App-based COVID-19 syndromic surveillance and prediction of hospital admissions in COVID Symptom Study Sweden

The app-based COVID Symptom Study was launched in Sweden in April 2020 to contribute to real-time COVID-19 surveillance. We enrolled 143,531 study participants (≥18 years) who contributed 10.6 million daily symptom reports between April 29, 2020 and February 10, 2021. Here, we include data from 19,161 self-reported PCR tests to create a symptom-based model to estimate the individual probability of symptomatic COVID-19, with an AUC of 0.78 (95% CI 0.74–0.83) in an external dataset. These individual probabilities are employed to estimate daily regional COVID-19 prevalence, which are in turn used together with current hospital data to predict next week COVID-19 hospital admissions. We show that this hospital prediction model demonstrates a lower median absolute percentage error (MdAPE: 25.9%) across the five most populated regions in Sweden during the first pandemic wave than a model based on case notifications (MdAPE: 30.3%). During the second wave, the error rates are similar. When we apply the same model to an English dataset, not including local COVID-19 test data, we observe MdAPEs of 22.3% and 19.0% during the first and second pandemic waves, respectively, highlighting the transferability of the prediction model

Prediction of Gas Phase Volumetric Variations In Diphasic Reservoir Oils

Abstract The gas and liquid phases present in diphasic mixtures often have distinctly different physical properties. Hence, the ability to predict the changes in their relative saturation as the conditionsvary during their flow in a conduit or in the porous media is highly desirable. This work presents analytical expressions relating the gas phase volume variations with physical properties of the reservoiroils. It was established that the gas phase volume variations, as pressure changes, can be correlated with the saturation pressure of the fluid and the dimensionless pressure regardless of thetemperature and the kind of fluid at conditions far from the critical state. These equations proved to provide the volume variations with remarkable accuracy and can be applied to surface separation processes, surface multiphasic pumping and flowmetering and e prediction of variations in the phase saturation in the reservoir. Introduction In several petroleum engineering applications gas and oil coexist, having established equilibrium either in the pores of the reservoir or as they flow in the production tubing or t1rrough the pipes and the surface separation unit. As a result of the reservoir depletion or of the fluid flow, the pressure of the system varies with time and distance. Hence, it is considered useful to be able to estimate the influence that the pressure change bears on the gas phase volume, acting both with the compressibility of the gas and with the incremental volume of the condensed liberated gas. This piece of information helps to evaluate variations of the fluid saturationsn the reservoir and the possible displacement of fluid interfaces, under certain conditions, during depletion or prolonged testing. For the applications concerning the flow at the surface, it can be used to determine the variations of the flowrates of each phase and consequently, the phase cuts as the stream passes through valves and restrictions and is subjected to subsequent pressure drops. The prediction of the gas void fraction (GVF) at operating pressure is reported as a key parameter in the design of the recently developed subsea multiphase pumping systems (1). The change of the gas phase volume can be quantified in two ways:as the fractional change that the fraction Vfg of the total volume of a mixture occupied by the gas phase undergoes as the pressure drops:Equation (1) Available In Full Paper.as the fractional change of the gas volume Vg of a mixture as the pressure changes: Equation (2) Available In Full Paper. The first expression relates the change of the gas volume to the total volume of the mixture and is used to express the change in the gas phase cut. The second expression, however, deals exclusively with the changes in the volume of the gas phase and is used to express the incremental volume of gas available in the system. Obviously the fractional changes of Vfgand Vg obtain the same values when a given mass of a mixture continues to occupy practically the same volume (Vt1, Vt2 even after it was subjected to a pressure change Δp. </jats:sec

DECONVOLUTION OF OVERLAPPING HPLC AROMATIC HYDROCARBONS PEAKS USING INDEPENDENT COMPONENT ANALYSIS (ICA)

Chemometric methods like Principal Component Analysis (PCA) and Evolving Factor Analysis (EFA) have been applied to improve peaks separation, especially in HPLC UV-DAD analysis. In this work, the Independent Component Analysis (ICA) was adopted for the separation of overlapping aromatic peaks and the simultaneous determination of the underlying spectra. The application of the method on middle petroleum fraactions showed an improved separation between the aromatic groups compared to the previously used methods. The determined by the ICA method UV spectra of the component groups can be further exploited for the compositional characterization of the aromatic fractions. CC 200