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Dynamics and acoustics of a spherical bubble rising under gravity in an inviscid liquid
No full textThe rising motion and the acoustic emission of a pulsating spherical gas/vapour bubble in an isochoric, inviscid liquid are investigated. The motion is driven by the uniform and constant force field due to the gravity. The liquid is assumed at rest at the initial time. Unlike previous work on this subject, the mass of the bubble is not neglected, so that the bubble motion is accurately simulated also in the presence of large volume variations. After developing the relationships between the bubble motion to the liquid flow, a system of two nonlinear ordinary differential equations (ODEs) for the radius and the position of the center of mass of the bubble is written. The near-field pressure disturbance produced in the liquid by the bubble motion is evaluated by means of elliptic integrals and an efficient approximation of it free from these special functions is also used. The numerical integration of the ODE system allows one to evaluate the acoustic signal. This is carried out with the above mentioned approximation, and several features of it are demonstrated through the study of a sample flow
Functional neuroimaging and clinical features of drug naive patients with de novo Parkinson?s disease and probable RBD
No full textIntroduction: The association between Parkinson Disease (PD) and REM sleep behavior disorder (RBD) has been related to a specific, malignant clinical phenotype. Definite RBD diagnosis requires videopolysomnography that is often unfeasible. A malignant clinical PD-RBD phenotype could be expected also in PD patients with probable RBD. Aim of this cross-sectional study was to evaluate whether a more severe neuropsychological and functional neuroimaging phenotype can be identified in PD patients with probable RBD. Methods: Thirty-eight de novo, drug na?ve PD patients underwent a first-line clinical assessment and a second-line multimodal assessment, including neuropsychological evaluation, 123I-FP-CIT-SPECT and 18FFDG- PET, which were compared between PD patients with (PD ? RBD?) and without (PD ? RBD-) probable RBD. Results: On first-line assessment, PD ? RBD ? patients had significantly more constipation (p ? 0.02) and showed worse olfaction (p ? 0.01) compared with PD ? RBD-while the two groups were similar as for age, presence of orthostatic hypotension, UPDRS-III and MMSE scores. On second-line assessment, PD ? RBD ? patients showed a worse neuropsychological test profile, more severe nigro-striatal dopaminergic impairment, mainly at caudate level in the less affected hemisphere (p ? 0.004) and impaired brain glucose metabolism, with relative hypometabolism in posterior cortical regions and relative hypermetabolism mainly in anterior regions of the more affected hemisphere (p ? 0.015). Conclusions: PD patients with probable RBD are likely to have a more severe neuropsychological and functional brain-imaging phenotype already at the time of diagnosis
Risposta del Branzino (dicentrarchus labrax) a diete che includono microalghe marine quali ingredienti sostenibili
No full textFor a sustainable aquaculture industry, current levels of fish meals/oils in aquafeeds need to be drastically reduced and mostly replaced by alternate counterparts. In this contest, the use of marine microalgae in aquafeeds has recently attracted much scientific attention due to their high protein content and lipid levels, including ?-3 long-chain PUFAs. In the present study, we investigated the growth performance and body composition of sea bass (Dicentrarchus labrax, L., 1758) in response to diets where graded levels of a blend of two marine microalgae (Isochrysis aff. galbana (T-ISO) and Tetraselmis suecica) were included in low fish meal/oil diets. The microalgae-containing aquafeeds were also compared to a diet (negative control) with a 30:70 fish to vegetable protein-lipid ratios. Fish given the positive control feed and those fed diets including graded levels of microalgae showed similar growth performance and feed conversion ratios which were significantly better than those attained by fish fed the negative control diet (B.W. 420 vs 388 g, SGR 0.69 vs 0.61, FCR, 1.7 vs 1.9, p<0.05). The effects of the dietary microalgae inclusion on fillet fatty acid composition and intestinal brush border enzyme activity were also considered
Past, present and future of the fish community of Lake Orta (Italy), one of the world\u27s largest acidified lakes
Get PDFSince 1926, the fishes in Lake Orta, one of Italy\u27s deepest natural lakes, were heavily damaged by profundal hypoxia and acidification linked to oxidation of ammonia from industrial effluents and by industrial metal pollution. Of the original 28 fish species, only perch survived the lake\u27s contamination. Recently, the water quality of the lake has been largely restored by reductions in pollutant inputs, and a massive liming intervention. These interventions restored fish habitat, but it is unclear whether the recent fish reintroductions were successful, and the present status of the fish community is unknown. Here we reviewed the history of the Lake Orta fish assemblage. Using an extensive 2014 sampling campaign, we compared the present fish community to both its pre-pollution composition and to the assemblages of nearby un-polluted, but otherwise similar lakes, Lake Mergozzo and Lake Maggiore. While nearshore fish density now appears normal in lake Orta, the open water community remains impoverished both in numbers and in species. Epilimnetic and hypolimnetic benthic nets were dominated by perch and roach in all the three lakes, but the catch of pelagic nets differed among lakes. Perch (Perca fluviatilis), rudd (Scardinius erythrophthalmus) and brown trout (Salmo trutta) dominated in Lake Orta while shad (Alosa fallax lacustris) and coregonids (Coregonus spp.) were dominant in the open waters of the other two lakes, but missing from Lake Orta. Many fully or partially migratory species, including marble trout (Salmo trutta marmoratus), eel (Anguilla Anguilla) and barbel (Barbus plebejus) were also missing from Lake Orta, a consequence of their initial extirpation and blocked re-colonization routes along the River Strona. In comparison with both pre-pollution and contemporary reference data, the fish community of Lake Orta has not been rehabilitated. The recovery of the littoral community is complete, but cold water species such as burbot (Lota lota), Arctic charr (Salvelinus alpinus) and bullhead (Cottus gobio) are still lacking, as are the pelagic zooplanktivores European whitefish (Coregonus lavaretus) and shad, which dominate offshore communities in the reference lakes, as they did a century ago in Lake Orta. To propose priorities for fish community rehabilitation in Lake Orta, we categorized the conservation, ecological and fishing values of each missing fish species in the lake, and evaluated the cost and probability of success of the needed intervention for each species. This analysis indicated that rehabilitation of shad and European whitefish should receive highest priority
Unexpected increases in rotifer resting egg abundances during the period of contamination of Lake Orta
Get PDFDespite their ecological importance and rapid response to environmental changes, rotifers are rarely included in palaeolimnological studies. Here, we describe changes in abundance (ABD) and morphotype (MTs) diversity of rotifer resting eggs in the sediments of deep subalpine Lake Orta, Italy, covering a period prior to (pre-) 1926, during long-term ammonia and metal pollution from a rayon factory, and subsequent recovery of water quality. Following the pollution and bacterial oxidation of the ammonia, Lake Orta became the largest and deepest acid lake in Europe. Recovery of water quality followed both a ban on the discharge of industrial wastes, and a liming intervention in 1989 and 1990. We sectioned a sediment core collected from the deepest part of the lake (ORTA 07/2A) to provide a high time resolution, given the ca. 3-4 y cm-1 of sediment accumulation. Rotifer resting egg (RRE) abundance and morphotypes were examined from the sediments and compared to limnological variables indicating the pollution. Rotifer resting egg abundance significantly increased with lake contamination (r=0.609 and -0.624 for copper and pH, respectively; P<0.001; n=27). A lake-water copper concentration threshold of ca. 40 ?g L-1discriminated among pre-, during-, and post- pollution compositions of the rotifer morphotype assemblages. Diversity and morphotype richness increased during the recovery from copper pollution and with complete restoration from acidity, while abundance increased during pollution. The persistence of presumably viable Brachionus resting eggs and of hatched egg cases during the heavy pollution phase suggests that, unlike most other organisms, which were extirpated by the pollution of the lake, rotifers survived producing resting eggs, which secured future generations
Demographic cost and mechanisms of adaptation to environmental stress in resurrected Daphnia
Get PDFA characteristic feature of the Daphnia (Crustacea: Cladocera) life cycle are the so-called ephippia, which are fertilised eggs that need to undergo diapause. When they are shed by the female, they sink to the lake bottom, where they may become embedded in the sediment and may remain viable for decades. Extracting and hatching ephippia in the laboratory and subjecting resurrected lineages to conditions representative of historic lake environments allows retrospective investigation of life-history responses to environmental change. Here we reanalyse data from such a resurrection experiment (Piscia et al., 2015: Bull. Environ. Contam. Toxicol. 94:46-51). Contemporary and past lineages of Daphnia galeata Sars 1863 were obtained from Lake Orta (Italy), a deep, subalpine lake with a well-documented history of industrial copper pollution. Experimental Daphnia were subjected to three copper treatments representative of two levels of historic as well as to current (i.e., unpolluted) lake conditions, and life-table data were collected. With these data at hand, we first estimated vital rates (survival, maturation, and reproduction) and used these rates to project the asymptotic population growth rates (?) for each population-by-treatment combination. Next, we performed life-table response experiments (LTRE) to estimate the contributions of the vital rates to observed differences in ?. Finally, we used elasticity analysis to explore the functional relationship between ? and each of the vital rates. We found that survival rates were only compromised at elevated copper levels. Moreover, past, resurrected Daphnia had a higher ? at low copper concentrations compared to unpolluted conditions, but a lower ? when exposed to high copper levels. Contemporary Daphnia, on the other hand, only reproduced successfully in unpolluted water. Under these conditions, however, they had a higher population growth rate than the past Daphnia, suggesting a cost of copper tolerance in the latter. This cost was mainly due to a lower probability of reproduction and reduced fecundity, whereas survival remained largely unaffected. Finally, we found higher elasticity values of ? to survival than to reproductive rates. This suggests that any change in the environment that will affect survival rather than reproductive parameters will have a much larger impact on Lake Orta\u27s current Daphnia population
Incorporating invertebrate conservation concern in prioritization of groundwater habitats
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Microcolony formation in non-axenic Synechococcus cultures: do the associated bacteria matter?
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A unifying definition for artifact and biological functions
No full textPhysical artifacts and biological systems have been studied from a variety of perspectives in different disciplines. These entities show many common characteristics and are investigated using similar notions except for one important aspect: functionality. Notwithstanding many attempts, the search for a unified notion of functionality that could encompass both the functions attributed to natural objects, like biological organisms, as well as those attributed to designed objects, like artifacts, to date has remained an open challenge. Deepening an earlier characterization of engineering functions, this paper starts with an introduction to the notions of behavior and context, which become the basic blocks for the construction of a general framework for a unified definition of function. The approach distinguishes three types of functional contexts (systemic, user and design) and clarifies the role of goals in defining biological and artifact functions. Finally, it shows that the notion of systemic function, as detailed in the paper, succeeds in comprising both biological and artifact functions. The proposal is evaluated against a collection of desiderata and examples taken from the literature
Lake La Salada de Chiprana (NE Spain), an example of an Athalassic Salt Lake in a cultural landscape
No full textOn a global scale, athalassic inland salt lakes are abundant, albeit restricted to semiarid and arid climates. La Salada de Chiprana is unique in Western Europe, because it is a permanent and relatively deep (up to 5.6 m) hypersaline lake (40-90 g total dissolved salt L-1) since 1700 AD. It forms part of a cultural landscape, which imposes a challenge for management. The aim of this paper is to describe the specific microbial biota and how they interacted with both animals and plant species during the last 25 years. The deeper parts regularly showed salinity stratification with an anoxic sulfide-rich hypolimnion and a bloom of green sulfur bacteria (Prosthecochloris aestuarii and Chlorobium vibrioforme) at the pycnocline. Despite highly eutrophic conditions, often the top water layer is transparent due to top-down control of phytoplankton populations by the brine shrimp, Artemia parthenogenetica. This allows for the development of submerged aquatic vegetation of the endemic foxtail stonewort Lamprothamnium papulosum var. papulosum f. aragonense, and microbial mat communities build by the cyanobacterium Coleofasciculus (Microcoleus) chthonoplastes coexisting with green filamentous nonsulfur bacteria (Chloroflexaceae). The microbial mats show photosynthetically induced precipitation of high-Mg calcite, which by incorporating viruses represents a mechanism for their fossilization