Optical control of the spin state of two Mn atoms in a quantum dot

We report on the optical spectroscopy of the spin of two magnetic atoms (Mn) embedded in an individual quantum dot interacting with a single electron, a single exciton, or a single trion. As a result of their interaction to a common entity, the Mn spins become correlated. The dynamics of this process is probed by time-resolved spectroscopy, which permits us to determine an optical orientation time in the range of a few tens of nanoseconds. In addition, we show that the energy of the collective spin states of the two Mn atoms can be tuned through the optical Stark effect induced by a resonant laser field.

Singular Temperatures Connected to Charge Transport Mechanism Transitions in Perylene Bisimides from Steady-State Photocurrent Measurements

Perylene bisimides (PBIs) are n-type semiconducting and photogenerating materials widely used in a variety of optoelectronic devices. Particularly interesting are PBIs that are simultaneously water-soluble and liquid-crystalline (PBI-W+LC) and, thus, attractive for the development of high-performing easily processable applications in biology and “green” organic electronics. In this work, singular temperatures connected to charge transport mechanism transitions in a PBI-W+LC derivative are determined with high accuracy by means of temperature-dependent photocurrent studies. These singular temperatures include not only the ones observed at 60 and 110 °C, corresponding to phase transition temperatures from crystalline to liquid-crystalline (LC) and from LC to the isotropic phase, respectively, as confirmed by differential scanning calorimetry (DSC), but also a transition at 45 °C, not observed by DSC. By analyzing the photocurrent dependence simultaneously on temperature and on light intensity, this transition is interpreted as a change from monomolecular to bimolecular recombination. These results might be useful for other semiconducting photogenerating materials, not necessarily PBIs or even organic semiconductors, which also show transport behavior changes at singular temperatures not connected with structural or phase transitions.

Engineer Leandro Badarán’s project to safeguard the fortresses of Alicante in 1794

After the construction of the San Carlos bastion in Alicante in the final decade of the seventeenth century, and the great trench which the English built around the district of San Francisco during their years of dominance in the War of Succession, the waters of the San Blas gully caused serious damage to these fortifications of the city and to the trade buildings of the port. In 1772, the diversion canal was built. It was designed to divert the riverbed of the gully and send the waters directly to the sea. The project had been initially designed by the Engineer General, Jorge Próspero de Verboom in 1721. This unique work of engineering had some defects, principally in the breakwater which prevented the waters from flowing down the former river course. On several occasions, the water returned to its original riverbed due to the weakness of the breakwater, the narrowness of the channel’s bed and its lack of regularisation, causing serious damage to the bastion, the Babel-facing façade, the traders’ warehouses and other buildings. This study describes the project that the military engineer Leandro Badarán carried out in 1794 in order to technically improve this canal and examines his report on the state of the fortifications. Similar works built in Spain are also explained. It also analyses the repeated disputes between the war department and the port throughout these years over finding a technical solution to the problem.

Tiburzio Spannocchi’s project for the fortifications of Fuenterrabía in 1580

Fuenterrabía (Hondarribia) is a town located on the Franco-Spanish border. Between the 16th and 19th centuries it was considered to be one of the most outstanding strongholds in the Basque Country due to its strategic position. The bastion system of fortification was extremely prevalent in this stronghold. It was one of the first Spanish towns to adopt the incipient Renaissance designs of the bastion. The military engineers subsequently carried out continuous fortification projects that enabled the structure to withstand the advances being made in artillery and siege tactics. After the construction of the citadel of Pamplona had begun in 1571, following the design of the prestigious military engineer, Jacobo Palear Fratín and being revised by Viceroy Vespasiano Gonzaga, the aforementioned engineer undertook an ambitious project commissioned by Felipe II to modernise the fortifications of Fuenterrabía. Neither the plans nor the report of this project have been conserved, but in the year 2000, César Fernández Antuña published the report written by Spannocchi on the state of the fortifications of Fuenterrabía when he arrived to the Spanish peninsula, discovered in the Archivo Histórico Provincial de Zaragoza. This document conducts an in-depth analysis of Spannocchi’s project and how it was related to Fratín’s previous project. It concludes that this project encountered problems in updating the new bastions at the end of the 16th century, and identifies the factors which prevented the stronghold from being extended as was the case in Pamplona after Fratín’s project.