Aims: Today, large ground-based instruments, like VISIR on the VLT, providing diffraction-limited (about 0.3 arcsec) images in the mid-infrared where strong PAH features appear enable us to see the flaring structure of the disks around Herbig Ae stars. Although great progress has been made in modelling the disk with radiative transfer models able to reproduce the spectral energy distribution (SED) of Herbig Ae stars, the constraints brought by images have not been yet fully exploited. Here, we are interested in checking if these new observational imaging constraints can be accounted for by predictions based on existing models of passive centrally irradiated hydrostatic disks made to fit the SEDs of the Herbig Ae stars. Methods: The images taken by VISIR in the 8.6 and 11.3 microns aromatic features reveal a large flaring disk around HD97048 inclined to the line of sight. In order to analyse the spatial distribution of these data, we use a disk model which includes the most up to date understanding of disk structure and physics around Herbig Ae stars with grains in thermal equilibrium in addition to transiently-heated PAHs. Results: We compare the observed spatial distribution of the PAH emission feature and the adjacent continuum emission with predictions based on existing full disk models. Both SED and spatial distribution are in very good agreement with the model predictions for common disk parameters. Conclusions: We take the general agreement between observations and predictions as a strong support for the physical pictures underlying our flared disk model.

We examine the evolution of Li in the Galactic disk,basing our model on the compilation of Li v.Fe observations in stars of iron abundance ranging between halo values,which give a baseline for the disk Li abundance,and 0.2 dex above solar.The upper envelope of these observations is taken to represent the locus of minimum stellar Li depletion,and thus to follow the Galactic IS Li abundance.The most striking feature of this envelope is its steep rise between Fe/H ~ -0.4 and -0.2,corresponding to a relatively late epoch.The Li abundance increases by an order of magnitude,from its halo value of logLi ~2.2 to the "current" value of ~3.2 within this narrow range of Fe abundances.It is well known that spallation reactions between CNO and 4He in the ISM produce Li,but models give a nearly tenfold shortfall for this process.The alpha+alpha fusion reaction appeared to yield too much early Li or too little current Li.These failures led to the exploration of stellar sources:supernovae,novae,and the He flash phase in AGB stars.The Li-Fe envelope is a strong constraint on any process.Our models can account for this in the context of disk chemical evolution with a near constant or growing rate of low metallicity gas infall,and a purely interstellar Li source: alpha-alpha fusion.The Li production rate is found to be proportional to the gas expulsion rate from intermediate and low mass stars.Low-energy alphas,emitted by these stars,but accelerated in more energetic processes associated with SNe,or the bow-shocks of stellar winds,can yield the observed abundance and its variation with Fe or O.Our model is consistent with the cosmic ray spectrum in the few MeV range,corrected for solar modulation and with new 7Li/6Li ratios found by Knauth et al.(2000) in the local ISM.