Segmented Flow Research Articles

A Control-Theoretic Approach for Scalable and Robust Traffic Density Estimation Using Convex Optimization

Monitoring and control of traffic networks represent alternative, inexpensive strategies to minimize traffic congestion. As the number of traffic sensors is naturally constrained by budgetary requirements, real-time estimation of traffic flow in road segments that are not equipped with sensors is of significant importance - thereby providing situational awareness and guiding real-time feedback control strategies. To that end, firstly we build a generalized traffic flow model for stretched highways with arbitrary number of ramp flows based on the Lighthill Whitham Richards (LWR) flow model. Secondly, we characterize the function set corresponding to the nonlinearities present in the LWR model, and use this characterization to design real-time and robust state estimators (SE) for stretched highway segments. Specifically, we show that the nonlinearities from the derived models are locally Lipschitz continuous by providing the analytical Lipschitz constants. Thirdly, the analytical derivation is then incorporated through a robust SE method given a limited number of traffic sensors, under the impact of process and measurement disturbances and unknown inputs. The estimator is based on deriving a convex semidefinite optimization problem. Finally, numerical tests are given showcasing the applicability, scalability, and robustness of the proposed estimator for large systems under high magnitude disturbances, parametric uncertainty, and unknown inputs.

Continuous biphasic chemical processes in a four-phase segmented flow reactor

A four-phase segmented flow regime for continuous biphasic reaction processes is introduced, characterized over 1500 automatically conducted experiments, and used for biphasic ligand exchange of CdSe quantum dots.

Exploring the Stability of Second Language Speech Ratings through Task Practice in Bilinguals’ Two Languages

This study examined the stability of second language (L2) speech ratings as a function of bilingual raters engaging in perspective taking through practice of the target speaking task. Thirty English-dominant English–French bilinguals evaluated narratives from 40 French speakers of L2 English for segmental errors, intonation, and flow. Before providing the ratings, 20 raters practiced the task in their more or less dominant language (10 per group), while 10 baseline raters performed no practice. Whereas the English practice enhanced raters’ evaluations for two of the three dimensions relative to baseline raters’ assessments, the French practice did not impact rating stability.

Semiautomatic cerebrovascular territory mapping based on dynamic ASL MR angiography without vessel-encoded labeling.

Characterizing vessel territories can provide crucial information for evaluation of cerebrovascular disorders. In this study, we present a novel postprocessing pipeline for vascular territorial imaging of cerebral arteries based on a noncontrast enhanced time-resolved 4D magnetic resonance angiography (MRA). Eight healthy participants, 1 Moyamoya patient, and 1 arteriovenous malformations patient were recruited. Territorial segmentation and relative blood flow rate calculations of cerebral arteries including left and right middle cerebral arteries and left and right posterior cerebral arteries were carried out based on the 4D MRA-derived arterial arrival time maps of intracranial vessels. Among healthy young subjects, the average relative blood flow rate values corresponding to left and right middle cerebral arteries and left and right posterior cerebral arteries were 35.9 ± 5.9%, 32.9 ± 7.5%, 15.4 ± 3.8%, and 15.9 ± 2.5%, respectively. Excellent agreement was observed between relative blood flow rate values obtained from the proposed 4D MRA-based method and reference 2D phase contrast MRI. Abnormal cerebral circulations were visualized and quantified on both patients using the developed technique. The vascular territorial imaging technique developed in this study allowed for the generation of territorial maps with user-defined level of details within a clinically feasible scan time, and as such may provide useful information to assess cerebral circulation balance in different pathologies.

Influence of Inlet Angle of Guide Vane on Hydraulic Performance of an Axial Flow Pump Based on CFD

Axial flow pump has been widely used in hydraulic engineering, agriculture engineering, water supply and sewerage works, and shipbuilding industry. In order to improve the hydraulic performance of pump under off-design working conditions, the influence of the inlet segment axial chord and inlet angle adjustment of the guide vane on the pump segment efficiency and flow filed was simulated by using the renormalization group (RNG) k − ε turbulent model based on the Reynolds-averaged Navier–Stokes equations. The results indicate that the inlet segment axial chord and inlet angle adjustment of guide vane have a strong influence on the pump segment efficiency. Considering the support function and hydraulic loss of the guide vane, the inlet segment axial chord is set to 0.25 times the axial chord of guide vane. On the basis of the inlet angle of the guide vane under design conditions, when the inlet segment angle is turned counterclockwise, the pump segment efficiency is improved in the lower flow rate region; moreover, the pump segment efficiency is improved in the larger flow rate region when the inlet segment angle is turned clockwise. As the conditions deviate from the design working conditions, the influence of the guide vane inlet angle on the pump segment efficiency increases. If the inlet segment angle is properly adjusted under off-design working conditions, the flow pattern in the guide vane is improved and the hydraulic loss is decreased, because the inlet segment angle matches with the flow direction of impeller outlet; consequently, the pump segment efficiency is increased.

Intermediate Gas Feed in Bi- or Triphasic Gas–Liquid(–Liquid) Segmented Slug Flow Capillary Reactors

Segmented slug flow systems in capillaries have already shown good potential for process intensification, due to their symmetry in the characteristic flow pattern. However, several challenges remain in this technology. For instance, in gas-consuming reactions, like Aliq + Bgas→Cliq, the gas droplets shrink and may even disappear, limiting the conversions and throughputs of capillary reactor systems. To overcome such shortcomings, an intermediate gas feed was developed. In order to maintain the well-defined slug flow characteristics, it is necessary to introduce the gas rapidly and precisely, in small aliquots of <10 µL. This allows us to preserve the well-defined alternating triphasic slug flow. A miniaturized electrolysis cell, together with a flow-observing system, was thus devised and implemented successfully as an intermediate gas feed. Feeding a new gas droplet into an existing liquid–liquid segmented flow had a success rate of up to 99%, whereas refilling an existing gas droplet is often limited by a lack of coalescence. Here, only at low volumetric flows, 70% of the gas bubbles were refilled by coalescence.

Internal Carotid Artery Dissection – A Case for Antithrombotic Therapy in the Era of (Minimally) Invasive Procedures

Objectives: Carotid artery dissection represents a common cause of stroke among people aged 30-45. We present two clinical cases and a review of the literature concerning the management of internal carotid artery dissections (ICADs). Materials and methods: The two patients are a 54-year-old male and a 40-year-old female. The first patient presented to our Neurology Department for one-week-old intense occipital headache. His clinical examination revealed left-sided miosis and upper eyelid ptosis. He underwent cerebral-cervical computed tomography (CT) and computed tomography angiography (CTA) scans and the latter revealed hemodynamically significant narrowing of both ICAs (right C1-C5 and left C1-C2 segments). Transcranial Doppler ultrasonography and Doppler ultrasonography (DUS) of the cervical-cerebral arteries showed right ICA occlusion at its origin (dissection fold and intraluminal thrombosis). Cervical magnetic resonance imaging (MRI) and time-of-flight magnetic resonance angiography (MRA) revealed a semilunar-shaped T2-weighted hypersignal present in the walls of the C1-C5 segments of the right ICA and of the C1-C2 segments of the left ICA, with bilaterally reduced intraluminal flow (right more than left). These findings indicated the presence of bilateral ICA intramural hematomas caused by subacute bilateral ICAD. The second patient presented to our Neurology Department for recurrent episodes of headache and lateral cervical pain on both sides. She underwent transcranial DUS and DUS of the cervicalcerebral arteries. They revealed right ICAD fold in its upper cervical segments. The CTA scan of the supra-aortic trunks showed hemodynamically significant narrowing with subsequent diminished blood flow in the upper cervical segments of right ICA. The patient was diagnosed with right ICAD. Results:Both patients were treated using antiplatelet therapy for primary prevention of ischaemic events. Follow-up at seven months and at six months, respectively, by means of CTA of the supra-aortic trunks or MRA of the cervical region, revealed the restoration of arterial patency with subsequent normal blood flow in both cases. Conclusions: The long-term outcomes of ICADs should be kept in mind when assigning medical or endovascular management on a case-by-case basis. Antiplatelet or anticoagulant therapy is a safe and effective first-line strategy in such patients, especially in cases that do not warrant particular management.

Photoelectric Sensor for Fast and Low-Priced Determination of Bi- and Triphasic Segmented Slug Flow Parameters.

Applying multiphase systems in microreactors leads to an intensification of heat and mass transport. Critical aspects of the well-studied segmented slug-flow, such as bubble generation and pump control, can be automated, provided a robust sensor for the reliable determination of velocity, phase lengths, and phase ratio(s) is available. In this work, a fast and low-priced sensor is presented, based on two optical transmission sensors detecting flow characteristics noninvasively together with a microcontroller. The resulting signal is mainly due to refraction of the bubble-specific geometries as shown by a simulation of light paths. The high performance of the processing procedure, utilizing the derivative of the signal, is demonstrated for a bi- and triphasic slug flow. The error of <5% is entirely reasonable for the purpose envisaged. The sensor presented is very fast, robust, and inexpensive, thus enhancing the attractiveness of parallelized capillary reactors for industrial applications.

Finite Element Model Based Determination of Local Membrane Conductivity of Polymer Electrolyte Fuel Cells

Polymer Electrolyte Fuel Cells (PEFCs) are an essential technology for future fast refill, long range and clean mobility. However, for better market penetration, their efficiency still needs to be improved. An important aspect, leading to different kinds of losses is the water management. Indeed, there exists a humidity gradient between the gas inlet and gas outlet in PEFCs with active areas of some hundred cm². This can lead to uneven membrane conductivity over the cell area which results in current density inhomogeneities, resulting in lower cell efficiency and shorter lifetime. Therefore, the measurement of localized membrane conductivity in technical cells is of great importance. Different to the typical invasive membrane conductivity measurement techniques, such as segmented flow field plates or shunt resistor boards, we propose a non-invasive method [1] which is able to provide localized information about the ionic conductivity in the membrane using electrical impedance tomography (EIT). EIT is based on the relationship that exists between one object’s conductivity distribution and the surface potential that one could measure when an alternating current is applied to the object. The objects surface potential is measured during the injection of an alternating current between two electrodes at the remaining electrodes (see Figure 1). Once enough injection-measurement pairs have been acquired, the objects inner conductivity can be reconstructed.This presentation will discuss the results of a numerical feasibility study of the application of EIT for the determination of the membrane conductivity in PEFCs. A finite element model (FEM) based representation of a simplified fuel cell geometry is used to solve the surface potential distribution as function of the membrane conductivity distribution and current injection. Using a minimization approach the membrane conductivity distribution is adjusted such that the mismatch between the surface potential of the FEM solution and synthetic measurement data is reduced. In order to simplify the problem and reduce the degree of freedoms in the minimization formulation, so far, the conductivity distribution in the membrane is estimated by 1D interpolations from cell inlet to cell outlet (see Figure 2). Finally, the working principle of the method is experimentally demonstrated using fuel cell relevant materials.[1] 2019P04382EP patent application Figure 1

Quantifying Lateral Current Spread While Measuring Performance Using a Segmented Polymer Electrolyte Water Electrolysis Cell

Conventional research and diagnostic techniques for fuel cells and electrolyzers, such as polarization curves and EIS measurements, predominantly probe macroscopic performance characteristics. The works of Schuler, et al. [1] have given a detailed understanding of transport mechanisms inside a polymer electrolyte water electrolyzer (PEWE) by drawing extensively on such ex-situ techniques. However, these techniques cannot be used to probe in-situ behaviors of a PEWE. A need for reliable experimental data that captures in-situ spatial and temporal current distribution is the motivation for the segmented cell used here. Current distribution measurement in PEWEs was performed by Bender et al. [2, 3] while Mench and coworkers pioneered the technique in similar flowing electrochemical systems [4, 5]; a major innovation was inclusion of a printed-circuit board (PCB) with an array of shunt resistors attached to each segment as shown in Figure 1a. The advantage of this design is that, although the PCB and flow-field are segmented and electronically isolated, the other components of the cell are not. However, this design is subject to error since current can spread laterally through the porous transport layer (PTL) as it passes from the catalyst layer to the segmented flow field. Since activity at the catalyst layer is of great interest, understanding current spread is a critical step to utilizing current distribution measurements.This work focuses on characterizing the lateral current spread through PTLs. Work by Philips, Ulsh, and Bender [3], showed that the experimental setup could be modified with the help of masks to characterize lateral current spread through the PTL. A set of experiments was thus designed to investigate current spread through the porous transport layer both “inward” and “outward” from a flow field segment. The goal of these experiments is to quantify current spread, allowing correction of its contribution to obfuscating measurement of current generated in the catalyst layer. High current was detected for the PCB segment corresponding to the unmasked area as expected, but substantial current was measured around the exposed area, as well (Figure 1b). If there was zero outward current spread, no current would be measured anywhere away from the single segment area generating current. Figure 1c shows average current density as a function of radial distance from a generating spot; Figure 1d plots normalized current density as a function of radial distance. This set provides calibration for how much current spread laterally outwards as detected at points located away from a current-generating area. Similarly, inward contributions were also mapped. These experiments were also carried out for two types of PTL – Ti-foil-based thin LGDLs [6] and Ti-based felt PTLs. Preliminary observations indicate that lateral current spread in the Ti-felt-based LGDLs is less than that of the Ti-based foil LGDLs. This work quantifies the lateral current spread seen inside a LGDL and also lays the groundwork to correct current spread recorded in a spatially-resolved current distribution measurement technique. It is part of DOE project #DE-EE0008426 "Developing novel electrodes with ultralow catalyst loading for high-efficiency hydrogen production in proton exchange membrane electrolyzer cells." References Schuler, T., T.J. Schmidt, and F.N. Büchi, Polymer Electrolyte Water Electrolysis: Correlating Performance and Porous Transport Layer Structure: Part II. Electrochemical Performance Analysis. Journal of The Electrochemical Society, 2019. 166(10): p. F555-F565. Reshetenko, T.V., et al., A segmented cell approach for studying the effects of serpentine flow field parameters on PEMFC current distribution. Electrochimica Acta, 2013. 88: p. 571-579. Phillips, A., et al., Utilizing a Segmented Fuel Cell to Study the Effects of Electrode Coating Irregularities on PEM Fuel Cell Initial Performance. Fuel Cells, 2017. 17(3): p. 288-298. Clement, J.T., D.S. Aaron, and M.M. Mench, In Situ Localized Current Distribution Measurements in All-Vanadium Redox Flow Batteries. Journal of The Electrochemical Society, 2015. 163(1): p. A5220-A5228. Ertugrul, T.Y., et al., In-situ current distribution and mass transport analysis via strip cell architecture for a vanadium redox flow battery. Journal of Power Sources, 2019. 437: p. 226920. Mo, J., et al., Discovery of true electrochemical reactions for ultrahigh catalyst mass activity in water splitting. Science Advances, 2016. 2(11): p. e1600690. Figure 1

Global and segmental absolute stress myocardial blood flow in prediction of cardiac events: [15O] water positron emission tomography study

PurposeWe evaluated the value of reduced global and segmental absolute stress myocardial blood flow (sMBF) quantified by [15O] water positron emission tomography (PET) for predicting cardiac events in patients with suspected obstructive coronary artery disease (CAD).MethodsGlobal and segmental sMBF during adenosine stress were retrospectively quantified in 530 symptomatic patients who underwent [15O] water PET for evaluation of coronary stenosis detected by coronary computed tomography angiography.ResultsCardiovascular death, myocardial infarction, or unstable angina occurred in 28 (5.3%) patients at a 4-year follow-up. Reduced global sMBF was associated with events (area under the receiver operating characteristic curve 0.622, 95% confidence interval (95% CI) 0.538–0.707, p = 0.006). Reduced global sMBF (< 2.2 ml/g/min) was found in 22.8%, preserved global sMBF despite segmentally reduced sMBF in 35.3%, and normal sMBF in 41.9% of patients. Compared with normal sMBF, reduced global sMBF was associated with the highest risk of events (adjusted hazard ratio (HR) 6.970, 95% CI 2.271–21.396, p = 0.001), whereas segmentally reduced sMBF combined with preserved global MBF predicted an intermediate risk (adjusted HR 3.251, 95% CI 1.030–10.257, p = 0.044). The addition of global or segmental reduction of sMBF to clinical risk factors improved risk prediction (net reclassification index 0.498, 95% CI 0.118–0.879, p = 0.010, and 0.583, 95% CI 0.203–0.963, p = 0.002, respectively).ConclusionIn symptomatic patients evaluated for suspected obstructive CAD, reduced global sMBF by [15O] water PET identifies those at the highest risk of adverse cardiac events, whereas segmental reduction of sMBF with preserved global sMBF is associated with an intermediate event risk.

Computer Vision-based Early Fire Detection Using Enhanced Chromatic Segmentation and Optical Flow Analysis Technique

Recent advances in video processing technologies have led to a wave of research on computer vision-based fire detection systems. This paper presents a multi-level framework for fire detection that analyses patterns in chromatic information, shape transmutation, and optical flow estimation of fire. First, the decision function of fire pixels based on chromatic information uses majority voting among state-of-the-art fire color detection rules to extract the regions of interest. The extracted pixels are then verified for authenticity by examining the dynamics of shape. Finally, a measure of turbulence is assessed by an enhanced optical flow analysis algorithm to confirm the presence of fire. To evaluate the performance of the proposed model, we utilize videos from the Mivia and Zenodo datasets, which have a diverse set of scenarios including indoor, outdoor, and forest fires, along with videos containing no fire. The proposed model exhibits an average accuracy of 97.2% for our tested dataset. In addition, the experimental results demonstrate that the proposed model significantly reduces the rate of false alarms compared to the other existing models

GO-SHIP Repeat Hydrography Nutrient Manual: The Precise and Accurate Determination of Dissolved Inorganic Nutrients in Seawater, Using Continuous Flow Analysis Methods

The GO-SHIP nutrient manual covers all aspects of nutrient analysis from basic sample collection and storage, specifically for Continuous Flow analysis using an Auto-Analyzer, and describes some specific nutrient methods for Nitrate, Nitrite, Silicate, Phosphate and Ammonium that are in use by many laboratories carrying out at-sea analysis and repeat hydrography sections across the world. The focus is on segmented flow analyzers not flow injection analyzers. It also covers laboratory best practices including quality control and quality assurance (QC/QA) procedures to obtain the best results, and suggests protocols for the use of reference materials (RM) and certified reference materials (CRMs).

GO-SHIP Repeat Hydrography Nutrient Manual: The Precise and Accurate Determination of Dissolved Inorganic Nutrients in Seawater, Using Continuous Flow Analysis Methods

The GO-SHIP nutrient manual covers all aspects of nutrient analysis from basic sample collection and storage, specifically for Continuous Flow analysis using an Auto-Analyzer, and describes some specific nutrient methods for Nitrate, Nitrite, Silicate, Phosphate and Ammonium that are in use by many laboratories carrying out at-sea analysis and repeat hydrography sections across the world. The focus is on segmented flow analyzers not flow injection analyzers. It also covers laboratory best practices including quality control and quality assurance (QC/QA) procedures to obtain the best results, and suggests protocols for the use of reference materials (RM) and certified reference materials (CRMs).

Experimental study and mass transfer modelling for extractive desulfurization of diesel with ionic liquid in microreactors

Conventional hydrodesulfurization technology was limited to treat aromatic heterocyclic sulfur compounds in ultralow-sulfur diesel. Extractive desulfurization (EDS) using ionic liquid (IL) exhibited good performance to address these issues, except for its long extraction time (15–40 min). To address this, microreactor was adopted to intensify the IL-based EDS, where dibenzothiophene was extracted from model diesel (MD) as the continuous phase to 1-butyl-3-methylimidazolium tetrafluoroborate as the dispersed phase under segmented flow (which appeared preferably at capillary numbers lower than 0.01). The effects of temperature, residence time and flow rate ratio on the desulfurization efficiency were investigated. The extraction equilibration time could be shortened from more than 15 min in conventional batch extractors to 120 s in microreactors. The extraction process was modeled according to the two-film model applied within a unit cell of the segmented flow, where the mass transfer resistance was considered primarily on the film side of the IL droplet. The mechanism for the improved EDS performance at higher temperatures or larger IL to MD flow ratios was investigated and validated, which was related to the significant increase in the diffusion coefficient or the specific interfacial area. These findings may shed important insights into the precise manipulation of IL-based EDS for a better process design and reactor optimization.

In Search of the Origins of Financial Fluctuations: The Inelastic Markets Hypothesis

We develop a framework to theoretically and empirically analyze the fluctuations of the aggregate stock market. Households allocate capital to institutions, which are fairly constrained, for example operating with a mandate to maintain a fixed equity share or with moderate scope for variation in response to changing market conditions. As a result, the price elasticity of demand of the aggregate stock market is small, and flows in and out of the stock market have large impacts on prices. Using the recent method of granular instrumental variables, we find that investing $1 in the stock market increases the market's aggregate value by about $5. We also develop a new measure of capital flows into the market, consistent with our theory. We relate it to prices, macroeconomic variables, and survey expectations of returns. We analyze how key parts of macro-finance change if markets are inelastic. We show how general equilibrium models and pricing kernels can be generalized to incorporate flows, which makes them amenable to use in more realistic macroeconomic models and to policy analysis. Our framework allows us to give a dynamic economic structure to old and recent datasets comprising holdings and flows in various segments of the market. The mystery of apparently random movements of the stock market, hard to link to fundamentals, is replaced by the more manageable problem of understanding the determinants of flows in inelastic markets. We delineate a research agenda that can explore a number of questions raised by this analysis, and might lead to a more concrete understanding of the origins of financial fluctuations across markets.

New indexes to evaluate the effect of segmental variations of distributed ditches on their pollutant retention in agricultural landscapes

Distributed drainage ditches and ponds in agricultural landscape can reduce chemicals export from farmlands; their distributed features, however, result in variations in pollutant removal capacities among different segments. In this paper, we proposed three descriptive indexes to characterize segmental variations of distributed ditches and ponds systems: a size index (α - segmental size vs. system size) to represent the static feature of the system, a flow index (β - segmental flow rate vs. system flow rate) and an initial concentration index (γ - segmental inflow concentration vs. initial field drainage concentration) to represent the dynamic feature of the system. Subsequently, a segmental efficiency indicator (η) was derived from these indexes to represent the pollutant removal differences calculated with and without considering segmental variations of distributed ditch systems. The proposed indexes were tested with two hypothetic ditch layouts first, and then applied to a case study site where 18 segments of ditches and ponds are distributed around paddy fields in southeastern China. The two hypothetical layouts include a ‘slender’ distribution and a ‘square’ distribution of ditches; both have the same number of identical segments and serve the same area. The ‘slender’ layout represents more spread distributions while the ‘square’ layout represents more concentrated systems. Calculated indexes showed that the ‘slender’ layout produced greater segmental variations than the ‘square’ layout. For the case study, the calculated size index and the flow index varied greatly due to segmental size differences and the complex flow connections. This in turn led to greater variation in the pollutant removal efficiencies (η), ranging from 0.021 to 0.63 for low removal rate, and 0.021–0.42 for high removal rate. The results indicate that the proposed indexes can be used to examine the variable nature of the distributed ditch systems and help provide technical guidance for proper management of the distributed buffer systems in agricultural landscapes.

Improving the slice interaction of 2.5D CNN for automatic pancreas segmentation.

Volumetric pancreas segmentation can be used in the diagnosis of pancreatic diseases, the research about diabetes and surgical planning. Since manual delineation is time-consuming and laborious, we develop a deep learning-based framework for automatic pancreas segmentation in three dimensional (3D) medical images. A two-stage framework is designed for automatic pancreas delineation. In the localization stage, a Square Root Dice loss is developed to handle the trade-off between sensitivity and specificity. In refinement stage, a novel 2.5D slice interaction network with slice correlation module is proposed to capture the non-local cross-slice information at multiple feature levels. Also a self-supervised learning-based pre-training method, slice shuffle, is designed to encourage the inter-slice communication. To further improve the accuracy and robustness, ensemble learning and a recurrent refinement process are adopted in the segmentation flow. The segmentation technique is validated in a public dataset (NIH Pancreas-CT) with 82 abdominal contrast-enhanced 3D CT scans. Fourfold cross-validation is performed to assess the capability and robustness of our method. The dice similarity coefficient, sensitivity, and specificity of our results are 86.21±4.37%, 87.49±6.38% and 85.11±6.49% respectively, which is the state-of-the-art performance in this dataset. We proposed an automatic pancreas segmentation framework and validate in an open dataset. It is found that 2.5D network benefits from multi-level slice interaction and suitable self-supervised learning method for pre-training can boost the performance of neural network. This technique could provide new image findings for the routine diagnosis of pancreatic disease.

A dynamic bolus phantom for the evaluation of the spatio-temporal resolution of MPI scanners

Magnetic particle imaging (MPI) is a tomographic imaging method to determine the spatial distribution of magnetic nanoparticles (MNP) within a defined volume. To evaluate the spatio-temporal resolution of existing MPI scanners, enabling the consistent comparison of the performance of different scanner setups, we developed dynamic MPI measurement phantoms based on segmented flow. These segmented flow phantoms comprise a defined bolus of ferrofluid tracer material, which can be pumped through a tube system with defined velocities. Using a hydrophobic organic carrier oil, cylindrically shaped boluses of different diameter, length, and flow velocity can be emulated. Moving boluses were imaged by different MPI scanner types and the correlation of spatial resolution und velocity of the bolus was investigated. For all bolus dimension and flow velocity combinations investigated, we observed a decreasing spatial resolution and increasing blurring for increasing bolus velocity and decreasing bolus volume.

Improving the reproducibility of size distribution of protein crystals produced in continuous slug flow crystallizer operated at short residence time

Continuous crystallization of proteins at short residence time and high supersaturation level is attractive in terms of the space-time yield and production efficiency. Nevertheless, it is rarely pursued due to its less-than-desirable crystal size distribution (CSD) characterized by the abundance of small crystals due to high nucleation rate. The small crystals were prone to random agglomeration, resulting in poor crystals’ residence time distribution, hence low CSD’s reproducibility. Herein we developed a segmented slug flow crystallizer (SFC) design operated at short residence time (<30 min) comprising a short nucleation segment and a growth segment operated at different temperature and fluid velocity. The SFC design improved the CSD’s reproducibility by limiting small crystals and large-sized agglomerates formations as evidenced by the small coefficient-of-variations between replicates (<10%). Lysozyme crystals having size of roughly 13–14 µm with well-preserved bioactivity were produced at yield and space-time yield of approximately 67% (w/w) and 93 g/L·h, respectively.