Tesis doctoral: Análisis del contenido en agua en formaciones salinas. Su aplicación al almacenamiento de residuos radioactivos

Rock salt formations are one of the suitable host rocks for high radioactive waste disposal. Among the site selection criteria, one of great importance is the presence of water in the host rock. Due to their genesis and to their mineralogical composition salt formations always contain small amounts of water. This water can be present as interstitial brine, in hydrated minerals and as intragranular fluid inclusions. In order to define the range of water content present in rock salt, as well as its relation between mineralogy and stratigraphical position, five rock salt types have been studied. For each sample water content and also mineralogical analysis has been performed. In most of the studied samples water is present as interstitial bnne and fluid inclusions. In some cases water can also be present in form of hydrated minerals. The distribution of the water content is usually of lognormal type. In some rock salt formations, severa1 subpopulations could be found. Total water content ranges from 0.01 to 3.50%.Mathematical treatment on the aforementioned data consisted of the estimation of the error related to the sampling procedure, statistical tests (univariant, ANOVA, correlation, PCA and trend analysis) and Geostatistics. These treatments have allowed to discern between waternch and water-poor rock salt and also to confirm that there are three factors controlling the amount of water content: mineralogical composition, halitic lithofacies and degree of tectonic stresses. Geostatistical analysis has shown that for detailed characterization purposes a sarnpling interval of 1 m is convenient, whereas for a first characterization of a salt formation a sampling interval of 5 m seems reasonable.Finally, trend analysis has confirmed that along a rock salt formation, alternancy of water-rich and water-poor zones may exist. The methodology described in this study can be very useful for site characterization purposes. Data arising from laboratory research on the aforementioned parameters combined with safety assessment methods can provide the technical basis to decide whether the proposed disposal site offers a satisfactory leve1 of safety

Comparación metodológica de la determinación del contenido en agua en rocas salinas mediante titulación de Karl Fischer y termogravimetría

Water rnay be present in geological formations, filling pores, as fluid inclusions or as hydrated minerals. This study shows a comparison different methodologies in the determination of the water content in rock salt subsamples, using Karl Fischer titration and thermogravimetry, in order to establish an efficient and routinary analytical methodology for water content determination. The study has shown significant discrepancies in the water content results for the same samples, depending on the methodology and the granulometry selected

Aplicación del análisis geoestadístico al diseño de programas de muestreos en formaciones salinas

Water content in salt formations is a regionalised variable rather than a random variable. This means that the yield of the variable in one location varies very slightly from that of close locations. This paper focus on the minimisation of uncertainties of the water content caused by spatial variability and limited number of samples, in order to assess optimised sampling intervals for representative sampling procedures in salt formations. Geostatistical analyses have been performed using small-scale and large-scale sampling intervals in several salt formations. Results show that geostatistical analyses can be successfully used, provided that the dimensions of the studied rockbody do not exceed the range of the regionalised variable by more than one order of magnitude. Otherwise, a simple statistical approximation should provide the degree of accuracy needed when estimating sample means

Polypharmacy in psychiatric practice in the Canary Islands

BACKGROUND: Polypharmacy with psychoactive drugs is an increasingly common and debatable contemporary practice in clinical psychiatry based more upon experience than evidence. The objective of this study was to evaluate the prevalence and conditioners of polypharmacy in psychiatric patients. METHOD: A cross-sectional survey was carried out using the Canary Islands Health Service Clinical Records Database. A representative sample (n = 2,647) of patients with mental disorders receiving psychotropic medication was studied. RESULTS: The mean number of psychoactive drugs prescribed was 1.63 ± 0.93 (range 1–7). The rate of polypharmacy was 41.9%, with 27.8% of patients receiving two drugs, 9.1% receiving three, 3.2% receiving four, and 1.8% of the patients receiving five or more psychotropic drugs. Multiple regression analysis shows that variables sex and diagnosis have a predictive value with regard to the number of psychotropic drug used, being men and schizophrenic patients the most predisposed. Benzodiazepines were the more prevalent drugs in monotherapy, while anticonvulsants and antipsychotics were the more used in combination with other treatment. A questionable very high degree of same-class polypharmacy was evidenced, while multi-class, adjunctive and augmentation polypharmacy seem to be more appropriate. CONCLUSIONS: Almost half of the psychiatric patients are treated with several psychotropics. Polypharmacy is common and seems to be problematic, especially when same class of drugs are prescribed together. Some diagnoses, such as schizophrenia, are associated with an increase risk of Polypharmacy but there is a lack of evidence based indicators that allows for quality evaluation on this practice

A further study of the kinetics of recrystallization and grain growth of cold rolled TWIP steel

Over last decades, the twinning - induced plasticity Fe-Mn-C (TWIP) steels have been the focus on huge amount of research works due to their prominent strength – ductility compounding which develops from the occurrence of extended mechanical twinning during plastic deformation under mechanical loads (Grässel and Frommeyer, 1998; Frommeyer et al., 2000; Cornette et al., 2005; Scott et al., 2006; Bouaziz et al., 2008; Hamada et al., 2010; Bouaziz et al., 2011; De Cooman et al., 2011; Galán et al., 2012; Gil Sevillano and De las Cuevas, 2012; Chen et al., 2013; De las Cuevas et al., 2014; Ghasri-Khouzani and McDermid, 2015; Pierce et al., 2015; De las Cuevas and Gil Sevillano, 2017). In TWIP steels, the fully austenitic microstructure can be retained by means of high level alloying with elements such as Mn, Al and Si. Al and Si are mainly used to adjust the magnitude of the stacking fault energy, gSFE, of austenite (Frommeyer et al., 2000). Furthermore, they also strengthen the steel by solid solution hardening and stabilize austenite owing to their ability of slowing down the precipitation of carbides, especially cementite, leaving more carbon available for the enrichment of austenite (Leslie and Rauch, 1978)

Mapping all classical spin models to a lattice gauge theory

In our recent work [Phys. Rev. Lett. 102, 230502 (2009)] we showed that the partition function of all classical spin models, including all discrete standard statistical models and all Abelian discrete lattice gauge theories (LGTs), can be expressed as a special instance of the partition function of a 4-dimensional pure LGT with gauge group Z_2 (4D Z_2 LGT). This provides a unification of models with apparently very different features into a single complete model. The result uses an equality between the Hamilton function of any classical spin model and the Hamilton function of a model with all possible k-body Ising-type interactions, for all k, which we also prove. Here, we elaborate on the proof of the result, and we illustrate it by computing quantities of a specific model as a function of the partition function of the 4D Z_2 LGT. The result also allows one to establish a new method to compute the mean-field theory of Z_2 LGTs with d > 3, and to show that computing the partition function of the 4D Z_2 LGT is computationally hard (#P hard). The proof uses techniques from quantum information.Comment: 21 pages, 21 figures; published versio

Unifying all classical spin models in a Lattice Gauge Theory

We show that the partition function of all classical spin models, including all discrete Standard Statistical Models and all abelian discrete Lattice Gauge Theories (LGTs), can be expressed as a special instance of the partition function of the 4D Z_2 LGT. In this way, all classical spin models with apparently very different features are unified in a single complete model, and a physical relation between all models is established. As applications of this result, we present a new method to do mean field theory for abelian discrete LGTs with d>3, and we show that the computation of the partition function of the 4D Z_2 LGT is a computationally hard (#P-hard) problem. We also extend our results to abelian continuous models, where we show the approximate completeness of the 4D Z_2 LGT. All results are proven using quantum information techniques.Comment: Published version. One new figure and some minor change

Single-channel transmission in gold one-atom contacts and chains

We induce superconductivity by proximity effect in thin layers of gold and study the number of conduction channels which contribute to the current in one-atom contacts and atomic wires. The atomic contacts and wires are fabricated with a Scanning Tunneling Microscope. The set of transmission probabilities of the conduction channels is obtained from the analysis of the $I(V)$ characteristic curve which is highly non-linear due to multiple Andreev reflections. In agreement with theoretical calculations we find that there is only one channel which is almost completely open.Comment: 4 pages, 2 figures. To be published in Phys. Rev. B, Rapid Communications (2003

Completeness of classical spin models and universal quantum computation

We study mappings between distinct classical spin systems that leave the partition function invariant. As recently shown in [Phys. Rev. Lett. 100, 110501 (2008)], the partition function of the 2D square lattice Ising model in the presence of an inhomogeneous magnetic field, can specialize to the partition function of any Ising system on an arbitrary graph. In this sense the 2D Ising model is said to be "complete". However, in order to obtain the above result, the coupling strengths on the 2D lattice must assume complex values, and thus do not allow for a physical interpretation. Here we show how a complete model with real -and, hence, "physical"- couplings can be obtained if the 3D Ising model is considered. We furthermore show how to map general q-state systems with possibly many-body interactions to the 2D Ising model with complex parameters, and give completeness results for these models with real parameters. We also demonstrate that the computational overhead in these constructions is in all relevant cases polynomial. These results are proved by invoking a recently found cross-connection between statistical mechanics and quantum information theory, where partition functions are expressed as quantum mechanical amplitudes. Within this framework, there exists a natural correspondence between many-body quantum states that allow universal quantum computation via local measurements only, and complete classical spin systems.Comment: 43 pages, 28 figure

Digital Quantum Simulation of the Statistical Mechanics of a Frustrated Magnet

Many interesting problems in physics, chemistry, and computer science are equivalent to problems of interacting spins. However, most of these problems require computational resources that are out of reach by classical computers. A promising solution to overcome this challenge is to exploit the laws of quantum mechanics to perform simulation. Several "analog" quantum simulations of interacting spin systems have been realized experimentally. However, relying on adiabatic techniques, these simulations are limited to preparing ground states only. Here we report the first experimental results on a "digital" quantum simulation on thermal states; we simulated a three-spin frustrated magnet, a building block of spin ice, with an NMR quantum information processor, and we are able to explore the phase diagram of the system at any simulated temperature and external field. These results serve as a guide for identifying the challenges for performing quantum simulation on physical systems at finite temperatures, and pave the way towards large scale experimental simulations of open quantum systems in condensed matter physics and chemistry.Comment: 7 pages for the main text plus 6 pages for the supplementary material