Entropy-Based Cavitation and Primary Atomization Analysis with a 2D Transparent Injector

International audienceA transparent scale-up injector with asymmetric incoming flow direction was designed to promote cavitation on mainly one-side of the orifice. This orifice has a rectangular cross-section that provides straightforward optical access to the internal flow. This geometry was designed to study the role of the internal flow, and particularly of the development of cavitation, on the modification of the primary atomization process occurring as soon as the liquid emanates from the injector. The internal flow is classified into four regimes based on the extent of the cavitation zone; 1-no-cavitation, 2-developing cavitation, 3-super cavitation and 4-semi-hydraulic flip cavitation. Image series of 500 images was recorded for different flow rates belonging to regimes 2-4. Image segmentation is applied to each individual image to identify liquid and vapour phase regions. Based on these segmented images, the mean and rms values of the cavitation extent are determined for each cavitating regime. Furthermore, a more detailed statistical analysis of the cavitation is obtained with the computation of an entropy image, bringing indication on interface between vapour and liquid and on the shed cavitation bubbles. The liquid jet fragmentation is qualified from the entropy analysis also. The primary atomization is associated with the region in the image where the liquid core is fragmented in detached ligaments and drops. This region is easily identified from the entropy analysis and the primary atomization is quantified through the computation of the area of this region. In the presence of cavitation, the primary atomization process is altered. The way liquid fragmentation is modified by cavitation is shown to be correlated to the extent of the cavitation zone in the orifice. In this paper we give a quantification of these modifications, clearly visible to the naked eye on the images

Simulations of Odd Microswimmers

We perform numerical simulations of odd microswimmers consisting of three spheres and two odd springs. To describe the hydrodynamic interaction, both the Oseen-type and the Rotne-Prager-Yamakawa (RPY)-type mobilities are used. For the Oseen-type mobility, the simulation results quantitatively reproduce the asymptotic expression of the average velocity. For the RPY-type mobility, on the other hand, the average velocity is smaller than that of the Oseen-type mobility and the deviation is more pronounced for larger spheres. We also perform simulations of microswimmers having different sphere sizes and show that the average velocity becomes smaller than that of the equal size case. The size of the middle sphere plays an important role in determining the average velocity

SWIRLING ANNULAR FLOW IN A STEAM SEPARATOR

ABSTRACT Effects of pick-off ring configuration on the separation performance of a downscaled model of a steam separator for a boiling water nuclear reactor are examined using various types of pick-off rings. The experiments are conducted using air and water. Pressure drops in a barrel and a diffuser, and diameters and velocities of droplets at the exit of the barrel are measured using differential pressure transducers and particle doppler anemometry, respectively. As a result, the following conclusions are obtained: (1) the separation performance does not depend on the shape of pick-off ring, but strongly depends on the width of the gap between the pick-off ring and the barrel wall, (2) the pressure drop in the barrel is well evaluated using the interfacial friction factor for unstable film flows, and (3) the radial distribution of droplet velocity at the exit of the separator is of use for the evaluation of carry-under

Odd elasticity of a catalytic micromachine

We perform numerical simulations of a model micromachine driven by catalytic chemical reactions. Our model includes a mechano-chemical coupling between the structural variables and the nonequilibrium variable describing the catalytic reactions. The time-correlation functions of the structural variables are calculated and further analyzed in terms of odd Langevin dynamics. We obtain the effective odd elastic constant that manifests the broken time-reversal symmetry of a catalytic micromachine. Within the simulation, we separately estimate the quantity called nonreciprocality and show that its behavior is similar to that of the odd elasticity.Our approach suggests a new method to extract the nonequilibrium properties of a micromachine only by measuring its structural dynamics

A new cosmic ray observation at Syowa Station in the antarctic

A set of Cosmic Ray detectors was newly installed in Syowa Station, in the Antarctic, to observe CR neutrons and muons simultaneously at the same location. The observing system has started working in February 2018 and is in stable operation with a high operation rate, >90%. We describe the new systems and show its stability

Silencing of p53 and CDKN1A establishes sustainable immortalized megakaryocyte progenitor cells from human iPSCs

iPS細胞を用いた人工血小板の作製の効率化に成功 血小板のテイラーメイド医療に向けた一歩. 京都大学プレスリリース. 2021-12-03.Platelet transfusions are critical for severe thrombocytopenia but depend on blood donors. The shortage of donors and the potential of universal HLA-null platelet products have stimulated research on the ex vivo differentiation of human pluripotent stem cells (hPSCs) to platelets. We recently established expandable immortalized megakaryocyte cell lines (imMKCLs) from hPSCs by transducing MYC, BMI1, and BCL-XL (MBX). imMKCLs can act as cryopreservable master cells to supply platelet concentrates. However, the proliferation rates of the imMKCLs vary with the starting hPSC clone. In this study, we reveal from the gene expression profiles of several MKCL clones that the proliferation arrest is correlated with the expression levels of specific cyclin-dependent kinase inhibitors. Silencing CDKN1A and p53 with the overexpression of MBX was effective at stably inducing imMKCLs that generate functional platelets irrespective of the hPSC clone. Collectively, this improvement in generating imMKCLs should contribute to platelet industrialization and platelet biology

Production and nonclinical evaluation of an autologous iPSC-derived platelet product for the iPLAT1 clinical trial

血小板減少症に対するiPS細胞由来血小板の自己輸血に関する臨床研究」の成果公表（論文発表）について. 京都大学プレスリリース. 2022-09-30.Donor-derived platelets are used to treat or prevent hemorrhage in patients with thrombocytopenia. However, ∼5% or more of these patients are complicated with alloimmune platelet transfusion refractoriness (allo-PTR) due to alloantibodies against HLA-I or human platelet antigens (HPA). In these cases, platelets from compatible donors are necessary, but it is difficult to find such donors for patients with rare HLA-I or HPA. To produce platelet products for patients with aplastic anemia with allo-PTR due to rare HPA-1 mismatch in Japan, we developed an ex vivo good manufacturing process (GMP)–based production system for an induced pluripotent stem cell–derived platelet product (iPSC-PLTs). Immortalized megakaryocyte progenitor cell lines (imMKCLs) were established from patient iPSCs, and a competent imMKCL clone was selected for the master cell bank (MCB) and confirmed for safety, including negativity of pathogens. From this MCB, iPSC-PLTs were produced using turbulent flow bioreactors and new drugs. In extensive nonclinical studies, iPSC-PLTs were confirmed for quality, safety, and efficacy, including hemostasis in a rabbit model. This report presents a complete system for the GMP-based production of iPSC-PLTs and the required nonclinical studies and thus supports the iPLAT1 study, the first-in-human clinical trial of iPSC-PLTs in a patient with allo-PTR and no compatible donor using the autologous product. It also serves as a comprehensive reference for the development of widely applicable allogeneic iPSC-PLTs and other cell products that use iPSC-derived progenitor cells as MCB

Transient activation of c-MYC expression is critical for efficient platelet generation from human induced pluripotent stem cells

A specific kinetic pattern of c-MYC expression is essential for optimal generation of functional platelets from human induced pluripotent stem cells

Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18–85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25–75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300–5000 mg/g who had received maximum labelled or tolerated renin–angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for ≥30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for ≥90 days, chronic dialysis for ≥90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4–2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49–0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85–2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75–1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie