Interatomic potentials of van der Waals dimers Hg2Hg_{2} and Cd2Cd_{2} : probing discrepancies between theory and experiment

Results of new all-electron ab initio calculations and revisit of experimental studies of the interatomic potentials of lower-lying ungerade excited and ground electronic energy states of the Hg_{2} and Cd_{2} van der Waals complexes are used as probes of discrepancies between theory and experiment. From simulations of the previously and presently measured LIF excitation and dispersed emission spectra new analytical representations of the excited- and the ground-state interatomic potentials are proposed. An inverted perturbation approach was also used to improve the studied interatomic potentials. The comparison of the new ab-initio calculated potentials with the results of the analyses illustrates an improve theory-to-experiment agreement for such a demanding system like Hg_{2} or Cd_{2}

Salt Contamination of Wooden Materials: the Case of Trondheim (Norway) Warehouses

Warehouses are big architectonical structures mostly made of spruce wood and utilized as storage buildings principally by food traders in Northern Countries. Trondheim’s warehouses currently observable along the river Nidelva, date back between the 17th and half of the 19th century were mostly used to stock and process fish. Therefore, where the food goods were stored, residuals are expected to be still present and/or to be responsible for the formation of alteration products on the wooden surfaces as well as inside the wooden structure. Here we propose a characterization of residual and neo-formed compounds inside and on the surface of wooden logs by means of vacuum microbalance that allowed both to individuate the type of salts, as well as, to estimate the maximum water film thickness adsorbed on the wooden samples at 93% of RH. These data have been related to variations in the acoustic emission (AE) intensity detected at the log surface and to the wood moisture content measured with capacitive and resistance operating moisture meters. The application of three independent techniques have allowed obtaining interestingly information indicating their potentiality as decay assessment techniques in the field of historical materials and specifically in the study of salts weathering on wood. The methodology allowed identifying a clear relationship between the amount of water in logs as a function of their distance from the ground and variations in the amplitude of the acoustic emission signals

Excitation spectra of CdRg (Rg = He, Ne, Xe) complexes recorded at the D1Σ0+←X1Σ0+D^{1}\Sigma _{0}^{+}\leftarrow X^{1}\Sigma _{0}^{+} transition : from the heaviest CdXe to the lightest CdHe

Laser-induced fluorescence excitation spectra of CdRg (Rg = He, Ne, Xe) complexes were recorded at the $D^{1}\Sigma _{0}^{+}\leftarrow X^{1}\Sigma _{0}^{+}$ bound $\leftarrow$ bound and free $\leftarrow$ bound transitions. In case of CdXe, analysis of the recorded profiles resulted in determination of the $D^{1}\Sigma _{0}^{+}$ -state potential energy curve and ground-state dissociation energy. In case of CdHe and CdNe, analysis of the free $\leftarrow$ bound profiles provided a repulsive part of the $D^{1}\Sigma _{0}^{+}$ -state potential. Valence ab initio calculations of the ground- and excited-state potentials and electronic transition dipole moments of the studied transition were performed taking scalar-relativistic and spin-orbit effects into account. The results were supplemented with those for CdAr and CdKr of our earlier study

The Kaiser effect in wood \u2013 does historic wood have a stress memory?

Acoustic emission (AE) signals generated under loading provide valuable information about structural changes undergoing in a material. For materials which have ability to remember load history, the AE activity is observed only above a load level that has been previously exerted on the same material. This ability to memorize the highest level of stress which the material has experienced in the past is known as the Kaiser effect. The persistence of the Kaiser effect in time for metals and mineral materials has been observed by many researchers. In case of organic materials such as wood, the evidence for the phenomenon is very limited. Earlier experimental evidence has shown that the Kaiser effect fades over the time for new seasoned wood. The process is accelerated by temperature and changes of moisture content in the tested material. In this article, a systematic study of the Kaiser effect in historic wood is presented. Measurements were performed in the laboratory on spruce beams from a roof timber structure of a historic palace in Northern Italy. The wood is almost 100 years old. The results clearly show that the Kaiser effect is observed even after one year between subsequent loadings. The observed long-time memory of historic wood can be explained by much higher ratio between the crystalline and amorphous phases of the material when compared to new wood, reported in the literature. The observation opens a new perspective for the determination of load history of wooden works of art and constructions, which is essential for assessing risk of their physical damage

Valutazione non distruttiva del degrado meccanico e ambientale in strutture murarie

Le strutture murarie storiche sono spesso soggette a danneggiamento meccanico e a degrado ambientale, fenomeni che richiedono di poter disporre di tecniche diagnostiche e di monitoraggio adeguate a valutare in sito lo stato di salute murario, possibilmente in maniera non invasiva e non distruttiva. Nell\u2019ambito del progetto SMooHS \ue8 in corso una sperimentazione in laboratorio su provini di muratura di laterizio che simulano murature storiche sottoposte a degrado ambientale e meccanico il cui danno \ue8 stato caratterizzato attraverso prove di monitoraggio (emissione acustica) e non distruttive (soniche). Gli scopi sono stati il monitoraggio dell\u2019evoluzione del danno e il corrispondente decadimento delle propriet\ue0 meccaniche attraverso la stima del modulo di elasticit\ue0 calcolato in maniera indiretta dalle prove soniche. A tali fini le prove sono state condotte su serie diverse di provini in stato integro e in presenza di fessure da danneggiamento meccanico o viceversa sottoposte a invecchiamento in condizione di esposizione naturale agli agenti atmosferici in aggiunta a risalita capillare con diverse soluzioni saline

Kaiser effect in historic timber elements

Timber elements are major structural and architectural components in historic buildings and at the same time belong to the category of materials vulnerable to degradation. The recovery of 150-year old timber beams from a roof of a historic building made possible the non-destructive investigation of their response to cyclic loading. The experimental study carried out using the acoustic emission technique provided evidence that historic wood shows the load memory known as the Kaiser effect. The effect was observed for different loading and unloading time windows. The observations open up a new perspective for the determination of defects in wooden objects and constructions, important for assessing their possible structural instability