The size effect in corrosion greatly influences the predicted life span of concrete infrastructures

Chloride-induced corrosion of reinforcing steel in concrete is the main cause for premature degradation of concrete infrastructures worldwide. Since mid of the last century, the conceptual approach to tackle this challenge in science and engineering is based on a threshold chloride concentration (Ccrit) for corrosion initiation. Here, we present an experiment that shows that Ccrit depends strongly on the exposed steel surface area. The smaller the tested specimen, the higher and the more variable becomes Ccrit. This size effect can be explained by the local conditions at the steel-concrete interface, which exhibit pronounced spatial variability. The size effect has major implications for the future use of the concept of Ccrit. It questions the reproducibility of typically small-scale laboratory testing and the applicability of laboratory results to engineering structures. We show that the weakest link theory is suitable to transform Ccrit from small to large dimensions, which lays the basis for taking into account the size effect in science and engineering of corrosion of infrastructures

Surface modification of food-grade PVC monitored by angle-resolved XPS

In this work the covalent functionalization of polyvinyl chloride (PVC) with (3-mercaptopropyl)trimethoxysilane (MPTMS) by nucleophilic substitution was investigated by X-ray photoelectron spectroscopy (XPS). The surface of food-grade PVC was characterized before and after treatment with ethanol and with 5% and 10% MPTMS solutions in ethanol. Special attention was paid to the determination of the chemistry, composition and thickness of the functionalized polymer surface by angle-resolved XPS (ARXPS). XPS analysis in standard mode and ARXPS spectra showed the presence of sulphur, silicon and oxygen from the MPTMS molecule. The quantitative analysis was in good agreement with the stoichiometry of the molecule. A small amount of chlorine, detected also at grazing angles, supported the formation of a layer, which resulted to be 2.2(0.2) nm thick including the hydrocarbon contamination usually detected by XPS on samples in contact with solutions. It is here demonstrated that XPS and ARXPS allow monitoring the surface functionalization and tune the conditions for achieving a good reproducibility during the functionalization of food-grade PVC by MPTMS. This is the starting point for further functionalization to obtain active food packaging with antimicrobial properties

The role of organic compounds in artificial saliva for corrosion studies: evidence from XPS analyses

Several formulations of artificial saliva have been used for corrosion studies. The present work focuses on the effect of different saliva formulations on the composition of the surface film formed on CuZn37 brass alloy by X-ray photoelectron spectroscopy (XPS), in order to clarify the corrosion mechanism of historical brass wind instruments when used. Three different saliva solutions, Darvell (D), Carter-Brugirard (C-B) and SALMO, were selected. They differ for the content of the organic compounds. The XPS results show the presence of a film made of CuSCN and zinc-phosphate on the brass exposed to C-B and SALMO. In the case of samples exposed to D formulation, phosphorus is not revealed, a decrease in the zinc content in the film is detected and the S 2p shows the presence of a second component together with the one ascribed to CuSCN. A comparison with the results obtained on the pure metals in the presence of the organic compounds suggests that the formation of zinc and copper complexes may lead to thin and less protective surface film and thus to the observed high corrosion rates

Losses in the Post-Collision Extraction Line

The CLIC beam delivery system focuses 1.5 TeV electron and positron beams to a nanometre-sized cross section when colliding them at the interaction point (IP). The intense focusing leads to large beam-beam effects, causing the production of beamstrahlung photons, coherent and incoherent e+e− pairs, as well as a significant disruption of the main beam. The transport of the post-collision beams requires a minimal loss extraction line, with high acceptance for energy deviation and divergence. The current design includes vertical bends close to the IP in order to separate the charged particles with a sign opposite to the main beam into a diagnostic-equipped intermediate dump, whilst transporting the photons and the main beam to the final dump. Photon and charged particle losses on magnet masks and dumps result in a complex radiation field and IP background particle fluxes. In this paper, the electromagnetic backgrounds at the IP arising from the losses occurring closest to the collision point are calculated

Photon backgrounds at the CLIC interaction point due to losses in the post-collision extraction line

The CLIC beam delivery system focuses 1.5~TeV electron and positron beams to a nanometre-sized cross section when colliding them at the interaction point (IP). The intense focusing leads to large beam-beam effects, causing the production of beamstrahlung photons, coherent and incoherent $e^+e^-$ pairs, as well as a significant disruption of the main beam. The transport of the post-collision beams requires a minimal loss extraction line, with high acceptance for energy deviation and divergence. The current design includes vertical bends close to the IP in order to separate the charged particles with a sign opposite to the main beam into a diagnostic-equipped intermediate dump, whilst transporting the photons and the main beam to the final dump. Photon and charged particle losses on magnet masks and dumps result in a complex radiation field and IP background particle fluxes. In this paper, the electromagnetic backgrounds at the IP arising from the losses occurring closest to the collision point are calculated

La realcalinización y la extracción electroquímica de los cloruros en las construcciones de hormigón armado

Realkalisation and electrochemical chloride removal techniques, developed for rehabiliting carbonated and chloride-containing structures, are presented. Electrolysis and electromigration mechanisms and consequences as well as electrochemical conditions at the reinforcement surface are discussed and compared with cathodic protection ones. Furthermore, possible side effects are commented

Parity Mixed Doublets in A = 36 Nuclei

The $\gamma$-circular polarizations ($P_{\gamma}$) and asymmetries ($A_{\gamma}$) of the parity forbidden M1 + E2 $\gamma$-decays: $^{36}Cl^{\ast} (J^{\pi} = 2^{-}; T = 1; E_{x} = 1.95$ MeV) $\rightarrow$ $^{36}Cl (J^{\pi} = 2^{+}; T = 1; g.s.)$ and $^{36}Ar^{\ast} (J^{\pi} = 2^{-}; T = 0; E_{x} = 4.97$ MeV) $\rightarrow$ $^{36}Ar^{\ast} (J^{\pi} = 2^{+}; T = 0; E_{x} = 1.97$ MeV) are investigated theoretically. We use the recently proposed Warburton-Becker-Brown shell-model interaction. For the weak forces we discuss comparatively different weak interaction models based on different assumptions for evaluating the weak meson-hadron coupling constants. The results determine a range of $P_{\gamma}$ values from which we find the most probable values: $P_{\gamma}$ = $1.1 \cdot 10^{-4}$ for $^{36}Cl$ and $P_{\gamma}$ = $3.5 \cdot 10^{-4}$ for $^{36}Ar$.Comment: RevTeX, 17 pages; to appear in Phys. Rev.

Neutrino physics at accelerators

Present and future neutrino experiments at accelerators are mainly concerned with understanding the neutrino oscillation phenomenon and its implications. Here a brief account of neutrino oscillations is given together with a description of the supporting data. Some current and planned accelerator neutrino experiments are also explained.Comment: 23 pages, 24 figures. Talk given at the Corfu Summer Institute on Elementary Particle Physics 200