On the importance of nonlinear modeling in computer performance prediction

Computers are nonlinear dynamical systems that exhibit complex and sometimes even chaotic behavior. The models used in the computer systems community, however, are linear. This paper is an exploration of that disconnect: when linear models are adequate for predicting computer performance and when they are not. Specifically, we build linear and nonlinear models of the processor load of an Intel i7-based computer as it executes a range of different programs. We then use those models to predict the processor loads forward in time and compare those forecasts to the true continuations of the time seriesComment: Appeared in "Proceedings of the 12th International Symposium on Intelligent Data Analysis

Properties of continuous Fourier extension of the discrete cosine transform and its multidimensional generalization

A versatile method is described for the practical computation of the discrete Fourier transforms (DFT) of a continuous function $g(t)$ given by its values $g_{j}$ at the points of a uniform grid $F_{N}$ generated by conjugacy classes of elements of finite adjoint order $N$ in the fundamental region $F$ of compact semisimple Lie groups. The present implementation of the method is for the groups SU(2), when $F$ is reduced to a one-dimensional segment, and for $SU(2)\times ... \times SU(2)$ in multidimensional cases. This simplest case turns out to result in a transform known as discrete cosine transform (DCT), which is often considered to be simply a specific type of the standard DFT. Here we show that the DCT is very different from the standard DFT when the properties of the continuous extensions of these two discrete transforms from the discrete grid points $t_j; j=0,1, ... N$ to all points $t \in F$ are considered. (A) Unlike the continuous extension of the DFT, the continuous extension of (the inverse) DCT, called CEDCT, closely approximates $g(t)$ between the grid points $t_j$. (B) For increasing $N$, the derivative of CEDCT converges to the derivative of $g(t)$. And (C), for CEDCT the principle of locality is valid. Finally, we use the continuous extension of 2-dimensional DCT to illustrate its potential for interpolation, as well as for the data compression of 2D images.Comment: submitted to JMP on April 3, 2003; still waiting for the referee's Repor

Eliciting policymakers' and stakeholders' opinions to help shape health system research priorities in the Middle East and North Africa region

Evidence-informed decisions can strengthen health systems. Literature suggests that engaging policymakers and other stakeholders in research priority-setting exercises increases the likelihood of the utilization of research evidence by policymakers. To our knowledge, there has been no previous priority-setting exercise in health policy and systems research in countries of the Middle East and North Africa (MENA) region. This paper presents the results of a recent research priority-setting exercise that identified regional policy concerns and research priorities related to health financing, human resources and the non-state sector, based on stakeholders in nine low and middle income countries (LMICs) of the MENA region. The countries included in this study were Algeria, Egypt, Jordan, Lebanon, Morocco, Palestine, Syria, Tunisia and Yemen. This multi-phased study used a combination of qualitative and quantitative research techniques. The overall approach was guided by the listening priority-setting approach, adapted slightly to accommodate the context of the nine countries. The study was conducted in four key phases: preparatory work, country-specific work, data analysis and synthesis, and validation and ranking. The study identified the top five policy-relevant health systems research priorities for each of the three thematic areas for the next 3-5 years. Study findings can help inform and direct future plans to generate, disseminate and use research evidence for LMICs in the MENA region. Our study process and results could help reduce the great chasm between the policy and research worlds in the MENA region. It is hoped that funding agencies and countries will support and align financial and human resources towards addressing the research priorities that have been identifie

Observaciones a partir del registro de evaluación cardiológica pos-COVID-19

Objective: To evaluate the prevalence and characteristics of “de novo” cardiovascular findings (DNCFs) among post-COVID patients based on a basic cardiovascular diagnostic procedure. Moreover, to describe the patients’ results obtained by means of different diagnostic methods, to determine the clinical variables associated with DNCFs during the examination and, finally, to find out the diagnostic value of different data from the medical records (MRs). Materials and methods: Patients aged > 18 years who had COVID-19 either at the hospital or at home were evaluated by clinical interviews, physical examination, electrocardiogram (EKG), echocardiogram, routine lab tests and cardiac biomarkers between 30 and 120 days after discharge. A total of 246 patients (age: 52 ± 13 years; women: 48 %; mild, moderate and severe COVID-19: 37 %, 39 % and 24 %, respectively) were included in the study. Twenty-four percent of the population were asymptomatic at the time of the evaluation. In those patients who developed symptoms, dyspnea was the most frequent one (28 %). Interviews were the method with the highest index of suspicion (45 %). Physical examination, EKG, echocardiogram and biomarkers showed normal values among 61 %, 60 %, 75 % and 96 % of the patients, respectively. Results: DNCFs were found in 62 patients (25.2 %): heart rhythm disorders in 42 (17 %) and ventricular dysfunction in 20 (8 %). Five patients had coronary artery disease, six had myocarditis and two had valvular heart disease. In addition, post-COVID pulmonary embolism (PE) was detected in 10 patients, six of whom (2.4 %) had to be rehospitalized. Furthermore, in a multivariate analysis, the independent predictive variables of DNCFs were prior history of chronic obstructive pulmonary disease (COPD), QTc > 440 msec, leukocytosis and intra-COVID cardiovascular complication. MRs showed both low sensitivity and positive predictive value for DNCFs. Conclusions: Although DNCFs were observed in 25 % of the population, only 2 % were significant. According to the data collected from this diagnostic procedure and in this time frame, special attention should be paid to patients with prior history of COPD and/or cardiovascular complications during the acute stage and/or prolonged QTc interval. Post-COVID symptoms were of limited value for the diagnosis of arrhythmias or ventricular dysfunction.Objetivo: Evaluar la prevalencia y características de los hallazgos cardiológicos “de Novo” (HCDN) en pacientes pos-COVID a partir de una secuencia diagnóstica cardiológica básica; asimismo, describir los resultados obtenidos en estos pacientes conlos distintos métodos diagnósticos, detectar variables clínicas asociadas a la aparición de HCDN durante la evaluación y, por último, detectar el valor diagnóstico de distintos datos de la historia clínica (HC). Materiales y métodos: Se evaluó a pacientes >18 años que padecieron la COVID-19, internados o en su domicilio, mediante interrogatorio, examen físico, electrocardiograma (ECG), ecocardiograma (ECO), rutina de laboratorio y biomarcadores cardíacos entre los 30 y 120 días después del alta. Se incluyeron 246 pacientes (edad: 52 ± 13 años; mujeres: 48 %; COVID-19 leve [37 %], moderado [39 %], grave [24 %]). El 24 % de la población no presentaba síntomas en el momento dela evaluación; en los sintomáticos, la disnea fue lo más frecuente (28 %). El interrogatorio fue el método que reveló mayor porcentaje de sospecha (45 %). El examen físico, el ECG, el ECO y los biomarcadores fueron normales en el 60 %, 55 %, 75 % y 96 % de los pacientes, respectivamente. Resultados: Se detectaron HCDN en 62 pacientes (25,2 %): trastornos del ritmo en 42 (17 %) y disfunción ventricular en 20 (8 %). Cinco presentaron enfermedad coronaria; 6, miocarditis, y 2, valvulopatías. Además, se detectó tromboembolismopulmonar (TEP) pos-COVID en 10 pacientes, de los cuales seis (2,4 %) debieron internarse nuevamente. Asimismo, en un análisis multivariado, las variables predictoras independientes de los HCDN fueron antecedentes de enfermedad pulmonar obstructiva crónica (EPOC), intervalo QTc > 440 ms, leucocitosis y complicación cardiológica intra-COVID (CCIC). La HCmostró baja sensibilidad y valor predictivo positivo para los HCDN. Conclusiones: Aunque los HCDN se observaron en un cuarto de la población, solo fueron relevantes en el 2 %. De acuerdo con estos datos, mediante esta secuencia diagnóstica y en este lapso, el énfasis debería estar puesto en los pacientescon antecedentes de EPOC y/o complicaciones cardiológicas durante la etapa aguda y/o intervalo QTc prolongado. Los síntomas pos-COVID tuvieron un valor limitado para el diagnóstico de arritmias o disfunción ventricular

Error Resilient Speech Coding Using Sub-band Hilbert Envelopes

Frequency Domain Linear Prediction (FDLP) represents a technique for auto-regressive modelling of Hilbert envelopes of a signal. In this paper, we propose a speech coding technique that uses FDLP in Quadrature Mirror Filter (QMF) sub-bands of short segments of the speech signal (25 ms). Line Spectral Frequency parameters related to au-toregressive models and the spectral components of the residual signals are transmitted. For simulating the effects of lossy transmission channels, bit-packets are dropped randomly. In the objective and subjective quality evaluations, the proposed FDLP speech codec is judged to be more resilient to bit-packet losses compared to the state-of-the-art Adaptive Multi-Rate Wide-Band (AMR-WB) codec at 12 kbps

Gender Dimorphism in Aspartame-Induced Impairment of Spatial Cognition and Insulin Sensitivity

Previous studies have linked aspartame consumption to impaired retention of learned behavior in rodents. Prenatal exposure to aspartame has also been shown to impair odor-associative learning in guinea pigs; and recently, aspartame-fed hyperlipidemic zebrafish exhibited weight gain, hyperglycemia and acute swimming defects. We therefore investigated the effects of chronic lifetime exposure to aspartame, commencing in utero, on changes in blood glucose parameters, spatial learning and memory in C57BL/6J mice. Morris Water Maze (MWM) testing was used to assess learning and memory, and a random-fed insulin tolerance test was performed to assess glucose homeostasis. Pearson correlation analysis was used to investigate the associations between body characteristics and MWM performance outcome variables. At 17 weeks of age, male aspartame-fed mice exhibited weight gain, elevated fasting glucose levels and decreased insulin sensitivity compared to controls (P<0.05). Females were less affected, but had significantly raised fasting glucose levels. During spatial learning trials in the MWM (acquisition training), the escape latencies of male aspartame-fed mice were consistently higher than controls, indicative of learning impairment. Thigmotactic behavior and time spent floating directionless was increased in aspartame mice, who also spent less time searching in the target quadrant of the maze (P<0.05). Spatial learning of female aspartame-fed mice was not significantly different from controls. Reference memory during a probe test was affected in both genders, with the aspartame-fed mice spending significantly less time searching for the former location of the platform. Interestingly, the extent of visceral fat deposition correlated positively with non-spatial search strategies such as floating and thigmotaxis, and negatively with time spent in the target quadrant and swimming across the location of the escape platform. These data suggest that lifetime exposure to aspartame, commencing in utero, may affect spatial cognition and glucose homeostasis in C57BL/6J mice, particularly in males