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1.
Food Chem ; 398: 133938, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-35987008

RESUMO

As a green and safe physical technology, irradiation is increasingly used to improve starch properties. In the study, oat starch was pre-gelatinized at 70 °C followed by spray drying. Subsequently, the spray-dried starch (SDS) was exposed to electron beam (e-beam) irradiation at different doses to obtain new pre-gelatinized starch. Spray drying caused a decrement in the ratio of long B3 chains and the molecular weight of starch. Spray-dried starch (SDS) slightly increased solubility and swelling power than native starch. When SDS was subjected to e-beam irradiation, its solubility and swelling power increased dramatically, but the pasting viscosities, gelatinization temperatures, apparent viscosity, storage modulus (G') and lost modulus (G″) reduced. The depolymerization of starch molecules and the breakage of amylopectin chains might be responsible for changing the physicochemical properties of e-beam irradiated starch. These results showed that spray drying combined with e-beam irradiation would potentially produce new pre-gelatinized starch.


Assuntos
Avena , Amido , Amilopectina , Amilose/química , Elétrons , Solubilidade , Secagem por Atomização , Amido/química , Viscosidade
2.
Food Chem ; 398: 133915, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-35988417

RESUMO

In this study, structural characteristics of Fenugreek (FG), Guar (GG), Locust bean (LBG), and Tara gums (TG) and their influence on physicochemical properties of corn starch (CS) gels were investigated. Results showed that FG presented a rigid rod structure, and GG, LBG, and TG showed an extended structure. The Mannose/Galactose (Man/Gal) ratio of FG, GG, LBG, and TG was 1.37, 1.96, 2.99, and 3.46, respectively. The molecular weight (Mw) of FG, GG, LBG, and TG was 0.89 × 106, 2.71 × 106, 3.61 × 106, and 2.77 × 106 Da, respectively. The structure-function relationship indicated that galactomannans with a high Man/Gal ratio and extended structure presented a higher apparent viscosity, formed gel more easily, and could limit retrogradation and improve freeze-thaw stability and textural profile of CS gels. Consequently, the results could be beneficial for the application of galactomannans in starch-based foods to improve their sensory characteristics and storage quality.


Assuntos
Amido , Zea mays , Galactose/análogos & derivados , Géis/química , Humanos , Mananas/química , Amido/química , Relação Estrutura-Atividade , Viscosidade , Zea mays/química
3.
J Biomech Eng ; 145(1)2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-35838330

RESUMO

Reactive viscoelasticity is a theoretical framework based on the theory of reactive constrained mixtures that encompasses nonlinear viscoelastic responses. It models a viscoelastic solid as a mixture of strong and weak bonds that maintain the cohesiveness of the molecular constituents of the solid matter. Strong bonds impart the elastic response while weak bonds break and reform into a stress-free state in response to loading. The process of bonds breaking and reforming is modeled as a reaction where loaded bonds are the reactants and bonds reformed into a stress-free state are the products of a reaction. The reaction is triggered by the evolving state of loading. The state of stress in strong bonds is a function of the total strain in the material, whereas the state of stress in weak bonds is based on the state of strain relative to the time that these bonds were reformed. This study introduces two important practical contributions to the reactive nonlinear viscoelasticity framework: (1) normally, the evaluation of the stress tensor involves taking a summation over a continually increasing number of weak bond generations, which is poorly suited for a computational scheme. Therefore, this study presents an effective numerical scheme for evaluating the strain energy density, the Cauchy stress, and spatial elasticity tensors of reactive viscoelastic materials. (2) We provide the conditions for satisfying frame indifference for anisotropic nonlinear viscoelasticity, including for tension-bearing fiber models. Code verifications and model validations against experimental data provide evidence in support of this updated formulation.


Assuntos
Modelos Biológicos , Dinâmica não Linear , Anisotropia , Elasticidade , Estresse Mecânico , Viscosidade
4.
BMC Anesthesiol ; 22(1): 285, 2022 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-36088303

RESUMO

PURPOSE: Aspiration is a feared complication that may occur during airway management, and can significantly contribute to morbidity and mortality. Availability of a suctioning device with a suction catheter capable of clearing the airway is mandatory for airway management. However, suction performance may be significantly different amongst different suction catheters. The aim of this study was to compare suction rates of a standard 14 Ch suction catheter (SC), a Yankauer catheter (Y) and a DuCanto catheter (DC) using 4 fluids with different viscosity. METHODS: In this simulation trial, 4 preparations with standardized viscosity were prepared using a Xanthane-based medical fluid thickener. Lowest viscosity was achieved using tap water without thickener, syrup-like viscosity was achieved by adding 10 g per liter tap water, honey-like viscosity was achieved by adding 20 g per liter, and a pudding-like viscosity was achieved by adding 30 g of thickening powder per liter tap water. Each preparation was suctioned for 15 s with the three different suctioning devices. Measurements were repeated four times. The amount of removed preparation by suctioning was measured using a tared scale. RESULTS: Suction rates for water were 580 ± 34 mg for SC, 888 ± 5 mg for Y and 1087 ± 15 for DC; for syrup-like viscosity it was 383 ± 34(SC) vs. 661 ± 64(Y) vs. 935 ± 42(DC); for honey-like viscosity it was 191 ± 21(SC) vs. 426 ± 34(Y) vs. 590 ± 68(DC); and for pudding-like viscosity 74 ± 13(SC) vs. 164 ± 6(Y) vs. 211 ± 8(DC). CONCLUSION: Suctioning liquids of different viscosity, the new DuCanto catheter was more effective than the Yankauer catheter that was more effective than a standard suctioning catheter. The relative superiority of the DuCanto was highest in fluids with high viscosity.


Assuntos
Cateterismo , Cateteres , Sucção , Viscosidade , Água
5.
Phys Rev Lett ; 129(10): 104502, 2022 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-36112448

RESUMO

Suspensions of DNA macromolecules (0.8 wppm, 60 kbp), modeled as finitely extensible nonlinear elastic dumbbells coupled to the Newtonian fluid, show drag reduction up to 27% at friction Reynolds number 180, saturating at the previously unachieved Weissenberg number ≃10^{4}. At a large Weissenberg number, the drag reduction is entirely induced by the fully stretched polymers, as confirmed by the extensional viscosity field. The polymer extension is strongly non-Gaussian, in contrast to the assumptions of classical viscoelastic models.


Assuntos
DNA , Polímeros , Fricção , Viscosidade
6.
Food Res Int ; 160: 111674, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-36076385

RESUMO

High shear rheometry was used to investigate the rheological behavior of high internal phase emulsions (HIPEs) stabilized by whey protein isolate (WPI). The physical stability of HIPEs was tested at extremely high shear rates generated by decreasing the gap height between parallel plates. Viscosity and yield stress, at narrow gaps, increased with protein concentration due to tighter packing of smaller droplets. Structural breakdown and recovery of HIPEs were affected by protein concentration and pH. The hysteresis behavior of HIPEs was either thixotropic or anti-thixotropic and was determined by protein concentration, whereas pH affected the magnitude of anti-thixotropy. At pH 3, emulsions showed greater stability against extreme shear and creaming due to higher deformability of oil droplets and increased interdroplet interaction compared to neutral pH. Challenging the physical integrity of concentrated emulsions under high shear is an effective way to characterize microstructural changes and stability of HIPEs in foods.


Assuntos
Emulsões , Emulsões/química , Concentração de Íons de Hidrogênio , Reologia , Viscosidade , Proteínas do Soro do Leite/química
7.
Carbohydr Polym ; 296: 119959, 2022 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-36088001

RESUMO

The role of amylose content in electrospinning starch nanofibres is well understood, but that is not the case for the roles of the molecular structures of amylose and amylopectin. Here, correlations between starch molecular-structure parameters and electrospinnability evaluation indices (average droplet number, average bead number, and average fibre diameter) and dope properties (shear viscosity, conductivity, and surface tension) were examined. Starches with lower amounts of short amylopectin chains, higher amounts of either/or long amylopectin chains and/or lower degree of branching showed decreased viscosity of the electrospinning dopes, and resulted in a reduced average droplet number of electrospun fibre mats. The molecular sizes of amylose and whole starch, and the average degree of polymerization for amylose chains, all correlated with the shear viscosity and surface tension of dopes, and thus influenced the average fibre diameter. This expands the current understanding between amylopectin molecular structure and starch electrospinning, thereby assisting a better choice of starches for desired electrospinnability properties.


Assuntos
Amilopectina , Amilose , Amilopectina/química , Amilose/química , Carboidratos , Fibras na Dieta , Estrutura Molecular , Amido/química , Viscosidade
8.
Nutrients ; 14(17)2022 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-36079712

RESUMO

The adaptation of liquids for patients with dysphagia requires precision and individualization in the viscosities used. We describe the variations of viscosity in water at different concentrations and evolution over time of the three compositions of commercial thickeners that are on the market (starch, starch with gums, and gum). By increasing the concentration in water, the viscosity of gum-based thickeners increases linearly, but it did not reach pudding texture, whereas the viscosity of the starch-based thickeners (alone or mixed with gums) rapidly reaches very thick textures. We modeled the viscosity at different concentrations of the four thickeners using regression analysis (R2 > 0.9). We analyzed viscosity changes after 6 h of preparation. The viscosity of gum-based thickeners increased by a maximum of 6.5% after 6 h of preparation, while starch-based thickeners increased by up to 43%. These findings are important for correct handling and prescription. Gum-based thickeners have a predictable linear behavior with the formula we present, reaching nectar and honey-like textures with less quantity of thickener, and are stable over time. In contrast, starch thickeners have an exponential behavior which is difficult to handle, they reach pudding-like viscosity, and are not stable over time.


Assuntos
Transtornos de Deglutição , Aditivos Alimentares , Aditivos Alimentares/análise , Humanos , Amido , Viscosidade , Água
9.
Biol Pharm Bull ; 45(9): 1300-1305, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36047198

RESUMO

Understanding a monoclonal antibody's (MAb) physicochemical properties early in drug discovery is important for determining developability. Viscosity is important because antibodies with high viscosity have limited administration routes. Predicting the viscosity of highly concentrated MAb solutions is therefore essential for assessing developability. Here, we measured the viscosity and diffusion interaction coefficient (kDiff) of 3 MAbs under 15 different formulation conditions (pH and salt) and evaluated correlations between parameters. We also used a computational approach to identify the key factors underlying differences in concentration-dependent curves for viscosity among the MAbs and formulation conditions. Results showed that viscosity increased exponentially at high concentrations, and that this concentration-dependency could be predicted from kDiff. Attempts to set viscosity criterion for use by subcutaneous (SC) and intramuscular (IM) administration suggested that solutions with kDiff greater than -20 mL/g may be candidates. Computational analysis suggested that the presence of a large negative charge in the complementarity determining region (CDR) is a major factor underlying the difference in concentration-dependency among the three MAbs under different formulation conditions. Because it is possible to predict the administration form of antibody solutions, determination of kDiff at the early discovery stage may be essential for effective antibody development.


Assuntos
Anticorpos Monoclonais , Regiões Determinantes de Complementaridade , Anticorpos Monoclonais/química , Viscosidade
10.
Nat Commun ; 13(1): 5180, 2022 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-36056012

RESUMO

How local stresses propagate through polymeric fluids, and, more generally, how macromolecular dynamics give rise to viscoelasticity are open questions vital to wide-ranging scientific and industrial fields. Here, to unambiguously connect polymer dynamics to force response, and map the deformation fields that arise in macromolecular materials, we present Optical-Tweezers-integrating-Differential -Dynamic-Microscopy (OpTiDMM) that simultaneously imposes local strains, measures resistive forces, and analyzes the motion of the surrounding polymers. Our measurements with blends of ring and linear polymers (DNA) and their composites with stiff polymers (microtubules) uncover an unexpected resonant response, in which strain alignment, superdiffusivity, and elasticity are maximized when the strain rate is comparable to the entanglement rate. Microtubules suppress this resonance, while substantially increasing elastic storage, due to varying degrees to which the polymers buildup, stretch and flow along the strain path, and configurationally relax induced stress. More broadly, the rich multi-scale coupling of mechanics and dynamics afforded by OpTiDDM, empowers its interdisciplinary use to elucidate non-trivial phenomena that sculpt stress propagation dynamics-critical to commercial applications and cell mechanics alike.


Assuntos
Microscopia , Polímeros , Elasticidade , Proteínas Associadas aos Microtúbulos , Pinças Ópticas , Viscosidade
11.
Anal Chim Acta ; 1226: 340192, 2022 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-36068051

RESUMO

Viscosity is an essential microenvironmental parameter, which is related to various diseases such as acute inflammation. So it is necessary to develop a probe to monitor viscosity changes during the inflammatory progression in vivo. Herein, a HPQ (2-(2'-hydroxyphenyl)-4(3H)-quinazolinone)-based fluorescent probe named HPQ-BI-V is prepared for detecting viscosity in biological systems. The introduction of benzindole groups extends the π conjugation of HPQ, resulting in far-red emission wavelength at 610 nm. When the viscosity raises from 3.11 cP to 567.1 cP, the fluorescence signal increases 711 times, indicating the high sensitivity of the probe. Furthermore, this probe displays excellent selectivity for viscosity in comparison with other interfering analytes. Furthermore, the probe has excellent photostability and outstanding response capability in the physiological pH range. Given these advantages, HPQ-BI-V can be applied for detecting viscosity changes in HepG2 cells and zebrafish. In particular, the probe can successfully visualize viscosity changes in acute inflammatory mice induced by LPS and the assessment of anti-inflammatory drug.


Assuntos
Corantes Fluorescentes , Peixe-Zebra , Animais , Modelos Animais de Doenças , Células HeLa , Humanos , Inflamação/induzido quimicamente , Camundongos , Mitocôndrias , Viscosidade
12.
Eur Phys J E Soft Matter ; 45(9): 76, 2022 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-36103057

RESUMO

We developed a simple method to investigate rheological properties of soft surfaces, such as polymeric liquids and colloidal suspensions, by capturing the images of a metal micro-needle inserted into the surface. At contact, a meniscus-like deformation is formed on the surface. By relating the shape of the deformation to the balance of applied forces, local elasticity and viscosity just inside the surface are obtained. With a facile setup and rapid measurement process, the present method can be implemented to variety of systems, for instance, drying sessile drops and small volume of liquid confined in a capillary.


Assuntos
Polímeros , Reologia , Viscosidade
13.
Molecules ; 27(17)2022 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-36080267

RESUMO

Starch is affected by several limitations, e.g., retro-gradation, high viscosity even at low concentrations, handling issues, poor freeze-thaw stability, low process tolerance, and gel opacity. In this context, physical, chemical, and enzymatic methods have been investigated for addressing such limitations or adding new attributes. Thus, the creation of biomaterial-based nanoparticles has sparked curiosity. Because of that, single nucleotide polymorphisms are gaining a lot of interest in food packaging technology. This is due to their ability to increase the mechanical and water vapor resistance of the matrix, as well as hide its re-crystallization during storage in high-humidity atmospheres and enhance the mechanical properties of films when binding in paper machines and paper coating. In medicine, single nucleotide polymorphisms (SNPs) are suitable as carriers in the field of drug delivery for immobilized bioactive or therapeutic agents, as well as wastewater treatments as an alternative to expensive activated carbons. Starch nanoparticle preparations can be performed by hydrolysis via acid hydrolysis of the amorphous part of a starch molecule, the use of enzymes such as pullulanase or isoamylase, or a combination of two regeneration and mechanical treatments with the employment of extrusion, irradiation, ultrasound, or precipitation. The possibility of obtaining cheap and easy-to-use methods for starch and starch derivative nanoparticles is of fundamental importance. Nano-precipitation and ultra-sonication are rather simple and reliable methods for nanoparticle production. The process involves the addition of a diluted starch solution into a non-solvent, and ultra-sonication aims to reduce the size by breaking the covalent bonds in polymeric material due to intense shear forces or mechanical effects associated with the collapsing of micro-bubbles by sound waves. The current study focuses on starch nanoparticle manufacturing, characterization, and emerging applications.


Assuntos
Nanopartículas , Amido , Embalagem de Alimentos , Nanopartículas/química , Polímeros , Amido/química , Viscosidade
14.
Molecules ; 27(17)2022 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-36080433

RESUMO

Non-isothermal differential scanning calorimetry (DSC) was used to study the influences of particle size (daver) and heating rate (q+) on the structural relaxation, crystal growth and decomposition kinetics of amorphous indomethacin. The structural relaxation and decomposition processes exhibited daver-independent kinetics, with the q+ dependences based on the apparent activation energies of 342 and 106 kJ·mol-1, respectively. The DSC-measured crystal growth kinetics played a dominant role in the nucleation throughout the total macroscopic amorphous-to-crystalline transformation: the change from the zero-order to the autocatalytic mechanism with increasing q+, the significant alteration of kinetics, with the storage below the glass transition temperature, and the accelerated crystallization due to mechanically induced defects. Whereas slow q+ led to the formation of the thermodynamically stable γ polymorph, fast q+ produced a significant amount of the metastable α polymorph. Mutual correlations between the macroscopic and microscopic crystal growth processes, and between the viscous flow and structural relaxation motions, were discussed based on the values of the corresponding activation energies. Notably, this approach helped us to distinguish between particular crystal growth modes in the case of the powdered indomethacin materials. Ediger's decoupling parameter was used to quantify the relationship between the viscosity and crystal growth. The link between the cooperativity of structural domains, parameters of the Tool-Narayanaswamy-Moynihan relaxation model and microscopic crystal growth was proposed.


Assuntos
Indometacina , Varredura Diferencial de Calorimetria , Cristalização , Indometacina/química , Temperatura , Temperatura de Transição , Viscosidade
15.
Sensors (Basel) ; 22(17)2022 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-36081147

RESUMO

Magnetic particle spectroscopy (MPS) in the Brownian relaxation regime, also termed magnetic spectroscopy of Brownian motion (MSB), can detect and quantitate very low, sub-nanomolar concentrations of molecular biomarkers. MPS/MSB uses the harmonics of the magnetization induced by a small, low-frequency oscillating magnetic field to provide quantitative information about the magnetic nanoparticles' (mNPs') microenvironment. A key application uses antibody-coated mNPs to produce biomarker-mediated aggregation that can be detected using MPS/MSB. However, relaxation changes can also be caused by viscosity changes. To address this challenge, we propose a metric that can distinguish between aggregation and viscosity. Viscosity changes scale the MPS/MSB harmonic ratios with a constant multiplier across all applied field frequencies. The change in viscosity is exactly equal to the multiplier with generality, avoiding the need to understand the signal explicitly. This simple scaling relationship is violated when particles aggregate. Instead, a separate multiplier must be used for each frequency. The standard deviation of the multipliers over frequency defines a metric isolating viscosity (zero standard deviation) from aggregation (non-zero standard deviation). It increases monotonically with biomarker concentration. We modeled aggregation and simulated the MPS/MSB signal changes resulting from aggregation and viscosity changes. MPS/MSB signal changes were also measured experimentally using 100 nm iron-oxide mNPs in solutions with different viscosities (modulated by glycerol concentration) and with different levels of aggregation (modulated by concanavalin A linker concentrations). Experimental and simulation results confirmed that viscosity changes produced small changes in the standard deviation and aggregation produced larger values of standard deviation. This work overcomes a key barrier to using MPS/MSB to detect biomarkers in vivo with variable tissue viscosity.


Assuntos
Magnetismo , Nanopartículas , Biomarcadores , Nanopartículas/química , Análise Espectral , Viscosidade
16.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 914-917, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36085967

RESUMO

In this paper, we present a validated, novel, in silico molecular dynamics (MD) model of eccrine sweat with approx. 35k atoms developed using Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) program. CHARMMS36m force field for constituent atoms and SPC/E water model are used to develop this model. The model outputs transport properties such as self-diffusivity computed using mean squared displacement and bulk viscosity computed via Green-Kubo correlations, which are compared with existing literature values and experimental studies and presented. This validated model is intended to serve as a tool to develop eccrine sweat based biosensors.


Assuntos
Técnicas Biossensoriais , Suor , Glândulas Écrinas , Simulação de Dinâmica Molecular , Viscosidade
17.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 1512-1515, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086082

RESUMO

The knowledge of the biomechanical properties of tissues is useful for different applications such as disease diagnosis and treatment monitoring. Reverberant Shear Wave Elastography (RSWE) is an approach that has reduced the restrictions on wave generation to characterize the shear wave velocity over a range of frequencies. This approach is based on the generation of a reverberant field that is generated by the reflections of waves from inhomogeneities and tissue boundaries that exist in the tissue. The Kelvin-Voigt Fractional Derivative model is commonly used to characterize elasticity and viscosity of soft tissue when using shear wave ultrasound elatography. These viscoelastic characteristics can be then validated using mechanical measurements (MM) such as stress relaxation. During RSWE acquisition, the effect of interface pressure, induced by pushing the probe on the skin through the gel pad, on the viscous and elastic characteristics of tissue can be investigated. However, the effect of interface pressure on the validity of the extracted viscous and elastic characteristics was not investigated before. Therefore, the purpose of this study was to compare the estimation of the viscoelastic parameters at different thickness of gel pad against the viscoelastic characteristics obtained from MM. The experiments were conducted in a tissue-mimicking phantom. The results confirm that the relaxed elastic constant (µ0) can be depreciated. In addition, a higher congruence was found in the viscous parameter (ηα) estimated at 6 and 7 mm. On the other hand, a difference in the order of fractional derivative (α) was found.


Assuntos
Técnicas de Imagem por Elasticidade , Elasticidade , Técnicas de Imagem por Elasticidade/métodos , Imagens de Fantasmas , Ultrassonografia , Viscosidade
18.
Biochim Biophys Acta Mol Basis Dis ; 1868(11): 166513, 2022 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-35932892

RESUMO

BACKGROUND: The mechanical state of the extracellular environment of the brain cells considerably affects their phenotype during the development of central nervous system (CNS) pathologies, and when the cells respond to drugs. The reports on the evaluation of the viscoelastic properties of different brain tumors have shown that both tissue stiffness and viscosity can be altered during cancer development. Although a compelling number of reports established the role of substrate stiffness on the proliferation, motility, and drug sensitivity of brain cancer cells, there is a lack of parallel data in terms of alterations in substrate viscosity. METHODS: Based on viscoelasticity measurements of rat brain samples using strain rheometry, polyacrylamide (PAA) hydrogels mimicking elastic and viscous parameters of the tissues were prepared. Optical microscopy and flow cytometry were employed to assess the differences in glioblastoma cells morphology, proliferation, and cytotoxicity of anticancer drug temozolomide (TMZ) due to increased substrate viscosity. RESULTS: Our results indicate that changes in substrate viscosity affect the proliferation of untreated glioma cells to a lesser extent, but have a significant impact on the apoptosis-associated depolarization of mitochondria and level of DNA fragmentation. This suggests that viscosity sensing and stiffness sensing machinery can activate different signaling pathways in glioma cells. CONCLUSION: Collected data indicate that viscosity should be considered an important parameter in in vitro polymer-based cell culture systems used for drug screening.


Assuntos
Antineoplásicos , Neoplasias Encefálicas , Glioblastoma , Glioma , Antineoplásicos/farmacologia , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/genética , Proliferação de Células , Glioblastoma/metabolismo , Glioma/patologia , Humanos , Hidrogéis/farmacologia , Hidrogéis/uso terapêutico , Polímeros , Temozolomida/farmacologia , Temozolomida/uso terapêutico , Viscosidade
19.
Lab Chip ; 22(18): 3489-3498, 2022 09 13.
Artigo em Inglês | MEDLINE | ID: mdl-35959658

RESUMO

We designed and fabricated a new microfluidic device to better enable study of foam microstructure and rheology in planar fractures. The design phase included stress-strain finite element analysis to enhance the pressure tolerance of the device. The optimized design is a 2 cm wide by 7.75 cm long rough fracture that includes 25 posts to anchor the glass cover plate. The posts simulate asperities and provide structural support during bonding of a glass cover plate to the device. Importantly, the new design illustrates improved ability to sustain large differential pressure compared to previous designs in the literature. The rheometer permits study of the relationship among foam bubble morphology, pressure drop, and flow rates. Our findings validated the previous, sparse microvisual studies mentioned in the literature and confirmed that small quality foam, ranging from 20 to 50% gas by volume, contains dispersed bubbles separated by liquid lenses. In this range, the distribution of bubble sizes was roughly 80-90% small uniform bubbles and only 10-20% of larger and more elongated bubbles. Additionally, our studies reveal that foam apparent viscosity is a strong function of foam quality, velocity, and texture (i.e., bubble size). Apparent viscosity of foam ranged from 100 to 600 cP for the conditions studied. High quality foams in fractures are independent of gas flow rates but very sensitive to liquid flow rates. On the other hand, low quality foams are sensitive to gas flow rates but independent of liquid flow rates.


Assuntos
Viscosidade , Reologia
20.
Bioinspir Biomim ; 17(6)2022 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-35998610

RESUMO

This work considers the two-dimensional flow field of an incompressible viscous fluid in a parallel-sided channel. In our study, one of the walls is fixed whereas the other one is elastically mounted, and sustained oscillations are induced by the fluid motion. The flow that forces the wall movement is produced as a consequence that one of the ends of the channel is pressurized, whereas the opposite end is at atmospheric pressure. The study aims at reducing the complexity of models for several physiological systems in which fluid-structure interaction produces large deformation of the wall. We report the experimental results of the observed self-sustained oscillations. These oscillations occur at frequencies close to the natural frequency of the system. The vertical motion is accompanied by a slight trend to rotate the moving mass at intervals when the gap height is quite narrow. We propose a simplified analytical model to explore the conditions under which this motion is possible. The analytical approach considers asymptotic solutions of the Navier-Stokes equation with a perturbation technique. The comparison between the experimental pressure measured at the midlength of the channel and the analytical result issued with a model neglecting viscous effects shows a very good agreement. Also, the rotating trend of the moving wall can be explained in terms of the quadratic dependence of the pressure with the streamwise coordinate that is predicted by this simplified model.


Assuntos
Viscosidade , Movimento (Física)
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