13 research outputs found
Modeling Shallow Water Flows on General Terrains
A formulation of the shallow water equations adapted to general complex
terrains is proposed. Its derivation starts from the observation that the
typical approach of depth integrating the Navier-Stokes equations along the
direction of gravity forces is not exact in the general case of a tilted curved
bottom. We claim that an integration path that better adapts to the shallow
water hypotheses follows the "cross-flow" surface, i.e., a surface that is
normal to the velocity field at any point of the domain. Because of the
implicitness of this definition, we approximate this "cross-flow" path by
performing depth integration along a local direction normal to the bottom
surface, and propose a rigorous derivation of this approximation and its
numerical solution as an essential step for the future development of the full
"cross-flow" integration procedure. We start by defining a local coordinate
system, anchored on the bottom surface to derive a covariant form of the
Navier-Stokes equations. Depth integration along the local normals yields a
covariant version of the shallow water equations, which is characterized by
flux functions and source terms that vary in space because of the surface
metric coefficients and related derivatives. The proposed model is discretized
with a first order FORCE-type Godunov Finite Volume scheme that allows
implementation of spatially variable fluxes. We investigate the validity of our
SW model and the effects of the bottom geometry by means of three synthetic
test cases that exhibit non negligible slopes and surface curvatures. The
results show the importance of taking into consideration bottom geometry even
for relatively mild and slowly varying curvatures
Oxidative responsiveness to multiple stressors in the key Antarctic species, Adamussium colbecki: interactions between temperature, acidification and cadmium exposure.
Abstract: High-latitude marine ecosystems are ranked to be among the most
sensitive regions to climate change since highly stenothermal and
specially adapted organisms might be seriously affected by global warming
and ocean acidification. The present investigation was aimed to provide
new insights on the sensitivity to such environmental stressors in the
key Antarctic species, Adamussium colbecki, focussing also on their
synergistic effects with cadmium exposure, naturally abundant in this
area for upwelling phenomena. Scallops were exposed for 2 weeks to
various combinations of Cd (0 and 40 μgL-1), pH (8.05 and 7.60) and
temperature (-1 and +1°C). Beside Cd bioaccumulation, a wide panel of
early warning biomarkers were analysed in digestive glands and gills
including levels of metallothioneins, individual antioxidants and total
oxyradical scavenging capacity, onset of oxidative cell damage like lipid
peroxidation, lysosomal stability, DNA integrity and peroxisomal
proliferation. Results indicated reciprocal interactions between multiple
stressors and their elaboration by a quantitative hazard model based on
the relevance and magnitude of effects, highlighted a different
sensitivity of analysed tissues. Due to cellular adaptations to high
basal Cd content, digestive gland appeared more tolerant toward other
prooxidant stressors, but sensitive to variations of the metal. On the
other hand, gills were more affected by various combinations of stressors
occurring at higher temperatur
Experimental analysis and modeling of self-standing curved crystals for focusing of X-rays
Novel applications can be attained through
the usage of bent crystals as optical components for
the challenge of focusing hard X andγrays by Bragg
diffraction. Nuclear astrophysics, nuclear medicine
and homeland security would highly benefit from
such optics, because they all share the same need for
efficient X- and γ-ray focusing systems. With this
aim, self-standing bent silicon crystals have been reproducibly attained thanks to the method of surface
grooving. An extensive study has been worked out to
understand the process of substrate deformation. By
adjusting experimental parameters, very good control
of the curvature is afforded. Process of deformation
has been modeled in terms of irreversible compression
occurring in the material close to the grooves. The underlying silicon was treated as an anisotropic medium
elastically reacting to the state of stress provided by
the grooves. Comparison between experimental results and theoretical expectations was satisfactorily
achieved
Antioxidant defenses in polar cod (Boreogadus saida) and responsiveness toward dietary crude oil exposure
Increasing anthropogenic activities in the Arctic pose the risk for accidental oil spills but our knowledge of ecotoxicological effects is still limited for Arctic organisms. This study aimed to provide insights in baseline levels of antioxidants in polar cod (Boreogadus saida) from different Arctic locations and investigate the susceptibility of this species to oxidative stress during a 32 day dietary crude oil exposure. Baseline levels of individual antioxidants and total oxyradical scavenging capacity (TOSC) varied among different Arctic fjords. Upon crude oil exposure, dose- and time-dependent polycyclic aromatic hydrocarbons (PAHs) biotransformation was evident through hepatic ethoxyresorufine-O-deethylase activity, glutathione S-transferase mRNA expression and biliary PAH metabolites. Changes in the activity of individual antioxidants and TOSC was, however, slight and transient upon exposure. In conclusion, biotransformation was clearly induced by the sub-lethal levels of crude oil in polar cod, while the antioxidant defense responded with high variability
Precision-Cut Tissue Slices (PCTS) from the digestive gland of the Mediterranean mussel Mytilus galloprovincialis: An ex vivo approach for molecular and cellular responses in marine invertebrates
Environmental Factors and Kawasaki Disease Onset in Emilia-Romagna, Italy
Kawasaki disease (KD)is an idiopathic acute febrile illness that primarily occurs in children <5 years of age and can lead to artery lesions if not promptly treated. Recent studies have shown possible correlations between KD onset and currents and air pollutants.The present study describes results on the correlation between environmental conditions, frequency, and variability ofKD onset in children under five years of age in Emilia-Romagna, a region of Northern Italy, over the period from 2000 to 2017. Since there are substantial climatic differences between the western-central (Emilia) and the eastern area (Romagna) of the region, the data for these areas are analyzed separately. The environmental factors considered are observed local surface daily temperature, daily precipitation, upper air wind regimes, and local air pollution. The results indicate that in Emilia-Romagna, KD onset occurs mainly during late autumn and early spring, which is in agreement with the literature. The frequency of KD onset in Emilia is significantly higher in months characterized by a high frequency of southerly flow, which is associated with milder than average night-time temperature, and in years with a prevailing south-westerly mean flow. These results are consistent with other studies, suggesting that certain wind conditions are more favorable for disease onset, which are possibly associated with one or more airborne agents