Combined use of SEM-EDS, OM and XRD for the characterization of corrosion products grown on silver roman coins

In the framework of the PROMET project (European Commission contract No. 509126) aimed to develop new analytical techniques and materials for monitoring and protecting metal artefacts and monuments from the Mediterranean region, the corrosion products grown on silver Roman coins during archaeological burial is studied by means of scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD) and optical microscopy (OM) techniques. PACS 68.55.Jk; 68.35.Dv; 68.37.Hk; 68.55.Nq; 81.05.Bx     

Peptide Ligands Stabilized by Small Molecules

Bicyclic peptides generated through directed evolution by using phage display offer an attractive ligand format for the development of therapeutics. Being nearly 100‐fold smaller than antibodies, they promise advantages such as access to chemical synthesis, efficient diffusion into tissues, and needle‐free application. However, unlike antibodies, they do not have a folded structure in solution and thus bind less well. We developed bicyclic peptides with hydrophilic chemical structures at their center to promote noncovalent intramolecular interactions, thereby stabilizing the peptide conformation. The sequences of the peptides isolated by phage display from large combinatorial libraries were strongly influenced by the type of small molecule used in the screen, thus suggesting that the peptides fold around the small molecules. X‐ray structure analysis revealed that the small molecules indeed formed hydrogen bonds with the peptides. These noncovalent interactions stabilize the peptide–protein complexes and contribute to the high binding affinity.     

Neutron bombardment of single wall carbon nanohorn (SWCNH): DSC determination of the stored Wigner-Szilard energy

Single wall carbon nanohorn (SWCNH) were neutron-bombarded to a dose of 3.28 × 10¹⁶ n/cm². The Wigner or stored energy was determined by a differential scanning calorimeter and was found 5.49 J/g, 50 times higher than the Wigner energy measured on graphite flakes treated at the same neutron dose. The activation energy for the thermal annealing of the accumulated radiation damage in SWCNH was determined in the range 6.3–6.6 eV against a typical activation energy for the annealing of the radiation-damaged graphite which is in the range of 1.4–1.5 eV. Furthermore the stored energy in neutron-damaged SWCNH is released at 400–430 °C while the main peak in the neutron-damaged graphite occurs at 200–220 °C. The radiation damaged SWCNH were examined with FT-IR spectroscopy showing the formation of acetylenic and aliphatic moieties suggesting the aromatic C=C breakdown caused by the neutron bombardment.     

Photoinduced Olefin Diamination with Alkylamines

Vicinal diamines are ubiquitous materials in organic and medicinal chemistry. The direct coupling of olefins and amines would be an ideal approach to construct these motifs. However, alkene diamination remains a long‐standing challenge in organic synthesis, especially when using two different amine components. We report a general strategy for the direct and selective assembly of vicinal 1,2‐diamines using readily available olefin and amine building blocks. This mild and straightforward approach involves in situ formation and photoinduced activation of N‐chloroamines to give aminium radicals that enable efficient alkene aminochlorination. Owing to the ambiphilic nature of the β‐chloroamines produced, conversion into tetra‐alkyl aziridinium ions was possible, thus enabling diamination by regioselective ring‐opening with primary or secondary amines. This strategy streamlines the preparation of vicinal diamines from multistep sequences to a single chemical transformation.     

Large scale investigation of chemical composition, structure and corrosion mechanism of bronze archeological artefacts from Mediterranean basin

A large number of Cu-based archaeological artefacts from the Mediterranean basin have been selected for investigation of their chemical composition, metallurgical features and corrosion products (i.e. the patina).The guidelines for the selection of the Cu-based artefacts have taken into account the representativeness of the Mediterranean archaeological context, the manufacturing technique, the degradation state and the expected chemical composition and structure of the objects.The results show wide variation of the chemical composition of the alloys that include all kinds of ancient Cu-based alloys such as low and high tin, and also leaded bronzes, copper and copper-iron alloys.The examination of the alloy matrix shows largely different metallurgical features thus indicating the use of different manufacturing techniques for producing the artefacts. The results of the micro-chemical investigation of the patina show the structures and the chemical composition of the stratified corrosion layers where copper or tin depletion phenomenon are commonly observed with a remarkably surface enrichment of some soil elements such as P, S, Ca, Si, Fe, Al and Cl. This information indicates the strict interaction between soil components and corrosion reactions and products. In particular, the ubiquitous and near constant presence of chlorine in the corrosion layers is observed in the patina of the archaeological Cu-based artefacts found in different contexts in Italy, Turkey, Jordan, Egypt, Spain and Tunisia. This latter occurrence is considered dangerous because it could induce a cyclic corrosion reaction of copper that could disfigure the artefact.The micro-chemical and micro-structural results also show that another source of degradation of the bronze archaeological artefacts, are their intrinsic metallurgical features whose formation is induced during the manufacturing of the objects, carried out in ancient times by repeated cycles of cold or hot mechanical work and thermal treatments. These combined treatments induce crystallisation and segregation phenomena of the impurities along the grain boundaries and could cause mechanical weakness and increase the extent of the inter-granular corrosion phenomena. PACS 68.55.Jk; 68.35.Dv; 68.37.Hk; 68.55.Nq; 81.05.Bx     

An algebraic version of Demailly's asymptotic Morse inequalities

We give an elementary algebraic proof of some asymptotic estimates (called by Demailly asymptotic Morse inequalities) for the dimensions of cohomology groups of the difference of two ample line bundles on a smooth complex projective variety of any dimension.

     

Reaction of Nitrogen‐Radicals with Organometallics Under Ni‐Catalysis: N‐Arylations and Amino‐Functionalization Cascades

Herein, we report a strategy for the generation of nitrogen‐radicals by ground‐state single electron transfer with organyl–Ni^I species. Depending on the philicity of the N‐radical, two types of processes have been developed. In the case of nucleophilic aminyl radicals direct N‐arylation with aryl organozinc, organoboron, and organosilicon reagents was achieved. In the case of electrophilic amidyl radicals, cascade processes involving intramolecular cyclization, followed by reaction with both aryl and alkyl organometallics have been developed. The N‐cyclization–alkylation cascade introduces a novel retrosynthetic disconnection for the assembly of substituted lactams and pyrrolidines with its potential demonstrated in the short total synthesis of four venom alkaloids.     

Granger causality for circular variables

In this Letter we discuss the use of Granger causality to the analyze systems of coupled circular variables, by modifying a recently proposed method for multivariate analysis of causality. We show the application of the proposed approach on several Kuramoto systems, in particular one living on networks built by preferential attachment and a model for the transition from deeply to lightly anaesthetized states. Granger causalities describe the flow of information among variables.     

Thermodynamical analysis of the EMC effect

Assuming that the sea quark distribution vanishes for x > 0.3, we analyse the F₂^Fe(x, Q²) and F₂^D(x, Q²) structure functions measured by the European Muon Collaboration in the framework of a thermodynamical model of the valence quarks. The experimental ratio $\text{F}{}_2{}^{\mathrm{<mtext>Fe</mtext>}}\text{(x)}\text{F}{}_2{}^{\mathrm{<mtext>D</mtext>}}\text{(x)}$ is well reproduced over the whole x range by the ratio of two valence quark distributions at different temperatures T and confinement volumes V. We obtain T_D?T_Fe≈3 MeV and $\text{V}{}_{\mathrm{<mtext>Fe</mtext>}}\text{V}{}_{\mathrm{<mtext>D</mtext>}}\text{≈ 1.3}$.