Bootstrap signal processing: doing the impossible?

Classical signal processing techniques are developed under prior statistical knowledge of the kind of data we are processing. Unfortunately, one does not know too much about reality in practice, therefore inferring information about the statistical behaviour of our data is needed in addition of processing. To properly infer information about the statistics, one may need more than one realization of the experiment, although this is not possible in some real-life environments, as one may have just a single realization of the random process or low amount of available samples. If one would like to tackle both issues at once using classical signal processing approaches, it may lead to an almost impossible problem. This is where Bootstrap statistical inference shines, which suits perfectly this kind of problems. Moreover, we want to fuse all available data, which comes from different sources, to improve our knowledge of the working environment and eventual accuracy in further operations, such as estimating some parameter. However, there is a risk of fusing too much corrupted data without taking into account how contaminated a data set is, so the integrity of the final estimation gets compromised. We will still consider small amount of data available to tackle this issue. In reponse to the mentioned problems, the purpose of this project is to explore and analyze the potentials of the Bootstrap techniques. In particular, we will focus on the issues of data integrity and getting benefits from data redundancy in Precise Point Positioning receivers, whose context suits perfectly this kind of framework.Las técnicas clásicas de procesamiento de señales se desarrollan a partir de conocimiento a priori de los datos que procesamos. Desgraciadamente, en la práctica uno puede desconocer este conocimiento a priori, entonces, tenemos la necesidad de inferir información del comportamiento estadístico de los datos, además del propio procesamiento. Para inferir de manera precisa, es necesaria más de una realización del experimento, pero es posible que el entorno de estudio no nos lo permita o haya datos insuficientes. Si se intentase resolver este problema usando técnicas clásicas, uno es podría encontrar un problema casi imposible. Aquí es donde las técnicas Bootstrap brillan, puesto que se adaptan muy bien a este tipo de problemas. Además del problema mencionado, también queremos fusionar todas los posibles fuentes de información, para mejorar el conocimiento que disponemos del medio de estudio y la eventual precisión en próximas operaciones, como estimar un parámetro dado. Por el contrario, hay un riesgo de fusionar demasiados datos corruptos, entonces la integridad de la estimación final se vería comprometida. Como respuesta de los problemas mencionados, el objetivo de este proyecto es el estudio de las técnicas Bootstrap en entornos que se adapten bien a los problemas mencionados.Les tècniques clàssiques de processament de senyal es desenvolupen a partir de coneixement a priori de les dades que processem. Malauradament, a la pràctica un pot desconèixer aquest coneixement, aleshores, hi ha la necessitat d'inferir informació del comportament estadístic de les dades, a més del propi processament. Per inferir de manera acurada, és necessària més d'una realització de l'experiment, però és possible que l'entorn d'estudi no ens ho permeti o hi hagi dades insuficients. Si s'intentés resoldre aquest problema fent servir tècniques clàssiques, un es podria trobar un problema gairebé impossible. Aquí és on les tècniques Bootstrap brillen, ja que s'adapten molt be a aquest tipus de problemes. A més del problema esmentat, també volem fusionar totes les possibles fonts d'informació, per millorar el coneixement que disposem del medi d'estudi i l'eventual precisió en pròximes operacions, com estimar un paràmetre donat. Per contra, hi ha un risc de fusionar masses dades corruptes, llavors la integritat de l'estimació final es veuria compromesa. Com a resposta dels problemes esmentats, l'objectiu d'aquest projecte és l'estudi de les tècniques Bootstrap en entorns que s'adaptin bé als problemes esmentats

Contributions to anomaly detection and correction in co-evolving data streams via subspace learning

During decades, estimation and detection tasks in many Signal Processing and Communications applications have been significantly improved by using subspace and component-based techniques. More recently, subspace methods have been adopted in many hot topics such as Machine Learning, Data Analytics or smart MIMO communications, in order to have a geometric interpretation of the problem. In that way, the Subspace-based algorithms often arise new approaches for already-explored problems, while offering the valuable advantage of giving interpretability to the procedures and solutions. On the other hand, in those recent hot topics, one may also find applications where the detection of unwanted or out-of-the-model artifacts and outliers is crucial. To this extend, we were previously working in the domain of GNSS PPP, detecting phase ambiguities, where we found motivation into the development of novel solutions for this application. After considering the applications and advantages of subspace-based approaches, this work will be focused on the exploration and extension of the ideas of subspace learning in the context of anomaly detection, where we show promising and original results in the areas of anomaly detection and subspace-based anomaly detection, in the form of two new algorithms: the Dual Ascent for Sparse Anomaly Detection and the Subspace-based Dual Ascent for Anomaly Detection and Tracking

Sparse-aware approach for covariance conversion in FDD systems

This paper proposes a practical way to solve the Uplink-Downlink Covariance Conversion (UDCC) problem in a Frequency Division Duplex (FDD) communication system. The UDCC problem consists in the estimation of the Downlink (DL) spatial covariance matrix from the prior knowledge of the Uplink (UL) spatial covariance matrix without the need of a feedback transmission from the User Equipment (UE) to the Base Station (BS). Estimating the DL sample spatial covariance matrix is unfeasible in current massive Multiple-Input Multiple-Output (MIMO) deployments in frequency selective or fast fading channels due to the required large training overhead. Our method is based on the application of sparse filtering ideas to the estimation of a quantized version of the so-called Angular Power Spectrum (APS), being the common factor between the UL and DL spatial channel covariance matrices.This work has been supported by the Spanish Ministry of Science and Innovation through project RODIN (PID2019-105717RB-C22 / AEI / 10.13039/501100011033) and by the Catalan Government (AGAUR) under grant 2017 SGR 578.Peer ReviewedPostprint (author's final draft

Data driven joint sensor fusion and regression based on geometric mean squared error

This paper explores the problem of estimating a temporal series measured from multiple independent sensors with unequal and stationary measurement errors with unknown variances. By formulating the data fusion problem as a joint Maximum Likelihood estimation of sensor covariances and a fusion rule, a batch data driven method is derived involving a residual covariance determinant minimization of a diagonal matrix. It is shown that yielding useful learning from data with good generalization properties in the joint regression and fusion approach requires the assumption of some structure on the sensor noises and/or on the temporal series to be estimated. An efficient data driven algorithm is proposed to obtain the best linear sensor combiner, whose performance is numerically analyzed and compared with the Cramer-Rao Lower Bound of the estimated parameters.This work has been supported by the Spanish Ministry of Science and Innovation through project RODIN (PID2019-105717RB-C22 / AEI / 10.13039/501100011033) and by the Catalan Government (AGAUR) under grant 2017 SGR 578.Peer ReviewedPostprint (author's final draft

The Burden of Hidradenitis Suppurativa Signs and Symptoms in Quality of Life: Systematic Review and Meta-Analysis

Hidradenitis suppurativa (HS) is a chronic, recurrent and debilitating inflammatory skin disease of the hair follicle that usually presents as painful, deep-seated inflamed lesions in the apocrine gland-bearing areas of the body. HS patients suffer from uncomfortable signs and symptoms, such as pain, pruritus, malodour and suppuration, which may impair patients’ quality of life (QoL). Although HS patients frequently experience these signs and symptoms, they are only occasionally assessed by clinicians and, unexpectedly, the scientific evidence available is limited and heterogeneous. The aim of this study is to summarize the evidence regarding the impact of HS signs and symptoms on QoL to serve as a basis for future research and help clinicians to consider them in the daily care of HS patients. A systematic review and meta-analysis were conducted following PRISMA Guidelines. The following search algorithm was used: (hidradenitis or “acne inversa”) and (pain or itch or odour or malodour or suppuration or oozing or drainage) and (“quality of life”). The literature search identified 836 references, 17 of them met the eligible criteria and were included for analysis, representing 4929 HS patients. Mean age of the participants was 36.28 years and there was a predominance of female sex among study participants. The BMI of the population was in the range of over-weight and about two out five patients were active smokers. Studies included patients with mild to moderate HS, with a mean disease duration of 13.69 years. The HS signs and symptoms assessed were pain, pruritus, malodour and suppuration. Overall, the higher intensity of a sign or symptom correlated with poorer general QoL or specific QoL dimensions including sexual distress, anxiety, depression and sleep. The most frequently employed tool to assess QoL was the Dermatology Life Quality Index (DLQI). DLQI was used in 52.9% of the studies (9/17) with a mean value of 10.70 (2.16 SD). The scores employed to assess signs and symptoms severity were subjective and varied between studies, being the numerical rating scale (NRS) for each of the most used symptoms. The mean NRS value for pain was 3.99 and the mean NRS for pruritus was 4.99. In conclusion, we have summarized, categorized and analyzed the scientific evidence regarding signs and symptoms in HS patients and their impairment in QoL. Their assessment should be thorough and included during routine evaluation of HS patients to motivate therapeutic modifications and increase patients’ health

Epidermal Barrier Function and Skin Homeostasis in Atopic Dermatitis: The Impact of Age

We would like to thank all the individuals who generously shared their time to participate in this research. The results of this study are part of the PhD work of Trinidad Montero-Vilchez.Skin is damaged in atopic dermatitis (AD) patients. Age is also believed to have a negative effect on epidermal barrier function. The aim of this study was to investigate skin barrier function changes with age in AD patients. A cross-sectional study was conducted including 162 participants, 81 AD patients and 81 healthy volunteers. Skin barrier function parameters, such as transepidermal water loss (TEWL), erythema, temperature, stratum corneum hydration (SCH), pH, and elasticity, were evaluated. Healthy volunteers were evaluated on the volar forearm. AD patients were measured on two regions: on an eczematous lesion on the volar forearm and on a non-involved area 5 cm from the affected area. TEWL was lower on healthy skin than uninvolved AD skin (9.98 vs. 25.51 g center dot m(-2)center dot h(-1), p < 0.001) and AD eczematous lesions (9.98 vs. 28.38 g center dot m(-2)center dot h(-1), p < 0.001). SCH was lower on AD eczematous lesions than uninvolved AD skin (24.23 vs. 39.36 AU, p < 0.001) and healthy skin (24.23 vs. 44.36 AU, p < 0.001). Elasticity was lower on AD eczematous lesions than uninvolved AD skin (0.69 vs. 0.74, p = 0.038) and healthy skin (0.69 vs. 0.77, p = 0.014). A negative correlation was found between age and elasticity in all the population (r = -0.383, p < 0.001). This correlation was stronger in AD patients (r = -0.494, p < 0.001) than in controls (r = -0.266, p = 0.092). After conducting a linear regression model in AD patients adjusted by age, sex, and SCORing Atopic Dermatitis (SCORAD), it was found that elasticity was impaired by an increasing age (beta = -0.004, p < 0.001) and a higher SCORAD (beta = -0.003, p < 0.001). The skin barrier function is impaired by age and AD, reflected mainly in poor elasticity values in older AD patients

Use of mesh windbreaks for soil erosion in olive groves in southeastern Spain

We used windbreak nets to reduce erosion and sediment transport in a semiarid area. A 13x30thread·cm-2 and 39% mesh net facing the wind increased average erosion reduction up to 72% at a height of 0.4 m in recently tilled olive groves. The use of sonic anemometry techniques for identifying wind movement patterns has rarely been exploited for improving field studies, and much less for windbreaks. Sample components collected in traps placed at different heights and distances from the windbreak were analyzed. A Principal Components Analysis was carried out analyzing the combined effect of height and windbreak distance on variables associated with the first two components. Component C1 identified the height at which data were obtained, while Component C2 identified windbreak distance from the sampling point. The effectiveness of this system is shown by the reduction in weight of material caught in traps, and is a cheap and reusable tool applicable after tilling

Multiphase CT Angiography Improves Prediction of Intracerebral Hemorrhage Expansion

Angiography; Intracerebral hemorrhage; PredictionAngiografía; Hemorragia intracerebral; PredicciónAngiografia; Hemorràgia intracerebral; PrediccióPurpose To determine the prevalence of the spot sign and the accuracy of using the spot sign to predict intracerebral hemorrhage (ICH) expansion with standardized multiphase computed tomographic (CT) angiography. Materials and Methods This prospective observational cohort study included 123 consecutive patients with acute ICH (onset 33% or >6 mL) at 24 hours. Associations between the presence of the spot sign and substantial hematoma expansion were assessed by using the Pearson χ2 test. Results The later the phase of CT angiography, the higher the frequency of the spot sign. The spot sign was seen in 29.3% of patients in phase 1, 43.1% of patients in phase 2, and 46.3% of patients in phase 3 (P B > C > D > no spot sign (P = .002). Conclusion Multiphase CT angiography can help differentiate among different forms of spot sign presentation and can help stratify patients at risk for hematoma expansion. The more arterial the spot sign pattern, the greater the frequency and extent of expansion

Concentración de vitamina D en niños diabéticos de tipo 1. Asociación con el control glucémico y el metabolismo óseo y lipídico

Introducción: debido a que la vitamina D juega un papel primordial en la regulación de la secreción de insulina y su déficit parece conferir un mayor riesgo de desarrollar diabetes mellitus, se ha pretendido analizar la prevalencia del déficit de vitamina D en nuestra población de niños diabéticos de tipo 1 y si se relaciona con un peor control de la enfermedad, así como con el metabolismo lipídico y óseo. Material y métodos: se trata de un estudio retrospectivo en el cual se disponía de los datos clínicos y analíticos de 124 niños diabéticos de tipo 1, controlados en la Unidad de Diabetes Pediátrica de nuestro hospital. Resultados: la concentración mediana de vitamina D del total de la muestra fue de 25,41 (7,43) ng/mL, siendo más elevada en el sexo masculino que en el femenino (p = 0,006). Un 43,55 % de los niños presentaron buen control metabólico, con hemoglobina glicosilada inferior al 7,5 %, siendo la concentración de glucosa y la de colesterol ligeramente más bajas, y la de fosfatasa alcalina ósea más elevada, cuando la concentración de vitamina D era ≥ 20 ng/ml. Conclusiones: no hemos encontrado diferencias significativas en el control metabólico de los niños con concentración suficiente o insuficiente de vitamina D. Los niños del estudio tenían concentraciones de vitamina D muy parecidas a las de un estudio similar en niños sanos, así como un buen control metabólico de su diabetes, siendo su perfil óseo y lipídico más favorable cuando presentaban buen control metabólico

Thrombectomy within 8 hours after symptom onset in ischemic stroke

BACKGROUND: We aimed to assess the safety and efficacy of thrombectomy for the treatment of stroke in a trial embedded within a population-based stroke reperfusion registry. METHODS: During a 2-year period at four centers in Catalonia, Spain, we randomly assigned 206 patients who could be treated within 8 hours after the onset of symptoms of acute ischemic stroke to receive either medical therapy (including intravenous alteplase when eligible) and endovascular therapy with the Solitaire stent retriever (thrombectomy group) or medical therapy alone (control group). All patients had confirmed proximal anterior circulation occlusion and the absence of a large infarct on neuroimaging. In all study patients, the use of alteplase either did not achieve revascularization or was contraindicated. The primary outcome was the severity of global disability at 90 days, as measured on the modified Rankin scale (ranging from 0 [no symptoms] to 6 [death]). Although the maximum planned sample size was 690, enrollment was halted early because of loss of equipoise after positive results for thrombectomy were reported from other similar trials. RESULTS Thrombectomy reduced the severity of disability over the range of the modified Rankin scale (adjusted odds ratio for improvement of 1 point, 1.7; 95% confidence interval [CI], 1.05 to 2.8) and led to higher rates of functional independence (a score of 0 to 2) at 90 days (43.7% vs. 28.2%; adjusted odds ratio, 2.1; 95% CI, 1.1 to 4.0). At 90 days, the rates of symptomatic intracranial hemorrhage were 1.9% in both the thrombectomy group and the control group (P = 1.00), and rates of death were 18.4% and 15.5%, respectively (P = 0.60). Registry data indicated that only eight patients who met the eligibility criteria were treated outside the trial at participating hospitals. CONCLUSIONS: Among patients with anterior circulation stroke who could be treated within 8 hours after symptom onset, stent retriever thrombectomy reduced the severity of post-stroke disability and increased the rate of functional independence