Tectono-stratigraphic response of the Sandino Forearc Basin (N-Costa Rica and W-Nicaragua) to episodes of rough crust and oblique subduction

The southern Central American active margin is a world-class site where past and present subduction processes have been extensively studied. Tectonic erosion/accretion and oblique/orthogonal subduction are thought to alternate in space and time along the Middle American Trench. These processes may cause various responses in the upper plate, such as uplift/subsidence, deformation, and volcanic arc migration/ shut-off. We present an updated stratigraphic framework of the Late Cretaceous– Cenozoic Sandino Forearc Basin (SFB) which provides evidence of sedimentary response to tectonic events. Since its inception, the basin was predominantly filled with deep-water volcaniclastic deposits. In contrast, shallow-water deposits appeared episodically in the basin record and are considered as tectonic event markers. The SFB stretches for about 300 km and varies in thickness from 5 km (southern part) to about 16 km (northern part). The drastic, along-basin, thickness variation appears to be the result of (1) differential tectonic evolutions and (2) differential rates of sediment supply. (1) The northern SFB did not experience major tectonic events. In contrast, the reduced thickness of the southern SFB (5 km) is the result of at least four uplift phases related to the collision/accretion of bathymetric reliefs on the incoming plate: (i) the accretion of a buoyant oceanic plateau (Nicoya Complex) during the middle Campanian; (ii) the collision of an oceanic plateau (?) during the late Danian–Selandian; (iii) the collision/accretion of seamounts during the late Eocene–early Oligocene; (iv) the collision of seamounts and ridges during the Pliocene–Holocene. (2) The northwestward thickening of the SFB may have been enhanced by high sediment supply in the Fonseca Gulf area which reflects sourcing from wide, high relief drainage basins. In contrast, sedimentary input has possibly been lower along the southern SFB, due to the proximity of the narrow, lowland isthmus of southern Central America. Moreover, two phases of strongly oblique subduction affected the margin, producing strike-slip faulting in the forearc basin: (1) prior to the Farallon Plate breakup, an Oligocene transpressional phase caused deformation and uplift of the basin depocenter, triggering shallowing-upward of the Nicaraguan Isthmus in the central and northern SFB; (2) a Pleistocene–Holocene transtensional phase drives the NW-directed motion of a forearc sliver and reactivation of the graben-bounding faults of the late Neogene Nicaraguan Depression. We discuss arguments in favour of a Pliocene development of the Nicaraguan Depression and propose that the Nicaraguan Isthmus, which is the apparent rift shoulder of the depression, represents a structure inherited from the Oligocene transpressional phase

Determinants of Aortic Stiffness: 16-Year Follow-Up of the Whitehall II Study

Aortic stiffness is a strong predictor of cardiovascular disease endpoints. Cross-sectional studies have shown associations of various cardiovascular risk factors with aortic pulse wave velocity, a measure of aortic stiffness, but the long-term impact of these factors on aortic stiffness is unknown.In 3,769 men and women from the Whitehall II cohort, a wide range of traditional and novel cardiovascular risk factors were determined at baseline (1991-1993) and aortic pulse wave velocity was measured at follow-up (2007-2009). The prospective associations between each baseline risk factor and aortic pulse wave velocity at follow-up were assessed through sex stratified linear regression analysis adjusted for relevant confounders. Missing data on baseline determinants were imputed using the Multivariate Imputation by Chained Equations.Among men, the strongest predictors were waist circumference, waist-hip ratio, heart rate and interleukin 1 receptor antagonist, and among women, adiponectin, triglycerides, pulse pressure and waist-hip ratio. The impact of 10 centimeter increase in waist circumference on aortic pulse wave velocity was twice as large for men compared with women (men: 0.40 m/s (95%-CI: 0.24;0.56); women: 0.17 m/s (95%-CI: -0.01;0.35)), whereas the opposite was true for the impact of a two-fold increase in adiponectin (men: -0.30 m/s (95%-CI: -0.51;-0.10); women: 0.61 m/s (95%-CI: -0.86;-0.35)).In this large prospective study, central obesity was a strong predictor of aortic stiffness. Additionally, heart rate in men and adiponectin in women predicted aortic pulse wave velocity suggesting that strategies to prevent aortic stiffening should be focused differently by sex

Experimental analysis of contact fatigue damage in case hardened gears for off-highway axles

none3noPitting is one of the main causes of failure in planetary gear sets of axles designed for agricultural vehicles. The high torque and the low wheel speed typical of such machines result in poor lubrication and promote the onset of contact fatigue failure by pitting, which generally occurs earlier in the sun gear than in both the planets and the ring of wheel hub planetary drives. In fact, sun gears are subjected to the highest contact pressure and, at the same time, unfavourable rolling-sliding working conditions. In this paper, six case hardened sun gears damaged by pitting during endurance tests were analysed. The aim of the analysis was to highlight the key aspects of the morphology and the evolution of pitting damage on the case hardened sun gears.ISSN: 1350-6307 eISSN: 1873-1961noneTerrin, A.; Dengo, C.; Meneghetti, G.Terrin, Andrea; Dengo, Carlo; Meneghetti, Giovann

Lifetime assessment of the rear axle for an off-road vehicle in a fatigue test bench by means of the Peak Stress Method

In this study the Peak Stress Method (PSM) has been applied to the fatigue assessment of the welds of an axle equipped in an off-road vehicle. In the fatigue design of welded joints, the PSM is a FE-based method to rapidly evaluate the NSIFs relevant to the opening, sliding and tearing modes by means of the linear elastic peak stresses extracted from the FE model. First, an axle, which consists of a central body and two lateral branches composed by several plates welded to a tube, has been fatigue tested under a vertical load in a test bench designed to replicate the frame-axle interface. Then, an FE model of the axle has been calibrated to simulate the behaviour observed during the fatigue test, where the reaction forces and the strains at pre-defined locations have been considered. Once the FE model has been calibrated, the PSM has been applied to the welds of the axle, taking advantage of an automatic procedure, and the crack initiation location has been estimated. Finally, the theoretical estimations have been compared with the experimental datum

Valutazione della resistenza a fatica multiassiale di giunti saldati a tratti in acciaio per applicazioni automotive con il metodo della tensione di picco

Il metodo della tensione di picco (PSM) \ue8 utilizzato nella progettazione a fatica di giunti saldati e permette la rapida stima dei fattori di intensificazione delle tensioni all\u2019apice di intaglio (NSIF), per mezzo delle tensioni di picco singolari, lineari elastiche, calcolate al piede o alla radice del cordone di saldatura da analisi agli elementi finiti realizzate con mesh rade. In questo contributo sono stati sottoposti a prova a fatica giunti in acciaio saldati con cordoni d\u2019angolo a tratti di interesse automotive, soggetti ad un carico esterno di trazione monoassiale, che genera stati di tensione locali multiassiali, sia al piede che alla radice del cordone di saldatura. Sono state sottoposte a prova due diverse geometrie, con cordoni in posizione ortogonale o parallela alla direzione di carico, sia in condizioni \u201cas-welded\u201d che \u201cstress relieved\u201d. La geometria locale dei cordoni di saldatura \ue8 stata digitalizzata per mezzo di scansione 3D ed \ue8 stata introdotta nei modelli utilizzati per le analisi FE. Il PSM applicato ai giunti sottoposti a prova ha dimostrato di prevedere le regioni d\u2019innesco delle cricche di fatica e di stimare in favore di sicurezza la vita a fatica

Size- and Temperature-Dependent Lattice Anisotropy and Structural Distortion in CsPbBr3 Quantum Dots by Reciprocal Space X-ray Total Scattering Analysis

Lead halide perovskite nanocrystals (NCs) have emerged as next-generation semiconductors capable of unifying superior photoemission properties, facile and inexpensive preparation, compositional and structural versatility. Among them, CsPbBr3 is a model system in theoretical and experimental studies owing to its intrinsic chemical stability. Nonetheless, knowledge of the precise magnitude and the size- and temperature-dependent lattice and structural distortions is lacking, and the static/dynamic nature of disorder in NCs remains an open question. Herein, robust reciprocal space X-ray total scattering analysis is applied and accurate lattice distortions, Pb-Br bond distances, and Pb-Br-Pb angles versus NCs size are extracted. The lattice anisotropy increases upon expansion on downsizing while, upon contraction on cooling, the lattice distortion behaves differently at intermediate (9 nm) and ultrasmall (5 nm) sizes and from the bulk. Bond distances (stretched by ≈1%) do not show any size dependence, whereas equatorial and axial angles denote more symmetric octahedral arrangements in the smallest sizes, where they differ by ≈2° compared to ≈8° in the bulk. Anomalously high atomic displacement parameters of axial bromine ions persisting down to cryogenic temperatures suggest statically disordered octahedral tilts. These results provide insights having important implications on size-dependent emission properties and the exciton fine structure