We experimentally demonstrate that a precipitation reaction at the miscible interface between two reactive solutions can trigger a hydrodynamic instability due to the buildup of a locally adverse mobility gradient related to a decrease in permeability. The precipitate results from an A þ B → C type of reaction when a solution containing one of the reactants is injected into a solution of the other reactant in a porous medium or a Hele-Shaw cell. Fingerlike precipitation patterns are observed upon displacement, the properties of which depend on whether A displaces B or vice versa. A mathematical modeling of the underlying mobility profile confirms that the instability originates from a local decrease in mobility driven by the localized precipitation. Nonlinear simulations of the related reaction-diffusion-convection model reproduce the properties of the instability observed experimentally. In particular, the simulations suggest that differences in diffusivity between A and B may contribute to the asymmetric characteristics of the fingering precipitation patterns. DOI: 10.1103/PhysRevLett.113.024502 PACS numbers: 47.55.P−, 47.15.gp, 47.56.+r, 47.70.Fw Chemical reactions are able to influence and even more strikingly induce hydrodynamic fingering instabilities of a frontal interface when a high mobility fluid displaces a less mobile one in a porous medium. This occurs in viscous fingering if a less viscous fluid displaces a more viscous one [1]. Fingering can also result from a change in permeability in a porous medium as in reactive dissolution instabilities [2][3][4][5][6][7][8][9][10]. In these cases, the invading fluid contains chemicals which dissolve the solid matrix of the porous medium, leading to a related increase in porosity behind the reaction front. As a result, the resistance to flow decreases in these higher mobility reactive zones, which favors further dissolution, giving, thus, a positive feedback leading to instability. Dispersion of reactants is the stabilizing factor counteracting the growth of fluid channels in order to provide a fingered pattern with a given characteristic wavelength [2,5,7,10]. The reverse case of precipitation is not expected to destabilize an interface as the related decrease in permeability and, hence, in mobility behind the front is expected to block the flow rather than destabilize it. There is, however, increased interest to understand the effect of precipitation reactions during flow displacements in porous media in the context of CO 2 sequestration techniques [11][12][13][14]. Mineralization by which CO 2 injected in a porous medium could undergo precipitation reactions (to yield carbonates, for instance [13][14][15][16]) is indeed promising in view of a permanent safe storage of CO 2 in geological strata. Understanding the conditions in which precipitations can affect the stability of the spreading CO 2 plumes [12] is, thus, particularly important.In this context, we demonstrate experimentally and explain theoretically how a precipitation reaction localized at th...

AimSubsyndromal delirium is associated with prolonged intensive care unit stays, and prolonged mechanical ventilation requirements. The Prediction of Delirium for Intensive Care (PRE‐DELIRIC) model can predict delirium. This study was designed to verify if it can also predict development of subsyndromal delirium.MethodsWe undertook a single‐center, retrospective observation study in Japan. We diagnosed subsyndromal delirium based on the Intensive Care Delirium Screening Checklist. We calculated the sensitivity and specificity of the PRE‐DELIRIC model and obtained a diagnostic cut‐off value.ResultsWe evaluated data from 70 patients admitted to the mixed medical intensive care unit of the Tokyo Medical University Hospital (Tokyo, Japan) between May 2015 and February 2017. The prevalence of subsyndromal delirium by Intensive Care Delirium Screening Checklist was 31.4%. The area under the receiver operating characteristic curve was 0.83 of the PRE‐DELIRIC model for subsyndromal delirium. The calculated cut‐off value was 36 points with a sensitivity of 94.3% and specificity of 57.1%. Subsyndromal delirium was associated with a higher incidence of delirium (odds ratio, 8.81; P < 0.01).ConclusionThe PRE‐DELIRIC model could be a tool for predicting subsyndromal delirium using a cut‐off value of 36 points.

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Aim Potentially inappropriate medications (PIMs) are associated with a lower medication adherence and a higher incidence of adverse events and medical costs among elderly patients. The current study aimed to examine the prescription status of elderly patients transported to tertiary emergency medical institutions to compare the proportion of elderly patients using PIMs at admission and discharge and to investigate the characteristics of PIMs at discharge and their associated factors. Methods In total, 264 patients aged 75 years or older who were transferred to and discharged from the emergency room at Tokyo Medical University Hospital, a tertiary care hospital, from September 2018 to August 2019 were included in this study. We quantified the number of PIMs at admission and discharge based on the Screening Tool of Older Persons’ Potentially Inappropriate Prescriptions (STOPP) criteria version 2. The primary outcomes were the proportion of elderly patients taking at least one PIM at admission and discharge. Results The proportions of patients taking PIMs at admission and discharge were 55% ( n = 175) and 28% ( n = 74), respectively. Old age, greater number of PIMs at admission, and greater number of medications at discharge were directly associated with PIMs at discharge. Conclusions Admission to tertiary care hospitals resulted in a lower number of prescribed PIMs. Elderly patients with a higher number of PIMs at admission and higher number of medications at discharge might have been prescribed with PIMs.