Introduction to the Proceedings of WGTTG2021

We describe the Italy-South Africa Research Program 2018–2020, focusing on the mobility scheme “Algebraic Graph Theory and Complex Networks” which supported a series of scientific initiatives between the University of Cape Town (Cape Town, South Africa) and the University of Naples Federico II (Naples, Italy) during the years 2018–2021. We sketch the relevant steps of the collaboration, focusing on the creation of a network of researchers between Italy and South Africa in the fields of Graph Theory and Combinatorics. In this context it becomes more relevant the role of the “Workshop on Graphs, Topology and Topological Groups 2021” and of the corresponding proceedings

Real decoupling ghost quantization of the CGHS model for two dimensional black holes

A complete RST quantization of a CGHS model plus Strominger term is carried out. In so doing a conformal invariant theory with $\kappa=\frac{N}{12}$ is found, that is, without ghosts contribution. The physical consequences of the model are analysed and positive definite Hawking radiation is found.Comment: 14 pages, latex, no figures, marginal errors correcte

Unforeseen high temperature and humidity stability of FeCl3_3 intercalated few layer graphene

We present the first systematic study of the stability of the structure and electrical properties of FeCl$_3$ intercalated few-layer graphene to high levels of humidity and high temperature. Complementary experimental techniques such as electrical transport, high resolution transmission electron microscopy and Raman spectroscopy conclusively demonstrate the unforeseen stability of this transparent conductor to a relative humidity up to $100 \%$ at room temperature for 25 days, to a temperature up to 150\,^\circC in atmosphere and up to a temperature as high as 620\,^\circC in vacuum, that is more than twice higher than the temperature at which the intercalation is conducted. The stability of FeCl$_3$ intercalated few-layer graphene together with its unique values of low square resistance and high optical transparency, makes this material an attractive transparent conductor in future flexible electronic applications.Comment: Scientific Reports, volume 5, article no. 760

On special quadratic birational transformations of a projective space into a hypersurface

We study transformations as in the title with emphasis on those having smooth connected base locus, called "special". In particular, we classify all special quadratic birational maps into a quadric hypersurface whose inverse is given by quadratic forms by showing that there are only four examples having general hyperplane sections of Severi varieties as base loci.Comment: Accepted for publication in Rendiconti del Circolo Matematico di Palerm

Assessing natural capital value in the network of Italian marine protected areas: A comparative approach

Marine and coastal natural capital stocks provide a bundle of ecosystem services vital for human well-being. The biophysical and economic assessment of the value of natural capital stocks is much needed for achieving nature conservation goals, while ensuring the sustainable exploitation of marine resources. Marine Protected Areas (MPAs) are increasingly being established worldwide to protect and conserve natural capital stocks from anthropogenic threats. In this study, a biophysical and trophodynamic model based on the emergy accounting method was used to assess the value of natural capital for a set of Italian MPAs. In particular, the assessment focused on four main macro-habitats: 1) sciaphilic hard bottom (SHB), 2) photophilic hard bottom (PHB), 3) soft bottom (SB), and 4) Posidonia oceanica seagrass beds (PSB). The emergy method allowed the assessment of natural capital stocks in terms of direct and indirect solar energy flows invested by nature for their generation. The SHB habitat showed the highest emergy density value in most of the investigated MPAs, confirming the high convergence of input resource flows in the formation of this habitat. When considering extensive indicators, the contribution of the PSB habitat to the total value of natural capital was higher than other habitats in most MPAs. In addition, to facilitate the understanding of the results in socio-economic contexts, the biophysical values of natural capital stocks were converted into monetary units. The total value of natural capital in the investigated MPAs ranged from about 8 to 1163 M€. In conclusion, assessing the value of natural capital can support local managers and policy makers in charge for achieving nature conservation targets while ensuring the sustainable exploitation of natural resources

Integrating Superconductive and Optical Circuits

We have integrated on oxidized silicon wafers superconductive films and Josephson junctions along with sol-gel optical channel waveguides. The fabrication process is carried out in two steps that result to be solid and non-invasive. It is demonstrated that 660 nm light, coupled from an optical fibre into the channel sol-gel waveguide, can be directed toward superconducting tunnel junctions whose current-voltage characteristics are affected by the presence of the radiation. The dependence of the change in the superconducting energy gap under optical pumping is discussed in terms of a non-equilibrium superconductivity model.Comment: Document composed of 7 pages of text and 3 figure