An astrophysical oscillator strength for the SII 94.7 nm resonance line and S abundances in DLAs

By using UV spectra for the O star HD 93521 taken with the ORFEUS II echelle spectrograph, we determine an ``astrophysical'' f value for the SII 94.7 nm line: f = 0.00498 (+0.00172)(-0.00138), error at 1 sigma level.This is almost a factor of 30 smaller than the guessed value found in the Kurucz database (f=0.1472), which was up to now the only one available for this transition. We use our ``astrophysical'' f to investigate the S abundance in two Damped Ly-alpha absorption systems (DLAs) observed with UVES at the ESO 8.2m Kueyen telescope. In the case of the absorber at zabs=3.02486 towards QSO 0347-3819 we find a sulphur column density which is consistent, within errors, with that determined by Centurion et al by means of the 125.9 nm line, thus providing an external check on the accuracy of our f value. For the damped absorber at zabs=4.4680 towards BR J0307-4945 we determine a high value of the S abundance, which, however, is probably the result of blending with Ly-alpha forest lines.Comment: Accepted by MNRA

THE MOSAIC OF THE FRIGIDARIUM OF “VILLA BONANNO” IN PALERMO: MINERALOGICAL AND PETROGRAPHIC ANALYSES FOR IN SITU CONSERVATION AND RESTORATION INTERVENTIONS

The topic of this study was the mineralogical and petrographic characterization of bedding mortars (made of different layers) and tesserae of Roman age (3rd century A.D.), taken from the mosaic of the Frigidarium of “Villa Bonanno”, brought to light by archaeological excavations conducted in the historical centre of Palermo. The collected samples have been analysed by thin-section optical microscopy (PLM), and scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS). The study was aimed to define the “recipe” (composition of aggregate and binder, aggregate size distribution, aggregate/binder ratio), in order to assess the provenance of raw materials (supply site/area) and to acquire useful information in order to formulate "restoration mortars" that should be most comparable with the original ones, for replacements and/or integration. Rock types constituting the coloured tesserae were also characterized by thin-section optical microscopy. The mineralogical and petrographic investigations allowed establishing two different recipes used for the formulation of the studied mortars in terms of both compositional and textural features. The aggregate is composed by diverse proportions of detritic calcareous granules (both bioclasts and limestone fragments deriving from the local outcropping biocalcarenites and limestones), siliceous sand (monocrystalline quartz, chert and quartzarenite fragments), volcanic ash (pozzolana) and sometimes cocciopesto. The resulting hydraulic binder was the product of the „pozzolanic reaction‟ between volcanic ash and the aerial lime (specifically made by the calcination of locally available magnesian limestone or dolostone). The coloured tesserae can be all classified as compact limestones of Mesozoic or Cenozoic age, likely of local provenance

Phenotypic and genotypic characterisation of Burkholderia cenocepacia J2315 mutants affected in homoserine lactone and diffusible signal factor-based quorum sensing systems suggests interplay between both types of systems

Many putative virulence factors of Burkholderia cenocepacia are controlled by various quorum sensing (QS) circuits. These QS systems either use N-acyl homoserine lactones (AHL) or cis-2-dodecenoic acid ("Burkholderia diffusible signal factor'', BDSF) as signalling molecules. Previous work suggested that there is little cross-talk between both types of systems. We constructed mutants in B. cenocepacia strain J2315, in which genes encoding CepI (BCAM1870), CciI (BCAM0239a) and the BDSF synthase (BCAM0581) were inactivated, and also constructed double (Delta cepI Delta BCAM0581, Delta cciI Delta BCAM0581 and Delta cepI Delta cciI) mutants and a triple (Delta cepI Delta cciI Delta BCAM0581) mutant. Subsequently we investigated phenotypic properties (antibiotic susceptibility, biofilm formation, production of AHL and BDSF, protease activity and virulence in Caenorhabditis elegans) and measured gene expression in these mutants, and this in the presence and absence of added BDSF, AHL or both. The triple mutant was significantly more affected in biofilm formation, antimicrobial susceptibility, virulence in C. elegans, and protease production than either the single or double mutants. The Delta BCAM0581 mutant and the Delta cepI Delta BCAM0581 and Delta cciI Delta BCAM0581 double mutants produced significantly less AHL compared to the WT strain and the Delta cepI and Delta cciI single mutant, respectively. The expression of cepI and cciI in Delta BCAM0581, was approximately 3-fold and 7-fold (p < 0.05) lower than in the WT, respectively. The observed differences in AHL production, expression of cepI and cciI and QS-controlled phenotypes in the Delta BCAM0581 mutant could (at least partially) be restored by addition of BDSF. Our data suggest that, in B. cenocepacia J2315, AHL and BDSF-based QS systems co-regulate the same set of genes, regulate different sets of genes that are involved in the same phenotypes and/or that the BDSF system controls the AHL-based QS system. As the expression of the gene encoding the C6-HSL synthase CciI (and to a lesser extent the C8-HSL synthase CepI) is partially controlled by BDSF, it seems likely that the BDSF QS systems controls AHL production through this system

Insegnamento della storia e/è public history

At the root of both the success of public history and the difficulties of history as a school subject is the same phenomenon of transformation of history, of its function and meaning in the society. School history no longer fulfills the task of forming collective identities, which are increasingly uncertain and supernational. Hence, at the same time, the impossibility to teach history according to traditional methods and canons, and the strong demand for history from non-specialized public to which public history tries to give an answer.Alla radice sia del successo della public history sia delle difficoltà della storia come materia scolastica vi è il medesimo fenomeno di trasformazione della storia, della sua funzione e significato nella società. La storia scolastica non assolve più al compito di formare le identità collettive, che sono sempre più incerte e supernazionali. Da qui, al tempo stesso, l’impossibilità di insegnare la storia secondo i metodi e i canoni tradizionali, e la forte domanda di storia proveniente da pubblico non specializzato alla quale cerca di rispondere la public history