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

The effect of the saliva composition on brass corrosion

The composition of natural saliva is strongly variable and unstable outside the oral cavity, therefore corrosion tests are usually performed in artificial saliva solutions. In this work the effect of the composition of various saliva solutions on the corrosion behaviour of a CuZn37 alloy, exposed for 1, 3 and 16 hours to the solutions, is investigated by using electrochemical measurements, optical microscopy and X-Ray Photoelectron Spectroscopy. The solutions investigated in this work are: Darvell (D), Carter-Brugirard (C-B) and SALMO, selected for their composition that mainly differs in the organic compounds content. Electrochemical measurements show that the open circuit potential (OCP) and the polarization resistance Rp increase with exposure time in the solutions, indicating a decrease in the corrosion rate. The corrosion rate (µm/year) in the Darvell solution is found to be two times higher than the other artificial saliva solutions and varies in the order: Darvell > Carter-Brugirard > SALMO. These data suggest that the presence of different organic compounds might limit the formation of a stable protective surface film as confirmed by XPS surface analyses

Urinary metabolome of infants with colic treated with Lactobacillus reuteri DSM 17938: a pilot randomized trial

Background: Lactobacillus reuteri DSM 17938 is the only probiotic recommended for treatment of colicky infants, but its mechanism of action is not clear. The study aim was to examine urinary metabolomic fingerprint of colicky breastfed infants before and after 1 month of orally administered Lactobacillus reuteri DSM 17938 or placebo. Methods: This randomized, blinded, placebo-controlled clinical trial was carried out with a well-documented probiotic. Thirty-two infants were enrolled, 16 in the probiotic group and 16 in the placebo group. Urine samples were collected from each subject before starting supplementation and at the end of the study period. Metabolomic profiles were obtained using a gas chromatography/mass spectrometry instrument. Subsequently, to compare groups before and after probiotic supplementation, univariate and multivariate statistical analysis were performed. Results: In the L. reuteri treated group all metabolites for all class of nutrients (sugars, amino acids, carboxylic acids) resulted more abundant after the study period. The comparison with a control group (placebo treated), confirmed this effect on urines. Conclusions: The metabolomic analysis of urine samples from infants treated with L. reuteri DSM 17938 allowed to detect some interesting features related to the effect of this treatment on urinary metabolome. To validate the results, a test on a larger cohort is required

Search for evidence of the type-III seesaw mechanism in multilepton final states in proton-proton collisions at s=13\sqrt{s} = 13 TeV

A search for a signal consistent with the type-III seesaw mechanism in events with three or more electrons or muons is presented. The data sample consists of proton-proton collisions at $\sqrt{s} = 13$ TeV collected by the CMS experiment at the LHC in 2016 and corresponds to an integrated luminosity of 35.9 inverse femtobarns. Selection criteria based on the number of leptons and the invariant mass of opposite-sign lepton pairs are used to distinguish the signal from the standard model background. The observations are consistent with the expectations from standard model processes. The results are used to place limits on the production of heavy fermions of the type-III seesaw model as a function of the branching ratio to each lepton flavor. In the scenario of equal branching fractions to each lepton flavor, heavy fermions with masses below 840 GeV are excluded. This is the most sensitive probe to date of the type-III seesaw mechanism