Excess-entropy scaling in supercooled binary mixtures

Supercooled liquids near the glass transition show remarkable non-Arrhenius transport phenomena, whose origin is yet to be clarified. Here, the authors use GPU molecular dynamics simulations for various binary mixtures in the supercooled regime to show the validity of a quasiuniversal excess-entropy scaling relation for viscosity and diffusion

Simplified Maneuvering Strategies for Rendezvous in Near-Circular Earth Orbits

The development of autonomous guidance control and navigation systems for spacecraft would greatly benefit applications such as debris removals or on-orbit servicing, where human intervention is not practical. Within this context, inspired by Autonomous Vision Approach Navigation and Target Identification (AVANTI) demonstration, this work presents new guidance algorithms for rendezvous and proximity operations missions. Analytical laws are adopted and preferred over numerical methods, and mean relative orbital elements are chosen as state variables. Application times, magnitudes and directions of impulsive controls are sought to minimize propellant consumption for the planar reconfiguration of the relative motion between a passive target spacecraft and an active chaser one. In addition, simple and effective algorithms to evaluate the benefit of combining in-plane and out-of-plane maneuvers are introduced to deal with 3D problems. The proposed new strategies focus on maneuvers with a dominant change in the relative mean longitude (rarely addressed in the literature), but they can also deal with transfers where other relative orbital elements exhibit the most significant variations. A comprehensive parametric analysis compares the proposed new strategies with those employed in AVANTI and with the global optimum, numerically found for each test case. Results are similar to the AVANTI solutions when variations of the relative eccentricity vector dominate. Instead, in scenarios requiring predominant changes in the relative mean longitude, the required Delta V exhibits a 49.88% reduction (on average) when compared to the original methods. In all the test cases, the proposed solutions are within 3.5% of the global optimum in terms of Delta V. The practical accuracy of the presented guidance algorithms is also tested with numerical integration of equations of motion with J2 perturbation

Earth dams: Damage mechanisms and limit states in seismic conditions

The paper summarizes the main damage mechanisms suffered by earth dams under both strong earthquakes and normal operation to identify the limit states that should be taken into account for dam seismic safety assessment. In addressing limit states, a distinction is made between seismic and post-seismic stages. The limit state of global instability under the effects of inertial loads is considered both in the seismic stage, taking into account the favourable contributions of ground motion asynchronism and during the post-seismic stages, when excess pore water pressures induced by seismic shaking and by a possible rapid drawdown could affect dam behaviour. The limit state of dam freeboard loss is then dealt with, showing the importance of estimating settlement rates during the seismic and post-seismic stages. Third, the limit state of water-tightness loss is discussed with reference to seismic-induced strain concentration or stress changes. Finally, the risk of liquefaction within the embankment or in the foundation is considered, discussing how the phenomenon could be affected by changes in particle grading possibly experienced by coarse-grained materials during normal operation of the dam

Immediate placement and loading of dental implants: A human histologic case report

Background: The possibility of immediately loading postextraction implants was proposed recently. However, histologic evidence of osteointegration in such cases is still lacking. In this case report, two implants placed into fresh extraction sites, one immediately loaded and the other one unloaded, were compared clinically and histologically. Methods: Two teeth in need of extraction and localized in two symmetric quadrants of one patient were extracted, and dental implants were placed immediately into fresh extraction sites. One of them was connected with a heating abutment (control), whereas the other one was loaded immediately (test) with a resin crown in occlusion with the antagonist teeth. Clinical examinations were made, and radiographs were taken at follow-up visits. After 6 months, control and test implants were removed, together with the peri-implant bone, and a histomorphometric analysis was made. Results: Both implants appeared radiographically osseointegrated and clinically stable at retrieval. Mineralized tissue was found at the implant interface. The percentage of bone-to-implant contact in the control and test implants was 58% +/- 4.0% and 52% +/- 3.2%, respectively. In the loaded implant, a more compact, mature, well-organized peri-implant bone was found with many areas of remodeling and some osteons, whereas the bone tissue surrounding the unloaded implant was constituted of only thin bone trabeculae. Conclusions: Immediate loading did not seem to impair osseointegration of an immediate postextraction implant compared to an unloaded postextraction one. Further studies with a larger number of samples are needed to confirm these preliminary results

Immediately Loaded Postextraction Implants: A Human Histologic Case Report

Objectives: The aim of this study was to clinically and histologically compare two implants placed into fresh extraction sites: one immediately loaded and the other one unloaded. Methods: Two teeth in need of extraction and localized in two symmetric quadrants were selected. Baseline clinical and radiographic exams were performed. Teeth were extracted and dental implants immediately inserted into fresh extraction sites. One of them was connected with a healing abutment (control), while the other one was immediately loaded (test) by a resin crown. Clinical and radiographic examinations were performed at follow-up visits. After six months both control and test implants were removed, together with the peri-implant bone, and histologically examined. Results: Both implants appeared radiographically osseointegrated and clinically stable at retrieval time. Mineralized tissue was found at the implant interface. The bone-to-implant contact percentage in the control and test implants was 58 ± 4.0% and 52 ± 3.2%, respectively. In the loaded implant a more compact, mature, well-organized peri-implant bone was found, with many remodelling areas and some osteons, whereas the bone tissue surrounding the unloaded implant was constituted only by thin bone trabeculae. Conclusions: Immediate loading did not seem to impair osseointegration of an immediately loaded postextraction implant, compared to an unloaded postextraction one. Further studies, with a larger number of samples, are needed to confirm these preliminary results

Immediately Loaded Postextraction Implants: A Controlled Human Histologic Case Report

Objectives: The aim of this study was to clinically and histologically compare two implants placed into fresh extraction sites: one immediately loaded and the other one unloaded. Methods: Two teeth in need of extraction and localized in two symmetric quadrants were selected. Baseline clinical and radiographic exams were performed. Teeth were extracted and dental implants immediately inserted into fresh extraction sites. One of them was connected with a healing abutment (control), while the other one was immediately loaded (test) by a resin crown. Clinical and radiographic examinations were performed at follow-up visits. After six months both control and test implants were removed, together with the peri-implant bone, and histologically examined. Results: Both implants appeared radiographically osseointegrated and clinically stable at retrieval time. Mineralized tissue was found at the implant interface. The bone-to-implant contact percentage in the control and test implants was 58 ± 4.0% and 52 ± 3.2%, respectively. In the loaded implant a more compact, mature, well-organized peri-implant bone was found, with many remodelling areas and some osteons, whereas the bone tissue surrounding the unloaded implant was constituted only by thin bone trabeculae. Conclusions: Immediate loading did not seem to impair osseointegration of an immediately loaded postextraction implant, compared to an unloaded postextraction one. Further studies, with a larger number of samples, are needed to confirm these preliminary results