Diffeomorphic Transformations for Time Series Analysis: An Efficient Approach to Nonlinear Warping

The proliferation and ubiquity of temporal data across many disciplines has sparked interest for similarity, classification and clustering methods specifically designed to handle time series data. A core issue when dealing with time series is determining their pairwise similarity, i.e., the degree to which a given time series resembles another. Traditional distance measures such as the Euclidean are not well-suited due to the time-dependent nature of the data. Elastic metrics such as dynamic time warping (DTW) offer a promising approach, but are limited by their computational complexity, non-differentiability and sensitivity to noise and outliers. This thesis proposes novel elastic alignment methods that use parametric \& diffeomorphic warping transformations as a means of overcoming the shortcomings of DTW-based metrics. The proposed method is differentiable \& invertible, well-suited for deep learning architectures, robust to noise and outliers, computationally efficient, and is expressive and flexible enough to capture complex patterns. Furthermore, a closed-form solution was developed for the gradient of these diffeomorphic transformations, which allows an efficient search in the parameter space, leading to better solutions at convergence. Leveraging the benefits of these closed-form diffeomorphic transformations, this thesis proposes a suite of advancements that include: (a) an enhanced temporal transformer network for time series alignment and averaging, (b) a deep-learning based time series classification model to simultaneously align and classify signals with high accuracy, (c) an incremental time series clustering algorithm that is warping-invariant, scalable and can operate under limited computational and time resources, and finally, (d) a normalizing flow model that enhances the flexibility of affine transformations in coupling and autoregressive layers.Comment: PhD Thesis, defended at the University of Navarra on July 17, 2023. 277 pages, 8 chapters, 1 appendi

High-temperature infrared emissivity of materials for alternative energy applications

xxv, 171 p.La emisividad es una propiedad termofísica que relaciona la cantidad de radiación térmica que emite un material con la radiada por un cuerpo negro. Se trata de una propiedad de gran importancia en ámbitos industriales y científicos, ya que condiciona las transferencias de calor en situaciones de alta temperatura o alto vacío. La presente tesis se divide en dos apartados fundamentales: por una parte, el desarrollo y mejora de métodos de medida de emisividad y, por otra, la aplicación de dichos métodos a la caracterización de materiales de interés industrial en el sector de las energías alternativas (solar térmica y nuclear de fusión). En primer lugar, se ha llevado a cabo una profunda revisión del aparato singular de medida de emisividad en la UPV/EHU, incluyendo mejoras instrumentales y metodológicas, así como un renovado análisis de sus fuentes de error. En segundo lugar, se han estudiado tres tipos de materiales: absorbentes solares selectivos multicapa para centrales solares térmicas de tubo, recubrimientos negros no selectivos para centrales de torre y una familia de aleaciones de vanadio para futuros reactores nucleares de fusión. El objetivo global de este trabajo es mejorar nuestro conocimiento sobre las propiedades de transferencia de calor por radiación de materiales clave para estos procesos energéticos alternativo

High-temperature infrared emissivity of materials for alternative energy applications

xxv, 171 p.La emisividad es una propiedad termofísica que relaciona la cantidad de radiación térmica que emite un material con la radiada por un cuerpo negro. Se trata de una propiedad de gran importancia en ámbitos industriales y científicos, ya que condiciona las transferencias de calor en situaciones de alta temperatura o alto vacío. La presente tesis se divide en dos apartados fundamentales: por una parte, el desarrollo y mejora de métodos de medida de emisividad y, por otra, la aplicación de dichos métodos a la caracterización de materiales de interés industrial en el sector de las energías alternativas (solar térmica y nuclear de fusión). En primer lugar, se ha llevado a cabo una profunda revisión del aparato singular de medida de emisividad en la UPV/EHU, incluyendo mejoras instrumentales y metodológicas, así como un renovado análisis de sus fuentes de error. En segundo lugar, se han estudiado tres tipos de materiales: absorbentes solares selectivos multicapa para centrales solares térmicas de tubo, recubrimientos negros no selectivos para centrales de torre y una familia de aleaciones de vanadio para futuros reactores nucleares de fusión. El objetivo global de este trabajo es mejorar nuestro conocimiento sobre las propiedades de transferencia de calor por radiación de materiales clave para estos procesos energéticos alternativo

Is Lactate an Oncometabolite? Evidence Supporting a Role for Lactate in the Regulation of Transcriptional Activity of Cancer-Related Genes in MCF7 Breast Cancer Cells.

Lactate is a ubiquitous molecule in cancer. In this exploratory study, our aim was to test the hypothesis that lactate could function as an oncometabolite by evaluating whether lactate exposure modifies the expression of oncogenes, or genes encoding transcription factors, cell division, and cell proliferation in MCF7 cells, a human breast cancer cell line. Gene transcription was compared between MCF7 cells incubated in (a) glucose/glutamine-free media (control), (b) glucose-containing media to stimulate endogenous lactate production (replicating some of the original Warburg studies), and (c) glucose-containing media supplemented with L-lactate (10 and 20 mM). We found that both endogenous, glucose-derived lactate and exogenous, lactate supplementation significantly affected the transcription of key oncogenes (MYC, RAS, and PI3KCA), transcription factors (HIF1A and E2F1), tumor suppressors (BRCA1, BRCA2) as well as cell cycle and proliferation genes involved in breast cancer (AKT1, ATM, CCND1, CDK4, CDKN1A, CDK2B) (0.001 < p < 0.05 for all genes). Our findings support the hypothesis that lactate acts as an oncometabolite in MCF7 cells. Further research is necessary on other cell lines and biopsy cultures to show generality of the findings and reveal the mechanisms by which dysregulated lactate metabolism could act as an oncometabolite in carcinogenesis

Effect of the kinetics of temperature variation on Saccharomyces cereuisiae viability and permeability

AbstractThe variation rate of the temperature increase was found to have a great effect on the viability of Saccharomyces cerevisiae subjected to heat perturbations between 25°C and 50°C. A low intensity of the increase rate of temperature could maintain an important viability of the cells (about 34% of the initial population) with regard to the corresponding viability (about 1%) observed after a sudden step change for the same final temperature level of 50°C. A cell volume reduction more important (22% of the initial volume) has been observed in cells submitted to a heat shock than for the cells which have been submitted to a slow kinetic of temperature increase (9%). Such an observation allowed to propose a relation between the membrane permeability and the kinetics of temperature variation

Survey of total mercury and arsenic content in infant cereals marketed in Spain and estimated dietary intake.

Due to the fact that infants and children are especially sensitive to mercury and arsenic 7 exposure, predominantly through diet, a strict control of the most widely consumed 8 infant foods, especially infant cereals, is of paramount importance. Levels of both total 9 mercury and arsenic in 91 different infant cereals from ten different manufacturers in 10 Spain were determined by flow injection adapted to cold vapor and hydride generation 11 atomic absorption spectrometry, respectively. Cereals were assessed in terms of the 12 different types, the predominating cereal in the formulation, the added ingredients, and 13 whether the cereal was organically or conventionally obtained. In general, the content of 14 toxic elements (median (Q1;Q3)) found in infant cereals based on conventionally obtained raw materials (n=74, Hg: 2.11 (0.42;4.58), As: 21.0 (9.4;50.9) μg·Kg-1 15 ) was 16 lower than in cereals produced by organic methods (n= 17, Hg: 5.48 (4.54;7.64), As: 96.3 (87.5;152.3) μg·Kg-1 17 ). Mercury content in infant cereals shows the higher values in 18 those formulations with ingredients susceptible to particulate contamination such as 19 gluten-free or cacao-based cereals. The highest arsenic content appears in the rice-based 20 cereals. The mercury and the inorganic arsenic dietary intakes for infants fed on the 21 infant cereals studied were assessed, taking into account the different stages of growth. 22 Organic infant cereals based on cocoa showed the highest risk intakes of mercury, very 23 close to exceeding the intake reference. Just the opposite, 95% of the organically 24 produced infant cereals and 70% of the conventional gluten-free infant cereals showed 25 an inadmissible risk of arsenic intake. Thus, it seems prudent to call for continued 26 efforts in standardizing routine quality control and in reducing arsenic levels in infant 27 cereals; in addition it is essential that relevant legislation be established and regulated 28 by EC regarding these two toxic elements

Surveillance of aflatoxin content in dairy cow feedstuff from Navarra (Spain)

Aflatoxins (B1, B2, G1 and G2) are produced by the fungi Aspergillus (A. flavus and A. parasiticus) in substrates used in cattle feed manufacturing. Aflatoxin M1 (AFM1) is a major metabolite of Aflatoxin B1 (AFB1) which may be present in milk from animals that consume contaminated feed. Levels of aflatoxins in 78 dairy cow feedstuff samples from 40 farms located in Navarra were determined by HPLC-FLD (High Performance Liquid Chromatography with fluorescence detection) and post-column derivatization. The influence of geographical location, season and type of feeding system on aflatoxin content was studied. The climatic profile of AFB1 pointed to spring as the season with the highest aflatoxin level (0.086 μg/kg), followed by winter and summer (0.075 and 0.030 μg/kg, respectively), and to a lesser degree, autumn (0.017 μg/kg). Moreover, wet and dry TMR (Total Mixed Ration) feeding systems (i.e. AFB1: 0.076 and 0.068 μg/kg; Aflatoxin G1 (AFG1): 0.050 and 0.011 μg/kg, respectively) showed a greater content of the analyzed aflatoxins in comparison with compound feed (i.e. AFB1: 0.039 μg/kg; AFG1: 0.007 μg/kg). The fact that the majority of the samples collected were based on compound feed shows that this type was preferred by most dairy farmers. The undetectable levels of aflatoxins in the organic homemade compound feedstuff are also worth mentioning. While none of the feedstuff samples contained amounts over those permitted under European legislation (5 μg/kg), the theoretical extrapolation of the carryover rate suggested in previously published experiments of AFB1 to AFM1 in secreted cow's milk predicts that only one of the feed samples studied had a positive aflatoxin level (53.4 ng/kg) higher than the legal limit for raw cow's milk

Estimation of dietary intake and content of lead and cadmium in infant cereals marketed in Spain

Lead and cadmium have become highly toxic metallic elements. There is an obvious 5 toxicological impact of these elements on infants since their intestinal absorption is 6 significantly higher than in adults, thus it is desirable to quantify lead and cadmium levels in 7 commonly consumed infant foods. Zeeman background correction, transversely heated 8 graphite furnace atomic absorption spectrometry, was used to determine both the lead and 9 cadmium content of 91 Spanish infant cereals. Cereals were assessed in terms of different 10 types, cereal predominant in formulation and whether it was obtained organically or 11 conventionally. Preliminary analysis revealed a noticeably higher content of lead and 12 cadmium (median, Q1-Q3) in organic cereals (n = 17, Pb: 26.07; 21.36-51.63; Cd: 18.52; 16.56-28.50 μg kg-1 13 ) in relation to conventional ones (n =74, Pb: 10.78; 6.43-19.33; Cd: 7.12; 4.40-11.77 μg kg-1 14 ). Three formulations exceeded European lead maximum levels. Added 15 ingredients (milk, cocoa, fruit and honey) to the cereal base provide lead enrichment. For 16 cadmium, this pattern was observed by cereal based on cocoa, but also the raw materials 17 contributed with a dilution phenomenon, decreasing the final cadmium concentration in infant 18 cereal. Apart from several organically produced cereals, lead content showed a narrow 19 variation, where gluten-free cereals provide lower cadmium content than formulations 20 containing gluten. Dietary intakes of both elements were assessed in comparison with the 21 reference intake values proposed by the EFSA Panel on Contaminants in the Food Chain. 22 Organic infant cereals based on honey and cocoa supplied the highest risk intakes of lead and 23 cadmium, respectively. In accordance with the actual state of knowledge on lead and 24 cadmium toxicity and attending to the upper limits calculated from risk intake values set by 25 EFSA, it seems prudent to call for a revision of both heavy metals content regulated by EC to set a maximum guideline values for infant cereal at 55 and 45 μg kg-1 26 , respectively