annulations of quinones were accomplished. Thus, a strategy is reported that provides step-economical access to valuable quinones with a wide range of applications. C−H/N−H activations for alkyne annulations of naphthoquinones provided challenging polycyclic quinoidal compounds by forming four new bonds in one step. The singular power of the thus-obtained compounds was reflected by their antileukemic activity.     

Electrooxidative Ruthenium‐Catalyzed C−H/O−H Annulation by Weak O‐Coordination

Electrocatalysis has been identified as a powerful strategy for organometallic catalysis, and yet electrocatalytic C?H activation is restricted to strongly N‐coordinating directing groups. The first example of electrocatalytic C?H activation by weak O‐coordination is presented, in which a versatile ruthenium(II) carboxylate catalyst enables electrooxidative C?H/O?H functionalization for alkyne annulations in the absence of metal oxidants; thereby exploiting sustainable electricity as the sole oxidant. Mechanistic insights provide strong support for a facile organometallic C?H ruthenation and an effective electrochemical reoxidation of the key ruthenium(0) intermediate.     

Electrooxidative Rhodium‐Catalyzed C−H/C−H Activation: Electricity as Oxidant for Cross‐Dehydrogenative Alkenylation

Rhodium(III) catalysis has enabled a plethora of oxidative C?H functionalizations, which predominantly employ stoichiometric amounts of toxic and/or expensive metal oxidants. In contrast, we herein describe the first electrochemical rhodium‐catalyzed C?H activation that avoids hazardous chemical oxidants. Environmentally benign twofold C?H/C?H functionalizations were accomplished with weakly coordinating benzoic acids and benzamides, employing electricity as the terminal oxidant and generating H₂ as the sole byproduct.     

Distal Weak Coordination of Acetamides in Ruthenium(II)‐Catalyzed C−H Activation Processes

C?H activations with challenging arylacetamides were accomplished by versatile ruthenium(II) biscarboxylate catalysis. The distal C?H functionalization offers ample scope—including twofold oxidative C?H functionalizations and alkyne hydroarylations—through facile base‐assisted internal electrophilic‐type substitution (BIES) C?H ruthenation by weak O‐coordination.     

Existence of sufficient regular conditional probabilities

If a-field is sufficient for a family of probability measures defined on a-field then there exist regular determinations of the conditional probability of P, given, which are independent of the special measure, provided that is-regular. A counterexample shows that the-regularity of cannot be replaced by the assumption that each is approximable by a fixed compact system. In particular if a-field is sufficient for a family of probability measures defined on a separable-field and if each admits a regular conditional probability, given, a common regular conditional probability, given, need not exist.     

Formation of atom wires on vicinal silicon

The feasibility of creating atomic wires on vicinal silicon surfaces via pseudomorphic step-edge decoration has been analyzed for the case of Ga on Si(112). Scanning tunneling microscopy and density functional theory calculations indicate the formation of Ga zigzag chains intersected by quasiperiodic vacancy lines or "misfit dislocations." This structure strikes a balance between the system's drive towards chemical passivation and its need for strain relaxation in the atom chains. Spatially fluctuating disorder, intrinsic to the reconstruction, originates from the two symmetry-degenerate orientations of the zigzag chains on vicinal Si.