scholarly journals Injectability of Thermosensitive, Low-Concentrated Chitosan Colloids as Flow Phenomenon through the Capillary under High Shear Rate Conditions

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2260
Author(s):  
Anna Rył ◽  
Piotr Owczarz
Keyword(s):  
Shear Rate ◽  
Structural Changes ◽  
Sol Gel ◽  
Thermally Induced ◽  
Flow Phenomenon ◽  
Injectable Scaffolds ◽  
Gel Phase ◽  
Injection Force ◽  
Needle Diameter ◽  
Injection Forces

Low-concentrated colloidal chitosan systems undergoing a thermally induced sol–gel phase transition are willingly studied due to their potential use as minimally invasive injectable scaffolds. Nevertheless, instrumental injectability tests to determine their clinical utility are rarely performed. The aim of this work was to analyze the flow phenomenon of thermosensitive chitosan systems with the addition of disodium β-glycerophosphate through hypodermic needles. Injectability tests were performed using a texture analyzer and hypodermic needles in the sizes 14G–25G. The rheological properties were determined by the flow curve, three-interval thixotropy test (3ITT), and Cox–Merz rule. It was found that reducing the needle diameter and increasing its length and the crosshead speed increased the injection forces. It was claimed that under the considered flow conditions, there was no need to take into account the viscoelastic properties of the medium, and the model used to predict the injection force, based solely on the shear-thinning nature of the experimental material, showed very good agreement with the experimental data in the shear rate range of 200–55,000 s−1. It was observed that the increase in the shear rate value led to macroscopic structural changes of the chitosan sol caused by the disentangling and ordering of the polysaccharide chains along the shear field.

Sol-Gel Process from Heterobimetallic Alkoxides to Incorporate Lanthanides in an Alumina Matrix

1992 ◽  
Vol 271 ◽  
Author(s):  
Chaitanya K. Narula
Keyword(s):  
Acetic Acid ◽  
Structural Changes ◽  
Sol Gel ◽  
Alumina Matrix ◽  
Slow Evaporation ◽  
Thermally Induced ◽  
Excess Water ◽  
Sol Gel Process ◽  
Amorphous Powders ◽  
Hydrolysis Of

ABSTRACTGels form on addition of seven or more moles of water diluted withi-PrOH to one mole of M[Al(O-i-Pr)4]3, M = La, Ce dissolved in i-PrOH. Thermal treatment of xerogels derived from La[AI(O-i-Pr)4]3gives amorphous powders below 900°C. LaAIO3crystallizes out at 900°C and residual alumina remains amorphous. CeO2starts to separate out above 600°C from the xerogels prepared from Ce[M(O-i-Pr)4]3. Thermally induced structural changes in xerogels prepared from the mixtures of La[AI(O-i-Pr)4]3and Ce[AI(0-i-Pr)4]3in 1:1 or 1:3 ratio are different from those prepared from individual precursors. These xerogels remain amorphous below 700°C. Crystalline CeO2forms on heating at 900°C but alumina remains amorphous. Sols are formed on hydrolysis of M[AI(0-/-Pr)4]3in excess water and acidifying the reaction mixture with acetic acid. Sols can be converted to gels by slow evaporation of volatiles. This method is useful in preparing coatings.

Porous Gel Coatings Obtained by Phase Separation in ORMOSIL System

2000 ◽  
Vol 628 ◽  
Author(s):  
Kazuki Nakanishi ◽  
Souichi Kumon ◽  
Kazuyuki Hirao ◽  
Hiroshi Jinnai
Keyword(s):  
Phase Separation ◽  
Reaction Time ◽  
Volume Fraction ◽  
Sol Gel ◽  
Reaction Times ◽  
Dip Coating ◽  
Coating Solution ◽  
Coating Method ◽  
Gel Phase ◽  
Dip Coating Method

ABSTRACTMacroporous silicate thick films were prepared by a sol-gel dip-coating method accompanied by the phase separation using methyl-trimethoxysilane (MTMS), nitric acid and dimethylformamide (DMF) as starting components. The morphology of the film varied to a large extent depending on the time elapsed after the hydrolysis until the dipping of the coating solution. On a glass substrate, the films prepared by early dipping had inhomogeneous submicrometer-sized pores on the surface of the film. At increased reaction times, relatively narrow sized isolated macropores were observed and their size gradually decreased with the increase of reaction time. On a polyester substrate, in contrast, micrometer-sized isolated spherical gel domains were homogeneously deposited by earlier dippings. With an increase of reaction time, the volume fraction of the gel phase increased, then the morphology of the coating transformed into co-continuous gel domains and macropores, and finally inverted into the continuous gel domains with isolated macropores. The overall morphological variation with the reaction time was explained in terms of the phase separation and the structure freezing by the forced gelation, both of which were induced by the evaporation of methanol during the dipping operation.

scholarly journals Temperature-dependent nanomechanics and topography of bacteriophage T7

2018 ◽  
Author(s):  
Zsuzsanna Vörös ◽  
Gabriella Csík ◽  
Levente Herényi ◽  
Miklós Kellermayer
Keyword(s):  
Structural Changes ◽  
Mechanical Stability ◽  
Genetic Material ◽  
Heat Inactivation ◽  
Infectious Agents ◽  
Temperature Dependent ◽  
Thermally Induced ◽  
Partial Denaturation ◽  
Induced Changes ◽  
T7 Bacteriophage

AbstractViruses are nanoscale infectious agents which may be inactivated by heat treatment. Although heat inactivation is thought to be caused by the release of genetic material from the capsid, the thermally-induced structural changes in viruses are little known. Here we measured the heat-induced changes in the properties of T7 bacteriophage particles exposed to two-stage (65 °C and 80 °C) thermal effect by using AFM-based nanomechanical and topographical measurements. We found that exposure to 65 °C caused the release of genomic DNA due to the loss of the capsid tail which leads to a destabilization of the T7 particles. Further heating to 80 °C surprisingly led to an increase in mechanical stability due to partial denaturation of the capsomeric proteins kept within the global capsid arrangement.

scholarly journals [MG49-LiClO4]:[TiO2-SiO2] Polymer Electrolytes: In Situ Preparation and Characterization

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Oon Lee Kang ◽  
Azizan Ahmad ◽  
Nur Hasyareeda Hassan ◽  
Usman Ali Rana
Keyword(s):  
Polymer Electrolytes ◽  
Structural Changes ◽  
Sol Gel ◽  
Ionic Conductivities ◽  
In Situ Techniques ◽  
In Situ Preparation ◽  
Solution Cast ◽  
Gel Technique ◽  
Cast Technique

In the present research, [MG49-LiClO4]:[HNO3-THF/TiO2-SiO2] and [MG49-LiClO4]:[ClHNO2-THF/TiO2-SiO2] polymer electrolytes were first prepared through simple stepwise in situ techniques: sol-gel technique and solution-cast technique. [MG49-LiClO4]:[HNO3-THF/TiO2-SiO2] and [MG49-LiClO4]:[ClHNO2-THF/TiO2-SiO2] polymer electrolytes were then characterized through different experimental techniques. [MG49-LiClO4]:[HNO3-THF/TiO2-SiO2] and [MG49-LiClO4]:[ClHNO2-THF/TiO2-SiO2] polymer electrolytes had exhibited significant structural changes upon different salt concentrations. In the present investigation, [MG49-LiClO4]:[HNO3-THF/TiO2-SiO2] and [MG49-LiClO4]:[ClHNO2-THF/TiO2-SiO2] polymer electrolytes had attained maximum ionic conductivities (σ~10-7 S/cm at ambient temperature; 10−4 S/cm at 100°C) upon 25 wt.% salt insertion. [MG49-LiClO4]:[HNO3-THF/TiO2-SiO2] and [MG49-LiClO4]:[ClHNO2-THF/TiO2-SiO2] polymer electrolytes had exhibited distinct conduction mechanisms in similar experimental configuration. [MG49-LiClO4]:[HNO3-THF/TiO2-SiO2] and [MG49-LiClO4]:[ClHNO2-THF/TiO2-SiO2] polymer electrolytes had exhibited different stability characteristics over certain operational condition.

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