276 research outputs found
Optimal location of resources and Steiner symmetry in a population dynamics model in heterogeneous environments
No full textThe subject of this paper is inspired by Cantrell and Cosner (1989) and Cosner, Cuccu and Porru (2013). Cantrell and Cosner (1989) investigate the dynamics of a population in heterogeneous environments by means of diffusive logistic equations. An important part of their study consists in finding sufficient conditions which guarantee the survival of the species. Mathematically, this task leads to the weighted eigenvalue problem in a bounded smooth domain , , under homogeneous Dirichlet boundary conditions, where and . The domain represents the environment and , called the local growth rate, says where the favourable and unfavourable habitats are located. Then, Cantrell and Cosner (1989) consider a class of weights corresponding to environments where the total sizes of favourable and unfavourable habitats are fixed, but their spatial arrangement is allowed to change; they determine the best choice among them for the population to survive.
In our work we consider a sort of refinement of the result above. We write the weight as sum of two (or more) terms, i.e. , where and represent the spatial densities of the two resources which contribute to form the local growth rate . Then, we fix the total size of each resource allowing its spatial location to vary. As our first main result, we show that there exists an optimal choice of and and find the form of the optimizers. Our proof relies on some results in Cosner, Cuccu and Porru (2013) and on a new property (to our knowledge) about the classes of rearrangements of functions. Moreover, we show that if is Steiner symmetric, then the best arrangement of the resources inherits the same kind of symmetry. (Actually, this is proved in the more general context of the classes of rearrangements of measurable functions
Transient inflammation in surgical scars following Covid‐19 mRNA vaccination
No full textThe current coronavirus disease 2019 pandemic has exceeded any epidemiologic prevision, but
increasing information suggests some analogies with the major viral outbreaks in the last century, and a
general warning has been issued on the possibility that coinfections can make the differential diagnosis
and treatment difficult, especially in tropical countries. Some reports have noted that the presence of
high dengue antibodies can give a false-negative result when testing for severe acute respiratory syndrome coronavirus 2. Mucocutaneous manifestations are very frequent, with an apparent overlap among
different pathogens. However, strong clinicopathologic correlation might provide some clues to address
differentials. Waiting for laboratory and instrumental results, the timing and distribution of skin lesions
is often pathognomonic. Histopathologic findings characterize certain reaction patterns and provide insights on pathogenetic mechanisms. Unfortunately, skin assessment, especially invasive examinations
such as biopsy, takes a back seat in severely ill patients. A literature retrieval was performed to collect
information from other epidemics to counteract what has become the most frightening disease of our tim
La caduta di Icaro: Su spazi e forme in Geografie di Anedda.
No full textA partire dal dialogo tra arte, ambienti raffigurati e scrittura nelle prose di Geografie, il saggio indaga i dispositivi formali adottati da Anedda nella rappresentazione degli spazi. Vengono prese in analisi le strategie narrative utilizzate per scardinare la dialettica tra spazio umano, risultato di una stratificazione temporale e culturale, e paesaggio indipendente dalla presenza umana: questa postura antiantropocentrica, insieme con gli elementi formali che ne derivano, fanno reagire l’opera di Anedda con la linea darwiniano-leopardiana che, nel Novecento, arriva fino a Italo Calvino.
English title: \u27The Fall of Icarus. On spaces and forms in Anedda\u27s Geografie\u27
Starting from the dialogue between art, depicted environments and writing in the prose of Geografie, this essay investigates the formal devices adopted by Anedda in representing spaces. The essay analyzes the narrative strategies used to unhinge the dialectic between human space, as a result of temporal and cultural stratification, and landscape, as a space independent from human presence: this anti-anthropocentric posture, together with the formal elements that derive from it, make Anedda\u27s work react with the Darwinian-Leopardian line that, in the twentieth century, reaches an author like Italo Calvino.
Aged titania nanoparticles. The simultaneous control of surface and massive properties
No full textTiO2 nanoparticles are obtained by combining a sol-gel preparative route with hydrothermal aging steps,
performed in mild conditions, of varying time lengths. Both aged and un-aged samples are thermally treated
at 300 and 600 °C, for the same length of time. The crystal structures, the phase composition, and crystallite
sizes are analyzed by powder X-ray diffraction. Raman spectra of anatase nanocrystals with average sizes of
7-10 nm are reported and the correlation between the Raman band shape of the main feature at 144 cm-1
and the crystallite size is discussed. Nitrogen physisorption by Brunauer-Emmett-Teller (BET) method is
adopted to evaluate the particles surface area and mesopore size and size distribution. The role played by the
hydrothermal step in affecting the physicochemical properties of the powders is discussed also with respect
to the H2O/TiO2 interactions as apparent from Raman spectroscopy investigations of the O-H stretching
range (3000-3800 cm-1)
«Geografie». La scrittura come esercizio
No full textIl saggio propone una riflessione intorno al lavoro poetico di Anedda mettendone in evidenza alcune delle matrici concettuali e delle soluzioni espressive che permettono di interpretare l’esperienza dell’autrice come forma di meditazione intorno alla temporalità. Per mostrare come si articoli questo «esercizio» dell’esposizione al tempo si prende in esame in particolare il libro Geografie.
Writing as Exercise
This essay offers a reflection on Anedda\u27s poetic work, highlighting some of her probable conceptual matrices and some of her main expressive solutions. The analysis delves on her recent book “Geografie”, and brings to the conclusion that the author\u27s experience is related to the tradition of meditation on temporality
Soglie dell\u27impermanenza: Lo spazio etico della poesia di Antonella Anedda
No full textThe article focuses on the relevance of space in Antonella Anedda\u27s work, understood as an experience of openness to reality and history, as well as loss of protection and guarantees. It is then highlighted how the author\u27s poetics of space can be usefully placed in dialogue with Benjamin\u27s reflection in the Passages on "threshold experiences". Subsequently, the article aims to show the peculiarity of the reception by Anedda of the German-speaking poet Paul Celan, in an ethical rather than an aesthetic or merely existential key, starting precisely from a proximity regarding the relationship between the poetic word and "threshold words", between silence and the need to speak (and testify), in both authors
Symmetry breaking in the minimization of the second eigenvalue for composite membranes
No full textLet Ω C RN be an open bounded connected set. We consider the eigenvalue problem -Δu = λρu in Ω with Dirichlet boundary condition, where ρ is an arbitrary function that assumes only two given values 0 < α < β and is subject to the constraint ∫ Ω ρ dx = αγ + β(|Ω| - γ) for a fixed 0 < γ < |Ω|. Cox and McLaughlin studied the optimization of the map ρ → λκ(ρ), where λκ is the kth eigenvalue. In this paper we focus our attention on the case when N ≥ 2, k = 2 and Ω is a ball. We show that, under suitable conditions on α, β and γ, the minimizers do not inherit radial symmetry
L'identità, la morte, l'ago della memoria. Salva con nome di Antonella Anedda
No full textIl saggio analizza e commenta la raccolta di poesie di Antonella Anedda "Salva con nome", con riferimenti intertestuali ad altre opere in versi e in prosa della stessa autrice. Individua puntuali caratteri di stile e i nuclei fondamentali della sua poetica, in particolare il significato della memoria, il rapporto con i morti, l'importanza dei gesti di cura, l'influenza delle radici geografiche e culturali.The essay analyzes and comments on the collection of poems by Antonella Anedda "Salva con nome", with intertextual references to other works in verse and prose by the same author. The essay identifies the core nuclei of Anedda's poetics, in particular the meaning of memory, the relationship with dead or desappeared beloved, the importance of gestures, the influence of geographic and cultural roots
«Onzi tandu naro una limba mia»: Aspetti, temi e problemi della poesia in «limba» di Antonella Anedda
No full textL’articolo si propone di analizzare la produzione in lingua sarda di Antonella Anedda. A partire dalla raccolta Dal balcone del corpo si mettono in evidenza i principali snodi tematici connessi a questa particolare zona creativa della poesia aneddiana, relazionandoli con quelli maggiori presenti anche negli altri libri della poetessa. A conclusione del discorso si propone una interpretazione che indaga i motivi e le implicazioni intertestuali comportate dalla scelta del dialetto sardo, inteso dall’autrice come una lingua “ibrida” che di necessità si relaziona con il proprio vissuto esistenziale.
The article aims to analyze Antonella Anedda\u27s poems in Sardinian language. Starting from the collection Dal balcone del corpo, the article point out the major themes inside Anedda’s works and investigates reasons and intertextual implications involved in the choice of the Sardinian dialect, understood by the author as a "hybrid" language that necessarily relates to one\u27s own existential experience
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