Ab initio calculation of the adhesion and ideal shear strength of planar diamond interfaces with different atomic structure and hydrogen coverage

We propose a method to calculate the ideal shear strength τ of two surfaces in contact by ab initio calculations. This quantity and the work of adhesion γ are the interfacial parameters usually derived from tip-based friction force measurements. We consider diamond interfaces and quantitatively evaluate the effects of surface orientation and passivation. We find that in the case of fully passivated interfaces, γ is not affected by the orientation and the alignment of the surfaces in contact. On the contrary, τ does show a dependence on the atomic-scale roughness of the interface. The surface termination has a major impact on the tribological properties of diamond. The presence of dangling bonds, even at concentrations low enough to prevent the formation of interfacial C-C bonds, causes an increase in the resistance to sliding by 2 orders of magnitude with respect to the fully hydrogenated case. We discuss our findings in relation to experimental observations.     

Extended Gini-Type Measures of Risk and Variability

ABSTRACT

The aim of this paper is to introduce a risk measure, Extended Gini Shortfall (EGS), that extends the Gini-type measures of risk and variability by taking risk aversion into consideration. Our risk measure is coherent and catches variability, an important concept for risk management. The analysis is made under the Choquet integral representations framework. We expose results for analytic computation under well-known distribution functions. Furthermore, we provide a practical application.     

Deuteron wave function and OPE potential

The deuteron wave function is calculated integrating from outside the Schredinger equation using as input its asymptotic behaviour. Some potentials are tested and the one pion exchange potential (OPEP) is shown to be the main responsible of the wave function structure up to distances of about 1 fm. The relevance of the short range part of the potential is analyzed and it is shown that a substantial enhancement of the OPEP central part is needed in the deuteron channel.     

Preparation of bicyclo[3.2.0]heptane-2-endo,7-endo-diols: 1,3-diols with a chiral rigid backbone

The easily available bicyclo[3.2.0]hept-3-en-6-ones (1a-f) have been converted into the corresponding bicyclo[3.2.0]heptane-2-endo,7-endo-diols (4a-f) in an efficient and stereoselective fashion. This preparation opens a route to a family of 1,3-diols with a chiral rigid backbone, potentially suitable as nonracemic precursors for bidentate ligands in asymmetric synthesis.     

Synthesis,Spectral, Cyclic Voltammetric Studies,and Single Crystal X‐Ray Structure Determination of the Planar NiS2P2, NiS2PN,and NiS2PC Chromophores

Synthesis, spectral and cyclic voltammetric characterization of [Ni(dedtc)(4‐MP)₂](ClO₄) ( 1 ), [Ni(dedtc)(4‐MP)(NCS)]( 2 ), [Ni(dedtc)(PPh₃)(NCS)] ( 3 ) and [Ni(dedtc)(PPh₃)(CN)] ( 4 ) (dedtc = diethyldithiocarbamate, 4‐MP = tri(4‐methylphenyl)phosphine, PPh₃ = triphenylphophine) are reported. IR spectra of complexes 1‐4 show the characteristic thioureide (C‐N) bands at higher wave numbers compared to that of the parent dithiocarbamate complex [Ni(dedtc)₂]. The d‐d transitions are observed in the region 452—482 nm. The CV studies clearly show the presence of reduced electron density on the nickel ions in mixed ligand complexes 1‐4 compared to the parent dithiocarbamate. Single crystal X‐ray structure studies show all the complexes to containplanar NiS₂P₂, NiS₂PN, and NiS₂PC chromophores in keeping with the observed diamagnetism. In all the complexes the Ni‐S distances are asymmetric. The thioureide C‐N distance of the complexes 1‐4 are less thanthe C‐N distance observed in the parent [Ni(dedtc)₂].     

A bicyclo[3.2.0]hept-3-en-6-one approach to prostaglandin intermediates

[reaction:see text] The substituted cyclopentanic structures, 6-benzyloxymethyl-7-hydroxy-2-oxabicyclo [3.3.0]octan-3-one (1), a Corey lactone derivative, and 6-exo-benzyloxymethyl-2-oxabicyclo[3.3. 0]oct-7-en-3-one (2), have been obtained stereoselectively through the bicyclo[3.2.0]hept-3-en-6-one approach via 5-benzyloxymethyl-3-hydroxy-6-heptenoic acid, easily accessible from the inexpensive monoprotected cis-2-butene-1,4-diol.