Dressed States Approach to Quantum Systems

Using the non-perturbative method of {\it dressed} states previously introduced in JPhysA, we study effects of the environment on a quantum mechanical system, in the case the environment is modeled by an ensemble of non interacting harmonic oscillators. This method allows to separate the whole system into the {\it dressed} mechanical system and the {\it dressed} environment, in terms of which an exact, non-perturbative approach is possible. When applied to the Brownian motion, we give explicit non-perturbative formulas for the classical path of the particle in the weak and strong coupling regimes. When applied to study atomic behaviours in cavities, the method accounts very precisely for experimentally observed inhibition of atomic decay in small cavities PhysLA, physics0111042

Cerium neodymium oxide solid solution synthesis as a potential analogue for substoichiometric AmO 2 for radioisotope power systems

The European Space Agency (ESA) is sponsoring a research programme on the development of americium oxides for radioisotope generators and heater units. Cubic AmO2-(x/2) with an O/Am ratio between 1.65 and 1.75 is a potentially suitable compound for pellet sintering. C-type (Ia-3) Ce1-xNdxO2-(x/2) oxides with 0.5 &lt; x &lt; 0.7 could be used as a surrogate for some Ia-3 AmO2-(x/2). A new Ce1-xNdxO2-(x/2) production process has been investigated where a nominally selected x value of 0.6 was targeted: Ce and Nd nitrates and oxalic acid were added drop-wise into a vessel, where they continuously reacted to create oxalate precipitates. The effect of temperature (25 °C, 60 °C) of the reactants (mixed at 250 revolutions per minute) on oxalate particle shape and size were investigated. Oxalates were calcined at 900 °C to produce oxide particles. Oxalate particle properties were characterised as these are expected to influence oxides particle properties and fuel pellet sintering.</p

Tracking Hydroclimate Changes and Human Impacts over the Last Millennium in Lake Sediment Records from Flores Island, the Azores

Since the Portuguese settlement of the Azores Archipelago in the 15th century humans have extensively modified the Azorean landscape, with exotic plants dominating the present-day vegetation and eutrophication in numerous lakes. However, it is uncertain whether hydroclimate variability contributed to changes in terrestrial and aquatic ecosystems and helped facilitate the arrival of humans in the Azores. To assess the role of climate in these processes, we developed complementary paleoecological and paleoclimate records from Lake Funda on Flores Island that span the last millennium. Low variability in precipitation amount, as recorded by leaf wax hydrogen isotopes (¿Dwax) from C30 fatty acids, suggests that the hydroclimate on Flores Island was relatively stable between c. 1000-1350 CE and drier between c. 1350-1450 CE when Portuguese explorers arrived in Flores Island (1452 CE). More depleted ¿Dwax values between c. 1450-1650 CE suggest wetter climate conditions may have contributed to the slow establishment of permanent settlements on Flores Island. Major changes in n-alkane average chain lengths (ACL27-33) and 5ß-stigmastanol indicate that major shifts in vegetation composition and the widespread introduction of livestock, respectively, took place over c. 100-years between c. 1500-1600 CE. Landscape changes were followed by a decrease in ¿15N as N2-fixation by cyanobacteria increased in Lake Funda. Around the same time, increases in the ratio of 5¿(H)-stanols/¿5-sterols suggest that the lake bottom water was more frequently experiencing reducing, i.e. hypoxic, conditions, thereby enhancing in-lake phosphorous cycling and increasing the lake trophic state. Evidence of eutrophication in Lake Funda persisted during the Little Ice Age despite increased variability in ¿Dwax between c. 1650-1850 CE, highlighting continued human impacts on the lake ecosystem. Reforestation efforts on Flores Island and a drier climate in the 20th century most likely reduced nutrient leaching and soil erosion in the catchment area of Lake Funda, yet eutrophication continues to be a problem. This research is funded by through the research projects PaleoModes (CGL2016-75281-C2) and DISCOVERAZORES (PTDC/CTA-AMB/28511/2017) and the Luso-American Foundation