scholarly journals Correlating rheology and printing performance of fiber-reinforced bioinks to assess predictive modelling for biofabrication

2021 ◽  
Author(s):  
David Sonnleitner ◽  
Stefan Schrüfer ◽  
Linn Berglund ◽  
Dirk W. Schubert ◽  
Gregor Lang
Keyword(s):  
Structural Changes ◽  
Structural Integrity ◽  
Cellulose Nanofibers ◽  
Viscoelastic Model ◽  
Complex Viscosity ◽  
Predictive Modelling ◽  
Fiber Reinforced ◽  
Rheological Experiments ◽  
Extrusion Printing ◽  
Analytical Tools

Abstract A crucial property for the evaluation of bioinks, besides biocompatibility, is printability, which is determined by resolution and shape fidelity. Recently, fiber reinforcement was used to overcome rheological limitations and introduce biomimetic structuring. This study provides a systematic approach to evaluate the printability of fiber reinforced hydrogels. Alginate and Pluronic hydrogels were blended with cellulose nanofibers (CeNF) and polycaprolactone (PCL) microfibers. SEM imaging revealed fiber-induced structural changes. Oscillatory rheological experiments showed that the addition of fiber fragments significantly altered the complex viscosity. A customized setup was utilized to determine strut spreading behavior in a real extrusion printing process. Strikingly, the data displayed excellent correlation with viscoelastic model-based predictions. CeNF increased the shape fidelity of both hydrogels, while PCL microfibers increased the viscosity but resulted in a time dependent loss of structural integrity in Pluronic. The results emphasize the need to complement shear-rheological analysis of bioinks by print-related customized analytical tools. Graphic abstract

Individual differences in white and grey matter structure associated with verbal habits of thought

2019 ◽  
Author(s):  
Justin C. Hayes ◽  
Katherine L Alfred ◽  
Rachel Pizzie ◽  
Joshua S. Cetron ◽  
David J. M. Kraemer
Keyword(s):  
Individual Differences ◽  
White Matter ◽  
Cognitive Processing ◽  
Grey Matter ◽  
Structural Changes ◽  
Structural Integrity ◽  
Diffusion Tensor ◽  
Self Report ◽  
White Matter Tracts

Modality specific encoding habits account for a significant portion of individual differences reflected in functional activation during cognitive processing. Yet, little is known about how these habits of thought influence long-term structural changes in the brain. Traditionally, habits of thought have been assessed using self-report questionnaires such as the visualizer-verbalizer questionnaire. Here, rather than relying on subjective reports, we measured habits of thought using a novel behavioral task assessing attentional biases toward picture and word stimuli. Hypothesizing that verbal habits of thought are reflected in the structural integrity of white matter tracts and cortical regions of interest, we used diffusion tensor imaging and volumetric analyses to assess this prediction. Using a whole-brain approach, we show that word bias is associated with increased volume in several bilateral language regions, in both white and grey matter parcels. Additionally, connectivity within white matter tracts within an a priori speech production network increased as a function of word bias. These results demonstrate long-term structural and morphological differences associated with verbal habits of thought.

scholarly journals The Structural Integrity of the Model Lipid Membrane during Induced Lipid Peroxidation: The Role of Flavonols in the Inhibition of Lipid Peroxidation

Antioxidants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 430 ◽  
Author(s):  
Anja Sadžak ◽  
Janez Mravljak ◽  
Nadica Maltar-Strmečki ◽  
Zoran Arsov ◽  
Goran Baranović ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Structural Changes ◽  
Structural Integrity ◽  
Lipid Membrane ◽  
Membrane Properties ◽  
Structural Reorganization ◽  
Unsaturated Lipids ◽  
Oxidative Attack

The structural integrity, elasticity, and fluidity of lipid membranes are critical for cellular activities such as communication between cells, exocytosis, and endocytosis. Unsaturated lipids, the main components of biological membranes, are particularly susceptible to the oxidative attack of reactive oxygen species. The peroxidation of unsaturated lipids, in our case 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), induces the structural reorganization of the membrane. We have employed a multi-technique approach to analyze typical properties of lipid bilayers, i.e., roughness, thickness, elasticity, and fluidity. We compared the alteration of the membrane properties upon initiated lipid peroxidation and examined the ability of flavonols, namely quercetin (QUE), myricetin (MCE), and myricitrin (MCI) at different molar fractions, to inhibit this change. Using Mass Spectrometry (MS) and Fourier Transform Infrared Spectroscopy (FTIR), we identified various carbonyl products and examined the extent of the reaction. From Atomic Force Microscopy (AFM), Force Spectroscopy (FS), Small Angle X-Ray Scattering (SAXS), and Electron Paramagnetic Resonance (EPR) experiments, we concluded that the membranes with inserted flavonols exhibit resistance against the structural changes induced by the oxidative attack, which is a finding with multiple biological implications. Our approach reveals the interplay between the flavonol molecular structure and the crucial membrane properties under oxidative attack and provides insight into the pathophysiology of cellular oxidative injury.

scholarly journals Phosphorylated cellulose nanofibers exhibit exceptional capacity for uranium capture

Cellulose ◽  
2020 ◽  
Vol 27 (18) ◽  
pp. 10719-10732
Author(s):  
Janika Lehtonen ◽  
Jukka Hassinen ◽  
Avula Anil Kumar ◽  
Leena-Sisko Johansson ◽  
Roni Mäenpää ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Structural Changes ◽  
Cellulose Nanofibers ◽  
Aqueous Media ◽  
Isotherm Models ◽  
Batch Adsorption ◽  
Maximum Adsorption Capacity ◽  
Electron Microscopies ◽  
Network Scanning ◽  
Aqueous Matrices

AbstractWe investigate the adsorption of hexavalent uranium, U(VI), on phosphorylated cellulose nanofibers (PHO-CNF) and compare the results with those for native and TEMPO-oxidized nanocelluloses. Batch adsorption experiments in aqueous media show that PHO-CNF is highly efficient in removing U(VI) in the pH range between 3 and 6. Gelling of nanofiber hydrogels is observed at U(VI) concentration of 500 mg/L. Structural changes in the nanofiber network (scanning and transmission electron microscopies) and the surface chemical composition (X-ray photoelectron spectroscopy) gave insights on the mechanism of adsorption. The results from batch adsorption experiments are fitted to Langmuir, Freundlich, and Sips isotherm models, which indicate a maximum adsorption capacity of 1550 mg/g, the highest value reported so far for any bioadsorbent. Compared to other metals (Zn, Mn, and Cu) and typical ions present in natural aqueous matrices the phosphorylated nanofibers are shown to be remarkably selective to U(VI). The results suggest a solution for the capture of uranium, which is of interest given its health and toxic impacts when present in aqueous matrices.

Rheological Behavior of Fugitive Organic Inks for Direct-Write Assembly

2007 ◽  
Vol 17 (1) ◽  
pp. 10112-1-10112-8 ◽  
Author(s):  
Daniel Therriault ◽  
Scott R. White ◽  
Jennifer A. Lewis
Keyword(s):  
Rheological Behavior ◽  
Room Temperature ◽  
Complex Viscosity ◽  
Direct Write ◽  
Master Curves ◽  
Numerical Predictions ◽  
Beam Analysis ◽  
Storage And Loss Moduli ◽  
Temperature Superposition ◽  
Rheological Experiments

Abstract The rheological behavior of a fugitive organic ink tailored for direct-write assembly of 3D microfluidic devices is investigated. Rheological experiments are carried out to probe the shear storage and loss moduli as well as the complex viscosity as a function of varying temperature, frequency and stress amplitude. Master curves of these functions are assembled using time-temperature superposition. The fugitive ink, comprised of two organic phases, possesses an equilibrium shear elastic modulus nearly two orders of magnitude higher than that of a commercial reference ink at room temperature and a peak in the relaxation spectrum nearly six orders of magnitude longer in time scale. The self-supporting nature of extruded ink filaments is characterized by direct video imaging. Comparison of the experimentally observed behavior to numerical predictions based on Euler-Bernoulli viscoelastic beam analysis yield excellent agreement for slender filaments.

scholarly journals Nanoscale mapping of chemical composition in organic-inorganic hybrid perovskite films

2019 ◽  
Vol 5 (10) ◽  
pp. eaaw6619 ◽  
Author(s):  
R. Szostak ◽  
J. C. Silva ◽  
S.-H. Turren-Cruz ◽  
M. M. Soares ◽  
R. O. Freitas ◽  
...  
Keyword(s):  
Structural Changes ◽  
Operating Conditions ◽  
Chemical Diversity ◽  
Local Composition ◽  
Inorganic Hybrid ◽  
Hexagonal Polytype ◽  
Hybrid Perovskite ◽  
Individual Grains ◽  
Analytical Tools ◽  
The Impact

Lead-based organic-inorganic hybrid perovskite (OIHP) solar cells can attain efficiencies over 20%. However, the impact of ion mobility and/or organic depletion, structural changes, and segregation under operating conditions urge for decisive and more accurate investigations. Hence, the development of analytical tools for accessing the grain-to-grain OIHP chemistry is of great relevance. Here, we used synchrotron infrared nanospectroscopy (nano-FTIR) to map individual nanograins in OIHP films. Our results reveal a spatial heterogeneity of the vibrational activity associated to the nanoscale chemical diversity of isolated grains. It was possible to map the chemistry of individual grains in CsFAMA [Cs0.05FA0.79MA0.16Pb(I0.83Br0.17)3] and FAMA [FA0.83MA0.17Pb(I0.83Br0.17)3] films, with information on their local composition. Nanograins with stronger nano-FTIR activity in CsFAMA and FAMA films can be assigned to PbI2 and hexagonal polytype phases, respectively. The analysis herein can be extended to any OIHP films where organic cation depletion/accumulation can be used as a chemical label to study composition.

Viscoelastic Characterization of Fiber-Reinforced Elastomeric Composites at Finite Strain

2010 ◽  
Vol 123-125 ◽  
pp. 603-606
Author(s):  
Mohammad Tahaye Abadi
Keyword(s):  
Constitutive Model ◽  
Large Deformation ◽  
Finite Strain ◽  
Mechanical Response ◽  
Viscoelastic Model ◽  
Constitutive Law ◽  
Micromechanical Modeling ◽  
Fiber Reinforced ◽  
Material Parameters ◽  
Elastomeric Composites

A viscoelastic model is developed to describe the mechanical response of fiber-reinforced elastomeric composites at large deformation. A continuum approach is used to model the macroscopic mechanical behavior of elastomeric materials reinforced with unidirectional fibers, in which the resin and fibers are regarded as a single homogenized anisotropic material. The anisotropic viscoelastic constitutive model is developed considering transient reversible network theory. An efficient computational algorithm based on micromechanical modeling is proposed to relate the material parameters of constitutive model to the mechanical properties of composite constituents at finite strain. The microstructure is identified by a representative volume element (RVE) and it is subjected to large deformation with considering the conformity of opposite boundaries. The material parameters of the viscoelastic constitutive law are determined based on the response of heterogeneous microstructure which is examined under different loading conditions.

Fracture Mechanics when Studying the Long-Term Strength of Concrete

2019 ◽  
Vol 945 ◽  
pp. 957-962
Author(s):  
I.L. Shubin ◽  
V.V. Dorkin ◽  
P.S. Sultygova
Keyword(s):  
Fracture Mechanics ◽  
Structural Changes ◽  
Structural Integrity ◽  
Term Strength ◽  
Short Term ◽  
Heterogeneous Structures ◽  
Temperature Action ◽  
Heating Up ◽  
Experimental And Theoretical Studies

The results of experimental and theoretical studies of the process of destruction of concrete by the methods of fracture mechanics are considered. Results of studies of long-term strength, durability and deformability of concrete subjected to a preliminary short-term temperature action up to 300° C and 400° C under load and without load are presented. It is shown that after short-term heating up to 300о С the long-term strength of concrete decreases insignificantly. It is established that heating up to 400° C can be considered the boundary of the structural integrity of concrete. The conditions for using the results of these studies in determining the values of a function that characterizes the change in the long-term strength of a material in the mechanics of heterogeneous structures are formulated. The function of the material destruction measure is introduced to describe the nature of the structural changes in the material at a given constant continuous load, and its change for different levels of a continuous load is considered.

Evaluation of Particle Beam Fourier Transform Infrared Spectrometry for the Analysis of Globular Proteins: Conformation of β-Lactoglobulin and Lysozyme

1994 ◽  
Vol 48 (10) ◽  
pp. 1255-1264 ◽  
Author(s):  
Vincent E. Turula ◽  
James A. de Haseth
Keyword(s):  
Solution Structure ◽  
Structural Changes ◽  
Structural Integrity ◽  
Particle Beam ◽  
Globular Proteins ◽  
Structural Features ◽  
Infrared Spectrometry ◽  
Order Structure ◽  
Carrier Liquid ◽  
Β Lactoglobulin

The efficacy of the particle beam LC/FT-IR interface, in its development as a tool for the determination of dynamic protein structure from experiments such as HPLC separations and folding/refolding intermediate analysis, is presented here. The particle beam apparatus can be used to desolvate proteins rapidly in preparation of IR measurements. Several experiments have been designed to determine whether the operation of the particle beam apparatus causes alteration to the complex structural features of globular proteins, and whether it produces a solid-state spectrum representative of protein solution structure. It is shown here that the structural integrity of β-lactoglobulin is maintained when nebulized, desolvated from solution, and deposited onto the IR-substrate. Since enzyme activity is dependent upon the maintenance of higher-order structure, a complementary series of spectrophotometric-activity experiments with lysozyme collected from the particle beam were performed to determine the state of the tertiary and quaternary structures. The lysozyme particle beam deposit not only produced a secondary structure estimate similar to that of solution; it also retained its biological activity. It is demonstrated that the particle beam can induce structural changes in proteins with a carrier-liquid concentration gradient; this characteristic is useful for band assignment.

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