Adsorption configurations of carbon monoxide on gold monolayer supported by graphene or monolayer hexagonal boron nitride: a first-principles study

Using density functional theory with a semiempirical van der Waals approach proposed by Grimme, the adsorption behavior of carbon monoxide on a gold monolayer supported by graphene or monolayer hexagonal boron nitride has been investigated. Based on the changes in the Dirac cone of graphene and a Bader charge analysis, we observe that the Au(111) monolayer gains a small charge from graphene and monolayer h-BN. The adsorbed CO molecule adopts similar adsorption configurations on Au(111)/graphene and Au(111)/h-BN with Au-C distance 2.17?2.50 Å and Au-C-O angle of 123.9°–139.6°. Moreover, we found that for low CO coverages, bonding to the gold surface is surprisingly energy-favorable. Yet the CO adsorption binding energy diminishes at high coverage due to the repulsive van der Waals interactions between CO molecules.     

The nitrogen-boron paramagnetic center in visible light sensitized N-B co-doped TiO(2). Experimental and theoretical characterization

Nitrogen boron co-doped TiO(2) prepared via sol-gel synthesis and active under visible light, contains two types of paramagnetic extrinsic defects, both exhibiting a well resolved EPR spectrum. The first center is the well characterized [N(i)O]˙ species (i = interstitial) also present in N-doped TiO(2), while the second one involves both N and B. This latter center (labeled [NOB]˙) exhibits well resolved EPR spectra obtained using either (14)N or (15)N which show a high spin density in a N 2p orbital. The structure of the [NOB]˙ species is different from that previously proposed in the literature and is actually based on the presence of interstitial N and B atoms both bound to the same lattice oxygen ion. The interstitial B is also linked to two other lattice oxygen ions reproducing the trigonal planar structure typical of boron compounds. The energy level of the [NOB]˙ center lies near the edge of the valence band of TiO(2) and, as such, does not contribute to the visible light absorption. However, [NOB]˙ can easily trap one electron generating the [NOB](-) diamagnetic center which introduces a gap state at about 0.4 eV above the top of the valence band. This latter species can contribute to the visible light activity.     

Knowledge exchange processes in Industrial Districts and the emergence of networks

This paper aims at exploring conditions under which the need for knowledge exchange within a small firms?? cluster generates a structure of links between firms. We focus in particular on small firms?? clusters called Industrial Districts (IDs). Specifically, we analyze IDs with flexible specialization, in which knowledge exchange is driven by the search for complementary knowledge assets. Previous works of the authors proposed an agent-based model of IDs to explore the properties of networks emerging from the interaction of firms prompted by the search and exchange of complementary specialized knowledge. This model showed that limited relational capability, due to the small size, and an exchange mechanism solely based on the barter of complementary knowledge are structural conditions that limit individual firms?? growth in IDs with flexible specialization. This paper presents a new version of this model to analyze the role of embeddedness of relationships among IDs firms in shaping the emergent network structures. The aim of the paper is to answer to the following research questions: Can knowledge complementariness explain the emergence of a stable network of firms within a small firms?? cluster? What are the structural properties of these networks? Which role does the embeddedness of relationships among firms play in shaping the structure of emerging networks?     

Threshold condition for global existence and blow-up to a radially symmetric drift-diffusion system

For a class of drift-diffusion systems Kurokiba et al. [M. Kurokiba, T. Nagai, T. Ogawa, The uniform boundedness and threshold for the global existence of the radial solution to a drift-diffusion system, Commun. Pure Appl. Anal. 5 (2006) 97-106.] proved global existence and uniform boundedness of the radial solutions when the L₁-norm of the initial data satisfies a threshold condition. We prove in this letter that this result prescribes a region in the plane of masses which is sharp in the sense that if the drift-diffusion system is initiated outside the threshold region of global existence, then blow-up is possible: suitable initial data can be built up in such a way that the corresponding solution blows up in a finite time.     

One-pot consecutive reactions based on the synthesis of conjugated enones by the re-catalysed meyer-schuster rearrangement

Re catalysis in one-pot reactions: An atom-economical, one-pot strategy that involves alkyne deprotonation and a subsequent rhenium(V)-catalysed Meyer-Schuster rearrangement of the alkynol to provide α,?-unsaturated enones in high yield has been developed. Subsequent in situ hydride reduction or Diels-Alder reaction of the enones provided products in good-to-high overall yields.     

Homogenization of heterogeneous masonry beams

This study presents a two-scale model to describe the out-of-plane masonry response. One-dimensional (1D) structural elements, like masonry columns or strips of long wall characterized by the periodic repetition of bricks and mortar arranged in stack bond, are considered. A damage-friction plasticity law is adopted to model the mortar joint constitutive response, while the bricks are assumed as linear elastic. A 1D beam formulation is introduced at both the structural and micromechanical scale, linking the two levels by means of a kinematic map. This expresses the microscopic beam strains in the masonry unit cell (UC) as function of the macroscopic generalized strains. The kinematic field in the UC is completed by adding an unknown periodic fluctuation term. A nonlinear homogenization procedure is developed, proposing a semi-analytical solution for the micromechanical problem, based on the fiber discretization of the mortar joints. A force-based beam-column finite element procedure is adopted at the structural scale and the solution algorithm for the element state determination is illustrated in details. Some numerical applications, showing the UC constitutive response and the behavior of masonry structural elements, are finally presented.     

Characterization of the interaction of CO and H2 at the ZnO surface by adsorption microcalorimetry

CO and H₂ are both chemisorbed by ZnO but H₂ is more sensitive than CO to the surroundings of adsorption sites. When the two gases are coadsorbed, a strong interaction occurs, ascribed to the formation of a possible precursor in methanol synthesis.

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CO H₂ ZnO, H₂ , , CO. , , .

     

Anomalous structural dynamics of minimally frustrated residues in cardiac troponin C triggers hypertrophic cardiomyopathy

Cardiac TnC (cTnC) is highly conserved among mammals, and genetic variants can result in disease by perturbing Ca²⁺-regulation of myocardial contraction. Here, we report the molecular basis of a human mutation in cTnC''s αD-helix (TNNC1-p.C84Y) that impacts conformational dynamics of the D/E central-linker and sampling of discrete states in the N-domain, favoring the “primed” state associated with Ca²⁺ binding. We demonstrate cTnC''s αD-helix normally functions as a central hub that controls minimally frustrated interactions, maintaining evolutionarily conserved rigidity of the N-domain. αD-helix perturbation remotely alters conformational dynamics of the N-domain, compromising its structural rigidity. Transgenic mice carrying this cTnC mutation exhibit altered dynamics of sarcomere function and hypertrophic cardiomyopathy. Together, our data suggest that disruption of evolutionary conserved molecular frustration networks by a myofilament protein mutation may ultimately compromise contractile performance and trigger hypertrophic cardiomyopathy.

Cardiac TnC (cTnC) is highly conserved among mammals, and genetic variants can result in disease by perturbing Ca²⁺-regulation of myocardial contraction.