Changes In Viscoelastic Properties Research Articles

A Photochemical Crosslinking Approach to Enhance Resistance to Mechanical Wear and Biochemical Degradation of Articular Cartilage

ObjectiveThe objective of this study was to evaluate photochemical crosslinking using Al(III) phthalocyanine chloride tetrasulfonic acid (CASPc) and light with a wavelength of 670 nm as a potential therapy to strengthen articular cartilage and prevent tissue degradation.DesignChanges in viscoelastic properties with indentation were used to identify 2 crosslinking protocols for further testing. Crosslinked cartilage was subjected to an in vitro, accelerated wear test. The ability of the crosslinked tissue to resist biochemical degradation via collagenase was also measured. To better understand how photochemical crosslinking with CASPc varies through the depth of the tissue, the distribution of photo-initiator and penetration of light through the tissue depth was characterized. Finally, the effect of CASPc on chondrocyte viability and of co-treatment with an antioxidant was evaluated.ResultsThe equilibrium modulus was the most sensitive viscoelastic measure of crosslinking. Crosslinking decreased both mechanical wear and collagenase digestion compared with control cartilage. These beneficial effects were realized despite the fact that crosslinking appeared to be localized to a region near the articular surface. In addition, chondrocyte viability was maintained in crosslinked tissue treated with antioxidants.ConclusionThese results suggest that photochemical crosslinking with CASPc and 670 nm light holds promise as a potential therapy to prevent cartilage degeneration by protecting cartilage from mechanical wear and biochemical degradation. Limitations were also evident, however, as an antioxidant treatment was necessary to maintain chondrocyte viability in crosslinked tissue.

Evaluation of Blood Coagulation by Optical Vortex Tracking.

Blood coagulation is a complicated dynamic process that maintains the blood’s fluid state and prevents uncontrollable bleeding. The real-time monitoring of coagulation dynamics is critical for blood transfusion guidance, emergency management of trauma-induced coagulopathy, perioperative bleeding, and targeted hemostatic therapy. Here, we utilize optical vortex dynamics to detect the blood coagulation dynamic process in a rapid and non-contact manner. To characterize the temporal changes in viscoelastic properties of blood during coagulation, we track the stochastic motion of optical vortices in the time-varying speckles reflected from 100 blood samples with varied coagulation profiles. The mean square displacement (MSD) of the vortices increases nonlinearly with time lag during blood coagulation reminiscent of the particles in viscoelastic fluids. The MSD curves with coagulation time are similar to the tracings of thromboelastography (TEG) during the blood coagulation. The retrieved coagulation parameters, such as reaction time and activated clotting time measured using the optical vortex method, exhibit a close correlation to those parameters acquired from TEG. These results demonstrate the feasibility of the optical vortex method for monitoring blood coagulation at the point of care. Our method is also applicable to measuring the viscoelasticity of complex fluids and turbid soft matters.

An in-House System for the Precise Measurement of Electrical Potentials and Mechanical Properties of Soft Tissues: Design and Validation Using Adult Mammalian Tendon Fascicle Bundles.

Tissues, such as skin, bones, and tendons, exhibit a piezoelectric effect, which may be an important phenomenon in terms of tissue renewal and regeneration as well as the possibility of modifying their mechanical behavior. In this article, we present the design and development of an in-house system for the precise measurement of electrical potentials and mechanical properties of tendons. The system was validated using tendon fascicle bundles derived from positional as well as energy-storing tendons from various adult mammals (porcine, bovine, and deer samples). The presented system is able to capture changes in elastic and viscoelastic properties of tissue as well as its time–voltage response and, thus, may be used in a broad spectrum of future studies to uncover factors influencing piezoelectric phenomena in tendons. This, in turn, will help to optimize current methods used in physiotherapy and postoperative treatment for effective tendon recovery.

Microinjections with hyaluronic acid in combination with glycerol: How do they influence biophysical viscoelastic skin properties?

Skin quality improvement with hyaluronic acid microinjections is increasing as a clinical treatment indication and as a scientific issue. This present study assessed changes in biomechanical viscoelastic skin properties after microinjections with the skin quality booster CPM-HA20G (Belotero Revive). Fifteen subjects have been randomized in a 2:1 ratio to receive either three treatments (total 3ml per side) or a single-dose treatment (total 1.5ml per side) with CPM-HA20G at dermal level into the lower cheeks via microinjections. Treatments were provided 4 weeks apart. Biophysical measurements were performed describing the viscoelastic skin properties and the underlying skin structure. The measurements were performed before injection (week 0) and on follow-up visits 4, 8, 16, 24, and 36 weeks after the last injection treatment. One (p=0.028) as well as three (p=0.003) consecutive treatments with CPM-HA20G improved statistically significant skin firmness (R0). For the multiple-treatment group improved significant differences were observed for skin fatigue (R3; p=0.007) and skin density (p=0.017) with stable skin thickness levels (p>0.05), too. There were zero-to-weak correlations between skin thickness and biomechanical skin properties (R0, rs =0.084; R3, rs =0.093). Overall, microinjections with CPM-HA20G improved biomechanical viscoelastic skin properties with a stronger and more pronounced effect in the multiple-treatment group. The observed changes may explain some of the skin quality improvements observed after treatment with CPM-HA20G.

Reliability and Validity of a New Diagnostic Device for Quantifying Hemiparetic Arm Impairments: An Exploratory Study.

ObjectiveTo assess test-retest reliability and validity of a new diagnostic device, the Shoulder Elbow Perturbator, to quantify muscle weakness, abnormal synergy, (muscle activity-related) spasticity, and changes in viscoelastic joint properties of the elbow.SubjectsStroke patients, adults with cerebral palsy and healthy controls.MethodsTest-retest reliability was evaluated using intra-class correlations (ICC) and assessment of measurement error. The device’s validity was evaluated by demonstrating differences between patients and healthy controls, and correlations of spasticity and abnormal synergy outcomes using the clinical Modified Tardieu Scale, the Fugl-Meyer Assessment, and the Test of Arm Selective Control.ResultsReliability was excellent, with an ICC > 0.75 for synergy and ICCs > 0.90 for all other impairments, with relatively small measurement errors. Validity was confirmed by group differences between patients and healthy controls for muscle weakness, spasticity, and viscoelastic joint properties, but not for abnormal synergy. Correlation analysis with clinical scales confirmed validity for spasticity, while, for synergy, correlations were found in the patients with stroke, but not those with cerebral palsy.ConclusionThis new diagnostic device is a reliable and valid instrument to assess multiple upper limb impairments in patients with neurological conditions, supporting its use in clinical practice. Further studies are needed to confirm these findings.LAY ABSTRACTReliable and valid quantitative measurement of arm impairments due to neurological conditions is important for clinical decision-making. Current clinical measurement tools are subjective and not reliable. The aim of this study was therefore to assess the reliability and validity of a new diagnostic device to quantify multiple arm impairments (muscle weakness, abnormal synergy, spasticity, changes in viscoelastic joint properties) in patients with stroke, adults with cerebral palsy (CP), and healthy controls. Reliability was excellent for all impairments and was analysed by testing the consistency of the results on 2 occasions in the same subject. Validity was confirmed by group differences between patients and healthy controls for all impairments, except for synergy. Also, correlations of the results with clinical measurement tools were found for spasticity and synergy, except for synergy in patients with CP. In conclusion, this new diagnostic device is a reliable and valid instrument to assess multiple impairments of the elbow in patients with neurological conditions. Further studies are needed to confirm these findings.

Determination of shift factor for long-term life prediction of carbon/fiber epoxy composites using the time-temperature superposition principle

This study presents the way to determine the shift factor for predicting the long-term behavior of a carbon fiber/epoxy composite using the time-temperature superposition (TTS) principle. We conducted the multi-frequency, creep TTS, and stress relaxation TTS tests and obtained the dynamic mechanical analysis responses such as the storage modulus, creep compliance, and relaxation modulus. A shift factor determining the data movement is essential in creating the master curves. The shift factor was estimated using several methods such as the Arrhenius equation, William–Landel–Ferry equation, and manual shift method. The change in viscoelastic properties over a wide range of time was investigated by comparing the master curves to determine the most rational approach for estimating the shift factor. The master curves were obtained from the three methods based on the storage modulus. For the Arrhenius equation, the smooth master curves could not be obtained when applying a constant activation energy value. Still, using two activation energy values for the carbon fiber reinforced composite, the smooth master curves could be obtained. However, the manual shift method could get the master curves that overlap smoothly in the creep TTS and stress relaxation TTS, even without calculating activation energy values. Since the proposed procedure can estimate the long-term viscoelastic properties reasonably, the life span of the structure can be predicted at the design stage by using the master curves considering the viscoelastic properties.

Experimental Evaluation and Modeling of Physical Hardening in Asphalt Binders.

The research described in this paper deals with the experimental evaluation and modeling of physical hardening in asphalt binders. The term physical hardening refers to a reversible phenomenon occurring at low temperatures that causes time-dependent changes in viscoelastic properties. The experimental approach, followed to quantitatively assess physical hardening, was based on flexural creep tests carried out by means of the Bending Beam Rheometer at various temperatures and conditioning times. The results obtained confirmed that hardening phenomena have a significant influence on the creep response of asphalt binders, to an extent that can be quantitatively assessed by referring to the appropriate rheological parameters and by applying the loading time–conditioning time superposition principle. The experimental data were fitted to a mechanical model proposed in the literature (composed of a single Kelvin–Voigt element) and thereafter to an improved model (with two Kelvin–Voigt elements in series). Both models were assessed in terms of their prediction accuracy. The improved model was found to better describe physical hardening effects in the case of both short- and long-term conditioning. Practical implications of the study were finally highlighted by referring to possible ranking criteria to be introduced in acceptance procedures for the comparative evaluation of asphalt binders.

Biaxial mechanics of thermally denaturing skin - Part 2: Modeling

Understanding the response of skin to superphysiological temperatures is critical to the diagnosis and prognosis of thermal injuries, and to the development of temperature-based medical therapeutics. Unfortunately, this understanding has been hindered by our incomplete knowledge about the nonlinear coupling between skin temperature and its mechanics. In Part I of this study we experimentally demonstrated a complex interdependence of time, temperature, direction, and load in skin’s response to superphysiological temperatures. In Part II of our study, we test two different models of skin’s thermo-mechanics to explain our observations. In both models we assume that skin’s response to superphysiological temperatures is governed by the denaturation of its highly collageneous microstructure. Thus, we capture skin’s native mechanics via a microstructurally-motivated strain energy function which includes probability distributions for collagen fiber orientation and waviness. In the first model, we capture skin’s response to superphysiological temperatures as a transition between two states that link the kinetics of collagen fiber denaturation to fiber coiling and to the transformation of each fiber’s constitutive behavior from purely elastic to viscoelastic. In the second model, we capture skin’s response to superphysiological temperatures instead via three states in which a sequence of two reactions link the kinetics of collagen fiber denaturation to fiber coiling, followed by a state of fiber damage. Given the success of both models in qualitatively and quantitatively capturing our observations, we expect that our work will provide guidance for future experiments that could probe each model’s assumptions toward a better understanding of skin’s coupled thermo-mechanics and that our work will be used to guide the engineering design of heat treatment therapies. Statement of significanceQuantifying and modeling skin thermo-mechanics is critical to our understanding of skin physiology, pathophysiology, as well as heat-based treatments. This work addresses a lack of theoretical and computational models of the coupled thermo-mechanics of skin. Our model accounts for skin microstructure through modeling the probability of fiber orientation and fiber stress-free states. Denaturing induces changes in the stress-free configuration of collagen, as well as changes in fiber stiffness and viscoelastic properties. We propose two competing models that fit all of our experimental observations. These models will enable future developments of thermal-therapeutics, prevention and management of skin thermal injuries, and set a foundation for improved mechanistic models of skin thermo-mechanics.

Effect of high‐pressure treatment and cellulase‐mediate hydrolysis on functional, rheological and microstructural properties of garden cress seed residual fibre

SummaryGarden cress (Lepidium sativum) is valued in Asia and some part of Africa for its seed oil and other parts of plant that retain curative activities and act as a tonic in traditional medicine. The residue left over after the oil and protein extraction is a rich source of bioactive compounds and dietary fibres. The garden cress seed residual fibre (GCRF) contained 99.82% total dietary fibre (TDF), 99.4% insoluble dietary fibre (IDF) and 0.38% soluble dietary fibre (SDF). To improve the industrial applications of the GCRF, an approach was taken to break down the IDF into the SDF following a treatment of enzymatic hydrolysis [cellulase at 2% or 5% (w/w)] and high‐pressure processing (600 MPa/15 min) or a combination of both. The combined treatment had significantly improved the SDF concentration by loosening the surface structure of the GCRF and enhanced the hydration properties. The structural changes were elucidated using the Fourier transform infrared spectroscopy, rheometry and scanning electron microscopy. The Fourier transform infrared spectrum revealed a major shift in the cellulose band because of the combined effect of high‐pressure processing and enzymatic hydrolysis. High‐pressure‐assisted enzymatic hydrolysis was determined the best combination to be ensured almost 18‐fold increase in SDF ratio and to be improved radical scavenging activity more than two times in addition to well‐documented change in viscoelastic properties of the GCRF.

The Effect of Subsequent Stress-Induced Martensite Aging on the Viscoelastic Properties of Aged NiTiHf Polycrystals

This study investigated the effect of stress-induced martensite aging under tensile and compressive stresses on the functional and viscoelastic properties in Ni50.3Ti32.2Hf17.5 polycrystals containing dispersed H-phase particles up to 70 nm in size obtained by preliminary austenite aging at 873 K for 3 h. It was found that stress-induced martensite aging at 428 K for 12 h results in the appearance of a two-way shape memory effect of −0.5% in compression and +1.8% in tension. Moreover, a significant change in viscoelastic properties can be observed: an increase in internal friction (by 25%) and a change in elastic modulus in tensile samples. The increase in internal friction during martensitic transformation after stress-induced martensite aging is associated with the oriented growth of thermal-induced martensite. After stress-induced martensite aging, the elastic modulus of martensite (EM) increased by 8 GPa, and the elastic modulus of austenite (EA) decreased by 8 GPa. It was shown that stress-induced martensite aging strongly affects the functional and viscoelastic properties of material and can be used to control them.

Changes of Viscoelastic Properties of Aptamer-Based Sensing Layers Following Interaction with Listeria innocua.

A multiharmonic quartz crystal microbalance (QCM) has been applied to study the viscoelastic properties of the aptamer-based sensing layers at the surface of a QCM transducer covered by neutravidin following interaction with bacteria Listeria innocua. Addition of bacteria in the concentration range 5 × 103–106 CFU/mL resulted in a decrease of resonant frequency and in an increase of dissipation. The frequency decrease has been lower than one would expect considering the dimension of the bacteria. This can be caused by lower penetration depth of the acoustics wave (approximately 120 nm) in comparison with the thickness of the bacterial layer (approximately 500 nm). Addition of E. coli at the surface of neutravidin as well as aptamer layers did not result in significant changes in frequency and dissipation. Using the Kelvin–Voight model the analysis of the viscoelastic properties of the sensing layers was performed and several parameters such as penetration depth, Γ, viscosity coefficient, η, and shear modulus, μ, were determined following various modifications of QCM transducer. The penetration depth decreased following adsorption of the neutravidin layer, which is evidence of the formation of a rigid protein structure. This value did not change significantly following adsorption of aptamers and Listeria innocua. Viscosity coefficient was higher for the neutravidin layer in comparison with the naked QCM transducer in a buffer. However, a further increase of viscosity coefficient took place following attachment of aptamers suggesting their softer structure. The interaction of Listeria innocua with the aptamer layer resulted in slight decrease of viscosity coefficient. The shearing modulus increased for the neutravidin layer and decreased following aptamer adsorption, while a slight increase of µ was observed after the addition of Listeria innocua.

Viscosidad sanguínea en pacientes COVID-19 con sordera súbita

AntecedentesLa alteración en las propiedades viscoelásticas de la sangre ha sido anteriormente propuesta como etiopatogenia de complicaciones severas por COVID-19 y algunos casos de sordera súbita (SS). Pretendemos verificar si la aparición de casos de SS en pacientes ingresados por infección por SARS-CoV-2 puede correlacionarse de este modo.Pacientes y métodosEstudio longitudinal prospectivo de pacientes ingresados en nuestro Centro por COVID-19, efectuando monitorización de la viscosidad sanguínea (VS) a alta velocidad de cizallamiento (300 seg-1) y un requerimiento periódico personal sobre hipoacusia. Esta determinación se extendió a casos atendidos por SS sin infección en 2019 y 2020 y un grupo control de sujetos sanos normoacúsicos.ResultadosEl rango de normalidad se situó en 4,16±0,62 cps. Entre el 24 de febrero de 2020 y el 24 de marzo de 2021 se evaluaron 330 casos ingresados por COVID-19, 85 asistidos en la Unidad de Cuidados Intensivos (UCI). Fueron identificadas tras anamnesis y Audiometría Tonal Liminar (ATL) todo lo inmediata que el status clínico lo permitió hasta nueve casos con SS, todos pertenecientes al grupo de UCI. La VS media fue 4,38±0,43 cps en el grupo de sala, 4,53±0,39 cps en los pacientes en UCI sin SS, y 4,85±0,52 cps en los casos con SS, con diferencias estadísticamente significativas. Las mayores elevaciones de la VS en los casos con SS se detectaron entre los días seis y 10 del ingreso hospitalario. En 2019 consultaron cuatro casos y otros 2 en 2020 sin diagnóstico de COVID-19, con valores normales de VS.ConclusionesDurante la infección por SARS-CoV-2 los pacientes pueden presentar elevación en la VS y SS, si bien se hacen necesarios un grupo control hospitalario y un volumen muestral mayor para confirmar la predisposición a la hiperviscosidad. La incidencia del daño auditivo resulta considerable si se tiene en cuenta su posible aparición en pacientes críticos con COVID-19.

Comparative Analysis of the Hemostasiological Profile in Sheep and Patients with Cardiovascular Pathology as the Basis for Predicting Thrombotic Risks During Preclinical Tests of Vascular Prostheses.

The aim of the investigation was to study the details of hemostasiological profile in sheep and patients with coronary heart disease (CHD) and to find the possibility of predicting thrombotic risks during preclinical tests of vascular prostheses on a large laboratory animal model.Materials and Methods.The functional activity of platelets was measured in platelet-rich plasma with inductors: ADP, epinephrine, collagen. Prothrombin activity, international normalized ratio, activated partial thromboplastin time (APTT), thrombin time, fibrinogen concentration, antithrombin III and protein C activity, fibrinolysis were determined in blood plasma. Changes in clot formation and viscoelastic properties of clots were assessed using thromboelastography.Results.Significant differences were found in the hemostasiological profile of sheep and CHD patients. Sheep platelets had increased response to ADP induction and practically no response to epinephrine induction; collagen-induced aggregation was comparable in the study groups. Coagulation hemostasis of sheep was characterized by increased activity of the prothrombin complex, shortened thrombin time, while APTT and fibrinogen values remained comparable. At the same time, sheep exhibited a significant decrease in the activity of anticoagulant and fibrinolytic systems as compared to CHD patients. When assessing dynamic changes in clot formation, it was observed that initiation phase was faster in animals, while clot density exceeded that in patients.Conclusion.The hemostasiological profile of sheep is characterized by the increased speed of thrombus formation, greater strength of the formed clot, and lower lysis ability as compared to CHD patients. The revealed details of the hemostasiological profile of sheep can be potential targets for therapy with antithrombotic drugs that minimize thrombotic risks in preclinical testing of vascular prostheses.

Resonant acoustic rheometry for non-contact characterization of viscoelastic biomaterials

Resonant Acoustic Rheometry (RAR) is a new, non-contact technique to characterize the mechanical properties of soft and viscoelastic biomaterials, such as hydrogels, that are used to mimic the extracellular matrix in tissue engineering. RAR uses a focused ultrasound pulse to generate a microscale perturbation at the sample surface and tracks the ensuing surface wave using pulse-echo ultrasound. The frequency spectrum of the resonant surface waves is analyzed to extract viscoelastic material properties. In this study, RAR was used to characterize fibrin, gelatin, and agarose hydrogels. Single time point measurements of gelled samples with static mechanical properties showed that RAR provided consistent quantitative data and measured intrinsic material characteristics independent of ultrasound parameters. RAR was also used to longitudinally track dynamic changes in viscoelastic properties over the course of fibrin gelation, revealing distinct phase and material property transitions. Application of RAR was verified using finite element modeling and the results were validated against rotational shear rheometry. Importantly, RAR circumvents some limitations of conventional rheology methods and can be performed in a high-throughput manner using conventional labware. Overall, these studies demonstrate that RAR can be a valuable tool to noninvasively quantify the viscoelastic mechanical properties of soft hydrogel biomaterials.

Role of temperature on bio-printability of gelatin methacryloyl bioink in two-step cross-linking strategy for tissue engineering applications

Additive manufacturing has shown promising results in reconstructing three-dimensional (3D) living tissues for various applications, including tissue engineering, regenerative medicine, drug discovery, and high-throughput drug screening. In extrusion-based bioprinters, stable formation of filaments and high-fidelity deposition of bioinks are the primary challenges in fabrication of physiologically relevant tissue constructs. Among various bioinks, gelatin methacryloyl (GelMA) is known as a photocurable and physicochemically tunable hydrogel with a demonstrated biocompatibility and tunable biodegradation properties. The two-step crosslinking of GelMA (reversible thermal gelation and permanent photo-crosslinking) has attracted researchers to make complex tissue constructs. Despite promising results in filament formation and printability of this hydrogel, the effect of temperature on physicochemical properties, cytocompatibility, and biodegradation of the hydrogel are to be investigated. This work studies the effect of thermoreversible, physical crosslinking on printability of GelMA. The results of 3D printing of GelMA at different temperatures followed by irreversible chemical photo-crosslinking show that the decrease in temperature improves the filament formation and shape fidelity of the deposited hydrogel, particularly at the temperatures around 15 °C. Time dependant mechanical testing of the printed samples revealed that decreasing the extruding temperature increases the elastic properties of the extruded filaments. Furthermore, our novel approach in minimizing the slippage effect during rheological study enabled to measure changes in linear and non-linear viscoelastic properties of the printed samples at different temperatures. A considerable increase in storage modulus of the extruded samples printed at lower temperatures confirms their higher solid behavior. Scanning electron microscopy revealed a remarkable decrease in porosity of the extruded hydrogels by decreasing the temperature. Chemical analysis by Fourier-transform infrared spectroscopy and circular dichroism showed a direct relationship between the coil-helix transition in hydrogel macromers and its physical alterations. Finally, biodegradation and cytocompatibility of the extruded hydrogels decreased at lower extruding temperatures.

Comparison of the Quantra QPlus System With Thromboelastography in Cardiac Surgery

Use of viscoelastic testing, such as thromboelastography (TEG), is recommended in cardiac surgery to monitor coagulation and to guide the transfusion of blood products. The Quantra QPlus System is a novel point-of-care platform that uses ultrasonic pulses to characterize dynamic changes in viscoelastic properties of a blood sample during coagulation. Despite the ability to assess similar aspects of clot formation, limited studies addressing the interchangeability of viscoelastic testing parameters exist. The primary aim of the present study was to assess the correlation and agreement between Quantra and TEG5000 results using blood samples from cardiac surgery patients. Tertiary care, academic medical center. Prospective observational study. Twenty-eight patients undergoing elective cardiac surgery undergoing cardiopulmonary bypass were evaluated. Perioperative blood samples were collected and assessed using Quantra, and results were compared with TEG and conventional coagulation testing. Method comparison analysis demonstrated that Quantra parameters (Quantra clot time, clot stiffness, and fibrinogen contribution to clot stiffness) significantly correlated with TEG R and TEG G after induction of anesthesia, during cardiopulmonary bypass, and after rewarming (rs = 0.83, rs = 0.84, and rs = 0.73, respectively). However, Quantra parameters demonstrated poor agreement compared with equivalent TEG5000 parameters. The Quantra QPlus System significantly correlated with TEG5000, suggesting that this test may be used in a similar clinical context. Despite the strength of correlation between Quantra and TEG parameters, measurements are not interchangeable.

Rheology-morphology relationships of new polymer-modified bitumen based on thermoplastic polyurethanes (TPU)

The present study reports a new type of polymer-modified bitumen (PMB) which considers the use of a thermoplastic polyurethane (TPU) as an alternative to conventional thermoplastic elastomers such as poly(styrene-b-butadiene-b-styrene) block copolymers. As for other block copolymers, the structure of the TPU, made of two types of segments which can microphase-separate, leads to its selective swelling by the oily fractions of bitumen. The poor compatibility of hard segments (HS) with bitumen is responsible for this partial swelling of the TPU by the maltene fractions. By varying the TPU content in the bitumen-TPU blend a dramatic change in viscoelastic properties for a TPU content close to 11 wt% is shown, with the appearance at high temperatures of an elastic response due to the percolation of the TPU-rich phase. This percolation phenomenon is highlighted by multiscale morphology characterizations and well described by a conventional mechanical percolation model. Different TPU architectures, i.e. different hard to soft segments ratios, are studied. The best compromise is found for a blend containing TPU with 13 wt% of HS as it displays a favorable swelling of percolated TPU rich phase while maintaining its viscoelastic behavior.

A Novel Approach to Structure Plant-Based Yogurts Using High Pressure Processing.

Current plant-based yogurts are made by the fermentation of plant-based milks. Although this imparts fermented flavors and probiotic cultures, the process is relatively longer and often leads to textural issues. The protein content of these plant-based yogurts is also lower than their dairy counterparts. To overcome these challenges, this paper explores the high pressure processing (HPP) of plant protein ingredients as an alternative structuring strategy for plant-based yogurts. Using mung bean (MB), chickpea (CP), pea (PP), lentil (LP), and faba bean (FB) proteins as examples, this work compared the viscosity and viscoelastic properties of high pressure-structured (600 MPa, 5 min, 5 °C) 12% (w/w) plant protein gels without, and with 5% (w/w) sunflower oil (SO) to commercial plain skim and whole milk Greek yogurts and discussed the feasibility of using HPP to develop plant-based yogurts. HPP formed viscoelastic gels (G’ > G’’) for all plant protein samples with comparable gel strength (G’~102–103 Pa; tan δ~0.2–0.3) to commercial dairy yogurts. The plant protein gel strength decreased in the order: CP~CPSO~LP~LPSO > MBSO~PPSO~FB~FBSO > PP >> MB. Modest addition of sunflower oil led to little change in viscoelastic properties for all plant protein samples except for MB and PP, where gel strength increased with incorporated oil. The emulsion gels were also more viscous than the hydrogels. Nonetheless, the viscosity of the plant protein gels was similar to the dairy yogurts. Finally, a process involving separate biotransformation for optimized flavor production and high pressure processing for consistent texture generation was proposed. This could lead to high protein plant-based yogurt products with desirable texture, flavor, and nutrition.

Effect of Smoking on Nasal Mucociliary Clearance.

Nasal mucociliary clearance (NMC) system is an important defence mechanism in respiratory tract. The contents present in the smoke are found to be toxic to cilia in vitro. Our study aims at evaluating the NMC in smokers so as to know effect of tobacco smoke on ciliary function and also comparing it with non smokers. We also studied effect of duration, intensity and pattern of smoking on the NMC. A total of 60 participants in the age group 21-40years (30 smokers and 30 non smokers) were included in the study. Saccharin test was performed in all participants. A 0.5mm diameter particle of saccharin was placed 1cm from the anterior end of the inferior nasal turbinate. The time duration was noted for the first appearance of sweet taste. The mean NMC in smoker group was 16.53min and in nonsmoker group was 9.28min On comparison it was found that NMC time in smoker group was significantly higher than nonsmoker group p < 0.001 also a positive correlation noted between pack years of smoking and NMC. Saccharin test is a simple test to assess NMC. The prolonged NMC in smokers may be due to reduced ciliary activity or due to changes in viscoelastic properties.

Real-time monitoring of oil-induced micellar transitions in viscoelastic surfactants by small-angle X-ray scattering

HypothesisViscoelastic surfactant solutions with entangled wormlike micelles (WLMs) display dramatic changes in rheological properties when exposed to hydrophobic substances. This change is key in the oil and gas industry and for drug delivery. The changes in viscoelastic properties are believed to be a result of changes in micellar shape due to the oil solubilization. The time dependence of the process has practical importance, yet its mechanism is unknown. We set out to map the structural changes with time using small-angle x-ray scattering (SAXS). ExperimentA surfactant system with erucamidopropyl hydroxypropyl sulfobetaine as the active ingredient was homogenized with three concentrations of n-decane (70 mM, 140 mM, 280 mM) in 600 mM CaCl2. The samples were monitored with time using SAXS. Model fits were used to determine the structures present in the sample at each time interval. FindingsThe entangled WLMs disappeared while spherical decane-swollen micelles formed with time, explaining the sharp decrease in viscosity. It was shown that the time at which the spherical swollen micelles appeared depends on the concentration of n-decane. This insight allows control of the spherical micelle appearance time, which is important for the successful application of WLMs in sectors that require WLMs to persist for a set time before they transform.