Perfect simulation for interacting point processes, loss networks and Ising models

We present a perfect simulation algorithm for measures that are absolutely continuous with respect to some Poisson process and can be obtained as invariant measures of birth-and-death processes. Examples include area- and perimeter-interacting point processes (with stochastic grains), invariant measures of loss networks, and the Ising contour and random cluster models. The algorithm does not involve couplings of the process with different initial conditions and it is not tied up to monotonicity requirements. Furthermore, it directly provides perfect samples of finite windows of the infinite-volume measure, subjected to time and space ``user-impatience bias''. The algorithm is based on a two-step procedure: (i) a perfect-simulation scheme for a (finite and random) relevant portion of a (space-time) marked Poisson processes (free birth-and-death process, free loss networks), and (ii) a ``cleaning'' algorithm that trims out this process according to the interaction rules of the target process. The first step involves the perfect generation of ``ancestors'' of a given object, that is of predecessors that may have an influence on the birth-rate under the target process. The second step, and hence the whole procedure, is feasible if these ``ancestors'' form a finite set with probability one. We present a sufficiency criteria for this condition, based on the absence of infinite clusters for an associated (backwards) oriented percolation model.Comment: Revised version after referee of SPA: 39 page

Loss network representation of Peierls contours

We present a probabilistic approach for the study of systems with exclusions, in the regime traditionally studied via cluster-expansion methods. In this paper we focus on its application for the gases of Peierls contours found in the study of the Ising model at low temperatures, but most of the results are general. We realize the equilibrium measure as the invariant measure of a loss-network process whose existence is ensured by a subcriticality condition of a dominant branching process. In this regime, the approach yields, besides existence and uniqueness of the measure, properties such as exponential space convergence and mixing, and a central limit theorem. The loss network converges exponentially fast to the equilibrium measure, without metastable traps. This convergence is faster at low temperatures, where it leads to the proof of an asymptotic Poisson distribution of contours. Our results on the mixing properties of the measure are comparable to those obtained with ``duplicated-variables expansion'', used to treat systems with disorder and coupled map lattices. It works in a larger region of validity than usual cluster-expansion formalisms, and it is not tied to the analyticity of the pressure. In fact, it does not lead to any kind of expansion for the latter, and the properties of the equilibrium measure are obtained without resorting to combinatorial or complex analysis techniques.Comment: 42 pages. Revised version after the first referee repor

Supplementary data for article: Perić, M.; García-Fuente, A.; Zlatar, M.; Daul, C.; Stepanović, S.; García-Fernández, P.; Gruden-Pavlović, M. Magnetic Anisotropy in “Scorpionate” First-Row Transition-Metal Complexes: A Theoretical Investigation. Chemistry - A European Journal 2015, 21 (9), 3716–3726. https://doi.org/10.1002/chem.201405480

Supporting information for: [https://doi.org/10.1002/chem.201405480]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1667

Supplementary data for the article: García-Fernández, P.; Aramburu, J. A.; Moreno, M.; Zlatar, M.; Gruden-Pavlović, M. A Practical Computational Approach to Study Molecular Instability Using the Pseudo-Jahn-Teller Effect. Journal of Chemical Theory and Computation 2014, 10 (4), 1824–1833. https://doi.org/10.1021/ct4011097

Supplementary material for: [https://doi.org/10.1021/ct4011097]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1765

Analysis of matched geographical areas to study potential links between environmental exposure to oil refineries and non-Hodgkin lymphoma mortality in Spain

BACKGROUND: Emissions from refineries include a wide range of substances, such as chrome, lead, nickel, zinc, arsenic, cadmium, benzene, dioxins and furans, all of which are recognized by the International Agency for Research on Cancer (IARC) as carcinogens. Various studies have shown an association between non-Hodgkin lymphoma (NHL) and residence in the vicinity of industrial areas; however, evidence of specific association between refineries and residence in the vicinity has been suggested but not yet established. The aim of this study is to investigate potential links between environmental exposure to emissions from refineries and non-Hodgkin lymphoma mortality in Spain. The spatial distribution of NHL in Spain has an unusual pattern with regions some showing higher risk than others. METHODS: We designed an analysis of matched geographical areas to examine non-Hodgkin lymphoma mortality in the vicinity of the 10 refineries sited in Spain over the period 1997-2006. Population exposure to refineries was estimated on the basis of distance from town of residence to the facility in a 10 km buffer. We defined 10 km radius areas to perform the matching, accounting for population density, level of industrialization and socio-demographic factors of the area using principal components analysis. For the matched towns we evaluated the risk of NHL mortality associated with residence in the vicinity of the refineries and with different regions using mixed Poisson models. Then we study the residuals to assess a possible risk trend with distance. RESULTS: Relative risks (RRs) associated with exposure showed similar values for women and for men, 1.09 (0.97-1.24) and 1.12 (0.99-1.27). RRs for two regions were statistically significant: Canary Islands showed an excess of risk of 1.35 (1.05-1.72) for women and 1.50 (1.18-1.92) for men, whilst Galicia showed an excess of risk of 1.35 (1.04-1.75) for men, but not significant excess for women. CONCLUSIONS: The results suggest a possible increased risk of NHL mortality among populations residing in the vicinity of refineries; however, a potential distance trend has not been shown. Regional effects in the Canary Islands and Galicia are significantly greater than the regional average

Cardiac-surgery associated acute kidney injury requiring renal replacement therapy. A Spanish retrospective case-cohort study

Acute kidney injury is among the most serious complications after cardiac surgery and is associated with an impaired outcome. Multiple factors may concur in the development of this disease. Moreover, severe renal failure requiring renal replacement therapy (RRT) presents a high mortality rate. Consequently, we studied a Spanish cohort of patients to assess the risk factors for RRT in cardiac surgery-associated acute kidney injury (CSA-AKI). METHODS: A retrospective case-cohort study in 24 Spanish hospitals. All cases of RRT after cardiac surgery in 2007 were matched in a crude ratio of 1:4 consecutive patients based on age, sex, treated in the same year, at the same hospital and by the same group of surgeons. RESULTS: We analyzed the data from 864 patients enrolled in 2007. In multivariate analysis, severe acute kidney injury requiring postoperative RRT was significantly associated with the following variables: lower glomerular filtration rates, less basal haemoglobin, lower left ventricular ejection fraction, diabetes, prior diuretic treatment, urgent surgery, longer aortic cross clamp times, intraoperative administration of aprotinin, and increased number of packed red blood cells (PRBC) transfused. When we conducted a propensity analysis using best-matched of 137 available pairs of patients, prior diuretic treatment, longer aortic cross clamp times and number of PRBC transfused were significantly associated with CSA-AKI.Patients requiring RRT needed longer hospital stays, and suffered higher mortality rates. CONCLUSION: Cardiac-surgery associated acute kidney injury requiring RRT is associated with worse outcomes. For this reason, modifiable risk factors should be optimised and higher risk patients for acute kidney injury should be identified before undertaking cardiac surgery

Supplementary data for the article: Fitzpatrick, A. J.; Stepanovic, S.; Müller-Bunz, H.; Gruden-Pavlović, M. A.; García-Fernández, P.; Morgan, G. G. Challenges in Assignment of Orbital Populations in a High Spin Manganese(Iii) Complex. Dalton Transactions 2016, 45 (15), 6702–6708. https://doi.org/10.1039/c5dt03914b

Supplementary material for: [https://doi.org/10.1039/c5dt03914b]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1912]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3395