197,902 research outputs found
Variance sum rule: proofs and solvable models
No full textWe derive, in more general conditions, a recently introduced variance sum rule (VSR) (Di Terlizzi et al 2024 Science 383 971) involving variances of displacement and force impulse for overdamped Langevin systems in a nonequilibrium steady state (NESS). This formula allows visualising the effect of nonequilibrium as a deviation of the sum of variances from normal diffusion 2Dt, with D the diffusion constant and t the time. From the VSR, we also derive formulas for the entropy production rate sigma that, differently from previous results, involve second-order time derivatives of position correlation functions. This novel feature gives a criterion for discriminating strong nonequilibrium regimes without measuring forces. We then apply and discuss our results to three analytically solved models: a stochastic switching trap, a Brownian vortex, and a Brownian gyrator. Finally, we compare the advantages and limitations of known and novel formulas for sigma in an overdamped NESS
Quantifying effects of pollution on biodiversity: a case study of highly-diverse molluscan assemblages in the Mediterranean
No full textStructured sampling designs are important in the assessment of environmental impacts of variable ecological systems. Recent developments have provided a useful framework extending existing univariate techniques into a multivariate context. Measures of taxonomic relatedness have also been introduced, which complement existing measures of diversity of assemblages. In this study, the potential effects of sewage discharge on spatial patterns of highly diverse molluscan assemblages in a Mediterranean rocky subtidal habitat were investigated. Nine 20 cmx20 cm quadrats were taken from each of three sites (80 m-100 m apart) within a putatively impacted location near a sewage outfall (I) and at each of two control locations (Cs) by destructive sampling by SCUBA divers at a depth of 3 m-4 m. A total of 5507 specimens of 151 species were collected. The average and the variance in total abundance of molluscs were greater, on average, at I than at Cs. Higher abundances at the sewage outfall were largely driven by greater numbers of juvenile molluscs. The Shannon diversity of molluscs (H') was significantly lower at I, but no difference among locations was detected for the total number of species (S). In addition, the taxonomic distinctness (Delta*) of molluscs was greater at Cs, although it was more variable at I. Multivariate analyses showed that there was a significant difference in the structure of assemblages at I compared with Cs. The location near the outfall was characterized by greater abundances of several species, including especially the gastropods Pusillina philippi, Bittium latreilli, and Bittium reticulatum. There was also greater variability in the structure of assemblages among sites and among quadrats at control locations compared to those near the outfall. Using a suite of univariate and multivariate measures, including diversity indices, detailed information on taxonomic structure and analyses of variability at different spatial scales, provided useful insights into the effects of sewage impacts on these diverse assemblages. These results also highlighted the importance of analysing measures of variance, as well as mean in considering effects of stress in natural communities
Existence of two serological subclusters of Plum pox virus, strain M
No full textA large-scale serological characterisation of Plum pox virus (PPV) isolates was carried out with 19 monoclonal antibodies (MAbs), including the universal MAb5B and the following strain-specific MAbs: AL (specific to PPV-M), 4DG5 (specific to PPV-D), TUV and AC (specific to PPV-C), and EA24 (specific to PPV-EA). The study involved 108 PPV isolates of different geographical origin (Albania, Bulgaria, Cyprus, Czech Republic, Egypt, France, Germany, Greece, Italy, Hungary, Moldova, Romania, Slovakia, Spain, Turkey and Yugoslavia) and hosts (almond, apricot, peach, plum and cherry). The inter- and intra-strain serological relationships of PPV isolates were evaluated by DASI-ELISA. High serological variability was detected, not only between strains, but also among isolates of the same strain. Computer-assisted analysis of serological data support the hypothesis of the existence of two distinct subclusters, denoted PPV-M-1 and PPV-M-2, which seem to prevail in Mediterranean and Eastern-Central European countries, respectively
A thermodynamic uncertainty relation for a system with memory
No full textWe introduce an example of thermodynamic uncertainty relation (TUR) for systems modeled by a generalised Langevin dynamics with memory, determining the motion of a micro-bead driven in a complex fluid. Contrary to TURs typically discussed in the previous years, our observables and the entropy production rate are one-time variables. The bound to the signal-to-noise ratio (SNR) of such state-dependent observables can only in some cases be mapped to the entropy production rate. For example, this is true for steady states and for a subclass of Markovian systems. In fact, the presence of memory in the system complicates the thermodynamic interpretation of the uncertainty relation
Nanoplastics in the oceans: Theory, experimental evidence and real world
No full textThis review critically analyses >200 papers collected by searching on Pubmed the word “nanoplastics”, a group of emerging contaminants which are receiving growing attention. The present review intends to provide an overview of current knowledge on nanoplastic pollution starting with the theory of polymer degradation, passing to laboratory confirmation of nanoplastic formation and ending with the possible occurrence in sea water samples. Most of the observations proposed focus the attention on polystyrene (PS) because the majority of research knowledge is based on this polymer. Moreover, we thoroughly describe what effects have been observed on different organisms tested in controlled conditions. Nanoplastics formation, fate and toxicity seem to be a very dynamic phenomenon. In light of this, we identify some aspects retained crucial when an ecotoxicological study with nanoplastics is performed and which elements of nanoplastics toxicity could be deeper covered
Exposure to pet-made microplastics: Particle size and pH effects on biomolecular responses in mussels
No full textThis study aims to evaluate the expression of biomarkers of oxidative stress (LPO, GPx, AtCh, SOD) in mussels (Mytilus galloprovincialis) following the exposure to suspensions of microparticles irregular shaped fibres of Polyethylene terephthalate of different sizes (small 5–60 μm, S-PET; medium 61–499 μm, M-PET; large 500–3000 μm, L-PET) at a single dose of 0.1 g/L. Mussels were tested under two different starting pH conditions of marine water: standard (8.0) and acidified (7.5). The results obtained from this study show that: i) PET microplastics are able to induce biochemical stress in mussels; ii) among the biomarkers tested, LPO and GPx were more effective in detecting the stress induced by microplastic in both initial pH conditions; iii) the expression of biomarkers was influenced by the size of the microparticle. In particular, greater effects were associated with the largest PET particle tested (0.5–3.0 mm); iv) regarding the effect of pH, in experiments starting from 7.5 pH the animals showed a lower biomarker expression than those starting from 8.0 pH
Gettare un sasso perché le cose accadano
No full textIl breve contributo accompagna tra, le molte testimonianze, il lavoro condotto da Ernesto Terlizzi sul tema delle migrazioni e del Mediterraneo come luogo di transito, di speranza, ma anche di morte. E' una ricerca pittorica quella dell'artista salernitano di grande intensità che questo volume, pubblicato in occasione della mostra presso il Museo MANN- Museo Archeologico Nazionale di Napoli, documenta con particolare raffinatezza impaginativa
Biofouling Processes in Industry - Fouling on artificial substrata
No full textFrom the initial adsorption of organic molecules, to the colonisation by microorganisms, to the development of complex and diverse sessile assemblages, fouling affects most man-made surfaces. Fouling affects the hulls of ships, oilrigs, mariculture cages, pipelines, heat exchangers and seawater intakes in general, resulting in significant economic costs. Fouled ships, for instance, need 40% more fuel in order to maintain the same speed. This leads to a global cost of about 1000 million per year (Alberte et al. 1992).
The costs of fouling are clearly not limited to ship hulls nor to the marine environment. Control of fouling in water intakes, piping systems and desalinisations plants cost over 10 billion per year (Jun & Puri 2005). Biofilm-associated infections extend hospital stays of an average of about three days and it is estimated that up to 65% of nosocomial infections are biofilm-based with an associated treatment cost in excess of $1 billion per year. Up to 82% of nosocomial bacteremias are the result of bacterial contamination of intravascular catheterizations (Archibald & Gaynes 1997).
Biofouling has been described as a four-step sequential ecological process (Wahl 1989). The first two steps, which produce a microbial biofilm, occur similarly whether on a surface in the sea or on a catheter in a hospital room. The following two steps are unique to aquatic habitats and involve the attachment of unicellular and multicellular eukaryotes to an inorganic or living surface.
The multi-step process results from the web of interactions in the initial biofilm and subsequent community of colonizers, culminating in the establishment of a mature community composed of prokaryotes, fungi, protists and adult invertebrates.
Biofouling assemblages on artificial substrata is a complex phenomenon resulting from several processes, the rate and extent of which are influenced by numerous physical, chemical and biological factors in the immediate proximity of the surface and cannot be defined as distinct and univocal entities.
The major structuring factors influencing the development of biofouling communities on artificial substrates are here considered. An emphasis is given on how the interaction between biological systems (micro and macrofouling) can interplay with the nature of substrate in regulating patterns of species settlement and assemblage development. Some guidelines on the use of artificial substrata in the management strategies for controlling fouling in industrial plans are also provided.Biofouling on artificial substrata results from several processes, whose rate and extent are influenced by the intertwining of numerous physical, chemical and biological factors in the immediate proximity of the surface. The importance of substratum features in influencing species settlement is considered here. An emphasis is given on how biological systems (micro- and macrofouling) can interplay with the nature of substratum in regulating patterns of biofouling development. The environmental issues related to the deployment of man-made structures in coastal waters are also discussed, and some guidelines on the use of artificial substrata in the management strategies for controlling fouling in industry are provided
Impact of offshore gas platforms on the structural and functional biodiversity of nematodes
No full textThe Mediterranean Sea hosts hundreds of offshore gas platforms, whose activity represents a potential threat to marine ecosystems. Evidence from several studies indicates that nematodes can be highly sensitive to changes in the environmental quality. Here, we investigated the response of nematode assemblages to the presence of offshore gas platforms (located in the central Mediterranean Sea) in terms of spatial heterogeneity, structural and functional diversity. Since the effect of the investigated offshore platforms on macrofaunal assemblages were previously assessed by Terlizzi et al. (2008), the study provided also the opportunity to compare the response of different benthic compartments to the same impact related to fossil fuel extraction on marine environments. The platforms had a significant impact on nematode assemblages up to 1000 m distance from the structure. The effects were evident in term of: a) more homogeneous spatial distribution of nematode assemblages, b) increased trophic diversity of deposit feeders and c) changes in life strategies with an increase of opportunistic species in sediments closer to the platforms. Such effects seemed to be related to the dimension of the platform structures, rather than to chemical pollution or changes in food availability. These findings suggest that the platforms exert a physical alteration of the surrounding environment that is reflected by altered structural and functional traits of nematode biodiversity. The use of nematodes for monitoring the effects of the platforms only partially matched with the results obtained using macrofauna, providing further insights on potential outcomes on the functional response of marine assemblages to fossil fuel extraction
Nestedness and turnover unveil inverse spatial patterns of compositional and functional β‐diversity at varying depth in marine benthos
No full textAim: The two additive components of β-diversity, namely turnover and nestedness, reflect the two basic mechanisms underlying the overall change in species identities across the landscape, the replacement of species or their loss, respectively. Analogously, functional turnover and nestedness express the replacement or loss of functional traits associated with variations in community composition. However, the extent to which patterns of compositional and functional nestedness and turnover may overlap, or diverge, is still uncertain in marine environments. Here, patterns of turnover and nestedness were quantified in marine benthic assemblages in order to assess their relative contribution to spatial patterns of compositional and functional β-diversity.
Location: Mediterranean Sea, NE Ionian Sea, Ionian Archipelago.
Methods: In this study, we investigated patterns of dissimilarity in species and functional trait composition in subtidal macrobenthic assemblages from Mediterranean islands in order to quantify compositional and functional β-diversity among islands, determine the relative contributions of turnover and nestedness, and compare β-diversity patterns occurring in shallow and deeper reefs.
Results: We found a complex relationship between functional and compositional β-diversity at varying depth. At 5 m, species and functional trait dissimilarity largely overlapped, with turnover being the dominant component in both cases. At 15 m, compositional β-diversity was mostly due to turnover, with a negligible contribution of nestedness, whereas the opposite occurred for functional β-diversity. Partitioning β-diversity components revealed this discrepancy and the presence of functional hotspots, which would remain unnoticed analysing the overall compositional and functional β-diversity.
Main conclusions: Our findings may have profound implications for the optimization of conservation planning, stressing the need for assessing habitat-dependent idiosyncrasies in components of functional and compositional β-diversity for a more comprehensive picture of possible protection scenarios that, besides structure, may also allow preserving the functioning of marine communities
- …
