1,721,171 research outputs found
Altitudinal dependences of meteoclimatic conditions in the Great Alpine Region: from observations and idealized simulations to climate change projections
No full textMountain environments are of a great importance in our lives, as they cover about 25% of the Earth’s surface, and all the population on the Earth depends on them directly or indirectly. Fresh water is important for the survival of humans and an important part is found in mountain settings, including glaciers, lakes, rivers. Mountains provide fresh water to more than half of the world’s population, for drinking and domestic use, agriculture, industry and hydropower production. Mountains provide
natural resources, they are a refuge for many species of flora and fauna, mountain environments have processes of resilience or adaptation to the negative factors of
climate change. At the same time, mountain regions are characterised by complex atmospheric dynamics that generate very local effects of larger scale variations, such
as global warming. Mountain ecosystems are particularly sensitive to the impacts of climate change and are being affected at a faster rate than other environments. Thus climate change is directly affecting mountain settings, but also all those who depend on them.
To shed further light on this important field, my research project deals with the study of the altitudinal dependencies of meteoclimatic conditions in the Great Alpine Region, one of the highest and most extensive mountain range system in Europe where both global and local anthropic activities impact it. To this goal, in my PhD research project at first I analyzed observational data to study the true representation of the status of atmospheric variables such as precipitation: the main goal was to shed light on the relationship between precipitation changes and elevation. Secondly, I worked with high resolution numerical simulations that allow to study with greater accuracy the underlying processes associated to air masses flow over complex orography areas: two distinct but complementing research topics have been tackled, one based on developing a better understanding of the climatic role that aerosols play in complex orography areas, and the other based on investigating the expected changes in climate over the Great Alpine Region with a greater emphasis in understanding changes with altitude
Generalized cluster correlation expansion theory for stimulated Raman adiabatic passage processes in the presence of a spin bath
No full textThe stimulated Raman adiabatic passage (STIRAP) is applied to a system coupled to a bath made of fully interacting two-level systems whose dynamics is studied by exploiting the generalized cluster correlation expansion (gCCE) theory.We specialize our analysis to a negatively charged silicon vacancy () in nonpurified 4H-SiC to assess the possibility of transferring population between two states of the ground manifold, also taking into account the interaction with a spherical nuclear-spin bath formed by nuclei of and . For this system, it is demonstrated that the presence of a small- or medium-sized bath has no effect on the protocol, finding in particular a set of parameter values for an efficient STIRAP process
EGA–MS study to characterize the thermally induced decomposition of Co(II), Ni(II), Cu(II) and Zn(II) complexes with 1,1-diaminobutane-Schiff base
No full textRecently, in addition to X-ray and spectroscopic approaches, thermal analysis is often applied to complete the characterization of precipitated metal complexes. However, thermogravimetry itself is frequently not sufficient to explain complex decomposition or releasing steps. To propose the decomposition mechanism of Co(II), Ni(II), Cu(II) and Zn(II) complexes with 1,1-diaminobutane-Schiff base, evolved gas analysis by mass spectrometry (EGA-MS) was used to define the thermally induced steps of precipitated complexes, synthesized following the literature and characterized by hyphenated thermogravimetry-mass spectrometry (TG-MS) that allowed to describe the releasing or decomposition steps. © 2015 Elsevier B.V. All rights reserved
Adiabatic manipulation of a system interacting with a spin-bath
Full text linkStimulated Raman Adiabatic Passage, a very efficient technique for
manipulating a quantum system based on the adiabatic theorem, is analyzed in
the case where the manipulated physical system is interacting with a spin bath.
Exploitation of the rotating wave approximation allows for the identification
of a constant of motion which simplifies both the analytical and the numerical
treatment, which allows for evaluating the total unitary evolution of system
and bath. The efficiency of the population transfer process is investigated in
several regimes, including the weak and strong coupling with the environment
and the off-resonance. The formation of appropriate Zeno subspaces explains the
lowering of the efficiency in the strong damping regime.Comment: 7 pages, 7 figures (5 captions
Adiabatically Manipulated Systems Interacting with Spin Baths beyond the Rotating Wave Approximation
Full text linkThe Stimulated Raman Adiabatic Passage (STIRAP) on a three-state system interacting with a spin bath is considered, focusing on the efficiency of the population transfer. Our analysis is based on the perturbation treatment of the interaction term evaluated beyond the Rotating Wave Approximation, thus focusing on the limit of weak system–bath coupling. The analytical expression of the correction to the efficiency and the consequent numerical analysis show that, in most of the cases, the effects of the environment are negligible, confirming the robustness of the population transfer
Sensitivity of measurement-based purification processes to inner interactions
No full textThe sensitivity of a repeated measurement-based purification scheme to additional undesired couplings is analyzed, focusing on the very simple and archetypical system consisting of two two-level systems interacting with a repeatedly measured one. Several regimes are considered and in the strong coupling limit (i.e., when the coupling constant of the undesired interaction is very large) the occurrence of a quantum Zeno effect is proven to dramatically jeopardize the efficiency of the purification process
Competition of direct and indirect sources of thermal entanglement in a spin-star network
No full textA spin-star system consisting of three peripheral two-state systems and a central one is considered, with the peripheral spins assumed to interact with each other, as well as with the central one. It is shown that such two couplings, each one being a thermal entanglement source, can significantly compete in the formation of quantum correlations in the thermal state to the point that they can destroy any thermal entanglement of the peripheral spins
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