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Advanced unsaturated soil mechanics and engineering
Analytical and comprehensive, this work examines the mechanics and engineering of unsaturated soils, as well as explaining the laboratory and field testing, and research that are the logical basis of this modern approach to safe construction in these hazardous geomaterials.
Book
Tailoring the Swelling‐Shrinkable Behavior of Hydrogels for Biomedical Applications
Hydrogels with tailor‐made swelling‐shrinkable properties have aroused considerable interest in numerous biomedical domains. For example, as swelling is a key issue for blood and wound extrudates absorption, the transference of nutrients and metabolites, as well as drug diffusion and release, hydrogels with high swelling capacity have been widely applicated in full‐thickness skin wound healing and tissue regeneration, and drug delivery. Nevertheless, in the fields of tissue adhesives and internal soft‐tissue wound healing, and bioelectronics, non‐swelling hydrogels play very important functions owing to their stable macroscopic dimension and physical performance in physiological environment. Moreover, the negative swelling behavior (i.e., shrinkage) of hydrogels can be exploited to drive noninvasive wound closure, and achieve resolution enhancement of hydrogel scaffolds. In addition, it can help push out the entrapped drugs, thus promote drug release. However, there still has not been a general review of the constructions and biomedical applications of hydrogels from the viewpoint of swelling‐shrinkable properties. Therefore, this review summarizes the tactics employed so far in tailoring the swelling‐shrinkable properties of hydrogels and their biomedical applications. And a relatively comprehensive understanding of the current progress and future challenge of the hydrogels with different swelling‐shrinkable features is provided for potential clinical translations.
Journal Article
Mechanical Properties of Alginate Hydrogels Cross-Linked with Multivalent Cations
Ionically, cross-linked alginate gels have a potential to be used in a wide range of biomedical, environmental and catalytic applications. The study deals with preparation of alginate hydrogels cross-linked with various cations and the analysis of their equilibrium swelling and mechanical properties. It is shown that the type of cations used in the cross-linking process affects the elastic moduli and the equilibrium degree of swelling of the gels. The experimental data in small-amplitude oscillatory tests are fitted with a model that involves two material parameters: the elastic modulus of a polymer network and a measure of its inhomogeneity. The influence of cations on these quantities is studied numerically. It is revealed that the dependence of the elastic modulus of ionically cross-linked alginate gels on their equilibrium degree of swelling differs from that predicted by the conventional theory for covalently cross-linked gels.
Journal Article
Effect of Natural Pozzolan on the Stabilization of Two Swelling Soils from the Western Region of Algeria
In recent times, a large number of studies have been carried out on swelling soils. It has been revealed that the swelling phenomenon, which still remains uncontrollable, is causing major disorders in several civil engineering structures around the world. The present study aims primarily to study the stabilization of two swelling clays. The first one comes from the region of M’zila, which is located in the Wilaya (Province) of Mostaganem, while the second is from the region of Bourmadia in the Wilaya of Relizane. This article also presents the results of geotechnical investigations that were carried out on two swelling soils that were treated with natural pozzolan (NP) from the town of Béni-saf, which is situated in north-western Algeria. The geotechnical parameters, such as consistency limits, as well as the proctor compaction test parameters and direct shear test parameters, along with the oedometer swelling test result analysis, were recorded and examined to evaluate the effects of adding different proportions of NP to these swelling soils. The results of the tests showed that several key properties of the above-mentioned soils were significantly enhanced after the introduction of NP. For instance, the rectilinear shear test at the Casagrande box showed that the cohesion coefficients of Bourmadia and M’zila soils containing 10% NP improved by 93.3% and 47.1%, respectively. In addition, the results of the oedometer test to determine the swelling potential indicated that NP was capable of inhibiting the swelling of both clay soils. Overall, the outcomes suggest that NP from the region of Béni-saf has remarkable potential for improving the geotechnical properties of expansive soils that are often encountered during the implementation of many civil engineering structures and construction projects.
Journal Article
pH Sensitive Hydrogels in Drug Delivery: Brief History, Properties, Swelling, and Release Mechanism, Material Selection and Applications
Improving the safety efficacy ratio of existing drugs is a current challenge to be addressed rather than the development of novel drugs which involve much expense and time. The efficacy of drugs is affected by a number of factors such as their low aqueous solubility, unequal absorption along the gastrointestinal (GI) tract, risk of degradation in the acidic milieu of the stomach, low permeation of the drugs in the upper GI tract, systematic side effects, etc. This review aims to enlighten readers on the role of pH sensitive hydrogels in drug delivery, their mechanism of action, swelling, and drug release as a function of pH change along the GI tract. The basis for the selection of materials, their structural features, physical and chemical properties, the presence of ionic pendant groups, and the influence of their pKa and pKb values on the ionization, consequent swelling, and targeted drug release are also highlighted.
Journal Article
Effect of the Cross-Linking Density on the Swelling and Rheological Behavior of Ester-Bridged β-Cyclodextrin Nanosponges
The cross-linking density influences the physicochemical properties of cyclodextrin-based nanosponges (CD-NSs). Although the effect of the cross-linker type and content on the NSs performance has been investigated, a detailed study of the cross-linking density has never been performed. In this contribution, nine ester-bridged NSs based on β-cyclodextrin (β-CD) and different quantities of pyromellitic dianhydride (PMDA), used as a cross-linking agent in stoichiometric proportions of 2, 3, 4, 5, 6, 7, 8, 9, and 10 moles of PMDA for each mole of CD, were synthesized and characterized in terms of swelling and rheological properties. The results, from the swelling experiments, exploiting Flory–Rehner theory, and rheology, strongly showed a cross-linker content-dependent behavior. The study of cross-linking density allowed to shed light on the efficiency of the synthesis reaction methods. Overall, our study demonstrates that by varying the amount of cross-linking agent, the cross-linked structure of the NSs matrix can be controlled effectively. As PMDA βCD-NSs have emerged over the years as a highly versatile class of materials with potential applications in various fields, this study represents the first step towards a full understanding of the correlation between their structure and properties, which is a key requirement to effectively tune their synthesis reaction in view of any specific future application or industrial scale-up.
Journal Article
Concrete bridges affected by internal swelling reactions: Reactions mitigation and structural rehabilitation
The increasing number of bridges affected by internal swelling reactions in concrete has raised significant concerns among bridge owners, given the serious consequences for their durability, serviceability and safety, which may involve high repair costs or even the replacement of severely damaged structures. This paper aims to provide an overview of the procedures used to prevent these reactions, with a particular emphasis on the methods used to mitigate their effects in affected bridges. Additionally, some examples of solutions applied to Portuguese bridges are presented.
Journal Article
Influence of UHMWPE on the expansion characteristics of expansive soil: Experimental studies
This paper investigates the effectiveness of using Ultra-High-Molecular-Weight Polyethylene (UHMWPE) Fiber to improve expansive soil. The test results indicate that the amount and length of UHMWPE significantly affect the swelling pressure and free swelling ratio of the reinforced soil. The swelling pressure of reinforced expansive soil exhibits a significant negative correlation with both the UHMWPE content ( p < 0.05) and its length. The free swelling ratio of reinforced expansive soil was significantly negatively correlated with both the content ( p < 0.05) and length of UHMWPE. When the UHMWPE content exceeds 0.3% the weight of the soil, there is no significant decrease in the swelling pressure of the reinforced soil ( p = 0.052, close to the threshold of significance). When the length of UHMWPE is greater than 9 mm, there is no significant decrease in the free swelling ratio of the reinforced soil ( p = 0.165). Thus, it is recommended to use 0.3% UHMWPE with a length of 9 mm for optimal results. Swelling pressure, free swelling ratio and fiber content follow a quadratic polynomial relationship. While, the relationship between swelling pressure and fiber length is linear. The relationship between free swelling ratio and fiber length is a power function.
Journal Article
Synthesis a novel nano graft co-polymer and studying the swelling behaviors using different molar ratios of acrylic acid monomer
In this work, the nanoparticle graft co-polymer was prepared, by using glycerol as material containing the three alcoholic groups, and that reacted with terphthalic acid which have two carboxylic group as a first step, and then added 0.5 mole of fumaric acid to prepared graft co-polymer, as a second step by solubilization process. The acrylic acid monomer was added to the nano graft co-polymer in different number of moles (1.5, 2.0 & 2.5 mole). The swelling ratio measurements of the graft co-polymer, in three different buffer solution (2.2, 7.0 and 8.0), in the constant temperature at 310 K. The results showed that the increases of number of the moles of the acrylic acid monomer, Leads to increase of swelling ratio.
Journal Article
Ion‐Mediated Gelation of Thermo‐Responsive Cellulose Nanofibril/Poly(N‐isopropylacrylamide) Hybrid Hydrogels with Tunable De‐Swelling Kinetics
The tunability of the lower critical solution temperature (LCST) of poly(N‐isopropylacrylamide) (PNIPAM) to lower or higher temperatures, as well as the ease of modulation of the LCST phase transition kinetics broadens the scope of application of PNIPAM‐based materials in biomedical fields. This work reports a facile approach to formulate a smart, injectable cellulose nanofibril (CNF)/PNIPAM hybrid gel. Hofmeister salts are used to induce ion‐mediated gelation of the nanofibrils and PNIPAM chains, resulting in an interpenetrating network (IPN) structure. From rheological measurements, the hybrid material displays excellent structural integrity at room temperature and tunable thermo‐stiffening around body temperature. De‐swelling kinetics can be modulated by varying the nature and concentration of the Hofmeister ion used. The successful realization of the IPN hybrid gel structure is dependent on the molecular weight of PNIPAM used. Moreover, the hybrid gels show good thermo‐reversibility during thermal cycling, as well as excellent injectability and remarkable self‐healing post‐injection, owing to shear‐thinning and thixotropic characters. Since rheology is a crucial technique in the analysis of soft matter and flow behavior is fundamental for the design and synthesis of application‐specific viscoelastic materials, the work reported herein provides a rheological basis for careful design and synthesis of smart gels. Hybrid gels whose stimuli‐responsive properties can be precisely modulated broaden the scope of their application in various biomedical fields. Based on fundamental rheological principles, this contribution introduces a smart CNF/PNIPAM hybrid gel formulated in the presence of Hofmeister salts. The hybrid material displays tunable mechanics and de‐swelling kinetics, as well as good thermo‐reversibility, excellent injectability, and remarkable self‐healing.
Journal Article