Water Entrapment Research Articles

Mass Timber Buildings: The associated risks of rainwater exposure during construction in the Portuguese climate

The increase in the number and complexity of wooden buildings creates a series of challenges, like moisture control and management during the construction phase. The risks associated with the direct exposure of timber elements to rain during construction depend on the severity of the climate and the specific details of each project and therefore must be analysed locally. In this context, the results of 16 weeks of moisture content monitorization of Cross Laminated Timber (CLT) floor-wall connection specimens exposed to the outdoors are presented and evaluated. The monitorization demonstrated that end-grain surfaces are the most sensitive to the action and movement of water in CLT and within a few days of exposure to rain reached alarming moisture content (MC>30 %), with water entrapment at the interface between elements, preventing drying in a reasonable time for construction workflow (MC>30 % after 39 days of drying). On the other hand, zones with faster drying exhibited severe physical damage such as delamination and cracks. Additionally, the study evaluates the feasibility of using satellite-obtained meteorological data to develop a degradation risk map (Scheffer Climate Index) for mainland Portugal. The high coefficient of determination (R2 ≥ 0.81) and model efficiency (EF ~ 0.80–0.90) demonstrate the reliability of the data. Finally, two degradation risk maps for mainland Portugal are presented.

Evaluation of a Volume-Averaged Species Transport Model with Micro-Macro Coupling for Breakthrough Curve Prediction.

In porous water filters, the transport and entrapment of contaminants can be modeled as a classic mass transport problem, which employs the conventional convection-dispersion equation to predict the transport of species existing in trace amounts. Using the volume-averaging method (VAM), the upscaling has revealed two possible macroscopic equations for predicting contaminant concentrations in the filters. The first equation is the classical convection-dispersion equation, which incorporates a total dispersion tensor. The second equation involves an additional transport coefficient, identified as the adsorption-induced vector. In this study, the aforementioned equations were solved in 1D for column tests using 3D unit cells. The simulated breakthrough curves (BTCs), using the proposed micro-macro-coupling-based VAM model, are compared with the direct numerical simulation (DNS) results based on BCC-type unit cells arranged one-after-another in a daisy chain manner, as well as with three previously reported experimental works, in which the functionalized zeolite and zero-valent iron fillings were used as an adsorbent to remove phosphorous and arsenic from water, respectively. The disagreement of VAM BTC predictions with DNS and experimental results reveals the need for an alternative closure formulation in VAM. Detailed investigations reveal time constraint violations in all the three cases, suggesting this as the main cause of VAM's failure.

Small-scale roughness entraps water and controls underwater adhesion.

While controlling underwater adhesion is critical for designing biological adhesives and in improving the traction of tires, haptics, or adhesives for health monitoring devices, it is hindered by a lack of fundamental understanding of how the presence of trapped water impedes interfacial bonding. Here, by using well-characterized polycrystal diamond surfaces and soft, nonhysteretic, low-surface energy elastomers, we show a reduction in adhesion during approach and four times higher adhesion during retraction as compared to the thermodynamic work of adhesion. Our findings reveal how the loading phase of contact is governed by the entrapment of water by ultrasmall (10-nanometer-scale) surface features. In contrast, the same nanofeatures that reduce adhesion during approach serve to increase adhesion during separation. The explanation for this counterintuitive result lies in the incompressibility-inextensibility of trapped water and the work needed to deform the polymer around water pockets. Unlike the well-known viscoelastic contribution to adhesion, this science unlocks strategies for tailoring surface topography to enhance underwater adhesion.

Fabrication of verrucarin-a-loaded zinc oxide nanocomposite for inducing apoptosis in triple-negative breast cancer cells

Due to its low bioavailability and insolubility in water, little is known about the biological effects of Verrucarin-A. Chitosan-coated zinc oxide (ZnO) nanoparticles were employed as a potential nanocarrier to transport Verrucarin-A to its target cells to enhance its bioavailability. Results showed improved water solubility, entrapment, drug release, and loading efficiencies for the fabricated Verrucarin-A clocked ZnO- nanocomposite (Ver-A@ZnNCs). Comparing Ver-A@ZnNCs to both non-cancerous epithelial (MCF-10A) cells and triple-negative breast cancer (MDA-MB-231) cells in an in vitro cell viability test (MTT), the latter showed greater biocompatibility. According to observations, verrucarin-A release from Ver-A@ZnNCs at cancer cell sites may be caused by the acidic tumor microenvironment. Apoptosis occurred in the cancer cells after increased nanoparticle uptake, which may have stimulated ROS generation. Further evidence of Ver-A@ZnNCs' in vitro anticancer activity was obtained through apoptosis investigations. After performing significant in vitro studies, it has been shown that Ver-A@ZnNCs is compatible with humanity and shows promise as an anticancer drug for triple-negative breast cancer patients.

Physiology and biomechanics researches of the special preparedness and contention activity of highly skilled kayakers

Purpose — development of methodology for individual evaluating special fitness and competitive activity of highly skilled kayakers.
 The rationality of the rower’s movement structure is largely determined by the character of work and interaction of the posterior and anterior bundles of the deltoid muscle, which perform the rower’s arm movements during applying both “pulling” and “pushing” efforts. The following causes of individual rowing technique errors significantly affecting sports result were identified: general muscle rigidity, lack of sufficiently complete and timely muscle relaxation; untimely involvement of muscles in work (appearance of mutual activity zones of antagonist muscles); late start of muscle activity (inertial moments of movement of rower's body biolinks are not provided before water entrapment); protracted, too long muscle activity (movement is performed entirely at the expense of muscular activity, without the use of inertial and propelling forces); low speed of muscle engagement in work leading, as a rule, to the “drop” of efforts on the oar. Two groups of athletes with diametrically opposite levels of physical capacity development and one group, which was characterized by their uniform development, were distinguished. The first group was distinguished by the high indices of power and efficiency of the work performed while covering the competitive distance. Such athletes showed higher sports results on short distances. The second group was distinguished by high indices of the efficiency of applying efforts, symmetry of movements, and successful performances on long competitive distances. Such rowers were classified as athletes with predominant development of special endurance quality. The rowers of the third group differed in the average values of the above mentioned indices and demonstrated equal success on both short and long competitive distances. Athletes with preferential development of speed-strength qualities and rowers with an advantageous development of special endurance have no significant difference in speed of covering 500 m distance and heart rate. However, there are significant differences in other indices of special fitness. Rowers with even development of physical qualities have differences in all recorded indices compared to those of the first two groups.
 The individual peculiarities of rowers’ movement coordination during covering a competitive distance of 500 m were determined. All rowers are divided into two groups. The first group is characterized by rational coordination of movements at the beginning of the distance covering and pronounced disturbances in the work dynamics of the muscles of the body turn and the nature of effort applied to the oar at the end of the distance. In the second group, we encounter the opposite phenomenon: with an irrational movement structure at the beginning of the distance, there is a transition of work to a more correct character at the end of its covering. The most preferable option for increasing the efficiency of athletes’ technical preparation is the use of the methodology for designing generalized and individual models of motor action structure. Preparation of rowers with account for their predisposition to the formation of the most important components of sportsmanship is the most preferable option. When drawing up individual plans for the preparation of athletes, the coaches should take into account these practical recommendations and adhere to the recommended directions of training. Repeated examinations (four months later) revealed the effectiveness of managing the process of technical preparation of kayakers based on the correction of intermuscular coordination.

Zwitterionic stabilized water-borne polymer colloids for antifouling coatings

This study presents antifouling waterborne (meth)acrylic coatings prepared through seeded semi-continuous emulsion polymerization, using trace amounts of a zwitterionic monomer 2-(methacryloyloxy)ethyl dimethyl-(3-sulfopropyl)ammonium hydroxide (DMAPS). DMAPS was introduced with a dual purpose, to establish a protective layer of DMAPS containing polymer chains on the films' surface, thereby imparting antifouling characteristics, while simultaneously provides in-situ colloidal stability to the emulsion during polymerization.By providing colloidal stability to (meth)acrylic polymer particles in aqueous dispersion (latex), DMAPS-rich units are distributed on the surface of the polymer particles and subsequently on the surface of the resulting polymer films. Subsequent analysis revealed that the films exhibited diminished hydrophilicity, a more textured surface, and diminished affinity for water entrapment compared to conventionally stabilized (meth)acrylic films. Such surfaces demonstrated high resistance to fouling and weak adhesion of the studied BSA protein. These effects were positively influenced by the quantity of DMAPS incorporated within the (meth)acrylic films that allow higher coverage with DMAPS rich polymer chains.The proposed methodology not only emphasizes a potent pathway for the development of environmentally-conscious, waterborne film-forming coating technology but also involves the simultaneous integration of a zwitterionic surface layer, conveying remarkable antifouling attributes to the resulting (meth)acrylic coating film.

Protein stability in a natural deep eutectic solvent: Preferential hydration or solvent slaving?

Deep eutectic solvents (DESs) emerged as potential alternative solvent media in multiple areas, including biomolecular (cryo)preservation. Herein, we studied the stability of a small protein (ubiquitin) in water and a betaine-glycerol-water (B:G:W) (1:2:ζ; ζ = 0, 1, 2, 5, 10) DES, through molecular dynamics. An AMBER-based model that accurately describes the density and shear viscosity of the DES is proposed. We find that water molecules are largely trapped in the solvent, precluding the formation of a full hydration layer, seemingly opposite to osmolytes’ preferential exclusion/preferential hydration mechanism. Although the protein is stable in the DES, structural fluctuations are largely suppressed and only recovered upon sufficient hydration. This is explained by a solvent-slaving mechanism where β-fluctuations are key, with the non-monotonic hydration of some amino acids with the water content providing an explanation to the non-monotonic folding of some proteins in aqueous DESs. A major thermal stability enhancement in the DES is also observed, caused by a similar slowdown of the backbone torsional dynamics. Our results support a kinetic stabilization of the protein in the DES, whereas a possible thermodynamic stabilization does not follow a preferential hydration or water entrapment mechanism.

Biotransformations with Imine Reductases: Design of a Practical Process Avoiding an Extractive Work‐Up by Entrapment of Water and Enzymes in an Immobilized Phase

AbstractA process concept for the asymmetric biocatalytic reduction of heterocyclic imines addressing the efficiency of the reaction as well as downstream‐processing steps was studied by utilizing a “heterogenized aqueous phase”, which contains the needed enzymes and cofactor within a superabsorber (polyacrylate) network, for the biotransformation. The immobilized biocatalytic system, which comprises an imine reductase (IRED), NADPH and an alcohol dehydrogenase for cofactor‐recycling, enables to run the reaction in pure organic medium. Thus, instead of an extractive work‐up as typical solution for biotransformations in aqueous medium, which, however, can be tedious due formation of emulsions, this type of IRED‐catalyzed process leads to a simplified work‐up consisting only of a decantation of the liquid organic reaction medium with the product from the heterogenized aqueous biocatalyst system. Exemplified for the (R)‐enantioselective reduction of 1‐methyl‐3,4‐dihydroisoquinoline by the IRED of Streptomyces viridochromogenes as a model reaction, a process was developed leading to 98 % conversion, 88 % yield and >99 % ee at a substrate concentration of 40 mM.

Pore doublet micromodel experiments of evaporation influence on pre-event water entrapment and pre-event and event water interaction

The stable isotopic signature of xylem water differs from those of rainfall and river water. Without considering the water exchange through the vapor phase, this phenomenon implies that when the event water (new water) infiltrates the soil, a part of the pre-event water (old water) is isolated. The isolation and immobilization of old water are suspected because of the low matrix potential. Because evaporation is the main process that can reduce the matrix potential after quick gravitational drainage, we conjectured that after evaporation, the old water hides in small pores and increases the likelihood of air entrapment, which separates the new and old water. To examine and visualize the potential effect of evaporation on the interactions between old and new water, we performed a series of wetting–drainage–evaporation–wetting experiments within pore doublet micromodels (PDMs). The experimental results showed that air bubbles are trapped when the menisci of the residual liquid are sufficiently far from the inlet and outlet of the PDM. Evaporation can increase these distances, resulting in the formation of larger air bubbles. The air bubble trapped upstream prevents the invading liquid from quickly flushing the original residual liquid out of the PDM. Nevertheless, the invading wetting liquid is still able to bypass the trapped air bubbles and mix with the residual wetting phase via corner flow. In addition, the remobilization of the upstream bubble enhances the process of removing the old trapped liquid.

The leaf of Agapanthus africanus (L.) Hoffm.: A physical-chemical perspective of terrestrialization in the cuticle

Although Agapanthus africanus (L.) Hoffm. is one of the most popular ornamental species in both hemispheres, it has an extremely restricted wild occurrence (Cape province, South Africa). This contradiction between generalized ornamental application and natural distribution was the basis for the analytical approach adopted in the present work. We hypothesized that characteristic features of the cuticular waxes were adopted by this species to help it cope with severe dehydration associated with marine salinity on account of the short distance of the wild populations to the sea. A comprehensive morpho-anatomical, histological and physical-chemical analysis was performed on the epicuticular and intracuticular layers of the adaxial and abaxial surfaces of leaves of specimens of A. africanus. The adaxial epicuticular surface is hydrophilic and the abaxial epicuticular surface exhibits globally hydrophobic behavior. The main chemical compounds detected in the wax layers of both surfaces of the leaf are the short-chain monocaprylin monoglyceride (C8), and very long-chain 1-hexacosanol (C26) and 1-octacosanol (C28) alcohols. While monocaprylin is particularly abundant in the intracuticular layers, the epicuticular adaxial surface revealed the highest concentration of both alcohols. We demonstrate that the smart combination of these two classes of molecules with opposite water affinity endows the A. africanus leaf cuticle with a unique water management system combining the efficient entrapment of water in the disordered α-gel phase formed by monocaprylin and the high resistance to water transport provided by ordered domains composed of tightly packed, all-trans alkyl chains of the above pair of alcohols. The remarkable structural similarity existing between the monocaprylin α-gel and the mucilage of algae is an evidence of the terrestrialization process.

Rheological properties of dairy desserts: Effect of rice bran protein and fat content.

Rice bran protein (RBP) is an alternative plant protein that can be used in a wide range of foods due to its unique functional, nutritional, and hypoallergenic properties. The interactions of RBP with other biopolymers have revealed its feasibility for application in dairy products such as whipped cream and dairy desserts. Therefore, the effects of RBP and fat content on the rheological properties of dairy desserts were investigated. The pH value was not influenced by protein, but the nonfat milk solid content was changed by fat and protein content. All the desserts showed thixotropic properties which were mainly related to the molecular disentanglement at high shear rates. By increasing fat like RBP, the apparent viscosity (ηa ) was increased. Rheological parameters such as n value, thixotropic index, storage (G'), and loss moduli (G'') were increased by RBP. Moreover, the dairy desserts containing RBP and whole milk presented generally higher G', G'', complex modulus, and complex viscosity values, and lower tan δ values. The RBP enriched samples also had a higher hardness and gumminess. Syneresis was decreased by RBP, which was related to the formation of ordered mesh-like structures which enabled the entrapment of more water. There was a positive correlation between the rheological, textural, and physical properties of the dessert with added RBP, and therefore dairy dessert attributes can be improved along with fat reduction. However, a sensory evaluation is needed to unravel the acceptability rate of RBP in fat reduction from the view point of consumers. PRACTICAL APPLICATION: Rice bran protein (RBP) has nutritional and hypoallergenic properties which enable it to apply to many products such as dairy desserts. One of the main concerns in dairy technology is the growing interest in low-fat products due to health problems. RBP showed unique properties which makes the creamy behavior. The rheological results have elucidated the creaminess associated with RBP and can assist in the proper simulation of mouthfeel.

Chitosans and Nanochitosans: Recent Advances in Skin Protection, Regeneration, and Repair

Chitosan displays a dual function, acting as both an active ingredient and/or carrier for pharmaceutical bioactive molecules and metal ions. Its hydroxyl- and amino-reactive groups and acetylation degree can be used to adjust this biopolymer’s physicochemical and pharmacological properties in different forms, including scaffolds, nanoparticles, fibers, sponges, films, and hydrogels, among others. In terms of pharmacological purposes, chitosan association with different polymers and the immobilization or entrapment of bioactive agents are effective strategies to achieve desired biological responses. Chitosan biocompatibility, water entrapment within nanofibrils, antioxidant character, and antimicrobial and anti-inflammatory properties, whether enhanced by other active components or not, ensure skin moisturization, as well as protection against bacteria colonization and oxidative imbalance. Chitosan-based nanomaterials can maintain or reconstruct skin architecture through topical or systemic delivery of hydrophilic or hydrophobic pharmaceuticals at controlled rates to treat skin affections, such as acne, inflammatory manifestations, wounds, or even tumorigenesis, by coating chemotherapy drugs. Herein, chitosan obtention, physicochemical characteristics, chemical modifications, and interactions with bioactive agents are presented and discussed. Molecular mechanisms involved in chitosan skin protection and recovery are highlighted by overlapping the events orchestrated by the signaling molecules secreted by different cell types to reconstitute healthy skin tissue structures and components.

Synthesis and In Vitro/Ex Vivo Characterizations of Ceftriaxone-Loaded Sodium Alginate/poly(vinyl alcohol) Clay Reinforced Nanocomposites: Possible Applications in Wound Healing

(1) Background: Nanocomposite films are widely applied in the pharmaceutical industry (e.g., nanodrug delivery systems—NDDS). Indeed, these nanomaterials can be produced at a large industrial scale and display valuable properties (e.g., antibacterial, renewability, biodegradability, bioavailability, safety, tissue-specific targeting, and biocompatibility), which can enhance the activity of conventional marketed drugs. (2) Aim: To fabricate and investigate the in vitro properties of the antibiotic ceftriaxone sodium (CTX) once encapsulated into sodium alginate (SA)/poly(vinyl alcohol)PVA-clay reinforced nanocomposite films. (3) Methods: Different ratios of the polymers (i.e., SA, PVA) and CTX drug were used for the synthesis of nanocomposite films by solvent casting technique. Montmorillonite (MMT), modified organically, was added as a nanofiller to increase their thermal and mechanical strength. The prepared samples were physically characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electronic microscopy (SEM), and energy-dispersive X-ray analysis (EDX). The physicochemical behavior (i.e., swelling, erosion, dissolution/drug release behavior and rat skin permeation) was also assessed. Comparisons were made with the currently marketed free CTX dosage form. (4) Results: TGA of the nanoformulation showed increased thermostability. XRD revealed its semi-crystalline nature. SEM depicted a homogeneous drug-loaded SA/PVA nanocomposite with an average size ranging between 300 and 500 nm. EDX confirmed the elemental composition and uniform distribution of mixing components. The water entrapment efficiency study showed that the highest swelling and erosion ratio is encountered with the nanoformulations S100(3) and S100D15(3). Ex vivo permeation revealed a bi-step discharge mode with an early burst liberation chased by continued drug discharge of devised nanoparticles (NPs). The dissolution studies of the drug-loaded polymer nanocomposites elicited sustained pH-dependent drug release. The cumulative drug release was the highest (90.93%) with S100D15(3). (5) Conclusion: S100D15(3) was the finest formulation. To the best of our knowledge, we also pioneered the use of solvent casting for the preparation of such nanoformulations. Polymers and reinforcing agent, concentrations and pH were rate-deterring features for the preparation of the optimized formulation. Thus, CTX-loaded SA/PVA-MMT reinforced nanocomposite appeared as a promising nanodrug delivery system (NDDS) based on its in vitro physicochemical properties.

The contribution of microbial activity to soil–water interactions and soil microstructural stability of a silty loam soil under moisture dynamics

Soil structure and its stability against external stresses is fundamental to various soil functions and ecosystem services. Particularly soil moisture dynamics and microbial activity can affect soil structure by promoting particle reorientation, cementation and spatio-temporal pore space remodeling. In this context, microbial exudates can serve as interparticulate binding agents and thus contribute to the formation of stable soil structures and basic physico-chemical soil properties. However, detailed interactions and relationships between microbial activity, soil pore water and the porous soil matrix itself are still unclear, especially in the context of dynamic moisture conditions. In this study, we aimed to increase the fundamental understanding of microbially-induced and moisture dynamic-affected soil microstructural stability and soil–water interactions. For this, a sterilized, untreated and substrate-enhanced silty loam soil was subjected either to constant moisture conditions or four consecutive drying-wetting cycles. At defined timepoints, soil samples were investigated for carbon dioxide release (respirometry), phospholipid fatty acid analysis, wetting behaviour (contact angle), rheological characteristics (rheometry) and water entrapment (1H nuclear magnetic resonance relaxometry) to respectively determine microbial activity, community structure and biomass, soil wettability, soil microstructural stability and the frequency distribution of water-filled pore sizes in soil (FDWPS). Results showed that substrate enhancement promoted soil microstructural stability compared to sterilized and untreated soil, whereby all soils reacted dynamically and irreversibly to the adjusted moisture conditions. Significant positive correlations were found between microbial activity, wettability, FDWPS and soil microstructural stability, which indicate that the presence of interparticulate microbial structures augmented the spatio-temporal reorganization effect induced by soil moisture dynamics. The irreversible dehydration of those interparticulate microbial structures resulted in an additional pore space cementation, water redistribution to smaller soil pores and thus a considerably increased microstructural stability due to stronger cohesive and capillary forces. The results help to understand the extent to which soil moisture dynamics can modulate microbial-induced soil processes and basic soil properties.

Protein Hydration in a Bioprotecting Mixture.

We combined broad-band depolarized light scattering and infrared spectroscopies to study the properties of hydration water in a lysozyme-trehalose aqueous solution, where trehalose is present above the concentration threshold (30% in weight) relevant for biopreservation. The joint use of the two different techniques, which were sensitive to inter-and intra-molecular degrees of freedom, shed new light on the molecular mechanism underlying the interaction between the three species in the mixture. Thanks to the comparison with the binary solution cases, we were able to show that, under the investigated conditions, the protein, through preferential hydration, remains strongly hydrated even in the ternary mixture. This supported the water entrapment scenario, for which a certain amount of water between protein and sugar protects the biomolecule from damage caused by external agents.

Formation of graphene nanostructures using laser induced vaporization of entrapped water

Facile construction of graphene nanostructures are potentially important for fundamental studies and various applications owing to its transparency and mechanical strength. Here we found that focused laser irradiation of a graphene/entrapped water/hydrophobic substrate leads to vaporization of entrapped water and consequent formation of graphene nanostructures. Graphene mechanically exfoliated on a hydrophobicized Si substrate was served as a transformable and impermeable nanocontainer in which water anisotropically and slowly diffuses from the weak edges into the van der Waals (vdW)-coupled interstitial volume between graphene and the substrate. Time-lapsed Raman mappings show that water entrapment promotes progressive lowering of the frequencies of the G and 2D bands of graphene and exhibits slower diffusion owing to vdW decoupling of substrate-induced doping and biaxial strain of graphene with hydrophobic substrate. Moreover, vaporized entrapped water promotes nanostructures by graphene sliding and bulging actions. This methodology represents viable approach to produce nanostructures from two dimensional materials.

Islatravir Case Study for Enhanced Screening of Thermodynamically Stable Crystalline Anhydrate Phases in Pharmaceutical Process Development by Hot Melt Extrusion.

The emergence of new active pharmaceutical ingredient (API) polymorphs in pharmaceutical development presents significant risks. Even with thorough polymorph screening, new pathways toward alternate crystal phases can present themselves over the course of formulation development; thus, further improvements in phase screening methods are needed. Herein, a case study is presented of a thermodynamically stable crystalline phase of the HIV drug Islatravir (MK-8591, EFdA) that was not isolated from initial pharmaceutical polymorph screening. In total, five Islatravir phases are identified: one monohydrate and four anhydrate phases. The new phase, anhydrate form IV, was unexpectedly discovered during hot melt extrusion (HME) process development of polymeric implant drug product formulations while probing extreme manufacturing process conditions (elevated shear forces). X-ray diffraction (XRD), differential scanning calorimetry (DSC), and solid-state nuclear magnetic resonance (ssNMR) were utilized as principal tools to identify the new polymorph. The result suggests that HME introduces conditions that may allow a thermodynamically stable crystalline phase to form and these conditions are not necessarily captured by routine pharmaceutical polymorph screening. Subsequent investigations identified procedures to generate the new anhydrate phase without HME equipment by the use of special thermal procedures. It is found that for a crystalline hydrate phase the rate of water loss as well as water entrapment in a heating vessel play a crucial role in phase conversions into different anhydrate polymorphs. Further, the polymer involved in the HME manufacturing process also plays a critical role in the phase conversion, likely by coating the API microparticles and thereby altering the phase conversion kinetics. Strategies presented herein to mimic phase changes during formulation manufacture hold promise for the identification of thermodynamically stable anhydrate forms in earlier stages of pharmaceutical development.

Engineering nanocellulose superabsorbent structure by controlling the drying rate

HypothesisThe absorption performance and structure of superabsorbents prepared from carboxylated nanocellulose are strongly influenced by the rate of water removal. Their structure can be engineered by changing the drying profile. ExperimentsTEMPO-oxidised nanocellulose superabsorbents were prepared using five different drying techniques, each providing a distinct drying rate. The absorption capacity of deionised water was measured as a function of time and the swelling kinetics was determined, modelled and related to the superabsorbent structure. Superabsorbent phytotoxicity was assessed through seed emergence tests. FindingsThe absorption performance of nanocellulose superabsorbents is controlled by the drying rate. In most cases, drying the nanocellulose superabsorbents via evaporation increases the absorption capacity compared to freeze-dried superabsorbents. The best nanocellulose superabsorbent was the air-dried, absorbing around 230 g water/g dry fibre. The high absorption capacity of the evaporative dried superabsorbents is due to their high pore area which increases the interaction between water molecules and fibres. This leads to a stronger physical entrapment of water by capillary forces. Seed germination studies demonstrated that oven-dried 50 °C superabsorbent increased germination by 40 %. Carboxylated nanocellulose superabsorbents emerge as high-performance renewable materials which can be used extensively in many applications, including agriculture.

Feasibility study of epoxy coated Poly Lactic Acid as a sustainable replacement for river sand

River sand is ruling construction industry due to its tremendous properties and composition. According to the statistics of World Industrial Silica Sand Demand, this need for sand will increase up to 123.4 millions of metric tons in 2025 in the United States and about 51 millions of metric tons in Asian countries. The increasing population has escalated the demand, in-parallel asking for an alternative material development from research community. The earlier study yielded a promising results on Polylactic acid as a replacement for river sand in steps of 0, 10, 30 and 50% inclusion in holding concrete matrix. Currently, the work focuses on reducing the degradation aspect of Polylactic acid, when it comes in contact with cement and aggregate. The work comprising of coating a Poly lactic acid with epoxy for better durability. Soil burial test was conducted from 0 to 50 days and weight of samples recorded. Further, the samples were subjected to Scanning Electron Microscopy study to check the water entrapment or air void filling by water droplets. After epoxy coating coupons were built to check any strength deterioration but results were quite convincing under simulation package ANSYS workbench along with experimental investigation. Compressive strength reduced by 43% in comparison to pristine PLA sample with previous work. As per Polylactic acid grade, a monomer and then polymer was built under the J-OCTA platform to extract the material properties, the same data were used in ANSYS Workbench for simulation. The results reveal that a good correlation with experimental and simulation for compressive strength of 21.7 MPa for the control mix of M30(based on previous work). In case of degradation study, the day-wise extracted reports reveal quite interesting facts, and with positive note, probably PLA in future can be considered as the most preferred material for replacement of river sand.

Effect of matric potential and soil-water-hydrogel interactions on biohydrogel-induced soil microstructural stability

Soil structure formation and its stability against external stress ensure sufficient water, air and nutrient supply for plants under varying environmental conditions. In this context, soil-born biohydrogels glue soil particles together and increase structural stability and water retention via the formation of swollen interparticulate hydrogel structures. However, interparticulate hydrogel behavior in soil under fluctuating water potentials remains still unclear. We addressed this by treating loamy sand and clayey loam with alginate, a hydrogel-forming biopolymer, at various concentrations and adjusted them to matric potentials of ψ = −0.3 kPa, −3.2 kPa and −6.3 kPa. For both soils, we assessed soil-water interactions in terms of mobility, distribution and freezability of water by 1H nuclear magnetic resonance relaxometry and differential scanning calorimetry. The measurements on water entrapment were complemented with the characterization of soil microstructural stability using rheometry (amplitude sweep tests).Alginate hydrogel increased soil microstructural stability and shifted pore-size distributions towards smaller pore sizes with more restricted water mobility. Interestingly, alginate-induced microstructural stability remained constant or further increased with decreasing matric potential, although the effect of alginate on the entrapment and mobility of water decreased with decreasing matric potential for both soils. Moreover, the direction and intensity of alginate-derived effects differed between both soils as water entrapment increased for the loamy sand and decreased for the clayey loam, respectively. This effect was attributed to the mutually restricted swelling of alginate and clay particles as result of various polymer-clay interactions in the clayey loam, which increased the relative amount of less strongly bound water in the soil matrix.The results indicate that the gel effect is composed of several components that strongly depends on various intrinsic and extrinsic factors, including the properties of the hydrogel-forming biopolymer itself and the complex interplay with the available water and mineral surfaces in soil.