Phases dynamics in VCSELs with delayed optical feedback and cross re-injection

We study theoretically the non linear polarization dynamics of Vertical-Cavity Surface-Emitting Lasers in the presence of an external cavity providing delayed optical feedback and cross polarization re-injection. We show that far from the laser threshold, the dynamics remains confined close to the equatorial plane of a Stokes sphere of a given radius and we reduce the dynamics to a dynamical system composed of two phases: the orientation phase of the quasi-linear polarization and the optical phase of the field. We explore the complex modal structure given by the double feedback configuration and recovers as particular cases the Lang-Kobayashi modes and the modes founds by Giudici et al. [1]. We also re-interpret the square waves switching dynamics as phase kinks.Comment: 10 pages, 7 figures, pre-submission to Phys. Rev.

Entrepreneurial workaround practices in severe institutional voids: Evidence from Kenya

Entrepreneurs in developing economies try to cope with weak or absent formal institutions – often referred to as ‘institutional voids’ – by relying extensively on intermediary organizations such as business incubators and development organizations or informal institutions such as political, kinship, or family relationships. However, in many African countries, intermediary support is limited and informal institutions are also unreliable, adding risks and costs to doing business and increasing the severity of institutional voids in the surrounding ecosystem. We investigate the practices followed by 47 commercial entrepreneurs in Kenya to ‘work around’ these severe institutional voids to achieve their goals of business creation and growth. We find that severe institutional voids stimulate the hybridization of goals to include social value creation, create a need for a more strategic orchestration of business relationships, and motivate entrepreneurs to proactively cross-brace the institutional infrastructure around them. We contribute by unveiling the important role of entrepreneurs as microinstitutional agents in developing economies and by detailing how commercial and social goals become intertwined in the context of African entrepreneurship

Intrinsic gap and exciton condensation in the nu_T=1 bilayer system

We investigate the quasiparticle excitation of the bilayer quantum Hall (QH) system at total filling factor $\nu_{\mathrm{T}} = 1$ in the limit of negligible interlayer tunneling under tilted magnetic field. We show that the intrinsic quasiparticle excitation is of purely pseudospin origin and solely governed by the inter- and intra-layer electron interactions. A model based on exciton formation successfully explains the quantitative behavior of the quasiparticle excitation gap, demonstrating the existence of a link between the excitonic QH state and the composite fermion liquid. Our results provide a new insight into the nature of the phase transition between the two states.Comment: 4 pages, 3 figure

An integrated approach project for the revaluation of a traditional sourdough bread production chain

The influence of organic and conventional farming systems on the performance of a panel of old and modern Italian bread wheat varieties has been evaluated, with the aim to individuate an agronomic protocol suitable for the production of a sourdough bread traditionally prepared in a hill zone of Emilia-Romagna. The agronomic and technological characterisation of the wheat samples obtained in organic and conventional farming conditions has been done and the sensorial qualities of the sourdough bread obtained have been evaluated

The use of hydrological and geoelectrical data to fix the boundary conditions of a ground water flow model: a case study

International audienceTo assess whether the hydrometric level of an artificial lake in a quarry near Milan (Italy) could be assigned as a Dirichlet boundary condition for the phreatic aquifer in a fine scale groundwater flow model, hydrological measurements of piezometric head and rainfall rate time series have been analysed by spectral and statistical methods. The piezometric head close to the quarry lake proved to be well correlated with seasonal variations in the rainfall. Furthermore, geoelectrical tomography detected no semi-permeable layer between the phreatic aquifer and the lake, so the contact between surface and ground water is good. Finally, a time-varying prescribed head condition can be applied for ground water flow modelling