Hydrodynamics in Recirculating Fluidized Bed Mimicking the Stripper Section of the Fluid Coker

The stripper section of a Fluid CokerTM consists of a system of baffles (sheds) that enhances the removal of interstitial and adsorbed hydrocarbon vapors from the fluidized coke-particles. Most of the hydrocarbon-vapors released below a stripper shed flow up to the stripper shed, where they may crack and form coke deposits that foul the shed. Extensive fouling changes the shapes of the sheds, makes them thicker and reduces the free-space between the adjacent sheds until downward solids flow is so impaired that the Coker has to be shut down. The Radioactive Particle Tracking (RPT) technique allows the determination of a radioactive tracer-particle location within a certain space inside a fluidized bed and has been the main tool used to study the motion of agglomerates and their interactions with internals. The research presents an innovative use of the RPT system, as a tool to measure the growth of internals fouling in time without the need of stopping the process. Moreover, the technique was able to characterize the type of interactions the agglomerate has with the sheds. In conjunction with a mathematical drying model, it was possible to predict the flow of organic vapors reaching each shed, thus estimating the risk of shed fouling, as well as the amount of liquid lost with the agglomerate as it leaves the stripper section. The investigation found that small agglomerates lose very quickly their liquid and therefore its ability to cause fouling. Moreover, experimental work showed that the solid recirculation rate is a very important parameter, e.g., decreasing it by half, quadruples the residence-time in all zones. The comparison of different types of sheds and configurations concluded that the Mesh-Shed type of internals performs the best. With regular sheds, the best configuration reduces the total open area by only 30%, instead of 50% as with the current sheds. A study of a ring-baffle that is inserted above the stripper section showed that its main advantage is that it increases the residence time of the agglomerates above the baffle, providing them with more time to dry. Adding flux-tubes to the baffle is detrimental to their performance

Measurement of penetration and cycle time of jets from an industrial fluid coking spray nozzle

Fluid CokingTM is a process to upgrade heavy oils through thermal cracking. Oil is injected in a downward-flowing bed of hot coke particles, where it heats up and cracks into smaller vapour molecules. The down-flowing coke particles are sent to a burner where they are reheated and send back to the reactor to provide heat for cracking reactions. Liquid sprayed with atomization gas into a fluidized bed forms a jet cavity that absorbs bubbles from the bubbling bed and periodically releases a large bubble from its tip. The jet penetration length, thus, cycles. With a faster jet cycle, the liquid is distributed more uniformly inside the bed, which is highly desirable. Poor liquid distribution increases the formation of wet agglomerates that slow down the coking reactions and lead to operating problems in commercial Fluid CokersTM. A novel method is proposed to measure the jet penetration and cycle time in large, room-temperature fluidized beds. It is applied to the study of jet cavities from commercial-size spray nozzles, with a liquid flowrate of 180 kg/min with a sand bed of 8 tonnes. Six cameras-probes are positioned along the jet cavity. Computerized analysis of the resulting videos shows that the average jet penetration length and cycle time is affected by fluidization velocity and atomization gas flowrate. Measuring the evolution of the bed electrical conductance provides the rate at which water is released from the wet agglomerates. This study shows how liquid distribution can be improved by adjusting jet penetration and cycle time

a cross-sectional study

Objectives We sought to determine the prevalence of anti-Toxoplasma gondii antibodies in Yoremes and to identify associations of T. gondii exposure with sociodemographic, clinical and behavioural characteristics of Yoremes. Design A cross-sectional survey. Setting Yoremes were enrolled in the locality of Tierra Blanca in the municipality of Navojoa in Sonora State, Mexico. Participants We studied 200 Yoremes (Mayos); they are an indigenous ethnic group living in a coastal region in northwestern Mexico. Primary and secondary outcome measures We assessed the prevalence of anti-Toxoplasma IgG and IgM antibodies in participants using enzyme-linked immunoassays. We used a standardised questionnaire to obtain the characteristics of Yoremes. The association of T. gondii exposure and Yoremes’ characteristics was assessed by bivariate and multivariate analyses. Results Of the 200 Yoremes studied (mean age: 31.50±18.43 years), 26 (13.0%) were positive for anti-T. gondii IgG antibodies and 19 (73.1%) of them were also positive for anti-T. gondii IgM antibodies. Seroprevalence of T. gondii infection did not vary with sex, educational level, occupation or socioeconomic status. In contrast, multivariate analysis of sociodemographic and behavioural characteristics showed that T. gondii exposure was associated with increasing age (OR=1.02; 95% CI 1.00 to 1.04; p=0.03) and consumption of squirrel meat (OR=4.99; 95% CI 1.07 to 23.31; p=0.04). Furthermore, seroprevalence of T. gondii infection was significantly higher in Yoremes with a history of lymphadenopathy (p=0.03) and those suffering from frequent abdominal pain (p=0.03). In women, T. gondii exposure was associated with a history of caesarean sections (p=0.03) and miscarriages (p=0.02). Conclusions We demonstrate, for the first time, serological evidence of T. gondii exposure among Yoremes in Mexico. Results suggest that infection with T. gondii might be affecting the health of Yoremes. Results may be useful for an optimal design of preventive measures against T. gondii infection

Pluripotency factors regulate the onset of Hox cluster activation in the early embryo

Pluripotent cells are a transient population of the mammalian embryo dependent on transcription factors, such as OCT4 and NANOG, which maintain pluripotency while suppressing lineage specification. However, these factors are also expressed during early phases of differentiation, and their role in the transition from pluripotency to lineage specification is largely unknown. We found that pluripotency factors play a dual role in regulating key lineage specifiers, initially repressing their expression and later being required for their proper activation. We show that Oct4 is necessary for activation of HoxB genes during differentiation of embryonic stem cells and in the embryo. In addition, we show that the HoxB cluster is coordinately regulated by OCT4 binding sites located at the 3′ end of the cluster. Our results show that core pluripotency factors are not limited to maintaining the precommitted epiblast but are also necessary for the proper deployment of subsequent developmental programs

Nanog regulates Pou3f1 expression at the exit from pluripotency during gastrulation.

Pluripotency is regulated by a network of transcription factors that maintain early embryonic cells in an undifferentiated state while allowing them to proliferate. NANOG is a critical factor for maintaining pluripotency and its role in primordial germ cell differentiation has been well described. However, Nanog is expressed during gastrulation across all the posterior epiblast, and only later in development is its expression restricted to primordial germ cells. In this work, we unveiled a previously unknown mechanism by which Nanog specifically represses genes involved in anterior epiblast lineage. Analysis of transcriptional data from both embryonic stem cells and gastrulating mouse embryos revealed Pou3f1 expression to be negatively correlated with that of Nanog during the early stages of differentiation. We have functionally demonstrated Pou3f1 to be a direct target of NANOG by using a dual transgene system for the controlled expression of Nanog Use of Nanog null ES cells further demonstrated a role for Nanog in repressing a subset of anterior neural genes. Deletion of a NANOG binding site (BS) located nine kilobases downstream of the transcription start site of Pou3f1 revealed this BS to have a specific role in the regionalization of the expression of this gene in the embryo. Our results indicate an active role of Nanog inhibiting neural regulatory networks by repressing Pou3f1 at the onset of gastrulation.This article has an associated First Person interview with the joint first authors of the paper.This work was funded by the Spanish government [grant BFU2017-84914-P to M.M.]. The Gottgens laboratory is supported by core funding from the Wellcome Trust and Medical Research Council to the Wellcome and Medical Research Council Cambridge Stem Cell Institute. The CNIC is supported by the Instituto de Salud Carlos III (ISCIII), the Ministerio de Ciencia, Innovación y Universidades (MCNU) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence [SEV-2015-0505]

Cause of Death and Predictors of All-Cause Mortality in Anticoagulated Patients With Nonvalvular Atrial Fibrillation : Data From ROCKET AF

M. Kaste on työryhmän ROCKET AF Steering Comm jäsen.Background-Atrial fibrillation is associated with higher mortality. Identification of causes of death and contemporary risk factors for all-cause mortality may guide interventions. Methods and Results-In the Rivaroxaban Once Daily Oral Direct Factor Xa Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation (ROCKET AF) study, patients with nonvalvular atrial fibrillation were randomized to rivaroxaban or dose-adjusted warfarin. Cox proportional hazards regression with backward elimination identified factors at randomization that were independently associated with all-cause mortality in the 14 171 participants in the intention-to-treat population. The median age was 73 years, and the mean CHADS(2) score was 3.5. Over 1.9 years of median follow-up, 1214 (8.6%) patients died. Kaplan-Meier mortality rates were 4.2% at 1 year and 8.9% at 2 years. The majority of classified deaths (1081) were cardiovascular (72%), whereas only 6% were nonhemorrhagic stroke or systemic embolism. No significant difference in all-cause mortality was observed between the rivaroxaban and warfarin arms (P=0.15). Heart failure (hazard ratio 1.51, 95% CI 1.33-1.70, P= 75 years (hazard ratio 1.69, 95% CI 1.51-1.90, P Conclusions-In a large population of patients anticoagulated for nonvalvular atrial fibrillation, approximate to 7 in 10 deaths were cardiovascular, whereasPeer reviewe

Effect of local hydrodynamics on the distribution of liquid sprayed into a Fluidized Bed

In industrial thermal cracking processes such as Fluid CokingTM, liquid feedstock is injected into a fluidized bed of hot particles. The quality of liquid-solid contact is crucial for optimizing the product yields and the process operability. The formation of undesired agglomerates, which are generated by poor liquid distribution on solids, needs to be minimized for better mass and heat transfer. Liquid distribution can be improved by either modifying the spray nozzle or adjusting the bed hydrodynamics. The present study focuses on modifying the local bed hydrodynamics by changing the local fluidization velocities. The Fluid CokingTM process is simulated by injecting an aqueous Gum Arabic solution in a warm bed of sand particles. The effects of velocity in the spray region and in the drying region in fluidized bed on liquid distribution are investigated using different velocity combinations. The fluidization velocity during injection characterizes the velocity in the spray region while the fluidization velocity after injection characterizes the velocity in the drying region. The mass of agglomerates in different size cuts, initial liquid/solid ratio in the agglomerates are measured and used to assess the effect of changing the local hydrodynamics. The fluidization velocity has a great impact on liquid distribution. A higher fluidization velocity in the spray region improves the liquid distribution by creating drier agglomerates, which break up more quickly. A higher velocity during drying accelerates agglomerate breakup by shear forces, resulting in a smaller mass of wetter agglomerates. Overall, increasing the fluidization velocity in the spray region is more effective than increasing the velocity during drying. The beneficial impact of the fluidization velocity on liquid distribution was observed with sprays of different quality

Nanog regulates Pou3f1 expression at the exit from pluripotency during gastrulation

Pluripotency is regulated by a network of transcription factors that maintain early embryonic cells in an undifferentiated state while allowing them to proliferate. NANOG is a critical factor for maintaining pluripotency and its role in primordial germ cell differentiation has been well described. However, Nanog is expressed during gastrulation across all the posterior epiblast, and only later in development is its expression restricted to primordial germ cells. In this work, we unveiled a previously unknown mechanism by which Nanog specifically represses genes involved in anterior epiblast lineage. Analysis of transcriptional data from both embryonic stem cells and gastrulating mouse embryos revealed Pou3f1 expression to be negatively correlated with that of Nanog during the early stages of differentiation. We have functionally demonstrated Pou3f1 to be a direct target of NANOG by using a dual transgene system for the controlled expression of Nanog Use of Nanog null ES cells further demonstrated a role for Nanog in repressing a subset of anterior neural genes. Deletion of a NANOG binding site (BS) located nine kilobases downstream of the transcription start site of Pou3f1 revealed this BS to have a specific role in the regionalization of the expression of this gene in the embryo. Our results indicate an active role of Nanog inhibiting neural regulatory networks by repressing Pou3f1 at the onset of gastrulation.This article has an associated First Person interview with the joint first authors of the paper.This work was funded by the Spanish government [grant BFU2017-84914-P to M.M.]. The Gottgens laboratory is supported by core funding from the Wellcome Trust and Medical Research Council to theWellcome and Medical Research Council Cambridge Stem Cell Institute. The CNIC is supported by the Instituto de Salud Carlos III (ISCIII), the Ministerio de Ciencia, Innovación y Universidades MCNU) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence [SEV-2015-0505].S