No abstract

Soils used in earth construction projects are mostly unsaturated, and they undergo frequent drying–wetting cycles (repeated hydraulic loads) due to changes in climatic conditions or variations of the ground water level, particularly at shallow depths. After compaction, changes in water content can significantly influence the hydromechanical response of the construction material, which therefore must be assessed for repeated hydraulic loads. This research investigates the effect of such loads on the microstructure and hydraulic behaviour of a silty soil, typically used in the construction of embankments and dykes, with the aim of providing a better understanding of the consequences of drying–wetting cycles on the response of the material over time. Experimental tests were performed to study the impact of drying–wetting cycles on the water retention, hydraulic conductivity, and fabric of compacted specimens. Fabric changes are documented to take place even without significant volumetric strains, promoting an irreversible increase in the hydraulic conductivity and a reduction in the capacity to retain water compared to the as-compacted soil. The fabric changes are interpreted and quantified by means of a hydromechanical model, which accounts for the evolving pore-size distribution at different structural levels. The proposed model reproduces quite well the microstructural observations, together with the evolution of the water retention behaviour and hydraulic conductivity.

The paper focuses on the hydromechanical behaviour of an unsaturated compacted clayey silt, accounting for fabric changes induced by drying–wetting cycles occurring at low stress levels. The response along isotropic compression and triaxial compression (shear) at constant water content was investigated by laboratory tests on both as-compacted and dried–wetted samples. Compaction induces a microstructural porosity pertinent to clay peds and a macrostructural porosity external to the peds. Drying–wetting cycles decrease the microporosity and increase the macroporosity, which reduces the water retention capacity, increases the compressibility, and promotes higher peak strengths with more brittle behaviour during triaxial compression. A coupled double-porosity elastic–plastic model was formulated to simulate the experimental results. A nonassociated flow rule was defined for the macrostructure, modifying a stress–dilatancy relationship for saturated granular soils to account for the increase in dilatancy with suction observed in the experiments. The average skeleton stress and suction were adopted as stress variables. As correctly predicted by the model, the shear strength at critical state is not significantly influenced by the degree of saturation or by the hydraulic history. On the contrary, the higher peak strength, brittleness, and dilatancy of the dried–wetted samples are mostly explained by their reduced water-retention capacity.

Forty-four nondiabetic patients with celiac disease (CD) were examined for the presence of insulin-dependent diabetes mellitus (IDDM)-related autoantibodies. Islet cell antibodies (ICA) were detected in 2 of 44 (4.5%). None of the 200 age- and sex-matched healthy controls was ICA positive (p < 0.05). Competitive anti-insulin antibodies (CIAA) were detected in 1 of 44 (2.5%) patients. First-phase insulin reserve (FPIR), stimulated insulin reserve (SIR), and glycosylated hemoglobin (GHB) levels were normal in the autoantibody-positive patients. Our data suggest that, like first-degree relatives of IDDM patients, CD patients are characterized by an increased prevalence of diabetes-related autoantibodies. Further follow-up is needed to determine whether the presence of these autoantibodies in nondiabetic CD patients predicts future IDDM.

Aim To compare the effect of low‐level laser therapy (LLLT) on postoperative pain after single‐visit root canal retreatment on mandibular molars. Methodology This randomized controlled clinical trial included 36 patients referred to the Department of Endodontics, Islamic Azad University, Tehran, Iran. Healthy patients who required root canal retreatment on symptomatic first or second mandibular molars, with a PAI index score of 2 or 3, preoperative tooth and percussion pain of <56 mm on a 170‐mm visual analogue scale (VAS) were included. After local anaesthesia using inferior alveolar nerve block followed by rubber dam isolation and access cavity preparation, the D RaCe retreatment system was used to remove the existing root filling material, and after canal negotiation and gaining patency, working length was determined with an apex locator. Further canal enlargement was carried out with size 35, 0.04 taper, and size 40, 0.04 taper RaCe rotary instruments and then canals were filled using laterally compacted gutta–percha points and AH Plus sealer. The patients were randomly assigned to treatment groups: In the LLLT group, a 980‐nm diode laser set at 6.89 W/cm2 energy density, 0.5 W power, and a tip diameter of 10 mm were activated from the buccal side on the mesial and distal root apices for 15 s. In the sham group, the laser handpiece was placed inside the patient's mouth at the same location, but the laser was not activated. Then patients were instructed to record their postoperative pain levels at 4, 8, 12 and 24 h and 2, 3 and 7 days after treatment on separate VAS scales. For data analysis, the independent sample t and the Mann–Whitney U tests were used. Nominal variables were analysed by using the chi‐square test. Results In the LLLT group, the most intense pain was reported 24 and 48 h post‐treatment [mean (SD) = 0.22 (0.54) for both], whereas in the sham group, the most intense pain level was observed 4 h post‐treatment [mean (SD) = 0.78 (0.80)]. At the 4‐h interval, pain intensity was significantly lower in the LLLT group (p = .016). Conclusions Low‐level laser therapy reduced postoperative pain after single‐visit root canal retreatment of mandibular molars only four hours following the procedure.