197,169 research outputs found
Da Giovanni B. Sertorio a Willy Kaufmann. Opere d’arte all’Immacolata di Lugano fra Otto e Novecento
No full textNel contributo sono ricostruite, con l'ausilio di fonti documentarie inedite, le vicende relative alla qualificazione artistica (stucchi, pitture, sculture, vetrate policrome) della chiesa dell'Immacolata di Lugano fra XIX e XX secolo: dal classicismo di Cristoforo Croci, all'accademismo citazionista di Giovanni Battista Sertorio, per giungere agli interventi degli anni Venti-Quaranta e Sessanta, con le pale d'altare di Piero Tamò, da leggersi in dialogo serrato con la storia decorativa della basilica del Sacro Cuore di Lugano, e le vetrate di Willy Kaufmann
Methane oxidation and emission in Lake Lugano (Southern Switzerland) : a lipid biomarker and isotopic approach
No full textMethane is an important greenhouse gas in Earth's atmosphere. The sources of atmospheric methane are largely biogenic, being produced under anoxic conditions by methanogenic Archaea. Wetlands, which include lakes, are important contributors to the atmospheric methane budget, since they commonly feature anoxic sediments or bottom water. Methane oxidising bacteria at the interface between oxic and anoxic sediments and water limit the efflux of methane. Furthermore, in the oceans, methane is oxidised anaerobically by Archaea, in a process coupled to sulfate reduction. In freshwater environments, where sulfate concentrations are orders of magnitude lower, this process is not thermodynamically favourable, and archaeal anaerobic oxidation of methane is often absent. It has been proposed in certain lake environments, however, that anaerobic oxidation of methane does take place.
One lake in which anaerobic oxidation of methane was proposed is the northern basin of Lake Lugano, southern Switzerland. Anaerobic oxidation of methane in this basin is explored in chapter 2 of this PhD thesis. Indeed we found methane concentration and carbon isotopic composition profiles characteristic of methane oxidation in the anoxic hypolimnion, more than 30 m below the interface between the oxic and anoxic waters. In addition, microbial biomass at these depths showed carbon isotope signatures of methane-derived carbon (d13C-values as low as -70‰ in C16:1 fatty acids), indicating that methane is used as a carbon source. However, no methane oxidation took place in incubation experiments under anoxic conditions. Addition of alternative potential electron acceptors did not stimulate methane oxidation, and methane oxidation was only observed in the presence of oxygen. Instead, we propose that episodic introduction of oxygenated water into the anoxic hypolimnion sustains a community of aerobic methanotrophs.
Carbon derived from methane oxidation has been shown in several studies to constitute an important carbon input to aquatic ecosystems. In the studies reported in chapters 2 and 3, compound specific stable carbon isotope analysis of lipid biomarkers was used to trace methane-derived carbon through the ecosystems at redox interfaces and in the anoxic hypolimnion of Lake Lugano. In the monomictic southern basin (chapter 3), an anoxic benthic nepheloid layer develops during the period of water column stratification. This layer was found to be derived from microbial production in the hypolimnion. Methane oxidising bacteria constituted up to 30% of total microbial cell numbers in the nepheloid layer, and 77% to 96% of the organic carbon in this layer was methane-derived. High rates of aerobic methane oxidation at the top of the anoxic nepheloid layer led to an oxygen consumption that was greater than the downward diffusion, causing the anoxic nepheloid layer to expand. Bacterial aerobic methanotrophs migrate upwards through the water column with the interface between the oxic hypolimnion and the anoxic nepheloid layer.
The extent of emission of methane to the atmosphere depends on the totality of sinks and sources in the lake basin. In both the northern and the southern basin of Lake Lugano, large amounts of methane are emitted from the sediments into the bottom water. However, consumption by aerobic methanotrophs at the oxic-anoxic redoxcline is near complete, and during stratified conditions, no methane escapes to the epilimnion. On the other hand, methane super-saturation in the surface water was observed throughout the year. Chapter 4 describes the results of three mapping campaigns of surface water methane concentrations in the northern basin of Lake Lugano, in spring and autumn. Additionally, methane concentration and carbon isotopic composition were measured on depth profiles down to 40 m depth in transects across the lake basin. Methane fluxes to the atmosphere were calculated from surface water concentration and wind speed. At a standardised wind speed of 1.6 m s-1 (average wind speed during the period from May until October) fluxes to the atmosphere were significantly higher in autumn (44 and 97 micromol m-2 d-1 in October 2011 and October 2012, respectively) than in spring (7 micromol m-2 d-1, May 2012). This difference is in part due to higher concentrations in autumn than in spring, and in part a result of a stronger dependence of the transfer velocity on buoyancy flux when the surface water cools. The source of methane in the surface water could not be determined with certainty. It is possible that internal waves at the thermocline induce friction at the sediment-water interface in the littoral zone, which leads to increased outgassing of sedimentary methane. However, the northern basin of Lake Lugano has steep shores along large parts of the basin, which offer little space for deposition of sediments, and the possibility of in situ production of methane in the water column must be considered
Inserto cartografico : Terre del Ticino, diocesi di Lugano
No full textInserto cartografico relativo alla situazione territoriale della diocesi di Lugano in differenti momenti storici
Restyling del Palazzo di Giustizia di Lugano - Progetto di concorso
No full textL’occasione di un progetto di riconversione del Palazzo di Giustizia di Lugano, pone di fronte a necessarie riflessioni di carattere compositivo e soprattutto tecnologico/funzionali. In particolare, data per conclamata la rappresentatività dell’edificio, che dispone di un prospetto su strada caratteristico, formale e significativo, si deve pensare ad un intervento che non vada ad intaccare la facciata principale e mantenga – e se possibile rafforzi – gli elementi di identificazione dei cittadini nell’istituzione che l’edificio rappresenta.
Il concept deriva dalla concezione del Palazzo di Giustizia come luogo in cui la società intera giudica i propri errori attraverso i reati dei propri individui, cellule-membra di un unico corpo (la società). Come per il sangue che porta ossigeno alle membra del corpo umano, sangue che attraverso il cuore viene depurato e rimesso in circolo, così nel Palazzo di Giustizia ENTRA l’individuo-società “in cerca di giustizia” ed ESCE “come nuova linfa sociale”
Renal function and icu
No full textIntroduction: The mortality of acute renal failure (ARF) is 50-80% in critically ill patients and has not fallen significantly despite numerous advances in critical care strategies and renal replacement technologies over several decades. (1) A major problem with conducting research into acute renal failure (ARF) is the lack of a consensus definition (2). More than 30 different definitions of ARF have been used in the literature. This lack of a common reference point created confusion and made comparisons difficult. The Acute Dialysis Initiative (ADQI) group of experts developed and published a consensus definition of ARF. This definition goes under the acronym of RIFLE. This definition classified the patients with renal dysfunction according to the degree of impairment into patient at risk (R), with injury (I), with failure (F), with sustained loss (L) and with end stage (E) status in relation to their renal function. (2) Rifle criteria were based on changes in the patients' glomerular filtration rate (GFR) and/or their urine output. (2)
Discussion: The prophylactic and therapeutic use of dopamine, the more studied vasoactive drug, actually has not been supported. For all other vasoactive drugs, at this moment, data available are contradictory and few conclusions can be made. To protect renal function, despite wide use of vasoactive drugs, only the maintenance of adequate volume replacement and perfusion pressure may be certainly recommended.
Conclusion: The use of vasoactive drugs is a pervasive practice in intensive care units, and hence, this area needs suitably powered, multi-center, randomized, placebo-controlled, double-blind studies to provide more rational indications for clinical practice
Collection Edward A. Sydenham Esq. M. A. de Oxford et d'un autre amateur : Aes grave italique monnaies romaines consulaires / Rodolfo Ratto
No full text[Vente. Art. 1928-02-07. Lugano]Appartient à l’ensemble documentaire : VenteMMAAvec mode texteCatalogues de vent
Cartoline per Lugano
No full textLa città di Lugano è stata meta di numerosi scrittori che vi hanno prodotto e stampato le opere, da Giacomo Casanova a Giuseppe Prezzolini, da Romano Amerio a Mario Postizzi
Year-round N2O production by benthic NOx reduction in a monomictic south-alpine lake
No full textNitrous oxide (N2O) is a potent greenhouse gas, generated through microbial nitrogen (N) turnover processes, such as nitrification, nitrifier denitrification, and denitrification. Previous studies quantifying natural sources have mainly focused on soils and the ocean, but the potential role of terrestrial water bodies in the global N2O budget has been widely neglected. Furthermore, the biogeochemical controls on the production rates and the microbial pathways that produce benthic N2O in lakes are essentially unknown. In this study, benthic N2O fluxes and the contributions of the microbial pathways that produce N2O were assessed using 15N label flow-through sediment incubations in the eutrophic, monomictic south basin of Lake Lugano in Switzerland. The sediments were a significant source of N2O throughout the year, with production rates ranging between 140 and 2605 nmol N2O h−1 m−2, and the highest observed rates coinciding with periods of water column stratification and stably anoxic conditions in the overlying bottom water. Nitrate (NO3−) reduction via denitrification was found to be the major N2O production pathway in the sediments under both oxygen-depleted and oxygen-replete conditions in the overlying water, while ammonium oxidation did not contribute significantly to the benthic N2O flux. A marked portion (up to 15%) of the total NO3− consumed by denitrification was reduced only to N2O, without complete denitrification to N2. These fluxes were highest when the bottom water had stabilized to a low-oxygen state, in contrast with the notion that stable anoxia is particularly conducive to complete denitrification without accumulation of N2O. This study provides evidence that lake sediments are a significant source of N2O to the overlying water and may produce large N2O fluxes to the atmosphere during seasonal mixing events
Nitrogen transformation pathways, rates, and isotopic signatures in Lake Lugano
No full textThe consequences of detrimental alterations caused to the natural nitrogen (N) cycle are manifold. To tackle problems, such as eutrophication of coastal marine and lacustrine environments, or increasing emissions of greenhouse gas nitrous oxide (N2O), requires a clear understanding of the microbial N cycle. A promising tool to study N transformations is the measurement of the stable isotope composition of N compounds. The overall goal of this project was to improve the understanding of N transformation pathways and associated isotope effects, using the meromictic northern and the monomictic southern basins of Lake Lugano as natural model systems. Toward this goal, we collected samples from the water column of both basins for dissolved inorganic nitrogen (DIN) analyses (including N2:Ar, N2O), molecular microbiological phylogenetic analyses, 15N-labeling experiments (water column and sediments), and stable N and O isotope (and N2O isotopomer) measurements.
First, we identified the main processes responsible for fixed N elimination in the Lake Lugano north basin. The stable redox transition zone (RTZ) in the mid-water column provides environmental conditions that are favorable for both, anaerobic ammonium oxidation (anammox), as well as sulfur-driven denitrification. Previous marine studies suggested that sulfide (H2S) inhibits the anammox reaction. In contrast to this we demonstrated that anammox bacteria coexist with sulfide-dependent denitrifiers in the water column of the Lake Lugano north basin. The maximum potential rates of both processed were comparatively low, but consistent with nutrient fluxes calculated from concentration gradients. Furthermore, we showed that organotrophic denitrification is a negligible nitrate-reducing pathway in the Lake Lugano north basin.
Based on these findings, we next interpreted the N and O isotope signatures in the Lake Lugano north basin. Anammox and sulfide-dependent denitrification left clear N (in NO3- and NH4+) and O (in NO3-) isotope patterns in the water column. However, the associated isotope effects were low compared to previous reports on isotope fractionation by organotrophic denitrification and aerobic ammonium oxidation. We attribute this apparent under-expression to two possible explanations: 1) The biogeochemical conditions (i.e., substrate limitation, low cell specific N transformation rates) that are particularly conducive in the Lake Lugano RTZ to an N isotope effect under-expression at the cellular-level, or 2) a low process-specific isotope fractionation at the enzyme-level. Moreover, an 18O to 15N enrichment ratio of ~0.89 associated with NO3- reduction suggested that the periplasmic dissimilatory nitrate reductase Nap was more important than the membrane-bound dissimilatory Nar.
While in the meromictic north basin, most fixed N elimination took place within the water column RTZ, seasonal mixing and re-oxygenation of the water column in the south basin suggests N2 production within the sediments. We showed that denitrification was the major benthic NO3- reduction pathway in the southern basin. Benthic anammox and dissimilatory nitrate reduction to ammonium (DNRA) rates remained close to the detection limit. A comparison between benthic N2 production rates and water column N2 fluxes revealed that during anoxic bottom water conditions, ~40% of total N2 production was associated with benthic and ~60% with pelagic processes. This quantitative partitioning was confirmed by N isotope analysis of water column NO3-. The N isotope enrichment factor associated with total NO3- reduction was ~14‰. This translates into a sedimentary N2 contribution of 36-51%, if canonical assumptions for N isotope fractionation associated with water column (15εwater = 20-25‰) and sedimentary (15εsed = 1.5-3‰) denitrification are made.
Finally, we compared the N2O production and consumption pathways in the northern and southern basin and found contrasting N2O dynamics. Maximum N2O concentrations in the south basin (>900 nmol L-1) greatly exceeded maximum concentrations in the north basin (32‰ in the south basin indicated nitrification via hydroxylamine (NH2OH) oxidation as the prime N2O source, whereas in the north basin N2O production was attributed to nitrifier denitrification. In the north basin, N2O was completely reduced within the RTZ. This chemolithotrophic N2O reduction occurred with an 18O to 15N enrichment ratio of ~2.5, which is consistent with previous reports for organotrophic N2O reduction.
In conclusion, our study highlights the importance of chemolithotrophic processes in aquatic ecosystems. Moreover, the expression of N isotope fractionation can be variable in nature and depends on various factors such as the pathways of NO3- dissimilation (organotrophic vs. chemolithotrophic), the main catalyzing enzymes, the pathways of NH4+ oxidation (nitrification vs. anammox), and the controlling environmental conditions (e.g., substrate limitation, cell specific N transformation rates). Hence, this study suggests to refrain from universal, canonical assumptions of N isotope fractionation in N budget calculations. Additional stable isotope measurements such as O isotopes in NO3-, or the 15N site preference in N2O are powerful tools to identify and quantify microbial N transformation pathways occurring simultaneously or in close vicinity. For a successful interpretation of such data, however, a mechanistic understanding of the processes leading to certain characteristic isotopic signatures in the environment is needed
M. Schnyder, Famiglie e potere. Il ceto dirigente di Lugano e Mendrisio tra Sei e Settecento
No full textCompte rendu de l'ouvrage de M. Schnyder, Famiglie e potere. Il ceto dirigente di Lugano e Mendrisio tra Sei e Settecent
- …
