Characterization of the boundary layer at Dome C (East Antarctica) during the OPALE summer campaign

The regional climate model MAR was run for the region of Dome C located on the East Antarctic plateau, during Antarctic summer 2011–2012, in order to refine our understanding of meteorological conditions during the OPALE observation campaign. A very high vertical resolution is set up in the lower troposphere, with a grid spacing of roughly 2 m. Comparisons are made with observed temperatures and winds near the surface and from a 45 m high tower as well as sodar and radiation data. MAR is generally in very good agreement with the observations but sometimes underestimates cloud formation, leading to an underestimation of the simulated downward long-wave radiation. Absorbed short-wave radiation may also be slightly overestimated due to an underestimation of the snow albedo and this influences the surface energy budget and atmospheric turbulence. Nevertheless the model provides sufficiently reliable information that represent key parameters when discussing the representativeness of chemical measurements made nearby the ground surface during field campaigns conducted at the Concordia site located at Dome C (3233 m a.s.l.)

Key parameters influencing wind-induced aeroelastic responses of single-axis solar trackers in photovoltaic plants

Single-axis solar trackers enhance energy production and cost-effectiveness in large-scale solar installations compared to fixed panels. However, their structural design must address unique challenges, particularly regarding wind resistance, due to reduced mechanical properties for cost savings. This article examines several key parameters of solar plants and evaluates their influence on tracker response, emphasizing wind-induced aeroelastic effects. These parameters include the layout arrangement of solar plants and the inter-row spacing. Tracker position has been evaluated in a 4-rows by 2-column corner region of rectangular tracker plant, with two ground cover ratios of 0.38 and 0.25. Moreover, the effects of the operational parameters of individual trackers have also been monitored, considering working pitch angles in the range between −60∘ and +60∘ and wind exposure angles of 0°, 15°, 30° and 45°. Structural properties were assumed to remain constant. The research combines experimental wind tunnel tests with numerical dynamic simulations based on a finite element model, monitoring the internal stress state to assess performance. Results show that large pitch angles (>45∘) exhibit stable aeroelastic behavior, while small pitch angles, between −30∘ and +30∘, become unstable after reaching a certain velocity threshold. Among the monitored pitches, inclinations between 15° and 30° are the most critical in terms of internal response. The research confirms that trackers on the perimeter are the most stressed in the plants. The largest load cases occur with wind directions normal to the tracker axis. Finally, the analysis of the spacing between rows showed no significant effect on the response

Structural analysis of MDM2 RING separates degradation from regulation of p53 transcription activity

MDM2–MDMX complexes bind the p53 tumor-suppressor protein, inhibiting p53's transcriptional activity and targeting p53 for proteasomal degradation. Inhibitors that disrupt binding between p53 and MDM2 efficiently activate a p53 response, but their use in the treatment of cancers that retain wild-type p53 may be limited by on-target toxicities due to p53 activation in normal tissue. Guided by a novel crystal structure of the MDM2–MDMX–E2(UbcH5B)–ubiquitin complex, we designed MDM2 mutants that prevent E2–ubiquitin binding without altering the RING-domain structure. These mutants lack MDM2's E3 activity but retain the ability to limit p53′s transcriptional activity and allow cell proliferation. Cells expressing these mutants respond more quickly to cellular stress than cells expressing wild-type MDM2, but basal p53 control is maintained. Targeting the MDM2 E3-ligase activity could therefore widen the therapeutic window of p53 activation in tumors