Outer edges of face-on spiral galaxies

We present deep optical imaging of three face-on disk galaxies together with a detailed description of the reduction and calibration methods used, in order to measure the intrinsic shape of their outer stellar edges. Whereas it is now well accepted that disks of spiral galaxies are not infinite exponential beyond galactocentric distances of about 3-5 radial scalelengths, the genuine structure of the truncation region is not yet well known. Our data quantitatively establish a smooth truncation behaviour of the radial surface brightness profiles and is best described by a two-slope model, characterised by an inner and outer exponential scalelength separated at a relatively well defined break radius. This result disagrees with the frequently assumed sharply truncated nature of the radial surface brightness profiles and implies the presence of stars and even star-formation beyond the break radius. In addition, we do not find a strong influence of a nearby companion on the ratio of the break radius to the radial scalelength. Our results denote new observational constraints for the search of the physical explanation for these smooth disk truncations.Comment: LaTeX, 10 pages, 17 figures, accepted to be published in A&A, minor changes to the quality of figure

COVID-19 and tourism: What can we learn from the past?

The impact of the COVID-19 crisis on tourism flows is without precedent in terms of speed and severity. In this paper, we try to infer a possible future scenario for the tourism sector, evaluating the medium-term effects of past pandemics on tourist arrivals. We find that pandemics lead to a persistent decline in tourist arrivals, with the effects being larger in developing and emerging countries. Interestingly, the effects are heterogeneous across countries and episodes, and depend on several economic conditions such as the overall health system performance, the severity of the shock, and the uncertainty induced by the pandemic event

Three-Dimensional Bar Structure and Disc/Bulge Secular Evolution

Kn-band imaging of a sample of 30 edge-on spiral galaxies with a boxy or peanut-shaped (B/PS) bulge is discussed. Galaxies with a B/PS bulge tend to have a more complex morphology than galaxies with other bulge types, unsharp-masked images revealing structures that trace the major orbit families of three-dimensional bars. Their surface brightness profiles are also more complex, typically containing 3 or more clearly separated regions, including a shallow or flat intermediate region (Freeman Type II profiles), suggestive of bar-driven transfer of angular momentum and radial redistribution of material. The data also suggest abrupt variations of the discs' scaleheights, as expected from the vertical resonances and instabilities present in barred discs but contrary to conventional wisdom. Counter to the standard `bulge + disc' model, we thus propose that galaxies with a B/PS bulge are composed of a thin concentrated disc (a disc-like bulge) contained within a partially thick bar (the B/PS bulge), itself contained within a thin outer disc. The inner disc most likely formed through bar-driven processes while the thick bar arises from buckling instabilities. Both are strongly coupled dynamically and are formed mostly of the same (disc) material.Comment: 6 pages, including 1 figure. To appear in "Island Universes: Structure and Evolution of Disk Galaxies", ed. R. de Jong (Springer: Dordrecht

Social media adoption in Italian firms. Opportunities and challenges for lagging regions

Social media are an important growth opportunity for firms, especially small-sized ones operating in peripheral and lagging regions. In this paper, we investigate not only whether firms are able to take this opportunity, but also if they are able to face the challenge of adopting social media at a professional level to obtain a significant economic impact, measured in terms of exporting activities. Exploring the Italian case, our empirical study indicates that smaller firms in lagging areas are more likely to adopt social media but at the same time less likely to use them at a professional level. This reflects poor strategic targets of social media adoption and lower probabilities of entering international markets

DERIVAZIONE DI IDROGRAMMI DI PIENA ATTRAVERSO L\u2019ACCOPPIAMENTO DI MODELLI STOCASTICI BIVARIATI DELLE PRECIPITAZIONI E E MODELLI AFFLUSSI - DEFLUSSI DISTRIBUTI

In questo studio viene presentata una procedura di tipo Monte Carlo per la derivazione delle curve di frequenza delle portate al colmo e dei volumi corrispondenti basata sull\u2019accoppiamento di un modello di generazione delle forzanti pluviometriche tramite copule e un modello di trasformazione afflussideflussi di tipo distribuito. Tale procedura \ue8 stata applicata ad un caso di studio siciliano; i risultati ottenuti hanno mostrato la bont\ue0 del modello a riprodurre le statistiche complesse delle grandezze idrologiche a fronte di un basso numero di parametri modellistici e di un ridotto sforzo computazionale

LINC00507 Is Specifically Expressed in the Primate Cortex and Has Age-Dependent Expression Patterns

Over the past decade, there has been an increase in the appreciation of the role of non-coding RNA in the development of organism phenotype. It is possible to divide the non-coding elements of the transcriptome into three categories: short non-coding RNAs, circular RNAs and long non-coding RNAs. Long non-coding RNAs are those transcripts that are greater than 200 nts in length and lack any significant open reading frames that produce proteins greater then 100 amino acids. Long intervening non-coding RNAs (lincRNAs) are a subclass of long non-coding RNAs. In contrast to protein coding RNAs, lincRNAs are expressed in a more tissue- and species-specific manner. In particular, many lincRNAs are only conserved amongst higher primates. This coupled with the propensity of many lincRNAs to be expressed in the brain, suggests that they are in fact one of the major drivers of organism complexity. We analysed 39 lincRNAs that are expressed in the frontal cortex and identified LINC00507 as being expressed in a cortex-specific manner in non-human primates and humans. The expression patterns of LINC00507 appear to be age-dependent, suggesting it may be involved in brain development of higher primates. Moreover, the analysis of LINC00507 potential to bind ribosomes revealed that this previously identified non-coding transcript may harbour a micropeptide

Optimal Surface Drainage Inlets Positioning Using Stochastic Pluvial Flooding Analysis

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Why Buckling Stellar Bars Weaken in Disk Galaxies

Young stellar bars in disk galaxies experience a vertical buckling instability which terminates their growth and thickens them, resulting in a characteristic peanut/boxy shape when viewed edge on. Using N-body simulations of galactic disks embedded in live halos, we have analyzed the bar structure throughout this instability and found that the outer third of the bar dissolves completely while the inner part (within the vertical inner Lindblad resonance) becomes less oval. The bar acquires the frequently observed peanut/boxy-shaped isophotes. We also find that the bar buckling is responsible for a mass injection above the plane, which is subsequently trapped by specific 3-D families of periodic orbits of particular shapes explaining the observed isophotes, in line with previous work. Using a 3-D orbit analysis and surfaces of sections, we infer that the outer part of the bar is dissolved by a rapidly widening stochastic region around its corotation radius -- a process related to the bar growth. This leads to a dramatic decrease in the bar size, decrease in the overall bar strength and a mild increase in its pattern speed, but is not expected to lead to a complete bar dissolution. The buckling instability appears primarily responsible for shortening the secular diffusion timescale to a dynamical one when building the boxy isophotes. The sufficiently long timescale of described evolution, ~1 Gyr, can affect the observed bar fraction in local universe and at higher redshifts, both through reduced bar strength and the absence of dust offset lanes in the bar.Comment: 7 pages, 4 figures, ApJ Letters, in pres

CONVERGENCE OF SIGNALING BY INTERLEUKIN-3, GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR, AND MAST CELL GROWTH FACTOR ON JAK2 TYROSINE KINASE

Mast cell growth factor (MGF) (also called stem cell factor) synergizes with several lymphokines, including interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF), to promote proliferation and differentiation of certain hemopoietic progenitor cells. Although similar patterns of tyrosine-phosphorylated proteins characterize cells stimulated by MGF, IL-3, and GM-CSF, only the MGF receptor is a tyrosine kinase, and the heterodimeric receptors for IL-3 and GM-CSF share a common beta subunit that is devoid of enzymatic activity. Here we show that signaling pathways utilized by all three cytokines include the cytoplasmic tyrosine kinase JAK2. Analysis of several factor-dependent myeloid cell lines indicated that JAK2 is physically associated with the common beta subunit and with MGF receptor (c-Kit) even prior to ligand binding. However, each of the ligands induced elevated tyrosine phosphorylation of JAK2 and a consequent increase in its catalytic activity. These results demonstrate for the first time the convergence within the same myeloid cells of signaling pathways originating in two distinct lymphokine receptors and a tyrosine kinase receptor on activation of a cytoplasmic tyrosine kinase