In this work, some new results to exploit the recurrence properties of quasiperiodic dynamical systems are presented by means of a two dimensional visualization technique, Recurrence Plots(RPs). Quasiperiodicity is the simplest form of dynamics exhibiting nontrivial recurrences, which are common in many nonlinear systems. The concept of recurrence was introduced to study the restricted three body problem and it is very useful for the characterization of nonlinear systems. I have analyzed in detail the recurrence patterns of systems with quasiperiodic dynamics both analytically and numerically. Based on a theoretical analysis, I have proposed a new procedure to distinguish quasiperiodic dynamics from chaos. This algorithm is particular useful in the analysis of short time series. Furthermore, this approach demonstrates to be efficient in recognizing regular and chaotic trajectories of dynamical systems with mixed phase space. Regarding the application to real situations, I have shown the capability and validity of this method by analyzing time series from fluid experiments. / In dieser Arbeit stelle ich neue Resultate vor, welche zeigen, wie man Rekurrenzeigenschaften quasiperiodischer, dynamischer Systeme für eine Datenanalyse ausnutzen kann. Die vorgestellten Algorithmen basieren auf einer zweidimensionalen Darstellungsmethode, den Rekurrenz-Darstellungen. Quasiperiodizität ist die einfachste Dynamik, die nicht-triviale Rekurrenzen zeigt und tritt häufig in nichtlinearen Systemen auf. Nicht-triviale Rekurrenzen wurden im Zusammenhang mit dem eingeschränkten Dreikörper-problem eingeführt. In dieser Arbeit, habe ich mehrere Systeme mit quasiperiodischem Verhalten analytisch untersucht. Die erhaltenen Ergebnisse helfen die Wiederkehreigenschaften dieser Systeme im Detail zu verstehen. Basierend auf den analytischen Resultaten, schlage ich einen neuen Algorithmus vor, mit dessen Hilfe selbst in kurzen Zeitreihen zwischen chaotischem und quasiperiodischem Verhalten unterschieden werden kann. Die vorgeschlagene Methode ist besonders effizient zur Unterscheidung regulärer und chaotischer Trajektorien mischender dynamischer Systeme.Die praktische Anwendbarkeit der vorgeschlagenen Analyseverfahren auf Messdaten, habe ich gezeigt, indem ich erfolgreich Zeitreihen aus fluid-dynamischen Experimenten untersucht habe.

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Hepatitis C virus recurrence (which is defined by detection of HCV RNA in serum) in post-transplanted liver is universal but the progression of infection remains unpredictable, varying from case to case. It has been estimated that 75%-80% of the HCV recurrence patients will suffer chronic hepatitis C infection and up to a third of them will progress into the development of fibrosis and cirrhosis within 5 years post-transplantation. Therefore, finding ways to predict early on the progression of fibrosis can contribute to better prognoses. Recent literatures have mentioned that the hepatitis C virus relies on the host microRNA-122 (miR-122) for assistance in replication of the viral genome in hepatocytes. Experimental depletion of miRNA-122 in the cell line Huh 7 has shown up to an 80% decrease in HCV whereas an increase of miRNA-122 has shown an increase of HCV. Since miRNAs are known to have numerous indirect roles by the binding of the target messenger RNAs (mRNAs) and repressing the expression of their proteins, we hypothesized that the elucidation of associations between miRNA-122 and the histological severity in HCV recurrence post-liver transplantation might serve as a biomarker in predicting the outcome of HCV recurrence severity in patients. We also evaluated the expression levels of BCAP31 (a predicted target of miRNA-122), and CD4 (T cell surface molecules involved in immune response) among the HCV recurrence severity groups. RNA samples were isolated from FFPE liver samples from patients with HCV recurrence post-transplantation, and Reverse Transcription and TaqMan Real-Time PCR were carried out for qualitative analysis. We did not see any association between the levels of miRNA-122 expression and severity of HCV recurrence, but we did find a positive correlation between the miRNA-122 expression and the HCV viral load in Group 3 (Severe) at time of HCV recurrence, which supports previous studies of the role of miRNA-122 in HCV replication. We did not find any associations between the expression of BCAP31 and the severity of HCV recurrence but we did discovery an inverse relationship between miRNA-122 and BCAP31 in Group 3 (Severe) at time of HCV recurrence, confirming our assumption of miRNA:mRNA interaction. Also, we did find CD4 expression being statistically significant between Group 1 (Benign) versus Group 3 (Severe), which may support the hypothesis that strong, adequate CD4+ T-cell response is associated with better outcome post-liver transplantation.

Hepatitis C virus (HCV) is the major cause of chronic hepatitis worldwide and a leading cause for liver transplant. Unfortunately, graft HCV infection is a universal phenomenon despite of pre-transplant prophylactic strategies. Acute HCV infection and innate immune responses elicit an inflammatory scenario that triggers the recruitment of adaptive immune response cells. Of those chronically infected, 30% experience accelerated fibrosis with concomitant cirrhosis development within 5 years post-LT and require re-transplant. With many patients responding unfavorably to antivirals and ineffective vaccines, much attention is now placed on T cell immunity in controlling HCV infection. This study represents a retrospective analysis that examined the association of T cells with respect to liver fibrosis severity progression in a prospective cohort of biopsy samples taken from 27 patients at the time of HCV recurrence disease diagnosis post-LT. For those patients, the fibrosis progression was scored 36 months post-LT by Metavir scoring system. Liver biopsies were classified based on fibrosis severity as Mild (G1; n = 12), Moderate (G2; n = 6), and Severe (G3; n = 9). Additionally, an independent set of liver biopsy samples, taken according to fibrosis severity progression, was classified (G1; n =3, G3; n = 4) and used as a validation set for CD4 gene expression. Real time PCR was performed to study the expression of immune-related genes using the Taqman® probe system. From the results analysis, the CD4 T cell marker encoding gene was down-regulated (2.9-fold) in G3 with respect to G1; although, only borderline significant (p = 0.052). This suggests an inverse relationship of CD4+T cell related-genes expression with respect to worse fibrosis progression in HCV recurrence diagnosed recipients. The validation samples showed a similar trend (1.8 fold decrease in G3 with respect to G1), although not significant. This may be due to impaired T cell function resulting from T cell exhaustion, poor dendritic cell priming and activation, or the use of immunosuppressant drugs. To conclude, CD4 could be a potential biomarker to help in identifying HCV recurrent patients with a high risk of fibrosis development soon after LT.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / OBJECTIVE: An estimated 20-30% of patients with primary Clostridium difficile infection (CDI) develop recurrent CDI (rCDI) within 2 weeks of completion of therapy. While the actual mechanism of recurrence remains unknown, a variety of risk factors have been suggested and studied. The aim of this systematic review and meta-analysis was to evaluate current evidence on the risk factors for rCDI. DESIGN: We searched MEDLINE and 5 other databases for subject headings and text related to rCDI. All studies investigating risk factors of rCDI in a multivariate model were eligible. Information on study design, patient population, and assessed risk factors were collected. Data were combined using a random-effects model and pooled relative risk ratios (RRs) were calculated. RESULTS: A total of 33 studies (n=18,530) met the inclusion criteria. The most frequent independent risk factors associated with rCDI were age≥65 years (risk ratio [RR], 1.63; 95% confidence interval [CI], 1.24-2.14; P=.0005), additional antibiotics during follow-up (RR, 1.76; 95% CI, 1.52-2.05; P<.00001), use of proton-pump inhibitors (PPIs) (RR, 1.58; 95% CI, 1.13-2.21; P=.008), and renal insufficiency (RR, 1.59; 95% CI, 1.14-2.23; P=.007). The risk was also greater in patients previously on fluoroquinolones (RR, 1.42; 95% CI, 1.28-1.57; P<.00001). CONCLUSIONS: Multiple risk factors are associated with the development of rCDI. Identification of modifiable risk factors and judicious use of antibiotics and PPI can play an important role in the prevention of rCDI.

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In this report we give an overview of some of the major results concerning the multiplicities of linear recurrence sequences. We first investigate binary recurrence sequences where we exhibit a result due to Beukers and a result due to Brindza, Pint&eacute;r and Schmidt. We then investigate ternary recurrences and exhibit a result due to Beukers building on work of Beukers and Tijdeman. The last two chapters deal with a very important result due to Schmidt in which we bound the zero-multiplicity of a linear recurrence sequence of order <em>t</em> by a function involving <em>t</em> alone. Moreover we improve on Schmidt's bound by making some minor changes to his argument.

In this report we give an overview of some of the major results concerning the multiplicities of linear recurrence sequences. We first investigate binary recurrence sequences where we exhibit a result due to Beukers and a result due to Brindza, Pint&eacute;r and Schmidt. We then investigate ternary recurrences and exhibit a result due to Beukers building on work of Beukers and Tijdeman. The last two chapters deal with a very important result due to Schmidt in which we bound the zero-multiplicity of a linear recurrence sequence of order <em>t</em> by a function involving <em>t</em> alone. Moreover we improve on Schmidt's bound by making some minor changes to his argument.

The purpose of this cross-sectional, secondary data analysis was to explore, non-modifiable (stable) trait factors and modifiable (transient) state factors associated with fear of recurrence (FOR) in breast cancer survivors. Antecedent trait factors included demographic, clinical, social/behavioral factors, postulated mediator state factors included pain, fatigue, sleep disturbances, depression, state anxiety and perceived stress, and FOR was the outcome variable. The study used baseline data from an R-21 NCI funded (grant #R21CA109168) randomized control trial that examined the effects of mindfulness based stress reduction in early stage breast cancer recovery. Instruments from this study for antecedent variables (trait factors) included a Demographic and Clinical History Form, STAI; instruments used for mediator variable (state factors) included CES-D, STAI, PSS and MDASI subscales for pain and fatigue, sleep; the instruments used for the outcome variable FOR - CARS overall fear and nature of worry. The study sample included 82 women within 18 months post breast cancer treatment (stage 0, I, II, III). The Theoretical Model for psychosocial nursing research was used as a heuristic framework to examine the associations between trait factors and state factors and their mediating effects on FOR. Aim 1 explored the relationship between the antecedent (trait) variables associated with FOR (CARS overall fear and CARS nature of worry) using Pearson's and Spearman's correlations and analysis of variance (ANOVA). The findings revealed a negative association between age and FOR, CARS overall fear (r = -.236, p = .033) and FOR, CARS nature of worry (r = -.269, p = .015). Trait anxiety was positively associated with FOR, CARS overall fear (r = .433, p = .000) and FOR, CARS nature of worry (r = .358, p < 0.001). Race/ethnicity, education, marital status, employment, exercise, cancer stage, cancer treatment, exercise, smoking, drinking, hormone use and family history of breast cancer were not associated with FOR. Aim 2 explored the relationship between postulated mediator (state) variables, such as pain, fatigue, sleep disturbances, state anxiety, depression, perceived stress associated with FOR (CARS overall fear and CARS nature of worry) using Pearson's correlations. Findings revealed that depression (r = .347, p = .001), state anxiety (r = .467, p < 0.001), perceived stress (r = .365, p = .001) were positively associated with FOR, CARS overall fear of recurrence, and that pain (r = .220, p = .047), fatigue (r = .247, p = .025), state anxiety (r = .369, p = .001), and perceived stress (r = .410, p < 0.001) were positively associated with FOR, CARS nature of worry. Aim 3 used a mediation analysis (bootstrapping method) to examine the indirect effects of the statistically significant modifiable mediator state factors on the statistically significant antecedent trait factors and FOR (CARS overall fear and CARS nature of worry). With trait anxiety as the antecedent variable, state anxiety was indirectly associated (a mediating variable) with FOR, CARS overall fear (β = .1381, 95% CI = .0053 - .3050, p = .0299). Similarly, with a composite age/trait anxiety antecedent variable, state anxiety was indirectly associated (a mediating variable) with FOR, CARS overall fear (β = .5579, 95% CI = .1201 - 1.1669, p = .0157). Perceived stress and depression did not mediate the relationship between age and trait anxiety and concerns about recurrence overall fear. With trait anxiety as the antecedent variable, perceived stress was indirectly associated (a mediating variable) with FOR, CARS nature of worry (β = .5474, 95% CI = .0178 - 1.3298, p = .0294). Similarly, a composite age/trait anxiety antecedent variable, perceived stress was indirectly associated (a mediating variable) with FOR, CARS nature of worry (β = 2.0375, 95% CI = .1136 - 4.5976, p = .0495). Pain, fatigue and state anxiety did not mediate the relationship between age and trait anxiety and FOR nature of worry. This study suggests that breast cancer survivors who are anxious at baseline and report a current state of anxiety or perceived stress may be at higher risk for fears of breast cancer recurrence. Understanding the individual patient characteristics such as age, history of anxiety and current status of perceived stress or anxiety and the relationship with fears of recurrence allow nurses to offer individualized interventions for patients at greatest risk for psychological distress.

Medulloblastoma (MB) is the most common malignant brain tumor affecting children. The transcription factors MYCN and SOX9 are associated with initiation, maintenance and recurrence of MB and are also connected to more aggressive tumors. In this study, a ChIP was performed to isolate DNA from genes that are transcriptionally regulated by these proteins. Identification of these target genes will reveal new potential drug targets and help us better understand the functions of MYCN and SOX9. The ChIP was not fully optimized during this project and the target genes were not sent for sequencing and identified. To study the connection between SOX9 and recurrence, cells with different levels of SOX9 were treated with drugs, after which cell viability was measured. No significant difference in resistance could be measured. Change in expression level of MYCN, SOX9 and other relevant genes after drug treatment was also studied. The results show an increase in SOX9 and HES1, suggesting that these genes are involved in tumor recurrence.