Theory of coherent optical nonlinearities of intersubband transitions in semiconductor quantum wells

We theoretically study the coherent nonlinear response of electrons confined in semiconductor quantum wells under the effect of an electromagnetic radiation close to resonance with an intersubband transition. Our approach is based on the time-dependent Schr\"odinger-Poisson equation stemming from a Hartree description of Coulomb-interacting electrons. This equation is solved by standard numerical tools and the results are interpreted in terms of approximated analytical formulas. For growing intensity, we observe a redshift of the effective resonance frequency due to the reduction of the electric dipole moment and the corresponding suppression of the depolarization shift. The competition between coherent nonlinearities and incoherent saturation effects is discussed. The strength of the resulting optical nonlinearity is estimated across different frequency ranges from mid-IR to THz with an eye to ongoing experiments on Bose-Einstein condensation of intersubband polaritons and to the speculative exploration of quantum optical phenomena such as single-photon emission in the mid-IR and THz windows

Location and survival of MNEs' subsidiaries: Agglomeration and heterogeneity of firms

Research summary Our study provides a quasi–replication of Shaver and Flyer (2000), which was among the first studies that challenged the positive role of agglomeration in determining companies' location choice and performances, thus changing the way management scholars view companies' attitude towards agglomeration forces. We employ the same research design, specification and tests, and a different population, to discuss the generalizability of the original study. Building on the framework of Shaver and Flyer (2000), our findings offer intriguing new empirical evidence highlighting the importance of the differential between entering foreign firms and host country firms as a crucial condition in understanding agglomeration forces and adverse selection mechanisms. Managerial summary Our exercise confirms that agglomeration forces act differently on stronger versus weaker multinational enterprises (MNEs). However, we find that stronger MNEs tend to avoid location in highly specialized areas when they are afraid of knowledge leakages towards host country–based rivals that have enough absorptive capacity to benefit and improve their competitive advantages. Managerial implications are quite relevant. Indeed, when MNEs avoid co–location in highly specialized areas, they also limit their own access to local knowledge and other agglomeration economies, such as supply networks and qualified workforce. Thus, MNEs managers need to design and implement devices that, on the one hand prevent local leakages of their knowledge and, on the other, do not hinder their access to local unique knowledge and resources

Programmazione integrata e sviluppo rurale del Piemonte

Quaderni di ricerca Ires ; n.11

Fluoro-profilassi in Italia

La patologia cariosa \ue8 una malattia infettiva a carattere cronico-degenerativo e a eziologia multifattoriale, ancora oggi molto diffusa. L\u2019educazione alla salute orale inizia in epoca prenatale, attraverso l\u2019intervento multidisciplinare del ginecologo e dell\u2019odontoiatra. Elemento essenziale per la prevenzione \ue8 il fluoro, che pu\uf2 essere somministrato secondo diverse modalit\ue0. Nonostante non ci siano dubbi sull\u2019effetto protettivo del fluoro contro la carie e nonostante le linee guida redatte dal ministero della Salute risultino esaustive, la sua assunzione in molti casi non \ue8 ottimale. \uc8 necessario vengano conosciute e rispettate le modalit\ue0 per una corretta fluoroprofilassi.Dental decay is a chronic-degenerative infection with a still widespread multifactorial aetiology. Oral health education begins in the prenatal period, through the intervention of the gynaecologist and the dentist. The principal element of prevention is fluorine, which can be administered in a variety of ways. Although there are no doubts about the protective effect of fluorine against tooth decay and notwithstanding the exhaustive guidelines of the Ministry of Health its intake is not always optimal. The proper procedures for fluorine prophylaxis must be known and correctly carried out