Evaporating Rayleigh-B\'enard convection: prediction of interface temperature and global heat transfer modulation

We propose an analytical model to estimate the interface temperature $\Theta_{\Gamma}$ and the Nusselt number $Nu$ for an evaporating two-layer Rayleigh-B\'enard configuration in statistically stationary conditions. The model is based on three assumptions: (i) the Oberbeck-Boussinesq approximation can be applied to the liquid phase, while the gas thermophysical properties are generic functions of thermodynamic pressure, local temperature, and vapour composition, (ii) the Grossmann-Lohse theory for thermal convection can be applied to the liquid and gas layers separately, (iii) the vapour content in the gas can be taken as the mean value at the gas-liquid interface. We validate this setting using direct numerical simulations (DNS) in a parameter space composed of the Rayleigh number ($10^6\leq Ra\leq 10^8$) and the temperature differential ($0.05\leq\varepsilon\leq 0.20$), which modulates the variation of state variables in the gas layer. To better disentangle the variable property effects on $\Theta_\Gamma$ and $Nu$, simulations are performed in two conditions. First, we consider the case of uniform gas properties except for the gas density and gas-liquid diffusion coefficient. Second, we include the variation of specific heat capacity, dynamic viscosity, and thermal conductivity using realistic equations of state. Irrespective of the employed setting, the proposed model agrees very well with the numerical simulations over the entire range of $Ra-\varepsilon$ investigated

Influence of Seascape on Coastal Lagoon Fisheries: the Role of Habitat Mosaic in the Venice Lagoon

Fisheries are a staple human activity supported by coastal lagoons. Together with water quality and trophic status, lagoon morphology is acknowledged as one of the main ecological drivers of fishery yields; however, the role of lagoon seascape structure is still poorly understood. This paper investigates how morphological variables, habitat distribution and seascape diversity and complexity affect yields of artisanal fishery performed with fyke nets in the Venice Lagoon (northern Adriatic Sea, Italy). Two spatial scales were considered in the analysis, with water quality parameters (temperature, salinity, dissolved oxygen, turbidity, water residence times, N, P and chlorophyll-a concentrations) being measured at a fine, fyke-net scale and morphological (average bottom elevation and sediment grain size) and habitat features (habitat proportion, diversity and complexity) being measured at a broader, seascape scale. Generalised linear mixed models were employed to model 8 years of nekton and green crab catches, disentangling the role of broad-scale morphology and seascape from that of fine-scale water quality. Broad-scale variables clearly influenced fishery target species. Among them, lagoon residents were associated with specific morphological and habitat characteristics, while marine migrants showed a stronger link with overall habitat diversity and complexity. This evidence emphasises how artisanal fishery in the Venice Lagoon relies on the conservation of morphological and habitat heterogeneity. Moreover, it highlights how habitat restoration performed at the seascape level should also be taken into account, in addition to controlling hydrology and water quality, when managing fishery resources in coastal lagoons

IMPLEMENTATION OF THE HABITAT FISH BIO-INDICATOR IN TWO WATER BODIES OF THE VENICE LAGOON: THE ROLE OF SEASONAL AND ENVIRONMENTAL VARIABILITY IN THE ASSESSMENT OF ECOLOGICAL STATUS OF FISH FAUNA

Under the Water Framework Directive (WFD; Dir. 2000/60/EC), fish are one of the Biological Quality Elements that need to be taken into account when evaluating the Ecological Status of transitional water bodies. The Habitat Fish Bio-Indicator (HFBI), a multi-metric index composed of six descriptors based on functional traits of fish assemblages, was recently developed to assess Italian transitional waters. In this study, HFBI was applied, following the national application protocol, to two water bodies in the Venice lagoon featuring different water and sediment physco-chemical properties and habitat distribution. The analysis highlighted that, in addition to seasonality, environmental variability along confinement gradients and presence and extent of seagrass meadows strongly influence the six metrics, the HFBI score and the subsequent assessment outcome. The selection of number and location of sampling sites must then be based on environmental characteristic and variability found within each water body, and is therefore a crucial step in the evaluation of Ecological Status in transitional water ecosystems

FISH FAUNA IN THE VENICE LAGOON: UPDATING THE SPECIES LIST AND REVIEWING THE FUNCTIONAL CLASSIFICATION

This work aims at reviewing the existing ecological classification of fish fauna in the Venice lagoon, and updating the list of species found during 15+ years of research in this ecosystem. The checklist encompass all fish life stages including ichthyoplankton, and contains 94 taxa, with 14 recorded only after 2010. The new functional classification, made of eight guilds including two guilds of lagoon residents and two of marine migrants, highlights the differences in species’ use of lagoon habitats in different seasons

DISTRIBUTION OF THE ALIEN SPECIES PALAEMON MACRODACTYLUS RATHBUN, 1902 IN THE VENICE LAGOON

Palaemon macrodactylus Rathbun (1902) is an estuarine shrimp native to north-western Pacific which, due to its wide environmental tolerance to chemical-physical conditions and its long breeding period, from 1957, probably carried by ship ballast water, massively colonized estuarine ecosystems worldwide. After its first record, in 2012, P. macrodactylus appears to have rapidly colonized the entire Venice lagoon, showing higher abundance in the confined saltmarsh stations of the northern sub-basin, probably due to the relatively low salinities values of this area. Records collected from 2014 to 2020 confirm the long reproductive period, comprised between Spring (mid-April) and Autumn (October), and the potential large invasion capacity of this species, which in the future could provoke competition with autochthonous species of the genus Palaemon and Crangon crangon

APPLICATION OF THE HABITAT FISH BIOLOGICAL INDEX (HFBI) FOR THE ASSESSMENT OF THE ECOLOGICAL STATUS OF PO DELTA LAGOONS (ITALY)

Fish fauna is one of the biological quality elements useful for assessing the ecological status of European transitional water bodies, for the purposes of applying the Water Framework Directive. For the assessment of the ecological status of Italian transitional aquatic ecosystems, the multimetric index “Habitat Fish Bio-Indicator” (HFBI), based on fish fauna, was developed and validated at national level. This paper reports the results of a study on the shallow-water fish fauna of 5 lagoon environments of the Po Delta (Northern Adriatic, Italy) which aimed to evaluate the ecological status of these water bodies by calculating the HFBI. The results made it possible to describe the taxonomic composition and the functional and trophic structures of the fish community characteristic of these delta lagoons. The shallow water fish assemblage was characterized by the presence of juvenile stages of marine migrating species (i.e., grey mullets of the genus Chelon, the sea bream Sparus aurata and the sea bass Dicentrarchus labrax) and by species of estuarine residents (i.e., small gobies Knipowitschia panizzae, Pomatoschistus marmoratus, and P. canestrinii, the silverside Atherina boyeri and the killfish Aphanius fasciatus). The guilds of hyperbentivores/zooplanktivores, microbentivores and detritivores were the most represented in the fish assemblage of the of investigated lagoons. The HFBI index, applied on an annual basis, made it possible to highlight marked differences in the ecological status of the Po Delta lagoons. Only Caleri lagoon resulted in a good state, Marinetta and Canarin lagoons in a moderate state, while Barbamarco and Scardovari lagoons resulted in a poor ecological state. Eutrophication, resulting from the large inputs of nutrients with freshwater from the Po River branches, and the modification of lagoon morphologies, a consequence of anthropogenic activities, are the main pressure factors that determine the ecological status of these transitional water bodies

Neuroimaging, Networking and Systems Biology: The New Way to Investigate Pathologies with Neurological System Implications. The example of Tourette Syndrome as a Pilot Study

Purpose: Recently, many academic research groups have focused their attention on changes in human brain networks related to several kinds of pathologies and diseases, generating the new discipline termed “Network Medicine”. Purpose of this paper is to investigate the ability of the Network Medicine to give deeper insights in the functionality of brain activity. Material and Methods: In the proposed study of Tourette syndrome, we have investigated with the functional magnetic resonance imaging the possibility that the mechanisms associated with the monitoring and internal control of movements were compromised in individuals with Tourette syndrome; we enrolled 20 Tourette Syndrome patients in comparison with a healthy Controls group of 15 subjects matching for age and sex distribution. We proposed, for the fMRI analysis, a novel task based on the execution of switching between complex movements on demand. Results: The elementary activation model found that the effort related to the task in comparing Tourettic vs Controls mainly concerns the areas of the Gyrus of the Cingulum, the precuneus and the thalamic area of the ventral-lateral nucleus. In particular, the BA11 plays an essential role in the Tourette Patients related to the continue tentative to correct the TIC. Considering the status of the pilot study of this work, we remark the power of proposed methods to investigate the complex interaction of the brain networks. Conclusion: Alteration in brain activity for a population of Tourette Syndrome patients is evaluable by the use of complex indexes, results confirm the literature about this pathology and these medical physics methods can be applied to all neurological diseases investigation by opportune task-driven experiments or by resting state fc-MRI experiments

An interface capturing method for liquid-gas flows at low-Mach number

Multiphase, compressible and viscous flows are of crucial importance in a wide range of scientific and engineering problems. Despite the large effort paid in the last decades to develop accurate and efficient numerical techniques to address this kind of problems, current models need to be further improved to address realistic applications. In this context, we propose a numerical approach to the simulation of multiphase, viscous flows where a compressible and an incompressible phase interact in the low-Mach number regime. In this frame, acoustics is neglected but large density variations of the compressible phase can be accounted for as well as heat transfer, convection and diffusion processes. The problem is addressed in a fully Eulerian framework exploiting a low-Mach number asymptotic expansion of the Navier-Stokes equations. A Volume of Fluid approach (VOF) is used to capture the liquid-gas interface, built on top of a massive parallel solver, second order accurate both in time and space. The second-order-pressure term is treated implicitly and the resulting pressure equation is solved with the eigenexpansion method employing a robust and novel formulation. We provide a detailed and complete description of the theoretical approach together with information about the numerical technique and implementation details. Results of benchmarking tests are provided for five different test cases