ESTRUTURAS SUPERFICIAIS NO ENTORNO DOS AREAIS DE QUARAÍ/RS – IDENTIFICAÇÃO DOS AGENTES MORFOGENÉTICOS E SUA RELAÇÃO COM AS VARIAÇÕES CLIMÁTICAS NO QUATERNÁRIO

A área de estudo está situada na unidade morfoescultural Cuesta do Haedo, no Rio Grande do Sul. O objetivo principal do estudo é identificar os agentes morfogenéticos responsáveis pela esculturação da paisagem. Como resultado identifica-se duas unidades estratigráficas: a) depósito de colúvio, ambiente úmido (Pleistoceno) e b) depósitos eólicos, ambiente árido ou semi-árido (Holoceno)

The Pampa-2016 experiment

ABSTRACTThe Pampa‐2016 experimental campaign was performed in a typical Pampa lowland South American region. It consisted of both surface flux measurements (at 3 and 29 m) and a radiosonde launched every 3 h. The resulting meteorological observations allowed for the analysis of turbulent properties associated with both a stable and a convective boundary layer. The combined analysis of the surface data and vertical soundings has revealed some general characteristics of the atmospheric boundary layer for both the nocturnal stable conditions and the daytime convective environment. The continuous surface measurements showed that the nocturnal stable inversion, occurring in calm winds, is basically generated by the radiative cooling mechanism that is established after the late afternoon transition. The analysis of night‐time surface data also showed that, under stable conditions in the case of vanishing wind speed, the friction velocity has unrealistic values that are very close to zero. This situation is undesirable for numerical models that generally use this quantity as a lower boundary condition. The analysis of night‐time temperature profiles revealed two contrasting patterns in agreement with the classical classification of radiative night (a very stable boundary layer) and a turbulent night (a weakly stable boundary layer). In contrast, the analysis of the daytime temperature profiles provided an estimation of the convective time scale that is of the order of 10 min, in agreement with experimental values. A spectral analysis and the consequent estimation of the spectral peaks under unstable and stable conditions were in agreement with literature values

Effect of pH variation on the subcritical crack growth parameters of glassy matrix ceramics

The goals of our study were to calculate the subcritical crack growth (SCG) parameters of two veneering ceramics stored in water or Streptococcus mutans (S. mutans) biofilm and remineralizing medium, with indentation flaws. Feldspar (VM7) and leucite‐reinforced (VM13) glass ceramic disks (Vita Zahnfabrik, Bad Säckingen, Germany) were made according to ISO 6872. Some specimens were indented with a Vickers diamond and the crack dimensions were measured. The specimens were fractured for a calculation of inert strength or further stored in water or submitted to pH variation, under preloading tension. Finally, the SCG parameters were calculated after the specimens were fractured under four stressing rates (MPa/s). Weibull analysis was conducted on non‐indented specimens. XPS was performed as qualitative analysis. The subcritical crack of leucite ceramic did not vary with the media storage, but the glass‐ceramic experienced a retarded growth after pH variation. The materials presented low Weibull modulus. Qualitative elemental analyses showed chemical modification on both ceramics. Therefore, the crack growth of leucite‐reinforced ceramic was less affected by the environment pH than glass‐ceramic

Influence of implant connection on the stress distribution in restorations performed with hybrid abutments

Aim This study evaluated the influence of prosthetic connection type (external hexagon [EH], internal hexagon [IH] and morse taper [MT]) on the stress distribution in an implant-supported prosthesis. Materials and methods Using modeling software, three sets were formed according to the prosthetic connection composed of ceramic crown, mesostructure, abutment, abutment screw, implant, cement layers and bone tissue. Solids were imported to the analysis software and bone model was fixed in the base. All materials were considered isotropic, linearly elastic and homogeneous. The static load (500 N, 30°) was applied in the central fossa. Stress distribution data were obtained according to Von-Mises and microstrain criteria. Results The type of prosthetic connection influenced the stress distribution. The stresses for the IH and MT connections were concentrated on the implant and abutment; for EH at the implant, abutment screw, at the implant platform, and at the cement layer between abutment and mesostructure. There is lower influence for the crown and mesostructure, with more promising results for the MT connection. For the bone tissue, all connections showed the same strain pattern. Stress peaks of 148, 142 and 138 MPa in the implant, 134, 129 and 62 MPa in the screw, and 86, 118 and 131 MPa were observed respectively for EH, IH and MT. Conclusions The morse taper connection showed promising performance with lower stress concentration in the abutment screw, implant platform and cement layers