In this paper we study cellular access networks which solely rely on renewable energy. We consider a cellular network in which a mesh of base stations (BSs) that are powered with renewable sources, and interconnected with wireless backhaul links, cover the service area, and provide connection to few, typically remote, wired network accesses to the national and international backbone. In particular, we study how to dimension BS power generators and energy storage. We start by discussing the BS energy need, that depends on both the BS consumption model and the BS traffic profiles. Focusing then on some specific locations, we consider the use of photovoltaic (PV) panels, and dimension them based on the daily energy need of the BS and on typical radiative power of sun in the considered locations. Once the PV system has been dimensioned, we also evaluate the energy storage capacity that is needed to absorb energy production variability due to both daily and seasonal radiative power variations. Finally, we investigate the effectiveness of integrating the PV system with wind turbines, as well as the benefit induced on the system by base station sleep modes.

The purpose of this in vitro study was to evaluate quantitatively the ability of four different filling materials to seal the orifices of root canals as a secondary seal after root canal therapy. Forty extracted human molar teeth were used. The top of pulp chambers and distal halves of the roots were removed using an Isomet saw. The canal orifices were temporarily sealed with a gutta-percha master cone without sealer. The pulp chambers were then treated with a self-etching primer adhesive system (Clearfil SE Bond), a wet bonding system (One-Step), a 4-methacryloyloxyethyl trimellitate anhydride adhesive system (C&B Metabond), or a reinforced zinc oxide-eugenol (IRM). The specimens were randomly divided into four groups of 10 each. A fluid filtration method was used for quantitative evaluation of leakage. Measurements of fluid movement were made at 2-min intervals for 8 min. The quality of the seal of each specimen was measured by fluid filtration immediately and after 1 day, 1 wk, and 1 month. Even after 1 month the resins showed an excellent seal. Zinc oxide-eugenol had significantly more leakage when compared with the resin systems (p < 0.05). Adhesive resins should be considered as a secondary seal to prevent intraorifice microleakage.

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