Oscillatory Shear Research Articles

Evaluation of Aortic Diseases Using Four-Dimensional Flow Magnetic Resonance Imaging.

The complex hemodynamic environment within the aortic lumen plays a crucial role in the progression of aortic diseases such as aneurysms and dissections. Traditional imaging modalities often fail to provide comprehensive flow dynamics that are essential for precise risk assessment and timely intervention. The advent of time-resolved, three-dimensional (3D) phase-contrast magnetic resonance imaging (4D flow MRI) has revolutionized the evaluation of aortic diseases by allowing a detailed visualizations of flow patterns and quantification of hemodynamic parameters. This review explores the utility of 4D flow MRI in the assessment of thoracic aortic diseases, highlighting the key hemodynamic parameters, including flow velocity, wall shear stress, oscillatory shear index, relative residence time, vortex, turbulent kinetic energy, flow displacement, pulse wave velocity, aortic distensibility, energy loss, and stasis. We elucidate the significant findings of studies utilizing 4D flow MRI in the context of aortic aneurysms and dissections, highlighting its role in enhancing our understanding of disease mechanisms and improving clinical outcomes. This review underscores the potential of 4D flow MRI to refine risk stratification and guide therapeutic decisions, ultimately contributing to better management of aortic diseases.

Wall Slip Behaviors of Crystallized Polypropylene under Oscillatory Shear

Wall Slip Behaviors of Crystallized Polypropylene under Oscillatory Shear

Linear and Nonlinear Rheological Investigations of Poly(3-hexylthiophene) H-Aggregated Gel Networks.

Owing to its facile synthesis and low cost, poly(3-hexylthiophene) (P3HT) has been extensively investigated in the field of organic electronics. Well-defined packing of P3HT chains and getting controlled morphologies, which solely depend on the polarity of the solvent, remain challenging. Herein, the aggregation behaviors of P3HT in organic solvents having different solvent polarities have been investigated to achieve different orderings of P3HT chains (H-type or J-type). The aggregation in the solution phase and the subsequent structural as well as morphological behaviors of P3HT chains have been investigated by absorption, X-ray powder diffraction, and topological studies, respectively. It has been noticed from absorption studies that P3HT forms H-type aggregates in anisole, phenetole, etc., whereas it produces J-type aggregates in toluene. More surprisingly, H-type aggregations of P3HT chains at low concentrations (CP3HT = 0.001 g/cm3) eventually lead to the formation of the gel network that ceases the flow of the solvents. Contrary to expectations, J-type aggregation in toluene does not produce the gel network at the said concentration. Further, to reveal the viscoelastic and microstructural properties, P3HT gel networks have been thoroughly investigated by small-amplitude oscillatory shear (SAOS) and large-amplitude oscillatory shear (LAOS) with varying concentrations, solvents, and molecular weights of P3HT. With quantitative analysis, the nonlinear rheological characteristics of higher harmonics, strain-stiffening ratio, shear-thinning ratio, dissipation ratio, intracycle transient moduli, and derivative of transient moduli have been evaluated for P3HT networks, which significantly provide the rheological information for the understanding of conducting polymer networks.

Rational Design of Hot‐Melt Biodegradable Tissue Adhesive for Bone Fracture Repair

ABSTRACTBiodegradable bone adhesives can be an effective alternative to metallic implants for stabilizing bone fractures, promoting healing, and restoring full function and mobility. Nonetheless, achieving strong adhesion to the bone under physiological conditions is complex. Herein, a polymer‐based hot‐melt biodegradable bone‐tissue adhesive was developed for bone fracture repair to provide strong bone adhesion in physiological (wet) conditions and is easy to apply. The incorporation of 3,4‐dihydroxyhydrocinnamic acid (HCA) and monobasic calcium phosphate monohydrate (MCPM) into the poly(ε‐caprolactone) (PCL) matrix via melt blending demonstrated successful adhesion of bovine bone slices under wet conditions. A mixture design of experiments was applied to optimize the adhesive formulation to maximize adhesion strength while minimizing the adhesive's melting temperature (Tm). The optimized composition of 50% PCL, 25% HCA, 25% MCPM achieved a Tm of 52°C ± 0.6°C and a lap shear adhesion strength of 294 ± 88 kPa after 30 min and 226 ± 51 kPa after 2 h of application. Time‐dependent oscillatory shear measurements revealed that HCA prolongs the setting time while MCPM reduces it. Furthermore, in vivo feasibility testing demonstrated successful adhesion of fractured bones. The hot‐melt adhesive represents a promising approach toward bone fracture repair.

Identification of viscoelastic properties with fluid inertia in a parallel plate with effective mechanical system analyses

Measurement of viscoelastic properties in small amplitude oscillatory shear (SAOS) can be affected by fluid inertia, especially at high frequencies. In this study, we introduce an effective mechanical system approach to address the effects of fluid inertia on the viscoelastic measurement with a SAOS test, employing a parallel plate geometry. In the effective mechanical system approach, viscous, elastic, and inertial properties of a fluid system are modeled systematically by a rotational drag coefficient, a torsional spring constant, and a second moment of inertia, respectively. In this way, we established the analytic solution for the linear viscoelastic behavior of a fluid in the presence of fluid inertia. The shear modulus on the frequency, obtained by the effective mechanical system, reveals that fluid inertia only affects the storage modulus and not the loss modulus. We investigate the behavior of the storage modulus as a function of the gap size, the oscillation frequency, and the disk radius, demonstrating the dependence on the gap size and the frequency. Comparison was made for the shear modulus from the effective mechanical system with viscoelastic flow simulation, employing two viscoelastic (Oldroyd-B and Giesekus) fluid models to validate the accuracy of this approach. The maximum error was found less than 3.3% over the frequency range from 1 to 100 rad/s.

Mathematical modeling and CFD investigation of the novel oscillating shear valve generating sinusoidal signals by fluid pressure fluctuation

The oscillating shear valve pulser is a critical component of advanced downhole high-speed transmission systems, playing a vital role in efficient drilling operations. It is highly valued for its flexible and accurate source signal modulation capabilities, as well as its ability to operate safely without blockages. Specifically, how to ensure that the oscillatory shear valve pulse generator produces high-quality sinusoidal differential pressure source signals is particularly crucial. Consequently, this paper initially considers the motion characteristics of the shear valve in acceleration-uniform speed-deceleration, derives the calculation formula of the throttle area of the valve hole based on the fan-arc-fillet-line, and adopts the latest unsteady-liquid thin-walled cutting-edge throttling mechanism (UTCTM) we discovered, innovatively proposing the mechanism model of the differential pressure signal generation of the oscillatory shear valve. Based on this model, a typical optimized four-blade oscillatory shear valve was obtained. Through a series of CFD computational fluid dynamics studies, the amplitude variation characteristics and sinusoidal morphology evolution laws of the differential pressure signal at different frequencies were revealed, forming a unique design method for oscillatory shear valves, which provides a solid theoretical basis and technical support for the development of a new generation of pulsers.

Chemical composition, rheological properties and calcium-induced gelation mechanism of Premna microphylla Turcz polysaccharide

The aim of this study was to investigate the chemical composition, molecular weight (Mw), and monosaccharide composition of Premna microphylla Turcz polysaccharide (PMP) and revealed the effects of calcium ions (Ca2+) on the rheological properties, thermal stability, texture properties, and structural properties of PMP gels. Additionally, the gelation mechanism of PMP was proposed. The results revealed that PMP was a negative charge acidic polysaccharide primarily composed of glucose, galactose and rhamnose. The results of small and large amplitude oscillatory shear experiments illustrated that the storage modulus (G′), loss modulus (G″), relaxation modulus (G(t)) of PMP gels showed a positive correlation with Ca2+ concentration, indicating the addition of Ca2+ improved the viscoelasticity and shear thinning capacity of PMP gels. Furthermore, the gel strength, hardness, and thermal stability of PMP gels were enhanced with increase of Ca2+ concentration. The microstructure of PMP gel was changed obviously after adding Ca2+, generating the lamellar and lump-like structure due to the PMP aggregation. The results of Zeta potential, X-ray diffraction, and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that electrostatic interactions played a crucial role in the formation of PMP gel and three-dimensional structure. These results suggested that PMP had great potential for application in the food industry due to their excellent gelation properties.

Analysis of the shear thickening behavior of a fumed silica suspension using QL-LAOS approach

The feasibility of applying quasi-linear large amplitude oscillatory shear (QL-LAOS) approach to a shear thickening (ST) fumed silica suspension was tested. While the characteristic time has been used as the parameter for the original QL-LAOS analysis of shear thinning fluids, we obtained that a description based upon increasing stiffness is more appropriate for ST fumed silica suspensions. Very low (≤1.5) third to first harmonics ratio were obtained indicating the need of alternative criteria to identify QL-LAOS behavior in ST suspensions. Consequently, a method based upon the best fit of an ellipse to the experimental Lissajous-Bowditch curves was proposed. Compliances were obtained from areas of viscous and elastic fitted ellipses. The dependence of the material functions obtained by using a Jeffrey´s mechanical viscoelastic framework with angular frequency supports the idea of ST microstructure evolves by increasing with shear the number of small hydroclusters.

Investigation on rheological performance of indigenously developed sustainable low clinker hybrid cementing binders

Cement production is a chief source of greenhouse gas emissions and is responsible for 5–8 % of anthropogenic CO2 emissions to the atmosphere worldwide. Incorporating Supplementary cementitious materials (SCMs) into cement production can lessen the need for parent materials and also reduce about 30 % of carbon dioxide (CO2) footprint. This study examines the rheological performance of the indigenously developed low-clinker hybrid cementing binders. The rheological behavior of blends could vary with different factors like the quantity of cement replacement, the type of mineral additive, the water-to-binder ratio, and the age of the paste. The rheological performance was learned through flow curves, constant shear rate, and small amplitude oscillatory shear tests. The results obtained from samples revealed that the binary blended (BB) mix exhibited higher shear stress, and the ternary (TB) and quaternary blends (QB) exposed low shear stress. From the analysis, the dynamic yield stress was increased by increasing the SCM proportion. Constant shear rate test results showed that the BB has the highest static yield stress, then other blends. Samples showed significant elasticity and linear viscoelasticity region. The resulting compressive strength of 28 days of curing showed that the quaternary mix QB1 had the highest ultimate compressive strength (52 MPa) increased by 101.9 %. While the BB has shown the least strength (80.3 %) among other blends. The characterization studies were opted to identify the properties of SCMs. The morphological study was conducted to recognize the effect of SCMs leading to the formation of denser structures to enhance compressive strength.

Dysphagia-oriented non-Newtonian flow analysis of mayonnaise on different timescales using large amplitude oscillatory shear (LAOS) models

Dysphagia is a condition that particularly affects the elderly, making dietary modification an essential treatment strategy. This involves using various thickened foodstuffs, which must be evaluated using unified, rheological, colloidal, and tribological techniques/standards. During swallowing, food bolus undergoes rapid, nonlinear, large deformations across a wide range of timescales. However, the ideal rheological profile for safe swallowing is still not known, and the study of foods under large deformation is inadequate. This work aimed to employ large-amplitude oscillatory shear (LAOS) analysis to describe the behavior of thicker foods under different timescales. Mayonnaise, a representative with complex rheological behaviors, is considered a suitable model for studying dysphagia-oriented foods. The study used multiple LAOS analysis models, including algebraic stress bifurcation to determine yield points, the Kamani–Donley–Rogers recovery rheology model to identify recoverable and unrecoverable components, and a data-driven constitutive model for precise LAOS behavior prediction. Other methods used included Fourier transform rheology, Lissajous curve, stress decomposition, strain-stiffening and shear-thickening ratios, dissipation ratio, and the sequence of physical processes. Importantly, it was observed that as the testing frequency increased, the apparent nonlinearity trajectories of mayonnaise collapsed inward with slight rotations. The timescale of deformation can strongly or weakly influence the intensity and type of non-Newtonian flows observed depending on the LAOS behaviors at different frequencies. This study enhanced the development and evaluation of dysphagia-oriented products at different timescales from a rheological perspective, which may bring new insight into the on-demand management of dysphagia and motivate innovative ideas in diet design and processing.

Computational fluid dynamics and shape analysis enhance aneurysm rupture risk stratification.

Accurately quantifying the rupture risk of unruptured intracranial aneurysms (UIAs) is crucial for guiding treatment decisions and remains an unmet clinical challenge. Computational Flow Dynamics and morphological measurements have been shown to differ between ruptured and unruptured aneurysms. It is not clear if these provide any additional information above routinely available clinical observations or not. Therefore, this study investigates whether incorporating image-derived features into the established PHASES score can improve the classification of aneurysm rupture status. A cross-sectional dataset of 170 patients (78 with ruptured aneurysm) was used. Computational fluid dynamics (CFD) and shape analysis were performed on patients' images to extract additional features. These derived features were combined with PHASES variables to develop five ridge constrained logistic regression models for classifying the aneurysm rupture status. Correlation analysis and principal component analysis were employed for image-derived feature reduction. The dataset was split into training and validation subsets, and a ten-fold cross validation strategy with grid search optimisation and bootstrap resampling was adopted for determining the models' coefficients. Models' performances were evaluated using the area under the receiver operating characteristic curve (AUC). The logistic regression model based solely on PHASES achieved AUC of 0.63. All models incorporating derived features from CFD and shape analysis demonstrated improved performance, reaching an AUC of 0.71. Non-sphericity index (shape variable) and maximum oscillatory shear index (CFD variable) were the strongest predictors of a ruptured status. This study demonstrates the benefits of integrating image-based fluid dynamics and shape analysis with clinical data for improving the classification accuracy of aneurysm rupture status. Further evaluation using longitudinal data is needed to assess the potential for clinical integration.

High wall shear stress is related to complicated AHA lesion type VI plaques in mild to moderate internal carotid artery stenosis - a 3D cardiovascular MRI study.

Complicated American Heart Association (AHA) lesion type VI plaques (cCAPs), characterized by the presence of intraplaque hemorrhage, surface defect or thrombus, are strongly associated with ischemic stroke and stroke recurrence. Hemodynamics seem to play a relevant role for their development. Thus, we investigated the association of 4D flow-MRI derived local wall shear stress (WSS) and oscillatory shear stress (OSI) with the presence of cCAPs in patients with mild to moderate internal carotid artery (ICA) stenosis. From a prospective and consecutive cross-sectional study with 121 patients with high cardiovascular risk, 39 patients (49 carotid arteries) demonstrated a 10-50% ICA-stenosis and were included in this analysis. Plaque composition was determined according to the modified AHA classification of lesions by high-resolution multi-contrast 3T-MRI. We determined WSS (minimum, mean and maximum) and OSI in vivo by 4D flow-MRI at different locations within the stenosis (upstream, stenosis center and downstream). We studied the association of each hemodynamic parameter with the presence cCAPs by logistic regression analysis adjusted for age, sex and plaque thickness. 11 (22.4%) of the 49 ICA-stenosis in our cohort showed cCAP. WSS and OSI at the beginning of the stenosis did not differ between complicated and stable plaques. By contrast, WSS was significantly higher in the stenosis center and poststenotic region in cCAPs. OSI was significantly higher in the stenosis center of stable plaques. Logistic regression analysis revealed a significant association for WSSmean (OR per SD increase 1.97, 95%-CI 1.14-3.39, p=0.015) and for WSSmax (OR per SD increase 1.84; 95%-CI 1.10-3.08; p=0.020), but not for WSSmin and OSI with the presence of cCAPs. Higher wall shear stress in ICA stenosis was significantly associated with the presence of cCAPs underlining the potential role of hemodynamics in their development. cCAP, complicated carotid artery plaque; WSS, wall shear stress; OSI, oscillatory shear index.

Effects of inlet boundary conditions on blood flow and thrombosis modelling in patients with chronic thromboembolic pulmonary hypertension

To investigate the impact of patient-specific boundary conditions (BC) on blood flow and thrombosis modelling for patients with chronic thromboembolic pulmonary hypertension (CTEPH), three types of BCs were utilized to construct CTEPH models based on computed tomography pulmonary angiography images. First BC type is the patient-specific velocity profiles at the main pulmonary artery using phase contrast MRI (PC-MRI). The other two simplified types are the pulsatile BC and steady BC, which are obtained by spatially and temporally averaging the PC-MRI BC. Hemodynamic features including helical density, time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI), and thrombosis were compared for the three types BCs. The results indicated that, compared to the MRI BC, steady BC overestimated helical density and TAWSS in the pulmonary arteries by approximately 63.1% and 60%, respectively. The impact of simplified pulsatile BC on TAWSS and OSI in most regions of the pulmonary arteries was negligible with differences within 5%. Regarding thrombosis, the area predicted under pulsatile BC was approximately 80% smaller than that under PC-MRI BC. In conclusion, compared to PC-MRI BC, steady inlet BC tend to overestimate hemodynamic parameters, while pulsatile inlet BC yield similar wall shear stress based on parameters in most regions of the pulmonary artery. Patient-specific PC-MRI inlet BC should be used for accurate predictions of helical flow pattern and thrombus formation.

Effect of the Ratio of Protein to Water on the Weak Gel Nonlinear Viscoelastic Behavior of Fish Myofibrillar Protein Paste from Alaska Pollock.

The linear and nonlinear rheological behaviors of fish myofibrillar protein (FMP) paste with 75%, 82%, and 90% moisture content were evaluated using small-amplitude oscillatory shear (SAOS) and large-amplitude oscillatory shear (LAOS) tests. SAOS revealed pastes with 75% and 82% moisture exhibited solid-like behavior, characterized by higher storage modulus (G') than loss modulus (G″), indicative of weak gel properties with a strong protein interaction. In contrast, the 90% moisture content showed more viscous behavior due to weakened protein-protein entanglements. The frequency exponent (n' and n″) from the power law equation varied slightly (0.24 to 0.36), indicating limited sensitivity to changes in deformation rate during SAOS. LAOS tests revealed significant structural changes, with Lissajous-Bowditch curves revealing early nonlinearities at 10% strain for 90% moisture content. Decomposed Chebyshev coefficients (e3/e1, v3/v1, S, and T) indicated strain stiffening at lower strains for the 75% and 82% moisture pastes (i.e., < 50% strain for 75% and < 10% strain for 82%), transitioning to strain thinning at higher strains. Additionally, numerical model confirmed the predictability of the 3D printing process from the nonlinear rheological data, confirmed the suitability of the 75% and 82% moisture pastes for applications requiring structural integrity. These insights are essential for optimizing processing conditions in industrial applications. The findings suggest that the 75% and 82% moisture pastes are suitable for applications requiring structural integrity, while the 90% moisture paste is ideal for flow-based processes. These insights are essential for optimizing processing conditions in industrial applications.

Rheology of Cellulosic Microfiber Suspensions Under Oscillatory and Rotational Shear for Biocomposite Applications

This study investigates the rheological behavior of cellulose microfiber suspensions derived from kahili ginger stems (Hedychium gardnerianum), an invasive species, in two adhesive matrices: a commercial water-based adhesive (Coplaseal®) and a casein-based adhesive made from non-food-grade milk, referred to as K and S samples, respectively. Rheological analyses were performed using oscillatory and rotational shear tests conducted at 25 °C, 50 °C, and 75 °C to assess the materials’ viscoelastic properties more comprehensively. Oscillatory tests across a frequency range of 1–100 rad/s assessed the storage modulus (G′) and loss modulus (G″), while rotational shear tests evaluated apparent viscosity and shear stress across shear rates from 0.1 to 1000 s−1. Fiber-free samples consistently showed lower moduli than fiber-containing samples at all frequencies. The incorporation of fibers increased the dynamic moduli in both K and S samples, with a quasi-plateau observed at lower frequencies, suggesting solid-like behavior. This trend was consistent in all tested temperatures. As frequencies increased, the fiber network was disrupted, transitioning the samples to fluid-like behavior, with a marked increase in G′ and G″. This transition was more pronounced in K samples, especially above 10 rad/s at 25 °C and 50 °C, but less evident at 75 °C. This shift from solid-like to fluid-like behavior reflects the transition from percolation effects at low frequencies to matrix-dominated responses at high frequencies. In contrast, S samples displayed a wider frequency range for the quasi-plateau, with less pronounced moduli changes at higher frequencies. At 75 °C, the moduli of fiber-containing and fiber-free S samples nearly converged at higher frequencies, indicating similar effects of the fiber and matrix components. Both fiber-reinforced and non-reinforced suspensions exhibited pseudoplastic (shear-thinning) behavior. Fiber-containing samples exhibited higher initial viscosity, with K samples displaying greater differences between fiber-reinforced and non-reinforced systems compared to S samples, where the gap was narrower. Interestingly, S samples exhibited overall higher viscosity than K samples, implying a reduced influence of fibers on the viscosity in the S matrix. This preliminary study highlights the complex interactions between cellulosic fiber networks, adhesive matrices, and rheological conditions. The findings provide a foundation for optimizing the development of sustainable biocomposites, particularly in applications requiring precise tuning of rheological properties.

Effect of agitation during the early-age hydration on thixotropy and morphology of cement paste

The effect of agitation during the early-age hydration on thixotropy and morphology of cement paste prepared with and without superplasticizers (SP) is investigated by applying penetration test, small amplitude oscillatory shear sweep test (SAOS), isothermal calorimetric test, scanning electron microscopy (SEM) and energy dispersive X-ray analyses (EDX). The results show that the agitation of cement paste during the induction period increases the heat flow rate and destroys existing structures of samples without changing the mineral composition of samples. Yet, if the agitation is applied during the acceleration period, the heat flow rate is significantly lowered and the morphology and mineral composition of samples undergo irreversible change, freshly formed syngenite is destroyed and no longer restored. The penetration force and the static yield stress grow linearly during the induction period and exponentially during the acceleration period. Agitation during the induction period destroys the structure, which causes the static yield stress and the penetration force values becoming nearly equal to zero. However, during the acceleration period, even after agitation the static yield stress and the penetration force exhibit high residual values, which indicates the impact of hydration to the structural build-up.

Insights from Computational Fluid Dynamics and In Vitro Studies for Stent Protrusion in Iliac Vein: How Far Shall We Go?

These findings provide significant implications for the enhancement of iliac vein stent implantation strategies and stent design. The prevalent use of stents for treating Iliac Vein Compression Syndrome (IVCS) has shown efficacy, yet the associated clinical adverse events, including stent restenosis and postoperative thrombosis, are significant concerns. Up to now, the mechanism how the stent implantation induces the restenosis and DVT is still unclear. Our study hypothesizes that these adverse outcomes arise from altered blood flow dynamics following stent implantation. Employing computational modeling and medical imaging, we simulated IVCS after various stenting procedures to assess their impact on venous blood flow characteristics, including wall shear stress (WSS), residence time (RRT), and oscillatory shear index (OSI). Our findings reveal that a stent protruding into the vena cava impedes blood circulation, with increased protrusion exacerbating this obstruction. This is particularly evident at the vein bifurcation, where low WSS and elevated OSI and RRT are observed. Moreover, a higher stent strut density further obstructs blood flow, deteriorating the hemodynamic environment. Consequently, stent protrusion into the vena cava can enhance the likelihood of adverse post-surgical events. These insights have profound implications for optimizing iliac vein stent implantation techniques and stent design.

Impact of Geometric Attributes on Abdominal Aortic Aneurysm Rupture Risk: An InVivo FSI-Based Study.

Reported in this paper is a cutting-edge computational investigation into the influence of geometric characteristics on abdominal aortic aneurysm (AAA) rupture risk, beyond the traditional measure of maximum aneurysm diameter. A Comprehensive fluid-structure interaction (FSI) analysis was employed to assess risk factors in a range of patient scenarios, with the use of three-dimensional (3D) AAA models reconstructed from patient-specific aortic data and finite element method. Wall shear stress (WSS), and its derivatives such as time-averaged WSS (TAWSS), oscillatory shear index (OSI), relative residence time (RRT) and transverse WSS (transWSS) offer insights into the force dynamics acting on the AAA wall. Emphasis is placed on these WSS-based metrics and seven key geometric indices. By correlating these geometric discrepancies with biomechanical phenomena, this study highlights the novel and profound impact of geometry on risk prediction. This study demonstrates the necessity of a multidimensional assessment approach, future efforts should complement these findings with experimental validations for an applicable approach for clinical use.

Intra-Aneurysmal High-Resolution 4D MR Flow Imaging for Hemodynamic Imaging Markers in Intracranial Aneurysm Instability.

Prediction of aneurysm instability is crucial to guide treatment decisions and to select appropriate patients with unruptured intracranial aneurysms (IAs) for preventive treatment. High-resolution 4D MR flow imaging and 3D quantification of aneurysm morphology could offer insights and new imaging markers for aneurysm instability. In this cross-sectional study, we aim to identify 4D MR flow imaging markers for aneurysm instability by relating hemodynamics in the aneurysm sac to 3D morphologic proxy parameters for aneurysm instability. In 35 patients with 37 unruptured IAs, a 3T MRA and a 7T 4D MRI flow scan were performed. Five hemodynamic parameters-peak-systolic wall shear stress (WSSMAX) and time-averaged wall shear stress (WSSMEAN), oscillatory shear index (OSI), mean velocity, and velocity pulsatility index-were correlated to 6 3D morphology proxy parameters of aneurysm instability-major axis length, volume, surface area (all 3 size parameters), flatness, shape index, and curvedness-by Pearson correlation with 95% CI. Scatterplots of hemodynamic parameters that correlated with IA size (major axis length) were created. WSSMAX and WSSMEAN correlated negatively with all 3 size parameters (strongest for WSSMEAN with volume (r = -0.70, 95% CI -0.83 to -0.49) and OSI positively (strongest with major axis length [r = 0.87, 95% CI 0.76-0.93]). WSSMAX and WSSMEAN correlated positively with shape index (r = 0.61, 95% CI 0.36-0.78 and r = 0.49, 95% CI 0.20-0.70, respectively) and OSI negatively (r = -0.82, 95% CI -0.9 to -0.68). WSSMEAN and mean velocity correlated negatively with flatness (r = -0.35, 95% CI -0.61 to -0.029 and r = -0.33, 95% CI -0.59 to 0.007, respectively) and OSI positively (r = 0.54, 95% CI 0.26-0.74). Velocity pulsatility index did not show any statistically relevant correlation. Out of the 5 included hemodynamic parameters, WSSMAX, WSSMEAN, and OSI showed the strongest correlation with morphologic 3D proxy parameters of aneurysm instability. Future studies should assess these promising new imaging marker parameters for predicting aneurysm instability in longitudinal cohorts of patients with IA.

PH-controlled-ion-mobility of Laponite-phosphate dispersion for physical hydrogel with improved mechanical properties and sensitivity to CO2

Self-assembled physical nanocomposite hydrogels based on bio-based poly(itaconic acid) and Laponite® nanoclays were prepared and tested as possible CO2 sensors in smart food packaging. The structure and mechanical properties of the fabricated hydrogels were controlled by changing the initial pH of the aqueous Laponite® dispersions stabilised by tetrasodium pyrophosphate. The dispersions were studied by SAXS and analysed using circular disc and fractal model to determine clay agglomeration tendency. Sodium and pyrophosphate ions mobility was investigated by 23Na and 31P 1D as well as spin-spin relaxation times T2 NMR measurements. The rheological behaviour of the produced hydrogels was studied by oscillatory shear measurements. It was found that decreasing the pH of the Laponite® nanodispersions up to 8 increases the strength of the physical interactions between the nanoclays, dispersant, and polyelectrolyte chains, which enables production of dimensionally stable and mechanically robust hydrogels. Their potential application as the CO2-sensitive matrix for construction of environmentally friendly colorimetric sensors was demonstrated showing the CO2 sorption capacity of 0.07 mmol CO2/g. A prototype device of hydrogel sensor was built and tested in a food packaging application to monitor the plum fruit respiration processes.