Continuous Flow Research Articles

The “4 + 1” strategy fabrication of iron single-atom catalysts with selective high-valent iron-oxo species generation

Single-atom catalysts (SACs) with atomic dispersion active sites have exhibited huge potentials in peroxymonosulfate (PMS)-based Fenton-like chemistry in water purification. However, four-N coordination metal (MN4) moieties often suffer from such problems as low selectivity and narrow workable pH. How to construct SACs in a controllable strategy with optimized electronic structures is of great challenge. Herein, an innovative strategy (i.e., the "4 + 1" fabrication) was devised to precisely modulate the first-shell coordinated microenvironment of FeN4 SAC using an additional N (SA-FeN5). This leads to almost 100% selective formation of high-valent iron-oxo [Fe(IV)═O] (steady-state concentration: 2.00 × 10-8 M) in the SA-FeN5/PMS system. In-depth theoretical calculations unveil that FeN5 configuration optimizes the electron distribution of monatomic Fe sites, which thus fosters PMS adsorption and reduces the energy barrier for Fe(IV)═O generation. SA-FeN5 was then attached to polyvinylidene difluoride membrane for a continuous flow device, showing long-term abatement of the microcontaminant. This work furnishes a general strategy for effective PMS activation and selective high-valent metal-oxo species generation by high N-coordination number regulation in SACs, which would provide guidance in the rational design of superior environmental catalysts for water purification.

Product-specific reaction kinetics in continuous uniform supersonic flows probed by chirped-pulse microwave spectroscopy.

Experimental studies of the products of elementary gas-phase chemical reactions occurring at low temperatures (<50K) are very scarce, but of importance for fundamental studies of reaction dynamics, comparisons with high-level quantum dynamical calculations, and, in particular, for providing data for the modeling of cold astrophysical environments, such as dense interstellar clouds, the atmospheres of the outer planets, and cometary comae. This study describes the construction and testing of a new apparatus designed to measure product branching fractions of elementary bimolecular gas-phase reactions at low temperatures. It combines chirped-pulse Fourier transform millimeter wave spectroscopy with continuous uniform supersonic flows and high repetition rate laser photolysis. After a comprehensive description of the apparatus, the experimental procedures and data processing protocols used for signal recovery, the capabilities of the instrument are explored by the study of the photodissociation of acrylonitrile and the detection of two of its photoproducts, HC3N and HCN. A description is then given of a study of the reactions of the CN radical with C2H2 at 30K, detecting the HC3N product, and with C2H6 at 10K, detecting the HCN product. A calibration of these two products is finally attempted using the photodissociation of acrylonitrile as a reference process. The limitations and possible improvements in the instrument are discussed in conclusion.

Impact of surface topography and hydrodynamic flow conditions on single and multispecies biofilm formation by Escherichia coli O157:H7 and Listeria monocytogenes in presence of promotor bacteria

Biofilm formation of E. coli O157:H7 and L. monocytogenes in the presence of promotor bacteria R. insidiosa was evaluated on equipment surfaces under different hydrodynamic flow conditions in a Centers for Disease Control and Prevention biofilm reactor (CBR). The CBR containing 330 ml bacterial suspension (6 log CFU/ml in 10% TSB) was used to grow the biofilms on SS 316 L, PTFE, Polycarbonate and EPDM rubber surface coupons under 100, 200 and 300 rpm (shear stresses 0.368, 1.218 and 2.462 N/m2, respectively) for 24 h in batch flow and additional 24 h in continuous flow conditions. Surface roughness and topography of coupons were measured by electron microscopy. Bacterial populations in biofilms were determined by scrapping of coupon surfaces and plating on selective media. Multispecies E. coli O157:H7 biofilm formations were affected by the surface and shear stress. SS, PTFE, and PC exhibited a significant increased biofilm growth at higher shear stress of 2.462 N/m2 compared to 0.368 N/m2. Multispecies L. monocytogenes biofilms formation decreased with increasing shear stress on all the surface materials. Our study emphasizes the importance of surface skewness and kurtosis besides surface's roughness while selecting the material for food processing environments.

Target Tracking Two Degrees of Freedom State Feedback Control for Continuous Flow Microfluidic Chips Temperature Controller

Microfluidic chips represent a cutting-edge technology for manipulating fluids within micrometer-scale spaces and are gradually becoming a new favorite platform in life science research. Precise and fast zonal temperature control is essential for accelerating biological experiments. However, current multi-channel temperature controllers typically rely on multiple channel sets to achieve single set-point control, which results in discrepancies between the fluid temperature distribution and sensor temperature due to the distributed temperature field in the fluid channel. To estimate the actual temperature and implement gradient temperature control, this paper introduces an extension of the target tracking (TT) two degrees of freedom (2DOF) state feedback control (SFC) method, followed by a presentation of simulation and experimental results. Through comparisons with an enhanced PID system in both simulation and experimentation, the paper demonstrates an 8.96% reduction in the maximum temperature difference across different regions and a 27.89% decrease in the time taken to reach various temperatures. This solution effectively addresses the existing challenges in temperature control for microfluidic chips, offering a more precise and stable control within the desired temperature range.

Sustainable treatment scheme for in-situ remediation of contaminated drains using engineered natural systems

Ensuring water security in resource-constrained, densely populated regions is a significant challenge globally. Due to insufficient treatment infrastructure, untreated sewage discharge into drainage channels is prevalent, especially in developing countries. This leads to the pollution of already dwindling water bodies and threatens future water availability. In this context, in-situ treatment within drains using nature-based systems is an attractive option. This study evaluates microbial bioremediation and phytoremediation as engineered natural solutions for in-stream treatment of municipal wastewater. A three-stage treatment system consisting of anoxic biofilm, aerobic biofilm, and hydroponic floating wetlands was adopted. Each stage was optimized for operational parameters through batch and continuous flow studies. The anoxic biofilm system using autoclaved aerated concrete (AAC) as the attachment media, at an optimized hydraulic retention time (HRT) of 2 h, showed the best performance with respect to COD removal. Comparable COD removal was observed in both externally aerated and non-aerated aerobic biofilm systems with coir fibre at 6 h HRT. However, aerated system outperformed non-aerated system at low HRTs. The hydroponic system with Canna indica effectively removed residual ammonia-N with an HRT of 2 h. The sequential continuous flow studies employing the optimized conditions showed significant removals of COD (86%) and ammonia-N (97.6%). The results highlight that locally available materials having a high specific surface area can be used as biofilm supports for COD removal, and floating wetlands employing indigenous macrophytes can be an ideal choice for in-situ nutrient removal. The Life Cycle Assessment (LCA) showed that the developed system did not have direct significant impacts on freshwater eco-toxicity and eutrophication. The proposed hybrid treatment system can be implemented as modular units without major drainage modifications or energy-intensive operations. The study, therefore, finds potential application in densely populated settlements in low-income countries where systematic sewage treatment options remain inadequate.

Optimizing pressure gradient on the MHD peristaltic blood flow of nanofluids by - response surface methodology

This study focuses on optimization of pressure gradient on MHD peristaltic nanofluid flow by response surface methodology (RSM). The governing equations, including continuity, motion, nanoparticle, and concentration force are solved by disregarding inertial forces and employing the approximation of long-wavelength. The perturbation method is used to solve the resultant nonlinear coupled partial differential equation analytically. Mathematical and graphical outputs for concentration, temperature, and pressure rise, considering all physical parameters, are presented. Numerical computation is applied to assess expressions for friction forces and pressure rise. Magnetohydrodynamics has various applications in various microchannel designs for efficacious flow control in pumping fluids for both pulsating and non-pulsating continuous flow. Finally, Response Surface Methodology (RSM) is used for performing sensitivity analysis and its optimization. ANOVA tables are generated with the help of MINITAB-19 which is a statistical software. The sensitivity results are displayed in tabular and graphical form and concluded that M is more sensitive than other input parameters for ΔPat the low level and the input parameter Nt is most sensitive among others at middle and high levels. Further, Temperature and pressure of the flow has different responses for various values of magnetic, thermophoresis and Brownian motion parameter.

Ultrasonic reactor set-ups and applications: A review

Sonochemistry contributes to green science as it uses less hazardous solvents and methods to carry out a reaction. In this review, different reactor designs are discussed in detail providing the necessary knowledge for implementing various processes. The main characteristics of ultrasonic batch systems are their low cost and enhanced mixing; however, they still have immense drawbacks such as their scalability. Continuous flow reactors offer enhanced production yields as the limited cognition which governs the design of these sonoreactors, renders them unusable in industry. In addition, microstructured sonoreactors show improved heat and mass transfer phenomena due to their small size but suffer though from clogging. The optimisation of various conditions of regulations, such as temperature, frequency of ultrasound, intensity of irradiation, sonication time, pressure amplitude and reactor design, it is also discussed to maximise the production rates and yields of reactions taking place in sonoreactors. The optimisation of operating parameters and the selection of the reactor system must be considered to each application’s requirements. A plethora of different applications that ultrasound waves can be implemented are in the biochemical and petrochemical engineering, the chemical synthesis of materials, the crystallisation of organic and inorganic substances, the wastewater treatment, the extraction processes and in medicine. Sonochemistry must overcome challenges that consider the scalability of processes and its embodiment into commercial applications, through extensive studies for understanding the designs and the development of computational tools to implement timesaving and efficient theoretical studies.

Predictive control method for mode transition process of multi-mode turbine engine based on onboard adaptive composite model

In order to achieve precise control of thrust and flow during the mode transition(MT) process of multi-mode turbine engine(MMTE) within the switching envelope and under the condition of engine performance degradation, research on multi-mode model predictive control method is conducted. A mode transition trajectory optimization method based on SQP is explored, and a small range of adjustable parameters that ensure the continuous thrust and flow is obtained. Based on this, a multi-mode onboard modeling approach based on the directional adjustment law scheduling of the variable geometry adjustment mechanism is proposed. Furthermore, an investigation into a predictive control method for MT process based on onboard adaptive composite model is conducted. The simulation results demonstrate that the proposed method exhibits a maximum thrust fluctuation of less than 0.66 % during MT process, under both normal and degraded engine component performance conditions, which is significantly superior to the conventional PID control of 2.8 %. Compared to the average single step calculation time of 7.24 ms using the SQP optimization method, the proposed approach only requires 0.204 ms. The methodology presented takes into consideration of control accuracy and computing efficiency, thereby offering promising prospects for engineering applications in MMTE MT control system design.

Carbonic anhydrase immobilized on Zn(II)-geopolymer membrane for CO2 capture

Inorganic membranes are widely used in water filtration and gas separation due to their many advantages. In this work, we proposed an innovative approach for enzyme immobilization using a geopolymer based tubular inorganic membrane (GM) as a carrier. The GM has abundant mesopores, excellent mechanical strength and strong stability for continuous flow systems in biocatalysis field, and carbonic anhydrase (CA) was successfully loaded into this mesoporous membrane using adsorption-crosslinking method, relying on the excellent ion exchange capacity of geopolymers and large number of hydroxyl groups naturally present in the membrane's mesopores. The results of the immobilization experiments showed that the immobilized enzyme composite membrane (GZnM-CA) could achieve 63.7% enzyme recovery. This is a significant improvement over the enzyme recoveries obtained on organic membranes which are typically less than 50%. In stability tests, the membrane retained more than 90.0% relative activity after 10 consecutive uses. In the CO2 capture assay, the CO2 capture efficiency developed dramatically under the catalytic of GZnM-CA. To our delight, the membrane has excellent separation capability for CO2 gas mixtures, especially at low CO2 concentrations, achieving 99.90% CO2 removal rate, and this result can be maintained for a long period of time in a pH = 8.0 environment.

EchoGrid: High-Throughput Acoustic Trapping for Enrichment of Environmental Microplastics.

The health hazards of micro- and nanoplastic contaminants in drinking water has recently emerged as an area of concern to policy makers and industry. Plastic contaminants range in size from micro- (5 mm to 1 μm) to nanoplastics (<1 μm). Microfluidics provides many tools for particle manipulation at the microscale, particularly in diagnostics and biomedicine, but has in general a limited capacity to process large volumes. Drinking water and environmental samples with low-level contamination of microplastics require processing of deciliter to liter sample volumes to achieve statistically relevant particle counts. Here, we introduce the EchoGrid, an acoustofluidics device for high throughput continuous flow particle enrichment into a robust array of particle clusters. The EchoGrid takes advantage of highly efficient particle capture through the integration of a micropatterned transducer for surface displacement-based acoustic trapping in a glass and polymer microchannel. Silica seed particles were used as anchor particles to improve capture performance at low particle concentrations and high flow rates. The device was able to maintain the silica grids at a flow rate of 50 mL/min. In terms of enrichment, the device is able to double the final pellet's microplastic concentration every 78 s for 23 μm particles and every 51 s for 10 μm particles at a flow rate of 5 mL/min. In conclusion, we demonstrate the usefulness of the EchoGrid by capturing microplastics in challenging conditions, such as large sample volumes with low microparticle concentrations, without sacrificing the potential of integration with downstream analysis for environmental monitoring.

Promoter Effect of Pt on Zr Catalysts to Increase the Conversion of Furfural to γ-Valerolactone Using Batch and Continuous Flow Reactors: Influence of the Way of the Incorporation of the Pt Sites.

The valorization of biomass and its transformation into fuels are highly interesting due to the abundance of biomass and its almost neutral carbon emissions. In this article, we show the production of γ-valerolactone (GVL), a valuable product, from furfural (FF), a compound that can be easily obtained from biomass. This FF to GVL transformation involves a catalytic cascade reaction with two hydrogenation steps. Pt and/or Zr supported on sepiolite catalysts have been prepared and tested in the FF transformation reaction. A physical mixture of a Zr-based and a Pt-based catalyst has reached a yield to GVL of ca. 50% after 16 h at 180 °C. This performance largely exceeds that obtained by each of the single Pt or single Zr metal catalysts independently, showing a strong synergistic effect. These data suggest that each metal (Pt and Zr) plays an important and complementary role in different reaction steps. Furthermore, the physical mixture appears to be much more efficient than bimetallic Pt/Zr catalysts synthesized with the same amount of metals. The role of the type of acidity and the oxidation state of the surface platinum species on the catalytic performance has been discussed. Moreover, this reaction has been carried out in batch and continuous flow reactors, and a comparative study between the two operation modes has been undertaken. A certain correlation between the catalytic results obtained by both operation modes has been found.

#2999 Renal venous congestion as a predictor of poor prognosis in patients with acute decompensated heart failure

Abstract Background and Aims Systemic venous congestion in acute decompensated heart failure (ADHF) is associated with a risk of end-organ damage and high in-hospital mortality. We aimed to assess the prevalence and severity of renal venous congestion using venous excess ultrasound (VExUS) protocol in intensive care unit (ICU) patients with ADHF, and to evaluate the association between type of intra-renal venous blood flow, incidence of acute kidney injury (AKI), and in-hospital death. Method A prospective single-center study included 99 patients who were admitted to the ICU with ADHF (mean age 71.1 ± 12.54 years, 56 (56.6%) males). Inclusion criteria: age ≥18 years, ADHF II–IV, signed informed consent. Exclusion criteria: acute coronary syndrome, severe concomitant diseases, refusal to participate in the study. Upon admission, routine clinical, laboratory and instrumental examinations, lung ultrasound using the BLUE protocol, and assessment of venous congestion using the pulse-wave dopplerography were performed. The presence of continuous blood flow was regarded as the absence of renal venous congestion, while intermittent (biphasic and monophasic blood flow) indicated venous congestion. The diagnosis of ADHF and AKI was established based on generally accepted criteria in accordance with modern international recommendations. All patients received optimal drug therapy. The end point was defined as death from cardiovascular causes during hospitalization. Statistical analysis was performed using SPSS Statistics, version 26.0. Results Upon admission, continuous renal venous blood flow was detected in 17 (17.2%) patients, intermittent in 82 (82.8%): biphasic in 47 (47.5%) and monophasic in 35 (35.3%). The patient groups were comparable in gender, age, frequency of coronary heart disease, diabetes mellitus, anemia. Atrial fibrillation was more common in case of monophasic (p &amp;lt; 0.006), and arterial hypertension in patients with continuous venous blood flow (p &amp;lt; 0.001). Patients with renal venous congestion, compared with patients without signs of congestion, had more severe heart failure: swollen neck veins: 5 (29.4%) vs 21 (45%) vs 28 (60%), p &amp;lt; 0.001; hepatomegaly 12 (72.6%) vs 40 (85.1%) vs 31 (88.6%), p &amp;lt; 0.001; edema 8 (47.3%) vs 40 (85.1%) vs 24 (68.6%), p &amp;lt; 0.001; NYHA functional class IV 8 (47.1%) vs 32 (68.1%) vs 26 (74.6%), p &amp;lt; 0.001; more B-lines on lung ultrasound, M+SD 28.82 ± 8.91 vs 34.38 ± 9.64 vs 35.37 ± 8.72, p &amp;lt; 0.001, higher NTproBNP levels, pg/l, Ме(IQR) 2100 (1800;4560) vs 3418 (2300;8434) vs 4100 (2500;9282), p &amp;lt; 0.001, and albuminuria levels mg/g, Ме(IQR) 85 (29;145) vs 127 (49;248) vs 139 (64;245), p &amp;lt; 0.001. The incidence of AKI (4 (23.5%) vs 23 (49%) vs 31 (88.6%), p &amp;lt; 0.001), and in-hospital death (0 (0) vs 11 (23.4%) vs 12 (34.3%), p &amp;lt; 0.003) was also higher in the group of patients with monophasic renal blood flow. The presence of renal venous congestion on admission was associated with an increased risk of death due to heart failure during hospitalization with RR 1.32 (95% CI: 1.16-2.64), p &amp;lt; 0.001, and RR 1.64 (95% CI: 1.48-2.83), p &amp;lt; 0.001 in patients with biphasic and monophasic renal venous blood flow respectively, and with development of AKI RR 3.29 (95% CI: 1.50-7.24), p &amp;lt; 0.003 in patients with monophasic renal venous blood flow. Conclusion In ICU patients with ADHF, the presence of renal venous congestion, assessed on admission with Doppler ultrasound of the intrarenal veins using the VEXUS protocol, is associated with a high risk of developing AKI and in-hospital death.

#3022 Rationale and design of the CORDIAL first-in-human clinical trial: a system for sorbent-assisted continuous flow peritoneal dialysis

Abstract Background and Aims Peritoneal dialysis has important disadvantages, including low plasma clearance and a limited technique survival. A new device for sorbent-assisted continuous flow peritoneal dialysis has been designed (Wearable Artificial KIDney, WEAKID) that is based on continuous recirculation (rapid cycling) of peritoneal dialysate via a single-lumen peritoneal catheter with regeneration of dialysate using sorbents. Anticipated benefits are a better plasma clearance a higher mass transfer area coefficient with continuous flow of dialysate and enhanced diffusion due to a higher time-averaged plasma-dialysate concentration gradient with sorbent-based dialysate regeneration, and a prolonged technique survival thanks to lower peritonitis risk (less (dis)connections) and a lower glucose exposure. Method This is a first-in-human, prospective, open-label, non-randomized, single-arm, multicenter study, that will be performed at the University Medical Center Utrecht (Utrecht, The Netherlands), Università degli studi di Modena e Reggio Emilia (Italy), and Instituto de Investigación Hospital Universitario La Paz, Servicio Madrileño de Salud (Spain). We aim to include 12 stable, adult PD patients. In the first week, blood, urine, and dialysate samples will be collected over three separate days to assess the efficacy of the patient's standard PD schedule. The WEAKID system will then be tested in a clinical setting on 6 days over a period of 2 weeks (three consecutive days per week). During the first week, participants will be treated with WEAKID without sorbents for 4h (first day) or 8h (second and third day). The second week, treatment will consist of WEAKID with sorbents for 4h (first day) or 8h (second and third day). This way, exposure to new components of the system is incremental and the effectiveness of continuous recirculation of dialysate and that the added effect of sorbent-based dialysate regeneration can be analyzed separately. Outcomes The primary aim of this first-in-human clinical trial is to evaluate the (short term) clinical safety and performance of WEAKID treatment in a clinical setting. The primary safety objective will be assessed by describing and examining the incidence of: Key secondary objectives include an evaluation of efficacy in terms of plasma clearance, ultrafiltration, net base release, and patient tolerance. Planning Inclusion of the first patient is expected in January 2024, the final inclusion is expected to take place in November 2024.

Mathematical Model-Based Optimization of Continuous Flow Photobioreactor Operating at Steady State Using MATLAB Optimization Function

AbstractMicroalgae have received great attention recently due to its potential for sustainable CO2 emission reduction and production of biofuel. These applications are highly dependent on microalgae biomass productivity of photobioreactor (PBR). The objective of this work is to optimize continuous flow PBR at steady state using a mathematical model describes growth of the microalgae species Chlorella vulgaris. The operating conditions that affect the performance of PBR are determined as pH, CO2 percentage in the gas feed, light intensity, and dilution rate. The MATLAB optimization function (fmincon) is used to find the best design and operating variables in the tested region. The maximum biomass productivity is achieved at the upper-bound of the range for pH, CO2 percentage in the gas feed, and light intensity, while for dilution rate, there exists an optimum value that guarantees maximum productivity. The maximum biomass productivity and specific growth rate were estimated as 4.03 and 0.196 billion cells/L h, respectively. This is achieved at optimum dilution rates of 0.049 and 1.0 h−1, respectively. The fmincon optimization results agree well with the literature that used different optimization methods. The model-based optimization predicts the best performance of PBR without conducting experiments. Sensitivity analysis of model constants on biomass concentration showed that mass transfer coefficient KLa has the highest sensitivity followed by µmax, KCL, and KE which has the lowest sensitivity for biomass production. The obtained results are of technological significance for processes such as CO2-fixation and biofuel production. Research effort is needed to exploit optimization results in large-scale cultivation.

Effect of Season and Machine Type on Performance of Semi- and Fully Mechanized Harvesting Systems in Beech-Dominated Stands

It is common to have large trees in mature hardwood-dominated stands. This is especially true for European beech (Fagussylvatica L.), which can also have a complex architecture. Such trees have predominantly been harvested using motor-manual operations. However, in an effort to increase occupational safety and allow for a more continuous wood flow to processing facilities, fully-mechanized systems are also being employed more frequently. This study was established to determine the effect of season (Fall or Winter) and harvester type (wheeled or tracked) on the performance of semi- and fully- mechanized harvesting systems deployed in beech-dominated stands. Time-and-motion analysis was conducted on a total of 927 trees located in two forest sites in Germany. The study indicated that new silvicultural prescriptions make it impossible to harvest all trees exclusively with mechanized systems, even in the case of the tracked harvester with its 14.5 m boom. Motor-manual intervention was needed with trees that were too large, malformed or out of reach. Motor-manual intervention was significantly more frequent for the wheeled (30%) than for the tracked harvester (18%). Once again, tree size had the strongest effect on time consumption in a linear model, which varied from 0.5 to over 6 min per tree. Season and machine effect were also significant but could only account for a small fraction of the total variability. For the same tree size, time consumption was higher with the wheeled harvester and during the fall. The model also indicated a significant relationship between tree form and time consumption, even though the explanatory contribution of this independent variable was relatively small, too. Good stem form resulted in a lower time consumption. The larger tracked harvester was generally more efficient, but also more expensive to own and operate: its higher costs must be weighed against the higher revenues. New silvicultural trends make it difficult to achieve full mechanization, but the results of this study may guide managers towards technical solutions that minimize motor-manual intervention to the advantage of higher productivity and better occupational safety.

Multiple Pleistocene refugia for Arctic Bell‐Heather revealed with genomic analyses of modern and historic plants

AbstractAimArctic plants survived the Pleistocene glaciations in unglaciated refugia. The number, ages, and locations of these refugia are often unclear. We use high‐resolution genomic data from present‐day and Little‐Ice‐Age populations of Arctic Bell‐Heather to re‐evaluate the biogeography of this species and determine whether it had multiple independent refugia or a single refugium in Beringia.LocationCircumpolar Arctic and Coastal British Columbia (BC) alpine.TaxonCassiope tetragona L., subspecies saximontana and tetragona, outgroup C. mertensiana (Ericaceae).MethodsWe built genotyping‐by‐sequencing (GBS) libraries using Cassiope tetragona tissue from 36 Arctic locations, including two ~250‐ to 500‐year‐old populations collected under glacial ice on Ellesmere Island, Canada. We assembled a de novo GBS reference to call variants. Population structure, genetic diversity and demography were inferred from PCA, ADMIXTURE, fastsimcoal2, SplitsTree, and several population genomics statistics.ResultsPopulation structure analyses identified 4–5 clusters that align with geographic locations. Nucleotide diversity was highest in Beringia and decreased eastwards across Canada. Demographic coalescent analyses dated the following splits with Alaska: BC subspecies saximontana (5 mya), Russia (~1.4 mya), Europe (&gt;200–600 kya), and Greenland (~60 kya). Northern Canada populations appear to have formed during the current interglacial (7–9 kya). Admixture analyses show genetic variants from Alaska appear more frequently in present‐day than historic plants on Ellesmere Island.ConclusionsPopulation and demographic analyses support BC, Alaska, Russia, Europe and Greenland as all having had independent Pleistocene refugia. Northern Canadian populations appear to be founded during the current interglacial with genetic contributions from Alaska, Europe and Greenland. We found evidence, on Ellesmere Island, for continued recent gene flow in the last 250–500 years. These results suggest that a re‐analysis of other Arctic species with shallow population structure using higher resolution genomic markers and demographic analyses may help reveal deeper structure and other circumpolar glacial refugia.

#2848 Persistent albuminuria is a marker of persistent congestion in patients with chronic heart failure

Abstract Background and Aims Albuminuria is prevalent in patients with heart failure (HF) and associated with poor prognosis. Initial reports indicate albuminuria as a congestion marker in HF. Frequency and associations of persistent albuminuria with kidney function, NT-proBNP and venous congestion in this population are not clearly understood. We aimed to evaluate the dynamics of albuminuria and its relationship with congestion and renal function in patients with chronic HF (CHF). Method The study included patients ≥18 years, observed in an outpatient HF center, who signed an informed consent. Patients receiving renal replacement therapy, with cancer or primary kidney diseases were excluded. The visits were carried out with an interval of 3 months. During each visit we performed routine physical examination, laboratory tests (NT-proBNP, urine albumin/creatinine ration (uACR), and serum creatinine) and pulse-wave Dopplerography to assess renal venous blood flow. Persistent albuminuria was defined as maintaining an uACR &amp;gt; 30 mg/g on two visits. Albuminuria level was assessed according to KDIGO guidelines 2012 (A1, A2, A3). The absence of venous congestion was defined as continuous renal blood flow, while venous congestion - as intermittent (biphasic or monophasic) blood flow. A P value &amp;lt;0.05 was considered statistically significant. We prospectively included 103 patients with CHF (46% male, mean age - 70 (61;75) Me (IQR) years, 53% with reduced ejection fraction (EF), mean EF 45(34;53)%, 92% hypertensive, 60% with atrial fibrillation, 34% with diabetes mellitus type 2, 51% with chronic kidney disease (CKD), 43% with coronary heart disease). Results Mean uACR values at the 1st visit was 18(8;56) mg/g, at the 2nd visit - 11(0;35) mg/g. The frequency of albuminuria levels at the 1st visit were A1-66%, A2-26%, A3-8%; at the 2nd visit – A1-73%, A2-23%, A3-4%. Persistent albuminuria was detected in 37 patients (36%). The mean values of albuminuria were higher in the persistent albuminuria group on the 1st visit (76(39;222) vs 10.5(0;19.5) for patients with and without persistent albuminuria, p&amp;lt;0.001) and on the 2nd visit (94(44;176) vs 7(0;13), p &amp;lt; 0.001). The patient groups were comparable in gender, age, frequency of comorbidities, EF. The administration of disease-modifying therapy was the same in the groups, however, the dose of loop diuretic was higher in the group of persistent albuminuria (20 (10;75) vs 10(5;20) mg respectively, p = 0.024 (doses in terms of furosemide)). Serum creatinine level was 95(79;121) mmol/l; GFR (CKD-EPI 2021)- 69(52;88) mL/min/ 1.73 m2 at the 1st visit. Kidney function did not statistically differ in the groups with and without persistent albuminuria (at the 1st visit eGFE - 63(52;87) vs 70 (50;90) mL/min/1.73 m2, p = 0.52 and the 2nd visit eGFR- 68(48;85) vs 66 (48;89) mL/min/1.73, p = 0.65 respectively). The level of NT-proBNP was higher in patients with persistent albuminuria during the 1st (926 (472;1820) vs 550(260;919), pg/ml p = 0.04) and the 2nd visit (1244(987;2000) vs 593(264;1405), pg/ml, p = 0.0008). Intermittent renal veins blood flow on the 2nd visit was observed in 26 patients (25%). In patients with persistent albuminuria persistence of intermittent venous renal blood flow was more frequently than in patients without it (43% vs 7%, p = 0.017, respectively). Figs. 1 and 2 demonstrate that renal venous congestion was more severe in group of persistent albuminuria on visit 1st and 2nd respectively. Conclusion Persistent albuminuria over 3 mounts in patients with stable chronic heart failure is associated with persisting congestion (higher NT-proBNP levels and higher incidence and severity of renal venous congestion). There was no association between changes in albuminuria and changes in renal function.

#2978 Formative usability test of a novel device for peritoneal dialysis (WEAKID)

Abstract Background and Aims Chronic kidney disease is a growing problem worldwide with a growing number of patients requiring kidney replacement therapy. In recent years we have developed a novel device for peritoneal dialysis (PD), the WEarable Artificial KIDney (WEAKID); composed of a wearable device connected to a dialysate reservoir. WEAKID uses both sorbent technology and continuous flow PD to improve dialysis efficacy. Formative usability testing aids to the identification of design issues that may interfere with a device's safe and effective use and thus may influence decisions made in the design process. Here, we present the results of an international, multicentre, formative usability study of WEAKID among nurses and patients. Method This study used a mixed-methods design and was conducted in hospitals in Italy (Modena University Hospital), Spain (La Paz University Hospital, Madrid), and the Netherlands (University Medical Center Utrecht) between November 2021 and December 2022. An individual, formative usability testing session was conducted with each participant (nurse or patient) under the conditions of simulated use. Participants were asked to perform basic operational procedures (i.e. turning the device on/off, input of dialysis settings, handling an alarm) with the device according to a usability task list. Their performance was observed and use errors (i.e., something that a participant does or fails to do that results in an unexpected or unintended outcome) were noted. Furthermore, participants were asked for feedback, both verbally and by means of completing the system usability scale (SUS), reflecting perceived usability on a scale from 0 (worst) to 100 (best). Results We included 14 participants (n = 6 nurses, n = 8 patients) in three participating centres. All nurses were female and had a median experience with PD of 20.5 years (range 0.5-32). Patients were generally highly educated (n = 5, 63%). In total, 22 use errors occurred, 10 in nurses and 12 in patients. These use errors included factors not related to the device, e.g. not taking appropriate hygiene measures. In particular, use errors occurred during the priming/connection of catheter and handling the alarm. Participants’ feedback mainly concerned the small screen (and thus font) size, user interface (e.g. lack of colour-coded soft buttons), and (short) length of the patient line. The mean SUS score was 70 (range 57.5–85) for nurses, and 71.9 (range 55–87.5) for patients. Conclusion Despite the slightly above-average perceived usability of the device's current design stage, participants made a lot of suggestions for improvements, and usability must be improved to make the device ready for market introduction.

Amplifying enantioselectivity in asymmetric transformations using heterogeneous chiral single-rhodium-site catalyst with sustained catalytic activity

Rhodium-catalyzed asymmetric reactions have played a pivotal role in the synthesis of functional chiral molecules. However, the ambiguous mechanism involving several plausible catalytically active species, the potential for catalyst deactivation and the need for constant reusability remain key challenges. Heterogeneous chiral Rh catalysts are highly desirable, but their performance has been hampered by low density and stability of catalytically active sites. Herein, we have devised a versatile methodology for fabricating highly efficient and robust chiral heterogeneous single-Rh-site catalysts by direct polymerization. The successful anchoring of single Rh-ligand species, the amplification of enantioselective inductive ability and the uniform distribution of atomic Rh sites within the resulting polymer matrix are identified as crucial factors contributing to their exceptional catalytic performance via comprehensive characterization and controlled experiments. In contrast to the corresponding homogeneous analogues, these chiral single-Rhodium-site catalysts exhibit outstanding performance, yielding enhanced enantioselectivity and broad applicability, even accommodating various functional groups. Remarkably, these results are achieved with just half catalyst dosage. Furthermore, their industrial potential is demonstrated through successful utilization in continuous flow processes and robust batch recycling. In future, we aim to expand the horizons of heterogeneous chiral single-metal-site catalysis, and bring us a step closer to practical asymmetric synthesis.

Mechanosensitive membrane domains regulate calcium entry in arterial endothelial cells to protect against inflammation.

Endothelial cells (ECs) in the descending aorta are exposed to high laminar shear stress, and this supports an anti-inflammatory phenotype. High laminar shear stress also induces flow-aligned cell elongation and front-rear polarity, but whether these are required for the anti-inflammatory phenotype is unclear. Here, we showed that Caveolin-1-rich microdomains polarize to the downstream end of ECs that are exposed to continuous high laminar flow. These microdomains were characterized by high membrane rigidity, filamentous actin (F-actin), and raft-associated lipids. Transient receptor potential vanilloid-type 4 (TRPV4) ion channels were ubiquitously expressed on the plasma membrane but mediated localized Ca2+ entry only at these microdomains where they physically interacted with clustered Caveolin-1. These focal Ca2+ bursts activated endothelial nitric oxide synthase (eNOS) within the confines of these domains. Importantly, we found that signaling at these domains required both cell body elongation and sustained flow. Finally, TRPV4 signaling at these domains was necessary and sufficient to suppress inflammatory gene expression, and exogenous activation of TRPV4 channels ameliorated the inflammatory response to stimuli both in vitro and in vivo. Our work revealed a polarized mechanosensitive signaling hub in arterial ECs that dampens inflammatory gene expression and promotes cell resilience.