Liquid–liquid mass transfer mechanism with slug flow in microreactor is investigated by means of experiments in square microchannels of 0.21 and 0.30mm width. An experimental bench has been designed ...and an analytical protocol developed in order to follow the transfer of a solute from the dispersed phase to the continuous phase. The methodology used allows the identification of droplet side mass transfer coefficients. Total flow rate ranges from 5 to 50mLh−1, resulting in droplets velocities of 0.02–0.35ms−1. Volumetric mass transfer coefficient kda values obtained in the present work ranges from 0.72 to 8.44s−1. The results reasonably fit with a model suggested by a previous study based on 2D direct numerical simulations. A comparison with other models available in the literature shows that in the operating conditions considered in this work, the flow pattern inside the confined droplets at microscale leads to an enhancement of mass transfer compared to droplets that are not confined.
•Experiments are carried out to study liquid–liquid mass transfer in microchannels.•Solute concentration in the continuous phase is measured function of contact time.•Droplet side mass transfer coefficients are identified from experimental results.•The results are compared with models available in literature.
•The characteristic time of coagulation of colloidal suspensions is studied.•The rate of coagulation is estimated using Brownian coagulation theory.•The collision efficiency is taken into account ...through a stability ratio.•Electrokinetic measurements are used to model the stability ratio.•The method is applied to a latex: coagulation times and mixing times are compared.
Coagulation is a key process particularly in the field of polymer production. Controlling this phenomenon at industrial scale is a significant challenge because it is highly dependent on the operating conditions and the equipment used for the coagulation process. Poor control of coagulation may strongly affect the quality and the reproducibility of the final aggregates. In the objective of facilitating the choice of both adequate operating conditions and suitable devices for coagulation processes, this paper presents a method to estimate characteristic coagulation time of colloidal suspensions as a function of pH, ionic strength and volume fraction of particles. This method is based on Brownian coagulation theory, assuming very small initial particles. The collision efficiency is taken into account by the introduction of a stability ratio. This ratio is calculated using models that have been adjusted using electrokinetic measurements. The developed methodology is then applied to an industrial latex in order to estimate the operating conditions to fully destabilized the latex. Orders of magnitude of characteristic coagulation time are also obtained. Since perfect mixing of the colloidal suspension and the coagulant is necessary to obtain satisfactory aggregate properties, the characteristic coagulation time is compared with the mixing time for different mixing technologies, providing useful information for process design.
•Coagulation in laminar flow leads to high fractal dimension clusters.•Two classes of particles are observed and related to erosion mechanism.•Size of the aggregates was found to scale with shear ...rate.•Scaling exponent well agrees with Zaccone et al. relation.
Aggregation of acrylic latex is investigated inside tubular millireactors working under laminar hydrodynamic conditions. The size distribution and fractal dimension of aggregates are measured using light scattering. Results show that the equilibrium between rupture and aggregation is achieved quickly, allowing the study of cluster size distribution and shape at the aggregation/rupture steady state. Both laminar hydrodynamic conditions and high shear rate are suspected to promote the formation of aggregates with a high fractal dimension, which means that the particles are almost spherical, thereby offering an interesting alternative to conventional batch processes. These results can provide useful information for industries aiming at producing aggregates at specified size and quality.
•Nitration of toluene in a continuous compact heat exchanger reactor is carried out.•A safety analysis is conducted to compare continuous and semi-batch processes.•The failures that can lead to ...thermal runaway are identified using HAZOP method.•The failure scenarios leading to the most dramatic consequences are simulated.•The thermal behaviors of both processes during failure are observed and compared.
The behavior of a continuous intensified heat exchanger (HEX) reactor in case of process failure is analyzed and compared to the behavior of a semi-continuous reactor. The nitration of toluene is considered as test reaction to identify the main failure scenarios that can lead to thermal runaway in both processes using the HAZOP method. No flow rate of process fluid and utility fluid in the continuous process. No stirring during feeding of the reactor followed by normal stirring for the semi-continuous reactor. These scenarios are simulated for both processes and the temperature profiles are observed. This study shows that the temperature is better controlled in the continuous process because of the intrinsic characteristics of the HEX reactor. In fact, this device has a low reactive volume relative to the mass of the reactor, allowing a good dissipation of the heat produced by the reaction, even in case of failure. This characteristic of the intensified reactor is confirmed by an experimental work.
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•A millimetric straight tube, coiled tube and Dean-Hex are studied using CFD.•Hydrodynamic and coagulation-related parameters are computed.•Lagrangian particle tracking is performed ...to obtain coagulation-related data.•Dean-Hex geometry appears to be a good candidate to intensify coagulation.
This study compares the hydrodynamics in three millimeter-scale continuous reactor geometries that can be easily used in laboratories and industries – a straight tube, a coiled tube and a Dean-Hex reactor – via numerical simulations and analyses the data in a way that is specifically relevant to coagulation processes, thereby offering insights for engineers to develop new coagulation reactors. A numerical approach based on Lagrangian particle tracking is presented to better understand the impact of the geometry and flow on properties that influence coagulation. The results show that the Dean-Hex meandering geometry provides narrower residence time and shear rate distributions, as well as higher mean average shear rates and Camp number distribution than the other geometries. This is attributed to the generation of transverse flows and radial mixing in the Dean-Hex reactor and suggests that a faster and more homogenous coagulation can be expected.
In January 2020, the Chinese authorities identified a new virus of the Coronaviridae family as the cause of several cases of pneumonia of unknown aetiology. The outbreak was initially confined to ...Wuhan City, but then spread outside Chinese borders. On 31 January 2020, the first case was declared in Spain. On 11 March 2020, The World Health Organization (WHO) declared the coronavirus outbreak a pandemic. On 16 March 2020, there were 139 countries affected. In this situation, the Scientific Societies SEMICYUC and SEEIUC have decided to draw up this Contingency Plan to guide the response of the Intensive Care Services. The objectives of this plan are to estimate the magnitude of the problem and identify the necessary human and material resources. This is to provide the Spanish Intensive Medicine Services with a tool to programme optimal response strategies.
Optimal management of sedation, analgesia and delirium offers comfort and security for the critical care patient, allows support measures to be applied more easily and enables an integral approach of ...medical care, at the same time that lowers the incidence of complications, wich translates in better patient outcomes.
To update the Guía de práctica clínica basada en la evidencia para el manejo de la sedoanalgesia en el paciente adulto críticamente enfermo published in Medicina Intensiva in 2007, and give recommendations for the management of sedation, analgesia, and delirium.
A group of 21 intensivists from 9 countries of the Federación Panamericana e Ibérica de Sociedades de Medicina Crítica y Terapia Intensiva, 3 of them also specialists in clinical epidemiology and methodology, gathered for the development of guidelines. Assessment of evidence quality and recommendations were made based on the Grading of Recommendations Assessment, Development and Evaluation system. Strength of recommendations was classified as 1=strong, or 2=weak, and quality of evidence as A=high, B=moderate, or C=low. Two authors searched the following databases: MEDLINE through PUBMED, The Cochrane Library and Literatura Latinoamericana y del Caribe en Ciencias de la Salud and retrieved pertinent information. Members assigned to the 11 sections of the guidelines, based on the literature review, formulated the recommendations, that were discussed in plenary sessions. Only those recommendations that achieved more than 80% of consensus were approved for the final document. The Colombian Association of Critical Medicine and Intensive Care (AMCI) supported the elaboration of this guidelines.
Four hundred sixty-seven articles were included for review. An increase in number and quality of publications was observed. This allowed to generate 64 strong recommendations with high and moderate quality of evidence in contrast to the 28 recommendations of the previous edition.
This Guidelines contains recommendations and suggestions based on the best evidence available for the management of sedation, analgesia and delirium of the critically ill patient, including a bundle of strategies that serves this purpose. We highlight the assessment of pain and agitation/sedation through validated scales, the use of opioids initially to apropiate analgesic control, associated with multimodal strategies in order to reduce opioide consumption; to promote the lowest level of sedation necessary avoiding over-sedation. Also, in case of the need of sedatives, choose the most appropiate for the patient needs, avoiding the use of benzodiazepines and identify risk factors for delirium, in order to prevent its occurrence, diagnose delirium and treat it with the most suitable pharmacological agent, whether it is haloperidol, atypical antipsychotics or dexmedetomidine, once again, avoiding the use of benzodiazepines and decreasing the use of opioids.
To know the fate of the rejected manuscripts in Medicina Intensiva journal (MI) from 2015 to 2017 with surveillance until 2019.
Retrospective observational study.
Biomedical journals publication.
...Rejected manuscripts in MI journal.
None.
Time of publication, impact factor (IF), generated citations and variables associated to publication.
The 69% (420) of analyzed articles (344 originals and 263 scientific letters) were rejected, and 205 (48.8%) were subsequently published, with 180 citations of 66 articles. Journal IF was lower in 173 (84.4%) articles. The number of FI-valid citations was higher than the FI of MI in 21 articles. Origin of manuscript OR 2,11 (IC 95% 1.29–3.46), female author OR 1.58 (IC 95% 1.03–2.44), english language OR 2,38 (IC 95% 1.41–4.0) and reviewed papers OR 1.71 (IC 95% 1.10–2.66) were associated to publication in PubMed database.
The rejected articles in MI have a mean publication rate in other journals. Most of these articles are published in journals with less IF and fewer citations than the IF of MI.
Conocer el destino de los trabajos rechazados en Medicina Intensiva (MI) en el período del 2015 al 2017 con seguimiento hasta el 2019.
Estudio retrospectivo observacional.
Publicaciones en revistas biomédicas.
Manuscritos rechazados en la revista Medicina Intensiva.
Ninguna.
Tiempo de publicación, factor de impacto (FI), citas generadas y variables asociadas con a la publicación.
De 344 originales y 263 cartas científicas, se rechazaron 420 (69,2%). Se publicaron después 205 (48,8%) y 66 de ellos generaron 180 citas. El FI de las revistas fue menor en 173 casos (84,4%). En 21, el número de citas válidas para FI fue mayor que el FI de MI. El origen del manuscrito odds ratio (OR) 2,11 (IC 95% 1,29 a 3,46), la mujer como autora OR 1,58 (IC 95% 1,03 a 2,44), que estuviera en lengua inglesa OR 2,38 (IC 95% 1,41 a 4,0) y que el artículo hubiera pasado a revisores OR 1,71 (IC 95% 1,10 a 2,66) se asociaron con mayor tasa de publicación en revistas indexadas en PubMed.
Los artículos rechazados en MI tienen una tasa media de publicación en otras revistas, principalmente con menos FI y generando menor número de citas que el FI de MI.
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