Spontaneous pattern formation in Turing systems

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Any: 2015, Tutor: Oleg BulashenkoWe give a general description of pattern forming systems and describe the linear stability analysis that allows to determine whether a system in a uniform state will spontaneously evolve to a patterned state. Such an analysis is performed on Turing systems and conditions for pattern formation are derived. As an example of a Turing system, we consider the Brusselator model, for which a variety of patterns are found numerically for different values of the bifurcation parameters

Isochrons (and applications to Neuroscience)

Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 205, Director: Àlex HaroMany biological systems exhibit a periodic behaviour. From a mathematical point of view they can be considered as systems moving along a stable limit cycle, that can be parametrised by its phase. The phase can be extended to the whole basin of attraction of the limit cycle via the asymptotic phase and the set of all points having the same asymptotic phase is called isochron. Isochrons were introduced in 1974 by Winfree in order to understand the behaviour of an oscillatory system under a brief stimulus, namely, the phase advance or delay that the system would experience when sent away from the periodic orbit. This helps understanding, for example, the synchronisation in neural nets. Soon after Winfree’s paper, Guckenheimer showed that isochrons are in fact the leaves of the stable foliation of the stable manifold of a periodic orbit. Different techniques have been developed to compute the isochrons. An important part of this undergraduate thesis consists on understanding the mathematical concept underlying the idea of isochron. In chapter 2 a definition is given and we describe some properties of isochrons with the objective of being able to find an approximation to first order. We also formulate a functional equation for the parametrisation of the invariant cycle and the tangent vector to the isochrons and we show how it can be solved using a quasi-Newton method. Our arguments are based in, where the parametrisation of the whole isochron is found. With some trans- formations we can simplify our equations and easily solve them. We end the chapter by giving some hints on how to proof the convergence of the method using KAM arguments. In chapter 3 we describe briefly a simplified version of the well-known Hodgkin-Huxley model for the neuron and try to get some insight on what isochrons can tell us about this model. Another important part of this thesis has been writing a program in language C to implement the algorithm described in chapter 2 in order to be able to apply it to the reduced Hodgkin-Huxley model. The program is described in chapter 4 and the source code is appended. In chapter 5 the results obtained with the program are discussed

Poetry as dialogue: translating Paul Celan’s Todesfuge

Traduir la poesia de Paul Celan és una qüestió de responsabilitat perquè ens fa reflexionar sobre la validesa d’uns valors —els occidentals— que no van ser capaços d’impedir el genocidi de milions d’homes a mans del nazisme. Però hom s’enfronta a uns poemes farcits de neologismes, ressonàncies i referències a les tradicions alemanya i hebrea. En aquest article discutim les dificultats que planteja la traducció de Todesfuge i confrontem diferents versions que han aparegut en català, castellà i anglès. De totes, les més destacades no són aquelles que se senten lligades a l’original, sinó les que l’agafen com a interlocutor per obrir una conversa fructífera. El traductor esdevé així el Tu abastable que reclamava Celan i resta obert al diàleg: el seu poema és una possible resposta al missatge que li arriba tancat dins d’una ampolla i que rescata de l’oblit.Translating Paul Celan’s poetry is a matter of responsibility because it makes us reflect on the validity of western principles, which after all could not prevent the genocide of millions of men under the Nazi rule. But the translator has to deal with poems full of neologisms, resonances and references to German and Hebrew traditions. In this article we discuss the difficulties that emerge when translating Todesfuge and compare some versions in Catalan, Spanish and English, the most outstanding ones being those that do not seem to be bound by the original, but rather take it as an interlocutor to open a fruitful conversation with. The translator thus becomes the addressable Thou that Celan demanded for his poems and remains ready for the dialogue. Their poem is a possible response to the message in a bottle that they receive and rescue from oblivion

Poesia i diàleg : les traduccions de Todesfuge, de Paul Celan

Traduir la poesia de Paul Celan és una qüestió de responsabilitat perquè ens fa reflexionar sobre la validesa d'uns valors -els occidentals- que no van ser capaços d'impedir el genocidi de milions d'homes a mans del nazisme. Però hom s'enfronta a uns poemes farcits de neologismes, ressonàncies i referències a les tradicions alemanya i hebrea. En aquest article discutim les dificultats que planteja la traducció de Todesfuge i confrontem diferents versions que han aparegut en català, castellà i anglès. De totes, les més destacades no són aquelles que se senten lligades a l'original, sinó les que l'agafen com a interlocutor per obrir una conversa fructífera. El traductor esdevé així el Tu abastable que reclamava Celan i resta obert al diàleg: el seu poema és una possible resposta al missatge que li arriba tancat dins d'una ampolla i que rescata de l'oblit.Translating Paul Celan's poetry is a matter of responsibility because it makes us reflect on the validity of western principles, which after all could not prevent the genocide of millions of men under the Nazi rule. But the translator has to deal with poems full of neologisms, resonances and references to German and Hebrew traditions. In this article we discuss the difficulties that emerge when translating Todesfuge and compare some versions in Catalan, Spanish and English, the most outstanding ones being those that do not seem to be bound by the original, but rather take it as an interlocutor to open a fruitful conversation with. The translator thus becomes the addressable Thou that Celan demanded for his poems and remains ready for the dialogue. Their poem is a possible response to the message in a bottle that they receive and rescue from oblivion

Assessing the coupling between local neural activity and global connectivity fluctuations: Application to human intracranial electroencephalography during a cognitive task

Cognitive-relevant information is processed by different brain areas that cooperate to eventually produce a response. The relationship between local activity and global brain states during such processes, however, remains for the most part unexplored. To address this question, we designed a simple face-recognition task performed in patients with drug-resistant epilepsy and monitored with intracranial electroencephalography (EEG). Based on our observations, we developed a novel analytical framework (named “local–global” framework) to statistically correlate the brain activity in every recorded gray-matter region with the widespread connectivity fluctuations as proxy to identify concurrent local activations and global brain phenomena that may plausibly reflect a common functional network during cognition. The application of the local–global framework to the data from three subjects showed that similar connectivity fluctuations found across patients were mainly coupled to the local activity of brain areas involved in face information processing. In particular, our findings provide preliminary evidence that the reported global measures might be a novel signature of functional brain activity reorganization when a stimulus is processed in a task context regardless of the specific recorded areasPeer ReviewedPostprint (published version

Time to blood culture positivity as a predictor of clinical outcomes and severity in adults with bacteremic pneumococcal pneumonia

Objectives: We aimed to investigate the association between the time to positivity of blood culture (TTP) with clinical outcome and severity of pneumococcal bacteremic pneumonia. Methods: Prospective observational study carried out in 278 hospitalized adult CAP patients with positive blood culture for Streptococcus pneumonia (2003-2015). Results: A total of 278 cases of bacteremic pneumococcal pneumonia were analyzed, median age 62 (46; 79) years. Fifty-one percent of the cases had PSI IV-V. Twenty-one (8%) died within 30-days after admission. The analysis of the TTP showed that the first quartile of the TTP (9.2h) was the best cut-off for differentiating 2 groups of patients at risk, early (TTP <9.2 h) and late (TTP ≥9.2 h) detection groups (AUC 0.66 [95% CI 0.53 to 0.79]). Early TTP was associated with a statistically significant risk of invasive mechanical ventilation (18% vs. 6%, p = 0.007), longer length of hospital stay (12 days vs. 8 days, p<0.001), higher in-hospital mortality (15% vs. 4%, p = 0.010), and 30-day mortality (15% vs. 5%, p = 0.018). After adjustment for potential confounders, regression analyses revealed early TTP as independently associated with high risk of invasive mechanical ventilation (OR 4.60, 95% CI 1.63 to 13.03), longer length of hospital stay (β 5.20, 95% CI 1.81 to 8.52), higher in-hospital mortality (OR 5.35, 95% CI 1.55 to 18.53), and a trend to higher 30-day mortality (OR 2.47, 95% CI 0.85 to 7.21) to be a contributing factor. Conclusion: Our results demonstrate that TTP is an easy to obtain surrogate marker of the severity of pneumococcal pneumonia and a good predictor of its outcome

Relationship among Streptococcus gallolyticus Subsp. gallolyticus, Enterococcus faecalis and Colorectal Neoplasms in Recurrent Endocarditis: A Historical Case Series.

Objectives: The role of colorectal neoplasms (CRN) as a common potential source of recurrent Streptococcus gallolyticus subsp. gallolyticus (SGG) and Enterococcus faecalis (EF) endocarditis remains unstudied. We aimed to investigate what proportion of episodes of recurrent endocarditis are caused by a succession of SGG and EF, or vice versa, and to assess the role of a colonic source in such recurrent episodes. Methods: we conducted a retrospective analysis of two prospective endocarditis cohorts (1979-2019) from two Spanish hospitals, providing descriptive analyses of the major features of the endocarditis episodes, colonoscopy findings, and histologic results. Results: among 1552 IE episodes, 204 (13.1%) were caused by EF and 197 (12.7%) by SGG, respectively. There were 155 episodes (10%) of recurrent IE, 20 of which (12.9%) were due to a succession of SGG/EF IE in 10 patients (the first episode caused by SGG in eight cases, and by EF in two cases). The median follow-up was 86 (interquartile range 34-156) months. In 8/10 initial episodes, the causative microorganism was SGG, and all patients were diagnosed with CRN either during the initial episode or during follow-up. During the second episode of IE or follow-up, colonoscopies revealed CRN in six patients. Conclusions: There seems to be an association between SGG and EF in recurrent endocarditis that warrants further investigation. Our findings reinforce the need for systematically performing colonoscopy in the event of endocarditis caused by both microorganisms

Adopting a High-Polyphenolic Diet Is Associated with an Improved Glucose Profile: Prospective Analysis within the PREDIMED-Plus Trial

Previous studies suggested that dietary polyphenols could reduce the incidence and complications of type-2 diabetes (T2D); although the evidence is still limited and inconsistent. This work analyzes whether changing to a diet with a higher polyphenolic content is associated with an improved glucose profile. At baseline, and at 1 year of follow-up visits, 5921 participants (mean age 65.0 ± 4.9, 48.2% women) who had overweight/obesity and metabolic syndrome filled out a validated 143-item semi-quantitative food frequency questionnaire (FFQ), from which polyphenol intakes were calculated. Energy-adjusted total polyphenols and subclasses were categorized in tertiles of changes. Linear mixed-effect models with random intercepts (the recruitment centers) were used to assess associations between changes in polyphenol subclasses intake and 1-year plasma glucose or glycosylated hemoglobin (HbA1c) levels. Increments in total polyphenol intake and some classes were inversely associated with better glucose levels and HbA1c after one year of follow-up. These associations were modified when the analyses were run considering diabetes status separately. To our knowledge, this is the first study to assess the relationship between changes in the intake of all polyphenolic groups and T2D-related parameters in a senior population with T2D or at high-risk of developing T2

Role of age and comorbidities in mortality of patients with infective endocarditis

[Purpose]: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. [Methods]: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups:<65 years,65 to 80 years,and ≥ 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. [Results]: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 ≥ 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients ≥80 years who underwent surgery were significantly lower compared with other age groups (14.3%,65 years; 20.5%,65-79 years; 31.3%,≥80 years). In-hospital mortality was lower in the <65-year group (20.3%,<65 years;30.1%,65-79 years;34.7%,≥80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%,≥80 years; p = 0.003).Independent predictors of mortality were age ≥ 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI ≥ 3 (HR:1.62; 95% CI:1.39–1.88),and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared,the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. [Conclusion]: There were no differences in the clinical presentation of IE between the groups. Age ≥ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group